Plenarvorträge - DPG-Tagungen

Plenarvortrag PV I Mo 08:30 H1
Bose-Einstein-Kondensation von Atomen und Molekülen —
•Wolfgang Ketterle — Dept. of Physics, MIT, Cambridge MA
02139-4307, USA
Ich werde über neue Experimente mit quanten-entarteten Gasen am
MIT berichten. Dies beinhaltet einen neuen Tiefsttemperaturrekord von
weniger als einem Nanokelvin, die Konversion von ultrakalten Atomen
in ultrakalte Moleköle, Bose-Einstein-Kondensation von Molekülen und
Experimente mit Bose-Einstein-Kondensaten auf Atomchips.
Plenarvortrag PV II Mo 18:00 H1
What single molecules can tell us about Nano- and Biosystems
— •Christoph Bräuchle — Ludwig-Maximilians-Universität
München, Physikalische Chemie und Center for NanoScience, Butenandtstr.
11, D-81377 München
Single molecule studies unravel the ensemble averaging in conventional
bulk experiments and allow to determine the distribution of values for an
experimental parameter in heterogeneous systems rather than just giving
the mean value. In addition mechanistic details show up in such experiments,
which are often hidden behind the averaging process in ensemble
experiments. We have applied single molecule detection techniques in
nano- as well as in biosciences. The observation of the dynamics of single
molecules in nanometer-sized channel and cage structures (e.g. molecular
sieves) is one aspect of such investigations. The visualization of the infection
pathway of a single dye-labeled virus into a living cell is another
aspect of single molecule experiments in biosciences. After a general introduction
the talk will concentrate on experiments in both areas.
Plenarvortrag PV III Di 08:30 H1
Surface Plasmon Photoni — •L. Martín-Moreno 1 and F. J.
García-Vidal 2 — 1 Departamento de Física de la Materia Condensada,
Universidad de Zaragoza, Spain — 2 Departamento de Física Teórica de
la Materia Condensada, Universidad Autónoma de Madrid, Spain
In this talk we present an overview of the field of optical properties of
(micro- and nano-) structured metals.
Metal surfaces are known to support electromagnetic modes, known
as surface plasmons (SP). In corrugated surfaces SP’s couple strongly to
radiation and, therefore, act as a sink of energy, which has traditionally
seen as a drawback of metal structures for optical applications. However,
in the last few years, advances in nano-fabrication have allowed the control
of the corrugation in the metal. This has opened the possibility of
using SP’s for efficient coupling to light (in- and out- the structure) and
for transporting energy in a controlled way.
As example of these new capabilities we will present both experimental
results and the theoretical description of properties such as the extraordinary
transmission of light in arrays of sub-wavelength holes in a metal
film, and the extraordinary transmission and beaming of light in single
apertures flanked by surface corrugations.
Plenarvortrag PV IV Di 13:30 H1
Plateaus and Jumps in Single Molecule DNA Unzipping Experiments
— •David R. Nelson — Lyman Laboratory of Physics
and Division and Engineering and Applied Physics, Harvard Univeristy,
Cambridge, MA 02138
We discuss the denaturation of long, double-stranded DNA pulled
apart by a constant force. When the force approaches a critical threshold,
a remarkable unzipping transition occurs which is strongly influenced by
randomness in the base pair sequence.[1] The DNA unzips via a series of
discrete jumps and plateaus which allow it to reach successively deeper
energy minima. Above the threshold force, the dynamics of unzipping is
related to that of a particle diffusing in a random force field. Recently, the
first observations of this striking behavior, carried out on several identical
molecules in parallel, have been reported.[2] The position and duration of
the pauses in the separation are reproducible from molecule to molecule
and depend on the applied force. For small forces, the DNA remains in
a partially unzipped state. We expect similar energy landscapes together
with anomalous drift and diffusion for certain molecular motors near the
stall force.
Plenarvorträge
Plenarvorträge
[1] D. K. Lubensky and D. R. Nelson, Phys. Rev. E 65, 031917 (2002).
[2] C. Danilowicz et. al. Prod. Natl. Acad. Sci. 100, 1694 (2003).
Plenarvortrag PV V Mi 08:30 H1
Nanotechnology and the Future of Information Technology —
•Thomas N. Theis — IBM T.J. Watson Research Center, P.O. Box
218, Yorktown Heights, NY 10598
Information technology has prospered as scientists and engineers have
learned to make ”bits”ever smaller. Current manufacturing processes cannot
build much structure into an object at a length scale less than the
minimum lithographic dimension of 90 nm, but there is no physical reason
we cannot learn to design and build objects with complex structure
defined on all length scales down to the atomic scale. Opinions on
how this might be done are often divided into apparently conflicting
camps – ”top down”versus ”bottom up”, lithography versus chemical
synthesis, ”nanobots”and ”molecular assemblers”versus ”self assembly”.
None of these distinctions is very meaningful from the point of view
of physics. What is meaningful is the error rate with which structural
information can be imparted to an object by some dynamical process.
”Digital”processes, with a few energetically accessible states, can have
very low error rates, but are energetically costly. ”Analog”processes, with
many accessible energy states, have higher error rates, but can be very
energy efficient. Both types of information transfer are discernible in every
manufacturing process. Above the scale of the minimum lithographic
dimension, lithography is inherently digital. Chemical synthesis tends to
be analog. The trick is to combine the two modes of imparting structural
information so that the complex, hierarchically-organized systems
of information technology can be manufactured at minimum cost. Conventional
optical lithography won’t allow us to impart structural information
at the atomic and molecular scale, but scanning-probe and other
emerging lithographic processes will. Combined with increasingly sophisticated
chemical synthetic processes, it should become possible over the
next few decades to design and control the structure of an object on all
length scales, from the atomic to the macroscopic, and to do so cheaply
and reliably in manufacturing. The emergence of such a mature nanotechnology
would ensure continued exponential reductions in the cost
of information technology hardware, and generate yet unimagined new
products and industries.
Plenarvortrag PV VI Mi 09:15 H1
Magnetism and X-Rays: Past, Present, and A Vision of the
Future — •Joachim Stöhr — Stanford Synchrotron Radiation Laboratory,
Stanford, CA 94309
In this talk I will discuss how developments in magnetism research over
the last fifteen years have been accompanied by the increased utilization
of x-ray techniques to address scientific challenges. Today’s magnetic materials
are not the bulk materials of old, but atomically engineered thin
film structures with ferromagnetic, antiferromagnetic and non-magnetic
components. Of special interest are structures with nanometer dimensions
and time responses of nanoseconds and faster. This development is
clearly fueled by the technological need for smaller and faster magnetic
devices. The understanding of advanced materials requires new experimental
techniques that are capable of probing them on the nanometer
length scale and sub-nanosecond time scale. I will show that this can be
uniquely accomplished by use of synchrotron x-rays that are tunable, polarized
and pulsed. As examples I will discuss x-ray resonant scattering,
x-ray absorption and x-ray spectro-microscopy studies, and their use to
elucidate the interfacial exchange coupling between thin magnetic layers,
the time-resolved response of magnetic nanostructures to sub-nanosecond
magnetic field pulses, and magnetic switching phenomena due to spin polarized
currents, so-called “spin-injection”. I will finish with my personal
vision of the future, where x-ray lasers will enable studies of the ultrafast
magnetic nanoworld by means of femtosecond snapshots.

Plenarvortrag PV VII Mi H1
Nanoscale Study of Quantum Phenomena: Influence of Dimension,
Magnetic Field and Disorder on Simple Electron Systems
— •Markus Morgenstern — Institute of Applied Physics, Hamburg
University, Jungiusstr. 11, D-20355 Hamburg, Germany — Träger des
Walter-Schottky-Preises 2004
Scanning Tunneling Spectroscopy is a tool to measure the local density
of states, which is the sum over squared single-particle wave functions.
Applying this technique to the simple, quasi-free electron systems of III-
V semiconductors allows to tackle the influence of interactions on the
local scale rather systematically. Basically four parameters,- dimension,
electron density, magnetic field, and disorder potential-, govern the phase
diagram of the system.
We started to vary these parameters and indeed found a rather different
appearance of the local density of states. Here, I concentrate on the
two-dimensional electron system investigated at different magnetic fields
and disorder strengths. Real-space visualizations of the influence of weak
localization, drift states in the quantum-Hall regime, and percolation are
given. In addition, the single-particle wave functions of strain-induced
InAs quantum dots will be shown.
Plenarvortrag PV VIII Mi 14:30 H1
Heavy-Fermion Superconductivity: 25 years after — •F.
Steglich — Max-Planck-Institut für Chemische Physik fester Stoffe,
01187 Dresden — Träger der Stern-Gerlach-Medaille 2004
25 years after the discovery of heavy-fermion superconductivity in
CeCu2Si2 it has been widely accepted by now that this state may develop
either out of a Landau-Fermi-liquid (LFL) state or out of a socalled
non-Fermi-liquid (NFL) state. The hexagonal compound UPd2Al3
belonging to the former class is the first and yet only superconductor for
which quasiparticle tunneling and inelastic neutron scattering strongly
point towards a non-phononic, i.e., magnetic-exciton mediated, Cooperpair
state.
For the tetragonal NFL superconductor CeCu2Si2 pronounced deviations
from LFL behavior are observed in its low-temperature normalstate
properties. These can be related to the vicinity of an antiferromagnetic
(AF) quantum critical point (QCP) at which a low-moment
incommensurate spin-density-wave (SDW) phase disappears in a continuous
way (TN → 0). For this compound, two distinct superconducting
phases can be well separated on the pressure (p) axis by deliberately
reducing the quasiparticle mean free path, i.e., by weak doping with
Ge: The low-p phase is centered around the AF QCP, while the high-p
phase occurs in the neighborhood of a weak first-order valence transition
[Ce 3+ → Ce (3+δ)+ ]. This observation highlights the (co-) existence of two
different types of pairing mechanisms mediated by soft fluctuations of
the spin density (at low p) and of the charge density (at high p).
While the NFL effects in CeCu2Si2 are consistent with an itinerant
(SDW ) scenario for the QCP, in YbRh2Si2 a new variant of quantum
criticality has been found which seems to be phenomenologically related
to that in the prototypical material CeCu5.9Au0.1. Here, the most critical
spin fluctuations are apparently of a local rather than an itinerant nature.
YbRh2Si2, isostructural to CeCu2Si2, is not a superconductor suggesting
that a local-moment QCP might be unfavorable for heavy-fermion superconductivity.
Plenarvortrag PV IX Mi 15:15 H1
Stress on the atomic scale: From surface reconstruction to stress
oscillations and magnetostriction of atomic layers — •Dirk
Sander — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2,
D-06120 Halle — Träger des Gaede-Preises 2004
Mechanical stress is an important factor, which governs a number
of fundamental aspects in surface science, film growth, and magnetic
anisotropy. Examples are e.g. the surface reconstruction of clean and
adsorbate-covered surfaces, oscillatory stress relaxation in nanosize islands,
and the magnetoelastic coupling in ferromagnetic monolayers.
Stress measurements by the cantilever bending technique are presented
for each example. Film stress in the GPa range, in excess of the tensile
strength of high-strength materials, is measured for epitaxially strained
layers. Structural relaxation due to island growth and coalescence, and
surface alloy formation are comparatively subtle effects, which are detected
by the respective stress signature. The in situ combination of
stress measurements during film growth with magnetoelastic stress measurements
upon magnetization reversal identifies a strain-induced change
of the magnetoelastic coupling constants from the respective bulk value.
Plenarvorträge
The impact on the peculiar magnetic anisotropy of ferromagnetic layers
is discussed.
Plenarvortrag PV X Mi 20:00 H1
Magnetorientierung bei Vögeln — •Wolfgang Wiltschko —
Zoologisches Institut, Universität Frankfurt a. M. — öffentlicher Abendvortrag
Plenarvortrag PV XI Do 08:30 H1
Unusual magnetic transition and its consequences — •Alexei
Abrikosov — Materials Science Division, Argonne National Laboratory,
9700 South Cass Avenue, Argonne, IL 60439, USA
A theory of the phase transition from an insulating antiferromagnet to
a metal in layered cuprates is constructed on the basis of a spin-density
wave model. The transition occurs to be of the second order at smaller
dopings and of the first order at larger ones. The influence of impurity
scattering is analyzed. A phenomenon of an infrared transparency
threshold is predicted for the insulating phase. For the metallic phase
the experimentally observed phenomena of anti-ferromagnetic “bubbles”
around nonmagnetic impurities and “week antiferromagnetism” in the
metallic and superconducting phases are explained.
This work was supported by the Department of Energy under the contracts
W-31-109-ENG-38.
Plenarvortrag PV XII Do 20:00 H1
Sind wir allein im Universum? — •Harald Lesch — Institut für
Astronomie and Astrophysik, Universität München, Scheinerstr. 1, D-
81679 München — öffentlicher Abendvortrag
Eine überaus interessante Frage. Die Anzahl der Science-Fiction Filme
übersteigt fast schon die Zahl der UFO-Sichtungen. Talkshows mit
” Entführten“ zühlen heute genauso zu unserem täglichen Fernsehangebot,
wie die Obduktion eines abgestürzten Außerirdischen. Die Außerirdischen
erfreuen sich ungeahnter Popularität.
Aber auch in der Astrophysik werden die Außerirdischen immer leben-
”
diger“, angesichts der Planeten, die um andere Sterne gefunden wurden.
Aber gibt es sie denn nun wirklich, die Anderen? Was kann die Astronomie
zu diesem Thema beitragen?
Die überwältigende Anzahl von Sternen und Sternsystemen, den Galaxien,
läßt die Frage ob wir alleine im Universum sind, als völlig sinnlos
erscheinen. Natürlich sind wir nicht allein, wird fast jeder antworten.
Die astrophysikalischen Grundlagen zur Entstehung von Sternen und
die sie umkreisenden Planeten werden diskutiert. Es wird gezeigt werden,
welche besonderen Umstände nötig sind, damit ein Planet überhaupt ein
sich selbst reproduzierendes biologisches System - ein Lebewesen - entwickeln
kann.
Es wird am Ende natürlich keine eindeutige Antwort geben, aber der
Zuhörer wird die wesentlichen Argumente gehört haben, warum zumindest
viele Astrophysiker zu dem Schluß kommen; wir sind ziemlich allein
im Universum!
Plenarvortrag PV XIII Fr 08:30 H1
Trillions of quantum dots, Fingerprints, Nanolithography with
diblock copolymers, Annealing and alignment of striped and
hexatic phases — •Paul Chaikin — Dept. of Physics, Princeton University,
Princeton, NJ 08544
We have been using monolayer films of cylindrical and spherical phase
diblock copolymers to make ultradense patterns over wide areas on arbitrary
substrates. For example we cover a three inch wafer with ∼ 3 trillion
posts, holes, etc. spaced by ∼ 25nm, to make quantum dots (for semiconductor
lasers), metal particles and wires (for UV polarizers) ... In trying
to understand how the polymer patterns order we have used atomic
force microscopy (AFM) to image the cylindrical phase which lies flat
on a substrate. The patterns look like fingerprints and Benard rolls and
the coarsening (annealing) law we observe is t (1/4) as in previous studies
of these striped phases. This law remained unexplained for decades.
However, guided by previous studies of fingerprints and their defects we
made time lapse AFM movies which show that the annealing dynamics
is governed by the attraction of disclination PAIRS, quadrupoles,
rather than simple +/– annihilation. This directly provides an explanation
for the alignment of the striped patterns as a function of time.
Thus these systems, while aimed at technological and fundamental electronic
applications are also ideal materials for studying the dynamics and
thermodynamics of ordering in two dimensions. Recently we have shown
that simple shear can lead to ordering of these nanometer patterns on
centimeter and larger scales.

Plenarvortrag PV XIV Fr 09:15 H1
Assault on storage density of 1 Terabit / sq-in and beyond —
•Dieter Weller — Seagate Research, 1251 Waterfront Place, Pittsburgh
PA 15222, U.S.A.
The areal density in magnetic recording has surpassed ∼50 Gbit/in 2 in
products and ∼100 Gbit/in 2 in laboratory demonstrations. These densities
have been achieved with recording media comprised of Co-alloy nanostructured
materials with horizontal orientation of the magnetization
(longitudinal recording). Grain sizes are 8-10 nm and grain size distributions
are near 20% (sigma over mean). Going much beyond 100 Gbit/in 2 requires
magnetically harder materials with smaller, thermally stable grains
(5–8 nm) and tighter distributions (

Chemische Physik und Polymerphysik Tagesübersichten
CHEMISCHE PHYSIK UND POLYMERPHYSIK (CPP)
Prof. Dr. Josef Friedrich
Physikdepartment E14
Lehrstuhl für Physik Weihenstephan
Technische Universität München
An-der-Saatzucht 5
85350 Freising
E-Mail: J.Friedrich@lrz.tu-muenchen.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsäle H 37, H 38, H 39)
Fachinternes Symposium
“Understanding and Controlling Complex Structures: From Synthetic Polymers to Biomaterials”
Organisation: Prof. Thomas Thurn-Albrecht
Martin-Luther-Universität Halle-Wittenberg, Fachbereich Physik, 06099 Halle
E-Mail: thurn-albrecht@physik.uni-halle.de
Dienstag, 9:30–17:00, H 37
Hauptvorträge
CPP 1.1 Mo 09:30 (H 37) Thin, nanostructured block copolymer films, Christine M. Papadakis
CPP 13.1 Di 09:30 (H 37) Hierarchical Structures in Biological Materials, Peter Fratzl
CPP 13.2 Di 10:00 (H 37) Polymer cystallization as an example for highly meta-stable structure
formation, Jens-Uwe Sommer, Günter Reiter
CPP 14.1 Di 14:00 (H 37) Competition of order in liquid crystalline/isotropic block copolymers,
Bernd Stühn, Wolfram Gronski, Rosina Staneva, Sergei Zhukov, Steffen Geppert
CPP 14.2 Di 14:30 (H 37) Bio- and biomimetic mineralization, Helmut Cölfen
Fachsitzungen
CPP 1 Polymer Surfaces I Mo 09:30–10:45 H 37 CPP 1.1–1.4
CPP 2 Polymer Surfaces II Mo 11:00–12:30 H 37 CPP 2.1–2.6
CPP 3 Magnetic Resonance Mo 10:00–11:15 H 38 CPP 3.1–3.5
CPP 4 Dynamics of Molecular Systems Mo 11:15–12:30 H 38 CPP 4.1–4.5
CPP 5 Computational Physics Mo 10:00–11:15 H 39 CPP 5.1–5.5
CPP 6 Self-organising Systems Mo 11:30–12:15 H 39 CPP 6.1–6.3
CPP 7 Physics of Polymers I Mo 14:00–15:30 H 37 CPP 7.1–7.6
CPP 8 Physics of Polymers II Mo 15:45–17:30 H 37 CPP 8.1–8.7
CPP 9 Single Molecule Spectroscopy Mo 14:00–15:30 H 38 CPP 9.1–9.6
CPP 10 Light Induced Phenomena Mo 15:45–17:30 H 38 CPP 10.1–10.7
CPP 11 Colloids and Nanoparticles I Mo 14:00–15:30 H 39 CPP 11.1–11.6
CPP 12 Colloids and Nanoparticles II Mo 15:45–17:15 H 39 CPP 12.1–12.6
CPP 13 SYMPOSIUM: Understanding and Controlling Complex
Structures: From Synthetic Polymers to Biomaterials
I
Di 09:30–12:30 H 37 CPP 13.1–13.9

Chemische Physik und Polymerphysik Tagesübersichten
CPP 14 SYMPOSIUM: Understanding and Controlling Complex
Structures: From Synthetic Polymers to Bioma-
terials II
Di 14:00–17:00 H 37 CPP 14.1–14.9
CPP 15 POSTER: Polymers and Biomaterials Di 17:00–19:00 B CPP 15.1–15.49
CPP 16 POSTER: Computational Physics, Complex Systems Di 17:00–19:00 B CPP 16.1–16.36
SYMPOSIUM
“LIFE SCIENCES ON THE NANOMETER SCALE – PHYSICS MEETS BIOLOGY (SYLS)”
siehe auch gesonderten Programmteil
Hauptvorträge
SYLS 1.1 Mi 14:00 (H 37) Aquaporin Proteins: Perfect filters, Helmut Grubmüller, Bert L. de Groot
SYLS 1.2 Mi 14:30 (H 37) Single-Molecule Cellular Signaling, Thomas Schmidt
SYLS 4.1 Do 09:30 (H 37) Single Molecule Mechanics of Cytoskeletal Proteins, Matthias Rief
SYLS 5.1 Do 11:15 (H 37) Mechano-Chemical Coupling in F1-ATPase, Kazuhiko Kinosita
Fachsitzungen
SYLS 1 Symposium ”Life Sciences on the Nanometer Scale –
Physics Meets Biology”
SYLS 2 Symposium ”Life Sciences on the Nanometer Scale –
Physics Meets Biology”
SYLS 3 POSTER: Symposium ”Life Sciences on the Nanometer
Scale – Physics Meets Biology”
SYLS 4 Symposium ”Life Sciences on the Nanometer Scale –
Physics Meets Biology”
SYLS 5 Symposium ”Life Sciences on the Nanometer Scale –
Physics Meets Biology”
Mi 14:00–15:00 H 37 SYLS 1.1–1.2
Mi 15:15–16:00 H 37 SYLS 2.1–2.3
Mi 16:00–18:30 B SYLS 3.1–3.58
Do 09:30–11:00 H 37 SYLS 4.1–4.5
Do 11:15–12:30 H 37 SYLS 5.1–5.4
SYMPOSIUM
“ORGANIC AND HYBRID SYSTEMS FOR FUTURE ELECTRONICS (SYOH)”
siehe auch gesonderten Programmteil
Hauptvorträge
SYOH I Fr 10:15 (H 1) Growth Control and Optics of Organic Nanoaggregates,
Horst-Günter Rubahn
SYOH II Fr 10:45 (H 1) Electronic Transport through Single Molecules, H. v. Löhneysen, F. Heinrich,
M. M. Kappes, R. Krupke, M. Major, J. Reichert, H. B. Weber
SYOH III Fr 12:10 (H 1) Inorganic Nanorods: Synthesis, Properties, Photovoltaic Applications,
D. Milliron, I. Gur, Paul Alivisatos
SYOH IV Fr 12:40 (H 1) Understanding Donor-Acceptor Photovoltaic Devices, Neil Greenham, Baoquan
Sun, Henry Snaith, James Barker, Richard Friend, Catherine Ramsdale

Chemische Physik und Polymerphysik Tagesübersichten
Fachsitzungen
SYOH 1 Geometric Organic Structures on Surfaces Do 14:00–14:45 H 37 SYOH 1.1–1.3
SYOH 2 Spectroscopy Do 14:45–15:45 H 37 SYOH 2.1–2.4
SYOH 3 Electronic Structure and Transport Properties Do 16:00–16:45 H 37 SYOH 3.1–3.3
SYOH 4 Hybrid Systems and Devices Do 16:45–17:45 H 37 SYOH 4.1–4.4
SYOH 5 Poster Do 18:00–21:00 B SYOH 5.1–5.90
SYOH 6 Hauptvorträge I-II Fr 10:15–11:15 H 1 SYOH 6.1–6.2
SYOH 7 Molecular Systems and Applications Fr 11:15–11:55 H 1 SYOH 7.1–7.2
SYOH 8 Hauptvorträge III-IV Fr 12:10–13:10 H 1 SYOH 8.1–8.2
Mitgliederversammlung des Fachverbands Chemische Physik und Polymerphysik
Mi 18:30–19:30 H 37

Chemische Physik und Polymerphysik Montag
Fachsitzungen
– Haupt-, Kurzvorträge und Posterbeiträge –
CPP 1 Polymer Surfaces I
Zeit: Montag 09:30–10:45 Raum: H 37
Hauptvortrag CPP 1.1 Mo 09:30 H 37
Thin, nanostructured block copolymer films — •Christine M.
Papadakis — Fakultät für Physik und Geowissenschaften, Universität
Leipzig, now at Physik Department, Technische Universität München
Block copolymer films can be used for patterning surfaces on a submicrometer
length scale. In order to understand the surface structures
observed as well as their stability and their response to outer stimuli, it
is important to gain knowledge both on the surface structures as well
as on the inner film structure. The combination of direct visualization
of the surface texture by atomic force microscopy with scattering methods
elucidating the inner film structure has proven to give a wealth of
information. By means of grazing-incidence small-angle X-ray scattering
(GISAXS), structures normal to the substrate as well as lateral structures
can be detected simultaneously. In addition, time-resolved GISAXS
measurements can be used to study the structural changes of the films
upon outer stimuli in-situ. In my talk, I will present results on thin films
of a series of polystyrene-polybutadiene diblock copolymers, where we
have found a previously unknown molar-mass dependence of the lamellar
orientation. The structural changes of he films when subjected to a
vapor atmosphere were monitored in-situ.
CPP 1.2 Mo 10:00 H 37
Volume Phase Transition of PNIPAM-Microgel Paricles Studied
with Laser-AFM — •Lothar Zitzler 1 , Frieder Mugele 1 ,
and Stephan Herminghaus 1,2 — 1 Angewandte Physik, Universität
Ulm, Albert-Einstein-Allee 11, 89081 Ulm — 2 Max-Planck-Institut für
Strömungsforschung, Bunsenstraße 10, 37073 Göttingen
Poly(N-isopropylacrylamide) (PNIPAM) is a polymer with a lower critical
solution temperature (LCST) of TLCST ≈ 32˚C. It shows a conformational
change from a coil to a globule state upon increasing the temperature
above TLCST. Here we present AFM-studies (in aqueous environment)
of PNIPAM-co-poly(vinyl acetic acid) microgel particles adsorbed
on glass substrates. Like in solutions the adsorbed particles also show
a pronounced change in volume of approximately 200% with respect to
the globular state. The different elastic properties of the particles in the
coil and globular states could be distinguished clearly in amplitude- and
phase-distance curves, obtained by AFM in Tapping Mode.
To study the dynamics of this coil to globule transition we combined the
AFM with an intense cw-laser (5W at 532nm). We generated laser pulses
of variable width (10ns-100µs) with an acousto-optical modulator. The
laser pulses were used to trigger the volume phase transition by heating
the particles above TLCST. By synchronizing the laser pulses with
CPP 2 Polymer Surfaces II
the cantilever oscillation and by varying the relative time delay one can
obtain information on the dynamics of the phase transition.
CPP 1.3 Mo 10:15 H 37
Influence of the chain microstructure in the surface properties
of polyketone terpolymers — •Sabine Hild 1 , Othmar Marti 1 ,
Frank Hollmann 2 , David Perez Foullerat 2 , and Bernhard
Rieger 2 — 1 Experimental Physics, University of Ulm, Albert-Einstein-
Allee 11, 89081 Ulm — 2 Inorganic Chemistry II, University of Ulm,
Albert-Einstein-Allee 11, 89081 Ulm
Terpolymers of carbonmonoxide (CO), ethene and propene combine
unique physical properties with intrinsic hydrophilic properties. Tailoring
the chain microstructure of such polyketones lead to polymeric materials
with adjustable mechanical properties. The aim of this study is
to investigated if also surface properties, resp. the surface energy, can be
influenced by varying the block structure of the copolymers. For this purpose
ethylene-CO-propylene-CO-(ECO-PCO) and ethylene-CO-hexene-
CO-(ECO-HCO) terpolymers with similar amount of ECO but different
block length have been synthesized. This results in copolymers featuring
either a triblock or multiblock structure. The surface morphology of this
terpolymers is investigated by Scanning Force Microscopy. The surface
tension has been estimated by from surface tension measurement. It has
been found, that if the ECO content is higher than 50 percent the surface
properties are determined by the microstructure of the ECO phase.
CPP 1.4 Mo 10:30 H 37
AFM-studies of layered Au/hexaphenyl nanofiber systems —
•Laxman Kankate 1 , Frank Balzer 1 , Horst Niehus 1 , and Horst-
Günter Rubahn 2 — 1 Humboldt-Universität zu Berlin, Institut für
Physik / ASP — 2 SDU Odense, Fysisk Institut, Denmark
In this paper we study in detail the growth of parahexaphenyl
nanofibers on ultrathin Au layers on mica. We use fluorescence microscopy
and atomic force microscopy to obtain the size distribution and
the alignment of the nanofibers. As a function of the thickness of the
Au layer in the range between 1 and 5 nm it is observed that the alignment
of the fibers decreases, whereas for thicker Au films no alignment
at all with the mica electric surface dipoles has been found. The mean
length of the fibers decreases from several ten µm to 1 µm, but their
mean height increases from 50 nm to 300 nm. Such sandwich systems of
organic and metallic constituents are important model systems for future
nanoelectronic applications.
Zeit: Montag 11:00–12:30 Raum: H 37
CPP 2.1 Mo 11:00 H 37
Scanning thermal microscopy for investigation of mechanical
properties of thin polymer films — •Martin Hinz 1 , Andreas
Kleiner 1 , Sabine Hild 1 , Othmar Marti 1 , Urs Dürig 2 , Bernd
Gotsmann 2 , Ute Drechsler 2 , Peter Vettiger 2 , and Tom R. Albrecht
2 for the IBM Research Division, Zurich Research Laboratory,
Switzerland collaboration — 1 Department of Experimental Physics, University
of Ulm, D-89069 Ulm — 2 IBM Research Division, Zurich Research
Laboratory, CH-8803 Rüschklikon
Mechanical properties of bulk polymers have been investigated by different
methods over decades, but in recent times the mechanics of thin
polymer films became of large interest. Scanning Force Microscopy (SFM)
provides a possibility to probe mechanical properties on nanometer scale.
In this study Scanning thermal microscopy (SThM) is applied to investigate
the temperature dependent indentation process of a pulse heated
SFM-tip (heating pulse less than 100 Mikroseconds) with tip temperatures
between 300 and 500 ◦ C on Polymethylmethacrylate films of 35
nm thickness which were produced by spin-coating on Silicon substrates.
Additional application of an electro-static force acting between tip and
sample enhances the indentation process. Additionally these experiments
are carried out on samples heated on a heating device. The remanent topography
is analysed as function of tip and sample temperature, heating
pulse duration and electrostatic force.
CPP 2.2 Mo 11:15 H 37
Homo- and heteropolymer adsorption onto homogeneous
and chemically structured surfaces: the role of correlations
— •Alexey Polotsky, Andreas Degenhard, and Friederike
Schmid — Universität Bielefeld, Fakultät für Physik, Universitätsstraße
25, 33615 Bielefeld
Using a variational approach, an analytical theory of adsorption was

Chemische Physik und Polymerphysik Montag
developed for the following systems: (1) random heteropolymers with exponentially
decaying and/or oscillating sequence correlations near planar
homogeneous surfaces; (2) homogeneous polymers near planar heterogeneous
surfaces; (3) random heterogeneous polymers near planar heterogeneous
surfaces. In all three cases simple equations for the adsorptiondesorption
transition line were obtained. Some of these results as well as
the validity of the applied variational technique were tested by a comparison
with numerical lattice calculations.
CPP 2.3 Mo 11:30 H 37
Imaging SAMs based on µ-CP in Terms of Dynamic Friction,
Adhesion and Stiffness Using the Digital Pulsed Force
Mode Technology — •Alexander Gigler 1 , Peter Spizig 2 ,
Stefan Walheim 3 , Othmar Marti 1 , and Thomas Schimmel 3 —
1 Experimental Physics, University of Ulm, D-89069 Ulm, Germany
— 2 WITec GmbH, www.WITec.de — 3 Institute for Nanotechnology,
Forschungszentrum-Karlsruhe GmbH, D-76021 Karlsruhe, Germany
AFM allows to measure local mechanical properties at the nanoscale.
Besides looking exclusively at the surface topography, one can also determine
e.g. stiffness and adhesion. The tool of choice is the force vs. distance
plot (FD-plot), but acquisition of FD-plots performed concurrently with
topographical imaging slows down the scanning speed by more than two
orders of magnitude. The Digital-Pulsed-Force-Mode was introduced to
acquire each force curve for every pixel of an image, but maintaining the
scanning speed. The complete data then allows to determine material
parameters from postprocessing the force curves without scanning the
sample more often.
To access dynamic friction parameters and the properties accessible
by PFM at the same time, the setup was extended to the COmbined-
DYnamical-Mode. The concurrent measurement of both friction and adhesion
is important, since both seem to be closely related.
This contribution reports on the implementation of the CODY Mode
method on a WITec α-SNOM setup and on tests with a SAM of octadecyltrichlorosilane
(OTS), which was deposited on a Si surface in a
laterally controlled manner by a lift-off technique, based on µ-CP [4].
CPP 2.4 Mo 11:45 H 37
Nanotomographie polymerer Materialien — •Nicolaus Rehse,
Sabine Marr, Sabine Scherdel, Larisa Tsarkova, Markus
Hund und Rober Magerle — Physikalische Chemie II, Universität
Bayreuth, D-95440 Bayreuth
Polymere Materialien haben auf der Nano- und Mikrometerskala oft
eine komplexe Struktur, die sich mit den meisten verfügbaren Mikroskopietechniken
nur zweidimensional abbilden läßt. Dies behindert viele
Untersuchungen und erschwert das detaillierte Verständnis von Struktur-
Eigenschafts-Beziehungen.
Die Nanotomographie [1] ist eine neue Methode zur hochauflösenden
Volumenabbildung, die einer Ausgrabung auf der Nanometer-Skala entspricht.
Von der zu untersuchenden Probe werden schrittweise wenige
Nanometer dicke Schichten abgetragen (z.B. durch Plasma- oder naßchemisches
Ätzen) und nach jedem Abtragschritt wird die freigelegte
Probenoberfläche mittels Rasterkraftmikroskopie abgebildet. Auf diese
Weise erhält man eine Reihe von Bildern mit nur wenigen Nanometern
Abstand, aus der die räumliche Struktur der Probe rekonstruiert wird.
Wir zeigen unsere aktuellen Ergebnisse zur Nanotomographie teilkristalliner
Polymere und der Mikrodomänenstruktur dünner Blockcopolymerfilme.
Dabei ist ein neuer Schwerpunkt die quantitative Charakteri-
CPP 3 Magnetic Resonance
sierung komplexer räumlicher Strukturen mit modernen Verfahren der
Bildverarbeitung, um Nanotomographiebilder quantitativ mit entsprechenden
Modellrechnungen zu vergleichen.
[1] R. Magerle, Phys. Rev. Lett. 85, 2749 (2000); European Patent EP
1144989; U.S. Patent 6,546,788.
CPP 2.5 Mo 12:00 H 37
Near-field infrared microscopy & nanospectroscopy of polymers
— •Thomas Taubner and Fritz Keilmann — Max-Planck-Institut
für Biochemie, Am Klopferspitz 18a, 82152 Martinsried
Nanoscale composites such as self-organizing block copolymers are an
elegant way of structuring templates for widely different applications.
Material discrimination of nanoscale compostites can be a difficult task,
because conventional optical and infrared microscopes are limited in resolution
and other methods such as electron microscopy or AFM either
lack contrast or are ambiguous. A new approach of near-field microscopy
is capable of high spatial resolution and chemical sensitivity[1] given by
an infrared spectrum.
We improved this scattering-type near-field infrared microscope (s-
SNIM) to determine for the first time the near-field infrared spectrum of
a 60-nm thin polymer film by tuning a CO-laser through a strong absorption
band of PMMA around 5.8 µm wavelength. The obtained near-field
spectrum is characteristically different from the usual lorentzian shape
of far-field absorption, but rather similar to a reflectivity spectrum. By
imaging at chosen wavelengths to maximize contrast we identify PMMA
in a 70 nm thin film of a nanoscale polymer blend. The smallest aggregates
of 70 nm diameter are easily resolved, promising a resolution of less
than 20 nm [2].
References: [1] B. Knoll and F. Keilmann, Nature 399, 134 (1999) [2]
T. Taubner, R. Hillenbrand and F. Keilmann, Journal of Microscopy 210,
311 (2003)
CPP 2.6 Mo 12:15 H 37
The mechanic of interphases in adhesive bonds as observed
by Brillouin microscopy — •Ulrich Mueller 1,2 , Jan Kristian
Krueger 1,2 , Ravindrakumar Bactavachalou 1,2 , Roland Sanctuary
1,3 , Wulff Possart 1,4 , and Wolfgang Manglkammer 1,2 —
1 Laboratoire Europeen de Recherche Universitaire Saarland-Lorraine
(LERUSL) — 2 Universititaet des Saarlandes, Geb. 38, D-66123
Saarbruecken — 3 Centre Universitaire de Luxembourg, 162a av. de la
Faiencerie, L-1511 Luxembourg — 4 Universtitaet des Saarlandes, Geb.
22, D-66123 Saarbruecken
Today, it is increasingly common to use organic adhesives for the realization
of mechanical joints between all kind of materials. For the understanding
of the mechanical properties of such compounds it is of great
interest to know the spatial variations of the elastic properties inside the
adhesive bond. From other examples in polymer physics it is well known
that elastic properties of polymers could become field quantities because
of molecular texture e.g. induced by injection moulding, extrusion or
transcrystallization on a solid surface. Our goal was to investigate the
elastic properties within interphases between an adhesive and substrates
(e.g. metals, silicon, etc.) using high spatial resolution as provided by the
recently developed Brillouin microscopy. It turns out that the interphases
as seen by their elastic properties strongly depend on the bond material,
the substrates and preparation conditions. Additionally we found an astonishing
width of the interphases with a magnitude of several hundred
micrometers.
Zeit: Montag 10:00–11:15 Raum: H 38
CPP 3.1 Mo 10:00 H 38
2 H-NMR-Studien zur Defektdynamik im Wirtsgitter von
Clathrat-Hydraten — •Franz Fujara 1 , Thomas M. Kirschgen
2 , Manfred D. Zeidler 2 und Burkhard Geil 1 — 1 Institut für
Festkörperphysik, TU Darmstadt, Hochschulstrasse 6, 64289 Darmstadt
— 2 Institut für Physikalische Chemie, RWTH Aachen, Templergraben
59, 52056 Aachen
2 H-NMR erlaubt das Studium der Wasser-Reorientierungsdynamik in
Eis- und eisähnlichen Phasen auf Zeitskalen oberhalb von 10 −6 s. In solchen
kristallinen Phasen ist ein translativer Protonentransport direkt
an die Rotationsdynamik gekoppelt. Wir nutzen diese Kopplung, um
im eisähnlichen Wirtsgitter von Clathrat-Hydraten die Migration von
Punktdefekten (Bjerrum- und ionische Defekte) zu studieren. Eine parameterfreie
Auswertung liefert detaillierte Informationen über Geometrie,
Zeitskala und Temperaturabhängigkeit des Elementarschrittes der Protonenwanderung.
CPP 3.2 Mo 10:15 H 38
Der Einfluß von Diffusionsprozessen auf die longitudinale
Magnetisierung in schichtselektiven NMR-Experimenten —
•Nikolaus Nestle 1 , Bernadeta Walaszek 2 und Markus Nolte 1
— 1 Institut für Festkörperphysik, TU Darmstadt, Hochschulstraße 6,
D-64289 Darmstadt — 2 Institute of physics, Jagiellonian University of
Krakow, Polen

Chemische Physik und Polymerphysik Montag
Während die Veränderung transversaler Kernspinmagnetisierungen
durch Diffusionsvorgänge in Gegenwart magnetischer Feldgradienten seit
langem bekannt ist und als eines der genauesten Verfahren zur meßtechnischen
Erfassung von Diffusionsphänomenen genutzt wird, wird
der Einfluß von Magnetfeldgradienten auf longitudinale Magnetisierungen
üblicherweise vernachlässigt. Das Zusammenwirken zwischen Diffusion
und longitudinaler Magnetisierung in schichtselektiven NMR-
Experimenten wurde von uns systematisch untersucht und eine theoretische
Beschreibung für verschiedene Anregungsprofile erarbeitet. Unter
bestimmten Voraussetzungen werden effektive longitudinale Relaxationszeiten
beobachtet, die durch die Diffusion bestimmt sind. Konsequenzen
für NMR-Mikroskopie-Experimente und Pespektiven der mechanisch detektierten
NMR werden diskutiert.
CPP 3.3 Mo 10:30 H 38
Study of Spin Dependent Recombination Mechanisms in Conjugated
Polymers and Oligomers — •Michael Pientka 1 , Eugene
Frankevich 2 , Jürgen Parisi 1 , and Vladimir Dyakonov 1 —
1 Institute of Physics, University of Oldenburg, 26111 Oldenburg, Germany
— 2 Institute for Energy Problems of Chemical Physics, 117828
Moscow, Russia
Recombination mechanisms of photo- and electrically generated excitations
in conjugated polymers is a matter of intense discussions as they
are directly related to the quantum yield of the light emission. By utilising
the spin sensitive techniques, such as optically detected magnetic
resonance, we analyse the contribution of molecular triplet excitons as
well as of Coulomb bound polaron pairs to recombination of singlet excitons
in conjugated oligomers and polymers. Both, the triplet-triplet
annihilation as well as the suppressed quenching of singlet excited states
by triplet excitons and polaron pairs, can in principle lead to an enhancement
of the photo- and electroluminescence, provided these processes are
spin dependent. By varying the excitation intensity and the modulation
frequency we were able to distinguish between these two mechanisms.
Independent evidences for the triplet-triplet annihilation were obtained
by the frequency modulation technique with recording the fluorescence
intensity on the second harmonic.
CPP 3.4 Mo 10:45 H 38
Radio frequency ESR imaging — •Marco Ulrich and Elmar
Dormann — Physikalisches Institut Universit¨t Karlsruhe (TH), D-
76128 Karlsruhe
CPP 4 Dynamics of Molecular Systems
During the last years the Magnetic Resonance Imaging (MRI) became
to one of the most important imaging methods especially in medical
techniques. Although this technology is mostly based on protons (NMR-
Imaging), it is in principle also possible to use ESR signals for producing
images. In this case the radical cation salt (Fluoranthene) 2PF 6
as an organic quasi-1d conductor has ideal properties for this so called
ESR-Imaging. Two different methods of 2D-ESR imaging of these
(Fluoranthene) 2PF 6 crystals could be realized. The Projection Reconstruction
(PR) is operating with two variable but static gradients which
are orthogonal to each other. On the other hand the Fourier Imaging (FI)
is using one static and one pulsed gradient to achieve the necessary spatial
encoding of the ESR signals which is the root of the whole imaging
process. Finally a tomographical software is reconstructing the images.
In both cases the big advantage of using pulsed ESR technology instead
of CW ESR is that it is also possible to get further information about
dynamical parameters like the transversal relaxation time T 2 or spin
diffusion constants of the analyzed material. The variation of the ESR
images with the temperature around the Peierls transition could also be
shown.
CPP 3.5 Mo 11:00 H 38
Spatially resolved and integral measurements of the electron
spin diffusion properties of an organic quasi-1d conductor —
•Malte Drescher, David Saez de Jauregui, and Elmar Dormann
— Physikalisches Institut, Universit¨t Karlsruhe (TH), D-76128
Karlsruhe
The radical cation salt (Fluoranthen)2PF6 is an organic quasi-1d conductor
showing a Peierls transition at TP = 186K. X-band-pulse-ESR
measurements were performed both below and above the semiconductormetall
phase transition. Using the static field gradient spin echo method
the electron spin diffusion was analyzed.
Special attention was payed to the electron spin diffusion coefficient
perpendicular to the molecular stacking axes a, because in this direction
diffusion seems mainly caused by a conducting electron hopping process.
The electron spin diffusion is affected by the density of defects which
can be influenced by irradiating the crystals with high-energetic protons
(EP = 25MeV). In order to unravel these effects a (Fluoranthen)2PF6
crystal was irradiated homogeneously as well as through a periodic grid
to result in a stripy pattern. We show a temperature dependent spatially
resolved ESR-analysis of this ”zebra-like” sample.
Zeit: Montag 11:15–12:30 Raum: H 38
CPP 4.1 Mo 11:15 H 38
Suche nach Vorläuferprozessen eines Glasübergangs von amorphem
Eis — •Franz Fujara 1 , Burkhard Geil 1 , Michael Marek
Koza 2 , Helmut Schober 2 und Francesca Natali 2 — 1 Institut für
Festkörperphysik, TU Darmstadt, Hochschulstrasse 6, 64289 Darmstadt
— 2 Institut Laue-Langevin, F-38042 Grenoble Cedex
Zur Zeit gibt es eine stark kontroverse Diskussion über die Natur des
niedrigdichten amorphen Eises (LDA). Handelt es sich dabei um das
(eingefrorene) Glas von unterkühltem Wasser oder um einen neuen Zustand,
der mit flüssigem Wasser thermodynamisch nicht verbunden ist?
Wir gehen diese Frage mit der Suche nach dynamischen Anomalien in
der Umgebung der hypothetischen Glastemperatur mittels Neutronenstreumessungen
(IN13 elastic scans) an. Unsere Messungen zeigen, daß
es unterhalb der Rekristallisationstemperatur keine Anzeichen einer solchen
Anomalie gibt.
CPP 4.2 Mo 11:30 H 38
Bewegungsmechanismen und Längenskalen in verschlauften
Polymerschmelzen — •Ekkehard Straube — Martin-Luther-
Universität Halle-Wittenberg, Fachbereich Physik, 06099 Halle
Mittels einer gitterfreien Monte-Carlo-Simulation werden Systeme von
Kugel-Feder-Ketten mit bis zu 512 Segmenten untersucht. Ausgehend
von einer äquilibriserten Schmelze wird die Dynamik von 16 Kopien eines
Systems betrachtet, die durch unterschiedliche Folgen von Zufallszahlen
realisiert werden. Auf diese Weise wird der Teil des Konfigurationsraums
einer Kette besucht, der mit den Einschänkungen verträglich
ist, die durch die Kettenverschlaufungen gegeben sind. Zur Analyse der
Bewegungsmechanismen werden aus den Segmentkoordinaten der 16 Ko-
pien jeweils Verschiebungs- bzw. Fluktuationstensoren gebildet und deren
Ausdehnung und Orientierung durch eine Hauptachsenanalyse bestimmt.
Diese Analyse zeigt die Anisotropie der Segmentbewegung in verschlauften
Systemen und ergibt aus der Bestimmung der Richtungskorrelationen
ein Maß für die Schrittweite des primitiven Weges. Die
Ergebnisse bevorzugen das ”binary contact model” für die relevanten
Längenskalen in verschlauften Systemen.
CPP 4.3 Mo 11:45 H 38
Free volume in polymeric membranes: comparison of positron
annihilation lifetime spectroscopy and evaluation of MD
simulations — •Jan Kruse 1 , Jörn Kanzow 1 , Klaus Rätzke 1 ,
Franz Faupel 1 , Matthias Heuchel 2 , and Dieter Hofmann 2 —
1 University of Kiel, Kaiserstr.2, 24143 Kiel — 2 GKSS-Research Center,
Kantstr. 55, 14513 Teltow
Gas separation by membranes is important for many technical applications.
The amount and distribution of free volumes in polymeric membranes
significantly determines the transport and separation properties.
In the present work these free volume characteristics were determined
directly from MD simulations via a new method [1,2]. Here a ”tracer
atom” probes the simulation cell to determine the unoccupied volume.
On the other hand the positron annihilation lifetime spectroscopy was
used to determine the average size of free volume cavities via a well established
correlation between lifetime and size. Characteristic results for
polyimides will be presented, comparison of both methods will be made,
and limitations of the standard model for the evolution of the positron
lifetime data will be discussed.
[1] E. Schmidtke, K. Günther-Schade, D. Hofmann, F. Faupel, J.
Mol. Graphics and Modelling, accepted. [2] C. Nagel, E. Schmidtke,

Chemische Physik und Polymerphysik Montag
K. Günther-Schade, D. Hofmann, D. Fritsch, T. Strunskus, F. Faupel,
Macromolecules, 33, 2242 (2000).
CPP 4.4 Mo 12:00 H 38
Local Modes in liquid Deuterium Fluoride — •Demmel Franz 1 ,
Gerhard Heusel 2 , Isabella Waldner 2 , Markus Kreitmeir 2 ,
and Helmut Bertagnolli 2 — 1 ILL, 38042 Grenoble, France —
2 Universitaet Stuttgart, Physikalische Chemie, Stuttgart
Hydrogen bonded liquids are certainly one of the most complex, but
also one of the most important liquids. Structure and dynamics is strongly
determined by the hydrogen bonds. Water, the most prominent model
system, shows a 3D network of bonds and has been studied for a long
time. In contrast to water liquid hydrogen fluoride is connected in onedimensional
hydrogen bonded chains. A MD simulation of liquid HF has
predicted an acoustic-like mode and a further optic-like mode in the spectra
of the longitudinal current correlation functions [1]. For the interpretation
of the optic mode a collective movement of HF molecules against
themselves was suggested. We performed an inelastic neutron scattering
experiment at the ILL, Grenoble, on liquid deuterium fluoride at two
temperatures. The corrected spectra show evidences for an optic mode
in a certain region of momentum transfer vectors as predicted by the
MD simulation. These indications weaken or even vanish at the higher
temperature near the triple point.
[1] D. Bertolini, G. Sutmann, A. Tani, R. Vallauri, PRL 81, (1998)
2080
CPP 5 Computational Physics
CPP 4.5 Mo 12:15 H 38
Lösung von Reaktions-Diffusionsgleichungen mit Hilfe der finiten
Elemente Methode — •Thomas Pletl, Michael Schulz und
Peter Reineker — Abteilung Theoretische Physik, Universität Ulm,
Albert-Einstein-Allee 11, D-89069 Ulm
Chemische Reaktionen im Festkörper oder Glas werden häufig mittels
eines Satzes von gekoppelten Reaktions-Diffusionsgleichungen beschrieben.
Ein Beispiel hierfür sind Gläser, die zunächst mit Ag + angereichert
werden, welche dann mittels H2 zu atomaren Silber reduziert werden. Die
Ag-Atome neigen sofort zur Clusterbildung und lagern sich in dünnen
Bändern innerhalb des Glases ab (sog. Liesegang-Strukturen). Damit
erhält man wohldefinierte Profile für den Brechungsindex dieser Gläser,
welche daher auch Anwendungen in der optischen Industrie finden.
Um Parametervariationen bei der Produktion solcher Gläser zu vermeiden,
müssen theoretische Modelle entwickelt werden. Bei der Lösung der
diesen Modellen zugrunde liegenden Reaktions-Diffusionsgleichungen zusammen
mit der Fokker-Planck-Gleichung, welche den Wachstumsprozeß
der Silbercluster beschreibt, kommt ein neu entwickeltes finite Elemente
(FE) Programm zum Einsatz. Erste Ergebnisse für die Konzentrationen
der beteiligten Atome und Ionen werden vorgestellt. Unser Programm
läßt sich auf beliebige Transport-Diffusions-Reaktions-Systeme erweitern,
die aufgrund der oft sehr speziellen gekoppelten Gleichungen mit handelsüblichen
FE-Programmen nicht berechenbar sind.
Zeit: Montag 10:00–11:15 Raum: H 39
CPP 5.1 Mo 10:00 H 39
Numerical Studies of Tethered Chains at Adsorbing Surfaces —
•Radu Descas 1 , Jens-Uwe Sommer 2 , and Alexander Blumen 1 —
1 Theoretische Polymerphysik, Univesität Freiburg — 2 Institut de Chemie
des Surfaces et Interfaces, Mulhouse Cedex
We present extensive Monte Carlo simulations of tethered chains on
adsorbing surfaces, considering the dilute case in good solvents, and analyze
our results using scaling arguments. We focus on the mean number
of chain contacts with the adsorbing wall, on the chain extension (the
radius of gyration) perpendicular and parallel to the adsorbing surface,
on the probability distribution of the free end and on the density profile
for all monomers. For the cross-over from non-adsorbed to adsorbed
behavior we obtain best results using a cross-over exponent of 0.59. We
also investigate the dynamical scaling behavior at the critical point of
adsorption, considering the end-to-end correlation function and the correlation
function of adsorbed monomers at the wall. We find that the
dynamic scaling exponent a (which describes the relaxation time of the
chain as a function of its length) is the same at the adsorption threshold
as that of free chains. Moreover, we find that tethered chains relax
quicker perpendicularly to the wall than parallel to it.
CPP 5.2 Mo 10:15 H 39
Viscoelastic Relaxation of Copolymeric Structures — •Cristian
Satmarel 1 , Alexander Blumen 1 , Andrei Gurtovenko 2 , and
Christian von Ferber 1 — 1 Theoretische Polymerphysik, Universitaet
Freiburg, Herman-Herder Str. 3, D-79104, Freiburg, Germany —
2 Institute of Macromolecular Compounds, Russian Academy of Sciences,
Bolshoi Prospect 31, V.O., St. Petersbug, 199004, Russia
We study theoretically the viscoelastic relaxation of copolymeric structures
(alternating copolymers chain, cross-linked alternating copolymers
chain and tree-like structures) in the framework of generalized Gaussian
structures, which are extensions of the Rouse model to arbitrary geometries.
The heterogeneity of these systems is attained by considering beads
which differ from each other due to different friction coefficients with
the solvent. For all the structures we were able to examine the complex
(shear) modulus using its real and imaginary components. These show
a multitude of features, which depend mainly on the difference in the
mobilities of the beads. In addition, for tree-like structures of arbitrary
functionality and number of generations, and with alternating arrangements
of the monomers, we developed an analytical method to determine
the eigenfrequencies.
CPP 5.3 Mo 10:30 H 39
Statistical Properties of Off-Lattice Heteropolymers —
•Michael Bachmann, Wolfhard Janke, and Handan Arkin —
Institut für Theoretische Physik, Universität Leipzig, Augustusplatz
10/11, 04109 Leipzig, Germany
We apply a multicanonical algorithm to variants of the AB model [1,2]
being an off-lattice model for heteropolymers. Heteropolymers are considered
as chains of hydrophobic (A) and hydrophilic (B) monomers only.
Into the energy function enter the bending energy and a Lennard-Joneslike
potential between nonbonded monomers, where short-range repulsion
and long-range attraction compete. Contacts between hydrophobic
monomers are favoured, thereby assuming that the global energy minimum
state of proteins is characterized by a compact hydrophobic core
screened from the solvent by a shell of hydrophilic residues. We calculate
thermodynamic quantities for known sequences by means of a modified
AB model [2] and identify the temperatures, where conformational
pseudo transitions are expected. Since the multicanonical algorithm allows
for an accurate sampling of the low-temperature region, we also
obtain good estimates for the global energy minimum. Therefore we apply
our algorithm to sequences where minimum energies are quoted [3]
and compare with lowest-energy states found by minimizing procedures.
[1] F. H. Stillinger, T. Head-Gordon, and C. L. Hirshfeld, Phys. Rev. E
48, 1469 (1993).
[2] A. Irbäck, C. Peterson, F. Potthast, and O. Sommelius, J. Chem.
Phys. 107, 273 (1997).
[3] H.-P. Hsu, V. Mehra, and P. Grassberger, e-print: cond-mat/0302545.
CPP 5.4 Mo 10:45 H 39
Collapse of Long Lattice Polymers — •Thomas Vogel, Michael
Bachmann, and Wolfhard Janke — Institut für Theoretische
Physik, Universität Leipzig, Augustusplatz 10/11, 04109 Leipzig,
Germany
Using the nPERM algorithm[1], we have investigated long polymer
chains on the simple cubic lattice in three and four dimensions. At the
so-called θ-point, there is a second-order phase transition from a globular
state to a coil-like state predicted from mean-field theory. Surprisingly, for
finite chains, in four dimensions this transition looks first-order-like[2].
We investigate this pseudo-first-order transition by means of thermodynamic
quantities such as the end-to-end distance and the radius of
gyration.
We will also report some details about the behaviour of the PERM algorithm
we found by analysing energy distributions near the critical temperature
and how to avoid strong correlations between growing chains.
[1] P. Grassberger, Phys. Rev. E 56 (1997) 3682; H.-P. Hsu, V. Mehra,

Chemische Physik und Polymerphysik Montag
W. Nadler, P. Grassberger, J. Chem. Phys. 118 (2002) 444.
[2] T. Prellberg, A.L. Owczarek, Phys. Rev. E 62 (2000) 3780.
CPP 5.5 Mo 11:00 H 39
Time-depedent density functional theory applied in molecules,
liquids and solids — •Ari P Seitsonen and Jürg Hutter — Universität
Zürich
Time-dependent density functional theory (TDDFT) is a versatile
method which can be applied also to the determination of excitation
CPP 6 Self-organising Systems
energies in materials similarly as the density functional theory (DFT)
in the ground state. We apply the new implementation [J. Hutter, JCP
(2003)] of the method in the CPMD code. This enables us to calculate
the excitation energies and properties such as forces on the ions in the excited
state, employing the plane wave basis set/pseudo potential method.
We report applications in molecules, liquids and solids, and we discuss
both the advantages and the shortcomings of the method. As examples
we mention small molecules, solvation of tetrazine and acetone in water
and defects in diamond.
Zeit: Montag 11:30–12:15 Raum: H 39
CPP 6.1 Mo 11:30 H 39
Combinatorial mapping of PS-b-P2VP-b-PtBMA triblock
copolymers in thin films — •S. Ludwigs 1 , K. Schmidt 1 , R.
Magerle 1 , G. Krausch 1 , C. Stafford 2 , M. Fasolka 2 , A. Karim 2 ,
E. Amis 2 , A. Zvelindovsky 3 , and A. Sevink 3 — 1 Physikalische
Chemie II, Universität Bayreuth, Bayreuth, Germany — 2 NIST
Combinatorial Methods Group, Gaithersburg, USA — 3 Leiden Institute
of Chemistry, Leiden, Netherlands
Using sequential living anionic polymerization we synthesized a series
of monodisperse PS-b-P2VP-b-PtBMA triblock copolymers (SVT)with
increasing molecular weight of the poly(tert butyl methacrylate) block 1 .
In the present contribution we show experimental results on the thin
film behavior of SVT with volume fractions φPS : φP2V P : φPtBMA =
1 : 1.2 : x (with x ranging from 3.05 to 4). Gradients in film thickness
were prepared via thin film flow coating of dilute solutions in chloroform.
On controlled annealing in a non-selective solvent the films form
terraces of well-defined thickness exhibiting a highly ordered perforated
lamellar structure. With an additional gradient in substrate surface energy
orthogonal to the gradually increasing film thickness we find that
the perforated lamellar phase is formed irrespective of the chemical nature
of the substrate which makes the structure useful for applications in
nanotechnology 2 . We support our experimental results with simulations
based on the dynamic density functional theory: with increasing size of
the simulation box we find a similar sequence of structures as in the experiments.
1 S. Ludwigs et al., Polymer 44, 6815 (2003). 2 S. Ludwigs et
al., Nature Materials 2, 744 (2003).
CPP 6.2 Mo 11:45 H 39
AFM CHARACTERIZATION OF SUPPORTED PHOSPHO-
LIPID LAYERS FORMED BY SOLUTION SPREADING —
•T. Spangenberg 1 , N.F. de Mello 2 , T.B. Creczynski-Pasa 3 ,
A.A. Pasa 4 , and H. Niehus 1 — 1 Humboldt-Universität zu Berlin, Institut
für Physik, Newtonstr. 15, 12489 Berlin — 2 Pós-graduação em
Química, Universidade Federal de Santa Catarina, Florianópolis, Brazil
— 3 Departamento de Ciências Farmacêuticas, Universidade Federal de
Santa Catarina, Florianópolis, Brazil — 4 Departamento de Física, Universidade
Federal de Santa Catarina, Florianópolis, Brazil
CPP 7 Physics of Polymers I
The morphology and the stability of supported phospholipid (DPPC,
DOPC) layers prepared by solution spreading on mica were investigated
by atomic force microscopy. The samples were analyzed after the solvent
evaporation, the hydration step and after immersion in a buffer solution.
The phospholipid layers prepared by solution spreading method were successfully
characterized by ex-situ and in-situ AFM measurements. This
sequence of measurements allows us to follow the surface rearrangement
of the lipidic material, from non-uniform deposits, through multilayer
structures, to a final pattern with large bilipidic terraces. The most significant
result was the imaging of the prepared phospholipid layers in-situ
after the immersion in the liquid cell. The systems investigated exhibited
a stable surface configuration during the measurements, which is suitable
for studying time dependent biological and physical phenomena.
CPP 6.3 Mo 12:00 H 39
Chemically driven running drops — •Uwe Thiele, Karin John,
and Markus Bär — Max-Planck Institut für Physik komplexer Systeme,
Nöthnitzer Str.38, 01138 Dresden
A continuous dynamic model for the movement of a drop on a solid
substrate is derived for (1) driving by an externally given gradient using
a wettability gradient as an example and (2) driving by a self-produced
wettability gradient. The latter case of self-propelled drops on reactive
substrates corresponds to such experimentally found free-running
droplets (Dos Santos, D. F. and Ondarcuhu, T., PRL 75, 2972 (1995)).
The moving-droplet solutions of the model are investigated in detail.
Zeit: Montag 14:00–15:30 Raum: H 37
CPP 7.1 Mo 14:00 H 37
Scaling properties of critical polymer blends and polymer solutions
near the glass transition — •Werner Köhler, Wolfgang
Enge, and Jürgen Rauch — Physikalisches Institut, Universität
Bayreuth, 95440 Bayreuth
Critical polymer blends show Ising-like critical scaling close to Tc and
mean-field behavior for larger ǫ = (T − Tc)/Tc. Because of the thermal
activation of the Onsager coefficient, however, the critical exponent γ cannot
be directly observed in the temperature dependence of the diffusion
coefficient D within the mean-field regime. Similarly, the diffusion coefficient
of semidilute and concentrated polymer solutions typically only approaches
the concentration scaling law but then rapidly decreases because
of the increasing glass temperature of the solution. Contrary to D, the
Soret coefficient ST is neither sensitive to thermal activation of the Onsager
coefficient nor to the increase of local friction at the glass transition
and shows clean scaling in both cases. Experiments have been performed
on semidilute and concentrated solutions of polystyrene in toluene and
on critical poly(dimethylsiloxane)/poly(ethyl-methylsiloxane) mixtures.
CPP 7.2 Mo 14:15 H 37
Surface glass transition of monodisperse polystyrenes and
their bimodal mixtures investigated by the embedding of
noble metal nanoclusters and the XPS-charging effect —
•Jörn Erichsen, Tesfaye Shiferaw, Jörn Kanzow, Ulrich
Schürmann, Vladimir Zaporojtchenko, and Franz Faupel —
Lehrstuhl für Materialverbunde, Faculty of Engineering,
The temperature dependent embedding process of noble metal nanoclusters
into polymers was used to probe the surface glass transition.
X-ray photoelectron spectroscopy (XPS) was applied to study the embedding
of Au nanoclusters into polystyrene [1]. Previously a small decrease
of glass transition temperature (Tg) at the surface compared to the bulk,
which decreases at low Mw, was detected with this method [1]. The Tg of
thin PS films was additionally determined by the charging and discharg-

Chemische Physik und Polymerphysik Montag
ing during XPS measurements. Transmission electron microscopy (TEM)
investigations yield the same cluster sizes and densities for a height and
a low molecular weight. Therefore, probe size effects can be excluded. In
order to understand the Tg depression in monodisperse polystyrenes we
present measurements on bimodal mixtures of monodisperse polystyrenes
(Mw = 3.5 and 1000 kg/mol). The results on the bimodal mixtures rule
out the interpretation that the Tg depression at the surface is due to an
enrichment of shorter chains.
[1] V. Zaporojtchenko, T. Strunskus, J. Erichsen, F. Faupel, Macromolecules,
34(5) (2001) 1125.
CPP 7.3 Mo 14:30 H 37
Structural and dynamic properties and aging mechanisms of
thin epoxy network layers — •Jörn Kanzow 1 , Franz Faupel
1 , Carsten Wehlack 2 , Wulff Possart 2 , Laszlo Liszkay 3 ,
Werner Egger 3 , Peter Sperr 3 , and Gottfried Kögel 3 —
1 Technische Fakultät, Lehrstuhl für Materialverbunde, Universität
Kiel — 2 Arbeitsgruppe Strukturforschung, Polymere, Grenzschichten,
Universität des Saarlandes — 3 Fakultät für Luft- und Raumfahrttechnik,
Universität der Bundeswehr München
Thin layers of the cured epoxy resin system DGEBA-DETA show a
strong variation of the glass transition temperature depending on the
film thickness, which is by far more extensive than expected from a confinement
effect discussed for thermoplastic polymers. Both bulk and surface
properties were studied due to a combination of a new method using
XPS to probe the surface embedding properties of metallic nanoclusters
[1,2] and positron annihilation lifetime spectroscopy (PALS). PALS
is an excellent experimental tool to determine free volume and therefore
structural and dynamic properties as well as aging mechanisms. Its
sensitivity to small concentrations of electron acceptors gives valuable
additional information. Aging mechanisms of cured thin epoxy network
layers were studied by performing a non-destructive depth-profiling using
the positron beam facility at the Universität der Bundeswehr, Munich.
[1] V. Zaporojtchenko, T. Strunskus, J. Erichsen, and F. Faupel,
Macromolecules, 34, 5, 1125 (2001). [2] J. Erichsen, J. Kanzow, U.
Schürmann, K. Dolgner, K. Günther-Schade, T. Strunskus, V. Zaporojtchenko,
and F. Faupel, Macromolecules, acc. 2003.
CPP 7.4 Mo 14:45 H 37
Kristallisation und Alterung des biosynthetischen Polymers
PHB — •Antje Bergmann 1 und Anthony Owen 2 — 1 a — 2 b
Die durch Massenkunststoffe verursachte Umweltproblematik lenkt die
Aufmerksamkeit immer mehr auf moderne abbaubare Materialien.
Das teilkristalline biosynthetische Polymer Poly-(R)-3-
Hydroxybuttersäure (PHB) birgt das Potential in sich, mit Kunststoffen
wie PE oder PP konkurrieren zu können. Nachteil ist die sog.
Alterung, die sich in einer zunehmenden Versprödung mit der Zeit
äußert. Sie wird in Verbindung mit einer progressiven Kristallisation
gebracht. Wir untersuchen diese Prozesse in Langzeitstudien mit
Hilfe struktureller Messmethoden. Dielektrische Messungen ergaben
überraschende Aussagen über die Kettenbeweglichkeit während und
nach der primären Kristallisation, am Synchrotron DESY gemachte
Streuversuche gewährten Einblick in den Kristallisationsablauf durch
CPP 8 Physics of Polymers II
zeitliche Momentaufnahmen und lieferten neue Erkenntnisse über die
Sphärolithstruktur und das Lamellenwachstum der Kristalle: Es ergaben
sich Hinweise auf einen fraktalen Charakter der Sphärolithe.
Die gewonnenen Ergebnisse können außerdem allgemein für teilkristalline
Polymere von Interesse sein.
CPP 7.5 Mo 15:00 H 37
On the Nature of the Chemically Induced Glass Transition
— •Thomas Britz 1 , Jan Kristian Krüger 1 , Ulrich Müller 1 ,
Ravindrakumar Bactavatchalou 1 , and Roland Sanctuary 2 —
1 Universität des Saarlandes, Fachrichtung 7.2 Experimentalphysik, Geb.
38, Postfach 151150, D-66041 Saarbrücken — 2 Centre Universitaire de
Luxembourg, Département des Sciences, Laboratoire 1.19, 162a Avenue
de la Faïencerie, L-1511 Luxembourg
We investigated the curing process in epoxy resins by means of
Brillouin and infrared scattering as well as refractive index measurements.
Longitudinal and transverse acoustic mode Grüneisen parameters
(MGPs) diverge during the freezing process, which indicates, that
the chemical glass transition is accompagnied by an anomaly of acoustic
anharmonicitiy. The MGPs jump from a higher level prior to a lower level
after the freezing process, which suggests, that the chemical glass transition
has phase transition character. During curing, the elastic moduli
c11 and c44 of all epoxy resins obey a generalized Cauchy-relation. This
relation is not affected by the glass transition. Epoxy resins filled with
nanoparticles of SiO2 show the same behavior as well as polyurethane
systems and a row of thermal glass formers.
CPP 7.6 Mo 15:15 H 37
Molecular dynamics of alternating maleimide copolymers
as studied by Broadband Dielectric Spectroscopy — •Julius
Tsuwi 1 , Dietmar Appelhans 2 , and Friedrich Kremer 1 —
1 Institute for Experimental Physics I, University of Leipzig, Linnestrasse
5, 04103, Leipzig, Germany — 2 Institute for Polymer Research Dresden,
Hohestrasse 6, 01069 Dresden, Germany
Dielectric study on the molecular dynamics in a set of poly(alkenealt-N-(perfluoro-)alkylmaleimide)
copolymers is presented. The polymers
are studied by Broadband dielectric spectroscopy in the frequency
range from 0.01Hz to 10MHz at temperatures between 120K and 500K.
The alternating maleimide copolymers possess two different types of
side chains: N-alkyl- or N-[4-N-(perfluoroheptylcarbonyl]aminobutyl]substituted
maleimide ring. Generally, four relaxation regions are observed
for the polymer systems with alkyl side chains. The low temperature
(high frequency) process is tentatively assigned to a local libration
at the end of the alkyl chain, which can well be described by Arrheniustype
temperature dependence. A further process that is faster than the
α-process is assigned to an out-of-plane motion of the succinimide ring.
Finally, a dynamic glass transition process is observed very closely tied
to a slower process that is assigned to fluctuations of the helical superstructure
of the maleimide rings. In contrast, the perfluorinated polymer
systems however show three relaxation regions only. The faster process at
low temperatures is assigned to the librational motion of the fluorinated
end groups while the other two processes are assigned to the α-process
and modes of the helical superstructure.
Zeit: Montag 15:45–17:30 Raum: H 37
CPP 8.1 Mo 15:45 H 37
The effect of spatially inhomogeneous mixing of polymers and
cross-links for end-linked polymer networks — •Michael Lang,
Dietmar Göritz, and Stefan Kreitmeier — Fakultät für Physik,
Universität Regensburg, 93040 Regensburg
We are studying the effects caused by the spatial inhomogeneity of
polymer and cross-links at the beginning of the cross-linking reaction.
For this purpose we use the Bond-Fluctuation-Method to create these
mixtures and to study the dynamics of the crosslinking process. The
structure of the generated networks has been analyzed by knot-theory
and graph-theory. The density and amount of the elastically active material
has been determined. Several structural parameters have been varied
as the dilution of the system or the length of the chains or the probability
of any reaction for several sizes and distributions of the initial domains.
The networks show the formation of micro-gels around the initial domains
of the cross-linking agents and a clear displacement of the gel-
point. The dynamics of the cross-linking reaction is slowed down and is
controlled by the initial size of the domains in almost the same manner
as the maximum extent of reaction. The densitiy of the elastically active
material is clearly affected by the size of the domains and the distance
to the next domain. Diluted systems form more short cycles but result
in a more homogeneous network. The homogeneity is also enhanced by
decreasing probability for reaction or decreasing length of the chains.

Chemische Physik und Polymerphysik Montag
CPP 8.2 Mo 16:00 H 37
Hypersonic relaxation in glass-formers: Thermodynamic theory
and experimental studies using Brillouin spectroscopy — •Jörg
Baller 1,2 , Jan Kristian Krüger 1,2 , Thomas Britz 1,2 , Wulff
Possart 1,3 , Wolfgang Manglkammer 1,2 , and Roland Sanctuary
1,4 — 1 Laboratoire Européen de Recherche Universitaire Saarland-
Lorraine (LERUSL) — 2 Universität des Saarlandes, Fakultät für Physik
und Elektrotechnik 7.2, Geb. 38, D-66041 Saarbrücken, Germany —
3 Universität des Saarlandes, Fakultät für Chemie, Pharmazie und Werkstoffwissenschaften
8.15, Geb. 22, D-66041 Saarbrücken, Germany —
4 Universitaire du Luxembourg, 162a av. de la Faïencerie, L-1511 Luxembourg,
Luxembourg
The presented work gives a theoretical framework for the relaxation
behaviour of the elastic moduli of glass-formers near the glass transition
temperature. Using linear irreversible thermodynamics, an expression for
the temporal evolution of the elastic moduli (measured at hypersonic frequencies)
after a step-like change of temperature is calculated. These theoretical
results are compared to measurements of the hypersonic elastic
modulus by Brillouin Light Scattering (BLS). Three different materials
- an oligomer, an epoxy resin and a classical polymer - have been examined
by measuring the relaxation behaviour of the hypersound velocity
after a temperature pertubation. A discussion of the importance and the
influence of thermodynamic equilibrium during accomplishment of an
relaxation experiment is given by comparison to the theoretical results.
CPP 8.3 Mo 16:15 H 37
Breakup of droplets in PS/PMMA blends after equibiaxial elongation
— •Ulrich A. Handge — Institute of Polymers, Department
of Materials, ETH Zürich, Switzerland
The breakup of liquid droplets in emulsions and molten blends of immiscible
polymers has attracted much attention since many decades. The
intensive research is motivated by the fundamentally oriented interest in
understanding the deformation of drops in definable fields of flow and
the technological relevance of dispersion processes. In this study, we investigated
the breakup of equibiaxially deformed PS droplets in molten
polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends using a
multiaxial elongational rheometer [1]. In equibiaxial deformation, the PS
drop is deformed into a flat circular disc. During subsequent relaxation,
the PS drop can retract to one single drop or breakup into many smaller
drops. The driving force for this phenomenon is the interfacial tension at
the interphase between the PS phase and the PMMA phase. During relaxation,
the interfacial tension attempts to minimize the surface area of
the PS drop. Using light microscopy, we observed the formation of fingers
and holes in the elongated PS drop which finally results in a breakup of
the extended drop into many smaller drops.
[1] P. Hachmann and J. Meissner, Rheometer for equibiaxial and planar
elongations of polymer melts, J. Rheol. 47, 989 (2003).
CPP 8.4 Mo 16:30 H 37
Microtribological Properties of Fluorine-Based Polymers Deposited
by Sol-Gel — •Phani Ayalasomayajula, Guiseppe Breliozzi,
Imad Ahmed, and Henry Haefke — CSEM Swiss Center
for Electronics and Microtechnology, Inc., Rue Jacquet-Droz 1, CH-2007
Neuchatel, Switzerland
The versatility of sol-gel processing makes this technology relevant to a
wide range of industries. Applications include high-performance, protective
coatings against scratch and corrosion, optical fibers and waveguides,
filters and membranes, etc. Compared to other deposition techniques, solgel
has many advantages, such as easy composition control, fabrication
of thin films on large surfaces area, film homogeneity, cost effectiveness
and simple operation cycles. In the present investigation, sol-gel deposition
has been applied to coat three fluorine-based polymer layers with a
maximum thickness of 50 nm onto silicon substrates. Prior to deposition,
the silicon substrates were etched using HF to remove the native oxide
layer. Adhesion, friction and wear were analyzed in the microNewton
load regime using a precision microtribometer and compared with the
properties of the native oxide covered silicon surface. Film composition,
wetting behavior and surface topography were characterized by Rutherford
backscattering spectroscopy, contact angle testing and atomic force
microscopy, respectively. The obtained structural data has been correlated
with the tribological results. It was also found that the degree of
hydrophobicity of the coating results in a decrease of the pull-off force.
Furthermore, an increase in the molecular weight of the polymer results
in a reduction of wear.
CPP 8.5 Mo 16:45 H 37
Strain-dependent localization, microscopic deformations, andmacroscopic
normal tensions in model polymer networks —
•Carsten Svaneborg 1 , Gary S. Grest 2 , and Ralf Everaers 1
— 1 Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzerstr.
38, 01187 Dresden, Germany — 2 Sandia National Laboratories, Albuquerque,
New Mexico 87185, USA
We use Molecular Dynamics simulations to characterize the microscopic
and macroscopic response of a polymer network to an imposed
macroscopic strain. Our motivation is to provide a framework for the
quantitative test and the controlled development of statistical mechanical
theories of rubber elasticity as well as for the validation of critical
steps in the data analysis of experiments addressing these issues. We
present a quantitative test of various tube models of rubber elasticity
and show that recent theory by Mergell and Everaers is quite successful
in rationalizing the observed behavior. By accounting for localization
effects due to chemical crosslinks and entanglements, the theory is able
to describe the length scale dependent microscopic deformations and to
predict the elastic response of the network. We also discuss the interpretation
of neutron scattering data for labelled paths through model polymer
networks.
CPP 8.6 Mo 17:00 H 37
Infrared ellipsometric study of miscibility in thin double layers
of two polymers — •K. Hinrichs 1 , A. Röseler 1 , E.H. Korte 1 ,
N. Nikonenko 2 , J. Pionteck 3 , and K.-J. Eichhorn 3 — 1 Institut
für Spektrochemie und Angewandte Spektroskopie - Institutsteil Berlin,
— 2 B.I. Stepanov Institute of Physics, National Academy of Sciences
of Belarus, F. Scaryna Ave. 68, 220072 Minsk, Belarus — 3 Institut für
Polymerforschung Dresden e.V., Hohe Str. 6, D-01069 Dresden
Mid infrared spectroscopic ellipsometry [1] has been applied for the
investigation of poly-(n-butyl methacrylate) / poly(vinyl chloride) double
layers (100 nm each) on gold substrates and to analyze the process
of mixing caused by interdiffusion during annealing [2]. Interpretation of
the ellipsometric spectra in optical layer models allows the determination
of the thickness, the high frequency refractive index and the parameters
of molecular vibrations of the different polymer compounds. For a more
detailed evaluation infrared ellipsometry is used in combination with a
regularized deconvolution method [3]. The deconvolution method allowed
to determine positions of overlapping vibrational bands and to investigate
the shape of their profile. Annealing induced spectral changes were
discussed with respect to the miscibility and conformational changes in
the polymer film. [1] Hinrichs, K., Tsankov, D., Korte, E.H., Röseler, A.,
Sahre, K., Eichhorn, K.-J. Appl. Spectrosc. 2002, 56, 737. [2] Dlubek G.,
Bondarenko, V., Pompe G., Taesler Ch., Petters K., Krause-Rehberg R.,
Macromolecules 2002, 35, 6313; Dlubek G., Pompe G., Pionteck J., Janke,
A., Kilburn, D. Macromol. Chem. Phys. 2003, 204, 1234. [3] Buslov, D.
K., Nikonenko, N. A. Appl. Spectrosc. 1997, 51, 666.
CPP 8.7 Mo 17:15 H 37
Generalized Cauchy-Relation and its Implications for Amorphous
and Nano-Structured Materials — •Jan Kristian
Krüger, Thomas Britz, Jörg Baller, Andrä le Coutre,
Wulff Possart, Patrick Alnot, and Roland Sanctuary —
Laboratoire Européen de Recherche Universitaire Saarland-Lorraine
(LERUSL). Universität des Saarlandes, Fakultät für Physik und
Elektrotechnik 7.2, Geb. 38, D-66041 Saarbrücken, Germany
The generalized Cauchy-Relation (GCR) shows an unexpected linear
transformation (LT) between the elastic stiffness constants c11 and c44
in materials with effective isotropic symmetry. The slope B of this LT is
identical to that of the classical Cauchy-relation (B=3) but the additive
constant A is far from beeing zero. The magnitude of A will be discussed
as a measure of nanostructuration. Astonishingly, the GCR holds true
during irreversible processes like the curing process of adhesives.
The thermal glass transition, on the other hand shows two different
behaviors of the GCR: on slow cooling, the glass transition is completely
hidden in the GCR whereas on fast cooling the parameter B deviates significantly
from its classical value. Thus, the GCR is able to distinguish
between two states of glasses. Aging drives the broken GCR towards the
undisturbed GCR

Chemische Physik und Polymerphysik Montag
CPP 9 Single Molecule Spectroscopy
Zeit: Montag 14:00–15:30 Raum: H 38
CPP 9.1 Mo 14:00 H 38
Controlled Fluorescence Bursts from Single Conjugated Polymers
induced by Triplet Quenching — •Florian Schindler 1 ,
John M. Lupton 1 , Ullrich Scherf 2 , and Jochen Feldmann 1 —
1 Photonics and Optoelectronics Group, Sektion Physik, LMU Munich —
2 FB Chemie, University Wuppertal
Single molecule spectroscopy provides fundamental insight into the
nature of emission from conjugated polymers. Triplet excitons are particularly
important in these materials. We demonstrate here that triplet
quenching by molecular oxygen can lead to dramatic fluorescence bursts
from conjugated polymers before photo-oxidation sets in. The fluorescence
burst is imaged in single molecules of a comparatively photostable
ladder-type poly(para-phenylene). Triplet shelving is identified as an important
mechanism limiting the fluorescence yield of conjugated polymers
due to both a reduction in photon cycling rates and singlet-triplet quenching
in the multichromophoric system. The fact that triplet quenching
clearly enhances the fluorescence intensity from polymers suggests that
intramolecular energy transfer of singlet excitons to long-lived triplet
states generated simultaneously on a single polymer chain can also form
a quenching pathway for singlet excitons. Besides enabling a direct monitoring
of oxygen diffusion through thin polymer films, the sudden fluorescence
burst provides a novel tool to study the properties of triplet
excitons in conjugated polymers at room temperature down to the single
molecule level.
CPP 9.2 Mo 14:15 H 38
Single molecule spectroscopy at cryogenic temperatures using
vibronic excitation and dispersed fluorescence detection
— •Alper Kiraz, Moritz Ehrl, Christoph Bräuchle, and Andreas
Zumbusch — Department Chemie, Ludwig-Maximilians Universität
München, Butenandtstr. 11, D-81377 München, Germany
Low temperature single molecule spectroscopy experiments often rely
on excitation from the purely electronic zero-phonon-line and collecting
the Stokes shifted fluorescence[1]. A major problem of this technique
however, is that only exceptionally photostable systems can be studied.
Because the absorbing zero-phonon-line is so narrow, already small spectral
jumps (>30 GHz) in absorption lead to a loss of the excitation.
Here we report vibronic excitation combined with spectrally resolved
zero-phonon-line detection as a novel technique for single molecule spectroscopy
at cryogenic temperatures. In contrast to zero-phonon-line excitation,
vibronic excitation benefits from large absorption bands (broadened
by 1-10 ps lifetimes and phonon sidebands) allowing for investigation
of large spectral jumps. We observed single terrylenediimide molecules
in both n-hexadecane (Shpol’skii matrix) and PMMA (polymer), and
recorded spectral jumps as large as 80 cm −1 with 1 sec time resolution[2].
This technique promises applications in spectroscopy of a wide-range of
single molecules in amorphous hosts including fluorescing proteins. It also
allows for investigation of the emission linewidth of a single molecule’s
zero-phonon-line.
[1] A.-M. Boiron et al., Chem. Phys. 247, 119 (1999).
[2] A. Kiraz et al., J. Chem. Phys. 118, 10821 (2003).
CPP 9.3 Mo 14:30 H 38
Single Molecule Diffusion in Nanostructured Molecular Sieves
— •Johanna Kirstein 1 , Christian Hellriegel 1 , Christoph
Bräuchle 1 , Peter Behrens 2 , Nikolay Petkov 1 , and Thomas
Bein 1 — 1 LMU München, Dept. Chemie, Butenandtstr. 11, 81377
München — 2 Universität Hannover, Callinstr. 9, 30167 Hannover
Single molecule spectroscopy (SMS) is used to characterise diffusion
in nanometre sized structures. Here we show the diffusion of single TDI
molecules incorporated as guests into the pores of a M41S-host using
single particle tracking (SPT). A major advantage of SPT compared to
e.g. FCS is the possibility to obtain the trajectory of a fluorescent dye
molecule.
This has been demonstrated recently for TDI molecules diffusing in
monoliths of M41S using confocal microscopy. New studies in similar,
spincoated samples using wide field imaging provide an improved temporal
resolution. X-Ray diffraction measurements will point out the existence
of a hexagonal or cubic order of the pores in an otherwise amorphous
solid body. With SPT we obtain structured trajectories, which
reflect the tortuosity of the channels. These trajectories help to understand
better the channel structure of the hosts and the influence of the
pores on the diffusional behaviour of the guest molecules.
CPP 9.4 Mo 14:45 H 38
Orientation of Single Molecules in Nanostructured Molecular
Sieves — •Christian Hellriegel, Christian Seebacher,
Christophe Jung, and Christoph Bräuchle — LMU München,
Dept. Chemie, Butenandtstr. 11, 81377 München
Revealing heterogeneities and measuring the distribution of a physical
property of a system is a major advantage of single molecule spectroscopy
(SMS) compared to conventional ensemble methods. Recently we have
shown that single fluorescent dye molecules can also be detected if the
molecules are incorporated as guests in inorganic molecular sieves. Furthermore,
it is possible to obtain the molecule’s emission spectrum and
to determine its orientation using a confocal setup.
In the presented study we examine the influence of molecular size
on the orientational distribution: Three differently sized Oxazine dye
molecules have been incorporated during synthesis into AlPO4-5 crystals
(unidimensional channels, pore diameter 760pm). By analysing the
orientation of many individual molecules with respect to the channel axis,
we determine the effect of the molecular size on the orientational distribution,
and to which extent the host’s structure influences the alignment
of the molecules. During the measurements we also observe spectral dynamic
events, and in rare cases orientational jumps.
CPP 9.5 Mo 15:00 H 38
Single Molecule Microscopy of Aligned Molecules in a Thin
Crystalline Film — •Robert Pfab, Jan Zimmermann, Christian
Hettich, Ilja Gerhardt, Alois Renn, and Vahid Sandoghdar
— Physical Chemistry Laboratory, Swiss Federal Institute of Technology
(ETH), CH-8093 Zurich, Switzerland
Thin films of terrylene doped para-terphenyl have been fabricated
and characterised with optical microscopy, AFM measurements and single
molecule microscopy. Individual terrylene molecules are found to be
aligned with their transition dipole moment perpendicular to the plane
of the film, as observed by their characteristic dipole emission patterns.
The fluorophores are shown to be extremely photochemically stable. The
homogeneity of the film makes such samples ideal for scanning probe microscopy
techniques, and the orientation of the molecules provide a well
defined system for studying dipole-dipole interactions.
CPP 9.6 Mo 15:15 H 38
Optical Polarization Tomography: A new method to determine
the three-dimensional orientation of single molecules
— •Michael Prummer 1 , Horst Vogel 1 , Beate Sick 2 , Bert
Hecht 3 , and Urs P. Wild 4 — 1 Institute of Biomolecular Sciences,
EPFL, CH-1015 Lausanne — 2 DNA-Array Facility, University of Lausanne,
CH-1015 Lausanne — 3 Institute of Physics, University of Basel,
CH-4056 Basel — 4 Physical Chemistry Laboratory, ETH-Hönggerberg,
CH-8093 Zürich
We apply the concept of tomography to polarization-sensitive optical
microscopy of single fluorophores to determine the three-dimensional
orientation of molecular absorption dipoles with isotropic sensitivity.
Wide-field microscopy provides the opportunity to monitor simultaneously
three-dimensional rotation and two-dimensional translation of
many molecules in parallel. For orientation determination the molecules
are illuminated from different directions of incidence with linearly polarized
light. In each exposure the excitation along a particular projection of
the absorption dipole on the electric field leads to a distinct fluorescence
intensity. Five exposures are sufficient to determine the full orientation
of the fluorophores.

Chemische Physik und Polymerphysik Montag
CPP 10 Light Induced Phenomena
Zeit: Montag 15:45–17:30 Raum: H 38
CPP 10.1 Mo 15:45 H 38
Investigations on the dynamics of a photorefractive polymer
— •Andre Leopold 1 , Dietrich Haarer 1 , Jolita Ostrauskaite 2 ,
and Mukundan Thelakkat 2 — 1 Experimentalphysik IV and BIMF,
University of Bayreuth, 95440 Bayreuth, Germany — 2 Makromolekulare
Chemie I and BIMF, University of Bayreuth, 95440 Bayreuth, Germany
The photorefractive effect is the non-local variation of the refractive
index caused by an inhomogenous illumination. This effect is in principle
suited for holographic and opto-electronic applications.
At the present time, there is no clear theoretical understanding of the
dynamics of the photorefractive effect in polymers. The first model for
polymers, developed by Cui et al., was published in 1999. This model and
the model for inorganic crystals are applied to a photorefractive guesthost
polymer. This material consists of a poly-TPD with a low glass
transition temperature, a dicyano dye and the fullerene C60 as sensitizer.
The model by Cui et al is sufficient to describe our measurements and
gives information on the dominant trap species.
Furthermore, we investigated the influence of the sensitizer concentration
on the dynamics and found a significant increase of the grating
erasure rate with increasing sensitizer concentration. Additionally, a close
correlation of the erasure rates and the conductivities under illumination
is observed. This has the potential to ease up the process of evaluating a
material’s characteristics.
CPP 10.2 Mo 16:00 H 38
Optisch induzierte Diffusion und mechanisches Erweichen azobenzenhaltiger
Polymerfilme — •Norman Mechau 1 , Dieter Neher
1 , Kenji Urayama 2 , Volker Börger 3 und Henning Menzel 3
— 1 Universität Potsdam, Am Neuen Palais 10, 14469 Potsdam — 2 Kyoto
University, Institute of Chemical Research, Uji, Kyoto-fu 611-0011, Japan
— 3 TU- Braunschweig, Institut für Technische Chemie, Hans-Sommer-
Str. 10, 38106 Braunschweig
Es ist bekannt dass eine inhomogene Beleuchtung azobenzolhaltiger
Polymerfilme zur Ausbildung von Oberflächengittern führt. In diesem
Beitrag sollen grundlegende Untersuchungen zu den mechanischen Eigenschaften
und deren Änderungen unter Bestrahlung vorgestellt werden.
Mittels des Messaufbaus der elektromechanischen Interferometrie wurde
die Kompressibilität von Polymerfilmen als Funktion der Temperatur
und Bestrahlung ermittelt. Bestrahlungen von einigen 100 mW/cm 2 induzieren
bei Raumtemperatur vergleichsweise kleine Änderungen in der
Kompressiblilität. Berechnungen zum freien Volumen, die auf Daten der
viskoelastischen Kompressibilitäten beruhen, zeigen, dass das lichtinduzierte
freie Volumen im Vergleich zum freien Volumen im Bereich der
Glasübergangstemperatur Tg gering ist. Gleichzeit wurde durch Bestrahlung
bei Raumtemperatur ein Aufwellen der Elektrodenoberfläche beobachtet,
wie es normalerweise nur bei Temperaturen oberhalb von Tg
auftritt. Weiterführende Untersuchen zeigen, dass das Aufwellen sowohl
von der Elektrodendicke, als auch von thermischer Vorbehandlung der
Polymerschicht abhängt.
CPP 10.3 Mo 16:15 H 38
In-Situ Investigation of Surface Relief Grating Formation by
X-Ray Scattering — •Oliver Henneberg, Thomas Geue, Marina
Saphiannikova, and Ullrich Pietsch — Universiy of Potsdam,
Physics, Structureanalysis, 14469 Potsdam
The formation of surface relief gratings in polymers is a quite phenomenon
with poential for many possible applications but many open
question concerning the underlying physical process. Surface relief gratings
are made by an interference pattern of blue laser light onto a flat
polymer film which contains azobenzene moieties. The cycling cis-trans
conformation change leads to a movement of polymer chains far below
the glass transition temperature.
We have probed the grating formation by combined in-situ visible light
and x-ray scattering methods. The use of two different wavelengths allowed
time depend information at two different length scales. With x-rays
it is possible to probe very sensitive the beginning of the grating formation.
Visible light scattering gives information for larger grating heights.
We could calculate the scattering intensities of both probes by theoretical
modelling of the polymer movement. It could be shown that a change
of the polymer density is involved during the formation of the surface
grating.
CPP 10.4 Mo 16:30 H 38
High Sensitivity Setup for Surface Plasmons — •Marc Schneider
1,2 , Audree Andersen 1 , and Hubert Motschmann 1 — 1 Max
Planck Institute of Colloids and Interfaces, D-14476 Golm — 2 INFM
Genoa, I-16146 Genoa
A surface plasmon is a bound electromagnetic wave propagating at the
metal-dielectric interface. In Surface Plasmon Resonance spectroscopy
(SPR), an external laser field drives the free electron gas of metal in a
distinct mode, the so-called surface plasmon. The spatial charge distribution
creates an electric field, which is localized at the metal-dielectric
interface.
Because of this particular localization of the field, no signal comes from
the bulk, the plasmon resonance is extremely sensitive to the prevailing
interfacial architecture. Thus, an absorption process leads to a shift in
the plasmon resonance, allowing one to measure the mass coverage at the
surface with very high accuracy.
In this contribution we are comparing advantages and disadvantages
for two schemes allowing to track the surface resonance in a kinetic mode
with a high temporal (µs) and angular resolution (0.0001 degree). The
results are illustrated by selected experiments. following the change in
refractive index due to temperature changes of air.
CPP 10.5 Mo 16:45 H 38
Strukturelle Kinetik von photochemischen Reaktionen in
Lösung — •Anton Plech 1 , Fabien Mirloup 2 , Rodolphe Vuilleumier
2 , Savo Bratos 2 und Michael Wulff 3 — 1 Fachbereich
Physik der Universität Konstanz, Universitätsstr. 10, 78457 Konstanz
— 2 Laboratoire de Physique Theorique des Liquides, Universit’e Pierre
et Marie Curie, 4, Place Jussieu, F-75252 Paris — 3 ESRF, BP 220,
F-38043 Grenoble
Seit der zeitaufgelösten Beobachtung von einfachen Photolysereaktionen
durch Femtosekundenlaserspektroskopie (Nobelpreis 1991 A. Zewail)
sind ultraschnelle strukturelle Relaxationen ein grosses Arbeitsfeld. Atomare
Auflösung wird allerdings erst erzielt, wenn Streumethoden mit
kurzwelliger Strahlung verwendet werden. Durch einen neuen Ansatz in
der zeitaufgelösten Röntgenstreuung ist es gelungen, die strukturelle Dynamik
der Photoreaktion von Iod in CCl4 zeitaufgelöst zu verfolgen. Die
Inversion der Streudaten erlaubt einen direkten Zugriff auf die Paarkorrelationen
der Moleküle und des Lösungsmittels. Durch Vergleich mit
Molekulardynamiksimulationen wird der Verlauf der Anregung im Jodmolekül
und der Übergang in das Lösungmittel nachgezeichnet. Die absolute
Bestimmung von Anregungsdichten und der hydrodynamischen
Reaktion des Lösungsmittels wird diskutiert.
CPP 10.6 Mo 17:00 H 38
Lichtinduzierte Prozesse auf der Basis metastabiler Elektronenzustände
— •Dominik Schaniel 1 , Marcus Werner 1 , Theo Woike
1 und Mirco Imlau 2 — 1 Institut für Mineralogie und Geochemie,
Universität zu Köln — 2 Fachbereich Physik, Universität Osnabrück
In Natriumnitrosylprussiat (Na2[Fe(CN)5NO]·2H2O, NaNP) können
mittels Lichtbestrahlung zwei metastabile Elektronenzustände erzeugt
werden. Diese zeichnen sich durch eine sehr grosse Lebensdauer von
τ > 10 8 s bei tiefen Temperaturen aus. Wir untersuchen die Anregung
und den Zerfall der metastabilen Zustände mittels zeitaufgelöster Spektroskopie.
Zu diesem Zweck werden die NaNP Kristalle mit kurzen intensiven
Lichtpulsen bestrahlt und die lichtinduzierte Absorptionsänderung
mit verschiedenen Tastwellenlängen als Funktion der Zeit und der Temperatur
aufgenommen. Die Lebensdauer dieser Zustände folgt dem Arrhenius
Gesetz, wobei bei Raumtemperatur immer noch eine Lebensdauer
im Bereich von Mikrosekunden gemessen wird. Da die metastabilen
Zustände auch in Lösung angeregt werden können und 1eV über dem
Grundzustand liegen, besteht die Möglichkeit durch Zugabe geeigneter
Katalysatoren weiterführende Prozesse zu initiieren.

Chemische Physik und Polymerphysik Montag
CPP 10.7 Mo 17:15 H 38
Optical investigations of the clathrate compound Ba6Ge25
and new band structure calculations — •V. Voevodin 1 , J.
Sichelschmidt 1 , S. Kimura 2 , W. Carrillo-Cabrera 1 , I. Zerec 1 ,
S. Paschen 1 , Y. Grin 1 , and F. Steglich 1 — 1 Max-Planck-Institut
für Chemische Physik fester Stoffe, Nöthnitzer Str.40, 01187 Dresden
— 2 Division of Structural Science, Graduate School of Science and
Technology Kobe University, Rokkodai, Nada-ku, Kobe 657-8501, Japan
The compound Ba6Ge25 has a cubic structure which consists of
large Ge cages with Ba atoms trapped within. At room temperature a
large Ba-atom displacement factor provided evidence for anharmonical
vibrations (”rattling”) of Ba atoms. At around TS = 200 K Ba6Ge25
undergoes a two-step first-order phase transition and Ba atoms are
locked into off-center positions in Ge cages. [1]
Recently new temperature dependent X-ray diffraction data on single
crystalline samples revealed that at this phase transition also some of
the cage-building Ge atoms are displaced from their room temperature
sites. Therefore strong band structure changes near the Fermi surface
are expected at T = TS. We present our optical investigations of
the electronic properties of Ba6Ge25 in comparison with theoretical
band structure calculations. Near normal reflectivity measurements
for energies 0.01 - 30 eV have been done for temperatures between
7 K and 300 K . Besides changes of the optical data at T = TS, below
T = 80 K a pronounced optical conductivity peak develops at 0.2 eV.
[1] S. Paschen et al., Phys. Rev. B 65, 134435(2002)
CPP 11 Colloids and Nanoparticles I
Zeit: Montag 14:00–15:30 Raum: H 39
CPP 11.1 Mo 14:00 H 39
Ordering of soft and hard colloidal particles confined in thin liquid
films — •Regine v. Klitzing, Tatjana Mauser, and Branko
Kolaric — Stranski-Laboratorium, TU Berlin, Strasse d. 17. Juni 112,
10623 Berlin
Small angle neutron scattering experiments at solutions containing
branched polyelectrolytes or Silica particles show a structure peak which
indicates interactions between the colloids. The position of the structure
peak qmax scales with the concentration c as qmax ∝ c 1/3 for the colloidal
dispersions which is predicted by theoretical models. In order to investigate
the effect of geometrical confinement the solutions are confined
in a free-standing surfactant film. The sum of interactions between the
film surfaces is determined quantitatively by the disjoining pressure (disjoining
pressure in dependence vs. film thickness) and it is measured by
varying the outer pressure in a so–called thin film pressure balance. For
both systems the film drains stepwise with increasing pressure due to oscillatory
structural forces. In polyelectrolyte films the step size depends
on the polyelectrolyte concentration and corresponds to the correlation
length in solution. In contrast to this, the step size in films containing
(hard) Silica particles is constant irrespective the particle concentration.
CPP 11.2 Mo 14:15 H 39
Hierarchische Strukturen von Füllstoffen eingemischt in Elastomeren
— •Gerald Schneider und Dietmar Göritz — Institut
für Physik, Universität Regensburg, 93040 Regensburg
Die mechanischen Eigenschaften von Elastomeren hängen stark von
der Art, Struktur und der Oberfläche des eingemischten Füllstoffes ab.
In dieser Arbeit wird untersucht, in welcher Weise bei einer uniaxialen
Dehnung die charakteristischen Größen des Füllstoffes geändert werden.
Als Methode wird die Röntgenklein- (SAXS) bzw. Ultrakleinwinkelstreuung
(USAXS) verwendet. Es wurden Röntgenstreuexperimente an Kieselsäure
gefüllten Polydimethylsiloxan (PDMS) während einer uniaxialen
Deformation durchgeführt.
Bereits die zweidimensionalen Streubilder lassen eine Veränderung
der Größe und Struktur des Füllstoffes erkennen. Eine Analyse der zugehörigen
Schnittbilder ermöglicht eine einfache Interpretation im Rahmen
von vorhandenen Streutheorien. In dieser Betrachtungsweise sind
Erkenntnisse sowohl über die geometrischen Abmessungen, als auch über
die massen- und oberflächenfraktale Dimension möglich. Erste Ergebnisse
weisen darauf hin, dass sowohl die Struktur als auch die oberflächenfraktale
Dimension für verschiedene Dehngrade gleich bleibt, jedoch
ändert sich durch die externe Deformation der massenfraktale Exponent.
CPP 11.3 Mo 14:30 H 39
Probing gradient noble metal nano-cluster surfaces with high
spatial resolution grazing incidence small-angle x-ray scattering
— •S.V. Roth 1 , H. Walter 2 , M. Burghammer 1 , C. Riekel 1 ,
and P. Müller-Buschbaum 3 — 1 ESRF, B.P. 220, F-38043 Grenoble
Cedex, France — 2 november AG, Ulrich-Schalk-Str. 3, D-91056 Erlangen,
Germany — 3 TU München Physik Department LS E13, James-Franck-
Str.1, D-85747 Garching, Germany
Noble metal nanometer-sized cluster layers play an important role in
many technological and scientific applications, e.g. biomedical analysis.
Especially for property optimization it is necessary to vary the struc-
ture and morphology of the cluster layer and to produce laterally heterogeneous
multilayer systems. We present a novel approach to characterize
non-destructively laterally heterogeneous nanostructured multilayers
based on grazing incidence small-angle x-ray scattering (GISAXS).
This new method called µGISAXS combines the advantages of micrometer
spatial resolution by using a 5µm-sized x-ray beam with the wellknown
order-of-magnitude increase in q-resolution of GISAXS method
[1,2]. This renders µGISAXS a powerful method to scan inhomogeneous
surfaces on a micrometer scale. We applied µGISAXS to investigate the
morphological changes of novel gradient noble metal cluster/polymer
multilayer systems, produced by different procedures.
[1] P. Müller-Buschbaum et al., Europhys. Lett. 61 639 (2003)
[2] S.V. Roth et al., Appl. Phys. Lett. 82 1935 (2003)
CPP 11.4 Mo 14:45 H 39
Electrical and optical properties of metal/PTFE nanocomposite
films prepared by RF magnetron sputtering — •Ulrich
Schürmann, Haile Takele, Susanne Kreitz, Vladimir Zaporojtchenko,
and Franz Faupel — Lehrstuhl für Materialverbunde,
Technische Fakultät der CAU Kiel, Kaiserstr. 2, 24143 Kiel, Germany
We present a study of physical-chemical properties of thin PTFE films
with embedded noble metals (Ag, Au, Cu). These Films were deposited
by RF magnetron sputtering from a composite (PTFE/metal) target.
The deposition rate was monitored by a quarz crystal microbalance,
which was calibrated by measuring film thickness after deposition with a
profilometer. To study optical and electrical properties, nanocomposites
with thickness of some hundred nanometers were deposited different substrates.
Based on TEM images, the influence of the RF parameters and
Ar pressure on the particle morphology was analyzed. A metal volume
fraction was monitored by SEM/EDX using a metal/polymer standard,
which was calibrate gravimetrically. We characterized the chemical composition
and the structure of the composites by using XPS and FTIR.
Variation of the resistivity and the dielectric constant as a function of
metal volume fraction were carried out on a impedance measurement
device. The variation of electrical properties of Ag/PTFE nanocomposites
close to the percolation threshold and the difference in the UV/Visspectra
depending on metal concentration, particle size and density were
observed.
CPP 11.5 Mo 15:00 H 39
ORDERING OF COLLOIDS USING A POLYMER SURFACE
RELIEF GRATING — •B. Reinhold, Th. Geue, K. Morawetz,
M. Saphiannikova, and J. Grenzer — University of Potsdam, Institute
of Physics, Am Neuen Palais 10, 14469 Potsdam, Germany
Crystalline ordering of monodisperse colloidal spheres is of great interest
for many applications. The preparation of large two dimensional
colloidal domains often fails. The aim of this work was to initiate colloidal
ordering on patterned substrate. Two methods were tested: The
first method was the gravity sedimentation of colloids from dispersions
and the second one was the LB-technique. For preparation we have chosen
420 nm sized spheres. The spheres were deposited on a polymer surface
relief gratings (SRG) with a period between d=700 nm and d=900 nm.
This grating was produced at room temperature by a holographic exposure
of an amorphous polymer film containing azobenzene-side chains to
visible light at a wavelength of about 488 nm.
The influence of the SRG on the ordering of spheres was investiagted

Chemische Physik und Polymerphysik Montag
by AFM and by grazing incidence x-ray small angle scattering (GISAX).
The LB-technique was found less effective than the gravity-sedimentation
method. Using the latter we could prepare samples with a nearly monolayer
covering (AFM).The GISAX measurement confirms that we produced
an almost homogeneous covering over a large sample area (2 mm
X 2 mm). Almost no agglomeration of colloidal spheres was observed.
CPP 11.6 Mo 15:15 H 39
Charged Interfaces of Colloidal Particles studied by Ellipsometric
Scattering — •Andreas Erbe, Reinhard Sigel, and Klaus
Tauer — Max Planck Institute of Colloids and Interfaces, D-14476
Potsdam-Golm
CPP 12 Colloids and Nanoparticles II
A combination of conventional light scattering equipment with polarization
optics can be used to obtain information about the interface
between a colloidal particle and the solvent.
Since charge-stabilized colloids are an important class of colloids, we
investigate the influence of the salt (NaCl) concentration on the colloid’s
interface. For this study, we use block copolymer particles with a
water-insoluble core of Poly(methyl-methacrylate) and a water soluble,
negatively charged layer consisting of Poly(styrenesulfonate).
In addition, the behaviour of Poly(styrene) colloids stabilized by the
surfactant perfluorooctancic acid (negatively charged under the chosen
conditions) are investigated with low amounts of salt present.
Zeit: Montag 15:45–17:15 Raum: H 39
CPP 12.1 Mo 15:45 H 39
SOLVENT-DEPENDENT CRYSTALLIZATION KINETICS
OF COLLOIDAL PARTICLES — •Roy Goldberg, Patrick
Wette und Thomas Palberg — Johannes Gutenberg-University
Mainz, Institute of Physics, Staudingerweg 7, D-55099 Mainz
For structural examinations of crystalline ordered particles and to avoid
aging (Ostwald-ripening) and later coagulation it is advantageous that
the crystals are kept in their original state. For this reason they will be
imbedded in polymer matrices.
By static light scattering we examined in which way the particleinteraction
in a monomer-solution compared to aquatic dispersions with
the same particle number density will change. Beside the investigation of
structural parameters, the determination and comparison of crystallite
sizes is possible and variations in the particle-interaction are thus directly
observable . Additionally, changes in lattice features of colloidal crystals
during imbedding in a polymer matrix and with further drying were investigated
with microscopical methods as atomic-force-microscopy and
electron-microscopy.
CPP 12.2 Mo 16:00 H 39
Wetting at the nanometric scale — •Hauke Schollmeyer 1 , Antonio
Checco 2 , Jean Daillant 1,3 und Patrick Guenoun 1 —
1 Service de Physique de l’Etat Condense, C.E.A. Saclay, F-91898 Orsay
Cedex, France — 2 Department of Physics, Brookhaven National Laboratory,
Upton, New York 11973 — 3 LURE, CNRS/CEA/MJENR, bat.
209D, Centre Universitaire Paris-sud, F-91898 Orsay Cedex, France
We have investigated the partial wetting of micrometric and nanometric
alkane droplets on model substrates using true non-contact atomic
force microscopy. The large droplet sizes accessible using this technique
allowed us to determine the contact line curvature dependence of contact
angle with unprecedented accuracy. Whereas previous studies aimed at
explaining such a dependence by a line tension effect, our results and
calculations on a model system exclude such an effect. Our results point
to an extreme sensitivity to weak substrate heterogeneities confirmed by
numerical simulations. Our goal is to prove this result for model substrates
without heterogeneities. For this we use self assembled monolayer
of long chained alkanes on silicon substrate. At room temperature these
form a smooth and solid surface.
CPP 12.3 Mo 16:15 H 39
Electrophoretic investigations of surface-modified silica nanoparticles
— •Holger Reiber and Thomas Palberg — Johannes
Gutenberg-Universität, Institut für Physik, Staudingerweg 7, D-55099
Mainz
Because of strong coulombic interactions, dispersions of electrostatically
stabilised colloidal silica particles show a characteristic behaviour
in the case of very low salt conditions. The strength of the interactions
between the single particles is a function of the surface charge, and therefore,
it also influences electrophoretic properties as for example the particle
mobility. For this reason, we investigate silica nano-particles which we
synthesised using a variation of the Stöber-syntheses by means of laser
Doppler velocimetry. The particles differ from each other only with respect
to number and/or type of the ionic surface groups, but not with
respect to typical properties such as diameter, density or polydispersity.
For this reason, our measurements can show the influence of a variable
surface charge on system properties of nano-particles such as the mobility.
CPP 12.4 Mo 16:30 H 39
Surface modification of carbon nanotubes: by deposition of
nanosized — •Miguel Correa-Duarte and Michael Giersig —
Caesar Research Center, Dept. Nanotechnology, Ludwig-Erhard Allee 2,
53175 Bonn
In this presentation we will discuss the covering of multi-walled carbon
nanotubes (MWCNTs) with nanosized metallic and semiconductor
nanoparticles. In the first step MWCNTs have been positively or
negatively charged (depending on the nanoparticles charge) by covering
with cationic poly(diallyldimethylammonium) chloride (PDDA) or
anionic poly(sodium 4-styrenesulfonate) (PSS) polyelectrolyte. The following
step was the deposition of nanosized metallic (Au, SiO2@Au) and
semiconductor (CdSe, CdTe) particles. The successive covering process
was optically registered and was correlated with the structural characterization
by high resolution transmission and scanning electron microscopy.
CPP 12.5 Mo 16:45 H 39
ION DISTRIBUTION AT CHARGED INTERFACES —
•Patrick Koelsch and Hubert Motschmann — Max-Planck-
Institute of Colloids and Interfaces, Am Muehlenberg, 14476 Potsdam
The distribution of ions close to a charged wall is a classical problem
in colloid and interface science. The traditional approach consists in a
mean field analysis of the counterion distribution leading to the Poisson-
Boltzmann theory. Recently this field has attracted renewed attention
with several theoretical papers addressing effects beyond the mean field
level such as fluctuations, discreteness of charges or 2D-correlations.
These papers reveal certain new features which are not captured in the
mean field picture. We already demonstrated, that the combination of
nonlinear (suface Second Harmonic Generation SHG) and linear optical
technics (Ellipsometry) allows a direct determination of the prevailing
ion distribution. A simple analytical expression was derived which can
be used to retrieve the number of condensed counterions within the compact
or so called Stern-layer. In this contribution we apply this formalism
on experimental data gained on aqueous cationic surfactants by varying
the counterions in order to quantify specific ion effects at the interface
following the Hofmeister series. The derived formalism relates the ellipsometric
signal to the surface charge and promises great potential in order
to discard or proof recently published theoretical approaches.
CPP 12.6 Mo 17:00 H 39
High-resolution photoemission study of CdS nanoparticles with
narrow size distribution: preparation, different sulfur components,
and beam damage effects — •Sanjeev Joshi 1 , L. Weinhardt
1 , C. Kumpf 1 , S. K. Kulkarni 2 , R. Fink 3 , C. Heske 1 , and
E. Umbach 1 — 1 Exp. Phys. II, Univ. Würzburg, 97074 Würzburg —
2 Dept. Physics, Univ. Pune, Pune 411 007, India — 3 Phys. Chem. II,
Univ. Erlangen, 91058 Erlangen
We report on high resolution X-ray photoemission data of very small
CdS nanoparticles of two different sizes, 1.4 nm and 2.7 nm diameter,
respectively. A detailed analysis is performed to identify the sizes and
their distribution and the various signal constituents. The signal is composed
of five S components, which can be assigned to the S atoms of
the particle in different environments. The peak assignment is done by
comparing the experimental data with intensity estimates, considering
the intensity attenuation and contributions of the various S atoms using
three structural models. Furthermore, it is discussed how beam damage

Chemische Physik und Polymerphysik Montag
can be induced and how it is identified and controlled by recording very
fast photoemission scans. A quantitative description based on successively
collected spectra is developed. The influence of different thin film
sample preparation methods on the photoemission signal is discussed as
well.
CPP 13 SYMPOSIUM: Understanding and Controlling Complex Structures: From
Synthetic Polymers to Biomaterials I
Zeit: Dienstag 09:30–12:30 Raum: H 37
Hauptvortrag CPP 13.1 Di 09:30 H 37
Hierarchical Structures in Biological Materials — •Peter
Fratzl — Max Planck Institute of Colloids and Interfaces, Department
of Biomaterials, D-14424 Potsdam
Natural mineralized tissues such as wood, collagen or bone are hierarchically
structured and optimized for mechanical performance at all
levels of hierarchy. The basic unit of bone is a collagen fibril reinforced
with calcium phosphate nanoparticles. Such fibrils are assembled into
a complex composite structure which is far from being completely understood.
The hierarchical structure in wood consists of parallel tubes
(the wood cells) with polymeric walls reinforced by thin cellulose fibrils.
Adaptive growth and remodelling are common denominators in biological
materials and responsible for functional adaptation all hierarchical
levels. A successful approach to study hierarchical structures and their
mechanisms of deformation is scanning microfocus x-ray scattering complemented
with scanning electron microscopy and nanoindentation. Size,
shape and arrangement of mineral nanoparticles in bone are found by
such methods to vary systematically with age or at interfaces. Their
detailed arrangement turns out to be essential for the mechanical performance
of the composite, since they seem to control both the rigidity
and the toughness of the tissue. Quite similarly, recent results show that
the exact geometrical arrangement of the cellulose fibrils in the plant cell
wall controls to a large extent its mechanical bahaviour. In conclusion,
mechanical behaviour seems to depend essentially on the complexity of
the structure which is controlled by functional adaptation.
Hauptvortrag CPP 13.2 Di 10:00 H 37
Polymer cystallization as an example for highly meta-stable
structure formation — •Jens-Uwe Sommer and Günter Reiter
— Institut de Chimie des Surfaces et Interfaces (CNRS-UHA), 15 rue
Jean Starcky, 68057 Mulhouse, FRANCE
Long chain molecules form crystalline structures by developing folded
conformations, thus incurring a large decrease of conformational entropy.
Generally, crystallization of polymers leads to structures far from thermodynamic
equilibrium. Many of the features of polymer crystallization
are thus only poorly understood and recent experiments show results
which are unexpected on the basis of existing theoretical models [1]. As
a general paradigm for complex structure formation, polymer crystals
develop through a series of intermediate states. We give an overview
about recent advances and open questions in the understanding of polymer
crystallization processes, considered from the point of view of nonequilibrium
structure formation processes. In particular the investigation
of crystallization processes in ultra-thin films sheds more light on these
complex systems. We have developed a generic lattice model which allows
us to understand and predict various aspects of morphogenesis and
non-equilibrium melting phenomena [2].
[1] J.-U. Sommer and G. Reiter: Polymer Crystallization: Observations,
Concepts and Interpretations, Lecture Notes in Physics , Vol. 606,
Springer Verlag (2003)
[2] J.-U. Sommer and G. Reiter: Morphogenesis of Polymer Chain Crystals,
Europhys. Lett. 56, 755 (2001)
CPP 13.3 Di 10:30 H 37
Melting and reorganization of polymer crystals on fast heating
(1,000 K/s) — •Christoph Schick 1 and Alexander Minakov 2 —
1 Universitaet Rostock, FB Physik, Universitaetsplatz 3, 18051 Rostock
— 2 Natural Science Center of General Physics Institute, Vavilov st. 38,
199911 Moscow, Russia
Reorganization of polymer crystals on heating is a well known phenomenon.
But kinetics of the process is mainly unknown because it is
very fast. Utilizing a thin film vacuum gauge as a calorimeter we are
able to extend the scanning rate range of commercial DSC’s (10E-6 K/s
to 10 K/s) to rates as high as 10,000 K/s. Because of the fast equilibration
time isothermal experiments can be performed after scanning at
several thousand K/s. The dead time after such a quench is in the order
of 10 ms and the time resolution is in the order of milliseconds. These
ultra fast calorimeters allow studying kinetics of crystal reorganization in
polymers, which appears on time scales in the order of 10 milliseconds.
Compared to crystallization from the isotropic melt at the same temperature
reorganization of existing polymer crystals is about two orders of
magnitude faster. For PET at highest rates only one single melting peak
is seen independent on crystallization temperature. This ’true’ melting
corresponds to the lowest endotherm in DSC curves.
CPP 13.4 Di 10:45 H 37
A model describing the tensile deformation properties of semicrystalline
polymers exemplified for a sample of low density
polyethylene — •Ke Hong, Ankur Rastogi, and Gert Strobl —
Physikalisches Institut, Albert-Ludwigs-Universität, Hermann-Herder-
Str.3, 79104 Freiburg, Germany
The tensile deformation behavior of a low density polyethylene was
studied with the aim of understanding the different contributing forces
and modelling the deformation properties of semicrystalline polymers.
The sample PEVA12 which was used is capable of uniform deformation.
In this way true stress-strain curves were obtained easily. Employing
stress-relaxation measurement, the viscous force included in the stress
was determined. The unrelaxable stress is quasi-stable and includes the
network force and the crystal skeleton contribution. The results so obtained
can be represented by means of a three components model in
which a first component describes the crystal skeleton behavior with
a spring combined with a finite-plastic element. Conventional Gaussian
chain statistics are employed in a second component which deals with
the stress arising from the entanglement network. A Hookean spring in
series with a Eyring dashpot represents as the third component the relaxatory
stress. Using this model experimental stress-strain curves, stress
relaxation curves, creep curves and load-unload-cycle-tests can be well reproduced.
15 min. Pause
CPP 13.5 Di 11:15 H 37
Quantifying and Controlling the Mechanical properties of polyelectrolyte
multilayer capsules: Towards mechanosensitive microcapsules
— •Andreas Fery, Frederic Dubreuil, Nils Elsner,
Julien Heuvingh, and Melmuth Möwald — MPI for Colloids
and Interfaces Golm
Quantifying the mechanical properties of microcapsules is of interest
for both a basic science understanding of those systems and for their
applications. Control of the mechanical properties could lead to new
”smart” materials like ”mechanosensitive” capsules that change their mechanical
properties in reaction depending on their environment.
In this context, hollow capsules made from polyelectrolyte multilayers
are promising, because they can be produced with well defined geometry,
wall thickness and from various materials.
We use AFM force-spectroscopy and optical microscopy to directly
probe the deformability of individual microcapsules in solvent environment.
Using continuum mechanics models, we can derive the elastic constants
of the wall material. We find that the Youngs-modulus of microcapsules
made from PAH (Polyallylamine)/PSS (Polystyrenesulfonate) is depending
on the solution salt concentration and pH. We discuss the effects
in terms of simple molecular pictures and present how this mechanosensitivity
can be used to control microcapsule adhesion properties.
CPP 13.6 Di 11:30 H 37
The Mobility of the Amorphous Phase in Polyethylene as a Determining
Factor for Slow Crack Growth — •Yongfeng Men 1 ,
Jens Rieger 1 , Hans-Friedrich Enderle 2 , and Dieter Lilge 2 —
1 BASF Aktiengesellschaft, Polymer Physics, 67056 Ludwigshafen, Germany
— 2 Basell Polyolefine GmbH, R&D, 65926 Frankfurt, Germany

Chemische Physik und Polymerphysik Dienstag
Polyethylene (PE) pipes generally exhibit a limited life-time, which is
considerably shorter than their chemical degradation period. Slow crack
growth failure occurs when pipes are used in long distance water or gas
distribution though being exposed to a pressure lower than the corresponding
yield stress. This slow crack growth failure is characterized by
localized craze growth and craze fibril rupture. In literature, the life-time
of PE pipes is often considered as being determined by the density of tie
chains connecting adjacent crystalline lamellae. But this consideration
cannot explain the excellent durability of the recent bimodal grade PE
for pipe application. We show the importance of the craze fibril length as
determining factor for the pipe life-time. The conclusions are drawn from
stress analysis. It is found that longer craze fibrils sustain lower stress
and are deformed to a lesser degree. The mobility of the amorphous phase
is found to control the amount of material that can be sucked in by the
craze fibrils and thus the length of the craze fibrils. The mobility of the
amorphous phase can be monitored by dynamic mechanical analysis measurements.
Excellent agreement between the mobility thus derived and
life-times of PE materials as derived from FNCT-tests (full notch creep
test) is given, thus providing an effective means to estimate the life-time
of PE pipes by considering well defined physical properties.
CPP 13.7 Di 11:45 H 37
Thermal Fluctuations of Individual Actin Filaments in Confined
Geometry — •Sarah Köster 1 , Alexander Otten 1 , Stephan
Herminghaus 1,2 und Thomas Pfohl 1 — 1 Angewandte Physik,
Universität Ulm, Albert-Einstein-Allee 11, 89081 Ulm — 2 Max-Planck-
Institut für Strömungsforschung, Bunsenstraße 10, 37073 Göttingen
The investigation of individual semiflexible biopolymers will bring new
insights concerning microfluidic in vitro applications as well as the understanding
of biomechanical processes within the cell. The chosen system,
F-actin, is experimentally accessible quite well and it is one of the most
important proteins in eucaryotic cells. Thermal fluctuations of individual
fluorescently labeled actin filaments in confined geometry can directly
be observed using microfluidic devices fabricated by soft lithography.
Analyzing the fluorescence microscopy images of the contour line of the
fluctuating biopolymers we have access to macromolecular characteristics
such as the mean square end-to-end distance, the bending energy, and the
tangent correlation function. While the tangent correlation function of
free semiflexible polymers shows a simple exponential decay, a completely
different behaviour can be observed when investigating individual actin
polymers in confining microchannels. In this case the decay is superposed
by an oscillation which allows for the determination of the deflection
length λ in addition to the persistence length LP.
CPP 13.8 Di 12:00 H 37
Synthetic collagen peptides give clues to triple helix stability —
•Christian Renner, Dirk Barth, Alexander Milbradt, Barbara
Sacca, Hans-Juergen Musiol, and Luis Moroder — MPI
fuer Biochemie, 82152 Martinsried
Collagen is the most abundant protein in mammals. It gives mechanical
strength to tissue through its unique molecular structure: In the
collagen triple helix three protein strands that each form a left-handed
helix pack together resulting in a right-handed super helix. Although collagens
have been investigated by biologists, chemists and physicists for
many decades, the rules governing triple helix stability and thus collagen
function have not yet been fully elucidated. Surprisingly, repetition of the
simple amino acid triplet (Gly-Pro-Pro/Hyp) is sufficient for generating
the supramolecular organisation of the collagen helix with high stability.
We have used synthetic collagen peptides, where one hydrogen atom of
each triplet is substituted by fluorine, to study the influence of the fluorinated
position on structure and stability (1). We found that current
explanations of triple helix stability are inadequately simple and have to
be replaced by a detailed and quantitative view of the combination of interactions
involved. Additional means for investigation and stabilisation
of triple helices are natural (2) or synthetic cystine knots (3).
(1) Barth, D., Milbradt, A. G., Renner, C. and Moroder, L. (2003)
ChemBioChem, in press. (2) Barth, D., Kyrieleis, O., Renner, C. and
Moroder L. (2003) Chem. Eur. J. 9, 3703-3714. (3) Renner, C., Sacca, B.
and Moroder, L. (2003) Biopolymers, in press.
CPP 13.9 Di 12:15 H 37
Structural modifications and electromechanical properties of inflated
cellular polypropylene films — •Michael Wegener, Enis
Tuncer, Werner Wirges, and Reimund Gerhard-Multhaupt —
University of Potsdam, Department of Physics, Am Neuen Palais 10, D-
14469 Potsdam
Voided space-charge electrets with internal charge layers show significant
piezoelectrical properties. In such materials, e.g. cellular polypropylene,
the piezoelectric coefficient strongly depends on the cell-size and
-shape distributions. The electrically charged cells represent macroscopic
dipoles. The typically air-filled cells can be deformed very easily by a
mechanical stress or an electrical field, which represents the direct and
inverse piezoelectric effects, respectively. By means of controlled inflation,
cell sizes and shapes can be varied over a rather large range. This
is achieved by altering pressure and temperature. Here, we describe various
inflation procedures with several different pressures, temperatures
and treatment times. After optimization the procedure yields high piezoelectric
coefficients that may be due to the low elastic moduli of the
inflated samples. The results are discussed with respect to the observed
micro-structure of cellular films (as seen in SEM cross-sections), and are
compared to the finite element analysis. The comparison to numerical
simulations explains the micro-structural changes during the inflation
process.
CPP 14 SYMPOSIUM: Understanding and Controlling Complex Structures: From
Synthetic Polymers to Biomaterials II
Zeit: Dienstag 14:00–17:00 Raum: H 37
Hauptvortrag CPP 14.1 Di 14:00 H 37
Competition of order in liquid crystalline/isotropic block
copolymers — •Bernd Stühn 1 , Wolfram Gronski 2 , Rosina
Staneva 1 , Sergei Zhukov 1 , and Steffen Geppert 2 — 1 Technische
Universität Darmstadt, Physics of Condensed Matter, D-64289
Darmstadt — 2 Albert Ludwigs Universität Freiburg, Institute of
Macromolecular Chemistry, D-79104 Freiburg
The formation of structure in block copolymers consisting of an
isotropic and a liquid crystalline block is governed by two factors. One is
the domain ordering caused by the strong repulsive interaction between
both blocks. As a second factor the orientational order of the mesogens
in the liquid crystalline block is to be considered.
We have investigated a series of di- and triblock copolymers with the
liquid crystalline block either confined within spherical, cylindrical or
lamellar domains or forming the continuous matrix. Small and wide angle
X-ray scattering has been applied to study structure on a wide range
of length scales. The dependence of domain order on the orientational
order is studied by variation of temperature and crossing the transition
temperature of the liquid crystalline phase. The nematic order of the
LC clearly favours the cylindrical over the spherical domain form thus
causing a variation of structure with temperature at the LC phase transition.
For one example we find a order-to-order transition in the domain
structure triggered by the nematic-isotropic phase transition of the liquid
crystalline matrix.
Hauptvortrag CPP 14.2 Di 14:30 H 37
Bio- and biomimetic mineralization — •Helmut Cölfen —
Max-Planck-Institute of Colloids and Interfaces, Colloid Cemistry, Am
Mühlenberg, D-14476 Golm
Nature is able to produce highly optimized materials by the process of
biomineralization at ambient temperature in water. These materials like
bones and teeth are organic-inorganic hybrid systems with hierarchical
order. Some basic principles of biomineralization will be introduced to illustrate
how these materials are formed. Biomineralization processes can
be successfully mimicked to produce advanced synthetic materials from
simple inorganic systems. Examples will be given, how polymers can be
used to direct crystallization processes resulting in hybrid materials with
complex shape.

Chemische Physik und Polymerphysik Dienstag
CPP 14.3 Di 15:00 H 37
Biorelevant Reactions in Microchannel Mixing Devices
Observed by Microbeam-SAXS — •Alexander Otten 1 , Sarah
Köster 1 , Bernd Struth 2 , Anatoly Snigirev 2 , and Thomas
Pfohl 1 — 1 Angewandte Physik, Universität Ulm, Albert Einstein Allee
11, D-89069 Ulm — 2 ESRF, 6 Rue Horowitz, 38043 Grenoble Cedex,
France
The application of microfluidic devices does not only allow to analyze
small volume fractions of e.g. biomaterial solutions but also gives
access to faster observations and improved sample characterization. We
use a microchannel device consisting of two crossed channels to examine
the behavior of biomacromolecules in elongational flow as well as
for studies on biomaterial aggregation. In our microfluidic focussing device
a microjet flow is achieved by hydrodynamically focussing a center
stream by two symmetric side streams. The elongational flow and
the biomaterial aggregation were studied by using the microbeam-SAXS
(small angle X-ray scattering) technique. To achieve a spatial resolution
of ≈20µm, the x-ray beam was focussed by compound refractive
lenses. We present SAXS data on the elongation of DNA molecules in
semi-dilute solutions and the increased orientation in the microjet flow.
Furthermore, we studied DNA condensation by positively charged countermolecules,
G4-Dendrimers. The mixing and the achieved aggregates in
respect to different DNA/Dendrimer concentrations were examined and
several structural phases were observed.
CPP 14.4 Di 15:15 H 37
Structure and elastic properties of a block-copolymer bilayer
doped with cationic surfactant — •Thomas Hellweg, Holger
Egger, and Gerhard Findenegg — TU Berlin, Stranski Laboratorium
f. Physikalische und Theoretische Chemie, Strasse des 17.Juni 112,
10623 Berlin
In recent years much attention was paid to the commercially available
triblock copolymers poly(ethylene oxide)-poly(propylene oxide)poly(ethylene
oxide) (PEO-PPO-PEO). The phase behavior of these
polymers, often called pluronics, is investigated intensively in binary systems
with water, as well as in ternary systems containing water and oil
or in polymer mixtures by a lot of different research groups.
In the present work we study the influence of the cationic surfactant noctyltrimethyl-ammonium-bromide
(C8TAB) on the triblock copolymer
based system (EO37-PO58-EO37)/water/o-xylene.
At sufficient high surfactant concentration the system shows an extended
lamellar phase (Lα). This phase is characterized in terms of interlamellar
spacing, thickness, and internal structure of the bilayers as a function
of composition. The Caillé-model is used to correlate the profile of the
first order Bragg peak with the elastic constants of the amphiphilic film.
It is possible to obtain general trends for the dependence of the elastic
constants κ and B of the block-copolymer-film on the surfactant concentration.
CPP 14.5 Di 15:30 H 37
Nanophase separation in side chain polymers and the dynamics
in self-assembled confinements — •Mario Beiner — FB Physik,
Martin-Luther-Universität Halle-Wittenberg, 06099 Halle, Germany
Structural and dynamic data for different series of amorphous side
chain polymers with long alkyl groups show consistently that a nanophase
separation of incompatible main and side chain parts on the one nanometer
scale is a common feature of such materials [1]. Long alkyl groups –
belonging to different monomeric units and chains – aggregate in the
melt and form alkyl nanodomains with a typical size of 0.5-2 nm. The
dynamics of the nanophase-separated side chain polymers is characterized
by the presence of an additional polyethylene-like glass transition αPE
within the alkyl nanodomains. Important features of this αPE process are
main chain independent. With increasing size of the alkyl nanodomains
a strong-to-fragile transition has been observed in the steepness index
of the αPE process as obtained from relaxation spectroscopy measurements.
This finding is discussed in the context of cooperative motions
in self-assembled confinements and will be related to the long and controversial
discussion about the size of dynamic heterogeneities in glasses.
This is an interesting link between central questions in glass transition
research and structural aspects in nanophase-separated materials. The
general importance of nanophase separation effects for an understanding
of the dynamics of complex materials in nanotechnology and nature is
demonstrated.
[1] M. Beiner and H. Huth, Nature Materials 2, 595 (2003)
15 min. Pause
CPP 14.6 Di 16:00 H 37
Structural Relaxation and Dynamic Heterogeneity in a Polymer
Melt at Attractive Surfaces — •Grant Smith — Department
of Materials Science and Engineering, University of Utah, Salt Lake City,
Utah, USA
Molecular dynamics simulation studies of polymer melts at attractive
flat and structured surfaces reveals slowed dynamics and increased dynamic
hetergeneity for polymer near the surface. For flat surfaces slow
dynamics and increased dynamic heterogeneity of interfacial polymer relative
to the bulk was found to be due to densification of the polymer in
a surface layer, while for structured surfaces the energy topography of
the surface played the dominant role in determining dynamics of interfacial
polymer. Much of the dramatic increase in structural relaxation
time for the interfacial polymer was found to be the result of dynamic
heterogeneity induced by the surfaces.
CPP 14.7 Di 16:15 H 37
Single Molecule Studies of Surface Melting in Free Standing
Polymer Films — •Frank Cichos 1 and Jörg Schuster 2 —
1 Institut für Physik 123705, TU Chemnitz, 09107 Chemnitz — 2 Institut
für Physik 121501, TU Chemnitz, 09107 Chemnitz
Thin polymer films show a drastic decrease of the glass transition temperature
with decreasing film thickness. While this effect depends on the
chain length if the radius of gyration of the polymer chain is on the order
of the film thickness, it is independent of it for small molecular weights
and thus points to a very general effect involved in the glass transition.
We present for the first time results of single molecule studies in free
standing polymer films far below the bulk glass transition temperature.
By tracking individual fluorescent molecules we are able to follow the
local dynamics in the film as a function of temperature. We show that
already at temperatures of about 40 K below the bulk glass transition
temperature a small highly mobile fraction of dye molecules coexists with
a large number of completely immobile molecules. The mobile fraction
shows translational diffusion which only weakly depends on temperature.
However, the number of molecules released from the film strongly
increases with increasing temperature. This increase is explained by the
desorption of dye molecules adsorbed at the polymer surface and by the
release of molecules from a growing ”molten” layer. We interpret these
findings in terms of an inhibition of the glass transition in the film by
the dynamics of the surface. This inhibition becomes more effective for
smaller film thicknesses and therefore effectively decreases the glass transition
temperature of the film compared to the bulk value.
CPP 14.8 Di 16:30 H 37
Monte Carlo Simulations of the phase behaviour of polymer
brushes — •Ludger Wenning, Marcus Müller, and Kurt
Binder — Johannes Gutenberg Universität Mainz
A polymer brush in a poor solvent is investigated by Monte Carlo (MC)
simulations of a bead-spring-model.
A new MC-Move for the inner part of a polymer chain has been devised
to efficiently equilibrate the chain conformations. This move is based on
the Configurational Bias (CB) algorithm, but in contrast to the CB-move
it needs no free end of the polymer chain. Therefore it works for grafted
polymers or ring polymers.
We observe the transition from a swollen, homogenous brush in a good
solvent to a laterally structured cluster phase in a bad solvent. This transition
depends on the solvent quality and the surface coverage. Unlike the
prediction of self-consistent field theory, clusters do not form a hexagonal
lattice, but rather arrange irregularly.
Further the influence of the way of grafting is studied. Random grafting
leads to slightly larger clusters, which are also more stable at better solvent
quality. Moreover we demonstrate how the locations of the clusters
correlate with density fluctuations in the grafting points.
CPP 14.9 Di 16:45 H 37
Polymeric nanostructures created by destabilization of confined
thin films — •P. Müller-Buschbaum 1 , R. Cubitt 2 , and W.
Petry 1 — 1 TU München Physik Department LS E13, James-Franck-
Str.1, 85747 Garching — 2 ILL, b.p. 156, 38042 Grenoble (France)
the concept of self-assembly. Recently, it was shown that from a destabilization
of confined ultra-thin films nano-structured polymeric surfaces
result [1]. Following the scaling laws of dewetting, due to the reduced
amount of polymeric material available, the size of the resulting struc-

Chemische Physik und Polymerphysik Dienstag
tures decreases with decreasing film thickness. Destabilizing confined
ultra-thin diblock copolymer films thus offers the opportunity to introduce
two intrinsic lateral length scales, the characteristic periodicity of
the micro phase separation structure Lo and the most prominent in-plane
length of the dewetting structure Λ. While on a local scale the surface
structure is nicely pictured by atomic force microscopy (AFM) to obtain
CPP 15 POSTER: Polymers and Biomaterials
a statistically significant information scattering is helpful. With grazing
incidence small-angle scattering a length regime from molecular to
micrometer-sized and thus comparable to AFM is addressed [2].
[1] P.Müller-Buschbaum, R.Cubitt, W.Petry, Langmuir 19, 7778 (2003)
[2] P. Müller-Buschbaum, Anal.Bioanal.Chem. 376, 3 (2003)
Zeit: Dienstag 17:00–19:00 Raum: B
CPP 15.1 Di 17:00 B
Phase-behavior of bidisperse ferrocolloids — •Gabriel M.
Range and Sabine H.L. Klapp — Stranski-Laboratorium für
Physikalische und Theoretische Chemie, Sekr. TC7, Fakultät II,
Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin,
Germany
Using density functional theory in the modified mean-field (MMF) approximation
we study the phase behavior of bidisperse ferrocolloids, consisting
of a binary mixture of dipolar hard spheres (DHS). We focus on
the fluid phase regime, where we consider both isotropic and anisotropic
phases.
In a recent MMF study of binary mixtures of equisized DHS, differing
only in their dipole moments, we found a rich phase behavior resulting
from the interplay of isotropic-to-ferroelectric and demixing transitions.
In systems with strongly asymmetric dipole moments the isotropic-toferroelectric
transition is shifted towards significantly lower temperatures
compared to the one-component case, while the demixing transition becomes
more and more dominating. We also found, that demixing is always
accompanied by spontaneous ferroelectricity in the MMF approach.
Based on these findings we analyze the relative importance of differing
sizes versus differing dipole moments on the phase-behavior of ferrocolloids.
We also investigate the influence of external fields, particularly on
demixing and size separation.
CPP 15.2 Di 17:00 B
Properties and Crystallization of PNIPAM-co-PS core-shell microgels
— •Thomas Hellweg — TU Berlin, Stranski Laboratorium,
Strasse des 17.Juni 112, 10623 Berlin
During the last decade thermosensitive hydrogels have received increasing
attention due to their potential with respect to applications
in drug delivery or as sensors. However, macroscopic gels have rather
long equilibration times with respect to swelling and deswelling. In some
cases it might take days until the equilibrium state is reached. Therefore,
with respect to applications as sensors or drug delivery systems
so called microgels have preferable properties compared to their macroscopic
homologues. Recently, these particles were also investigated with
respect to their crystallization behaviour. Due to their low polydispersity
they form colloidal crystals in solution as usual hard-sphere colloids.
Additionally, their response to temperature allows to vary the volume
fraction over a wide range. Here, we are going to discuss the properties
of poly((N-isopropyl acrylamide)-co-polystyrene (PNIPAM-co-PS) coreshell
microgel particles with extended PNIPAM shells. The particles are
characterized by dynamic light scattering (DLS), electron microscopy and
SANS.
CPP 15.3 Di 17:00 B
Elastic and Thermal Properties of Nano-Particle Composites
within Polymer Matrices — •Andrä le Coutre 1,2 , Bernd
Wetzel 3 , Jörg Baller 1,2 , Ravi Bactavatchalou 1,2 , Ulrich
Müller 1,2 , and Jan K. Krüger 1,2 — 1 Laboratoire Européen de
Recherche Universitaire Saarland-Lorraine (LERUSL) — 2 Universität
des Saarlandes, Fakultät für Physik und Elektrotechnik 7.2, Geb. 38,
Saarbrücken, Germany — 3 Universität Kaiserslautern, Institut für
Verbundwerkstoffe GmbH, Germany
Composite systems gain importance in material science as well as in
industrial applications. One aim is the improvement of the mechanical
properties by reinforcement of polymer matrices with particles or fibers.
By means of Brillouin spectroscopy we investigated the effective elastic
modulus (compressional and shear modulus) of DGEBA/DETA-epoxies
filled with Al2O3 and SiO2 nanoparticles with sizes below 50 nm. In addition
to the stiffening as expected by averaging models of elastic properties,
an enhanced stiffness for particle concentrations below 6% volume
fraction is observed. The reason for this is assumed either to be an ef-
fect of a special chemical affinity of the hardening component (DETA)
to the nanoparticle surface or a structurizing effect of the surface on the
surrounding epoxy matrix. As a kind of inverse situation DGEBA-filled
nanoporous glass matrices were investigated giving hints for a structurizing
effect of the inner surfaces to the DGEBA molecules.
CPP 15.4 Di 17:00 B
Micro-Nanopattern by Block Copolymer Micelle Nanolithography
— •Roman Glass 1 , Martin Moeller 2 , and Joachim Spatz 1
— 1 Institute for Physical Chemistry, Biophysical Chemistry, University
of Heidelberg, Germany — 2 Deutsches Wollforschungsinstitut at the
RWTH Aachen, Germany
A key issue in the fabrication of functional nanostructures is the defined
placement and connection of nanometre sized objects in periodic or
aperiodic arrangements on surfaces with different chemical composition
and electrical properties. The basis of our approach is the self-assembly
of polystyrene-b-poly[2-vinylpyridine (HAuCl4)] diblock copolymer micelles
into uniform monomicellar films on solid supports such as Si-wafers
or glass cover slips. Subsequent hydrogen plasma treatment of micellar
film causes deposition of Au-nanoparticles (between 2 and 8 nm) onto
the substrate by entire removal of the polymer. The limitation of the
separation distance between individual dots or the pattern geometry is
overcome by combining self-assembly of diblock copolymer micelles with
pre-structures formed by photo or e-beam lithography. Capillary forces of
a retracting liquid film due to solvent evaporation on the pre-structured
substrate push micelles in the corners of these defined topographies. A
more direct process is demonstrated by applying monomicellar films as
negative e-beam resist. This process is also feasible on electrical isolating
substrates if the monomicellar film is coated in addition with a 5 nm
thick conductive layer of carbon before e-beam treatment.
CPP 15.5 Di 17:00 B
Chemical Modification of microphase-separated Triblock Terpolymer
Films — •Kristin Schmidt, Sabine Ludwigs, Andrej
Voronv, Robert Magerle, and Georg Krausch — Physikalische
Chemie II, Universität Bayreuth, Bayreuth, Germany
In this presentation we discuss a polystyrene-b-poly(2vinylpyridine)-b-poly(tertbutylme
thacrylate) triblock terpolymer
(SVT) exhibiting a core-shell cylinder structure in bulk
(φPS = 0.16, φP2V P = 0.21, φPtBMA = 0.63, Mw = 140k, Mw/Mn = 1.02)
which was synthesized via sequential living anionic polymerization 1 .
After annealing in controlled solvent vapour atmosphere thin films of
these triblock terpolymer self-assemble into a highly ordered perforated
lamellae structure with PS-core and a P2VP-shell in the PtBMA matrix
phase.
A chemical modification of the poly(tertbutylmethacrylate) matrix
phase to poly(methacrylic acid) via acid-catalyzed saponification leads
to a pH-responsive nanostructure which was investigated with scanning
force microscopy in aqueous environment. Furthermore, we show that
the perforated lamella might serve as a lithographic mask by selective
UV-depolymerization of the poly(tertbutylmethacrylate) matrix phase 2 .
1 Ludwigs, S.; Böker, A.; Abetz, V.; Müller, A.H.E.; Krausch, G. Polymer
2003, 44, 6815
2 Ludwigs, S.; Böker, A.; Voronov, A.; Rehse, N.; Magerle, R.; Krausch,
G. Nature Materials 2003, 2, 744
CPP 15.6 Di 17:00 B
Response of polyelectrolyte multilayers to external stimuli —
•Regine v. Klitzing 1 , John Wong 1 , and Roland Steitz 2 —
1 Stranski-Laboratorium, TU Berlin, Strasse d. 17. Juni 112, 10623 Berlin
— 2 Hahn-Meitner-Institut, Glienicker Strasse 100, 14109 Berlin
The polymer films presented in this study were made by alternate adsorption
of polyanions and polycations from aqueous solution onto solid

Chemische Physik und Polymerphysik Dienstag
substrates (Silicon, glass) using the layer-by-layer method developed in
the early 1990s by Decher. In the present work the response of external
stimuli like relative humidity and outer salt concentration is investigated.
The multilayer structure is investigated by ellipsometry, AFM X-ray and
neutron reflectometry. We found that the amount of water absorbed by
the polymer film increases with increasing film thickness, but the net
percentage of water absorbed decreases after reaching a maximum for
a certain number of layers. The absorbed amount of water depends on
the type of polyelectrolyte in the outer layer which leads to an odd/even
effect in swelling. While small changes in salt concentration have a pronounced
effect on the multilayer structure during the dipping process,
high amounts of salt are required to change the structure after the adsorption
process has been finished.
CPP 15.7 Di 17:00 B
Polymer films with thickness gradients: A new class of heterogenous
films — •T. Titz 1 , N. Hermsdorf 2 , and P. Müller-
Buschbaum 1 — 1 TU München Physik Department LS E13, James-
Franck-Str.1, 85747 Garching (Germany) — 2 IPF Dresden, Hohe Str.
6, 01069 Dresden
applications such as functional coatings. Polymer gradient samples resemble
a powerful tool to investigate nanostructures and their creation
process by changing an external variable along one direction of the sample.
A film thickness gradient was prepared by solution casting on a tilted
substrate. The thickness gradient increase from 30 to more than 300 nm
over a distance of 50 mm. The prepared polymer film is homogenous perpendicular
to the thickness gradient to allow for an investigations based
on scattering techniques. We applied x-ray reflectivity and gracing incidence
small angle x-ray scattering (GISAXS) to determine the density
profile as well as the lateral structuring. In addition optical microscopy
and AFM were performed to give access to the real space surface structure.
From the continuous change of the film thickness changes in the
surface and bulk morphology of the polymer films resulted.
CPP 15.8 Di 17:00 B
Influence of substrate cleaning on the dewetting of thin
polystyrene films — •E. Bauer 1 , M. Stamm 2 , and P. Müller-
Buschbaum 1 — 1 TU München Physik Department LS E13,
James-Franck-Str.1, 85747 Garching — 2 IPF Dresden, Hohe Str. 6,
01069 Dresden
applications, such as coatings and dielectrics. As the first basic step
in any dewetting experiment resembles the cleaning of the substrate,
to guarantee equal starting conditions, we treated silicon substrates
by different cleaning procedures. Next, the dewetting behavior of thin
polystyrene films, spin-coated on top, was investigated by exposure to
heat load. Different stages of dewetting, beginning by hole creation and
ending-up with drops were observed. These structures were locally probed
by AFM and additionally investigated by grazing incidence small angle
x-ray scattering (GISAXS) to get a statistical relevant information about
the whole sample. We observed a strong influence of the chosen surface
clean on the time scales of the dewetting. This underlines the importance
of giving detailed information about this preparation step to allow for a
comparison of experiments.
CPP 15.9 Di 17:00 B
Phase separation of ternary polymer blend films: A kinetic investigation
— •P. Panagiotou 1 , E. Maurer 1 , R. Cubitt 2 , and P.
Müller-Buschbaum 1 — 1 TU München Physik Department LS E13,
James-Franck-Str.1, 85747 Garching (Germany) — 2 ILL, b.p. 156, 38042
Grenoble (France)
polymers with different molecular weights and glass transition temperatures
is investigated with neutron reflectometry and AFM. Thin films
were prepared by spin-coating on top of pre-cleaned silicon substrates.
Afterwards the samples were annelead yielding changes in the surface
morphologies due to phase separation. In a subsequent preparation step
the pre-annealed samples were stored under a solvent vapor atmosphere.
The resulting morphological changes were monitored in-situ with neutron
reflectometry. A high time resolution was achieved by applying a timeof-flight
(TOF) mode at the neutron reflectometer D17 at ILL. AFM
(atomic force microscopy) pictures the topography resulting in the most
prominent length scales parallel to the surface as calculated with 2d-
Fourier analysis.
CPP 15.10 Di 17:00 B
The effect of surface interactions on the molecular dynamics
under the confinement of thin layers — •Anatoli Serghei and
Friedrich Kremer — Institute for Experimental Physics I, University
of Leipzig, Linnestr. 5, 04103, Leipzig, Germany
A novel method for preparation of thin polymeric films was developed
and employed to investigate the molecular dynamics of cis-polyisoprene
under confinement using BDS (Broadband Dielectric Spectroscopy, 0.1
Hz-10 MHz, 200 K-400 K). The method consists in placing a thin polymer
film via spin-coating or solvent-casting between two hard, flat, conductive
electrodes (optical polished highly doped silicon wafers having a
macroscale roughness of 2 nm), as spacers being used silica nanocolloids
with a well-defined size distribution. The film thickness, reaching values
of tens of nanometers, can be additionally controlled by measuring the
sample capacity. By chemically treating the surface of one or of both electrodes,
our method allows us to investigate the effect of the interfacial
interactions on the dynamics of thin films.
CPP 15.11 Di 17:00 B
Active Networks Studied by Magnetic Tweezers Microrheometry
and Torsional Macrorheometry — •R. Tharmann, J. Zhang,
M. Bärmann, and A. R. Bausch — Technische Universität München,
James-Franck-Straße 1, Garching, 85747 Germany
Although the defining property of polymer networks is their viscoelastic
behavior, a microscopic understanding of the underlying mechanisms
is still lacking. In biological processes, e.g. the migration of cells, the
temporal and spatial regulation of the activation of cross-linkers is very
important, yet not understood. Even more importantly, biology uses a
huge number of distinct cross-linkers which have different effects on the
viscoelastic behavior of biological networks.
One class of cross-linkers are molecular motors such as myosins. Under
ATP-rich conditions the molecular motors are active, while in the ATP
depleted regime the motors act as passive cross-linkers (rigor mortis).
Here we use both the technique of Magnetic Tweezers Microrheometry
and Torsional Macrorheometry to study the local and the averaged viscoelastic
properties of actin networks which are linked by myosin II,
myosin V and HMM fragments at different ATP concentrations.
CPP 15.12 Di 17:00 B
Water-Soluble Terpolymer Mediated Calcium Carbonate Crystal
Modification — •Ranith Krishna Pai 1 , Sabine Hild 1 , Othmar
Marti 1 , and Andreas Ziegler 2 — 1 Experimental Physics, University
of Ulm, Albert-Einstein-Allee 11, 89081 Ulm — 2 Department
Electronmicroscopy, University of Ulm, Albert-Einstein-Allee 11, 89081
Ulm
The structure of the polymeric substrates plays an important role
in the nucleation of calcium carbonate crystals. In this study a
synthetic water-soluble poly (acrylamide-co-2-acrylamido-2-methyl-1propane
sodium sulfonate-co-n-vinyl pyrrolidone) will be introduced
which is a substrate favoring the nucleation of polymorphs of calcium
carbonate crystals under specific experimental conditions. Morphological
characterization of the polymorphs was done using Atomic Force Microscopy,
Scanning Electron Microscopy, Energy Dispersive Spectroscopy,
FTIR Analysis and X-ray Diffraction. If calcium carbonate was precipitated
in presence of the polymer a remarkable increase in nucleation
density was observed. Stacked crystals of rhombohedral morphology were
formed may be due to the presence of sodium sulfonate groups on the
terpolymer. However, in the presence of polymer and poly-L-aspartic
acid only hollow crystals of aragonite with needle like or plate like morphologies
had been found. This change in calcium carbonate morphology
could be explained by the variation of the polymer conformation if poly-
L-aspartic acid is present.
CPP 15.13 Di 17:00 B
Grazing-incidence small-angle X-ray scattering on thin lamellar
diblock copolymer films: Modelling the scattering cross section
— •Christine M. Papadakis 1 , Peter Busch 1 , Markus Rauscher
2 , Detlef-M. Smilgies 3 und Dorthe Posselt 4 — 1 Fakultät
für Physik und Geowissenschaften, Universität Leipzig — 2 MPI für Metallforschung,
Stuttgart — 3 CHESS, Cornell University — 4 Roskilde University,
Denmark
Grazing-incidence small-angle X-ray scattering (GISAXS) is a powerful
method to elucidate the mesoscopic structures formed by thin polymer
films. We have studied a series of thin films of lamellar polystyrenepolybutadiene
(PS-PB) diblock copolymers. In this system, the lamellar

Chemische Physik und Polymerphysik Dienstag
orientation (parallel or perpendicular to the substrate) can be controlled
by block copolymer molar mass [1].
For low angles of incidence, the scattering intensity is maximum and
details are most pronounced. This results in short measuring times, thus
allowing for time-resolved measurements as well [2]. Interpreting the twodimensional
GISAXS maps, the refraction of the X-rays at the surface of
the polymer film as well as their reflection by the substrate need to be
taken into account. This is possible by calculating the scattering cross
section in the framework of the distorted-wave Born approximation. Both
for the case of parallel and perpendicular lamellae, the model compares
well with the experimental results.
[1] P. Busch et al., Macromolecules 36, 8717 (2003).
[2] D.-M. Smilgies et al., Synchr. Rad. News 15, 35 (2002).
CPP 15.14 Di 17:00 B
Charakterisierung von Ruß-Kautschuk-Mischungen mittels
dielektrischer Spektroskopie — •Jöerg Ludwig und Dietmar
Göritz — Universitätsstraße 31, 93040 Regensburg
Zur Charakterisierung von Ruß-Kautschuk-Mischungen wurde eine
modifizierte dielektrische Meßmethode entwickelt. Hierbei werden neben
der eigentlichen Probe zwei zusätzliche Isolierschichten in den Meßkondensator
eingebracht. Dadurch wird die Reproduzierbarkeit der Ergebnisse
erheblich verbessert.
Anhand einer auf dieses System angepaßten Modellfunktion können
Parameter gewonnen werden, die das dielektrische Verhalten der jeweiligen
Mischung beschreiben. Aus diesen Parametern wiederum sind Informationen
hinsichtlich der inneren Struktur der Mischungen zu erhalten.
So kann z. B. die Dicke von gebundenen Kautschukschichten zwischen
perkolierenden Aggregaten abgeschätzt werden.
Untersucht wurde eine Reihe von Rußen, die sich in den üblichen Kenngrößen
stark unterscheiden. Die Probenserie für jede Rußsorte besteht
sowohl aus perkolierten als auch aus nicht perkolierten Mischungen. Die
Ergebnisse für sämtliche Ruße und Füllgrade können in einem einheitlichen
Rahmen interpretiert werden.
CPP 15.15 Di 17:00 B
Investigation of temperature dependent mechanical properties
of thin polymer films by AFM — •Andreas Kleiner 1 , Martin
Hinz 1 , Sabine Hild 1 , Othmar Marti 1 , Urs Duerig 2 , Bernd
Gotsmann 2 , and Tom R. Albrecht 2 — 1 Dept. of Exp. Physics, University
of Ulm, 89069 Ulm — 2 IBM Research Division, Zurich Research
Laboratory, CH-8803 Rueschlikon
Atomic Force Microscopy provides the possibility to probe mechanical
properties on nanometer scale. Combining the AFM with a heating
device for sample temperatures up to 420 K enables to investigate mechanical
properties and the thermal stability of nanostructures on thin
films at temperatures below and above the glass transition. In this study,
polymethylmethacrylate films with a molecular weight of 350 kg/mol and
a bulk glass transition temperature of 388 K are used, prepared by spincoating
on silicon substrates. The indentation behavior of a AFM tip
gives characteristic quantities like stiffness or the energy of hysteresis. In
addition to these force curve measurements, the thermal stability of the
nanostructures is determined by measuring the time evolution of the topography.
The velocity of the observed polymer relaxation as function of
the sample temperature reveals clearly the glass transition of the PMMA
film.
CPP 15.16 Di 17:00 B
Adhesion behavior of poly(urethane) foam on thermoplastics
— Karsten Busse, Nasir Mahmood, Jörg Kressler, Karsten
Busse, Nasir Mahmood, and •Jörg Kressler — Fachbereich Ingenieurwissenschaften,
Martin-Luther-Universität Halle-Wittenberg
Detailed characterization of polymer surface properties under structural
and morphological aspects is a high priority activity In our study
three formulations of poly(urethanes) are foamed in contact with different
thermoplastic materials. A thin PU-film at the interface is responsible
for the adhesion behaviour which is investigated XPS, ToF-SIMS, TEM,
NR and other methods. It was found that silicon oil remains on the foam
side after skinning from TP and parts of the foam are linked to the TP
surface. The thin film at the interface is regularly structured with alternating
layers with a typical thickness of 250-300 nm.
CPP 15.17 Di 17:00 B
EFFECT OF CROSS-LINKING AND REDUCED DIMEN-
SIONS ON THE INTERNAL FRICTION IN POLYMERS —
•Tatjana Haramina, Hans-Georg Brion, and Reiner Kirchheim
— Institut fuer Materialphysik, Uni-Goettingen, Tammanstr. 1, D-37077
Goettingen
The capacity of materials to damp out vibrations (internal friction)
is a function of a time lag between stress and strain and is related to
anelastic strain. The anelastic strain of polymer materials results from
sliding of chains, movements of segments and side groups. This internal
friction can be observed by means of mechanical spectroscopy.
The vibrating reed apparatus is developed to measure the damping of
supported amorphous polymer films. The damping is observed at about
520Hz at the temperature range from 300K to 500K. The relaxation processes
lead to peaks in mechanical spectra.
Photo-cross-linking of Poly(Vinyl Cinnamate) should decrease mobility
of polymer chains and influence the internal friction. The opposite effect
is expected from thin polymer films, where because of the big influence
of the opened surface the molecular mobility should increase.
CPP 15.18 Di 17:00 B
Domain structure of novel amphiphilic polymers in bulk and
in thin films — •Sofiya Raleva 1 , Bernd Stühn 1 , Karsten
Busse 2 , Jörg Kressler 2 , Holger Kautz 3 , and Holger Frey 4
— 1 Institute of Solid State Physics, Technische Universität Darmstadt,
D-64289 Darmstadt — 2 Department of Engineering Science, Martin-
Luther-University Halle-Wittenberg, D-06099 Halle — 3 Institute of
Macromolecular Chemistry, University of Freiburg, D-79104 Freiburg
— 4 Institute of Organic Chemistry, Johannes Gutenberg University,
D-55128 Mainz
We have investigated novel amphiphilic polymers with linear and hyperbrached
architecture. One series of amphiphiles are linear blockcopolymers
of PEO and Perfluorohexylethylmethacrylate (PFMA). A second
series are linear-dendritic poly(propylene oxide)-polyglycerol surfactants.
Langmuir-Blodgett films from these materials were deposited from chloroform
solutions with concentration 2 mg/ml onto silicon substrates at
room temperature and at a surface pressure of 35 mN/m.
Their structural properties were studied using X-ray reflection. The
results provide information on film thickness, surface roughness and electron
density variation perpendicular to the film surface. Layered structures
were found for most samples. The bulk structure was determined
using small angle X-ray scattering in Kratky geometry. Layered as well
as three dimensional structures were found. We compare the results with
the bulk properties of the materials in particular with respect to the
stability of the thin films.
CPP 15.19 Di 17:00 B
Crystallization of poly(ethylene-co-octene) studied by timedependent
polarized and depolarized light scattering —
•Takahiko Kawai and Gert Strobl — Fakultät für Physik,
Universität Freiburg, Freiburg, Germany
Isothermal crystallization of poly(ethylene(0.86)-co-octene(0.14)) from
the melt was studied by time-resolved simultaneous vv(polarized) and
hv(depolarized) light scattering measurements. The scattering pattern
showed that poly(ethylene-co-octene) formed spherulite independing on
the crystallization temperature. The power law of the forward scattering
intensity I0 was 3.5, which seemed to be quite unusual for the normal
spherulitic growth(one expects I0 ∼ t 6 ). At low crystallization tempera-
ture, both I vv
0 and Invariant Q vv goes over maximum as expected from
theory, while two step increase was observed in Q vv at high temperature.
It implies that densification occurs prior to the formation of crystals.
CPP 15.20 Di 17:00 B
Rigid amorphous fraction and reversing melting of semicrystalline
polypropylene — •Heiko Huth, Dmitry Mordvintsev,
and Christoph Schick — Universität Rostock, Fachbereich Physik,
Universitätsplatz 3, 18051 Rostock
For semicrystalline polymers the observed relaxation strength at glass
transition is often significantly smaller than expected assuming a two
phase model with crystalline and non-crystalline fraction. This observation
leads to the three phase model introducing the rigid amorphous
fraction (RAF) as a third fraction beside crystalline and non-crystalline
fraction. This RAF is non-crystalline and in a glassy state at temperatures
above the common glass transition. The RAF does not contribute to
the heat of fusion or X-ray crystallinity nor to the relaxation strength at

Chemische Physik und Polymerphysik Dienstag
glass transition. Determination of the three fractions using calorimetric
measurements is possible, knowing crystallinity and baseline heat capacity.
Unfortunately, often an excess heat capacity due to reversing melting
is observed. It is frequency dependent and disappears at higher frequencies.
Using different methods for measuring frequency dependent heat
capacity it is possible to determine baseline heat capacity in the high
frequency limit. This approach was applied to polypropylene.
CPP 15.21 Di 17:00 B
Infrared ellipsometry for investigation of heterogeneous
polyethylene films — •K. Hinrichs 1 , M. Gensch 1 , A. Röseler 1 ,
U. Schade 2 , H. M. Heise 3 , and E. H. Korte 1 — 1 Institut für
Spektrochemie und Angewandte Spektroskopie - Institutsteil Berlin, —
2 Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung
mbH, Albert- Einstein-Str. 15,D- 12489 Berlin — 3 Institut für
Spektrochemie und Angewandte Spektroskopie - Institutsteil Dortmund
Free standing films of different polyethylene grades are investigated
by infrared ellipsometry. In order to determine the optical constants the
measured ellipsometric spectra are simulated in an optical layer model.
The investigation in a reflection geometry is of advantage because the
about 0.5 mm thick films are not transparent in the spectral range of
the absorption bands of the CH2 bending and stretching vibrations. The
ellipsometric spectra using a globar source or the radiation of the synchrotron
storage ring at BESSY II are discussed with respect to a lateral
heterogeneity in thickness and chemical structure.
CPP 15.22 Di 17:00 B
Fingering Instability in Dewetting Films Induced by Slippage
— •Chiara Neto 1,2 , Andreas Münch 3 , and Karin Jacobs 2 —
1 Australian National University, Dept. of Applied Mathematics, Canberra
— 2 Saarland University, FR 7.2 Experimental Physics, Saarbrücken
— 3 Humboldt University, Faculty of Mathematics, Berlin
Polystyrene thin films are not stable on hydrophobised silicon wafers
and upon annealing they dewet, giving rise to circular holes. The rim
formed at the border of these holes becomes unstable and presents fingerlike
patterns. Here we present the results of our studies performed on
this type of instability, that is not driven by external forces, both experimentally
and theoretically. Results obtained in experiments can be
well explained by a theoretical lubrication model that allows for liquid
slippage at the liquid/solid interface.
CPP 15.23 Di 17:00 B
FT-IR Spectroscopy on Ferroelectric Liquid Crystal Polymers
and Elastomers — •Michael Tammer 1 , Rudolf Zentel 2 , and
Friedrich Kremer 1 — 1 University of Leipzig, Faculty for Physics and
Earth Siences, Linnestr. 5, 04103 Leipzig — 2 University of Mainz, Institute
of Organic Chemistry, Duesbergweg 10-14, 55099 Mainz
Time-resolved polarized Fourier Transform Infrared (FTIR) Spectroscopy
is employed to analyse the structure and dynamics in ferroelectric
liquid crystal (FLC) polymers and elastomers. The specifity of
the IR-spectroscopy enables us to study for the different molecular moieties
the response to external mechanical end electrical excitations. By
that, subtle details of the microscopic motion such as angular excursion,
reorientation time, order parameter, asymmetries in the reorientational
behaviour or elastomeric memory effects can be unravelled for the system
under study.
CPP 15.24 Di 17:00 B
Influence of molecular weight on structure and dynamics in a series
of nanophase-separated poly(n-butyl methacrylates) — •K.
Schröter, E. Hempel, S. Hiller, and M. Beiner — FB Physik,
Martin-Luther-Universität Halle-Wittenberg, 06099 Halle, Germany
A series of monodisperse n-butyl methacrylate (nBMA) systems reaching
from high molecular weight polymers with about 400 monomeric
units down to oligomers with only six units per chain and including also
dimer and monomer was investigated by conventional and temperaturemodulated
calorimetry, dielectric spectroscopy as well as X-ray scattering
methods. There are two main aspects that are of interest here: (i) For
high molecular weight samples indications for a nanophase separation of
incompatible main and side chain parts were observed. Main arguments
are the coexistence of two relaxation processes with typical features of
a dynamic glass transition and a prepeak in X-ray scattering data indicating
a Bragg spacing of about 1.2 nm. It will be shown here that the
prepeak starts to disappear below 25 monomeric units in the main chain.
This shows that a certain chain length is required before nanophase sepa-
ration effects will occur. (ii) Changes in the conventional glass transition
(α) with chain length are analyzed based on data for our nBMA series.
Of special interest is the dependence of fragility – as obtained from dielectric
data for the α relaxation and calorimetric data – on chain length
in a series of samples including long polymer chains as well as small
molecule liquids. Thermodynamic fragility and steepness index are compared
and discussed in the light of recent discussions about this topic in
the literature.
CPP 15.25 Di 17:00 B
High frequency microtribology of polymer thin films with
quartz crystal resonators — •Binyang Du and Diethelm
Johannsmann — Institute of Physical Chemistry, Technical University
Clausthal,Arnold-Sommerfeld-Str. 4, 38678 Clausthal-Zellerfeld,
Germany
In present experiments, quartz crystal resonators coated with a
polystyrene film in contact with a ceramic sphere have been used to study
the micro scale tribology at high frequency (15MHz)and a shear amplitude
in the nanometer range. The experiment is based on the ring-down
of the resonator, where the electrical excitation is periodically interrupted
and the free decay of the oscillation is analyzed. When a small ceramic
sphere is put onto the center of quartz surface, the shear motion of the
quartz is perturbed due to the external stress of sphere, which can be
used to study force ∼ displacement and force ∼ speed relations in the
contact zone. A nonlinear spring constant κ(x) and a nonlinear friction
coefficient ξ( ˙x) are explicitly derived. Two transitions are observed with
increasing shear amplitude, one is from stick-to-partial slip and the other
is from partial slip to-total slip. The nonlinear spring constant is in good
agreement with the microslip model, which indicates a maximum lateral
force and diverges in the transition of partial slip to total slip. The friction
force depends linearly on lateral speed in the partial slip region and
nonlinearly in total slip region, respectively.
CPP 15.26 Di 17:00 B
Dynamische Vorgänge bei der Deformation — •Marcus Wacha
und Stefan Kreitmeier — Fakultät für Physik, Polymerphysik, Universitätsstr.
31, 93053 Regensburg
Anhand eines kontinuierlichen Bondfluktuationsmodells wurde das Deformationsverhalten
von verschlauften Polymerketten untersucht.
Dazu wurden sogennante cnfined self avoiding walks mittels Applikation
externer Potentiale bei untrschiedlichen Dehngraden und bei Temperaturn
ober- und unterhalb des Glasübergangs simuliert.
Zur Beschreibung der dynamischen Vorgänge wurden, die mitteleren
Verschiebungsquadrate g1, g2 und g3 berechnet und diskutiert.
CPP 15.27 Di 17:00 B
Fingering Instability in Dewetting Films Induced by Slippage
— •Chiara Neto 1,2 , Andreas Münch 3 , and Karin Jacobs 2 —
1 Australian National University, Dept. of Applied Mathematics, Canberra
— 2 Saarland University, FR 7.2 Experimental Physics, Saarbrücken
— 3 Humboldt University, Faculty of Mathematics, Berlin
Polystyrene thin films are not stable on hydrophobised silicon wafers
and upon annealing they dewet, giving rise to circular holes. The rim
formed at the border of these holes becomes unstable and presents fingerlike
patterns. Here we present the results of our studies performed on
this type of instability, that is not driven by external forces, both experimentally
and theoretically. Results obtained in experiments can be
well explained by a theoretical lubrication model that allows for liquid
slippage at the liquid/solid interface.
CPP 15.28 Di 17:00 B
Soft particle model for block-copolymer systems — •Alexei
Karatchentsev 1 , Frank Eurich 1 , Wolfgang Dieterich 1 , and
Philipp Maass 2 — 1 Fachbereich Physik, Universität Konstanz, Germany
— 2 Institut für Physik, Technische Universität Ilmenau, Germany
We extend earlier work on the Gaussian ellipsoid model for homopolymers
[1,2] to diblock copolymers by developing a soft disphere model. In
this model diblock copolymers are described as two spheres connected by
an effective bond potential. The radii of the spheres and the monomer
densities within the spheres are derived from the Gaussian chain model.
By means of Monte-Carlo simulations we explore the complex phase diagram
of microphase segregation for the disphere model and compare our
results with experimental phase diagrams and with those obtained from
self-consistent field theory. In particular we discuss the scaling of characteristic
domain sizes with respect to the Flory-Huggins parameter and

Chemische Physik und Polymerphysik Dienstag
the chain length. Furthermore we show how the kinetics of microphase
ordering can be studied on large time and length scales, where entanglement
effects are negligible.
[1] F. Eurich and P. Maass, J. Chem. Phys. 114, 7655 (2001).
[2] F. Eurich, P. Maass, and J. Baschnagel, J. Chem. Phys. 117, 4564 (2002).
CPP 15.29 Di 17:00 B
Changes in the mechansim during isothermal polymer crystallizations:
Indications in scattering experiments on P(E-co-O)
andPεCL — •Barbera Heck, Peter Kohn, and Gert Strobl —
Physikalisches Institut der Albert-Ludwigs-Universität, 79104 Freiburg,
Germany
The kinetics of crystallization in polymer systems can be followed in
different experiments, and a comparison of the corresponding isotherms
provides special insights with regard to the mechanism. We carried
out such comparative studies for samples of poly(ethylene(0.86)-cooctene(0.14))
and poly(ε-caprolactone), employing time-dependent absolute
intensity SAXS coupled with WAXS, density measurements by
dilatometry and optical microscopy.
The measurements on P(E-co-O) showed a strict proportionality of the
Porod-coefficient P and a Bragg-reflection intensity I, but strong deviations
of the development of the density. Optical microscopy shows objects
with constant size but increasing birefringence rather then growing
spherulites. Obviously some densification occurs prior to the formation
of crystals.
For PCL it was found that the power-laws describing the increase in P
and I during the initial stage differ from each other, which is indicative for
a change of the inner order of the growing lamellae. The WAXS-pattern
includes in addition to contributions associated with melt-like regions and
crystals also a third contribution associated with a mesomorphic phase.
CPP 15.30 Di 17:00 B
Orientation of the Microdomains in Concentrated Block
Copolymer Solutions using Electric Fields: Confinement
Effects and Mechanisms — •Kristin Schmidt 1 , Helmut
Hänsel 1 , Frank Schubert 1 , Heiko Zettl 1 , Thomas Weiss 2 ,
Franz Fischer 3 , Volker Abetz 4 , Alexander Böker 1,5 , and
Georg Krausch 1 — 1 Physikalische Chemie II, Universität Bayreuth,
Bayreuth, Germany — 2 ESRF, Grenoble, France — 3 Kristallographie,
Universität Bayreuth, Bayreuth, Germany — 4 Makromolekulare Chemie
II, Universität Bayreuth, Bayreuth, Germany — 5 Department of
Polymer Science & Engineering, University of Massachusetts, Amherst,
USA
We investigate the microdomain orientation of concentrated block
copolymer solutions exposed to a DC electric field by time-resolved synchrotron
SAXS. As a model system, we use a lamellar polystyrene-bpolyisoprene
block copolymer dissolved in toluene. Depending on the
polymer concentration we can identify two different microscopic mechanisms
which dominate the orientation process, i.e. nucleation and growth
of domains and grain rotation. The former dominates close to the ODT,
while the latter prevails under more strongly segregated conditions.
Reduction of the electrode spacing from 2mm to 200µm leads to a
dramatic increase in the time constant of the orientation process, i.e.
it is slowed down significantly. This finding is attributed to a confinement
effect which finally results in complete trapping of the process.
Furthermore, in the case of highly segregated samples we observe that
increasing confinement suppresses the grain rotation mechanism, favoring
nucleation and growth for highly confined systems.
CPP 15.31 Di 17:00 B
Evidence of pre-order in polymer melts revealed from dielectric
spectroscopy — •Andreas Wurm, Ragab Soliman,
and Christoph Schick — Universität Rostock, Fachbereich Physik,
Universitätsplatz 3, 18051 Rostock
Existence and formation of pre-ordered structures as the initial step of
polymer crystallization are discussed controversially. Most of the findings
and interpretations are based on scattering experiments, which test small
density differences between the assumed precursors of the crystals and
the surrounding melt. Because of the low contrast the interpretation of
experimental results becomes often speculative. Contrary relaxation experiments
are probing motions in the sample and are therefore independent
on density contrast. During crystallization material is transformed
from the liquid to the solid state. Consequently, motions (fluctuations)
typical for a liquid become impossible and do not longer contribute to
the measured relaxing signal. For pre-ordered structures we expect some
decrease in mobility too because of the changes in conformation on preordering.
On the other hand due to the formation of regions with different
order new internal surfaces will be formed. At such surfaces Maxwell-
Wagner-Sillars charge carrier relaxation may occur and contribute to the
measured dielectric signal.
We have studied the complex dielectric permittivity of polycaprolactone
(PCL) and polypropylene (sPP) during non-isothermal and isothermal
crystallization in the frequency range from 0.01 Hz to 10 MHz.
CPP 15.32 Di 17:00 B
Electric field induced structural fluctuations in lamellar block
copolymers — •Xiuli Jiang 1 , Thomas Thurn-Albrecht 1 ,
Thomas Gutberlet 2 , Mukul Gupta 2 , and Daniel Clemens 2 —
1 Martin-Luther-Universitaet Halle-Wittenberg,Fachbereich Physik,D-
06099 Halle — 2 Paul Scherrer Institut,Lab. f. Neutron Scattering,5232
Villigen PSI,Switzerland
Lamellar microphase structures formed in symmetric diblock copolymers
[1], as well as cylindrical microdomains formed in asymmetric diblock
copolymers [2], can be oriented by an external electric field. Though
the mechanism of the orientation is not fully understood yet, it is believed
that the electric field induces an instability connected with structural
fluctuations or undulations leading eventually to a disruption of
the original structure which facilitates alignment to set in. Using neutron
reflectometry the current study investigates these undulations in
films of different thicknesses with and without application of an electric
field. To map the intensity in the relevant range of reciprocal space we
use the newly established time-of-flight (TOF) mode on the AMOR neutron
reflectometer at the Paul-Scherrer-Institute. Our results show that
thermally excited fluctuations always exist. The film thickness was shown
to be an important parameter governing the length scale as well as the
amplitude of the undulations. As expected the electric field leads to an
amplification of undulations with smaller wavelengths. [1] K. Amundson,
E. Helfand, D. D. Davis, X. Quan, S. S. Patel and S. D. Smith, Macromolecules
24, 6546 (1991). [2] T. Thurn-Albrecht, J. DeRouchey, T. P.
Russell and R. Kolb, Macromolecules 35, 8106 (2002).
CPP 15.33 Di 17:00 B
Phase Diagram and Morphologies of Crystalline/Crystalline
Poly (Vinylidene Fluoride)/Poly (3-Hydroxybutyrate) Blends
— •Jieping Liu and Bernd-J Jungnickel — Deutsches Kunststoff-
Institut, Schlossgartenstr. 6, D-64289 Darmstadt, Germany
The melting point depression and a single glass transition in the
phase diagram evidence that PVDF and PHB are completely miscible
in the melt. PVDF crystallizes first and PHB second upon cooling. At
isothermal two-step crystallization, the components behave quite different.
Crystallization temperature and rate, respectively, of PVDF decrease
with increasing PHB content since PHB acts as a diluent; the PVDF crystallization
is ruled only by crystallization temperature and initial composition.
In contrast, PHB crystallization depends on the already existent
PVDF morphology since PHB may be included in or rejected from the
PVDF spherulites depending on the PVDF crystallization temperature.
The inclusion of PHB into PVDF dendrites reduces the available dimension
for PHB crystal growth (Avrami exponent n = 2) whereas the
PHB crystallizes undisturbed tri-dimensionally with athermal nucleation
in the surroundings of globular PVDF spherulites (n = 3). At a given
temperature, the crystallization rate of PHB inside the PVDF spherulites
is distinctly larger than that of PHB outside. These results underline the
microscopic findings on the complex supermolecular structure in that
blend.
CPP 15.34 Di 17:00 B
Charakterisierung der Strukturbildung in Blockcopolymeren
mit Minkowskifunktionalen — •S. Scherdel 1 , A. Horvat 1 , K.
R. Mecke 2 und R. Magerle 1 — 1 Physikalische Chemie II, Universität
Bayreuth — 2 Max-Planck-Institut für Metallforschung, Heisenbergstr. 3,
70569 Stuttgart
Blockcopolymere sind langkettige Moleküle, die aus zwei unterschiedlichen
Komponenten bestehen. Durch Mikrophasenseparation bilden
Blockcopolymere komplexe Strukturen mit Mikrodomänen im 10-100 nm
Bereich. Die physikalischen Eigenschaften des Materials hängen wesentlich
von seiner räumlichen Struktur ab. Häufig ist diese unregelmäßig,
was die Analyse und Interpretation der Struktur-Eingeschafts-Beziehung
sehr erschwert. Wir verwenden die aus der Integralgeometrie bekannten
Minkowskimaße, um Mikrodomänenstrukturen zu charakterisieren.

Chemische Physik und Polymerphysik Dienstag
Wir berechnen z.B. die mittlere radiale Dichteverteilung in einer Mikrodomäne.
Ferner haben wir mit Minkowskifunktionalen die Dynamik
von Strukturwandlungen zwischen geordneten und ungeordneten Phasen
untersucht, die wir mit dynamischer Dichtefunktionaltheorie simulieren.
Wir vergleichen unsere Ergebnisse mit Fourieranalysen und Analysen von
Skeletten der Mikrodomänenstrukturen.
CPP 15.35 Di 17:00 B
Adsorption of a heteropolymer on a structured surface —
•Thorsten Bogner, Friederike Schmid, and Andreas Degenhard
— Condensed Matter Theory, Fakutät für Physik, Universität
Bielefeld, Postfach 100131, 33501 Bielefeld
The specific adsorption of a molecule, especially of a protein, on a
surface is of interest in biological processes as well as for technical applications.
The specificity within such molecular recognition processes
results from unspecific non-covalent interactions. For proteins in a solvent,
the spatial arrangements of the single monomers is determined by
the same non-covalent interactions that lead to molecular recognition. As
a result, the structure and therefore the physical shape of the protein is
affected by the adsorption.
We have calculated the energy spectra of a single heteropolymer for
both, the non adsorbed as well as the adsorbed case, considering all possible
compact folds. The heterogeneity of the polymer, as well as the
structure of the surface was characterised by a sequence or respectively
a pattern of hydrophobic and hydrophilic (polar) sites.
Our calculations allowed to identify a preference of a surface pattern
and to make a first attempt to define selectivity. We found general features
among sequences that are selective for a particular surface pattern.
These allow to identify relevant positions on the polymer chain, that decide
if a particular surface is recognised. Furthermore, we were able to
find sets of sequences that can recognise all surfaces by a process similar
to mutations.
CPP 15.36 Di 17:00 B
Brillouin-microscopy, a versatile technique to study the
mechanical properties of polymers — •Ravindrakumar BAC-
TAVATCHALOU 1,2 , Roland SANCTUARY 1,3 , Jan Kristian
KRÜGER 1,2 , Uli MÜLLER 1,2 , and Wolfgang MANGLKA-
MMER 1,2 — 1 Laboratoire Européen de Recherche Universitaire
Saarland-Lorraine (LERUSL) — 2 Universität des Saarlandes, Experimentalphysik,
Postfach 151150, D-66041 Saarbrücken, Germany
— 3 Université du Luxembourg, Avenue de la Faïencerie, L-1511,
Luxembourg
Brillouin spectroscopy (BS) is a versatile method to study the elastic
properties of bulk and film-like samples. In contrast to the well established
micro-Raman technique such a spatial resolving technique was not
yet available for BS. We propose here a new kind of Brillouin microscopy
(BM) without using a standard optical microscope, instead we use a home
made optical magnifier in combination with a spatial filtering and scanning
set-up. We will show that this new Brillouin technique is especially
valuable for the investigation of polymers. Recently, a spatial resolution
about 1µm was demonstrated (J. Phys. D: Appl. Phys. 36 (2003) 2738-
2742). In order to prove the capability of BM we present and discuss the
mechanical properties of interphases in ’substrate-1/adhesive/substrate-
2’ sandwiches.
CPP 15.37 Di 17:00 B
Slippage and Nanorheology of Thin Polymer Films — •Renate
Konrad and Karin Jacobs — Experimental Physics, Saarland University,
POB 151 150, 66041 Saarbrücken
The properties of a liquid in contact with a solid interface are very
important for applications involving e.g. flow through porous media or
in lab-on-a-chip devices. Solving the hydrodynamic equations for a liquid
flowing over a solid surface, one usually assumes the relative velocity
between liquid and solid to be zero, which is the so-called ”no-slip boundary
condition”. Experiments with complex fluids and, very recently, also
with simple (Newtonian) fluids have shown that there can be a non-zero
velocity (”slippage”) at the boundary. The sizes involved are expected to
be on the nm-scale. On the same scale we therefore determine the velocity
and the shape of a moving liquid front. Both are known to serve as
extremely sensitive ”nano-rheometers”. It is expected from theory that
slippage is enforced for smooth and low surface-energy substrates. In our
experiments, we vary the substrate properties as well as the ones of the
liquid like viscosity and viscoelasticity. A significant correlation between
these system properties and the sliding friction can be found.
CPP 15.38 Di 17:00 B
Microdomain Ordering and Slippage of a Structured Liquid —
•Daniel Podzimek and Karin Jacobs — Saarland University, FR
7.2 Experimental Physics, D-66123 Saarbrücken
In this contribution we present flow properties and flow induced microdomain
ordering of a confined structured liquid that is dewetting a
solid substrate. The microdomains emerge, since the two blocks of the
copolymer poly(styrene-ethylene/propylene) are incompatible and phase
separate. The equilibrium film structure shows lamellae which are aligned
parallel to the substrate. We find that dewetting induced shear causes a
structural rearrangement of the microdomains into cylinders. AFM observations
furthermore show that the dewetting process can be separated
into two distinct stages. The first stage is characterized by round hole formation
and structural rearrangements of the domains. The second stage
of dewetting is defined by an irregular hole shape and the alignment of
the microdomain structure along the three phase contact line. Additional
to the experiments on the polymer surface we present AFM scans of the
film-substrate interface. Effects due to slippage of the melt are apparent.
CPP 15.39 Di 17:00 B
Characterisation of plasma treated fluorinated copolymers —
•Thorsten Meyer, Manfred ap. Prof. Neumann, Markus
Bach, and Andreas Selinger — Universität Osnabrück, FB Physik,
Barbarastrasse 7, 49069 Osnabrück
The functionalisation of polymer surfaces with plasma is established
for many fields and has several advantages compared to other chemical
modification methods.
For many industrial applications a rapid switching from hydrophobic to
hydrophilic surfaces is required. With plasma treatments chemical modifications
can be obtained, not reachable by simple wet chemical treatment.
In order to study and optimize the inner parameters of the plasma
treatment, the processing was studied under ultra clean conditions. The
plasma treated surfaces were investigated by x-ray photoelectron spectroscopy
(XPS), and atomic force microscopy (AFM) in combination with
contact angle measurments. The relation between the fractal dimension
and the wettability of the surface was studied.
CPP 15.40 Di 17:00 B
Zum Glaszustand dünner adsorbierter Polymerschichten —
•Richard Hofmann und Dietmar Göritz — Fakultät für Physik,
Universität Regensburg, 93040 Regensburg
Die Frage der Beweglichkeit von Polymerketten dünner adsorbierter
Schichten konnte bisher experimentell und theoretisch nicht widerspruchsfrei
geklärt werden. Insbesondere besteht Uneinigkeit über den
Einfluss des Trägermaterials auf die Glastemperatur und die kinetischen
Vorgänge in dessen Umgebung. Ziel unserer Untersuchungen ist es, den
Zustand der adsorbierten Polymerschicht durch die Messung der mechanischen
Eigenschaften des Adsorbats auf einem Füllstoff zu erfassen.
Die Experimente wurden an dem Modellsystem Hochorientierter Graphit
(HOPG) und Polymer mit Hilfe der AFM durchgeführt.
CPP 15.41 Di 17:00 B
Influence of preparation conditions on the piezoelectric activity
of ferroelectric polyamide 11 — •Alexander Kremmer1 , Peter
Fruebing1 , Michael Wegener1 , Werner Wirges1 , Reimund
Gerhard-Multhaupt1 , and Harald Goering2 — 1Department of
Physics, University of Potsdam, Am Neuen Palais 10, 14469 Potsdam —
2Federal Institute for Materials Research and Testing, Unter den Eichen
87, 12205 Berlin
The piezoelectric d33 coefficient of electrically poled commercial
polyamide-11 films as well as of ferroelectric films, prepared by melting
the powder in a hot press at 210◦C, quenching in ice-water, uniaxially
stretching with a ratio of 3:1 and subsequent electrical poling above the
coercive field (75 MV/m) is studied by use of dynamic piezoelectrical
measurements where a force acts on the film periodically and the piezoelectric
voltage across the film is measured. The influence of processing
conditions (particularly stretching and annealing temperatures) on the
piezoelectric activity and the temperature dependence of the piezoelectric
coefficient is investigated in detail. The aim is the enhancement of
the piezoelectric coefficient of the film material without losing its excellent
thermal stability up to temperatures just below the melting region.

Chemische Physik und Polymerphysik Dienstag
CPP 15.42 Di 17:00 B
Formation of thin PNIPAM layers on a metal surface by electrochemically
initiated free-radical polymerisation — •Helke
Reinhardt 1 , Ashok Kumar 2 , Andreas Bund 2 , and Diethelm Johannsmann
1 — 1 Institut fuer Physikalische Chemie, TU Clausthal,
Arnold-Sommerfeld-Str. 4, D-38678 Clausthal-Zellerfeld — 2 Institut fuer
Physikalische Chemie und Elektrochemie, TU Dresden, Mommsenstrasse
13, D-01062 Dresden
The aim of this work is the formation of thin PNIPAM layers on metal
electrodes. A quartz crystal microbalance was used for monitoring the
polymerisation.
The polymerisation of NIPAM crosslinked with bisacrylamide was ini-
tiated by metallic ions from sacrificial anodes in the presence of peroxy-
disulfate. The formation of the anion radicals SO •−
4 as initiator and the
consequent polymerisation is therefore controlled by the current flowing
through the system. Since polymerisation starts at the electrode the gel
forms at the surface. We now concentrate on improving adhesion properties.
Depending on the temperature of polymerisation and degree of
crosslinking, PNIPAM layers show a lower critical solvent temperature
(LCST) behaviour and as a consequence, the formation of a lateral
structure.
Layer properties are investigated as a function of temperature, of applied
voltage, degree of crosslinking, of monomer concentration, and other
system parameters.
CPP 15.43 Di 17:00 B
Micellization Behaviour of Diblock Copolymers based on
2-(acetoacetoxy)ethyl methacrylate — •Reinhard Sigel,
Theodora Krasia, and Helmut Schlaad — Max Planck Institute
of Colloids and Interfaces, D-14476 Potsdam-Golm
Micelles of poly(n-butyl methacrylate)-block-poly[2-
(acetoacetoxy)ethyl methacrylate] (PBMA-b-PAEMA) block copolymers
in cyclohexane were investigated by static and dynamic light scattering.
A shape transition from spherical micelles to wormlike chains is
induced by shortening the soluble BMA block or swelling the AEMA
core with the selective solvent 2,2,2-trifluoroethanol. The discussion
within a model introduced by Förster and Antonietti [1] connects the
occurence of this shape transition to the high value of the Flory-Huggins
interaction parameter χ, which is estimated to be χ ≈ 0.8.
[1] S. Förster, M. Zisenis, E. Wenz, M. Antonietti; J. Chem. Phys. 104,
9956 (1996)
CPP 15.44 Di 17:00 B
Diffusion in entquollene Polymernetzwerke — •Ralf Delto
und Rüdiger Brenn — Physikalisches Institut, Universität Freiburg,
Hermann-Herder-Str.3, 79104 Freiburg
Wir untersuchen die Diffusion linearer Polymerketten (deuteriertes PS)
in eine Matrix aus vernetztem Polymer (protoniertes PS).
Die Polymernetzwerke werden durch Bestrahlung dünner (einige 100
nm) Polymerschichten auf Si-Substraten mit MeV-Ionen erzeugt. Mithilfe
statistischer Theorien lässt sich die Netzpunktdichte mit der Ionenstrahldosis
verknüpfen und über eine Grössenordnung gezielt einstellen.
Der nicht vernetzte Sol-Anteil wird chemisch gelöst, wodurch (eindimensional)
entquollene Netzwerke zurückbleiben. Im zweiten Schritt
wird eine Schicht aus linearem Polymer (dPS) aufgebracht. Die Diffusion
wird durch Tempern oberhalb der Glastemperatur ermöglicht.
Diffusionstiefenprofile der deuterierten Komponente werden mit MeV-
Ionenstrahlanalytik bestimmt.
Die Eindiffusion linearer Ketten führt das deformierte entquollene
Netzwerk in einen energetisch begünstigteren Zustand über, wobei der
elastische Energiebeitrag reduziert wird. Daher erwartet man eine schnellere
Diffusion als bei nicht entquollenen Systemen. Die Untersuchung
des zeitlichen Diffusionsverlaufs in solchen Systemen ermöglicht Aussagen
über Netzwerkmodelle, z.B. Clustermodelle mit Heterogenitäten der
Netzpunktdichte.
CPP 15.45 Di 17:00 B
Infrarotellipsometrie zur Untersuchung dünner anisotroper organischer
Filme — •M. Gensch 1 , K. Hinrichs 1 , K. Sahre 2 , K.-J.
Eichhorn 2 , Th. Köpnick 3 , B. Schulz 3 , N. Esser 1 , E.H. Korte
1 und A. Röseler 1 — 1 Institut für Spektrochemie und Angewandte
Spektroskopie - Institutsteil Berlin, Albert-Einstein-Straße 9, D-12489
— 2 Institut für Polymerforschung, Hohe Straße 6, D-01062 Dresden —
3 Institut für Dünnschichttechnologie und Mikrosensorik e.V., Kantstraße
55, D-14513 Teltow
Die Infrarot (IR) Ellipsometrie liefert in einem Experiment einen umfangreichen
Datensatz, der die Bestimmung der Dicke und der optischen
Konstanten von anisotropen Filmen erlaubt. Zur Bestimmung werden
iterative Berechnungen verwendet, die auf einem Modell aus der klassischen
elektromagnetischen Theorie beruhen. Aus der Interpretation der
anisotropen optischen Konstanten lassen sich Rückschlüsse auf strukturelle
Eigenschaften in einer Schicht ziehen [1]. Verschiedene mittels eines
”spincoating” Verfahrens präparierte Polymerfilme wurden untersucht.
Präparationsabhängige Unterschiede der anisotropen optischen Eigenschaften,
wie sie z.B. im Bereich der Carbonylstreckschwingung von unterschiedlich
dicken PI2611 Filmen auftreten, werden hinsichtlich daraus
ableitbarer Strukturmodelle diskutiert. [1] K. Hinrichs, D. Tsankov, E.H.
Korte, A. Röseler, K. Sahre, K.-J. Eichhorn, Appl. Spectrosc. 56,737-743
(2002)
CPP 15.46 Di 17:00 B
Holographische Untersuchungen an photoadressierbaren Blockcopolymeren
— •Michael Häckel 1 , Lothar Kador 1 , Carsten
Frenz 2 und Hans-Werner Schmidt 2 — 1 Experimentalphysik IV,
Universität Bayreuth, 95440 Bayreuth — 2 Makromolekulare Chemie I,
Universität Bayreuth, 95440 Bayreuth
Es wurde die Doppelbrechung verschiedener Blockcopolymere, die in
ihren Seitenketten Azobenzol-Chromophore und Mesogene enthalten, für
Anwendungen als optische Datenspeicher untersucht. Die Charakterisierung
erfolgte sowohl zwischen gekreuzten Polarisatoren mit gleichförmiger
Lichtintensität als auch mittels holographischer Gitter. Der Einfluss
mehrerer Parameter wurde gemessen.
Weiterhin konnte ein grundlegender optischer Effekt nachgewiesen werden,
der bei der Beugung an dicken Hologrammen auftritt und sich aus
den Kramers-Kronig-Relationen ergibt. In der Umgebung des Bragg-
Winkels erfährt das transmittierte (ungebeugte) Licht infolge der Beugung
in die 1. Ordnung nicht nur eine Abschwächung, sondern auch eine
Phasenverschiebung, die vom Einfallswinkel in die Probe abhängt. Die
Größe der Phasenverschiebung für Gitter unterschiedlicher Beugungseffizienzen
ist in guter Übereinstimmung mit analytischen Rechnungen.
CPP 15.47 Di 17:00 B
UV depletion of space charge studied with the Laser Intensity
Modulation Method — •Francisco Camacho González,
Axel Mellinger, and Reimund Gerhard-Multhaupt — Institut
für Physik, Universität Potsdam, Am Neuen Palais 10, 14469 Potsdam,
Germany
Recent experiments have indicated the presence of deeply trapped
space charges in polymeric electrets [1]. To obtain further information
on the trap depths, various polymer films (e.g. polyethylene terephthalate,
cycloolefin copolymers, and amorphous Teflon r○ AF) were charged
with either a corona–discharge or contacting electrodes. The charge and
the polarization profiles during UV irradiation were monitored in situ
using the Laser Intensity Modulation Method (LIMM).
A key advantage of this technique is its capability to non–destructively
probe of space–charge distributions in electrets. The experimental data
was analyzed using a combination of the scanning function method and
an iterative approach [2]. This novel technique is capable of reconstructing
unsmooth distributions without requiring a–priori assumptions about
the shape of the polarization profile.
[1] A. Mellinger, F. Camacho González, and R. Gerhard-Multhaupt,
Appl. Phys. Lett. 82 254 (2003)
[2] A. Mellinger, F. Camacho González, and R. Gerhard-Multhaupt, “Iterative
Solution of the LIMM Equation,” 4 th Asian Meeting on Ferroelectrics,
(Bangalore, India), December 12–15, 2003
CPP 15.48 Di 17:00 B
Complete phase diagram of a polymer chain from Monte Carlo
Simulations. — •Federica Rampf, Wolfgang Paul, and Kurt
Binder — Institut für Physik, Johannes Gutenberg-Universität, 55099
Mainz, Germany

Chemische Physik und Polymerphysik Dienstag
The collapse transition of polymer chains was studied for a long time,
inspired by the protein or DNA folding problems. Only recently it has become
possible to study the liquid-solid transition of the collapsed globule
through advanced Monte Carlo techniques. Here we study a single polymer
chain using the bond fluctuation lattice model for which we have developed
a fast and efficient simulation program, incorporating pivot and
slithering snake moves in addition to the normal random hopping moves.
A hierarchical search algorithm is employed to check the excluded volume
interaction and interacting neighbors. We use a random walk algorithm
in energy space to obtain an estimate of the density of states in a wide
energy range. From the density of states we determine thermodynamic
quantities such as free energy and specific heat capacity as a function of
temperature. From this we can identify the coil-globule transition as well
as the liquid-solid transition of the collapsed globule.
CPP 15.49 Di 17:00 B
Floating nanobuoys (Molecular Dynamics simulations of a
nanoparticle floating on polymeric liquid film) — •Juan G.
Diaz O., Martin Aichele, Wolfgang Paul, and Kurt Binder
— Institute for Physics, Johannes Gutenberg University, Staudinger
Weg 7, D-55099 Mainz, Germany
In this investigation we want to understand the dynamics of nanoparticles
(in the order of 5nm) on thin polymeric films, using Molecular Dynamics
techniques. We consider in our simulations a bead-spring model of
a polymer film adsorbed on a non-structured atractive wall. The particle
is modelled as a Lennard-Jones one and we study its equilibrium height
in the film as well as its dynamics at the film surface. The response of
the polymer to the presence of the nanoparticle also is investigated.
CPP 16 POSTER: Computational Physics, Complex Systems
Zeit: Dienstag 17:00–19:00 Raum: B
CPP 16.1 Di 17:00 B
Monte Carlo methods for propagating multi-dimensional
wave packets and density matrices — •M. Schröder 1,2 , U.
Kleinekathöfer 1,2 , and M. Schreiber 2 — 1 International University
Bremen, 28725 Bremen, Germany — 2 Institut für Physik, Technische
Universität Chemnitz, 09107 Chemnitz
The calculation of the time evolution of multi-dimensional wave packets
and density matrices can be a very CPU-time and memory consuming
process. Here we propose new mechanisms to reduce the dimensionality
of the problem at the expense of an additional stochastic process.
For density matrices a new method for stochastic unraveling of general
time-local quantum master equations (QME) which involve the reduced
density operator at time t only is proposed. The present kind of jump algorithm
enables a numerically efficient treatment of QMEs which are not
of Lindblad form [1]. A similar formalism is developed for the propagation
of multi-dimensional wave packets. As in a time-dependent Hartree
approach only one-dimensional wave packets have to be propagated. The
correlation between the dimensions is reintroduced through the stochastic
process.
[1] U. Kleinekathöfer, I. Kondov and M. Schreiber, Phys. Rev. E 66,
037701 (2002); J. Chem. Phys. 119, 6635 (2003).
CPP 16.2 Di 17:00 B
Optical absorption of water and ice calculated from first principles
— •Patrick H. Hahn, Wolf G. Schmidt, Kaori Seino, Martin
Preuss, and Friedhelm Bechstedt — Institut für Festkörpertheorie
und Theoretische Optik, Friedrich-Schiller-Universität Jena, Max-Wien-
Platz 1, 07743 Jena
The electronic excitations of water as the most important solvent play
a crucial role for many biological, chemical and physical processes. We
present first-principles calculations on the structural, electronic and optical
properties of cubic and hexagonal ice and of single water-molecules.
Thereby we proceed in three steps: (i) DFT-GGA calculations are used
to determine the structurally relaxed ground state, (ii) self-energy effects
are included within the GW approximation, and (iii) the Bethe-Salpeter
equation is solved using an equation of motion approach [1] to include
the effects of electron-hole attraction. The inclusion of many-particle effects
in the calculation of both ice and single water molecules leads to an
excellent agreement with the experimental results.
[1] Phys. Rev. Lett. 88, 016402 (2002).
CPP 16.3 Di 17:00 B
Tunable discotic building blocks for liquid crystalline displays
— •Michael Schreiber 1 , Sibylle Gemming 1 , Werner Thiel 2 ,
Thomas Heine 3 , Gotthard Seifert 3 , Heitor Avelino de
Abreu 3,4 , and Helio Anderson Duarte 4 — 1 Institut für Physik,
Technische Universität, D-09107 Chemnitz, Germany. — 2 Institut
für Chemie, Technische Universität, D-09107 Chemnitz, Germany.
— 3 Institut für Physikalische und Elektrochemie, Technische Universität,
D-01062 Dresden, Germany. — 4 Departamento de Quimica,
Universidade Federal de Minas Gerais, 31.270-901 Belo Horizonte MG,
Brasil.
Derivatives of 1,3,5-trispyrazolylbenzene (TPB) have been studied by
density-functional and semi-empirical methods to assess their potential
as building blocks for discotic liquid crystals. Structural and vi-
brational data provide evidence that TPB derivatives exibit properties
which favour the desired columnar stacking and allow the tuning of the
side chains. The molecules are planar and have a three-fold rotational
symmetry. According to a vibrational analysis all investigated molecules
exhibit sufficient rigidity for columnar stacking. Yet, they are also flexible
enough in order to tolerate small deformations which may occur as packing
effects. In addition, the dipole moments of the most stable conformers
are directed perpendicular to the molecular plane, thus they favour the
stacking to three-fold symmetric columns. It is therefore concluded that
TPB derivatives fulfill the necessary prerequisites for the formation of a
discotic-columnar phase with lateral order.
CPP 16.4 Di 17:00 B
Theoretical investigations of excited states of C3 — •Alexander
Terentyev, Reinhard Scholz, and Michael Schreiber — Institut
für Physik, Technische Universität Chemnitz
In this work, we present ab initio calculations for the potential energy
surfaces of C3 in different electronic configurations, including the singlet
ground state [ � X 1 Σ + g , (1 A1)], the triplet ground state [ã 3 Πu, ( 3 B1, 3 A1)],
and some higher excited states. The geometries studied include triangular
shapes with two identical bond length, but different bond angles between
them. For the singlet and triplet ground states in the linear geometry,
the total energies resulting from the B3LYP and QCISD approaches as
implemented in the gaussian98 package reproduce the experimental values,
i.e. the triplet occurs 2.1 eV above the singlet. In the geometry of
an equilateral triangle, we find a low-lying triplet state with an energy
of only 0.8 eV above the energy of the singlet in the linear configuration,
so that the triangular geometry yields the lowest excited state of C3. For
the higher excited states up to about 8 eV above the ground state, we
apply time-dependent density functional theory (TD-DFT) based on the
mixed B3LYP functional. Even though the systematic error produced by
this approach is of the order of 0.4 eV, the results give new insight into
the potential energy landscape for higher excitation energies.
CPP 16.5 Di 17:00 B
Different Modes of Spinodal Dewetting in a Two-Layer System
— •Andrey Pototsky 1 , Michael Bestehorn 1 , Domnic Merkt 1
und Uwe Thiele 2 — 1 lefrsuhl fue theoretische physik II, BTU, Erich-
Weinert Str. 1, D-03046, Cottbus, Germany — 2 MPI fuer Physik komplexer
Systeme, Noethnitzer Str. 38, D-01187, Dresden, Germany
We consider two ultra thin layers of different liquids on a solid substrate.
Using long wave theory coupled evolution equations for the free
liquid-liquid and liquid-gas interfaces are derived taken into account nonretarded
Van der Waals forces. Analisis of their linear and non-linear behavior
shows that, both, varicose and zigzag modes can be unstable and
lead to film rupture at the inner interface or substrate. The results are
exemplified using a Si/PS/PMMA/air system.

Chemische Physik und Polymerphysik Dienstag
CPP 16.6 Di 17:00 B
Photogeneration of charge carriers in blends of conjugated
polymers and semiconducing nanoparticles — •Johannes
Sieger 1 , Michael Pientka 1 , Jürgen Parisi 1 , Vladimir
Dyakonov 1 , Andrey Rogach 2 , Dimitri Talapin 3 , and Horst
Weller 3 — 1 Institute of Physics, Energy and Semiconductor Research,
University of Oldenburg, 26111 Oldenburg, Germany — 2 LMU Munich,
Photonics and Optoelectronics, 80799 Munich — 3 Physical Chemistry,
University of Hamburg, 20146 Hamburg
We investigated photoinduced charge transfer reactions in blends of
CdSe, InP nanoparticles with conjugated polymer OC1C10-PPV. The
particle size was in the range 3.1nm-4.1nm. They were capped with a
HDA-TOPO TOP shell and pyridine washed. Photoinduced absorption
spectroscopy (PIA) reveals structured features which are attributed to
photoexcited polaronic states on the polymer chain. Additionally the
photoluminescence in the blends is strongly quenched. We find a broad
distribution of lifetimes and a nearly square root behaviour in the laser
intensity dependence which altogether is characteristic for dispersive recombination.
The temperature dependence of the PIA signal shows an
unusual increase from low temperature up to 300K. By applying light
induced electron spin resonance the charge transfer process between the
polymer and the nanoparticles is confirmed by determining the g- factor
of the polaronic anion of the polymer.
CPP 16.7 Di 17:00 B
Oberflächenstruktur- und Verstärkungseigenschaften von Carbon
Black — •Gerald Schneider, Antje Bergmann, Tobias
Pöpperl, Ulrich Schwenk, Andreas Weigert und Dietmar
Göritz — Institut für Physik, Universität Regensburg, 93040 Regensburg
Die Oberfläche von Carbon Black besteht aus Nanokristallen, die
aus drei bis vier graphitähnlichen Schichten mit den Abmessungen von
2 nm × 2 nm aufgebaut sind. Beim Prozess der Graphitierung, dem
Tempern bei 2700 ◦ C, wachsen die Nanokristalle zu ausgedehnten Graphitebenen
zusammen und die verstärkende Wirkung des Carbon Black
nimmt ab. Mit den Methoden der Rastertunnelmikroskopie und der
Röntgenkleinwinkelstreuung werden die Größe und die Anordnung der
Nanokristalle auf der Oberfäche verfolgt. Die Ergebnisse werden im Vergleich
zu Daten, gewonnen an Carbon Blacks unterschiedlicher Aktivität,
im Bezug auf ihren Verstärkungsmechanismus diskutiert.
CPP 16.8 Di 17:00 B
Nanoparticle superstructures in carbonaceous matrix upon ion
irradiation of polymer-metal nanocomposites — •Oral Cenk
Aktas 1 , Abhijit Biswas 1 , Devesh Kumar Avasthi 2 , Dietmar
Fink 3 , Jörn Kanzow 1 , Ulrich Schürmann 1 , Usman Saeed 1 ,
Vladimir Zaporojtchenko 1 , and Franz Faupel 1 — 1 Lehrstuhl
für Materialverbunde, Technische Fakultät der CAU, Kaiserstr. 2, D -
24143, Kiel, Germany — 2 Nuclear Science Centre, New Delhi - 110067,
India — 3 Hahn-Meitner-Institut, Glienicker Str. 100, D - 14109, Berlin,
Germany
Nanoparticle re-arrangement is observed upon 120 MeV Au ion beam
irradiation of nanocomposites (ca. 100 nm) of Teflon AF containing different
metallic clusters at ion fluences ranging from 1 x 10 11 ions/cm 2 to
3 x 10 12 ions/cm 2 . Two dimensionally distributed Au clusters are found
to be transformed into long cluster chains of seemingly helical pattern in
the organic matrix like pearls on a string. Comparatively diluted three
dimensionally arranged Ag nanoparticles are observed to be concentrated
in the formed mesh of carbon-enriched nanoregions upon irradiation. Diffusionally
moving clusters are assumed to be trapped in the ion beam
induced additional free volume leading to different nanostructures.
CPP 16.9 Di 17:00 B
Size-dependent Assembly and Segregation of Nanoparticles at
Liquid-liquid Interfaces — •Heiko Zettl 1 , Yao Lin 2 , Alexander
Böker 2 , Habib Skaff 2 , David Cookson 3 , A.D. Dinsmore 4 ,
Todd Emrick 2 , Georg Krausch 1 , and Thomas P. Russell 2 —
1 Physikalische Chemie II, Universität Bayreuth, D-95440 Bayreuth, Germany
— 2 Department of Polymer Science and Engineering, University of
Massachusetts, Amherst, MA 01003, USA — 3 Advanced Photon Source,
Argonne National Laboratory, Argonne, IL 60439, USA and Australian
Nuclear Science and Technology Organization, PMB 1, Menai 2234, Australia
— 4 Department of Physics, University of Massachusetts, Amherst,
MA 01003, USA
The self-assembly of nanoparticles at fluid-fluid interfaces driven by
the reduction in interfacial energy was investigated. With nanoparticles
(2–6nm), thermal fluctuations compete with the interfacial segregation
giving rise to a size-dependent self-assembly of the nanoparticles and a
two-dimensional phase separation at the fluid interface. Studies on the
dynamics of the nanoparticles and the self-assembled structures formed
at the interface, using a pendant drop tensiometer, fluorescence photobleaching
methods and in-situ grazing incidence small angle x-ray scattering
(GISAXS), suggest a liquid-like behavior and ordering at the interfaces.
CPP 16.10 Di 17:00 B
Single Molecule Spectroscopy of Supramolecular Dye Assemblies
— •Erwin Lang 1 , Rainer Dobrawa 2 , Armin Sautter 2 ,
Frank Würthner 2 , and Jürgen Köhler 1 — 1 Experimental Physics
IV, University of Bayreuth — 2 Institute for Organic Chemistry, University
of Würzburg
Self-assembly processes of atoms and small molecules lead to
supramolecular structures with unbelievable variety and complex
functionality. One of the most intriguing examples in nature is the
light-harvesting system of purple bacteria, where bacteriochlorophyll
dyes are arranged in concentric rings by non-covalent interactions within
a self-assembled protein scaffold. As a model system for self-assembly
processes we study four pyridine-substituted perylene bisimide dyes and
four cis-Pt(II) metal centres, which form supramolecular squares by
metal-ion-directed coordination of the dye molecules.
In order to suppress inhomogenous line-broadening effects and to characterize
the mutual interactions between the subunits we apply singlemolecule
spectroscopic techniques. We present fluorescence-excitation
spectra of individual perylene bisimide dyes and preliminary studies of
individual multichromophoric perylene bisimide assemblies at low temperatures.
CPP 16.11 Di 17:00 B
Optical absorption of dendrimers — •Christoph Supritz, Andreas
Engelmann, and Peter Reineker — Department of Theoretical
Physics, University of Ulm, 89069 Ulm
Dendrimers are highly branched molecules, which are expected to be
useful for example as efficient artificial light harvesting systems in nanotechnological
applications. There exist two different classes of dendrimers:
compact dendrimers in which the distance between neighbouring branching
points is constant throughout the macromolecule and extended dendrimers,
where this distance increases from the system periphery to the
center. We investigate the linear absorption spectra of these dendrimer
types using the Frenkel exciton concept. To investigate the influence of
static disorder, we have chosen the localized exciton energies to be randomly
distributed. In our calculations we have taken the electron-phonon
interaction into account by introducing a heath bath, that interacts with
the exciton in a stochastic manner.
CPP 16.12 Di 17:00 B
Hydrogen Bonds and Molecule Trapping in Calix[4]hydroquinone
Nanotubes Investigated by Solid-State MAS NMR — •Anke
Hoffmann, Daniel Sebastiani, Erli Sugiono, Hans Wolfgang
Spiess, and Ingo Schnell — Max Planck Institut fuer
Polymerforschung, Postfach 3148, 55021 Mainz, Germany
Recent progress in solid-state NMR has opened up new possibilities for
investigations of supramolecular order phenomena. We use these methods
to study nanotubes built from calix[4]hydroquinones in the course of
a self-assembly process. In presence of water the bowl-shaped molecules
form the tubular structure via chains of hydrogen bonds, in which bridging
water molecules are inserted between hydroxyl groups of the hydroquinone
moieties. In the crystallites, these tubes form bundles with intertubular
aromatic-aromatic interactions (displaced π-π stacking pairs)
in chessboard like arrays of rectangular structure. The structure of the
hydrogen bonds and the localisation of aromatic π-electron systems as
well as the dynamics of solvent molecules trapped in the tubes are characterised
by 1H and 2H solid-state NMR experiments. The assignment
and interpretation of the 1H resonance frequencies is aided by 1H shift
calculations under periodic boundary conditions performed in the framework
of DFT. Future work will focus on the inclusion of metal ions as
well as on the formation of metal ”nanowires” inside the hydroquinone
tubes.

Chemische Physik und Polymerphysik Dienstag
CPP 16.13 Di 17:00 B
Foamy Emulsions confined in Channels: Digital Microfluidics
— •Gangyao Wen 1,2 , Stephan Herminghaus 1,2 , and Ralf Seemann
1,2 — 1 Abteilung Angewandte Physik, Universitaet Ulm — 2 MPI
fuer Stroemungsforschung, Goettingen
Microfluidics is usually concerned with single phase liquids transported
along solid microchannels. In the present project, we demonstrate possibilities
of using instead a compartmented liquid consisting of an emulsion
of water in oil, where the oily phase has a very small volume fraction.
This is geometrically quite analogous to a foam, which exhibits a variety
of transitions in its topology upon interaction with an externally provided
(temporally variable) geometric constraint. The main issue here
is the interplay of the internal length scale of the fluid, i.e., the size of
the droplets, with the lateral dimension of the channels. We exploit the
(potentially well controlled) manipulation of the emulsion droplets by
the channel geometry in order to position, sort, exchange, compile and
redistribute liquid compartments with different chemical contents.
CPP 16.14 Di 17:00 B
Switching of wetting morphologies by electrowetting: open microfluidics
— •Ralf Seemann 1,2 , Jean-Christophe Baret 1,3 , and
Stephan Herminghaus 1,2 — 1 Abteilung Angewandte Physik, Universitaet
Ulm — 2 MPI fuer Stroemungsforschung, Goettingen — 3 Philips
Research, Eindhoven
We have studied, both experimentally and theoretically, the wetting
behavior of a liquid in rectangular grooves with chemically homogeneous
walls. The length scale has been chosen to be small compared to the
capillary length in order to avoid gravitational effects, but large enough
that for long range wetting forces (such as the van der Waals force) to be
irrelevant. We derived (theoretically) the morphological phase diagram
of liquid channels confined in the grooves as a function of aspect ratio
and contact angle. Droplets form elongated morphologies for large aspect
ratios and high wettability of the substrate. For sufficient large contact
angles or small aspect ratios no confinement occurs. For manipulating
small amounts of liquids on that substrate we used electrowetting. This
way we could change the contact angle of the liquid on the substrate and
switch in between various equilibrium wetting morphologies of the free
liquid surface. Using this effect, liquids could be transported on a substrate
bearing appropriate steps and grooves. Particular emphasis will be
on the switching behavior of the various liquid morphologies.
CPP 16.15 Di 17:00 B
Comparison of forces in free-standing films and wetting films —
•Regine v. Klitzing and Kasia Ciunel — Stranski-Laboratorium,
TU Berlin, Strasse d. 17. Juni 112, 10623 Berlin
Thin aqueous surfactant films give the opportunity to study the interactions
between two opposing interfaces. The sum of interactions between
the film surfaces is determined quantitatively by the disjoining pressure
(disjoining pressure vs. film thickness) and is measured by varying the
outer pressure in a so-called thin film pressure balance. To study the effect
of interfaces the results of foam films (two air/liquid interfaces) and
wetting films (one air/liquid interface and one solid/liquid interface) will
be compared. In dependence on the surface charge a transition from a
Common Black Film (CBF, thickness determined by DLVO forces) to a
Newton Black Film (NBF, thickness determined by steric forces) can be
induced or avoided. This has a decisive effect on the film stability.
CPP 16.16 Di 17:00 B
The self-assembly of alkyl-trichlorosilanes on model surfaces
of biphenylthiols — •Svetlana Stoycheva 1 , Michael Himmelhaus
1 , Abraham Ulman 2 , and Michael Grunze 1 — 1 Lehrstuhl f”ur
Angewandte Physikalische Chemie, Universit”at Heidelberg, Im Neuenheimer
Feld 253, 69120 Heidelberg — 2 Dept. of Chem. Eng., Chem., and
Mat. Sci., Polytechnic University, Brooklyn, New York 11201, USA
Despite of its technological relevance, the self-assembly of monolayers
of alkyl-trichlorosilanes onto oxidized semiconductor surfaces is still not
fully understood. Phenomena, such as island formation and polymerization,
hamper the formation of a densely packed and well-oriented monolayer
in many cases. In particular, it has been found that the amount
of surface- adsorbed water plays a crucial role for the process of film
formation.
In our study we aim at elucidating the process of film formation
of alkyl-trichlorosilanes by adsorbing the molecules from solution onto
model surfaces with a well-defined density of anchor sites. Thereby, we
utilize mixed self-assembled films of hydroxyl- and methyl-terminated
biphenylthiols on gold. By variation of the mixing ratio, surfaces with
controlled surface hydrophilicity and different number of anchor sites
can be fabricated.
The model surfaces as well as the bilayer assemblies are characterized
by contact angle measurements, spectral ellipsometry, infrared reflection
absorption spectroscopy, and X-ray photoelectron spectroscopy.
CPP 16.17 Di 17:00 B
Characterisation of water/hydrophobic interfaces — •Marco
Maccarini 1 , Michael Himmelhaus 1 , Jörg Fick 1 , Michael
Grunze 1 , and Roland Steitz 2 — 1 Ruprecht Karls Universität
Heidelberg , Im Neuenheimer Feld 253, D-69120 Heidelberg — 2 Berlin
Neutron Scattering Center, Hans Meitner Institut, Glienicker St 100
Solid/liquid interfaces between water and hydrophobic surfaces are of
great interest because of the crucial role they play in the stabilisation
of supramolecular structures, mesoscopic assemblies, nanoparticles and
micelles in chemical technology and in biological systems, and of proteins,
membranes and cells in aqueous environment. Theoretical studies
(Lum 1999,Pertsin 2002) predicted a depletion layer, i.e. a layer of water
with reduced density, near the hydrophobic surface/water interface.
This extends to a thickness in the order of nm into the bulk water and
is thermodynamically less stable than the vapour phase. In order verify
experimentally the density changes occurring on such a short lengthscale,
stable hydrophobic model surfaces, flat on a molecular scale, are
needed. We assessed the stability of two different hydrophobic surfaces,
passivated silicon and HDMS coated silicon (contact angle ∼ 90 ◦ ) with a
roughness of the order of few ˚A, against water: changes in hydrophobicity
and surface oxidation were determined by contact angle, ellipsometry,
and XPS. Preliminary studies on on the water depletion layer have been
carried out by Neutron Reflectometry on HMDS coated silicon, oxided
silicon, self assembling monlayers (SAM) of alkanthiols on gold.
CPP 16.18 Di 17:00 B
The Interaction of Water with Oligo(Ethylene Glycol)-
Terminated Self-Assembled Monolayers on Gold and Silver
Investigated by IR and Vibrational Sum-Frequency Spectroscopy
— •Rong-Yao Wang, Jörg Fick, Sascha Herrwerth,
Wolfgang Eck, Michael Himmelhaus, and Michael Grunze
— Lehrstuhl für Angewandte Physikalische Chemie, Universität
Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg
Due their unique protein repulsion properties, self-assembled monolayers
of oligo(ethylene glycol)-terminated alkanethiols have been intensively
studied throughout the last decade. Particularly the structure of
the films in contact to aqueous solutions has been at the focus of interest,
recently.[1]
In the study presented here, we applied infrared reflection absorption
spectroscopy (IRRAS) and vibrational sum frequency generation
spectroscopy (VSFS) to investigate water-induced structural changes in
methyl (1-mercaptoundec-11-yl) hexa (ethylene glycol)-terminated alkanethiols
(EG6) formed on thin Au and Ag films. Spectra were recorded
right after preparation of the monolayers as well as after their exposure
to water. In the case of gold as a substrate, the films were also investigated
during water contact. The spectra indicate that water causes
pronounced disorder effects in the EG6 layers, which are only partially
reversible after drying of the films. Further, VSFS turns out to be more
sensitive than IRRAS in particular to subtle changes induced by bound
water molecules.
[1] Langmuir, 16, 5849, 2000; Langmuir 19, 2284, 2003
CPP 16.19 Di 17:00 B
Physical characterization of iodine-labelled Calixarene
self-assembled monolayers — Peter Siffalovic 1 , •Martin
Michelswirth 1 , Peter Bartz 1 , Björn Decker 2 , Ceno Agena 2 ,
Christian Schäfer 2 , Stephan Molter 3 , Robert Ros 3 , Markus
Bach 4 , Manfred Neumann 4 , Dario Anselmetti 3 , Jochen
Mattay 2 , Ulrich Heinzmann 1 , and Markus Drescher 1 —
1 Molekül- und Oberflächenphysik, Fakultät für Physik, Universität
Bielefeld — 2 Organische Chemie I, Fakultät für Chemie, Universität
Bielefeld — 3 Experimentelle Biophysik, Fakultät für Physik, Universität
Bielefeld — 4 Elektronenspektroskopie, Fachbereich Physik, Universität
Osnabrück
The Calixarenes’ chemical variability and their flexible cage-type structure
make them versatile model hosts for studies of molecular recognition.
Dynamical information about the guest-host interaction could be derived
from time-resolved ESCA (Electron Spectroscopy for Chemical Analy-

Chemische Physik und Polymerphysik Dienstag
sis) which would provide temporal as well as local information about the
chemical environment if one labels the host (or guest) molecule with an
atomic marker. To this end, we labelled Calixarenes with iodine markers
and attached them to gold substrates with dialkyl-sulfide linkers. The
film stechiometry, thickness and density were studied with XPS, AFM
and imaging ellipsometry, respectively. The results support the expected
elemental composition and a film thickness compatible with the molecular
orientation perpendicular to the surface.
CPP 16.20 Di 17:00 B
Single Molecule Diffusion under Confinement and Shear —
•Arne Schob und Frank Cichos — Institut für Physik 123705, TU
Chemnitz, 09107 Chemnitz
Liquids at solid surfaces may show a completely different structure
compared to the bulk structure, since they may form a layering structure
parallel to the surface. Such a structural difference immediately implies
dynamical differences, which shows up in an anisotropic Brownian motion
or even in a different shear viscosity. An understanding of this behavior is
a key to understand lubrication and friction on a molecular scale. We employ
fluorescent dye molecules to measure molecular mobility in ultrathin
liquid films confined between two atomically flat surfaces. We use highly
doped liquid films to measure the film thickness as a function of applied
force. In this way we are able to calibrate our setup for single molecule
experiments and to compare our results with other publications. Single
molecules are tracked with a wide field fluorescence microscope coupled
to a surface forces apparatus. The experiments show, that corresponding
to measurements on free liquid films the diffusion of molecules is slowed
down due to the interaction with the solid interface. We are further able
to apply shear to the liquid film by moving one of the confining solid surfaces.
By seperating their diffusive motion from the shear-driven motion,
we have acces to the velocity within the sheared liquid on a molecular
scale.
CPP 16.21 Di 17:00 B
Single Molecule Adsorption and Desorption on Solid Surfaces
— •Jörg Schuster 1 , Frank Cichos 2 , and Christian von Borczyskowski
1 — 1 Institut für Physik 121501, TU Chemnitz, 09107
Chemnitz — 2 Institut für Physik 123705, TU Chemnitz, 09107 Chemnitz
Adsorption and desorption are key elements in many processes in physical
chemistry such as self assembly, self organization, surface chemical
reactions or even chromatography. By means of single molecule tracking
in wide field fluorescence microscopy we are able to follow directly the
absorption and desorption of molecules on a solid surface. Experiments
on ultrathin liquid films on solid surfaces show, that the re-adsorption
process of single molecules on the surface is directly influenced by the
reduced film thickness. While the re-adsorption time for a molecule at a
liquid solid boundary is usually expected to follow a power law statistics,
we observe an exponential statistics for liquid films of a few nanometer
thickness. The exponential statistics is the result of the reflection of dye
molecules on the liquid vapor interface. Therefore the mean re-adsorption
time gets finite compared to an infinite time in the bulk and shows further
an exponential tail. The decay time of the exponential tail is directly
related to the film thickness and the diffusion constant perpendicular to
the surface. The measurement of the film thickness and the re-adsorption
statistics thus allows for the first time the determination of the diffusion
constant perpendicular to the surface in a 4 nm film. The experiments
show, that this diffusion is slowed down by 4 orders of magnitude compared
to the in plane diffusion. Thus diffusion in liquid films close to solid
surfaces can be extremely anisotropic.
CPP 16.22 Di 17:00 B
Roughness-Induced Acoustic Second Harmonic Generation
(ASHG) During Electrochemical Metal Deposition on the
Quartz Crystal Microbalance — •Katrin Wondraczek 1 ,
Susanne Wehner 2 , Andreas Bund 2 , and Diethelm Johannsmann
1 — 1 Institut fuer Physikalische Chemie, TU Clausthal,
Arnold-Sommerfeld-Str. 4, D-38678 Clausthal-Zellerfeld — 2 Institut fuer
Physikalische Chemie und Elektrochemie, TU Dresden, Mommsenstrasse
13, D-01062 Dresden
When operating a quartz crystal with a rough surface in liquids, there
is an emission of shear and compressional waves at twice the frequency
of the exciting wave (acoustic second harmonic generation, ASHG). We
used electrochemically deposited copper layers whose roughnesses could
be tuned via current density.
Roughness is a source of ASHG if the liquid flow at the surface is
not entirely laminar. The calculation of the Reynolds number shows that
slight deviations from laminar flow can be reached at high amplitudes of
shear oscillation. However, nonlinear effects in the operation of the QCM
in liquids are small.
Our experiments show that a rough surface is much more efficient
in generating acoustic second harmonic waves than a smooth one. We
present a model that relates ASHG to a roughness parameter independently
obtained from resonance frequency and bandwidth. Such a parameter
allows to distinguish the effects of trapped liquid and hydrodynamics
on rough surfaces from the effects of deposited mass.
CPP 16.23 Di 17:00 B
Phtalocyanines at ZnO-Single Crystals — •Peter Kunze 1 , Malgorzata
Boruszczak 2 , Christine Mattheus 1 , Derck Schlettwein
1 , and Katharina Al-Shamery 1 — 1 Institute of Pure and Applied
Chemistry, Faculty V, University of Oldenburg, Oldenburg, Germany
— 2 Uniwersytet Lodz, Lodz, Poland
The aim of this study is to build up solar cells made of zinc oxide
and organic pigments, especially phthalocyanines and perylenes. This requires
accurate knowledge about the structures and binding between the
Zinc oxide and the organic component. In a UHV-chamber phthalocyanines,
subphthalocyanine and MePTCDI have been deposited onto Zinc
oxide of (0001)- and (10-10)-orientation. UV-VIS measurements reveal
the formation of different film morphologies depending on the different
surface orientations of zinc oxide. RHEED investigations showed no lateral
ordering of the phthalocyanines either at the (0001) or the (10-10)
surface. Additionally AFM measurements have been performed on these
samples. They indicate Vollmer-Weber growth with Islands up to 15nm
height and up to 100nm width at ZnO (0001). At ZnO (10-10) Stranski-
Krastanov-growth is observed with the build up of closed monolayers on
which islands of about 10nm height and up to 40nm width can be found.
None of the phthalocyanines, but PcVO showed lateral ordering in the
RHEED pictures. According to the AFM pictures PcVO showed elongated
islands of about 100nm length and only 10nm width which appear
to be ordered in small domains. Beside domains of different orientations
unordered areas could be seen as well. This supports the results of the
RHEED investigations.
CPP 16.24 Di 17:00 B
Debonding of pressure sensitive adhesives — •E. Maurer 1 , S.
Loi 1 , E. Bauer 1 , T. Mehaddene 1 , S. Cunis 2 , and P. Müller-
Buschbaum 1 — 1 TU München Physik Department LS E13, James-
Franck-Str.1, 85747 Garching — 2 HASLYAB, Notkestr. 85, 22607 Hambung
important class in adhesive technology. Typical examples in daily life
are adhesive stickers, Scotch tape or stick-on notes. Symptomatic for this
kind of adhesives is the dependence of adhesions quality on the bonding
history. Important parameters are contact pressure and contact time. In
most applications of PSA later a controlled debonding of the glued devices
is desired. Despite high technological relevance, the physical mechanism
of adhesion are still not fully understood. In addition the function of
the fibrils appearing during debonding is not sufficiently clear. A macroscopic
understanding of adhesion is provided by the so called tack test.
A cylindrical punch is pressed under defined conditions (contact force,
contact time) onto an adhesive film. While redrawing the punch with
a constant velocity the force is measured. A microscopic investigation
of the adhesion can be achieved by a scattering experiment during the
tack test. We applied small angle x-ray scattering (SAXS). The combination
of both, macroscopic mechanical data and microscopic information,
is a promising attempt on the way to a detailed understanding of the
mechanism underlying adhesion.
CPP 16.25 Di 17:00 B
Ultra-fast calorimetry using thin film sensor — •Sergey
Adamovsky and Christoph Schick — Universitätsplatz,3, 18055,
Rostock, Germany
An application of an ultra-fast thin film calorimeter to polymer materials
is described. A commercially available sensor, thermal conductivity
gauge TCG-3880 (Xensor Integrations, NL) was utilized as a measuring
cell for calorimetric measurements. The sensor consists of a 500-nm
thin SiN membrane with a semiconducting heater and a semiconducting
thermopile, which are produced using integrated-circuit (IC) technology.
To allow fast scanning, sample size should be small too. Samples with
masses of about 100 nanograms were measured.
Heating as well as cooling with rates up to 10,000 K/s were realized.

Chemische Physik und Polymerphysik Dienstag
Essentially non-adiabatic conditions were taken into account to get sample
properties. A time resolution of better than 10 ms was achieved in
calorimetric measurements.
CPP 16.26 Di 17:00 B
Calorimetry on thin films — •Heiko Huth — Universität Rostock,
Fachbereich Physik, Universitätsplatz 3, 18051 Rostock
There is an increasing interest in the behavior of confined geometries
as small samples and thin films in the last years. Interesting questions are
the influence on glass transition or the change in crystallization behavior
in the nm range. Beside dielectric methods and structural investigations,
calorimetric data as heat capacity are of interest in such systems.
For small sample mass as thin films in the µm...nm range we run into
problems with the standard calorimetric methods like commercial DSC
because of the limited sensitivity. One method to solve these problems
are thin film calorimeter used by different authors. These systems are
developed to achieve fast heating rates not possible with usual commercial
DSC. To realize this, small samples and sensors are used. This idea
can also be applied for measuring frequency dependent heat capacity of
small samples. We present a measuring system based on thin film sensors
which makes it possible to measure heat capacity of thin films down to
the nm range with sample mass in the µg range or below. First results
are presented.
CPP 16.27 Di 17:00 B
Sum-Frequency Generation Spectroscopy: Monitoring the Hydrophobic
Recovery of PDMS Stamps after Plasma Etching
— •Dominik M.P. Hoffmann, Klaus Kuhnke, and Klaus Kern
— Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, D-
70569 Stuttgart
Polydimethylsiloxane (PDMS) is a polymer widely employed in the
fabrication of stamps for micro-contact-printing, as substrates for microfluidic
cells, and water-proof protection layers. The PDMS surface, which
is hydrophobic in its native state, becomes hydrophilic by oxygen plasmaetching.
Contact angle measurements have established that the hydrophobicity
recovers on the time scale of a few weeks.
Sum-frequency generation (SFG) spectroscopy can access the preferential
orientation of a specific chemical group near an interface. We monitor
the hydrophobic recovery by SFG vibrational spectroscopy of the methyl
groups. For typical plasma etching parameters (15 s etching time at nominally
190 W plasma power) the contact angle decreases from 110 ◦ to 0 ◦
reflecting the substantial decrease of hydrophobicity while SFG spectroscopy
finds that only one third of the preferentially oriented methyl
groups disappear. In addition, the characteristic time for the hydrophobic
recovery observed by SFG is shorter than the time observed by contact
angle measurements. The observations will be discussed in terms of a
model with two different recovery processes.
CPP 16.28 Di 17:00 B
Solvation and Solvation Dynamics of Hydrogen Bonding Dyes
Solvation and Solvation Dynamics of Hydrogen Bonding Dyes
— •Dzmitry Starukhin 1 , Frank Cichos 2 , and Christian von
Borczyskowski 1 — 1 Institut für Physik 122501, TU Chemnitz, 09107
Chemnitz — 2 Institut für Physik 123705, TU Chemnitz, 09107 Chemnitz
Hydrogen bonding is a key element of many biological macromolecules
to ensure function and structure. To study hydrogen bonding effects in
relation to solvent dynamics, we employ a resorufin dye, which is sensitive
to solute-solvent hydrogen bonds. We show that the dye emission wavelength
in different solvents is not governed by dielectric effects such as
dipolar solvation but rather completely determined by hydrogen bonds.
Steady state spectroscopy of the dye in protic solvents shows, that ground
and excited state of the dye possess the same number of hydrogen bonds,
but at different positions of the molecule. This results in two spectroscopically
distinguishable forms of the molecule, which exchange upon photoexcitation.
Due to the exchange the fluorescence decay of the dye studied
by time correlated single photon counting shows mainly two different
timescales. One very fast component is due to a braking and making of
hydrogen bonds and is accompanied by a structural relaxation of the solvent.
The structural relaxation shows time constants which are close to
the typical time constants found in dipolar solvation dynamics measurements.
These experimental findings are further supported by quantum
chemical calculations as well as molecular dynamics simulations.
CPP 16.29 Di 17:00 B
Two-photon single-molecule spectroscopy on a ladder type conjugated
polymer — •Richard Hildner 1 , Uli Lemmer 2 , Ullrich
Scherf 3 , and Jürgen Köhler 1 — 1 Experimentalphysik IV, Universität
Bayreuth — 2 Lichttechnisches Institut, Universität Karlsruhe —
3 Makromolekulare Chemie, Bergische Universität Wuppertal
Conjugated polymers are interesting both for basic and applied research
owing to their high potential for applications in optoelectronic
devices as in organic light emitting diodes and polymer displays. However,
the nature of their electronically excited states is unclear as yet.
Our approach is to use single-molecule spectroscopy, which avoids ensemble
averaging and disorder induced inhomogeneous broadening of the
spectral lines of conjugated polymers. Hence single-molecule spectroscopy
allows a direct verification of theoretical models.
In this contribution we present the first results of two-photon excitation
spectroscopy on single chains of a methyl substituted ladder type
poly(para-phenylene) (MeLPPP) at low temperatures. These results are
discussed in the context of current models of conjugated polymers.
CPP 16.30 Di 17:00 B
Fluorescence Correlation Spectroscopy Investigations of Watersoluble
Polymers — •Tune B. Bonné 1 , Karin Lüdtke 2 , Rainer
Jordan 2 , Petr ˇ Stěpánek 3 , and Christine M. Papadakis 1 —
1 Faculty of Physics and Earth Sciences, University of Leipzig, D-04103
Leipzig, Germany — 2 Faculty of Chemistry, Technische Universität
München, D-85747 Garching, Germany — 3 Institute of Macromolecular
Chemistry, Academy of Sciences of the Czech Republic, Prague
Fluorescence correlation spectroscopy (FCS) is a method to study the
self-diffusion of fluorescence-labeled molecules. The detection volume is
very small (∼ 1 µm 3 ), and the measurements are carried out on the basis
of very few molecules in the detection volume.
Using FCS, we have studied the micellization of fluorescence-labeled
poly(methyloxazoline)-poly(nonyloxazoline) diblock copolymers in aqueous
solution. This polymer system is very versatile with respect to the
degree of hydrophobicity of the blocks. In order to investigate the influence
of the dye on the aggregation behavior, polymers with the dye
attached to either the hydrophilic or the hydrophobic end were investigated.
The critical micelle concentrations were determined with FCS. By
comparing with results from dynamic light scattering (DLS), it is shown
that the hydrodynamic radius of the micelles can reliably be determined
using FCS. Temperature-resolved DLS showed, however, that after dissolution
of the polymers in water at room temperature, large aggregates
are formed, and stable micelles form only after heating the solutions.
CPP 16.31 Di 17:00 B
Photoelectron Spectroscopy on Thin Films of Metal-Free and
Copper Extended Porphyrazines — •D. Pop 1 , B. Winter 1 , W.
Freyer 1 , I. V. Hertel 1 , and W. Widdra 2 — 1 Max-Born-Institut,
Max-Born Str. 2A, D-12489 Berlin — 2 Martin-Luther-Universität Halle-
Wittenberg, D-06099 Halle
We report photoemission measurements using synchrotron radiation
for a series of metal-free and copper benzo-annelated porphyrazines, respectively.
Such systems of molecules allow to investigate the evolution
of the electronic structure with the increasing π-electron system of the
molecule. For the copper set of compounds information about metal-toligand
and ligand-to-metal charge transfer processes are inferred from
the ratios between the copper satellites and main lines. The results are
discussed for both the Cu2p and valence regions of the photoemission
spectra.
CPP 16.32 Di 17:00 B
Fluorescence Correlation Spectroscopy (FCS) of Single Dye-
Labelled Polymers in Organic Solvents — •Heiko Zettl 1 , Wolfgang
Häfner 1 , Alexander Böker 2 , Holger Schmalz 3 , Michael
Lanzendörfer 3 , Axel H.E. Müller 3 , and Georg Krausch 1 —
1 Physikalische Chemie II, Universität Bayreuth, 95440 Bayreuth, Germany
— 2 Department of Polymer Science and Engineering, University of
Massachusetts, Amherst, MA 01003, USA — 3 Makromolekulare Chemie
II, Universität Bayreuth, 95440 Bayreuth, Germany
We discuss the use of fluorescence correlation spectroscopy (FCS) to
study the diffusion of single, dye-labelled polymer chains in organic solvents.
Monodisperse batches of polystyrenes labelled with a single Rhodamine
B molecule have been synthesized via anionic polymerisation of
styrene and ethylene oxide end capping followed by a polymer analogous
coupling reaction. MALDI-ToF mass spectrometry is used to character-

Chemische Physik und Polymerphysik Dienstag
ize the resulting material. A commercial FCS system has been modified
to permit FCS measurements in volatile organic solvents. FCS was used
to determine the molecular weight dependence of the diffusion coefficient
of 10 nM solutions of end-labelled polystyrenes in toluene. The data is
ultilized to establish a calibration procedure for FCS measurements in
organic solvents.
CPP 16.33 Di 17:00 B
Confocal Raman Spectroscopy of Ruthenium Dyes and their
Application in Organic Solar Cells — •Carmen Pérez León 1 ,
Lothar Kador 1 , Bin Peng 2 , and Mukundan Thelakkat 2 —
1 University of Bayreuth, Institute of Physics and Bayreuther Institut
für Makromolekülforschung (BIMF), 95440 Bayreuth — 2 University
of Bayreuth, Makromolekulare Chemie I and Bayreuther Institut für
Makromolekülforschung (BIMF), 95440 Bayreuth
With confocal Raman spectroscopy we investigated a new Ru dye (Ru-
TPA2) and compared it with a similar commercial compound (N179).
We measured the spectra of the dyes in powder, in solution, and in a
solution containing silver nanoparticles to obtain surface enhancement
effects (SERS). Since we are interested in the performance of the dyes in
solid-state organic solar cells, we recorded their signals when they were
chemisorbed on TiO2 nanoparticles and contained in the complete photovoltaic
cells. In the latter case, to identify characteristic Raman lines
and assign them to specific compounds, we also measured the spectra of
cells, in which only part of the constituents were present. The spectra
show some peaks which indicate the formation of new chemical bonds
between the constituents.
CPP 16.34 Di 17:00 B
Fluorescence Lifetime Investigations of DNA mediated
Dye/Gold Nanoparticle Conjugates — •M. Ringler 1 , E.
Dulkeith 1 , T. Niedereichholz 1 , T. A. Klar 1 , and J. Feldmann
1 , A. Munoz-Javier 2 , and W. J. Parak 2 — 1 Photonics and
Optoelectronics Group, University of Munich — 2 CeNS, University of
Munich
Gold nanoparticles have been shown to be extremely efficient quenchers
of luminescence from dye molecules attached to their surface [1]. In the
present study we investigated how the quenching efficiency depends on
the distance between the dye molecule and the nanoparticle using carbon
chain spacers of different lengths. An increase of the fluorescence lifetime
with spacer length is observed.
In a subsequent experiment we replaced the carbon spacers with single
stranded oligonucleotides (ssDNA). We can spectroscopically determine
the number of ssDNA bound to a nanoparticle. Varying the degree
of ssDNA coverage we observe that the fluorescence lifetime becomes
significantly longer when the number of ssDNA per nanoparticle is increased.
This gives evidence that the conformation of DNA bound to
gold nanoparticles changes from wrapped to stretched when the surface
coverage is increased [2].
[1] E. Dulkeith et al., Phys. Rev. Lett. 89, 203002 (2002)
[2] W. J. Parak et al., Nano Letters 3, 33-36 (2003)
CPP 16.35 Di 17:00 B
Optical microresonators formed by cholesteric liquid crystals —
•Jürgen Schmidtke 1 , Werner Stille 1 , and Heino Finkelmann 2
— 1 Physikalisches Inst., Albert-Ludwig-Universität, Freiburg — 2 Inst.
für Makromolekulare Chemie, Albert-Ludwig-Universität, Freiburg
Due to the periodic helical order of the mesogens, cholesteric liquid
crystals (CLCs) act as polarization-sensitive, one dimensional photonic
crystals. Indeed, modified fluorescence as well as photonic band edge lasing
of dye doped CLCs has been repeatedly demonstrated.
In an analytical treatment[1], we discuss different ways to realize
cholesteric optical microresonators by introducing artficial defects in the
helical molecular order. A conventional defect can be realized, if one interrupts
the cholesteric helix by an optically isotropic defect layer: the defect
layer acts as the resonator cavity, which is sandwiched between dielectric
mirrors formed by the cholesteric medium. A unique photonic defect can
be realized in a CLC by an abrupt phase jump in the cholesteric helix
(‘twist defect’[2]). A combination of defect layer and twist defect allows
for an independent tuning of resonance frequency and resonator quality.
We discuss the optics of these defects and the drastic effect of a finite
sample thickness on the polarization properties of the resonant modes,
and compare our findings with experimental results on the twist defect
mode laser emission[3] of a polymeric CLC film.
[1] J. Schmidtke and W. Stille, Eur. Phys. J. E (in press)
[2] V. I. Kopp and A. Z. Genack, PRL 89, 083902 (2002)
[3] J. Schmidtke, W. Stille, and H. Finkelmann, PRL 90, 083902 (2003)
CPP 16.36 Di 17:00 B
13 C-Knight-Verschiebung in Di- Naphthalin-Hexafluoroarsenat
(NA)2AsF6 — •A. Kaiser — Physikalisches Institut, Universität
Karlsruhe (TH), D-76128 Karlsruhe
Mit magnetischen Kernspinresonanzmessungen an 13 C-Kernen werden
Eigenschaften der Leitungselektronen im Radikalkationensalz (NA)2AsF6
charakterisiert. Die Leitungselektronen bewegen sich in diesem quasieindimensionalen
Leiter auf den Stapeln aus Naphthalinmolekülen
(C10H8). Messungen an den 13 C-Kernen der Naphthalinmoleküle zeigen
aufgrund der Hyperfeinwechselwirkung zwischen den Kernspins und den
Leitungselektronenspins in den Frequenzspektren Linien, die eine Knight-
Verschiebung aufweisen. Um eine Hochauflösung der 13 C- Festkörperspektren
zu erzielen, wurde als Messmethode eine Kombination aus der
Rotation unter dem magischen Winkel und einem Doppelresonanzverfahren
verwendet. Die Knight-Verschiebung der 13 C- Linien wurde bei
verschiedenen Temperaturen gemessen. Die auftretenden Linien im Frequenzspektrum
werden durch einen Vergleich mit theoretisch berechneten
Knight- Verschiebungen und durch eine Doppelresonanzmessung
mit verzögerter Entkopplung den einzelnen Kohlenstoffplätzen auf dem
Naphthalinmolekül eindeutig zugeordnet. Aus der Temperaturabhängigkeit
der Knight- Verschiebungen werden zusammen mit der ”lokalen” Leitungselektronensuszeptibilität
die Hyperfeinwechselwirkungskonstanten
bestimmt. Aus diesen lassen sich die Spindichten der Leitungselektronen
am Ort der Kohlenstoffatome ermitteln und somit kann die vollständige
Spindichteverteilung auf einem Naphthalinmolekül bestimmt werden.

Dielektrische Festkörper Tagesübersichten
Hauptvorträge
DIELEKTRISCHE FESTKÖRPER (DF)
Prof. Dr. Horst Beige
Martin-Luther-Universität Halle
Fachbereich Physik
Fachgruppe Physik ferroischer Materialien
Friedemann-Bach-Platz 6
06108 Halle
e-mail: beige@physik.uni-halle.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsäle H11, H23, Poster C)
DF 1.1 Mo 09:30 (H11) Ferroelectric liquid crystals: Electrooptical modes and applications,
Wolfgang Haase
DF 2.1 Mo 14:30 (H11) Charge induced insulator-metal transition and resistive memory in doped
perovskites, J. Georg Bednorz
DF 3.1 Di 09:30 (H23) Theory of the glass transition for systems with trivial statics, Rolf Schilling,
Grzegorz Szamel
DF 4.1 Di 14:30 (H23) Dynamische Heterogenität ungeordneter Festkörper, Roland Böhmer, Manfred
Winterlich, Sven Berndt, Gregor Diezemann, Ken R. Jeffrey
DF 6.1 Do 09:30 (H11) Probing ferroelectricity at small length and short time scales, Theo Rasing
DF 6.2 Do 10:10 (H11) Charakterisierung von PZT-Keramiken mit hochauflösender
Röntgenspektroskopie, M. J. Hoffmann
DF 7.1 Do 14:30 (H11) Jahn-Teller Polaronen in oxidischen Perovskiten, Ortwin Schirmer
Fachsitzungen
DF 1 Elektrische und optische Eigenschaften I Mo 09:30–11:50 H11 DF 1.1–1.6
DF 2 Elektrische und optische Eigenschaften II Mo 14:30–16:50 H11 DF 2.1–2.6
DF 3 Gläser I (gemeinsam FV DF/DY) Di 09:30–12:30 H23 DF 3.1–3.10
DF 4 Gläser II (gemeinsam FV DF/DY) Di 14:30–17:45 H23 DF 4.1–4.12
DF 5 Poster Mi 14:30–18:00 Poster C DF 5.1–5.15
DF 6 Nanostrukturen, Schichten und Keramiken Do 09:30–12:30 H11 DF 6.1–6.7
DF 7 Phasenübergänge und Spektroskopie Do 14:30–16:50 H11 DF 7.1–7.6
Symposium SYNP ”Functional Nanoparticles”
Di 09:30–13:00 H1
Mitgliederversammlung des Fachverbands Dielektrische Festkörper
Di 18:00–19:00 H23
Tagesordnung:
1. Zur Arbeit des Fachverbandes
2. Vorbereitung der 69. Physikertagung im World Year of Physics (Berlin 2005)
3. Verschiedenes

Dielektrische Festkörper Montag
Fachsitzungen
– Haupt-, Kurzvorträge und Posterbeiträge –
DF 1 Elektrische und optische Eigenschaften I
Zeit: Montag 09:30–11:50 Raum: H11
Hauptvortrag DF 1.1 Mo 09:30 H11
Ferroelectric liquid crystals: Electrooptical modes and applications
— •Wolfgang Haase — Technische Universität Darmstadt,
Institut für Physikalische Chemie, Petersenstr. 20, 64287 Darmstadt
Ferroelectric Liquid Crystals are chiral mesophases arranged in a twodimensional
layered structure (SmC). Due to the absence of mirror symmetry,
the electrical dipole moment within each layer is macroscopically
non compensated, hence the external electrical field can interact. For application
in devices or displays the FLC’s are promising candidates due
to short switching time in the microsecond range, large viewing angle etc,
but there are hardly to align compared to nematics. Nowadays there are
several electrooptical modes among them the recently discovered V-shape
switching mode allowing grey scaling and the high frequency DHF (Deformed
Helical Ferroelectric) mode. Principal aspects of applying such
modes for various devices for telecommunication, image processing, polarimetry
and displays will be demonstrated. Along the talk it will be
shown how FLC’s are usable for tunable mirrorless lasing. Short pitch
mixtures allowing the stop band in the visible range were prepared.
DF 1.2 Mo 10:10 H11
Energieverteilung der ferroelektrischen Elektronenemission von
der freien Oberfläche von TGS — •M. Klais 1 , H.W. Gundel 2 und
G. Schönhense 1 — 1 Johannes Gutenberg-Universität, Inst.f.Physik,
Mainz — 2 Université de Nantes, Frankreich
Unter Einfluss eines elektrischen Wechselfeldes senkrecht zur spontanen
Polarisation eines Ferroelektrikums wird die Polarisation ,,geschaltet“.
Ist die eine Oberfläche mit einer strukturierten Elektrode versehen,
so können Feldverteilungen auf der Oberfläche entstehen, die zur Elektronenemission
ins Vakuum führen [1]. Diese Emission hat eine vom angelegten
elektrischen Feld abhängige Energieverteilung. An Triglyzinsulfat
(TGS) wurde diese Energieverteilung gemessen. Hierzu wurde ein Zylindrischer
Sektor Analysator (CSA) eingesetzt. Des Weiteren wurde die
lokale Energieverteilung mit Hilfe der Emissions-Elektronenmikroskopie
(EEM) aufgenommen. Dafür wird ein abbildender Gegenfeldanalysator
(RFA) [2] verwendet.
[1] M. Klais et al., Appl. Phys. A 78 (2003) S. 67
[2] M. Merkel et al., Surf. Sci. 480 (2001) S. 196
DF 1.3 Mo 10:30 H11
Electrical and optical properties of PbTiO3 single crystals at
room temperature — •Hassan Chaib, Frank Schlaphof, Tobias
Otto, and Lukas Eng — Institute of Applied Photophysics, University
of Technology Dresden,D-01062 Dresden, Germany
We present a theoretical approach for studying the electrical and optical
properties of lead titanate (PbTiO3). The microscopic model bases
on the orbital approximation in correlation with the dipole-dipole approximation
and accounts for the electronic polarizability anisotropy of
all constituent ions, their ionic shifts, as well as the crystalline deformations.
The model was previously tested for other ferroelectric oxide materials
when calculating the properties of mono-domain tetragonal BaTiO3,
KNbO3, and rhombohedral LiNbO3, i.e. the ferroelectricity and optical
birefringence, as well as the electrooptical coefficients.[1] Furthermore
the same model could successfully be applied for modeling electrical and
optical properties within 90 ◦ and 180 ◦ domain walls in BaTiO3.[2]
Our calculation shows that the experimental data of the spontaneous
polarization and refractive indices of PbTiO3 at room temperature are
well explained by considering the nonlinearity and anisotropy of the first-,
second-, and third-order electronic polarizabilities of the constituent ions,
particularly those of the O 2−
z -ions. Neverthless, the apparent deviation
between calculated and measured values might be due to the existence
of hybridized orbitals which were not taken into account in this work.
[1] H. Chaib et al., Nonlinear Optics 23, 97 (1999); J. Phys.: Cond.
Matter 12, 2317 (2000); Phys. Rev. B 67, 174109 (2003).
[2] H. Chaib et al., Phys. Stat. Sol. (b) 233, 250 (2002).
DF 1.4 Mo 10:50 H11
Phasenübergänge in PbTiO3 unterhalb Raumtemperatur — •M.
Dietrich 1 , U. Dorda 2,3 , M. Deicher 4 , H. Haas 3 und die ISOLDE-
Kollaboration 3 — 1 Technische Physik, Universität des Saarlandes,
66041 Saarbrücken — 2 Technische Universität Wien, Karlplatz 13, A-
1040 Wien — 3 CERN, EP-Division, CH-1211 Genf 23 — 4 Fachbereich
Physik, Universität Konstanz, 78457 Konstanz
Die Existenz von Phasenübergängen in PbTiO3 unterhalb Raumtemperatur
wird in der Literatur widersprüchlich diskutiert. Der elektrische
Feldgradient (EFG) am Ort eines Gitteratoms reagiert sehr empfindlich
auf die Punktsymmetrie und die Abstände der Sondenatome zu den
nächsten Nachbarn. Die radioaktive Sonde 204m Pb stellt ein Wirtselement
dar, beeinflusst das Material nicht und erlaubt mit der Methode
der gestörten γ-γ-Winkelkorrelation (PAC) die Bestimmung der Größe
und Symmetrie des EFG. Im Bereich von 40 K bis Raumtemperatur lassen
sich alle gemessenen Spektren mit einem axialsymmetrischen EFG
mit η = 0.0(1) anpassen. Die Stärke des EFG ändert sich stetig von
Vzz = 4.5 × 10 21 V/m 2 bei 40 K zu 4.0 × 10 21 V/m 2 bei Raumtemperatur.
Wir finden im Rahmen unserer Messgenauigkeit keinen Hinweis auf
einen Phasenübergang. Allerdings gibt es bei der Temperatur von 130 K
Hinweise auf dynamische Prozesse im Gitter.
Diese Arbeit wurde vom BMBF gefördert (05 KK1TSA/7).
DF 1.5 Mo 11:10 H11
Dehnungsgekoppelter Hall-Effekt in Ferroelektrika — •Doru
Constantin Lupascu — Inst. f¨r Materialwissenschaft, TU Darmstadt,
Petersenstr. 23, 64287 Darmstadt
Die meisten Ferroelektrika sind a priori sehr gute Isolatoren. Trotzdem
führt die Umlagerung von Punktdefekten zu den bekannten Alterungsund
Ermüdungserscheinungen. Um eine Zahlengrundlage für die Beschreibung
des Ladungstransports zu erhalten, ist die Kenntnis der dominanten
Ladungsträgertyps und dessen Beweglichkeit sehr relevant. In
diesem Vortrag wird eine Methode vorgestellt, mit der auch in undurchsichtigen
Proben die langsame Umlagerung von Punktdefekten im Hall-
Feld über die Kopplung an die Dehnung bestimmt werden kann. Ergebnisse
für Blei-Zirkonat-Titanat werden vorgestellt und die Perspektiven
für die Methode gezeigt.
DF 1.6 Mo 11:30 H11
Kolossale dielektrische Konstanten in CaCu3Ti4O12? — •R.
Fichtl 1 , P. Lunkenheimer 1 , B. Renner 2 , S.G. Ebbinghaus 2 , A.
Reller 2 und A. Loidl 1 — 1 Experimentalphysik V, Elektronische
Korrelationen und Magnetismus, Institut für Physik, Universität
Augsburg, 86159 Augsburg — 2 Festkörperchemie, Institut für Physik,
Universität Augsburg, 86159 Augsburg
Die Entdeckung kolossaler dielektrischer Konstanten von ε ′ >∼ 10 4
in CaCu3Ti4O12 (CCTO) entfachte großes Interesse, da große Permittivitäten
für elektronische Anwendungen (kapazitive Bauelemente) enorme
Möglichkeiten versprechen. Zur Klärung der Frage nach dem Ursprung
dieser riesigen dielektrischen Konstanten wurden Messungen an CCTO
bei verschiedenen Temperaturen, mit unterschiedlichen Kontakten und
Probendicken, über einen sehr großen Frequenzbereich durchgeführt.
Die Separation nicht-intrinsischer Beiträge, wie Kontakte oder Korngrenzen,
von den interessierenden intrinsischen Eigenschaften wurde mit
Hilfe einer Ersatzschaltbildanalyse vorgenommen. Es wurde festgestellt,
dass die gefundenen dielektrischen Konstanten von mehr als 10 4 nicht
intrinsisch sind. Stattdessen ergaben sich intrinsische, weitgehend frequenzunabhängige
Permittivitäten von etwa 100 - von den erhofften riesigen
Werten zwar weit entfernt, jedoch im Vergleich zu bisher in der
Elektronik verwendeten Materialien noch immer sehr groß.
Neben den Messungen an CaCu3Ti4O12 werden auch Ergebnisse am
isostrukturellen Cu2Ta4O12 vorgestellt, das ebenfalls scheinbar kolossale
dielektrische Konstanten zeigt.

Dielektrische Festkörper Montag
DF 2 Elektrische und optische Eigenschaften II
Zeit: Montag 14:30–16:50 Raum: H11
Hauptvortrag DF 2.1 Mo 14:30 H11
Charge induced insulator-metal transition and resistive memory
in doped perovskites — •J. Georg Bednorz — IBM Research
Laboratory, Säumerstrasse 4, CH-8803 Rüschlikon, Switzerland
Certain doped perovskites exhibit a charge induced insulator-metal
transition with a resistive memory effect. When exposed to an electrical
field, the resistivity of the doped perovskite is reduced by several
orders of magnitude. Consecutive electrical current pulses (typically 100
ns) of opposite polarity switch the resistance of the perovskite reversibly
between a higher-resistance and a lower-resistance state. These two different
states persist after removal of the applied electrical bias. Since these
compounds show long retention times they are interesting candidates for
non-volatile memory applications.
Bulk single crystals of doped SrTiO3 are a model system for this class
of materials to study the drastic resistivity changes under applied electrical
field and the memory effect. Optical changes in the crystal that are
observed during this transformation indicate a gradual transformation of
the bulk through injection of charges. Large birefringence of the crystal
is observed in the conducting state during current flow. This is shown to
be caused by mechanical stress due to sample heating. A rather homogeneous
pattern, however, suggests a uniform current distribution. Charge
transfer processes possibly mediate the conduction process as indicated
by optical absorption spectroscopy on doped crystals. Electron spin resonance
measurements give a hint at the presence of different valence states
in the insulating and conducting state.
DF 2.2 Mo 15:10 H11
Elektronenstrahlinduzierte Modifizierung optischer
Festkörperspektren für Anwendungen in der Sensorik
der elektrischen Feldstärke — •M. König 1 , H. Balzer 1 , R.
Bauer 2 , I. Sildos 3 und U. Bogner 1 — 1 Institut Physik II, Uni
Regensburg — 2 BGS Beta-Gamma-Service, Saal/Donau — 3 Institute of
Physics, University of Tartu, Estonia
Für die optische Sensorik der elektrischen Feldstärke wurden in Diamant
und Al2O3 spezielle Festkörperstörstellen (FKS) durch Bestrahlung
mit 10 MeV Elektronen erzeugt. Grundlage der Methode ist der
Einfluss elektrischer Felder auf stabile spektrale Löcher, die mit einem
schmalbandigen Laser in die Nullphononlinie der FKS gebrannt werden.
Wir konnten durch Elektronenbestrahlung und anschießendes Tempern
Farbzentren als besonders geeignete FKS in natürlichen und künstlichen
Diamantmaterialien mit N-Dotierung erzeugen. Zur Realisierung eines
bildgebenden Verfahrens auf der Oberfläche von Hochleistungselektronikbauelementen
soll ein Sensorfilm (Diamantpulver in Polymer) aufgetragen
werden. Für die E-Feld-Sensorik in den gesinterten Al2O3-
Keramiksubstraten der Bauelemente wurden sowohl Farbzentren als auch
Mn 4+ -Ionen (die bei Mn-Dotierung nach Elektronenbestrahlung beobachtet
wurden) untersucht.
DF 2.3 Mo 15:30 H11
Dynamic simulation of the pressure transformations in crystalline
Al2O3 — •Sandro Jahn 1 , Mark Wilson 2 , and Paul A.
Madden 1 — 1 PTCL, Oxford University, South Parks Road, Oxford OX1
3QZ, UK — 2 Department of Chemistry, UCL, 20 Gordon Street, London
WC1H 0AJ, UK
The high pressure phase behavior of crystalline Al2O3 is studied using
molecular dynamics. For the atomic interactions we use an ashperical
ion model (AIM), which incorporates both many-body polarization and
short-range ion distortion. The model parameters are obtained by fitting
to system properties extracted from well directed electronic structure calculations.
The application and removal of pressure results in two phase
transformations to and from the Rh2O3-II and an orthorhombic perovskite
structure, respectively. The high pressure phases are understood
in terms of changes in the ion coordination environments and corundum
grain boundaries. The observed structures may have significant implications
for the frequencies of the fluorescence lines of Cr + -doped Ruby
pressure markers at extreme pressures.
DF 2.4 Mo 15:50 H11
Untersuchung von Initialstreu- und Verstärkungsprozessen
bei der nicht-linearen Lichtstreuung — •K. Bastwöste 1 , U.
Völker 1 , U. Dörfler 1 , M. Wöhlecke 1 , Th. Woike 1 , M. Imlau 1
und M. Goulkov 2 — 1 Fachbereich Physik, Universität Osnabrück,
Barbarastr. 7, D-49069 Osnabrück — 2 Institute of Physics, Kiev,
Ukraine
Die Untersuchung der isotropen holographischen Lichtstreuung bietet
in photorefraktiven Materialien die Möglichkeit, sowohl neue Erkenntnisse
über deren optische Eigenschaften als auch einen Einblick in die
initialen Prozesse der holographischen Streuung zu gewinnen. Unter der
Annahme, dass die Initialstreuung und der Betrag des holographischen
Verstärkungsfaktors für zwei symmetrische Streuwinkel gleich ist, lässt
sich aus dem Intensitätsprofil der Streulichtverteilung auf die Initialstreuung
zurückschließen. Zusätzlich wird hierbei der Absorptionskoeffizient
mit dem Wert Null genähert. Um diese Annahmen zu prüfen, haben wir
die räumliche Streulichtverteilung von verschieden stark Cer-dotierten
Strontium-Barium-Niobat-Kristallen (Sr0.61Ba0.39Nb2O6, SBN) als Funktion
der Wellenlänge untersucht. Dabei zeigt sich, dass die Absorption
zu kleineren Wellenlängen für die Analyse des Streubildes berücksichtigt
werden muss. Wir stellen unsere Ergebnisse im Rahmen des Modells zur
holographischen Streuung vor und diskutieren in diesem Zusammenhang
die Rolle des electron-hole-competition-factor.
Gefördert durch die DFG (Graduiertenkolleg 659).
DF 2.5 Mo 16:10 H11
Kinetics of holographic recording in optically bistabile systems
— •Martin Fally 1,2 , Stephan Hausfeld 1 , Theo Woike 1 ,
Mirco Imlau 1 , Romano A Rupp 2 , and Mostafa Ellabban 2 —
1 Fachbereich Physik, Universität Osnabrück, Barbarastr. 7, D-49069
Osnabrück, Germany — 2 Institut für Experimentalphysik, Universität
Wien, Boltzmanngasse 5, A-1090 Wien, Austria
Recently a new photorefractive effect was discovered in centrosymmetric
crystals that could not be attributed to electrooptics. Subsequently
the appealing properties of holographic scattering were revealed and since
then the kinetics of diffraction and transmission have been a subject of
study. Although the photosensitive properties of systems like sodium nitroprusside
(Na2[Fe(CN)5NO] · 2H2O), garnets or even dye-doped polymers
are of completely different origin, they astonishingly show similar
behavior in their diffraction dynamics.
In this contribution we present a model that describes the nonlinear
kinetics of grating formation during holographic recording in optically
bistable systems. We compare the experimentally observed diffraction kinetics
of various centrosymmetric crystals to the predictions of the model.
The far-reaching consequences will be discussed and further experiments
will be proposed.
M.F. is grateful for a Mercator-Gastprofessur funded by the DFG
(OS 55/12-1). Financial support by the Austrian Science Fund FWF
(P-15642) is acknowledged.
DF 2.6 Mo 16:30 H11
Time domain electric field relaxation, accessing the low temperature
dependence of the ionic conductivity in Li3xLa2/3−xTiO3
— •Alberto Rivera 1,2 , Jacobo Santamaria 1 , Carlos Leon 1 ,
Thomas Blochowicz 2 , Catalin Gainaru 2 , and Ernst Roessler 2
— 1 GFMC, Dpto. Fisica Aplicada III, Universidad Complutense de
Madrid, 28040 Madrid, Spain — 2 Experimentalphysik II, Universität
Bayreuth, 95440 Bayreuth, Germany
The measurements of the modulus in the time domain, that is the relaxation
of the electric field at constant dielectric displacement D, presents
several advantages over the more spread permittivity technique. In particular,
the electric response of ionic conductors can only be probed in
the time domain by a modulus experiment. We analyze the dynamics
of a fast ionic conductor, namely crystalline Li0.18La0.61TiO3. We introduce
a capacity correction algorithm to obtain the spectra of the electric
response from time domain measurements allowing a standard data analysis
in the frequency domain. In this way ionic dynamics are investigated
in the frequency range 10 −5 − 10 2 Hz and for conductivity values in the
range 10 −14 −10 −8 S/cm. The DC ionic conductivity shows an Arrhenius
temperature dependence below 300 K and down to 120 K, in contrast to
the non-Arrhenius behavior found at higher temperatures, making it impossible
to apply the Vogel-Fulcher-Tammann law.

Dielektrische Festkörper Dienstag
DF 3 Gläser I (gemeinsam FV DF/DY)
Zeit: Dienstag 09:30–12:30 Raum: H23
Hauptvortrag DF 3.1 Di 09:30 H23
Theory of the glass transition for systems with trivial statics —
•Rolf Schilling 1 and Grzegorz Szamel 2 — 1 Institut für Physik,
Johannes Gutenberg-Universität, D-55099 Mainz — 2 Department of
Chemistry, Colorado State University, Ft. Collins, CO 80523, USA
The mode coupling theory (MCT) derived and investigated in great
detail by Götze and his coworkers has been the most important step towards
the microscopic understanding of the structural glass transition.
MCT yields a glass transition if the static correlations reach a critical
value. However, there exist systems with trivial statics where static correlations
even vanish. Nevertheless they exhibit a discontinuous glass
transition which can not be described by MCT in its present form. In
a first step we have derived a self-consistent equation for the diffusion
constant which yields a continuous transition, in contrast to simulational
results. We show how this drawback can be eliminated by a modification
of the MCT-approximations. As a result MCT-equations are obtained
which are complementary to the original ones. The glass transition is not
driven by the growth of static correlations but by the increase of collision
events between 2, 3 and 4 particles.
DF 3.2 Di 10:15 H23
Mode coupling equations for molecular crystals — •Michael
Ricker und Rolf Schilling — Universität Mainz, Staudinger Weg 7,
55099 Mainz
We have derived the mode coupling equations for molecular crystals
of axially symmetric particles, describing the time evolution of the tensorial
orientational correlators Slm,l ′ m ′(q, t), where lm and l′ m ′ are pairs
of indices for spherical harmonics. These equations have a similar structure
as those for molecular liquids. Differences arise from the possibility
of umklapp-processes in reciprocal space and from the anisotropy of the
lattice. Because of the latter, the three-point correlation function of orientational
density fluctuations, which occurs due to projections during the
calculations, can not be approximated in such an elegant and insightful
way as for liquid systems. Another difference is that only tensorial orientational
correlators with l, l ′ > 0 are involved, since the l = 0 and/or
l ′ = 0 correlators vanish.
If these mode coupling equations can describe the formation of orientational
glasses is currently tested for hard ellipsoids of revolution on a
simple cubic lattice. The static orientational structure factors Slm,l ′ m ′(q),
which are needed as input, are taken from MC simulations and from the
solution of the Ornstein-Zernike equation using the Percus-Yevick approximation.
DF 3.3 Di 10:30 H23
Das β-peak Phänomen in glasbildenden van-der-Waals
Flüssigkeiten — •Matthias Sperl und Wolfgang Götze —
Physik-Department T37, TU München, 85747 Garching
Messungen der Suszeptibilität mittels Optischem Kerr Effekt an Salol
und Benzophenon zeigen strukturelle Relaxation über bis zu fünf
Grössenordnungen in der Zeit. Dabei entsprechen bis zu drei Dekaden
im Anschluß an die Transiente nicht den universellen Skalengesetzen der
Modenkopplungstheorie. Dieses Problem der Datenanalyse wird durch
den Fit der Daten in einem schematischen Modenkopplungsmodell geklärt.
Der bisher unerklärte Zeitbereich in den Daten kann als Charakteristik
eines β-peak Phänomenes verstanden und analytisch beschrieben
werden.
DF 3.4 Di 10:45 H23
Dielectric relaxation in binary organic glass formers: β process
vs. HF-wing scenario and heterogeneous dynamics — •Thomas
Blochowicz and Ernst Rössler — Universität Bayreuth
We study a series of binary mixtures using 2-picoline in oligomeric
styrenes, in particular tri-styrene. The binary mixtures were characterised
by broad band dielectric spectroscopy in the dynamic range 10 −6 −10 7 Hz.
Although neither of the substances shows a secondary relaxation peak in
the neat phase, there appears a strong β-process in the spectra of the
picoline molecules in the mixture. In fact a careful lineshape analysis of
χ ′′ (ω) with a set of appropriate model functions shows that the same process
that is seen as a high frequency wing at high picoline concentrations
becomes a β relaxation at lower concentrations due to a separation of
time scales. Moreover, in the intermediate concentration range a strong
broadening of the spectra as compared to neat picoline is observed. Nonresonant
dielectric hole burning reveals that this broadening is on the
one hand due to pronounced, long-lived dynamic heterogeneities but to
some part also due to intrinsically non-exponential relaxation.
DF 3.5 Di 11:00 H23
Structure and dynamics of Al–Ni melts: Computer simulations
studies — •Jürgen Horbach, Subir Kumar Das, and Kurt
Binder — Institut für Physik, Johannes Gutenberg-Universität,
Staudingerweg 7, D-55099 Mainz
A combination of Monte Carlo (MC) and Molecular Dynamics (MD)
computer simulation techniques is used to study the structure and dynamics
of Al–Ni melts. As a model to describe the interactions between
the atoms we use an embedded atom potential that was recently proposed
by Mishin et al. [Phys. Rev. B 65, 224114 (2002)]. Monte Carlo
simulations in the semigrandcanonical ensemble yield well–equilibrated
configurations that are used in MD runs to study structural and dynamic
properties. For the case of Al4Ni we demonstrate that our simulation is
in very good agreement with the static structure factor and the diffusion
constants as measured recently with neutron scattering by Meyer et al.
We give an interpretation of the prepeak that appears in the total static
structure factor of Al rich melts around 1.3 ˚A −1 . Furthermore we analyze
the dynamics of Al4Ni by means of mode coupling theory and we discuss
the possibility of a fluid–fluid phase separation in Al–Ni mixtures.
DF 3.6 Di 11:15 H23
The mixed alkali effect in ternary silicates: computer simulation
studies — •Hans Knoth, Jürgen Horbach, and Kurt Binder —
Institut für Physik, Staudinger Weg 7, Johannes Gutenberg–Universität,
D–55099 Mainz
Molecular dynamics computer simulations are used to investigate
ternary alkali silicates (1 − x)Li2O·xK2O·2SiO2 (0 ≤ x ≤ 1). These systems
are typical ion conductors which is due to a high mobility of the
alkali ions. The structure and dynamics is studied for molten systems, as
well as at lower temperatures at which only the alkali ions show a diffusive
motion. Our aim is to understand the origin of the so-called mixed
alkali effect (MAE) which is the phenomenon that the diffusion of the
alkali ions is much slower in ternary systems (e.g. x = 0.5) than in the
corresponding binary systems (i.e. x = 0 and x = 1). Preferable sites for
the alkali diffusion are found that are located in a network of channels. In
the ternary system, each alkali species moves in its own channel network
leading to a stronger localization of alkali sites and the MAE.
DF 3.7 Di 11:30 H23
Nearly constant loss behavior in molecular glass-formers —
•Catalin Gainaru, Alberto Rivera, Thomas Blochowicz,
Christian Tschirwitz und Ernst A. Roessler — Experimentalphysik
II, Universitaet Bayreuth, Germany
We study the dielectric response of molecular glass formers showing no
Johari-Goldstein relaxation (type A systems) below the glass transition
temperature by applying the new Andeen Hagerling ultra-precision capacitance
bridge (50 Hz - 20 KHz). In all glass formers we find a nearly
constant loss behavior extending over several decades in frequency and
exhibiting an exponential temperature dependence. Below say 50 K a
crossover to another relaxation phenomena with a pronounced peak is
observed (5 K - 50 K).
DF 3.8 Di 11:45 H23
Secondary relaxation processes in organic glasses - comparison
between dielectric and NMR spectroscopy — •Sorin Adrian
Lusceac, Peter Medick, Catalin Gainaru, and Ernst A.
Rössler — Experimentalphysik II, Universitaet Bayreuth, Germany
Secondary relaxation processes in glasses were discovered using dielectric
spectroscopy. While dielectric spectroscopy is the preferred technique
to study them for obtaining time constants, NMR spectroscopy is a good
candidate to offer extra-information about their nature, in particular
concerning geometry and hindrance of molecular motion. Several organic
glass formers (polybutadiene Mw= 80000g/mol, mixture of benzene and
polybutadiene Mw= 777 and 2110g/mol) are investigated using multidimensional
NMR spectroscopy and the results are compared with those
provided by dielectric spectroscopy. The main purpose is to find a link

Dielektrische Festkörper Dienstag
between the dielectric strength of the secondary relaxation process and
suitable 2 H NMR measurable.
DF 3.9 Di 12:00 H23
Mapping supercooled liquids on simple trap models for the
long-time dynamics: justification and consequences — •Andreas
Heuer, Aimorn Saksaengwijit, and Katharina Hobbeling —
Institut für Physikalische Chemie, Corrensstr. 30, D-48149 Münster
For a long time it has been realized that the potential energy landscape
(PEL) viewpoint is useful for characterizing supercooled liquids
and glasses. To this end, one considers the high-dimensional vector of
all particle coordinates as a point moving on the surface of the total
potential energy. It turns out from computer simulations of a binary
mixture Lennard-Jones system that the dynamics can be described as a
random-walk between stable structures on the PEL, denoted metabasins
[1]. Furthermore it turns out that the metabasins act as traps. Escaping
a metabasin requires an activation energy which is proportional to the
depth in the PEL. Thus the dynamics of the glass-forming liquid is very
similar to the dynamics within a trap model. Some consequences of this
mapping for the application of modern equilibration routines like parallel
tempering are discussed.
[1] B. Doliwa and A. Heuer, Phys. Rev. Lett. (in press).
DF 4 Gläser II (gemeinsam FV DF/DY)
DF 3.10 Di 12:15 H23
Relating the macroscopic dynamics of liquid silica to its potential
energy landscape — •Aimorn Saksaengwijit and Andreas
Heuer — Westfälische Wilhelms–Universität, Institut für Physikalische
Chemie, D-48149 Münster
We have studied the dynamics of liquid silica in terms of the potential
energy landscape (PEL) defined in configuration space. The concept
of superstructures of PEL minima, denoted metabasins, is used to extract
the relevant properties of the PEL. On the level of metabasins it
turns out that the average residence time 〈τ〉 is inversely proportional
to the diffusion constant, i.e. D(T) = c/〈τ(T)〉. The temperature dependence
of the residence time can be obtained from the analysis of local
escape processes out of individual metabasins. Furthermore we show that
the fragile-to-strong transition of silica can be reproduced by using the
PEL analysis. This allows us to obtain an improved understanding of the
underlying nature of this transition. A comparison to a fragile system
(Lennard-Jones liquid) is included.
Zeit: Dienstag 14:30–17:45 Raum: H23
Hauptvortrag DF 4.1 Di 14:30 H23
Dynamische Heterogenität ungeordneter Festkörper —
•Roland Böhmer 1 , Manfred Winterlich 1 , Sven Berndt 1 ,
Gregor Diezemann 2 und Ken R. Jeffrey 3 — 1 Experimentelle
Physik III, Universität Dortmund, 44221 Dortmund — 2 Institut für
Physikalische Chemie, Johannes Gutenberg-Universität, 55099 Mainz —
3 Department of Physics, University of Guelph, Canada
Die Natur der nichtexponentiellen Relaxation von Flüssigkeiten und
Polymerschmelzen ist in letzter Zeit sowohl theoretisch als auch experimentell
intensiv erforscht worden [1]. Im Bereich der Festkörper gab es
bislang aber nur wenige Aktivitäten. Neuere Untersuchungen mit der dielektrischen
Spektroskopie und mit der kernmagnetischen Resonanz konzentrieren
sich hier auf die Rotationsdynamik ungeordneter plastischer
Kristalle [2] und auf die Translationsdynamik von festen Ionenleitern
[3,4].
[1] H. Sillescu, J. Non-Cryst. Solids 243, 81 (1999)
[2] M. Winterlich, G. Diezemann, H. Zimmermann, R. Böhmer, Phys.
Rev. Lett. 91, (2003)
[3] R. Richert, R. Böhmer, Phys. Rev. Lett. 83, 4337 (1999)
[4] M. Vogel, C. Brinkmann, H. Eckert, A. Heuer, cond-mat/0310256
DF 4.2 Di 15:00 H23
Rotationsdynamik einzelner Moleküle in unterkühlten
Flüssigkeiten — •Gerald Hinze — Institut für Physikalische
Chemie, Johannes Gutenberg-Universität, 55099 Mainz
Die Dynamik in unterkühlten Flüssigkeiten ist durch eine große Bandbreite
an vorkommenden Zeitskalen, Amplituden und Bewegungsmechanismen
gekennzeichnet. Neben der sehr signifikanten Temperaturabhängigkeit
des primären Relaxationsprozesses sind nichtexponentielle
Korrelationsfunktionen typisch und werden in praktisch allen Glasbildnern
bzw. unterkühlten Flüssigkeiten gefunden. Eine damit verknüpfte
und zur Zeit sehr kontrovers diskutierte Fragestellung betrifft die dynamische
Heterogenität in der Nähe der kalorischen Glastemperatur. Während
einige Experimente Hinweise dafür liefern, dass die Moleküle einer Probe
relativ einheitlich reorientieren, bzw. Unterschiede sich auf der Zeitskala
der Rotation herausmitteln, ergeben andere Experimente deutlich
getrennte Zeitskalen für die Rotation und die Änderung der Rotationskorrelationszeiten.
Mit Hilfe der konfokalen Fluoreszenzmikroskopie ist es
möglich, die Rotationsdynamik einzelner Moleküle zu verfolgen. Damit
bietet sie prinzipiell die Möglichkeit, dynamische Heterogenitäten und
deren Lebensdauern zu bestimmen, da keine Ensemble-Mittelungen auftreten.
Wir stellen Einzelmolekülexperimente in der amorphen Matrix
PDE (Phenolphthalein-dimethylether) vor. Die erhaltenen Rotationskorrelationsfunktionen
werden mit einfachen Rotationsmodellen verglichen.
DF 4.3 Di 15:15 H23
Dynamical heterogeneities in simulated amorphous Ni0.5Zr0.5:
correlations with density and order parameter fluctuations —
•Imad Ladadwa and Helmar Teichler — Institut für Materialphysik,
and SFB 602, Universität Göttingen
Dynamical heterogeneity is a fundamental aspect of particle motion in
supercooled liquids and glasses. For metallic alloy system, a great part of
the information on dynamical heterogeneity comes from computer simulations,
leaving open so far, however, a detailed answer concerning the
origin of heterogeneity. In order to approach this question, we have carried
out molecular dynamics simulations for an amorphous Ni0.5Zr0.5 model,
generating well relaxed structures at 700, 760, and 810 K, that means
well below the dynamical glass temperature Tc = 1120K. From analyzing
long-time simulations over 0.7µs for medium size systems (N = 5184,
periodic boundary conditions), we find striking interrelationship between
spatial fluctuations of the atomic mobility, that means dynamical heterogeneity,
and of the fluctuation of topological order and of the chemical
composition in the system. The results indicate an anti-correlation between
local Ni content and Ni atoms mobility, on the one hand, and
a correlation between the local order and the Ni mobility on the other
hand. The talk will present the definitions of suitable measuring tools for
these quantities and quantitative estimates for the inherent correlations.
DF 4.4 Di 15:30 H23
Short-range order fluctuations and the boson peak in simulated
amorphous NiZr — •M. Guerdane and H. Teichler — Institut
für Materialphysik, Universität Göttingen
The boson peak is a striking feature in the vibration spectrum of glassy
systems. We here present results from molecular dynamics simulations
for Ni30Zr70, relating the boson peak of the system to local fluctuations
in the short-range order. Analysis of the topology around Ni atoms in
the system shows that Ni in the amorphous state on average has a coordination
number < Z >= 9, where in detail a mixture of perfect or
slightly distorted trigonal prisms (TP, Z = 9) or archimedean antiprisms
(AAP, Z = 10) and environments with Z = 8 predominate. Both TP and
AAP represent the basic structural units in the crystalline intermetallic
compounds NiZr (B33-Type) and NiZr2 (C16-Type) respectively. We
show that the boson peak in the amorphous NiZr system is related to
fluctuations in time between local environments of different coordination
numbers Z.
DF 4.5 Di 15:45 H23
Molecular Dynamics in Phosphate Glasses — •Oliver Baldus
and Ernst Rössler — Lehrstuhl für Experimentalphysik II, Universität
Bayreuth, Universitätsstr. 30, 95440 Bayreuth
The molecular dynamics of the glass formers tricresylphosphate (TCP),
triphenylphosphite (TPP) and mixtures with polystyrene are investigated
by NMR methods. The observed deviations from the KWW-

Dielektrische Festkörper Dienstag
behaviour of the relaxation function obtained in stimulated echo measurements
are explained. Further it will be discussed whether those deviations
are a sign of the so called wing phenomenon that is seen in
dielectric spectra and how far the measurements are influenced by limitations
of the stimulated echo method. Restrictions of the stimulated
echo method are shown by simulations.
DF 4.6 Di 16:00 H23
Ionic transport in alkali-borate glasses — •F. Berkemeier,
Á.W. Imre, S. Voss und H. Mehrer — Institut für Materialphysik,
Wilhelm–Klemm–Str. 10, 48149 Münster, Westfählische–Wilhelms–
Universität Münster, Sonderforschungsbereich 458
We studied the ionic transport in binary and ternary alkali-borate glasses
of the compositions y Na2O·(1 − y) B2O3, y Rb2O ·(1 − y) B2O3 and
0.3 [x Na2O·(1−x) Rb2O]·0.7 B2O3. The total alkali content of the binary
glasses ranges from y = 0.04 up to y = 0.30 while the relative composition
of the mixed glasses varied in between x = 0 and x = 1. First, the ionic
transport was observed by temperature dependent measurements of the
dc conductivity which is connected to the long range transport of the cations.
For each glass composition we observed an Arrhenius behaviour of
the dc conductivity and determined an activation enthalpy ∆H. For the
binary systems we found decreasing values of ∆H with increasing alkali
content while for the mixed glasses we observed a maximum of the activation
enthalpy at the composition range around x ≈ 0.4. Conductivity
measurements only reveal the sum of the contributions of the different
cations. Because of this we measured additionally the diffusivities of 22 Na
and 86 Rb in the mixed glasses at 380 ◦ C using the radiotracer technique.
We observed an exponential decrease of the Rb-diffusivity with decreasing
Rb-content, while the Na-diffusivity also decreases with decreasing
Na-content on the Na-rich side, but remains nearly constant on the Rbrich
side. Both diffusivities intersect at the composition range around
x ≈ 0.2. A similar behaviour was reported from our laboratory for mixed
glasses with a total alkali content of y = 0.2.
DF 4.7 Di 16:15 H23
Diffusion von Na und Ca und ionische Leitfähigkeit in Standard-
Kalk-Natron-Gläsern — •Eugène Molière, Tanguep Njiokep
und Helmut Mehrer — Institut für Materialphysik, Westfälische-
Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster
Als Standardsubstanzen für die wichtigsten physikalischen und chemischen
Prüfmethoden in der Glastechnologie hat die Deutsche Glastechnologie
Gesellschaft (DGG) zwei Flachgläser (Standard-Kalk-Natron-
Gläser) von hoher Reinheit und Homogenität herstellen lassen. Bei der
Physikalisch-Technischen-Bundesanstalt (PTB) wurden das Viskositäts-
Temperatur-Verhalten und die Bruchbarkeit dieser Gläser als Viskosität-
Standard untersucht. Diese Gläser weisen keine Störung durch Entglasung
und Entmischung auf. Neben der praktischen Bedeutung der Standards
liegen hier gut definierte Gläser vor, über deren verschiedensten
Eigenschaften nun umfangreiche Daten existieren. Dagegen gibt es noch
keine Informationen über die Beweglichkeit der im SiO2-Netzwerk eingebauten
Alkali- und Erdalkaliionen. Um Informationen über die Transportprozesse
der Netzwerkwandler zu gewinnen, wurden die ionische
Leitfähigkeit der Proben im Frequenzbereich zwischen 5Hz und 1.28MHz
mit der Impedanz-Spektroskopie und die Diffusion von 22 Na und 45 Ca
mit der Radiotracermethode im Temperaturbereich zwischen 490K und
759K untersucht. Die Tracerdiffusions- und Leitfähigkeitsmessungen werden
verglichen und diskutiert.
DF 4.8 Di 16:30 H23
Ion dynamics in single and mixed alkali silicate glasses studied
by molecular dynamics simulations — •Heiko Lammert and
Andreas Heuer — Westfälische Wilhelms–Universität, Institut für
Physikalische Chemie, Corrensstraße 30, D-48149 Münster
We use molecular dynamics (MD) simulations to study the ion dynamics
in alkali silicate glasses with the general composition
x K2O · (1 − x) Li2O · 2 SiO2, for x = 0, 0.5, 1.
All individual alkali sites provided by the frozen network can be identified
by a statistical analysis of MD trajectories, for both the single
and the mixed alkali systems. Sites are located by a cluster search on a
discretised alkali population density.
The ion dynamics can be analyzed in terms of fast hops between these
sites, also yielding average residence times to characterize the sites. As
the number of free sites is low compared to the number of ions, correlated
back jumps are found to be probable, especially for ions on fast sites. The
mobility of ions can be correlated to the local network structure around
their site, particularly to the occurence of bridging oxygens.
DF 4.9 Di 16:45 H23
Mixed-alkali effect in sodium rubidium borate glasses: ionic conductivity
and diffusivity — •Árpád W. Imre, Stephan Voss, and
Helmut Mehrer — Institut für Materialphysik, Universität Münster,
Wilhelm-Klemm-Strasse 10, D-48149 Münster, Germany and Sonderforschungsbereich
458
Measurements of the tracer diffusion coefficient and ionic conductivity
have been made in a series of 0.2[XNa2O · (1 − X)Rb2O] · 0.8B2O3
glasses where X=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 in order to investigate
the mixed-alkali effect. The glasses were characterised with differential
scanning calorimetry, density measurements and X-ray diffraction experiments.
Both 22Na and 86Rb tracer diffusion coefficients were determined
as a function of temperature and composition. For each composition the
temperature dependence of the tracer diffusion coefficients and dc conductivity
times temperature σdc × T follow the Arrhenius law. The manifestations
of the mixed-alkali effect were observed: i) the ionic conductivity
shows a minimum with composition near X =0.4, ii) the activation
enthalpy of σdc × T has a maximum near X =0.4, iii) the glass-transition
temperature has a minimum near X=0.2, iv) the diffusivities of 22Na and 86Rb crossover near X =0.2. The diffusivity crossover is found to be
temperature independent. The composition dependence of the tracer diffusivities
has an asymmetric character. The tracer diffusion coefficients
are compared with ionic conductivity and the corresponding Haven ratios
obtained. In contrast to 0.2Na2O · 0.8B2O3 glass, the Haven ratio in the
0.2Rb2O · 0.8B2O3 depends on temperature.
DF 4.10 Di 17:00 H23
From binary Na-silicate to ternary Na-alumino-silicate melts:
the evolution of Na dynamics and intermediate range order
— •Florian Kargl 1 , Andreas Meyer 1 , and Helmut Schober 2
— 1 Physikdepartment E13, TU München, 85748 Garching — 2 Institut
Laue-Langevin, 38042 Grenoble, France
Neutron scattering investigations of binary alkali silicate melts revealed
correlations on intermediate lengthscales of 6-8 ˚A. Within MDsimulations
on Na-silicates evidence was found that these correlations
arise from Na-rich channels percolating in the remaining SiO-network.
Fast Na-diffusion takes place via these channels [1]. Substituting the
network forming component SiO2 by GeO2 leads to a change in structure
and in the microscopic transport mechanism, respectively, as verified
by inelastic neutron scattering. We present our recent investigations on
sodium alumino-silicate melts containing besides SiO2 a second network
former, Al2O3. Our main aim was to study the interplay between
microscopic dynamics and structure and its influence on macroscopic
properties. From quasielastic neutron scattering experiments we
conclude that the channel structure is disrupted by adding Al2O3 to the
Na-silicates resulting in an increase of viscosity as well as a decrease of
Na-relaxation times [2].
[1] A. Meyer, J. Horbach, W. Kob, F. Kargl, H. Schober (submitted)
[2] F. Kargl, A. Meyer, Chem. Geol. (submitted)
DF 4.11 Di 17:15 H23
Fragilität niedermolekularer organischer Glasbildner unter
Druck — •Andreas Reiser, Gernot Kasper und Siegfried
Hunklinger — Kirchhoff-Institut für Physik, Universität Heidelberg,
Im Neuenheimer Feld 227, 69120 Heidelberg
Die Fragilität einer glasbildenden Flüssigkeit ist definiert durch die
Steigung bei der Glasübergangstemperatur Tg im Angell-Plot. Sie erlaubt
eine Klassifikation in starke bzw. fragile Glasbildner. Stark bedeutet ein
Arrheniusverhalten der Relaxationszeit über den gesamten Temperaturbereich
T ≥ Tg. Die Relaxationszeit fragiler Glasbildner dagegen zeigt
eine stärkere Temperaturabhängigkeit. Wir haben den Einfluss von hohem
hydrostatischen Druck auf die Fragilität von typischen organischen
Glasbildnern mit dielektrischer Spektroskopie gemessen: Glycerin und
meta-Fluoranilin sind Vertreter wasserstoffgebrückter Glasbildner. Glycerin
rangiert im Zwischengebiet zwischen stark und fragil, wohingegen
meta-Fluoranilin und der Van-der-Waals-Glasbildner Propylencarbonat
vom fragilen Typ sind. Im untersuchten Druckbereich (0 −600 MPa) zeigen
alle drei Glasbildner keine Druckabhängigkeit der Fragilität im Rahmen
der Fehlergrenzen von ±5%.

Dielektrische Festkörper Dienstag
DF 4.12 Di 17:30 H23
A binary colloidal mixture in 2D: An ideal model system for the
glass transition — •Hans König — Fachbereich Physik, Universität
Konstanz, 78457 Konstanz
Investigating a binary 2D colloidal glass former with a repulsive (1/r 3 )
potential we have measured particle positions as a function of time by
video-microscopy. The local packing of the big and small particles as well
as the heterogeneous dynamics were analysed depending on the system
temperature. Finally, we could describe the amorphous 2D short-range
order by local density-optimized triangles. However, there is one triangle
DF 5 Poster
for each 3-particle combination of big and small colloids. Regions with
structural frustration occur between clusters of optimally packed triangles.
For decreasing system temperature the number of densely packed
triangles increased and they began to form clusters. For low system temperatures
such local density-optimized regions moved cooperatively resulting
in heterogeneous dynamics. By structural and dynamical investigations
we identify the 2D glass transition as a percolation of local
density-optimized triangles, which form a stable frame through the whole
glass former. At last, we call this glass description the concept of local
density-optimized crystallite clusters.
Zeit: Mittwoch 14:30–18:00 Raum: Poster C
DF 5.1 Mi 14:30 Poster C
Well-ordered arrays of ferroelectric BaTiO3 and SrBi2Ta2O9
nanostructures grown by pulsed laser deposition — Wenhui Ma,
•Dietrich Hesse, and Ulrich Gösele — Max-Planck-Institut für
Mikrostrukturphysik Halle
Monolayers of monodisperse latex spheres of micron and submicron size
were used as deposition masks to fabricate arrays of ferroelectric nanostructures
by pulsed laser deposition (PLD). First, arrays of well-ordered
BaTiO3 and SrBi2Ta2O9 amorphous structures were prepared on Nbdoped
SrTiO3 (100) substrates (STO:Nb) by PLD at room temperature.
These as-deposited structures were shown to have a pyramid-like shape
with lateral sizes between 100 and 200 nm, forming a hexagonal pattern.
Post-deposition annealing was used to crystallize these nanostructures.
The ferroelectric properties of the crystalline nanostructures were investigated
using scanning force microscopy in piezoresponse mode (PFM).
Depending on material and size of the nanostructures, piezoelectric hysteresis
loops of different shape and size were recorded, demonstrating
that BaTiO3 and SrBi2Ta2O9 nanostructures of 100 to 200 nm lateral
size have a remanent polarization and are switchable by an electric field,
i.e. they are indeed ferroelectric.
DF 5.2 Mi 14:30 Poster C
Properties of high-k dielectric materials studied by conducting
Atomic-Force Microscopy — •Harald Wurmbauer 1 , Sascha
Kremmer 1 , Christian Teichert 1 , Friedemar Kuchar 1 , and
Grazia Tallarida 2 — 1 Department of Physics, University of Leoben,
A-8700 Leoben — 2 Laboratorio MDM - INFM, I-20041 Agrate Brianza,
Milano
The steadily shrinking device dimensions in semiconductor devices demand
for advanced electrical characterization methods operating on the
nanometer scale. One suitable technique already used for the evaluation
of silicon gate oxide quality is Conducting Atomic-Force Microscopy (C-
AFM).
Here, C-AFM is used to study different high-k dielectric materials with
regard to their electric properties and homogeneity. Therefore, materials
like ZrO2 and HfO2, grown by atomic layer chemical vapor deposition on
a silicon substrate are studied by C-AFM in ultra high vacuum (UHV).
The UHV conditions are mandatory to avoid surface modifications during
the experiments. Local current-voltage measurements are used to obtain
a statistical distribution of the leakage current as a function of voltage.
This provides an insight into the influence of the amorphous or crystalline
structure of the films depending on their thickness and heat treatment.
Further, two-dimensional current scans with a positive voltage applied to
the sample are performed to obtain the local distribution of the leakage
current.
DF 5.3 Mi 14:30 Poster C
Wet chemical deposition of semiconducting materials into
porous Al2O3 — •L. Nosova 1,2 , A. Belaidi 1 , T. Guminskaya 1 , S.
Gavrilov 3 , R. Bayon 1 , I. Sieber 1 , V. Timoshenko 4 , I. Urban 5 ,
N. Grigorieva 1,6 , and Th. Dittrich 1 — 1 Hahn-Meitner-Institut,
Glienicker Str. 100, D-14109 Berlin, Germany — 2 permanent address:
Heat Physics Department, Uzbek Academy of Sciences, 700135
Tashkent, Uzbekistan — 3 Moscow Institute of Electronic Engineering
— 4 M. V. Lomonosov Moscow State University, Physics Department,
119899 Moscow, Russia — 5 Bundesanstalt für Materialforschung, Unter
den Eichen 87, D-12205 Berlin — 6 permanent address: St. Petersburg
State University, Department of Solid State Physics, Ulyanovskaya 1,
198504 St. Petersburg, Russia
Porous Al2O3 with ordered pores is prepared by two-step anodization.
Different deposition techniques (successive ion layer adsorption reaction,
chemical bath deposition, ion layer gas reaction, electrochemical
deposition) are used to deposit semiconducting materials as CdS, PbS,
CuO, CuxS, ZnO into pores with diameters between 20 and 200 nm.
The samples are characterized by secondary and transmission electron
microscopy, infrared spectroscopy, optical transmittance and photovoltage
techniques. The different deposition techniques are evaluated with
respect to the quality of the prepared nanocomposites.
DF 5.4 Mi 14:30 Poster C
Integrated electromagnetic bandgap structures for micro- and
millimeter waves — •Michael Schuster and Norbert Klein —
Forschungszentrum Jülich, 52428 Jülich
2dimensional EBG structures are most promising for a possible application
as integrated structure for microwave and optoelectronical devices
due to their advantages in terms of stability, EBG properties and applicable
machining processes. Combining microwave range sized models,
full electromagnetic field simulation software and silicon micromachining
processes it is feasible to built up an integrated circuit technology
based on EBG materials for frequencies from several 10 GHz up to the
millimeter wave range of several 100 GHz.
Starting from the investigation of modular structures for frequencies
as low as 10 GHz, we have been investigating the fabrication of EBG
structures for frequencies around 30 GHz employing a lost Mould technique.
We are investigating line and point defect structures in these 2
dimensional EBG lattices, Q factors of excited modes and the optimisation
of impedance matching between integrated EBG structures and
conventional external waveguiding devices.
For even higher frequencies around 100GHz and the lower Terahertz
regime, we are investigating the fabrication and the properties of high
resistive silicon 2D EBG structures fabricated by a chemically assisted
silicon etching process by frequency and time domain mmeasurements.
DF 5.5 Mi 14:30 Poster C
Holographische Datenspeicherung als Technik zur Langzeitarchivierung
— •Marcus Werner 1 , Theo Woike 1 und Mirco Imlau
2 — 1 Institut für Mineralogie, Universität zu Köln — 2 Universität
Osnabrück
Für die dauerhafte Konservierung elektronischer Daten existiert bis
jetzt kein zukunftssicheres System. Ein Lösungsansatz ist die holographische
Speicherung von Daten in ferroelektrischen Kristallen.
Im Poster werden die speziellen Anforderungen an ein holographisches
Langzeitspeichersystem aufgezeigt. Speziell für das Speichermedium Lithiumniobat
wird ein Versuchsaufbau vorgestellt, der sowohl hohe Datendichte
(10 GBit/qcm) als auch eine lange Speicherdauer (> 100 Jahre)
ermöglicht.
Das System ermöglicht die gemischte Aufzeichnung analoger und digitaler
Daten, wobei sich die Analogdaten (ähnlich wie beim Mikrofilm) mit
einfachsten Hilfsmitteln auslesen lassen. Die kombinierte Speicherung von
Analog- und Digitaldaten genügt daher einerseits den erhöhten Anforderungen
der Archivare bezüglich der Zukunftssicherheit eines Speichermediums,
andererseits ist die ständige digitale Verfügbarkeit der Daten
gewährleistet.

Dielektrische Festkörper Mittwoch
DF 5.6 Mi 14:30 Poster C
Vergleich dielektrischer und mechanischer Spektroskopie
an Poly(methylmethacrylat) — •Peter Rösner 1 , Konrad
Samwer 1 , Robert Wehn 2 , Peter Lunkenheimer 2 , Alois Loidl 2 ,
Erik Süske 3 und Hans-Ulrich Krebs 3 — 1 I. Physikalisches Institut,
Georg-August-Universität Göttingen, 37077 Göttingen — 2 Lst. für
Experimentalphysik V, Universität Augsburg, 86159 Augsburg —
3 Institut für Materialphysik, Georg-August-Universität Göttingen,
37077 Göttingen
Poly(methylmethacrylat), PMMA, ist ein Polymer, das in seinem dielektrischen
Verlust neben dem primären α-Prozess durch viskoses Fließen
einen stark ausgeprägten β-Peak zeigt. Da die Seitengruppen das
Hauptdipolmoment des Moleküls tragen, koppelt das anregende elektrische
Feld hier besonders effektiv an.
In vergleichenden Messungen wurde an dünnen PMMA-Schichten temperaturabhängig
sowohl der dielektrische, als auch der mechanische Verlust
bei derselben Frequenz untersucht. Bei den mechanischen Messungen
wurde dazu ein Doppel-Paddel-Oszillator als Substrat verwendet und in
Torsion bei 5400 Hz der komplexe Schermodul gemessen. Die mechanischen
Spektren zeigen signifikante Unterschiede zu den dielektrischen
Messungen. Dabei stellt sich insbesondere die Frage, wieweit α- und β-
Relaxation als unabhängige Phänomene betrachtet werden dürfen und
auf welche Weise sich das in dielektrischen Messungen beobachtete merging
auf mechanische Untersuchungen übertragen lässt.
Die Arbeit wird von der DFG im Rahmen des GRK 782 und des SFB
602 Projekt B8 gefördert.
DF 5.7 Mi 14:30 Poster C
Brownian oscillator model for nonresonant holeburning in the
Terahertz-regime — •Uli Häberle and Gregor Diezemann — Institut
für physikalische Chemie, Johannes-Gutenberg-Universität Mainz,
D-55099 Mainz
The response to the field sequence of nonresonant hole burning, a
pump-wait-probe experiment originally designed to investigate slow relaxation
in complex systems, is calculated for a model of Brownian oscillators.
The model allows to treat both overdamped and underdamped
motion. The case of underdamped oscillations is of particular interest
when low-frequency excitations in glassy systems are considered. Our
main focus lies on the possibility to discriminate between dynamic homogeneous
and heterogeneous relaxation. We show that a frequency selective
modification of the response should be feasible. This means that it
is possible to specifically adress certain parts of the spectrum. An experimental
realization of nonresonant holeburning in the Terahertz-regime
is therefore expected to shed further light on the nature of the vibrations
around the so-called boson peak.
DF 5.8 Mi 14:30 Poster C
Dielektrische Untersuchungen an Bleizinkniobat-Bleititanat —
•Tarek El Goresy und Roland Böhmer — Experimentelle Physik
III, Universität Dortmund, 44221 Dortmund
Wie alle Relaxorferroelektrika zeichnet sich Bleizinkniobat-Bleititanat
[Pb(Zn1/3Nb2/3)O3]1−x[PbTiO3]x (kurz: PZN-xPT) durch einen diffusen
Phasenübergang aus. In der Nähe der morphotropen Phasengrenze (0,09
≤ x ≤ 0,14) besitzt es ungewöhnlich hohe piezoelektrische Koeffizienten
[1]. Diese Eigenschaft macht PZN-xPT für viele Anwendungen interessant.
Andererseits ist der Polarisationsmechanismus noch weitgehend
ungeklärt. Wir präsentieren dielektrische Alterungsmessungen an
PZN-10PT in der Nähe des Maximums des dielektrischen Verlustes. Bei
Temperaturzyklen konnten wir nach dem Altern bei einer konstanten
Temperatur Gedächtnis- und Verjüngungseffekte beobachten. Des weiteren
untersuchten wir die dielektrischen Eigenschaften von PZN-10PT
mittels dielektrischer Lochbrennspektroskopie. Beide Methoden erlauben
Rückschlüsse auf den Polarisationsmechanismus.
[1] Chi-Shun Tu, J. Appl. Phys. 87, 2327 (2000)
DF 5.9 Mi 14:30 Poster C
Microscopic ion dynamics in lithium silicate glasses studied
by molecular dynamics simulations — •Magnus Kunow and
Andreas Heuer — Westfälische Wilhelms-Universität, Institut für
Physikalische Chemie, and Sonderforschungsbereich 458, Corrensstraße
30, D-48149 Münster
We use molecular dynamics computer simulations to investigate the
microscopic ion dynamics in a system consisting of 50 SiO2. Below the
computer glass transition temperature the long range alkali dynamics is
decoupled from the glass forming species, which provide a quasi-frozen
network structure.
To obtain an improved understanding of the alkali dynamics we have
varied the conditions of the simulations in two different ways. First, we
have artifically immobilized the network. It turns out that the activation
energy of the Li diffusion strongly increases. Thus the occurrence of single
Li hops strongly depends on local network dynamics. We find that
the saddle for a transition between two minimum positions is lowered
by the local dynamics of the network. Detailed analysis of trajectories
revealed that oxygen atoms near the saddle perform motions opening a
”doorway” for the hopping Li ion. Second, we have applied strong electric
fields (E ≥ 5 ∗ 10 5 V/cm) to our simulations. In this way we obtain
information about the current density function of the system in the nonlinear
response regime which can be directly compared to experimental
data from non-linear conductivity measurements. This comparison may
help to clarify the information content of this type of experiments.
DF 5.10 Mi 14:30 Poster C
Charakterisierung laserbearbeiteter Gläser mit optischen und
Röntgenmethoden — •L. Müller 1,2 , U. Klemradt 1 , R. Poprawe
2 , E.W. Kreutz 2 , R. Wagner 2 , J. Gottmann 2 und A. Horn 2 —
1 II Physikalisches Inst., RWTH Aachen — 2 Lehrstuhl für Lasertechnik,
RWTH Aachen
Mit ultrakurz gepulster Laserstrahlung (τ = 100fs) werden in Silikat-
Gläsern Modifikationen hervorgerufen, die unter anderem zu Brechungsindexveränderungen
führen und zur Herstellung von Wellenleitern im
Volumen genutzt werden. Die Brechungsindexänderung wird durch laserinduzierte
Defekte und Dichteänderung im Glas erzeugt. Ziel der
Untersuchungen ist, eine Dichteänderung der erzeugten Strukturen in
Quarzglas und einem Borsilikatglas zu quantifizieren. Mittels eines Wellenleitermessplatzes
werden Dämpfung, Streuung, geführte Moden und
die numerische Apertur der resultierenden optischen Wellenleiter gemessen
und der effektive Brechungsindex ermittelt. Spekulare und diffuse
Röntgenreflexionsmessungen sollen eine Dichteänderung im Material aufzeigen,
so dass deren Anteil an der optischen Brechungsindexänderung
festgestellt werden kann.
DF 5.11 Mi 14:30 Poster C
Temperaturabhängigkeit der Quadrupolwechselwirkung für
111-In in Saphir — •J. Penner und R. Vianden — Helmholtz -
Institut für Strahlen- und Kernphysik, Nußallee 14–16, 53115 Bonn
Temperaturabhängige Messungen der Hyperfeinwechselwirkung der
111 In Sonde in Saphir zeigen, dass nach der Implantation mit 111 In und
Ausheilen bei 1000 ◦ C der ungestörte Anteil fu reversibel zwischen 50%
bei 4K, 5% bei 100K und 80% bei 973K schwankt.
Als mögliche Erklärung des Verhaltens bietet sich das Auftreten eines
sogenannten ”after effects” nach dem EC-Zerfall des 111 In zu 111 Cd an.
Dabei ensteht zunächst ionisiertes 111 Cd das anschließenden durch Aufnahme
von Elektronen aus der Umgebung in den Grundzustand übergeht.
Die dazu notwendige Elektronen erreichen das Cd Ion bei höheren Temperaturen
durch sogenannte Hüpfprozesse (inkohärentes Tunneln) und
bei tiefen Temperaturen durch kohärentes Tunneln.
Zur Bestätigung dieses Modells sind Messungen mit 111m Cd in Al2O3
geplant.
DF 5.12 Mi 14:30 Poster C
Studies on local structure and Li diffusion in LiAlO2 single crystals
using 7 Li and 27 Al NMR spectroscopy — •Sylvio Indris 1 ,
Daniel Albrecht 1 , Paul Heitjans 1 , and Reinhard Uecker 2 —
1 Institut für Physikalische Chemie und Elektrochemie, Universität Hannover,
30167 Hannover, Germany — 2 Institut für Kristallzüchtung, 12489
Berlin, Germany
We studied the local structure of LiAlO2 single crystals by 7 Li and 27 Al
NMR spectroscopy. Lineshape measurements with different orientations
of the crystals with respect to the magnetic field give the possibility to
probe the electric field gradients at the sites of the Li and Al ions, respectively,
and thus yield information about the local symmetry of these sites.
The dynamics of the Li ions was studied via the temperature dependence
of the 7 Li NMR lineshapes and 7 Li spin-lattice relaxation times T1. These
measurements were done at temperatures between 300K and 1000K and
for different crystallographic orientations. The results are discussed with
respect to the hopping rate of the Li ions and the activation barriers
for single ion jumps and are compared with results from conductivity
measurements and quantum chemical calculations.

Dielektrische Festkörper Mittwoch
DF 5.13 Mi 14:30 Poster C
Molecular dynamics studies of the thermodynamic and structural
temperature behaviour of Li2B4O7 — •Volodymyr V.
Maslyuk 1 and Herbert Pfnür 2 — 1 Uzhhorod National University,
Ukraine — 2 Institut Für Festkörperphysik, Universität Hannover, Germany
By ab initio calculation we show that B atoms in triangular BO3 and
tetragedral BO4 configurations are non equivalent. Whereas B in BO3
carries a one charge, it is another charged in BO4, will corresponding consequences
on the lateral interactions with the oxygen atoms. We generate
effective potentials that gives a good description of the (1−x)Li2OxB2O3
system. Molecular dynamics calculation carried out will this effective description
allows to determinate the temperature behaviour of lattice parameters,
angles between atoms and the heat capacity of Li2B4O7. An
abnormal behaviour of lattice parameter c was found that is in excellent
agreement with experimental data [1].
[1] V. V. Zaretski and Ya. V. Burak, Physics of the Solid State, 31, 6,
960-963, 1989
DF 5.14 Mi 14:30 Poster C
Orientation-dependent ELNES of TiO2: a comparison of
theory and experiment — •Christian Heiliger 1,2 , Frank
Heyroth 1 , Frank Syrowatka 1 , Wolfram Hergert 2 , and
Ingrid Mertig 2 — 1 Center of Materials Science, Martin-Luther-
University Halle-Wittenberg, Hoher Weg 8, 06120 Halle, Germany —
2 Martin-Luther-University Halle-Wittenberg, Department of Physics,
Von-Seckendorff-Platz 1, 06120 Halle, Germany
In this poster we present a spectroscopic investigation of titanium oxid
(TiO2). The usage of the ultra high vacuum STEM (scanning transmission
electron microscope) VG HB 501 equipped with a Gatan Enfina
PEELS detector gives the opportunity to detect EELS (electron energy
loss spectra) with a high energy resolution. For that reason one can observe
characteristic differences in the spectra between the 3 phases of
TiO2: rutile, anatase and brookite. In addition it is possible to investigate
the orientation dependence of the samples.
Apart from the experimental discussion a comparison to theoretical
calculations is presented. The calculation is based on the DFT (density
functional theory) within the LDA (local density approximation) using
the Stuttgart-LMTO-47 (linearized muffin tin orbitals) package. Taking
into account the core hole effect in the Z+1 or Z+2 approximation a very
good agreement in the peak positions is observed. The peak intensities
however are not correctly reflected.
DF 5.15 Mi 14:30 Poster C
The structure of plain and stepped BaTiO3 surfaces — •Walter
Alsheimer, Sibylle Gemming, and Gotthard Seifert — Institut
für Physikalische Chemie und Elektrochemie, TU Dresden, D-01062 Dresden
In the framework of miniaturization of semiconductor devices ferroelectric
compounds in the perovskite structure attract much interest. For
example one of our aims is to deliver a density-functional based understanding
of an organic field effect transistor on a ferroelectric template
like BaTiO3.
Because of the low computational costs the density-functional based
tight binding (DFTB) method allows one to study complex and large
structures. Therefore in a first step we choosed this technique to perform
calculations on the relaxation of plain and stepped surfaces with a
slab model geometry. Trends for the interplanar spacings and the local
coordination at the step edge are discussed for vicinal (10n) surfaces.
DF 6 Nanostrukturen, Schichten und Keramiken
Zeit: Donnerstag 09:30–12:30 Raum: H11
Hauptvortrag DF 6.1 Do 09:30 H11
Probing ferroelectricity at small length and short time scales
— •Theo Rasing — NSRIM Institute, University of Nijmegen, Toernooiveld
1, NL-6525 ED Nijmegen, The Netherlands
Future applications of ferroelectric materials in nanoelectronic or storage
devices require the control and manipulations/switching of ferroelectricity
on small (submicron) length scales and short (subnanosecond)
time scales. These developments in turn ask for methods to probe ferroelectric
properties at these length and time scales as well.
Our recent progress report in this area will be discussed, demonstrating
in particular the use of scanning probe and nonlinear optical methods to
investigate the static and dynamic properties of ferroelectrics with a lateral
resolution down to the nanometer regime (using a scanning probe)
and a time resolution down to the picosecond regime (using nonlinear
optical microscopy). Finally, the possibility to combine the best of both
worlds, namely the time resolution offered by femto-second lasers with
the lateral resolution of scanning probe methods will be demonstrated.
Hauptvortrag DF 6.2 Do 10:10 H11
Charakterisierung von PZT-Keramiken mit hochauflösender
Röntgenspektroskopie — •M. J. Hoffmann — Institut für Keramik
im Maschinenbau, Zentrallaboratorium der Universität Karlsruhe,
Haid-und-Neu-Str.7, 76131 Karlsruhe
Keramiken auf der Basis von Bleizirkonattitanat (PZT) haben, aufgrund
ihrer herausragenden piezoelektrischen Eigenschaften, eine große
technische Bedeutung im Bereich der Sensorik und Aktorik. Die di- und
piezoelektrischen Eigenschaften erreichen ihre Maximalwerte bei Zusammensetzungen
in der Nähe der morphotropen Phasengrenze (MPB), die
durch die Koexistenz einer ferroelektrisch tetragonalen und einer ferroelektrisch
rhomboedrischen Phase charakterisiert ist. Im Rahmen des
Vortrags wird zunächst die Wechselwirkung beider Phasen im Gefüge
anhand der oberflächensensitiven Röntgenspektroskopie diskutiert. Es
werden mögliche Phasenumwandlungen bis zur Curie-Temperatur und
deren Einfluss auf die Materialeigenschaften diskutiert. Im zweiten Teil
des Vortrags werden hochauflösende Synchrotronmessungen vorgestellt,
mit denen der extrinsische (Domänenschaltprozesse) und intrinische (Piezoeffekt)
Beitrag zur Gesamtdehnung einer PZT-Keramik quantifiziert
werden kann. Es wird gezeigt, dass die höchste piezoelektrische Dehnung
nicht der Richtung der spontanen Polarisation entspricht. Anschließend
werden die Unterschiede in der Beweglichkeit von nicht-180 0 Domänen
für beide ferroelektrische Phasen diskutiert. Aus einem Vergleich der Volumenanteile
von schaltbaren Domänen beider ferroelektrischer Modifikationen
wird deutlich, dass die nicht-180 0 Domänenwandbeweglichkeit
in tetragonalem PZT sehr viel niedriger ist als in rhomboedrischem.
DF 6.3 Do 10:50 H11
Electrical fatigue of PZT ferroelectric films: in-situ structural
investigations — •J.L. Cao 1 , U. Klemradt 1 , A. Solbach 1 , U.
Böttger 2 , U. Ellerkmann 2 , P. Gerber 2 , P. J. Schorn 2 , and
R. Waser 2 — 1 II. Physikalisches Inst., RWTH Aachen, Germany —
2 Institut für Werkstoffe der Elektrotechnik 2, RWTH Aachen, Germany
Synchrotron radiation from Hasylab was used to study the structural
evolution of thin ferroelectric Pb(Zr0.3Ti0.7)O3 (PZT) films under the influence
of an external AC field. In order to be sensitive to the evolution
of structural disorder or transitional layers at the electrode/PZT interfaces,
grazing incidence x-ray reflectivity was used instead of conventional
diffraction. Reflectivity curves were measured under in-situ conditions for
up to 108 electrical cycles, corresponding to different fatigue states. The
simulation of the reflectivity curves points at the growth of a very thin
Pt/PZT interfacial transition layer that is possibly correlated with the
electrical fatigue of the capacitor structure. The relationship between ferroelectric
fatigue and structural features of PZT thin films is discussed
with emphasis on the possibility of a mechanism which develops disorder
at the interface and contributes to the observed electrical properties.
DF 6.4 Do 11:10 H11
The contribution of misfit dislocations to polarization instabilities
of epitaxial ferroelectric Pb(Zr 0.52 Ti0.48)O 3 nanoislands —
M.-W. Chu, I. Szafraniak, R. Scholz, C. Harnagea, M. Alexe,
and •D. Hesse — Max-Planck-Institut für Mikrostrukturphysik Halle
(001)-oriented Pb(Zr 0.52 Ti0.48)O 3 (PZT) epitaxial nanoislands of d≈
9 nm average height were grown on niobium-doped SrTiO3 (001) substrates
(STO:Nb) by chemical solution deposition (CSD) at 800 ◦ C. Due
to the lattice mismatch, edge-type misfit dislocations are formed at
the PZT/STO:Nb interface. Using high-resolution electron microscopy
(HREM), the nature of these misfit dislocations has been analyzed, resulting
in a Burgers vector b a〈100〉. Applying the geometric phase imag-

Dielektrische Festkörper Donnerstag
ing method of quantitative HREM, the asymmetric strain fields of the
misfit dislocations have been visualized. It turns out that they extend
into a PZT region with dimensions as large as ∼4 nm in height and ∼
8 nm in width. Within this region the lattice deviates from the regular
PZT crystal structure, implying a reduced or even vanishing spontaneous
polarization. Piezoresponse force microscopy indicates that PZT
nanoislands of d≈ 9 nm indeed do not show ferroelectricity, whereas PZT
islands of d≈ 20 nm and also misfit dislocation-free PbTiO3 islands of
d≈ 9 nm are ferroelectric. It is concluded that a stable polarization in
nanostructured ferroelectrics requires misfit engineering.
DF 6.5 Do 11:30 H11
Infrared near-field microscopy of focused ion beam patterned
SiC — •Nenad Ocelic and Rainer Hillenbrand —
Nano-Photonics Group, Max-Planck-Institut für Biochemie, 82152
Martinsried
We used a home-built scattering-type (or apertureless) scanning nearfield
infrared microscope (s-SNIM) to study the local dielectric properties
of a SiC surface patterned by focused ion beam implantation with spatial
resolution of less than 100nm. In our experiment the sharp probing tip of
an atomic force microscope (AFM) is illuminated by infrared light from
a CO2 laser and both the amplitude and phase of backscattered light are
detected.
Tuning the laser between λ = 10.6µm and λ = 11.2µm, we found
phonon-polariton resonance of the tip-sample near-field interaction [1]
whose magnitude and spectral position strongly depend on the sample’s
local dielectric function ǫ(λ). Since ǫ(λ) depends on the local crystal
structure, we can differentiate between crystalline SiC and amorphous
SiC regions produced by implantation, as well as the transition regions
between them. Thus, our method could be used to map radiation damage
caused by the implantation process employed for semiconductor doping
or to study crystal defects in thin film growth.
[1] R.Hillenbrand, T.Taubner, F.Keilmann, Nature, 418, 159-162
(2002)
DF 6.6 Do 11:50 H11
First investigations of MIM capacitors using Pr2O3 dielectrics
— •Christian Wenger, Gunther Lippert, Hans-Joachim Muessig,
Peter Zaumseil, Roland Sorge, and Jaroslaw Dambrowski
— IHP Microelectronics GmbH, Im Technologiepark 25, 15236 Frankfurt
(Oder)
DF 7 Phasenübergänge und Spektroskopie
Metal-insulator-metal(MIM) capacitors with Pr2O3 as high-k material
have been investigated for the first time. The results show that Pr2O3
MIM capacitors can provide higher capacitance densities than Si3N4 MIM
capacitors while still maintaining comparable voltage coefficients of capacitance.
The Pr2O3 dielectric material seems to be suitable for use in
silicon RF applications.
DF 6.7 Do 12:10 H11
CURRENT TRANSPORT AND SIZE-EFFETCS IN ULTRA-
THIN FERROELECTRIC BARRIERS — •H. Kohlstedt 1 , N.
A. Pertsev 2 , J. Rodriguez-Contreras 1 , A. Gerber 1 , J. Schubert
3 , C. Jia 1 , U. Poppe 1 , and R. Waser 1 — 1 Forschungszentrum
Jülich, Institut für Festkörperforschung and CNI, 52425 Jülich, Germany
— 2 A. F. Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia,
— 3 Forschungszentrum Jülich, Institut für Schichten- und Grenzflächen
and CNI, 52425 Jülich, Germany
We will present our development of so-called ferroelectric tunnel
junctions with the following layer sequence: SrTiO3(substrate)/
SrRuO3(electrode)/BaTiO3 or PbZrxTi1−xO3 (as ferroelectric)/SrRuO3
or Pt as top electrode. These heterostructures have been investigated by
XRD, RBS, AFM and HRTEM.
The aim of our work is to study fundamental aspects of electron tunnelling
and electron transport through a ferroelectric material and the
influence of the transport current on the ferroelectric polarization state
of the barrier material. The I-V characteristics voltages showed switching
events with two resistive states. The origin of the switching will be
discussed in the framework of direct electron tunnelling, resonant tunneling,
and electron transport via defects. For inelastic transport processes
we found for temperatures below 100 K Glazman-Matveev tunneling and
above 100 K a transition to Mott-hopping.
Moreover we will present a theoretical approach on the basis of the
deformation potential model to combine the tunneling transfer matrix
element with the strain state of the barrier.
Zeit: Donnerstag 14:30–16:50 Raum: H11
Hauptvortrag DF 7.1 Do 14:30 H11
Jahn-Teller Polaronen in oxidischen Perovskiten — •Ortwin
Schirmer — Fachbereich Physik, Universität Osnabrück
Polaronen sind quasifreie Ladungsträger zusammen mit der von ihnen
erzeugten Gitterverzerrung. Ihre Dynamik ergibt ergibt sich aus dem
Wechselspiel von Selbstlokalisierung und Tunneln zwischen äquivalenten
Plätzen. Es ist üblich, die Eigenschaften von Polaronen durch Messungen
der elektrischen Leitfähigkeit bei optischen und niedrigen Frequenzen
zu analysieren. Dabei werden die Beiträge verschiedener gleichzeitig vorhandener
Ausprägungen von Polaronen superponiert. In günstigen Fällen
können EPR-Untersuchungen diese Komponenten voneinander trennen.
Es gelang, BaTiO3-Kristalle so zu dotieren, dass mit EPR nachweisbare
Ti 3+ (3d 1 ) Polaronen im LB entstehen. Anwendung einachsigen Druckes
und Temperaturvariation identifizierte folgende Ausprägungen: kleine
Polaronen (Radius ca. Bindungslänge), intermediäre Polaronen (Radius
grösser) und Bipolaronen (durch gemeinsame Gitterverzerrung gebundenes
Polaronenpaar). Zur Stabilisierung trägt jeweils auch die Aufhebung
der Bahn-Entartung bei (Jahn-Teller Effekt).
Weiter werden Defektelektronen behandelt, die nach Erzeugung durch
geeignete Einstrahlung an einem von mehreren äquivalenten Sauerstoff-
Ionen neben Akzeptor-Defekten in BaTiO3 und KTaO3 als O − (2p 5 ) eingefangen
werden; dabei wird die Äquivalenz durch Gitterverzerrung gebrochen,
es entsteht ein gebundenes Polaron. Auch hier unterstützt ein
lokaler JTE die Stabilisierung. Eine neuartige, symmetrie-erhaltende dynamische
Ausprägung des JTE an Polaronen wird behandelt.
DF 7.2 Do 15:10 H11
Zeitliches Verhalten lichtinduzierter Polaronen in oxidischen
Kristallen — •Th. Woike 1,2 , P. Herth 1 , T. Granzow 1 , M.
Wöhlecke 2 und M. Imlau 2 — 1 Institut für Mineralogie, Zülpicher
Str. 49b, 50674 Köln — 2 Fachbereich Physik, Universität Osnabrück
In oxidischen Kristallen werden bei Beleuchtung mit kurzen, intensiven
Laser-Pulsen Elektronen von energetisch tiefen Niveaus in lokale
Zentren angeregt. Wenn diese angeregten Elektronen eine Verzerrung
des Kristall-Gitters hervorrufen, die ihrerseits das Elektron an seiner
neuen Position stabilisiert, bezeichnet man das Elektron-Deformations-
Ensemble als Polaron. In den letzten Jahren konnte gezeigt werden, dass
für dotierte Kristalle einfache Mehr-Zentren-Modelle zur Beschreibung
der zeitlichen Entwicklung der Polaronen nicht greifen. Statt dessen muss
auch die räumliche Entfernung zwischen Polaron und tiefer Störstelle
berücksichtigt werden. Eine analoge Beschreibung der Anregung und des
Zerfalls von Polaronen in undotierten Kristallen, in denen keine tiefen
Zentren vorhanden sind, steht bisher noch aus.
In diesem Vortrag wird die Anregung und der Zerfall von Polaronen
in undotierten Lithium-Niobat-, Strontium-Barium-Niobat- und Kalium-
Niobat-Kristallen vorgestellt und diskutiert. Die Detektion des Verhaltens
erfolgt über Messung der durch Polaronen hervorgerufenen lichtinduzierten
Absorption nach Anregung des Kristalls mit kurzen, intensiven
Laserpulsen. Die zeitliche Entwicklung wird durch Summen von gestreckten
Exponentialfunktionen beschrieben, und es wird gezeigt, welche Aussagen
sich daraus über die Natur der an diesem Prozess beteiligten tiefen
bzw. flachen Energieniveaus gewinnen lassen.

Dielektrische Festkörper Donnerstag
DF 7.3 Do 15:30 H11
Relaxor-Verhalten von Strontium-Barium-Niobat: Einfluß der
Domänengröße — •T. Granzow 1 , Th. Woike 1,2 , M. Wöhlecke 2 ,
M. Imlau 2 , W. Kleemann 3 und M. Goulkov 4 — 1 Institut für Mineralogie,
Zülpicher Str. 49b, 50674 Köln — 2 Fachbereich Physik, Universität
Osnabrück — 3 Angewandte Physik, Universität Duisburg-Essen —
4 Institute of Physics, Kiev, Ukraine
Zum Verständnis des Phasenübergangs im Relaxor-Ferroelektrikum
Strontium-Barium-Niobat (Sr0.61Ba0.39Nb2O6, SBN) sind detaillierte
Kenntnisse über die Wechselwirkung zwischen polaren Bereichen,
ihren Grenzflächen und im Kristall eingefrorenen elektrischen Feldern
nötig. Während der Einfluß der internen Felder auf die makroskopische
ferroelektrische Polarisation gut charakterisiert werden konnte, steht die
direkte Untersuchung des Verhaltens mikro- und nanoskopischer polarer
Strukturen noch am Anfang. Hier bieten sich Untersuchungen der
Winkelverteilung holographisch gestreuten Lichts an: Bei Bestrahlung
von SBN mit einem kohärenten Lichtstrahl baut sich eine charakteristische
Streulichtverteilung auf, die Rückschlüsse sowohl auf die
makroskopische Polarisation als auch auf die lokale Domänenstruktur
ermöglicht. In diesem Vortrag wird die Entwicklung mikroskopischer
polarer Strukturen in Cer-dotiertem SBN beim Aufheizen über die Phasenübergangstemperatur
gezeigt und auf der Basis des Modells interner
Zufallsfelder diskutiert. Dabei zeigt sich, dass die Zerfallstemperatur
einer Domäne entscheidend von ihrer Größe abhängt. Dieses Ergebnis
wird mit Phasenübergangs-Beobachtungen anderer Messmethoden
verglichen.
Gefördert durch die DFG (SPP1056 WO618/3-4) und INTAS 01-0173
DF 7.4 Do 15:50 H11
High frequency dielectric response of strontium barium niobate
in the relaxor and ferroelectric regimes — •J. Banys 1 , W.
Kleemann 2 , J. Macutkevic 1 , R. Grigalaitis 1 und R. Pankrath 3
— 1 Physics Department, University of Vilnius, Vilnius, Lithuania —
2 Angewandte Physik, Universität Duisburg-Essen, 47048 Duisburg —
3 Fachbereich Physik, Universität Osnabrück, 46069 Osnabrück
The dielectric permittivity of SBN:0.02% Co 2+ , ǫ ′ +iǫ ′′ , is measured at
frequencies 20 < f < 6 ·10 8 Hz and temperatures 300 < T < 450 K both
in the poled and unpoled state. Below Tc = 348 K the unpoled sample
reveals the well-known [1] relaxation behavior of pinned domain walls [2]
extending up to the highest frequencies, while a flat dispersion regime up
to 10 6 Hz and a broad step within 10 6 < f < 10 9 Hz characterize ǫ ′ of the
unpoled sample at T > Tc and the poled sample at all temperatures. The
latter behavior is also reflected by a broad peak of ǫ ′′ at f = 10 7 - 10 9 Hz
and is attributed to the relaxation of random-field pinned precursor clusters
of the polarization [3]. The data are successfully described in terms of
Cole-Cole and Havriliak-Negami-type dispersion relations and best-fitted
to distribution functions of relaxation times, which show typical relaxor
behavior.
[1] W. Kleemann et al., Phys. Rev. B 65 (2002) 220101R.
[2] T. Nattermann et al., Phys. Rev. B 42 (1990) 8577.
[3] W. Kleemann et al., Eur. Phys. Lett. 57 (2002) 14.
DF 7.5 Do 16:10 H11
Diffuse phase transition in BaTi1−xSnxO3 — •Volkmar Müller 1 ,
Horst Beige 1 , and Hans-Peter Abicht 2 — 1 FB Physik, Martin-
Luther-Universität Halle — 2 FB Chemie, Martin-Luther-Universität
Halle
We investigated the influence of Sn-substitution on the diffuse phasetransition
(DPT) of BaTixSn1−xO3 (BTS) solid solutions. Thermal expansion,
dielectric and electromechanical experiments have been carried
out, both for the pure compounds (x = 0 and x = 1, respectively), and
for various BTS compositions with 0.025 ≤ x ≤ 0.2. This composition
range covers both the diffuse phase transition state and the ferroelectric
relaxor state of BTS. The thermal expansion of BTS is nonlinear, both
due to thermally generated impurities and, below the Burns-temperature
Td, due to nanopolar regions in the paraelectric phase. Deviations from
the Curie-Weiss law of the permittivity and the non-Debye dispersion
due to the precursor polarization in the Burns-phase of BTS are studied.
Resonance-like spectra of DC-biased bar-shaped samples provide information
about the complex coupling factor and the elastic anomaly
accompanying the DPT. Large-field electromechanical and dielectric experiments
reveal the decisive role of the Sn-content on the unhysteretic
P(E)-dependence in the slim-loop region as well as on the coupling between
polarization and electromechanical strain.
This contribution was supported by Deutsche Forschungsgemeinschaft,
Schwerpunktprogramm ”Substitutionseffekte in ionischen Festkörpern”
DF 7.6 Do 16:30 H11
Gigantischer magnetoelektrischer Effekt im ferroelektrischen
Antiferromagneten HoMnO3 — •Th. Lottermoser 1 , Th. Lonkai
2 , U. Amman 2,3 , J. Ihringer 2 , D. Hohlwein 4 und M. Fiebig 1 —
1 Max-Born-Institut, Max-Born-Straße 2A, 12489 Berlin — 2 Institut für
Angewandte Physik, Universität Tübingen, 72076 Tübingen — 3 Institut
Laue-Langevin, 6 Rue J. Horowitz, BP 156-38042 Grenoble, France —
4 Hahn-Meitner-Institut, Glienicker Straße 100, 14109 Berlin
Die Entdeckung des linearen magnetoelektrischen (ME) Effekts – Induktion
einer elektrischen Polarisation durch ein magnetisches Feld bzw.
Induktion einer Magnetisierung durch ein elektrisches Feld – stieß in den
1960er Jahren auf großes Interesse: Die Wechselwirkung eröffnete neue
Freiheitsgrade für die Entwicklung von Bauteilen, die auf der gegenseitigen
Kontrolle des magnetischen und elektrischen Zustands beruhen. Wegen
der generell geringen Größenordnung des Effekts schlug die Entwicklung
eines ” ME Schalters“ jedoch fehl. Vor kurzem wurden in Kompositmaterialien
und magnetischen Ferroelektrika ein ” gigantischer“, steuerbarer
ME Effekt entdeckt, was erneut zu großem Interesse in dieser Materieleigenschaft
führte. Wir beschreiben die Kontrolle der magnetischen
Ordnung in HoMnO3 durch ein elektrisches Feld. Eine ferromagnetische
Ordnung der Ho 3+ -Spins wird durch ein elektrisches Feld ein- bzw. ausgeschaltet.
Der Prozess wird mithilfe der optischen zweiten Harmonischen
beobachtet und anhand von Neutronendiffraktionsmessungen mikroskopisch
erklärt. Er beruht auf dem ME Beitrag zur freien Energie, der
mikroskopisch induziert wird durch eine Asymmetrie der Ho 3+ − Mn 3+ -
Superaustauschpfade aufgrund der ferroelektrischen Verzerrung.

Dünne Schichten Tagesübersichten
Hauptvorträge
DÜNNE SCHICHTEN (DS)
Prof. Dr. Bernd Rauschenbach
Leibniz-Institut für Oberflächenmodifizierung
Permoserstr. 15
04318 Leipzig
E-Mail: bernd.rauschenbach@iom-leipzig.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsäle HS 31, HS 32, Poster B)
DS 2.1 Mo 11:45 (HS 31) Semiconductors under ion bombardment - studied by RBS in situ at 15
K, Elke Wendler, Werner Wesch
DS 5.1 Mo 09:30 (HS 32) Eigenschaften amorpher, tetragonal gebundener Kohlenstoffschichten,
Bernd Schultrich
DS 8.1 Mo 14:30 (HS 32) Electron holography, Hannes Lichte
DS 11.1 Mi 14:30 (HS 31) InGaAsN als aktives Material für langwellige oberflächenemittierende Laser,
Henning Riechert
DS 16.1 Do 14:30 (HS 31) Plasma-assisted deposition and crystal growth of thin metal oxide films,
Rainer Hippler
FV-internes Symposium ” Analytische Elektronenmikroskopie“
DS 10.1 Di 09:30 (HS 32) Quantitative konvergente Elektronenbeugung und ihre Anwendungen,
Joachim Mayer
DS 10.2 Di 10:10 (HS 32) Quantitative Z-Kontrast-Abbildung zur Mikrostrukturcharakterisierung,
Helge Heinrich
DS 10.3 Di 10:50 (HS 32) Electron Energy-loss Spectrometry in the Electron Microscope,
Ferdinand Hofer
DS 10.4 Di 11:30 (HS 32) Energy-filtering transmission electron microscopy in materials science,
Wilfried Sigle
DS 10.5 Di 12:10 (HS 32) Kantenfeinstrukturen in Elektronen-Energieverlustspektren, Helmut Kohl
FV-internes Symposium ” Dünne Schichten für die Photovoltaik I“
DS 19.1 Do 09:30 (HS 32) Thin-film photovoltaics with crystalline Si using porous Si for layer transfer
(PSI process), Rolf Brendel, Heiko Plagwitz, Richard Auer
DS 19.2 Do 10:10 (HS 32) Photoelectron spectroscopy of thin film solar cell interfaces, Andreas Klein
DS 19.3 Do 10:50 (HS 32) Elektrische Analyse von polykristallinen Halbleiter-Dünnschichtsystemen
für die Photovoltaik, Uwe Rau
DS 19.4 Do 11:30 (HS 32) Präparationsverfahren für Chalkopyrit-Solarmodule, Reiner Klenk
DS 19.5 Do 12:10 (HS 32) Plasmagestützte Schichtabscheideverfahren für Dünnschichtsolarzellen:
Prinzipien und Anwendungen, Klaus Ellmer

Dünne Schichten Tagesübersichten
Fachsitzungen
DS 1 Ionenimplantation I Mo 09:30–11:45 HS 31 DS 1.1–1.9
DS 2 Ionenimplantation II Mo 11:45–12:30 HS 31 DS 2.1–2.1
DS 3 Ionenimplantation III Mo 14:30–16:00 HS 31 DS 3.1–3.6
DS 4 Prozesscharakterisierung Mo 16:00–17:00 HS 31 DS 4.1–4.4
DS 5 Spezielle Schichten I Mo 09:30–10:15 HS 32 DS 5.1–5.1
DS 6 Spezielle Schichten II Mo 10:15–11:30 HS 32 DS 6.1–6.5
DS 7 Spezielle Schichten III Mo 11:30–12:30 HS 32 DS 7.1–7.4
DS 8 Dünnschichtanalytik I Mo 14:30–15:15 HS 32 DS 8.1–8.1
DS 9 Dünnschichtanalytik II Mo 15:15–17:15 HS 32 DS 9.1–9.8
DS 10 FV-internes Symposium Analytische Elektronenmi-
”
Di 09:30–12:50 HS 32 DS 10.1–10.5
kroskopie an dünnen Schichten“
DS 11 Schichteigenschaften I Mi 14:30–15:15 HS 31 DS 11.1–11.1
DS 12 Schichteigenschaften II Mi 15:15–16:45 HS 31 DS 12.1–12.6
DS 13 Schichteigenschaften III Mi 16:45–18:00 HS 31 DS 13.1–13.5
DS 14 Schichtwachstum Mi 14:30–16:15 HS 32 DS 14.1–14.7
DS 15 Oberflächenmodifizierung Mi 16:15–18:00 HS 32 DS 15.1–15.7
DS 16 Schichtherstellung I Do 14:30–15:15 HS 31 DS 16.1–16.1
DS 17 Schichtherstellung II Do 15:15–16:45 HS 31 DS 17.1–17.6
DS 18 Schichtherstellung III Do 16:45–18:15 HS 31 DS 18.1–18.6
DS 19 FV-internes Symposium Dünne Schichten für die
”
Do 09:30–12:50 HS 32 DS 19.1–19.5
Photovoltaik I“
DS 20 Dünne Schichten für die Photovoltaik II Do 14:30–15:45 HS 32 DS 20.1–20.5
DS 21 Dünne Schichten für die Photovoltaik III Do 15:45–17:00 HS 32 DS 21.1–21.5
DS 22 Postersitzung Di 14:30–17:00 Poster B DS 22.1–22.58
Mitgliederversammlung des Fachverbands Dünne Schichten
Di 17:00–18:00 HS 32
Tagesordnung:
1. Bericht des Sprechers
2. Symposien und Hauptvorträge 2005
3. Verschiedenes
Die detaillierte Tagesordnung wird kurz vor der Tagung auf der Homepage des Fachverbandes veröffentlicht.

Dünne Schichten Montag
Fachsitzungen
– Haupt-, Kurzvorträge und Posterbeiträge –
DS 1 Ionenimplantation I
Zeit: Montag 09:30–11:45 Raum: HS 31
DS 1.1 Mo 09:30 HS 31
Untersuchung der Heliumimplantation als Schlüsselprozess in
der Relaxation von pseudomorphischen SiGe/Si Heterostrukturen
— •N. Hueging 1 , M. Luysberg 1 , D. Buca 2 , S. Mantl 2 ,
M. Morschbacher 3 , P. Fichtner 3 , R. Loo 4 , M. Caymax 4 und K.
Urban 1 — 1 Institut für Festkörperforschung IFF, Forschungszentrum
Jülich, 52425 Jülich — 2 Institut für Schichten und Grenzflächen ISG,
Forschungszentrum Jülich, 52425 Jülich — 3 University Federal do Rio
Grande do Sul, Porto Alegre, Brasil — 4 IMEC, Leuven, Belgium
Eine Möglichkeit die Leistungsfähigkeit von siliziumbasierten Bauelementen
zu erhöhen ist die Verwendung von verspanntem Silizium. Ein
Weg diese verspannten Schichten zu erzeugen ist die Nutzung von relaxierten
SiGe Schichten auf Si-Substrat, die durch Heliumimplantation
und thermische Behandlung hergestellt werden.
Dieser Prozess wird mittels Ergebnisse aus ex-situ und in-situ TEM
Untersuchungen sowie Resultaten aus RBS und ERDA Messungen diskutiert.
Untersucht werden mittels CVD gewachsene Heterostrukturen
mit Ge-anteilen von 20 - 30 % und SiGe-Schichtdicken von 80 - 400 nm.
Die Proben wurden mit geringer Dosis (0.5–1·10 16 cm −2 ) implantiert
und verschiedenen thermischen Behandlungen von bis zu 950 ◦ C ausgesetzt.
Bei Temperaturen von ca. 400 ◦ C bilden sich plattenförmige
He-Ausscheidungen, die bei weiterer Erwärmung einen Übergang zu einer
kugelförmigen Morphologie aufweisen und an denen Versetzungsringe
nukleieren. Diese beginnen bei Temperaturen von 600 ◦ C im Interface
ein Misfitversetzungsnetzwerk auszubilden, so daß Relaxationsgrade von
70 % nach 950 ◦ C erreicht werden.
DS 1.2 Mo 09:45 HS 31
Spuren hochenergetischer Ionen in NiO — •Beate Schattat 1 ,
Wolfgang Bolse 1 , Hartmut Paulus 1 , Siegfried Klaumünzer 2
und Roland Scholz 3 — 1 Institut für Strahlenphysik, Universität
Stuttgart — 2 Hahn-Meitner-Institut, Berlin — 3 Max-Planck-Institut
für Mikrostrukturforschung, Halle
Obwohl NiO unter Hochenergie-Ionenbestrahlung eine Reihe von
Phänomenen (Ionenmischen, Selbstorganisationseffekte) zeigt, die ein
kurzzeitiges Aufschmelzen des Materials entlang der Ionenbahn nahelegen,
konnten bislang keine latenten amorphen Ionenspuren nachgewiesen
werden. Wir konnten jetzt zeigen, dass bei hinreichend großem Energieeintrag
durch das Ion tatsächlich eine kurzfristig aufgeschmolzene Ionenspur
gebildet wird, die aber nach der Erstarrung offensichtlich wieder
vollständig rekristallisiert. Wir haben etwa 100 nm dicke NiO-Einkristalle
mit 90 MeV bis 350 MeV Ar-, Kr-, Xe- und Au-Ionen mit kleinen Fluenzen
von 3 − 4 · 10 10 cm −2 bestrahlt, so dass die Ioneneinschläge hinreichend
weit voneinander separiert waren. 200 kV TEM Untersuchungen
der Ar bestrahlten Probe zeigen keinerlei Veränderung gegenüber der unbestrahlten
Probe, wohingegen die mit den schwereren Ionen bestrahlten
Proben spurartige strukturelle Veränderungen aufweisen. Dieses Verhalten
ist im Einklang mit dem Schwellenverhalten, das auch bei den oben
genannten Effekten beobachtet wurde. Während bei Kr nur erste Spuransätze
beobachtet werden, bilden sich bei Xe- bzw. Au-Bestrahlung hohle
Kanäle von etwa 3 nm Durchmesser aus, an deren Enden (Ein- bzw.
Austrittspunkt des Ions) sich kugelförmige Ausscheidungen mit etwa 10
nm Durchmesser befinden.
DS 1.3 Mo 10:00 HS 31
Self-organisation of thin ceramic films under swift heavy
ion bombardment. — •Dereje Etissa-Debissa 1 , Melih
Kalafat 1 , Hartmut Paulus 1 , Wolfgang Bolse 1 , and Siegfried
Klaumünzer 2 — 1 Institut für Strahlenphysik, Universität Stuttgart
— 2 Hahn-Meitner Institut, Berlin
Layers consisting of 5 to 260 nm NiO deposited onto SiO2 have been
irradiated with swift heavy ions at liquid nitrogen temperature and large
tilt angle (θ > 60) between the target surface normal and the beam
direction. At low fluences, the initially smooth und coherent NiO-layer
revealed periodic cracks, which at increasing fluences reorganize into periodic
lamellae. The lamellae are oriented perpendicular to the beam
direction projected onto the surface and have a height of 1 µm, a thickness
of about 0,1 µm and an average distance of 1-3 µm [1,2]. Here we
will report on the relationships between the NiO-layer thickness and the
average cracking distance as well as between the incidence angle of the
ion beam and the threshold layer thickness, below which cracking does
not occur anymore. In addition we will present data on the dependence of
the lamellae growth rate on the material and beam parameters. Finally,
we will discuss first attempts to utilize this phenomenon for functional
nano-structuring of thin-film coatings.
[1] Ando Feyh, diploma thesis, University Stuttgart, 2002
[2] W. Bolse, B. Schattat, A. Feyh, Appl. Phys. A77, 11 (2003)
DS 1.4 Mo 10:15 HS 31
Monte-Carlo-Simultation der Selbstorganisation amorpher nanometrischer
SiCx-Ausscheidungen in Silizium während C + -
Ionen-Implantation — •F. Zirkelbach, M. Häberlen, J. K. N.
Lindner und B. Stritzker — Institut für Physik, Universität Augsburg,
Universitätsstrasse 1, D-86135 Augsburg
Die Implantation von C + -Ionen in Si mit hoher Dosis resultiert bei hinreichend
niedrigen Temperaturen (Ti ≤ 400 ◦ C) in der Bildung amorpher
SiCx-Ausscheidungen. Diese ordnen sich mit regelmäßigen Abständen an
und können sich zu amorphen Lamellen von wenigen nm Dicke verbinden,
wodurch sich eine Stapelung von wenigen nm dicken amorphen und
kristallinen Schichten ergibt. Dieser auch in anderen Materialsystemen
[1,2] beobachtbare Effekt wird auf die Übersättigung mit Fremdatomen,
gefolgt von Ausscheidungsbildung und Spannungen in der Umgebung der
Ausscheidungen zurückgeführt.
Um diesen Selbstorganisationsprozess zu beschreiben wurde ein Monte-
Carlo-Simulationscode entwickelt, der Keimbildung, Wachstum, Diffusion,
Amorphisierung und Rekristallisation berücksichtigt. Erste Ergebnisse
werden vorgestellt und mit elektronenmikroskopischen Daten verglichen.
[1] A.H. van Ommen, NIM B 39 (1989) 194
[2] J.K.N. Lindner, Appl. Phys. A 77 (2003) 27
DS 1.5 Mo 10:30 HS 31
Damage formation and annealing in InP due to swift heavy ions
— •Andrey Kamarou, Werner Wesch, and Elke Wendler —
Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Max-
Wien-Platz 1, 07743 Jena
Indium phosphide (InP) is a much promising material suitable for various
electronic and optoelectronic applications [1-3]. However, the effects
of the increasing electronic energy deposition in InP are not studied very
well if one moves from conventional ion energies to MeV ions which are
widely used for a device-device and active layer-substrate electrical isolation
as well as for quantum well intermixing.
We irradiated pre-damaged as well as virgin InP samples with 140 MeV
Kr, 390 MeV Xe and 600 MeV Au ions. We have registered both a relatively
weak effect of the damage accumulation in virgin InP and a very
significant defect annealing in the pre-damaged InP due to 140 MeV Kr
irradiation. The damaging of virgin InP with 390 MeV Xe and 600 MeV
Au is a much more efficient process with respect to damage formation as
compared to 140 MeV Kr. Further, annealing of the pre-damaged InP due
to 390 MeV Xe and 600 MeV Au irradiation does hardly occur. At liquid
nitrogen temperature InP appears to be much more radiation-resistant
to 390 MeV Xe than at room temperature.
[1] D. Streit, in Compound Semiconductors, May 2002.
[2] B. Humphreys and A. O.Donell, in Compound Semiconductors,
August 2003.
[3] D. Lammers, in Electronic Engineering Times, September, 12, 2002.

Dünne Schichten Montag
DS 1.6 Mo 10:45 HS 31
Ionenstrahlinduzierte Grenzflächendurchmischung in isotopenmarkierten
Schichtsystemen — •Mirjam Beuttler 1 , Wolfgang
Bolse 1 , Ulrich Kreissig 2 und Wolfgang Bohne 3 — 1 Institut für
Strahlenphysik, Universität Stuttgart — 2 Forschungszentrum Rossendorf,
Dresden — 3 Hahn-Meitner-Institut, Berlin
Bei unseren bisherigen Untersuchungen zum Hochenergie-
Ionenmischen von oxidkeramischen Schichtpaketen [1] wurden,
bedingt durch die Beschränkung auf die Rutherford Rückstreumethode
bei der Bestimmung der Konzentrationsprofile, alle Aussagen zum
Mischprozess und den zugrundeliegenden Mechanismen anhand des
Verhaltens der metallischen Komponenten gemacht. Da a priori nicht
klar ist, ob der Sauerstoff sich identisch verhält, haben wir dessen
Verhalten mit Hilfe der elastischen Rückstoß Analyse (Elastic Recoil
Detection Analysis, ERDA) an isotopenmarkierten Doppelschichten
untersucht. Hierzu wurden TiO2-, NiO-, Fe2O3- und SiO2-Schichten
mittels reaktiven Magnetronsputterns in einer natürlichen Sauerstoffatmosphäre
auf eine SiO2-Schicht mit isotopenangereichertem 18 O
deponiert und bei 80K mit Kr-, Xe- und Au-Ionen der Energien 100–350
MeV bestrahlt. Die Verbreiterung der 18 O-Grenzflächenprofile wurde
mit Hilfe von Flugzeit-ERDA bestimmt und mit dem Verhalten der
metallischen Komponenten verglichen. Von besonderem Interesse ist
das System Si nat O2/Si 18 O2, da hier erstmals die von hochenergetischen
Ionen induzierten Transportprozesse in einem chemisch homogenen
System untersucht werden konnten.
[1] B. Schattat, Dissertation, Universität Stuttgart, 2003
DS 1.7 Mo 11:00 HS 31
Interface modification of non-miscible multilayer systems by
swift heavy ions — •W. Bolse 1 , C. Rumbolz 1 , B. Schattat 1 ,
D. Kabiraj 2 , D.K. Avasthi 2 , and R.S. Chauhan 3 — 1 Institut für
Strahlenphysik, Universität Stuttgart, Germany — 2 Nuclear Science
Centre, New Delhi, India — 3 R.B.S. College, Agra, India
Thin film packages of thermally miscible materials can, as a rule, also
be intermixed by means of swift heavy ion irradiation, as was shown
for a number of ceramic, semiconducting and also metallic systems. In
the present study we have investigated the response of thermally nonmiscible
Fe-Ag- and Fe-Au multilayers on the low temperature irradiation
with swift heavy ions, ranging from 90 MeV Ar- to 350 MeV Au-ions.
In addition, the (non-irradiated) Fe-Au multilayers were also heated in
Ar-atmosphere to test the thermally induced behaviour. The elemental
distribution in the films before and after irradiation or heating, respectively,
was determined by means of Rutherford Backscattering Spectrometry
(RBS). While the Fe-Ag didn’t show any effect, the RBS-spectra of
the Fe-Au samples indicated a reduction of the interface roughness upon
irradiation (except for Ar ions). According to RBS simulations the Aulayer
transforms from a rough structure of half-sphere like islands into
a smooth layer. Heating of the multilayers on the other hand resulted
in broadening of the RBS-spectra, which we interprete as due to the
formation of Au-spheres. The results will be discussed in terms of the reduction
of the interface energy by ion beam and heat induced structural
rearrangements.
DS 1.8 Mo 11:15 HS 31
Properties of buried waveguides produced by He-irradiation
in KTP and Rb:KTP — •F. Schrempel 1 , Th. Opfermann 1 , J.-
P. Ruske 2 , U. Grusemann 2 , and W. Wesch 1 — 1 Friedrich-Schiller-
Universität Jena, Institut für Festkörperphysik, Max-Wien-Platz 1, D-
07743 Jena — 2 Friedrich-Schiller-Universität Jena, Institut für Angewandte
Physik, Max-Wien-Platz 1, D-07743 Jena
DS 2 Ionenimplantation II
Buried waveguides were produced by He-irradiation with energies between
1 and 3 MeV and ion fluences, which are sufficient to generate
multiple buried amorphous layers in KTP and Rb:KTP, respectively.
Within these layers the refractive index is decreased and they act as
barriers for light guiding. The irradiation also causes the formation of
defects within the waveguide, reducing the optical transmittance. By
post-irradiation thermal annealing light scattering and absorption inside
the waveguides are significantly reduced. In the case of Rb:KTP
rapid thermal annealing up to temperatures of of 770 K was found to
be suitable to abolish point defects and to prevent the Rb-diffusion at
the same time. Due to adjacent regions of different refractive indices non
symmetrical electric field distributions are obtained within the waveguide.
For the completely irradiated waveguides the homogeneous refractive
indexes around the waveguide cause fiber like symmetrical electric
field distributions in a singlemode waveguide undisturbed by surface effects.
The samples were analyzed by means of various complementary
methods (Rutherford backscattering spectrometry, cross-sectional transmission
electron microscopy, m-line spectroscopy). The nearfield pattern
and the attenuation of the waveguides were measured.
DS 1.9 Mo 11:30 HS 31
Conditions resulting in an epitaxial growth of cubic boron nitride
films on diamond substrates by ion beam assisted deposition
— •X.W. Zhang, H. Yin, R. Lang, H.-G. Boyen, and P.
Ziemann — Abteilung Festkörperphysik, Universität Ulm, D-89069 Ulm
Cubic boron nitride (c-BN) films were grown on highly (100)-oriented
chemical vapour deposited diamond films at various substrate temperatures
(TS) ranging from 420 ◦ C to 1000 ◦ C by using Ion Beam Assisted Deposition
(IBAD). The resulting c-BN films were characterized by Fourier
transformed infrared spectroscopy, high-resolution transmission electron
microscopy, Rutherford backscattering spectroscopy as well as X-ray
diffraction. The results demonstrate that the epitaxial growth of c-BN
films on diamond can be realized only at high values of TS ( 900 ◦ C), while
at e.g. 420 ◦ C, an intermediate hexagonal BN layer is formed between the
substrate and the c-BN film as it is usually observed for c-BN growth
on top of Si. This may be due to the amorphization or graphitization
of the diamond surface at low TS due to the assisting ion bombardment
during c-BN nucleation. The plasmon energies of the diamond substrates
that were held at various temperatures and bombarded by a mixture of
argon and nitrogen ions were determined from in situ low-energy electron
energy loss spectra. The results indicate that at higher TS values radiation
damage can be annealed out thereby maintaining an sp 3 -dominated
substrate surface, hence allowing epitaxial growth of c-BN. Furthermore,
a 500 nm thick c-BN film was deposited on a (001) single crystal diamond
substrate under optimum conditions. The rocking angles of 0.2 ◦ C)
as observed by x-ray diffraction, point to a strongly improved alignment.
Zeit: Montag 11:45–12:30 Raum: HS 31
Hauptvortrag DS 2.1 Mo 11:45 HS 31
Semiconductors under ion bombardment - studied by RBS in
situ at 15 K — •Elke Wendler and Werner Wesch — Institut
für Festkörperphysik, Friedrich-Schiller-Universität Jena, Max-Wien-
Platz 1, D-07743 Jena
Ion implantation into semiconductors is a well established and important
step in device fabrication. The study of the primary processes of
the ion-solid interaction is therefore of both technological and scientific
interest. The defect concentration within the implanted layers remaining
after implantation strongly depends on the target temperature, because
the mobility of intrinsic defects may result in strong annealing already
during the irradiation. A special target chamber was built up to do ion
implantation and ion beam analysis at 15 K without change of the temperature
of the sample. This allows us to study the primary ion beam
induced effects, whereas thermal effects can be widely excluded. The
paper presents results for different III-V semiconductors implanted and
measured at 15 K using a wide range of ion species. The effectiveness
of damage formation and the mechanisms of amorphisation during the

Dünne Schichten Montag
implantation are compared for the various materials investigated. The
results are discussed in the framework of models taking into account
DS 3 Ionenimplantation III
fundamental physical properties of the semiconductors.
Zeit: Montag 14:30–16:00 Raum: HS 31
DS 3.1 Mo 14:30 HS 31
Kinetics of ion-irradiation induced stress modifications in thin
film of different microstructure — •S.G. Mayr — I. Physikalisches
Institut, Georg-August-Universität Göttingen, Tammannstr. 1, 37077
Göttingen
Ion beam irradiation induced changes in the stresses operating in thin
films are correlated with the thermodynamic phases of the films and the
evolution in the films microstructure and morphology. We investigate using
a combination of experiments and molecular dynamics computer simulations
the kinetics of the processes, which lead to residual stress changes
in amorphous, nanocrystalline, columnar polycrystalline and single crystal
thin films. It is shown that - while local viscous relaxation within the
collision cascade underlies all stress changes - the initial microstructure
controls the final state of stress.
Financially supported by the DFG - SFB 602, TP B3.
DS 3.2 Mo 14:45 HS 31
Charakterisierung mittels Plasma-Immersions-Ionenimplantation
und -Deposition hergestellter DLC-Schichten — •Götz
Thorwarth 1,2 , Claus Hammerl 2 , Marcus Kuhn 2 , Walter
Assmann 3 und Bernd Stritzker 1 — 1 Lehrstuhl für Experimentalphysik
IV, Universität Augsburg, 86135 Augsburg — 2 AxynTeC
Dünnschichttechnik GmbH, Am Mittleren Moos 48, 86167 Augsburg
— 3 Sektion Physik der LMU München, Am Coulombwall 6, 85748
Garching
Diamantähnlicher Kohlenstoff (DLC) besitzt dank seiner speziellen
mechanischen, chemischen und elektrischen Eigenschaften ein großes
Anwendungspotential. Die Einsetzbarkeit des Materials insbesondere
im mechanischen Bereich erfordert den Einsatz großflächiger Behandlungsverfahren
mit hohen Beschichtungsraten. Ein diesen Ansprüchen
nahekommender Prozeß konnte auf Basis der Plasma-Immersions-
Ionenimplantation und -Deposition (PIII&D) entwickelt werden. Die resultierenden
Schichten wurden mittels Elastischer Rückstoßspektroskopie
(ERDA), Ramanspektroskopie, verschiedener tribologischer Verfahren
(Tribotest, Nanoindent, Impakt- und Scratchtest) sowie Korrosionstests
charakterisiert. Der Vortrag gibt einen Überblick über die Ergebnisse und
diskutiert die Abhängigkeit von den PIII&D–Prozeßparametern.
DS 3.3 Mo 15:00 HS 31
Plasma Immersion Ion Implantation of Martensitic Stainless
Steel — •Darina Manova, Stephan Mändl, Horst
Neumann, and Bernd Rauschenbach — Leibniz-Institut für
Oberflächenmodifizierung, Leipzig
Lattice expansion after energetic nitrogen implantation at medium
temperatures around 400 ◦ C, in conjunction with a significant wear reduction
by several orders of magnitude, is the common result for austenitic
stainless steels. In contrast, martensitic stainless steels are rarely investigated.
In this comprehensive investigation, different martensitic steel
grades are implanted with nitrogen using plasma immersion ion implantation
in the temperature range between 350 and 400 ◦ C. A closed surface
layer of expanded martensite extending several micrometer into the
sample was observed in all samples with a hardness of up to 2000 HV
and a wear reduction by two orders of magnitude. The layer thickness
is a function of steel grade and implantation parameters. Metallographic
cross-sections are investigated to correlate the mechanical properties with
the microstructure.
DS 3.4 Mo 15:15 HS 31
Ni depletion of a NiTi surface by ion implantation for biomedical
applications — •Natalia Shevchenko and Manfred Maitz
— FZ Rossendorf, Postfach 510119, 01314 Dresden
The NiTi alloy is interesting for medical applications because of its
either superelastic or memory shape properties. However, clinical acceptance
of the alloy still is limited due to its high nickel content.
The aim of this work is to reduce the Ni concentration in a NiTi surface
by ion implantation and study the influence on surface stability and
biocompatibility.
Modification of the NiTi samples was performed by N or/ and Ar
ion implantation at different parameters: ion energy (20 - 40 keV and
200 keV), fluence (10 17 − 10 18 cm −2 ), substrate temperature (RT - 400
C). The modified layers were examined by Auger electron spectroscopy,
grazing incidence X-ray diffraction analysis and transmission electron microscopy.
The corrosion resistance and biocompatibility were investigated
by the electrochemical corrosion analysis and cell culture tests with bone
forming cells, respectively.
Ion implantation could reduce the surface nickel content down to approx.
0.5 at %. Below the Ni depleted surface a Ni enriched zone is
formed, which indicates an increased mobility either of Ni from the surface
to the bulk or of Ti from the sub-surface to the surface. A reactive
diffusion mechanism for the nickel depletion in this system is discussed.
The corrosion stability increases by this treatment. In preliminary studies
with bone forming cells no decrease in biocompatibility was seen by
this treatment.
DS 3.5 Mo 15:30 HS 31
Swift heavy ion beam induced solid-state reaction at metaloxide/silicon
interfaces — •Ammar Elsanousi 1 , Wolfgang
Bolse 1 , Beate Schattat 1 , and Siegfried Klaumünzer 2 —
1 Institut für Strahlenphysik, Universität Stuttgart — 2 Hahn-Meitner
Institut, Berlin
We have studied the induced effects that occur at the interfaces of
metal-oxide/silicon bi-layers due to the irradiation with swift heavy
ions. Three different systems were investigated: NiO/Si, TiO2/Si, and
Fe2O3/Si. The irradiations were carried out at liquid nitrogen temperature
with ions ranging from 140 MeV Kr 10+ to 350 MeV Au 26+ at fluences
up to 3·10 15 ions/cm 2 . The samples were characterized by means of
Rutherford Backscattering Spectrometry (RBS), Scanning Electron Microscopy
(SEM) and X-Ray Diffraction (XRD). The as-deposited NiO
films exhibit a large shift and broadening of the XRD peaks, which indicates
strong in-plane stresses. At low irradiation fluences NiO/Si and
Fe2O3/Si showed the usual random walk mixing behavior △σ 2 = kφ,
while in TiO2/Si a non-linear scaling △σ 2 = kφ + mφ 2 was observed,
which indicates that mixing is driven by a chemical solid-state reaction.
At higher fluences plateau-formation was observed at the low-energy Niedge
in the RBS-spectra of NiO/Si, which indicates the formation of the
Olivinephase Ni2SiO4. However, the XRD-spectra did not show any evidence
for the crystalline form of this compound. At very high fluences,
dewetting occurs for NiO and Fe2O3 and the former coherent oxide films
agglomerate in small islands with micrometer dimension on top of the Si
substrate.
DS 3.6 Mo 15:45 HS 31
Ionenstrahlinduzierter Atomtransport an den Grenzflächen
dünner Alkalihalogenid-Schichten — •Hartmut Paulus, Christian
Dais und Wolfgang Bolse — Institut für Strahlenphysik,
Universität Stuttgart
Die Arbeitsgruppe Nukleare Festkörperphysik des Instituts für Strahlenphysik
der Universität Stuttgart hat in den letzten Jahren systematisch
das Mischverhalten dünner Schichtpakete unter Beschuß mit
schnellen Schwerionen untersucht. Bisher wurden Keramik/Keramik, Metall/Keramik
und Metall/Halbleiter Systeme untersucht. Als neue Materialklasse
sind jetzt die Alkalihalogenide dazu gekommen. Diese zeigen
heftige Reaktionen auf den Beschuß mit schnellen Schwerionen: das Material
schwillt, bildet Hügel auf der Oberfläche und weist sehr hohe, stark
richtungsabhängige Sputterraten auf [1]. Diese Eigenschaften machen sie
auch für eine Untersuchung hinsichtlich ihres Transportverhaltens an
Grenzflächen interessant. Präsentiert werden erste Ergebnisse der Untersuchung
von Alkalihalogenid-Schichten auf einem SiO2-Substrat, die mit
einer metallischen Sputterbarriere an der Oberfläche abgedeckt waren.
[1] M. Toulemonde, W. Assmann, C. Trautmann, and F. Grüner Phys.
Rev. Lett., 88, 057602 (2002)

Dünne Schichten Montag
DS 4 Prozesscharakterisierung
Zeit: Montag 16:00–17:00 Raum: HS 31
DS 4.1 Mo 16:00 HS 31
Epitaxial Growth of Thin, Atomically Flat Cu-Films on
GaAs(110) — •J. Müller, M. Wenderoth, N. Quaas, T. C. G.
Reusch, and R. G. U. Ulbrich — IV. Physikalisches Institut der
Universität Göttingen, Tammanstrasse 1, 37077 Göttingen
We present STM-studies of thin Copper films in the thickness range
from 5 to 19 monolayers grown at 80K on UHV-cleaved GaAs(110). After
annealing to room temperature the Cu films show clear evidence
for a morphology resembling 2D layer by layer growth. Long-time STMinvestigations
reveal a continuously reduction of the film roughness, leading
to atomically flat films. In comparison with a single crystal the atom
dynamics on the surface is reduced. After annealing to 380K, we observe
a transition from Schottky- to metal-type behaviour in the STS-current
associated with a flat morphology. Our study confirms the theoretical
assumption that this system can be described by the model of electronic
growth [1]. The work was financially supported by the SFB 602.
[1] Z. Zhang, Q. Niu, C.-K. Shih, Phys.Rev.Lett. 80, 5381 (1998)
DS 4.2 Mo 16:15 HS 31
Time-resolved Langmuir double probe measurement in a asymmetric
bipolar pulsed magnetron discharge for the deposition of
MgO thin films — •Thoralf Dunger, Thomas Welzel, Hartmut
Kupfer, and Frank Richter — TU Chemnitz, Institut für
Physik, 09107 Chemnitz
In an asymmetric bipolar pulsed magnetron discharge which is used for
MgO thin film deposition the time dependent behaviour of the charge carrier
density and the electron temperature has been investigated by using
a time-resolved Langmuir double probe method. The charge carrier density
shows a typical temporal evolution in the ”on time” where several
maxima (up to 10 11 cm −3 ) and minima can be observed. Between the
maxima a change of one order of magnitude is possible for different discharge
conditions. It was found that this temporal evolution is changed
by the pulse frequency, the duty cycle and the gas mixture. The electron
temperature remains nearly constant. A time evolution similar to that of
the charge carrier density was only observed near the magnesium target.
DS 4.3 Mo 16:30 HS 31
Nanostructure Development in Compound, Magnetron-
Sputtered PVD Thin Films — •Vladislav Spassov, Alan
Savan, and Henry Haefke — CSEM Swiss Center for Electronics
and Microtechnology, Inc., Rue Jaquet-Droz 1, CH 2000, Neuchatel,
Switzerland
DS 5 Spezielle Schichten I
Nanostructured PVD thin films are newly emerging materials with a
great potential in diverse applications such as for mechanical (e.g. tribological),
chemical (e.g. catalyst), optical (i.e. photosensitive films), electronic
(e.g. nonvolatile memory devices) coatings. A better understanding
of how the nanostructure of a growing thin film forms, is a key factor
in controlling and engineering the architecture of new materials and to
make the best use of their properties. We have studied the development
of nanocomposite thin films in the system TiAlCN-MoS2 deposited by
nonreactive sputtering from segmented ceramic targets. The influence of
the chemical composition and deposition parameters on the structure
is studied with transmisiion electron microscopy and energy-dispersive
X-ray spectroscopy.
DS 4.4 Mo 16:45 HS 31
Beschleunigte Festphasenkristallisation von amorphem Silizium
auf polykristallinen Saatschichten — •Silke Hübner, Erhard
Conrad, Martin Muske, Stefan Gall und Walther Fuhs —
Hahn-Meitner-Institut, Abt. Silizium-Photovoltaik, Kekuléstr.5, D-12489
Berlin
Durch Festphasenkristallisation von amorphem Silizium (a-Si) auf
einer polykristallinen Si (poly-Si) Saatschicht lassen sich grobkörnige
Si-Schichten herstellen. Diese sollen als Absorberschichten in Si
Dünnschichtsolarzellen auf Fremdsubstraten dienen.
Dazu wird mittels Al-induzierter Kristallisation eine poly-Si
Schicht auf Glas hergestellt. Dies geschieht durch die Umwandlung
eines Glas/Al/a-Si:H Schichtpakets in einem Temperschritt in eine
Schichtfolge Glas/poly-Si/Al(Si). Eine intrinsische a-Si:H-Schicht wird
auf dieser aluminiumhaltigen Saatschicht durch plasma-unterstützte
Gasphasendeposition (PECVD) abgeschieden. In einem weiteren
Temperschritt wird diese Schicht kristallisiert.
Dieser Prozess ist als Funktion der Zeit, der Schichtdicke und der
Temper-Temperatur mit Ramanspektroskopie analysiert worden. Dabei
zeigte sich, dass der Kristallisationsprozess, im Vergleich zu der a-Si:H
Kristallisation auf einem einfachen Glassubstrat, wesentlich beschleunigt
ist. Bereits nach 4 Stunden Temperung konnte eine vollständige Kristallisation
beobachtet werden. Als Ursache für diese Beschleunigung wird die
Kristallstruktur der Saatschicht sowie das darin enthaltene Al gesehen.
Die Diffusion des Al während des Temperprozesses führte außerdem zu
einer p-Dotierung der Absorberschicht.
Zeit: Montag 09:30–10:15 Raum: HS 32
Hauptvortrag DS 5.1 Mo 09:30 HS 32
Eigenschaften amorpher, tetragonal gebundener Kohlenstoffschichten
— •Bernd Schultrich — Fraunhofer-Institut fuer
Werkstoff.- und Strahltechnik, Winterbergstrasse 28, 01277 Dresden
Kohlenstoff bildet in fester Form Dreier- bzw. Viererkoordinationen
aus. Dementsprechend bilden sich zweidimensionale bzw. dreidimensionale
Netzwerke wie im Graphit bzw. im Diamant aus. Beide Modifikationen
zeigen hinsichtlich ihrer mechanischen, elektrischen und optischen Eigenschaften
ein komplementaeres Erscheinungsbild. Mit PVD-Verfahren
laesst sich Kohlenstoff als amorphes Material abscheiden, in dem bei-
DS 6 Spezielle Schichten II
de Bindungstypen frei miteinander kombiniert werden koennen. Unter
Verwendung energiereicher Teilchen ist es moeglich, amorphe Kohlenstoffstrukturen
mit bis zu 80 wird ein Ueberblick ueber die Eigenschaften
derartiger ta-C-Schichten und über deren Modifikation durch gezielte
Veränderung der Beschichtungsbedingungen gegeben. Die ta-C-Schichten
stellen hochgradige Nichtgleichgewichts-Strukturen dar. Sie sind zwar bis
zu Temperaturen um 500 Grad stabil, lassen sich aber durch lokalen
Energieeintrag in graphitische Strukturen überfuehren. Es werden daraus
resultierende Moeglichkeiten zur Herstellung von Mikro- und Nanostrukturen
vorgestellt.
Zeit: Montag 10:15–11:30 Raum: HS 32
DS 6.1 Mo 10:15 HS 32
Mechanical Stability of Nanocrystalline Diamond Films on Silicon
— •Giuseppe Bregliozzi, Werner Haenni, and Henry Haefke
— CSEM Swiss Center for Electronics and Microtechnology, Inc.,
Rue Jacquet-Droz 1, CH-2007 Neuchatel, Switzerland
Diamond is an excellent film material due to its outstanding hardness,
thermal conductivity and chemical stability and low friction when sliding
against itself. In many specific applications (e.g. electrodes and MEMS),
these outstanding properties make diamond the best choice. A limiting
feature, however, is that only very few support materials have the necessary
affinity to stick to diamond: silicon carbide, silicon nitride, silicon
as well as refractory carbides. Even with these materials, testing dia-

Dünne Schichten Montag
mond film affinity is a problem due to its superb mechanical properties.
This work shows that an excellent technique to test film affinity is to use
cavitation erosion, which probes the properties of diamond films under
dynamic conditions. In this work, two types of silicon with different surface
topographies have been tested for their suitability as a support for a
nanocrystalline diamond film. It was found that the surface roughness of
the substrate has a strong influence upon the cavitation erosion behavior.
Higher roughness results in the presence of more defect sites. Wear
damage of the diamond films initiate from these film defects, which then
rapidly propagate across the entire film surface. The microwear mechanism
of the examined diamond film is characteristic of brittle materials
and occurs without any visible deformation as is commonly observed in
metals.
DS 6.2 Mo 10:30 HS 32
Diffusion of iron in an Fe3Si film — •Daniel Kmiec 1 , Bogdan
Sepiol 1 , Marcel Sladecek 1 , Gero Vogl 1 , Jozef Korecki 2 ,
Tomasz Slezak 2 , Rudolf Rüffer 3 , Koen Vanormelingen 4 und
Andre Vantomme 4 — 1 Institut für Materialphysik der Universität Wien,
Strudlhofgasse 4, A-1090 Wien, Austria — 2 Faculty of Physics and
Nuclear Techniques, Univesity of Mining and Metallurgy, Mickiewicza
30, PL-30-239 Cracow, Poland — 3 ESRF, F-38043 Grenoble, France —
4 Instituut voor Kern- en Stralingsfysica KU Leuven, Celestijnenlaan 200
D, B 3001 Leuven, Belgium
Diffusion of iron in bulk Fe3Si proceeds via nearest-neighbour jumps
[1]. The access to x-rays of third generation synchrotron radiation sources
enables studies of dynamics in metallic systems in grazing incidence geometry
paving the way for surface investigations. An interesting task is
the comparison of diffusion in a near-surface layer and in the bulk crystal
of Fe3Si. On an Fe3Si thin film produced by annealing of an Fe/Si
multilayer created by molecular beam epitaxy, grazing incidence studies
of synchrotron Mössbauer spectroscopy have been performed. The diffusion
coefficient of Fe atoms in the bulk is in good agreement with results
from previous measurements. We report about enhanced diffusion in a
near-surface layer.
This work was supported by the Austrian Fonds zur Förderung der
wissenschaftlichen Forschung (FWF, P-15421), bm:bwk (GZ 45.529/2-
VI/B/7a/2002) and ÖAD BWTZ (15/2002).
[1] B. Sepiol, G. Vogl, Phys. Rev. Lett. 71 (1993) 731; B. Sepiol et al.,
Phys. Rev. Lett. 76 (1996) 3220; Phys. Rev. B 57 (1998) 10433
DS 6.3 Mo 10:45 HS 32
Sputterepitaxie von Fe(001) und Fe/Si/Fe(001) auf GaAs(001)
und MgO(001) Substraten — •Thorsten Damm, Alexandra
Schindler, Matthias Buchmeier, Daniel E. Bürgler, Peter
Grünberg und Claus M. Schneider — IFF, Forschungszentrum
Jülich, 52425 Jülich
Epitaktische Fe(001) Schichten werden meist mittels Molekularstrahlepitaxie
(MBE) auf sorgfältig präparierten Substraten wie GaAs(001)
oder auf Puffersystemen deponiert. An solchen MBE-gewachsenen
Fe/Si/Fe(001) Schichtsystemen wurde eine starke antiferromagnetische
Austauschkopplung (AFK) von über 6 mJ/m 2 gefunden [1].
Epitaktisches Wachstum von Fe auf GaAs(001) kann auch mittels
Ionenstrahlsputtern erzielt werden [2], jedoch ist wenig über den Einfluss
der Sputterparameter auf die Qualität der Schichten bekannt. In einem
DS 7 Spezielle Schichten III
ersten Schritt stellen wir 10 nm dicke Fe-Schichten bei verschiedenen
Sputterparametern her und analysieren ihre Eigenschaften. Ein Maß
für die Qualität der Epitaxie liefern die Linienbreite der ferromagnetischen
Resonanz (FMR). Weiterhin werden MOKE-Hystereseschleifen
gemessen und die Anisotropiekonstante aus winkelabhängigen Magnetotransportmessungen
und FMR bestimmt. Dabei überrascht,
dass gutes epitaktisches Fe Wachstum auch auf nicht vorbehandelten
Substraten möglich ist. LEED-Bilder von gesputterten Fe/Si/Fe(001)
Schichtsystemen bestätigen für den kompletten Stapel epitaktisches
Wachstum. Die Schichtungen zeigen AFK. Deren Abhängigkeit von den
Sputterparametern wird untersucht.
[1] R.R. Gareev et. al., J. Magn. Magn. Mater. 240, 235 (2002)
[2] S.D. Bernstein et.al., J. Appl. Phys. 72 4358 (1992)
DS 6.4 Mo 11:00 HS 32
Akustische Oberflächenresonanzen zur Bestimmung des Elastizitätstensors
von dünnen W 2C-Schichten — •T. Wittkowski
1 , G. Distler 1 , K. Jung 1 , B. Hillebrands 1 und J.D. Comins 2
— 1 Fachbereich Physik und Forschungsschwerpunkt MINAS, Technische
Universität Kaiserslautern, Erwin-Schrödingerstr. 56, 67663 Kaiserslautern
— 2 Department of Physics, University of the Witwatersrand, Johannesburg,
Wits 2050, South Africa
Die Phasengeschwindigkeiten dispersiver akustischer Anregungen, die
in einer dünnen Wolframkarbidschicht geführt werden, wurden mit der
Brillouin-Lichtstreuspektroskopie vermessen. Ausgehend von der so gewonnenen
Datenbasis wird gezeigt, dass zusätzlich zur Dispersion diskreter
akustischer Oberflächenmoden (Rayleigh- und generalisierte Lamb-
Moden), die Auswertung resonanter Anregungen oberhalb der transversalen
Grenzgeschwindigkeit ergänzende, wertvolle Informationen über die
Schicht liefert. Im vorliegenden Fall wird dadurch die präzise Bestimmung
von vier unabhängigen Komponenten des Elastizitätstensors ermöglicht.
Die Ergebnisse an polykristallinem W 2C zeigen unter anderem, dass sich
das sehr steife Schichtmaterial elastisch anisotrop verhält.
DS 6.5 Mo 11:15 HS 32
Modeling thin films of SiO(2), ZrO(2) and HfO(2) with various
densities as effective optical medium. — •Dieter Mergel 1 , Martin
Jerman 2 , and Qiao Zhaohui 1 — 1 Universität Duisburg-Essen,
Campus Essen, Fb-7 Physik — 2 Universität Duisburg-Essen, Campus
Essen, Optische Werkstatt und Fb-7
Amorphous films of SiO(2), ZrO(2) and HfO(2) with various packing
densities and thicknesses between 150 to 1500 nm were prepared by electron
beam evaporation. The density of the films decreases with increasing
background pressure similar to the case of TiO(2) [1]. The functional dependence
of the refractive index on the density was modeled on the basis
of the Bruggeman effective medium approach [2]. For the SiO(2) series,
the results were compared with the general refractivity formula obtained
from experiments with densified silicate glass [3]. A best fit of the model
to the experimental series is obtained when it is assumed that the bulk
amorphous grains of SiO(2) films are quartz-like (i.e. similar density and
refractive index). A similar, but less detailed theoretical investigation of
the (rho, n) results or ZrO(2) suggests baddeleyite-like amorphous grains.
[1]Mergel D, Buschendorf D, Eggert S, Grammes R, Samset B, Thin Solid
Films 371 (2000) 218 - 24 [2]Mergel D, Thin Solid Films 397 (201) 216-22
[3]Arndt J, Hummel W, Phys. Chem. Minerals 15 (1988) 363-9
Zeit: Montag 11:30–12:30 Raum: HS 32
DS 7.1 Mo 11:30 HS 32
Tunable multiple plasmon resonance wavelengths response
from multicomponent polymer-metal nanocomposite systems
— •Oral Cenk Aktas, Abhijit Biswas, Ulrich Schürmann,
Usman Saeed, Thomas Strunskus, Vladimir Zaporojtchenko,
and Franz Faupel — Nanocomposite Research Laboratory, Lehrstuhl
für Materialverbunde, Technische Fakultät der CAU, Kaiserstr. 2, D -
24143, Kiel, Germany
Nanocomposite thin films formed by noble metal nanoparticles embedded
in a dielectric matrix show attractive optical properties at the surface
plasmon resonance wavelength due to dielectric and quantum confinements
effects. A simple method of vapor phase co-deposition has been
used at elevated target temperature (∼ 120 ◦ C) coupled with selective
masking technique to produce a multicomponent optical material with
seven different UV/Vis optical active planes. Such system consists of different
nanocomposites (∼ 100 nm) of Teflon AF/Ag, Teflon AF/Au and
Teflon AF/Cu with sharp interfaces. The fabricated system has regions
of single nanocomposite plane together with multilayer structures facilitating
tunable double and triple particle plasmon resonance wavelength
response from a single system.

Dünne Schichten Montag
DS 7.2 Mo 11:45 HS 32
Growth and structure of phthalocyanine thin films on SiO2 and
octadecyltriethoxisilanes — •Dimas Garcia de Oteyza 1 , Esther
Barrena 1 , J. Oriol Ossó 2 , and Helmut Dosch 1,3 — 1 Max
Planck Institut für Metallforschung, 70569 Stuttgart, Deutschland —
2 Institut de Ciència de Materials de Barcelona CSIC, 08190 Bellaterra,
Spanien — 3 Institut für Theoretische und Angewandte Physik, Universität
Stuttgart, 70569 Stuttgart
A key element for the controlled growth of organic thin films is the
substrate, since the resulting structure depends on the delicate balance
between the substrate-molecule and the intermolecular interaction. The
functionalization of the surfaces by self assembling monolayers (SAMs) allows
tailoring the surface properties while preserving the morphology. We
have used AFM and X-ray diffraction techniques to study the growth and
structure of copper hexadecafluorophthalocyanine (F16CuPc) on SiO2
and on functionalized SiO2 by octadecyltriethoxisilanes (OTE). OTE is a
methyl terminated SAM with a lower surface energy than SiO2. F16CuPc
films grown on SiO2 are smooth and show good out of plane order with
very low mosaicity (0.015 ◦ ).Their (001) plane is oriented parallel to the
surface, with the molecules essentially upright. Films grown on OTE
show a dewetting structure consisting of big elongated crystallites up to
the size of microns. In spite of the morphological differences, the films on
OTE exhibit the same out-of-plane lattice parameter and low mosaicity.
In-plane X-ray measurements indicate that the domain size is larger for
the films on OTE compared to those on SiO2, in agreement with the
AFM images.
DS 7.3 Mo 12:00 HS 32
Effect of surface structure on hydrophobicity — •Phani Ayalasomayajula,
Yvonne Gerbig, and Henry Haefke — CSEM Swiss
Center for Electronics and Microtechnology, Inc., CH-2007 Neuchatel,
Switzerland
Super hydrophobic surfaces can lead to applications in various fields.
This work reports on a key feature of super hydrophobicity: the combined
effect of chemistry and surface topography. Using the sol-gel technique,
hydrophobic surfaces that are smooth and crack-free based on Poly[4,5 difluoro
2,2-bis (trifluoromethyl)-1,3 dioxole]-co-tetrafluoroethylene (TFE)
DS 8 Dünnschichtanalytik I
were grown on glass. These were characterized using contact angle testing,
UV-visible spectroscopy (UV-vis) and Fourier transform infrared
(FTIR) spectroscopy to determine their wettabilty, optical absorbance
as well as vibrational and stretching bands of the deposited films, respectively.
Besides being hydrophobic, the deposited films are oleophobic,
transparent with antireflective properties and hard. TFE films with
thicknesses ranging from 5 nm to 50 nm were deposited on nanostructured
chromium nitride coatings to investigate the combined effect of surface
topography and chemistry upon film hydrophobicity. It was found
that TFE coatings on a specific columnar growth structure formation of
chromium nitride lead to an increase in the contact angle from 120 o to
147 o. Surface properties of the films have been examined using scanning
electron microscopy (SEM) and energy dispersive X-ray analysis (EDX)
for morphology and elemental composition, respectively. The precise effect
of surface morphology and roughness is discussed.
DS 7.4 Mo 12:15 HS 32
AFM investigation of oligophenyl thin films on crystalline substrates
— •G. Hlawacek 1 , C. Teichert 1 , S. Müllegger 2 , A. Winkler
2 , R. Resel 2 , S. Berkebile 3 , and M. Ramsey 3 — 1 Department
of Physics, University of Leoben, A-8700 Leoben, Austria — 2 Department
of Solid State Physics, Graz Technical University, A-8010 Graz, Austria
— 3 Department of Experimental Physics, University of Graz, A-8010
Graz, Austria
Crystalline films of conjugated organic semiconductors as parasexiphenyl
(PSP, C36H26) and para-quaterphenyl (PQP, C24H18) offer
attractive potential for optoelectronic applications. Here, Atomic
Force Microscopy (AFM) is used to investigate the nanometer-scale
morphology of PQP on various gold substrates and PSP on TiO2(110).
These oligophenylens can form complex arrays of three-dimensional
crystallites, where the long axis of the molecules are nearly parallel to
the surface. The orientation of these arrays is controlled by the geometry
of the substrate surface. On polycrystalline gold and TiO2(110) we could
also observe terrace structures composed of upright standing molecules.
Growth hillocks – consisting of several such layers – and crystallites coexist
within close proximity.
Zeit: Montag 14:30–15:15 Raum: HS 32
Hauptvortrag DS 8.1 Mo 14:30 HS 32
Electron holography — •Hannes Lichte — Institut fuer Strukturphysik,
TU Dresden, 01062 Dresden
Today, the performance of transmission electron microscopy (TEM)
is well developed to a resolution limit of close to 0.1nm; in particular
since the recently successful correction of spherical aberration of electron
lenses, the interpretability of electron images allows quantitative analysis
of most interesting structures, e.g. at defects and interfaces. Nevertheless,
a conventional electron microscope is still a poor phase contrast micro-
DS 9 Dünnschichtanalytik II
scope, i.e. it is virtually blind for pure phase structures such as electric
or magnetic fields. Electron holography has overcome this blindness: by
superposition of a reference wave on the object wave, a hologram is produced,
from which the phase structure of the object wave can quantitatively
be determined. This allows access to electric and magnetic fields,
from mesoscopic to atomic dimensions, as well as the determination of
atom species in compound specimen. Recent applications in the field of
nanomagnetics, dopant profiling in semiconductors, and in ferroelectrics
show the state of the art and the limits of the holographic method.
Zeit: Montag 15:15–17:15 Raum: HS 32
DS 9.1 Mo 15:15 HS 32
Untersuchung der Titan-Koordination in strukturell modulierten
Einkristallen und Gläsern der Zusammensetzung A2TiX2O8
(mit A = Ba, Sr und X = Si, Ge) — •Thomas Höche 1 , Frank
Heyroth 2 , Ralf Keding 3 und Peter van Aken 4 — 1 Leibniz-
Institut für Oberflächenmodifizierung e.V., Permoserstraße 15, D - 04318
Leipzig, Germany — 2 Interdisziplinäres Zentrum für Materialwissenschaften,
Martin-Luther-Universität Halle-Wittenberg, Hoher Weg 8, D -
06120 Halle a.d. Saale, Germany — 3 Otto-Schott-Institut für Glaschemie,
Friedrich-Schiller-Universität, Fraunhoferstraße 6, D - 07743 Jena, Germany
— 4 Institut für Angewandte Geowissenschaften, Technische Universität
Darmstadt, Schnittspahnstraße 9, D - 64287 Darmstadt, Germany
Kristalline Titanate mit der Fresnoitstruktur (Ba2TiSi2O8, Sr2TiSi2O8
und Ba2TiGe2O8) enthalten ausschließlich fünffach koordiniertes Ti 4+ .
Für das Verständnis des Kristallisationsverhaltens ist die Bestimmung
der Titan-Koordination in Schmelzen identischer Zusammensetzung es-
sentiell. Durch Quenchen der Schmelzen wurden Gläser erhalten, die anschließend
in einem Rastertransmissionselektronenmikoskop untersucht
wurden. Aus Elektronenenergieverlustspektren (spektrale Auflösung: ca.
0,4 eV) kann die Koordination von Übergangsmetallen bestimmt werden.
Dies wird anhand der Ti-L2,3-Ionisationskantenfeinstruktur von Gläsern
der Zusammensetzung Ba2TiSi2O8, Sr2TiSi2O8 und Ba2TiGe2O8 gezeigt
und die Ergebnisse werden mit früheren integralen Messungen (XPS,
XANES) der Titan-Koordination in Gläsern verglichen und den Kantenfeinstrukturen
der Einkristalle gegenübergestellt.
DS 9.2 Mo 15:30 HS 32
Diffraction patterns of modulated permutation twins —
•Ulrich Gebhardt 1 , P. Wochner 1 , A. Vigliante 2 , H.U. Habermeier
3 , and F. Razavi 4 — 1 MPI f. Metallforschung, Heisenbergstr.
3, 70569 Stuttgart — 2 Bruker AXS GmbH, Karlsruhe — 3 MPI f.
Festkörperforschung, Stuttgart — 4 Brock University, St. Catherines,
Ontario, Canada

Dünne Schichten Montag
We studied the structural properties of epitaxial, thin film and low-
Sr-doped lanthanum-manganites, grown on a SrTiO3(001) substrate, as
function of thickness by means of X-ray diffraction. The observed structure
of these thin film manganites differ from bulk materials because of
the presence of strain due to the lattice mismatch between substrate and
film. Dependent on film thickness and on the chosen Bragg-peak the observed
intensity distribution resembles something between a periodically
modulated or a twinned structure. By assuming a nearly periodic array
of twin domains we found by statistical calculation a good agreement of
the model with the measured data.
DS 9.3 Mo 15:45 HS 32
Structure and thickness-dependant lattice parameters of ultrathin
epitaxial Pr2O3 films on Si(001) studied by SR-GIXRD —
•Thomas Schroeder 1 , Tien Lin Lee 1 , Laure Libralesso 1 , Jörg
Zegenhagen 1 , Peter Zaumseil 2 , Christian Wenger 2 , and Hans
Joachim Müssig 2 — 1 E.S.R.F., Beamline ID 32, 6, Rue Jules Horowitz,
38043 Grenoble, France — 2 IHP, Im Technologiepark 25, 15236 Frankfurt
(Oder)
Heteroepitaxial Pr2O3 films on Si(001) show promising results for applications
as high-K dielectrics in future silicon-based microelectronics
devices. To solve the epilayer structure and monitor the evolution of
the lattice parameters over the technologically important thickness range
from 1 to 10 nm, a Synchrotron-grazing incidence X-ray diffraction (SR-
GIXRD) study was performed. The oxide film structure is characterized
by the growth of the cubic Pr2O3 phase (Ia3) with its rectangular (101)
plane on the Si(001) substrate. The resulting two orthogonal rotation
domains of the oxide layer are identified by the four-fold symmetry of
the oxide reflections. The azimuthal orientation of these oxide domains
is determined by measuring the oxide in-plane reflections. These in-plane
measurements together with theta - 2theta scans allow to monitor the
evolution of the oxide unit cell lattice parameters as a function of film
thickness. The transition from almost perfect pseudomorphism to bulk
values is detected from 1 to 10 nm film thickness. The intensity analysis
of the oxide reflections points to a change in the structure factor of oxide
films thinner than 4 nm, probably due to silicate formation at the oxide
/ Si interface.
DS 9.4 Mo 16:00 HS 32
Investigations of Pr2O3 growth modes on 4H-SiC(0001) Surfaces
— •Andriy Goryachko 1 , Guido Beuckert 1 , Peter Zaumseil
2 , Guenter Wagner 3 , and Dieter Schmeisser 1 — 1 Department
for Applied Physics / Sensorics, BTU Cottbus, Universitaetsplatz 3-4,
D-03046 Cottbus, Germany — 2 IHP, Im Technologiepark 25, D-15236
Frankfurt (Oder), Germany — 3 IKZ, Max Born Str. 2, D-12489 Berlin,
Germany
The SiC is suited especially well for high power and high voltage semiconductor
devices. In order to increase the reliability against electrical
breakdown of metal-insulator-semiconductor (MIS) structures, one needs
to use the insulator with possibly higher dielectric constant. Pr2O3 is
shown to posses a much higher dielectric constant (equals 30) than traditionally
used SiO2. Therefore, Pr2O3/SiC is an excellent material combination
for high voltage MIS devices. The 4H-SiC(0001) substrates are
characterised with scanning tunneling microscopy, while the Pr2O3 surface
- with atomic force microscopy technique. We show distinct growth
modes of Pr2O3 film, such as 3D and layer by layer growth. The crystalline
structure and film thickness are determined by X-ray diffraction
and its chemical composition by X-ray photoelectron spectroscopy. The
Pr2O3 film characteristics are optimised for high-quality MIS structures
in terms of lateral uniformity, low interface states density and leakage
current, as well as physical integrity.
DS 9.5 Mo 16:15 HS 32
Mainfold nonosized metallic composites preparation and theoretical
simulations. — •Witold Kandulski 1,2 and Adam Kosiorek
1,2 — 1 CAESAR research center, Dept. Nanoparticle Technology,
Ludwig-Erhard-Allee 2, 53175 Bonn, Germany — 2 Poznan University of
Technology, ul. Nieszawska 13a, 60-965 Poznan, Poland
Nanosphere lithography is a known method for creating ordered metallic
nanostructures. We present a modification of this inexpensive and
varied full technique, which extends the possibilities of creating different
morphologies. Computer simulations were used to determine geometric
configurations of the metal deposition system for creating various
structures. We will show some examples of bimetallic nanosized periodicoriented
large areas of nanostructures. Very good correlations between
the predicted simulation and experimental results were achieved. An additional
goal was the prevention of magnetic particles from oxidation.
Presented arrays of nanostructures have interesting magnetic and optical
properties due to complex geometry, different to previously investigated
spherical shapes which are obtainable by standard geometric configuration.
The possible application will be also discussed.
DS 9.6 Mo 16:30 HS 32
Examination of diamond seed-layers on Ir/ SrTiO3 using Scanning
Electron Microscopy and Auger Electron Spectroscopy —
•P Bernhard 1 , Ch. Ziethen 1 , M. Schreck 2 , S. Gsell 2 , H. Karl 2 ,
G. Schaefer 3 und S. Schoenhense 1 — 1 University of Mainz, D-55099
Mainz — 2 University of Augsburg, D-86135 Augsburg — 3 OMICRON
Nanotechnology GmbH, D-65232 Taunusstein
The growth of diamond films of macroscopic dimensions without grain
boundaries (quasi single crystalline) is greatly influenced by the characteristics
of the diamond seed-layers. These diamond seed-layers grown on
top of an Ir/ SrTiO3 sample using a BEN (Bias Enhanced Nucleation)
process [1] have been analysed using a UHV SEM and a small spot AES
based on a Gemini column.
A peculiarity of this nucleation process is the accumulation of the
diamond nuclei in clear bounded domains with negligible nucleation outside.
In this work we focussed our interest on the determination of the
carbon-layer thickness inside and outside the domains by measuring the
attenuation of the iridium Auger lines. For the calculation the Auger
electron inelastic mean free path in diamond was used.
After Focused Ion Beam structuring of the sample we also determined
the layer thickness of a carbon precursor [2], using the same technique
of SEM/ AES and we examined the contribution of subplantation to the
growth of the diamond layer.
References [1] M. Schreck et al., Apl. Phys. Lett. 78 (2001) 192 [2] Th.
Bauer et al., Diamond and Rel. Mat., 11 (2002) 493
DS 9.7 Mo 16:45 HS 32
In situ Prozessanalytik mit Hilfe der Ramanstreuung und der
spektroskopischen Ellipsometrie — •M. Schubert 1 , N. Ashkenov
1 , C. Bundesmann 1 , M. Lorenz 1 , M. Grundmann 1 , E. Schubert
2 , H. Neumann 2 , B. Rauschenbach 2 , A. Braun 3 und G. Lippold
3 — 1 Fakultät für Physik und Geowissenschaften, Institut für Experimentelle
Physik II, Universität Leipzig, Linnéstraße 5, 04103 Leipzig
— 2 Institut für Oberflächenmodifizierung Leipzig e.V., 04303 Leipzig —
3 Solarion GmbH, Photovoltaik, 04288 Leipzig
Mit Hilfe der in-situ Ramanstreuung und der spektroskopischen in-situ
Ellipsometrie gelingt die zerstörungsfreie, berührungslose und schnelle
Bestimmung von optischen und strukturellen Dünnschicht-Eigenschaften
während des Dünnschichtwachstums. Erfolgt die Messung und Analyse
schnell genug, können die gewonnenen Informationen zur automatischen
Steuerung des laufenden Prozesses in vorgegebenen Parameterbereichen,
und damit zur Langzeitstabilitat von Qualtitätsmerkmalen
verwendet werden. Wir berichten über Anwendungen auf das Wachstum
von CuInSe2-Solarzellenabsorberschichten, ZnO-Dünnschichten, und
Mo-Si Röntgenreflexionsschichstrukturen.
DS 9.8 Mo 17:00 HS 32
Impact of design parameters of coupled parallel beam X-ray
mirrors and channel cut monochromators on divergence, beam
width and monochromacy — •T. Holz 1 , D. Korytar 2 , and T.
Böttger 3 — 1 AXO DRESDEN GmbH, Siegfried-Rädel-Str. 31, D-
01809 Heidenau — 2 Institute of Electrical Engineering, DTDS, Vrbovska
110, SK-92101 Piestany, Slowakia — 3 Fraunhofer Institute for Material
and Beam Technology (IWS), Winterbergstr. 28, D-01277 Dresden
Intensity and beam divergence in high resolution X-ray diffraction arrangements
are mainly influenced by the quality of the surface shaping
of parallel beam multilayer mirrors, when the beam is coupled into a
channel cut monochromator.
First results of optimisation process of matching of divergence between
multilayer and crystal monochromator are presented.
The resulting beam characteristics are deduced from rocking scan measurements
and coupled Θ −2Θ scans of a silicon single crystal reflection.
Different modifications of V-cut beam compressing crystals are compared
to standard symmetric channel cuts.
Based on the results achieved for Mo-Kα1 radiation which were presented
at the APD-III (NIST, Gaithersburg, 2001) we want to give the
appropriate solution with the highest Cu-Kα1 intensity to a user.

Dünne Schichten Dienstag
DS 10 FV-internes Symposium ” Analytische Elektronenmikroskopie an dünnen
Schichten“
Zeit: Dienstag 09:30–12:50 Raum: HS 32
Hauptvortrag DS 10.1 Di 09:30 HS 32
Quantitative konvergente Elektronenbeugung und ihre Anwendungen
— •Joachim Mayer — Gemeinschaftslabor für Elektronenmikroskopie,
RWTH Aachen, Ahornstr. 55, 52074 Aachen
Im Vortrag soll ein Überblick über die neuen Möglichkeiten der quantitativen
konvergenten Elektronenbeugung (convergent beam electron diffraction,
CBED) gegeben werden. Im Transmissionselektronenmikroskop
werden dabei Beugungsbilder kristalliner Bereiche mit kegelförmiger Beleuchtung
aufgenommen. Durch Energiefilterung lässt sich der durch inelastisch
gestreute Elektronen entstehende Untergrund entfernen, was
eine quantitative Auswertung mit höchster Genauigkeit ermöglicht. In
den Beugungsbildern entsteht für jeden angeregten Reflex ein Beugungsscheibchen,
dessen Intensitätsverteilung einem zweidimensionalen
Rocking-Profil für den gegebenen Reflex entspricht. Eine quantitative
Auswertung des Einflusses von Reflexen aus höheren Laue-Zonen
ermöglicht die Bestimmung von Gitterverzerrungen in dünnen Schichten
mit hoher Genauigkeit. Die Analyse der dynamischen Streueffekte
für niedrigindizierte Reflexe erlaubt eine dreidimensionale Analyse
der elektronischen Bindungsladungsdichten zwischen den Kristallatomen.
Anhand verschiedener materialwissenschaftlicher Anwendungen soll das
Potential der Methode veranschaulicht werden.
Hauptvortrag DS 10.2 Di 10:10 HS 32
Quantitative Z-Kontrast-Abbildung zur Mikrostrukturcharakterisierung
— •Helge Heinrich — ETH Zürich, Institut für Angewandte
Physik, CH-8093 Zürich — jetzt: Advanced Materials Processing
and Analysis Center (AMPAC), University of Central Florida, Box
162455, Orlando, FL 32816-2455
Transmissionselektronenmikroskopie (TEM) mit einer Feldemissionsquelle
ermöglicht im Rastermodus (STEM) die Abbildung individueller
Atomsäulen. Detektoren in verschiedenen Streuwinkelbereichen messen
Streuintensitäten als Funktion der Elektronenstrahlposition. Durch
Rutherfordstreuung dominiert, hängt das Messsignal eines ringförmigen
Weitwinkel-Dunkelfelddetektors (HAADF) annähernd quadratisch von
der Ordnungszahl der Atome ab. Das Signal bei hohen Streuwinkeln
kann in erster Näherung mit einem inkohärenten Abbildungsmodell beschrieben
werden. Damit sind dynamische Streueffekte bei der HAADF-
Abbildung weniger wichtig als bei konventioneller TEM. Mit geeigneten
Eichmethoden erlaubt daher HAADF-STEM eine direkte Analyse individueller
Atomsäulen in binären kristallinen Materialien mit ausreichend
hohem Unterschied der Ordnungszahlen. Anwendungsbeispiele und Grenzen
der HAADF-Methode sowie die für eine quantitative Interpretation
notwendigen Eich- und Simulationsverfahren werden diskutiert.
Hauptvortrag DS 10.3 Di 10:50 HS 32
Electron Energy-loss Spectrometry in the Electron Microscope
— •Ferdinand Hofer — Research Institute for Electron Microscopy,
Graz University of Technology, Steyrergasse 17, A-8010 Graz
Electron energy-loss spectrometry (EELS), carried out in a transmission
electron microscope (TEM), is now routinely used to measure chemical
and structural properties of very small regions of a thin specimen.
The power of this technique depends significantly on two parameters: its
spatial resolution and the energy resolution available in the spectrum or
in an energy-filtered TEM image. EELS constitutes a wide spectral band
DS 11 Schichteigenschaften I
spectroscopy giving access to both collective phenomena in the low-loss
spectral region and excitation of the inner-shell levels with high collection
efficiency and high sensitivity for the light elements. In this lecture the
basics of EELS will be explained such as quantitative elemental analysis
and derivation of dielectric data from the low-loss region. This will be
supplemented by examples from material science, physics and chemistry.
Finally, new instrumental developments such as high energy resolution
EELS in a monochromized TEM will be addressed.
Hauptvortrag DS 10.4 Di 11:30 HS 32
Energy-filtering transmission electron microscopy in materials
science — •Wilfried Sigle — Max-Planck-Institut für Metallforschung,
Heisenbergstraße 3, 70569 Stuttgart
Electron energy filters have become a standard equipment of modern
transmission electron microscopes. Such filters enable the microscopist
to select electrons which have undergone specific energy losses during
their path through the specimen. The final image is formed only from
the selected electrons. The main advantage of this technique is to obtain
chemical information from relatively large specimen areas with a spatial
resolution close to or even below 1 nm.
In this lecture the different methods of energy-filtering TEM will be
explained such as zero-loss filtering, the three-window technique and the
acquisition of energy-filtered series. This will be supplemented by examples
from materials science, demonstrating the kind of chemical and
physical information which can be extracted from energy-filtered images.
Finally, new developments in the design of electron energy filters will be
addressed.
For further information see: Ludwig Reimer: Energy-Filtering Transmission
Electron Microscopy (Springer Series in Optical Sciences 71,
Springer, Berlin, Heidelberg, 1995).
Hauptvortrag DS 10.5 Di 12:10 HS 32
Kantenfeinstrukturen in Elektronen-Energieverlustspektren —
•Helmut Kohl — Physikalisches Institut, Westfälische Wilhelms-
Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster
In modernen Transmissionselektronenmikroskopen ist es möglich, den
Elektronenstrahl auf einen kleinen Fleck mit einem Durchmesser von weniger
als einem nm zu fokussieren und von diesem Bereich ein Energieverlustspektrum
aufzuzeichnen. Von besonderem Interesse sind hierbei
die charakteristischen Kanten im Spektrum, die der Ionisation innerer
Schalen entsprechen. Während die Kante selbst zum Elementnachweis
genutzt wird, liefert die Feinstruktur oberhalb der Kante Informationen
über die Umgebung des Atoms und über die Bindungsverhältnisse.
Für die Deutung der Kantenfeinstrukturen unterscheidet man den
kantennahen Bereich, bei dem der Energieverlust die Bindungsenergie
um weniger als 50 eV übersteigt, vom kantenfernen Bereich.
Die kantenfernen Strukturen lassen sich anschaulich durch die Interferenz
der von Nachbaratomen zurückgestreuten Anteile der Sekundärelektronenwelle
mit der auslaufenden Welle deuten. Für die
kantennahen Strukturen muß auch die Mehrfachstreuung der Sekundärelektronen
berücksichtigt werden. Formal läßt sich die Feinstruktur
durch eine lokale, symmetrieprojizierte Zustandsdichte beschreiben.
Die Analogien zur Röntgenabsorptionsspektroskopie werden ebenso diskutiert
wie die Methoden zur Messung des linearen und des zirkularen
Dichroismus.
Zeit: Mittwoch 14:30–15:15 Raum: HS 31
Hauptvortrag DS 11.1 Mi 14:30 HS 31
InGaAsN als aktives Material für langwellige oberflächenemittierende
Laser — •Henning Riechert — Infineon Technologies, Corporate
Research Photonics, 81739 München
Oberflächenemittierende Laser (VCSELs = vertical cavity surface
emitting lasers) mit einer Emissionswellenlänge von 1300 nm sind
ideal geeignet als kostengünstige Lichtquellen zur Datenübertragung
über optische Fasern. Der derzeit vielversprechendste Ansatz zur
Realisierung solcher Bauelemente liegt in der Nutzung der konventionellen
GaAs/AlAs VCSEL-Technologie, kombiniert mit der neuartigen
Legierung InGaAsN als aktivem Material.
Der Vortrag gibt einen Überblick über das Wachstum und die physikalischen
Eigenschaften von InGaAsN / GaAs QWs sowie über den Stand
und die momentanen Grenzen von InGaAsN-basierenden Lasern.

Dünne Schichten Mittwoch
DS 12 Schichteigenschaften II
Zeit: Mittwoch 15:15–16:45 Raum: HS 31
DS 12.1 Mi 15:15 HS 31
Ab-initio calculations of the optical properties of phase-change
materials — •Manfred Niesert, Gustav Bihlmayer, and Stefan
Blügel — Institut für Festkörperforschung, Forschungszentrum Jülich,
52425 Jülich
The results of ab-initio calculations of the dielectric function and the
reflectivity of bulk GeTe and AgTe systems will be presented. These materials
are promising candidates for memory devices exploiting the change
of the optical properties depending on the structural phase-change and
are thus subject of intensive investigations. Different atomic configurations
have been computed and the influence on the dielectric function
has been investigated. We focus on the degree of symmetry, comparing
cubic with lower symmetry. The dielectric function considering the longwavelength
limit and neglecting local-field effects, is implemented within
the FLEUR code, an implementation of the full-potential linearized augmented
plane-wave (FLAPW) method.
DS 12.2 Mi 15:30 HS 31
Transporteigenschaften ultradünner Metallfilme — •Peter
Zahn 1 , Dimitry Fedorov 1,2 , and Ingrid Mertig 1 — 1 Fachbereich
Physik, Martin-Luther-Universität Halle, Deutschland — 2 Physical-
Technical Institute, Ural Branch of Russian Academy of Sciences,
Izhevsk, Russia
Experimental investigations of optical and transport properties of ultrathin
metallic layers gave evidence that quantum size effects, caused
by the reduced thickness, strongly influence macroscopic properties and
transport coefficients. A KKR Green’s function formalism was used to
determine the electronic structure of ultrathin metallic films ab initio.
In addition, the perturbation induced by point defects was determined
self consistently solving a Dyson equation for the Greens function of the
system including defects. The anisotropy of the scattering was involved
by solving the Boltzmann equation including the vertex corrections and
the scattering probability amplitudes derived from the potential perturbation
caused by the defects.
We discuss the influence of the reduced symmetry of the films and the
position and type of defects in the layers on the electronic structure and
transport coefficients. First results for Fe films with thicknesses of one to
32 monolayers will be presented.
DS 12.3 Mi 15:45 HS 31
Temperature stability and charge transport in thin (d < 4 nm)
metal oxide films: A comparative investigation of aluminium oxide
and tantalum oxide — •Yanka Jeliazova 1 , Michael Kayser 1 ,
Beate Mildner 1 , Eckart Hasselbrink 1 , and Detlef Diesing 2 —
1 Institut für Physikalische Chemie, Universität Duisburg-Essen, Campus
Essen — 2 Institut für Schichten und Grenzflächen 3, Forschungszentrum
Jülich
Thin layers of insulating metal oxides with high dielectric constant are
currently considered as a possible replacement for the conventional silicon
oxide gate dielectric. To suppress leakage currents the energy barrier
at the metal/oxide interface must be sufficiently high. Additionally high
temperature stability is desirable for the application in integrated circuits.
In order to characterize the energy dependence (application of a
bias voltage) of charge transport across the oxide film tunnel systems of
metal/metal oxide/silver were grown. These systems consist of thin films
of aluminium or tantalum and their oxides, and silver film as a second
electrode. The thickness of the oxides was 3 nm. An energy barrier of
1.3 eV at the Ta/TaOx interface and 2.4 eV at Al/AlOx interface was
found. To distinguish pure electronic conduction from ionical and thermally
activated charge transport sample temperatures were varied from
85 K to 510 K. The Ta/TaOx samples were found to withstand this temperature
range, while the Al/AlOx samples show a dielectric breakdown
at T > 400 K. The temperature dependence of the current through the
oxide films suggest an electronic tunnel contribution at T < 350 K and
a strong thermally activated charge transport at T > 450 K.
DS 12.4 Mi 16:00 HS 31
Optimierung der Leitfähigkeit einer dünnen Silberschicht —
•Achim Breitling, Oliver Kappertz, Selvaraj Venkataraj,
Henning Dieker und Matthias Wuttig — I.Physikalisches Institut,
RWTH-Aachen, 52056 Aachen
Transparente Silberschichten (Größenordnung 10nm) mit einer
möglichst hohen Leitfähigkeit sind für verschiedene technische Anwendungen
(z.B. organische LEDs) von äußerst großer Bedeutung. Daher
haben wir den elektrischen Widerstand von Silberschichten als Funktion
der Schichtdicke auf unterschiedlichen Substraten bestimmt. Anschließend
wurden die Silberschichten auf verschiedene Eigenschaften wie
spezifischer Widerstand, Ladungsträgerbeweglichkeit und Textur mittels
4-Punkt-Widerstandsmessungen, Röntgenreflektometrie (XRR) und
-diffraktometrie (XRD) bzw. Ellipsometrie untersucht. Dabei zeigt sich,
dass sich die Silberleitfähigkeit durch Bufferschichten drastisch verändern
lässt. Als Kandidaten für die Bufferschicht wurden verschiedene Metalloxide
bzw. -nitride verwendet, die mittels reaktivem DC Magnetronsputterns
hergestellt wurden. Für einige der Buffermaterialien wurde bei der
Silberschicht eine gegenüber dem bufferschichtfreien Fall sehr viel höhere
spezifische Leitfähigkeit beobachtet. Es werden Modelle vorgestellt, die
die Eigenschaften der Silberschicht bzw. der Bufferschicht mit dem beobachteten
Verhalten verknüpfen.
DS 12.5 Mi 16:15 HS 31
Elektromigration in Gold-Nanodrähten — •Burkhard Stahlmecke
und Günter Dumpich — Experimentalphysik, AG Farle, Universität
Duisburg-Essen, Standort Duisburg, Lotharstraße 1, 47057 Duisburg
Die Untersuchung von Elektromigrationseffekten ist industriell aufgrund
der sich weiter verkleinernden Strukturen wichtig, da die Elektromigrationsschäden
den Hauptgrund für das Versagen von integrierten
Bauteilen darstellen. Gleichzeitig sind die grundlegenden physikalischen
Prozesse, die zum Versagen einer Leiterbahn führen, bislang noch
nicht vollständig verstanden. Gold-Leiterbahnen mit Breiten im Nanometerbereich
wurden mittels Elektronstrahllithographie hergestellt und
so kontaktiert, daß im Rasterelektronenmikroskop (SEM) in-situ Widerstandsmessungen
vorgenommen werden konnten. Diese Methode bietet
den Vorteil, die Bildung und das Wachstum der sogenannten ”Voids”
dynamisch in Echtzeit vorfolgen zu können. Die gleichzeitig aufgenommenen
Strom-Spannungs-Kennlinien bzw. Widerstands-Zeit-Kennlinien
zeigen ein charakteristisches Verhalten in Abhängigkeit der Stromstärke
und der Leiterbahnparameter. Die Messungen wurden sowohl mit eingeprägtem
Strom wie auch mit eingeprägter Spannung durchgeführt. Bei
typischen Stromdichten von einigen 10 8 Acm −2 kann die Bildung von
”Voids” und ”Hillocks” systematisch untersucht werden.
Gefördert durch die DFG im Rahmen des SFB 616.
DS 12.6 Mi 16:30 HS 31
Preparation and characterization of nanocrystalline anatase
TiO2 films — •A. Orendorz, B. Huber, J. Wüsten, H. Gnaser,
and C. Ziegler — Department of Physics, University of Kaiserslautern,
D-67663 Kaiserslautern, Germany
Using TiO2 particles with nominal sizes of 6 nm, 12 nm, or 20 nm,
nanocrystalline anatase TiO2 films with a typical thickness of some µm
were deposited on various substrates. Structural investigations of the
films by means of TEM and XRD revealed that, as in the primary TiO2
particles, only the anatase phase of TiO2 occurs in the films and that no
preferential orientation of the nanoparticles exists. The average particle
sizes in the films determined from the XRD data agree within about 10 %
with the above-quoted size values of the primary particles. Depth profiles
by SIMS showed a homogeneous distribution of Ti and O throughout the
films and a low concentration of impurity species (atomic concentrations
< 10 −4 ). The electrical conductivity σ of the nanocrystalline films was
determined as a function of the sample temperature T and of the oxygen
partial pressure p(O2) under UHV conditions. Over a wide range
of p(O2) and for 200 ◦ C ≤ T ≤ 500 ◦ C a dependence σ ∝ p(O2) −n
was observed. Furthermore, it was noted that the exponent n exhibits a
pronounced dependence on the particle size and on T, but also on the
type of substrate. The values derived for n (∼ 0.5 ≤ n ≤ 1.3) are distinctly
larger than those reported for TiO2 bulk specimens; hence, in the
nanocrystalline films σ decreases more rapidly with increasing p(O2). In
first measurements obtained by UPS and by IPE, the electronic structure
of the nanocrystalline films was probed in the region of the band gap.

Dünne Schichten Mittwoch
DS 13 Schichteigenschaften III
Zeit: Mittwoch 16:45–18:00 Raum: HS 31
DS 13.1 Mi 16:45 HS 31
Microtribology of Nanocomposite Self-lubricating Coatings —
•Vladislav Spassov, Imad Ahmed, Giuseppe Bregliozzi, Alan
Savan und Henry Haefke — CSEM Swiss Center for Electronics and
Microtechnology, Inc., Rue Jaquet-Droz 1, CH 2000, Neuchatel, Switzerland
Tribological coatings deposited by sputter PVD or arc PVD methods
from compound targets often contain microparticles embedded in, and
projecting through, the coating. When using macroscopic tribological
characterisation methods such as pin-on-disk (POD) and linear, oscillating
sliding (SRV) tribometer tests, it is difficult to separate the influence
of factors such as debris generation and microparticles. Often the debris
built-up makes it impossible to measure the real friction coefficient of
the coating against the selected material. Therefore, micro-scale analogues
of the abovementioned methods have to be applied in order to
study the tribological properties of a PVD coating without the influence
of debris or microparticles. In the current work, the authors have used a
microtribometer to examine the tribological properties of TiAlCN+MoS2
nanocomposite self-lubricating coatings against 100 Cr 6 (DIN 1.3505)
steel having oscillating relative movement. The results are discussed and
compared to data obtained from macroscopic pin-on-disk tests.
DS 13.2 Mi 17:00 HS 31
Mechanical properties of laser deposited PMMA films — •Erik
Süske 1 , Thorsten Scharf 1 , Peter Schaaf 2 , Elena Panchenko 3 ,
Dorit Nelke 3 , Michael Buback 3 , Harald Kijewski 4 , and Hans-
Ulrich Krebs 1 — 1 Institut für Materialphysik, Tammannstr. 1, 37077
Göttingen — 2 II. Phys. Institut, Tammannstr. 1, 37077 Göttingen —
3 Institut für physikalische Chemie, Tammannstr. 6, 37077 Göttingen —
4 Institut für Rechtsmedizin, Windausweg 2, 37073 Göttingen
Poly-(methyl methacrylate) (PMMA) films were laser deposited at a
wavelength of 248 nm in UHV at substrate temperatures up to 250 ◦ C
and characterized by infrared spectroscopy (FTIR), size eclusion chromatography
(SEC), thermogravimetric analysis (TGA) and microhardness
measurements. The FTIR spectra indicate a chemical structure
closed to the bulk material, probably caused by a radical polymerization
mechanism, with a small amount of cross-linked polymer. Nevertheless,
after deposition the chain length of the PMMA is reduced to about 6000
g/mol. Due to this changes, the mechanical properties of the films vary
dramatically from the bulk polymer, e.g. the hardness increases by a factor
of five. During annealing the mechanical properties of the films can
be systematically varied to values closed to that of bulk samples. The
deposition process and properties of the films are discussed with respect
to changes in chemical structure, number of cross links and chain length,
while the changes in mechanical properties are concerned with relaxation
effects and the stability of the polymer.
DS 13.3 Mi 17:15 HS 31
Effect of Microwave radiation on structural and mechanical
properties of Al2O3 thin films deposited by sol-gel process
— •Phani Ayalasomayajula and Henry Haefke — CSEM Swiss
Center for Electronics and Microtechnology Inc., CH-2007 Nuechatel,
Switzerland
The lower temperatures and shorter processing time associated with
microwave irradiation might be ascribed to the activating and facilitating
effect of microwave energy on solid phase diffusion. Unlike other preparation
methods, microwave heating is generally significantly faster, simpler,
DS 14 Schichtwachstum
and very energy efficient. In the present work, alumina has been chosen
because of its high hardness, chemical resistance, and scratch resistance
properties. Thin films of Al2O3 have been deposited on quartz substrates
at room temperature by a sol-gel dip coating technique. Two kinds of
treatments have been applied to the as-deposited films for comparison:
(1) furnace annealing at different temperatures ranging from 200oC to
1000oC for 5 hours and (2) exposure to different microwave radiation
(2.45 MHz), with powers ranging from 200 W to 1000 W for 5 minutes.
X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy
dispersive x-ray (EDX)analysis techniques have been employed to
characterise the structural, morphological and elemental composition of
the films. Nanohardness indentation tests of the films exposed to microwaves
(600W and above) have shown a hardness of 8.5 GPa with an
elastic modulus of 140 GPa compared to the annealed sample having 3.3
GPa with an elastic modulus 57 GPa.
DS 13.4 Mi 17:30 HS 31
Characterization of the amorphous-crystalline silicon interface
by time resolved surface photovoltage and photoluminescence
techniques — •Abdelazize Laades, Klaus Kliefoth, Rolf
Stangl, Manfred Schmidt, and Walther Fuhs — Hahn-Meitner-
Institut Berlin, Abt. Silizium Photovoltaik, Kekuléstr. 5, D-12489
Berlin
Amorphous silicon/crystalline silicon interfaces (a-Si:H/c-Si) were prepared
by plasma enhanced chemical vapor deposition and analyzed by
time resolved surface photovoltage method (TR-SPV) and photoluminescence
spectroscopy (PL). To characterise the interfaces formed by varying
the process parameters, the c-Si substrate is excited through the a-Si:H
layer by high intensity laser pulses such that the excess carriers are predominantly
generated in c-Si. It is shown that TR-SPV and PL methods
are sensitive to the nonradiative recombination at the a-Si:H/c-Si interface.
A qualitative approach to interpret SPV transients is presented
and discussed. Applying this approach, we come to the conclusion that
the best interface quality is reached at a substrate temperature around
230 ◦ C and that the a-Si:H film thickness in the range between 5 nm and
200 nm has no influence on the a-Si:H/c-Si interface properties.
DS 13.5 Mi 17:45 HS 31
Nachweis akustischer Oberflächenphononen in BNbeschichteten
Kohlenstofffasern — •T. Wittkowski 1 , K.
Jung 1 , B. Hillebrands 1 , S. Stöckel 2 , K. Weise 2 und G. Marx 2
— 1 Fachbereich Physik und Forschungsschwerpunkt MINAS, Technische
Universität Kaiserslautern, 67663 Kaiserslautern — 2 Institut für
Chemie, Physikalische Chemie, Technische Universität Chemnitz, Straße
der Nationen 62, 09107 Chemnitz
Mit der Brillouin-Lichtstreuspektroskopie (BLS) wurden akustische
Oberflächenphononen auf dünnen, unbeschichteten und beschichteten Fasern
nachgewiesen. Die BLS-Analysetechnik greift bei der Messung nicht
in das Materialverhalten ein, sie ist zerstörungsfrei und kann auch bei
komplizierteren Probengeometrien erfolgreich eingesetzt werden.
Die mit der BLS gemessene Geschwindigkeitsdispersion der Rayleigh-
Mode in diesem Schicht-Substrat-System führt zu präzisen Aussagen
über das elastische Verhalten der Bornitridbeschichtung. Die Ergebnisse
dokumentieren den erwünschten Effekt einer deutlichen Verringerung
der Schersteifigkeit der beschichteten im Vergleich zu den unbeschichteten
Fasern im oberflächennahen Bereich. Aus der Dispersion erhält man
zusätzliche Informationen über die Infiltration des Faserbündels während
des thermischen CVD-Beschichtungsprozesses.
Zeit: Mittwoch 14:30–16:15 Raum: HS 32
DS 14.1 Mi 14:30 HS 32
Microstructure of polymer-metal composite thin films grown
by pulsed laser deposition — •Jörg Faupel, Thorsten Scharf,
and Hans-Ulrich Krebs — Institut für Materialphysik, Universität
Göttingen, Tammannstrasse 1, D-37077 Göttingen
Polymer-metal composites have a wide range of applications ranging
from food-packaging to microelectronics. Using an excimer laser of
248nm wavelength and 30ns pulseduration, polymer-metal composites
were prepared in UHV at room temperature. For the polymer matrix
BPA-polycarbonate (PC) was used, as metals Ag, Au, Cu and Pd. The
samples were characterised by x-ray reflectivity and TEM using top and
also cross-sectional view. The size of the spherical Ag and Au grains,
embedded in a PC matrix, can be controlled by the pulse number during
deposition. In the case of Cu and Pd in comparison, smaller and more
grains and also a different growth behaviour is found. For polymer/metal

Dünne Schichten Mittwoch
multilayers deposited the first time by pulsed laser deposition, the interface
roughness strongly depends on the used metal.
Differences between the polymer-metal systems are discussed with respect
to the different diffusion coefficients, reactivities and growth mechanisms
of the used metals on the polymer surface.
DS 14.2 Mi 14:45 HS 32
In-situ x-ray diffraction during sputtering of Shape Memory
Alloy (SMA) Ni-Ti thin films — •R.M.S. Martins 1,2 , N.
Schell 1 , F.M.B. Fernandes 2 , and R. Silva 2 — 1 Institute of Ion
Beam Physics and Materials Research, Forschungszentrum Rossendorf,
P.O. Box 510119, D-01314 Dresden, Germany — 2 CENIMAT, Campus
da FCT/UNL, 2829-516 Monte de Caparica, Portugal
Ni-Ti thin films present great advantages for the fabrication of microactuactuators.
The phase transformation and precipitation which are responsible
for the shape memory effect have been widely studied in bulk
material and thin films. However, in-situ studies have been limited to the
aging/annealing treatments after deposition. In-situ study of the sputter
deposition of Ni-Ti thin films has not yet been reported. Thus a magnetron
sputter deposition chamber has been installed into the six-circle
diffractometer of the ROssendorf BeamLine (ROBL-CRG) at the ESRF,
Grenoble [1], and in consequence the crystallization kinetics have been
followed in situ by x-ray diffraction during sputter deposition of Ni-Ti
thin films.
[1] W. Matz, N. Schell, J. Bøttiger et al., Rev. Sci. Instr. 72, 3344 (2001)
DS 14.3 Mi 15:00 HS 32
Early Stages of Self-assembled Nanostructure Formation during
Cu Deposition onto VSe2 Crystals — •S. Hollensteiner 1 ,
E. Spiecker 1 , W. Jäger 1 , H. Haselier 2 , and H. Schroeder 2 —
1 Technische Fakultät der CAU zu Kiel — 2 Forschungszentrum Jülich
Recent investigations have shown that Cu deposition onto surfaces of
layered VSe2 crystals may lead to self-assembled networks of nanostructures.
TEM, SEM and AFM have been applied to characterize evolution,
lateral arrangements, orientations, and the microscopic nature of the surface
structures. The nanostructures were created applying UHV electron
beam evaporation of Cu onto cleaved layered VSe2 crystals. The nominal
Cu coverages are ranging from 0.4 nm to 2.5 nm. At the lowest coverage
large isolated nanostructures with lateral dimensions > 100 nm are observed
having a roof-like tile structure. At coverages of 1 nm and above
a uniform network of linear nanostructures of smaller lateral dimension
(∼ 20 nm) with mainly hexagonal meshes develops on substrate terraces
in addition to the large nanostructures. Like the large nanostructures the
smaller ones are composed of two crystalline strands. Inside the meshes,
a thin layer of a new phase of uniform thickness has evolved being almost
completely contiguous but separates into three equivalent orientation
variants with epitaxial relationship to the substrate. These results
and the absence of Cu clusters point to the formation of an intercalation
phase. A dense network of dislocations has formed at the interface
indicating the presence of in-plane strain. The role of strain for the formation
and evolution of both the nanoroofs and the network of smaller
nanostructures is discussed.
DS 14.4 Mi 15:15 HS 32
Non-linear effects in the Monte Carlo simulation of sputterinduced
surface morphology — •Oluwole E. Yewande, Alexander
K. Hartmann, and Reiner Kree — Institute for Theoretical
Physics, University of Göttingen, Tammannstr.1, 37077 Göttingen, Germany.
We study the ion-beam sputtering of a solid surface using the (2+1)dimensional
discrete Monte Carlo model on a lattice recently introduced 1 .
We have studied two different surface diffusion mechanisms; one without
and the other including a term accounting for Schwoebel barriers, and
at times long enough to observe the dependence of long-time effects on
surface diffusion. At short times, propagating ripple-like periodic height
modulations appear on the surface. The velocity dispersion and the ripple
wavelength obey scaling relations that are in qualitative agreement
with experimental results 2 . At long-times, where non-linear effects are
significant, the ripples vanish, and the surface topography exhibits the
non-linear behaviour S(k) ∼ k −2.5 , governed by the Kardar-Parisi-Zhang
universality class.
[1] A. K. Hartmann, R. Kree, U. Geyer and M. Kölbel, Phys. Rev. B 65,
193403(2002).
[2] S. Habenicht, K. P. Lieb, J. Koch and A. D. Wieck, Phys. Rev. B 65,
115327(2002).
DS 14.5 Mi 15:30 HS 32
Structural evolution in chromium nitride thin films: A
comparison with structure-zone models — •Yvonne Gerbig 1 ,
Corinne Nouveau 2 , and Henry Haefke 1 — 1 CSEM Swiss Center
for Electronics and Microtechnology Inc, Rue Jaquet-Droz 1, CH-2007
Neuchatel, Switzerland — 2 Ecole Nationale Superieure d’Arts et
Metiers, LA.Bo.MA.P, F-71250 Cluny, FranceCluny
The correlation between micro/nanostructure of thin films and their
deposition conditions is scientifically interesting as well as technologically
relevant for the engineering of functional surfaces. In the last decades,
several structure-zone models (SZMs) have been developed for thin films
grown by pvd techniques to improve the under-standing of the depositionstructure
relationship.
The well-known SZMs of Movchan & Demchishin, Thornton and
Messier consider only a few selected deposition parameters. Recently,
Kelly has created a SZM using more universal energy related parameters.
However, all these SZMs were developed for metal thin films and
their extension to other materials, e.g. ceramic thin films, is not clear.
In this study the validity of various SZMs were evaluated for CrN thin
films synthesized through reactive sputtering by varying the most important
deposition parameters. By applying the thickness gradient technique,
the structural and morphological evolution of CrN thin films was
examined using SEM, AFM and XRD. The observed microstructures and
topographical features are discussed and classified as a function of deposition
parameters in a new SZM based on the approaches of Thornton,
Messier and Kelly.
DS 14.6 Mi 15:45 HS 32
Control of surface roughness in amorphous thin film growth
— •Frank Elsholz 1 , Eckehard Schöll 1 , Hans Eichler 2 , Chris
Scharfenorth 2 , and Arkadi Rosenfeld 3 — 1 Institut für Theoretische
Physik, Technische Universität Berlin, Hardenbergstrasse 36, D–
10623 Berlin — 2 Optisches Institut, Technische Universität Berlin, Hardenbergstrasse
36, D–10623 Berlin — 3 Max-Born-Institut, Max-Born-Str.
2a, 12489 Berlin
The growth of optical layers of SiO2 and Nb2O5 on amorphous substrates
is investigated. We develop a kinetic Monte-Carlo model which
mimics the amorphous structure by randomly fluctuating binding energies.
The resulting surface profiles are characterized by their root mean
square roughness, height-height correlation functions, and growth exponents.
For strong random fluctuations the growth exponents exceed the
value 0.5, in good agreement with experiment.
DS 14.7 Mi 16:00 HS 32
Porous Thin Films Grown by Size-Selected Si-Nanoparticles
— •Felix Voigt 1 , Rudolf Brüggemann 1 , Friedrich Huisken 2
und Gottfried H. Bauer 1 — 1 Fakultät V, Institut für Physik, CvO-
Universität Oldenburg, 26111 Oldenburg — 2 Laborastrophysik-Gruppe,
Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, 07743
Jena
Size selected Si-nanoparticles (Si-nc) with diameters ≥ 3 nm prepared
in a flow reactor with CO2 laser induced SiH4 decomposition and showing
strong luminescence in the visible regime after oxidation of their
surface [1] have been accumulated as thin films on different substrates.
These films contain clusters of conglomerated Si-nc which conserve the
electronic properties of the single Si-nc such as the compression of electronic
wave functions which has been verified by spectral pl-measurements.
The degree of volume filling has been analyzed experimentally to about
0.3. This number is supported by a simplified numerical stick-ball model
for the local arrangement of the Si-nc versus film growth time. We
have studied the growth of these porous thin films by simultaneous coplanar
charge transport measurements (interdigital metal contacts) and see
three regimes: i) negligible transport at the beginning of film growth due
to missing connections, ii) a superlinear increase of current with exponent
3/2 which will be discussed in terms of percolation transport, and iii) a
linear increase with further film thickness. [1] G. Ledoux, O. Guillois, D.
Porterat, C. Reynaud, F. Huisken, B. Kohn, V. Paillard, Phys. Rev. B.
62, 15 942 (2000).

Dünne Schichten Mittwoch
DS 15 Oberflächenmodifizierung
Zeit: Mittwoch 16:15–18:00 Raum: HS 32
DS 15.1 Mi 16:15 HS 32
Self-organized pattern formation on Si surfaces by ion beam
erosion — •Bashkim Ziberi, Frank Frost, and Bernd Rauschenbach
— Leibniz-Institut für Oberflächenmodifizierung e. V., Permoserstraße
15, D-04318 Leipzig, Germany
The spontaneous formation of regular structures with nanometer dimensions
(< 100 nm) on semiconductor surfaces originates from selforganisation
processes during ion beam erosion and offers a promising
tool for the fabrication of large-area nanostructured surfaces.
In this study the self-organized pattern formation on Si surfaces during
low-energy Ar + ion beam erosion (ion energy ≤ 2000 eV) under normal
and oblique ion incidence with and without sample rotation was investigated.
It is shown that ordered nanodots are formed at normal ion
incidence for ion energies ≥ 1000 eV and, additionally, for ion energies ≤
2000 eV at oblique ion incidence angles between 70 ◦ and 80 ◦ with respect
to the surface normal. The dots generated under oblique ion incidence
conditions show a remarkable high degree of ordering comparable to dot
patterns on III/V semiconductors. In the case of no sample rotation remarkable
highly ordered ripple patterns can be produced at ion incidence
angles slightly deviating from normal ion incidence.
DS 15.2 Mi 16:30 HS 32
Morphology investigations of ion-eroded SiGe alloy layers —
•Christian Hofer 1 , Stephan Abermann 1 , Christian Teichert 1 ,
Markus Wächter 2 , Thomas Bobek 2 , Heinrich Kurz 2 , Klara
Lyutovich 3 , and Erich Kasper 3 — 1 Department of Physics, University
of Leoben, Austria — 2 Institute of Semiconductor Technology,
RWTH Aachen, Germany — 3 Institute of Semiconductor Engineering,
University of Stuttgart, Germany
The possibility to generate well-ordered nanostructures through ionbombardment
of III-V semiconductor surfaces [1] motivated the investigation
of normal incidence Ar + -ion bombardment on already selforganized
SiGe films [2]. The role of different dislocation densities and
starting morphologies on the subsequent pattern formation was investigated
by high resolution AFM.
Two different energy regimes were found. For ion-energies of 500 eV
and below the surface roughens and craters with a diameter of 70 nm
evolve. At higher energies smoothening mechanisms take place. The influence
of misfit dislocations on the SiGe pattern formation [3] and the
evolution of size and distribution of the nanostructure array depending
on ion-energy are discussed in the framework of current theories of ionbombardment
induced pattern formation.
[1] S. Facsko, et al., Science 285, 1551 (1999); F. Frost, et al., Phys.
Rev. Lett. 85, 4116 (2000).
[2] C. Teichert et al., Thin Solid Films 380, 28 (2000).
[3] C. Hofer et al., Nucl. Instr. and Meth. B, in print.
This work was partly supported by FWF Austria, P14009-TPH.
DS 15.3 Mi 16:45 HS 32
Relaxations- und Kristallisationsprozesse bei der ioneninduzierten
Amorphisierung von In2Au-Filmen — •Paul Ziemann und
Thomas Müller — Abteilung Festkörperphysik, Universität Ulm, D-
89069 Ulm
Ionenbestrahlung bietet die Möglichkeit, ausgehend von polykristallinen
Schichten binärer Legierungen, diese schrittweise zu amorphisieren.
Damit lassen sich Proben mit verschiedenen Anteilen amorpher Phase
präparieren und der Einfluss dieses Anteils auf Relaxationsprozesse und
Kristallisationstemperatur kann untersucht werden. Solche Experimente
wurden an In2Au-Filmen durch Bestrahlung mit 300 keV Ar-Ionen bei
80 K durchgeführt und mit in-situ Widerstandsmessungen kombiniert.
Über diese Ergebnisse wird berichtet.
DS 15.4 Mi 17:00 HS 32
Plastic deformation of amorphous silicon under swift heavy
ion irradiation — •André Hedler 1 , Siegfried Klaumünzer 2 , and
Werner Wesch 1 — 1 Institut für Festkörperphysik, Friedrich-Schiller-
Universität Jena, Max-Wien-Platz 1, 07743 Jena — 2 Hahn-Meitner-
Institut Berlin, Glienicker Str. 100, 14109 Berlin
All the investigated amorphous materials show an anisotropic plastic
deformation under swift heavy ion irradiation (ion hammering). In
the past years this effect has been discussed controversially whereas the
viscoelastic theory by Trinkaus et al. represents a good description for
glasses. However, a verification of the model for amorphous semiconductors
has not been undertaken. With its well-known physical properties Si
seems to be a suitable candidate to be investigated first.
Single-crystalline Si wafers were amorphized by low energy Si ion implantation
and post-irradiated with MeV Au and Xe ions at 77 K and
300 K. For a constant electronic stopping power a linear increase of the
plastic deformation of amorphous Si with increasing ion fluence was observed
at both temperatures and was assigned to corresponding deformation
yields per ion. Our results show for the first time a dependence
of the deformation yield on the electronic stopping power and on the
temperature for amorphous Si and therefore provide a basis to verify the
theory.
DS 15.5 Mi 17:15 HS 32
Elektrischer Transport in epitaktischen, dünnen, ionenbestrahlten
Gold-Filmen — •Gerd Kästle, Thomas Müller, Hans-Gerd
Boyen, Alexander Schröder und Paul Ziemann — Abteilung
Festkörperphysik, Universität Ulm, 89069 Ulm
Der Einfluss der Ionenbestrahlung auf die Temperaturabhängigkeit des
Widerstands epitaktischer, glatter Goldfilme wurde untersucht. Die Experimente
wurden an He- oder Ar-bestrahlten Filmen unterschiedlicher
Dicke durchgeführt, um Oberflächen- und Volumeneffekte zu trennen.
Neben der erwarteten Widerstandserhöhung durch Ionenstrahlinduzierte
Defekte wird im Rahmen einer Size-Effekt Analyse eine starke
Absenkung der Debye-Temperatur beobachtet. Mit zunehmender Bestrahlungsdosis
verhalten sich die Gitterschwingungen der Goldfilme weicher.
Wie bei sehr dünnen Filmen scheint durch die erhöhte Defektkonzentration
das für den Transport relevante Oberflächen- zu Volumenverhältnis
zu steigen, was sich letztlich in der Absenkung der Debye-
Temperatur bemerkbar macht.
DS 15.6 Mi 17:30 HS 32
Influence of gas pressure and substrate temperature on diffusion
process of carbon/nitrogen in 304 AISI using PIII — •A. M. Abd
El-Rahmann 1,2 , F. M. El-Hossary 1 , N. Z. Negm 1 , F. Prokert 2 ,
E. Richter 2 , and W. Möller 2 — 1 Physics Department, Faculty of Science,
South Valley University, Sohag Branch, Sohag, Egypt — 2 Institute
of Ion Beam Physics and Material Research, Centrum Rossendorf, Dresden,
Germany
Plasma immersion ion implementation (PIII) has been used to modify
the surface properties of 304 austenitic stainless steel (AISI). The influence
of the working gas pressure in a range from 0.2 up to 1.0 Pa and
the substrate temperature from 300 ◦ C to 500 ◦ C on the microstructure,
nitrogen/carbon concentration depth profile and surface microheadness
were investigated at fixed gas composition (25 % C2H2, 75 % N2), 350 W
rf plasma power and -30 kV negative biased potential. The experimental
results show that the substrate temperature and the diffusion process of
nitrogen and carbon is affected by the increase of gas pressure. The thickness
of the modified layer is more than 30 µm. The results provide recent
diffusion rate is about 3.4 × 10 −1 µm 2 /sec with a surface microhardness
of about 1880 kg/mm 2 .
DS 15.7 Mi 17:45 HS 32
Improvement in adhesion of noble metals on polymer surfaces
modified with low energy ions — •Jurgita Zekonyte, Sebastian
Wille, Ulrich Schürmann, Vladimir Zaporojtchenko,
and Franz Faupel — Lehrstuhl für Materialverbunde, Technische
Fakult ¨ *t der CAU, Kaiserstr. 2, 24143 Kiel
The influence of ion-beam treatment with low energy Ar+, N+ and
O+ ions at ion fluences of 10E12 - 10E17 ions/cm2 on the early stage
of metal/polymer interface formation, and the adhesion strength of Cu
and Au on PS and PP was investigated. The ion bombardment changed
the polymer surface chemical structure introducing new oxygen and/or
nitrogen containing functional groups, that influenced metal/polymer interaction.
Metals of low reactivity such as Cu or Au formed 3D-clusters
during the vapour phase deposition. In the case of PS and PP the incomplete
condensation was observed on the untreated surfaces at RT.
The ion bombardment created a defined concentration of defects that
acted as a new adsorption sites on polymer surfaces, leading to an increase
in the cluster density with ion fluence, and the enhancement in the

Dünne Schichten Mittwoch
condensation coefficient, which approached unity at ion fluence of 10E15
ions/cm2. The surface treatments improved the adhesion between metal
and polymer by two orders of magnitude compared to the untreated poly-
DS 16 Schichtherstellung I
mer. The locus of failure changed from interfacial failure for untreated
polymer surfaces to cohesive failure, which took place in the polymer, for
modified surfaces.
Zeit: Donnerstag 14:30–15:15 Raum: HS 31
Hauptvortrag DS 16.1 Do 14:30 HS 31
Plasma-assisted deposition and crystal growth of thin metal oxide
films — •Rainer Hippler — Institut für Physik, Ernst-Moritz-
Arndt-Universität Greifswald, Domstraße 10a, 17489 Greifswald
Metal oxide films are of significant technological relevance and play an
DS 17 Schichtherstellung II
important role, e.g., as protective coatings and in the fabrication of solar
cells. Plasma-assisted deposition employing magnetron discharges are
frequently employed. Formation and crystal growth of, e.g., indium tin
oxide (ITO) films show pronounced dependencies on plasma parameters.
The influence on chemical composition, crystal structure, density, etc.,
as well as possible reasons will be discussed.
Zeit: Donnerstag 15:15–16:45 Raum: HS 31
DS 17.1 Do 15:15 HS 31
Investigations on the long-time stability of thin PrxOy-films on
Si(100) grown by Pulsed Laser Deposition — •Markus Ratzke,
Dirk Wolfframm, Mathias Kappa, and Jürgen Reif — LS Experimentalphysik
II, BTU Cottbus and JointLab IHP/BTU, Universitaetsplatz
3-4, 03044 Cottbus, Germany
We have studied the long-time stability of thin PrxOy-films on Si(100),
produced by Pulsed Laser Deposition from sintered Pr6O11 targets. In
particular, the surface morphology and the chemical layer/interface composition
were investigated.
For PrxOy films grown at 650 ◦ C substrate temperature, we find clear
evidence of a change in surface morphology with time after film preparation:
while the surface immediately after deposition is characterized by
large splashes (mainly Pr2O3) superimposed on a background of mixed
oxides (Pr2O3, Pr6O11), after the surface becomes more homogeneous.
No similar effect was observed for layers grown at 900 ◦ C substrate temperature.
An analysis of XPS spectra (Pr 3d, O 1s, Si 2p) showed that not only
the line shape of the Pr 3d and O 1s core level spectra changed but also
the Pr 3d/O 1s intensity ratio. This transition of chemical environment
suggests the formation of Praseodymium Hydroxide. Since Pr6O11 is well
known for its strong hygroscopic behaviour, Pr(OH)3 will preferably be
formed between the splashes (Pr2O3), accompanied by the appearance of
PrO2.
DS 17.2 Do 15:30 HS 31
Polymers and polymer metal composite thin films prepared
by pulsed laser deposition — •Thorsten Scharf, Erik Süske,
Jörg Faupel, and Hans-Ulrich Krebs for the collaboration — Institut
für Materialphysik, Universität Göttingen, Tammannstrasse 1, 37077
Göttingen
On the way to materials for new applications thin films play an important
role. Pulsed laser deposition (PLD) is a very flexible method to
deposit thin films out of many materials. The possibility to deposit polymers
and metals in a one-step-process in ultra high vacuum raises the
possibility to achieve new material classes.
Polymer (PMMA, PC) and polymer-metal (Cu,Ag,Au,...)-composites
were laser-deposited under different parameters. Depending on the used
polymer and metal there are different solubilities of metals in polymers.
For lower metal concentrations the metal is solved in the polymer, but
changes its material properties. Above this limit the metals form clusters
already during the deposition process. The size-distribution and abundance
of clusters also strongly depends on the used materials. The process
of film growth and its impact on the properties will be discussed.
DS 17.3 Do 15:45 HS 31
Herstellung und Charakterisierung von verkippten ZnO Filmen
— •Martin Peruzzi, Johannes D. Pedarnig und Dieter
Bäuerle — Universität Linz, Abteilung für Angewandte Physik, Altenbergerstr.
69, A-4040 Linz
Die Methode der gepulsten Laserdeposition (PLD) erlaubt die Herstellung
verschiedenster Materialen in Form dünner Filme. Darunter finden
sich unter anderem Hochtemperatur-supraleiter, Halbleiter, Ferro- und
Piezoelektrika, Polymer, etc. [1].
Im Vortrag wird die Herstellung von dünnen ZnO Filmen mit unterschiedlicher
kristallographischer Orientierung auf SrTiO3 Substraten
vorgestellt. ZnO zeichnet sich vor allem durch seine piezoelektrischen Eigenschaften
aus und wird unter anderem als Transducer-Material in der
Sensorik und für HF-Filter eingesetzt. Verschiedene Schwingungsmoden
können angeregt werden, abhängig von der ZnO Kristallorientierung und
der Elektrodenstruktur. Mit der PLD-Methode ist es gelungen, dünne
ZnO Filme mit unterschiedlicher kristallographischer Orientierung der
Einheitszelle relativ zum Substrat herzustellen. XRD und TEM Analysen
bestätigen ein verkipptes Wachstum von ZnO und sehr gute epitaktische
Eigenschaften. Der Einfluss der Herstellungsparameter auf das verkippte
Wachstum der verkippten Filme wird diskutiert.
[1] Bäuerle D.: Laser Processing and Chemistry 3rd ed. (Springer, Berlin,
Heidelberg 2000)
DS 17.4 Do 16:00 HS 31
FEL produzierte texturierte TiN-Schichten — •P. Schaaf 1 , E.
Carpene 1 und M. Shinn 2 — 1 Universität Göttingen, Zweites Physikalisches
Institut, Tammannstrasse 1, D-37077 Göttingen. — 2 FEL, Jefferson
Lab, Newport News, VA 23606, USA.
Oberflächen und Funktionsschichten spielen eine immer wichtigere Rolle
bei der Anwendung moderner Materialien. Der Aufwand für die Herstellung
dieser Schichten wird immer grösser und Laserstrahlung wird
hierbei häufig eingesetzt [1,2]. Am Beispiel von Titan haben wir erstmals
mit dem Freie-Elektronen-Laser (FEL) durch eine reaktive Bestrahlung
in reinem Stickstoff TiN Oberflächen mit sehr hoher Geschwindigkeit
und grossen Schichtdicken hergestellt [3,4]. Der FEL hat die Besonderheit,
dass man seine Mikropulse von 2 ps Dauer zeitlich fast beliebig zu
Makropulsen formen kann [3]. Die Phasenbildung und die Schichtmorphologie
werden im Zusammenhang mit den Bearbeitungsparametern,
insbesondere der Laserpulsfolge, diskutiert. Die teilweise gefundene starke
kristallograhische (002)-Texturierung des TiN in der Oberfläche kann
auf die Bearbeitunsparameter und das damit beeinflusste Erstarrungsverhalten
zurückgeführt werden [4].
[1] P. Schaaf. Laser Nitriding of Metals. Progr. Mater. Sci. 47 (2002) 1.
[2] P. Schaaf, M. Han, K.-P. Lieb, and E. Carpene. Appl. Phys. Lett. 80
(2002) 1091.
[3] E. Carpene, P. Schaaf, M. Han, K.-P. Lieb and M. Shinn. Appl. Surf.
Sci. 186 (2002) 195.
[4] E. Carpene, M. Shinn, P. Schaaf. in preparation.
DS 17.5 Do 16:15 HS 31
Mössbauerspektroskopie bei tiefer Temperatur an epitaktischen
c-FeSi-Filmen auf MgO(100) — •M. Walterfang 1 ,
W. Keune 1 und U. Rücker 2 — 1 Angewandte Physik, Universität
Duisburg-Essen, 47048 Duisburg — 2 Forschungszentrum Jülich, Institut
für Festkörperforschung, 52425 Jülich
Die metastabile c-FeSi-Phase mit B2-Struktur wurde durch Kodeposition
molekularstrahlepitaktisch auf MgO(100) mit einer Fe-Pufferschicht
bei unterschiedlichen 57 Fe/Si-Konzentrationsverhältnissen hergestellt.
Die Anpassung der 57 Fe-Mössbauer(CEM-)Spektren erfolgte jeweils
mit einem asymmetrischen Quadrupoldublett D1, das die metastabile
stöchiometrische c-FeSi-Phase representiert, sowie einem zusätzlichen
asymmetrischen Dublett D2, das aus einer statistischen Verteilung von

Dünne Schichten Donnerstag
überschüssigen Fe-Atomen auf Si-Gitterplätzen in der B2-Gitterstruktur
resultiert. Mit abnehmenden Temperaturen bis auf 4.2 K nimmt die spektrale
Fläche des D1-Dubletts stark ab und diejenige des D2-Dubletts entsprechend
zu, verbunden mit einer starken Linienverbreiterung des D2-
Dubletts. Als Ursache für die Linienverbreiterung kann eine Zunahme der
Quadrupolwechselwirkung aufgrund von zunehmender Gitterverzerrung
ausgeschlossen werden. Dies folgt aus Röntgenbeugungsresultaten bei
tiefer Temperatur. Die beobachteten Effekte bei Abkühlung sind wahrscheinlich
auf magnetische Ordnungseffekte zurückzuführen.
Gefördert durch die Deutsche Forschungsgemeinschaft (GRK 277).
DS 17.6 Do 16:30 HS 31
Stabilität kolloidaler Nanomasken unter Ionenbestrahlung —
•Jörg K.N. Lindner, Bernhard Gehl, Michael Drexel und
Bernd Stritzker — Universität Augsburg, Institut für Physik, D-
86135 Augsburg
Durch gezieltes Eintrocknen kolloidaler Suspensionen in Form von Monolagen
lassen sich auf einer Festkörperoberfläche vergleichsweise einfach
DS 18 Schichtherstellung III
großflächige Schattenmasken herstellen, deren Öffnungen periodisch angeordnet
sind und wahlweise Durchmesser zwischen einigen Mikrometern
und wenigen 10 Nanometern besitzen. Um diese auch als Implantationsmasken
einsetzen zu können, müssen die Kolloidpartikel aus einem
Element hoher Ordnungszahl und geringer Sputterrate bestehen. Um
zudem schwer entfernbare Kontaminationen zu vermeiden, verwenden
wir wässrige Suspensionen aus SiO2-Kugeln mit 100 nm Durchmesser
auf reinen Silizium-Substraten. Die Stabilität solcher Nano-Masken unter
Ionenbestrahlung ist Gegenstand der vorgestellten Untersuchungen.
Mittels SEM, AFM, XTEM und EFTEM wird gezeigt, dass die Hochdosisimplantation
von C-Ionen bereits mit Energien im keV-Bereich zu
merklichen Änderungen der Größe und Form der Kolloidpartikel führt.
Hierbei überlagern sich ein Schrumpfungsvorgang individueller Kolloidpartikel
und das Zusammenwachsen benachbarter Kugeln. Die beobachtbare
Meniskenbildung zwischen bestrahlten Nachbarkugeln deutet auf
eine ionenstrahl-induzierte Verringerung der Viskosität hin, die zur Reduzierung
der Oberflächenspannung der SiO2-Kugelmasken führt.
Zeit: Donnerstag 16:45–18:15 Raum: HS 31
DS 18.1 Do 16:45 HS 31
Preparation of biaxial textured buffer layers using ion-beam assisted
deposition — •R. Hühne 1 , S. Fähler 1 , W. Skrotzki 2 , L.
Schultz 1 , and B. Holzapfel 1 — 1 Institut für Metallische Werkstoffe,
IFW Dresden — 2 Institut für Strukturphysik, TU Dresden
Different applications require the preparation of films on biaxial textured
templates. Ion-beam assisted deposition (IBAD) offers the possibility
to prepare thin textured films on amorphous or non-textured substrates.
It was shown that thin cube textured MgO layers can be produced
on amorphous Si3N4 using this technique [1]. To study the mechanism
of texture formation in detail MgO films as well as other materials with
a rocksalt structure (i.e. TiN etc.) were deposited on various amorphous
substrates using ion-beam assisted pulsed laser deposition and investigated
in-situ using high energy electron diffraction (RHEED). Above
250 ◦ C a cube texture with a 〈110〉 direction parallel to the ion beam is
observed in films thinner than 10 nm at ion incidence angles between 35 ◦
and 55 ◦ . During further growth this nucleation texture changes in a way
that the 〈200〉 direction becomes parallel to the ion beam. The texture
development can be explained by a combination of thermodynamically
preferred growth orientations, anisotropic sputter rates and stress induced
effects. First results will be presented on the epitaxial growth of
oxides as well as magnetic and superconducting layers on these biaxial
textured templates.
[1] Wang et al., APL 71 (1997) 2955
DS 18.2 Do 17:00 HS 31
High-Fluence C-Implantation into 3C-SiC: Synthesis of Buried
Diamond-Nanocrystals — •Hannes Weishart 1 , Viton Heera 1 ,
Frank Eichhorn 1 , Bela Pecz 2 , Lajos Toth 2 , and Wolfgang
Skorupa 1 — 1 Forschungszentrum Rossendorf, PO Box 510119, D-01314
Dresden — 2 Research Institute for Technical Physics and Materials Science,
H-1525 Budapest, Hungary
Their outstanding properties, such as wide band gap, high thermal
conductivity and saturated electron drift velocity, make silicon carbide
and diamond useful semiconductors for applications under harsh conditions.
A combination of both materials on a microscopic scale may be a
promising way to novel devices.
Ion Beam Synthesis (IBS) is an excellent method for creating precipitates
inside any matrix without thermodynamic constraints. We previously
demonstrated the synthesis of nanocrystalline 3C-SiC inside diamond
by high-fluence Si implantation. In this work we investigate phase
formation in carbon-implanted 3C-SiC substrates. Implantations were
performed with fluences ranging from 3 × 10 17 cm −2 to 3 × 10 18 cm −2 .
Additionally, the influence of implantation temperature and dose rate was
studied using X-ray diffraction (XRD), Raman spectrometry and highresolution
cross-sectional transmission electron microscopy (HRTEM).
Low implantation temperatures and high dose rates favor the formation
of graphite precipitates, while in all other cases epitaxial diamond
nanocrystals grow. Hence, a critical temperature for diamond formation
exists, which depends on dose rate. Increasing the fluence leads to bigger
nanocrystals. Diamond platelets of up to 20 nm length were found.
DS 18.3 Do 17:15 HS 31
Mechanische Spannungen und Strukturbildung in reaktiv gesputterten
Übergangsmetalloxiden und -nitriden — •Friedel
Koerfer, S. Venkataraj, J.M. Ngaruiya, D. Severin und M.
Wuttig — I. Physikalisches Institut (IA), Lehrstuhl für Physik neuer
Materialien, RWTH Aachen, 52056 Aachen
Schichten von Übergangsmetalloxiden und -nitriden haben ein breites
Anwendungsspektrum in der Dünnschichttechnologie (z.B. optische
Funktionsschichten). Die hier verwendete Methode zur Herstellung dieser
Schichten ist das DC-Magnetron-Sputtern.
Es wird eine systematische Studie über den Einfluss der Prozessparameter
auf die Schichteigenschaften wie Struktur, Spannung und
Stöchiometrie durchgeführt. Die mechanischen Spannungen werden
mittels einer wafer-curvature-Methode bestimmt. Ferner werden
die strukturellen und optischen Eigenschaften der Schichten über
Röntgenbeugungsmethoden bzw. Spektroskopie bestimmt.
Die Studie zeigt einen systematischen Trend sowohl für die mechanischen
Spannungen als auch für die strukturellen Eigenschaften. Die Oxide
der Gruppe IV (TiO2, ZrO2 und HfO2) zeigen die höchsten Spannungen
und sind in der Regel kristallin, während die übrigen Oxide (Gruppen
V/VI: V2O5, Nb2O5, Ta2O5, MoO3 und WO3) amorphe Filme mit
wesentlich niedrigeren Spannungen bilden. Diese Ergebnisse werden mit
verschiedenen Übergangsmetallnitriden verglichen, welche ebenfalls beträchtliche
Spannungen aufweisen. Ein Modell, das in der Lage ist diese
systematischen Variationen zu reproduzieren wird diskutiert.
DS 18.4 Do 17:30 HS 31
Elektrodeposition von Co unter dem Einfluss äußerer Magnetfelder
— •Andreas Krause, Margitta Uhlemann, Annett Gebert
und Ludwig Schultz — Leibniz-Institut für Festkörper- und
Werkstoffforschung Dresden, PF 270116, 01171 Dresden, Deutschland
Durch Überlagerung von äußeren Magnetfeldern während des elektrochemischen
Abscheideprozesses können der Mechanismus der Abscheidung
und damit die Struktur und die Eigenschaften der abgeschiedenen
Schichten gezielt verändert werden. In der Arbeit wird der Einfluss von
homogenen Magnetfeldern in Abhängigkeit von Stärke und Orientierung
auf die elektrochemische Abscheidung von Co untersucht. Eine Erhöhung
der Abscheiderate wird durch Konvektion in der Nähe der Elektrodenoberfläche
durch die Wirkung von Lorentzkräften erreicht, wenn das magnetische
Feld parallel zur Oberfläche ausgerichtet ist. Eine Überlagerung
der magnetisch induzierten konvektiven Effekte mit der natürlichen Konvektion
wird dabei berücksichtigt. Neben der Abscheidung von Co findet
gleichzeitig die Wasserstoffreduktion statt. Bei negativen Abscheidepotentialen
wird die Ausbeute von Co erhöht und die Wasserstoffabscheidung
zurückgedrängt. Die Morphologie und Struktur der Schichten wird
dadurch verbessert. Die Wirkung paramagnetischer Kräfte auf die einzelnen
Teilschritte des elektrochemischen Prozesses wird diskutiert.

Dünne Schichten Donnerstag
DS 18.5 Do 17:45 HS 31
Morphologie von lokal elektrochemisch erzeugten Metallstrukturen
- Untersuchung der Einflußparameter — •Angelika Bunk,
Anne-D. Müller, Falk Müller und Michael Hietschold — TU
Chemnitz, Institut für Physik, 09107 Chemnitz
Mit Hilfe einer elektrolytdurchflossenen Glaskapillare als Bestandteil
einer elektrochemischen Zelle wurden punkt- und linienförmige Metallstrukturen
mit Abmessungen im µm-Bereich erzeugt. Dimensionen und
Morphologie dieser Strukturen hängen von dem elektrischen Feld unter
der Kapillarstirnfläche ab, das sich aus angelegter Arbeitsspannung,
Elektrolytleitfähigkeit, Kapillargeometrie und Arbeitsabstand zum Substrat
ergibt. Weitere Einflußgrößen insbesondere auf die Morphologie der
Metallkristalle sind die chemische Natur der Elektrolytlösung und das
Substratmaterial. Die Auswirkungen der wichtigsten Parameter auf den
Abscheidevorgang selbst hinsichtlich Materialtransport und Kristallnukleation
werden demonstriert und interpretiert.
DS 18.6 Do 18:00 HS 31
Charakterisierung und Herstellung von Ba(Ti1−yZry)O3 (BTZ)
durch Metallorganische Chemische Gasphasenabscheidung
(MOCVD) — •Jochen Puchalla — Forschungszentrum Jülich
GmbH, Institut für Festkörperforschung (IFF), 52425 Jülich
Keramische hoch-epsilon Dünnschichten sind Gegenstand von Untersuchungen
zur Ersetzung von SiO2 als Dielektrikum in integrierten Schaltkreisen,
um die Dimensionierung der Bauelemente weiter reduzieren zu
können. Mögliche Anwendungen sind zukünftige Gbit DRAM Schaltkreise
und modulierbare Mikrowellenbauelemente, der industriell favorisierte
Depositionsprozess ist die Metallorganische Chemische Gasphasenabscheidung
(MOCVD). Dünne Schichten aus Ba(Ti1−yZry)O3 (BTZ) aus
CSD- oder Sputter-Anlagen zeigen interessante elektrische Eigenschaften,
die den Anforderungen an integrierte Kondensatorstrukturen gewachsen
sind.
In der Arbeit wird BTZ mit der Hilfe der Metallorganischen Chemischen
Gasphasenabscheidung hergestellt, welche kompatibel zu heutigen
State-of-the-art Integrationsprozessen ist und sich aussergewöhnlich gut
für konformes 3D-Wachstum eignet. In einem AIX-200 Horizontalreaktor
an einem TriJet TM Verdampfermodul werden BTZ-Schichten auf einem
Pt/Si-Wafer abgeschieden. Besonderes Augenmerk liegt auf den Zusammenhängen
zwischen den Prozessbedingungen und den Schichteigenschaften
wie Stöchiometrie, Textureffekte und Oberflächenbeschaffenheit.
Weitere Untersuchungen gelten der elektrischen Charakterisierung und
den Beziehungen zwischen physikalisch-chemischen Eigenschaften und
der elektrischen Response der Schicht.
DS 19 FV-internes Symposium ” Dünne Schichten für die Photovoltaik I“
Zeit: Donnerstag 09:30–12:50 Raum: HS 32
Hauptvortrag DS 19.1 Do 09:30 HS 32
Thin-film photovoltaics with crystalline Si using porous Si for
layer transfer (PSI process) — •Rolf Brendel, Heiko Plagwitz,
and Richard Auer — Bavarian Center for Applied Energy Research
(ZAE Bayern), Am Weichselgarten 7, D-91058 Erlangen, Germany
Thin-film photovoltaics aims at replacing 300 micron thick wireconnected
crystalline Si wafers by at least 10 times thinner modules
that have an integrated series connection. This talk reviews a largely
unexplored approach to fabricate thin-film modules by using layer
transfer with porous Si (PSI process).
We porosify the surface of a Si substrate by anodic etching. The porous
Si layer is monocrystalline and permits the homoepitaxial growth of a Si
film. The porous surface layer becomes mechanically weak during annealing
and thus a transfer of the epitaxial film to a glass carrier is possible.
The growth substrate is re-used to fabricate further cells. We achieve an
independently confirmed power conversion efficiency of 15.4 percent with
a 25 micron thick cell that is processed without using photolithography.
Layer transfer enables novel technologies for implementing an integrated
series connection, since both sides of the epitaxial film are freely
accessible for processing. We introduce a module design that interconnects
adjacent cells by a single metallization step. A first implementation
of this scheme yields a module efficiency of 10.0 percent.
Good surface passivation is vital for thin cells. We demonstrate a novel
low-temperature process to passivate and locally contact thin-film solar
cells. The average surface recombination velocity of the contacted rear
side is 100 cm/s.
Hauptvortrag DS 19.2 Do 10:10 HS 32
Photoelectron spectroscopy of thin film solar cell interfaces —
•Andreas Klein — Darmstadt University of Technology, Institute of
Materials Science, Surface Science Division
Interfaces are of crucial importance in semiconductor devices. The
properties of crystalline Si and III-V semiconductor interfaces are experimentally
and theoretically intensively investigated and well understood.
However, important interfaces in thin film solar cells include
II-VI semiconductors like CdTe or CdS and related chalcopyrites
(Cu(In,Ga)(S,Se)2), transparent conducting oxides (ZnO, SnO2, In2O3)
and partly also with amorphous and organic materials. The resulting
complexity of the interfaces, which is even increased by the variety of
deposition and processing techniques used for manufacturing high efficiency
thin film solar cells, is to date not completely resolved. In this
talk the phenomena occuring at thin film solar cell interfaces and the use
of integrated surface analysis and preparation systems, which are used in
Darmstadt for their investigation, will be described. For interface analysis
we mostly use photoelectron spectroscopy (XPS, UPS), since this
technique allows to determine not only chemical and morhpological, but
also the electronic properties of the interfaces.
Hauptvortrag DS 19.3 Do 10:50 HS 32
Elektrische Analyse von polykristallinen Halbleiter-
Dünnschichtsystemen für die Photovoltaik — •Uwe Rau
— Institut für Physikalische Elektronik, Universität Stuttgart
Nach langjähriger Forschung und Entwicklungsarbeit werden Solarzellen
aus den polykristallinen Dünnschichthalbleitern CdTe und
Cu(In,Ga)Se2 derzeit am Markt eingeführt. Mittelfristig sollen diese
neuen Technologien zur weiteren Kostensenkung bei der photovoltaischen
Energiegewinnung beitragen. Die elektrische Analyse von Schichten
und Bauelementen dient sowohl dem grundlegenden Materialverständnis
als auch der Qualitätskontrolle. Der Vortrag wird am Beispiel von
ZnO/CdS/Cu(In,Ga)Se2 Solarzellen grundlegende Methoden zur Analyse
der elektrischen Materialeigenschaften und Modelle zur Funktionsweise
von Dünnschichtsolarzellen diskutieren. Ausgehend von der Analyse
der Hauptverlustmechanismen wird der Einfluss von Defekten und
elektrischen Metastabilitäten auf die Leistungsfähigkeit von Solarzellen
und -modulen diskutiert. Bestrahlungsexperimente mit hochenergetischen
Teilchen zeigen, dass Cu(In,Ga)Se2 strahlenresistenter als alle
anderen bekannten photovoltaischen Materialien ist. Dieses Resultat legt
eine Anwendung von Cu(In,Ga)Se2 für Weltraumsolarzellen in besonders
strahlungsintensiven Orbits nahe.
Hauptvortrag DS 19.4 Do 11:30 HS 32
Präparationsverfahren für Chalkopyrit-Solarmodule — •Reiner
Klenk — Hahn-Meitner-Institut, Glienickerstr. 100, D-14109 Berlin
Die Dünnschichtphotovoltaik stellt hohe Anforderungen an die
Präparationsverfahren. Im Gegensatz zu vielen anderen Anwendungsbereichen
müssen die Prozesse zusätzlich zur großflächigen, homogenen
Abscheidung bei geringen Kosten und hoher Ausbeute auch definierte
elektronische Eigenschaften der Dünnschichten erreichen. Für ein
Chalkopyrit-Solarmodul sind vier oder mehr Schichten erforderlich; zum
Teil kann die Sputtertechnik (Kathodenzerstäubung) eingesetzt werden,
die sich in der industriellen Produktion schon bewährt hat. Für die
Absorber- und Pufferschicht müssen aber auch neue, bisher nur im Labormaßstab
etablierte Technologien für den industriellen Einsatz adaptiert
werden. Dieser Beitrag definiert ausgehend vom physikalischen Funktionsprinzip
der Chalkopyrit-Solarzelle die notwendigen Eigenschaften der
verschiedenen Schichten und stellt geeignete Präparationsverfahren vor.
Hauptvortrag DS 19.5 Do 12:10 HS 32
Plasmagestützte Schichtabscheideverfahren für Dünnschichtsolarzellen:
Prinzipien und Anwendungen — •Klaus Ellmer —
Hahn-Meitner-Institut, SE5, 14109 Berlin
Dünnschichtsolarzellen sind aufgrund ihres geringen Materialver-

Dünne Schichten Donnerstag
brauchs (µm-Bereich) bevorzugt für eine künftige photovoltaische
Energieversorgung. Um den notwendigen Umbau der Energieversorgung
erreichen zu können, sind Flächen in der Grössenordnung von 10
Millionen m 2 /Jahr zu beschichten, vergleichbar mit der gegenwärtigen
Beschichtungskapazität für Architekturglas. Daneben ist der Energieaufwand
für die Herstellung der Dünnschichtsolarzellen zu minimieren,
um die Energierückführzeit klein zu halten gegen die Nutzungsdauer
von Solarzellenmodulen.
Plasmagestützte Schichtabscheideverfahren können diese Forderungen
erfüllen und werden für die Herstellung von Dünnschichtsolarzellen auf
der Basis von amorphem Silizium und hochabsorbierenden Verbindungshalbleitern
bereits eingesetzt oder entwickelt. Sie zeichnen sich aus durch:
- niedrige Abscheidetemperaturen,
- hohe Abscheideraten,
- hohe chemische Reaktivität der gasförmigen Komponenten,
- die einfache Skalierbarkeit auf grosse zu beschichtende Flächen.
Es werden die physikalischen Grundprinzipien der plasmagestützten
chemischen Gasphasenabscheidung (PECVD) für amorphes Silizium und
des Magnetronsputterns (RMS) für Metalle und halbleitende Schichten
(CuInS2 )erläutert.
DS 20 Dünne Schichten für die Photovoltaik II
Zeit: Donnerstag 14:30–15:45 Raum: HS 32
DS 20.1 Do 14:30 HS 32
Photolumineszenz von epitaktischem Dünnschichtsilizium in
unterschiedlichen Wachstumstemperatur-Regimen — •Kai Petter,
Björn Rau, Klaus Lips und Walther Fuhs — Hahn-Meitner-
Institut Berlin, Kekuléstr. 5, Abt. Silizium-Photovoltaik, D-12498 Berlin,
Germany
Die in dieser Arbeit untersuchten Proben wurden mittels der Elektron-
Zyklotron Resonanz unterstützten Gasphasenabscheidung (ECR-CVD)
gewachsen. Diese Methode zeichnet sich dadurch aus, dass sie epitaktisches
Wachstum unterhalb der Glaserweichungstemperatur ermöglicht
und somit potentiell bei der Herstellung von Dünnschichtsolarzellen auf
Glassubstrat einsetzbar ist. Um Informationen über beim Wachstum entstehende
Defekte und Verunreinigungen zu bekommen, wurden ca. 1 µm
dicke nominell undotierte Silizium-(Si)-Schichten auf (100)-orientiertes
Si-Substrat abgeschieden und mittels Photolumineszenz (PL) untersucht.
Abhängig von der Wachstumstemperatur (420 ◦ C - 595 ◦ C) erhält man
charakteristische PL-Spektren. Für Temperaturen unter 500 ◦ C sind die
Schichten noch lokal ungeordnet und es ergeben sich mehrere breite PL-
Banden zwischen 0.8 und 1.1 eV. Im Bereich ab 500 ◦ C findet das Wachstum
dann mit guter kristallografischer Qualität statt und es sind scharfe
PL-Peaks bei 0.89 , 0.90 und 1.11 eV zu erkennen. Für Wachstumstemperaturen
oberhalb von 560 ◦ C sind diese Peaks ebenfalls zu erkennen,
es bilden sich aber auch im Substrat optisch aktive Defekte aus und ein
starker Abfall der integrierten PL-Intensität aus der Schicht wird beobachtet.
Der Zusammenhang dieser PL-Linien mit strukturellen Defekten
(self-interstitials) und thermischen Donatoren wird diskutiert.
DS 20.2 Do 14:45 HS 32
Polykristalline Siliziumschichten auf metallbeschichten Glassubstraten
— •Kati Hübener, Stefan Gall, Martin Muske,
Jens Schneider und Walther Fuhs — Hahn-Meitner-Institut, Abt.
Silizium-Photovoltaik, Kekuléstr.5, D-12489 Berlin
Durch Al-induzierte Kristallisation von amorphem Silizium (a-Si) lassen
sich grobkristalline poly-Si Filme auf Glas herstellen, die als Keimschichten
für epitaktische Verdickung dienen können. Ein Schichtstapel
Glas/Al/a-Si wird in einem einfachen Temperschritt in eine Schichtfolge
Glas/poly-Si/Al(Si) umgewandelt. Als entscheidend für den Schichtaustauschprozess
hat sich eine dünne Schicht aus Al-Oxid erwiesen, durch
die die Kinetik des Prozesses und die Korngröße empfindlich beeinflusst
werden. In diesem Beitrag berichten wir über eine Realisierung
des Schichtaustausches in dem inversen System, bei dem aus Glas/a-
Si/Al eine Schichtfolge Glas/Al(Si)/poly-Si erzeugt wird. Die technologische
Bedeutung dieser Schichtfolge liegt darin, dass ein solches System
als Rückkontakt einer Dünnschichtzelle dienen kann. Durch thermische
Oxidation des a-Si bei verschiedenen Temperaturen wurden Zwischenschichten
aus Si-Oxid erzeugt. Es zeigte sich, dass die Zwischenschicht
für einen Schichtaustausch notwendig ist und die Nukleationszeit, die
Wachstumsgeschwindigkeit der Körner und die Korngröße entscheidend
bestimmt. Das Verhalten wird in einem Modell gedeutet, bei dem die
Si-Oxid Zwischenschicht ähnlich wie bei der inversen Struktur das Al-
Oxid als Membran wirkt, die den Massentransport über die Grenzfläche
kontrolliert.
DS 20.3 Do 15:00 HS 32
Ultrathin hydrogenated amorphous silicon layers on crystalline
silicon: a-Si:H gap state density distribution and a-Si/c-Si interface
properties — •Lars Korte, Klaus Kliefoth, Abdelazize
Laades, and Manfred Schmidt — Hahn-Meitner-Institut Berlin,
Abt. Silizium-Photovoltaik, Kekuléstr. 5, 12489 Berlin
The application of hydrogenated amorphous silicon as emitter layer in
high-efficiency heterostructure solar cells requires an optimization of the
a-Si:H bulk and a-Si/c-Si interface electrical properties. Information on
these properties can be obtained by photoelectron spectroscopy (PES)
and the surface photovoltage technique (SPV), respectively. By PES, the
Fermi level Ef as well as the distribution of states Nocc(E) in the valence
band and the energy gap up to Ef can be measured [1]. The information
depth at the used low excitation energies (hν = 4 − 7 eV) increases to
5-10 nm, equal to the optimum emitter thickness. Thus, Nocc(E) is an
average of the a-Si:H density of states (DOS). For samples of n-doped
a-Si:H deposited on c-Si by PECVD, Ef −Ev varies from 1.15 eV for undoped
layers to a saturation value of 1.47 eV at a doping of [P] = 10 4 ppm
in the gas phase. Also, an increase of the Urbach energy from 51 meV to
101 meV and of the DOS at midgap is observed, indicating an increase
of disorder and dangling bond concentration. From SPV, the band bending
at the a-Si:H/c-Si interface can be determined. The interface gap
states distribution Dit(E) is measured by bias voltage-dependent SPV
and proves the excellent passivation of the c-Si surface by the a-Si:H
network, with a Dit as low as that of H-terminated c-Si.
[1] M. Schmidt et al., MRS Proc. 762, A19.11.1 (2003).
DS 20.4 Do 15:15 HS 32
Metal organic molecular beam epitaxy (MOMBE) of CuInS2 on
Si(111) — •Carsten Lehmann, Wolfram Calvet, and Christian
Pettenkofer — Hahn-Meitner-Insititut, Glienicker Strasse 100, 14109
Berlin
The ternary compound semiconductor CuInS2 with a direct band gap
of 1.53 eV seems to be very promising as absorber material for thin
film solar cells. We report on thin epitaxial CuInS2 layers prepared on
hydrogen terminated Si(111) by metal organic molecular beam epitaxy
(MOMBE). The deposition steps are monitored in situ with photoelectron
spectroscopy (PES) and low energy electron diffraction (LEED). Ex
situ, x-ray diffraction (XRD) and secondary electron microscopy (SEM)
complement the film analysis. The film growth is improved by additional
ultraviolet (UV) light leading to epitaxial films showing ordered (1x1)
LEED patterns of the surface. Additionally, the segregation of elemental
In occurs in the In-rich regime of preparation. No carbon contamination
is detected in the film indicating a clean reaction of the sulfur precursor.
Further, the formation of Cu2Si is observed at the interface during the
nucleation phase. From SEM it can be deduced that this additional phase
penetrates into the Si substrate forming extended hillocks. Obviously, the
quality of the CuInS2 films is sensitively influenced by the initial growth
conditions.
DS 20.5 Do 15:30 HS 32
8% efficient CuInS2 (CIS) solar cells with electrochemically
removed Cu-S-phases — •Thomas Wilhelm, Baptiste Berenguier,
Mohammed Aggour, Mirko Gaul, Momme Winkelkemper,
Michael Kanis, Eder Goncalves, Helmut Jungblut, and
Hans-Joachim Lewerenz — Hahn-Meitner-Institut, Glienicker Str.
100, D-14109 Berlin
In the pursuit of replacing toxic processing steps and materials in CIS
solar cells we have employed various electrochemical conditioning procedures
for the removal of the deleterious Cu-S-phases. This development
of the electrochemical processing is reviewed and a specific anodisation
procedure in a V(II)/V(III) redox electrolyte is presented. Potential profiles
encompassing the successive dissolution of CuS, Cu2S and CIS have
been applied, resulting in Cu-S-phase free surfaces as evidenced by surface
analyses (photoelectron spectroscopy and atomic force microscopy).

Dünne Schichten Donnerstag
In a series of efficiency measurements solid state devices with η = 8% were obtained.
DS 21 Dünne Schichten für die Photovoltaik III
Zeit: Donnerstag 15:45–17:00 Raum: HS 32
DS 21.1 Do 15:45 HS 32
Cd-freie Pufferschichten für die Anwendung in
CuInS2Dünnschichtsolarzellen — •Olga Papathanasiou 1 ,
Susanne Siebentritt 1 , Wolfgang Bohne 1 , Erik Strub 1 ,
Jorg Röhrich 1 , Wolfram Calvet 1 , Christian Pettenkofer
1 , Christian Kristukat 2 und Martha Lux-Steiner 1 —
1 Hahn-Meitner-Institut Berlin — 2 Technische Universität Berlin
Die höchsten Wirkungsgrade bei CuInS2-Solarzellen werden mit einer
wenige Nanometer dicken Pufferschicht zwischen Absorber und ZnO-
Fensterschicht erreicht. Bislang wird hierfür eine nasschemisch abgeschiedene
CdS-Schicht verwendet. Mittels MOCVD (Metal Organic Chemical
Vapor Deposition) abgeschiedenes ZnSe bietet aufgrund seiner größeren
Bandlücke (2.7 eV) und seiner geringeren Toxizität eine konkurrenzfähige
Alternative. Hinzu kommt, dass der MOCVD-Prozess ein trockenes Abscheideverfahren
ist, und die Mo”glichkeit einer industriellen in-line Integration
bietet. Mit photounterstützter MOCVD sind Abscheidetemperaturen
bis hinunter zu 250 ◦ C bis 200 ◦ C möglich. Mit diesen Temperaturen
sind Wirkungsgrade bis zu 8% erzielt worden. An epitaktischen
Si/CuInS2/ZnSe Strukturen wurden HI-ERDA (Heavy Ion Elastic Recoil
Detektion Analysis) und IRS (Infra Red Spectroscopy) Messungen durchgeführt,
um ein besseres physikalisches Verständnis der CuInS2/ZnSe
Grenzschicht zu erhalten.
DS 21.2 Do 16:00 HS 32
In-situ analysis of transparent conducting oxides — •Yvonne
Gassenbauer, Frank Säuberlich, Robert Schafranek, and Andreas
Klein — Darmstadt University of Technology, Institute of Materials
Science, Surface Science Division
Transparent conducting oxides (TCO) as ZnO, SnO2 and In2O3 are
used in all thin film solar cells. Although they are mostly used in degenerately
n-doped form as electrodes, undoped films are often inserted
between the TCO and the semiconductor. Obviously the interfaces are
important for device efficiency. To understand the interfaces of different
TCOs we present our results on the electronic surface properties of different
TCOs. The films were prepared by RF and DC magnetron sputtering
in an ultrahigh vacuum deposition chamber, which was attached to the
integrated surface analysis and preparation system DAISY-MAT (Darmstadt
Integrated System for MATerials research). Film composition and
surface Fermi level position in the band gap for un-doped and doped
ZnO, SnO2 and In2O3 will be presented and discussed.
DS 21.3 Do 16:15 HS 32
Modifikation elektronischer und chemischer Eigenschaften von
TiO2 - Oberflächen durch Abscheidung extrem dünner oxidischer
und sulfidischer Schichten — •H.-J. Muffler, A. Belaidi,
M. Vogel, T. Guminskaya, Ch.-H. Fischer und Th. Dittrich —
Hahn-Meitner-Institut, SE2, Glienicker Str. 100, D-14109 Berlin, Germany
Mittels des ILGAR (ion layer gas reaction) Verfahrens wurden extrem
dünne hydroxidische (Al(OH)3, oxidische (Al2O3) und sulfidische (In2S3,
CuxS) Schichten auf dünne TiO2 Schichten abgeschieden. Die TiO2 -
DS 22 Postersitzung
Schichten wurden im sol - gel - Verfahren (sglux GmbH) hergestellt. Die
Charakterisierung der Proben erfolgte nach Beschichten und Tempern in
Luft bzw. in Ar/H2S - Atmosphäre mit XPS, Kelvin-Sonden und transienter
und spektraler Photospannung. Je nach Oberflächenbehandlung
variiert die Austrittsarbeit um bis zu 0.6 V und wechselt die Photospannung
das Vorzeichen. Die Entstehung von Volumendefekten im TiO2 nach
Tempern in H2S wird durch Aufbringen von Al2O3 stark unterdrückt. Die
Korrelation zwischen elektronischen und chemischen Eigenschaften wird
diskutiert.
DS 21.4 Do 16:30 HS 32
Fingerprints of not thermal distributed charge carriers in the
photocurrent of an InP photovoltaic structure at low temperatures.
— •Matthias Neges, Klaus Schwarzburg, and Frank
Willig — Glienicker Str. 100, 14109 Berlin, Germany
Photocurrent excitation spectra of a InP/SnO2 hetero junction photovoltaic
device have been measured in the temperature range of 10-300
K. Below 80 K, the spectra show a periodic modulation with a beat frequency
that corresponds to the LO phonon frequency. Minima in the
photocurrent spectra correspond to a LO phonon cascade that scatters
an electron close to the band edge. Outside this resonance, the photocurrent
is enhanced with respect to the photocurrent observed at higher
temperatures (>80 K).
Monte Carlo simulations reveal the principal mechanism that is responsible
for the photocurrent enhancement at lower temperatures. In
addition, they give insight into the energetic distribution of the photogenerated
carriers. At lower temperatures, the distribution departs strongly
from a thermal distribution. At room temperature, a large portion of the
excess carriers is thermalized within a few 100 ps. Nonetheless, a clear
deviation from a thermalized charge carrier distribution can be observed.
Implications of these findings for 3rd generation photovoltaic devices will
be discussed.
DS 21.5 Do 16:45 HS 32
Dünnschichtsolarzellen auf flexiblen Trägern — •Karsten Otte
und Gerd Lippold — Solarion GmbH, Ostende 5, 04288 Leipzig
Dünnschichtsolarzellen mit CuInSe2 (CIS) als Absorberschicht auf
flexiblen Trägermaterialien erlauben neue Anwendungsmöglichkeiten
der Photovoltaik. Ein weiterer Vorteil ist die Herstellung in hochproduktiven
Rolle-zu-Rolle Prozessen. Die industrielle Produktion dieser
Dünnschichtsolarzellen auf flexiblen Trägern (insbesondere Polyimid)
wird vorgestellt und an Hand von einigen Beispielen diskutiert.
Aufgrund ihres geringen Gewichtes, eignen sich diese Solarzellen ausgezeichnet
für Anwendungen in der Luft- und Raumfahrt - eine Optimierung
des Schichtaufbaus und des Wirkungsgrades sind jedoch dafür
unerlässlich. Anhand von komplementären Verfahren der spektroskopischen
Echtzeitanalytik wird die Abscheidung der CIS-Absorberschicht
erstmals in einem industriellen Prozess kontrolliert und optimiert. Die
Möglichkeiten und Vorteile der verwendeten spektroskopischen in-situ-
Ramanstreuung und in-situ-Röntgen-Fluoreszenzanalytik für die Kontrolle
der Schichtzusammensetzung, der Schichtdicke und der Phasenzusammensetzung
wird vorgestellt.
Zeit: Dienstag 14:30–17:00 Raum: Poster B
DS 22.1 Di 14:30 Poster B
In-Situ Reflectance Anisotropy Spectra (RAS) Investigation —
•Thorsten Bork 1 and A. Bakin 2 — 1 Hahn-Meitner-Institute, Berlin,
Germany — 2 Institute for Semiconductor Technology - Technical University
of Braunschweig, Germany
For the industrial development of the benefits of III/V and Si monolithical
integration it is necessary to grow these structures on exactly oriented(001)Si
substrates. A detailed investigation of the growth of a buffer
layer is described here. In our present work we also develop thick InP layer
growth on Si. The growth of InP layers was performed in horizontal IR-
heated MOVPE AIX-200 machines. The growth of 40-nm thick InP buffer
layers was performed employing phosphine (PH3) and as alternative
phosphorus source TBP. The further growth of the 2000-4000nm thick
InP layers was performed employing the phosphorus source TBP. In-situ
reflectance anisotropy spectra (RAS) investigations have been for the first
time employed to monitor and optimize the InP growth on Si. The samples
were investigated using atomic-force microscopy(AFM), scanning
electron microscopy (SEM), transmission electron microscopy(TEM), xray
diffraction (XRD), x-ray photoelectron spectroscopy (XPS) as well
as defect etching and optical microscopy with Nomarski contrast. The
process of InP growth observed is discussed. The influence of different

Dünne Schichten Dienstag
source gas flows and growth temperatures is investigated.
DS 22.2 Di 14:30 Poster B
MOVPE von A III B V -Verbindungen auf Ge-Substraten —
•Sebastian Scholz 1 , Helmut Herrnberger 1 , Volker Gottschalch
1 und Dietmar Hirsch 2 — 1 Universität Leipzig, Institut für
Anorganische Chemie, Linnestr. 3, 04103 Leipzig — 2 Leibniz-Institut
für Oberflächenmodifizierung e.V, Permoserstr. 15, 04303 Leipzig
Der Einsatz von Ge-Substraten ist für die Applikation von Mehrschichtsolarzellen
auf A III B V -Basis von besonderem Interesse.
Mit der LP-MOVPE wurden im Standardsystem (TMGa, AsH3)
GaAs-Schichten unterschiedlicher Dicken auf (100)- und fehlorientierten
Ge-Substraten mit dem Ziel der Baufehlerminimierung abgeschieden.
Das Studium des Wachstums, und speziell des Anfangswachstums,
erfolgte bei Variation des V/III-Verhältnisses, der Züchtungstemperatur
und der Wachstumsrate. Zur strukturellen Charakterisierung des epitaktischen
Materials wurden AFM-, Röntgen-, TEM-Messungen und
die chemische Ätztechnik eingesetzt. GaAs-Schichten mit guter Oberflächenmorphologie
und Monolagenstufen wurden im Temperaturbereich
von 650 bis 700 ◦ C bei einem optimalen V/III-Verhältnis gezüchtet.
DS 22.3 Di 14:30 Poster B
Herstellung von A III B V Nanoröhren aus epitaktischen Dünnschichtsystemen
— •Ole Lühn, Jens Bauer, Helmut Herrnberger
und Volker Gottschalch — Universität Leipzig, Institut
für Anorganische Chemie, Linnestr. 3, 04103 Leipzig
Planare Schichtfolgen von (BGa)As/(GaIn)As auf GaAs und
(AlIn)As/(GaIn)As auf InP mit definierter Spannungsverteilung und
Schichtdicken im nm-Bereich dienten zur Herstellung von A III B V
Nanoröhren. Durch materialselektives Ätzen der verschiedenen
Opferschichten (AlAs, (GaIn)P, InP) erfolgte die Röllchenbildung.
Die planaren Schichtkombinationen wurden mittels MOVPE hergestellt
und die Spannungs- und Schichtdickenverhältnisse mittels Doppelkristalldiffraktometrie
und Transmissionselektronenmikroskopie bestimmt.
Die Charakterisierung der hergestellten Nanoröhren erfolgte mit der
Rasterelektronenmikroskopie und der Kathodolumineszenz.
Erste optische Untersuchungen an (BGa)As/(InGa)As Nanoröhren
weisen im Vergleich zu planarem Material eine Rotverschiebung infolge
Spannungsabbaus auf.
DS 22.4 Di 14:30 Poster B
Plasma modification of nano-particles and nano-fibres —
•Holger Kersten 1 , Gabi Thieme 2 , and Volker Brueser 1 —
1 INP Greifswald, F.-L.-Jahn-Str.19, D-17489 Greifswald — 2 University
of Greifswald, Department of Physics, Domstr.10a, D-17487 Greifswald
Nano-particles and nano-fibres are treated in different plasma environments
as rf-discharge at low pressure and dielectric barrier discharge
at atmospheric pressure, respectively. The results of the surface modification
(functionalization, thin film deposition) have been proved by
scanning electron microscopy and contact angle measurement.
During the plasma interaction the particles are charged. The different
forces which act onto the particles due to their charge are estimated and
used for an active influencing of the particles and fibres.
DS 22.5 Di 14:30 Poster B
Influence of X-ray Radiation on the Chemical Composition of
Plasma Deposited Fluorocarbon Films — •Vasil Yanev 1 , Stefan
Krischok 1 , Andreas Opitz 1 , Norbert Schwesinger 2 , Helmut
Wurmus 1 , and Juergen A. Schaefer 1 — 1 Zentrum für Mikround
Nanotechnologien, TU Ilmenau, 98693 Ilmenau — 2 FB Mikrostrukturierte
mechatronische Systeme, TU München, 80290 München
Teflon-like fluorocarbon (FC) films are of interest for low dielectric interlayer
material. Thin teflon-like FC-films were deposited via plasma
polymerization of trifluoromethane (CHF3) onto silicon substrates in
a commercial reactive ion etching system (RIE, radio-frequency 13.56
MHz). Changes in the chemical composition of the deposited FC films as
a function of exposure time to the X-ray radiation was investigated by
X-ray photoelectron spectroscopy (Mg Kα). Surface charging of the FC
films during the X-ray exposure was observed. This charging, leading to
shifts in the XPS peaks, was dependent on the X-ray exposure time of
the FC-films. XPS of the C 1s core levels reveals that the percentages
of (-CF3), (-CF2) and (CF) bonds fall off sharply and the percentages of
(-C-CF) type bonds increase.
DS 22.6 Di 14:30 Poster B
Ionenstrahlgestützte Molekularstrahlepitaxie von wurtzitischem
Galliumnitrid auf Lithiumaluminat-Substraten — •A.
Hofmann, J.W. Gerlach, T. Höche und B. Rauschenbach —
Leibniz-Institut für Oberflächenmodifizierung, Permoserstraße 15, 04318
Leipzig
Auf der LiAlO2(100)-Ebene abgeschiedene GaN-Schichten weisen eine
m-Ebenen-Orientierung auf. Daraus resultiert eine Gitterfehlanpassung,
die wesentlich geringer ist als die von GaN-Schichten auf den
herkömmlichen Substraten Saphir und SiC. Zudem ist m-Ebenen-GaN,
im Gegensatz zu typischerweise c-Ebenen-orientiertem GaN, nicht-polar.
In diesem Beitrag wird gezeigt, wie bei der ionenstrahlgestützten Deposition
von GaN-Schichten auf LiAlO2 durch geeignete Parameterwahl
die kristalline Qualität der Schichten nachhaltig beeinflusst werden kann.
Hierzu wurde Gallium verdampft und das auf dem Substrat kondensierende
Gallium bei verschiedenen Substrattemperaturen mit niederenergetischen
Stickstoffionen bestrahlt. Die hergestellten Schichten wurden
mittels hochaufgelöster Röntgen-Strahlbeugung und Transmissionselektronenmikroskopie
charakterisiert. Die Ergebnisse zeigen, dass die Schichten
ausschliesslich m-Ebenen-orientiert und von hoher kristalliner Qualität
sind. Allerdings führen die unterschiedlichen thermischen Ausdehnungskoeffizienten
von Substrat und Schicht zu mechanischen Spannungen.
Der Einfluss der Herstellungsparameter auf die Schichteigenschaften
wird diskutiert.
DS 22.7 Di 14:30 Poster B
Elektrische und optische Eigenschaften von Ionenstrahlgestützt
hergestellten Galliumnitrid-Schichten — •S. Sienz 1 ,
J.W. Gerlach 1 , T. Höche 1 , A. Sidorenko 2 , T.G. Mayerhöfer 3 ,
G. Benndorf 4 und B. Rauschenbach 1 — 1 Leibniz-Institut für
Oberflächenmodifizierung e.V., Permoserstraße 15, 04303 Leipzig —
2 Institut für Physikalische Chemie, Universität Tübingen — 3 Institut für
Physikalische Chemie, Friedrich-Schiller-Universität Jena — 4 Institut
für Experimentelle Physik II, Universität Leipzig
Hohe kristalline Qualität stellt die Voraussetzung für gute optische
und elektrische Eigenschaften von Galliumnitrid-Schichten dar. Es
wurde bereits gezeigt, wie sich diese durch den Einsatz von Ionenstrahl-gestützter
Molekularstrahlepitaxie (IBA-MBE) statt konventioneller
Molekularstrahlepitaxie (MBE) deutlich verbessern ließ. Dazu
wurden Galliumnitrid-Schichten auf 6H-SiC bei einer Substrattemperatur
von 630 ◦ C mit beiden Verfahren unter sonst gleichen Bedingungen
hergestellt. Transmissions-Elektronenmikroskop-Aufnahmen zeigen
den Glättungseffekt der IBA-MBE, welcher sich durch die Ionenstrahlinduzierte
Oberflächendiffusion während des Schichtwachstums erklären
lässt. Damit einher geht auch die geringere Defektdichte dieser Schichten.
Photolumineszenz-Spektren zeigen die verbesserten optischen Eigenschaften
von Ionenstrahl-gestützt hergestellten Schichten. Aus Fourier-
Transformations-Infrarot-Spektren wurde die Ladungsträgerdichte berechnet.
Diese ist im Fall der IBA-MBE deutlich geringer als im Fall
der MBE.
DS 22.8 Di 14:30 Poster B
Herstellung und Charakterisierung laserablatierter Spin-Valve
Systeme — •R. Steiner, J. Sihler, M. Krieger, A. Plettl,
H.-G. Boyen und P. Ziemann — Abteilung Festkörperphysik, Universität
Ulm, D-89069 Ulm
Es wurden Spin-Valve Systeme mittels Pulsed Laser Deposition
hergestellt. Hierzu wurde ein spezielles Verfahren am Materialsystem
Co/Cu/Co entwickelt [1], wobei die Deposition der Cu-Zwischenschicht
knapp oberhalb der Ablationsschwelle erfolgte, um so den Anteil
energiereicher Ionen und damit Mischungseffekte an der Grenzfläche
zu minimieren. Andererseits unterstützt dieser Effekt in Systemen
wie Fe/B eine Grenzflächenamorphisierung [2]. Durch Kombination
der Verfahren lassen sich Spin-Valve Systeme mit weichmagnetischem
a-FeB herstellen. Für diese Schichten werden Magnetisierungs- und
Magnetotransportmessungen vorgestellt. Außerdem wurde der Einfluss
einer Exchange Bias Schicht (CoO) auf die Spin-Valve Systeme
untersucht.
[1] M. Krieger, A. Plettl, R. Steiner, H.-G. Boyen, P. Ziemann, Applied
Physics A, in press
[2] R. Steiner, H.-G. Boyen, M. Krieger, A. Plettl, P. Widmayer, P. Ziemann,
F. Banhart, R. Kipler, P. Oelhafen, Applied Physics A, 76, 5-13
(2003)

Dünne Schichten Dienstag
DS 22.9 Di 14:30 Poster B
Wachstum von HfO2-Schichten auf Si(100) mittels Pulsed Laser
Deposition — •Mathias Kappa, Dirk Wolfframm, Markus
Ratzke, Simona Kouteva-Arguirova und Jürgen Reif — LS
Experimentalphysik II, BTU Cottbus und JointLab IHP/BTU, Universitätsplatz
3-4, 03044 Cottbus
Dünne HfO2-Schichten wurden bei Raumtemperatur auf Silizium (100)
Substraten mittels Pulsed Laser Deposition hergestellt. Als Targets sind
gesinterte HfO2 Tabletten eingesetzt worden.
Oberflächenmorphologie-Untersuchungen zeigen, dass die Struktur der
HfO2-Schichten von der Laserwellenlänge abhängt. Aufgrund der Wechselwirkung
zwischen Laserpuls und Target-Material kommt es neben dem
üblichen Verdampfungsprozess auch zur Ablation geschmolzener Hafniumoxidpartikel
(Splashes). Mit zunehmender Laserwellenlänge erhöht sich
die mittlere Größe der HfO2-Splashes (355 nm: 0.6 µm; 1064 nm: 1.0 µm).
Die maximale Größe der Partikel steigt rapide an (355 nm: 2.6 µm; 1064
nm: 6.5 µm).
Mikro-Raman-Spektroskopie Untersuchungen haben ergeben, dass die
30 nm dünnen HfO2-Schichten eine Verspannung der obersten Lagen des
Si(100) Substrates hervorrufen. Eine negative Verschiebung des stärksten
Si-Peaks bei 520 cm −1 nach dem Schichtwachstum deutet auf eine Dehnung
des Siliziums hin. Ein Vergleich der Gitterkonstanten unterstützt
dieses Ergebnis.
DS 22.10 Di 14:30 Poster B
Phasenbildung in dünnen Ni/C- und Ni/Ti-Doppelschichten
auf Si(001) — •Lutz Budzinski, A. Mogilatenko, O. Filonenko,
G. Beddies und H.-J. Hinneberg — Technische Universität Chemnitz,
Institut für Physik, 09107 Chemnitz
Mit der weiteren Verringerung der Dimensionen mikroelektronischer
Bauelemente ist für die Realisierung extrem flacher Kontakte auch eine
Verringerung des Siliciumverbrauchs bei der Bildung der Siliciumkontaktschichten
erforderlich. Nickelmonosilicid stellt daher zu den bisher eingesetzten
Disiliciden eine echte Alternative da. Limitiert wird der Einsatz
des Nickelmonosilicides noch durch dessen begrenzte thermische Stabilität.
Durch Magnetronsputtern wurden Ni/C- und Ni/Ti-Doppelschichten
auf Si(001)-Substraten abgeschieden und mittels Kurzzeittemperung (N2,
30 s, 450 ◦ C bis 1000 ◦ C) thermisch nachbehandelt. Zur Charakterisierung
der so gebildeten Silicidschicht wurden RBS-, XRD-Messungen, REMund
TEM-Untersuchungen, sowie Messungen des spezifischen elektrischen
Widerstandes durchgeführt. Es wurde der Einfluss von Kohlenstoff
und Titan auf die thermische Stabilität des Nickelmonosilicides auf
Si(001) untersucht.
DS 22.11 Di 14:30 Poster B
Einfluss vo C und Ti auf die Silicidbildung dünner Co-Schichten
auf Si(001) — •P. Simon, F. Allenstein, H. Hortenbach, A. Mogilatenko,
O. Filonenko, G. Beddies und H.-J. Hinneberg —
Technische Universität Chemnitz, Institut für Physik, 09107 Chemnitz
Für die Realisierung des Leitbahn- und Kontaktsystems hochintegrierter
mikroelektronischer Bauelemente werden gegenwärtig polykristalline
Silicidschichten eingesetzt. Mit der weiteren Zunahme der Integrationdichte
und der damit verbundenen Verringerung der Bauelementedimensionen
werden auch extreme Anforderungen an die Grenzflächenrauhigkeit
der Kontakte gestellt. Epitaktisch auf Si(001) gewachsene
CoSi2-Schichten haben den Vorteil der Bildung atomar glatter
Grenzflächen. In [1] wurde gezeigt, dass ein geringer C-Gehalt in Si-
Substraten die Co-Silicidreaktion stark beeinflusst und zu einem teilweise
epitaktischen Wachtum führt.
Es wurde der Einfluss dünner (0 bis 4 nm) C-Barrieren sowie Ti-
Deckschichten (0 bis 20 nm) auf die Co-Si(001)-Reaktion untersucht. Die
erforderlichen Schichtabscheidungen erfolgten durch Elektronenstrahlverdapfung
(Ti, Co, Si) und Sublimation (C) im UHV auf Si(001).
Die thermische Behandlung (450 ◦ C bis 1050 ◦ C, 30 s, N2) der Proben
erfolgte in einer RTA-Anlage. Zur Charakterisierung der so gebildeten
Silicidschichten wurden RBS-, XRD-Messungen, REM- und TEM-
Untersuchungen, sowie Messungen des spezifischen Widerstandes durchgeführt.
[1] S. Teichert et. all, Micro. Eng. 50 2000 193
DS 22.12 Di 14:30 Poster B
Neon ion sputtering of Si(111) — •Stefan Krischok, Vasil
Yanev, Annette Läffert, Henry Romanus, Ronny Wagner,
Rastislav Kosiba, Gernot Ecke, Oliver Ambacher, and Juergen
A. Schaefer — Zentrum für Mikro- und Nanotechnologien, TU
Ilmenau, 98693 Ilmenau
The bombardment of surfaces with ions of high kinetic energy is often
used for surface cleaning under ultra high vacuum (UHV) conditions.
However, many effects like changes in the chemical surface composition,
amorphization or the incorporation of incoming ions may occur. We have
studied the incorporation of neon into Si(111) using neon ions with a kinetic
energy of 500 and 5000eV and an incident angle of 45 ◦ with respect
to the surface normal. The ion bombarded surfaces were investigated
by X-ray photoelectron spectroscopy (XPS, Mg Kα), thermal desorption
spectroscopy (TDS) and transmission electron microscopy (TEM).
In both cases Ne is incorporated into the silicon as shown by XPS. The
observed Ne(1s) line is splitted into two peaks. They show a strong dependence
on the kinetic energy of the Ne ions. The two observed Ne
states are discussed on the basis of our XPS, TDS and TEM data.
DS 22.13 Di 14:30 Poster B
Hochdosis-Magnesium-Implantation in Silizium — •M.
Häberlen 1 , W. Y. Cheung 2 , J. K. N. Lindner 1 , S.P. Wong 2
und B. Stritzker 1 — 1 Institut für Physik, Universität Augsburg,
Universitätsstrasse 1, D-86135 Augsburg — 2 Department for Electronic
Engineering and Materials Science and Technology Research Center,
The Chinese University of Hong Kong, Hong Kong, China
Die Bildung binärer Siliziumverbindungen durch Hochdosis-
Implantation wurde in den vergangenen Jahren intensiv untersucht.
Insbesondere die Bildung von Ausscheidungen mit kubischer Kristallstruktur,
die entweder sehr gut (z.B. NiSi2 und CoSi2), oder nur
bei großem negativem Misfit (3C-SiC) in das Wirtsgitter passen,
wurde dabei intensiv studiert. Wenig bekannt ist über die Bildung
und Eigenschaften von Alkali-Metallsiliziden. Magnesium bildet als
einzige stabile Phase das kubische Mg2Si, mit einem Misfit von +17 %
gegenüber c-Si.
Die Bildung Magnesium-reicher Phasen noch Hochdosis-Mg-MEVVA-
Implantation bei Temperaturen zwischen 200 ◦ C und 350 ◦ C wurde systematisch
mittels RBS, XRD, XTEM und EDX untersucht.
DS 22.14 Di 14:30 Poster B
Einfluss von Ionenbestrahlung auf innere und äußere Grenzflächen
von nicht mischbaren, metallischen Systemen — •Jan
Petersen und Stefan Mayr — I. Physikalisches Institut, Universität
Göttingen, Tammannstr. 1, D-37077 Göttingen
Ionenbestrahlung bietet die Möglichkeit, innere und äußere Grenzflächen
zu modifizieren und optimieren. Die wesentlichen morphologischen
Änderungen in metallischen Systemen umfassen Glättung bzw.
Aufrauung von Grenzflächen, sowie strahlungsinduziertes Kornwachstum.
Wir untersuchen mittels Rastersondenmikroskopie und Weitwinkelröntgenbeugung
die Kinetik derartiger Prozesse mit dem Ziel, die zugrundeliegenden
atomaren Mechanismen zu identifizieren. Eine wesentliche
Rolle kommt hierbei dem thermal Spike zu, der einerseits eine Strukturglättung
durch viskoses Fließen hervorrufen kann, andererseits auch
Rauigkeit und Ionenmischen induziert.
Dieses Projekt wird im Rahmen des SFB 602, Teilprojekt B3, von der
DFG gefördert.
DS 22.15 Di 14:30 Poster B
Smoothing of Si surface by low-energy ion beam erosion —
•Frank Frost, Bashkim Ziberi, and Bernd Rauschenbach —
Leibniz-Institut für Oberflächenmodifizierung e. V., Permoserstraße 15,
D-04318 Leipzig, Germany
Low-energy ion beam erosion is a versatile tool for surface polishing
down to 0.1 nm root mean square (rms) roughness level showing a great
promise for large-area surface processing, which is essential for many advanced
optical applications.
Exemplarily, the surface smoothing of Si surfaces by Ar + ion beams
(ion energy ≤ 2000 eV) was analyzed. Atomic force microscopy has been
used to systematically investigate the topography evolution of the surfaces
with respect to different process parameters (ion energy, ion incidence
angle, erosion time, sample rotation). From the AFM measurements
the surface roughness was quantitatively characterized by the first
order (rms roughness) and second order (power spectral density - PSD)
statistical quantities. Based on the time evolution of these roughness

Dünne Schichten Dienstag
parameters the relevant surface relaxation mechanisms (ion-induced viscous
flow, surface erosion smoothing) responsible for surface smoothing
have been discussed. Additionally, it is shown that surface smoothing by
ion-induced viscous flow can operate on different length scales.
DS 22.16 Di 14:30 Poster B
Non-conventional plasma sheath diagnostics for thin film
deposition — •Holger Kersten 1 , Ruben Wiese 2 , and Marcel
Haehnel 2 — 1 INP Greifswald, F.-L.-Jahn-Str.19, D-17489 Greifswald
— 2 University of Greifswald, Department of Physics, Domstr.10a,
D-17487 Greifswald
Plasma and sheath diagnostics of sources used in thin film deposition
is an essential issue for optimization and improvement of the related processes
(sputtering, PECVD etc.). Often, complicated and expensive diagnostic
methods (as mass spectrometry, spectroscopy, Langmuir probes
etc.) have to be employed.
However, in certain cases these methods may be completed by relatively
simple methods which can reveal information on the densities,
energies and fluxes of the involved species, too. Such non-conventional
methods are : energy flux measurements by thermal probes, analytical
sheath photometry, and sheath diagnostics by charged micro-particles.
These procedures will be reviewed and their advantages, but also their
disadvantages and limits will be summarized.
DS 22.17 Di 14:30 Poster B
Reactive plasma jet etching of Si - Gas flow models and
mass spectrometry — •Thomas Arnold 1 , Sergey Grabovski 2 ,
Axel Schindler 1 , and Hans-Erich Wagner 2 — 1 Leibniz-Institut
für Oberflächenmodifizierung e.V. Leipzig — 2 Ernst-Moritz-Arndt-
Universität Greifswald
A low pressure microwave driven reactive Ar/SF6 plasma jet used for
high rate etching of Si and SiO2 is investigated by appearance potential
mass spectrometry (APMS) and electron attachment mass spectrometry
(EAMS). Spatially resolved measurements of neutral radicals and stable
products in the active and passive plasma region have been accomplished.
The concentration of atomic fluorine was determined for different process
parameters such as gas mixture and microwave power. The experimental
results are compared to a previously built gas phase reaction kinetics
model, which considers the formation of reactive F and F− radicals and
the production of SFx and SF− x by electron impact, electron attachment
and significant reverse processes. Two-dimensional computational fluid
dynamics simulations of a simplified plasma jet model are compared to
the experimentally obtained species concentrations on a substrate surface.
Additionally, results of surface analysis of etched Si substrates by
means of XPS and optical profilers are presented.
DS 22.18 Di 14:30 Poster B
Single domain growth of C60 on modified InP(001) and chemical
passivation of the molecular structure — •Maxim Eremtchenko,
Stefan Döring, Ruslan Temirov, and Juergen A. Schaefer —
Institut für Physik und Zentrum für Mikro- und Nanotechnologien, Technische
Universität Ilmenau, P.O. Box 100565, 98684 Ilmenau, Germany
Fullerenes and its functionalisation are very promising in nanoscale
fabrication. Its performance is often limited by structural inhomogenities
and chemical instability. Recently, we reported upon single domain
growth of C60 on InP(001), which is technologically very promising. In
this contribution growth of C60 on InP(001) covered with indium clusters,
the most prominent defect on InP was investigated. Single domain
growth is still registered by LEED and STM. The reaction of atomic hydrogen
with the single domain of C60 was studied using HREELS. The
cages are easily cracked by hydrogen and hydrocarbons are formed. This
layer is stable against further reaction with atomic hydrogen, oxygen or
air. It seems that this technique of passivation can be applied for the
protection of various molecular structures in technological processes.
DS 22.19 Di 14:30 Poster B
Growth of ITO thin films by ion beam assisted deposition —
•Karola Thiele 1 , Jörg Hoffmann 2 , Sibylle Sievers 1 , and Herbert
C. Freyhardt 1,2 — 1 Institut für Materialphysik, Tammannstr.1,
37077 Göttingen — 2 Zentrum für Funktionswerkstoffe, Windausweg 2,
37073 Göttingen
Indium Tin Oxide (ITO), a doped, wide-band-gap highly degenerated
oxide semiconductor exhibits high transmittance in the visible region
and high electrical conductivity. Therefore, ITO thin films are widely
used as transparent conducting electrodes for a variety of electro/optical
devices. For many applications on temperature sensitive substrates, deposition
at room temperature is desired. Furthermore, highly textured
ITO films might be useful as an electrically conductive buffer layer for
HTS applications.
Biaxially aligned ITO thin films were prepared by an Ion-Beam Assisted
Deposition (IBAD) process at low temperatures. The influence of
various deposition parameters on the growth is discussed as well as the
microstructure evolution, mechanisms of texture development and electrical
properties.
The quality of IBAD-ITO as a highly transparent and highly conductive
material has been demonstrated and the suitability as a buffer layer
for high-current carrying YBCO thin films has been proved.
DS 22.20 Di 14:30 Poster B
Interface roughness of laser deposited Fe/MgO multilayers
— •Andreas Meschede 1 , Christian Fuhse 2 , and Hans-Ulrich
Krebs 1 — 1 Institut für Materialphysik, Universität Göttingen,
Tammanstrasse 1, 37077 Göttingen — 2 Institut für Röntgenphysik,
Universität Göttingen, Geiststrasse 11, 37073 Göttingen
Metal/MgO multilayers with double layer periods in the nanometer
range were deposited by pulsed laser deposition (PLD) in ultra high vacuum
and in an inert gas atmosphere (Ar). The interface roughness of
less than 0.5 nm mainly depends on the bilayer thickness and increases
for ultrathin films, but only slightly depends on the number of bilayers.
To understand the important mechanisms of roughening und smoothing
during the deposition of multilayers, Fe-MgO bilayers were produced
and characterized by x-ray reflectivity. That shows that the MgO-Layer
smooths the rough Fe-surface and so avoids a cumulative accreation of
the interface roughness with increasing number of bilayers. The obtained
interface roughness also strongly depends on the gas pressure and thus
on the kinetic energies of the deposited particles, which will be discussed.
DS 22.21 Di 14:30 Poster B
Gasdruckabhängige Phasenbildung beim Laser-Carburisieren
von Eisen — M. Kahle, E. Carpene und •P. Schaaf — Universität
Göttingen, Zweites Physikalisches Institut, Tammannstrasse 1, D-37077
Göttingen.
Das Laser-Carburisieren - hier die gepulste Laserbestrahlung in
Methan-Atmosphäre - ist ein effizientes Verfahren zum Kohlenstoffeintrag
in die Oberfläche von verschiedenen Werkstoffen [1,2]. Für
reines Eisen hängt die Phasenbildung beim Laser-Carbusieren sehr vom
Methan-Gasdruck ab. Von amorphen Kohlenstoffschichten über die
hexagonale ε-Phase zur θ-Phase (Zementit) können mit ansteigendem
Druck fast alle Phasen gebildet werden. Obwohl das Eisen-Kohlenstoff-
System eine sehr wichtige Rolle für die Anwendung moderner Werkstoffe
spielt, ist die hexagonale ε-Phase noch relativ unbekannt, da sie bisher
nicht als reine oder massive Phase hergestellt werden konnte. Die
Phasen- und Strukturbildung, sowie die resultierenden Eigenschaften
der Schichten werden in Abhängigkeit von der Laserbehandlung bei
verschiedenen Gasdrücken von 0.1 bis 10 bar diskutiert [2].
[1] E. Carpene and P. Schaaf. Appl. Phys. Lett. 80 (2002) 891.
[2] M. Kahle, E. Carpene, and P. Schaaf. Phys. Rev. B in preparation.
DS 22.22 Di 14:30 Poster B
Magnetic properties and crystallinity of NiMn / FeNi(CoFe)
bi-layer systems with different seed layers — •Stefka
Groudeva-Zotova 1 , Reiner Kaltofen 1 , Dieter Elefant 1 ,
Volker Hoffmann 1 , Juergen Thomas 1 , Claus Schneider 2 ,
Wolfgang Michalke 3 , and Roland Mattheis 3 — 1 Leibniz
Institut IFW-Dresden, Helmholtzstrasse 20, D-01069 Dresden —
2 IFF-Forschungszentrum Juelich — 3 IPHT Jena, Winzerlaerstr. 10,
D-07745 Jena
This work presents an investigation of the influence of the seed layer on
the structural and magnetic characteristics of AFM/FM systems 30nm
NiMn / 4nm FeNi(CoFe) deposited by dc and rf magnetron sputtering of
alloy targets. We compare bi-layers deposited on Ta, Cr and permalloy
seed layers in different combinations and with variable thickness. The asgrown
and the field-annealed and -cooled samples are characterised by
GDOS depth-profile analysis for the film composition, by XRD and TEM
for the crystalline structure and by MOKE and AGM measurements for
the magnetic characteristics. A special accelerated post-deposition annealing
and field-cooling procedure is used for the achieving a stable AFM
state in the NiMn film and for generating an uni-directional anysotropy in
the bi-layer AFM/FM system. It was found that the use of different seed

Dünne Schichten Dienstag
layers results in the formation of NiMn films with different structural and
morphological characteristics (phase composition, texture and crystallite
grain size)which signicantly influence the magnetic characteristics of the
respective annealed and field-cooled AFM/FM bi-layers.
DS 22.23 Di 14:30 Poster B
Mikrostruktur orientierter magnetischer NiMnAl-Formgedächtnisschichten
und ab-initio-Simulationsrechnungen —
•Sigurd Thienhaus 1 , Ralf Hassdorf 1 , Thomas Büsgen 1 ,
Jürgen Feydt 1 , Rene Borowski 1 , Markus Boese 2 und Michael
Moske 1 — 1 Forschungszentrum caesar, 53175 Bonn — 2 Universität
Bonn, Institut für Anorganische Chemie, 53117 Bonn
Magnetische NiMnAl-Formgedächtnisschichten wurden unter Verwendung
der Gradiententechnik mittels Molekularstrahlepitaxie hergestellt.
Die Variation der Zusammensetzung liegt für jede Komponente bei ca.
10 at.% und erlaubt den direkten Vergleich des chemisch/strukturellen
Zusammenhangs mit der martensitischen Umwandlung und der magnetischen
Ordnung in einem großen Konzentrationsbereich sowie eine effiziente
Identifizierung der relevanten Bereiche für die Phasenstabilität.
Besonderer Wert wurde auf die strukturellen Aspekte der Phasentransformation
gelegt, welche unter Verwendung von Röntgen-Mikrodiffraktion
innerhalb einer speziell konstruierten Heizkammer untersucht wurden.
Querschliff-TEM-Untersuchungen bei Raumtemperatur zeigen die Koexistenz
zweier Martensitphasen (2M, 14M) in mesoskopisch-periodischer
Anordnung, von denen die eine (14M) eine langperiodische Shuffling-
Struktur aufweist. Solche Strukturen wurden mit ab-initio-Rechnungen
verglichen. Hierbei konnte die Metastabilität und die Bevorzugung der
magnetischen Phase in einem definierten Konzentrationsbereich nachgewiesen
werden.
DS 22.24 Di 14:30 Poster B
Optical and electrical properties of Teflon AF/Au nanocomposite
prepared by vapor phase co - deposition — •Haile Takele,
Cenk Aktas, Christian Pochstein, Ulrich Schürmann, Abhijit
Biswas, Vladimir Zaporotchenko, and Franz Faupel —
Lehrstuhl für Materialverbunde, Technische Fakultät der CAU Kiel,
Kaiserstr. 2, 24143 Kiel, Germany
We have prepared nanocomposite films (100-200 nm) of Teflon AF containing
Au nanoparticles by using vapor phase co - deposition technique
in high vacuum deposition system. Au cluster size, shape and distribution
in Teflon AF matrix have been investigated using TEM analysis.
XPS and FTIR are also applied to study the chemical composition and
structure of the composite. The metal filling factor in the polymer matrix
has been estimated by SEM/EDX measurement. The optical properties
of Teflon AF/Au prepared at different substrate temperatures of 80 o C
to 250 o C and various metal filling factors have been studied by UV-
Visible spectroscopy. Similarly, the variation of electrical properties of
Teflon AF/Au nanocomposite at various metal filling factors near the
percolation threshold are reported.
DS 22.25 Di 14:30 Poster B
Excess noise in current-biased ultra-thin superconducting nanostructures
— •Alexei Semenov, Heiko Richter, Andreas Engel,
and Heinz-Wilhelm Hübers — DLR Institute of Planetary Research
Noise properties of ultra-thin films deserve particular interest because
they shine light on the dynamics of the superconducting phase transition
and are of importance in metrology and detector technology. We
have studied electrical noise appearing in nano-structured current-biased
superconducting rectangular (length - l, width - w) bridges made from
ultra-thin NbN films. For both wide (w > l) and narrow (w < l) bridges
we have observed similar behaviour: at currents close to the critical current,
the noise increased rapidly in excess to generation-recombination,
shot or thermal fluctuation noise. The magnitude and temperature dependence
of the excess noise evidences that this noise most likely originates
from random formation of the phase-slip centres (PSC). The spectrum
of the excess noise suggests the intrinsic lifetime of a PSC is of the
order of the electron-phonon interaction time.
DS 22.26 Di 14:30 Poster B
Optische in-situ Untersuchungen des gaschromen Schaltens von
Wolframoxid — •François Vertommen, Christian Salinga und
Matthias Wuttig — I. Physikalisches Institut (IA), Lehrstuhl für
Physik neuer Materialien, RWTH Aachen
Wolframoxid (WOx) ist unter Luft bzw. sauerstoffhaltiger Atmosphäre
transparent. Unter wasserstoffhaltiger Atmosphäre färbt sich die Schicht
im sichtbaren Bereich blau, da eine Absorption im Infraroten generiert
wird. Ein atomistisches Modell für die Generierung der Absorption sagt
voraus, dass beim Färbeprozess aus den an der Platin-Katalysatorschicht
dissoziierten Wasserstoffatomen und dem Sauerstoff aus der WOx-Schicht
in deren porösen Schichtstruktur Wasser geformt wird.
Ein FTIR-Spektrometer wurde um einen Gasmischstand erweitert
um in-situ FTIR-Messung an gaschrom schaltbaren Schichtsystemen zu
ermöglichen. Die Probenkammer des Spektrometers kann mit diversen
Gasgemischen bis zu einem Gesamtdruck von 0,8 bar gefüllt werden. Abpumpen
bis auf einen Restdruck von 2 mbar ist möglich.
Die Messergebnisse des gaschromen Ein- und Entfärbens unter H2bzw.
O2-haltiger Atmosphäre von WOx-Schichten zeigen mit zunehmender
Zeit unter der jeweiligen Gasatmosphäre eine klare Entwicklung
der Absortion im Infraroten Spektralbereich und der unterschiedlichen
Vibrationsbanden. Die relative Stärke der entstehenden Wasserbanden
wurde ermittelt, um Annahmen für das atomare Färbemodell
zu überprüfen. In-situ Messungen mittels Ellipsometrie, Transmission im
UV/VIS, Röntgenbeugung und Wafer-Curvature unterstützen die Ergebnisse
der FTIR-Analysen.
DS 22.27 Di 14:30 Poster B
TOF-PEEM investigation of photoelectron emission from cesium
covered silver nanoparticle films — •D.A. Valdaitsev, M.
Cinchetti, A. Gloskovskii, S.A. Nepijko, and G. Schönhense —
Johannes Gutenberg-Universität Mainz, Institut für Physik, Staudingerweg
7, D-55099 Mainz
The present study continues the time-of-flight photoemission electron
microscopy investigation of emission properties of Ag nanoparticles under
fs-laser excitation (hν = 3.1 eV, ∆ = 80 fs, fluence 6.4 µJcm −2 ). Earlier
it was demonstrated that the energy distribution of electrons emitted
from the particles considerably differs from the well-known 2PPE spectrum
typical for bulk silver [1]. To understand the emission mechanisms
in more detail we studied the change of energy spectra of electrons emitted
from the nanoparticle films (particle size from 1 to 50 nm) caused
by deposition of Cs. This allows to observe switching between different
electron emission mechanisms in the same system. Lowering of the work
function led to the shift of the low-energy edge and allowed to consider
the electron energy distribution in a wider range. Exponential behavior
of the spectrum in the low-energy region points to a significant contribution
of electron gas heating processes to the total emission yield from
sufficiently small particles.
[1] M. Cinchetti, D.A. Valdaitsev, A. Gloskovskii, A. Oelsner, S.A.
Nepijko, G. Schönhense, J. Elec. Spec. Relat. Phenom., in print
DS 22.28 Di 14:30 Poster B
Investigation of the local electron emission from currentcarrying
silver nanoparticle films by means of emission electron
microscopy — •A. Gloskovskii, D.A. Valdaitsev, S.A. Nepijko,
and G. Schönhense — Johannes Gutenberg-Universität Mainz,
Institut für Physik, Staudingerweg 7, D-55099 Mainz
Emission electron microscopy is a very convenient tool for the investigation
of emission properties of metal nanoparticle films during passage
of tunnel current [1]. In these systems the electron emission arises in the
non-linear region of the current-voltage characteristic of the conduction
current and has a local character (stems from separate emission centers).
Owing to the energy and angle distributions of emitted electrons,
the emission center is visualised in an emission electron microscope in the
form of an elongated spot. Its size and shape enable to make quantitative
estimations of the value of the electric field strength in the vicinity of the
emission center and the energy spread of emitted electrons. The upper
limit of the electric field strength near the emission center is 1.5·10 6 V/cm
that is not enough to initiate field emission. An energy distribution with
a width of 0.3 eV confirms our assumption about a thermal mechanism
of the electron emission.
[1] A. Gloskovskii, D.A. Valdaitsev, S.A. Nepijko, N.N. Sedov and G.
Schönhense Appl. Phys. A (published online 23 September 2003)
DS 22.29 Di 14:30 Poster B
Preparation and characterization of a Teflon AF/Fe-Ni-Co
nanocomposite for magnetic UHF applications — •H. Greve 1 ,
U. Saeed 1 , A. Biswas 1 , J. Kanzow 1 , V. Zaporojtchenko 1 , F.
Faupel 1 , M. Frommberger 2 , and E. Quandt 2 — 1 Lehrstuhl für
Materialverbunde, Technische Fakultät der CAU, Kaiserstr. 2, 24143
Kiel — 2 CAESAR, Ludwig-Erhard-Allee 2, 53175 Bonn

Dünne Schichten Dienstag
Nanocomposites of finely dispersed magnetic nanoparticles in a polymer
matrix can be tailored to achieve the requirements for future GHz
frequency inductive component applications. Principle requirements for
such soft magnetic films are a high saturation magnetization Ms, a low
but finite anisotropic field and minimized eddy-current losses. We describe
solvent-free preparation of Teflon AF/Fe-Ni-Co nanocomposite by
coevaporation. Analysis of the magnetic properties and morphology as
function of the filling factor was done by TEM, EDX, VSM and complex
AC permeability measurements. Films with filling factors of ∼ 20 % show
a narrow particle size distribution of 6-8 nm, a high Ms ∼ 2 Tesla and
a cut-off frequency > 1 GHz. It is shown that the atomic composition of
the alloy remains constant after evaporation.
DS 22.30 Di 14:30 Poster B
Viskositätsmessung an dünnen Schichten des Phasenwechselmediums
AgIn-Sb2Te mit einem bulge-tester — •Martin Salinga,
Stefan Ziegler, Andreas Schropp, Johannes Kalb und Matthias
Wuttig — I.Physikalisches Institut A, RWTH-Aachen, Postfach,
52065 Aachen
Auf der Suche nach neuen Materialien für die optische Datenspeicherung
auf Basis von Phasenwechselmedien ist das Verständnis der Kristallisationskinetik
essentiell. Einer der zentralen zu optimierenden Aspekte
ist die Geschwindigkeit des Kristallwachstums, welche einer der Schlüsselparameter
für die Datenübertragungsrate ist.
Das Wachstum lässt sich durch Grenzflächen-nahe Diffusion beschreiben.
Da die Stokes-Einstein-Gleichung einen direkten Zusammenhang
zwischen Diffusion und Viskosität herstellt, besteht die Möglichkeit,
durch Messung der Viskosität auf Diffusionseigenschaften und damit auf
die Wachstumsgeschwindigkeit zu schließen.
Die hier vorgestellten Ergebnisse beruhen auf Experimenten mit AgIn-
Sb2Te an einem bulge-tester, bei denen die Temperaturabhängigkeit der
Viskosität unterhalb der Glasübergangstemperatur Tg gemessen wird.
Die auf diese Art ermittelten Daten werden mit Messungen oberhalb
Tg verglichen.
DS 22.31 Di 14:30 Poster B
Evolution of stress in sputtered-deposited cobalt and copper
thin films — •Mirela Pletea 1 , Winfried Brückner 1 , Horst
Wendrock 1 , Rainer Kaltofen 1 , and Claus M. Schneider 2 —
1 Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, PF
270116, D-01171 Dresden — 2 Institute of Electronic Properties, Department
of Solid State Research, Research Center Jülich, D-52425 Jülich
In order to study the stress development during sputter deposition of
the magnetic multilayers we redesigned and reconstructed the dedicated
set-up for in-situ stress measurements of single thin films. This novel setup
is able to monitor the stress development during sequential sputter
deposition of two materials and to simultaneously control the substrate
temperature. In this paper we present the first results from in-situ stress
measurements using this new set-up during and after growth of Co and
Cu single thin films with different thickness and sputtered under various
sputtering conditions. The first results reveal: (i) an increasing of
tensile stress and (ii) a tensile-compressive-tensile stress evolution during
deposition under the same sputtering conditions of Co and Cu thin
films, respectively. A special attention is paid on the stress evolution and
growth processes of Cu and Co single thin films during the early stage of
deposition. In order to find the mechanisms responsible for stress generation
and relaxation in Co and Cu thin films, microstructure investigations
performed by SEM, EBSD and AFM in combination with plasma diagnostics
are carried out.
DS 22.32 Di 14:30 Poster B
New possibilities in nanoindentation — •Maksim Karniychuk 1 ,
Thomas Chudoba 2 , Norbert Schwarzer 1 , and Frank Richter 1
— 1 Chemnitz University of Technology, Institute of Physics, 09107
Chemnitz — 2 ASMEC Advanced Surface Mechanics, Dresden
Nanoindentation with normal force is widely used for the investigation
of mechanical properties of thin films. Using a lateral force in addition
would allow investigating new properties.
We have developed a theoretical model of the mechanical contact of a
spherical indenter and a coated substrate under both normal and lateral
load. Together with a novel Lateral Force Unit (LFU) this will enable us
to determine mechanical properties of thin films which were not accessible
so far. The aim of the poster is to present these new possibilities:
1) Poisson’s ratio can be determined from the lateral displacement of
the maximum deformation under normal and lateral load.
2) During loading with a lateral force, tensile stress is formed near the
film surface which cause cracks. The relevant stress components can be
determined.
3) Determination of yield stress of very thin films: Measuring the yield
stress of very thin and hard films on less hard substrates is difficult since
the substrate can be plastically deformed first. The lateral force provides
possibilities to increase the stress in the film but to save the substrate.
DS 22.33 Di 14:30 Poster B
Charakterisierung von dünnen Fe100−xZrx-Schichten mittels Laserakustik
— •Andreas Grob und Ulrich Herr — Abteilung
Werkstoffe der Elektrotechnik, Universität Ulm, 89081 Ulm
Seltene Erd-Übergangsmetalllegierungen lassen sich über einen weiten
Konzentrationsbereich amorph herstellen. An den Randbereichen des
Phasendiagramms erhält man die kristallinen Gleichgewichtsphasen. Dieses
Verhalten wurde bereits ausgiebig mit strukturellen und magnetischen
Analysemethoden untersucht.
Wir berichten von laserakustischen Messungen an gesputterten
Fe100−xZrx-Schichten. Dabei werden mittels eines gepulsten Lasers Oberflächenwellen
generiert. Aus den Ausbreitungseigenschaften der Rayleigh-
Welle gewinnt man Informationen über die mechanischen Eigenschaften
der Schichten. Es wurde ein Konzentrationsbereich untersucht, der
sowohl eisenreiche kristalline Schichten, als auch amorphe Schichten
umfasst. Die Ergebnisse zeigen eine deutliche Abhängigkeit des Elastizitätsmoduls
von der Schichtzusammensetzung und der Struktur. Die
Werte werden mit Ergebnissen aus Nanoindentationstests (Hysitron) verglichen.
DS 22.34 Di 14:30 Poster B
In-situ Charakterisierung der Phasenbildung während
der Hochenergie-Sauerstoffionen-Implantation in
Übergangsmetalle — •Y. Bohne 1 , N. Shevchenko 2 , F.
Prokert 2 , J. von Borany 2 , B. Rauschenbach 1 und W.
Möller 2 — 1 Leibniz-Institut für Oberflächenmodifizierung e.V.,
Leipzig — 2 Forschungszentrum Rossendorf e.V., Dresden
Die Ionenimplantation ist ein Verfahren zur gezielten Modifizierung
dünner Schichten und oberflächennaher Bereiche. Voraussetzung für
die Aufklärung der physikalischen Prozesse der implantationsinduzierten
Phasen- und Defektbildung als auch thermisch stimulierter Prozesse
in implantierten Materialien sind Untersuchungen zur Struktur und
Zusammensetzung während der Implantation in einem weiten Temperaturbereich.
Anhand der Synthese von Oxiden der Übergangsmetalle
Titan und Molybdän wurden während der Hochenergie-Sauerstoffionen-
Implantation in-situ Untersuchungen mittels Röntgenbeugungstechnik
durchgeführt, um die Phasenbildung dosis- bzw. zeitabhängig zu charakterisieren.
Dazu wurden, in einer Hochtemperatur-Vakuumkammer
Sauerstoffionen (1,5 MeV, Fluenzen bis 3×10 18 O + /cm 2 ) in polykristallines
Molybdän bzw. Titan implantiert. Die chemische Zusammensetzung
der implantierten Proben wurde mittels Auger Elektronen Spektroskopie
(AES) untersucht. Die Bildung von Molybdänoxid (MoO2) konnte beobachtet
werden. Der Beginn der Phasenbildung wird durch die Targettemperatur
beeinflußt. In-situ Temperversuche (bis 600 ◦ C) mit implantierten
Proben zeigten ein zusätzliches Wachstum von MoO2 Präzipitaten.
DS 22.35 Di 14:30 Poster B
Structure and interface characterisation of Exchange Bias
FeMn-FeNi films — •Danica Solina 1 , Maciej-Oskar Liedke 2 ,
Ursula Tietze 1 , Jürgen Fassbender 2 , and Andreas Schreyer 1
— 1 Institute for Materials Research, Dept. WFN (Neutron-/Synchrotron
Scattering), GKSS-Research Center, PO Box 1160, D-21494 Geesthacht,
Germany — 2 Fachbereich Physik, Universität Kaiserslautern,
Erwin-Schrödinger-Straße 56, 67663 Kaiserslautern, Germany
X-ray and neutron scattering studies have been carried out on thermally
evaporated FeMn-FeNi exchange bias systems before and after ion
irradiation by helium ions. Helium ion dosages of 10 14 - 10 17 ions cm −2
have been used. The ion irradiation has shown to alter the exchange bias
characteristics of the samples with dose and rate. X-ray diffraction measurements
on the samples were made to assess the epitaxy of the layers
to the substrate. In order to assess the effect of ion irradiation on these
films, both neutron and x-ray reflectivity measurements were performed
and the data modelled simultaneously. A final model was chosen that
approximated both sets of data well. The reflectivity data suggest that
the samples are prone to etching of the surface layer by the ions and that
ion irradiation encourages interlayer mixing resulting in a smearing of the

Dünne Schichten Dienstag
oscillations. Increased ion dosages result in a complete loss of exchange
bias properties which is supported with loss in inter-layer definition by
ion irradiation.
DS 22.36 Di 14:30 Poster B
TEM Investigation of the Structure and Geometry of Nanotunnels
formed upon Cu Deposition on VSe2 Surfaces — •E.
Spiecker, S. Hollensteiner, and W. Jäger — Technische Fakultät
der Christian-Albrechts-Universität zu Kiel
Linear nanostructures formed in the early stages of Cu deposition onto
VSe2 crystal surfaces have been studied in detail by TEM in plan-view
geometry. The nanostructures are found to be made up of two parallel
strands each of them consisting of a linear array of VSe2 platelets. Combining
diffraction analyses with tilt experiments the platelets of the two
strands are shown to be symmetrically inclined by ∼ 30 o with respect
to the surface, thus forming a roof-like nanotunnel with triangular crosssection.
Along the strands the platelets show only minor misorientations
with respect to each other. No gaps are observed at the substrate-platelet
interfaces and at the interfaces along the ridges. The symmetry of the
configuration and the sharpness of these interfaces indicate the presence
of linear structure modifications with lateral dimensions of only few
nanometers. These structures might be composed of special structural
units, such as the topological defects discussed for caps of MoS2 nanotubes.
Our observations of the presence of substrate dislocations which
are spatially correlated with the nanoroofs indicate that the nanoroof formation
is connected with dislocation injection, thus providing a mechanism
for strain relaxation during the early deposition stages. A formation
model will be presented which extends earlier suggestions attributing the
formation of nanotunnels to the relaxation of compressive surface strain.
DS 22.37 Di 14:30 Poster B
Heteroepitaxial growth of cubic boron nitride films on Single
Crystalline (001) Diamond Substrates — •H. Yin, X.W. Zhang,
H.-G. Boyen, and P. Ziemann — Abteilung Festkörperphysik, Universität
Ulm, D-89069 Ulm
In addition to hard coating applications, cubic boron nitride (c-BN)
is also considered as a starting material for high-temperature electronic
devices. In order to use c-BN for such a purpose, a high structural quality
of the corresponding samples appears necessary. To approach this goal,
heteroepitaxial c-BN films were grown by ion beam assisted deposition
(IBAD) on highly oriented (100) diamond substrates at high temperatures
(∼1000 ◦ C). Combination of several characterization techniques
showed that 100% pure c-BN films prepared at elevated temperatures
on top of (100) diamond nucleate and grow directly on this substrate
without an interfering hexagonal BN layer. Atomic force microscopy of
such high quality c-BN films shows a well-defined square pattern with
an average lateral grain size of 3 µm reflecting the grain boundaries of
the underlying diamond substrate. As opposed to c-BN growth on top of
heteroepitaxially prepared CVD diamond films delivering typical rocking
widths of ∆Ω = 4.6 ◦ , c-BN films deposited on single crystalline (001)
diamond substrates exhibit significantly improved values of 0.2 ◦ . The
smooth surface and extremely high hardness and Young’s modulus are
further indications of the high quality epitaxial growth of c-BN films on
single crystalline diamond substrates.
DS 22.38 Di 14:30 Poster B
Adjusting Wettability, Adhesion, and Residual Stress of Hard
Carbon Coatings — •Nicolas Wöhrl, Stephan Reuter, Oleksiy
Filipov, and Volker Buck — Thin Film Technology Group, Dept.
of Physics, University of Duisburg-Essen, Universitätsstr. 3-5, 45141 Essen,
Germany
In this work hard carbon coatings are grown with a dc-arc. As a carbon
source, graphite electrodes are used and the films are deposited on
double-side polished (100) Si-Substrate in a hydrogen atmosphere. The
variation of process-parameters like gas flow, pressure, or gas-mixture
is used to influence the properties of the films. Nitrogen, Argon and
Tetramethyl-Silane is used as gas admixture. Properties like mechanical
stress in the film, adhesion of the film on the substrate and wettability
can be adjusted in a wide range. The adhesion of the films to the substrate
is tested by cavitation erosion tests. The cavitation erosion test is
a quantitative measurement system for adhesion, in which the ablation
of the film as a function of measuring time is used to characterize the
adhesion of the film. The advantage of this method compared to conventional
adhesion tests (such as nanoindenter scratch tests) is the lack
of wear of the test-equipment. The mechanical stress is analysed by an
optical setup, measuring the substrate curvature. The films are also analysed
by Fourier-transformed infrared spectroscopy (FTIR), micro-Raman
measurements, and scanning electron microscopy (SEM).
DS 22.39 Di 14:30 Poster B
Growth and Thermal (In-)Stability of Mulitlayers and
Nanowires on Facetted Alumina Templates — •Carsten
Herweg 1 , Jörg Hoffmann 2 , and Herbert C. Freyhardt 1,2 —
1 Institut für Materialphysik, Universität Göttingen, Tammannstr. 1,
D-37077 Göttingen — 2 Zentrum für Funktionswerkstoffe ZFW gGmbH,
Windausweg 2, D-37073 Göttingen
Annealing of α-Al2O3 (10¯10), (m-plane) at ∼ 2
3 · Tm (Tm: melting temperature)
in air results in the formation of a highly ordered facetted
alumina surface. Investigation by Atomic Force Microscopy (AFM) and
cross-section ransmissionelectronmicroscopy (TEM) reveal a periodicity
of ∼300 nm at a hill-to-valley hight of ∼50 nm. In such a way prepared
alumina surfaces were utilised as substrate for the deposition of multilayers
and nanowires. Metallic multilayers consisting of two immiscible
components are known to be transformable into a nanostructered system
of non-statistically distributed nearly spherical particles in a surrounding
matrix of the complementary component by an annealing process. The
influence of the underlying substrate structure, i.e. local curvature, on the
film growth and on the microstructural transformation during the heat
treatment is analysed by means of XRD, AFM, TEM and electrical transport
measurement. AFM analysis and MOKE of nanowires prepared by
grazing incident sputter deposition show, dependent on deposited material
either overgrowing of the facets or well-defined, separated wires
with a width of ∼100–150 nm, whereas the length is limited only by the
macroscopic substrate dimensions.
DS 22.40 Di 14:30 Poster B
Eigenschaften magnetischer Tunnelelemente mit ECWR-
Plasma oxidierten Barrieren — •Rainer Kaltofen, Ingolf
Mönch, Joachim Schumann, Dieter Elefant und Hartmut
Vinzelberg — IFW Dresden, Postfach 270116, 01171 Dresden
Für die Verwendung von magnetischen Tunnelelementen als Sensoren
oder Speicher sind Tunnelbarrieren mit unterschiedlichen Widerständen
erforderlich. Die chemisch-strukturelle und morphologische Perfektion
der eingesetzten Tunnelbarrieren bestimmt den Tunnelwiderstand, das
magnetische Schaltverhalten und die Stabilität der Elemente. In dieser
Arbeit wird die Herstellung von AlOx-Barrieren durch Oxidation von Al-
Schichten unterschiedlicher Dicke in einem Elektron-Zyklotron-Wellen-
Resonanz angeregten Sauerstoffplasma untersucht. In Abhängigkeit von
den Betriebsbedingungen der Plasmaquelle variiert die Dissoziation der
Sauerstoffmoleküle in O-Atome und -Ionen zwischen 20 und 80%, die kinetische
Energie der Ionen beim Auftreffen auf die Al-Schicht zwischen
20 und 50 eV. Es wurden Tunnelwiderstände zwischen 100kΩµm 2 und
100MΩµm 2 eingestellt, und aus den Tunnelkennlinien Parameter der Barriere
ermittelt. Der Tunnelmagnetowiderstand wurde für ungetemperte
und zur Bildung der antiferromagnetischen NiMn-Phase bis 700K getemperte
NiMn/CoFe/AlOx/CoFe/FeNi Schichtstapel bestimmt.
DS 22.41 Di 14:30 Poster B
Die Heusler-Basislegierung Co2CrAl als Elektrodenmaterial für
Dünnschicht-TMR-Elemente — •Joachim Schumann, Alexander
Burkov, Jochen Werner, Günter Behr, Hartmut Vinzelberg,
Dieter Elefant und Rainer Kaltofen — Leibniz-Institut
für Festkörper- und Werkstoffforschung Dresden, Helmholtzstr. 20, D-
01069 Dresden
Magnetische Tunnelelemente mit großem Magnetowiderstand (≥ 40%)
benötigen Elektroden mit hoher Spinpolarisation. Halbmetallische Heuslerlegierungen
erfüllen dank ihrer Bandlücke in nur einem Spinkanal diese
Anforderung, wobei jedoch die Schichtdarstellung sicherstellen muß, daß
der halbmetallische Charakter der Heuslerschichten unmittelbar an den
inneren Grenzflächen der Tunnelstrukturen keine Degradation erfährt.
Untersuchungen zur Struktur- und Phasenbildung an den für die Targetpräparation
und die Einkristallzüchtung erforderlichen polykristallinen
Ausgangsmaterialien verdeutlichen, daß nur durch eine definierte
Wärmebehandlung die Heuslerphase zu stabilisieren ist, was durch Transportmessungen
in Abhängigkeit von der Temperatur bestätigt wurde. An
Sputterschichten konnte gezeigt werden, daß die Targetzusammensetzung
in den Schichten reproduziert werden kann. Für die Ausprägung eines
optimalen magnetischen Verhaltens erweist sich eine Temperbehandlung
als notwendig. Eine Präparationstechnologie für Heusler-basierte Tunnel-

Dünne Schichten Dienstag
strukturen mit Al2O3-Barriere wird vorgestellt.
DS 22.42 Di 14:30 Poster B
MgO films for PDP applications - the measurement of the ion
induced secondary electron emission and optical properties in
dependence on the deposition parameters — •Ronny Kleinhempel,
Hartmut Kupfer, Frank Richter, Thomas Welzel,
and Thoralf Dunger — TU Chemnitz, Institut für Physik, 09107
Chemnitz
MgO films were deposited by a reactive pulsed mid-frequency sputtering
technique using a bipolar dual magnetron source. The transition
range of the target was used to get a high deposition rate.
The optical properties (refractive index n and optical absorption k)
were measured using the spectral ellipsometry. Beside n and k the ion
induced secondary electron emission coefficient γ plays an important role
for characterising dielectric layers (MgO) which are used in plasma display
panels (PDP). The γ was estimated measuring the breakdown voltages
in a He atmosphere in a simple diode-discharge device. MgO films
show γ values of about 0.5. The γ decreases to 0.3 at the transition to
the oxide state and the metallic state as well.
Atomic force microscopy (AFM), X-ray diffraction (XRD) and X-ray
reflectometry (XRR) were applied to characterise the structure of the
films. Structural information are compared to the behaviour of the γ
value as a function of O2 flow rate in the transition range of the target.
DS 22.43 Di 14:30 Poster B
Multitechnique characterization of tantalum oxynitride films
prepared by reactive DC magnetron sputtering. — •Selvaraj
Venkataraj, Achim Breitling, and Matthias Wuttig — I.
Physikalisches Institut (1A) der RWTH Aachen, 52056-Aachen
Reactive DC magnetron sputtering is an important technique to deposit
optical coatings, which frequently employ transition metal oxides.
Since sputtering of such oxides often is accomplished by process instabilities
(arcing) and low deposition rates, we have deposited oxynitride films
by sputtering in a mixed gas atmosphere. The total pressure was kept
constant at 0.8 Pa, and both oxygen and nitrogen partial pressures have
been adjusted to maintain a constant total pressure. The corresponding
films have been characterized by a variety of techniques including X-ray
diffraction, X-ray reflectometry, optical spectroscopy, spectroscopic ellipsometry
and Rutherford backscattering. Addition of nitrogen leads to
a beneficial increase of film properties. The sputter rate increases from
0.27 to 0.46 nm/s and also the film density increases from 7.15 to 8.65
g/cm 3 . This leads to an increase of refractive index of the films. Even for
films with a high refractive index around 2.5, the band gap is found to be
above 2.5 eV, i.e., fully transparent films are obtained. The correlation of
deposition parameters and the resulting film properties will be discussed.
Acknowledgement: One of the authors (S.Venkataraj) would like to
thank Alexander von Humboldt-Stiftung for a fellowship to carry out
this work at I. Physikalisches Institut (IA) der RWTH-Aachen.
DS 22.44 Di 14:30 Poster B
Optische Spektroskopie der Lateraldynamik von Proteinen in
Biomembranen — •Johannes Renner 1 , Emil Endreß 2 , Lukas
Worschech 1 , Angelika Sapper 2 , Martin Kamp 1 , Thomas
Bayerl 2 und Alfred Forchel 1 — 1 Lehrstuhl Techn. Physik, Uni
Würzburg — 2 Lehrstuhl Exp. Physik V, Uni Würzburg
Es wurden laserspektroskopische Untersuchungen an natürlichen,
festkörperunterstützten SR-Membranen und Mikrosomen durchgeführt.
Die in der Membran enthaltenen Proteine wurden mit einem fluoreszierenden
Farbstoff markiert und lokal durch einen fokussierten Laserstrahl
ausgebleicht. Zeitabhängige Photolumineszenzstudien (Fluorescence recovery
after photobleaching = FRAP) erlauben eine Bestimmung der
Eigendiffusion und Driftgeschwindigkeit der Membranproteine. Wir stellen
unsere Untersuchungen für unterschiedliche Substrate wie Glas, Gold
auf Glas, aber auch halbleitende Materialien wie Si und GaAs vor. Ziel
der Untersuchungen ist, optimierte Substratbedingungen zu finden und
Aussagen über das dynamische Verhalten der Proteine in Abhängigkeit
der Substratzusammensetzung zu treffen.
DS 22.45 Di 14:30 Poster B
Surface Modification of Titanium Alloys by Phospholipid Membrane
Systems — •D. Pressl 1 , G. Hlawacek 1 , C. Teichert 1 , F.
Feyerabend 2 , R. Willumeit 2 , and H. Clemens 3 — 1 Department of
Physics, University of Leoben, A-8700 Leoben, Austria — 2 GKSS Research
Center, 21502 Geesthacht, Germany — 3 Dept. of Physical Metallurgy
and Materials Testing, Universtiy of Leoben, A-8700 Leoben, Austria
High-resolution atomic force microscopy (AFM) is used to study the
formation of solid-supported lipid bilayers on polished Ti6Al4V and
Ti6Al7Nb samples. The resulting film morphology and the change of the
surface roughness are investigated as a function of the initial roughness
of the substrate.
The spontaneous deposition of liposomes in solution is characterized
by the formation of a variety of regions with different film thickness and
morphology. Areas with high lipid coverage show a higher roughness and
the formation of dome structures. Areas with thinner coverage are characterized
by the existence of a low number of bilayers showing terrace
structures. The height of the single bilayers varies between 4 and 7 nm
depending on hydration. Phase imaging proves the existence of single bilayers
on the metal substrate. Furthermore, experiments in the fluid cell
of an AFM are accomplished in order to allow direct comparisons to the
results in the dry environment.
DS 22.46 Di 14:30 Poster B
Real time spectroscopic in situ ellipsometry monitoring of
Mo/Si multilayer growth — •E. Schubert, A. Köhler, J. W.
Gerlach, Frank Frost, G. Wagner, H. Neumann, and B.
Rauschenbach — Leibniz-Institut für Oberflächenmodifizierung e. V.,
Permoserstraße 15, D-04318 Leipzig, Germany
Mo/Si multilayer mirrors with 10 or 50 bilayer periods are grown by
Ar ion beam sputtering onto [100] Si substrates. The growth is monitored
by spectroscopic in situ ellipsometry (visible spectral region) in real time.
The model analysis of the experimental data allows the determination of
Mo and Si single layer thickness with a certainty of ± 0.3 nm. Therefore
the reflection restricting parameters bilayer thickness and thickness
ratio of the Mo and Si layers (Γ) can be precisely determined. Additionally
the Mo/Si multilayers are characterized by CuKα reflectometry,
EUV reflectometry at λ = 13.4 nm and TEM. The investigations reveal
homogenous vertical thickness distribution within the multilayer stack
The bilayer thickness obtained by in situ ellipsometry is confirmed by
the other techniques. Surface roughness was determined by AFM and
amounts RMS = 0.13 nm for 50 periods multilayers and RMS = 0.11 nm
for 10 periods multilayers, respectively.
DS 22.47 Di 14:30 Poster B
Elektrische Untersuchungen an Si-CrSi2 Multilagen — •Chr.
Drobniewski 1 , D. Decker 1 , G. Beddies 1 , H.-J. Hinneberg 1 und
J. Schumann 2 — 1 Technische Universität Chemnitz, Institut für Physik,
09107 Chemnitz, Deutschland — 2 Leibnitz-Institut für Festkörperund
Werkstoffforschung, Abt. Dünnschichtsysteme und Nanostrukturen,
01171 Dresden
Aufgrund seiner chemischen und thermischen Stabilität sowie thermoelektrischen
Eigenschaften besitzt CrSi2 ein hohes Potential für thermoelektrische
Anwendungen. Es hat sich gezeigt, dass besonders hohe thermoelektrische
Effektivitäten (ZT) für Multilagenschichten erreicht werden,
da hier zusätzliche Streuung der Phononen an Grenzflächen erfolgt.
Durch alternierende Abscheidung von Si und CrSi2 wurden Si/CrSi2-
Multilagenstrukturen mit verschiedenen Einzellagendicken sowie Zusammensetzungen
(CrSi2±x) der Silicidschicht abgeschieden. Als Substrate
wurden oxidierte (dox = 1µm) 3 ′′ Si(001)-Scheiben verwendet. Die nach
der Abscheidung amorphen Stapelsysteme wurden in einer RTA-Anlage
bei unterschiedlichen Temperaturen (450 ◦ C . . . 600 ◦ C) getempert. Zur
Charakterisierung der Multilagen wurden im Temperaturbereich von
1,3 K bis 300 K Messungen von RH, ̺ und ∆̺/̺ durchgeführt. Die
Messergebnisse werden auf Grundlage eines Schichtmodells mit unterschiedlichen
Parametern für Silicidschichten und Si/CrSi2-Grenzflächen
sowie einer Weglängentheorie interpretiert. Die Abhängigkeit der elektrischen
Parameter von der Wärmebehandlung und der Dicke der Silicidlagen/Lagenanzahl
im Schichtstapel wird diskutiert.

Dünne Schichten Dienstag
DS 22.48 Di 14:30 Poster B
Temperature-dependent surface photovoltage of polycrystalline
Cu(In,Ga)Se2 from photoemission studies using synchrotron radiation
— Thomas Schulmeyer, Ralf Hunger, and •Andreas
Klein — Technische Universität Darmstadt, Petersenstrasse 23, D-
64287 Darmstadt
A deep insight of surfaces and interfaces is essential for improving
the knowledge of the complex interface behaviour of Cu-chalcopyrites.
In this contribution, temperature-dependent photovoltage measurements
with synchrotron radiation induced photoelectron emission of polycrystalline
Cu(In,Ga)Se2 surfaces and Cu(In,Ga)Se2/CdS interfaces are presented.
Clean Cu(In,Ga)Se2 surfaces are prepared with the Se de-capping
procedure. Additionally, defined oxidized Cu(In,Ga)Se2 and de-capped
CuGaSe2 absorbers were investigated. All chalcopyrite surfaces show a
Cu-poor surface composition.
DS 22.49 Di 14:30 Poster B
Aluminum-induced crystallization of amorphous silicon: Al/a-
Si-interface influence on seed layer formation — •Jens Schneider,
Juliane Klein, Martin Muske, Stefan Gall, and Walther
Fuhs — Hahn-Meitner-Institut Berlin, Kekuléstr. 5, D-12489 Berlin,
Germany
Crystallization of seed layers on inexpensive foreign substrates and
their subsequent epitaxial thickening is a promising approach for the formation
of thin-film crystalline silicon cells. Such seed layers can be formed
by Al-induced crystallization of an amorphous silicon (a-Si) layer. The kinetics
of Al-induced crystallization of a-Si are studied by variation of the
thickness of an Al-oxide layer between the initial Al and a-Si films. The
results show that the thickness of this Al-oxide layer strongly determines
the nucleation time and the number of Si-grains (nucleation) and has only
little influence on the growth velocity of the grains. The diameter of the
grains increases in good approximation linearly with time and is strongly
influenced by the annealing temperature. The general behavior suggests
that the process kinetics of the aluminum-induced layer exchange are determined
by the silicon diffusion across the interface which can be altered
by the thickness of the oxide layer.
DS 22.50 Di 14:30 Poster B
Development system for advanced CdTe Thin Film Solar Cells
— •Jochen Fritsche, Daniel Kraft, Bettina Späth, Andreas
Thißen, Andreas Klein, and Wolfram Jaegermann — Darmstadt
University of Technology, Institute of Materials Science, Surface
Science Division, Germany
CdTe thin film solar cells promise a high potential to reach good conversion
efficiencies with a low cost production process. A large scale production
of CdTe modules (120 cm × 60 cm) is realized by ANTEC Solar
Energy GmbH with average conversion efficiencies of 6,7 %. In the production
a layer sequence is used, which is based on empirical development.
However, the highest obtained efficiency with CdTe is 16,5 %. We have
analyzed electronic and chemical properties of surfaces und interfaces
in the CdTe solar cell. Major obstacles to obtain higher efficiencies and
lower production costs within this system are related to interfacial issues
as barrier heights for charge transport, interface recombination and film
nucleation. A better understanding of these properties will help to prepare
improved front and back contacts as well as to reduce the CdS and
CdTe layer thickness. In order to explore possible advanced cells with
a better control and knowledge about interface properties, we have set
up DAISY-Sol (DArmstadt Integrated SYstem for Solar cell research),
which combines a full vacuum production of CdTe solar cells with an
in-situ analysis to investigate and modify the electrical and chemical
properties of all surfaces and interface.
DS 22.51 Di 14:30 Poster B
CuInS 2 Solar Cells Deposited by Reactive Magnetron Sputtering
— •Thomas Unold, Jan Hinze, and Klaus Ellmer — Hahn-
Meitner Institut, Glienicker Str. 100, D-14109 Berlin, Germany
We have deposited CuInS 2 films in a reactive magnetron sputtering
system, specially designed for the deposition of sulfides by sputtering
in Ar-H2S mixtures. The substrate temperature was varied from
350 to 500C and the deposition rate was about 50 nm/min. The magnetron
plasma was excited by a DC power supply. The contacts (Mo,
ZnO/ZnO:Al) and the buffer layer (CdS) were prepared by the standard
processes of the Hahn-Meitner-Institut. Up to now solar cell efficiencies
of up to 8.1 have been obtained. The electronic and optical properties
of the solar cell devices were analyzed by dark and illuminated current-
voltage characteristics, quantum efficiency and photoluminescence measurements.
We find that although the short circuit current is comparable
to that of cells prepared by the two-step process (sulfurization of sputtered
precursor metals), the open-circuit voltage is about 100meV lower.
This is consistent with the quantum efficiency analysis where we find a
decreased collection efficiency at long wavelengths compared to cells from
the two-step process. From photoluminescence we conclude that the efficiency
of our cells is limited by the defect density in the absorber layer.
DS 22.52 Di 14:30 Poster B
Epitaxial growth and characterization of Cu0.5In0.5Se (Te)
films grown on GaAs by pulsed laser deposition. — •Liudmila
Roussak, Gerald Wagner, and Klaus Bente — Institute of Mineralogy,
Crystallography and Materials Science, Linnestr. 3-5 (TA), D-
04103 Leipzig
Alloys of Cu0.5In0.5Se(Te), as an attractive material for solar cell applications,
have been grown on (001) oriented GaAs substrates by pulsed
laser deposition (PLD). Epitaxial growth was found to occur for substrate
temperatures ranging between 380 and 600 ◦ C. The structural, compositional,
morphological and electrical properties of the Cu0.5In0.5Se(Te)
films depend strongly on the substrate temperature, laser energy density
and deposition rate. Applying optimized growth conditions it is possible
to obtain the films of required electrical and structural characteristic.
The detailed examination of late the absorber and buffer forming the heterostructure
as well as their interface are very important for the efficient
of thin film solar cells.
DS 22.53 Di 14:30 Poster B
Influence of the substrate preparation on the low-temperature
epitaxy of Si by electron-cyclotron resonance chemical vapor
deposition — •Patrick Clemens, Björn Rau, Ina Sieber, Stefan
Gall, and Walther Fuhs — Hahn-Meitner-Institut, Abt. Silizium
Photovoltaik, Kekuléstr. 5, D-12489 Berlin
We report on a study of substrate preparation for the low-temperature
Si homo-epitaxy by electron-cyclotron resonance chemical vapor deposition
(ECRCVD). The background of the research is the development of
a low-temperature epitaxial thickening process for Si thin-film solar cells
on large-grained polycrystalline Si seed layers on glass.
Different from conventional high-temperature Si deposition methods
the conditions of the substrate surface, its crystal orientation and its
contamination are very critical for the successful epitaxial growth of Si
at substrate temperatures below 600 ◦ C. Both, wet chemical surface pretreatments
and in-situ treatments are applied to obtain an ideal substrate
surface for Si epitaxy. Using a HF/alcohol instead of HF/water solution
the roughness of the surface of Si wafers decreases, the surface contaminations
are reduced, and the H-termination of the Si surface is improved.
During substrate heating in-situ H-treatment is used to increase the stability
of this surface and prevent reoxidation. This substrate preparation
leads to a successful epitaxial growth of Si on Si(100) wafers at low temperatures.
The influence of the preparation on the Si epitaxy is analyzed
by structural and electrical characterizations of the grown films.
DS 22.54 Di 14:30 Poster B
Majority-carrier properties of low-temperature epitaxial Si —
•S. Brehme, U. Knipper, B. Rau, and W. Fuhs — Hahn-Meitner-
Institut Kékulestr. 5 12489 Berlin
In this contribution we report the results of electrical investigations on
thin Si films grown epitaxial at temperatures below 600 ◦ C. Such films
are possible candidates for absorber layers in thin-film solar cells on glass.
Films were grown by Electron Cyclotron Resonance Chemical Vapor Deposition
(ECR-CVD) on Si substrates. n- and p-type wafers of varying
conductivity were used in the same run to render possible different types
of electrical measurements such as capacitance voltage (CV), Hall effect
(HE), and Deep Level Transient Spectroscopy (DLTS). The nominally
undoped thin films were found to have room temperature electron concentrations
in the range 10 16 cm −3 to 10 17 cm −3 depending on certain details
of the growth process. From CV measurements similar results were
obtained. Hall mobilities in the range 400 to 700 cm 2 /Vs were observed.
Considering the ratio R of experimentally observed mobilities to values
in a Si wafer of the same doping level, R values of typical 50 % are found
in thin films with doping levels Nd of about 1 × 10 16 cm −3 . For layers
with higher Nd R increases indicating different degrees of compensation.
DLTS measurements show the presence of several electron-emitting trap
levels with a dominant peak P1 at EC - 0.27 eV. Concentrations of P1

Dünne Schichten Dienstag
of some 10 14 cm −3 were determined from peak heights. Since the peaks
of all the observed traps were broadened, real concentration values are
still higher. Nevertheless, shallow levels dominate the conductivity. That
is further approved by HE measurements down to 25 K.
DS 22.55 Di 14:30 Poster B
Photospannungsuntersuchungen an In(OH)xSy - und PbS -
Dünnschichten und -systemen — •T. Guminskaya 1 , R. Bayon
1 , G. Urban 2 , N. Grigorieva 3 und Th. Dittrich 1 — 1 Hahn-
Meitner-Institut, SE2, Glienicker Str. 100, D-14109 Berlin, Germany —
2 Bundesanstalt für Materialforschung, Unter den Eichen 87, D-12205
Berlin — 3 permanent address: St. Petersburg State University, Department
of Solid State Physics, Ulyanovskaya 1, 198504 St. Petersburg, Russia
Schichten aus In(OH)xSy oder PbS lassen sich über chemische Badabscheidung
relativ einfach herstellen und sind als Puffer- bzw. Absorberschichten
für photovoltaische Anwendungen interessant. Transiente und
spektrale Photospannungsuntersuchungen wurden an Einzelschichten
von In(OH)xSy und PbS und an Schichtsystemen auf Glas/SnO2:F- Substraten
durchgeführt. Einige Schichtsysteme wurden mit Transmissions-
Elektronenmikroskopie und optischer Transmission charakterisiert. Anhand
der Präparationsbedingungen können die Bandlücken der Materialien
und die Bedingungen für die Ladungstrennung stark variiert werden.
Außerdem spielen heiße Ladungsträger bei Anregung mit Photonenenergien
oberhalb der Bandlücke eine große Rolle.
DS 22.56 Di 14:30 Poster B
On the role of buffer layers in solar cells with extremely thin absorbers
— •A. Belaidi, R. Bayon, Th. Dittrich, H. Muffler, C.-
H. Fischer, and M.C. Lux-Steiner — Hahn-Meitner-Institut, SE2,
Glienicker Str. 100, D-14109 Berlin, Germany
Solar cells with extremely thin absorbers have a highly developed internal
surface what makes them vulnerable for surface recombination. Buffer
layers as aluminum oxides and hydroxides (”Al2O3”), In2S3, In(OH)xSy
between the thin absorber layer and the electron and/or hole conductors
can be used to decrease surface recombination. CBD (chemical bath deposition)
and ILGAR (ion layer gas reaction) techniques have been used
to prepare buffer and absorber layers on porous TiO2 substrates. The
role of the buffer layers will be demonstrated on the TiO2 / In(OH)xSy
/ PbS / PEDOT and TiO2 / Al2O3 / In2S3 / CuInS2 systems.
DS 22.57 Di 14:30 Poster B
Polykristalline WSx- und MoSx -Schichten als Absorbermaterial
in Dünnschichtsolarzellen — •Stefan Seeger 1 , Volkmar
Weiß 1 , Helmut Tributsch 1 , Thomas Dittrich 1 , Tanja Guminskaya
1 , Rainald Mientus 2 und Klaus Ellmer 1 — 1 Hahn-Meitner-
Institut, Solare Energetik, Berlin — 2 OUT e.V., Berlin
Hohe Absorptionskoeffizienten (> 10 5 cm −1 ) im sichtbaren Bereich des
Sonnenspektrums und Bandlücken von Eg = 1,3 − 1,8 eV der natürlich
gewachsenen und synthetisch hergestellten MS2 (M=Mo, W) Schichtgitterkristalle
zeichnen die Übergangsdichalkogenide für den Einsatz als
Absorberschichten in Dünnschichtsolarzellen aus. Für die Übertragung
der guten photoelektronischen Eigenschaften der Schichtgitterkristalle
auf großflächige polykristalline dünne Schichten ist das reaktive Magnetronsputtern
eine attraktive Beschichtungstechnik. Die Herstellung photoaktiver
polykristalliner MoSx- und WSx-Schichten erfordert es, texturierte
Schichten mit grossen Kristalliten herzustellen. Das Wachstum von
reaktiv gesputterten MoSx- und WSx-Schichten wird mit in situ EDXRD
(energy dispersiv x ray diffraction) an einer Synchrotronquelle untersucht.
Es werden die elektrischen Eigenschaften (Leitfähigkeit, Hall-
Beweglichkeit, Ladungsträgerdichte und Leitungstyp) sowie die photoelektrischen
Eigenschaften (spektrale Photospannung) der polykristallinen
MoSx- und WSx-Schichten in Abhängigkeit von den Beschichtungsparametern
gezeigt.
DS 22.58 Di 14:30 Poster B
Modulation Doping as a Means to Overcome the Mobility Limitation
of Zinc Oxide Transparent Electrodes? — •Goetz Vollweiler
und Klaus Ellmer — Hahn-Meitner-Institut, Solar Energy
Research, Glienicker Straße 100, 14109 Berlin
Heavily doped ZnO, which belongs to the material class of transparent
conductive oxides, finds an important application as transparent electrode
in thin film solar cells. As recent reviews have shown, there exists a
lower limit in the range of 1.4 to 2.0×10 −4 Ωcm concerning the resistivity
of this material, which is caused by a low mobility due to ionized impurity
scattering. The aim of this work is to proof a concept to overcome this
limitation. The idea is, to create a system consisting of small adjacent
domains with undoped and doped ZnO, a so-called modulation doped
structure. Charge carriers from the doped areas with low mobility would
diffuse to the undoped domains with low ionized impurity scattering and
consequently high mobility. For the film preparation magnetron sputtering
from two different targets has been used to grow multi-sandwich
films of thin doped and undoped ZnO-films on sapphire substrates. In
order to widen the bandgap of the doped films, which is a prerequisite
for the modulation doping principle, MgO was added. The electrical
parameters carrier concentration and Hall mobility and the crytallographic
quality of the films will be given in dependence of the deposition
parameters.

Dynamik und Statistische Physik Tagesübersichten
Hauptvorträge
DYNAMIK UND STATISTISCHE PHYSIK (DY)
Prof. Dr. Franz Schwabl
Technische Universität München
Physik-Department T34
James-Franck-Straße
85748 Garching
E-Mail: schwabl@ph.tum.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsäle H2 und H3)
DY 10.1 Mo 09:30 (H2) Critical Dynamics in Pure Fluids and Binary Mixtures, Reinhard Folk
DY 12.5 Mo 12:30 (H2) Local scale invariance in ageing phenomena, Malte Henkel
DY 20.1 Di 09:30 (H2) Statistical Physics for Complex Cosmic Structures, Luciano Pietronero
DY 23.4 Di 12:30 (H3) Statistical Physics of RNA Secondary Structures, Ralf Bundschuh
DY 24.1 Di 14:30 (H2) Physical Aspects of Cell Division, Karsten Kruse
DY 28.1 Di 09:30 (H23) Theory of the glass transition for systems with trivial statics, Rolf Schilling,
Grzegorz Szamel
DY 29.1 Di 14:30 (H23) Dynamische Heterogenität ungeordneter Festkörper, Roland Böhmer, Manfred
Winterlich, Sven Berndt, Gregor Diezemann, Ken R. Jeffrey
DY 40.1 Do 09:30 (H2) Lyapunov instability of many-body systems, Harald A. Posch
DY 42.5 Do 12:30 (H2) Long-range correlations in nature: On test-beds for climate models, global
warming and natural clustering of hazardous floods, Armin Bunde
DY 44.1 Do 14:30 (H2) Phase transitions and segregation phenomena in granular systems,
Christof Krülle
DY 50.1 Fr 10:15 (H2) How can entanglement between three or more qubits be measured?,
Jens Siewert, Andreas Osterloh
Hauptvorträge im Symposium SYPF: Physics of Foams
gemeinsam veranstaltet von den Fachverbänden M und DY
Hauptvorträge
SYPF 1.1 Mi 14:00 (H16) The foam/emulsion analogy in structure and drainage, Stefan Hutzler, Nicolas
Peron, Denis Weaire, Wiebke Drenckhan
SYPF 3.1 Mi 16:20 (H16) Die Stabilität metallischer Schäume, Dietmar Leitlmeier
Hauptvorträge im Symposium SYFT: Fat-Tail Distributions - Applications from Physics to Finance
gemeinsam veranstaltet vom Arbeitskreis AKSOE und dem Fachverband DY
Hauptvorträge
SYFT 1.1 Do 09:30 (H1) Fat Tail Statistics and Beyond, Joachim Peinke
SYFT 1.2 Do 10:00 (H1) Use and Abuse of Ito vs. non-Ito Stochastic Calculus, Peter Hänggi
SYFT 1.3 Do 10:30 (H1) Non-Gaussian option pricing, Hagen Kleinert
SYFT 2.1 Do 11:30 (H1) Credit Risk in Banking - Methods, Problems, Implications,
Axel Müller-Groeling, Jan-Hendrik Schmidt

Dynamik und Statistische Physik Tagesübersichten
SYFT 2.2 Do 12:00 (H1) Understanding large fluctuations in stock market activity using methods
of statistical physics, H. Eugene Stanley
Hauptvorträge im Symposium SYSN: Quantum Shot Noise in Nanostructures
gemeinsam veranstaltet von den Fachverbänden TT, DY und HL
Hauptvorträge
SYSN 1.1 Mo 13:30 (H1) Quantum Shot Noise in Nanostructures: From Schottky to Bell,
Markus Büttiker
SYSN 1.2 Mo 14:00 (H1) Mesoscopic transition in the shot noise of diffusive SNS junctions,
Francois Lefloch, Christian Hoffmann, Marc Sanquer, Bernard Pannetier
SYSN 1.3 Mo 14:30 (H1) Quantum Noise: Challenge and Prospect, Yuli V. Nazarov
SYSN 2.1 Mo 16:00 (H1) Environmental effects in the third moment of voltage fluctuations in a
tunnel junction, Bertrand Reulet, J. Senzier, Daniel E. Prober
SYSN 2.2 Mo 16:30 (H1) Full Counting Statistics of Multiple Andreev Reflections,
Juan Carlos Cuevas
Fachsitzungen
DY 10 Critical Phenomena Mo 09:30–11:15 H2 DY 10.1–10.6
DY 11 Ferrofluids Mo 10:30–12:00 H3 DY 11.1–11.6
DY 12 Dynamical Phenomena Mo 11:30–13:00 H2 DY 12.1–12.5
DY 14 Solitons and Stochastic Dynamics Mo 14:30–16:45 H2 DY 14.1–14.9
DY 15 Fluids I Mo 14:30–16:15 H3 DY 15.1–15.7
DY 16 Phase Transitions Mo 16:45–18:00 H2 DY 16.1–16.5
DY 17 Fluids II Mo 16:30–18:00 H3 DY 17.1–17.6
DY 20 Fractals and Nonlinearity I Di 09:30–11:15 H2 DY 20.1–20.6
DY 21 Neural Networks Di 10:15–11:30 H3 DY 21.1–21.5
DY 22 Fractals and Nonlinearity II Di 11:30–12:30 H2 DY 22.1–22.4
DY 23 Statistical Physics of RNA Di 11:45–13:00 H3 DY 23.1–23.4
DY 24 Dynamic Instabilities in Biophysics Di 14:30–16:45 H2 DY 24.1–24.8
DY 25 Growth and Roughness Di 15:00–16:30 H3 DY 25.1–25.6
DY 26 General Statistical Physics Di 16:45–18:00 H2 DY 26.1–26.5
DY 27 Quantum Chaos Di 16:30–18:15 H3 DY 27.1–27.7
DY 28 Glasses I (joint session DF/DY) Di 09:30–12:30 H23 DY 28.1–28.10
DY 29 Glasses II (joint session DF/DY) Di 14:30–17:45 H23 DY 29.1–29.12
DY 34 Nonlinear Dynamics and Chaos I Mi 14:30–16:30 H2 DY 34.1–34.8
DY 35 Symposium SYPF: Physics of Foams Mi 14:00–18:30 H16 DY 35.1–35.1
DY 36 Nonlinear Dynamics and Chaos II Mi 16:30–18:00 H2 DY 36.1–36.6
DY 40 Lyapunov Instability of Many-Body Systems Do 09:30–11:30 H2 DY 40.1–40.7
DY 41 Symposium SYFT: Fat-Tail Distributions - Applica- Do 09:30–13:00 H1 DY 41.1–41.1
tions from Physics to Finance
DY 42 Long-Range Correlations and Multifractals Do 11:30–13:00 H2 DY 42.1–42.5
DY 44 Granular Systems Do 14:30–16:00 H2 DY 44.1–44.5
DY 46 Poster Do 16:00–18:00 Poster D DY 46.1–46.98
DY 50 Entanglement and Decoherence Fr 10:15–12:15 H2 DY 50.1–50.7
DY 51 Polymers and Colloids Fr 10:45–12:30 H3 DY 51.1–51.7

Dynamik und Statistische Physik Tagesübersichten
Posterbeiträge
Zuordnung der Poster zu den Themenkreisen
DY 46.1-46.6 Statistical Physics (General)
DY 46.7-46.10 Glasses
DY 46.11-46.12 Neural Networks
DY 46.13-46.15 Brownian Motion
DY 46.16-46.17 Nonlinear Stochastic Systems
DY 46.18-46.35 Nonlinear Dynamics, Synchronization and Chaos
DY 46.36-46.43 Quantum Chaos
DY 46.44-46.45 Statistical Physics Far From Thermal Equilibrium
DY 46.46-46.57 Soft Matter
DY 46.58-46.60 Statistical Physics in Biological Systems
DY 46.61-46.61 Statistical Physics of Complex Networks
DY 46.62-46.65 Fluid Dynamics
DY 46.66-46.71 Growth Processes and Interface Features
DY 46.72-46.74 Granular Matter / Contact Dynamics
DY 46.75-46.82 Ferrofluids / Liquid Crystals
DY 46.83-46.95 Critical Phenomena and Phase Transitions
DY 46.96-46.98 Lattice Dynamics and Nonlinear Excitations
Mitgliederversammlung des Fachverbands Dynamik und Statistische Physik
Do 18:30–19:15 H2
1. Bericht des Sprechers
2. Tagungen
3. Verschiedenes
gez. Franz Schwabl

Dynamik und Statistische Physik Montag
Fachsitzungen
– Haupt-, Kurzvorträge und Posterbeiträge –
DY 10 Critical Phenomena
Zeit: Montag 09:30–11:15 Raum: H2
Hauptvortrag DY 10.1 Mo 09:30 H2
Critical Dynamics in Pure Fluids and Binary Mixtures —
•Reinhard Folk — Institut für Theoretische Physik, Universität Linz,
A-4040 Linz, Österreich
The critical behavior of transport coefficients (e.g. thermal conductivity,
mass diffusion, shear viscosity) near continuous phase transitions
(PT) is still of great interest. In the last years progress has been made on
the experimental as well as on the theoretical side, which allows a quantitative
comparison between theory and experiment. Such a comparison
is presented for the gas-liquid PT, the demixing PT as well as for the
suprafluid PT in He4 and He4-He3 mixtures. Especially for this last case
the recent field theoretic two loop calculations are presented. In addition
light scattering experiments, sound velocity and sound absorption
measurements will be discussed shortly.
DY 10.2 Mo 10:00 H2
Phase Diagram of the Generalized Complex |ψ| 4 Model — •E.
Bittner und W. Janke — Institut für Theoretische Physik, Universität
Leipzig, Augustusplatz 10/11, 04109 Leipzig, Germany
Using Monte Carlo simulations, we analyze the critical behaviour of
the complex |ψ| 4 theory in the presence of an additional fugacity term.
With this modification we can show that the complex |ψ| 4 theory can
be tuned to undergo a first-order transition by varying the strength of
the new term in the generalized Hamiltonian. From a finite-size scaling
analysis we determine the critical endpoint of the line of first-order phase
transitions for several values of the strength of the new term in the generalized
Hamiltonian. Based on these results we sketch the phase diagram
of the generalized complex |ψ| 4 model.
DY 10.3 Mo 10:15 H2
Quantum Phase Diagram for Bose Gases — •Hagen Kleinert 1 ,
Axel Pelster 1 , and Sebastian Schmidt 2 — 1 Institut für Theoretische
Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
— 2 Department of Physics, Yale University, P.O. Box 208120, New
Haven, CT 06520-8120, USA
We locate the quantum phase transition for a dilute homogeneous Bose
gas in the plane of s-wave scattering length as and temperature T. This
is done by improving a lowest-order result for the thermodynamic potential
with the help of recent high-order perturbative calculations on
the leading shift of the critical temperature due to a weak atomic repul-
sion using variational perturbation theory. The quantum phase diagram
shows a nose above the interaction-free critical temperature T (0)
c , so that
we predict the existence of a reentrant transition above T (0)
c , where an
increasing repulsion leads to the formation of a condensate. Furthermore,
we obtain a similar quantum phase diagram for a bose gas trapped in an
optical lattice as a function of effective scattering length aeff and temperature
T.
[1] H. Kleinert, S. Schmidt, and A. Pelster, cond-mat/0307412
DY 10.4 Mo 10:30 H2
Critical Dynamics: theory for time-dependent intensity correlations
measured by X-ray microdiffraction — •Klaus Mecke 1 ,
Cristian Mocuta 2 , and Harald Reichert 1 — 1 MPI für Metallforschung,
D-70569 Stuttgart, Germany — 2 ESRF, F-38043 Grenoble,
France
We studied the dynamics of critical fluctuations in Fe3Al, which exhibits
an order-disorder phase transition (DO3-B2, TC =780 K). In the
experiments we used a well focused beam to probe a sub-micron sized
single crystalline sample, so that the size of fluctuating domains is large
compared to the probed volume due to the diverging correlation length
close to TC. Pronounced effects on the time-course of the intensity of
a superstructure peak (characteristic for the chemical order) were measured.
Starting from a stochastic Langevin equation for the fluctuations
of a non-conserved order-parameter (model A) the four-point structure
function can be calculated and directly related to the measured timedependent
intensity-intensity correlation function. The analytical expression
fits very well the experimental data sets fixing the correlation time
τ as only free parameter of the theory. We find a strong dependence on
temperature, in particular an increase of τ close to the critical point. The
agreement of theory and experiments - even for various spatial and time
resolutions - demonstrate the potential of partially coherent x-ray microbeams
for the direct observation of fluctuation phenomena at critical
phase transition.
DY 10.5 Mo 10:45 H2
Exact renormalization group analysis of the O(2) theory including
all marginal and relevant coupling parameters — •Nils Hasselmann,
Sascha Ledowski, and Peter Kopietz — Institut für
Theoretische Physik, Universität Frankfurt, Robert-Mayer-Str. 8, 60054
Frankfurt/Main
We use the exact renormalization group formalism to study the critical
regime of the O(2) theory in dimensions 4 > D ≥ 3 analytically. Besides
the two relevant parameters, the mass parameter and the constant part of
the 4-point vertex, our analysis tracks also the flow of all three marginal
parameters at D = 3. Two marginal parameters characterize the lowest
order momentum dependence of the 4-point vertex and the third is the
momentum-independent part of the 6-point vertex. We find competitive
results for the critical exponents ν and η.
DY 10.6 Mo 11:00 H2
Non-Equilibrium Relaxation method for the critical Analysis of
the Hubbard Model — •Hans-Georg Matuttis 1 and Nobuyasu
Ito 2 — 1 The University of Electrocommunications, Department of Mechanical
and Control Engineering, Chofu Chofugaoka 1-5-1,Tokyo 182-
8585,Japan — 2 The University of Tokyo, Department of Applied Physics,
7-3-1 Hongo, Bunkyo-Ku, Tokyo 113-8565 Japan
The non-equilibrium relaxation (NER) analysis for critical phenomena
goes back to work by M. Suzuki in the 1970’s. One can show that the
relaxation from a non-equilibrium configuration (e.g. ordered state) to
equilibrium (e.g. disordered state) does not only tell whether the temperature
is below, above or at the critical temperature, but it is even
possible to extract the critical exponents from the time series of the relaxation.
In recent years, the NER-method has been applied to the computational
analysis of critical phenomena ranging from discrete over continous
spin models, Kosterlitz-Thouless-Transisions and spin-glas models up to
transitions in molecular dynamics systems. In this talk, the application
of the NER-analysis to auxiliary field quantum Monte-Carlo simulations
will be explained and results for the transition to the anti-ferromagnetic
phase in the groundstate at halffilling will be presented.

Dynamik und Statistische Physik Montag
DY 11 Ferrofluids
Zeit: Montag 10:30–12:00 Raum: H3
DY 11.1 Mo 10:30 H3
Investigation of the microstructure of ferrofluids using small
angle neutron scattering (SANS) — •Loredana Pop 1 , Stefan
Odenbach 1 und Albrecht Wiedenmann 2 — 1 ZARM, University of
Bremen, Am Fallturm 28359 Bremen — 2 Hahn-Meitner-Institut Berlin,
Glienicker Str. 100, 14109 Berlin
Experimetal studies made for different ferrofluid samples under shear
flow have shown that increasing the magnetic field strength yields an
increase of the fluids viscosity, the so called magnetoviscous effect, while
increasing shear rate leads to a decrease of the magnitude of the viscosity
(shear thinning). The change of the viscosity with magnetic field strength
is theoretically explained as an effect of chain-like structure formation in
ferrofluids whereas its magnitude depends on the particle-particle interaction.
Both effects, the shear thinning and the magnetoviscous effect, can
therefore be related to the microstructure and microstructure dynamics
of ferrofluids. Using a specially designed rheometer, ferrofluids having
different magnitude of the magnetoviscous effect were investigated by
SANS. Correlated to the structure formation in the fluid, the scattered
intensity shows a variation with the magnetic field and shear rate only
in the case of the fluids with a high magnetoviscous effect. The results
which will be presented show that there is a strong connection between
the rheological behaviour of ferrofluids and their microstructure.
DY 11.2 Mo 10:45 H3
Structure and Viscosities of Ferrofluids in Stationary Shear
Flow — •Patrick Ilg 1 , Martin Kröger 2 , and Siegfried Hess 1 —
1 Institut für Theoretische Physik, TU Berlin, Hardenbergstr. 36, 10623
Berlin — 2 Institut für Polymere, ETH Zürich, Sonneggstr. 3,8092 Zürich
Thanks to their superparamagnetic properties, the viscosities of ferrofluids
are influenced by external magnetic fields - the so-called magnetoviscous
effect [1]. This effect opens various technical as well as medical
applications. In order to better understand the relationship between microscopic
structure and magnetoviscous properties, we consider ferrofluids
subject to a stationary shear flow. The model systems under consideration
are studied both, with the help of mean-field approximations [2,3],
as well as with nonequilibrium many particle simulations. The dependence
on the magnetic field of the mass diffusion, viscosities and normal
stress differences, cluster sizes and structure factors are presented. It is
found, that mean-field approximations lead to satisfactory results within
their range of validity, but cannot be extrapolated straightforwardly. Additional
comparisons of the simulation results with SANS and rheological
experiments on ferrofluids give valuable information on the importance
of magnetic field and shear flow dependent structure formation for the
strength of the magnetoviscous effect.
[1] M. Kröger, P. Ilg, and S. Hess, J. Phys.: Condens. Matter 15 (2003)
S1403-S1423. [2] P. Ilg, M. Kröger, S. Hess, and A. Yu. Zubarev, Phys.
Rev. E 67 (2003) 061401. [3] P. Ilg and S. Hess, to appear in Z. Naturforsch.
2003.
DY 11.3 Mo 11:00 H3
The Hysteresis of the Normal Field Instability — •Reinhard
Richter — Experimentalphysik 5, Univ. Bayreuth, 95440 Bayreuth
Ferrofluids or magnetic liquids are colloidal suspensions of magnetic
nanoparticles. Their behaviour can be controlled by external magnetic
fields. E.g. a horizontally extended layer of magnetic liquid, subjected
to a normally oriented magnetic field forms liquid spikes when a threshold
of the field amplitude is surpassed. This normal field or Rosensweig
instability can be described by a sub critical bifurcation.
We analyse the profile of the liquid spikes and their field dependence
by means of contact radiography near the onset and in the hysteretic regime,
in order to pave the way for a more precise description by amplitude
equations.
DY 11.4 Mo 11:15 H3
Wave number selection and secondary instabilities of ridge patterns
on magnetic fluids — •Rene Friedrichs — ABB AG, Corporate
Research Center Germany, Wallstadter Str. 59, D-68526 Ladenburg
When the free surface of a magnetizable fluid is subjected to a homogeneous
vertical magnetic field the flat surface becomes unstable above
a certain threshold for the field strength. If, additionally, an appropriate
magnetic field oriented tangential to the fluid interface is applied this so
called “Rosensweig instability“ gives rise to parallel fluid ridges [1].
We perform a nonlinear analysis of the static ridge pattern by means
of an energy variational method [2]. The dependence of the wave number
on the external magnetic field and the detailed shape of the corresponding
ripples are theoretically determined. Using a high order expansion
of the energy we investigate the influence both of the wave number and
the permeability of the fluid on the bifurcations of the periodic patterns.
Secondary instabilities of the quasi-one-dimensional surface and the nonlinear
wave number selection are studied by combining a Floquet Ansatz
with the variational approach.
[1] Y. D. Barkov and V. G. Bashtovoi, Magnetohydrodynamics 13, 497
(1977)
[2] R. Friedrichs, Phys. Rev. E 66, 066215 (2002)
DY 11.5 Mo 11:30 H3
Nonlinear oscillations of a torsional pendulum filled with ferrofluid
— •Michael Zaks 1 and Mark Shliomis 2 — 1 Institut für
Physik, Humboldt-Universität Berlin — 2 University of Beer-Sheva, Israel
We consider torsional motions of a sphere filled with ferrofluid and
suspended on an elastic fiber. In presence of the linearly polarized horizontal
magnetic field microscopic rotational motions of magnetic grains
can sum up into a collective motion of the ferrofluid. Dynamics of the
fluid magnetization and the angle of pendulum deflection is governed by
a non-autonomous differential equation of the 4th order. We perform the
detailed bifurcation analysis of this system.
If the frequency of the magnetic field strongly exceeds the pendulum
eigenfrequency, separation of timescales reduces the problem to the 2nd
order equation of the Van-der-Pol type with supercritical or subcritical
onset of oscillations. If two frequencies are of the same order, bifurcation
scenarios are more complicated. In contrast to the conventional picture
of Arnold tongues, presence of physical symmetries causes a hysteresis
near the resonances: coexistence of periodic states which correspond
to “phase-locked” torsional motions with quasiperiodic oscillations. Our
estimates show that these effects can be observed in experiments with
moderate magnetic fields.
DY 11.6 Mo 11:45 H3
The dispersions relation of surface waves on ferrofluids - an
experimental investigation — •Jan Embs — Universität des Saarlandes,
FR 7.3 Technische Physik
The surface of a ferrofluid undergoes a spontaneous instability [1] in a
static magnetic field oriented perpendicular to the surface. The new configuration
consists of�a hexagonal arrangement of peaks, with the critical
wave number kc =
ρg0/σ (ρ mass density, σ surface tension of the
ferrofluid and g0 ). This behavior may be understood in terms of the dispersion
relation ω 2 0(k) of free surface waves: if the magnetization reaches
a certain value, the dispersion relation becomes non-monotonic with a
local minimum and an anomalous dispersion branch; when the minimum
reaches the ω 2 0 = 0-axis at k = kc , the so-called Rosensweig instability
occurs. In my talk I will show how the anomalous dispersion branch can
be measured by generating surface waves due to the Faraday instability.
Furthermore it is possible to prepare experimentally situations in which
both instabilities occur simultaneously; in these bi-critical situations new
and interesting patterns can be observed.
[1] M. D. Cowley, R. E. Rosensweig, J. Fluid. Mech. 30, 671 (1967)

Dynamik und Statistische Physik Montag
DY 12 Dynamical Phenomena
Zeit: Montag 11:30–13:00 Raum: H2
DY 12.1 Mo 11:30 H2
Out-of-equilibrium critical dynamics at surfaces: Cluster dissolution
and non-algebraic correlations — •Michel Pleimling 1
and Ferenc Iglói 2,3 — 1 Institut für Theoretische Physik I, Universität
Erlangen-Nürnberg, D-91058 Erlangen — 2 Research Institute for Solid
State Physics and Optics, P.O.Box 49, H-1525 Budapest — 3 Institute of
Theoretical Physics, Szeged University, H-6720 Szeged
We study nonequilibrium dynamical properties at free surfaces after
the system is quenched from the high-temperature phase into the critical
point. We show that if the spatial surface correlations decay sufficiently
rapidly the surface magnetization and/or the surface manifold correlations
have a qualitatively different universal short time behavior than the
same quantities in the bulk. At a free surface cluster dissolution may take
place instead of domain growth and as a result dynamical correlations
decay in a non-algebraic, stretched exponential form. This phenomenon
takes place in the three-dimensional Ising model and should be observable
in real ferromagnets.
DY 12.2 Mo 11:45 H2
Paradoxical non-linear response of a Brownian particle — •Ralf
Eichhorn and Peter Reimann — Universität Bielefeld, Fakultät für
Physik, D-33615 Bielefeld
We consider a single, classical Brownian particle in a periodic potential
landscape far from thermal equilibrium, that shows the following remarkable
response behavior to an external static force: Though the system is
far from equilibrium, its linear response is exactly the same as in the
equilibrium case; in particular, the particle motion follows the direction
of the external static force. However, upon increasing the static force to
the non-linear response regime, the particle suddenly starts to move in
the direction opposite to the static bias. These astonishing properties of
our system are investigated analytically and numerically.
DY 12.3 Mo 12:00 H2
Novel universality classes of a coupled driven diffusive system
— •Abhik Basu and Erwin Frey — Abteilung Theorie (SF5), Hahn-
Meitner-Institute, D-14109 Berlin
Motivated by the phenomenologies of dynamic roughening of strings
in random media and magnetohydrodynamics, we examine the universal
properties of driven diffusive system with coupled fields. We demonstrate
that cross-correlations between the fields lead to amplitude-ratios and
scaling exponents varying continuosly with the strength of these cross-
DY 14 Solitons and Stochastic Dynamics
correlations. The implications of these results for experimentally relevant
systems are discussed.
DY 12.4 Mo 12:15 H2
Critical Behavior of Coupled Oscillators. Renormalization
Group and Universality Class. — •Thomas Risler 1 , Jacques
Prost 2 , and Frank Jülicher 1 — 1 Max-Planck-Institut für Physik
komplexer Systeme, Nöthnitzer Str. 38, D-01187 Dresden. — 2 Ecole
Supérieure de Physique et de Chimie Indutrielles, 10 rue Vauquelin,
75231 Paris Cedex 05, France.
We study the behavior of coupled oscillators in the vicinity of a uniform
oscillatory instability or Hopf bifurcation in the presence of fluctuations.
A Hopf bifurcation is an example for a dynamic critical point.
The corresponding field theory is described by a complex Ginzburg Landau
equation with noise. We apply perturbative renormalization group
techniques in a 4 − ǫ dimensional space and find that the critical behavior
is related to the fixed point of the dynamic O(2) model. While the
dynamics is far from equilibrium and breaks the fluctuation dissipation
theorem, a universal relation between correlation and response exists at
the critical point.
Hauptvortrag DY 12.5 Mo 12:30 H2
Local scale invariance in ageing phenomena — •Malte Henkel
— Laboratoire de Physique des Matériaux, Université Henri Poincaré
Nancy I, B.P. 239, F - 54506 Vandœuvre-lès-Nancy, France
The temporal behaviour of ageing systems is described by the two-time
correlators C(t, s) and the response function R(t, s), where t is the observation
time and s is the waiting time. The dynamical scaling in ageing
systems leads to the scaling form R(t, s) = s −1−a f(t/s). The extension of
dynamical scaling to a local scale invariance, in close analogy to conformal
invariance, is studied. In particular, if the dynamical exponent z = 2,
we show that through a Ward identity, Galilei invariance implies local
scale invariance. This in turn leads to an explicit form of f(x), which is
tested via extensive simulation in the ageing 2D/3D Glauber-Ising model.
This provides the first evidence for Galilei invariance in an ageing
system. In addition, local scale invariance allows to reliably extract the
exponent a from integrated response functions (dynamical susceptibilities).
[1] M. Henkel, Nucl. Phys. B641, 405 (2002). [2] M. Henkel, J.
Unterberger, Nucl. Phys. B660, 407 (2003) [3] M. Henkel, M. Pleimling,
Phys. Rev. E, cond-mat/0302482 [4] M. Henkel, M. Paessens, M.
Pleimling, Europhys. Lett. 62, 664 (2003) and cond-mat/0310761.
Zeit: Montag 14:30–16:45 Raum: H2
DY 14.1 Mo 14:30 H2
Investigation of the dynamics of dissipative solitons using
stochastic data analysis — •Hendrik U. Bödeker 1 , Andreas W.
Liehr 1 , Till D. Frank 2 , Rudolf Friedrich 2 , and Hans-Georg
Purwins 1 — 1 Westfälische Wilhelms-Universität Münster, Institut für
Angewandte Physik, Corrensstr. 2/4, 48149 Münster — 2 Westfälische
Wilhelms-Universität Münster, Institut für Theoretische Physik,
Wilhelm-Klemm-Str. 9, 48149 Münster
We develop methods to analyze the dynamics and the interaction of dissipative
solitons in the form of localized current filaments under the influence
of strong fluctuations in a quasi-2-dimensional planar gas-discharge
system with high-ohmic barrier. The form of the experimentally recorded
trajectories motivates a modelling of the dynamics by stochastic differential
equations in the form of Langevin equations. Methods of stochastic
data analysis allow for a quantitative separation of the deterministic and
the stochastic part of the dynamics of isolated dissipative solitons from
the recorded data series. In this case, both intrinsically stationary and intrinsically
propagating solitons can be found. The transition takes place
via a supercritical bifurcation with a typical scaling law. This is also the
result of theoretical predictions. An extension of the Langevin equations
by generalized interaction forces enables the description of interaction
processes between several filaments. The determination of the interaction
function of mutually interacting dissipative solitons from experimentally
recorded data series reveals a distance-dependent interaction law with
varying regions of attraction and repulsion.
DY 14.2 Mo 14:45 H2
Vielteilchen-Phänomene in Reaktions-Diffusions-Systemen —
•A. W. Liehr, M. C. Röttger und H.-G. Purwins — Westfälische
Wilhelms-Universität Münster, Institut für Angewandte Physik, Corrensstr.
2/4, 48149 Münster
Dissipative Solitonen sind großamplitudige lokalisierte Strukturen mit
ausgeprägten Teilcheneigenschaften, die in diesem Beitrag anhand eines
dreikomponentigen Reaktions-Diffusions-Systems untersucht werden.
In der Nähe der Drift-Bifurkation kann die Dynamik und Wechselwirkung
der dissipativen Solitonen mittels einen Teilchenansatzes durch
Ordnungsparametergleichungen beschrieben werden, wobei als relevante
Größen die Positionen und die Propagatormodenamplituden der dissipativen
Solitonen erfasst werden [1]. Dies ermöglicht die Untersuchung
von Vielteilchensystemen, für die wir charakteristische Phänomene wie
Kompressionsfronten in kondensierten Phasen oder das Auflösen kondensierter
Phasen durch Rauscheinfluss diskutieren.
[1] Bode, M. et al.: Interaction of dissipative solitons: particle-like behaviour
of localized structures in a three-component reaction-diffusion system. Physica
D 161, 2002, S. 45ff.

Dynamik und Statistische Physik Montag
DY 14.3 Mo 15:00 H2
On a Fokker-Planck perspective of stochastic systems with delay
— •Till Frank — Institute for Theoretical Physics, University of
Münster,Wilhelm-Klemm-Str. 9, 48149 Münster, Germany
We will describe non-Markov processes defined by stochastic delay
differential equations from the perspective of Fokker-Planck equations.
First, we will derive a multivariate Fokker-Planck equation for stochastic
processes with delay. Second, it will be shown how to derive the delay
Fokker-Planck equation proposed by Guillouzic et. al. from this multivariate
Fokker-Planck equation. Third, we will derive the exact stationary
solution of a linear stochastic delay equation. Finally, we will briefly
address the issue of data analysis for stochastic delay systems. (S. Guillouzic
et al., Phys. Rev. E 59 (1999) 3970; T.D. Frank and P.J. Beek,
PRE 64 (2001) 021917; T.D. Frank, PRE 66 (2002) 011914; T.D. Frank
et al. PRE 68 (2003) 021912)
DY 14.4 Mo 15:15 H2
Path Integral Solutions for Continuous Time Random Walks
— •Adrian Baule — Institut für theoretische Physik, Westfälische
Wilhelms-Universität, 48149 Münster
Continuous time random walks are successful in modelling the stochastic
process underlying the velocity statistics of turbulence in a lagrangian
framework. Recent experimental results motivate the investigation of two
point probability density functions of the velocity increments. The knowledge
of the joint probability distributions is required for definitely assessing
the stochastic process of lagrangian motions. A path integral formulation
of continuous time random walks is introduced and solutions are
presented.
DY 14.5 Mo 15:30 H2
Probabilistic Description of Traffic Flow — •Reinhard
Mahnke 1 , Jevgenijs Kaupuˇzs 2 , and Ihor Lubashevsky 3 — 1 FB
Physik, Univ. Rostock, D–18051 Rostock — 2 Univ. Latvia, LV–1459
Riga, Latvia — 3 Physics Inst., Russian Acad. Sc., Moscow, Russia
A stochastic description of traffic flow, called probabilistic traffic flow
theory, is developed. The general master equation is applied to relatively
simple models to describe the formation and dissolution of traffic congestions.
Our approach is mainly based on spatially homogeneous systems
like periodically closed circular rings without on– and off–ramps. We consider
a stochastic one–step process of growth or shrinkage of a car cluster
(jam). As generalization we discuss the coexistence of several car clusters
of different sizes. The basic problem is to find a physically motivated
ansatz for the transition rates of the attachment and detachment of individual
cars to a car cluster consistent with the empirical observations
in real traffic. The emphasis is put on the analogy with first–order phase
transitions and nucleation phenomena in physical systems like supersaturated
vapour. The results are summarized in the flux–density relation,
the so–called fundamental diagram of traffic flow, and compared with
empirical data. Different regimes of traffic flow are discussed: free flow,
congested mode as stop–and–go regime, and heavy viscous traffic. The
traffic breakdown is studied based on the master equation as well as
the Fokker–Planck approximation to calculate mean first passage times
or escape rates. In conclusion, the calculated flux–density relation and
characteristic breakdown times coincide with empirical data measured
on highways.
DY 14.6 Mo 15:45 H2
The Totally Asymmetric Exclusion Process with Langmuir Kinetics
— •Thomas Franosch, Andrea Parmeggiani, and Erwin
Frey — Hahn-Meitner Institut
We discuss a new class of driven lattice gases obtained by coupling
the one-dimensional totally asymmetric exclusion process to Langmuir
kinetics. In the limit where these dynamics compete, the resulting nonconserved
flow of particles on the lattice leads to stationary regimes for
large but finite systems. We observe unexpected properties such as localized
boundaries (domain walls) that separate coexisting regions of
low and high density of particles (phase coexistence). We rationalize the
findings for the average density and current profiles obtained from simulations
within a mean-field approach in the continuum limit. The ensuing
analytic solution is expressed in terms of Lambert W-functions. It allows
to fully describe the phase diagram and to extract unusual mean-field
exponents that characterize the critical properties of the domain wall.
DY 14.7 Mo 16:00 H2
Lattice models for movements of molecular motors — •Stefan
Klumpp and Reinhard Lipowsky — Max-Planck-Institut für Kolloidund
Grenzflächenforschung, 14424 Potsdam
Movements of molecular motors which bind to and unbind from cytoskeletal
filaments can be studied using lattice models. Motors bound
to filaments perform biased random walks, while unbound motors perform
symmetric random walks. Motor–motor interactions such as mutual
exclusion from binding sites of the filaments are easily incorporated into
these models, which then represent new variants of driven lattice gas
models or exclusion processes, where the driving is localized to the filaments.
These models exhibit stationary states characterized by traffic jams
and by the coexistence of a crowded region with a low density region
[1] and boundary-induced phase transitions related to those of the onedimensional
asymmetric simple exclusion process [2].
[1] R. Lipowsky, S. Klumpp, and T. M. Nieuwenhuizen, Phys. Rev. Lett.
87, 108101 (2001).
[2] S. Klumpp and R. Lipowsky, J. Stat. Phys. 113, 233 (2003).
DY 14.8 Mo 16:15 H2
Noise induced oscillations in resonant tunneling structures —
•Grischa Stegemann and Eckehard Schöll — Institut für Theoretische
Physik, Technische Universität Berlin, 10623 Berlin, Germany
The presence of noise can strongly affect the behaviour of (deterministic)
dynamical systems. In particular we study noise induced current oscillations
in the double barrier resonant tunneling diode using a reactiondiffusion
model. Oscillating spatio-temporal patterns corresponding to
breathing current filaments may be induced in a regime where the deterministic
system does not exhibit self-sustained oscillations.
DY 14.9 Mo 16:30 H2
Consequences of coarse grained Vlasov equations — •K.
Morawetz 1,2 and R. Walke 3 — 1 Institute of Physics, Chemnitz
University of Technology, 09107 Chemnitz, Germany — 2 Max Planck
Institute for the Physics of Complex Systems, Nöthnitzer Str. 38, 01187
Dresden, Germany — 3 Max-Planck-Institute for demographic research,
Rostock, Germany
The Vlasov equation is analyzed for coarse grained distributions resembling
a finite width of test-particles as used in numerical implementations.
It is shown that this coarse grained distribution obeys a kinetic equation
similar to the Vlasov equation, but with additional terms. These terms
give rise to entropy production indicating dissipative features due to a
nonlinear mode coupling The interchange of coarse graining and dynamical
evolution is discussed with the help of an exactly solvable model for
the selfconsistent Vlasov equation and practical consequences are worked
out. The condition for approaching a stationary solution is derived. Observable
consequences of this coarse graining are: (i) spatial correlations
in observables, (ii) too large radii of clusters or nuclei in self-consistent
Thomas-Fermi treatments, (iii) a structure term in the response function
resembling vertex correction correlations or internal structure effects and
(iv) a modified centroid energy and higher damping width of collective
modes.
[1] K. Morawetz, R. Walke, Physica A 330/3-4 (2003) 475–501

Dynamik und Statistische Physik Montag
DY 15 Fluids I
Zeit: Montag 14:30–16:15 Raum: H3
DY 15.1 Mo 14:30 H3
Different Modes of Spinodal Dewetting in a Two-Layer system
— •Andrey Pototsky 1 , Michael Betsehorn 1 , Domnic Merkt 1
und Uwe Thiele 2 — 1 Lehrstuhl fuer Theoretische Physik II, BTU Cottbus,
Erich-Weinert Str. 1, D-03046 Cottbus, Germany — 2 MPI komplexer
Systeme, Noethnitzer Str. 38, D-01187, Dresden, Germany
We consider two ultra thin layers of different liquids on a solid substrate.
Using long wave theory coupled evolution equations for the free
liquid-liquid and liquid-gas interfaces are derived taken into account nonretarded
Van der Waals forces. Analisis of their linear and non-linear behavior
shows that, both, varicose and zigzag modes can be unstable and
lead to film rupture at the inner interface or substrate. The results are
exemplified using a Si/PS/PMMA/air system.
DY 15.2 Mo 14:45 H3
Dynamics of self-excited droplet oscillations in electrowetting
— •Jean-Christophe Baret 1,2 , Dagmar Steinhauser 1 , Ralf
Seemann 1 , Stephan Herminghaus 1,3 , and Frieder Mugele 1
— 1 Universitaet Ulm, Abt. Angewandte Physik, D-89069 Ulm —
2 Philips Research, Eindhoven (NL) — 3 Max Planck Institut fuer
Stroemungsforschung, D-37018 Goettingen
Under suitable conditions, liquid droplets in electrowetting experiments
can perform self-excited oscillations, as shown recently in Ref.
1. Here, we present an extension of these previous experiments to higher
and much better defined oscillation frequencies. We deposited droplets
of a conductive liquid (≈ 1 nl) on top of a Si wafer, with an insulation
layer (1 µm SiO2) and a monolayer of octadecyltrichlorosilane. We applied
an AC voltage (10 kHz) between the substrate and a Pt wire that
was immersed into the droplet at a distance d above the surface. Upon
increasing the voltage U from zero to 100 V, the contact angle decreased
from 130 deg to 70 deg. If d was chosen close to the height of the droplet
at zero voltage, the droplet detached from the Pt wire upon increasing
the voltage. Within a certain range of d and U, droplets periodically
jumped on and off the wire. The oscillation frequency varied between 50
Hz and 120 Hz for droplet sizes between 1mm and 0.1mm. Close to the
critical values of d and U, where the oscillations cease, we found chaotic
behavior. Furthermore, we demonstrate microfluidic mixing in oscillating
droplets.
(1) A. Klingner, S. Herminghaus, and F. Mugele, Appl. Phys. Lett. 82,
4187 (2003)
DY 15.3 Mo 15:00 H3
Holes and fingers in vertically vibrated aqueous suspensions.*
— •Florian S. Merkt 1,2 , Robert D. Deegan 1 , Daniel I. Goldman
1 , Erin C. Rericha 1 , and Harry L. Swinney 1 — 1 University of
Texas at Austin — 2 presently at the Fritz-Haber-Institut der MPG
We have observed stable holes in a sinusoidally oscillated 0.5 cm deep
aqueous suspension of cornstarch for accelerations a above 10g and frequencies
of 50-200 Hz. Holes appear only if a finite perturbation is applied
to the layer. They are circular and approximately 0.5 cm wide and can
persist for more than 10 5 oscillation periods. Above a ≈ 17g the rim
of the hole becomes unstable producing finger-like protrusions or hole
division. At even higher accelerations, the hole delocalizes and grows to
cover the entire surface with erratic undulations. We have found similar
behavior in an aqueous suspension of glass microspheres and argue that
shear thickening fluids in general exhibit these patterns.
*Supported by DOE Grant DE-FG03-93ER14312
DY 15.4 Mo 15:15 H3
On the formation of the primary bead in the droplet detachment
process of an elastic liquid — •Christian Wagner 1 ,
Yacine Amarouchene 2 , Daniel Bonn 2 , and Jens Eggers 3 —
1 Experimentalphysik, Universität des Saarlandes, Postfach 151150, 66041
Saarbrücken, Germany — 2 Laboratoire de Physique Statistique, UMR
CNRS 8550, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris
Cedex 05, France — 3 School of Mathematics, University of Bristol, University
Walk Bristol BS8, 1TW United Kingdom
The droplet detachment process of an elastic liquid is characterized
by the suppression of the finite time singularity and appearance of a
cylindrical filament between the droplet and the nozzle. Synchronously
to the appearance of the filament secondary droplets, so called beads
on the string can be observed too. Most reports concern the appearance
of beads at the final stage of the droplet detachment process but under
certain conditions they are to observe from the beginning of the filament
forming process. In this study we present the phase boundaries for these
beads. Their appearance is connected with a transition from a symmetric
to an asymmetric shape of the droplet neck in the Newtonian regime
before the onset of the elastic behavior. This transition is is properly
described with a crossover from the symmetric instability solution of the
pending droplet to a self similar solution for the pinch of behavior of low
viscous Newtonian liquids and the phase boundaries are determined by
the ratio of the elongational rate and the Reynoldsnumber.
DY 15.5 Mo 15:30 H3
Phase-field model for evaporation with convection in two-layer
systems — •Rodica Borcia and Michael Bestehorn — Lehrstuhl
für Theoretische Physik II, Brandenburgische Technische Universität
Cottbus, Erich-Weinert-Straße 1, 03046, Cottbus, Germany
We propose a phase-field model for analyzing the influence of evaporation
phenomenon on Marangoni convection in liquid-vapor systems. The
phase-field model treats the problem continuously (all the system parameters
vary continuously from one medium to another), and avoids interface
conditions. Therefore, evaporation with convection in multi-layers
structures can be discussed in a more natural way. The theoretical description
is based on the Navier-Stokes equation with some extra-terms
responsible for describing Marangoni convection [1], the heat equation
with a supplementary term responsible for describing evaporation phenomena
[2], and the continuity equation. We report on two-dimensional
simulations for both Marangoni instabilities in linear approximation and
we compare the results with the literature.
[1] R. Borcia, M. Bestehorn, Phys. Rev. E 67, 066307 (2003).
[2] R.J. Braun, B.T. Murray, J. Cryst. Growth 174, 41 (1997).
DY 15.6 Mo 15:45 H3
Schwingungsverhalten und innere Strömung bei verdampfenden
Wassertropfen — •Frank Rietz, Wolfgang Jantoß und
Stefan C. Müller — Universität Magdeburg, Fakultät für Naturwissenschaften,
Abteilung Biophysik
Wird eine kleine Menge Wasser auf eine heiße Platte gegeben, so
schwebt der sich bildende Tropfen aufgrund des Leidenfrost-Effekts.
Dies ist jedem bekannt. Dass sich aber unter bestimmten Bedingungen
faszinierende Strukturbildungsphänomene des Wassertropfens beobachten
lassen, entzieht sich der allgemeinen Kenntnis. Es entstehen
nämlich sternförmige Oszillationen, die durch Schwankungen der Oberflächenspannung
und des Temperaturgradienten angeregt werden. Der
Tropfen kann mit bis zu 4 cm Durchmesser in zahlreichen Moden schwingen,
deren Kenngrößen vorgestellt werden sollen. Neben diesen Ergebnissen
liegt das Augenmerk auf die durch Particle Image Velocimetry beobachtbare
Konvektion im Inneren des Tropfens. Die zugrunde liegenden
Mechanismen verleiten zu dem Schluss, die Schwingungen in Zusammenhang
mit der Marangoni-Instabilität zu betrachten.
DY 15.7 Mo 16:00 H3
Dynamics in spatially confined dipolar liquids — •Sabine H.L.
Klapp — Stranski-Laboratorium für Physikalische und Theoretische
Chemie, Sekr. TC 7, Fakultät II, Technische Universität Berlin, Straße
des 17 Juni 124, 10623 Berlin, Germany
Based on Molecular Dynamics simulations we investigate the interplay
between static and dynamic properties of confined films of simple dipolar
fluids, which can be considered as model systems for confined polar
liquids or ferrocolloid films. Previous Monte Carlo studies (1,2) on such
systems have shown that the specific properties of dipolar interactions,
combined with the presence of confining walls, yields interesting orientational
effects such as wall–induced chain formation in the contact layer
and spontaneous global polarization at pressures lower than in the bulk.
Here we discuss the implications of these features on translational and
rotational time correlation functions and on resulting transport coefficients.
1) S. H. L. Klapp and M. Schoen, J. Chem. Phys. 117, 8050 (2002).
2) S. H. L. Klapp and M. Schoen, in press (2003).

Dynamik und Statistische Physik Montag
DY 16 Phase Transitions
Zeit: Montag 16:45–18:00 Raum: H2
DY 16.1 Mo 16:45 H2
Vortex Loop Percolation in XY and Ginzburg-Landau Model —
•Axel Krinner, Elmar Bittner, and Wolfhard Janke — Institut
für Theoretische Physik, Universität Leipzig, Augustusplatz 10/11,
04109 Leipzig, Germany
We study the geometrically defined vortex network in the vicinity of
the critical point in the XY and Ginzburg-Landau model. Using highprecision
Monte Carlo techniques we consider the alternative formulation
of the geometrical excitations in relation to the global O(2)-symmetry
breaking, and check if both of them exhibit the same critical behaviour
leading to a consistent description of the phase transition. Different percolation
observables are taken into account and compared with each other.
DY 16.2 Mo 17:00 H2
Equilibrium Crystal Shapes in Three Dimensions — •Andreas
Nußbaumer, Elmar Bittner, and Wolfhard Janke — Institut
für Theoretische Physik, Universität Leipzig, Augustusplatz 10/11, 04109
Leipzig, Germany
The multimagnetic algorithm simulates an artifical ensemble where every
value of the magnetisation has the same probability. Still, simulations
of simple models show barriers in the magnetisation that scale with the
inverse temperature β and the system size L. Making use of analytic
work by Leung and Zia [1], Neuhaus and Hager [2] recently explained
this behaviour in the case of the two-dimensional Ising model with the
occurrence of a geometrically induced first-order transition from a droplet
to a strip domain.
Using Fourier coefficients to define the geometric anisotropy of a configuration
a comparison with an analytical description of the transition
behaviour (deformation of a droplet into a stripe) was possible. From the
scaling of the anisotropy for different system sizes when simulated with
Kawasaki dynamics (M = const.) a value for the barrier size was obtained.
For the three-dimensional case a set of new transitions could be
identified and the crystal shapes during the transitions were measured.
[1] K. Leung and R. Zia, Geometrically induced transitions between equilibrium
crystal shapes, J. Phys. A 23, 4593 (1990).
[2] T. Neuhaus and J. Hager, 2D crystal shapes, droplet condensation,
and exponential slowing down in simulations of first-order phase transitions,
Stat. Phys. 113, 47 (2003).
DY 16.3 Mo 17:15 H2
The Harris-Luck Criterion for Random Lattices — •Wolfhard
Janke and Martin Weigel — Institut für Theoretische Physik, Universität
Leipzig, Augustusplatz 10/11, 04109 Leipzig, Germany
The Harris-Luck criterion judges the relevance of (potentially) spatially
correlated, quenched disorder induced by, e.g., random bonds, randomly
diluted sites or a quasi-periodicity of the lattice, for altering the critical
behavior of a coupled statistical mechanics system. We investigate the
applicability of this type of criterion to the case of spin variables coupled
to random lattices. Their aptitude to alter critical behavior depends
on the degree of spatial correlations present, which is quantified by a
wandering exponent. We consider the cases of Poissonian random graphs
resulting from the Voronoï-Delaunay construction and of planar, “fat” φ 3
DY 17 Fluids II
Feynman diagrams and precisely determine their wandering exponents.
The resulting predictions are compared to various exact and numerical
results for the Potts model coupled to these quenched ensembles of random
graphs.
[1] W. Janke and M. Weigel, The Harris-Luck criterion for random lattices,
Leipzig preprint LU-ITP 2003/021, e-print cond-mat/0310269.
DY 16.4 Mo 17:30 H2
On the Structure of Microcanonical Entropy Surfaces of Finite
Systems — •Hans Behringer — Institut für Theoretische Physik
I, Universität Erlangen-Nürnberg, Staudtstrasse 7, D - 91058 Erlangen,
Germany
The basic quantity in the microcanonical approach to statistical properties
of magnetic systems is the entropy S(E, M) = ln Ω(E, M) where
Ω(E, M) is the density of states. The spontaneous magnetization and
the response functions like the magnetic susceptibility and the specific
heat are obtained from the curvature properties of the entropy surface.
Even for finite system sizes they show features which are typical of phase
transitions. The appearance of classical exponents characterising the singularities
of thermostatic quantities of finite systems can be understood
from the analyticity of the entropy surface. Symmetry properties of the
microcanonical entropy are deduced directly from the invariance group
of the Hamiltonian. These properties allow further general statements on
the global structure of the entropy surface.
[1] H.Behringer, Symmetries of Microcanonical Entropy Surfaces, J.
Phys. A: Math. Gen. 36, 8739 (2003)
[2] H.Behringer, Microcanonical Entropy for Small Magnetisations, to
appear in J. Phys. A, preprint cond-mat/0311211
DY 16.5 Mo 17:45 H2
Performance Limitations of Flat Histogram Methods — •Simon
Trebst — Theoretische Physik, Eidgenoessische Technische Hochschule
Zuerich, CH-8093 Zuerich, Schweiz
We determine the optimal scaling of local-update flat-histogram methods
with system size by using a perfect flat-histogram scheme based upon
the exact density of states of 2D Ising models. The typical tunneling time
needed to sample the entire bandwidth does not scale with the number of
spins N as the minimal N 2 of an unbiased random walk in energy space.
While the scaling is power law for the ferromagnetic and fully frustrated
Ising model, for the ±J nearest-neighbor spin glass the distribution of
tunneling times is governed by a fat-tailed Fréchet extremal value distribution
that obeys exponential scaling. The shape parameter of these
distributions furthermore indicate that statistical sample means become
ill-defined already for moderate system sizes within these complex energy
landscapes. We discuss ways to overcome these limitations by improved
sampling mechanisms.
References: P.Dayal, S.Trebst, S.Wessel, D.Wurtz, M.Troyer,
S.Sabhapandit, S.N.Coppersmith, cond-mat/0306106, accepted for publication
in Phys. Rev. Lett.
Zeit: Montag 16:30–18:00 Raum: H3
DY 17.1 Mo 16:30 H3
Raumzeitliches Verhalten zweier nichtmischbarer
Flüssigkeitsfilme — •Domnic Merkt 1 , Andreij Pototsky 1 ,
Michael Bestehorn 1 und Uwe Thiele 2 — 1 Erich-Weinert-Strasse
1, 03046 Cottbus — 2 Nöthnitzer Strasse 38, 01187 Dresden
Zwei nichtmischbare, dünne Flüssigkeitsschichten, begrenzt durch feste
Ränder, können durch eine Evolutionsgleichung der Grenzfläche
der beiden Flüssigkeiten beschrieben werden (Schmiermittelnäherung).
Die Mobilitäten dieser Gleichung haben eine grundlegend andere und
kompliziertere Form als die Mobilitäten der ausführlich untersuchten
Dünnfilmgleichungen eines einzelnen Fluids. Die Möglichkeiten auftretender
Instabilitäten werden durch diese Mobilitäten, bedingt durch Materi-
alparamter, vergrössert. Es wird der Einfluss verschiedener, auf das System
wirkender Kräfte vorgestellt (Gravitation, Marangonieffekt). Neben
linearen Untersuchungen werden auch Langzeitentwicklungen der vollen
nichtlinearen Gleichung gezeigt.
DY 17.2 Mo 16:45 H3
Shape transformations of fluid micrustructures induced by electrowetting
— •Anke Klingner, Renate Nikopoulos, Juergen
Buehrle, Stephan Herminghaus und Frieder Mugele — Universitaet
Ulm, Abt. Angewandte Physik, Albert-Einstein-Allee 11, D-89081
Ulm
A growing number of applied sciences as DNA analysis and proteomics
are in need of microfluidic devices, which are able to control small

Dynamik und Statistische Physik Montag
amounts of liquid. We used the electrowetting effect in order to manipulate
liquid droplets. The droplets were placed either on top of a single
substrate with a stripe electrode, or between two substrates with stripe
electrodes on each side. We studied systematically the behaviour of
the liquid as a function of the applied voltage, the substrate separation,
and the relative orientation of opposed stripe electrodes. The experimental
results are compared to both a simple analytical model as well as
numerical calculations using the Surface Evolver.
DY 17.3 Mo 17:00 H3
Statistische Eigenschaften eines Punktwirbelmodells für die
zweidimensionale Turbulenz — •Oliver Kamps und Rudolf
Friedrich — Institut für Theoretische Physik der Universität Münster,
Wilhelm-Klemm-Strasse 9, 48149 Münster
Ausgehend von einer Punktwirbelbeschreibung einer getriebenen zweidimensionalen
Strömung werden statistische Eigenschaften der Lagrangeschen
Flüssigkeitsdynamik numerisch untersucht. Im Zentrum des Interesses
stehen die Lagrangeschen Wahrscheinlichkeitsverteilungen für Ort
und Geschwindigkeit
DY 17.4 Mo 17:15 H3
Thermal noise in thin liquid films — •Markus Rauscher 1,2 ,
Klaus Mecke 1,2 , and Günther Grün 1,2 — 1 Max-Planck-Institut für
Metallforschung, Stuttgart — 2 ITAP, Universität Stuttgart
Thermal noise becomes more and more important the smaller a system
is. Recent studies of thin film evolution indicate that thermal noise
might influence characteristic time-scales of film dewetting [J. Becker et
at., Nature Materials Vol. 2, 59 (2003)]. Up to now, thin film flow was
only studied with deterministic equations.
We develop a stochastic version of the thin film equation. In the thin
film approximation, the stochastic incompressible hydrodynamic equations
[Landau and Lifshitz, Vol. IV] reduce to the deterministic thin film
equation plus a conserved noise term. We show that the noise term is
consistent with the thermodynamical equilibrium distribution of the film
thickness.
DY 17.5 Mo 17:30 H3
Adsorption of an asymmetric binary mixture at a selective solid
wall — •Dirk Woywod, Jörg Silbermann, and Martin Schoen
— Stranski-Laboratorium für Physikalische und Theoretische Chemie
TU Berlin
Sekretariat TC 7
Strasse des 17.Juni 124
10623 Berlin
DY 20 Fractals and Nonlinearity I
We consider a binary (A-B) mixture fluid near a selective planar homogenous
wall. Using a lattice-gas model and mean-field approximation
to the intrinsic free-energy functional, we obtain a closed expression for
the potential density in the grand canonical ensemble (V, T, µA = µB).
This expression depends on the attraction strength of the fluid-fluid interactions
(ǫAA > ǫBB, ǫAB), the fluid-wall interactions (ǫAW < ǫBW), and
the local densities (ρA, ρB). Minimizing the potential density numerically
gives us access to complete phase diagrams including wetting films [1].
In this presentation, we choose bulk parameters in order to promote the
formation of demixed A-rich liquid phases near coexistence with a gas
phase. Introducing a preference of the wall for molecules of component B,
first-order phase transitions between adsorbed mixed, A-rich and B-rich
films are observed. Besides multiple surface critical points, we also find
a peculiar temperature dependence of the concentration of component B
within a B-rich mixed film.[2]
[1] D. Woywod, M. Schoen, Phys. Rev. E 67, 026122 (2003)
[2] J. Silbermann, D. Woywod, M. Schoen, Phys. Rev E, in press (2003)
DY 17.6 Mo 17:45 H3
Microscopic theory for interfaces of binary liquid mixtures —
•Thorsten Hiester 1,2 and Klaus Mecke 1,2 — 1 Max-Planck-Institut
für Metallforschung, Heisenbergstraße 3, 70569 Stuttgart — 2 Institut
für Theoretische und Angewandte Physik, Pfaffenwaldring 57, 70569
Stuttgart
Binary liquid interfaces, in particular, their nanoscopic structure is still
poorly understood. In addition to capillary waves and density fluctuations
there are simultaneously fluctuations of the composition. Beginning
with a density functional theory for binary mixtures of inhomogeneous
fluids we derive an effective Hamiltonian for interfaces of binary liquid
mixtures beyond the well-known capillary-wave model. Explicit expressions
for the surface tension, the bending ridigities and especially the coupling
constants of compositional capillary waves in terms of two number
densities are obtained. Finally, we make predictions for grazing-incidence
x-ray scattering experiments.
Zeit: Dienstag 09:30–11:15 Raum: H2
Hauptvortrag DY 20.1 Di 09:30 H2
Statistical Physics for Complex Cosmic Structures — •Luciano
Pietronero — Dipartimento di Fisica, Universita’ di Roma La
Sapienza, 00185 - Roma, Italy
The amount of data in the field of astrophysics is growing exponentially
since a few years and it will grow even more in the future. This
situation is producing a dramatic change in which many speculations and
conjectures can finally be tested. This large amount of data permits the
detailed application of concepts from modern statistical physics. For the
galaxy distribution these led to a new general perspective and, in particular,
we presented strong evidence for self-similar and fractal structures
extending to the limits of the data. This led to a large debate in the
field which is nicely described in the recent book: “Discovery of Cosmic
Fractals” by Y. Baryshev and P. Tirikorpi (World Scientific, 2002)
http://www.wspc.com/books/popsci/4896.html. Recently we have extended
the applications of these methods also to the Cosmic Microwave
Background Radiation (which is very smooth) and to the N-body simularions
(which should link the two properties). We provide an overview
of the general situation of a field which represents an ideal playground of
interdisciplinary research between astrophysics and statistical physics.
DY 20.2 Di 10:00 H2
Generalization of Oboukhov’s Model for the Description of
Turbulent Lagrangian Statistics — •Rafaela Hillerbrand and
Rudolph Friedrich — Wilhelm-Klemm-Str. 9, 48149 Münster
Within the Langrangian framework for the description of fluid flows
a model for the stochastic evolution of a particle in a turbulent flow is
introduced. As a fractional Fokker-Planck equation the considered model
takes into account longtime correlations. In this model the Lagrangian
probability distribution function can be stated as an integral transform
of the solution of an ordinary Fokker-Planck equation, where the kernel
of the transformation contains the one-sided Lévy distribution. This
relates the stochastic behavior of a Lagrangian particle to the class of
continuous time random walks.
DY 20.3 Di 10:15 H2
Theoretical and experimental study of feedback-mediated drift
of spiral waves — •Vladimir Zykov and Harald Engel — Technische
Universitaet Berlin, Institut fuer Theoretische Physik, Sekr. PN
7-1, Hardenbergstr. 36, D-10623 Berlin
An efficient method is proposed to determine a velocity field describing
feedback induced drift of spiral waves. This method can be applied to
quite different feedback mechanisms as, for example, the one-channel and
the global feedback. It is shown that a smooth variation of eccentricity of
an elliptical domain subjected to the global feedback induces a cascade
of bifurcations that can drastically change the spiral wave evolution. In
a square shaped domain a set of point attractors appears instead of the
circular resonance attractor typical for a circular domain. These predictions
are in good quantitative agreement with performed numerical integrations
of an excitable reaction-diffusion system and with experimental
data obtained for the light-sensitive Belousov-Zhabotinsky reaction.

Dynamik und Statistische Physik Dienstag
DY 20.4 Di 10:30 H2
Interaction of filaments in an excitable chemical reaction —
•Ulrich Storb 1 , Camilo Rodriguez Neto 2 , Markus Bär 3 , and
Stefan C. Müller 1 — 1 Otto-von-Guericke-Universität, Institut für
Experimentelle Physik, Universitätsplatz 2, D-39106 Magdeburg — 2 Carl
von Ossietzky Universität, Institut für Chemie und Biologie des Meeres,
Carl-von-Ossietzky 9-11, D-26111 Oldenburg — 3 Max-Planck-Institute
für die Physik komplexer Systeme, Nöthnitzer Strasse 38, D-01187 Dresden
Two-dimensional Belousov-Zhabotinsky reaction systems (BZRsystems)
are often dominated by spiral waves, i.e. a spiral shaped reaction
front spatially mediates a certain frequency behavior. In three
dimensions the variety of exhibited wave phenomena is much broader.
Organizing centers of these dynamical structures are phase singularities,
which in three dimensions take the shape of curves (filaments). Along a
filament the spatially distributed oscillations become synchronized. Temporally
and spatially resolved observations of chemical wave structures
are possible by optical tomography. We present results of a study on the
interaction of such vortex like wave structures, resp. their filaments. It
is known that the frequency of a spiral is effected by the presence of
a further phase singularity; the effect thereby depends on the distance
between the spiral cores. In three dimensions the distance between the
organizing centers is not unique, therefore there is a competition of various
frequency determining processes. The result is a complex interaction
which will be reported.
DY 20.5 Di 10:45 H2
Modeling of filament interactions in a three-dimensional excitable
reaction-diffusion system — •Markus Bär 1 , Camilo Rodriguez
Neto 1,2 , Ulrich Storb 3 , and Stefan C. Müller 3 — 1 Max-
Planck-Institute für die Physik komplexer Systeme, Nöthnitzer Strasse
38, D-01187 Dresden — 2 Carl von Ossietzky Universität, Institut für
Chemie und Biologie des Meeres, Carl-von-Ossietzky 9-11, D-26111 Oldenburg
— 3 Otto-von-Guericke-Universität, Institut für Experimentelle
Physik, Universitätsplatz 2, D-39106 Magdeburg
Motivated by recent experiments in a chemical reaction, we study the
interaction of scroll waves, the three dimensional extension of rotating
DY 21 Neural Networks
spirals. Such scroll waves in excitable media possess in any planar cut
through the volume a singularity around which the concentration profile
rotates. The line that connects these centers is known as a filament.
Here, we look at the interaction of corotating and counterrotating nonparallel
filaments in numerical simulations of a generic excitable media,
the Barkley model. In both cases, we observe repulsion and reconnection
of the filaments in the areas where they approach each other closest. The
interaction is accompanied by the generation of a local twisting and bending
of the filament. This effects are explained by a decrease of rotation
frequency around the filament due to local interactions. The bending is
crucial for the unusual reconnection of corotating filaments, which is usually
forbidden by topological arguments. We also discuss related effects
in two-dimensions and three-dimensional heterogeneous media.
DY 20.6 Di 11:00 H2
Detecting non-linearities in data sets. Characterization of
Fourier phase maps using the Weighting Scaling Indices. —
•Roberto Monetti, Wolfram Bunk, Ferdinand Jamitzky,
Christoph Raeth, and Gregor Morfill — CIPS, Max-Planck-Inst.
f. extraterr. Physik, Gaching
The analysis of the linear properties (LP) (power spectrum, etc) is the
first step in the characterization of data sets. However, given an image
for instance one can generate a new one by shuffling the Fourier phases.
The new image looks different though the phase shuffling process keeps
the LP. Then, the Fourier phases contain information beyond the LP
called non-linear properties (NLP). A challenging problem is the characterization
of the information contained in the Fourier phases. We present
a method to detect NLP in arbitrary data sets. With a set of Fourier
phases {φ� k } and a phase shift � ∆, we represent the phase information on
a 2D space via the phase maps M = {(φ� k , φ� k+ � ∆ )}. The information rendered
on this space is analyzed using the spectrum of weighting scaling
indices to detect phase coupling at any scale � ∆. We have applied our
method to the time series of the logarithmic stock returns of the Dow
Jones. Applications to higher dimensional data are straighforward. The
results indicate that the Dow Jones time series exhibits highly significant
signatures of a strong non-linear behavior.
Zeit: Dienstag 10:15–11:30 Raum: H3
DY 21.1 Di 10:15 H3
Localized solutions in neural fields — •Hecke Schrobsdorff,
Michael Herrmann, and Theo Geisel — MPI für
Strömungsforschung und Institut für Nichtlineare Dynamik der
Universität Göttingen, Bunsenstr. 10, D-37073 Göttingen
Neural fields provide a macroscopic description of the dynamics of activations
in a layer of neurons. For one-dimensional layers the neural field
equation has been solved virtually completely in an elegant way [1] . For
the two-dimensional problem most work has been devoted to spatially
extended solutions. While being the point of main interest in [1], localized
solutions have been treated analytically only for the trivial case of
concentric configurations subject to circular perturbations [2] . Although
we can provide numerical evidence for the stable solutions being indeed
concentric, a general analytical proof of this fact seems very difficult. In
this contribution we simplify the model by the assumption of a specific
form of the interactions. The model shows circular stable solutions and
unstable solution of more complex shapes. Further we discuss applications
of neural fields in neurobiology and robotics.
[1] Amari S (1977) Biol Cybern 27.77-87.
[2] Taylor J (1999) Biol Cybern 80, 393-409.
DY 21.2 Di 10:30 H3
Modelling Brain Function under Noise and Time-Delayed Feedback:
First Results — •Oliver Holzner and Eckehard Schöll
— Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse
36, D–10623 Berlin
Starting from an oscillator model of individual neurons, clusters and
meta-clusters of neurons (inhomogeneous, noisy, with transmission delay,
and asymmetric coupling) will be described, as well as the influence of
time-delayed internal and external feedback on electromagnetic observables.
This type of model is believed to be of clinical relevance, e.g. for
symptom blocking in case of Parkinson’s disease and/or epilepsy.
DY 21.3 Di 10:45 H3
Topological Speed Limits to Network Synchronization — •Marc
Timme, Fred Wolf, and Theo Geisel — Max-Planck-Institut für
Strömungsforschung, Bunsenstr. 10, 37073 Göttingen
Pulse-coupled oscillators constitute a paradigmatic class of dynamical
systems interacting on networks because they model a variety of biological
systems including flashing fireflies and chirping crickets as well as
pacemaker cells of the heart and neural networks. Synchronization is one
of the most simple and most prevailing kinds of collective dynamics on
such networks.
Here we study collective synchronization of pulse-coupled oscillators interacting
on asymmetric random networks. Using random matrix theory
we accurately predict the speed of synchronization in such networks in
dependence on the dynamical and network parameters [1]. As might be
expected, the speed of synchronization increases with increasing coupling
strengths. Surprisingly, however, it stays finite even for infinitely strong
interactions. Our results indicate that the speed of synchronization is
limited by the connectivity of the network.
[1] M. Timme, F. Wolf, and T. Geisel, cond-mat/0306512 (2003).
DY 21.4 Di 11:00 H3
A statistical mechanics approach to approximate analytical
Bootstrap averages — •Dörthe Malzahn 1 and Manfred Opper
2 — 1 Institut für Mathematische Stochastik, Universität Karlsruhe,
76128 Karlsruhe — 2 Neural Computing Research Group, Aston University,
Birmingham B4 7ET, United Kingdom
Information processing systems are often described by models with a
large number of degrees of freedom which interact by a random energy
function. We consider the problem of learning from example data where
the randomness is induced by the data. Bootstrap is a general method
to evaluate the average learning performance. It estimates averages over

Dynamik und Statistische Physik Dienstag
the true data generating distribution (the disorder) by an average over
an ensemble of surrogate data sets which are generated by sampling from
a set of available data. This offers the advantage that the data generating
process is known and can be controlled by the experimenter. Using tools
from the physics of disordered materials, we develop a general framework
to calculate approximate analytical Bootstrap averages. We apply
our method to the Bootstrap of Gaussian process models which can be
understood as (Bayesian) feed-forward neural networks with infinitely
many neurons in the hidden layer. Our method for the analytical calculation
of Bootstrap averages works on real data and yields quantitative
results which are reliable and faster to compute than Monte-Carlo averages.
The results can be used to evaluate and optimize the learning
performance.
DY 21.5 Di 11:15 H3
Strukturen polymer Netzwerke im Vergleich — •Michael Lang,
Dietmar Göritz und Stefan Kreitmeier — Fakultät für Physik,
Universität Regensburg, 93040 Regensburg
DY 22 Fractals and Nonlinearity II
Makroskopische Eigenschaften eines polymeren Netzwerkes werden auf
mikroskopischer Skala durch dessen chemische und topologische Struktur
definiert. Diese Struktur kann insbesondere mit statistischen Methoden
analysiert und beschrieben werden. Dieser Beitrag fokussiert dabei auf die
Unterschiede, die die Verwendung verschiedener Reaktionsmechanismen
bezüglich der entstehenden Struktur zeigen, und die Auswirkungen die
sich auf das Verhalten des Gesamtsystems abschätzen lassen. Die theoretischen
Überlegungen werden dabei durch zusätzliche Simulationen der
Netzwerkbildung ergänzt und gestützt.
Im Einzelnen wird eine allgemeine Theorie zur Beschreibung der Kettenlängen
zwischen den Netzstellen abgeleitet, die Berechnung des Zyklenranges
eines Netzwerkes verallgemeinert, und anschließend die gewonnenen
Ergebnisse für besondere Netzwerktypen im Vergleich vorgestellt.
Unter anderem kann dabei gezeigt werden, daß nahezu ideale endvernetzte
Syteme kaum realisiert werden können, und statistische Vernetzungsreaktionen
deutlich weniger anfällig gegenüber Störungen der
Reaktion sind.
Zeit: Dienstag 11:30–12:30 Raum: H2
DY 22.1 Di 11:30 H2
Noise Induced Transition from Translational to Rotational
Motion of Swarms — •Udo Erdmann 1 , Werner Ebeling 1 ,
and Alexander S. Mikhailov 2 — 1 Institut für Physik, Humboldt-
Universität zu Berlin, Newtonstraße 15, 12489 Berlin — 2 Department of
Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft,
Faradayweg 4-6, 14195 Berlin
We report a new type of noise-induced transition represented by the
exchange of stability between the translational and rotational modes of
a system of Active Brownian particles. Active Brownian particles are a
promising model to resemble the basic features of biological active motion
of swarms. First we discuss the basic model of interacting Active
Brownian particles in two dimensions and introduce the Rayleigh model
of active friction. New solutions for the translational modes are presented
in the deterministic and in the stochastic descriptions. The border of stability
of the translational mode is investigated. A noise induced transition
to the rotational mode is observed and investigated. Finally the theory
is compared with simulations.
DY 22.2 Di 11:45 H2
Neural Cryptography by Synchronisation of Chaotic Maps —
•Wolfgang Kinzel 1 and Ido Kanter 2 — 1 Theoretische Physik, Universität
Würzburg — 2 Theoretical Physics, Bar Ilan Universty, Israel
Synchronisation of neural networks by mutual learning is combined
with synchronisation of chaotic maps by an external signal. Analytical
and numerical calculations show that the security of neural cryptography
is improved by this new mechanism.
Ref.: R. Mislovaty, E. Klein, I. Kanter and W. Kinzel, Phys. Rev. Lett.
91, 118701 (2003)
DY 23 Statistical Physics of RNA
DY 22.3 Di 12:00 H2
Detection of mutual phase synchronization by space-time clustering
— •Axel Hutt — Weierstrass-Institute fuer Angewandte Analysis
und Stochastik, Mohrenstr.39, 10117 Berlin
Recent findings in biomedical signal analysis revealed the importance
of phase synchronization for the understanding of the dynamics of biological
systems. Especially mutual phase synchronization is assumed
to reflect self-organized microscopic behaviour. The talk introduces the
major idea of a novel segmentation algorithm for mutual phase synchronization
in multivariate time series. The major feature is an extention of
the k-means algorithm in the topological plane to the k-means algorithm
on the n-dimensional torus. Applications to coupled chaotic systems and
empirical brain signals demonstrate properties of the method.
DY 22.4 Di 12:15 H2
Propagation von Reaktions-Diffusions-Wellen in einem
Belousov-Zhabotinsky-System mit anomaler Dispersion —
•Niklas Manz und Oliver Steinbock — Department of Chemistry
and Biochemistry, Florida State University, Tallahassee, FL 32306-4390,
USA
Wir präsentieren neuartige Wellendynamiken in einem homogen katalysierten
Reaktions-Diffusions-System mit anomaler Dispersion. In der
verwendeten Belousov-Zhabotinsky-Reaktion wird das klassische organische
Substrat Malonsäure durch 1,4-Cyclohexandion ersetzt. Die nichtmonotone
Dispersionsrelation führt zu Wechselwirkungen zwischen einer
führenden und einer nachfolgenden Welle, die in Systemen mit monoton
steigender Dispersionsrelation nicht zu finden sind. Dieses Verhalten
wird als ”stacking”, ”merging” und ”tracking” bezeichnet. Befindet sich
das System im ”tracking”-Regime ergibt sich ausserdem die Möglichkeit
einer bisher nicht beobachteten Spiraldrift.
Zeit: Dienstag 11:45–13:00 Raum: H3
DY 23.1 Di 11:45 H3
Dependence of the RNA secondary structure from the energy
model — •Bernd Burghardt and Alexander K. Hartmann —
Institut für Theoretische Physik, Universität Göttingen
In the literature mainly two different types of energy models are considered
for RNA secondary structures: On the one hand side every paired
base pair is assigned an energy, on the other hand only so called stacked
base pairs, e.g. two or more consecutive base pairs, are assigned an energy.
We examined a model that uses both types of energy contributions,
and therefore we were able to study the transition from one type of the
above mentioned energy models to the other one. We have done numerical
studies on statistical quantities, where we used algorithms that are able
to calculate the partition function and the ground-state energy exactly
in polynomial time.
DY 23.2 Di 12:00 H3
Bundle Formation of DNA like polyelectrolytes — •Christian
Holm, Hans Jörg Limbach, and Mehmet Sayar — Max-Planck-
Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz
The physics of attractive interactions among like-charged polyelectrolytes
such as biopolymers like DNA and F-actin, as well as synthetic
polymers has been an active area of research in recent years. Such attractive
forces contradict the expectations of mean field theories. These forces
could lead to formation of well-defined nanoscale organizations, and
therefore a through understanding of this mechanism is of fundamental
importance for design and control of biological and synthetic nanoscale
systems. Here, bundle formation in semi-flexible polyelectrolytes with
short ranged hydrophobic interactions is studied via molecular dynamics
simulations. Bundles with finite radial and axial aggregation number
have been observed in experiments conducted on such polyelectrolytes.

Dynamik und Statistische Physik Dienstag
Coarse grained models are utilized for studying the effect of electrostatics
and hydrophobicity on the aggregation behavior of these molecules.
A phase diagram is constructed for these molecules, which clearly shows
that the interplay of electrostatics and hydrophobicity leads to finite size
aggregates.
DY 23.3 Di 12:15 H3
Fractional diffusion model of ion channel gating — •Igor Goychuk
and Peter Hänggi — Institut für Physik, Universität Augsburg,
Germany
We have put forward a fractional diffusion model of ion channel gating
which is capable to explain the origin of non-exponential distributions of
the residence time intervals as they are observed in several types of ion
channels. The model presents a generalization of the discrete diffusion
model by Millhauser, Salpeter and Oswald [Proc. Natl. Acad. Sci. USA
85, 1503 (1988)] to the case of continuous, anomalously slow conformational
diffusion which is described within the mathematical framework
of the fractional diffusion equation approach. Our model contains three
parameters only: the mean residence time, the conformational diffusion
time and the index of fractional diffusion 0 < α ≤ 1. A tractable analytical
expression for the characteristic function of the residence time
distribution is derived which in the normal diffusion case, α = 1, reduces
to our earlier result in [1]. Our new result captures a description of the
residence time distributions that do exhibit a decaying power law in time
with an (negative) exponent that differs from the normal diffusive behavior;
i.e. a value for the exponent given by 3/2. It is shown that depending
on the parameters of the studied model the residence time distribution
DY 24 Dynamic Instabilities in Biophysics
may exhibit up to three characteristic time-regimes: initially a stretched
exponential and then two different power laws.
[1] I. Goychuk and P. Hänggi, Proc. Natl. Acad. Sci. USA 99, 3552 (2002);
Physica A 325, 9 (2003).
Hauptvortrag DY 23.4 Di 12:30 H3
Statistical Physics of RNA Secondary Structures — •Ralf
Bundschuh — Department of Physics, The Ohio State University. 174
West 18th Avenue, Columbus, Ohio 43210-1106, U.S.A.
In addition to its importance for the biological function of RNA
molecules RNA secondary structure formation is an interesting system
from the statistical physics point of view. The ensemble of secondary
structures of random RNA sequences shows a rich phase diagram with
distinct native, denatured, molten, and glassy phases separated by thermodynamical
phase transitions. These phase transitions are driven by
the competition between thermal fluctuations, the disorder frozen into
the specific sequence of a given RNA molecule, and the evolutionary bias
towards the formation of some biologically relevant structure. Yet, in
contrast to the protein folding problem which is driven by very similar
principles and shows a similar phase diagram RNA secondary structure
formation can be represented by a simple diagrammatic language which
allows the application of various analytical and numerical methods. This
makes RNA secondary structure formation an ideal model system for
heteropolymer folding. In the talk, I will characterize and explain the
complex behaviour of RNA folding using several simple models and discuss
possible implications to biological processes.
Zeit: Dienstag 14:30–16:45 Raum: H2
Hauptvortrag DY 24.1 Di 14:30 H2
Physical Aspects of Cell Division — •Karsten Kruse — Max
Planck Institut für Physik komplexer Systeme, Nöthnitzer Str. 38, 01187
Dresden
Cell division is one of the truly fundamental processes in biology and
consists of a highly controlled sequence of dynamic events. However, essential
features of some of these events can be understood as emerging
from dynamic instabilities. Two systems will be presented to illustrate
this point. In the bacterium Escherichia coli, division occurs at the cell’s
center. Selection of the division site relies on pole-to-pole oscillations of
the proteins MinC, MinD, and MinE. In animal cells, division often occurs
off the center. Asymmetric division is achieved by displacing the
mitotic spindle, a bipolar structure of filamentous proteins. This displacement
is accompanied by oscillations of the spindle poles. For both
systems, the oscillations will be shown to result from dynamical instabilities.
These examples suggest, that self-organization is an essential
principle underlying cell division.
DY 24.2 Di 15:00 H2
Barrier crossing of semiflexible polymers — •Pavel Kraikivski,
Jan Kierfeld, and Reinhard Lipowsky — MPI für Kolloid- und
Grenzflächenforschung, 14424 Potsdam
We study the motion of semiflexible polymers in double-well potentials.
We calculate shape, energy, and effective diffusion constant of kink
excitations, and in particular their dependence on the bending rigidity
of the semiflexible polymer. For symmetric potentials, the kink motion is
purely diffusive whereas kink motion becomes directed in the presence of
a driving force on the polymer. We determine the average velocity of the
semiflexible polymer based on the kink dynamics. The Kramers escape
over the potential barriers proceeds by nucleation and diffusive motion of
kink-antikink pairs, the relaxation to the straight configuration by annihilation
of kink-antikink pairs. Our results apply to the activated motion
of biopolymers such as DNA and actin filaments or synthetic polyelectrolytes
on structured substrates.
DY 24.3 Di 15:15 H2
A Continuum Model for Bacterial Ripple Pattern Formation —
•Uwe Börner and Markus Bär — Max-Planck-Institut für Physik
komplexer Systeme, Nöthnitzer Str. 38, 01187 Dresden
We study pattern forming instabilities in a continuum model of coupled
hypberbolic partial differential equations that describe active motion and
chemical interaction between starving myxobacteria. The decisive param-
eter is a refractory time during which bacteria are unable to respond to
signals by other bacteria. It is shown that if the refractory time crosses
a threshold value, an ensemble of bacteria experiences a density instability
that is in line with the characteristic experimental rippling patterns.
Moreover, we show that this instability is robust against the incorporation
of diffusion and compares well to earlier simulation and mean-field
results in the analogous discrete medium.
DY 24.4 Di 15:30 H2
Dynamics of Neurons with Residual Post-Spike Response to
Synaptic Input Currents — •Christoph Kirst, Marc Timme,
and Theo Geisel — Max-Planck-Institut für Strömungsforschung
and Fakultät für Physik, Universität Göttingen, Bunsenstr. 10, 37073
Göttingen
Since the precise timing of spikes is believed to play an important role
for information processing in the brain, many recent studies have been
devoted to the spiking dynamics of neural networks. The response of a
biological neuron to incoming post-synaptic currents strongly depends
on whether or not it has just emitted an action potential (spike). This
effect, however, has so far been neglected in most theoretical studies of
driven single neurons as well as of neural networks, see e.g. [1,2].
Here we investigate the influence of a reduced post-spike neuronal response
in spike-driven neural oscillators. Intriguingly, we find that the
dynamics of a single neuron changes qualitatively, even if an arbitrarily
small fraction of the post-synaptic current is lost due to spike emission.
Implications for the dynamics of networks of neurons are discussed.
[1] K. Pakdaman, Phys. Rev. E 63:041907 (2001).
[2] P.C. Bressloff and S. Coombes, Neural Comput. 12:91 (2000).
DY 24.5 Di 15:45 H2
What Determines the Speed of Neural Processing? — •Björn
Naundorf, Theo Geisel, and Fred Wolf — Max-Planck Institut
für Strömungsforschung and Fakultät für Physik, Universität Göttingen,
37073 Göttingen, Germany
In a generic neuron model, we present the linear response theory for the
firing rate in response to both time dependent input currents and noise
amplitudes. In both cases the signal transmission is strongly attenuated
for frequencies above the stationary firing rate. For high frequencies both
the mean input and the noise transmission function decay as ω −2 , independent
of model details. Moreover we study a sparse two-population
network consisting of inhibitory and excitatory neurons focusing on the

Dynamik und Statistische Physik Dienstag
dependence of the transmission speed on coupling strength.
Our results indicate that previously suggested mechanisms for near instantaneous
transmission of small signals at single neuron level [1,2] are
not consistent with the spike generating mechanism of real neurons.
[1] N.Brunel el al., PRL 86, 2186 (2001)
[2] B.Lindner, and L.Schimansky-Geier, PRL 86, 2934 (2001)
DY 24.6 Di 16:00 H2
Theorie der AFM-Kraftspektroskopie an Rezeptor-Liganden-
Systemen — •Martin Raible und Peter Reimann — Fakultät für
Physik, Universität Bielefeld, PSF 100131, 33501 Bielefeld
Einzelmolekülprozesse in Rezeptor-Liganden-Systemen können mit dynamischer
AFM-Kraftspektroskopie experimentell untersucht werden. In
den meisten Fällen benutzt man dabei ein Rasterkraftmikroskop (AFM),
und die Kraft nimmt (approximativ) linear mit der Zeit zu: F(t) = µ · t.
Die allgemein akzeptierte Grundannahme [1] in allen diesbezüglichen Untersuchungen
ist ein Ratengesetz mit einer nur von der momentan wirksamen
Kraft F(t) abhängigen Zerfallsrate ν(F(t)). Bei der Anwendung
einer neuen Methode [2] zur Auswertung der Kraftprokolle auf gemessene
Daten [3] zeigte sich eine Inkompatibilität mit dieser Grundannahme.
Ansätze zur Erklärung dieser Inkompatibilität werden diskutiert.
[1] E. Evans and K. Ritchie, Biophys. J. 72, 1541 (1997).
[2] M. Evstigneev and P. Reimann, PRE (rapid communications) 68,
045103(R) (2003).
[3] F.W. Bartels, B. Baumgarth, D. Anselmetti, R. Ros, and A. Becker,
J. Struct. Biol. 143, 145 (2003), F.W. Bartels and R. Ros, private communication.
DY 24.7 Di 16:15 H2
Spectra and Waiting-Time Distribution of Stochastic
FitzHugh-Nagumo Neurons — •Tatiana Verechtchaguina,
Lutz Schimansky-Geier, and Igor M. Sokolov — Institut für
Physik, Humboldt Universität zu Berlin, Newton Str. 15, 12489 Berlin
A reponse of a neural cell to an external stimulus can follow one of the
two patterns: Cells of the first type (non-resonant neurons) monotonously
DY 25 Growth and Roughness
relax to the resting state. Neurons of the second type (resonant neurons)
show subthreshold oscillations leading to selective response to periodic
pulse sequences or noisy signals. We discuss how do these resonant
properties of neurons affect power spectra of their response to a random
(noise-like) signal.
The dynamics of a neuron is modelled by a FitzHugh-Nagumo (FN)
system; the two types of neurons differ in the values of parameter ǫ,
characterizing separation of time-scales of the slow and the fast variables.
We show that corresponding spectra obtained numerically can be
well described as spectra of sequences of pulses of the same form following
a given waiting-time distribution, and can be calculated using the
Stratonovich formula for spectra of point processes. Thus, the probability
density function of interspike intervals contains practically the whole
information about the response of a neuron, and can in some cases be
more useful than spectral characteristics.
DY 24.8 Di 16:30 H2
Bewegung biologischer Agenten am Beispiel der Wasserflöhe
(Daphnia) — •Niko Komin — Humboldt Universität zu Berlin, Institut
für Physik, Newtonstr. 15,12489 Berlin
Wasserflöhe (Daphnien) sind kleine Krebstiere, die weit unten in der
Nahrungskette der Süßwasserfauna stehen (analog zu den Copepoden im
Salzwasser). Unter bestimmten Lichtbedingungen führen Schwärme mit
vielen Individuen großräumig gemeinschaftliche Bewegungen aus (Vortices).
Die Bewegung kann durch verschiedene Modelle beschrieben werden.
Die stoßhafte Schwimmbewegung mit anschließender Änderung
der Bewegungsrichtung legt das diskrete Modell des Random Walker
nahe. Merkmale wie Diffusionskoeffizient und Volumen- bzw.
Flächenabdeckung lassen sich durch Simulationen und Theorie
bestimmen.
Die kontinuierliche Modellierung als Brownsche Teilchen (Langevingleichung)
läßt erwarten, daß sich die Selbstorganisation durch Wechselwirkungseffekte
einfach beschreiben läßt.
Beide Modelle werden vorgestellt und die Ergebnisse diskutiert.
Zeit: Dienstag 15:00–16:30 Raum: H3
DY 25.1 Di 15:00 H3
Interfacial melting of ice - the influence of roughness on the
melting process — •Simon Engemann 1 , Harald Reichert 1 ,
Helmut Dosch 1 , and Jörg Bilgram 2 — 1 MPI für Metallforschung,
Heisenbergstr. 3, D-70569 Stuttgart — 2 Laboratorium für
Festkörperphysik, ETH, CH-8093 Zürich
Using a high-energy X-ray transmission-reflection scheme, we have
studied ice-SiO2 model interfaces. We observed the formation of a premelting
quasiliquid layer and determined its thickness and density as a
function of temperature. The influence of surface roughness was investigated
by using SiO2 substrates with different morphology. While the
overall picture does not change with the roughness, the details as the
layer thickness are modified. We discuss the implications for the understanding
of the water structure.
DY 25.2 Di 15:15 H3
Three Dimensional Reconstruction of Experimentally Grown
Xenon Dendrites and Doublons. — •Herman M. Singer and
Jörg H. Bilgram — Laboratorium für Festkörperphysik, ETH Zürich,
8093 Zürich (Schweiz)
We investigate in our in situ experiments three dimensional xenon
crystals during free growth into pure supercooled melt. Supercooling is
the only control parameter of the system and determines the morphology
of the crystal. We present a method of reconstructing quantitatively
the three dimensional shape of an experimentally grown xenon dendrite
based on a hybrid approach of sophisticated image processing and measured
parameters of dendrites. This new method can readily be applied
to other experimental fields where transparent substances are to be investigated.
We can prove that the development of the fourfold symmetry of
the fins is not merely a result of a modulating perturbation but an inherent
structure formation process. We have found a power law dependence
for volume and surface on distance from the tip and time. We present the
3D reconstruction of experimental doublons and their temporal evolution
as well as their relaxation.
DY 25.3 Di 15:30 H3
Glättung von amorphen Oberflächen durch Schichtwachstum -
Experiment und Simulation — •Christoph Streng, Stefan G.
Mayr und Konrad Samwer — I. Physikalisches Institut, Universität
Göttingen, Tammannstr. 1, 37077 Göttingen
Das Wachstum amorpher dünner Schichten und die daraus resultierende
Oberflächenmorphologie ist für viele Bereiche sowohl experimentell
als auch durch Simulationen untersucht worden. Die mit STM gemessenen
Rauigkeiten sind hierbei abhängig von dem untersuchten System.
Es kann gezeigt werden, dass eine Übereinanderschichtung voneinander
abweichender Systeme zu einem Rauigkeitsübergang führt. Hierbei entspricht
die resultierende Rauigkeit derjenigen einer vollständigen Schicht
des zuletzt deponierten Materials. Auf diese Weise können Übergänge zu
größeren wie auch zu geringeren Rauigkeiten erzeugt werden. Die experimentellen
Ergebnisse können mit Hilfe des schon bekannten Kontinuummodells
dargestellt und diskutiert werden.
Dieses Projekt wird gefördert durch die DFG, SFB602, TP B3.
DY 25.4 Di 15:45 H3
Thermal Roughening of an SOS-Model with Elastic Interaction
— •C. Pütter, F. Gutheim, and H. Müller-Krumbhaar — Institut
für Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich
We analyze the effects of a long-ranged step-step interaction on thermal
roughening of a crystal surface within the framework of a SOS (solid-onsolid)
model by means of Monte Carlo simulation. A repulsive step-step
interaction is modeled by elastic dipoles located on sites adjacent to the
steps. The interaction energy based on long-ranged potentials is calculated
by a multi-grid scheme. In comparison with results for short-range
interactions the roughening temperature increases drastically as a consequence
of anti-correlations between surface defects. In order to investigate
the kinetics of crystal growth, a driving force has been included in the
model. We present our analytical and numerical results.

Dynamik und Statistische Physik Dienstag
DY 25.5 Di 16:00 H3
Fast Crack Growth by Surface Diffusion — •Robert Spatschek
and Efim Brener — Institut für Festkörperforschung, Forschungszentrum
Jülich, 52425 Jülich
Fracture is an intriguing irreversible phenomenon that plays an important
role in our day-to-day-life. Crack propagation is responsible for the
vast field of material failure but is also an interesting subject of physical
research. In particular, it exhibits several peculiarities for higher propagation
velocities. Here we present a continuum theory which describes
the fast growth of a crack by surface diffusion. By introducing a fully
dynamical theory of elasticity, it is possible to obtain a self-consistent
selection of the crack tip radius. This theory describes the complicated
dynamics of a crack tip, the saturation of the steady state velocity appreciably
below the Rayleigh speed, and the blunting of the crack tip.
Furthermore, it includes the possibility of a tip splitting instability for
high applied tensions.
DY 25.6 Di 16:15 H3
Stabilität hexagonaler Erstarrungsmuster — •Mathis Plapp —
Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique,
91128 Palaiseau, Frankreich
DY 26 General Statistical Physics
Hexagonale Muster bilden sich in vielen Nichtgleichgewichtssituationen,
wenn eine zweidimensionale Translationinvarianz durch eine dynamische
Instabilität gebrochen wird. Bei der gerichteten Erstarrung von
Legierungen bilden sich oberhalb einer kritischen Erstarrungsgeschwindigkeit
zelluläre Strukturen, die sich im dreidimensionalen Fall zu hexagonalen
Mustern ordnen. In Dünnschichtexperimenten und numerischen
Arbeiten wurde gezeigt, dass die Stabilität solcher Erstarrungszellen in
zwei Dimensionen erheblich von der Anisotropie der Grenzfläche abhängt.
Hier wird nun mittels Phasenfeld-Simulationen der dreidimensionale Fall
untersucht. Die räumliche Struktur der Instabilitätsmoden wird von der
Symmetrie des Zellenmusters bestimmt; die Stabilitätsgrenzen hängen
stark von der Anisotropie ab. Quadrat- und Streifenmuster sind unstabil.
Ausser Sechsecken wurde ein weiteres stabiles Muster gefunden: Tripletts,
die aus drei assymmetrischen Zellen bestehen. Sie lassen sich durch
zeitlich begrenzte Störungen kontrolliert aus Sechsecken erzeugen.
Zeit: Dienstag 16:45–18:00 Raum: H2
DY 26.1 Di 16:45 H2
Long-term correlations distinguish coarsening mechanisms
in alloys — •Lorenz-M. Stadler 1 , Bogdan Sepiol 1 , Richard
Weinkamer 2 , Markus Hartmann 2 , Peter Fratzl 2 , Jan W.
Kantelhardt 3 , Federico Zontone 4 , Gerhard Grübel 4 , and
Gero Vogl 1 — 1 Institut für Materialphysik, Universität Wien, 1090
Wien, Austria — 2 Max-Planck-Institute of Colloids and Interfaces,
Department of Biophysics, 14424 Potsdam, Germany — 3 Institut
für Theoretische Physik III, Justus-Liebig-Universität Giessen, 35392
Giessen, Germany — 4 ESRF, BP 220, 38043 Grenoble Cedex, France
We determine long-term correlations in the time series of fluctuating
x-ray speckle intensities. A fluctuation analysis of small angle x-ray
scattering data of the two phase-separating alloys Al-6at.%Ag and Al-
9at.%Zn at late stages of phase separation reveals long-term correlations
that are dramatically different for the two systems. From a comparison
with recent Monte Carlo simulations we conclude that two different coarsening
mechanisms are predominant in the two alloys—coarsening either
by diffusion of single atoms or by movement of whole precipitates.
We acknowledge financial support from the Austrian Federal Ministry
for Education, Science and Culture (project GZ 45.529/2-VI/B/7a/2002)
and the Hahn-Meitner-Institute Berlin in cooperation with the University
of Potsdam.
DY 26.2 Di 17:00 H2
Domain-Wall Energy Analysis of exact Ground States for
±J SG model in D=2 — •Amoruso Carlo and Alexander
K.Hartmann — Institute for Theoretical Physics, Göttingen
Computing ground states of Spin Glasses is a NP-hard problem, this
means that only algorithms are known, where the running time in the
worst case increases exponentially with the system size. For the special
case of two-dimensional spin glasses without an external field and with
periodic boundary conditions in at most one direction, efficient polynomial
algorithms for the calculation of exact ground states are available.
By using a matching algorithm, we computed exact ground states of two
dimensional Ising Spin Glasses with a certain concentration of antiferromagnetic
bonds p up to size L = 700. We calculated with high precision
the critical concentration of pc at which the ferromagnetic phase ceases to
exist, obtaining pc = 0.103(1). If the Nishimori point pN is located on the
phase boundary (as believed), the phase diagram has a small reentrance,
since pN ∼ 0.110. Besides we show that there is no spin-glass phase at
finite temperature.
DY 26.3 Di 17:15 H2
Ground-state structure of the vertex-cover problem —
•Wolfgang Barthel and Alexander K. Hartmann — Institute
for Theoretical Physics, Göttingen
Hard combinatorical optimization problems play an important role in
Theoretical Computer Science. One is especially interested in the time
complexity of such problems, i.e. how fast a typical instance can be solved
depending on its size. It is expected that this is strongly connected to
the landscape of the ground state structure of this problems. Here we
consider the vertex-cover problem: Take a random graph consisting of
undirected edges that meet at vertices and put guards on the vertices
such that there is one at at least one endpoint of every edge. Solutions
are covers which need a minimal number of guards and usually there is
an exponential number of them. We numerically analyze the landscape
of the solution space. A change in the ground state structure is observed
at the point where all known fast algorithms fail.
DY 26.4 Di 17:30 H2
High-Loop Variational Calculation of the Effective Potential —
•Sebastian Brandt and Axel Pelster — Institut für Theoretische
Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
The thermodynamic properties of a quantum mechanical point particle
moving in a one-dimensional potential V (x) follow from its effective potential
Veff(X) where X denotes the path average. For zero temperature
we present an efficient high-loop calculation of Veff(X) based on algebraic
recursion relations. In case of an anharmonic oscillator with x 3 and x 4
interactions we resum the divergent loop expansion via variational perturbation
theory. Using both frequency and position of a trial oscillator
as variational parameters, we determine the ground-state energy of the
above anharmonic oscillator for arbitrary coupling strength. For pure x 4
interaction, we furthermore extend our approach to D spatial dimensions
and investigate, in particular, the large D-limit.
DY 26.5 Di 17:45 H2
Three-phase contact line interface profiles in electric fields
— •Juergen Buehrle, Stephan Herminghaus, and Frieder
Mugele — University of Ulm; Applied Physics Department; D-89069
Ulm
Conductive or electrolytic liquid droplets in electric fields assume an
apparent contact angle (the angle assumed by the droplet shape far away
from the contact line) which is different from Young’s angle. This effect
was investigated in detail and new quantitative expressions for the contact
angle deviation are derived. In the vicinity of the contact line longrange
electric fields deform the liquid interface profile. We have investigated
the equilibrium profiles by balancing electrostatic and capillary
forces locally at the liquid vapor interface. Numerical results suggest that
the contact angle at the contact line is equal to Young’s angle. Simultaneously,
the local curvature displays a weak algebraic divergence. We
present an asymptotic analytical model, which confirms these results and
elucidates the scaling behavior of the profile close to the contact line. (see
also J. Buehrle, S. Herminghaus, and F. Mugele, Phys. Rev. Lett., 2003,
91, 86101)

Dynamik und Statistische Physik Dienstag
DY 27 Quantum Chaos
Zeit: Dienstag 16:30–18:15 Raum: H3
DY 27.1 Di 16:30 H3
Microwave measurements on dielectric quadrupole billards —
•R. Schäfer and H.-J. Stöckmann — Fachbereich Physik, Philipps-
Universität Marburg, Renthof 5, D-35032 Marburg, Germany
Quadrupole dielectic billiards have received a lot of attention because
of their highly directed emission patterns [1] which is a welcome effect in
the design of microdisc lasers. We measured transmission spectra from a
fixed antenna inside the disc to a moveable antenna, thus scanning both
the inside and outside region of the teflon disc. A Fourier transform of
the spectra yields the pulse propagation. The long time behavior is dominated
by the whispering gallery modes, which decay very slowly due to
total internal reflection. The emission pattern of the quadrupole billiard
is strongly influenced by the structures of its mixed phase space. Even for
strong deformations with no stable islands left, a high directionality of
the emission is found. This can be explained by the unstable manifolds of
periodic orbits [2]. The internal dynamics of the pulse has been analyzed
by means of Husimi distributions, while for the outer region the Poynting
vector was calculated to obtain the emission pattern. Both are compared
with classical ray dynamics taking into account the curvature-corrected
Fresnel formula.
[1] J.U. Nöckel, A.D. Stone, Nature 385, 45 (1997)
[2] H.G.L Schwefel et al., arXiv:physics/0308001
DY 27.2 Di 16:45 H3
Quantum Chaos on Networks — •Holger Schanz — Max-Planck
Institut für Strömungsforschung und Institut für Nichtlineare Dynamik
der Universität Göttingen, Bunsenstr. 10, 37073 Göttingen
Quantized networks are simple models which allow to study quantum
signatures of classical chaos. They allow analytical approaches to unsolved
problems in quantum chaos, including periodic-orbit theories for
spectral correlations, transport and localization phenomena as well as
scarring of wavefunctions. A brief account of the model and the obtained
results will be given.
H. Schanz and U. Smilansky, Phys. Rev. Lett. 84(00)1427.
G. Berkolaiko, H. Schanz, R. S. Whitney, Phys. Rev. Lett. 88(02)104101.
H. Schanz and T. Kottos, Phys. Rev. Lett. 90(03)234101.
H. Schanz, M. Puhlmann and T. Geisel, Phys. Rev. Lett. 91(03)134101.
DY 27.3 Di 17:00 H3
Ray-wave correspondence in a fully chaotic quasi-stadium laser
resonator — •J. Wiersig 1 , T. Fukushima 2 , and T. Harayama 3
— 1 Universität Bremen — 2 Okayama Prefectural University, Okayama,
Japan — 3 ATR Adaptive Communication Research Laboratories, Kyoto,
Japan
The relation between resonator modes and unstable periodic orbits in
a fully chaotic quasi-stadium laser resonator is investigated. The complicated
wavelength dependence of the power coupling coefficient is explained
by a simple coupling model, which considers some unstable periodic
orbits.
DY 27.4 Di 17:15 H3
Semiclassical approximations for open systems: transport and
decay — •Mathias Puhlmann, Holger Schanz, Tsampikos Kottos,
and Theo Geisel — Max-Planck Institut für Strömungsforschung
und Institut für Nichtlineare Dynamik der Universität Göttingen, Bunsenstr.
10, 37073 Göttingen
DY 28 Glasses I (joint session DF/DY)
Important and diverse physical applications like electronic transport
through mesoscopic devices or microcrystal lasers require an understanding
of open quantum systems with chaotic classical limit. For many interesting
processes in such systems the interference between classical trajectories
is decisive. Therefore the standard semiclassical theory based on
the diagonal approximation is not accurate or fails at all. Using quantum
graphs as model systems we show how one can improve the semiclassical
description such that shot noise and the short-time devitions from a
simple exponential probability decay are reproduced.
H. Schanz, M. Puhlmann and T. Geisel, Phys. Rev. Lett. 91(03)134101.
DY 27.5 Di 17:30 H3
Semiclassical approach to shot noise in chaotic systems —
•Andreas Lassl, Marko Turek, and Klaus Richter — Institut
für Theoretische Physik, Universität Regensburg, D-93040 Regensburg
We propose a semiclassical approach to shot noise in clean chaotic
systems [1]. Starting from the semiclassical expression for the transmission
we derive the Fano factor in terms of classical paths. As expected
the application of the diagonal approximation yields a vanishing result
for the Fano factor. Therefore one has to include action correlations between
classical paths which can be expressed in terms of a crossing angle
distribution as in [2]. Here we present detailed numerical studies of this
crossing angle distribution in open systems.
[1] C.W.J. Beenakker and C. Schönenberger, Physics Today, 56 (5), 37-
42 (2003)
[2] K. Richter and M. Sieber, PRL 89, 206801 (2002)
DY 27.6 Di 17:45 H3
Universal spectral form factor for chaotic dynamics I: The
Hadamard-Gutzwiller model — Stefan Heusler, •Sebastian
Müller, Petr Braun, and Fritz Haake — Fachbereich Physik, Universität
Duisburg-Essen, 45117 Essen
We consider the semiclassical limit of the spectral form factor K(τ) of
the Hadamard-Gutzwiller model. Starting from the Gutzwiller type double
sum over classical periodic orbits we set out to recover the universal
behavior predicted by random-matrix theory, both for dynamics with and
without time reversal invariance. For times smaller than half the Heisenberg
time TH ∝ ¯h −f+1 , we extend the previously known τ-expansion to
include the cubic term. Our results exemplify the “diagrammatic rules”
determining the families of orbit pairs responsible for all orders of the
τ-expansion.
DY 27.7 Di 18:00 H3
Universal spectral form factor for chaotic dynamics II: General
systems — •Stefan Heusler, Sebastian Müller, Petr Braun
und Fritz Haake — Fachbereich Physik, Universität Duisburg-Essen,
45117 Essen
We consider the semiclassical limit of the spectral form factor K(τ)
of general, fully hyperbolic dynamics. Generalizing results for the
Hadamard-Gutzwiller model, we discuss the families of orbit pairs giving
rise to higher-order contributions to the spectral form factor.
Zeit: Dienstag 09:30–12:30 Raum: H23
Hauptvortrag DY 28.1 Di 09:30 H23
Theory of the glass transition for systems with trivial statics —
•Rolf Schilling 1 and Grzegorz Szamel 2 — 1 Institut für Physik,
Johannes Gutenberg-Universität, D-55099 Mainz — 2 Department of
Chemistry, Colorado State University, Ft. Collins, CO 80523, USA
The mode coupling theory (MCT) derived and investigated in great
detail by Götze and his coworkers has been the most important step to-
wards the microscopic understanding of the structural glass transition.
MCT yields a glass transition if the static correlations reach a critical
value. However, there exist systems with trivial statics where static correlations
even vanish. Nevertheless they exhibit a discontinuous glass
transition which can not be described by MCT in its present form. In
a first step we have derived a self-consistent equation for the diffusion
constant which yields a continuous transition, in contrast to simulational

Dynamik und Statistische Physik Dienstag
results. We show how this drawback can be eliminated by a modification
of the MCT-approximations. As a result MCT-equations are obtained
which are complementary to the original ones. The glass transition is not
driven by the growth of static correlations but by the increase of collision
events between 2, 3 and 4 particles.
DY 28.2 Di 10:15 H23
Mode coupling equations for molecular crystals — •Michael
Ricker und Rolf Schilling — Universität Mainz, Staudinger Weg 7,
55099 Mainz
We have derived the mode coupling equations for molecular crystals
of axially symmetric particles, describing the time evolution of the tensorial
orientational correlators Slm,l ′ m ′(q, t), where lm and l′ m ′ are pairs
of indices for spherical harmonics. These equations have a similar structure
as those for molecular liquids. Differences arise from the possibility
of umklapp-processes in reciprocal space and from the anisotropy of the
lattice. Because of the latter, the three-point correlation function of orientational
density fluctuations, which occurs due to projections during the
calculations, can not be approximated in such an elegant and insightful
way as for liquid systems. Another difference is that only tensorial orientational
correlators with l, l ′ > 0 are involved, since the l = 0 and/or
l ′ = 0 correlators vanish.
If these mode coupling equations can describe the formation of orientational
glasses is currently tested for hard ellipsoids of revolution on a
simple cubic lattice. The static orientational structure factors Slm,l ′ m ′(q),
which are needed as input, are taken from MC simulations and from the
solution of the Ornstein-Zernike equation using the Percus-Yevick approximation.
DY 28.3 Di 10:30 H23
Das β-peak Phänomen in glasbildenden van-der-Waals
Flüssigkeiten — •Matthias Sperl und Wolfgang Götze —
Physik-Department T37, TU München, 85747 Garching
Messungen der Suszeptibilität mittels Optischem Kerr Effekt an Salol
und Benzophenon zeigen strukturelle Relaxation über bis zu fünf
Grössenordnungen in der Zeit. Dabei entsprechen bis zu drei Dekaden
im Anschluß an die Transiente nicht den universellen Skalengesetzen der
Modenkopplungstheorie. Dieses Problem der Datenanalyse wird durch
den Fit der Daten in einem schematischen Modenkopplungsmodell geklärt.
Der bisher unerklärte Zeitbereich in den Daten kann als Charakteristik
eines β-peak Phänomenes verstanden und analytisch beschrieben
werden.
DY 28.4 Di 10:45 H23
Dielectric relaxation in binary organic glass formers: β process
vs. HF-wing scenario and heterogeneous dynamics — •Thomas
Blochowicz and Ernst Rössler — Universität Bayreuth
We study a series of binary mixtures using 2-picoline in oligomeric
styrenes, in particular tri-styrene. The binary mixtures were characterised
by broad band dielectric spectroscopy in the dynamic range 10 −6 −10 7 Hz.
Although neither of the substances shows a secondary relaxation peak in
the neat phase, there appears a strong β-process in the spectra of the
picoline molecules in the mixture. In fact a careful lineshape analysis of
χ ′′ (ω) with a set of appropriate model functions shows that the same process
that is seen as a high frequency wing at high picoline concentrations
becomes a β relaxation at lower concentrations due to a separation of
time scales. Moreover, in the intermediate concentration range a strong
broadening of the spectra as compared to neat picoline is observed. Nonresonant
dielectric hole burning reveals that this broadening is on the
one hand due to pronounced, long-lived dynamic heterogeneities but to
some part also due to intrinsically non-exponential relaxation.
DY 28.5 Di 11:00 H23
Structure and dynamics of Al–Ni melts: Computer simulations
studies — •Jürgen Horbach, Subir Kumar Das, and Kurt
Binder — Institut für Physik, Johannes Gutenberg-Universität,
Staudingerweg 7, D-55099 Mainz
A combination of Monte Carlo (MC) and Molecular Dynamics (MD)
computer simulation techniques is used to study the structure and dynamics
of Al–Ni melts. As a model to describe the interactions between
the atoms we use an embedded atom potential that was recently proposed
by Mishin et al. [Phys. Rev. B 65, 224114 (2002)]. Monte Carlo
simulations in the semigrandcanonical ensemble yield well–equilibrated
configurations that are used in MD runs to study structural and dynamic
properties. For the case of Al4Ni we demonstrate that our simulation is
in very good agreement with the static structure factor and the diffusion
constants as measured recently with neutron scattering by Meyer et al.
We give an interpretation of the prepeak that appears in the total static
structure factor of Al rich melts around 1.3 ˚A −1 . Furthermore we analyze
the dynamics of Al4Ni by means of mode coupling theory and we discuss
the possibility of a fluid–fluid phase separation in Al–Ni mixtures.
DY 28.6 Di 11:15 H23
The mixed alkali effect in ternary silicates: computer simulation
studies — •Hans Knoth, Jürgen Horbach, and Kurt Binder —
Institut für Physik, Staudinger Weg 7, Johannes Gutenberg–Universität,
D–55099 Mainz
Molecular dynamics computer simulations are used to investigate
ternary alkali silicates (1 − x)Li2O·xK2O·2SiO2 (0 ≤ x ≤ 1). These systems
are typical ion conductors which is due to a high mobility of the
alkali ions. The structure and dynamics is studied for molten systems, as
well as at lower temperatures at which only the alkali ions show a diffusive
motion. Our aim is to understand the origin of the so-called mixed
alkali effect (MAE) which is the phenomenon that the diffusion of the
alkali ions is much slower in ternary systems (e.g. x = 0.5) than in the
corresponding binary systems (i.e. x = 0 and x = 1). Preferable sites for
the alkali diffusion are found that are located in a network of channels. In
the ternary system, each alkali species moves in its own channel network
leading to a stronger localization of alkali sites and the MAE.
DY 28.7 Di 11:30 H23
Nearly constant loss behavior in molecular glass-formers —
•Catalin Gainaru, Alberto Rivera, Thomas Blochowicz,
Christian Tschirwitz und Ernst A. Roessler — Experimentalphysik
II, Universitaet Bayreuth, Germany
We study the dielectric response of molecular glass formers showing no
Johari-Goldstein relaxation (type A systems) below the glass transition
temperature by applying the new Andeen Hagerling ultra-precision capacitance
bridge (50 Hz - 20 KHz). In all glass formers we find a nearly
constant loss behavior extending over several decades in frequency and
exhibiting an exponential temperature dependence. Below say 50 K a
crossover to another relaxation phenomena with a pronounced peak is
observed (5 K - 50 K).
DY 28.8 Di 11:45 H23
Secondary relaxation processes in organic glasses - comparison
between dielectric and NMR spectroscopy — •Sorin Adrian
Lusceac, Peter Medick, Catalin Gainaru, and Ernst A.
Rössler — Experimentalphysik II, Universitaet Bayreuth, Germany
Secondary relaxation processes in glasses were discovered using dielectric
spectroscopy. While dielectric spectroscopy is the preferred technique
to study them for obtaining time constants, NMR spectroscopy is a good
candidate to offer extra-information about their nature, in particular
concerning geometry and hindrance of molecular motion. Several organic
glass formers (polybutadiene Mw= 80000g/mol, mixture of benzene and
polybutadiene Mw= 777 and 2110g/mol) are investigated using multidimensional
NMR spectroscopy and the results are compared with those
provided by dielectric spectroscopy. The main purpose is to find a link
between the dielectric strength of the secondary relaxation process and
suitable 2 H NMR measurable.
DY 28.9 Di 12:00 H23
Mapping supercooled liquids on simple trap models for the
long-time dynamics: justification and consequences — •Andreas
Heuer, Aimorn Saksaengwijit, and Katharina Hobbeling —
Institut für Physikalische Chemie, Corrensstr. 30, D-48149 Münster
For a long time it has been realized that the potential energy landscape
(PEL) viewpoint is useful for characterizing supercooled liquids
and glasses. To this end, one considers the high-dimensional vector of
all particle coordinates as a point moving on the surface of the total
potential energy. It turns out from computer simulations of a binary
mixture Lennard-Jones system that the dynamics can be described as a
random-walk between stable structures on the PEL, denoted metabasins
[1]. Furthermore it turns out that the metabasins act as traps. Escaping
a metabasin requires an activation energy which is proportional to the
depth in the PEL. Thus the dynamics of the glass-forming liquid is very
similar to the dynamics within a trap model. Some consequences of this
mapping for the application of modern equilibration routines like parallel
tempering are discussed.
[1] B. Doliwa and A. Heuer, Phys. Rev. Lett. (in press).

Dynamik und Statistische Physik Dienstag
DY 28.10 Di 12:15 H23
Relating the macroscopic dynamics of liquid silica to its potential
energy landscape — •Aimorn Saksaengwijit and Andreas
Heuer — Westfälische Wilhelms–Universität, Institut für Physikalische
Chemie, D-48149 Münster
We have studied the dynamics of liquid silica in terms of the potential
energy landscape (PEL) defined in configuration space. The concept
of superstructures of PEL minima, denoted metabasins, is used to extract
the relevant properties of the PEL. On the level of metabasins it
DY 29 Glasses II (joint session DF/DY)
turns out that the average residence time 〈τ〉 is inversely proportional
to the diffusion constant, i.e. D(T) = c/〈τ(T)〉. The temperature dependence
of the residence time can be obtained from the analysis of local
escape processes out of individual metabasins. Furthermore we show that
the fragile-to-strong transition of silica can be reproduced by using the
PEL analysis. This allows us to obtain an improved understanding of the
underlying nature of this transition. A comparison to a fragile system
(Lennard-Jones liquid) is included.
Zeit: Dienstag 14:30–17:45 Raum: H23
Hauptvortrag DY 29.1 Di 14:30 H23
Dynamische Heterogenität ungeordneter Festkörper —
•Roland Böhmer 1 , Manfred Winterlich 1 , Sven Berndt 1 ,
Gregor Diezemann 2 und Ken R. Jeffrey 3 — 1 Experimentelle
Physik III, Universität Dortmund, 44221 Dortmund — 2 Institut für
Physikalische Chemie, Johannes Gutenberg-Universität, 55099 Mainz —
3 Department of Physics, University of Guelph, Canada
Die Natur der nichtexponentiellen Relaxation von Flüssigkeiten und
Polymerschmelzen ist in letzter Zeit sowohl theoretisch als auch experimentell
intensiv erforscht worden [1]. Im Bereich der Festkörper gab es
bislang aber nur wenige Aktivitäten. Neuere Untersuchungen mit der dielektrischen
Spektroskopie und mit der kernmagnetischen Resonanz konzentrieren
sich hier auf die Rotationsdynamik ungeordneter plastischer
Kristalle [2] und auf die Translationsdynamik von festen Ionenleitern
[3,4].
[1] H. Sillescu, J. Non-Cryst. Solids 243, 81 (1999)
[2] M. Winterlich, G. Diezemann, H. Zimmermann, R. Böhmer, Phys.
Rev. Lett. 91, (2003)
[3] R. Richert, R. Böhmer, Phys. Rev. Lett. 83, 4337 (1999)
[4] M. Vogel, C. Brinkmann, H. Eckert, A. Heuer, cond-mat/0310256
DY 29.2 Di 15:00 H23
Rotationsdynamik einzelner Moleküle in unterkühlten
Flüssigkeiten — •Gerald Hinze — Institut für Physikalische
Chemie, Johannes Gutenberg-Universität, 55099 Mainz
Die Dynamik in unterkühlten Flüssigkeiten ist durch eine große Bandbreite
an vorkommenden Zeitskalen, Amplituden und Bewegungsmechanismen
gekennzeichnet. Neben der sehr signifikanten Temperaturabhängigkeit
des primären Relaxationsprozesses sind nichtexponentielle
Korrelationsfunktionen typisch und werden in praktisch allen Glasbildnern
bzw. unterkühlten Flüssigkeiten gefunden. Eine damit verknüpfte
und zur Zeit sehr kontrovers diskutierte Fragestellung betrifft die dynamische
Heterogenität in der Nähe der kalorischen Glastemperatur. Während
einige Experimente Hinweise dafür liefern, dass die Moleküle einer Probe
relativ einheitlich reorientieren, bzw. Unterschiede sich auf der Zeitskala
der Rotation herausmitteln, ergeben andere Experimente deutlich
getrennte Zeitskalen für die Rotation und die Änderung der Rotationskorrelationszeiten.
Mit Hilfe der konfokalen Fluoreszenzmikroskopie ist es
möglich, die Rotationsdynamik einzelner Moleküle zu verfolgen. Damit
bietet sie prinzipiell die Möglichkeit, dynamische Heterogenitäten und
deren Lebensdauern zu bestimmen, da keine Ensemble-Mittelungen auftreten.
Wir stellen Einzelmolekülexperimente in der amorphen Matrix
PDE (Phenolphthalein-dimethylether) vor. Die erhaltenen Rotationskorrelationsfunktionen
werden mit einfachen Rotationsmodellen verglichen.
DY 29.3 Di 15:15 H23
Dynamical heterogeneities in simulated amorphous Ni0.5Zr0.5:
correlations with density and order parameter fluctuations —
•Imad Ladadwa and Helmar Teichler — Institut für Materialphysik,
and SFB 602, Universität Göttingen
Dynamical heterogeneity is a fundamental aspect of particle motion in
supercooled liquids and glasses. For metallic alloy system, a great part of
the information on dynamical heterogeneity comes from computer simulations,
leaving open so far, however, a detailed answer concerning the
origin of heterogeneity. In order to approach this question, we have carried
out molecular dynamics simulations for an amorphous Ni0.5Zr0.5 model,
generating well relaxed structures at 700, 760, and 810 K, that means
well below the dynamical glass temperature Tc = 1120K. From analyzing
long-time simulations over 0.7µs for medium size systems (N = 5184,
periodic boundary conditions), we find striking interrelationship between
spatial fluctuations of the atomic mobility, that means dynamical heterogeneity,
and of the fluctuation of topological order and of the chemical
composition in the system. The results indicate an anti-correlation between
local Ni content and Ni atoms mobility, on the one hand, and
a correlation between the local order and the Ni mobility on the other
hand. The talk will present the definitions of suitable measuring tools for
these quantities and quantitative estimates for the inherent correlations.
DY 29.4 Di 15:30 H23
Short-range order fluctuations and the boson peak in simulated
amorphous NiZr — •M. Guerdane and H. Teichler — Institut
für Materialphysik, Universität Göttingen
The boson peak is a striking feature in the vibration spectrum of glassy
systems. We here present results from molecular dynamics simulations
for Ni30Zr70, relating the boson peak of the system to local fluctuations
in the short-range order. Analysis of the topology around Ni atoms in
the system shows that Ni in the amorphous state on average has a coordination
number < Z >= 9, where in detail a mixture of perfect or
slightly distorted trigonal prisms (TP, Z = 9) or archimedean antiprisms
(AAP, Z = 10) and environments with Z = 8 predominate. Both TP and
AAP represent the basic structural units in the crystalline intermetallic
compounds NiZr (B33-Type) and NiZr2 (C16-Type) respectively. We
show that the boson peak in the amorphous NiZr system is related to
fluctuations in time between local environments of different coordination
numbers Z.
DY 29.5 Di 15:45 H23
Molecular Dynamics in Phosphate Glasses — •Oliver Baldus
and Ernst Rössler — Lehrstuhl für Experimentalphysik II, Universität
Bayreuth, Universitätsstr. 30, 95440 Bayreuth
The molecular dynamics of the glass formers tricresylphosphate (TCP),
triphenylphosphite (TPP) and mixtures with polystyrene are investigated
by NMR methods. The observed deviations from the KWWbehaviour
of the relaxation function obtained in stimulated echo measurements
are explained. Further it will be discussed whether those deviations
are a sign of the so called wing phenomenon that is seen in
dielectric spectra and how far the measurements are influenced by limitations
of the stimulated echo method. Restrictions of the stimulated
echo method are shown by simulations.
DY 29.6 Di 16:00 H23
Ionic transport in alkali-borate glasses — •F. Berkemeier,
Á.W. Imre, S. Voss und H. Mehrer — Institut für Materialphysik,
Wilhelm–Klemm–Str. 10, 48149 Münster, Westfählische–Wilhelms–
Universität Münster, Sonderforschungsbereich 458
We studied the ionic transport in binary and ternary alkali-borate glasses
of the compositions y Na2O·(1 − y) B2O3, y Rb2O ·(1 − y) B2O3 and
0.3 [x Na2O·(1−x) Rb2O]·0.7 B2O3. The total alkali content of the binary
glasses ranges from y = 0.04 up to y = 0.30 while the relative composition
of the mixed glasses varied in between x = 0 and x = 1. First, the ionic
transport was observed by temperature dependent measurements of the
dc conductivity which is connected to the long range transport of the cations.
For each glass composition we observed an Arrhenius behaviour of
the dc conductivity and determined an activation enthalpy ∆H. For the
binary systems we found decreasing values of ∆H with increasing alkali
content while for the mixed glasses we observed a maximum of the activation
enthalpy at the composition range around x ≈ 0.4. Conductivity
measurements only reveal the sum of the contributions of the different

Dynamik und Statistische Physik Dienstag
cations. Because of this we measured additionally the diffusivities of 22 Na
and 86 Rb in the mixed glasses at 380 ◦ C using the radiotracer technique.
We observed an exponential decrease of the Rb-diffusivity with decreasing
Rb-content, while the Na-diffusivity also decreases with decreasing
Na-content on the Na-rich side, but remains nearly constant on the Rbrich
side. Both diffusivities intersect at the composition range around
x ≈ 0.2. A similar behaviour was reported from our laboratory for mixed
glasses with a total alkali content of y = 0.2.
DY 29.7 Di 16:15 H23
Diffusion von Na und Ca und ionische Leitfähigkeit in Standard-
Kalk-Natron-Gläsern — •Eugène Molière, Tanguep Njiokep
und Helmut Mehrer — Institut für Materialphysik, Westfälische-
Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster
Als Standardsubstanzen für die wichtigsten physikalischen und chemischen
Prüfmethoden in der Glastechnologie hat die Deutsche Glastechnologie
Gesellschaft (DGG) zwei Flachgläser (Standard-Kalk-Natron-
Gläser) von hoher Reinheit und Homogenität herstellen lassen. Bei der
Physikalisch-Technischen-Bundesanstalt (PTB) wurden das Viskositäts-
Temperatur-Verhalten und die Bruchbarkeit dieser Gläser als Viskosität-
Standard untersucht. Diese Gläser weisen keine Störung durch Entglasung
und Entmischung auf. Neben der praktischen Bedeutung der Standards
liegen hier gut definierte Gläser vor, über deren verschiedensten
Eigenschaften nun umfangreiche Daten existieren. Dagegen gibt es noch
keine Informationen über die Beweglichkeit der im SiO2-Netzwerk eingebauten
Alkali- und Erdalkaliionen. Um Informationen über die Transportprozesse
der Netzwerkwandler zu gewinnen, wurden die ionische
Leitfähigkeit der Proben im Frequenzbereich zwischen 5Hz und 1.28MHz
mit der Impedanz-Spektroskopie und die Diffusion von 22 Na und 45 Ca
mit der Radiotracermethode im Temperaturbereich zwischen 490K und
759K untersucht. Die Tracerdiffusions- und Leitfähigkeitsmessungen werden
verglichen und diskutiert.
DY 29.8 Di 16:30 H23
Ion dynamics in single and mixed alkali silicate glasses studied
by molecular dynamics simulations — •Heiko Lammert and
Andreas Heuer — Westfälische Wilhelms–Universität, Institut für
Physikalische Chemie, Corrensstraße 30, D-48149 Münster
We use molecular dynamics (MD) simulations to study the ion dynamics
in alkali silicate glasses with the general composition
x K2O · (1 − x) Li2O · 2 SiO2, for x = 0, 0.5, 1.
All individual alkali sites provided by the frozen network can be identified
by a statistical analysis of MD trajectories, for both the single
and the mixed alkali systems. Sites are located by a cluster search on a
discretised alkali population density.
The ion dynamics can be analyzed in terms of fast hops between these
sites, also yielding average residence times to characterize the sites. As
the number of free sites is low compared to the number of ions, correlated
back jumps are found to be probable, especially for ions on fast sites. The
mobility of ions can be correlated to the local network structure around
their site, particularly to the occurence of bridging oxygens.
DY 29.9 Di 16:45 H23
Mixed-alkali effect in sodium rubidium borate glasses: ionic conductivity
and diffusivity — •Árpád W. Imre, Stephan Voss, and
Helmut Mehrer — Institut für Materialphysik, Universität Münster,
Wilhelm-Klemm-Strasse 10, D-48149 Münster, Germany and Sonderforschungsbereich
458
Measurements of the tracer diffusion coefficient and ionic conductivity
have been made in a series of 0.2[XNa2O · (1 − X)Rb2O] · 0.8B2O3
glasses where X=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 in order to investigate
the mixed-alkali effect. The glasses were characterised with differential
scanning calorimetry, density measurements and X-ray diffraction experiments.
Both 22Na and 86Rb tracer diffusion coefficients were determined
as a function of temperature and composition. For each composition the
temperature dependence of the tracer diffusion coefficients and dc conductivity
times temperature σdc × T follow the Arrhenius law. The manifestations
of the mixed-alkali effect were observed: i) the ionic conductivity
shows a minimum with composition near X =0.4, ii) the activation
enthalpy of σdc × T has a maximum near X =0.4, iii) the glass-transition
temperature has a minimum near X=0.2, iv) the diffusivities of 22Na and 86 Rb crossover near X =0.2. The diffusivity crossover is found to be
temperature independent. The composition dependence of the tracer diffusivities
has an asymmetric character. The tracer diffusion coefficients
are compared with ionic conductivity and the corresponding Haven ratios
obtained. In contrast to 0.2Na2O · 0.8B2O3 glass, the Haven ratio in the
0.2Rb2O · 0.8B2O3 depends on temperature.
DY 29.10 Di 17:00 H23
From binary Na-silicate to ternary Na-alumino-silicate melts:
the evolution of Na dynamics and intermediate range order
— •Florian Kargl 1 , Andreas Meyer 1 , and Helmut Schober 2
— 1 Physikdepartment E13, TU München, 85748 Garching — 2 Institut
Laue-Langevin, 38042 Grenoble, France
Neutron scattering investigations of binary alkali silicate melts revealed
correlations on intermediate lengthscales of 6-8 ˚A. Within MDsimulations
on Na-silicates evidence was found that these correlations
arise from Na-rich channels percolating in the remaining SiO-network.
Fast Na-diffusion takes place via these channels [1]. Substituting the
network forming component SiO2 by GeO2 leads to a change in structure
and in the microscopic transport mechanism, respectively, as verified
by inelastic neutron scattering. We present our recent investigations on
sodium alumino-silicate melts containing besides SiO2 a second network
former, Al2O3. Our main aim was to study the interplay between
microscopic dynamics and structure and its influence on macroscopic
properties. From quasielastic neutron scattering experiments we
conclude that the channel structure is disrupted by adding Al2O3 to the
Na-silicates resulting in an increase of viscosity as well as a decrease of
Na-relaxation times [2].
[1] A. Meyer, J. Horbach, W. Kob, F. Kargl, H. Schober (submitted)
[2] F. Kargl, A. Meyer, Chem. Geol. (submitted)
DY 29.11 Di 17:15 H23
Fragilität niedermolekularer organischer Glasbildner unter
Druck — •Andreas Reiser, Gernot Kasper und Siegfried
Hunklinger — Kirchhoff-Institut für Physik, Universität Heidelberg,
Im Neuenheimer Feld 227, 69120 Heidelberg
Die Fragilität einer glasbildenden Flüssigkeit ist definiert durch die
Steigung bei der Glasübergangstemperatur Tg im Angell-Plot. Sie erlaubt
eine Klassifikation in starke bzw. fragile Glasbildner. Stark bedeutet ein
Arrheniusverhalten der Relaxationszeit über den gesamten Temperaturbereich
T ≥ Tg. Die Relaxationszeit fragiler Glasbildner dagegen zeigt
eine stärkere Temperaturabhängigkeit. Wir haben den Einfluss von hohem
hydrostatischen Druck auf die Fragilität von typischen organischen
Glasbildnern mit dielektrischer Spektroskopie gemessen: Glycerin und
meta-Fluoranilin sind Vertreter wasserstoffgebrückter Glasbildner. Glycerin
rangiert im Zwischengebiet zwischen stark und fragil, wohingegen
meta-Fluoranilin und der Van-der-Waals-Glasbildner Propylencarbonat
vom fragilen Typ sind. Im untersuchten Druckbereich (0 −600 MPa) zeigen
alle drei Glasbildner keine Druckabhängigkeit der Fragilität im Rahmen
der Fehlergrenzen von ±5%.
DY 29.12 Di 17:30 H23
A binary colloidal mixture in 2D: An ideal model system for the
glass transition — •Hans König — Fachbereich Physik, Universität
Konstanz, 78457 Konstanz
Investigating a binary 2D colloidal glass former with a repulsive (1/r 3 )
potential we have measured particle positions as a function of time by
video-microscopy. The local packing of the big and small particles as well
as the heterogeneous dynamics were analysed depending on the system
temperature. Finally, we could describe the amorphous 2D short-range
order by local density-optimized triangles. However, there is one triangle
for each 3-particle combination of big and small colloids. Regions with
structural frustration occur between clusters of optimally packed triangles.
For decreasing system temperature the number of densely packed
triangles increased and they began to form clusters. For low system temperatures
such local density-optimized regions moved cooperatively resulting
in heterogeneous dynamics. By structural and dynamical investigations
we identify the 2D glass transition as a percolation of local
density-optimized triangles, which form a stable frame through the whole
glass former. At last, we call this glass description the concept of local
density-optimized crystallite clusters.

Dynamik und Statistische Physik Mittwoch
DY 34 Nonlinear Dynamics and Chaos I
Zeit: Mittwoch 14:30–16:30 Raum: H2
DY 34.1 Mi 14:30 H2
Angewandte Verkehrsprognose - ein multimodaler Ansatz im
Betrieb — •Roland Chrobok, Sigurdur F. Hafstein, Florian
Mazur, Andreas Pottmeier und Michael Schreckenberg
— Universität Duisburg-Essen, Physik von Transport und Verkehr, Lotharstr.
1, 47048 Duisburg
Verschiedene Ansätze sind in der Vergangenheit unternommen worden,
Verkehr zu prognostizieren. Bei der Wahl des richtigen Prognosemodells
spielt der Prognosehorizont eine entscheidende Bedeutung. Für langfristige
Prognosen über Jahrzehnte, wie sie in der Verkehrsplanung von Bedeutung
sind, müssen gewisse Annahmen über Bevölkerungsentwicklung
und Wirtschaftswachstum getroffen werden. Für mittelfristige Prognosen
über Tage, Wochen und Monate, wie sie zur Reiseplanung herangezogen
werden, haben sich Heuristiken, also Erfahrungswerte, bewährt. Bei
Kurzfristprognosen über einen Zeitraum von einigen Minuten bis hin zu
mehreren Stunden gewinnt die Kenntnis über den aktuellen Verkehrszustand
an Bedeutung. Phasenraummodelle, parametrisierte Regression
oder verwandte Verfahren sind in vielen Bereichen im Einsatz.
Vorgestellt wird ein multimodaler Ansatz zur Mittel- und Kurzfristprognose,
wie er in einem viel benutzten Verkehrsinformationssystem
verwendet wird. Hauptaugenmerk liegt neben der Prognosegenauigkeit
und der variablen Wahl des Prognosehorizontes auf der praktikablen Implementierung
und der ökonomischen Anwendbarkeit.
DY 34.2 Mi 14:45 H2
Latency effects in time-delay feedback control of chaos —
•Philipp Hövel 1 , Eckehard Schöll 1 , Joshua E. S. Socolar 2 ,
and Wolfram Just 3 — 1 Technische Universität Berlin, 10623 Berlin,
Germany — 2 Duke University, Durham, North Carolina, USA —
3 Queen Mary/ University of London, London, UK
Unstable periodic orbits can be controlled by time-delay feedback
methods. We present a stability analysis in the case of extended timedelay
autosynchronization. Our analysis includes effects of non-zero latency
time, i.e., the time associated with the generation and injection of
the feedback signal. We derive a theoretical explanation for experimentally
observed, nontrivial features of the domain of control, e.g., gaps,
maximum latency times. The explanation is done in the background of
Floquet theory and we take both the unstable eigenmode and a single
stable eigenmode into account.
DY 34.3 Mi 15:00 H2
Minimal model for tag-based cooperation — •Arne Traulsen
and Heinz Georg Schuster — Institut für theoretische Physik und
Astrophysik, Christian-Albrechts Universität, Olshausenstr. 40, 24098
Kiel
Recently, Riolo et al. [Riolo et al., Nature 414, 441 (2001)] showed
by computer simulations that cooperation can arise without reciprocity
when agents donate only to partners who are sufficiently similar to themselves.
One striking outcome of their simulations was the observation that
the number of tolerant agents that support a wide range of players was
not constant in time, but showed characteristic fluctuations. The cause
and robustness of these tides of tolerance remained to be explored. We
clarify the situation by solving a minimal mean-field version of the model
of Riolo et al. [Traulsen and Schuster, Phys. Rev. E. 68, 046129 (2003)].
It allows us to identify a net surplus of random changes from intolerant
to tolerant agents as a necessary mechanism that produces these oscillations
of tolerance, which segregate different agents in time. This provides
a new mechanism for maintaining different agents, i.e., for creating biodiversity.
In our model the transition to the oscillating state is caused
by a saddle node bifurcation. The frequency of the oscillations increases
linearly with the transition rate from tolerant to intolerant agents.
DY 34.4 Mi 15:15 H2
Recovering the dynamical system from short and contaminated
segments of a chaotic trajectory — •Luis Sandoval and Rafael
Gutiérrez — Grupo de Sistemas Complejos, Universidad Antonio
Nariño, Calle 58A 37-94, Bogotá, Colombia
In this work we determine the sufficient characteristics of a trajectory
segment of known chaotic attractors to recover the corresponding dynamical
model. The sufficient conditions correspond to: the size of the
trajectory segment, the localization of the trajectory segment, and the
density of points or sampling frequency. The contamination and resolution
of the data points make the sufficient conditions vary. The dynamical
models considered have all possible nonlinearities up to order two characterized
by thirty parameters. The values of the parameters are obtained
from each trajectory segment and then compared with the corresponding
values of the known dynamical system with chaotic solutions. In many
cases the chaotic solutions are not very sensitive to variations of some parameter
values making the comparison of similar but different dynamical
systems not well defined in terms of their corresponding chaotic solutions.
We solve this problem by using synchronization and estimation of
dynamical measures.
DY 34.5 Mi 15:30 H2
Retinotopic Projections between Discrete Euclidean Manifolds
— •Martin Güßmann 1 , Axel Pelster 2 , and Günter Wunner 1
— 1 Institut für Theoretische Physik 1, Universität Stuttgart, Pfaffenwaldring
57, D-70550 Stuttgart — 2 Institut für Theoretische Physik,
Freie Universität Berlin, Arnimallee 14, D-14195 Berlin
In the course of ontogenesis of vertebrate animals well-ordered neural
connections are established between retina and tectum, a part of the
brain which plays an important role in processing optical information.
As a result of this self-organization process a retinotopic projection is
formed, i.e. neighbouring retinal cells project onto neighbouring cells of
the tectum. We generalize the model of Ref. [1] to obtain order parameter
equations for the connection strengths between two manifolds of
arbitrary geometry. Here we consider the case of discrete n-dimensional
Euclidean manifolds. For the linear chain we are interested in the question
under which circumstances retinotopic or non-retinotopic modes become
unstable. Furthermore, we investigate the generation of retinotopic projections
between two planes. An important result consists in the fact that
this case cannot be reduced to two linear problems, i.e. there is no trivial
decoupling of the two dimensions. The existence of a potential dynamics
of the order parameters is discussed in detail.
[1] A.F. Häussler and C. von der Malsburg, J. Theoret. Neurobiol. 2, 47
(1983)
DY 34.6 Mi 15:45 H2
Spatio-Temporal Structures in a Biological Model with Delay
and Diffusion — •Martin Ohlerich 1 , Michael Bestehorn 1 und
Elena Grigorieva 2 — 1 Lehrstuhl Theoretische Physik II, BTU Cottbus,
Erich-Weinert Strasse 1, 03046 Cottbus, Germany — 2 Belarus State
University, Department of Physics, 220050 Minsk, Belarus
Pattern formation described by differential-difference equations with
diffusion is investigated. It is shown that an arbitrarily small diffusion
induces space-time turbulence just at instability threshold of the homogeneous
stationary solution. We prove this property deriving a complex
Ginzburg-Landau equation on the basis of normal form analysis.
Well above threshold, such turbulent structures give way to synchronized
states ordered by spirals and targets.
paper submitted to Phys. Rev. E
DY 34.7 Mi 16:00 H2
Synchronisationseffekte in global gekoppelten Netzwerken als
— •Alexander Skupin — Humboldt Universität zu Berlin, Newtonstr.14,
10245 Berlin
Aus biologisch-medizinischer Motivation werden (De)Synchronisationeffekte
in globale gekoppelten Netzwerken untersucht und als Modell eines
an Parkinson erkrankten Thalamus verwendet. Dabei wird ein Vergleich
zwischen dem Phasenoszillatoren-Netzwerk (Kuramoto) und einem
FitzHugh-Nagumo-Netzwerk (FHN) gezogen. In beiden Fällen werden
Ordnungsparameter Z eingeführt und die Wirkung eines externes Signal
(Stimulus) auf diese gezeigt. Damit wird im Kuramotomodell ein optimaler
Stimulus zur Desynchronisation gesucht und das Verhalten des
FHN-Netzwerk auf diesen untersucht.
DY 34.8 Mi 16:15 H2
Synchronization of Random Walks with Reflecting Boundaries
— •Andreas Ruttor, Georg Reents, and Wolfgang Kinzel —
Institut für Theoretische Physik, Universität Würzburg, Am Hubland,
97074 Würzburg
Neural networks can synchronize by mutual learning. If the learning

Dynamik und Statistische Physik Mittwoch
algorithm changes the values of the weights only in discrete steps of equal
size, the dynamics of each weight can be described as a random walk. In
this case it is possible to calculate statistical properties of the synchronization
process by replacing neural networks with ensembles of random
walks.
We consider two random walks with reflecting boundaries. In each step
both random walkers are moved in the same, randomly chosen direction.
If one hits the boundary, the distance between both is decreased. This
DY 35 Symposium SYPF: Physics of Foams
leads to synchronization after some steps. We calculate the mean and
the variance of the synchronization time analytically. By using the probability
distribution of this quantity, we can also determine the average
number of steps, after which two ensembles of random walks reach a synchronized
state.
For publications and preprints see:
http://theorie.physik.uni-wuerzburg/TP3/publi.html
Zeit: Mittwoch 14:00–18:30 Raum: H16
DY 35.1 Mi 14:00 H16
Symposium SYPF: Physics of Foams — • —
Details zum Programm sind unter SYPF zu finden.
DY 36 Nonlinear Dynamics and Chaos II
Zeit: Mittwoch 16:30–18:00 Raum: H2
DY 36.1 Mi 16:30 H2
Experimente zur Dynamik zeitverzögert gekoppelter Halbleiterlaser
bei kurzen Kopplungszeiten — •Eric Wille, Michael
Peil, Ingo Fischer und Wolfgang Elsässer — TU Darmstadt,
Institut für Angewandte Physik, Schlossgartenstr. 7, 64289 Darmstadt
Eine Verzögerung in der Kopplung zweier nichtlinearer Oszillatoren hat
einen wesentlichen Einfluss auf deren Dynamik. Gekoppelte Halbleiterlaser
sind hervorragend dazu geeignet, solche Einflüsse auf das dynamische
Verhalten experimentell zu untersuchen. Darüber hinaus besitzen gekoppelte
Halbleiterlaser Potential für neue technologische Anwendungen.
Wir präsentieren experimentelle Ergebnisse zu zwei gegenüberstehenden,
einmodigen Halbleiterlasern mit identischen Parametern,
deren endliche Kopplungszeit in der Größenordnung der Periode
der Relaxationsoszillationen ist. In Abhängigkeit von der optischen Frequenzverstimmung
der zwei Laser finden wir sowohl Locking-Bereiche
mit stabiler Emission, als auch instabile Intensitätsdynamik. Wir diskutieren
die charakteristischen Zusammenhänge zwischen den auftretenden
Oszillationsfrequenzen, der Frequenzverstimmung, und der endlichen
Kopplungszeit. Die Ergebnisse werden sehr gut durch Modellrechnungen
unterstützt.
DY 36.2 Mi 16:45 H2
Noise-Induced Crisis in a Electronic Circuit — •Thomas Stemler,
Johannes Werner, and Hartmut Benner — Institut für
Festkörperphysik, TU Darmstadt
We report the experimental observation of noise-induced crises in a
Chua-type nonlinear electronic oscillator. Here, the merging of two precritical
sub-attractors is induced by noise and results in chaos-chaos intermittency.
We analyse the influence of different kinds of noise, e.g.
white Gaussian noise and coloured noise, on the system dynamics. Close
to a critical control parameter Rc a merging crisis occurs which can be
characterized by the mean residence time τ on each sub-attractor. This
characteristic time is expected to scale like[1]: τ ∼ σ −γ g((Rc − R)(σ))
where σ is the noise strength, γ the critical exponent of the crisis in the
absence of noise, and g(·) is a nonuniversal function depending on the
kind of noise. Our data, which are in very good agreement with the predicted
scaling, support the detailed understanding of related aperiodic
stochastic resonance experiments in this system.
[1] J.C. Sommerer, E. Ott, C. Grebogi Phys. Rev. A 43, 1754 (1991)
DY 36.3 Mi 17:00 H2
Numerische und Analytische Betrachtung zur Strukturbildung
in Lasern mit Rückkopplung — •Guido Krüger, Rudolf Friedrich
und Till Frank — Institut für Theoretische Physik,Wilhelm-
Klemm-Str. 9,48149 Münster
Einspiegelrückkopplungsexperimente mit einem Laser in Natrium-
Dampf führen zu einer Vielfalt an Strukturbildungsprozessen [1].
Wir entwickeln diese Strukturbildungsprozesse ausgehend von den
Blochschen Feldgleichungen die in [2] entwickelt wurden, indem reduzierte
Swift-Hohenberg-artige Gleichungen abgeleitet werden.
Die numerische Auswertung der gefundenen Gleichungen zeigt dabei
verschiedene Strukturen, so z.B. Quadrate und Hexagone. Ziel der Arbeit
ist es anhand von den reduzierten Gleichungen und den numerischen
Resultaten vorherzusagen, welche Strukturen entstehen und warum sich
diese Strukturen ergeben.
[1] W.Lange, Yu. A. Logvin und T.Ackemann SSpontaneous optical
patterns in an atomic vapor: observation and simulation”Physica D
96, 230-241 (1996) [2] F.Mitschke, R.Deserno, W.Lange und J.Mlynek
”Magnetically induced self-pulsing in a nonlinear resonator”Phys.Rev.A
Vol.33 No.5 (1986) 3219-3231
DY 36.4 Mi 17:15 H2
On global properties of time-delayed feedback control —
•Wolfram Just 1 , Clemens v. Loewenich 2 , and Hartmut
Benner 2 — 1 Department of Mathematics, Queen Mary/University of
London, UK — 2 Institut für Festkörperphysik, TU Darmstadt
While control of chaos by time-delayed feedback is meanwhile quite
well understood from the point of view of linear stability analysis, almost
nothing is known about global features of the control problem. From
an experimental point of view the question which type of initial condition
yields successful stabilisation, i.e. in theoretical terms the basin of
attraction, is of utmost importance. Applying general arguments from
bifurcation theory we propose that discontinuous transitions at the control
boundaries, i.e. subcritical behaviour, severely limits such basins. We
illustrate our theoretical concept by numerical simulations and electronic
circuit experiments.
DY 36.5 Mi 17:30 H2
Rejection of the output power noise in a multimode solid state
laser by pure electronic feedback — •L. Ehlkes 1,2 , T. Letz 1,2 , K.
Pyragas 3 , and A. Kittel 1 — 1 Energy and Semiconductor Research
Group, Department of Physics, University of Oldenburg — 2 Max Planck
Institute for the Physics of Complex Systems, Dresden — 3 Semiconductor
Physics Institute, Vilnius, Lithuania
Intracavity frequency doubled solid state laser that emit light in the
visible spectral range have great potential for technical applications. The
display technology sector is one example where this powerful green and
blue light sources are necessary at a low price and compact design.
The optical nonlinear crystal responsible for the frequency conversion is
placed inside the laser cavity in order to maximize efficiency. The drawback
of a simple, low cost setup is a fluctuating output power known as
the green problem.
In order to stabilize the output intensity of a frequency-doubled
Nd:YAG- laser we use a pure electronic proportional feedback loop. The
infrared intensities of two orthogonal directions of polarization are used
to determine corrections which alter the currents through two orthogonal
polarized pump diodes. The method seems promising for technical
application.
DY 36.6 Mi 17:45 H2
Synchronisationsanalyse physiologischer Daten in den Schlafstadien
— •Stephan Zschiegner 1,2,3 , Jan W. Kantelhardt 1 , Armin
Bunde 1 , Shlomo Havlin 2 und Thomas Penzel 3 — 1 Institut für
Theoretische Physik III, Justus-Liebig-Universität, Giessen, Germany —
2 Dept. of Physics and Minerva Center, Bar-Ilan University, Ramat-Gan,
Israel — 3 Klinik für Innere Medizin, Klinikum der Philipps-Universität,
Marburg, Germany
Wir untersuchen mit Methoden der statistischen Physik, wie sich die

Dynamik und Statistische Physik Mittwoch
Phasensynchronisation von Herzschlag und Atmung [1] bei gesunden Probanden
in den verschiedenen Schlafstadien (Leicht-, Tief-, und REM-
Schlaf) unterscheiden. In der Schlafphase sind Störungen durch willentliche
Aktivitäten ausgeschaltet, welche die interessierenden intrinsischen
Schwankungen überdecken und somit eine Erkennung der Regulationsmechanismen
erschweren können. Bei der Phasensynchronisation wird
zu jedem Datensatz durch Hilbert-Transformation die zugehörige kom-
plexe Reihe gebildet und daraus die Phasenreihe berechnet. Man spricht
von Phasensynchronisation, wenn die Phasendifferenz zweier Reihen modulo
2 Pi statistisch zu einem Wert tendieren. Um den Einfluss einer
Zeitverzögerung zu ermitteln, analysieren wir die Phasensynchronisation
auch unter Verschiebung um verschiedene Zeitintervalle.
[1] C. Schäfer, M.G. Rosenblum, J. Kurths, H.H. Abel, Nature 392
(1998) 239.
DY 40 Lyapunov Instability of Many-Body Systems
Zeit: Donnerstag 09:30–11:30 Raum: H2
Hauptvortrag DY 40.1 Do 09:30 H2
Lyapunov instability of many-body systems — •Harald A.
Posch — Institute for Experimental Physics, University of Vienna,
Boltzmanngasse 5, A-1090 Wien, Austria
The evolution of classical many-body systems is highly unstable with
respect to (infinitesimal) perturbations of phase-space states. Such perturbations
grow, or shrink, exponentially with time. This is described by
a set of rate constants, the Lyapunov spectrum. We demonstrate that in
thermodynamic equilibrium the perturbations associated with the slowest
growth rates are coherently spread out in space, reminiscent of the
modes of fluctuating continuum mechanics. The “Lyapunov modes” display
a linear dispersion relation for small wave numbers, which allows to
construct the relevant part of the Lyapunov spectrum for systems close to
the thermodynamic limit. For dynamically- thermostated systems in stationary
nonequilibrium states the phase-space probability distribution
is a fractal set with a dimension smaller than the dimension of phase
space. This reduction in dimensionality is computed from the Lyapunov
spectrum. It is shown to be an extensive quantity and may, by far, exceed
the dimensions contributed by the thermostated degrees of freedom.
The fractal nature of phase space is a fingerprint of the second law of
thermodynamics and is the consequence of a constant rate of entropy
production.
DY 40.2 Do 10:00 H2
Static and Dynamic Correlations in Many-Particle Lyapunov
Vectors — •Günter Radons and Hongliu Yang — Institut für
Physik, Theoretische Physik I, Technische Universität Chemnitz, D-
09107 Chemnitz
We introduce static and dynamic correlation functions for the spatial
densities of Lyapunov vector fluctuations. They enable us to show,
for the first time, the existence of hydrodynamic Lyapunov modes in
chaotic many-particle sytems with soft core interactions. Our investigations
for Lennard-Jones fluids yield in addition to the Lyapunov exponent
- wave vector dispersion, the collective dynamic excitations, which dominate
a given Lyapunov vector. In contrast to the Lyapunov vectors, which
are time-dependent quantities, the Lyapunov vector correlation functions
represent global properties of the dynamical system. For purely translational
Lyapunov modes they reduce to the ordinary static and dynamic
structure factor of many-particle systems.
DY 40.3 Do 10:15 H2
Examination of Taylor hypothesis — •Stephan Barth, Stephan
Lueck, and Joachim Peinke — University of Oldenburg
In open flows Taylor-hypothesis is commonly used to investigate small
scale turbulence. The Taylor-hypothesis enables transfering temporal
measurements with a localized probe to spatial structures of turbulence.
Here we examine the validity of the Taylor-hypothesis in a turbulent
wake flow. By means of two X-hotwire-probes positioned transversal to
the mean flow and a LDA positioned in flow direction in front of one
hotwire-probe measurements are performed. The Taylor-hypothesis was
verified on the basis of the statistics of small scale turbulence including intermittency
effects. The statistics of the longitudinal and the transversal
velocity increments obtained by Taylor-hypothesis and by direct measurements
at two points in the flow are compared.
DY 40.4 Do 10:30 H2
Force driven Stokes-flow between parallel plates — •Marcin
Kostur 1 , P Talkner 1 , Z Guttenberg 2 , S Keller 3 , J.O Rädler 3 ,
and A Wixforth 1 — 1 Institut für Physik, Universität Augsburg 86135
Augsburg — 2 Advalytix AG, EugenSanger Strasse 53.0 85649 Brunnthal
— 3 Ludwig-Maximilians-Universität München, 80539 München
Mixing and moving of small amounts of fluid poses a severe prob-
lem caused by the inherently small Reynolds numbers in micro- and
nanoflows. Surface acoustic waves that can be excited by the application
of a radio frequency wave to an interdigital transducer on a piezoelectric
substrate generate a localized force field acting on a fluid placed above
the transducer. We present the analytical as well as numerical solution of
the 3-dimensional flow generated by a line force. The calculated velocity
field is compared with experimental results for a 0.2mm thick fluid layer
driven by surface acoustic waves.
DY 40.5 Do 10:45 H2
Diffusion on a solid surface: Anomalous is normal — •Sokolov
Igor 1 , Sancho Jose Maria 2 , Lindenberg Katja 3 , Lakasta Ana
Maria 4 , and Romero Aldo 5 — 1 Institut für Physik, Humboldt Universitæt
zu Berlin — 2 Facultat de Física, Universitat de Barcelona, Spain
— 3 Department of Chemistry and Biochemistry, University of California,
San Diego, USA — 4 Departament de Física Aplicada, Universitat
Politècnica de Catalunya, Barcelona, Spain — 5 Advanced Materials Department,
IPICyT, San Luis Potosí, Mexico
We discuss results of a numerical study of classical particles diffusing
on a solid surface. The particles’ motion is modeled by an underdamped
Langevin equation with additive thermal noise under delailed-balance
conditions. The particle-surface interaction is described by a periodic or
a random two dimensional potential. The model leads to a rich variety
of different transport regimes, some of which correspond to anomalous
diffusion such as has recently been observed in experiments and Monte
Carlo simulations. We show that this anomalous behavior is controlled
by the friction coefficient, and stress that it emerges naturally in a system
described by ordinary canonical Maxwell-Boltzmann statistics.
DY 40.6 Do 11:00 H2
Short-range type critical behavior in spite of long-range interactions:
phase transition of a Coulomb system on a lattice —
•Arnulf Möbius and Ulrich K. Rößler — Leibniz-Institut für
Festkörper- und Werkstoffforschung, D-01171 Dresden
The problem under which conditions Coulomb glasses exhibit genuine
phase transitions has been under controversial debate for a long time,see
e.g. [1,2]. In this context, the relation to the Ising model with short-range
interaction is of great interest. It would be very useful to know how replacing
its nearest-neighbor coupling by an “antiferromagnetic” long-range
Coulomb interaction modifies the critical behavior of a system without
static disorder.
One- to three-dimensional hypercubic lattices half-filled with localized
particles interacting via a Coulomb potential are investigated numerically.
Temperature dependences of specific heat, mean staggered occupation,
and of a generalized susceptibility indicate order-disorder phase
transitions in two- and three-dimensional systems. The critical properties,
clarified by finite-size scaling analysis, are consistent with those of
the Ising model with short-range interaction [3]. Thus, in spite of the
long-range interaction, the Coulomb system considered seems to belong
to the same universality class as the Ising model with short-range interaction.
This suggests that the lattice Coulomb-glass model might have
the same critical properties as the random-field short-range Ising model.
[1] E.R. Grannan, C.C. Yu, Phys. Rev. Lett. 71, 3335 (1993).
[2] T. Vojta, M. Schreiber, Phys. Rev. Lett. 73, 2933 (1994).
[3] A. Möbius and U.K. Rößler, cond-mat/0309001.
DY 40.7 Do 11:15 H2
Anomalous behavior of the localization length in onedimensional
Anderson localization. — •Rüdiger Zillmer —
Institut für Physik, Universität Potsdam
A common example of exponential localization of the wavefunction
in disordered systems is given by the Anderson model. The localization

Dynamik und Statistische Physik Donnerstag
length can be assigned to the Lyapunov exponent of the corresponding
product of random transfer matrices. We consider the largest Lyapunov
exponent and the second generalized one, which are associated to different
average procedures. In case that single parameter scaling holds, these
two exponents coincide. We show analytically and numerically that at the
band center the largest exponent is not differentiable with respect to the
energy whereas the generalized exponent behaves regularly. This difference
corresponds to a different behavior of the typical and the average
conductivity, respectively.
DY 41 Symposium SYFT: Fat-Tail Distributions - Applications from Physics to Finance
Zeit: Donnerstag 09:30–13:00 Raum: H1
DY 41.1 Do 09:30 H1
Symposium SYFT: Fat-Tail Distributions - Applications from
Physics to Finance — • —
Details zum Programm sind unter SYFT zu finden.
DY 42 Long-Range Correlations and Multifractals
Zeit: Donnerstag 11:30–13:00 Raum: H2
DY 42.1 Do 11:30 H2
Effects of Membrane Potential Slope and Refractoriness
on Spike Synchronization — •Sven Goedeke 1 , Tom Tetzlaff
1,2 , Theo Geisel 1 , and Markus Diesmann 1,2 — 1 MPI für
Strömungsforschung und Institut für Nichtlineare Dynamik der
Universität Göttingen — 2 Neurobiologie und Biophysik, Biologie III,
Universität Freiburg
Neuron models based on the instantaneous spiking probability f(t) are
a convenient mathematical tool in the study of neural networks. Often f
is expressed in terms of a state variable, e.g. the membrane potential u(t).
Recent studies [1,2] have applied f(u)-models to spike synchronization
in feed-forward networks, emphasizing the dominant role of refractoriness.
We show that f(u) is inconsistent with integrate-and-fire dynamics.
An expression exhibiting the dependence of f on u and its temporal
derivative ˙u is derived. We use a bilinear f(u, ˙u) for an analytical investigation
of feed-forward synchronization. The system displays bistability
and quantitatively reproduces integrate-and-fire simulation results. The
˙u-dependence is a powerful mechanism of synchronization, taking effect
prior to refractoriness. The main function of refractoriness is normalizing
the number of spikes.
[1] Gewaltig M-O (2000) Aachen, Germany: Shaker
[2] Kistler WM & Gerstner W (2002) Neural Comput 14:987
DY 42.2 Do 11:45 H2
Controlling noise-induced motion by time-delayed feedback
— •Natalia Janson 1,2 , Alexander Balanov 1 , and Eckehard
Schöll 1 — 1 Institut für Theoretische Physik, Technische Universität
Berlin, 10623 Berlin, Germany — 2 Department of Mathematical Science,
Loughborough University, Leicestershire, LE11 3TU, UK
Time delayed feedback control that was earlier introduced by Pyragas
for the purpose of control of deterministic chaotic oscillations in nonlinear
dynamic systems, is exploited for controlling noise-induced motion.
Such noise-induced oscillations are widespread in systems near bifurcations,
and in excitable systems. Under appropriate choice of time delay,
one can either increase or decrease the regularity of motion. In an excitable
system, delayed feedback stabilizes the frequency of oscillations
against variation of noise strength. Also, for fixed noise intensity, the phenomenon
of entrainment of basic periods of oscillations by the delayed
feedback is found. This allows one to steer the timescales of noise-induced
motion by changing the time delay.
DY 42.3 Do 12:00 H2
Multifractal Detrended Fluctuation Analysis: Application to
Rainfall Records — •Diego Rybski 1,2 , Jan W. Kantelhardt 1 ,
Armin Bunde 1 , and Shlomo Havlin 2 — 1 Institut für Theoretische
Physik III, Justus-Liebig-Universität Giessen — 2 Department of Physics
and Minerva Center, Bar-Ilan University, Ramat-Gan, Israel
We use the Multifractal Detrended Fluctuation Analysis (MF-DFA)
[1] in order to characterize the fluctuations of long daily precipitation
records. We find that the records cannot be characterized by a single
multifractal model. For some records, the multifractal spectrum is described
by a modified binomial multifractal process, while for others a
bifractal model is most appropriate. For positive moments, the Lovejoy-
Schertzer ansatz provides a good fit to most records.
[1] J.W. Kantelhardt et al., Physica A 316, 87 (2002).
DY 42.4 Do 12:15 H2
Rückkopplung in chemischen Reaktionen — •Knud Zabrocki
und Steffen Trimper — Fachbereich Physik, Friedmann-Bach-Platz,
06108 Halle
Die klassischen Ratengleichungen in den diffusions- bzw. reaktionsgesteuerten
Regimes werden durch den Einschluss nicht-Markovscher
Terme erweitert. Solche Terme ergeben sich durch Ankopplungen an
zusätzliche Freiheitsgrade und stellen gewöhnlich konkurrierende Mechanismen
für die konventionellen instantanen nichtlinearen Kopplungen
dar. Wir untersuchen systematisch zwei verschiedene Fälle, die als
äußere bzw. innere Rückkopplungen charakterisiert werden. Während
im Fall externer Kopplung die Gedächtniseffekte durch deterministische
Funktionen hervorgerufen werden, sind es im Falle interner Kopplungen
selbst-organisierte Mechanismen. Relevante Realisierungen äußere
Rückkopplungen führen auf endliche Laufzeiteffekte, allmähliches oder
gedämpft periodisches Abschalten der Gedächtnisterme. Während in
diesem Fall die stationären Fixpunkte ungeändert bleiben, führt ein
interner Feedback zu neuen stabilen Fixpunkten, die das Phasendiagramm
entscheidend beeinflussen. Die Modelle werden durch den Einschluss
räumlich variierender Terme und inhomogene Anfangsbedingungen
zusätzlich verallgemeinert. Die analytischen Ergebnisse werden durch
numerische Untersuchungen gestützt. Mögliche Anwendungen auf Transportprozesse
in ungeordneten Medien und in der Biologie werden diskutiert.
Hauptvortrag DY 42.5 Do 12:30 H2
Long-range correlations in nature: On test-beds for climate
models, global warming and natural clustering of hazardous
floods — •Armin Bunde — Institut für Theoretische Physik III, Universität
Giessen, D-35392 Giessen
A large number of natural records (e.g. temperatures, river flows, heartbeat
intervals, internet traffic) exhibit long-term correlations characterized
by a power-law decay of the auto-correlation functions C(s) ∼ s −γ .
Typical values of γ are γ = 0.7 for continental temperature records,
γ = 0.4 for sea surface temperatures, γ = 0.3 for river flows, and γ = 0.4
for heartbeat intervals during REM-Sleep. Here we discuss applications
and consequences of the long-term correlations. We show that (i) the temperature
correlations can be used as an effective test-bed for climate models
and discuss (ii) the effect of long-term correlations on the estimation
of global warming. Finally we show explicitely that (iii) long-term correlations
represent a natural mechanism for clustering of extreme events,
by which both the observed clustering of hazardous floods in Europe as
well as (at least partially) the increase of floods in the past decades can
be explained.

Dynamik und Statistische Physik Donnerstag
DY 44 Granular Systems
Zeit: Donnerstag 14:30–16:00 Raum: H2
Hauptvortrag DY 44.1 Do 14:30 H2
Phase transitions and segregation phenomena in granular systems
— •Christof Krülle — Experimentalphysik V, Universität
Bayreuth, 95440 Bayreuth
For a collection of macroscopic particles, which are agitated by external
forces to perform stochastic movements, a ‘granular temperature’ can
be defined as mean kinetic energy in the center-of-mass system. For describing
the physical properties of this ensemble one can ask – in analogy
to thermodynamic phase transitions: (i) Are there critical temperatures
at which the internal structure undergoes qualitative changes? (ii) Which
order parameters characterize the dynamics of the transition? (iii) What
are the consequences for granular mixtures? We present results from experiments
in granular systems, which are excited by vertical and horizontal
vibrations [1,2]. The transitions between different dynamic states
depend on internal properties of the granulate (e.g. the density of particles)
as well as external parameters of the driving shaker. Peculiar to
granular systems are counterintuitive phenomena, like the crystallization
by increasing the vibration amplitude and thereby the energy input, or
the rise of large particles in a sea of smaller ones (Brazil-nut effect).
For horizontal shaking of a bidisperse system the demixing of small and
large particles is found to occur at the same critical particle density as the
liquid-solid transition, which leads to the conclusion that both phenomena,
segregation and phase transition, are closely related. [1] A.P.J. Breu,
H.-M. Ensner, C.A. Kruelle, and I. Rehberg, Phys. Rev. Lett. 90, 014302
(2003), [2] S. Aumaître, T. Schnautz, C.A. Kruelle, and I. Rehberg, Phys.
Rev. Lett. 90, 114302 (2003).
DY 44.2 Do 15:00 H2
Exploring the phase space of granular material — •Matthias
Schröter, Daniel I. Goldman, and Harry L. Swinney — University
of Texas at Austin
Edwards and Oakeshott (Physica A 157, 1080 (1989)) proposed a thermodynamic
approach to granular media, which is based on the idea that
only a finite number of mechanically stable configurations fit a given
number of particles in a fixed volume. They introduce a temperaturelike
state variable named Compactivity. The only experiment designed
to measure this quantity was done by Nowak et al. (Phys. Rev. E 57, 1971
(1998), who tapped a column of granular material and measured the the
asymptotic density fluctuations. This approach was, however, hampered
by long relaxation times and a small range of achievable densities. We
will show that the spatially homogeneous driving in a fluidized bed avoids
this problem. Our approach allows a test the applicability of the Edwards
hypothesis.
DY 44.3 Do 15:15 H2
Granular surface waves upon circular shaking — •Andreas
Götzendorfer 1 , Almudena Garcia 1 , Christof Krülle 1 ,
Ingo Rehberg 1 , Rafal Grochowski 2 , Peter Walzel 2 , Hamid
Elhor 3 , and Stefan J. Linz 3 — 1 Experimentalphysik V, Universität
Bayreuth — 2 Mechanische Verfahrenstechnik, Universität Dortmund —
3 Theoretische Physik, Universität Münster
DY 46 Poster
We study the behaviour of dry granular material on vibratory conveyors.
These machines are ubiquitous in industry and utilized for transport
of small components, coal pieces, cereal grains, fertilizer granulates,
sands, powders ... It is already known that for vertical sinusoidal vibrations
above a critical shaking intensity the granular material shows
surface waves. In our experiment we superpose the vertical vibration
with a horizontal vibration of the same amplitude and a phase shift of
π/2. That means that the support follows a circular trajectory. For this
kind of shaking non-stationary waves are observed in a certain driving
range. These pattern formation phenomena have a direct impact on the
transport properties of the conveyor and are therefore of importance for
industrial applications.
DY 44.4 Do 15:30 H2
Sound propagation in dense granular media — •Stefan Luding
— Particle Technology, DCT, TUDelft, Julianalaan 136, 2628 BL Delft,
Netherlands
The goal of the presented research is to understand information propagation
in dense assemblies of spherical, polydisperse granular media.
Using a discrete element method (DEM) simulation, the wave propagation
is studied. After relaxation to an isotropic static equilibrium state, a
wave is agitated by moving one side wall. First, the effect of the contact
force-law is examined for a cubic sample; second, the effects of singular
and periodic agitations are studied with Fourier analysis; third, pressure
effects and an-isotropy are examined.
DY 44.5 Do 15:45 H2
Horizontal brazil nut effects in a swirled bowl — •Tobias
Schnautz 1 , Christoph Kruelle 1 , Ricardo Brito 2 und Ingo Rehberg
1 — 1 Experimentalphysik V, Universitaet Bayreuth, D-95440 Bayreuth,
Germany — 2 Dep. Fisica Aplicada I, Universidad Complutense,
28040- Madrid, Spain
We present both, the behavior of a monodisperse layer of spheres, rolling
on a circularly vibrating table, and experimental results on on the
segregation of a binary mixture of spheres. When increasing the filling
fraction, a monodisperse layer of spheres shows two transitions between
states characterized by a different mobility of particles. The critical particle
densities for the liquid-solid transition are found to be independent
of the driving frequency, but decrease with increasing vibration amplitude.
Depending on the material properties, segregation occurs in the
liquid-like and in the solid-like state. The particle velocity distributions
show a transition from two peaks, located symmetrically around zero, to
one single peak at zero. The experimental results are compared with a
simplified two- dimsnional model system.
Zeit: Donnerstag 16:00–18:00 Raum: Poster D
DY 46.1 Do 16:00 Poster D
Period orbit expansion for simple spin systems — •Sarah
Hallerberg 1 , Wolfram Just 2 , and Günter Radons 1 — 1 Institute
of Physics, Chemnitz University of Technology, Chemnitz, Germany
— 2 Department of Mathematics, Queen Mary/University of London,
London, UK
We investigate the properties of zeta functions and the corresponding
expansion in terms of periodic orbits for spin chain models. In particular
we focus on mean field models which display phase transitions. The properties
of the zeta function and the periodic orbit expansion in different
phases and near the phase transition will be investigated by analytical
methods.
DY 46.2 Do 16:00 Poster D
Numerical Results for the Generalized Mittag-Leffler Function
— •Hansjörg Seybold 1 and Rudolf Hilfer 1,2 — 1 ICA-1 Universität
Stuttgart, 70569 Stuttgart, Germany — 2 Institut für Physik, Universität
Mainz, 55099 Mainz, Germany
Results of extensive calculations for the generalized Mittag-Leffler
function Eα,β(z) are given in the complex plane: Discussion of the distribution
of the zeros and the dependency of the parameters α > 0 and
β ∈ R. This function is related to the eigenfunction of the fractional
derivative operator of order α and type α + β(1 − α) [1].
[1] R. Hilfer, Applications of fractional calculus in physics, World Scientific,
Singapore (2000)

Dynamik und Statistische Physik Donnerstag
DY 46.3 Do 16:00 Poster D
Characterization of Carbonates Using Local Porosity Theory
— •Ali Moosavi 1 and Rudolf Hilfer 1,2 — 1 ICA-1, universität
Stuttgart, 70569 Stuttgart, Germany — 2 Institut für Physik, Universität
Mainz, 55099 Mainz, Germany
Local porosity theory is used to provide a quantitative description of
two carbonate samples. The degree of heterogeneity, anisotropy and connectivity
of the samples is discussed. Also, the effect of resolution on the
results is studied. The results emphasize the necessity to take into accoun
micro-nano scale pores when studying or modeling carbonates.
DY 46.4 Do 16:00 Poster D
Universal energy distribution for interfaces in a random field
environment — •Semjon Stepanow und Andrei A. Fedorenko
— Universität Halle, Fachbereich Physik, 06099 Halle
We study the energy distribution function ρ(E) for interfaces in a
random field environment at zero temperature by summing the leading
terms in the perturbation expansion of ρ(E) in powers of the disorder
strength, and by taking into account the non perturbational effects of the
disorder using the functional renormalization group. We have found that
the average and the variance of the energy for one-dimensional interface
of length L behave as, < E >∝ LlnL, ∆E ∝ L, while the distribution
function of the energy tends for large L to the Gumbel distribution of
the extreme value statistics.
DY 46.5 Do 16:00 Poster D
Dynamics and shock formation in an exclusion process with
creation and annihilation — •Róbert Juhász 1 , Martin Evans 2 ,
and Ludger Santen 1 — 1 Theoretische Physik, Universität des Saarlandes,
66041 Saarbrücken, Germany — 2 School of Physics, University
of Edinburgh, Mayfield Road, Edinburgh, EH9 3JZ, United Kingdom
We investigate an asymmetric exclusion process with creation and annihilation
of particles in the bulk. We show how the continuum meanfield
equations can be studied analytically and hence derive the phase
diagrams of the model. Fluctuations of the shock position are also investigated
by using a phenomenological random walk picture of the shock
dynamics. The case where bulk creation- and annihilation rates vanish
faster than the inverse of the system size N is also analyzed. We point
out that shock localization is possible even for rates proportional to N −a ,
1 < a < 2. The maximum current phase is studied by means of scaling
arguments and numerical simulation. Here, the length- and the time
scale are found to be finite as opposed to the algebraically decaying correlations
of the totally asymmetric simple exclusion process (TASEP).
Critical exponents of the transition to the TASEP are determined.
DY 46.6 Do 16:00 Poster D
Kritische Dynamik von Modell C — •Günter Moser 1 und Reinhard
Folk 2 — 1 Institut für Physik und Biophysik, Universität Salzburg,
Österreich — 2 Institut für Theoretische Physik, Universität Linz,
Österreich
Die kritische Dynamik eines relaxierenden n-komponentigen Ordnungparameters
reller Relaxationskoeffizient Γ), der an eine erhaltene skalare
Dichte (Onsagerkoeffizient λ) koppelt wird durch das Modell C beschrieben.
Es werden die feldtheoretischen Funktionen eines generalisierten
Modell C (Modell C ∗ ), mit komplexem Ordnungsparameter und mit komplexem
Relaxationskoeffizienten Γ, in Zweischleifennäherung berechnet.
Es stellt sich heraus, dass der Imaginärteil von Gamma nur den Fixpunktwert
Null besitzt, und somit die Fixpunkte identisch zu jenen von
Model C sind. Die Rechnungen korrigieren einerseits die bisherigen feldtheoretischen
Ergebnisse [1] für Model C andererseits wird gezeigt, dass
der anomale Bereich, in dem die Skaleneigenschaften unklar blieben, nicht
existiert. Ferner wird der Fluss des dynamischen Zeitskalenverhältnisses
w = Γ/λ berechnet und gezeigt dass der asymptotische Bereich nur sehr
langsam erreicht wird. Das bedeutet, dass auch für die Fälle n = 2, 3, wo
die erhaltene Dichte entkoppelt und damit die Asymptotik durch Model
A bestimmt wird, Model C relevant ist. [1] E. Brezin und De Dominicis,
Phys. Rev. B 12, 4954 (1975); V. Dohm, Phys. Rev. B 44, 2697 (1991)
[2] B. I. Halperin, P. C. Hohenberg und S.-K. Ma, Phys. Rev. B 10, 139
(1974); 13, 4119 (1976)
DY 46.7 Do 16:00 Poster D
Zusammenhang von α- und (langsamer) β-Relaxation in Glasbildnern
— •Manfred Winterlich und Roland Böhmer — Experimentelle
Physik III, Universität Dortmund, 44221 Dortmund
Bei einigen Glasbildnern existiert neben der α-Relaxation eine (lang-
same) β-Relaxation. Durch stimulierte Deuteronenechos kann die α-
Relaxationszeit im Bereich von Millisekunden bis Sekunden gemessen
werden. Hier wird gezeigt, dass bei manchen Glasbildnern (z. B. ortho-
Terphenyl) eine Verringerung der Relaxationszeit des stimulierten Echos
auftritt, falls vor dem Echoexperiment nicht der Kernspingleichgewichtszustand
vorliegt. Die Relaxation in das Gleichgewicht des Spinsystems
wird durch Prozesse auf der Mikrosekundenzeitskala (Larmorfrequenz)
bewirkt, in der die (langsame) β-Relaxation liegt, wenn die α-Relaxation
einige Millisekunden beträgt. Es wird gezeigt, dass die Beschleunigung
der stimulierten Echorelaxation durch Annahme einer Relaxationszeitenverteilung
qualitativ beschrieben werden kann, falls man eine Konnektivität
zwischen α- und β-Relaxation unterstellt.
DY 46.8 Do 16:00 Poster D
Einfluss der anharmonischen Wechselwirkung auf den ”Boson-
Peak” — •Edith Maurer 1 , Walter Schirmacher 1 und Markus
Pöhlmann 1,2 — 1 Phys.-Dept. E13, TU MMünchen, 85747 Garching —
2 Institut Laue-Langevin, Grenoble
Mit feldtheoretischen Methoden haben wir eine Mean-Field-Theorie
für das Schwingungsspektrum ungeordneter und schwach anharmonischer
Festkörper entwickelt. Im harmonischen Limes ergibt sich die niederfrequente
Erhöhung der Schwingungszustandsdichte bezüglich des Debye-
Gesetzes (”Boson-Peak”) als Folge der Unordnung in den elastischen
Konstanten. Mit ansteigender Unordnung (Varianz der fluktuierenden
elastischen Konstanten) verstärkt sich der Boson-Peak und verschiebt
sich zu niedrigeren Frequenzen, wie es im Experiment beobachtet wird.
Die Anwesenheit anharmonischer Wechselwirkung führt zu einem Anstieg
des Spektrums mit der Temperatur unterhalb des Boson-Peaks,
ebenfalls in Übereinstimmung mit den Experimenten. Die Theorie sagt
einen Übergang zu einer nichtergodischen Phase voraus. Der Boson-Peak
lässt sich als Precursor-Phänomen dieses Übergangs interpretieren. Die
Bosonpeakeigenschaften der Zustandsdichte übertragen sich auf die Temperaturabhängigkeit
der spezifischen Wärme. Unterhalb des Boson-Peaks
sagt unsere Theorie eine anomale, von der Debye-Theorie abweichende
Temperaturabhängigkeit voraus.
DY 46.9 Do 16:00 Poster D
Identification of Ion Sites in Glasses from Equilibrium Molecular
Dynamics Configurations — •Renata Brosińska 1 , Junko
Habasaki 2 , and Philipp Maass 1 — 1 Institut für Physik, Technische
Universität Ilmenau, Germany — 2 Tokyo Institute of Technology, Japan
For an understanding of the complex ion dynamics in glasses it is important
to identify and characterise the sites that are occupied by the
mobile ions during their jump motion through the glassy network [1].
Recently this task was undertaken by means of molecular dynamics simulations
[2,3]. In these simulations the number of ion sites and their
occupation probabilities were determined by examining how many times
a small region (cell) in the simulation box is occupied by a mobile ion.
Here we investigate the question if an identification of the same sites is
possible based on equilibrium configurations only. To this end we perform
an analysis of the ionic potential energy surface with respect to the
minima and their connectivity features.
[1] P. Maass, J. Non-Cryst. Solids 255, 35 (1999)
[2] H. Lammert, M. Kunow, and A. Heuer, Phys. Rev. Lett. 90, 215901 (2003)
[3] J. Habasaki and Y. Hiwatari, Phys. Rev. B, in print
DY 46.10 Do 16:00 Poster D
Vacancy model for the mixed alkali effect — •Robby Peibst,
Stephan Schott, Hartmut Grille, and Philipp Maass — Institut
für Physik, Technische Universität Ilmenau, Germany
In ionically conducting glasses, all properties associated with longrange
ionic motion show large deviations from a simple additive behavior
upon mixing of two different types of mobile ions. This phenomenon
is called the mixed alkali effect and is of particular theoretical interest
due to its crucial role for the general understanding of ion transport in
glasses. Recent molecular dynamics simulations and further general considerations
suggest that the number of vacant sites in the glassy network
is rather small. Motivated by these findings and by taking into account
the existence of different energies of the ion sites [3], we discuss possible
szenarios to explain the mixed alkali effect by a vacancy mechanism.
[1] H. Lammert, M. Kunow, and A. Heuer, Phys. Rev. Lett. 90, 215901 (2003)
[2] J. Habasaki and Y. Hiwatari, Phys. Rev. B, in print
[3] Ph. Maass, J. Non-Cryst. Solids 255, 35 (1999)

Dynamik und Statistische Physik Donnerstag
DY 46.11 Do 16:00 Poster D
Magnification control of concave/convex learning in selforganizing
neural maps and neural gas — Thomas Villmann 1
and •Jens Christian Claussen 2 — 1 Cl. for Psychotherapy,
University Leipzig — 2 Theoretical Physics, University Kiel
The self-organizing neural maps (SOM) by Kohonen and the neural
gas (NG) by Martinetz are paradigms of neural winner-take all feedforward
computation and are widely applied for vector quantization tasks.
A data representation maximizing mutual information corresponds to an
magnification exponent of 1, which is not reached by SOM and (finitedimensional)
NG. Recently we presented magnification approaches for
NG by an additive winner-relaxing term [1] (extending an approach for
SOM [2, 3, 4]) as an alternative to localized learning [4].
In this work [5] an alternative learning rule, the concave/convex learning
[6], is investigated with respect to its magnification behaviour. We
present an analytical derivation of the magnification exponent for SOM
(in 1D) and for NG in arbitrary dimensions from a continuum theory. The
results are validated by numerical calculation of the entropy for a standardized
test system. We observe a dependence on the learning exponent
in agreement with the theoretical predictions.
[1] J.C.C. and T.V., Proc. ESANN 2003; J.C.C. and T.V. (subm.)
[2] J.C.C. cond-mat/0208414; [3] J.C.C. Complexity 8(4), 15 (2003).
[4] J.C.C., Math.Mod.Comp.Biol.Med. p.17, ed.V.Capasso, Bologna, 2003.
[5] M. Hermann, T.V., Proc. ICANN 1997.
[6] T.V. and J.C.C., Proc. WSOM 2003; T.V. and J.C.C. (subm.)
[7] Y.Zheng, J.F.Greenleaf, IEEE Trans. Neur. Netw. 7, 87 (1996).
DY 46.12 Do 16:00 Poster D
The Dynamics of Learning Vector Quantization — •Michael
Biehl 1,2 , Ansgar Freking 2 , and Georg Reents 2 — 1 Institute for
Mathematics and Computing Science, University of Groningen, P.O. Box
800, NL-9700 AV Groningen — 2 Institut fuer Theoretische Physik und
Astrophysik, Universitaet Wuerzburg, Am Hubland, D-97074 Wuerzburg
Learning Vector Quantization (LVQ) is a widely used method for the
implementation of classification schemes, in particular in the context of
structured (”clustered”) data. Here, we analyse LVQ by means of the
statistical physics theory of on-line learning in high-dimensional weight
space.
We show how variations of LVQ can be interpreted as interpolating between
”unsupervised clustering” (without a teacher) and the supervised
learning of a rule. The focus is on the phenomen of symmetry breaking
phenomena and the role of initial conditions for the learning process.
DY 46.13 Do 16:00 Poster D
Parameters estimation of hidden diffusion processes —
•Abdelhadi Benabdallah and Günter Radons — TU Chemnitz,
Institut für Physik , D-09107 Chemnitz, Germany
Diffusion processes, continuous in time and space, often cannot be
observed directly but only via functions reflecting the measurement process.
Within this work we investigate the parameter estimation problem
for hidden diffusion processes in a periodic potential. We propose a discrete
model as an approximation of continuous partially observed diffusion
Processes. Using the EM (Expectation-Maximisation) algorithm
we estimate the drift and the diffusion parameters which characterise
the diffusing state variable via an approximation by a discrete random
walk.A comparison with the particle filter are made. Numerical results
confirm our analytical estimation.
DY 46.14 Do 16:00 Poster D
Duality Transformation for Quantum Ratchets — •Joël Peguiron
1,2 and Milena Grifoni 2 — 1 Departement of Nanoscience, Delft
University of Technology, 2628 CJ Delft, The Netherlands — 2 Institut
für Theoretische Physik, Universität Regensburg, 93040 Regensburg
We investigate a duality transformation between weak-binding models
and tight-binding models for quantum ratchet systems. Ratchets are periodic
structures with broken spatial symmetry yielding the possibility of
a directed current in presence of noise and unbiased external forces. The
duality transformation would allow to relate results that we obtained on
few-bands quantum ratchets in the incoherent tunneling regime [1] with
existing results on weakly corrugated ratchets [2]. It would also make
possible to extend the parameter range of applicability of these results
and especially check their classical limit. We are also interested to see
how the symmetry conditions under which the ratchet current vanishes
in both models map onto each other.
[1] M. Grifoni et al., PRL 89, 146801 (2002)
[2] S. Scheidl and V. M. Vinokur, PRB 65, 195305 (2002)
DY 46.15 Do 16:00 Poster D
Velocity fluctuations in ratchets — •Lukasz Machura 1,2 and Peter
Hänggi 1 — 1 Theoretishe Physik I, Institut für Physik, Universität
Augsburg, Germany — 2 Department of Theoretical Physics, Institute of
Physics, University of Silesia, Poland
The quantity of foremost interest in the context of transport in periodic
systems, like Brownian ratchets, is the mean velocity of the particle.
However, the quality of the transport depends also on some other characteristics
like effective diffusion or shape of the potential. In this work
we use simulations to investigate the velocity correlation function in the
inertia Brownian ratchet. The connection between its behavior and the
optimal transport conditions is presented.
DY 46.16 Do 16:00 Poster D
Dynamics and interaction of dissipative solitons — •Hendrik
U. Bödeker 1 , Andreas W. Liehr 1 , Till D. Frank 2 , Rudolf
Friedrich 2 , Ulf-Hendrik Hansen 1 , and Hans-Georg Purwins 1
— 1 Westfälische Wilhelms-Universität Münster, Institut für Angewandte
Physik, Corrensstr. 2/4, 48149 Münster — 2 Westfälische Wilhelms-
Universität Münster, Institut für Theoretische Physik, Wilhelm-Klemm-
Str. 9, 48149 Münster
We present new results concerning the investigation of the dynamics
and the interaction of dissipative solitons occurring as current filaments
in a planar DC gas-discharge system with high-ohmic barrier. The dissipative
solitons exhibit interesting particle-like properties like generation
and annihilation, scattering, and formation of molecules. Processes in
which the number of solitons stays preserved can be understood by analyzing
the dynamics using means of stochastic data analysis. In this way,
both intrinsically standing and propagating solitons can be found, corresponding
to Brownian and active Brownian particles [1]. In addition,
a distance-dependant interaction law between mutually interacting dissipative
solitons can be determined, quantitatively explaining the experimentally
observed interaction phenomena. Generation and annihilation
processes taking place on a short time scale can be observed using fast
cameras, revealing different basic scenarios.
[1] H. U. Bödeker, M. C. Röttger, A. W. Liehr, T. D. Frank, R. Friedrich
and H.-G. Purwins, Noise-covered drift bifurcation of dissipative solitons in a
planar gas-discharge system, PRE 67 (2003) 056220.
DY 46.17 Do 16:00 Poster D
Characterisation of atrial fibrillation by analysis of ECG
records — •Th. Hennig 1 , A. Heinen 2 , St. Heinrichs 2 , D. Jäger 3 ,
and Ph. Maass 1 — 1 Institut für Physik, Technische Universität Ilmenau,
Germany — 2 Fachbereich Physik, Universität Konstanz, Germany
— 3 Medizinische Klinik II – Kardiologie, Städtisches Krankenhaus
Friedrichshafen, 88048 Friedrichshafen
We investigate the heartbeat of patients with atrial fibrillation (AF),
which is a cardiac arrhythmia where the normal pacemaking by the sinus
node is dysfunctional. The analysis of AF mechanisms and characteristics
is an important task, since it allows one to decide for the right diagnosis
and to improve possible therapies. Because standard ECG records
taken in hospitals are influenced by many different processes, it is difficult
to extract information from the ECG, which is particularly sensitive
to AF. We present novel methods to tackle this problem by employing
time series analysis and modeling, where AF is described by a stationary
process of irregular electrical excitations and the ventricular excitations
result from certain properties of the AV node. Our techniques allow us to
identify physiological parameters that otherwise can only be determined
invasively.
DY 46.18 Do 16:00 Poster D
Stochastic resonance in colloidal systems — •Dusan Babic 1,2 ,
Carmen Schmitt 1 , Igor Poberaj 2 , and Clemens Bechinger 1
— 1 2. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57,
70550 Stuttgart — 2 Faculty of mathematics and physics, University of
Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
The concept of stochastic resonance (SR) has been used to describe
very different effects such as the periodic occurence of the ice ages, the
feeding behavior of paddlefish or human balance control and visual perception.
The essential feature of SR is that in nonlinear systems noise
can improve the detection of weak periodic signals.
Although characteristic features of SR have been observed in several
experiments, there are only few examples where the effect is studied on

Dynamik und Statistische Physik Donnerstag
a microscopic level. Colloids - mesoscopic particles which are coupled to
a thermal bath and therefore undergo Brownian motion - are a system
with intrinsic noise where the time and length scales are conveniently
accessible with experiments. As such they provide an excellent model
system for fundamental experiments of SR. We investigate the dynamics
of a colloidal particle in a double-well potential, the latter being created
by optical tweezers. For asymmetric modulation of the potential
(corresponding to a tilt) we observe the typical signatures of SR in the
residence time distribution and in the power spectrum. In contrast, if we
only modulate the height of the potential barrier we do not observe any
synchronization between the modulation and the particle dynamics.
DY 46.19 Do 16:00 Poster D
Exact Analytical Solutions and Unpredictability of the Lorenz
System — •Oliver Strebel — Handjerystr. 31, 12159 Berlin
For the Lorenz equations [1] exact analytical solutions are given. Special
care was taken to construct graphs of solution curves by evaluating
the analytical formula up to the accuracy of the floating point arithmetic
of numbers in the used computer system. In addition to an analytical
check the solution and its time derivative are evaluated on a computer
and the difference between the left and right hand side of the Lorenz
equations is calculated. This results in a tiny difference of several hundreds
times the floating point precision constant stemming from different
rounding errors during the evaluations of the formulas for the solution
and its time derivative.
For the chaotic case of the Lorenz system it is demonstrated that for
a given accuracy of the initial conditions it becomes undetermined after
a few time units whether the system will reside in the left or right
half space having a x coordinate less or greater than zero. This indicates
fast transition to unpredictability of the system. The dynamics has for
large regions of initial conditions a close resemblence to a Smale horseshoe
[2], where adjacent initial conditions generate completely different
trajectories.
[1] C. Sparrow, The Lorenz Equations: Bifurcations, Chaos and Strange
Attractors, Springer AMS 41, Berlin (1982).
[2] S. Wiggins, Global Bifurcations and Chaos, Springer AMS 73,
Berlin (1988).
DY 46.20 Do 16:00 Poster D
Online-Simulation von Fahrzeugen auf komplexen Straßennetzwerken
mit einem Zellularautomatenmodell — •Florian Mazur,
Roland Chrobok, Sigurdur F. Hafstein, Andreas Pottmeier
und Michael Schreckenberg — Universität Duisburg-Essen,
Physik von Transport und Verkehr, Lotharstr. 1, 47048 Duisburg
Das Konzept der Online-Simulation ist eine Abbildung des realen Verkehrs
im Computer. Dabei wird jedes Fahrzeug mit Hilfe von gemessenen
Verkehrsdaten virtuell nachgebildet. Sehr effektive Modelle mit verhältnismäßig
wenig Rechenaufwand sind die so genannten Zellularautomaten-
Modelle. Mit diesen Modellen ist es möglich, den Verkehr realistisch zu
beschreiben und zu analysieren. Ein Ansatz, der auf dem von Nagel und
Schreckenberg 1992 veröffentlichten Verkehrsmodell basiert, ist mittlerweile
in der Lage, den kompletten Verkehr in einem komplexen Netzwerk
realitätsgetreu zu simulieren. Um den Grad an Realität weiter zu
erhöhen, wird der simulierte Verkehr mit Online-Daten abgeglichen, welche
durch Induktionsschleifen jede Minute gemessen werden. Damit kann
auch auf unvorhersehbare Ereignisse (z.B. Unfälle) reagiert werden.
DY 46.21 Do 16:00 Poster D
Konzeption und Anwendung des Verkehrsinformationssystems
OLSIM — •Florian Mazur, Roland Chrobok, Sigurdur F.
Hafstein, Andreas Pottmeier und Michael Schreckenberg —
Universität Duisburg-Essen, Physik von Transport und Verkehr, Lotharstr.
1, 47048 Duisburg
Seit Dezember 2003 kann man neben dem aktuellen Verkehrszustand
und der 30-Minuten-Prognose im Internet unter www.autobahn.nrw.de
eine 60-Minuten-Prognose des Autobahnverkehrs in Nordrhein-Westfalen
abrufen. Hinter den Farben grün für freien Verkehr bis rot für Stau verbirgt
sich eine komplizierte nichtlineare Dynamik. Da die Autobahnen in
NRW nur lokal mit Zählschleifen ausgestattet sind, werden die Verkehrsstufen
für das komplette Netzwerk in einer Simulation per Computer
berechnet. Ebenso wird eine Verkehrsprognose aus einer in mehrfacher
Echtzeit laufenden Simulation und Erfahrungswerten aggregiert. Unfälle,
Baustellen und Spursperrungen beeinflussen diese Hochrechnungen, wie
auch das Verhalten der mittlerweile über 300.000 Nutzer pro Tag, die ihre
Reiseplanung (Routenwahl, Reisezeitpunkt) nach den veröffentlichten
Prognosen erstellen. Inwieweit sich Staus in NRW zurückgebildet oder
nur verlagert haben ist Gegenstand gegenwärtiger Forschungen.
DY 46.22 Do 16:00 Poster D
Comparison of different coupling schemes for time-delayed
feedback control — •Andreas Borck 1 , Wolfram Just 2 , and
Günter Radons 1 — 1 Institute of Physics, Chemnitz University of
Technology, Chemnitz, Germany — 2 Department of Mathematics,
Queen Mary/University of London, London, UK
For time-independent target states we investigate the control performance
of time-delayed feedback control for different coupling schemes of
the control force. Applying linear stability analysis we obtain, in dependence
on the coupling scheme and the properties of the target state, the
corresponding transcendental characteristic equation. Properties of the
eigenvalue spectra are discussed by analytical methods. In this way an
optimal control scheme can be designed.
DY 46.23 Do 16:00 Poster D
Improvement of time-delayed feedback control by oscillating
feedback — Andreas Fichtner 1 , Wolfram Just 2 , Günter
Radons 1 , •Andreas Fichtner 1 , and Wolfram Just 2 — 1 Institute
of Physics, Chemnitz University of Technology, Chemnitz, Germany
— 2 Department of Mathematics, Queen Mary/University of London,
London, UK
By imposing time dependent modulation on the control amplitude the
performance of time-delayed feedback control may be enhanced. The relative
phase between the control loop and the target state plays the crucial
role. We investigate these features by analytical methods in a simple time
discrete model. The linear stability analysis clearly shows the dependence
of the control properties on the relative phase of the periodic orbit.
DY 46.24 Do 16:00 Poster D
Erregungswellen in quasi-zweidimensionalen, gekrümmten
Reaktions-Diffusions-Systemen — •Niklas Manz 1,2 und Stefan
C. Müller 2 — 1 Institut für Experimentelle Physik, Otto-von-Guericke-
Universität, D-39106 Magdeburg — 2 Department of Chemistry and
Biochemistry, Florida State University, Tallahassee, FL 32306-4390,
USA
Die chemische Belousov-Zhabotinsky-Reaktion stellt ein ideales System
zur Untersuchung der Dynamik von Reaktions-Diffusions Mustern
dar, die in den unterschiedlichsten biologischen, chemischen und physikalischen
Systemen zu beobachten sind. Obwohl diese propagierenden
Strukturen auch in gekrümmten Medien wie der Herzoberfläche
oder der Retina vorkommen, befaßten sich die experimentellen Untersuchungen
überwiegend mit planaren raumzeitlichen Strukturen. Wir stellen
ein Verfahren zur Herstellung quasi-zweidimensionaler, nichtebener
Medien vor [1]. Mit Hilfe dieser gleichmäßig bzw. nichtgleichmäßig gekrümmten
Systemen werden propagierende Wellen und Spiralen in verschiedenen
nichtebenen Systemen untersucht. Die experimentellen Ergebnisse
werden im Rahmen der kinematischen Theorie der Ausbreitung
von Reaktions-Diffusions-Wellen erörtert.
[1] N. Manz and S.C. Müller, Fabrication of quasi-two-dimensional,
heterogeneously curved Belousov-Zhabotinsky systems, Rev. Sci. Instrum.
74(12) (2003), in print
DY 46.25 Do 16:00 Poster D
Lyapunov Instabilities in Lennard-Jones Fluids — •Hongliu
Yang and Günter Radons — Institut für Physik, Theoretische Physik
I, Technische Universität Chemnitz, D-09107 Chemnitz
We present new results on Lyapunov spectra and Lyapunov vectors for
Lennard-Jones fluids. The density and temperature dependence of these
quantities is discussed in detail. The spatio-temporal behavior of the hydrodynamic
Lyapunov modes is obtained by studying its dependence on
the Lyapunov exponent, frequency and wave number. In contrast to this
wave-like behavior, the Lyapunov vectors for large Lyapunov exponents
show localized behavior in phase space, as is seen by evaluating the corresponding
participation ratios.
DY 46.26 Do 16:00 Poster D
Hydrodynamic Lyapunov Modes in Coupled Map Lattices —
•Hongliu Yang and Günter Radons — Institut für Physik, Theoretische
Physik I, Technische Universität Chemnitz, D-09107 Chemnitz
We present numerical results, which indicate that hydrodynamic Lyapunov
modes also exist for Coupled Map Lattices. We discuss under
which conditions these modes can be observed. The role of conserved

Dynamik und Statistische Physik Donnerstag
quantities, dissipation and of boundary conditions is elaborated. The
questions are investigated for standard maps and circle maps with different
types of couplings. We find, for instance, that diffusive couplings do
not support hydrodynamic Lyapunov modes. In contrast, for force-like
interactions between maps such modes can be found.
DY 46.27 Do 16:00 Poster D
The OFC earthquake model in d = 1 dimension — •Felix Wissel
and Barbara Drossel — Institut für Festkörperphysik TU-Darmstadt
Hochschulstrasse 6 64285 Darmstadt
We present analytical and numerical results for the one-dimensional
version of the earthquake model by Olami, Feder and Christensen. In the
analytical part, we prove that trajectories in state space approach each
other when they have the same toppling sequence. This implies that the
dynamics of the model cannot show chaos. In the numerical part, we
study the transition time into the stationary state as function of the system
size N and the coupling parameter α, and the statistical properties
of the stationary state.
DY 46.28 Do 16:00 Poster D
Magnetic Billiards as Hamiltonian Ratchets — •Manamohan
Prusty and Holger Schanz — Max-Planck Institut für Strömungsforschung
und Institut für Nichtlineare Dynamik der Universität
Göttingen, Bunsenstr. 10, 37073 Göttingen
Hamiltonian ratchets are periodic systems which show directed and
ballistic transport due to the presence of a mixed regular and chaotic
phase space and a mechanism breaking time-reversal symmetry. We show
that certain billiard chains can be a paradigm for this type of behaviour.
A magnetic field perpendicular to the billiard plane separates in a suitable
geometry regularly skipping trajectories from chaotic ones. Both
sets of trajectories transport ballistically in opposite directions. We show
how one can apply a classical sum rule for ratchet transport to predict
the chaotic transport velocity analytically and confirm the result by numerical
simulations. We study also the quantized versions of the billiard
ratchets and discuss their spectral properties.
[1] H. Schanz et al., Phys. Rev. Lett. 87(01)070601.
DY 46.29 Do 16:00 Poster D
Traveling waves in a reaction-diffusion system under periodic
forcing — •E. P. Zemskov 1 , K. Kassner 1 , and S. C. Mueller 2
— 1 Institut fuer Theoretische Physik, Otto-von-Guericke-Universitaet,
Universitaetsplatz 2, 39106 Magdeburg — 2 Institut fuer Experimentelle
Physik, Otto-von-Guericke-Universitaet, Universitaetsplatz 2, 39106
Magdeburg
A one-component reaction-diffusion system under external force is considered.
The simplest case of a periodic forcing of cosine type is chosen.
Exact analytical solutions for the two basic types of traveling waves,
fronts and pulses, are obtained in the case of a piecewise linear approximation
of the non-linear reaction term. Velocity equations are derived
from the matching conditions. Restrictions that arise during the derivation
of the pulse velocity equations are stated and their origin is explained.
It is found that in the presence of nonconstant forcing there
exists a set of wave solutions with different phases (matching point coordinates).
The general characteristic feature is that nonmoving waves
become movable under forcing. However, for specific choices of forcing
parameters, the traveling waves are pinned (stopped). The pinning conditions
are obtained and discussed. It is found that in the case of periodic
forcing there are infinite sets of the pinning positions. The phase portraits
of specific types of solutions are shown and briefly discussed.
References
E. P. Zemskov, K. Kassner, S. C. Mueller, Eur. Phys. J. B 34, 285
(2003).
DY 46.30 Do 16:00 Poster D
Dynamics of colloidal particles in a toroidal optical trap —
•Michael Reichert and Holger Stark — Universität Konstanz,
Fachbereich Physik, D-78457 Konstanz, Germany
A theoretical study of the collective non-Brownian motions of colloidal
particles circulating in a toroidal trap is presented. We consider equalsized
spheres in the regime of low Reynolds numbers whose interactions
are solely of hydrodynamic origin. The concrete physical situation we
have in mind are optical vortices, i.e., focussed helical light modes carrying
an orbital angular momentum [1]. We mimick this in our simulations
by applying a tangential driving force and a harmonic radial trap force
on each particle.
The orbital velocities of the circulating particles depend on the particle
number and the ring radius. We analyze them for different arrangements,
e.g., regular symmetric or random configurations. It turns out that the
random configurations lead effectively to a higher velocity compared to
the regular arrangements due to “drafting” effects.
Furthermore, we study the time-dependent dynamics of the random
configurations. The simulations show that, after an irregular transient
regime, the system tends towards a periodic dynamic state of oscillating
particle distances. During this synchronisation process, the viscous drag
is lowered.
[1] J. E. Curtis, D. G. Grier, Phys. Rev. Lett. 90, 133901 (2003).
DY 46.31 Do 16:00 Poster D
Dissipative Solitonen-Moleküle in Reaktions-Diffusions-
Systemen — •A. W. Liehr, M. C. Röttger und H.-G. Purwins
— Westfälische Wilhelms-Universität Münster, Institut für Angewandte
Physik, Corrensstr. 2/4, 48149 Münster
Dissipative Solitonen sind großamplitudige lokalisierte Strukturen mit
ausgeprägten Teilcheneigenschaften, die in diesem Beitrag anhand eines
dreikomponentigen Reaktions-Diffusions-Systems untersucht werden.
In der Nähe der Drift-Bifurkation kann die Dynamik und Wechselwirkung
der dissipativen Solitonen mittels einen Teilchenansatzes durch
Ordnungsparametergleichungen beschrieben werden, wobei als relevante
Größen die Positionen und die Propagatormodenamplituden der dissipativen
Solitonen erfasst werden [1]. Ausgehend von dieser reduzierten
Dynamik diskutieren wir die Eigenschaften gebundener Zustände dissipativer
Solitonen, sogenannte dissipative Solitonen-Moleküle, wobei sowohl
dynamische Eigenschaften starrer Moleküle [2,3], als auch innere
Freiheitsgrade größerer Moleküle behandelt werden.
[1] Bode, M. et al.: Interaction of dissipative solitons: particle-like behaviour
of localized structures in a three-component reaction-diffusion system. Physica
D 161, 2002, S. 45ff.
[2] Moskalenko, A. S. et al.: Rotational bifurcation of localized dissipative
structures. Europhysics Letters 63, 2003, S. 361ff.
[3] Liehr, A. W. et al.: Transition from stationary to rotating bound states of
dissipative solitons. In: E. Krause (Hrsg.), W. Jäger (Hrsg.), M. Resch (Hrsg.):
High Performance Computing in Science and Engineering ’03, Springer 2003,
S. 225ff.
DY 46.32 Do 16:00 Poster D
Universal behavior in complex front systems — •Andreas
Amann, Andreas Wacker, and Eckehard Schöll — Institut für
Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse
36, D–10623 Berlin
We show that the bifurcation scenario in a high-dimensional system
with interacting fronts can be related to the universal U-sequence which
is known from the symbolic analysis of iterated one-dimensional maps.
This connection is corroborated for a model of a semiconductor superlattice
[1], which describes the complex dynamics of electron accumulation
and depletion fronts. By a suitable Poincaré section we reduce the dynamics
to a low dimensional iterated map, for which in the most elementary
case the bifurcation points can be determined analytically.
[1] A. Amann, K. Peters, U. Parlitz, A. Wacker, E. Schöll
Phys. Rev. Lett. 91, 066601 (2003).
DY 46.33 Do 16:00 Poster D
The effect of long-term correlations on clustering of extreme
events — •Jan F. Eichner 1 , Armin Bunde 1 , Jan W. Kantelhardt
1 , and Shlomo Havlin 2 — 1 Institut für Theoretische Physik
III, Justus-Liebig-Universität, Giessen, Germany — 2 Dept. of Physics
and Minerva Center, Bar-Ilan University, Ramat-Gan, Israel
Long-term correlations, indicated by a power-law decay of the autocorrelation
function C(s) ∼ s −γ , appear in many natural records (e.g.
temperatures, river flows, and heartbeat intervals). In uncorrelated data
the return intervals r between events above a certain threshold q are
uncorrelated and follow the Poissonian statistics. We show that in the
presence of long-term correlations, the return intervals are also correlated
with the same correlation exponent γ, and follow a stretched exponential
distribution. As a consequence the extreme events show a tendency of
clustering. We give many examples of observational and reconstructed
data where this behavior is observed. The long-term correlations may
present a natural mechanism for the observed clustering of hazardous
floods between 1300 and 2000.

Dynamik und Statistische Physik Donnerstag
DY 46.34 Do 16:00 Poster D
Transport von Sauerstoff in dünne Flüssigkeitsfilme —
•Marcus J. B. Hauser und Stefan C. Müller — Otto-von-
Guericke-Universität, Institut für Experimentelle Physik, Abteilung
Biophysik, Universitätsplatz 2, 39106 Magdeburg
Der Transport von Sauerstoff aus der Gasphase in 1,5 mm dicken
Filme aus Schwefelsäure bzw. Wasser wird untersucht. Dazu wird der
zeitliche Verlauf der Sauerstoffkonzentration in den Flüssigkeitsfilmen
höhenabhängig (im Abstand von 0,1 mm) gemessen. Daraus werden die
Konzentrationsprofile berechnet. Während der Transport von Sauerstoff
in einen Wasser-Film über Diffusion erfolgt, ist die Situation im Falle der
Schwefelsäure-Filme komplexer. Der Sauerstofftransport in Schwefelsäure
zeigt oberfl#achenspannungsgetriebene (Marangoni) Konvektion, die in
den ersten 0,5 mm von der Grenzfläche (gasförmig / flüssig) auftritt. Der
Transport in tieferen Schichten des Schwefelsäure-Films (0,5 mm leq h ≤
1,5 mm) lässt sich gut durch Diffusion beschreiben. Über die Ursachen
für dieses Verhalten wird berichtet.
DY 46.35 Do 16:00 Poster D
Dynamics and Control of a 2-D Passive Dynamic Walker —
•Joachim Haß 1 , Norbert Mayer 2 , and Michael Herrmann 1 —
1 Max-Planck-Institut für Strömungsforschung, Göttingen, Germany —
2 GMD - Japan Research Laboratory Collaboration Center, Kitakyushu,
Japan
From the biomechanical point of view, bipedal locomotion can be considered
as the dynamics of a set of rigid bodies, connected by joints,
springs, and specifically placed actuators. A passive walker [1] is an even
more simplified model which is capable of stable walking on a downhill
slope with no actuation or control whatsoever.
Combining experimental, numerical and theoretical methods, stability
and speed of a modified walker closer to human gait dynamics were examined.
Both of them crucially depended on precise tuning of the walkers
internal parameters, which were optimized using a genetic algorithm in
the numerical simulations.
The basins of attraction in parameter space could be significantly
broadened by incorporating actuators and nonlinear control algorithms
into the model. Aside from increasing the walker’s stability, this also enabled
it to walk very efficiently on arbitrarily shallow slopes at a range of
different speeds. Furthermore, we considered more biologically motivated
forms of control, like synchronizing the body movements with a central
pattern generator.
[1] McGeer T. (1993) Int. J. Robotics Res. 9:2, 62-82.
DY 46.36 Do 16:00 Poster D
Calculation of periodic orbits and spectral correlations in pseudointegrable
systems — •Jesper Mellenthin and Stefanie Russ
— Institut für Theoretische Physik III, Universität Giessen, D-35392
Giessen, Germany
We investigate pseudointegrable quantum billiards of different genus
numbers g. We calculate numerically the periodic orbits and compare
them to the Fourier transform of the density of states. We find a very
good agreement between both. From the periodic orbits we calculate
the spectral correlation of the corresponding quantum system, i.e. the
spectral rigidity ∆3. We study how ∆3 depends on the energy and investigate
the difference between the diagonal approximation and the full
semiclassical expression over diagonal and non-diagonal terms. We find
that ∆3 for pseudointegrable systems is intermediate between integrable
and chaotic systems and that the contribution of very long orbits can be
neglected.
DY 46.37 Do 16:00 Poster D
Resonance-assisted tunneling in the kicked rotor —
•Christopher Eltschka and Peter Schlagheck — Institut
für theoretische Physik, Universität Regensburg
We investigate tunneling in the quantum kicked rotor, which manifests
itself in small eigenphase splittings between symmetric and antisymmetric
combinations of “left-moving” and “right-moving” quasi-modes. Our
special interest lies in the role of nonlinear resonances, which appear as
island chains in the classical phase space and which induce couplings that
substantially enhance the tunneling process [1]. Semiclassical reproductions
of the splittings, which are based on the resonance-assisted coupling
mechanism, are compared with the exact quantum splittings, which are
calculated by using multiple precision arithmetics.
[1] O. Brodier, P. Schlagheck, and D. Ullmo, Phys. Rev. Lett. 87,
064101 (2001), Ann. Phys. 300, 88 (2002).
DY 46.38 Do 16:00 Poster D
Level dynamics in pseudointegrable billiards: an experimental
study — •Yuriy Hlushchuk 1 , Stefanie Russ 1 , Ulrich Kuhl 2 , and
Hans-Jürgen Stöckmann 2 — 1 Institut für Theoretische Physik III,
Universität Giessen, D-35392 Giessen, Germany — 2 Fachbereich Physik,
Philipps-Universität Marburg, Renthof 5, D-35032 Marburg, Germany
The level dynamics of pseudointegrable systems with different genus
numbers g was studied experimentaly using microwave cavities. The
eigenvalue velocity distribution is found to be Gaussian, like in GOE
systems, and shows no dependances on the genus number g of the system.
Although the distributions of large curvatures in our pseudointegrable
systems correspond to the distribution in chaotic systems, the
small curvatures show the intermediate behavior between chaotic and integrable
systems. With growing genus number g the distribution of small
curvatures goes from that one for integrable systems in direction of the
distribution for pure GOE systems.
According to the conjecture of Yukawa the parametric motion of the
eigenvalues in a system can be treated as a motion of particles in a 1D
gas. The level dynamics of an integrable system corresponds to a 1D
gas without interaction between particles, while a chaotic level dynamics
corresponds to a 1D gas with a long-range interaction. The model of a
short-rage interaction between eigenvalue particles for the description of
the level dynamics in pseudointegrable systems is discussed.
DY 46.39 Do 16:00 Poster D
Soft wall quantum dots modelled with microwave cavities —
•Y.-H. Kim 1 , U. Kuhl 1 , H.-J. Stöckmann 1 , and J. P. Bird 2 —
1 Fachbereich Physik, Philipps-Universität Marburg, Renthof 5, D-35032
Marburg, Germany — 2 Department of Electrical Engineering and Center
for Solid State Electronics Research, Arizona State University, Tempe,
AZ 85287-5706, USA
By an adiabatic change of the height of flat microwave cavities quantum
billiards with soft wall potentials can be modelled [1]. Eigenresonances
and eigenfunctions are investigated for an harmonic oscillator like billiard,
serving as a test example, and a billiard corresponding to a quantum dot
with soft walls [2]. For the harmonic oscillator a good agreement between
measurements and theory is found. In case of the quantum dot billiard
the behaviour of the resonances corresponding to bouncing ball states is
investigated in detail.
[1] H.M. Lauber, Ph.D. thesis, Universität Heidelberg, 1994.
[2] de Moura et al, Phys. Rev. Lett. 88, 236804 (2002).
DY 46.40 Do 16:00 Poster D
Distribution of reflection coefficients for microwave cavities
in dependence of coupling and absorption strength — •U.
Kuhl 1 , H.-J. Stöckmann 1 , R. A. Méndez-Sánchez 2 , and C. H.
Lewenkopf 3 — 1 Fachbereich Physik, Philipps-Universität Marburg,
Renthof 5, D-35032 Marburg, Germany — 2 Centro de Ciencias Físicas
UNAM, A.P 48-3, 62210, Cuernavaca, Morelos, México — 3 Instituto de
Física, UERJ, R. São Francisco Xavier 524, 20550-900 Rio de Janeiro,
Brazil
The reflection spectra of rectangular microwave cavities, with a half
circular inset attached to one of the walls, have been measured in dependence
of the position of the inset. To cover the range from weak up
to strong absorption, for part of the measurements one wall was coated
with a layer of absorbing material. The distribution of reflection coefficients
was investigated in dependence of the antenna coupling strength
and the absorption within the cavities. The results are in good agreement
with numerical calculations, as well as with the theoretical predictions
for the limiting case of strong absorption [1]. In spite of the fact that
the system is time-reversal invariant, it is found that Gaussian unitary
ensemble calculations can be used to describe the results, if only the
coupling parameter is rescaled by a factor of two [2].
[1] E. Kogan, P.A. Mello, and H. Liqun, Phys. Rev. E 61, R17 (2000).
[2] D.V. Savin and H.-J. Sommers, Phys. Rev. E 68, 036211 (2003).
DY 46.41 Do 16:00 Poster D
TRANSPORT AND DYNAMICAL PROPERTIES OF THE
COSINE BILLIARD.THEORY V.S. EXPERIMENT. — •G.A.
Luna-Acosta 1,2 , U. Kuhl 1 , J.A. Mendez-Bermudez 3 und H.-J.
Stöckmann 1 — 1 Fachbereich Physik der Philipps Universität Marburg,
Renthof 5,D-35032 — 2 Instituto de Fisica, BUAP, Puebla, Mexico. —
3 Max Planck Institute für Strömungsforschung, Göttingen.
We investigate the properties of waves and particles reflected by and
transmitted through 2D chaotic waveguides, using the cosine billiard

Dynamik und Statistische Physik Donnerstag
as a prototype. We calculate the scattering probability matrix elements
| Sn,m | 2 , wave functions, and Husimi distributions for a set of geometrical
parameters producing weak, mixed, and strong chaotic ray dynamics.
Comparison of these quantities with their classical counterparts allows
us, on the one hand, to understand important global properties of waveguides
in terms of purely classical dynamics and, on the other, to unveil
drastic differences between wave and particle behavior. Further, we compare
our predictions with experimental results obtained in a microwave
realization of the cosine billiard.
DY 46.42 Do 16:00 Poster D
How optical microresonators radiate — •Martina Hentschel 1
and Henning Schomerus 2 — 1 Department of Physics, Duke University,
Durham, NC 27708-0305, U.S.A. — 2 MPI Physik komplexer Systeme,
Noethnitzer Str. 38, D-01187 Dresden
Optical microresonators have broad application potential in optical
communication devices, and are interesting model systems in the field
of Wave Chaos. Most of our qualitative understanding of their radiation
characteristics rests on the simple ray-optics picture, which however
requires a wave length much smaller than the geometric features of
the system. This is not realized in the most interesting applications. We
highlight effects that lead to substantial deviations from the ray picture.
Notably, at curved interfaces, the Goos-Haenchen effect causes deviations
from both Snell’s and Fresnel’s laws. We analyse the resulting deviations
in the radiation characteristics using four appropriately defined Husimi
functions, corresponding to incident and emerging rays on either side of
the interface. These four phase-space representations of the electromagnetic
wave function naturally allow to read-off the radiation directions,
and replace the single Husimi function used in hard-wall systems.
DY 46.43 Do 16:00 Poster D
Stochastic Webs and Localization in a Quantum Mechanical
Kick System — •Ulf Martin Engel and Peter Eckelt — Institut
für Theoretische Physik, Universität Münster, Wilhelm-Klemm-Straße 9,
D-48149 Münster
The classical kicked harmonic oscillator is characterized by a very special
scenario of weak chaos: in the case of resonance between the eigenfrequency
of the harmonic oscillator and the frequency of the periodic
forcing, periodic stochastic webs in phase space are generated [1]. We
investigate the quantum dynamics [2] of this model system and show
that the resulting Husimi distributions in quantum phase space exhibit
the same web-like structures as in the classical case. The quantum dynamics
is characterized by diffusive energy growth — just as the classical
dynamics in the channels of the webs. In the case of nonresonance, the
classically diffusive dynamics is quantum mechanically suppressed. We
explain this bounded energy growth (which corresponds to localization
in quantum phase space) by mapping the system onto the Anderson
model, in a way that is motivated by the standard treatment of the quantum
kicked rotor [3].
[1] G. M. Zaslavsky et al., Weak Chaos and Quasi-Regular Patterns,
Cambridge University Press, Cambridge 1991. [2] G. P. Berman,
V. Y. Rubaev and G. M. Zaslavsky, Nonlinearity, 4 543 (1991).
[3] S. Fishman, D. R. Grempel and R. E. Prange, Phys. Rev. Lett. 49,
509 (1982). [4] U. M. Engel, Dissertation Universität Münster (2003).
DY 46.44 Do 16:00 Poster D
Path integral approach to the dissipative curve-crossing dynamics
— •Alexey Novikov 1,2 , Ulrich Kleinekathöfer 1,2 , and
Michael Schreiber 2 — 1 International University Bremen, Bremen,
Germany — 2 Institut für Physik, Technische Universität Chemnitz,
Chemnitz, Germany
The dynamics of a curve-crossing system is considered using path integrals
in a combined phase space and coherent state representation.
The relevant system consists of two one-dimensional potential energy
surfaces, the dissipation is described by its interaction with the bath
of non-interacting harmonic oscillators. The Lagrangian function of the
electronic subsystem is written in the coherent state representation using
mapping approach while the vibrational degrees of freedom are treated
by the Feynman-Vernon path integral. The non-Gaussian part of the
path integral is calculated by introducing the effective bias and hopping
constants for the electronic states. Finally, the dynamics of a Gaussian
wave packet and the population of electronic levels is analyzed within
the presented method.
DY 46.45 Do 16:00 Poster D
Non-Markovian density matrix theories based on the decomposition
of the spectral density — •U. Kleinekathöfer 1,2 and M.
Schreiber 2 — 1 International University Bremen, 28725 Bremen, Germany
— 2 Institut für Physik, Technische Universität Chemnitz, 09107
Chemnitz
For the description of dynamical effects in quantum mechanical systems
on ultra-short time scales memory effects play an important role.
Here we propose two different theories [1] which are either based on
the time-convolution Nakajima-Zwanzig projection operator formalism
or the time-convolutionless Hashitsume approach. The proposed theories
as well as the method by Meier and Tannor [2] are based on a numerical
decomposition of the spectral density. For the example of the damped
harmonic oscillator these non-Markovian theories are compared among
each other, to Markovian approaches neglecting the memory effect and to
path integral calculations. Some of the proposed non-Markovian theories
treat explicitly time-dependent system Hamiltonians nonperturbatively.
Therefore these method can be used for the description of experiments
with arbitrary large laser fields.
[1] U. Kleinekathöfer, J. Chem. Phys. (submitted).
[2] C. Meier and D.J. Tannor, J. Chem. Phys. 111, 3365 (1999).
DY 46.46 Do 16:00 Poster D
PHASE BEHAVIOUR AND ELASTICITY OF COLLOIDAL
MODEL SUSPENSIONS — •Larysa Shapran, Patrik Wette,
Hans Joachim Schöpe, and Thomas Palberg — Johannes
Gutenberg-University Mainz, Institute of Physics, Staudinger Weg 7,
D-55099 Mainz
We have measured the phase behaviour and the elasticity of crystallizing
systems of submicron polystyrene spheres in low salt aqueous suspension.
Microscopy and static light scattering (SLS) yield the fluid-crystal
transition lines including the coexistence region in the particle number
density n salt concentration c plane. SLS shows further that the crystal
phase is b.c.c. Torsional resonance spectroscopy [1] yields the static
shear modulus G, which is observed to increase with n at constant c=0
and to decrease at n=const with increasing c. We compare our phase
behaviour predictions from computer simulation [2,3] using the effective
charge Z*(n,c) derived from the elasticity measurement. Use of the elasticity
effective charge instead of previously often employed conductivity
charge improves the consistency significantly.
[1] H.J.Schöpe, T.Palberg, J. Colloid Interface Sci. 234, 149-161 (2001)
[2] M.O.Robbins, K.Kremer and G.S.Grest, J. Chem. Phys. 88, 3286
(1988)
[3] E.J.Meijer and D.Frenkel, J. Chem. Phys. 94, 2269 (1991)
DY 46.47 Do 16:00 Poster D
Solid friction at model metal interfaces studied via NEMD computer
simulations — •Igor Stankovic 1 , Martin Kröger 2 , and
Siegfried Hess 1 — 1 Institute of Theoretical Physics, PN 7-1, Technical
University of Berlin, Hardenbergstr. 36, D - 10623 Berlin — 2 Polymer
Physics, ETH Zurich, ML H18, Sonneggstr. 3, CH-8092 Zurich
The embedded atom method is adopted to study structural changes
and mechanical alloying at model metal interfaces during dry solid friction
[1,2,3]. The main constitutive properties of real metals, i.e., cohesive
energy, elastic constants, and heat of solution, are reproduced by a set
of a few basic model parameters. The model metal is subjected to shear
deformation and strong flow via non-equilibrium molecular dynamics in
order to discuss the origins of some qualitative properties observed more
specific embedded atom potentials. The mechanisms leading to mechanical
alloying at interface are observed and discussed [3]. Information about
crystal structure inside NEMD configurations is obtained with ”common
neighbor analysis”, based on planar graphs [4].
1. M. S. Daw and M. I. Baskes, Phys. Rev. Lett. 50, 1285 (1983).
Phys. Rev. B 29, 6443 (1984).
2. I. Stankovic, M. Kröger, and S. Hess, Phys. Rev. E, accepted 2003.
3. M. Kröger, I. Stankovic, and S. Hess, Multiscale Model. Simul. 1,
25-39 (2003).
4. I. Stankovic, M. Kröger, and S. Hess, Comput. Phys. Commun. 145,
371 (2002).

Dynamik und Statistische Physik Donnerstag
DY 46.48 Do 16:00 Poster D
Monte-Carlo Simulations of Structural and Elastic Properties
in a two dimensional Model Colloidal Crystal — •Kerstin
Franzrahe and Peter Nielaba — Lehrstuhl für Theoretische Physik,
Fachbereich Physik, Universität Konstanz, D-78457 Konstanz
With the help of Monte-Carlo Simulations the elastic and structural
properties of a two dimensional hard disk system are studied. Simulations
in the NPT ensemble are done in order to analyse lattice formation
in binary mixtures, while simulations in the NVT ensemble enable us to
calculate the elastic constants of the system from microscopic strain fluctuations
[1]. This method was used to study the influence of impurities
on the elastic properties of a two dimensional hard disk system.
[1] S. Sengupta, P. Nielaba, M. Rao, K. Binder Phys. Rev. E 61,1072
(1999)
DY 46.49 Do 16:00 Poster D
Computer simulation studies of structures and elastic properties
of model colloids — •Peter Henseler and Peter Nielaba
— Lehrstuhl für Theoretische Physik, Fachbereich Physik, Universität
Konstanz, D-78457 Konstanz
We perform classical Monte-Carlo simulations to calculate isothermal
elastic constants of crystal phases of mono-disperse hard-sphere colloids.
The elastic constants are determined from microscopic fluctuations of the
instantaneous local Lagrangian strain ǫij(r,t), measured with respect to
a static reference lattice, and the use of a finite-size scaling theory. This
approach is a generalization of the method of Sengupta et al. [1] to three
dimensions.
We furthermore investigate structures of three dimensional colloidal
mixtures with different composition and diameter ratios.
[1] S. Sengupta, P. Nielaba, M. Rao, K. Binder, Phys. Rev. E 61, 1072
(2000)
DY 46.50 Do 16:00 Poster D
Laserinduziertes Gefrieren und Schmelzen in 3D — •Wolfram
Quester, Wolfram Strepp und Peter Nielaba — Fachbereich
Physik, Universität Konstanz
Seit den achtziger Jahren des vorigen Jahrhunderts werden die
Phänomene des laserinduzierten Gefrierens und Schmelzens in 2D
untersucht. Man versteht darunter zwei Phänomene, bei denen sich ein
flüssiges System von Kolloiden in seiner kristallinen Phase anordnet,
wenn es einem periodischen äußeren Potential ausgesetzt wird. Wird die
Amplitude des äußeren Potentials vergrößert, so geht das System in eine
modulierte Flüssigkeit über.
Es wurde das Auftreten dieser Phänomene in 3D für zwei Wechselwirkungspotentiale
untersucht. Einmal handelt es sich um harte Kugeln,
einmal um Lennard-Jones-Teilchen. Als Indikatoren für den Phasenübergang
dienten hauptsächlich der Strukturfaktor S( � k) und die Paar-
Korrelationsfunktion. Im Lennard-Jones-Fall konnte sehr gut das Gefrieren
beobachtet werden. Allerdings ergeben sich keine Anzeichen für ein
Schmelzen des Systems bei Erhöhung des externen Potentials. Bei den
harten Kugen verläuft das Gefrieren fast identisch wie im Lennard-Jones-
System, allerdings erreicht der Ordnungsparameter ein Maximum, um
dann mit zunehmendem Potential wieder leicht abzufallen. Diese Abnahme
des Ordnungsparameters reicht allerdings nicht aus, um von einem
Schmelzen zu sprechen.
DY 46.51 Do 16:00 Poster D
Structure formation in ultrathin films of soft matter on chemically
(in)homogeneous reactive and non-reactive substrates
— •Uwe Thiele 1 , Michael Bestehorn 2 , Karin John 1 , and
Markus Bär 1 — 1 Max-Planck-Institut für Physik komplexer Systeme,
Nöthnitzer Str.38, 01187 Dresden — 2 Lehrstuhl für Statistische Physik
und Nichtlineare Dynamik, BTU-Cottbus, Erich-Weinert-Strasse 1,
03046 Cottbus
A continuos model for an ultrathin partially wetting liquid film on a
solid substrate is employed to study the structure formation of such a
film on a heterogeneous substrate. We describe (1) film profiles on periodically
patterned substrates, (2) sliding drops on substrates with an
externally imposed wettability gradient and (3) moving droplets on a
reactive substrate.
DY 46.52 Do 16:00 Poster D
Construction of an optical line tweezer for colloidal particles
— •Raquel Chulia Jordan, Hans Joachim Schöpe, and Thomas
Palberg — Johannes Gutenberg-Universität Mainz, Institut für Physik,
Staudingerweg 7, D-55099 Mainz
Line tweezers are a valuable tool for investigations of pair interactions
in colloidal suspensions. We report on the construction of such a device
implementing a beam positioning by an acousto-optic modulator, a set of
counter-propagating beams with λ=532nm and an imaging optics with
depolarized back scattered light. Construction principle, calibration and
performance are discussed in detail.
DY 46.53 Do 16:00 Poster D
Swelling Behaviour of Hydrogels — •Bernward A. Mann 1 ,
Ralf Everaers 2 , Christian Holm 1 , and Kurt Kremer 1 —
1 Max-Planck-Institute für Polymerforschung; Ackermannweg 10;
55128 Mainz; Germany — 2 Max-Planck-Institut für Physik komplexer
Systeme; Nöthnitzerstr. 38; 01187 Dresden; Germany
The equilibrium swelling behaviour of a charged polymer network and
the dependence of its properties on the system parameters is studied in
numerical experiments. The results of these computer simulations is related
to current theoretical models and the scaling laws predict therein.
DY 46.54 Do 16:00 Poster D
The influence of confining disordered materials on the equilibrium
behavior of Stockmayer fluids — •Carsten Spöler and
Sabine H.L. Klapp — Stranski-Laboratorium für Physikalische und
Theoretische Chemie, Sekr. TC 7, Fakultät II, Technische Universität
Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
The phase behavior of fluids is very sensitive to the nature of intermolecular
interactions as well as to the presence of confining material
on a nanometer scale. In the present work, which is based on integral
equation theory (Reference Hypernetted Chain Approximation) in combination
with the replica method we consider dipolar Stockmayer fluids
exposed to disordered porous materials. The latter is modeled by a) a
hard sphere matrix, b) a hard sphere matrix with additional Lennard-
Jones fluid-matrix attraction c) a dipolar hard sphere matrix. As shown
on this poster, we find for all systems a remarkable shift of the boundaries
of the homogeneous, isotropic high temperature phase relatively
to the bulk[1,2]. Our previous studies, however, require a cumbersome
treatment of the orientational dependence of the dipolar potential. It is
known for bulk Stockmayer fluids that angle-averaged potentials like the
Keesom potential lead to remarkable well predictions of the condensation
transition (as long as the dipole moment remains relatively small).
Here we test the performance of the angle-averaged potential for the confined
systems [e.g. model a)], considering particularly the behavior of the
isothermal compressibility and adsorption isotherms.
[1] C. Spöler and S.H.L. Klapp, J. Chem. Phys. 118, 3628 (2003)
[2] C. Spöler and S.H.L. Klapp, submitted
DY 46.55 Do 16:00 Poster D
Crystallization in one and two component charged colloidal systems
— •Patrick Wette, Hans Joachim Schöpe, and Thomas
Palberg — Institut für Physik der Universität Mainz
We investigated the nucleation kinetics of aqueous suspensions of
Polystyrene spheres in the deionized state using static light scattering
and Avrami theory. Phase behaviour and growth kinetics were determined
in parallel from microscopy. For a mixture of 68nm and 100nm
sized particles the phase diagram shows a pronounced minimum at 20%
68nm particles which is reflected in both crystallization kinetics and elasticity.
DY 46.56 Do 16:00 Poster D
Crystallization in one and two component charged colloidal systems
— •Patrick Wette, Hans Joachim Schöpe, and Thomas
Palberg — Institut für Physik der Universität Mainz
We investigated the nucleation kinetics of aqueous suspensions of
Polystyrene spheres in the deionized state using static light scattering
and Avrami theory. Phase behaviour and growth kinetics were determined
in parallel from microscopy. For a mixture of 68nm and 100nm
sized particles the phase diagram shows a pronounced minimum at 20%
68nm particles which is reflected in both crystallization kinetics and elasticity.

Dynamik und Statistische Physik Donnerstag
DY 46.57 Do 16:00 Poster D
Ruin & Recreate – A Method to Overcome Barriers in the
Energy Landscape — •Johannes J. Schneider — Department of
Physics, Johannes Gutenberg University, Staudinger Weg 7, D-55122
Mainz
When simulating or optimizing a system with Monte Carlo techniques,
usually the so-called Local Search approach is used in which an initial
configuration is iteratively altered by small changes. Therefore, the application
of such a small move leads to a new configuration in the neighborhood
of the current configuration, which is quite similar to it. We showed
in [1] that the application of larger moves leads to better results in shorter
times than the classic Local Search concept. However, these larger moves
we used did not lead to thermal equilibrium, such that they could only
be used for optimization purposes but not for simulating a system at
a given temperature. Now we have altered this approach, such that the
moves lead to a Boltzmann equilibrium at each temperature. Moreover,
as these larger moves change the configuration to a much larger extent
than the small moves, we are able to overcome barriers in the energy
landscape more easily. We will present computational results both for
the classic Local Search and the new Ruin & Recreate approach for a
colloidal system.
[1] G. Schrimpf, J. Schneider, H. Stamm-Wilbrandt, and G. Dueck, J.
Comp. Phys. 159, 139, 2000.
DY 46.58 Do 16:00 Poster D
HP Proteins on Generalized Lattices — •Thomas Vogel,
Michael Bachmann, and Wolfhard Janke — Institut für
Theoretische Physik, Universität Leipzig, Augustusplatz 10/11, 04109
Leipzig, Germany
We investigated HP proteins[1] in three dimensions on simple cubic
lattices and on the fcc lattice. Employing the nPERM algorithm[2] to
selected sequences, we searched for ground states on both lattices and
compared the density of states and the heat capacity of sequences which
are designed on the simple cubic lattice.
PERM is a chain growth algorithm which combines the Rosenbluth
method with the “Go with the Winners” strategy. Population control is
implemented by cloning and pruning growing conformations depending
on variable thresholds which are computed adaptively during the simulation.
[1] K.F. Lau, K.A. Dill, Macromol. 22 (1989) 3986.
[2] H.-P. Hsu, V. Mehra, W. Nadler, P. Grassberger, J. Chem. Phys. 118
(2002) 444.
DY 46.59 Do 16:00 Poster D
Stable multiarmed spiral structure and their interaction in
excitable media — •Maria Inmaculada Rodriguez-Ponce and
Franz Schwabl — Lehrstuhl 5 fuer theoretische Physik, Physik Department,
Technische Universitaet Muenchen (Germany)
We study the dynamic properties and interaction of stable multiarmed
spiral structures in excitable media. The model is based on the equations
that describe the early stage of development in the self-organization of
Dictyostelium discoideum cells. We discuss the stability of the different
patterns, focusing on the interplay between the maximum number of
arms in a multiarmed spiral and the presence of local hetereogeneities
(defects) as well as between excitability properties. The interaction between
structures is analyzed in terms of core drifts and frequency changes.
DY 46.60 Do 16:00 Poster D
Poisoning of membrane patches — •Gerhard Schmid, Igor Goychuk,
and Peter Hänggi — Institut für Physik, Universität Augsburg
We consider the influence of intrinsic channel noise on the spontaneous
spiking activity of poisoned excitable membrane patches by use
of a stochastic generalization of the Hodgkin-Huxley model. Internal
noise stemming from the stochastic dynamics of individual ion channels
is known to affect the collective properties of the whole cluster [1]. In
particular, there exists an optimal size of the membrane patch for which
solely the internal noise causes a most regular spontaneous generation
of action potentials. This phenomenon is termed intrinsic coherence resonance.
In addition to the variation of the size of ion channel clusters,
the living organisms may adopt the densities of ion channels in order
to regulate the spontaneous spiking activity. In our model, we vary the
densities resp. the number of the specific ion channels for a given patch
size. Experimentally, this task could be achieved, e.g., by blocking the
ion channels of a given sort with a specific channel poison. Interestingly,
by poisoning the potassium, or the sodium ion channels in a certain proportion
one can increase, or decrease the regularity of the spike train [2].
This work is supported by DFG (SFB 486).
[1] J.A. White, J.T. Rubinstein, and A.R. Kay, Trends Neurosci. 23, 131
(2000).
[2] G. Schmid, I. Goychuk, and P. Hänggi, Physica A.
DY 46.61 Do 16:00 Poster D
Assortative random networks: Construction and properties —
•Ramon Xulvi-Brunet and Igor M. Sokolov — Newtonstr 15,
D-12489 Berlin
Since recently it got clear that many social networks exhibit assortative
mixing [M. E. J. Newman, Phys. Rev. Lett. 89, 208701 (2002)] so
that the predictions of uncorrelated models might be inadequate. To analyze
the role of assortativity we introduce an algorithm which changes
correlations in a network and produces assortative mixing to a desired
degree. This degree is governed by one parameter p; changing this parameter
one can construct networks ranging from fully random (p = 0)
to totally assortative (p = 1). We apply the algorithm to the Barabási-
Albert scale-free construction and show that the degree of assortativity is
an important parameter governing geometrical and transport properties
of networks. Thus the diameter of the network and the clustering coefficient
increase remarkably with the degree of assortativity. Moreover, the
concentration dependences of the size of giant cluster in the node percolation
problem for uncorrelated and assortative networks are strongly
different [R. Xulvi-Brunet, W. Pietsch, and I. M. Sokolov, Phys. Rev. E
68, 036119 (2003)].
DY 46.62 Do 16:00 Poster D
Two phase flow in porous media — •Toby Joseph 1 and Rudolf
Hilfer 1,2 — 1 ICA-1, Universität Stuttgart, 70569 Stuttgart, Germany
— 2 Institut für Physik, Universität Mainz, 55099 Mainz,Germany
Our understanding of two phase flow in porous media is still very incomplete.
Although Darcy’s law has been modified to deal with two fluids
flowing in a porous medium by introducing extra parameters like the relative
permeabilities, its domain of validity is still a matter of scientific
debate. Moreover, it is well known that the relative permeability curves
are history dependent and even the residual saturations in an invasion
process depends on the way in which the invasion is driven as is clear
from the capillary saturation curves. We present here a micro-to-macro
upscaling that takes into consideration some of these problems.
DY 46.63 Do 16:00 Poster D
Macromolecule- Flow Interaction — •Achim Jung and Christian
Wagner — Experimentalphysik, Universität des Saarlandes
We present measurements on the flow of diluted polymer solutions in
basic flow geometries. Our goal is to connect the statistical conformation
of the macromolecules with macroscopic sample parameters such as shear
or elongational viscosity. An example of basic flow geometry is the extensional
flow in a droplet detachment process where the sample is confined
in the thread between droplet and nozzle. Existing theoretical models are
not able to explain our findings on the elongational viscosity of diluted
polyelectrolyte DNA-solutions in different salinities and thus with different
polymer chain flexibilities. In order to gain more insight into the
microscopic conformations of the macromolecules we are setting up optical
tweezers. The focus of our microscopic studies will be the meaning
of hydrodynamic interaction, an effect that has been neglected in most
of the theoretical predictions of macroscopic material parameters.
DY 46.64 Do 16:00 Poster D
Fluctuation Measurements of a Passive Scalar with Miniaturized
Thermocouples — •Marco Munzel, J. Peinke, and A. Kittel
— Carl von Ossietzky University of Oldenburg, Faculty of Physics,
26111 Oldenburg, Germany
The measurement of thermal fluctuations is important for investigating
transport features of a passive and active scalar in fluids. We present
a thermal sensor based on a miniaturized thermocouple. Its coaxial setup
results from the fabrication as a micropipette normally used in neurobiology.
The glass micropipettes contain a core of platinum or constantan
wire and are coated with gold. The achieved tip diameters are 1µm and
less which enhance the spatial and temporal resolution significantly. Because
of their chemically inert coating, these sensors are applicative for
detecting temperature fluctuations in large variety of liquids and gases.
The sensors were tested in turbulent free-jets of heated water and air.
The presented results are compared to a commercially availiable cold wire

Dynamik und Statistische Physik Donnerstag
setup.
DY 46.65 Do 16:00 Poster D
Turbulente Geschwindigkeitsprofile über rauhen Ebenen —
•Nikolaus von der Heydt und Irmgard von der Heydt
— Institut für Umweltphysik Göttingen - Physik zum Leben -
Landolfshausen
In atmosphärischen Luftströmungen wurden in Höhen bis zu 100 m
erhebliche Abweichungen von der logarithmischen Höhenformel u(z) =
w z ln( ) festgestellt: Die Anpassung der vermeintlich geländetypischen,
κ z0
sogenannten Rauhigkeitslänge z0 ergab an ein und demselben Ort in
Abhängigkeit von der Schubspannungsgeschwindigkeit w = � σ
ρ (zwischen
0, 2 und 1 m/s) Werte von 1 mm bis 1 m. Ausgehend von neueren
Ergebnissen der Turbulenzforschung zeigen wir, dass Prandtl’s Ansatz
für die Wirbelzähigkeit νPr = κwz, der zur Log-Formel führt, verbessert
werden kann, und leiten damit eine DGL für u(z) her, deren Lösung für
z >> ν (ν kinemat. Viskosität) selbstähnlich ist und mit den Messdaten
w
übereinstimmt.
DY 46.66 Do 16:00 Poster D
Heterogeneous Nucleation of charged sphere suspensions on
shear induced precursors — •Thomas Palberg, Andreas Stipp,
Ralf Biehl, Hans Joachim Schöpe, Jianing Liu, and Thorsten
Preis — Institut f. Physik, Universität Mainz, Staudinger Weg 7, 55128
Mainz
Growth of oriented single crystals may be obtained from shear melts
of colloidal particles after nucleation at the container walls. Using different
microscopic and scattering techniques we here studied precursors of
such nuclei induced by steady shear. In all cases we observed shear layer
structures which were oriented with their densest plane parallel to the
container wall and their densest packed direction parallel to the flow. A
strong correlation between the modes of motion and the type of interlayer
registering is observed. Depending on the shear geometry used, the
equilibrium phase, the strength and the range of interaction such layer
structures either disappear upon increase of the shear rate or grow to
macroscopic objects. Stop of shear may lead to an interesting competition
between the decay of these usually meta-stable structures in favour
of the shear melt and their stabilisation through coverage by an epitaxially
growing wall crystal. In the latter case the shear layer residues act
as pre-structured substrate.
DY 46.67 Do 16:00 Poster D
Lattice-Boltzmann scheme for the dendritic growth in presence
of convection — •Dmitry Medvedev and Klaus Kassner — Institut
fuer Theoretische Physik / Computerorientierte Theor. Physik, Ottovon-Guericke-Universitaet
Magdeburg, Postfach 4120, D-39016 Magdeburg
Dmitry Medvedev, Klaus Kassner, Otto-von-Guericke Universität
Magdeburg
A combined phase-field/lattice-Boltzmann scheme is proposed to simulate
dendritic growth from a supercooled melt.
The phase change part of the problem is treated with the phase-field
approach of Karma and Rappel, whereas the flow of the liquid is simulated
by a standard lattice-Boltzmann-BGK (LBGK) method with interactions
with solid and thermal convection incorporated. To simulate
conductive and convective heat transfer we use the multicomponent LBE
method. The step of flow simulation can be dropped out in the case of
purely diffusional growth.
Test simulations without convection reproduce the dendrite tip velocity
of the exact solution.
Depending on the level of anisotropy, dendrites or doublons were obtained
in the simulations.
Dendritic growth in a shear flow was simulated for different flow velocities,
as well as the growth with natural thermal convection with different
orientations of the crystal in the gravitational field.
DY 46.68 Do 16:00 Poster D
Kinetic roughening of laser deposited polymer films: Crossover
from single particle to continuous growth — •Jörg Hachenberg
1 , Christoph Streng 1 , Erik Süske 2 , Sebastian Vauth 1 , Stefan
G. Mayr 1 , Hans-Ulrich Krebs 2 , and Konrad Samwer 1 — 1 I.
Physikalisches Institut, Universität Göttingen — 2 Institut für Materialphysik,
Universität Göttingen, Tammannstr. 1, 37077 Göttingen
Thin film samples are prepared by pulsed laser deposition (PLD) of
Bisphenol-A (BPA) polycarbonate targets at room temperature and un-
der UHV conditions. Atomic force microscopy (AFM) is used to investigate
the development of the surface roughness as a function of the
thickness and the deposition angle.
We find that the roughness increases proportional to the film thickness
by the growth exponent of 1/4 between 20nm and more than 4µm.
This is interpreted within computer simulations and theoretical models.
Similar results have been shown in amorphous metallic systems, but
on different scales. For lower film thicknesses than 20nm we observed a
crossover to even steeper slopes where the particle character dominates
the roughening and a continuous description is no longer valid. Additional
investigations under variation of the laser fluency have been performed.
This project is supported by the DFG, SFB 602, TP B3 and GRK 782.
DY 46.69 Do 16:00 Poster D
Shape of mounds and scaling behaviour in unstable epitaxial
crystal growth — •Markus Walther, Sebastian Weber,
and Michael Biehl — Institut für Theoretische Physik,Universität
Würzburg, Am Hubland, 97074 Würzburg
We study the influence of an Ehrlich-Schwoebel like barrier at corners
in the diffusion of adatoms along step edges. The presence of an infinite
barrier determines the shape of mounds in unstable growth and the
coarsening dynamics of the surface.
The investigation is realized by two different methods of Monte Carlo
simulations leading to similar results: Kinetic Monte Carlo simulations
and a single particle representation. We investigate the effect of a finite
barrier and its role in a dynamical phase transition with respect to surface
morphology and scaling behaviour.
DY 46.70 Do 16:00 Poster D
Comparison of Three-dimensional Simulations of Dendrites
with Experimentally Grown 3D Xenon Crystals — •Herman M.
Singer and Jörg H. Bilgram — Laboratorium für Festkörperphysik,
ETH Zürich, 8093 Zürich (Schweiz)
Dendritic growth from a pure substance into supercooled melt was simulated
in two- and three-dimensional calculations of two different phase
field models ([A.A. Wheeler, B.T. Murray and R.J. Schaefer, Physica D
66, 243 (1993)] and [A. Karma and W.-J. Rappel, Phys. Rev. E 57, 4323
(1998)]). By means of large scale parallel molecular dynamics simulations
for a Lennard-Jones potential, estimates for the anisotropy of interfacial
free energy for our experimental model substance were calculated. In our
in situ experiments three dimensional xenon crystals during free growth
can be observed. Apart from dendrites, doublon and seaweed morphologies
as well as morphology transitions are observed. Those structures can
be simulated by using special initial conditions. A morphology diagram
for 2D and 3D simulations is presented and compared with the results of
experiments and analytical studies.
DY 46.71 Do 16:00 Poster D
Analysis of Solidification Dynamics by Wavelet Transformation
Techniques — •Oliver Wittwer and Jörg H. Bilgram — Laboratorium
für Festkörperphysik, ETH Zürich, 8093 Zürich (Schweiz)
Complex structures develop during solidification processes. Changes
in growth morphology can be initiated in our experiments by changing
the temperature distribution in the environment of a growing crystal [I.
Stalder and J.H. Bilgram, Europhys, Lett. 56, 829 (2001)]. These transitions
have gained interest since they have been discovered in metallic
samples [K. Dragevski et al., Phys. Rev. Lett. 89, 215502 (2002)]. To
study transitions in growth morphology and to monitor quasi stationary
growth of dendrites we apply wavelet transformation techniques. We are
able to detect changes in growth behaviour in a much earlier state as it is
possible by determining growth parameters such as typical length scales
or growth rates.
DY 46.72 Do 16:00 Poster D
Temperaturabhängige Dynamik von Au-Clustern auf amorphen
C-Substratfilmen — •Ralph Werner 1 , Matthias Wanner 2 ,
Dagmar Gerthsen 2 und Stefan-Sven Jester 3 — 1 Institut für
Theorie der Kondensierten Materie,Universität Karlsruhe (TH), 76128
Karlsruhe — 2 Laboratorium für Elektronenmikroskopie, Universität
Karlsruhe (TH), 76128 Karlsruhe — 3 Institut für Physikalische Chemie,
Universität Karlsruhe (TH), 76128 Karlsruhe
Kleine, deponierte Au-Cluster zeigen in verschiedener Hinsicht dynamisches
Verhalten. Im einzelnen kann man (i) unterschiedliche kristallographischen
Modifikationen (fcc-Kuboktaeder, Ikosaeder, Dekaeder), (ii)

Dynamik und Statistische Physik Donnerstag
Translation und Rotation von Clustern in Abhängigkeit von Größe, Temperatur
und Substratwechselwirkung, sowie (iii) Veränderung der Partikelgröße
Infolge von Diffusionsprozessen beobachten. Es werden einige
experimentelle Ergebnisse dargestellt sowie Monte-Carlo-Simulationen.
Die Proben wurden durch Beschuss von mit amorpher C-Folie bespannten
Cu-Netzen mit Au-Clustern präpariert, die in einer Laser-
Ablationsapparatur erzeugt wurden.
DY 46.73 Do 16:00 Poster D
Simulation of biaxial compression of two-dimensional granular
materials — •Hans-Georg Matuttis and Shinichi Morita —
The University of Electrocommunications, Department of Mechanical
and Control Engineering, Chofu Chofugaoka 1-5-1,Tokyo 182-8585,Japan
For experimental triaxial compression of granular materials, the maximum
of the yield curve corresponds to the maximum of the bulk density.
After the failure sets in, the granular compressibility decreases, as does
the bulk density.
In this work, we simulate a two-dimensional granular assembly of particles
of various sizes and shapes (round, polygonal, elliptic, with various
elongations) via molecular dynamics, hence the process corresponding to
experimental tri-axial compression becomes bi-axial compression. For the
given boundary conditions and size dispersions, only elongated particles
with friction show the maximum of the yield curve, and a maximum of
the bulk density. For round particles, we find neither a maximum in the
yield curve nor in the bulk density.
DY 46.74 Do 16:00 Poster D
Particle imaging velocimetry study of a horizontally shaken
granular bed — •Olaf Br”okmann and Achim Kittel — Energy
and Semiconductor Research Group, Department of Physics, University
of Oldenburg
The study of shaken granular matter has become very popular in recent
years. Surprisingly most of these studies only investigate the behavior of
vertical shaken particles. Thinking about transportation of grain e.g. horizontal
shaking has a great practical importance and therefore has to be
more investigated. Using particle image velocimetry (PIV) we studied
the velocity fields of horizontal shaken granular matter. The experiments
include a variation of the shaking frequency, shaking amplitude and the
size of the investigated particles.
DY 46.75 Do 16:00 Poster D
THE MAGNETIC SORET EFFECT — •Thomas Völker und
Stefan Odenbach — ZARM, University of Bremen, Am Fallturm
28359 Bremen
Investigations were made to determine the Soret coefficient of magnetic
particles in a ferrofluid under the influence of a magnetic field. This
so called magnetic Soret effect was theoretically determined to be two
to three orders of magnitude smaller than the conventional Soret effect.
In contrast former experiments have shown that the magnetic Soret effect
is much higher than the theoretical predictions. However in those
experiments the influence of buoyancy and magnetic driven convection
could not be excluded. So the question how large the magnetic Soret
effect can be is still open. Thus an experimental setup was developed to
minimize parasitic effects and thus to simplify the analysis of the experimental
results. These results show that the magnetic Soret effect can
even be higher than the conventional one and confirm therewith former
experimental results.
DY 46.76 Do 16:00 Poster D
Examination of the magnetisation dynamics of rotating ferrofluids
— •Sonia May 1,2,3 , Jan Embs 1,2 , Christian Wagner 1 , Klaus
Knorr 1 , and Manfred Lücke 2 — 1 Technische Physik, Universität
des Saarlandes — 2 Theoretische Physik, Universität des Saarlandes —
3 Department of Physics, University of Hull
Ferrofluids are colloidal suspensions of nanometre sized magnetic particles
in a magnetically inert liquid which, being coated by polymeric
surfactants do not agglomerate. External magnetic fields exert forces and
torques on the particles that are transmitted via viscous friction on the
ferrofluid as a whole. In equilibrium ferrofluids show (super) paramagnetic
behaviour in a magnetic field H with magnetisation M and field H
being parallel to each other.
Under non-equilibrium conditions where the ferrofluid rotates M and H
are no longer parallel to each other. For such situations various theoretical
models for the dynamic magnetisation equation have been proposed
that are not yet properly tested; in particular in regimes where the (lo-
cal) vorticity Ω is comparable to or larger than the Brownian rotational
relaxation rate 1/τ.
Experiments have been performed on ferrofluids rotating with constant
frequency Ω. The magnetisation component normal to the applied field
is measured using a Hall sensor as a function of applied fields of up to 60
kA/m and as a function of rotational frequencies of up to 2,500 rad/s.
Experimental results for the non-equilibrium situation are compared
with theoretical models.
DY 46.77 Do 16:00 Poster D
Bewegung von Domänenwänden — •Matthias Müller und Ingo
Rehberg — Physikalisches Institut, Universität Bayreuth
Bei Elektrokonvektionsexperimenten in nematischen planar orientierten
Flüssigkristallen treten unter anderem Domänen mit abnormalen
Rollen auf. Diese lassen sich mittels Ellipsometrie sichtbar machen. Wir
untersuchen die Bewegung der Domänenwände, die die zwei Sorten der
abnormalen Rollen trennen.
Theoretische Berechnungen [1] sagen einen linearen Zusammenhang
zwischen der Geschwindigkeit der Domänenwände und der treibenden
Wechselspannung voraus, was für Bewegungsinstabilitäten ein ungewöhnliches
Verhalten darstellt. Das Ziel unserer Arbeit ist es diesen
Zusammenhang experimentell zu untersuchen.
[1] H. Zhao und L. Kramer, Phys. Rev. E 62, 5092-5100 (2000)
DY 46.78 Do 16:00 Poster D
Growth rate of amplitudes of surface instabilities in ferrofluids
— •Holger Knieling, Reinhard Richter, and Ingo Rehberg —
Universität Bayreuth, Lehrstuhl Experimentalphysik V, 95440 Bayreuth
The surface of magnetic fluids subjected to a normal magnetic field is
becoming unstable when a certain threshold of the magnetic induction
is surpassed and the initially flat surface exhibits a stationary array of
peaks (Rosensweig or normal field instability). The more general case is
a field, which is tilted towards the normal of the surface of the magnetic
liquid. In that case you can observe at first liquid ridges instead of the
peaks. Increasing further the magnetic induction a stretched hexagonal
pattern of crests is emerging on top of the liquid ridges.
The amplitudes of all these instabilities and their relaxation can be
measured with the help of a linear array of 32 Hall sensors which
are placed directly under the ferrofluid. Sensors situated under a ridge
(trough) detect higher (lower) values of the local magnetic induction.
With a time resolution of the sensors of about a half millisecond the
maximal growth rate of the modes of the Rosensweig instability can be
measured and compared to a theoretical prediction [1].
[1] A. Lange, Europhys. Lett., 55 (3), 327-333 (2001)
DY 46.79 Do 16:00 Poster D
Differences of the magnetic susceptibility in alternating and rotating
fields — •Robert Krauß, Reinhard Richter, and Ingo
Rehberg — Experimentalphysik V, 95440 Bayreuth
Considering a layer of ferrofluid set in motion by a rotating magnetic
field raises the question how the velocity depends on the frequency of the
field. Investigations and calculations on this effect (referred to as magnetic
pumping) yield that the velocity is a function of the real and imaginary
parts of the complex magnetic susceptibility. In a first approach
the susceptibility was measured in a toroidal channel with a linear alternating
field. We found substantial differences between the measured
velocity and the one calculated from the complex susceptibility. However
taking into account the complex susceptibility measured in a rotating
field, leads to a better understanding of the fluid motion. The ferrofluid
applied shows a strong coupling parameter of λ ≈ 3. This fact indicates
that aggregates in the fluid exist and are responsible for the non-linear
behaviour obtained.
DY 46.80 Do 16:00 Poster D
A phenomenological model for ferrofluid droplet dynamics in
a shear flow — •Nana Sadowsky, Patrick Ilg, and Siegfried
Hess — Institut für Theoretische Physik, Technische Universität Berlin,
Hardenbergstr. 36, D-10623 Berlin
Hydrostatics and hydrodynamics of ferrofluid droplets give valuable
information on magnetic and dynamical properties of the magnetizable
fluid [1].
While the equilibrium deformation of the ferrofluid droplet as a function
of the applied magnetic field is known experimentally [1], the nonequilibrium
dynamics remain rather unknown so far. Here, we propose
a phenomenological model for the dynamics of ferrofluid droplets in the

Dynamik und Statistische Physik Donnerstag
presence of shear flow. Generalizing the approach of [2], ferrofluid droplets
are modeled as deformable and orientable ellipsoids of revolution.
The combined effects of a magnetic field and a shear flow on the orientation
and deformation of the droplets are studied. It is found that the
hydrodynamic drag leads to a flow alignment of the droplet orientation.
Predictions for the alignment angle as a function of the applied field are
presented. Some comparisons to experimental data [3] in the absence of
shear are made.
[1] E. Blums, A. Cebers, M.M. Maiorov, Magnetic Fluids, deGruyter,
Berlin 1997.
[2] P. Ilg and M. Kröger, Phys. Rev. E 66, 021501-1 (2002)
[3] A. Lebedev, A. Engel, K.I. Morozov and H. Bauke, New Journal of
Physics 5, 57.1-57.20 (2003)
DY 46.81 Do 16:00 Poster D
The corkscrew instability in a nematic liquid crystal —
•Alberto de Lozar, Wolfgang Schoepf, Lorenz Kramer, and
Ingo Rehberg — Universitaet Bayreuth
A liquid crystal with slightly positive dielectric anisotropy is investigated
in the planar configuration. This system allows for competition
between electroconvection and the homogeneous Frèedericksz transition,
leading to a rather complicated bifurcation scenario. We report measurements
of a novel instability leading to the ”corkscrew” pattern. This state
is closely connected to the Frèedericksz state as it manifests itself as a regular
modulation along a Frèedericksz domain wall, although its frequency
dependence indicates that electroconvection must play a crucial role. It
can be understood in terms of a pitchfork bifurcation from a straight
domain wall. Quantitative characterization is performed in terms of amplitude,
wavelenght and relaxation time. Its wavelenght is of the order of
the probe thickness, while its ondulation amplitude is an order of magnitude
smaller. The relaxation time is comparable to the one obtained for
electroconvection.
DY 46.82 Do 16:00 Poster D
Magneto-rheological study in inverse magnetic fluids using
polystyrene particles — •Saldivar-Guerrero Ruben 1 , Richte
Reinhard 1 , Rehberg Ingo 1 , and Rodriguez-Fernandez Oliverio
2 — 1 Universitaet Bayreuth, Experimentalphysik V — 2 Centro de
Investigacion en Quimica Aplicada
Ferrofluids are colloidal suspensions of magnetic nanoparticles, which
change their behaviour under control of an external magnetic field. But
when for example, they are mixed with polystyrene particles, they present
another interesting properties. The magneto-rheological fluid (MRF) obtained
in this way, can show a solid-fluid transition by an application
of a moderate magnetic field similar to electro-rehological fluids (ERF)
under a electric field. It excels ERF’s because only moderates currents
instead of high voltages are necessary. We study the rheological influence
of the diameter of the immersed polymer particle in MRF and the relation
between the coupling parameter l and the yield point ty for different
magnetic fields applied. The results show that the rheological properties
are increased when the particle diameter increases in a constant magnetic
field. Also we investigate structure formation in the fluid by video
microscopy when a magnetic field is applied.
DY 46.83 Do 16:00 Poster D
Smectic and crystalline order in colloidal monolayers on periodic
one-dimensional substrate potentials — •Jörg Baumgartl
1 , Matthias Brunner 2 , and Clemens Bechinger 1 — 1 2.
Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550
Stuttgart — 2 Fachbereich Physik, Universität Konstanz, 78457 Konstanz
There is growing interest in the phase behavior of two-dimensional
(2D) colloids in the presence of one-dimensional (1D) periodic substrate
potentials. The phase behavior of such systems is determined by two factors:
(i) the relative orientation between the 2D crystal and the periodic
potential troughs which selects a set of Bragg planes running parallel to
the troughs and (ii) the commensurability ratio p = a ′ /d of the spacing
a ′ between these Bragg planes to the period d of the periodic potential.
So far, only the phase behavior for p = 1 was investigated and the following
phases were observed for increasing (non zero) potential strength:
modulated liquid and light-induced crystal. For other commensurability
ratios additional, more complex phases are predicted.
We investigated experimentally the phase behavior for the case p = 2
with the 1D periodic potential being created by two interfering laser
beams. We observed for the first time the theoretically predicted intermediate
phase between modulated liquid and light-induced crystal which
is termed locked smectic. By analyzing the structure factor and the pair
correlation function, this phase is characterized by liquid-like behavior
along the potential troughs. In contrast to the modulated liquid the ordering
perpendicular to the troughs is similar to the crystalline state,
with particles occupying only each second trough.
DY 46.84 Do 16:00 Poster D
Commensurability effects of colloidal monolayers on hexagonally
patterned substrates — •Stefan Bleil 1 , Matthias Brunner
2 , and Clemens Bechinger 1 — 1 2. Physikalisches Institut, Universität
Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart — 2 Fachbereich
Physik, Universität Konstanz, 78457 Konstanz
Colloidal suspensions are excellent model systems for investigations
of phase transitions in two-dimensional (2D) systems. While most of
the previous work concentrated on homogeneous substrates, much less
is known about the phase behavior on patterned substrates although
the latter closely resembles the behavior of atomic adsorbates on crystalline
surfaces. In our experiments we mimic 2D patterned substrates
for colloidal particles by the interference pattern of several laser beams
which lead to triangular substrate potentials. We present results where
the number density of charge stabilized colloidal particles was systematically
varied. This allowed us to study the effect of the filling fraction
η (i.e. the ratio between the number of colloidal particles and the number
of substrate wells) on the observed structure of the colloidal system.
Depending on the filling fraction we observe commensurate and incommensurate
structures. We also compare our results with recent numerical
simulations.
DY 46.85 Do 16:00 Poster D
Phasetransitions in Quantum fluids: PIMC - Studies — •Guido
Günther and Peter Nielaba — Lehrstuhl für Theoretische Physik,
Fachbereich Physik, Universität Konstanz, D-78457 Konstanz
Exploiting path integral Monte Carlo methods we studied the behavior
of the fluid phase of quantum mechanical hard sphere- and disk- systems.
We focused on the superfluid phase transition of Bose systems
analyzing, among other quantities, the superfluid fraction which in
periodic boundary conditions is related to the winding number of the
Trotter-chains [0].
[0] E.L. Pollock, D.M. Ceperley; Phys. Rev. B 36, 8343 (1987)
DY 46.86 Do 16:00 Poster D
Microcanonical entropy of classical spin systems with a continuous
symmetry — •Andreas Richter, Michel Pleimling,
and Alfred Hüller — Institut für Theoretische Physik I, Universität
Erlangen-Nürnberg, D-91058 Erlangen
Critical phenomena of classical spin systems may be studied in many
ways. In our approach we determine and analyse the microcanonical entropy
S which is related to the density of states by S = kB ln Ω, where kB
is the Boltzmann constant. Due to the huge amount of possible configurations
it is in general impossible to calculate Ω exactly, even for systems
of moderate size. The density of states can, however, be computed approximately
from a numerical method using transition variables. Discrete
classical systems, like the Ising or Potts model, were already studied with
this method in the past [1,2]. We now extend this method to systems with
continuous spins and apply it to the three-dimensional XY model. In addition,
we discuss the determination of critical quantities directly from
the numerically determined microcanonical entropy.
[1] A. Hüller, M. Pleimling, Int. J. Mod. Phys. C 13, 947 (2002)
[2] H. Behringer, J. Phys. A: Math. Gen 36, 8739 (2003)
DY 46.87 Do 16:00 Poster D
A Topological Rule-of-Thumb for Percolation Thresholds —
•Richard Neher and Herbert Wagner — Sektion Physik, Universität
München
Randomly assembled structures exhibit a density driven percolation
transition, beyond which an unbounded component is formed. Since properties
of those structures change dramatically at the percolation threshold,
its accurate knowlegde is important and various empirical formulas,
predicting percolation thresholds, have been suggested. The mean Euler
characteristic is a topological measure for such random sets and it has
been suggested to use its zero crossing to estimate the threshold. In contrast
to other formulas, this estimation does not rely on a fit to known
thresholds.
We further investigated this matter and found, that for a great variety

Dynamik und Statistische Physik Donnerstag
of two-dimensional lattices the site percolation threshold is bound from
above and below by the zero and the inflection point of the Euler characteristic,
respectively. In the case of site percolation on three-dimensional
lattices, bond-site percolation and continuum percolation, the thresholds
are bound from above by the zero of the Euler characteristic.
DY 46.88 Do 16:00 Poster D
Phase transitions in periodic pinning arrays — •Konrad
Mangold 1 , Michael Köppl 1 , Paul Leiderer 1 , and Clemens
Bechinger 2 — 1 Universität Konstanz, Fachbereich Physik —
2 Universität Stuttgart, 2.Physikalisches Institut
We study by means of videomicroscopy the phase behavior of twodimensional
(2D) paramagnetic colloidal systems on periodic pinning arrays,
the latter being created by a hollographic optical tweezer technique.
When the particle interacion is decreased by changing an external magnetic
field the colloidal monolayer shows a melting transition from an
incommensurable solid to a liquid phase. An undisturbed 2D system exhibits
a two-stage melting as described by the KTHNY theory. With
an additional pinning array the 2D system shows a rich phase behavior.
The details of the diffusion of interstitial particles through a matrix
of pinned particles depend among other things on the geometry of the
pinning lattice (square or hexagonal) and on density ratio of pinned to
diffusing particles. We compare our results with numerical studies on
vortex melting in periodic pinning arrays.
We also present first results where the particle transport through a
channel under non-equilibrium conditions is studied. A topological channel
is created by means of electron lithography and the motion of the
particles are studied for different particle interactions and channel geometries.
DY 46.89 Do 16:00 Poster D
Short-Time Dynamics — •Eric Lorenz and Wolfhard Janke
— Institut für Theoretische Physik, Universität Leipzig, Augustusplatz
10/11, 04109 Leipzig, Germany
The 2d Ising model on a square lattice is quenched from a state at
high temperature to the critical temperature and its dynamic relaxation
is investigated with Monte Carlo methods. In the case of a small initial
magnetization, a critical initial increase of the magnetization is observed
during early time of the dynamic evolution. With power laws derived
from the scaling relation being valid already in non-equilibrium, one can
determine estimates for the critical exponents θ, z, and β/ν. This procedure
of observing quantities in non-equilibrium prevents critical slowing
down caused by the divergence of the spatial correlation length at the
critical temperature in equilibrium. In this work special attention is paid
to a comparison of algorithms. The dynamics produced by heat-bath,
Metropolis and Glauber updates are found to be universal, despite surprising
differences during the very early time evolution, which are investigated
in some detail.
DY 46.90 Do 16:00 Poster D
Damage Spreading in Ising Lattice — •Rodrigo Megaides and
Wolfhard Janke — Institut für Theoretische Physik, Universität
Leipzig, Augustusplatz 10/11, 04109 Leipzig, Germany
We study the “damage spreading phenomenon” in a two-dimensional
Ising lattice of different sizes. The phenomenon consists in the propagation
of a small modification, in the initial state of the lattice, to the
whole system without changing the random noise. The method is first
equilibrating the system and then performing a time average over final
“Hamming distances”(a measure of the number of spins in opposition in
two similar systems) of initial pairs of lattices (the first one taken for such
average and the second one being identical to the former except for the
individual state of several spins, the so called “damage”). In every individual
measurement, we find one of these three types of “final”Hamming
distances (HD) : HD = 0 or healing (the damage disappears at the first
sweeps), HD ≃ 0.5 or 0.5-spreading (the damage spreads until it reaches
one half of the lattices, except for some fluctuations), HD = 1 or infinite
spreading (the damage fills the lattice). The probabilities of such cases
are obtained (for different temperatures and lattice sizes) from the time
average, as well as a mean value of the Hamming distance which is easily
calculated from the mentioned probabilities. Some scaling properties are
proposed.
DY 46.91 Do 16:00 Poster D
Desorption behaviour of binary quench-condensed noble gas
mixtures — •M. Layer, A. Netsch, A. Fleischmann, and S. Hunklinger
— Kirchhoff-Institut für Physik, Universität Heidelberg, Im
Neuenheimer Feld 227, D-69120 Heidelberg
Due to their simple van der Waals interaction noble gas crystals are
commonly considered as model system for condensed matter. This holds
in particular for binary mixtures. Freezing theories as well as molecular
dynamical simulations predict the existence of structural ordered
phases in good agreement with each other. We studied the desorption behaviour
of quench-condensed noble gas films by means of high-frequency
surface acoustic waves. In contrast to theoretical investigations quenchcondensed
films are in a state far away from thermal equilibrium. By annealing,
these films are relaxing into thermodynamically more favorable
phases. Over a wide range of preparation conditions (including substrate
temperature, gas temperature, composition of the mixture) we found evidence
for the formation of ordered film structures. Furthermore it turned
out that in particular the ratio of diameters of the two components is relevant
to the occurence of ordered film structures. Desorption processes of
several condensed binary mixtures (Ne/Ar, Ne/Kr, Ar/Kr) are presented
and the forming of possible van der Waals compounds is discussed.
DY 46.92 Do 16:00 Poster D
Computer Simulations of the 3–Dimensional Abelian Higgs
Model — •Sandro Wenzel, Elmar Bittner, Wolfhard Janke,
and Arwed Schiller — Institut für Theoretische Physik, Universität
Leipzig, Augustusplatz 10/11, 04109 Leipzig, Germany
Using multicanonical and heat–bath Monte Carlo algorithms we
investigated the 3–dimensional Abelian Higgs model [1] on the lattice
with compact gauge fields and fluctuating Higgs amplitudes (λ �= ∞).
Special consideration was given to the first–order regime of the
confinement–deconfinement phase transition. The existence and location
of a (tri–)critical point was explored using reweighting techniques.
[1] S.Mo, J.Hove, A. Sudbø, Phys. Rev. B 65 (2002) 104501.
DY 46.93 Do 16:00 Poster D
3-Zustands Potts-Modell auf Voronoi-Delaunay Zufallsgraphen
in 2 Dimensionen — •Goetz Kähler, Martin Weigel und Wolfhard
Janke — Institut für Theoretische Physik, Universität Leipzig,
Augustusplatz 10/11, 04109 Leipzig, Germany
Im Rahmen der Diplomarbeit erstellten wir Voronoi-Delaunay Zufallsgitter
in verschiedenen 2D-Topologien (Torus, Kugeloberfläche). Auf
diesen wurde dann ein modifiziertes, reichweitenabhängiges 3-Zustands
Potts-Modell mit Hilfe des Wolff’schen Clusteralgorithmus auf vielen
Realisierungen des Zufallsgitters simuliert. Ergebnisse dieser Arbeit, insbesondere
in Bezug auf das kritische Verhalten von Magnetisierung und
Suszeptibilität [1] werden hier vorgestellt.
[1] F.W.S. Lima, U.M.S. Costa, M.P. Almeida und J.S. Andrade Jr., Eur.
Phys. J. B17, 111 (2000).
DY 46.94 Do 16:00 Poster D
The Bragg glass - Vortex glass transition — •Roland Schorr,
Ludger Santen, and Heiko Rieger — Universität des Saarlandes,
FR 7.1 Theoretische Physik, 66041 Saarbrücken
Many phase diagrams of high Tc superconductors obtained experimentally,
e.g. in Bi2Sr2CaCu2O8+y (BSCCO) and Y Ba2Cu3O7−δ (YBCO),
reveal a very complicated landscape of various phases. The most significant
modifications applied to a naive idea of a type II superconductor,
which discriminates only between Meissner (H < Hc1) and Abrikosov
(Hc1 < H < Hc2) phase, have to take into account the impact of termal
fluctuations and disorder. This leads to a water-like melting phenomenon
in the regime of the Abrikosov phase with a melting line terminating at
fields that are much lower than Hc2. The phase below the melting line
is called Bragg glass whereas above the line one has to distinguish between
Vortex glass and Vortex liquid. We focus on the phase transition
between Bragg glass and Vortex liquid and Vortex glass, respectively,
induced by the disorder at finite temperatures. As a starting point of
our simulation we choose an elastic description of fluxlines fluctuating
in a random potential. We perform a Monte Carlo Simulation applying
cluster updates in order to sample the configuration space. Whereas local
updating schemes seem to be problematic due to slowing down and a
dynamical critical exponent z = 2, our cluster algorithm works well with
z ≈ 0. This enables us to realize the three phases for system sizes up to
L = 32.

Dynamik und Statistische Physik Donnerstag
DY 46.95 Do 16:00 Poster D
Monte Carlo Study of the Bond-Diluted 3D Ising Model —
Pierre Emmanuel Berche 1 , Christophe Chatelain 2 , Bertrand
Berche 2 , and •Wolfhard Janke 3 — 1 Groupe de Physique des
Matériaux, Université de Rouen, 76821 Mont Saint-Aignan Cedex,
France — 2 Laboratoire de Physique des Matériaux, Université Henri
Poincaré, Nancy 1, BP 239, 54506 Vandœuvre les Nancy Cedex, France
— 3 Institut für Theoretische Physik, Universität Leipzig, Augustusplatz
10/11, 04109 Leipzig, Germany
We study by Monte Carlo simulations the influence of bond dilution on
the three-dimensional Ising model. This paradigmatic model in its pure
version displays a second-order phase transition with a positive specific
heat critical exponent α. According to the Harris criterion the influence
of disorder should hence lead to a new fixed point governed by new critical
exponents. We have determined the phase diagram of the diluted
model, starting from the pure model limit down to the neighbourhood
of the percolation threshold. For the estimation of critical exponents, we
have first performed a finite-size scaling study, where we concentrated on
three different dilutions to check the stability of the disorder fixed point.
Particular emphasis is placed on cross-over phenomena between the pure,
disorder and percolation fixed points which lead to effective critical exponents
dependent on the concentration. Furthermore, the temperature
behaviour of physical quantities has been studied in order to characterize
the disorder fixed point more accurately. The question of non-selfaveraging
at the disorder fixed point is also investigated and compared
with recent results for the bond-diluted q = 4 Potts model.
DY 46.96 Do 16:00 Poster D
Photoangeregte Nanopartikel im starken Nichtgleichgewicht —
•Vassilios Kotaidis 1 , Samuel Gresillion 2 , Gero von Plessen 3
und Anton Plech 1 — 1 Fachbereich Physik der Universität Konstanz,
Universitätsstr. 10, 78457 Konstanz — 2 ESPCI 10, rue Vauquelin, F-
75005 Paris — 3 RWTH Aachen, I. Physikalisches Institut A, D-52074
Aachen
Metallische Nanopartikel stellen ideale Systeme dar, um elementare
dynamische Prozesse im Nichtgleichgewicht zu untersuchen. Durch optische
Anregung mit Femtosekundenlasern kann innerhalb einer Pikosekunde
dem System geung Energie zugeführt werden, um Gittertemperaturen
von einigen Tausend Kelvin zu erreichen. Mit der Kombination
aus Laseranregung mit 150 fs Pulsen und Röntgenpulsabfrage werden
irreversible Strukturänderungen in den metallischen Nanopartikeln aus
Silber und Gold untersucht.
Schmelzprozesse bzw. Fragmentationsprozesse werden auf der 100 ps
Zeitskala aufgezeichnet und in Beziehung zu der Ankopplung an das Medium,bzw.
eine glatte Oberfläche gesetzt.
DY 50 Entanglement and Decoherence
DY 46.97 Do 16:00 Poster D
2-D Crystals on Curved Surfaces — •Peter Lipowsky, Hans-
Georg von Ribbeck, Michael G. Nikolaides, and Andreas
R. Bausch — TU Muenchen, Physik-Department E22, James-Franck-
Strasse, D-85747 Garching
Determining the minimum-energy configuration of repulsive particles
on spherical surfaces is a rather difficult problem. Euler’s theorem states
that twelve pentagons are required to close a hexagonal network. Theory
and computer simulation have shown that, with rising system size, the
strain induced by single pentagonal disclinations will be lowered by the
introduction of additional pairs of bound 5-7 defects. An experimental
system to test the theoretical predictions has been developed. We use
surface-modified microspheres self-assembled onto the surface of water
droplets in an organic solvent. Crystalline structures are observed as soon
as the area density of particles at the interface is high enough. As predicted
by theory, we find that these crystals form distinctive high-angle
grain boundaries. The number of excess defects in these scars grows linearly
with the system size. Using digital video microscopy, particle tracking
algorithms, and triangulation routines, the dynamical behaviour of
the defects and the movements of single particles in the spherical lattice
are explored. The elastic potential of the lattice, the Young modulus, and
the diffusion constant are determined. First results demonstrating typical
phase transitions between fluid and crystalline phases are presented. Binary
mixtures formed by beads of two different diameters at the interface
were investigated.
DY 46.98 Do 16:00 Poster D
First-principle investigations of phonon spectra of crystalline
ice — •Waheed Adeniyi Adeagbo 1 , Peter Entel 1 und Jürgen
Hafner 2 — 1 Institute of Physics, University of Duisburg-Essen, 47048
Duisburg, Germany. — 2 Material Physics Institute, University of Vienna,
Austria
Lattice dynamical calculations have been carried out for a tetrahedrally
coordinated crystalline ice structure using Vienna Ab-initio Simulation
Package (VASP). A one directional periodically replicated unit cell
containing 24 molecules of water, whose constituents molecules are arranged
according to Bernal-Fowler ice rules is employed in our phonon
calculations. Dynamical properties were determined within the harmonic
approximations by finite difference evaluation of the dynamical matrix
from atomic forces. We investigated the effect of polarization arising from
dipole-dipole interactions on our phonon spectra by carrying out two separate
calculations with and without effect of induced polarization. The
polariazation was taken into account by switching on the evaluation of the
usual Berry phase expression for the electronic polarization of an insulating
ground state system in the VASP code. This produces a significant
effect in the splitting of longitudinal and transverse optic modes. Our
results are discussed with respect to the neutron diffraction scattering
data.
Zeit: Freitag 10:15–12:15 Raum: H2
Hauptvortrag DY 50.1 Fr 10:15 H2
How can entanglement between three or more qubits be measured?
— •Jens Siewert 1 and Andreas Osterloh 2 — 1 Institut
fuer Theoretische Physik, Universitaet Regensburg, D-93040 Regensburg,
Germany — 2 Dipartimento di Metodologie Fisiche e Chimiche per
l’Ingegneria, Universita di Catania, I-95125 Catania, Italy
Entanglement is, apart from its importance as a fundamental concept
in quantum mechanics, a key resource for quantum information processing.
While it is easy to say whether or not a given pure state of N qubits
is factorizable, it is a much more delicate question to quantify how much
it is entangled, even more so for mixed states. A well-known entanglement
measure for two qubits is the so-called concurrence (or 2-tangle)
[1,2] which is applicable for both pure and mixed states. While there exists
an analogous measure for pure states of three qubits [2], no N-tangle
is known for N = 3 mixed states or any state with N > 3. In this contribution,
the question is discussed what the “underlying principles” for
the N-tangle are, and how they can be generalized to N > 3.
[1] S. Hill and W.K. Wootters, Phys. Rev. Lett. 80, 2245 (1998).
[2] V. Coffman, J. Kundu, and W.K. Wootters, Phys. Rev. A 61,
052306 (2000).
DY 50.2 Fr 10:45 H2
Probing the decoherence of an oscillator with light — •Carsten
Henkel 1 , Mathias Nest 2 , Peter Domokos 3 , and Ron Folman 4
— 1 Institut für Physik, Universität Potsdam, Germany — 2 Institut für
Chemie, Universität Potsdam, Germany — 3 Institute for Solid State
Physics and Optics, Budapest, Hungary — 4 Physics Department, Ben
Gurion University, Beer Sheva, Israel
The decoherence of an oscillating particle due to the coupling to its
environment can be modelled in the framework of quantum Brownian
motion. From the average motion of the particle, some of the relevant
parameters (damping rate, equilibrium distribution) can be extracted,
but many details of the environmental bath remain arbitrary. We suggest
that experiments using an optical interferometer can obtain more
detailed information [1,2,3]. We show that the optical signal can differentiate
between master equations for different models for the environmental
coupling [4]. The scaling with particle mass and possible enhancements
using an optical cavity are discussed.
[1] S. Bose et al., Phys. Rev. A 56 (1997) 4175
[2] S. Mancini et al., Phys. Rev. Lett. 88 (2002) 120401
[3] W. Marshall et al., Phys. Rev. Lett. 91 (2003) 130401
[4] quant-ph/0310160

Dynamik und Statistische Physik Freitag
DY 50.3 Fr 11:00 H2
Exact decoherence to pointer states in free open quantum systems
is universal — •Jens Eisert — Institut für Physik, Universität
Potsdam, Am Neuen Palais 10, D-14469 Potsdam
In this talk it is shown that exact decoherence to minimal uncertainty
Gaussian pointer states is generic for free quantum particles coupled to
a heat bath. More specifically, the paper is concerned with damped free
particles linearly coupled to a heat bath at arbitrary temperature, with
arbitrary coupling strength and spectral densities covering the ohmic,
subohmic, and supraohmic regime. Then it is true that there exists a time
tc such that for times t > tc the state can always be exactly represented as
a mixture (convex combination) of particular minimal uncertainty Gaussian
states, regardless of the initial state. This exact ‘localisation’ is hence
not only a feature of the high temperature and weak damping limit, but
rather a generic property of damped free particles.
DY 50.4 Fr 11:15 H2
Semiclassical form factor for spectral and matrix element fluctuations
— •Marko Turek 1 , Dominique Spehner 2 , Sebastian
Müller 2 , and Klaus Richter 1 — 1 Institut für theoretische Physik,
Universität Regensburg, D-93040 Regensburg — 2 Fachbereich Physik,
Universität Duisburg-Essen, D-45117 Essen
We present a semiclassical analysis of the spectral form factor in hyperbolic
chaotic systems that includes classical action correlations. Our
calculation is based on recent developments [1] which extend the original
configuration space approach [2] towards a phase space approach but are
still restricted to two-dimensional systems. Here we present a calculation
of the spectral form factor for systems with more than two degrees of
freedom showing that the leading contributions do not depend on the
dimensionality of the system. Furthermore we consider a generalization
towards a form factor for matrix element fluctuations.
[1] D. Spehner, J. Phys. A: Math. Gen. 36, 7269 (2003); M. Turek
and K. Richter, J. Phys. A: Math. Gen. 36, L455 (2003); S. Müller,
Eur. Phys. Jour. B 34, 305 (2003)
[2] M. Sieber and K. Richter, Physica Scripta T90, 128 (2001)
DY 50.5 Fr 11:30 H2
Is the Quantum Dynamics of an Open Quantum System always
Linear? — •Peter Hänggi, Peter Talkner, and Karen M.
Fonseca-Romero — Institut für Physik, Universität Augsburg, Universitätsstr.
1, D-86135 AUGSBURG
We study the influence of the preparation of an open quantum systerm
on its reduced time evolution. In contrast to the widely studied case of
an initial preparation where the total density matrix factorizes into a
product of system density matrix and bath density matrix the time evo-
DY 51 Polymers and Colloids
lution generally is no longer governed by a linear map. Put differently,
the evolution is truely nonlinear and cannot be cast into the form of a
linear map plus a term that is independent of the initial denisty matrix of
the open system (no affine time evolution). As a consequence, the inhomogeneity
that emerges in formally exact generalized master equatins is
in fact a nonlinear term that vanishes only for a factorizing initial state.
The general results are elucidated with the example of two interacting
spins prepared in thermal equilibrium with one spin subjected to external
fields.
DY 50.6 Fr 11:45 H2
Statistical Relaxation Behaviour in closed Quantum Systems
— •Jochen Gemmer — Institut für Theoretische Physik I, Universität
Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart
It is known that quantum systems like atoms, spins etc. tend to decay
from exited states to their ground states in a purely statistical manner,
i.e. by an exponential decay process. This behaviour is explained
by famous concepts like Fermi’s Golden Rule, Weisskopf-Wigner Theory
or Quantum-Masterequations. All those concepts, however, rely on
additional assumptions or infinitely large environments.
We present a model of a spin coupled to a finite environment, in which
the spin shows a statistical relaxation behaviour, while the dynamics of
the full system are treated strictly according to the Schrödinger equation.
DY 50.7 Fr 12:00 H2
Quantum Reversibility: Is there an Echo? — •Moritz Hiller 1 ,
Tsampikos Kottos 1 , Doron Cohen 2 , and Theo Geisel 1 — 1 Max-
Planck-Institut für Strömungsforschung und Fakultät Physik der Universität
Göttingen, Bunsenstraße 10, 37073 Göttingen, Germany —
2 Department of Physics, Ben-Gurion University, Beer-Sheva 84105, Is-
rael
We study the possibility to undo the quantum mechanical evolution in
a time reversal experiment [1]. The naive expectation, as reflected in the
common terminology (“Loschmidt echo”), is that maximum compensation
results if the reversed dynamics extends to the same time as the
forward evolution. We challenge this belief, and demonstrate that the
time tr for maximum return probability is in general shorter. We find
that tr depends on λ = εevol/εprep, being the ratio of the error in setting
the parameters (fields) for the time reversed evolution to the perturbation
which is involved in the preparation process. Our results should be
observable in spin-echo experiments where the dynamical irreversibility
of quantum phases is measured.
[1] M.Hiller, T.Kottos, D.Cohen and T.Geisel, quant-ph/0308112
Zeit: Freitag 10:45–12:30 Raum: H3
DY 51.1 Fr 10:45 H3
Field-theoretic description of semiflexible polymers — •Semjon
Stepanow — Universität Halle, Fachbereich Physik, 06099 Halle
In using the connection between the Kratky-Porod model of a semiflexible
polymer and the quantum rigid rotator in an external homogeneous
field, and its treatment in the framework of the quantum mechanical
propagator method we have shown that most relations for flexible
polymers can be generalized to semiflexible ones, if one replaces
the Edwards-de Gennes propagator, 1/(k 2 /3 + p), through the matrix
P(k, p) = (I + ikDM) −1 D, where the infinite rank matrices D and M
are related to the spectrum of the quantum rigid rotator.
Within this framework we have expressed the distribution function for
a semiflexible polymer in half space in terms of the end-to-end distribution
function of free semiflexible polymer. We present results of the
study of the behaviour of a semiflexible polymer in the vicinity of a wall,
and of adsorption of a semiflexible polymer in weak interface and surface
potentials.
DY 51.2 Fr 11:00 H3
Motion of colloidal crystals and fluids in homogeneous electric
fields — •Thomas Palberg and Martin Medebach — Johannes
Gutenberg Universität Mainz, Institut f. Physik, KOMET 336,
Staudinger Weg 7, D - 55128 Mainz
A charged particle subjected to an electric field E will acquire a constant
velocity v due to the balance of accelerating electrostatic forces
and friction forces. Within the standard electrokinetic model the mobility
u = v/E depends on the surface or Zeta-potential and thus on the
particle charge. In this contribution we present a super-heterodyne reference
beam Doppler Velocimetry experiment to accurately measure the
mobility u under conditions of strong particle interaction. Integral flow
measurements are used for fluid samples, while spatially resolved measurements
are needed for crystalline suspensions. The rich flow scenario
observed there is presented in some detail. A prescription to determine
the true mobility in the presence of non-parabolic flow profiles (e.g. partial
plug-flow or shear banding)is proposed. The mobility is observed to
coincide with expectations based on the standard electrokinetic model
and a numerically determined effective renormalised charge only in the
crystalline state. For fluid order or isolated spheres significant deviations
towards lower values are observed.

Dynamik und Statistische Physik Freitag
DY 51.3 Fr 11:15 H3
Nematic-mediated interaction between colloidal particles with
opposing anchoring: a Derjaguin approach — •Maria Inmaculada
Rodriguez-Ponce 1 , Jose Manuel Romero-Enrique 2 , and
Luis F Rull 3 — 1 Lehrstuhl 5 fuer theoretische Physik, Physik Department,
Technische Universitaet Muenchen (Germany) — 2 Imperial
College of Science, Technology and Medecine. Department of Mathematics
(London, U. K.) — 3 Departamento de Fisica Atomica, Molecular y
Nuclear. Area de Fisica Teorica, Universidad de Sevilla (Sp ain)
We will consider the effect of a nematic solvent on the effective interction
between two colloidal particles which favour homeotropic and
planar anchoring, respectively. Neglecting the effect of the nematic director
field distorsion at large distances, the short-distance effective interaction
between colloidal particles can be related to the hybrid slit
pore solvation force via Derjaguin approximation. We present the rich
phenomenology that the hybrid slitpresents as the anchoring potential
strengths are tuned. This study has been performed in the framework of
the Density Functional Theory.
DY 51.4 Fr 11:30 H3
Phase behavior of a 2D colloidal system on a triangular lattice
— •Andreja Sarlah 1 , Thomas Franosch 1 , and Erwin Frey 1,2 —
1 Hahn-Meitner-Institut, Glienicker Straße 100, D-14109 Berlin, Germany
— 2 Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
We studied the phase behavior in 2D colloidal systems under the influence
of an external periodic potential created by the interference pattern
of laser beams forming a triangular lattice. In the special case, where the
numbers of colloidal particles and of potential minima are commensurate,
an integer number of particles gathers in each potential minimum. The
colloidal particles within a single potential minimum form a composite
object whose effective degrees of freedom are a few discrete orientational
states. Upon increasing the strength of the external potential, first the
composite objects orient, however, above some higher critical value, the
long-range orientational order is lost. In particular, we are interested in
systems with composite objects of 2 or 3 colloidal particles, i.e., dimers
or trimers, respectively. In these systems, the orientational ordering provides
a realization of 2D discrete spin models. The case of trimers can
be mapped to the spin-1/2 Ising model whereas the system of dimers
is mapped to a spin model characterized by several independent control
parameters leading to a richer phase diagram. Our theoretical results are
in good agreement with the recently reported experimental results. We
predict that by varying the strength of the screened interaction among
colloidal particles at least a part of the phase diagram of a spin model
for dimers should be accessible by experimental studies.
DY 51.5 Fr 11:45 H3
Phase diagram of random copolymers — •Christian Wald 1 , Annette
Zippelius 1 und Ben Vollmayr-Lee 2 — 1 Institut für Theoretische
Physik, Universität Göttingen — 2 Department of Physics, Bucknell
University, Lewisburg, PA 17837, USA
The phase diagram of random copolymers is still controversial: Whereas
Flory-Huggins theory predicts a sequence of separations into many homogeneous
phases [1], Landau theory favors microphase separation into
self-organized microstructures [2]. Simulations disagree with both models
[3].
We show that the Flory-Huggins free energy can be obtained by coarse-
graining the same microscopic model which also yields the Ginzburg-
Landau expansion for a second order transition. The phase diagram is
discussed for both pictures. Within Landau theory we find a sequence
of transitions from a disordered phase to two macroscopic phases and
finally to microphases. In contrast to the literature [1] we also find that
the microphase transition is always of first order and characterized by
a finite length scale. Consequently, a coexistence of three phases should
be observable. The treatment of both theories is extended to include the
effects of compressibility.
[1] A. Nesarikar et al., J. Chem. Phys. 98(9), 7385 (1993)
[2] G. H. Fredrickson et al., Macromol. 25(23), 6341 (1992)
[3] J. Houdayer and M. Müller, Europhys. Lett. 58(5), 660 (2002)
DY 51.6 Fr 12:00 H3
Rheology and Microscopic Topology of Entangled Polymeric
Liquids — •Ralf Everaers 1 , Sathish K. Sukumaran 2 , Gary S.
Grest 3 , Carsten Svaneborg 1 , Arvind Sivasubramanian 2 , and
Kurt Kremer 2 — 1 Max-Planck-Institut f¨r Physik komplexer Systeme,
Nöthnitzerstr. 38, 01187 Dresden, Germany — 2 Max-Planck-Institut für
Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany — 3 Sandia
National Laboratories, Albuquerque, New Mexico 87185, USA
The viscoelastic properties of entangled polymeric liquids are dominated
by topological constraints on a molecular level. These entanglements
confine the motion of individual polymers to a curvilinear diffusion
along the coarse grained chain contours, the reptation tube. The relationship
between the reptation tube and the static structure of the entangled
polymers, however, has remained unclear. Here, we present a “primitive
path” analysis of the microscopic topological state of (bead-spring)
model polymer solutions and melts and show that the predicted plateau
moduli, G 0 N, are in quantitative agreement with the experimentally determined
values for all major classes of synthetic polymers. Our approach
opens the way to a systematic study of structure-property relations and a
direct observation of the major relaxation mechanisms for polymers discussed
in the literature: reptation, constraint release and contour length
fluctuations of the primitive path.
DY 51.7 Fr 12:15 H3
Simulation of Polymer Dynamics in a Mesoscopic Solvent —
•Kiaresch Mussawisade, Marisol Ripoll, Roland G. Winkler,
and Gerhard Gompper — Institut Theorie II, Forschungszentrum
Jülich, D-52425 Jülich
We study the dynamics of a polymer chain in a mesoscopic solvent
by combining Multi-Particle-Collision dynamics (MPCD) and molecular
dynamics simulations (MD). In particular, we are interested in hydrodynamic
interactions obtained by this method and their influence on the
dynamics of the polymer chain. One of the advantages of this method,
compared to other simulation methods, is that the viscosity of the solvent
can easily be tuned by changing the system parameters. We observe
an increased diffusion coefficient of the polymer chain in our simulations
which we attribute to the hydrodynamic interactions. On the other hand,
by considering the relaxation modes of the polymer chain, we find that
the strength of the hydrodynamic interactions depends strongly on the
particular choice of the parameter set so that both Rouse- and Zimm-like
dynamics can be obtained. We have studied chains with and without excluded
volume interactions between the polymer beads. Zimm-like scaling
of the relaxation mode amplitudes is found in both cases at large Schmidt
numbers.

Halbleiterphysik Tagesübersichten
Hauptvorträge
HALBLEITERPHYSIK (HL)
Prof. Dr. R. Haug
Institut für Festkörperphysik
Universität Hannover
Appelstraße 2
30167 Hannover
E-Mail: haug@nano.uni-hannover.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsäle H13, H14, H15, H17)
HL 1.1 Mo 09:30 (H15) Three-dimensional Photonic Crystals: Fabrication, characterization and
physics, M. Wegener, M. Deubel, G. von Freymann, S. Pereira, K. Busch, C.M.
Soukoulis, A. Kaso, S. John
HL 7.1 Mo 14:30 (H15) Structural properties of semiconductor nanostructures from x-ray scattering,
Julian Stangl, Anke Hesse, Vaclav Holy, Rainer T. Lechner, Tomas Roch,
Mojmir Meduna, Zhenyang Zhong, Günther Bauer
HL 13.1 Di 09:30 (H15) Quantum dots: Building blocks of quantum devices? , M. Bayer
HL 18.1 Di 14:30 (H15) Confinement effects in Si nanostructures, Margit Zacharias, Johannes Heitmann,
Vadim G. Talalaev, Roland Scholz, Florian M. Kolb, Herbert Hofmeister
HL 26.1 Mi 14:30 (H15) Strains and stresses in GaN heteroepitaxy - sources and control,
Armin Dadgar
HL 34.1 Do 09:30 (H15) Spin Qubits with Quantum Dots, L. P. Kouwenhoven
HL 39.1 Do 14:30 (H15) The Dramatic Developments of Optical Lithography, W. Kaiser
HL 46.1 Fr 10:15 (H15) Carbon Nanotubes - A Successor to Silicon Technology?,
Wolfgang Hoenlein, Franz Kreupl, Georg Duesberg, Andrew Graham, Maik
Liebau, Werner Pamler, Robert Seidel, Eugen Unger
Symposium: Photonische Kristalle
HL 2.1 Mo 10:15 (H15) Photonic crystal waveguide devices: Dispersion characteristics, anomalous
refraction phenomena and their potential applications.,
Remigius Zengerle
HL 2.2 Mo 10:45 (H15) 2D Photonic Crystals for Integrated Optics, Anne Talneau
HL 2.3 Mo 11:15 (H15) Photonic Crystals for Telecom Applications and Ultrafast Optics,
Andreas Tünnermann, Markus Augustin, Thomas Schreiber, Jens Limpert, Stefan
Nolte, and Ernst-Bernard Kley
HL 2.4 Mo 11:45 (H15) Diffraction Control and Enhanced Transmission through Sub-Wavelength
Apertures, Thomas W. Ebbesen
HL 2.5 Mo 12:15 (H15) Metallic photonic crystals, Harald Giessen, Andre Christ, Thomas Zentgraf, Stefan
Linden, Kai Schubert, Dietmar Nau, Sergei Tikhodeev, Nikolai Gippius, and
Jürgen Kuhl
Symposium: Quanten-Hall-Systeme
HL 14.1 Di 10:15 (H15) Radiation induced zero-resistance states in high mobility GaAs/AlGaAs
devices, Ramesh Mani

Halbleiterphysik Tagesübersichten
HL 14.2 Di 10:45 (H15) Oscillatory photoconductivity of a 2D electron gas in magnetic field,
D.G. Polyakov, I.A. Dmitriev, M.G. Vavilov, I.L. Aleiner, and A.D. Mirlin
HL 14.3 Di 11:15 (H15) Optical Probe of Fractionally-Charged Quasiholes, C. Schüller, K.-B.
Broocks, P. Schröter, Ch. Heyn, D. Heitmann, T. Chakraborty, V. M. Apalkov,
M. Bichler, and W. Wegscheider
HL 14.4 Di 11:45 (H15) Coulomb Drag as a Probe of the Nature of Compressible States in a
Magnetic Field, Sjoerd Lok, K. Muraki, S. Kraus, W. Dietsche, K. Von Klitzing,
D. Schuh, M. Bichler, and W. Wegscheider
HL 14.5 Di 12:15 (H15) Coulomb drag in high Landau levels, von Oppen Felix, Mirlin A.D., and Gornyi
I.V.
HL 14.6 Di 12:45 (H15) Momentum resolved tunnel spectroscopy: Investigating interactions at
quantum Hall edges, Matthew Grayson und Matthew Grayson
Symposium: 50 Jahre Solarzelle
HL 19.1 Di 15:15 (H15) History and Principles of Solar Cells, H. J. Queisser
HL 19.2 Di 15:45 (H15) Progress in Manufacturable High-Efficiency Silicon Solar Cells, R. Hezel
HL 19.3 Di 16:15 (H15) Second and third generation photovoltaics: dreams and reality.,
J. H. Werner
HL 19.4 Di 16:45 (H15) Material & Device Concepts for Organic Photovoltaics: Towards Competitive
Efficiencies, C. J. Brabec
HL 19.5 Di 17:15 (H15) The Crystalline Silicon Solar Cell - Its History, Achievements And Perspectives,
G. Willeke
Symposium: Ferromagnetische Halbleiter
HL 37.1 Do 10:15 (H15) Magnetic Anisotropy in Ferromagnetic III-Mn-V Semiconductors: Issues
and Observations, Jacek K. Furdyna
HL 37.2 Do 10:45 (H15) High gap diluted magnetic semiconductors, David Ferrand
HL 37.3 Do 11:15 (H15) ZnO-MOVPE: Present State and Prospective Applications in Optoelectronics
and Magnetoelectronics, Andreas Waag
HL 37.4 Do 11:45 (H15) Disorder effects in diluted magnetic semiconductors, Carsten Timm
HL 37.5 Do 12:15 (H15) Hydrogen-control of ferromagnetism in Ga1−xMnxAs thin films,
Sebastian T. B. Goennenwein, Hans Huebl,Thomas A. Wassner, Christoph Bihler,
Martin Stutzmann, Achim Koeder, Wladimir Schoch, Andreas Waag, Martin S.
Brandt
HL 37.6 Do 12:45 (H15) Modified magnetic properties of ordered arrays of (II,Mn)VI quantum
wires due to reduced lateral dimensions, P.J. Klar, L. Chen, W. Heimbrodt,
F.J. Brieler, M. Fröba, T. Kurz, H.-A. Krug von Nidda, A. Loidl
HL 37.6 Do 13:15 (H15) GaN-based semiconductor compounds for spin electronics,
Bernd Beschoten
Symposium: Quantum Shot Noise in Nanostructures, Mo, siehe SYSN
Symposium: Functional Nanoparticles, Di, siehe SYNP
Symposium: Non-Fermi Liquids in Quantum Structures, Do, siehe SYNF
Symposium: Organic and Hybrid Systems for Future Electronics, Fr, siehe SYOH

Halbleiterphysik Tagesübersichten
Fachsitzungen
HL 1 Hauptvortrag Wegener Mo 09:30–10:15 H15 HL 1.1–1.1
HL 2 Symposium Photonische Kristalle Mo 10:15–12:45 H15 HL 2.1–2.5
HL 3 Quantenpunkte und -drähte: Herstellung und Charakterisierung
Mo 10:15–13:15 H17 HL 3.1–3.12
HL 4 Ultrakurzzeitphänomene Mo 10:15–13:15 H13 HL 4.1–4.12
HL 5 Transporteigenschaften Mo 10:15–12:45 H14 HL 5.1–5.10
HL 6 Photonische Kristalle I Mo 12:45–13:30 H15 HL 6.1–6.3
HL 7 Hauptvortrag Stangl Mo 14:30–15:15 H15 HL 7.1–7.1
HL 8 Photonische Kristalle II Mo 15:15–16:30 H15 HL 8.1–8.5
HL 9 Heterostrukturen I Mo 15:15–16:30 H17 HL 9.1–9.5
HL 10 Baulemente Mo 15:15–16:30 H13 HL 10.1–10.5
HL 11 Neue Materialien Mo 15:15–16:30 H14 HL 11.1–11.5
HL 12 Poster I Mo 16:30–19:00 Poster A HL 12.1–12.98
HL 13 Hauptvortrag Bayer Di 09:30–10:15 H15 HL 13.1–13.1
HL 14 Symposium Quanten-Hall-Systeme Di 10:15–13:15 H15 HL 14.1–14.6
HL 15 Photonische Kristalle III Di 10:15–13:30 H17 HL 15.1–15.13
HL 16 GaN: Bauelemente Di 10:15–12:45 H13 HL 16.1–16.10
HL 17 II-VI Halbleiter I Di 10:15–13:30 H14 HL 17.1–17.13
HL 18 Hauptvortrag Zacharias Di 14:30–15:15 H15 HL 18.1–18.1
HL 19 Symposium 50 Jahre Solarzelle Di 15:15–17:45 H15 HL 19.1–19.5
HL 20 Photonische Kristalle IV Di 15:15–17:30 H17 HL 20.1–20.9
HL 21 II-VI Halbleiter II Di 15:15–16:45 H13 HL 21.1–21.6
HL 22 Transport im hohen Magnetfeld/Quanten-Hall-Effekt Di 15:15–18:00 H14 HL 22.1–22.11
HL 23 Organische Halbleiter Di 16:45–19:00 H13 HL 23.1–23.9
HL 24 Photovoltaik I Di 17:45–19:15 H15 HL 24.1–24.6
HL 25 Heterostrukturen II Di 18:00–19:15 H14 HL 25.1–25.5
HL 26 Hauptvortrag Dadgar Mi 14:30–15:15 H15 HL 26.1–26.1
HL 27 GaN: Präparation und Charakterisierung Mi 15:15–19:15 H15 HL 27.1–27.16
HL 28 Optische Eigenschaften Mi 15:15–17:45 H17 HL 28.1–28.10
HL 29 Spinabhängiger Transport I Mi 15:15–18:15 H13 HL 29.1–29.12
HL 30 Photovoltaik II Mi 15:15–16:45 H14 HL 30.1–30.6
HL 31 Grenz- und Oberflächen Mi 16:45–18:15 H14 HL 31.1–31.6
HL 32 Halbleiterlaser I Mi 17:45–19:15 H17 HL 32.1–32.6
HL 33 III-V Halbleiter I Mi 18:15–19:30 H14 HL 33.1–33.5
HL 34 Hauptvortrag Kouwenhoven Do 09:30–10:15 H15 HL 34.1–34.1
HL 35 Symposium Ferromagnetische Halbleiter Do 10:15–13:45 H15 HL 35.1–35.7
HL 36 Quantenpunkte und -drähte: Optische Eigenschaften I Do 10:15–13:30 H17 HL 36.1–36.13
HL 37 Quantenpunkte und -drähte: Transporteigenschaften Do 10:15–13:30 H13 HL 37.1–37.13
HL 38 Halbleiterlaser II Do 10:15–13:15 H14 HL 38.1–38.12
HL 39 Hauptvortrag Kaiser Do 14:30–15:15 H15 HL 39.1–39.1
HL 40 SiC I Do 15:15–16:30 H15 HL 40.1–40.5
HL 41 Spinabhängiger Transport II Do 15:15–16:30 H17 HL 41.1–41.5
HL 42 Quantenpunkte und -drähte: Optische Eigenschaften II Do 15:15–16:30 H13 HL 42.1–42.5
HL 43 III-V Halbleiter II Do 15:15–16:30 H14 HL 43.1–43.5
HL 44 Poster II Do 16:30–19:00 Poster A HL 44.1–44.89
HL 46 Hauptvortrag Hoenlein Fr 10:15–11:00 H15 HL 46.1–46.1
HL 47 Quantendrähte und Korrelationseffekte Fr 11:00–13:00 H15 HL 47.1–47.8
HL 48 Kohlenstoff/Diamant Fr 11:00–11:30 H17 HL 48.1–48.2
HL 49 Spinabhängiger Transport III Fr 11:00–12:00 H13 HL 49.1–49.4
HL 50 Quantenpunkte und -drähte: Optische Eigenschaften III Fr 11:00–13:30 H14 HL 50.1–50.10
HL 51 Si/Ge Fr 11:30–12:15 H17 HL 51.1–51.3
HL 52 SiC II Fr 12:15–13:00 H17 HL 52.1–52.3
HL 53 Elektronentheorie Fr 12:00–12:30 H13 HL 53.1–53.2

Halbleiterphysik Tagesübersichten
Mitgliederversammlung des Fachverbands Halbleiterphysik
Do 19:00–20:00 H15
1. Begrüßung und Bericht
2. Stichwortkatalog
3. Verschiedenes

Halbleiterphysik Tagesübersichten
Postersitzungen:
Für die Postersitzungen (Mo und Do) die Poster bitte vormittags aufhängen und abends nach der Postersitzung abnehmen.
Zeit Vorträge
11.03.2001 MONTAG
Nr. Sitzung Ort
09:30 - 10:15 Hauptvortrag HL 1 M. Wegener: Three-dimensional Photonic Crystals: Fabrication,
characterization
H15
10:15 - 12:45 Symposium HL 2 Photonische Kristalle H15
10:15 - 13:15 Kurzvorträge HL 3 Quantenpunkte und -drähte: Herstellung und Charakterisierung
H17
10:15 - 13:15 HL 4 Ultrakurzzeitphänomene H13
10:15 - 12:45 HL 5 Transporteigenschaften H14
12:45 - 13:30 HL 6 Photonische Kristalle I H15
14:30 - 15:15 Hauptvortrag HL 7 J. Stangl: Structural properties of semiconductor nanostructures
from x-ray scattering
H15
15:15 - 16:30 Kurzvorträge HL 8 Photonische Kristalle II H15
15:15 - 16:30 HL 9 Heterostrukturen I H17
15:15 - 16:30 HL 10 Baulemente H13
15:15 - 16:30 HL 11 Neue Materialien H14
16:30 - 19:00 Postersitzung
12.03.2001 DIENSTAG
HL 12 Poster I Poster A
09:30 - 10:15 Hauptvortrag HL 13 M. Bayer: Quantum dots: Building blocks of quantum
devices?
H15
10:15 - 13:15 Symposium HL 14 Quanten-Hall-Systeme H15
10:15 - 13:30 Kurzvorträge HL 15 Photonische Kristalle III H17
10:15 - 12:45 HL 16 GaN: Bauelemente H13
10:15 - 13:30 HL 17 II-VI Halbleiter I H14
14:30 - 15:15 Hauptvortrag HL 18 M. Zacharias: Confinement effects in Si nanostructures H15
15:15 - 17:45 Symposium HL 19 50 Jahre Solarzelle H15
15:15 - 17:30 Kurzvorträge HL 20 Photonische Kristalle IV H17
15:15 - 16:45 HL 21 II-VI Halbleiter II H13
15:15 - 18:00 HL 22 Transport im hohen Magnetfeld / Quanten-Hall-Effekt H14
16:45 - 19:00 HL 23 Organische Halbleiter H13
17:45 - 19:15 HL 24 Photovoltaik I H15
18:00 - 19:15
13.03.2001 MITTWOCH
HL 25 Heterostrukturen II H14
14:30 - 15:15 Hauptvortrag HL 26 A. Dadgar: Strains and stresses in GaN heteroepitaxy -
sources and control
H15
15:15 - 19:15 Kurzvorträge HL 27 GaN: Präparation und Charakterisierung H15
15:15 - 17:45 HL 28 Optische Eigenschaften H17
15:15 - 18:15 HL 29 Spinabhängiger Transport I H13
15:15 - 16:45 HL 30 Photovoltaik II H14
16:45 - 18:15 HL 31 Grenz- und Oberflächen H14
17:45 - 19:15 HL 32 Halbleiterlaser I H17
18:15 - 19:30 HL 33 III-V Halbleiter I H14

Halbleiterphysik Tagesübersichten
Zeit Vorträge
14.03.2001 DONNERSTAG
Nr. Sitzung Ort
09:30 - 10:15 Hauptvortrag HL 34 L. P. Kouwenhoven: Spin Qubits with Quantum Dots H15
10:15 - 13:45 Symposium HL 35 Ferromagnetische Halbleiter H15
10:15 - 13:30 Kurzvorträge HL 36 Quantenpunkte und -drähte: Optische Eigenschaften I H17
10:15 - 13:30 HL 37 Quantenpunkte und -drähte: Transporteigenschaften I H13
10:15 - 13:15 HL 38 Halbleiterlaser II H14
14:30 - 15:15 Hauptvortrag HL 39 W. Kaiser: The Dramatic Developments of Optical Li- H15
thography
15:15 - 16:30 Kurzvorträge HL 40 SiC I H15
15:15 - 16:30 HL 41 Spinabhängiger Transport II H17
15:15 - 16:30 HL 42 Quantenpunkte und -drähte: Optische Eigenschaften II H13
15:15 - 16:30 HL 43 III-V Halbleiter II H14
16:30 - 19:00 Postersitzung HL 44 Poster II Poster A
19:00 - 20:00 Mitgliederversammlung HL 45
15.03.2001 FREITAG
H15
10:15 - 11:00 Hauptvortrag HL 46 W. Hoenlein: Carbon Nanotubes - A Successor to Silicon H15
Technology?
11:00 - 13:00 Kurzvorträge HL 47 Quantendrähte und Korrelationseffekte H15
11:00 - 11:30 HL 48 Kohlenstoff/Diamant H17
11:00 - 12:00 HL 49 Spinabhängiger Transport III H13
11:00 - 13:30 HL 50 Quantenpunkte und -drähte: Optische Eigenschaften III H14
11:30 - 12:15 HL 51 Si/Ge H17
12:15 - 13:00 HL 52 SiC II H17
12:00 - 12:30 HL 53 Elektronentheorie H13

Halbleiterphysik Montag
Fachsitzungen
– Haupt-, Kurzvorträge und Posterbeiträge –
HL 1 Hauptvortrag Wegener
Zeit: Montag 09:30–10:15 Raum: H15
Hauptvortrag HL 1.1 Mo 09:30 H15
Three-dimensional Photonic Crystals: Fabrication, characterization
and physics — •M. Wegener 1,2 , M. Deubel 3,2 , G. von
Freymann 3,2 , S. Pereira 4,2 , K. Busch 4,2 , C.M. Soukoulis 5 , A.
Kaso 6 , and S. John 6 — 1 Institut für Angewandte Physik, Wolfgang-
Gaede-Straße 1, Universität Karlsruhe (TH), D-76131 Karlsruhe, Germany
— 2 DFG-Center for Functional Nanostructures (CFN), Wolfgang-
Gaede-Straße 1, D-76131 Karlsruhe, Germany — 3 Institut für Nanotechnologie,
Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft,
Postfach 3640, D-76021 Karlsruhe, Germany — 4 Institut für Theorie
der Kondensierten Materie, Wolfgang-Gaede-Straße 1, Universität Karlsruhe
(TH), D-76131 Karlsruhe, Germany — 5 Ames Laboratory and
Department of Physics and Astronomy, Iowa State University, Ames,
Iowa 50011, U.S.A. — 6 Department of Physics, University of Toronto, 60
St.George Street, Toronto, Ontario, Canada M5S 1A7
HL 2 Symposium Photonische Kristalle
Photonic Crystals can be viewed as semiconductors for light. Despite
intensive efforts throughout the past decade, the holy grail of inexpensive
fabrication techniques for high-quality, large-scale three-dimensional
Photonic Crystals with photonic gaps in the telecommunication range or
even in the visible remains elusive. Here, we review our corresponding
work along the lines of two compatible and complementary techniques,
namely holographic lithography and direct laser writing. Results from
optical spectroscopy are compared with detailed theoretical calculations,
revealing the high quality of the structures.
Zeit: Montag 10:15–12:45 Raum: H15
HL 2.1 Mo 10:15 H15
Photonic crystal waveguide devices: Dispersion characteristics,
anomalous refraction phenomena and their potential applications.
— •Remigius Zengerle — Technical University of Kaiserslautern,
Chair of Electromagnetics and optical Communications, Erwin
Schroedinger street 11, D-67663 Kaiserslautern
author: R. Zengerle Early own experimental investigations on one- and
two-dimensional strongly corrugated optical waveguides revealed both
the existence of photonic bandgaps and anomalous refraction phenomena.
Today strongly one-, two- or three-dimensional periodic structures
with an omnidirectional photonic bandgap are well known as ”photonic”
crystals. For applications in new or improved functional components
used in communications we currently investigated in more detail two
unique properties which may be of special interest: Chromatic dispersion
and anomalous refraction phenomena. Based on our experimental
results, the dispersive and anomalous refraction properties of one- and
two-dimensional photonic crystal waveguides are explained both phenomenologically
and by simulations using Maxwells Theory. Possible new
ways for applications of semiconductor photonic bandgap devices in optical
communications will also be discussed.
HL 2.2 Mo 10:45 H15
2D Photonic Crystals for Integrated Optics — •Anne Talneau
— CNRS / LPN Laboratoire de Photonique et de Nanostructures, Route
de Nozay, F- 91460 Marcoussis
2D Photonic Crystals could be an interesting alternative for Photonic
Integrated Circuits, increasing the compactness and the integration of
optical functions. The in-plane confinement is obtained through the photonic
band gap generated by the periodic holes pattern, and the out-ofplane
confinement is reached through total internal reflection. We present
quantitative performances of passive and active structures in the 1.55 micron
wavelength domain. We will discuss possible applications, keeping
in mind the trade-off between design and technological limitation.
HL 2.3 Mo 11:15 H15
Photonic Crystals for Telecom Applications and Ultrafast
Optics — •Andreas Tünnermann, Markus Augustin, Thomas
Schreiber, Jens Limpert, Stefan Nolte, and Ernst-Bernard
Kley — Institut für Angewandte Physik, FSU Jena
Over the course of a few years photonic crystal nanostructures have
developed into a fast growing field attracting great interest. Especially
structures showing high dispersion or photonic crystal cavities with high
quality factors can find many applications in modern optics. In this pre-
sentation the potential of photonic crystal nanostructures in slab and
fiber geometry is discussed. Both types of structures are realized in materials
with a low index contrast. A thorough analysis of propagation
properties - attenuation, modal structure and dispersion - of photonic
crystal fibers and photonic crystal slab waveguides is given. Different application
examples, like the use of devices with tailored dispersion for
continuum generation or ultrashort pulse compression are given.
HL 2.4 Mo 11:45 H15
Diffraction Control and Enhanced Transmission through Sub-
Wavelength Apertures — •Thomas W. Ebbesen — ISIS, University
Louis Pasteur, 8 rue Gaspard Monge, 67000 Strasbourg, France
Periodically structured metallic films perforated with one or more subwavelength
holes ( 150 nm) can transmit the light with an efficiency orders
of magnitude larger than what theory predicts for single holes. The
efficiency can even be much larger than the fractional area occupied by
the hole, which means that even the light falling beside the hole emerges
on the other side of the sample. This extraordinary transmission is due to
the coupling of the incident light with the surface plasmons. The transmission
spectrum contains peaks attributed to surface-plasmon modes
that depend on both the symmetry and the 2D lattice parameter of
the surface corrugation. Another fundamental problem of sub-wavelength
apertures, namely optical diffraction, can also be controlled using surface
plasmons. Most recently, it has been found that even isolated single subwavelength
apertures (in the absence of periodic surface corrugations)
can give rise to transmission peaks due the presence of localized surface
plasmon modes induced at the aperture ridge. These findings have broad
fundamental and practical implications and show that, with modern fabrication
techniques, surface plasmons can be engineered and controlled
to yield unique optical properties which could find application in high
density data storage, photonic integration, near field probes, etc..
HL 2.5 Mo 12:15 H15
Metallic photonic crystals — •Harald Giessen 1 , Andre Christ 2 ,
Thomas Zentgraf 2 , Stefan Linden 2 , Kai Schubert 2 , Dietmar
Nau 1 , Sergei Tikhodeev 3 , Nikolai Gippius 3 , and Jürgen Kuhl 2
— 1 Institute of Applied Physics, University of Bonn, Germany — 2 Max-
Planck-Institut für Festkörperforschung, Germany — 3 General Physics
Institute RAS, Moscow, Russia
We prepare two-dimensional gold nanodot arrays with a diameter of
100 nm and a thickness of 20 nm on a waveguide substrate. Upon light
illumination, particle plasmons are formed inside the gold dots. These
localized plasmons form an extended state via photonic interaction me-

Halbleiterphysik Montag
diated by the waveguide underneath. The coupling leads to a strong
and spectrally narrow reduction of the absorption within the plasmon
spectrum [1]. We can measure the dispersion of these 2-dimensional
metallic photonic crystals. Changing the structure to 1-dimensional gold
nanowires allows even stronger coupling. Polaritons with a normal mode
splitting of more than 250 meV are formed [2]. Furthermore, we demonstrate
control of the dephasing times in the particle plasmons and quan-
tum beats in the 20 fs range by varying the geometric arrangement [3]. A
number of possible applications of these novel systems will be presented.
This work was financially supported by DFG and BMBF.
[1] S. Linden et al., Phys. Rev. Lett. 86, 4688 (2001).
[2] A. Christ et al., Phys. Rev. Lett. 91, 183901 (2003).
[3] K. Schubert et al., phys. stat. sol. (c) 0, 1412 (2003).
HL 3 Quantenpunkte und -drähte: Herstellung und Charakterisierung
Zeit: Montag 10:15–13:15 Raum: H17
HL 3.1 Mo 10:15 H17
Mix-and-Match Prozess zur Herstellung verzweigter elektronischer
Wellenleiter unter Verwendung von elektronenstrahlsensitivem
Calixaren und konventionellem Fotolack — •Michael
Knop 1 , Mirja Richter 1 , Ulrich Wieser 1 , Ulrich Kunze 1 , Dirk
Reuter 2 und Andreas D. Wieck 2 — 1 Lehrstuhl für Werkstoffe
und Nanoelektronik, Ruhr-Universität Bochum, D-44780 Bochum —
2 Lehrstuhl für Angewandte Festk örperphysik, Ruhr-Universität Bochum,
D-44780 Bochum
Es wird ein Verfahren zur Herstellung nanoskaliger, modulationsdotierter
GaAs/Al1−xGaxAs- Feldeffektstrukturen beschrieben.
Im ersten Prozessschritt wird eine Wellenleiterstruktur durch
Niederenergie-Elektronenstrahlithographie im Negativresist Calixaren
definiert. Zur Minimierung des Proximity-Effektes verwenden wir eine
Beschleunigungsspannung von 2 kV. Im zweiten Prozessschritt wird
durch UV-Lithographie die Mesa- und Kontaktstruktur des Transistors
in einem konventionellen Fotolack erzeugt. Die entstandene Kombination
aus Calixaren und Fotolack wird in einem einzigen nasschemischen
Ätzschritt in die Heterostruktur übertragen. Auf diese Weise lassen sich
minimale Strukturabmessungen von etwa 20 nm erzeugen. Die Wellenleiter
werden durch Transportmessungen charakterisiert.
HL 3.2 Mo 10:30 H17
Threedimensional Kinetic Monte Carlo Simulation of Formation
of Microstructures in Liquid Droplets — •Michael Block 1 ,
Roland Kunert 1 , Eckehard Schöll 1 , Torsten Boeck 2 , and
Thomas Teubner 2 — 1 Institut für Theoretische Physik, Technische
Universität Berlin, Hardenbergstr. 36, 10623 Berlin — 2 Institut für
Kristallzüchtung Berlin, Max-Born-Str. 2, 12489 Berlin
We simulate the epitaxy of Indium droplets on a glass surface and
the crystallization of Silicon inside these droplets utilizing kinetic Monte
Carlo methods. The influence of the growth temperature, the flux of
incoming particles, the surface coverage, and in particular an energy parameter
(comparable to the surface binding energy) upon the morphology
of growth is analysed. According to the experimental conditions of crystallization,
a temperature gradient and diffusion in spherical droplets is
included. The simulations result in the formation of pyramidal structures
in agreement with the experiment. The dependence of their shape and
the conditions of formation on the growth parameters is investigated in
detail.
HL 3.3 Mo 10:45 H17
NANOENGINEERING OF LATERAL STRAIN-
MODULATION IN QUANTUM WELL HETEROSTRUC-
TURES — •Jörg Grenzer 1 , S.A. Grigorian 1 , S. Feranchuk 1 ,
U. Pietsch 1 , U. Zeimer 2 , J. Fricke 2 , H. Kissel 2 , A. Knauer
2 , and M. Weyers 2 — 1 University of Potsdam, Institute of Physics,
Am Neuen Palais 10, 14469 Potsdam, Germany — 2 Ferdinand-Braun-
Institut fuer Hoechstfrequenztechnik, Albert-Einstein-Str. 11, 12489,
Berlin, Germany
We have developed a method to design a lateral band-gap modulation
in a single quantum well heterostructure (SQW). The lateral strain variation
is induced by patterning of a stressor layer grown on top of the SQW
which itself is not patterned. The 3D strain distribution is calculated using
linear elasticity theory implemented trough a finite element method
(FEM). The local variation of the band-gap energy is derived from the
strain distribution with the help of the deformation potential approach.
For a given vertical layer structure we optimized the geometrical parameters
to provide a nanostructure with maximum lateral band-gap
variation.
Experimentally such a structure was realized by etching a surface grat-
ing into a InGaP stressor layer grown on top of a InGaAs-SQW. The 3D
strain distribution and the band-gap variation are probed by X-ray grazing
incidence diffraction and photoluminescence (PL), respectively. We
found a splitting of the PL line of about 50 meV as predicted by FEM.
A planarization of the grating structure during a second epitaxy reduced
the induced band-gap variation. However, for the planar structure we
found still a splitting of larger than 22 meV.
HL 3.4 Mo 11:00 H17
Shape transition during growth of InAs/GaAs quantum dots
— •Peter Kratzer 1 and Quincy Liu 2 — 1 Fritz-Haber-Institut der
Max-Planck-Gesellschaft, Berlin — 2 Hahn-Meitner-Institut, Berlin
Recent STM studies have revealed that free-standing MBE-grown InAs
quantum dots on GaAs(001) appear in at least two varieties, as flat structures
mainly bounded by (137) facets [1], or also as larger objects with
an aspect ratio > 0.3, showing a variety of bounding facets [2]. We investigate
theoretically the energetics associated with these island shapes,
employing a hybrid approach [3]: surface energies and surface stress are
calculated using density functional theory, taking into account the specific
atomic structure. The bulk elastic energy in both the islands and the substrate
is calculated within continuum elasticity theory, using the finiteelement
method. We find that the flat island shape with (137) facets is
energetically preferable for small island volumes, while the steeper shape
becomes energetically lower for larger islands. Tensile surface stress and
the associated lowering of the surface energy on strained facets plays a
decisive role in this cross-over. We discuss implications of our findings for
the growth kinetics of InAs islands, in particular for the two-dimensional
growth mode of new atomic layers on the strained side facets of the island.
[1] J. Marquez et al., Appl. Phys. Lett. 78, (2001) 2309
[2] G. Costantini et al., Appl. Phys. Lett. 82, (2003) 3194
[3] E. Pehlke et al., Appl. Phys. A 65, (1997) 525
HL 3.5 Mo 11:15 H17
InAs quantum dots grown on the GaAs(2, 5, 11)A and B surfaces:
a STM and PL study — •Yevgeniy Temko, Takayuki
Suzuki, Ming Chun Xu und Karl Jacobi — Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin
InAs quantum dots (QDs) were grown by molecular beam epitaxy on
GaAs(2, 5, 11)A [1] and B surfaces. By atomically resolved in situ scanning
tunnelling microscopy we determine the main bounding facets on
the QDs. On both substrates the QDs are faceted by 110-, 111-surfaces
and a rounded region formed by vicinal (001) stacking. The latter becomes
faceted on large islands. There is no mirror symmetry on the QDs
in agreement with substrate symmetry. Besides this similarity there are
also differences: On the (2, 5, 11)A substrate the QDs shape is elongated
whereas those on the GaAs(-2,-5,-11)B are rather rounded similar to the
InAs QDs grown on GaAs(113)A and B [2,3,4]. The size distribution of
the islands on the B face is much sharper than on the A face which is also
confirmed by the low-temperature photoluminescence measurements.
[1] L.Geelhaar, J.Marquez, P.Kratzer, and K.Jacobi, Phys. Rev. Lett. 86,
3815 (2001)
[2] T.Suzuki, Y.Temko, and K.Jacobi, Appl. Phys. Lett. 80, 4744 (2002)
[3] Y.Temko, T.Suzuki, and K.Jacobi, Appl. Phys. Lett. 82, 2142 (2003)
[4] Y.Temko, T.Suzuki, M.C.Xu, and K.Jacobi, Appl. Phys. Lett. 83,
3680 (2003)

Halbleiterphysik Montag
HL 3.6 Mo 11:30 H17
Multi-Dot Floating-Gates in MOSFETS for Nonvolatile
Memories - Their Ion Beam Synthesis and Morphology —
•T. Müller 1 , K.-H. Heinig 1 , C. Bonafos 2 , H Coffin 2 , G.
Ben Assayag 2 , S. Schramm 2 , G Zanchi 2 , A. Claverie 2 , M.
Tence 3 , and C. Colliex 3 — 1 Forschungszentrum Rossendorf, Institut
für Ionenstrahlphysik und Materialforschung, Dresden, Germany —
2 CNRS/CEMES, Toulouse, France — 3 Laboratoire de Physique des
Solides, Universite Paris-Sud, Orsay, France
Scalability and performance of current FLASH memories could be improved
substantially by novel devices based on Multi-Dot Floating Gate
MOSFETS. Here, we present experimental and theoretical studies on
the low-energy ion beam synthesis of narrow Si nanocrystal (NC) layers
embedded in thin SiO2 films. NCs are produced by Si + implantation
into SiO2 and subsequent thermal treatment during which Si phase separates
from the supersaturated SiO2. Till now, the study of the phase
separation suffered from the weak mass contrast in TEM between the
Si and SiO2 phases. In this contribution, we investigate the morphology
of the Si quantum dot floating gate by Energy Filtered Scanning Transmission
Electron Microscopy (EFSTEM). A comparison of the observed
Si pattern with predictions of kinetic lattice Monte Carlo (MC) simulations
has been performed. It was found that the morphology of the
synthesized multi-dot Si floating gate changes with increasing ion fluence
(Si concentration) from isolated, spherical NCs to percolated structures.
The pattern of the phase separated Si predicted by kinetic Monte Carlo
simulations and observed by Electron Microscopy agree remarkably well.
HL 3.7 Mo 11:45 H17
Piezoelectric effect on confining potentials of gate-induced
quantum wires — •D. Schuster, Ch. Heyn, and W. Hansen
— Institut für Angewandte Physik und Zentrum für Mikrostrukturforschung,
Universität Hamburg, Jungiusstraße 11, D-20355 Hamburg,
Germany
We investigate a quasi one-dimensional electron gas in a metalinsulator-semiconductor
structure on (100) GaAs. The quantum wires are
electrostatically induced beneath lithographically defined metal gates on
top of the heterostructure. The metal stripes are known to induce a lateral
potential via the piezoelectric effect. We investigate quantum wires
beneath gates oriented along [010] and [011] directions. The piezoelectric
effect is expected to be absent in the case of [010] direction. We
employ so-called sidegates to tune the strength of the confinement. We
use magneto-capacitance spectroscopy to evaluate the strength of the
confinement from subband quantization energies. Surprisingly, we find
similar confinements in cristallographically different directions. This is
in contrast to our transport measurements on a similar sample where
almost no commensurability oscillations are observed in [010] direction.
HL 3.8 Mo 12:00 H17
Real Space Observation of Anisotropic Electron Scattering
in a quasi 1d-System with a Point Scatterer — •J. K. Garleff
1 , M. Wenderoth 1 , R. G. Ulbrich 1 , C. Sürgers 2 , and H. v.
Löhneysen 2 — 1 IV. Physikalisches Institut, Universität Göttingen, D-
37077 Göttingen — 2 Physikalisches Institut, SFB 195, Universität Karlsruhe,
D-76128 Karlsruhe
The Si-(111)-2×1 surface is described by the π-bonded chain model.
Band structure calculations [1] reveal a strong anisotropy with a steep
dispersion along the chains and almost no dispersion perpendicular to
them. The free surface as well as near-surface donors have been investigated
by STM and STS at T = 8 K with atomic resolution and a
spectral width of ∆E ≈ 50 meV. In the vicinity of donors the local density
of states (LDOS) shows a highly anisotropic contrast below EF. It
extends ∼10 nm along the reconstruction and ∼1 nm perpendicular. For
donors in the top layer only one chain is affected. The LDOS near the
donor is increased by a factor 3-4 compared with the free surface value
and shows a dip at the centre of the donor site, if the donor is close
to the surface. We interpret the observations as the scattering of “quasi
1-dimensional”-electrons by the donor. The quasi-1d system is provided
by the Si-(111)-2×1 surface band structure. Additional features near EF
support these findings.
[1] M. Rohlfing and S. G. Louie, Phys. Rev. Lett. 83, 856 (1999)
HL 3.9 Mo 12:15 H17
Untersuchung des Einflusses von Stickstoffbeimischungen in
InAs/GaAs Quantenpunkte mit Rastertunnelmikroskopie
an Querschnittsflächen — •Mandy Baudach 1 , Sebastian Kai
Becker 1 , Holger Eisele 1 , Rainer Timm 1 , Jan Grabowski 1 ,
Tai-Yang Kim 1 , Lena Ivanova 1 , Andrea Lenz 1 , Ferdinand
Streicher 1 , Mario Dähne 1 , Oliver Schumann 2 , Lutz Geelhaar
2 und Henning Riechert 2 für die -Kollaboration — 1 Institut
für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36,
D-10623 Berlin — 2 Infineon Technologies,Corporate Research Photonics,
D-81730 München
Mittels Rastertunnelmikroskopie an Querschnittsflächen (XSTM) wurden
vergrabene InAs Quantenpunkt-Doppelstapel mit einer GaAs-
Zwischenschicht untersucht, die mit Molekularstrahlepitaxie (MBE) gewachsen
wurden. Hierbei werden insbesondere Ergebnisse über den Einluss
geringer Stickstoffbeimischungen entweder direkt in den Quantenpunkten
als auch in der Zwischenschicht vorgestellt. Während eine
geringe Beimischung von Stickstoff in der Zwischenschicht die Struktur
der darauffolgenden InAs-Quantenpunkte nicht wesentlich verändert
und lediglich einen Einbau von Stickstoff in die InAs-Schicht bemerkt,
führt der Stickstoffeinbau direkt in die Quantenpunktschicht zu drastischen
Formänderungen und einer teilweisen Auflösung der Benetzungsschicht.
Detaillierte XSTM-Daten der einzelnen Strukturen mit atomarer
Auflösung werden gezeigt.
HL 3.10 Mo 12:30 H17
Untersuchung von GaSb/GaAs-Quantenpunkten mit Rastertunnelmikroskopie
an Querschnittsflächen — •Jan Grabowski,
R. Timm, H. Eisele, A. Lenz, S. K. Becker, T.-Y. Kim, L.
Müller-Kirsch, K. Pötschke, U. W. Pohl, D. Bimberg und M.
Dähne — Technische Universität Berlin, Institut für Festkörperphysik,
Hardenberstr. 36, 10623 Berlin
GaSb-Quantenpunkte in einer GaAs-Matrix weisen eine Typ-II-
Bandstruktur mit einer großen Bindungsenergie der Löcher, aber
ungebundenen Elektronen auf. Dies führt zu einer hohen Exzitonenlebensdauer
durch die räumliche Trennung der Ladungsträger,
vielversprechend für die Anwendung in Speichern.
Eine sehr geeignete Methode, überwachsene Nanostrukturen in atomarer
Auflösung zu untersuchen und somit sowohl strukturelle als auch
chemische Informationen über das Probensystem zu erhalten, ist die Rastertunnelmikroskopie
an Querschnittsflächen (XSTM). Es wurden mittels
metallorganischer Gasphasenepitaxie (MOCVD) gewachsene GaSb-
Quantenpunkte in GaAs mit XSTM untersucht und dabei die Form und
Größe der Quantenpunkte bestimmt. Aus den gemessenen Daten konnten
ebenso Informationen über die Stöchiometrie und Verspannung im Probensystem
gewonnen werden. Die Auswertung der Daten ergibt eine inhomogene
Antimonkonzentration in den Quantenpunkten von ∼ 75−100%,
wogegen die Benetzungsschicht durch stärkere Vermischung einen Antimonanteil
von bis zu 35% aufweist. In unregegelmäßigen Abständen wurden
zudem deutliche Unterbrechungen der Benetzungsschicht festgestellt.
HL 3.11 Mo 12:45 H17
Geordnete CdSe/ZnSSe-Quantenpunkte — •Thomas Schmidt 1 ,
Torben Clausen 1 , Gabriela Alexe 1 , Siegrid Bernstorff 2 ,
Detlef Hommel 1 und Jens Falta 1 — 1 Universität Bremen —
2 ELETTRA Synchrotron Light Source, Trieste
Die vertikale und laterale Korrelation von mittels MEE in ZnSSe-
Abstandslagen eingebetteten CdSe-Quantenpunktstapeln wurde vor allem
mit Kleinwinkelröntgenstreuung untersucht. In Abhängigkeit unterschiedlicher
Wachstumsparameter läßt sich durch das Auftreten von Satellitreflexen
eine Ordnung der Quantenpunkte nachweisen. Die Ergebnisse
lassen sich mit einem auf der Verspannung der Strukturen basierten
Modell von Tersoff et al. [1] erklären, allerdings ist auch eine starke Temperaturabhängigkeit
zu beobachten, die auf eine kinetische Limitierung
bei tieferen Temperaturen hindeutet.
[1] J. Tersoff, C. Teichert, and M. G. Lagally, Phys. Rev. Lett. 76, 1675
(1996)

Halbleiterphysik Montag
HL 3.12 Mo 13:00 H17
Structural properties of self-assembled InAs quantum dots —
•Christian Heyn 1 , Arne Bolz 1 , Theophilos Maltezopoulos 1 ,
Robert L. Johnson 2 , and Wolfgang Hansen 1 — 1 Institut für
Angewandte Physik, Universität Hamburg, Jungiusstr. 11, 20355 Hamburg,
Germany — 2 Institut für Experimentalphysik, Universität Hamburg,
Luruper Chaussee 149, 22761 Hamburg, Germany
We fabricate self-assembled InAs quantum dots (QDs) with solid-
HL 4 Ultrakurzzeitphänomene
source molecular beam epitaxy (MBE) on GaAs and AlAs substrates.
The structural properties of the QDs are studied using in situ electron
diffraction (RHEED), atomic force microscopy (AFM), and x-raydiffraction,
with emphasis on the growth parameter dependence of the
QD density, size, and composition as well as on the critical coverage up to
QD formation. In a second step, we develop a kinetic rate-equations based
model of the strain-induced InAs quantum dot formation and refine the
model assumptions by comparing calculation results with experimental
data.
Zeit: Montag 10:15–13:15 Raum: H13
HL 4.1 Mo 10:15 H13
Microscopic theory of carrier-wave Rabi flopping in semiconductors
— Q. T. Vu 1 , L. Bányai 1 , H. Haug 1 , O. D. Mücke 2 , •T.
Tritschler 2 , M. Wegener 2 , U. Morgner 3 , and F. X. Kärtner 4
— 1 Institut für Theoretische Physik, Universität Frankfurt, 60054 Frankfurt
am Main, Germany — 2 Institut für Angewandte Physik, Wolfgang-
Gaede-Straße 1, Universität Karlsruhe (TH), 76131 Karlsruhe, Germany
— 3 Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg,
Germany — 4 Department of Electrical Engineering and Computer
Science and Research Laboratory of Electronics, MIT, Cambridge,
MA 02139, U.S.A.
Carrier-wave Rabi flopping refers to a Rabi oscillation, the frequency of
which becomes comparable to the carrier frequency of light. Recently, we
have performed corresponding experiments on 50-100nm thin GaAs films
excited with intense 5fs pulses. However, the semiconductor problem has
only been discussed in terms of two-level systems [1]. Consequently, scepticism
has been expressed that this simple although intuitive description
is able to properly catch the underlying physics. Here, we will show that
the experimental spectra are nicely reproduced by a microscopic theory
based on the semiconductor Bloch equations, treating the GaAs band
structure via a tight-binding approach and accounting for the wave-vector
and carrier-density dependent relaxation and dephasing processes in a realistic
manner. This shows that our intuitive interpretation in terms of
carrier-wave Rabi flopping is correct indeed.
[1] O.D. Mücke et al., Phys. Rev. Lett. 89, 127401 (2002)
HL 4.2 Mo 10:30 H13
Dephasing of excitonic and biexcitonic polarization: Intensity
and temperature dependence — •Lars Wischmeier, Hans
Georg Breunig, Tobias Voss, Ilja Rückmann, and Jürgen
Gutowski — Institut für Festkörperphysik, Universität Bremen, P.O.
Box 330440, D-28334 Bremen
The decay of coherent excitonic and biexcitonic polarization was investigated
in a high quality 10 nm ZnSe/ZnS0,07Se single quantum well
as a function of intensity, temperature (4 − 70 K), and polarization
of the 110 fs excitation pulses. The spectral position of the pulses was
tuned such that the resonances of the 1s heavy-hole exciton and the
biexciton were exclusively excited. The dephasing rates were obtained
by both four-wave-mixing (FWM) and pulse-transmission measurements.
The experimental results were fitted with the temperature dependence of
the homogeneous linewidth due to phonon scattering. From the temperature
dependence of the decay of the FWM signal of the excitonic and
biexcitonic polarizations the acoustic- and optical-phonon-scattering coefficients
were determined.
Additionally the contrast ratio obtained from coherent-control measurements
with two phase locked pulses was studied as a function of
temperature and intensity.
HL 4.3 Mo 10:45 H13
Kohärente und inkohärente Ladungsträgerdynamik in
Quantentopf-Infrarot-Photodetektoren — •Thomas Maier 1 ,
Harald Schneider 1 , Hui Chun Liu 2 , Martin Walther 1 und Peter
Koidl 1 — 1 Fraunhofer-Institut für angewandte Festkörperphysik,
Tullastr. 72, D-79108 Freiburg — 2 Institute for Microstructural Sciences,
National Research Council, Ottawa K1A 0R6, Canada
Wir untersuchen Quantentopf-Infrarot-Photodetektoren (QWIPs), die
so konzipiert sind, dass drei energetisch äquidistante Niveaus entstehen.
Während die ersten beiden Zustände gebunden sind, stellt das dritte
Niveau eine Kontinuumsresonanz dar. Da Elektronen, die zum Photostrom
beitragen, über eine Zwei-Photon-Absorption in das Kontinuum
gelangen, ergibt sich eine quadratische Abhängigkeit des Photostroms
von der einfallenden Leistungsdichte. Führt man nun interferometrische
Autokorrelationsmessungen zweiter Ordnung an ultrakurzen Pulsen mit
einem solchen QWIP als Detektor durch, ist dessen Ansprechverhalten
durch die Lebensdauer und die Dephasierungszeit des Zwischenzustands
bestimmt. Eine numerische Analyse basierend auf den optischen Bloch-
Gleichungen ergibt Lebensdauern im Bereich von 500 fs (750 fs) und Dephasierungszeiten
von ca. 100 fs (250 fs) in topf-(modulations-)dotierten
Strukturen.
HL 4.4 Mo 11:00 H13
THz emission from GaSb samples with modified surfaces —
•Stephan Winnerl, Thomas Dekorsy und Manfred Helm — Institut
für Ionenstrahlphysik und Materialforschung, Forschungszentrum
Rossendorf, PF 510119, 01314 Dresden
The optimization of emitters for THz radiation pulses has gained a
lot of interest in recent years. They can be based on accelerating charge
carriers, which are photoexcited by fs-laser pulses in the surface field
of a semiconductor. We studied the THz emission from GaSb samples
that were annealed at different temperatures in the range from 300 ◦ C
to 700 ◦ C. Without annealing, no THz emission was observed under fs
excitation at 800 nm. This is consistent with the fact, that for GaSb no
surface states in the band gap have been found [1]. The THz emission
was strongest for the annealing temperature of 450 ◦ C with amplitudes
comparable to that of an InGaAs emitter. We attribute the THz emission
to a surface field caused by decomposition of the surface of the annealed
samples. The decomposition is confirmed by measuring the surface
stoichiometry using Auger electron spectroscopy. We suggest that the
decrease of THz intensity for the higher annealing temperatures is due
to a lowering of the carrier mobility. Our experiment demonstrates the
possibility to modify materials for THz emission in a very simple way.
[1] P.W. Chey, I.A. Babalado, T. Sukegawa, and W.E. Spicer, Phys.
Rev. Lett. 35, 1602 (1975).
HL 4.5 Mo 11:15 H13
Coherent switching of polariton modes and their quantum beats
in four-wave mixing and real-time resolved pulse-transmission
experiments on ZnSe SQWs — •I. Kudyk, T. Voss, H. G. Breunig,
I. Rückmann, and J. Gutowski — Institute of Solid-State
Physics, University of Bremen, POB 330440, D-28334 Bremen, Germany
For layer thicknesses above 20 nm the optical properties of ZnSe nanostructures
are usually dominated by the existence of different polariton
modes and their interactions.
Optical coherent control of these polariton modes is investigated by
use of a pair of 100 fs long phase-locked pulses in both pulse-transmission
experiments with real-time resolution and four-wave-mixing (FWM) experiments.
It is shown that for low excitation densities the contributions
of the different resonances can be selectively enhanced or diminished.
When continuously changing the inter-pulse delay time a succession of
constructive and destructive interference is observed separately for each
resonance. The coherent control of polariton modes also allows for a directed
manipulation of the beat structures on the real-time transients as
well as in the FWM signals.
Furthermore, the dephasing time of the polariton modes is analyzed in
spectrally resolved, two-pulse degenerate FWM experiments and studied
as a function of the excitation density and temperature. By additional
measurements of the polarization states of the different spectral components
the relative phase of the polariton modes is investigated.

Halbleiterphysik Montag
HL 4.6 Mo 11:30 H13
Ladungsträger-Dynamik in Stickstoff-implantiertem GaAs —
•S. Sinning, T. Dekorsy und M. Helm — Forschungszentrum Rossendorf,
Postfach 51 01 19, 01314 Dresden
III-V-Halbleitern mit geringen Stickstoffkonzentrationen gelten
sowohl als Materialsystem als auch für Anwendungen seit einiger
Zeit größeres Interesse. Neben epitaktischen Methoden bietet die
Ionen-Implantation einen effektiven Weg zur Einbringung des Stickstoffs
in das Substrat. Nachteil dieses Verfahrens ist der dem Gitter durch die
Ionen-Implantation zugefügte Schaden.
Wir untersuchen die Effektivität des Einbaus von aktivem Stickstoff
nach Implantation und thermischer Ausheilung (RTA). Bei RTA-
Bedingungen von 650 ◦ C/30s ist der Einbau des Stickstoffs in die Matrix
optimal. Eine Verbesserung der Gitterqualität kann durch Implantation
bei erhöhten Temperaturen (T > 200 ◦ C) erreicht werden. Die Ladungsträger-Dynamik
im sub-Pikosekunden-Bereich für Implantationen
bei Raumtemperatur und bei erhöhten Temperaturen wird mit der von
nicht-implantiertem GaAs verglichen. Es werden signifikante Unterschiede
beobachtet, die auf eine starke Modifizierung der Bandstruktur des
stickstoffhaltigen GaAs zurückzuführen sind.
HL 4.7 Mo 11:45 H13
Stimulated bosonic scattering in the exciton-biexciton system
of a ZnSe single quantum well — Daniel Hägele, •Stefan
Pfalz, and Michael Oestreich — Universität Hannover, Institut
für Festkörperphysik, Abteilung Nanostrukturen, Appelstraße 2, 30167
Hannover
Although it has been long known that semiconductor excitons and
biexcitons are quasiparticles of bosonic nature, all experiments claiming
bosonic effects are discussed controversially. Here, we give direct experimental
evidence that the decay of a spin-zero biexciton into an exciton
and a photon with opposite spins (±1) is subject to bosonic enhancement
caused by the presence of other excitons. In an optically created
spin polarized gas of excitons, biexcitons decay preferentially into that
final state whose resulting exciton has the same spin orientation as the
majority of excitons. We measure in a 10 nm ZnSe quantum well a photoluminescence
polarization degree of up to 8 % at the biexciton emission
line due to stimulated bosonic scattering. The biexcitonic PL polarization
is opposite to that of the excitons which exhibit a polarization degree of
−50 %. While the polarization of the exciton line can be fully understood
by the usual optical spin selection rules, the biexcitonic polarization can
only be explained by the bosonic nature of excitons.
HL 4.8 Mo 12:00 H13
How fast is the insulator-to-metal transition in VO2? — •T.
Dekorsy 1 , A. Cavalleri 2 , H.H. Chong 2 , J.C. Kiefer 3 , and R.W.
Schoenlein 2 — 1 Forschungszentrum Rossendorf, 01314 Dresden —
2 Materials Sciences Division, Lawrence Berkeley National Laboratory,
Berkeley, CA — 3 Universite du Quebec, INRS energie et materiaux,
Varennes, Quebec
We investigate the photo-induced insulator-to-metal transition in VO2,
a strongly correlated semiconductor with monoclinic structure. The
insulator-to-metal transition (Tc= 341 K) is initiated by photo-doping
of holes into the correlated valence band with high-power femtosecond
laser pulses. Experiments with time-resolutions ranging from the 100fs
regime down to 10-fs reveal a minimum time constant for the phase
transition to be accomplished of approximately 75 fs. This observation
gives evidence for a temporal bottleneck of the phase transition since an
atomic rearrangement and symmetry increase for the formation of the
high-temperature metal phase has to take place. Femtosecond excitation
of VO2 with low power laser pulses reveals the excitation of low-energy coherent
phonons which have displacements along the coordinates relevant
for the phase transition. Interestingly the observed temporal bottleneck
coincides with half the period of these phonons. Our findings demonstrate
a new approach for the investigation of the interplay between atomic and
electronic structure on ultrashort time scales.
HL 4.9 Mo 12:15 H13
Optically induced realspace-transfer between mesoscopic quantum
dots — •Claus Metzner and Dominik Stehr — Technische
Physik I, Universität Erlangen Nürnberg, Erwin-Rommel-Str. 1, 91052
Erlangen
We theoretically investigate a physical scenario in which packets of
electrons (less than 100) are moving coherently over mesoscopic distances
in a two-dimensional potential landscape, created by laterally selective
doping of a quantum well. The motion of the charge packets is controlled
and monitored in a purely optical way by using ultrashort light (or THz)
pulses, acting as time-dependent electric driving forces. In the strong field
regime, the interacting few-particle system shows a complex, nonlinear,
collective dynamics, partially corrupted by stochastic phonon scattering
events. Nevertheless, a controlled transfer between metastable states
(corresponding to spatially separated potential minima, or ‘meso-dots’)
can be achieved with proper light pulses. The pulse parameters can be
found automatically by evolutionary optimization.
HL 4.10 Mo 12:30 H13
THz photomixer based on quasi-ballistic transport in AlGaAs
nipnip-superlattices — •Frank H. Renner 1 , O. Klar 1 , S.
Malzer 1 , M. Eckardt 1 , A. Schwanhäußer 1 , G. Loata 2 ,
T. Löffler 2 , H. Roskos 2 , D. Driscoll 3 , M. Hanson 3 , A.C.
Gossard 3 , and G.H. Döhler 1 — 1 Insitut für Technische Physik I,
Universität Erlangen-Nürnberg , Germany — 2 Lehrstuhl für Ultrakurzzeitphysik,
Universität Frankfurt a.M., Germany — 3 Materials
Departement, UC Santa Barbara, U.S.A.
Conventional THz-photomixers are antenna-structures on a LT-GaAslayer
and are based on the photoconductivity of LT-GaAs, characterized
by an extremely short carrier-lifetime . We have developed a novel concept
for photomixing based on the quasi-ballisitic transport of electrons
in AlGaAs-i-layers. In this concept, the emitter is not limited by the lifetime
of the photogenerated carriers and its efficiency proves to be higher
than in conventional LT-photomixers.
The emitter consists of a stack of nano-pin-diodes. The lengths and
Al-contents of the i-layers in this nipnip-superlattice are optimized for
the transport of the carriers. Recombination of the photogenerated carriers
takes place inside the recombination-enhanced np-diodes between the
nano-pin-diodes. The THz-modulated current is fed into an attached planar
antenna, which is either a resonant dipole-antenna or a non-resonant
spiral- or log. periodic-antenna.
In this contribution we present the concept of the nipnip-emitter and
its realization in the AlGaAs material system, including experimental
results on the THz-output and frequency response of the emitter.
HL 4.11 Mo 12:45 H13
Unipolar impact ionization in GaAs/AlGaAs heterostructures
— •O. Schmidt 1 , M. Eckardt 1 , A. Schwanhäusser 1 , G.H.
Döhler 1 , S. Trumm 2 , M. Betz 2 , F. Sotier 2 , M. Hanson 3 , and
A.C. Gossard 3 — 1 Technische Physik I, Universität Erlangen-
Nürnberg — 2 Physik-Department E11, Technische Universität München
— 3 Materials Department, UCSB Santa Barbara, USA
Impact ionization and the resulting avalanche multiplication in pindiodes
represent one of the technically most feasible methods for detecting
and amplifying small optical signals. The ratio of the electron and
hole ionization coefficient α/β determines the ultimate multiplication and
noise performance of Avalanche Photodiodes. This study indicated, that
the ratio α/β is much higher in a specially designed heterostructure than
in a comparable homogeneous AlGaAs-diode.
Our bandgap engineered AlGaAs pin heterostructure allows for spatially
selective carrier injection by a wavelength adapted pump pulse. This
makes it possible to measure multiplication factors for unipolar initiated
transport and deduce the ionization coefficient for electrons and holes, respectively.
From steady state experiments we found that in graded band
structures the electron ionization coefficient is similar to that of homogeneous
structures, whereas the hole coefficient is much smaller.
Our Monte-Carlo calculations are supporting these findings. To gain more
information about differences of electron and hole impact ionization with
a resolution of fs in time and nm in space, in addition, we are performing
two color fs pump and probe experiments.
HL 4.12 Mo 13:00 H13
Phasenaufgelöste Pulsreflexion an gepumpten ZnSe-Schichten
— •Matthias Seemann, Frank Kieseling, Heinrich Stolz,
Günter Manzke und Klaus Henneberger — Universität Rostock,
Fachbereich Physik, D-18051 Rostock
Wir berichten über Reflexionsexperimente eines schwachen 150 fs Testpulses
an einer ZnSe-Epitaxieschicht. Die Reflexion kann durch die komplexe
dielektrische Funktion (DF) beschrieben werden. Diese kann im
linearen Fall mit Hilfe der spektralen Interferometrie ohne Kenntnis der
Phase des Testpulses bestimmt werden. Der Halbleiter wird durch einen
nichtkollinearen resonanten Anregungspuls optisch gepumpt. Dieser generiert
Ladungsträger (Exzitonengas oder ein Elektron-Loch-Plasma),

Halbleiterphysik Montag
die die optischen Eigenschaften verändern. In Abhängigkeit von der
Verzögerungszeit und der Leistung des Anregungspulses kann das Umklappen
eines Pi-Phasensprunges am Schwerlochexziton gegenüber dem
ungepumpten Halbleiter beobachtet werden. Das Verhalten widerspie-
HL 5 Transporteigenschaften
gelt sich in der theoretischen Beschreibung des Systems, die den Einfluß
der Vielteilcheneffekte auf die DF im Rahmen der Halbleiter-Bloch-
Gleichungen berücksichtigt.
Zeit: Montag 10:15–12:45 Raum: H14
HL 5.1 Mo 10:15 H14
Lateral tunneling spectroscopy in a two-dimensional electron
gas — •Jean-Laurent Deborde 1 , Saskia F. Fischer 1 , Ulrich
Kunze 1 , Dirk Reuter 2 , and Andreas D. Wieck 2 — 1 Lehrstuhl
für Werkstoffe und Nanoelektronik, Ruhr-Universität Bochum,
D-44780 Bochum — 2 Lehrstuhl für Angewandte Festkörperphysik,
Ruhr-Universität Bochum, D-44780 Bochum
A direct observation of lateral tunneling, via electron energy
spectroscopy, in a two dimensional electron gas (2-DEG) is reported.
A lateral tunneling field-effect transistor has been fabricated using a
GaAs/AlGaAs heterostructure and atomic force microscope (AFM)
lithography. This technique permits to form a groove with a low width
to height aspect ratio (3.5 and less). A furrow is dynamically ploughed
by the vibrating tip of the AFM into a 5 nm thick polymer layer on the
surface of the semiconductor [1]. Wet chemical etching transfers the line
pattern resulting in a 70 nm wide and 20 nm deep groove generating a
tunneling barrier in the channel. A Schottky gate is deposited on the
top of the device in order to control both the charge carrier density and
the barrier height. The characteristic conductance vs. source-drain bias
shows structures which indicate electron tunneling through the potential
barrier. The 2-DEG Fermi energy of 13 meV is determined from the
tunneling spectrum.
The realization of a lateral resonant tunneling field-effect transistor
using this particular fabrication technique is further anticipated.
[1] U. Kunze, Superlatt. Microstruct. 31, 3 (2002).
HL 5.2 Mo 10:30 H14
Phonon-assisted Transport through Stacks of Quantum Dots —
•C. Gnodtke 1 , G. Kiesslich 1 , A. Wacker 1,2 , and E. Schöll 1 —
1 Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr.
36, 10623 Berlin — 2 Department of Physics, University of Lund,
Box 118, SE-22100 Lund, Sweden
A fully self-consistent theory based on nonequilibrium Green’s functions
is used to calculate the stationary properties of a system of coupled
quantum dots under the influence of phonon scattering. The currentvoltage
characteristic is computed, revealing peaks due to phononabsorption
and emission processes. The dependence of these peaks on the
coupling of the dots to contacts and the interdot coupling are studied in
detail, showing a particularly strong sensitivity to the coupling between
the dots. A comparison with a simplified model for the scattering processes,
i.e. diagonal self-energies, shows that this tends to overestimate
the phonon-assisted tunneling contributions to the overall current.
HL 5.3 Mo 10:45 H14
Nichtparabolizität und Rashba-Spinaufspaltung in InGaAs —
•C. Zehnder 1 , Y.S. Gui 1 , J. Knobbe 2 , T. Schäpers 2 , D. Heitmann
1 und C.-M. Hu 1 — 1 Institut für Angewandte Physik, Universität
Hamburg, Jungiusstraße 11, 20355 Hamburg — 2 Institut für Schichten
und Grenzflächen, Forschungszentrum Jülich, 52425 Jülich
InGaAs als Halbleiter mit einer schmalen Bandlücke zeigt eine starke
Nichtparabolizität und den Rashba-Effekt. Es ist bekannt, daß die
Berücksichtigung der Nichtparabolizität zu einer Reduktion des Rashba-
Parameters α führt. Es ist deshalb interessant, zusätzlich die Nichtparabolizität
durch Messung der Zyklotronresonanz genau zu bestimmen.
Wir untersuchen eine In0,77Ga0,23As/InP Heterostruktur mit Magnetotransport
und spektralaufgelöster Photoleitung mit einem Ferninfrarotspektrometer
bei einer Temperatur von 1,5K und Magnetfeldern bis 12 T.
Die Transportmessung zeigt eine klare Schwebung bei niedrigen Magnetfeldern
wegen des Rashba-Effektes. Die Spektren zeigen eine Spinaufspaltung
bei hohen Magnetfeldern auf Grund der Nichtparabolizität. Wir haben
ein Modell erstellt, das Nichtparabolizität, Rashba-Spinaufspaltung
sowie einen energieabhängigen g-Faktor enthält. Mit diesem Modell simulieren
wir unsere Transportmessungen und berechnen die Position der
Zyklotronresonanz. In beiden Fällen erreichen wir eine gute Übereinstimmung,
wobei wir für den Rashba-Parameter α = 3, 7·10 −12 eV m erhielten.
Die Simulationen des Magnetotransports ergaben bei kleinen Magnetfeldern
eine klare Abhängigkeit der Knotenposition der Schwebung von
der Stärke der Nichtparabolizität. Die Spinaufspaltung der Zyklotronresonanz
wird aber erst bei höheren α beeinflußt.
HL 5.4 Mo 11:00 H14
Nonplanar two-dimensional electron gases in InAs heterostructures
on GaAs — •S. Löhr, Ch. Heyn, and W. Hansen — Institut
für Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität
Hamburg, Jungiusstraße 11, D-20355 Hamburg, Germany
We present transport properties of a two-dimensional electron gas
(2DEG) in an InAs/InGaAs quantum well grown by molecular beam
epitaxy on a GaAs substrate. The experiments are performed in magnetic
fields tilted with respect to the sample normal. Depending on the
relative orientation of the current flow and the tilt direction, i.e., the
direction of the magnetic field component parallel to the sample substrate,
we observe a pronounced positive magnetoresistance and a strong
damping of the Shubnikov-de Haas oscillations. Both effects increase with
the tilt angle. We show that these findings are direct evidence of a nonplanar
2DEG, resulting from the lattice-mismatched epitaxial growth of
this InAs-based structure on GaAs, which also causes a cross-hatch topography
at the sample surface. An estimation of the 2DEG curvature
suggests that the strength of the curvature-induced spin-orbit interaction
(M.V.Entin etal., PRB 64, 85330 (2001)) may be comparable to
the Rashba spin-orbit coupling found in this kind of heterostructure.
HL 5.5 Mo 11:15 H14
Bistabiles Schalten in asymmetrischen Y-Schaltern — •David
Hartmann, Stephan Reitzenstein, Lukas Worschech und Alfred
Forchel — Technische Physik, Universität Würzburg, Am Hubland,
97074 Würzburg
Wir stellen ein neuartiges Konzept eines planaren Nanoschalters
vor und demonstrieren, dass dessen Gate-Effektivität dynamisch über
einen intrinsischen Rückkopplungsmechanismus zwischen Drain und
Gate erhöht wird. Der Nanoschalter basiert auf einer Y-förmigen
Kanal-Verzweigung [1]. Im lateralen elektrischen Feld asymmetrisch
betrieben stellt sich heraus, dass ein Ast die Funktion eines effektiven
Gates erfüllt. Zum Beispiel werden Spannungsvariationen dVg an
einem Ast in Spannungsänderungen dVd an dem zweiten Ast mit einer
differentiellen Spannungsverstärkung g = −dVg/dVd von mehr als 1000
verstärkt. Unsere Analyse zeigt, dass Änderungen der Ausgangsspannung
die Zustandsdichte des Gates und somit die Quantenkapazität
drastisch verändert. Die positive Rückkopplung bewirkt bei Variation
der Gatespannung eine Zunahme der Verstärkung bis hin zum bistabilen
Schalten.
[1] S. Reitzenstein, L. Worschech, P. Hartmann, M. Kamp, A. Forchel,
Phys. Rev. Lett. 89, 226804 (2002)
HL 5.6 Mo 11:30 H14
The Influence of Weak Disorder on Ballistic Transport in Mesoscopic
Systems — •Kai Bröking und Ragnar Fleischmann —
MPI für Strömungsforschung, Bunsenstr. 10, 37073 Göttingen
Recent experimental and theoretical work [1] has given new insight
into the properties of the electron flow in two-dimensional electron gases
at low temperatures: small angle scattering leads to a pronounced branching
of the electron flow.
Studying the electron motion on length scales shorter than the mean free
path in the single-electron picture, we focus on the effects of branching
on transport phenomena which are assumed to be ballistic.
[1] Topinka, Leroy, Fleischmann, Westervelt, Shaw, Heller, Maranowski
and Gossard, Nature, 410 (2001), pp. 183-186

Halbleiterphysik Montag
HL 5.7 Mo 11:45 H14
Quantum Dots as Quantum Bits — •Daniel Schröer 1 , Andreas
K. Hüttel 1 , Stefan Ludwig 1 , Werner Wegscheider 2 , and
Jörg Kotthaus 1 — 1 CeNS und Sektion Physik der LMU München —
2 Institut für Angewandte und Experimentelle Physik der Universität Re-
gensburg
We create lateral quantum dots by depleting the two-dimensional electron
system of an AlGaAs/GaAs heterostructure with lithographically
defined Schottky gates. The advantage of this lateral approach is the
flexibility in number and orientation of leads and gates. Multiple quantum
dots can be coupled capacitively or via tunnel barriers. The coupling
strengths and the number of free charge carriers per dot are tuned by
means of gate voltages. A double quantum dot is often regarded as an
artificial molecule, as the discrete states of both dots split into molecular
bonding and antibonding states. These form a two-level system that is
applicable as a qubit for quantum information processing. The complexity
of the molecular states increases with the number of free electrons per
dot. Hence, we aim to reduce the dot sizes and integrate suitable tools to
read out the number of charge carriers (e.g. a quantum point contact).
The molecular states are probed by analysing the charging diagram of
the system. In addition we will attempt to couple more than two quantum
dots to study the interaction of several qubits. First results will be
presented.
HL 5.8 Mo 12:00 H14
Scattering Wavefunctions in Ballistic Rectifyers
— •Oliver Bendix, Ragnar Fleischmann, and Theo Geisel —
MPI für Strömungsforschung and Institut für Nichtlineare Dynamik, Universität
Göttingen, Bunsenstraße 10, 37073 Göttingen
Electron transport in mesoscopic systems in semiconductors with typical
length scales shorter than the mean free path can be assumed to
be ballistic. Recent experimental and theoretical work has revealed an
unexpected rectification effect based on ballistic transport in mesoscopic
cross-junctions with broken symmetry[1,2,3].
In our simplified model[2] a crucial role is played by the energydependence
of the number of current-carrying modes. In a more detailed
description this corresponds to the energy-dependence of the scattering
coefficients. Here we present numerical results for the scattering wavefunctions
in ballistic rectifyers.
HL 6 Photonische Kristalle I
[1] A. M. Song et al., PRL 80 (1998) 3831
[2] R. Fleischmann and T. Geisel, PRL 89 (2002) 16804
[3] S. de Haan et al., PRL (in press)
HL 5.9 Mo 12:15 H14
Preparation of curved two dimensional electron systems in
InGaAs-microtubes — •Stefan Mendach, Olrik Schumacher,
Christian Heyn, Holger Welsch, and Wolfgang Hansen — Institut
für Angewandte Physik, Universität Hamburg, Jungiusstrasse 11,
D-20355 Hamburg, Germany
We present a preparation method to realise transport measurements
on evenly curved two-dimensional electron systems (2 DESs). By
combining the method of self-rolling strained double-layers [1,2] with
a special lithographic procedure we are able to roll-in and contact
AlGaAs/GaAs/AlGaAs quantum well structures into tubes or curved
lamellas, respectively. Applying a magnetic field to such structures
results in a strong modulation with changing sign of the magnetic field
components perpendicular to the curved 2 DES plane. Our preparation
method allows transport measurements along or perpendicular to
this modulation. We present and discuss our first magneto-transport
measurements on such rolled 2 DESs.
[1] V. Ya. Prinz et al., Physica E6 (2000) 828-831.
[2] O.G. Schmidt, K. Eberl, Nature 410 (2001) 168.
HL 5.10 Mo 12:30 H14
Bosonization method for disordered and chaotic systems — •G.
Schwiete 1 , K. B. Efetov 1,2 , and K. Takahashi 1 — 1 Theoretische
Physik III, Ruhr-Universität Bochum, 44780 Bochum, Germany — 2 L.
D. Landau Institute for Theoretical Physics, 117940 Moscow, Russia
Using a supersymmetry formalism we derive a new supermatrix representation
of the generating functional for the problem of electron motion
in an external potential. Non-linear sigma models derived previously for
disordered systems can be obtained from this model using a coarse graining
procedure. As an example we treat smooth disorder in an infinite system.
As a new application, we consider scattering on strong impurities
for which the Born approximation cannot be used. Possible applications
to quantum chaotic systems and the interacting disordered electron gas
will be discussed.
Zeit: Montag 12:45–13:30 Raum: H15
HL 6.1 Mo 12:45 H15
Space-dependent optical and electronic properties of semiconductor
photonic-crystal structures — •B. Pasenow, M. Reichelt,
T. Meier, T. Stroucken, P. Thomas, and S.W. Koch
— Fachbereich Physik und Wissenschaftliches Zentrum für Materialwissenschaften,
Philipps-Universität, Renthof 5, D-35032 Marburg
The optical and electronic properties of a semiconductor heterostructure
are modified in the vicinity of a structured dielectric environment,
e.g., a photonic crystal [1-3]. In such structures the band gap and the
Coulomb interaction potential are space dependent, which results in a
spatial variation of the spectral position of the exciton resonance and its
binding energy [2]. Therefore one can create spatially non-homogeneous
carrier distributions by spectrally selective optical excitation [3]. Following
the excitation, the carrier distributions show initially an interesting
coherent wave packet dynamics, before they eventually approach an incoherent
thermal quasi-equilibrium distribution.
[1] T. Stroucken, R. Eichmann, L. Banyai, and S.W. Koch, J. Opt. Soc.
Am. B 19, 2292 (2002).
[2] R. Eichmann, B. Pasenow, T. Meier, T. Stroucken, P. Thomas, and
S.W. Koch, Appl. Phys. Lett. 82, 355 (2003).
[3] Semiconductor Optics in Photonic Crystal Structures, T. Meier and
S.W. Koch, to appear in Photonic Crystals - Advances in Design, Fabrication
and Characterization, Eds. K. Busch, S. Lölkes, R.B. Wehrspohn,
and H. Föll, Wiley, 2004.
HL 6.2 Mo 13:00 H15
Strongly localized discrete solitons in photonic crystal defect
chains — •Rumen Iliew, Christoph Etrich, Ulf Peschel, and
Falk Lederer — Inst. für Festkörpertheorie und Theoretische Optik,
Friedrich-Schiller-Univ. Jena, Max-Wien-Platz 1, 07743 Jena
We found strongly localized solitons in a linear chain of coupled point
defects embedded in a Kerr-type nonlinear photonic crystal.
The dynamics of such a coupled-resonator optical waveguide (CROW)
can be described in tight-binding approximation by a set of coupled
modal equations [1] which were shown to allow for strongly localized soliton
solutions [2]. To compare these results with the full system, for the
first time, to our knowledge, the temporal dynamics of localized excitations
is investigated in a two-dimensional (2D) nonlinear photonic crystal
by employing 2D TM finite-difference time-domain simulations including
Kerr-nonlinearity. Our model system is a 2D hexagonal photonic crystal
with a TM photonic band gap in the linear regime where a chain
of point-defects was embedded. Depending on the pump parameters we
found strongly localized solitons in the nonlinear regime at frequencies
below the miniband, as predicted by the tight-binding approach.
We will present results of FDTD simulations and compare them against
the results obtained from the modal equations.
[1] D. N. Christodoulides and N. K. Efremidis, Opt. Lett. 27, 568 (2002).
[2] F. Lederer, S. Darmanyan, and A. Kobyakov, Spatial Solitons,
Springer Series in Optical Science 82, S. Trillo and W. E. Torruellas
(eds.), (Springer-Verlag New York 2001), pp. 269–292.
HL 6.3 Mo 13:15 H15
Tuneable Opals — •A. von Rhein 1 , T. Kramer 2 , T. Roeder 2 ,
K. Huber 2 , and S. Greulich-Weber 1 — 1 University of Paderborn,
Fakulty of Science, Physics Department, D-33098 Paderbron, Germany
— 2 University of Paderborn, Fakulty of Science, Chemistry Department,
D-33098 Paderbron, Germany
Photonic crystals already have been realized thru a wide range of methods.
In particular nature has developed a selfassembling technique of creating
photonic crytals. Nanospheres of about 200-400 nm diameter build

Halbleiterphysik Montag
up a so called colloidal crystal. These crystals are also known as opals.
Mankind has developed further methods to invert opals by filling up the
space around the spheres with another material and expunge the spheres.
HL 7 Hauptvortrag Stangl
By means of new research results on fireopals, we will show first principles
of tuneable photonic crystals and we will also extend these to inverted
opals which are made of titanium dioxide.
Zeit: Montag 14:30–15:15 Raum: H15
Hauptvortrag HL 7.1 Mo 14:30 H15
Structural properties of semiconductor nanostructures from
x-ray scattering — •Julian Stangl 1 , Anke Hesse 1 , Vaclav
Holy 1,2 , Rainer T. Lechner 1 , Tomas Roch 1 , Mojmir Meduna 1 ,
Zhenyang Zhong 1 , and Günther Bauer 1 — 1 Instut für Halbleiterund
Festkörperphysik, Johannes Kepler Universität Linz, Altenbergerstr.
69, A-4040 Linz, Austria — 2 Department of Condensed Matter Physics,
Faculty of Science, Masaryk University, Kotláˇrská 2, 611 37 Brno, Czech
Republic
New device concepts and the possibility to realize simple quantum
mechanical systems drive the interest in semiconductor nanostructures.
In structures smaller than the DeBroglie wavelength of carriers, typi-
HL 8 Photonische Kristalle II
cally several nm, quantum confinement strongly influences the electronic
properties. The latter depend on size, shape, chemical composition and
strain distribution, which again vary with growth conditions. In order to
understand and control nanostructure growth, their structural properties
have to be determined. X-ray diffraction allows for the non-destructive
investigation of uncapped and buried structures, which are needed for
application.
The talk will present different scattering techniques sensitive to shape,
composition and strain of nanostructures. Results will be presented on
the shape and positional correlation of SiGe islands in superlattices, and
on the composition and strain profile in self-assembled SiGe islands. The
effect of capping on has been studied as well.
Zeit: Montag 15:15–16:30 Raum: H15
HL 8.1 Mo 15:15 H15
Microwave resonators for the optical detection of magnetic resonance
on the basis of photonic crystals — •M. Wanjek, E.
Waldmueller, and S. Greulich-Weber — University of Paderborn,
Fakulty of Science, Physics Department, D-33098 Paderbron, Germany
Electron paramagnetic resonance (EPR) is an important tool for the
study of the microscopic and electronic structure of defects in solids. Via
the optical detection of magnetic resonance(ODMR) the optical properties
of a defect can be related to its microscopic structure. Since today
often only small samples are available (e.g. epi layers) the sensitivity of
EPR has to be increased. In this regard efforts have been made to use high
frequencies, e.g. measuring EPR at 95 GHz instead of 9.5 GHz. Usually
EPR is measured using a microwave bridge with a microwave resonator
containing the sample. At low frequencies cylindrical or rectangular resonators
are used providing also sufficient space for field modulation coils.
At high frequencies the resonator becomes considerably smaller supplying
no space for field coils. External field coils would be shielded by the
metallic resonator itself. Furthermore for ODMR optical access to the
sample is needed, which can not be realized with usual resonators. High
frequency microwave resonator designs fitting to all requirements will be
presented on the basis of photonic crystals.
HL 8.2 Mo 15:30 H15
Doping of colloidal photonic crystals — Bettina Friedel 1 ,
Siegmund Greulich-Weber 1 , Carsten Blum 2 , Heinrich
Marsmann 2 , •Bettina Friedel 1 , Siegmund Greulich-Weber 1 ,
Carsten B lum 2 , and Heinrich Marsmann 2 — 1 Fakultaet fuer
Naturwissenschaften, Department Physik, Universitaet Paderborn,
Warburger Str. 100, DE-33098 Paderborn — 2 Fakultaet fuer Naturwissenschaften,
Department Chemie, Universitaet Paderborn, Warburger
Str. 100, DE-33098 Paderborn
Photonic crystals based on colloidal crystals grown from monodisperse
spherical silica particles have received considerable attention in the recent
years. To increase the relatively low refraction index contrast concerning
to air, many different techniques were proposed: for example coating the
silica spheres with dyes or doping with II-VI compound semiconductors.
For the implementation of photonic devices, like optical waveguides
or microcavities, it is necessary to change the refractive index of single
spheres in order to create point and line defects in the colloidal crystal.
Procedures are presented which allow a local doping of photonic crystals
using established silicon technology. Basic results on doping possibilities
and change of the optical properties are given.
HL 8.3 Mo 15:45 H15
Photonic crystal templates based on holographic lithography
working in a wide spectral range — •C. Enkrich 1,2 , A. Blanco 1,3 ,
K. Busch 4,2 , and M. Wegener 1,3,2 — 1 Institut für Angewandte Physik,
Universität Karlsruhe (TH), 76128 Karlsruhe — 2 DFG-Center for Functional
Nanostructures, Universität Karlsruhe (TH), 76131 Karlsruhe
— 3 Institut für Nanotechnologie, Forschungszentrum Karlsruhe in der
Helmholtz-Gemeinschaft, 76021 Karlsruhe — 4 Institut für Theorie der
Kondensierten Materie, Universität Karlsruhe (TH), 76128 Karlsruhe
The fabrication of three-dimensional photonic crystals is a major challenge
in materials science, especially when the periodicity lies in the optical
region [1]. Here we present a flexible method based on holographic
lithography [2] to fabricate photonic crystal templates. By interference
of four laser beams it is possible to create 3D microporous structures in
a photosensitive resin (SU-8) arranged in an fcc lattice with the periodicity
in the submicron region [3]. By changing experimental parameters
it is possible to tune their photonic properties. We show that the polymer
filling fraction can be varied from around 20% to 80% producing
photonic gaps covering a wide spectral range from the visible to the near
infrared. Comparison with theoretical calculations allows to optimize the
design and therefore the photonic properties. These structures can be
used as templates in which materials with a high dielectric constant can
be infiltrated to produce full photonic band gap crystals.
[1] For a recent review see C. Lopez, Adv. Mater. 15, 1679 (2003).
[2] M. Campbell et al., Nature 404, 53 (2000).
[3] Yu. V. Miklyaev et al., Appl. Phys. Lett. 82, 1284 (2003).
HL 8.4 Mo 16:00 H15
Nahfeldtransmissionsspektroskopie an 1-D metallischen Photonischen
Kristallen — •N. Rau 1 , U. Neuberth 1 , S. Linden 1 , M.
Wegener 1 , A. Christ 2 , J. Kuhl 2 , S. Pereira 3 und K. Busch 3
— 1 Institut für Angewandte Physik, Universität Karlsruhe (TH), 76128
Karlsruhe — 2 Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart
— 3 Institut für Theorie der Kondensierten Materie, Universität
Karlsruhe (TH), 76128 Karlsruhe
Wir stellen Nahfeldtransmissionsexperimente an periodischen 1D-
Gold-Nanodrahtstrukturen auf einem dielektrischen Wellenleiter vor. Die
Probe wird über eine Linse mit linear polarisiertem Weißlicht beleuchtet.
Das transmittierte Licht wird über eine Apertursonde aufgesammelt
und anschließend mit einem Monochromator und einer CCD-Kamera
spektral aufgelöst. Als Sonde werden geätzte Al-bedampte Glasfasern
mit ca. 75nm kleinen Aperturen verwendet, die eine Ortsauflösung von
ca. 100nm ermöglichen. In den orts- und spektral aufgelösten Transmissionsdaten
können perioden- und polarisationsabhängige Effekte mit
feinskaligen Strukturen und hohem Kontrast beobachtet werden. Diese
lassen sich abhängig von der Polarisationsrichtung auf die Anregung von
Wellenleitermoden bzw. des Partikelplasmon-Wellenleiter-Polaritons[1]
zurückführen. Die Ergebnisse werden mit numerischen Simulationen

Halbleiterphysik Montag
basierend auf Streumatrixmethoden[2] verglichen.
[1] A. Christ et al., Phys. Rev. Lett. 91, 183901 (2003)
[2] Chapter 1 in K. Busch et al., Photonic Crystals – Advances in Design,
Fabrication, and Characterization, Wiley VCH (2004)
HL 8.5 Mo 16:15 H15
Focussing Effects in 2D Photonic Crystals — •Frank Hagmann
1 , Kurt Busch 1,2 , and Peter Wölfle 1 — 1 Institut für Theorie
der Kondensierten Materie, Universität Karlsruhe — 2 School of Optics/CREOL
and Department of Physics/University of Central Florida,
Orlando, U.S.A.
HL 9 Heterostrukturen I
Using the multiple multipole method [1] we analyze the optical properties
of finite-sized two-dimensional Photonic Crystal waveguiding structures.
In particular, we study the beaming and focussing abilitites of
various types of straight waveguides and the connection of these effects
to surfaces modes. We show how different surface terminations as
well as surface impedance variations of waveguides allow one to obtain
control over the focussing properties. These enhanced beaming properties
will aid in the design and development of future Photonic Crystal
based devices and of optical interconnects between Photonic Crystal
functional elements and standard index guiding optical components.
[1] A.A.Asatryan, K.Busch, R.C.McPhedran, L.C.Botton, C.M.de Sterke
and N.A.Nicorovici, Waves in Random Media 13,9(2003)
Zeit: Montag 15:15–16:30 Raum: H17
HL 9.1 Mo 15:15 H17
Sputter depth profiling of GaN/InAlGaN multi quantum well
structures — •Gernot Ecke 1 , Rastislav Kosiba 1 , Gabriel Kittler
1 , Nikos Pelekanos 2 , and Oliver Ambacher 1 — 1 Center of
Micro- and Nanotechnologies, TU Ilmenau, D-98693 Ilmenau, Germany
— 2 Foundation for Research and Technology - Hellas, P.O. Box 1527,
GR 71110 Heraklion, Crete, Greece
Multi quantum well (MQW) structures play a crucial role in the design
of many optoelectronic devices. The regularity of these structures,
the composition of the layers, and the quality of the interfaces between
the layers are very important for the device functionality. In this contribution,
the sputter depth profiles across the MQW consisting of seven
GaN/InAlGaN layer pairs with thickness of 7 nm will be presented. The
sputter depth profiling was carried out by Auger electron spectroscopy
in conjunction with argon ion sputtering. Grazing incidence and low ion
energy provided good sputtering conditions for highly depth resolved
measurements. For the evaluation of the depth profiles the factor analysis
of the nitrogen KLL and overlapping Al LMM and Ga MNN Auger
transitions was applied. The deterioration of the true depth profile due
to the sputtering itself as well as due to the information depth of the
Auger electrons was followed by the dynamic Monte Carlo simulation
code TRIDYN. From the good agreement between the measurement and
the simulation the regularity of the measured MQW structure as well as
good interface quality could be proven.
HL 9.2 Mo 15:30 H17
Time-domain THz spectroscopy of electronic exitations in
GaAs/AlGaAs superlattices — •André Dreyhaupt, Stephan
Winnerl, Thomas Dekorsy, and Manfred Helm — Institut
für Ionenstrahlphysik und Materialforschung, Forschungszentrum
Rossendorf, Postfach 51 01 19, 01314 Dresden
We investigate the electronic properties of weakly and more strongly
coupled n-doped GaAs/AlGaAs superlattices by time-domain THz spectroscopy
in the low frequency range from about 0.5 to 3.5 THz. The
sample properties are modulated either by applying an AC voltage via a
gate electrode or by injecting a vertical current. The transmission signal
is detected at the frequency of the modulation voltage with a lock-in amplifier
leading to a signal-to-noise ratio superior compared to conventional
FTIR spectroscopy in this frequency range. We will discuss the observation
of inter-miniband transitions, confined donor transitions, plasmon
excitations and the measurement of intra-miniband THz conductivity in
a wide range of lattice temperatures.
HL 9.3 Mo 15:45 H17
Dynamics of Excitons in Coupled Quantum Well Structures —
•Andreas Gärtner 1 , D. Schuh 2 , and J. P. Kotthaus 1 — 1 CeNS
und Sektion Physik der LMU, München — 2 Walter Schottky Institut,
TU München
The experiments to learn more about motion and interaction of longliving
excitons in coupled quantum wells (QW) [1] are carried out in
semiconductor heterostructures at low temperatures (4 K). These epitaxially
grown samples contain two GaAs-QWs which are separated by
a thin tunnelling barrier.
Metallic gates applied to a sample generate an electrical field perpendicular
to the QW layers. This causes the transition from direct to
spatially indirect excitons, i.e. electron and hole are located in different
QWs. Thus, the overlap of their wave functions is reduced and the exci-
tonic life time increases.
By means of the quantum confined stark effect (QCSE) the vertical electric
field affects the effective excitonic potential [2]. It can be modulated
by interdigitated gate structures [3] leading to in-plane dift phenomena.
In our experimental pump-and-probe-setup we observed these effects
on photo generated excitons by analyzing their emitted photoluminescence
spatially, temporally and spectrally. An intensified CCD-Camera
featuring a temporal resolution in the sub-nanosecond regime allows further
detailed studies on the dynamics of excitonic drift.
[1] Butov et al., Nature 417, 47 (2002)
[2] S. Zimmermann et al., Phys. Rev. B 56, 13414 (1997)
[3] J. Krauß et al., Phys. Rev. Lett. 88, 036803 (2002)
HL 9.4 Mo 16:00 H17
Piezo-electric fields in InGaAsP induced by spontaneous selfordering
— •S. Krämer 1 , G. H. Döhler 1 , S. Neumann 2 , W.
Prost 2 , and T. J. Tegude 2 — 1 Institut für Technische Physik I,
Universität Erlangen-Nürnberg, Erwin-Rommel-Str. 1, D-91058 Erlangen
— 2 Fachbereich Halbleitertechnik/Halbleitertechnologie, Universität
Duisburg, Lotharstr. 55 LT, D-47048 Duisburg
InGaAsP grown by MOCVD under specific growth conditions form
a monolayer superlattice along the [111] B direction (”spontaneous selfordering”).
This superlattice can be formed by InP-GaAs or InAs-GaP.
Because of the different bond lengths in these combinations the resulting
two ”versions” of InGaAsP would have varying distances between
the alternating layers compared to unstrained bulk material. For In-
GaAsP, grown lattice matched on an InP-substrate, these different layer
sequences lead to significant piezo-electric fields in the range of about 100
kV/cm. The existence of order-induced piezo-electric fields for ordered
GaInP, lattice matched to GaAs, has been discussed controversially in
the literature [1], [2], [3]. To investigate the occurrence, sign, and magnitude
of piezo-electric fields in the InGaAsP-system, we embedded an
InGaAsP - quantum well in an InP - pin and - nip structure, respectively.
By observing the quantum confined Stark effect in the photocurrent signal
in both structures we were able to determine the strength (and sign)
of the piezo-electric field to about 130 kV/cm in ordering direction.
[1]: S. Froyen et al. APL 68, 2852 (1996)
[2]: P. Ernst et al. ICPS 23 World Scientific 1996
[3]: J. D. Perkins et al. JAP, 84 (1998)
HL 9.5 Mo 16:15 H17
Distribution of C-acceptors in delta-doped GaAs studied with
Cross-sectional Scanning Tunneling Microscopy — •L. Winking
1 , M. Wenderoth 1 , T.C.G. Reusch 1 , R.G. Ulbrich 1 , P.-J.
Wilbrandt 2 , R. Kirchheim 2 , S. Malzer 3 , and G. Döhler 3 — 1 IV.
Phys. Inst., Universität Göttingen, Tammannstr.1, D-37077 Göttingen —
2 Inst. f. Materialphysik, Universität Göttingen, Tammannstr.1, D-37077
Göttingen — 3 Inst. f. Techn. Physik I, Universität Erlangen-Nürnberg,
Erwin-Rommel-Str. 1, D-91058 Erlangen
We present XSTM investigations of the C-acceptor-distribution in
delta-doped GaAs. At the intended positions of the C-delta-layers we
found at area-densities of 3×10 12 cm −2 up to extremely high area-densities
of 1 × 10 14 cm −2 a monolayer-sharp spatial distribution of C-acceptors in
growth direction. The slight broadening of less than 0.85nm is found to
be almost symmetric around the intended position of the delta-layer up
to the highest concentration investigated. These results point out that
even at the elevated growth temperature of 570 ◦ C and a very high dopant

Halbleiterphysik Montag
concentration, which was confirmed by SIMS measurements, neither segregation
nor coulombic repulsion plays an important role in the system
HL 10 Baulemente
discussed here.
This work was supported by the DFG, SFB 602 TP A7.
Zeit: Montag 15:15–16:30 Raum: H13
HL 10.1 Mo 15:15 H13
Efficiency of High-Brightness AlGaInP LEDs: Model and Experiment
— •P. Altieri, A. Jaeger, R. Windisch, N. Linder, P.
Stauss, R. Oberschmid, and K. Streubel — OSRAM Opto Semiconductors
GmbH, Wernerwerkstr. 2, 93049 Regensburg
We present a quantitative analysis of the internal quantum efficiency
of high-brightness AlGaInP light-emitting devices (LEDs) with an emission
wavelength ranging from 650 nm to 560 nm. The wavelength is
adjusted by varying the Aluminum content in the active region. The
evaluation is based on measurements of the external quantum efficiency
of the LEDs as a function of the operating current (0.1-20 mA) and
temperature (298-360 K). The determination of the internal quantum efficiency
is performed by means of a model that takes into account the
radiative and nonradiative recombination in the active layer, the diffusive
leakage of charge carriers into the confining InAlP layers and the influence
of photon recycling on the light extraction efficiency. In the current
range here analyzed red emitting LEDs show maximum internal quantum
efficiencies close to 100 %. The maximum efficiency decreases with
decreasing wavelength down to about 7 % for green LEDs. This reduction
is mainly due to leakage which accounts for the loss of about 75 % of the
injected carriers. In addition, the nonradiative recombination increases
by approximately one order of magnitude from red to green LEDs.
HL 10.2 Mo 15:30 H13
The Source-Gated Thin-Film Transistor — •Thomas Lindner 1 ,
Gernot Paasch 1 , and Susanne Scheinert 2 — 1 IFW Dresden —
2 TU Ilmenau
In thin-film transistors as usual the channel is controlled by the gate
and the current saturates when the drain end of the channel becomes
depleted due to the drain voltage. For this operation the channel contacts
to source and drain must be ohmic. Recently, source-gated thin-film
transistors (SGT) made by undoped a-Si:H have been introduced 1 . In the
SGT there is no direct contact between source and the channel. This design
is essentially the same as that one of the top contact (TOC) organic
field-effect transistor (FET) 2,3 . In the SGT in addition the source contact
is chosen as a depletion (Schottky) contact. In Refs.(2,3) the TOC
FET has been investigated also for Schottky contacts. In contrast to the
advantages of the SGT proposed in Ref.(1) we found that apart from
the unusual voltage dependencies of the current, the main feature of the
Schottky-contacted TOC FET is a strongly reduced current due to the
series resistance between source and the channel. Here a detailed simulation
study for the a-Si:H based SGT is presented revealing the operation
mode of this device.
1 J.M. Shannon, E.G. Gerstner, IEEE ED Letters 24 (2003) 405.
2 S. Scheinert, G. Paasch, T. Lindner, Synth. Met. 137 (2003) 1451.
3 T. Lindner, G. Paasch, S. Scheinert, J. Mat. Res., submitted.
HL 10.3 Mo 15:45 H13
Patterning of sub 50 nm structures for diffusion investigations
in vertical Double-Gate MOSFETs — •Jürgen Moers 1 , Stefan
Trellenkamp 1 , Susan Kluth 2 , Patrick Kluth 2 , David Alvarez
3,4 , Johannes Kretz 4 , Siegfried Mantl 1 , and Hans Lüth 1
— 1 Institute of Thin Films and Interfaces, Forschungszentrum Jülich, D-
52425 Jülich — 2 Australien National University, Canberra, ACT 0200,
Australia — 3 IMEC, Kapeldreef 75, B-3001 Leuven, Belgium — 4 Infineon
Technologies AG, D-81730 Munich
The tremendous increase in computational efficiency was made possible
by shrinking the dimension of microelectronic devices. This downsizing
led to the well known Short Channel Effects (SCE). To account for these
SCE the lateral layout was improved. For future CMOS applications this
will be not sufficient, therefore new architectures must be investigated.
One architecture is the Double-Gate-MOSFET, where the channel forming
thin silicon layer is sandwiched between two gates; these two gates
control the electric field in the silicon very efficiently and hence reduce
SCE. Heart of this device is a silicon ridge of ∼20 nm width, in which
the dopants are implanted. The channel length of the device is defined
by the implantation energy and the diffusion during the subsequent thermal
treatment. Therefore it is essential to investigate the diffusion in
nanostructures.
Sub 50 nm structures in silicon were prepared using electron beam
lithography and high selective reactive ion etching. First results show a
different boron diffusion due to reduced transient enhanced diffusion. A
qualitative interpretation of the effects are given.
HL 10.4 Mo 16:00 H13
Electrical characterization of temporary devices fabricated
with a double-tip AFM on semiconductive surfaces — •A.-D.
Müller 1 , F. Müller 1 , T.D. Long 1 , L.Q.T. Dung 1 , J. Mehner 2 ,
and M. Hietschold 1 — 1 Chemnitz University of Technology, Institute
of Physics, Solid Surface Analysis Group, 09107 Chemnitz — 2 Chemnitz
University of Technology, Institute of Electrical Engineering and
Information Technology, 09107 Chemnitz
Using a multiple cantilever device, semiconductor devices can be created
temporarily on a semiconductor`s surface to perform an electrical
measurement. The obtained electrical characteristics of such devices represent
the local electrical surface properties at the moment of the measurement.
This contribution presents the application of a double cantilever, which
has two tips with a lateral distance of 10 µm. Each tip has its own vertical
actuator, so that they can be placed on the surface independently of
each other with a detectable contact force in an Atomic Force Microscope
set-up. The observed electrical characteristics are compared with circuit
simulations using a MESFET model instead of the temporary device. On
silicon (111) with a natural oxide layer, for instance, a high surface conductivity
and a high barrier at the temporarily formed Pt/Si-interfaces
have been found.
HL 10.5 Mo 16:15 H13
Simulation and fabrication of complementary tunneling transistors
in silicon — •Peng-Fei Wang, Thomas Nirschl, Marcus
Weis, Doris Schmitt-Landsiedel, and Walter Hansch — Institute
for Technical Electronics, Technical University Munich, Arcisstr. 21,
80333 Munich, Germany
In this paper, a surface-tunneling transistor called TFET is fabricated
using the CMOS compatible technologies. The gate controlled band-toband
tunneling is realized in this transistor. The gate controlled surface
Esaki tunneling current is also observed at room temperature. Due to the
distinct working principle of this novel transistor, the low sub-threshold
leakage current and perfect drain current saturation can be obtained.
Compared to the conventional NMOS, the lower leakage current and
smaller Vth roll-off can be achieved. Since the impact ionization in this
transistor is caused by the electrons injected from tunneling junction,
TFET is also a hot electron transistor where the impact ionization can
be controlled by the gate voltage. In addition, the complementary TEFT
are fabricated on the same silicon substrate. The performances of the
n-channel TFET and the p-channel TFET will be discussed in detail.

Halbleiterphysik Montag
HL 11 Neue Materialien
Zeit: Montag 15:15–16:30 Raum: H14
HL 11.1 Mo 15:15 H14
Ab initio Untersuchungen binärer Phasenwechselmedien —
•Martina Müller, Ralf Detemple, Stefan Ziegler und
Matthias Wuttig — I. Physikalisches Institut A, RWTH Aachen
Phasenwechselmedien stellen die Grundlage der modernen optischen
Datenspeicherung dar. Sie basieren auf Legierungen, die unter Laserbestrahlung
reversibel zwischen amorpher und kristalliner Phase geschaltet
werden können. Entscheidend für deren Erfolg als optische Datenspeicher
ist eine hohe Geschwindigkeit der Phasenumwandlung, die eng mit
der Komplexität der vorliegenden Struktur einhergeht. Neueste Untersuchungen
belegen, dass kubische Strukturen diese Eigenschaften erfüllen,
während dies für tetragonale Systeme nicht der Fall ist.
Ziel der Untersuchungen ist es, deren charakteristische Eigenschaften
am Beispiel binärer tetragonaler III-V und kubischer IV-VI Legierungen
zu untersuchen. Ab initio Untersuchungen mittels Dichtefunktionaltheorie
liefern das theoretische Fundament, um die Energetik sowie elektronische
Eigenschaften von Phasenwechselmaterialien zu bestimmen. Es
werden grundlegende strukturelle Unterschiede beider Materialklassen
untersucht, die Rückschlüsse auf die energetische Stabilität abhängig von
der vorliegenden Form der chemischen Bindung zulassen. Darüberhinaus
wird eine weiterführende Analyse ausgewähler geometischer und elektronischer
Eigenschaften vorgenommen. In Korrelation mit strukturellen Ergebnissen
zeigen sie intrinische Unterschiede der beiden Materialklassen
auf, was eine Übertragung auf die grundlegende Frage nach der Einsetzbarkeit
kubischer Phasenwechselmedien ermöglicht.
HL 11.2 Mo 15:30 H14
Entwicklung neuer Phasenwechselmaterialien mittels DFT und
kombinatorischer Materialsynthese — •Ralf Detemple, Daniel
Wamwangi, Han-Willem Wöltgens und Matthias Wuttig — I.
Phys. Inst. IA / RWTH Aachen / Postfach / 52056 Aachen
Phasenwechselmaterialien basieren auf der reversiblen Transformation
der strukturellen Ordnung dünner Tellurlegierungsfilme. Bisher wurden
diese Materialien durch empirische Ansätze optimiert, während hier
2 komplementäre Alternativen vorgestelt werden: Die Dichtefunktionaltheorie
und die kombinatorische Materialsynthese.
Die Dichtefunktionaltheorie erlaubt die Prognose der energetisch
günstigsten Struktur und deren optische und elektrische Eigenschaften
zu verstehen. Unsere Rechnungen zeigen, dass ternäre Silber-Legierungen
mit einer unterschiedlichen Anzahl von Valenzelektronen eine Umwandlung
von einer Chalcopyrit zu einer Kochsalzstruktur aufweisen. Unsere
experimentellen Ergebnisse belegen, dass nur die Kochsalzstruktur einen
ausreichend hohen Dichte- und Optikkontrast aufweist.
Da auch die Struktur anderer Te-Legierungen durch die Anzahl der
Valenzelektronen bestimmt ist, erlaubt dieses Kriterium die Vorhersage
geeigneter Phasenwechselmaterialien.
HL 11.3 Mo 15:45 H14
Silicon Nanowires – Analysis of the SiO/VLS Growth Mechanism
— •Florian M. Kolb, Herbert Hofmeister, Roland
Scholz, Margit Zacharias, and Ulrich Gösele — Max–Planck–
Institut für Mikrostrukturphysik, 06120 Halle(Saale)
Silicon nanowires are possible building blocks for new nanoscale devices
and can provide a system for investigating the physics of lowdimensional
semiconductor structures. We have successfully produced silicon
nanowires on gold-coated silicon substrates by evaporation of silicon
monoxide (SiO), according to the Vapor-Liquid-Solid (VLS) mechanism.
Transmission electron microscope investigations, including HRTEM, electron
diffraction and energy-dispersive X-ray spectroscopy, were used to
analyze the structure of the nanowires and to confirm the VLS growth
mechanism. We found that the nanowires exhibit different crystallographic
growth directions than those from CVD processes. Based on these
investigations we suggest a model which combines the VLS mechanism
with SiO evaporation. The phenomena of nanowire diameter-oscillations
and the effect of the growth parameters are discussed.
HL 11.4 Mo 16:00 H14
Self-Organization of Nanocluster δ-Layers at Ion-Beam-Mixed
Si-SiO2 Interfaces — •Lars Röntzsch, Karl-Heinz Heinig, and
Bernd Schmidt — FZ-Rossendorf, Bautzner Landstraße 128, 01328
Dresden
The Multidot Nano-flash Memory suggested by Tiwari
[APL69(1996)1232] is a promising candidate for succeeding the
Floating Gate Flash Memory.
Its most challenging configurational feature is a layer of Si nanoclusters
(NCs) within the oxide of a MOS-like structure.
Here, we present experimental evidence that the concept predicting the
self-organization of a Si NCs δ-layer at an ion irradiated Si-SiO2 interface
is valid (cf. Heinig [APA77(2003)17]).
Unconventionally, a 15nm thin SiO2 layer, which is enclosed by a 50nm
poly-Si capping layer and the Si substrate, is irradiated with Si + ions.
Ion impact drives the system to a state far from thermodynamic equilibrium,
i.e. the local composition of the target is modified to a degree
unattainable in common processes. A region of SiOx (x

Halbleiterphysik Montag
HL 12 Poster I
Zeit: Montag 16:30–19:00 Raum: Poster A
HL 12.1 Mo 16:30 Poster A
Herstellung und Charakterisierung optisch gepumpter,
oberflächenemittierender Halbleiterlaser — •S. Hövel 1 , N.C.
Gerhardt 1 , M. Hofmann 1 , J. Yang 2 , D. Reuter 2 und A.D.
Wieck 2 — 1 AG Optoelektronische Bauelemente und Werkstoffe, Ruhr-
Universität Bochum — 2 Lehrstuhl für Angewandte Festkörperphysik,
Ruhr-Universität Bochum
Wir charakterisieren die Emission eines optisch gepumpten
oberflächenemittierenden GaInAs/GaAs-Halbleiterlasers (engl. verticalcavity
surface-emitting laser, VCSEL). Die Struktur wurde mittels
Molekularstrahlepitaxie (engl. Molecular beam epitaxy, MBE) gewachsen.
Sie enthält einen λ-Resonator mit drei 6 nm dicken Ga0.80In0.20As
Quantenfilmen, platziert im Maximum des optischen Feldes. Als Spiegel
wurden symmetrische GaAs/AlAs Bragg-Reflektoren (Oben: 16 Paare,
Unten 19.5 Paare) verwendet. Der Laser emittiert bei 1000 nm mit einer
Schwelle von 2.5kW/cm 2 bei Raumtemperatur und Anregung mit einem
gepulsten Ti:Saphir-Laser (100 fs - Pulse bei 800 nm).
Die Abhängigkeit der Laseremission von den Anregungsbedingungen
wird analysiert und diskutiert.
Wir danken der DFG für Unterstützung im GRK384 und SFB491.
HL 12.2 Mo 16:30 Poster A
Deep level transient spectroscopy on copper indium gallium
diselenide thin film solar cells with different gallium content —
•V. Mertens 1 , R. Reineke-Koch 2 , M. Köntges 2 , and J. Parisi 1 —
1 University of Oldenburg, 26111 Oldenburg — 2 Instiute for Solar Engery
Research, 31860 Emmerthal
One approach to increase the open circuit voltage Voc of Cu(In, Ga)Se2
solar cells is to widen the bandgap Eg by using higher gallium contents
than in the standard composition which has a gallium to gallium plus indium
ratio (GGI) of about 0.28. However further investigations on these
materials showed that their Voc is lower than expected from the empirical
relationship Voc = Eg −0.5V which holds for Eg ≤ 1.3eV . To understand
more about the whole alloy system, we focused on the defects and the
change in their characteristics with composition. For our measurements
we use a home build deep level transient spectrometer based on a Boonton
7200B capacitance bridge. We investigated different samples covering the
whole alloy range with different DLTS techniques as majority and minority
carrier DLTS, reverse-bias pulsed DLTS. We found that the transients
are poorly described by a sum of several monoexponential decays. Therefore
other analyses were conducted to determine the underlying physical
mechanism.
HL 12.3 Mo 16:30 Poster A
Five source PVD for the deposition of CIGSS thin films —
•Mario Gossla 1,2 and William N. Shafarman 1 — 1 Institute of Energy
Conversion, University of Delaware, 451 Wyoming Road, Newark,
DE 19716, USA — 2 Institut für Festkörperphysik, Friedrich-Schiller-
Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany
CuIn1−xGax(Se1−ySy)2 (CIGSS) films are being investigated as absorber
layer materials for the wide-band-gap cell in a tandem or multijunction
thin-film solar cell. To become a viable option for high performance
photovoltaics, tandem or multijunction solar cells based on polycrystalline
thin films will require a wide band gap top cell with at least
15 % efficiency, optical band gap in the range 1.7 ≤ Eg ≤ 1.9 eV, and
small sub-band gap absorption.
A new five-source deposition system was developed for the deposition
of CIGSS thin films. Thin films within the complete compositional range
of 0 ≤ x ≤ 1, and 0 ≤ y ≤ 1 were deposited on Mo-coated soda lime
glass at different temperatures. The films were analyzed by means of IR,
SEM, and XRD. The incorporation of sulfur in the films depends strongly
on the sulfur concentration in the vapor phase, substrate temperature,
and Cu/In ratio. Complete Mo/CIGSS/CdS/-ZnO/NiAl solar cells with
a typical area of 0.5 cm 2 were prepared. Cell performance was monitored
by QE and I-V measurements and is shown to strongly depend on sulfur
content.
HL 12.4 Mo 16:30 Poster A
Surface-heat-emittance optimization of CIS-based flexible solar
cells — •Carsten Bundesmann 1 , Ferdinand Dürr 1,2 , Mathias
Schubert 1 , and Karsten Otte 2 — 1 Fakultät für Physik und
Geowissenschaften, Institut für Experimentelle Physik II, Universität
Leipzig, Linnéstraße 5, 04103 Leipzig — 2 Solarion GmbH, Ostende 5,
04288 Leipzig
CuInSe2 based flexible thin film solar cells on polyimide substrates are
possible alternatives for crystalline silicon or GaAs based solar cells in
space applications due to their low weight. Still their feasibility has to be
proven. In order to achieve high specific power (W/kg), important optimization
parameters parameters are, for instance, efficiency and surface
heat emittance. The later is studied here for CuInSe2 based thin film solar
cells grown on flexible polyimide substrates in a web-coater based process.
It is shown that the maximum values of the surface heat emittance
depends strongly on the layer structure and the layer optical properties.
The dielectric functions of each single layer is extracted by infrared spectroscopic
ellipsometry. Using these data a layer model is established, the
reflectivity and the surface heat emittance is calculated. Upon varying
the model parameters the maximum of the surface heat emittance is determined.
The simulated results are compared with measured values of
real solar cell structures.
HL 12.5 Mo 16:30 Poster A
Stray current contributions in photo-assisted tunneling spectroscopy
on CIGSe absorbers: an aid or a nuisance? — •U.
Herber 1 , C. Heske 1 , E. Umbach 1 , F. Karg 2 , T. P. Niesen 2 ,
G. Hanna 3 , and U. Rau 3 — 1 Experimentelle Physik II, Universität
Würzburg, 97074 Würzburg — 2 Shell Solar, München — 3 Institut für
Physikalische Elektronik, Universität Stuttgart, 70569 Stuttgart
Polycrystalline Cu(In,Ga)Se2 solar cell absorbers are investigated with
photo-modulated scanning tunneling spectroscopy. For RTP (rapid thermal
processing) absorbers, we find pronounced lateral inhomogeneities of
the photo-induced tunneling current (PITC), as reported earlier [1]. In
addition, similar inhomogeneities are also found on co-evaporated CIGSe
absorbers.
However, every modulated process in scanning probe microscopies is
accompanied by stray effects, in particular by an additional current contribution
via the capacitance between sample and tip. The complex phase
and amplitude of this stray signal can be measured separately, and thus
its contribution can be subtracted from the PITC scan data. On the other
hand, the stray signal is strongly determined by the (chemical) condition
of the surface. The situation within a series of sputter-and-heat cycles
is compared with corresponding photo-emission data and interpreted in
the framework of the equivalent circuit approach.
[1] D. Eich et al., Thin Solid Films 361, 258 (2000)
HL 12.6 Mo 16:30 Poster A
Epitaxial growth of CuGaS2 on Si substrates investigated by
high resolution X-ray diffraction — •J. Cieslak 1 , A. Dietz 1 , J.
Eberhardt 1 , M. Gossla 1 , Th. Hahn 1 , J. Kräusslich 2 , H. Metzner
1 , U. Reislöhner 1 , W. Witthuhn 1 , and F. Wunderlich 2 —
1 Friedrich-Schiller-Universität Jena, Institut für Festkörperphysik, Max-
Wien-Platz 1, 07743 Jena — 2 Friedrich-Schiller-Universität Jena, Institut
für Optik und Quantenelektronik Max-Wien-Platz 1, 07743 Jena
The wide-band gap chalcopyrite semiconductor CuGaS2 (CGS) has recently
attracted some attention since its direct band gap of Egap=2.5eV
(T=5K) makes it suitable for applications in tandem solar cells. We reported
the epitaxial growth of high-quality CGS layers on Si(111) [1].
In this work we elucidate the epitaxial growth and structural properties
of these heteroepitaxial layers. High resolution X-ray diffraction
(HRXRD) was performed at the European Synchrotron Radiation Facility
(ESRF) in Grenoble (France). High-precision ω/2θ-scans with different
in-plane diffraction vectors were carried out.
It was found, that the CGS layers show lattice parameters resembling
those reported in literature for bulk material and that any existence of
metastable ordering, prominent in epitaxial layers of CuInS2, can be ruled
out. This behaviour is discussed within the context of the observed epitaxial
relations between CGS and Si(111) as well as Si(100) substrates.
[1] H. Metzner et al., Appl. Phys. Lett., 81(1), 156 (2002).

Halbleiterphysik Montag
HL 12.7 Mo 16:30 Poster A
Intrinsic Defect Levels in Epitaxial CuGaS2 on Si(111) — •J.
Eberhardt 1 , J. Cieslak 1 , R. Goldhahn 2 , Th. Hahn 1 , H. Metzner
1 , U. Reislöhner 1 , and W. Witthuhn 1 — 1 Friedrich-Schiller-
Universität Jena, Institut für Festkörperphysik, Max-Wien-Platz 1, 07743
Jena — 2 Institut für Physik, TU Ilmenau, PF 100565, 98684 Ilmenau
The chalcopyrite semiconductor CuGaS2 (CGS) with its direct band
gap of Egap=2.5eV (T=5K) is a promising wide-band gap material for
photovoltaic applications such as tandem solar cells. However, the performance
of these devices depends cruically on the intrisic defects in CGS
responsible for its electrooptical properties.
In this work, photoluminesence (PL) measurements were performed
on thin CGS films which were grown epitaxially on Si(111) by means of
Molecular Beam Deposition (MBE).
Excitonic emissions were observed throughout the whole covered temperature
range from 5 to 300 K. Additionally emissions related to shallow
defect levels were detected between 2.35 and 2.45eV at low temperatures.
Based on the identification of two free-to-bound and the two
related donor-acceptor transitions, a model for intrinsic defect levels in
CGS including one shallow donor and two acceptor states is proposed.
HL 12.8 Mo 16:30 Poster A
Application of the steady-state photocarrier grating technique
to polymorphous silicon — •Nacera Souffi and Rudolf
Brüggemann — Institut für Physik, Carl von Ossietzky Universität
Oldenburg
The steady-state photocarrier grating (SSPG) technique has become a
standard tool for the characterisation of the minority carrier properties in
amorphous silicon. We apply the technique to a similar thin-film semiconductor,
labelled polymorphous silicon. Polymorphous silicon is discussed
as an alternative to amorphous silicon in photovolatic applications. Values
for the minority carrier diffusion length in polymorphous silicon are
in the range between 170 and 250 nm, comparable to high-quality amorphous
silicon. In this contribution we detail the strong dependence of the
diffusion-length value on the photogeneration rate and relate this dependence
to features in the density-of-states (DOS) profile, which we discuss
in comparison with the DOS in amorphous silicon.
HL 12.9 Mo 16:30 Poster A
Developing design criteria for phase change alloys — •Daniel
Severin, Daniel Wamwangi, Mengbo Luo, and Matthias Wuttig
— I. Physikalisches Institut IA, RWTH-Aachen
Phase change materials that are based upon the reversible switching
between an amorphous and a crystalline state are widely used as
rewritable data storage media. This work constitutes the ongoing search
to establish selection criteria for new phase change alloys. The role of the
average number of s and p valence electrons in structure formation is examined
for a series of chalcogenide alloys: AgInTe2, AgSnTe2, AgSbTe2,
AuInTe2, AuSnTe2 and AuSbTe2. Our results have shown that the chalcopyrite
based AgInTe2 and AuInTe2 alloys have low optical contrast
between the amorphous and crystalline state. This also correlates with
the low density change of about 2 percent. The low optical contrast renders
these materials unsuitable for phase change applications. On the
other hand, it has been observed that the remaining alloys show a 6
fold coordination. They also have a high density change (larger than 4
percent) and show sufficient optical contrast. A closer look at the alloys
which have a metastable NaCl structure reveals that their average
number of s and p valence electrons is larger than 4. This suggests, that
a simple selection criterion has been found which should facilitate the
identification of suitable new phase change alloys.
HL 12.10 Mo 16:30 Poster A
Optical properties of Zn1−xMnxSe studied by spectroscopic ellipsometry
— •J. Kvietkova 1 , B. Daniel 1 , M. Hetterich 1 , M.
Schubert 2 , D. Spemann 2 , D. Litvinov 3 , and D. Gerthsen 3 —
1 Institut für Angewandte Physik and Center for Functional Nanostructures
(CFN), Universität Karlsruhe, D-76131 Karlsruhe — 2 Institut für
Experimentelle Physik II, Fakultät für Physik und Geowissenschaften,
Universität Leipzig, D-04103 Leipzig — 3 Laboratorium für Elektronenmikroskopie
and CFN, Universität Karlsruhe, D-76128 Karlsruhe
The ternary diluted magnetic semiconductor ZnMnSe is a suitable candidate
for the use in optoelectronic devices either as a spin aligner or a
waveguide layer. We study the optical properties of cubic Zn1−xMnxSe
thin films grown on GaAs (001) substrates by molecular-beam epitaxy.
We present the complex dielectric function obtained by variable-angle
spectroscopic ellipsometry in the photon energy range from 0.75 to 4.5 eV
using the point-by-point inversion approach. A critical-point parametric
model was employed to fit the experimental data for photon energies between
0.75 and 3.3 eV, which led to an excellent agreement. The best-fit
model calculation parameters are given for ZnSe as well as for Mn contents
of 13.6% and 21%. The below-band-gap index of refraction is well
represented by a simple Cauchy dispersion formula.
HL 12.11 Mo 16:30 Poster A
Verstärkungseigenschaften von Ferninfrarotantennen —
•Steffen Groth, André Wirthmann, Carsten Zehnder,
Christian Heyn, Detlef Heitmann und Can-Ming Hu —
Institut für Angewandte Physik und Mikrostrukturzentrum, Universität
Hamburg, Jungiusstraße 11, 20355 Hamburg
Bei der Spektroskopie von einzelnen Nanostrukturen mit Strahlung im
Terahertz-bereich treten zwei technische Schwierigkeiten auf: die kleine
Absorptionsfläche und die geringe Intensität der vorhandenen Lichtquellen.
Es ist daher vorteilhaft, die Intensität des vorhandenen Lichtes im
Bereich der Nanostruktur zu erhöhen. Mit Hilfe von unterschiedlichen
breitbandigen Antennentypen auf InAs- und GaAs-Heterostrukturen
wurde die Fokussierung des Lichtes untersucht. Besonderes Augenmerk
wurde hierbei auf die Verstärkungseigenschaften von verschiedenen
planaren Antennen, wie zum Beispiel der Log-Periodischen- und der
Bowtie-Antenne gelegt. Diese wurden direkt auf die Oberfläche der Heterostruktur
aufgedampft. Zu ihrer Charakterisierung wurden mit einem
Ferninfrarot-Spektrometer spektralaufgelöste und spektralintegrierte
Photoleitungsmessungen der Zyklotronresonanz eines zweidimensionalen
Elektronengases an einem 50 µm breiten Hallbar im Fokus der Antenne
in einem Magnetfeld von 0 T bis 8 T und einer Temperatur von 4,2 K
durchgeführt. Als Referenz dienten Messungen an nicht von der Antenne
verstärkten Abschnitten des selben Hallbars. Als weitere Parameter
wurde der laterale Abstand zwischen Antenne und Hallbar verändert
und durch verschieden tiefes Ätzen die Distanz zwischen den Ebenen
des 2DEG und der planaren Antenne variiert.
HL 12.12 Mo 16:30 Poster A
µ-Photolumineszenzspektroskopie der Resonanzfluoreszenz aus
Quantenpunkten — •Rico Schwartz, Daniel Schwedt und
Heinrich Stolz — Universität Rostock, Fachbereich Physik, AG
Halbleiterphysik, Universitätsplatz 3, 18051 Rostock
Die Untersuchung der Resonanzfluoreszenz aus Quantenpunkten mittels
µ-Photolumineszenzspektroskopie ist aufgrund des dominierenden
Anteils der Rayleigh-Streuung noch ein offenes Problem. Bisherige Experimente
gingen daher immer von nicht resonanter Anregung aus (z. B.
[1]).
Die räumliche Separation von Anregungs- und Detektionskanal erlaubt
uns effiziente Streulichtunterdrückung, so daß wir hier über erste Experimente
berichten können.
[1] Michler, P. and Kiraz, A. and Becher, C. and Schoenfeld, W. V. and
Petroff, P. M. and Lidong Zhang and Hu, E. and Imamoglu, A.; Science
290, 2282 (2000).
HL 12.13 Mo 16:30 Poster A
Elektron-Phonon-Wechselwirkung in InAs-Antidots — •Ch.
Menk, K. Bittkau, Ch. Heyn, D. Heitmann und C.-M. Hu —
Institut für Angewandte Physik, Universität Hamburg, 20355 Hamburg
Wir haben Photoleitung an einem InAs 2DES mit mäanderförmigen
Hallbar durchgeführt, in den mittels holographischer Lithographie und
chemischen Nassätzen Antidots mit einem Durchmesser von 200 nm und
einer Gitterkonstante von 800 nm erzeugt wurden. Mit einem Fourier-
Spektrometer wurden für Temperaturen von 1,5 K bis 10 K spektral
aufgelöste Messungen in Magnetfeldern von 0 bis 12 T durchgeführt.
Es werden Magnetoplasmonen und Edge-Magnetoplasmonen beobachtet.
Das Magnetoplasmon lässt sich in hohen Magnetfeldern durch die
Reststrahlenbande tunen. Durch die Auswirkungen der Phononen zeigen
die Intensitäten des Photoleitungssignals der Plasmonen eine andere
Temperaturabhängigkeit als die der unbeeinflussten Plasmonen in niedrigen
Magnetfeldern.
Desweiteren haben wir Absorptionsrechnungen durchgeführt. Durch
Vergleich mit den Messungen zeigt sich, dass sowohl Polaronkopplung
als auch dielektrische Effekte wichtig sind.

Halbleiterphysik Montag
HL 12.14 Mo 16:30 Poster A
Diamagnetic Shift and Localization of Excitons in Disordered
Quantum Wells — •Michal Grochol, Frank Grosse, and
Roland Zimmermann — Institut für Physik der Humboldt-Universität
zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
Recent nearfield photoluminescence experiments of excitons in quantum
wells (QWs) [1] have shown that the diamagnetic shift varies among
individual exciton lines. We present calculations for exciton states in QWs
with alloy and interface disorder under the influence of a perpendicular
magnetic field. Since a separation of the centre-of-mass motion would lead
to a fixed diamagnetic shift for all states, we solve the full Schrödinger
equation for the electron and hole in-plane coordinates [2]. We compare
several numerical treatments like the Leapfrog method and the Lanczos
method. The state-dependent diamagnetic shift gives additional information
about exciton localization and can explain experimental data.
[1] C. Ropers, Diploma thesis, Univ. Göttingen, 2003.
[2] R. Zimmermann, F. Grosse, and E. Runge, Pure and Applied Chemistry,
69 1179 (1997).
HL 12.15 Mo 16:30 Poster A
Energy dependent optical selection rules for spin orientation in
quantum wells — •Tobias Nowitzki 1 , Stefan Pfalz 1 , Roland
Winkler 1 , Daniel Hägele 1 , Andreas Wieck 2 , and Michael
Oestreich 1 — 1 Universität Hannover, Institut für Festkörperphysik,
Abteilung Nanostrukturen, Appelstraße 2, 30167 Hannover —
2 Ruhr-Universität Bochum, I. Institut für Experimentalphysik,
Universitätsstraße 150, 44780 Bochum
Spin-polarized charge carriers are generated in a quantum well by optical
excitation with circularly polarized light. By analyzing the degree of
polarization of the time resolved photoluminescence (PL), we determine
the initial degree of spin polarization of the excited electrons. We measure
the initial polarization degree in the PL of a GaAs/AlGaAs sample
with quantum well thicknesses between 5 nm and 20 nm for different
photon energies of the exciting laser beam. Commonly, such initial degree
of polarization is calculated using the angular momentum selection
rules for optical transitions between different band edge electron and hole
states in a bulk semiconductor. However, due to Coulomb interaction and
coupling between heavy and light holes, the generated excitons usually
contain substantial contributions from electron and hole states with different
angular momentum components. We compare the experimental
spectra with calculated spectra that fully take into account Coulomb
interaction and heavy-hole light-hole coupling.
HL 12.16 Mo 16:30 Poster A
Optical bandgap determination of MOVPE-grown hexagonal
InN — •Raimund Kremzow, Bert Rähmer, Massimo Drago,
Christoph Werner, and Wolfgang Richter — TU-Berlin, Institut
für Festkörperphysik, Hardenbergstr. 36, 10623 Berlin
The electronic properties of hexagonal InN were intensively discussed
in the recent years. Particularly different bandgap values were reported
for MBE-grown or sputtered materials [1]. In this work we present photoluminescence
studies of MOVPE-grown InN. For epitaxial growth similar
problems occur as for GaN, due to the high lattice mismatch of the nitrides
in comparison to substrate commonly used. We used GaN buffer
layers to reduce this misfit and grew epitaxial InN layers [2]. To reduce
the defect density the samples were thermally annealed. The bandgap of
samples with different doping was determined ex-situ by photoluminescence
and optical absorption spectroscopy. First results confirm bandgap
values at 0.7-0.8 eV similar to those found for MBE-grown samples [1].
[1] V. Yu. Davydov et al., phys. stat. sol. (b) 230, No. 2, R4-6 (2002)
[2] M. Drago et al., phys. stat. sol. (a) 195, No. 1, 3-10 (2003)
HL 12.17 Mo 16:30 Poster A
MIR Fourier transformation spectroscopy on Cu2O — •M.
Jörger, K.C. Agarwal, T. Fleck, and C. Klingshirn — Institut
für Angewandte Physik, Universität Karlsruhe, D-76128 Karlsruhe
While the far infrared (FIR) optical properties of the direct semiconductor
Cu2O are well understood and dominated by the fundamental
phonon modes, the situation in the mid infrared (MIR) is quite different.
Based on the absorption data of a series of naturally grown samples
from different sources, with different thicknesses and orientations, we discuss
miscellaneous absorption bands in the range of 100-400meV, which
partly show a pronounced temperature dependence. It will be analysed to
what extent the occurring bands can be explained in terms of biphonon
or multiphonon states, intrinsic impurities or, at higher temperatures, in
terms of excitonic/electronic transitions.
Depending on the combination of the involved valence and conduction
band, there are four different exciton series in Cu2O. Those are
(with increasing band gap) the yellow, green, blue and violet ones. In
a so-called pump and probe experiment (cw excitation) we investigate
whether 1s(ortho/para)→2p,3p,... transitions within the yellow series can
be observed. Furthermore we examine if transitions from the yellow 1s
(ortho/para) exciton to states of the higher exciton series appear.
HL 12.18 Mo 16:30 Poster A
Mikroskopische Lumineszenzuntersuchungen an ZnMgO —
•Sören Giemsch 1 , F. Bertram 1 , J. Christen 1 , Th. Gruber 2 und
A. Waag 3 — 1 Institut für Experimentelle Physik, Otto-von-Guericke
Universität, — 2 Abteilung Halbleiterphysik, Universität Ulm, Albert
Einstein Allee 45, — 3 Institut für Halbleitertechnologie, Technische
Universität
Im ternären Materialsystem MgZnO lässt sich die Bandlücke gezielt
durch Erhöhung der Mg-Konzentration vergrößern. Zusätzlich ist mittels
MgZnO das Wachstum von Heterostrukturen, wie z.B. Quantum Wells,
möglich. MgZnO dient dabei als Barrierenmaterial und ZnO als aktive
Schicht. Hier präsentieren wir Ergebnisse von ortsaufgelösten Kathodolumineszenzmessungen
(KL) an einem MgZnO/ZnO Single Quantum Well
(SQW). Die SQW-Struktur wurde auf einem ZnO/GaN/Saphir Template
aufgewachsen. Sie besteht aus einer 350 nm dicken Mg0,06Zn0,94O
Barrierenschicht und dem 2 nm dicken ZnO SQW. Als abschließende
Deckschicht diente eine 50 nm starke MgZnO Schicht. Die Oberflächenmorphologie
der SQW-Struktur ist überwiegend planar, besitzt
jedoch hexagonale Krater (Dichte ca. 1, 3 × 10 8 cm −2 ). Das Integrale
KL-Spektrum zeigt drei spektrale Bereiche: die SQW- (3,383eV),
Barrieren- (3,4542eV) und ZnO-Pufferlumineszenz (3,356 eV). Sowohl
die SQW, wie auch die Barrierenlumineszenz, bestehen aus zwei spektralseparaten
Anteilen: jeweils der niederenergetischere Peak dominiert; die
höherenergetischere Linie kommt dagegen besonders an den hexagonalen
Kratern zum Vorschein.
HL 12.19 Mo 16:30 Poster A
Lokalisierungs- und Temperatureffekte bei der Transportdynamik
von Exzitonen in ZnSe Quantenfilmen — •B. Dal Don 1 , G.
Schwartz 1 , H. Zhao 1 , H. Kalt 1 , C. Bradford 2 , K. Prior 2 und I.
Galbraith 2 — 1 Institut für Angewandte Physik der Universität Karlsruhe
(TH), Wolfgang-Gaede Str. 1, 76131 Karlsruhe — 2 Heriot-Watt
University, Edinburgh, EH14 4AS, United Kingdom.
Wir untersuchen die Transportdynamik von Exzitonen in Zn-
Se/ZnMgSSe und ZnSe/MgS mehrfach-Quantenfilmen. Die zwei
Systeme unterscheiden sich durch die Stärke ihrer Lokalisierung.
Zur Messung benutzen wir einen Mikrophotolumineszenzaufbau
mit Immersionslinse mit einer Ortsauflösung von ca. 250 nm. Der
Detektionsspot wird unabhängig vom Anregungsspot bewegt und die
räumliche Verteilung der Photolumineszenz wird mit einer Zeitauflösung
von 5 ps gemessen.
Bei 5 K beobachten wir in den ersten 50 ps bei beiden Systemen eine
räumliche Oszillation der Exzitonenverteilung. Dies kann bei den Zn-
Se/ZnMgSSe Proben mit Hilfe einer Monte-Carlo Simulation der Exzitonendynamik
reproduziert und mit der Emission akustischer Phononen
verbunden werden. Die Oszillation verschwindet bei 20 K wegen der zunehmenden
Absorption von akustischen Phononen, was von der Simulation
qualitativ bestätigt wird.
In den ZnSe/MgS Proben spielt die Lokalisierung eine wesentliche Rolle.
Wir beobachten eine schnelle räumliche Ausbreitung des Lumineszenzspots
in den ersten 30 ps, gefolgt von einer statischen Phase, in der sich
der Lumineszenzfleck sich nicht mehr weiter ausdehnt.
HL 12.20 Mo 16:30 Poster A
Femtosecond control of electronic motion in semiconductor double
quantum wells — •Alex Matos-Abiague und Jamal Berakdar
— Max-Planck-Institut für
The quantum dynamics and emission properties of a AlxGa1−xAs based
symmetric double quantum well driven by a train of ultrashort halfcycle
electromagnetic pulses. By numerically solving the time-dependent
Schrödinger equation it is shown that an appropriate design of the train
of pulses allows to control the electron motion on a sub-picosecond scale
and to achieve and maintain a predefined final electron state. It is also
shown that the emission spectrum can be designed by appropriately choosing
the parameters of the pulses. The effects of absence of generalized
parity of the Floquet modes on the dynamics of the system are discus-

Halbleiterphysik Montag
sed. Phenomena such as coherent suppression of tunnelling in absence
of accidental degeneration of the quasienergies, low-frequency generation
and half harmonic generation are observed. A simplified analytical model
that reproduces the main features of the numerical calculations is presented
and is utilized to derive simple relations for the values of the pulse
parameters that optimize the control process of the electron motion and
its emission spectrum.
HL 12.21 Mo 16:30 Poster A
Photomixing at 1.55µm - Application of the nipnip-THz-emitter
concept to long wavelength materials — •Frank H. Renner 1 , O.
Klar 1 , S. Malzer 1 , M. Eckardt 1 , G. Loata 2 , T. Löffler 2 , H.
Roskos 2 , D. Driscoll 3 , M. Hanson 3 , A.C. Gossard 3 , and G.H.
Döhler 1 — 1 Insitut für Technische Physik I, Universität Erlangen-
Nürnberg , Germany — 2 Lehrstuhl für Ultrakurzzeitphysik, Universität
Frankfurt a.M., Germany — 3 Materials Departement, UC Santa Barbara,
U.S.A.
We have recently developed a novel concept for photomixing based
on the quasi-ballisitic transport of electrons in a nipnip-superlattice. We
were already able to observe THz-radiation from AlGaAs-based samples.
For these samples excitation is performed by photomixing around 830nm
(see oral presentation of our group).
Technologically more favourable would be a photomixer operating
around 1.55µm. Several workgroups are currently trying to find a suitable
photomixer, operating around this wavelength. In this contribution
we extend our nipnip-THz-emitter concept towards 1.55µm by using the
(Al)InGaAs-semiconductor alloy system. Monte Carlo simulations prove
this material system to be substantially superior to AlGaAs. We will discuss
design and concept of the InGaAs-nipnip-emitter, compare it to the
AlGaAs design and report on first results on its realzation.
HL 12.22 Mo 16:30 Poster A
Molecular fluorescence in and near nanostructures — Lavinia
Rogobete 1 , Vahid Sandoghdar 1 , and •Carsten Henkel 2 —
1 Physical Chemistry, ETH Zurich, Switzerland — 2 Institut für Physik,
Universität Potsdam
Single molecular dipoles provide unique opportunities to perform scanning
optical near field microscopy with pointlike sources and detectors.
The electromagnetic interaction with nanostructured probes and with
the scanning tip itself significantly modifies the fluorescence dynamics.
We discuss a simplified, two-dimensional model for the radiative decay
of a single dipole in a complex dielectric or metallic environment [1]. The
electromagnetic fields are computed numerically using boundary integral
equations. The resulting decay rates inside sub-wavelength host particles
compare well with an electrostatic calculation.
[1] Opt. Lett. 28 (2003) 1736.
HL 12.23 Mo 16:30 Poster A
Optical superlattices based on surface acoustic waves — •M. M.
de Lima, Jr., R. Hey, and P. V. Santos — Paul-Drude-Institut,
Berlin
We present a novel concept for the fabrication of dynamic optical superlattices
based on the modulation of a planar photonic microresonator
by surface acoustic waves (SAWs). The microresonator consists of a λ/4
GaAs cavity layer sandwiched between GaAs/AlAs Bragg reflectors. The
optical superlattice is formed by SAW beams, which laterally modulate
the cavity optical properties. The strong light field in the cavity layer
considerably enhances the acousto-optic interaction, thus leading to high
diffraction intensities. We report the observation of stop bands in the light
dispersion as wide as 1.4 meV induced by the lateral periodicity imposed
by the SAWs. We also demonstrate the formation of two-dimensional
superlattices by the interference of orthogonal SAW beams.
HL 12.24 Mo 16:30 Poster A
Emission stimulation in opals — •Sergei Romanov 1 , Dmitry
Chigrin 1 , Clivia Sotomayor Torres 1 , Nikolai Gaponik 2 , Alexander
Eychmueller 2 und Andrei Rogach 3 — 1 Inst. of Materials
Science and Dept. of Electrical and Information Engineering, University
of Wuppertal, 42097, Germany — 2 Inst. of Physical Chemistry, University
of Hamburg, 20146, Germany — 3 Dept. of Physics, University of
Munich, 80799, Germany
Light sources in photonic crystals (PhCs) attract considerable attention
owing to improvement of emitter parameters. We studied the ballistic
emission of CdTe nanocrystals, which were layer-by-layer embedded in
thin opal films, near the Bragg PBG as a function of excitation power
and angle of detection. Two-parameter exponential fit to the emission
intensity vs. excitation power curve was used to extract the power radiated
by saturated emitter and the saturation threshold. In the PBG the
spectrum of the former shows a minimum in contrast to the maximum of
the latter. The decrease of the saturated emission power was associated
with the suppression of the spontaneous emission rate in a given optical
mode and the increase the saturation threshold - as the acceleration of
the radiative recombination.
We argue that photons emitted along the bandgap direction are coupled
to highly inhomogeneous PhC eigenmodes propagating with low
group velocity. This imposes resonator conditions and the backreaction
of the radiation to emitters stimulates the radiative recombination.
HL 12.25 Mo 16:30 Poster A
Light scattering in thin opal films — •Sergei Romanov — Institute
of Materials Science and Department of Electrical and Information
Engineering, University of Wuppertal, 42097 Wuppertal, Germany
Reflectance and transmission are conventionally used to measure light
interaction with photonic crystals (PhCs), whereas the light scattered
off the incidence direction is neglected. In this work the scattering was
used as an independent tool to study the light propagation in slightly
disordered three-dimensional PhCs. In such crystals the regime of weak
scattering is realised, when scattered photons experience only one collision
along their paths, i.e. they mimic light emitted by an internal light
source.
The intensity of light scattered by thin opal films in forward and backward
configurations was studied as a function of wavelength and direction.
It was shown that diffraction-related minima of forward scattered
light do not depend on the actual lightpath, but correspond to directions
of the incidence and detection with respect to (111) planes. Angle diagrams
of the scattered light were assigned to the resonant scattering,
moreover, they show a modulation by shadows of respective bandgaps.
Oppositely, the backscattering appears more effective at bandedges of
the Bragg gap.
As an example, the light scattering was used to characterise the light
propagation across the PhC heterojunction.
HL 12.26 Mo 16:30 Poster A
Asymptotic analysis of radiation pattern of a classical dipole in
a photonic crystal — •Dmitry Chigrin and Clivia Sotomayor
Torres — Institute of Materials Science and Department of Electrical,
Information and Media Engineering, University of Wuppertal, D-42097
Wuppertal, Germany
Photonic crystals (PhCs) possess a complicated photonic band structure,
where allowed bands display strong dispersion and anisotropy. Recently,
there has been a growing interest in studies of energy flow inside
PhCs. Being a strongly anisotropic material, a PhC displays the beam
steering effect: the group velocity direction does not necessarily coincide
with the wavevector direction. As a consequence, the emission of an optically
active material placed within a PhC can reveal unusual properties.
In this contribution, an asymptotic analysis of the electromagnetic
field of a classical point dipole situated in PhC possessing an incomplete
bandgap is presented. The simple formula to calculate an angular distribution
of radiated power is introduced. Redistribution of the radiated
power is predicted. Within given approximation, the radiated power becomes
infinite in certain directions. These are directions in which the
direction of the group velocity of the crystal eigenmodes is stationary
with respect to a small variation in the wavevector direction. Predictions
of asymptotic analysis are substantiated with FTDT calculation.
HL 12.27 Mo 16:30 Poster A
Dynamics and entanglement of photon pulses in a photonic
crystal — Geesche Boedecker and •Carsten Henkel — Institut
für Physik, Universität Potsdam
In a photonic crystal, the dispersion relation of light can be tailored to
a great extent. Close to a band edge, for example, the group velocity is
significantly reduced. For a finite crystal slab, multiple reflections from
the end faces lead to a transmitted pulse train. We discuss the entanglement
properties of the transmitted pulses. The pulse shape inside the
crystal is analyzed for a one-dimensional model [1] in the regime of small
group velocities.
[1] Opt. Express 11 (2003) 1590

Halbleiterphysik Montag
HL 12.28 Mo 16:30 Poster A
Tuning a 2-D silicon photonic crystal using nonlinear optics —
•Stefan L. Schweizer 1 , Hong W. Tan 2 , Henry M. van Driel 2 ,
Ralf B. Wehrspohn 1 , and Ulrich Gösele 3 — 1 Universität Paderborn,
Dept. Physik, 33095 Paderborn — 2 Department of Physics, University
of Toronto, Canada — 3 MPI für Mikrostrukturphysik, Weinberg
2, 06120 Halle
Photonic crystals (PC) have unusual dispersion properties that can be
used to control the propagation characteristics of light beams. However,
for some potential active devices, one desires methods to tune these optical
properties quickly. We use pump-probe reflectivity experiments with
130 fs pulses to demonstrate how the real (Kerr) and imaginary (two
photon absorption) parts of a third order optical nonlinearity can tune
the long (1.6 µm) and short wavelength (1.3 µm) band-edges of a stop
gap in a 2-D silicon photonic crystal. A 2 µm pump pulse induces optical
tuning of the 1.3 µm edge via the Kerr effect whereas a 1.76 µm
pump pulse induces tuning of the 1.6 µm band edge via both Kerr and
Drude effects with the latter related to 2-photon induced generation of
free carriers with a lifetime of ≈900ps.
HL 12.29 Mo 16:30 Poster A
Trimming of two dimensional photonic crystal structures —
•Markus Schmidt 1 , Gunnar Boettger 1 , Karolin Preusser-
Mellert 1 , Manfred Eich 1 , Uwe Huebner 2 , and Hans-Georg
Meyer 2 — 1 Technische Universitaet Hamburg-Harburg, AB 4-09, Eissendorfer
Str. 38, D-21073 Hamburg — 2 Institut fuer Physikalische
Hochtechnologie Jena e. V., Abt. Kryoelektronik, Winzerlaer Str. 10 D-
07745 Jena
We present a new concept to adjust the transmission properties of a
two dimensional photonic crystal based on photobleaching. A square lattice
of 500 nm lattice constant and 300 nm hole diameter was fabricated
by etching air holes into a slab waveguide consisting of a polymethylmethacrylate
polymer covalently functionalized with 10 mol % of the
Disperse Red 1 chromophore. While illuminating the photonic crystal
with UV light the azo molecule bonds degenerate, resulting in a considerable
refractive index change and a slightly reduced slab waveguide core
layer thickness. Wavelength and polarization dependent measurements
show that the dielectric band edge can be shifted strongly, achieving maximum
shifts of 35 nm in TE and 27 nm in TM polarization. Bleaching
of a finite 2d-resonator results in a 22 nm higher resonance wavelength.
In practical applications much smaller shifts are needed to tune Dense
Wavelength Division Multiplexing (DWDM) - devices. Our novel concept
therefore allows to compensate fabrication inaccuracies and to trim
photonic crystal transmission properties.
HL 12.30 Mo 16:30 Poster A
Reflection from two- and three-dimensional Photonic Crystals
— •Marcus Diem 1 , Suresh Pereira 1,2 , and Kurt Busch 1,3 —
1 Institut für Theorie der Kondensierten Materie, Universität Karlsruhe
— 2 Department of Physics, University of Toronto, Canada — 3 School of
Optics/CREOL & Department of Physics, University of Central Florida,
Orlando, USA
We employ a Scattering-Matrix-Method [1] to calculate transmissionand
reflection properties of two- and three-dimensional finite-sized Photonic
Crystal structures. The angle and frequency dependent data can
be directly compared with measurements [2] and allow one to investigate
the quality and parameters of the sample. Peaks in the reflection
spectra associated with different Bragg-orders can be used to determine
the coupling to the modes of the periodic system. This coupling depends
strongly on the surface termination of the Photonic Crystal illustrating
certain complications when interpreting measurements using only the
bandstructures of bulk systems.
In addidtion, we employ this method to determine mode losses in periodically
structured planar waveguides based on optically active polymer
films evaporated onto surface-relief gratings.
[1] D.M. Whittaker and I.S. Culshaw, Phys. Rev. B 60, 2610 (1999)
[2] G. von Freymann et.al, Appl. Phys. Lett 83, 614 (2003)
HL 12.31 Mo 16:30 Poster A
Loss mechanisms in Photonic Crystal slabs — •Meikel Frank 1 ,
Suresh Pereira 1 , and Kurt Busch 2 — 1 Institut für Theorie der Kondensierten
Materie, Universität Karlsruhe, 76128 Karlsruhe, Germany
— 2 School of Optics/CREOL and Department of Physics, University of
Central Florida, Orlando, USA
A scattering matrix method [1] is used to study the optical properties
of Photonic Crystal slabs. Of special interest is the effect of fabricational
tolerances on the propagation characteristics of the modes that are guided
in the ideal system. It is shown that modes in dielectric and air bands,
respectively, exhibit significantly different behavior for certain types of
disorder. For instance, dielectric modes are rather insensitve to errors in
the pore radii, whereas they are strongly affected by variations in the
lattice constant. In addition, it is shown how reflection and transmission
data from finite-sized Photonic Crystal samples may be used to obtain
partial information about fabricational imperfections.These results allow
one to specify critical parameters for the fabrication of Photonic Crystals.
[1] E.Silberstein, P.Lalanne, J.-P.Hugonin and Q.Cao J.Opt.Soc.Am.A
18 2865 (2001)
HL 12.32 Mo 16:30 Poster A
2D photonic crystal slab structures of high refractive index
in inorganic glasses — •Karolin Preusser-Mellert 1 , Markus
Schmidt 1 , Gunnar Boettger 1 , Uwe Huebner 2 , and Manfred
Eich 1 — 1 Technische Universität Hamburg-Harburg, Arbeitsbereich Materialien
der Elektrotechnik und Optik, Eissendorfer Str. 38, D-21073
Hamburg, Germany — 2 Institut für Physikalische Hochtechnologie e. V.,
Abt. Magnetik/Quantenelektronik, Winzerlaer Str. 10, D-07745 Jena,
Germany
Semiconductors are common materials used for fabricating twodimensional
photonic crystals because of their high refractive index and
the existing fabrication technology. But as it comes to integrate photonic
crystal structures, these high refractive index materials show larger
coupling losses than lower index systems. We have found an alternative
way of realizing a high vertical index contrast: We use inorganic glasses
as a waveguiding material with a relatively high refractive index - such
as titanium dioxide (n=2.5) - and we increase the vertical index contrast
with the help of a very low refractive index material: mesoporous
silica (n=1.14). This approach combines the advantages of air-bridgestructures
and solid substrates excluding their drawbacks. First structures
and simulations are presented.
HL 12.33 Mo 16:30 Poster A
Characterization and Structure Determination of Mesoporous
Silica Films for Optical Applications — •Denan Konjhodzic 1 ,
Markus Schmidt 2 , Helmut Bretinger 1 , Manfred Eich 2 , and
Frank Marlow 1 — 1 Max-Planck-Institut für Kohlenforschung, D-
45470 Mülheim an der Ruhr — 2 TU Hamburg-Harburg, D-21077 Hamburg
Mesoporous silica thin films were synthesized in a sol-gel process using
a nonionic triblock copolymer PEO-PPO-PEO as a template. Due to high
pore volume of these films, the effective index of refraction is very low
(n=1.14 at 1300 nm determined by the prism coupling method). Because
of their high mechanical, chemical and thermal stability, high optical
transparency, low optical scattering and especially because of the very
low refractive index, these films are useful as substrates for 2D photonic
crystals.
SAXS diffraction patterns obtained with an area detector clearly show
a partially ordered structure of the channels in one type of as-synthesized
films with a spacing of about 8 nm. There is no preferred direction of
the channels parallel to the surface, which is in agreement with optical
measurements. Other types of pore ordering have also been found. Calcination
leads to the shrinkage of the structure. Surface properties have
been investigated using AFM. The film surface is very smooth (roughness
below 1 nm) but with certain defects in one structure type.
Based on these findings we propose structure models for our mesoporous
films and for the defects inside. We discuss their implications for
photonic crystal research.
HL 12.34 Mo 16:30 Poster A
Crystal orientation dependence of pores in InP for photonic
crystal applications — •Stefan Lölkes, Sergiu Langa, Jürgen
Carstensen, and Helmut Föll — Technische Fakultät, Christian-
Albrechts-Universität zu Kiel, Kaiserstr. 2, 24143 Kiel
For the field of Photonic Crystals (PhCs), electrochemically etched
macroporous Si has set milestones[1]. All III/V semiconductor based
PhCs have so far been produced by plasma-etching. In 2003, Langa et
al.[2] showed uniform electrochemical pore etching in InP with tremendous
aspect ratios for 2D InP PhCs. To produce PhCs with a full 3D
photonic band gap, several authors have proposed fabrication methods
where first a set of slanted pores is drilled electrochemically [3], followed
by highly directional dry etching to introduce a second pore set orthog-

Halbleiterphysik Montag
onal to the first one. On Si, slanted pores can be fabricated by using
custom cut wafers[4]. These experiments are transferred to InP to investigate
the orientation dependence of pore growth, in order to make a first
step towards the still elusive large scale full 3D PBG.
[1] A. Birner, R.B. Wehrspohn, U. Gösele,and K. Busch, Adv. Mater.
13, 377 (2001).
[2] S. Langa, I.M. Tiginyanu, M. Christophersen, J. Carstensen, and
H.Föll, Appl- Phys. Lett., 82 (2003) 278.
[3] A. Chelnokov, K. Wang, S. Rowson, P. Garoche, and J.-M. Lourtioz,
Appl. Phys. Lett. 77, 2943 (2000).
[4] CHRISTOPHERSEN, M., CARSTENSEN, J., RÖNNEBECK, S.,
JÄGER, C., JÄGER, W., FÖLL, H., J. Electrochem. Soc. 148 (6), E267
(2001).
HL 12.35 Mo 16:30 Poster A
Gas Sensors Based on 2D Photonic Crystals — •Torsten M.
Geppert 1 , Stefan L. Schweizer 2 , Ralf. B. Wehrspohn 2 , and
Armin Lambrecht 3 — 1 Max-Planck-Institut für Mikrostrukturphysik,
Weinberg 2, 06120 Halle, Germany — 2 Universität Paderborn, Dept.
Physik, Warburger Str. 100, 33098 Paderborn, Germany — 3 Fraunhofer-
Institut für Physikalische Messtechnik, Heidenhofstr. 8, 79110 Freiburg,
Germany
We investigate a new kind of gas sensor devices utilizing 2D photonic
crystals (PhCs) made up of straight air pores electrochemically etched
into Si wafers. Based on the reduction of the group velocity of light
in a PhC the interaction time between gas and light should be drastically
increased allowing to minimize the size of the gas sensing device as
compared to currently used gas sensor systems. To achieve this miniaturization,
three requirements have to be met by the PhC. First, the
photonic bandstructure should have only a very small slope for the frequency
of interest to achieve a low group velocity. Second, the electric
field has to be concentrated in the pores to allow interaction between
the light and the gas. Third, the symmetry of the field distribution in
the PhC has to allow the coupling of the incoming light to the photonic
bandstructure. Unfortunately, due to the low group velocity, the reflection
at the interface air-photonic crystal is very high resulting in a low
coupling efficiency. This shortcoming could be circumvented by the use
of appropriate tapers. In our study we investigate several geometries of
the photonic crystal lattice and taper concepts to allow the use of 2D
PhCs as gas sensor devices.
HL 12.36 Mo 16:30 Poster A
Controlling spontaneous emission from colloidal II-VI
nanocrystals in microcavities — •Robert Kraus 1 , Dmitry
Talapin 2 , Andrey L. Rogach 1 , John M. Lupton 1 , Jochen
Feldmann 1 , and Horst Weller 2 — 1 Lehrstuhl für Photonik und
Optoelektronik, Ludwig-Maximilians-Universität München — 2 Institut
für Physikalische Chemie, Universität Hamburg
Colloidal II-VI nanocrystals are an interesting class of materials for optoelectronic
devices. The solution-based synthesis of these nanoparticles
typically results in a certain degree of polydispersity, which in turn gives
rise to substantial spectral broadening of the ensemble. We demonstrate
here that we are able to deposit composite nanocrystal/polymer films of
excellent optical quality, which can be used as the active layer in microcavities.
These provide well-defined optical resonances, to which only a
spectrally narrow ensemble of the nanocrystals couple, thereby resulting
in an enhancement in spontaneous emission. We present data on time
resolved fluorescence from these emitters embedded in microcavities and
discuss the possibility of using the cavity induced field-enhancement to
control energy transfer processes.
HL 12.37 Mo 16:30 Poster A
Lasertätigkeit in zweidimensionalen photonischen Kristallen —
•Karen Forberich 1 , Andreas Gombert 2 , Marc Stroisch 3 , Uli
Lemmer 3 , Marcus Diem 4 , Suresh Pereira 4 und Kurt Busch 4,5
— 1 Freiburger Materialforschungszentrum, Universität Freiburg —
2 Fraunhofer Institut für Solare Energiesysteme ISE, Freiburg —
3 Lichttechnisches Institut, Universität Karlsruhe — 4 Institut für
Theorie der Kondensierten Materie, Universität Karlsruhe — 5 School
of Optics/CREOL & Department of Physics, University of Central
Florida, Orlando, USA
Organische Photonische Kristall-Laser lassen sich durch das Aufbringen
eines organischen Farbstoffs auf ein mikrostrukturiertes Substrat herstellen.
Die so erzeugten Strukturen werden mit einer semiklassischen
Theorie der Lasertätigkeit in photonischen Kristallen beschrieben [1]. Im
Rahmen dieser Theorie lassen sich effektive Parameter herleiten, mit denen
die Lasereigenschaften charakterisiert werden können.
Die Berechnung der Verstärkung erfolgt durch zweidimensionale
Bandstrukturrechnungen, wobei die tatsächliche Oberflächenstruktur
durch einen planaren Wellenleiter mit ortsabhängiger Dicke angenähert
wird. Die Verluste werden durch Reflexionsrechnungen mit Hilfe
einer Streu-Matrix-Methode bestimmt. Durch den Vergleich von
Emissionsmessungen mit diesen Bandstruktur- und Verlustrechnungen
können die tatsächlichen Lasermoden bestimmt werden.
[1] L. Florescu, K. Busch, and S. John, J. Opt. Soc. Am. B 19, 2215–2223
(2002)
HL 12.38 Mo 16:30 Poster A
Structure of Spin-Flip Excitations in Interacting Electron Systems
at High Magnetic Fields — •U. Schmitt and G. Meissner
— Theoretische Physik, Universität des Saarlandes, Postfach 15 11 50,
D-66041 Saarbrücken
Similarities found in the structure of certain inter-Landau level and
intra-Landau level collective excitations of systems exhibiting the integer
and the fractional quantum Hall effect, respectively, are examined. Therefore,
we compare results obtained, e.g., for the dispersion relation of the
spin-flip mode between the filled lowest Landau level and the next and
for the collective excitations of Laughlin’s incompressible quantum liquid
at the corresponding filling factor one third according to the composite
Fermion picture. Modifications due to finite thickness effects in these interacting
two-dimensional electron systems at high magnetic fields are
discussed in view of a comparison of the calculated dispersion relations
with inelastic light-scattering experiments.
HL 12.39 Mo 16:30 Poster A
Strukturierungsmethoden überwachsener Heterostruktur-
Spaltkanten — •Markus Lermer, Dieter Weiss und Werner
Wegscheider — Institut für Experimentelle und Angewandte Physik,
Universität Regensburg, 93040 Regensburg
Wir präsentieren neue Methoden zur Strukturierung der mittels MBE
überwachsenen Spaltfläche von AlxGa(1−x)As/GaAs Heterostrukturen
und deren elektrische Charakterisierung im Magnetotransportexperiment.
Eine spezielle Sandwichtechnik erlaubt die Definition von Mesastrukturen
bis an den Rand der weniger als 100µm breiten Spaltfläche.
Kleinere Strukturen im 10nm Bereich werden elektronenstrahllithographisch
in an der Oberfläche adsorbierte, dünne selbstorganisierte Molekülmonolagen
geschrieben und anschließend nasschemisch übertragen.
Mit letztgenannter Methode periodisch dichtemodulierte 2-dimensionale
Elektronensysteme zeigen deutliche Kommensurabilitätseffekte in ihrem
Magnetotransportverhalten. Im Zusammenhang mit den Transportuntersuchungen
an cleaved-edge overgrowth Strukturen wurde auch der Transport
durch das darunterliegende Übergitter kleinster Periode im äußeren
Magnetfeld untersucht und eine Spannungspositionsabhängigkeit der Bereiche
negativer differentieller Leitfähigkeit festgestellt.
HL 12.40 Mo 16:30 Poster A
Density of States Tails in Random Magnetic Fields —
•Riccardo Mazzarello, Stefan Kettemann, and Bernhard
Kramer — I Institut fuer Theoretische Physik, Universitaet Hamburg,
20355 Hamburg, Germany
Recently, the problem of a quantum particle moving in a random magnetic
field (RMF) has been met in a number of contexts in the physics
of 2D-systems. For instance, in the Composite Fermion (CF) theory of
the Fractional Quantum Hall Effect, electrons are transformed into particles
with statistical flux attached to them: CFs experience a fictitious,
statistical magnetic field proportional to their density in addition to the
external one. The presence of a random, scalar potential induces fluctuations
in the CFs density which give rise to a static RMF. We studied
the tails of the density of states (DOS) of fermions subject to a constant
magnetic field B plus a weak RMF with zero mean in the framework of
the Optimum Fluctuation Method. We show that, near the centres of
the broadened Landau levels, the DOS is a Gaussian, whereas the energy
dependence of the DOS is non-analytic near the band edge (E=0). The
B-dependence of the DOS in both regions is also estimated.

Halbleiterphysik Montag
HL 12.41 Mo 16:30 Poster A
Leitfähigkeit von QH-Systemen im subkritischen Bereich und
ihr Einfluß auf den Zusammenbruch des QHE — •Andre Buß 1 ,
Frank Hohls 2 , Fritz Schulze Wischeler 2 , Günter Hein 3 ,
B. Erol Sagol 3 , Rolf J. Haug 2 und Georg Nachtwei 1 —
1 Institut für Technische Physik, TU-Braunschweig, Mendelssohnstr.2,
38106 Braunschweig — 2 Institut für Festkörperphysik, Abteilung
Nanostrukturen, Universität Hannover, Appelstr. 2, 30167 Hannover
— 3 Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116
Braunschweig
Wir haben frequenz- und temperaturabhängige Messungen an QH-
Systemen mit Corbino-Geometrie im kritischen und subkritischen Bereich,
d.h. kurz unterhalb der kritischen Spannung durchgeführt. Unsere
Intention war, das Verhalten der Längsleitfähigkeit lokalisierter Elektronen,
welche im Hot-Electron-Model (HEM) vorgeschlagen wurde, zu
untersuchen. Unsere Ergebnisse zeigen eine mit zunehmender Frequenz
abnehmende Leitfähigkeit, einhergehend mit einer Vergrößerung der Hysteresis
in der I-U-Kennlinie. Dieses Verhalten entspricht dem des HEM.
Die Ergebnisse der temperaturabhängigen Messungen lassen jedoch noch
keine klaren Schlüsse zu, um welche Transportmechanismen (thermisch
aktivierter Transport, Hopping-Leitfähigkeit oder Tunnelprozesse) es sich
hierbei handelt.
HL 12.42 Mo 16:30 Poster A
Untersuchungen an QH-FIR-Detektoren in Mäander- und Corbino-Geometrie
— •A. Hirsch 1 , C. Stellmach 1 , J. M. Guldbakke
2 , G. Hein 3 und G. Nachtwei 1 — 1 Inst. f. Techn. Physik,
TU-Braunschweig, Mendelssohnstr. 2, D-38106 Braunschweig — 2 Inst.
f. Hochfrequenztechnik, TU-Braunschweig, Schleinitzstr. 22, D-38106
Braunschweig — 3 Phys.-Techn. Bundesanstalt, Bundesallee 100, D-38116
Braunschweig
Wir präsentieren Photoleitfähigkeits-(PL)-Messungen im Ferninfrarot
(FIR) an Quanten-Hall-(QH)-Systemen. Als Strahlungsquelle wurde ein
p-Ge Laser im Pulsbetrieb verwendet, der Messungen im Wellenlängenbereich
zwischen ca. 120 µm ≤ λ ≤ 180 µm erlaubt. Es wurden QH-
Systeme mit großen photoaktiven Flächen (A ≈ 6 mm 2 ) in Mäanderund
Corbino-Geometrie untersucht. Das Photosignal wurde in Abhängigkeit
von Magnetfeld, Ladungsträgerkonzentration (steuerbar über eine
Gate-Spannung) und Probenstrom bzw. Probenspannung gemessen. Es
zeigte sich, dass die spektrale Auflösung der Detektoren in Mäanderbzw.
Corbino-Geometrie eine Funktion des Probenstroms bzw. der Probenspannung
ist. Weiterhin wurden zeitaufgelöste PL-Messungen durchgeführt.
Aus den impedanzangepassten Messungen an der Corbino-Probe
ergaben sich Zeitkonstanten im Bereich um 0.6 µs.
HL 12.43 Mo 16:30 Poster A
Einfluß der Austausch-Wechselwirkung auf den Quantentransport
in spin-polarisierten Elektronensystemen in
GaInAs-Quantengräben — •F. Vogt 1 , G. Nachtwei 1 , G. Hein 2
und H. Künzel 3 — 1 Institut für Technische Physik und Hochmagnetfeldanlage
der Technischen Universität Braunschweig, Mendelssohnstr.
2, D-38106 Braunschweig — 2 Physikalisch-Technische Bundesanstalt,
Bundesallee 100, D-38116 Braunschweig — 3 Heinrich-Hertz-Institut für
Nachrichtentechnik GmbH, Einsteinufer 37, D-10587 Berlin
An GaInAs-Quantengräben in AlInAs-Barrieren wurden Messungen
des Shubnikov-de Haas- (SdH) und Quanten-Hall-Effekts (QHE) in Magnetfeldern
bis 17.5 T durchgeführt. Bei den Füllfaktoren 1 und 3 ist das
zweidimensionale Elektronensystem im Quantengraben teilweise spinpolarisiert,
was zu einer Erhöhung des effektiven Landé-Faktors g ∗ führt.
Für diesen Fall wurden bei höheren Probenströmen asymmetrische und
hysteretische SdH-Oszillationen theoretisch vorhergesagt. Für den Füllfaktor
1 (höhere Spin-Polarisation) konnte diese Asymmetrie bestätigt
werden. Aus temperaturabhängigen Messungen konnten der Wert für g ∗
und für die Zustandsdichte in der Spin-Energielücke ermittelt werden.
Durch Drehen der Probe im Magnetfeld konnte der Füllfaktor ν = 3
bei hohen Magnetfeldern (B ≈ 15 T) realisiert und ein entsprechendes
Minimum im Probenwiderstand erzeugt werden. Trotzdem waren die erreichbare
Spin-Energielücke und die Spin-Polarisation bei ν = 3 bislang
zu gering, um auch hier die vorhergesagte Asymmetrie und Hysteresis im
SdH-Effekt nachzuweisen.
HL 12.44 Mo 16:30 Poster A
The Mesoscopic Chiral Metal-Insulator Transition in Quantum
Hall Wires — •Stefan Kettemann 1 , Alexander Struck 1 ,
Bernhard Kramer 1 , and Tomi Ohtsuki 2 — 1 I. Institut f. Theoretische
Physik, Univ. Hamburg, Jungiusstr. 9 20355 Hamburg —
2 Department of Physics, Sophia Univ. Kioi-Choi 7-1, Chiyoda-Ku, Tokyo
102-8554, Japan
The localization properties of chiral edge states as function of energy
in disordered quantum wires subject to a strong magnetic field are shown
analytically and numerically to be driven by crossovers from two- to onedimensional
localization of the bulk states [1]. Chiral-metal to insulator
transitions associated with these crossovers are predicted. They are characterized
by jumps of the localization length of the edge states from an
exponentially large to a finite value. As a result, the two-terminal conductance
exhibits at zero temperature discontinuous transitions between
exactly integer plateau values and zero, reminiscent of first order phase
transitions. [1] S. Kettemann, B. Kramer, T. Ohtsuki, cond-mat/0307044
HL 12.45 Mo 16:30 Poster A
Tunneling of quasiholes in the fractional quantum Hall regime
— •Moritz Helias and Daniela Pfannkuche — I. Institut für
Theoretische Physik, Universität Hamburg, Jungiusstr. 9, 20355 Hamburg,
Germany
The elementary low energy excitations in the fractional quantum Hall
(FQH) regime are known to be fractionally charged quasiparticles and
quasiholes. Basing on the edge state picture, a non-equilibrium transport
theory [1] prepared the ground for experiments on tunneling of quasiparticles
between the edges of a quantum point contact (QPC) [2].
Recent measurements [3] on a QPC whose edges carry a dilute current
of quasiparticles led to surprising results at low temperature: Quasiparticle
tunneling appears to be forbidden in this regime, instead Andreev
reflexion could explain the experimental results [4].
In our work we treat a QPC in a finite FQH system by exact numerical
diagonalization. Quasiholes are injected, their time evolution is
investigated and information about possible tunneling processes can be
infered.
[1] Kane, Fisher, PRL 72, p.724 (1994)
[2] Saminadayar et al., PRL 79, p.2526 (1997); Griffith et al., PRL 85,
p.3918 (2000)
[3] Chung et al., PRB 67, 201104 (2003)
[4] Kane, Fisher, PRB 67, 045307 (2003)
HL 12.46 Mo 16:30 Poster A
Interactions and Integer Quantum Hall Fluctuations —
•Christoph Sohrmann und Rudolf A. Römer — Department of
Physcis and Centre for Scientific Computing, University of Warwick,
Coventry CV4 7AL, UK
The integer quantum Hall effect appears to be well-describable by models
of non-interacting electrons in a strong magnetic field. Results seem
in very good agreement with experiments. Even mesoscopic conductance
fluctuations can be shown do have similarly broad distributions as in the
experimental situation [1]. However, in 1999 Cobden et al. [2] reported
strong evidence for a profound effect of the electron-electron interactions
in the integer regime. The authors investigated sample specific conductance
fluctuations in mesoscopic MOSFET devices. In contrast to the
random behaviour of the conductance as a function of one parameter —
such as, e.g., the magnetic field — they found regular patterns for the
conductance when viewed as a function of the two parameters magnetic
field and gate voltage. Using a numerical approach, we are studying these
fluctuations within a Hartree-Fock formulation and check whether the
interaction can indeed lead to the observed behavior.
HL 12.47 Mo 16:30 Poster A
Spectroscopic and transport measurements in the quantum Hall
regime on an optimized structure — •Claas Bierwisch 1 , Stefanie
Döhrmann 1 , Daniel Hägele 1 , Peter Tranitz 2 , Werner
Wegscheider 2 , and Michael Oestreich 1 — 1 Universität Hannover,
Institut für Festkörperphysik, Abteilung Nanostrukturen, Appelstr. 2,
D-30167 Hannover — 2 Universität Regensburg, Institut für Angewandte
und Experimentelle Physik, D-93040 Regensburg
We combine optical and transport measurements on a two-dimensional
electron gas (2DEG) in the quantum Hall regime on a sample with optimized
properties for optical investigations. The sample is a MBE grown
modulation doped 20 nm GaAs/AlxGa1−xAs single quantum well struc-

Halbleiterphysik Montag
ture with an electron density of about 10 11 cm −2 and a high mobility of
∼ 10 6 cm 2 V −1 s −1 . A high reflectance AlGaAs/AlAs Bragg mirror below
the 2DEG together with the reflecting top layer of the sample constitute
a cavity around the optical active quantum well. Simulations of the
expected optical Faraday-signal in reflection geometry exhibit a signal enhancement
of almost one order of magnitude due to the presence of the
mirror. Using a Hall bar, we observe the integer quantum-Hall-effect and
Shubnikov-de Haas-oscillations in a magnetic field up to 8 T at a temperature
of 1.8 K. Time-resolved photoluminescence (PL) experiments using
a streak camera system yield electron and hole spin dynamics inside the
quantum well. Simultaneous PL and transport measurements at different
filling factors will be presented.
HL 12.48 Mo 16:30 Poster A
Terahertz Photoleitungs- und Transmissionsspektroskopie an
tunnelgekoppelten doppellagigen zweidimensionalen Elektronengasen
— •L. H. Böttger, S. Holland, C.-M. Hu, Ch. Heyn
und D. Heitmann — Institut für Angewandte Physik, Universität Hamburg
Es wurden spektral aufgelöste Photoleitungs- und Transmissionsmessungen
im Terahertzbereich an einem tunnelgekoppelten GaAs/AlGaAs
Doppelquantentopf durchgeführt. Auf die Probe wurde ein Mäander-
Hallbar mit einer Breite von 50µm und einer Länge von etwa 13cm
präpariert. Ein Gitterkoppler aus Gold mit einer Periode von 1µm bedeckt
den Hallbar, so dass die Goldstreifen senkrecht zum Rand über
den Kanal laufen. Der Versuchsaufbau bestand aus einem Fourierspektrometer,
das mit einem Waveguide mit einem Magnet-Kryostaten verbunden
war. Die Probe wurde in Magnetfeldern von 0 bis 12T bei einer
Temperatur von 1.8K gemessen. Es wurde sowohl in Photoleitung
als auch in Transmission die Zyklotronresonanz und ein Magnetoplasmon
über nahezu den gesamten Magnetfeldbereich beobachtet. Ein Vergleich
der Moden-Energien aus beiden Messmethoden zeigte eine gute
Übereinstimmung bei ganzzahligen Füllfaktoren (ν=2,3,...). Zwischen
den Füllfaktoren jedoch verschob sich die Zyklotronresonanz in den Photoleitungsmessungen
zu höheren Energien während die Magnetoplasmonmode
stark gedämpft wurde.
HL 12.49 Mo 16:30 Poster A
Breakdown of the quantum Hall effect in samples with intentionally
introduced defects — •Dorina Diaconescu, Sascha
Hoch, Dirk Reuter, and Andreas Wieck — Lehrstuhl für Angewandte
Festkörperphysik, Ruhr-Universität Bochum, Germany
We study the role of electron scattering on the onset of the quantum
Hall effect breakdown in 2-dimensional electron systems with intentionally
introduced defects. The defects are Ga ions or vacancies in the
crystal lattice introduced by focused ion beam (FIB) implantation. The
defects can be introduced lateral homogenously, over the whole area of
the Hall-bar, or with spatial resolution. The dependence of the breakdown
current as a function of defect density was investigated in samples
with a lateral homogenous implantation. For low implantation doses, the
critical current increases with the ion dose. Further increase of the ion
dose leads to a reduction of the critical current. The results confirm the
work of Nachtwei et al. [1], where antidot arrays have been patterned on
the GaAs/AlxGa1−xAs heterostucture. The initial increase of the critical
current with the ion dose can be explained by an increased inelastic
scattering rate at the defects. It results a more effective cooling of the
hot electrons. Higher defect densities increase the impurity-assisted inter-
Landau level transitions, and a significant decrease of the critical current
is observed.
[1] G.Nachtwei, G.Lütjering, D.Weiss, Z.H.Liu, K.von.Klitzing, and
C.T.Foxton, Phys.Rev.B.55, 6731 (1996).
HL 12.50 Mo 16:30 Poster A
Strong increase of the electron effective mass in GaAs incorporating
boron and indium — •Tino Hofmann 1 , Claas von
Middendorff 1 , Gunnar Leibiger 2 , Volker Gottschalch 2 , and
Mathias Schubert 1 — 1 Fakultät für Physik und Geowissenschaften,
Institut für Experimentelle Physik II, Universität Leipzig, Linnéstraße
5, 04103 Leipzig — 2 Fakultät für Chemie und Mineralogie, Halbleiterchemie,
Universität Leipzig, Linnéstraße 3, 04103 Leipzig
The strain-free boron- and indium-containing GaAs compounds are
promising candidates for novel III-V semiconductor solar cell absorber
materials with lattice match to GaAs, for which experimental data of the
electronic band structure are widely unknown. We employ far-infrared
magnetooptic ellipsometry to determine the electron effective mass in
non-degenerate, silicon-doped, n-type B0.03In0.06Ga0.91As with a electron
concentration ranging from 2·10 17 to ∼ 1 · 10 18 cm −3 and observe a strong
increase of the electron effective mass of 44% in B0.03In0.06Ga0.91As compared
to In0.06Ga0.94As. Further we report on the vibrational lattice mode
behavior of this quaternary alloy. For BAs, an experimentally obscure
compound, the curvature of the same conduction band extrapolates to
the free electron mass.
HL 12.51 Mo 16:30 Poster A
Optical spectroscopy of perovskitic oxynitrides — •M.
Güngerich 1 , P.J. Klar 1 , W. Heimbrodt 1 , A. Jayakar 2 ,
A. Weidenkaff 2 , S. Ebbinghaus 2 , and A. Reller 2 — 1 FB
Physik und WZMW, Philipps-Universität, Marburg — 2 Lehrstuhl für
Festkörperchemie, Universität Augsburg, Augsburg
Substitution of O by N in mixed metal oxide perovskites are possible
candidates for novel colour pigments. Several different oxynitrides with
ABO3 perovskite structure have been synthesized. Raman spectroscopy
was employed to investigate structural changes taking place when annealing
in air or nitrogen atmosphere. For samples annealed in air, Raman
signals from different types of intermediate states occur in the transition
from the oxynitrides to the corresponding oxides depending on the
type of cations in the crystal. In all the investigated compounds N2 entities
in the crystal lattices were identified by a sharp Raman feature
at 2330cm −1 after heating at temperatures ranging from 500 to 800 ◦ C.
Raman spectra of the untreated and of the partially annealed oxynitrides
show significantly broader signals than the oxides after annealing
at approx. 900 ◦ C. A possible explanation is that the crystalline order is
strongly increased after the full transition of the oxynitrides to the oxides.
Reflectance measurements of single crystals were performed to gain
insight into the correlations between band structure changes and visible
colour changes during the transition from oxides to oxynitrides.
HL 12.52 Mo 16:30 Poster A
Controlled fabrication of well-aligned single-crystalline ZnO
nanowires — •Hongjin Fan, Florian M. Kolb, Roland Scholz,
Margit Zacharias, and Ulrich Gösele — Max-Planck-Institute of
Microstructure Physics, Weinberg 2, 06120 Halle, Germany
Fabrication of ZnO nanowires with controlled morphology, size, and
orientation is essential for their applications in room-temperature UV
nanolasers. By using a vapor transport and condensation process based
on vapor-liquid-solid (VLS) mechanism, ZnO nanowire arrays were successfully
synthesized on sapphire substrates. Electron microscopy investigations
show that the nanowires are aligned mainly vertical to the
sapphire substrate, having heights up to 8 µm and diameters of 30–
150 nm. The nanowires were identified to be single-crystalline hexagonal
wurtzite ZnO and unidirectioned along 〈0001〉. They are structurally uniform
without observable dislocations or an amorphous sheath. In order
to tune the diameter and length of the nanowires, the thickness of the
catalyst Au film and growth time were varied respectively. In addition,
when the Au particles on the substrate were predefined, the position
and density of the ZnO nanowire arrays can be subsequently controlled.
Room-temperature photoluminescence measurements show a sharp UV
emission peak near the band gap of ZnO at 3.36 eV, and a very broad
green emission associated with ionized oxygen vacancy defects.
HL 12.53 Mo 16:30 Poster A
Influence of Bi doping upon the phase change characteristics
of Ge2Sb2Te5 — •Ke Wang, Daniel Wamwangi, and Matthias
Wuttig — I. Physikalisches Institut IA, RWTH Aachen, 52056 Aachen
Ge2Sb2Te5 is a material which is commonly used in rewritable optical
data storage. In this recording technology, the Ge-Sb-Te based alloys have
been successfully developed as commercial products for PD and DVD-
RAM applications due to their relatively short erasing time (30 100ns
for Ge-Sb-Te). To ensure the future success of phase change recording
the data transfer rate needs to be improved further. To achieve this goal
faster materials are required. To this end doping of Ge2Sb2Te5 has been
suggested. Here we report on the influence of Bi doping on the speed
of recrystallization (erasing) process, which is the time limiting step in
optical recording. These experiments were performed by using both a
static tester and an atomic force microscope. The evolution of bit topography
and optical reflectivity under the irradiation of the erasing laser
with different pulse duration is presented. For this Bi doped Ge2Sb2Te5
film, ultrafast erasing is demonstrated and a second amorphization phenomenon
is found during the erasing process. This behavior is related to
structural properties and the activation barrier for the structure transi-

Halbleiterphysik Montag
tion in this material. Acknowledgement One of the authors (K. Wang)
would like to thank the Alexander von Humboldt Foundation for the
fellowship.
HL 12.54 Mo 16:30 Poster A
Controlled growth of zinc oxide nano-pillars with a vapor-solidliquid
process — •Anton Reiser, Andreas Ladenburger, Xinmin
Cao, Uwe Röder, Rolf Sauer, and Klaus Thonke — Abt.
Halbleiterphysik, Universität Ulm, D-89069 Ulm
We have produced ordered zinc oxide nano-pillars using a vapor-liquidsolid
process [1]. A-plane sapphire substrates were covered with regularly
arranged gold particles in different ways via self-organizing processes.
The gold particles act as catalysts in the high temperature growth of the
zinc oxide pillars. Depending on the process parameters we generated
pillars with diameters from 30 nm to 2 µm and heights from 500 nm to
several micrometers. The created nano-structures were investigated by
scanning electron microscopy, X-ray diffraction and photoluminescence
spectroscopy revealing excellent crystalline material quality.
[1] M. H. Huang et al, Science 292 (2001), 1897
HL 12.55 Mo 16:30 Poster A
Regular silicon nano-pillars with high aspect ratios etched via
self-organizing nano-porous polymer masks — •Andreas Ladenburger
1 , Anton Reiser 1 , Feng Yan 2 , Johannes Konle 1 , Werner
A. Goedel 2 , Rolf Sauer 1 , and Klaus Thonke 1 — 1 Abt. Halbleiterphysik,
Universität Ulm, D-89069 Ulm — 2 Abt. Organische Chemie III,
Universität Ulm, D-89069 Ulm
We have produced regular silicon pillars with high aspect ratios on the
nanometer scale. In the process, first a nano-porous membrane defined by
the imprints of self-organizing colloidal particles was created on a silicon
wafer. Due to the self-organization the nano-pores form an array with
hexagonal ordering. Then a gold film was deposited on the structure and
the polymer membrane was removed. The remaining regular pattern of
gold disks was used as a mask in a deep reactive ion etching process. The
produced nano-pillars are 1.4 µm high and they have diameters less than
200 nm. As a by-product in the creation of the gold mask we obtained a
regular gold grid, which can be applied as an optical short pass filter.
HL 12.56 Mo 16:30 Poster A
Conductance spectroscopy of an AFM-engraved quantum
point contact — •B. Harke 1 , C. Fricke 1 , F. Hohls 1 , R.
J. Haug 1 , D. Reuter 2 , and A. D. Wieck 2 — 1 Institut für
Festkörperphysik, Abteilung Nanostrukturen, Universität Hannover,
Appelstr. 2, 30167 Hannover, Germany — 2 Lehrstuhl für angewandte
Physik, Ruhr-Universität Bochum, 44780 Bochum, Germany
We used the mechanical Atomic Force Microscope (AFM) lithography
to write insulating trenches in a two dimensional electron gas (2DEG) realized
by a GaAs/AlGaAs-heterostructure. To get insulated areas in the
2DEG which is located about 50 nm below the surface we wrote 10 nm
deep lines to deplete the 2DEG underneath the trench. We achieved isolating
lines with a breakdown voltage of at least 20V. For this lithography
we used a diamond tip for precise structuring of a quantum point contact
with the width of 500nm. Our characterization measurements show
distinct quantization of the conductivity in dependence of gatevoltage as
expected. Furthermore we show conductance spectroscopy measurements
for different magnetic fields. We observe a pronounced 0.7 anomaly which
was analyzed in dependence of magnetic field up to 15 Tesla and temperature
between 1.5 K and 10 K.
HL 12.57 Mo 16:30 Poster A
The manipulation of the energy levels in InAs-quantum dots
by thermal treatment — •Victorina Stavarache, Dirk Reuter,
and Andreas Wieck — Lehrstuhl für Angewandte Festkörperphysik,
Ruhr-Universität Bochum, Bochum, Germany
We have investigated the effect of thermal treatment on QD samples
by photoluminiscence (PL) measurements. The sample structure contains
10 QD layers separated by 100nm GaAs. The QDs have been grown by
MBE on a semi-insulating GaAs(100) substrate. After growth, the 4x4
samples were cleaved and annealed for 30s at temperatures from 800 o C
to 960 o C using a rapid thermal annealing system. With increasing annealing
temperature, the PL peaks show a shift to smaller wavelength.
Simultaneously, the energy separation between adjacent peaks becomes
smaller. These observation point to an increase of the energy difference
between electron and hole levels (from E=1,054eV for unannealed sample
to E=1,389eV for an annealing temperature of 960 o C) whereas the
intersublevel spacing decreases (from ∆E=52,7meV for unannealed sample
to ∆E=17,3meV for an annealing temperature of 960 o C). We explain
this blueshift due to the diffusion of the Ga atoms into the QD and the
out diffusion of the In atoms from the QD during the thermal annealing
process.
HL 12.58 Mo 16:30 Poster A
Chemical Vapour Deposition of Silicon Nanowires — •Volker
Schmidt, Stephan Senz, and Ulrich Goesele — Max Planck Institut
für Mikrostrukturphysik, 06120 Halle
Silicon nanowires are synthesized by chemical vapour deposition in
ultra high vacuum environment via the vapour-liquid-solid growth mechanism.
For this process silane is used as the precursor gas and gold dots
act as catalysts. The diameter of a single nanowire is determined by the
size of the gold particle. We investigate by scanning electron microscopy
and transmission electron microscopy the quality of the epitaxial growth
of the nanowires on silicon substrates of different orientation ((100) and
(111)). The effects of substrate temperature and silane partial pressure
on the growth of the nanowires are analyzed. We also investigate the
influence of a 2.45 GHz microwave plasma on the synthesis of the silicon
nanowires. The minimum substrate temperature is reduced and some of
the nanowires change their growth direction.
HL 12.59 Mo 16:30 Poster A
Investigation of Experimentally Observed InAs Quantum Dots
with an Analytical Bond-Order Potential — •Thomas Hammerschmidt
and Peter Kratzer — Fritz-Haber-Institut der Max-Planck-
Gesellschaft, Faradayweg 4-6, 14195 Berlin
A thorough understanding of the experimentally observed shape of
InAs quantum dots (QD) calls for non-equilibrium simulations that take
kinetic growth-effects into account. The modeling of such effects requires
large system sizes and long simulation times.
We address this issue with a new analytical bond-order potential of
the Abell-Tersoff type for InGaAs that was derived from previously published
potentials. We optimized the new potential for reconstructions of
the GaAs (001) surface with preserving the previous adoptions to GaAs
bulk phases. Furthermore, we adjusted the potential to capture different
In and InAs bulk phases, as well as InAs surfaces, more accurately.
With the new potential we determined the potential energy surface
and various diffusion barriers on high-index surfaces and compare with
density functional calculations. Additionally we relaxed uncapped InAs
QD in different experimentally observed shapes and investigate strain
effects.
HL 12.60 Mo 16:30 Poster A
Resonant tunneling through self organized InAs Quantum
dots — •T. Lüdtke 1 , F. Hohls 1 , R. J. Haug 1 , and K. Pierz 2
— 1 Universität Hannover, Germany, Solid State Physics, Department
Nanostructures — 2 Physikalisch-Technische Bundesanstalt
Braunschweig
The aim of our work was to do electron transport measurements on
resonant tunnelling devices containing only a few Quantum Dots (QD).
The sample is an GaAs/AlAs/GaAs tunnelling diode containing one layer
and in another one a double layer of self-organized InAs QD’s (1.5 - 2
ML) embedded in the AlAs barrier which lies about 1µm above the top.
The diodes with dimension of a about 50µm down to a few micrometers
were defined by electron beam lithography (EBL). The interesting problem
of contacting the small diodes to a bonding wire was solved with a
polyimide (PI) layer surrounding the mesa. Then a hole above the diode
is defined by EBL, and wet etching through the PI layer gave the opportunity
to connect the diode to a top contact of about 80µm. Temperature
dependent characterization measurements down to 1.5 K as well as magnetic
field variations were realized to study Coulomb Blockade, tunnel
coupling in double QD’s and to calculate g-Factors.
HL 12.61 Mo 16:30 Poster A
Capacitance-voltage (CV) measurements on a InAs quantum
dot ensemble and on single InAs quantum dots embedded in a
GaAs matrix — •Heidemarie Schmidt 1 , Stefan Jaensch 1 , Gerald
Wagner 2 , and Marius Grundmann 1 — 1 Universität Leipzig,
Fakultät für Physik und Geowissenschaften — 2 Institut für Nichtklassische
Chemie an der Universität Leipzig
Using Stranski-Krastanov growth mode, self-assembled InAs quantum
dots (QD) have been incorporated at 485 ◦ C in n-type GaAs grown by
MBE on (100)-GaAs n + -substrates. A typical dot diameter of 11.4 ± 2

Halbleiterphysik Montag
nm and a dot density of 8×10 10 cm −2 with a mean dot distance of ca. 40
nm was deduced from transmission electron microscopy. The InAs wetting
layer thickness amounts to one monolayer. Temperature dependent
CV measurements using Au-Schottky contacts with an area of 10 −3 cm 2
that cover an ensemble of 10 8 QD, show a plateau in the bias region from
-2 V to -5 V. That CV plateau is due to charge carrier accumulation
at the position of the QD and wetting layer. Scanning capacitance microscopy
(SCM) allows for CV measurements at room temperature on
the 25-50 nm conductive tip diameter scale, and will be compared to the
CV experiments on large ensembles.
HL 12.62 Mo 16:30 Poster A
Ordering and strain in lateral InAs quantum dot molecules —
•B. Krause 1 , T. H. Metzger 1 , R. Songmuang 2 , A. Rastelli 2 ,
and O. G. Schmidt 2 — 1 European Synchrotron Radiation Facility,
BP 220, F-38043 Grenoble Cedex, France — 2 Max-Planck-Institut für
Festkörperforschung, Heisenbergstraße 1, D-70569 Stuttgart, Germany
Lateral quantum dot molecules are ordered arrangements of several
quantum dots placed one near the other. For InGaAs and InAs on
GaAs(100), it has been shown that they can be produced by molecular
beam epitaxy exploiting a self-organization process: the quantum
dots nucleate preferentially around nanoholes in the substrate [1,2]. The
number of quantum dots forming one molecule can be controlled by the
substrate temperature.
The growth of the quantum dot molecules results from a combination
of kinetic and energetic effects including surface diffusion, strain and interdiffusion
in the quantum dots. Here, the results of x-ray diffraction
experiments are presented giving insight into the shape, the size, the
strain, and the ordering of the quantum dot molecules. This information
is necessary for the understanding of the formation process of the dot
molecules.
[1] O. G. Schmidt et al., IEEE J. Sel. Top. Quantum electorn 8, 1025
(2002)
[2] R. Songmuang et al., Appl. Phys. Lett. 82, 2892 (2003)
HL 12.63 Mo 16:30 Poster A
Observation of aligned and self-assembled InAs quantum dots
on a cleaved (110) GaAs surface — •R. Schulz, E. Uccelli,
J. Bauer, D. Schuh, M. Bichler und G. Abstreiter — Walter
Schottky Institut, Technische Universität München, Am Coulombwall 3,
D-85748 Garching
We report on a new approach for the spatial self-aligning of InAs quantum
dots at well defined positions on a (110) GaAs surface. In contrast
to other attempts [1-3] our method requires no lithografic processes but
uses molecular beam epitaxy (MBE) itself for generating the template.
By MBE on (001)GaAs, we have fabricated a GaAs/AlAs superlattice
with different periods. Using the cleaved edge overgrowth technique
(CEO), we obtain a smooth (110) surface with alternating GaAs and
AlAs-layers in (001)-direction. After deposition of InAs on this surface,
we observe the formation of InAs quantum dots. These are well aligned
along the AlAs layers. The structural properties of these quantum dots
have been investigated by AFM for different growth temperatures, different
coverages of InAs, and different superlattice periods.
[1] R. Songmuang, S. Kiravittaya, O. G. Schmidt, Appl. Phys. Lett.
82(17)2892 (2003)
[2] H. Lee, J. A. Johnson, J. S. Speck, P. M. Petroff, J. Vac. Sci. Technol.
B 18(4)2193 (2000)
[3] T. Mano, R. Nötzel, G. J. Hamhuis, Z.J. Eijkemans, J. H. Wolter
Appl. Phys. Lett. 81(9)1705 (2002)
HL 12.64 Mo 16:30 Poster A
Präparation und elektrische Charakterisierung von Quantendrähten
in modulationsdotierten Si/SiGe-Heterostrukturen —
•Sorin Poenariu 1 , Ulrich Wieser 1 , Ulrich Kunze 1 , Thomas
Hackbarth 2 und Ulf König 2 — 1 Werkstoffe und Nanoelektronik,
Ruhr-Universität Bochum, D-44780 Bochum — 2 DaimlerChrysler Forschungszentrum
Ulm, Wilhelm-Runge-Strasse 11, D-89081 Ulm
Es wird ein schädigungsarmes Verfahren zur Präparation von Quantendrähten
in modulationsdotierten Si/SiGe-Heterostrukturen vorgestellt.
Die Drähte werden zunächst durch Niederenergie-Elektronenstrahllithografie
definiert. Als hochauflösenden Negativresist verwenden
wir eine 1 %-ige Lösung von Calixarene. Durch Bestrahlung bei 2 kV wird
der Proximity-Effekt gering gehalten. Anschließend wird in einem Mixand-Match
Verfahren die Mesastruktur des Transistors mit konventioneller
UV-Lithografie ergänzt. Die so definierten Resiststrukturen werden
gemeinsam in einem schädigungsarmen Trockenätzschritt unter CF4/O2-
Plasma in die Heterostruktur übertragen. Mit diesem Verfahren werden
Quantendrähte mit einer minimalen Breite von etwa 50 nm und einer
Länge bis 1 µm realisiert. Die über eine Topgate-Elektrode steuerbaren
Quantendrähte werden durch Messung der Strom-Spannungs-Kennlinien
und des differentiallen Leitwerts bei 4.2 K charakterisiert.
HL 12.65 Mo 16:30 Poster A
Kinetic Monte Carlo simulations of quantum dot stacks —
•Roland Kunert and Eckehard Schöll — Institut für Theoretische
Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin
By means of kinetic Monte Carlo simulations the growth of semiconductor
nanostructures consisting of quantum dot stacks is investigated
[1].
The key ingredient in the simulations is the anisotropic strain field
induced by the lattice mismatch. It is computed in the framework of
elasticity theory and only the material dependent elastic constants enter
as input parameters.
Here, a hybrid method is chosen where the growth of the quantum
dot fundaments is simulated by Monte Carlo and the resulting threedimensional
strain field of these dots is incorporated self-consistently in
the growth simulations of the following layers.
[1] M. Meixner, and E. Schöll: Phys. Rev. B 67, 121202 (2003)
HL 12.66 Mo 16:30 Poster A
Monolithic cantilever magnetometers with integrated quantum
wires — •J.I. Springborn, M.A. Wilde, O. Rösler, M.P.
Schwarz, Ch. Heyn, D. Heitmann, and D. Grundler — Institut
für Angewandte Physik, Universität Hamburg, Jungiusstraße 11, 20355
Hamburg
The magnetization M is a fundamental thermodynamic quantity and
monitors the change of the ground state energy U of an electron system
in a magnetic field B. We are in particular interested in the ground state
energy of confined and interacting electrons. For this, we have developed
highly sensitive micromechanical cantilever magnetometers which
incorporate the nanostructured electron systems [1]. Here, we discuss
quantum wires which are prepared of modulation-doped AlGaAs/GaAsheterostructures
by means of laser-interference lithography and reactiveion
etching. The smallest quantum-wire width is 200 nm where only a few
one-dimensional subbands are occupied. Magnetization data are obtained
at low temperatures down to 270 mK and in fields B up to 16 T. We
find de Haas-van Alphen like oscillations of M. They directly reflect the
effect on U of both, the confinement potential and the electron-electron
interaction in a one-dimensional electron system.
We are grateful for being supported by the Deutsche Forschungsgemeinschaft
via “SFB 508” and “Gr1640/1-2” in the “Schwerpunktprogramm
Quanten-Hall Systeme”.
[1] M.P. Schwarz, D. Grundler, M. Wilde, Ch. Heyn, and D. Heitmann,
J. Appl. Phys. 91, 6875 (2002).
HL 12.67 Mo 16:30 Poster A
Einfluß von Hintergrundladungen auf das elektrische Verhalten
von Poly-Silizium Einzelelektron-Transistoren — •Michael
Skender und Dieter P. Kern — Institut für Angewandte Physik,
Auf der Morgenstelle 10, 72076 Tübingen
Einzelelektron-Transistoren (SETs) werden auf ihre Einsatzmöglichkeiten
in Logikschaltungen und Speicherelementen
untersucht. Hierbei ist die Empfindlichkeit der Funktion dieser
Strukturen auf Hintergrundladungen eine immer wieder auftretende
Frage.
Zur Untersuchung dieser Fragestellung wurden SET-Strukturen auf
SOI-Basis hergestellt und im Tieftemperatur-Rasterelektronenmikroskop
(TTREM) untersucht.
Auf thermisch oxidierten Si-Wafern wird LPCVD-Poly-Silizium abgeschieden.
Mittels Elektronenstrahllithographie und Reaktivem Ionen-
Ätzen wird die SET-Struktur in die Poly-Si-Schicht übertragen und anschließend
mittels Oxidation verkleinert.
Im TTREM werden mit definierten Elektronenpulsen Elektronen gezielt
in der Nähe des Quantenpunktes plaziert, und die daraus resultierenden
Änderungen der elektrischen Eigenschaften des SETs detektiert
und analysiert.

Halbleiterphysik Montag
HL 12.68 Mo 16:30 Poster A
Optische Charakterisierung von ZnO:P- und ZnO:Li,N-PLD-
Dünnfilmen — •Susanne Heitsch, Carsten Bundesmann, Evgeni
M. Kaidashev, Holger von Wenckstern, Daniel Spemann,
Mathias Schubert, Gabriele Benndorf, Michael Lorenz und
Marius Grundmann — Universität Leipzig, Fakultät für Physik und
Geowissenschaften, Institut für experimentelle Physik II, Linnéstr. 5, D-
04103 Leipzig
ZnO-Dünnfilme dotiert mit Phosphor bzw. Lithium und Stickstoff wurden
auf Saphir mittels Pulsed Laser Deposition (PLD) abgeschieden.
Photolumineszenz-Spektren (2 K) weisen teilweise neue, meist breite
Bänder im UV- Bereich auf. Bei den ZnO:Li,N-Filmen konnte ein
Donator-Akzeptor-Übergang beobachtet werden, in dem möglicherweise
N als Akzeptor fungiert. Zusätzlich zeigen diese Filme Lumineszenz im
grünen Spektralbereich, während man bei den P-dotierten Proben ein
Lumineszenzband im roten Bereich findet, welches ein Hinweis auf Kristalldefekte
sein kann.
Infrarot-spektroskopische Ellipsometrie-Untersuchungen zeigen stark
verbreiterte Phononenmoden besonders bei den ZnO:P-Filmen, während
Ramanspektren zusätzliche Moden enthalten, deren Ursprung im Einbau
der Dotieratome oder in Fehlern der Kristallstruktur liegt.
HL 12.69 Mo 16:30 Poster A
MgxZn1−xO-Mischkristalle für UV-Bragg-Reflektoren — •Anke
Carstens, Rüdiger Schmidt-Grund, Holger Hochmuth, Bernd
Rheinländer, Daniel Spemann, Andreas Rahm, Michael Lorenz
und Marius Grundmann — Universität Leipzig , Fakultät für
Physik und Geowissenschaften, Institut für Experimentelle Physik II,
Linnéstr. 5, 04103 Leipzig
Für optoelektronische Bauelemente mit optischen Resonatoren auf der
Basis von ZnO werden UV-Bragg-Reflektoren benötigt. Das Mischkristallsystem
MgxZn1−xO ist dafür gut geeignet. Es wurden MgxZn1−xO-
Einzelschichten mit x = (0...1) auf c-orientierten Saphir-Substraten mittels
PLD (pulsed-laser-deposition) mit Dicken im Bereich (100...400) nm
abgeschieden. Der Brechungsindex für die Schichtmaterialien wurde im
Spektralbereich (0,75...4,50) eV mittels spektroskopischer Ellipsometrie
durch Anpassung an ein Cauchy-Modell bestimmt. Berücksichtigt man
die x-Abhängigkeit der fundamentalen Absorptionskante [1], dann kommt
für UV-Bragg-Reflektoren der x-Bereich von 0,2 bis 1,0 in Frage. Dazu
gehören Schichten mit wurtzitischer und kubischer Struktur. Da unsere
Untersuchungen gezeigt haben, dass sich eine abwechselnde Folge von
wurtzitischen und kubischen Schichten abscheiden lässt, erlauben die
Brechungsindices die Herstellung von Bragg-Reflektoren für eine zentrale
Photonenenergie von ca. 3,4 eV mit 15 bis 25 Schichtpaaren, um ein
maximales Reflexionsvermögen über 0,9 zu erreichen.
[1] R. Schmidt, B. Rheinländer, M. Schubert, D. Spemann, T. Butz,
J. Lenzner, E. M. Kaidashev, M. Lorenz, H. C. Semmelhack, and M.
Grundmann, Appl. Phys. Lett. 82, 2260 (2003)
HL 12.70 Mo 16:30 Poster A
Energy transfer from band states into the Mn 3d 5 shell of
(Zn,Mn)S nanowires — •J. Kampmann 1 , L. Chen 1 , P.J. Klar 1 ,
W. Heimbrodt 1 , F.J. Brieler 2 , and M. Fröba 2 — 1 FB Physik und
WZMW, Philipps-Universität, Marburg — 2 Institut für Anorganische
and Analytische Chemie, Justus-Liebig Universität, Gießen
The energy transfer from the band states into the Mn 3d 5 shell in
(II,Mn)VI wide-gap diluted magnetic semiconductors is a well known
feature of the bulk compounds. As a result the luminescence properties
of these materials are dominated by the yellow luminescence band of the
lowest transition in the Mn 3d 5 shell between the 4 T1 (S = 3/2) first
excited state to the 6 A1 (S = 5/2) ground state. The energy transfer
between the two subsystems, extended band states and Mn 3d 5 shell, is
a Dexter-Förster like process. The mechanisms for overcoming the violation
of the spin selection rule ∆S = 0 are still under debate. We present
first studies of the luminescence and transfer dynamics of the yellow Mnluminescence
in Zn1−xMnxS nanowires with diameters ranging from 3 to
9nm and x between 0.01 and 0.3.
HL 12.71 Mo 16:30 Poster A
A novel high-pressure pulsed laser deposition process for ZnO
nanostructures — •E. M. Kaidashev, M. Lorenz, H. Hochmuth,
D. Natusch, T. Nobis, A. Rahm, J. Lenzner, and M. Grundmann
— Universität Leipzig, Fakultät für Physik und Geowissenschaften,
Linnéstr. 5, D-04103 Leipzig, Germany
According to a schematic proposal of Lieber et al. [1], a novel Pulsed
Laser Deposition (PLD) process for the controlled growth of ZnO nanostructures
has been established. By means of an KrF excimer laser a
sintered pure ZnO target is ablated in a high pressure (100 mbar) Ar gas
stream. Well aligned ZnO micro- and nanocrystalline structures grow at
temperature around 900 ◦ C on thin gold template films on a-plane sapphire
substrates. The main advantages of this novel PLD process are the
absence of graphite in the source target which is used in the carbothermal
growth as reducing agent, and the ability to grow in-situ nanoheterostructures
simply by changing the laser targets. The free standing
ZnO nanostructures with diameter from 0.1 to 3 µm and length up to
100 µm selectively grown on the gold coated areas of the substrate show
well established hexagonal facets. Cathodoluminescence of single selected
micro- and nanocrystals at 300 K demonstrates intensive ultraviolet emission
around 3.25 eV and very weak (factor 10 −3 ) green emission around
2.3 eV. This indicates a high structural quality of the as-grown ZnO
microcrystals. Scanning cathodoluminescence imaging is used to characterize
the homogeneity of PLD grown nanowire arrays.
Supported by the DFG within FOR 522, project P1 (Gr 1011/1-1).
[1] A. M. Morales, C. M. Lieber, Science 279 (1998) 208.
HL 12.72 Mo 16:30 Poster A
Selective area growth of self-organized ZnSe structures on
patterned GaAs with SiO2, Si3N4 or carbonaceous masks by
molecular-beam epitaxy — •J. Lupaca-Schomber 1 , B. Daniel 1 ,
M. Hetterich 1 , P. Pfundstein 2 , and D. Gerthsen 2 — 1 Institut für
Angewandte Physik and Center for Functional Nanostructures (CFN),
Universität Karlsruhe, D-76131 Karlsruhe, Germany — 2 Laboratorium
für Elektronenmikroskopie and CFN, Universität Karlsruhe, D-76128,
Germany
We describe the selective area growth of self-organized ZnSe structures
on patterned GaAs (001) surfaces. Growth was performed by molecularbeam
epitaxy (MBE) on masked GaAs substrates at temperatures ranging
from 280 ◦ C to 340 ◦ C. The mask consisted of either carbon, SiO2 or
Si3N4. The carbonaceous mask deposition was achieved by electron-beam
irradiation in a scanning electron microscope, the other mask types were
prepared by electron beam lithography. The same pattern was used for
all masks, namely a periodical arrangement of square areas with sizes
from 0.5 × 0.5 µm 2 to 1.5 × 1.5 µm 2 . To assess the grown structures we
used optical and scanning electron microscopy (SEM) as well as atomic
force microscopy (AFM).
HL 12.73 Mo 16:30 Poster A
High luminescence yield of N-doped ZnO thin films on sapphire
grown by PLD — •M. Lorenz 1 , H. Hochmuth 1 , J. Lenzner 1 ,
G. Benndorf 1 , H. von Wenckstern 1 , A. Rahm 1 , A. Schön 2 , S.
Borenstain 2 , and M. Grundmann 1 — 1 Universität Leipzig, Fakultät
für Physik und Geowissenschaften, Linnéstr. 5, 04103 Leipzig, Germany
— 2 El-Mul Technologies Ltd., Soreq, Yavne 81104, Israel
Pulsed Laser Deposition (PLD) has proved to be a highly flexible technique
for the epitaxy of high-quality ZnO thin films on c-, and a-plane
sapphire substrates. A remarkable improvement of cathodoluminescence
intensity at room temperature and homogeneous luminescence across the
substrate (typically 10x10 mm 2 , presently up to 2”) were achieved for
heavily N-doped ZnO thin films with MgO buffer layer in comparison to
nominally undoped ZnO. The N-doping level of the ZnO films was controlled
by the N2 partial pressure during PLD growth. Clear correlation
of maximum luminescence efficiency, and FWHM of excitonic emission
peak at 300K to the nitrogen doping level was found. The N-doped ZnO
films with highest luminescence intensity show n-type carrier concentration
around 10 19 cm −3 .
Supported by BMBF within Wachstumskern INNOCIS (03WKI09)
and DFG (SPP 1136 and FOR 522).
HL 12.74 Mo 16:30 Poster A
Growth studies and n-type doping of Zn1−xMnxSe semimagnetic
heterostructures — •B. Daniel 1 , P. Baumann 1 , K.C. Agarwal 1 ,
C. Klingshirn 1 , M. Hetterich 1 , D. Litvinov 2 , P. Pfundstein 2 ,
and D. Gerthsen 2 — 1 Institut für Angewandte Physik and Center
for Functional Nanostructures (CFN), Universität Karlsruhe, D-76131
Karlsruhe, Germany — 2 Laboratorium für Elektronenmikroskopie and
CFN, Universität Karlsruhe, D-76128 Karlsruhe, Germany
Zn1−xMnxSe - either as an alloy or as a short-period ZnSe/MnSe superlattice
- exhibits interesting magnetic and magneto-optical phenomena.
In particular it has recently been demonstrated to be useful as a
spin aligner, an important ingredient for a future spin-based electron-

Halbleiterphysik Montag
ics. In this contribution we investigate the growth of these materials by
molecular-beam epitaxy. In situ RHEED measurements of the in-plane
lattice parameter are used to monitor the elastic and plastic strain relaxation
in thin MnSe layers deposited on top of ZnSe. Additionally, transmission
electron microscopy of samples containing several MnSe layers
with increasing thickness is used in order to determine the critical thickness
for MnSe/ZnSe. Finally, we have fabricated n-doped Zn1−xMnxSe:Cl
material with various compositions. The grown epilayers are characterized
electrically by Hall measurements in the van der Pauw geometry
and optically by infrared reflection spectroscopy carried out in a Fourier
transform spectrometer.
HL 12.75 Mo 16:30 Poster A
Bestimmung des effektiven Mn-Gehalts und der Landé-
Faktoren von semimagnetischen Zn1−xMnxSe Schichten —
•Daniel Tröndle, Hendrik Burger, Wolfgang Löffler,
Bruno Daniel, Michael Hetterich, Elena Tsitsishvili und
Heinz Kalt — Institut für Angewandte Physik, Wolfgang-Gaede-Str.1,
76128 Karlsruhe
Das semimagnetische Halbleitermaterial ZnMnSe spielt in der aktuellen
Forschung im Bereich Spintronic eine bedeutende Rolle als Spinaligner.
Im Magnetfeld zeigen Leitungs- und Valenzband aufgrund von sd-
bzw. p-d-Austauschwechselwirkung eine erhebliche Aufspaltung, durch
die sich spinpolarisierte Ladungsträger in Nanostrukturen wie z.B. Quantenpunkte
injizieren lassen.
Wir haben verschiedene Zn1−xMnxSe-Schichten mit einem Mangangehalt
x von 0 bis 0.28 mit MBE gewachsen und daran Photolumineszenz
in Abhängigkeit vom Magnetfeld (0-14T) sowie der Temperatur (4-77K)
gemessen. Daraus bestimmen wir den effektiven Mn-Gehalt sowie die
effektiven Landé-Faktoren.
Bis ca. x = 0.15 steigt die Magnetisierung mit zunehmender Mn-
Konzentration an, bei höherem Gehalt sinkt sie wieder. Dies ist auf die
antiferromagnetische Kopplung benachbarter Mn-Ionen zurückzuführen,
die mit zunehmender Konzentration Cluster bilden und nicht mehr zur
Erhöhung der Magnetisierung beitragen. Als effektive Landé-Faktoren
ergeben sich Werte von g ≫ 10 bei T = 4 K und B = 0 T , die für
steigende Temperaturen und Magnetfelder deutlich abnehmen. Die Werte
sind jeweils in guter Übereinstimmung mit theoretischen Rechnungen.
HL 12.76 Mo 16:30 Poster A
Composition-dependent structural and optical material parameters
of Zn1−xMnxSe epilayers grown by molecular-beam epitaxy
— •M. Hetterich 1 , B. Daniel 1 , P. Baumann 1 , C. Klingshirn
1 , P. Pfundstein 2 , D. Litvinov 2 , D. Gerthsen 2 , K. Eichhorn
3 , and D. Spemann 4 — 1 Institut für Angewandte Physik and
Center for Functional Nanostructures (CFN), Universität Karlsruhe,
D-76131 Karlsruhe — 2 Laboratorium für Elektronenmikroskopie and
CFN, Universität Karlsruhe — 3 Institut für Kristallographie, Universität
Karlsruhe — 4 Fakultät für Physik und Geowissenschaften, Universität
Leipzig, D-04103 Leipzig
Zn1−xMnxSe has recently been demonstrated to be useful as a spin
aligner, an important ingredient for a possible spin-based electronics. We
investigate cubic Zn1−xMnxSe epilayers grown by MBE on GaAs(001).
The film quality is assessed by transmission electron microscopy. To determine
the Mn concentration, RBS, PIXE and EDX are used. ZnSe and
short-period ZnSe/MnSe superlattices serve as a reference for the careful
calibration of the EDX system, because the average composition of
such pseudoalloys can easily be determined by measuring the individual
layer thicknesses through RHEED oscillations. In the next step we determine
the elastic constants of Zn1−xMnxSe and measure the concentrationdependent
lattice parameter using X-ray diffraction. Finally, low temperature
absorption, photoluminescence (PL), reflectance and PL excitation
spectroscopy (PLE) are applied to learn more about the influence of Mn
on the Zn1−xMnxSe band gap as well as the exciton binding energy.
HL 12.77 Mo 16:30 Poster A
Preparation of Mn-doped ZnO thin films for spintronics —
•Erick Guzmán, Holger Hochmuth, Michael Lorenz, Daniel
Spemann, Holger von Wenckstern, Rüdiger Schmidt-Grund,
Peter Busch, Annette Setzer, Pablo Esquinazi, Heidemarie
Schmidt, and Marius Grundmann — Universität Leipzig, Fakultät
für Physik und Geowissenschaften
Room temperature ferromagnetism has been theoretically predicted
in p-type Mn-doped ZnO [1]. We have grown Mn-doped ZnO thin films
on c-plane sapphire substrates by pulsed laser deposition (PLD). The
first target was prepared from ZnO and MnO powders above 1000 ◦ C.
The structural, electrical, and magnetical thin film properties have been
determined by RBS, AFM, ellipsometry, Hall, SQUID, and MFM. The
Mn concentration amounts to 4% and is higher than that of the target
(nominally 3%). All investigated films are strongly compensated (n ≤
10 16 cm −3 ) with respect to undoped, naturally n-type ZnO thin films. At
10 K the saturation magnetization of one of those Mn-doped ZnO thin
films amounts to 0.018 emu/g, i.e., 0.006 µB/Mn-site, whereas at room
temperature no significant ferromagnetic contribution was observed. Encouraged
by [2], we prepared another target from ZnO and MnO2 powders,
at temperatures below 500 ◦ C. In that way the dependence of the
magnetic behaviour in Mn-doped ZnO on charge carrier compensation
and Mn clustering can be discussed comparing the two different sample
series.
[1] T. Dietl et al.,Science 287 (2000) 1019.
[2] K. V. Rao et al., Nature Materials 2 (2003) 673.
HL 12.78 Mo 16:30 Poster A
Nitrogen doping of ZnO and post-growth rapid thermal annealing
— •Nikolay Oleynik 1 , Armin Dadgar 1 , Daniel Forster 1 ,
Frank Bertram 1 , Jürgen Bläsing 1 , Andre Krtschil 1 , Annette
Diez 1 , Thomas Hempel 1 , Karsten Fehse 1 , Jürgen Christen 1 ,
Alois Krost 1 , Markus Seip 2 , and Arnd Greiling 2 — 1 Otto-von-
Guericke University Magdeburg IEP, FNW, Postfach 4120, 39016 Magdeburg,
Germany — 2 mochem GmbH, Marburg, Germany
Nitrogen doping is a promising way to achieve p-type doping of ZnO
layers. We have systematically investigated MOVPE grown N-doped ZnO
layers. For N doping we have used NH3, NO or UDMHy as precursors.
ZnO layers were grown using a two step growth procedure on GaN on
Sapphire templates starting with a low-temperature buffer layer on which
a high-temperature ZnO layer is grown using N2O and DMZn at 750 -
1050 ◦ C. The UDMHy flows were varied from 0-150 sccm, and NO flows
were varied from 0-750 sccm. We observe a brownish color of the ZnO
layers either at low growth temperature or high UDMHy or NH3 flows.
Upon annealing under O2 ambient at 800-900 ◦ C the color is bleached out.
No change in color was observed for NO-doped ZnO. We will report on
structural, morphological, optical and electrical properties of the films.
HL 12.79 Mo 16:30 Poster A
Zeitaufgelöste Spektroskopie von ZnO - Epitaxieschichten
— •Robert Hauschild 1 , Heiko Priller 1 , Thomas Gruber 2 ,
Christoph Kirchner 2 , Andreas Waag 3 , Claus Klingshirn 1
und Heinz Kalt 1 — 1 Institut für Angewandte Physik der Universität
Karlsruhe (TH), Wolfgang-Gaede Str. 1, 76131 Karlsruhe — 2 Abteilung
Halbleiterphysik, Universität Ulm, Albert Einstein Allee 45, 89081 Ulm
— 3 Institut für Halbleitertechnik, TU Braunschweig, Hans Sommer Str.
66, 38106 Braunschweig
Für auf ZnO basierende optoelektronische Anwendungen im ultravioletten
Spektralbereich ist die Untersuchung der Relaxationsdynamik von
Exzitonen relevant. Hierzu wird als Anregungsquelle ein frequenzverdreifachter
Ti:Sa-Laser mit einer Leistung von bis zu 12 mW bei einer Anregungswellenlänge
im Bereich von 280 nm verwendet. Wir erreichen eine
Zeitauflösung von 5 ps durch eine Anregung mit Femtosekunden - Pulsen
kombiniert mit der Detektion durch eine Synchroscan - Streakkamera,
die an ein Spektrometer angekoppelt ist. In Abhängigkeit der Temperatur
und der Anregungsintensität werden zeitaufgelöste Spektren von
ZnO - Epitaxieschichten, ZnO/ZnMgO - Quantenfilmen und ZnO - Nanorods
vorgestellt. Der Einfluss von nichtlinearen Effekten, wie Exziton
- Exziton - Streuung und die Bildung von Biexzitonen, wird diskutiert.
HL 12.80 Mo 16:30 Poster A
Temperaturverlauf der Bandlücke von ZnO bei hohen Temperaturen
— •Jan Brückner, Heiko Priller, Claus Klingshirn
und Heinz Kalt — Institut für Angewandte Physik der Universität
Karlsruhe (TH), Wolfgang-Gaede Str. 1, 76131 Karlsruhe
Zur Bestimmung der Bandlücknenenergie wurden an einer ZnO-
Epitaxieschicht Transmissionsmessungen im Temperaturbereich von 10 K
bis 800 K durchgeführt. Dazu wurde das Licht einer Xenonlampe auf die
sich in einem Ofen bzw. in einem Kryostaten befindende Probe fokussiert
und das transmittierte Licht mit Hilfe eines Doppelmonochromators
mit aufmontiertem Photomultiplier detektiert. Aus den gewonnenen
Spektren läßt sich zu jeder Temperatur eine untere Grenze für die
Bandlückenenergie angeben. Zusätzlich wurde durch Photolumineszenzmessungen,
wobei ein He-Cd-Laser mit einer Wellenlänge von 325 nm als

Halbleiterphysik Montag
Anregungsquelle diente, die Position des freien A-Exzitons im Bereich
von 10 K bis Raumtemperatur bestimmt. Ein Vergleich dieser Daten
zeigt eine gute Übereinstimmung der Temperaturverläufe. Mit Hilfe unserer
Messungen werden wir verschiedene Modelle zur Beschreibung der
Temperaturabhängigkeit der Bandlücke diskutieren.
HL 12.81 Mo 16:30 Poster A
Einfluss von verschiedenen Nukleationsschichten auf die Eigenschaften
von ZnO-Dünnfilmen — •Holger von Wenckstern,
Andreas Rahm, Jörg Lenzner, Michael Lorenz, Holger Hochmuth
und Marius Grundmann — Universität Leipzig, Institut für
Experimentelle Physik II, Linnéstraße 5
ZnO-Dünnfilme wurden epitaktisch mittels gepulster Laser Deposition
auf Saphir abgeschieden. Dabei wurde der Einfluss verschiedener
Nukleationsschichten (ZnO, MgO) auf die strukturellen, optischen
und elektrischen Eigenschaften mittels Röntgen-, SNMS-, RHEED-,
Kathodolumineszenz- und Halleffektmessungen untersucht. Die kritischen
Züchtungsparameter für der Nukleationsschichten wie Temperatur,
Art und Druck des Restgases wurden ebenfalls variiert. Zudem wurde der
Einfluss der Orientierung des Substrates in die Untersuchungen einbezogen.
HL 12.82 Mo 16:30 Poster A
Nano structured material in electrodynamic traps — •Silko
Barth and Dieter Gerlich — Department of Physics, Technische
Universität Chemnitz, 09126 Chemnitz, Germany
The goal of this project is the mass spectrometrical and optical characterization
of simple structures of ligand stabilized clusters. Small agglomerates
(e.g., dimers or trimers) of these chemically produced nanoparticles
are stored in a controlled inert atmosphere or under UHV conditions
using time dependent electric fields. The new trapping apparatus offers
numerous possibilities for determining physical and chemical properties
of single isolated objects. Experimental parameters are n, the number of
particles in an agglomerate, its charge and temperature, and the environment
(e.g., buffer or reactant gas). Optical detection and analysis is
based on laser methods such as differential light scattering, laser induced
fluorescence, or non linear optical effects. The method is applied to water
soluble CdTe nanoparticles and small agglomerates (n < 10) of them.
In a first step the material is injected via µm sized water droplets. The
evaporation process if followed in real time. After complete drying only
the semiconductor particles remain, allowing one to investigate them in
detail. Finally, it is also planned to modify or remove the ligand shell.
HL 12.83 Mo 16:30 Poster A
Real-time spectroscopic ellipsometry monitoring of a ZnO thin
film pulsed laser deposition growth — •N. Ashkenov 1 , M. Schubert
1 , H. Hochmuth 1 , M. Lorenz 1 , M. Grundmann 1 , and B.
Johs 2 — 1 Fakultät für Physik und Geowissenschaften, Institut für Experimentelle
Physik II, Universität Leipzig, Linnéstraße 5, 04103 Leipzig
— 2 J. A. Woollam Co., 650 ’J’ Street, Suite 39,Lincoln, NE 68508 USA
Real-time in-situ optical monitoring and control of thin-film growth processes
provides depth-resolved optical properties of heteroepitaxial layer
structures. Semiconductor device structures based on ZnO and its isolectronically
mixed (Mg,Cd)xZn1−xO compounds are promising candidates
for next-generation UV optoelectronics, which can be grown by pulsed
laser deposition (PLD). Substrate temperature, growth rate, layer thickness
and composition can be accessed by in-situ spectroscopic ellipsometry.
A two-step PLD growth mode of a (0001) ZnO thin film on (0001)
Al2O3 substrate at 1053 K was monitored in-situ in the photon energy
range from 1.25 eV to 3.335 eV. Changes in the growth rate and in the
optical properties of the ZnO film throughout the deposition process are
determined utilizing the generalized virtual interface approach. Detailed
knowledge about the unintentional variations in the deposition conditions
can be used for feed-back control in order to optimize the PLD growth
process. A simple ZnO dielectric function model approach is developed,
which can be used to control the ZnO film growth in real time.
HL 12.84 Mo 16:30 Poster A
Elektrische Charakterisierung von n-leitendem ZnO mittels
Schottky Kontakten — •Holger von Wenckstern, Swen Weinhold,
Gisela Biehne, Rainer Pickenhain, Holger Hochmuth,
Michael Lorenz und Marius Grundmann — Universität Leipzig,
Institut für Experimentelle Physik II, Linnestraße 5
Der transparente II-VI Halbleiter ZnO ist aufgrund seiner vorteilhaften
Eigenschaften, wie z. B. der hohen Exzitonbindungsenergie von
ca. 60 meV , in den letzten Jahren ins Zentrum des Interesses vieler
Festkörperphysiker gerückt. Nominell undotiertes ZnO ist n-leitend, was
auf den Einbau von effektiv Masse Donatoren und/oder auf den Einbau
von Wasserstoff zurückzuführen ist (letzteres insbesondere bei der Abscheidung
mittels Gasphasentransportmethoden). Außerdem ist die Bildungsenergie
von donatorartigen intrinsischen Defekten wie Sauerstoffvakanzen
bzw. Zink auf Zwischengitterplätzen (beides tiefe Störstellen
in ZnO) deutlich geringer als die von akzeptorartigen intrinsischen
Störstellen. Aus diesen Gründen ist die Herstellung von dauerhaft pleitendem
ZnO bis jetzt noch nicht reproduzierbar gelungen. Um die
Paramater und Formationsmechanismen von tiefen Störstellen in ZnO
zu studieren, wurden DLTS-Messungen in einem Temperaturbereich von
4 K bis 450 K mittels Schottky Kontakten vorgenommen. Diese wurden
auf ZnO Einkristallen und auf mittels gepulster Laser Deposition
auf Saphir abgeschiedenen ZnO-Dünnfilmen aufgedampft und mit Kapazitäts-Spannungs-,
Strom-Spannungsmessungen und Admittanzspektroskopie
charakterisiert. Zudem wurde der Photostrom in einem Temperaturbereich
von 4 K bis 300 K gemessen.
HL 12.85 Mo 16:30 Poster A
Identifizierung von flachen Donatoren in ZnO — •H. Alves 1 ,
B.K. Meyer 1 und A. Rodina 2 — 1 I. Physikalisches Institut, Justus-
Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen — 2 Ioffe
Institut, St. Petersburg, Rußland
ZnO zeigt eine Vielzahl von exzitonischen Übergängen, die in der Vergangenheit
sowohl Donator- als auch Akzeptor-gebundenen Exzitonen
zugeordnet wurden. Über die Beobachtung der angeregten Zustände der
gebundenen Exzitonen (TES) können die Rekombinationen von I4 bis
I10 zweifelsfrei als neutrale Donator-gebundene Exzitonen identifiziert
werden. Ihre Lokalisierungsenergien folgen der Regel von Haynes die sich
aus der theoretischen Modellierung der angeregten Zustände und der Aufspaltung
der 2s- und 2p-Zustände ergibt.
HL 12.86 Mo 16:30 Poster A
Temperature-dependent band-gap energies and optical constants
of ZnO — •N. Ashkenov, M. Schubert, W. Chakai, G.
Benndorf, H. Hochmuth, M. Lorenz, and M. Grundmann —
Fakultät für Physik und Geowissenschaften, Institut für Experimentelle
Physik II, Universität Leipzig, Linnéstraße 5, 04103 Leipzig
We report the temperature dependencies of the fundamental band-toband
transition energies and the below-band-gap refractive index in ZnO.
Spectroscopic ellipsometry data, taken from a (0001)-cut ZnO single crystal
at temperatures between 300 K and 1154 K, and for photon energies
from 1.25 eV to 3.335 eV, are analyzed by using model dielectric function
approaches, augmented by excitonic continuum contributions. A strong
and linear red-shift of the three wurtzite-type Γ-point transition energies
is observed. The increase of the valence band splitting energies upon
temperature is indicative for an increase of the quasi-cubic model parameters.
Results of photoluminescence studies between 4.4 K and 300 K are
used to supplement the high-temperature band-gap data. For ZnO, the
phonon dispersion must be considered appropriately in order to model
the temperature dependence of the fundamental band-to-band transition
energy. We obtain strong contributions due to optical phonons at elevated
temperatures, whereas acoustic phonons dominate the electron-phonon
coupling at low temperatures.
HL 12.87 Mo 16:30 Poster A
Verspannungs- und Temperaturabhängigkeit der Energiebandstruktur
von wurtzitischem ZnO mittels Empirischer
Pseudopotential (EPP)-Rechnungen unter Berücksichtigung
der Spin-Bahn-Wechselwirkung — •Daniel Fritsch, Heidemarie
Schmidt und Marius Grundmann — Universität Leipzig,
Fakultät für Physik und Geowissenschaften
Beim Züchten von ZnO-Filmen auf Substraten bzw. in Heterostrukturen
treten aufgrund der Gitterfehlanpassung Verspannungseffekte auf.
Der Einfluß der Verspannungseffekte auf die Energiebandstruktur von
ZnO wird in der Rechnung über eine Variation der Gitterkonstanten a0
und c0 des unverspannten Volumenmaterials berücksichtigt, wobei die
verwendeten übertragbaren, strukturunabhängigen Parameter r i und z i
der ionaren Modellpotentiale von Zn und O iterativ aus experimentell
bestimmten Tieftemperaturübergangsenergien binärer Halbleiterverbindungen
gewonnen wurden.
Desweiteren bilden die experimentell bestimmten temperaturabhängigen
a und c Gitterkonstanten 1 von ZnO den Ausgangspunkt
für EPP-Rechnungen zur theoretischen Untersuchung der Temperatur-

Halbleiterphysik Montag
abhängigkeit der ZnO-Valenzbandstruktur im Vergleich zur experimentell
bestimmten Vergrößerung der Spin-Bahn-Wechselwirkung ∆so und
der Kristallfeldaufspaltung ∆cf. 2
[1] R.R.Reeber, J. Appl. Phys. 41, 5063 (1970)
[2] N.Ashkenov et al., eingereicht bei Phys. Rev. B
HL 12.88 Mo 16:30 Poster A
Room temperature UHV bonding of Si to GaAs — •Alin Mihai
Fecioru, Stephan Senz, and Ulrich Goesele — Max-Planck-
Institut für Mikrostrukturphysik, 06120 Halle
The traditional method of wafer bonding of Si to GaAs at room temperature
followed by heating to high temperatures is not possible due to
the difference in the thermal expansion coefficients of the two materials.
Our interfaces were obtained by ultrahigh vacuum (UHV) wafer bonding
at room temperature, without any intermediate layer. The cleaning
of Si wafers was done with RCA solution followed by HF tip. In the UHV
the hydrogen is thermally desorbed at 480 ◦ C. A UV/ozone treatment is
applied to GaAs wafers in order to remove organic contamination. This
induces the formation of a complex oxide which will be thermally desorbed
at 450 ◦ C in UHV. An atomic hydrogen induced modification of
Ga2O3 into Ga2O enhances the process.
Electrical properties of n-GaAs (100)/ p-Si (100) interfaces were investigated
by temperature dependent current-voltage measurements. A
high concentration of electrically active defects is observed at the interface.
Additional tunneling contributions (for highly doped samples) cause
a high leakage current.
HL 12.89 Mo 16:30 Poster A
a-Si/SiOx Bragg-Reflektoren auf mikro-strukturierten Halbleitern
— •Rüdiger Schmidt-Grund 1 , Thomas Nobis 1 , Bernd
Rheinländer 1 , Volker Gottschalch 2 , Helmut Herrnberger 2
und Marius Grundmann 1 — 1 Universität Leipzig, Fakultät für Physik
und Geowissenschaften, Institut für Experimentelle Physik II, Linnéstr.
5, 04103 Leipzig — 2 Universität Leipzig, Fakultät für Chemie und Mineralogie,
Linnéstr. 3, 04103 Leipzig
Laterales Bragg-Confinement von Mikroresonator-Lichtemittern
erhöht das Verhältnis der Zahl der axial resonanten Moden zur Zahl
der spontan emittierten lateralen Moden. Hoch reflektierende Si/SiOx
Bragg-Reflektoren (BR) eignen sich gut zur Verbesserung des optischen
Confinements in mikro-strukturierten Resonatoren.
Sowohl Metall-, a-Si- und SiOx-Einzelschichten als auch a-Si/SiOx BR
wurden mittels PECVD für den Wellenlängenbereich von (500 - 830)
nm mit kleiner Paarzahl N (typisch N = 4,5) auf Glas-, InP- und GaAs-
Substraten mit verschiedenen 3-dimensionalen und gekrümmten Strukturen
abgeschieden. Die optischen Eigenschaften wurden mittels der neuen
Methode der detektions-fokalen räumlich-aufgelösten spektroskopischen
Ellipsometrie und der Methode der konfokalen räumlich-aufgelösten spektroskopischen
Ellipsometrie untersucht. Aus der Modell-Analyse der ellipsometrisch
gemessenen Spektren der Mueller-Matrix konnten das Reflexionsvermögen
(R) und die Schichtdicken berechnet und Rückschlüsse auf
die Probengeometrie gezogen werden. Das aus der ellipsometrischen Analyse
berechnete R wurde mit dem R, welches mittels konfokaler Mikro-
Reflexion bestimmt wurde, verglichen.
HL 12.90 Mo 16:30 Poster A
Free-charge carrier properties in AlGaAs/GaAs superlattices
investigated by magnetooptic ellipsometry — •Claas von Middendorff
1 , Tino Hofmann 1 , Gunnar Leibiger 2 , and Mathias
Schubert 1 — 1 Fakultät für Physik und Geowissenschaften, Institut
für Experimentelle Physik II, Universität Leipzig,Linnéstraße 5, 04103
Leipzig — 2 Fakultät für Chemie und Mineralogie, Halbleiterchemie, Universität
Leipzig, Linnéstraße 3, 04103 Leipzig
Far-infrared magnetooptic ellipsometry is employed to determine the
electron effective mass, the mobility and concentration in Si-doped
AlGaAs/GaAs-superlattices at temperatures ranging from 70 to 290 K.
We observe a directional dependence of the free-charge carrier mobility.
As expected for a system of reduced dimensionality the in-plane mobility
is much larger than its out-of-plane component. The parameters
are determined by modelling the observed magneto-optic birefringence
originating from the far-infrared free-charge carrier excitations in the
AlGaAs/GaAs-heterojunctions without any need for additional electrical
measurements.
HL 12.91 Mo 16:30 Poster A
The Boltzmann Equation in Semiconductor Superlattices —
•Bernhard Rieder and Joachim Keller — Institute of Theoretical
Physics, University of Regensburg, 93040 Regensburg
We model the electron motion in semiconductor superlattices with the
help of the Boltzmann equation in the relaxation time approximation. A
smooth transition from the superlattice to the bulk region of the semiconductor
material is assumed. We derive corrections to the Boltzmann
equation in this transition region, because the model of the boundaries
is crucial for the behavior of the system. Instabilities, which hindered
the application of the superlattices as TeraHertz-source up to now, will
develop there. In experiments these instabilities lead to periodic behavior
of the system. Up to now no realistic model including the boundaries was
set up which reproduces this behavior. With our model we find periodic
behavior and investigate the effect of the electric circuit which is coupled
to the superlattice.
HL 12.92 Mo 16:30 Poster A
The Correlation between Emission Spectra and Atomic Scale
Structure of GaAs/AlGaAs Quantum Wells — •M. Erdmann 1 ,
C. Ropers 1 , M. Wenderoth 1 , L. Winking 1 , T. C. G. Reusch 1 ,
R. G. Ulbrich 1 , S. Malzer 2 , and G. Döhler 2 — 1 IV. Physikalisches
Institut der Universität Göttingen, Tammannstraße 1, 37077
Göttingen — 2 Inst. für techn. Physik, Universität Erlangen-Nürnberg,
Erwin-Rommel-Straße 1, 91058 Erlangen
We have performed cross-sectional Scanning Tunneling Microscopy and
Micro-Photoluminescence experiments on GaAs/AlGaAs quantum wells
and correlated the structural and optical data. The emission spectra were
obtained using a scanning Micro-PL microscope with lateral resolution
of 500 nm. Large X-STM topographs with atomic resolution were converted
into potentials by linear scaling, serving as starting point for a
numerical simulation in Envelope Function approximation of the optical
spectra of the studied real structure. We assume a laterally isotropic
aluminium distribution and use a model recently introduced by Runge
and Zimmermann [2]. In real quantum films, interface fluctuations lead
to localization of excitons in the disorder potential of the quantum well
interfaces [1]. The resulting inhomogeneous broadening of the optical
spectra is quantitatively reproduced by the simulated spectra [3].
[1] A. Zrenner et al., Phys. Rev. Lett. 72 (1994) 3382
[2] R. Zimmermann, F. Große, and E. Runge, Pure Appl. Chem. 69 (1997)
1179
[3] C. Ropers, M. Wenderoth, L. Winking, T.C.G. Reusch, M. Erdmann,
R.G. Ulbrich, S. Malzer and G. Döhler, Phys. Rev. Lett. (submitted)
HL 12.93 Mo 16:30 Poster A
Micro- and nanotubes made of strained metal/semiconductor
double layers — •Olrik Schumacher, Stefan Mendach, Christian
Heyn, Holger Welsch, and Wolfgang Hansen — Institut
für Angewandte Physik, Universität Hamburg, Jungiusstrasse 11, D-
20355 Hamburg, Germany
The method of self-rolling strained semiconductor double layers first
introduced by Prinz [1] enables to build tubes with radii varying between
some nanometers and some microns. Here we show that by
choosing adequate preparation parameters it is also possible to roll
metal/semiconductor double layers into micro- and nanotubes. By evaporating
metals with different layer thicknesses onto InGaAs-layers we
achieve strained double layers resulting in tubes with tuneable diameter.
The dependence between diameter and layer composition as well as the
rolling anisotropy will be shown and compared to conventional semiconductor
tubes. Furthermore possible applications will be discussed.
[1] V. Ya. Prinz et al., Physica E6 (2000) 828-831.
HL 12.94 Mo 16:30 Poster A
FWM-Experimente an dotierten Einzel-Quantumwells —
•Patrick Schröter 1 , Bertram Su 1 , Christian Schüller 1 ,
Max Bichler 2 und Werner Wegscheider 3 — 1 Institut für
Angewandte Physik, Universität Hamburg — 2 Walter-Schottky-Institut,
TU-München — 3 Institut für Angewandte und Experimentelle Physik,
Universität Regensburg
Wir präsentieren die nach unserem Wissen ersten spektral aufgelösten
Vier-Wellen-Misch-Experimente (SR-FWM) an modulationsdotierten
GaAs/AlGaAs-Einzel-Quantumwells. Die optisch dünnen Proben
sind mit einem Gate zur Variation der Ladungsträgerdichte versehen. Die
Experimente wurden in einem optischen 3 He-Magnet-Kryostaten durchgeführt,
der Temperaturen bis 0,4 K und Magnetfelder bis zu 11,5 T er-

Halbleiterphysik Montag
laubt. Wir finden für Füllfaktoren ν < 2 und bei resonanter Anregung des
untersten Landaulevels ein Quantumbeating, welches auf die kohärente
Kopplung der untersten beiden Landaulevel, vermittelt durch Magnetoplasmonen,
zurückgeführt werden kann. Durch die Möglichkeit die 2D-
Ladungsträgerdichte der Probe über ein Gate zu variieren, sind wir in der
Lage SR-FWM auch im Übergangsbereich vom 2D-Elektronengas zum
exzitonischen Regime durchzuführen.
Diese Arbeit wird von der DFG im Rahmen der Projekte SCHU1171/1
und SCHU1171/2 gefördert.
HL 12.95 Mo 16:30 Poster A
Optical properties of organic – inorganic mixed layers in dependence
on preparation conditions — •Marieta Levichkova,
Jacky Assa, Hartmut Fröb, and Karl Leo — Institut für
Angewandte Photophysik, TU Dresden, 01062 Dresden, Germany,
www.iapp.de
Thin films of organic dyes incorporated in silicon dioxide matrix are
obtained by co-evaporation of both host and dye in high vacuum. The
technique allows preparation of mixed layers independent on dye’s solubility
in the matrix. This in principle possible variation of dye concentration
provides the opportunity to investigate the behavior of even very
diluted solid solutions compared to pure dye layers. Luminescence and
absorption spectroscopy are applied to study the optical properties of
the layers. Significant alterations in absorption and luminescence spectra
in dependence on dye concentration are explained in consequence
of aggregation effects and energy transfer. It is demonstrated that the
evaporation geometry and preparation conditions offer an effective way
to reduce the possibilities for non-radiative transitions thus increasing
the photoluminescence quantum yield.
HL 12.96 Mo 16:30 Poster A
Investigation of charge carrier dynamics in polymer/fullerene
solar cells by means of photoinduced reflection/absorption spectroscopy
— •Christian Arndt 1 , Uladzimir Zhokhavets 1 , Martina
Mohr 1 , Gerhard Gobsch 1 , Maher Al-Ibrahim 2 , and Steffi
Sensfuss 2 — 1 Institute of Physics, Ilmenau Technical University, 98684
Ilmenau, Germany — 2 TITK Institute Rudolstadt, Department Functional
Polymer Systems, 07407 Rudolstadt, Germany
The discovery of a photoinduced charge transfer between conjugated
polymers and fullerenes led to the development of bulk heterojunction
polymer/fullerene solar cells. This kind of organic solar cells currently
offers an efficiency up to 3.5%. In order to improve this efficiency, a detailed
knowledge of the generation and recombination dynamics of the
charge carriers is essential.
The photoinduced absorption spectroscopy is a powerful tool to investigate
the generation and recombination dynamics of polarons. Up to now,
most of this spectroscopic studies were done on thin films, whereas little
is known about the behaviour of the photoinduced charge carriers in the
real device. In this work, we investigated the generation and recombination
dynamics of polarons in bulk heterojunction MDMO-PPV/PCBM
solar cells on flexible substrates, which give AM 1.5 efficiencies up to 3%
by means of photoinduced reflection/absorption spectroscopy. Due to the
HL 13 Hauptvortrag Bayer
reflection geometry of the photoinduced absorption experiment we were
able to study the generation and recombination dynamics of polarons
within these devices.
HL 12.97 Mo 16:30 Poster A
Exciton transport in PTCDA layers studied by time-resolved,
temperature dependent luminescence quenching experiments.
— •R. Schüppel, K. Leo, and M. Hoffmann — Institut für Angewandte
Photophysik, TU Dresden, 01062 Dresden, Germany
For opto-electronic applications of organic semiconductors, the properties
of the photo-excited states (excitons) have to be understood in detail.
In particular, the transport properties of excitons, which are described in
terms of diffusion, are significant for the optimization process of devices,
e.g. solar cells. We performed luminescence quenching experiments with
thin vapor-deposited films of PTCDA (perylene-3,4:9,10-tetracarboxylicdianhydride),
which are partially covered by a quenching layer, in our case
TiOPc (titanyl-phthalocyanine). From the time-resolved PTCDA luminescence,
we can distinguish between primarily excited states (lifetime
τa 1ns). The transport, which
is accessible from the luminescence quenching by a variation of the layer
thickness, shows no temperature dependence for the short-living states.
The transport in the emitting states is thermally activated for high temperatures
(T>60K), which suggests incoherent hopping transport. For
low temperatures, we observe no temperature dependence, which can be
explained by several transport mechanisms.
HL 12.98 Mo 16:30 Poster A
Determination of the excitonic dispersion in α-PTCDA with
electron energy loss spectroscopy and optical spectroscopy —
•Reinhard Scholz, Igor Vragović, and Michael Schreiber —
Institut für Physik, Technische Universität Chemnitz
In the present work, recent experimental findings concerning electron
energy loss spectroscopy, linear optical spectroscopy and low temperature
photoluminescence are interpreted with model calculations based on the
transfer of Frenkel excitons. It can be shown in detail that the exciton
transfer between non-degenerate vibronic sublevels results in deviations
of the excitonic dispersion from a simple cosine-shape [1]. Moreover, these
off-diagonal parts of the exciton transfer have a strong influence on the
oscillator strength of the vibronic sublevels: In optical absorption at the
Γ-point of the Brillouin zone, the coupling strength is redistributed to
the upper levels [2], whereas at the surface of the Brillouin zone, it accumulates
in the vibronic ground state. The wave vector dependence of
the lineshape observed with electron energy loss spectroscopy (EELS)
reflects this behaviour [3]. The photoluminescence band dominating at
low temperatures results from a vertical recombination process starting
from the minimum of the lowest branch of the excitonic dispersion [1].
[1] I. Vragović and R. Scholz, Phys. Rev. B 68, 155202 (2003).
[2] I. Vragović, R. Scholz, and M. Schreiber, Europhys. Lett. 57, 288
(2002).
[3] I. Vragović, Frenkel exciton model of excitation and recombination
processes in crystalline α-PTCDA, Dissertation, Technische Universität
Chemnitz (2003).
Zeit: Dienstag 09:30–10:15 Raum: H15
Hauptvortrag HL 13.1 Di 09:30 H15
Quantum dots: Building blocks of quantum devices? — •M.
Bayer — Universität Dortmund, Experimentelle Physik II, Otto-Hahn
Str.4, 44227 Dortmund
Quantum dots have attracted considerable attention recently for their
potential to implement modern fields of physics such as quantum optics
or quantum information processing in a solid state environment. While
quite some progress has been made to manifest this potential, still a lot of
open questions remain. In this contribution we will try to present some of
these dot applications and discuss related problems and strategies how
to overcome them. In quantum optics, for example, single dots might
be used as light sources for single photons or entangled photons. For
these purposes a high degree of control of the light-matter interaction
is required, which can be obtained by placing the dots in a resonator.
The current status of these activities will be considered. For quantum
information applications quantum bits with controllable interactions between
them are needed, in order to realize gates. Such gates might be
obtained by coupling of dots. Results of studies on demonstration of coherent
coupling, on control of coupling and on decoherence of excitons
will be presented.

Halbleiterphysik Dienstag
HL 14 Symposium Quanten-Hall-Systeme
Zeit: Dienstag 10:15–13:15 Raum: H15
HL 14.1 Di 10:15 H15
Radiation induced zero-resistance states in high mobility
GaAs/AlGaAs devices — •Ramesh Mani — Harvard University,
Gordon McKay Laboratory of Applied Science, 9 Oxford Street, Cambridge,
MA 02138 USA — Max-Planck-Institut FkF, Heisenbergstr. 1,
70569 Stuttgart, Germany
We report the experimental detection of novel zero-resistance states [1],
which are induced by electromagnetic wave excitation in ultra high mobility
GaAs/AlGaAs heterostructure devices including a two-dimensional
electron system. Radiation-induced vanishing-resistance states, which do
not exhibit concomitant Hall resistance quantization, are demonstrated
in the large filling factor, low magnetic field limit, at liquid helium temperatures.
It is shown that the observed resistance minima follow the
series B = [4/(4j+1)] Bf with j=1,2,., where Bf = 2pfm*/e, m* is an
effective mass, e is electron charge, and f is the radiation frequency. The
dependence of the effect is reported as a function of experimental parameters
such as the electromagnetic wave frequency, incident power,
temperature, and the current.
HL 14.2 Di 10:45 H15
Oscillatory photoconductivity of a 2D electron gas in magnetic
field — •D.G. Polyakov 1 , I.A. Dmitriev 1 , M.G. Vavilov 2 ,
I.L. Aleiner 3 , and A.D. Mirlin 1,4 — 1 Institut für Nanotechnologie,
Forschungszentrum Karlsruhe, 76021 Karlsruhe — 2 Physics Dept.,
Massachusetts Institute of Technology, Cambridge, MA 02139, USA —
3 Physics Dept., Columbia University, New York, NY 10027, USA —
4 Institut für Theorie der kondensierten Materie, Universität Karlsruhe,
76128 Karlsruhe
An intriguing development in the study of magnetotransport in highmobility
2DEGs was the observations by Zudov et al. and by Mani et
al. of magnetooscillations of the photoconductivity, evolving with increasing
microwave power into zero-resistance states. We discuss the
nature of the oscillations and develop theory which is in good agreement
with the experimental data. The most important mechanism of
the oscillations [1,2] is related to a radiation-induced change of the
electron distribution function. We consider nonlinear effects, with respect
to both the dc field and the microwave power, as well as the
temperature dependence due to the inelastic relaxation. We also study
[3] the oscillations governed by quasiclassical memory effects. For low
B, this mechanism, in combination with microwave-dependent screening,
may dominate over that based on the Landau quantization. [1]
I.A.Dmitriev, A.D.Mirlin, and D.G.Polyakov, cond-mat/0304529; [2]
I.A.Dmitriev, M.G.Vavilov, I.A.Aleiner, A.D.Mirlin, and D.G.Polyakov,
cond-mat/0310668; [3] I.A.Dmitriev, A.D.Mirlin, and D.G.Polyakov, to
be published.
HL 14.3 Di 11:15 H15
Optical Probe of Fractionally-Charged Quasiholes — •C.
Schüller 1 , K.-B. Broocks 1 , P. Schröter 1 , Ch. Heyn 1 , D. Heitmann
1 , T. Chakraborty 2 , V. M. Apalkov 3 , M. Bichler 4 , and
W. Wegscheider 5 — 1 Institut für Angewandte Physik, Universität
Hamburg — 2 Institute for Mathematical Sciences, Chennai, India —
3 University of Utah, Salt Lake City, USA — 4 Walter-Schottky-Institut,
Garching — 5 Institut für Experimentelle und Angewandte Physik,
Universität Regensburg
We perform optical experiments on dilute two-dimensional electron
systems (2DES) at very low temperatures (T < 0.1 K) and high magnetic
fields [1]. In photoluminescence experiments on a 2DES subjected
to a quantizing magnetic field around ν = 1/3, we have observed an
anomalous dispersion of the charged excitons [2]. We have found that
the anomaly exists only at a very low temperature (0.1 K) and an intermediate
electron density (0.9 × 10 11 cm −2 ). It is explained to occur
due to the perturbation of the incompressible liquid at ν = 1/3. The
perturbation is induced by the close proximity of a localized charged exciton
which creates a fractionally-charged quasihole in the liquid [3]. The
intruiging experimentally observed puzzle that the anomaly (2 meV) can
be destroyed by applying a small thermal energy of ∼ 0.2 meV is thereby
resolved, as this energy is enough to close the quasihole energy gap. This
work presents a probe of the quasihole gap in a quantum Hall system.
[1] C. Schüller et al., Phys. Rev. B 65, 081301(R) (2002).
[2] K.-B. Broocks et al., Phys. Rev. B 66, 041309(R) (2002).
[3] C. Schüller et al., Phys. Rev. Lett. 91, 116403 (2003).
HL 14.4 Di 11:45 H15
Coulomb Drag as a Probe of the Nature of Compressible States
in a Magnetic Field — •Sjoerd Lok 1 , K. Muraki 1 , S. Kraus 1 ,
W. Dietsche 1 , K. Von Klitzing 1 , D. Schuh 2 , M. Bichler 2 , and
W. Wegscheider 2 — 1 Max Planck Insitut für Festkörperforschung,
Heisenbergstrasse 1 70569 Stuttgart — 2 Walter Schottky Insitut, Technische
Universität München, Am Coulomb Wall, 85748 Garching
Magneto-drag reveals the nature of compressible states and the underlying
interplay of disorder and interactions. At filling factor 3/2 a clear
T 4/3 dependence is observed, which signifies the metallic nature of the
N=0 Landau level. In contrast, drag in higher Landau levels reveals an
additional contribution, which anomalously grows with decreasing T before
turning to zero following a thermal activation law. The anomalous
drag is discussed in terms of electron-hole asymmetry arising from disorder
and localization, and the crossover to normal drag at high fields as
due to screening of disorder.
HL 14.5 Di 12:15 H15
Coulomb drag in high Landau levels — •von Oppen Felix 1,2 ,
Mirlin A.D. 3,4 , and Gornyi I.V. 3 — 1 Inst. f. Theor. Physik, FU
Berlin, Arnimallee 14, 14195 Berlin — 2 Dept. of Cond. Matter Physics,
Weizmann Inst. of Science, Rehovot, Israel — 3 Inst. f. Nanotechnologie,
FZ Karlsruhe, 76021 Karlsruhe — 4 Inst. f. Theorie der Kond. Materie,
Uni Karlsruhe, 76128 Karlsruhe
Coulomb drag between two parallel two-dimensional electron systems
provides insight that is complementary to conventional transport measurements.
Recent experiments [1] found several surprises in Coulomb
drag in strong magnetic fields, in the limit of high Landau level filling
factor, including negative drag and an anomalous temperature dependence.
In this talk, we present a theory of Coulomb drag in high Landau
levels which is perturbative in the interlayer interaction and treats disorder
within the framework of the self-consistent Born approximation. We
show that in the experimentally relevant ballistic regime, there are several
contributions to Coulomb drag which differ parametrically but are
numerically of comparable magnitude in typical experiments. One class
of contributions is associated with the breaking of particle-hole symmetry
by the Landau-level density of states, while another, more conventional,
contribution arises from the breaking of this symmetry by the curvature
of the electron dispersion. We show that the interplay of these contributions
allows for a qualitative understanding of many features of the
existing experiments.
[1] J.G.S. Lok et al., Phys. Rev. B 63, 041305 (2001); K. Muraki et al.,
cond-mat/0311151 (2003).
HL 14.6 Di 12:45 H15
Momentum resolved tunnel spectroscopy: Investigating interactions
at quantum Hall edges — •Matthew Grayson und Matthew
Grayson — Walter Schottky Institut, Tech. Univ. Muenchen
We present experimental results on magneto-tunneling between a single
quantum Hall (QHE) edge and an orthogonal high-mobility twodimensional
contact in a T-shaped quantum well configuration. Simultaneous
conservation of energy E and canonical momentum k parallel to
the QHE edge allows us to directly probe the E vs. k dispersion relation
of individual integer QHE edge channels with excitation energies up to
100 meV. At high voltages, screening in the QHE edge is found to significantly
distort the dispersion relation in a fashion that is in excellent
agreement with Hartree calculations of the real-space edge potential. At
low voltages of order the Coulomb interaction energy, we find evidence for
an exchange-enhanced spin splitting of the integer quantum Hall effect
edge.

Halbleiterphysik Dienstag
HL 15 Photonische Kristalle III
Zeit: Dienstag 10:15–13:30 Raum: H17
HL 15.1 Di 10:15 H17
Dye functionalization of living photonic crystals — •Thomas
Fuhrmann, Stefan Landwehr, and Melanie El Rharbi-Kucki
— Makromolekulare Chemie und Molekulare Materialien, Fachbereich
Naturwissenschaften und Center for Interdisciplinary Nanostructure Science
and Technology, Universität Kassel
Biological structures offer a convenient way for producing photonic
crystals. The silica cell wall of centric diatoms can be regarded as hexagonal
and quadratic slab waveguide photonic crystals with partial bandgaps
in the visible spectral range. In order to address the question how absorption
and emission of light is influenced in these structures, organic dyes
have to implemented into the cell wall. We demonstrate some techniques
of dye functionalization with laser dyes, including a chemical as well as
a biological approach. This project is part of the DFG priority program
on photonic crystals.
HL 15.2 Di 10:30 H17
Periodically Arranged Point Defects in a Two Dimensional
Photonic Crystal — •Stefan Richter 1 , Stefan Schweizer 2 , Cecile
Jamois 1 , Reinald Hillebrand 1 , Nikolai Gaponik 3 , Andrey
Rogach 4 , Ralf Wehrspohn 2 , and Margit Zacharias 1 — 1 Max-
Planck-Institut für Mikrostrukturphysik — 2 Universität Paderborn —
3 Universität Hamburg — 4 Ludwig-Maximilians-Universtität München
We present and charcterize hexagonal point defects in a two dimensional
photonic crystal based on macroporous silicon. These point defects
are prepatterned periodically, forming a superstructure within the
photonic crystal after electrochemical etching. Spatially resolved, optical
investigations related to morphological properties, like defect concentration
and pore radius, are compared to bandstructure calculations. The
confined defect states are identified and their interaction is evaluated
quantitatively. To investigate the influence of the cavity on internal light
emitters, colloidal HgTe quantum dots have been infiltrated into single
cavities and their emission was measured by photoluminescence.
HL 15.3 Di 10:45 H17
Tunable Photonic Crystal circuits: Novel concepts and designs
— •Matthias Schillinger 1 , Sergei Mingaleev 1,2 , Daniel Hermann
1 , and Kurt Busch 1,3 — 1 Institut für Theorie der Kondensierten
Materie — 2 Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine
— 3 School of Optics/CREOL and University of Central Florida, Department
of Physics, Orlando, USA
Over the past years, substantial research efforts have been directed at
investigations of Photonic Crystals (PCs) with embedded defects such
as microcavities and waveguides. These structures hold tremendous potential
for the creation of very compact all-optical photonic integrated
circuits which are required for the next generation of high-throughput
optical communications systems.
In this talk, we suggest that tunable PC circuits can be created by
infiltrating individual pores of bulk 2D PCs such as macroporous silicon,
with liquid crystals or polymers. We show that a row of infiltrated
pores can be used as a single-mode PC waveguide, and demonstrate very
efficient broad-band transmission through sharp waveguide bends. For
infiltration with liquid crystals, we illustrate different types of tunability
of PC circuits. Such functional elements can be designed accurately and
efficiently through a Wannier function approach [1] in combination with
the guided-mode scattering matrix approach [2].
[1] K. Busch et al., J. Phys.: Condens. Matter 15, R1233-R1256 (2003)
[2] S.F. Mingaleev and K. Busch, Opt. Lett. 28, 619-621 (2003)
HL 15.4 Di 11:00 H17
Photonic crystals with complete three-dimensional bandgap in
macoporous silicon — •Sven Matthias 1 , Frank Müller 1 , Cécile
Jamois 1 , Ralf B. Wehrspohn 2 , and Ulrich Gösele 1 — 1 Max
Planck Institute of Microstructure Physics, Weinberg 2, Halle 06120, Germany
— 2 Department of Physics, University Paderborn, Warburger Str.
100, Paderborn 33098, Germany
Photonic crystals – artificial structures with periodic refractive index
variations – are the ”semiconductors” for the electro-magnetic wave propagation.
Suppression of spontaneous emission or loss-less waveguiding via
line defects in three-dimensional photonic bandgap materials are some
of the fascinating potential applications. Here, we describe the fabrica-
tion of a three-dimensional photonic crystal of overlapping air-spheres
in silicon in a simple cubic lattice. Our inexpensive and fast fabrication
method combines the advantages of the high accuracy of standard
photolithography with a large area three-dimensional etching process. 20
lattice constants in depth and thousands lateral lattice constants with
sharply modulated pores were grown and widened to obtain overlapping
air-spheres in silicon. We observed the optical properties in reflection
and transmission experiments along various crystal axes. They agree
well with bandstructure calculations. Together with the scanning electron
micrographs these are strong indications for a realised complete
three-dimensional photonic bandgap of about 3 % centred at 3 microns.
The large area of our structure and the variability in design enable for
all-optical microchips-approaches.
HL 15.5 Di 11:15 H17
Low loss GaAs based photonic crystal waveguides — •Helmut
Scherer1 , Martin Kamp1 , Stefan Deubert1 , Hans-Peter Reithmaier1
, Alfred Forchel1 und Reinhard März2 — 1Technische Physik, Am Hubland, D-97074 Würzburg — 2Infineon Technologies AG,
Corporate Research, D-81730 München
Photonic crystal (PhC) waveguides are important building blocks for
more complex PhC based devices. An important parameter, especially
for passive devices, is the loss of the waveguides. We have investigated
the loss of GaAs based photonic crystals at a wavelength of 1.3 µm.
The crystals are realized by an hexagonal array of air holes etched into
a GaAs/AlGaAs slab waveguide. Electron beam lithography is used to
define the PhC pattern in a resist layer, which is then used to pattern
an intermediate SiO2 mask. The holes are etched into the semiconductor
with an Cl2/Ar based ECR/RIE process. Holes with smooth sidewalls
and a depth of 1 µm are achieved. Measurements of the waveguide losses
are performed with an external tunable laser source covering a wavelength
range between 1240 and 1340 nm. The losses are determined from the
contrast of the Fabry-Perot resonances of the cavity formed by the two
cleaved facets and the PhC waveguide. This technique is not sensitive to
the coupling efficiency and therefore suitable for PhC waveguides, where
efficient coupling to an external source is often a concern. Comparing the
losses of waveguides with different lengths, it is possible to extract the
waveguide loss per length. The losses of the fundamental mode are about
5.1 db for W3-waveguides (3 rows missing in the PhC lattice) and about
for W5-waveguides.
mm
2.5 db
mm
HL 15.6 Di 11:30 H17
Photonic Molecule Formation in Microsphere Ensembles
Doped With Quantum Dots — •Björn M. Möller 1 , Mikhail
V. Artemyev 1 , Reinhold Wannemacher 2 , and Ulrike Woggon 1
— 1 Universität Dortmund — 2 Universität Leipzig
Semiconductor nanocrystals in spherical microcavities represent a
promising material system for the development of thresholdless lasers
and studies of light-matter-interaction regimes [1].
In this work, we report on the experimental observation of coherent
cavity field coupling in ensembles of spherical poystyrene microcavities
doped with CdSe quantum dots. The spatial dependence and polarization
nature of both the unperturbed cavity fields and the coupled binding
resonances are studied spectrally resolved in various one- and twodimensional
multisphere geometries. A mode mapping analysis [2] clearly
reveals the symmetry properties of the agglomerates for both types of resonances
and offers a detailed view of the optical confinement in sphere
based photonic molecules impregnated with nanoemitters.
The financial commitment of the DFG (SPP 1113) is gratefully acknowledged.
[1] U. Woggon et al., J. Appl. Phys. B 77, (2003)
[2] B. Möller et al., Appl. Phys. Lett. 83, (2003)

Halbleiterphysik Dienstag
HL 15.7 Di 11:45 H17
Kristallographie holographisch hergestellter dreidimensionaler
Photonischer Kristalle. — •Daniel C. Meisel 1,2 , Martin Wegener
1,3,2 und Kurt Busch 2,4,5 — 1 Inst. f. Nanotechnologie, Forschungszentrum
Karlsruhe in der Helmholtz-Gemeinschaft, D-76021 Karlsruhe
— 2 DFG-Centrum für funktionelle Nanostrukturen. — 3 Inst. f. Angewandte
Physik, Univ. Karlsruhe (TH), D-76128 Karlsruhe — 4 Inst.
f. Theorie der Kondensierten Materie, Univ. Karlsruhe (TH), D-76128
Karlsruhe — 5 School of Optics/CREOL and Dep. of Physics, Univ. of
Central Florida, Orlando, USA.
Mittels holographischer Lithographie hergestellte poröse Photolackstrukturen
können als Template für photonische Kristalle dienen. Die
Einstrahlrichtungen der Laserstrahlen legen dabei den Gittertyp fest, die
Polarisationen und Intensitäten hingegen das Motiv der Kristallstruktur.
Der Einfluss dieser beiden Parametergruppen wird systematisch unter
kristallographischen Aspekten diskutiert. Im Mittelpunkt des Interesses
stehen derzeit zwei Vierstrahlanordnungen mit paarweise gegenläufigen
bzw. gleichgerichteten Strahlen, welche i.a. orthorhombische bzw. rhomboedrische
Translationssymmetrien ergeben. Insbesondere wird auch die
Punktsymmetrie des Motivs in die Betrachtungen mit einbezogen. Aus
dieser vervollständigten Beschreibung werden die möglichen Gesamtsymmetrien
von herstellbaren Photolackstrukturen abgeleitet. Entsprechende
Bandstrukturrechnungen ergaben verschiedene, auch praktisch interessante,
Möglichkeiten zur Realisierung vollständiger dreidimensionaler
Bandlücken. Es wird über die theoretischen und experimentellen Resultate
bei Belichtung mit 532 nm berichtet.
HL 15.8 Di 12:00 H17
Herstellung und Charakterisierung zweidimensionalperiodischer
Photonischer Kristalle mittels holographischer
Lithographie — •M. Hermatschweiler 1,2 , D. C. Meisel 3,2 , M.
Diem 4,2 , K. Busch 4,2,5 und M. Wegener 1,3,2 — 1 Inst. f. Angewandte
Physik, Universität Karlsruhe (TH), 76128 Karlsruhe — 2 DFG-Center
for Functional Nanostructures — 3 Inst. f. Nanotechnologie, Forschungszentrum
Karlsruhe in der Helmholtz-Gemeinschaft, 76021 Karlsruhe
— 4 Inst. f. Theorie der Kondensierten Materie, Universität Karlsruhe
(TH), 76128 Karlsruhe, Germany — 5 School of Optics/CREOL and
Dep. of Physics, Univ. of Central Florida, Orlando, USA
Die holographische Lithographie mit drei Strahlen stellt eine sehr
flexible Methode dar, um großflächig zweidimensional-periodische Photolackstrukturen
herzustellen. Dazu wird eine ca. 25 µm dicke SU-8-
Photolackschicht mit einem Interferenzmuster bei 355 nm Wellenlänge
belichtet und anschließend entwickelt. Verschiedene Strukturen bestehend
aus unterschiedlich geformten Luftsäulen in hexagonaler und graphitähnlicher
Anordnung mit einer Gitterkonstanten von ca. 620 nm
wurden hergestellt. In ΓM-Richtung wurden Stoppbänder im sichtbaren
Spektralbereich und im nahen Infrarot als Transmissionsminima und
entsprechende Reflexionsmaxima polarisationsabhängig mit einem FTIR
nachgewiesen. Die Transmission wurde durch ca. 200 µm ausgedehnte
Proben gemessen. Trotz der geringen Brechzahl (n=1,6) ergaben sich Reflexionsmaxima
von bis zu 70%. Die optischen Messungen sind in guter
Übereinstimmung mit Transmissions- und Reflexionsrechnungen sowie
Bandstrukturrechnungen.
HL 15.9 Di 12:15 H17
Near-field Microscopy of Photonic Crystals — •Ben Buchler,
Patrick Kramper, Wolfgang Stumpf, Femius Koenderink, and
Vahid Sandoghdar — Laboratory of Physical Chemistry, ETH Zurich,
Switzerland
Using scanning near-field optical microscopy (SNOM), we have imaged
the propagation of light in 2D photonic crystal defects. The samples
are made from macroporous silicon with a bandgap ranging from 3.3 to
5.4µm. We show that applying SNOM to the surface of the crystal allows
measurement of the spatial mode of a resonant point defect microcavity
[1]. The intensity pattern obtained can be explained by small (

Halbleiterphysik Dienstag
HL 15.13 Di 13:15 H17
Tunable mirrorless lasing based on short pitch Ferroelectric Liquid
Crystals — •W. Haase, K. Yoshino, M. Kasano, and M.
Ozaki — Technische Universitaet Darmstadt, Institut fuer Physikalische
Chemie, Petersenstr. 20, 64287 Darmstadt
The helical pitch of Ferroelectric Liquid Crystals can be tuned via
heating or via variyng the strength of the applied external electrical
field. The so called short pitch FLC-materials allowing the selective reflection
of external laser light, hence they are acting as stop band. The
HL 16 GaN: Bauelemente
applied external field can influence the length of the helical pitch by ca.
30 nm. Preparing specific mixtures is giving rise for a broad wavelength
range mirrorless lasing (1,2). Along the talk the fundamentals and the
experimental conditions will be discussed. 1)Electrically tunable waveguide
laser based on ferroelectric liquid crystals, M. Kasano, M. Ozaki, K.
Yoshino, D. Ganzke, W. Haase Appl. Phys. Lett., 82, 4026-4028 (2003). 2)
Electro-Tunable Liquid-Crystal Laser M. Ozaki, M. Kasano, T. Kitasho,
D. Ganzke, W. Haase, K. Yoshino, Adv. Mater., 15, 974-977 (2003)
Zeit: Dienstag 10:15–12:45 Raum: H13
HL 16.1 Di 10:15 H13
Pt/GaN Schottky Diodes for Hydrogen Gas Sensors — •M. Ali 1 ,
V. Cimalla 1 , V. Tilak 2 , D. Merfeld 2 , P. Sandvik 2 und O. Ambacher
1 — 1 Technical University Ilmenau, Center of Micro- and Nanotechnologies,
Gustav-Kirchhoff-Str. 1, D-98693 Ilmenau, Germany —
2 General Electrics, General Electrics Global Research Europe, Wehrle
Strasse 13, D-81675 München, Germany
The performance of Pt/GaN Schottky diodes with different thickness
of the catalytic metal were investigated as hydrogen gas detectors. The
sensors were fabricated based on epitaxial Si-doped Ga-face GaN layer
(ND = 9 × 10 16 cm −3 ) grown up to a thickness of about 3µm by metalorganic
chemical vapour deposition on c-plane sapphire substrates. The
area as well as the thickness of the Pt were varied between 250µm 2 and
1000µm 2 , 80 and 400˚A, respectively. The Pt-Schottky-diodes exhibited at
room temperature ideality factors, saturation currents and barrier heights
between 1.3 and 3.3, 6 × 10 −11 and 1.25 × 10 −7 A and 0.64 and 0.99eV,
respectively. The sensitivity to hydrogen gas was investigated in dependence
on active area, Pt thickness and the operating temperature for 1%
hydrogen in synthetic air. The change in gate voltage of the diode at a
fixed current was monitored as the diode was exposed to hydrogen gas
and for comparison to dry air in order to determine the sensor sensitivity.
We observed a significant increase of sensitivity and decrease of response
time by increasing the temperature of operation to about 350 ◦ C and by
decreasing the Pt thickness down to 80˚A.
HL 16.2 Di 10:30 H13
Modification of GaN and AlGaN Surfaces for Nano- and Picofluidic
Sensors — •G. Kittler, V. Cimalla, V. Lebedev, M.
Fischer, V. Yanev, S. Krischok, J. A. Schaefer, and O. Ambacher
— Technical University Ilmenau, Center for Micro- and Nanotechnologies,
Gustav- Kirchhoff-Str. 1, D-98693 Ilmenau
Because of strong spontaneous polarization and piezoelectric coefficients
of GaN layers and AlGaN/GaN-heterostructures free carrier concentration
profiles inside these materials are very sensitive to any manipulation
of surface charge. This physical effect can be used to develop
novel sensors for ion fluxes, gases and polar liquids. We have used
AlGaN/GaN-heterostructures with polarization induced two dimensional
electron gases in order to determine volume, pH-value, or the polarity of
water based nano- and picoliter droplets. To enable the determination of
physical and chemical properties of such droplets a precise control of the
droplet position on the active areas of the sensors is required. Firstly miscellaneous
procedures of oxidation were used to optimize the wetting of
the thin GaN-cap layers, and secondly thin structured hydrophobic layers
were investigated for this purpose. For the latter method different materials
e.g. silicon nitride, aluminum oxide, and fluorine-carbon-compounds
were examined with respect to their hydrophobic properties. Effective
procedures in controlling the wetting behavior of GaN and AlGaN surface
were proven by Atomic Force Microscopy (AFM), X-ray Photoelectron
Spectroscopy (XPS), and contact-angle-measurements and will be
presented in respect to the results obtained by electrical characterization
of the first nanofluidic sensors.
HL 16.3 Di 10:45 H13
Studies on sub-band gap absorption of AlGaN based solar-blind
photodetectors — •R. Wagner 1 , G. Cherkastinin 1 , V. Lebedev 1 ,
A. T. Winzer 2 , R. Goldhahn 2 , and O. Ambacher 1 — 1 Center of
Micro- and Nanotechnologies, TU Ilmenau, D-98684 Ilmenau, Germany
— 2 Institute of Physics, TU Ilmenau, D-98684 Ilmenau, Germany
AlGaN-based UV-detectors with high responsivities in a narrow spectral
range were grown by molecular beam epitaxy on sapphire substrates.
These devices are based on heterostructure combining three epitaxial Al-
GaN layers with different alloy composition acting as optical filter, insulator
and detector, respectively. Spectrally resolved photocurrent, photothermal
deflection spectroscopy and in situ cathodoluminescence have
been applied to obtain a sub- and near band gap absorption in AlGaN
layers to provide detailed information about defect states in a wide energy
range. By optimizing the alloy compositions and thickness of the
filter layer, a peak responsivity of up to 35 A/W was achieved over a
narrow range of wavelength with a peak position at 276 nm. The rejection
of visible light response with respect to the peak responsivity was
about 2 orders of magnitude. This type of sensors can be designed to
have a highly selective response suitable for UV flame- and bio-sensors.
However, a device performance of AlGaN structures is mainly limited by
a high density of defects responsible for reduced UV/visible contrast and
slow photoresponse. Thus, the detailed knowledge of the defect structure
is necessary for the further performance improvements.
HL 16.4 Di 11:00 H13
Facetten-Alterung von (Al,In)GaN Laserdioden — •Thomas
Schoedl 1 , Ulrich T. Schwarz 1 , Volker Kümmler 2 , Alfred
Lell 2 und Volker Härle 2 — 1 Institut für Angewandte und
Experimentelle Physik, Universität Regensburg, Universitätsstr. 31,
93053 Regensburg, Germany — 2 OSRAM Opto Semiconductors GmbH,
Wernerwerkstr. 2, 93049 Regensburg, Germany
Wir untersuchen das Alterungsverhalten von (Al,In)GaN Laserdioden
(LD) auf SiC Substraten in Abhängigkeit verschiedener Verspiegelungsarten.
So können wir zeigen, dass es zusätzlich zum Volumeneffekt auch
einen Beitrag der Laserfacetten zum Alterungsprozess gibt. Unverspiegelte
LD altern deutlich schneller als verspiegelte LD. Selbst das Aufbringen
einer λ/2 Schicht reduziert die Alterung deutlich, wobei die λ/2 Schicht
die optischen Eigenschaften der Facette nicht verändert. Um zu prüfen,
ob die Alterung lichtinduziert oder strominduziert ist, wurde eine unverspiegelte
LD an Luft gealtert. Die Stromdichte wurde so gewählt, dass
die LD am Anfang im Laserbetrieb war, nach einer Minute effektiver
Betriebszeit aber unter die Laserschwelle fällt. Dadurch ändert sich die
Photonendichte um mehrere Größenordnungen, die Alterungskurve zeigt
aber keine nennenswerte Änderung im Verlauf. Weitere Versuche mit unverspiegelten
LD in verschiedenen Atmosphären wie Ar, N2, O2 und H2
zeigen eine langsame Alterung. Das Hinzufügen von Wasserdampf lässt
die Diode wieder schnell altern. Dies lässt auf die Bildung einer Oxid-
Schicht auf der Facette schließen, die die internen Verluste vergrößert
und so zur Alterung führt.
HL 16.5 Di 11:15 H13
Biofunctionalization of AlGaN surfaces — •Barbara Baur,
Georg Steinhoff, Martin Hermann, Oliver Purrucker,
Motomu Tanaka, Martin Stutzmann, and Martin Eickhoff —
Walter Schottky Institut, TU München, D-85748 Garching
Biosensor applications of semiconductor devices for operation in aqueous
electrolyte solutions are a current topic of intense research. Wide
bandgap semiconductors, such as group III-nitrides are regarded as
promising candidates for these applications as they combine high chemical
inertness with optical transparency and low thermal noise. To combine
those materials with organic systems, a detailed understanding as well as
experimental techniques for the realization and control of the anorganic/
organic interface are a basic requirement.
We have investigated the functionalization of AlGaN surfaces by deposition
of self-assembled monolayers (SAMs) based on silanes (silanization)
for subsequent formation of lipid membranes. Silanization is performed
by a self-assembly process from an organic solution of silane molecules.

Halbleiterphysik Dienstag
During the silanization process, hydroxyl groups which are formed on
oxidic surfaces and act as covalent coupling sites for alkylsilane have
to be provided. Thermally and chemically oxidized AlGaN surfaces are
compared with respect to their efficiency in the silanization process. We
have applied X-ray photoelectron spectroscopy (XPS) and contact angle
measurements to characterize the SAM formation and to investigate the
properties (coverage, hydrophobicity) of the functionalized layer.
HL 16.6 Di 11:30 H13
Improvement of GaN Schottky Diodes by Thermal Oxidation
— •Olaf Weidemann 1 , Eva Monroy 2 , Eike Hahn 3 , Martin Hermann
1 , Edgar Zaus 1 , Martin Stutzmann 1 , and Martin Eickhoff
1 — 1 Walter Schottky Institut, TU München, 85748 Garching —
2 CEA-CNRS-UJF Nanophysique et Semiconducteurs, CEA-Grenoble,
38054 Grenoble, France — 3 Laboratorium für Elektronenmikroskopie,
Universität Karlsruhe, 76128 Karlsruhe
GaN Schottky contacts have gathered increasing interest for the application
as UV detectors and, more recently, as high temperature gas
sensitive devices and GasFETs with catalytic Schottky contacts. However,
Schottky contacts on GaN suffer from high reverse currents due to
the presence of threading dislocations. To improve the device characteristics
and to guarantee reproducible electronic properties, a passivation
of these defects is desirable.
We have investigated the effect of thermal oxidation on the electronic
characteristics of Schottky contacts on heteroepitaxial n- and p-type GaN
layers grown by plasma assisted molecular beam epitaxy. Thermal oxidation
was found to lead to significant device improvement, notably a
decrease in reverse leakage current and an enhanced rectification ratio,
which has been quantified by IV- and CV-measurements. Analysis of the
oxidized layers by TEM and AFM revealed that preferential oxidation
at crystal defects is the dominating mechanism for the observed device
improvement.
HL 16.7 Di 11:45 H13
AlGaN/GaN Field Effect Transistors for Chemical and Biological
Sensor Applications — •Georg Steinhoff, Barbara
Baur, Martin Hermann, Martin Stutzmann, and Martin Eickhoff
— Walter Schottky Institut, Technische Universität München, Am
Coulombwall 3, 85748 Garching
Field effect transistors based on AlGaN/GaN heterostructures are of
great interest for chemical and biochemical sensor applications. The electrical
properties of the polarization induced 2DEG, which is formed at the
AlGaN/GaN heterointerface are highly sensitive to changes in the surface
potential. Additionally, the device surface is chemically inert in aqueous
solutions and non-toxic to living cells. We have studied the response
of nonmetallized gate regions of AlGaN/GaN transistors and transistor
arrays to changes in the concentration of specific ions in the ambient electrolyte.
The potential drop at the interface between the gate surface and
the electrolyte solution was measured and used as a sensor signal. A linear
sensor response of approximately 55 mV/pH was found for variations
in the H + -concentration between 10 -1 and 10 -13 mol/l, which is close to
the theoretical Nernst limit, determined by the native oxide layer present
on the surface. Sensitivity towards Na + , K + , Ca 2+ and Cl – -ions and long
term stability of the transistor devices in aqueous solutions were also investigated.
As a first biophysical application of these sensors we discuss
the detection and analysis of ionic signals of cells cultivated directly on
the device surface.
HL 16.8 Di 12:00 H13
Optimized Specific Contact Resistance of p-GaN — •Jens Dennemarck
1 , Tim Böttcher 1 , Detlef Hommel 1 und Anna Piotrowska
2 — 1 Institute of Solid State Physics, University of Bremen, D-
28359 Bremen — 2 Institute of Electron Technology, Al. Lotnikow 32/46,
02-668 Warsaw, Poland
Nowadays GaN-based high performance devices are available, which
needs high current densities during operation. For example, a GaN-based
laser diode needs a current density in the range of some 1 kA/cm 2 . To
operate devices reliable with such high driving conditions, ohmic contacts
with quite low specific contact resistances are necessary.
In the case of p-type GaN a metal with a large work function is necessary.
Then the difference between vacuum and Fermi level is large,
that holes can get into the metal without a barrier.
Two approaches were performed to reduce the specific contact resistance:
first a highly doped cap layer with a thickness of 15nm was added.
This should increase the number of acceptor levels with the effect of a
decreased barrier height. The second approach was a InGaN subcontact
layer about 20 nm. In respect of the induced strain the thickness of the
barrier decreased. To measure the specific contact resistance, the transfer
length method (TLM) was used. The problems of this measurement are
current spreading and current crowding. The cTLM method (circular
TLM) was considered to be the better method.
A number of metallization with different work functions were applied.
The best results were achieved by Pd/Au contacts with a specific contact
resistance of 1-2*10-5 A/cm 2 .
HL 16.9 Di 12:15 H13
Heat Dissipation in GaN LEDs and LDs - Simulation and
Experiment — •Stephan Figge 1 , Tim Böttcher 1 , Sven
Einfeldt 1 , Detlef Hommel 1 , Christoph Zellweger 2 , Mark
Ilegems 2 , Patrick Waltereit 3 , and James Speck 3 — 1 Institut
für Festkörperphysik, Universität Bremen — 2 Institut de photonique et
d’electronique quantiques, Ecole Polytechnique Federale de Lausanne
— 3 The Interdisciplinary Center for Wide Band-Gap Semiconductors,
University of California, Santa Barbara
The heating due to joule heat plays an important role in the device
characteristics of high power GaN light emitting diodes (LEDs) and laser
diodes (LDs). In this talk we will show two and three dimensional finite
elements calculations on the heat dissipation in LEDs and LDs and will
compare them with experiential results taken from devices grown on sapphire
substrates. The data of the simulations are in excellent agreement
with the experiential data such as the wavelength shift and the dependence
of output power taken from devices in DC and pulsed operation.
The talk will discuss the influence of the duty cycle and the pulse parameters
on the heating within the active region. In addition the dependence
of the thermal resistance on the device geometry (layer thicknesses, die
size, substrate material) will be shown.
HL 16.10 Di 12:30 H13
In,Ga,Al,N-Wellenleiter- und Laserstrukturen im blauen Spektralbereich
auf Si-Substraten — •Andre Strittmatter, Lars
Reissmann und Dieter Bimberg — Technische Universität Berlin,
Institut für Festköerperphysik, Sekr. PN 5-2, Hardenbergstr. 36, 10623
Berlin
Mittels Transfermatrizen und Lösung der Modengleichung wurden aus
epitaktischer Sicht realisierbare In,Ga,Al,N-Wellenleiterstrukturen auf
Si-Substraten für den Wellenlängenbereich 400-460 nm untersucht. Es
zeigt sich, dass bei geeigneter Dimensionierung einer GaN-Pufferschicht
und der AlGaN-Mantelschichten auch Fundamentalmoden innerhalb des
Wellenleiterkerns geführt werden. Dies ist zunächst überraschend, da der
Realteil des Brechungsindexes des Si-Substrats im interessierenden Spektralbereich
deutlich über den Brechungsindizes der Nitrid-Schichten liegt.
Die Modellierungen ergeben jedoch, daß gerade die absorbierenden Eigenschaften
des Si zu der gewünschten Wellenführung beitragen. Des weiteren
sind auch die bisher beim Wachstum rissfreier Nitridschichten unverzichtbaren
AlN-Zwischenschichten für die Führung der optischen Mode
vorteilhaft, da sie zu einer Reduktion der Eindringtiefe der optischen Mode
in die Mantelschichten führen. Ausgehend von diesen Erkenntnissen
präsentieren wir den Aufbau von Laserdioden auf Si-Substraten bei einer
Wellenlänge von 460 nm, die bei einer Gesamtdicke von 1.4-1.6 mum mit
nur 2-3 AlN-Zwischenschichten im n-dotierten Bereich der Diodenstruktur
realisiert wurden.

Halbleiterphysik Dienstag
HL 17 II-VI Halbleiter I
Zeit: Dienstag 10:15–13:30 Raum: H14
HL 17.1 Di 10:15 H14
Optische dielektrische Funktionen im Photonenenergiebereich
(4,0 - 9,5) eV von (1120) ZnO untersucht mittels generalisierter
spektroskopischer Ellipsometrie — •Rüdiger Schmidt-Grund 1 ,
Daniel Fritsch 1 , Mathias Schubert 1 , Bernd Rheinländer 1 ,
Heidemarie Schmidt 1 , Evgeni M. Kaidashev 1 , Michael
Lorenz 1 , Craig M. Herzinger 2 und Marius Grundmann 1 —
1 Universität Leipzig, Fakultät für Physik und Geowissenschaften,
Institut für Experimentelle Physik II, Linnéstr. 5, 04103 Leipzig —
2 J. A. Woollam Co., Inc. 645 M Street, Suite 102, Lincoln, Nebraska,
68508m, USA
Wurtzit-ZnO ist attraktiv für Anwendungen in der Optoelektronik.
Die Eigenschaften der E0-Band-Band Übergänge sowie der ordinäre und
extraordinäre Brechungsindexverlauf im Transparenzbereich sind gut bekannt.
Die Eigenschaften der höheren Band-Band Übergänge sind jedoch
weitgehend unbekannt.
Die optischen dielektrischen Funktionen eines mittels gepulster Laser-
Abscheidung (PLD, pulsed-laser-deposition) auf r-plane (1102) Al2O3
Substrat abgeschiedenen wurtzitischen a-plane (1120) ZnO-Dünn-Films
wurden mittels generalisierter spektroskopischer Ellipsometrie im Energiebereich
von 4,0 eV bis 9,5 eV bestimmt. Die dielektrischen Funktionen
zeigen Strukturen, welche bereits an uniaxialen AlGaN beobachtet wurden
und als E1-, E1+∆1-, E2-, and E ′ 0-Typ Band-Band Übergänge identifiziert
wurden. Die aus der ellipsometrischen Modell-Analyse bestimmten
energetischen Positionen dieser Übergänge werden mit Pseudopotential-
Bandstruktur-Rechnungen verglichen.
HL 17.2 Di 10:30 H14
Blue ZnO: New insides from highly concentrated alcoholic colloids
— •Michael Hilgendorff and Michael Giersig — caesar
research center, Ludwig-Erhard-Allee 2, 53175 Bonn, Germany
UV illumination of colloidal ZnO-solutions generates electron-hole
pairs in the nanoparticles which are diffuse to the particles surface where
they can react with molecules in solution. While the electrons mainly
react with oxygen the holes oxidize solvent molecules and surfactants. In
the absence of oxygen the number of surface electrons increases which is
accompanied by the occurrence of a broad absorption in the red and near
infrared. Thus, ZnO-colloids become blue, which is visible with the naked
eye in colloids having a concentration greater than 0.1 M. The influence
of n- and p-doping of ZnO on this effect will be discussed.
HL 17.3 Di 10:45 H14
Wachstum und strukturelle Charakterisierung von ZnO Mikrokristallen
und Nanodrähten — •Andreas Rahm, Thomas Nobis,
Evgeni Kaidashev, Michael Lorenz, Jörg Lenzner und Marius
Grundmann — Universität Leipzig, Fakultät für Physik und Geowissenschaften,
Institut für Experimentelle Physik II, Linnestr. 5, D-04103
Leipzig
Für potentielle Anwendungen in der Nanotechnologie kommen facettierte
säulenartige Kristalle und Drähte beispielsweise als Nanokavitäten
für Laseranwendungen in Betracht. Dafür ist Zinkoxid durch das c-
Achsen dominierte Wachstum und seine hohe Excitonen-Bindungsenergie
besonders interessant. ZnO Mikrokristalle und Nanorasen wurden mittels
PLD und thermischer Verdampfung auf Saphirsubstraten unter Verwendung
von Gold als Wachstumskatalysator (VLS growth) hergestellt.
Mit dem Ziel der Optimierung von Aspektverhältnis, Kristallgüte, Bedeckungsgrad
und lateraler Homogenität wurde dabei der Einfluss kritischer
Züchtungsparameter, wie Temperatur, Restgasdruck, Targetzusammensetzung,
etc. untersucht. Sowohl Nanorasen als auch durch Ultraschall
vereinzelte Nanofäden (∼100nm Durchmesser) wurden mittels
XRD, SEM und AFM hinsichtlich epitaktischer Relation, Qualität, Geometrie
und Wachstum charakterisiert. Dieses Projekt wird von der DFG
im Rahmen der FOR 522 (Projekt P1) unterstützt.
HL 17.4 Di 11:00 H14
Stimulierte Emission in ZnO-Epitaxieschichten — •Heiko Priller
1 , J. Brückner 1 , Th. Gruber 2 , Ch. Kirchner 2 , A. Waag 3 ,
H.J. Ko 4 , T. Yao 4 , H. Kalt 1 und C. Klingshirn 1 — 1 Institut für
Angewandte Physik, Universität Karlsruhe — 2 Abteilung Halbleiterphysik,
Universität Ulm — 3 Institut für Halbleitertechnik, TU Braunschweig
— 4 Institute for Material Research, Tohoku University, Japan
Wir untersuchen ZnO-Epitaxieschichten die mit MBE (Molecular Beam
Epitaxy) und MOVPE (Metal Organic Vapor Phase Epitaxy) hergestellt
wurden und bestimmen ihre Eigenschaften unter optischer Hochanregung.
Als Anregungsquelle dient ein Excimer-Laser mit einer Anregungswellenlänge
von 308 nm (4.024 eV) und einer Pulslänge von 15 ns,
so dass wir im quasi-kontinuierlichen Bereich sind. Bei niedrigen Anregungsintensitäten
wird das Photoluminsezenzspektrum bei tiefen Temperaturen
durch die Emission von gebundenen Exzitonen dominiert. Erhöht
man die Exzitonendichte beobachten wir eine zusätzliche Emissionsbande
die von Exziton-Exziton-Streuung herrührt. Bei weiterer Erhöhung der
Exzitonendichte dominiert diese Bande und bei noch grösseren Dichten
beobachten wir die Bildung eines Elektron-Loch-Plasmas mit einer sehr
breiten Emissionsbande. Die Spektren der optischen Verstärkung werden
mit der Strichlängenmethode bestimmt.
HL 17.5 Di 11:15 H14
Ortsaufgelöste Kathodolumineszenz an ZnO Mikrokristallen
und Nanodrähten — Th. Nobis, A. Rahm, E. M. Kaidashev,
M. Lorenz, J. Lenzner, M. Grundmann, •Th. Nobis, A. Rahm,
E. M. Kaidashev, M. Lorenz, J. Lenzner und M. Gr undmann
— Universität Leipzig, Fakultät für Physik und Geowissenschaften,
Linnéstr. 5, D-04103 Leipzig
Zur ortsaufgelösten optischen Untersuchung von Nanostrukturen wurde
die Steuerungssoftware entwickelt, mit deren Hilfe ein Rasterelektronenmikroskop
zur Erstellung von Kathodolumineszenz-Images (CLI) genutzt
werden kann. Die externe Steuerung der Strahlposition erlaubt
das Scannen einer etwa 15 × 20 µm 2 großen Fläche und somit die
punktweise Aufzeichnung der Kathodolumineszenz-Intensität der Probe.
Die Messungen an ZnO Mikrokristallen und Nanodrähten zeigen deutlich
die lokalen Unterschiede der Lumineszenz im UV (3.3 eV) und im
Grünen (2.3 eV). Somit weisen die CLIs auf Regionen unterschiedlicher
Kristallgüte hin. Außerdem wurden ortsabhängige Verschiebungen
der Spektralmaxima festgestellt, die vermutlich Verspannungen in den
Mikrokristallen sichtbar machen. Die CLIs wurden bei unterschiedlichen
Temperaturen und an verschiedenen Geometrien (Pyramiden, Säulen,
Drähten) aufgenommen.
Gefördert durch die DFG, FOR 522, Projekt P1 (Gr 1011/1-1).
HL 17.6 Di 11:30 H14
Elektronische Bandstruktur von wurtzitischem ZnO,
Zn1−xMgxO und Zn1−yCdyO mittels Empirischer Pseudopotential
(EPP)-Rechnungen unter Berücksichtigung der
Spin-Bahn-Wechselwirkung — •Daniel Fritsch, Heidemarie
Schmidt, Rüdiger Schmidt-Grund und Marius Grundmann —
Universität Leipzig, Fakultät für Physik und Geowissenschaften
Aus experimentell bestimmten Tieftemperaturübergangsenergien
binärer Halbleiterverbindungen werden iterativ die übertragbaren,
strukturunabhängigen Modellpotentialparamter r i und z i der ionaren
Modellpotentiale von Zn, Mg, Cd und O für EPP-Rechnungen
gewonnen. Auf der Grundlage dieser Modellpotentialparameter wird
die elektronische Bandstruktur des ZnO-Hostsystems und der durch
isovalente Kationensubstitution erhaltenen ternären Mischkristalle
Zn1−xMgxO und Zn1−yCdyO für verschiedene Mischungsverhältnisse x
bzw. y mittels EPP-Rechnungen bestimmt.
Die Berücksichtigung der Spin-Bahn-Wechselwirkung ermöglicht die
Ermittlung der effektiven Massen und der Luttinger-ähnlichen Parameter
ohne k · p-Näherung direkt aus der berechneten Bandstruktur.
Ein Vergleich der entlang hochsymmetrischer Linien der Brillouinzone
berechneten elektronischen Bandstruktur von ZnO und seiner
ternären Mischkristalle mit den mittels spektroskopischer Ellipsometrie
bei Raumtemperatur gewonnenen Band-Band-Übergangsenergien erlaubt
eine Zuordnung der E1-, E1+∆1-, E2- und E ′
0-Ellipsometriewerte zu
Übergangsenergien an bestimmten kritischen Punkten der Brillouinzone.
HL 17.7 Di 11:45 H14
Atomistic Simulations of Static and Dynamic Defect Properties
of Zinc Oxide — •Paul Erhart und Karsten Albe — Institut für
Materialwissenschaft, Technische Universität Darmstadt, Petersenstr. 23,
64287 Darmstadt
Zinc oxide is a wide band-gap semiconductor material which has wide

Halbleiterphysik Dienstag
spread applications in electronic devices. It has been found to be very
difficult to synthesize p-type conducting material. While it is commonly
assumed that point defects are the origin of this behavior, the precise
nature of these defects is still a matter of debate. We present an interatomic
potential for the Zn-O system based on the bond-order concept
as introduced by Tersoff and Brenner but extended to include Coulombic
(monopole) interactions. Thereby, it is possible to account for the
mixed covalent-ionic bonding character of zinc oxide. The reactive potential
enables simulations of the dynamic behavior taken into account
the effects of temperature and pressure in computationally efficient calculations.
Using the new potential in conjunction with classical molecular
dynamics simulations we have studied the thermodynamic properties of
point defects. Particular attention has been paid to the behavior of the
oxygen interstitial configuration.
HL 17.8 Di 12:00 H14
Exact-Exchange-Based Quasiparticle Calculations of II-VI
Compounds — •Patrick Rinke 1 , Abdallah Qteish 2 , Jörg
Neugebauer 3 , and Matthias Scheffler 1 — 1 Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Berlin — 2 Department of Physics,
Yarmouk University, Irbid - Jordan — 3 Dekanat Physik, Universität
Paderborn
We present ab initio electronic structure calculations for the II-VI compounds
ZnO, ZnS and ZnSe in the zinc-blende structure. In this context,
the GW-approximation to the self-energy has successfully been applied
to a wide range of materials. The presence of the shallow semicore delectrons
of Zn, however, poses a conceptual as well as computational
challenge. Previous quasiparticle calculations for ZnS and ZnSe have in
common that GW was applied as a perturbation to a density-functional
theory (DFT) calculation within either the local-density or a generalised
gradient approximation, but differ crucially in the pseudopotentials used.
Here we present DFT calculations in the exact-exchange (EXX) formalism,
which gives good agreement with quasiparticle calculations and also
with experiment for standard semiconductors [1]. We apply the EXX
approximation consistently using the newly developed approach of KLIpseudopotentials.
Furthermore we use the EXX energies and wavefunctions
as input for a GW calculation to examine the role of the 3d-electrons
and the p - d repulsion.
W. G. Aulbur, M. Städele and A. Görling, Phys. Rev. B 62 7121 (2000)
HL 17.9 Di 12:15 H14
Synthese und Charakterisierung von ZnO1−xSx — •Thorsten
Krämer 1 , Angelika Polity 1 , Changzhong Wang 1 , Yunbin He 1 ,
Dietmar Hasselkamp 1 , Baker Faragis 1 , Bruno K. Meyer 1 ,
Ute Haboeck 2 und Axel Hoffmann 2 — 1 I. Physikalisches Institut,
Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen
— 2 Institut für Festkörperphysik, Technische Universität Berlin,
Hardenbergstr. 36, 10623 Berlin
Dünne Schichten der ternären Legierung ZnO1−xSx wurden im gesamten
Kompositionsbereich mittels Radiofrequenzkathodenzerstäubung auf
Saphir- und Glassubstraten abgeschieden. Als Zerstäubungstarget wurde
hierbei keramisches ZnS verwendet und Argon bzw. Sauerstoff wurden
als Arbeits- bzw. Reaktivgas eingesetzt. Die Schichten wachsen in
der Wurzitstruktur und sind c-Achsen orientiert, was durch XRD(Xray
diffraction)-Messungen gezeigt wurde. Ihr c-Achsenparameter variierte
linear mit der Komposition, welche mit XPS(X-ray photoelectron
spectroscopy)- und RBS(rutherford backscattering)-Messungen bestimmt
wurde. Ramanmessungen zeigten eine Verschiebung der spektralen
Position der A1(LO)-Mode in Abhängkeit der Schichtzusammensetzung.
Die Abhängigkeit der Bandlückenenergie von der Komposition
konnte mit Absorptionsmessungen bestimmt werden. Hierbei wurde ein
Bowingverhalten der Bandlücke beobachtet. Die niedrigsten Energien betragen
2,7 bis 2,8eV für eine Komposition von x=0,5. Der Bowingparameter
beträgt etwa 2,5eV.
HL 17.10 Di 12:30 H14
Stickstoffdotierung in ZnO — •J. Sann 1 , B. Farangis 1 , B.K.
Meyer 1 und G. Pensl 2 — 1 I. Physikalisches Institut, Justus-Liebig-
Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen — 2 Institut für
Angewandte Physik, Universität Erlangen
Unter den möglichen p- Dotanden in ZnO wird Stickstoff auf Sauerstoffplatz
favorisiert. Wir berichten über den Einbau von Stickstoff
über Implantation, durch Dotierung während des Wachstums in CVD-
Epitaxieschichten sowie über Diffusionsexperimente aus der Gasphase.
Die Photolumineszenzuntersuchungen zeigen unabhängig von der Dotiermethode
das Auftreten eines Donator-Akzeptor-Paar Übergangs bei 3.23
eV.
HL 17.11 Di 12:45 H14
Magnetische Resonanzuntersuchungen in ZnO Volumenkristallen
und Quantenpunkten — •D. Pfisterer 1 , D.M. Hofmann 1 , N.
Volbers 1 , B.K. Meyer 1 , S. Orlinski 2 und J. Schmid 2 — 1 I. Physikalisches
Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring
16, 35392 Gießen — 2 Universität Leiden, Niederlande
Die Identifizierung von extrinsischen Störstellen in ZnO, die
hauptsächlich als Restverunreinigungen vorliegen, ist im Hinblick auf
eine gezielte Modifizierung des Ladungsträgertyps (n- nach p-Leitung)
von grundlegendem Interesse. In Volumenkristallen können Aluminium,
Gallium, Indium und Wasserstoff durch ESR/ENDOR Experimente als
Donatoren und Stickstoff als Akzeptor identifiziert werden. In ZnO Quantenpunkten
kann über die Wahl der Ausgangsstoffe in der Synthese insbesondere
Lithium eingebaut werden. Wir berichten über Hochfeld-ESR
Experimente, die demonstrieren, dass Lithium in zwei verschiedenen Modifiaktionen
vorliegt. Die unterschiedlichen Defektkonfigurationen werden
diskutiert.
HL 17.12 Di 13:00 H14
Eigenschaften von Li-, Sb-, und P-dotierten ZnO Dünnfilmen
— •H. von Wenckstern, C. Bundesmann, S. Heitsch, G. Benndorf,
D. Spemann, E. M. Kaidashev, M. Lorenz, M. Schubert
und M. Grundmann — Universität Leipzig, Institut für Experimentelle
Physik II, Linnéstraße 5
ZnO, ein derzeit intensiv untersuchter II-VI Halbleiter mit einer fundamentalen
Bandlücke von ca. 3.37 eV bei Zimmertemperatur (RT),
ist aufgrund seiner hohen Exzitonenbindungsenergie von etwa 60 meV
ein Kandidat für die Realisierung effektiver, im UV bei RT arbeitender,
exzitonischer Bauelemente. Dazu muss es gelingen, hochwertiges pleitendes
ZnO zu produzieren. Es wurde der Einfluss verschiedener Dotanden
auf die elektrischen, optischen und phononischen Eigenschaften
von ZnO-Dünnfilmen untersucht, welche mittels gepulster Laser Deposition
auf Saphir epitaktisch abgeschieden wurden. Die Dotanden Li,
Sb bzw. P wurden mit verschiedenen Anteilen in die Targets gemischt.
Der Typ der Majoritätsladungsträger, deren Konzentration und deren
Mobilität wurden mit Halleffektmessungen bestimmt. Der Großteil der
Proben ist n-leitend, der andere Teil der Proben (vor allem Sb- und Pdotierte
Proben) nichtleitend. Photolumineszenzmessungen bei 4 K zeigen
den Einfluss der verschiedenen Dotanden auf das Rekombinationsspektrum.
Es wurden zusätzlich temperaturabhängige Photolumineszenzmessungen
durchgeführt, um die Ursache der verschiedenen Rekombinationsbanden
zu verstehen. Die Phononenmoden wurden mit Raman-
Messungen untersucht. Zusätzlich wurde ein Großteil der Proben mit
Infrarot-spektroskopischer Ellipsometrie charakterisiert.
HL 17.13 Di 13:15 H14
Epitaxie von ZnO auf ZnO Substraten — •Arndt Zeuner,
Christian Neumann, Joachim Sann und Bruno K. Meyer — I.
Physikalisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-
Ring 16, 35392 Gießen
Wir untersuchten die Möglichkeiten des Wachstums von ZnO
auf ZnO Substraten. In den gewachsenen Schichten wurden mit
Röntgendiffraktometrie verschiedene Gitterkonstanten beobachtet. Des
weiteren wurden die ZnO Schichten mit Stickstoff dotiert. Die ZnO:N
Schichten wiesen einen Donator-Akzeptor-Paar Übergang auf. Die ZnO
Schichten wurden mit Sekundärionen Massenspektroskopie und Rasterelektronenmikroskopie
untersucht.

Halbleiterphysik Dienstag
HL 18 Hauptvortrag Zacharias
Zeit: Dienstag 14:30–15:15 Raum: H15
Hauptvortrag HL 18.1 Di 14:30 H15
Confinement effects in Si nanostructures — •Margit Zacharias,
Johannes Heitmann, Vadim G. Talalaev, Roland Scholz, Florian
M. Kolb, and Herbert Hofmeister — Max-Planck- Institut
für Mikrostrukturphysik, Weinberg 2, 06120 Halle
Silicon is the main base material for modern microelectronics. Due to
its indirect band structure it is not ideally suited for optoelectronic purposes.
Nevertheless, because of its importance in microelectronics major
research and development efforts have been undertaken to change sili-
HL 19 Symposium 50 Jahre Solarzelle
con into a photonics material. The present lecture will highlight areas in
which silicon promises to have an increasing impact in the area of photonics.
Approaches developed in our group will be presented on how to
transform silicon so that it can be used as an efficient light emitter in the
visible and infrared. Especially the interaction of quantum confinement
and migration effects of the excitons and the energy transfer to doping
materials, i.e. Erbium, is investigated in details. The presented strategies
for size controlled growth of nanocrystals and nanowires play a major
role for the described investigations and perspective applications.
Zeit: Dienstag 15:15–17:45 Raum: H15
HL 19.1 Di 15:15 H15
Slow Solar Ascent — •H. J. Queisser — Max-Planck-Institute for
Solid State Research, D-70506 Stuttgart
Limited attention arose from the miniscule note by Chapin, Fuller,
and Pearson on a new solar cell, as received on January 11, 1954 by the
Journal of Applied Physics. Pentagon engineers sneered at this feeble
power source; trials failed for rural telephony. The initial theory for solar
cells relied on mere extensions for the forward current – voltage relations
of p – n junctions. Later work simply attempted reductions of all loss
mechanisms. The Sputnik shock suddenly rekindled active research. The
optimal semiconductor was to be found. A thermodynamic theory was
proposed on the basis of detailed balance and a restriction to radiative
recombination. Silicon proved to be close to maximal efficiency.
HL 19.2 Di 15:45 H15
Progress in Manufacturable High-Efficiency Silicon Solar Cells
— •R. Hezel — Institut für Solarenergieforschung GmbH, Am Ohrberg
1, 31860 Emmertal
As an important step towards making photovoltaics an economic
source of energy, the efficiency of industrial crystalline silicon solar cells
has to be drastically increased. In this way not only more power is gained
with less silicon, but simultaneously also all other area-related costs of
the PV system are reduced. It is of great importance to bridge the efficiency
gap between the present industrial solar cells with values of 14% to
16% and the sophisticated laboratory cells with a record efficiency close
to 25%. Recently new technologies are emerging or existing ones being
upgraded aiming for the ambitious goal to manufacture silicon solar cells
with efficiency above 20% cost effectively in an industrial environment.
Four different promising approaches of high efficiency silicon solar cells
are presented in this paper, including one with bifacial sensitivity.
HL 19.3 Di 16:15 H15
Second and third generation photovoltaics: dreams and reality.
— •J. H. Werner — Institut für Physikalische Elektronik, Universität
Stuttgart
To more than 90 %, the present world market of solar cells is dominated
by one material: crystalline silicon. Is has become common to term
photovoltaics based on silicon wafers as ”first generation” photovoltaics.
Research on ”second generation” photovoltaics, i.e. on thin film solar
cells started as early as 1956 when the first Cu2S/CdS solar cell was prepared.
Research on this type of cells was essentially given up around 1980
because 10 % efficiency have never been exceeded. At the same time, substantial
research started on amorphous silicon, which now stands at 13 %
(stable) efficiency compared to almost 25 % for the world best cells from
crystalline silicon. Thus, early second generation photovoltaics did not
fulfil the dreams of a cheap, highly efficient thin film technology. Nowadays,
two other materials second generation are going into the production
of commercial modules: CdTe and Cu(In,Ga)Se2. This presentation gives
a critical assessment of these two materials which are highly interesting
for research but as commercial products may suffer either from their toxicity
or from their polycrystallinity. In particular, the inherent structural
inhomogeneity of the polycrystalline films results in an electronic inhomogeneity
which limits the performance of cells and modules in several
ways. As a consequence, even in the case of second generation photovoltaics,
the material of choice probably will be again crystalline silicon.
Only photovoltaic materials which either supplement crystalline silicon
or lead to new principles for the conversion of solar radiation into electricity
seem to be interesting for innovative research. From this point of
view, research on ”third” generation photovoltaics, i.e. solar cells with
potential efficiencies above the classic Shockley/Queisser limit of 30 %,
including recent publications on ZnMnTe, will be critically discussed.
HL 19.4 Di 16:45 H15
Material & Device Concepts for Organic Photovoltaics: Towards
Competitive Efficiencies — •C. J. Brabec — SIEMENS
AG, CT MM1, Innovative Polymers, Paul Gossenstr. 100, D-91052 Erlangen,
Germany
The talk gives an overview on the technology of polymer photovoltaics,
addressing device, production, packaging and business aspects. The focus
is however placed on the function of bulk-heterojunction devices. Even
10 years after the introduction of the bulk-heterojunction concept, basic
physical processes in these devices are still under discussion. A model to
describe bulk heterojunction solar cells in introduced. The performance
potential of state of the art organic bulk-heterojunction photovoltaic devices
is analysed at the hand of this model, and guidelines towards higher
device efficiencies are presented. The concept relies on the identification
and determination of the relevant material parameters (lifetime, mobility,
bandgap, trap density.....) for the pristine components and for the
blended photovoltaic composites. Results from simulation are compared
to experimental device performance. Based on these findings, material
and device parameters for highly efficient bulk heterojunction devices
are presented and a roadmap for the polymer photovoltaic is suggested.
HL 19.5 Di 17:15 H15
The Crystalline Silicon Solar Cell - Its History, Achievements
And Perspectives — •G. Willeke — Fraunhofer ISE, Heidenhofstr.
2, D-79110 Freiburg, Germany
With a long history of successful market deployment, the crystalline
silicon solar cell currently celebrates its 50th anniversary. On this occasion
it is useful and appropriate to analyse the rate of progress in the
past and to highlight its further development potential for the markets
to come. Subsequent to finding a suitable market in space 5 years after
its conception, crystalline silicon developed into the workhorse technology
of the terrestrial power market which was stimulated by the oil crises
25 years ago. In the first 25 years of its existence, all the technological
features were already demonstrated on a lab-scale that are now incorporated
in the mass-manufacturing lines such as a screen printed front
finger grid, textured and passivated surfaces, the back surface field and
even the now very successful block-casting technique was researched then.
The early terrestrial devices in the late 70s took a great benefit from the
space development and first modules were 8 inch single crystalline wafers.
In comparison, today’s product is made from 125mm quasi-square substrates
(150mm full square are currently under development) with module
efficiencies in the range of 11-15 efficiency of 6 technology. The wafer
size here has increased from 10x10 cm 2 to 12.5x12.5 cm 2 (15x15 cm 2 being
introduced into manufacturing). In all these technologies the wafer
thickness has been hardly reduced in this quarter century from 400 m 2
to 300 m 2 . The task of the next decade will be to bring 20 technology
into production, bring the wafer size to 20x20 cm 2 and at the same time
reduce the wafer thickness considerably. That the manufacturing of 50
m 2 thin crystalline silicon wafers into 40 m 2 thin 20 technique LFC, has

Halbleiterphysik Dienstag
been recently demonstrated in our laboratory. A challenge lies in the massproduction of 50 m 2 wafers with cost-effective methods.
HL 20 Photonische Kristalle IV
Zeit: Dienstag 15:15–17:30 Raum: H17
HL 20.1 Di 15:15 H17
Optical characterisation of opal heterojunctions — •Sergei
Romanov 1 , Dmitry Chigrin 1 , Vladimir Solovyev 1 , Clivia
Sotomayor Torres 1 , Nikolai Gaponik 2 , Alexander Eychmueller
2 , and Andrei Rogach 3 — 1 Inst. of Materials Science
and Dept. of Electrical and Information Engineering, University of
Wuppertal, 42097, Germany — 2 Inst. of Physical Chemistry, University
of Hamburg, 20146, Germany — 3 Dept. of Physics, University of
Munich, 80799, Germany
Interfacing of photonic crystals (PhCs) is a step towards their functionalisation.
The anticipated effects are engineered PBG, light confinement
and directing of the light flow. Hetero-opals were prepared by sandwiching
two thin film opals assembled from latex beads of different diameters,
while staying with preparation by self-assembly. Angle-resolved
reflectance, transmission, scattering and emission of light were used to
characterise hetero-opals.
Anomalous transmission minimum was observed in between two Bragg
gaps of the hetero-opal constituents and associated with the interface.
This observation was supplemented by reflectance and scattering experiments.
Finite difference time domain modelling of light propagation in
2D PhC hetero-junction was used to study this effect.
Anomalies of emission spectra of CdTe nanoparticles embedded in
hetero-opals, which were observed at frequencies of the interface gap,
agree the interface gap model.
HL 20.2 Di 15:30 H17
EFFECTS OF DISORDER IN MICROWAVE REALI-
ZATIONS OF 1D PHOTONIC CRYSTALS: — •G.A.
Luna-Acosta 1,2 , H. Schanze 1 , U. Kuhl 1 und H.-J. Stöckmann 1
— 1 Fachbereich Physik der Philipps Universität Marburg, Renthof 5,
D-35032 — 2 Instituto de Fisica, BUAP, Puebla, Mexico.
We experimentally investigate the effects of structural and impurity
disorder in 1D photonic lattices and superlattices of finite length. These
lattices are realized in the microwave regime by an array of teflon pieces
of length dT alternating periodically with air spacings of length dA in a
single-mode microwave guide experiment. Structural ( positional) disorder
is achieved by an uncorrelated random variation ξ of the air spacings
and/or the teflon inserts. Impurity disorder is realized by placing a few
teflon pieces of length dimp within the air spacing of the ideal crystal. The
manifestation in the transmission measurements of weak, intermediate,
and strong disorder of both types of disorder is analyzed and compared
with simple transfer matrix calculations. We also discuss our results in
connection with theories of correlated and uncorrelated random disorder
in 1D potentials.
HL 20.3 Di 15:45 H17
Resonant 2D-PC structures of moderate refractive index
materials — •Gunnar Böttger, Markus Schmidt, Karolin
Preusser-Mellert, Alexander Petrov, and Manfred Eich —
Technische Universität Hamburg-Harburg, AB 4-09, 21071 Hamburg
We present simulations and experimental measurements of transmission
properties of photonic crystal slab structures defined by air holes
etched into polymeric slab waveguides. Geometric defects in otherwise
regular photonic crystal slab structures strongly localize optical fields,
forming resonators of significant quality factors that may e.g. be used
in novel filtering devices for optical telecommunications (1330 and 1550
nm). We show what influence parameters like etching depth and vertical
contrast have on attainable quality factors and on transmission as well
as coupling efficiencies. First results are presented on the use of ultra low
index substrates.
HL 20.4 Di 16:00 H17
Emitting quantum dots under photonic confinement: composite
materials design and fabrication — •Nikolai Gaponik 1 , Richard
Capek 1 , Alexander Eychmüller 1 , Andrey Rogach 2 , Clivia Sotomayor
Torres 3 , and Sergei Romanov 3 — 1 Institute of Physical
Chemistry, University of Hamburg, 20146 Hamburg — 2 Photonics and
Optoelectronics Group, Department of Physics and CeNS, University
of Munich, 80799 Munich — 3 Institute of Materials Science and Department
of Electrical and Information Engineering, University of Wuppertal,
42097 Wuppertal
Strongly luminescent colloidal quantum dots (QDs) were integrated
into various types of opal-based photonic structures and microcavities.
The post-preparative treatment of QD surface was demonstrated to be a
powerful tool to give precise control over the luminescent photonic composite
materials properties. Both the layer-by-layer assembly and solventcontrolled
precipitation techniques were optimized to be used for formation
and selective modification of light-emitting hetero-opals. Structural
and optical properties of fabricated composite materials are reported.
HL 20.5 Di 16:15 H17
Cavity QED phenomena in Photonic Crystal Microcavities containing
self-assembled Quantum Dots — •A. F. Kreß, F. Hofbauer,
H. J. Krenner, D. Schuh, R. Meyer, and J. J. Finley —
Walter Schottky Institut, TU München, 85748 Garching, Germany
We present optical investigations of active photonic crystal defect mircocavities
(PCµC) formed from a hexagonal lattice of air-holes in a GaAs-
(Al)GaAs slab waveguide. Incorporation of one or more layers of self assembled
InGaAs quantum dots (QD) into the waveguide enable us to
directly probe the nature of the cavity modes using spatially resolved
photoluminescence (µPL) spectroscopy. Moreover, cavity-QED phenomena
have been directly observed using time resolved spectroscopy.
The fully localised PCµC modes show strongly enhanced light emission
with Q>500 for a modevolume of ∼ 3(λ/n) 3 . Time resolved measurements
clearly demonstrate Purcell enhancement of the spontaneous
emission rate with Purcell factors up to ∼4 having been observed.
Control of the design and symmetry of the PCµC allows us to engineer
the cavity modes. µPL measurements on a series of H2 PCµCs
demonstrate our ability to tune the wavelength of the cavity modes over
∼ ±30nm around ∼950nm with a precision better than ∼1nm. Tuneable
cavity states are investigated in different hexagonal crystals and exhibit
mode structure in good accordance with our calculations. Improved
PCµC designs for reduced symmetry ultra high Q-cavities will also be
presented. Finally, we will discuss a device concept for an electronically
tuneable PCµC for planned single QD cavity QED experiments.
HL 20.6 Di 16:30 H17
Metal-Dielectric Photonic Crystals from Gold Coated opals
— •Andrei Susha 1 , Paul Miclea 2 , Clivia Sotomayor Torres 2 ,
Sergei Romanov 2 , and Frank Caruso 3 — 1 Dept. of Physics, University
of Munich, 80799, Germany — 2 Inst. of Materials Science, Dept. of
Electrical and Information Engineering, University of Wuppertal, 42097,
Germany — 3 Dept. of Chemical and Biomolecular Engineering, University
of Melbourne, Victoria 3010, Australia
The promise of metal-dielectric (MD) opals is to be photonic crystals
(PhC) with wide and robust photonic bandgap (PBG). To prepare
films of MD opals, the latex spheres were coated by 5nm Au nanoparticles
(NP). The angular-resolved reflectance spectroscopy in the visible
and near-infrared ranges, the surface diffraction and light scattering were
used to study their PBG.
The surface plasmon resonance of Au NPs changes in opals from the
single peak to the set of peaks in correspondence to the shape of NCs
aggregates. The diffraction resonance in Au-opals evolves away from the
dielectric-type behaviour, when it overlaps the plasmon resonance. Increase
of the Au content up to 50 wt. emerging bands with unusual
angular dispersion. Experimental data are discussed in the light of theory
predictions.

Halbleiterphysik Dienstag
HL 20.7 Di 16:45 H17
Nonlinear Wave Interaction Processes in Photonic Crystals —
•Lasha Tkeshelashvili 1 , Jens Niegemann 1 , and Kurt Busch 1,2 —
1 Institut für Theorie der Kondensierten Materie, Universität Karlsruhe
— 2 School of Optics/CREOL and Department of Physics, University of
Central Florida, Orlando, USA
We show that nonlinear wave interaction processes in Photonic Crystals
exhibit certain peculiar properties which originate from the rich photonic
band structure of such systems. These include the creation and manipulation
of gap solitons in defect-free systems as well as the trapping
of solitons at defect sites. In view of applications of these phenomena
in all-optical logic elements, we emphasize that the stability of solitary
waves in these systems is very important.
HL 20.8 Di 17:00 H17
Nanopillars photonic crystal waveguides — •Dmitry Chigrin,
Andrei Lavrinenko, and Clivia Sotomayor Torres — Institute
of Materials Science and Department of Electrical, Information and Media
Engineering, University of Wuppertal, D-42097 Wuppertal, Germany
Photonic crystals (PhCs) are known for offering some new options to
control the flow of light. PhC waveguide (PCW) is one example of PhCs
application. In PCW, light confinement is due to a complete photonic
bandgap. In this work, we present a novel type of PCW, which consists
of a several rows of periodically placed dielectric cylinders. In such a
structure, light confinement is due to the total internal reflection, while
guided modes dispersion is strongly affected by waveguide periodicity.
A single row of periodically placed dielectric cylinders acts as a sin-
HL 21 II-VI Halbleiter II
gle mode waveguide. By adding new rows of cylinders, one transforms a
single-row waveguide into a coupled waveguide array. Guided modes, a
number of which is equal to the number of waveguide in the array, are
bounded by lowest bands of infinite 2D PhC, possessing unique dispersion
and being nearly equidistant.
In this work, factors playing the major role in tuning frequency positions
and separation of guided modes are analyzed. The possibilities of
the specific mode excitation and application of a nanopillars PCW as a
laser cavity are discussed.
HL 20.9 Di 17:15 H17
Light control mediated by electron-hole transport in GaAs photonic
cavities — •M. M. de Lima, Jr., R. Hey, J. A. H. Stotz,
and P. V Santos — Paul-Drude-Institut, Berlin
Most investigations concerning photonic structures have addressed the
control of light flow by structuring a dielectric medium. We demonstrate
an alternative concept for photon control based on the manipulation of
photogenerated electron-hole pairs by surface acoustic waves (SAWs) in
photonic structures. Specifically, photogenerated carriers in a microcavity
containing (In,Ga)As quantum wells are transported over long distances
(> 100 µm) at room temperature by the SAW piezoelectric field. The
photons are then retrieved after the transport by inducing electron-hole
recombination. The important aspect is that the recombination (and thus
the photon emission) sites are determined by a switch composed of orthogonal
SAW beams, which can be used as a basic control gate for
optical information processing based on ambipolar transport.
Zeit: Dienstag 15:15–16:45 Raum: H13
HL 21.1 Di 15:15 H13
Spinflip-Raman-Messungen an dotierten semimagnetischen
ZnMnSe-Proben — •M. Lentze 1 , D. Wolverson 2 , P. Grabs 1 , D.
Keller 1 und J. Geurts 1 — 1 Physikalisches Institut der Universität
Würzburg, EP III, Am Hubland, D-97074 Würzburg — 2 University of
Bath, Dep. of Physics, Bath BA2 7AY, UK
Semimagnetische Materialien stellen einen wichtigen Baustein
der neuen spinbasierten Informationstechnologie ( ” Spintronics“).
Schwerpunkt unserer Arbeiten bilden Manganhaltige ZnSe Proben:
volumenartige BeZnMnSe-Epitaxieschichten mit Elektronenkonzentrationen
zwischen 10 17 cm −1 und 10 19 cm −1 und modulationsdotierte
BeZnSe/ZnMnSe-Quantentröge mit einem zweidimensionalen Elektronengas.
Die Quantentrogbreite liegt dabei zwischen 50 nm und 10
nm. Durch die Analyse der Ramansignale erhält man Aufschluss über
die Mn-Konzentration, die effektiven g-faktoren sowie die Spinpolarisation.
Durch Messungen unter verschiedenen Einfallswinkeln des
Laserlichts wurde der Impulsübertrag der Ramanstreuung variiert.
Hierbei sind Rückschlüsse auf die Spinpolarisation der Proben möglich.
Die angeführten Untersuchungen wurden an extrem hochdotierten
Proben durchgeführt. Die optische Charakterisierung bildet somit
einen unverzichtbaren Bestandteil der Spintronic. Weiterhin sind bei
einigen Proben Anisotropien des Spinflip-Signals unter verschiedenen
Winkeln beobachtbar. Untersuchungen der Halbwertsbreite der Signale
in Abhängigkeit der Anregungsenergie zeigen weiterhin eine inhomogene
Verbreiterung.
HL 21.2 Di 15:30 H13
Stabilisierung von ZnSe-basierenden Laserdioden durch Einführung
spannungskompensierender Barrieren — •Arne Gust,
Matthias Klude, Akio Ueta, Elena Roventa und Detlef Hommel
— Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-
Allee NW1, 28359 Bremen
Die Verwendung von CdZnSSe-Quantentrögen in ZnSe-basierenden
Laserdioden ermöglicht durch Variation des Cd-Gehaltes eine Laseremission
im gelb-grünen Spektralbereich. Die Lebensdauer wird jedoch
signifikant durch die Stabilität der Quantentröge beeinflusst und ist derzeit
auf einige hundert Stunden begrenzt [1].
Ein Hauptgrund hierfür ist die hohe kompressive Spannung im Gebiet
der aktiven Zone infolge des hohen Cd-Gehaltes in den Quantentrögen
und der damit verbundenen Defektgeneration. Zusätzlich erfolgt während
des Betriebes eine Cd-Ausdiffusion in die umliegenden Schichten.
Ein Ansatz zur Reduzierung dieser Degradationsmechanismen stellt die
Einführung spannungskompensierender ZnSSe-Barrieren dar. Diese den
Quantentrog umgebenden Schichten hohen S-Gehalts haben eine kleinere
Gitterkonstante und bewirken dadurch eine Spannungsreduzierung im
aktiven Gebiet.
Zur Untersuchung der Quantentrogstabilität wurden mittels
Molekularstrahlepitaxie mehrere identische Laserdioden mit verschieden
positionierten Barrieren hergestellt. Je nach Anordnung der Barrieren
konnte eine Verbesserung der Lebensdauer bis zu einer Größenordnung
gezeigt werden.
[1] E. Kato et al., Electron. Lett. 34, 282 (1998).
HL 21.3 Di 15:45 H13
Microscopic Spatial Distribution of bound excitonic luminescence
in high-quality ZnO — •Daniel Forster, Frank
Bertram, Jürgen Christen, Nikolay Oleynik, Armin
Dadgar, and Alois Krost — Institute of Experimental Physics,
Otto-von-Guericke-University Magdeburg, Germany
ZnO has received much attention as a material for opto-electronic devices
because of its direct wide band gap and high exciton binding energy.
The ZnO epitaxial layers investigated were grown by MOCVD on 1µm
thick GaN layers on sapphire template using a two step growth process:
First, a low-temperature ZnO buffer was deposited at 450 ◦ C. In
the second step, a high-temperature ZnO layer was grown above 800 ◦ C.
This final ZnO layer exhibits supreme crystalline and optical quality. Using
highly spatially and spectrally resolved cathodoluminescence (CL)
microscopy a direct correlation of the structural and the optical properties
of these ZnO sandwich layers has been achieved on a microscopic
scale. The laterally integrated spectrum of each sample is dominated by
narrow (

Halbleiterphysik Dienstag
to approximately 400 hours. An increase of lifetime can be expected for
improved current confinement by processing the LD as a ridge structure.
The results of electro-optical characterization of planar and ridge
ZnSe laser diodes will be presented. Measurements concerning L-Icharacteristic,
lifetime, temperature-sensitive wavelength-shift and far
field pattern were accomplished.
The results show a distinct reduction of the threshold-current density.
This leads to increased lifetimes and a higher stability of lateral modes.
Measurements were mainly taken on quantum well lasers but also quantum
dot lasers were briefly tested. Ridge QD Lds show a significant reduction
of threshold-current density by a factor of five.
This indicates that the processing as a ridge structure is promising
approach for ZnSe-laser diodes in oder to increase device lifetime.
HL 21.5 Di 16:15 H13
Nachweis rückstoß-induzierter Defekte zur Untersuchung der
grünen Bande in ZnO — •Th. Agne 1 , M. Dietrich 1 , H. Wolf 1 ,
Th. Wichert 1 und ISOLDE Kollaboration 2 — 1 Universität des
Saarlandes, Technische Physik, D-66123 Saarbrücken — 2 CERN, EP Division,
CH-1211 Genf 23, Schweiz
Um PL-Untersuchungen mit kurzlebigen Isotopen (t1/2 ≤ 1 d), das sind
insbesondere Isotope leichter Elemente, zu ermöglichen, wurde am Isotopenseparator
ISOLDE/CERN ein PL-Labor eingerichtet. Als Pilotexperiment
wurde mit dieser PL-Apparatur die so genannte ” grüne Bande“ im
ZnO untersucht. Der Ursprung dieser grünen Bande wird in der Literatur
kontrovers diskutiert. Zur Erklärung wurden entweder ein Cu 2+ -Defekt
oder Leerstellen vorgeschlagen. Um dieser Frage nachzugehen, wurden
sowohl das radioaktive Isotop 64 Cu → 64 Ni/ 64 Zn (t1/2 = 12,7 h) als auch
das Isotop 65 Ni → 65 Cu (t1/2 = 2,5 h) in ZnO implantiert und mittels PL-
Spektroskopie untersucht. Erstaunlicherweise zeigen beide Experimente,
dass die Intensität der grünen Bande mit der Zeit ansteigt; und zwar mit
der Halbwertszeit des jeweils implantierten Isotops. Da beim β-Zerfall
beider Mutterisotope ein Rückstoß mit einer Energie von mehr als 24
eV auf die Tochterisotope übertragen wird, und diese Energie oberhalb
der Versetzungsenergie eines Zn-Atoms im ZnO Kristallgitter (∼ 19 eV)
liegt, wird der Anstieg der Intensität der grünen Bande durch die Entstehung
eines rückstoß-induzierten intrinsischen Defekts erklärt. D.h., die
grüne Bande in ZnO wird von intrinsischen Defekten, wie beispielsweise
der Zn-Leerstelle, verursacht.
Gefördert durch das BMBF im Rahmen des Projekts 05KK1TSA.
HL 21.6 Di 16:30 H13
Einfluss stöchiometrischer Änderungen auf die Diffusion von Ag
und Cu in CdTe — •H. Wolf, F. Wagner und Th. Wichert —
Universität des Saarlandes, Technische Physik, D-66123 Saarbrücken
Die Diffusion von Ag und Cu in CdTe wurde mit Hilfe der Radiotracer
111 Ag und 67 Cu untersucht, wobei sehr unterschiedliche, meist ungewöhnliche
Profilformen beobachtet wurden. In nicht vorbehandelten
bzw. unter Te Atmosphäre vorgetemperten Kristallen werden nach Diffusion
von Ag bzw. Cu unter Cd Atmosphäre bei 800 K (60 min) symmetrische
Profile beobachtet, die in der Mitte des Kristalls eine hohe und in
den bis zu 250 µm tiefen Randzonen eine niedrige Ag (Cu) Konzentration
zeigen. Dagegen zeigt ein unter Cd Atmosphäre vorgetemperter Kristall
unter sonst gleichen Diffusionsbedingungen für Ag eine homogene Verteilung
über die gesamte Probe auf einem niedrigem Konzentrationsniveau.
Erfolgt die Ag Diffusion unter Te Atmosphäre, wird dagegen in den Randbereichen
eine erhöhte Ag Konzentration beobachtet. Die Diffusionsprofile
lassen sich im Rahmen eines Modells erklären, das die Veränderung der
stöchiometrischen Bedingungen durch die Diffusion intrinsischer Defekte
berücksichtigt. Dabei zeigt sich, dass Ag (Cu) in Bereichen mit einer
hohen Konzentration von Cd Leerstellen, VCd, substitutionell eingebaut
und aus Bereichen mit niedriger VCd Konzentration verdrängt wird. Anhand
von Simulationsrechnungen wird gezeigt, welche Anforderungen an
das Material gestellt werden müssen, um die beobachteten Profilformen
zu erklären.
Gefördert durch die DFG, Projektnummer WI 715/7-1/7-3/7-4
HL 22 Transport im hohen Magnetfeld/Quanten-Hall-Effekt
Zeit: Dienstag 15:15–18:00 Raum: H14
HL 22.1 Di 15:15 H14
Phonon spectroscopy in the fractional quantum Hall effect
regime — •F. Schulze-Wischeler 1 , F. Hohls 1 , U. Zeitler 1,2 ,
R. J. Haug 1 , D. Reuter 3 , and A. D. Wieck 3 — 1 Institut für
Festkörperphysik, Universität Hannover, Appelstraße 2, D-30167 Hannover,
Germany — 2 High Field Magnet Laboratory, NSRIM, University
of Nijmengen, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands —
3 Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum,
Universitätsstraße 150, 44780 Bochum, Germany
At low temperatures the energies und wavelength of phonons become
comparable to the typical energies- und length scales of two-dimensional
electron systems (2DESs). So they can couple efficiently to 2DESs and
make collective excitations. We have measured the absorption of ballistic
non-equilibrium phonons by a 2DES in the fractional quantum Hall effect
(FQHE) regime. With phonon spectroscopy we can measure the specific
heat of 2DESs and energy gaps unaffected by disorder on length scales
larger than phonon wavelength (in contrary to transport experiments).
For various filling factors and electron densities energy gaps in the FQHE
are measured. A comparison with theory gives insight into the interesting
nature of these collective states.
HL 22.2 Di 15:30 H14
Renormalizing into the mesoscopic quantum Hall insulator —
•Philipp Cain 1 , Rudolf A. Römer 2 , and Michael Schreiber 1
— 1 Institut für Physik, Technische Universität, D-09107 Chemnitz —
2 Department of Physics, University of Warwick, Coventry CV4 7AL, UK
Using the Chalker-Coddington network model as a drastically simplified,
but universal model of integer quantum Hall physics, we investigate
the plateau-to-insulator transition at strong magnetic field by means of a
real-space renormalization approach. Our results suggest that for a fully
quantum coherent situation, both the Hall insulator with diverging Hall
resistance RH and the quantized Hall insulator with RH ≈ h/e 2 can be
observed depending on the precise nature of the averaging procedure.
HL 22.3 Di 15:45 H14
Quantum Hall Effect in Highly Oriented Pyrolytic Graphite —
•Heiko Kempa 1 , Pablo Esquinazi 1 , and Yakov Kopelevich 2 —
1 Abteilung Supraleitung und Magnetismus, Universität Leipzig, Linnestrasse
5, D-04103 Leipzig — 2 Instituto de Fisica, UNICAMP, Campinas,
Sao Paulo, Brasil
Recently published work indicates the existence of the quantum Hall
effect in pyrolytic graphite samples [1]. In this work we have studied this
effect in detail using two different geometries: the van der Pauw electrode
arrangement and the Corbino disc. Clear quantized plateaus were
obtained in the Hall conductivity with the van der Pauw method. A
rough estimate provides the correct value for the quantized conductivity
for a single graphite layer at the plateaus within a factor of two. In
the Corbino disc geometry we have measured the voltage from different
electrodes positioned between the center and outer-ring electrodes. For
electrodes localized at equal distances from the center electrode we have
measured several well defined plateaus in agreement with those measured
with the van der Pauw method. Taking into account the current penetration
depth and the field dependence of the c-axis/a-axis resistivity ratio
we obtain the well known absolute quantization of the plateaus, which
indicates an integer quantum Hall effect. However, this “Hall”-voltage
in the Corbino geometry does not change sign after changing the direction
of the magnetic field. We discuss our results in terms of recently
published theoretical work.
[1] Y. Kopelevich et al., Phys. Rev. Lett. 90, 156402 (2003).
HL 22.4 Di 16:00 H14
Spectroscopy of energy gaps between landau bands in the vicinity
of a thin tunnelling barrier — •M. Habl 1 , W. Wegscheider 1 ,
D. Schuh 2 , M. Bichler 2 , and G. Abstreiter 2 — 1 Institut für Experimentelle
und Angewandte Physik, Universität Regensburg, 93040 Regensburg
— 2 Walter Schottky Institut, Technische Universität München,
85748 Garching
Studying the transport of two laterally adjacent two-dimensional electron
systems separated by an atomically precise extended barrier with
a thickness in the order of the magnetic length is made possible by the

Halbleiterphysik Dienstag
method of cleaved edge overgrowth [1]. For high barriers there are small
energy gaps (∆ ≪ ¯hωc) at the crossing points of the bent Landau bands
of the left and the right electron systems due to the weak coupling of the
counter propagating opposite edge channels. We present the solutions
of the Schrödinger equation for the whole system in the one electron
approximation which is especially interesting in the low barrier regime
(e.g. V0 = 3 ¯hωc) when the results strongly deviate from more crude approximations.
For low aluminium concentrations in the AlGaAs barrier
the dispersion relation can no longer be calculated as a superposition of
two symmetric Landau spectra. Instead a complete numerical calculation
must be performed in order to find the correct gaps and their positions.
Our theoretical results are compared to experimental data of CEO samples
which reveal energy gaps bigger and at different filling factors than
expected. The project is supported by the DFG Schwerpunktsprogramm
1092 Quanten-Hall-Systeme.
[1] W. Kang et al., Nature 403, 59 (2000)
HL 22.5 Di 16:15 H14
Spin structures in inhomogeneous fractional quantum Hall systems
— •Karel Vyborny and Daniela Pfannkuche — I. Institute
of Theoretical Physics, University of Hamburg, Jungiusstr. 9, D-20355
Hamburg, Germany
Huge longitudinal magnetoresistance effect in 2D electron systems was
shown to be a way to manipulate and measure spin of the host material
nuclei [1] and it can thus have important applications in the field of
quantum computers. Since there are two nearly degenerate ground states
of the electronic part of the system (polarized and singlet-state incompressible
liquids at filling factor 2/3) it is widely believed that the effect
is due to formation of domains which results into an enhanced resistance.
To our best knowledge there is however no direct evidence of existence
of such domains so far.
We study a finite size model of electrons in the lowest Landau level
which was formerly used to study the Fractional Quantum Hall Effect
(torus geometry, [2]). The system is now also subject to magnetic inhomogeneity
which makes one of the ground states more favorable in one
part and less favorable in another part of the system. We investigate how
the system answers to various types of inhomogeneities in spin quantities
and particle densities as well as in correlation functions.
[1] S. Kronmüller et al., Phys. Rev. Lett., 81, 2526 (1998), J. Smet
et al., Nature, 415, 281 (2002), S. Kraus et al., Phys. Rev. Lett, 89,
266801 (2002)
[2] D. Yoshioka, Phys. Rev. B, 29, 6833 (1984), T. Chakraborty,
Surf. Sci., 229, 16 (1990)
HL 22.6 Di 16:30 H14
On ground states of interacting Composite Fermions with spin
at half filling — •Matteo Merlo 1 , Nicodemo Magnoli 2 , Maura
Sassetti 1 , and Bernhard Kramer 3 — 1 Dipartimento di Fisica,
INFM-LAMIA, Università di Genova, Via Dodecaneso 33, I-16146 Genova,
Italy — 2 Dipartimento di Fisica, INFN, Università di Genova, Via
Dodecaneso 33, I-16146 Genova, Italy — 3 I. Institut für Theoretische
Physik, Universität Hamburg, Jungiusstraße 9, D-20355 Hamburg, Germany
The effects of interactions in a 2D electron system in a strong magnetic
field at the coincidence of two Landau levels with opposite spins and at
filling factors 1/2 are studied. Via the Chern-Simons gauge transformation,
the system is mapped to Composite Fermions. The fluctuations of
the gauge field induce an effective interaction between the Composite
Fermions which can be attractive in both the particle-particle [1,2] and
in the particle-hole channel. As a consequence, spin-zero ground states of
Composite Fermion particle-particle or particle-hole pairs can exist. The
competition between the two possible ground states is discussed and the
results are compared with experiments.
[1] E. Mariani, N. Magnoli, F. Napoli, M. Sassetti, and B. Kramer,
Phys. Rev. B 66, 241303 (2002) .
[2] B. Kramer, N. Magnoli, E. Mariani, M. Merlo, F. Napoli, and M.
Sassetti, in Quantum Phenomena in Mesoscopics Physics, Proceedings
of the International School of Physics Enrico Fermi, Varenna, 2002.
HL 22.7 Di 16:45 H14
Two-dimensional High Mobility Holes on (110) GaAs — •Frank
Fischer, Matthew Grayson, Dieter Schuh, Max Bichler, and
Gerhard Abstreiter — Walter Schottky Institut, Technische Universität
München, Garching, Germany
High mobility two-dimensional hole gases (2DHG) in GaAs have
previously been realised by using Si as dopant on the (311)A surface
[1]. On the (110) GaAs surface Si can act as both, donor and acceptor
[2]. But up to now only high-mobility two-dimensional electron gases
have been achieved on that orientation. We report on the first growth
of high mobility two-dimensional modulation doped hole gases on the
(110) GaAs orientation. We were able to achieve a 1.2K mobility of
µ = 1.7 × 10 5 cm 2 /Vs at a density of n = 2.3 × 10 11 /cm 2 .
We will report studies of anisotropic conduction in this system as
previously performed on the (311) surface [3].
[1] M. Henini, P. J. Rodgers, P. A. Crump, B. L. Gallagher, G. Hill, J.
Cryst. Growth 150(1-4), 441 (1995)
[2] E. S. Tok, J. H. Neave, M. J. Ashwin, B. A. Joyce, T. S. Jones, J.
Appl. Phys. 83(8), 4160 (1998)
[3] S. J. Papadakis, E. P. De Poortere, M. Shayegan, R. Winkler, Phys.
Rev. Lett. 84 (24), 5592 (2000)
HL 22.8 Di 17:00 H14
A non-perturbative solution for Bloch electrons in constant
magnetic fields — •Alex Trellakis and Peter Vogl — Walter
Schottky Institut, Technische Universität München, 85748 Garching
A general theoretical approach for the non-perturbative Bloch solution
of Schrödinger’s equation in the presence of a periodic crystal potential
and a constant magnetic field is presented. Using a singular gauge transformation
based on a two-dimensional lattice of magnetic flux lines, an
equivalent quantum system with a now periodic vector potential is obtained.
For rational values of the magnetic field the periods of the vector
potential and the crystal potential become commensurable, and the system
forms a magnetic superlattice for which then Bloch’s theorem applies.
Extensions of the approach to particles with spin and many-body
systems and connections to the theory of magnetic translation groups are
discussed.
HL 22.9 Di 17:15 H14
Spin-polarisierte Randzustände von Quanten-Hall Systemen
auf Siliziumbasis — •Carsten A. G. Kentsch und Dieter P.
Kern — Institut für Angewandte Physik, Auf der Morgenstelle 10, 72076
Tübingen
Spin-polarisierte Elektronen finden sich in den Randzuständen
zweidimensionaler Elektronengase (2DEG) im starken Magnetfeld. Sie
können dazu dienen, mittels Transportmessungen Streuung zwischen
Spinzuständen zu untersuchen. 2DEG-Systeme in Silizium erfahren
in letzter Zeit wieder Beachtung, da das Hauptisotop von Silizium
keinen Kernspin hat und somit die Spin-Streuung von Elektronen
mit dem Grundmaterial viel geringer ausfällt als z.B. bei GaAs.
Eine längere Lebensdauer spin-polarisierter Elektronen ist die Folge.
Diese können zur Detektion von Kerndrehimpuls-Zustände von gezielt
eingebrachten Phosphoratomen dienen, die sich als Quanten-Bits in
Quanten-Computern eignen.
Es wurden Hallbar-Srukturen auf Basis von MOSFET-Transistoren
mit Poly-Silizium Topgate hergestellt und bei 8 Tesla und 1,5 Kelvin charakterisiert.
Landau-Niveaus wurden bis zum n=1 Niveau bei Shubnikovde
Haas Oszillationen beobachtet. Die Randzustände sollen durch Split-
Gate Anordnungen im Topgate manipuliert werden.
HL 22.10 Di 17:30 H14
Equilibration between spin split edge channels studied by timeresolved
measurements — •Gennadiy Sukhodub, Frank Hohls,
and Rolf Haug — Institut für Festkörper Physik, Universität Hannover,
Appelstraße 2, D-30167 Hannover, Germany
The concept of edge channels (EC) utilizes a two-dimensional electron
system in the regime of integer quantum Hall effect as an object for study
of the interactions between one-dimensional (1D) channels. Particularly,
the scattering between these 1D states can be investigated in a sample
which allows for selective population of different EC. In our system a
short voltage pulse is applied to one of the two EC at filling factor ν = 2.
After interaction over a distance of 20µm with a not excited state these
two EC are separated and a time-resolved current in each channel is detected
independently. Selective population and detection is realized by
well-established cross gates technique. Dependent on the polarity of the
applied pulse two scattering regimes with significantly different equilibration
lengths are possible. We studied the influence of the pulse amplitude
on the equilibration in the case of weak scattering. We obtain characteristic
time scales for the adiabatic and the equilibrated regime of the current
transport. There is a strong indication of the involvement of the higher

Halbleiterphysik Dienstag
Landau levels in the scattering between EC at higher voltage biases.
HL 22.11 Di 17:45 H14
Transporteigenschaften von 2D-Elektronengasen unter dem
Einfluss von benachbarten InAs-Quantenpunkten — •Marco
Ruß 1 , Axel Lorke 1 , Dirk Reuter 2 und Andreas Wieck 2 —
1 Laboratorium für Festkörperphysik, Universität Duisburg-Essen,
Lotharstr. 1, 47057 Duisburg — 2 Angewandte Festkörperphysik,
Ruhr-Universität Bochum, Universitätsstr. 150, 44780 Bochum
Wir untersuchen die Transporteigenschaften zweidimensionaler Elektronengase
(2DEGs) unter dem Einfluss eines steuerbaren Störpotentials.
Dazu verwenden wir eine wenige Nanometer vom 2DEG entfernte
HL 23 Organische Halbleiter
Schicht von selbstorganisierten InAs-Quantenpunkten, die gezielt mit
jeweils 0-6 Elektronen geladen werden können. Der Ladungszustand
der Quantenpunkte wird durch Kapazitätsmessungen (CV) bestimmt.
(Magneto-)CV Messungen und Messungen des Quanten-Hall-Effektes erlauben
darüber hinaus Rückschlüsse auf die Beweglichkeit und Ladungsträgerkonzentration
des 2DEG. Wir beobachten, dass die klassische Hall-
Gerade die QH-Plateaus asymmetrisch schneidet, wie es für 2DEGs unter
dem Einfluss von negativ geladenen Störstellen typisch ist. Dieses Verhalten
ist jedoch – wie auch die Beweglichkeit – nur schwach abhängig vom
Ladungszustand der Quantenpunkte. Dies lässt auf einen dominierenden
Einfluss des (piezoelektrischen) Verspannungspotentials der Inseln
schliessen.
Zeit: Dienstag 16:45–19:00 Raum: H13
HL 23.1 Di 16:45 H13
Charge-carrier mobilities in ultrapure organic crystals: Theory
and modelling — •Karsten Hannewald and Peter Bobbert —
Technische Universiteit Eindhoven, P. O. Box 513, 5600 MB Eindhoven,
The Netherlands
We present a novel theory of charge-carrier mobilities in organic crystals,
based on an analytical evaluation of the Kubo formula within a
mixed Holstein-Peierls model. In combination with ab-initio calculations
of the material parameters, our theory represents a direct and easy-to-use
method to calculate the temperature dependence of the mobilities. This
is exemplified for naphthalene crystals where our results [1] agree well
with the experimental data.
[1] K. Hannewald and P. A. Bobbert, submitted to Phys. Rev. Lett.
HL 23.2 Di 17:00 H13
Alterung organischer Feld-Effekt Transistoren mit Pentacen —
•Christoph Pannemann, Thomas Diekmann und Ulrich Hilleringmann
— Universität Paderborn, Fakultät EIM-E, Sensorik, Warburger
Str. 100, D-33098 Paderborn
Organische Feld-Effekt Transistoren (OFET) wurden durch thermisches
Verdampfen von Pentacen auf p-leitenden 100-Silizium-Substraten
mit SiO2 als Dielektrikum hergestellt. Eine Alterung über neun Monate
unter Laborbedingungen hatte deutlichen Einfluss auf die Ladungsträger
Beweglichkeit, die on-off Rate, die Schwellspannung und den maximalen
Einschaltstrom. Sauerstoff und Wasserdampf aus der Umgebungsluft erzeugen
geladene Störstellen an den Korngrenzen der Kristallite des organischen
Films. Trotz einer Abnahme des Einschaltstroms um drei und
der Ladungsträger-Beweglichkeit um mehr als zwei Größenordnungen
zeigten die OFETs über den gesamten Beobachtungszeitraum typisches
Transistorverhalten. Eine thermische Nachbehandlung unter Vakuum-
Bedingungen in einem anderen Experiment führte zu einer Verminderung
der Ladungsträger Beweglichkeit und des maximalen Einschaltstroms
sowie einer Verschiebung der Schwellspannung, verursacht durch
Alterung vergleichbar mit dem dangling-bond Mechanismus in Silizium-
Transistoren.
HL 23.3 Di 17:15 H13
Structural anisotropy of different conjugated polymer films —
•Tobias Erb 1 , Sofiya Raleva 1 , Uladzimir Zhokhavets 1 , Gerhard
Gobsch 1 , Bernd Stühn 1 , Pavel Schilinsky 2 , Christoph
Brabec 2 , Maher Al-Ibrahim 3 , and Steffi Sensfuss 3 — 1 Institute
of Physics, Ilmenau Technical University, 98684 Ilmenau, Germany —
2 Siemens AG, CT MM 1 Innovative Electronics, 91052 Erlangen, Germany
— 3 TITK Institute Rudolstadt, Department Functional Polymer
Systems, 07407 Rudolstadt, Germany
The morphology and especially the structural anisotropy of thin
polymer films are decisive for their optical and transport properties
in view of application in organic solar cells. The structural
anisotropy of thin spin-coated pure P3OT- (poly[3-octylthiophene]),
P3HT- (poly[3-hexylthiophene]), MDMO-PPV-films (poly[2-methoxy, 5-
3’,7’-dimethyl-octyloxy]-p-phenylene vinylene) and their blends with
fullerene derivatives on miscellaneous substrates (silicon, glass/ITO and
glass/ITO/PEDOT) were studied by X-ray diffraction. We have investigated
the influence of annealing and the regularity of polymer side chains.
In addition, the mean size of polymer crystallites and their orientation
within the film have been estimated.
HL 23.4 Di 17:30 H13
Field effect in organic MIS structures — •Marcus Ahles,
Roland Schmechel, and Heinz von Seggern — Materialwissenschaft,
elektronische Materialeigenschaften, TU-Darmstadt,
Petersenstra”se 23, 64287 Darmstadt
Organic field effect transistors are attracting more and more attention
due to their flexibility and low cost. Charge injection and charge accumulation
are basic processes in such devices. To study these processes in
more detail, we present the characterisation of the field effect in metal
insulator semiconductor (MIS) devices by impedance spectroscopy. The
impedance spectra show a strong dependence on the applied bias voltage.
Introducing an equivalent circuit and a simple hopping model of charge
transport in the organic semiconductor the impedance spectra can be
well explained and the centre of the charge distribution in the organic
layer can be extracted. Further, charge injection at the semiconductor
metal interface is studied. For pentacene we observe both electron and
hole accumulation. Unlike holes, which are found close to the insulator
interface, electrons are immobilized in the vicinity of the injecting electrode.
This is interpreted by the presence of deep electron trap states.
The role of those states is further discussed with respect to hysteresis
effects in the C-V characteristics as well as in the transistor characteristics.
Finally we show, that a gold contact causes an effective p-doping in
pentacene. This fact plays an important role in respect to short channel
effects in field effect transistors.
HL 23.5 Di 17:45 H13
Polymer-Fullerene Solar Cells with 3.1% Power Conversion Efficiency
— •Ingo Riedel, Jürgen Parisi, and Vladimir Dyakonov
— Energy- and Semiconductor Research Laboratory, Institute of Physics,
University of Oldenburg, D-26111 Oldenburg, Germany
Polymer-fullerene bulk heterojunction solar cells have run through a
rapid development over the past 8 years. Power conversion efficiencies
in the range 2.5 % - 3 % have been demonstrated. For commonly used
absorber materials the insufficient transport properties of the semiconductors
require low absorber thickness of 100 nm or below and therefore
limit the absorption. A higher active layer thickness, however, is required
to increase the amount of absorbed photons and consequently to increase
the short-circuit photocurrent of the solar cell.
In this work we demonstrate that by using material components with
relatively high mobility-lifetime product it is possible to overcome the
transport limitation of the photocurrent. For solar cells based on regioregular
poly[3-hexylthiophene 2,5 diyl]:phenyl-C61 butyric acid methyl ester
(P3HT:PCBM) composites, the active layer thickness was increased from
50 nm to 350 nm with respective photocurrent densities ranging from 5.7
mA/cm 2 to 15.4 mA/cm 2 . For the device with 350 nm absorber thickness
a power conversion efficiency of 3.1 % at 100 mW/cm 2 white light
illumination was obtained.
HL 23.6 Di 18:00 H13
Infrared ellipsometry characterization of organic conducting
thin films — •M. Schubert 1 , C. Bundesmann 1 , G. Jakopic 2 , A.
Haase 2 , H. Arwin 3 , N. C. Persson 3 , F. Zhang 3 , and O. Inganäs 3
— 1 Fakultät für Physik und Geowissenschaften, Instititut für Experimentelle
Physik II, Universität Leipzig, Linnéstraße 5, 04103 Leipzig —
2 JOANNEUM Research Forschungsgesellschaft mbH, Steyrergasse 17, A-
8010 Graz, Austria — 3 Department of Physics and Measurement Technology,
Linköping University, SE-581 83 Linköping, Sweden

Halbleiterphysik Dienstag
Infrared spectroscopic ellipsometry (IRSE) for wave numbers from 333
to 4000 cm −1 is demonstrated as useful technique for characterization
of structural, vibrational, and free-charge-carrier properties of conducting
organic thin layers deposited on electrically conducting as
well as on isolating substrates. Pentacene, poly(3,4-ethylenedioxy thiophene)/poly(styrenesulfonate)
(PEDOT:PSS), C60 and polyfluorene are
studied exemplarily. For all materials the infrared dielectric functions
are reported, which can serve as fingerprints for multiple-layer structures
analysis. PEDOT:PSS layers deposited onto n-type and p-type silicon
substrates reveal different conductivity response, indicative for charge
transfer at the semiconductor/polymer interface, whereas the IRSE data
show that the pentacene layers on glass are rendered highly resistive.
HL 23.7 Di 18:15 H13
Ultrafast excitonic relaxation processes in perylene derivatives
— •E. Engel, M. Koschorreck, M. Hoffmann, T. W. Canzler,
T. Hasche, and K. Leo — Institut für Angewandte Photophysik, TU
Dresden, 01062 Dresden, Germany, www.iapp.de
Perylene derivatives are interesting model systems because of
their quasi-1D organic molecular crystal structure, their strong
molecular interaction and their potential for use in low-cost optoelectronic
devices. We investigated polycrystalline thin films of
N-N’-dimethyl-perylene-3,4,9,10-dicarboximide (MePTCDI) and
perylene-3,4,9,10-tetracarboxylic-dianhydride (PTCDA). Using ultrafast
pump-probe spectroscopy, we temporally resolved the relaxation process
of free excitons from the absorbing states down to the indirectly emitting
states. The time constant, measured by photoinduced absorption, is
about 30fs. Furthermore, we investigated signal contributions from
stimulated emission and ground state bleaching. The relaxation
processes are discussed within the framework of an exciton band
structure model[1].
HL 24 Photovoltaik I
[1] M. Hoffmann, Z. G. Soos and K. Leo, Nonlinear Optics 29, 227
(2002)
HL 23.8 Di 18:30 H13
Ultrafast Relaxation between Davydov Components in
Crystalline N-N’-dimethyl-perylene-3,4,9,10-dicarboximide
(MePTCDI) — •Marco Koschorreck, Egbert Engel,
Karl Leo, and Michael Hoffmann — Institut für Angewandte
Photophysik, TU Dresden, 01062 Dresden, Germany, www.iapp.de
We investigated polarization anisotropies in polycrystalline films of the
organic semiconductor N-N’-dimethyl-perylene-3,4,9,10-dicarboximide
(MePTCDI) by means of pump-probe and time-resolved luminescence
measurements. The timescale of the observed processes range from tens
of femtoseconds to several picoseconds.
On the shorter timescale (50fs), the equilibration process of the initially
differently populated Davydov components was observed. The
textbook model for polarization anisotropies was extended to the case
of two coupled Davydov components. Through this it is possible to
predict the remaining anisotropy after this very fast relaxation process.
The experimental results agreed well with the theoretical values. The behavior
at longer timescales (100ps) could be explained by exciton diffusion
between randomly oriented crystallites. While crossing the crystallite
boundaries, the excitons lose their polarization memory and the polarization
anisotropy goes to zero. Temperature dependent measurements
indicate an incoherent thermally activated hopping process.
HL 23.9 Di 18:45 H13
N,N’-perarylated -2,2’-bithiophene - as a new typ of hole transporting
materials — •Olaf Zeika — Novaled GmbH 01069 Dresden
Zellescher Weg 17
Synthesis, characterisation and possible use in OLED
Zeit: Dienstag 17:45–19:15 Raum: H15
HL 24.1 Di 17:45 H15
Doping experiments with HfSxSe2−x — •Steffen Duhm, Ralf
Severin, Alicia Krapf, Christoph Janowitz, and Recardo
Manzke — Institut f. Physik, Humboldt-Unversität zu Berlin,
Newtonstr. 15, 12489 Berlin
HfSxSe2−x is an indirect semiconductor of the group of transition metal
dichalcogenides, the band-gap of which ranges from 1.1 eV (HfS2) to 2
eV (HfSe2) with a nearly linear dependence on x. Due to this property it
can be used as a source material for a two junction cell (ideal band-gap
1.1 eV and 1.8 eV). In the present work, niobium doped HfS1Se1 (bandgap
∼ 1.5 eV) crystals with different doping concentrations were grown
by chemical vapour transport (CVT). The crystals were characterized by
energy dispersive X-ray analysis (EDX) and absorption measurements.
Despite the indirect band-gap of HfSxSe2−x the absorption coefficient is
very high and enables thin-film solar cells. The quasi two-dimensional
character of HfSxSe2−x prevents surface states and dangling bonds. As
the material is thus highly suitable for a Schottky contact, the work
function was measured using a Kelvin probe.
HL 24.2 Di 18:00 H15
Investigation of the chemical and electronic properties of the
ZnO/Cu(In,Ga)(S,Se)2 interface in thin film solar cells — •G.
Storch 1 , L. Weinhardt 1 , C. Heske 1 , E. Umbach 1 , S. Visbeck 2 ,
T.P. Niesen 2 , and F. Karg 2 — 1 Experimentelle Physik II, Universität
Würzburg, Am Hubland, D-97074 Würzburg — 2 Shell Solar, 81739
München
Thin film solar cells based on Cu(In,Ga)(S,Se))2 (CIGSSe) commonly
contain a CdS buffer layer between the absorber and the (i-ZnO/n-ZnO)
window layer. For environmental reasons, it is desirable to replace the
Cd-containing buffer, either by alternative materials or by direct deposition
of the window layer on the absorber. However, depositing the standard
window layer directly on the absorber results in poor efficiencies.
In contrast, the use of (Zn,Mg)O instead of i-ZnO leads to cells showing
satisfactory performance. Until today, the reason for this discrepancy is
unknown. As a first step towards an understanding, we have investigated
the i-ZnO/CIGSSe interface by using X-ray photoelectron spectroscopy
(XPS), X-ray emission spectroscopy (XES) and UV-photoelectron spectroscopy
(UPS) combined with inverse photoemission (IPES). The result-
ing chemical and electronic picture of the interface, including the band
alignment in both the valence and conduction band, will be discussed and
compared to results from related interfaces (e.g., i-ZnO/CdS) as well as
alternative preparation methods.
HL 24.3 Di 18:15 H15
Band alignment at the i-ZnO/CdS interface in Cu(In,Ga)(S,Se)2
thin film solar cells — •L. Weinhardt 1 , C. Heske 1 , E. Umbach 1 ,
S. Visbeck 2 , T.P. Niesen 2 , and F. Karg 2 — 1 Exp. Physik II, Universität
Würzburg — 2 Shell Solar GmbH, Munich
In solar cells based on Cu(In,Ga)(S,Se)2 (CIGSSe) one potential target
for further optimization of cell performance is the commonly used ZnO
window layer. Today, an n-ZnO/i-ZnO structure is generally used, separated
from the CIGSSe absorber by a CdS buffer layer. Apart from important
bulk parameters of the ZnO layer, such as window transmission and
resistivity, particularly the properties of its interface to the CdS buffer
layer represent a crucial component for the optimization of solar cells. For
a further improvement of this interface a detailed understanding of the
chemical and electronic properties is needed. We have thus investigated
the ZnO/CdS interface using X-ray photoelectron spectroscopy to probe
its chemical properties, and we have used UV and inverse photoemission
for a direct determination of the band gaps and band alignments at the
heterojunction. The results will be discussed in view of a level alignment
model for the complete CIGSSe thin film solar cell device, taking into
account the previously found electronic and chemical structure of the
CdS/CIG(S)Se interface [1,2] as well as new results for absorbers with
varied sulfur content at the surface.
[1] L. Weinhardt et al., Proc. 17th EPSEC Munich 2001, p. 1261.
[2] M. Morkel et al., Appl. Phys. Lett. 79 (2001) 4482.
HL 24.4 Di 18:30 H15
Formation mechanism of the metastable defect in Cz-silicon solar
cells — •Karsten Bothe, Rudolf Hezel, and Jan Schmidt
— Institut für Solarenergieforschung Hameln/Emmerthal (ISFH), Am
Oherberg 1, D-31860 Emmerthal
The efficiency of solar cells made on boron-doped oxygen-contaminated
crystalline silicon decreases under illumination or minority-carrier injection
in the dark by up to 10 % relative. This performance degradation has

Halbleiterphysik Dienstag
its origin in the formation of a recombination active boron- and oxygenrelated
metastable defect centre. The formation process of this defect is
investigated on Cz-Si solar cells as a function of an applied voltage in
the dark at temperatures ranging from 298 to 373 K. We show that the
defect formation is not only a consequence of illumination or the application
of a forward bias voltage but also occurs at elevated temperatures
in the dark. Taking into account that the application of a reverse bias
partly suppresses the defect formation, our results provide clear experimental
evidence that a recombination-enhanced mechanism correlated
with the total recombination rate is the driving force of the formation of
the metastable defect.
HL 24.5 Di 18:45 H15
Topological Features and Luminescence of Cu(InGa)Se2 Absorbers
with Sub-Micron Lateral Resolution — •Levent Gütay,
Richard Fuhrmann, and Gottfied Heinrich Bauer — Institute
of Physics, Carl von Ossietzky University Oldenburg
In a confocal microscope with sub-micron resolution we have
simultaneously recorded optical reflection and photoluminescence of
Cu(InGa)Se2 absorbers and layer structures [1]. The optical reflection
provides not a direct information on structural topological properties
such as grain boundaries but is composed of photons reflected from the
illuminated surface and weightened by a step-like acceptance function of
the microscope aperture. Furthermore the reflection signal vs. topology
is not unambiguous since in a wavy topology with spatial wave vector k
as analyzed e.g. by afm-scans, the optical reflection measures intensities
and may show maximum signal for reflection from tops and from valleys
as well; the according pattern consequently contains wave vectors with
2k. We have created artificial optical reflection patterns by converting
HL 25 Heterostrukturen II
numerically afm-topology into 2D reflection. We compare 2D Fourier
transforms of experimental with those of calculated reflection patterns
and correlate laterally resolved pl-yields with topological features in the
k-space.
[1] K. Bothe, G.H. Bauer, T. Unold, Thin Solid Films 362, 453 (2001)
HL 24.6 Di 19:00 H15
Admittance spectroscopy on single crystalline chalcopyrite thin
films — •A. Dietz 1 , J. Cieslak 1 , J. Eberhardt 1 , M. Gossla 1 ,
Th. Hahn 1 , H. Metzner 1 , N. Rega 2 , U. Reislöhner 1 , S. Siebentritt
2 , and W. Witthuhn 1 — 1 Friedrich-Schiller-Universität Jena, Institut
für Festkörperphysik, Max-Wien-Platz 1, 07743 Jena — 2 Hahn-
Meitner-Institut, Glienicker Str. 100, 14109 Berlin
Thin films of the chalcopyrite semiconductors CuInS2 (CIS), CuGaS2
(CGS) and CuGaSe2 (CGSe) were grown heteroepitaxially on Si- (CIS,
CGS) and GaAs-substrates (CGSe), respectively. For the growth of the
sulphur compounds, Molecular Beam Epitaxy (MBE) from elemental
sources was utilized, while CGSe was deposited via metal organic vapour
phase epitaxy (MOVPE).
After deposition, the samples were etched in KCN. Various metals including
Al, Ti, Ni, Cr, Ag, and a Ga/In-eutectic were tested for their
contact properties on the chalcopyrite epilayers. Schottky contacts were
obtained by the evaporation of Al, while Ni gave reliable ohmic contacs.
Thermal admittance spectroscopy (TAS) was performed on these samples
to reveal their shallow doping. The TAS spectra show typically one large
capacitance step representing a p-type dopant. The results are compared
to those obtained for polycrystalline CGSe layers in solar cells.
Zeit: Dienstag 18:00–19:15 Raum: H14
HL 25.1 Di 18:00 H14
Band offset determination of InGaAsN quantum well structures
employing surface photovoltage — •Massimo Galluppi, Gheorghe
Dumitras, Lutz Geelhaar, and Henning Riechert — Infineon
Technologies, Corporate Research Photonics, 81730 Munich, Germany
The band offset of semiconductor quantum well (QW) structures is
one of the most important parameters one needs to know in order to predict
the properties of electronic or optoelectronic devices based on such
structures. The here presented method is based on surface photovoltage
(SPV) experiments [1].The band offset and the band alignment result
directly from examining the SPV spectrum. In contrast to conventional
techniques, this method has the advantage that no fitting procedures are
needed and that the exact knowledge of the potential across the QW is
not required.
The method was employed to investigate InGaAs and InGaAsN single
QW structures. A good accordance with the results predicted by theory
and measured by conventional experimental techniques was found.
In addition, the dependence of the band offsets on the indium and on
the nitrogen concentration was studied. While the indium concentration
affects both the conduction and the valence band offsets, the nitrogen
concentration changes only the conduction band offset.
[1] Gh. Dumitras et al., PRB 66, 205324 (2002); Gh. Dumitras et al.,
JAP 94, 3955 (2003).
HL 25.2 Di 18:15 H14
Edge magneto plasmons in GaAs and GaN-based heterojunctions
— •Hans Huebl, Thomas Vallaitis, Sebastian T. B. Goennenwein,
and Martin S. Brandt — Walter Schottky Institut, Technische
Universität München, München, Germany
Various processes can influence the microwave properties of lowdimensional
electron systems, such as absorption caused by cyclotron
resonance, spin resonance or quantum oscillations. However, also
collective excitations such as plasmons can be excited in experimental
set-ups used to study these processes. Since absorption by plasmons
can be very strong, it can easily dominate the spectra observed. In
this contribution, we report a detailed investigation of the absorption
caused by edge magneto plasmons (EMPs) in two-dimensional electron
gases (2DEG). EMPs in InGaAs quantum well structures as well as in
GaN-AlGaN heterostructures have been studied, allowing a variation
of the charge carrier density by more than one order of magnitude.
Very good agreement with the theory of Allen et al.[1] is found, while
the more elaborate theory of Volkov and Mikhailov[2] is not required
to account for the experimental data. Therefore, 2DEG samples with
circumferences of > 1 cm or < 50 µm e.g. in checkerboard arrangement
will be necessary to study spin effects.
[1] S. J. Allen, H. L. Störmer and J. C. M. Hwang, PRB28, 4875 (1983)
[2] V. Volkov and S. A. Mikhailov, Landau Level Spectroscopy, ed. by
G. Landwehr and E. I. Rashba, Springer Verlag, Berlin, Chapter 15, p.855
(1991)
HL 25.3 Di 18:30 H14
Strukturuntersuchungen an dünnen InAs/GaAs Schichten
mittels Rastertunnelmikroskopie an Querschnittsflächen
— •Ferdinand Streicher, Holger Eisele, Tai-Yang Kim,
Jan Grabowski, Rainer Timm, Andrea Lenz, Konstantin
Pötschke, Udo W. Pohl, Dieter Bimberg und Mario Dähne
— Technische Universität Berlin, Institut für Festkörperphysik,
Hardenbergstr. 36, D-10623 Berlin
Mittels Querschnitts-Rastertunnelmikroskopie (XSTM) wurde die
Struktur dünner InAs/GaAs Quantentröge (wells) mit atomarer
Auflösung untersucht. Hierbei wurde insbesondere die atomare Anordnung
des InAs in den 0,6 - 1,8 ML dicken Schichten beobachtet.
Ausgehend von lateralen Inhomogenitäten geben die Untersuchungen
Auskunft über Ansätze von Inselbildungen, bevor das Quantenpunktwachstum
bei ca. 1,8 ML einsetzt.
Weiterhin zeigt sich eine Intensivierung des elektrischen Kontrastes in
den XSTM-Bildern mit zunehmender Schichtdicke, was auf die gleichzeitig
wachsende Anzahl von quantisierten Zuständen in der Schicht
zurückzuführen ist.
HL 25.4 Di 18:45 H14
Elektronische Eigenschaften von in-situ geätzten und
überwachsenen GaAs/AlGaAs Grenzflächen — •Stephan
Schulz, Christian Heyn und Wolfgang Hansen — Institut
für Angewandte Physik und Zentrum für Mikrostrukturforschung,
Universität Hamburg, Jungiusstraße 11, 20355 Hamburg
In-situ Trockenätzen und anschließendes MBE-Überwachsen von vorstrukturierten
Substraten bietet vielfältige Möglichkeiten zur Herstellung
neuartiger Quantenstrukturen. Als Ätzprozesse verwenden wir Chemi-

Halbleiterphysik Dienstag
cally Assisted Ion Beam Etching (CAIBE) sowie Chemical Gas Etching
(CGE) unter Verwendung von Argon und Chlor als Prozessgase. Diese
Prozesse charakterisieren und optimieren wir hinsichtlich niedriger
Störstellendichten und Rauhigkeiten der Grenzflächen mit Deep Level
Transient Spectroscopy (DLTS), Magnetotransport-Messungen und Rasterkraftmikroskopie.
Die Störstellendichten, Elektronenbeweglichkeiten
und Rauhigkeiten hängen stark von den gewählten Prozessparametern
ab. In diesem Vortrag werden insbesondere die Ergebnisse der DLTS-
Messungen vorgestellt.
HL 25.5 Di 19:00 H14
Relaxation times in type I and type II (Ga,In)As/Ga(N,As)
quantum wells — •K Hantke, J. D. Heber, H. Grüning, P. J.
Klar, W. Heimbrodt, J. Koch, S. Nau, W. Stolz, and W. W.
Rühle — FB Physik und WZMW, Philipps-Universität Marburg, 35032
Marburg
HL 26 Hauptvortrag Dadgar
The incorporation of small quantities of nitrogen into GaAs or
(Ga,In)As leads to a strong red shift of the band gap due to a level repulsion
between the localized nitrogen level above the conduction band edge
and the conduction band of the host material itself. Therefore, emitters
in the technologically important wavelength region around 1.3 µm can
be realized with these materials. The influence of this incorporation of
nitrogen on the conduction band discontinuity of (Ga,In)As/Ga(N,As)
quantum wells was determined as a function of temperature and excitation
density by time-resolved photoluminescence measurements. With
increasing nitrogen concentration in the barriers, ranging from about
0.48% to 2.2%, a switch in band-offset from type I to type IIb was found.
At intermediate nitrogen concentrations of around 0.75% to 1.25% the
actual band-offset is shown to strongly depend on temperature and excitation
density.
Zeit: Mittwoch 14:30–15:15 Raum: H15
Hauptvortrag HL 26.1 Mi 14:30 H15
Strains and stresses in GaN heteroepitaxy - sources and control
— •Armin Dadgar — Institut für Experimentelle Physik, Otto-von-
Guericke-Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg
GaN epitaxy, either on sapphire, SiC or Si leads to strained layers due
to several sources such as thermal strain, lattice mismatched layers as Al-
GaN or InGaN, strain by island growth and strain generated by doping.
Using an in-situ curvature measurement technique we can observe the
strain state of GaN during growth. With theoretical models we describe
the evolution of stress during growth, in our case for GaN on Si. By the
in-situ technique the influence of different layer schemes and of doping
on stress evolution can be investigated in detail. In the case of doping we
show the influence of different layer schemes on the evolution of stress.
The control of strain is also important to avoid cracking of thicker layers
during growth or when cooling and to obtain low-curvature layers for
further processing. We show ways to control stresses and strains in GaN
heteroepitaxy to achieve these goals and present latest results for GaN
based devices on Si.
HL 27 GaN: Präparation und Charakterisierung
Zeit: Mittwoch 15:15–19:15 Raum: H15
HL 27.1 Mi 15:15 H15
MOVPE-Wachstum und röntgenografische Strukturuntersuchungen
von GaN-Schichten auf Si(001) — •F. Schulze, J.
Bläsing, A. Dadgar und A. Krost — Otto-von-Guericke-Universität
Magdeburg, PF 4120, 39016 Magdeburg
Zur Integration von GaN-basierten Bauelementen in die etablierte Optoelektronik
ist es vorteilhaft (001)-orientiertes Silizium als Substratmaterial
zu verwenden, da dies die Standardoberfläche der gesamten Si-
Technologie ist. Mittels MOVPE wurden daher GaN-Schichten auf Si
(001)-Substraten abgeschieden. Durch Variation der Pufferschichtstruktur
sowie der Wachstumsparameter konnten dabei gezielt unterschiedliche
GaN-Orientierungen realisiert werden. Mit Hilfe von hochauflösender
Röntgenbeugung (HRXRD) und verschiedenen Messmethoden wie: θ/2θscans,
ω-scans und Polfiguren konnten die jeweiligen Texturen bestimmt
und qualitativ ausgewertet werden. Zum einen wächst das GaN mit der
(1012) Ebene auf dem Si (001) mit 4 Orientierungsmöglichkeiten auf,
wobei die (100) Ebene der Si-Elementarzelle und die (1012) Ebene der
GaN-Einheitszelle um 45 ◦ zueineinder verdreht sind, was mit einer besseren
Gitteranpassung erklärt werden kann. Von den 4 Orientierungen
kann eine durch Fehlorientierung des Substrates bevorzugt werden. Zum
anderen konnte unter anderen Wachstumsbedingungen eine ausgeprägte
c-Achsen-Orientierung des GaN erreicht werden. Kubische Phasenanteile
des GaN konnten dabei ausgeschlossen werden.
HL 27.2 Mi 15:30 H15
Spektroskopie von versetzungskorrelierten Energieniveaus
in GaN mit thermisch und optisch angeregter Oberflächenpotentialmikroskopie
— •Andre Krtschil und Alois
Krost — Institut für Experimentelle Physik, Otto-von-Guericke-
Universität Magdeburg
Es ist bekannt, daß Rasteroberflächenpotentialmikroskopiemessungen
(SSPM) sensitiv für den Ladungszustand von Versetzungen in GaN sind.
Am Beispiel von unterschiedlich dotierten, MOCVD-gewachsenen GaN-
Schichten auf Saphirsubstrat wird erläutert, wie die SSPM-Technik zur
Spektroskopie der korrespondierenden Energieniveaus erweitert werden
kann. Zum einen wurde die Temperaturabhängigkeit des SSPM-Signals
untersucht, wobei sich die thermische Aktivierungsenergie der Versetzungsniveaus
aus einer Arrheniusdarstellung der Potentialpeakhöhe be-
stimmen lässt. Weiterhin wurden zur Detektion von energetisch tiefer liegenden
Niveaus die Versetzungsdurchstöße während der SSPM-Messung
über eine Glasfaseroptik mit monochromatischem Licht angeregt. Aus
dem lokalen Spektrum lässt sich dann bei resonanter Anregung auf die
optische Übergangsenergie der Versetzungsniveaus schließen. Erste Ergebnisse
für Schraubenversetzungen in GaN:Mg ergaben thermische Aktivierungsenergien
von 200-350 meV sowie eine breite optische Resonanzbande
um 2.95 eV. Diese Ergebnisse sowie die Resultate für die anderen
Versetzungstypen und ihre Abhängigkeit von der Schichtdotierung werden
im Detail diskutiert.
HL 27.3 Mi 15:45 H15
Optimierung eines neuen GaN MOVPE-Wachstumsprozesses
mit reduzierten parasitären Depositionen — •Roger Steins, Nicoleta
Kaluza, Konrad Wirtz, Hilde Hardtdegen und Hans
Lüth — Centre of Nanoelectronic Systems for Information Technology,
Institut für Schichten und Grenzflächen, Forschungszentrum Jülich,
52425 Jülich
Eine der größten Herausforderungen bei der MOVPE von GaN ist reproduzierbare
Schichtabscheidung. Verantwortlich für die Nichtreproduzierbarkeit
sind parasitäre Depositionen auf den Reaktorwänden, welche
die Gasphasenzusammensetzung und Reaktortemperatur erheblich beeinflussen.
Gerade in Horizontal-Reaktorsystemen entstehen vergleichsweise
große katalytisch wirkende Oberflächen.
Der hier vorgestellte Ansatz zur Vermeidung der parasitären Depositionen
verringert die TMGa Konzentration in der Nähe der heißen
Reaktorwände. Bewerkstelligt wird dies hauptsächlich durch einen
veränderten Gaseinlass. Üblicherweise wird die Gruppe V Quelle wegen
des inkongruenten Verdampfens dieser Elemente bevorzugt in die Nähe
des Substrates gebracht. Vom Hydridfluß separiert wird das Metallorganikum
oberhalb davon -in der kalten Zone des Reaktors- eingeleitet.
Somit vertauscht der neue Prozess im Wesentlichen die Gasflüsse von
Gruppe III Metallorganikum und Gruppe V Hydrid und vermeidet damit
parasitäre Deposition. Dieser neue Prozess wird vorgestellt und die
Auswirkungen auf die Schichtabscheidung präsentiert.

Halbleiterphysik Mittwoch
HL 27.4 Mi 16:00 H15
Anisotropy of the Dielectric Function for wurtzite InN — •R.
Goldhahn 1 , A.T. Winzer 1 , V. Cimalla 2 , O. Ambacher 2 , C. Cobet
3 , N. Esser 3 , J. Furthmüller 4 , F. Bechstedt 4 , H. Lu 5 , and
W.J. Schaff 5 — 1 Institute of Physics, TU Ilmenau, PF 100565, 98684
Ilmenau — 2 Center for Micro- and Nanotechnologies, TU Ilmenau —
3 TU Berlin — 4 FSU Jena — 5 Cornell University, Ithaca, U.S.A.
Theoretical calculations of the dielectric function (DF) for wurtzite InN
predict a pronounced anisotropy in the range of the high-energy critical
points of the band structure. Neither for MBE/MOVPE grown layers
(gap energy ∼ 0.7 eV) nor sputtered films (absorption edge ∼ 1.9 eV)
such an anisotropy has been reported yet. We succeeded in growing aplane
InN on r-plane sapphire substrate by plasma-assisted MBE. Those
layers offer the advantage that the light can be polarized parallel and perpendicular
to the optic axis (c-axis) allowing the direct determination of
both the ordinary and extraordinary component of the DF tensor. Here,
results of spectroscopic ellipsometry measurements in the energy range
from 0.7 up to 9.5 eV (partly using synchrotron radiation) are presented.
For the first time, strong optical anisotropy of InN is demonstrated in the
energy range above 4.5 eV. The data are compared with results of firstprinciples
band structure and DF calculations. Data analysis in the near
band gap range proves in addition a strong non-parabolicity of the conduction
band. All results provide further evidence that InN is a narrow
band gap semiconductor.
HL 27.5 Mi 16:15 H15
Verspannung und Wingtilt von ELOG GaN auf SiC Substraten
— •Nikolaus Gmeinwieser 1 , Karl Engl 1 , Peter Gottfriedsen
1 , Ulrich T. Schwarz 1 , Josef Zweck 1 , Werner Wegscheider
1 , Stephan Miller 2 , Andreas Leber 2 , Andreas Weimar 2 ,
Alfred Lell 2 und Volker Härle 2 — 1 Naturwissenschaftliche Fakultät
II- Physik, Universität Regensburg — 2 OSRAM Opto Semiconductors
GmbH, Wernerwerkstr. 2, 93049 Regensburg
Zur Herstellung defektreduzierter GaN Schichten auf SiC Substraten
verwenden wir den ELOG (epitaxial lateral overgrowth) Prozess.
Die Flügel der ELOG-Streifen sind gegenüber den Fenstern weniger
verspannt und weisen intensivere Photolumineszenz (PL) mit
schmäleren Linienbreiten auf. TEM Aufnahmen zeigen über den ELOG-
Maskenrändern eine hohe Dichte von Versetzungslinien, die entlang der
ELOG-Streifen verlaufen und durch den Wingtilt der Proben verursacht
werden. Micro-Photolumineszenz (µPL) Messungen ergaben im Bereich
der Maskenränder und in den angrenzenden 2 µm der Flügel niedrigere
PL-Intensität, höhere Linienbreiten und stärkere tensile Verspannung gegenüber
sowohl den Fenstern als auch den Flügeln. Durch einen Wechsel
des ELOG-Maskenmaterials von SiO2 zu SiNx konnte der Wingtilt um
eine Größenordnung auf ca. 0,4 Grad reduziert werden. Die so hergestellten
Proben zeigen kein Anzeichen reduzierter Materialqualität entlang
der Maskenränder.
HL 27.6 Mi 16:30 H15
Selforganized superlattice formation in AlGaN grown by
MOVPE — •Andreas Able, Karl Engl, Josef Zweck, and
Werner Wegscheider — Institut für Experimentelle und Angewandte
Physik, Universität Regensburg, Universitätsstr. 31, D-93053
Regensburg, Germany
Phase separation and demixing processes are well known phenomena
in the system of group-III nitrides. Especially the clustering of indium
in InGaN quantumwells is investigated thoroughly as it may be the key
for lasing. In contrast to that, not much is yet known about large scale
selforganization in the AlGaN ternary system. Few groups have reported
formation of selforganized superlattices in this system, but no further
studies were published 1 .
To clarify this process, we have grown a series of AlGaN structures
on Si(111) by metal organic chemical vapor phase epitaxy (MOVPE).
The samples were characterized using high resolution xray diffraction
(HRXRD), high resolution transmission electron microscopy (HRTEM)
as well as photoluminescence measurements.
The formation of superlattices with periods of about 3.1nm has been
observed within a wide range of growth parameters. The results of these
measurements are presented and a model for the underlying process is
proposed.
1 B. Neubauer, A. Rosenauer, D. Gerthsen, O. Ambacher and M. Stutzmann,
Appl. Phys. Lett. 73, 930 (1998)
HL 27.7 Mi 16:45 H15
Chemically ordered AlxGa1−xN alloys: Spontaneous formation
of natural quantum wells — •L. Lymperakis 1 , M. Albrecht 2 ,
J. Neugebauer 1,3 , J.E. Northrup 4 , L. Kirste 5 , and H.P.
Strunk 2 — 1 Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin
— 2 Universität Erlangen-Nürnberg, Lehrstuhl Mikrocharakterisierung
— 3 Universität Paderborn — 4 Palo Alto Research Center, CA 94304,
U.S.A. — 5 Freiburger Materialforschungszentrum, Universität Freiburg
We have combined density-functional theory (DFT) calculations with
x-ray and transmission electron microscopy experiments to study formation,
stability, and structural and optical properties of ordered
AlxGa1−xN. Our calculations show that ordered structures are thermodynamically
unstable against disorder. We have therefore explored whether
kinetics may be used to achieve ordering. Based on our calculations we
find that adatom kinetics at surface steps can induce ordering. An analysis
of the computed electronic structure showed that ordering significantly
affects the electronic structure: it causes a redshift in the band
gap by 100 meV. The theoretical predictions have been confirmed by
the experimental studies. Under appropriate growth conditions an alternating
1 × 1 AIN/GaN superlattice forms. While transmission electron
microscopy shows the presence of ordered domains, annealing under high
pressure and high temperature leads to disappearance of the superlattice,
accompanied by a blue shift of the luminescence up to 140 meV.
HL 27.8 Mi 17:00 H15
Beobachtung eines Be-korrelierten Donator-Zustandes in GaN
mittels Radiotracer-Spektroskopie — •F. Albrecht 1 , J. Grillenberger
2 , U. Reislöhner 1 , G. Pasold 1 , M. Dietrich 3 , W. Witthuhn
1 und die ISOLDE Collaboration 4 — 1 Friedrich-Schiller-
Universität Jena, Institut für Festkörperphysik, Max-Wien-Platz 1, 07743
Jena — 2 Fysisk institutt, Postboks 1048 - Blindern, 0316 Oslo, Norwegen
— 3 Technische Physik, Universität des Saarlandes, 66041 Saarbrücken —
4 CERN, CH-1211, Geneva 23, Schweiz
Mit Hilfe der in dieser Studie erstmalig angewendeten Radiotracer
Thermal Admittance Spectroscopy (TAS) wurde ein Be-korrelierter
Donator-Zustand in der Bandlücke von GaN identifiziert. Hierfür wurde
das radioaktive Isotop 7 Be sowohl in p- als auch in n-leitende GaN-
Schichten implantiert. Wiederholt an n-Typ GaN aufgenommene TAS-
Spektren zeigen die Existenz eines Donator-Zustandes bei 390 meV oberhalb
der Valenzbandkante, dessen Konzentration entsprechend der Elementumwandlung
von 7 Be zu 7 Li (T1 /2 = 53.3 d) abnimmt. Daraus folgt
ein direkter Zusammenhang zwischen diesem Donator-Zustand und Be.
Die Implantation vergleichbarer Dosen des Isotops 7 Be in p-Typ GaN
hingegen führte zu einer signifikanten elektrischen Aktivierung des zum
Zwecke der p-Dotierung eingebrachten Mg-Akzeptors.
HL 27.9 Mi 17:15 H15
Oberflächenbedeckung und Lumineszenzverhalten von Nitrid-
Quantenfilmen — •A. Buchholz, D. Fuhrmann, U. Rossow und
A. Hangleiter — Institut für Technische Physik, Technische Universität
Braunschweig, Mendelssohnstr. 2, 38106 Braunschweig
Das Zusammenwirken von spontanem und piezoelektrischem Feld
hat einen großen Einfluss auf die optischen Eigenschaften von
Gruppe-III-Nitriden. Oberflächenbelegungen können dabei abschirmend
auf das spontane Feld wirken. Bei früheren Kathodolumineszenz
(KL)-Messungen an InGaN/GaN-Quantenfilmen zeigte sich eine
Blauverschiebung der Lumineszenzlinie, die auf elektronenstimulierte
Desorption schwach gebundener Spezies von der Oberfläche zurückgeführt
wurde. Systematische Untersuchungen erfolgen nun in einem
Ultrahochvakuum(UHV)-System, in dem die Proben mittels temperaturabhängiger
KL charakterisiert werden, wobei die Restgaszusammensetzung
durch ein Quadrupolmassenspektrometer bestimmt wird. Eine
Vielzahl der Proben (GaN/InGaN- und AlGaN/GaN-Kompositionen)
zeigte in der KL eine von der Anregungsleistung abhängige Dynamik
der Intensitätsentwicklung. Ein Ausheizen der Proben im UHV nimmt
dabei Einfluss auf diesen Effekt; die gleichzeitig beobachtete Zunahme
des Wasserdampfanteils in der Kammer, begleitet von der Tatsache, dass
sich die Proben an Atmosphäre ” regenerieren“ lassen, lässt vermuten,
dass die Entwicklung durch ein ” Reinigen“ der Oberfläche, vornehmlich
von Wasser, verursacht wird. Das definierte Ausheizen erlaubt dabei die
Präparation unterschiedlich stark belegter Oberflächen, die im Weiteren
auch mittels Photolumineszenz (PL) untersucht werden sollen.

Halbleiterphysik Mittwoch
HL 27.10 Mi 17:30 H15
Zeitaufgelöste Photolumineszenz an GaInN/GaN-Strukturen:
Laserqualität contra Quantenausbeute — •C. Netzel, F. Hitzel,
S. Lahmann, U. Rossow und A. Hangleiter — Institut für Technische
Physik, Technische Universität Braunschweig, D-38106 Braunschweig
GaN-basierte Halbleiterstrukturen, ob LEDs oder Laserdioden, mit
Emissionswellenlängen von grün bis ins UV, werden seit einigen Jahren
hergestellt. Trotz der Entwicklungserfolge konnten grundlegende Fragen,
die strahlende und nichtstrahlende Rekombination in dem defektreichen
Materialsystem betreffend, bisher nicht eindeutig geklärt werden.
In dieser Arbeit soll durch Untersuchungen von GaInN/GaN-
Heterostrukturen, die mit MOVPE auf Saphir/SiC gewachsen wurden,
ein tieferer Einblick in die Rekombinationsabläufe gewonnen werden. Es
wurden auf hohe optische Verstärkung optimierte Laserstrukturen mit
zeitaufgelöster Photolumineszenz untersucht und mit auf hohe Quantenausbeute
optimierten MQWs verglichen. Sämtliche Probenreihen zeigen
in der Photolumineszenz neben der erwarteten Linienposition mindestens
eine weitere hochenergetische Emission. Die Ausprägungen der Emissionslinien
sind abhängig vom jeweiligen Optimierungsgrad. Vergleichsmessungen
mittels SNOM (Scanning Nearfield Optical Microscope) deuten
auf eine räumliche Trennung der Emissionen hin. Zeitaufgelöste Messungen
zeigen eine unterschiedliche Zerfallskinetik der Emissionen auf.
Eine Erhöhung der Quantenausbeute scheint mit dem verstärkten Auftreten
der hochenergetischen Emission einherzugehen. Die Laserqualität
wird dabei jedoch verschlechtert.
HL 27.11 Mi 17:45 H15
MOVPE growth of GaN/AlGaN quantum well structures and
its impact on the optical properties — •D. Fuhrmann 1 , M.
Greve 1 , N. Riedel 1 , U. Rossow 1 , G. Ade 2 , P. Hinze 2 , J. Bläsing 3 ,
A. Krost 3 , and A. Hangleiter 1 — 1 TU Braunschweig, Inst. f. Techn.
Phys., 38106 Braunschweig; d.fuhrmann@tu-bs.de — 2 Physikalisch Technische
Bundesanstalt, 38116 Braunschweig — 3 Otto-von-Guericke-Univ.,
Inst. f. Exp. Phys., 39016 Magdeburg
GaN/AlxGa1−xN (x≥20%) quantum well (QW) structures were grown
by MOVPE on sapphire and SiC substrates in order to realize efficient UV
light emitters. It will be shown how growth parameters (substrate, III-
V-ratio, Si-doping, pressure) affect the optical properties, determined by
photoluminescence (PL) spectroscopy. TEM and XRD measurements reveal
smooth surfaces for the upper and lower GaN/AlxGa1−xN-interface.
AFM pictures of GaN QW-structures on sapphire show microholes, which
can be correlated to defects inside the AlGaN buffer layer. In addition,
a PL emission around 3.65 eV arising from these defects is observed,
whereas for structures on SiC both AFM and PL do not show these features.
Varying QW-thickness for QWs on SiC or sapphire yields a nearly
linear shift for the PL peak position with different slopes. It is found
that for short growth times a nucleation phase takes place for QWs on
sapphire which is not seen in the case of SiC substrates. In order to increase
the potential barrier, AlN/GaN MQW structures have been grown
for comparison. Differences between AlxGa1−xN barriers and AlN barriers
arising from a different morphology and structural quality as well as
different electric fields inside the quantum well will be discussed.
HL 27.12 Mi 18:00 H15
Temperature dependence of the built-in electric field strength
in AlGaN/GaN Heterostructures grown on Si(111) — •A.T.
Winzer 1 , R. Goldhahn 1 , G. Gobsch 1 , A. Dadgar 2 , A. Krtschil 2 ,
H. Witte 2 , and A. Krost 2 — 1 Institute of Physics, TU Ilmenau, 98684
Ilmenau — 2 Institute of Experimental Physics, Otto-von-Guericke University
Magdeburg, 39016 Magdeburg
Previous studies of the barrier electric field strength F of AlGaN/GaN
heterostructures grown on sapphire revealed a strong temperature dependence.
This was attributed to the change of piezoelectric polarization
due to the large mismatch of thermal expansion coefficients between the
nitride layers and the sapphire.
Here, we report for the first time on similar studies for AlGaN/GaN
heterostructures on Si(111)-substrate. The samples were grown by
MOCVD with different Al-contents in the top AlGaN layer, utilizing a
thin low temperature AlN interlayer for strain reduction.
Hall and C(V) measurements as well as spatially resolved surface potential
measurements were carried out in order to determine the density
of the 2DEG. In the AlGaN layers, F was determined by analyzing the
Franz-Keldysh-Oscillations in photoreflectance spectroscopy. Their energetic
splittings indicate that F is nearly independent from the temper-
ature, which can be attributed to a constant piezoelectric polarization
and thus to a constant strain state.
This interpretation is corroborated by temperature dependent reflectance
measurements. The results are compared with self-consistent
conduction band calculations.
HL 27.13 Mi 18:15 H15
Silicon doping of heteroepitaxial AlN films grown by MBE —
•Martin Hermann, Florian Furtmayr, Martin Stutzmann, and
Martin Eickhoff — Walter Schottky Institut, Am Coulombwall 3,
85748 Garching
Recently, Si-doped AlN has attracted increasing interest due to its
possible application in wide bandgap semiconductor devices, such as n-
AlN/p-diamond heterojunction diodes. So far, these devices suffer from
a large serial resistance because of the high ionization energy of Si in
AlN. We have investigated Si doping of heteroepitaxial AlN films grown
by plasma assisted molecular beam epitaxy.
The influence of the Si concentration on the structural properties has
been investigated by high resolution X-ray diffraction measurements. The
surface morphology of the AlN:Si samples has been examined by atomic
force microscopy. The dependence of the Si donor activation energy on
the doping concentration was analyzed by temperature dependent conductivity
measurements. Optical absorption measurements were used to
detect the formation of impurity induced defects, especially the by Si
donor, and to examine their influence on the optical properties of AlN:Si.
HL 27.14 Mi 18:30 H15
Verspannungsgradienten in dicken GaN-Schichten auf Silizium
Substrat — •U. Haboeck 1 , A. Hoffmann 1 , C. Thomsen 1 , T. Riemann
2 , F. Bertram 2 , J. Christen 2 , A. Dadgar 2 und A. Krost 2
— 1 Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr.
36, 10623 Berlin, Germany — 2 Institut für Experimentelle
Physik, Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2,
39106 Magdeburg, Germany
Die Gitterfehlanpassung sowie die extrem unterschiedlichen thermischen
Ausdehnungskoeffizienten erschweren das Wachstum von Galliumnitrid
(GaN) auf Siliziumsubstrat (Si (111)). Selbst dünne Schichten sind
in der Regel deutlich tensil verspannt und können reissen. Mittels Mikro-
Raman-Spektroskopie und Kathodolumineszenz Mikroskopie haben wir
mehrere dicke GaN/Si-Schichten untersucht. Unsere Experimente belegen
den günstigen Einfluss von eingefügten Aluminiumnitridzwischenschichten
und Siliziumnitridmasken auf die strukturellen und optischen
Eigenschaften von nominell undotierten und Si-dotierten Proben. Ortsaufgelöste
Messungen über die Probenkanten ermöglichen einen Einblick
in die Entwicklung der Verspannung vom Substrat zur Oberfläche hin.
Obwohl die Relaxation in den ca. 6 Mikrometer dicken Schichten sprunghaft
erfolgt, waren die Oberflächen homogen und frei von Rissen.
HL 27.15 Mi 18:45 H15
Electro-optic Effects in Nitride Semiconductors: Investigation
and Application for Characterisation — •S. Shokhovets 1 , G.
Gobsch 1 , O. Ambacher 2 , M. Hermann 3 , and M. Eickhoff 3 —
1 Institute of Physics, TU Ilmenau, PF 100565, 98684 Ilmenau, Germany
— 2 Center for Micro- and Nanotechnologies, TU Ilmenau, PF 100565,
98684 Ilmenau — 3 Walter Schottky Institute, TU Munich, Am Coulombwall
3, 85748 Garching
We report on the results of electroreflectance (ER) and impedancevoltage
(ZV) studies of GaN and AlGaN diodes with a semitransparent
Pt Schottky gate. The data analysis was carried out using the multi-layer
formalism which allows us to consider the electric field inhomogeneity.
The field-dependent contribution of excitons and excitonic continuum
to the dielectric function (a) and the linear electro-optic effect (b) were
identified to be the main mechanisms of the electro-optical response. The
first effect leads to the so-called rotation ER spectra in a region of the
excitonic absorption and reduces to the Franz-Keldysh-like oscillations
above the band gap. The second one is responsible for the electro-optical
response below the band gap. Further, applications for characterisation
(exciton energies and broadening parameters for the zero-field limit, band
bending, concentration of ionised impurities and electric field strength in
the depletion region as a function of the temperature) are presented and
compared with the ZV measurements.

Halbleiterphysik Mittwoch
HL 27.16 Mi 19:00 H15
Optische Charakterisierung von Nitridhalbleitern und deren
Oberflächen mittels spektroskopischer Ellipsometrie —
•Christoph Cobet 1 , Munise Rakel 1 , Thomas Säuberlich 1 ,
Thorsten Schmidtling 1 , Massimo Drago 1 , Rüdiger Goldhahn
2 , Wolfgang Richter 1 und Norbert Esser 3 — 1 Institut für
Festkörperphysik, Technische Universität Berlin — 2 Institut für Physik,
Technische Universität Ilmenau — 3 Institute of Spectrochemistry and
Applied Spectroscopy Department Berlin-Adlershof
Mittels spektroskopischer Ellipsometrie wurde von den Nitridhalbeitern
GaN, AlN und InN sowie deren Mischkristalle die dielektrische Funktion
(ε/εxyz) im Spektralbereich des optischen Bandabstandes sowie der
höheren Interbandübergänge (1-30eV) gemessen. Aus den charakteristi-
HL 28 Optische Eigenschaften
schen Strukturen der dielektrischen Funktion werden Lage und Art der
Interbandübergängen bzw. Core-level-Anregungen bestimmt und durch
den Vergleich der optischen Daten verschieden präparierter Proben Informationen
über kristalline Orientierung und Qualität gewonnen. Darüber
hinaus werden mit Hilfe von ab-initio-DFT-LDA-Rechnungen Aussagen
über die elektronische Struktur abgeleitet. Die sehr hohe Genauigkeit der
spektroskopischen Ellipsometrie gegenüber Oberflächenterminierungen
ermöglichte uns weiterhin eine Untersuchung der Oberfläche während des
Kristallwachstums in der MOVPE (Metal-Organic Vapor Phase Epitaxy)
und in der PAMBE (Plasma-Assisted Molecular Beam Epitaxy).
Dadurch konnten für die beide Wachstumsmethoden unterschiedliche
Oberflächenrekonstruktionen und Oberflächenterminierungen nachgewiesen
werden.
Zeit: Mittwoch 15:15–17:45 Raum: H17
HL 28.1 Mi 15:15 H17
Exciton-Phonon Dynamics in Disordered Quantum Wells beyond
the Markov Approximation — •Gianandrea Mannarini
and Roland Zimmermann — Institut für Physik der Humboldt-
Universität zu Berlin, Newtonstr.15, 12489 Berlin, Germany
Exciton motion in semiconductors is coupled to the thermal bath of
phonons due to carrier-lattice interactions. Within the density-matrix
formalism, a hierarchy of equations of motion is derived which contains
memory (non-Markovian) effects. Assuming very short collision times,
the exciton-phonon interaction can be described in terms of scattering
rates. This Markov approximation could explain quantitatively the spectral
properties of the excitonic secondary emission [1]. However, in ultrafast
experiments a more complex dynamics is expected. Actually, a non
-Markovian dynamics was predicted and observed for the electron-LO
phonon system [2]. Here, we adopt a non-Markovian treatement for localized
excitons in single quantum wells coupled to acoustical phonons via
deformation potential interaction. The equations of motion with memory
for the exciton polarization and density matrix are integrated and
the effect on the time-resolved dynamics of the secondary emission and
the speckle pattern is calculated. [1] G. Mannarini, R. Zimmermann,
G. Kocherscheidt, and W. Langbein, phys. stat. sol. (b), 238, 494 (2003).
[2] C. Fürst, A. Leitenstorfer, A. Laubereau, and R. Zimmermann, Phys.
Rev. Lett. 78, 3733 (1997).
HL 28.2 Mi 15:30 H17
Dynamic band gap renormalization in Cu2O studied on a
µeV scale — •Giorgio Baldassarri Höger von Högersthal 1 ,
Gregor Dasbach 1 , Dietmar Fröhlich 1 , Heinrich Stolz 2 ,
Manfred Bayer 1 , Robert Klieber 1 , and Dieter Suter 1 —
1 Institut für Physik, Universität Dortmund, D-44221, Germany —
2 Fachbereich Physik, Universität Rostock, D-18051, Germany
Owing to the large exciton binding energy and the long radiative lifetime,
cuprous oxide (Cu2O) is considered a prototype material for the
study of excitons. Especially the quadrupole allowed lowest yellow exciton
transition has always attracted much interest. This state has been
recently investigated with ultra-high spectral resolution using a tunable
single frequency dye laser, revealing extremely sharp exciton linewidths of
< 1 µeV [1]. Here we investigate this system in the high density regime.
Using pulsed excitation we get access to dynamic line shifts on a sub
µeV energy scale and a ms time scale. The experiments show dynamic
red shifts of the exciton transition as the excitation power is increased.
These findings are explained by an absorption induced renormalization
of the band gap.
[1] G. Dasbach et al., Phys. Rev. Lett. 91, 107401 (2003).
HL 28.3 Mi 15:45 H17
Nichtlineare Polariton-Propagation in dünnen Halbleiterschichten
— •Stefan Schumacher, Gerd Czycholl und Frank Jahnke
— Institut für Theoretische Physik, Universität Bremen
Das Wechselspiel von kohärenten optischen Nichtlinearitäten und
Polariton-Propagationseffekten in dünnen Halbleiterschichten wird
im Rahmen des DCT-Formalismus (dynamics-controlled truncation)
untersucht. Dabei werden für ein räumlich inhomogenes System alle
exzitonischen und biexzitonischen Beiträge bis zur dritten Ordnung im
optischen Feld berücksichtigt.
In den betrachteten, typischerweise einige Exziton-Bohrradien dicken,
Halbleiterschichten wird die gekoppelte Lichtfeld-Exziton-Dynamik unter
mikroskopischen Randbedingungen gelöst. Die räumliche Lokalisierung
der Ladungsträger in der Halbleiterschicht führt dabei im Vergleich zum
Volumenmaterial zu einer energetischen Aufspaltung der exzitonischen
Zustände.
Untersucht wird insbesondere der Einfluss der Coulombwechselwirkung
zwischen mehreren 1s-artigen exzitonischen Eigenzuständen auf
die Nichtlinearitäten in optischen Transmissionsspektren in Pumpund
Teststrahl-Geometrie. Ergebnisse werden sowohl für Teststrahl-
Transmissionsspektren als auch für die entsprechende Zeitentwicklung
für verschiedene Anregungsbedingungen dargestellt.
HL 28.4 Mi 16:00 H17
Excitons and Plasma: Two Sources for Excitonic Photoluminescence:
— •Sangam Chatterjee 1,2 , Sorin Mosor 2 , Claudia Ell 2 ,
Galina Khitrova 2 , Hyatt M. Gibbs 2 , Walter Hoyer 1 , Mackillo
Kira 1 , Stephan W. Koch 1 , John P. Prineas 3 und Heinrich
Stolz 4 — 1 Fachbereich Physik und Wissenschaftliches Zentrum für
Materialwissenschaften, Philipps-Universität Marburg, Renthof 5, 35032
Marburg. — 2 The University of Arizona, Optical Sciences Center, 1630
E. University Blvd, Tucson, AZ 85721, USA. — 3 University of Iowa, Iowa
City, IA 52242, USA. — 4 Fachbereich Physik, Universität Rostock,
D-18051 Rostock
Photoluminescence from InGaAs quantum well structures exhibits a
strong peak at the energetic position of the 1s exciton resonance. This
is independent of the presence of an incoherent excitonic population. We
perform time-resolved photoluminescence experiments over a large range
of carrier density and lattice temperatures. A detailed analyses using a
microscopic theory identifies the plasma and excitonic contributions to
the emission. A phase diagram for the bright incoherent excitonic contributions
is then extracted. At low lattice temperatures, 4K, and intermediate
and low densities small fractions of bright excitons can completely
dominate the emission. For larger lattice temperatures, 50K, the excitonic
contributions is negligibly small.
HL 28.5 Mi 16:15 H17
Electro-optical properties of ZnO-BaTiO3-ZnO heterostructures
grown by pulsed laser deposition — •M. Schubert 1 , N.
Ashkenov 1 , T. Hofmann 1 , M. Lorenz 1 , H. v. Wenckstern 1 ,
M. Grundmann 1 , and G. Wagner 2 — 1 Fakultät für Physik und
Geowissenschaften, Instititut für Experimentelle Physik II, Universität
Leipzig, Linnéstraße 5, 04103 Leipzig — 2 Institut für Nichtklassische
Chemie, Universität Leipzig, 04318 Leipzig, Germany
Electro-optical birefringence measurements by spectroscopic ellipsometry
on ZnO-BaTiO3-ZnO heterostructures, grown by pulsed laser deposition
on (0001) sapphire are reported. Wurtzite-structure ZnO layers serve as
transparent conducting electrodes. An interesting hysteresis is observed,
tentatively assigned due to coupling between wurtzite and ferroelectric
polarization, and ferroelectric phase transition.
HL 28.6 Mi 16:30 H17
Temperature dependence of efficient silicon light-emitting
diodes prepared by ion implantation — •Jiaming Sun, Thomas
Dekorsy, Wolfgang Skorupa, Bernd Schmidt, and Manfred
Helm — Institut für Ionenstrahlphysik und Materialforschung,
Forschungszentrum Rosendorf, 01314 Dresden

Halbleiterphysik Mittwoch
Efficient electroluminescence (EL) was observed from silicon pn diodes
prepared by boron implantation [1]. The temperature dependences of the
EL intensity are strongly related to the boron implantation doses, the
creation of excess defects and the injection current. Effective suppression
of the electron-hole recombination through non-radiative channels is observed
at a high dose boron implantation (larger than 1×10 15 cm −2 ) or
at a high current injection. The dependences of the EL intensity on the
injection current at different temperatures can be well calculated with
a rate equation model. The theoretical calculations indicate that bound
excitons, which are responsible for the increase of the band-edge emission
at elevated temperatures, have a much higher thermal emission rate as
compared to the recombination rate in the diodes implanted with a high
boron dose.
[1] J.M. Sun et al., Appl. Phys. Lett. 83, 3885 (2003).
HL 28.7 Mi 16:45 H17
Breitband-Emission und geringe Absorption in Microdisks mit
AlGaAs-Quantenfilmen — •T. Kipp, K. Petter, Ch. Heyn, D.
Heitmann und C. Schüller — Institut für Angewandte Physik und
Zentrum für Mikrostrukturforschung, Universität Hamburg
Mittels holographischer Lithographie, reaktivem Ionenätzen und einem
selektiven nass-chemischen Ätzverfahren wurden großflächige Arrays von
Microdisks mit eingebetteten Al0.2Ga0.8As/Al0.4Ga0.6As-Quantenfilmen
aus einer mittels Molekularstrahlepitaxie gewachsenen Halbleiterschichtstruktur
hergestellt [1]. Wir beobachten in Mikro-Photolumineszenz-
Messungen an einzelnen dieser Microdisks über 20 Whispering-Gallery-
Modes in einem bemerkenswert breiten Energiebereich von über 250
meV. Die Spektren unterscheiden sich damit deutlich von den bislang publizierten
Spektren für Quantenfilm-Microdisks, in denen typischerweise
nur ein bis zwei optische Moden auftreten [2], und ähneln eher Microdisks
mit eingebetteten selbstorganisiert gewachsenen Quantenpunkten
[3]. Aus unseren Experimenten schließen wir, dass an Störstellen gebundene
Zustände unterhalb der Energie freier Elektron-Loch-Paare innerhalb
der ternären Quantenfilme zu einem effizienten, breitbandingen internen
Emitter mit geringer Absorption führen.
Diese Arbeit wird von der DFG im Rahmen des SFB 508 und dem
Graduiertenkolleg ” Felder und lokalisierte Atome“ gefördert.
[1] K. Petter et al., Appl. Phys. Lett. 81, 592 (2002)
[2] S. L. McCall et al., Appl. Phys. Lett. 60, 289 (1992)
[3] B. Gayral et al., Appl. Phys. Lett. 75, 1908 (1999)
HL 28.8 Mi 17:00 H17
Photonic Band Gap Structures in the 25-60 GHz Range —
•Rados Gajic 1,2 , Ronald Meisels 1 , Fridemar Kuchar 1 , Jelena
Radovanovic 2 , Alexander Woess 3 , and Juergen Stampfl 4
— 1 Insitut fuer Physik, Montanuniversitaet Leoben, Oesterreich
— 2 Institute of Physics, P:O. Box 68, 11080 Belgrade, Serbia and
Montenegro — 3 Erich Schmidt Institut fuer Materialwissenschaften,
Oesterreichische Akademie der Wissenschaften, Leoben, Oesterreich
— 4 Institut fuer Werkstoffkunde und Materialpruefung, TU Wien,
Oesterreich
In this work we present experimental and numerical results on 2D and
3D photonic band gap structures (PBGS) in the frequency range between
HL 29 Spinabhängiger Transport I
25 and 60 GHz (millimeter waves). For the fabrication of the PBGS we
used commercially available alumina rods as well as a rapid prototyping
method. In the 3D case, the woodpile (layer-by-layer) structure was
investigated in order to find the optimal configuration regarding the gapto-midgap
ratio. We also demonstrated the presence of higher in our 2D
and 3D PBGS. We compared these experimental findings with numerical
calculations based on the transfer matrix method. It was found that a
slight change of the cubic fcc structure towards the tetragonal fct geometry
yields increased gap-to-midgap ratios (higher than 30 procent). This
work is supported by Austrian FWF project No. 15513 and the Serbian
Ministry of Science project No. 1469.
HL 28.9 Mi 17:15 H17
Impact of oxidation on InN layer properties investigated by
Spectroscopic Ellipsometry — •Tobias L. Schenk, Torsten
Schmidtling, Massimo Drago, Christoph Cobet, and Wolfgang
Richter — TU Berlin, PN6-1, Hardenbergstr. 36, 10623 Berlin
MOVPE grown InN films on sapphire by Spectroscopic Ellipsometry
(SE) in the range of 0.8-6.5eV have been investigated. The observed
range is extended to include the newly assumed band gap position of
about 0.9eV. The exact position is indeed unknown yet, since oxidation,
poor layer quality, and high number of intrinsic defects influence the optical
properties. An important fact seems to be the oxidation of the still
defective layers. Therefore MOVPE grown layers in different grades of
oxidation are prepared and studied under controlled conditions and also
compared to MBE grown and sputtered ones. We find a strong dependence
of the band gap position on the oxidation state. This demonstrates
that oxidation is a critical factor contributing to the uncertainty of the
determination of the band gap value. Furthermore the oxidation influence
on the optical constants is evident in the whole spectral region leading
to a strong decrease in the dielectric response of the higher transitions.
HL 28.10 Mi 17:30 H17
MOVPE growth of InN layers: in-situ control of the growth
parameters by Spectroscopic Ellipsometry — •Massimo Drago,
Christoph Werner, Tobias L. Schenk, Torsten Schmidtling,
Udo W. Pohl, and Wolfgang Richter — TU Berlin, PN6-1, Hardenbergstr.
36, 10623 Berlin
The growth of indium nitride by MOVPE is a challenging issue, particularly
due to the low enthalpy of formation and the large lattice mismatch
to available substrates, like e.g. sapphire. At present, the quality of
MOVPE samples is not yet comparable with the MBE ones, and further
optimisation is necessary. In-situ Spectroscopic Ellipsometry (SE) control
turned up to be an excellent tool to understand the critical processes
occurring during growth [1]. It is shown how in-situ SE can monitor the
effects of changes in temperature, total pressure and V/III ratio. The
ellipsometric parameters measured and the effective dielectric function
behaviour are effectively related to growth rate, surface smoothening and
roughening. Improved quality layers obtained through optimised growth
parameters are characterised through SEM and XRD. [1] M. Drago, T.
Schmidtling, U. W. Pohl, S. Peters and W. Richter; phys. stat. sol. (c),
1-4 (2003) / DOI 10.1002/pssc.200303429
Zeit: Mittwoch 15:15–18:15 Raum: H13
HL 29.1 Mi 15:15 H13
Dephasing in Rashba–Spin precession along mutli–channel
quantum wires and nanotubes — •Wolfgang Häusler —
Physikalisches Institut, Albert-Ludwigs-Universität, Hermann-Herder-
Str. 3, 79104 Freiburg
Coherent Rashba spin precession along interacting multi-mode quantum
channels is investigated, revisiting the theory of coupled Tomonaga-
Luttinger liquids, and extending the theory [1]. We identify susceptibilities
as the key-parameters to govern all low energy properties, also in
spin sector. In semiconducting quantum wires spins of different transport
channels are found to dephase as a result of the interaction. This could
explain the experimental difficulty to realize the Datta Das transistor. In
single wall carbon nanotubes, on the other hand, interactions are found
to suppress dephasing between the two flavor modes at small doping.
[1] W. Häusler, Phys. Rev. B 63, 121310 (2001)
HL 29.2 Mi 15:30 H13
Spin Polarization of Two-Dimensional Hole Systems — •R. Winkler
1 , E. Tutuc 2 , S. Melinte 2 , M. Shayegan 2 , D. Wasserman 2 ,
and S. A. Lyon 2 — 1 Institut für Festkörperphysik, Abt. Nanostrukturen,
Universität Hannover — 2 Department of Electrical Engineering,
Princeton University
Hole systems are conceptually different from electron systems due to
the fact that hole states have an effective spin j = 3/2. Subband quantization
in quasi two-dimensional (2D) systems yields a quantization of
angular momentum with z component of angular momentum m = ±3/2
for the heavy hole (HH) states and m = ±1/2 for the light hole (LH)
states. The quantization axis of angular momentum that is enforced by
HH-LH splitting is pointing perpendicular to the plane of the quasi 2D
system. On the other hand, in general the effective Hamiltonians for
B = 0 spin splitting and Zeeman splitting in an in-plane magnetic field
B > 0 tend to orient the spin vector parallel to the plane of the quasi

Halbleiterphysik Mittwoch
2D system. Obviously it is not possible to have a “second quantization
axis of angular momentum” on top of the perpendicular quantization
axis due to HH-LH splitting. We will thus discuss how spin splitting and
spin polarization in quasi 2D HH systems compete with HH-LH splitting.
We will compare the results of calculations and experiments showing the
depopulation of the upper spin subband in quasi 2D HH systems as a
function of an in-plane magnetic field. We will demonstrate theoretically
and experimentally that the shape of the confinement potential greatly
affects the spin subband depopulation field.
HL 29.3 Mi 15:45 H13
Strukturelle und Magnetische Eigenschaften von epitaktischen
NiMnSb-Schichten — •P. Bach 1 , A. Bader 1 , C. Gould 1 , G.
Schmidt 1 , L.W. Molenkamp 1 , R. Urban 2 , G. Woltersdorf 2 und
B. Heinrich 2 — 1 Physikalisches Institut, Experimentelle Physik III,
Universität Würzburg, Am Hubland, 97074 Würzburg — 2 Simon Fraser
University, 8888 University Drive, Burnaby, British Columbia, V5AIS6,
Canada
Halbmetallische Ferromagneten wie die Halb-Heusler-Legierung
NiMnSb, die 100% Spinpolarisation bei Raumtemperatur aufweisen,
sind ideale Kandidaten für Spininjektionsbauelemente.
Es wurden qualitativ hochwertige NiMnSb-Schichten auf
In0.53Ga0.47As/InP mittels MBE gewachsen. Hochauflösende
Röntgendiffraktometrie (HRXRD) zeigt die hervorragende strukturelle
Qualität des NiMnSb und gibt Aufschluss über das Relaxationsverhalten
dieser Schichten.
Die Magnetischen Eigenschaften wurden mit Hilfe von Magnetooptischem
Kerr Effekt (MOKE), Ferromagnetischer Resonanz (FMR) und
SQUID Magnetometrie untersucht. Abhängig von der Schichtdicke wurden
verschiedene uniaxiale und vierfache Anisotropien beobachtet.
HL 29.4 Mi 16:00 H13
Very large Magnetoresistance in ferromagnetic (Ga,Mn)As
wires with Nanoconstrictions — •Christian Rüster, Tatjana
Borzenko, Charles Gould, Georg Schmidt, and Laurens
Molenkamp — Physikalisches Institut, Universität Würzburg, Am
Hubland, D-97074 Würzburg
It was recently pointed out by Flatté and Vignale [APL 78, (2001)
1273] that a very large magnetoresistance should be observable from domain
walls in (Ga,Mn)As. We have now fabricated, using e-beam lithography
and dry etching, (Ga,Mn)As based nanostructures where domain
walls can be pinned by sub-20 nm constrictions. Controlled by shape
anisotropy we can switch the regions on either side of the constriction to
either parallel or antiparallel magnetization. All samples exhibit a positive
magnetoresistance when a domain wall is trapped at the constriction.
We clearly observe the exponential I/V -characteristics predicted by
Flatté and Vignale. For samples in the diffusive transport regime, we find
a magnetoresistance up to 8%, while in samples where, due to depletion
at the constriction, a tunnel barrier is formed, we observe magnetoresistance
up to 2000%. Preliminary data on the manipulation of domain
walls using electrical current is also presented.
HL 29.5 Mi 16:15 H13
Growth and Characterization of GaMnAs on GaAs (001) and
(311)A — •M. Reinwald, U. Wurstbauer, M. Döppe, K. Wagenhuber,
P. Tranitz, W. Wegscheider, and D. Weiss — Institut für
Experimentelle und Angewandte Physik, Universität Regensburg, 93040
Regensburg, Germany
Ga1−xMnxAs-layers with manganese content x of about 5% have been
grown by molecular beam epitaxy on GaAs (001) and (311)A substrates.
SQUID measurements on the as-grown and on annealed samples show
that samples on both growth surfaces are ferromagnetic, but differ both
in the curie temperature and the magnetic anisotropy. Magnetotransport
measurements with in plane magnetic field show a planar hall effect, so
that it is possible to study the angular dependence of the switching fields
by rotating the sample in the field.
Although many GaMnAs samples have been grown, it is still possible
to grow GaAs/AlGaAs-heterostructures with high electron mobilities in
the same growth chamber. PL measurements on these heterostructures
reveal, that no manganese was incorporated into these samples. A second
growth chamber specially designed for highest electron mobilities, allows
the combination of ferromagnetic layers and high electron mobility structures,
to carry out spin injection experiments.
This work is supported by BMBF Verbundprojekt ” Spinelektronik und
Spinoptoelektronik in Halbleitern“
HL 29.6 Mi 16:30 H13
Rashba effect induced localization in quantum networks
— •Dario Bercioux 1 , Michele Governale 2 , Vittorio
Cataudella 1 , and Vincenzo Marigliano Ramaglia 1 —
1 Coherentia-INFM and Dipartimento di Fisica Universitá Federico II
Napoli Italy — 2 NEST-INFM and Scuola Normale Superiore Pisa Italy
Quantum networks are graphs of one-dimensional wires connected at
nodes. It has been shown recently that in a particular two-dimensional
quantum network, the so called T∋, quantum interference due to the
Aharon-Bohm effect and to the topology of the network can induce strong
localization [1,2]. For two-dimensional networks made up of quantum
wires realized in semiconductor heterostructures, spin-orbit coupling due
to the structural inversion asymmetry (Rashba effect[3]) may play an
important role. We study a quantum network extending in only onedimension
(chain of square loops connected at one vertex) made up of
quantum wires with Rashba spin-orbit coupling. This system is a simplified
version of a T∋, and exhibits the same kind of localization when a
magnetic field is applied. We show that the Rashba effect may give rise to
a localization phenomenon similar to the one induced by magnetic flux.
This localization effect can be attributed to the spin precession due to
the Rashba effect. Furthermore, we study the effect of disorder on the
transport properties of this network .
[1] J. Vidal, R. Mosseri and B. Douçot, Phys. Rev. Lett. 81, 5888
(1998). [2] C. Naud et al., Physica E 12, 190 (2001). [3] Yu A. Bychkov
and E.I. Rashba, J. Phys. C: Solid State Phys. 17, 6039 (1984).
HL 29.7 Mi 16:45 H13
Molecular-beam epitaxy of (Zn,Mn)Se on Si(100) for spintronics.
— •T. Slobodskyy, D. Keller, A. Slobodskyy, C. Gould,
P. Grabs, G. Schmidt , and L.W. Molenkamp — Physikalisches Institut,
Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
Experiments on spin injection into silicon are very important for industrial
applications of spintronics devices. Due to the conductance mismatch[1],
diluted magnetic semiconductors like (Zn,Mn)Se are required
for spin injection experiments in the diffusive transport regime.
(Zn,Mn)Se films were grown by molecular beam epitaxy on Si(100)
substrates. A low temperature surface cleaning technique, in combination
with subsequent Arsenic passivation, yields a surface suitable for
II-VI epitaxy. A low temperature growth start involving atomic layer
epitaxy and molecular enhanced epitaxy has been optimized.
The structural properties of the films were determined by high resolution
X-ray diffraction and optical measurements. The surface investigated
using both optical and scanning electron microscopy. SQUID and
magneto-optical measurements show the expected magnetic properties
of the films. Preliminary transport measurements have also been carried
out.
[1] G. Schmidt, L. W. Molenkamp, A. T. Filip, and B. J. van Wees,
Phys. Rev. B. 62, R4790 (2000).
HL 29.8 Mi 17:00 H13
Resonant tunneling diodes with magnetic emitters for spin injection
experiments — •A. Slobodskyy, A. Gröger, C. Gould,
T. Slobodskyy, P. Grabs, G. Schmidt, and L. W. Molenkamp
— Physikalisches Institut der Universität Würzburg EP3, Am Hubland,
D-97074 Würzburg, Germany
All II-VI magnetic resonant tunneling diodes (RTD) were grown by
Molecular Beam Epitaxy (MBE). The emitter of the ZnSe/(Zn,Be)Se
RTD contains 6% manganese, making it suitable for the injection of spinpolarized
electrons at low temperatures and moderate magnetic fields.
Using this type of structure, spin injection into resonant tunneling diodes
(and quantum dots when patterned to sub-micron size) can be studied.
After patterning, the samples were inserted into a He bath cryostat
equipped with a 16 T superconducting magnet. The I/V characteristics
were measured with magnetic field applied either perpendicular to, or
in the plane of the quantum well. The I/V curves of the device show
characteristic resonant tunneling diode behavior. When subjected to an
external magnetic field the resonance shifts in agreement with the Zeeman
splitting that we expect from the DMS layer.

Halbleiterphysik Mittwoch
HL 29.9 Mi 17:15 H13
Rashba spin precession of two-dimensional holes — •Michele
Governale 1,2 , Marco G. Pala 3,2 , Jürgen König 4,2 , and Ulrich
Zülicke 5,2 — 1 Scuola Normale Superiore, Pisa, Italy — 2 Institut für
Theoretische Festkörperphysik, Universität Karlsruhe, Germany —
3 Dipartimento di Ingegneria dell’Informazione, Università degli studi di
Pisa, Italy — 4 Institut für Theoretische Physik III, Ruhr-Universität
Bochum, Germany — 5 Institute of Fundamental Sciences, Massey
University, New Zealand
Spin-orbit coupling due to structural inversion asymmetry plays an
important role in the field of phase-coherent spintronics.
We present a study of spin precession due to Rashba spin splitting[1]
of holes[2] in semiconductor quantum wells. Based on a simple analytical
expression that we derive for the current modulation in a broad
class of experimental situations of ferromagnet/nonmagnetic semiconductor/ferromagnet
hybrid structures, we conclude that the Datta-Das
spin transistor[3] (i) is feasible with holes and (ii) its functionality is not
affected by integration over injection angles.
The current modulation shows a universal oscillation period, irrespective
of the different forms of the Rashba Hamiltonian for electrons and
holes. The analytic formulas approximate extremely well exact numerical
calculations of a more elaborate Kohn–Luttinger model.
[1] E. I. Rashba, Fiz. Tverd. Tela (Leningrad) 2, 1224 (1960)
[Sov. Phys. Solid State 2, 1109 (1960)].
[2] R. Winkler, Phys. Rev. B 62, 4245 (2000).
[3] S. Datta and B. Das, Appl. Phys. Lett. 56, 665, (1990).
HL 29.10 Mi 17:30 H13
ZnMnSe–Spinaligner on inverted GaAs/AlGaAs–2DEGs — •T.
Leeb 1 , M. Döppe 1 , M. Reinwald 1 , H.-P. Tranitz 1 , D. Weiss 1 , W.
Wegscheider 1 , P. Grabs 2 , G. Schmidt 2 , and L. Molenkamp 2 —
1 Institut für Experimentalphysik, Universität Regensburg, D-93040 Regensburg,
Germany — 2 Physikalisches Institut, Universität Würzburg,
D-97074 Würzburg, Germany
The optical detection of spin injection in ZnBeMnSe/GaAs/AlGaAs–
semiconductor heterostructures represents a convincing, however, indirect
result of voltage driven spin transfer across a semiconductor interface.
In contrast, spin injection into a two dimensional electron gas
(2DEG) has not yet been clearly proven in magnetotransport experiments.
We have fabricated n-doped Zn1−x−yBexMnySe–spinaligner contacts
on an inverted GaAs/AlGaAs–2DEG–structure which was applied
to avoid barriers along the current path. The GaAs surface preparation
and the conditions of the ZnMnSe growth initiation are crucial for achieving
a low barrier electronic structure at the ZnMnSe/GaAs–interface. A
strong Zeeman splitting in the conduction band of the Mn–doped II–VI
semiconductor is observed in photoluminescence measurements at small
external magnetic fields. This verifies the spin aligning capability of the
ZnMnSe contact due to a strongly reduced transmission coefficient for
HL 30 Photovoltaik II
minority spin electrons. Magnetotransport measurements have been performed
on a microstructured Hall contact geometry which was developed
according to theoretical considerations concerning spin equilibration between
quantum hall edge channels. This work is supported by DFG via
SFB 348 and by BMBF 13N8282.
HL 29.11 Mi 17:45 H13
InAs-LEDs für Spininjektionsexperimente — •P. Grabs 1 ,
I. Chado 1 , R. Fiederling 1 , A. Slobodskyy 1 , C. Gould 1 , G.
Schmidt 1 , L. W. Molenkamp 1 , C. J. Meining 2 und B. D.
McCombe 2 — 1 Physikalisches Institut, Experimentelle Physik 3,
Universität Würzburg, Am Hubland, 97074 Würzburg — 2 University at
Buffalo, The State University of New York, Buffalo, New York 14260
InAs ist dank seiner hohen Elektronenbeweglichkeit und der starken
Spin-Bahn-Kopplung ein interessantes Material für Spininjektionsexperimente.
Mit Cd1−xMnxSe, einem verdünnten magnetischen Halbleiter
(DMS), der gitterangepasst auf InAs gewachsen werden kann, steht ein
passender Spinaligner zur Verfügung.
Wir berichten über das MBE-Wachstum und die Charakterisierung
von asymmetrischen LEDs mit einer p-Barriere aus AlSb1−xAsx, einem
InAs-Quantentrog und Cd1−xMnxSe als n-Barriere und Spininjektor.
Die zirkulare Polarisation des emittierten Lichts einer solchen LED kann
als Maß für die Effizienz der Spininjektion dienen. Es werden Ergebnisse
von Elektrolumineszenz- und Transportmessungen an den Strukturen
gezeigt.
Diese Arbeit wird unterstützt durch das DARPA SPINS Program.
HL 29.12 Mi 18:00 H13
Spin polarization due to Rashba spin-orbit and boundary
scattering — •Kai Dittmer 1 , Jun-Ichiro Ohe 1,2 , and Bernhard
Kramer 1 — 1 1. Institut für Theoretische Physik, Universität Hamburg
— 2 Physics Department of Sophia University (Tokio)
We calculate spin resolved transport properties of a three terminal [1]
fork-shaped structure with spin-orbit coupling of the Rashba type. For
the calculation of the conductance we apply the transfer matrix method
for the Ando model of the Rashba hamiltonian in the ballistic regime. The
conductance is computed as a function of the Fermi energy for different
values of the spin-orbit coupling constant and for different geometrical
structures and sizes of the model. We observe high polarization and transmission
in the conductance in certain regions of the Fermi energy that
can be explained by spin-orbit and boundary scattering [2]. The dependence
of the spin polarization of the current in different regions of the
sample and the corresponding probability density of the scattering states
is investigated. The possibility of observing the effects in experiment is
discussed.
[1] Kiselev and Kim, Appl. Phys. Lett. 78, 775 (2001); J. Appl. Phys.
94, 4001 (2003).
[2] Chen et al., cond-mat/0308569
Zeit: Mittwoch 15:15–16:45 Raum: H14
HL 30.1 Mi 15:15 H14
Photospannung bei Ladungsträgerinjektion von Farbstoffmolekülen
in transparente Löcher- und Elektronenleiter — •B.
Mahrov 1 , Th. Dittrich 2 , G. Boschloo 1 , L. Dloczik 2 und A.
Hagfeldt 1 — 1 Department of Physical Chemistry, University of Uppsala,
Box 579, 75123 Uppsala, Sweden — 2 Hahn-Meitner-Institut, SE2,
Glienicker Str. 100, D-14109 Berlin, Germany
Transiente und spektrale Photospannung (PV) wurde für Ladungsträgerinjektion
von Farbstoffmolekülen (Ru(dcbpyH2)2(NCS)2) in transparente
Löcher- (CuSCN, CuI, CuAlO2) und Elektronenleiter (TiO2,
SnO2:F) untersucht. Das PV-Signal steigt innerhalb von 10 ns bis 10
µs und die effektiven Lebensdauern variieren zwischen 100 ns und 1 ms
je nach verwendetem Substrat und Mechanismus der Ladungstrennung.
Die Injektionseffizienz ist für Löcher und Elektronen von der gleichen
Größenordnung. Die Injektionsschwelle ist stark vom Substrat abhängig
und liegt zwischen 1.2 und 1.9 eV.
HL 30.2 Mi 15:30 H14
Influence of Film Texture on Grain Boundary Activity in
Cu(In,Ga)Se2 Films — •G. Hanna 1 , N. Ott 2 , H.P. Strunk 2 ,
T. Glatzel 3 , S. Sadewasser 3 , U. Rau 1 , and J.H. Werner 1 —
1 Institut für Physikalische Elektronik, Universität Stuttgart, Pfaffenwaldring
47, 70569 Stuttgart — 2 Institut für Werkstoffwissenschaften
VII, Universität Erlangen Nürnberg — 3 Hahn Meitner Institut, Berlin
A preferred (220/204) crystallographic orientation (texture) of
Cu(In,Ga)Se2 (CIGS) absorber layers is beneficial for the performance
of finished CIGS solar cells as compared to (112) textured CIGS layers
[1,2]. We study the laterally resolved electronic properties of CIGS thin
films with different textures by means of Cathodoluminescence (CL)
mapping, measured in a transmission electron microscope, and Kelvin
Probe Force Microscopy (KPFM). The (220/204) textured samples have
a very homogenous lateral CL-intensity whereas the (112) textured
samples exhibit strong contrasts in the CL-signal. The line scans of the
work function Φ across grain boundaries (GBs) measured with KPFM
exhibit a dip of more than 300 meV across the GB at a (112)-textured
sample while a (220/204) sample shows no comparable dip of Φ at the
GB but rather small spikes. Both measurement methods show that
the superior properties of CIGS solar cells with (220/204)-textured

Halbleiterphysik Mittwoch
absorbers as compared to (112)-textured absorbers are due to a lower
electronic activity of the film’s GBs resulting in a lower recombination
of minority carriers at the GBs.
[1] M. A. Contreras et al., Prog. Photovolt. Res. Appl. 7 311 (1999).
[2] S. Chaisitsak et al., Jpn. J. Appl. Phys. 41 507 (2002).
HL 30.3 Mi 15:45 H14
Quasi-Fermi-Level-Splitting in Cu(In1−xGax)Se2 from 300K-
Photoluminescence — •Gottfried Heinrich Bauer 1 , Rudolf
Brüggemann 1 , and Stephane Vignoli 2 — 1 Institute of Physics,
Carl von Ossietzky University Oldenburg — 2 Lab. PMCN (CNRS)
University Claude Bernard Lyon1, France
The splitting of Quasi-Fermi levels in Cu(In1−xGax)Se2 prepared under
pilot line production conditions with final cell efficiencies of 15 % has
been studied with calibrated luminescence YPL at 300K and with AM1equivalent
photon fluxes. The PL data have been evaluated with respect
to the chemical potential of the electron-hole ensemble/quasi-Fermi level
splitting according to Planck’s generalized law for the emission of nonthermal
equilibrium radiation from matter [1]. We have separated the
Bose-Term of the luminescence by dividing the pl-yield by the absorptivity
A(ω) derived from transmission/reflection. The spectral absorption
of CIGS shows considerable subgap absorption in the entire regime of
composition indicating a substantial density of states located in the gap,
supported by recent photo capacitance experiments [2]. In comparison
to the shift of the band gap with Ga concentration YPL shifts in energy
only very weakly. Accordingly the energetic separation of the quasi-Fermi
levels at 300K, determining maximum Voc, only marginally increases.
[1] P. Würfel, Physics of Solar Cells Physics, Wiley, 2003
[2] J.T.Heath, J.D. Cohen et al., Appl. Phys. Lett. 80, 4540 (2002).
HL 30.4 Mi 16:00 H14
Quantitative Photoluminescence In a-Si:H/c-Si
Heterostructures- Determination Of Quasi-Fermi Level
Splitting — •Saioa Tardon, Rudolf Brüggemann, and
Gottfried H. Bauer — Institute of Physics, Carl von Ossietzky
University Oldenburg
Photoluminescence is broadly applied for probing the electronic structure
of materials and is mostly recorded in arbitrary units, whereas absolute
luminescence additionally yields the information on the quality
of the photoexcited state of matter. We consider the experimentally detected
luminescence as spectrally selective radiation from matter in thermal
non-equilibrium and describe the emitted spectral photon flux by
Planck’s generalised law. Via this approach the luminescence flux from
semiconductors is related to the chemical potential of the electron-holeensemble/splitting
of quasi-Fermi levels and also to the concentrations
of electrons/holes in the initial/final states of the radiative transitions.
We have applied these diagnostics to a-Si:H/c-Si heterostructures with
different emitter a-Si:H-layers and with various methods of c-Si surface
passivation. The magnitude of the quasi-Fermi level splitting will be used
to predict the maximum achievable open circuit voltage in the final de-
vices.
HL 31 Grenz- und Oberflächen
HL 30.5 Mi 16:15 H14
Structural, optical and electronic properties of Cu(In,Ga)S2
epitaxial layers and heterostructures on Si(111) — •Th. Hahn 1 ,
A. Chuvilin 1 , J. Cieslak 1 , A. Dietz 1 , J. Eberhardt 1 , R. Goldhahn
2 , M. Gossla 1 , F. Hudert 2 , U. Kaiser 1 , J. Kräusslich 3 , H.
Metzner 1 , U. Reislöhner 1 , H.-W. Schock 4 , S. Siebentritt 5 , W.
Witthuhn 1 , and F. Wunderlich 2 — 1 Friedrich-Schiller-Universität
Jena, Institut für Festkörperphysik, Max-Wien-Platz 1, 07743 Jena
— 2 Institut für Physik, TU Ilmenau, PF 100565, 98684 Ilmenau —
3 Friedrich-Schiller-Universität Jena, Institut für Optik und Quantenelektronik
Max-Wien-Platz 1, 07743 Jena — 4 Universität Stuttgart, Institut
für Physikalisches Elektronik, Pfaffenwaldring 47, 70569 Stuttgart
— 5 Hahn-Meitner-Institut, Abteilung Heterogene Materialsysteme,
Glienicker Str. 100, 14109 Berlin
Epitaxial thin films of the quasi-ternary chalcopyrite compound
CuIn1−xGaxS2 (0 < x < 1) (CIGS) were grown epitaxially on Si(111)
substrates using Molecular Beam Epitaxy (MBE). The samples were
characterized using X-Ray diffraction (XRD) in various geometries, High
Resolution Transmission Electron Microscopy (HRTEM), Rutherford
Backscattering Spectroscopy (RBS), and Photoreflection (PR).
The layers show a continuous variation of band gap, lattice constants,
growth mechanism, and the appearence of various metastable orderings
with x. First I(U)-characteristics of heteroepitaxial CIGS solar cells are
presented, which were processed in a standard process involving KCNetching,
chemical bath deposition of CdS, and a ZnO:Al window layer.
HL 30.6 Mi 16:30 H14
Einfluss von CrGa- und FeGa-Paaren in Ga-dotiertem
Czochralski Silicium auf die Lebensdauer der Minoritätsladungsträger
— •Svetlana Beljakowa 1 , Dieter Karg 1 ,
Gerhard Pensl 1 und Jan Schmidt 2 — 1 Lehrstuhl für Angewandte
Physik, Universität Erlangen-Nürnberg, Staudtstr. 7/A3, D-91058
Erlangen — 2 Institut für Solarenergieforschung Hameln-Emmerthal
(ISFH), Am Ohrberg 1, D-31860 Emmerthal
Ga-dotiertes Czochralski Silicium wurde mit Cr und Fe durch Implantation
bzw. Diffusion verunreinigt. Die Bildung und Vernichtung
der CrGa- und FeGa1-Paare wurde mit Deep Level Transient Spectroscopy
(DLTS) untersucht. Es wurden die Aktivierungsenergien für
die Bildung und Vernichtung des CrGa- bzw. FeGa1-Komplexes bestimmt.
Bei gleichen Temperaturen erfolgen Bildung und Dissoziation
des FeGa1-Komplexes schneller als die des CrGa-Komplexes. Die
Wirkung der CrGa- und FeGa1-Paare auf die Lebensdauer der Minoritätsladungsträger
wurde mittels Microwave-detected Photoconductance
Decay (MW-PCD) untersucht. Die Lebensdauermessungen haben gezeigt,
dass interstitielles Chrom im Gegensatz zu CrB-Paaren rekombinationsaktiver
als der CrGa-Komplex ist. Interstitielles Eisen dagegen
erweist sich als weniger rekombinationsaktiv als der FeGa1-Defekt.
Zeit: Mittwoch 16:45–18:15 Raum: H14
HL 31.1 Mi 16:45 H14
Theoretical description of the nonlinear optical properties
of semiconductor surfaces — •T. Meier 1 , M. Reichelt 1 , M.
Rohlfing 2 , C. Voelkmann 1 , U. Höfer 1 , and S.W. Koch 1 —
1 Fachbereich Physik und Wissenschaftliches Zentrum für Materialwissenschaften,
Philipps-Universität, Renthof 5, D-35032 Marburg —
2 School of Engineering and Science, International University Bremen,
P.O. Box 750 561, D-28725 Bremen
The description of the nonlinear optical properties of semiconductor
surfaces is discussed via two examples. First, a microscopic approach,
which uses quasiparticle wavefunctions and dispersions obtained from
ab-initio band-structure theory as an input for Bloch equations [1], is
presented. Using this method, excitonic effects in the linear absorption
spectra of the Si(111)-(2×1) surface are obtained and light-intensitydependent
absorption changes of the surface exciton are predicted.
Second, experiments studying the coherent optically induced dynamics
at a Si(001) surface via a five-wave mixing set-up using three ultrashort
laser pulses are analyzed using optical Bloch equations. The measurements
show an unexpected slow rise of the signal intensity as function
of a particular pulse delay which extends well beyond the pulse duration
[2]. This response can be described by considering rapid scattering of the
photoexcited carriers to other states.
[1] M. Reichelt, T. Meier, S.W. Koch, and M. Rohlfing, Phys. Rev. B 68,
045330 (2003).
[2] C. Voelkmann, M. Reichelt, T. Meier, S.W. Koch, and U. Höfer, submitted.
HL 31.2 Mi 17:00 H14
DLTS investigation of UHV bonded Si interfaces — •Alin Mihai
Fecioru, Stephan Senz, Roland Scholz, and Ulrich Goesele
— Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle
Si-Si interfaces were obtained by ultrahigh vacuum (UHV) wafer bonding.
The electrical properties were characterized by deep level transient
spectroscopy (DLTS) measurements correlated with temperature dependent
current-voltage (I-V) measurements.
For a p-p interface a high density of defects was observed, indicated
by a peak in the DLTS spectrum correlated with a thermally active potential
barrier. Typical values of activation energy corresponding to the

Halbleiterphysik Mittwoch
middle of the bandgap are obtained.
For p-n samples the DLTS spectra feature a peak whose corresponding
activation energy is depending on the relative doping of the sample: very
close to the middle of the bandgap for weakly doped and p+n samples
and of about 0.26 eV for n++p samples. Further study by Laplace DLTS
shows a continuos distribution in energy for non-annealed samples, and
fine structure for annealed samples.
Room temperature bonded samples are compared with samples bonded
at 250 ◦ C yielding a decrease of the defect density at the interface. Additionally,
TEM investigations were showing a more regular dislocation
network for the high temperature bonded samples.
HL 31.3 Mi 17:15 H14
Stability and electronic properties of silicates in the system
SiO2 - Pr2O3 - Si(001) — •Dieter Schmeißer 1 and Hans-Joachim
Müssig 2 — 1 BTU Cottbus, Lehrstuhl Angewandte Physik II / Sensorik,
Universitätsplatz 3-4, 03044 Cottbus, Germany — 2 IHP, Im Technologiepark
25, D-15236 Frankfurt (Oder), Germany
Hetero- oxides are the candidates to replace SiO2 as the gate dielectric
material for sub-0.1µm CMOS technology. In particular, the basic interaction
mechanisms at the interface are a key issue and a solid knowledge
of these mechanisms is required to address reliability issues. The challenge
in material science is to understand the chemical bonding of the
hetero oxides and Si on a microscopic scale. This report focuses on the interaction
of the high dielectric constant (DK) material Pr2O3 with SiO2
and the bare Si(001) surface. Photoelectron spectroscopy (PES) using
tunable Synchrotron radiation (undulator U49/2 at BESSY II) is shown
to provide spectroscopic information which is used for characterization
of the electronic structure elements at the interface as well as for a nondestructive
depth profiling. The chemical state of the Si atoms at the interface
is identified and the chemical stability of the various oxide phases
is discussed. We determine the variation of the elemental composition
across the interface and follow the stability of the silicate phase.
HL 31.4 Mi 17:30 H14
Molekül-induzierte Transferdotierung von H-terminiertem Diamant
— •Paul Strobel, Marc Riedel, Jürgen Ristein und Lothar
Ley — Institut für Technische Physik II, Universität Erlangen-
Nürnberg, Erwin-Rommel-Str. 1, 91058 Erlangen
Nach H-Absättigung weist die Oberfläche von undotierten Diamanten
eine Oberflächenleitfähigkeit (OFL) von bis zu 10 −4 S auf. Unter
Atmosphärenbedingungen geht diese OFL auf eine Löcherakkumulation
aufgrund eines elektrochemischen Ladungsübertrages vom Diamantvalenzband
in solvatisierte Ionen auf der Oberfläche zurück.[1]
Wegen der flüchtigen Natur der Adsorbate und der Komplexität der
Austauschreaktion ist diese Art der Transferdotierung jedoch nur schwer
kontrollierbar, und die von ihr hervorgerufene OFL ist bereits geringfügig
HL 32 Halbleiterlaser I
oberhalb von Raumtemperatur instabil.
Es ist uns gelungen, die OFL von Diamant in gleicher Größenordnung
alternativ durch Abscheidung einer wenige Monolagen betragenden
Adsorbatschicht im Ultrahochvakuum zu induzieren. Dabei ist sichergestellt,
daß der Transport im Diamanten und nicht innerhalb der
Adsorbatschicht erfolgt. Diese Methode bestätigt das Modell der Transferdotierung
und eliminiert die durch Variation in den atmosphärischen
Bedingungen hervorgerufenen Instabilitäten.
[1] F. Maier et al., Phys. Rev. Lett. 85(16), 3472 (2000)
HL 31.5 Mi 17:45 H14
reconstruction of theCuGaSe2 (001) surface — •Thalia Deniozou
1 , Norbert Esser 1 , and Susanne Siebentritt 2 — 1 Institut für
Festkörperphysik, TU Berlin, Hardenbergstr. 36, 10623 Berlin — 2 Hahn-
Meitner-Institut Berlin, Glienicker Str. 100, 14109 Berlin
Although chalcopyrites have been used as absorber in thin film solar
cells for nearly 30 years not much is known about their surface reconstruction,
which might be an important information towards interface optimization.
We have studied the chalcopyrite CuGaSe2 (001) surface preparation
by Ar+ ion bombardment and annealing. The samples were grown
by MOCVD on a (001) GaAs substrate on axis with a near-stoichiometric
ratio Cu/Ga. The preparation was optimized so that we finally obtained
a flat, well-ordered surface. The composition was analyzed with AES and
a reconstruction of the surface was observed with LEED for the first time.
HL 31.6 Mi 18:00 H14
Electrical force spectroscopy of silicon surfaces - experiment
and theory — •J. Yukecheva 1 , F. Müller 1 , Y. Suzuki 2 , A.-
D. Müller 1 , H. Angermann 3 , and M. Hietschold 1 — 1 Chemnitz
University of Technology, Institut of Physics, Solid Surface Analysis
Group, 09107 Chemnitz — 2 Chemnitz University of Technology, Institut
of Physics, Semiconductor Physics, 09107 Chemnitz — 3 Hahn-Meitner-
Institut, Department Silicon photovoltaics, Berlin, Kekulestr. 5, 12489
Berlin
In dynamic noncontact-mode in Atomic Force Microscopy, the simultaneous
detection of surface potentials and tip-sample capacitances is
possible during the acquisition of images. On the semiconductor devices,
this method allows the detection of oxide thicknesses, contamination layers
or dopant density variations.
Here, these electrical signals are detected on silicon surfaces in dependence
on the applied bias between tip and sample. This method, the
electrical force spectroscopy, is highly sensitive for surface states. Therefore,
small changes in the silicon preparation already lead to a tremendous
change in the measured characteristics. The curves are discussed in
comparison with numerical simulations of the measurements, where the
known surface states are also included.
Zeit: Mittwoch 17:45–19:15 Raum: H17
HL 32.1 Mi 17:45 H17
Breitstreifen-Halbleiterlaser im externen Resonator: Einfluss
der Rückkopplungsstärke auf das Emissionsverhalten — •Shyam
K. Mandre, Ingo Fischer und Wolfgang Elsässer — Institut für
Angewandte Physik, TU Darmstadt
Der Ausgangsleistung von Breitstreifen-Halbleiterlasern (BSL) von einigen
Watt stehen eine niedrige Strahlqualität und geringe räumliche
Kohärenz gegenüber. Dabei äußert sich die verminderte Strahlqualität
nicht nur durch statische Strahlparameter, vielmehr dominiert eine komplexe,
nichtlineare raum-zeitliche Dynamik das Emissionsverhalten.
Kürzlich konnten wir zeigen, dass das Prinzip der räumlich gefilterten
optischen Rückkopplung zur Stabilisierung der Emissionsdynamik geeignet
ist [1].
Weitergehende Untersuchungen zeigen, dass die Rückkopplungsstärke
(RS) entscheidenden Einfluss auf den Charakter der Emissionsdynamik
hat. Je nach RS beobachten wir zum einen durch den externen Resonator
hervorgerufene Instabilitäten, die sich vollkommen von denen des
solitären BSLs unterscheiden. Zum anderen können bei geeigneter Wahl
der RS die Instabilitäten des solitären Lasers weitgehend unterdrückt
werden. Somit ist die Kenntnis des Einflusses der RS für die Konzeption
eines optimierten externen Resonators von großer Bedeutung, was hier
diskutiert werden soll.
[1] Mandre et al., Opt. Lett. 28 (13), 1135 (2003).
HL 32.2 Mi 18:00 H17
Raumzeitliche Emissionsdynamik von VCSELn: Entwicklung
der Modenstrukturen während des Anschaltvorgangs — •Klaus
Becker, Ingo Fischer und Wolfgang Elsässer — Institut für Angewandte
Physik, Halbleiteroptik, TU Darmstadt
VCSEL sind hochentwickelte Strukturen mit zahlreichen Einsatzgebieten,
allen voran der optischen Datenübertragung. Die Charakterisierung
der Emissionsdynamik beim Anschaltvorgang ist nicht nur aus
technologischer Sicht von Interesse, sondern erlaubt zudem tiefe Einblicke
in die Mechanismen, die die Dynamik hervorrufen und bestimmen.
Wir präsentieren Experimente zur Dynamik des Anschaltvorgangs von
selektiv-oxidierten VCSELn mittlerer Aperturgröße. Die über viele Anschaltereignisse
gemittelte Dynamik wurde mit TRIDA (Temporally Resolved
Imaging by Differential Analysis) mit einer Zeitauflösung von bis
zu 10 ps charakterisiert. In diesem Beitrag konzentrieren wir uns auf
die Ausbildung der Moden. Wir zeigen, dass die Modenstrukturen raumzeitlicher
Dynamik unterliegen. Weiterführende Messungen in Form von
Einzelschuss-Aufnahmen mit Belichtungszeiten von 600 ps belegen, dass
die Modenausbildung zudem von Puls zu Puls einen unterschiedlichen
Verlauf nimmt. Der Einfluss von lokalen Nichtlinearitäten auf die Aus-

Halbleiterphysik Mittwoch
bildung der Modenstrukturen wird diskutiert.
HL 32.3 Mi 18:15 H17
Modeling of optical properties for type-II semiconductor
lasers — •Christoph Schlichenmaier 1 , Jörg Hader 2 , Jerry V.
Molony 2 , Angela Thränhardt 1 , Mackillo Kira 1 , and Stephan
W. Koch 1 — 1 Philipps-Universität & Wissenschaftliches Zentrum für
Materialwissenschaften Marburg — 2 Arizona Center for Mathematical
Sciences and Optical Sciences Center, University of Arizona, Tucson,
AZ 85721
Design of advanced semiconductor laser structures demands the insightful
use of compound materials consisting of many constituents.
Smart alignment of heterostructure layers like type-II structures is an
additional way of band gap engineering. Quantum optical modeling of
electron and photon dynamics[1,2] connected with a realistic band structure
explains optical properties and device performance and helps to map
out the parameter space. We discuss gain, α-factors and luminescence for
various systems.
[1] A. Girndt, S.W. Koch, and W.W. Chow, Appl. Phys. A 66, 1 (1998).
[2] M. Kira, F. Jahnke, W. Hoyer, and S.W. Koch, Prog. Quantum Electron.
23, 189 (1999).
HL 32.4 Mi 18:30 H17
Microscopic Modelling of Semiconductor Laser Dynamics
— •Angela Thränhardt 1 , Christoph Schlichenmaier 1 ,
Stephan W. Koch 1 , Jörg Hader 2 , and Jerome V. Moloney 2
— 1 Fachbereich Physik und Zentrum f*r Materialwissenschaften,
Philippsuniversit*t Marburg, Renthof 5, 35032 Marburg — 2 Arizona
Center of Mathematical Sciences and Optical Sciences Center, University
of Arizona, Tucson, Arizona 85721
To predict the optical properties of semiconductor laser structures, a
microscopic treatment of the carrier dynamics is essential. We calculate
the dynamics of semiconductor laser structures, fully including carriercarrier
as well as carrier-LO phonon scattering effects. The dynamics
depends on parameters such as the excitation energy and intensity. We
discuss the detailed dynamics which can only be modelled microscopically
as well as the validity of simple rules of thumb for scattering rates
and temperature of injected carriers.
HL 32.5 Mi 18:45 H17
Microscopic Calculation of Relaxation Times in Semiconductor
Laser Structures — •Sascha Becker 1 , Angela Thränhardt 1 ,
Stephan W. Koch 1 , Jörg Hader 2 , Jerome V. Moloney 2 , and
Weng W. Chow 3 — 1 Fachbereich Physik und Zentrum für Materialwissenschaften,
Philippsuniversität Marburg, Renthof 5, 35032 Marburg —
2 Arizona Center of Mathematical Sciences and Optical Sciences Center,
University of Arizona, Tucson, Arizona 85721 USA — 3 Sandia National
Laboratories, Albuquerque, NM 87185-0601 USA
HL 33 III-V Halbleiter I
In semiconductor laser structures, scattering times were classically obtained
by fits to experiment. Although this allows one to fit experimental
spectra, this “theory” has no predictive capability. A microscopic
inclusion of scattering, on the other hand, is very complex and timeconsuming.
We attempt to remedy this dilemma by extracting effective
scattering rates from a microscopic calculation and using these in a relaxation
time model, obtaining good agreement with a microscopic model
for the general features. We discuss dependencies of relaxation times on
different parameters, e.g. carrier distribution and band structure.
HL 32.6 Mi 19:00 H17
Intersubbandelektrolumineszenz von Quantendrahtkaskadenstrukturen
bei 8.5 µm — •Stefan Schmult 1 , Thomas Herrle 1 ,
Werner Wegscheider 1 , Max Bichler 2 , Dieter Schuh 2 und
Gerhard Abstreiter 2 — 1 Universität Regensburg, Institut für
Experimentelle und Angewandte Physik, 93040 Regensburg — 2 Walter
Schottky Institut, Technische Universität München, Am Coulombwall,
85748 Garching
Basierend auf theoretischen Berechnungen [1] wurden Quantendrahtkaskadenemitterstrukturen
im GaAs/AlGaAs-Heterosystem hergestellt.
Die Herstellung der Quantendrahtstrukturen erfolgte mittels des epitaktischen
Überwachsens von atomar glatten Spaltflächen (CEO). Elektrolumineszenz
wurde bei einer Wellenlänge von 8.5µm bei 20K beobachtet
[2]. Überhalb eines Schwellstroms von 200mA ist die emittierte Leistung
pumpstromabhängig und beträgt bis zu 17nW. Der Vortrag beschreibt
zusammenfassend Design und Herstellung der Quantendrahtstrukturen
und stellt Ergebnisse ihrer elektrischen und optischen Charakterisierung
dar. [1] I. Keck, S. Schmult, W. Wegscheider, M. Rother, A.P. Mayer,
Phys. Rev. B 67, 125312 (2003). [2] S. Schmult, I. Keck, T. Herrle, W.
Wegscheider, M. Bichler, D. Schuh, G. Abstreiter, Appl. Phys. Lett. 83,
1909 (2003).
Zeit: Mittwoch 18:15–19:30 Raum: H14
HL 33.1 Mi 18:15 H14
GaMnAs grown by MOVPE under RAS control — •Alexander
Philippou, Stefan Weeke, Markus Pristovsek, and Wolfgang
Richter — Institut für Festkörperphysik, SFb 296, Technische Universität
Berlin
Under the aspect of spin electronics dilute magnetic III-V semiconductors
are of great interest. In this contribution we report on Mn doped
III-V semiconductors which were grown by metal organic vapor phase
epitaxy (MOVPE). In contrast to Molecular Beam Epitaxy the growth
temperatures are much higher (≥ 500 ◦ C). Thus the need for in-situ control
is even more severe for MOVPE. We used reflectance anisotropy
spectroscopy (RAS) to monitor the doping level and roughness during
growth. We determine the critical layer thickness of GaMnAs and correlate
the results with in-situ ellipsometry and ex-situ x-ray diffraction
studies.
HL 33.2 Mi 18:30 H14
Electronic properties of Carbon and Zinc acceptors in GaAs
studied with Low Temperature Scanning Tunneling Microscopy
— •S. Loth 1 , M. Wenderoth 1 , T.C.G. Reusch 1 , L. Winking 1 ,
R.G. Ulbrich 1 , S. Malzer 2 , and G. Döhler 2 — 1 IV. Physikalisches
Institut, Universität Göttingen, D-37077 Göttingen — 2 Institut für Technische
Physik, Universität Erlangen-Nürnberg, D-91058 Erlangen
The electronic properties of single carbon and zinc acceptors located
near {110} surfaces of GaAs were studied with a low temperature UHV
Scanning Tunneling Microscope at 8K. Zn is a substitutional acceptor
on a Ga site with a covalent radius about 30% larger than the replaced
Ga atom. C on the other side is a substitutional acceptor on an As site
and contracts the bonds to the adjacent Ga atoms by about 15%. In
voltage-dependant constant current topographies (-3V to +4.5V) both
dopants show comparable patterns, with a variety of different contrasts.
The orientation of the features is clearly linked to the exact orientation
of the surface under investigation, i.e. (110) vs. (1¯10). Especially at low
voltages the C as well as the Zn acceptor appear as nearly equilateral
triangular protrusions extended over several nanometers. At higher voltages
the symmetry of the triangle evolves into a prolate shape oriented
along (100).

Halbleiterphysik Mittwoch
This work was supported by the DFG, SFB 602 TP A7
HL 33.3 Mi 18:45 H14
Annealing of InN layers in a MOVPE reactor investigated by insitu
Spectroscopic Ellipsometry. — •Christoph Werner, Massimo
Drago, Torsten Schmidtling, Udo W. Pohl, and Wolfgang
Richter — TU-Berlin, Institut für Festkörperphysik, Hardenbergstr.
36, 10623 Berlin
Spectroscopic Ellipsometry (SE) is a powerful optical in-situ analysis
tool for growth monitoring of non-cubic materials, as already demonstrated
for GaN epitaxy [1].
Therefore we use SE in order to study annealing of epitaxial InN layers
grown under different gaseous ambients (NH3, N2 and H2) in the growth
temperature regime.
It was found that a hydrogen ambient during annealing leads to a
surface roughening. In contrast, pure nitrogen induces surface smoothening
for temperatures above 540 ◦ C, while roughening becomes dominant
at temperatures exceeding 580 ◦ C. A small addition of ammonia to the
N2 ambient, however, induces surface roughening already at 550 ◦ C. This
shows that, in contrast to GaN, ammonia is not suitable to stabilize InN
at growth temperature. This might be due to the presence of hydrogen
as a consequence of ammonia decomposition.
[1] S. Peters, T. Schmidtling, T. Trepk, U. W. Pohl, J.-T. Zettler, W.
Richter, J. Appl. Phys. 88, 4085 (2000)
HL 33.4 Mi 19:00 H14
MOVPE in-situ monitoring and analysis of substrate deoxidation
of GaSb(100) — •Kristof Möller 1 , Lars Töben 1 , Zadig
Kollonitsch 1 , Christoph Giesen 2 , Michael Heuken 2 , Frank
Willig 1 , and Thomas Hannappel 1 — 1 Hahn-Meitner-Institut, SE-
4, Glienicker Str. 100, D-14109 Berlin, Germany — 2 AIXTRON AG,
Kackertstr. 15-17, D-52072 Aachen, Germany
The crucial deoxidation of GaSb prior to epitaxy was investigated insitu
with reflectance anisotropy spectroscopy (RAS). Substrates were annealed
in an AIX-200 MOVPE reactor in the presence of triethylanti-
HL 34 Hauptvortrag Kouwenhoven
mony in H2 ambient. Deoxidation was carried out between 475 − 575 ◦ C.
RAS signals show the progress in deoxidation for different chemical pretreatments,
annealing temperatures, and annealing times. ”Epi-ready”
substrates annealed without any chemical pre-treatment showed the formation
of anisotropic, nanometer-scaled 3D-structures during deoxidation.
The anisotropic roughness was observed in-situ as an unusual increase
of the RAS signal. This enhanced RAS signal vanished after deoxidation
was completed. RAS Signals showed the absence of roughness
for chemically pre-treated substrates. The surface of the substrates was
investigated with UPS and XPS spectroscopy. The RAS-correlated information
on electronic structure and chemical surface composition is essential
for understanding and improving the deoxidation process of GaSb.
HL 33.5 Mi 19:15 H14
Exzitonenlokalisation in InGaN-Schichten — •T. Finger, J.
Christen, Th. Hempel, A. Dadgar und A. Krost — Institut für
Experimentelle Physik, Otto-von-Guericke Universität Magdeburg
Legierungsunordnung und Entmischung verursachen im ternären In-
GaN mikroskopische Kompositionsfluktuationen, die zu lokalen Potentialfluktuationen
führen. Diese Unordnungseffekte erzeugen ein charakteristisches
Temperaturverhalten der Rekombinationsenergie das von dem
üblichen Eg(T)-Verlauf (z.B. Varshni) signifikant abweicht. Mit sinkender
Temperatur T tritt zunächst eine Rotverschiebung um −σ 2 /kBT auf.
In Folge des Ausfrierens der Ladungsträger bei weiter sinkendem T erfolgt
dann eine Blauverschiebung. Es ergibt sich somit eine charakteristische
s-förmige T-Abhängigkeit der bandkantennahen Lumineszenz. Bei
Erhöhung der Anregungsleistung wird ebenfalls eine Blauverschiebung
beobachtet, die mit einem Auffüllen der statistischen Energieverteilung
erklärt werden kann. Wir haben an 100 nm dicken MOCVD-gewachsenen
InGaN-Epitaxieschichten unterschiedlichen In-Gehaltes (21% - 47%)
Temperatur- und Anregungsdichte-abhängige Lumineszenzmessungen
durchgeführt. Es traten starke Intensitätsmodulationen der Spektren
durch Fabry-Perot Interferenzen in dem Luft+InGaN/GaN (1,2 µm)+Si-
Substrat Schichtpaket auf.
Zeit: Donnerstag 09:30–10:15 Raum: H15
Hauptvortrag HL 34.1 Do 09:30 H15
Spin Qubits with Quantum Dots — •L. P. Kouwenhoven —
Technische Universiteit Delft
Qubits are 2-level systems suitable for control over the level occupation
including superpositions. In solid state, two qubit examples are the effective
2-level system in appropriately designed superconducting devices
and single-electron spin states in semiconductor quantum dots. Qubit
control is demonstrated with NMR-type pulse techniques such as Rabi
flops and spin-echo. The readout of a qubit state is an important part of
the qubit circuit since any backaction can shorten the coherence lifetime.
We discuss a recent realization of a single-shot readout of the spin of a
single electron.
HL 35 Symposium Ferromagnetische Halbleiter
Zeit: Donnerstag 10:15–13:45 Raum: H15
HL 35.1 Do 10:15 H15
Magnetic Anisotropy in Ferromagnetic III-Mn-V Semiconductors:
Issues and Observations — •Jacek K. Furdyna — University
of Notre Dame, Notre Dame, Indiana, USA
Magnetic anisotropy in III-V-based ferromagnetic (FM) semiconductor
alloys (e.g., Ga1−xMnxAs) is interesting from two points of view. First,
it can be “engineered” by imposing appropriate strain conditions on the
FM film; and second, magnetic anisotropy is expected to play an essential
role in designing spin-injection devices based on these materials.
In this paper we present the information on MA in FM semiconductors
obtained through a series of complementary methods: ferromagnetic
resonance (FMR), planar Hall effect, direct imaging of FM domains by
magneto-optical methods, and SQUID magnetization data. Special attention
will be given to the recently-observed re-orientation of the easy
axis in several of the III1−xMnxV alloys as a function of temperature
and/or illumination, and to the somewhat surprising uniaxial anisotropy
in the sample plane which some of these materials exhibit, presumably
as a consequence of surface reconstruction during the growth.
HL 35.2 Do 10:45 H15
Carrier induced ferromagnetism in p type doped II-VI heterostructures
— •David Ferrand — CEA-CNRS-UJF Joint Group,
Laboratoire de Spectrometrie Physique, BP 87 38402 Saint Martin
d’Heres, France
Carrier-induced ferromagnetism in diluted magnetic semiconductors
(D.M.S) has been reported in IV-VI bulk alloys, III-V epilayers and in
II-VI heterostructures. In comparison to III-V, the Curie temperatures
are dramatically lower in II-VI DMS, but II-VI compounds are ideal materials
for fundamental studies, in which localized spins and holes can be
introduced and controlled independently and where dimensionality effects
can be examined in modulation doped heterostructures. We will present
here an overview of our experimental studies, we have done on degenerate
Zn(1−x)MnxTe thick layers and modulation-doped Cd(1−x)MnxTe quantum
wells. Zn(1−x)MnxTe with Mn content up to several percents can be
easily doped p-type using a nitrogen cell up to 10 20 cm −3 , two orders of
magnitude larger than the density for metal-insulator transition. While
the usual antiferromagnetic behavior is observed on the susceptibility of
undoped layers, we observed (SQUID and anomalous Hall effect) positive
Curie-Weiss temperatures between 1.5 and 3K and characteristic ferromagnetic
hysteresis cycles, for layers with hole densities above a few 10 19
cm −3 . In the case of Cd(1−x)MnxTe quantum wells, the magnetic signal

Halbleiterphysik Donnerstag
appears to be too small to be measured directly and is determined indirectly
from magneto-optical spectroscopy. Curie temperatures up to 3K
have been observed for single quantum wells with Mn content up to 4%
and with hole densities between few 10 10 and 6·10 11 cm −2 . In both cases,
the experimental Curie temperatures are in good agreement with mean
field predictions. Finally, we will conclude this presentation by showing
our recent work on MBE growth and characterization of high gap diluted
magnetic semiconductor epilayers GaMnN and ZnCoO.
HL 35.3 Do 11:15 H15
ZnO-MOVPE: Present State and Prospective Applications in
Optoelectronics and Magnetoelectronics — •Andreas Waag —
Institut für Halbleitertechnik, TU Braunschweig
Due to its band gap of 3.3 eV and exciton binding energy of 60 meV,
ZnO is a very interesting candidate for UV optoelectronics. Beyond that,
the incorporation of magnetic impurities allows to fabricate semimagnetic
semiconductors, which are transparent and ferromagnetic at room
temperature. The combination with n-type doping makes magnetic ZnO
very interesting for spinelectronics. Here, we give an overview on our activities
concerning the MOVPE growth of ZnO-related thins films and
heterostructures. After a thourough optimisation of the growth process,
ZnMgO-ZnO quantum well structures could be fabricated, indicating a
good optical quality. The incorporation of Cd, however, suffers from phase
separation, and two distinctly different Cd concentrations have been detected
in ZnCdO films. In addition, the self-organised growth of ZnO
nanorods could be demonstrated by a suitable choice of MOVPE growth
parameters. Nanorods of 30 nm diameter and a height of up to 5 µm
could be achieved. The optical quality of these nanorods is very good,
indicating that open lying surfaces play a minor role in terms of nonradiative
recombination. The incorporation of magnetic ions has been
achieved, both into normal layers as well as nanrods, and ferromagnetic
behaviour has been detected.
HL 35.4 Do 11:45 H15
Disorder effects in diluted magnetic semiconductors —
•Carsten Timm — Institut für Theoretische Physik, Freie Universität
Berlin, Arnimallee 14, 14195 Berlin
Diluted magnetic semiconductors (DMS) are promising materials for
technological applications as well as interesting from the basic-physics
point of view. In the last years it became clear that disorder plays a
crucial role in DMS due to the presence of many charged defects and
the random positions of impurity spins. In this talk the effect of disorder
on transport properties and magnetism in DMS is discussed. It is
argued that the impurity positions are partially correlated. These correlations
are crucial for the understanding of magnetic properties and
the observed metal-insulator transition. In the final part of the talk, a
calculation of the RKKY-like interaction between impurity spins is presented,
starting from a realistic band structure. This interaction is found
to be highly anisotropic, which, together with the disorder, leads to magnetic
frustration and might explain the incomplete magnetization at low
temperatures.
HL 35.5 Do 12:15 H15
Hydrogen-control of ferromagnetism in Ga1−xMnxAs thin
films — •Sebastian T. B. Goennenwein 1,2 , Hans Huebl 1 ,
Thomas A. Wassner 1 , Christoph Bihler 1 , Martin Stutzmann 1 ,
Achim Koeder 3 , Wladimir Schoch 3 , Andreas Waag 3 , and
Martin S. Brandt 1 — 1 Walter Schottky Institut, Technische Universität
München, Am Coulombwall 3, D-85748 Garching, Germany —
2 Department of Nanoscience, Delft University of Technology, Lorentzweg
1, 2628 CJ Delft, The Netherlands — 3 Abteilung Halbleiterphysik,
Universität Ulm, D-89069 Ulm, Germany
Dilute magnetic semiconductors (DMS) are investigated vigorously at
present, as these materials combine magnetic ordering with the versatile
properties of semiconductors. In the prototype DMS Ga1−xMnxAs, which
we discuss here, the ferromagnetic exchange interaction between the lo-
calized Mn magnetic moments is mediated by itinerant holes, so that the
density of both Mn moments and of holes is crucial for the magnetism.
We show that upon exposure to a remote DC deuterium plasma, the hole
density p in Ga1−xMnxAs thin films with x = 0.037 and x = 0.051 can
be reduced by several orders of magnitude. At the same time, the density
of Mn magnetic moments is not significantly affected by the plasma
treatment. Nevertheless, the ferromagnetism clearly present in the asgrown
samples has vanished after the deuteration. We analyze the effect
of the deuteration in detail, comparing the results of secondary ion mass
spectroscopy, DC magnetization, and Fourier-transform infra-red optical
experiments. We also address possible applications of this post-growth
”hydrogen-control” of the magnetic properties of Ga1−xMnxAs.
HL 35.6 Do 12:45 H15
Modified magnetic properties of ordered arrays of (II,Mn)VI
quantum wires due to reduced lateral dimensions — •P.J.
Klar 1 , L. Chen 1 , W. Heimbrodt 1 , F.J. Brieler 2 , M. Fröba 2 , T.
Kurz 3 , H.-A. Krug von Nidda 3 , and A. Loidl 3 — 1 Dept. Physics
and Material Sciences Center, Philipps-University of Marburg, Germany
— 2 Institute of Inorganic and Analytical Chemistry, Justus-Liebig University
of Gießen, Germany — 3 Dept. Physics, University of Augsburg,
Germany
We present a novel way of synthesising highly ordered arrays of
(II,Mn)VI quantum wires with lateral dimensions of 3nm to 9nm and
Mn-contents x between 0% and 100% by incorporating the semiconductor
into mesoporous SiO2 matrices. Quantum confinement increases the
band gap by about 200meV for Cd1−xMnxS and by about 150meV for
Zn1−xMnxS in the narrowest wires. A stronger p−d-hybridisation related
band-gap bowing as a function of x occurs in the (Cd,Mn)S wires compared
to bulk. The magnetic properties also change significantly. Compared
to the bulk (II,Mn)VI compounds, a reduced antiferromagnetic
coupling between the magnetic moments of the Mn 2+ ions is found. For
x ≥ 0.8, a full suppression of the paramagnetic to antiferromagnetic
phase transition of the Mn-system is observed for the 3nm wires. For
6nm and 9nm wires a phase transition occurs, but the Néel temperatures
are smaller than in bulk. The observed behavior yields information
about the length scale of the antiferromagnetic ordering. Similar effects
are also anticipated for ferromagnetic wires.
HL 35.7 Do 13:15 H15
GaN-based semiconductor compounds for spin electronics —
•Bernd Beschoten — 2. Physikalisches Institut, RWTH Aachen, Templergraben
55, 52056 Aachen
According to recent predictions of room temperature ferromagnetism
in Mn-doped GaN, the material might be promising for spintronic applications.
In the first part, the talk will focus on the material science aspects
and magnetic properties of Mn-doped GaN layers grown by molecular
beam epitaxy. Samples with low Mn content are homogeneous alloys
showing spin-glass like behavior at low temperatures, but they are NOT
ferromagnetic. Samples with higher Mn content additionally exhibit ferromagnetism
with Curie temperatures of about 750 K, which originates
from nm-scale Mn-rich clusters formed during growth.
The second part of the talk is devoted to the study of spin coherence
and spin dephasing in n-type GaN, which is another important aspect
for GaN-based spintronics. Despite densities of charged threading dislocations
of 5 ×10 8 cm −2 , this coherence studied by time-resolved Faraday
rotation yielding lifetimes of ∼ 20 ns at T = 5 K, and persists to room
temperature. The doping dependence of spin dephasing is compared to
n-GaAs, suggesting a common origin for spin relaxation in these systems.
Work done in collaboration with D.D. Awschalom, O. Brandt, L.
Däweritz, S. Dhar, A. Dohmen, K.J. Friedland, G. Güntherodt, E. Hu, E.
Johnston-Halperin, J. Keller, K.H. Ploog, and A. Trampert. Supported
by the German Federal Ministry of Education and Research (BMBF).
[1] S. Dhar et al., Appl. Phys. Lett. 82, 2077 (2003).
[2] B. Beschoten et al., Phys. Rev. B 63, 121202 (2001).

Halbleiterphysik Donnerstag
HL 36 Quantenpunkte und -drähte: Optische Eigenschaften I
Zeit: Donnerstag 10:15–13:30 Raum: H17
HL 36.1 Do 10:15 H17
Structural Relaxation and the Optical Properties of Ge and
Si Nanocrystals – ab initio Calculations — •Weißker Hans-
Christian 1 , Giancarlo Cappellini 2 , Jürgen Furthmüller 1 ,
and Friedhelm Bechstedt 1 — 1 IFTO, Friedrich-Schiller-Universität
Jena, Max-Wien-Platz 1, 07743 Jena — 2 Universitá di Cagliari, Cittadella
Universitaria, Strada Prov.le Monserrato-Sestu, Km 0.700, Italy
Though much effort has been put into the description of the properties
of nanocrystals, ab initio calculations of such systems are still a demanding
task. The ionic degrees of freedom, i.e., the structural relaxation, have
only recently become amenable to ab initio methods for larger clusters
because of the large computational requirements. The use of ultrasoft
pseudopotentials and of the projector-augmented-wave method helps to
alleviate this problem. Size-dependent electron-hole pair excitation energies
calculated by means of a DSCF method are presented.
The ionic relaxation is a twofold problem. First, there is the technical
problem of finding reasonable model structures for the crystallites. This
involves the question of the influence of the ground-state structural relaxation
on the desired quantities. For the optical properties, we demonstrate
that a proper account of the relaxation effects is indispensable
for the quantitative, and in some cases even the qualitative, description.
The second problem is the structural relaxation after electronic excitation,
which results in a contribution of a single nanocrystal to the Stokes
shift measurable for an experimental sample. Model calculations of the
Stokes shift are presented and discussed.
HL 36.2 Do 10:30 H17
Dephasing in Quantum Dots: Quadratic Coupling to Acoustic
Phonons — •Egor Muljarov 1,2 , Frank Grosse 1 , and Roland
Zimmermann 1 — 1 Institut für Physik der Humboldt-Universität zu
Berlin, Newtonstr. 15, 12489 Berlin, Germany — 2 General Physics Institute
RAS, Vavilova 38, Moscow 119991, Russia
A microscopic theory of optical transitions in quantum dots with
carrier-phonon interaction is developed. Virtual transitions into higher
confined states with acoustic phonon assistance add a quadratic phonon
coupling to the standard linear one, thus extending the independent Boson
model. Summing infinitely many diagrams in the cumulant, an exact
solution for the interband polarization is found. Its full time dependence
and the absorption lineshape of the quantum dot are calculated.
A temperature-dependent broadening of the zero-phonon line is obtained
and compared with available experimental data.
HL 36.3 Do 10:45 H17
Investigation of the coupling-dependence on the dephasing in
coupled quantum dots — •Matthias Schwab 1 , P. Borri 1 , W.
Langbein 1 , U. Woggon 1 , M. Bayer 1 , S. Fafard 2 , Z. Wasilewski 2 ,
and P. Hawrylak 2 — 1 Experimentelle Physik II, Otto-Hahn Strasse 4,
44221 Dortmund, Germany — 2 Institute for Microstructural Science, National
Research Concil, Ottawa, K1A 0R6, Canada
Due to their atom-like density of states semiconductor quantum dots
(QD) are often referred to as artificial atoms. QDs receive a lot of attention
as they are possible candidates in the field of quantum information
and cryptography. By shrinking the distance between two QDs, one can
bring the single-particle wave function to an overlap creating so called
semiconductor quantum dot molecules.
A prerequisite for any application of their quantum mechanical properties
is a detailed knowledge of their electronic levels and their coupling
to the environment.
In this talk we report on measurements of the dephasing times of the
exciton in InAs/GaAs quantum dot molecules having different interdot
barrier thicknesses. A heterodyne four-wave-mixing (FWM) technique is
used to measure the dephasing times in a temperature range from 5 K to
60 K. The results are compared to a quantum dot single layer. Systematic
dependencies of the homogeneous linewidth on barrier thickness and on
the temperature are reported.
HL 36.4 Do 11:00 H17
Structure Dependent Few-particle Effects in InAs Quantum
Dots — •Andrei Schliwa, Sven Rodt, Florian Guffarth,
Robert Heitz, Robert Seguin, and Dieter Bimberg — Institut
für Festkörperphysik, Technische Universität Berlin
Interaction between strongly localized charge carriers in zerodimensional
systems like quantum dots (QDs) depend sensitively on
their geometrical properties. Few-particle properties, like the biexciton
binding energies, may vary not only in size but also in sign. Based on
the configuration interaction method those properties are calculated
for realistic InAs QDs as function of their structural properties. The
wavefunctions are obtained from eight-band k·p calculations including
strain and piezoelectric effects.
The problem of correlating calculated and measured spectra can be circumvented
exploiting the monolayer splitting in photoluminescence (PL)
-spectra in appropriately grown samples. Detailed analysis of those spectra
shows that (i) the QDs are very flat, (ii) the QDs have well-defined
interfaces and (iii) each peak represents a subensemble of QDs sharing
the same height. With decreasing transition energy the height of the related
QD-ensemble increases subsequently by one monolayer. Single dot
spectra revealing details of few-particle effects are obtained by cathodoluminescence
measurements with shadow masks. Transition from positive
to negative biexciton binding energy with increasing exciton energy due
to decreasing dot size is observed and understood in the framework of
the above theory.
HL 36.5 Do 11:15 H17
Coulomb effects in the optical spectra of semiconductor quantum
dots — •Norman Baer, Paul Gartner, and Frank Jahnke
— Institute for Theoretical Physics, University Bremen
Emission spectra of individual self-assembeld quantum dots show a rich
structure due to Coulomb correlated multi-exciton states. We present a
theoretical investigation of this system based on a full diagonalisation
scheme for the localized states. In addition to a discussion of the renormalized
electronic energies this procedure allows a direct calculation of
the optical spectra in terms of the Coulomb correlated states.
The resulting multi-exciton spectra are discussed and a simplified
Hamiltonian is introduced in order to explain the main features of the
emission spectra. This simplified Hamiltonian, which is based on the relative
importance of the interaction matrix elements, provides an intuitive
picture for the structure of the multi-exciton emission spectra.
In addition to the spectra resulting from neutral excitons the emission
spectra of excitons in the presence of spectator charges will be discussed.
HL 36.6 Do 11:30 H17
Many-body theory of carrier capture and relaxation in semiconductor
quantum-dot lasers — •Torben Roland Nielsen, Paul
Gartner, and Frank Jahnke — Institute for Theoretical Physics,
University of Bremen, 28334 Bremen, Germany
In quantum-dot laser devices containing a quasi two-dimensional wetting
layer, a pump process initially populates the letting-layer states. The
scattering of carriers from these spatially-extended quasi two-dimensional
states into the quantum-dot states as well as the relaxation of carriers
between the quantum-dot levels are studied theoretically.
Based on the wave functions for the coupled quantum-dot/wettinglayer
system interaction matrix elements are calculated for carrier-carrier
Coulomb interaction and carrier-phonon interaction. Scattering rates
for various capture and relaxation processes are evaluated under quasiequilibrium
conditions.
For elevated carrier densities in the wetting layer, Coulomb scattering
provides processes with capture (relaxation) times typically faster
than 10ps (1ps). When energy conservation allows for interaction with
LO-phonons, comparable rates are obtained.
HL 36.7 Do 11:45 H17
Optical properties of semiconductor microcavity pillars — •J.
Wiersig 1 , N. Baer 1 , P. Gartner 1 , F. Jahnke 1 , M. Benyoucef
2 , S.M. Ulrich 2 und P. Michler 2 — 1 Universität Bremen —
2 Universität Stuttgart
A recent experiment demonstrated the generation of triggered photon
pairs due to cascaded biexciton-exciton emission from a single In-
GaAs/GaAs quantum dot in a cylindrical micropillar [1]. Such experiments
are based on the altered spontaneous emission of carriers in the
microcavity as well as on the selection of optical transitions by the resonator.
Within a detailed theory-experiment comparison we study op-

Halbleiterphysik Donnerstag
tical modes and the resulting emission properties in micropillars with
decreasing diameter. Calculations of the electromagnetic mode structure
are based on two alternative methods: direct solutions of the Lippmann-
Schwinger equation for the electromagnetic vector field, and a generalized
vectorial transfer matrix approach.
[1] M. Benyoucef, S.M. Ulrich, P. Michler, J. Wiersig, F. Jahnke, A.
Forchel, unpublished.
HL 36.8 Do 12:00 H17
Microphotoluminescence studies on CdSe/Zn(S,Se) quantum
dots and InGaN/GaN structures — •H. Lohmeyer, K. Sebald,
J. Gutowski, S. Einfeldt, and D. Hommel — Institut für
Festkörperphysik, Universität Bremen, Otto-Hahn-Allee, 28359 Bremen
The use of quantum dots (QD) as active medium promises laser structures
with superior properties in comparison to conventional quantumwell
lasers, especially with respect to the threshold current. A systematic
optical characterization with high spatial resolution is indispensable for
the realization of such new devices and is possible by means of microphotoluminescence
(µ-PL) measurements. We present µ-PL results for two
material systems emitting in the green and blue spectral range.
To get access to few or even single QDs, mesa structures with diameters
down to 120nm were etched out of the investigated self-organized
grown CdSe/Zn(S,Se)-QD sample. The µ-PL spectra of a 120 nm mesastructure
shows clearly separated excitonic emission lines. Additionally,
these excitonic states were characterized by µ-PL excitation spectroscopy
and time resolved measurements. As a result the spectrally broad optical
phonon replica and the first excited state of the exciton have been
identified. The recombination time of the excitonic state is determined
to 230ps, which is independent of the excitation density.
Furthermore first µ-PL results of InGaN/GaN samples with respect to
the identification of characteristic QD luminescence are discussed.
HL 36.9 Do 12:15 H17
Effects of oxidation on silicon nanocrystallites — •Luis Ramos,
Jürgen Furthmüller, and Friedhelm Bechstedt — FSU Jena -
IFTO Max-Wien-Platz, 1 D-07743 Jena Germany
The luminescence observed in porous silicon (p-Si) is known to be related
to quantum confinement of carriers in the nanostructures formed at
the surface of this material. Experimental observation confirms also that
optical properties depend on the level of oxidation in p-Si. Spherical-like
silicon nanocrystallites (NCs) have attracted special attention and several
investigations have focused in the influence of surface passivation of
Si NCs with H, with group OH, and with few Si=O bond terminations.
However, fully oxidized shells and defects in Si NCs have not been considered
so far.We apply the VASP code with PAW pseudopotentials and
DFT-LDA to study the influence of oxidation on the structural and electronic
properties of Si NCs. The absorption spectra of NCs obtained by
means of effective medium theory are compared to experimental data. To
discuss HOMO-LUMO gaps and excitonic effects we consider in addition
pair excitation energies and gaps calculated in a GW approximation.
HL 36.10 Do 12:30 H17
Dynamik von Energie- und Phasenrelaxationsprozessen in
In(Ga)As/GaAs Quantenpunkten — •Patrick Zimmer 1 , Matthias
Dworzak 1 , Harald Born 2 , Axel Hoffmann 1 , Florian
Guffarth 1 und Dieter Bimberg 1 — 1 Institut für Festkörperphysik,
Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin —
2 Georgia State University, Department of Physics and Astronomy,
Atlanta, Georgia GA-30303
Für das Verständnis von Energie- und Phasenrelaxationsprozessen
in Quantenpunktstrukturen sind Messungen mit hoher Zeitauflösung
von zentraler Bedeutung. Hierzu bedient man sich der Zweistrahl-
Messtechnik, deren zeitliche Auflösung ausschliesslich durch die Laserpulsbreite
gegeben ist und im Bereich von wenigen Pikosekunden liegt.
Derartige Messungen an In(Ga)As-Quantenpunkten ergaben bei Anregung
oberhalb der Bandkante von GaAs eine Sättigung des Probe-Signals
in Anwesenheit des Pumpstrahls. Die beobachtete Sättigung ist abhängig
von der zeitlichen Verzögerung von Pump- und Probestrahl. Es wurde
eine Zeitkonstante von etwa 1 ns gemessen, was der strahlenden Lebensdauer
der Exzitonen in diesem System entspricht. Bei resonanter Anregung
des Systems tritt diese Zeitkonstante ebenfalls auf. Zusätzlich wird
eine deutlich kürzere Zeitkonstante im Bereich von etwa 30 ps detektiert.
Ähnliche Zeitkonstanten werden auch in anderen Experimenten beobachtet
und derzeit als Phasenrelaxationszeit der Exzitonen diskutiert.
HL 36.11 Do 12:45 H17
Resonant Raman Scattering in In(Ga)As/GaAs Quantum Dots
— •Alexander Paarmann, Florian Guffarth, Till Warming,
Axel Hoffmann, and Dieter Bimberg — TU Berlin, Institut für
Festkörperphysik, Hardenbergstr. 36, 10629 Berlin, Germany
The local vibrational properties of self-organized quantum dots (QDs)
are still a pending question. We have performed resonantly excited
Raman measurements on self-organized MOCVD and MBE grown
In(Ga)As/GaAs QD, which clearly show characteristics of local optical
phonons.
Compared to bulk LO- and TO-phonon modes an enhanced excitonphonon
coupling and a low-energy-shift when reaching resonance with
the QDs ground-state exciton energy is observed. The local modes depend
on QD shape and local strain-field. Flat and pyramidal QDs were
examined as well as multiple and single QD layers.
This work was funded by the Nanomat project of the European Commission
Growth Programme, contract number G5RD-CT-2001- 00545,
Intas project 2001-774, and SFB 296 of DFG.
HL 36.12 Do 13:00 H17
Time resolved spectroscopy of annealed InAs/GaAs selfassembled
quantum dots — •Cedric Bardot 1 , M. Schwab 1 , M.
Bayer 1 , D. Reuter 2 , and A. D. Wieck 2 — 1 Experimentelle Physik
II, Otto-Hahn Strasse 4, 44221 Dortmund, Germany — 2 Angewandte
Festkoerperphysik, Ruhr-Universitaet Bochum, Universitaetsstr. 150,
44780 Bochum, Germany
Understanding the optical properties of semiconductor quantum dots
is very important due to their high potential interest in pure optical
applications and for quantum computing science as well. Despite many
years of intense study several questions are still debated. Existence of a
phonon bottleneck that would slow down carrier relaxation is still unclear
for instance. Spin relaxation dynamics also needs to be clarified to
understand fully the radiative process of excitons on nanosecond scale.
Subjecting InAs/GaAs quantum dot samples to post-growth rapid
thermal anneals makes it possible to vary the dimension and the confinement
potential of quantum dots and consequently their electronic
structure. The influence of this one on optical properties can then be
analysed.
In this talk we report on measurements of the rise time and radiative
lifetime of photo-excited carriers in InAs/GaAs quantum dots for a series
of high quality annealed samples. Dependence of these two important
quantities with experimental parameters such as temperature, excitation
energy, excitation density and polarization of light is presented and interpreted.
HL 36.13 Do 13:15 H17
Quantum coherences in semiconductor quantum dots — •Hans
Christian Schneider 1 and Weng W. Chow 2 — 1 Fachbereich
Physik, TU Kaiserslautern, Postf. 3049, 67653 Kaiserslautern — 2 Sandia
National Laboratories, Albuquerque, NM 87185-0601, USA
Inversionless gain, electromagnetically induced transparency, refractive
index enhancement and group-velocity reduction are studied for semiconductor
quantum-dot structures under transient conditions. Substantial
deviations from atomic quantum coherence phenomena exist because of
many-body effects. Results on the influence of excitation-induced dephasing
in a semiconductor quantum-dots will also be presented.

Halbleiterphysik Donnerstag
HL 37 Quantenpunkte und -drähte: Transporteigenschaften
Zeit: Donnerstag 10:15–13:30 Raum: H13
HL 37.1 Do 10:15 H13
Spin Blockade in Capacitively Coupled Quantum Dots — •M.
C. Rogge, C. Fühner, U. F. Keyser, and R. J. Haug — Institut
für Festkörperphysik, Universität Hannover, D-30167 Hannover
We present transport measurements on a lateral double dot produced
by combining local anodic oxidation and electron beam lithography [1].
Our device is based on a GaAs/AlGaAs heterostructure containing a
two-dimensional electron system (2DES) 34 nm below the surface. We
use an atomic force microscope (AFM) to write the basic double dot
structure by local anodic oxidation (LAO) [2]. We complete our device
with a metallic top gate patterned with e-beam lithography to add the
function of controlled tunability of the interdot coupling. We investigate
our device in transport measurements in a 3He/4He dilution refrigerator
and demonstrate, that we can switch between capacitive and tunnel
coupling with top gate voltage. In the regime of capacitive coupling we
focus on the magnetic field dependence in the Coulomb blockade regime.
We observe oscillating peak positions and peak amplitudes for transport
over one dot. This is explained by the phenomenon of spin blockade [3],
which has not been observed in LAO-devices so far. We investigate this
effect and analyze the influence of capacitive interdot coupling in this
regime [4].
[1] M. C. Rogge et al., Appl. Phys. Lett. 83, 1163 (2003)
[2] U. F. Keyser et al., Appl. Phys. Lett. 76, 457 (2000)
[3] M. Ciorga et al., Phys. Rev. B 61, R16315 (2000)
[4] M. C. Rogge et al., cond-mat/0310469 (2003)
HL 37.2 Do 10:30 H13
Wave-function mapping of InAs quantum dots by scanning
tunneling spectroscopy — •Theophilos Maltezopoulos, Arne
Bolz, Christian Meyer, Christian Heyn, Wolfgang Hansen,
Markus Morgenstern, and Roland Wiesendanger — Institute of
Applied Physics, University of Hamburg, Jungiusstr. 11, D-20355 Hamburg,
Germany
Low temperature UHV scanning tunneling spectroscopy is used to investigate
the single-electron states and the corresponding squared wavefunctions
of individual and free-standing strain-induced InAs quantum
dots grown on GaAs(001) by molecular beam epitaxy. Several peaks are
found in dI/dV -curves above the dots, which belong to different singleelectron
states. Spatially resolved dI/dV -images at the peak positions
reveal (000)-, (100)-, (010)-, (200)-, and (300)-states, where the numbers
describe the number of nodes in [110]-, [110]-, and [001]-direction, respectively.
It is found, that the total number and energetic sequence of
states is different for different dots. Additionally, the (010)-state is often
missing, even when (200)- and (300)-states are present. This electronic
anisotropy is attributed to the shape asymmetry of the dots.
HL 37.3 Do 10:45 H13
Direct observation of tunneling escape from InAs/GaAs
quantum dots — •Erik Stock, Martin Geller, Roman Sellin,
and Dieter Bimberg — Technische Universität Berlin, Institut für
Festkörperphysik Hardenbergstr. 35, 10623 Berlin
A major challenge in the investigations of quantum dots (QDs) is to
distinguish between two competing charge carrier emission processes:
thermal activated and tunneling emission [1]. We report here the first
observation of the hole tunneling process via time resolved capacitance
transient spectroscopy (DLTS) measurements at low temperature, where
thermal emission is negligible. The escape time observed by us is independent
from the temperature but strongly depends on the applied reverse
bias, which determines the electric field in the QD layer. The measured
hole tunneling emission time constant is in the order of seconds (for electric
fields of about 100kV/cm), approximately three orders of magnitude
larger than for the ground state tunneling of electrons. The dependence of
the tunneling time constant on the electric field is compared to a model,
assuming a triangular barrier with a potential depth measured directly
by DLTS and photoluminescence excitation (PLE) measurements.
This work was funded by the Nanomat project of the European Commission
Growth Programme, contract number G5RD-CT-2001-00545, Intas
project 2001-774, and SFB 296 of DFG.
[1] C.M.A. Kapteyn et al. Phys. Rev. B 60, (20), 14265 (1999)
HL 37.4 Do 11:00 H13
Spin effects in quantum dots — •Jens Könemann 1 , D. K.
Maude 2 , V. Avrutin 3 , A. Waag 3 , and R. J. Haug 1 — 1 Institut
für Festkörperphysik, Universität Hannover, Appelstrasse 2, D-30167
Hannover, Germany — 2 High Magnetic Field Laboratory, CNRS, 25
Avenue des Martyrs, BP 166, F-38042 Grenoble cedex 9, France —
3 Abteilung Halbleiterphysik, Universität Ulm, Albert-Einstein-Allee
45,D-89069 Ulm, Germany
We present spin-resolved measurements of the transport spectrum of
an individual localized state in a double-barrier resonant tunneling device
probed by single-electron tunneling [1]. We investigated the spin splitting
of ground and excited states and found a deviation to a linear increase
of spin splitting with magnetic field beyond 18 T. Astonishingly, we observed
at high magnetic fields above 14 T a flip of the resonance position
of the energetically higher spin component to a lower energy, whereas the
other spin-component remained unchanged. A hysteresis effect appeared
at the spin flip region as well. Such ”spin-flip”behaviour was observed
on different Fock-Darwin levels, where it occurred at different magnetic
fields. We relate this effect to the presence of magnetic impurities residual
inside the quantum well.
[1] J. Könemann et al., to appear in Physica E
HL 37.5 Do 11:15 H13
Coulomb effects in tunneling through a quantum dot stack — H.
Sprekeler, •G. Kießlich, A. Wacker, and E. Schöll — Institut
für Theoretische Physik, TU Berlin, Hardenbergstr. 36, 10623 Berlin
Resonant tunneling through two vertically coupled self-organized quantum
dots is studied by means of a Pauli master equation model. The
observation of double peaks in the current-voltage characteristic in a recent
experiment [1] as a signature of Coulomb interaction is analyzed in
terms of the tunnel coupling between the quantum dots and the coupling
to the contacts. Different regimes for the emitter chemical potential indicating
different peak scenarios in the tunneling current are discussed. By
comparison with a density matrix approach we show that the interplay
of coherent and incoherent effects in the stationary current can be fully
described by this approach.
[1] M. Borgstrom, T. Bryllert, T. Sass, B. Gustafson, L.-E. Wernersson,
W. Seifert, and L. Samuelson, Appl. Phys. Lett. 78, 3232 (2001)
[2] H. Sprekeler, G. Kießlich, A. Wacker, and E. Schöll, cond-mat/0309696
(unpublished)
HL 37.6 Do 11:30 H13
Fano and Kondo Resonances in Three-Leaded Quantum Dot
Systems — •Armin C. Welker, David Quirion, Juergen Weis
und Klaus v. Klitzing — Max-Planck-Institut fuer Festkoerperforschung,
D -70569 Stuttgart, Heisenbergstr. 1, Germany
The spectral function or density of states of a quantum dot coupled
to two leads can be investigated by weakly coupling a third lead to the
quantum dot. For doing so, the differential conductance to this third lead
is measured as a function of the bias voltage applied to this probing lead
in reference of the two main leads. The feasibility of this approach for
investigating the out-of-equilibrium splitting of the Kondo resonance has
been theoretically explored [1]. We present our preliminary experimental
results on a split-gate quantum dot indicating this splitting.
In addition, measurements on a quantum dot system are shown in the
regime of strong coupling to the two main leads where Fano-like resonances
occur. A peak in the differential conductance to the third lead is
observed whenever a Fano-like resonance is obtained in the conductance
between the two main leads. [1] E. Lebanon and A. Schiller, Phys. Rev.
B 65, 035308 (2002).
HL 37.7 Do 11:45 H13
Hole transport through an array of self-assembled Ge quantum
dots — •Kai-Martin Haendel 1 , U. Denker 2 , O. G. Schmidt 2 ,
and R. J. Haug 1 — 1 Institut für Festkörperphysik, Universität
Hannover, Appelstr. 2, 30167 Hannover — 2 Max-Planck-Institut für
Festkörperforschung, Heisenbergstr. 1, 70569 Stuttgart
In recent years, several features of quantum states in self-assembeld Ge
quantum dots have been demonstrated by various spectroscopic studies,
such as admittance, capacitance-voltage analysis, photoluminescence and
photoluminescence excitation spectroscopy.

Halbleiterphysik Donnerstag
We use transport spectroscopy to determine the electronic properties of
self-assembeld Ge hut cluster quantum dots that are embedded in the
quantum well of a Si/SiGe-based resonant tunnelling diode. At temperatures
below 300 mK and high magnetic fields scaling behavior in the
non-linear current-voltage (I − V ) characteristic, switching events and
hysteresis are observed and are dedicated to states of a collective charge
mode.
HL 37.8 Do 12:00 H13
Transport through a quantum dot spin valve — •Matthias
Braun 1,2 , Jan Martinek 2 , and Jürgen König 1 — 1 Theoretische
Physik III, Ruhr-Universität Bochum, D-44780 Bochum — 2 Institut
für Theoretische Festkörperphysik, Universität Karlsruhe, D-76128 Karlsruhe
We study transport through a quantum dot that is weakly coupled to
ferromagnetic leads. The interesting aspect of this structure is that it
combines two physical paradigms. Due to the polarized leads, the tunnel
rates of the electrons becomes spin dependent leading to the spin
valve effect. On the other hand the low capacity of a quantum dot
strongly enhances the importance of electron-electron interaction leading
to Coulomb blockade.
In a non-equilibrium situation spin accumulates on the dot for
non-parallel aligned electrode magnetizations. Due to the interplay
of Coulomb interaction and coupling to ferromagnetic leads, this
accumulated spin experiences an exchange field which leads to spin
precession.
Spin and charge accumulation as well as the precession of the accumulated
spin in the exchange field influence the dot state. The resulting
complex dynamics of the dot spin is visible in the linear and non-linear
transport characteristics of the device.
HL 37.9 Do 12:15 H13
Frequenzabhängige Kapazitätsspektroskopie am Löchersystem
von InAs Quantenpunkten — •Peter Kailuweit, Peter Schafmeister,
Dirk Reuter und Andreas D. Wieck — Angewandte
Festkörperphysik, Ruhr-Universität Bochum, Universitätsstraße 150, D-
44780 Bochum
Mittels frequenzabhängiger Kapazitätsspektroskopie wurde das
Löchersystem von InAs Quantenpunkten untersucht. Es wurden bis zu
acht getrennte Ladepeaks beobachtet und es konnte der Energieunterschied
zwischen den einzelnen Peaks abgeschätzt werden. Alle Ladepeaks
werden mit zunehmender Meßfrequenz kleiner, jedoch ist die Signalabnahme
umso stärker, desto geringer die Energie des Lochlevels ist. Ein
Vergleich mit den Ergebnissen zum Elektronensystem ähnlicher Quantenpunkte
zeigt, daß alle Lochniveaus einen Schwerlochcharakter haben,
mit einer Effektiven Masse von 0, 73me.
HL 37.10 Do 12:30 H13
Resonance Kondo tunneling through a double quantum dot at
finite bias — •Mikhail Kiselev 1 , Konstantin Kikoin 2 , and Laurens
W. Molenkamp 3 — 1 Institut für Theoretische Physik und Astrophysik,
Universität Würzburg, 97074 Würzburg, Germany — 2 Ben-
Gurion University of Negev, Beer-Sheva 84105, Israel — 3 Physikalisches
Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany
It is shown that the resonance Kondo tunneling through a double quantum
dot (DQD) with even occupation and singlet ground state may arise
at a strong bias, which compensates the energy of singlet/triplet excitation.
Using the renormalization group technique we derive scaling
equations and calculate the differential conductance as a function of an
auxiliary dc-bias for parallel DQD described by SO(4) symmetry. We
analyze the decoherence effects associated with the triplet/singlet relaxation
in DQD and discuss the shape of differential conductance line as a
function of dc-bias and temperature.
HL 37.11 Do 12:45 H13
Magnetodispersion wechselwirkender eindimensionaler Wellenleiter
— •S.F. Fischer 1 , G. Apetrii 1 , U. Kunze 1 , D. Schuh 2 und
G. Abstreiter 2 — 1 Werkstoffe und Nanoelektronik, Ruhr-Universität
Bochum, D-44780 Bochum — 2 Walter-Schottky-Institut, Technische Universität
München, D-85748 Garching
Nanostrukturierung von GaAs/AlGaAs-Heteroschichten mit hochbeweglichen
2D-Elektronengasen ermöglicht elektronische Wellenleiter
hoher 1D-Subbandenergieabstände (> 10 meV) herzustellen. Dies
begünstigt 1D-Energieniveauentartung bzw. -aufspaltung wechselwirkender
1D-Elektronensysteme experimentell zu ermitteln. In dieser Arbeit
wurden 1D-Engstellen aus einem 2D-Elektronensystem (beiseidig modulationsdotierten
Quantentopf von 30 nm Breite) mit zwei besetzten
Subbändern (vertikalen Moden) mit dem Rasterkraftmikroskop nanostrukturiert
[1]. 1D-ballistischer Transport zeigt sich in der Leitwertquantisierung
in Stufen von 2e 2 /h bei 4.2 K. Bei Besetzung der zweiten
vertikalen Mode treten Leitwertanomalien auf [2]. Im transversalen Magnetfeld
führt die unterschiedliche Ausdehnung der Wellenfunktionen der
vertikalen Moden zu verschiedenen Magnetodispersionen. Dies ermöglicht
Koinzidenzen von 1D-Energieniveaus der zwei vertikalen Moden, wobei
gleiche Parität zu einer Aufhebung der Energieentartung führt. Es wurde
eine Energieaufspaltung ∆E von etwa 1 meV ermittelt.
HL 37.12 Do 13:00 H13
Shot noise measurements of InAs quantum dots — •N. Maire 1 ,
A. Nauen 1 , F. Hohls 1 , R. J. Haug 1 , and K. Pierz 2 — 1 Institut
für Festkörperphysik, Universität Hannover, D-30167 Hannover —
2 Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116
Braunschweig
We investigate the noise properties of self-assembled InAs quantum
dots embedded into a GaAs-AlAs-GaAs heterostructure. The I-V -
characteristic shows a step-like dependence which can be directly linked
to resonant tunneling through the ground states of single quantum dots.
This allows us to measure the noise properties of single 0-dimensional
states.
The resulting noise power shows a frequency independent spectrum
from 1-10 kHz, the so called shot noise. This noise power is suppressed
compared to the theoretical value 2eI of a single tunneling barrier as it is
indeed expected for a double barrier resonant tunneling structure. This
suppression is characterized by the dimensionless Fano factor α = S/2eI;
S being the average noise power density. Measurements at high magnetic
fields show a transition from a single step to a double step in the I-V -
characteristic due to Zeeman splitting and a shifting of α as a transition
from a spin nondegenerate ground state to a degenerate ground state
occurs. Furthermore the temperature dependence of α on the Fermi occupation
function of the emitter is observed.
HL 37.13 Do 13:15 H13
Controlling Spin States in Lateral Quantum Dots — •Clemens
Rössler 1 , Andreas K. Hüttel 1 , Stefan Ludwig 1 , Dieter
Schuh 2 , and Jörg P. Kotthaus 1 — 1 Center for NanoScience and
Sektion Physik Ludwig-Maximilians-Universität, Geschwister Scholl
Platz 1, D-80539 München, Germany — 2 Walter-Schottky-Institut, Am
Coulombwall 3, D-85748 Garching, Germany
Conventional semiconductor based electronics rely on the charge of
many electrons for triggering transistors. In contrast, we attempt to reach
the regime in which a logical bit is defined by a single electron spin. Here,
quantum information processing promises new prospects regarding the
basic notions of computing. Qubits defined by single electron spin states
in lateral quantum dots can combine long coherence times with an easily
tunable electrostatic confinement.
We discuss our novel split gate geometries and present first results towards
manipulating electron spin states in quantum dots in the limit of
few electrons.

Halbleiterphysik Donnerstag
HL 38 Halbleiterlaser II
Zeit: Donnerstag 10:15–13:15 Raum: H14
HL 38.1 Do 10:15 H14
T-förmige Wellenleiter für Quantendrahtkaskadenlaser —
•Thomas Herrle, Stefan Schmult, Markus Pindl, Ulrich
Schwarz und Werner Wegscheider — Institut für Experimentelle
und Angewandte Physik Universität Regensburg, 93040 Regensburg
Theoretische Berechnungen sagen eine Verringerung von nichtstrahlenden
Übergängen in Quantendrahtkaskadenemitterstrukturen
gegenüber herkömmlichen Quantenkaskadenemitterstrukturen voraus
[1]. Eine solche Struktur wurde im GaAs/AlGaAs-Heterosystem mittels
des epitaktischen Überwachsens von atomar glatten Spaltflächen (CEO)
realisiert [2]. Um in derartigen Strukturen Lasertätigkeit zu erzielen, ist
ein Wellenleiter notwendig, der auf das CEO-Wachstum zugeschnitten
ist. In diesem Vortrag werden zwei Methoden zur Wellenleiterberechnung
in derartigen Strukturen vorgestellt und miteinander verglichen, nämlich
die Transfermatrixmethode kombiniert mit der effektiven Brechungsindexmethode
und die Lösung der zweidimensionalen Wellengleichung
in einer Quantendrahtkaskadenemitterstruktur. Es wird gezeigt, dass
mithilfe eines T-förmigen Wellenleiters die optische Grundmode nahe der
optisch aktiven Region in einer Quantendrahtkaskadenemitterstruktur
eingeschlossen werden kann.
[1] I. Keck, S. Schmult, W. Wegscheider, M. Rother, A. P. Mayer, Phys.
Rev. B 67, 125312 (2003).
[2] S. Schmult, I. Keck, T. Herrle, W. Wegscheider, M. Bichler, D. Schuh,
G. Abstreiter, Appl. Phys. Lett. 83, 1909 (2003).
HL 38.2 Do 10:30 H14
Vier-Wellen-Mischen in einem durchstimmbaren Zwei-Moden
Halbleiterlaser — •Icksoon Park, Ingo Fischer und Wolfgang
Elsässer — Institut für Angewandte Physik, TU Darmstadt
Ein im THz-Differenzfrequenzbereich durchstimmbarer Zwei-Moden
Halbleiterlaser ist einerseits eine attraktive Lichtquelle zur Erzeugung
von Dauerstrich-THz-Strahlung durch Photomischen auf photoleitenden
Antennenstrukturen. Andererseits führt die simultane Zwei-Moden-
Emission aufgrund der nichtlinearen Wechselwirkung mit dem Halbleitermedium
zu Four-Wave Mixing (FWM). FWM im Halbleiterlaser findet
in letzter Zeit erhebliches Interesse für Anwendungen in optischen
Kommunikationssystemen. Darüber hinaus bietet Intracavity-FWM im
THz-Bereich eine spektroskopische Methode für die Untersuchung der
ultraschnellen Ladungsträgerdynamik in Halbleiterlasern.
Wir präsentieren experimentelle Untersuchungen von FWM in einem
Zwei-Moden Halbleiterlaser, realisiert durch Rückkopplung von zwei
in einem externen Doppel-Resonator selektierten Moden. Wir untersuchen
dabei sowohl die Abhängigkeit der Konversionseffizienz des FWM-
Signals von der Differenzfrequenz bis in den THz-Bereich, deren Verlauf
Rückschlüsse auf die ultraschnelle Ladungsträgerdynamik erlaubt,
als auch den Einfluß des Fabry-Perot-Resonators auf das FWM-Signal.
HL 38.3 Do 10:45 H14
Einfluss defektreduzierender Massnahmen auf die Alterung von
(AlIn)GaN-Laserdioden — •M. Furitsch, S. Miller, A. Leber,
G. Brüderl, A. Lell und V. Härle — OSRAM Opto Semiconductors
GmbH, Wernerwerkstr. 2, 93049 Regensburg
Halbleiterlaser im blau-violetten Spektralbereich sind insbesondere für
optische Speicheranwendungen und hochauflösende Laserdrucktecknik
interessant. Für die industrielle Anwendung ist allerdings eine gute Lebensdauer
Voraussetzung.
OSRAM OS stellt kantenemittierende Halbleiterlaser im Wellenlängenbereich
von λ = 390nm − 420nm her. Die epitaktischen
Schichten werden mittels MOVPE auf leitendem SiC-Substraten
abgeschieden, was einen vertikalen Stromfluss ermöglicht. Einen starken
positiven Einfluss auf die Lebensdauer von (AlIn)GaN-Laserdioden hat
die Reduktion der Defektdichte [1].
In diesem Beitrag wird der Einfluss verschiedener Prozessparameter auf
das Alterungsverhalten untersucht in dem unmontierte, gewinngeführte
Oxidstreifenlaser gealtert wurden. So führt eine Anpassung der Wachstumstemperatur
in der aktiven Zone zu verlängerten Lebensdauern. Es
wurde gezeigt, dass eine zusätzliche SiN-Schicht im epitaktischen Aufbau
zu einer Verringerung der Defektdichte führt. An Laserdioden mit optimiertem
in-situ SiN kann eine deutlich verlangsamte Anfangsalterung
gegenüber einem Laser ohne Defektreduzierung gezeigt werden.
[1] T. Tojyo et. al., IPAP Conf. Series 1, pp 878-882 (2000)
HL 38.4 Do 11:00 H14
THz-Strahlungserzeugung mit Zwei-Farben Halbleiterlaser —
•Stefan Hoffmann und Martin Hofmann — AG Optoelektronische
Bauelemente und Werkstoffe, Ruhr-Universität Bochum, IC2-156,
D-44780 Bochum
Bei der Untersuchung der Emissionsspektren von Zwei-Farben Halbleiterlasern
konnten wir Vier-Wellen-Misch-Seitenbänder bis hin zu einer
Differenzfrequenz von 4.2 THz detektieren. Das Vier-Wellen-Mischsignal
spricht dafür, dass das Ladungsträgerplasma des Lasers mit der Differenzfrequenz
der Zwei-Farben-Emission moduliert wird. Wir konnten
nun experimentell zeigen, dass die im THz-Bereich liegende Differenzfrequenz
auch direkt aus der Laserdiode emittiert wird. Damit schlagen wir
ein neues und einfaches Konzept zur Erzeugung von schmalbandiger und
durchstimmbarer THz-Strahlung bei Raumtemperatur vor.
HL 38.5 Do 11:15 H14
Index- und gewinngeführte (In,Al)GaN-Laserdioden auf SiC-
Substraten — •Andreas Leber, Andreas Weimar, Michael
Furitsch, Stephan Miller, Georg Brüderl, Alfred Lell und
Volker Härle — OSRAM Opto Semiconductors GmbH, Wernerwerkstrasse
2, D-93049 Regensburg
Die Lebensdauer GaN-basierender Laserdioden für den blau-violetten
Spektralbereich um 400nm wird vor allem durch hohe Schwellenstromdichten
(einige kA/cm 2 ) begrenzt. Diese resultieren aus den großen Defektdichten
(typisch 10 9 cm −2 ), die bei der Heteroepitaxie von GaN-
Schichten auf nicht-defektreduzierten SiC-Substraten enstehen.
Für die Prozessierung der Laserdioden ist es daher wichtig, Strukturen
zu finden, die einen hohen Wirkungsgrad ermöglichen. Ridge
Waveguide-Laserdioden (RWG-LD) sind deshalb besonders geeignet, weil
sich durch die Indexführung der optischen Mode und die Begrenzung des
Strompfades ein hoher lateraler Füllfaktor realisieren läßt.
Bei OSRAM OS werden RWG-LD in einem selbstjustierenden Prozess
durch reaktives Ionenätzen (RIE) mit Strukturbreiten von 1 – 10µm
hergestellt. Eine Modifikation dieses Prozesses erlaubt es, zusätzlich gewinngeführte
Oxidstreifen-LD neben den RWG-LD gemeinsam auf einem
Laserbarren zu strukturieren. Diese Oxidstreifen-LD dienen als Referenzstrukturen
bei der elektro-optischen Charakterisierung, da ihre Eigenschaften
vorwiegend vom vertikalen Epitaxie-Schichtaufbau abhängen.
Wir untersuchten die Einflüsse von lateralem Brechzahlprofil sowie
Breite und Ätztiefe des Ridge Waveguides auf die elektrischen und optischen
Eigenschaften der RWG-LD.
HL 38.6 Do 11:30 H14
Pikosekunden-Dynamik von Breitstreifen-Halbleiterlasern
— •Joachim Kaiser 1 , Ingo Fischer 1 , Wolfgang Elsäßer 1 ,
Edeltraud Gehrig 2 und Ortwin Hess 2 — 1 Institut für Angewandte
Physik, TU Darmstadt — 2 Advanced Technology Institute, University
of Surrey, England
Wir präsentieren kombinierte experimentelle und theoretische Untersuchungen
der Pikosekunden-Emissionsdynamik von Breitstreifenlasern
(BSL).
BSL sind gekennzeichnet durch laterale und longitudinale Multimodenemission
sowie eine komplexe raum-zeitliche Dynamik. Unter anderem
zeigen sie schnelle Intensitätspulsationen durch eine schwache longitudinale
Selbstmodenkopplung aufgrund der intrinsischen Nichtlinearitäten.
Wir können diese Modenkopplung durch zusätzliche Injektion eines
einzelnen Pikosekunden-Pulses ganz erheblich verstärken. Der BSL zeigt
dann nahezu vollständige Pulsemission und erzeugt 13 ps kurze Pulse.
Modellierungen basierend auf Multimoden Maxwell-Bloch-Gleichungen
zeigen, wie die dynamische Wechselwirkung des injizierten Pulses mit
dem internen Laserfeld eine effiziente Modenkopplung erzeugt und die
Emission über die gesamte Breite synchronisiert. Unsere Resultate erlauben
somit Einsicht in das komplexe Wechselspiel zwischen lateraler und
longitudinaler Dynamik und deuten gleichzeitig das Potential von BSL
für die Kurzpulserzeugung durch Modenkopplung an.

Halbleiterphysik Donnerstag
HL 38.7 Do 11:45 H14
THz Silizium Laser — •Heinz-Wilhelm Hübers 1 , Pavlov Sergey
1 , Hovenier Niels 2 , Klaassen Tjeerd 2 , Riemann Helge 3 ,
Orlova Ekatarina 4 , Zhukavin Roman 4 und Shastin Valery 4 —
1 Deutsches Zentrum für Luft- und Raumfahrt, Rutherfordstr. 2, 12489
Berlin — 2 Technische Universität Delft, P.O. Box 5046, 2600 GA Delft,
Niederlande — 3 Institut für Kristallzüchtung, Max-Born-Str. 2, 12489
Berlin — 4 Institut für Physik der Mikrostrukturen, Russische Akademie
der Wissenschaften, 603600 Nizhni-Novgorod, Russland
Ein Silizium Laser für den Terahertz (THz) Spektralbereich wird vorgestellt.
Besetzungsinversion kann zwischen Energieniveaus von Donatoren
der Gruppe V (P,As, Sb,Bi) in Silizium bei Temperaturen unterhalb von
ca. 30 K erzeugt werden. Die Anregung erfolgt durch Photoionisation der
Donatoren vom Grundzustand in das Leitungsband (z.B. mit einem CO2-
Laser) oder durch direkte otpische Anregung (z.B. mit einem FEL)in die
oberen Energieniveaus der Donatoren. Die angeregten Elektronen verlieren
Energie durch Emission von optischen und akustischen Phononen.
Dieser kaskadenartige Prozess führt zu Besetzungsinversion zwischen für
die jeweilige Donatorenart spezifischen Energieniveaus. Auf diese Weise
können Laser mit Emissionfrequenzen zwischen 1.3 THz und 6.3 THz
realisiert werden. Es werden die verschiedenen Lasermechanismen dargestellt
und ihre Eigenschaften diskutiert. Insbesondere werden Ergebnisse
zum Einfluss von Dotierung, Kompensationsgrad, Temperatur, externem
Magnetfeld und externem Druck präsentiert.
HL 38.8 Do 12:00 H14
Erhöhung der direkten Modulationsbandbreite durch Mehrsektionshalbleiterlaser
— •Wolfgang Kaiser 1 , Lars Bach 1 , Johann
Peter Reithmaier 1 , Alfred Forchel 1 , Tommy W. Berg 2 und
Biarne Tromborg 2 — 1 Technische Physik, Universität Würzburg, Am
Hubland, D-97074 Würzburg — 2 COM, Technical University of Denmark,
DK-2800 Lyngby, Denmark
Im Halbleiterlaser ist die direkte Modulationsbandbreite durch die
Rekombinationszeit der Ladungsträger begrenzt. Durch Ausnutzung
höherer Resonanzen in Laserkavitäten kann die Modulationsbandbreite
signifikant erhöht werden. Diese Resonanzen treten zusätzlich zur
Elektron-Photon-Resonanz in der Modulationstransferfunktion auf. Aufbauend
auf diesem Effekt wurde das CCIG (Coupled Cavity Injection
Grating)-Laserkonzept entwickelt. Bei diesem Mehrsektionskonzept kann
man diese Resonanzen durch Anpassung der Phase und der Kopplungsstärke
und somit auch die Modulationsbandbreite gezielt kontrollieren.
Für einen CCIG-Laser konnte mit einer direkten Modulationsbandbreite
von 37 GHz der derzeitige Rekordwert auf GaInAsP/InP-Material bei
einer Wellenlänge von 1,5 µm erreicht werden.
HL 38.9 Do 12:15 H14
1.3 µm InAs/InGaAs-Laser mit asymmetrisch eingebauten
Quantenpunkten — •Stefan Deubert, Roland Krebs, Johann
Peter Reithmaier und Alfred Forchel — Technische Physik,
Universität Würzburg, Am Hubland, 97074 Würzburg
Der Einbau von InAs-Quantenpunkten in eine InGaAs-
Quantenfilmstruktur erlaubt es Laser für den 1.3 µm Wellenlängenbereich
auf GaAs-Substraten zu realisieren. Durch Variation der Quantenfilmdicke,
und somit einen asymmetrischen Einbau der Quantenpunkte, konnten
die optischen Eigenschaften von 1.3 µm Lasern signifikant verbessert
werden. Es konnten mit Hilfe dieser asymmetrischen aktiven Schicht die
Schwellenströme halbiert und die Effizienzen um 30% gesteigert werden,
so dass 400 µm lange RWG-Laser mit Schwellenströmen von nur 2 mA
realisiert werden konnten. Gleichzeitig führt der asymmetrische Einbau
der Quantenpunkte zu einer Erhöhung der Temperaturstabilität und charakteristischen
Temperaturen von 130 K. Auch monomodige DFB-Laser
die auf dieser Struktur basieren zeigen geringere Schwellenströme und
gleichzeitig verbesserte Hochfreqenzeigenschaften mit Modulationsbandbreiten
von 7.5 GHz.
HL 38.10 Do 12:30 H14
Entwicklung von InGaAsP/InP-Lasern hoher Brillanz bei 1.4 -
1.5 µm — •Senta Kallenbach, Marc Tibor Kelemen, Jürgen
Weber, Rolf Aidam, Rainer Lösch, Gudrun Kaufel und Michael
Mikulla — Fraunhofer-Institut für Angewandte Festkörperphysik,
Tullastr. 72, D-79108 Freiburg
InP-basierte Hochleistungslaser mit hoher Strahlqualität bei 1.4 -
1.5 µm finden Anwendung als Pumplaser in erbiumdotierten Faserverstärkern
und Ramanverstärkern. Im Gegensatz zu bisher verwendeten
Ridge- oder Buried-Heterostructure-Designs, die eine Ausgangsleistung
von maximal einigen 100 mW zulassen, verfolgen wir das Konzept des
Ridge-Trapezlasers, das eine hohe Brillanz ermöglicht, d.h. hohe Leistungen
(> 1 W) mit hoher Strahlqualität vereint. Die hier vorgestellten
Schichtstrukturen wurden überwiegend mittels Feststoffquellen-MBE
epitaxiert. Wellenführung und aktive Zone bestehen aus InGaAsP, wobei
die Quantentöpfe 1 % kompressive Verspannung aufweisen. Variationen
in der Vertikalstruktur wurden anhand von Breitstreifenlasern untersucht,
um Einflüsse durch das Lateral- und Longitudinaldesign separat
analysieren zu können. Abstrahlwinkel, Verluste und Schwellstromdichten
wurden für Wellenleiterbreiten zwischen 0.3 und 1.6 µm sowie
Füllfaktoren von 1.4 bis 2.5 % hinsichtlich einer optimierten Vertikalstruktur
für Trapezlaser untersucht.
HL 38.11 Do 12:45 H14
Monomodige GaAs/AlGaAs Quantenkaskadenlaser mit monolithisch
integrierten Halbleiter-Luft Bragg-Spiegeln — •Sven
Höfling 1 , Marc Fischer 2 , Jochen Seufert 2 , Adriana Wolf 1 ,
Monika Emmerling 1 , Johann-Peter Reithmaier 1 und Alfred
Forchel 1 — 1 Technische Physik, Universität Würzburg, Würzburg —
2 Nanoplus, Nanosystems und Technology GmbH, Gerbrunn
Monomodige GaAs/AlGaAs-basierende Quantenkaskadenlaser wurden
realisiert durch die monolithische Integration von Bragg-Spiegeln mit einer
photonischen Bandlücke nahe der Emissionswellenlänge (λ ≈ 10 µm).
Die Bragg-Spiegel auf beiden Seiten der Kavität bestehen aus tiefgeätzten
Halbleiter-Luft Gittern.
Bauelemente mit einer Resonatorlänge von 365 µm zeigen einen
Schwellenstrom von 1,0 A (80 K) und können bis 260 K betrieben werden.
Dies ist eine signifikant höhere Betriebstemperatur im Vergleich
zu einem 1000 µm langen Referenzlaser mit Spaltfacetten (200 K).
Zudem konnten mit diesem Verfahren die bisher kürzesten Quantenkaskadenlaser
mit 180 µm Resonatorlänge hergestellt werden. Bei diesen
Lasern ist wegen ihres großen freien Spektralbereichs und der begrenzten
Verstärkungsbandbreite monomodiger Betrieb ohne zusätzliches
Rückkopplungsgitter möglich.
HL 38.12 Do 13:00 H14
Ridge-Trapezlaser hoher Brillanz — •Marc Kelemen, Jürgen
Weber und Michael Mikulla — Fraunhofer Institut für Angewandte
Festkörperphysik, Tullastr. 72, D-79108 Freiburg
Hochleistungslaser hoher Brillanz, d.h. bei gleichzeitig hoher Ausgangsleistung
und hoher Strahlqualität, gewinnen zunehmend für die Spektroskopie,
die Frequenzverdopplung und in der Drucktechnik an Bedeutung.
Das aussichtsreichste Konzept bietet hier im Moment das Konzept
des Ridge-Trapezlasers, der im Moment nahezu beugungsbegrenzte Ausgangsleistungen
von bis zu 2 W bietet.
In dieser Arbeit werden BPM-Simulationen und experimentelle Ergebnisse
vorgestellt, um erstmals nahezu beugungsbegrenzte Ausgangsleistungen
von bis zu 5 W bei einer Wellenlänge von 980 nm zu erreichen.
Dazu werden der Einfluß von Montage- und Designparametern auf
die Leistungs- und Strahleigenschaften von Trapezlasern mittels BPM-
Simulationen untersucht. Experimentell werden die Trapezlängen zwischen
1.5 und 3 mm variiert. Die verschiedenen Trapezdesigns werden
einerseits elektro-optisch und bezüglich ihres Temperaturverhaltens untersucht.
Zusätzlich wird die Strahlqualität durch Nahfelder, Fernfelder
und Messungen von M2 experimentell charakterisiert.

Halbleiterphysik Donnerstag
HL 39 Hauptvortrag Kaiser
Zeit: Donnerstag 14:30–15:15 Raum: H15
Hauptvortrag HL 39.1 Do 14:30 H15
The Dramatic Developments of Optical Lithography — •W.
Kaiser — Carl Zeiss SMT AG, 73446 Oberkochen
Lithography is the key technology in the chip manufacturing process
to enable continuous shrinking of electronic components on modern ICs,
resulting in cheaper, faster, and less power consumptive devices.
Based on optical design concepts for photographic and microscopy
lenses the optical lithography has experienced a fulminant development
HL 40 SiC I
seen through the last three decades.
The most advanced systems today work at a wavelength of 193nm
and are able to achieve resolution of 90nm and below in high volume
production.
In this presentation the actual state of the art for these systems and
the optical technologies will be shown.
Also recent developments like Immersion Lithography, the trend to
shorter wavelength (157nm) and the long-term perspective to EUV-
Lithography will be addressed.
Zeit: Donnerstag 15:15–16:30 Raum: H15
HL 40.1 Do 15:15 H15
Homoepitaxial growth of 4H-SiC:Ge alloys on 4H-SiC (0001)
substrates by Molecular Beam Epitaxy — •Petia Weih 1 ,
Thomas Stauden 1 , Lothar Spieß 2 , Henry Romanus 2 , Oliver
Ambacher 1 , and Jörg Pezoldt 1 — 1 FG Nanotechnologie, Zentrum
für Mikro- und Nanotechnologien, TU Ilmenau, PF100565, D-98693
Ilmenau, Germany — 2 FG Werkstofftechnologie, Zentrum für Mikround
Nanotechnologien, TU Ilmenau, PF100565, D-98693 Ilmenau,
Germany
Up to date the only intrinsic heterostructures based on SiC are beta-
SiC/alpha-SiC heterojunctions using different bandgaps of different polytypes,
which could not be improved into commercial applications because
of unsolved technological problems. The epitaxy of SiC:Ge alloys provides
the opportunity of bandgap engineering and the realization of alternative
SiC based heterostructures. The draw backs of SiC:Ge alloys are
the thermodynamic instability and the immiscibility of Ge in SiC, which
must be overcome by nonequilibrium material synthesis methods such
as ion beam synthesis or molecular beam epitaxy. In this work for the
first time SiC:Ge thin films were grown homoepitaxially by solid source
molecular beam epitaxy applying (a) continuous fluxes of Si-, C- and Geflux
or (b) atomic layer epitaxy (subsequent deposition of C and Si/Ge)
on on-axis 4H-SiC (0001) substrates. The surface morphology, the chemical
composition and the structure of the grown layers were analysed by
atom force microscopy, scanning electron microscopy with accompanying
energy dispersive X-ray analysis, secondary ion mass spectroscopy and
transmission electron microscopy, respectively.
HL 40.2 Do 15:30 H15
Micro-electromechanical systems based on 3C-SiC/Si heterostructures
— •Christian Förster, Volker Cimalla,
Michael Fischer, Klemens Brückner, Matthias Hein, Jörg
Pezoldt, and Oliver Ambacher — FG Nanotechnologie und FG
Hochfrequenztechnik, Zentrum für Mikro- und Nanotechnologien, TU
Ilmenau, PF100565, 98693 Ilmenau
Wide bandgap semiconductors like SiC are excellent materials for high
temperature, high frequency and high power applications. Furthermore
the properties of SiC are typical for materials suitable for modern applications
in micro-sensors, micro-actuators as well as in micro- and nanoelectromechanical
systems (MEMS, NEMS). Novel applications of SiC/Si
based MEMS and NEMS are dosing and sensor systems for micro- and
nano-fluidic systems, e.g. for fast and reliable biomedical testing and
analysis. We have developed a technology for processing SiC/Si-based
MEMS and NEMS. A micro dosing head for pulmonary amount of liquid
in very small area are realized. This dosing head consist of parallel
operating multi micro pipes running at a defined pressure. Furthermore,
we used 3C-SiC/Si heterostructures to process resonator bars having geometries
in the sub micro meter range. These bars open the possibility
to evaluate the viscosity of water based nano-droplets or to measure the
mass of particles, for example proteins, positioned on the bars.
HL 40.3 Do 15:45 H15
Deep Levels of Gadolinium in Silicon Carbide — •Gunnar
Pasold 1 , Fanny Albrecht 1 , Christian Hülsen 1 , Rainer Sielemann
2 , Wolf Dietrich Zeitz 2 , and Wolfgang Witthuhn 1 —
1 Friedrich-Schiller-Universität Jena, Institut für Festkörperphysik, Max-
Wien-Platz 1, 07743 Jena — 2 Hahn- Meitner- Institut Berlin, Glienicker
Straße 100, D-14109 Berlin
Epitaxial layers of hexagonal silicon carbide (SiC) were doped with
the radioactive isotope 149 Gd by recoil-implantation at the HMI (Berlin).
Deep Level Transient Spectra (DLTS) were taken, repeatedly, during the
elemental transmutation 149 Gd → 149 Eu (T1 /2 =9.5 d)
Spectra taken on p-type SiC reveal two deep levels
(ET=EV+0.94±2 eV and ET=EV+0.45±1 eV), undergoing a decrease
in concentration with a half-life of 11±1 d identifying them as Gd
correlated. Whereas the deeper one has been found in 4H and 6H-SiC,
the lower one is observable in the 4H polytype only.
Deep levels with increasing concentrations indicating levels caused by
the daughter element Eu were not observed in the part of the band-gap
of SiC investigated. N-type SiC samples implanted with 149 Gd show no
time dependent deep level concentrations.
HL 40.4 Do 16:00 H15
Oxynitrides on 4H-SiC(0001) — •Patrick Hoffmann and Dieter
Schmeißer — BTU Cottbus, Lehrstuhl Angewandte Physik II /
Sensorik, Universitätsplatz 3-4, 03044 Cottbus
It will be reported on the growth of oxynitride thin layers (≤10nm) on
(0001)-oriented 4H-SiC surfaces. The oxynitride layers were grown by a
thermal treatment of the samples in low pressure N2O ambient. By varying
the growth conditions (N2O pressure, sample temperature, growth
time) different layers were made.
The grown layers were investigated by photoelectron spectroscopy
(XPS) for chemical analysis and by AFM/STM for analysis of the surface
morphology. Concerning the chemical analysis it will be discussed
the general nitrogen content of the samples, the composition of the films
(e.g. content of silicon nitride Si3N4 and silicon oxynitride SiOxNy) and
the sub-oxides which build the interface between SiC and the oxynitride
layers. Concerning the surface morphology mainly the roughness will be
discussed.
The so obtained results for oxynitride thin films on 4H-SiC will be
compared to similarly prepared oxynitride layers on Si(111) investigated
in the past.
HL 40.5 Do 16:15 H15
The sequential annealing of radiation-induced intrinsic defects
in SiC — •M.V.B. Pinheiro, U. Gerstermann, E. Rauls, Th.
Frauenheim, S. Greulich-Weber, and J.-M. Spaeth — Departament
Physik, Universit”at Paderborn, Warburger Str. 100, 33098, Paderborn
, Deutschland
The understanding of sequential annealing dynamics of radiationinduced
defects in SiC has been of highly technological interest. The
main reason for this is that most SiC devices require ion-implantation
doping, which generates intrinsic defects with a high thermal stability.
In this work we present a complete model for the sequential annealing
of several defects generated by electron-irradiation in SiC. Among these
defects there are several unidentified ones that disappear above 150C, the
isolated silicon vacancy that between 600C and 750C is converted in the
silicon antisite - carbon vacancy pair, and finally the D1 center whose concentration
strongly increases above 900C. The latter is the end-product
visible with photoluminescence up to 1700C. Our model is based on a
systematic isochronal annealing investigation performed in 6H-SiC and
4H-SiC with photoluminescence (PL), electron-paramagnetic resonance
(EPR) and magnetic circular dichroism of the absorption (MCDA), and
is fully consistent with ab-initio calculations.

Halbleiterphysik Donnerstag
HL 41 Spinabhängiger Transport II
Zeit: Donnerstag 15:15–16:30 Raum: H17
HL 41.1 Do 15:15 H17
Laterale Py-InAs Spinventil-Geometrie: Magnetische
Domänen, Schaltverhalten und Grenzflächeneigenschaften —
•T. Last, S. Hacia, S.F. Fischer und U. Kunze — Werkstoffe und
Nanoelektronik, Ruhr-Universität Bochum, D-44780 Bochum
Schaltverhalten, magnetostatische Wechselwirkung, Domänenkonfiguration
und Grenzflächeneigenschaften der Elektroden einer lateralen
Py-InAs Spinventil-Geometrie wurden mittels Magnetotransport, Magnetkraftmikroskopie
und SQUID-Magnetometrie untersucht. Als Elektroden
dienen nanostrukturierte 20 bis 50 nm dicke Permalloydrähte (Breiten:
0.4 µm, 2.0 µm) mit Aspektverhältnissen von 10 und 50, die sich
in Remanenz in einem Eindomänenzustand befinden. Der longitudinale
anisotrope Magnetowiderstand einzelner hochremanenter Py-Drähte
zeigt einen klaren Anstieg des Schaltfeldes mit abnehmender Breite. Die
Wechselwirkung dreier benachbarter parallel geschalteter Drähte (Abstand:
1.3 µm - 2.9 µm) wird anhand des Entmagnetisierungsfeldes µ0HD
im transversalen Magnetfeld diskutiert. µ0HD verringert sich mit abnehmendem
Abstand zwischen den Drähten. Mit Messungen der magnetischen
Hysterese (5 K) nach Abkühlung im Magnetfeld (35 mT) wurde
die Spinordnung an der Py/InAs-Grenzfläche untersucht. Nur (mit Gold)
abgedeckte dünne Py-Schichten (t ≤ 6 nm) auf InAs zeigen symmetrische
magnetische Hysteresen. Dies deutet auf eine für die Spininjektion geeignete
kollineare Spinordnung an der Py-InAs-Grenzfläche hin.
HL 41.2 Do 15:30 H17
Anomalous Spin Dephasing in (110) GaAs Quantum Wells —
•Daniel Hägele 1 , Stefanie Döhrmann 1 , Jörg Rudolph 1 , Dieter
Schuh 2 , and Michael Oestreich 1 — 1 Universität Hannover, Institut
für Festkörperphysik, Abteilung Nanostrukturen, Appelstr. 2, D-30167
Hannover — 2 Walter Schottky Institut, Technische Universität München,
Am Coulombwall, D-85748 Garching
GaAs quantum wells grown on (110) oriented substrates are considered
prime candidates for room temperature spintronics. The electron
spin lifetime in such structures had recently been demonstrated to exceeded
the lifetime found in (100) grown quantum wells by about an
order of magnitude [1]. However, we observe a strong anisotropy of electron
spin decoherence in n-doped (110) GaAs/(AlGa)As quantum wells.
We measure long lifetimes for electron spin along (110) direction, but the
lifetime for spin perpendicular to (110) is dramatically reduced by up to
a factor of ten, which has direct implications for the design of spintronic
devices. We also observe that spin lifetimes decrease monotonically for
both spin orientations above a temperature of 80 and 120 K, respectively.
In case of (110) spin orientation the decrease is very surprising and cannot
be explained with the usual Dyakonov Perel dephasing mechanism.
A novel spin dephasing mechanism is put forward based on scattering of
electrons between different quantum well subbands.
[1] Y. Ohno et al., Phys. Rev. Lett. 83, 4196 (1999)
HL 41.3 Do 15:45 H17
Influence of magnetic-field induced tuning of disorder and band
structure on the magnetoresistance of dilute magnetic semiconductors
— •C. Michel, P.J. Klar, S.D. Baranovskii, P. Thomas,
and W. Heimbrodt — FB Physik und WZMW, Philipps-Universität,
Marburg
We study theoretically the magneto-transport in p-type wide-gap dilute
magnetic semiconductors in the paramagnetic phase. Two models
(referred to as mobility model and network model) based on a minimal
description of the valence band structure and the acceptor state of the
DMS are discussed. In both models, band filling effects, magnetic-field
splitting of the band states due to the p-d exchange interaction as well
as effects of magnetic-field independent disorder are included whereas
carrier-carrier interactions other than those responsible for the local magnetism
of the Mn ions are neglected. Despite the exclusion of many-body
effects in the bands, positive as well as negative MR effects are predicted
which show a qualitative agreement with recent experiments on p-type
dilute magnetic semiconductors [Ye et al., J. Supercond.: INM 16, 159
(2003), Nam et al., J. Supercond.: INM 16, 335 (2003)]. The differences
between the two models arise from a different, model-specific weighting
of disorder and occupation effects.
HL 41.4 Do 16:00 H17
Large spin splittings in GaSb/AlSb heterostructures with
absolute conduction minima deriving from the L valley —
•Reinhard Scholz 1 , Jean-Marc Jancu 2 , Giuseppe La Rocca 2 ,
and Paul Voisin 3 — 1 Institut für Physik, Technische Universität
Chemnitz — 2 Scuola Normale Superiore and INFM, Pisa — 3 Laboratoire
de Photonique et de Nanostructures, CNRS, Marcoussis
Recently, it has been proposed to develop so-called spintronic devices
based on spin-dependent properties in semiconductor nanostructures.
The subsequent investigations of the spin splitting in semiconductor
heterostructures have been focusing on quantized states resulting from
the Γ valley of the conduction band in III-V compounds. Around Γ, the
spin-orbit coupling is proportional to the Dresselhaus or k 3 term in leading
order, resulting in spin splittings of the order of 0.1 meV close to the
Fermi energy in doped GaAs/AlAs heterostructures [1]. On the other
hand, around the L point, k-linear spin-orbit coupling is allowed for the
tranverse directions. For heterostructures with the absolute conduction
minimum deriving from the L point of the bulk material, these k-linear
terms result in large spin splittings for wave vectors orthogonal to the
growth direction. Using narrow GaSb quantum wells between AlSb barriers
as a model system with quantum well states related to the L valley,
we demonstrate that spin splittings exceeding 10 meV can be achieved,
more than 2 orders of magnitude above typical values resulting from the
Dresselhaus term around the Γ point.
[1] J. Kainz, U. Rössler, and R. Winkler, Phys. Rev. B 68, 075322 (2003).
HL 41.5 Do 16:15 H17
Grundlagen und Anwendungen der gepulsten elektrisch detektierten
magnetischen Resonanzspektroskopie — •Christoph
Böhme — Hahn-Meitner-Institut Berlin, Abteilung Siliziumphotovoltaik,
Kekulestrasse 5, 12489 Berlin
Elektrisch detektierte magnetische Resonanz (EDMR) ist ein Experiment
mit dem sich spinabhängige elektronische Übergänge die einen Einfluß
auf die Leitfähigkeit haben (Transport, Rekombination) untersuchen
lassen. Die gepulste EDMR beruht auf der transienten Messung von Halbleiterströmen
nach einer sehr kurzen, kohärenten Anregung paramagnetischer
Zentren. Durch das Messen des Probenstromes in Abhängigkeit
von der Zeit, der Pulsanregung und dem Magnetfeld, erschließt sich eine
Fülle experimenteller Daten, mit denen weitaus bessere Aussagen über
die untersuchten Mechanismen gemacht werden können als mit der traditionellen
EDMR, einem adiabatischen Magnetfeldvorschubexperiment.
Die Anwendung von gepulster EDMR erstreckt sich jedoch nicht nur auf
die genaue Analyse von elektronischen Prozessen zur Materialcharakterisierung,
sie ermöglichte kürzlich auch zum ersten Mal die elektrische Detektion
von Spinkohärenz mit einer Empfindlichkeitsgrenze von wenigen
hundert Elektronen. Letzteres bedeutet einen großen Fortschritt für die
Suche nach empfindlichen Ausleseverfahren für spinbasierte Festkörper-
Quanteninformationssysteme. In diesem Beitrag werden die theoretischen
und experimentellen Grundlagen der gepulsten EDMR kurz vorgestellt,
bevor verschiedene experimentelle Ergebnisse von gepulsten EDMR Messungen
an unterschiedlichen Halbleitersystemen gezeigt werden.

Halbleiterphysik Donnerstag
HL 42 Quantenpunkte und -drähte: Optische Eigenschaften II
Zeit: Donnerstag 15:15–16:30 Raum: H13
HL 42.1 Do 15:15 H13
Investigations of electrically contacted single quantum dots —
•U. Scholz 1 , R. Schmidt 1 , M. Vitzethum 1 , R. Fix 1 , S. Malzer 1 ,
C. Metzner 1 , P. Kailuweit 2 , D. Reuter 2 , A. Wieck 2 , M.C.
Hübner 3 , S. Stufler 3 , A. Zrenner 3 , and G.H. Döhler 1 —
1 Technische Physik I, Universität Erlangen-Nürnberg — 2 Angewandte
Festkörperphysik, Ruhr-Universität Bochum — 3 AG Nanostructure
Optoelectronics, Universität Paderborn
We investigate single quantum dots (QDs) embedded in the intrinsic
region of a micro-LED. The active area of the LED is defined by the
intersection of a p- and a n-doped stripe. The bottom stripe is defined
by focussed ion beam implantation (FIB) which easily provides the necessary
lateral resolution of a few 100 nm. The perpendicular top stripe is
fabricated by wet chemical etching to µm or sub-µm width. As the dot
densities of our samples are typically less than 10 9 cm −2 , the active area
of the LED, on the average, contains one QD. We find single QD spectra
in EL measurements. Extremely sharp recombination lines are observed
up to the third excited state (f-shell). Within the different shells several
emission peaks are visible, which can be attributed to differently charged
excitons. All the lines show a pronounced red shift with increasing bias
voltage due to the Stark effect. Polarisation resolved measurements suggest
for the p-shell an anisotropy of the lateral confinement potential. We
will also discuss voltage dependent photo current measurements and the
application for a single photon turnstile device.
HL 42.2 Do 15:30 H13
Inelastic light scattering of few-electron collective excitations in
charge-tunable artificial atoms — •T. Brocke 1 , A. Stührk 1 , M.-
T. Bootsmann 1 , M. Tews 2 , B. Wunsch 2 , D. Pfannkuche 2 , Ch.
Heyn 1 , W. Hansen 1 , D. Heitmann 1 , and C. Schüller 1 — 1 Institut
für Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität
Hamburg, Jungiusstraße 11, D-20355 Hamburg — 2 I. Institut
für Theoretische Physik, Universität Hamburg, Jungiusstraße 9, D-20355
Hamburg
We report the investigation of electronic excitations in InGaAs selfassembled
quantum dots using resonant inelastic light scattering. By applying
a voltage between a metallic front gate and a back electrode, the
dots can be charged with N = 1...6 electrons. We observe excitations,
which are identified as transitions of electrons from the s to the p shell
(s-p transitions) and from the p- to the d-shell (p-d transitions) of the
quasiatoms. We find that the s-p transition energy decreases and the observed
band broadens, when the p shell is filled with 1 to 4 electrons. By
a theoretical model, which takes into account the full Coulomb interaction
in the few-electron artificial atom, we can confirm the experimental
results to be an effect of the Coulomb interaction in the quantum dot.
This project is funded by the DFG via SFB 508 and SCHU1171/2.
HL 42.3 Do 15:45 H13
Nahfeld-Photolumineszenz einzelner InGaAs-Quantenpunkte
bei tiefen Temperaturen — •Christian Griesche, Kai Hodeck
und Mario Dähne — Technische Universität Berlin, Institut für
Festkörperphysik, Hardenbergstr. 36, 10623 Berlin
Spektroskopische Untersuchungen einzelner InGaAs-Quantenpunkte
mit Optischer Rasternahfeld-Mikroskopie (SNOM) bei 80 K zeigten unter
variierender Anregungsintensität im Signal des Grundzustandsübergangs
neu auftretende Linien. Diese wurden der Bildung von Trionen und Biexzitonen
zugeordnet und weisen eine sehr hohe Bindungsenergie für Exzitonenkomplexe
aus [1].
HL 43 III-V Halbleiter II
Um dieses Phänomen anhand detaillierter Messungen mit höherer
spektraler Auflösung genauer zu analysieren, wurde ein neues
Tieftemperatur-SNOM für den Betrieb bei 4 K aufgebaut. Durch eine
innovative Versuchsanordnung wird hierbei ein zuverlässiger Betrieb
trotz des extrem geringen Platzangebots im Kryostaten gewährleistet.
Erste Photolumineszenz-Untersuchungen an einzelnen InGaAs-
Quantenpunkten bei tiefen Temperaturen werden derzeit mit diesem
Gerät durchgeführt.
[1] K. Hodeck et. al., phys. stat. sol. (c)0, No.4, 1209 (2003)
HL 42.4 Do 16:00 H13
Excitonic Complexes in Single InGaN Quantum Dots —
•Robert Seguin 1 , Sven Rodt 1 , Andre Strittmatter 1 , Dieter
Bimberg 1 , Eike Hahn 2 , and Dagmar Gerthsen 2 — 1 TU Berlin,
Institut für Festkörperphysik, Sekr. PN 5-2, Hardenbergstr. 36,
D-10623 Berlin, Germany — 2 Laboratorium für Elektronenmikroskopie,
Universität Karlsruhe, D-76128 Karlsruhe, Germany
InGaN quantum dots (QDs) are very promising for future light emitting
devices covering the visible region. But little is known about their
electronic structure like excitonic complexes.
We present results obtained by cathodoluminescence spectroscopy on
single InGaN/GaN QDs grown by MOCVD on Silicon(111) substrate. To
probe single QDs metallic shadow masks are evaporated onto the sample
surface. The QDs consist of In-rich regions within an inhomogenous In-
GaN layer, as is demonstrated by high-resolution cross-section transmission
electron microscopy. The existence of zero-dimensional localization
centers is confirmed by the observation of δ-function like emission lines
at low temperatures and temperature dependent measurements.
The spectral jitter [1] of the various emission lines, enables us to identify
up to 5 lines originating from the same QD. Excitation density and
polarization dependent measurements reveal more information about the
electronic origin of these lines.
[1] V. Türck, S. Rodt, R. Heitz, O. Stier, M. Straßburg, U.W. Pohl, and
D. Bimberg, Physica E 13, 269 (2002).
HL 42.5 Do 16:15 H13
The Nature of the Excitonic Ground State in coupled QD
Molecules — •H. J. Krenner, M. Sabathil, W. Prestel, D.
Schuh, M. Bichler, J. J. Finley, and G. Abstreiter — Walter
Schottky Institut, TUM, Am Coulombwall 3, 85748 Garching
We present a combined theoretical and experimental investigation of
excitonic states in individual QDMs subject to axial electric fields (F).
Theoretical calculations of the interband spectra including a full treatment
of strain and Coulomb interactions, demonstrate that the electron
dot-dot coupling is significantly stronger than for holes. This gives rise
to a field driven transition of the nature of the excitonic ground state
between optically active (direct) and optically inactive (indirect) states.
We have experimentally tested this prediction of a field driven anticrossing
by performing photoluminescence on single QDMs. Over the
field range for which the ground state is predicted to be dark, a characteristic
emission multiplet is observed from each QDM following quasi
resonant excitation into the wetting layer. This structure is attributed to
optically active few particle states in the nominally dark QD, a conclusion
supported by experiments using non-resonant excitation above the
barrier band gap where only one emission line is observed. Furthermore,
indirect excitons are shown to exhibit a strongly anomolous linear Stark
shift consistent with a large intrinsic e-h separation (∼2-3 nm).
Zeit: Donnerstag 15:15–16:30 Raum: H14
HL 43.1 Do 15:15 H14
Raman spectroscopy of Ga(As,N) epitaxial layers under hydrostatic
pressure — •M. Güngerich 1 , P.J. Klar 1 , W. Heimbrodt 1 ,
J. Koch 1 , W. Stolz 1 , M.P. Halsall 2 , and P. Harmer 2 — 1 FB
Physik und WZMW, Philipps-Universität, Marburg, Germany — 2 Dept.
Physics, UMIST, Manchester, United Kingdom
Vibrational modes of GaAs1−xNx layers were studied by Raman spec-
troscopy at hydrostatic pressures up to 20GPa. Lattice vibrations of
Ga(As,N) show a two-mode behaviour typical of a system where the impurity
atoms are considerably lighter than the host atoms. The N atoms
vibrate independently of the GaAs-like phonons and give rise to a local
vibrational mode (LVM) visible in the spectra for x > 0.005. Pure
GaAs is known to undergo a phase transition from the zincblende structure
to an orthorhombic structure in the pressure range between 15 and

Halbleiterphysik Donnerstag
20GPa. In the investigated GaAs0.915N0.085 sample the phase transition
indicated by the disappearance of the GaAs-like phonons takes place at
about 19GPa. Up to that pressure, the pressure coefficients of the optical
phonons are similar to those of GaAs. The LVM shifts to higher
frequencies at a significantly higher rate. This behaviour can be understood
assuming that the pressure induced changes of the bond lengths
are the same as in pure GaAs. It can be shown that the anharmonicity
of the Ga-N bonds in Ga(As,N) is smaller than in GaN.
HL 43.2 Do 15:30 H14
Zirkular photogalvanischer Effekt bei Interband-Anregung in
Quantentrögen — •Petra Schneider 1 , S.D. Ganichev 1 , V.V.
Bel’kov 2 , C. Back 1 , M. Oestreich 3 , J. Rudolph 3 , D. Hägele 3 ,
L.E. Golub 2 , W. Wegscheider 1 und W. Prettl 1 — 1 Institut für
Experimentelle und Angewandte Physik, Universität Regensburg, 93041
Regensburg — 2 A. F. Ioffe Physico-Technical Institute, 194021 St. Petersburg,
Russland — 3 Institut für Festkörperphysik, Universität Hannover,
30167 Hannover
Der zirkular photogalvanische Effekt konnte zum ersten Mal bei
Interband-Anregung nachgewiesen werden. Die Messung wurde an
p-leitenden (113)A MBE-gewachsenen GaAs/AlGaAs Quantentrögen
durchgeführt. Die spektrale Abhängigkeit des Photostroms wurde zusammen
mit dem Polarisationsgrad im Energiebereich von 1.45 bis 1.8 eV gemessen.
Ergebnisse bzgl. der Spinrelaxationszeiten bei Raumtemperatur
in dem untersuchten Spektralbereich werden präsentiert.
HL 43.3 Do 15:45 H14
Determination of the nitrogen distribution in GaInNAs/GaAs
quantum wells by transmission electron microscopy and correlation
with spectroscopic data — •M. Hetterich 1 , A. Grau 1 ,
D. Litvinov 2 , A. Rosenauer 2 , D. Gerthsen 2 , Ph. Gilet 3 , and L.
Grenouillet 3 — 1 Institut für Angewandte Physik and Center for Functional
Nanostructures (CFN), Universität Karlsruhe, D-76131 Karlsruhe,
Germany — 2 Laboratorium für Elektronenmikroskopie and CFN, Universität
Karlsruhe, Germany — 3 LETI/DOPT/SLIR, CEA-Grenoble,
38054 Grenoble cedex 9, France
We report on a new technique for the determination of the nitrogen
concentration in GaInNAs heterostructures by transmission electron
microscopy and correlate the obtained results with spectroscopic data
(temperature-dependent photoluminescence and photoreflectance spectroscopy).
Two almost identical samples grown by gas-source molecular
beam epitaxy on GaAs (001) were investigated, containing InGaAs and
GaInNAs quantum wells, respectively. Both samples had the same nominal
well thickness and In concentration. They only differed in the nitrogen
content. The In concentration profile of the InGaAs/GaAs quantum
wells was determined by composition evaluation of lattice fringe analysis
(CELFA) based on the chemical sensitivity of the (002) reflection in
the zincblende structure. The N concentration in the GaInNAs wells was
HL 44 Poster II
then evaluated by the comparison of CELFA results obtained for both
samples. The presented technique may be useful for future investigations
into the mechanisms behind the influence of annealing on the optical
properties of GaInNAs quantum wells.
HL 43.4 Do 16:00 H14
Real-time growth monitoring using multichannel-RAS —
•Ch. Kaspari, F. Poser, S. Weeke, and W. Richter for the
NanOp collaboration — Technische Universität Berlin, Institut für
Festkörperphysik, Sekr. PN 6-1, Hardenbergstraße 36, D-10623 Berlin
Since its development by Berkovits, Aspnes and co-workers in the
1980ies, reflectance anisotropy spectroscopy (RAS) has become an important
in situ-technique to investigate the epitaxial growth of semiconductor
surfaces and interfaces. However, for growth monitoring on a
sub-second time scale one is usually restricted to transient measurements
at one single photon energy.
We have developed a special RAS setup that is capable of measuring
transients at eight different photon energies simultaneously in the spectral
range between 1.4 and 4.5 eV, thus allowing for a simple 8-point
RAS spectrum every 100 ms. This technique was used to investigate fast
growth processes in III-V-MOVPE, e.g. oxide desorption, GaAs buffer
growth and N/As group V switching processes.
HL 43.5 Do 16:15 H14
Optical cross sections of the deep defect centers in low temperature
grown GaAs — C. Steen 1 , C. Metzner 1 , R. Schmidt 1 , P.
Kiesel 2 , S. Malzer 1 , and •G.H. Döhler 1 — 1 Institut für Technische
Physik I, FAU Erlangen-Nürnberg, Erlangen, Germany — 2 Palo Alto
Research Center Incorporated, Palo Alto, California
“Low Temperature Grown GaAs”(LT-GaAs) grown by molecular beam
epitaxy (MBE) at low substrate temperatures (190 ◦ C - 300 ◦ C) contains
a high concentration of (non-stoichiometric) excess As, which is incorporated
as EL2-like point defects (AsGa) and As precipitates. At low
temperatures, where the thermal emission rates are negligible, the occupation
of the deep defects can be changed optically. A determination
of the (wavelength-dependent) optical cross sections is possible if initial
conditions can be adjusted where all defects are depleted or filled, respectively.
We have determined the optical cross sections σn and σp of
the defects in LT-GaAs. We have used a p-i-n structure with a thin, only
a few nm thick, layer of LT-GaAs embedded in the i-region of a n-i-p
diode. By applying a reverse bias we are able to control the charge in the
LT-GaAs layer [1]. The charge of the LT-GaAs layer is directly correlated
with the channel conductance Gnn of the (thin) top n-layer. The optical
cross sections for both electrons and holes were deduced by determining
the initial slope of the Gnn change when the illumination starts. The
results were confirmed by the determination of the ratio of σn and σp
deduced from the steady Gnn value under illumination.
[1] K.-F.-G. Pfeiffer et al., Appl. Phys. Lett. 77, 2349 (2000)
Zeit: Donnerstag 16:30–19:00 Raum: Poster A
HL 44.1 Do 16:30 Poster A
Unified Description of Spin-Polarized Electron Transport in
Ferromagnet-Semiconductor Structures — •U. Wille and R.
Lipperheide — Abteilung Theoretische Physik (SF5), Hahn-Meitner-
Institut Berlin, Glienicker Str. 100, D-14109 Berlin, Germany
Generalizing our recent work [PRB 68, 115315 (2003)] on electron
transport in semiconductor structures, we develop a unified description
of ballistic and diffusive spin-polarized transport in ferromagnetsemiconductor
structures. A “thermoballistic” current is introduced, in
which electrons move ballistically in the band edge potential of the semiconductor,
and are thermalized at certain randomly distributed equilibration
points. Spin relaxation is allowed to occur in the ballistic intervals
between the equilibration points. An integral equation for the density spin
polarization in the semiconductor is derived. For constant band edge potential,
this equation can be converted to a differential equation, which
is identical to the spin diffusion equation, except that the spin diffusion
length is renormalized by the factor (1+τ/τs) −1/2 , where τ and τs are the
momentum and spin relaxation times, respectively. The ballistic element
in the unified description gives rise to discontinuities in the chemical
potential at the ferromagnet-semiconductor interfaces. The spin polarization
injected into the semiconductor and the position dependence of
the polarization inside the semiconductor are obtained for any value of
the ratio τ/τs.
HL 44.2 Do 16:30 Poster A
Herstellung einer lateralen Py/GaSb/InAs Spinventil-
Geometrie — •M. Wahle 1 , T. Last 1 , S.F. Fischer 1 , U. Kunze 1 ,
C. Schwender 2 und H. Fouckhardt 2 — 1 Werkstoffe und Nanoelektronik,
Ruhr-Universität Bochum, 44780 Bochum — 2 FB Physik, TU
Kaiserslautern, 67653 Kaiserslautern
Für den elektrischen Nachweis der Spinakkumulation in einem Halbleiter
in lateraler Spinventil-Geometrie wird eine GaSb(5 nm)/InAs(15
nm)/AlSb(20 nm)-Heterostruktur mit hochremanenten Permalloy-(Py)-
Elektroden kontaktiert. Aufgrund der Ausbildung einer Schottky-
Barriere zwischen Py und GaSb kann diese als Tunnelbarriere zum
InAs-Transportkanal dienen. Mittels Magnetotransportmessungen wurden
die Elektronendichte n ≈ 1.5·10 12 cm −2 und die mittlere Beweglichkeit
µ ≈ 30000 cm 2 /Vs des 2DEGs im InAs bestimmt. Die Herstellung
der lateralen Nanostrukturen erfolgt in drei Schritten. Eine Isolation
des Ferromagnet-Halbleiter Kontaktes von der Metallkontaktierung wird
durch Aufsputtern von 200 nm SiO2 erzielt. In einem optischen Lithographieschritt
wird ein 20 µm breites Kontaktfenster zum GaSb geöffnet. Die

Halbleiterphysik Donnerstag
Py-Elektroden (Länge: 150 µm, Breiten: 2 µm, 0.4 µm, Abstand: 200 nm,
Dicke: 30 nm) werden mittels Elektronenstrahllithographie, Elektronenstrahlverdampfung
und anschließendem Lift-off über dieses Kontaktfenster
gelegt. Erste Ergebnisse zum winkelabhängigen Magnetowiderstand
werden präsentiert.
HL 44.3 Do 16:30 Poster A
Tunneling Through Single-Crystal GaAs(001) Barriers —
•Marcus Zenger, Jürgen Moser, Peifeng Chen, Stephan
Kreuzer, Werner Wegscheider, and Dieter Weiss —
Universität Regensburg
We investigate transport through epitaxial GaAs(001) barriers (6-10
nm) sandwiched between evaporated polycrystalline metal films. To realize
a metal/GaAs(001)/metal sandwich we use the epoxy-bond-andstop-etch-technique.
Previous experiments have shown a non-linear I-Vcharacteristic
and a small but clear TMR ratio of 0.2-0.5%. To increase
the TMR ratio we reduced the temperatures during the fabrication process.
This leads to a higher TMR ratio of about 1.7% which corresponds
to a polarization of about 9% in the Julliére model. A negative MR which
is observed at high magnetic fields together with the still low degree of polarization
suggests that spin-flip scattering is important at the Fe/GaAs
interface. The negative MR in Fe/GaAs/Fe junctions will be compared
to the corresponding high-field MR of nonmagnetic sandwiches, which
grows quadratically. If this nearly temperature independent positive contribution
is subtracted from our high-field TMR data a linear negative
MR results. The latter seems to contain information about the spin-flip
scattering process.
HL 44.4 Do 16:30 Poster A
Präparation von Aluminiumoxid-Tunnelbarrieren für den spinpolarisierten
Transport — •Christine M. S. Johnas, Alexander
van Staa, Toru Matsuyama und Guido Meier — Institut für Angewandte
Physik und Zentrum für Mikrostrukturforschung, Jungiusstraße
11, 20355 Hamburg
Im Bereich magnetischer Tunnelelemente sind Al2O3-Barrieren bereits
etabliert und werden industriell eingesetzt. Für den spinpolarisierten
Transport in Hybridsystemen aus Ferromagneten und Halbleitern ist
theoretisch vorhergesagt, dass Tunnelbarrieren an der Grenzfläche zwischen
Ferromagnet und Halbleiter eine Erhöhung der Spininjektionsrate
bewirken [1,2]. In diesem Beitrag befassen wir uns mit der Herstellung
und Charakterisierung von Al2O3 als Tunnelbarriere. Es werden in situ
oxidierte Au/Al2O3/Au-Kontakte und Ni80Fe20/Al2O3/Normalleiter-
Kontakte untersucht. Hierzu variieren wir die Oxidationszeit, die
Al2O3-Schichtdicke und die Kontaktgeometrie im Größenbereich von
1 × 1µm 2 bis 8 × 8µm 2 . In zukünftigen Experimenten sollen die
Al2O3-Barrieren auch an Ferromagnet-Halbleiter-Grenzflächen erforscht
werden. Als Halbleiter wird p-Typ InAs verwendet werden, das an der
Oberfläche ein zweidimensionales Elektronengas ausbildet und eine
starke, abstimmbare Spin-Bahn-Wechselwirkung aufweist [3].
[1] C.-M. Hu and T. Matsuyama, Phys. Rev. Lett. 87, 066803 (2001).
[2] E. I. Rashba, Phys. Rev. B 62, 16267 (2000).
[2] T. Matsuyama et al., Phys. Rev. B 61, 15588 (2000).
HL 44.5 Do 16:30 Poster A
Magnetotransport in (GaMn)As/MnAs and (GaInMn)As/MnAs
paramagnetic-ferromagnetic hybrids — •S. Ye, P.J. Klar, W.
Heimbrodt, M. Lampalzer, S. Hara, and W. Stolz — FB Physik
und WZMW, Philipps-Universität, Marburg
The (GaMn)As/MnAs and (GaInMn)As/MnAs paramagneticferromagnetic
granular hybrids were grown by metal organic vapour
phase epitaxy. By varying the growth conditions different cluster sizes
and different orientations of the MnAs clusters with respect to the matrix
can be obtained. We have performed magnetoresistance (MR) and Hall
measurements in magnetic fields up to 10T and hydrostatic pressures up
to 15kbar at temperatures between 1.6 and 300K. The (GaMn)As/MnAs
system exhibits a large MR (≈ 160%) at 10T, and changes from a negative
to a positive MR with increasing temperature. The MR depends
strongly on the cluster size, the chosen transport geometry and an the applied
pressure. However the observed effects for the (GaInMn)As/MnAs
are considerably smaller even for comparable cluster sizes and similar
layer thickness. It is suggested that the interaction between MnAs ferromagnetic
clusters and paramagnetic matrix plays an important role for
the magnetotransport in such magnetic semicondutor hybrids, which can
be adjusted by the cluster size, the chosen transport geometry and the
type of paramagnetic matrix material.
HL 44.6 Do 16:30 Poster A
Laser threshold reduction in a room-temperature spintronic
device — •Jörg Rudolph 1 , Joachim Fritzsche 1 , Wolfgang
Stolz 2 , Daniel Hägele 1 , and Michael Oestreich 1 — 1 Universität
Hannover, Institut für Festkörperphysik, Abteilung Nanostrukturen,
Appelstr. 2, 30167 Hannover — 2 Wissenschaftliches Zentrum für Materialwissenschaften,
Philipps-Universität Marburg, Hans-Meerwein-Strasse,
35032 Marburg
Despite the progress in the field of spintronics, commercial applications
are still missing. We demonstrate that the injection of spin polarized electrons
into a V ertical Cavity Surface Emitting Laser (VCSEL) leads via
the optical selection rules to a reduction of the laser threshold which is
a key figure for semiconductor laser applications.
We formerly demonstrated this threshold-reduction only for low temperatures
[1]. Now we present time-resolved photoluminescence experiments
with a VCSEL-structure at elevated temperatures showing that
the threshold reduction takes place even at room-temperature. The
spintronic-VCSEL has therefore the potential to become a real-world
spintronic device.
[1] J. Rudolph, D. Hägele, H.M. Gibbs, G. Khitrova, and M. Oestreich,
Appl. Phys. Lett. 82, 4516 (2003)
HL 44.7 Do 16:30 Poster A
Magnetotransportuntersuchen an (311)a-(Ga,Mn)As —
•Matthias Döppe, Ursula Wurstbauer, Matthias Reinwald,
Werner Wegscheider und Dieter Weiss — Institut für Experimentelle
und Angewandte Physik, Universität Regensburg, D-93040
Regensburg
In den letzten Jahren rückte das bei tiefen Temperaturen (Tc ≈ 80K)
ferromagnetische (001)-(Ga,Mn)As als potentielles Material für Spininjektionsexperimente
in den Mittelpunkt experimenteller Untersuchungen.
Effekte wie der Anisotrope Magnetowiderstand (AMR), das stark negative
Magnetowiderstandsverhalten bei hohen Feldern und der GPHE
(Giant Planar Hall Effekt [1]) sind kennzeichnend für dieses Materialsystem,
das bislang hauptsächlich in (001)-Orientierung untersucht wurde.
Im Rahmen dieses Projektes untersuchen wir Magnetotransport in unterschiedlichen
kristallographischen Richtungen von (Ga,Mn)As Schichten
auf (311)A. Das in-plane Magnetfeld wurde hierbei in Schritten von
6 ◦ bzw. 12 ◦ variiert. Gemessen wurde das in-plane Schaltverhalten der
Schichten mittels AMR und planarem Halleffekt.
[1] H. X. Tang, R. K. Kawakami, D. D. Awschalom and M. L. Roukes,
Phys. Rev. Lett. 90, 107201 (2003)
HL 44.8 Do 16:30 Poster A
Spin-orbit interaction in quantum wires in transverse magnetic
field — •S. Debald 1 , T. Brandes 2 , and B. Kramer 1 — 1 I. Institut
für Theoretische Physik, Universität Hamburg — 2 Dept. of Physics,
UMIST, PO Box 88, Manchester M60 1QD, UK
The effect of spin-orbit interaction on spectral and transport properties
of quasi one-dimensional electron systems in a transverse magnetic
field is investigated in the ballistic regime.
Spin-orbit interaction previously has been reported to significantly
change the structure of electronic subbands if the spin precession length
is comparable to the width of the wire [1,2]. We extend these calculations
by introducing a transverse magnetic field.
We apply exact numerical and perturbative approaches to identify different
regimes dependent on the relative strength in the interplay of confinement,
spin-orbit coupling and magnetic field. This interplay leads to
new effects like a finite subband-dependent spin-splitting at k = 0 being
absent without magnetic field.
[1] A.V. Moroz and C.H.W. Barnes, Phys. Rev. B 60, 14272 (1999).
[2] M. Governale and U. Zülicke, Phys. Rev. B 66, 073311 (2002).
HL 44.9 Do 16:30 Poster A
Mn Doped ZnO: A Diluted Magnetic Semiconductor? — •Karl-
Wilhelm Nielsen 1 , Stefanie Wagner 1 , Daniel Reisinger 1 , Jan
Boris Philipp 1 , Petra Majewski 1 , Lambert Alff 1 , Jürgen Simon
2 , and Rudolf Gross 1 — 1 Walther-Meißner-Institut, Walther-
Meißner-Str. 8, 85748 Garching — 2 Institut für Anorganische Chemie,
Universität Bonn, Römerstraße 164, 53117 Bonn
Over the last years the interest in spintronics has grown continuously.
The use of magnetic semiconductors is of particular interest since it would
allow for all semiconductor spintronic devices. In diluted magnetic semiconductors
the semiconductor ions are partly replaced by transition metal

Halbleiterphysik Donnerstag
ions. It is expected that the localized moments of the transition metal
ions are coupled ferromagnetically via the mobile charge carriers of the
semiconductor. It is predicted that Mn doped ZnO is a promising candidate
for spintronics with a Curie temperature above room-temperature.
We have grown thin Mn doped ZnO films using Pulsed Laser Deposition
(PLD) at different temperatures and gas atmospheres. Transmission
Electron Microscopy shows a large amount of growth defects which might
lead to an enrichment of Mn ions at these defects. The magnetization
shows ferromagnetic behavior at low temperatures for Mn doped films
grown at 200 ◦ C without further carrier doping. Films grown at higher
temperatures do not show a ferromagnetic hysteresis. Also, carrier doping
by supplying a high flux of N atoms during growth does not lead to
ferromagnetism in the system.
HL 44.10 Do 16:30 Poster A
Optical and Electronic Methods to Observe Spin Injection
— •Fang-Yuh Lo 1 , Dirk Reuter 1 , Andreas Wieck 1 , Ellen
Schuster 2 , and Aleksey Dremin 3 — 1 Ruhr-Universitaet Bochum,
Lehrstuhl fuer Angewandte Festkoerperphysik, Universitaetsstr. 150,
D-44780 Bochum — 2 Universitaet Duisburg-Essen, Laboratorium fuer
Angewandte Physik, Lotharstr. 1, D-47048 Duisburg — 3 Universitaet
Dortmund, Experimentelle Physik II , Otto-Hahn-Strasse 4, D-44227
Dortmund
The spin injection from magnetic metal films into semiconductors attracts
great interests since it is proposed in the early 1990s. There are
two possibilities to investigate this phenomenon, optical or electronic.
Due to the optical transition rule, the emitted light will have either left
or right circularly-polarization with respect to the different kinds of spins
of the injected carriers. The electronic way is to look at the differences of
resistance with the different spin alignment of the magnetic electrodes,
which are used to inject carriers. There are some reported works, and
most of them are using optical methods. In this work, we apply both the
optical and electronic method to investigate spin-injection phenomenon.
The optical method is to analyze the degree of the polarization of the
emission from semiconductor quantum structures. Both of the focused
ion beam implantation and cleaved-edge overgrowth techniques are applied
to form micro- and nano-structures for the electronic observations
of spin injection into semiconductors.
HL 44.11 Do 16:30 Poster A
Measurement of the barrier height of Ni-Schottky contacts on
GaAs in high magnetic fields — •Holger von Wenckstern 1 ,
Michael Ziese 1 , Rainer Pickenhain 1 , Gisela Biehne 1 , Volker
Gottschalch 2 , Pablo Esquinazi 1 , and Marius Grundmann 1 —
1 Universität Leipzig, Institut für Experimentelle Physik II, Linnéstraße 5,
04103 Leipzig — 2 Universität Leipzig, Institut für Anorganische Chemie,
Linnéstraße 3, 04103 Leipzig
In recent years spin injection into semiconductors and spin transport
phenomena have attracted a growing interest in the physical society. The
evidence that spin was injected and transported has mainly been provided
by optical means [1]. In this contribution we make a first step
towards probing the spin polarization of a metal on a semiconductor by
electrical measurements. We have tested a simple model concerning a
Schottky contact between a ferromagnet and a semiconductor predicting
the lowering of the Schottky barrier due to the Zeeman effect [2]. We
have employed this new method to Ni-Schottky contacts on n-type GaAs
which were prepared by evaporating this ferromagnetic metal onto the
surface of the semiconductor. The Schottky-barrier height of the contacts
was determined from capacitance-voltage and current-voltage measurements
in a temperature range from 10 to 300 K. The applied magnetic
field was varied between 0 and 9 T.
[1] H. J. Zhu et al., PRL 87, 016601 (2001).
[2] “Spin Electronics”, edited by M. Ziese and M. J. Thornton, Springer
Verlag, Heidelberg, 2001, p. 24.
HL 44.12 Do 16:30 Poster A
Einfluss der Pseudopotential-Näherung auf die elektronische
Selbstenergie — •Arno Schindlmayr 1 , Takao Kotani 2 und Stefan
Blügel 1 — 1 Institut für Festkörperforschung, Forschungszentrum
Jülich, 52425 Jülich — 2 Department of Physics, Osaka University, 1-1
Machikaneyama, Toyonaka, Osaka 560-0043, Japan
Obwohl die Dichtefunktionaltheorie häufig auch zur Untersuchung
der elektronischen Struktur von Festkörpern verwendet wird, geben die
Kohn-Sham-Eigenwerte nicht die tatsächliche Bandstruktur wider und
weisen insbesondere bei der Bandlücke von Halbleitern systematische
Fehler auf. Eine exakte Beschreibung des Anregungsspektrums ist dagegen
im Rahmen der Vielteilchen-Störungstheorie möglich. In praktischen
Anwendungen hat sich insbesondere die GW-Näherung für die elektronische
Selbstenergie als überaus erfolgreich erwiesen. Herkömmliche
Implementierungen, die Pseudopotentiale und ebene Wellen verwenden,
stimmen für typische Halbleiter innerhalb von 0,1 eV mit experimentell
gemessenen Bandstrukturen überein. Neuere Rechnungen, die auf
die Pseudopotential-Näherung verzichten, zeigen jedoch eine größere Abweichung
und stellen die bisherigen Resultate in Frage. Die Ursache für
die beobachtete Diskrepanz ist unklar. Um Licht ins Dunkel zu bringen,
führen wir Bandstruktur-Rechnungen innerhalb der GW-Näherung mit
und ohne Pseudopotentiale durch, wobei im zweiten Fall die FLAPW-
Methode verwendet wird. In einer Gegenüberstellung untersuchen wir
systematische Unterschiede in den Beiträgen zur Selbstenergie.
HL 44.13 Do 16:30 Poster A
Bestimmung der lokalen Empfindlichkeit eines EMR-Sensors
mittels Mikromagneten — •M. Hoener 1 , O. Kronenwerth 1 , M.
Holz 2 , Ch. Heyn 1 , D. Grundler 1 und D. Heitmann 1 — 1 Institut
für Angewandte Physik und Zentrum für Mikrostrukturforschung der
Universität Hamburg, Jungiusstr. 11, 20355 Hamburg — 2 I.Institut für
Theoretische Physik Universität Hamburg, Jungiusstr. 9, 20355 Hamburg
Metall-Halbleiter-Hybridstrukturen zeigen einen großen geometrischen
Magnetowiderstand. Dieser sogenannte Extraordinary-
Magnetoresistance-(EMR)-Effekt könnte zukünftig für die Herstellung
von Magnetfeldsensoren bzw. Festplatten-Leseko¨pfe geeignet sein.
Wir haben mikrostruktrierte Hybridsysteme hergestellt, bestehend
aus einem zweidimensionalen Elektronensystem (2DES) in einer
InAs/GaAs-Heterostruktur und einem Au-Film. Der Au-Film wurde
mittels Cleaved Edge Overgrowth auf der (110)-Spaltfläche im Bereich
der 2DES-Mesa präperiert. Weiter haben wir auf verschiedene EMR-
Sensoren einzelne Mikromagnete aus Fe integriert, die lokal definierte
Streufelder erzeugten. Damit wurde die lokale Magnetfeldempfindlichkeit
der EMR-Sensoren untersucht. Dazu führten wir bei 4,2 K
Magnetotransportmessungen durch, bei denen ein äußeres Magnetfeld
den Magnetisierungszusand der Mikromagnete steuerte. Durch Variation
der Dicke des Mikromagneten, seiner Position auf dem EMR-Sensor, der
2DES-Ladungsträgerdichte sowie der Geometrie des Sensors wurde aus
den Transportdaten Parameter für optimierte EMR-Sensoren ermittelt.
Diese Arbeit wurde von der DFG im Rahmen des SFB 508 gefördert.
HL 44.14 Do 16:30 Poster A
Magnetoresistance of Schottky Diodes — •M. Ziese — Division
of Superconductivity and Magnetism, University of Leipzig, Linnéstrasse
5, 04103 Leipzig.
The magnetoresistance of commercial Schottky diodes was investigated.
The current-voltage characteristics of passivated Si-Schottky contacts
obtained from various suppliers were measured in an applied magnetic
field up to 8 T at temperatures between 5 K and 300 K. All samples
studied showed similar behaviour. Down to 80 K the current-voltage
characteristics can be understood within thermionic emission theory, between
80 K and 50 K a crossover to tunnelling is seen. Below 50 K the
charge carriers freeze in and an appreciable series resistance develops. Below
30 K a second nonlinear conduction process appears at high voltages.
This process is strongly magnetic field dependent and at 5 K a significant
shift of the current-voltage characteristics in an applied field is observed.
The magnetoresistance reaches +40% in 5 T at 10 K, decays strongly
with increasing temperature and vanishes above 30 K; it depends on the
relative direction between current and magnetic field. These findings are
discussed within a model of nonlinear current transport.
HL 44.15 Do 16:30 Poster A
Semiconductor–Metal Hybrid Structures as Optimized
Magnetic–Field Sensors — •Matthias Holz 1,2 , Oliver Kronenwerth
3 , Matthias Hoener 3 , and Dirk Grundler 3 — 1 I. Institut
für Theoretische Physik, Universität Hamburg — 2 FB Elektrotechnik,
Universität der Bundeswehr Hamburg — 3 Institut für Angewandte
Physik, Universität Hamburg
Recent experimental results show that non–magnetic semiconductor–
metal hybrid structures can exhibit a very large magnetoresistance effect,
the so–called Extraordinary Magnetoresistance (EMR) effect. Such structures
do not suffer from the drawbacks of current magnetic–field sensors
based on the giant magnetoresistance (GMR) or tunnel magnetoresistance
(TMR) effect, like magnetic noise or demagnetisation. In addition
to its physical significance, the EMR effect is thus interesting for im-

Halbleiterphysik Donnerstag
proved magnetic–field sensors [1-3].
In our work, we study the EMR effect theoretically by means of the
finite–element method. We show how hybrid structures can be optimized
for magnetic–field sensors and, in particular, for read heads. As a result,
we find several design rules for EMR read heads and show that magnetoresistance
effects of more than 100 % are realistic. This renders this
kind of hybrid structures promising for future applications.
We gratefully acknowledge financial support from the DFG via SFB
508 and from BMBF via 01BM905.
[1] S. A. Solin, et al., Science 289, 1530 (2000).
[2] M. Holz, et al., Phys. Rev. B 67, 195312 (2003).
[3] M. Holz, et al., Appl. Phys. Lett. 83, 3344 (2003).
HL 44.16 Do 16:30 Poster A
Ortsaufgelöste Beobachtung der Exzitonendynamik in ZnSe-
Quantenfilmen anhand der Phononenseitenbande — •Gregor
Schwartz, Bénédicte Dal Don und Heinz Kalt — Institut für
Angewandte Physik der Universität Karlsruhe(TH), 76128 Karlsruhe
Die Phononenseitenbande im Lumineszenzspektrum von ZnSe-
Quantenfilmen entsteht durch Rekombination von Exzitonen mithilfe
von LO-Phononen. Berücksichtigt man die Energieabhängigkeit des
Matrixelements der Streuung von Exzitonen mit LO-Phononen, so kann
man aus der Phononenseitenbande direkt auf die Verteilung von heißen
Exzitonen schließen.
Wir benutzen einen mit einer Immersionslinse verbesserten Mikrophotolumineszenzaufbau
mit nachgeschalteter Streakkamera. Die Anregung
erfolgt konfokal mit 150fs-Pulsen von einem frequenzverdoppelten
Ti:Saphir-Laser. Die Detektionsstelle wird mit einem Pinhole in der Bildebene
unabhängig von der Anregung ausgewählt. Damit erreichen wir
eine Ortsauflösung von 250nm und eine zeitliche Auflösung von 5ps.
Wir beobachten eine innerhalb unserer Auflösung instantane Bildung
heißer Exzitonen, während die Nullphononenlinie etwa 15ps später einsetzt,
zu der nur relaxierte Exzitonen beitragen. Das Abkühlen der heißen
Exzitonen passiert innerhalb einiger 100ps, wobei der dabei stattfindende
Transport nicht-diffusiv ist.
Mit einer Monte-Carlo-Simulation können wir die beobachteten Eigenschaften
der Exzitonendynamik verstehen.
HL 44.17 Do 16:30 Poster A
Low temperature transport in a two-dimensional superlattice
— •T. Feil 1 , M. Reinwald 1 , H.-P. Tranitz 1 , W. Wegscheider 1 ,
D. Schuh 2 , M. Bichler 2 , and G. Abstreiter 2 — 1 Institut für Experimentalphysik,
Universität Regensburg, 93040 Regensburg, Germany
— 2 Walter Schottky Institut, TU München, Am Coulombwall, 85748
Garching, Germany
We study negative differential conductance in atomically precise,
short-period modulated two dimensional electron systems realized with
the Cleaved-Edge-Overgrowth method. The device allows the densitydependent
study of electron transport in cosine-like minibands. For low
densities we find stable NDC in the current-voltage-characteristics which
is in agreement with numerical simulations that describe the time evolution
of density fluctuations in the system. Microwave absorption experiments
show a shift and suppression of the NDC peak which is expected
when the NDC is based on Bloch oscillations. The Bloch oscillation picture
is further confirmed by studying the density dependence of the low
field conductance. When we increase the density and therefore subsequently
fill the miniband we reach a point where the overall transport is
quenched as expected theoretically due to the fact that a filled miniband
cannot carry any current. This density dependence of the transport also
leads to a relation between the electron density and the gate voltage of
the system, which in turn gives a density value for the transition from
stable to unstable NDC. This transition point quantitatively agrees well
with our simulations. Supported by DFG via SFB348 and by BMBF
01BM918.
HL 44.18 Do 16:30 Poster A
AFM-Lithography on Cleaved Edges of Ga[Al]As-
Heterostructures — •E. Reinwald 1 , M. Lermer 1 , M. Reinwald 1 ,
W. Wegscheider 1 , D. Weiss 1 , D. Schuh 2 , M. Bichler 2 , and G.
Abstreiter 2 — 1 Universität Regensburg, Institut für Experimentelle
und Angewandte Physik, 93040 Regensburg — 2 Walter Schottky
Institut, Technische Universität München, Am Coulombwall, 85748
Garching
We use the technique of local anodic oxidation with an atomic
force microscope (AFM) to modulate two-dimensional electron systems
(2DES) on cleaved surfaces of GaAs/AlGaAs heterostructures. In
combination with the atomically precise modulation by cleaved-edge
overgrowth (CEO) employing a GaAs/AlGaAs superlattice various
interesting structures can be realised. Our aim is to create a twodimensional
electron system with modulation in both directions. In
these systems magnetotransport experiments are supposed to reveal an
energy signature, known as the Hofstadter butterfly. So far we have
fabricated one dimensional lattices with periods down to 50 nm on
flat GaAs(110) 2DES. The modulation of the 2DES can be measured
in magnetotransport experiments. Furthermore we have developed a
method to contact and measure the two-dimensional electron system on
the cleaved surface in hallbar geometry.
This project is supported by the DFG Schwerpunktprogramm 1092
and by the BMBF (01BM918).
HL 44.19 Do 16:30 Poster A
Anisotropic Thermopower in Si-Al-Multilayers — •Amir Kyarad
und Hans Lengfellner — Institut für Angewandte und Experimentelle
Physik, Universität Regensburg, 93040 Regensburg, Germany
Semiconductor-metal multilayer structures A-B-A... show, according
to model calculations, large anisotropy in their electrical and thermal
transport properties: For n-type silicon (A) and aluminum (B), the anisotropy
of the thermopower ∆S = S�−S⊥ where S� and S⊥ represent the
Seebeck coefficients along and perpendicular to the layers, is more than
an order of magnitude larger than that for a pure metallic structure A-
B-A... made of constantan (A) and copper (B). In samples prepared with
a tilt angle between sample surface and layer planes, radiation heating of
the sample surface induces a surface perpendicular temperature gradient
and, due to the anisotropy of the thermopower, generates a surface parallel
thermoelectric field E ∼ ∆S. This transverse Seebeck effect suggests
applications for radiation detection. The preparation of Si-Al multilayer
samples is described and their use as rugged, self-powered and nearly
wavelength independent detectors for laser radiation is demonstrated.
HL 44.20 Do 16:30 Poster A
Resonante Tunneldioden mit Mikrometerabmessungen als potentielle
Spinfilter und Spindetektoren — •Andreas Gröger,
Peter Grabs, Taras Slobodskyy, Tatjana Borzenko, Frank
Lehmann, Charles Gould, Georg Schmidt und Laurens W.
Molenkamp — Physikalisches Institut, Universität Würzburg, Am
Hubland, D-97074 Würzburg
Resonante Tunneldioden (RTDn) mit semimagnetischem Trog zeigen
in einem äußeren Magnetfeld eine Aufspaltung der diskreten Energiezustände,
so dass separate Resonanzen für die beiden möglichen Spinrichtungen
auftreten. Eine derartige Aufspaltung wurde bereits experimentell
in Mn-dotierten ZnSe-RTDn beobachtet [Physical Review Letters Vol.
90, 246601 (2003)]. Um nicht nur die Aufspaltung nachzuweisen, sondern
auch die Spinpolarisation des Stromes zu detektieren, ist es erforderlich,
zwei kleine RTDn herzustellen, die als Injektor und Detektor dienen und
deren Abstand nicht größer als die Spinfliplänge ist. Wir haben ZnSebasierte
RTDn mit Abmessungen von ca. 1 µm x 1 µm hergestellt und
zeigen die Aufspaltung der Resonanzen an Transportexperimenten in einzelnen
und gekoppelten Bauelementen.
HL 44.21 Do 16:30 Poster A
Implantation magnetischer Ionen in GaAs/AlGaAs Hetrostrukturen
— •Sinan Ünlübayir, Alexander Melnikov und Andreas
D. Wieck — Ruhr-Universität Bochum D-44780 Bochum
Wir untersuchen den Einfluss magnetischer Ionen auf die elektrischen
Transporteigenschaften eines 2 dimensionalen Elektronengases
(2DEG). Zur Realisierung des 2DEGs wird eine selektiv dotierte
GaAs/AlGaAs Heterostruktur verwendet. Verschiedene Ionensorten
(Mn,Fe,Ni,Gd,Ho,Er), welche viel versprechende Kandidaten dafür sind
das sie ihr hohes magnetisches Moment auch im Wirtskristall beibehalten
und sowie als Referenz Ga werden mit der Technik der fokussierten Ionenimplantation
in die Heterostruktur implantiert. Es werden Dosen von
1x10 9 cm −2 bis 1x10 13 cm −2 verwendet wobei die Ionenenergie zwischen
100 und 200 keV liegt. Ferner wird der Einfluss eines schnellen thermischen
Ausheilschrittes (750 ◦ C für 30 s)untersucht. Die magnetischen
Eigenschaften der implantierten Strukturen werden mit Magnetotransportmessungen
untersucht.

Halbleiterphysik Donnerstag
HL 44.22 Do 16:30 Poster A
Streuung von Elektronen und 3D longitudinalen Phononen in
ungeordneten Bulk-Materialien — •Frank Löcse — TU Chemnitz,
Institut für Physik, 09107 Chemnitz
Für die Berechnung der Energierelaxationsrate der Elektron-Phonon
Streuung in ungeordneten Bulk-Materialien gibt es im wesentlichen zwei
sich widersprechende Theorien. In deren Ergebnis hängt die Energierelaxationsrate
1/τe−ph von Phononenwellenzahl q und mittlerer elastischer
freier Weglänge l der Elektronen im Bereich ql < 1 wie 1/τe−ph ∼ ql/τ0
bzw. wie 1/τe−ph ∼ 1/(ql)τ0 ab. Beide Abhängigkeiten werden durch
das Experiment bestätigt. Hier ist 1/τ0 ∼ T 3 die Relaxationsrate im
reinen Material. Anhand eines einfachen Modells zeigen wir, daß sich
beide Abhängigkeiten aus einem einzigen Ausdruck für die Energierelaxationsrate
im Bereich ql < 1 ableiten lassen und zwar in Abhängigkeit
von Temperatur des Phononengases und Schallgeschwindigkeit. Grundlage
der analytischen Rechnung ist eine von uns entwickelte semiklassische
Methode zur Berechnung der geeignet gemittelten Übergangswahrscheinlichkeiten.
HL 44.23 Do 16:30 Poster A
Field-dependence in the steady-state photocarrier grating
technique: application to microcrystalline silicon — •Rudolf
Brüggemann 1 and Rashad I. Badran 2 — 1 Instut für Physik, Carl
von Ossietzky Universität Oldenburg — 2 Physics Department, The
Hashemite University, Zarqa, Jordan
The steady-state photocarrier grating (SSPG) technique has become
a standard tool for the characterisation of the minority carrier properties
in amorphous and microcrystalline silicon. In the standard application
the photocurrent response under the presence of spatially modulated
photogeneration is measured at low electric fields. Here, we exploit the
electric-field variation experimentally for microcrystalline silicon samples.
The experimental results show a variation in the influence that the
electric field imposes on the excess charge carriers, depending on the individual
sample. For poor-quality samples there is hardly any influence
in the measured SSPG parameter. In contrast, samples with high diffusion
lengths show a large variation in the SSPG parameters. Analysis of
our data with the theory by Abel et al. (1995) shows good correlation
between experimental and theoretical values for a wide range of electric
field, in particular in the transition region between diffusion dominated
and drift-dominated transport.
HL 44.24 Do 16:30 Poster A
Trench-insulated IPG transistors for active matrix displays
— •A. Lapanik and A.D. Wieck — Ruhr-Universitaet Bochum,
Lehrstuhl fuer Angewandte Festkoerperphysik, Universitaetsstrasse 150,
D-44780 Bochum
We already reported on theoretical investigations of IPG transistors
(formed by Focused Ion Beams), new techniques of preparation of transistors
and results that shows possibilities of using IPG transistors for active
matrix liquid crystal displays (AMLCD). Here, we report of further
research results on trench insulated IPG transistors on poly-Si on quartz
in contrast to previous work on GaAs (1990. Nieder et al). The geometry
of IPG transistors was changed to obtain higher process performance and
lower leakage current to be more suitable for AMCLD developing. New
mask layers were used for sputtering of the Si and we present here results
for transistors with a better gate insulation. This is obtained by wider
insulating lines between gate and the source-drain areas, respectively.
The annealing temperature dependence of the transistor parameters are
discussed. Also, we would like to report on the technology improvement
of IPG transistor fabrication. In particular, chemical process steps were
improved and new were added to perform a ”cleaning” of the sputtered
area and sputtered trenches.
HL 44.25 Do 16:30 Poster A
Fabrication of Resonant-Tunneling Diodes by B Surfactant
Modified Growth of Si Films on CaF2/Si — •C.R. Wang, M.
Bierkandt, B.H. Müller, S. Paprotta, E. Bugiel, T. Wietler,
and K.R. Hofmann — Institute for Semiconductor Devices and Electronic
Materials, University of Hannover, Appelstr. 11A, 30167 Hannover,
Germany
Boron (B) surfactant enhanced solid phase epitaxy (SPE) of thin Si
films on CaF2/Si(111) substrates has been studied. Room temperature
deposition of amorphous Si films followed by the deposition of one monolayer
B atoms resulted in continuous and smooth epitaxial Si layers on
CaF2 with a sharp B-induced √ 3x √ 3R30 ◦ surface reconstruction after
annealing to about 635 ◦ C. This growth technique was used to fabricate
CaF2/Si/CaF2 double-barrier resonant tunneling diodes (RTDs) in SiO2
windows patterned on Si(111) substrates. A negative differential resistance
(NDR) peak was found at ∼0.2 V at 77 K, and the current density
at the NDR peak was estimated to be 6 orders of magnitude higher than
that found in earlier reports.
HL 44.26 Do 16:30 Poster A
Elektronischer Transport in einzelnen und verzweigten Wellenleitern
— •Mirja Richter 1 , Michael Knop 1 , Ulrich Wieser
1 , Ulrich Kunze 1 , Dirk Reuter 2 und Andreas D. Wieck 2
— 1 Lehrstuhl für Werkstoffe und Nanoelektronik, Ruhr-Universität Bochum,
D-44780 Bochum — 2 Lehrstuhl für Angewandte Festkörperphysik,
Ruhr-Universität Bochum, D-44780 Bochum
Auf einer modulationsdotierten GaAs/Al1−xGaxAs-Heterostruktur
werden einzelne und gekreuzte elektronische Wellenleiter in einem
Mix-and-Match Prozess hergestellt. Der Prozess kombiniert
Niederenergie-Elektronenstrahllithographie mit konventioneller
Fotolithographie.
Wellenleiter mit einer Breite bis minimal 50 nm und einer Länge von einigen
Mikrometern werden durch elektronische Transportmessungen bei
tiefen Temperaturen charakterisiert. Die Wellenleiter zeigen quantisierten
Leitwert in Vielfachen von 2e 2 /h und eine Separation der untersten
Subbänder von bis zu 19 meV. An gekreuzten Wellenleitern kann der
Knickwiderstand R1324 (bend resistance) im ballistischen Transportregime
in Abhängigkeit von der Geometrie der Kreuzungsstelle und der
Steuerspannung an der Topgateelektrode untersucht werden.
HL 44.27 Do 16:30 Poster A
Magnetotransportspektroskopie an einem GaAs/AlGaAs-
Quantenring — •A. Mühle 1 , U. F. Keyser 1 , R. J. Haug 1 , W.
Wegscheider 2 und M. Bichler 3 — 1 Institut für Festkörperphysik,
Universität Hannover, D-30167 Hannover — 2 Angewandte und
Experimentelle Physik, Universität Regensburg, D-92040 Regensburg —
3 Walter Schottky Institut, TU München, D-85748 Garching
Ein Quantenring, der auf der Oberfläche einer GaAs/AlGaAs-
Heterostruktur durch lokale anodische Oxidation mit einem Rasterkraftmikroskop
hergestellt wurde, [1] wurde untersucht. Über zwei
In-plane-Gates konnten sowohl die Energie der Elektronen auf dem Ring
als auch die Ankopplung der Struktur an die Zuleitungen durchgestimmt
werden.
Für verschiedene Kopplungsstärken wurde das Transportverhalten in
Abhängigkeit von einem senkrechten Magnetfeld und einer Gatespannung
über große Bereiche gemessen. Aus den sich ergebenden Mustern
in der grafischen Darstellung konnten dann bei wenigen Elektronen auf
dem Ring deren Anzahl und ihre Spinverteilung bestimmt werden.
Weiterhin wurden bei sehr kleinen Feldern im Regime weniger Elektronen
in einigen Bereichen Oszillationen der differentiellen Leitfähigkeit mit
dem Magnetfeld beobachtet, die über Level-crossings im Grundzustand
des Ringes erklärt werden könnten.
[1] U. F. Keyser et al., Phys. Rev. Lett. 90, 196601-1 (2003)
HL 44.28 Do 16:30 Poster A
Noise measurements of individual and coupled InAs quantum
dots — •P. Barthold 1 , N. Maire 1 , F. Hohls 1 , A. Nauen 2 ,
R.J. Haug 1 , K. Pierz 3 , and T. Bryllert 2 — 1 Institut für
Festkörperphysik, Universität — 2 Div. of Solid State Physics, Lund
University, P.O. BOX 118, SE-221 00 Lund — 3 Physikalisch- Technische
Bundesanstalt, Bundesallee 100, D-38116 Braunschweig
We present noise measurements of resonant single electron tunnelling
through individual and coupled self-organised InAs quantum dots (QDs)
at temperatures down to 1.5 K.
In the first case our samples consist of a GaAs/AlAs/GaAs tunnelling
structure with self-organised InAs QDs embedded in the AlAs. We investigate
the noise generated by the sample with a current amplifier in a
range from 0 to 10 kHz, and use a Fast Fourier Transformation analyser
for spectral decomposition. Above 1 kHz the noise shows a frequencyindependent
behaviour indicating the presence of shot noise. Depending
on bias voltage we find that the shot noise is suppressed in respect to
the Poissonian value 2eI expected for a single barrier. We observe the
effect of asymmetric tunnelling barriers on the shot noise suppression.
This suppression is characterised by the Fano factor α = S/2eI whose
modulation was perceived in the experiment.
In the second case the sample consists of a GaInAs/InP/GaInAs structure
with two layers of self-organised InAs QDs embedded in the InP

Halbleiterphysik Donnerstag
barrier. We observe definite peaks in the current and a modulations of α
as a function of the bias voltage.
HL 44.29 Do 16:30 Poster A
Electron Spin Decay Rates in single and coupled Quantum Dots
— •Johannes Voss and Daniela Pfannkuche — I. Institut für
Theoretische Physik, Universität Hamburg, Jungiusstr. 9, 20355 Hamburg,
Germany
Quantum systems with discrete spectra have become a field of both
experimental[1] and theoretical[2] research of particular interest for quantum
computing and electronics. Especially two level systems, e.g. the spin
of a single electron in a magnetic field, are suitable to represent qubits.
In this contribution we present numerical estimates for electron spin
decay rates in few electron quantum dots caused by hyperfine interaction
with the nuclear spins. For the calculations single quantum dots and laterally
coupled systems were considered. We investigate how the rates are
influenced by external magnetic fields and different forms of confining
potentials.
[1] R. Hanson et al., Phys. Rev. Lett. 91, 196802 (2003)
[2] A. Khaetskii, D. Loss, and L. Glazman, Phys. Rev. B 67, 195329
(2003)
HL 44.30 Do 16:30 Poster A
Strong magneto-resistance in double quantum dots due to
charge polarization — •Bernhard Wunsch 1 , David Jacob 2 , and
Daniela Pfannkuche 1 — 1 I. Institute of Theoretical Physics, University
of Hamburg, Jungiusstr. 9, D–20355 Hamburg, Germany —
2 Department of Applied Physics, University of Alicante, Cra San Vicente,
03690 San Vicente del Raspeig (Alicante), Spain
We report on magnetic field induced ground state crossings for vertically
coupled double quantum dots between states with same angular
momentum and spin but different isospin parity. In contrast to the
well known crossings between states of different angular momentum [1]
a crossing between states that differ only in parity can lead to a vertical
charge polarization.
We show that the polarization of the three electron ground state can be
detected in a transport experiment through the double quantum dot[2].
At the magnetic field, where originally the crossing occurred, we find a
strong suppression of the Coulomb peak associated with a transition between
two and three electrons in the double dot, due to the polarization
of the three electron ground state. Finally we want to point out, that for
a low electric field the mixing of the crossing states is very sensitive to
the magnetic field, which may prove to be useful for a realization of a
charge qubit in double quantum dots.
[1] H.Imamura and P. A.Maksysm and H.Aoki, Phys.Rev.B.59, 5817
(1999)
[2] S. Amaha and D. G. Austing and Y. Tokura and K. Muraki and
K. Ono and S.Tarucha, Solid State Commun. 119, 183 (2001)
HL 44.31 Do 16:30 Poster A
Thermoelectrical properties of single quantum dots — •Ralf
Scheibner, Hartmut Buhmann, and Laurens W. Molenkamp —
Experimentelle Physik III, Universität Würzburg
We analyze the thermoelectrical properties of lateral single quantum
dots in the coulomb blockade regime. For measuring the thermopower it
is necessary to apply a temperature gradient across the device. This is
achieved by an electron gas heating technique. The ability to tune the
temperature of the whole system and the coupling of the quantum dot
to the leads allows us to investigate the sequential, the cotunneling as
well as the Kondo regime. Temperature dependent measurements show
a crossover between the sequential and the cotunneling regime that we
compare with the calculations from [1]. In the Kondo regime the comparison
of conductance and thermopower measurements shows deviations
from Mott’s law suggesting a possible contribution of the electronic spin
entropy to the total entropy current that is the likely source of enhanced
thermopower in Co oxides [2].
[1] M.Turek and K.A. Matveev, ArXiv: cond-mat/ 0112445.
[2] Y. Wang, et.al., Nature, 423, 425, (2003).
HL 44.32 Do 16:30 Poster A
Classical and quantum-mechanical behavior of the magnetoresistance
in open quantum dots — •Roland Brunner 1 ,
Ronald Meisels 1 , Friedemar Kuchar 1 , Mohamed Elhassan 2 ,
Jon Bird 2 , and Koji Ishibashi 3 — 1 Department of Physics, University
of Leoben, Austria — 2 Department of Elecctrical Engineering, ASU,
USA — 3 Semiconductor Laboratory, Saitama, Riken, Japan
We report on the investigation of ballistic magneto-transport in open
AlGaAs/GaAs dots and its response to microwaves in the frequency range
around 50 GHz. The results allow to distinguish between backscattering
peaks and Shubnikov-de-Haas oscillations in the transition range from
classical to quantum-mechanical behaviour. /par A particularly interesting
aspect of the physics of quantum dots regards the crossover from the
classical to the quantum-mechanical regime in open dots. In this contribution
we focus on the behaviour exhibited by open quantum dots in low
and medium magnetic fields. Open quantum dots are strongly coupled
to the 2DEG reservoirs via short constrictions. /par The experiments
were carried out in an array of three dots which were defined by contiguous
finger gate structures on top of a two dimensional electron system
in AlGaAs/GaAs using electron beam lithography. The connections to
neighbouring dots and to the 2DEG reservoirs are made by constrictions
(lithographic width 70 nm). The electronic dot diameter was determined
to be 185 nm. The experimental results are discussed with respect to
quasi-classical and quantum-mechanical calculations. Work supported by
FWF, project 15513, Austria.
HL 44.33 Do 16:30 Poster A
Fluorescence and Scattering Properties of Composites made
from Gold and Semicoductor Nanoparticles — •Melanie M.
de Souza, Eric Dulkeith, Gunar Raschke, Andrey L. Rogach,
Thomas A. Klar, and Jochen Feldmann — Photonics
and Optoelectronics Group, Department of Physics and CeNS, Ludwig-
Maximilians -Universität, Amalienstr. 54 D-80799 Munich, Germany
In the last decade there has been considerable interest in the field of
nanostructured materials. Intense research has centred on controlling the
surface properties of both metal and semiconductor nanoparticles (NPs)
to determine the surface/property relationships. Here we report on a
composite system comprising of stable colliods of both metal (Au) and
semiconductor (CdTe) NPs in solutions. In this composite system we observe
both efficient quenching of CdTe NP fluorescence and a change in
the scattering spectra of Au NPs. By creating well-defined spacer units
between nanoparticles (through the self-assembly of polyelectrolyte films
or the formation of a covalent bond) the distance-dependent fluorescence
of CdTe NPs is also investigated.
HL 44.34 Do 16:30 Poster A
Experimental indications for coherent coupling of two quantum
dots — •Gerhard Ortner 1 , M. Bayer 1 , A.V. Larionov 1 , I. Yugova
1 , G. Baldassarri H.v.H. 1 , P. Hawrylak 2 , S. Fafard 2 , and
Z. Wasilewski 2 — 1 Experimentelle Physik II, Otto-Hahn-Str. 4, 44221
Dortmund, Germany — 2 Institute of Microstructual Sciences, National
Research Council, Ottawa, K1AOR6, Canada
Semiconductor Quantum Dots (QDs) have attracted considerable interest
recently because of its potential for possible applications in quantum
information processing. For this purpose a quantum gate which entangles
the states of two quantum bits as the essential block of a quantum
processor is needed.
A pair of vertically aligned QDs has been suggested as a promising
candidate for an optically driven quantum gate. Recently the coherent
coupling of the exciton states in a single QD molecule due to tunneling
of carriers has been demonstrated in various experiments. These are:
anti-crossings in the fine structure of excitons in single QD molecules
and diamagnetic shifts in Faraday- and Voigt-configuration which depend
systematically on barrier width between the two dots. Similar systematic
dependences have been found for spin-splitting and biexciton properties
in single QD molecules.
HL 44.35 Do 16:30 Poster A
Tight-Binding Modellierung von Halbleiterquantenpunkten —
•Stefan Schulz und Gerd Czycholl — Institut für Theoretische
Physik, Universität Bremen
Es werden die elektronischen Eigenschaften von Halbleiterquantenpunkten
mit Hilfe eines empirischen scp 3 a Tight-Binding (ETB) Modells,
bei Berücksichtigung übernächster Nachbarkopplung, untersucht.
Dadurch ist eine mikroskopische Behandlung dieser niederdimensionalen

Halbleiterphysik Donnerstag
Strukturen möglich.
Die Tight-Binding-Parameter werden durch Anpassen an Bandstrukturdaten
der Bulkmaterialien von CdSe und ZnSe bestimmt.
Ergebnisse für unterschiedliche Modellgeometrien eines CdSe Quantenpunktes
in einer ZnSe-Matrix werden vorgestellt. Des weiteren wird
das verwendete scp3 a-ETB-Modell mit einem ETB-Modell verglichen, welches
nur ein Leitungs- und ein Valenzband beinhaltet. Auf diese Weise
kann untersucht werden, welchen Einfluß die Berücksichtigung mehrerer
Bänder auf die elektronischen Eigenschaften der CdSe Quantenpunkte
hat.
Die Ergebnisse des ETB-Modells werden mit denen eines Modells mit
effektivem Einschlußpotential verglichen.
HL 44.36 Do 16:30 Poster A
Influence of size and shell on blinking dynamic of CdSe quantum
dots — •Kirill V. Anikin 1 , Andrei Yu. Kobitski 1 , Colin
D. Heyes 1 , Vladimir V. Breus 1 , and G. Ulrich Nienhaus 1,2 —
1 Department of Biophysics, University of Ulm, D - 89069 Ulm, Germany
— 2 Department of Physics, University of Illinois Urbana-Champaign,
Urbana, IL 61801, USA
Quantum dots are promising for many scientific and industrial applications,
one of which is using them as fluorescence labels in the study
of biological species by means of single molecule spectroscopy. They are
bright, posses the possibility to change the emission color by variation of
size, can be made biocompatible, and are much more photostable than
commercially available dyes. However, they have a disadvantage which is
intrinsic for single molecules: blinking, the intermission of luminescence
intensity under CW excitation.
In this work we perform a systematic study of the blinking dynamics
(on/off-time distribution) of single uncapped CdSe QDs and capped
CdSe/ZnS core-shell QDs immobilized in a poly(methyl methacrylate)
(PMMA) matrix as a function of core size, thickness of shell(from 0 to 4
monolayers) and excitation intensity to understand the basic mechanisms
governing the blinking. As method of investigation we have chosen Total
Internal Reflection Fluorescence Microscopy (TIRFM) because this technique
provides the advantage of recording the time-resolved fluorescent
signal of many single QDs simultaneously, thus allowing data with high
statistical confidence to be obtained in a relatively short time.
HL 44.37 Do 16:30 Poster A
Strained GaAs/InAlAs single quantum wire structures with
high confinement energies — •R. Schuster 1 , H. Hajak 1 , M.
Reinwald 1 , W. Wegscheider 1 , D. Schuh 2 , M. Bichler 2 , S. Birner
2 und G. Abstreiter 2 — 1 Institut für Experimentelle und Angewandte
Physik, Universität Regensburg, 93040 Regensburg, Germany —
2 Walter Schottky Institut, Technische Universität München, Am Coulombwall,
85748 Garching, Germany
Purely strain induced single quantum wires (QWRs) form where an
(011) oriented quantum well (QW) is subject to lateral strain variations
due to InAlAs stressor films which were introduced in the [100] direction.
These structures were fabricated by molecular beam epitaxy employing
the cleaved edge overgrowth technique. A systematic study of the dependence
of the confinement on the widths of the overgrown and the stressor
layer is carried out by using the high spectral and spatial resolution of
a micro-photoluminescence setup. By reducing the the excitation power,
the confinement energy can be enhanced to 51.5 meV. For all excitation
powers, smooth line shapes of the photoluminescence peaks indicate
the absence of pronounced exciton localization. In plane polarization is
expected and observed for the light emitted by the QW, whereas the
QWR signals are preferably polarized perpendicular to the QW plane.
The strain distribution in these structures is numerically simulated in order
to optimize the strain induced confinement. This work is supported
by the Deutsche Forschungsgemeinschaft in the framework of SFB 348.
HL 44.38 Do 16:30 Poster A
Spektroskopie einzelner InAs-Quantenpunkte mit AlAs-
Barrieren — •L. Karsten, G. Chilla, T. Brocke, F. Wilde, C.
Schüller, A. Bolz, Ch. Heyn und D. Heitmann — Institut für
Angewandte Physik der Universität Hamburg, Jungiusstraße 11, 20355
Hamburg
Die Herstellung von Quantenpunkten (QP), deren Photolumineszenz
im sichtbaren Wellenlängenbereich liegt, ist technologisch interessant z.B.
zur Herstellung von QP-Lasern für den sichtbaren Bereich, erleichtern
aber auch die Spektroskopie einzelner QPe, weil typische Detektoren in
diesem Bereich empfindlicher sind. Das InAs/AlAs-QP-System erreicht
die Blauverschiebung durch kleinere QP, eine energetisch höhere Barriere
und eine höhere Bandlücke in den QP durch einen Aluminiumanteil im
InAs. Mit einem Mikrophotolumineszenzaufbau und mit Hilfe von Nanoaperturen
mit 230nm Durchmesser in einer Schattenmaske können
wir einzelne QP spektroskopieren. Die Spektren zeigen eine typische
Signatur aus drei Linien in Energieintervallen von 3meV. Eine lineare
Abhängigkeit der Intensität von der Anregungsdichte deutet darauf
hin, dass die Linien Rekombinationen aus einfachen Exzitonenkomplexen
sind. Eine quadratische Abhängigkeit, wie sie für Biexzitonen erwartet
wird, wurde nicht beobachtet. In Photolumineszenzanregungsspektroskopie
beobachten wir eine effiziente Phonon-unterstützte Anregung und bei
höheren Energien eine kontinuierliche Hintergrundabsorption.
Die Arbeit wird durch die DFG im Rahmen des SFB 508 unterstützt.
HL 44.39 Do 16:30 Poster A
Damping of Rabi oscillations in quantum dots due to carrierphonon
resonance — •Pawe̷l Machnikowski, Vollrath Martin
Axt, and Tilmann Kuhn — Institut für Festkörpertheorie, Universität
Münster, Wilhelm-Klemm-Str. 10, 48149 Münster
We describe the dynamics of an exciton in an InAs/GaAs quantum dot
under coherent optical excitation in the presence of coupling to lattice
modes (acoustical and optical phonons). We show that the interaction
between the confined carriers and the surrounding lattice under external
driving of the carrier dynamics has a dynamical, resonant character.
By solving the non-Markovian Master equation for the reduced density
matrix of the carrier subsystem (in Born approximation, i.e. including
one-phonon effects) we find the dot occupation upon excitation with a
Gaussian pulse of fixed duration and varying amplitude. Coupling to lattice
modes reduces the amplitude of these oscillations, the effect being
small for short pulses and increasing for longer pulses. However, for still
longer pulses, the quality of Rabi oscillation again improves. We show
that only for long pulses a truly coherent control is realized, while short
pulses drive the system through unstable (decohering) states, corresponding
to non-equilibrium lattice state. We show that the damping of Rabi
oscillations is due to a resonance between the induced carrier dynamics
and the lattice modes.
HL 44.40 Do 16:30 Poster A
Ramanspektroskopie an stark tunnelgekoppelten Quantendrähten
— •A.F. Dethlefsen, D. Heitmann, Ch. Heyn und C.
Schüller — IAP Institut für Angewandte Physik und Zentrum für
Mikrostrukturforschung, Universität Hamburg
Mit Hilfe der inelastischen Lichtstreuung (Raman-Spektroskopie) werden
von uns kollektive elektronische Anregungen in doppellagigen vertikal
tunnelgekoppelten Quantendrähten untersucht. Hierbei handelt es sich
um mittels holografischer Lithografie definierte tiefmesageätzte GaAs-
Doppel-Quantendrähte mit starker Kopplung. Durch Metallisierung der
strukturierten Oberflächen und Definition eines Rückkontaktes zu den
Elektronensystemen lassen sich diese durch Anlegen eines äußeren Feldes
manipulieren.
Wir haben sowohl die Spannungs- als auch die Wellenvektorabhängigkeit
von kollektiven akustischen und optischen Intra- und
Intersubband-Anregungen untersucht. Insbesondere beobachten wir
auch Anregungen, die wir als akustische und optische Spindichteanregungen
interpretieren. Die Energien dieser Anregungen sind maßgeblich
durch die Interlayer-Austausch-Wechselwirkung beeinflusst. Eine
diskontinuierliche Energieänderung der Anregungen unter Variation der
Ladungsträgerdichte deutet auf eine spontane Pseudospinpolarisation
hin.
Diese Arbeit wird durch das BMBF gefördert.
HL 44.41 Do 16:30 Poster A
Selective binding of a peptide to semiconductor surfaces —
•Karsten Goede, Peter Busch, and Marius Grundmann — Faculty
of Physics and Geosciences, Universität Leipzig, Germany
Self-orgainzed hybrid nanostructures of anorganic semiconductors and
organic molecules are being increasingly investigated. Possible future
applications, such as bio-sensors and nanoscale electronic or optoelectronic
devices, are based on the understanding of the molecular attachment
process. This work is focussed on the attachment of a 12-mer peptide
to various III-V and group-IV semiconductor surfaces (GaAs, AlAs,
GaP, InP, Si, Ge) on the nanometer scale. Tapping-mode atomic force
microscopy reveals clearly varying attachment properties of the different
surfaces. The semiconductor-specific area coverages are reproducibly

Halbleiterphysik Donnerstag
found to cover more than two orders of magnitude. These quantitative results
will be discussed with respect to chemical and structural properties
of both the semiconductors and the peptide. Measuring the phase-lag signal
of the probing tip offers further insight into the size-dependent cluster
properties on the surface. The dependence of the attachment result on
the peptide concentration in solution and the surface washing process
will also be presented.
HL 44.42 Do 16:30 Poster A
INVESTIGATIONS OF 3C-SiC GROWTH ON Si (001) —
•Mohamed Torche 1 , Klaus Mueller 1 , Karsten Henkel 1 ,
Grzegorz Lupina 1 , Andrey Goryako 1 , Jürgen Wollweber 2 ,
and Dieter Schmeisser 1 — 1 BTU Cottbus, Angewandte Physik-
Sensorik, 03013 Cottbus, P.O.Box 101344, Germany — 2 Institut für
Kristallzüchtung, Adlershof, Berlin
Carbide was grown on Si (001) - substrates with supply of C2H2. Investigation
of the interface Si/SiC (buffer layer) is essential for optimized
preparation conditions, leading to a high quality of the growing SiC crystal.
In addition to the lattice mismatch of 20 per cent between Si and
SiC, which causes defects like dislocations or stacking faults, the chemical
homogeneity of this layer is important. XPS was used to characterize the
first state of SiC crystal growth on the Si substrate. Carbonizing with
C2H2 leads to surface reactions which build up the buffer layer. By using
electron spectroscopy, it was possible to characterize the SiC/Si (001)
buffer layer, depending on the following reaction parameters: Tsubstrate
, PC2H2 , PH2 , the ratio of pressures and the reaction time. The measurements
were performed in terms of the content of carbide, oxide and
roughness/etching-efficiency (Profilometer) for the reaction parameters
above. We found, that the most critical parameter is the temperature of
the substrate (Tsubstrate).
HL 44.43 Do 16:30 Poster A
Elektronische Eigenschaften schneller Phasenwechsellegierungen
— •Henning Dieker, Iris Klöcker, Wojciech We̷lnic, Daniel
Severin und Matthias Wuttig — I. Physikalisches Institut 1a,
RWTH-Aachen
Chalkogenidlegierungsschichten, die Anwendung in wiederbeschreibbaren
optischen Datenspeichern wie CD-RW oder DVD±RW finden, zeigen
neben einem starken optischen Kontrast zwischen der kristallinen
und der amorphen Phase einen noch ausgeprägteren Unterschied der
Widerstände der beiden Phasen. Daher sind diese Legierungen die Kandidaten
für künftige nicht flüchtige elektronische Speicher auf resistiver
Basis, die sogenannte OUM/Phase-Change RAM Technologie. Die geeigneten
Legierungen fallen alle in den Bereich der IV-VI Halbleiter. Unsere
Bandstrukturrechnungen auf Basis der Dichtefunktionaltheorie zeigen
dabei systematische Trends in Abhängigkeit der Stöchiometrie auf. Parallel
dazu wird die Stöchiometrieabhängigkeit durch Messung der optischen
Bandlücke, der Aktivierungsbarriere für den elektronischen Transport
sowie der Photolumineszenz an amorphen und kristallinen Schichten
bestätigt. Dieses systematische Verständnis ermöglicht die Auswahl der
optimalen Legierung für die jeweilige Anwendung.
HL 44.44 Do 16:30 Poster A
Elektrische Eigenschaften von Gold in plastisch verformten Silizium
— •Oliver Voß 1 , Vitaly Kveder 2 , Wolfgang Schröter 1 ,
Karsten Thiel 1 und Michael Seibt 1 — 1 IV. Physikalisches Institut
der Universität Göttingen, Tammannstr. 1, 37077 Göttingen — 2 Institute
of Solid State Physics, Russian Academy of Science, Chernogolovka,
142432 Moscow reg., Russland
Unter Ausnutzung der Diffusionseigenschaften von Gold in plastisch
verformtem Silizium konnten unterschiedlich stark golddotierte Bereiche
einer n-Siliziumprobe mittels DLTS untersucht werden. Neben den
wohlbekannten Maxima des DLTS-Spektrums von versetzungshaltigem
Silizium zeigte das Spektrum mit höherer Goldkonzentration ein Maximum,
das bei geringerer Konzentration nicht aufgelöst werden konnte.
Die Punktdefekteigenschaften dieses Maximums sind vergleichbar denen
des Gold-Akzeptorniveaus. Außerdem zeigt es das Verhalten eines Punktdefektes
mit Einfangbarriere.
HL 44.45 Do 16:30 Poster A
Effect of the magnetic field on tunnel ionization of deep impurities
by terahertz radiation — •Sergey N. Danilov, S.D.
Ganichev, J. Zimmermann, and W. Prettl — Institut für Experimentelle
und Angewandte Physik, Universität Regensburg, 93040 Regensburg
A suppression of tunnelling ionization of deep impurities in terahertz
frequency electric fields by an external magnetic field is observed. It is
shown that the ionization probability at external magnetic field, B, oriented
perpendicular to the electric field of terahertz radiation, E, is substantially
smaller than that at B � E. The effect occurs at low temperatures
and high magnetic fields demonstrating, that the tunnelling carrier
has a semiclassical trajectory below the tunnelling barrier being affected
by the Lorentz force.
HL 44.46 Do 16:30 Poster A
Experimentelle Bestimmung der Rashba- und Dresselhaus-
Beiträge zur Spin-Bahn-Wechselwirkung — •Petra Schneider
1 , S. D. Ganichev 1 , V. V. Bel’kov 2 , S. Giglberger 1 , E.
L. Ivchenko 2 , L. E. Golub 2 , W. Wegscheider 1 , D. Weiss 1
und W. Prettl 1 — 1 Institut für Experimentelle und Angewandte
Physik, Universität Regensburg, 93040 Regensburg — 2 A. F. Ioffe
Physico-Technical Institute, 194021 St. Petersburg, Russland
Es wird die experimentelle Bestimmung des relativen Verhältnisses
der Rashba- und Dresselhaus-Terme, durch welche die Spin-Bahn-
Wechselwirkung in Halbleiter Quantentrogstrukturen beschrieben wird,
an n-leitenden InAs Quantentrögen präsentiert. Eine neue Messtechnik
soll dargestellt werden, die sich die Winkelabhängigkeit des spingalvanischen
Effekts und des zirkular photogalvanischen Effekts zunutze
macht. Das Verhältnis der Rashba- und Dresselhaus-Koeffizienten kann
direkt anhand des Experiments bestimmt werden und bedarf keinerlei
durch die Theorie berechneten Größen. Aufgrunddessen eröffnen unsere
Experimente einen neuen Weg, die verschiedenen Beiträge zur Spin-
Bahn-Wechselwirkung auf einfache Art und Weise zu bestimmen.
HL 44.47 Do 16:30 Poster A
Magnetotransport in doped GaAsN and GaInNAs layers — •J.
Teubert, P.J. Klar, W. Heimbrodt, K. Volz, and W. Stolz —
FB Physik und WZMW, Philipps-Universität, Marburg
Incorporation of small amounts of nitrogen into GaAs and GaInAs
results in large changes of the electronic properties of these materials.
Whereas the optical properties are already extensively studied, there is
only little knowledge about the effects of nitrogen incorporation onto the
electronic transport behaviour of these III-V alloys. Magnetoresistance
(MR) and Hall measurements at temperatures between 2 and 280K and
fields up to 10T show large negative MR effects and anomalous Hall
effects for n-type samples whereas p-type samples behave like conventional
III-V alloys. This can be explained qualitatively with the energetic
and spatial disorder induced by N in the conduction band. We present
first magnetotransport measurements under hydrostatic pressure up to
20kbar for n-type GaNAs samples with low N concentrations. In these
samples applying hydrostatic pressure allows one to tune the energetic
positions of the localized N-cluster states with respect to the conduction
band edge. The effects on the transport properties are discussed.
HL 44.48 Do 16:30 Poster A
Monolithisch Integrierte Module als Konzentrator-Solarzellen
— •Rüdiger Löckenhoff 1 , Sascha van Riesen 1,2 und Andreas
Bett 1 — 1 Fraunhofer-Institut für Solare Energiesysteme ISE, Heidenhofstr.
2, 79110 Freiburg i. Br. — 2 Freiburger Materialforschungszentrum,
Stefan-Meier-Straße 21, D79104 Freiburg i. Br.
Hocheffiziente GaAs-Solarzellen sind im allgemeinen zu teuer für die
Stromerzeugung auf der Erde. Sie können allerdings mit Silizium konkurrieren,
wenn sie unter konzentriertem Sonnenlicht betrieben werden.
Günstige Hohlspiegel oder Linsen ersetzen dann teure Zellfläche.
Wird aber das Licht eines großen Parabolspiegels auf eine einzige
Zelle konzentriert, lassen sich die entstehenden großen Ströme nicht
mehr abführen. Dieses Problem lässt sich durch die serielle Verschaltung
schmaler Einzelsegmente zu einem ” Monolithisch Integrierten Modul“
(MIM) auf einem gemeinsamen semi-isolierenden Substrat lösen.
Bei vervielfachter Spannung wird der Strom dann von der Fläche eines
Segments bestimmt.
Am Fraunhofer ISE wurden MIMs mit Wirkungsgraden bis über 20%
bei 10V Spannung hergestellt. Erste MIMs auf der Basis von noch effizienteren
Tandem-Zellen wurden realisiert. Ziel sind hohe Wirkungsgrade
bei einer Konzentration von 1000 Sonnen und letztendlich ein Feldversuch.
Das Funktionsprinzip und die Herstellungstechnologie der MIMs sowie
die auf MIMs angepassten Charakterisierungsverfahren sollen auf diesem
Poster vorgestellt werden.

Halbleiterphysik Donnerstag
HL 44.49 Do 16:30 Poster A
PAC Untersuchungen an Seltenen Erden Sonden in GaN und
ZnO — •R. Nédélec 1 , R. Vianden 1 und die ISOLDE Kollaboration
2 — 1 Helmholtz - Institut für Strahlen- und Kernphysik, Nußallee
14–16, 53115 Bonn — 2 ISOLDE, CERN, CH-1211 Genève 23
Halbleiter mit großer Bandlücke, wie die Gruppe-III-Nitride und Zinkoxid,
haben in den letzten zehn Jahren enorm an Bedeutung gewonnen.
Für die Anwendung in der Optoelektronik sowie Hochleistungs- und
Hochtemperaturelektronik ist eine Strukturierung der Bauelemente mittels
Ionenimplantation von Vorteil.
Nach Dotierung von Halbleitern mit großer Bandlücke (insbesondere
GaN [1]) mit verschiedenen Seltenen Erden konnten Lumineszenzeffekte
in unterschiedlichen Wellenlängenbereichen des sichtbaren Spektrums
beobachtet werden.
Wir zeigen erste Ergebnisse der Untersuchungen zum Ausheilprozess
der Implantationsschäden sowie der temperaturabhängigen Messungen
mit der Methode der gestörten γ-γ-Winkelkorrelation (PAC). Dazu verwenden
wir die 91–1094keV Kaskade der PAC-Sonde 172-Lu(172-Yb).
[1] A.J. Steckl, J.M. Zavada, MRS Bulletin, Sept. 1999, p. 33
HL 44.50 Do 16:30 Poster A
Photoluminescence of GaAs/AlGaAs heterostructures grown in
a manganese contaminated MBE system — •Klaus Wagenhuber,
Hans-Peter Tranitz, Matthias Reinwald, and Werner
Wegscheider — Institut für Experimentelle und Angewandte Physik,
Universität Regensburg, Universitätsstr. 31, D-93053 Regensburg
Photoluminescence is a highly sensitive tool for the detection of residual
impurities in semiconductor crystals. We used this technique to determine
the quality of modulation doped single interface (MDSI) Al-
GaAs/GaAs structures. The samples were grown in an MBE chamber,
which is also used for the epitaxy of GaMnAs layers. Manganese on a
gallium-site forms a shallow acceptor level at about 0.11 eV above the
top of the GaAs valence Band. Due to free-to-bound and donor-acceptor
pair transitions a characteristic emission band appears at a well-known
position of the luminescence spectrum. Our samples exhibit bright and
narrow excitonic recombination lines in the PL-signal but even at high
excitation densities no manganese peak could be observed. That leads
to the conclusion that these layers are, to a high degree, free of the unwanted
manganese impurity. Magneto-transport measurements show low
temperature electron mobilities in excess of 5 · 10 6 cm 2 /Vs and thus confirm
these results.
This work is supported by BMBF Verbundprojekt ” Spinelektronik und
Spinoptoelektronik in Halbleitern“
HL 44.51 Do 16:30 Poster A
Phonon modes and infrared dielectric functions of Cu-, Fe-,
Ga-, Li-, N-, P-, Sb-doped ZnO thin films — •Carsten Bundesmann,
Mathias Schubert, Holger von Wenckstern, Michael
Lorenz, Evgeni Kaidashev, and Marius Grundmann — Fakultät
für Physik und Geowissenschaften, Institut für Experimentelle Physik II,
Universität Leipzig, Linnéstraße 5, 04103 Leipzig
Raman spectroscopy and mid-infrared spectroscopic ellipsometry was
applied to study Cu-, Fe-, Ga-, Li-, N-, P-, Sb-doped ZnO thin films
deposited on differently orientated sapphire substrates using the pulsed
laser deposition technique. Raman spectroscopy reveals additional modes
related to the different dopant species, while spectroscopic ellipsometry
allows the determination of wave numbers and broadening parameters
of the ZnO-type phonon modes, and free charge carrier parameters. The
broadening parameters are closely related to the thin film quality. Furthermore,
infrared spectroscopic ellipsometry can be used to determine
crystal orientation as shown for ZnO thin films grown on a-plane oriented
sapphire.
[1] C. Bundesmann et al., Appl. Phys. Lett. 83, 1974 (2003)
HL 44.52 Do 16:30 Poster A
Well-width dependent electron spin dephasing in (110) GaAs
QWs — •Stefanie Döhrmann 1 , Maik Begoin 1 , Dieter Schuh 2 ,
Max Bichler 2 , Daniel Hägele 1 , and Michael Oestreich 1
— 1 Universität Hannover, Institut für Festkörperphysik, Abteilung
Nanostrukturen, Appelstr. 2, 30167 Hannover — 2 Technische Universität
München, Walter-Schottky-Institut, Am Coulombwall, 85748 Garching
Recently the electron spin in semiconductors has become a focus of
intense research in the context of spintronics. A prime condition for the
development of potential applications is the understanding of spin decoherence
in semiconductor structures. We have measured spin dephasing
times in (110) GaAs quantum wells (QWs) in dependence on well width
in a temperature range from 6 to 300 K. The sample under investigation
is an undoped, wedge shaped GaAs/AlGaAs multiple quantum well
grown on (110) oriented substrate. The electron spin dephasing times
were determined by means of time and polarization resolved photoluminescence
spectroscopy using a synchroscan streakcamera for detection.
HL 44.53 Do 16:30 Poster A
Electron spin dephasing in biased GaAs quantum wells —
•Joachim Fritzsche 1 , Jörg Rudolph 1 , Daniel Hägele 1 , Markus
Beck 2 , Stefan Malzer 2 , Gottfried Döhler 2 und Michael
Oestreich 1 — 1 Institut für Festkörperphysik, Universität Hannover,
Appelstr. 2, D-30167 Hannover — 2 Institut für Technische Physik I, Universität
Erlangen-Nürnberg, Erwin-Rommel-Str. 1, D-91058 Erlangen
Electron spin dephasing times are of basic interest in the course of
”spintronics” and its potential for applications. One important spindephasing
mechanism depends on electron hole exchange interaction which
is determined by the overlap of electron and hole wavefunctions and,
therefore, can be tuned by external electric fields.
We measure electron spin dephasing times in a biased GaAs quantum
well in dependence of temperature and electric field applied perpendicular
to the layers. The sample consists of a single undoped 20 nm
GaAs quantum well sandwiched between 100 nm Al0.35Ga0.65As barriers.
Electron and holes are excited by ps-pulses of an 80 MHz mode-locked
Ti:Sapphire laser. Electron spin dephasing times are determined by time
and polarization-resolved photoluminescence which is detected by a
synchroscan streakcamera.
HL 44.54 Do 16:30 Poster A
Charge carriers in columnar nanostructures of porous GaAs and
InP using micro-Raman scattering — •Pavel Prunici 1 , Gert
Irmer 1 , Jochen Monecke 1 , and Ivan Tiginyanu 2 — 1 Institut für
Theoretische Physik, TU Bergakademie Freiberg, Bernhard-von-Cotta-
Str. 4, D-090596 Freiberg, Germany — 2 Institute of Applied Physics,
Technical University of Moldova, Boulevard Stefan cel Mare 168, MD-
2004 Chisinau, Moldova
Raman scattering spectra of columnar nanostructures of porous GaAs
and InP were investigated at room temperature and at 77 K using different
laser excitation wavelengths in the visible and in the near infrared
region. The samples have two layers with different porosity structures
which were well characterized by scanning electron microscope. In the
case of porous GaAs the cylinders have radii in the range of 50-100 nm
and about 10000 nm long. The radii of the InP cylinders are in the
range of 25-50 nm. The distribution of the charge carriers in individual
cylinders as well as in groups of well-oriented parallel cylinders was studied
using micro-Raman scattering. The bands observed are compared
with calculations predicting coupled LO-phonon-plasmon and coupled
Fröhlich-plasmon modes using a dielectric function derived on the basis
of an appropriate two-dimensional effective-medium theory.
HL 44.55 Do 16:30 Poster A
BxGa1−x−yInyAs und InxGa1−xNyAs1−y als neuartige Absorbermaterialien
in Dünnschichtsolarzellen — •Claudia Krahmer,
Gunnar Leibiger, Helmut Herrnberger und Volker Gottschalch
— Universität Leipzig, Institut für Anorganische Chemie, Linnestr.
3, 04103 Leipzig
(BGaIn)As- und (InGa)(NAs)- Mischkristalle, gitterangepasst
an (001) GaAs-Substrate, sind infolge der Reduzierung der
Bandlückenenergie gegenüber GaAs potentielle Absorbermaterialien
für Dünnschichtsolarzellen.
Mittels MOVPE (Metallorganische Gasphasen-Epitaxie) wurde unter
Verwendung von Trimethylgallium, Trimethylindium, Triethylbor,
Dimethylhydrazin, Diethylzink und Disilan p- und n- leitendes
BxGa1−x−yInyAs und InxGa1−xNyAs1−y bei 550 ◦ C bzw. 560 ◦ C auf GaAs
abgeschieden. Der Einfluss des Zn- und Si- Einbaus auf das epitaktische
Wachstum konnte ermittelt werden.
Die veränderten Solarzelleneigenschaften bei Verwendung von
(InGa)(NAs)- bzw. (BGaIn)As- Absorberschichten werden diskutiert. Als
Vergleich dienten GaAs- Solarzellen verschiedener Struktur, die im Hinblick
auf die Optimierung der Zellen gezüchtet wurden.

Halbleiterphysik Donnerstag
HL 44.56 Do 16:30 Poster A
Intrinsische C-Dotierung von AlGaAs — •Volker Gottschalch
1 , Gunnar Leibiger 1 , Gabriele Benndorf 2 und
Dietmar Hirsch 3 — 1 Universität Leipzig, Institut für Anorganische
Chemie, Linnestr. 3, 04103 Leipzig — 2 Universität Leipzig, Institut für
Experimentelle Physik II, Linnestr. 5 , 04103 Leipzig — 3 Leibniz-Institut
für Oberflächenmodifizierung e.V, Permoserstr. 15, 04303 Leipzig
Bei der MOVPE kann die intrinsische C-Dotierung zur Erzielung hoher
Löcherkonzentrationen und definierter Dotierungsprofile genutzt werden.
Wir haben den C-Einbau bei der MOVPE von AlxGa1−xAs
in Abhängigkeit der Mischkristallzusammensetzung, der
Züchtungstemperatur und des V/III-Verhältnisses im System
TMGa, TMAl, AsH3, bzw. TBAs untersucht. Die Charakterisierung
des epitaktischen Materials erfolgte mittels Doppelkristalldiffraktometrie,
Hallmessungen, Photolumineszenz, Ellipsometrie,
Transmissionselektronen- und Kraftmikroskopie.
Löcherkonzentrationen von 10 18 bis 10 20 cm −3 konnten durch eine Variation
des V/III-Verhältnisses von 50 bis 3 und der Wachstumstemperatur
zwischen 600 und 540 ◦ C reproduzierbar eingestellt werden. Ein Zusammenhang
zwischen dem C-Einbau und der Mischkristallzusammensetzung
wurde beobachtet.
Die erhalten Laserdaten an Doppel-QW-Strukturen (λ ∼ 1200 nm)
mit Zn- bzw. C-dotierten Mantelschichten werden diskutiert.
HL 44.57 Do 16:30 Poster A
Ellipsometrie an C-dotiertem AlGaAs: Grundlagen und Anwendungen
— •Gunnar Leibiger 1 , Volker Gottschalch 1 und Tino
Hofmann 2 — 1 Universität Leipzig, Institut für Anorganische Chemie,
Linnestr. 3, 04103 Leipzig — 2 Universität Leipzig, Institut für Experimentelle
Physik II, Linnestr. 5, 04103 Leipzig
Die intrinsische C-Dotierung von MOVPE-gewachsenen AlGaAs-
Schichten ermöglicht die Erzielung abrupter Dotierungsprofile und bietet
damit eine interessante Alternative zur p-Dotierung mittels Zink.
Die Bestimmung der Aluminium-Konzentration dieser Schichten ist
wegen des zusätzlichen C-Einbaus mittels Röntgenbeugung allein nicht
möglich. In dieser Arbeit wird ein Verfahren zur Bestimmung der Aluminiumkonzentration
vorgestellt, das auf der Verschiebung des kritischen
Punktes E1 beruht. Dazu wurden alle Schichten mittels Ellipsometrie
im infraroten bis ultravioletten Spektralbereich untersucht. Aus den
Infrarot-Ellipsometrie-Untersuchungen wurden Trägerkonzentrationen
und Beweglichkeiten gewonnen.
Anwendungen der untersuchten Schichten in Tunneldioden und als
Wellenleiterschichten in kantenemittierenden Laserdioden werden vorgestellt.
Letztere werden verglichen mit entsprechenden Laserdioden, in
denen Zn-dotierte AlGaAs-Schichten als p-Wellenleiter fungieren.
HL 44.58 Do 16:30 Poster A
Wachstum von nadelförmigen III-V-Kristallen mittels MOV-
PE — •Jens Bauer 1 , Helmut Herrnberger 1 , Volker Gottschalch
1 und Gerald Wagner 2 — 1 Universität Leipzig, Institut für
Anorganische Chemie, Linnestr. 3, 04103 Leipzig — 2 Universität Leipzig,
Institut für Mineralogie, Kristallographie und Materialwissenschaft,
Scharnhorststr.20 , 04275 Leipzig
Die VLS-Methode (vapor-liquid-solid) ermöglicht die Abscheidung von
nadelförmigen Halbleiterstrukturen aus der Gasphase. Unter Verwendung
von Goldtropfen, die beim Schmelzen einer dünnen Goldschicht
selbstorganisiert entstehen, oder Ga- bzw. In-Tropfen, die sich insitu bei
niedrigem V/III-Verhältnis ausbilden, wurden auf verschiedenen Substraten
(GaAs, Ge, Si, Al2O3) GaAs- und InAs-Nadeln mit unterschiedlichem
Habitus und Durchmesser bis zu 200nm hergestellt. Der Einfluss
der Wachstumsbedingungen und der Tröpfchengröße auf die Morphologie
wird diskutiert. Mittels Transmissionselektronen-mikroskopie
und hochaufgelöster Transmissionselektronenmikroskopie konnte senkrecht
zur Wachstumsrichtung eine Stapelfehler- und Zwillingsbildung
nachgewiesen werden. Bei Durchstrahlung in Wachstumsrichtung ergab
sich eine perfekte Kristallstruktur.
HL 44.59 Do 16:30 Poster A
Berechnung der Leitfähigkeit von amorphen Nickelsilizid —
•Andre Löser — TU Chemnitz, Strasse der Nationen 62, 09111 Chemnitz
Für unterschiedliche Strukturmodelle wurde die Leitfähigkeit von
amorphen Nickelsilizid im Rahmen eines Vielfachstreuansatzes für quasieindimensionale
Strukturen berechnet. Die Berechnung des Widerstandes
erfolgte mit einer verallgemeinerten Büttiker-Formel unter Einbeziehung
inkohärenter Streuung. In Abhängigkeit von der inkohärenten Streuung
wird die Leitfähigkeit der verschiedenen Strukturmodelle verglichen und
die kritische Nickelkonzentration bestimmt. Es werden die Unterschiede
im Einfluss der unordnungsinduzierten Kohärenzeffekte auf der metallischen
und isolierenden Seite des MIT diskutiert.
HL 44.60 Do 16:30 Poster A
Thermoelectric Properties of Disordered Systems — •A. Croy 1 ,
R.A. Römer 2 , A. MacKinnon 3 , and M. Schreiber 1 — 1 Institut für
Physik, Technische Universität Chemnitz, 09107 Chemnitz, Germany —
2 Dept. of Physics & Centre for Scientific Computing, University of Warwick,
Coventry CV4 7AL, UK — 3 Blackett Laboratory, Imperial College
London, London SW7 2BW, UK
The electronic properties of disordered systems have been the subject
of intense study for several decades. Thermoelectric properties, such as
thermopower and thermal conductivity, have been relatively neglected.
Based on the recursive Green’s function method [1] and the Chester-
Thellung-Kubo-Greenwood formula [2] we have developed an algorithm
for calculating all kinetic coefficients Lij on long strips or bars [3]. From
these we can deduce the electrical conductivity σ, the Seebeck and Peltier
coefficients S & Π and the thermal conductivity κ, as well as the Lorenz
number L0. We can realize strips or bars with different lattice types,
e.g. square, triangular or hexagonal lattices — useful for investigating
the properties of nanotubes. We present initial results for 1D, 2D and 3D
systems. In 1D we observe a Lorentzian distribution for the thermopower
which is modified by the presence of inelastic scattering. This could give
rise to non-negligible quantum fluctuations in macroscopic systems at
low temperatures.
[1] A. MacKinnon, Z. Phys. B59, 385 (1985)
[2] G. V. Chester, A. Thellung, Proc. Phys. Soc. London 77, 1005 (1961)
[3] R. A. Römer, A. MacKinnon, C. Villagonzalo, J. Phys. Soc. Jpn. 72
Suppl. A, 167–168 (2003)
HL 44.61 Do 16:30 Poster A
Computation of the local density of states for a 2D disordered
electron system — •Jorge Stephany 1,2 , Rudolf Römer 1 , and
Markus Morgenstern 3 — 1 Department of Physics and Centre for
Scientific Computing, University of Warwick,Coventry CV4 7AL, UK —
2 Departamento de Física, Universidad Simón Bolívar, Apartado 89000,
Caracas 1080A,Venezuela. — 3 Institute of Applied Physics, Hamburg
University, Jungiusstrasse 11, D-20355 Hamburg, Germany
The potential landscape for a 2D disordered electron system obtained
by depositing Fe atoms on the InAs(110) surface has been determined experimentally
[1]. We use this potential as the input to compute the local
density of states of this system by a direct diagonalization of the associated
Anderson localization hamiltonian using a modified Lanczos algorithm.
The result is then compared with the experimental local density
of states obtained by scanning tunneling spectroscopy. We next perform
the correspondig computation for the case in which an external magnetic
field is applied where Landau quantization has been recently observed[2].
[1] M.Morgenstern et al, Phys. Rev. Lett., 89, (2002) 136806
[2] M.Morgenstern et al, Phys. Rev. Lett., 90, (2003) 056804
HL 44.62 Do 16:30 Poster A
Der strukturelle Übergang zwischen c-Si/a-Ge entlang der
Grenzfläche — •Karsten Thiel 1 , Nikolai Borgardt 2 , Boris
Plikat 3 , Tore Niermann 1 und Michael Seibt 1 — 1 IV. Phys. Inst.
der Uni Göttingen und SFB 602, Tammannstr. 1, 37077 Göttingen —
2 Moscow Inst. of Electronic Technologie, 124498 Moscow, Russland —
3 Infineon Technologies, Regensburg
Der strukturelle Übergang zwischen amorphen und kristallinen Materialien
wird auf der Basis der hochauflösenden Transmissionselektronenmikroskopie
(HRTEM) mittels einer Methode, die die Mittelung der
Abbildungen entlang der Grenzfläche beinhaltet, am System c-Si/a-Ge
untersucht. Diese gemittelten Abbildungen können unter Verwendung einer
zwei-dimensionalen Verteilungsfunktion, die auf der amorphen Seite
durch die mittlere atomare Dichte an der Grenze und auf der kristallinen
Seite durch die bekannten Positionen der Atome beschrieben wird,
mittels konventioneller Verfahren simuliert werden.
Durch Verschieben des Mittelungsbereiches und Variationen in der
Grösse ist es desweiteren möglich, Informationen über den Verlauf des
Übergangs entlang der Grenze zu erhalten.
Es zeigt sich, dass das amorphe Germanium lagenartig auf dem kristallinen
Substrat aufwächst. Dabei ist die erste Lage homogen entlang
der Grenzfläche verteilt und kann als tetragonal verspanntes kristalli-

Halbleiterphysik Donnerstag
nes Germanium aufgefasst werden. Laterale Variationen im strukturellen
Übergang machen sich im Wesentlichen in der zweiten und dritten Lage
bemerkbar.
[1] N.I. Borgardt et al., Ultramicroscopy 90 (2002), 241.
HL 44.63 Do 16:30 Poster A
Reifung von Versetzungsringen in Silizium während Aluminiumgettern
— •Carsten Rudolf, Yue-Lin Huang und Michael
Seibt — IV. Physikalisches Institut der Universität Göttingen, Tammannstrasse
1, D-37077 Göttingen, Deutschland
Wir haben die Reifung von extrinsischen Versetzungsringen in Si
während Aluminiumgettern (AlG) untersucht. Das Ziel war herauszufinden,
ob beim AlG an der Grenzfläche zwischen der Al:Si-Schmelze
Eigenfehlstellen entstehen und in das Si-Substrat eindiffundieren.
Extrinsische Versetzungsringe sind Ausscheidungen von Eigenzwischengitteratomen
und reagieren auf Ströme von Eigenfehlstellen durch
Wachstum oder Schrumpfen. Mit Dunkelfeld-Transmissionselektronenmikroskopie
haben wir die Anzahl der in den Versetzungsringen
gespeicherten Atome vor und nach AlG sowie in Referenzproben ohne
Al-Schicht in Abhängigkeit von der Dauer der Temperaturbehandlung
gemessen.
Der Vergleich der gegetterten Proben mit dem Ausgangsmaterial deutet
auf eine schwache Injektion von Eigenzwischengitteratomen hin. Die
Messungen an den Referenzproben zeigen allerdings eine vergleichbare
Injektion, so dass sich insgesamt schließen lässt, dass das AlG die Konzentration
von Eigenfehlstellen nicht wesentlich beeinflusst.
HL 44.64 Do 16:30 Poster A
UHV-wafer bonding of heterostructure semiconductor materials
using low energy hydrogen ion beam surface cleaning
— •Nasser Razek 1 , Axel Schindler 1 , Volker Gottschalch 2 ,
Gerald Wagner 3 , and Bernd Rauschenbach 1 — 1 Leibniz-Institut
für Oberflächenmodifizierung e. V., Permoserstrasse 15, D-04318 Leipzig,
Germany — 2 Universität Leipzig, Institut für Anorganische Chemie,
Linnestr. 3, 04103 Leipzig — 3 Institut für Nichtklassische Chemie e. V.,
Permoserstr. 15, 04318 Leipzig, Germany
A room temperature wafer bonding process without applying external
pressure based on low energy hydrogen ion beam (300 eV) surface cleaning
has been studied for GaAs and other III-V-semiconductors. Successful
bonding has also been performed between III-V-wafers and Si or Ge, respectively.
X-ray photoelectron spectroscopy, atomic force microscopy,
ultrasonic microscopy, HR-TEM cross section, photoluminescence and
electrical characterization and post-processing steps were performed to
evaluate the ion beam treated surfaces and the formed bonded interfaces.
HL 44.65 Do 16:30 Poster A
Inhomogeneities in Au:GaAs(110) Schottky Barriers Studied
with Cross-sectional Scanning Tunneling Spectroscopy —
T.C.G. Reusch, •M. Wenderoth, and R. G. Ulbrich — IV.
Physikalisches Institut, Universität Göttingen, D-37077 Göttingen
Inhomogeneities in Au:GaAs(110) Schottky barriers have been investigated
with Cross-Sectional Scanning Tunnelling Spectroscopy. The influence
of metal-induced gap states and the electrostatic potential of
the depletion layer are visible in spatially resolved measurements. The
electrostatic potential of the depletion layer shifts the current onsets in
the tunneling spectra. By extracting the shift and from comparison with
simulations, we are able to map variations in the local electrostatic potential
in the depletion layer parallel and perpendicular to the interface
on a near-atomic scale. This information is complementary to Ballistic
Electron Emission Microscopy. The extracted SBH is in the range of 690
meV , which is somewhat smaller than the reported SBH of 950 meV for
Au:GaAs(110) contacts prepared under similar conditions. The observed
fluctuations of the potential at the interface of 2σ ≈ 60 meV are in good
accordance with reported values of BEEM investigations.
HL 44.66 Do 16:30 Poster A
Time-Resolved THz Spectroscopy Of Graphite Sheets —
•Tobias Kampfrath, Luca Perfetti, Christian Frischkorn,
and Martin Wolf — Fachbereich Physik der Freien Universität
Berlin, Arnimallee 14, 14195 Berlin
Pump-and-probe transmission measurements were performed with approximately
30 nm thick highly oriented pyrolitic graphite sheets at
room temperature in air. The sample was excited by a pump pulse centered
at 775 nm. A delayed probe pulse probed the linear optical re-
sponse parallel to the basal plane in a frequency range from about 10
to 30 THz. The field-resolved sampling of the probe pulses allows for
the determination of the temporally changing in-plane component of the
dielectric function. Data analysis shows that the transient signal decays
on timescales of 200 fs and 2 ps, respectively, which we attribute to
carrier relaxation.
HL 44.67 Do 16:30 Poster A
Optical properties of pulsed-laser deposited carbon films —
•P.V. Tolstykh 1 , S.P. Sernov 1 , V.K. Goncharov 2 , M.V. Puzyrou
2 , S. Shokhovets 3 , and G. Gobsch 3 — 1 BNTU Minsk, Skaryna
Prosp. 65, 220027 Minsk, Belarus — 2 Institute of Applied Physics Problems,
Kurchatov Str. 7, 220064 Minsk, Belarus — 3 Institute of Physics,
TU Ilmenau, PF 100565, 98684 Ilmenau, Germany
Optical properties (refractive index n and extinction coefficient k) in a
spectral region from 1.2 eV to 5.5 eV and the thickness d of thin carbon
films were determined by spectroscopic ellipsometry and optical transmission
measurements. The films were deposited on different substrates
(quartz, silicon and bronze) by sputtering of a graphite target placed in
a vacuum chamber (residual gas pressure was 1.3 mPa) using a Nd-glass
laser with wavelength and pulse duration of 1060 nm and 30 ns, respectively.
We studied the dependence of n, k and d on the laser pulse energy
(2 J to 8 J, 100 laser pulses) and the substrate temperature (295 K to
500 K) during the deposition. Further, we compare the properties of the
studied films with those of amorphous hydrogenated diamond-like and
arc-evaporated carbon films and discuss correlations between their optical,
structural and mechanical properties, as well as optimum conditions
for growing films suitable for different applications.
HL 44.68 Do 16:30 Poster A
Undercooling and Solidification of Liquid Silicon — •C. Panofen
1 , R.P. Liu 2 , G. Lohöfer 1 und D.H. Herlach 1 — 1 Institut für
Raumsimulation, DLR, Köln — 2 Yanshan University, Qinhuangdao, P.R.
China
Containerless processing by electromagnetic and electrostatic levitation
techniques was applied to undercool and solidify pure Si melts in a
high purity environment. Without surrounding crucible walls we achieved
large undercoolings of up to 330K below the melting point due to the
reduction of heterogeneous nucleation sites. A pyrometric sensor measured
the sample temperature contactlessly. We stimulated crystallization
by triggering with a silicon wafer at the desired undercooling. The velocity
of the solidification front as a function of undercooling was directly
determined by photo sensors and a high speed camera. We analyzed the
growth behavior within current theories of crystal growth in undercooled
melts. Special emphasis was placed to a microstructure transition from
faceted to dendritic growth. The results of the growth measurements
were correlated to microstructure formation upon undercooling prior to
solidification.
This work was supported by DFG under contract No. HE1601/16-1
and the Sino-German Science Center Beijing.
HL 44.69 Do 16:30 Poster A
Züchtung von Silizium-Nanowhiskern mittels Molekularstrahlepitaxie
(MBE) — •Luise Schubert, Peter Werner,
Nikolai Zakharov, Gerhard Gerth, Vadim Talalaev und
Ulrich Gösele — Max-Planck-Institut für Mikrostrukturphysik,
06120 Halle
Das Interesse an der Züchtung und Anwendung von Halbleiter-
Nanostrukturen ist in den vergangenen Jahren stark gestiegen. Wir
präsentieren die Möglichkeit, Si- Nanowhisker mittels Molekularstrahlepitaxie
(MBE) erfolgreich herzustellen. Vor der Si-Abscheidung wurden
die (111)-Silizium Substrate mit Gold bedampft, welches in Form von
Clustern auf der Substratoberfläche als Keime für das Whiskerwachstum
dient. Die bereits bekannte Wachstumstheorie, der sogenannte ”vaporliquid-solid”-
Mechanismus (VLS), liegt in dieser Art der Herstellung in
einer abgewandelten Form vor. Die Strukturen wurden mittels SEM und
TEM analysiert. Dabei kann gezeigt werden, dass die Länge mit der Breite
der Whisker korreliert. Der modifizierte VLS-Wachstumsmechanismus
wird diskutiert.

Halbleiterphysik Donnerstag
HL 44.70 Do 16:30 Poster A
Übergangsmetall-Donator Paare in Si — •R. Vianden 1 , D.
Brett 2 , A. Byrne 3 und M. Ridgway 2 — 1 Helmholtz-Institut für
Strahlen- und Kernphysik, Nußallee 14-16, D-53115 Bonn — 2 Dep.
of Electronic Materials Engineering — 3 Dep. of Nuclear Physics,
RSPhysSE, Australian National University, Canberra ACT 0200,
Australia
Die Wechselwirkungen zwischen Übergangsmetallverunreinigungen
und Dotierungsatomen können die Funktion von Halbleiterbauelementen
gravierend beeinflussen. Da die Löslichkeit der Übergangsmetalle in
Halbleitern wie Si und Ge sehr klein ist, ist es oft unmöglich, ihr Verhalten
mit klassischen Methoden zu beobachten. Die Methode der gestörten
γ-γ Winkelkorrelation (PAC) kommt dagegen mit extrem geringen Fremdatomkonzentrationen
aus. Wir haben das PAC-Sondenatom 100 Pd in As
dotiertes Silizium implantiert, um die Wechselwirkung geringer Pd Verunreinigungen
mit den Donatoratomen zu beobachten. Erste Ergebnisse
zeigen, dass bis zu 30% der Pd Sonden an As Donatoratomen eingefangen
werden. Die beobachtete Quadrupolwechselwirkung, νQ = 10,2(1) MHz,
η = 0 und eine 〈111〉 Orientierung des elektrischen Feldgradienten legen
den Einbau auf einem dem As benachbarten substitutionellen Gitterplatz
nahe.
HL 44.71 Do 16:30 Poster A
Ab-initio investigation of the high-pressure phase transition
cd→β-tin under nonhydrostatic pressure in Si and Ge —
•Katalin Gaál-Nagy and Dieter Strauch — Institut für
Theoretische Physik, Universität Regensburg, 93040 Regensburg
In this contribution we present an ab-initio study of the high-pressure
phase transition from the cubic-diamond (cd) to the β-tin phase in Si and
Ge. Our main interest is here the influence of non-hydrostatic pressure
to the transition. In a first step we calculated the full curve of the equation
of state from a enthalpy surface including energies and enthalpies for
the complete set of parameters which are allowed to vary. This the H(p)
curve is calculated by evaluating the hydrostatic pressure concerning the
components of the diagonal stress tensor beeing equal. Next a similar procedure
can be done for non-equal components for non-hydrostatic pressure.
Last we included the effect of strain in our calculations. We find
an essentual lowering of the transition pressure under non-hydrostatic
conditions. The calculations were performed within the framework of
the density functional theory using ultrasoft pseudopotentials and the
local density as well as the generalized gradient approximation for the
exchange-correlation potential implemented in VASP [1].
[1] G. Kresse, J. Furthmüller, Comput. Mat. Scie. 6, 15 (1996)
HL 44.72 Do 16:30 Poster A
Hydrogen-induced platelets in Ge — •Martin Hiller, Edward
Lavrov, and Jörg Weber — Institut für Angewandte Physik - Halbleiterphysik,
TU Dresden, 01062 Dresden
Germanium treated in hydrogen and/or deuterium plasmas has been
investigated by means of Raman scattering at RT. Two Raman lines
at ∼ 2000 and 4150 cm −1 are observed after H-plasma treatment at
150 ◦ C. The former is identified as local vibrational modes (LVMs) of
Ge–H bonds, whereas the latter was shown to originate from a LVM of
H2. Polarization Raman measurements revealed that both lines possess
a trigonal symmetry. Based on this and the similarity of the two signals
in Ge and Si we identify the 2000 cm −1 line as hydrogen-induced {111}
platelets, whereas the 4150 cm −1 line belongs to H2 trapped within these
platelets.
HL 44.73 Do 16:30 Poster A
XRD analysis of Ge- and GexSi1−x-layers grown by surfactant
mediated epitaxy — •T. Wietler and K.R. Hofmann — Institute
for Semiconductor Devices and Electronic Materials, University of
Hannover, Appelstr. 11A, 30167 Hannover, Germany
Strained Si/Ge-heterodevices provide the opportunity to combine enhanced
carrier mobilities with silicon technology. The controlled growth
of relaxed virtual GexSi1−x substrates with high Ge content is a vital precondition
for the fabrication of strained layer structures. By surfactant
mediated epitaxy (SME) employing Sb as surfactant relaxed GexSi1−x
films can be realized.
GexSi1−x films with Ge content variying from x=0.7 to 1 were grown
by SME on Si(111) substrates. The crystalline quality and the degree
of strain relaxation were studied by high resolution X-ray diffraction
(HXRD). X-Ray reflection (XRR) was used to measure the surface roughness
and film thickness. The X-ray analysis results are compared to those
obtained by etch pit density (EPD), auger electron spectroscopy (AES)
depth profiling and atomic force microscopy (AFM).
HL 44.74 Do 16:30 Poster A
Contactless determination of temperature variations in single
junction thermal converters — •V. Schlosser 1 , G. Heine 2 , W.
Waldmann 2 , M. Garcocz 2 , and G. Klinger 3 — 1 Institut für Materialphysik,
Universität Wien — 2 Bundesamt für Eich- und Vermessungswesen,
Wien — 3 Institut für Meteorologie und Geophysik, Universität Wien
The ac-dc transfer standard is one of the basic electrical standards,
by which the ac voltage and ac current are deduced from their dc counterparts.
A well established method is the comparison of electric power
between ac- and dc- voltage by converting the power to force or heat.
Converters may be recognised as reference standard and the system is
called the ”ac-dc transfer standard”. Differences in the signal between
ac- and dc- power generation depend on frequency and waveform. In
the low frequency regime the thermal ripple dominates the error introduced
by the thermal converter. The purpose of this work was to develop
an experimental set up which is capable to record the time dependend
temperature fluctuations caused by ac- currents. The infrared radiation
which is emitted by the heated filament and bead of a thermal converter
was monitored using a scanning infrared radiation imaging set up. The
method will be presented and first results will be discussed.
HL 44.75 Do 16:30 Poster A
Investigations of the local and temporal temperature changes
in precision shunt resistors — •G. Klinger 1 , V. Schlosser 2 , G.
Heine 3 , W. Waldmann 3 , and M. Garcocz 3 — 1 Institut für Meteorologie
und Geophysik, Universität Wien — 2 Institut für Materialphysik,
Universität Wien — 3 Bundesamt für Eich- und Vermessungswesen, Wien
The most accurate determination of alternating electrical currents or
voltages is based on a comparison with direct current measurements
which can be resolved with a far higher precision. A widely used method
is the conversion of the electric power to heat in a thermal converter.
Because the range of thermal converters is restricted to currents below
15 mA and voltages of less than 3 V higher currents and voltages are
measured by a step-up transformation. In the case of high currents precision
shunt resistors are used. The knowledge of the temporal and spatial
temperature distribution of the resistor during operation is an essential
prerequisite to (i) perform an error correction and to (ii) optimize the
design of the resistor. In the present work we used a thermo camera to
investigate the temperature distribution of shunt resistors. Additional
measurements with thermo couples were carried out in order to correct
measurement deviations caused by optical surface properties. The results
of the measurements and model calculations of the resistor’s temperature
dependence will be discussed.
HL 44.76 Do 16:30 Poster A
Herstellung und Vermessung von lateralen p-n-Übergängen —
C. Werner, D. Reuter, A.D. Wieck, •C. Werner, D. Reuter
und A.D. Wieck — Lehrstuhl für Angewandte Festkörperphysik der
Ruhr-Universität Bochum
Wir haben auf Basis von Al0,33Ga0,67As/In0,1Ga0,9As/GaAs-
Heterostrukturen laterale p-n-Übergänge erzeugt, indem wir eine in der
MBE gewachsene und mit Kohlenstoff modulationsdotierte Heterostruktur
überkompensiert haben. Dieses geschieht durch lokale Implantation
von Silizium-Atomen in einer Anlage zur Erzeugung fokussierter Ionenstrahlen.
Für laterale p-n-Übergänge wurden interessante Voraussagen
bezüglich des Verhaltens der Ausbreitung der Verarmungszone und
der Sperrschichtkapazität als Funktion der angelegten Sperrspannung
gemacht. So sollte sich die Verarmungszone linear mit der Sperrspannung
ausbreiten [1, 2]. Um dies nachzuprüfen, wurde an diesen Proben der
optisch induzierte Sperrstrom gemessen und daraus die Länge der
Verarmungszone bestimmt. Die Sperrschichtkapazität hingegen sollte
nur sehr schwach von der Sperrspannung abhängen [2]. Dieses wurde
mittels Kapazitätsmessungen überprüft.
[1] U. Dötsch, A.D. Wieck, Nanodevices produced with focussed ion
beams, Nuclear Instruments and Methods in Physics Research B 139, 12
(1998)
[2] A.Sh. Achoyan et al., Two-Dimensional p-n Junction under Equlibrium
Conditions, Semiconductors 36, 903 (2002)

Halbleiterphysik Donnerstag
HL 44.77 Do 16:30 Poster A
Local bandgap modulation of AlGaAs grown on patterned
GaAs substrates — •Wolfgang Limmer, Karl Bitzer, and Rolf
Sauer — Abteilung Halbleiterphysik, Universität Ulm, D-89069 Ulm
The growth of AlGaAs layers on patterned GaAs(001) substrates by
molecular-beam epitaxy is strongly determined by the interfacet surface
migration of Ga adatoms, leading to a pronounced variation of the local
Al concentration. Taking advantage of this migration process, we
have overgrown mesa structures, that consist of intersecting stripes or
partially overlapping squares, to obtain a local maximum or minimum,
respectively, of the AlGaAs bandgap on top of the mesas. While the surface
morphologies were imaged by scanning electron microscopy, the local
Al concentrations and thus the local AlGaAs bandgaps were mapped by
spatially resolved micro-photoluminescence spectroscopy.
HL 44.78 Do 16:30 Poster A
Lateral resolution for two-dimensional electron gas fabrication
by overgrowth of implantation doped AlxGa1−xAs — •Christof
Riedesel, Dirk Reuter, and Andreas D. Wieck — Angewandte
Festkörperphysik, Ruhr-Universität Bochum, Universtitätsstr. 150,
44780 Bochum
We use the technique of molecular beam epitaxy (MBE) overgrowth of
focused ion beam (FIB) implanted AlxGa1−xAs to fabricate laterally patterned
two-dimensional electron gases (2DEGs) [1]. Having established
a process that yields pure 2DEGs with high electron mobilities up to
1.5x10 6 cm2/V s [2], in this contribution we will present investigations on
the lateral resolution of the process.
Although FIB lithography offers the possibility to introduce the
dopants laterally resolved into the heterostructure, so far no successful
fabrication of sub-micron patterned 2DEGs has been reported for this
approach. Our experiments have shown that the resolution of the process
is not solely determined by the beam diameter of the ion beam but is
strongly affected by the thermal treatment used to cure implantation
damage and activate the ions electrically. By optimizing the annealing
conditions we have achieved a lateral resolution of less than 500 nm.
Financial support of the German Federal Ministry of Education and
Research via grant No. 01BM908/6 is gratefully acknowledged.
[1] H. Arimoto, A. Kawano, H. Kitada, A. Endoh, and T. Fujii, J. Vac.
Sci. Technol. B 9 (1991) 2679.
[2] D. Reuter, C. Riedesel, P. Schafmeister, C. Meier, and A.D. Wieck,
Appl. Phys. Lett. 82 (2003) 481.
HL 44.79 Do 16:30 Poster A
Characterization of crack-free and relaxed bulk-like GaN grown
on 2” sapphire — •A. Kasic 1 , D. Gogova 1 , H. Larsson 1 , C.
Hemmingsson 1 , I. Ivanov 1 , B. Monemar 1 , C. Bundesmann 2 , M.
Schubert 2 , and M. Heuken 3 — 1 Linköping University, Department of
Physics and Measurement Technology, S-581 83 Linköping, Sweden —
2 Universität Leipzig, Institut für Experimentelle Physik II, Linnéstr. 5,
D-04103 Leipzig — 3 Aixtron AG, Kackerstraße 15-17, D-52072 Aachen
We demonstrate the growth of high-quality and stress-free bulk-like (300-
µm-thick) GaN by hydride vapor phase epitaxy (HVPE) in a vertical
atmospheric-pressure reactor. The crystalline quality and the residual
stress in the 2” GaN wafer were investigated by various characterization
techniques. The lateral homogeneity of the wafer was monitored by
low-temperature photoluminescence mapping. Precise µ-Raman scattering
profiling measurements provide the vertical strain distribution and
the evolution of the crystalline quality with increasing film thickness. The
high crystalline quality on the Ga-face was proved by high-resolution Xray
diffraction and photoluminescence measurements. The position of the
main near-band-gap photoluminescence line and the phonon spectra obtained
by infrared spectroscopic ellipsometry show consistently that the
2” crack-free GaN is virtually stress-free over a diameter of approximately
4 cm.
Such GaN material can serve as a substrate for further homoepitaxial
strain-relaxed and crack-free growth needed for fabrication of device
structures.
HL 44.80 Do 16:30 Poster A
Infrared and VIS/UV optical properties of GaN/AlN superlattices
grown on Si substrate — •A. Kasic 1 , B. Monemar 1 ,
M. Schubert 2 , A. Dadgar 3 , F. Schulze 3 , and A. Krost 3 —
1 Linköping University, Department of Physics and Measurement Technology,
S-581 83 Linköping, Sweden — 2 Universität Leipzig, Institut
für Experimentelle Physik II, Linnéstr. 5, 04103 Leipzig — 3 Otto-von-
Guericke-Universität Magdeburg, Institut für Experimentelle Physik,
Universitätsplatz 2, 39016 Magdeburg
We report optical properties of 20-period GaN/AlN superlattice (SL)
structures from the mid-infrared to the ultraviolet spectral range. The
MOCVD-grown hexagonal SL structures with effective Al-content of 24%
were either intentionally undoped, Si- or Mg-doped, and deposited on Si
substrate using SiN in-situ masks and AlN interlayers.
Infrared ellipsometry spectra reveal a superlattice-related LO phonon
mode of A1 symmetry, which is subject to a distinct blue shift towards
the respective value for AlN with increasing SL sublayer dimensions. Information
on the SL strain is extracted from the phonon modes of the
GaN- and AlN-SL sublayers.
Regarding the SL’s as effective homogeneous mediums, their UV dielectric
function properties are examined by spectroscopic ellipsometry.
Quantum-size affected electronic band-to-band-transitions of the superlattice
structures are observed and compared to photoluminescence measurements.
HL 44.81 Do 16:30 Poster A
Einbau von Phosphor in GaN auf Si(111) mittels MOVPE —
•Karsten Fehse, Armin Dadgar, Annette Diez, Fabian Schulze,
Thomas Hempel, Till Riemann, Peter Veit und Alois Krost
— Otto-von-Guericke Universität, Magdeburg, Institut für Experimentelle
Physik, Fakultät für Naturwissenschaften, Universitätsplatz 1, 39016
Magdeburg
Im Augenblick gibt es sehr wenige Erfahrungen zur Herstellung von
ternären GaN1−xPx Verbindungen. Lediglich zur Stickstoffdotierung von
GaP:N liegen Erfahrungen vor. Wir untersuchen den Einbau von Phosphor
in GaN mittels MOVPE. Es wurden GaN:P auf GaN/Si(111) gewachsen.
Photolumineszenz- und Kathodolumineszenzmessungen zeigen
starke Änderungen der Spektren in Abhängigkeit von der Wachstumstemperatur
und dem Phosphinangebot. XRD-Messungen und REM-
Aufnahmen der Oberflächenmorphologie zeigen einen deutlichen Umschwung
der strukturellen Eigenschaften aufgrund des unterschiedlich
starken Phosphoreinbaus. Anhand von TEM-Aufnahmen der GaN:P-
Proben wird das Einbauverhalten bei einem Phosphinangebot von 0.05 -
5ml/min bei 800 ◦ C bis 1100 ◦ C diskutiert.
HL 44.82 Do 16:30 Poster A
Photoelektrochemische Strukturierung von SiC und laterales
überwachsen mit GaN/AlxGa1−xN — •B. Postels, N. Riedel,
D. Fuhrmann, U. Rossow und A. Hangleiter — TU Braunschweig,
Inst. f. Techn. Physik, 38106 Braunschweig; b.postels@tu-bs.de
Laterales Wachstum erzielt eine Defektreduktion, die für eine
verlängerte Lebensdauer von blauen und ultravioletten Leuchtdiodenund
Lasern nötig ist. Hier wird laterales Wachstum auf strukturiertem
SiC betrachtet. Zur Strukturierung des chemisch sehr beständigen
SiC wurde ein photoelektrochemischer Ätzprozess entwickelt, wobei typischerweise
mit Schwefelsäure SiC in den Fenstern von Metallmasken oxidiert
wird. Das Oxid wird mit HF entfernt, wobei 1-2µm tiefe Gräben entstehen.
Durch Variation der Ätzbedingung wird versucht noch tiefere und
bessere Ätzprofile zu erhalten. Dabei scheinen Diffusionsprozesse im Elektrolyt
in der Nanostruktur des Oxids begrenzend zu sein. Die so erhaltenen
Stegstrukturen wurden mit GaN und AlxGa1−xN überwachsenen.
Bei GaN konnte laterales Wachstum ausgehend von den Stegseitenflächen
mit reduzierter Defektdichte und vollständiger Koaleszenz sowohl beim
undotierten als auch beim n-dotierten GaN festgestellt werden. Problematischer
war das überwachsen mit AlxGa1−xN, bei dem bei vergleichbaren
Wachstumsbedingungen eine geringere laterale Wachstumsrate festgestellt
wurde. Zudem ergab sich in Photolumineszenzuntersuchungen
deutlich separierte bandkantennahe Emissionen, die darauf hindeuten,
daß die Aluminiumkonzentrationen xAl in den lateral gewachsenen Bereichen
reduziert ist. Das Verhalten unterscheidet sich zwischen den Stegorientierungen
in [1¯100 und [11¯20] Richtung.

Halbleiterphysik Donnerstag
HL 44.83 Do 16:30 Poster A
Zusammensetzungsanalyse an getemperten InGaN-
Quantumwell-Strukturen mittels hochauflösender Transmissionselektronenmikroskopie
(HRTEM) — •C. Bilzer 1 , K.
Engl 1 , J. Zweck 1 , A. Leber 2 , A. Weimar 2 , A. Lell 2 und V.
Härle 2 — 1 Institut für Experimentelle und Angewandte Physik,
Universität Regensburg, Universitätsstr. 31, D-93053 Regensburg,
Germany — 2 OSRAM Opto Semiconductors GmbH, Wernerwerkstr. 2,
D-93049 Regensburg, Germany
Die Eigenschaften von Halbleiterlasern auf GaN-Basis hängen wesentlich
vom Aufbau der aktiven Zone ab. Durch die Transmissionselektronenmikroskopie
wird die Abbildung der aktiven Zone mit atomarer
Auflösung ermöglicht. Die Auswertung entsprechender HRTEM
Abbildungen mittels des Software-Pakets DALI (Digital Analysis of
Lattice Images) [1] liefert aus den Gitterabständen den lokalen In-
Gehalt in den Quantumwells. Untersucht wurden Einfach- und Mehrfach-
Quantumwellstrukturen mit unterschiedlichem In-Gehalt. Insbesondere
wurde die Auswirkung von variierenden Temperschritten auf die Homogenität
der In-Verteilung in den Quantumwells analysiert.
[1] A. Rosenauer et al.: Optik 102(2), 63 (1996)
HL 44.84 Do 16:30 Poster A
TEM-Analyse zur Defektdichtereduzierung mittels in situ deponierten
SiNx Zwischenlagen in AlGaN/GaN-Heterostrukturen
auf SiC und Al2O3 — •M. Beer 1 , K. Engl 1 , J. Zweck 1 , S. Miller 2 ,
S. Bader 2 , G. Brüderl 2 , A. Lell 2 und V. Härle 2 — 1 Institut für
Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstr.
31, D-93053 Regensburg, Germany — 2 OSRAM Opto Semiconductors
GmbH, Wernerwerkstr. 2, D-93043 Regensburg, Germany
Bei standardmäßig mit MOVPE gewachsenen GaN-Heterostrukturen
auf SiC liegt die Versetzungsdichte im Bereich von 10 9 cm −2 . Für
blaue Laser mit guten Leistungsdaten und hoher Lebensdauer benötigt
man hohe kristalline Qualität und niedrige Versetzungsdichten. Eine
einfache Möglichkeit, die Versetzungsdichte bei MOVPE gewachsenen
GaN-Heterostrukturen zu reduzieren, ist das Einbringen einer SiNx-
Zwischenschicht in (Al)GaN. Die (Al)GaN-Oberfläche wird bei der
Behandlung mit NH3 und SiH4 teilweise mit SiNx bedeckt. Diese
bedeckten Bereiche werden wegen des geringeren Haftkoeffizienten von
(Al)GaN auf SiNx lateral überwachsen, was zur Auslöschung von
Versetzungen und somit zur Reduzierung der Versetzungsdichte führt.
Der Verlauf der Versetzungen und die Versetzungsdichte wurden mittels
TEM untersucht. Es zeigt sich eine Reduzierung der Versetzungsdichte
um ca. eine Größenordnung, die im wesentlichen auf die Reduzierung
von Stufenversetzungen zurückgeführt werden kann.
HL 44.85 Do 16:30 Poster A
Ultraschmale Linienbreiten von InGaN Quantenfilmemissionen
mit hochaufgelöster optischer Rasternahfeldspektroskopie —
•G. Klewer, F. Hitzel, U. Rossow und A. Hangleiter — Institut
für Technische Physik, Technische Universität Braunschweig, Mendelssohnstr.
2, D-38106 Braunschweig
Trotz industrieller Fertigung von InGaN basierten Lichtemittern gibt
es in diesem Materialsystem noch immer viele offene Fragen, eine davon
die Unwirksamkeit der Defekte als nichtstrahlende Rekombinationszentren.
In diesem Zusammenhang wurden derartige Strukturen bei tiefen
Temperaturen von etwa 20 K mit einem optischen Nahfeldmikroskop
(SNOM) untersucht. Dieses liefert einerseits eine sehr hohe örtliche
Auflösung und andererseits an jedem Punkt der Probe ein komplettes
optisches Spektrum. In vielen Fällen lieferte die Beobachtung mit dem
SNOM neben der Hauptemission von ca. 2,9 eV viele weitere Emissionen
mit Linienbreiten von ca. 2 nm, die allein durch das spektrale Auflösungsvermögen
der Apparatur begrenzt wurden. Diese liegen im Vergleich zur
Hauptemission etwa 150 - 200 meV höherenergetisch. Ebenso sind sie
lokal begrenzt, jede Emission tritt nur in einem kleinen Gebiet von ca.
200 - 300 nm Durchmesser auf. Aus anderen für diese Proben eher untypischen
Emissionsmerkmalen konnte eine räumliche Auflösung in der
Größenordnung von λ/10 festgestellt werden. Entgegen der landläufigen
Meinung, dass die Emission in InGaN Quantenfilmen von lokal begrenzten
Gebieten kleinerer Bandlücke herrührt, zeigen diese Messungen eher
ein entgegengesetztes Verhalten, nämlich dass in der Tat Gebiete andersartiger
Bandlücke existieren, diese aber eine größere Bandlücke besitzen.
HL 44.86 Do 16:30 Poster A
Growth of GaN on Si(111) by Molecular Beam Epitaxy —
•Ralph Meijers, Raffaella Calarco, and Hans Lüth — Institut
für Schichten und Grenzflächen (ISG-1) and cni - Center of Nanoelectronic
Systems for Information Technology , Forschungszentrum Jülich,
52425 Jülich, Germany
The growth of GaN on Si(111) substrate was performed by molecular
beam epitaxy (MBE) with an RF-plasma source. Different III-N flux
ratios and substrate temperatures were chosen as optimization parameters.
The layers were characterized with atomic force microscopy (AFM),
X-ray diffraction (XRD) and Rutherford backscattering measurements
(RBS). Significant improvement of the GaN properties was reached using
an AlN seed layer. First, few aluminium monolayers were deposited on
the Si substrate (Tsub=770 ◦ C), then nitrogen exposure followed to form
AlN, thus preventing amorphous silicon nitride formation on the clean
Si substrate. With the aim to provide a better lattice match for the subsequent
growth of GaN, an AlGaN interlayer with different thicknesses
and alloy composition was grown on top of the AlN nucleation layer. The
GaN on top was grown under different growth conditions. In conclusion
the AlN/AlGaN buffer layer improves the GaN growth on Si(111).
HL 44.87 Do 16:30 Poster A
TEM investigation on selforganized superlattice formation in
AlGaN on Si(111) — •Karl Engl, Andreas Able, Josef Zweck,
and Werner Wegscheider — Institut für Experimentelle und Angewandte
Physik, Universität Regensburg, Universitätsstr. 31, D-93053 Regensburg,
Germany
AlGaN/GaN heterostructures were grown on Si(111) substrates by
metal organic vapour phase epitaxy (MOVPE) to investigate the selforganized
superlattice formation in AlGaN. The samples were characterized
using high resolution transmission electron microscopy (HRTEM),
high resolution x-ray diffraction (HRXRD) and photoluminescence measurements.
We observe a formation of selforganized superlattices with
periods around 3.1nm. We present results on the influence of different
growth parameters on the selforganization in AlGaN layers and suggest
a model for the mechanism of selforganized superlattice formation.
HL 44.88 Do 16:30 Poster A
Epitaktisch gewachsene Palladium-Kontakte auf p-GaN
(0001) — •Andreas Tausendfreund, Jens Dennemarck, Tim
Böttcher, Sven Einfeldt und Detlef Hommel — Institut
für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, 28359
Bremen
Die Realisierung niederohmiger Kontakte auf p-GaN ist bis zum
heutigen Tag eine große technische Herausforderung. Die Vorbehandlung
der p-GaN-Oberfläche und die abschließende thermische Behandlung
der Kontakte spielen hierbei die wesentliche Rolle und werden
in dieser Arbeit systematisch untersucht. Zur Reinigung der in der
Metallorganischen Dampfphasenepitaxie (MOVPE) erzeugten p-GaN-
Oberflächen kamen verschiedene Naßätz- und Plasmareinigungsverfahren
zur Anwendung. Diese vorbehandelten Oberflächen wurden mit Hilfe
der Röntgen-Photoelektronen-Spektroskopie bezüglich Deoxidation und
Passivierung gegenüber Oxidation untersucht. Danach wurden dünne
Palladium-Filme verschiedener Dicke in der Molekularstrahlepitaxieanlage
(MBE) aufgebracht und deren Wachstum über Reflexionselektronenbeugung
(RHEED) und Rasterkraftmikroskopie (AFM) kontrolliert.
Es konnte gezeigt werden, dass ein relaxierter Palladium-Film epitaktisch
unter Bildung einer zweidimensionalen Terassenstruktur in (111)-
Richtung aufwächst. Die gewachsenen Palladium-Kontakte wurden mit
Gold bedampft und die gemessenen Kontaktwiderstände in Abhängigkeit
von der Vorbehandlung und der thermischen Nachbehandlung untersucht.
HL 44.89 Do 16:30 Poster A
Einfluss von AlN-Zwischenschichten auf die Lumineszenz von
InGaN-Filmen — •Anja Brostowski, Lars Reissmann, Andre
Strittmatter und Dieter Bimberg — Technische Universität
Berlin, Institut für Festköerperphysik, Sekr. PN 5-2, Hardenbergstr. 36,
10623 Berlin
Bauelement-relevante Schichtdicken von Nitrid-Heterostrukturen auf
Si-Substraten lassen sich bisher nur durch die Verwendung von AlN-
Zwischenschichten rissfrei herstellen. Andererseits fügen solche AlN-
Schichten große Diskontinuitäten in die Bandstruktur der Bauelemente
ein und nichtleitende Eigenschaften besitzen. Daher sind auch negative
Auswirkungen auf elektrische und optische Eigenschaften von

Halbleiterphysik Donnerstag
Bauelementen denkbar. Es ergibt sich die Frage der geeigneten Platzierung
dieser AlN-Schichten innerhalb einer Bauelement-Struktur, um
mit einer möglichst geringen Anzahl die Rissfreiheit der Struktur zu
gewährleisten. Wir haben die Abhängigkeit der Lumineszenzausbeute
von InGaN-Schichten von der Dicke und der Komposition einer über
einer AlN-Zwischenschicht gewachsenen AlGaN-Schicht untersucht. Bei
einer Schichtdicke von 100 nm GaN bricht die Lumineszenzintensität
HL 46 Hauptvortrag Hoenlein
gegenüber vergleichbaren Proben ein, die auf einem 900 nm dicken
GaN/AlGaN-Puffer ohne AlN-Zwischenschicht gewachsen wurden. Dagegen
erholt sich die Lumineszenzintensität der InGaN-Schicht wieder,
wenn auf die AlN-Schicht eine Kombination aus 200 nm AlGaN und 70
nm GaN abgeschieden wird. Als mögliche Ursachen dieser Abhängigkeit
werden piezoelektrische Effekte oder kristallographische Defekte vermutet.
Zeit: Freitag 10:15–11:00 Raum: H15
Hauptvortrag HL 46.1 Fr 10:15 H15
Carbon Nanotubes - A Successor to Silicon Technology? —
•Wolfgang Hoenlein, Franz Kreupl, Georg Duesberg, Andrew
Graham, Maik Liebau, Werner Pamler, Robert Seidel,
and Eugen Unger — Infineon Technologies AG, Corporate Research,
Otto-Hahn-Ring 6, D-81739 Muenchen
Carbon nanotubes (CNTs) are powerful candidates for both interconnects
and field-effect transistors with better performances than silicon
based devices. The CNTs can be selectively produced in microelectronics
compatible processes using catalyst mediated CVD growth. One promis-
HL 47 Quantendrähte und Korrelationseffekte
ing concept for the integration of CNT’s into the existing silicon technology
is the replacement of metal wires at places of critical current density.
The recent results from CNT field-effect transistor devices will be reviewed
and compared with state-of-the-art silicon devices. Further, ideal
and non-ideal CNT transistors have been simulated and their properties
compared with the expectations for the 2016 silicon transistor. Based
on this, a concept for a 3-dimensional CNT based technology will be
presented. We will also identify the key success factors of the silicon
technology and assess the emerging CNT technology with respect to the
mature silicon technology.
Zeit: Freitag 11:00–13:00 Raum: H15
HL 47.1 Fr 11:00 H15
Coulomb blockade and Non-Fermi-liquid behavior in quantum
dots — •Frithjof Anders 1 , Eran Lebanon 2 , and Avraham
Schiller 2 — 1 Insititut für Theoretische Physik, Universität Bremen,
Postfach 330 440, D-28334 Bremen — 2 Racah Institute of Physics, The
Hebrew University, Jerusalem 91904, Israel
The non-Fermi-liquid properties of an ultrasmall quantum dot coupled
to a lead and to a quantum box are investigated using a new variant of
Wilson’s numerical renormalization group. Below the charging energy of
the quantum box, a second screening channel is dynamically generated.
Tuning the ratio of the tunneling amplitudes to the lead and box, we
find a two-channel Kondo fixed point for arbitrary Coulomb repulsion on
the dot, proving that the two-channel Kondo effect is far more generic
to this setting than the original scenario of Oreg and Goldhaber-Gordon.
At T = 0, a step-like structure is found in the conductance of a twolead
setting, the height of which depends on the dot occupancy. The
temperature scale below which the two-channel Kondo effect sets in is
greatly enhanced away from the local-moment regime, making this effect
accessible in realistic devices.
HL 47.2 Fr 11:15 H15
Inducing field-free currents in mesoscopic rings — •Alex
Matos-Abiague and Jamal Berakdar — Max-Planck-Institut für
Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
We show theoretically that a sequence of two orthogonal linearly polarized
half-cycle pulses applied to a mesoscopic ballistic ring may induce
a non-equilibrium current. The post-pulses (and therefore field-free) current
lasts as long as the coherence is preserved. The dependence of the
sign and amplitude of the current on the different system parameters is
studied. The possibility of experimentally detecting the post-pulse current
is also discussed.
HL 47.3 Fr 11:30 H15
High frequency measurements on an AFM-structured quantum
point contact — •C. Fricke 1 , J. Regul 1 , F. Hohls 1 , R. J. Haug 1 ,
D. Reuter 2 , and A. D. Wiek 2 — 1 Institut für Festkörperphysik,
Abteilung Nanostrukturen, Universität Hannover — 2 Lehrstuhl für
Angewandte Festkörperphysik, Ruhr-Universität Bochum, 44780
Bochum, Germany
We fabricated a single quantum point contact by Atomic Force Microscope
(AFM) lithography. We used a diamond tip for structuring
the two dimensional electron gas (2DEG) realized by a GaAs/AlGaAsheterostructure.
The 2DEG is about 50 nm below the surface. Isolated
areas were written by about 10 nm deep lines. The quantum point contact
was designed for high frequency measurements using a special scheme
with strip-lines to source and drain contact and with nonmetallic in-
plane-gates.
Our measurements show the frequency dependence of the imaginary part
of the complex admittance between 100 and 400 MHz. Therefore a very
accurate measurement of the phase was necessary. The real part of the
admittance shows a good agreement with DC characterization. For the
imaginary part we observe a linear frequency dependence as expected by
theory.
HL 47.4 Fr 11:45 H15
Numerical calculation of electronic transport in molecular wires
— •Robert Dahlke and Ulrich Schollwöck — LMU – Sektion
Physik, Lehrstuhl von Delft, Theresienstr. 37, 80333 München
We present a numerical method for the calculation of electronic transport
through molecular systems. It combines quantum chemistry with a
scattering matrix approach to calculate a bias dependent transmission
function. The current is obtained by use of the Landauer formula. The
method can be used for STM-image calculations and can also be applied
for studying transport properties of molecular wires. We present results
for current/voltage calculations of self-assembled mono-layers of (1,4)phenylene
diisocyanide molecules attached to gold leads and compare
them to experimental data.
HL 47.5 Fr 12:00 H15
Spin-charge separation in one-dimensional quantum dots: nonlinear
transport and Negative Differential Conductance — •Fabio
Cavaliere 1,2 , Alessandro Braggio 2 , Juergen Stockburger 3 ,
Maura Sassetti 2 und Bernhard Kramer 1 — 1 I. Institut für Theoretische
Physik, Universität Hamburg, Hamburg — 2 Dipartimento di Fisica,
INFM-Lamia, Università di Genova, Genova, Italy — 3 II. Institut
für Theoretische Physik, universität Stuttgart, Stuttgart
The study and control of the spin degree of freedom is nowadays the
subject of many theoretical as well as experimental investigations. In few
electrons quantum dots, the spin selection rules are considered the cause
of the spin-blockade phenomenon [1] that leads to negative differential
conductance (NDC). In the present work [2] we find that in 1D quantum
dots the spin selection rules alone are not sufficient to give rise to NDC.
On the contrary, in the framework of the Luttinger liquid theory we find
that the separation of charge and spin degrees of freedom is responsible
for the emergence of NDC in quantum dots with asymmetric barriers.
The NDC phenomenon is related to the occupation of states with spin
higher than the one in the ground state, therefore the effect of spin-flip
relaxation processes is analyzed.
[1] D. Weinmann, et al. Phys. Rev. Lett 74, 984 (1995)
[2] F. Cavaliere et al. Submitted to Phys. Rev. Lett.

Halbleiterphysik Freitag
HL 47.6 Fr 12:15 H15
Realization of a new quantum wire structure fabricated by double
cleaved-edge overgrowth — •S. F. Roth, M. Grayson, M.
Bichler, D. Schuh, and G. Abstreiter — Walter Schottky Institut
TUM, 85748 Garching
We demonstrate a new quantum wire structure, in which the potential
over the whole length of the channel can be modulated with atomic
precision. Theory [1] shows, that if one exact potential barrier can be
introduced into the channel, the conductance obeys a power law in temperature.
With two barriers, effects associated with the Coulomb blockade
can be observed. Even a Mott-insulating state can be achieved by
inserting multiple barriers to modulate the potential periodically and
tuning the electron density with a gate. The geometry of our double
cleave wires is analogous to quantum wires grown by single cleaved-edge
overgrowth [2, 3], except that the channel is oriented along the substrate
growth direction. Therefore a variation in the substrate potential is directly
transferred to the adjacent quantum wire. The first step to realize
the more complicated structures mentioned above is to demonstrate a
simple quantum wire in this double cleave geometry. Preliminary results
show a conductance plateau at a value of about 2e 2 /h, which indicates
the existence of such a quantum wire. We will report on the behavior of
this feature with density, temperature and magnetic field.
[1] C. L. Kane, M. P. Fisher, Phys. Rev. B, 46, 15233 (1992)
[2] A. Yacoby, H. L. Stormer, N. S. Wingreen, L. N. Pfeiffer, K. W.
Baldwin and K. W. West, Phys. Rev. Lett., 77, 4612 (1996)
[3] M. Rother, Ph.D. thesis, Walter Schottky Institut TUM (1999)
HL 47.7 Fr 12:30 H15
Zur Streuung von Elektronen und Schallquanten in Quantendrähten
— •Frank Löcse — TU Chemnitz, Institut für Physik, 09107
Chemnitz
HL 48 Kohlenstoff/Diamant
Untersucht wird die Streuung von Elektronen und Schallquanten in
ballistischen und ungeordneten quasi-eindimensionalen Heterostrukturen
bei tiefen Temperaturen. Die zu diesem Zweck neu entwickelte semiklassische
Methode wird vorgestellt. Sowohl die analytischen als auch
die numerischen Ergebnisse zeigen, daß die Reduktion des Phasenraumes
eine Aufwertung der Streuprozesse im Hinblick auf den Energieumsatz
zur Folge hat. Die Streuung muß, im Gegensatz zur Elektronen-
Schallquanten Streuung in Bulk-Systemen, als inelastisch angesehen werden.
HL 47.8 Fr 12:45 H15
Theoretical prediction of a transport quantum logic gate —
•Matthias Sabathil and Peter Vogl — Walter Schottky Institut,
TU Muenchen
We present a systematic theoretical study of the realization of a quantum
logic gate based on a laterally structured high mobility 2DEG.
The realistic electronic structure has been calculated solving the 3D
Schroedinger-Poisson equation selfconsistently. For the prediction of the
transport properties we used the recently developed contact block reduction
(CBR) method that allows for the effiecient calculation of the
ballistic transmission for large 3D devices with multiple leads.
In ballistic quantum devices, a single Qubit may be realized by electrons
propagating within two adjacent quantum wires, representing the
0 and 1, respectively. Narrow windows in the barrier region between the
wires act as beam splitters, allowing the 0 and 1 states to interfer. Additional
gates are needed to control the phase shift within one of the
wires. Here, we propose a Mach-Zender type interferometer based on
an AlGaAs/GaAs high mobility 2DEG where the lateral confinement is
produced by top gates. We find that this device can operate up to a temperature
of several hundred mK. The calculations show a pronounced
switching behavior as a function of the applied gate voltage.
Zeit: Freitag 11:00–11:30 Raum: H17
HL 48.1 Fr 11:00 H17
Diamond based ion-sensitive field effect transitors — •Andreas
Härtl, Tobias Heimbeck, Jose Garrido, and Martin Stutzmann
— Walter Schottky Institut, Am Coulombwall 3, 85748 Garching
The surface termination of diamond by hydrogen induces a quasi twodimensional
hole accumulation directly at the surface with high carrier
concentrations (around 10 13 cm −2 ) and reasonable mobilities (50 - 100
cm 2 /V · s). This unique feature can be used for a novel design of ionsensitive
field effect transistor (ISFET) devices on diamond. The electrolyte
is in direct contact with the conductive channel. The species to
be detected interact with the surface of the diamond and change the resistance
of the hole channel. The sensitivity of these devices is expected
to be high due to the proximity of the electrolyte and the conductive
channel, in contrast to common silicon based devices, where an insulating
layer separates the electrolyte from the conductive channel. Other
advantages of diamond are its high degree of biocompatibility as well as
its large electrochemical potential window.
We have investigated ISFETs on H-terminated polycrystalline diamond.
With the surface completely hydrogenated, no pH-sensitivity was
found, whereas partially oxidized devices show pH-sensitivity with values
up to 70 mV/pH, exceeding the Nernst limit. Coulombic interaction between
surface adsorbates and charge carriers has tentatively been used to
HL 49 Spinabhängiger Transport III
explain this behaviour. With a suitable biofunctionalization of the surface,
the detection of enzymes, proteins and other biomolecules will be
possible.
HL 48.2 Fr 11:15 H17
Raman based structure assignment of Single-Walled Carbon
Nanotubes — •Hagen Telg 1 , Janina Maultzsch 1 , Stephanie
Reich 2 , Christian Thomsen 1 , and Frank Hennrich 3 — 1 Institut
für Festkörperphysik, Technische Universität Berlin, Germany —
2 Department of Engineering, University of Cambridge, United Kingdom
— 3 Institut für Physikalische Chemie, Universität Karlsruhe, Germany
Nanotube samples made by any method still contain all types of tubes
which differ in chiral angle and diameter. The radial breathing mode
(RBM), which strongly depends on the tube diameter, is frequently used
to determine the chiral angle of the tubes. We studied Raman spectra of
several samples varying in diameter distribution. We also distinguished
between isolated tubes in aqueous surfactant suspensions and bulk samples.
In order to obtain band gap information we took resonance profiles
for different energy regions in the visible. To assign the RBMs to a specific
nanotube type we compared our data with results from photoluminescence
measurements and theoretical predictions.
Zeit: Freitag 11:00–12:00 Raum: H13
HL 49.1 Fr 11:00 H13
Spin-Hall effect and anisotropic charge transport in semiconductors
— •John Schliemann, J. Carlos Egues, and Daniel Loss
— Department of Physics and Astronomy, University of Basel, Switzerland
In a two-dimensional electron gas as realized by a semiconductor quantum
well, the presence of spin-orbit coupling of both the Rashba and
Dresselhaus type leads to anisotropic dispersion relations and Fermi contours.
We study the effect of this anisotropy on the electrical conductivity
in the presence of fixed impurity scatterers. The conductivity also shows
in general an anisotropy which can be tuned by varying the Rashba coefficient.
This effect provides a method of detecting and investigating
spin-orbit coupling by measuring spin-unpolarized electrical currents in
the diffusive regime.
Moreover, we investigate the spin-Hall effect of both electrons and holes
in semiconductors using the Kubo formula in the correct zero-frequency
limit taking into account the finite momentum relaxation time of carriers
in real semiconductors. This approach allows to analyze the range of validity
of recent theoretical findings. In particular, the spin-Hall conductivity
vanishes for vanishing spin-orbit coupling if the correct zero-frequency

Halbleiterphysik Freitag
limit is performed.
References: J. Schliemann, J. C. Egues, and D. Loss, Phys. Rev. Lett.
90, 146801 (2003).
J. Schliemann and D. Loss, Phys. Rev. B 68, 165311 (2003).
J. Schliemann and D. Loss, cond-mat/0310108.
HL 49.2 Fr 11:15 H13
Two-dimensional hole precession in an all-semiconductor spin
field effect transistor — •Marco G. Pala 1,2 , Michele Governale
1,3 , Jürgen König 1,4 , Ulrich Zülicke 1,5 , and Giuseppe Iannaccone
2 — 1 Institut für Theoretische Festkörperphysik, Universität
Karlsruhe, Germany — 2 Dipartimento di Ingegneria dell’Informazione,
Università degli Studi di Pisa, Italy — 3 NEST-INFM & Scuola Normale
Superiore, Pisa, Italy — 4 Institut für Theoretische Physik III, Ruhr-
Universität Bochum, Germany — 5 Institute of Fundamental Sciences,
Massey University, New Zealand
We present a theoretical study of a spin field-effect transistor
[1] realized in a quantum well formed in a p–
doped ferromagnetic-semiconductor- nonmagnetic-semiconductorferromagnetic-semiconductor
hybrid structure. Based on an envelopefunction
approach for the hole bands, we derive the full theory of coherent
transport through the device, which includes both heavy- and light-hole
subbands, proper modeling of the mode matching at the interfaces,
integration over injection angles, Rashba spin precession [2], interference
effects due to multiple reflection, and gate-voltage dependence. [1]
S. Datta and B. Das, Appl. Phys. Lett. 56, 665, (1990). [2] E. I. Rashba,
Fiz. Tverd. Tela (Leningrad) 2, 1224 (1960) [Sov. Phys. Solid State 2,
1109 (1960)].
HL 49.3 Fr 11:30 H13
Magnetic moment induced by spin-polarized currents in a
semiconductor heterostructure — •Frank Lehmann, Charles
Gould, Christian Rüster, Peter Grabs, Georg Schmidt, and
Laurens W. Molenkamp — Unversität Würzburg, Physikalisches
Institut (EP 3), Am Hubland, D-97974 Würzburg, Germany
In recent years, several experiments have successfully demonstrated the
electrical injection of spin-polarized currents into semiconductors. These
experiments are sensitive to the polarization of the current but not to the
magnetic moment induced by the spin-polarized carriers. We have now
successfully performed SQUID experiments that provide direct evidence
of a current induced magnetization in an electrical spin injection device.
The magnetic moment of a ZnBeMnSe/GaAs heterostructure was measured
using a SQUID magnetometer and lock-in technique at various
magnetic fields, currents, and temperatures. When the background magnetic
moment that results from Biot-Savart‘s law is eliminated, we observe
a clear change in the magnetic moment at the field and current
configurations for which spin injecton is expected. The field and temperature
dependence show that the effect is related to the magnetization
of the DMS. We interpret our results in terms of (i) the band bending
that occurs in the DMS at higher eletric fields and that reduces the spinpolarization
in the magnetic material and (ii) spin accumulation in the
GaAs.
HL 49.4 Fr 11:45 H13
Positive cross correlations in a three-terminal quantum dot with
ferromagnetic contacts — •Wolfgang Belzig, Audrey Cottet,
and Christoph Bruder — Department für Physik, Universität Basel,
Klingelbergstr. 82, 4056 Basel, Schweiz
We study current fluctuations in a three-terminal quantum dot with
ferromagnetic leads in the sequential tunneling regime. Dynamical spin
blockade on the dot leads to positive zero-frequency cross-correlations of
the currents in the output leads. We include the influence of spin-flip scattering
and identify favorable conditions for the experimental observation
of this effect with respect to polarization of the contacts and tunneling
rates.
HL 50 Quantenpunkte und -drähte: Optische Eigenschaften III
Zeit: Freitag 11:00–13:30 Raum: H14
HL 50.1 Fr 11:00 H14
Optical Detection of Single-Electron Spin Decoherence in
a Quantum Dot — •Oliver Gywat 1 , Hans-Andreas Engel
1 , Daniel Loss 1 , R.J. Epstein 2 , F. Mendoza 2 , and D.D.
Awschalom 2 — 1 Department of Physics and Astronomy, University
of Basel, Switzerland — 2 Center for Spintronics and Quantum
Computation, University of California, Santa Barbara, USA
We propose a method based on optically detected magnetic resonance
(ODMR) to measure the decoherence time T2 of a single electron spin in
a semiconductor quantum dot. The electron spin resonance (ESR) of a
single excess electron on a quantum dot is probed by circularly polarized
laser excitation. Due to Pauli blocking, optical excitation is only possible
for one of the electron spin states. The photoluminescence is modulated
due to the ESR which enables the measurement of electron spin decoherence.
We study different possible schemes for such an ODMR setup.
(cond-mat/0307669)
HL 50.2 Fr 11:15 H14
Optical properties of localized excitons in InGaN quantum
structures — •Til Bartel 1 , Matthias Dworzak 1 , Martin
Strassburg 2 , Axel Hoffmann 1 , Andre Strittmatter 1 , and
Dieter Bimberg 1 — 1 Institut für Festkörperphysik, Technische
Universität Berlin, Hardenbergstr. 36, 10623 Berlin — 2 Georgia State
University, Dep. of Physics and Astronomy, Atlanta, GA-30303
Although InGaN structures already find application in optoelectronics,
its optical transitions are still poorly understood and are subject to
current investigation. Indium fluctuations in InGaN quantum-wells are
centers of localization for excitons and show quantum dot-like behavior
at low temperatures.
Wurzite InGaN/GaN single quantum wells were grown by metal organic
chemical vapor deposition on Si(111) and their luminescence was
investigated. High resolution µ-photoluminescence (µ-PL) spectra of
masked samples showed lines as narrow as the resolution limit. This is
interpreted as an indication for δ-shaped density of states. Excitation
density dependence allows the identification of excitons and biexcitones
with positive and negative binding energies. Time resolved PL experiments
show decay rates of less than 1 ns and investigation of temperature
dependence of the photoluminescence reveal typical S-shape behavior.
These results demonstrate the quantum dot-like character of the indium
fluctuations.
HL 50.3 Fr 11:30 H14
Selective optical charging of self-assembled InGaAs quantum
dots — •Miro Kroutvar, Yann Ducommun, Jon J Finley, Max
Bichler, and Gerhard Abstreiter — Walter Schottky Institut,
Technische Universit”at M”unchen, Am Coulombwall 3, 85748 Garching,
Germany
Charge and spin excitations in individual quantum dots (QDs) have
been proposed as QBITS for implementation of quantum logic. One of
the main challenges for these applications is the selective creation of
electrons in such systems and control of their spin degree of freedom.
We present a QD charging device which enables to optically generate
single charges and potentially spins in sub-ensembles of self-assembled
InGaAs QDs. The device consists of a single layer of InGaAs QDs embedded
within the intrinsic region of a GaAs Schottky photodiode. The
charge storage mechanism relies on selective exciton ionization following
resonant optical generation. Our results demonstrate unambiguously
selective charging with extremely long (¿25 µs) charge storage lifetimes
at low temperatures (10K). Analysis of the energy and temperature dependence
of the charge storage signal permits investigation of the role of
exciton-phonon coupling during the QD resonant absorption process. In
addition, thermally-activated redistribution of resonantly stored charge
among the QD ensemble is identified to be the cause of a time-dependent
loss of spectral selectivity at elevated temperatures. Our storage device
enables to probe directly resonant carrier excitation processes and potentially
electron spin dynamics in micro-ensembles of semiconductor QDs.

Halbleiterphysik Freitag
HL 50.4 Fr 11:45 H14
TE- and TM-polarization resolved spectroscopy under normal
incidence — •M. Schardt 1 , C. Dotzler 1 , S. Malzer 1 , J.
Müller 2 , G. Rurimo 2 , S. Quabis 2 , G. Leuchs 2 , and G.H. Döhler 1
— 1 Institut für Technische Physik I — 2 Institut für Optik, Universität
Erlangen-Nürnberg, Germany
Normally, optical experiments performed under normal incidence on
semiconductor structures with broken symmetry regarding the direction
perpendicular to the surface (quantum wells and quantum dots, e.g.)
yield information only about transitions involving in-plane (px- and py-
) components of the hole wave functions, because of the in-plane (TE)
polarization of the light. Transitions sensitive to the pz components are
interacting only with TM-polarized light. Recently it has been demonstrated
that a radially polarized laser beam focused through a microscope
objective with a high numerical aperture (NA ≥ 0.9) is perfectly polarized
along the optical axis in its focus. The light is mostly TM polarized
within the whole focus area. So far, experimental evidence of this feature
has been limited to an indirect proof by comparing the resulting spot size
and shape with the theoretical predictions [1]. We are now presenting an
approach allowing for a direct proof of the TM polarization. It is based
on photo current studies of heavy- and light-hole excitonic absorption in
quantum wells and self-assembled dots embedded in pin diodes. At the
same time, this approach represents a novel technique for polarization
resolved spectroscopy.
[1] S. Quabis et al., Optics Communications 179 (2000) 1-7
HL 50.5 Fr 12:00 H14
Influence of nitrogen containing barrier layers on the emission
wavelength of InAs/GaAs quantum dots — •Oliver Schumann,
Lutz Geelhaar, and Henning Riechert — Infineon Technologies
AG, Corporate Research Photonics, 81730 München
We study the effect of varying the matrix material on the emission
wavelength of InAs QDs. The addition of different combinations of nitrogen
and indium into the matrix allows to tune the confining potential of
the QDs and the local and global stress.
Samples have been grown by solid-source MBE assisted by a RF
plasma source for nitrogen incorporation. They were examined by PL
spectroscopy and TEM. We used a self-consistent Schroedinger-Poisson
solver as a simple simulation tool for the changing confinement.
While growing the QDs on a GaAsN layer almost does not affect the
PL wavelength, one can see a red shift of the emission wavelength greater
than 100 nm after introducing nitrogen in the capping layer above the
QDs. In this way an emission wavelength beyond 1.3 µm can easily be
achieved. This tremendous red shift is mainly attributed to the change
in the confining potential. By comparing QDs with quantum wells and
samples with different concentrations of indium and/or nitrogen in the
barrier layers, the role of stress with respect to the emission wavelength
will also be discussed.
HL 50.6 Fr 12:15 H14
Blinking and Bleaching of Individual Silicon Nanocrystals and
Nanocrystal Ensembles — •Jörg Martin 1,2 , Frank Cichos 1 und
Christian von Borczyskowski 2 — 1 Institut für Physik 123705, TU
Chemnitz, 09107 Chemnitz — 2 Institut für Physik 122501, TU Chemnitz,
09107 Chemnitz
We present for the first time detailed studies of individual silicon nanocrystals
by confocal microscopy. Individual nanocrystals obey narrow
emission spectra (150 meV) in the range between 500 nm and 600 nm.
The emission of single nanocrystals shows a strong intermittency (so
called blinking), which is the consequence of an electron tunneling to
surrounding trap states. The blinking process itself obeys a power law
statistics, which is equivalent to a non-stationary behavior. Indeed we
can show, that characteristic times of the blinking, especially the mean
lifetime of dark periods during the blinking are a function of the observation
time. This non-stationarity shows up as a bleaching of the ensemble,
which we can fully explain by the blinking statistics. In addition, an excitation
intensity dependence of the blinking statistics is observed. This
intensity dependence is the result of different tunneling mechanisms, such
as Auger assisted tunneling, which becomes active or inactive at different
excitation intensities. A further consequence of the charge tunneling to
trap states in the environment is a delayed luminescence of nanocrystal
ensembles, which results from the return of charges from the traps to the
nanocrystals conduction band. This delayed luminescence fits well to the
observed blinking behavior of individual nanocrystals.
HL 50.7 Fr 12:30 H14
How individual are individual CdSe nanocrystals? A single
nanocrystal study. — •Frank Cichos 1 , Abey Issac 2 , Thomas
Blaudeck 1 , and Christian von Borczyskowski 2 — 1 Institut für
Physik 123705, TU Chemnitz, 09107 Chemnitz — 2 Institut für Physik
121501, TU Chemnitz, 09107 Chemnitz
The control of the emission intermittency (”blinking”) of single semiconductor
nanocrystals is one of the challenging tasks to create nanounits
i.e. for optoelectronic applications. Such a control has to be based
on the understanding of the blinking process itself, which is currently
only poorly understood. For this purpose we study the blinking process
of individual ZnS capped CdSe nanocrystals over long time periods
to compare the behavior of different nanocrystals. While fluorescent dye
molecules commonly show a very specific blinking statistics, which differs
from molecule to molecule due to the local environment of the molecule,
all studied nanocrystals obey the same blinking statistics within the measurement
accuracy. Further, a change of the surrounding matrix does
not influence the statistics of the blinking process. Therefore, the processes
behind the blinking have to be hierarchical processes. We propose
that one of these processes, which is responsible for the dark periods in
the emission time traces of individual nanocrystals is a charge diffusion
through trap states in the direct vicinity of the nanocrystal. A more detailed
analysis of the blinking further reveals that the processes which
limit the emitting (on) and non-emitting (off) periods of the nanocrystal
are partly decoupled, since on and off periods follow different statistical
laws.
HL 50.8 Fr 12:45 H14
Femtosecond nonlinear spectroscopy of two quantum dots
coupled by dipole-dipole interaction — •Kerstin Müller 1 ,
Thomas Unold 1 , Christoph Lienau 1 , Thomas Elsaesser 1 , and
Andreas D. Wieck 2 — 1 Max-Born-Institut für Nichtlineare Optik
und Kurzzeitspektroskopie, 12489 Berlin — 2 Ruhr-Universität Bochum,
D-44870 Bochum
The transient optical nonlinearities of single semiconductor quantum
dots (QDs) are intensely investigated as QDs receive attention for implementations
of quantum logic. For realizing potentially scalable quantum
gates it is essential to demonstrate coherent interactions between different
quantum dots, e.g. via dipole-dipole coupling[1]. Here, we report the
first study of the transient optical nonlinearities of two coupled interface
quantum dots. With a 2-ps pump laser, we excite the excitonic resonance
of a first QD (QD 1) and monitor the pump-induced biexcitonic
nonlinearity of this QD with an ultrafast probe laser in a near-field spectrometer[2].
Varying the intensity of the pump laser, pronounced Rabi
oscillations are observed. We simultaneously monitor also the excitonic
nonlinearities of one neighboring QD within the 200 nm spot size of the
near-field experiment. We find a clear pump-induced spectral shift of the
exciton resonance of QD 2 due to the dipole-dipole interaction between
both QDs. The observation of Rabi oscillations on the second quantum
dot after resonant excitation of QD 1 unambiguously establishes dipoledipole
coupling between two individual quantum dots.
[1] E. Biolatti et al., Phys. Rev. Lett. 85, 5647 (2000).
[2] T. Guenther et al., Phys. Rev. Lett. 89 057401 (2002).
HL 50.9 Fr 13:00 H14
Optische Spektroskopie an selbstorganisierten InAs–Quantenpunkten
— •Stephan Lüttjohann 1 , Cedrik Meier 1 , Axel
Lorke 1 und Dirk Reuter 2 — 1 Laboratorium für Festkörperphysik,
Universität Duisburg–Essen, Lotharstraße 1, 47048 Duisburg —
2 Angewandte Festkörperphysik, Ruhr-Universität Bochum, Universitätsstraße
150, 44780 Bochum
Die Photolumineszenz (PL) von selbstorganisierten InAs–Quantenpunkten,
eingebettet in eine Feldeffekttransistor–Struktur (MISFET),
wird in Abhängigkeit der angelegten Spannung und der Anregungsleistung
untersucht. Bei moderaten Anregungsleistungen (P ≤ 2mW/cm 2 )
können dabei gleichzeitig Kapazitäts–Spannungs-Spektren (CV) aufgenommen
und so die Anzahl der Elektronen pro Quantenpunkt bestimmt
werden. Es zeigt sich, dass mit zunehmender Anregungsleistung die CV–
Spektren zu kleineren Gatespannungen verschieben. Dies lässt sich auf eine
Löcherakkumulation an der GaAs/AlGaAs–Grenzfläche der MISFET–
Struktur zurückführen. Die bei mittlerer Anregungsleistung auftauchende
Rekombination aus p–Zuständen ist damit nicht auf Pauli–Blocking
zurückzuführen, sondern hängt mit der Verschiebung der Gatespannungsskala
zusammen, die durch die zunehmende Grenzflächenladung verursacht
wird. Darüber hinaus kann aus der gatespannungsabhängigen PL

Halbleiterphysik Freitag
die Energiedifferenz zwischen X 2− – und X 3− –Rekombination zu 2,6 meV
bestimmt werden.
HL 50.10 Fr 13:15 H14
Wavelength selective carrier storage in self-organized quantum
dots — •Till Warming 1 , F. Guffarth 1 , R. Heitz 1 , M. Geller 1 ,
P. Brunkov 2 , V.M. Ustinov 2 , and D. Bimberg 1 — 1 Institut für
Festkörperphysik, Technische Universität Berlin, — 2 A.F.Ioffe Physico-
Technical Institute RAS, 194021 St-Petersburg, Russia
Wavelength selective carrier storage in self-organized InAs/GaAs quantum
dots (QDs) is investigated. The small homogeneous broadening of
HL 51 Si/Ge
the exciton transition of a single quantum dot is in high contrast to the
large inhomogeneous broadening of the ground state transition energy
of an ensemble of self-organized QDs. This benefit enables in addition
to the spatially addressing wavelength parallel data storage in future
memory devices. Here we analyze the data storage process in two-color
photocurrent experiments and investigate the dependencies of the electric
field, the temperature and the laser power. This work was funded by the
Nanomat project of the European Commission Growth Programme, contract
number G5RD-CT-2001- 00545, Intas project 2001-774, and SFB
296 of DFG.
Zeit: Freitag 11:30–12:15 Raum: H17
HL 51.1 Fr 11:30 H17
Selective wet chemical etching of Ge islands grown on Si(001)
— •Georgios Katsaros, Carlos Manzano, Giovanni Costantini,
Alexander Bittner, Ulrich Denker, Mathieu Stoffel,
Oliver Schmidt, and Klaus Kern — Max Planck Institut für
Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
Although Ge quantum dots on Si(001) have been thoroughly studied,
relatively little is known about their composition which, on the other
hand, is a very important factor in determining their optical and electronic
properties. We tackle this problem by means of selective chemical
etching in which Ge is removed preferentially over Si (or vice versa). By
quantitatively knowing the selectivity of the etchant, the atomic force
microscopy images of the structures that remain after the etching of a
quantum dot sample can be interpreted in terms of a spatially resolved
map of the quantum dot composition. The results obtained by applying
this technique to pyramid and dome islands show that the composition
of both types of dots is highly anisotropic. This can be ascribed to the
kinetic pathway that is responsible for the dot formation, growth and
transformation (pyramid-to- dome transition). For every possible application
in a device the Ge quantum dots have to be overgrown with Si. By
applying selective etching of Si over Ge we were able to remove the Si cap
and to get information on the intermixing and the shape changes that
take place during capping as well as on the composition of the remaining
dots. Finally, using the quantum dots as an etching-resistant ”mask” we
could produce interesting free- standing Ge-rich nanostructures.
HL 51.2 Fr 11:45 H17
Metal-Induced Crystallization of Silicon-Germanium Alloys —
•Mario Gjukic, Michael Buschbeck, Robert Lechner, Jens
Lübke, and Martin Stutzmann — Walter Schottky Institut, Technische
Universität München, Am Coulombwall 3, D-85747 Garching
The fabrication of large-grained polycrystalline silicon and silicongermanium
(poly-SiGe) thin films is increasingly important for largearea
electronic devices such as flat panel displays or thin film solar
cells. Fundamental for both applications is the use of cheap and transparent
substrates, such as glass, requiring low temperature processing
steps (T < 500 ◦ C). One method which is known to lead to poly-Si layers
with good structural and electronic properties is the ALuminum-
Induced Layer Exchange (ALILE) process. Here, a bilayer structure of
HL 52 SiC II
aluminum (Al) and amorphous silicon (a-Si) is deposited on a glass substrate
and annealed below the eutectic temperature of the binary Al-Si
system (T < 577 ◦ C). If the layers are separated by a thin oxide film, for
example aluminum oxide or silicon oxide, the annealing process results
in a complete layer exchange (Al and Si change positions) and the formation
of a coherent poly-Si film. Here, we report the successful realization
of poly-SiGe layers over the entire composition range on glass substrates
via the ALILE process. We have investigated if the ALILE process is
also applicable to binary semiconductors such as SiGe or if significant
phase segregation occurs. In addition, optical and electronic properties
of the resulting poly-SiGe layers have been studied. The possibility to
use the obtained alloy films as seed layers for thin film solar cells will be
discussed.
HL 51.3 Fr 12:00 H17
Thermal Conductivity of Isotopically Enriched 28 Si: Revisited
— •R. K. Kremer 1 , M. Cardona 1 , H.-J. Pohl 2 , G. G. Devyatych
3 , and P. G. Sennikov 3 — 1 MPI für Festkörperforschung,
Heisenbergstr. 1, D-70569 Stuttgart, Germany — 2 VITCON Projectconsult
GmbH, Otto-Schott-Str. 13, D-07745 Jena, — 3 Institute of Chemistry
of Highly-Pure Substances, Russian Academy
The thermal conductivity of isotopically enriched 28 Si recently has attracted
particular attention because of a claim of a 60% higher roomtemperature
thermal conductivity of 28 Si as compared to that of Si with
a natural isotope mixture nat Si [1]. It was argued, however, that this result
cannot be reconciled with theoretical estimates which give, at most,
a 20% increase. Because of the potential technological importance of a
significantly larger thermal conductivity of isotopically pure samples of
Si we have, with a steady-state heat-flow technique, redetermined the
thermal conductivity of the previously measured samples and new single
crystal samples of 28 Si and nat Si between 10K and 320K. To estimate
and reduce the disturbing influence of thermal radiation losses at elevated
temperature we have particularly taken care to utilize samples with identical
geometrical dimensions. Close to room-temperature we consistently
find an increase in the thermal conductivity of 28 Si with respect of that
of nat Si of about 10 ± 2 %, whereas the values of this enhancement below
100K are close to that reported in ref. [1].
[1] T. Ruf et al., Solid State Commun., 115, 243 (2000).
Zeit: Freitag 12:15–13:00 Raum: H17
HL 52.1 Fr 12:15 H17
Wird Coimplantation von Donatoren (P, N) mit Si oder C in
4H-SiC dominiert vom Site-competition-Effekt oder der Erzeugung
elektrisch neutraler Defekte? — •Frank Schmid und Gerhard
Pensl — Institut für Angewandte Physik, Universität Erlangen-
Nürnberg
Durch vergleichende Hall-Effekt Messungen an Phosphor
(P)/Stickstoff (N) implantierten und Kohlenstoff (C) oder Silizium (Si)
coimplantierten p-Typ 4H-SiC Epischichten wurde das Ausheilverhalten
von P- bzw. N-Donatoren untersucht. Bei den P- und C/P-implantierten
Proben konnte eine identische elektrische Aktivierung der P Atome
festgestellt werden, während sich bei der Si/P-implantierten Probe die
Konzentration der P-Donatoren um 40% verringerte. Damit ist gezeigt,
dass das Ausheilverhalten der P-implantierten Proben durch den Sitecompetition-Effekt
dominiert wird. Im Vergleich zur N-implantierten
Probe, zeigt die C/N-implantierte Probe eine Reduktion (40%) der elektrisch
aktiven N Atome, was möglicherweise auf den Site-competition-
Effekt zurückgeführt werden kann. Jedoch zeigt die Si/N-implantierte
Probe eindeutig eine starke Verringerung der freien Elektronenkonzentration
(75%) und der Konzentration der Kompensation (20%). Als Ursache
wird die Bildung von thermisch stabilen und elektrisch neutralen
VSi(N)4-Defektkomplexen vorgeschlagen.

Halbleiterphysik Freitag
HL 52.2 Fr 12:30 H17
Störbandleitung in Al-dotiertem 6H-SiC — •Michael Krieger,
Kurt Semmelroth und Gerhard Pensl — Lehrstuhl für Angewandte
Physik, Universität Erlangen-Nürnberg, Staudtstr. 7/A3, D-91058 Erlangen
Al-dotiertes 6H-SiC wurde mittels Kapazitäts-Spannungs- (C-
V), Admittanzspektroskopie- (AS), Leitfähigkeits- und Hall-Effekt-
Messungen untersucht. Für C-V und AS wurden Schottky-Kontakte
auf Wafer-Bereichen mit unterschiedlicher Al-Konzentration präpariert
([Al] = 1.8 × 10 17 cm −3 . . . 3.4 × 10 18 cm −3 ). C(T)- bzw. G/ω(T)-Kurven,
aufgenommen an Kontakten mit niedriger [Al], zeigen jeweils eine Stufe
bzw. einen Peak, die dem Al-Akzeptor zugeordnet wird. Eine zweite Stufe
bzw. ein zweiter Peak wurde an Kontakten mit [Al] ≥ 7 × 10 17 cm −3
beobachtet. Der Arrhenius-Plot der G/ω(T)-Peak-Maxima ergibt eine
Aktivierungsenergie von 17meV, die als thermische Aktivierungsenergie
für Hopping-Leitung in einem Störband interpretiert wird. Die gleiche
Energie wurde auch aus Leitfähigkeitsmessungen an dem gleichen Wafer-
Bereich wie für AS ermittelt. Für T > 160K entspricht die Steigung der
ρ(1/T)-Kurve der Aktivierungsenergie des Al-Akzeptors; für T < 160K
wurde aus der Steigung eine Aktivierungsenergie von 17meV ermittelt.
Bei T ≈ 75K ändert der Hall-Effekt, gemessen an der gleichen Probe,
sein Vorzeichen von plus nach minus. Die Ergebnisse werden im Rahmen
der Arbeiten über Störbandleitung von Mott und Twose bzw. Shklovskii
und Efros diskutiert.
HL 53 Elektronentheorie
HL 52.3 Fr 12:45 H17
Low Density of Interface States in 4H-SiC MOS Capacitors
Generated by Nitrogen Implantation — •Florin Ciobanu 1 ,
Gerhard Pensl 1 , Valeri Afanas’ev 2 , and Günter Wagner 3
— 1 Lehrstuhl für Angewandte Physik — 2 Department of Physics,
University of Leuven, Belgium — 3 Institut für Kristallzüchtung, Berlin
Nitrogen (N)-doped 4H-SiC epilayers (thickness = 8µm, [N] =
2.2·10 16 cm −3 ) were, in addition, implanted with N at concentrations varying
between 1·10 17 cm −3 and 3·10 19 cm −3 (Gaussian profile with maximum
located 30nm apart from the wafer surface). MOS capacitors were fabricated
on the N-implanted surface by nominally dry oxidation at 1120 ◦ C
for 24 h (oxide thickness = 110nm) followed by a post-oxidation anneal at
the same temperature in Ar for 60 min. High-frequency conductance measurements
reveal an interface state density DIT in the low 10 10 eV −1 cm −2
- range close to the conduction band edge. This value is about 3 orders of
magnitude lower than corresponding values for standard-processed 4H-
SiC MOS capacitors. However, the N implantation causes a negative
flatband shift of the C-V characteristics, which probably originates from
a fixed charge at the interface (≈ 10 12 elementary charges/cm 2 ). The effect
of the implanted N concentration on the density of interface states
and on the flatband shift is investigated and discussed.
Zeit: Freitag 12:00–12:30 Raum: H13
HL 53.1 Fr 12:00 H13
A renormalization approach for the Anderson model in d = 1
and d = 2 at the band edge: Scaling of the localization length
— •Stefanie Russ — Institut für Theoretische Physik III, Universität
Giessen, D-35392 Giessen, Germany
A renormalization procedure for the electronic wave functions of the
one- and two-dimensional Anderson model with diagonal disorder is developed
that applies close to the band edges. This theory leads in d = 1 to
a scaling form of the localization length λ ∼ 〈ǫ 2 〉 −1/3 f((2 − |E|)/〈ǫ 2 〉 2/3 ),
in agreement with former works. In d = 2 a similar scaling form applies
for the localization volume V (participation ratio), i.e. V 1/2 ∼
〈ǫ 2 〉 −1/2 g((4 − |E|)/〈ǫ 2 〉). Here, 〈ǫ 2 〉 is the variance of the site potentials,
E is the energy and f(x) and g(x) are the scaling functions
(f(0) = g(0) = 1).
λ and V close to the band edges are studied by numerical simulations
and confirm this scaling ansatz. The scaling functions f(x) and g(x) show
a crossover between the two regimes x ≪ 1 and x ≫ 1. It is shown that
these two regimes refer to Λ ≫ λ0 and Λ ≪ λ0, respectively where Λ is
the wavelength, λ0 in d = 1 is the localization length at the band edge
and λ0 in d = 2 is the effective localization length V 1/2 at the band edge.
HL 53.2 Fr 12:15 H13
A Ground State based Exact-Exchange Formalism: Implementation
and Applications — •Matthias Wahn 1 und Jörg Neugebauer
2 — 1 Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg
4-6, D-14195 Berlin-Dahlem — 2 Universität Paderborn, Fakultät
für Naturwissenschaften, FB 6 Physik, Warburger Straße, D-33095 Paderborn
Recent studies have shown that the exact treatment of the exchangepotential
(EXX-method) within the Kohn-Sham formalism significantly
improves the description of bandgaps within density-functional theory [1].
The original formulation is based on a Greens function approach requiring
the calculation of a large number of unoccupied states thus making
the approach computationally rather expensive. We have therefore developed
an alternative formulation [2], recently also proposed by [3], which
is solely based on ground-state quantities and implemented it into our
plane wave pseudopotential program SFHIngX. Compared to the original
formulation it speeds up the calculations significantly and requires
also much less memory. The new approach has been successfully applied
on various III-V and II-VI semiconductors. Also, it turned out that it
provides a direct way to analyze and visualize electronic self-interaction
effects.
[1] M. Städele, M. Moukara, J.A. Majewski, P. Vogl, and A. Görling,
Phys. Rev. B 59, 10031 (1999).
[2] Matthias Wahn, Diplomarbeit, TU Berlin (2002)
[3] S. Kümmel and J.P. Perdew, Phys. Rev. Lett. 90, 043004 (2003)

Magnetismus Tagesübersichten
Hauptvorträge
MAGNETISMUS (MA)
Prof. Dr. Eberhard Wassermann
Institut für Physik
Universität Duisburg-Essen
Lotharstraße 1
47048 Duisburg
E-Mail: waterman@ttphysik.uni-duisburg.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsäle H10, H22, H23, Poster Bereich A)
MA 1.1 Mo 09:30 (H10) Numerical micromagnetics in granular microstructures , Josef Fidler, Thomas
Schrefl
MA 5.1 Mo 14:00 (H10) Vom Superpara- zum Ferromagneten im Stoner-Wohlfarth Bild, J. Hesse
MA 5.2 Mo 14:30 (H10) Breakthrough in magneto-optical near-field microscopy, Andreas Bauer, Gereon
Meyer, Tristan Crecelius, Irene Mauch, Günter Kaindl
MA 9.1 Di 09:30 (H10) Experimental observation of symmetry breaking soliton modes in an active
ring, Sergej O. Demokritov, Alexander A. Serga, Vladislav E. Demidov, Burkard
Hillebrands, Michail P. Kostylev, Boris A. Kalinikos
MA 12.1 Di 14:00 (H10) Progress in Designing Multilayered Thin Films for Magnetoelectronic
Applications, Andreas Hütten
MA 12.2 Di 14:30 (H10) Confined Antiferromagnets**, Samuel Bader
MA 14.1 Mi 14:00 (H10) Exchange Biased Nanostructures, J. Eisenmenger, Zhipan Li, O. Petracic, I. V.
Roshchin, Kai Liu, J. Nogués, C. Leighton, H. Masuda, K. Nishio, Ivan K. Schuller
MA 14.2 Mi 14:30 (H10) Ultrafast magnetization dynamics in pump probe experiments,
M. Münzenberg, M. Lüttich, P. Moschkau, M. Djordjevic, G. Eilers, S. Bretschneider,
A. Parge, P. Guderian, T. Kampfrath, R. G. Ulbrich, B. Sass, F. Leuenberger,
W. Felsch, T. H. Kim, J. S. Moodera
MA 19.1 Do 09:30 (H10) Magnetic field generation in planets and laboratory dynamos,
Andreas Tilgner
MA 23.1 Do 10:15 (H23) Martensite: Introductory Remarks, E.F. Wassermann
MA 23.2 Do 10:45 (H23) Ferromagnetische Formgedächtnis Legierungen, Manfred Wuttig
MA 23.3 Do 11:15 (H23) The magnetic, structural and dynamical properties of the Heusler alloys,
Alexey Zayak, Peter Entel
MA 25.1 Do 14:00 (H10) The physics of magnetic domain wall motion in nanostructures,
André Thiaville, Yoshinobu Nakatani, Jacques Miltat
MA 25.2 Do 14:30 (H10) Magnetotransport and current induced domain wall propagation in ring
structures with constrictions, Mathias Kläui, C. A. F. Vaz, J. A. C. Bland, L.
J. Heyderman, W. Wernsdorfer, U. Rüdiger
MA 29.1 Fr 10:15 (H10) Ferromagnetische Nanostäbe und Nanoröhren in selbstgeordneten
Aluminiumoxid-Membranen, Kornelius Nielsch
Fachsitzungen
MA 1 Hauptvortrag Fidler Mo 09:30–10:00 H10 MA 1.1–1.1
MA 2 Mikromagnetismus / Computational Magnetism Mo 10:15–12:00 H10 MA 2.1–2.7
MA 3 Anisotropie / Magnetoelastizität Mo 12:00–13:00 H10 MA 3.1–3.4

Magnetismus Tagesübersichten
MA 4 Oberflächenmagnetismus Mo 10:15–13:15 H22 MA 4.1–4.12
MA 5 Hauptvorträge Hesse / A. Bauer Mo 14:00–15:00 H10 MA 5.1–5.2
MA 6 Magnetische Partikel / Cluster Mo 15:15–18:30 H10 MA 6.1–6.13
MA 7 Magnetische Abbildungsverfahren Mo 15:15–15:45 H22 MA 7.1–7.2
MA 8 Elektronentheorie Mo 15:45–18:00 H22 MA 8.1–8.9
MA 9 Hauptvortrag Demokritov Di 09:30–10:00 H10 MA 9.1–9.1
MA 10 Exchange Bias Di 10:15–13:00 H10 MA 10.1–10.11
MA 11 Magnetische Materialien Di 10:15–13:00 H22 MA 11.1–11.11
MA 12 Hauptvorträge Hütten / Bader Di 14:00–15:00 H10 MA 12.1–12.2
MA 13 Poster:Schichten(1-23),Spinabh.Trsp(24-
41),Exch.Bias(42-56),Spindyn.(57-
67),Mikromag.(68-76),Partikel(77-
90),Spinelektr.(91-97),Elektr.Theo.(98-
99),Mikromag+PhasÜ+Aniso.(100-
105),Magn.Mat.(106-118),Messmethod.(119-
121),Obflm.+Abbverf.(122-123)
Di 15:00–19:00 Bereich A MA 13.1–13.123
MA 14 Hauptvorträge Eisenmenger / Münzenberg Mi 14:00–15:00 H10 MA 14.1–14.2
MA 15 Magnetische dünne Schichten I Mi 15:15–17:45 H10 MA 15.1–15.10
MA 16 Magn. Kopplungsphänomene Mi 15:15–17:30 H22 MA 16.1–16.9
MA 17 Spinstrukturen /Magn. Phasenübergänge Mi 17:45–18:45 H10 MA 17.1–17.4
MA 18 Magnetische Messmethoden Mi 17:30–18:45 H22 MA 18.1–18.5
MA 19 Hauptvortrag Tilgner Do 09:30–10:00 H10 MA 19.1–19.1
MA 20 Magnetische dünne Schichten II Do 10:15–13:00 H10 MA 20.1–20.11
MA 21 Bio- und molekularer Magnetismus Do 10:15–12:15 H22 MA 21.1–21.8
MA 22 Spinabhängiger Transport I Do 12:15–13:00 H22 MA 22.1–22.3
MA 23 Hauptvorträge - Symposium Magnetic Shape Memory
Alloys (zusammen mit M)
Do 10:15–11:45 H23 MA 23.1–23.3
MA 24 Symposium Magnetic Shape Memory Alloys (zusammen
mit M)
Do 11:45–13:15 H23 MA 24.1–24.6
MA 25 Hauptvorträge Thiaville / Kläui Do 14:00–15:00 H10 MA 25.1–25.2
MA 26 Mikro- und nanostrukturierte Materialien Do 15:15–18:45 H10 MA 26.1–26.14
MA 27 Spinabhängiger Transport II Do 15:15–18:45 H22 MA 27.1–27.14
MA 28 Spindynamik / Ummagnetisierungsvorgänge Do 15:15–18:45 H23 MA 28.1–28.14
MA 29 Hauptvortrag Nielsch Fr 10:15–10:45 H10 MA 29.1–29.1
MA 30 Magnetische dünne Schichten III Fr 10:45–12:45 H10 MA 30.1–30.8
MA 31 Spinelektronik Fr 10:45–12:45 H22 MA 31.1–31.8
Mitgliederversammlung des Fachverbands Magnetismus
Do 19:00–20:00 H10
1. Bericht
2. Wahl des Vorsitzenden
3. Verschiedenes

Magnetismus Montag
Fachsitzungen
– Haupt-, Kurzvorträge und Posterbeiträge –
MA 1 Hauptvortrag Fidler
Zeit: Montag 09:30–10:00 Raum: H10
Hauptvortrag MA 1.1 Mo 09:30 H10
Numerical micromagnetics in granular microstructures —
•Josef Fidler and Thomas Schrefl — Technische Universitaet
Wien, Institut fuer Festkoerperphysik, Wiedner Hauptstr. 8-10, A-1040
Wien, Austria
Studying the magnetisation reversal processes of nanostructured magnetic
devices, such as magnetic recording heads and media, micro-sensors
based on the switching of magnetic thin films and future magnetic random
access memory cells has become a very attractive field of research.
The interpretation of experimental results of the switching behaviour is
mostly based on numerical micromagnetic simulations. We discuss our recent
results concerning the influence of the granular microstructure on the
fast switching processes of typical CoCrPtX, FePt and CoPd thin films
used for high density magnetic recording with longitudinal and perpendicular
anisotropy. In detail, we will show that the degree of the exchange
coupling between neighbouring grains, the Gilbert damping parameter
and the grain size and its distribution finally control the magnetisation
reversal properties and demonstrate that new and fascinating mesoscopic
effects are predicted by solving the Landau-Lifshitz Gilbert equation in
the framework of finite element micromagnetics.
MA 2 Mikromagnetismus / Computational Magnetism
Zeit: Montag 10:15–12:00 Raum: H10
MA 2.1 Mo 10:15 H10
Eindomänengrenze in Permalloy-Dünnschichtelementen —
•Riccardo Hertel und Jürgen Kirschner — Max-Planck-Institut
für Mikrostrukturphysik, Weinberg 2, 06120 Halle
Dünne, weichmagnetische Plättchen sind wesentliche Bestandteile moderner
Elemente der Magnetoelektronik. Für deren zuverlässige Arbeitsweise
ist es erforderlich, dass die Plättchen magnetisch bistabil ist, also
nur in zwei verschiedenen, nahezu homogenen Magnetisierungszuständen
auftreten können, die als logische ”0” bzw. ”1” ausgewertet werden
können. Im Gegensatz zu diesem idealen Verhalten werden selbst in
Teilchen von lediglich 200 nm Größe Domänenstrukturen mit geschlossenem
magnetischen Fluß beobachtet, die in technologischer Hinsicht
unbrauchbar sind [1]. Mikromagnetische Simulationen zeigen, dass die
Eindomängrenze in rechteckigen Permalloy-Dünnschichtelementen empfindlich
von der Schichtdicke abhängt. Ein Phasendiagramm des energetisch
günstigsten Magnetisierungszustands wurde für Plättchen mit
Kantenlängenverhältnis 2:1 im Bereich zwischen 250 nm und 1000 nm
Länge und 2.5 nm bis 30 nm Schichtdicke berechnet [2]. Damit kann
der Größenbereich von Teilchen bestimmt werden, die hochremanente
Grundzustände haben und somit sinnvoll in Bausteinen der Spinelektronik
eingesetzt werden können. [1]A. Yamasaki et al., PRL 91, 1272011,
2003 [2] R. Hertel, Z.Metallkd. 93 957, 2002
MA 2.2 Mo 10:30 H10
Measurement and simulation of domains in permalloy
microstructures — •Markus Bolte, Miriam Barthelmeß,
Christian Pels, Alexander Thieme, and Gu ido Meier — Institut
für Angewandte Physik und Zentrum für Mikrostrukturforschung,
Jungiusstraße 11, 20355 Hamburg
We have measured the stray fields of thin permalloy (Ni83Fe17) microstructures
with different geometries in the range of 1 × 1µm 2 to
4 × 4µm 2 and ten different thicknesses between 10 nm and 100 nm by
magnetic-force microscopy (MFM). The MFM images are compared to
corresponding images calculated from micromagnetic simulations. For
the present calculations, the MFM tip is considered a magnetic point
dipole. To describe the real thin film tip within the framework of this approximation,
the dipole moment must be located at an elevated position
within the tip volume [2]. In particular, the type of 180 ◦ domain walls
is well described by the model. We observe a transition from cross-tie
to asymmetric Bloch walls between 70 nm and 100 nm film thickness in
good agreement with simulation.
[1] M. Barthelmess, C. Pels, A. Thieme, and G. Meier, submitted 2003.
[2] J. Lohau, S. Kirsch, A. Carl, G. Dumpich, and E. F. Wassermann, J.
Appl. Phys. 86, 3410 (1999).
MA 2.3 Mo 10:45 H10
Optimierung der Schaltzeiten magnetischer Ummagnetisierungsprozesse
über die Schichtdicke von Dünnschichtelementen
— •D. Goll — Max-Planck-Institut für Metallforschung, Stuttgart
Ein wichtiger Aspekt bei der Vergrößerung der Speicherdichten in der
magnetischen Datenspeichertechnik ist die genaue Kenntnis der magnetischen
Ummagnetisierungsprozesse, um die damit verbundenen Schaltzeiten
gezielt beeinflussen zu können. Die Schaltzeit ist festgelegt durch die
Probengeometrie, das verwendete magnetische Material und die Art und
Stärke des angelegten Magnetfelds. Um die Schaltzeit von ferromagnetischen
Dünnschichtelementen zu ermitteln, wird die Gilbert-Gleichung
unter Benutzung der dreidimensionalen Finite-Elemente-Methode numerisch
gelöst und mit Ergebnissen analytischer Rechnungen verglichen.
Dabei zeigt sich, dass die Schaltzeit einer gegebenen Schicht bei einem bestimmten
Wert der Dämpfung des Systems minimal wird. Die Lage dieses
Minimums lässt sich über die Schichtdicke und die Stärke des angelegten
Magnetfelds stark beeinflussen. Diese Arbeit wurde gefördert vom Deutschen
Akademischen Austauschdienst, Bonn, während eines Aufenthalts
am Center for Magnetic Recording Research, La Jolla, USA.
MA 2.4 Mo 11:00 H10
Kritische Dicken für die Domänenbildung in dünnen Filmen
und kugel- bzw. würfelförmigen kleinen Teilchen — •H.
Kronmüller 1 , D. Goll 1 und R. Hertel 2,3 — 1 Max-Planck-Institut
für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart — 2 Max-
Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle —
3 Laboratoire Louis Néel, Grenoble
Hochremanente Eindomänenteilchen sind die Voraussetzung, um hohe
Speicherdichten bei der magnetischen Datenspeicherung zu erzielen.
Analytische mikromagnetische Berechnungen sind in der Regel nur grobe
Abschätzungen, da bei der Berechnung des Streufelds starke Vereinfachungen
gemacht werden müssen. Mit Hilfe der dreidimensionalen
Finite-Elemente-Methode wurden die remanenten Magnetisierungsmuster
von hart- und weichmagnetischen Dünnschichtelementen und kugelbzw.
würfelförmigen kleinen Teilchen bestimmt. Der Vergleich der numerischen
Ergebnisse mit analytischen Rechnungen zeigt, dass die Genauigkeit
der analytischen Rechnungen entscheidend von der Energie der
Vortexstruktur abhängig ist. Die Rolle der Austauschlängen, Materialkonstanten
(Härte 2K1/µ0M 2 s ) und der Probenform wird an einigen ausgewählten
Beispielen diskutiert.
MA 2.5 Mo 11:15 H10
Diagram of the states in arrays of iron nano-cylinders —
•fabrizio porrati and michael huth — Physikalisches Institut, J.
W. Goethe-Universität, Robert-Mayer-Str. 2-4, D-60054 Frankfurt a.M.
Micromagnetic simulations are performed to study the magnetic states
of two-dimensional arrays of iron nano-cylinders. Quasi-single domain

Magnetismus Montag
states and curling configurations are obtained as a function of the thickness
and diameter of the cylinders and their relative distance. The results
of the investigation are presented in diagrams of the states including regions
of stability and metastability. The transitions between different
ground state are outlined. It is found that they take place either continuously
or abruptly. These investigations may have some relevance for
identifying instability regions of magnetic storage arrays.
MA 2.6 Mo 11:30 H10
Simulation von Temperatureffekten im mikromagnetischen Modell
— •Oliver Lemcke, André Kubetzka und Roland Wiesendanger
— Universität Hamburg, Institut für angewandte Physik, Rastersensormethoden
Die mikromagnetische Theorie ist eine deterministische Theorie, die
die Dynamik eines magnetischen Systems bei T = 0 K beschreibt. Um
die Temperatur zu berücksichtigen, wird die bekannte Landau-Lifshitz
Differentialgleichung (DGL) um ein fluktuierendes H-Feld erweitert. Bei
der Integration der so erhaltenen DGL vom Langevin-Typ ist zu beachten,
dass es verschiedene Definitionen des stochastischen Integrals gibt
(Ito, Stratonovich).
Wir haben die Implementation als Erweiterung der Open Source
Software OOMMF[1] (Object Oriented MicroMagnetic Framework) realisiert,
so dass auch temperaturabhängige Prozesse, wie z.B. Schaltvorgänge
und thermisches Rauschen, behandelt werden können. Das Programm
wurde einer eingehenden Validierung unterzogen, um Grenzen
und Möglichkeiten des Modells zu ermitteln.
[1] http://math.nist.gov/oommf
MA 3 Anisotropie / Magnetoelastizität
MA 2.7 Mo 11:45 H10
Molekül-Nachweis über magnetische Beads - Computer-
Simulation — •Willi Schepper, Jörg Schotter, Hubert
Brückl und Günter Reiss — Universität Bielefeld, Fakultät für
Physik, Universitätsstraße 25, 33501 Bielefeld
Moleküle können mit hoher Empfindlichkeit bis hin zum Einzelmolekül-Nachweis
mit Hilfe von magnetischen Beads detektiert werden, dabei
werden die Moleküle durch chemische Präparation an die Beads gebunden.
Der Bead-Nachweis gelingt in GMR/TMR/SP-Elementen über
deren Widerstandsänderung ∆R/R, weil die magnetischen Beads mit
ihren Streufeldern die Spinausrichtung in den magnetischen Schichten
bestimmen. Zur Simulation der Magnetowiderstands-Kurven wurde die
lokale Feldmethode [1] genutzt und qualitative Übereinstimmung mit den
Meßkurven gefunden. Neben der Nachweis-Empfindlichkeit spielt die Linearität
des Sensorsignals mit der Bead-Konzentration eine entscheidende
Rolle, in diesem Punkt verhalten sich die Sensoren unterschiedlich.
Insbesondere wurde bei der Untersuchung des Zusammenwirkens von Signalgeber
(Bead) und Sensor (GMR, TMR, SP) festgestellt, dass die Berechnung
der Änderung der Sensor-Charakteristik unter dem Einfluss der
Bead-Felder zu einfach ist, so dass in die Simulation das Gesamtsystem
einbezogen werden muss. Die Verkopplung der Sensoren und Beads über
die gegenseitigen Streufelder führt zu komplexen Vortex-Strukturen.
[1] W. Schepper, K. Diplas, and G. Reiss, 3D-simulations of magnetic
structures in af-coupled layers with pinholes, J. Appl. Phys. 87, 6597
(2000)
Zeit: Montag 12:00–13:00 Raum: H10
MA 3.1 Mo 12:00 H10
Struktur und Magnetismus ultradünner Fe Filme auf glatten
und gestuften Pt-Substraten — •A. Enders 1 , T.Y. Lee 1 , K.
Kuhnke 1 , D. Repetto 1 , J. Honolka 1 , C. Grazioli 2 , S.R. Krishnakumar
3 , M. Veronese 2 , C. Carbone 2 und K. Kern 1 —
1 MPI für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart
— 2 Institute for Structure of the Matter, CNR, Trieste, Italy — 3 he
Abdus Salam International Centre for Theoretical Physics, Trieste, Italy
Struktur und Magnetismus ultradünner Fe-Filme auf Pt(111) und
Pt(997) wurden mit Heliumstreuung (TEAS), Beugung langsamer Elektronen
(LEED), magneto-optischem Kerr-Effekt (MOKE) und zirkularem
Röntgendichroismus (XMCD) untersucht. Die Experimente zeigen,
daß atomare Ketten und Monolagen von Fe mit geringster Defektdichte
bei Substrat-Temperaturen von 300K < T < 400K hergestellt
werden können. Die magnetischen Untersuchungen an keilförmigen Fe-
Filmen auf Pt(997) zeigen eine Reorientierung der Magnetisierung mit
zunehmender Filmdicke von senkrecht zur Ebene in die Filmebene über
einen gekanteten Zwischenzustand. Im Gegensatz dazu konnte mit XM-
CD an Fe/Pt(111) keine remanente senkrechte Magnetisierung nachgewiesen
werden. Der Vergleich der magnetischen Eigenschaften der Fe-
Filme auf beiden Substraten zeigt daher, daß die Stufenkanten entscheidend
zur senkrechten magnetischen Anisotropie beitragen. Die Ergebnisse
von Element-spezifischen XMCD-Messungen und integralen MOKE-
Experimenten lassen vermuten, daß im Pt-Substrat ein magnetisches Moment
induziert wird, welches wesentlich zum magnetischen Gesamtmoment
beiträgt.
MA 3.2 Mo 12:15 H10
Magnetic anisotropies in MBE-grown MnAs — •M. Bowen, L.
Däweritz, K.J. Friedland, and K.H. Ploog — Paul Drude Institute
for Solid-State Electronics, Hausvogteiplatz 5-7, D-10117 Berlin
The challenge of integrating spin electronics with semiconductor technologies
has spurred much research into understanding the physics of
magnetic semiconductors. In particular, control of the magnetization
reversal process is essential to harnessing the carrier spin in such heterostructures.
As a model system exhibiting room temperature ferromagnetism,
MnAs has been extensively studied but the magnetic anisotropies
at play are still poorly understood. Using the Hall effect as a sensitive
probe of in-plane and out-of plane magnetic anisotropies, we have investigated
MnAs(001)//GaAs(001) and MnAs(311)//GaAs(001) systems to
isolate the role of the c-axis uniaxial magnetic anisotropy relative to other
contributions.
MA 3.3 Mo 12:30 H10
Strong change of the crystal structure of Tb0.5Dy0.5Cu2 induced
by an external magnetic field — •Sebastian Raasch 1,2 , Mathias
Doerr 1 , Martin Rotter 3 , Andreas Kreyssig 1 , Jens-Uwe
Hoffmann 2 , Ulrike Witte 1,2 , and Michael Loewenhaupt 1 —
1 TU Dresden, Institut fuer Festkoerperphysik, Germany 01062 Dresden
— 2 Hahn Meitner Institut Berlin — 3 Universitaet Wien, Institut fuer
physikalische Chemie
Magnetic fields of 4 T applied to a single crystal Tb0.5Dy0.5Cu2 along
the (magnetic hard) c axis affect a change of the crystalline structure.
Concurrently the symmetry axes change. Neither decreasing the magnetic
field to zero nor warming up the crystal to room temperature led
to a virgin state crystal. Further a change of the magnetic anisotropy
has been observed. This behaviour, which was also observed at similar
orthorhombic RCu2 (R = Rare Earth) compounds, can not be explained
only by a competition of single ion and exchange anisotropy.
In our recent neutron-scattering experiment at the E2 flat cone diffractometer
of the HMI Berlin we proved, that this structural conversion is
associated with the decay of the single-domain crystal into three (crystallographic)
variants, rotated by 60 degrees within the pseudo hexagonal
ac-plane. Models of the converted crystal structure are compared to the
results of the experiment.
MA 3.4 Mo 12:45 H10
Spontaneous Magnetostriction of Uranium Monosulfid (US)
— •Ulrike Nitzsche, Ingo Opahle, Manuel Richter, Klaus
Koepernik, and Helmut Eschrig — Leibniz Institute for Solid State
and Materials Research Dresden, P.O.B. 270016, 01171 Dresden, Germany
Uranium sulfid forms in the NaCl-type cubic structure and exhibits
ferromagnetic order below Tc = 177K with a strong magnetic anisotropy
[1]. The easy axis of magnetization points along [111]. Due to spin-orbit
coupling there is a symmetry reduction taking place below the Curie
temperature. We investigate the magnetically induced lattice distortion
from cubic to trigonal symmetry and estimate the structure parameters
for the ferromagnetic ground state using fully relativistic full-potential
local orbital method (RFPLO) in the framework of LSDA.
[1] G.H. Lander, M.S.S. Brooks, B.Lebech, P.J. Brown, O.Vogt and K.
Mattenberger, Appl. Phys. Lett. 57 (10), 1990.

Magnetismus Montag
MA 4 Oberflächenmagnetismus
Zeit: Montag 10:15–13:15 Raum: H22
MA 4.1 Mo 10:15 H22
Structure and magnetism in the MnCu/Cu(001)-c(2x2) and
p2gg-(4x2) surface alloys — •Popescu R. 1 , Meyerheim H.L. 1 ,
Sander D. 1 , Ernst A. 1 , Robach O. 2 , Ferrer S. 2 , Kirschner J. 1 ,
and Bruno P. 1 — 1 MPI für Mikrostrukturphysik, Weinberg 2, 06120
Halle, Germany — 2 ESRF, BP 220, F-38043 Grenoble, France
The two-dimensional magnetic alloy phases formed by deposition of Mn
on Cu(001) in the coverage range between about 0.5 and 1 monolayer
(ML, 1ML=1.53×10 15 atoms/cm 2 ) were investigated by surface x-ray
diffraction (SXRD) and calculations based on the full potential layered
Korringa-Kohn-Rostoker-method implemented within the DFT. While
for the c(2x2) phase formed at 0.5 ML the basic two dimensional alloy
structure model with Mn-atoms replacing every other Cu surface atom
is confirmed (Mn at 0.20± 0.05 ˚Aabove the Cu-layer), in detail an accurate
fit to the 228 reflections (unweighted R≈ 0.07) is only obtained by
taking into account 0.5 ML of Cu atoms above the alloy layer and a fraction
of 20 percent anti-phase domains. The calculations show, that the
magnetic moment of the Mn-atoms is in the 3.8 µB-range independent
of the presence or absence of the Cu-adlayer. The p2gg-(4x2) superstructure
is also characterized by a single MnxCu1−x alloy layer, where the
Mn-concentration (x) is in the range of about 0.8 and the corrugation in
the 0.4˚Arange. The implications of the increased Mn-concentration (x)
on the magnetic moment is discussed.
MA 4.2 Mo 10:30 H22
Magnetism-induced symmetry breaking in photoelectron
diffraction patterns — A. Chassé 1 , •W. Kuch 2 , M. Kotsugi 3 ,
Xingyu Gao 2 , F. Offi 2 , S. Imada 3 , S. Suga 3 , H. Daimon 4 , and
J. Kirschner 2 — 1 Fachbereich Physik, Martin-Luther-Universität
Halle-Wittenberg, D-06099 Halle — 2 Max-Planck-Institut für
Mikrostrukturphysik, Weinberg 2, D-06120 Halle — 3 Graduate School of
Engineering Science, Osaka University, 1–3 Machikaneyama, Toyonaka
560-8531, Japan — 4 Graduate School of Materials Science, Nara
Institute of Science and Technology, Ikoma, Nara 630-0192, Japan, and
CREST-JST, Japan
The influence of spin-polarized photoelectron scattering on the circular
dichroism of 2p3/2 photoelectrons from a ferromagnetic Fe(001)
single crystal surface is studied experimentally and theoretically. Twodimensional
photoelectron intensity angular distribution patterns are
presented. They were recorded at 482.5 eV kinetic energy for both helicities
and for opposite magnetization directions by a display-type spherical
mirror analyzer, which allows simultaneous energy and momentum analysis
of emitted photoelectrons. Multiple-scattering cluster photoelectron
diffraction calculations agree well with the experiment, and reproduce
even fine details of the observed photoelectron diffraction features. A
breaking of symmetry in the circular dichroism of the Fe 2p3/2 photoelectron
angular distribution patterns, related to the presence of magnetic
moments on the Fe atoms, is observed both in the experiment and the
calculation. Backed by theoretical calculations, such measurements bear
the potential to study also systems with complicated spin structures.
MA 4.3 Mo 10:45 H22
Search for structural relaxations upon spin reorientation of
Ni-monolayers by x-ray diffraction and MOKE — •Meyerheim
H. L. 1 , Sander D. 1 , Popescu R. 1 , Robach O. 2 , Ferrer S. 2 , and
Kirschner J. 1 — 1 MPI für Mikrostrukturphysik, Weinberg 2, 06120
Halle, Germany — 2 ESRF, BP 220, F-38043 Grenoble, France
Using surface x-ray diffraction (SXRD) and magneto-optical Kerr effect
(MOKE) measurements, the correlation between adlayer induced
spin reorientation and structure relaxation was investigated in the trilayer
system Ni/Fe/Ni on W(110). While the deposition of one Fe layer
on the Ni film [Ni-thickness: 5, 8 and 10 layers on W(110)] induces a
switching of the easy axis from in-plane to out-of-plane, subsequent deposition
of another Ni layer reverts the easy axis back to in-plane. SXRD
measurements along the reciprocal lattice rods before and after ad-layer
deposition indicate that changes of peak positions, if present at all, must
be below about 5×10 −4 reciprocal lattice units. This corresponds to a
change in the interlayer spacing in the order of 0.002 ˚Aand represents
the limit of the experimental accuracy. The analysis of the peak shapes
does not provide any evidence for film structure in-homogeneities. The
results are discussed in terms of strain and surface contributions to the
magnetic anisotropy.
MA 4.4 Mo 11:00 H22
Convergence in ab initio nonlinar surface magneto-optics of a
Ni/Cu (001) bilayer — •Torsten Andersen 1,2 , Rajeev Ahuja 1 ,
and Wolfgang Hübner 2 — 1 CMT, Dept. of Physics, Uppsala Universitet
(S) — 2 CMT, FB Physik, TU Kaiserslautern (D)
We discuss some aspects of creating a well-converged optical secondharmonic
spectrum from a Ni/Cu bilayer in an ab initio calculation. It
turns out that the convergence of the nonlinear optical susceptibility
requires much more than a simple convergence of the band structure to
1/1000th of the optical energy. Whereas both magnetic and nonmagnetic
symmetries can be resolved using the nonlinear optical intensity at this
level convergence, the symmetries of the individual tensor elements in the
nonlinear optical susceptibility can not. We show by varying the magnetization
direction in the Ni/Cu bilayer that even nonmagnetic tensor
elements require a much higher level of convergence than what is needed
for a simple recognition of the crystal magnetic symmetry. Convergence
is reached by increasing the demands on the band structure, and by a
dense sampling in reciprocal space.
MA 4.5 Mo 11:15 H22
Ab initio study of the magnetic structure of fcc Fe grown on a
Cu(001) substrate — •Bogdan Yavorsky and Ingrid Mertig —
Fachbereich Physik, Martin-Luther-Universität Halle, Deutschland
First-principle total energy studies of Fe films on a Cu (001) substrate
are presented. The films are modeled by symmetric 6Fe/8Cu/6Fe slabs.
Both collinear and noncollinear magnetic configurations are considered.
The effect of the surface relaxation on the total energy of the system is
discussed. It was found that the energy difference between the favored
collinear double-layered antiferromagnetic state and the noncollinear configurations
is reduced by contraction of the Fe sublayer but still remains
positive. The possibility of stable noncollinear magnetic configurations in
the system is discussed.
MA 4.6 Mo 11:30 H22
Spin waves in ultrathin Fe films on Co/Cu(001) — •Markus Etzkorn
1 , P. S. Anil Kumar 1 , W. Tang 1 , R. Vollmer 1 , H. Ibach 2 ,
and J. Kirschner 1 — 1 Max-Planck Institut für Mikrostrukturphysik,
Weinberg 2, 06120 Halle — 2 Institut für Schichten und Grenzflächen
ISG3, Forschungszentrum Jülich, 52425 Jülich
By using spin polarized electron energy loss spectroscopy (SPEELS)
we measured spin-wave excitations in 3 ML Fe on 1 ML Co/Cu(001).
Similar to Co on Cu(001) [1], the spin waves appear as a single peak in
the SPEEL-spectra that can be followed up to the surface Brillouin zone
(SBZ) boundary. The spin-wave energy at the SBZ boundary is about
140 meV. The ratio of spin-wave width to spin-wave energy is about one
for large wave vector spin waves. This suggests that these spin waves
strongly interact with Stoner excitations. In contrast to the case of Co
the dispersion in Fe can not be fitted by a nearest neighbor (NN) Heisenberg
model with a single exchange coupling constant J. In theoretical
calculations [2] the exchange coupling constant of the surface layer of Fe
on Cu(001) is enhanced by about a factor of 2 compared to its bulk value.
Using a NN Heisenberg model with an enhanced surface exchange coupling
constant J1 = 2J a spin-wave stiffness of about 150 meV˚A 2 results
from the fit to the data. This is significantly lower than the value of bulk
bcc Fe (280 meV˚A 2 ).
[1] R. Vollmer, M. Etzkorn, P. S. Anil Kumar, H. Ibach, and J. Kirschner,
Phys. Rev. Lett. 91 (2003) 147201.
[2] M. Pajda, J. Kudrnovsk´y, I. Turek, V. Drchal, and P. Bruno, Phys.
Rev. Lett. 85 (2000) 5424.
MA 4.7 Mo 11:45 H22
Spin-Polarized Scanning Tunneling Spectroscopy of Co Islands
on Cu(111) — •Oswald Pietzsch, Stefan Heinze, André Kubetzka,
Matthias Bode, and Roland Wiesendanger — Institute
of Applied Physics, University of Hamburg, Jungiusstrasse 11, 20355
Hamburg, Germany
Spin-averaged and spin-polarized scanning tunneling spectroscopy at
low temperature was performed on nanometer-scale triangular Co islands
grown epitaxially on Cu(111) in the sub-monolayer coverage regime. Two

Magnetismus Montag
structurally different island types can clearly be distinguished by their
spin-averaged electronic structure. Spin-polarized measurements allow a
separation of spectral contributions arising from different island stacking
or from opposite magnetization states, respectively. We compare these
results with ab initio electronic band structure calculations.
In an applied magnetic field both island types are found to be magnetized
perpendicular to the surface, with large values of saturation field,
remanence, and coercivity. It is found that for one island type the saturation
field is significantly higher than for the other.
As was shown in spin-averaged measurements [1], bias-voltage dependent
oscillation patterns of the local density of states (LDOS) due to
electron confinement can be observed on the Co islands. Here we present
spin-polarized data revealing the oscillation amplitude to depend on the
spin direction.
[1] L. Diekhöner et al., Phys. Rev. Lett. 90, 236801 (2003).
MA 4.8 Mo 12:00 H22
Magnetism of Fe on W(001) — •Kirsten von Bergmann,
Matthias Bode, and Roland Wiesendanger — University of
Hamburg, Institute of Applied Physics, Jungiusstr. 11, 20355 Hamburg,
Germany
There has been a lot of interest in the magnetic properties of the highly
strained pseudomorphic layers of Fe on W(001). Using spatially averaging
methods contrary results have been reported concerning the anisotropy
axis [1-3]. To overcome this discrepancy we used spin-polarized scanning
tunneling microscopy (SP-STM) to investigate this system: the method
is magnetically sensitive and has a high spatial resolution which allows
not only the investigation of magnetic properties but also a direct correlation
to electronic structure measurements and detailed topographic
studies.
The domain structure of Fe on W(001) in the low coverage regime is
imaged and the four fold anisotropy can directly be deduced from maps
of differential conductance (dI/dU). Quantitative analysis of the intensity
of the dI/dU signal reveals a layer-dependent anisotropy axis in the
pseudomorphic regime: the magnetic easy axis rotates by 45 ◦ from 〈110〉
in layers with a local coverage of 2 and 3ML to 〈100〉 at a local coverage
of 4ML.
[1] G. A. Mulhollan et al., Phys. Rev. B 43, 13645 (1991).
[2] T. L. Jones and D. Venus, Surf. Sci. 302, 126 (1994).
[3] W. Wulfhekel et al., Europhys. Lett. 49, 651 (2000).
MA 4.9 Mo 12:15 H22
Spin-orbit interaction at the Gd(0001) and O/Gd(0001) surfaces
— •O. Krupin 1 , G. Bihlmayer 2 , S. Gorovikov 3 , J. E. Prieto
1 , K. Döbrich 1 , G. Kaindl 1 , S. Blügel 2 , and K. Starke 1 —
1 Institut für Experimentalphysik, Freie Universität Berlin — 2 Institut
für Festkörperforschung (IFF), Forschungszentrum Jülich — 3 MAX-Lab,
Lund University, Sweden
We compare experimental angle-resolved photoemission investigations
with first-principles DFT calculations, including spin-orbit interaction,
of Gd(0001) and O/Gd(0001) surface states. For both systems, experimental
and theoretical results reveal that the energy dispersion of the
surface state depends on the relative orientation of the propagation direction
of the electrons and the spin-quantisation axis. While for the clean
Gd surface only the majority state of the exchange split surface states is
occupied, both the minority and majority states appear below the Fermi
level upon oxygen adsorption. Angle-resolved photoemission experiments
on these two surface states directly demonstrate that the observed effect
on the energy dispersion is caused by spin-orbit interaction. In addition,
oxygen adsorption leads to a modified near-surface electronic structure
that results in an increased spin-orbit interaction.
MA 4.10 Mo 12:30 H22
Rashba splitting of surface states at Gd(0001) surfaces — •G.
Bihlmayer 1 , O. Krupin 2 , J.E. Prieto 2 , S. Blügel 1 , G. Kaindl 2 ,
and K. Starke 2 — 1 Institut für Festkörperforschung, Forschungszentrum
Jülich, Germany — 2 Fachbereich Physik, Freie Universität Berlin,
Germany
By angle resolved photoemission measurements on clean and O-covered
Gd(0001) surfaces a dependence of the dispersion of the surface state on
the magnetization direction of the sample was found. We present results
of first-principles calculations showing that this behavior is a direct
manifestation of a relativistic effect, known as Rashba effect in the field
of semiconductor heterostructures. Normally, this tiny effect is difficult
to observe directly or to access with ab-inito calculations, but on some
metal surfaces it is large; we discuss, why the strength of this ’spin-orbit
splitting’ is big for some states (O/Gd(0001)) and rather small for others
(clean Gd(0001)). Our results are in good quantitative agreement with
measured data. The differences to the nonmagnetic surfaces, on which
this effect also has been observed (e.g. Au(111)) are addressed. Other
systems, on which this effect could be observed experimentally are suggested.
MA 4.11 Mo 12:45 H22
Theoretical study of magnetic and spectroscopic properties of
supported transition metal clusters — •J. Minar 1 , H. Ebert 1 ,
V. Popescu 1 , I. Cabria 2 , R. Zeller 2 , and P.H. Dederichs 2 —
1 Dep. Chemie/Phys. Chemie, Universty of Munich, Muenchen, Germany
— 2 Forschungszentrum Juelich, Juelich
Magnetic clusters receive recently a lot of attention in academic but
also in technological research. On the one hand side, the interest is caused
by the fact that clusters provide a bridge between atoms and bulk material
often showing quite peculiar properties. On the other hand, the
ongoing need for miniaturizing, in particular in data storage technology,
leads to smaller and smaller functional units leading finally to small clusters.
In this work the fully relativistic spin-polarized KKR method has
been used to study the magnetic and spectroscopic properties for supported
clusters. For clusters supported on a transition metal substrate it
is shown that the magnetic properties depend on many different parameters
as substrate type, cluster size and shape and so on. This applies especially
if one considers properties that are caused by spin-orbit coupling
as the X-ray circular dichroism. In line with recent experimental findings
a very pronounced magnetic circular dichroism in X-ray absorption is
found for Co-clusters on Pt(111). The results for the MCXD spectra and
their connection with the spin, orbital and spin dipolar moments will be
discussed on the basis of the so-called sum rules.
MA 4.12 Mo 13:00 H22
Electronic structure versus spin polarization in NiMnSb —
•Jürgen Braun, Hristo Kolev, Georgi Rangelov, and Markus
Donath — Physikalisches Institut, Westfälische Wilhelms-Universität
Münster, Wilhelm-Klemm Str. 10, 48149 Münster
Half-metallic semi Heusler alloys like NiMnSb have been ascribed
promising materials for spintronic devices, because of a theoretically
predicted high spin polarization at the Fermi level. Unfortunately, from
our spin-resolved Appearance Potential Spectroscopy (SRAPS) measurements
an unexpected low spin polarization was observed. This result is
in agreement with experimental findings from other groups but yet not
understood. To investigate the physical origin of this discrepancy we
performed a quantitative theoretical analysis of the experimental data.
Using a fully relativistic theory of SRAPS, which describes the measured
spectra as the self-convolution of the matrix-element weighted, orbitallyresolved
unoccupied density of states, we are able to present a quantitative
explanation for the small spin polarization experimentally found in
(semi) Heusler alloys.

Magnetismus Montag
MA 5 Hauptvorträge Hesse / A. Bauer
Zeit: Montag 14:00–15:00 Raum: H10
Hauptvortrag MA 5.1 Mo 14:00 H10
Vom Superpara- zum Ferromagneten im Stoner-Wohlfarth
Bild — •J. Hesse — Institut für Metallphysik und Nukleare
Festkörperphysik, TU Braunschweig, Mendelssohnstr. 3, 38106
Braunschweig, Germany
Stoner und Wohlfarth führten 1948 in den Magnetismus kleine eindomänige
Teilchen ein. Ausgehend vom idealisierten Bild kohärenter
Rotation der Magnetisierung bei Ummagnetisierungsprozessen bildet
die den Teilchen zugeordnete magnetische Anisotropie-Energie eine
wesentliche Grundlage zum Verständnis des heute aktuellen Nano-
Magnetismus. Beginnend mit idealem Superparamagnetismus werden
Magnetisierungsexperimente diskutiert die neben den etablierten Messungen
der Hysteresis-Kurve und der Temperaturabhängigkeit der Magnetisierung
auch andere Wege aufzeigen um über die magnetischen Eigenschaften
von nanoskaligen Teilchensystemen Informationen zu gewinnen.
Hauptvortrag MA 5.2 Mo 14:30 H10
Breakthrough in magneto-optical near-field microscopy —
•Andreas Bauer, Gereon Meyer, Tristan Crecelius, Irene
Mauch, and Günter Kaindl — Freie Universität Berlin, Institut für
Experimentalphysik, Arnimallee 14, 14195 Berlin
MA 6 Magnetische Partikel / Cluster
Magneto-optical microscopy is a powerful technique for studying magnetic
properties of thin films. The major drawback of conventional optical
microscopy, however, is the diffraction-limited spatial resolution,
which renders studies of sub-µm structures difficult. Rather promising
was therefore the development of scanning near-field optical microscopy
(SNOM) almost two decades ago by which resolutions beyond the diffraction
limit could be achieved. However, due to persistent technical problems
such as diminished magneto-optical signals caused by depolarisation
effects, magnetic SNOM is still not established as a high-resolution
magnetic-microscopy technique.
We have constructed a magnetic SNOM that overcomes most of the
problems [1]. It can be operated either in air or ultrahigh vacuum, at variable
sample temperature and external magnetic fields. Its resolution and
sensitivity is high enough to allow for imaging of a few hundred nm-wide
magnetic-stripe domains in ultrathin films of Fe/Cu(100). We also studied
the transformation of the stripe-domain phase in external magnetic
fields. The high sensitivity as well as suppression of artefacts is provided
by a Sagnac interferometer which is a unique technique for detecting
magneto-optical effects. The Sagnac-SNOM should also be ideally suited
for ultrafast magnetization-dynamics measurements of nanostructures.
[1] G. Meyer et al., Appl. Phys. Lett. 83, 1394 (2003).
Zeit: Montag 15:15–18:30 Raum: H10
MA 6.1 Mo 15:15 H10
Wechselspiel zwischen strukturellen und magnetischen Freiheitsgraden
in kleinen Fe Clustern — •Georg Rollmann, Sanjubala
Sahoo und Peter Entel — Theoretische Tieftemperaturphysik,
Universität Duisburg-Essen, Lotharstr. 1, D-47048 Duisburg
Übergangsmetallpartikel kommen vielfach in magnetischen Anwendungen
oder im Bereich der Katalyse zum Einsatz. Die atomaren magnetischen
Momente solcher Cluster sind im Vergleich zu den entsprechenden
Bulk-Werten oftmals erhöht und steigen mit abnehmender Teilchengröße
weiter an. Über ihre relativen Orientierungen zueinander, das Auftreten
von nichtkollinearem Magnetismus, ist allerdings erst wenig bekannt.
Wir präsentieren hier Resultate aus ab initio Rechnungen zu strukturellen
und magnetischen Eigenschaften kleiner Fe Cluster. Die Rechnungen
wurden im Rahmen der Dichtefunktionaltheorie durchgeführt und
basieren auf der Projector Augmented Wave Methode in Kombination
mit ebenen Wellen als Basisfunktionen. Es stellt sich heraus, daß die magnetischen
Eigenschaften der Partikel durch deren Geometrie bestimmt
werden, wobei sich für spezielle, zumeist sehr symmetrische Anordnungen
der Atome nichtkollineare magnetische Momente ausbilden. Für andere
Geometrien, insbesondere verzerrte Strukturen, stimmt die lokale
Richtung der Magnetisierungsdichte jedoch mit der globalen Quantisierungsachse
überein, so daß die energetischen Grundzustände der Partikel
zumeist durch gewöhnliche kollineare magnetische Strukturen gegeben
sind.
MA 6.2 Mo 15:30 H10
Electronic Structure and X-Ray Photo-Emission Spectra Calculations
of Ordered and Disordered Iron-Platinum Clusters —
•S. Bornemann, J. Minár und H. Ebert — Department Chemie /
Physikalische Chemie, Universität München, Butenandstr. 5-13, D-81377
München, Germany
Spin polarised relativistic Korringa-Kohn-Rostocker electronic bandstructure
calculations were performed for ordered and disordered fcc
Iron-Platinum clusters. Various models of ordered clusters, differing in
size as well as iron-platinum ratio were examined within the Local Spin
Density Approximation. In order to describe the ensemble averaged electronic
properties of such clusters an extension of the Coherent Potential
Approximation method was developed and successfully applied to systems,
containing iron and platinum in equal proportions. On the basis
of these results X-ray photo-emmision spectra were calculated for the
ordered and disordered systems respectively.
MA 6.3 Mo 15:45 H10
Electronic and Magnetic Properties of Ligand-Free FePt
Nanoparticles — •H.-G. Boyen 1 , K. Fauth 2 , B. Stahl 3 , P.
Ziemann 1 , G. Kästle 1 , F. Weigl 1 , F. Banhart 4 , M. Heßler 2 ,
G. Schütz 3 , N.S. Gajbhiye 5 , J. Ellrich 6 , H. Hahn 6 , M.
Büttner 7 , M.G. Garnier 7 , and P. Oelhafen 7 — 1 Abteilung
Festkörperphysik, Universität Ulm, D-89069 Ulm — 2 Experimentelle
Physik IV, Universität Würzburg, Am Hubland, D-97074 Würzburg —
3 MPI für Metallforschung, Heisenbergstraße 1, D-70689 Stuttgart —
4 Zentrale Einrichtung Elektronenmikroskopie, Universität Ulm, D-89069
Ulm — 5 Institut für Nanotechnologie, Forschungszentrum Karlsruhe,
D-76021 Karlsruhe — 6 Fachbereich Material- und Geowissenschaften,
Petersenstr. 23, TU Darmstadt, D-64287 Darmstadt — 7 Institut für
Physik, Universität Basel, Klingelbergstr. 82, CH-4056 Basel
Ordered arrays of well separated and atomically pure FePt nanoparticles
(diameter 3.7 nm) have been prepared under UHV conditions by
employing a combination of oxygen/hydrogen plasmas allowing to completely
remove the organic ligands which are present after particle synthesis.
The plasma treatments conserve, however, the order of the particle
arrangement. This enables us to investigate, for the first time, the electronic
structure and the magnetic properties of bare, ligand-free fcc FePt
particles by means of X-ray induced photoelectron spectroscopy (XPS)
and X-ray Magnetic Circular Dichroism (XMCD), respectively. First results
about the electronic density of states and the magnetic behavior of
the nanoparticle array will be presented.
MA 6.4 Mo 16:00 H10
Magnetische Resonanz an FexPt1−x-Nanopartikeln — •C. Antoniak,
M. Ulmeanu und M. Farle — Experimentalphysik-Ag Farle,
Universität Duisburg-Essen, Lotharstr. 1, 47048 Duisburg
Chemisch ungeordnete monodisperse Fe0.7Pt0.3-Nanopartikel mit einem
Durchmesser von (2.6 ± 0.3)nm, mit organischen Liganden umhüllt
und als 2D-Lage auf einem Si-Wafer aufgebracht, wurden mittels Para-
/Ferromagnetischer Resonanz zwischen 20K und 350K untersucht. Bei
300K konnte aus frequenzabhängigen Messungen das Verhältnis von
Bahn- zu Spinmoment zu µ eff
L /µ eff
S = 0.016 [1] bestimmt werden. Für
tiefere Temperaturen verschiebt sich die Resonanzposition zu Br = 0.18T
bei 35K, d.h. um 0.15T, was durch die effektive Magnetisierung in
der Partikel-Lage bestimmt wird. Gleichzeitig zeigt die Intensität bei
200K ein Maximum, welches im Zeitfenster der Messung (Nanosekunden)
der Blocking-Temperatur entspricht. Durch den Vergleich mit SQUID-
Messungen (Zeitfenster: Minuten) wurde damit die effektive Anisotropie-
Konstante der Nanopartikel abgeschätzt: Keff ≈ 10 6 J/m 3 .

Magnetismus Montag
Unterstützt durch die Europäische Gemeinschaft.
[1] M. Ulmeanu, C. Antoniak, U. Wiedwald, M. Farle, Z. Frait, S. Sun,
Phys. Rev. B, in press
MA 6.5 Mo 16:15 H10
Bimetallische Kern-Hülle-Nanosysteme — •Neli Sobal 1 , M.
Giersig 1 und H. Sauer 2 für die Uni Duisburg-Kollaboration und die
CEA Grenoble-Kollaboration — 1 Forschungszentrum CAESAR, Bonn
— 2 Fritz-Haber-Institut, Berlin
Durch die Herstellung von neuen Nanokomposit-Materialien mit geeigneten
Zusammensetzung sollte höhere Sättigungsmagnetisierung, Kristallanisotropiekonstante
sowie Oxidationsbeständigkeit im Vergleich zu
reinen der 3d-Elementen erzielt werden. Wir präsentieren ein neues
nasschemisches Verfahren, das Herstellung von bimetallischen kolloidalen
Systeme in einem organischen Lösungsmittel ermöglicht. Platin-,
Palladium- oder Silber-Edelmetallkerne konnten mit einer unterschiedlich
dicken ferromagnetischen Kobalt-Hülle beschichtet werden. Im Fall
der Pd@Co Partikel erfolgte die Herstellung der Kobaltschale sowohl
mit einer kubisch flächenzentrierten (fcc) als auch hexagonal dicht
gepackten (hcp) Kristallstruktur. Transmissionselektronenmikroskopie
(TEM), Röntgenfluoreszensanalyse (EDX), SQUID-Magnetometrie und
Röntgenabsorptionsspektroskopie wurden für die Charakterisierung der
strukturellen und magnetischen Eigenschaften der bimetallischen Nanopartikeln
eingesetzt.
MA 6.6 Mo 16:30 H10
Selbstorganisierte Umhüllung magnetischer Nanopartikel aus
der Gasphase auf Phospholipid-Vielfachschichten — •B. Rellinghaus
1 , A. Terheiden 2 , Ch. Mayer 2 und M. Acet 3 — 1 Inst.
für Verbrennung und Gasdynamik — 2 Inst. für Chemie — 3 Inst. für Physik.
SFB 445, Universität Duisburg-Essen, D-47048 Duisburg
In nasschemischen Verfahren können periodische Anordnungen organisch
umhüllter FePt Nanopartikel erzeugt werden [1], die zur Einstellung
der magnetisch hochanisotropen L10-Struktur jedoch thermisch nachbehandelt
werden müssen, wodurch die regelmäßige Anordnung wieder
zerstört wird. In der Gashase können FePt-Partikel bereits vor der Deposition
in die L10-Struktur überführt werden [2], jedoch mit dem Nachteil
regelloser Partikelanordnungen auf dem Substrat. Wir stellen ein alternatives
Verfahren vor, dass die Vorteile beider Methoden kombiniert: In
der Gasphase präparierte und thermisch gesinterte FePt Nanopartikel
werden auf Si-Substraten deponiert, die mit Viellagenschichten verschiedener
Phospholipide beschichtet sind. Rasterelektronenmikroskopische
Untersuchungen zeigen, dass die so hergestellten Partikel eine eindeutige
Tendenz zur Ausbildung regelmäßiger Partikelanordnungen aufweisen
und räumlich von einander getrennt sind. Der Grad der Regelmäßigkeit
der Anordnung sowie der interpartikuläre Abstand hängen dabei stark
von der Wahl des Lipids sowie der Depositionstemperatur Tdep ab. Diese
müssen so gewählt sein, dass Tdep in der Nähe der Temperatur für einen
Übergang des Lipids in seine flüssigkristalline Phase liegt.
[1] S. Sun et al., Science 287 (2000) 1989.
[2] S. Stappert et al., J. Cryst. Growth 252 (2003) 440.
MA 6.7 Mo 16:45 H10
3 nm amorphe Fe-Teilchen mit Graphithülle — •Thorsten Enz 1 ,
Branko Stahl 1,2 , Markus Winterer 3 , Sarbari Bhattacharya 1
und Horst Hahn 1 — 1 Fachbereich Material- und Geowissenschaften,
Petersenstr. 23, TU Darmstadt, 64287 Darmstadt — 2 Institut für Nanotechnologie,
Forschungszentrum Karlsruhe, 76021 Karlsruhe — 3 Institut
für Verbrennung und Gasdynamik, Universität Duisburg-Essen, Lotharstraße
1, 47057 Duisburg
Mit der chemischen Gasphasensynthese (CVS) wurden Fe-
Nanoteilchen hergestellt. Sie zeigen keinerlei Oxidation und sind unter
Umgebungsbedingung stabil. XANES, Mössbauerexperimente und die
strukturelle Charakterisierung mit XRD zeigen den rein metallischen
Charakter der Teilchen. Sie sind umgeben von Graphithüllen, die zum
Teil zur Ausbildung von C-Nanoröhren führen. Unter bestimmten Prozessbedingungen
lassen sich amorphe Fe-Teilchen mit einem mittleren
Durchmesser von 3 nm und einer engen Größenverteilung herstellen. Der
amorphe Zustand wird durch C stabilisiert. Dennoch bilden sich bei der
Kristallisation der Proben keine Carbide, was auf die geringe Größe der
Teilchen zurückgeführt wird.
MA 6.8 Mo 17:00 H10
Untersuchungen zur ’ bottom-up‘ Herstellung granularer Strukturen
mittels magnetischer Kobalt-Nanopartikel — •Inga Ennen
1 , Andreas Hütten 1 , Daniela Sudfeld 1 , Klaus Wojczykowski
2 , Karsten Rott 1 , Peter Jutzi 2 und Günter Reiss 1 —
1 Universität Bielefeld, Fakultät für Physik, Universitätsstr. 25, D-33615
Bielefeld — 2 Universität Bielefeld, Fakultät für Chemie, Universitätsstr.
25, D-33615 Bielefeld
Eine physikalisch interessante Anwendung von magnetischen Partikeln
liegt in der Herstellung granularer Strukturen mit nahezu monodisperser
Teilchengrößenverteilung. Die hierfür notwendige Partikelstabilität wurde
an ligandenstabilisierten Co-Teilchen sowohl unter Atmosphärenbedingungen,
als beim Tempern im Vakuum sowie unter dem Einfluss von
technischem Formiergas (95% N2, 5% H2) untersucht. Dazu wurden die
Änderungen der strukturellen Eigenschaften mit elektronenmikroskopischen
Aufnahmen und die Veränderung der magnetischen Eigenschaften
mittels AGM-Messungen bei Raumtemperatur beobachtet und korreliert.
Darüber hinaus wird eine Strategie zur Herstellung granularer Strukturen
mit Co-Partikeln vorgestellt und erste Ergebnisse von XMR-
Messungen an solchen Systemen diskutiert.
MA 6.9 Mo 17:15 H10
Ternäre legierte magnetische Nanopartikel — •Daniela
Sudfeld 1 , Andreas Hütten 1 , Inga Ennen 1 , Daniel Meißner 2 ,
Klaus Wojczykowski 2 , Peter Jutzi 2 und Günter Reiss 1 —
1 Universität Bielefeld, Fakultät für Physik, Universitätsstraße 25,
D-33615 Bielefeld — 2 Universität Bielefeld, Fakultät für Chemie,
Universitätsstraße 25, D-33615 Bielefeld
Nach [1] sind ligandenstabilisierte FexCoyPt100−x−y Nanocluster hergestellt
worden durch simultane Reduktion von Pt(acac)2 und Co(acac)2
und die thermische Zersetzung von Fe(CO)5. Desweiteren ist die Synthese
mit Co2(CO)8 durchgeführt worden.
1 H-NMR- und FT-IR-Messungen haben Aufschluß gegeben über die
Reduktion und Zersetzung der Precursoren. Mittels hochaufgelöster
Transmissionselektronenmikroskopie sind sowohl die Teilchengrößen- und
Teilchenabstandsverteilungen als auch die Teilchen-Zusammensetzungen
mit EDX nachgewiesen worden. Darüber hinaus sind XRD-Messungen
zur Phasenbestimmung durchgeführt worden.
Das Magnetisierungsverhalten ist mit AGM bei Raumtemperatur und
nach Auslagerungsexperimenten untersucht worden, um eine Einstellung
der Anisotropie der mit Pt legierten Partikel nachweisen zu können.
Literatur: [1] M. Chen und D. E. Nikles, Nanoletters 2002, vol.2, no.
3, pp. 211-214.
MA 6.10 Mo 17:30 H10
Equation of State of Fe3C nanoparticles — •E. Duman, M. Acet,
T. Hülser, and E.F. Wasserman — Experimentalphysik, AG Farle,
Universität Duisburg-Essen
Fe3C, which incorporates only Fe as a metallic element with valence
electron concentration e/a = 8, is an Invar material [1]. The p electrons
of the interstitial carbon atoms hybridize with the d-band of the
metal, so that the electron concentration per Fe atom becomes 8.67 for
Fe3C, which fits into the Invar composition range. We have measured
the pressure dependence up to 30 GPa of the lattice parameters of Fe3C
nanoparticles (∼ 40nm) at room temperature and at 550 K using energy
dispersive X-ray diffraction. The pressure-volume data was analysed with
the third order Birch-Murnaghan equation and the isothermal bulk modulus
of both samples were obtained at room temperature and 550 K. The
bulk modulus of Fe3C nanoparticles at room temperature (Bo = 201
GPa) was found to be approximately %14 smaller than that of the value
at 550 K (Bo = 235 GPa). This difference is comparable with the relative
difference in the bulk modulus of Fe65Ni35 Invar in a similar temperature
range [2]. No pressure or temperature induced phase transition
was observed. Supported by DFG (SFB 445) [1]W. Pepperhof, M. Acet,
Constitution and Magnetism of Iron and its Alloys, Springer- Verlag,
Berlin-Heidelberg, 2001 [2]Philippe Renaud, Ph. D Thesis, Universite de
Lausanne, Faculte des Sciences, 1988
MA 6.11 Mo 17:45 H10
Magnetic hyperfine fields of Fe in Cd host — •Mohammad
Ghafari 1 , Elisa Baggio-Saitovitch 2 , and K. E. Munayco 2 —
1 TU Darmstadt, Material- und Geowissesnchaften, Petersenstr. 23, 64287
Darmstadt — 2 CBPF/ Centro Brasileiro de Pesquisas Fisicas, Rio de
Janeiro Brazil
Isolated impurity Fe atoms in a Cd matrix are expected to develop

Magnetismus Montag
a local magnetic moment. The local density of the state, N(E), at the
Fermi level at impurity site and the Stoner parameter, I, play a decisive
role for the onset of a magnetic moment. Theoretical calculations show
that the Stoner criteria, N(E) ·I > 1 for the development of Fe moments
are fulfilled in the Cd host. The magnetic properties of Fe impurities in
Cd are of particular interest as theoretical calculations predict a large
magnetic moment for Fe atoms in the Cd host on the other hand there
is no experimental information available about the magnetic moment of
Fe in Cd. The aim of the present work is to clarify the magnetic properties
of nanoscale Fe atoms in a Cd. Diluted Fe in Cd can be prepared
by co-evaporation of Fe and Cd under ultra high vacuum (UHV) conditions.
Of special interest is the determination of the internal magnetic
hyperfine field which is correlated to the magnetic moment of Fe. In the
CdFe system magnetic clusters have an average size of about 5 atoms;
this means that the Fe atoms are surrounded by Cd atoms and can therefore
be treated effectively as surface atoms. Such ferromagnetic clusters
with surface properties offer a new kind of material for which detailed
theoretical and experimental investigations are desirable.
MA 6.12 Mo 18:00 H10
Remagnetization dynamics in Permalloy microparticles
observed on the nanosecond time scale. — •Andrew Kuksov 1 ,
Aleksander Krasyuk 2 , Andreas Oelsner 2 , Daniel Neeb 2 ,
Gerd Schoenhense 2 , and Claus Schneider 3 — 1 IFW, Helmholz
str.20, 01069 Dresden — 2 Universitat Mainz, Staudingerweg 7, 55128
Mainz — 3 Forschungszentrum Juelich Institut fur Festkoerperforschung,
D-52425 Juelich
We have investigated the time evolution of the magnetization distribution
in Permalloy microparticles with time-resolved X-Ray Photo Emission
Electron Microscopy. The stroboscopic pump-probe experiments
with sub-nanosecond time resolution have been carried out at the synchrotron
facilities BESSY II and ESRF using soft X-ray magnetic circular
dichroism as magnetic contrast mechanism. The particles had a thickness
of 30 nm and the following shapes with linear dimensions of 40 microm-
MA 7 Magnetische Abbildungsverfahren
eters: rings, squares and diamonds (square rotated by 45 degree). As
the static domain patterns are dominated by the shape anisotropy, the
local magnetization M has well-defined directions (parallel, antiparallel,
orthogonal, 45 degree) with respect to the external magnetic field H generated
by a current pulse through the micro stripline. Depending on the
orientation between M and H the magnetization dynamics varies significantly.
The best time resolution achieved in these measurements was in
the range of 130ps.
MA 6.13 Mo 18:15 H10
Theoretical study of magnetic and spectroscopic properties of
supported transition metal clusters — •Ján Minár 1 , H. Ebert 1 ,
V. Popescu 1 , I. Cabria 2 , R. Zeller 2 und P. H. Dederichs 2 für die
ABRA-Kollaboration — 1 Department Chemie / Physikalische Chemie,
Universität München, Butenandstr. 5-13, D-81377 München, Germany
— 2 Inst. für Festkörperforschung, Forschungszentrum Jülich, Postfach
1913, D-52425 Jülich, Germany
Magnetic clusters receive recently a lot of attention in academic but
also in technological research. On the one hand side, the interest is caused
by the fact that clusters provide a bridge between atoms and bulk
material often showing quite peculiar properties. On the other hand, the
ongoing need for miniaturizing, in particular in data storage technology,
leads to smaller and smaller functional units leading finally to small clusters.
In this work the fully relativistic spin-polarized KKR method has
been used to study the magnetic and spectroscopic properties for supported
clusters. For clusters supported on a transition metal substrate it is
shown that the magnetic properties depend on many different parameters
as substrate type, cluster size and shape and so on. This applies especially
if one considers properties that are caused by spin-orbit coupling
as the X-ray circular dichroism. In line with recent experimental findings
a very pronounced magnetic circular dichroism in X-ray absorption is
found for Co-clusters on Pt(111). The results for the MCXD spectra and
their connection with the spin, orbital and spin dipolar moments will be
discussed on the basis of the so-called sum rules.
Zeit: Montag 15:15–15:45 Raum: H22
MA 7.1 Mo 15:15 H22
Stroboscopic wide-field Kerr microscopy with ps time resolution
— •Andreas Neudert, Jeffrey McCord, Rudolf Schäfer, and
Ludwig Schultz — Leibniz-Institut für Festkörper- und Werkstoffforschung
Dresden, P.O. Box 270016, D-01171 Dresden, Germany
We have extended a standard wide-field Kerr microscope with a pulsed
solid-state laser as illumination source to investigate magnetization processes
with a temporal resolution of about 30 ps. This is achieved by stroboscopic
imaging, thus limiting the observation to repeatable processes.
The repetition frequency of the laser pulses is 23 MHz, thus limiting the
time frame of the observation to 43 ns. The spatial resolution is about
0.3 µm. Due to the good SNR ratio, integration times for the pictures
are down to 50 ms/frame. The magnetic samples are excited by using
standard pulse generators with rise-times down to 100 ps, which are directly
triggered by the pulsed laser source. First results, demonstrating
the capabilities of the experimental setup, on the vortex movement in
structured Permalloy elements will be shown. A clearly different behavior
of the motion of a vortex compared to quasistatic remagnetization
processes is observed. The vortex structure first broadens and then restores
some µm away in a new equilibrium state.
This work is funded by the DFG Schwerpunktprogramm 1133 ”Ultrafast
magnetization processes”.
MA 7.2 Mo 15:30 H22
Noise and artifact suppression for near-field magneto-optical
microscopy through improved data preprocessing and piloted
wavelet analysis — •Fabian Kiendl and Gernot Güntherodt —
II. Physikalisches Institut der RWTH Aachen, D-52056 Aachen, Germany
The extraction of information about a sample from the raw data acquired
by our magneto-optical SNOM set-up [1,2] needs to be improved.
We propose a refined pre-processing of raw data into a raw image and a
wavelet de-noising that is tailored to SNOM images.
We make the pre-processing more resilient to outliers, base it additionally
on previously unused portions of the raw data, and refine the
suppression of low-frequency noise. Image features are pronounced much
more clearly in the resulting raw image, and the previously present stripelike
artifacts are removed. To tackle high-frequency noise, we adjust the
parameters of wavelet de-noising [3,4] to a given noisy SNOM image by
de-noising a superposition of this SNOM image with a known pilot image.
Additionally, we overcome the tendency of wavelet de-noising to produce
directional artifacts.
We find that images are de-noised well enough for our recently proposed
deconvolution method [5] to further enhance them. Yet we find
de-noising not to be restricted to SNOM images.
[1] G. Eggers, PhD thesis, Aachen University, ISBN 3-89825-065-2 (1999)
[2] A. Rosenberger, PhD thesis, Aachen University (2000)
[3] F. Kiendl, G. Güntherodt, 269th WE-Heraeus seminar (2002)
[4] W. Bäni, Wavelets, ISBN 3-486-25427-8, Oldenbourg (2002)
[5] F. Kiendl, G. Güntherodt, Verh. DPG (VI) 37, 1/215 (2002)

Magnetismus Montag
MA 8 Elektronentheorie
Zeit: Montag 15:45–18:00 Raum: H22
MA 8.1 Mo 15:45 H22
High-field magnetic susceptibility of ferromagnetic metals —
•Sergiy Mankovskyy and Hubert Ebert — Dept. Chemie/Phys.
Chemie, Universität München, Butenandtstr. 5-13, D-81377 München,
Germany
The results of a theoretical study of the high-field magnetic susceptibility
of ferromagnetic metals and alloys are presented. The theoretical
description of the magnetic susceptibility is based on a combination of
a linear response approach and the fully relativistic Green’s function
formalism. Additional contributions to the magnetic susceptibility (e.g.
spin-charge response function, contribution related to a Fermi level shift)
become important in the ferromagnetic state if compared with the paramagnetic
one. Illustrating examples are presented for various 3d transition
metal systems. In particular, the magnetic susceptibilities have been calculated
for weak magnetic systems such as ZrZn2 and TiBe2. As is known
from experiment [1,2] they are ferromagnetic under substitution of some
Zn and Be atoms by vacancies and Cu atoms, respectively. The calculations
have been performed both for the ferromagnetic and paramagnetic
states of ZrZnx and TiBexCu1−x alloys. The XMCD spectra of ferromagnetic
solids in the presence of an external magnetic fields are calculated
and compared to those obtained for the case without any fields. [1] B. T.
Mattias and R. M. Bozorth, Phys. Rev., 109 (1958) 604. [2] G. S. Knapp,
F. Y. Fradin and H. L. Culbert, J. Appl. Phys., 42 (1971) 1041.
MA 8.2 Mo 16:00 H22
Structural and magnetic PD–pMOKE of low symmetric Co
— •Helmut Rathgen 1,2 , Mikhail I. Katsnelson 1 , Olle Eriksson
1 , and G. Zwicknagl 2 — 1 Condensed Matter Theory, Department
of Physics, Uppsala University, Box 530, S-75121 Uppsala, Sweden
— 2 Institut für Mathematische Physik, Technische Universität Braunschweig,
Mendelssohnstraße 3, 38106 Braunschweig, Germany
We calculate for the first time the polar MOKE of low symmetric systems
from ab initio methods with a full electrodynamics approach. By
that, a new anisotropy effect is investigated, which is the dependence of
the polar MOKE on the direction of the polarization vector relative to
the crystal lattice. We call this effect PD–pMOKE.
The problem of reflection and transmission from multilayer systems is
solved accurately with a numerical approach. With this, we present a new
computational tool that covers a broad range of magneto–optical effects
of bulk materials as well as multilayer systems. E.g. MOKE, the Farraday
effect, x–ray standing wave effects and the optical response from a Bloch
wall. Results are presented for the Kerr effect of fcc 110 Co as well as
mono–, poly–, and bi–crystalline hcp 11¯20 Co. Pronounced PD–pMOKE
is found, with magnitudes resolvable by experiments. Exceptional frequencies
are predicted at which anisotropies vanish. The special role of
bi–crystals is explained. A short glance is taken on the possibilities of
the new approach. Expectations are presented concerning experiments
on the PD–pMOKE of Co as well as low symmetric FePt.
MA 8.3 Mo 16:15 H22
Influence of dynamical correlation effects on magneto-optical
properties of 3d metals — •Stanislav Chadov 1 , Alexander
Perlov 1 , Hubert Ebert 1 , Livio Chioncel 2 , Alexander Lichtenstein
2 , and Michael Katsnelson 3,4 — 1 Phys. Chemistry Institute,
University of Munich, D-80333 Munich, Germany — 2 University of Nijmegen,
NL-6525 ED Nijmegen, The Netherlands — 3 Institute of Metal
Physics, 620219 Ekaterinburg, Russia — 4 Department of Physics, Uppsala
University, Box 530, SE-75121 Uppsala, Sweden
The optical and magnetooptical properties of 3d metals are theoretically
investigated taking into account dynamical correlation effects. Various
schemes to approximate the effective self-energy, including Second
Order Perturbation Theory and Dynamic Mean Theory+Fluctuation Exchange
methods have been implemented and investigated. It is shown
that accounting for many-body correlation effects is very important for
3d metals to get a quantitative agreement with experimental results.
While LSDA-based calculations of optical and magnetooptical properties
in general lead to a satisfying qualitative agreement with experimental
spectra, inclusion of correlation effects in particular give the correct
position of prominent spectral features.
MA 8.4 Mo 16:30 H22
Bestimmung magnetischer 5d-Momente seltener Erden mittels
XMCD — •H. Wende 1 , A. Scherz 1 , C. Sorg 1 , K. Baberschke 1 ,
A.L. Ankudinov 2 und J.J. Rehr 2 — 1 Institut für Experimentalphysik,
Freie Universität Berlin, Arnimallee 14, D-14195 Berlin — 2 Department
of Physics, Box 351560, University of Washington, Seattle, WA 98195
Die Bestimmung der 5d-Momente seltener Erden mittels magnetischem
Röntgenzirkulardichroismus (XMCD) an den L2,3-Kanten wird nicht nur
durch elektrische Quadrupol-Beiträge (E2: 2p → 4f) erschwert, die
zusätzlich zu den elektrischen Dipol-Beiträgen (E1: 2p → 5d) auftreten
[1]. Vielmehr zeigt es sich, dass die Dipol-Übergangsmatrixelemente eine
starke Spin- und Energieabhängigkeit aufweisen. Daher ist das dichroische
Signal an den L2,3-Kanten seltener Erden selbst nach Trennung
der E1- und E2-Beiträge nicht proportional zur Spin-Zustandsdichte.
Wird die Spin- und Energieabhängigkeit der Matrixelemente bei der Anwendung
der integralen Summenregeln nicht berücksichtigt, so wird sogar
fälschlicherweise eine antiparallele Orientierung der 5d- zu den 4f-
Momenten bestimmt. Wir zeigen hier, wie die Ergebnisse der Anwendung
der Summenregeln am Beispiel experimenteller Tb-Spektren mit
Hilfe von ab initio Rechnungen korrigiert werden können. Gefördert durch
BMBF (05 KS1 KEB4).
[1] H. Wende et al., J. Appl. Phys. 91 (2002) 7361
MA 8.5 Mo 16:45 H22
The electronic structure of ordered and disordered, doped
Heusler alloys: Co2Cr1−xFexAl — •H. C. Kandpal, G. H.
Fecher, S. Wurmehl, H.-J. Elmers, G. Schönhense, and C.
Felser — Johannes Gutenberg - Universität, 55099 Mainz
Doped Heusler alloys and compounds of the type Co2Cr1−xFexAl with
varying Cr to Fe ratio x were investigated experimentally and theoretically.
The electronic structure of the doped Heusler compound was calculated
using different types of band structure calculations (FLAPW,
LMTO, SPRKKR). The ordered compounds turned out to be ferrimagnetic
with the Al magnetic moment being aligned anti-parallel to the 3d
transition metal moments. Only the pure compound Co2CrAl shows - in
non-relativistic calculations - clearly a gap in the minority bands around
the Fermi-energy. The ordered pure compounds exhibit an indirect minority
gap, whereas the ordered, doped compounds exhibit a direct gap.
Magnetic circular dichroism (MCD) in X-ray absorption was measured at
the LII,III edges of Co, Fe, and Cr of the pure compounds and the x = 0.4
alloy in order to determine element specific magnetic moments. Calculations
and measurements show an increase of the magnetic moments
with increasing iron content. The experimentally observed reduction of
the magnetic moment of Cr can be explained by Co-Cr site-disorder. The
presence of the gap in the minority bands of Co2CrAl can be attributed
to the occurrence of pure Co2 and mixed CrAl (001)-planes in the L21
structure. It is retained in structures with different order of the CrAl
planes but vanishes in the X-structure with alternating CoCr and CoAl
planes.
MA 8.6 Mo 17:00 H22
Über die Spinpolarisation von ”halbmetallischen Ferromagneten”
— •Gerhard H. Fecher und Claudia Felser — Institut
für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-
Universität, 55099 Mainz
Materialien mit einer vollständigen Spinpolarisation an der Fermienergie
werden als halbmetallische Ferromagnete bezeichnet. Diese Definition
setzt eine vollständige Trennung der Spin und Bahn Freiheitsgrade
der Elektronen im Festkörper voraus. Anhand von Symmetrieargumenten
wird aufgezeigt, daß Materialien mit vollständiger Spinpolarisation
prinzipiell unmöglich sind. Dies ist eine direkte Konsequenz der Dirac
Gleichung. Spin-Bahn Wechselwirkung alleine - z.B. als Störung in nichtrelativistischen
Theorien - löst diesen Konflikt nicht, solange nicht voll
relativistische Wellenfunktionen betrachtet werden. Voll-relativistische
Berechnungen der elektronischen Struktur zeigen, daß halbmetallische
Ferromagnete nur als Näherung im nicht-relativistischen Grenzfall existieren.
Letzteres schliesst das Auftreten von Materialien mit extrem hoher
Spinpolarisation in der Nähe der Fermie-energie nicht aus.

Magnetismus Montag
MA 8.7 Mo 17:15 H22
Magnetic and elastic properties of YCo5 under pressure —
•Daniela Koudela 1 , Ingo Opahle 1 , Manuel Richter 1 , Klaus
Koepernik 1 , Ulrike Nitzsche 1 , Helge Rosner 2 , Michael
Kuzmin 3 , and Helmut Eschrig 1 — 1 IFW Dresden, PF 270116, 01171
Dresden — 2 MPI-cPfS Dresden, Nöthnitzer Straße 40, 01187 Dresden
— 3 Instituto de Ciencia de Materiales de Aragon, Zaragoza; Spain
We computed the total energy and the magnetic moment of YCo5
in dependence of the lattice parameters. Our calculations are based on
density functional theory in the local spin density approximation. In accordance
with earlier calculations of Yamada et al. [J. Phys.: Condens.
Matter 11 (1999) 483] we find a transition from high spin to low spin under
applied pressure. On the other hand our calculations show a strong
dependence of the magnetic moment on volume in the low spin state close
to the transition volume not observed by the previous authors. This is
connected with a change in the bulk modulus from about 200 GPa to 60
GPa at the transition, which takes place at a pressure of about 9 GPa.
The calculations were done with the full-potential local-orbital method
(FPLO).
MA 8.8 Mo 17:30 H22
Magnetismus und elektronische Struktur von Gadolinium
— •C. Santos 1 , V. Eyert 2 und W. Nolting 1 — 1 Lehrstuhl
Festkörpertheorie, Institut für Physik, Humboldt-Universität zu Berlin
— 2 Institut für Physik, Theoretische Physik II, Universität Augsburg
Durch Kombination einer vielteilchentheoretischen Auswertung des
Kondo-Gitter-Modells mit einer ,,ab initio“ Bandstrukturrechnung bestimmen
wir sowohl die temperaturabhängige elektronische Struktur als
MA 9 Hauptvortrag Demokritov
auch die magnetischen Eigenschaften von HCP-Gadolinium. Das Vielteilchenproblem
wird mit der in Phys. Rev. B 65 144419 vorgestellten Green-
Funktion-Theorie behandelt. Diese haben wir auf das Mehrband-Kondo-
Gitter Modell erweitert und anschließend mit einer ASW-Bandstruktur
kombiniert, wobei Doppelzählung von relevanten Wechselwirkungen vermieden
werden konnte. In diesem Beitrag werden Ergebnisse der selbstkonsistent
berechneten Curie-Temperatur TC, der Magnetisierung 〈S z 〉
und der temperaturabhängigen Quasiteilchen-Bandstruktur vorgestellt.
Es ergibt sich eine fast quantitative Übereinstimmung mit experimentellen
Daten.
MA 8.9 Mo 17:45 H22
Structure and Magnetism of Light Actinides and Their Compounds:
Theorie — •Manuel Richter, Ingo Opahle, Ulrike
Nitzsche, Klaus Koepernik, and Helmut Eschrig — IFW Dresden,
PF 270116, D-01171 Dresden
Structural and magnetic properties of actinides and actinide compounds
are much influenced by spin-orbit interaction and other relativistic
effects. By means of the recently developed fully relativistic fullpotential
local-orbital (R-FPLO, [1]) scheme, we have evaluated equilibrium
volume, bulk modulus, and structural energies of light actinide
metals in the framwork of the local density approximation. In particular,
we find evidence for the existence of a hexagonal Uranium phase
in thin films on W(110) and for the possible existence of cubic Protactinium.
Using the local spin density approximation with orbital polarization
corrections, the magnetic properties of cubic Uranium Sulfide are
investigated.
[1] http://www.ifw-dresden.de/FPLO/
Zeit: Dienstag 09:30–10:00 Raum: H10
Hauptvortrag MA 9.1 Di 09:30 H10
Experimental observation of symmetry breaking soliton modes
in an active ring — •Sergej O. Demokritov 1 , Alexander
A. Serga 1 , Vladislav E. Demidov 1 , Burkard Hillebrands 1 ,
Michail P. Kostylev 2 und Boris A. Kalinikos 2 — 1 Fachbereich
Physik, Technische Universitaett Kaiserslautern, Erwin-Schroedinger-
Strasse 56, 67663 Kaiserslautern, Germany — 2 St. Petersburg Electrotechnical
University, 197376 St. Petersburg, Russia
Solitons are large-amplitude, spatially confined wave packets in nonlinear
media. A unique feature is their propagation without a change in
shape owing to the stabilizing effect of the nonlinearity. We report on the
first experimental study of solitons in an active ring and their novel pro-
MA 10 Exchange Bias
perties due to phase quantization [1]. As a model system, we constructed
an active nonlinear ring based on spin-wave propagation in a magnetic
film. To address individually each eigen-mode of the ring a newly developed
mode selecting mechanism based on phase sensitive amplification
has been used. Several novel symmetry-breaking soliton-like modes are
found, such as Möbius solitons, which break the fundamental symmetry
of 2p-periodicity in the phase change acquired per loop: a Möbius soliton
needs to travel twice around the ring to meet the initial phase condition.
A phase sensitive interaction between soliton-like modes has been discovered.
This interaction provides the phase correlation between two travelling
solitons if their distance is decreasing. [1] S.O. Demokritov et al.
Nature 426, 159 (2003).
Zeit: Dienstag 10:15–13:00 Raum: H10
MA 10.1 Di 10:15 H10
Exchange coupling in thin Fe-films on NiO(001) — •U. Mick,
W. G. Park, V. Bocatius, H. Meinert, and E. Kisker — Institut
für Angewandte Physik, Universität Düsseldorf
The domain formation and exchange coupling of thin Fe-Films on
NiO(001) have been investigated by x-ray magnetic linear dichroism
(XMLD) and x-ray magnetic circular dichroism (XMCD) in photoemission
electron microscopy (PEEM).
In-situ cleaved NiO crystals provide atomically defined clean NiO(001)surfaces
as is shown in complementary STM-measurements. Thin Fe-films
grown by MBE at room temperature on these NiO(001)-surfaces exhibit
a collinear coupling of their magnetic moments to the spin structure of
by the NiO(001)-substrate as is revealed in angular dependent PEEMmeasurements.
Fe-films grown on freshly cleaved NiO(001) can induce
changes in the NiOs AF-domains, which are presumably thermodynamically
unstable. Thermally relaxed NiO(001) surfaces, that have been annealed
above Neel-temperature, show a rearrangement in their domain
structure that is not altered by subsequent deposition of Fe anymore while
the Fe-films still show collinear coupling after the onset of FM-coupling,
as has been investigated for different film thicknesses of Fe from 1 ML to
15 ML.
Neither x-ray absorption spectroscopy (XAS) nor PEEM-investigations
on Ni-MCD gave any evidence for significant interface reactions between
the Fe-films grown at room temperature and the NiO substrate.
This work has been performed at BESSY-UE52 and was supported by
the BMBF under grant No. 05KS1PFB/1
MA 10.2 Di 10:30 H10
Soft X-ray Resonant Magnetic Scattering studies on CoO/Fe
exchange bias bilayers — •Florin Radu, Gregor Nowak, Johannes
Grabis, Alexei Nefedov, and Hartmut Zabel — Experimentalphysik/Festkoerperphysik,
Ruhr-Universitaet Bochum, 44780
Bochum, Germany
We have used the ALICE diffractometer and soft X-ray Resonant Magnetic
Scattering (XRMS) techniques to search for the presence of an effective
ferromagnetic moment in an antiferromagnetic (AF) layer which
is in close contact with a ferromagnetic (F) layer. Using rf-sputtering we
have prepared two samples in a single run: one is a CoO(25 ˚A)/Fe(150
˚A) exchange bias system and the other is a single CoO(25 ˚A) AF layer
deposited on a sapphire substrate. The samples were cooled in a field of
+2000 Oe from above the TN=291 K of the CoO AF layer to T=30 K.
Taking advantage of the element specificity of the XRMS technique, we
have measured hysteresis loops of both Fe and CoO layers. The result is
that a single layer of CoO deposited on a substrate shows no ferromagnetic
signal while for the CoO layer deposited on the Fe ferromagnetic
layer we observe hysteresis loops. From these measurements we conclude

Magnetismus Dienstag
that the proximity of the F layer induces a magnetic moment in the AF
layer. The F moment in the AF layer has two components: one is frozen
and does not follow the applied magnetic field and the other one follows
in phase the ferromagnetic magnetization of the F layer. This work was
supported by SFB 491 and BMBF03ZAE7BO.
MA 10.3 Di 10:45 H10
Optische Kontrolle der Magnetisierung in austauschgekoppelten
NiFe/FeMn Filmen auf der Pikosekundenzeitskala —
•Markus Christian Weber, Hans Nembach und Jürgen Fassbender
— Fachbereich Physik und Forschungsschwerpunkt MINAS,
Erwin-Schrödinger-Str. 56, Technische Universität Kaiserslautern, 67663
Kaiserslautern
Eine 9 Pikosekunden kurze Laseranregung (Pulsenergie: 10 nJ, Spotgröße:
25 µm) wird zur thermischen Kontrolle der Magnetisierung eines
NiFe/FeMn Bilagensystems auf der Pikosekundenzeitskala eingesetzt.
Aufgrund der Erzeugung eines heissen Phononen- /Spingases durch den
anregenden Laserpuls wird die Austauschkopplung an der Grenzfläche
zwischen Ferro- und Antiferromagnet teilweise unterdrückt. Innerhalb
von 20 Pikosekunden wird eine schnelle Reduktion der Austauschkopplung
mittels longitudinalem Kerr-Effekt des zeitverzögerten Probepulses
sowohl für die magnetisch leichte als auch harte Richtung nachgewiesen.
Dies führt zu einer Reduktion des Austausch-Verschiebungsfeldes
von ca. 50 Prozent, bzw. zu einem dramatischen Anstieg der Nullfeld-
Suszeptibilität. Diese Effekte können durch ein nahe an die sogenannte
Blocking-Temperatur Tb (155 o C für NiFe/FeMn) erwärmtes Gitter
an der FM/AFM-Grenzfläche verstanden werden. Dem schnellen thermischen
Unterdrücken der Austauschkopplung folgt eine langsamere Erholung
des Austausch-Verschiebungsfeldes bzw. der Nullfeld-Suszeptibilität
mit einer Zeitkonstante von ca. 170 ps.
MA 10.4 Di 11:00 H10
Modifikation der magnetischen Eigenschaften austauschgekoppelter
NiFe/FeMn Filme durch Beschuss mit Ga + -Ionen
— •Steffen Blomeier 1 , Jürgen Fassbender 1 , Burkard Hillebrands
1 , Damien McGrouther 2 , Robin O’Neill 2 , Stephen
McVitie 2 und John N. Chapman 2 — 1 Fachbereich Physik und
Forschungsschwerpunkt MINAS, Erwin-Schrödinger-Str. 56, Technische
Universität Kaiserslautern, 67663 Kaiserslautern — 2 Department
of Physics and Astronomy, Kelvin Building, University of Glasgow,
Glasgow G12 8QQ, Scotland, United Kingdom
Der Einfluss der Bestrahlung von 30 keV Ga + -Ionen auf die magnetischen
Eigenschaften des polykristallinen NiFe/FeMn Austausch-Bias-
Systems wurde untersucht. In diesem Zusammenhang wurde ein Modell
getestet, welches die Änderung der magnetischen Eigenschaften der bestrahlten
Systeme einer ioneninduzierten Änderung ihrer Struktur zuschreibt.
Dieses Modell war ursprünglich für die Bestrahlung mit He + -
Ionen entwickelt worden und macht die Erzeugung von Punktdefekten
für die beobachteten Veränderungen verantwortlich. Diesbezüglich wurde
auch eine Simulation durchgeführt, die den Beschuss durch He + - und
Ga + -Ionen vergleicht. Es konnte gezeigt werden, dass sich das oben genannte
Modell auf die Bestrahlung mit Ga + -Ionen übertragen lässt und
durch die Ergebnisse der Simulation unterstützt wird. Überdies wurde getestet,
ob sich das untersuchte System durch die Bestrahlung mit Ga + -
Ionen magnetisch strukturieren lässt. Es konnte nachgewiesen werden,
dass auf einer Skala von 10 2 - 10 3 nm eine magnetische Strukturierung
mit bestimmten Einschränkungen möglich ist.
MA 10.5 Di 11:15 H10
Investigation of the Fe19Ni81/Fe50Mn50 exchange bias system
with varying Cu spacer layer for partial decoupling — •Oskar
Liedke, Hans Nembach, Jürgen Fassbender, and Burkard
Hillebrands — Fachbereich Physik und Forschungsschwerpunkt MI-
NAS, Technische Universität Kaiserslautern, Erwin-Schrödinger-Str. 56,
67663 Kaiserslautern
In order to modify the exchange interaction in a Fe19Ni81/Fe50Mn50
exchange bias system a Cu interlayer of varying thickness and position
with respect to the interface has been introduced. In one direction the
position of the intervening Cu layer varies from the interface to the top
surface of the Fe50Mn50 layer at a constant Cu thickness, and in the other
direction the Cu thickness itself varies. The introduction of the Cu layer
leads to a partial exchange decoupling. The samples were grown in a
UHV MBE system and investigated by magneto-optic Kerr effect magnetometry.
Two-dimensional maps are obtained, which provide global
information about the influence of the partial decoupling of the antifer-
romagnet as a function of Cu thickness tCu and FeMn thickness tFeMn. In
order to obtain more quantitative information several line scans along the
horizontal and vertical axes were evaluated. The influence of the partial
decoupling on the origins of exchange bias will be discussed.
MA 10.6 Di 11:30 H10
Elementspezifische Untersuchungen an austauschverschobenen
Bilayern mit NiO als Antiferromagnet vor und nach Beschuss
mit 10keV He-Ionen mit resonanter Röntgenreflektometrie —
•A. Ehlers 1 , D. Engel 1 , H. Schmoranzer 1 , A. Ehresmann 1 ,
H. C. Mertins 2 , D. Abramsohn 2 und W. Gudat 2 — 1 Technische
Universität Kaiserslautern, Fachbereich Physik, Erwin-Schrödinger-Str.,
D-67663 Kaiserslautern — 2 BESSY GmbH, Albert-Einstein-Str.15, D-
14195 Berlin
Austauschgekoppelte Zweilagenschichtsysteme mit NiO als Antiferromagnet
wurden nach ihrer Herstellung mit 10keV He-Ionen in einem
äußeren Magnetfeld beschossen. Es ist möglich durch diesen Beschuss
Stärke und Richtung des Exchange Bias Feldes Heb gezielt zu verändern.
Eine der Ursachen dieser Veränderungen ist die Defekterzeugung in
der Nähe der Grenzfläche zwischen Ferromagnet (F) und Antiferromagnet
(AF). Untersuchungen mit Hilfe resonanter Reflexion von weicher
Röntgenstrahlung an diesen Schichtsystemen wurden mit dem BESSY-
Polarimeter am UE56/1-PGM durchgeführt. Mit dieser Methode wurde
elementspezifisch an den L-Kanten der in den Schichtsystemen vorhandenen
Elemente u.a. Θ-2Θ Scans durchgeführt, um Informationen über
die Veränderung der Rauhigkeit an der F/AF- Grenzfläche zu gewinnen.
MA 10.7 Di 11:45 H10
Austauschanisotropie in Fe/V2O3 und Co/V2O3-Doppellagen:
Untersuchung des unterschiedlichen Verhaltens mit XMCD —
•Björn Sass 1 , Christian Tusche 1 , Wolfgang Felsch 1 , Franck
Fortuna 2 , Philippe Ohresser 2 und Francois Bertrand 2 —
1 I.Physikalisches Institut, Universität Göttingen — 2 LURE, Universite
Paris Sud XI
Magnetisierungmessungen an Fe- und Co-Schichten, deponiert auf einkristallinen
V2O3(11¯20)-Schichten hoher Qualität zeigen ein deutlich unterschiedliches
Verhalten: charakteristisch für die Co-Schichten ist eine
ausgeprägte Austauschanisotropie (exchange bias) unterhalb von 160K,
verursacht durch die Wechselwirkung mit den V2O3-Schichten in deren
antiferromagnetisch isolierender Phase. Für die Fe-Schichten wird dieser
Effekt nicht beobachtet. Messungen des zirkularen magnetischen Röntgendichroismus
(XMCD) an den L2,3-Kanten von Fe und Co zeigen im
Fall des Fe die Ausbildung einer unmagnetischen Lage an der Grenzfläche
mit dem V2O3, was das Ausbleiben des exchange bias erklären kann. Messungen
des Co-Momentes zeigen, dass es hier nicht zur Ausbildung einer
unmagnetischen Lage kommt!
MA 10.8 Di 12:00 H10
Ursache der asymmetrischen Ummagnetisierung im Exchange-
Bias-System Fe/FeF2 — •S. Oertker 1 , A. Tillmanns 1 , B. Beschoten
1 , G. Güntherodt 1 , J. Eisenmenger 2 , I.K. Schuller 2 ,
C. Leighton 3 und J. Nogués 4 — 1 2. Physikalisches Institut, RWTH
Aachen, D-52056 Aachen — 2 Department of Physics, UC San Diego —
3 Department of Chemical Engineering and Materials Science, University
of Minnesota — 4 epartament de Fisica, Universitat Autònoma de Barcelona
Austauschgekoppelte ferro-/antiferromagnetische Schichtsysteme zeigen
unterhalb TNeel eine unidirektionale Anisotropie, den sogenannten
Exchange Bias (EB). EB-Systeme sind die einzigen bekannten Systeme,
die eine asymmetrische Ummagnetisierung aufweisen: kohärente Rotation
auf der einen Seite der Hysteresekurve sowie Domänen-Nukleation
und -Propagation auf der anderen. Zur Untersuchung dieser Ummagnetisierungsprozesse
an dem EB-System Fe/FeF2 wurde der magnetooptische
Kerr Effekt sowohl in longitudinaler als auch in transversaler
Geometrie ausgenutzt. Letzterer misst die transversale Komponente
der Magnetisierung, mit der eine kohärente Rotation der Magnetisierung
identifiziert werden kann. Durchgeführt wurden systematische Messungen
in Abhängigkeit von der Einkühlrichtung und Probenorientierung.
Abhängig von der Probenorientierung finden wir entweder kohärente Rotation
auf beiden Seiten oder auf jeweils nur einer Seite der Hysterese.
Ein einfaches, ausschließlich auf kohärenter Rotation basierendes theoretisches
Modell kann dieses unterschiedliche Ummagnetisierungsverhalten
erklären. Unterstützt durch DFG / SPP 1133.

Magnetismus Dienstag
MA 10.9 Di 12:15 H10
New physics from perpendicular coupled magnetic films —
•Olav Hellwig 1 , Andreas Berger 2 , Jeffrey B. Kortright 3 ,
and Eric E. Fullerton 2 — 1 BESSY GmbH, Albert Einstein Str. 15,
12489 Berlin, Germany — 2 Hitachi San Jose Research Center, 650 Harry
Road, San Jose, CA 95120, USA — 3 Materials Science Division, Lawrence
Berkeley National Laboratory, Berkeley, CA 94720, USA
Magnetic storage technologies exploit antiferromagnetic (AF)
exchange coupling in state of the art media and head designs [1].
Although current devices have the magnetization of the layers within
the film plane, in the future there may be advantages in having the
magnetization perpendicular to the plane. This is certainly the case
for recording media and may apply to other devices as well. Motivated
by this, we explored the magnetic properties of a model system of
AF-coupled films with perpendicular anisotropy. In this geometry the
dipolar fields and the interlayer exchange coupling compete with each
other, thus resulting in novel phase transitions and a surprisingly
rich array of domain structures not seen with in-plane systems [2,3].
Imaging studies of these domains will be presented with simple energy
calculations that explain our observations.
[1] Eric E. Fullerton et al, Appl. Phys. Lett. 77 (2000) 3806
[2] Olav Hellwig et al, Nature Materials 2 (2003) 112
[3] Olav Hellwig et al, Phys. Rev. Lett. 91 (2003) 197203
MA 10.10 Di 12:30 H10
Ummagnetisierungsmoden und Koerzitivfelder in Exchange-Bias
Systemen — •Björn Beckmann, Gregor Scholten, Ulrich Nowak
und K. D. Usadel — Theoretische Physik, Universität Duisburg-
Essen
Experimentell können in Exchange-Bias Systemen u. U. deutliche
Asymmetrien der Hysteresekurve beobachtet werden. In Computersimulationen
im Rahmen des Domain-State Modells wird dieser Effekt
sowohl an Systemen mit einkristallinen als auch an solchen mit ver-
MA 11 Magnetische Materialien
zwillingten Antiferromagneten untersucht. Beobachtet wird, daß sowohl
die Richtung des äußeren Feldes als auch die Richtung des Feldes beim
Einkühlen jeweils in bezug auf die leichten Achsen des Antiferromagneten
eine entscheidende Rolle spielen. Daraus folgen u. a. asymmetrische
Ummagnetisierungsmoden bei der Hysterese [1]. Ferner wird die Temperaturabhängigkeit
der Koerzitivfelder und des Exchange-Bias Feldes
untersucht.
Gefördert durch die Deutsche Forschungsgemeinschaft im Rahmen des
SFB 491.
[1] B. Beckmann, U. Nowak, K. D. Usadel, Phys. Rev. Lett. 91, 187201
(2003)
MA 10.11 Di 12:45 H10
Separation der unterschiedlichen Anisotropien (rotierbare, unidirektionale
und uniaxiale) in Exchange Bias-Systemen bei quasistatischer
und dynamischer Anregung — •Roland Mattheis 1
und Jeff McCord 2 — 1 IPHT Jena, Albert-Einstein-Str. 9, D-07745
Jena — 2 IFW Dresden, Helmholtzstr. 20, D-01169 Dresden
Die Wechselwirkung an der Grenzfläche zwischen einem Ferromagneten
(FM) und einem Antiferromagneten (AF) führt zu einer unidirektionalen
Anisotropie, die als Exchange Bias einen breiten Einsatz in Bauelementen
der Magnetoelektronik gefunden hat. Diese Wechselwirkung verursacht
zusätzlich eine starke Erhöhung der Koerzitivfeldstärke des Ferromagneten,
die einhergeht mit großen Rotationsverlusten. Mittels unterschiedlicher
Messverfahren, mittel transversaler Suszeptibilität (quaistatisch)
und mittels Pulsanregung im psec-Bereich (dynamisch) werden
die jeweiligen Anisotropiebeiträge unidirektional, uniaxial und rotierbar
in Abhängigkeit von der Schichtdicke des Antiferromagneten unabhängig
voneinander bestimmt. Unterschiede in den statischen und dynamischen
Messergebnissen sind auf den viskosen Charkter des AF zurückzuführen.
Zusätzliche Einflüsse des AF auf die effektive magnetische Dämpfung des
FM werden diskutiert.
Zeit: Dienstag 10:15–13:00 Raum: H22
MA 11.1 Di 10:15 H22
Magnetic Carbon: An explicit evidence on ferromagnetism induced
by proton irradiation — •Pablo Esquinazi, Daniel Spemann,
Roland Höhne, Annette Setzer, Kyoo-hyun Han, and
Tilman Butz — Institut für Experimentelle Physik II, Universität
Leipzig, Linnestrasse 5, D-04103 Leipzig
The recently found ferromagnetic signals in pure graphite and in polymerised
fullerenes are received mainly with scepticism by most of the
scientific community. Actually, before those results were published, there
were several reports claiming an unusually large magnetization in pyrolytic
carbon and oxidized fullerenes, without attracting the attention
of the community. This scepticism may be well founded since not always
a careful and systematic impurity study was provided to quantify ferromagnetic
impurities. In this contribution we present SQUID and MFM
results on ferro- or ferrimagnetism induced by proton irradiation on pure
pyrolytic graphite. The impurity concentration (< 0.3µg Fe in 1g C)
was measured by RBS and PIXE at each irradiation stage. The overall
results including those obtained from presure- and photo-polymerised
fullerenes indicate that room-temperature ferromagnetism in metal-free
carbon structures containing only s- and p-electrons is a reality.
MA 11.2 Di 10:30 H22
Magnetische Hyperfeinwechselwirkung eines Defektes in
α-Eisen — S. Unterricker 1 , V. Samokhvalov 1 , F. Schneider 1 ,
M. Dietrich 2 , die ISOLDE - Collaboration 3 , •S. Unterricker
1 , V. Samokhvalov 1 , F. Schneider 1 , M. Dietrich 2 und die
ISOLDE - Collaboration 3 — 1 Institut für Angewandte Physik,
TU Bergakademie Freiberg, D-09596 Freiberg/Sachsen — 2 Technische
Physik, Universität des Saarlandes, D-66041 Saarbrücken — 3 CERN,
CH-1211 Geneva 23, Switzerland
In Nickel (fcc) wurde nach Implantation von 111 In( 111 Cd) von mehreren
Gruppen mit PAC (= perturbed angular correlations) neben dem
Hyperfeinfeld Bhf,s = - 6.7 T für Substitution ein zweites Feld von Bhf,d
= - 2.7 T beobachtet, das von einem Defekt mit kubischer Punktsymmetrie
stammt. Die Struktur dieses Defektes wird kontrovers diskutiert.
Wir haben 111 In( 111 Cd)-Sonden am ISOLDE-Separator mit 50 keV in α-
Eisen (bcc) implantiert und neben dem Feld für substituiertes Cd (Bhf,s
= - 38.2 T) ein zweites Feld (Bhf,d = + 11.4 T) beobachtet, das gleichfalls
Umgebungen mit kubischer Symmetrie entspricht. Dieses zweite Feld
tritt erst auf, wenn bei höheren Temperaturen Defekte beweglich werden.
Konfigurationen, die einen solchen Defekt verursachen können, werden
besprochen.
MA 11.3 Di 10:45 H22
The effect of the spin-orbit coupling on the half-metallic band
gap — •Phivos Mavropoulos 1 , Kazunori Sato 1 , Rudi Zeller 1 ,
Peter Dederichs 1 , Voicu Popescu 2 , and Hubert Ebert 2
— 1 IFFForschungszentrum Jülich, D-52425 Jülich — 2 Department
Chemie/Physikalische Chemie, University of Munich,Butenandtstr.
5-13, D-81377 Munich
We present ab-initio calculations on the effect of spin-orbit coupling to
the band gap of half-metals. Due to spin-orbit coupling the majority-spin
states are partly flipped and a 100% spin polarisation P cannot exist. As
typical systems, we choose the Heusler alloy NiMnSb, the zinc-blende
alloys CrAs, CrSb, and MnBi, and the diluted magnetic semiconductors
(Ga,Mn)As and (Ga,Mn)N. We find that the majority-spin states
are partly reflected into the minority band gap. The DOS for minority
electrons in this energy region depends mainly on the strength of the
spin-orbit coupling, heavier sp elements resulting in a higher ratio of minority/majority
spin DOS. We see a trend of decreasing P at EF as we
go from CrAs (99.6%) to CrSb (98.6%) and finally to MnBi (77%). In
NiMnSb we find P = 99%. Also, majority states close to the gap edges
are easier spin-flipped. This results in P = 92% at EF for (Ga,Mn)As.
MA 11.4 Di 11:00 H22
Ab - initio calculations of the electronic and magnetic properties
of NiMnSb — •Marjana Leˇzaić, Gustav Bihlmayer, and
Stefan Blügel — Institut für Festkörperforschung, Forschungszentrum
Jülich, 52425 Jülich
Due to their 100% spin polarization at the Fermi level, spin-gap materials
are presently receiving much of attention as potential materials for

Magnetismus Dienstag
spintronic devices. A class of such materials are the half-metallic Heusler
alloys. Here we present a study, based on density functional theory, of the
electronic and magnetic properties of the half-Heusler alloy NiMnSb. Using
the FLEUR code, an implementation of the Full-potential Linearized
Augmented Plane Wave (FLAPW) method, we investigate the influence
of the spin-orbit interaction and find that it reduces the spin-polarization
at the Fermi level by less then 1%. Performing spin-spiral calculations
to obtain the spin-wave dispersion in the frozen magnon approximation
we estimate the Curie-temperature in the RPA. The obtained value of
780K is in close agreement with the experimental results (∼ 730K). The
applicability of the force theorem in these calculations is investigated.
MA 11.5 Di 11:15 H22
Investigation of intra- and inter-atomic mechanisms in
La1−xBaxMnO3: A combined x-ray spectroscopic study —
•Karsten Kuepper 1 , Manfred Neumann 1 , Vadim Galakhov 2 ,
Kevin Prince 3 , Maurizio Matteucci 4 , and Mihaela Falub 5 —
1 Universität Osnabrück, FB Physik, Barbarastr. 7, 49069 Osnabrück —
2 Institute of Metal Physics,Russian Academy of Sciences - Ural Division,
620219 Yekaterinburg, Russia — 3 Sincrotrone Trieste, in Area Science
Park, Basovizza (Trieste), Italy — 4 Institute of Condensed Matter,
National Research Council c/o Sincrotrone Trieste, Italy — 5 Paul
Scherrer Inst., Swiss Light Source, WSLA-R 226, CH-5232 Villingen,
Switzerland
The electronic properties of the colossal magneto resistance (CMR)
compounds La1−xBaxMnO3 (0 ≤ x ≤ 0.55) are investigated by a detailed
spectroscopic study. A combination of different techniques, namely x-ray
photoelectron spectroscopy (XPS), x-ray emission spectroscopy (XES),
x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering
(RIXS), is used to reveal a detailed picture of the electronic structure
in the presence of Ba doping in different concentrations. The results are
compared with available theory. The valence band is dominated by La 4d,
Mn 3d and O 2p states, and strong hybridization between Mn 3d and O
2p states is present over the whole range of Ba concentration. XAS spectra
indicate that the hole doping leads to mixed Mn 3d - O 2p states.
Furthermore, RIXS at the Mn L edge probed d − d transitions between
the Mn d bands as well as transitions between strongly hybridized Mn
3d - O 2p states.
MA 11.6 Di 11:30 H22
Influence of nitrogen on the magnetic properties of LaFe11.4Si1.6
— •Aru Yan, Kalyan Mandal, Axel Handstein, Dieter
Eckert, Konstantin Nenkov, Oliver Gutfleisch, and Karl-
Hartmut Müller — Leibniz Institute of Solid State and Materials
Research Dresden, POB 270116, 01171 Dresden
Recently, it was found that the intrinsic magnetic properties of La(Fe,
M)13 compounds (M = Al, Si) can be modified with interstitial H, C
and N atoms, but the reported values of magnetic properties of the
La(Fe, M)13 interstitially modified compounds are much lower than those
of the 2:17 and 1:12 interstitially modified compounds. In this work,
LaFe11.4Si1.6Nx compounds have been prepared by nitrogen absorption
and their magnetic properties have been investigated. It was found that
the cubic NaZn13-type structure of the Si containing compounds remains
unchanged, while the lattice constant at room temperature is increased
from 11.47 to 11.56 ˚A after nitrogen absorption at 973 K, leading to
a large volume expansion of 2.4%. A drastic improvement of magnetic
properties has been observed after the introduction of interstitial nitrogen.
The Curie temperature is significantly increased from 200 K to 995
K and a high saturation magnetization of 93 emu/g is obtained. Further
analysis revealed that the volume expansion plays a predominant role
in improving the magnetic properties of La(FexSi1−x)13Nx. In particular,
the significant increase of Curie temperature in LaFe11.4Si1.6Nx can be attributed
to the enhancement of the exchange interaction by the nitrogen
absorption.
MA 11.7 Di 11:45 H22
Hartmagnetische Eigenschaften von amorphen Nd60FexCo30xAl10
Legierungen — •Olivier Perroud 1 , Elvira Garcia-
Matres 1 , Albrecht Wiedenmann 1 und Golden Kumar 2 —
1 Hahn-Meitner Institut Berlin, Glienickerstr.100 D-14109 Berlin —
2 Institut fuer Festkoerper- und Werkstoffforschung, PFf 270116, D-01171
Dresden
Wir berichten über strukturelle und magnetische Untersuchungen an
Nd60FexCo30-xAl10 (x=20, 7.5) und Nd80Fe20, das durch langsames
Abkühlen im Gussverfahren hergestellt wurde.
Magnetische Messungen belegen hartmagnetisches Verhalten für
Nd60FexCo30-xAl10 mit zwei charakteristischen Curietemperaturen.
(Tc1= 50 K und Tc2= 500 K)
Durch Kleinwinkelstreuung mit polarisierten Neutronen (SANSPOL)
konnten magnetischen Nanostrukturen nachgewiesen werden. Die Untersuchungen
erfolgen im Temperaturbereich zwischen 2K und 550K und
im außern magnetischen Feld bis 6 Tesla. In Übereinstimmung mit Magnetisierungsmessungen
konnten zwei Nd-reich Nanokristallite detektiert
werden mit mitleren Radien von 1.8nm und 5.7nm. Oberhalb Tc1 werden
die Nd-Nanopartikeln paramagnetisch und oberhalb Tc2 wird die Matrix
paramagnetisch.
Diese Arbeit wird im Rahmen des DFG Schwerpunktprogramms 1120
gefördert.
MA 11.8 Di 12:00 H22
Interaction domains in NdFeB magnets in dependence on the
degree of texture — •Kirill Khlopkov, Oliver Gutfleisch, Dietrich
Hinz, Axel Handstein, Karl-Hartmut Müller, and Ludwig
Schultz — IFW Dresden, Postfach 270016, 01171 Dresden
The magnetic domain structure of die-upset NdFeB magnets with different
degrees of texture has been investigated using the magneto-optical
Kerr effect and magnetic force microscopy (MFM). For the non-textured
i.e. isotropic hot pressed starting material interaction domains could not
yet be observed by optical Kerr-microscopy. Interaction domains could
be observed by Kerr-microscopy in die-upset samples with a deformation
degree of more than 52% (medium degree of texture). In contrast
MFM reveals the presence of interaction domains already for considerably
lower degrees of texture. Magnetostatic interaction is assumed to cause
the interaction domains since the grains are separated by thin amorphous
Nd-rich grain boundaries of about 1 nm thickness which are expected to
suppress exchange coupling between the grains. The interaction domains
are cooperative phenomena on a length scale much larger than the grain
size of typically 100nm × 400nm for highly textured sample with a deformation
degree of about 76%.
This work was supported by SFB463.
MA 11.9 Di 12:15 H22
Corrosion behaviour of polymer-bonded Nd-Fe-B-based
nanocrystalline magnets — •Mihaela Rada, Anke Kirchner,
Annett Gebert, Oliver Gutfleisch, and Ludwig Schultz —
IFW Dresden, Helmholtzstr. 20, 01069, Dresden
The corrosion resistance of polymer bonded nanocrystalline NdFeB
magnets with Nd-rich, stoichiometric and Fe-rich compositions and that
of their main single phases is assessed in aqueous environments. For the
evaluation of corrosion properties, gravimetric tests as well as potentiodynamic
polarization measurements were performed in different nitrogenpurged
electrolytes: 0.1 M sulfuric acid (pH 0.7), 0.5 M phthalate buffer
(pH 5) and 0.1 M sodium hydroxide (pH 13). Before and after corrosion
testing, the sample surfaces were investigated by means of high-resolution
scanning electron microscopy. The single phases show anodic dissolution
in strong acidic environment and stable passivation in alkaline solution. In
weakly acidic phthalate buffer Nd-rich and Fe phases exhibit limited passive
regions, whereas Fe3B and Nd2Fe14B do not show stable passivation.
Polymer-bonded magnets of different compositions have a significantly
improved resistance towards strongly acidic environments as compared
to hot pressed magnets. Enrichment in Fe content and additions like Co
and Nb improve their corrosion behavior.
MA 11.10 Di 12:30 H22
Microstucture of bulk SmCo2.5Cu2.5 and magnetisation in high
pulse fields — •Peter Kerschl 1 , Kirill Khlopkov 1 , Axel
Handstein 1 , Dieter Eckert 1 , Juan-Carlos Tellez-Blanco 2 ,
Roland Grössinger 2 , Karl-Hartmut Müller 1 , and Ludwig
Schultz 1 — 1 Leibniz-Institut für Festkörper- und Werkstoffforschung
Dresden, Postfach 270116, D-01171 Dresden, Germany — 2 Institut für
Festkörperphysik, Technische Universität Wien, Wiedner Hauptstraße 8-
10, A-1040 Wien, Austria
SmCo5 has a very good performance as permanent magnet material.
It is known that a strong influence of Cu substitution on the magnetic
properties exists: An unusual jump from low to high magnetisation state
in an increasing external field is observed. To obtain a better insight,
a SmCo2.5Cu2.5 compound was prepared. Phase composition and microstructure
have been investigated by X-ray diffraction, scanning electron
microscopy and EDX analysis. The results of high field magnetisation
measurements in pulse fields up to 48 T at temperatures from

Magnetismus Dienstag
4.2 K up to 300 K are discussed. The coercivity at low temperatures is
up to about µ0JHC ≈ 15 T at 4.2 K. At high fields, a metamagnetic
transition occurs. The critical field of this transition increases with decrasing
temperature reaching about 28 T at 4.2 K. The influence of the
field changing rate on the observed magnetic properties is discussed. This
work is supported by the BMBF project 03 SC 5 DRE.
MA 11.11 Di 12:45 H22
Korrosionsverhalten von Sm-Co-Permanentmagneten in oxidierenden
Medien — •Stefan Kardelky, Annett Gebert, Oliver
Gutfleisch, Axel Handstein und Ludwig Schultz — Leibniz-
Institut für Festkörper- und Werkstoffforschung Dresden, PF 270116,
01171 Dresden, Deutschland
Die Kenntnis des Oxidationsverhaltens von Sm(Co, Fe, Cu, Zr)z-
Permanentmagneten des Typs Sm2Co17 ist notwendig für die Einschätzung
ihrer Stabilität unter Anwendungsbedingungen bis zu 500 o C.
MA 12 Hauptvorträge Hütten / Bader
Gesinterte Magnete wurden hinsichtlich Oxidsschichtbildung bei verschiedenen
Auslagerungstemperaturen und Auslagerungszeiten O2/Ar
und Luft studiert. Oxidschichtwachstumprozesse wurden mittels thermogravimetrischer
Analyse verfolgt. Die oxidierten Magnetoberflächen wurden
nachfolgend mit Licht- und Rasterelektronenmikroskopie (incl. EDX)
charakterisiert. Anhand der zeitabhängigen Massenänderungen wurden
unter Anwendung bekannter Wachstumsgesetze parabolische Zunderkonstanten
bestimmt, die die Oxidsschichtbildung der Sm(Co, Fe, Cu, Zr)z-
Magnete beschreiben. Eine Oxidschichtdicke von 135µm wurde nach 312h
Auslagerungszeit an Luft bei einer Temperatur von 500 o C gemessen. Die
äußersten Oxidschichtbereiche werden hauptsächlich durch oxidierte Feund
Co-Oxide gebildet. Die Oxidschicht weist Co-reiche und Sm-reiche
Regionen sowie Cu-reiche Abscheidungen in der Nähe von Mikrorissen
auf. Das Langzeitoxidationsverhalten kann mit einer aus Kurzzeitversuchen
bestimmten Zunderkonstante vorhergesagt werden.
Zeit: Dienstag 14:00–15:00 Raum: H10
Hauptvortrag MA 12.1 Di 14:00 H10
Progress in Designing Multilayered Thin Films for Magnetoelectronic
Applications — •Andreas Hütten — Department of
Physicis, P.O.Box 100131, D-33501 Bielefeld, Germany
Today’s successful design of multilayered thin films for magnetoelectronic
applications requires the knowledge of (1) tuning their magnetic
switching behavior in a given field range, (2) enhancing their temperature
stability and (3) enhancing the spin polarization of the involved
magnetic electrodes. The magnetic switching can be controlled by utilizing
the appropriate magnetic interaction mechanisms known as the interlayer
exchange coupling, the anti- and ferromagnetic biasing and the
ferromagnetic strayfield coupling. The key to enhance the temperature
stability is to make use of recrystallization processes so as to reduce the
interfacial roughness and the microstructural paths of high atomic mobility.
To enhance the spin polarization new magnetic electrodes such as
half metallic oxides or Heusler alloys are currently evaluated world wide.
The objective of this talk is to discuss exemplary the design aspects (1)
and (2) relevant for spin-valves and multilayers interacting with hard
magnetic FePt- and CoCrPt- thin films. The attention then will be focused
on aspect (3) using the Co2SiMn Heusler alloy to report on the
experimentally realized spin polarization in magnetic tunnel junctions.
Hauptvortrag MA 12.2 Di 14:30 H10
Confined Antiferromagnets** — •Samuel Bader — Materials Science
Division 223, Argonne National Laboratory, Argonne, IL 60439,
USA
Confinement on the nanoscale can give rise to new and interesting
properties. In the present study the incommensurate antiferromagnetic
spin density wave (SDW) structure of Cr is altered via interleaving in
a superlattice geometry with a commensurate antiferromagnet (AF) in
order to minimize interfacial roughness effects. Even though neither AFlayer
exhibits hysteretic magnetic ordering, when put into proximity
subtle hysteretic effects arise from the boundary conditions. Epitaxial
Cr/Cr97.5Mn2.5(001) superlattices were studied via neutron scattering
and transport measurements. The Mn doping creates a high Nèel temperature
layer that confines the Cr SDW order. Transitions are observed
with temperature cycling that show significant hysteresis when the number
of SDW nodes within the Cr layer change by an odd number, while
there is no hysteresis for changes of an even number of nodes. This results
from the competition between maintaining the spin structure at
the interfaces and introducing a spin slip at the nodes of the Cr SDW. *
Supported by US DOE/BES-MS under contract W-31-109-ENG-38. **In
collaboration with E.E. Fullerton, J.L. Robertson, A.E.R. Prinsloo, and
H.L. Alberts.
MA 13 Poster:Schichten(1-23),Spinabh.Trsp(24-41),Exch.Bias(42-56),Spindyn.(57-
67),Mikromag.(68-76),Partikel(77-90),Spinelektr.(91-97),Elektr.Theo.(98-
99),Mikromag+PhasÜ+Aniso.(100-105),Magn.Mat.(106-118),Messmethod.(119-
121),Obflm.+Abbverf.(122-123)
Zeit: Dienstag 15:00–19:00 Raum: Bereich A
MA 13.1 Di 15:00 Bereich A
Präparation und Charakterisierung von epitaktischen
CrO2(100)-Schichten hergestellt mit CrO2Cl2-Ausgangsmaterial
— •C. König 1 , T. Lohmann 1 , Yu. S. Dedkov 1 , M. Fonin 1 , U.
Rüdiger 2 und G. Güntherodt 1 — 1 2. Physikalisches Institut,
RWTH-Aachen, D-52056 Aachen — 2 Fachbereich für Physik,
Universität Konstanz, D-78457 Konstanz
Die für halbmetallische Ferromagnete zu erwartende hohe Spinpolarisation
macht CrO2 (theoretisch 100 % Spinpolarisation an der Fermienergie
[1]) zu einem Kandidaten für den Einsatz in spinelektronischen
Bauelementen.
Epitaktische CrO2(100)-Schichten wurden mittels zweier verschiedener
CVD-Verfahren auf TiO2(100) Substraten gewachsen. CrO2(100)-
Schichten, die mit dem festen Ausgangsmaterial CrO3 gewachsen wurden,
wiesen bei Raumtemperatur eine Spinpolarisation von 95 ± 5 %
an der Fermienergie auf [2]. Die bei diesen Schichten noch zu beobachtende
hohe Oberflächenrauigkeit konnte durch die Verwendung eines
flüssigen Ausgangsmaterials (CrO2Cl2) bis auf eine rms-Rauigkeit
von 0.5nm reduziert werden. Röntgendiffraktometrische Untersuchungen
zeigten bei den mittels CrO2Cl2-CVD hergestellten (100)-orientierten
Schichten eine starke Reduktion des Cr2O3-Fremdphasenanteils. Das ma-
gnetische Sättigungsmoment pro Chromatom dieser Schichten wurde mittels
SQUID-Magnetometrie zu 2.1µB bei T = 5K bestimmt.
[1] K. H. Schwarz, J. Phys. F: Met. Phys. 16, L211 (1986);
[2] Yu. S. Dedkov et al., Appl. Phys. Lett. 80, 4181 (2002).
Diese Arbeit wurde unterstützt durch das BMBF (FKZ 05KS1PAA/7).
MA 13.2 Di 15:00 Bereich A
Giant 2p→3d Resonant Photoemission of Half-Metallic Ferromagnetic
CrO2 — •Yuriy Dedkov 1 , Mikhail Fonin 1 , Martin
Sperlich 1 , Christian König 1 , Alexandr Vinogradov 2 , Denis
Vyalikh 3 , Serguei Molodtsov 3 , Ulrich Rüdiger 4 , and Gernot
Güntherodt 1 — 1 II. Physikalisches Institut, Rheinisch-Westfälische
Technische Hochschule Aachen, D-52056 Aachen, Germany — 2 Institute
of Physics, St.-Petersburg State University, 198904 St.-Petersburg, Russia
— 3 Institut für Festköperphysik, Technische Universität Dresden, D-
01062 Dresden, Germany — 4 Fachbereich Physik, Universität Konstanz,
D-78457, Konstanz, Germany
The electronic structure of high quality half-metallic ferromagnetic
CrO2(100) films was investigated by means of x-ray adsorption spectroscopy
(XAS) and resonance photoelectron spectroscopy (Res-PES)

Magnetismus Dienstag
performed at the O K- and Fe L2,3-edges. First principles calculations
made on the basis of the local spin-density approximation (LSDA and
LSDA+U) to the density-functional theory have been carried out to
study the influence of the electron correlation effects on the electronic
structure of CrO2. Recent resonance photoelectron spectroscopy data
emphasize the strength of 2p-3d resonance photoemission for studying
the electronic structure of correlated systems, for example CrO2. The
present spectroscopy data (XAS and Res-PES) show that band structure
calculations on the basis of the LSDA+U approach are more suitable for
the description of the electronic structure of half-metallic CrO2.
MA 13.3 Di 15:00 Bereich A
Influence of thickness on microstructural and magnetic properties
in Fe3O4 thin films produced by PLD — •A. Bollero,
M. Ziese, R. Höhne, H. C. Semmelhack, U. Köhler, A. Setzer,
and P. Esquinazi — Division of Superconductivity and Magnetism,
University of Leipzig, Linnéstrasse 5, 04103 Leipzig
Films of magnetite (Fe3O4) have been prepared on (100) MgAl2O4
substrates by pulsed laser deposition (PLD) with a thickness ranging
from 10–350 nm. Epitaxial growth of the films has been verified by insitu
RHEED measurements. The relaxation degree of the films and the
micro-strains between the grains have been studied by X-ray diffraction.
Scanning tunnelling microscopy has revealed a homogeneous microstructure
for very thin films, a columnar disposition of elongated grains for
films with thicknesses of 80 and 160 nm and the formation of islands for
the 350 nm thick film, as those typically observed in bulk magnetite. The
Verwey transition at TV has been investigated via SQUID magnetometry;
magnetisation has been measured as a function of the applied field
at 300 and 5 K for each sample. Additionally, hysteresis loops have been
measured at selected temperatures from 300 to 5 K for two films with
thicknesses of 30 and 350 nm. At the isotropic point, Ti ∼ 130 K, coercivity
goes through a minimum and then rises cooling below TV . Higher
coercivities are obtained for the thinner film attributed to the strong
interfacial strain induced in the film by the lattice mismatch with the
substrate.
MA 13.4 Di 15:00 Bereich A
Structure and Electronic Properties of Fe3O4(100) and
Fe3O4(111) Surfaces — •M. Fonin 1 , Yu. Dedkov 1 , D. Vyalikh 2 ,
M. Sperlich 1 , S. Molodtsov 2 , F. Matthes 3 , L. N. Tong 3 ,
C. M. Schneider 3 , U. Rüdiger 4 , and G. Güntherodt 1 — 1 II.
Physikalisches Institut, Rheinisch-Westfälische Technische Hochschule
Aachen, D-52056 Aachen, Germany — 2 Institut für Festköperphysik,
Technische Universität Dresden, D-01062 Dresden, Germany — 3 Leibniz
Institute for Solid State and Materials Research Dresden, PF 270116,
D-01171 Dresden, Germany — 4 Fachbereich Physik, Universität
Konstanz, D-78457, Konstanz, Germany
Since years ferromagnetic transition-metal oxide (TMO) films have
been a subject of intensive research due to possible applications in various
fields of technology. Highly spin-polarized TMO films, among them
magnetite (Fe3O4) are claimed to have a large potential for future applications
in spin-electronic devices.
High-quality thin epitaxial Fe3O4(100) and Fe3O4(111) films were prepared
by MBE and the crystalline surface structure of the films was
studied by LEED and STM. The surface electronic structure of thin epitaxial
Fe3O4 films has been investigated at room temperature by means
of spin- and angle-resolved photoelectron spectroscopy. A maximum spin
polarization value of about −(55±10)% was found near EF at room temperature
for the Fe3O4(100) films on MgO(100) substrates. For epitaxial
Fe3O4(111) films higher spin polarization values up to about −(80 ±5)%
were observed near EF at room temperature.
MA 13.5 Di 15:00 Bereich A
Room temperature TMR-effect in magnetite based magnetic
tunnel junctions — •D. Reisinger, P. Majewski, M. Schonecke,
J. Schuler, M. Opel, A. Erb, L. Alff, and R. Gross — Walther-
Meissner-Institut, Bayerische Akademie der Wissenschaften, Walther-
Meissner-Str. 8, 85748 Garching
Magnetite (Fe3O4) is an interesting candidate for new spintronic devices.
It has been predicted to be a half-metal at room temperature [1].
We prepared magnetite epitaxial thin films by pulsed laser deposition
(PLD) [2,3]. These films have been combined with a tunneling barrier
and a Ni top electrode. Five different materials have been tested for the
tunneling barrier. From this trilayers magnetic tunnel junctions with area
ranging between 10 × 10µm 2 to 20 × 40µm 2 have been fabricated using
optical lithography and ion beam etching. The magnetic properties, in
particular the coupling within the trilayers have been investigated using
a SQUID magnetometer. The magnetotransport behavior of the tunnel
junctions has been measured as a function of temperature and applied
magnetic field. The junctions showed reproducible a tunneling magnetoresistance
(TMR) effect at room temperature with almost ideal switch
behavior.
[1] Z. Zhang, and S. Satpathy, Phys. Rev. B, 44, 13319 (1991).
[2] D. Reisinger, B. Blass, J. Klein, J. B. Philipp, M. Schonecke, A. Erb,
L. Alff, and R. Gross, Appl. Phys. A, 77, 619 (2003).
[3] D. Reisinger, M. Schonecke, T. Brenninger, M. Opel, A. Erb, L. Alff,
and R. Gross, Jour. Appl. Phys., 94, 1857 (2003).
MA 13.6 Di 15:00 Bereich A
Spinpolarisation in dünnen Co2MnSi Filmen — •Firmin Leutloff,
Sven Kämmerer, Andreas Hütten und Günter Reiss —
Universität Bielefeld, Universitätsstrasse 25, 33615 Bielefeld
Bei der Suche nach hoch spinpolarisierten Materialien ist Co2MnSi ein
vielversprechender Kandidat. Zum einen wird dieser Heuslerlegierung
eine Spinpolarisation von 100% theoretisch vorausgesagt, zum anderen
ist die hohe Curietemperatur vorteilhaft für Anwendungen. Nachdem
an relativ dicken Schichten (≈ 100nm) eine Spinpolarisation von
34% bei Raumtemperatur und 61% bei 10K mittels MTJs gemessen
wurde, wird nun Stöchiometrie und Qualität des Grenzflächenbereichs
zur Aluminiumoxidbarriere untersucht. Um außer der im Vergleich
zu Co-Schichten sehr hohen Spinpolarisation ein weiteres Indiz dafür
zu besitzen, daß wir keine nicht-stöchiometrischen Aussscheidungen
an der Grenzfläche zur Barriere besitzen, wurde eine Co-Schicht
zwischen Barriere und Heuslerlegierung eingefügt. Beobachtet werden
konnte ein drastischer Abfall der TMR-Amplitude bei sehr geringer
Co-Anreicherung, bevor hin zu größeren Schichtdicken die TMR-
Amplitude in die einer Einzelkoba! ltschicht sättigt. Unterstützend
wurden AES-Messungen durchgeführt, die eine der Heuslerlegierung
entsprechende Stöchiometrie bestätigten. Zur weiteren Optimierung der
Spinpolarisation wird momentan die Abhängigkeit der Spinpolarisation
von der Heuslerschichtdicke untersucht.
MA 13.7 Di 15:00 Bereich A
Magnetische und magneto-optische Eigenschaften von
CrxPt1−x/Pt-Multischichtsystemen — •I. Jursic, D. Zur,
M. Marutzky, D. Menzel und J. Schoenes — Institut für
Halbleiterphysik und Optik, Mendelssohnstr. 3, 38106 Braunschweig
CrPt3 besitzt eine senkreche magnetische Anisotropie. Frühere Untersuchungen
an dünnen Filmen ergaben eine Kerr-Rotation von 0.2 ◦ im
blauen Spektralbereich. Daher ist CrPt3 ein vielversprechender Kandidat
für die magneto-optische Speichertechnologie. Der Einflußder Herstellungsparameter
auf die magneto-optischen Effekte ist von besonderer
Bedeutung. So zeigen geringere Schichtdicken des CrPt3 eine Vergrößerung
der Kerr-Drehung [1].
In den hier betrachteten CrxPtx−1/Pt-Multilagenschichten wird die Auswirkung
unterschiedlicher Pt-Schichtdicken auf die Kopplung unterschiedlich
dicker CrxPtx−1-Schichten untersucht. Dies macht sich in den
magnetischen und magneto-optischen Eigenschaften der Filme bemerkbar.
Die Filme wurden mittels MBE auf SrTiO3 Substraten hergestellt.
Untersuchungen mit einem SQUID-Magnetometer zeigen eine signifikante
magnetische Anisotropie senkrecht zur Filmebene. Die magnetooptischen
Eigenschaften wurden mit einem Labor-Kerr-Spektrometer bestimmt.
Ergänzend wurde der Magnetowiderstand der Multilagenschichten
bei Feldern bis 2 T untersucht.
[1] J. Schoenes et al. Proc. ICM 2003, J. Magn. and Magn. Materials
MA 13.8 Di 15:00 Bereich A
Herstellung und elektronische Strukturen von CrxPt1−x/Pt-
Multischichtsystemen — •D. Zur, I. Jursic und J. Schoenes —
Institut für Halbleiterphysik und Optik, Mendelssohnstr. 3, 38106 Braunschweig
Das Cr-Pt-System ist aufgrund seiner magnetischen und magnetooptischen
Eigenschaften für die Anwendung in der Speichertechnologie von
besonderem Interesse. In früheren Arbeiten wurden chemisch geordnete
und ungeordnete CrPt3-Legierungen untersucht [1]. Um die Kopplungsmechanismen
besser zu verstehen und das Anisotropieverhalten zu untersuchen,
wurden Multischichtsysteme von CrxPt1−x/Pt in unterschiedlicher
Dicken und Folgen auf SrTiO3 (100) und (111) Substraten mittels
MBE hergestellt. Das Schichtwachstum wurde mittels RHEED beobach-

Magnetismus Dienstag
tet. Die chemische Zusammensetzung wurde mit der Augerelektronenspektroskopie
überprüft. Mit einer Labor-ARUPS-Anlage (He-I-Linie)
wurden die elektronischen Strukturen der Multilagenfilme untersucht und
die Unterschiede zu den CrPt3-Filmen herausgestellt.
[1] A. Borgschulte et al., Phys. Rev. B 66, 144421 (2002)
MA 13.9 Di 15:00 Bereich A
Fermifläche und Valenzbandstruktur von Tb- und Y-Filmen im
Vergleich — •K. M. Döbrich 1 , J. E. Prieto 1 , K. Rossnagel 2 , H.
Koh 2 , E. Rotenberg 2 , G. Bihlmayer 3 , S. Blügel 3 , G. Kaindl 1
und K. Starke 1 — 1 Fachbereich Physik, Freie Universität Berlin, Germany
— 2 Advanced Light Source, Lawrence Berkeley National Laboratory,
U.S.A. — 3 IFF, Forschungszentrum Jülich, Germany
Die Elemente Tb und Y bilden im bulk ein hcp-Gitter mit fast identischen
Gitterkonstanten und weisen daher oberhalb der Curie-Temperatur
von Tb (ca. 230K) eine sehr ähnliche Bandstruktur und Fermifläche auf.
Im Gegensatz zu Y besitzt Tb lokalisierte magnetische 4f-Momente, die
in der Tieftemperaturphase zu austauschaufgespaltenen Valenzbändern
führen. In der Fermifläche von Tb sind bei 30K daher charakteristische
Merkmale zu beobachten, die es in Y nicht gibt.
Wir präsentieren mittels winkelaufgelöster Photoemission aufgenommene
elektronische Strukturen von epitaktisch auf W(110) aufgedampften
Tb- und Y-Filmen, die eine gute Übereinstimmung mit neuen DFT-
Bandstrukturrechnungen zeigen.
MA 13.10 Di 15:00 Bereich A
Wechselwirkung von antiferromagnetischer Kopplung und magnetischer
Anisotropie mit drastischem Einfluss auf die GMR-
Kennlinien von Multilagen — •Dieter Elefant, Rudi Schäfer,
Rainer Kaltofen, Ludwig van Loyen, Jürgen Thomas und
Hartmut Vinzelberg — IFW Dresden, Postfach 270116, 01171 Dresden
Im allgemeinen übertrifft in magnetischen Multilagen das antiferromagnetische
Kopplungsfeld Hafm das Anisotropiefeld HK, was zu einer spin
flop Struktur der magnetischen Schichten führt, resultierend in relativ
breiten GMR-Kennlinien.
In magnetrongesputterten keilförmigen (NiFe/Cu)x40 Multilagen im
2. afm Maximum (GMR>30% bei T=4,2 K) konnten wir den Fall
HK>Hafm bei Raumtemperatur realisieren. Für parallel zur leichten
Richtung angelegte Magnetfelder H zeigten GMR-Kennlinien und Magnetisierung
diskontinuierliches Schalten, z.T. verbunden mit magnetischem
Kriechen. MOKE und Kerr-Mikroskopie zeigten dieses Schalten
für die oberflächennahen Bereiche der Multilage bei höherem H, wobei
plötzliche Domänenwandverschiebungen nachgewiesen wurden. Die beobachteten
Effekte stehen im Einklang mit dem Auftreten einer collinearen
ferrimagnetischen Phase in Multilagen nach. Höhere Temperaturen
bis 470K führten zu ausgeprägten treppenförmigen GMR Kennlinien. In
Richtung tiefer Temperaturen wird HK

Magnetismus Dienstag
len: einen mit einer linearen Zunahme von K·d für Schichtdicken kleiner
15 Monolagen (ML) und einen mit einer linearen Abnahme von K·d für
Schichtdicken größer 15 ML. Zwei lineare Bereiche der Anisotropie, durch
einen Knick voneinander getrennt, werden in verspannten Systemen mit
senkrechter Magnetisierung gefunden [1]. Das Auftreten zweier linearer
Bereiche ist auch bei uniaxialer Anisotropie und Magnetisierung in der
Ebene ein starkes Indiz für eine Verspannung bzw. Spannungsabbau. Die
Existenz derartiger Verspannungen steht im Widerspruch zu jüngsten
Messungen von Chandesris et al. [2]. Im Gegensatz zu diesen Messungen
zeigen wir, daß die Dickenabhängigkeit der Anisotropie sowie eine
von Null verschiedene z-Komponente der Magnetisierung [3] durch Verspannungen
und eine dem gestuften System angepaßte Formanisotropie
beschrieben werden kann.
[1] M. T. Johnson Rep. Prog. Phys. 59, 1409 (1996)
[2] D. Chandesris et al., J. Phys. C 15, S657 (2003)
[3] N. Mikuszeit et al., J. Mag. Mag. Mater. 268, 340 (2003)
MA 13.16 Di 15:00 Bereich A
Spin-wave excitation in Co/Cu(001), Fe/Co/Cu(001), and
Fe/W(110) by spin-polarized electron energy loss spectroscopy
— •R. Vollmer 1 , M. Etzkorn 1 , P. S. Anil Kumar 1 , W.
Tang 1 , H. Ibach 2 , and J. Kirschner 1 — 1 Max-Planck-Institut für
Mikrostrukturphysik, Weinberg 2, 06120 Halle — 2 Institut für Schichten
und Grenzflächen ISG3, Forschungszentrum Jülich, 52425 Jülich
Recently, we have shown for the case of fcc Co films on Cu(001) that
surface spin-wave excitations can be observed up to the surface Brillouin
zone boundary by spin-polarized electron energy loss spectroscopy
(SPEELS) [1]. In this contribution we compare these results with new
SPEELS measurements on a 3 ML Fe film on 1 ML Co/Cu(001) and on 5
ML Fe on W(110). The SPEEL spectra of 3 ML Fe on 1 ML Co/Cu(001)
show a clear spin-wave signal as well. Similar to Co, only one spin-wave
loss peak is visible in the spectrum. Its width is significantly broader than
that of the spin-wave peak in Co films. For 5 ML Fe on W(110) we find
merely an extremely broad feature without clear maximum. It extends
up to about 400 meV independent of the wavevectors. While a strong
spin-wave signal can be observed only for low energies E0 of the incident
electrons below about 10 eV in the case of Co/Cu(001) and 3 ML Fe
on 1 ML Co/Cu(001), it is almost independent of E0 for Fe on W(110).
We compare our experimental results to new theoretical calculations of
spin-wave spectra of Co and Fe films [2].
[1] R. Vollmer, M. Etzkorn, P. S. Anil Kumar, H. Ibach, and J. Kirschner,
Phys. Rev. Lett. 91, 147201 (2003).
[2] R. B. Muniz and D. L. Mills, Phys. Rev. B 66, 174417 (2002).
MA 13.17 Di 15:00 Bereich A
Influence of substrates on hard magnetic Nd-Fe-B films — •Ah-
Ram Kwon, Ullrich Hannemann, Sebastian Fähler, Volker
Neu, Bernhard Holzapfel, and Ludwig Schultz — IFW Dresden,
Helmholzstr. 20, 01069 Dresden and SFB 463
Nd2Fe14B has excellent intrinsic properties such as high anisotropy
and high saturation magnetization. This material is already used in high
performance bulk magnets. Thin films are interesting for application in
microelectromechanical systems. In both cases, high remanence is required
which can be achieved in the film by textured growth. This can
be controlled by suitable choice of buffer and substrate materials as well
as deposition conditions.
Nd-Fe-B films were prepared by pulsed laser deposition on Ta or Ir
buffer layers using Al2O3(0001), MgO(100) or amorphous SiN substrates.
They possess an out-of-plane c-axis texture and therefore show a high
remanence to saturation magnetization ratio around 0.95. The films exhibit
coercivities between 1.3 T and 2.0 T when measured perpendicular
to the film plane, i.e. parallel to the c-axis (easy magnetization axis). We
compare results of phase formation, microstructure and magnetic properties
of hard magnetic Nd-Fe-B films deposited on different buffers and
substrates.
MA 13.18 Di 15:00 Bereich A
Textured and highly coercive SmCo5 PLD thin films on
amorphous substrates — •S. Leinert, V. Neu, S. Fähler, B.
Holzapfel, and L. Schultz — IFW Dresden, Helmholtzstr. 20,
01069 Dresden and SFB 463
Hardmagnetic SmCo5 thin films have been prepared by pulsed laser
deposition from elemental targets under UHV conditions on amorphous
SiN substrates. The films have Cr buffer and cover layers to prevent oxidation.
Experiments have been carried out that show the dependence of
the phase formation on pulse frequency and pulse alternation. These deposition
parameters, apart from the intended film thickness, determine
the deposition time and thus decide the available time for atomic diffusion.
For the best developed phases room temperature coercivities as
high as 3.5T for a film thickness around 100nm were achieved. Beyond
that, efforts have been made to improve the texture of the films with
the aim to orient the easy magnetisation axis along one axis within the
film plane. Investigations concentrated on substrate tilting (inclined substrate
deposition) and ion beam assisted deposition with low energy Ar
ions (different ion energies, beam currents and angles of incidence). Ion
beam etching experiments on SmCo have been performed to find possible
texturing mechanisms in the IBAD process.
MA 13.19 Di 15:00 Bereich A
Magnetic and Magneto-Optical Properties of UH3 Thin Films
— •D. Kolberg 1 , A. Navratil 1 , T. Gouder 2 , F. Wastin 2 , and J.
Schoenes 1 — 1 Institut für Halbleiterphysik und Optik und Magnetfeldanlage,
TU Braunschweig, Mendelssohnstr. 3, D-38106 Braunschweig,
Germany — 2 European Commission, Joint Research Centre, Institute for
Transuranium Elements, Postfach 2340, D-76125 Karlsruhe, Germany
The first ever observed ferromagnet among actinide compounds was
UH3 with its astonishingly high TC of 180 K [1]. Bulk uranium metal
powderises during hydrogen loading, which makes it impossible to investigate
optical and magneto-optical properties of UH3. This drawback can
be circumvented when growing thin films of uranium with a cap layer of
Pd. However, subsequent H loading leads to inhomogeneous films and
possible destruction [2]. Our new approach is to grow uranium thin films
and to hydrogenate them at the same time. The protection against oxydation,
i.e., the Pd cap layer, is grown on top of the UH3 films. The
cleanliness of the films will be checked via in-situ XPS. Secondly, we
monitor the hydrogen uptake using SQUID magnetometry. Finally, we
investigate the magneto-optical properties of UH3 films in magnetic fields
up to 11.5 Tesla and in the range 0.2 eV < ¯h ω < 5 eV.
Financial support of the DFG (Scho 642/2-2) is acknowledged.
[1] R. Troć and W. Suski, J. Alloys Comp. 219 (1995) 1 [2] D. Kolberg
et al., Verhandl. DPG (VI) 38 (2003) 324
MA 13.20 Di 15:00 Bereich A
Temperature-dependent surface state and magnetization of thin
ferromagnetic EuS films — •W. Nolting and W. Müller —
Lehrstuhl Festkörpertheorie, Institut für Physik, Humboldt-Universität
zu Berlin
We present results for the temperature- and layer-dependent electronic
structure of thin ferromagnetic EuS (100) films. A combination
of a many-body evaluation of a multiband Kondo-lattice model and a
first-principles band structure calculation (TB-LMTO) is used to get as
realistically as possible temperature- and correlation effects. The calculated
layer dependent magnetization shows a good agreement with the
experiment. The results are discussed in terms of spectral densities, densities
of states and band-structures. Special attention is devoted to the
appearance of magnetic 5d-surface states.
MA 13.21 Di 15:00 Bereich A
Strukturelle und magnetische Eigenschaften epitaktischer Manganat
Multilagen — •Oswaldo Moran 1 , Thorsten Schwarz 1,2 ,
Dirk Fuchs 1 und Rudolf Schneider 1 — 1 Karlsruhe, Institut für
Festkörperphysik, 76021 Karlsruhe — 2 Universität Karlsruhe, Fakultät
für Physik, 76128 Karlsruhe
Zur Untersuchung der Austauschwechselwirkung und des Exchange Bias
zwischen ferromagnetischen und antiferromagnetischen Systemen sind
Multilagenstrukturen besonders geeignet. Ein hervorragendes Beispiel
hierfür sind Schichtsysteme bestehend aus La2/3Ca1/3MnO3, ferromagnetisch
(FM) mit TC = 250 K, und La1/3Ca2/3MnO3, antiferromagnetisch
(AFM) mit TN = 170 K. Aufgrund der chemischen und strukturellen
Ähnlichkeit beider Komponenten können sehr hohe Wachstumsgüten bei
epitaktischen Übergitterstrukturen erzielt werden. Die Präparation epitaktischer
Manganat Multilagen mittels Laserdeposition sowie die Charakterisierung
der strukturellen und magnetischen Eigenschaften durch
Röntgendiffraktion und DC-SQUID-Magnetometrie werden vorgestellt
und diskutiert.

Magnetismus Dienstag
MA 13.22 Di 15:00 Bereich A
Rastertunnelspektroskopie an dünnen Manganatfilmen —
•Thomas Becker, Christoph Streng, Arnold Giske, Bernd
Damaschke, Yuansu Luo und Konrad Samwer — I. Physikalisches
Institut, Universität Göttingen, Tammannstr. 1, D-37077 Göttingen
Manganate zeigen interessante Eigenschaften in der Nähe des Metall-
Isolator-Übergangs, die sich im Rahmen eines Perkolationsmodells verstehen
lassen. Experimentell ist es gelungen, metallische und isolierende
Bereiche mit Hilfe der Rastertunnelspektroskopie ortsaufgelöst darzustellen
[PRL 89, 237203-1 (2002)]. Die von uns entwickelte Methode konnte
erfolgreich auf La0.7Sr0.3MnO3 (LSMO) Proben auf einem metallischen
Ir-Film angewandt werden, was die Untersuchungen mit dem STM stark
vereinfacht. Außerdem konnte in einer weiteren Messreihe an sauerstoffreduzierten
LCMO-Proben der gesamte Übergang bis weit in die isolierende
Phase hinein untersucht werden und mit einer Widerstands-Netzwerk-
Simulation und einem Vergleich mit den Transportdaten analysiert werden.
Das Projekt wird gefördert durch die DFG, SFB 602, TP A2
MA 13.23 Di 15:00 Bereich A
Tunnelspektroskopie an Manganatoberflächen in frühen Wachstumsstadien
dünner Schichten — •Arnold Giske, Thomas Becker,
Bernd Damaschke, Yuansu Luo, Vasily Moshnyaga und
Konrad Samwer — I. Physikalisches Institut Universität Göttingen,
Tammannstr. 1, D-37077 Göttingen
Der Metall-Isolator-Übergang in Manganaten wird als Folge einer Perkolation
der metallischen Bereiche im phasenseparierten System diskutiert.
Untersuchungen mittels Rastertunnelspektroskopie an den Oberflächen
zeigen eine Phasenseparation in metallische und isolierende Bereiche
[1].
Im Rahmen dieser Arbeit werden Manganatschichten
(La0.67Sr0.33MnO3 und La0.67Ca0.33MnO3) epitaktisch auf (001)
orientierten Iridiumschichten hergestellt und mittels Rastertunnelspektroskopie
untersucht. Die gesputterten Manganatschichten zeigen auf
Iridium Vollmer-Weber-Wachstum. Bei nomineller Schichtdicke d unter
5 nm entstehen einzelne Inseln. Während die Oberfläche von geschlossenen
Schichten (d = 20 nm) eine Phasenseparation in metallische
und isolierende Bereiche zeigt, weisen die Inseln unabhängig von der
Temperatur jeweils metallisches Verhalten in der Tunnelspektroskopie
auf. Als Ursache für die Unterdrückung des isolierenden Verhaltens wird
Einfluss des metallischen Substrats vermutet.
Diese Arbeit wird durch die DFG innerhalb des SFB 602 TP A2
gefördert.
[1] T. Becker et al. PRL 83, 237203 (2002)
MA 13.24 Di 15:00 Bereich A
Magnetowiderstand von Co-Filmen auf nicht- und halbleitendem
Silizium — •Woosik Gil und Jürgen Kötzler — Institut für
Angewandte Physik, Universität Hamburg, D- 20355 Hamburg
An dynamisch gesputterten Co-Filmen (d=20nm) wurden zunächst
bei 300K Widerstandsänderungen ∆R in Feldern bis zu H = 120 kOe
untersucht. Dabei wurde die H-Richtung variiert relativ zu einem in
der Filmebene liegenden uniaxialen Anisotropiefeld, HF = 30 Oe, das
aus Magnetisierungs- und FMR-Messungen bestimmt wurde. Während
für H||HF kein signifikanter Magnetowiderstand (MW) auftrat, beobachteten
wir für H ⊥ HF in der Umgebung von H ≈ HF eine durch
den Drehprozeß der spontanen Magnetisierung, MS = 17 kOe hervorgerufene
Änderung, |∆R/R| ≤ 1%. Ein analoges Verhalten wurde in
Feldern senkrecht zur Filmebene gefunden, allerdings erstreckten sich
hier die Drehprozesse bis zu dem wesentlichen größeren Anisotropiefeld,
Heff = MS - HA ≈ 10 kOe. Auf isolierendem Silizium besitzt der
MW, ∆R/∆B, das für Co bekannte negative Vorzeichen, das auf p + -
dotiertem Si (1.6 ·10 18 cm −3 ) wechselt, während alle richtungsabhängigen
Phänomene des MW qualitativ gleich bleiben. Aus Messungen der Temperaturabhängigkeit
des Widerstandes zwischen Co und p + -Si folgte eine
Schottky- Barriere, ES = 0.33(2)eV. Diese ermöglicht bei 300K einen
Übergang von Co-Ladungsträgern in das p + -Si, wo ∆R/∆B > 0 ist,
während bei tiefen Temperaturen das Substrat unbeteiligt bleibt und erwartungsgemäß
der normale, negative MW der Co auftritt. Wir untersuchen
gegenwärtig die Frage, ob und gegebenenfalls wie der positive MW
des p + -Si die Vorzeichenumkehr im richtungsabhängigen MW beeinflußt.
MA 13.25 Di 15:00 Bereich A
Magnetowiderstände in Permalloy-Mikrostrukturen —
•Marcus Steiner, Christian Pels, Miriam Barthelmess,
Guido Meier und Ulrich Merkt — Institut für Angewandte
Physik und Zentrum für Mikrostrukturforschung, Universität Hamburg,
Jungiusstr. 11, 20355 Hamburg
Der elektrische Widerstand von ferromagnetischen Metallen setzt
sich aus verschiedenen Beiträgen zusammen, von denen insbesondere
der Widerstandsbeitrag von Domänenwänden nicht eindeutig
geklärt ist. In mikrostrukturierten Permalloyelementen mit definierter
Domänenkonfiguration, die mittels Magnetkraftmikroskopie bestimmt
wird, läßt sich der Magnetowiderstand in Vierpunktmesstechnik gezielt
untersuchen. Der klassische anisotrope Magnetowiderstand (AMR)
kann eindeutig von Umschaltprozessen unterschieden werden. In quasi
eindomänigen Proben wird ein “curling”-artiges Umschaltverhalten
beobachtet, daß durch ein analytisches Modell beschrieben werden
kann [1]. Proben mit multidomänen Konfigurationen zeigen ein komplexes
Magnetowiderstandsverhalten mit reversiblen und irreversiblen
Ummagnetisierungsprozessen, die zum Teil auf Domänenwandeffekte
zurückgeführt werden können. Umfassende Messungen der Filmdicken-,
Temperatur- und Winkelabhängigkeit werden durchgeführt, um das
mikromagnetische und magnetoresistive Verhalten der Proben zu
untersuchen.
[1] A. Aharoni, J. Appl. Phys. 82, 1281 (1997).
MA 13.26 Di 15:00 Bereich A
Spinabhägiger Transport in Filmen bestehend aus Co Clustern
und C60 Molekülen — •H. Zare-Kolsaraki und H. Micklitz — II.
Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937
Köln
Spinabhängiger Transport in künstlich strukturierten, magnetisch inhomogenen
Systemen ist ein aktuelles Forschungsgebiet. Ein neues isolierendes,
granulares System bestehend aus wohldefinierten Co Clustern
und C60 Molekülen ist hergestellt und untersucht worden. Die Proben
mit verschiedenen Co Volumenanteil vCo wurden durch gemeinsame Deposition
von im Strahl vorgefertigten Co Clustern (mittlere Clustergrösse
≈ 4,5 nm) und C60 Molekülen hergestellt. Die Probenwiderstände wurden
in-situ in Abhängigkeit von der Temperatur und einem externen
Magnetfeld (B ≤ 1.2 T) gemessen. Dabei zeigen Proben mit einem Co
Volumenanteil 0.23 ≤ vCo ≤ 0.34 das für isolierende, granulare Systeme
erwartete lnρ ∝ T −1/2 -Verhalten. Der Tunnelmagnetowiderstand TMR
(definiert als TMR = [R(BC)-R(BS)]/R(BC), mit Koerzitivfeld BC bzw.
Sättigungsfeld BS) wurde in Abhängigkeit von vCo und der Temperatur
untersucht. Der TMR in diesem System ist im Vergleich zu den wechselwirkungsfreien
granularen Co/Edelgas-Systemen stark erhöht und sinkt
mit steigendem vCo. Die Erhöhung des TMR wird auf eine WW zwischen
C Atomen und Co Clusteroberfläche zurück geführt, die Abnahme des
TMR mit vCo kann erklärt werden durch Spin-flip Prozesse beim Tunneln
durch elektron-dotierte C60 Moleküle.
MA 13.27 Di 15:00 Bereich A
Extraordinary magnetoresistance effect in a ferromagnetic and
half-metallic double perovskite — •Petra Majewski, Stephan
Geprägs, Mitja Schonecke, Jan B. Philipp, Andreas Erb,
Matthias Opel, Lambert Alff, and Rudolf Gross — Walther-
Meißner-Institut, Bayerische Akademie der Wissenschaften, Walther-
Meißner-Str. 8, 85748 Garching
The EMR (extraordinary magnetoresistance) effect, which was recently
shown at low magnetic fields in semiconductor-metal hybrid structures,
can be understood in terms of a magnetic field dependent deflection of
current around the highly conducting metal. The interesting point is
that a large positive magnetoresistance effect can be achieved in a nonmagnetic
system.
Here, we report on novel magnetoresistance effects in a ferromagnetic,
half-metallic material, namely the double perovskite Sr2CrWO6, grown
on conducting Nb doped SrTiO3 as well as on undoped SrTiO3 substrates.
The high quality Sr2CrWO6 films were grown by UHV laser-MBE with
the growth process monitored by an in-situ RHEED system. The sample
surfaces were examined in-situ by AFM, and the crystalline properties
were determined by x-ray diffraction. Magnetotransport and magnetic
properties have been measured between 4 and 300K at various applied
fields. We show that the described system is of interest to study the
influence of ferromagnetism on the EMR effect.

Magnetismus Dienstag
MA 13.28 Di 15:00 Bereich A
Scaling of the Extraordinary Hall Effect in Manganite Films —
•M. Ziese — Division of Superconductivity and Magnetism, University
of Leipzig, Linnéstrasse 5, 04103 Leipzig.
There has been a long-standing debate about the anomalous Hall effect
in manganites. Whereas traditionalists explained the data in the
conventional side-jump und skew-scattering models, other groups argued
in favour of a new mechanism induced by the Berry phase. Strong support
for the latter came from reports of a one-parameter scaling of the
Hall effect with the reduced magnetization [1]. Using Hall effect data
measured on La0.7Ca0.3MnO3 and La0.7Ba0.3MnO3 films it is shown that
a one-parameter scaling does not hold; instead a two-parameter scaling
is observed. The scaling function can be derived within the basic double
exchange model assuming a side jump mechanism.
[1] Y. Lyanda-Geller, S. H. Chun, M. B. Salamon, P. M. Goldbart,
P. D. Han, Y. Tomioka, A. Asamitsu and Y. Tokura, Phys. Rev. B 63,
184426 (2001).
MA 13.29 Di 15:00 Bereich A
Properties of CMR-manganite films: Pr0.7Ca0.3MnO3 —
•Wilko Westhäuser, Karsten Guth, Harald Jarzina, and
Christian Jooss — Institut für Materialphysik, Universität Göttingen,
Tammannstrasse 1, 37077 Göttingen, Germany
The CMR-effect describes a colossal drop in resistance caused by
a phase transition from a charge-ordered antiferromagnetic state to a
charge-delocalized ferromagnetic state. As the charge-ordered state of
Pr0.7Ca0.3MnO3 is unstable under external perturbations, this transition
can be switched by applying an electrical field, a magnetic field or
using photon exposure.
Mixed powder of Pr6O11, CaCO3 and MnO3 with a defined ratio was
calcined in air at 1050C for 48h and then pressed into a 25-mm diameter
target. By using pulsed laser deposition, thin films were grown on singlecrystalline
SrTiO3-substrates (001). The calcined powder and the ablated
thin films were analysed by XRD, DSC, REM and EDX to determine the
crystallographic structure and the chemical composition.
Transport properties, in particular the metallic-insulator transition in
electrical fields, are analysed as a function of temperature.
MA 13.30 Di 15:00 Bereich A
Transport in nanocontacts: An ab initio description — •Michael
Czerner, Alexej Bagrets, and Ingrid Mertig — Martin-Luther-
University Halle-Wittenberg, Department of Physics, Von-Seckendorff-
Platz 1, 06120 Halle, Germany
We present ab-initio calculations of the transport properties of metallic
atomic-sized nanocontacts. The nanocontacts were modelled by atomic
chains of Cu and Co suspended between two semi-infinite leads. We used
the first principle screened Korringa-Kohn-Rostoker method to calculate
the electronic properties of the systems, treating the leads and atomic
chains on the same footing without any model parameters. The Landauer
formalism was applied to investigate the conductance. Quantum
size effects and the influence of impurity scattering is discussed in detail.
MA 13.31 Di 15:00 Bereich A
Fabrication and charakterization of monocrystalline
Fe/ZnSe/Fe tunnel contacts — •Martin Dumm and Günther
Bayreuther — Institut für Experimentelle und Angewandte Physik,
Universität Regensburg, 93040 Regensburg
Theoretical work predicts high magneto-resistance values for
monocrystalline tunnel contacts with semiconductor barriers.
Fe/ZnSe/Fe trilayers have been fabricated by molecular beam epitaxy
(MBE) using two separate MBE-Systems, where the samples can
be transferred from one chamber to the other without breaking the
vacuum using a portable UHV chamber. High resolution transmission
electron microscopy on cross sections and reflective high energy electron
diffraction prove that the whole system is grown epitaxially on the
GaAs(001) substrate. The 20nm thick Fe bottom layer has a dominating
fourfold magnetic anisotropy with the easy axes along [100] and [010],
whereas a uniaxial anisotropy with easy axis along [110] prevails in the
2nm thick Fe top layer. Magnetization loops for the Fe/ZnSe/Fe show
that the coercive field of the top layer is smaller than that of the bottom
layer between 300K and 80K, whereas below 80K both Fe films switch
at the same magnetic field. This means that at low temperature the
switching of the thinner top layer is triggered by the switching of the
thicker bottom layer.
Finally, first magneto-transport measurements across the tunnel barrier
at 100K are reported.
MA 13.32 Di 15:00 Bereich A
Characterization and optimization of Co/Al2O3/Co/CoO magnetic
tunnelling junctions — •Erik Verduijn and Kurt Westerholt
— Institut für Experimentalphysik/Festkörperphysik, Ruhr-
Universität Bochum, 44780 Bochum
Co/Al2O3/Co magnetic tunnel junctions (MTJs) are well established
in literature and ideally suited as a reference system for the development
and optimization of the techniques relative for the design and
fabrication of microstructured tunnel junctions. To this end we have
performed magnetotransport and SQUID magnetometry measurements
on Co/Al2O3/Co/CoO MTJs and atomic force microscopy studies of
Co/Al2O3/Co/CoO layers fabricated under a variety of different growth
conditions in order to optimize several critical MTJ parameters, in particular
the optimization of the tunnel barrier oxidation parameters, roughness
of the bottom ferromagnetic electrode and the magnetic switching
behaviour of the ferromagnetic electrodes. Furthermore we report on
the microlithographic technique based on ion beam etching and electron
beam lithography we use for the fabrication of micrometer scale MTJs.
MA 13.33 Di 15:00 Bereich A
Temperature and bias voltage dependent transport in magnetic
tunnel junctions with low energy Ar-ion irradiated barriers —
•Jan Schmalhorst and Guenter Reiss — University of Bielefeld,
Department of Physics, Nano Device Group, P.O. Box 100131, 33501
Bielefeld, Germany
Magnetic tunnel junctions (Mn83Ir17/Co70Fe30/AlOx/Ni80Fe20) are investigated,
whose barriers are irradiated by a low energy Ar + ion beam
immediately after plasma oxidation of the aluminium film. The tunneling
magnetoresistance prior to irradiation is up to 71% at 10K. The ion
irradiation increases the area resistance product up to a factor 40 for ion
energies up to 150V. Further, the tunneling magnetoresistance and the
dielectric stability is strongly reduced with increasing ion energies. From
the analysis of the temperature and the voltage dependence of the tunneling
magnetoresistance we conclude, that this is due to an irradiation
induced local change of the coordination of the Al- und O-atoms in the
barrier. This leads to a thicker barrier and an increase of the precursor
density for the dielectric breakdown. Further, an increase of hopping
conductance through localized states is discussed. At energies larger than
150V the resistance breaks down rapidly and the tunneling magnetoresistance
vanishes completely. This results from the enhanced intermixing
and sputtering of the barrier and electrode material. The results are also
supported by investigations of the magnetic and the noise properties of
the junctions and the Cu-Kα- reflectivity of AlOx multilayers.
MA 13.34 Di 15:00 Bereich A
Barrierenmodifikation von magnetischen Tunnelelementen —
•Marc Sacher, Jan Sauerwald, Jan Schmalhorst und Günter
Reiss — Universität Bielefeld, Fakultät für Physik, Universitätsstr. 25,
33615 Bielefeld
Es werden doppelt gepinnte, magnetische Tunnelelemente (Mn83Ir17/
Co / Al2O3/ Co/ Mn83Ir17) mit systematisch variierter Barrieren-
Grenzfläche hergestellt. Die Proben werden im Magnetfeld gesputtert,
und zeigen dadurch ohne anschließendes Tempern das Exchange-Bias. So
kann eine thermisch aktivierte Veränderung der Tunnelbarrieren ausgeschlossen
und auftretende Effekte auf die Bestrahlung zurückgeführt werden.
Die Barrierenmodifikation erfolgt mittels niederenergetischer Argonionen
(10...100eV) in zwei verschiedenen Experimenten:
1. Die Aluminiumschicht wird direkt nach der Oxidation bestrahlt. Der
Tunnelwiderstand wächst exponentiell mit der Bestrahlungsdauer auf das
400-fache (100s) an. Dabei ist der TMR bis zu einer Energie von 60eV
konstant auf dem Wert des Referenzelementes. Erst darüber sinkt er
leicht ab. Bei einer anschließenden Auslagerung der Probe reduziert sich
der Widerstand auf die Größenordnung des Referenzwertes.
2. Nach der Oxidation des Aluminiums wird zunächst eine dünne Kobaltschicht
(1...20˚A) aufgebracht, anschließend bestrahlt und erst danach
das restliche Kobalt (auf 6nm) gesputtert. Hier verschwindet der TMR
bei einer Kobaltdicke von 0,4nm, nimmt aber ab 1,5nm wieder zu.
Ziel dieser Versuche ist ein tieferes Verständnis der Einflüsse von z.B.
Grenzflächenrauigkeit auf den Tunnelprozess.

Magnetismus Dienstag
MA 13.35 Di 15:00 Bereich A
Epitaxial tunnel junctions based on highly spin-polarized
Fe(110) electrodes — growth, fabrication, and transport
properties — •J.O. Hauch 1 , M. Fraune 1 , H. Kittur 1 , P.
Turban 1 , U. Rüdiger 2 , and G. Güntherodt 1 — 1 II. Physikalisches
Institut, RWTH Aachen, 52056 Aachen — 2 Fachbereich für Physik,
Universität Konstanz, 78457 Konstanz
Recently theoretical and experimental efforts have been spent
on the study of epitaxial magnetic tunnel junctions (MTJs). Such
model systems are essential for the fundamental understanding of
the spin-dependent tunneling mechanism. We present the epitaxial
growth, the fabrication process, and the transport properties of epitaxial
Fe(110)/MgO(111)/Fe(110) MTJs. The highly spin-polarized Fe(110)
electrodes [1] separated by an MgO(111) barrier of 4nm thickness are
grown on an Al2O3(1120) substrate by using a Mo(110) seed layer.
Tunnel junctions are prepared from these thin film samples using
optical and electron beam lithography combined with ion beam etching.
The application of the Rowell criteria as well as the Poole-Frenkel
analysis [2] to the temperature dependent conductivity confirm an MgO
barrier of a high quality. TMR measurements show actually an MR of
approximately 13% at T = 16K.
This work was supported by the BMBF, contract no. 13N7329.
[1] Yu. S. Dedkov, U. Rüdiger and G. Güntherodt, Phys. Rev. B 65,
064417 (2002).
[2] P. Rottländer et al., Phys. Rev B 65, 054422 (2002).
MA 13.36 Di 15:00 Bereich A
Röntgenabsorption und magnetischer Zirkulardichroismus in
magnetischen Tunnelelementen — •Jan Schmalhorst 1 , Kai
Starke 2 , Marc Sacher 1 , Andy Thomas 1 und Guenter Reiss 1
— 1 Fakultät für Physik, Universität Bielefeld, Universitätsstr. 25, 33615
Bielefeld — 2 Fakultät für Physik, Freie Universität Berlin, Arnimallee
14, 14195 Berlin
Das Interesse an magnetischen Tunnelelementen (MTJ) hat in den vergangen
Jahren aufgrund ihrer vielversprechenden Anwendbarkeit stark
zugenommen. Feldabhängige Widerstandsänderungen (TMR) von bis zu
60% bei RT wurden erreicht. Die thermische Stabilität von MTJs ist
durch einen deutlichen Anstieg des TMR bis zu einer optimalen Auslagerungstemperatur
von typischerweise 300 o C charakterisiert, nach Auslagerung
bei höheren Temperaturen fällt der TMR aufgrund von unerwünschten
Diffusionsprozessen dann relativ schnell ab.
In der hier vorgestellten Arbeit wurden die elementspezifischen magnetischen
Momente und chemischen Zustände in hochwertigen MTJs mittels
Röntgenabsorption (XAS) und magnetischem Zirkulardichroismus
(XMCD) in Abhängigkeit von der Auslagerungstemperatur vermessen
und in Relation zu den Transporteigenschaften der MTJs gesetzt. Für
eine konsistente Deutung aller Ergebnisse muss der Einfluss der strukturellen
Mikrostruktur berücksichtigt werden.
MA 13.37 Di 15:00 Bereich A
Magnetische Doppeltunnelbarrieren mit antiferromagnetisch
gekoppelter Zwischenschicht — •Andreas Stabaginski, Hubert
Brückl und Günter Reiss — Universität Bielefeld, Fakultät für
Physik, Universitätsstraße 25, 33615 Bielefeld
Der spinabhängige Elektronentransport wurde bei magnetischen Tunnelelementen
(TMR-Elementen) mit Doppelbarriere untersucht. Zwischen
den beiden Tunnelbarrieren soll ein antiferromagnetisch gekoppeltes
Dreilager eingefügt werden. Hierfür wurde das Schichtsystem Si/ Cu
(30nm)/ Py (1.7nm)/ MnIr (15nm)/ Co (3nm)/ Al (1.4nm) +Ox/ Py
(3.5nm)/ Co (3.3nm)/ Cu (x nm)/ Co (3.5 nm)/ Al (1.4nm) +Ox/ Py
(3nm)/ Ta (5nm)/ Cu (10nm)/ Ta (5nm)/ Au (30nm) mit variierter
Kupferdicke x hergestellt. Es wurden die obere sowie die untere Barriere
elektrisch charakterisiert, ebenso wurden Magnetisierungskurven mit
MOKE aufgenommen.
MA 13.38 Di 15:00 Bereich A
Grenzflächeneigenschaften von Fe-Al2O3-TMR-Strukturen —
•Holger Schmitt 1 , Branko Stahl 1,2 , Ljubomira Schmitt 1 ,
Joachim Brötz 1 , Mohammad Ghafari 1 und Horst Hahn 1
— 1 Fachbereich Material- und Geowissenschaften, Petersenstr. 23,
TU Darmstadt, 64287 Darmstadt — 2 Institut für Nanotechnologie,
Forschungszentrum Karlsruhe, 76021 Karlsruhe
Fe/Al- bzw. Fe/Al2O3-Schichtsysteme wurden mittels Molekularstrahlepitaxie
auf oxidiertem Silizium mit Ta- bzw. Pd-Bufferschichten
präpariert. In situ wurden 57Fe-Mössbauerspektren mit DCEMS
(Konversionselektronen-Mössbauerspektroskopie im UHV, 10-300 K)
aufgenommen. Abhängig von Position, Dicke und Rauhigkeit der
57Fe-Tracerlage konnten die Oxidations- und Temperaturbehandlungen
mit Submonolagenempfindlichkeit verfolgt werden. Ergänzend wurden
ex situ XPS- (X-Ray Photoelektronen Spektroskopie), HRTEM- und
Röntgenreflektometrie-Untersuchungen durchgeführt. Die Struktur- und
Phaseninformationen werden anhand derselben Proben mit Magnetowiderstandsmessungen
(TMR) in Zusammenhang gebracht.
MA 13.39 Di 15:00 Bereich A
Spin-polarized tunneling in FM/I/Al junctions based on ferromagnetic
oxides — •Stefanie Wagner, Petra Majewski, Mitja
Schonecke, Daniel Reisinger, Andreas Erb, Lambert Alff,
Matthias Opel, and Rudolf Gross — Walther-Meißner-Institut,
Bayerische Akademie der Wissenschaften, Walther-Meißner-Str. 8, 85748
Garching
Ferromagnet/insulator/superconductor (FM/I/SC) junctions are useful
to determine the spin polarization of the charge carriers at the Fermi
level in ferromagnetic materials [1]. Due to the Zeeman splitting in the
quasiparticle density of states in superconductors, a non-zero spin polarization
in the ferromagnet leads to an asymmetric tunnelling conductivity.
We have grown high quality thin films of La2/3Ba1/3MnO3 and Sr2CrWO6
on SrTiO3 substrates using UHV laser-MBE. The structural and magnetic
properties of the films have been determined by x-ray diffraction
and magnetization measurements. The insulating barriers (SiO2, Al2O3,
SrTiO3) with a typical thickness of 2nm have been deposited in-situ by
UHV laser-MBE or electron beam evaporation. The surface morphology
of both the ferromagnetic layer and the insulating barrier have been examined
in-situ by atomic force microscopy. Finally, a thin superconducting
layer of Al (Tc = 2.5K) is deposited by electron beam evaporation.
After fabricating small tunnel junctions using optical lithography, we
measure the conductivity across the junctions as a function of magnetic
field at temperatures below 2K.
[1] P.M. Tedrow and R. Meservey, Phys. Rev. Lett. 26, 191 (1971).
MA 13.40 Di 15:00 Bereich A
Towards a Tunneling-Spinvalve-Transistor with epitaxial
Schottky-Barrier — •Thomas Hagler, Martin Dumm, and
G”unther Bayreuther — Institut f”ur Experimentelle und
Angewandte Physik, Universit”at Regensburg, 93040 Regensburg
Ballistic electron transport through GMR-structures into a semiconductor
have already shown large magnetocurrent effects [1]. In our work
we aim to get information about different transport processes involved.
We examine layered systems like GaAs/CoFe/Cu/NiFe/Al2O3/Al.
The CoFe Schottky contact is epitaxially grown on n+ doped GaAs(001).
The total thickness of the CoFe/Cu/NiFe pseudo spinvalve is about 10nm
to allow ballistic transport. Magnetron sputtering and natural oxidation
of 0.7nm Al (three repetitions) is used for the tunneling barrier.
Optical lithography is used to structure and contact the samples. With
SIMS-controlled ion beam etching we are able to stop etching in the GMR
trilayer. The different contacts on each sample are isolated by SiO2, using
PECVD. Contact pads of about 250nm Au finally deposited on top
allow to bond the samples for electrical measurements.
For magnetic characterisation we use MOKE and SQUID magnetometers.
Through I-V-measurements at different fields, temperatures and
electron energies we obtain barrier and magnetotransport parameters.
[1] R. Jansen et. al., JAP 89 (2001) 7431
MA 13.41 Di 15:00 Bereich A
Characterization of Fe/GaAs Schottky barriers — •A. Spitzer,
P. Kotissek, M. Bailleul, and G. Bayreuther — Institut für Experimentelle
und Angewandte Physik, Universität Regensburg
Recent results [1] show that Schottky barriers, which are formed at
metal/semiconductor-contacts under certain conditions, are promising
candidates for efficient injection of spinpolarized electrons into semiconductors.
The subject of this work are epitaxial Fe films on GaAs. The
properties of the Schottky-barriers are investigated with respect to the
doping-density, preparation conditions of the substrat and its crystal orientation.
The GaAs surfaces are prepared in a UHV system by annealing
and ion sputtering and subsequently coated with Fe by molecular beam
epitaxy. To characterize the barriers temperature dependent (10K to
300K) current-voltage-curves and room temperature capacitance-voltagecurves
are measured. From the data we are able to determine the different
transport-regimes - thermionic emission and tunneling. The effect of the

Magnetismus Dienstag
termination and the doping level of the GaAs surface on the characteristic
parameters of the Schottky barriers is investigated.
Support by Deutsche Forschungsgemeinschaft is gratefully acknowledged.
[1] A.T. Hanbicki et al, Appl. Phys. Lett., 80, 1240 (2002)
MA 13.42 Di 15:00 Bereich A
Growth and structural properties of epitaxial CoO(111) thin
films on sapphire substrates — •Gregor Nowak, Florin Radu,
Kurt Westerholt, and Hartmut Zabel — Experimentalphysik /
Festkörperphysik, Ruhr - Universität Bochum, Deutschland
Although CoO is widely used as antiferromagnetic layer in exchange
biased heterostructures, a systematic study of the growth-property relationship
has not been reported yet. We used rf-sputtering techniques
for the deposition of CoO films on Al2O3(00.1) substrates. By varying
the partial oxygen pressure we could change the stoichiometry, which results
in a variation of the ferromagnetic signal. We have optimized the
partial oxygen pressure as to have minimum ferromagnetic signal of the
antiferromagnetic CoO layer. In addition, the substrate temperature was
varied between 100 ◦ C to 600 ◦ C to optimized the structural parameters.
We observe the best quality of CoO at about 400 ◦ C. The samples were
studied by x-ray reflectivity and x-ray diffraction. We find an improved
crystallinity of the CoO(111) layer on Al2O3(00.1), as recognized by (00l)
Bragg peaks accompanied by Laue oscillations. Small angle reflectivity
measurements reveal very small roughness values of 0.5-0.6 nm for a
20 nm thick film, has been confirmed by AFM measurements. Determination
of the exchange field as a function of stoichiometry and growth
temperature is in progress. This work was supported by SFB 491
MA 13.43 Di 15:00 Bereich A
Observation of out-of-plane spin components in antiferromagnetic
NiO(100) — •W. G. Park, U. Mick, and E. Kisker — Institut
für Angewandte Physik, Universität Düsseldorf, Universitätsstrasse
1, 40225 Düsseldorf
By using x-ray magnetic linear dichroism(XMLD) we investigated an
in-situ cleaved NiO(100) surface. We present data obtained by surface
sensitive techniques like X-ray photoemission microscopy (XPEEM), xray
absorption spectroscopy (XAS) together with images showing inplane
and out-of-plane spin alignments. Local images show clearly uncompensated
surface and antiferromagnetic domains with perpendicular
components to the surface. This kind of domain was not directly observed
both in bulk NiO and in thin film until now because of the small
domain size (≈50nm) in the film, symmetry breaking and surface properties.
Ni L2 XAS of the sample annealed over the Neel-temperature
(523K) indicates the missing local exchange field described in the atomic
multiplet theory and shows its polarization dependence. Interface oxidation
between an antiferromagnetic oxide and a ferromagnetic thin film as
speculated earlier was not observed in Fe-overlayers evaporated on the
NiO surface at the room temperature. We thank Dr.Senf (BESSY) for
his support. This work was supported by the BMBF (Grant No. 05KS
1PFA/3).
MA 13.44 Di 15:00 Bereich A
CEMS and NRS investigation of the spin structure in exchange
biased Fe/FeF2 bilayers — •B. Sahoo 1 , W. A. A. Macedo 2,3 ,
J. Eisenmenger 2,4 , W. Keune 1 , R. Röhlsberger 5 , T. Klein 6 ,
J. Nogues 7 , V. Kuncser 1,8 , I. K. Schuller 2 , K. Liu 9 , I. Felner
10 , O. Leupold 11 , and R. Rüffer 11 — 1 Universität Duisburg-
Essen, Duisburg, Germany — 2 University of California, San Diego, USA
— 3 CDTN, Belo Horizonte, Brazil — 4 Universität Ulm, Ulm, Germany
— 5 HASYLAB at DESY, Hamburg, Germany — 6 Universität Rostock,
Rostock, Germany — 7 ICREA and Universitat Autonoma de Barcelona,
Bellaterra, Spain — 8 NIPM, Bucharest, Romania — 9 University of California,
Davis, USA — 10 Hebrew University, Jerusalem, Israel — 11 ESRF,
Grenoble, France
By cooling down the exchange biased Fe/FeF2 bilayer system below
the Néel temperature (TN) of the AFM, a change of the spin structure
in the FM layer is observed by CEMS. The ferromagnetic spins are always
in the sample plane, and an average in-plane rotation of the spins
equivalent to a spin fanning is observed. This spin fanning is reduced farther
away from the interface. The NRS results are consistent with CEMS
observations. A small out-of-plane spin component at the interface of the
AFM layer is also observed. The interfacial spin structure of the AFM
layer is modeled by an ellipsoidal spin distribution.
Acknowledgement: Supported by DFG (SFB 491)
MA 13.45 Di 15:00 Bereich A
Electric control of exchange bias — •Andreas Hochstrat,
Christian Binek, Xi Chen, Pavel Borisov, and Wolfgang
Kleemann — Universität Duisburg-Essen, Campus Duisburg, Fakultät
für Naturwissenschaften, Institut für Physik, Laboratorium für
Angewandte Physik, 47048 Duisburg
Electric field controlled exchange bias is studied on Molecular Beam
Epitaxy grown magnetic heterostructures based on antiferromagnetic
Cr2O3, the prototypical system for investigations of the magneto-electric
effect. An electric field E applied to the sample gives rise to an additional
magnetic moment in the antiferromagnetic component. The magnetoelectric
coefficient as a function of temperature is investigated using Superconducting
Quantum Interference Device (SQUID) magnetometry. In
accordance with the phenomenological approach of Meiklejohn and Bean
the additional magnetic moment is the origin for electric access to the
exchange bias. The effect of antiferromagnetic domain states on the controllability
of the exchange bias is explored by SQUID-magnetometry.
Magneto-electrically annealed antiferromagnetic single domain states reveal
exchange bias fields, which depend on the freezing conditions, but
remain virtually independent of E below the blocking temperature. However,
preparation of a magneto-electric multi-domain state enables substantial
electric control of the exchange bias in the frozen state which is
probably due to flopped domain wall spins.
MA 13.46 Di 15:00 Bereich A
Kontrolle der magnetischen Ordnung durch ein elektrisches
Feld in HoMnO3 — •Th. Lottermoser 1 , Th. Lonkai 2 , U. Amman
2,3 , J. Ihringer 2 , D. Hohlwein 4 und M. Fiebig 1 — 1 Max-Born-
Institut, Max-Born-Straße 2A, 12489 Berlin — 2 Institut für Angewandte
Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen
— 3 Institut Laue-Langevin, 6, Rue J. Horowitz, BP 156-38042 Grenoble,
France — 4 Hahn-Meitner-Institut, Glienicker Straße 100, 14109 Berlin
Die Entdeckung des linearen magnetoelektrischen (ME) Effekts – Induktion
einer elektrischen Polarisation durch ein magnetisches Feld bzw.
Induktion einer Magnetisierung durch ein elektrisches Feld – stieß in den
1960er Jahren auf großes Interesse: Die Wechselwirkung eröffnete neue
Freiheitsgrade für die Entwicklung von Bauteilen, die auf der gegenseitigen
Kontrolle des magnetischen und elektrischen Zustands beruhen. Wegen
der generell geringen Größenordnung des Effekts schlug die Entwicklung
eines ” ME Schalters“ jedoch fehl. Vor kurzem wurden in Kompositmaterialien
und magnetischen Ferroelektrika ein ” gigantischer“, steuerbarer
ME Effekt entdeckt, was erneut zu großem Interesse in dieser Materieleigenschaft
führte. Wir beschreiben die Kontrolle der magnetischen
Ordnung in HoMnO3 durch ein elektrisches Feld. Eine ferromagnetische
Ordnung der Ho 3+ -Spins wird durch ein elektrisches Feld ein- bzw. ausgeschaltet.
Der Prozess wird mithilfe der optischen zweiten Harmonischen
beobachtet und anhand von Neutronendiffraktionsmessungen mikroskopisch
erklärt. Er beruht auf dem ME Beitrag zur freien Energie, der
mikroskopisch induziert wird durch eine Asymmetrie der Ho 3+ − Mn 3+ -
Superaustauschpfade aufgrund der ferroelektrische Verzerrung.
MA 13.47 Di 15:00 Bereich A
Strukturelle Untersuchung ionenbestrahlter Austausch-
Verschiebungsschichtsysteme — •Steffen Blomeier 1 , Jürgen
Fassbender 1 , Burkard Hillebrands 1 , Damien McGrouther 2 ,
Stephen McVitie 2 und John N. Chapman 2 — 1 Fachbereich
Physik und Forschungsschwerpunkt MINAS, Erwin-Schrödinger-Str.
56, Technische Universität Kaiserslautern, 67663 Kaiserslautern —
2 Department of Physics and Astronomy, Kelvin Building, University of
Glasgow,Glasgow G12 8QQ, Scotland, United Kingdom
Vor Kurzem konnte gezeigt werden, dass die magnetischen Eigenschaften
von Austausch-Verschiebungssystemen durch Ionenbestrahlung gezielt
beeinflusst werden können. Ein Modell wurde vorgeschlagen, welches
die Änderung der magnetischen Eigenschaften der bestrahlten Systeme
einer ioneninduzierten Änderung ihrer Struktur zuschreibt. Insbesondere
wird die Erzeugung von Punktdefekten für die beobachteten
Veränderungen verantwortlich gemacht. Um dieses Modell zu testen, wurde
das ionenbestrahlte System NiFe/FeMn mit Hilfe von Transmissionselektronenmikroskopie
untersucht. Es wurden Hellfeld-, Dunkelfeld- und
Beugungsbilder von dem System aufgenommen und ausgewertet. Daraus
wurden Morphologie, Partikelgrößen und kristallographische Struktur
des Systems bestimmt und deren Abhängigkeit von der Bestrahlung
durch 5 keV He + -Ionen und 30 keV Ga + -Ionen untersucht. Es konnte
gezeigt werden, dass sich weder Partikelgrößen noch kristallographische
Struktur mit zunehmender Ionendosis signifikant verändern. Diese Er-

Magnetismus Dienstag
gebnisse unterstützen die Theorie der defektinduzierten Modifikation der
Austausch-Verschiebung.
MA 13.48 Di 15:00 Bereich A
Zeitabhängige Veränderung des Austauschverschiebungsfeldes
von Bilayern nach Beschuss mit keV He-Ionen — •D. Backes 1 ,
D. Junk 1 , A. Ehlers 1 , D. Engel 1 , H. Schmoranzer 1 , A. Ehresmann
1 , A. Paetzold 2 und K. Röll 2 — 1 Technische Universität Kaiserslautern,
Fachbereich Physik, Erwin-Schrödinger-Str., D-67663 Kaiserslautern
— 2 Universität Kassel, Fachbereich Physik, Heinrich-Plett-
Str.40, D-34132 Kassel
Austauschverschobene (Exchange Bias) Schichtsysteme basierend z.B.
NiO und FeMn als Antiferromagnet wurden nach ihrer Herstellung mit
10keV He-Ionen in einem externen Magnetfeld parallel und antiparallel
zur ursprünglichen Anisotropierichtung beschossen. Die durch den Beschuss
erzielten Modifikationen des Exchange Bias Feldes verändern sich
nach dem Beschuss unter bestimmten Bedingungen mit der Zeit. Diese
Prozesse hängen u.a. von der Korngrößenverteilung in der polykristallinen
antiferromagnetischen Schicht ab. Erste Ergebnisse zu dieser zeitlichen
Veränderung werden vorgestellt und im Rahmen eines erweiterten
Modells basierend auf dem Relaxationsmodell von Fulcomer und Charap
erklärt.
MA 13.49 Di 15:00 Bereich A
Gezielte Richtungsänderung der unidirektionalen Anisotropie
in austauschverschobenen Schichtsystemen durch
keV-Ionenbeschuss — •D. Engel, D. Junk, A. Ehlers, H.
Schmoranzer und A. Ehresmann — Technische Universität
Kaiserslautern, Fachbereich Physik, Erwin-Schrödinger-Str., D-67663
Kaiserslautern
Durch He-Ionenbeschuss von austauschverschobenen Schichtsystemen
in einem äußeren Magnetfeld kann man die Stärke und Richtung des Austauschverschiebungsfeldes
Heb nachträglich verändern. Indem man das
äußere Magnetfeld beim Beschuss gegenüber der ursprünglichen unidirektionalen
Anisotropierichtung des Schichtsystems dreht, ist es möglich
eine neue Anistropierichtung durch den Ionenbeschuss zu fixieren. Diese
Modifikationen sind lateral begrenzbar und bieten vielfältige Anwendungsmöglichkeiten
für magnetische Sensoren und Speicherelemente. Es
werden erste Ergebnisse für Schichtsystme mit oxidischen und metallischen
Antiferromagneten, die mit 10keV He-Ionen beschossen wurden,
vorgestellt.
MA 13.50 Di 15:00 Bereich A
Modifikation von NiO basierten Bilayern durch 10 keV He-
Ionenbeschuss — •T. Jacob, A. Ehlers, D. Engel, H. Schmoranzer
und A. Ehresmann — Technische Universität Kaiserslautern,
Fachbereich Physik, Erwin-Schrödinger-Str., D-67663 Kaiserslautern
Die Veränderung des Austauschverschiebungsfeldes Heb von Zweilagenschichtsystemen
(Bilayern) mit NiO als Antiferromagnet durch He-
Ionenbeschuss wurde in Abhängigkeit von der Ionendosis untersucht. Es
ist möglich durch keV He-Ionenbeschuss in einem äußeren Magnetfeld in
diesen Schichtsystemen Heb zu erhöhen, zu reduzieren und die unidirektionale
Anisotropierichtung zu verändern. Es werden erste Ergebnisse für
unterschiedliche Ferromagneten präsentiert.
Bei diesen Schichtsystemen kann es zu einem zweigeteilten Magnetisierungsprozess
entlang der schweren Richtung kommen. Deshalb wurden
zusätzlich zu dem Ionenbeschuss diese Bilayer auch einem erneuten
Feldkühlungsprozess unterzogen, d.h. über die Néeltemperatur von NiO
erhitzt und anschließend in einem äußeren Magnetfeld auf Raumtemperatur
wieder abgekühlt. Durch unterschiedliche Reihenfolge von Beschuss
und Annealing wurde die Veränderung von Heb und dem Magnetisierungprozess
entlang der schweren Richtung untersucht.
MA 13.51 Di 15:00 Bereich A
Thermally induced changes of magnetic coupling in a pinned
artifical antiferromagnet used in magnetic tunnel junctions
— •Jan Schmalhorst 1 , Hubert Brueckl 1 , Guenter Reiss 1 ,
Guenter Gieres 2 , and Joachim Wecker 2 — 1 University of Bielefeld,
Department of Physics, Nano Device Group, P.O. Box 100131, 33501
Bielefeld, Germany — 2 Siemens AG, Corporate Technology CT MM 1,
P.O. Box 3220, 91050 Erlangen, Germany
The thermally induced changes of the magnetic coupling in an artifical
antiferromagnet exchange biased by an antiferromagnetic layer in a magnetic
tunnel junction (Mn-Ir / Co-Fe / Ru / Co-Fe / AlOx / Ni-Fe) is
investigated for annealing temperatures up to 450 o C. Beside the usual in-
crease of the tunneling magnetoresistance by annealing (maximum TMR
43.9%@325 o C) the degradation of the artificial antiferromagnet causes
a well defined 90 o -coupling of the Co-Fe layers in a narrow temperature
window around 325 o C. At higher temperature, both Co-Fe layers
are coupled ferromagnetically but the exchange biasing by the Mn-Ir is
still present. This behaviour results from an interplay of different coupling
mechanisms of the two Co-Fe layers: (1) indirect antiferromagnetic
interlayer exchange coupling across the Ru spacer, (2) ferromagnetic coupling
by pinholes in the Ru spacer and (3) exchange coupling between
the lower Co-Fe layer and the antiferromagnet Mn-Ir. The importance of
each contribution is discussed with respect to thermally activated diffusion
processes.
MA 13.52 Di 15:00 Bereich A
Kerr observations of asymmetric magnetization reversal in
CoFe-IrMn bi-layer systems — •Jeffrey McCord 1 and Roland
Mattheis 2 — 1 IFW Dresden, Helmholtzstr. 20, 01169 Dresden —
2 IPHT Jena, Albert-Einstein-Str. 9, 07745 Jena
The magnetization reversal process in the ferromagnetic layer of
exchange-biased CoFe-IrMn film structures, deposited by dc-magnetron
sputtering, is imaged Kerr microscopy. The amount of magnetization
rotation at different field directions is quantified by measuring the
longitudinal and transversal magnetization components during reversal.
A strong asymmetry, both in domain behavior and magnetization
loops, between the forward and recoil branch of the magnetization reversal
is found. The magnitude of asymmetry strongly depends on small
angle misalignments between the direction of exchange-bias and the external
magnetic field. The observed behavior is explained by anisotropy
dispersion in the ferro- and antiferromagnetic layer. Influencing the effective
anisotropy distribution in the CoFe-IrMn system leads to differently
pronounced asymmetries. The differences for both branches of the hysteresis
loop are described in terms of domain nucleation mechanisms due
to changes leading to an effectively wider anisotropy distribution.
MA 13.53 Di 15:00 Bereich A
Magnetic domain investigation in Co/Cu/FeMn trilayers — J.
Wang, •W. Kuch, F. Offi, L. I. Chelaru, M. Kotsugi, and J.
Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Weinberg
2, D-06120 Halle
The as-grown magnetic domain patterns of epitaxial single-crystalline
Co/Cu/FeMn trilayers were investigated by magnetic circular dichroism
domain imaging using photoelectron emission microscopy (XMCD-
PEEM). Small domains were observed when Co was deposited directly
on top of antiferromagnetic FeMn films. Inserting a Cu spacer layer between
the ferromagnetic Co layer and the antiferromagnetic FeMn layer,
the as-grown domain size increases continuously with increasing Cu layer
thickness, which is attributed to the decrease of the interlayer exchange
coupling between Co and FeMn layers. The average as-grown domain size
of the Co layer on top of a wedge-shaped Cu spacer layer as a function of
Cu thickness is analyzed in terms of interface coupling between Co and
FeMn across the Cu layer, using a model of random fields at the surface
of the antiferromagnetic FeMn layer [1]. The apparent coupling energy
estimated from that model was found to depend also on Co thickness.
This is ascribed to kinetic barriers hindering the formation of larger domains
from smaller domains. No evidence for an oscillatory behavior of
the exchange coupling was found.
[1] S. Zhang et al., J. Magn. Magn. Mater. 198–199, 468 (1999).
MA 13.54 Di 15:00 Bereich A
Magnetische Grenzflächenanisotropien in Fe/V2O3 und
Co/V2O3-Doppellagen — •Christian Tusche, Björn Sass und
Wolfgang Felsch — I.Physikalisches Institut, Universität Göttingen
Die magnetische Anisotropie in Dünnschichtstrukturen wird wesentlich
durch Beiträge von Grenzflächen und Oberflächen bestimmt. Zur
Untersuchung solcher Effekte wurden dünne Schichten aus Fe und Co
(d=5-10nm) auf (11¯20) orientierte V2O3-Schichten deponiert. Die V2O3-
Schichten wachsen epitaktisch auf Saphir und zeigen die Eigenschaften
des Volumenmaterials, insbesondere den charakteristischen Übergang aus
der paramagnetisch metallischen (PM) in die antiferromagnetisch isolierende
Phase (AFI) bei etwa 160K[1]. Die Fe- und Co-Schichten zeigen
eine ausgeprägte magnetische Anisotropie in der Schichtebene, die
auf dipolare Wechselwirkung, induziert durch die facettierte Oberfläche
der V2O3-Schichten, zurückgeführt werden kann. Bei den Co-Schichten
kommt in der AFI-Phase eine deutliche Austauschanisotropie (exchange
bias) hinzu, die zu einer Reorientierung der magnetisch leichten Richtung

Magnetismus Dienstag
in der Schichtebene führt. Bei den Fe-Schichten tritt die Austauschanisotropie
überraschenderweise nicht auf. Die Effekte werden an Hand von
detaillierten Magnetisierungsmessungen diskutiert
[1] B. Sass et al., submitted to J. Phys. C
MA 13.55 Di 15:00 Bereich A
Magneto-Transport Properties of Multilayer Antidot Arrays
— •Kornelius Nielsch, Fernando J. Castaño, and Caroline
A. Ross — Department of Materials Science and Engineering, Massachusetts
Institute of Technology, Cambridge, MA, USA
The magneto-transport properties of Pseudo-spin-valve (PSV) thin
film structures grown onto sub-200 nm porous alumina templates have
been investigated. Hexagonal and quadratic pore arrangements were
achieved by defining a grid in silicon substrates using a combination
of interference lithography and reactive ion etching. An aluminum layer
was then evaporated and anodized, resulting in large area porous structures
with interpore distance of 180 nm (quadratic lattice) and 208 nm
(hexagonal lattice) and a pore diameter ranging from 80 to 150 nm. The
PSV antidot arrays were fabricated by depositing NiFe/Cu/CoFe thin
film structures onto the alumina templates. The room temperature hysteresis
loops of the antidot structures show the distinct switching of both
soft and hard magnetic layers, as well as a significant shearing of the
loop, as compared with that of the PSV thin film structure on a Si substrate.
Magnetic anisotropies induced by the different arrangements will
be discussed. Surprisingly the giant magnetoresistance ratio of the PSV
antidot arrays is only slightly smaller than that of the PSV thin film
structure.
MA 13.56 Di 15:00 Bereich A
Interlayer exchange coupling of magnetic rare-earth thin films
— •J.E. Prieto, K. Döbrich, O. Krupin, F. Heigl, G. Kaindl,
and K. Starke — Institut für Experimentalphysik, Freie Universität
Berlin, Arnimallee 14, 14195 Berlin
Exchange coupling between magnetic layers determines the properties
of magnetic heterostructures. Magnetic moments in rare-earth metals
are strongly localized and couple only indirectly through the conduction
electrons. In the case of magnetic films separated by nonmagnetic spacer
layers, the thickness and electronic structure of the latter determine the
sign and magnitude of the coupling. We have studied epitaxial Gd/Y/Tb
trilayers on W(110) element-specifically by means of x-ray magnetooptical
Kerr effect (XMOKE) performed at the M4,5 absorption thresholds
of Gd and Tb. The two magnetic rare-earth films have different coercivities.
For applied magnetic fields smaller than the Tb coercivity, shifted
Gd hysteresis curves are observed. A strong dependence of this exchange
bias on the thickness of the Y spacer layer as well as on the temperature
is found.
MA 13.57 Di 15:00 Bereich A
Transition rates via Bethe ansatz for the XXZ and the XX
chain — •Daniel Biegel 1 , Michael Karbach 1,2 , Gerhard
Müller 2 , and Klaus Wiele 1 — 1 Bergische Universität Wuppertal,
Fachbereich Mathematik und Naturwissenschaften, Physik, 42097
Wuppertal — 2 Department of Physics, University of Rhode Island,
Kingston, RI 02881-0817, USA
As part of a study that investigates the dynamics of the s = 1
2 XXZ
model in the planar regime |∆| < 1, we discuss the singular nature of
the Bethe ansatz equations for the case ∆ = 0, i.e. the XX model. We
identify the general structure of the Bethe ansatz solutions for the entire
XX spectrum, which include states with real and complex magnon momentas.
We present determinantal expressions for transition rates of spin
fluctuation operators between Bethe wave functions. As an application,
we calculate lineshapes for dynamic structure factors relevant for experiments.
The predominant excitations are identified within the framework
of quasiparticles excited from a corresponding vacuum.
MA 13.58 Di 15:00 Bereich A
Generation of ultrashort current pulses with photoconductive
switches — •S. Bretschneider 1 , A. Parge 1 , J. Seeger 2 , T.
Salditt 2 , A. Förster 3 , and M. Münzenberg 1 — 1 IV. Phys. Inst.
Universität Göttingen — 2 Inst. für Röntgenphysik Universität Göttingen
— 3 Inst. für Schichten und Grenzflächen (ISG1) Forschungszentrum
Jülich
Ultra short current pulses can be generated by excitation of a photoconductive
switch with fs-laser pulses from a TiSa-laser system. As material
for the switches we use low temperature grown GaAs (LT-GaAs).
Due to the short carrier life time in LT-GaAs current pulses of the optical
switches are in the ps-time scale. It is shown how to prepare the
switches with ebeam- and optical lithography and how to characterize
the current pulses with auto correlation and photoconductive sampling
techniques. In the future these current pulses will be used to study the
magnetization dynamics of magnetic micro- and nanostructures which is
for example important for magnetic switching in MRAM-elements.
MA 13.59 Di 15:00 Bereich A
Simulation of ultrafast dynamics in all optical pump probe experiments
on nanoscale Permalloy elements — •G. Eilers and
M. Münzenberg — IV. Phys. Inst., Universität Göttingen
Nano-size ferromagnetic structures are of strong interest for future high
speed magnetic random access memory and ultra high density magnetic
storage. Magnetic precession Eigen modes depending on the length/width
ratio of rectangular nanostructures of Permalloy are studied using the
Landau-Lifshitz-Gilbert equation. Aim is to investigate the limits of precessional
switching speed in the limit of smallest sized elements.
Demagnetization effects observed in all optical pump probe experiments
with ultrafast Ti:Sapphire lasers still lacks the theoretical background:
electrons are excitated by a pump laser pulse and a subsequent
demagnetization of the spin system in the order of 5% is observed. We
used a demagnetization effect of a laser spot in between 5 to 100 %
in lateral ferromagnetic thin films and nanostructured rectangular ferromagnetic
elements in our simulations. Magnetization dynamics in the
ps to ns range is compared to precession modes observed in all optical
pump probe experiments. For the simulation the oommf micromagnetic
simulation tool is used.
MA 13.60 Di 15:00 Bereich A
Multiples Schaltverhalten von Nanoleiterbahnen komplexer
Geometrie — •Mario Brands 1 , Britta Hausmanns 2 und
Günter Dumpich 1 — 1 Experimentalphysik, AG Farle, Institut für
Physik, Fakultät IV, Universität Duisburg-Essen, Standort Duisburg,
Lotharstrasse 1, 47048 Duisburg — 2 AG Magnetismus, Fachbereich
Physik, Technische Universität Kaiserslautern, Erwin-Schrödinger-Str.
56, 67663 Kaiserslautern
Es wurden Widerstandsmessungen an dünnen Kobalt-Leiterbahnen bei
einer Temperatur von T = 4, 2K und in einem äußeren Magnetfeld von
bis zu B = 4, 5T durchgeführt. Die Leiterbahnen wurden mittels eines
Zwei-Schritt-Elektronenstrahllithografie (EBL)-Prozesses auf GaAs Substraten
hergestellt und haben eine konstante Länge von l = 400µm wohingegen
ihre Breite (w = 100nm bis w = 2000nm) und ihre Schichtdicke
(t = 7nm bis t = 32nm) systematisch variiert wurde. Zum Schutz vor
Oxidation wurden die Leiterbahnen in-situ mit einer t = 2nm dicken Platinschicht
abgedeckt. Der Magnetowiderstand (senkrecht, out-of-plane)
ist negativ und kann im wesentlichen auf den Anisotropen Magnetowiderstand
(AMR) zurückgeführt werden. In longitudinaler Geometrie werden
bei geringen Magnetfeldern (Bsw ≈ 100mT) charakteristische Peaks
im Magnetowiderstand beobachtet, die den Ummagnetisierungsprozess
einzelner Leiterbahnabschnitte charakterisieren. Auf der Basis dieser Ergebnisse
wird das Auftreten von Domänenwandwiderstandsbeiträgen diskutiert.
Diese Arbeit wird gefördert von der DFG im Rahmen des SFB 491.
MA 13.61 Di 15:00 Bereich A
Inductive time-domain measurement of magnetization dynamics
in epitaxial Fe1−xCox-films — •Tobias Martin, B. Becker, S.
Ganzer, T. Hagler, W. Kipferl, M. Sperl, and G. Bayreuther
— Institut für Experimentelle und Angewandte Physik, Universität Regensburg,
93040 Regensburg
For the development of faster memory-technologies, it is important to
study the magnetization dynamics in thin magnetic films.
Here, the precessional motion of the magnetization is excited by a
fast magnetic field step or pulse with a risetime of about 70ps, which is
produced by a current guided through a coplanar waveguide. The precession
of the magnetization induces a signal in the same or in a second
waveguide, which is detected by a digital sampling oscilloscope with a
bandwidth of 20 Ghz.
This setup is used to investigate the magnetization precession in epitaxially
grown Fe1−xCox-films. The film and the waveguide are brought into
close proximity thus allowing for simple changing of samples and pulsefield
angle. The magnetization dynamics, i.e. precessional frequency and
damping coefficient, are determined for different values of the uniaxial
and fourfold magnetic anisotropies, which can be controlled by the thick-

Magnetismus Dienstag
ness and composition of the films, as well as the substrate (GaAs(001)
and Au(001)).
This work is supported by the Deutsche Forschungsgemeinschaft
(SPP1133).
MA 13.62 Di 15:00 Bereich A
Spin-Wave Modes in an Inhomogeneously Magnetized Stripe —
•C. Bayer 1,2 , J.P. Park 2 , H. Wang 2 , M. Yang 2 , C.E. Campbell 2 ,
and P. Crowell 2 — 1 Fachbereich Physik und Forschungsschwerpunkt
MINAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern —
2 School of Physics and Astronomy, University of Minnesota, Minneapolis,
Minnesota 55455, USA
Soft magnetic materials such as permalloy often have a very simple
magnetic microstructure which is not single domain. It is physically interesting
to ask whether such systems have collective excitations, i.e.
spin-wave modes. We have studied the dynamic properties of an inhomogeneously
magnetized 18nm thick and 2.3µm wide permalloy stripe
using time-resolved Kerr microscopy. If the magnetic field, which is applied
along the width of the stripe, is close to the shape anisotropy field,
the equilibrium magnetization is strongly inhomogeneous: at the edges it
is parallel to the stripe whereas it is aligned parallel to the applied field
in the center. For this case we find a new class of modes at higher frequencies
than that of the ordinary precessional mode at the center. These
modes span the entire width of the stripe and are therefore collective excitations
of the inhomogeneously magnetized region. Their effective wave
vector increases over an order of magnitude from the edges to the center.
Therefore this modes are totally dipolar dominated at the edges and have
mainly exchange character in the center. We will present experimental
data and semi-analytical calculations to confirm the proposed character
of these modes.
MA 13.63 Di 15:00 Bereich A
Zeitaufgelöste Magnetisierungsmessungen an Ferromagneten —
•J. Podbielski, F. Giesen, T. Korn, D. Heitmann und D. Grundler
— Institut für Angewandte Physik, Universität Hamburg, Jungiusstraße
11, 20355 Hamburg
Aktuelle Fragestellungen in der magnetischen Speichertechnologie betreffen
insbesondere die Dynamik von Magnetisierungsprozessen in ferromagnetischen
Mikrostrukturen. In diesem Zusammenhang sind gerade
in letzter Zeit neuartige zeitaufgelöste Messtechniken realisiert worden.
Wir präsentieren Messungen an strukturierten ferromagnetischen
Dünnfilmen, die wir mit Hilfe eines gepulst-induktiven Mikrowellenmagnetometers
(PIMM) durchgeführt haben. Im PIMM wird durch einen
schnellen Magnetfeldpuls in einem Mikrostreifenleiter die Magnetisierung
des Films ausgelenkt und das durch die Magnetisierungsdynamik induzierte
Spannungssignal mit einem Oszilloskop gemessen. Wir beobachten
ausgeprägte Oszillationen der Magnetisierung, die wir mit numerischen
Lösungen der Landau-Lifshitz-Gilbert-Gleichung vergleichen. Dieser Vergleich
läßt Rückschlüsse auf intrinsische Materialeigenschaften wie die
Dämpfung und auch auf die Trajektorie des Magnetisierungsvektors zu.
Wir finden im Speziellen, dass die exakte Pulsform einen deutlichen Einfluss
auf die Magnetisierungsdynamik nimmt. Wir danken für finanzielle
Förderung im Rahmen des BMBF-Projekts ” Spintronik“ (13N8283) und
des Graduiertenkollegs der DFG ” Nanostrukturierte Festkörper“.
MA 13.64 Di 15:00 Bereich A
Pump-Probe-Experimente zur Magnetisierungsdynamik von
Eisen-Mikrostrukturen — •Daniel Ravlic, Tobias Korn,
Jan Podbielski, Fabian Giesen, Christian Schüller und
Dirk Grundler — Institut für Angewandte Physik, Zentrum für
Mikrostrukturforschung, Universität Hamburg, Jungiusstraße 11, 20355
Hamburg
Die Untersuchung der Spin- und Magnetisierungsdynamik in ferromagnetischen
Mikrostrukturen ist grundlagenphysikalisch und technologisch
von großem Interesse. In unserem Experiment zur zeitaufgelösten Magnetisierungsmessung
benutzen wir im Speziellen schnelle Photoschalter, die
in Mikrostreifenleiter integriert sind. Mit einem ”pump“-Strahl aus einem
fs-Titan-Saphir-Laser generieren wir so Strompulse mit einer Anstiegszeit
von kleiner als 100 ps. Die kurzen Strompulse erzeugen Magnetfeldpulse,
die die Magnetisierung von Eisen-Mikrostrukturen auf dem Mikrostreifenleiter
auslenken. In ”pump-and-probe“-Konfiguration messen
wir dann den magneto-optischen Kerr-Effekt mit sub-ps-Zeitauflösung.
Wir beobachten ein oszillatorisches Verhalten der Magnetisierung, das die
durch die Strompulse angeregte Präzessionsbewegung der Magnetisierung
widerspiegelt. Mit einem statischen Hintergrundsmagnetfeld kann dabei
die zeitliche Periode von etwa 150 ps gezielt verändert werden. Die experimentellen
Ergebnisse vergleichen wir mit Simulationsrechungen, indem
wir die Landau-Lifschitz-Gilbert-Gleichung unter Einbeziehung der genauen
Pulsform numerisch lösen. Das Vorhaben wird gefördert durch das
Graduiertenkolleg der DFG ”Nanostrukturierte Festkörper“ und durch
das BMBF über Projekt 13N8283.
MA 13.65 Di 15:00 Bereich A
Dynamic time scales in all optical pump probe experiments —
•M. Djordjevic 1 , M. Lüttich 1 , P. Moschkau 1 , P. Guderian 1 ,
T. Kampfrath 1 , R.G. Ulbrich 1 , B. Sass 2 , F. Leuenberger 2 , W.
Felsch 2 , T.H. Kim 3 , J.S. Moodera 3 , and M. Münzenberg 1 —
1 IV. Phys. Inst., Universität Göttingen — 2 I. Phys. Inst., Universität
Göttingen — 3 Francis Bitter Magnet Laboratory, MIT, USA
Ultrafast and coherent optical control of magnetization in ferromagnetic
materials in the sub ns regime is a special field of interest for developing
spintronics. Magnetization dynamics upon laser heating is investigated
(Ti: Sapphire laser with 50fs duration of the pulse). Time
resolved magneto optical Kerr effect with double modulation technique
is used to simultaneously measure reflectivity, Kerr rotation and ellipticity
of ferromagnetic and non-magnetic thin films (Fe, Ni, Co, Al, Cu).
Optical artefacts lead to a non-magnetic contribution to the magnetic
signal but they can be controlled, for example, by a two colour probe
experiment. The mechanisms involved in ultrafast demagnetization can
be described with the three temperature model by relating electron and
spin temperature in the ps regime. In the domain of longer time scales
>100ps, standing spin waves and shock waves are observed. From the
precession dynamics the intrinsic Gilbert damping parameter and the
Eigen frequency of the magnetic precessional states can be determined.
MA 13.66 Di 15:00 Bereich A
Spin dynamics in Ca2+xY2−xCu5O10 — •Verena Kargl, Alex
Mirmelstein, and Peter Böni — Physik-Department E21, TU
München, 85748 Garching
Due to hole doping of its parent compound the copper oxide
Ca2+xY2−xCu5O10 features particularly remarkable charge and spin
dynamics. Consisting of only spin chains the compound series is
characterized as a 3D Heisenberg antiferromagnet in the doping range
0 ≤ x ≤ 1.2 with the magnetic moment and the the Néel-temperature
decreasing with higher Cu-valence [1]. Above the critical concentration
x ∼ 1.2, a dynamical spin chain behaviour dominates, changing to a
new spin coherent state in the highly doped composition Ca4.15Cu5O10
[2]. µSR- and neutron scattering measurements give insight in the static
and dynamic spin behavior developing with a change in the Ca/Y-ratio.
[1] A. Hayashi et al., Phys. Rev. B 58, 2678 (1998)
[2] G. I. Meijer et al., Phys. Rev. B 58, 14452 (1998)
MA 13.67 Di 15:00 Bereich A
Ultrafast Magnetization Dynamics in Antiferromagnets —
•N.P. Duong 1 , T. Satoh 1,2 , Th. Lottermoser 1 , and M. Fiebig 1
— 1 Max-Born-Institut, Max-Born-Straße 2A, 12489 Berlin — 2 RCAST,
The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904
Japan
The dynamic behavior of antiferromagnets is expected to be substantially
different from that of ferromagnets. Magnetic switching is facilitated
by the absence of a macroscopic magnetic moment, and reversal
of the antiferromagnetic order parameter within ∼ 10 fs was predicted.
Over the last decade the demagnetization behavior of many ferromagnetic
compounds and heterostructures has been studied. However, the spin dynamics
of antiferromagnets remains largely unknown. Here we report investigation
of antiferromagnetic Cr2O3, NiO, and RMnO3 (R = Y, Ho) by
optical pump-and-probe experiments. Magnetic second harmonic generation
(SHG) is used as probe of the antiferromagnetic order. Comparison
to crystallographic SHG and optical transmission and reflection allows
us to distinguish between the dynamics of the magnetic and nonmagnetic
sublattices. All three components exhibit temporal evolution of the
magnetic and crystallographic contributions on independent time scales,
thus indicating weak spin-lattice interaction. In NiO an oscillation of
the magnetic moment after the excitation is observed. In Cr2O3 different
temporal behavior of amplitude and phase of the magnetic signal is
demonstrated. In the hexagonal manganites the temporal evolution of a
magnetic phase transition is revealed.

Magnetismus Dienstag
MA 13.68 Di 15:00 Bereich A
Hall-Magnetometrie an mikrostrukturiertem Ni2MnIn, Permalloy
und Nb — •René Eiselt, Christian Uhrich, Guido Meier
und Ulrich Merkt — Institut für Angewandte Physik und Zentrum
für Mikrostrukturforschung, Jungiusstraße 11, 20355 Hamburg
Wir haben mikrostrukturierte Elektroden aus Ni2MnIn und
Permalloy hergestellt, die für Experimente zum spinpolarisierten
Transport in Ferromagnet/Halbleiter-Hybridsystemen geeignet sind.
Mit Hilfe der Hall-Magnetometrie werden die Elektroden bezüglich
ihres mikromagnetischen Verhaltens und der von ihnen ausgehenden
Streufelder auf GaAs-Heterostrukturen untersucht. Zudem wird die
Domänenstruktur der Elektroden ortsaufgelöst in Abhängigkeit eines
externen Magnetfeldes mit dem Magnetkraft-Mikroskop analysiert.
Es ist geplant, die Elektroden auf Hall-Barstrukturen elektrisch
anzukontaktieren und Tunneltransport-Experimente durchzuführen.
Desweiteren haben wir auch mikrostrukturierte Ringe und Scheiben aus
Niob auf Hall-Kreuzen präpariert. Über die Verdrängung des externen
Magnetfelds im Sensorbereich können Rückschlüsse auf Flusszustände
in den Ringstrukturen bzw. den Scheiben gezogen werden. Innerhalb
bestimmter Magnetfeldbereiche beobachten wir stabile Vortice-Zustände
[1]. Ferner lassen sich unterschiedlich große Ringstrukturen mit Scheiben
gleicher Radien vergleichen.
[1] A. K. Geim, S. V. Dubonos, J. J. Palacios, I. V. Grigorieva, M. Henini,
and J. J. Schermer, Phys. Rev. Lett. 85, 1528 (2000).
MA 13.69 Di 15:00 Bereich A
Hall-Magnetometrie an nanostrukturierten Permalloyringen —
•Michael Berginski, Haiko Rolff, Christian Heyn, Detlef
Heitmann und Dirk Grundler — Institut für Angewandte Physik
und Mikrostrukturforschung, Universität Hamburg
In hochintegrierten Schaltungen aus magnetoelektronischen Bauelementen
sind ferromagnetische Strukturen mit geringen Streufeldern
und stabilen Magnetisierungszuständen von besonderem Interesse.
Ringförmige Magnetstrukturen wurden in diesem Zusammenhang
bereits früh diskutiert [1]. Wir haben einzelne Permalloy-Nanoringe auf
mikrostrukturierte Hall-Sensoren integriert und im Detail untersucht.
Die Hysteresekurven zeigen ausgeprägte Sprünge als Funktion eines
äußeren Magnetfeldes, das in der Ebene der Ringe angelegt wird. Die
Sprünge spiegeln die charakteristischen Ummagnetisierungsprozesse
der Nanomagnete wider, was durch mikromagnetische Simulationsrechnungen
bestätigt wird. Insbesondere können wir in Abhängigkeit
von der Weite der Nanostruktur zwischen Ringzuständen mit und
ohne magnetischem Vortex unterscheiden. Die Sprungfelder zwischen
den Zuständen variieren systematisch mit der Größe und Weite
der Ringe. Die Arbeiten werden gefördert durch die DFG über das
Graduiertenkolleg ”Nanostrukturierte Festkörper”.
[1] G. Prinz, US patent 5,542,868 and 6,381,170.
MA 13.70 Di 15:00 Bereich A
Influence of point defects on magnetic vortex structures —
•Michael Rahm 1 , Vladimir Umansky 2 , Werner Wegscheider 1 ,
and Dieter Weiss 1 — 1 Institut für Experimentelle und Angewandte
Physik, Universität Regensburg, D-93040 Regensburg, Germany —
2 Braun Center for Submicron Research, Weizmann Institut, Rehovot
76100, Israel
Micro-Hall magnetometry represents a highly advanced experimental
technique to measure hysteresis loops of individual ferromagnetic particles.
Investigating submicron-sized Permalloy disks, it was shown that
a magnetic vortex structure can be pinned at a lithographically defined
point defect [1]. Here, we compare our Hall measurements with micromagnetic
calculations based on LLG [2] in order to draw a detailed picture
of the pinning process. By simulating the point defect simply as a
hole in the disk, excellent agreement between experiment and calculation
can be achieved, while more complex models of the defect result in
larger deviations from the measurement. These investigations are crucial
to understand the behavior of particles containing two or more defects.
First results showing interesting multistable switching behavior in disks
containing up to four defects are presented.
[1] M. Rahm, J. Biberger, V. Umansky, and D. Weiss, Vortex pinning
at individual defects in magnetic nanodisks, J. Appl. Phys. 93 (10), 7429
(2003). [2] M. Scheinfein, see http://llgmicro.home.mindspring.com/
MA 13.71 Di 15:00 Bereich A
Single crystalline epitaxial Mo(110) strip-line for time resolved
observation of magnetization dynamics. — •D.A. Valdaitsev,
J. Prokop, A. Kukunin, H.J. Elmers, and G. Schönhense — Johannes
Gutenberg-Universität Mainz, Institut für Physik, Staudingerweg
7, D-55099 Mainz
Single crystalline Mo(110) strip-lines have been prepared on α-
Al2O3(11¯20). They are dedicated for temporally and spatially resolved
observation of magnetization dynamics of thin epitaxial magnetic films.
On the strip-line substrate, epitaxial Co(0001) film was deposited in UHV
by molecular beam epitaxy and subsequently covered by a Au capping.
The structure of the Mo(110) strip-line and the Co layer were investigated
using low energy electron diffraction. Atomic force microscopy
and scanning tunneling microscopy (STM) were used for the morphology
characterization and the magnetic properties of Co were investigated exsitu
using magneto-optical Kerr magnetometry. The STM measurements
showed monoatomic terraces of widths varied between 10 and 200 nm on
the molybdenum surface. The quality of the obtained strip-line substrate
is similar to single crystal Mo substrates. The epitaxial hcp Co layer
grown on the strip-line reveals a uniaxial in-plane magnetic anisotropy.
The magnetic easy axis lies in [1¯100] direction parallel to Mo[1¯10], while
the hard axis shows along Mo[001] direction. We demonstrate that the
epitaxial Co films grown on the strip-line are appropriate for investigations
with spin-polarized low energy electron microscopy (SP-DREEM).
We show first images of these samples taken with SP-DREEM in diffraction
and real-image modes.
MA 13.72 Di 15:00 Bereich A
Dipolar induced anisotropy and self ordering in patterned
films — •Katharina Theis-Bröhl 1 , Boris Toperverg 2 , Jeff
McCord 3 , Karsten Rott 4 , Hubert Brückl 4 , and Hartmut
Zabel 1 — 1 Department of Experimental and Solid State Physics,
Ruhr-University Bochum, 44780 Bochum, Germany — 2 Petersburg
Nuclear Physics Institute, 188300 Gatchina, St. Petersburg, Russia —
3 Material Research Institute, Helmholtzstr. 20, 01169 Dresden, Germany
— 4 Department of Physics, University Bielefeld, Universitätsstr. 25,
33615 Bielefeld, Germany
A periodic magnetic stripe array has been studied with a combination
of real and reciprocal space methods: Kerr microscopy and polarized
neutron reflectivity. The basic features of our data are well reproduced
by a theoretical model using DBWA and providing a set of parameters
quantifying the magnetization arrangement in the stripe array system.
While the specular neutron reflectivity measures a mean value of the optical
potential averaged over a number of structural elements within the
neutron coherence length, Bragg diffraction filters out magnetic correlation
effects in the system of individual magnetic units within this length
scale. Off-specular diffuse scattering probes correlations of magnetization
fluctuations on a scale smaller than the coherence length. This all
together gives access to a detailed understanding of the magnetization
arrangement which appears to be quite complex and hardly accessible by
other methods. We acknowledge funding by DFG, SFB 491 and BMBF
032AE8BO.
MA 13.73 Di 15:00 Bereich A
Stress induced domains in patterned magnetic thick films —
•Jeffrey McCord — IFW Dresden, Helmholtzstr. 20, 01169 Dresden
The understanding of domain formation in patterned elements is of
great importance for applications in inductive devices. We report on
the formation of non-Landau-like domain structures due to magnetoelastic
effects in patterned electroplated NiFe and CoNiFe-films with different
composition and saturation-magnetostriction varying from 2 to
+20x10 −6 . Novel domain patterns are observed in the 1µm thick structures.
No closure domains form in the negative magnetostriction samples.
For the first time edge curling walls, known from laminated films, are
seen in µm thick single-layer films. Even small changes in composition
drastically alter the domain structures in the tensile stressed films. For
positive magnetostrictive films, an anisotropy-structured domain pattern
is observed. The domain patterns are discussed in terms of stress-induced
local anisotropy variations derived from finite-element analysis and confirmed
by local anisotropy measurements with µm resolution. Changes
with lateral dimensions down to 1µm are shown. The importance of locally
induced stress anisotropy for the modeling of magnetic devices will
be discussed.

Magnetismus Dienstag
MA 13.74 Di 15:00 Bereich A
Magnetization of a two phase nano-amorphous ferromagnet —
•H. Bremers, J. Hesse, O. Hupe, C. Hofmeister, and O. Michele
— Institut für Metall- und Nukleare Festkörperphysik, TU Braunschweig,
Mendelssohnstr. 3, 38106 Braunschweig
At the last spring conference we have presented a description of magnetization
measurements of the System Fe-Nb-Cu-B after different heat
treatments. With increasing temperature of the treatment this leads to
an increasing concentration of nanometer sized iron bcc grains in a remaining
ferromagnetic amorphous matrix. The parameters gained by this
description allow us to give a complete, but idealized picture of the magnetic
behaviour of such systems. By using this description we are able to
extend the magnetization curve towards high tempartures which are not
accessible to measurements due to further crystallisation of the sample.
MA 13.75 Di 15:00 Bereich A
Magnetic relaxation and ordering in nanostructured thin films
during growth: A cluster Monte Carlo study — •Roman Brinzanik,
Peter J. Jensen, and Karl Heinz Bennemann — Institut
für Theoretische Physik, Freie Universität Berlin, Arnimallee 14, D-14195
Berlin, Germany
We calculate the nonequilibrium and equilibrium remanent magnetization
of inhomogeneous island-type thin films. The transition from
dipole-coupled islands at low coverages to a strongly connected ferromagnetic
film at high coverages during film growth is analysed [1]. The
single-island magnetic anisotropy and inter-island dipole and exchange
couplings are taken into account. A cluster Monte Carlo method is developed
which includes coherent magnetization rotations of connected
islands. This method enables calculations of the magnetic properties in
the whole coverage range within the same model [2].
For coverages below the percolation threshold, we obtain collectively
ordered magnetic states due to the dipole interaction with ordering temperatures
of 1 – 10 K for the assumed model parameters. The anisotropy
causes pronounced nonequilibrium effects with blocking temperatures of
the order 10 – 100 K. The dipole interaction somewhat increases the
blocking temperatures.
[1] U. Bovensiepen, P. Poulopoulos, W. Platow, M. Farle, K. Baberschke,
J. Magn. Magn. Mater. 192, L386 (1999)
[2] R. Brinzanik, P. J. Jensen, K. H. Bennemann, Phys. Rev. B 68, 174414
(2003)
MA 13.76 Di 15:00 Bereich A
Phasengrenze und statische Ummagnetisierung in zylinderförmigen
Mikromagneten — •F. Steinbauer, C. Back und
H. Hoffmann — Institut für Experimentelle und Angewandte Physik,
Universität Regensburg
Die analytische Berechnung der (Grundzustands-)Phasengrenze zwischen
vortex-Zustand und single-domain-Zustand in zylinderförmigen
Mirkomagneten hat gezeigt [H. Hoffmann and F. Steinbauer, J. Appl.
Phys. 92 (2002) 5463], daß durch Einbringen einer magnetischen Anisotropie
der in dünnen Mikromagneten ansonsten bevorzugte vortex-
Zustand durch den nun energetisch günstigeren single-domain Zustand
verdrängt wird.
Durch hochauflösende MOKE-Messungen wurden nun die Magnetisierungskurven
von einzelnen dünnen zylinderförmigen Mikromagneten
bis hinab zu einem Durchmesser von 1µm aufgenommen. Durch diese
Messungen konnte das Auftreten des single-domain Zustandes nachgewiesen
werden. Weiterhin wurde die Ummagnetisierung in Abhängigkeit
des Durchmessers und magnetischer Parameter systematisch untersucht.
Dabei zeigt sich, daß das Schaltfeld zu kleineren Durchmessern hin zunimmt.
MA 13.77 Di 15:00 Bereich A
Bildung von Fe und Fe-C Nanopartikeln in einem Heißwandreaktor
— •B. Rellinghaus 1 , J. Knipping 1 , P. Roth 1 , T. Hülser 2 ,
E. Duman 2 und M. Acet 2 — 1 Institut für Verbrennung und Gasdynamik
— 2 Institut für Physik. SFB 445, Universität Duisburg-Essen,
D-47048 Duisburg
Fe und Fe-C Nanopartikel wurden in einem Heißwand-Gasflussreaktor
bei Temperaturen im Bereich 400 o C ≤ TR ≤ 700 o C unter Verwendung
von Fe(CO)5 als Precursormaterial und unter (optionaler) Zugabe von
C2H4 präpariert. Die Partikel wurden durch thermische Zersetzung von
Fe(CO)5 und nachfolgende homogene Nukleation und Brown’sche Koagulation
im kontinuierlichen N2-Gasstrom gebildet. Das C2H4 wurde dabei
durch heterogene Katalyse an den Eisenkeimen dissoziiert. Die Partikel
wurden ex-situ mit XRD, (HR)TEM, EELS und SQUID-Magnetometrie
charakterisiert. Partikel, die unter Ausschluss von C2H4 gewonnen wurden,
bestehen aus Eisenkernen, die nach der Entnahme aus dem Reaktor
an der Oberfläche oxidisch passiviert sind. Magnetisierungskurven dieser
Partikel besitzen nach Kühlen in externen Magnetfeldern unterhalb von
T = 50K die typische durch die Austauschanisotropie bewirkte Asymmetrie
(Hex(5K) = 0.55kOe). Unter Zugabe von C2H4 wurden abhängig
von TR und der Verweilzeit τR im Reaktor zunächst mit Zementit (Fe3C)
umhüllte Fe-Partikel (0.05s ≤ τR ≤ 1.5s, 400 o C ≤ TR ≤ 600 o C) und
schließlich einphasige Fe3C-Partikel gebildet (τR = 1.5s, TR = 700 o C).
Das metastabile Fe3C zerfällt bei thermischer Nachbehandlung der Partikel
in Fe und Graphit. Die strukturellen und magnetischen Eigenschaften
sowie die Bildungskinetik dieser Kern-Hülle Partikel werden diskutiert.
MA 13.78 Di 15:00 Bereich A
Selbstorganisation von Kobaltpartikeln in Lösung und auf
Substraten — •Daniela Sudfeld 1 , Inga Ennen 1 , Andreas
Hütten 1 , Günter Reiss 1 , Klaus Wojczykowski 2 , Peter Jutzi 2 ,
Oliver Michele 3 , Heiko Bremers 3 und Jürgen Hesse 3 —
1 Universität Bielefeld, Fakultät für Physik, Universitätsstraße 25,
D-33615 Bielefeld — 2 Universität Bielefeld, Fakultät für Chemie,
Universitätsstraße 25, D-33615 Bielefeld — 3 Institut für Metallphysik
und Nukleare Festkörperphysik, Technische Universität Braunschweig,
Mendelssohnstraße 3, D-38106 Braunschweig
Die Selbstorganisation von ligandenstabilisierten Kobalt-Nanoteilchen
ist ausgehend vom ferrofluiden Zustand in der Lösung bis hin zur Bildung
von Monolagen auf unterschiedlichen Substraten untersucht worden.
Zur Teilchengrößencharakterisierung in dem gefrorenen Ferrofluid sind
Sqiud-Messungen als Mikrostruktursonde eingesetzt worden. Die resultierenden
Teilchengrößenverteilungen der Kobaltmonolagen sind mit Hilfe
von Transmissionselektronenmikroskopie bestimmt worden. Der Vergleich
beider Messungen erlaubt Rückschlüsse über die Umsetzung der
Teilchengröße im Ferrofluid auf diejenige der Monolage im Festkörper.
Darüber hinaus lassen sich die magnetischen Wechselwirkungen der
Kobaltmonolage, die bei Raumtemperatur mittels AGM bestimmt werden
konnten, mit denen im Ferrofluid vergleichen.
MA 13.79 Di 15:00 Bereich A
Magnetization experiments on frozen ferrofluids — •O.
Michele 1 , J. Hesse 1 , H. Bremers 1 , E. K. Polychroniadis 2 ,
K. G. Efthimiadis 2 , and H. Ahlers 3 — 1 Institut für Metallphysik
und Nukleare Festkörperphysik, TU Braunschweig, Mendelssohnstr.
3, 38106 Braunschweig, Germany — 2 Department of Physics,
Aristotle University of Thessaloniki, GR 54006 Thessaloniki, Greece
— 3 Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116
Braunschweig, Germany
Particle ensembles consisting of nano-Co particles fixed in space by
freezing ferrofluids are investigated. In frozen ferrofluids a well defined low
temperature magnetic state of the nanoparticle system can be achieved.
We distinguish between textured samples (preferred orientation of easy
axes) and non-textured with randomly oriented easy axes. Considering
the magnetization curves of such systems bears in principle the possibility
to distinguish between influences arising from particles anisotropy
and particle-particle interaction. Our intention is to present new experimental
strategies aiming to separate these influences from magnetization
measurements versus temperature. In another approach we analyzed the
susceptibility derived from magnetization measurements and determined
the mean magnetic moment of the particles and an additional field which
may be caused by the anisotropy of the particles or the interaction between
them. Transmission electron microscopy was used for the direct
measurement of the particles sizes and their size distribution.
MA 13.80 Di 15:00 Bereich A
Magnetic characterization of monodispersed and oxide-coated
Fe cluster assemblies — •O. Michele 1 , J. Hesse 1 , H. Bremers 1 ,
D.L. Peng 2 , K. Sumiyama 2 , T. Hihara 2 , S. Yamamuro 2 , H.
Ahlers 3 , and K. Weyand 3 — 1 Institut für Metallphysik und
Nukleare Festkörperphysik, TU Braunschweig, Mendelssohnstr. 3, 38106
Braunschweig, Germany — 2 Department of Materials Science and
Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
— 3 Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116
Braunschweig, Germany
Monodispersed and oxide-coated Fe cluster assemblies were prepared
using a plasma-gas-condensation style cluster beam deposition apparatus.
The characterization of four different samples is presented using electron

Magnetismus Dienstag
microscopy and SQUID magnetometry. The evaluation is based on the
preparation of different low temperature magnetic states of the samples
and measuring its magnetization depending on temperature.
MA 13.81 Di 15:00 Bereich A
Magnetization of fcc FexPt1−x nanoparticles: from Langevin to
Stoner-Wohlfarth behaviour — •Frank Wiekhorst and Jürgen
Kötzler — Institut f. Angewandte Physik, Univ. Hamburg, D-20355
Hamburg
We present field-dependent magnetizations of chemically disordered
nanocrystals, d = 4 mm, imbedded in an organic matrix, recorded between
350 K and 5 K. Taking into account an effective uniaxial anisotropy,
the temperature dependence of which has been determined by FMR
[1] and by low-frequency absorption in zero field, we are able to describe
quantitatively the crossover from isotropic Langevin behaviour,
via anisotropic superparamagnetism [2], to the hysteretic regime below
the blocking temperature. Our model considers the effects of anisotropy
on both the equilibrium and non-equilibrium magnetization in a consistent
way and involves the averaging upon randomly distributed axes.
Possible origins of the temperature dependent anisotropy are discussed.
[1] F. Wiekhorst et al., Proc. ICM 2003, Rome, J.Magn.Magn. Mat.,
accepted
[2] F. Wiekhorst et al., Phys. Rev. B 67, 224416 (2003)
MA 13.82 Di 15:00 Bereich A
Oberflächeneffekte und magnetische Nahordnung in FePt Nanoteilchen
— •Jens Ellrich 1 , Branko Stahl 1,2 , Gerhard Miehe
1 und Horst Hahn 1 — 1 Fachbereich Material- und Geowissenschaften,
Petersenstr. 23, TU Darmstadt, 64287 Darmstadt — 2 Institut für
Nanotechnologie, Forschungszentrum Karlsruhe, 76021 Karlsruhe
FePt Nanoteilchen wurden nasschemisch auf unterschiedlichen Syntheserouten
hergestellt. Durch die Verwendung verschiedener Liganden und
Precursoren konnte der Einfluss der Oberfläche auf die magnetischen Eigenschaften
der Nanoteilchen mit Hilfe der Mössbauerspektroskopie demonstriert
werden.
Zur weiteren strukturellen Charakterisierung wurde sowohl
Röntgendif-fraktometrie als auch hochauflösende Transmissionselektronenmikroskopie
eingesetzt. Trotz unterschiedlicher Syntheserouten
und Precursoren besitzen die Teilchen die kubisch flächenzentrierte
Struktur der ungeordneten Hochtemperaturphase im System Fe-
Pt. Unterschiede in der Nahordnung und deren Korrelation mit
magnetischen Eigenschaften konnten durch Untersuchungen mittels
Röntgenabsorptionsspektroskopie (EXAFS) näher beleuchtet werden.
MA 13.83 Di 15:00 Bereich A
Magnetic ordering transition in a dense frozen ferrofluid — •S.
Bedanta 1 , S. Sahoo 1 , Xi Chen 1 , W. Kleemann 1 , D. Sudfeld 2 ,
K. Wojczykowski 2 , and A. Hütten 2 — 1 Angewandte Physik, Universität
Duisburg-Essen, D-47048 Duisburg — 2 Fachbereich Physik, Universität
Bielefeld, Postfach 100131, 33501 Bielefeld
Magnetic properties of a dense frozen ferrofluid [Fe55Co45/hexane] are
measured with SQUID magnetometry and susceptometry. Above the
blocking temperature, Tb ≈ 25 K, of the particles with size 4.6 nm,
Langevin-type M(H) curves reveal small moments per particle, µ ≈ 50
µB, and biased minor hysteresis loops (non-saturating for µ0H ≤ 5 T) after
field-cooling to below Tb. Sharp peaks of χ ´ (T) and a sizeable decrease
of the coercive field at Tc ≈ 9 K seem to indicate a transition with critical
behavior of both susceptibility and spontaneous magnetization. Two
heterogeneous models are discussed to explain these features. Either the
nanoparticles contain a ferromagnetic core and a disordered shell [1], possibly
stabilized by an oxidic surface layer, or they are non-collinearly antiferromagnetic
with uncompensated net moments [2]. Within the frame of
the above models the observed transition might then be either exchangedriven
into an intra-shell frozen cluster arrangement [1] or dipolar-driven
into an inter-particle ferromagnetic ground state [3].
[1] R. D. Zysler et al., J. Magn. Magn. Mater. 266, 233 (2003).
[2] R. H. Kodama et al., Phys. Rev. Lett. 79, 1393 (1997).
[3] J. P. Bouchaud and P. G. Zérah, Phys. Rev. B 47, 9095 (1993).
MA 13.84 Di 15:00 Bereich A
Magnetic relaxation of interacting ferromagnetic nanoparticle
systems — •Xi Chen 1 , S. Sahoo 1 , S. Bedanta 1 , O. Petracic 1 ,
W. Kleemann 1 , S. Cardoso 2 , and P. P. Freitas 2 — 1 Angewandte
Physik, Universität Duisburg-Essen, D-47048 Duisburg, — 2 INESC, Rua
Alves Redol 9-1, 1000 Lisbon, Portugal
The relaxation of the thermoremanent magnetisation of granular multilayers
[Co80Fe20(tn)/Al2O3(3 nm)]10 is investigated by SQUID magnetometry
at various nominal thicknesses tn of the CoFe layers. In agreement
with Monte Carlo simulations of random dipolarly interacting ferromagnetic
nanoparticle systems [1] we find asymptotic stretched exponential
decay for superspin glasses at low nanoparticle densities, tn = 0.9
- 1.0 nm [2], while power law decay with finite asymptotic remanence is
observed for superferromagnets at higher densities, tn = 1.2 - 1.6 nm [3].
Efforts are put into localizing the marginal density, tn ≈ 1.1 nm, where
the stretched exponential is supposed to convert into a power law without
remanence [1].
[1] M. Ulrich, J. Garcia-Otero, J. Rivas, and A. Bunde, Phys. Rev. B
67, 024416 (2003).
[2] S. Sahoo, O. Petracic, Ch. Binek, W. Kleemann, J. B. Sousa, S.
Cardoso, and P. P. Freitas, J. Phys.: Condens. Matter 14, 6729 (2002).
[3] Xi Chen, W. Kleemann, O. Petracic, O. Sichelschmidt, S. Cardoso,
and P. P. Freitas, Phys. Rev. B 68, 054433 (2003).
MA 13.85 Di 15:00 Bereich A
Resonant Soft X-Ray Scattering from Magnetic Nanoparticles
— •E. Schierle 1 , E. Weschke 1 , Holger Ott 1 , C. Schüßler-
Langeheine 1,2 , G. Kaindl 1 , J.-M. Tonnère 3 , C. Meyer 3 , B.
Stahlmecke 4 , and G. Dumpich 4 — 1 Institut für Experimentalphysik,
Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany —
2 II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77,
D-50937 Köln, Germany — 3 Laboratoire Louis Néel, CNRS, BP 166,
38042 Grenoble cedex 9, France — 4 Experimentalphysik Arbeitsgruppe
Farle, Fakultät für Naturwissenschaften, Institut für Physik, Universität
Duisburg-Essen Campus Duisburg, Lotharstr. 1, 47057 Duisburg
The application of magnetic nanoparticle arrays as data storage media
requires independently addressable non-interacting dots. A characterization
of such arrays in terms of spatial and magnetic correlations
is therefore important, which can be obtained by scattering techniques.
Particularly useful in this respect is resonant scattering in the soft xray
region, i.e., at the L2,3 edges of the 3d transition metals and at the
M4,5 edges of the lanthanide metals. At these photon energies, the wavelengths
nicely match the distances in these systems and the resonances
provide very high sensitivity to the specific nanoparticle. Furthermore,
the magnetic part of the resonant scattering amplitude allows to study
magnetic correlations. First results from monocrystalline Tb nanoparticles
and from well-ordered arrays of CoPt multilayer dots are discussed.
The setup of a new UHV-compatible x-ray diffractometer will be presented,
which also allows in-situ preparation under UHV conditions. This
work was supported by the BMBF, project 05 KS1KEE/8.
MA 13.86 Di 15:00 Bereich A
Coulomb-Blockade and spin-dependent tunneling in cobalt
nanoparticles — •Herbert Graf, Johann Vancea, Christian
Back, and Horst Hoffmann — Institut für Experimentelle und
Angewandte Physik, Universität Regensburg, 93040 Regensburg,
Germany
We report on the observation of the Coulomb blockade at room temperature
and 77 K in cobalt nanoparticles with sizes ranging between 2
and 5 nm. The Co particle-arrays are contacted via in-plane point contacts.
The sharp point contacts have a separation between 10 and 70
nm. Prior to the deposition of the Co particles, we evaporate a thin 1 -
3 nm thick layer of AlOx onto the gap structures. The particles are then
grown onto the AlOx layer at temperatures between 300 K and 500 K.
The electrical measurements are performed inside the same UHV apparatus.
Magnetoresistance measurement loops with an in-situ electro-magnet
show magnetoresistance values of a few percent at 77 K. An enhanced
magnetoresistance above the threshold voltage of the particle array was
observed. We suppose that this enhancement is related to the Coulomb
blockade effect.

Magnetismus Dienstag
MA 13.87 Di 15:00 Bereich A
Stochastic growth of magnetic alloy nanostructures on surfaces
— •S. Heinrichs 1 , M. Kessler 1 , W. Dieterich 1 , Ph. Maass 2 , and
A. Majhofer 3 — 1 Fachbereich Physik, Universität Konstanz, Germany
— 2 Institut für Physik, Technische Universität Ilmenau, Germany —
3 Institute of Experimental Physics, Warsaw University, Poland
Nanostructures of certain magnetic fcc-alloys on surfaces can exhibit
perpendicular magnetic anisotropy and hence are promising materials
for magnetic storage technologies. In CoPt3 nanoclusters the magnetic
anisotropy emerges from a frozen-in anisotropic short range order created
during deposition at temperatures where bulk diffusion is negligible[1].
By Monte Carlo simulation we investigate a structural model that is consistent
with the observed chemical ordering in the bulk[2], surface facets
and surface segregation, and in addition includes the van der Waals interaction
with the substrate. We discuss the subtle connection of kinetic
growth history with the emerging non-equilibrium structures and relate
them to the parameters of a phenomenological magnetic model.
[1] M. Albrecht et al., Europhys. Lett. 56, 884 (2001)
[2] M. Kessler et al., Phys. Rev. B, 67, 134201 (2003)
MA 13.88 Di 15:00 Bereich A
Mass-filtered ferromagnetic alloy clusters on surfaces — •M.
Getzlaff 1 , R.K. Gebhardt 1 , F. Bulut 1 , D. Schmitz 2 , E. Holub-
Krappe 2 , H. Maletta 2 , A. Kleibert 3 , R.-P. Methling 3 , J.
Bansmann 3 , and K.-H. Meiwes-Broer 3 — 1 Institut für Angewandte
Physik, Uni Düsseldorf — 2 HMI Berlin — 3 Fachbereich Physik, Uni
Rostock
Clusters with their enlarged magnetic moments are promising materials
for ferromagnetic thin film devices. Fe and FeCo clusters with diameters
of 6...12 nm were prepared in a new developed, continuously
working arc cluster ion source (ACIS) and subsequently mass filtered
by means of an electrostatic quadrupole deflector. The clusters were deposited
on ferromagnetic (Ni/W(110), Co/W(110)) and nonmagnetic surfaces
(W(110), Si(001)). AFM measurements prove a height being smaller
than the diameter for free particles which can be explained by particlesupport
interaction. HRTEM measurements confirm that the stoichiometry
in deposited FeCo clusters is very similar to the chosen bulk material.
Magnetic properties were determined by X-ray magnetic circular
dichroism (XMCD) with specificity to different elements at BESSY. We
observed very large total magnetic moments of both Fe and Co when
compared to their resp. bulk properties. Analogously to pure clusters
in this size regime, the orbital moments ml in FeCo alloy clusters on
Ni(111) are significantly enhanced with respect to bulk material. Thus,
ml of FeCo clusters play the dominant role for reaching total magnetic
moments above the known bulk value although their contributions are
about one order of magnitude smaller than the spin moments ms.
MA 13.89 Di 15:00 Bereich A
Magnetic structures of 3d clusters on Ni(100) and Fe(110) — •S.
Lounis 1,2 , Ph. Mavropoulos 2 , S. Blügel 2 , and P. H. Dederichs 2
— 1 Fachbereich Physik, Universität Osnabrück, 49069Osnabrück. —
2 Institut für Festkörperforschung, Forschungszentrum Jülich, D–52425
Jülich.
We present ab initio calculations on the magnetic properties of 3d
transition-metal clusters at the (100) surface of Ni and the (110) surface
of Fe. Adatoms, dimers and trimers are investigated. We focus on the
local magnetic moments in the clusters and the substrates, the energetical
stability of different magnetic configurations within the cluster and
the coupling to the substrates. The magnetic hyperfine fields are also
presented. The results are obtained using the Korringa–Kohn–Rostoker
(KKR) Green’s function method within density functional theory (DFT)
in the local spin density approximation (LSDA).
MA 13.90 Di 15:00 Bereich A
Monte Carlo Simulation of Temperature Dependence of
Magnetic Properties of Small Metall Clusters — •Svitlana
Polesya and Hubert Ebert — Dept. Chemie/Phys. Chemie,
Universität München, Butenandtstr. 5-13,
D-81377 München, Germany
Temperature dependent magnetic properties of small clusters of 3delements
and their compounds both unsupported and deposited on metallic
surfaces have been studied using MC simulations together with the
extended Heisenberg model. The exchange parameters of the systems under
consideration have been obtained from ab initio spin-polarized KKR
calculations of electronic structure. It is shown that the temperature
TC of a transition from magnetically ordered to a disordered state for
clusters consisting of few atoms is strongly determined by the magnetic
anisotropy of the system. The dependence of TC on the cluster size is
analyzed and compared to the value obtained for an infinite crystal.
MA 13.91 Di 15:00 Bereich A
Punktkontakt Andreev Spektroskopie und R(T)-Messungen an
der Heuslerlegierung Ni2MnIn — •Jan M. Scholtyssek, Sebastian
von Oehsen, Christian Pels, Malte Kurfiss, Guido Meier
und Ulrich Merkt — Institut für Angewandte Physik und Zentrum
für Mikrostrukturforschung, Universität Hamburg, Jungiusstr. 11, 20355
Hamburg
Für die Heuslerlegierung Ni2MnIn wird an der Grenzfläche zu InAs eine
Spinpolarisation an der Fermi-Kante von 100 Prozent vorhergesagt [1].
Sie ist deshalb von besonderem Interesse für die Spinelektronik. Die von
uns untersuchten Ni2MnIn-Proben werden durch thermisches Verdampfen
[2] und durch DC-Magnetron-Sputtern hergestellt. Zur Bestimmung
der Spinpolarisation werden die Proben unterschiedlicher Schichtdicken
mit Point-Contact-Andreev-Reflection (PCAR) bei verschiedenen Temperaturen
untersucht. Der spezifische Widerstand der Proben wird temperaturabhängig
in Vierpunkt-Geometrie gemessen. Diese R(T)-Daten
liefern Hinweise auf die elektronische Struktur der Schichten.
[1] K.A. Kilian and R.H. Victora, IEEE Trans. Mag. 37, 1976 (2001).
[2] M. Kurfiss and R. Anton, J. Alloys and Compounds 361, 36 (2003).
MA 13.92 Di 15:00 Bereich A
Ni2MnIn-Schichten: Herstellung sowie elektrische und magnetische
Charakterisierung — •Franziska Schultz, Malte Kurfiß,
Rainer Anton, Christian Pels, Guido Meier und Ulrich
Merkt — Universität Hamburg, Institut für Angewandte Physik und
Zentrum für Mikrostrukturforschung, Jungiusstr.11, 20355 Hamburg
Die Heusler-Legierung Ni2MnIn ist ein halbmetallischer Ferromagnet,
für den 100% Spinpolarisation an der Grenzfläche zu InAs vorausgesagt
wird [1]. In der Spinelektronik ist diese hohe Spinpolarisation für die Injektion
von polarisierten Elektronen in Halbleiter von großer Bedeutung.
Für die Herstellung der Schichten werden zwei Methoden verwendet:
thermisches Koverdampfen im Ultrahochvakuum und DC-Magnetron-
Sputtern. Als Substrate dienen InAs, Si und C. Das Materialsystem
Ni2MnIn/InAs(100) bildet keine Schottky-Barriere an der Grenzfläche
und besitzt eine vorzügliche Gitteranpassung. In Wachstumsreihen mit
variierten Substrattemperaturen wird die Kristallstruktur optimiert. Die
Stöchiometrie der Schichten wird mit Röntgenspektroskopie (EDX) im
Transmissions- und Rasterelektronenmikroskop kontrolliert, die Struktur
durch Elektronenbeugung. Die Schichten werden für die elektrische und
magnetische Charakterisierung mikrostrukturiert. Die elektrische Charakterisierung
geschieht durch R(T)-Messungen, die magnetischen Eigenschaften
werden mit SQUID- und Hall-Mikromagnetometrie sowie mit
dem Magnetkraftmikroskop untersucht. Mittels Punktkontakt-Andreev-
Spektroskopie [2] wird der Grad der Spinpolarisation bestimmt.
[1]K.A.Kilian und R.H.Victora, IEEE Trans.Mag. 37, 1976 (2001).
[2]R.J.Soulen et al., Science 282, 85 (1998).
MA 13.93 Di 15:00 Bereich A
Transport Properties of Magnetite-Nb:SrTiO3 Interfaces — •M.
Ziese, U. Köhler, R. Höhne, A. Bollero, and P. Esquinazi —
Division of Superconductivity and Magnetism, University of Leipzig,
Linnéstrasse 5, 04103 Leipzig.
The magnetotransport properties of contacts between magnetite and
Nb-doped SrTiO3 were studied. Magnetite films were deposited on metallic
Nb(0.1%):SrTiO3 single crystal substrates by pulsed laser deposition.
During deposition the substrate temperature was 430 ◦ C and oxygen partial
pressure 10 −5 mbar. At these conditions epitaxial films with Verwey
temperatures of 115 K were obtained. The magnetotransport properties
at the interface were investigated by four probe measurements in
current-perpendicular-to-plane configuration by recording current (I)–
voltage (V ) characteristics at various temperatures (60 K ≤ T ≤ 300 K)
and magnetic fields (µ0H ≤ 6 T). The I-V -characteristics showed rectifying
behaviour, especially below the Verwey transition. The data could be
successfully analyzed within a Schottky-barrier model; below the Verwey
transition an energy barrier of about 0.1 eV was extracted, which vanished
above the transition. The ideality factor n increases from a value
near unity below 80 K to n ∼ 4 above 135 K. The magnetoresistance
of this interface depends strongly on the bias voltage. When analyzed
within thermionic emission theory taking a barrier potential shift due to

Magnetismus Dienstag
the Zeeman effect into account, a spin polarization of −60% was obtained.
MA 13.94 Di 15:00 Bereich A
Cobalt doping of a low-energy interface in anatase — Rebecca
Janisch 1,2 , Sibylle Gemming 1 , •Michael Schreiber 1 , and Nicola
Spaldin 2 — 1 Institut für Physik, Technische Universität, 09107 Chemnitz,
Germany — 2 Materials Research Laboratory, University of California,
Santa Barbara CA 93106, USA
About two years ago Co-doped TiO2 anatase has been discovered to
exhibit ferromagnetism at and above room temperature, i.e. to be a magnetically
robust diluted magnetic semiconductor (DMS). Since then it has
attracted considerable interest, but there is still controversy over the origin
of the magnetism as well as the influencing factors.
In this work a low-energy Σ5(113)[-110] grain boundary in anatase
is studied by density-functional band-structure calculations employing
norm-conserving pseudopotentials and plane waves [1].
The interfacial structure in pure anatase exhibits close structural and
electronic similarity to the pure bulk anatase crystal. Yet, the grain
boundary acts as a sink for dopant atoms, such as Co. This result confirms
the importance of the investigation of grain boundaries in the discussion
of DMS properties. The influence of inner interfaces on the magnetic
properties of Co-doped TiO2 is subject to ongoing investigations, the
results of which will be shown on the poster.
[1] The ABINIT code is a common project of the Université
Catholique de Louvain, Corning Inc., and other contributors (URI
http://www.abinit.org).
MA 13.95 Di 15:00 Bereich A
Unordnung in verdünnten Spinsystemen
— •S. Hilbert und W. Nolting — Lehrstuhl Festkörpertheorie, Institut
für Physik, Humboldt-Universität zu Berlin
Der Einfluss der Substitutionsunordnung auf die magnetischen Eigenschaften
von verdünnten Heisenberg-Spinsystemen wird in Hinblick auf
die magnetische Stabilität von ferromagnetischen verdünnten Halbleiten
(DMS) untersucht. Dazu wird die im Rahmen einer Tyablikov-Näherung
erhaltene Bewegungsgleichung für die Magnon-Green-Funktion eines endlichen
Systems numerisch gelöst. Die aus dieser Green-Funktion folgenden
Spektraldichten werden verwendet, um die Magnetisierung und die
Curie-Temperatur eines unendlich ausgedehnten Systems abzuschätzen.
Die Methode eignet sich für beliebige ferromagnetische Austauschwechselwirkung.
Neben verschiedenen Gitterstrukturen und Größe der Spins
werden insbesondere Austauschintegrale mit unterschiedlicher Reichweite
untersucht. Als Ergebnis zeigt sich, dass für Austausch kurzer Reichweite
keine magnetische Ordnung bei Konzentrationen der Spins unterhalb der
kritischen Perkolations-Konzentration auftritt, während für langreichweitige
Wechselwirkung die Curie-Temperatur proportional zur Konzentration
ist.
MA 13.96 Di 15:00 Bereich A
Magnetic properties of Mn, Cr or V implanted GaN. —
•V.A. Guzenko 1 , N. Thillosen 1 , A. Dahmen 1 , N. Kaluza 1 ,
Th. Schäpers 1 , M. Luysberg 2 , and L. Houben 2 — 1 Institute of
Thin Films and Interfaces (ISG1) and CNI - Center of Nanoelectronic
Systems for Information Technology , Research Centre Jülich, 52425
Jülich, Germany — 2 Institute of Solid State Research and CNI - Center
of Nanoelectronic Systems for Information Technology , Research Centre
Jülich, 52425 Jülich, Germany
The possible application of dilute magnetic semiconductors (DMS) in
spintronics devices impelled intensive search for materials with Curie
temperatures above 300K. On the basis of theoretical predictions a
promising candidate is GaN, doped by Mn up to 5 at.%. Recently, many
groups reported on the successful fabrication of ferromagnetic GaN:Mn
layers grown by molecular beam epitaxy. We followed a different approach
by implanting 3d-transition metals into GaN.
GaN layers grown by MOVPE on sapphire substrates were implanted
with Mn, Cr or V ions with a dose of 5×10 16 cm −2 . The implantation
energy was 200 keV. Subsequently, rapid thermal annealing in N2 atmosphere
for 5 min at 700 ◦ C was performed. The magnetization of our
samples, investigated by SQUID-magnetometer, as a function of magnetic
field as well as temperature revealed paramagnetic behaviour for
all samples. Depending on measurement conditions a hysteresis in magnetization
could be observed. These results can be explained by the presence
of clusters of a 3d-metal rich secondary phase, which is confirmed
by TEM and channelling measurements.
MA 13.97 Di 15:00 Bereich A
Spannungs- und Temperaturabhängigkeit des Magnetowiderstandes
von mit Co kontaktierten Kohlenstoffnanoröhren —
•Hartmut Vinzelberg, Bin Zhao, Ingolf Mönch und Joachim
Schumann — IFW Dresden, Postfach 270116, 01171 Dresden
Da die auf der Si-Technologie beruhende Mikroelektronik bei weiterer
Miniaturisierung natürliche Grenzen erreicht, wird verstärkt an der
Realisierung einer Elektronik gearbeitet, bei der einzelne Atome, Moleküle
oder metallische bzw. halbleitende Nanostrukturen als Transistoren,
Sensoren oder Leiter verwendet werden. Kohlenstoffnanoröhren (carbon
nanotubes - CNT) sind auf Grund ihrer strukturellen und elektronischen
Eigenschaften geeignet als Bausteine in einer molekularen Elektronik/Spintronik
eingesetzt zu werden. In diesem Beitrag werden Techniken
zur Kontaktierung von mehrwandigen CNT mit metallischen Elektroden
vorgestellt und Untersuchungen der elektrischen und magnetischen
Transporteigenschaften diskutiert. Beobachtet werden positive und negative
Magnetowiderstände (MR) bis 60% bei kleinen Spannungen und
4.2K. Mit steigender Temperatur und bei Erhöhung der Spannung nimmt
der MR ab. Es wird auch ein Vorzeichenwechsel des MR bei Umpolung
der Spannung beobachtet, der mit einer Inversion der Spinpolarisation
einer ferromagnetischen Elektrode erklärbar ist.
MA 13.98 Di 15:00 Bereich A
Local Self-interaction Corrections in the Korringa-Kohn-
Rostoker Method — •Diemo Ködderitzsch 1,2 , Martin Lüders 2 ,
Markus Däne 1 , Arthur Ernst 3 , Wolfram Hergert 1 , Dzidka
Szotek 2 , Walter Temmerman 2 , Balas Györfy 4 , Patrick
Bruno 3 , and Axel Svane 5 — 1 Dpt. of Physics Martin-Luther-
University Halle-Wittenberg, Germany — 2 Daresbury Laboratory,
Warrington, UK — 3 MPI of Microstructure Physics, Halle, Germany —
4 HH Wills Physics Laboratory, University of Bristol, UK — 5 Dept. of
Astronomy and Physics, University of Aahus Denmark
Strong correlation effects which underline the electronic structure of
transition metal oxides or lanthanide and actinide metals and their compounds
cannot be adequately described in the framework of the local spin
density approximation (LSDA) in the density functional theory (DFT).
This can partly be attributed to the substantial self-interaction included
in the LDA. To go beyond the LSDA-DFT self-interaction corrections
(SIC) can be implemented in the band-picture. Such an approach has
been used to describe, e.g., the magnetic properties of NiO or the γ → α
phase transition of Ce.
We will present a simplified local rotationally invariant SIC scheme
which can be efficiently implemented in the multiple scattering theory.
The SIC within the Green’s function Korringa-Kohn-Rostoker (KKR)
method can be used together with the coherent potential approximation
(CPA) to treat alloy problems for correlated systems. The method is
illustrated on the electronic structure study of NiO, the γ → α phase
transition of Ce and CeTh alloys.
MA 13.99 Di 15:00 Bereich A
Magnetic anisotropy of transition metal compounds — •Ingo
Opahle 1 , Lutz Steinbeck 2 , Denis Mertz 1 , Manuel Richter 1 ,
Michael D. Kuz’min 3 , Klaus Koepernik 1 , and Helmut Eschrig 1
— 1 IFW Dresden, P.O.B. 270016, D-01171 Dresden, Germany — 2 ZMD
Dresden, Germany — 3 Instituto de Ciencia de Materiales de Aragón,
Zaragoza, Spain
Magnetocrystalline anisotropy properties of a number of transition
metal compounds have been calculated in the framework of density functional
theory in the local spin density approximation (LSDA). The results
have been obtained using the highly accurate relativistic FPLO method
and the relativistic optimized LCAO method. The influence of lattice
geometry and orbital polarization, a correction to the LSDA taking into
account Hund’s second rule, is discussed. Results are presented for CoPt,
YCo5 and related compounds as well as for R2T17Nx compounds. A critical
comparison with experimental and theoretical data from the literature
is given.
MA 13.100 Di 15:00 Bereich A
Dynamics of ferromagnetic nanomagnets with vortex or
single-domain configuration — •Rainer Höllinger, Andreas
Killinger, and Uwe Krey — Inst. Physik II, Univ. Regensburg
We study the dynamics of flat circular permalloy (Py) nanomagnets
for 1.) magnetic vortex and 2.) single-domain configurations, using micromagnetic
simulation.
Ad 1.): Dynamical studies for isolated vortex structures show that

Magnetismus Dienstag
both the vorticity, and the polarity of the out-of-plane component can
be switched fast (50-100 ps). However, the stability and dynamics of arrays
of such nanostructures may differ from the behaviour of the single
unit.
Ad 2.): Micromagnetic simulations of the switching process in thin
cylindrical Py nanoparticles with an initial stable single-domain state
show nearly homogeneous single-domain behaviour followed by excitation
of spin waves.
MA 13.101 Di 15:00 Bereich A
Discrepancy between local and global structure in magnetically
frustrated ZnV2O4 — •P. Pfalzer, M. Preisinger, M. Klemm,
and S. Horn — Universität Augsburg, Experimentalphysik II, Universitätsstr.
1, 86135 Augsburg
Development of unusual magnetic properties like spin fluctuations
down to lowest temperatures have aroused interest in geometrically
frustrated magnets. Among these are the cubic spinel system LiV2O4,
the first transition-metal oxide to show heavy fermion behavior, and
the isostructural system ZnV2O4. For the latter compound a symmetry
breaking structural phase transition was reported for polycrystalline material,
presumably lifting this degeneracy, followed by a transition into
an antiferromagnetic state. In single crystals, however, this structural
transition is suppressed and a spin-glass-like ground state develops. To
clarify whether local structural distortions or fluctuations play a role in
the formation of this low temperature behavior, we have performed EX-
AFS measurements on single crystals of ZnV2O4 as well as on various
powder samples. We have shown that the cubic symmetry expected from
XRD is broken on a local scale in single crystals of ZnV2O4. In particular
the octahedral oxygen neighborhood of the vanadium ions is distorted
leading to the formation of two nonequivalent oxygen sites.
MA 13.102 Di 15:00 Bereich A
Critical small angle scattering of polarised neutrons in MnSi —
•Robert Georgii 1 , Peter Böni 1 , Daniel Lamago 1 , Sergey Grigoriev
2 , Sergey Maleyev 2 , Alexey Okorokov 2 , Helmut Eckerlebe
3 , Klaus Pranzas 3 , and Bertrand Roessli 4 — 1 Technische
Universität München, 85747 Garching, Germany — 2 Petersburg Nuclear
Physics Institute, Gatchina, St.Petersburg 188300, Russia — 3 GKSS
Forschungszentrum, 21502 Geesthacht, Germany — 4 Laboratory for Neutron
Scattering, ETH & PSI, 5232 Villigen, Switzerland
The chiral fluctuations in the weak itinerant magnet MnSi have been
studied by means of polarised neutron scattering. Because of a lack of
a centre of symmetry the magnetic moments are arranged along a lefthanded
spiral due to the Dzyaloshinskii-Moriya interaction. Therefore,
the chiral fluctuations can be investigated without the need of application
of a magnetic field. The experiments show that the incommensurate
magnetic peaks evolve with increasing temperature into diffuse scattering
that is mainly concentrated in spheres around the nuclear Bragg peaks.
The scattering is fully polarised for q � P0 and is depolarised for q ⊥ P0.
This manifests the purely chiral nature of the scattering. From these data
we have determined the critical exponents of the correlation length of the
chiral fluctuations.
MA 13.103 Di 15:00 Bereich A
Magnetische, optische und magneto-optische Eigenschaften von
einkristallinem DyS — •A. Navratil 1 , D. Kolberg 1 , D. Menzel
1 , M. Marutzky 1 , U. Barkow 1 , F. Hulliger 2 und J. Schoenes
1 — 1 Institut für Halbleiterphysik und Optik und Hochmagnetfeldanlage,
TU Braunschweig, Mendelssohnstr. 3, D-38106 Braunschweig —
2 Lab. f. Festkörperphysik ETH, CH-8093 Zürich
Aus der Gruppe der Monochalcogenide der Seltenen Erden wurden die
magnetischen und magneto-optischen Eigenschaften von DyS bisher nur
wenig untersucht. DyS ist bei tiefen Temperaturen antiferromagnetisch
und zeigt eine Gitterverzerrung von NaCl-Struktur zu pseudo-tetragonal
bei etwa 35 Kelvin [1].
SQUID-Messungen wurden von 1,7 K bis 340 K bei Feldstärken bis
5 Tesla durchgeführt. Die paramagnetische Curie-Temperatur beträgt
ΘP = −75 K, und das effektive magnetische Moment liegt bei µeff =
10, 3 µB.
Zusätzlich wurden die optischen Konstanten mit Hilfe der Ellipsometrie
am BESSY II im Bereich von 1 eV bis 10 eV bestimmt.
Desweiteren werden die magneto-optischen Eigenschaften vorgestellt.
Hierzu wurden im Bereich von 0,5 eV bis 5 eV Kerr-Effektmessungen bei
bis zu 11,5 T aufgenommen.
[1] F. Hulliger, M. Landolt and R. Schmelczer in ” The Rare Earths in Mo-
dern Science and Technology, Vol. 3“, eds. McCarthy, Silber and Rhyne,
Plenum (1982) p. 455
MA 13.104 Di 15:00 Bereich A
Optische Anisotropie von UPtGe-Einkristallen — •M. Marutzky
1 , U. Barkow 1 , S. Weber 1 , R. Troć 2 und J. Schoenes 1 —
1 Institut für Halbleiterphysik und Optik und Hochmagnetfeldanlage, TU
Braunschweig, Mendelssohnstr. 3, D-38106 Braunschweig — 2 Institute
for Low Temperature and Structure Research, Polish Academy of
Sciences, P.O. Box 1410, 50-950 Wroc̷law, Poland
UPtGe kristallisiert in einer orthorombischen EuAuGe-Struktur mit
den Gitterkonstanten a=4,33, b=7,19 und c=7,52 ˚A. Es ordnet unter 50
K in einer antiferromagnetischen, inkommensurablen helikalen Spinstriktur.
Sowohl die magnetischen als auch die elektrischen Eigenschaften des
UPtGe sind anisotrop [1], wobei jeweils die größte Anisotropie entlang
der b-Achse auftritt, die die magnetisch harte Achse darstellt.
Es wurde die Reflektivität von Einkristallen im Bereich 6 meV bis 10
eV bestimmt, bei hohen Energien am VUV-Ellipsometer am BESSY II
in Berlin. Die Reflektivität im Infraroten zeigt für alle Kristallachsen
metallisches Verhalten und ist für E�b verglichen mit E�a um ca. 5 %
höher. Die Anisotropie der optischen Leitfähigkeit korreliert mit der DC-
Leitfähigkeit. Bei höheren Energien treten in den Spektren Strukturen
auf, die auf elektronische Übergänge hinweisen. Es werden mit der Drude-
Theorie Oszillatoren an die Messungen angepasst, um Aussagen über die
elektronische Struktur zu treffen. Erste Ergebnisse der Untersuchung der
magnetooptischen Eigenschaften werden vorgestellt.
[1] R. Troć et al., erscheint in Phys. Rev. B
MA 13.105 Di 15:00 Bereich A
Out-of-plane and in-plane magnetic anisotropies in thin
Co(0001) films on Mo(110). — •J. Prokop, D.A. Valdaitsev,
A. Kukunin, M. Pratzer, H.J. Elmers, and G. Schönhense
— Johannes Gutenberg-Universität Mainz, Institut für Physik,
Staudingerweg 7, D-55099 Mainz
We have measured magnetic out-of-plane and in-plane anisotropy constants
of thin Co(0001) films prepared in a wedge formed Mo/Co(0-
50ML)/Mo(110) sample grown by molecular beam epitaxy in UHV on
α-Al2O3(11¯20). Our deposition procedure allows the preparation of comparatively
inexpensive single crystalline samples that are equivalent to
single crystal Mo(110) substrates and facilitates electrical transport measurements.
Using low energy electron diffraction (LEED) we have monitored the
structure of the prepared films and the elastic strain in the cobalt film.
Cobalt grows epitaxially on Mo(110) in the Nishiyama-Wassermann orientation,
where Mo[001]�Co[11¯20]. The Co films are expanded with constant
strain in both lateral direction for D < 30 ML.
Magnetic measurements were performed using Kerr magnetometry
in polar and longitudinal geometry. The Co films reveal an uniaxial
anisotropy with an easy axis in Co[1¯100] direction. Magnetic anisotropies
are dominated by volume-type strain anisotropies. We find an in-plane
anisotropy constant Kv,p = 0.079 MJ/m 3 . In contrast to Co/W(110) films,
the surface type anisotropies are very small. This fact might be attributed
to the smaller spin-orbit coupling at the interface.
MA 13.106 Di 15:00 Bereich A
Magnetic properties of multiwall carbon nanotubes — •Roland
Höhne 1 , Pablo Esquinazi 1 , and Teresa Martínez 2 — 1 Abteilung
Supraleitung und Magnetismus, Universität Leipzig, Linnestrasse 5, D-
04103 Leipzig — 2 Instituto de Carboquimica, CSIC, Miguel Luesma Castan
4, 50015-Zaragoza, Spain
The magnetization of carbon nanotubes composed of a few strands of
multiwalled tube were measured with a SQUID magnetometer. The used
preparation method allows us to obtain samples without ferromagnetic
impurities. The magnetization of the samples shows a diamagnetic behavior
at 4 K≤ T ≤ 300 K without any paramagnetic upturn at low
temperatures. After substracting the linear diamagnetic response, the
field dependence of the magnetization shows hysteresis with a remanence
Mrem ≃ 6×10 −4 emu/g at 5 K. The hysteresis curves however do not show
the usual ferromagnetic behavior but apparently the superposition of additional
effects. Samples heat treated in hydrogen (45 bar at 350 C for 2
hours) show no appreciable difference. The hysteresis has been measured
with the SQUID using two different measuring modes.

Magnetismus Dienstag
MA 13.107 Di 15:00 Bereich A
Well-Aligned Co-Filled Carbon Nanotubes: Preparation and
Magnetic Properties — •Radinka Kozhuharova 1 , Dieter
Elefant 1 , Andreas Graff 1,2 , Albrecht Leonhardt 1 , Ingolf
Mönch 1 , Thomas Mühl 1 , Manfred Ritschel 1 , Claus M.
Schneider 1,3 , and Stefka Zotova 1 — 1 Leibniz-Institute of Solid
State and Materials Research Dresden, Helmholtzstr. 20, D-01069
Dresden — 2 present address: Max Planck Institute of Microstructure
Physics, Halle — 3 present address: Research Center Jülich GmbH,
D-52425 Jülich
Carpet-like flakes (area < 3mm x 3mm; thickness < 500nm) of wellaligned
Co-filled multi walled carbon nanotubes were grown by decomposition
of cobaltocene. The product was analysed by scanning (FE-SEM,
Leo 1530)- and transmission (TEM, Tecnai F30 with GIF200)- electron
microscopy. The phase composition and the crystalline structure were
determined by X-ray difffraction and selected area electron diffraction.
Using alternating gradient magnetometry the ferromagnetic behaviour
of the filled nanotubes was investigated. The nanotubes have outer diameter
of 50-90nm and diameter of the metal core of 15-30nm. They are
discontinuously filled with fcc Co nanowires having a length of up to a few
micrometers. Magnetometry measurements show a weak uniaxial magnetic
anisotropy with the easy axis along the nanowires. A high coercivity
of about 59mT at room temperature is observed, which is significantly
higher than in bulk Co.
MA 13.108 Di 15:00 Bereich A
PAC-Untersuchungen an amorphen Ferromagnetika — •V. Samokhvalov
1 , F. Schneider 1 , S. Unterricker 1 , M. Dietrich 2 und
die ISOLDE - Collaboration 3 — 1 Institut für Angewandte Physik,
TU Bergakademie Freiberg, D-09596 Freiberg/Sachsen — 2 Technische
Physik, Universität des Saarlandes, D-66041 — 3 CERN, CH-1211 Geneva
23, Switzerland
Amorphe ferromagnetische Materialien, wie z. B. Fe80B20, sind mit
dem Mößbauer-Effekt sehr ausführlich untersucht worden. Mit der Sonde
57 Fe wurden dabei über die Verteilungen der Hyperfeinfelder wesentliche
Aussagen zur Nahordnung in der Umgebung der Eisenatome gewonnen.
Allerdings bereitet die Interpretation der immer vorhandenen
Quadrupolwechselwirkung Probleme. Wir haben amorphes Fe80B20 mit
der Methode PAC (= perturbed angular correlations) und den Sonden
111m Cd, 111 In( 111 Cd) und 62 Zn( 62 Cu), die am ISOLDE-Separator mit einer
Energie von 50 keV implantiert wurden, untersucht. Messungen nach
unterschiedlichen Wärmebehandlungen werden vorgestellt und die auftretenden
Feldverteilungen diskutiert.
MA 13.109 Di 15:00 Bereich A
Electronic Structure of Transition-Metal Dicyanamides
Me[N(CN)2]2 (Me = Mn, Fe, Co, Ni, Cu) — •Takács Albert 1 ,
Chiuzbăian Sorin 1 , Crainic Traian Ionica 1 , Demchenko D.
O. 2 , Filkenstein L.D. 3 , Galakhov V.R. 3 , Kmety Carmen
R. 4 , Kurmaev E. Z. 3 , Liu Amy Y. 2 , Moevs A. 5 , Neumann
Manfred 1 , and Stevensson Knneth L. 6 — 1 Universität Osnabrück
— 2 Department of Physics, Georgetown University, Washington —
3 Institute of Metal Physics, Yekaterinburg — 4 Argonne National
Laboratory, USA — 5 University of Saskatchewan, Canada — 6 Purdue
University Indiana , USA
The electronic structure of Me[N(CN)2]2 (Me=Mn, Fe, Co, Ni, Cu)
molecular magnets has been investigated using x-ray emission spectroscopy
(XES) and x-ray photoelectron spectroscopy (XPS) as well as
theoretical density-functional-based methods. Both theory and experiments
show that the top of the valence band is dominated by Me 3d
bands, while a strong hybridization between C 2p and N 2p states determines
the valence band electronic structure away from the top. The
2p contributions from non-equivalent nitrogen sites have been identified
using resonant inelastic x-ray scattering spectroscopy with the excitation
energy tuned near the N 1s threshold. The binding energy of the Me 3d
bands and the hybridization between N 2p and Me 3d states both increase
in going across the row from Me = Mn to Me = Cu. Calculations
indicate that the ground-state magnetic ordering is largely dependent on
the occupation of the metal 3d shell and that structural differences in the
superexchange pathways for different compounds play a secondary role.
MA 13.110 Di 15:00 Bereich A
X-ray magnetic and natural circular dichroism above and below
the Verwey transition in a Fe3O4 single crystal — •S. Gold, E.
Goering, and G. Schütz — Max-Planck-Institut für Metallforschung,
70569 Stuttgart
Recently Fe3O4 has become an intensive studied system, due to its
proposed and experimentally observed high spin polarization at the fermi
energy and its related applicability in future spin electronic devices. In
addition, at the so called Verwey transition, which has been investigated
over many decades, a dramatic change in the electrical resistivity appears.
We show detailed X-ray magnetic circular dichroism (XMCD) experiments
at 1T applied magnetic field performed above and below the
Verwey transition and along different crystallographic directions ((100),
(110) and (111)). We have observed very small changes in the XMCDspectra
of this cubic system as a function of temperature and orientation,
which has not been observed before in a cubic system. Changes in the
differences of the projected orbital moments along the given crystallographic
axes above and below the Verwey transition are consistent to the
observed change of the easy axis. In addition a directly observable and
unexpected large nonmagnetic natural circular dichroism (XNCD) signal
has been observed by flipping the helicity of the synchrotron beam. This
is a sign of an unexpected local non centro symmetric charge distribution
at the 3d transition metal site. Our investigations give new insight to the
microscopic ground state and excited state properties of Fe3O4 related
to the magnetic behavior and the Verwey transition.
MA 13.111 Di 15:00 Bereich A
First principles electronic structure of spinel LiCr2O4: A
possible half-metal? — •Markus Lauer 1 , Roser Valenti 2 ,
H.C. Kandpal 3 , and Ram Seshadri 4 — 1 Fachrichtung Theoretische
Physik, Universitaet des Saarlandes, Postfach 15 11 50, D-66041
Saarbruecken — 2 Institut fuer Theoretische Physik, Universitaet
Frankfurt, Robert-Mayer-Strasse 8, D-60043 Frankfurt — 3 Institut
fuer Anorganische Chemie, Universitaet Mainz, Duesberg Weg 10-14,
D-55099 Mainz — 4 Materials Department, University of California,
Santa Barbara, CA 93106 USA
We have employed first-principles electronic structure calculations to
examine the hypothetical oxide spinel LiCr2O4 with the d 2.5 electronic
configuration. The cell and internal (oxygen position) structural parameters
have been obtained for this compound through structural relaxation
in the first-principles framework. Within the one-electron band picture,
we find that LiCr2O4 is magnetic, and a candidate half-metal. The
electronic structure is substantially different from the closely related rutile
half-metal CrO2. Comparisons with superconducting LiTi2O4, heavy
fermion LiV2O4 and charge-ordering LiMn2O4 suggest the effectiveness
of a nearly-rigid band picture involving simple shifts of the position of
EF in these very different materials. Comparisons are also made with the
electronic structure of ZnV2O4, a correlated insulator that undergoes a
structural and antiferromagnetic phase transition.
MA 13.112 Di 15:00 Bereich A
Magnetic properties in chromium-chalcogenide systems —
•Diana Benea 1 , Hubert Ebert 1 , Wolfgang Bensch 2 , and
Zhong-Le Huang 2 — 1 Chemistry Department, University of Munich,
Butenandtstr. 5-13, D-81377 München, Germany — 2 Institute for
Inorganic Chemistry, Olshausenstr. 40, D-24098 Kiel, Germany
A theoretical investigation of magnetic properties of the systems
Cr1+x(Se,Te)2 and (Cr,Ti)1+xTe2 is presented. The crystallographic structure
of these compounds was refined in the space group P¯3m1 with four
crystallographically different sites for both metal and chalcogen atoms.
The chalcogen layers are fully occupied, whilst in the metal layer there
are vacancies. The preferential occupation of the metal layers is discussed.
The density of states (DOS) are calculated and the influence of
the Cr/Ti content on the magnetic moments in the system is discussed.
The magnetic behaviour of the systems has been investigated using the
Korringa-Kohn-Rostoker (KKR) band structure method. The disorder in
the system has been accounted for by means of the Coherent Potential
Approximation (CPA).

Magnetismus Dienstag
MA 13.113 Di 15:00 Bereich A
Untersuchung der martensitischen Umwandlung in den
Heusler-Systemen Ni-Mn-Ga-Al und Ni-Co-Al durch Magnetisierungsmessungen
und Abbildung der Mikrostruktur
— •T. Krenke, E. Duman, M. Acet und E.F. Wassermann —
Experimentalphysik AG Farle, Universität Duisburg-Essen, Standort
Duisburg, Lotharstrasse 1, 47048 Duisburg
Es werden Ergebnisse von mikrostrukturellen und magnetischen Messungen
an den Heusler-Sytemen Ni-Mn-Ga-Al und Ni-Co-Al präsentiert.
Es wurden Legierungen Ni50Mn25(Ga1−xAlx)25 0.2 < x < 0.8 hergestellt,
um den Einfluss von Aluminium (Gallium) auf die bekannte Formgedächtnis-Legierung
Ni2MnGa (Ni2MnAl) zu studieren. Die Fragestellung
lautet hier, inwieweit sich die magnetische Ordnung und die Mikrostruktur
durch Zulegieren entwickeln und ob der magnetische Formgedächtnis-Effekt
(MFGE) dabei erhalten bleibt. Als Indiz für den MFGE
werden Magnetisierungskurven in kleinen Feldern (50 Oe) herangezogen,
die mit früheren Messungen an Ni-Mn-Ga und Ni-Mn-Al verglichen werden
können. Ni-Co-Al weist, im Gegensatz zu den Mangan-Legierungen,
durch die Existenz einer A1-Phase in Korngrenzen duktile Eigenschaften
auf. Es wurden drei verschieden Konzentrationsreihen im ternären
Phasendiagramm zwischen 7.4 < e/a < 8.0 gewählt und sowohl die Magnetisierungskurven
auf das Vorhandensein eines MFG-Effektes als auch
die Mikrostruktur untersucht.
MA 13.114 Di 15:00 Bereich A
Characterization of doped Heusler alloys: Co2Cr1−xFexAl — •S.
Wurmehl 1 , G. H. Fecher 1 , H. C. Kandpal 1 , K. Kroth 1 , H.-J.
Elmers 1 , G. Schönhense 1 , C. Felser 1 , J. Morais 2 , Y. Hwu 3 , and
R. Klauser 4 — 1 Johannes Gutenberg - Universität, D-55099 Mainz,
Germany — 2 Universidade Federal do Rio Grande do Sul, 91501-970
Porto Alegre, Brazil — 3 Academia Sinica, Taipei, 11529, Taiwan —
4 National Synchrotron Radiation Research Center, Hsinchu, 30077, Tai-
wan
Doped Heusler alloys and compounds of the Co2Cr1−xFexAl with varying
Cr to Fe ratio x were produced and experimentally investigated. Most
of the samples showed pronounced disorder instead of the expected L21
structure. The sample surfaces exhibited a strong selective oxidation of
chromium. The bulk samples were characterized by standard methods
such as X-ray diffraction, SQUID magnetometry, and depth profiling.
X-ray absorption was used together with XMCD to examine different
oxidation stages in bulk and powder samples and to determine element
specific magnetic moments. Surface sensitive methods, like low energy ion
scattering, photoemission, PEEM, and scanning XPS microscopy, were
used to examine the oxidation process. The nature of the selective oxidation
of chromium in these compounds will be discussed on hand of the
experimental findings.
MA 13.115 Di 15:00 Bereich A
Photogenerierte Raumladungen im ladungsgeordneten Zustand
von Pr0.63Ca0.37MnO3 Einkristallen — •V. Morchshakov 1 , M.
Boshta 1 , K. Bärner 1 , I. Medvedeva 2 , C. Martin 3 und B. Raveau
3 — 1 Fachbereich Physik, 4. Phys. Institut, Universität Göttingen,
Tammannstr.1, D-37077 Göttingen, FRG — 2 Institut für Metallphysik,
Kovalevskaya Str. 18, 620219 Ekaterinburg, Russland — 3 ISMRA, Caen,
Frankreich
Zeitaufgelöste Thermokraftsmessungen (TTE) an Volumeinkristallen
nahe der Zusammensetzung Pr2/3Ca1/3MnO3 zeigen einen zweiten Spoannungstransienten
V2(t) unterhalb der Ladungsordnungstemperatur
Tco. Dieser Transient ist schneller als der Transient der quasistatische
Thermokraft, V3(t), der üblicherweise bei Manganitkeramik als einziger
beobachtet wird, und kann daher leicht separiert werden. Aus V3(t)
erhalten wir die Wärmeleitfaehigkeit und die Thermokraft im Temperaturbereich
30K¡ T ¡ 350K. Der ausserordentliche Transient wird dem
Abbau einer ambipolaren Raumladung zugeschrieben die sich anschliessend
an eine Photoerzeugung von Ladungstraegern ausbildet, aber nur
dann wenn die thermische Reemission aus den Haftstellen gering bleibt.
MA 13.116 Di 15:00 Bereich A
Doping and lattice effects in the half-metallic double perovskite
Sr2CrWO6 — •Stephan Geprägs, Petra Majewski, Jan
B. Philipp, Andreas Erb, Matthias Opel, Lambert Alff, and
Rudolf Gross — Walther-Meißner-Institut, Bayerische Akademie der
Wissenschaften, Walther-Meißner-Str. 8, 85748 Garching
The double perovskite Sr2CrWO6 and related compounds combine
Curie-temperatures TC well above room temperature and a half-metallic
ferromagnetic behavior, that is, they are expected to have a full spin
polarization of the charge carriers at the Fermi level. This fact makes
them very attractive for spintronic devices. In the compound Sr2FeMoO6
electron doping achieved by the substitution of Sr 2+ by trivalent La 3+
has been reported to lead to an increase of TC [1]. On the other hand,
in Sr2CrWO6 the same substitution leads to a clear decrease of TC [2].
We have fabricated a series of high-quality polycrystalline samples of the
two compounds with different La doping in order to compare carefully
the effect on TC. All samples were characterized by x-ray powder diffractometry,
magnetization and transport measurements. The results are of
particular interest with respect to the physical mechanism stabilizing the
high TC values: Within a double-exchange model one would rather expect
an increase of TC with carrier doping, whereas a kinetic energy driven
exchange mechanism is expected to result in a decrease of TC.
[1] J. Navarro et al., Phys. Rev. B 64, 092411 (2001).
[2] J. B. Philipp et al., Phys. Rev. B 68, 144431 (2003).
MA 13.117 Di 15:00 Bereich A
The effect of Zn and Cr doping on structural and magnetic
properties of Sr2FeReO6 — •A. Jung, I. Bonn, J. Ensling, V.
Ksenofontov, C. Felser, and W. Tremel — Johannes Gutenberg -
Universität, Institut für Anorganische Chemie und Analytische Chemie,
55099 Mainz
Magnetic properties of doped double perovskites with formula
Sr2Fe1−xMxReO6 (M = Zn, Cr) strongly correlate with their structure.
The relation of ionic radii of iron and substituting transitional metals
is a decisive factor which determines the cubic or tetragonal modifications
of doped Sr2FeReO6. We report on the magnetic and structural
properties of solid solutions Sr2Fe1−xMxReO6 in a wide range of concentrations
0 ≤ x ≤ 1. 57 Fe Mössbauer spectroscopic studies revealed that
the relation of amount of Fe 2+ and Fe 3+ ions is another important factor
influencing the structure of these compounds. Magnetic properties
of doped double perovskites are interpreted by means of FLAPW band
structure calculations using the WIEN97 software package.
MA 13.118 Di 15:00 Bereich A
X-ray resonance exchange scattering from 4d transition metal
compounds — •Ioannis Zegkinoglou 1 , Joerg Strempfer 1 ,
Christie S. Nelson 2 , John P. Hill 2 , Jonathan Lang 3 , George
Srajer 3 , and Bernhard Keimer 1 — 1 Max-Planck-Institut fuer
Festkoerperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
— 2 Department of Physics, Brookhaven National Laboratory, Upton,
NY 11973-5000, USA — 3 Advanced Photon Source, Argonne National
Laboratory, Argonne, IL 60439, USA
We present results of x-ray resonance exchange scattering (XRES)
from single crystal Ca2RuO4, performed at the Ru L2 and L3 absorption
edges at photon energies between 2.8 keV and 3 keV. A large resonance
enhancement of the magnetic signal is observed. Its origin lies
in the 2p → 4d dipolar electronic transitions that probe directly the 4d
orbitals, which are responsible for magnetism. This provides new possibilities
of studying the magnetic properties, as well as possible chargeand
orbital- ordering in 4d transition metal compounds. The enhancement
at K-edges, where the d-orbitals are only probed indirectly via the
p-orbitals, is generally much weaker.
MA 13.119 Di 15:00 Bereich A
Design for a low temperature spin-polarized scanning tunnelling
microscope — •Nathaniel Janke-Gilman, Wulf Wulfhekel,
and Jürgen Kirschner — Max Planck Institut für Mikrostrukturphysik
We present the design of a new ultrahigh vacuum (UHV) spin polarized
scanning tunnelling microscope (SP-STM). The apparatus is designed to
operate inside a closed 4K chamber, allowing for excellent vacuum conditions
and exceedingly long sample lifetimes. Magnetic fields of up to 0.5
Tesla may be applied at the sample position in the parallel or perpendicular
direction either before or during SP-STM operation. Sample and tip
exchange is possible with visual control. Both in-plane and out-of-plane
spin polarization is measurable by using either a ring or sharp tip at the
tunnelling junction, respectively.

Magnetismus Dienstag
MA 13.120 Di 15:00 Bereich A
Fluxgate-Sensoren mit verbesserter Ausleseelektronik —
•Rainer Piel, Kai Kuchenbrandt, Kerstin Franke, Frank
Ludwig und Meinhard Schilling — Institut für Elektrische
Messtechnik und Grundlagen der Elektrotechnik, TU Braunschweig,
Hans-Sommer-Str. 66, D-38106 Braunschweig
Zur weiteren Erhöhung der Empfindlichkeit, zur Reduktion des Elektronikbeitrages
zum Systemrauschen sowie zur Verbesserung der dynamischen
Eigenschaften der von uns hergestellten drahtgewickelten und
Dünnschicht-Fluxgate-Sensoren haben wir eine verbesserte Ausleseelektronik
entwickelt, die auf der Detektion der zweiten Harmonischen der
Anregungsfrequenz basiert. Kernpunkt ist dabei eine deutliche Erhöhung
der Anregungsfrequenz von bisher 15 kHz auf 1 MHz. Zur Optimierung
der Schaltung wurden der Fluxgate-Sensor und die Rückkoppelelektronik
mittels PSPICE simuliert. Das Fluxgate-Modell zeigt eine sehr gute
Übereinstimmung mit den experimentellen Ergebnissen, die mit der 15
kHz-Elektronik an drahtgewickelten Fluxgate-Sensoren gemessen wurden.
Parallel zur Entwicklung einer verbesserten Rückkoppelelektronik wurde
an der weiteren Entwicklung der Technologie für die Herstellung von
Dünnschicht-Fluxgate-Sensoren gearbeitet. Zentraler Punkt ist dabei die
Optimierung der Herstellung des magnetischen Kerns, der gegenwärtig
aus einem Permalloy-Dünnfilm gefertigt wird. Der aktuelle Stand der
Sensorfertigung und Messergebnisse an Dünnschicht-Fluxgatesensoren
werden präsentiert.
MA 13.121 Di 15:00 Bereich A
Nutzung des GMI-Effektes bei Dünnfilm-Magnetfeldsensoren
— •H. Yakabchuk, C. Bethke, V. Tarasenko, H. Hammer und
E. Kisker — Institut für Angewandte Physik, Heinrich-Heine Universität
Düsseldorf, 40225 Düsseldorf
Extrem empfindliche Magnetfeldsensoren lassen sich auf der Basis des
GMI-Effektes (GMI: Giant Magneto-Impedance) realisieren. Hierbei wird
der Wechselspannungsabfall am Sensor als Funktion des angelegten externen
Magnetfeldes bei gegebenem HF-Strom gemessen. Die resultierende
Impedanzänderung kann bei geeignetem Sensormaterial und -aufbau
mehrere hundert Prozent betragen.
Während die meisten GMI-Sensoren mit weichmagnetischen, amorphen
Mikrodrähten realisiert sind, nutzen wir gesputterte, dreilagige Schichtsysteme
der Anordnung FeCuNbSiB/Cu/FeCuNbSiB. Der große Vorteil
gegenüber den GMI-Drähten ist die ausgeprägte Anisotropie dieser
Schichtsensoren bezüglich der Richtung eines angelegten externen Magnetfeldes.
Die Schichtsensoren eignen sich daher besonders gut zur Detektion
magnetischer Partikel.
Wir berichten über den Einfluß des Sensoraufbaus und Präparationsbedingungen
auf Größe und Phase des GMI-Effektes als Funktion der Frequenz
und Amplitude des HF-Stromes, sowie des äußeren Feldes. Sich
daraus ergebende Sensorkonzepte werden vorgestellt.
Gefördert vom BMBF, Förderkennzeichen 13N8128.
MA 13.122 Di 15:00 Bereich A
Thickness dependence of the spin-wave dispersion in ultrathin
Co films — •Markus Etzkorn 1 , P. S. Anil Kumar 1 , W. Tang 1 , R.
Vollmer 1 , H. Ibach 2 , and J. Kirschner 1 — 1 Max-Planck Institut für
Mikrostrukturphysik, Weinberg 2, 06120 Halle — 2 Institut für Schichten
und Grenzflächen ISG3, Forschungszentrum Jülich, 52425 Jülich
We present spin polarized electron energy loss spectra of surface spin
waves in ultrathin Co films on Cu(001). Starting from our earlier studies
on 8 ML [1] we have explored the influence of reduced thickness on the
spin-wave dispersion down to 2,5 ML Co. The measured spin-wave energies
can be fitted surprisingly good by a dispersion curve derived from a
nearest neighbor Heisenberg model. Our analysis of the dispersion curves
indicates that the exchange coupling constant at the Co surface is not
significantly enhanced compared to its bulk value, in disagreement with
theoretical expectations [2,3]. At the surface Brillioun zone boundary the
spin-wave energy is independent of the thickness down to 2,5 ML indicating
a rather short range exchange coupling interaction not much beyond
the NN distance.
[1] R. Vollmer, M. Etzkorn, P. S. Anil Kumar, H. Ibach, and J. Kirschner,
Phys. Rev. Lett. 91 (2003) 147201.
[2] M. Pajda, J. Kudrnovsk´y, I. Turek, V. Drchal, and P. Bruno, Phys.
Rev. Lett. 85 (2000) 5424.
[3] S. S. A. Razee, J. B. Staunton, L. Szunyogh, and B. L. Györffy, Phys.
Rev. B 66 (2002) 094415.
MA 13.123 Di 15:00 Bereich A
Magnetkraftmikroskopische Untersuchungen ferromagnetischer
La0.7Ca0.3MnO3−δ/LaAlO3-Filme in variablen Magnetfeldern —
•Uwe Kaiser 1 , M. Liebmann 2 , A. Schwarz 1 , R. Wiesendanger 1 ,
U. H. Pi 3 , Z. G. Khim 3 , T. W. Noh 3 und D. W. Kim 4 — 1 IAP,
Mikrostrukturzentrum, Universität Hamburg — 2 Department of Mechanical
Engineering, Yale University, USA — 3 Seoul National University,
Seoul, Süd-Korea — 4 SAIT, Suwon, Süd-Korea
Mit einem Eigenbau-Magnetkraftmikroskop (Hamburg-Design [1])
wurden ferromagnetische La0.7Ca0.3MnO3−δ-Proben im Ultrahochvakuum,
bei tiefen Temperaturen und in variablen Magnetfeldern von bis zu
2 T untersucht. Die vier verwendeten Proben wurden mittels gepulster
Laserdeposition in zwei verschiedenen Schichtdicken (50 und 100 nm)
auf LaAlO3-Substrate epitaktisch aufgewachsen, wobei zwei der Proben
durch unterschiedliche Präparationen einen defizitären Sauerstoffgehalt
aufweisen (δ ≪ 1). Die Magnetisierung und die elektrische Leitfähigkeit
der Proben wurden mittels SQUID bzw. Vierpunktmessung bei
variabler Temperatur untersucht. Aufgrund der hohen Stabilität des
experimentellen Aufbaus des verwendeten Magnetkraftmikroskops
ist neben der Abbildung der Domänenstruktur im Nullfeld auch
die ununterbrochene Bildaufnahme während einer sehr langsamen
Magnetfeldrampe entlang der Hystereseschleife der Proben möglich.
Insbesondere können durch Differenzbildung aufeinander folgender
Bilder die einzelnen Ummagnetisierungsprozesse sichtbar gemacht
werden, um so das Domänenwachstum detailliert zu untersuchen.
[1] M. Liebmann et al., Rev. Sci. Instr. 73, 3508 (2002).
MA 14 Hauptvorträge Eisenmenger / Münzenberg
Zeit: Mittwoch 14:00–15:00 Raum: H10
Hauptvortrag MA 14.1 Mi 14:00 H10
Exchange Biased Nanostructures — •J. Eisenmenger 1,2 , Zhipan
Li 1 , O. Petracic 1 , I. V. Roshchin 1 , Kai Liu 3 , J. Nogués 4 , C.
Leighton 5 , H. Masuda 6 , K. Nishio 6 , and Ivan K. Schuller 1
— 1 Department of Physics, University of California, San Diego —
2 Abteilung Festkörperphysik, Universität Ulm, — 3 Department of
Physics, University of California, Davis — 4 ICREA and Departament de
Física, Universitat Autònoma de Barcelona, Bellaterra — 5 Department
of Chemical Engineering and Materials Science, University of Minnesota,
Minneapolis — 6 Applied Chemistry Department, Tokyo Metropolitan
University, Hachioji
increasing attention in recent years, motivated by the interesting physical
phenomena present and the potential for applications in the sensor
and storage industries. Magnetic nanostructures become particularly interesting
when they are in contact with other dissimilar magnetic materials,
e.g. ferromagnetic nanostructures which are in contact with an
antiferromagnetic substrate. In such exchange biased configurations, a variety
of interesting phenomena arise; the reversal mode of the ferromagnet
changes considerably, there is a noticeable change in the domain structure
and the magnetization can be stabilized by the additional anisotropy
which is an important aspect for small magnetic particles where thermal
fluctuation can easily cause superparamagnetic behavior. In a series of
experiments we studied these phenomena in nanostructured Fe/FeF2 bilayers
patterned by electron beam lithography and self assembly. Work
supported by AvH Foundation, AFOSR, DOE, NSF, and Cal(IT) 2 .

Magnetismus Mittwoch
Hauptvortrag MA 14.2 Mi 14:30 H10
Ultrafast magnetization dynamics in pump probe experiments
— •M. Münzenberg 1 , M. Lüttich 1 , P. Moschkau 1 , M. Djordjevic
1 , G. Eilers 1 , S. Bretschneider 1 , A. Parge 1 , P. Guderian 1 ,
T. Kampfrath 1 , R. G. Ulbrich 1 , B. Sass 2 , F. Leuenberger 2 , W.
Felsch 2 , T. H. Kim 3 , and J. S. Moodera 3 — 1 IV. Phys. Inst., Universität
Göttingen — 2 I. Phys. Inst., Universität Göttingen — 3 Francis
Bitter Magnet Laboratory, MIT, USA
Ultrafast magnetization dynamics is a new evolving field having tools
at hand to reach new frontiers in ultrafast spin dynamics: all optical
pump experiments with Ti:Sapphire oscillators can explore electron excitations
on a timescale of 50 fs to >100 ps. They are accompanied by
a change in the reflectivity due to the nonequlibrium distribution of the
MA 15 Magnetische dünne Schichten I
excited electrons. In ferromagnetic systems the spin system is almost instantaneously
demagnetized. Origin is a coupling of the electron, spin
and lattice temperatures (three temperature model). Changing optical
properties lead to a change in the Kerr rotation and ellipticity with non
magnetic origin but can be separated by a variation of the probe beam
wave length as proposed by Kampfrath. This is even more important on
a longer time scale where phonon shock waves and magnetic excitations
dominate the dynamics. For this regime we simulate the demagnetization
effect in the order of 5-10% using the oommf code: the magnetic Eigen
states of nanostructured rectangular structures are strongly dominated
by the dipolar stray fields of the curling magnetization of the S state. Ultrafast
dynamics is also accessible by the use of photoconductive switches
that allow to excite the spin system directly.
Zeit: Mittwoch 15:15–17:45 Raum: H10
MA 15.1 Mi 15:15 H10
Co/Cu/Ni-Dreilagen nahe ihrer Curie-Temperaturen: Untersuchungen
mittels magnetischem Röntgenzirkulardichroismus —
•C. Sorg, M. Bernien, H. Wende, A. Scherz, N. Ponpandian und
K. Baberschke — Institut für Experimentalphysik, Freie Universität
Berlin, Arnimallee 14, D-14195 Berlin-Dahlem, Germany
Mittels magnetischem Röntgenzirkulardichroismus (XMCD) wird die
elementspezifische Ni-Magnetisierung in Co/Cu/Ni-Dreilagen untersucht.
In diesen Dreilagen sind die beiden ferromagnetischen Schichten
aus Ni und Co über die Cu-Zwischenschicht indirekt gekoppelt. Frühere
Experimente haben gezeigt, dass sich die Ni-Ordnungstemperatur T Ni
C
in Anwesenheit einer Interlagenaustauschkopplung deutlich um ∆TNi
zu höheren Temperaturen verschiebt [1]. Theoretische Untersuchungen
schreiben diesen Effekt dem Einfluss von Spin-Fluktuationen in
zweidimensionalen (2D) Systemen zu. Diese Rechnungen ergeben, dass
die relative Verschiebung ∆TNi/T Ni
C sowohl mit abnehmender Ni-Dicke
als auch mit zunehmender Kopplungsstärke Jinter zunimmt [2]. Um
den Einfluss der Kopplung systematisch zu studieren, untersuchen
wir ∆TNi/T Ni
C für zwei Serien von Proben: In der ersten Serie wird
ausschließlich die Cu-Dicke und damit Jinter geändert. In der zweiten
variieren wir nur die Ni-Schichtdicke. Es zeigt sich, dass für dünnere
Ni-Filme der Effekt der Spin-Fluktuationen zunimmt. Gefördert durch
BMBF (05 KS1 KEB 4).
[1] P. Poulopoulos and K. Baberschke, Lecture Notes in Physics, Springer
580, 283 (2001)
[2] P. Jensen et al., Phys. Rev. B 60, R14994 (1999)
MA 15.2 Mi 15:30 H10
Magnetische und elektronische Eigenschaften von zweidimensionalen
Fe-Mn und Co-Fe Legierungen — •Marco
Pratzer und Hans-Joachim Elmers — Institut für Physik,
Universität Mainz, Staudingerweg 7, D-55099 Mainz
Die magnetischen und elektronischen Eigenschaften von binären Legierungsmonolagen
können sich von den entsprechenden Volumenlegierungen
stark unterscheiden. Eine Schlüsseleigenschaft ist die Magnetisierung,
die sich mit der mittleren Zahl der Elektronen pro Atom N ändert (Slater-
Pauling-Kurve). Nimmt man an, die Bandstruktur sei unabhängig von
der Legierungszusammensetzung, so würde sich mit der Zunahme von N
nur die Fermie-Energie erhöhen. Mit der Variation von N sollte es somit
möglich sein, die Fermie-Energie auf ein Maximum der Zustandsdichte
einzustellen, um eine möglichst grosse Magnetisierung zu erreichen. Daher
haben wir Fe-Mn und Co-Fe Legierungsmonolagen auf einem W(110)
Substrat präpariert. Wie aus LEED-Untersuchungen hervorgeht wachsen
alle Legierungen für Bedeckungen unter 0,7 ML pseudomorph. Damit ist
die Gitterkonstante für alle Zusammensetzungen gleich. Mit Hilfe von
Tunnelstromspektroskopie und Kerr-Magnetometrie konnten wir einen
direkten Zusammenhang zwischen den magnetischen Eigenschaften und
der lokalen Zustandsdichte zeigen. Anders als bei den entsprechenden
Volumenlegierungen findet man ein Maximum von TC und der Kerr-
Drehung bei der reinen Fe-Monolage. Für die Fe-Mn Legierungen nimmt
die Kerr-Drehung bei kleiner werdender Fe-Konzentration mit einer Rate
von ∆µ/∆ x=(-8±2)µB/Atom rasch ab.
MA 15.3 Mi 15:45 H10
Phase diagram of thin FexCo1−x alloy films on Cu(100) —
•Hristo Kolev 1 , Georgi Rangelov 1 , Jürgen Braun 1 , Hyungdon
Kang 2 , and Markus Donath 1 — 1 Physikalisches Institut, Universität
Münster, Wilhelm-Klemm-Str. 10, 48149 Münster — 2 Max-
Planck-Institut für Plasmaphysik, 85748 Garching
The technological relevance of thin magnetic alloy films has triggered
much scientific activity.
We studied the structure of thin FexCo1−x alloy films grown on Cu(100)
as a function of the film thickness d and Fe concentration x. Low-energy
electron diffraction was applied to determine the geometrical structure
of the films. Electronically structure information from appearance potential
spectroscopy gave us additional insight in the structural order of the
films. For this purpose, a detailed theoretical analysis of the appearance
potential spectroscopy data was necessary.
Three different regions of structural order have been observed in the alloy
as a function of x and d. In the first region, characterized by low Fe
concentrations, an fcc-structure was found. In the second region a tendency
against the fcc-structure has been observed. A mixture of fcc- and
bcc-order was identified in the alloy. For very high Fe concentrations the
fcc-structure recovers for films thinner than 10 ML.
Combining our structural information with data from the literature [1] we
were able to develop a comprehensive phase diagram of the thin FexCo1−x
films at room temperature for the two parameters Fe concentration x
and film thickness d. [1] Dittschar et al., J. Magn. Magn. Mat. 212, 307
(2000).
MA 15.4 Mi 16:00 H10
Thermal spin excitations in epitaxial ultrathin Fe films
on Au(001) — •W. Kipferl, M. Dumm, M. Sperl, and G.
Bayreuther — Institut für Experimentelle und Angewandte Physik,
Universität Regensburg, Universitätsstr. 31, 93040 Regensburg
Epitaxial ultrathin Fe films were grown on epitaxial Au surfaces by
molecular beam epitaxy. Epitaxial growth was achieved by using an Fe
seed layer and a Ag buffer layer on a GaAs(001) substrate. Epitaxial
quality and surface structure were verified in situ by RHEED and STM.
The magnetic properties of the samples were investigated by MOKE,
AGM and SQUID magnetometry between 10 and 350 K. All films have a
four-fold anisotropy with the easy axis along [110] below a thickness of 7
monolayers (ML) and along [100] for films thicker than 7 ML 1 . The temperature
dependence of the spontaneous magnetization for T < 0.5TC
can be well described by Bloch’s law, M(T) = M(0) × (1 − B T 3/2 ), for
all samples. With decreasing film thickness the spin wave parameter B
increases significantly compared to the bulk. Fe/Au(001) shows a dominating
four-fold anisotropy, while in Fe films on GaAs(001) 2 for the
thinnest films the magnetic behaviour is governed by a strong uniaxial
anisotropy. Thus, the comparison allows us to study the influence of the
intrinsic anisotropy on the spin excitations.
Support by the Deutsche Forschungsgemeinschaft (DFG) is gratefully
acknowledged (Grant No. FOR 370).
References:
1 M. Brockmann et al., J. Appl. Phys. 81, 5047 (1997)
2 W. Kipferl et al., J. Appl. Phys. 93, 7601 (2003)

Magnetismus Mittwoch
MA 15.5 Mi 16:15 H10
Thickness and temperature driven Spin Reorientation Transition
in ultrathin Co films on Pd(110) — •L. Yan, Y. Lu,
H. Meyerheim, M. Przybylski, W. Wang, J. Barthel, and J.
Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Weinberg
2, 06120 Halle
Morphology, structure and magnetism of ultrathin Co films (0.1 to
3ML) grown epitaxially on Pd(110) at room temperature (RT) were studied.
The elongated Co stripes resulting from the anisotropy of Pd(110)
surface are observed by STM. These Co stripes become ferromagnetic
above 0.2ML at low temperature (LT=80K), and are magnetized outof-plane.
Between 0.5ML and 1.1ML, the polar MOKE signal (measured
in remanence) decreases with increasing Co coverage. The magnetization
rotates towards the film plane showing an increasing longitudinal
component to the total Kerr signal. With further increasing coverage,
another spin reorientation transition occurs. At the thickness of about
2ML the film magnetization is again oriented out-of-plane at LT. However,
with increasing temperature the magnetization rotates towards the
film plane and no polar MOKE signal is detected at RT. The films are
magnetized in-plane independently of the temperature above a thickness
of about 2.7ML. We suggest that such magnetic behaviors are attributed
to the morphology and structural reconstruction which the film experiences
with increasing thickness.
MA 15.6 Mi 16:30 H10
Prinzipielle Unterschiede bei Ni/Pd-Grenzflächen — •Y.
Manzhur 1 , K. Potzger 1 , M. J. Prandolini 1 , H. H. Bertschat
1 und Mark Dietrich 2 — 1 Hahn-Meitner-Institut, Bereich
Festkörperphysik, Glienicker Strasse 100, 14109 Berlin — 2 Mark
Dietrich, ISOLDE-Collaboration, EP Division, CERN, CH 1211 Genf
Ni/Pd-Grenzflächen können u. a. durch Aufdampfen von Pd auf Ni-
Einkristallen erzeugt werden oder durch Aufdampfen von Ni auf Pd-
Einkristallen. Pd auf Ni ist ein häufiger studiertes System und wurde
auch von uns mit der PAC-Spektroskopie unter Verwendung von radioaktiven
Proben untersucht [1]. Das mehrfach bestätigte Ergebnis ist, dass
wenige Monolagen Pd auf Ni eine ferromagnetische Ordnung annehmen.
Dagegen gibt es neben der PAC so gut wie keine Experimentiermethode,
um das magnetische Verhalten von Ni bedecktem Pd zu erforschen. In
einen früheren Experiment [2] fanden wir, dass in Pd einige Atomlagen
von der Grenzfläche entfernt induzierte magnetische Wechselwirkungen
nachzuweisen sind, Pd aber paramagnetisch bleibt. Nun konnten wir zeigen,
dass auch die oberste Pd-Atomlage des Einkristalls, die sich in direktem
Kontakt zu Ni befindet, keine ferromagnetische Ordnung annimmt,
im Kontrast zu dünnem Pd auf Ni.
Die Messungen wurden am Massenseparator ISOLDE / CERN durchgeführt.
[1] Phys. Rev. Lett. 80, 2721 (1998).
[2] Phys. Rev. Lett. 78, 342 (1997).
MA 15.7 Mi 16:45 H10
Spin-Polarisation von EuS oberhalb 77 K: Temperaturabhängige
MOKE- und XMCD-Messungen an dünnen
Co/EuS-Vielfachlagen-Filmen — •C. Müller, H. Lippitz, J.J.
Paggel und P. Fumagalli — Institut für Experimentalphysik, Freie
Universität Berlin, Arnimallee 14, 14195 Berlin
Sein großes Spin-Moment (mS = 7/2) macht den Halbleiter EuS interessant
für Spintronics-Anwendungen. Demgegenüber steht die niedrige
Curie-Temperatur (TC=16.5 K), die eine kommerzielle Nutzung
ausschließt. Messungen des magnetischen Röntgen-Circulardichroismus
(X-MCD) an Vielfachlagen von Co und EuS zeigen eine Spin-Polarisation
von EuS bei einer Temperatur größer als 77 K. Als Ursache wird eine
antiferromagnetische Kopplung zwischen Co und EuS festgestellt, d.h.
die Polarisation des EuS wird durch das Co induziert. Tieftemperatur-
Messungen (10 K) des magnetooptischen Kerr-Effektes (MOKE) können
dies bestätigen: Nichtlinearitäten in Hysterese-Kurven werden durch
einen solchen Kopplungs-Effekt erklärt. Bei Raumtemperatur liefern
MOKE-Messungen keinen eindeutigen Nachweis für die Existenz einer
antiferromagnetischen Kopplung.
Diese Arbeit wurde unterstützt durch die Deutsche Forschungsgemeinschaft
im Rahmen des SFB 290.
MA 15.8 Mi 17:00 H10
Pulsed Laser Deposition of Epitaxial SmCo Thin films — •A.
Singh 1 , R. Tamm 2 , V. Neu 1 , S. Leinert 1 , S. Fähler 1 , C.-G. Oertel
2 , W. Skrotzki 2 , L. Schultz 1 , and B. Holzapfel 1 — 1 IFW
Dresden, Helmholtzstr. 20, 01069 Dresden — 2 Inst. f. Strukturphysik,
TU Dresden, 01062 Dresden
To explore the potential of a permanent magnetic material with uniaxial
anisotropy, a well aligned easy magnetisation axis is required. One way
to achieve this is by growing epitaxial films on single crystal substrates.
With the same aim and motivation of achieving high coercivity and remanance
along a crystallographic direction, epitaxial SmCo on Cr buffered
(100) and (110) MgO single crystal substrates was deposited. These films
were prepared using PLD from elemental targets, and showed the epitaxial
relation: MgO(001)[100]-Cr(001)[110]-SmCo(110)[001], which indicates
an in plane direction of the easy axis. But besides this the easy axis
also shows a 60 ◦ out of plane component coming from a (1 1 16) texture.
These results have been reached at by careful analysis of several pole figures
measured in the texture goniometer and magnetic measurements in
the SQUID. The volume fractions of these two texture components show
a strong dependence on the deposition temperature. The exact contributions
of these two components will be discussed in relation to the results
from magnetic properties.
MA 15.9 Mi 17:15 H10
Magnetic microstructure of granular epitaxial NdFeB films —
•V. Neu, S. Melcher, U. Hannemann, and S. Fähler — IFW
Dresden, Helmholtzstr. 20, 01069 Dresden
Epitaxial NdFeB films combine a perfect alignment of the easy magnetic
axis perpendicular to the substrate with a high coercivity up to 2
T [1]. They possess high nucleation fields and the coercivity is mainly
limited by local stray fields. Furthermore they grow in isolated, rectangular
grains, which makes these films an ideal system to locally study
the magnetic domains of a self-organized microstructure.
In this paper we used Magnetic Force Microscopy (MFM) and global
magnetization measurements to examine a series of Nd-rich NdFeB films
deposited at different temperatures. At deposition temperatures around
545 ◦ C the films neither have a perfect degree of texture nor do they switch
homogeneously. The microstructure consists of a small grained film of Nd-
FeB with the Nd-rich phase segregated as large spherical grains. At the
optimum temperature of 630 ◦ C uniform switching occurs and a coercivity
of 2 T is obtained. These films consist of rectangular, µm-sized NdFeB
grains, which show typical stripe domains with an average width of 150
nm. At higher temperatures (670 ◦ C) the grain size distribution broadens
significantly. This is reflected in a less uniform switching behavior, which
is observed with global and local measurement techniques.
[1] U. Hannemann, S. Fähler, V. Neu, B. Holzapfel, L. Schultz, Appl.
Phys. Lett. 82, 3710 (2003)
MA 15.10 Mi 17:30 H10
Highly coercive and highly remanent Nd-Fe-B films —
•Sebastian Fähler, Jörg Buschbeck, Ah-Ram Kwon, Ullrich
Hannemann, Volker Neu, Bernhard Holzapfel, and Ludwig
Schultz — IFW Dresden, Helmholtzstr. 20, 01069 Dresden and SFB
463
Miniaturised magnets with high remanences are needed for microelectromechanical
systems (MEMS). A possible solution is epitaxially
grown Nd2Fe14B films which exhibit due to the perfect alignment of the
c-axis (easy magnetisation direction) very high remanence to saturation
magnetisation ratios close to unity. Furthermore these films reach coercivities
up to 2 T [1]. Films, which were deposited at lower temperatures
and subsequently annealed at higher temperatures, show similar results
despite the different temperature treatment [2]. One result of the different
temperature treatment is a change in the morphology of the films,
which consists of isolated grains for the epitaxial films or appears continuous
for the post-deposition annealed films. We present a study of the
effect of the 2 different deposition conditions on the microstructure and
consequently on the magnetic properties of the films.
[1] U.Hannemann, S. Fähler, V. Neu, B. Holzapfel, L.Schultz, Appl.
Phys. Lett. 82 (2003) 3710
[2] L.K.E.B Serrona, A. Sugimura, N. Adachi et al., Appl. Phys. Lett.
82 (2003) 1751

Magnetismus Mittwoch
MA 16 Magn. Kopplungsphänomene
Zeit: Mittwoch 15:15–17:30 Raum: H22
MA 16.1 Mi 15:15 H22
Temperature Dependence of Interlayer Exchange Coupling
— •Stephan Schwieger and Wolfgang Nolting — Humboldt-
Universität zu Berlin, Institut für Physik, Newtonstr.15, 12489
Berlin
The coupling of two magnetic layers (e.g. Co,Ni) seperated by a nonmagnetic
spacer (e.g.Cu) is well understood in terms of the quantum
interference model as e.g. proposed by P. Bruno.
The dominant contribution to it’s temperature dependence is less certain.
Two mechanisms that are discussed are the softening of the Fermi
surface within the spacer and the interaction of spin wave excitations
within the magnetic material.
Here another mechanism is proposed, that is based on the strong temperature
dependence of thermodynamic potentials as the free energy.
This reflects the fact, that expectation values like 〈 ¯ Sia ¯ Sib〉 , where ¯ Sia
and Sib indicate spins in different magnetic layers, are strongly temperature
dependent compared to excitations like spin waves or the softening
of the Fermi surface.
This approach is evaluated within the Heisenberg model and compared
to FMR experiments.
MA 16.2 Mi 15:30 H22
Untersuchung der antiferromagnetische Kopplung in CoFeB-
Systemen — •Nils Wiese1,2 , Theodoros Dimopoulos1 , Manfred
Rührig1 , Joachim Wecker1 , Hubert Brückl2 und Günter
Reiss2 — 1Siemens AG, Corporate Technology, Erlangen — 2Universität Bielefeld, Nano Device Group, Bielefeld
In Systemen aus zwei ferromagnetischen Schichten, die durch ein nichtmagnetisches
Material voneinander getrennt sind, kommt es bei dünnen
Zwischenschichtlagen zu einer Kopplung der ferromagnetischen Schichten.
Es wird gezeigt, daß in Systemen, bestehend aus zwei Lagen aus
amorphen CoFeB und einer dünnen Ru-Zwischenschicht, eine oszillierende
Kopplung bei Variation der Zwischenschichtdicke beobachtet wird.
Die Größe der antiferromagnetischen Kopplung J beträgt im ersten Maximum
der Kopplung J = −0.8 J
m2 und ist damit um einen Faktor 10
kleiner als in synthetischen Antiferromagneten aus CoFe/Ru/CoFe.
Die Koerzitivfeldstärke Hc kann über Q = m1+m2 eingestellt werden,
m1−m2
wobei m1, m2 die magnetischen Momente der Einzelschichten sind,[1] und
ändert sich für CoFeB linear mit Q zwischen 0.3 und 1.4 kA
m .
[1] v.d. Berg et al., IEEE Trans. Magn. 32, 4624 (1996)
MA 16.3 Mi 15:45 H22
Evidence for three-dimensional non-collinear antiferromagnetic
order in single-crystalline FeMn ultrathin films — •W. Kuch,
L. I. Chelaru, F. Offi, J. Wang, M. Kotsugi, and J. Kirschner
— Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120
Halle
Experimental evidence for a three-dimensional non-collinear antiferromagnetic
spin structure in ultrathin single-crystalline fcc Fe50Mn50 layers
is obtained from magnetic circular dichroism photoelectron emission
microscopy (XMCD-PEEM) and x-ray magnetic linear dichroism. Layerresolved
as-grown domain images of epitaxial trilayers grown on Cu(001)
are presented in which FeMn is sandwiched between ferromagnetic layers
with different easy axes. Measurements of trilayers using Co or Ni
as the bottom layer, and combinations of Co and Ni as top layer reveal
the simultaneous presence of antiferromagnetic spin components in the
film plane and normal to the film plane. The absence of x-ray magnetic
linear dichroism at the Fe L3 absorption edge in FeMn/Co bilayers points
towards an FeMn spin structure with no collinear order in the film plane
even when in contact with a saturated ferromagnetic layer. This result
has important implications on theoretical models of the magnetic interface
coupling between ferromagnetic and antiferromagnetic layers and
for understanding the exchange bias effect along different magnetization
components.
MA 16.4 Mi 16:00 H22
Magnetically frustrated regions in ultrathin antiferromagnetic
Mn films on Fe(001) — •U. Schlickum, N. Janke-Gilman, B.
Slowik, W. Wulfhekel, and J. Kirschner — Max-Planck-Institut
für Mikrostrukturphysik, Weinberg 2, 06120 Halle
By using spin-polarized scanning tunneling microscopy [1], we studied
the magnetic behavior of ultra-thin antiferromagnetic Mn films grown on
a ferromagnetic Fe(001) substrate. Mn on Fe(001) is a topological antiferromagnet,
so that adjacent Mn layers couple antiferromagnetically to
each other. Where Mn overgrows a step of the underlying Fe(001) substrate,
the thickness of Mn on different sides of the step edge differs by
one monolayer (ML). This results in a magnetically frustrated region at
the step edges. As theoretically predicted [2], this frustration resembles
a 180 ◦ domain wall in the Mn film. We investigated the width of these
topologically enforced walls in the antiferromagnet as a function of Mn
film thickness (between 2 and 20 monolayers). A linear broadening of the
wall width with increasing Mn thickness was found. The width of the
wall is twice the Mn thickness. The experimental results are compared
to theoretical calculations.
[1] U. Schlickum et al., Appl. Phys. Lett. 83, 2016 (2003). [2] D. Stoeffler
et al., J. Magn. Magn. Mater.147, 260 (1995).
MA 16.5 Mi 16:15 H22
Reduction of Néel ”orange peel”coupling in magnetic tunnel
junctions due to interface smoothing using low energy ion beams
— •P.A. Beck, B.F.P. Roos, S.O. Demokritov und B. Hillebrands
— Fachbereich Physik und Forschungsschwerpunkt MINAS,
Technische Universität Kaiserslautern, Erwin-Schrödinger-Str. 56, 67663
Kaiserslautern
The most decisive and sensitive characteristic of magnetic tunnel junctions
(MTJ), which are used in magnetic sensors and memory, is a small
and reproducible switching field. Due to the magnetic dipole coupling
(Neel ”orange peel”coupling) between the free and the pinned magnetic
layers this field is strongly affected by the morphology of the interfaces
in MTJ.
In this work we have used normal incident argon ions with their energy
of 20 − 90eV to smooth the interfaces of MTJs. First, to study the
influence of the ion bombardment a single layer 15nm Ni80Fe20 /SiO2/Si,
identical to a free magnetic layer of a typical MTJ has been used. We
have studied the influence of the ion energy on the smoothing and have
determined the optimum conditions for this process. The morphology of
the layer surface has been imaged using an in-situ scanning tunneling
microscope (STM). The obtained images document the reduction of the
roughness of over 40% after the bombardment. Second, MTJs were prepared
based on the smoothed layers, and their remagnetization curves
have been recorded. In agreement with the STM results, the ”orange
peel”coupling determined from the curves is significantly reduced due to
bombardment.
MA 16.6 Mi 16:30 H22
Two dimensional recrystallization, the key towards temperature
stable Co/Cu multilayers — •Sonja Heitmann 1 , Andreas
Hütten 1 , Guido Schmitz 2 , and Günter Reiss 1 — 1 Universität
Bielefeld, Fakultät für Physik, Universitätsstraße 25, 33615 Bielefeld —
2 Westfälische Wilhelms-Universität Münster, Institut für Materialphysik,
Wilhelm-Klemm-Straße 10, 48149 Münster
One of the major concerns for automotive sensor application is the temperature
stability at elevated temperatures. The breakdown of the GMReffect
amplitude of Co/Cu multilayers beyond 250 ◦ C [1] and 350 ◦ C [2] for
Co layer thickness of 1nm and 1.5nm, respectively, reveals the weakness
of conventionally prepared multilayer systems.
However, the objective of this talk is to demonstrate that alternatively
prepared Cu/Co multilayers are very much able to withstand high temperature
without a degradation of the GMR-effect amplitude. The key
is to utilize a two dimensional recrystallization process at sufficient high
temperatures around 500 ◦ C. It will be shown that these multilayers are
stable upon subsequent annealing at temperatrures between 400 ◦ C and
500 ◦ C. The microstructural evolution will be linked to results concerning
transport, magnetic and microstructure measurements and will reveal
the interplay of layer quality, grain size and orientation with crystalline
anisotropy, antiferromagnetic coupling and GMR.
MA 16.7 Mi 16:45 H22
90 ◦ coupling in (Fe/Cr/Fe)AFM/Cr/Fe system epitaxially
grown on GaAs(001) — •M. Przybylski 1 , J. Grabowski 1 , W.
Wulfhekel 1 , M. Rams 2 , and J. Kirschner 1 — 1 Max-Planck-
Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle — 2 Institute
of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow, Poland

Magnetismus Mittwoch
Single-crystalline (Fe/Cr/Fe)AFM/Cr/Fe structures were epitaxially
grown on atomically flat GaAs(001). The (Fe/Cr/Fe)AFM layered antiferromagnet
shows an easy-axis of magnetization along the [110] direction
which is due to the uniaxial anisotropy existing in the bcc-Fe(001)
films grown on GaAs(001). Choosing the same thickness of the antiferromagnetically
(AFM) coupled two Fe layers, the net magnetization of
the (Fe/Cr/Fe)AFM is balanced to zero. This holds in particular up to
a spin-flop transition when the field is applied along the [110] direction.
Adding a second Cr and a third Fe layer of such thicknesses that the top
Fe layer is weakly magnetically coupled to the bottom (Fe/Cr/Fe)AFM
structure, low field MOKE and SQUID magnetization loops show reversal
in only the top Fe layer of the (Fe/Cr/Fe)AFM/Cr/Fe structures. In
particular, a strong increase of coercivity (by factor of 12) is found at
low temperatures. 90 ◦ coupling is detected which affects the minor loops
measured along the [-110] and [100] direction.
MA 16.8 Mi 17:00 H22
Spin polarized neutron reflectivity measurements on Heusler
[Co2MnGe/V]n multilayers — •Andre Bergmann, Johannes
Grabis, Vincent Leiner, Hartmut Zabel, and Kurt Westerholt
— Institut für Experimentalphysik IV Ruhr Universität
Bochum,
The Heusler alloy Co2MnGe has been predicted to be a half metallic
ferromagnet by electronic band structure calculations, making this alloy
highly attractive for applications in spin electronic devices. We report
spin polarized neutron reflectivity measurements of the magnetic order
in [Co2MnGe/V]n multilayers prepared by rf-sputtering. In the neutron
reflectivity scans we detect a half order magnetic Bragg peak which can
be suppressed by applying a weak external magnetic field. The half order
peak provides clear evidence for a doubling of the multilayer period due
to antiferromagnetic (af) superlattice ordering in [Co2MnGe/V]n. The af
ground state exists in the thickness range 1.5 nm ≤ dV ≤ 3nm without
an indication of an oscillatory character of the interlayer exchange
interaction.
MA 16.9 Mi 17:15 H22
Zweifarben-Pump-Probe Messungen an magnetischen Oberflächen
*) — •Timo Damm, Jan Podsiadly, Lisong Yang und
Paul Fumagalli — Institut für Experimentalphysik, Freie Universität
Berlin, Arnimallee 14, 14195 Berlin, Germany
Im Rahmen einer Diplomarbeit wurde ein Aufbau für durchstimmbare
fs-Laserpulse erweitert, um mittels Zweifarben-Pump-Probe Messungen
dynamische Prozesse an ferromagnetischen Oberflächen zu untersuchen.
Speziell soll die Dynamik der Magnetisierung als Funktion der Zeit und
der Temperatur aufgenommen und ausgewertet werden, um theoretische
Modelle zur Austauschwechselwirkung in ferromagnetischen Halbleitern
zu verifizieren.
Durch einen ultravioletten Pump-Puls sollen Elektronen in das leere
Leitungsband des Halbleiters angeregt und die Entwicklung einer transienten
Magnetisierung in Abhängigkeit von der Temperatur mit Hilfe
eines Probe-Pulses über den magnetooptischen Kerr-Effekt im nahen Infrarotbereich
untersucht werden.
*) im Rahmen des DFG SPP 1133: ” Ultraschnelle Magnetisierungsprozesse“
MA 17 Spinstrukturen /Magn. Phasenübergänge
Zeit: Mittwoch 17:45–18:45 Raum: H10
MA 17.1 Mi 17:45 H10
The half-metal to metal transition in magnetite - a densityfunctional-theory
study — •Martin Friák 1 , Arno Schindlmayr
1,2 , and Matthias Scheffler 1 — 1 Fritz-Haber-Institut,
Faradayweg 4-6, D-14195 Berlin. — 2 Institut für Festkörperforschung,
Forschungszentrum Jülich.
We analyze the influence of various external conditions (uniaxial and
biaxial stress, pressure, substitutional dopants) that induce a half-metal
to metal transition leading to a loss of the material’s desirable halfmetallic
properties. Total energies, electronic structure, and magnetic
moments are calculated by DFT using the full-potential linearized augmented
plane-wave method. Results obtained within the generalized gradient
approximation (GGA) show excellent agreement with experimental
findings. In response to uniaxial, biaxial or triaxial pressure, a half-metal
to metal transition occurs, which shifts the Fermi energy from the gap of
the majority-spin electrons under the top of the valence band so that both
spin channels become metallic. We also performed a detailed total-energy
analysis of five different structural and spin configurations simulating the
substitution Fe2.5X0.5O4 (X = Mn, Co, Ni). The lowest-energy configurations
are in good agreement with experimental observations. For Mn
substitution we find a purely metallic character, qualitatively similar to
the stress-induced transition in pure magnetite.
MA 17.2 Mi 18:00 H10
Fermifläche und Valenzbandstruktur von Tb(0001)-Filmen —
•K. M. Döbrich 1 , J. E. Prieto 1 , K. Rossnagel 2 , H. Koh 2 , E.
Rotenberg 2 , G. Kaindl 1 und K. Starke 1 — 1 Fachbereich Physik,
Freie Universität Berlin, Germany — 2 Advanced Light Source, Lawrence
Berkeley National Laboratory, U.S.A.
Die elektronischen Zustände in der Nähe der Fermienergie bestimmen
die Leitfähigkeit von Festkörpern und beeinflussen ihre magnetischen Eigenschaften.
Letzteres ist insbesondere bei den Lanthaniden der Fall,
deren lokalisierte magnetischen 4f-Momente durch die itineranten 5d-
Elektronen gekoppelt sind (RKKY -Wechselwirkung). Winkelaufgelöste
Photoemissionsspektroskopie bei variabler Photonenenergie ermöglicht
Messungen der Fermifläche und der elektronischen Valenzbandstruktur
im gesamten k-Raum.
Unsere Messungen an epitaktisch auf W(110) aufgedampften Tb-
Filmen zeigen signifikant unterschiedliche Fermiflächen in der paramagnetischen
und ferromagnetischen Phase. Sowohl die experimentellen Fermiflächen
als auch die Valenzbandstruktur stimmen gut mit theoretischen
Rechnungen überein.
MA 17.3 Mi 18:15 H10
Spinpolarisierte Rastertunnelmikroskopie der Cr(001)-
Oberfläche bei variabler Temperatur — •Stefan Krause,
Torben Hänke, Matthias Bode und Roland Wiesendanger —
Institut für Angewandte Physik, Universität Hamburg, Jungiusstraße 11,
20355 Hamburg
Die magnetische Struktur der Cr(001)-Oberfläche bei Raumtemperatur
ist charakterisiert durch atomar flache Terrassen mit alternierender
Oberflächenmagnetisierung [1,2], die in der Probenebene liegt [3]. Die
im Volumen vorhandenen inkommensurablen Spindichtewellen (SDW)
transversaler Polarisation breiten sich daher senkrecht zur Oberfläche
aus. Bei Temperaturen unter 123K sind diese SDW longitudinal polarisiert
[4], so daß sich die Oberflächenmagnetisierung bei tiefen Temperaturen
— und gleichbleibender Ausbreitungsrichtung der SDW — senkrecht
aus der Ebene herausdrehen sollte.
Unser neu entwickeltes Rastertunnelmikroskop für spinpolarisierte
Messungen ermöglicht die Untersuchung der Cr(001)-Oberfläche zwischen
20K und 300K. Messungen mit Fe-beschichteten W-Spitzen, die
eine Sensitivität auf die Magnetisierung in der Probenebene aufweisen,
zeigen jedoch im gesamten untersuchten Temperaturbereich einen
gleichbleibenden Kontrastwechsel zwischen benachbarten Terrassen.
Mögliche Erklärungsmodelle hierfür werden diskutiert.
[1] S. Blügel et al., Phys. Rev. B. 39, 1392 (1989).
[2] R. Wiesendanger et al., Phys. Rev. Lett. 65, 247 (1990) u. M. Kleiber
et al., Phys. Rev. Lett. 85, 4606 (2000).
[3] M. Kleiber et al., J. Magn. Magn. Mater. 240, 64-69 (2002).
[4] H. Zabel, J. Phys.: Condens. Matter 11, 9303 (1999).
MA 17.4 Mi 18:30 H10
Einfluß der Temperatur auf Domänenwände in ferromagnetischen
Nanostrukturen — •Robert Wieser, Natalia Kazantseva,
Ulrich Nowak und Klaus D. Usadel — Universität Duisburg-
Essen
Zunächst werden Blochwände im eindimensionalen Grenzfall mittels
einer Molekularfeldnäherung untersucht. Hierbei zeigen sich bereits interessante
Phänomene wie das Auftreten eines zweiten Ordnungsparameters
(Magnetisierung senkrecht zur leichten Achse). Mit steigender Temperatur
wird zunächst die senkrechte Magnetisierung Null, bevor dann bei
der Curietemperatur auch die parallele Komponente der Magnetisierung
verschwindet.
Weiterhin werden Domänenwände in ausgedehnten Nanostrukturen
betrachtet. Dabei werden zunächst die statischen Aspekte untersucht.

Magnetismus Mittwoch
Neben bereits bekannten Oberflächeneffekten treten hier ebenfalls neue
Phänomene auf, wie eine stärkere Abnahme der Magnetisierung am Core
einer Vortex Wand. Schließlich wird die Temperaturabhängigkeit der
Domänenwandmobilität mittels eines Langevin-Dynamik Verfahrens un-
MA 18 Magnetische Messmethoden
tersucht.
Gefördert durch die Deutsche Forschungsgemeinschaft im Rahmen des
SFB 491.
Zeit: Mittwoch 17:30–18:45 Raum: H22
MA 18.1 Mi 17:30 H22
Höchstempfindlicher und dennoch sehr einfacher Magnetfeldsensor
basierend auf dem Procopiu-Effekt — •J. Velleuer 1 , E.
Kisker 1 , A. Hackl 1 und V. Uzdin 2 — 1 Institut für Angewandte Physik,
Heinrich-Heine Universität Düsseldorf, 40225 Düsseldorf — 2 St. Petersburg
University, V.O. 14 Linia 29, 199178 St. Petersburg, Russia
Als Procopiu-Effekt wird das Auftreten einer Induktionsspannung Uind
in einer Pickup-Spule bezeichnet, die einen von einem Wechselstrom
durchflossenen magnetischen Leiter umschliesst, wenn ein externes statisches
Magnetfeldes Hz angelegt wird. Bei Verwendung eines extrem
weichmagnetischen Leiters, einer geeigneten Leiter/Spulengeometrie und
geeignetem Leiter-Wechselstrom (u.a. die Stromstärke und die Frequenz
betreffend) erreichen wir ein sehr gutes Signal/Untergrund-Verhältnis.
Die induzierte Spannung hängt dabei über mehrere Dekaden quasi-linear
vom angelegten Magnetfeld ab. Wegen der hohen Empfindlichkeit und
der einfachen Konstruktion verspricht dieser Sensor interessante Anwendungsgebiete.
Wir werden die Besonderheiten (u.a. die Abwesenheit einer
Koerzitivfeldstärke in der Uind(Hz)-Abhängigkeit) des Procopiu-Effektes
erläutern.
Gefördert vom BMBF (13N8128).
MA 18.2 Mi 17:45 H22
Analytik superparamagnetisch markierter biologischer Makromoleküle
mittels GMI-Sensorik — •C. Bethke 1 , H. Yakabchuk 1 ,
V. Tarasenko 1 , H. Hammer 1 , E. Kisker 1 , E. Koppers 2 , S. Christoph
2 , R. Zirwes 2 und J. Müller 2 — 1 Institut für Angewandte Physik,
Heinrich-Heine Universität Düsseldorf, 40225 Düsseldorf — 2 Evotec
Technologies GmbH, Schnackenburgallee 114, D-22525 Hamburg
Als GMI-Effekt (GMI: Giant Magneto-Impedance) wird die starke Abhängigkeit
der Impedanz weichmagnetischer Mikrodrähte oder dünner
Schichtsysteme von der Größe eines relativ kleinen externen Feldes bezeichnet.
Dabei eignen sich zu Montage- und Integrationszwecken die
Dünnschicht-Systeme besser als die Mikrodrähte. Wir haben uns daher
auf die Entwicklung und Charakterisierung von Dünnschichtsensoren
konzentriert. Diese bestehen aus drei gesputterten Schichten in der Anordnung
FeCuNbSiB/Cu/FeCuNbSiB. Zur Funktionalisierung wird noch
eine Goldschicht aufgebracht. Im Gegensatz zu den GMI-Drähten zeigen
die Schichtsensoren eine ausgeprägte Anisotropie bezüglich der Richtung
eines angelegten externen Magnetfeldes.
Wir beschreiben verschiedene Möglichkeiten der Messung des GMI-
Effektes und zeigen, dass kleinste Mengen superparamagnetischer Partikel
detektiert werden können. Bei der Anwendung im Bereich der Analytik
biologischer Assays lagern sich diese Partikel dann durch spezifische
Interaktion zwischen biomolekularen Bindungspaaren (z.B. Antikörper-
Antigen, Rezeptor-Ligand, DNA-DNA etc.) selektiv an einen GMI-Sensor
an und können dort hochempfindlich nachgewiesen werden.
Gefördert vom BMBF, Förderkennzeichen 13N8127-8.
MA 18.3 Mi 18:00 H22
Digital method of magnetoresistive measurements based on Finite
Impulse Response filters — •N. Kozlova, M. Kozlov, D.
Eckert, K.-H. Müller, and L. Schultz — IFW Dresden, Postfach
270116, 01171 Dresden
A magnetoresistive technique has been developed for a pulsed field facility
with fields up to 60 T. Four-probe AC measuring technique is used
for magnetoresistance measurements. A digital approach for obtaining reliable
signal-to-noise ratio results has been developed. Algorithms based
on the least square method and the discrete Fourier transform were analyzed.
The algorithm based on a Finite Impulse Response filter has been
implemented. The Finite Impulse Response filter approach built around
the zero-phase delay Parks-McClellan filter implementation shows a better
signal to noise ratio in comparison with the least square method and
the discrete Fourier transform algorithm. The filter parameter calculation
and filtering has been solved in the Matlab Runtime integrated in
VEE Pro 6.0. The digital approach was successfully tested with measurements
on a superconducting bulk and thin film as well on semiconductor
materials.
This work is supported by BMBF project 03 SC5 DRE.
MA 18.4 Mi 18:15 H22
Einsatz von Fluxgates zur Magnetorelaxometrie an magnetischen
Nanoteilchen — •Erik Heim, Markus Havemann, Frank
Ludwig und Meinhard Schilling — Institut für elektrische Messtechnik
und Grundlagen der Elektrotechnik, TU Braunschweig, Hans-
Sommer-Str. 66, D-38106 Braunschweig
Magnetische Nanoteilchen aus Magnetit (Fe3O4) mit Durchmessern
unter 20 nm zeigen bei Raumtemperatur superparamagnetische Eigenschaften.
Wir untersuchen die Relaxation der Magnetisierung dieser Teilchen
in Abhängigkeit von der Zeit und der Feldamplitude der Aufmagnetisierung.
Die Relaxation zeigt grundsätzlich zwei verschiedene
Phänomene: Die Brownsche Relaxation hängt stark von der Teilchengröße
und dem umgebenden Medium ab. Die Néelsche Relaxation beschreibt
den Zerfall der externen Magnetisierung durch Gleichverteilung
der inneren Magnetisierung des einzelnen Teilchens. Durch Auswahl der
Teilchengröße lassen sich diese beiden Relaxationsvorgänge zeitlich trennen.
Eine Anwendung der magnetischen Nanoteilchen verwendet Antikörper
auf ihrer Oberfläche, um sie spezifisch an Biomoleküle zu binden.
Aufgrund der drastisch erhöhten Relaxation der gebundenen Teilchen
läßt sich ihre Konzentration aus dem Zeitsignal direkt nachweisen. In unserem
Messaufbau verwenden wir eine Helmholtzspule und ein Fluxgate-
Magnetometer, um die zeitliche Änderung der Magnetisierung der Nanoteilchen
nach dem Abschalten des externen Magnetfeldes zu messen. Der
Aufbau des Systems und erste Messungen werden vorgestellt.
MA 18.5 Mi 18:30 H22
Magneto-optische Spektroskopie mittels SHG — •Jan Peter
Podsiadly, Christian Müller und Paul Fumagalli — Institut
für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195
Berlin
Magneto-optische Second Harmonic Generation (MSHG) eröffnet eine
weitere Möglichkeit zur Erforschung magnetischer Schichten. Die Methode
ist besonders durch ihre Sensitivität für Grenz-und Oberflächeneffkte
interessant. Untersucht wurde der Einfluß verschiedener Deckschichten
auf die magneto-optischen Eigenschaften dünner Kobalt-Filme mittels
linearer magneto-optischer Kerr-Effekt(MOKE)-Spektroskopie sowie
MSHG- Spektroskopie. Für die MSHG-Messungen steht ein Ti:Saphir Lasersystem
zur Verfügung, welches mittels eines Optischen Parametrischen
Oszillators und einer Frequenzverdoppler-/verdreifacher-Einheit fast kontinuierlich
einen Spektralberich von 0,8eV bis 5eV abdeckt. Mit diesem
System kann ebenfalls der longitudinale magneto-optischer Kerreffekt gemessen
werden. Messungen des polaren magneto-optischen Kerreffektes
wurden an einem Kerr- Spektrometer in einem Spektralbereich von ebenfalls
0,8eV bis 5eV durchgeführt.

Magnetismus Donnerstag
MA 19 Hauptvortrag Tilgner
Zeit: Donnerstag 09:30–10:00 Raum: H10
Hauptvortrag MA 19.1 Do 09:30 H10
Magnetic field generation in planets and laboratory dynamos —
•Andreas Tilgner — Institut für Geophysik, Universität Göttingen,
Herzberger Landstr. 180, 37075 Göttingen
Most celestial bodies (the sun, most planets, stars and galaxies) generate
a large scale magnetic field by converting mechanical into magnetic
energy. In such a “dynamo process” electric currents are generated inside
a moving conductor which in turn create a magnetic field. In commercial
dynamos in use in cars or on bicycles, these currents flow inside especially
designed coils. In the earth however, the currents responsible for
the magnetic field flow in the liquid conductor (mostly iron) constitut-
MA 20 Magnetische dünne Schichten II
ing the core, which is spherical, devoid of electric structure and acts like
a massive short circuit. It was therefore disputed until the late 1950’s
whether the earth is capable of dynamo action. Doubts have been removed
on a theoretical basis and an experiment has demonstrated the
dynamo effect on a laboratory scale with a flow qualitatively resembling
the flow believed to exist in the core. Insights into the flow actually
realized in the core may be gained from numerical simulations, whereas
observations of the variations of the earth’s magnetic field allow to determine
the velocity at the boundary between the core and the electrically
insulating, solid mantle. We do not know yet what is driving the core
flow. The most probable mechanism is convection, but the precession of
the earth’s axis of rotation may also play a role.
Zeit: Donnerstag 10:15–13:00 Raum: H10
MA 20.1 Do 10:15 H10
Magnetic properties of cobalt thin films grown on Ni3Al(001)
— •Stella Maris Van Eek, Ioan Costina, Vitali Podgurski,
and René Franchy — Institut of Thin Films and Interfaces (ISG 3),
Forschungszentrum Juelich GmbH, D 52425 Juelich, Germany
The growth and the magnetic properties of thin cobalt films on
Ni3Al(001) at 300 K were investigated using Auger spectroscopy, low
energy electron diffraction, scanning tunneling microscopy and magneto
optic Kerr effect (MOKE). Hysteresis loops of the Co layer were seen
with MOKE in situ. The Co films were prepared with thicknesses from
1.8 ML to 8 ML and all were ferromagnetic at room temperature. The
coercivity of the Co film increased with deposited material up to 5 ML
and then decreased very slowly. We picked up a thickness of each one
of these two regions: 3 ML and 7 ML to investigate the magnetic properties.
At room temperature Co(001) grows fcc epitaxially due to the
small misfit between the lattice constant of fcc-Co and Ni3Al and forms
two-dimensional islands. Annealing up to 700 K did not show interdiffusion
but a coalescence and a flatening of the Co islands. The coercivity
field increased with annealing at 700 K, for example the coercivity of
the 7 ML Co sample showed an increase from 32(2) Oe to 43(2) Oe. For
the 3 and 7 ML Co samples the evolution of the magnetic properties
was investigated with the temperature. The magnetic ordering temperature
values for the different thicknesses are reduced compared to the
bulk one, this was explained with the scaling theory, which predicts a
weakened magnetic order at the surface.
MA 20.2 Do 10:30 H10
Absorptionsfeinstruktur an den L2,3 Kanten der leichten 3d
Übergangsmetalle — •A. Scherz, H. Wende, C. Sorg, K. Baberschke
und E.K.U. Gross — Fachbereich Physik, Freie Universität
Berlin, Arnimallee 14, 14195 Berlin-Dahlem, Germany
Eine systematische Studie des magnetischen Zirkulardichroismus (XM-
CD) leichter 3d Übergangsmetalle (TM’s) ist an Fe/TM/Fe(110) Dreilagen
durchgeführt worden. Im Gegensatz zu den schweren 3d TM’s weisen
die XMCD-Spektren eine Vielzahl von Absorptionsfeinstrukturen auf. Es
ist bekannt, daß Korrelationseffekte mit dem Rumpfloch die spektrale
Verteilung der L2,3 Kanten in den isotropen Absorptionsspektren (XAS)
beeinflussen. Dennoch besteht bislang keine umfassende theoretische Beschreibung
der Rumpflocheffekte in Absorptionsspektren entlang der 3d
Reihe für den Festkörper. Ein einfaches Modell wurde erarbeitet, welches
es ermöglicht, die Korrelationsenergien aus den experimentellen XAS-
Spektren zu bestimmen. In Verbindung mit der Analyse der XMCD-
Spektren kann direkt gezeigt werden, daß die gewohnte Anwendung der
Summenregeln zur Bestimmung von Spin- und Bahnmomenten, µS und
µL, aufgrund dieser Korrelationseffekte für die leichten 3d TM’s versagt.
Eine alternative Herangehensweise zur Bestimmung von µS und µL, die
die spektrale Linienform des XMCD analysiert, wird daher vorgeschlagen.
Die Ergebnisse der systematischen Studie erlauben einerseits eine
Abschätzung der magnetischen Momente aus experimentellen Daten als
auch andererseits eine Überprüfung zukünftiger Theoriemodelle, die die
Rumpflocheffekte in Absorptionsspektren von magnetischen Festkörpern
beschreiben. Gefördert durch das BMBF (05KS1 KEB4).
MA 20.3 Do 10:45 H10
MODIFICATION OF THE SPIN DENSITY WAVE OF CR
IN FE/CR MULTILAYERS BY INSERTION OF SN — •D.
Lott 1 , D. Solina 1 , M. Almokhtar 2 , K. Mibu 3 , W. Schmidt 4 ,
and A. Schreyer 1 — 1 GKSS Research Center, Geesthacht, Germany
— 2 Physics Department, Assiut University, Egypt — 3 Research Center
for Low Temperature and Materials Sciences, Kyoto University, Japan
— 4 Institut Laue Langevin, Grenoble, France
Recently, the SDW behavior of Cr in Fe/Cr/Sn/Cr multilayers were
studied by Moessbauer spectroscopy. The monolayer (ML) of Sn inserted
into the Cr layers serves as a Moessbauer probe permitting the
study of the magnetic local environment around Sn providing details
about of the magnetic stucture of Cr. In this work, complimentary
neutron diffraction studies were carried out on a set of Fe/Cr(t) and
Fe/Cr(t/2)/Sn(2˚A)/Cr(t/2) multilayers with t=80˚Aand t=160˚A. The
magnetic order of the Cr layers was examined, systematically comparing
the systems with and without Sn inserted in the Cr layers. The multilayers
with Sn show major changes with additional asymmetric modulations
in the diffraction spectra along (00L). Even more dramatic are the
changes for the Fe/Cr/Sn/Cr sample with t=80˚A. Instead of a CSDW
to ISDW transition with increasing T as seen in the sample without Sn,
a dominant CSDW component is observed at low T transforming into a
ISDW phase with higher T. Measurements and evaluations clearly show
that the general SDW behavior of the Cr layers in Fe/Cr multilayers are
changed drastically by insertion of Sn allowing to tailor the magnetic
properties of the Fe/Cr system in a new way.
MA 20.4 Do 11:00 H10
Temperature-dependent magnetotransport measurements of
epitaxial Fe/Cr/Fe systems with antiferromagnetic interlayer
coupling — •Matthias Buchmeier, Michael Breidbach,
Henning Dassow, Daniel E. Bürgler, and Peter Grünberg
— Institut für Festkörperforschung, Forschungszentrum Jülich GmbH,
52425 Jülich
We have prepared epitaxial Fe/Cr/Fe trilayers with antiferromagnetic
interlayer coupling on an Au(001)/GaAs(001) buffer-system. Lithographically
patterned thin stripes are characterized by current-in-plane magnetoresistance
(CIP-MR) measurements, for which the magnitude as well
as the in-plane direction of the external magnetic field are swept. The
temperature dependence (4–270 K) of the in-plane anisotropy, the interlayer
exchange coupling, and the giant and anisotropic magnetoresistance
(GMR and AMR) are quantitatively determined by simultaneously fitting
the angular and field dependence of the MR curves. The experimental
curves are nicely reproduced within a single domain model including fourfold
magnetocrystalline anisotropy and bilinear and biquadratic coupling
terms for temperatures above 50 K. Below 50 K, however, we observe an
anomaly which can be interpreted as an exchange bias (EB) effect with
an exchange anisotropy of the order of 5 mT. Possible origins for the
appearance of EB is a paramagnet-antiferromagnet phase transition of
the Cr spacer or an Fe-oxide layer on top of the uncapped sample with
a thickness of approximately 1 nm as determined by X-ray scattering.

Magnetismus Donnerstag
MA 20.5 Do 11:15 H10
Proximity effect of vanadium on spin-density wave magnetism
in Cr films — •Evgeny Kravtsov 1 , Björgvin Hjörvarsson 2 ,
Andreas Hoser 3 , Alexei Nefedov 1 , Florin Radu 1 , Arndt
Remhof 1 , and Hartmut Zabel 1 — 1 Institut für Experimentalphysik/Festkörperphysik,
Ruhr-Universisät Bochum, Bochum —
2 Department of Physics, Uppsala University, Uppsala, Sweden —
3 Institut für Kristallographie, RWTH-Aachen, Aachen
Spin-density wave (SDW) state in thin Cr films is known to be under
influence of proximity effects from neighboring layers. To date the main
attention has been given to effects arising from exchange interactions at
interfaces, for example, in Fe/Cr systems, and few papers are devoted to
other types of boundary conditions. Here we report on a combined neutron
and X-ray scattering study of proximity effects in Cr/V films where
the boundary conditions are due to V-Cr hybridization at interfaces. The
neutron measurements have been performed at the triple-axis spectrometer
UNIDAS in Forschungszentrum Jülich, the synchrotron measurements
at the ID20 beamline in ESRF. From the above experiments, we provide
evidence that the V/Cr interface causes a strong and long-range influence
on the SDWs behavior in Cr. The V-Cr interface hybridization changes
the SDW polarisation and propagation direction as well as the SDW period.
The Cr magnetic moment in Cr/V bilayers was found to decrease
quasi-linearly with temperature that is not observed so far in bulk Cr
and other Cr-based thin film systems. The research was supported by
SFB 491 and INTAS.
MA 20.6 Do 11:30 H10
Thin epitaxial films of the Heusler compound Co2Cr0.6Fe0.4Al —
•Gerhard Jakob 1 , Frederick Casper 1,2 , Virginie Beaumont 1,2 ,
Stefan Falk 1 , Hans-Joachim Elmers 1 , and Claudia Felser 2
— 1 Institut für Physik, Universität Mainz, Staudinger Weg 7, 55099
Mainz — 2 Institut für Anorganische und Analytische Chemie, Universität
Mainz, Düsbergweg 10-14, 55099 Mainz
A tunnel magnetoresistive element has recently been reported based
on thin polycrystalline films of the Heusler compound Co2Cr0.6Fe0.4Al
[1]. According to band structure calculations this material is half metallic,
i.e. there exists only one spin direction for the charge carriers at the
Fermi edge. We prepared thin epitaxial films of this compound in the
B2 structure on a-plane (1120) Al2O3 substrates by sputtering. Films
grown at high temperatures (T=600 o C) are fully epitaxial with the (110)
and (110) planes of the film parallel to the (1120) and (0001) planes of
the substrate, respectively. The films show nearly rectangular hysteresis
loops with coercitive fields of the order of 10mT. Magnetooptical Kerr
measurements show an in-plane anisotropy of the magnetization with the
easy axis in {001} direction. Hall measurements show a strong anomalous
Hall effect and a weak normal Hall voltage signalling the existence of a
compensated Fermi surface.
[1] K. Inomata et al., Jpn. J. Appl. Phys. 42, L419 (2003)
MA 20.7 Do 11:45 H10
Spin polarization of single-crystalline Co2MnSi films grown by
PLD on GaAs(001) — •W. Wang, W. Kuch, L. Chelaru, J.
Wang, Y. Lu, J. Barthel, M. Przybylski, and J. Kirschner —
Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle
Recent theoretical calculations have shown that the full-Heusler alloy
Co2MnSi is a promising candidate to be a half-metallic ferromagnet. In
this contribution we report on the growth, magnetic and electronic characterization
of single crystalline Co2MnSi thin films deposited by Pulsed
Laser Deposition (PLD) on GaAs(001) substrates. In situ Reflection High
Energy Electron Diffraction (RHEED) and Auger spectroscopy confirmed
the high-quality growth (in particular at 450K growth temperatures) and
stoichiometry. Spin-resolved photoemission measurements at BESSY-II
of the single-crystal Co2MnSi films reveal spin-resolved density of states
that are in qualitative agreement with recent band structure calculations.
However, the spin polarization of photoelectrons close to the Fermi level
is found to be at most 25%, in contrast to the predicted half-metallic behavior.
Moreover, the magnetic moments we obtained by sum rule analysis
of x-ray magnetic circular dichroism (XMCD) measurements of thin
Co2MnSi films are lower in comparison to what is predicted theoretically.
We suggest that these discrepancies may be attributed to a non-magnetic
surface region and/or partial chemical disorder in the Co2MnSi lattice.
MA 20.8 Do 12:00 H10
Resonante magnetische Röntgenstreuung an Co2MnGe-
Heusler-Einzelfilmen und -übergittern — •Johannes Grabis,
Alexei Nefedov, Andre Bergmann, Kurt Westerholt
und Hartmut Zabel — Institut für Experimentalphysik/
Festkörperphysik, Ruhr-Universität Bochum, 44780 Bochum
Halbmetallische, ferromagnetische Heuslerlegierungen wie Co2MnGe
besitzen ein großes Anwendungspotential im Bereich von spinelektronischen
Bauelementen. Gesputterte Einzelfilme und Übergitter
mit Au oder V als Zwischenschicht wurden mit Hilfe des magnetischen
Zirkulardichroismus (XMCD) und der resonanten magnetischen
Röntgenstreuung (XRMS) im Bereich der L2,3 Kanten von Co und Mn
untersucht. Während anhand der Absorptionsspektren die elemetspezifischen
Beiträge zum magnetischen Spin- und Bahnmoment berechnet
und die magneto-optischen Konstanten bestimmt werden können, bietet
die resonante Röntgenstreuung zusätzlich eine Möglichkeit der tiefenselektiven
Analyse der Schichtsysteme. Aus der spekulären Reflektivität
kann ein Magnetisierungstiefenprofil gewonnen werden. Die diffuse Streuung
liefert weitere Informationen über die Beschaffenheit der Grenzfläche
wie Rauhigkeiten und Korrelationslängen. Dieses Projekt wird gefördert
durch das BMBF, O3ZAE7BO.
MA 20.9 Do 12:15 H10
Magnetische Eigenschaften dünner epitaktischer Cobaltat- und
Manganat-Schichten — •Thorsten Schwarz 1,2 , Oswaldo Moran
1 , Dirk Fuchs 1 und Rudolf Schneider 1 — 1 Forschungszentrum
Karlsruhe, Institut für Festkörperphysik, D-76021 Karlsruhe —
2 Universität Karlsruhe, Fakultät für Physik, D-76128 Karlsruhe
Mit abnehmender Schichtdicke beobachtet man bei Cobaltat- und
Manganat-Schichten eine starke Änderung der magnetischen Eigenschaften.
Ferromagnetische Schichten, La0.7A0.3CoO3 (A = Ca, Sr, Ba) und
La2/3Ca1/3MnO3, zeigen beispielsweise eine starke Abnahme der Curie-
Temperatur mit abnehmender Schichtdicke, was sich mit einem Skalenverhalten
sehr gut beschreiben lässt. Weiterhin ist ebenfalls eine Reduktion
des effektiven magnetischen Sättigungsmomentes im Vergleich
zu Einkristall-Werten erkennbar. Zusätzliche Beiträge zur Anisotropie-
Energie aufgrund epitaktischer Verspannungen zeigen einen starken Einfluß
auf die Magnetisierungseigenschaften und könnten daher eine zentrale
Rolle für dieses Verhalten spielen. Die Schichtpräparation mittels
Laserablation sowie die Charakterisierung der strukturellen und
magnetischen Eigenschaften mittels Röntgenbeugung und DC-SQUID-
Magnetometrie werden vorgestellt und diskutiert.
MA 20.10 Do 12:30 H10
Sr2FeMoO6 Thin Film Preparation, Properties and Prospects
— •Nicole Auth 1 , Diana Sanchez 2 , and Gerhard Jakob 1 —
1 Johannes Gutenberg Universität, Mainz — 2 Instituto de Ciencia de Materiales
de Madrid, CSIC
Since the first report of room temperature magneto-resistance in polycrystalline
Sr2MoFeO6 (SFMO) this double-perovskite material has been
widely studied. Due to its high Curie temperature of 420 K and band
structure calculations predicting 100% spin polarisation, SFMO is a potential
candidate for spintronic devices. Yet most studies are concerned
with bulk material while the preparation of good quality thin films has
proven to be a non-trivial task.
We prepared epitaxial thin films of SFMO on SrTiO3 (100) substrates
by pulsed laser deposition. Differing from previous reports a postdeposition
annealing step in vacuum with a low oxygen partial pressure
was introduced. The structural, magnetic and transport properties are
studied in detail. We also investigated film growth on a Ba0.4Sr0.6TiO3
(BST) buffer layer and on DyScO3 substrates. Both types of seed crystals
offer a nearly perfect lattice match for the formation of the SFMO
thin film. While the DyScO3 substrate has a perfect c-axis orientation
the BST buffer layer exhibits a large angular spread of the crystallites
leading to a clear change in the magneto-transport properties.
We succeeded in growing samples with comparably smooth surface as
a prerequisite for multilayer preparation. For studying the TMR effect we
are working on nanoscale patterning of mesa-structures by a combination
of photolithography, focussed ion beam etching and e-beam lithography.

Magnetismus Donnerstag
MA 20.11 Do 12:45 H10
Epitaxial growth and ferroelectric and ferromagnetic properties
of La0.7Sr0.3MnO3 / Pb(Zr,Ti)O3 bilayers — •C. Thiele, K.
Dörr, T. Walter, K.-H. Müller, and L. Schultz — IFW Dresden,
Postfach 270116, 01171 Dresden
Magnetic and electrical properties of ferromagnetic manganites crucially
depend on lattice constants. Thus, it was suggested to control epitaxial
strain of thin films using the piezoeffect of a Pb(Zr,Ti)O3 (PZT)
toplayer [1]. Thereby, it seems possible to modify the resistivity in a wide
temperature range including 300 K, the magnetoresistance and magne-
MA 21 Bio- und molekularer Magnetismus
tization behavior of the ferromagnetic films. Pulsed laser deposition has
been utilized to investigate the growth of La0.7Sr0.3MnO3 / PZT bilayers
on single-crystalline substrates in order to obtain high structural quality
and undisturbed magnetic / ferroelectric properties. We discuss measurements
of resistance, magnetization and ferroelectrical polarization in
relation to the stoichiometry and microstructure of the bilayers. The latter
was investigated by x-ray diffraction, atomic force microscopy and
x-ray photoelectron spectroscopy.
This work is supported by DFG, FOR 520.
[1] H. Tabata et al., IEICE Trans. Electron. E80-C, 918 (1997).
Zeit: Donnerstag 10:15–12:15 Raum: H22
MA 21.1 Do 10:15 H22
Physics of a new copper-based triangular chain — •Jürgen
Schnack 1 , Hiroyuki Nojiri 2 , Paul Kögerler 3 , and Leroy
Cronin 4 — 1 Universität Osnabrück, Fachbereich Physik, D-49069
Osnabrück, Germany — 2 Dept. of Physics, Okayama University,
Tsushimanaka 3-1-1, Okayama, 700-8530 Japan — 3 Ames Laboratory,
Iowa State University, Ames, Iowa 50011, USA — 4 Dept. of Chemistry,
The University of Glasgow, Glasgow, G12 8QQ, UK
We report the synthesis and magnetic characterization of a new class
of one-dimensional chains of antiferromagnetically coupled copper triangles.
Since the copper triangles are coupled via hydrogen bonds, which
naively are assumed to be weak exchange pathways, one expects that
the chain shows a pronounced plateau at 1/3 of the saturation magnetization.
The high field magnetization curve shows, however, no plateau.
The observed magnetization and susceptibility curves are successfully interpreted
by a theoretical model, in which the inter- and intra-triangle
exchange parameters are of similar size. In effect the infinite chain turns
out to be an interesting example of a frustrated spin system with competing
interactions.
MA 21.2 Do 10:30 H22
High-field magnetization study of the S = 1/2 antiferromagnetic
Heisenberg chain [PM Cu(NO3)2(H2O)2]n with field-induced
gap — •S. Süllow 1 , A.U.B. Wolter 1 , H. Rakoto 2 , M. Costes 2 ,
A. Honecker 3 , W. Brenig 3 , A. Klümper 4 , H.-H. Klauss 1 , F.J.
Litterst 1 , R. Feyerherm 5 , and D. Jérome 6 — 1 IMNF, TU Braunschweig,
Braunschweig — 2 Laboratoire National des Champs Magnétique
Pulsés, Toulouse, France — 3 ITP, TU Braunschweig, Braunschweig,
— 4 FB Physik, Bergische Universität Wuppertal, Wuppertal — 5 HMI
GmbH, Berlin — 6 Université Paris-Sud, Orsay
We present a high-field magnetization study of the S=1/2 antiferromagnetic
Heisenberg chain [PM Cu(NO3)2(H2O)2]n. For this material, as
result of the Dzyaloshinskii-Moriya interaction and a staggered g-tensor,
the ground state is characterized by an anisotropic field induced spin
excitation gap and a staggered magnetization. Our data reveal the qualitatively
different behaviour in the directions of maximum and zero spin
excitation gap. The data are analyzed via exact diagonalization of a linear
spin chain with up to 20 sites and on basis of the Bethe ansatz equations,
respectively. For both directions we find very good agreement between
experimental data and theoretical calculations. We extract the magnetic
coupling strength J/kB along the chain directions to 36.3(5) K and determine
the field dependence of the staggered magnetization component
ms. This work has partially been supported by funds of the European
contract no. HPRI-CT-1999-40013 and by the DFG under contract no.
SU229/6-1.
MA 21.3 Do 10:45 H22
Observation of a transverse magnetization in the S=1/2 antiferromagnetic
chain [PM·Cu(NO3)2·(H2O)2]n by 13 C-NMR —
A.U.B. Wolter 1 , P. Wzietek 2 , D. Jerome 2 , S. Süllow 1 , F.J. Litterst
1 , A. Honecker 3 , W. Brenig 3 , R. Feyerherm 4 , and •H.-H.
Klauss 1 — 1 Institut für Metallphysik und Nukleare Festkörperphysik,
TU Braunschweig — 2 Laboratoire de Physique des Solides, Universite
Paris-Sud, Orsay, France — 3 Institut für Theoretische Physik, TU Braunschweig
— 4 Hahn-Meitner-Institut, Berlin
We present 13 C-NMR studies of the static and dynamic magnetic properties
of the S=1/2 antiferromagnetic chain [PM·Cu(NO3)2·(H2O)2]n. In
this system the spin-orbit interaction gives rise to an anisotropic magnetic
field induced spin excitation gap. The microscopic model used to
describe the thermodynamic properties (M. Oshikawa and I. Affleck, PRL
79 2883) proposed the existence of a staggered magnetization component
transverse to the applied field which cannot be measured macroscopically.
We measured the local susceptibility via the NMR frequency shift
at three different carbon sites in the pyrimidine molecule as a function
of temperature and magnetic field orientation. The transverse staggered
magnetization is identified as a low temperature deviation from the linear
correlation between local and global susceptibility. The observed magnitude
and temperature dependence are consistent with the theoretical
model. The spin excitation gap is determined from the temperature dependence
of the T1 relaxation rate. These measurements reveal additional
excitations in the gap.
MA 21.4 Do 11:00 H22
Charge-induced modulation of magnetic interactions in a
[2 × 2] metallo-organic grid-complex — •Christian Romeike 1 ,
Maarten R. Wegewijs 1 , Wolfgang Wenzel 2 , and Herbert
Schoeller 1 — 1 Institut für Theoretische Physik A, RWTH Aachen,
52045 Aachen — 2 Institut für Nanotechnologie, Forschungszentrum
Karlsruhe, Postfach 3640, 76021 Karlsruhe
We study the electronic spin and charge degrees of freedom of a [2×2]transition
metal-grid complex cation at different stages of its reduction[1]
in a phenomenological low temperature model. We show that extra electrons
on the bridging ligands can drastically change the coupling of the
spins on the metal sites and lead to maximal total spin states of the
molecular complex (spin of unpaired electrons on the metals and ligands)
due to the Nagaoka mechanism [2]. For a low-spin Fe 2+ -[2×2]-grid
electrons can move between the ligands using an empty orbital on the
metal as a bridge. In contrast to this, for a low-spin Co 2+ -[2 × 2]-grid
the metal bridge contains a localized electron which can interact or exchange
with the passing electrons. The presence of a localized spin on
each bridging metal-ion in the case of Co 2+ has two main effects: (1) the
total spin achievable in the fully polarized Nagaoka state is larger and (2)
the threshold Coulomb interaction required to achieve this state can be
diminished to values close to those of Fe only if direct exchange coupling
between the metal-ions and ligands is taken into account. It has to be of
the same order as the exchange coupling obtained in perturbation theory.
[1] M.Ruben et al., Chem.Eur.J. 2003, 9, No.1
[2] Y. Nagaoka, Phys. Rev.147, 392 (1966)
MA 21.5 Do 11:15 H22
Magnetic correlations in oxalate spin ladders — •C. Mennerich
1 , M. Bröckelmann 1 , J. Kreitlow 1 , A. Wolter 1 , S.
Süllow 1 , F.J. Litterst 1 , R. Klingeler 2 , B. Büchner 2 , D.-J.
Price 3 , and H.-H. Klauss 1 — 1 Institut für Metallphysik und Nukleare
Festkörperphysik, TU Braunschweig — 2 Leibniz-Institut für Festkörperund
Werkstoffforschung, Dresden — 3 Department of Chemistry, Univ.
of Southampton, United Kingdom
We present studies of the magnetic behaviour in the isostructural spin
ladder materials Na2T2(C2O4)3(H2O)2 with T= Ni, Co, Fe, Mn (J. Chem.
Soc., Dalton Trans. 2000, 3566 ). Here the oxalate (C2O4) 2− molecule acts
as the bridging element in the rungs and legs of the transition metal ladder.
We performed magnetic susceptibility and high field magnetization
as well as Moessbauer spectroscopy (Fe system only). The susceptibility
of all systems shows a pronounced maximum between 10 and 25 K indicating
an antiferromagnetic interaction. The data can be described using
a dimer model representing two metal centers in the 2+ high spin state
with a dominant magnetic interaction along the rungs of the ladder. An

Magnetismus Donnerstag
additional weak interaction along the legs is treated in mean field approximation.
Moessbauer spectroscopy on the Fe compound revealed a
temperature dependent electric field gradient (EFG) due to crystal field
splitting and prove a Fe(II) S=2 configuration. No magnetic order is
found down to 2K.
MA 21.6 Do 11:30 H22
ESR analysis of the cyclic cluster [Na@Fe6(tea)6]·ClO4·2MeOH
— •Ilka Keilhauer 1 , Bernd Pilawa 1 , Danira Marinov 2 , Arthur
Grupp 3 , and Stefan Knorr 3 — 1 Physikalisches Institut, Universität
Karlsruhe (TH), D-76128 — 2 Anorganische Chemie, LMU, D-81377
München — 3 2. Physikalisches Institut, Universität Stuttgart,D-70550
Stuttgart
The six Fe III -ions of Na@Fe6(tea)6 (1) are antiferromagnetically coupled.
The magnetic anisotropy can be analysed by ESR measurements.
The crystal structure of (1) is triclinic with two magnetically nonequivalent
Fe6 clusters per unit cell. This gives rise to complicated spectra
composed of the resonances of the two clusters X and Y. It will be shown
that the splittings of the first excited states S=1,2 and 3 and the orientation
of the molecular symmetry axes can be determined for both clusters
by the analysis of the ESR spectra taken at 7K and 20K. The parameters
of the single ion on-site anisotropy are d/kB=−0.2875±0.0023K and
d/kB=−0.2921±0.0035K, respectively.
The relative angle between the cluster axes of 69.7 ◦ ±1 ◦ determined at
low temperature deviates considerably from the room temperature value
of 54 ◦ . This might indicate a structural phase transition which can be
caused by the temperature dependent motion of the ClO4 tetraeders.
MA 21.7 Do 11:45 H22
1 H-NMR on Fe2(hpdta), Fe4(hpdta)2 and Fe6(hpdta)3 clusters
— •Roland Leppin and Bernd Pilawa — Physikalisches Institut,
Universität Karlsruhe (TH)
1 H-NMR measurements on cyclic Fe6 clusters have shown the importance
of the energy level scheme for the nuclear relaxation. The investigation
of the Fe2(hpdta) dimer is an interesting approach for a better
understanding of the spindynamics, as it can be used as a building block
MA 22 Spinabhängiger Transport I
for more complex clusters like the Fe4(hpdta)2 and Fe6(hpdta)3 systems,
where the metal ions form a square and roof-like structure, respectively.
The 1H T −1
1 rate measurements at 52 MHz in a magnetic field of 1.2
T show differences between the systems. For the Fe2 dimer, the T −1
1 rate
increases monotonously. For Fe4 it starts at a comparatively high value
at low temperatures, goes down to a minimum around 15 K and increases
again with increasing temperature. For the Fe6 sample there is a broad
maximum around 30 K which reminds the results obtained for the cyclic
Fe6(tea)6 samples.
MA 21.8 Do 12:00 H22
Magnetic Resonance Spectroscopic Studies of Magnetization
Relaxation in Single-Crystalline Mn12Ac — •Joris van
Slageren 1 , Suriyakan Vongtragool 1 , Nadeschda Kirchner 1 ,
Martin Dressel 1 , Alexander Mukhin 2 , and Boris Gorshunov 2
— 1 1. Physikalisches Institut, Universität Stuttgart, Stuttgart, Germany
— 2 General Physics Institute, Russian Academy of Sciences, Moscow,
Russia
New, spectroscopic experiments on the magnetization relaxation of the
single molecule magnet Mn12Ac are presented. These studies were performed
using frequency domain magnetic resonance spectroscopy on single
crystalline samples. Special attention is paid to the consequences of
the known distribution of zero-field splitting parameters on the relaxation
dynamics. It is also shown, that the resonance spectrum of the
magnetized sample recorded in zero external field has a peculiar shape in
Faraday geometry, due to a combination of the resonance phenomenon
and the Faraday effect. The nonmagnetized sample shows a normal spectral
shape. In this way it is possible to study magnetization relaxation
in zero external field. Finally, we have succeeded in performing selective
magnetodipolar excitations on one side of the potential energy double
well, by using circularly polarized radiation. This offers another possibility
for studying magnetization relaxation in zero external field, which is
not possible when using linearly polarized radiation. These studies are
important to investigate the role of accidental transverse magnetic field
on the relaxation behaviour of single molecule magnets.
Zeit: Donnerstag 12:15–13:00 Raum: H22
MA 22.1 Do 12:15 H22
Imaging tunnel magnetoresistance related to magnetic microdomain
distribution along a La2/3Ca1/3MnO3 grain boundary
— •Wagenknecht Michael 1 , Timo Nachtrab 1 , Markus Turad
1 , Dieter Koelle 1 , Reinhold Kleiner 1 , Jan Boris Philipp 2 ,
and Rudolf Gross 2 — 1 Physikalisches Institut-Experimentalphysik
II, Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen,
Germany — 2 Walther-Meißner-Institut, Bayerische Akademie der
Wissenschaften, Walther-Meißner Straße 8, D-85748 Garching, Germany
We present electrical transport measurements across an artificial grain
boundary in a La2/3Ca1/3MnO3 thin film grown on a 24 ◦ bicrystal SrTiO3
substrate. In the ferromagnetic-metallic phase below Tc ≈ 220K the grain
boundary acts as a tunneling barrier. Applying an in-plane magnetic field
up to 40mT parallel to the grain boundary we observe several discrete
jumps in the magnetoresistance across the barrier. We explain the resistance
steps by formation of microdomains along the grain boundary.
Using low temperature laser scanning microscopy allows us to image the
tunnelling conductance distribution along the grain boundary for the
discrete resistance steps. By this we are able to map the fraction of parallel/antiparallel
aligned microdomains versus magnetic field and to correlate
the domain distribution with the overall resistance across the grain
boundary.
MA 22.2 Do 12:30 H22
Magnetoresistance and resistance relaxation of La0.7Ca0.3MnO3
step-edge junctions in pulsed magnetic fields up to 50 T — •K.
Dörr 1 , N. Kozlova 1 , M. Ziese 2 , M. Kozlov 1 , K.-H. Müller 1 ,
and L. Schultz 1 — 1 IFW Dresden, Postfach 270116, 01171 Dresden
— 2 Division of Superconductivity and Magnetism, University of Leipzig,
Linnéstrasse 5, 04103 Leipzig
The magnetoresistance (MR) of step-edge junctions in La0.7Ca0.3MnO3
films [1] has been investigated in magnetic fields up to 47 T between
4.2 K and 125 K. Step-edge junctions show similar electrical properties
as grain boundaries [1], including the low-field MR attributed to spin-
polarized tunneling. A tendency towards saturation in high fields and a
large hysteresis with pronounced remanent MR are characteristic results.
Time-dependent resistance data R(t) recorded after field pulses of 7 T
follow a logarithmic law for 30 ms < t

Magnetismus Donnerstag
MA 23 Hauptvorträge - Symposium Magnetic Shape Memory Alloys (zusammen mit M)
Zeit: Donnerstag 10:15–11:45 Raum: H23
Hauptvortrag MA 23.1 Do 10:15 H23
Martensite: Introductory Remarks — •E.F. Wassermann — Experimentalphysik,Universität
Duisburg-Essen, D-47048 Duisburg,
As a general introduction to the field of magnetic shape memory alloys
(MSMA), we briefly define what is a martensitic phase transformation
(MPT) in general and what are the characteristic features. We then focus
on the metallic elements and systems, where we distinguish between
Fe-based systems, in which the austenite has fcc structure and the martensite
is bcc (or bct), and the Hume-Rothery systems, in which the
opposite structural behavior is observed. Typical for the latter systems is
the phonon softening occurring at certain q-vectors of the Brillouin Zone
at temperatures above Ms. We will briefly discuss these precursor effects
and their relevance to MPTs. We will then highlight in general the shape
memory behavior, the one way-, the two way- and the all round-effect,
and briefly touch the present microscopic knowledge of these effects. Finally,
a short overview of practical applications of SMA will be given.
Hauptvortrag MA 23.2 Do 10:45 H23
Ferromagnetische Formgedächtnis Legierungen — •Manfred
Wuttig — Stiftung Caesar, Ludwig-Erhard-Allee 2, 53175 Bonn — Department
of Materials Science, University of Maryland, MD,USA
Ferromagnetische Formengedächtnis Legierungen (FGDLn) wurden
Mitte der 80iger Jahre interessant als bekannt wurde, dass solche Materialien
eine außerordentlich große ’ Magnetostriktion‘ aufweisen. Für die
am meisten untersuchten und am besten bekannten Materialien, basierend
auf der Heusler Legierung Ni2MnGa, kann die magnetfeld-indizierte
Dehnung 10 % erreichen. Die explosionsartige Entwicklung in diesem
Feld hat dazu geführt, dass im Moment FGDLn bestehend aus fast allen
Kombinationen von (Fe,Ni,Co)2Mn(Ga,Al) bekannt und teilweise charakterisiert
sind. Andere wichtige Elemente sind Pt und In. Die Stabi-
lität der Legierungen, i.e. die martensitischen Umwandlungstemperatur,
folgt der mittleren Elektronenkonzentration und die Curie Temperatur
in etwa dem bekannten Bethe-Slater Zusammenhang. Beide Temperaturen
variieren in entgegengesetzter Richtung, wie schon seit Zener bekannt.
Die ’ Magnetostriktion‘ der FGLn beruht auf der magnetfeldinduzierten
Bewegung der Zwillingswände zwischen martensitischen Varianten.
Um diese Art der (Um)magnetisierung gegenüber Drehungen
der Sättigungsmagnetisierung zu bevorzugen ist eine große Kristallanisotropie
nötig wie auch an Ni2MnGa gemessen. Die FGDLn haben Anwendungspotential
als Sensoren und Aktoren obwohl ihre magnetische
Energiedichte besondere Vorkehrungen für die letzteren erfordert. Der
Vortrag wird diese und mehr ins Einzelne gehende Tatsachen enthalten.
Hauptvortrag MA 23.3 Do 11:15 H23
The magnetic, structural and dynamical properties of the
Heusler alloys — •Alexey Zayak and Peter Entel — Theoretische
Tieftemperaturphysik, Universität Duisburg-Essen, 47048
Duisburg
We have performed first-principles calculations of a series of Heusler
compounds. In particular, the ferromagnetic alloys Ni2MnGa and
Ni2MnAl are of interest because of their shape-memory properties. The
ab-initio methods allow an accurate description the cubic, tetragonal and
orthorhombic as well as the long-range modulated structures. The latter
were found to be critically important for the stability of the martensitic
states allowing for c/a ratios smaller then 1. In addition we have calculated
the phonon spectra. The high symmetry cubic structure L21 turned
to be unstable at zero temperature, both for Ni2MnGa and Ni2MnAl, due
to the transverse acoustic mode which softens with the wave vector close
to 1/3[110](2π/2). The obtained results are analysed in terms of the electronic
configuration and charge transfer.
MA 24 Symposium Magnetic Shape Memory Alloys (zusammen mit M)
Zeit: Donnerstag 11:45–13:15 Raum: H23
MA 24.1 Do 11:45 H23
Electronic and Magnetic Properties of Heusler-type Magnetic
Shape Memory Alloys — •Mehmet Acet, Thorsten Krenke,
and Eberhard F. Wassermann — Experimentalphysik, Universität
Duisburg-Essen, 47048 Duisburg
The presence of large magnetic field ( 1 Tesla) induced strains ( 6
percent) found in the martensitic state of the magnetic shape memory
Heusler compound Ni2MnGa is believed to be due to twin boundary
motion. The attractive technological implications of this property has
provided the motivation for intensive research in the field of magnetic
shape memory. Efforts to improve the mechanical properties of otherwise
brittle Ni2MnGa have been paralleled by theoretical and experimental
research aimed at understanding the mechanism of the magnetic shape
memory effect and predicting the existence of other Heusler based systems
that may well exhibit this effect. By examining the electron concentration
dependence of the martensitic transformation temperatures in
various Heusler systems, it is possible construct a method with which it
is possible to choose sample systems that can be potential candidates for
magnetic shape memory alloys. We show by magnetization measurements
and microscopy that a series of ferromagnetic ternary and quasiternary
Heusler based compounds such as Ni-Co-Al and Ni-Mn-In-Al can undergo
martensitic transformations and have a large magnetocrystalline
anisotropy in the martensitic state.
MA 24.2 Do 12:00 H23
Influence of composition and heat treatment on structure
and magnetic properties of NiMnGa shape memory alloys
— •Stefan Roth 1 , Norbert Mattern 1 , and Andrea Böhm 2
— 1 IFW Dresden, POB 270116, D-01171 Dresden — 2 FhG IWU,
Bamberger Strasse 7, D-01187 Dresden
Ferromagnetic Ni(100-x-y)Mn(x)Ga(y) - alloys were prepared by arc
melting pure constituents with (x,y) = (26,22) and (29 or 30, 20 or 21).
The Curie temperature and the martensitic transformation temperature
were determined by a Faraday magnetometer and differential scanning
calorimetry, respectively. Magnetisation as a function of field and temperature
was measured by a vibrating sample magnetometer and the
crystalline structure was investigated using XRD. The magnetic anisotopy
field was derived from the field dependence of the magnetisation.
Annealing above the order temperature and cooling at different rates
causes changes in the magnetic properties and the transformation behaviour
which are correlated to changes in the degree of order, changes
in the lattice parameters and in the amount of remaining austenite.
MA 24.3 Do 12:15 H23
A study of ferromagnetic NiMnGa sputtered films including
shape memory properties — •Holger Rumpf 1 , Corneliu Craciunescu
2 , Manfred Wuttig 1,3 , and Eckhard Quandt 1 — 1 Stiftung
Caesar, Ludwig-Erhard-Allee 2, 53175 Bonn, D — 2 Politehnica University
of Timisoara, Romania — 3 Department of Materials Science, University
of Maryland, College Park, MD, U.S.A.
Off-stoichiometric Ni2MnGa thin films were deposited by DC
magnetron sputtering technique. Freestanding thin films as well as
Ni50Mn30Ga20/Mo composites were fabricated. Rapid thermal annealing
at temperatures equal or higher 500C led to polycrystalline films
revealing the reversible martensitic transformation. Transformation temperatures
and work output of the transformation were strongly influenced
by the temperature of the annealing process as demonstrated by DSC results
and cantilever deflection mode measurements. Magnetization experiments
disclose a Curie temperature of 103C in accordance with results
from NiMnGa single crystals. The shape of the ferromagnetic hysteresis
is significantly effected by the annealing temperature. Magnetic field induced
strains of freestanding films biases by an external load of several
MPa revealed elongations of ca. 0.1 per cent at 200 mT.

Magnetismus Donnerstag
MA 24.4 Do 12:30 H23
MAGNETIC-FIELD-INDUCED STRAINS IN FERROMAG-
NETIC SHAPE-MEMORY ALLOYS — •U.K. Rößler 1 ,
A.N. Bogdanov 1,2 , A. DeSimone 3 , S. Müller 2 , and F. Otto 4
— 1 Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden,
Postfach 270116, 01171 Dresden — 2 Max-Planck-Institut für Mathematik
in den Naturwissenschaften, Inselstr. 22 - 26, 04103 Leipzig
— 3 International School for Advanced Studies, via Beirut 2-4, 34014
Trieste — 4 Institut für Angewandte Mathematik, Universität Bonn,
Wegelerstr. 10, 53115 Bonn
Phenomenological equations for multivariant states in a ferromagnetic
martensitic materials have been derived [1]. We apply the theory to describe
the evolution of a tetragonal twinned martensitic microstructure
consisting of two variants. Analytical solutions for the components of the
strain tensor can be obtained as functions of external stresses and the
volume fractions of the twin variants. Equilibrium magnetic parameters
have been calculated within phase theory approximation and for a model
of stripe domains. Critical lines between multivariant (twinned) states
and the two types of homogeneous states and corresponding field-stress
phase diagrams have been calculated. Sufficiently high stresses can block
multivariant states. Then, the transition between the two homogeneous
states occurs as a first-order process. Time-dependent processes can be
simulated based on a kinetic equation within this phenomenological theory.
[1] A.N. Bogdanov, A. DeSimone, S. Müller, U.K. Rößler, J. Magn.
Magn. Mater. 261, 204 (2003).
MA 24.5 Do 12:45 H23
Modulated martensitic structures in MBE-grown NiMnAl
magnetic shape memory alloys — •Sigurd Thienhaus 1 , Ralf
Hassdorf 1 , Jürgen Feydt 1 , Rene Borowski 1 , Markus Boese 2 ,
and Michael Moske 1 — 1 Forschungszentrum caesar, 53175 Bonn —
2 Universität Bonn, Institut für Anorganische Chemie, 53117 Bonn
Composition spreads close to the Heusler alloy Ni2MnAl were grown
onto four-inch wafer substrates by molecular beam epitaxy. Compositional
variations of around 10 at.% relative to each constituent enable a
direct comparison of the chemical-structural relationship with respect to
martensitic transformation and to magnetic ordering as well as an efficient
identification of the emerging phase stability regions. In our study,
MA 25 Hauptvorträge Thiaville / Kläui
we set the primary focus on the structural aspects of the transformation
behavior as confirmed by X-ray microdiffraction in combination with a
specially designed heating stage. Notably, high-resolution cross-sectional
TEM imaging of the respective composition areas reveals a laminated
two-phase martensitic structure within the single grains, identified as
a sequence of 2M and 14M variants. Stress relief upon transformation
is observed during thermal processing in a bending-beam stress apparatus
and ranges from 50 to 200 MPa depending on the composition.
Vibrating-sample magnetometry so far suggests magnetic ordering to occur
well below room temperature. In this context, the compositional and
microstructural aspects of the phase stabilities will be discussed.
MA 24.6 Do 13:00 H23
Ab-initio Struktur-Simulationsrechnungen zur magnetischen
Formgedächtnislegierung Ni-Mn-Al — •Thomas Büsgen 1 ,
Jürgen Feydt 1 , Ralf Hassdorf 1 , Sigurd Thienhaus 1 , Markus
Boese 2 , Alexey Zayak 3 , Peter Entel 3 und Michael Moske 1
— 1 Center of Advanced European Studies and Research (caesar),
Ludwig-Erhard-Allee 2, 53175 Bonn, Germany — 2 Universität Bonn,
Institut für Anorganische Chemie, 53117 Bonn, Germany — 3 Gerhard-
Mercator-Universität Duisburg-Essen, Lotharstr. 1, 47048 Duisburg,
Germany
Es werden die Ergebnisse von ab-initio Berechnungen, basierend auf
DFT und PAW Basissätzen, zur magnetischen Formgedächtnislegierung
Ni-Mn-Al vorgestellt. Dabei wurde die Abhängigkeit der Stabilität und
physikalischer Eigenschaften von der Zusammensetzung verfolgt. Es kann
gezeigt werden, dass der Grundzustand der Legierung bei einer festen
Ni-Konzentration von 50 at.% im Bereich von 14 bis 31 at.% Mn ferromagnetisch
ist. Die magnetische Eigenschaften werden u.a. anhand der
Zustandsdichten erklärt.
Desweiteren wurden die martensitischen Phasen 2M, 10M und 14M
mit langperiodischen Modulationen für Ni2MnAl simuliert. Alle untersuchten
Martensitphasen sind metastabil für die exakt stöchiometrische
Zusammensetzung. Ihre Stabilität wird in Bezug zu Zustandsdichten und
Ladungsverteilung zwischen den Atomen diskutiert. Aus den relaxierten
Strukturdaten wurden Röntgendiffraktogramme berechnet, die zusammen
mit TEM-Untersuchungen die Existenz der 2M- und 14M-Phase in
Proben belegen, die mittels Molekular-Strahl-Epitaxie hergestellt wurden.
Zeit: Donnerstag 14:00–15:00 Raum: H10
Hauptvortrag MA 25.1 Do 14:00 H10
The physics of magnetic domain wall motion in nanostructures
— •André Thiaville, Yoshinobu Nakatani, and Jacques Miltat
— CNRS-Uni. Paris-sud, Lab. physique des solides, 91405 Orsay, France
This talk will present our work on the domain wall motion in lithographically
defined flat nanowires (thickness 5-10 nm, width 100-200 nm).
These structures show domain walls and a dynamic behaviour that are
slightly more complex than a one-dimensionnal (1d) solution, whose prototype
is the Walker theory for a 1d Bloch wall. First I will discuss field
driven propagation (field along the wire axis), which is characterized by
the magnetization precession around the applied field. As the wire is too
wide to be 1d the so-called Walker breakdown, where a continuous precession
of the magnetic moment of the domain wall sets in, is shown to
be replaced by the periodic injection and disappearance of an antivortex.
This phenomenon is very sensitive to the edges perfection : a wire having
rough edges will not undergo this mechanism and hence support fast wall
propagation at high fields. Then I will explain our study of the domain
wall motion induced by a current in the nanowire, due to the spin-transfer
torque. As the form of this torque is not yet fully agreed on, especially
in the wire geometry, I will present calculations incorporating different
formulations of this torque.
Hauptvortrag MA 25.2 Do 14:30 H10
Magnetotransport and current induced domain wall propagation
in ring structures with constrictions — •Mathias Kläui 1,2 ,
C. A. F. Vaz 2 , J. A. C. Bland 2 , L. J. Heyderman 3 , W. Wernsdorfer
4 , and U. Rüdiger 1 — 1 Universität Konstanz, Fachbereich
Physik, 78457 Konstanz, Deutschland — 2 Cavendish Laboratory, Madingley
Road, Cambridge, CB3 0HE, UK — 3 LMN, Paul Scherrer Institut,
5232 Villigen-PSI, Schweiz — 4 Laboratoire Louis Neel-CNRS, BP 138,
38274 Grenoble, Frankreich
The key to using magnetic nano-elements in applications is the presence
of well-defined remanent states and reproducible switching. A possible
geometry that fulfills these criteria is the ring geometry where due to
the high symmetry particularly simple states and switching occur [1]. In
addition to the flux-closure vortex state, the high-moment ’onion state’
was observed, which is characterized by two transverse or vortex headto-head
domain walls [1].
Owing to the constant curvature, rings have been found to be an ideal
geometry for probing domain wall properties. Using magnetoresistance
measurements, the behaviour of the different types of domain walls at
constrictions has been investigated (attraction or repulsion). Furthermore
the change of resistance as a domain wall moves into a constriction
can be accounted for by the change in spin structure. Finally, high current
densities are used to displace head-to-head domain walls. Such currentinduced
domain wall propagation is explained by a spin-torque effect. [2]
[1] M. Kläui et al., Topical Review in J. Phys. Condens. Matter 15, 985
(2003) [2] M. Kläui et al., Appl. Phys. Lett. 83, 105 (2003)

Magnetismus Donnerstag
MA 26 Mikro- und nanostrukturierte Materialien
Zeit: Donnerstag 15:15–18:45 Raum: H10
MA 26.1 Do 15:15 H10
MAGNETIC PROPERTIES OF BULK AMORPHOUS Fe-
Cr-Mo-Ga-P-C-B ALLOYS — •Mihai Stoica 1 , Stefan Roth 1 ,
Jürgen Eckert 1,2 , and Ludwig Schultz 1 — 1 IFW Dresden, Institut
für Metallische Werkstoffe, Postfach 270016, D-01171 Dresden, Deutschland
— 2 TU Darmstadt, FG Physikalische Metallkunde, Petersenstrasse
23, D-64287 Darmstadt, Deutschland
The Fe65.5Cr4Mo4Ga4P12C5B5.5 bulk amorphous alloy exhibits good
soft magnetic properties. However, the maximum achievable diameter of
these Fe-based alloys is limited to only a few millimeters. Amorphous
rods with diameters of 1.5-3 mm and discs with 10 mm diameter and
1 mm thickness were prepared by copper mold casting. The coercivity
of as-cast rods and disc is around 5 A/m, decreasing up to less than 1
A/m upon annealing. The coercivity is expected to depend on the volume
fraction of crystalline inclusions. The saturation polarization is around
0.8 T and the magnetostriction constant λ = 9 ppm.
On the other hand, bulk amorphous samples with larger sizes or various
shapes can be prepared by powder metallurgical methods, i.e. mechanical
alloying or ball milling combined with subsequent consolidation of
the resulting powders. The aim of present work is to compare the magnetic
properties of as-cast amorphous samples obtained by copper mold
casting with samples prepared by hot pressing of ball milled melt-spun
ribbons.
MA 26.2 Do 15:30 H10
Domain observations in nanocrystalline ribbons — •Sybille Flohrer
1 , Rudolf Schäfer 1 , Ludwig Schultz 1 und Giselher Herzer
2 — 1 Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden,
P.O. Box 270016, D-01171 Dresden, Germany — 2 Vacuumschmelze
GmbH & Co. KG, Grüner Weg 37, D-63450 Hanau, Germany
Soft-magnetic nanocrystalline ribbons of the FeCuNbSiB type consist
of 10-15 nm wide crystalline grains of ferromagnetic FeSi, which are magnetically
coupled by a ferromagnetic metallic glass matrix. The exchange
coupling between the two magnetic phases leads to a seemingly uniform
magnetic material from the viewpoint of magnetic microstructure.
Kerr-microscopy observations on a variety of Fe73Cu1Nb3Si16B7 ribbons
treated under different conditions are presented. Magnetization
processes of annealed ring cores with strong and weak permeability are
compared, and the domains in ribbons with creep- and magnetizationinduced
anisotropy have been observed. Differences in the domain behavior
between high and low permeability material are explained in terms of
the random anisotropy model considering the ratio of average magnetocrystalline
and induced anisotropy.
MA 26.3 Do 15:45 H10
Nanocrystalline hard magnetic FePt powders — •Julia Lyubina
1 , Oliver Gutfleisch 1 , Nora M. Dempsey 2 , Axel Handstein
1 , Karl-Hartmut Müller 1 , and Ludwig Schultz 1 — 1 IFW
Dresden, P.O. Box 270016, D-01171 Dresden, Germany — 2 Laboratoire
Louis Neel, 25 Avenue des Martyrs, BP 166, 38042, Grenoble, France
The ordered FePt (L10) compound possesses high magnetocrystalline
anisotropy (K1 = 6.6 MJm −3 ) and saturation polarisation (Js = 1.43
T), as well as excellent mechanical properties and corrosion resistance.
Thus, it is a promising candidate for permanent magnet applications,
for instance in micro-electromechanical systems (MEMS). In the present
work we report on the preparation of nanocrystalline hard magnetic
Fe50+xPt50−x (x = 0; 5; 10.5) powders by mechanical milling at liquid
nitrogen temperature followed by annealing. The evolution of phase composition,
chemical order, and magnetic properties is studied as a function
of composition and annealing conditions. All the powders contain a mixture
of highly ordered L10 FePt (up to 90 vol. %), disordered FePt, as
well as Fe3Pt and FePt3 phases. The highest coercivity of µ0JHc = 0.7 T
was achieved in the Fe50Pt50 powder annealed at 450 0 C for 48 h, which
is substantially higher compared to that of conventional bulk FePt. The
microstructure of the annealed FePt powders has a lamellar character
with a typical grain size of about 40 nm. The coercivity increases with
increasing volume fraction of the L10 phase and degree of chemical order.
The authors are grateful to the DFG SFB 463 for financial support.
MA 26.4 Do 16:00 H10
Deep-submicron magnetic tunnel junctions patterned with
hydrogen silsesquioxane — •M. Krämer 1 , R. Adam 1 , A. van der
Hart 1 , H. Kohlstedt 2 , M. Weides 2 , H. Dassow 2 , and J. Schelten
1 — 1 Institut für Schichten und Grenzflächen, Forschungszentrum
Jülich GmbH, D-52425 Jülich — 2 Institut für Festkörperforschung,
Forschungszentrum Jülich GmbH, D-52425 Jülich
Nanostructuring of magnetic thin films is a necessary step in the investigation
of physical phenomena like single domain behaviour or superparamagnetism,
as well as, in the development of ultrasmall magnetic
tunnel junctions (MTJs) for high density magnetic memories. The aim
of our work is to fabricate magnetic tunnel junctions with lateral dimensions
far below one micrometer. To reach this goal a negative tone resist
based technique for the fabrication of deep-submicron magnetic tunnel
junctions using hydrogen silsesquioxane (HSQ) has been devised. HSQ is
an inorganic three dimensional polymer exhibiting SiO2-like properties
after annealing and was reported to behave as a negative e-beam resist
with a resolution better than 50 nm. This was used to pattern magnetic
trilayers into lines with a minimum width smaller than 60 nm connected
to external bonding pads. MTJs were then formed by placing a second
line across the first after edge isolation. Magnetoresistance measurements
performed on MTJs smaller than 100 nm are presented.
MA 26.5 Do 16:15 H10
Magnetic recording on nanostructures — •Manfred Albrecht 1 ,
Charles T. Rettner 2 , Andreas Moser 3 , Margaret E. Best 3 ,
and Bruce D. Terris 3 — 1 University of Konstanz, Dept. of Physics,
P.O.Box M631, D-78547 Konstanz, Germany — 2 IBM Almaden Research
Center, 650 Harry Road, San Jose, CA 95120, USA — 3 Hitachi San Jose
Research Center, 650 Harry Road, San Jose, CA 95120, USA
The creation of lithographic magnetic nanostructures for single-bit
data storage is recognized as a promising approach to overcoming the
areal density limit for magnetic recording imposed by superparamagnetism
[1].
Isolated tracks of magnetic single-domain nanostructures with lateral
sizes of up to 30 nm have been fabricated by patterning perpendicular
Co70Cr18Pt12 continuous films using focused ion beam lithography. We
demonstrate writing and reading of individual nanostructures using a
scanning magnetoresistive microscope. We present results on transition
position jitter and signal-to-noise ratio (SNR) for nanostructure arrays
and compare them with those on equivalent unpatterned strips of the media.
We observe that patterning dramatically reduces jitter and improves
SNR, which is independent of track width [2]. Moreover, the synchronization
requirements needed for writing bits in patterned media was
investigated and a novel type of magnetic pattern for servo control was
introduced [3].
[1] D. Weller and A. Moser, IEEE Trans. Magn. 35, 4423 (1999).
[2] M. Albrecht et al., Appl. Phys. Lett. 81, 2875 (2002).
[3] M. Albrecht et al., Appl. Phys. Lett. 83, (2003) in press.
MA 26.6 Do 16:30 H10
Lorentzmikroskopische Untersuchungen an Permalloy-
Kreisringen — •Thomas Uhlig, Christian Dietrich und Josef
Zweck — Institut für Experimentelle und Angewandte Physik,
Universität Regensburg, Universitätsstr. 31, 93053 Regensburg
Ringförmige magnetische Strukturen im µm-Bereich wurden in den
vergangenen Jahren verstärkt untersucht [1], da sie als potentielle Kandidaten
für die Verwirklichung magnetoresistiver Speicherelemente gelten
[2]. Die besondere Eignung folgt aus dem minimalen Streufeld und den
definierten Magnetisierung- und Schaltzuständen.
Durch den Einsatz der differentiellen Phasenkontrastmikroskopie
(DPC) [3] am Transmissionselektronenmikroskop kann sowohl die
Domänenkonfiguration als auch die Hysteresekurve eines einzelnen
Rings bestimmt werden. Durch gezielte geometrische Variationen an
den Proben lässt sich das Ummagnetisierungsverhalten beeinflussen.
Die dadurch veränderten Induktionskonfigurationen im Objekt können
simultan direkt beobachten werden.
[1] z.B. Rothman J., Kläui M., Lopez-Diaz L., Vaz C.A.F., Bleloch A.,
Bland J.A.C., Cui Z., Speaks R., Phys.Rev.Lett. 86, 6 (2001), 1098
[2] Zhu J.G., Zheng Y., Prinz G.A., J.Appl.Phys. 87 (2000), 6668
[3] Chapman J.N., Batson P.E., Waddell E.M., Ferrier R.P., Ultrami-

Magnetismus Donnerstag
croscopy 3 (1978), 203
MA 26.7 Do 16:45 H10
Magnetisierungsstruktur überlappender Permalloy-
Nanoscheiben — •Michael Huber, Josef Biberger, Thomas
Haug, Thomas Uhlig, Josef Zweck und Dieter Weiss — Institut
für Experimentelle und Angewandte Physik, Universität Regensburg,
D-93040 Regensburg
Nanostrukturierte ferromagnetische Kreisscheiben zeigen oberhalb des
single-domain Limits eine magnetische Vortex-Struktur. In dieser Arbeit
wird untersucht, welche Magnetisierungskonfigurationen sich ausbilden
können, wenn zwei solcher Kreisscheiben mit jeweils gleichem Scheibendurchmesser
in Überlapp gebracht werden. Dazu wurden Strukturen aus
Permalloy mit Kreisdurchmessern von etwa 200 nm bis zu 1 µm und einem
Überlappungsgrad von 20 % des Scheibendurchmessers hergestellt.
Die Abbildung der Magnetisierung der Doppelscheiben erfolgte mit einem
Lorentz-Transmissions-Elektronenmikroskop (L-TEM).
Diese Magnetisierungszustände und ihr Umschaltverhalten in einem in
der Schichtebene angelegten Magnetfeld werden untersucht und mit mikromagnetischen
Simulationsrechnungen verglichen. Die Ergebnisse werden
vor dem Hintergrund einer Anwendung in MRAM Elementen, wie
von A. Arrott kürzlich vorgeschlagen [1], diskutiert werden. [1] A. Arrott:
Magnetic random access memories, Brown’s paradox und hysterons,
Journal of Magnetism and Magnetic Materials 258-259 (2003) 25-28
MA 26.8 Do 17:00 H10
Switching of single domain circular Permalloy dots observed
by electron holography — •Martin Heumann and Josef Zweck
— Universität Regensburg, Institut für Experimentelle und Angewandte
Physik, 93040 Regensburg
The switching behavior of deep submicron circular Permalloy nanomagnets
fabricated by electron beam lithography has been investigated.
The specimens were observed using a transmission electron microscope.
Holographic imaging provides sufficient magnetic resolution to observe
the switching of single nanodots with diameters down to 80nm at a thickness
of 6nm.
Permalloy dots of some hundred nanometers in diameter show a vortex
magnetization scheme in remanence while with decreasing size and thickness
a single domain magnetization scheme is expected to be energetically
more favorable. Theoretical considerations lead to a phase-transition-like
behavior.
Particles with about 100nm diameter and 6nm film thickness are expected
to be in a single domain state. The experiment shows a single
domain state during the whole switching process which takes place at
external fields of only a few Oerstedt.
For slightly larger and thicker particles (e.g. 160nm diameter and 8nm
thickness) the magnetization reversal runs via the formation of a c-state.
But no vortex is formed either.
MA 26.9 Do 17:15 H10
First-principles calculations of metallic nanowires and carbon
nanotubes on the base of FLAPW method: magnetism in hybrid
structures — •Yuriy Mokrousov, Gustav Bihlmayer, and
Stefan Blügel — Institut für Festkörperforschung, ForschungszentrumJülich,
Germany
We present a new method for carrying out ab initio calculations of the
ground state electronic properties of metallic nanowires and carbon nanotubes
within density functional theory. The method is implemented in
the FLEUR code, an implementation of the full-potential linearized augmented
plane-wave method. Our method allows to include a wide variety
of chiral symmetries known for tubular and one-dimensional systems. To
show the power and correctness of the method we concentrate on some
typical model structures explored in the field of nanospintronics: hybrid
structures Fe@Au(6,0) and Fe(6,3)@SWNT(9,0). We apply our recently
developed method for calculating band structures, densities of states, total
energies, forces, atomic relaxations, spin-orbit coupling effects and
magnetism in these systems using LDA and GGA. The results are compared
with those in literature where available.
MA 26.10 Do 17:30 H10
Multipolare Anisotropie magneto-statisch gekoppelter periodischer
Nanostrukturen — •Nikolai Mikuszeit, Elena Y. Vedmedenko
und Hans Peter Oepen — Institut für Angewandte Physik,
Universität Hamburg, Jungiusstr. 11a, 20355 Hamburg
Die magnetostatische Energieminimierung erzwingt in magnetischen
Strukturen die Ausbildung von Domänen. Gleichzeitig wird das Streufeld
sehr klein oder verschwindet sogar. Unterhalb einer kritischen Größe werden
Mikromagnete eindomänig und erzeugen Streufelder [1]. Folglich koppeln
eindomänige magnetische Partikel in periodischen Überstrukturen.
Grundsätzlich läßt sich die Kopplung analytisch berechnen; dieses ist
für komplexe Teilchengeometrien und große Teilchenzahlen aufwendig.
Zur Vereinfachung beschränken sich Rechnungen oft auf die Dipol-Dipol-
Wechselwirkung [2]. Wenn mit zunehmender Miniaturisierung der Teilchenabstand
in die Größenordnung der Teilchenabmessungen gelangt, ist
die Dipol-Näherung nicht mehr ausreichend [3]. Höhere Multipolmomente
tragen merklich zur Kopplungsenergie bei. Die Symmetrie der höheren
Momente führen zur Anisotropien höherer Ordnung. Wir stellen unsere
Ergebnisse zur Multipolentwicklung und Multipolwechselwirkung vor
und zeigen, daß die Symmetrie der Nanostrukturen und der periodischen
Anordnung zu Anisotropiebeiträgen führen.
[1] W. F. Brown, Phys. Rev. 105, 1482 (1957)
[1] T. Aign et al., Phys. Rev. Lett. 81, 5656 (1998)
[3] P. Politi et al., Phys. Rev. B, 66, 214414 (2002)
MA 26.11 Do 17:45 H10
Alterungsverhalten einzelner nanostukturierter Permalloy-
Drähte — •S.F. Fischer, S. Hacia, T. Last und U. Kunze —
Werkstoffe und Nanoelektronik, Ruhr-Universität Bochum, D-44780
Bochum
Magnetische Hysteresen von weichmagnetischen Permalloy (Py)
Mikro- und Nanostrukturen können bei geeigneter Wahl der Geometrie
massgeschneidert werden. Bei Dicken von wenigen Nanometern kann
jedoch Alterung durch Oxidation der Oberflächen, Strukturkanten
sowie Korngrenzen die elektrischen und magnetischen Eigenschaften
modifizieren. In dieser Arbeit wird das Alterungsverhalten von
Py-Drähten, wie sie als Elektroden in lateralen Spinventilstrukturen
[1] verwendet werden, in Abhängigkeit der Drahtbreite (200-5000 nm)
und Drahtdicke (5-50 nm) sowie von Au-Deckschichten untersucht.
Py-Drähte (150 µm Länge) wurden mittels Elektronenstrahllithographie,
-verdampfung und anschließendem Lift-off hergestellt und einzeln
kontaktiert [2]. Zunahme des Drahtwiderstands, Nicht-Linearitäten
in Strom-Spannungskennlinien, sowie Hystereseasymmetrien des
anisotropen Magnetowiderstands nach Abkühlen im Magnetfeld treten
als Alterungseffekte infolge von Oxidbildung (Ni-O, Fe-O) auf.
[1] S. Hacia, et al., J. Superconductivity 16, 187 (2003).
[2] T. Last, et al., J.Magn.Mat.Mater. (2004), in press.
MA 26.12 Do 18:00 H10
Domain wall orientation in magnetic nanowires: Anisotropy of
the exchange interaction — •André Kubetzka, Elena Vedmedenko,
Kirsten von Bergmann, Oswald Pietzsch, Matthias
Bode, and Roland Wiesendanger — Institute of Applied Physics,
University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
Scanning tunneling microscopy reveals that domain walls in two atomic
layers thick Fe nanowires on W(110) are oriented along the [1¯10] crystallographic
direction, regardless of the orientation of the wires. Micromagnetic
continuum theory with an isotropic exchange stiffness, however,
predicts the walls to be oriented perpendicular to the wire axis. We
demonstrate by MC simulations on a discrete lattice that the wall orientation
is determined by the atomic lattice structure and the strength
of an anisotropic Heisenberg-like exchange interaction. The magnetic
anisotropy and the magnetostatic energy which can govern wall directions
in bulk material do not play any role in the ultrathin film limit.
MA 26.13 Do 18:15 H10
Ummagnetisierungsverhalten alternierender magnetischer Elemente
— •Katharina Theis-Bröhl 1 , Andreas Westphalen 1 ,
Hartmut Zabel 1 , Karsten Rott 2 und Hubert Brückl 2 —
1 Institut für Experimentalphysik/ Festkörperphysik, Ruhr-Universität
Bochum, 44780 Bochum — 2 Institut für Physik, Universität Bielefeld,
Universitätsstr. 25, 33615 Bielefeld
Eine periodische Anordnung schmaler und breiter magnetischer Streifen
wurde hinsichtlich ihres Ummagnetisierungsverhaltens untersucht.
Die laterale Struktur besteht aus 90 nm dicken Fe-Streifen mit einer
Länge von 30 µm und Breiten von 1 bzw. 1.6 µm. Die Streifen sind alternierend
angeordnet und haben einen Zischenraum von 0.7 µm. Die
magnetische Anisotropie der Streifen ist zweizählig und wird durch ihre
Geometrie bestimmt. Die leichte Achse liegt entlang der Streifenrichtung.
Durch die unterschiedliche Breite der Streifen ist die Formaniso-

Magnetismus Donnerstag
tropie verschieden, was in unterschiedlichen Koerzitivfeldern resultiert.
Deshalb gibt es einen Feldbereich, in dem die Streifen antiparallel zueinander
ausgerichtet sind. Die antiparallele Ausrichtung kann man sehr
gut mit polarisierter Neutronenreflektometrie nachweisen. Im Gegensatz
zu Multilagen, bei denen bei antiparalleler Ausrichtung ein halbzahliger
spekulärer Reflex erscheint, nimmt hier die Intensität am halbzahligen
lateralen Bragg-Reflex stark zu. Außerdem beobachten wir eine starke
Zunahme der Spin-Flip-Intensität an diesem Peak. Dieses Projekt wurde
gefördert durch die DFG, SFB 491 und durch das BMBF unter der
Projektnummer 032AE8BO.
MA 26.14 Do 18:30 H10
Investigations of remagnetization processes with Bragg-MOKE
— •Andreas Westphalen, Katharina Theis-Bröhl, and Hartmut
Zabel — Institut für Experimentalphysik/Festkörperphysik, Ruhr-
Universität Bochum, 44780 Bochum
MA 27 Spinabhängiger Transport II
The Bragg-MOKE technique extends the information of standard
MOKE measurements by making use of diffraction from regular arrays
of magnetic microstructures. Here we have explored the properties of
Bragg-MOKE for the investigation of magnetic stripe arrays. The nth
order diffraction spot is particularly sensitive to the nth order Fourier
component of the magnetization distribution. Accordingly, the shape of
the hysteresis loops changes characteristically as a function of n. Furthermore
an amplification of the magneto-optical signal is possible. The
samples under investigation are stripes of CoFe-alloy and Fe with different
grating parameters and stripe widths, which display a variety of
different magnetic reversal behaviour.
We would like to thank K. Rott and H. Brückl for the preparation of
the CoFe samples, and we acknowledge financial support through SFB
491.
Zeit: Donnerstag 15:15–18:45 Raum: H22
MA 27.1 Do 15:15 H22
Magnetismus und Magnetowiderstand in Fe/V/Fe und
Cr/V/Cr — •Heike Herper und Peter Entel — Theoretische
Tieftemperaturphysik, Universität Duisburg-Essen, Standort Duisburg,
Lotharstr. 1, 47048 Duisburg
Wir untersuchen die elektrischen Transporteigenschaften sowie das
Verhalten der magnetischen Momente von Vanadium in Fe/V/Fe(110)
und Cr/V/Cr(100) Dreifachlagen. Der elektrische Transport wird dabei
im Rahmen des Kubo-Greenwood-Formalismus behandelt; zur Berechnung
der elektronischen und magnetischen Eigenschaften wird ein vollrelativistisches
Screened-Korringa-Kohn-Rostoker-Verfahren verwendet.
In Fe/V/Fe Dreifachlagen finden wir in Übereinstimmung mit experimentellen
Untersuchungen (H. Wende et al., J. Appl. Phys. 91 8760
(2002)), dass die magnetischen Momente des Vanadium mit wachsender
Schichtdicke schnell abnehmen. Inwieweit dies die Leitfähigkeit und den
Magnetowiderstand beeinflußt, ist Gegenstand weiterer Untersuchungen.
In beiden Größen beobachten wir eine sprunghafte Änderung bei ca. 4
Monolagen Vanadium. Im Cr/V/Cr System, das wir auf ein Fe(100) Substrat
aufgebracht betrachten, hingegen beeinflußt Vanadium die Größe
des Magnetowiderstands nur geringfügig.
Gefördert durch die Deutsche Forschungsgemeinschaft im Rahmen des
SFB 491
MA 27.2 Do 15:30 H22
An ab-initio embedded Green function formulation of
spin-dependent electron transport — •Stefan Blügel 1 ,
Daniel Wortmann 1,2 , and Hiroshi Ishida 3 — 1 Institut für
Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich —
2 Research Institute for Computational Sciences, AIST, Tsukuba, Japan
— 3 College of Humanities and Sciences, Nihon-University, Tokyo, Japan
Parallel to the recent experimental progress in the fabrication of nanostructures,
the theoretical investigation of spin-dependent transport in
such systems became a focus field of research. Different schemes extending
the application of electronic structure calculations using the densityfunctional
theory (DFT) have been proposed to describe transport within
the independent particle picture of the Kohn-Sham eigenstates.
Following the same idea we will demonstrate a new approach starting
from the description of a scattering volume sandwiched between two
semi-infinite leads. Using the embedding method, the Green function of
this scattering region can be evaluated enabling us to obtain the conductance.
Different formulations of transport will be compared and the
extension of the formalism taking into account the non-linear effect of a
finite applied bias using the non-equilibrium Green function formulation
will be presented. The actual implementation is based on the FLEUR
code and the full-potential linearized augmented plane method. Results
of the code applied to model systems as well as to the Fe/MgO/Fe tunnelmagneto-resistance
(TMR) junction will be shown.
MA 27.3 Do 15:45 H22
Domänenwandmagnetowiderstand in (Co/Pt)10-Multilagen-
Leiterbahnen — •Britta Hausmanns 1 , Ulrich Nowak 2 und
Günter Dumpich 1 — 1 Universität Duisburg-Essen, Experimentelle
Physik, Lotharstr. 1, D-47048 Duisburg — 2 Universität Duisburg-Essen,
Theoretische Physik, Lotharstr. 1, D-47048 Duisburg
Die eindeutige Separation des Domänenwandmagnetowiderstandes
(DWMR) von anderen konkurrierenden Magnetowiderstandseffekten,
insbesondere vom anisotropen Magnetowiderstand (AMR), konnte durch
die Untersuchung des transversalen Magnetowiderstandes einzelner
(Co/Pt)10-Multilagen-Leiterbahnen erzielt werden. Da die magnetisch
leichte Achse dieser Nanodrähte senkrecht zur Schichtebene orientiert ist,
ist bei transversal angelegtem Magnetfeld die Magnetisierung während
des Ummagnetisierungsprozesses senkrecht zur Stromrichtung ausgerichtet.
Der wesentliche Vorteil dieser Messmethode ist, dass sogar die Magnetisierung
innerhalb der Domänenwände senkrecht zur Stromrichtung
orientiert ist und so ein zusätzlicher AMR-Beitrag ausgeschlossen werden
kann. Die Interpretation des Magnetowiderstandsverhaltens wird unterstützt
durch Monte Carlo-Simulationen, die die Magnetisierungsverteilung
innerhalb des Nanodrahtes während des Ummagnetisierungsprozesses
widerspiegeln. Es kann gezeigt werden, dass das beobachtete Verhalten
des transversalen Magnetowiderstandes nicht von der Änderung
der Anzahl der Domänenwände während des Ummagnetisierungsprozesses,
sondern von der Domänenwandbreite abhängt.
Diese Arbeit wird gefördert von der DFG im Rahmen des SFB 491.
MA 27.4 Do 16:00 H22
Abklinglänge des magnetischen Tunneleffekts für eine magnetische
Ni / CoFe Doppelelektrode — •Dirk Brinkmann 1 , Andy
Thomas 2 , Hubert Brückl 1 und Günter Reiss 1 — 1 Universität Bielefeld,
Universitätsstr. 25, 33615 Bielefeld — 2 MIT Francis Bitter Magnet
Labs. 02139 Cambridge, MA USA
Ausgegangen wurde von einem magnetischem Tunnelelement mit einer
Al2O3-Barriere und einer unteren Co-Elektrode sowie einer oberen Ni /
CoFe Doppelelektrode. Für eine systematische Untersuchung wurde die
Nickeldicke variiert und der Tunnelwiderstand sowohl bei Raumtemperatur
wie auch bei tiefen Temperaturen (10K) vermessen. Aufgrund der
im Vergleich zu CoFe niedrigeren Spinpolarisation des Ni kann man eine
charakteristische Abklinglänge beobachten. Aus der Abklinglänge ist zu
ersehen, dass nur Elektronen aus der direkten Umgebung der Barriere
(wenige Monolagen) Einfluss auf den Tunnelprozess haben.
MA 27.5 Do 16:15 H22
Osizillierender Tunnelstrom in CMR- Tunnelkontakten —
•Yuansu Luo, Arnold Giske und Korand Samwer — I.Phys.
Institut, Universität Göttingen, Tammannstr.1 37077 Göttingen
CMR- Tunnelkontakte von Ir/LCMO/Al2O3/LCMO/Al wurden auf
MgO(100)- Substraten bei 700 o C präpariert, um den Tunneleffekt in
Abhängigkeit vom äußeren Magnetfeld zu untersuchen. Strukturelle
Epitaxie zwischen Ir und LCMO bzw. zwischen LCMO und Al2O3 wurde
durch Röntgenmessungen bestätigt. Die Kontaktfläche ist 50x50 µm 2 .
Die Dicke der Al2O3-Barriere beträgt 2nm und die Dicke der unteren
bzw. oberen LCMO- Elektrode jeweils 45nm und 20nm. Dabei dient die

Magnetismus Donnerstag
metallische Schicht von Ir (25nm) bzw. Al (5nm) als Zuleitung. Erste
Ergebnisse zeigen eine anomale Oszillation des Tunnelstroms beim Anlegen
eines Magnetfeldes und extremale Punkte auf der entsprechenden
I-V Kurve. Bei kleiner Spannungen sind die Oszillationen ausgeprägt mit
Maxima jeweils bei ca. ±0.5, ±2.5 und ±5.5T, wobei eine Änderung vom
Tunnelstrom von ca. 100 % beobachtet wurde. Bei hohen Temperaturen
(≥100 K) und großer Spannung (≥200 mV) verschwinden sich die Oszillationen
und die Kurve lässt sich durch den CMR- Effekt erklären.
(Unterstützt durch die DFG, Projekt SA 337 / 9-1)
MA 27.6 Do 16:30 H22
Ladungstransport in mit He-Ionen bestrahlten Tunnelelementen
— •V. Höink 1 , J. Schmalhorst 1 , G. Reiss 1 , D. Engel 2 , D.
Junk 2 , A. Ehlers 2 und A. Ehresmann 2 — 1 Universität Bielefeld, Fakultät
für Physik, Universitätsstr. 25, D-33615 Bielefeld — 2 Technische
Universität Kaiserslautern, Fachbereich Physik, Erwin-Schrödinger-Str.,
D-67663 Kaiserslautern
TMR-Schichtsysteme (NiFe/CoFe/Al2O3/CoFe/MnIr) wurden zur Erzeugung
einer unidirektionalen Kopplung (Exchange Bias) zwischen dem
Antiferromagneten MnIr und der angrenzenden CoFe-Schicht im Magnetfeld
mit He-Ionen beschossen.
Der dabei erreichte TMR-Wert beträgt bis zu 90% des am selben System
nach Vakuumauslagern im Magnetfeld gemessenen TMR-Effekts von
44%. Eine deutliche Veränderung des Widerstandes wurde hierbei nicht
beobachtet. Damit sollte eine Anwendung des He-Ionenbeschusses für eine
magnetische Nanostrukturierung der hartmagnetischen Referenzelektrode
möglich sein. Außerdem wurde der Einfluss einer Erwärmung der
bestrahlten Probe auf den Ladungstransport in der Barriere untersucht.
MA 27.7 Do 16:45 H22
Magnetic tunnel junctions with CoFeB electrodes —
•Theodoros Dimopoulos, Günter Gieres, and Joachim
Wecker — Siemens AG, Corporate Technology, Erlangen
Amorphous ferromagnets are well known for their soft magnetic properties
and they are used as cast ribbons e.g. in transformer cores for
more than 20 years. Previous results have shown that indeed in magnetic
tunnel junctions (MTJs) amorphous CoFeNiSiB detection layers
show a low coercivity of about 2 Oe with a tunnel magnetoresistance
(TMR) of about 22% [1]. Here, we study the influence of amorphous
CoFeB soft electrodes on the TMR and the tunneling characteristics
(i.e. I(V) curves). Combined with crystalline CoFe as the hard electrode
we find TMR signals as high as 51%. In contrast to MTJs with only crystalline
electrodes we see a different dependence of the barrier parameters
(height and thickness as extracted from fitting I(V) data with the Simmons
model) on temperature. Using CoFeB also as the hard electrode
(in this case pinned to IrMn) one can tailor the interfaces to get pure
symmetric I(V) curves.
[1] A.Käufler et al., J.Appl.Phys. 91, 1701 (2002)
MA 27.8 Do 17:00 H22
Magnetische Tunnelsysteme mit Elektroden aus Eisen-Gold Legierungen
— •Andrea Niemeyer, Hubert Brückl und Günter
Reiss — Universität Bielefeld, Fakultät für Physik, Universitätstr. 25,
33615 Bielefeld
Es wurden magnetische Tunnelsysteme hergestellt, bei denen eine der
ferromagnetischen Elektroden aus einer FeAu-Legierung besteht. Dabei
wurden verschiedene Legierungen (Fe85Au15...Fe35Au65) realisiert und für
jede Legierung auch die Dicke der Elektrode in einem Bereich von 0nm bis
9nm variiert. In Tieftemperaturmessungen zwischen 10K und 330K wurde
die Abhängigkeit des Tunnelmagnetowiderstandes vom Legierungsverältnis
und von der Dicke der Elektrode untersucht. Dabei zeigt sich
eine Abnahme des TMR mit zunehmendem Goldanteil in der Legierung.
Bei einer Legierung von Fe46Au54 ist eine Oszillation des TMR mit steigender
Elektrodendicke zu beobachten.
MA 27.9 Do 17:15 H22
Spin-dependent tunneling in Fe/vacuum/Cr system — •Jussi
Enkovaara 1 , Daniel Wortmann 1,2 , and Stefan Blügel 1,3 —
1 Institut für Festkörperforschung, Forschungszentrum Jülich, 52425
Jülich — 2 Research Institute for Computational Sciences, Tsukuba,
Japan — 3 Fachbereich Physik, Universität Osnabrück, 49069 Osnabrück
Advances in spin-polarized scanning tunneling microscopy (SP-STM)
have enabled the imaging of surface magnetism in sub-nm scale. The
use of an antiferromagnetic tip material (or coating) is one possibility
for obtaining the atomic scale spin sensitivity without generating a magnetic
stray field. In this work, we study spin-polarized tunneling theoretically
in a simple model system. We consider planar junction where
a semi-infinite ferromagnetic Fe is separated from a semi-infinite antiferromagnetic
Cr by a vacuum barrier. We employ a first-principles Green
function approach based on the full-potential linearized augmented plane
wave (FLAPW) method as implemented in the FLEUR code. The semiinfinite
structures are treated with an embedding method. The tunneling
current is calculated both within the Landauer and Bardeen formalisms.
The results are compared to those obtained from a simple density of
states picture.
MA 27.10 Do 17:30 H22
Theoretical Investigations on Spin-Dependent Electronic
Transport in Magnetic Tunnel Junctions — •Voicu Popescu 1 ,
Hubert Ebert 1 , Rudolf Zeller 2 , and Peter H. Dederichs 2
— 1 Department Chemie/Physikalische Chemie, University of Munich,
Butenandtstr. 5-13, 81377 Munich, Germany — 2 Inst. für
Festkörperforschung,Forschungszentrum Jülich, Postfach 1913, D-52425
Jülich, Germany
Spin-dependent transport between two ferromagnetic electrodes separated
by either an insulator or a semiconductor has received a lot of
interest in the last years due to its potential technological applications.
The impressive theoretical work done in this field, however, still lacks a
fair quantitative agreement with the experimental results.
Some possible sources leading to the existing discrepancies have been
investigated and will be presented and discussed. For this we have applied
a Tight-Binding Spin-Polarised Relativistic Multiple Scattering Theory
(TB-SPR-KKR) method in calculating the electronic structure of an
Fe/GaAs/Fe magnetic tunnel junction. Interface relaxation, interface inderdiffusion
by means of a Coherent Potential Approximation (CPA) and
Spin-Orbit Coupling (SOC) have been accounted for.
The transport properties are calculated according to the Landauer-
Büttiker formalism on a relativistic level. Model calculations allowed us
to investigate in detail the spin-flip contribution to the conductance, at
the Fe/GaAs interface and/or within the semiconductor spacer.
MA 27.11 Do 17:45 H22
Disorder effects on tunneling magnetoresistance — •Michael
Wimmer und Klaus Richter — Institut fü Theoretische Physik, Universität
Regensburg
Spin-dependent transport phenomena have gathered a lot of interest
in the past decade. Among those is the tunneling magnetoresistance effect
(TMR). Nowadays Al2O3-based tunnel junctions show a significant
TMR effect. However, recent experiments on Fe/GaAs-based junctions
found an effect much less than expected from simple models. It was suggested
that spin-flip scattering may explain the low value of the TMR.
(S. Kreuzer et al., Appl. Phys. Lett. 80, 4582 (2002) )
We study the effects of disorder on the TMR in a phenomenological
model that we solve numerically using a recursive Green’s function
technique. This model includes a position-dependent effective mass, spinconserving
and spin-flip scattering.
We investigate the effect of disorder at the interfaces and find that
disorder tends to decrease the TMR effect. Surprisingly, the decrease is
almost identical for spin-conserving and spin-flip scattering.
Additionally we compute the magnetic field dependence of the conductance
of a tunnel junction in the presence of impurities.
MA 27.12 Do 18:00 H22
Magnon-assisted transport due to itinerant electron exchange
scattering in ferromagnetic tunnel junctions — •Grigory Tkachov
— Institute for Theoretical Physics, Regensburg University, 93040
Regensburg, Germany
We propose an itinerant electron model for inelastic tunneling spectra
of ferromagnetic junctions observed in recent experiments [1]. In our
approach the exchange (Fock) part of the Coulomb interaction between
electrons with opposite spins is used to derive a transfer Hamiltonian
describing single-electron tunneling with a simultaneous spin flip [2]. In
such an inelastic process a tunneling electron (e.g. a spin-up one) excites
an electron from a ”spin-down” Fermi sea of the other ferromagnet
into an empty state above the Fermi level while substituting the latter
inside the ”spin-down” Fermi sea. These exchange-induced spin flips
can be treated as a collective spin excitation of the Fermi sea electrons.
Since the electron-magnon coupling is mediated by the Coulomb potential,
the tunneling matrix elements of the inelastic current depend on the

Magnetismus Donnerstag
magnon wave-vector and, therefore, on its energy. This dependence can
explain strongly non-monotonous inelastic tunneling spectra measured in
Refs.[1].
[1] J.S. Moodera, J. Nowak, and R.J.M. van de Veerdonk,
Phys.Rev.Lett. 80, 2941 (1998); Y. Ando, J. Murai, H. Kubota, and T.
Miyazaki, J. Appl. Phys. 87, 5209 (2000); J.H. Yu, H.M. Lee, Y. Ando,
and T. Miyazaki, Appl. Phys. Lett. 82, 4735 (2003).
[2] S. Zhang, P.M. Levy, A.C. Marley, and S.S.P. Parkin,
Phys.Rev.Lett. 79, 3744 (1997).
MA 27.13 Do 18:15 H22
Persistent Spin Currents in Helimagnets — •Jürgen König 1 ,
Jan Heurich 2 , and Allan H. MacDonald 3 — 1 Institut für Theoretische
Physik III, Ruhr-Universität Bochum — 2 Institut für Theoretische
Festkörperphysik, Universität Karlsruhe — 3 Department of Physics,
University of Texas at Austin
We study collective spin transport in helimagnets, e.g., in systems with
ground states that possess spiral magnetic order. It is demonstrated that
weak external magnetic fields generate dissipationless spin currents in
these systems, whereas the spiral ground state in the absence of a magnetic
field does not support collective spin transport. Our conclusions are
based on phenomenological considerations and on microscopic mean-field
theory calculations for an illustrative toy model [1]. We discuss similarities
and differences of these results to our recent analysis of spin supercurrents
in thin film ferromagnets [2], and we speculate on possible
applications of this effect in spintronic devices.
[1] J. Heurich, J. König, and A.H. MacDonald, Phys. Rev. B 68, 064406
(2003).
[2] J. König, M.C. Bønsager, and A.H. MacDonald, Phys. Rev. Lett. 87,
187202 (2001).
MA 27.14 Do 18:30 H22
Anomalous Hall effect and Berry Phase in Ferromagnets —
•Mathieu Taillefumier 1,2 , Vitalii Dugaev 1,3 , and Patrick
Bruno 1 — 1 Max Planck Institut für mikrostrukturphysik, Weinberg 2,
06120 Halle, Germany — 2 Laboratoire Louis Néel, CNRS, Boite Postale
166,, 38042 Grenoble Cedex 09, France — 3 Institute for Problems of
Materials Science, NASU, Vilde 5, 58001 Chernovtsy, Ukraine
We propose a new mechanism of anomalous Hall effect (AHE) in twodimensional
ferromagnets and magnetic nanostructures with inhomogeneous
magnetization. In contrast to the usual theories (side jump and
skew scattering mechanism) of AHE, the presented theory does not necessary
require spin-orbit interaction, and is induced by a Berry phase of
the wavefunctions of the electrons moving a inhomogeneous magnetization
field. We obtain a nonvanishing contribution to the Hall conductivity
provided that the topology of the magnetization field is nontrivial like in
the case of separated magnetic domains or periodic lattice of magnetic
domains.
We propose an experiment with a structure containing two-dimensional
electrons or holes of diluted magnetic semiconductor subject to the stray
field of a lattice of magnetic nanocylinders. The striking behavior predicted
for such a system (of which all revelant parameters are well known)
allows to distinguish it from the other mechanisms.
MA 28 Spindynamik / Ummagnetisierungsvorgänge
Zeit: Donnerstag 15:15–18:45 Raum: H23
MA 28.1 Do 15:15 H23
A new method for atomistic spin-dynamics simulations with abintio
accuracy — •Reinhard Singer, Ralf Drautz, and Manfred
Fähnle — MPI für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart,
Germany
We propose a new method to simulate the adiabatic spin dynamics in
systems with magnetization singularities (vortex structures, Bloch points,
extremely narrow domain walls in nanostripes etc.) with ab-initio accuracy
but orders of magnitude faster than the conventional ab-initio spin
dynamics simulation. It is based on the same equation of motion as the
conventional simulation, i.e., a Gilbert like equation with a precission
term and a damping term. In the conventional simulation the effective
fields entering the precission term have to be calculated by the full abinitio
electon theory which renders the method very costly. In contrast,
we determine the effective fields by our recently proposed spin-clusterexpansion
technique which represents an analytical expression for the
magnetic energy of a spin system with arbitrary multi-spin interactions.
The expansion coefficients thereby are determined by the ab-initio density
functional electron theory. Therefore the construction of the expansion
is costly, but once a converged spin-cluster expansion is generated it can
be used to calculate the energy of any spin configuration very effectively
and probably with ab-initio accuracy.
MA 28.2 Do 15:30 H23
Atomic-scale model of thermal effects on magnetic anisotropy
and dynamic switching properties of FePt nano-particles —
•Ulrich Nowak 1,2 , Oleg Mryasov 1 , Konstantin Guslienko 1 , and
Roy Chantrell 1 — 1 Seagate Research, 1251 Waterfront Place, Pittsburgh,
PA, 15222, USA — 2 Institut für Physik, Universität Duisburg-
Essen, Germany
We propose a microscopic atomic-scale model of magnetic interactions
in ordered L10 FePt based on an effective, classical spin Hamiltonian
which is constructed with the use of first-principles calculations for noncollinear
magnetic configurations and site-resolved magneto-crystalline
anisotropy energies. Our effective Hamiltonian contains, in addition to
the isotropic exchange, an effective, anisotropic exchange due to the
strong single-ion anisotropy of the Pt atoms.
This model is studied numerically using Monte-Carlo methods as well
as Langevin dynamics. The model allows to describe correctly the observed
temperature dependence of the magnetic anisotropy energy of ordered
FePt films. In particular the dependence of the anisotropy constant
K1(T) on the reduced magnetization is found to be in excellent agree-
ment with experimental results. Furthermore, the model is used to study
the thermally induced switching behavior of FePt nano-particles. We find
a strong deviation from the Neel-Brown theory for mean switching times
due to the temperature dependence of the activation energy barrier.
MA 28.3 Do 15:45 H23
Zur Wechselwirkung von Magnetisierungswellen mit Néel-
Wänden — •Riccardo Hertel, Wulf Wulfhekel und Jürgen
Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Weinberg
2, 06120 Halle
Magnetisierungswellen treten in ferromagnetischen Teilchen auf der
Zeitskala von Piko- bis Nanosekunden auf, wenn die magnetischen Teilchen
angeregt werden oder Energie freigesetzt wird, beispielsweise bei
einem Ummagnetisierungsprozess. Vor kurzem konnten lokalisierte Magnetiserungswellen,
die sich in einem Ferromagneten ausbreiten, resonant
erzeugt und untersucht werden [1]. Mit mikromagnetischen Simulationen
wird die Ausbreitung von Magnetisierungswellen in schmalen, dünnen
Permalloy-Streifen (6 nm x 36 nm x 300 nm) untersucht, die sich infolge
einer anfänglichen Störung des Gleichgewichts entlang des Streifens
ausbreiten. Die Simulationen zeigen, dass diese Magnetisierungswellen
eine Néelwand in den Streifen ungehindert passieren können. Dabei
ändert sich jedoch die Phase der Welle. Dieser Effekt wird anhand
eines ringförmigen Spinwelleninterferometers untersucht, bei dem Magnetisierungswellen
auf kontrollierte Weise zu konstruktiven oder destruktiven
Interferenzerscheinungen führen können, je nachdem ob sich
Domänenwände in den jeweiligen Zweigen des Interferometers befinden.
[1] Serga et al., J. Appl. Phys. 93 (10) 8585 (2003)
MA 28.4 Do 16:00 H23
Vortex-Dynamik in weichmagnetischen Dünnschichtelementen
— •Riccardo Hertel und Jürgen Kirschner — Max-Planck-
Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle
Ferromagnetische Nanoteilchen treten entweder in nahezu homogener
Magnetisierungsstruktur auf oder zerfallen in magnetische
Domänenstrukturen mit geschlossenem magnetischen Fluß. Solche
Domänenstrukturen beinhalten magnetische Wirbel (Vortex-
Strukturen), die vor kurzem mit hoher Auflösung abgebildet werden
konnten [1]. Mit Hilfe mikromagnetischer finite-Elemente Simulationen
werden die dynamischen Eigenschaften von Vortexstrukturen untersucht.
Dabei wird der Einfluß eines äußeren Wechselfelds auf die magnetische
Vortexstruktur einer Permalloy-Kreisscheibe von 300 nm Durchmesser
und 3 nm Dicke simuliert. Bei einer Frequenz von ca. 200 MHz tritt eine

Magnetismus Donnerstag
resonante Mode auf, bei der die Position des Vortex auf einer Kreisbahn
um den Mittelpunkt der Kreisscheibe mit der Frequenz des angelegten
Felds rotiert [2]. Bei höherer Frequenz von ca. 5 GHz enteht eine resonante
Mode anderen Typs, bei der stehende Wellen innerhalb der Kreisscheibe
angeregt werden. [1] A. Wachowiak et al., Science 298, (5593)
577 (2002) [2] Guslienko et al., J. Appl. Phys. 91 (10) 8037 (2002)
MA 28.5 Do 16:15 H23
Spin Dynamics in Permalloy Disks with Vortex Structure
— •Matthias Buess 1,2 , Rainer Höllinger 1 , Thomas
Haug 1 , Korbinian Perzlmaier 1 , Michael R. Scheinfein
3 , Danilo Pescia 2 , and Christian H. Back 1 — 1 Institut
fürExperimentelle und Angewandte Physik, Universität Regensburg,
Universitätsstrasse 31, 93040 Regensburg, Germany — 2 Laboratorium
für Festkörperphysik,Eidgenössische Technische Hochschule Zürich,
CH-8093Zürich,Switzerland — 3 Simon Fraser University, 8888 University
Drive, Burnaby BC U5A 156, Canada
Micron sized ferromagnetic permalloy disks exhibiting a ferromagnetic
vortex structure are excited by a magnetic field pulse. The fast rise time
pulse field is generated by an optically triggered electrical pulse in a lithographically
fabricated microcoil. The excitation is imaged using time resolved
magneto-optic polar Kerr microscopy - a stroboscopic experiment.
We present the spatially resolved magnetic maps at different delay times,
stitched together to form a magnetic movie. The dynamical excitations
are composed of symmetric and non-sysmmetric parts which can not be
separated at first glance. However, in the Fourier transformation of the
magnetic movie we identify several modes which can be accounted for
in a simple model based on purely dipolar interactions. The model is
supported by micromagnetic simulations and shows good quantitative
agreement in the resonance frequencies for different modes and sample
dimensions.
MA 28.6 Do 16:30 H23
NANOSECOND TIME-SCALE SWITCHING OF THIN FILM
PERMALLOY ELEMENTS — •Dmitry Chumakov, Rudolf
Schäfer, Jeffrey McCord, and Ludwig Schultz — IFW-Dresden,
Helmholtzstr. 20, D-01069 Dresden, Germany
We have studied the dynamic magnetization switching behaviour of
thin film Permalloy elements by gated ICCD camera-based time-resolved
wide-field Kerr microscopy. The structures were subject to pulsed magnetic
fields of different strengths from 1600 A/m to 5200 A/m. Their
reversal was observed with 250 ps time-resolution. By interpreting the
experimental results we point out the peculiarities of the nanosecond
timescale switching. Like in the quasistatic case, the dynamic remagnetization
process is dominated by the generation of concertina-like domain
patterns. Whereas such ”blocked” domains decay irreversibly in several
steps during quasistatic switching, the blocking is resolved by continuous
rotation in a locally inhomogeneous way for dynamic switching. This
process lasts several nanoseconds and leads to significant delays in element
switching. The influence of magnetic field amplitude, rise-time,
and element shape on the switching behaviour will be shown at various
examples.
MA 28.7 Do 16:45 H23
Magnetization Dynamics of Micron Sized Permalloy Squares —
•Korbinian Perzlmaier, Christian Back, Matthias Buess, and
Rainer Höllinger — Institut für Experimentelle und Angewandte
Physik, Universität Regensburg, Universitätsstrasse 31, 93040 Regensburg
We investigate the dynamic response of the magnetization in micron
sized Permalloy squares by measuring the polar Kerr component in a
time resolved Kerr-microscope. The sample is excited with a fast rise
time magnetic field pulse (typically pulse fields are smaller than 100 Oe)
applied perpendicular to the sample plane. Magnetic movies are recorded
with a frame rate of 10 ps. From the Fourier transform of the data we
obtain information about the modal frequencies.
Numerical methods based on the LLG equation are commonly used
to simulate the dynamic response of magnetic elements. We extract the
modal structure from simulated movies of squares in the size range between
300 nm and 4 micron. The results are compared to our experiments.
MA 28.8 Do 17:00 H23
Investigation of magnetization dynamics of microstructured
magnetic thin films by means of Time-Resolved Photoemission
Electron Microscopy. — •A. Krasyuk 1 , A. Oelsner 1 , S.A.
Nepijko 1 , D. Neeb 1 , A. Kuksov 2 , C.M. Schneider 2 und G.
Schönhense 1 — 1 Johannes Gutenberg-Universität Mainz, Institut
für Physik, Staudinger Weg 7, 55099 Mainz, Germany — 2 Institut für
Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich, Germany
The magnetisation reversal dynamics of the lithographically prepared
Permalloy particles with different forms and thickness ranging from
10nm up to 40nm was observed exploiting the Magnetic X-Ray Circular
Dichroism (MXCD) contrast at the Ni L3 X-ray absorption edges in subns
range by means Time-Resolved Photoemission Electron Microscope.
The experiment has been performed in single-bunch mode at the BESSY
II (Berlin) and 16-bunch mode at the ESRF (Grenoble). [1] A. Krasyuk,
A. Oelsner, S.A. Nepijko, A. Kuksov, C.M. Schneider, G. Schönhense.,
Appl.Phys.A, 2003, 76, No.6, 863-868. [2] A. Oelsner, A. Krasyuk, D.
Neeb, S.A. Nepijko, A. Kuksov, C.M. Schneider, G. Schönhense., J. Electr.
Spectr. Rel. Phenom, accepted
MA 28.9 Do 17:15 H23
Damping in thin NiFe films — •Hans Nembach, Markus C. Weber,
Jürgen Fassbender, and Burkard Hillebrands — Fachbereich
Physik und Forschungsschwerpunkt MINAS, Technische Universität
Kaiserslautern, Erwin-Schrödinger-Str. 56, 67663 Kaiserslautern
We investigated the damping and spin wave creation in thin NiFe films
with time-resolved magneto-optic Kerr effect magnetometry for small and
large angle excitations. To gain further insight in the underlying damping
process we employ a special measurement procedure, which allows
us to determine all three magnetization vector components and therefore
the length of the magnetization vector. A reduction of the magnitude
of the magnetization vector indicates the creation of spin waves. These
spin waves can be created directly by the stripline or by multi-magnon
processes.
The experimentally determined magnetization trajectory is compared
with numerical simulations based on the Landau-Lifshitz equation, and
the damping constant is extracted from these simulations
MA 28.10 Do 17:30 H23
Dependence of magnetization reversal dynamics on magnetic
anisotropy and interlayer coupling — •K. Fukumoto 1 , W.
Kuch 1 , J. Vogel 2 , J. Camarero 3 , S. Pizzini 2 , Y. Pennec 2 ,
F. Offi 1 , M. Bonfim 4 , A. Fontaine 2 , and J. Kirschner 1 —
1 Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120
Halle, Germany — 2 Laboratoire Louis Néel, CNRS, 25 Avenue des
Martyrs, B. P. 166, F-38042 Grenoble Cedex 9, France — 3 Dpto. Física
de la Materia Condensada, Universidad Autónoma de Madrid, E-28049
Madrid, Spain — 4 Departamento de Engenharia Elètrica, Universidade
do Paraná, CEP 81531-990, Curitiba, Brazil
Time- and element-resolved magnetic domain imaging measurements
were performed using x-ray magnetic circular dichroism photoelectron
emission microscopy (XMCD-PEEM). Two types of spin-valve-like samples
(Fe20Ni80/Cu/Co) were used in this study, one with and one without
magnetic anisotropy in the film plane. Magnetization reversal during
nanosecond-short magnetic field pulses was investigated by a pumpprobe
technique. Domain wall motion induced by the field pulses (pump)
was imaged using photon pulses from single bunch operation of BESSY
(probe). Magnetization reversal and domain structure of the permalloy
layer in the sample showing no anisotropy in the plane are strongly influenced
by local pinning. In the sample with in-plane anisotropy, domain
patterns during the reversal of the permalloy layer are less reproducible,
and more influenced by the local coupling with the Co layer. Reversal
mechanism, speed of domain wall motion, and the effect of magnetic
interlayer coupling were also studied using single-pulse measurements.
MA 28.11 Do 17:45 H23
All optical probe of coherent spin waves in exchange bias
systems — •B. Beschoten 1 , A. Tillmanns 1 , S. Oertker 1 , G.
Güntherodt 1 , I.K. Schuller 2 , C. Leighton 3 , and J. Nogués 4
— 1 2. Physikalisches Institut, RWTH Aachen, 52056 Aachen —
2 Department of Physics, UC San Diego — 3 Department of Chemical
Engineering and Materials Science, University of Minnesota —
4 Departament de Fisica, Universitat Autònoma de Barcelona
Time-resolved Kerr rotation is used to generate and to probe coherent
spin waves in exchange biased ferro-/antiferromagnetic bilayer films of

Magnetismus Donnerstag
Fe/MnF2. The exchange bias results from an unidirectional anisotropy
which is established below the Néel temperature of the antiferromagnetic
layer and can be identified as a shift of the magnetic hysteresis loop. In
time-resolved Kerr rotation, an ultrashort laser pump pulse generates an
unidirectional anisotropy field pulse which triggers coherent precession
of the magnetization in the ferromagnetic layer. This coherent precession
is monitored by a time-delayed laser probe pulse yielding a quantitative
method to study magnetic anisotropy, ultrafast switching and damping
phenomena.
Work supported by DFG through SPP 1133, grant no. BE 2441/2-1
MA 28.12 Do 18:00 H23
Evidence of spin-pumping effect in the FMR of coupled trilayers
— •T. Toliński 1,2 , K. Lenz 1 , J. Lindner 1,3 , E. Kosubek 1 , and
K. Baberschke 1 — 1 Institut für Experimentalphysik, Freie Universität
Berlin, Arnimallee 14, 14195 Berlin, Germany — 2 Permanent address: Institute
of Molecular Physics, PAS, Smoluchowskiego 17, 60-179 Poznań,
Poland — 3 New address: Institut für Physik, Universität Duisburg-Essen,
Lotharstr. 1, 47048 Duisburg, Germany
The spin dynamics between two ultrathin ferromagnetic layers (Ni, Co)
exchange coupled via a nonmagnetic Cu spacer of a few monolayers is
studied using in situ ferromagnetic resonance. The angular and the temperature
dependence of the linewidth shows pronounced changes that can
be understood assuming the presence of an additional Gilbert damping
resulting from a spin-current pumped through the interface between the
ferromagnetic and nonmagnetic layers and by considering the dynamical
part of the interlayer exchange coupling. In contrast to investigations on
Fe films decoupled by thick Au spacers [1] the effect of the interlayer
exchange coupling on this phenomenon is presented here. The competition
between the Gilbert damping inherent in the ferromagnetic film
and the Gilbert damping developed by the interface leads to an irregular
behavior of the temperature dependence of the resonance linewidth for
both the in-phase and out-of-phase precessing modes. It is shown that
the oscillatory nature of the coupling is also revealed in the dependence
of the resonance linewidth ∆H on the spacer thickness. Supported by
the DFG (Sfb 290, TP A2).
[1] B. Heinrich et al., Phys. Rev. Lett. 90, 187601 (2003).
MA 28.13 Do 18:15 H23
Comparison of Network Analyzer Ferromagnetic Resonance
(NA-FMR) with pulsed inductive Measurements — •Ingo
Neudecker 1 , Georg Woltersdorfer 2 , Matthias Buess 1 , Christian
Back 1 , and Bret Heinrich 2 — 1 Fakultaet fuer experimentelle
und angewandte Physik, Universitaet Regensburg, Universitaetstrasse
31, 93044 Regensburg — 2 Simon Fraser University, 8888 University
Drive, Burnaby, British Columbia V5A-1S6, Canada
MA 29 Hauptvortrag Nielsch
We placed a 20 ML thick Fe film on top of a lithographically fabricated
coplanar waveguide. In a 20 GHz high frequency setup the ferromagnetic
system was excited first with a continuous sinusoidal excitation using a
Vector Network Analyzer and second without changing the setup with a
field pulse (pulse generator with 70 ps rise time) using a 20 GHz sampling
Oscilloscope to detect the signal.
By means of the resonance line one obtains from the NA-FMR both
the resonance frequency from its position and the damping constant from
its width. From the pulsed inductive measurement one extracts the resonance
frequency using Fourier transformation and the damping constant
from the decay of the observed oscillations.
Varying the magnetic bias field one can consequently derive the resonance
behavior for the two methods.
Our purpose was to compare the fairly new NA-FMR method with its
excellent signal to noise ratio which yields data in the frequency domain
with the pulsed inductive measurement providing a time domain access
to the resonance properties of the system.
MA 28.14 Do 18:30 H23
Coherent magnetization dynamics on Gd(0001) at 3 THz and its
temperature dependence — •Uwe Bovensiepen, Alexey Melnikov,
Ilie Radu, Oleg Krupin, Kai Starke, Eckart Matthias,
and Martin Wolf — Freie Universität Berlin, Fachbereich Physik,
Arnimallee 14, 14195 Berlin
Resonant absorption of femtosecond laser pulses at the exchange split
surface state of Gd(0001) excites coherent optical phonons, which lead
to a periodic modulation of the distance between surface and subsurface
layer with a frequency of 3 THz [1]. This vibration has been investigated
in situ by time-resolved second harmonic (SH) generation on Gd(0001)
films grown in ultrahigh vacuum on W(110). The magnetic SH contribution
has been extracted by analysis of the SH yield for opposite magnetization
directions. As a function of pump-probe delay a modulation of the
surface magnetization at 3 THz is detected, which is attributed to a modulation
of the exchange coupling due to the lattice vibration. We suggest,
that this quasi-instantaneous phonon-magnon coupling is observed near
the surface due to a crossing of phonon and magnon dispersion relations.
As a function of temperature the lattice and the magnetic oscillation
amplitude decrease and vanish near the Curie temperature.
Coherent bulk dynamics is observed by transient reflectivity at 10%
higher frequency. These modes are excited due to coupling of the subsurface
region to the surface vibration.
[1] A. Melnikov et al.; Phys. Rev. Lett., (2003) in press.
Zeit: Freitag 10:15–10:45 Raum: H10
Hauptvortrag MA 29.1 Fr 10:15 H10
Ferromagnetische Nanostäbe und Nanoröhren in selbstgeordneten
Aluminiumoxid-Membranen — •Kornelius Nielsch
— BMBF-Nachwuchsgruppe für Multifunktionale Nanostäbe und
Nanoröhren, Max-Planck-Institut für Mikrostrukturphysik, Halle
Die potentiellen Anwendungsgebiete für magnetische Nanoröhren und
Nanostäbe reichen von Biotechnologie zu MRAMs. Aufgrund der potentiellen
Anwendung als Datenspeicherung haben magnetische Nanostabensembles
eine besondere wissenschaftliche Aufmerksamkeit in jüngster
Zeit erfahren. Als Formstruktur wurden bienenwabenförmige Al2O3-
Membranstrukturen zur Herstellung der Ni-, Fe- oder Co-Stabensembles
mit periodischen Abständen von 65 nm und 100 nm und Durchmessern
von 25 bis 55 nm verwendet. Aufgrund von Selbstorganisation sind
die Nanostäbe hexagonal im 2D-Gittern quasi polykristallin angeordnet.
Vor allem Nickel-Nanostabensemles zeigten eine geringe Dipolwechselwirkung
im Ensemble und wurden intensiv mit SQUID-Magnetometer
und MFM charakterisiert. Mittels Imprint-Lithographie konnten großflächig
perfekt geordnete Stabensembles erzeugt werden. Ferner wurden
mittels Brillouin-Lichstreuung quantisierte Energiezustände in den
Magnetstäben nachgewiesen. Durch Polymerbeschichtung der Membranwände
konnten Kobalt-Nanoröhren mit einer Wandstärke von 5 bis
20 nm und einem Durchmesser von 200 bis 500 nm hergestellt werden.
Diese Arbeit fand in Zusammenarbeit mit den Arbeitsgruppen von Prof.
C.A. Ross (MIT, Boston, USA), Prof. H. Kronmüller (MPI-Stuttgart),
Prof D. Weiss (Uni Regensburg) und Prof. M.H. Kuok (National Universität
Singapur) statt.

Magnetismus Freitag
MA 30 Magnetische dünne Schichten III
Zeit: Freitag 10:45–12:45 Raum: H10
MA 30.1 Fr 10:45 H10
A XMCD study of GdN thin films and GdN/Fe Multilayers
— •Frank Leuenberger 1 , Anne Parge 1 , Kai Fauth 2 , François
Baudelet 3 , Christine Giorgetti 3 , Thomas Neisius 4 , Olivier
Mathon 4 und Wolfgang Felsch 1 — 1 I. Physikalisches Institut
Göttingen, Bunsenstr. 9, 37073 Göttingen — 2 Experimentelle Physik
IV, Universität Würzburg — 3 LURE, Centre Universitaire Paris-Sud,
France — 4 ESRF, BP 220, F-38043 Grenoble Cedex, France
In contrast to most rare-earth pnictides that are semimetals, there is
an uncertainty about the ferromagnet GdN. Recent calculations predict
GdN to be a semiconductor with a narrow indirect gap of 0.8eV [1], but
it is not clear if the gap closes below TC (∼60K) leading to a half- or
semimetal. The ferromagnetic exchange in GdN via 4f-5d-4f as well as
the antiferromagnetic via 5d-2p-5d is shown here by measureing the Gd
L2,3-, Gd M4,5- and the N K- edge dichroic signal. In case of the N-K dichroism
a preliminary LSDA+U calculation from H. Ebert an coworkers
shows a rough consistence with the measured signal, but can not explain
the whole singal. In GdN/Fe multilayers XMCD is the ideal method to
extract magnetic effects at the interface. Measurements of the dichroism
at the L and M edges of Gd show that the Fe induces magnetic order
on the Gd-5d and 4f states above TC(GdN) on a length scale of a few ˚A
near the interfaces by strong 3d-5d hybridization.
[1] W. R. L. Lambrecht, Phys. Rev. B, 62, 13538 (2000)
[2] R. E. Camley, Phys. Rev. B, 39, 12316 (1989)
MA 30.2 Fr 11:00 H10
Magnetism of thin Fe films on GaAs — •Michal Kosuth, Voicu
Popescu, and Hubert Ebert — Department Chemie / Physikalische
Chemie, Universität München, Butenandstr. 5-13, D-81377 München,
Germany
The electronic and magnetic properties of thin Fe layers on GaAs have
been studied using the fully-relativistic TB-KKR band structure method.
The most important features observed in the magnetisation profiles are
that no magnetically dead layers occur and there is an appreciable induced
magnetisation in the semiconductor subsystem. An increase of
the orbital moment in the Fe layers both at the surface as well as at
the Fe/semiconductor interface has been observed. Calculations of the
magnetocrystalline anisotropy energy for thin layers of Fe on a semiconductor
substrate confirm the preferable in-plane magnetisation with a
noticeable uniaxial character in accordance with experiments. To go beyond
the ideal Fe/GaAs interface, relaxation of the interface layer has
also been accounted for. Its quantitative and qualitative effects to the
magnetic properties will be presented and discussed.
MA 30.3 Fr 11:15 H10
Magnetismus an Fe/InAs(001) Grenzflächen — •Robert Peters
und Werner Keune — Laboratorium für Angewandte Physik, Universität
Duisburg-Essen, 47048 Duisburg, Germany
Die Injektion von spinpolarisierten Elektronen von einem Ferromagneten
in einen Halbleiter ist ein aktuelles Forschungsthema. Fe/InAs
ist ein möglicher Kandidat [1]. Dabei ist die Grenzflächenbeschaffenheit
ein wichtiger Aspekt [2]. Mit Mössbauerspektroskopie (CEMS) und
der Sondenschichtmethode ist es möglich, das magnetische Verhalten
des Fe-Films direkt an der Grenzschicht zu untersuchen. Zu diesem
Zweck wurde eine 4 ML dicke 57 Fe-Sondenschicht an der Grenzfläche
bei verschiedenen Substrattemperaturen TS = -125, 20 und 100 ◦ C
mittels MBE deponiert und mit RHEED kontrolliert. Die CEM
Spektren der Grenzflächensondenschicht wurden mit zwei Unterspektren
charakterisiert: (1) Ein reines bcc-Fe-Unterspektrum (Hyperfeinfeld
Bhf = 33.0 T) und (2) gestörtes bcc-Fe an der Grenzfläche mit einer
magn. Hyperfeinfeldverteilung P(Bhf), welche ein mittleres Hyperfeinfeld
〈Bhf〉 von 23 − 27 T ergibt. Dies entspricht einem relativ großen
lokalen Moment µFe von ≈ 1.5 − 1.8 µB an der Grenzfläche. Bei einem
Abstand der 57 Fe-Sondenschicht von 4 ML zur Grenzfläche sind die
Grenzflächeneffekte noch deutlich zu erkennen, aber bei einem Abstand
von 20 ML sind sie vernachlässigbar. Die Effekte sind vermutlich auf in
bcc-Fe gelöste As-Atome zurückzuführen.
Gefördert durch DFG (SFB 491).
[1] H. Ohno et al., Jpn. J. Appl. Phys 43 (2003) L87
[2] M. Zwierzycki et al., Phys. Rev. B 67 (2003) 092401
MA 30.4 Fr 11:30 H10
Struktur und Magnetismus von L10-geordneten FePt-Schichten
auf GaAs(001) — •Ellen Schuster 1 , Werner Keune 1 , Till
Schmitte 2 und Hartmut Zabel 2 — 1 Angewandte Physik, Universität
Duisburg-Essen, 47048 Duisburg, Germany — 2 Experimentalphysik
/ Festkörperphysik, Ruhr-Universität-Bochum, 44780 Bochum, Germany
Dünne Schichten mit senkrechter magnetischer Anisotropie (PMA)
auf Halbleitern sind für Anwendungen interessant. Es werden Resultate
an epitaktischen FePt-Schichten auf GaAs(001) (4 × 6) vorgestellt,
welche in der L10-Struktur eine große uniaxiale magnetokristalline
Anisotropie aufweisen. Untersucht wurden Proben, die mittels MBE
durch Lagenwachstum sowie durch Koverdampfen stöchiometrischer wie
auch nichtstöchiometrischer Legierungen bei unterschiedlichen Wachstumstemperaturen
TS hergestellt wurden. RHEED Untersuchungen zeigen,
dass diese FePt-Schichten auf einer 30˚A dicken Fe-Keimschicht, gefolgt
von einer 60˚A dicken Pt-Pufferschicht, epitaktisch wachsen. Die
langreichweitige Ordnung der L10-Stuktur konnte durch Röntgenbeugung
(XRD) bestimmt werden. Der chemische Ordnungsparameter steigt mit
zunehmender TS von nahezu Null bei TS = 200 ◦ C auf etwa 0,7 für
TS = 350 ◦ C an. Die lokalen magnetischen Eigenschaften wurden mittels
57 Fe-Mössbauerspektroskopie (CEMS) bei Raumtemperatur bestimmt.
Aus den CEM-Spektren wurden die Anteile der L10-geordneten und der
ungeordneten Phase bestimmt. Beide Phasenanteile zeigten bevorzugt
senkrechte Fe-Spinorientierung. Makroskopisch wurde die PMA anhand
von mittels polarem MOKE gemessenen Hystereseschleifen nachgewiesen.
Gefördert durch DFG (SFB491)
MA 30.5 Fr 11:45 H10
Phase formation, microstructure and hard magnetic properties
of electrodeposited FePt films — •Karin Leistner, Elke
Backen, Barbara Schüpp, Martin Weisheit, Ludwig Schultz,
Heike Schlörb, and Sebastian Fähler — IFW Dresden, Helmoltzstr.
20, 01069 Dresden
FePt is interesting for use in microelectromechanical systems and magnetic
recording due to its high magnetocrystalline anisotropy. Studies
up to now concentrate on films deposited by physical vapour deposition.
However, electrodeposition would be a more effective way to produce
films for such applications. FePt films of different compositions have
been electrodeposited on Cu coated Si substrates. After deposition, films
were annealed at temperatures of 400 - 900 ◦ C for 10 min in vacuum
or hydrogen atmosphere. Phase formation, microstructure and magnetic
properties are analysed. From these measurements, relationships between
microstructural features and magnetic properties are discussed and necessary
conditions to obtain good hard magnetic films are concluded. Magnetisation
values and coercivities strongly improve when annealing takes
place in the hydrogen atmosphere rather than in vacuum. Coercivity
reaches a maximum value of 1.1 T after annealing at 600 ◦ C, which is
higher than any value reported in literature for electrodeposited FePt
films.
MA 30.6 Fr 12:00 H10
Textured growth of highly coercive L10 ordered FePt thin films
— •Martin Weisheit, Ludwig Schultz, and Sebastian Fähler
— IFW Dresden, Helmoltzstr. 20, 01069 Dresden
Due to its high uniaxial magnetocrystalline anisotropy, the L10 ordered
FePt phase is seen as a future candidate for high density magnetic recording.
FePt thin films have been prepared by pulsed laser deposition onto
heated (001) oriented single crystalline (MgO, SrTiO3) as well as amorphous
substrates (Si3N4, glass) with and without a (001) textured MgO
buffer layer. Although all films have been prepared under identical conditions,
significant differences in coercivity are observed. Very high values
of µ0Hc = 5.6 T and 4.0 T have been measured for epitaxial films on
MgO and SrTiO3, respectively, while on the amorphous substrates the
coercivities range between 0.8 and 2.0 T. We discuss whether changes
in intrinsic or extrinsic properties due to a modified microstructure are
responsible for these differences.

Magnetismus Freitag
MA 30.7 Fr 12:15 H10
Herstellung, Präparation und Anwendung hartmagnetischer
FePt Bufferschichten — •Ingo Rohde, Sonja Heitmann, Andreas
Hütten und Günter Reiss — Universität Bielefeld, Fakultät für
Physik, Universitätsstr. 25, D-33615 Bielefeld
Um die Einsatzmöglichkeiten von GMR Sensoren für Anwendungen bei
verschiedenen Magnetfeldbereichen zu erweitern, ist es erforderlich, deren
Kennlinien durch Pinnen einer der magnetischen Elektroden anzupassen.
Hierzu wurden bisher überwiegend antiferromagnetische Buffer eingesetzt,
wobei hingegen in dieser Arbeit alternativ ein ferromagnetisches
Pinning durch eine hartmagnetische Schicht realisiert wurde.
Als Material wurde hierfür eine Fe45Pt55 Legierung gewählt, welche
in der fct Kristallphase sehr hohe Koerzitivfelder bei einer hohen
Sättigungsmagnetisierung aufweist. Es konnten hartmagnetische FePt
Schichten mit Schichtdicken von unter 5 nm präpariert werden, deren
strukturelle und magnetische Eigenschaften mittels XRD- und MOKE-
Untersuchungen bestimmt wurden. Die Eignung dieser Schichten zum
Pinnen von GMR Schichtsystemen konnte an GMR Dreilagern demonstriert
werden.
MA 30.8 Fr 12:30 H10
Resonante magnetische Röntgenstreuung an Co2MnGe-
Heusler-Einzelfilmen und -übergittern — •Johannes Grabis,
Alexei Nefedov, Andre Bergmann, Kurt Westerholt und
Hartmut Zabel — Institut für Experimentalphysik/ Festkörperphysik,
Ruhr-Universität Bochum, 44780 Bochum
MA 31 Spinelektronik
Halbmetallische, ferromagnetische Heuslerlegierungen wie Co2MnGe
besitzen ein großes Anwendungspotential im Bereich von spinelektronischen
Bauelementen. Gesputterte Einzelfilme und Übergitter
mit Au oder V als Zwischenschicht wurden mit Hilfe des magnetischen
Zirkulardichroismus (XMCD) und der resonanten magnetischen
Röntgenstreuung (XRMS) im Bereich der L2,3 Kanten von Co und Mn
untersucht. Während anhand der Absorptionsspektren die elemetspezifischen
Beiträge zum magnetischen Spin- und Bahnmoment berechnet
und die magneto-optischen Konstanten bestimmt werden können, bietet
die resonante Röntgenstreuung zusätzlich eine Möglichkeit der tiefenselektiven
Analyse der Schichtsysteme. Aus der spekulären Reflektivität
kann ein Magnetisierungstiefenprofil gewonnen werden. Die diffuse Streuung
liefert weitere Informationen über die Beschaffenheit der Grenzfläche
wie Rauhigkeiten und Korrelationslängen. Dieses Projekt wird gefördert
durch das BMBF, O3ZAE7BO.
Zeit: Freitag 10:45–12:45 Raum: H22
MA 31.1 Fr 10:45 H22
Ultrafast Relaxation and Dephasing of Hot Electron Spins
in n-GaAs — •Lars Schreiber, Marcus Heidkamp, Bernd
Beschoten, and Gernot Guentherodt — II. Physikalisches
Institut, RWTH Aachen, 52056 Aachen
Electron spins in n-doped GaAs exhibit longest spin lifetimes (> 100
ns) near the chemical potential for doping concentrations close to the
metal-insulator transition [1]. However, the relaxation and dephasing of
hot electron spins, which is of interest for spin-tunnel devices [2], is widely
unexplored. Therefore, we investigate the relaxation of hot electron spins
in n-GaAs for Si doping concentrations ranging from 2 × 10 15 cm −3 to
1 ×10 18 cm −3 at 6 K and 100 K using two-color time-resolved Kerr rotation
utilizing two phase-locked fs-lasers. This set-up allows to coherently
pump electron spins with excess kinetic energy and to monitor their intraband
relaxation for which the probe energy can be tuned independently.
Ultrafast relaxation (< 10 ps) of hot electron spins into both conduction
and donor band states is observed for all samples. Their subsequent
dephasing, however, strongly depends on the doping concentration and
the pump energy. Only for samples close to the metal-insulator transition
(nc ∼ = 2 × 10 16 cm −3 ) spin lifetimes are virtually independent of
the pump energy for all temperatures. For the degenerate samples an
ultra-fast transfer of spin angular momentum to the total electron sea is
observed indicating a collective interaction mediated by electron-electron
exchange. Supported by BMBF FKZ 01BM160 and 13N8244
[1] J. M. Kikkawa and D. D. Awschalom, PRL 80 (19), 4313 (1998)
[2] X. Jiang et. al., PRL 90 (25), 256603 (2003)
MA 31.2 Fr 11:00 H22
Utilizing the Rashba-effect at metal surfaces — •O. Krupin 1 ,
G. Bihlmayer 2 , S. Gorovikov 3 , J. E. Prieto 1 , K. Döbrich 1 ,
G. Kaindl 1 , S. Blügel 2 , and K. Starke 1 — 1 Institut für Experimentalphysik,
Freie Universität Berlin, Germany — 2 Institut für
Festkörperforschung (IFF), Forschungszentrum Jülich — 3 MAX-Lab,
Lund University, Sweden
Traditionally, semiconductor-heterostructures are considered as a base
for spintronic devices where the Rashba effect is exploited. An important
step for practical use, e.g. in coherent spin rotators and spin interference
devices, is to find structures that allow manipulation of electron spin
without an external magnetic field. Because of the large resistivity mismatch
at the ferromagnet/semiconductor interface, experiments based on
the idea to inject spin-polarised electrons from ferromagnetic metals have
so far shown only limited success. The Rashba effect, however, is much
more general and probably metals can be used as Rashba active media.
Surface states on closed packed surfaces of noble and rare earth metals
reveal a significant spin-orbit splitting. In addition, they also represent a
quasi two-dimensional electronic system in which the Rashba interaction
can be modified by adsorption. We characterize some of these surfaces
and discuss possible advantages and drawbacks of these systems.
MA 31.3 Fr 11:15 H22
Exchange interactions and Curie temperatures in diluted
magnetic semiconductors — •P. Dederichs 1 , K. Sato 1 , and H.
Katayama-Yoshida 2 — 1 IFF,Forschungszentrum Jülich, D-52425
Jülich — 2 ISIR, Osaka University, Ibaraki, Osaka 567-0047, Japan
The magnetic properties of diluted magnetic semiconductors are calculated
within the framework of the KKR-CPA, using a mapping on a
Heisenberg model. Effective exchange coupling constants are evaluated
by embedding two impurities in the CPA medium. Curie temperatures
(Tc) are estimated by the mean-field approximation (MFA), the random
phase approximation (RPA) and by monte carlo methods. In MFA and
RPA, Tc is proportional to the square root of Mn concentration c for
(Ga, Mn)N, while in (Ga, Mn)Sb Tc is linear to c. Since the extended
hole states mediate the ferromagnetism in (Ga,Mn)Sb (p-d) exchange),
the interaction is long range leading to a flat spin wave dispersion. Thus,
the MFA gives similar results as the RPA. In (Ga, Mn)N, due to the
broadening of the impurity bands in the gap, the ferromagnetic state is
stabilized by double exchange. Since the impurity states are well localized,
the exchange interaction is short range leading to dispersive magnon
bands and the MFA values deviate from the RPA values. However the
reliability of both MFA and RPA are in this case questionable.
MA 31.4 Fr 11:30 H22
Magnetic Circular Dichroism Study of Ferromagnetic GaMnN
— •J. Keller 1 , A. Dohmen 1 , B. Beschoten 1 , G. Güntherodt 1 ,
S. Dhar 2 , O. Brandt 2 , A. Trampert 2 , L. Däweritz 2 , K.J.
Friedland 2 , and K.H. Ploog 2 — 1 2. Physikalisches Institut, RWTH
Aachen, D-52056 — 2 Paul-Drude-Institut für Festkörperelektronik,
Hausvogteiplatz 5-7, D-10117 Berlin
Because of possible applications in spinelectronics, there is a renewed
interest in diluted magnetic semiconductors. We have investigated GaN
thin films doped with Mn [1]. Depending on the Mn concentration, the
GaMnN films are paramagnetic or ferromagnetic. At low temperatures,
all samples exhibit spin-glass like behavior. Structural characterization
reveals that Mn-rich clusters are formed in the ferromagnetic samples,
while the paramagnetic samples form a uniform alloy of (Ga,Mn)N. To
further investigate the magnetic properties of these samples, we have per-

Magnetismus Freitag
formed magnetic circular dichroism (MCD) measurements in the visible
spectral range of light. The MCD spectra of all samples show peak structures
around 1.5eV and a very broad structure around 2.5eV with a superimposed
substructure. In addition, the paramagnetic samples exhibit
a peak around 1.8eV. According to [2], the peak at 1.5eV can be assigned
to an excited neutral acceptor state and the peak at 1.8eV to a transition
from Mn 3+ to Mn 2+ , while according to [3] the peak at 1.5eV corresponds
to the charged acceptor state. Supported by BMBF/FKZ01BM160.
[1] S. Dhar et al., Appl. Phys. Lett. 82, 2077 (2003)
[2] T. Graf et al., Appl. Phys. Lett. 81, 5159 (2002)
[3] R.Y. Korotkov et al., Appl. Phys. Lett. 80, 1731 (2002)
MA 31.5 Fr 11:45 H22
Which Mn is ferromagnetic in Ga1−xMnxAs? — •O. Rader 1 ,
K. Fauth 2 , G. Schott 2 , G. Schmidt 2 , L. Molenkamp 2 , G.
Schütz 3 , F. Kronast 1 , and W. Gudat 1,4 — 1 BESSY, 12489 Berlin
— 2 Physikalisches Institut, Universität Würzburg, 97074 Würzburg
— 3 MPI für Metallforschung, 70569 Stuttgart — 4 Institut für Physik,
Universität Potsdam, 14415 Potsdam
The origin of ferromagnetism in the diluted magnetic semiconductor
Ga1−xMnxAs is a matter of controversy. In spite of important contributions
from electron spectroscopy, understanding the electronic structure
has been hampered by an indistinguishability of Mn atoms. We combine
sensitivity to atomic number, chemical shifts, and to magnetic order in a
field-dependent (0-2.4 T) magnetic circular x-ray dichroism study at the
Mn L-edge and observe three constituents of distinct magnetic behavior.
We find that ferromagnetic Mn deviates more strongly from a 3d 5 configuration
than assumed previously, that superparamagnetic clusters of
20µB are formed, and that interstitial Mn, previously considered the key
to highest TC’s, does not contribute to the ferromagnetism.
MA 31.6 Fr 12:00 H22
Nonequilibrium spin transport in ballistic ferromagnetic - semiconductor
structures — •Dmitri Ryndyk — Institut für Theoretische
Physik, Universität Regensburg, 93040 Regensburg
We consider spin injection and spin accumulation in ferromagnetic(F)
- semiconductor(Sc) structures. In particular, spin-dependent
transport phenomena can be observed in tunneling through a (un-
doped) semiconductor barrier and in double F-I-Sc-I-F tunnel junctions.
Using nonequilibrium Green function technique, nonequilibrium
spin states, and crossover from coherent to incoherent quantum transport
in ferromagnetic-semiconductor-ferromagnetic junctions are studied
theoretically beyond the Landauer framework of ballistic transport.
MA 31.7 Fr 12:15 H22
Transport properties of Fe/MgO/Fe interfaces — •Bogdan Yavorsky,
Peter Zahn, and Ingrid Mertig — MLU Halle-Wittenberg,
Fachbereich Physik, D-06099 Halle, Germany
The transport properties and tunneling magnetoresistance (TMR) of
an Fe/MgO/Fe tunnel junction have been studied by means of an ab initio
electronic structure calculation. The electronic structure was calculated
within a tight-binding Korringa-Kohn-Rostoker (TB-KKR) method. The
influence of structural relaxation, formation of an FeO - layer and noncollinear
magnetic order at the interface on the conductance and TMR
are discussed.
MA 31.8 Fr 12:30 H22
Nanosecond Pulse Characterization of Magnetic Tunnel Junctions
— •Roman Adam 1 , Jakob Schelten 1 , Michael Siegel 2 , and
Hermann Kohlstedt 3 — 1 Institute of Thin Films and Interfaces, Research
Center Jülich, D-52425 Jülich, Germany — 2 Institute of Solid
State Research, Research Center Jülich, D-52425 Jülich, Germany —
3 Institut für Elektrotechnische Grundlagen der Informatik, Universtät
Karlsruhe D-76187 Karlsruhe, Germany
We fabricated and tested Co/Al2O3/Co magnetic tunnel junctions
(MTJ) embedded in coplanar strip (CPS) transmission lines designed for
high-frequency device measurements. MTJs were defined by photolithography
and by Ar ion-beam etching resulting in device area ranging from
2 × 6µm 2 to 3 × 18µm 2 . After MTJ and CPS fabrication, selected chip
area was covered with SiO2 thin film for isolation. Control lines passing
in 400 nm distance above MTJs were finally defined by lift-off. Our MTJs
show a magnetoresistance effect up to 17.5 % at room temperature. To
characterize device high-frequency response, MTJs were excited by 5- to
50-ns-long electrical pulses applied to the control line. Device response
due to the MTJ top electrode magnetization reversal was observed experimentally
and compared with simulations.

Metallphysik Tagesübersichten
Hauptvorträge
METALLPHYSIK (M)
Prof. Dr. Winfried Petry
Physik Department E13 und ZWE FRM-II
Technische Universität München
James-Franck-Str. 1
85748 Garching
E-Mail: winfried.petry@frm2.tum.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsäle H16)
M 1.1 Mo 09:30 (H16) Diffraction experiments on undercooled metallic melts, Dirk Holland-Moritz
M 6.1 Mo 14:00 (H16) Computer Simulations of Transport Processes in Multicomponent Melts,
Jürgen Horbach
M 11.1 Di 09:30 (H16) Ab-initio thermodynamics of metal alloys: From the atomic to the mesoscopic
scale, Stefan Müller
M 17.1 Di 14:00 (H16) Metal Physics in Heat Treatment Technology - Carburization and Decarburization
of Steels, Jürgen Gegner, Peter-J. Wilbrandt, Reiner Kirchheim,
Wolfgang Nierlich
M 19.1 Mi 14:00 (H16) Combined Reaction Processing of Fe-Pd based Ferromagnetic Intermetallics,
Jorg Wiezorek
M 23.1 Do 09:30 (H16) Plasticity in body-centred cubic structures with emphasis on lowtemperature
behaviour, Dieter Brunner
M 28.1 Do 14:00 (H16) Noble gases as model systems to study solidification behaviour of metals,
J.H. Bilgram
Fachsitzungen
M 1 Hauptvortrag Dirk Holland-Moritz Mo 09:30–10:00 H16 M 1.1–1.1
M 2 Flüssige und amorphe Metalle I Mo 10:15–11:15 H16 M 2.1–2.4
M 3 Wasserstoff in Metallen Mo 10:15–11:15 H4 M 3.1–3.4
M 4 Flüssige und amorphe Metalle II Mo 11:45–12:45 H16 M 4.1–4.4
M 5 Elektronische Eigenschaften Mo 11:45–12:45 H4 M 5.1–5.4
M 6 Hauptvortrag Jürgen Horbach Mo 14:00–14:30 H16 M 6.1–6.1
M 7 Glasdynamik Mo 14:45–16:00 H16 M 7.1–7.5
M 8 Phasenumwandlungen I Mo 14:45–16:00 H4 M 8.1–8.5
M 9 Flüssige und amorphe Metalle III Mo 16:30–18:00 H16 M 9.1–9.6
M 10 Diffusion Mo 16:30–18:00 H4 M 10.1–10.6
M 11 Hauptvortrag Stefan Müller Di 09:30–10:00 H16 M 11.1–11.1
M 12 Phasenumwandlungen II Di 10:15–11:15 H16 M 12.1–12.4
M 13 Mechanische Eigenschaften I Di 10:15–11:15 H4 M 13.1–13.4
M 14 Flüssige und amorphe Metalle IV Di 10:15–11:30 H6 M 14.1–14.5
M 15 Phasenumwandlungen III Di 11:45–12:45 H16 M 15.1–15.4
M 16 Mechanische Eigenschaften II Di 11:45–12:45 H4 M 16.1–16.4
M 17 Hauptvortrag Jürgen Gegner Di 14:00–14:30 H16 M 17.1–17.1
M 18 Postersitzung Di 14:30–16:30 Saal C M 18.1–18.29

Metallphysik Tagesübersichten
M 19 Hauptvortrag Jorg Wiezorek Mi 14:00–14:30 H16 M 19.1–19.1
M 20 Nanoskalige Materialien I Mi 14:45–16:00 H4 M 20.1–20.5
M 21 Nanoskalige Materialien II Mi 16:30–17:30 H4 M 21.1–21.4
M 22 Intermetallische Phasen Mi 16:30–18:00 H6 M 22.1–22.6
M 23 Hauptvortrag Dieter Brunner Do 09:30–10:00 H16 M 23.1–23.1
M 24 Nanoskalige Materialien III Do 10:15–11:15 H16 M 24.1–24.4
M 25 Mechanische Eigenschaften III Do 10:15–11:15 H4 M 25.1–25.4
M 26 Nanoskalige Materialien IV Do 11:45–12:45 H16 M 26.1–26.4
M 27 Mechanische Eigenschaften IV Do 11:45–12:45 H4 M 27.1–27.4
M 28 Hauptvortrag Jörg Bilgram Do 14:00–14:30 H16 M 28.1–28.1
M 29 Quasikristalle I Do 14:45–16:00 H16 M 29.1–29.5
M 30 Mechanische Eigenschaften V Do 14:45–16:00 H4 M 30.1–30.5
M 31 Quasikristalle II Do 16:30–18:00 H16 M 31.1–31.6
M 32 Grenzflächen und Wachstum Do 16:30–17:30 H4 M 32.1–32.4
Symposia
Physics of Foams (SYPF), gemeinsam mit FV DY
Mittwoch 10.03.2004, 14:45-18:00, Hörsaal H16
Postersitzung (SYPF-5) Dienstag 9.03.2003, 14:30-16:30, Saal C
Magnetic Shape Memory Alloys (MA-23 und MA-24), gemeinsam mit FV MA
Donnerstag 11.03.2004, 10:15-13:15, Hörsaal H23
Mitgliederversammlung des Fachverbands Metallphysik
Di 16:30–18:00 B305
Tagesordnung
Berichte des Fachverbandvorsitzenden und des AGM Vorsitzenden
Frühjahrstagung 2004, Beiträge, Statistiken
Neue Themenfelder und Symposia für die Metallphysik
Vörschläge für Hauptvorträge
Sonstiges
Sitzung der AGM, Donnerstag 11.03.2003, 20:00 Uhr, gesonderte Einladung

Metallphysik Montag
Fachsitzungen
– Haupt-, Kurzvorträge und Posterbeiträge –
M 1 Hauptvortrag Dirk Holland-Moritz
Zeit: Montag 09:30–10:00 Raum: H16
Hauptvortrag M 1.1 Mo 09:30 H16
Diffraction experiments on undercooled metallic melts — •Dirk
Holland-Moritz — DLR, Institut für Raumsimulation, D-51170 Köln
Following the pioneering work of Frank in 1952, an icosahedral shortrange
order should be energetically favoured in undercooled metallic
melts. Although this hypothesis is nearly 50 years old, direct experimental
information on the short-range order prevailing in undercooled metallic
liquids is only available for a short time. This work presents recent investigations
on the short-range order of stable and deeply undercooled liquids
of the pure elements Ni, Co, Zr and Fe and alloys forming polytetrahedral
phases (Al13(Fe, Co)4). The liquids were containerlessly processed
und undercooled by use of the electromagnetic levitation technique which
was combined with techniques of elastic neutron scattering and energy
M 2 Flüssige und amorphe Metalle I
dispersive diffraction of synchrotron radiation in order to determine the
structure factors of the liquids as a function of the temperature.
The measured structure factors are well described if an icosahedral
short-range order is assumed to prevail in the melt. This short-range order
is observed even at temperatures above the melting temperature and
gets more pronounced if the liquids are undercooled. In the case of the
Al-based alloy melts forming polytetrahedral phases, the investigations
are indicative of a pronounced chemical order such that the first coordination
shell around a transition metal atom consists preferentially of
Al-atoms.
This work was supported by DFG under contract Nos. Ho1942/1,
Ho1942/2 and Ho1941/4.
Zeit: Montag 10:15–11:15 Raum: H16
M 2.1 Mo 10:15 H16
Medium range order in molten intermetallic alloys: Dynamics
of the prepeak — •Sandro Jahn 1 and Jens-Boie Suck 2 — 1 PTCL,
Oxford University, South Parks Road, Oxford OX1 3QZ, UK — 2 Institut
of Physics, Materials Research and Liquids, TU Chemnitz, 09107 Chemnitz
In molten intermetallic alloys of the Zintl-type a structural feature is
observed in the static structure factor S(Q) at Q around 10 nm −1 . This so
called prepeak represents correlations on length scales beyond the nearest
neighbour atomic distance, which occur as a result of charge transfer
between the different species and the formation of ionic and partly covalent
bonds. Computer simulations show the persistence of polyanionic
networks in the liquid state. Here we present first dynamic measurements
around the prepeak region for three different alloy systems, Na-Sn, Rb-
Sb and K-Sb, using cold neutron quasielastic scattering. From the width
of the quasielastic line we can estimate the lifetime of the structures responsible
for the prepeak. The decay of the correlation function is slowed
down considerably in the prepeak region, but the actual decay time depends
strongly on the size of the ions.
M 2.2 Mo 10:30 H16
Aerodynamisch Levitieren und elektromagnetisch Heizen -
ein neues Anlagenkonzept für Strukturuntersuchungen an
unterkühlten Schmelzen — •Gerhard Mathiak und Ivan Egry
— Institut für Raumsimulation, DLR, Linder Höhe, 51170 Köln
Der kombinierte Einsatz von behälterfreien Techniken und hochenergetischer
Strahlung (Röntgenstrahlung, Neutronen) ermöglicht Strukturuntersuchungen
an korrosiven und unterkühlten Schmelzen. Im Rahmen
eines DFG/CNRS-Projektes wird hierzu in Zusammenarbeit mit D. Price
(CRHMT Orleans) eine neuartige Anlage entwickelt, die die aerodynamische
Levitation mittels einer konischen Düse mit elektromagnetischem
Heizen verbindet. Vorteile und Konzept dieser Anlage werden diskutiert.
Insbesondere wird ein Spulensystem vorgestellt, das die Probe isotrop
stabilisiert und das Probenvolumen gleichmäßig induktiv heizt. Erste
Röntgenbeugungs- und Absorptionsexperimente an binären metallischen
Schmelzen sind für 2004 am ESRF (Grenoble) geplant.
M 2.3 Mo 10:45 H16
Zur Struktur flüssiger Elemente — •Peter Häussler — TU
Chemnitz, Institut für Physik, D-09107 Chemnitz
Eines der großen ungelösten Probleme der Physik kondensierter Materie
stellt noch immer die Frage dar, wie sich aus der Unordnung heraus
beim Abkühlen langreichweitige Ordnung bildet. Im Allgemeinen nimmt
man an, dass die lokale Quantenchemie die Hauptrolle spielt und globale
Effekte eine vernachlässigbare oder keine Rolle spielen (die Packung
harter Kugeln bestimmt auch die Lage der Atome im mittleren Abstandsbereich).
In meinem Beitrag soll gezeigt werden, dass es globale Effekte
gibt und dass ihre Kenntnis es erlaubt Vorhersagen zur Struktur flüssiger
und amorpher Systeme zu machen. Das Modell wird vorgestellt und auf
alle bekannten flüssigen und amorphen Elemente vom Wassertoff (OZ=1)
bis zu Wismut (OZ=83) angewendet.
M 2.4 Mo 11:00 H16
Struktur amorphen Wismuts — •Peter Häussler und Michael
Lang — TU Chemnitz, Institut für Physik, D-09107 Chemnitz
Wismut ist das erste metallische Glas, das weltweit in den fünfziger
Jahren entdeckt wurde. Abhängig von der Dicke des Films kristallisiert
es bereits bei 9K < T < 15K. Die Amorphizität wurde damals mittels
Elektronenbeugung in Transmission gemessen, wobei die Verteilung der
gestreuten Elektronen jedoch nur durch die Schwärzung, die sie auf einer
Photoplatte erzeugen, qualitativ gemessen wurde.
Dies hat damals genügt, doch gibt es mittlerweile quantitative Methoden
und außerdem gibt es eine Weiterentwicklung der Vorstellung
darüber, was bei der Strukturbildung einer Phase in den frühen Stadien
geschieht. Wir wissen heute, dass Resonanzen zwischen der Gesamtheit
aller Valenzelektronen und der sich bildenden Struktur eine große Rolle
spielen. Außerdem konnte in der Vergangenheit festgestellt werden, dass
nur geringe Zusätze von Gold zu einer einfach kubischen Phase führen.
Unter diesen Gesichtspunkten haben wir die Struktur von Bi mittels Elektronenbeugung
quantitativ durch einen Halbleiterzähler aufgenommen
und auch die Paarverteilung im Realraum mittels Fouriertransformation
berechnet. Die Ergebnisse werden vorgestellt und im Zusammenhang mit
fundamentalen Szenarien der Strukturbildung diskutiert.

Metallphysik Montag
M 3 Wasserstoff in Metallen
Zeit: Montag 10:15–11:15 Raum: H4
M 3.1 Mo 10:15 H4
Pd-H culsters: Like and faraway from bulk-like behaviour —
•M. Suleiman 1 , N. M. Jisrawi 2 , C. Borchers 1 , C. Bähtz 3 , D.
Marcano 1 , R. Kirchheim 1 , and A. Pundt 1 — 1 Institut für Materialphysik,
Tammannstr. 1, D-37077 Göttingen — 2 Dept. of Physics,
Berzeit university POB 14, Berzeit, Palestine — 3 Darmstadt University
of Technology, Institute of Material Science, 64287 Darmstadt
The thermodynamic and the kinetic absorption behaviour of the Hydrogen
in nanometer-sized Palladium clusters will be discussed. Pressureconcentration
isotherms (P-x-T) obtained from gravimetric measurements
will be presented. The absorption isotherms resemble those for
bulk palladium above the critical temperature showing a sloped plateau.
However, adsorbtion isotherms show the existence of a hysteresis even in
the smallest (3.0 nm ) clusters indicating a phase transition. Structural
information obtained by in-situ XRD measurements during Hydrogen
loading will be presented. The large Pd clusters show the (α-β) phase
transition common for bulk Pd, whereas smaller clusters show another
type of phase transition. The effect of the cluster size and structure on
these observations will be discussed.
M 3.2 Mo 10:30 H4
Raman spectroscopy on β-YH2+δ and β-YD2+δ thin films — •A.-
M. Carsteanu, M. Rode, D. Zur, A. Borgschulte, H. Schröter,
and J. Schoenes — Institut für Halbleiterphysik und Optik, TU Braunschweig,
Mendelssohnstrasse 3, 38106 Braunschweig, Germany
The hydrides of yttrium and other rare-earth metals have been the
subject of increasing research due to their switchable optical properties.
The metal insulator transition of Y films grown on (111) CaF2 substrates
and capped with Pd is monitored using Raman spectroscopy. In the β
phase of YH2+δ and YD2+δ we find changes in the spectra, showing the
existence of a new intermediate phase. The new spectrum is also observed
for an in situ grown YH2+δ film. An analysis of the factor group of this
system indicates that the intermediate phase has the I4/mmm structure.
Temperature dependent measurements point to a short-range ordering of
the hydrogen sublattice above 150 K.
M 3.3 Mo 10:45 H4
NMR mit hyperpolarisierten Protonen — •Christoph Bommas,
Andre Engelbertz, A Sameh und Karl Maier — HISKP Bonn,
Nussallee 14-16, 53113 Bonn
M 4 Flüssige und amorphe Metalle II
Konventionelle NMR benötigt ca. 10e18 Kerne für ein Induktionssignal
bei Raumtemperatur. Die Hauptursache für diese geringe Empfindlichkeit
ist ein Boltzmannfaktor von wenigen ppm in einem Magnetfeld von
einem Tesla. NMR Experimente an Wasserstoff sind daher nur in Metallen
mit extrem großer Wasserstofflöslichkeit in der alpha-Phase möglich.
Mit einem polarisierten Protonenstrahl reichen 10e13 Kerne für ein NMR
Signal aus. Diese Protonenzahl wird bei 40 K in einem Strahlpuls mit 7
MeV in Au, PtRh und W-Folien implantiert und durch Messung des
freien Induktionszerfalls (FID) analysiert.
M 3.4 Mo 11:00 H4
NMR studies of hydrogen dynamics in metal-hydrides —
•Farida Grinberg 1 , Ahmad Telfah 1 , Günter Majer 1 , Richard
G. Barnes 2 , and Alexander V. Skripov 3 — 1 Max-Planck-Institut
für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart — 2 Ames
Laboratory, Iowa State University, Ames, Iowa 50011, USA — 3 Institute
of Metal Physics, Urals Branch of the Academy of Sciences, Ekaterinburg
620219, Russia
Hydrogen is undisputedly a promising source of new clean and renewable
energy. Nowadays, a successful introduction of the hydrogen based
fuel systems still demands solving many fundamental and technical problems.
One of the major challenges is connected with the development of
suitable materials for hydrogen storage designed to meet international
requirements (storage volume and mass density, kinetics, reversibility,
safety and cost). Currently, various metal-hydrogen systems are intensively
investigated as potentially efficient hydrogen carriers. This work
represents a proton NMR study of such systems including yttrium hydrides
and hydrides of intermetallic (Ta-V) compounds. We discuss the
information on the microstructure of the material and the hydrogen dynamics
obtained on the basis of proton spectra, relaxation rates and diffusivities
measured in a broad temperature range. The emphasis will be
done on some striking findings like, in particular, an extraordinary large
Pake-like doublet splitting observed in YH3 and an extremely strong dependence
of hydrogen diffusivity on the material composition in Ta-V
compounds.
Zeit: Montag 11:45–12:45 Raum: H16
M 4.1 Mo 11:45 H16
Bildung dendritischer Mikrostrukturen in Glaskompositen
bei der Erstarrung mehrkomponentiger Schmelzen — •Y.-L.
Huang 1 , S. Schneider 1 , M. Seibt 1 und K. Samwer 2 — 1 IV.
Physikalisches Institut, Universität Göttingen, 37077 Göttingen — 2 I.
Physikalisches Institut, Universität Göttingen, 37077 Göttingen
Glaskomposite entstehen während des Abkühlens aus mehrkomponentigen
Schmelzen. Bei der Erstarrung aus der Schmelze entstehen dabei
kristalline Dendrite, die in einer Glasmatrix eingebettet sind. Diese
intrinsischen Glaskomposite zeigen sehr gute mechanische Eigenschaften.
Die Mikrostruktur und die Zusammensetzungen der Dendriten und
der Glasmatrix wurden mittels analytischer Transmissionselektronenmikroskopie
(TEM) ermittelt. Die thermische Stabilität und das Kristallisationsverhalten
der Matrix wurden mit dem TEM, Weitwinkelröntgenbeugung,
kalorimetrischer Methoden (DSC) und Kleinwinkelneutronenstreuung
(SANS) untersucht. Vergleiche zwischen dem Kristallisationsverhalten
von der Glasmatrix der Komposite und homogen aus der
Schmelze erstarrte Gläser zeigen ähnlichkeiten hinsichtlich ihrer Zusammensetzung,
der kalorimetrischen Eigenschaften und der Tendenz Quasikristalle
zu bilden. Das Auftreten von Grenzflächeninstabilitäten, die zum
Dendritenwachstum in glasbildenden Systemen führen, und eine mögliche
Beschreibung mit einem erweiterten Phasenfeldmodell werden diskutiert.
Das Projekt wird von der DFG im Schwerpunktprogramm 1120
gefördert.
M 4.2 Mo 12:00 H16
Dreidimensionale Phasenfeld-Simulationen der Erstarrung eutektischer
Legierungen — •Mathis Plapp und Andrea Parisi —
Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique,
91128 Palaiseau, Frankreich
Die Phasenfeld-Methode hat sich in den letzten Jahren als Methode
der Wahl für die Simulation von Mikrostrukturbildung bei der Erstarrung
etabliert. Eine ihrer herausragenden Eigenschaften ist, dass komplizierte
dreidimensionale Strukturen dynamisch behandelt werden können. Wir
wenden diese Methode hier auf die gerichtete Erstarrung einer eutektischen
Legierung an und untersuchen insbesondere lamellare Strukturen.
Seit den Arbeiten von Jackson und Hunt ist bekannt, dass eine Familie
von stationären Zuständen existiert, die durch den Lamellenabstand parametrisiert
wird. Die Stabilität solcher Zustände ist bisher nur in zwei
Dimensionen untersucht worden. In drei Dimensionen treten neue Instabilitäten
auf, die den Bereich stabiler Abstände wesentlich einschränken.
Wir stellen ein Stabilitätsdiagramm auf und diskutieren die daraus resultierenden
Konsequenzen für die Verteilung der Lamellenabstände in
ausgedehnten Systemen.
M 4.3 Mo 12:15 H16
Numerical simulations of growth morphologies and characteristic
microsrtucture quantities in a binary eutectic alloy — •Denis
Danilov and Britta Nestler — Fachhochschule Karlsruhe
Recently, a generalized phase-field model has been formulated by Gar-

Metallphysik Montag
cke, Nestler and Stinner that is especially appropriate for modelling
phase transitions in alloy systems with multiple components and multiple
phases. In this work we explore characteristic microsrtuctures occuring
in different regions of a typical binary eutectic phase diagram
using uniform approach based on the generalized phase-field model both
for simulation of single phase growth and for two phase growth structures.
To obtain numerical solution of governing equations we use finite
element method with an adaptive mesh refinement. Simulations include
single primary phase growth and melting of eutectic structure above the
eutectic temperature and eutectic and off-eutectic solidification below.
Components redistribution in the liquid along the solidification front and
along the growth direction for different growing structures, dependence
of two phase lammelar growth on value of surface entropy densities are
analysed and compared with theoretical predictions.
M 4.4 Mo 12:30 H16
A Multiscale 3D Simulator for Dendritic and Eutectic Structure
Formation — •Frank Wendler and Britta Nestler — University
of Applied Sciences Karlsruhe, Germany
Diffuse interface models allow for an effective computational treatment
M 5 Elektronische Eigenschaften
of free boundary problems with complicated interface morphology. Here
different solidification phenomena of pure metals, binary and ternary alloys
are studied relying upon the formerly introduced multi-phase-field
model [1,2].
After an appropriate choice of thermophysical and numerical parameters,
quantitative 2D and 3D calculations of dendritic solidification in a
pure melt (Ni) and in binary (Ni-Cu) and ternary alloys were performed.
The following analysis of the simulation data provides the dynamical and
geometrical parameters. For the dendritic phases these quantities are the
tip speed, the tip radius and the primary arm spacing, which are compared
with theoretical and experimental data. Also, a strong influence
of the interplay between kinetic and surface anisotropy on the dendrite
morphology is observed. Smooth anisotropic and facetted patterns are
simulated and compared. For the examined binary and ternary eutectic
systems, characteristic lamellae spacings are found and related to the
classical theory of Jackson and Hunt and to a new analytical extensions
of this theory for ternary systems.
[1] B. Nestler, A.A. Wheeler, Physica D 138 (2000) 114-133
[2] H. Garcke, B. Nestler und B. Stinner, SIAM J. on Appl. Math., in
print
Zeit: Montag 11:45–12:45 Raum: H4
M 5.1 Mo 11:45 H4
Perfectly transferable many-body potentials and related generalized
cluster expansions not confined to lattices — Ralf
Drautz 1 , •Manfred Fähnle 1 , and Juan M. Sanchez 2 — 1 MPI für
Metallforschung, Heisenbergstr. 3, 70569 Stuttgart, Germany — 2 Texas
Materials Institute, The University of Texas at Austin, Austin, Texas
78712
There are two main streams for the parametrized representation of the
energy of a system of atoms, the expansion into many-body potentials
(which focusses on the positional degrees of freedom) and the conventional
cluster-expansion technique [1] (which focusses on the ordering
degrees of freedom in multicomponent lattice systems). To accelerate
the convergence of the many-body expansion, often empirical effective
and environment-dependent many-body potentials with fitting parameters
are used which have the disadvantage that they are accurate only
for configurations close to certain reference configurations. We demonstrate
how perfectly transferable many-body potentials can be generated
by ab-initio total energy calculations. The so-defined many-body potentials
can be used to compare empirical energy parametrizations on the
basis of the behaviour of their respective potential expansion. It is shown
how the techniques of the many-body expansion and of the conventional
cluster-expansion can be merged to a generalized cluster-expansion not
confined to lattices.
[1] J. M. Sanchez et al., Physica 128A, 334 (1984).
M 5.2 Mo 12:00 H4
A quantum chemical ab-initio calculation of the cohesive energy
of mercury — •Beate Paulus 1 and Krzysztof Rosciszewski 1,2 —
1 Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Straße
38, D-01187 Dresden — 2 Institute of Physics, Jagellonian University,
Reymonta 4, Pl 30-059 Krakow, Poland
The cohesive energy of solid mercury in the rhombohedral structure
is determined within an ab-initio many-body expansion for the correlation
part. Very good agreement with the experimental value is obtained.
The self-consistent field ( Hartree-Fock) part is repulsive, the binding is
entirely due to correlations. The correlation of the closed 5d shell contributes
about half the cohesive energy. Relativistic effects are found to
be very important.
M 5.3 Mo 12:15 H4
Initial and final state band contributions in angle resolved
photoemission spectra of Bi(111) — •Christian Ast 1,2 and
Hartmut Höchst 1 — 1 Synchrotron Radiation Center, University of
Wisconsin-Madison, Stoughton, WI, USA — 2 Max-Planck-Institut für
Festkörperforschung, Stuttgart
Establishing the bulk valence band dispersion Ei(k) from angle resolved
photoemission spectra is still an ongoing challenge since the final
state bands Ef(k) are generally not known. However, using a broad range
of photon energies the measurements extend over several bulk Brillouin
zones which can then be used to extract information about the valence
band states. An analysis is presented in which the final and initial state
dispersion along ΓT is extracted from photoemission spectra of Bi(111).
We will show that the free electron final state (FEFS) model is valid
above 60eV. For lower photon energies, we establish an energy dependent
extension of the FEFS’s. Because of direct and umklapp transitions
into multiple final states we observe emission gaps indicating avoided
crossings in certain branches of the final state bands. Once the origin of
these additional features is identified, the true bulk valence band dispersion
can be established.
M 5.4 Mo 12:30 H4
Oktaederverkippung in ACu3Ru4O12 (A=Na, Ca, Sr, La, Nd) —
•Udo Schwingenschlögl, Volker Eyert und Ulrich Eckern —
Theoretische Physik II, Institut für Physik, Universität Augsburg, 86135
Augsburg
Wir haben die elektronischen Eigenschaften der perovskit-artigen Verbindungen
ACu3Ru4O12 (A=Na, Ca, Sr, La, Nd) anhand von Bandstrukturrechnungen
basierend auf der Dichtefunktionaltheorie und der lokalen
Dichtenäherung untersucht [1]. Die elektronische Struktur dieser Materialien
wird in erheblichem Maß von kovalenten Bindungsanteilen zwischen
Übergangsmetal d- und Sauerstoff p-Zuständen beeinflusst. Insbesondere
ist die charakteristische Verkippung der RuO6 Oktaeder auf starke Cu-O
Hybridisierung zurückzuführen. Im Gegensatz dazu werden sowohl die
Ru-O als auch die A-O Bindungslängen durch das Verkippen der Oktaeder
kaum beeinflusst. Die beobachteten ungewöhnlich kleinen A-O Bindungsabstände
und damit das Fehlschlagen des Bond-Valence Modells
sind eine Folge der im Vergleich zu den Cu-O Bindungen nur schwachen
A-O Hybridisierung. Unsere Ergebnisse erlauben ein besseres Verständnis
der Oktaederverkippung als universellen Mechanismus der Optimierung
von Bindungsabständen in perovskit-artigen Materialien. Gerade bei der
Suche nach neuartigen Materialeigenschaften ist dies wegen der Auswirkungen
der strukturellen Verzerrung auf die physikalischen Eigenschaften
von speziellem Interesse.
[1] U. Schwingenschlögl, V. Eyert, and U. Eckern, Chem. Phys. Lett.
370, 719 (2003)

Metallphysik Montag
M 6 Hauptvortrag Jürgen Horbach
Zeit: Montag 14:00–14:30 Raum: H16
Hauptvortrag M 6.1 Mo 14:00 H16
Computer Simulations of Transport Processes in Multicomponent
Melts — •Jürgen Horbach — Institut für Physik, Johannes
Gutenberg-Universität Mainz, Staudingerweg 7, 55099 Mainz
We use molecular dynamics (MD) computer simulations to investigate
the atomic transport in multicomponent metallic and oxide melts. The
detailed information as obtained by MD allows to elucidate the interplay
between structure, dynamics and phase behavior of liquid mixtures. We
present simulation results for realistic models of ion–conducting alkali silicate
melts and Al–Ni alloys. These systems exhibit intermediate range
M 7 Glasdynamik
order that is reflected by prepeaks in static structure factors. In Al–rich
Al–Ni melts a prepeak is found due to an inhomogeneous distribution of
the Ni atoms and we discuss the importance of this structure for diffusion
dynamics and phase behavior. The intermediate range order in the alkali
silicates provides the presence of diffusion channels for the fast alkali
ion motion. The interplay of the latter channel stucture with non–trivial
transport phenomena such as the mixed alkali effect in ternary alkali silicates
is demonstrated. We show that many aspects of the dynamics in
the considered systems can be understood by the mode coupling theory
of the glass transition.
Zeit: Montag 14:45–16:00 Raum: H16
M 7.1 Mo 14:45 H16
P-32 diffusion in the undercooled melt of Pd43Cu27Ni10P20 —
•Alexander Bartsch 1 , Klaus Rätzke 1 , Volker Zöllmer 1 , Andreas
Meyer 2 , and Franz Faupel 1 — 1 Technische Fakultät, Univ.
Kiel, Kaiserstr.2, 24143 Kiel — 2 TU München, Physik Department E13,
James-Franck-Str., 85747 Garching
Since the development of bulk metallic glasses the undercooled melt is
accessible for diffusion experiments [1]. In an earlier study we have for
the first time determined diffusivity and isotope effect for the Pd-Cu-Ni-P
alloy from the glass to the melt [2]. While in the equilibrium melt diffusivity
and viscosity coincide according to the Stokes Einstein (SE) equation,
they diverge with decreasing temperature down to the glassy state up to
four orders of magnitude. The following questions remain: At which temperature
does the divergence start? Does any constituent determines the
viscosity? In the present study the P-32- and Co-57 tracer diffusion were
studied simultaneously in the range 550 K to 700 K with the radiotracer
technique. The present, preliminary data show: the Co-diffusivities are
in the expected range. The P-32 diffusivities are a factor of two smaller.
Hence, Phosphorus does not determine the viscosity despite its covalent
bonding character.
[1] F. Faupel, W. Frank, M.-P. Macht, H. Mehrer, V. Naundorf, K.
Rätzke, H. R. Schober, S. K. Sharma, H. Teichler, Review of Modern
Physics 75 (2003) 237 [2] V. Zöllmer, K. Rätzke, F. Faupel, A. Meyer,
Phys. Rev. Lett., 90, 195502-1 (2003).
M 7.2 Mo 15:00 H16
On the relation between fragility, thermodynamic properties
and thermal stability of Pd-rich bulk-glass forming alloys —
•Gerhard Wilde — Forschungszentrum Karlsruhe, Institute of Nanotechnology,
P.O.B. 3640, 76021 Karlsruhe
It has been suggested that thermal stability and fragility of (metallic)
glasses are related such that the less fragile systems are more stable.
Moreover, it has been proposed that fragility and the temperature dependence
of the excess thermodynamic properties, e.g. the differences
in specific heat between the undercooled melt and the crystalline equilibrium
phases are directly correlated. Consequently, it would be expected
that the most fragile systems show the highest stability and the
largest temperature dependence of the excess thermodynamic properties,
especially if chemically similar alloys are compared. In order to check
these assumptions, a complete set of experimental data for different Pdrich
bulk glass forming alloys, i.e. Pd40Ni40P20, Pd77.5Cu6Si16.5 and
Pd43Cu27Ni10P20, has been used to perform a detailed comparison between
the fragility characteristics and the thermal stability of the chemically
similar alloys.
M 7.3 Mo 15:15 H16
Mechanical spectroscopy of the bulk metallic glasses
Zr52.5Ti5Cu17.9Ni14.6Al10 and Pd40Cu30Ni10P20.
— •Maik Eggers 1 , Alexander Strahl 1 , V.A. Khonik 2 , and
Hartmut Neuhäuser 1 — 1 TU Braunschweig, Institut für Metallphysik
u. Nukleare Festkörperphysik, Mendelssohnstr. 3, D-38106
Braunschweig — 2 Institute of General Physics, State Pedagogical
University, Voronezh, Russia
By means of the vibrating reed technique, measurements of internal
friction have been performed in the temperature range of 120 to 800K
during heating and cooling with a constant rate of 2K/s, in order to
monitor the structural relaxation during these thermal treatments. This
is compared for bulk glasses (produced with rather low quenching rate)
and for the same materials in form of ribbons quenched rapidly from the
melt. Special investigation is devoted to a low temperature relaxation
peak around 270K (for first flexural vibration mode between 100 and
400Hz) which has been found in the Zr-based alloy, and which may arise
either from trapped hydrogen or from ”dislocations” introduced by plastic
deformation into the amorphous structure. Therefore in particular the
amplitude dependence of damping has been measured.
M 7.4 Mo 15:30 H16
Mechanische Spektroskopie am amorphen ZrAlCu-System -
Hinweise auf einen ” excess wing“ in metallischen Gläsern —
•Peter Rösner, Susanne Schneider und Konrad Samwer — I.
Physikalisches Institut, Georg-August-Universität Göttingen, Tammann-
Str. 1, 37077 Göttingen
Mit dem Doppel-Paddel-Oszillator (DPO) als Substrat wurden mechanische
Eigenschaften von aus der Gasphase kokondensierten, dünnen
Schichten des amorphen, metallischen Glases ZrAlCu untersucht. Dazu
wurde der DPO bei einer Frequenz von 5400 Hz in seiner antisymmetrischen
Torsionsmode angeregt und temperaturabhängig der Einfluss der
Schicht auf die Eigenfrequenz und und die Dämpfung gemessen.
Aus den Daten lässt sich die innere Reibung und der komplexe Schermodul
der Schichten bestimmen. Der Verlustmodul kann bei Temperaturen
oberhalb des Glasübergangs durch eine Havriliak-Negami-Funktion
mit einer Vogel-Fulcher-Tammann abhängigen Relaxationszeit beschrieben
werden. In der Nähe des Glasübergangs in Richtung tiefere Temperaturen
zeigt sich ein klares Abweichen der Messwerte von dieser Funktion.
Dies könnte auf die Existenz eines ” excess wing“ auch in metallischen
Gläsern hinweisen, was die These stützen würde, dass es sich hierbei um
eine universelle Glaseigenschaft handelt. Jedenfalls sind die Messdaten
sehr ähnlich solchen, die durch dielektrische Spektroskopie in vielen anderen
amorphen Materialien beobachtet wurden.
Die Arbeit wird von der DFG im Rahmen des GRK 782 und des SFB
602 Projekt B8 gefördert. Der Dank der Autoren gilt insbesondere P.
Lunkenheimer und A. Loidl für viele hilfreiche Diskussionsbeiträge.
M 7.5 Mo 15:45 H16
Mechanisms of ion irradiation-induced viscous flow in glasses:
the role of point defects — •S.G. Mayr — I. Physikalisches Institut,
Georg-August-Universität Göttingen, Tammannstr. 1, 37077 Göttingen
The nature of ion irradiation-induced viscous flow in amorphous solids
is inverstigated using experiments and molecular dynamics computer simulations.
Experimentally, relaxation of film stresses and smoothing of
rough surfaces illustrate, that many amorphous solids undergo Newtonian
flow far below their respective glass temperature during ion bombardement
[1]. Using molecular dynamics computer simulations we study the
atomic-scale mechanisms governing radiation-induced viscous flow under
conditions, where local melting along the ion tracks is not dominant. We
show, that injection of interstitial- and vacancy-like defects induces the
same amount of flow as recoil events, indicating, that point-defect-like
entities in the amorphous matrix act as local shear instabilities and mediate
viscous flow [2].
Financially supported by the DFG - SFB 602, TP B3

Metallphysik Montag
[1] S.G. Mayr and R.S. Averback, Phys. Rev. Lett. 87 (2001), 196106
[2] S.G. Mayr, Y. Ashkenazy, K. Albe and R.S. Averback, Phys. Rev.
Lett. 90 (2003), 55505
M 8 Phasenumwandlungen I
Zeit: Montag 14:45–16:00 Raum: H4
M 8.1 Mo 14:45 H4
Precipitates in Al-Li: The existence of a precursor phase —
•Stefan Müller1 , Walter Wolf2 , and Raimund Podloucky3 — 1Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen —
2Materials Design s.a.r.l., 44.av.F.-A. Bartholdi, 7200 Le Mans, France —
3Universität Wien, Institut fuer Physikalische Chemie, Liechtensteinstr.
22A, A-1090 Wien
Although it is generally believed that the δ ′ phase of Al3Li is directly
formed from the fcc-based α solid solution by quenching and aging the
sample, X-ray small angle scattering results report the existence of a precursory
structure in the early stage of the decomposition. By combining
density functional theory calculations with a mixed-space cluster expansion
and Monte-Carlo simulations we will show that the existence of such
a precursor phase sensitively depends on the chosen Li-concentration.
Our calculations allow to predict the ground-state diagram, short-range
ordering, the size-shape-temperature relation of the L12 precipitates, as
well as the coherent phase boundaries for both the precursor phase and
the δ ′ phase.
M 8.2 Mo 15:00 H4
Magnetic effects on the nucleation in undercooled Co-Pd melts
— •Dirk Holland-Moritz 1,2 and Frans Spaepen 2 — 1 DLR, Institut
für Raumsimulation, D-51170 Köln — 2 Harvard University, Division
of Engineering and Applied Sciences, Cambridge, MA 02138, USA
For all known ferromagnetic metallic materials the Curie temperature
is lower than the liquidus temperature. Therefore, ferromagnetism has
not been observed in stable metallic melts. By use of advanced undercooling
techniques it is however possible to undercool melts of Co-based
alloys near their Curie temperature. Preceding undercooling experiments
on melts of Co-Pd alloys as a function of the alloy composition indicated
a change of the nucleation mechanism if the temperature of the liquid
is approaching the Curie temperature. Therefore the measured composition
dependence of the nucleation temperatures cannot be described in
the framework of classical nucleation theory.
In this work we present a thermodynamic model which extends classical
nucleation theory by adding magnetic contributions to the driving
free energy for crystallization. The inclusion of these contributions allows
a quantitative description of experimental results on the undercoolability
of Co-Pd melts in the entire composition range from 50-100 at.% Co.
This work was supported by the Deutsche Forschungsgemeinschaft
(DFG) under contract Nos. Ho1942/1 and Ho1942/2, by the Alexander
von Humboldt Stiftung and by the National Space and Aeronautics
Administration (NASA).
M 8.3 Mo 15:15 H4
In situ observation of nucleation processes in Ti-V during
phase separation — •Ingo Ramsteiner, Andreas Schöps, Harald
Reichert, and Helmut Dosch — Max-Planck-Institut für Metallforschung,
Heisenbergstr. 3, 70569 Stuttgart
Ti and V form a disordered bcc solid solution at high temperatures,
which phase separates into various structures at low temperatures. We
M 9 Flüssige und amorphe Metalle III
performed time resolved in situ x-ray measurements on the phase separation
process in Ti2V3, TiV and Ti3V2 single crystals. High energy
x-rays (70-80 keV) allow to penetrate bulk samples of more than 1 mm
thickness in transmission geometry. Using a fast 2D detector system we
resolve the evolution of the diffuse scattering on an almost flat plane in
reciprocal space within seconds. Upon cooling the sample from the high
temperature equilibrium phase into the miscibility gap we observe the
formation and evolution of Bragg reflections indicating the nucleation
of precipitates. The corresponding positions in reciprocal space allow to
determine the alignment of the nuclei with respect to the parent lattice.
The experiments demonstrate, that a controlled variation of the thermal
history leads to nucleation of different structures.
M 8.4 Mo 15:30 H4
Nucleation processes in Au-Ni alloys — •H. Reichert, A.
Schöps, I. Ramsteiner und H. Dosch — MPI für Metallforschung,
Heisenbergstr. 3, D-70569 Stuttgart
Au-Ni alloys exhibit a pronounced competition between ordering and
phase separation. In the ground state the system is phase separated. We
have investigated the early stages of phase separation in Au-Ni alloys after
quenching alloy single crystals from the disordered high temperature
phase into the miscibility gap. Time-resolved measurements of the diffuse
scattering of Au3Ni2 alloy single crystals demonstrate the existence of
two distinct nucleation channels in the precipitation of Au-rich particles
from the host matrix. We find a fast nucleation channel which is producing
extremely well-aligned Au precipitates in the host matrix. From
the scattering data we can deduce a direct influence of the electronic
structure of the host matrix onto the phase separation process
M 8.5 Mo 15:45 H4
Characterization of hard magnetic phase in mould-cast and directionally
solidified Nd-Fe alloys — •G. Kumar 1 , R. Sato 2 , J.
Eckert 3 , W. Löser 1 , L. Schultz 1 , and R. Grössinger 2 — 1 IFW
Dresden, Institute for Metallic Materials, D-01171 Dresden, Germany
— 2 Institut für Experimentalphysik, TU Wien, A-1040 Vienna, Austria.
— 3 TU Darmstadt, FB 11 Materials- und Geowissenschaften, FG
Physikalische Metallkunde, D-64287 Darmstadt, Germany.
In this work, Nd80Fe20 alloys were prepared by copper mould casting
and directional solidification (DS) to obtain a coarse microstructure. The
mould-cast samples exhibit a fine globular eutectic structure and show
high room temperature coercivity ( 5 kOe). The DS samples exhibit
large grains (composition close to NdFe2) in peritectic morphology but
show no coercivity. The NdFe2 grains (formed in the DS samples) show
clear magnetic domains with uniaxial anisotropy indicating that NdFe2
is not a cubic phase. HRTEM equipped with selected area diffraction
(SAD) was used to identify the crystal structure of NdFe2-type phase
observed in the DS samples. AC susceptibility and Mössbauer studies
were used to identify different magnetic phases. Acknowledgement The
work was supported by the German Science Foundation (DFG) via the
DFG priority program ”Phasenumwandlungen in mehrkomponentigen
Schmelzen”under grant Ec 111/11-1,2.
Zeit: Montag 16:30–18:00 Raum: H16
M 9.1 Mo 16:30 H16
Phase separation in bulk metallic glasses — •Shantanu Madge 1 ,
Gerhard Wilde 1 , and Lindsay Greer 2 — 1 Institute of Nanotechnology,
Forschungszentrum Karlsruhe, P.O.B. 3640, D-76021, Germany —
2 Department of Materials Science and Metallurgy, University of Cambridge,
Cambridge CB2 3QZ, U.K
Phase separation has recently seen much attention in explaining
nanocrystallisation in bulk metallic glasses. In the present paper, we explore
two bulk glass-forming systems, namely, Mg-Ni-Nd and Zr-Ta-Cu-
Ni-Al. Energy-filtered TEM shows that the alloy Mg65Ni20Nd15 phase-
separates into Ni-rich and Ni-poor liquids during quenching. However,
very surprisingly, annealing a phase-separated glass causes homogenisation,
instead of crystallisation. The nature of the miscibility gap is
considered. Secondly, a range of Zr-Ta-Cu-Ni-Al bulk glasses has been
cast. Based on preliminary results and thermodynamic considerations, it
appears that these alloys could be phase-separating prior to crystallisation.
The prospects of using phase separation for optimising mechanical
properties would be discussed.

Metallphysik Montag
M 9.2 Mo 16:45 H16
Microstructure, thermal stability and mechanical properties
of slowly cooled Zr-based composites containing dendritic bcc
phase precipitates — •Nicolle Radtke 1 , Juergen Eckert 2 , Uta
Kuehn 1 , Mihai Stoica 1 , and Ludwig Schultz 1 — 1 IFW Dresden,
Institut fuer Metallische Werkstoffe, Postfach 270016, 01171 Dresden,
Germany — 2 TU Darmstadt, Institut fuer Physikalische Metallkunde,
Petersenstr. 23, 64287 Darmstadt, Germany
We report on the microstructure, the thermal stability and the mechanical
properties of slowly cooled Zr-Nb-Cu-Ni-Al alloys with ductile
bcc phase precipitates embedded in a glassy or nanocrystalline matrix.
The samples were prepared in form of rods by injection casting into a
copper mold. The phase formation and the microstructure of the composite
material were investigated by X-ray diffraction, EDX analysis and
scanning and transmission electron microscopy. The thermal stability
was examined by differential scanning calorimetry and the mechanical
behavior was investigated by compression tests under quasistatic loading
at room temperature. The formation of bcc phase dendrites and a glassy
or nanocrystalline matrix is strongly governed by the alloy composition
and the actual cooling rate during solidification. Besides, changes in composition
and cooling rate lead to different volume fraction and size of the
bcc phase precipitates and, hence, to different values of yield strength,
elastic and plastic strain. Illustrated by the presented results we show
the possibility of obtaining tailored mechanical properties by control of
composition and solidification conditions.
M 9.3 Mo 17:00 H16
Crystallization Behavior of Zr-Ti-Ni-Cu-Be type glasses — •s.
Mechler, N. Wanderka, and M.-P. Macht — Hahn-Meitner-
Institut Berlin, Glienicker Strasse 100, 14109 Berlin
The Zr-Ti-Ni-Cu-Be bulk metallic glasses belong to the best glassformers
and most stable glasses. However, the stability of the individual
glasses of this family depends on their composition. Accordingly
their crystallization behavior differs with composition and temperature
. To investigate these dependencies the crystallization behavior
of Zr41Ti14Ni10Cu12.5Be22.5 (V1), Zr46.8Ti8.2Ni10Cu7.5Be27.5 (V4) and
Zr50Ti5Ni10Cu10Be25 (V12) is studied by differential scanning calorimetry
(DSC), X-ray diffraction (XRD) and transmission electron microscopy
(TEM). Samples of the glasses were annealed isothermally at 643 K, as
well as after constant heating in the DSC with a rate of 4K/min. The
phase characterization from the XRD patterns is performed by use of
a Rietveld–Refining Procedure. During isothermal annealing icosahedral
quasicrystals form in V1 and V4. The quasicrystals are depleted of Be
and enriched in Ti. Mainly one crystalline phase, but no quasicrystals,
crystallizes in V12. After constant heating of the glasses up to higher
temperatures in the DSC only in V1 the first phase was quasicrystalline.
During further heating, these quasicrystals transform into a Laves phase,
whereas the remaining amorphous phase crystallizes into several phases,
like Be2Zr. During constant heating of the V4 and V12 glass mainly
a tetragonal phase crystallizes.The lattice constants of this tetragonal
phase alter systematically with increasing temperature. Simultaneously
to this alterations intermetallic phases appear in the microstructure.
M 9.4 Mo 17:15 H16
Zr-Nb-Cu-Ni-Al glass or nanocrystalline matrix composites
containing dendritic bcc phase precipitates — •Uta Kuehn,
Juergen Eckert, Nicolle Radtke, Norbert Mattern, and Ludwig
Schultz — IFW Dresden, P.O. Box 270016, D-01171 Dresden
This work presents results on the microstructure and the resulting mechanical
properties of the Zr66Nb13Cu8Ni6.8Al6.2 multicomponent alloy
with a glassy or a nanocrystalline matrix and ductile bcc precipitates.
This composite material was prepared by arc-melting, copper mold casting
and melt spinning with different sample dimensions and, therefore,
different cooling rates and microstructures. The structure of the samples
was investigated by XRD, OM, SEM, TEM and DSC. Room temperature
compression tests were realized with an electromechanical testing
device under quasistatic loading. The bulk samples exhibit significantly
improved mechanical behaviour compared to monolithic glass, since the
in-situ formed nanocrystalline matrix composites undergo work hardening
and plastic deformation prior to failure, whereas monolithic glass
forms highly localized shear bands, which consequently leads to catastrophic
failure. High ultimate compression stress combined with high
plastic strain is mainly dominated by a well-balanced ratio of the extant
phases. Surprisingly also a nanocrystalline matrix leads to high elastic
strain values. Illustrated by the composition presented in this study and
different cooling rates we show the possibility of obtaining tailored mechanical
properties for such composite materials.
M 9.5 Mo 17:30 H16
Quasicrystal Formation in Decomposed V4 Metallic Glass — •S.
Mechler, M. Wollgarten, N. Wanderka, and M.-P. Macht —
Hahn-Meitner-Institut Berlin, Glienicker Strasse 100, 14109 Berlin
The bulk metallic glass Zr46.75Ti8.25Ni10Cu7.5Be27.5 (V4) is one of the
most stable metallic glasses. The stability of this glass has been attributed
to a strong long range decomposition before crystallization occurs. In order
to characterize the first stages of crystallization and to relate the
crystallization to the decomposition of the glass, the early stages of these
phase transformations are investigated by means of differential scanning
calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy
(TEM) and the 3-dimensional atom probe (3-DAP). After annealing
of the glass at 643 K for 6 h and at 593 K for 21 d an icosahedral
quasicrystalline phase is detected in the glass by XRD. After annealing
of the glass at 573 K for 42 d the alloy is still amorphous and a decomposition
of the initially homogeneous glass is observed by TEM and
3-DAP.Heating of such a decomposed glass in the DSC with a heating
rate of 4 K/min up to 709 K, leads to the formation of a icosahedral
quasicrystalline phase, which is different in composition and its quasilattice
constant from the quasicrystals after isothermal annealing. Even
after prolonged pre-annealing (84 d) at 573 K the alloy stays still amorphous
and also icosahedral quasicrystals form after the DSC treatment.
However, also these quasicrystals differ in composition and quasilattice
constants from both phases quoted above. One prominent feature of all
three quasicrystalline phases is their strong depletion of Be and enrichement
in Ti compared to the initial glass matrix.
M 9.6 Mo 17:45 H16
Atomare Struktur und Widerstand von amorphen
(In50Sb50)100−xAux — •Dirk Hauschild, Michael Lang
und Peter Häußler — TU-Chemnitz, Institut für Physik, D-09107
Chemnitz
In den letzten Jahren konnte festgestellt werden, dass amorphe und
flüssige Halbleiter / Halbleiterlegierungen duch ein Wechselspiel zwischen
dem Elektronensystem und der sich bildenden atomaren Struktur stabilisiert
werden. Man spricht dabei von einer Resonanz zwischen diesen
beiden Systemen. Wir berichten in dieser Arbeit über Messungen an
In50Sb50, bei dem wir durch Zulegieren von Gold den Durchmesser der
Fermikugel verkleinern. Wir untersuchen durch Elektronenbeugung und
durch Messung des spezifischen Widerstandes, wie sich dabei die atomare
Struktur anpassen kann und welche Konsequenzen dies für den elektr.
Transport hat. Die Ergebnisse werden zusammen mit anderen Halbleitersystemen
(reine Elemente und Legierungen) diskutiert. Die Schichten
wurden für diese Messungen in-situ bei 4K durch sequentielles Flashverdampfen
hergestellt. Sowohl direkt nach dem Aufdampfen, als auch
bei verschiedenen Temperstufen wurde die Struktur untersucht und der
Widerstand über den gesamten Temperaturbereich mittels Vier-Punkt-
Messung bestimmt.

Metallphysik Montag
M 10 Diffusion
Zeit: Montag 16:30–18:00 Raum: H4
M 10.1 Mo 16:30 H4
Diffusion in nanokristallinen Magnetwerkstoffen — •Simone
Herth 1 , Martin Eggersmann 1 und Roland Würschum 2 —
1 Institut für Nanotechnologie, Forschungszentrum Karlsruhe — 2 Institut
für Technische Physik, Technische Universität Graz
An strukturell stabilen, porenfreien nanokristallinen (n-) Legierungen
wurden Selbstdiffusionsuntersuchungen mit dem Ziel durchgeführt, Erkenntnisse
über die mikroskopischen Prozesse zu erlangen, die zur induzierten
magnetischen Anisotropie führen. Aufgrund intergranularer amorpher
Restphasen ist die Grenzflächendiffusion in weichmagnetischem n-
Fe73,5Si13,3B9Nb3Cu1 und n-Fe90Zr7B3 im Vergleich zu herkömmlicher
Korngrenzendiffusion verlangsamt. Messungen der Ge-Diffusion in n-
Fe73,5Si13,3B9Nb3Cu1 deuten darauf hin, dass die Induzierung der magnetischen
Anisotropie durch die langsame Si-Selbstdiffusion in den Fe3Si-
Nanokristalliten bestimmt wird. In hartmagnetischem n-Nd2Fe14B konnte
die Tracerdiffusion am Schmelzübergang der Nd-reichen Korngrenzenphase
untersucht werden.
M 10.2 Mo 16:45 H4
Positronlebensdauerspektroskopie an Al-Cu-Modellegierungen
— •Christine Negrini, Matz Haaks, Ingo Müller, Torsten E.
M. Staab und Karl Maier — Helmholtz Institut für Strahlen- und
Kernphysik, Universität Bonn, Nußallee 14-16, D-53115 Bonn, Germany
Aluminium-Kupfer-Legierungen sind wichtige Leichtbauwerkstoffe. Bei
diesen Legierungen behindern die Kupferausscheidungen, sogenannte
Guinier-Preston-Zonen, die Versetzungsbewegung. Die Defektverteilung
in Umgebung der GP-Zonen wird mit der Positronenannihilationsspektroskopie
(PAS) und der Dopplerverbreiterung untersucht. Ein besonderes
Interesse besteht in der Klärung der Frage, inwiefern die makroskopischen
Eigenschaften der Legierungen von der mikroskopischen Struktur,
speziell von der Größe und der Verteilung der Kupfer-Ausscheidungen
bestimmt werden. Die Konzentration des Legierungselements Kupfer variiert
von 0 bis 17 Atomprozent. Über verschiedene Deformationsgrade
bis zu 60 Prozent wurden im Zugversuch unterschiedliche Versetzungskonzentrationen
erzeugt. Ergänzend zur Positronenlebensdauerspektroskopie
wurden die Daten mit Messungen der Härte korreliert.
M 10.3 Mo 17:00 H4
EXAFS-Messungen zum Nachweis von Kupfer während
der Bildung von kupferreichen Ausscheidungen in Al-Cu-
Legierungen — •Torsten E. M. Staab 1 , Christiane Zamponi 1 ,
Ingo Müller 1 , Michael Röbel 1 , Karl Maier 1 und Hartwig
Modrow 2 — 1 Helmholtz Institut für Strahlen- und Kernphysik,
Universität Bonn, Nußallee 14-16, D-53115 Bonn, Germany —
2 Physikalisches Institut, Universität Bonn, Nußallee 12-14, D-53115
Bonn, Germany
Die Festigkeit ausscheidungsgehärteter Aluminiumwerkstoffe wird
durch Verteilung und Größe kupferreicher, nanoskaliger Cluster — sogenannter
Guinier-Preston-Zonen — bestimmt, da diese Ausscheidungen
effektiv die Versetzungsbewegung behindern. Die atomare Umgebung
des Legierungselementes Kupfer wird mittels EXAFS-Messungen an der
Kupfer k-Kante nachgewiesen. Durch Vergleich mit ab-initio Rechnungen
kann gezeigt werden, daß sich Kupferatome direkt nach dem Abschrecken
vorzugsweise auf substitutionellen Gitterplätzen, d.h. umgeben von Al-
Atomen, befinden. Dagegen ändert sich während der Bildung von Ausscheidungen
die atome Umgebung der Kupferatome. Sie wird durch die
Anlagerung weiter Kupferatome immer kupferreicher, bis sie sich schließlich
der Zusammensetzung der Gleichgewichtsphase Al2Cu annähert.
M 10.4 Mo 17:15 H4
Leerstellenaffinität von Ausscheidungen in der Legierung Al-
Cu — •Michael Röbel, Torsten E. M. Staab und Karl Maier
— Helmholtz Institut für Strahlen- und Kernphysik, Universität Bonn,
Nußallee 14-16, D-53115 Bonn, Germany
Aluminiumwerkstoffe im Flugzeugbau unterliegen starken Belastungen.
Die Festigkeit dieser Werkstoff wird durch Größe, Struktur und
Verteilung von Ausscheidungen — kupferreiche Nanocluster oder sog.
Guinier-Preston Zonen — bestimmt, die durch Hinderung der Versetzungsbewegung
die Härte bestimmen. Die Mikrostruktur dieser Werkstoffe
wird durch Lösungsglühen, Abschrecken und Auslagern bei moderaten
Temperaturen passend eingestellt. Leerstellen, die beim Abschrecken eingefroren
wurden, spielen eine entscheidende Rolle beim Materialtransport
von Kupfer zu den Ausscheidung. Die Diffusivität der Leerstellen ist entscheidend
für die Kinetik der Ausscheidungsbildung. Mit ab-initio Rechnungen
wurde die Stärke der Bindung von Leerstellen an Cu-Atome und
kupferreiche Ausscheidungen untersucht. Zusätzlich wurden Positronenannihilationsparameter
bestimmt, um die Rechnungen direkt mit Experimenten
vergleichen zu können.
M 10.5 Mo 17:30 H4
Lithium Spin-Alignment Echo NMR-Spektroskopie zur Untersuchung
der Dynamik und Geometrie langsamer Ionenbewegungen
in kristallinen Ionenleitern — •Martin Wilkening und
Paul Heitjans — Universität Hannover, Institut für Physikalische Chemie
und Elektrochemie
Das genaue Studium einzelner Sprungprozesse von Ionen ist wichtige
Voraussetzung für das Verständnis komplexer Diffusionseigenschaften
fester Ionenleiter. In Analogie zur quasielastischen Neutronenstreuung
ermöglicht die Spin-Alignment Echo NMR-Spektroskopie [1–3] die Aufzeichnung
von Korrelationsfunktionen, die grundsätzliche Informationen
über Zeitskala der Ionendynamik und Details der bevorzugten Diffusionswege
enthalten. Langsame Translationsprozesse mit Sprungraten auf der
kHz bis sub-Hz Zeitskala können durch die Aufzeichnung von Alignment-
Echos erfasst werden. Am Beispiel verschiedener kristalliner Ionenleiter,
z.B. LixTiS2, Li4SiO4, Li3N, wird die Leistungsfähigkeit der Methode vorgestellt
und diskutiert.
[1] H. W. Spiess, J. Chem. Phys. 72, 6755 (1980).
[2] G. Fleischer, F. Fujara, in NMR, Principles and Progress, edited by
P. Diehl, E. Fluck, H. Günter, R. Kosfeld, and J. Seelig (Springer, Berlin,
1994), Vol. 30, p. 159.
[3] F. Qi, T. Jörg, R. Böhmer, Solid State Nucl. Magn. Res. 22, 484
(2002).
M 10.6 Mo 17:45 H4
Ni and Mn self-diffusion in Ni-Mn alloys — •Serguei Peteline
and Helmut Mehrer — Institut für Materialphysik, Universität
Münster, D-48149, Münster, Germany
Ni and Mn self-diffusion has been investigated in Ni50Mn50 alloys over
wide temperature ranges. The alloys were prepared by the group of Prof.
Chang at the University of Wisconsin, USA. The diffusion of 63 Ni and
54 Mn was measured by the radiotracer method in disordered fcc, B2 and
L1(0) structure regions present in this compound at different temperatures.
The diffusivity of Mn was found to be significantly faster than
the Ni diffusivity in all single phase structure regions. More than one
order of magnitude diffusivity change was observed upon the fcc ↔ B2
transition. The activation enthalpy of Ni self-diffusion in the disordered
fcc phase is almost 90 kJ/mol higher than the corresponding value for
Mn. In the B2 phase there is only a slight difference between the activation
enthalpies of the components which lies within the error bars. A
comparison of the present experimental data on tracer self-diffusion with
literature data on interdiffusion in the Ni-Mn system shows good agreement
between experimental interdiffusion coefficients and those deduced
using the Darken-Manning equation from the present tracer diffusion coefficients.
The thermodynamical factor was found to vary from 3 to 4
depending on the structure.

Metallphysik Dienstag
M 11 Hauptvortrag Stefan Müller
Zeit: Dienstag 09:30–10:00 Raum: H16
Hauptvortrag M 11.1 Di 09:30 H16
Ab-initio thermodynamics of metal alloys: From the atomic to
the mesoscopic scale — •Stefan Müller — Universität Erlangen-
Nürnberg, Lehrstuhl für Festkörperphysik, Staudtstr. 7, D-91058 Erlangen
The combination of density functional theory calculations (DFT) with
Cluster Expansion methods (CE) gives access to both huge parameterspaces
(e.g. for ground-state searches) and systems containing more than
a million of atoms (e.g. for microstructure studies). It will be shown how,
together with Monte-Carlo simulations, this ansatz can be applied to
M 12 Phasenumwandlungen II
study alloy properties which possess a delicate temperature-dependence
like mixing enthalpies, short-range order or microstructure evolution
without any empirical parameters, but with an accuracy that a quantitative
comparison with experimental data becomes possible. Regarding
microstructures I will focus on so-called coherent precipitates whose sizeshape
relations can be of technical relevance in alloys like Al-Li, Al-Zn,
or Al-Cu. The presented methods will be extended to alloy surfaces in
order to investigate ordering at surfaces and surface segregation, i.e. the
deviation of the alloy’s composition in the near-surface region compared
to the bulk.
Zeit: Dienstag 10:15–11:15 Raum: H16
M 12.1 Di 10:15 H16
Screening effects in the binary alloy systems Cu-Au, Cu-Pd, and
Au-Ni — •H. Reichert, A. Schöps, I. Ramsteiner und H. Dosch
— MPI für Metallforschung, Heisenbergstr. 3, D-70569 Stuttgart
Electronic screening effects are one of the origins of long-range interactions
in many binary metallic alloys. Experimentally this can be
studied via the singularities in the response functions at specific points
in reciprocal space (Kohn anomalies, 2kF Fermi surface nesting). These
singularities are the origin of a marked fine structure of the diffuse scattering
in binary systems. We have investigated the fine structure of the
diffuse scattering in-situ as a function of temperature in various binary
alloy systems (Cu-Au, Cu-Pd, Au-Ni) using high energy x-ray scattering.
In the diffuse scattering maps we found unique signatures of electronic
screening in all systems. The corresponding nesting constructions are immediately
apparent from the scattering data. The data sets we present
are a test bench for electronic structure calculations.
M 12.2 Di 10:30 H16
In-situ Determination of Phase Selection Sequences in Undercooled
Ti-Fe-Si-O Melts — •Oliver Heinen, Dirk Holland-
Moritz, Thomas Volkmann, Jörn Strohmenger, Thomas Lierfeld,
Sven Reutzel, and Dieter M. Herlach — DLR, Institut für
Raumsimulation, D-51170 Köln
The alloy system Ti-Fe-Si-O shows a great variety of complex stable
and metastable phases. Depending on the composition and the undercooling
different solidification pathways are found. The large number of alloy
phases in Ti-Fe-Si-O leads to a strong competition of phase selection
during rapid solidification of undercooled melts. In order to determine
the phase formation sequence in these alloys as function of composition
and to examine possible dependencies on the short-range order of the
undercooled liquid, in situ investigations of the solidification pathways
and the short-range order of the liquid were performed. The containerless
processing technique of electromagnetic levitation for deeply undercooled
metallic melts was combined with energy dispersive diffraction of
synchrotron radiation at the European Synchrotron Radiation Facility
(Grenoble). This enables us to directly determine the crystal structure of
the solid phases formed during rapid solidification with a time resolution
of 1-2 seconds and study the short-range order of the liquid in the same
experiment. Depending on the undercooling, several different solidification
sequences were found. This work was financially supported by DFG
under contract No. Ho1942/4 and by ESRF.
M 12.3 Di 10:45 H16
Metastable Phase formation in electromagnetically levitated
Nd-Fe-B-melts investigated by in-situ diffraction experiments
with synchrotron radiation. — •Jörn Strohmenger 1 , Thomas
Volkmann 1 , Jianrong Gao 2 , Dirk Holland-Moritz 1 , Oliver
Heinen 1 und Dieter Herlach 1 — 1 Institute of Space Simulation, German
Aerospace Center (DLR), D-51170 Cologne — 2 Key Lab of Electromagnetic
Processing of Materials (EMP), Northeastern University, Shenyang
110004, China
Nd-Fe-B alloys are of special interest due to the excellent hardmagnetic
properties of the intermetallic compound Nd2Fe14B1 (Φ-phase).
Competitive crystallisation of stable and metastable phases in undercooled
Nd-Fe-B melts with Nd-contents between 11.8 and 18.0 at.% at
the ratio of Nd
B
= 2
1
was investigated by the electromagnetic levitati-
on technique in combination with in-situ diffraction experiments at the
European Synchrotron Radiation Facility (ESRF) in Grenoble. Under
equilibrium conditions the solidification sequence is primary γ-Fe followed
by the peritectic formation of the Nd2Fe14B1 phase. It is shown that
in the undercooled melt the crystallisation of the γ-Fe-phase is suppressed
in favour of the Φ phase. Moreover, the crystallisation of a metastable
phase could be directly observed. A phase selection diagram showing the
different solidification pathways as a function of undercooling and alloy
composition will be presented.
Financial support by the Deutsche Forschungsgemeinschaft under contract
No. HE1601/14 and the European Synchrotron Radiation Facility is
gratefully acknowledged. J.G. appreciate support from AvH-foundation.
M 12.4 Di 11:00 H16
Nucleation and Orientation Relationships during partial
alpha-gamma-Phase Transformation in microalloyed Steels
— I. Lischewski, C.-M. Park, G. Gottstein, •I. Lischewski,
C.-M. Park, and G. Gottstein — Institut fuer Metallkunde und
Metallphysik, RWTH Aachen, Kopernikusstr.14, D-52056 Aachen,
Germany
The orientation relationships and the selection of crystallographic variants
during partial ferrite to austenite transformation in a microalloyed
steel were studied, to obtain new insights into the nucleation of this phase
transformation. The samples were encased with a CrNi-18/9 steel foil and
annealed at a low transformation temperature. Nickel, which diffused
from the steel wrap into the transformed sample, stabilized the austenite
nuclei.Therefore it was possible to establish a direct correspondence between
prior ferrite and subsequent austenite crystallography. The local
crystallography was measured by EBSD in a high resolution FEG-SEM.
The austenite was observed to nucleate at random triple junctions of
pre-existing ferrite grain boundaries and satisfied the K-S (Kurdjumov-
Sachs) orientation relationship surprisingly, no apparent variant selection
was observed during incipient stages of austenite nucleation. The preferential
nucleation of austenite at random ferrite triple junctions was
considered in a triple junction weighted orientation distribution which
compared well with experimental results.

Metallphysik Dienstag
M 13 Mechanische Eigenschaften I
Zeit: Dienstag 10:15–11:15 Raum: H4
M 13.1 Di 10:15 H4
Development of high strength Cu-based conductor materials —
•J. Freudenberger, E. Botcharova, A. Gaganov, E. Mohn, and
L. Schultz — Leibniz-Institute for Solid State and Materials Research
Dresden, PO Box 270016, 01171 Dresden
There is a need for high-strength and highly-conducting materials for
applications such as pulsed high magnetic field coils. Different approaches
were studied in order to strengthen copper-based conductor materials.
On the one hand, microcomposite Cu-Nb and Cu-Ag alloys yield high
strength as a consequence of their nanoscale microstructure and, on the
other hand, a Cu-based macrocomposite can be strengthened by the use
of a steel jacket. In all cases the increase of strength coincides with a decrease
of conductivity and a reduced ductility. Thus, the ideal material
balances between these competing properties. The present investigations
at the IFW Dresden will be presented.
M 13.2 Di 10:30 H4
Mikrostruktur in der Randzone bei spanender Bearbeitung:
Abbildung der lokalen Schädigung mit Positronen als Sondenteilchen
— •Matz Haaks 1 , Hans Tönshoff 2 und Karl Maier 1
— 1 Helmholtz Institut für Strahlen- und Kernphysik, Universität Bonn,
Nußallee 14-16, D-53115 Bonn, Germany — 2 Institut für Fertigungstechnik,
Schloßwerdersrt. 5, 30159 Hannover
Während des Zerspanvorgangs werden Werkstück und Span plastisch
verformt. Zusätzlich kommt es in den sekundären Scherzonen
zu einer Temperatureinwirkung durch die bei der Umformung freiwerdende
Wärme. Die plastische Verformung und der Temperatureinfluss
bestimmen das Gefüge in der Randzone, dem oberflächennahen Bereichs
des Werkstücks. Die Methode der ortsaufgelösten Positronen-
Annihilationsspektroskopie (PAS) ermöglicht einen direkten Einblick in
das Gefüges. Der aus Zugversuchen bekannte empirische Zusammenhang
zwischen dem S-Parameter der PAS und der Verfestigung erlaubt eine
Zuordnung des Verformungsgrades. Durch eine bildgebende Messung des
S-Parameters gelang es, die Verformungs- und Scherzonen in Spanwurzeln
aus dem Eisenwerkstoff C45E direkt abzubilden. Aus den Ergebnis-
M 14 Flüssige und amorphe Metalle IV
sen kann der Einfluss der Prozessparameter Schnittgeschwindigkeit und
Schnittiefe auf die Schädigung in der Randzone ermittelt werden. Es zeigt
sich, dass die Schädigungstiefe in der Randzone weitgehend unabhängig
von der Schnittgeschwindigkeit ist, jedoch mit zunehmender Schnittiefe
ansteigt.
M 13.3 Di 10:45 H4
Hochfeste Cu/SS Makroverbunde — •E. Mohn, J. Freudenberger,
A. Gaganov und L. Schultz — Leibniz-Institut für Festkörperund
Werkstoffforschung Dresden, Postfach 270016, 01171 Dresden
Die Entwicklung hochfester Leiterwerkstoffe für die zerstörungsfreie
Erzeugung hoher gepulster Magnetfelder stellt stets ein Optimierungsproblem
der Eigenschaften des Leiters dar. Ziel dieser Entwicklung ist
ein Leiter mit einer Zugfestigkeit von σUTS > 1, 2 GPa, einer elektrischen
Leitfähigkeit von > 50%IACS bei Raumtemperatur und Bruchdehnungen
von ε > 3%. In diesem Beitrag wird der Einfluss von Stickstoff als Legierungselement
auf die Verfestigung des Stahlmantels vorgestellt und die
Abhängigkeiten der Eigenschaften von den Herstellungsparametern, die
durch das Spulendesign gegeben sind, verdeutlicht.
M 13.4 Di 11:00 H4
Fatigue properties of squeeze cast AZ31 — •Zuzana Zuberova
1 , Torbjørn Lamark 1 , Ralph J. Hellmig 1 , Ludvik Kunz 2 und
Juri Estrin 1 — 1 Institut für Werkstoffkunde und Werkstofftechnik,
TU Clausthal, Agricolastr. 6, 38678 Clausthal-Zellerfeld — 2 Academy of
Sciences of the Czech Republic, Institute of Physics of Materials, Brno,
Czech Republic
In this work we investigated the influence of loading frequencies on the
fatigue life of squeeze cast AZ31 magnesium alloy. The density of AZ3–SC
was determined to be 99,5 % of the theoretical value. The experiments
were performed in the high cycle fatigue regime. The fatigue limit (for
10 −7 cycles) for 20 Hz and 10 Hz was in the range of 40 – 45 MPa. Fatigue
cracks were found to be initiated on the specimen surface. No porosity
was detected at the crack initiation sites by optical and scanning electron
microscopy.
Zeit: Dienstag 10:15–11:30 Raum: H6
M 14.1 Di 10:15 H6
Deformation-induced crystallization in amorphous Al88Y7Fe5
alloy — •Rainer Hebert 1 , Gerhard Wilde 1 , and John H.
Perepezko 2 — 1 Institut für Nanotechnologie, Forschungszentrum
Karlsruhe, Postfach 3640, D-76021 Karlsruhe, Germany — 2 Department
of Materials Science and Engineering, University of Wisconsin-Madison,
1509 University Ave., Madison, WI 53706, USA
Melt-spun amorphous Al88Y7Fe5 ribbons reveal a primary crystallization
reaction of fcc-Al at 276C (heating rate: 20K/min). At roomtemperature,
primary crystallization of fcc-Al can be induced during
intense deformation based on repeated cold-rolling and folding. The
deformation-induced crystallization reaction is investigated based on
XRD, TEM, SAXS and DSC analysis and discussed in light of nanocrystallization
in shear-bands. The comparison between thermally-induced
and mechanically-induced primary crystallization demonstrates that in
terms of the size distributions for the Al-nanocrystals, both processing
routes yield similar distributions, but the reaction pathways are different.
Following annealing at 220C for 10min, the particle volume density in the
rolled ribbons increases approximately one order of magnitude to about
10 22 m −3 . Under the same annealing conditions, nanocrystals are not observed
in the as-spun ribbon. The kinetics of the deformation-induced
crystallization reaction is examined with the strain as a metric for the
transformation. The experiments demonstrate that intense deformation
of metallic glasses in combination with annealing offers the opportunity
to catalyze higher nanocrystal densities than for annealing only, without
adding additional elements to the alloy.
M 14.2 Di 10:30 H6
Study on Crystallization Kinetics of Metallic Glass Composite
— •Shankar Venkataraman 1 , Jürgen Eckert 1,2 , Ludwig
Schultz 1 , and Daniel Sordelet 3 — 1 IFW Dresden, P F 270016,
D 01171, Dresden, Germany — 2 Technische Universität Darmstadt,
FB 11 Material- und Geowissenschaften,FG Physikalische Metallkunde,Petersenstrasse
23, D-64287, Darmstadt, Germany — 3 Ames
Laboratory, 107 Metals Development, Ames, IA 50011 USA
Cu47Ti33Zr11Ni8Si1 metallic glass powders were prepared by gas atomization
and reinforced with Cu metallic particles by ball milling. The
characterisations of the resultant composite mixtures were performed using
x-ray diffraction, differential scanning calorimetry and microscopy.
The kinetics of crystallization of the multicomponent metallic glass as
well as a ball milled metallic glass composite has been investigated by
differential scanning calorimetry under isochronal and isothermal conditions.
From the constant rate heating (isochronal) measurements the
Kissinger analysis has been used to find the activation energy for crystallization
whereas the Johnson-Mehl-Avrami (JMA) analysis has been
employed to understand the crystallization mechanism occurring under
isothermal conditions. The activation energy values obtained for the
metallic glass as well as the ball milled composites are nearly identical.
The addition of Cu reinforcement does not affect the crystallization
kinetics of the amorphous matrix composites.

Metallphysik Dienstag
M 14.3 Di 10:45 H6
A nanoindentation study of the effect of crystal-size on shear
banding in Mg-based nanophase composites — •Shantanu
Madge 1 , Gerhard Wilde 1 , and Lindsay Greer 2 — 1 Institute
of Nanotechnology, Forschungszentrum Karlsruhe, D-76021, Germany.
— 2 Department of Materials Science and Metallurgy, University of
Cambridge, Cambridge CB2 3QZ, U.K.
Nanoindentation has been used to study the efficacy of crystals in obstructing
shear band propagation in two nanophase composites obtained
by partial devitrification of Mg-based bulk metallic glasses. Pronounced
steps are observed in the loading curves for the as-cast glasses, which reflect
shear banding in the material. The composition Mg65Cu15Ag10Y10
(at. effective in blocking shear band propagation in the partly crystallized
material. On the other hand, the glass Mg66Ni20.4Nd13.6 (at. crystals
that are much coarser and consequently, are more effective in blocking
shear band propagation. The implications of these results for optimising
the mechanical properties of bulk glasses are discussed.
M 14.4 Di 11:00 H6
Widerstand, Thermokraft und Struktur amorpher Al100−xTix-
Legierungen — •Jan Werner 1 , Inna Plyushchay 2 und Peter
Häussler 1 — 1 TU Chemnitz, 09107 Chemnitz — 2 Taras Shevchenko
University, 03022 Kiew, Ukraine
Al-ÜM-Legierungen mit frühen ÜM (Sc, Ti, V, Cr) haben hochinteressante
Eigenschaften bezüglich des elektronischen Transports, z.B. drastische
Veränderungen des Temperaturkoeffizienten des Widerstand bei
mittleren Temperaturen, sie können Memory-Effekte zeigen und sind als
amorphe Legierungen sehr stabil. Wir stellen solche Legierungen in situ
bei T= 4K unter HV-Bedingungen zunächst amorph her und tempern
die Proben dann bis in den kristallinen Zustand.
M 15 Phasenumwandlungen III
Es wird die statische Struktur durch Elektronenbeugung, der spezifische
Widerstand und die Thermokraft jeweils als Funktion der Temperatur
und der Zusammensetzung gemessen.
Die Ergebnisse dieser Legierung mit einem frühen ÜM sollen mit Vorhersagen
eines allgemeineren Modells für Al-ÜM-Legierungen, welches
durch Messungen der Legierungen Al100−x ÜMx (Mn, Fe, Co, Ni) bestätigt
wurde, verglichen werden. Die Struktureigenschaften und das Transportverhalten
werden als Ergebnis optimierter Resonanzen zwischen dem
Elektronensystem und der statischen Struktur mit Konsequenzen für die
Phasenstabilität und den Transport diskutiert.
M 14.5 Di 11:15 H6
Widerstand und Struktur amorpher Al100−XNiX-Legierungen —
•M. Lang, P. Häussler und J. Barzola — TU Chemnitz, Institut
für Physik, D-09107 Chemnitz
Amorphe Aluminium-Legierungen mit späten Übergangsmetallen
(Mn, Fe, Co, Ni) haben in der Vergangenheit gezeigt, dass sie durch
Hybridisierungseffekte zwischen den Al-p- und den unbesetzten
ÜM-d-Elektronen ihre effektive Valenz derart variieren können,
dass der Durchmesser der Fermikugel gerade so großist, dass er die
Pseudobrillouin-Zone berühren kann. Es tritt ein die Phase stabilisierendes
Pseudogap in der elektronische Zustandsdichte auf, das zusätzlich
zu Transportanomalien führt.
Die hier vorgestellten Schichten werden insitu bei 4K hergestellt, mittels
Elektronenbeugung bzgl. der atomaren Struktur, sowie durch Messung
des spezifischen Widerstandes charakterisiert.
Die Struktureigenschaften und das Transportverhalten werden als Ergebnis
optimierter Resonanzen zwischen dem Elektronensystem und der
statischen Struktur, zusammen mit anderen Al-ÜM-Legierungen, diskutiert.
Zeit: Dienstag 11:45–12:45 Raum: H16
M 15.1 Di 11:45 H16
Temperature dependence of lattice misfit in a creep deformed
single crystal superalloy using synchrotron X-radiation —
•Weiye Chen 1 , Nora Darowski 2 , Ivo Zizak 2 , Gerhard Schumacher
2 , Nelia Wanderka 2 , Hellmuth Klingelhoeffer 3 , and
Wolfgang Neumann 1 — 1 Humboldt-Universitaet zu Berlin, Institut
fuer Physik — 2 Hahn-Meitner-Institut Berlin, Bereich Strukturforschung
— 3 Bundesanstalt fuer Materialforschung und -pruefung Berlin
At high temperatures the application of an external load can lead to
directional growth (gamma prime rafting) of gamma prime precipitates
in single crystal superalloys. The lattice misfit between the gamma prime
precipitates and the gamma matrix is one of the parameters which determine
the kinetics and morphology of the gamma prime rafts. In the
present study the gamma/gamma prime lattice mismatch in specimens
of single crystal superalloy SC16 creep deformed at 1223 K and 150 MPa
to a creep strain of 0.5 means of X-ray diffraction using synchrotron
radiation. The measurements have been performed between room temperature
and 1173 K in the both directions parallel and perpendicular
to the [001] load axis. At room temperature the gamma/gamma prime
lattice mismatch measured on the (002) reflection has a positive sign
and is larger compared to the mismatch in the non-deformed specimen,
while the mismatch measured on the (200) reflection is slightly negative
and its value is smaller than that of the non-deformed specimen.
In both directions the gamma/gamma prime lattice mismatch decreases
with increasing temperature.
M 15.2 Di 12:00 H16
Phase transition of Ni12at.%Al by plastic deformation —
•Peter Drechsler 1 and Ferdinand Haider 2 — 1 Abteilung für
Funktionswerkstoffe der Medizin und Zahnheilkunde, Universität
Würzburg, Pleicherwall 2, 97070 Würzburg — 2 Lehrstuhl für Experimentalphysik
I, Universität Augsburg, Universitätsstraße 1, 86159
Augsburg
The cyclic behavior of the stress response of polycrystalline Ni12at.%Al
under lcf loading at mean plastic strain rates between 10 −3 1/s and
10 −1 1/s and temperatures between 298K and 773K shows after the inital
hardening caused by the nucleation of psb either further hardening or
saturation and softening. The behavior of the flow stress can be related
to the particle size of the γ ′ -precipitates as tem investigation revealed.
Depending on strain rate and temperature one can distinguish two ranges
in which the average radius of the precipitates shrinks or grows. This effekt
can be simulated by means of a model, that includes the shrinking of
the precipitates by dislocation cutting as well as the deformation induced
accelerated diffusion for the growth of the particles. The calculated values
for the diffusion coefficient agree with values of Militizer et al. for the
deformation induced vacancy production. The model predicts the values
of the radii of the precipitates qualitatively and quantitatively. The tem
investigation and the model clearly show the two ranges of shrinking
and growth. The average particle grows with increasing temperature and
decreasing strain rate.
M 15.3 Di 12:15 H16
Structural transformations in AS21X alloy — •Miloˇs Janeček,
Torbjørn Lamark und Juri Estrin — Institut für Werkstoffkunde
und Werkstofftechnik, TU Clausthal, Agricolastr. 6, 38678 Clausthal-
Zellerfeld
The evolution of precipitation processes in a commercial magnesium
alloy AS21X was studied using transmission electron microscopy (TEM),
electron diffraction and energy dispersive X–ray analysis. Three different
states, namely the as cast state and two annealed states after 1000 and
2000 hours, were selected for the investigation of precipitation processes
in this alloy. Furthermore, it was demonstrated by TEM analysis that
twinning is the predominant deformation mechanism in this alloy under
the conditions studied.
M 15.4 Di 12:30 H16
Charakterisierung der Frühstadien der Entmischung in
binären Legierungen mit der radialen Verteilungsfunktion
— •Alexander Heinrich, Talaat Al-Kassab und Reiner
Kirchheim — Institut für Materialphysik, Tammanstraße 1, 37077
Göttingen
Die Systeme Cu0.7at.%Fe und Cu2.0at.%Co wurden mit dem Feldionenmikroskop
(FIM) und der der Tomographischen Atomsonde (TAP)
untersucht. Proben von Cu-Co wurden dabei für Zeiten von einigen Stunden
bis 15 min bei 853 K und 703 K ausgelagert, Proben von Cu-Fe für
Zeiten von 16h bis 15 min bei 803 K und 703K.
Besonderes Augenmerk der Analysen gilt hierbei den Frühstadien der
Keimbildung. Ein neues Auswerteverfahren zur Charakterisierung der

Metallphysik Dienstag
Entmischung aus den TAP-Daten wird vorgestellt. Ergebnisse aus der
Auswertunge der Analysen an beiden Systemen, die neue Aspekte zum
Entmischungsverhalten liefern, werden diskutiert.
M 16 Mechanische Eigenschaften II
Zeit: Dienstag 11:45–12:45 Raum: H4
M 16.1 Di 11:45 H4
Diskrete Versetzungssimulation der dynamischen Stabilität von
Lomer Locks — •Daniel Weygand — Institut für Zuverlässigkeit
von Bauteilen und Systemen (IZBS), Universität Karlsruhe, Kaisserstr.12,
76131 Karlsruhe
Das plastische Verhalten von Kleinstbauteilen und Strukturen soll mit
Hilfe der diskreten Versetzungsdynamikmethode (discrete dislocation dynamics:
DDD) simuliert werden. Die DDD erlaubt die Entwicklung der
Versetzungsmikrostruktur und somit das plastische Verhalten zu berechnen.
Die Wechselwirkung zwischen den Versetzungen kann zur Bildung von
Lomer Locks führen, welche einen Beitrag zum Verfestigungsverhalten
des Materials liefern. Die Stabilität des Locks unter verschiedenen Lastzuständen
wird bestimmt. Darüberhinaus wird die Dynamik des Lockbildungprozesses
untersucht. Es zeigt sich, dass sowohl der Belastungsweg,
als auch die Trägheit der Versetzung die Stabilität des Locks stark abschwächen
können, insbesondere bei kleiner charakteristischer Länge der
Versetzungskonfiguration.
M 16.2 Di 12:00 H4
Hochfeste Cu-Nb Leitermaterialien — •Ekaterina Botcharova,
Jens Freudenberger und Ludwig Schultz — Leibniz-Institut
für Festkörper- und Werkstoffforschung Dresden
Für die Anwendung in gepulsten Hochfeldmagneten werden Leitermaterialien
hoher Festigkeit benötigt. Hierzu eignen sich Drähre auf der
Basis von Cu-Nb-Legierungen, die durch mechanisches Legieren und anschließendes
Heißpressen und Umformen hergestellt werden. Durch mechanisches
Legieren ist es möglich bis zu 10 at.% Niob in Kupfer zu lösen,
was auf schmelzmetallurgischem Weg nicht möglich ist, da Niob fast keine
Löslichkeit in Kupfer aufweist. Die nachfolgende Wärmebehandlung
führt zu der Ausscheidung von Niob aus dem Mischkristall in Form von
feinen Teilchen, deren Größe von Dauer und Temperatur der Behandlung
abhängt. Die Pulver werden kompaktiert und anschließend umgeformt.
Das Umformen des Preßstücks zu einem Draht bewirkt die Bildung
von sehr feinen Niob-Filamenten. Dies fürt z. B. für eine Cu-10at.%Nb-
Legierung zu einer Festigkeit von über 1,2GPa bei einer Leitfähigkeit
von ca. 50% IACS bei Raumtemperatur (International Annealing Copper
Standart). Der Zusammenhang zwischen Gefüge und den Eigenschaften
wird modelliert, wobei die Korngröße der Matrix der wesentliche Parameter
ist.
M 17 Hauptvortrag Jürgen Gegner
M 16.3 Di 12:15 H4
Mikrostruktur und mechanische Eigenschaften von Cu-Ag Legierungen
— •A. Gaganov, J. Freudenberger und L. Schultz —
Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, Helmholtzstr.
20, 01069 Dresden
Die wichtigsten Anforderungen an Leiter für gepulste Hochfeldmagnete
sind eine hohe mechanische Festigkeit, eine gute elektrische Leitfähigkeit
und eine ausreichende Duktilität. Ein vielversprechendes Leitermaterial
basiert auf Cu-Ag-Legierungen, wobei deren Zusammensetzung zwischen
7 und 24 m.-% Ag liegt. Die Mikrostruktur der Legierungen wird wesentlich
durch den Ag-Gehalt bestimmt. Die Cu-24m.-%Ag-Legierung zeigt
eine zweiphasige Mikrostruktur, die aus einem Cu-reich Mischkristall und
dem Cu-Ag-Eutektikum besteht. Das Gefüge der Cu-7m.-%Ag-Legierung
hingegen besteht aus primär erstarrten Cu(Ag)-Mischkristallen sowie
kleineren Ag-Teilchen. Cu-Ag-Mikroverbundwerkstoffe werden durch Ziehen
hergestellt, wobei die Zusammensetzung die Verfestigungsrate stark
beeinflußt. Um einen Leiter mit einer Zugfestigkeit von 1 GPa durch
Kaltumformung herzustellen ist ein Umformgrad von η = 3, 7 (Cu-7m.-
%Ag), bzw η = 3, 1 (Cu-24m.-%Ag) erforderlich. Um einen maximalen
Aushärteeffekt zu erreichen werden Legierung mit weniger als 7m.% vor
der Aushärtung homogenisiert, wobei sich folgende Vorteile ergeben: (i)
Ag-Einsparung, (ii) geringere Neigung zur Scherbandbildung, (iii) höhere
elektrische Leitfähigkeit.
M 16.4 Di 12:30 H4
Zerstörungsfreie Lebensdauervorhersage dynamisch beanspruchter
Bauteile — •Ingo Müller 1 , K. Bennewitz 2 , M.
Haaks 1 , C. Zamponi 1 , T. E. M. Staab 1 , T. Lampe 2 und Karl
Maier 1 — 1 Helmholtz Institut für Strahlen- und Kernphysik, Universität
Bonn, Nußallee 14-16, D-53115 Bonn, Germany — 2 Zentrallabor
Volkswagen AG, 38436 Wolfsburg
Für die Konstruktion dynamisch beanspruchter Bauteile ist die Vorhersage
der Lebensdauer von großer Bedeutung. Bereits im Jahre 1858
hat August Wöhler erste Messungen zur Dauerfestigkeit von Eisenbahnschienen
durchgeführt. Bis heute ist jedoch der Zeit- und Kostenaufwand
für das Messen eines kompletten Wöhlerdiagramms sehr hoch.
In Umlaufbiegeversuchen zeigte sich, daß die ortsaufgelöste Positronen-
Annihilationsspektroskopie (OPAS) es ermöglicht, die Zahl der Proben
auf einige wenige zu reduzieren. Dieses Verfahren wurde nun auch an
Zug-Druck-Versuchen mit verschiedenen Eisen-Werkstoffen getestet.
Zeit: Dienstag 14:00–14:30 Raum: H16
Hauptvortrag M 17.1 Di 14:00 H16
Metal Physics in Heat Treatment Technology - Carburization
and Decarburization of Steels — •Jürgen Gegner 1 , Peter-J.
Wilbrandt 2 , Reiner Kirchheim 2 , and Wolfgang Nierlich 1 —
1 SKF GmbH, Material Physics, Ernst-Sachs-Str. 5, D-97424 Schweinfurt
— 2 University of Göttingen, Institute of Material Physics, Tammanstr.
1, D-37077 Göttingen
Thermochemical processes in rim zones of steels represent a close point
of contact of metal physics to classical engineering industry. Carburization
is a well-established hardening technique, whereas case decarburization
is primarily relevant to heat treatment and hot-working operations as
undesired side effect. The technological background is sketched. Experi-
mental results illustrate the influence on the edge zone. By metallography,
microhardness and X-ray diffraction measurements, the microstructure
and mechanical properties are characterized. Their relation to the carbon
distribution is of special interest. A novel microchemical measuring
technique, based on secondary ion mass spectrometry, is used to determine
carbon depth profiles with high concentration accuracy and spatial
resolution. A numerical simulation tool is adopted for data analysis. The
model takes into account phase transformations as well as blocking surface
layers. Reliable predictions of carbon profiles require knowledge of
the concentration-dependent carbon diffusivities in steels. These data are
determined by a new isothermal powder pack decarburization technique.

Metallphysik Dienstag
M 18 Postersitzung
Zeit: Dienstag 14:30–16:30 Raum: Saal C
M 18.1 Di 14:30 Saal C
Molecular dynamics study of local atomic structures in liquid
metals — •Magnus Kreth and Peter Entel — Institut für Physik,
Universität Duisburg-Essen, 47048 Duisburg
In this work we study local atomic structures in liquid aluminum and
iron using molecular dynamics simulations. Interatomic interactions are
modelled using an embedded-atom method potential. Local atomic structures
in the liquid are identified using a common-neighbor analysis. Static
structure factors are calculated from the pair distribution function to
compare our results with recent neutron diffraction experiments on liquid
metals.
M 18.2 Di 14:30 Saal C
Elektronenmikroskopische Untersuchungen an Nd60Fe30Al10-
Legierungen — •T. Niermann 1 , A. Bracchi 2 , M. Seibt 1 ,
K. Samwer 2 und S. Schneider 1 — 1 IV. Physikalisches Institut
der Universität Göttingen, Tammannstr. 1, 37077 Göttingen — 2 I.
Physikalisches Institut der Universität Göttingen, Tammannstr. 1,
37077 Göttingen
Die Mikrostruktur von Nd60Fe30Al10-Proben wurde mittels hochauflösender
Transmissionselektronenmikroskopie (HRTEM) und
energiedispersiver Röntgenanalyse (EDX) untersucht, sowie die magnetischen
Eigenschaften der Proben mit einem SQUID-Magnometer bei
unterschiedlichen Temperaturen gemessen. Die untersuchten Proben
wurden bei verschiedenen Abkühlraten hergestellt: dünne Schichten,
schnell abgeschreckte Folien (Splat-Quenching) und massive Proben.
Die TEM-Aufnahmen zeigen nanokristalline Nd-Ausscheidungen eingebettet
in einer amorphen Matrix. Im Amorphen lassen sich außerdem
zwei verschiedene Nahordnungen finden. Die bei der vorgefundenen Mikrostruktur
zu erwartenden domain-wall-pinning Prozesse und die magnetische
Kopplung zweier amorpher Phasen können das magnetische
Verhalten erklären.
Gefördert durch die DFG im Rahmen des SFB 602.
M 18.3 Di 14:30 Saal C
Tomographic atom probe (TAP) study of the chemical ordering
in Zr60Ni25Al15 bulk amorphous alloy — •Ahmed Shariq,
Talaat Al-Kassab, and Reiner Kirchheim — Institut fuer Materialphysik,
Uni- Goettingen, Tammanstr.1,D- 37077, Goettingen, Germany
Bulk amorphous alloys are advanced engineering materials owing to
their excellent static and dynamic mechanical properties, wear properties,
low coefficient of friction, magnetic properties and corrosion properties.
The new amorphous alloys have much wider supercooled liquid region
defined as the difference between crystallisation and glass transition temperatures
which may extend up to 100K for some alloys. This wider range
allows to explore the kinetics and thermodynamics in this region. The
alloys with stabilized supercooled liquid state have three features in their
alloy components i.e., multicomponent system, significant atomic size ratios
above 12 percent and negative heat of mixing. Molecular-Dynamics
(MD) simulations for a model Zr60Ni25Al15 ternary amorphous alloy
already had shown two types of chemical short range ordering of Al and
Ni sub systems. The 3D-tomographic atom probe (TAP) is proved to be
currently the best experimental tool to gain experimental information
on chemical heterogeneities at the atomic scale. The data from TAP has
been used to elucidate the atomic distances among neighbouring atoms.
The chemical short range ordering in the supercooled liquid region will
be discussed on the basis of TAP results.
M 18.4 Di 14:30 Saal C
Dichte und Oberflächenspannung flüssiger Fe-Ni-Cu Legierungen
— •Jürgen Brillo und Ivan Egry — Deutsches Zentrum für
Luft- und Raumfahrt e.V., Institut für Raumsimulation, 51147 Köln
Es werden Messungen der Dichte und Oberflächenspannung an den
flüssigen Legierungssystemen Nickel-Eisen, Kupfer-Nickel und Kupfer-
Eisen vorgestellt. Die Messungen werden mit Hilfe der elektromagnetischen
Levitation sowohl bei Temperaturen oberhalb wie unterhalb des
Schmelzpunktes durchgeführt. Die Oberflächenspannung wird mit der
Methode des schwingenden Tropfens aus den Frequenzen der Oberflächenschwingungen
bestimmt. Die Dichte folgt aus einer Volumenbestimmung
des levitierten Tropfens. Die Messergebnisse werden anhand
von Modellen diskutiert. Es zeigen sich charakteristische Unterschiede
zwischen den drei binären Legierungssystemen.
M 18.5 Di 14:30 Saal C
Phase-field Simulations of Dendritic Patterns in Solidification
of a Pure Substance — •Denis Danilov 1 , Britta Nestler 1 , and
Peter Galenko 2 — 1 University of Applied Sciences Karlsruhe, Germany
— 2 Institute for Space Simulation, DLR, Cologne, Germany
We present a critical analysis of the existing phase-field models of
solidification patterns in pure substances. For comparison of the predictions
and asymptotic solutions, we apply the phase-field model recently
developed by Garcke, Nestler, Stinner [2] including the ”thininterface”analytical
results by Karma et al. [1]. The model equations
describing are numerically solved using two different methods: A finitedifference
discretization and an adaptive finite-element method. Simulation
results of solidifying 2D and 3D dendritic morphologies are presented.
The numerical methods are examined with respect to the influence
of grid anisotropy and computational efficiency. The phase-field
model predictions of the tip radius and velocity for different undercoolings
are compared with the analytical model of Brener [3] and with new
experimental results of solidified nickel dendrites by Funke et al. [4].
[1] A. Karma and W.-J. Rappel, Physical Review E 53 (1996) R3017 and
Physical Review E 60 (1999) 3614
[2] H. Garcke, B. Nestler und B. Stinner, SIAM J. on Appl. Math., in
print
[3] E. Brener, J. Cryst. Growth 99 (1990) 165
[4] O. Funke, G. Phanikumar, P.K. Galenko, M. Kolbe, D.M. Herlach,
Physical Review E (2004) submitted
M 18.6 Di 14:30 Saal C
Phase-field modeling of stress-induced instabilities during directional
solidification of a binary alloy — •Bo Liu and Klaus Kassner
— Institut für Theoretische Physik, Otto-von Guericke-Universität
Magdeburg
A phase-field approach is developed to investigate the effect of elastic
stresses on the morphological instability during directional solidification
of a binary alloy. Governing equations are developed to simulate
microstructural pattern formation based on a combination of the quantitative
model for alloy solidification by Karma (Phys. Rev. Lett. 87,
115701 (2001)) and the model for the Grinfeld instability by Kassner et
al. (Phys. Rev. E 63, 036117 (2001)). Simulations in two dimensions are
carried out to test the accuracy of the present model and its numerical
utility by reproducing some known results. We then proceed to investigate
the combined effects of thermal and compositional strains as well as
experimental control parameters on the morphological instability.
M 18.7 Di 14:30 Saal C
A relativistic description for the positron annihilation in solids
— •Diana Benea 1 , Zsuzsanna Major 2 , and Hubert Ebert 1 —
1 Department Chemie / Physikalische Chemie, Universität München, Butenandstr.
5-13, D-81377 München, Germany — 2 H. H. Wills Physics
Laboratory, University of Bristol, Tyndall Avenue, BS8 1TL Bristol, UK
A fully relativistic formulation for the of spin resolved momentum
density is presented together with a corresponding scheme to determine
the two dimensional projection of the electron-positron momentum
density for metals. This formalism is set up within the framework of
spin-polarised relativistic Korringa-Kohn-Rostoker (SPR-KKR) method
of bandstructure calculations. The resulting two dimensional projection
of the electron-positron momentum density is usually identified with the
two-dimensional angular correlation of the annihilation radiation (2D-
ACAR) experimental spectra. Various two dimensional projections of
the electron-positron momentum density of vanadium are presented and
compared with nonrelativistic LMTO calculation and experimental data.
M 18.8 Di 14:30 Saal C
Phase formation by interfacial reactions in the BaO - TiO2 system
— •Andreas Graff, Stephan Senz, and Dietrich Hesse —
Max-Planck-Institut für Mikrostrukturphysik, Halle, Germany
Model experiments concerning phase formation during BaTiO3 genesis
by interfacial reactions in ceramics were performed to identify the
reaction mechanism. Reaction products between BaO vapour and ru-

Metallphysik Dienstag
tile (TiO2) single crystals with different orientations were investigated
by XRD and analytical TEM. BaTiO3 was found at the surface of the
reaction layer. It had a well-defined orientation relation to the rutile substrate.
In addition to BaTiO3, Ti-rich phases and pores were formed. This
observation is discussed by an outdiffusion of titanium and oxygen from
the BaTiO3-TiO2 interface. For a more detailed study of this behavior,
reaction couples of BaTiO3 thin films on rutile single crystal substrates
were prepared. Solid state reactions were initiated by heat treatment in
air. These experiments are compared with the BaO-TiO2 reaction.
M 18.9 Di 14:30 Saal C
Structure and reactivity at the Titanium-Silicon interface —
•Michael Schreiber, Igor Chaplygin, and Sibylle Gemming —
Institut für Physik, Technische Universität, D-09107 Chemnitz
The preparation of structurally and electronically well-defined interfaces
between metallic Ti and semi-conducting Si is complicated by the
formation of crystalline and amorphous binary compounds with a wide
compositional range. Molecular-dynamics density-functional calculations
[1] are carried out for the prototype interface Ti(0001)—Si(111), where
Ti5Si3, TiSi, and TiSi2 phases were observed experimentally. In accordance
with those results, the first steps of the compound formation show
that an amorphous film is accessible at temperatures, for which the crystalline
binary compounds do not yet exhibit melting. The interface reaction
is accompanied by an equilibration and reduction of the stress
tensor components, which are present in the atomically flat interface due
to the lattice mismatch between Si(111) and Ti(0001). Thus, the silicide
formation is not only driven by the electronegativity difference of Ti and
Si, but enhanced by an elastic contribution. [1] www.abinit.org
M 18.10 Di 14:30 Saal C
Positronenspektroskopische Untersuchung von Magnesiumdruckgusslegierungen
mit einem Koinzidenz-Doppler-
Spektrometer — •Christoph Hugenschmidt und Martin
Stadlbauer — Physikdepartment E21, Lichtenbergstraße 1,
Technische Universität München, 85747 Garching
Leichtmetalllegierungen auf Magnesiumbasis spielen insbesondere aufgrund
des niedrigen spezifischen Gewichts eine herausragende Rolle. Legierungsbestandteile
wie Aluminium und Zink der in der Automobilindustrie
am häufigsten verwendeten Legierung AZ91 verbessern die mechanischen
Eigenschaften, die Korrosionsbeständigkeit sowie die Giesseigenschaften.
Druckgussproben dieses Materials unterschiedlicher Porosität
sowie thermisch behandelte Proben wurden mit der Positronenspektroskopie
studiert. Hierzu wurden mit einem Koinzidenz-Doppler-
Spektrometer unter Verwendung einer 22 Na-Quelle hochauflösende Messungen
der 511 keV - Annihilationslinie durchgeführt. Die nahezu untergrundfreien
Messungen lassen eine Linienformanalyse des Hochimpulsanteils
im Bereich grö¨ser 513 keV zu, wodurch man Impulsinformation
über die an der Zerstrahlung beteiligten Rumpfelektronen erhält. Die
hierdurch mögliche Elementspezifizierung in der Ungebung von Fehlstellen
wird diskutiert.
M 18.11 Di 14:30 Saal C
Resistometric investigations of ”order-order”kinetics in intermetallics
with varying superstructure stability — •Ewa Partyka
and Rafal Kozubski — M. Smoluchowski Institute of Physics,
Jagiellonian University, Reymonta 4, 30-059 Krakow, Poland
Investigations of long - range ordering kinetics in ternary intermetallic
systems of superstructure L12 were carried out. Two groups of compounds:
Ni75Al25−xFex and Pt75Co25−xFex , showing opposite relationships
between the stability of L12 superstructure and concentration of
Fe, were examined by means of isochronal residual resistivity.
The effect has been analyzed within the Schulze- Lücke formalism [1]
enabled separate estimation for vacancy formation EF and migration
EM energies being components of the overall activation energy EA for
ordering kinetics. It was found out that in both systems an increase of
activation energy EA accompanying an increase of L12 superstructure
stability is due the increasing tendency of the vacancy formation energy
EF, the activation energy for vacancy migration EM shows either
week decrease with x (Pt75Co25−xFex) or no Fe-concentration dependence
(Ni75Al25−xFex).
References:
[1] Schulze A, Lücke K. Acta Metall 1972;20:529.
M 18.12 Di 14:30 Saal C
Berechnung wahrer Teilchengrößenverteilungen aus Schnittbildern
— •Jürgen Gegner — SKF GmbH, Werkstoff-Physik, Ernst-
Sachs-Str. 5, D-97424 Schweinfurt
Partikelverteilungen innerhalb einer metallischen Matrix, die etwa bei
Ausscheidungsreaktionen oder innerer Oxidation entstehen, werden zumeist
durch licht- oder rasterelektronenmikroskopische Schliffaufnahmen
charakterisiert. Da bei einem solchen Flächenschnitt ein bestimmtes Teilchen
im Allgemeinen nicht zentral, sondern an einer beliebigen Position
geschnitten wird und die Wahrscheinlichkeit für seine Erfassung mit der
Ausdehnung zunimmt, weicht die Größenverteilungen in der Schnittebene
von der gesuchten wahren Größenverteilung im Volumen ab. Die notwendige
Umrechnung erfordert eine stereologische Analyse. Im vorliegenden
Beitrag wird hierfür ein mathematisches Korrekturverfahren abgeleitet
und diskutiert. Ein Computerexperiment mit 20000 statistisch verteilten
Kugelobjekten, deren Größen einer für natürliche polydisperse Partikelsysteme
typischen Lognormalverteilung gehorchen, bestätigt die Anwendbarkeit
der Methode. Die Verschiebung der aus dem Flächenschnitt
entnommenen Größenverteilung hin zu kleineren Durchmessern wird zutreffend
vorhergesagt. Das stereologische Analyseverfahren wird exemplarisch
auf ein diskontinuierliches Dualphasengefüge angewandt.
M 18.13 Di 14:30 Saal C
Evaluation of Carbon Diffusivities in Steels from
Concentration-Distance Curves with Phase Transformation
by Finite Element Analysis — •Jürgen Gegner — SKF
GmbH, Material Physics, Ernst-Sachs-Str. 5, D-97424 Schweinfurt
Application of the isothermal Rhines pack decarburization technique
for the determination of composition-dependent diffusion coefficients of
carbon in the austenite phase of low-alloyed steels at common austenitising
temperatures between 1070 and 1170 K results in an austenite-ferrite
phase transformation in the edge zone of the sample caused by the carbon
loss. This is shown by the concrete example of through-hardenable
rolling bearing steel SAE 52100 (German denotation: 100Cr6) annealed
at 1123 K for 5 h, where the decarburization profile is measured with
high accuracy and spatial resolution by secondary ion mass spectrometry.
Due to the phase transformation, a modified Matano analysis cannot
be applied. Thus, a FE code is developed that permits data fitting by automatized
profile simulation. This way, the carbon diffusivity in austenitic
SAE 52100 is derived from the measuring curve. The obtained result is
compared with literature data on binary Fe-C and ternary Fe-Cr-C.
M 18.14 Di 14:30 Saal C
Determination of Mechanical Characteristics of Adhesively
Bonded Metal Joints by Experiment and Finite Element Data
Analysis — •Jürgen Gegner 1 and Andreas Öchsner 2 — 1 SKF
GmbH, Material Physics, Ernst-Sachs-Str. 5, D-97424 Schweinfurt —
2 University of Aveiro, Department of Mechanical Engineering, Campus
Universitário de Santiago, 3810-193 Aveiro, Portugal
In all fields of industry, modern adhesives are in a position to costeffectively
join metal parts into complex components for e.g. structural
bonding or sealing applications. Thus, computer-aided product design
requires in situ determination of mechanical parameters. The thickadherend
tensile-shear test has established itself as the most important
destructive testing method in adhesive technology. In the present work,
this technique is improved relative to the standard ISO 11003-2 in the experimental
and evaluation part. Stepped metal substrates ensure a more
uniform stress state by increasing the stiffness of the assembly. The total
displacement of the joint is measured directly at the overlap zone to minimize
the influence of adherend deformation, which is considered by the
numerical analysis of a dummy sample. Test evaluation is extended by a
finite element simulation technique that additionally allows derivation of
Young´s modulus from measured shear stress-strain curves. As concrete
examples, steel and aluminum substrates were tested at various temperatures
applying anaerobic and silicon adhesives with different bond gaps.

Metallphysik Dienstag
M 18.15 Di 14:30 Saal C
Materialforschung mit der Bonner Positronen Mikrosonde —
•M. Haaks 1 , I. Müller 1 , S. Sonneberger 1 , T. E. M. Staab 1 , C.
Zamponi 1 , K. Maier 1 , H. Bihr 2 , G. Tempus 3 , K. Bennewitz 4 , T.
Lampe 4 , H. Tönshoff 5 und S. Eichler 6 — 1 Helmholtz Institut für
Strahlen- und Kernphysik, Universität Bonn, Nußallee 14-16, D-53115
Bonn — 2 LEO Elektronenmikroskopie GmbH, Carl-Zeiss-Str. 56, 73447
Oberkochen — 3 Airbus GmbH, Hünefeldstraße 1-5, 28199 Bremen —
4 Zentrallabor Volkswagen AG, 38436 Wolfsburg — 5 Institut für Fertigungstechnik,
Schloßwerdersrt. 5, 30159 Hannover — 6 Freiberger Compound
Materials GmbH, Am Junger Löwe Schacht 5, 09599 Freiberg
Mit der Bonner Positronen Mikrosonde (BPM) steht ein modernes Laborgerät
zur ortsaufgelösten Untersuchung von Defekten in Festkörpern
zur Verfügung. Das Gerät besteht aus einem Feinfokus Positronenstrahl
in Kombination mit einem konventionellen Rasterelektronenmikroskop.
Es werden Ergebnisse der ortsaufgelösten Positronen Annihilationsspektroskopie
aus unterschiedlichen Bereichen der Materialforschung vorgestellt:
• Die Untersuchung der plastischen Zone vor Ermüdungsrissen
in den Aluminiumlegierungen AA 2024 und AA 6013. (3) • Eine neue
Methode der Lebensdauerabschätzung im Bereich der dynamischen Beanspruchung
von Werkstoffen. (4) • Abbildung der lokalen Schädigung
in Spanwurzeln im Eisenwerkstoff C45E. (5) • Die Schädigung durch
Einkorn-Kratzen im oberflächennahen Bereich an GaAs-Wafern. (6)
M 18.16 Di 14:30 Saal C
Magnetische und strukturelle Eigenschaften extrem verformter
CuCo Legierungen — •Bernhard Stöcker, Kai Klement und
Ferdinand Haider — Universität Augsburg
Extreme plastische Verformung erzeugt eine hohe Zahl von Nichtgleichgewichtsdefekten
wie Versetzungen und Leerstellen und kann Phasengleichgewichte
stark verschieben. Dies wurde an CuCo-Proben untersucht,
die mittels ECAP (equal channel angular pressing) bis zu ε=0,68
pro Zyklus verformt wurden. Die Größe der Co-Ausscheidungen nach
der Verformung wurde durch Messung des Koerzitivfeldes bestimmt. Das
Ausheilen der eingebrachten Defekte macht sich in einer Änderung des
Volumens und der Enthalpie bemerkbar, was durch interferometrische
Längenmessung und DSC untersucht wurde.
M 18.17 Di 14:30 Saal C
DFT investigation of nanostructured binary compounds —
•Michael Schreiber 1 , Sibylle Gemming 1,2 , and Gotthard
Seifert 2 — 1 Institut für Physik, Technische Universität, D-09107
Chemnitz — 2 Institut für Physikalische und Elektrochemie, Technische
Universität, D-01062 Dresden.
Density-functional band-structure calculations were carried out for
two-shell metallic nanowires from Au and from AgAu and PdAu alloys.
All structures are local minima of the formation energy and more stable
than the planar Au(111) surface. The stability of the most favourable
structure increases in the order PdAu8 < Au9 < AgAu8. This trend coincides
with the tensile stress acting on the central monatomic chain.
An analysis of the electronic structure shows that the binding between
the two shells is not strongly directional. Yet, the interatomic interaction
along the central chain is weakened compared to the interaction in the
monatomic wire, thus the tensile stress along this direction is alleviated.
In Au9 and AgAu8 the central conductance channel is depopulated, in
PdAu8 not. These findings rationalise the lower conductivity of PdAu
nanocontacts compared with AgAu contacts obtained recently by break
junction experiments. [1] www.abinit.org
M 18.18 Di 14:30 Saal C
Investigation of oxide tunnel barriers by atom probe tomography
(TAP) — •Mario Kuduz 1 , Guido Schmitz 2 , and Reiner
Kirchheim 1 — 1 Institut für Materialphysik, Tammannstr. 1, D-37077
Göttingen, Germany — 2 Institut für Materialphysik, Whilhelm-Klemm-
Str. 10, D-48149 Münster, Germany
Oxide tunnel barriers (TMR) are currently of interest for application in
magnetic sensor and storage devices. Compared to giant magneto resistance
(GMR) devices, tunnel barriers are distinguished by an improved
effect amplitude and a higher base resistivity, so that they may be used
in ’current perpendicular to plane’ arrangements.
We investigated the nano-structure of such TMR devices using field ion
microscopy in combination with a 2D-detection setup. Spin valve structures
consisting of Co and Ni79Fe21 electrodes and Al2O3 barriers were
prepared by sputter deposition on tips of 30 to 50nm curvature radius
suitable for field ion microscopy. In spite of the isolating character of
the barrier material, the chemical structure can be reasonably characterized
by analytical field ion microscopy. The 3D spatial distribution of the
atomic species, in particular the distribution of oxygen, is discussed in
dependence on various deposition methods.
M 18.19 Di 14:30 Saal C
Thermal-Spike-Induced Crystal Growth in Nanocrystalline
Nickel — •Th. Zumkley, G. Schumacher, and S. Klaumünzer
— Hahn-Meitner-Institut Berlin, Glienicker Strasse 100, D-14109 Berlin
In nanocrystalline materials many physical properties are altered compared
to their coarser-grained counterparts because 30% of the atoms
belong to or are affected by the presence of interfaces. Due to their distorted
structure these interfaces are expected to affect also the behavior
of radiation-induced defects and the time evolution of thermal spikes. It
is argued that a small grain size leads to a reduced thermal conductivity
and, consequently, to an enhancement of the spike lifetime.
Nanocrystalline Ni foils of 100 µm thickness were irradiated uniformly
with 200 MeV Kr, 230 MeV Xe or 350 MeV Au ions. For the evaluation
of the x-ray diffraction data both the (111) and (200) peaks have been
used.
Obviously, at the beginning ion bombardment induces a rapid crystal
growth accompanied by a rapid decrease of microstrains. This process
ends on a fluence scale of a few 10 13 ions/cm 2 and is followed by a comparatively
slow process. Therefore, the fast process is definitively caused
by the electronic energy loss. We deduce from the data an increase of
the mean diameter of the nanocrystals by (1±0.1)nm prior to and after
irradiation. If we assume that crystal growth proceeds isotropically this
finding implies that about 25% of the specimen atoms are involved in
the fast process. Probably, a thermal spike released by the electronic excitations
in a radius of about 2 nm around a projectile ′ s path induces a
rearrangement of all atoms to a final position in the grain boundaries.
M 18.20 Di 14:30 Saal C
Microstructural investigations on single crystalline Ni-rich NiTi
shape memory alloys — •Klaus Neuking, Jens Michutta, Alejandro
Yawny, Christoph Somsen, and Gunther Eggeler —
Ruhr-Universität Bochum, Institut für Werkstoffe, 44780 Bochum
In polycrystalline Ni-rich Ni-Ti shape memory alloys the precipitation
of 4 families of Ni4Ti3 occurs heterogeneous on grain boundaries.
As a result on cooling multiple-step phase transformations can be observed.
To overcome this heterogeneous precipitation single crystalline
Ni-rich (50.8 at.%) NiTi samples have been produced by using the Bridgman
technique. Compression-aging treatments tests at temperatures of
500 ◦ C and 550 ◦ C were carried out in order to nucleate only one family
of Ni4Ti3 precipitates under a compression stress of 50MPa in the
[111]-direction. Microstructural investigations with transmission electron
microscopy (TEM) reveal that the nucleation of the other three families
is suppressed completely under compression aging. Differential scanning
calorimetry (DSC) was used to determine the influence of different aging
times on the martensitic transformation behaviour on cooling and on
heating. For the aging temperature of 500 ◦ C only a two step transformation
can be detected throughout the chosen time range between 2ks and
360ks. By increasing the temperature to 550 ◦ C a multiple-step transformation
occurs at aging times of 8ks and above. At aging times below
8ks a two step transformation is present. The martensitic transformation
behavior is analyzed by in-situ cooling TEM investigations.
M 18.21 Di 14:30 Saal C
Hochgenaue Elektronenbeugung an FeCr2S4 — •Markus Mertinat,
Ferdinand Haider und Vladimir Tsurkan — Institut für
Physik, Universität Augsburg
Proben aus FeCr2S4–Einkristallen in [110]– und [111]–Orientierung
wurden präpariert und mittels Transmissionselektronenmikroskopie unter
Verwendung eines Kühlhalters untersucht. Zur Strukturuntersuchung
wurden die Beugungsmuster von verschiedenen Temperaturen
mit selbst geschriebenen Programmen ausgewertet. Mit der parallelen
(Feinbereichs–) Elektronenbeugung lassen sich die sehr kleinen Gitterveränderungen
gerade noch beobachten. Es wurde bei Tm = 45 bis 55 K
eine Veränderung der Gitters beobachtet. Unterhalb dieser Temperatur
wandelt sich das fcc–Gitter in eine trikline Struktur um. Die relative
Änderung liegt in der Größenordnung von 5 · 10 −4 . Die erstmalige Beobachtung
der nach magnetischen Messungen vermuteten Umwandlung
könnte einige bislang unverstandene Phänomene erklären. Die Daten des
triklinen Gitters konnten konsistent mit den Beobachtungen angepasst

Metallphysik Dienstag
werden.
M 18.22 Di 14:30 Saal C
Monte Carlo Simulation of Binary Alloys Including Elastic Relaxations
— •Rolf Anders 1 , Gururajan Mogadalai Pandurangan
1,2 , and Ferdinand Haider 1 — 1 Univ. Augsburg, Institut f. Physik
— 2 Indian Institute of Science, Dept. f. Metallurgy
We developped a real space technique which includes local atomic relaxation
during each atomic jump, allowing thus to study phase transformations
with strong elastic contributions. For each atomic jump, the
activation energy is computed using phenomenological interaction potentials.
After a succesful jump the atomic coordinates of the vicinity of the
jumping atom are relaxed in order to minimise the total energy.
This technique was applied to a binary alloy with vacancy diffusion using
the Lennard-Jones potential. The influence of temperature T, misfit
σB/σA and chemical interaction εAB/εA on precipitate size and precipitation
kinetics was studied. Precipitation was only observed at medium
temperatures. At low T diffusion is too slow while at high T the thermal
energy is greater than the energy loss per atom through precipitation. A
similar behaviour was found with respect to chemical interaction. A value
of εAB/εA considerably smaller than 1 slows down precipitation and at
εAB/εA ≈ 1 no precipitates are formed due to the low energy difference.
Increasing σB/σA also causes a slowing down of precipitation.
M 18.23 Di 14:30 Saal C
Covalent bonding in approximants of Quasicrystals and the
electronic transport — •Torsten Schmidt, Heinrich Solbrig,
and Philipp Plaenitz — Technische Universitaet Chemnitz, Institut
fuer Physik, D-09107 Chemnitz, Germany
Recent X-Ray diffraction data indicates the existance of well pronounced
inhomogenities of the elctronic charge density acting as covalent
interatomic bonds[1]. The present work attemps to prove these findings
by ab-initio calculations of the electronic density in 1/1-approximants.
For Al-TM systems (TM = Mn,Fe,Re,Ru) it is shown that covalent
charge bridges (i) stabilize the typical clusters (comparison with free
clusters) and (ii) connect them to establish a network of clusters.We see
these bonding properties as an essential source of the observed transport
anomalies. These idea is proved upon examining the changes in both: the
bonding and the electronic transport after introducing arbitrary defects
of chemical decoration and structure.
Transport parameters are obtained by means of the Kubo-Greenwood
formula employing the elctronic states as produced by the ASA-LMTO
method. Valence charge densities are calculated by the ABINIT structure
code and by GAMESS for isolated molecule clusters, respectively.
[1] K. Kirihara (et.al), Covalent bond and their crucial effects on pseudogap
formation in alpha-Al(Mn,Re)Si icosahedral quasicrystalline approximant,
Phys. Rev. B 68, 014205, (2003)
M 18.24 Di 14:30 Saal C
Non-icosahedral equilibrium surfaces of icosahedral Al-Pd-
Mn quasicrystals — •Mariya Yurechko, Benjamin Grushko,
Philipp Ebert, and Knut Urban — Institut für Festkörperforschung,
Forschungszentrum Jülich, D-52425 Jülich
LEED and STM investigations of the structure of Al-Pd-Mn quasicrystal
surfaces prepared with essentially identical preparation methods,
yielded widely varying surface structures, even with different symmetries.
We show on a basis of a precision determination of the ternary
Al-Pd-Mn phase diagram, which of those surface structures are equilibrium
surfaces of icosahedral quasicrystals and how they are formed. We
find that the equilibrium surface of icosahedral Al-Pd-Mn quasicrystals
can have non-icosahedral (i.e. decagonal and orthorhombic) structures,
depending on the exact initial composition of the quasicrystal. Only in
a narrow composition range of the icosahedral Al-Pd-Mn phase after
annealing or under kinetically limited (non-equilibrium) cleaning procedures,
icosahedral surfaces can be obtained. These effects are attributed
to the phase equilibrium of the ternary alloy system.
M 18.25 Di 14:30 Saal C
Adhesion of metal films on polymer substrates determined by
a hydrogen loading method — •Eugen Nikitin, Reiner Kirchheim,
and Astrid Pundt — Institut für Materialphüsik, Tammannstr.
1, 37077 Göttingen
Expansion of Nb-films on polymer substrates during hydrogen loading
leads to local delamination of the films with the shape of buckles.
This happens above a critical hydrogen concentration ccrit which can
be obtained both in optical and substrate curvature measurements. The
critical concentration is directly linked to the adhesion energy by assuming
pure elastic stress release within the delamination buckle [1,2]. In
this work we will present optical and stress measurements on the critical
concentrations ccrit of films with different film thickness. Also, the influence
of the substrate thickness will be presented. The technique enables
a quantitative determination of the adhesion energy between the polymer
and a metal film. [1] A. Pundt, P. Pekarski, Scripta Mat. 48 (2003)
419-423, [2] A. Pundt, E. Nikitin, P. Pekarski, R. Kirchheim, Acta Mater.
(accepted).
M 18.26 Di 14:30 Saal C
Optische Eigenschaften von EuHx-Filmen — •S. Weber, M.
Rode und J. Schoenes — Institut für Halbleiterphysik und Optik,
Mendelssohnstr. 3, 38106 Braunschweig
Europium durchläuft beim Beladen mit Wasserstoff einen Metall-
Isolator-Übergang. Dabei wird aus dem antiferromagnetischem Metall
ein ferromagnetischer Isolator, d.h. auch die optischen Eigenschaften der
Filme ändern sich dramatisch von einem undurchsichtigen zu einem optisch
transparenten Film.
Die Transmission und Reflexion der dünnen Filme auf CaF2 wurde im
Energiebereich von 6meV bis 5eV gemessen. Da die Filme auch mit einer
funktionellen Palladium-Deckschicht versehen werden müssen, wurde
im Rahmen eines Vielschichtmodells die dielektrische Funktion der
Filme ermittelt. Mit Hilfe verschiedener Ansätze wurde die Bandlücke
von EuH2−δ abgeschätzt. Das Schaltverhalten beim Beladen mit Wasserstoff
wurde mittels Widerstandsmessungen auch elektrisch untersucht
und dem optischen Schaltverhalten gegenüber gestellt.
M 18.27 Di 14:30 Saal C
Temperaturabhängigkeit der infrarot- und Raman-aktiven Phononen
im System YH3−δ — •M. Rode, A.-M. Carsteanu, D. Zur
und J. Schoenes — Institut für Halbleiterphysik und Optik, TU Braunschweig,
Mendelssohnstr. 3, D-38106 Braunschweig
Das System YHx (0 ≤ x ≤ 3) zeigt beim Wechsel von x = 2 nach
x = 3 einen Metall-Isolator-Übergang. Sowohl die Theorie des Metall-
Isolator-Übergangs, als auch die Kristallstruktur des YH3 sind bis heute
noch umstritten. Aus diesem Grund sind die optisch aktiven Phononen
der YH3-Phase untersucht worden. Dazu wurden temperaturabhängige
Infrarotreflexions- und Ramanmessungen an dünnen YH3−δ-Filmen
durchgeführt. Die Spektren beider Meßmethoden werden mit entsprechenden
Linienformen angepaßt. Die temperaturabhängig auftretenden
Veränderungen der Linienformen werden im Rahmen eines störungstheoretischen
Modells diskutiert. Aus dem Vergleich zwischen Experiment
und Modell werden Grüneisenparameter und Anharmonizität der einzelnen
Phononenmoden bestimmt.
M 18.28 Di 14:30 Saal C
Optische Eigenschaften von Yttrium und YH2+δ im Energiebereich
von 1 eV bis 10 eV — •H. Schröter, U. Barkow und J.
Schoenes — Institut für Halbleiterphysik und Optik, Mendelssohnstraße
3, 38106 Braunschweig
Seit längerem ist bekannt, dass Seltene Erdmetalle wie Yttrium, einen
Metall-Isolator-Übergang zeigen, wenn sie einer Wasserstoffatmosphäre
ausgesetzt werden. Die damit verbundene, Änderung der optischen Eigenschaften
wurde mittels Ellipsometrie, u.a. am VUV-Ellipsometer am
BESSY II, untersucht. Um den Mechanismus des Metall-Isolator-Übergangs
zu verstehen, wurden Messungen an dünnen Yttriumfilmen mit unterschiedlicher
Konzentration von Wasserstoff durchgeführt. Die Schichten
wurden mittles Molekularstrahlepitaxie (MBE) in einer Wasserstoffatmosphäre
hergestellt. Je nach Höhe des angelegten H-Druckes, konnten
bislang Schichten mit einem Wasserstoffanteil bis hin zu YH2 hergestellt
werden. Der technisch bedingte maximal mögliche Hintergrunddruck
beim Schichtwachtum mittels MBE, begrenzte dabei den H-Gehalt
der Schichten. Duch einen direkt auf das Substrat gerichteten H-Strahl,
konnten nun erstmals auch Schichten mit einem höherem Wasserstoffanteil
(YH2+δ) gewachsen werden. Zusätzlich wurden Untersuchungen zur
Haltbarkeit der Proben durchgeführt, insbesondere wurde die Auswirkung
der Oxidation an der Probenoberfläche, auf die optischen Eigenschaften
der Proben betrachtet.
M 18.29 Di 14:30 Saal C
Electronic density of states in the LaHx-System — •Sandra
Heck, Stephan Leyer, Gerda Fischer, and Elmar Dormann —
Physikalisches Institut, Universität Karlsruhe, D-76128 Karlsruhe

Metallphysik Dienstag
As has been known for more than fourty years, rare-earth dihydrides
like LaH2.0 are metals and the trihydrides (LaH3.0) are semiconductors.
The metal-non-metal transition of the LaHx-system was first observed in
1957 [1]. Shinar et al. ([2] 1990) determined the transition concentration
to x=2.86. Whereas it is well known that band filling and atomic order
play a significant role in this transition, important aspects are currently
not understood. Recent interest in this field dates from the observation
that rare-earth hydride mirrors can be switched reversibly from reflectivity
to transparency for visible light via the hydrogen content. We carried
out measurements of the Pauli-susceptiblility, the 139 La Knight-shift and
the 139 La spin-lattice relaxation rate in order to obtain the concentration
M 19 Hauptvortrag Jorg Wiezorek
dependence of the electronic density of states at the Fermi-level (DOS).
These results are compared with earlier NMR [3] and specific-heat [4]
data. We thank R. Barnes and G. Majer for disposal of samples.
[1] B. Stalinski, Bull. Acad. Pol. Sci. Cl.III 5, 1001 (1957)
[2] J. Shinar, B. Dehner, R. G. Barnes and B. J. Beaudry, Phys. Rev.
Lett. 64, 563 (1990)
[3] R. G. Barnes, C. T. Chang, G. Majer, U. Kaess, J. Alloys Compounds
137, 356-357 (2003)
[4] K. Kai, K. A. Gschneidner, Jr., B. J. Beaudry, D. T. Peterson, Phys.
Rev. B 40, 6591 (1989)
Zeit: Mittwoch 14:00–14:30 Raum: H16
Hauptvortrag M 19.1 Mi 14:00 H16
Combined Reaction Processing of Fe-Pd based Ferromagnetic
Intermetallics — •Jorg Wiezorek — UPitt: MSE, University of
Pittsburgh, 848 Benedum Hall, Pittsburgh, PA 15261, USA
Jörg M.K. Wiezorek Department of Materials Science and Engineering,
University of Pittsburgh, 848 Benedum Hall, Pittsburgh, PA, USA.
Alloys based on Fe and Pd are of interest for permanent magnet applications
due to the large uniaxial magnetocrystalline anisotropy associated
with the formation of the L1o-ordered intermetallic phase, gamma1-
FePd. However, the magnetic properties of FePd after conventional processing
are disappointing. Optimization of the technical properties of
M 20 Nanoskalige Materialien I
FePd ferromagnets requires the development of a detailed understanding
of the phase-transformation and microstructural transformation behavior.
Here, thermo-mechanical processing, termed combined reaction
(CR) processing, was used to control microstructural scale and morphology
and to improve the properties of FePd. CR processing exploits the
interplay between recrystallization and the ordering transformation during
annealing after cold-work at T

Metallphysik Mittwoch
erstaunlicher, da Pd eine im Vergleich zu Al noch höhere Stapelfehler
besitzt. Zu diesem Zweck wurde nanokristallines Pd mit einer durchschnittlichen
Korngröße von ungefähr 15 nm mittels Edelgaskondensation
hergestellt. Die Verformung der Probe erfolgte durch Kalt-Walzen
bei einer Dehnrate von 0.3 s −1 bis zu einer wahren Dehnung von 0.32.
Die Ergebnisse werden mit molekulardynamischen Simulationen aus der
neueren Literatur verglichen.
M 20.5 Mi 15:45 H4
Abgleitung über Korngrenzen als Verformungsmechanismus in
nanokristallinem Palladium — •J. Markmann 1,2 , H. Rösner 1 ,
K.W. Liu 3 , R. Birringer 2 , H. Gleiter 1 und J. Weissmüller 1,2
— 1 Forschungszentrum Karlsruhe, Institut für Nanotechnologie, 76021
Karlsruhe — 2 Universität des Saarlandes, FR 7.3 Technische Physik,
66041 Saarbrücken — 3 Universität des Saarlandes, FR 8.15 Werkstoffwissenschaften
und Fertigungstechnik, 66041 Saarbrücken
Verformung von kristallinen Metallen über die Bewegung und Ver-
M 21 Nanoskalige Materialien II
vielfältigung von Versetzungen werden mit kleiner werdender Korngröße
unterdrückt, was zu einer deutlichen Erhöhung ihrer Festigkeit führt.
Jedoch zeigen Verformungsexperimente an vielen nanokristallinen (nk)
Materialien, daß diese als Hall-Petch Relation bekannte Beziehung bei
nk Metallen außer Kraft treten kann. In dieser Studie wurde nk edelgaskondensiertes
Palladium (Pd) sukzessive mit einer Verformungsrate
von ca. 0.1 s −1 gewalzt. Die Auswertung der Röntgenweitwinkelstreuung
an nk Pd Proben zeigte einen anfänglichen Anstieg in der Stapelfehlerdichte,
der bei weiterer Verformung in eine Sättigung lief, was auf Versetzungsaktivitäten
schließen läßt. Polfiguren, welche bei einer angelassenen,
grobkristallinen Referenzprobe typische Walztexturen aufdeckten,
deuteten auf keinerlei Orientierungsausrichtung der Kristallite in den nk
Proben. Auch zeigten TEM Aufnahmen dieser Proben nach dem Walzen
keine sichtbaren Verformungen der Körner. Weiterhin wurden Korngrenzen
gefunden, die entlang von geraden Linien angeordnet waren. Dies
deutet auf mesoskopische Scherbänder und damit auf Korngrenzengleiten
als dominanten Verformungsmechanismus.
Zeit: Mittwoch 16:30–17:30 Raum: H4
M 21.1 Mi 16:30 H4
Herstellung und magnetische Eigenschaften formanisotroper
Eisen-Nanopartikel — •Christian Lang, Andreas Tschöpe und
Rainer Birringer — Universität des Saarlandes
Mithilfe der Edelgaskondensation im erzwungenen Gasfluss wurden nanorods
aus Eisen synthetisiert. In situ Coating mit Ölsäure ermöglicht
es, die nanorods in einem organischen Lösungsmittel zu einem stabilen
Ferrofluid zu dispergieren. Wir diskutieren erste Experimente zu den
magnetischen und magnetoviskosen Eigenschaften dieser Systeme. Insbesondere
wird der Einfluss der Formanisotropie auf die magnetfeld- und
scherratenabhängige Viskosität der nanorod-Ferrofluide untersucht und
diesbezügliche Modelle diskutiert bzw. mit experimentellen Befunden an
konventionellen Ferrofluiden verglichen.
M 21.2 Mi 16:45 H4
Bestimmung von Kristallitgrößen und Mikrostrukturparametern
in ultrafeinkörnigen Werkstoffen mit Röntgenverfahren —
•Markus Dinkel, Florian Pyczak und Mathias Göken — Werkstoffwissenschaften
1, Universität Erlangen-Nürnberg, Martensstr. 5,
91058 Erlangen
Ultrafeinkörnige metallische Werkstoffe können mit SPD-Verfahren
(severe plastic deformation) mit Korngrößen zwischen 300 und 600 nm
hergestellt werden. Aufgrund ihrer hohen Festigkeit, sind sie Kandidaten
für eine Reihe von Anwendungen, z.B. in der Medizintechnik.
Röntgenbeugungsverfahren werden schon lange zur Bestimmung der
Korngröße verwendet. In ultrafeinkörnigen Materialien ergeben sich allerdings
Schwierigkeiten, da die beim Herstellungsprozess eingebrachten
massiven Verformungen die Röntgenprofile verbreitern. Gelingt es diese
Verbreiterung von der Verbreiterung des Röntgenprofils aufgrund der
Korngröße zu trennen, können, neben der Korngröße, auch Versetzungsdichten
und andere mikrostrukturellen Parametern bestimmt werden.
Anhand der Ergebnisse von Messungen an unterschiedlichen ultrafeinkörnigen
Materialien, werden die Möglichkeiten und Grenzen der Methode
gezeigt und mit anderen Untersuchungsverfahren, wie beispielsweise
der Transmissionselektronenmikroskopie, verglichen.
M 21.3 Mi 17:00 H4
Grenzflächenspannung in nanokristallinem Ag/Ni Komposit —
•Patrik Zimmer und Rainer Birringer — FR 7.3 Technische Physik,
Universität des Saarlandes, Geb. 43B, D-66123 Saarbrücken
In nanokristallinen Materialien mit einer hohen Anzahl innerer Grenzflächen
generieren Grenzflächenspannungen positiven oder negativen
Druck in den angrenzenden kristallinen Bereichen. In Ag/Ni Multilagen
wird eine Dehnung des Nickelgitters gefunden und somit eine negative
Flächenspannung der Ag/Ni Phasengrenze impliziert. Da die mittlere
isotrope Flächenspannung unabhängig von der Grenzflächenkrümmung
ist, wird diese an partikulären Ag/Ni Nanokompositen mit Hilfe der
Röntgenbeugung studiert. Die Nanokomposite bieten den Vorteil, dass
durch Ostwald Reifung der Ni-Nanokristalle in der Ag-Matrix die damit
einhergehende Änderung des Ni-Gitterparameters eine belastbare Bestimmung
der Flächenspannung ermöglicht und somit auch den Vergleich
mit Vorhersagen aus der Elastizitätstheorie und Computersimulationen
erlaubt.
M 21.4 Mi 17:15 H4
Grenzflächen- und Linienspannungen in nanokristallinem Gadolinium
— •D. Michels 1 , C. E. Krill III 1 , M. Brunelli 2 und R.
Birringer 1 — 1 FR 7.3 Technische Physik, Universität des Saarlandes,
Geb. 43B, D-66123 Saarbrücken — 2 The European Synchrotron Radiation
Facility (ESRF), 38043 Grenoble Cedex 9, France
In einem polykristallinen Festkörper werden die durch innere Grenzflächen
induzierten Flächenspannungen 〈f〉 im mechanischen Gleichgewicht
durch Volumenspannungen in den Kristallen kompensiert. Die
damit verbundene Volumenänderung in den Kristalliten skaliert wie
〈f〉/〈L〉, wobei 〈L〉 die mittlere Kristallitgröße des Materials ist. D. h.
nanokristalline Materialien sind geradezu prädestiniert, den Einfluss der
Flächenspannungen quantitativ zu erfassen. Im Grenzfall kleiner 〈L〉-
Werte (ca. 4 nm) wird neben den Flächenspannungen auch der Einfluss
von Linienspannungen, die von Tripellinien herrühren, signifikant. Die
quantitative Ermittlung der unterschiedlichen Spannungen wird anhand
eines Diffraktionsexperiments (ESRF, Grenoble, ID 31: High Resolution
Powder Diffraction Beamline) an nanokristallinem Gadolinium erörtert.

Metallphysik Mittwoch
M 22 Intermetallische Phasen
Zeit: Mittwoch 16:30–18:00 Raum: H6
M 22.1 Mi 16:30 H6
Ordering and Magnetism in Fe-Co: Quasi-Continuous Sequence
of Ground-State Structures — •Ralf Drautz 1 , Alejandro Diaz-
Ortiz 2 , Manfred Fähnle 3 , and Helmut Dosch 3 — 1 Department of
Materials, University of Oxford, OX1 3PH, UK — 2 Advanced Materials
Department, Instituto Potosino de Investigacion Cientifica y Tecnologica,
A.C., 78231 San Luis Potosi, S.L.P., Mexico — 3 Max-Planck-Institut
für Metallforschung, Heisenbergstraße 3, D-70569 Stuttgart
We have discovered that Fe-Co alloys develop a series of ordered
ground-state structures for different compositions additionally to the
known CsCl-type structure. This new set of ground-state structures was
found from a combinatorial ground-state search of 1.5 × 10 10 bcc-based
structures. The energies of the searched bcc structures were constructed
with the cluster expansion method from few first-principles calculations
for ordered Fe-Co structures.
To explain the sequence of ordered ground-state structures found in
FeCo, a hypothesis for the precondition to find a continuous sequence
of ground states in a binary alloy is proposed. In accordance with our
findings from the combinatorial ground-state search the system FeCo is
found to slightly violate the conditions for a continous ground state. This
naturally explains the found finite set of ground state structures.
M 22.2 Mi 16:45 H6
Magnetic Properties and Single Crystal Growth of the Er2PdSi3
intermetallic compound. — •Irina Mazilu 1 , Wolfgang Löser 1 ,
Günter Behr 1 , Kartik K Iyer 2 , P.L. Paulose 2 , E.V. Sampathkumaran
2 , and Ludwig Schultz 1 — 1 Leibniz-Institut for Solid
State and Materials Research Dresden, Helmholtzstr. 20, D-01171 Dresden,
Germany — 2 Tate Institute of Fundamental Research, Homi Bhabha
Road, Colaba, Mumbai-400005, India
Rare Earth (RE)- Transition Metal-Silicides are of general interest for
their magnetic and magnetoelectric properties and complex magnetic ordering.
Single crystals of Er2PdSi3 intermetallic compound with a hexagonal
AlB2 type crystal structure were grown by a floating zone method
with optical heating. The control of the oxygen impurity content was
the crucial point of crystal growth process. The preferred growth direction
was near [10-10]. The crystals exhibits an inferior depletion in Pd
and enrichment in Si with respect to the stoichiometric composition.
Growth relevant Er-Pd-Si phase diagram features have been revealed by
differential thermal analysis and additional microstructure investigations.
Magnetic measurement on oriented samples of Er2PdSi3 single crystals
exhibit antiferromagnetic order with a transition temperature at 7 K and
a relative small anisotropy compared to other RE2PdSi3, (RE=Tb,Ho).
However, anisotropic electrical properties as function of the temperature
were revealed. Neutron diffraction studies of the magnetic ordering are
in progress.
M 22.3 Mi 17:00 H6
Structural changes of TiAl deformed by high-strain torsion
— Guang-hui Cao, Werner Skrotzki, Carl-georg Oertel,
•Guang-hui Cao, Werner Skrotzki, and Carl-georg Oertel
— Institut fur Strukturphysik, Technische Universitat Dresden, 01062
Dresden, Germany
High-temperature extruded two-phase TiAl/Ti3Al intermetallics have
been deformed by torsion and their microstructures have been investigated
by transmission electron microscopy. The microstructural changes
observed consist of break-down of the lamellar structure and deformation
induced precipitation of TiAl3 and Ti2Al. The study is expected to
be helpful for understanding the relationship between the microstructure
and mechanical properties which can be changed drastically by highstrain
torsion.
M 22.4 Mi 17:15 H6
High-strain torsion of NiAl — •Burghardt Klöden 1 , Werner
Skrotzki 1 , Carl-Georg Oertel 1 , Roland Tamm 1 , Ulf Garbe 2 ,
and Erik Rybacki 3 — 1 Institut für Strukturphysik, Technische
Universität Dresden, 01062 Dresden, Germany — 2 DESY-HASYLAB,
Notkestraße 85, 22603 Hamburg, Germany — 3 Geoforschungszentrum
Potsdam, Telegrafenberg, 14473 Potsdam, Germany
High-temperature extruded polycrystalline NiAl, an intermetallic compound
with the B2-structure, has been deformed in torsion at temperatures
between 800K and 1300K in a Paterson-type rock deformation
machine under 400 MPa Argon confining pressure. The maximum strain
rate was about 10 −4 s −1 , the maximum shear strain about 15.6. Samples
with two different initial preferred orientations were deformed. With increasing
shear strain the shear stress goes over a maximum and reaches
a steady state value, indicating dynamic recrystallization. In addition, a
shortening of the torsion samples takes place (Swift effect). The results
will be discussed with respect to microstructure and texture formation.
M 22.5 Mi 17:30 H6
MODEL ALLOY BASED ON HIGH NI CONTAINING
MARAGING STEEL INVESTIGATED BY 3 DIMEN-
SIONAL ATOM PROBE — •Stefan Höring 1 , N. Wanderka 1 ,
J. Banhart 1 , H. Clemens 2 , and H. Leitner 2 — 1 Hahn-Meitner-
Institut Berlin, Glienicker Str. 100, 14109 Berlin — 2 Institut für
Metallkunde und Werkstoffprüfung, Montanuniversität Leoben,
Franz-Josef-Strasse 18, A - 8700 Leoben
The high Ni containing maraging steels are widely used for aerospace
as well for tools and dies because of their good mechanical properties.
The high strength of these steels is achieved by dispersion of precipitates
in nanometer scale. A model alloy based on the maraging steel
with the composition 75.08Fe-13.09Cr-8.38 Ni- 1.08 Si -0.96 Ti-0.69 Al
-0.57Mo-0.11 Mn -0.05 C (in at.%) was solution heat treated at 1273
K for 1 h and subsequently aged at 748 K for 12 h and 100 h. The microstructure
of the annealed specimens were studied by high resolution
methods such as three dimensional atom probe (3DAP) and high resolution
transmission electron microscopy (HRTEM). After 12 h annealing
time small precipitates of spherical morphology and of about 2 nm in diameter
were formed. They are enriched in Ni, Al, Ti and Si. After 100h
two additional phases were produced. One of them is enriched in Al, Ti
and Ni and the other one is mainly enriched in Cr.
M 22.6 Mi 17:45 H6
Three-dimensional finite element analysis of mismatch-induced
stresses and elastic strain energy distribution around precipitates
in INCONEL 706 alloy — •Vitaliy Kindrachuk, Nelia
Wanderka, Weiye Chen, and John Banhart — Hahn-Meitner-
Institut Berlin, Glienicker Str. 100, 14109 Berlin, Germany
The good mechanical properties of Inconel 706 up to 600 ◦ C are due to
strengthening by γ ′ , γ ′′ and γ ′ -γ ′′ precipitates. To better understand the
microstructure behaviour (the morphological and phase changes) during
the heat treatment is the stressed state on the interfaces of great interest.
The three-dimensional finite element (FE) analysis was used to investigate
the stress and strain energy features arising from a mismatch of
crystal lattices of coexisting phases.
The FE model was built based on characterization of the precipitates
and matrix by three-dimensional atom probe, high resolution transmission
electron microscopy, X-ray and synchrotron measurements. The precipitates
were modelled to have an oval morphology, negative misfit and
oriented parallel to the lattice direction of the γ matrix. The individual
precipitate variants of γ ′ ,γ ′′ and γ ′ -γ ′′ co-precipitates were analysed
under stress-free conditions. To obtain the long-range stress field we
have simulated the combination of precipitates taking into account their
mutual spatial arrangement. Prediction of the selective variant growth
was realized by addition the coupling between the applied stress and the
strain caused by the precipitates.

Metallphysik Donnerstag
M 23 Hauptvortrag Dieter Brunner
Zeit: Donnerstag 09:30–10:00 Raum: H16
Hauptvortrag M 23.1 Do 09:30 H16
Plasticity in body-centred cubic structures with emphasis on
low-temperature behaviour — •Dieter Brunner — Max-Planck-
Institut für Metallforschung, Heisenbergstrasse 3, 70569 Stuttgart
Materials crystallizing in the body-centred cubic (bcc) structure exhibit
plastic behaviour which differs impressively from that of differently
structured materials. The different behaviour is related to different slip
and work hardening mechanisms. The dependence of the yield stress on
temperature, strain-rate, and both the concentration and configuration
of atomic lattice defects is very pronounced in contrast to fcc materials.
These differences are particularly large in the low-temperature regime
below a characteristic temperature TK. At low temperatures, high purity
and sufficiently small sample dimensions are prerequisites for tensile
M 24 Nanoskalige Materialien III
tests. In the talk, relevant results of measurements with single crystals
of the metals α-Fe, Mo, W, Nb, Ta, the intermetallic alloy NiAl, the alkali
metal potassium, and the oxide ceramic SrTiO3 will be addressed.
The crucial point in the interpretation of the plasticity of bcc metals,
for example, is based on < 111 >a0/2 screw dislocations whose motion
governs the plastic behaviour and which possess a non-planar core structure.
Accordingly, they are rather sessile but can be moved by thermally
activated kink-pair formation on screw dislocations. Seeger’s kink-pair
theory developed in the 1980s has proved to be in excellent agreement
with the experimental results. Applying this model enables the macroscopic
behaviour to be described in terms of few kink parameters that can
be determined from deformation experiments for the above mentioned
materials.
Zeit: Donnerstag 10:15–11:15 Raum: H16
M 24.1 Do 10:15 H16
Melting behavior of Pb and In nanoparticles dispersed in AlYFe
matrix — •Nancy Boucharat, Harald Roesner, and Gerhard
Wilde — Forschungszentrum Karlsruhe, Institute of Nanotechnology,
Postfach 3640, 76021 Karlsruhe
Nanocomposites consisting of nanoscale Pb or In particles dispersed
within a crystalline Al matrix have attracted particular attention since
considerable deviations in the Pb and In melting temperatures have
been observed compared to that of the bulk. Beyond the nano-size effect,
several proposals involving contributions of the crystalline matrix
(e.g. grain boundaries, strains and defects, lattice orientation relationship)
have been advanced to account for the modified melting behavior.
Thus, the incorporation of Pb and In nanoparticles in marginal glass
formers gives a new opportunity to wider the understanding of the impact
of the matrix on the melting behavior, especially to study the sizedependent
melting behavior without the constraints imposed on the particles
by a crystalline matrix. Therefore, the melting behavior of Pb and
In nanoparticles embedded in rapidly quenched AlYFe glass have been
investigated by calorimetry and structural analyses. The results indicate
a general decrease of both melting temperatures. Moreover, the shift of
melting temperatures was found to be strongly correlated to the matrix
microstructure, i.e. whether the matrix is in an amorphous state, contains
Al-nanocrystal dispersions or is in a fully crystallised state.
M 24.2 Do 10:30 H16
Analysis of nanocrystalline CuBi-layers — •Daniel Wolde-
Giorgis, Talaát Al-Kassab und Reiner Kirchheim — Universität
Göttingen, Institut für Materialphysik, Tammanstraße 1, 37077 Göttingen
The segregation behaviour of Bi in nanocrystalline Cu-layers was investigated
by means of the tomographic atom probe (TAP) and field ion
microscopy (FIM). The investigated layers were prepared by sputter deposition
on W-substrates. These substrates have the shape of tips with a
radius of curvature of up to 60nm. Using a Kaufmann Ar-ionsource and
a deposition rate of 0.4 ˚A, we obtain a nanocrystalline CuBi-layer. FIM
analyses confirm the nanocrystalline structure of the deposited layers.
TAP analyses show an increased concentration of Bi. This value is about
two orders of magnitude higher than the solubility of Bi in Cu which
amounts up to 100ppm at 577K. A strong segregation at grain boundaries
is expected to occur while annealing. These supersaturated CuBi
alloys are therefore ideal model systems for the investigation of the microstructural
development.
M 24.3 Do 10:45 H16
Thermal reaction and stability of GMR Cu/NiFe thin films —
•Constantin Buzau Ene 1 , Guido Schmitz 2 , and Reiner Kirchheim
1 — 1 Tammann-Str. 1, D-37077 Göttingen — 2 Wilhelm-Klemm-Str.
10, D-48149 Münster
In recent years reading heads based on the giant magnetoresistance effect
(GMR) made possible a dramatic increase in magnetic recording density.
However, for many potential applications the thermal stability of the
magnetic multilayers are an important issue. In our study Cu/Ni79Fe21
(permalloy) multilayer stacks were deposited onto needle-shaped W tips
by ion beam sputtering and analyzed by atom probe tomography after
appropriate heat treatments. This analysis technique has been proven
to yield a real three-dimensional quantitative chemical and structural
analysis at a subnanometer scale.
After annealing at 250 ◦ C for 30min, no significant structural or chemical
transformation of the initial layer system is detected, although such a
heat treatment reduces the magnetoresistivity already appreciably. Clear
grain boundary wetting is observed after annealing at 400 ◦ C for 30min.
Further annealing at 500 ◦ C for 20min and 40min still preserves the layered
structure with a homogeneous solution of Ni inside the Cu layers of
up to 25 at.% Ni.
M 24.4 Do 11:00 H16
Strukturelle und magnetische Eigenschaften von Nd60Fe30Al10:
massive Proben, Splat-cooled und dünne Schichten — •A. Bracchi
1 , K. Samwer 1 , T. Niermann 2 , M. Seibt 2 und S. Schneider 2
— 1 I. Physikalisches Institut, Universität Göttingen, Tammannstr. 1, D-
37077 Göttingen — 2 IV. Physikalisches Institut, Universität Göttingen,
Tammannstr. 1, D-37077 Göttingen
Dünne Schichten, schnell abgekühlte Folien und massive Proben
der Zusammensetzung Nd60Fe30Al10 wurden mit unterschiedlichen
Präparationsmethoden hergestellt, wobei Abkühlraten zwischen 10 K/s
und 10 10 K/s erreicht wurden. Strukturelle und magnetische Eigenschaften
wurden mittels Hochenergie-Weitwinkel-Röntgen-Diffraktometrie,
Kleinwinkelneutronenstreuung (SANS), hochauflösender Elektronenmikroskopie
(HRTEM) und SQUID Magnetometer Messungen
untersucht. Die SANS Untersuchungen wurden mit und ohne Magnetfeld
durchgeführt, um den Kern-Beitrag von der magnetischen
Streuung zu trennen. Die Mikrostruktur zeigt ein fraktales Verhalten
mit Massen-Fraktaldimension zwischen 2.3 und 2.5, was auf eine
Phasenseparation in der unterkühlten Schmelze zurückgeführt werden
kann. Die Wechselwirkung von domain-wall-pinning Prozessen und
magnetischer Kopplung zwischen zwei unterschiedlichen magnetischen
Phasen wird diskutiert und die Abhängigkeit der Curietemperatur von
der Abkühlrate wird berücksichtigt, um das magnetische Verhalten der
massiven Proben und der Nd60Fe30Al10 Schichten zu erklären.
Gefördert von der DFG in Rahmen des SFB 602 (TP A5) und vom
Land Niedersachsen durch das “Georg Lichtenberg Programm”.

Metallphysik Donnerstag
M 25 Mechanische Eigenschaften III
Zeit: Donnerstag 10:15–11:15 Raum: H4
M 25.1 Do 10:15 H4
Modelling modulus mismatch strengthening for dislocation dynamics
simulations — •Volker Mohles — Institut für Materialphysik,
Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster
Modulus mismatch strengthening is investigated by simulating the
glide of dislocations through obstacle fields and determining the critical
resolved shear stress. For the interaction between dislocations and
the modulus mismatched particles a heuristic stress function is assumed.
This is necessary because a an accurate treatment is not known; moreover
the computational effort for such a treatment would be too high at
present. The heuristic stress function accounts for the interaction’s essential
properties, like symmetry operations and the dependence on the
magnitude of the Burgers vector. The coefficients of this function are
to be adjusted to atomistic simulations (Embedded Atom Method, e.g.
Nedelcu et al., Osetsky et al.).
M 25.2 Do 10:30 H4
Computer Simulations of carbon and vacancy related anelasticity
in Fe-Al. — Mikhail S. Blanter 1 , •Igor S. Golovin 2 , and
Hans-Rainer Sinning 2 — 1 Moscow State Academy of Instrumental
Engineering and Information Science, Moscow, Russia — 2 TU Braunschweig,
Institut fuer Werkstoffe, Langer Kamp 8, D-38106 Braunschweig
Special attention is paid in this research to the interpretation of the
S and X peaks (see previous abstracts) in Fe-Al alloys. Peculiarities of
carbon diffusion in Fe-Al alloys were studied as a function of interatomic
C-Fe, C-Al, C-C, and C-vacancy interactions. Parameters of carbon mobility
in solid solution were evaluated using temperature-dependent internal
friction measurements (the S and the X relaxation). The ordering of
Al atoms enhances C diffusion in the Fe-Al solid solution, while a high vacancy
concentration and carbon-vacancy interaction lead to a new relaxation
effect with higher activation energy (so-called the X peak). Parameters
of the carbon-vacancy interatomic interaction in D03 ordered Fe-Al
alloys and correspondingly parameters of the X peak depend on positions
which are occupied by vacancies. The employed atom-interaction model
is based on the long-range strain-induced (’elastic’) interaction supplemented
by a short-range ’chemical’ interaction. The model assumes that
the interactions of dissolved atoms affect both the distribution (shortrange
order) and energies of carbon atoms and consequently the activation
energy of their diffusion.
M 25.3 Do 10:45 H4
Mechanical Spectroscopy of Fe-(0-40at.%)Al alloys. — •Igor S.
Golovin 1 , Alexander Strahl 2 , Svetlana B. Golovina 2 , Tatjana
Pavlova 3 , and Hartmut Neuhäuser 2 — 1 TU Braunschweig,
Institut fuer Werkstoffe, Langer Kamp 8, D-38106 Braunschweig — 2 TU
Braunschweig, Institut für Metallphysik u. Nukleare Festkörperphysik,
Mendelssohnstr. 3, D-38106 Braunschweig — 3 Physics of Metals Department
of Tula State University, Tula, Russia
M 26 Nanoskalige Materialien IV
Iron-Aluminium alloys in ordered and quasi disordered states have
been investigated after various thermal (quenching, annealing) and mechanical
(cold work) treatments to find out the origin of a few internal
friction peaks observed. As main instrumentation the vibrating-reed
technique with simple beam and an tuning-fork shaped specimen and
inverted torsion pendulum were used. The aluminium concentration was
varied from 6 up to 40 at.%. The temperature and amplitude dependence
of damping and of Young’s modulus has been measured, during
heating / cooling cycles between 80 and 920K. Various damping peaks
including the Snoek-type peak (S peak), X peak, Zener (Z) peak and a
low temperature dislocation-related (D) peak have been systematically
studied with respect to alloy composition and ordering. The mechanisms
of these peaks are discussed. Additional alloying by Cr, Ti, Nb (less than
2%) was used to distinguish between carbon and vacancy contribution
to internal friction.
M 25.4 Do 11:00 H4
Mechanical Spectroscopy of Fe-Al-Cr, Fe-Al-Si, Fe-Al-Co
alloys. — •Alexander Strahl 1 , Igor S. Golovin 2 , Tatjana
Pavlova 3 , Heiko Bremers 1 , Christa Grusewski 2 , and Hartmut
Neuhäuser 1 — 1 TU Braunschweig, Institut für Metallphysik u.
Nukleare Festkörperphysik, Mendelssohnstr. 3, D-38106 Braunschweig
— 2 TU Braunschweig, Institut fuer Werkstoffe, Langer Kamp 8,
D-38106 Braunschweig — 3 Physics of Metals Department of Tula State
University, Tula, Russia
Our investigation of internal friction in binary Fe-Al alloys (see previous
abstracts) has been extended to ternary Fe-Al-Cr, Fe-Al-Si, and
Fe-Al-Co alloys with a fixed content of substitute atoms in iron: [Fe-
(Al,Cr)30, Fe-(Al,Si)25, Fe-(Al,Co)25 at.%]. The idea of studying internal
friction in these compositions is based on the opportunity to vary the
degree of order in the alloys and the formation of carbides: Si improves
D03 order in Fe-Al, Co increases the tendency to the B2 order into Fe-
Al, and substitution of Al by Cr decreases the order in Fe-Al and also
forms the chromium carbides. The structure of the alloys was carefully
examined using X-ray and TEM, the order-disorder transition intervals
by DSC measurements. Temperature and amplitude dependent internal
friction effects were studied in Hz and kHz ranges of resonance frequency
with a heating rate of 1K/min (the same heating rate was used in DSC
measurements).
Zeit: Donnerstag 11:45–12:45 Raum: H16
M 26.1 Do 11:45 H16
Synthesis and Copper Intercalation Studies of Nanostructured
Transition Metal Sulphides — •H. A. Therese, F. Rocker, E. W.
Finckh, J. Li, A. Gloskovskij, G. H. Fecher, G. Schönhense,
U. Kolb, and W. Tremel — Johannes Gutenberg - Universität, 55099
Mainz
Research on nanostructure materials has grown exponentially during
the last decade due to their interesting properties exhibited by quantum
confinement of electrons. In particular, the ability of layered materials to
curl up into nanotubes has drawn the attention of many scientists which
in turn opened up a new era in nanotechnology. Further, layered transition
metal chalcogenides have potential applications as cathode materials
for rechargeable high-energy density lithium batteries, as catalysts for hydrosulfurisation
or as lubricants. The main goal of our research is to synthesise
nanostructured transition metal sulphides and studying their behaviour
if intercalated by copper. Nanostructured MoS2 (amorphous) was
prepared by thermal decomposition of (NH4)2Mo3S13 x H2O at 720K in
sealed tubes and nanotubes of MoS2 were prepared by coating technique
using SiO2 tubes as template. Intercalation of Cu into MoS2 was carried
out by computer-controlled galvanostatic cathodic reduction of MoS2
with a three electrode arrangement. The samples were characterised by Xray
diffraction (XRD), High resolution transmission electron microscopic
(HRTEM) and X-ray absorption spectroscopic (XANES) techniques.
M 26.2 Do 12:00 H16
Agglomerationsverhalten von SiO2- und Al2O3-Nanopulvern in
wässrigen Lösungen verschiedener Ionenkonzentration zur Herstellung
von Nickeldispersionswerkstoffen — •Gabriele Vidrich,
Jean-Frederic Castagnet und Hans Ferkel — Institut für
Werkstoffkunde und Werkstofftechnik, TU Clausthal, Agricolastraße 6,
38678 Clausthal-Zellerfeld
Im Rahmen der Koabscheidung von keramischen Nanopulvern und Metallen
aus galvanischen Bädern ist das Dispersions- und Agglomerationsverhalten
der Partikel im Elektrolyten von wesentlicher Bedeutung, da

Metallphysik Donnerstag
dies einen großen Einfluss auf die Homogenität der Nanopartikelverteilung
in der entstehenden Metallschicht hat.
Es wurden Partikelgrößenverteilungen mittels Photokorrelations-
Spektroskopie sowie Zetapotentiale der in Wasser dispergierten Nanoteilchen
bei verschiedenen pH-Werten, Pulverkonzentrationen und Elektrolytkonzentrationen
bestimmt. Wie zu erwarten, war ein deutlicher Einfluss
des pH-Wertes auf die Partikelagglomeration erkennbar, die vor allem
im Bereich des Isoelektrischen Punktes (IEP) stark ausgeprägt ist.
Durch Steigerung der Ionenkonzentration konnte der IEP zu höheren
pH-Werten verschoben werden. Die erhöhte Ionenkonzentration führte
deutlich weniger als erwartet zu einer Kompression der elektrolytischen
Doppelschicht der Partikel, was sich unmittelbar auf das Zetapotential
und damit auch auf das Agglomerationsverhalten der Partikel auswirkt.
M 26.3 Do 12:15 H16
Bestimmung der Flächenspannung nanokristallinen Ceroxids —
•Stefan Monz, Andreas Tschöpe und Rainer Birringer — FR
7.3 Technische Physik, Universität des Saarlandes, Geb. 43B, D-66123
Saarbrücken
Basierend auf der verallgemeinerten Kapillargleichung von Weissmüller
und Cahn wurde anhand der Kristallitgrößenabhängigkeit der Gitterkonstanten
die mittlere Flächenspannung von nanokristallinem Ceroxid
zu 5,8 N/m bestimmt. Um den Einfluss der Grenzflächenchemie auf
die Flächenspannung zu studieren, wurden nanoskalige Pulverproben
durch in situ Röntgenbeugung in einer Gasatmosphäre mit kontrolliert
eingestelltem Sauerstoffpartialdruck vermessen. Durch ergänzende
M 27 Mechanische Eigenschaften IV
Sauerstoffbeladungsmessungen konnte der Zusammenhang zwischen
Flächenspannung und Sauerstoffdefizit der Ceroxidoberfläche charakterisiert
werden.
M 26.4 Do 12:30 H16
Der Einfluss von Korngrenzen auf die ionische Gesamtleitfähigkeit
polykristalliner Sauerstoffionenleiter — •Sasa
Kilassonia, Andreas Tschöpe und Reiner Birringer — FR. 7.3.
Technische Physik, Universität des Saarlandes, 66041 Saarbrücken
Die ionische Gesamtleitfähigkeit eines polykristallinen Sauerstoffionenleiters
ist im Vergleich zu Einkristallen gleicher Zusammensetzung erheblich
verringert. Um die Ursache dieses Korngrenzeneffektes zu erforschen,
wurden Probenserien aus mikrokristallinem Gd-, La- und Y-dotiertem
Ceroxid mit unterschiedlichen Akzeptorkonzentrationen hergestellt und
die Volumen- sowie die Gesamtleitfähigkeit mittels Impedanzspektroskopie
untersucht. Die verschiedenen Akzeptorionen zeigten einen qualitativ
ähnlichen Einfluss auf die ionische Leitfähigkeit. Die Volumenleitfähigkeit
der Kristallite stieg mit zunehmender Konzentration zunächst an, erreicht
bei etwa 15 Mol-% ein Maximum und nimmt danach wieder ab.
Der beobachtete Verlauf wurde im Hinblick auf Assoziatbildung analysiert.
Die Gesamtleitfähigkeit war wegen des zusätzlichen Korngrenzenwiderstandes
reduziert, wobei dieser Effekt bei geringen Akzeptorkonzentrationen
(< 3%) bis zu 3 Größenordnungen betrug und bei hohen
Konzentration vernachlässigbar klein wurde. Als Ursache für diesen
Korngrenzeneffekt werden Raumladungszonen entlang der Korngrenzen
diskutiert.
Zeit: Donnerstag 11:45–12:45 Raum: H4
M 27.1 Do 11:45 H4
Dynamic Recrystallization in Steady-State Regime —
•Matthias Frommert and Günter Gottstein — Institut für
Metallkunde und Metallphysik, RWTH Aachen, D-52056 Aachen
The typical flow curve of a material which undergoes dynamic recrystallization
can be either described by a single-peak or a multiple-peak
behaviour followed by a steady-state stress level at higher strains. Investigations
on a large variety of materials have shown that the dynamically
recrystallized grain size does not change in the steady-state regime and
can be correlated to the steady-state flow stress. In the current study
compression tests were performed with an austenitic steel Alloy 800H
at constant and transient strain rates in order to investigate the physical
mechanisms of steady-state dynamic recrystallization. Microstructure
and microtexture were studied by optical microscopy and SEM. When the
true strain rate is changed at a defined strain during experiment the dynamically
recrystallized grain size readjusts within a short strain interval
according to the resulting change of steady-state flow stress. The macrotexture
was measured using X-ray diffraction; the inverse pole-figures
show that during the early stages of high temperature deformation a
typical deformation texture evolves which is randomized by the onset of
dynamic recrystallization.
M 27.2 Do 12:00 H4
Microstructure and Texture Development during Recrystallization
of Rolled Molybdenum Sheets — •Carl-Georg Oertel 1 ,
Ingwar Hünsche 1 , Werner Skrotzki 1 , and Wolfram Knabl 2
— 1 Dresden University of Technology, Institute of Structural Physics,
D-01062 Dresden, Germany — 2 PLANSEE Aktiengesellschaft, Technologiezentrum,
A-6600 Reutte/Tyrol, Austria
Recrystallization is an important tool to adjust the grain size and texture
of polycrystalline materials in order to optimise their properties. In
the present work the recrystallization kinetics and the development of
texture has been studied on rolled molybdenum sheets as a function of
temperature and time. The microstructure was investigated by orientation
contrast in a scanning electron microscope. The kinetics of recrystallization
displayed in a JMAK plot yields Avrami coefficients decreasing
with temperature from 2.5 to 1.1. The activation energy amounts to 4.4
eV, which agrees well with the coefficient of self-diffusion. The textures
of the sheet surface and centre layer were measured by X-ray diffraction.
The rolling texture in the centre of the sheets is characterised by
a strong α-fibre with the rotating cube component {100} domi-
nating. Besides that, there exists a weak γ-fibre. In contrast, the surface
layer is characterised by a weak cube component. During recrystallization
changes in texture are insignificant. With long annealing times all texture
components tend to degrade. The investigations are intended to control
the structure parameters in the rolling process in order to optimise the
deep-drawing properties of molybdenum sheets.
M 27.3 Do 12:15 H4
Mechanical properties of ECAP–deformed copper —
•Aikaterini Zi 1 , Ralph J. Hellmig 1 , Min Hong Seo 2 , Hyoung
Seop Kim 2 und Juri Estrin 1 — 1 Institut für Werkstoffkunde und
Werkstofftechnik, TU Clausthal, Agricolastr. 6, 38678 Clausthal-
Zellerfeld — 2 Department of Metallurgical Engineering, Chungnam
National University, Daejeon, Korea
Ultrafine grained copper was produced using ECAP (equal channel
angular pressing) following the well known processing Route C up to 8
passes. Using transmission electron microscopy a cell structure having a
medium cell size of 200 nm having a log–normal size distribution was observed.
The deformed copper shows a strong increase in tensile strength
accompanied by a loss in ductility directly after pressing. To investigate
the homogeneity of ECAP processed specimens, Vickers hardness maps
with a small imprint spacing were determined. They reflect the strain
inhomogeneity inside the specimens due to die geometry and strain hardening.
After several ECAP passes a more homogeneous hardness distribution
was observed.
M 27.4 Do 12:30 H4
Mechanical properties and microstructure of ECAP–deformed
AZ31 — •Mikhail V. Popov, Markus G. Krieger, Miloˇs Janeček,
Ralph J. Hellmig und Juri Estrin — Institut für Werkstoffkunde
und Werkstofftechnik, TU Clausthal, Agricolastr. 6, 38678
Clausthal-Zellerfeld
A squeeze cast AZ31 magnesium alloy was deformed using ECAP
(equal channel angular pressing). Compression tests on AZ31 specimens
that did not undergo ECAP were used to optimize the pressing conditions.
The microstructure of the ECAP–deformed material was determined
using transmission electron microscopy. For example, after a single ECAP
pass at 240 ◦ C a partially recrystallized structure containing grains with
an average size of about 1 µm was observed. Mechanical properties as
determined using uniaxial compression tests and Vickers hardness investigations
were correlated with the strain accumulated.

Metallphysik Donnerstag
M 28 Hauptvortrag Jörg Bilgram
Zeit: Donnerstag 14:00–14:30 Raum: H16
Hauptvortrag M 28.1 Do 14:00 H16
Noble gases as model systems to study solidification behaviour
of metals — •J.H. Bilgram — Laboratorium für Festkörperphysik,
ETH, CH 8093 Zürich (Switzerland)
Rare gases have low melting entropy and form a ”simple liquid” similar
to metals and can therefore be used as model substances to simulate
transparent metals. In these systems the solidification process can be
M 29 Quasikristalle I
studied in situ. Two new features have been introduced into the study of
solidification by model experiments: 1.) the study of various morphologies
and morphological transitions, and 2.) the possibility to reconstruct
the shapes of transparent 3D objects. Morphology changes seem to lead
to an explanation of grain refinement in metals. The determination of the
3D shape of objects formed during freezing provides for the first time the
possibility to determine 3D shape parameters necessary to apply theories
in casting processes.
Zeit: Donnerstag 14:45–16:00 Raum: H16
M 29.1 Do 14:45 H16
Force-Matched EAM Potentials for Decagonal AlNiCo —
•Peter Brommer and Franz Gähler — Universität Stuttgart,
Institut für Theoretische und Angewandte Physik, 70550 Stuttgart
Aluminum mobility in decagonal AlNiCo displays interesting peculiarities.
At 80 % of the melting temperature some aluminum atoms
can move around the quasicrystal, while others remain firmly locked in
place. Molecular dynamics simulations can offer insights into the dynamics
of this system. Ideally one would use ab-initio methods to evaluate
the many-body quantum mechanical equations, but those methods are
limited to a few hundred atoms. On the other hand, the application
of effective potentials allows much larger systems. Then the problem is
to find suitable potentials, which are not available for complex systems
like quasicrystals. Force Matching is a way to derive effective potentials
from quantum-mechanical input data, thereby combining the advantages
of the two methods. The idea is that a potential that reproduces the
forces correctly also yields the correct dynamics. The application of this
method to the decagonal AlNiCo quasicrystalline phase is described and
test simulations with the derived potentials will be presented.
M 29.2 Do 15:00 H16
Phason-elastische Energie eines Modellquasikristalls — •Ulrich
Koschella, Franz Gähler, Johannes Roth und Hans-Rainer
Trebin — Universität Stuttgart, Institut für Theoretische und Angewandte
Physik, Pfaffenwaldring 57/VI, 70550 Stuttgart
Wir betrachten die phason-elastische Energie eines zweidimensionalen
binären Modellquasikristalls mit Paarwechselwirkungen bei Temperatur
null. Indem wir die Häufigkeiten der auftretenden atomaren
Abstände über die zugehörigen Akzeptanzbereiche berechnen, können wir
die phason-elastische Energie als Funktion der phasonischen Verzerrung
bestimmen, parametrisiert durch die Paarpotentialwerte an den auftretenden
Abständen.
Bis zu einem relativ großen Abschneideradius ist die phason-elastische
Energie eine quadratische Form in der phasonischen Verzerrung, wie von
der erweiterten linearen Elastizitätstheorie beschrieben. Durch Analyse
der phason-elastischen Konstanten können Aussagen über die Gestalt der
Potentiale gemacht werden, die den Quasikristall stabilisieren.
Erst bei sehr großen Wechselwirkungsradien kommen nicht-analytische
Terme in der phason-elastischen Energie ins Spiel, wie sie von der locked
state Theorie vorausgesagt werden [1]. Es wird diskutiert, inwieweit damit
ein atomares Modell mit locked state Verhalten verwirklicht werden
kann.
[1] H.-C. Yeong und P. J. Steinhardt, Phys. Rev. B 48 (1993) 9394.
M 29.3 Do 15:15 H16
Spectral Properties and Anomalous Diffusion in Octonacci Quasicrystals
— •Viktor Cerovski 1 , Uwe Grimm 2 , and Michael
Schreiber 1 — 1 Institute für Physik, Technische Universität, D-09107
— 2 The Open University, Applied Mathematics Dept., Milton Keynes,
MK7 6AA, UK
Properties of the spectrum and characteristics of the eigenstates as well
as the anomalous diffusion in octonacci quasicrystals in d = 1, 2, and 3
dimensions are studied using large-scale numerical calculations of the return
probability C(t) and the spreading of the wavepacket d(t) for various
values of the hopping strength v. In all dimensions we find C(t) ∼ t −δ ,
with δ < 1 in d = 1 and a crossover from δ < 1 to δ = 1 when v is varied
in d = 2, 3, which is related to the change of spectrum from singular
continuous to absolute continuous. The obtained scaling d(t) ∼ t −β with
0 < β(v) < 1 corresponds to the anomalous diffusion, and the values of
the exponent suggest that β is dimensionally independent. We show a
numerical experiment illustrating some unusual features of the anomalous
diffusion of a particle in quasiperiodic systems, such as spreading of
the wave packet via a hierarchical sequence of stages in which the packet
almost remains localized, as well as the system sensitivity to the position
at which a single impurity is added.
M 29.4 Do 15:30 H16
Crack propagation in icosahedral quasicrystals — •Frohmut
Rösch 1 , Christoph Rudhart 1 , Peter Gumbsch 2,3 , and Hans-
Rainer Trebin 1 — 1 Universität Stuttgart, Institut für Theoretische
und Angewandte Physik, 70550 Stuttgart — 2 Universität Karlsruhe, Institut
für die Zuverlässigkeit von Bauteilen und Systemen, 76131 Karlsruhe
— 3 Fraunhofer Institut für Werkstoffmechanik, 79194 Freiburg
We present numerical experiments on the propagation of mode I cracks
in a three dimensional icosahedral model quasicrystal. In particular, the
dependence on the plane structure and the influence of clusters have
been investigated. For this purpose samples in different orientations are
endowed with atomically sharp seed cracks and subsequently loaded by
linear scaling of the displacement field. The response of the system is
then monitored by molecular dynamics simulations.
Brittle fracture without any crack tip plasticity is observed. The fracture
surfaces turn out to be rough on the scale of the clusters. These
are not strictly avoided, but to some extent intersected by the dynamic
crack. However, compared to the flat seed cracks the clusters are cut less
often. Hence the roughness of the crack surfaces can be attributed to
the clusters, whereas the constant average heights of the fracture surfaces
reflect the plane structure of the quasicrystal. Moreover a distinct
anisotropy with respect to the in-plane propagation direction is found.
M 29.5 Do 15:45 H16
Diffusion in ikosaedrischen und dekagonalen Quasikristallen
und einem Approximanten — •Robert Galler 1 , Stefan
Flege 2 und Helmut Mehrer 1 — 1 Institut für Materialphysik,
Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Straße 10,
48149 Münster — 2 TU Darmstadt, FB Material- und Geowissenschaften,
FG Chemische Analytik, Petersenstraße 23, 64287 Darmstadt
Unsere Untersuchungen zur Diffusion von 65 Zn in ikosaedrischen
ZnMgY Quasikristallen und einem hexagonalen ZnMgY Approximanten
wurden mit der Radiotracermethode durchgeführt. Die Profilanalyse
erfolgte durch Präzisionsschleifen bzw. Sputtern bei kurzer Eindringtiefe.
Die Ergebnisse werden mit früheren Messungen in I-ZnMgHo sowie mit
Literaturdaten zur Zn-Selbstdiffusion diskutiert.
Zudem wurde die Diffusion von Ga in einkristallinen dekagonalen Quasikristallen
mit der Tracermethode untersucht. Die Eindringprofile der
Isotope 69 Ga und 71 Ga wurden mittels SIMS analysiert. Wir diskutieren
die Ergebnisse zusammen mit früheren Experimenten zur Selbstdiffusion
von Co und Ni in D-AlNiCo und MD-Simulationen von Gähler und
Hocker zur Selbstdiffusion von Al in D-AlNiCo.

Metallphysik Donnerstag
M 30 Mechanische Eigenschaften V
Zeit: Donnerstag 14:45–16:00 Raum: H4
M 30.1 Do 14:45 H4
Plastizität von Strontiumtitanateinkristallen unterhalb 320
K — •Dieter Brunner, Ilsemarie Lakemeyer und Manfred
Rühle — Max-Planck-Institut für Metallforschung, Heisenbergstr.3,
70569 Stuttgart
Erstmals wurde die plastische Verformbarkeit von Einkristallen der
Elektrokeramik Strontiumtitanat in dynamischen Druckversuchen bei
Temperaturen unterhalb 320 K detailliert untersucht. Die Druckachse
der Proben lag in < 001 > Richtung, die Dehnrate betrug 2.2x10 −4 s −1 .
Plastische Verformbarkeit war möglich bis etwa 45 K, darunter brachen
die Proben spröde. Die Verformbarkeit bei höheren Temperaturen (> 120
K) wird meist mit zunehmender plastischer Dehnung durch Rissbildung
innerhalb der Proben beendet. Zwischen 320 K und 250 K nimmt die aus
Spannungs-Dehnungskurven bestimmte kritische Fliessspannung (KFS)
nur unwesentlich zu. Unterhalb 250 K steigt die KFS dann stark an von
120 MPa bis auf etwa 350 MPa bei 45 K. Doch diese Zunahme erfolgt
nicht monoton sondern ist durch Bereiche unterschiedlich starker Temperaturabhängigkeit
der KFS geprägt. Nach einer zunächst parabolischen
Zunahme zwischen ≈250 K und ≈200 K, erfolgt ein abrupter Übergang
zu einem deutlich geringeren Anstieg der KFS mit sinkender Temperatur,
bis bei unterhalb etwa 100 K erneut starke Zunahme erfolgt. Diese
Phänomene erinnern deutlich an die starke und nicht monotone Temperaturabhängigkeit
der KFS kubisch raumzentierter Metalle. Es wird ein
erster Versuch vorgestellt, die Ergebnisse im Rahmen der Theorie thermisch
aktivierter Kinkpaarbildung in Versetzungen (Kinkpaarbildungstheorie)
zu interpretieren.
M 30.2 Do 15:00 H4
[010]-Versetzungen in der komplexen intermetallischen Phase
ξ’-Al-Pd-Mn — •M. Feuerbacher 1 und D. Caillard 2 — 1 Institut
für Festkörperforschung, Forschungszentrum Jülich GmbH, 52425 Jülich,
Germany — 2 CEMES-CNRS, 29 rue Jeanne Marvig, BP4347, F-31055
TOULOUSE Cedex 4, France
In der komplexen intermetallischen Phase ξ’-Al-Pd-Mn kommen
Verformungsmechanismen zum Tragen, die sich in einigen Aspekten
grundsätzlich von denen in einfacheren Metallen unterscheiden.
In diesem Beitrag charakterisieren wir eine Klasse von Versetzungen,
die sich auf (010)-Ebenen der ξ’-Al-Pd-Mn-Struktur bewegen und
ein ungewöhnliches Kontrastverhalten im Transmissionselektronenmikroskop
zeigen. Es wird gezeigt, dass es sich um prismatische [0 1 0]-
Stufenversetzungen handelt, die sich durch einen reinen Kletterprozess
ausbreiten. Die [0 1 0]-Versetzungen spalten in charakteristischer Weise
in vier Partialversetzungen auf. Die Aufspaltung wird im Rahmen eines
Strukturmodells diskutiert und wir argumentieren, dass die gesamte
Burgersvektorlänge und die der Partialversetzungen 16,56 ˚A bzw. 4,14 ˚A
betragen.
M 30.3 Do 15:15 H4
On the influence of obstacles (precipitates/particles) on the
PLC effect in Al-Mg alloys — •Hanno Dierke, Fabian Krawehl,
and Hartmut Neuhäuser — TU Braunschweig, Institut für Metallphysik
und Nukleare Festkörperphysik, Mendelssohnstr. 3, 38106 Braunschweig
Due to their low weight and high mechanical strength AlMg alloys
provide a large variety of applications as material for lightweight construction.
However, the practical benefit is limited due to instabilities
and inhomogeneities caused by correlated movement of dislocations during
plastic deformation (PLC effect). By addition of unshearable obstacles
the formation of dislocation avalanches may be prevented or at least
reduced.
The alloy AA5754 was investigated particularly with regard to the influence
of obstacles on the movement of dislocations. For this purpose on
the one hand in the samples precipitates were produced by heat treatments,
on the other hand metal matrix composites (MMCs) with different
volume fractions of Al2O3 particles were investigated. The experiments
were performed in strain controlled experiments at room temperature and
at strain rates between 1 · 10 −6 and 5 · 10 −3 s −1 . In addition some samples
were investigated by TEM to find correlations between deformation
behaviour and microstructure.
M 30.4 Do 15:30 H4
Propagation modes of Lüders and PLC bands in Cu-Al and
Al-Mg during strain-rate and stress-rate controlled tensile
deformation. — •Frank Klose 1 , Felix Hagemann 1 , Verena
Grützun 1 , Peter Hähner 2 , and Hartmut Neuhäuser 1 — 1 TU
Braunschweig, Institut für Metallphysik u. Nukleare Festkörperphysik,
Mendelssohnstr. 3, 38106 Braunschweig — 2 Institute for Energy, Joint
Research Centre of the European Commission, PO Box 2, NL-1755 ZG
Petten, Netherlands
Propagating plastic instabilities, like Lüders bands and Portevin-
LeChâtelier (PLC) bands are investigated by means of laser scanning
extensometry during tensile tests with different deformation modes (constant
strain-rate and constant stress-rate).
This extensometry technique permits to investigate the kinetics of local
strain within up to 44 zones (1 mm width) at a sampling rate of 50 Hz.
Therefore, the band velocities and band widths, as well as the strain concentrations,
characterizing the specific mode of band propagation, can be
determined in relation to the type and quality of the deformation mode.
Cu-15at.%Al and Al-3at.%Mg polycrystals have been investigated experimentally
at various temperatures and strain rates. The findings are
compared with recent results of numerical simulations [1,2], focusing on
fundamental differences observed with the above mentioned types of deformation
mode.
[1] E. Rizzi et al., Acta Mater. 51(2003)3385
[2] P. Hähner et al., PRB 65(2002)134109
M 30.5 Do 15:45 H4
Metaversetzungen und Metaversetzungsnetzwerke in der komplexen
intermetallischen phase ξ’-Al-Pd-Mn — •M. Heggen, M.
Feuerbacher und K. Urban — Institut für Festkörperforschung, Forschungszentrum
Jülich GmbH, 52425 Jülich
Komplexe intermetallische Phasen zeichnen sich aus durch eine hohe
Zahl von Atomen je Einheitszelle und große Gitterparameter. Die strukturellen
Defekte und die Mechanismen der plastischen Verformung dieser
Materialklasse sind derzeit noch weitgehend unbekannt. In den vergangenen
Jahren wurden bei Untersuchungen der komplexen intermetallischen
Phase ξ’-Al-Pd-Mn bereits mehrere neuartigen Mechanismen der plastischen
Verformung nachgewiesen. Besonders hervorzuheben ist hierbei
ein Defekttyp, welcher als Metaversetzung bezeichnet wird (H. Klein et
al., Phys. Rev. Lett. 82, 3468,1999). Metaversetzungen sind Partialversetzungen,
deren Burgersvektorlängen in einem irrationalen Verhältnis
zum Gitterparameter stehen, die sich jedoch aufgrund ihrer speziellen
Struktur durch das Material bewegen können, ohne dass Stapelfehler eingebracht
werden. Metaversetzungen können Netzwerke bilden, die insgesamt
vollständige Versetzungen in der ξ’-Al-Pd-Mn-Struktur darstellen.
Obwohl der Betrag des Burgersvektors des gesamten Netzwerks groß ist
(z.B. 12.56 ˚A), ist die elastische Energie durch die lokale Verteilung der
Verzerrung auf mehrere Metaversetzungen gering.

Metallphysik Donnerstag
M 31 Quasikristalle II
Zeit: Donnerstag 16:30–18:00 Raum: H16
M 31.1 Do 16:30 H16
Decagonal quasicrystals in the Al-Pd-Re alloy system —
•Sergiy Balanetskyy 1,2 and Benjamin Grushko 1 — 1 IFF,
Forschungszentrum Juelich, D-52425 Juelich — 2 I.N. Frantsevich
Institute for Problems of Materials Science, 03680 Kiev 142, Ukraine
The Al-Pd-Re alloy system is known to contain a stable icosahedral
phase similarly to that in Al-Pd-Mn (Mn and Re belong to the same
column in the periodic table). Apart from this, Al-Pd-Mn contains a
decagonal phase with about 1.2 nm periodicity in the specific direction.
Extensive investigation of the Al-rich part of the Al-Pd-Re phase diagram
revealed the formation of a decagonal phase also in this alloy system. In
contrast to that in Al-Pd-Mn the Al-Pd-Re decagonal phase has about
2.4 nm periodicity. Preliminary investigation of this phase and its formation
conditions will be reported.
M 31.2 Do 16:45 H16
Formation and stability of the Al-Cu-Ru icosahedral phase —
•Benjamin Grushko and Shaobo Mi — IFF, Forschungszentrum
Juelich, D-52425 Juelich
The Al-Cu-Ru icosahedral (I) phase is formed in a wide compositional
range elongated between about Al61Cu26Ru13 and Al70.5Cu12.5Ru17.
The powder X-ray diffractograms only revealed some variation in the
intensities of the lines as a function of the composition but no their apparent
shift. The I-phase is formed by a peritectic reaction at 1057 C,
its stability was confirmed down to 600 C. At lower temperatures the
equilibration of the relevant samples is difficult. Extrapolated towards
lower Cu the I-region clearly reaches the binary composition of about
Al78-80Ru20-22. At close compositions a similar I-phase has also be reported
to form in rapidly solidified alloys. The elongated geometry of
the stability region is consistent with a suggestion that the ternary Al-
Cu-Ru I-phase is a solid solution of Cu in a metastable binary Al-Ru
I-phase. The shape of the I-region corresponds to an approximately constant
electron-to-atom ratio.
M 31.3 Do 17:00 H16
Influence of Al and Zr on quasicrystalline phase formation in Zr-
Ti-Nb-Cu-Ni-Al metallic glasses — •Sergio Scudino 1 , Jürgen
Eckert 2 , Uta Kühn 1 , Hergen Breitzke 3 , Klaus Lüders 3 und
Ludwig Schultz 1 — 1 IFW Dresden, Institut für Metallische Werkstoffe,
Postfach 270016, D-01171 Dresden, Germany — 2 Fachbereich
Material- und Geowissenschaften, FG Physikalische Metallkunde, Technische
Universität Darmstadt, Petersenstrasse 23, D-64287 Darmstadt,
Germany. — 3 Fachbereich Physik, Freie Universität Berlin, Arnimallee
14, D-14195 Berlin, Germany
The influence of Al and Zr on the crystallization behavior of Zr-Ti-Nb-
Cu-Ni-Al melt-spun glassy ribbons with different Al and Zr content have
been investigated. The devitrification is characterized by the formation of
a quasicrystalline phase even for the alloy without Al, demonstrating that
Al is not essential for quasicrystal formation in the present alloys. With
decreasing Al content, the temperature range of stability of quasicrystals
increases whereas the thermal stability of the amorphous phase decreases
together with a slight decrease of the extension of the supercooled liquid
region. Furthermore, the grain size of the quasicrystalline phase increases
with decreasing Al content. An equivalent effect on both thermal stability
and microstructure can be achieved by increasing Zr content. This
suggests the possibility to use Al and Zr for tuning the thermal stability
as well as the microstructure evolution upon heating. This work was supported
by the German Science Foundation under grants Ec 111/10-1,2
and Lu 217/17-1
M 31.4 Do 17:15 H16
Micro-and nanoindentation studies of single quasicrystalline
phase in Al-Ni-Co system — •Nilay Krishna Mukhopadhyay,
Andre Belger und Peter Paufler — Institut fuer Strukturphysik
TU Dresden, D-01062 Dresden, Germany
Single crystals of Al-Ni-Co decagonal phase have been employed for
the study of mechanical propertied using the micro- and nano- indentation
techniques. Decagonal quasicrystal gives rise to decagonal prismatic
morphology exhibiting 10-fold and 2-fold planes as external facets. The
microindentation, using load from 25g to 150g was performed on 10 fold
and 2-fold planes. Meyers Hardness calculated from these studies was
found to vary from 13.3GPa to 10.6GPa. The variation of hardness with
load, which is known as indentation size effect (ISE), was clearly noticed.
Nanoindentation experiments were carried out using Hysitron Triboscope
attached to scanning probe microscope. From load-penetration
curve nanohardness and elastic modulus were found out and compared
with the data available from other techniques. The discontinuity in the
load-penetration curve, which can be understood as pop-in-effect, characteristic
of yielding, was observed at low load regime. It is interesting to
point out that the pop-in effect is more prominent in case of 10fold plane.
Attempts will be made to discuss the results obtained from the present
investigation in the light of our current understanding of the mechanical
responses of these aperiodic crystals.
M 31.5 Do 17:30 H16
Hydrodynamic excitations of icosahedral quasicrystals —
•Christof Walz and Hans-Rainer Trebin — Universität
Stuttgart, Institut für Theoretische und Angewandte Physik, 70550
Stuttgart
Hydrodynamic variables for quasicrystals are, aside from mass-,
momentum-, energy-density, and phonon displacements, also phason displacements,
at least in certain temperature ranges. Different derivations
of the hydrodynamic equations exist, either on a phenomenological basis
or by Poisson bracket methods, which we have compared and checked.
They were solved numerically for special boundary and initial conditions
to mimic experiments like internal friction. We also derived material
laws of anelasticity from the hydrodynamic equations to model relaxation
mechanisms directly.
M 31.6 Do 17:45 H16
chains of 2 n interpenetrated icosahedra in hexagonal
Zn-Mg-RE (Y, Sm, Gd) phases — •D.W. Deng 1,2 ,
K.H. Kuo 2 , M. Feuerbacher 1 , and K. Urban 1 — 1 Institut für
Festkörperforchung, Forschungszentrum Jülich GmbH, D-52425 Jülich,
Germany — 2 Beijing Laboratory of Electron Microscopy, Institute of
Physics, Chinese Academy of Sciences, PO Box 603, 100080 Beijing, PR
China
The crystal structure of the hexagonal Zn3MgY phase has been determined
by single-crystal X-ray diffraction. The structural model, refined
to a final R value of 0.047, has the composition Zn60.68Mg18.28Y21.04,a
= 9.082(2) ˚A and c = 9.415(5) ˚A and the space group P63/mmc. The
structure of Zn3MgY is characterized by a layer structure consisting of
FP(FP)’ layers stacked along the c axis, where F and P denote flat and
puckered layers, respectively, and (FP)’ is related to FP by a 63 screw.
The Zn3 icosahedra, in the PFP’ layer block are fused into pairs in the
directions. At the same time, the hexagonal Zn3MgY phase is
known to consist of 2 interpenetrated Zn icosahedra along directions.
This can be considered as the fundamental period (n = 1) of a
series of 2n super-periodic icosahedral chains. The hexagonal S, M, and
L or µ3, µ5, and µ7 phases of larger a parameters are found to have superperiodic
chains containing 2n = 4, 6, and 8, respectively, interpenetrated
icosahedra in directions. The estimated periodicity of this series
of super-periodic 2n (n = 2, 3 and 4) interpenetrated icosahedral chain
agrees with most cases of the experimental a parameter of the hexagonal
S, M, and L or µ3, µ5, and µ7 phases.

Metallphysik Donnerstag
M 32 Grenzflächen und Wachstum
Zeit: Donnerstag 16:30–17:30 Raum: H4
M 32.1 Do 16:30 H4
Interface Structure and Segregation Effects of Nanocrystalline
PdZr in Dependence of Temperature — •H. Weigand 1 , W.
Sprengel 1 , T. Wejrzanowski 2 , C. E. Krill 3 , R. Röwer 1 , M.
Kelsch 4 , and H.-E. Schaefer 1 — 1 Inst. f. Theor. u. Angew. Phys.,
Univ. Stuttgart, D-70569 Stuttgart — 2 Faculty of Mat. Science. a. Engin.,
Warsaw Univ. of Techn., 02-507 Warszawa, Poland — 3 Techn. Phys.,
Univ. d. Saarlandes, D-66041 Saarbrücken — 4 MPI f. Metallf., D-70569
Stuttgart
Grain growth of n-PdZr alloys is expected to be reduced by segregation
of Zr in the grain boundaries. Positron annihilation spectroscopy
was employed to study this effect and the temperature dependence of
the interface structure, showing a decrease of the fraction of nanovoids,
the size of 10 to 15 missing atoms, upon isochronal annealing up to 1100
K.
Temperature dependent studies after annealing at 1100 K show a reversible
increase of the mean positron lifetime with temperature due to
a reversible change of the positron trapping behavior at interfacial free
volumes. The variation of the interfacial composition with temperature
is investigated.
M 32.2 Do 16:45 H4
Monte Carlo Simulation and Statistical Theory of Normal Grain
Growth in Two and Three Dimensions — •Dana Zoellner and
Peter Streitenberger — Otto-von-Guericke-Universitaet Magdeburg,
Institut fuer Experimentelle Physik, Abteilung Materialphysik, PF
4120, D-39016 Magdeburg
A modified Monte Carlo algorithm for single-phase normal grain
growth is presented, which allows one to simulate the time development
of the microstructure of very large grain ensembles in two and three dimensions.
The emphasis of the present work lies on the investigation
of the interrelation between the local geometric properties of the grain
network and the grain size distribution function in the quasi-stationary
self-similar growth regime. It is found that the topological size correlations
between neighbouring grains and the resulting average statistical
growth law, both in two and three dimensions, deviate strongly from the
assumptions underlying the classical Lifshitz-Sloyzov-Hillert theory. The
average local geometric properties of the simulated grain structures are
used in a statistical mean-field theory to calculate the grain size distribution
functions analytically. By comparison of the theoretical results
with the simulated grain size distributions it is shown how far normal
grain growth in two and three dimensions can successfully be described
by a mean-field theory and to what extent stochastic fluctuations in the
average growth law must be taken into account.
M 32.3 Do 17:00 H4
Grain Growth under the Influence of Mechanical Stress Fields
— •Myrjam Winning — Institut für Metallkunde und Metallphysik,
RWTH Aachen
The motion of grain boundaries is the key phenomenon of recrystallization
and grain growth and dominates the evolution of texture and
microstructure, i.e the macroscopic physical and mechanical properties
of a material, in particular of a part in service. The reaction of grain boundaries
to mechanical stresses is reviewed. It was found that the motion
of low angle grain boundaries as well as of high angle grain boundaries
can be induced by the imposed external stress. The observed activation
enthalpies allow conclusions on the migration mechanism of the stress induced
grain boundary motion. From these experiments can be seen that
mechanical stress fields can change the dynamical behaviour of grain
boundaries. Therefore in the following the influence of mechanical stresses
on grain growth was studied. The experiments should investigate the
change of the grain growth kinetics as well as the microstructure and
texture evolution in polycrystalline high-purity aluminium under the influence
of different mechanical stress fields. The fact that boundaries can
also be moved by mechanical forces sheds new light on microstructure
evolution during elevated temperature deformation.
M 32.4 Do 17:15 H4
Crossover-Vergröberungsverhalten von AlSn-Legierungen —
•M. Ziehmer 1 , C. E. Krill III 1 , L. Helfen 2 und R. Birringer 1
— 1 FR 7.3 Technische Physik, Universität des Saarlandes, Geb. 43B,
D-66123 Saarbrücken — 2 ESRF, BP 220, F-38043 Grenoble Cedex
Konventionelle AlSn-Legierungen stellen Modellsysteme zum Studium
der Ostwald-Reifung von Al-Kristalliten in einer flüssigen Sn-Matrix dar.
Im Grenzfall hoher Volumenanteile der festen Phase (> 90%) ist a priori
unklar, ob die bekannte Ostwald-Reifungskinetik noch gültig ist. Wir berichten
über erste experimentelle Ergebnisse an solchen Legierungen, die
eine ” Crossover-Kinetik“ zwischen konventioneller Ostwald-Reifung und
normalem Kornwachstum belegen. Diese Befunde implizieren, daß bei
einer weiteren Vergrößerung des festen Phasenanteils, aber endlicher Sn-
Konzentration, eine Vergröberungskinetik nach den Gesetzmäßigkeiten
des normalen Kornwachstums zu erwarten ist. Solche Systeme sind
prädestiniert für Untersuchungen des Echtzeit-Kornwachstums mittels
Röntgentomographie.

Oberflächenphysik Tagesübersichten
Hauptvorträge
OBERFLÄCHENPHYSIK (O)
Prof. Dr. Wolf-Dieter Schneider
Institut de Physique des Nanostructures
Ecole Polytechnique Fédérale de Lausanne (EPFL)
CH-1015 Lausanne, Schweiz
E-Mail: wolf-dieter.schneider@epfl.ch
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsäle H1, H36, H38, H39, H43, H44, H45, Poster Bereich C)
O 1.1 Mo 09:30 (H36) Electron-phonon coupling and spin-orbit splitting in quasi twodimensional
metals: the surfaces of Bi, Philip Hofmann
O 2.1 Mo 10:15 (H36) Tailoring electronic properties of atomic chains assembled in the STM,
Niklas Nilius, Thomas M. Wallis, Wilson Ho
O 7.1 Mo 14:00 (H36) Magnetism of mass-filtered nanoparticles on ferromagnetic supports,
Joachim Bansmann
O 8.1 Mo 14:45 (H36) Spin-polarized scanning tunneling microscopy: From nanomagnetism to
the spin-resolved bandstructure, M. Bode, K. von Bergmann, A. Kubetzka, O.
Pietzsch, R. Wiesendanger, M. Heide, S. Blügel
O 15.1 Di 09:30 (H36) Electron Spectroscopy of Many-Body Interaction using Scanning Tunneling
Microscopy, M. Alexander Schneider, Lucia Vitali, Peter Wahl, Lars
Diekhöner, Gero Wittich, Michael Vogelgesang, Klaus Kern
O 16.1 Di 10:15 (H36) Electronic Interactions and Phase Transitions at Surfaces and in Low
Dimensions, Jörg Schäfer
O 21.1 Di 14:00 (H36) Manipulation of large molecules by low temperature STM: model systems
for molecular electronics, Francesca Moresco
O 22.1 Di 14:45 (H36) Electronic structure and morphology of supported clusters as observed
by photoemission and STM/STS, Heinz Hövel
O 27.1 Mi 15:15 (H1) Stress on the atomic scale: From surface reconstruction to stress oscillations
and magnetostriction of atomic layers, Dirk Sander
O 29.1 Do 09:30 (H36) Beyond the (p=0 Pa, T=0 K) limit: Surface Phase Diagrams and Growth
Kinetics from First Principles, Rossitza Pentcheva
O 30.1 Do 10:15 (H36) Surface chemistry studied by in-situ x-ray photoelectron spectroscopy,
Reinhard Denecke
O 35.1 Do 14:00 (H36) Femtosecond ultraviolet photoelectron spectroscopy for the study of ultrafast
surface processes, Michael Bauer
O 36.1 Do 14:45 (H36) Dynamics of electron relaxation and exciton formation on Si(001),
Martin Weinelt
O 42.1 Fr 10:15 (H36) Reflectance Difference Spectroscopy : a powerful tool for surface analysis,
Michael Hohage
Fachsitzungen
O 1 Hauptvortrag Hofmann Mo 09:30–10:15 H36 O 1.1–1.1
O 2 Hauptvortrag Nilius Mo 10:15–11:00 H36 O 2.1–2.1
O 3 Nanostrukturen I Mo 11:15–13:15 H36 O 3.1–3.8
O 4 Organische Dünnschichten I Mo 11:15–13:15 H43 O 4.1–4.8

Oberflächenphysik Tagesübersichten
O 5 Epitaxie und Wachstum I Mo 11:15–13:15 H44 O 5.1–5.8
O 6 Struktur und Dynamik reiner Oberflächen Mo 11:15–13:15 H45 O 6.1–6.8
O 7 Hauptvortrag Bansmann Mo 14:00–14:45 H36 O 7.1–7.1
O 8 Hauptvortrag Bode Mo 14:45–15:30 H36 O 8.1–8.1
O 9 Rastersondentechniken I Mo 15:45–18:30 H36 O 9.1–9.11
O 10 Teilchen und Cluster I Mo 15:45–17:45 H43 O 10.1–10.8
O 11 Elektronische Struktur (Experiment und Theorie) I Mo 15:45–18:30 H44 O 11.1–11.11
O 12 Magnetismus in reduzierten Dimensionen Mo 15:45–17:00 H45 O 12.1–12.5
O 13 Methodisches (Experiment und Theorie) Mo 17:00–17:30 H45 O 13.1–13.2
O 14 Postersitzung (Adsorption an Oberflächen, Epitaxie
und Wachstum, Organische Dünnschichten, Oxide
und Isolatoren, Phasenübergänge, Rastersondentechniken,
Struktur und Dynamik reiner Oberflächen)
Mo 18:00–21:00 Bereich C O 14.1–14.84
O 15 Hauptvortrag M. A. Schneider Di 09:30–10:15 H36 O 15.1–15.1
O 16 Hauptvortrag Schäfer Di 10:15–11:00 H36 O 16.1–16.1
O 17 Elektronische Struktur (Experiment und Theorie) II Di 11:15–13:15 H36 O 17.1–17.8
O 18 Adsorption an Oberflächen I Di 11:15–13:15 H38 O 18.1–18.8
O 19 Teilchen und Cluster II Di 11:15–13:15 H39 O 19.1–19.8
O 20 Oberflächenreaktionen I Di 11:15–13:15 H45 O 20.1–20.8
O 21 Hauptvortrag Moresco Di 14:00–14:45 H36 O 21.1–21.1
O 22 Hauptvortrag Hövel Di 14:45–15:30 H36 O 22.1–22.1
O 23 Rastersondentechniken II Di 15:45–18:15 H36 O 23.1–23.10
O 24 Nanostrukturen II Di 15:45–18:30 H38 O 24.1–24.11
O 25 Epitaxie und Wachstum II Di 15:45–18:15 H39 O 25.1–25.10
O 26 Adsorption an Oberflächen II Di 15:45–18:00 H45 O 26.1–26.9
O 27 Gaedepreisvortrag Sander Mi 15:15–16:00 H1 O 27.1–27.1
O 28 Postersitzung (Elektronische Struktur, Grenzfläche
fest-flüssig, Halbleiteroberflächen und -grenzflächen,
Magnetismus und Symposium SYXM, Methodisches,
Nanostrukturen, Oberflächenreaktionen, Teilchen
und Cluster, Zeitaufgelöste Spektroskopie)
Mi 16:00–19:00 Bereich C O 28.1–28.86
O 29 Hauptvortrag Pentcheva Do 09:30–10:15 H36 O 29.1–29.1
O 30 Hauptvortrag Denecke Do 10:15–11:00 H36 O 30.1–30.1
O 31 Oberflächenreaktionen II Do 11:15–13:00 H36 O 31.1–31.7
O 32 Nanostrukturen III Do 11:15–13:15 H38 O 32.1–32.8
O 33 Organische Dünnschichten II Do 11:15–13:00 H39 O 33.1–33.7
O 34 Oxide und Isolatoren Do 11:15–13:00 H45 O 34.1–34.7
O 35 Hauptvortrag Bauer Do 14:00–14:45 H36 O 35.1–35.1
O 36 Hauptvortrag Weinelt Do 14:45–15:30 H36 O 36.1–36.1
O 37 Zeitaufgelöste Spektroskopie I Do 15:45–17:30 H36 O 37.1–37.7
O 38 Adsorption an Oberflächen III Do 15:45–18:15 H38 O 38.1–38.10
O 39 Epitaxie und Wachstum III Do 15:45–18:15 H39 O 39.1–39.10
O 40 Halbleiteroberflächen und -grenzflächen Do 15:45–18:45 H45 O 40.1–40.12
O 42 Hauptvortrag Hohage Fr 10:15–11:00 H36 O 42.1–42.1
O 43 Adsorption an Oberflächen IV Fr 11:15–13:15 H36 O 43.1–43.8
O 44 Elektronische Struktur (Experiment und Theorie) III Fr 11:15–13:15 H38 O 44.1–44.8
O 45 Zeitaufgelöste Spektroskopie II Fr 11:15–13:00 H39 O 45.1–45.7
O 46 Grenzfläche fest-flüssig Fr 11:15–12:45 H45 O 46.1–46.6

Oberflächenphysik Tagesübersichten
Mitgliederversammlung des Fachverbands Oberflächenphysik
Do 19:30–20:00 H36
Vorläufige Tagesordnung:
- Bericht des Fachverbandsvorsitzenden
- Neuwahl des Fachverbandsvorsitzenden
- Verschiedenes
Plenarvortrag des Fachverbands Oberflächenphysik:
PV X Surface Plasmon Photonics, Luis Martin-Moreno
HINWEISE:
Postersitzung O14 am Montag (18:00-21:00 Uhr) im Bereich C in der Nähe der Hörsäle H43-H45
Die Poster können ab Montag 8:30 Uhr aufgehängt werden und sollten bis Dienstag 18:00 Uhr entfernt werden. Der Abend
wird unterstützt von Omicron Vakuumphysik GmbH.
Postersitzung O28 am Mittwoch (16:00-19:00 Uhr) im Bereich C in der Nähe der Hörsäle H43-H45
Die Poster können ab Mittwoch 8:00 Uhr aufgehängt werden und sollten bis Mittwoch 19:30 Uhr entfernt werden.
Postdeadline Sitzung O42 am Donnerstag von 20:00-21:00 Uhr im Hörsaal H36, von 21:00-23:30 Uhr im
Bereich C in der Nähe der Hörsäle H43-H45 (Cafeteria der Chemie)
Deadline für die Anmeldung ist der 18. Februar 2004.
Die Sitzung wird unterstützt von SPECS GmbH gemeinsam mit BESTEC GmbH, VTS CREATEC GmbH und
Oxford Scientific.
GEMEINSAME VERANSTALTUNGEN UND SYMPOSIEN MIT ANDEREN FACHVERBÄNDEN:
O27 - Gaedepreisvortrag (Mittwoch, 15:15 Uhr, Hörsaal H1):
Stress on the atomic scale: From surface reconstruction to stress oscillations and magnetostriction of atomic
layers, Dirk Sander
Gemeinsame Sitzung der Fachverbände DS, VA, HL und O.
Symposium X-Ray Magneto-Optics (SYXM)
Dienstagnachmittag - Programm siehe dort.
Gemeinsam mit den Fachverbänden MA, HL, DS, O.
Symposium Organic and Hybrid Systems for Future Electronics (SYOH)
Donnerstagnachmittag und Freitagvormittag - Programm siehe dort.
Gemeinsam mit den Fachverbänden CPP, HL, O.

Oberflächenphysik Montag
Fachsitzungen
– Haupt-, Kurzvorträge und Posterbeiträge –
O 1 Hauptvortrag Hofmann
Zeit: Montag 09:30–10:15 Raum: H36
Hauptvortrag O 1.1 Mo 09:30 H36
Electron-phonon coupling and spin-orbit splitting in quasi twodimensional
metals: the surfaces of Bi — •Philip Hofmann — Institute
for Storage Ring Facilities, University of Aarhus, Ny Munkegade,
DK-8000 Aarhus C
Bi is a group V semimetal with a very low density of states at the
Fermi level. Several low-index surfaces of Bi support metallic surface
states which turn them into considerably better metals than the bulk.
Indeed, it is fair to view these surfaces as quasi two-dimensional met-
O 2 Hauptvortrag Nilius
als on an almost insulating substrate. We have studied the effect of the
electron-phonon coupling and the spin-orbit interaction on such systems.
For the former we find that the coupling strength depends strongly on
the binding energy of the states and it is therefore not possible to determine
the electron-phonon mass enhancement parameter λ from the
temperature-dependent width of surface states at higher binding energies.
For all Bi surfaces the spin-orbit splitting of the bands is very large
and dominates the two-dimensional dispersion. The consequences of this
on phenomena like screening or the formation of charge density waves
will be discussed.
Zeit: Montag 10:15–11:00 Raum: H36
Hauptvortrag O 2.1 Mo 10:15 H36
Tailoring electronic properties of atomic chains assembled in the
STM — •Niklas Nilius 1 , Thomas M. Wallis 2 , and Wilson Ho 2
— 1 Fritz-Haber-Institut der MPG, Berlin — 2 University of California,
Irvine, USA
The physical and chemical properties of ultra-small metal aggregates
sensitively depend on number and precise position of atoms in the structure.
Various applications in heterogeneous catalysis, optics and electronics
take advantage of this size-dependent behavior. However, preparation
and analysis of well-defined metal aggregates on surfaces are demanding
and interrelations between structural and electronic properties are not
well understood on the atomic level. In the present work, atom manipulation
techniques with an STM tip have been employed to construct
O 3 Nanostrukturen I
precise metal structures on a NiAl(110) surface. Single Au and Pd atoms
were assembled to atomic chains, whereby discrete adatom-resonances
develop into a series of quantum well states showing a parabolic dispersion.
Modifications of structural chain parameters, such as inter-atomic
distance, elemental composition and local impurities, decisively influence
the electronic properties of the atomic chains. Adsorption of a single
CO molecule on a Au chain interrupts the coupling between neighboring
chain atoms, breaking the chain into two independent electron systems.
A similar effect is observed upon introducing a single Pd atom into Au
chains. On the other side, the regular alternation of Pd and Au atoms
in alloy chains leads to properties in between those of pure Au and Pd
chains. The experiments demonstrate the possibility to manufacture and
characterize quantum systems with a well-defined electronic structure.
Zeit: Montag 11:15–13:15 Raum: H36
O 3.1 Mo 11:15 H36
Co nanostructures on Ag/v-Cu(111) — •Frank Ostendorf,
Andreas Bachmann, Georgi Rangelov, and Markus Donath
— Physikalisches Institut, Westfälische Wilhelms-Universität Münster,
Wilhelm-Klemm-Str. 10, 48149 Münster
Magnetic nanostructures play an important role in magnetic storage
technology. An important aim in this context is the customization of
the design parameters. The first step in preparing such nanostructures
is the controlled production of a suitable template. A new possibility to
produce regularly spaced nanostripes with controllable periodicity is the
deposition of Ag on vicinal Cu(111) surfaces [1]. Depending on the Ag
coverage, a rippled structure is formed in which Ag and Cu nanostripes
alternate with a periodicity between 10 and 30 nm. On the atomic scale,
the driving force for Ag-induced faceting is the lattice-matching between
the Ag overlayer and the faceted Cu substrate. The unique property of
this system is that the periodicity L of the nanostripes can be controlled
via the Ag coverage. Magnetic nanostructures can be produced by selective
deposition of magnetic material on the Ag or Cu facets of this
template. We report results of Co nanostripes with a thickness of a few
atomic layers, investigated by STM. The tunability of the spacing between
the stripes may lead to a detailed understanding of the magnetic
coupling between the nanostripes.
[1] A.R. Bachmann, F.Ostendorf and S. Speller, J. Phys.: Condens.
Matter, 15 (2003), 1-25
O 3.2 Mo 11:30 H36
Size-Effekt und Elektron-Phonon Kopplung in epitaktischen,
dünnen Gold-Filmen — •Gerd Kästle, Hans-Gerd Boyen,
Alexander Schröder, Alfred Plettl und Paul Ziemann — Abteilung
Festkörperphysik, Universität Ulm, 89069 Ulm
Epitaktische, glatte Goldfilme wurden auf Saphir mittels einer Niob
Keimschicht gewachsen. Die Temperaturabhängigkeit des Widerstand
wurde für Schichtdicken zwischen 2 und 50nm untersucht. Die Widerstandsmessungen
werden im Rahmen klassischer Size-Effekt Modelle analysiert.
Überraschenderweise beschreibt das ursprüngliche Model von
Fuchs-Sondheimer die Daten am besten und physikalisch konsistent -
auch für ultradünne Filme. Es zeigt sich allerdings, dass mit abnehmender
Schichtdicke die aus den Messungen abgeleitete Debye-Temperatur
stark reduziert ist. Im Gegensatz zu dicken Filmen wird in dünneren Filmen
die für den Transport relevante effektive Debye-Temperatur nicht
mehr durch die Debye-Temperatur von Bulk-Material sondern durch die
Debye-Temperatur der Oberfläche dominiert. Die Zunahme des Oberflächen-
zu Volumenverhältnisses führt somit zu einer Änderung der
Elektron-Phonon Kopplung im elektrischen Widerstand dünner Filme.
O 3.3 Mo 11:45 H36
Tip-substrate interactions: structure and electronic states —
•A.L. Klavsyuk 1 , V.S. Stepanyuk 2 , I. Mertig 2 , W. Hergert 1 , P.
Bruno 2 , and J. Kirschner 2 — 1 Fachbereich Physik, Martin-Luther-
Universität, Von-Seckendorff-Platz 1, 06120 Halle, Germany — 2 Max-
Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle,
Germany
Atom resolved scanning tunneling microscopy images are known to de-

Oberflächenphysik Montag
pend on the nature of the tip and its interaction with the surface. Using
ab-initio KKR Green’s function method we calculate electronic structure
of the tip and the substrate in a fully relaxed geometry. Atomic
relaxations are performed using ab-initio based many body potentials in
the tight-binding approximation. Parameters of potentials are fitted to
KKR results for low dimension system. We concentrate on Co adatoms
on Cu(001) and study the interaction of the Cu tip with Co/Cu(001). We
demonstrate that due to the tip-substrate interaction one can produce
1D embedded Co structures. Recent experiments [1] have reported that
such structures can be stable even at room temperature.
[1] O.Kurnosikov et al., Europhys. Lett., 64 (1), pp. 77-83 (2003).
O 3.4 Mo 12:00 H36
Wachstum und elektronische Struktur von Seltenerdsilizid-
Nanodrähten auf Si(001)-Vizinalflächen — •C. Preinesberger 1 ,
D.V. Vyalikh 2 , S.L. Molodtsov 2 , F. Schiller 2 , G. Pruskil 1 ,
C. Laubschat 2 und M. Dähne 1 — 1 Institut für Festkörperphysik,
Technische Universität Berlin — 2 Institut für Festkörperphysik,
Technische Universität Dresden
Das selbstorganisierte Wachstum von Seltenerdsilizid-Nanodrähten auf
der planaren Si(001)-Oberfläche ist in den letzten Jahren intensiv untersucht
worden [1,2]. Über die elektronischen Eigenschaften war allerdings
bisher kaum etwas bekannt. Wir präsentieren hier erstmalig
Ergebnisse zu den strukturellen und elektronischen Eigenschaften von
Dysprosiumsilizid-Nanodrähten auf einer Si(001)-Vizinalfläche. Mit Rastertunnelmikroskopie
konnten wir das Wachstum von Nanodrähten mit
einheitlicher Ausrichtung beobachten, im Gegensatz zu der Situation auf
der planaren Oberfläche, auf der sich die Ausrichtung an Stufen um 90 ◦
dreht. Untersuchungen mit winkelauflösender Photoemission zeigen deutlich
einen entlang der Drahtrichtung stark dispergierenden Zustand, der
die Fermienergie schneidet und somit metallischen Charakter hat. Senkrecht
zu den Nanodrähten wird dagegen kaum Dispersion beobachtet, was
auf eine starke Lokalisierung der Ladungsträger in den einzelnen Drähten
hinweist.
[1] C. Preinesberger, S. Vandré, T. Kalka, and M. Dähne-Prietsch, J.
Phys. D: Appl. Phys. 31, L43 (1998).
[2] C. Preinesberger, S.K. Becker, S. Vandré, T. Kalka, and M. Dähne,
J. Appl. Phys. 91, 1695 (2002).
O 3.5 Mo 12:15 H36
Sandwich-like nanowire formation on Ir(100) — •Andreas
Klein, Chiara Giovanardi, Andreas Schmidt, Lutz Hammer,
and Klaus Heinz — Lehrstuhl für Festkörperphysik , Universität
Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen
As shown recently [1], the stable quasi-hexagonal (5×1) reconstruction
of the clean Ir(100) surface restructures by exposure to hydrogen.
The new phase corresponds to a lateral superlattice of almost defect-free
monoatomic Ir nanowires arranged on the unreconstructed, i.e. (1×1)symmetric
substrate. The average lateral spacing of the wires is 1.36 nm
and their length in the range of micrometers. Investigations by scanning
tunnelling microscopy (STM) and low-energy electron diffraction (LEED)
show that this hydrogen-induced phase of Ir(100) can be used as a template
to produce other nanostructures. So, deposition of e.g. iron leads to
the decoration of both sides of the Ir wires. Hereby, the Fe atoms occupy
fourfold-symmetric substrate sites. This corresponds to the formation of
FeIrFe sandwich-like nanowires which are as perfect as the original Ir
wires. At 0.4 ML Fe coverage the new phase is equivalent to a vacancy
spaced lateral {FeIrFe} superlattice. Its crystallographic structure has
been analyzed by quantitative LEED.
[1] L. Hammer, W. Meier, A. Klein, P. Landfried, A. Schmidt, and K.
Heinz, Phys. Rev. Lett. 91 (2003) 156101
O 3.6 Mo 12:30 H36
Crystalline metallic nanostructures via e-beam lithography
— •T. Block, V. Zielasek, and H. Pfnür — Institut
für Festkörperphysik, Universität Hannover, Appelstrasse 2, 30167
Hannover
A combination of epitaxial metal growth with a UHV-capable lithography
method offers the possibility to form 2D crystalline metallic nanostructures
of arbitrary shape. Such a system can be used to study the
electrical properties of metallic nanosystems, especially conductivity in
low dimensions. In our experiments we use a combined SEM-STM instrument
in which the 25kV electron beam and the tunneling tip can
be used simultaneously at the same position of the sample. This enables
us to perform electron beam lithography and subsequent investigations
with STM within the same instrument. We use a lithography method
based on electron beam assisted oxgen desorption from ultrathin (≈ 1
nm) SiO2 layers on a Si(111) or Si (100)surface. Additional heating up to
≈ 780 o C leads to the desorption of SiO and pure crystalline Si windows.
Ag deposited on top of these structures at 130K and subsequent annealing
forms non-percolated clusters on the remaining SiO2 and crystalline
Ag wires on the pure Si areas with nearly step free surfaces, probably due
to an electronic growth mechanism. A minimum width of 20nm, which
is much smaller than the grain size of the Ag films, and a wire length of
several µm have been obtained. Further optimization will decrease the
linewidth. TiSi contacts, produced with conventional e-beam lithography,
and the STM tip are used to connect these wires for conductivity
measurements. The influence of distinct defects on electrical transport in
the structures will be discussed.
O 3.7 Mo 12:45 H36
Gleichgewichtsform und Gleichgewichtsfluktuationen auf der
rekonstruierten Au(100)-Oberfläche — •Christian Bombis und
Harald Ibach — Institut für Schichten und Grenzflächen ISG 3, Forschungszentrum
Jülich, 52425 Jülich, Germany
Adatom- und Leerstelleninseln wurden durch Aufdampfen von Gold
bzw. Sputtern im Submonolagenbereich auf der temperierten rekonstruierten
Au(100)-Oberfläche erzeugt. Wie bereits in anderen Arbeiten
gezeigt, erhält man längliche rechteckige Wachstumsformen mit
der langen Kante entlang der parallelen Rekonstruktionsreihen. Das
Längenverhältnis der langen zur kurzen Seite dieser Wachstumsformen,
das Aspektverhältnis, liegt in der Größenordnung von 10. Der einsetzende
Inselzerfall korreliert mit einer Abnahme des Aspektverhältnisses bis
hin zu etwa 1 und variiert dann nur noch stochastisch um diesen Wert.
Wir konnten Adatominseln bei T = 353 K beobachten, die über lange
Zeiträume weder wachsen noch zerfallen und deren Aspektverhältnis
stochastisch um diesen Mittelwert von etwa eins schwankt. Wir nehmen
daher an, dass diese Inseln sich im thermodynamischen Gleichgewicht
oder nahe dabei befinden. Durch Mittelung über die Inselränder haben
wir dann eine Gleichgewichtsform für die angegebene Temperatur bestimmt.
Aus Inselrandfluktuationen dieser Inseln bestimmten wir eine
mittlere freie Stufenenergie zu 160 meV pro Atom.
O 3.8 Mo 13:00 H36
Lateral Ir-spaced superlattices of Fe, Co and Ni on Ir(100) —
•Andreas Schmidt, Andreas Klein, Chiara Giovanardi, Lutz
Hammer, and Klaus Heinz — Festkörperphysik, Universität Erlangen-
Nürnberg, Staudtstr. 7, D-91058 Erlangen
The stable phase of Ir(100) exhibits a quasi-hexagonal top layer with
six atomic rows fitting to five rows of the second layer (Ir(100)-(5×1)hex).
Exposure to hydrogen lifts this reconstruction by expelling the 20%
extra atoms accommodated in the top layer to the very surface. This
Ir(100)-(5×1)-H phase is characterized by monoatomic, almost defect
free Ir wires of up to micrometer length which reside in 5×1 long-range
order on the unreconstructed substrate. By deposition of Fe, Co or Ni the
space between these wires can be filled, whereby the three elements differ
by their growth modes as is observed by scanning tunnelling microscopy
(STM). For e.g. Fe, deposition the final state at 0.8ML coverage corresponds
to a lateral superlattice, {Fe4Ir}. Its crystallographic structure
as determined by the measurement and quantitative dynamical analysis
of low-energy electron diffraction (LEED) intensities is reported. When
iron is deposited on Ir(100)-(5×1)-hex rather than on Ir(100)-(5×1)-H),
locally the same Fe4Ir surface compound results, yet with a considerably
lower degree of long-range order.

Oberflächenphysik Montag
O 4 Organische Dünnschichten I
Zeit: Montag 11:15–13:15 Raum: H43
O 4.1 Mo 11:15 H43
Optische in situ Spektroskopie der TiOPc-PTCDA-Grenzfläche
— •Thomas Dienel, Holger Proehl, Robert Nitsche, Karsten
Walzer, Torsten Fritz und Karl Leo — Institut für Angewandte
Photophysik, Technische Universität Dresden, 01062 Dresden, Germany
Die Grenzflächen zwischen verschiedenen organischen Molekülen spielen
eine entscheidende Rolle im Aufbau von Bauelementen wie Leuchtdioden
(OLEDs) oder organischen Solarzellen. Um eine definierte Struktur
zu erhalten, wurde mit organischer Molekularstrahlepitaxie Titanylphthalocyanin
(TiOPc) auf einer ebenfalls hochgeordneten 3,4,9,10-Perylen-
Tetracarbonsäure-Dianhydrid-Schicht (PTCDA) abgeschieden.
Die verwendete Differentielle Reflexionsspektroskopie (DRS) gibt uns
die Möglichkeit, die optischen Eigenschaften und ihre Änderung während
des Schichtwachstums zu untersuchen. Für dünne Schichten auf transparenten
Substraten spiegelt das DRS-Signal die Absorption der adsorbierten
Moleküle wieder, und ermöglicht so die Beobachtung des Übergangs
vom Monomerspektrum des Einzelmoleküls zur Kristallabsorption.
Ebenfalls mit einer Auflösung im Submonolagenbereich lässt sich die
Photolumineszenz untersuchen. Dazu wurde die Kristallemission einer
5nm PTCDA-Schicht angeregt und deren Intensität während des Aufwachsens
der TiOPc-Moleküle beobachtet. Mit dem Verschwinden der
PTCDA-Emission werden die Banden des TiOPc-Monomers sichtbar, die
im weiteren in die TiOPc-Kristallemission übergehen.
O 4.2 Mo 11:30 H43
Molecular orientation in perylene thin films on
Al2O3/Ni3Al(111) — •M. B. Casu, A. Schöll, K. R. Bauchspieß,
D. Hübner, Th. Schmidt, C. Heske, and E. Umbach —
Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074
Würzburg
Organic Field Effect Transistors (OFETs) are a rapidly developing field
and many efforts are directed towards their optimisation. We have investigated
thin films of perylene, a model candidate as OFET material, grown
by organic molecular beam deposition (OMBD) on Al203/Ni3Al(111). By
means of Near-Edge X-ray Absorption Fine Structure (NEXAFS), we
studied the influence of the growth parameters on the molecular orientation
and the consequential changes in the electronic fine structure. We
find that it is possible to tailor the molecular orientation of perylene by
using different sets of growth parameters. Thus, it is possible to grow
films in which the chosen molecular orientation is optimal for a charge
transport between source and drain. We also investigated their thermal
stability and their vacuum stability as a function of time (perylene is
characterised by a high vapour pressure). As will be discussed, the overall
results are helpful to understand the interactions between the organic
molecules and the substrate and to answer the question whether perylene
can be used for real OFET devices. (Financed by DFG, SP 1121,
Um 618-2)
O 4.3 Mo 11:45 H43
Growth of para-hexaphenyl microrings — •Frank Balzer 1 and
Horst-Günter Rubahn 2 — 1 Humboldt-Universität zu Berlin, Institut
für Physik / ASP — 2 SDU Odense, Fysisk Institut, Denmark
Recently we have shown, that on freshly cleaved mica the growth of
mutually aligned fibers of para-hexaphenyl is favored because of a dipoleassisted
self-assembly process [1]. Typical heights and widths of these
fibers are in the range of a few ten to hundred nanometers, but lengths
up to one millimeter can be obtained. However, altering the mica surface
dipoles leads to the growth of para-hexaphenyl microrings instead
of parallel fibers. These rings possess a narrow size distribution of a few
micrometers in diameter with wall widths and heights of a few hundred
nanometers. Polarized two-photon luminescence on single rings reveals
that these rings resemble bent single crystalline fibers [2]. Possible applications
of the microrings are discussed.
[1] F. Balzer and H.-G. Rubahn, Appl. Phys. Lett. 79 (2001) 3860.
[2] F. Balzer, J. Beermann, S.I. Bozhevolnyi, A.C. Simonsen, and H.-G.
Rubahn, Nano Letters 3 (2003) 1311.
O 4.4 Mo 12:00 H43
Self-organization of Phthalocyanine films on Al2O3 substrates:
in-plane alignment and ordering — •Esther Barrena 1 , J.Oriol
Ossó 2 , Frank Schreiber 3 , M.Isabel Alonso 2 , Miquel Garriga 2 ,
and Helmut Dosch 1,4 — 1 Max-Planck-Institut für Metallforschung,
Heisenbergstr.3, 70569 Stuttgart, Germany — 2 Institut de Ciència
de Materials de Barcelona CSIC, 08190 Bellaterra, Spain — 3 Physical
and Theoretical Chemistry Laboratory, University of Oxford, Oxford
OX13QZ, UK — 4 Institut für Theoretische und Angewandte Physik,
For the development of organic electronic devices, such as Organic
Field Effect Transistors, the controlled growth of ordered films is prerequisite.
However, it is still challenging to find systems where the balance
between intermolecular forces and interaction with the substrate leads
to the formation of layered films with defined in-plane orientation. In
this work we show that F16CuPc molecules self-organize on Al2O3 (11¯20)
substrates forming unidirectionally oriented needle-like structures. X-ray
diffraction reveals a highly ordered layered structure with the (001) plane
parallel to the surface. The morphology, investigated by Atomic Force Microscopy
(AFM), is smooth and consists of long (microns) and narrow
(tens of nm) needle-like terraces unidirectionally aligned along one of the
main crystallographic directions of the Al2O3 (11¯20) surface. Molecularly
resolved AFM reveal in-plane molecular order with the molecular stacking
parallel to the needle-like terraces. We discuss different mechanisms
leading to this anisotropic structure.
O 4.5 Mo 12:15 H43
Preparation of stacked alkylsiloxane bilayers by spin coating
— •Rafael Bautista, Steffen Franzka, Daniel Dahlhaus, and
Nils Hartmann — Universität Duisburg-Essen, Fachbereich Chemie,
Universitätsstr. 5, 45141 Essen
A simple one-step procedure for the preparation of stacked alkylsiloxane
bilayers is suggested. Solutions of alkyltrichlorosilanes have been spin
coated onto oxidized and H-terminated silicon substrates, respectively.
Subsequently, the samples are inspected by optical and atomic force microscopy.
On the oxidized substrates the coating results in the formation
of macroscopic cellular structures. Whereas, ordinary alkylsiloxane islands
can be identified within the cells, stacked alkylsiloxane bilayers are
formed close to the rim of these structures. In contrast, a macroscopically
more homogeneous coating with stacked alkylsiloxane bilayers results on
the H-terminated substrates. Initially, the bilayers show a remarkable
flexibility. Using the tip of the atomic force microspcope, they can be
easily shifted between the levels maintaining the vertical alignment of
the molecular units. Only after some days, lateral cross-linking appears
to set in.
O 4.6 Mo 12:30 H43
Order and symmetries of sexithiophene within thin films
studied by angle-resolved photoemission — •Cynthia Heiner 1 ,
Bernd Winter 1 , Jens Dreyer 1 , Hans-Hermann Ritze 1 , I.V.
Hertel 1 , and Wolf Widdra 2 — 1 Max-Born-Institut, D-12489 Berlin
— 2 Universität Halle-Wittenberg, D-06099 Halle
We present angle-resolved photoemission (PE) spectra of ordered multilayer
sexithiophene (6T) films, 2000 ˚A thickness, grown on a Au(110)
single crystal. Structural order is crucial for film properties, particularly
with regard to the performance of organic electronic devices. The measurements
were performed at the MBI undulator beamline at BESSY,
using photon energies < 100 eV. By simultaneous laser irradiation a
compensation for film charging is achieved. The resulting spectra possess
sharp features, which we show to have a strong intensity dependency
on the experimental geometry. The molecules’ relative orientation, as interpreted
through symmetry selection rules, is discussed in relation to
various conformers. Our results firmly suggest the need for alternative
molecular symmetries from the reported C2h symmetry for the 6T’s bulkcrystalline
structure [1]. [1] R. N. Marks, M. Muccini, E. Lunedi, R. H.
Michel, M. Murgia, R. Zamboni, C. Taliani, G. Horowitz, F. Garnier, M.
Hopmeier, M. Oestreich, R. F. Mahrt, Chem. Phys. 227, 49 (1998).

Oberflächenphysik Montag
O 4.7 Mo 12:45 H43
Electronic Structure of Self-Assembled Bacterial S-Layers
— •Serguei Molodtsov 1 , Denis Vyalikh 1 , Steffen
Danzenbächer 1 , Michael Mertig 2 , Alexander Kirchner
2 , Wolfgang Pompe 2 , and Yuriy Dedkov 3 — 1 Inst. f.
Festkörperphysik, TU Dresden — 2 Inst. f. Werkstoffwissenschaft, TU
Dresden — 3 II. Physikalisches Institut, RWTHA
The discovered possibility to grow thin self-organized biological films
on appropriate substrates is one of the mostly important recent achievements
of materials science. Various branches of microelectronics already
advance by this unique possibility. To make further progress in these
fields, thorough information about electronic structure of grown layers is
required. The corresponding data are lacking, however, since the biological
substances are quite sensitive to exposure and can easily be destroyed
by irradiation as necessary for spectroscopic techniques usually used to
study electronic structure of solids.
We present first results of photoemission and x-ray absorption study of
ordered films of bacterial cell well proteins (S-layer) of Bacillus sphaericus
and Sporosarcina ureae. The films under study are found to be wide-gap
semiconductors. Similar to organic materials both the occupied and the
unoccupied electron densities of states represent series of peaks, which
O 5 Epitaxie und Wachstum I
can be related to the molecular-like electron orbitals.
O 4.8 Mo 13:00 H43
Calculation of the optical constants of thin films from just one
spectral measurement and its application to organic films —
•Robert Nitsche, Holger Pröhl, Thomas Dienel, and Torsten
Fritz — Institut für Angewandte Photophysik, TU Dresden
The interpretation of optical thin film spectra is usually not straight
forward since the shape of the spectra is strongly influenced by the substrate.
Therefore, one has to extract the optical constants of the film,
namely the index of refraction n and the absorption coefficient k. Here,
we present a new method which allows to determine the optical constants
from just one spectral measurement. The algorithm makes explicit use of
the fact that n and k are connected by a Kramers-Kronig transformation.
The successful application of the method is demonstrated on both, analytically
generated and experimentally recorded examples. For this contribution
we chose a Differential Reflectance Spectrum (DRS) of a thin film
of the organic semiconductor PTCDA (3,4,9,10-perylenetetracarboxylic
dianhydride) on HOPG (Highly Oriented Pyrolytic Graphite). This example
has been selected since its optical spectrum does not resemble the
material’s absorption at all.
Zeit: Montag 11:15–13:15 Raum: H44
O 5.1 Mo 11:15 H44
Growth dynamics of Ge islands on high index Si surfaces
— •Marcel Himmerlich 1,2 , Woochul Yang 1 , Robert J. Nemanich
1 , and Juergen A. Schaefer 2 — 1 Department of Physics,
North Carolina State University, Raleigh, NC 27695 — 2 Institut für
Physik and Zentrum für Mikro- und Nanotechnologien, TU Ilmenau,
98684 Ilmenau
The growth dynamics of Ge islands on Si substrates with surface orientation
close to (113) has been studied in situ by photoelectron emission
microscopy (PEEM) at 450 ◦ -550 ◦ C and during annealing up to 700 ◦ C.
The growth rate was varied between 0.1 and 0.6 ML/min. Photoelectrons
were excited by UV-light generated by the UV free electron laser at Duke
University. First, up to 3-4ML, uniform emission was observed indicating
the growth of a strained wetting layer. Then 3D-growth occurred with
different island shapes. Low growth rates result in elongated islands in
[332] direction, indicating anisotropical strain. At higher deposition rates
round islands were created. There, during continuous deposition, islands
enlargement was observed with no further nucleation. During annealing,
the density of round islands decreased while the average size increased
(ripening), whereas the elongated structures undergo a shape transformation
leading to indentations.
O 5.2 Mo 11:30 H44
Nucleation in the presence of adatom insertion: Co/Pt(111) —
•Philipp Buluschek, Stefano Rusponi, Mehdi El Ouali, Emmanuel
Vargoz, Klaus Kern, and Harald Brune — Institut de
Physique des Nanostructures, Ecole Polytechnique Fédérale de Lausanne,
CH-1015 Lausanne, Switzerland
We used variable temperature STM to study submonolayer nucleation
of Co/Pt(111). The Pt(111) surface is under tensile stress and undergoes
a reconstruction above 1330 K, or upon Pt deposition at 400 K. For Co
deposition, adatom incorporation into the first atomic plane has been reported
upon deposition at 300 K. We show that conventional on-surface
diffusion and nucleation takes place up to 180 K. Above this temperature
the island density continues to decrease but with a smaller slope
in its Arrhenius representation. Our experiments demonstrate that this
coincides with the onset of inclusion.
We present kinetic Monte-Carlo simulations revealing that insertion
leads to the creation of repulsive point and line defects. The comparison
between simulations and experiment enables access to the energy barriers
for surface diffusion, insertion and the repulsion at the defects.
O 5.3 Mo 11:45 H44
Untersuchungen des Wachstums von Mn-Filmen auf Si(100) —
•Holger Lippitz, Kai Schwinge, Jens J. Paggel und Paul Fumagalli
— Institut für Experimentalphysik, Freie Universität Berlin,
Arnimallee 14, 14195 Berlin
Die bisherigen Untersuchungen von Mn und Mn-Verbindungen kon-
zentrierten sich häufig auf die magnetischen und strukturellen Eigenschaften
relativ dicker Mn-Filme. Hier werden die Strukturen dünner
Mn-Schichten (von 1/10 ML bis zu 5 ML) auf Si(100) und 4 ◦ fehlorientierten
Si(100) Substraten im UHV untersucht. Die Ausheiltemperaturen
und Schichtdicken werden variiert. Zur Untersuchung der Proben stehen
STM, RHEED, LEED und AES zur Verfügung. Es werden mehrere Arten
der Inselbildung (temperatur- und schichtdickenabhängig), aber keine
atomar glatten und geschlossenen Filme beobachtet. Es treten Strukturen
auf, die auf eine Bildung von MnSi oder Mn5Si3 hindeuten. Generell
wird eine Zunahme der Defektdichten auf dem Substrat gefunden. Die
beobachtete Inselgröße wird von der Stufendichte des Substrats beeinflusst.
Alle Ergebnisse weisen auf ein Filmwachstum in Form eines Silizids
anstatt eines Mn-Filmes hin. Gefördert von der Deutschen Forschungsgemeinschaft
durch den SFB 290.
O 5.4 Mo 12:00 H44
Hochempfindliche Messung von Oberflächenverspannung — Peter
Kury, Michael Horn-von Hoegen, •Peter Kury und Michael
Horn-von Hoegen — Inst. f. Laser- und Plasmaphysik, Universität
Duisburg-Essen
Die Verspannung von Oberflächen (surface stress) ist eine der wichtigsten
physikalischen Größen für das Verständnis von Phänomenen im
Bereich der Epitaxie. Eine Messung der Verspannung kann mit optischen
Biegebalkenmethoden wie SSIOD (surface stress induced optical
deflection) erfolgen, wobei ohne großen Aufwand eine Auflösung von etwa
0.2N/m erreichbar ist. Eine Steigerung der Empfindlichkeit, um Verspannungen
ab 0.05N/m sicher detektieren zu können, erfordert aufwändige
Änderungen des Meßaufbaus im Bereich des Detektors, des Lasersystems
und der Probe. Diese Modifikationen und ihre Auswirkungen werden anhand
von neuen Adsorptions- und Filmwachstumsmessungen auf Si Substraten
vorgestellt.
O 5.5 Mo 12:15 H44
Growth of Vanadiumoxide and Niobiumoxide on Cu3Au(100)
— •Jürgen Middeke, Ralf-Peter Blum, and Horst Niehus —
Humboldt-Universität zu Berlin, Institut für Physik, ASP, Newtonstr.
15, 12489 Berlin
Thin crystalline 2-dim vanadiumoxide films can be prepared with controlled
stoichiometry by implantation of oxygen into Cu3Au(100) and
deposition of vanadium, followed by annealing [1]. The keystep of this
procedure is the formation of an amorphous vanadiumoxide layer during
the deposition of vanadium that locally has the desired ratio of vanadium
to oxygen. With no mass transport necessary, annealing to 700K is sufficient
for crystallisation. Depending on the amount of oxygen implanted
into the Cu3Au(100)-surface, VO2, V2O3 and VO can be obtained.
As a check if this growth method can be applied also to other transition
metal oxides, we exchanged vanadium by niobium. The result is that also
flat 2-dim Niobiumoxide films can be prepared. As an example, we get a

Oberflächenphysik Montag
Nb2O3 structure, a surprising result because Nb2O3 is not known as bulk
material. It can be concluded that our growth method is not restricted
to the growth of vanadiumoxide.
[1] H. Niehus et al., Phys. Stat. Sol. a 187 (2001) 151
O 5.6 Mo 12:30 H44
Growth of a GaSe half-sheet on Si(111) — •Bengt Jaeckel,
Rainer Fritsche, Andreas Klein, and Wolfram Jaegermann
— Darmstadt University of Technology, Surface Science Division, Department
of Materials Science, Petersenstr. 23, 64287 Darmstadt
The evolution of the Si(111):GaSe surface termination is investigated
with scanning tunneling microscopy (STM), low energy electron diffraction
(LEED) and SXPS. GaSe is evaporated from an effusion cell filled
with GaSe compound as source material onto Si(111)-(7×7) surfaces held
at 540 ◦ C substrate temperature. Although both Gallium and Selenium
are exposed during the formation process, the surface passes through different
reconstructions, which are known for Ga-terminated Si(111) surfaces.
The passivated surface is characterized by a three-fold symmetry
of the LEED-pattern, a hexagonal periodicity of the lattice imaged with
atomic resolved STM and flat-band conditions measured with SXPS.
In the beginning a √ 3 × √ 3 R30 ◦ - Ga surface is formed, followed by a
6.3 × 6.3 and a 6.3 √ 3 × 6.3 √ 3 - Ga surface, which corresponds to one
third, 0.7 and 1 monolayer of Gallium. No Si(111)-(1 × 1):GaSe terminated
areas are observed below one third monolayer coverage.
O 5.7 Mo 12:45 H44
STM Studies of ultrathin SixGe1−x films grown on Si(111)
by Chemical Vapour Deposition — •Selvi Gopalakrishnan, H.
Rauscher, and R.J. Behm — Abt. Oberflächenchemie und Katalyse,
Universität Ulm, 89069 Ulm
The influence of terrace width, temperature and gas composition on
the morphology and composition of epitaxial SixGe1−x films grown on
Si(111) by chemical vapour deposition (CVD) was investigated by STM
and XPS. Si2H6 and GeH4 were used as the precursor gases. Investigations
were carried out with two different GeH4:Si2H6 gas ratios, (a) a 7:3
ratio with an effective Ge:Si ratio of about 1:1 and (b) a 9:1 ratio where
the effective ratio of Ge:Si is about 4:1. SiGe layers were deposited at
a constant pressure of 2.5×10 −6 mbar on wafers with two different terrace
widths (average terrace widths of 2000 A and up to 6000 A) and at
deposition temperatures of 750 K and 850 K. At 750 K, hydrogen is completely
desorbed from the Ge surface and at 850 K the rate of hydrogen
desorption from the Si surface is a maximum. The large terrace widths
allow the study of the SiGe CVD process, in particular the nucleation
behaviour, at low pressures and higher temperatures and derive data on
the mobility of the mobile Si and Ge containing species.
O 5.8 Mo 13:00 H44
Vergleich der ab-initio berechneten elektronischen Struktur verschiedener
Stapelfolgen von Co (0001) — •Lilli Sacharow 1 ,
Stefan Heinze 1 , Gustav Bihlmayer 2 , Stefan Blügel 2 , Jens
Wiebe 1 , Markus Morgenstern 1 und Roland Wiesendanger 1 —
1 Institut für Angewandte Physik, Universität Hamburg, Jungiusstrasse
11, D-20355 Hamburg; — 2 Institut für Festkörperforschung, Forschungszentrum
Jülich, D-52425 Jülich
In dieser Arbeit wurden DFT-LDA Berechnungen der elektronischen
Struktur eines 11-Lagen Co-Films in verschiedener
Stapelfolge durchgeführt. Insbesondere wurden im Hinblick auf
Rastertunnelspektroskopie-Messungen der reine hcp-Film (...ABAB) und
der hcp-Film mit einem Stapelfehler an der Oberfläche (...ABAC) untersucht.
Die Zustandsdichte im Vakuum, bei Abständen zur Oberfläche
unter 5 ˚A, ist in beiden Fällen dominiert von einem Minoritätspeak
0.6 eV unterhalb der Fermikante. Bei der Oberfläche mit stapelfehler
ist dieser ca. 20% grösser als bei reinem hcp-Film. Die Verteilung der
Zustände in der Brillouin Zone zeigt, dass er hauptsächlich von einem
Bandminimum zwischen Γ-Punkt und dem Brillouinzonenrand getragen
wird, während der Γ-Punkt selbst nur mit ca 5% beiträgt.
O 6 Struktur und Dynamik reiner Oberflächen
Zeit: Montag 11:15–13:15 Raum: H45
O 6.1 Mo 11:15 H45
Co Subsurface Segregation in CoAl(111) — •Lutz Hammer,
Volker Blum, Christian Schmidt, Ole Wieckhorst, Wolfgang
Meier, Stefan Müller, and Klaus Heinz — Lehrstuhl
für Festköerperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7,
D-91058 Erlangen
The geometrical and chemical structure of the CoAl(111) surface is
investigated by quantitative low-energy electron diffraction (LEED) and
calculations applying density functional theory (DFT). It is found that
the surface assumes an Al-Co-Co-Co layer stacking within the top few
layers and the usual alternating B2 stacking below. The topmost layers
thus form a unit cell of the bcc-based D03 crystal structure (i.e. a A3B
superlattice of bcc(111) atomic planes), despite of the fact that the bulk
phase diagram of CoAl shows no D03 phase. Its stability at the surface is
due to a slight Co excess of the nominally stoichiometric sample, which
is incorporated in the bulk by forming Co antisite defects. These defects
are enriched in undercoordinated surface sites, there replacing Al atoms
which assume fully coordinated sites in the bulk, in effect lowering the
total energy. The process competes with the energetically favourable Al
termination of the surface, so that the Co antisites concentrate in the
still undercoordinated third layer rather than in the top layer, leading to
the observed termination.
O 6.2 Mo 11:30 H45
Multilayer relaxations of the Cu(11{2n+1}) surfaces calculated
with the FLAPW method — •Juarez L. F. Da Silva, Kurt
Schroeder, and Stefan Blügel — Institut für Festkörperforschung,
Forschungszentrum Jülich, D-52425 Jülich, Germany
We report a systematic first-principles study of the multilayer relaxation
of the stepped Cu(11{2n + 1}) surfaces, for 2n + 1 = 3, 5, 7, and
9. Our calculations are based on density-functional theory, employing
the all-electron full-potential linearized augmented plane wave (FLAPW)
method. We found that Cu(113), Cu(115), Cu(117), and Cu(119) have
a multilayer relaxation sequence represented by, − + − · · ·, − − + − · · ·,
− − −+− · · ·, and − − − −+−· · ·, respectively, where − and + indicate
an interlayer distance contraction and expansion, respectively. Thus, our
FLAPW calculations confirm the trend obtained by low-energy electron
diffraction (LEED) intensity analysis for Cu(113), Cu(115), and Cu(117),
i.e., in a stepped metal surface with n + 1 atom rows in the terraces the
first n interlayer spacings contract, the n + 1 interlayer spacing expands.
However, for Cu(115), our result is in disagreement with those obtained
by surface x-ray diffraction, which obtained −+−−· · ·. Furthermore, we
found in general a good agreement with the magnitude of the interlayer
relaxations and by LEED.
O 6.3 Mo 11:45 H45
X-ray reflectivity study of the aqueous solution-gas interface —
•Michael Paulus, Michael Sprung, Christian Gutt, and Metin
Tolan — Experimentelle Physik I, Universität Dortmund, 44221 Dortmund
Interfacial properties of aqueous salt solutions are important in many
biological and geological systems.e.g. for the reactivity of sea salt aerosols
in the marine boundary layer.
In the past a large number of theoretical work has been performed to
study the liquid - gas interface of aqueous alkali halide electrolyte solutions.
Molecular dynamics simulations revealed a partial ion enrichement
of alkali halides solution close to the liquid-gas interface. This finding is
in contrast to expectations based on classical electrostatic calculations.
It has been reported that this effect is most prominent if sodium iodide is
used as the electrolyte. The expected thickness of the ion enriched region
is of the order of 1nm.
We report on x-ray reflectivity experiments of aqueous solutions of
sodium iodine of different concentrations. The experiments provided for
the first time a detailed picture of the electron density profile of aqueous
salt solutions close to the liquid-gas interface. In contrast to the results
of molecular dynamic simulations, we observed for all investigated concentrations
a water enriched region of thickness 1-2 nm at the surface.

Oberflächenphysik Montag
O 6.4 Mo 12:00 H45
Dynamik in einer Eisen-Submonolage auf Wolframsubstrat —
•Marcel Sladecek 1 , Bogdan Sepiol 1 , Jozef Korecki 2,3 , Tomasz
Slezak 2,3 , Rudolf Rüffer 4 , Daniel Kmiec 1 und Gero Vogl 1 —
1 Institut für Materialphysik der Universität Wien, Strudlhofgasse 4, A-
1090 Wien, Austria — 2 Faculty of Physics and Nuclear Techniques, University
of Mining and Metallurgy, Mickiewicza 30, Pl-30-059 Cracow,
Poland — 3 Institute of Catalysis and Surface Chemistry, PAS, Cracow,
Poland — 4 ESRF, F-38043 Grenoble, France
Bei höheren Temperaturen wird die Struktur und die Eigenschaften
von Nanostrukturen durch die Dynamik bestimmt. Die kernresonante
Streuung von Synchrotronstrahlung erlaubt die Untersuchung sowohl
magnetischer als auch dynamischer Eigenschaften dünner Schichten.
Die Methode verbindet die hohe Brillanz der Synchrotronstrahlungsquellen
der dritten Generation mit den exzellenten Merkmalen der
Mößbauerspektroskopie. Die atomspezifische Empfindlichkeit wurde zur
Untersuchung der Dynamik und der Hyperfeinwechselwirkungen (elektrischer
Feldgradient) in einer Submonolage von Eisen auf Wolframsubstrat
genutzt. Die Relaxation des elektrischen Feldgradients führte zur Bestimmung
des Diffusionskoeffizienten. Es ergibt sich eine überraschend
niedrige Aktivierungsenergie.
Unterstützt durch: FWF (P-15421), bm:bwk (GZ45.529/2-VI/B/7a/
2002), ÖAD BWTZ.
O 6.5 Mo 12:15 H45
Kohärente Röntgenbeugung (XPCS) an Oberflächen mit weisser
Strahlung — •Tobias Panzner 1 , W. Leitenberger 1 , J.
Grenzer 1 , K. Morawetz 1 , U. Pietsch 1 und H. Möhwald 2 —
1 Institut für Physik, Universität Potsdam, 14415 Potsdam, Deutschland
— 2 MPI für Kolloid- und Grenzflächenforschung, 14476 Potsdam-Golm,
Deutschland
In den letzten Jahren hat sich die kohärente Röntgenstreuung als
zerstörungsfreie Methode zur Messung der Dynamik an Oberflächen etabliert.
Unter Ausnutzung der Energieabhängigkeit des Streuvektors wurde
im letzten Jahr an der energie-dispersiven (EDR)-Beamline bei BES-
SY II eine Reflektionsanordung zur Messung von Speckle-Pattern an rauhen
Oberflächen etabliert. Der von einem Ablenkmagneten erzeugte weiße
Strahl liefert eine nutzbare Intensität im Energiebereich zwischen 5-
20 keV. Erste Beugungsexperimente an Lochblenden mit Durchmessern
zwischen 5 und 50 µm sowie Lochpaaren erlaubten die energieabhängige
Messung der transversalen Kohärenzlänge (ca. 35µm bei 6 keV) sowie
die Bestimmung der virtuellen Quellgrösse.
Statische Reflektionsexperimente mit kohärenter weißen Strahlung an
verschiedartigen Probenoberflächen (organischer Film auf Si, Al-Schicht
auf Si, Au auf Si) lieferten ortsabhängig stark variierende Reflexionskurven
(Specklemuster), die sich zu normalen Parratschen Reflektionskurven
aufsummieren ließen. Durch Wahl des Einfallswinkels lassen sich die erhaltenen
Specklemuster entweder der räumlichen Fluktuation der Materialdichte
im Inneren der Filme oder der Rauhigkeit der Probenoberfläche
zuordnen.
O 7 Hauptvortrag Bansmann
O 6.6 Mo 12:30 H45
Verteilung atomarer Ensembles in PdCu-Filmen auf Ru(0001)
— •Eleonora Filonenko, Barbara Richter, Harry Hoster,
Hubert Rauscher und R. J. Behm — Abt. Oberflächenchemie und
Katalyse, Universität Ulm, 89081 Ulm
Als Grundlage für die Charakterisierung der Chemie bimetallischer Pd-
Cu Katalysatoren wurde das Mischungsverhalten in bimetallischen Pd-
Cu Monolagenfilmen auf Ru(0001) mittels hochauflösendem STM untersucht.
Filme mit unterschiedlichen Pd/Cu Verhältnissen wurden durch
sequenzielles Aufdampfen von Pd und Cu oder Cu und Pd und anschließendes
Tempern präpariert. Die statistische Auswertung atomar
aufgelöster STM-Bilder mit chemischem Kontrast zeigt klare Abweichungen
der atomaren Verteilung von einer Zufallsverteilung, mit deutlicher
Präferenz für Pd-Cu Nachbarn gegenüber Pd-Pd und Cu-Cu. Dies hat
Konsequenzen auf die Ensemblegrößenverteilung. Die Ergebnisse werden
mit dem Verhalten anderer bekannter PdCu-Systeme wie PdCu3 oder Pd
auf Cu(111) verglichen. Auswirkungen auf die Zahl aktiver Zentren und
das katalytische Verhalten werden diskutiert.
O 6.7 Mo 12:45 H45
Surface phase diagram of the CoAl(100) surface — •Ole Wieckhorst
1 , Stefan Müller 1 , Lutz Hammer 1 , Klaus Heinz 1 , Ralph
Drautz 2 und Manfred Fähnle 2 — 1 Universität Erlangen-Nürnberg,
Lehrstuhl für Festkörperphysik, Staudtstr. 7, 91058 Erlangen — 2 Max-
Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart
For ideal bulk stoichiometry, the (100)-surface of B2-ordered Co-Al
shows a termination by the Al-sublattice. However, a tiny surplus of Coatoms
in the bulk leads to the segregation of these so called anti-site
atoms to the (100)-surface [1]. We use a combination of density functional
theory with cluster expansions and Monte-Carlo simulations to study
not only the local atomic structure of these antisites, but also temperature
dependent short-range order phenomena at the surface. This leads
to the construction of a phase diagram of the near surface layers. The
stable structures predicted are in excellent agreement with those received
from LEED structure determinations. (supported by DFG)
[1] V. Blum et al., Phys. Rev. Lett. 89, 266102 (2002)
O 6.8 Mo 13:00 H45
Legieren und Entmischen nichtmischbarer Metalle in dünnen
Filmen: Co,Ag/Ru(0001) — •Moritz Becker, Hubert Zajonz
und Helmut Dosch — MPI für Metallforschung, Heisenbergstr.3,
70569 Stuttgart
Binäre Legierungen, die im Volumen nicht realisierbar sind, können
als zweidimensionale Systeme verwirklicht werden, welche neue katalytische
und magnetische Grenzflächeneigenschaften aufweisen können.
Ein bekanntes Beispiel hierfür sind dünne Ag-Co Legierungsfilme auf
Ru(0001). Wir haben insitu Röntgendiffraktionsexperimente an diesem
System durchgeführt und ein unerwartetes thermodynamisches Verhalten
beobachtet. Die Experimente und Ergebnisse werden diskutiert.
Zeit: Montag 14:00–14:45 Raum: H36
Hauptvortrag O 7.1 Mo 14:00 H36
Magnetism of mass-filtered nanoparticles on ferromagnetic supports
— •Joachim Bansmann — Fachbereich Physik, Universität Rostock,
Universitätsplatz 3, D-18051 Rostock
The magnetic properties of 3d-metal clusters significantly differ from
bulk behavior. In small clusters with less than 500 atoms the magnetic
moments are enhanced and strongly depend on the number of atoms within
each cluster. Such phenomena are caused by a narrowing of electronic
states and the high ratio of surface to bulk giving rise to large magnetic
orbital moments. However, even large Fe nanoparticles on cobalt with up
to 100.000 atoms per cluster showed enhanced orbital moments.
Here, I will report on results obtained from element-specific X-ray Magnetic
Circular Dichroism (XMCD) studies at mass-filtered Fe and FeCo
alloy clusters (6 - 12nm) deposited onto ferromagnetic surfaces. At a low
coverage XMCD data for large iron clusters on a cobalt film display enhanced
orbital moments with nearly a doubled value when compared to
bulk behaviour. With increasing coverage, the orbital moment is clearly
reduced. The data are compared to much smaller iron clusters.
Moreover, Fe0.5Co0.5 alloy clusters on a nickel substrate have been investigated.
According to the Slater-Pauling curve, FeCo alloys exhibit
the highest magnetic moments for soft magnetic materials. When searching
materials with even higher saturation magnetizations, FeCo alloy
clusters might be ideal candidates. The spin and orbital moments of iron
and cobalt in FeCo nanoparticles with sizes of 6nm and 7.5nm have been
determined. Enhanced orbital moments may play the dominant role
although their contributions are smaller than the spin moments.

Oberflächenphysik Montag
O 8 Hauptvortrag Bode
Zeit: Montag 14:45–15:30 Raum: H36
Hauptvortrag O 8.1 Mo 14:45 H36
Spin-polarized scanning tunneling microscopy: From nanomagnetism
to the spin-resolved bandstructure — •M. Bode 1 , K.
von Bergmann 1 , A. Kubetzka 1 , O. Pietzsch 1 , R. Wiesendanger
1 , M. Heide 2 , and S. Blügel 2 — 1 Institut für Angewandte Physik,
Universität Hamburg, Jungiusstr. 11, 20355 Hamburg — 2 Institut für
Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich
In recent years spin-polarized scanning tunneling microscopy (SP-
STM) has been developed to become a powerful method with a focus
on high-resolution imaging of domain structures of (anti)ferromagnetic
surfaces and nanostructures[1]. This traditional field of application will
be exemplified by data measured on ferro- and superparamagnetic Fe
islands.
O 9 Rastersondentechniken I
Furthermore, scanning tunneling spectroscopy (STS) allows the imaging
of the spatial distribution of the electronic density of states close to
the Fermi level. Wherever the translational invariance of the surface is
disturbed, the superposition of incoming and reflected electron wave functions
leads to interference patterns, which contains information about the
life time and the dispersion relation of the electronic states involved[2].
Experiments performed with magnetic probe tips on a magnetic surface
show a striking dependence of the intensity of the interference pattern
on the relative magnetic orientation of tip and sample. This allows the
direct identification of the spin-character of the electronic states involved
in the scattering process.
[1] M.Bode, Rep. Prog. Phys. 66, 523 (2003)
[2] J.Kliewer, R.Berndt, and S.Crampin, New J. Phys. 3, 22 (2001)
Zeit: Montag 15:45–18:30 Raum: H36
O 9.1 Mo 15:45 H36
Three-dimensional force fields of single wall carbon nanotubes
by scanning dynamic force spectroscopy — •Makoto Ashino 1 ,
Timo Behnke 1 , Alexander Schwarz 1 , Keith A. Williams 2 , Cees
Dekker 2 und Roland Wiesendanger 1 — 1 Institute of Applied Physics,
University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
— 2 Department of Applied Physics and DIMES, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
We measured three-dimensional (3D) force fields above single wall carbon
nanotubes (SWNTs) in ultra-high vacuum by scanning dynamic force
microscopy and spectroscopy at low temperature (< 12 K). The 3D
force field measurement was based on the systematic recording of the
frequency shift of the cantilever oscillation, caused by the tip−sample
interaction [1]. The atomic-resolution carbon lattice images were obtained
in noncontact mode observation before and after the 3D force field
measurement. The image contrast of the carbon lattice in SWNTs was
different from that in the graphite (HOPG). We analyzed the spatial
distribution of the force between tip and surfaces of individual SWNTs
and a SWNT bundle in terms of long- and short-range contribution to
the tip-sample interaction. On the basis of this analysis, we will discuss
the adsorption sites of other molecules on to the surfaces of individual
SWNTs and SWNT bundles.
[1] H. Hölscher et al., Appl. Phys. Lett. 81, 4428 (2002).
O 9.2 Mo 16:00 H36
Untersuchung der Volumen-Bandstruktur von Nb mittels Rastertunnelspektroskopie
— •Berndt Koslowski, Christof Dietrich
und Paul Ziemann — Abt. Festkörperphysik, Universität Ulm
Die Volumen-Bandstruktur von Nb wurde mittels Rastertunnelspektroskopie
auf Nb(110) untersucht. Zur Anwendung kamen sowohl die
herkömmliche I-V -Spektroskopie als auch die selten benutzte Z-V -
Spektroskopie. Letztere erweitert den adressierbaren Energiebereich auf
±5 eV. In diesem Bereich können viele Signaturen in der experimentell
bestimmten lokalen Zustandsdichte gefunden werden, die sich kritischen
Punkten der Volumenbandstruktur von Nb zuordnen lassen.
Wir vergleichen unsere Ergebnisse mit Bandstruktur-Rechnungen und
mit Ergebnissen aus der Photoemissionsspektroskopie. Die gefundene
Übereinstimmung ist bemerkenswert.
O 9.3 Mo 16:15 H36
Bau eines kostengünstigen UHV-STM von Studierenden im
Fortgeschrittenenpraktikum — •T.-Y. Kim, J. Grabowski, L.
Amsel, F. Bechtel, N. Tschirner, I. Mantouvalou, F. Streicher,
S.K. Becker, A. Lenz, R. Timm, K. Hodeck, G. Pruskil,
H. Eisele und M. Dähne — Technische Universität Berlin, Institut für
Festkörperphysik, Hardenbergstr. 36, 10623 Berlin
Seit der Erfindung der Rastertunnelmikroskopie (STM) 1981 ist sie die
wichtigste Methode zur Charakterisierung von Halbleiter- und Metalloberflächen
mit atomarer Auflösung im Realraum geworden. Da finanzielle
Mittel in den Praktika relativ gering sind, ist es kaum möglich diese mit
kommerziellen Geräten auszustatten und Studierenden moderne Messmethoden
wie die Rastertunnelmikroskopie nahe zu bringen.
Wir zeigen, wie man innerhalb eines Semesters mit sechs Physikstudierenden
im Fortgeschrittenenpraktikum ein STM mit begrenzten finanziellen
Mitteln aufbaut. Das STM sollte in der Lage sein, atomar aufgelöste
Messungen an Siliziumoberflächen durchzuführen.
Die Studierenden arbeiteten zeitlich nacheinander in drei Teilprojekten,
welche jeweils vier Wochen dauerten. Die erste Gruppe entwickelte
das Dämpfungssystem, welches das STM von der Umgebung abkoppelt,
und setzte die UHV-Kammer in Betrieb. Die zweite Gruppe konstruierte
den Walker mit Trägheitsmotor und eingebautem Rasterkopf sowie
die Probenhalter für das STM. Die dritte Gruppe baute den UHV-
Vorverstärker und vollendete die restlichen Arbeiten. Nach einer erfolgreichen
Inbetriebnahme des STM mit Goldspitze auf Goldprobe an Luft
wurde mit einer Wolframspitze auf Silizium gemessen.
O 9.4 Mo 16:30 H36
Anisotropy of bulk band structure observed by electron scattering
at subsurface impurities in Ag(111) — •A. Weismann, M.
Wenderoth, N. Quaas, and R. G. Ulbrich — IV. Phys. Institut,
Universität Göttingen, D-37075 Göttingen
Dilute magnetic alloys, prepared by co-deposition of Co and Ag on
a Ag(111)-Surface (0,4% Co), are investigated by means of Scanning
Tunnel Microscopy (STM) and spatially resolved Scanning Tunnel Spectroscopy
(STS) at 8K. Single impurities lying shallow below the surface
emerge in atomically resolved (111) surface topographies as complex
structures on different length scales. By means of Fourier-transformed
STM different scattering mechanisms can be extracted. Apart from the
atomic lattice we observe the well known radially symmetric oscillations
of the surface state. Additional oscillations with a much shorter wavelength
and triangular shape can be observed. We attribute this pattern
to the scattering of bulk electrons. The observed threefold symmetry reflects
the symmetry of the fcc - Brillouinzone in (111)-direction. This
work is supported by the DFG, SFB 602.
O 9.5 Mo 16:45 H36
Optischer Nahfeldkontrast in anisotropen Dielektrika —
•Susanne Schneider, Christian Loppacher, Ulrich Zerweck,
Stefan Grafström und Lukas Eng — Institut für Angewandte
Photophysik, TU Dresden, 01062 Dresden
Die aperturlose Nahfeldmikroskopie (s-SNOM) basiert auf der Wechselwirkung
zwischen einem optisch streuenden Nanocluster (AFM-Spitze)
und der zu untersuchenden dielektrischen Probe. Hierbei bestimmt die
Größe des Clusters die erreichbare Auflösung des Mikroskops, welche im
nm-Bereich liegt. Auf dieser Skala müssen die optisch anisotropen Eigenschaften
der Probe mit berücksichtigt werden, selbst wenn sich diese
makroskopisch gesehen isotrop verhält.
Dieser Beitrag diskutiert anhand des analytischen Dipol-Dipol-Modells
die Wechselwirkung zwischen einem Cluster und einer anisotropen Probe.
So zeigt sich z.B. für den im s-SNOM gemessenen Bildkontrast zwischen
verschiedenartigen Domänen des ferroelektrischen Perowskits BaTiO3,
dass gegenüber dem bekannten Spiegelladungsproblem in isotropen Dielektrika
eine zusätzliche Spiegelflächenladung im Bulk des Ferroelektrikums
angenommen werden kann, welche die Asymmetrie der Dielektri-

Oberflächenphysik Montag
zitätskonstanten widerspiegelt.
O 9.6 Mo 17:00 H36
Warum die ”shear force” Distanzregelung auch im UHV funktioniert
— •S. Hoppe, G. Ctistis, J.J. Paggel und P. Fumagalli
— Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee
14, 14195 Berlin
Die Messung der Kräfte, zwischen einer lateral oszillierenden Spitze
und der Substratoberfläche ist eine gängige Methode die Abstandskontrolle
eines Nahfeldmikroskops zu realisieren. Diese Methode gehört zwar
zum Standard, jedoch ist die Natur der Wechselwirkung weitgehend unbestimmt.
Obwohl die Spitze bei Messungen im Ultrahochvakuum in mechanischem
Kontakt zur Probe zu sein scheint, ist keine Beschädigung
der Probenoberfläche erkennbar. Die Kombination aus sogenannten Distanzkurvenmessungen
und Strommessung bietet die Möglichkeit, die
Wechselwirkung zwischen Probe und Spitze genauer zu untersuchen.
Mit Hilfe des Modells des harmonischen Oszillators werden Feder- und
Dämpfungskonstante bestimmt. Durch Messung des elektrischen Kontaktes
kann der Punkt der Probenberührung identifiziert werden. Die
Messungen wurden an metallischen Oberflächen durchgeführt. Diese Arbeit
wurde unterstützt durch die Deutsche Forschungsgemeinschaft im
Rahmen des SFB 290.
O 9.7 Mo 17:15 H36
Study of particle-substrate interaction by nanomanipulation experiments
with dynamic scanning force microscopy — •Claudia
Ritter 1 , Markus Heyde 2 , and Klaus Rademann 1 — 1 Humboldt-
Universität zu Berlin, Institute of Chemistry, Brook-Taylor-Str. 2, D-
12489 Berlin, Germany — 2 Fritz-Haber-Institute of the Max-Planck-
Society, Faradayweg 4-6, D-14195 Berlin, Germany
We utilise an advanced homebuilt SFM in the dynamic mode, in
conjunction with a special homebuilt software, to perform precise
nanomanipulation experiments. The corresponding experimental technique
should be denoted as Dynamic Surface Modification (DSM), comprising
both the dynamic technique of the SFM, as well as the manipulation
(translation, in-plane rotation, cutting) of structurally unchanged
particles on a given substrate surface. It is easily possible to switch between
imaging mode and DSM mode, enabling the direct manipulation
of nanoparticles under ambient conditions with high precision and simultaneously
studying particle-substrate interaction to give evidence about
motion and tribological values of the sample system. We have successfully
manipulated miscellaneous nanoparticles on surfaces, e.g. antimony
islands, gold islands, tin islands, nanotubes, small latex spheres as well
as cells.
O 9.8 Mo 17:30 H36
STM Imaging of PTCDA Multilayers with Submolecular Resolution
— •Daniel Braun, Andre Schirmeisen, and Harald
Fuchs — Physikalisches Institut and CeNTech, University of Muenster,
Wilhelm-Klemm Str. 10, 48149 Muenster, Germany
Organic semiconductors have attracted intensive research interest over
the last decade, ever since the demonstration of a low-voltage-powered
OLED [1]. Charge transport and luminescence properties are governed
by the structural properties of the thin films, like molecular aggregation,
packing and orientation [2]. Understanding and tuning the epitaxy
of large aromatic adsorbates by molecular design is a task, which has
attracted much attention in the last years [3].
We investigate the growth of the archetype molecular compound
PTCDA, a semiconducting organic molecule, using UHV-STM. On the
thin multilayer films we observe submolecular features of the PTCDA
not only from the top-layer but also from the next layer, allowing us to
study directly the quasi-epitaxial growth.
[1] C.W.Tang, S.A.VanSlyke, Appl.Phys.Lett.51 (1987) 913
[2] C.Seidel, A.Schaefer, H.Fuchs, Surf.Sci.459 (2000) 310
[3] M.Eremtchenko, J.A.Schaefer, F.S.Tautz, Nature 425 (2003) 602
O 9.9 Mo 17:45 H36
Damping mechanisms in dynamic force microscopy —
•Andre Schirmeisen, Hendrik Hölscher, and Harald Fuchs
— Physikalisches Institut und CeNTech, Universität Münster,
Wilhelm-Klemm-Str.10, 48149 Münster
Dynamic force microscopy (DFM) in ultrahigh vacuum (UHV) is a
powerful tool to measure interatomic forces with molecular resolution.
However, apart from conservative forces the DFM is also capable of measuring
dissipative tip sample interactions. A considerable dispute has
arisen, as to what the underlying physical mechanisms are for the observed
energy dissipation. Atomic instabilities, electric damping mechanisms
and even feedback artefacts have been argued to govern the dissipation.
We performed force and energy dissipation spectroscopy experiments
on HOPG in UHV, where our instrument is operated in two
different dynamic modes: The constant excitation (CE) and constant
amplitude (CA) mode. First, we show that spectroscopy measurements
from both modes yield equivalent quantitative results, which allows us
to exclude artefacts induced by the amplitude feedback system inherent
only to the CA mode. Secondly, we present a series of spectroscopy experiments
acquired with different oscillation amplitudes, which allows us
extract the velocity dependence of the dynamic friction coefficient. In
fact, we will show that the velocity dependence is negligible and we will
argue that hysteretic mechanisms based on atomic instabilities govern
the energy dissipation in our case.
O 9.10 Mo 18:00 H36
Observation of the complete graphite unit cell with a lowtemperature
atomic force microscope — •Stefan Hembacher 1 ,
Franz J. Giessibl 1 , Jochen Mannhart 1 , and Calvin F. Quate 2 —
1 Universität Augsburg, Lehrstuhl für Experimentalphysik VI, Zentrum
für Elektronische Korrelationen und Magnetismus — 2 Ginzton Laboratory,
Stanford University, Stanford CA 94305
A new helium-temperature scanning tunneling/dynamic force microscope
employing the qPlus sensor is introduced. First measurements on
HOPG (highly oriented pyrolytic graphite), where the benefits of combined
STM/AFM measurements at helium temperature are clearly evident,
are presented. At low temperatures, thermal drift is only of the
order of 25 pm/h enabling slow scanning in constant height mode. Because
the noise in ∆f measurements scales as B 3/2 , tiny forces can be
measured with good S/N ratio.
Graphite has a hexagonal structure with two atoms in the surface unit
cell. While the α-atoms have a neighbor directly underneath, the β-atoms
have no direct neighbor in the layer below the surface layer. In scanning
tunneling microscopy experiments, only the β-atoms are visible. In AFM,
with repulsive forces, both α- and β-atoms should appear. Simultaneously
recorded frequency shift and tunneling current images in constant height
mode show the α- and the β-atoms in the frequency shift channel, while
in the current channel only the β-atoms are observed.
O 9.11 Mo 18:15 H36
Atomic Force and Scanning Tunnelling Microscopy Measurements
at Low Temperatures — •Markus Heyde, Maria Kulawik,
Hans-Peter Rust, and Hans-Joachim Freund — Fritz-
Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195
Berlin, Germany
Atomic force and scanning tunneling microscopy (AFM/STM) are the
most important tools for the investigation of surfaces on the atomic scale
in real space. While the STM is sensitive to the local density of states
and requires a conductive surface, the AFM can be used also on insulating
samples. Essential for achieving atomic resolution with an AFM is
a force-detector with a low noise performance and enhanced sensitivity
to short-range forces. For a detailed analysis and interpretation of surface
structures, an image sensor with the capability to record AFM and
STM image at the same surface area is highly desirable. A double quartz
tuning fork sensor for low temperature ultra-high vacuum atomic force
and scanning tunneling microscopy is presented. The features of the new
sensor are discussed. In addition, a low temperature, low noise ac signal
amplifier has been developed to pick-up the oscillation amplitude of the
tuning fork. First atomic force measurements are shown, allowing for the
resolution of different domains on a thin Al2O3 film on NiAl(110).

Oberflächenphysik Montag
O 10 Teilchen und Cluster I
Zeit: Montag 15:45–17:45 Raum: H43
O 10.1 Mo 15:45 H43
From single particle to conducting film: percolation behaviour
of a Au colloidal thin film — •Agnes A. Mewe, E. Stefan Kooij,
Herbert Wormeester, and Bene Poelsema — Mesa+ Research Institute,
University of Twente, P.O. Box 217, NL 7500 AE Enschede
Deposition of citrate stabilized gold nanoparticles on silicon oxide is
only feasible after a suitable preparation of the substrate surface. This
surface functionalization is obtained by immersion into a solution of
amino-functionalized molecules, or locally, by microcontact printing. In
the latter case, upon immersion in a nanocolloidal Au suspension, the colloids
only adsorb on the functionalized part of the surface. The contrast
in Au colloid deposition was found to strongly depend on the specific
amino molecule used for patterning. In a final step electrical conductivity
is achieved by electroless deposition of gold or silver onto the isolated
gold nanocrystals. Spectroscopic ellipsometry is used to characterize the
thin film structures in the visible and near infrared range, thereby providing
information on their conductivity. The results exhibit the gradual
enlargement of the particles past the percolation threshold of the overall
structure.
O 10.2 Mo 16:00 H43
Messung der Dephasierungszeit des Oberflächen-Plasmon-
Polaritons in Gold-Nanoteilchen: Effekte der reduzierten
Dimension — •C. Hendrich, T. Ziegler, T. Vartanyan, F.
Hubenthal und F. Träger — Experimentalphysik I, Institut für
Physik und Center for Interdisciplinary Nanostructure Science and
Technology - CINSaT, Universität Kassel, Heinrich-Plett-Straße 40,
D-34132 Kassel
Die optischen Eigenschaften von metallischen Nanoteilchen werden von
Oberflächen-Plasmon-Resonanzen (OPR) dominiert. Die Dephasierungszeit
T2 der OPR ist ein wichtiger Parameter, da sie direkt proportional
zur Feldverstärkung in der Nähe der Teilchenoberfläche ist. Viele Techniken
zur Messung von T2 sind auf die Untersuchung einzelner großer
Partikel oder auf Teilchenensembles mit einer Größen- und Formverteilung
beschränkt. Eine von uns entwickelte lasergestützte Methode, die
auf spektralem Lochbrennen basiert, erlaubt es trotz der inhomogenen
Verbreiterung der OPR deren Breite und damit T2 zu bestimmen [1]. Für
Gold-Nanoteilchen haben wir T2 in Abhängigkeit der Plasmonenergie gemessen.
Bei Nanoteilchen mit Radien unterhalb von 10 nm treten deutlich
größere Dämpfungen auf als von sie in der dielektrischen Funktion des
Gold-Festkörpers enthalten sind. Bei festgehaltener Plasmonenergie von
1.85 eV wurde daher das größenabhängige Verhalten der Dephasierungzeit
untersucht. Chemische Dämpfung und Oberflächenstreuung konnten
als Ursache für die Verkürzung der Dephasierungszeit identifiziert werden.
[1] J. Bosbach, C. Hendrich, F. Stietz, T. Vartanyan, F. Träger, Phys.
Rev. Lett. 89, 257404 (2002)
O 10.3 Mo 16:15 H43
Oxidation von Ni-Nanopartikeln — •Alexander Reinholdt 1 ,
Andrey L. Stepanov 2 , Thomas E. Weirich 3 und Uwe Kreibig 1
— 1 I. Physikalisches Institut 1A, RWTH Aachen — 2 Institut für Experimentalphysik,
Karl-Franzens-Universität Graz — 3 Gemeinschaftslabor
für Elektronenmikroskopie, RWTH Aachen
Ferromagnetische Nickel-Nanopartikel, deren mittlerer Teilchendurchmesser
≥ 5nm ist, wurden durch Laserverdampfung und adiabatische
Expansion an der Nanopartikelstrahlanlage LUCAS hergestellt.
Diese Teilchen wurden in-situ schrittweise oxidiert und der Oxidationsvorgang
wurde elektronenmikroskopisch kontrolliert. Die EFTEM-
Aufnahmen zeigen die Ausbildung einer NiOx-Hülle, die einen Ni-Kern
umschließt.
Die Erzeugung solcher Oxidhüllen ist von Interesse (a) für die Untersuchung
des teilchengrößenabhängigen Übergangs zum Superparamagnetismus
(unter Einfluss des NiOx) und (b) zur Stabilisierung der Teilchen
für eine mögliche Verwendung in Ferrofluids.
In diesem Vortrag werden sowohl die Ergebnisse der Materialanalyse
der oxidierten Nickelteilchen als auch erste magnetische Untersuchungen
präsentiert.
O 10.4 Mo 16:30 H43
Quenching of surface magnetic moments in rare gas isolated
Ni clusters — •Kai Fauth 1,2 , Markus Heßler 1,2 und Gisela
Schütz 2 — 1 Physikalisches Institut der Universität Würzburg, Am Hubland,
97074 Würzburg — 2 MPI für Metallforschung, Heisenbergstraße 3,
70569 Stuttgart
X-ray magnetic circular dichroism (XMCD) is a method well suited for
the element specific analysis of magnetic moments in transition metals.
The XMCD technique allows their quantitative analysis in terms of spin
and orbital contributions. The application of XMCD to small clusters
is only possible if these are deposited on a substrate. Their deposition
into rare gas matrices is the best possible approximation to noninteracting
clusters. While this approach is succesful in the case of Fe and Co
clusters, we show here that the same is not true in the case of small Ni
clusters. The observed magnetizations are by far smaller than expected.
Their size dependence suggests a quenching of the magnetic Ni moments
to occur at the cluster surface, induced by the presence of the Ar environment.
Similar results were theoretically obtained previously for Ni
clusters encapsulated by a He shell [1].
[1] G. Pacchioni, S. C. Chung, S. Krüger and N. Rösch, Chem. Phys.
184, 125 (1994)
O 10.5 Mo 16:45 H43
Photon Emission Spectroscopy on Individual Oxide-Supported
Ag-Au Alloy Clusters — •W. Benten, N. Nilius, N. Ernst,
and H.-J. Freund — Fritz-Haber-Institut der Max-Planck-Gesellschaft,
Faradayweg 4-6, 14195 Berlin
Intermixing of different metals to small bimetallic particles causes distinct
changes in physical and chemical properties. Since plasmon-induced
light emission is sensitive to the composition of the alloy particles, optical
emission spectroscopy can be used to determine details of the alloying
process. We have combined photon emission spectroscopy with scanning
tunnelling microscopy to analyse optical properties of individual Ag-Au
clusters deposited on a thin Al2O3 film on a NiAl (110) substrate. For
pure Ag and Au clusters, we measured well-defined photon emission peaks
at around 320 nm and 510 nm, respectively, attributed to Mie-plasmon
excitations. After mixing of both materials, intermediate photon emission
peaks are observed indicating the formation of alloy clusters on the surface.
Peak positions and widths are examined for different composition
and compared with theoretical predictions based on Mie-theory.
O 10.6 Mo 17:00 H43
Nanostrukturen aus monodispersen Clustern: Herstellung und
Eigenschaften — •B. Stegemann 1,2 , B. Kaiser 1 , K. Rademann 1 ,
T. Gleitsmann 2 , T. M. Bernhardt 2 und L. Wöste 2 — 1 Institut für
Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, D-12489
Berlin — 2 Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee
14, D-14195 Berlin
Cluster können völlig neuartige Eigenschaften aufweisen, die sich gezielt
über die Anzahl ihrer konstituierenden Atome steuern lassen. Die
kontrollierte Deponierung monodisperser Cluster auf einem Substrat
eröffnet somit neue Wege des Designs technologisch interessanter, nanostrukturierter
Materialien, die charakteristische Eigenschaften der Ausgansgcluster
aufweisen.
Ein gut geeigneter Modellcluster für das Studium grundlegender Cluster/Oberfläche-Wechselwirkungsphänomene
stellt Sb4 dar. Es wird gezeigt,
daß eine intakte Deponierung von Sb4-Clustern aus der Gasphase
sowie ein lagenweises Wachstum und die spontane Anordnung zu periodischen
dreidimensionalen Cluster-Kristallen erreicht werden kann.
Darüber hinaus werden Ergebnisse zum Fluoreszenzverhalten und zur
elektronischen Struktur deponierter, monodisperser Silbercluster vorgestellt
und deren Potential für den Einsatz in neuartigen optischen Datenspeichern
diskutiert.
O 10.7 Mo 17:15 H43
Molecular dynamics simulations of self-sputtering of silver under
bombardment with Ag4 projectiles — •Andreas Duvenbeck
and Andreas Wucher — Institut für experimentelle Physik, Universität
Duisburg-Essen, 45117 Essen
The self-sputtering of a Ag(111) surface with Ag4 projectiles has been
investigated by classical molecular dynamics (MD) simulations using the

Oberflächenphysik Montag
many body MD/MC-Corrected Effective Medium potential developed by
De Pristo et al. The calculation of a set of several thousands of trajectories
in the energy range from 1 − 8keV has been carried out for a
microscopic study of nonlinear yield enhancements that have been observed
in recent polyatomic sputtering experiments. We will show that
the application of Ag4 instead of monoatomic silver projectiles at the
same impact velocity, i.e the same energy per projectile atom, leads to
an exponential yield enhancement as a function of the impact velocity.
A detailed analysis of the kinetic energy transfer processes during the
spatial and time evolution of the collision cascade shows that this phenomenon
cannot only be explained by a higher energy density at the
surface due to the strongly localized overlap of collison cascades.
O 10.8 Mo 17:30 H43
Leitfähigkeitsuntersuchungen an freien Silber-Nanodrähten —
•Dieter Wagner 1 , Andreas Graff 2 und Uwe Kreibig 1 — 1 I. Physikalisches
Institut 1A, RWTH Aachen, 52056 Aachen — 2 MPI für Mikrostrukturphysik,
06120 Halle
Es wurden auf chemischem Wege Silber-Nanodrähte hergestellt, an
denen elektrische Leitfähigkeitsmessungen durchgeführt wurden. Diese
Drähte können mit Durchmessern zwischen 15 und 80 nm, und Längen
bis 60 000 nm präpariert werden. Durch TEM-Analysen wurden einkristalline
Struktur und Oberfläche der Drähte eingehend untersucht.
Elektronische Eigenschaften solcher Drähte mit Durchmessern auf der
Nanometerskala weichen erheblich von den Eigenschaften dickerer Drähte
ab. Um den Einfluss von Einbettmedien bzw. Substrat während der elektrischen
Messungen auszuschliessen, war es notwendig, daß die Drähte
freitragend sind. Es werden Ergebnisse vorgestellt die unter angelegtem
äußeren Magnetfeld (≤ 1T) und bei tiefen Temperaturen (∼ 4, 2 K) gewonnen
wurden .
O 11 Elektronische Struktur (Experiment und Theorie) I
Zeit: Montag 15:45–18:30 Raum: H44
O 11.1 Mo 15:45 H44
Electronic Structure Dependence of the Electron-Phonon Interaction
in Ag — •Jens Paggel 1 , Dah-An Luh 2 , Tom Miller 3 ,
and Tai-Chang Chiang 3 — 1 Freie Universität, Institut für Experimentalphysik,
14195 Berlin — 2 Stanford Linear Accelerator Center, Menlo
Park, CA 94015 (USA) — 3 Department of Physics, University of Illinois
at Urbana-Champaign, Urbana, IL 61801 (USA) and Frederick Seitz Materials
Research Laboratory, University of Illinois at Urbana-Champaign,
Urbana, IL 61801 (USA)
The line widths of sp- and d-band derived electronic quantum well
states in thin films of Ag on Fe(100) are measured as a function of temperature
to yield the electron-phonon coupling parameters. The results
vary by a factor of up to 35 among the different states. The origin of
these huge differences is traced to the decay path selection for the various
initial states of the holes created by the photoemission process. The
electron-phonon coupling parameter for the top d-band quantum well
state, 0.015 ± 0.006, is the smallest ever reported.
Supported by the US National Science Foundation, the Petroleum Research
Fund of the American Chemical Society, the US Department of
Energy, and the Deutsche Forschungsgemeinschaft.
O 11.2 Mo 16:00 H44
Electron phonon coupling and electron correlations in the adsorbate
system Cu(100)c(2x2)N — •Thordis Michalke, Jürgen
Hager, and René Matzdorf — Institut für Physik, Universität Kassel
We investigated the self organized nanopatterned surface of nitrogen
covered Cu(100) by means of photoelectron spectroscopy (PES), scanning
tunneling microscopy (STM) and spectroscopy (STS).
With STS we imaged the local density of states of certain eigenstates in
the 5x5 nm 2 islands. The quasi particle lifetime of these states was measured
in dependence of their quantum number, and the effective mass
has been determined to be m ⋆ =1.1 m0.
In photoelectron spectra one can observe several adsorbate induced
states. Temperature dependent measurements show that these two dimensional
states couple strongly to phonons. The mass enhancement
factor was calculated with the Einstein model and known phonon energy
of 40 meV to be between λ = 0.5 and λ = 1.4 for different states. One
of the adsorbate states shows exceptional behaviour when approaching
the Fermi energy. Here the band renormalization due to electron phonon
coupling may be visible.
O 11.3 Mo 16:15 H44
Global electronic structure and charge-density-wave mechanism
in 2H-TaSe2 — •Kai Rossnagel 1,2 , Eli Rotenberg 1 , N.V. Smith 1 ,
O. Seifarth 2 , and L. Kipp 2 — 1 Advanced Light Source, Lawrence
Berkeley National Laboratory, Berkeley, CA 94720, USA — 2 Institut
für Experimentelle und Angewandte Physik, Universität Kiel, D–24098
Kiel, Germany
The simple layered charge-density-wave system 2H-TaSe2 has received
renewed interest recently because it may share important physical properties
with the high-temperature superconducting cuprates, such as quasi-
two-dimensionality, qualitatively similar resisitivity curves and optical
responses, saddle bands close to the chemical potential, and a possible
correlation between the opening of a gap on parts of the Fermi surface
and the occurence of a strong energy renormalization on ungapped parts.
We present here a detailed angle-resolved photoelectron spectroscopy
study of the near-EF electronic structure of 2H-TaSe2, focusing on Fermi
surface topology, energy gaps, and band renormalization effects. Our results
provide important clues as to the similarities to the electronic structure
of cuprates and the origin of the still-debated charge-density-wave
mechanism in 2H-TaSe2.
The experiments were carried out at the Electronic Structure Factory
at beamline 7 of the Advanced Light Source in Berkeley. K.R. gratefully
acknowledges support by the Alexander von Humboldt Foundation. Work
at the University of Kiel is supported by DFG Forschergruppe FOR 353.
O 11.4 Mo 16:30 H44
The electronic structure of Pb films on Si(111) — •Ad Ettema 1 ,
Anton Mans 1 , Hugo Dil 2 , JeongWon Kim 2 , and Karsten
Horn 2 — 1 TUDelft (NL) — 2 Fritz Haber Institute, Berlin
The Pb/Si(111) system shows a rich variety of interesting physical
properties and phenomena, such as the magic height of islands, vertical
Friedel oscillations [1] , a competition between classical and quantum mechanical
effects in the shape relaxation [2], anomalous optical absorption
[3] and anomalous behaviour in the Hall effect as a function of thickness.
In this contribution we present the results of photoemission experiments
carried out at the synchrotron radiation facilities of MAX-lab
in Lund (Sweden) and BESSY in Berlin. The results show an anomalously
large in-plane effective mass of the 2D quantum well state bands,
whereas the original bulk band has a strong dispersion and a free electron
behaviour. Moreover, band structure calculations for bulk and thin
film slabs predict bands with predominantly free electron character. Our
analysis suggests that this phenomenon may be due to a strong electron
correlation effect in the 2D bands of the Pb quantum well states.
[1] W.B. Jian, W.B. Su, C.S. Chang and T.T.Tsong, Physical Review
Letters 90, 6603 (2003). [2] H Okamoto, D. Chen, T. Yamada , Physical
Review Letters 89, 6101 (2002). [3]M Jalochowski et al, Physical Review
B 66, 205417 (2002).
O 11.5 Mo 16:45 H44
Sub-Monolayer growth of Pb on Ag(111) — •Gero Wittich,
Lucia Vitali, Peter Wahl, M. Alexander Schneider, Christian
Ast, Lars Diekhöner und Klaus Kern — Max-Planck-Institut
für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
The growth of ultrathin Pb films deposited on Ag(111) surfaces is studied
by low temperature scanning tunneling microscopy (STM). Pb is
known to form surface alloys with e.g. Cu although it is immiscible with
noble metals in the bulk. In the system Pb/Ag(111) we observe, that the
Pb atoms are incorporated in the first Ag layer and repel each other.
With increasing coverage a long range ordered ( √ 3 x √ 3 )R30 ◦ surface
alloy forms. Above 0.3 monolayers, dealloying starts and hexagonal clo-

Oberflächenphysik Montag
se packed Pb regions, showing a moiré pattern, coexist with the surface
alloy phase.
We discuss the formation of these phases as well as the electronic properties
of this system, investigated by means of scanning tunnelling spectroscopy
(STS).
O 11.6 Mo 17:00 H44
Quantum well states and their influence on layer restructuring
in Pb/Cu(111) — •Hugo Dil 1 , JeongWon Kim 1 , Shubha Gokhale
2 und Karsten Horn 1 — 1 Fritz-Haber-Institut der MPG, 14195 Berlin
— 2 Indira Gandhi National Open University, New Delhi, India
Quantum well states in thin metal films, arising from one-dimensional
confinement of the conduction electrons, may have a profound influence
on their physical properties. Quantum well states may induce preferred
magic heights in thin film growth, and this has been observed several
systems. We have studied the electronic structure of Pb layers on
Cu(111) grown under different conditions, using angle-resolved photoelectron
spectroscopy. Our results for Pb films deposited at 100 K show
a series of well-resolved peaks in the s-p-derived valence band near the
Fermi level, the energy and intensity of which evolve in a complex manner
with Pb deposition. These data are analysed in terms of the phase
accumulation model, shown to account for quantum well states in a large
number of systems. Upon annealing, the layers undergo a restructuring,
and preferred layer height emerge as shown by their quantum well spectrum
signature. We interpret this process in terms of electronic energy
minimization.
O 11.7 Mo 17:15 H44
First Principles Study of Lead Surfaces — •Dengke Yu and
Matthias Scheffler — FHI der MPG, Berlin-Dahlem
Motivated by recent experimental work [1] and hitherto conflicting
theoretical results of various groups, we studied the surface energies
(and other properties) of Pb(111), Pb(100), and Pb(110) surfaces using
density-functional theory. All numerical parameters and approximations
are carefully checked, as for example the plane-wave cutoff, k-mesh
density, slab thickness, and non-linearity of the core-valence exchangecorrelation
interaction. Using local-density approximation the surface energies
(absolute and relative numbers) are found to be in excellent agreement
with recent experimental results. However, for the generalized gradient
approximation deviations from experimental results are significant.
All three surfaces are found to exhibit a pronounced first-layer contraction,
followed by a damped oscillatory multilayer relaxation. Our data are
consistent with previous low energy electron diffraction analysis. Based
on the calculated surface energies we predict a bilayer growth mode for
the thin film growth of Pb(100) and Pb(111) on a nonmetallic substrate.
For Pb(111) this has been indeed seen in recent experimental studies.[2]
[1] C. Bombis, A. Emundts, M. Nowicki, H. P. Bonzel, Surf. Sci. 511,83
(2002)
[2] M. Hupalo and M. C. Tringides, Phys. Rev. B, 65, 115406 (2002)
O 11.8 Mo 17:30 H44
Structure and dynamics of ultra-thin Ag films on Au(111) —
•Dunja Popović 1 , F. Forster 1 , V. Grigorian 2 , M. Springborg 2 ,
F. Reinert 1 , S. Hüfner 1 , H. Cercellier 3 , Y. Fagot-Revurat 3 ,
B. Kierren 3 , and D. Malterre 3 — 1 FR 7.2 Experimentalphysik, Universität
des Saarlandes, 66041 Saarbrücken — 2 FR 8.13 Physikalische
Chemie, Universität des Saarlandes, 66041 Saarbrücken — 3 Laboratoire
de Physique des Matériaux, Université Henri Poincaré, Nancy I - B.P.
239 F-54506 Vandœuvre-lès-Nancy
Epitaxial Ag ultra-thin films grown on Au(111) have been studied
by angle-resolved photoemission spectroscopy (ARPES). High resolution
measurements on Au(111) reveal the splitting of the dispersive surface
Shockley band in two spin-orbit contributions. Surface states corresponding
to completed Ag monolayers are analysed with respect to their band
minima and spin-orbit splitting and compared with the results of slablayer
band-structure calculations. Interdiffusion is found to play a significant
role in the formation of the first monolayer. Moreover, it has
been shown by ARPES that low deposition temperatures lead to poorly
defined surface states of the overlayer, whereas scanning-tunneling microscopy
revealed that post-annealed films grown at room temperature
show no sharp interface but an alloy formation.
O 11.9 Mo 17:45 H44
Spin polarization of the L-gap surface states on Au(111) —
•Jürgen Henk, Arthur Ernst, and Patrick Bruno — MPI für
Mikrostrukturphysik, Halle (Saale), Germany
The electron spin polarization (ESP) of the L-gap surface states
on Au(111) is investigated theoretically by means of first-principles
electronic-structure and photoemission calculations. The surface states
show a large spin-orbit induced in-plane ESP which is perpendicular to
the in-plane wavevector, in close analogy to a two-dimensional electron
gas with Rashba spin-orbit interaction. The surface corrugation, i.e., the
in-plane asymmetry of the surface potential in the (1 ×1) unit cell, leads
to a small ESP component normal to the surface, being not reported so
far. The surface-states ESP can be probed qualitatively and quantitatively
by spin- and angle-resolved photoelectron spectroscopy, provided
that the initial-state ESP is retained in the photoemission process and
not obscured by spin-orbit induced polarization effects. Relativistic photoemission
calculations provide detailed information on what photoemission
set-ups allow to conclude from the photoelectron ESP on that of the
surface states.
O 11.10 Mo 18:00 H44
Interface states of rare gas covered noble metal surfaces —
•Frank Forster 1 , Dunja Popovic 1 , Stefan Schmidt 1 , Brigitte
Eltner 1 , Friedrich Reinert 1 , Stefan Hüfner 1 , Valeri Grigoryan
2 , and Michael Springborg 2 — 1 FR 7.2 Experimentalphysik,
Universität des Saarlandes, 66041 Saarbrücken — 2 FR 8.13 Physikalische
Chemie, Universität des Saarlandes, 66041 Saarbrücken
On the example of surfaces in (111)-direction of Cu, Ag and Au we
demonstrate that even one monolayer of physisorbed adsorbates like
Ar, Kr and Xe essentially influences the electronic structure of these
systems. Thus, angular resolved photoemission spectroscopy (ARPES)
(∆E = 3.5 meV, ∆Θ = 0.3 ◦ ) is not only able to measure subtle and
characteristic shifts of the binding energies of the L-gap Shockley states
of the substrates towards or even above the Fermi-level, but also — in the
case of Au(111) — an increase of the spin-orbit-splitting by about 30%.
Furthermore, we studied the influence of the surface reconstruction in
the case of the commensurate growth of one Xe layer on Cu(111) on the
bulk and surface states. Our results have been supported by slab-layercalculations
that also result in a detailed understanding of the electronic
processes in the adsorbate-substrate-interface.
O 11.11 Mo 18:15 H44
Surface state splitting in thin Mg films — •Frederik Schiller 1,2 ,
Vito Servedio 3 , and Clemens Laubschat 1 — 1 Institut für Festkörperphysik,
TU Dresden, D-01062 Dresden, Germany — 2 Donostia
International Physics Center, E-20018 Donostia/San Sebastian, Spain
— 3 Sezione INFM and Dip. di Fisica, Università “La Sapienza”, P. le
A. Moro 2, I-00185 Roma, Italy
Thin Mg films deposited onto a W(110) surface show a hexagonal closepacked
structure in (0001) direction. Photoemission spectra in normalemission
geometry reveal a surface state inside the Shockley-inverted
energy gap and quantum well oscillations on both sides of the gap.
We study the evolution of the surface and the quantum well states depending
on the emission direction and Mg thickness. For Mg films exceeding
12 ML, both, surface and quantum well states disperse parabolic-like
around the ¯Γ point of the surface Brillouin zone. In thinner films, however,
in off-normal geometry the surface state splits into several branches
with different effective masses. We ascribe this phenomenon to the lattice
mismatch between the Mg film and the underlying W substrate that may
lead (i) to distortions of the surface geometry and (ii) variations of the
confinement conditions at the Mg/W interface that reveal a periodicity
different from that of the Mg lattice.

Oberflächenphysik Montag
O 12 Magnetismus in reduzierten Dimensionen
Zeit: Montag 15:45–17:00 Raum: H45
O 12.1 Mo 15:45 H45
Magnetische Röntgenstreuung an lateral strukturierten
Co/CoO Filmen — •Arndt Remhof, Johannes Grabis,
Alexei Nefedov und Hartmut Zabel — Experimentalphysik/Festkörperphysik,
Ruhr-Universität Bochum
Nano- und Mikrostrukturierung von dünnen magnetischen Systemen
ermöglicht das Ummagnetisierungsverhalten, d. h. die Hystereseschleife,
gezielt zu verändern. Wir haben ein quadratisches Muster aus Co/CoO
Inseln mittels Elektronenstrahl-Lithographie hergestellt. Die Inseln haben
einen Durchmesser von 1µm und eine Periode von 3µm. Die magnetische
Hysterese wurde mit Bragg-MOKE und mit resonanter magnetischer
Röntgenstreuung (XRMS) an der Co L2,3 bei verschiedener Ordnung der
Interferenz bestimmt. Bragg-MOKE liefert eine Fourieranalyse des Magnetisierungsprofils
während des Ummagnetisierungs-prozesses. Analog
dazu liefern auch Hysteresen, die mit XRMS an verschiedenen Ordnungen
von Bragg-Reflexen gemessen werden, eine Fourieranalyse der Ummagnetisierung.
Im Vergleich zu Bragg-MOKE zeichnet sich XRMS durch
Elementspezifität und durch höhere Eindringtiefen aus. Wir präsentieren
erste Ergebnisse, die mit Bragg-MOKE und XRMS an strukturierten
Co/CoO Proben gewonnen wurden, und vergleichen die Ergebnisse.
Gefördert durch SFB 491.
O 12.2 Mo 16:00 H45
Spin effects in Coulomb blockade of Fe/MgO/Fe — •Wulf
Wulfhekel 1 , F. Zavaliche 1,2 , M. Klaua 1 , C.C. Kuo 1,3 , M.T.
Lin 1,3 , and J. Kirschner 1 — 1 MPI für Mikrostrukturphysik, Weinberg
2, 06120 Halle — 2 Departement de physique, Universite de Montreal,
Quebec H3C 3J7, Canada — 3 Department of Physics, National Taiwan
University, Taipei 106, Taiwan
The Coulomb blockade (CB) of nanometer sized Fe islands grown on
single crystalline MgO films on Fe(001) was studied using scanning tunneling
microscopy (STM) at 25 K in ultra high vacuum. After deposition
of 3-4 monolayers (ML) MgO, a sub-ML amount of Fe was deposited
leading to the formation of Fe islands on the MgO films as observed by
STM. Scanning tunneling spectroscopy was then used to locally measure
the tunneling characteristics for tunneling from the tip via the island
into the Fe substrate. The I(V) curves showed the characteristic steps of
CB. The position of the steps in the I(V) characteristics of periodicity
UC are proportional to the Coulomb charging energy e/C, where e is
the electron charge and C the islands capacitance. A plot of UC versus
e/C for the Fe islands, where C was estimated from the island size as
observed with STM, reveals a linear dependence in agreement with CB.
We, however, observe a constant and positive offset in UC by 1 eV, which
cannot be explained by spin independent tunneling. We propose a model
for spin-dependent CB, that relates the offset to the exchange the additional
electron feels in the Fe islands. No systematic offset in UC has
been found for identical experiments with Pd islands indicating that the
observed offset is related to the island material.
O 12.3 Mo 16:15 H45
Valence band electronic structure and chemical reactivity in
MgO/Fe(100) and MgO/Co/Fe(100) oxide-metal interfaces
grown on GaAs(100) — •Liu-Niu Tong 1 , Frank Matthes 1 ,
and C.M. Schneider 2 — 1 Leibniz Institut für Festkörper- und
Werkstoffforschung — 2 Institut für Elektronische Eigenschaften,
Forschungszentrum
O 13 Methodisches (Experiment und Theorie)
The interface electronic structure of MgO/Fe(100) and MgO/Co/
Fe(100) films epitaxially grown on GaAs(100) was studied by employing
spin-polarized photoemission spectroscopy (SPPES) and magnetic circular
dichroism (MCD) techniques. With increasing excitation energy from
30 eV to 60 eV, we observe an enhanced spectral intensity in the SPPES
data of pure Fe for transitions from bulk ∆ 1 and ∆ 5 initial states near
the Fermi energy that is accompanied with an increase in the detected
spin polarization. After covering the Fe(100) surface by 0.5 ML MgO,
the shape of the Fe ∆ 5 minority-spin peak becomes significantly broadened,
while the shape of the Fe ∆ 1 majority-spin peak is only weakly
affected. Additionally, we observed that 1 ML MgO on top of Fe(100)
suppresses almost all contribution from the Fe ∆ 5 minority transition in
the measured spin polarization data. This observed effect is especially
strong for an excitation energy of 40 eV. Furthermore, our MCD data
show that the O 2p peak is shifting towards the Fermi level as a function
of time after preparation, indicating a slow change in the film chemistry.
This chemical reaction can also be seen for MgO/Fe samples that were
immediately covered after preparation with an additional Fe film on top.
O 12.4 Mo 16:30 H45
X-ray magnetic circular dichroism sum rule correction for the
light transition metals — •Eberhard Goering — Max-Planck-
Insitut für Metallforschung, 70569 Stuttgart
Quantum mechanical mixing of the L2 and L3 edge excitations strongly
increases with reduced 2p spin-orbit-splitting. For a large number of
2p→3d absorption spectra the shape has been fitted nearly perfectly by a
model, which takes into account lifetime and jj-mixing effects. X-ray magnetic
circular dichroism (XMCD) sum rule correction factors have been
determined for V and Cr, which are consistent to complementary investigations.
This fitting procedure and the estimated correction factors are
the basis for a future light element XMCD effective spin renormalization
technique.
O 12.5 Mo 16:45 H45
Spin-resolved inverse photoemission with improved energy resolution
— •Michael Budke, Volker Renken, Helmut Liebl,
Georgi Rangelov, and Markus Donath — Physikalisches Institut,
Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster
Spin-resolved inverse photoemission (IPE) is a powerful tool that measures
the spin-dependend electronic structure above the Fermi level of
magnetic surfaces and thin films. We have developed a source for spinpolarized
electrons with variable energy resolution from 150 meV to 400
meV (FWHM) at currents between 0.5 µA and 5 µA on the sample. The
photon detector consists of a conventional Geiger tube filled with either
acetone or iodine [1,2]. MgF2 is used as entrance window, followed by a
SrF2- or CaF2-window. The transmission cutoff was shifted by varying
the temperature of the windows. With this arrangement the energy resolution
of the counters is continuously variable between 150 meV and 400
meV (FWHM). Depending on the experimental requirements the total
energy resolution of our IPE system can therefore be varied between 500
meV and nearly 200 meV. The latter value is an improvement of the
energy resolution by a factor of two compared to previous spin-resolved
IPE systems [3]. [1] Dose V., Appl. Phys. 14, 117 (1977) [2] Funnemann
D., Merz H., J. Phys. E: Sci. Instrum. 19, 554 (1986) [3] Dose V., Fauster
T., Schneider R., Appl. Phys. A 40, 203 (1986)
Zeit: Montag 17:00–17:30 Raum: H45
O 13.1 Mo 17:00 H45
Experimente mit kinematischen stehenden Röntgenwellen an
CaF2/Si(111) — •Martin Tolkiehn 1 , Dmitri V. Novikov 1 und
Cunrang Wang 2 — 1 HASYLAB am DESY, Notkestraße 85, D-22603
Hamburg — 2 Institut für Halbleiterbauelemente und Werkstoffe, Universität
Hannover, Appelstraße 11A, D-30167 Hannover
Die Methode der stehenden Röntgenwellen (XSW) ist sehr gut geeignet
zur Bestimmung der Position von Adsorbatatomen an Oberflächen
und Dotieratomen in perfekten Kristallen [1,2]. Sie beruht auf der Ver-
änderung der Phase des stehenden Wellenfelds in der Nähe eines Bragg–
Reflexes, die mit Hilfe der dynamischen Theorie der Röntgenbeugung
berechnet wird. Die Anwendung dieser Theorie auf nicht perfekte Kristalle
ist ohne weiteres nicht möglich. Das stehende Wellenfeld ist jedoch
auch noch bei größeren Abweichungen vom Braggwinkel vorhanden, bei
denen die kinematische Näherung gilt.
Wir zeigen theoretisch und experimentell am Beispiel CaF2/Si(111)
[3], daß sich der Bereich fern vom Bragg–Winkel zur Bestimmung der
Adsorbatposition nutzen läßt und dasselbe Ergebnis liefert wie die kon-

Oberflächenphysik Montag
ventionelle XSW–Datenanalyse.
[1] B.W. Batterman, H. Cole, Rev. Mod. Phys. 36, 681 (1964)
[2] J. Zegenhagen, Surf. Sci. Rep. 18, 202 (1993)
[3] C.R. Wang, B.H. Müller, K.R. Hofmann, Thin Solid Films 410, 72
(2002)
O 13.2 Mo 17:15 H45
Design and Construction of a Pulsed 10 keV-ps-Electron Gun —
•A. Janzen, B. Krenzer, and M. Horn-von Hoegen — Universität
Duisburg-Essen, Institut für Laser- und Plasmaphysik, 45117 Essen
Lately, there was tremendously growing success in the application of
ultrafast electron diffraction (UED). UED is becoming the up-to-date
technique to monitor time-dependent structural changes at surfaces subsequent
to excitation with ultraintense femtosecond laser pulses.
At present, we are designing and setting up a fs-laser driven
10 keV electron gun. The goal is the production of well collimated electron
pulses with pulse lengths below 1 ps. The electrons are created by
a 20...30 fs-laser pulse via photoemission from a thin Au or Ag film
deposited onto a sapphire substrate. This talk will cover the mechanisms
responsible for the broadening of the electron pulse in time as well as
methods to minimize or compensate for these effects. Furthermore, studies
on the suitable preparation of photocathodes and the simulation of
electron trajectories in a modified LEED/RHEED electron gun will be
presented.
O 14 Postersitzung (Adsorption an Oberflächen, Epitaxie und Wachstum, Organische
Dünnschichten, Oxide und Isolatoren, Phasenübergänge, Rastersondentechniken,
Struktur und Dynamik reiner Oberflächen)
Zeit: Montag 18:00–21:00 Raum: Bereich C
O 14.1 Mo 18:00 Bereich C
Adsorption properties of Ru-dyes on TiO2 — •M. Dürr, A.
Schmid, S. Rosselli, A. Yasuda, and G. Nelles — Materials Science
Laboratories, Sony Int. (Europe) GmbH, D - 70327 Stuttgart
Photosensitization of wide band-gap semiconductor surfaces with organic
dye molecules has led to the development of high-efficiency solar
cells [1]. Within these cells, which are mainly based on nano-crystalline
TiO2, fast electron transfer from the photo-excited dye to the conduction
band of the TiO2 takes place and the dye molecule is regenerated from
a redox couple in electrolyte. Therefore the number of dye molecules adsorbed,
the type of binding to the surface as well as the evolution of the
dye at the interface are crucial for the solar cell’s operation.
For a better understanding of degradation processes of the cell based
on dye desorption into the electrolyte, we have investigated the adsorption
properties of Ru-dyes on nano-porous TiO2 by means of FTIR
spectroscopy under ambient conditions. The type of binding of the dye
molecule via its carboxylic acid groups on the TiO2 has been determined.
The influence of the number of established bonds per molecule on the
desorption properties in ethanol was studied as a model system for the
desorption process. For comparison, dye molecules with a reduced number
of COOH groups have been investigated.
[1] B. O’Regan and M. Grätzel, Nature 353, 737 (1991).
O 14.2 Mo 18:00 Bereich C
Non-dipolar contributions in XPS: X-ray standing wave experiments
on ultrathin organic films — •A. Gerlach 1 , S. Sellner 2,3 ,
F. Schreiber 1 , H. Dosch 2,3 , I.A. Vartanyants 4 , J. Zegenhagen 5 ,
T. L. Lee 5 , and B.C.C. Cowie 5 — 1 Physical Chemistry Laboratory,
Oxford University, UK — 2 MPI für Metallforschung, Stuttgart, Germany
— 3 Institut für Theoretische und Angewandte Physik, Universität
Stuttgart, Germany — 4 Department of Physics, University of Illinois,
Urbana, USA — 5 ESRF, Grenoble, France
We study the adsorption behaviour of organic molecules by means
of the X-ray Standing Wave (XSW) technique. By measuring XPS and
Auger intensities this method allows the precise and direct determination
of absorbate/substrate geometries. Our XSW experiments with the
aromatic molecules PTCDA (perylenetetracarboxylic dianhydride) and
F16CuPc (perfluorinated copper-phthalocyanine) show that higher multipole
excitations can be non-negligible. In fact, the breakdown of the
dipole approximation, which can qualitatively change the signal, is a
fundamental issue in XPS in general and a challenge for theory. Depending
on the atomic number, orbital momentum, photon and initial state
energy these non-dipole contributions can significantly influence the resulting
effective coherent position and fraction. We discuss approaches to
the analysis of these fundamental effects that can be relevant for many
XSW applications.
O 14.3 Mo 18:00 Bereich C
Quantum dynamics of the H2 interaction with metal surfaces
— •Arezoo Dianat, Sung Sakong und Axel Groß — Physik-
Department T30, Technische Universität München, 85747 Garching, Germany
The adsorption and scattering of H2 on metal surfaces have been studied
by high-dimensional quantum dynamical simulations. The potential
energy surfaces (PES) of the H2-metal interaction were derived from ab
initio total-energy calculations. The open structure of the Pd(110) surface
leads to a strongly corrugated and anisotropic PES for H2/Pd(110).
This has significant consequences on the interaction dynamics as a function
of the angle of incidence and the rotational state. As one of the
consequences we predict rotational heating in desorption which has not
been observed before in H2 desorption from metal surfaces. In addition,
we obtain high intensities in the off-specular and rotationally inelastic
diffraction peaks. Furthermore, we will address the adsorption of H2 on
Rh(111) where experimentally the opening up of an additional adsorption
channel at higher kinetic energies has been predicted [1].
[1] M. Beutl, J. Lesnik, and K.D. Rendulic, Surf. Sci. 429, 71 (1999).
O 14.4 Mo 18:00 Bereich C
Far Infrared study of ultrathin metal films on MgO — •A.
Priebe, G. Fahsold, M. Lust, O. Skibbe, and A. Pucci —
Kirchhoff-Institut für Physik, Universität Heidelberg,
With far infrared spectroscopy it is possible to determine the dynamic
conductivity of ultrathin metal films and their change due to adsorbates.
Metal deposition strongly changed the reflectivity at the TO phonon frequency
of MgO. This effect leads to an enhanced sensitivity with respect
to the metal film charge carriers. Exposure of CO lead to further spectral
changes which are clearly visible at the TO frequency of MgO, too. From
the spectral structures we calculate adsorbate induced changes of the relaxation
rate of the free charge carriers in the metal. Also, we discuss
the influence of the polarization and of the incident angle of the infrared
beam on this spectral feature.
O 14.5 Mo 18:00 Bereich C
Adsorption energies on bimetallic overlayer systems at the
solid-vacuum and solid-liquid interface — •Ataollah Roudgar
and Axel Groß — Physik-Department T30g, Technische Universität
München, James-Franck-Strasse 1, 85747 Garching, Germany
We have determined the adsorption energies of atomic hydrogen and
of CO on bimetallic surfaces as a microscopic probe of the reactivity. The
calculations have been performed using density functional theory (DFT)
calculations within the generalized gradient approximation. For PdCu
bimetallic surfaces, we find a rather strong interaction between the Pd
and Cu atoms. Consequently, both Pd/Cu and Cu/Pd overlayer systems
exhibit an intermediate behavior between pure Cu and pure Pd. This is
in contrast to the sustem Pd/Au where both the expansion of the pseudomorphic
Pd overlayers and the relatively weak interaction between Pd
and Au lead to hydrogen and CO adsorption energies that are even larger
than on clean Pd surfaces.
Furthermore, we have studied the local reactivity of one layer pseudomorphic
Pd overlayers on Au(111) surface in the presence of a water
layer. We find a two-dimensional ice-like hexagonal structure of water on
the metal surface to be energetically most favorable. We also find that
the water-metal interaction is rather weak. The hydrogen and CO adsorption
energies are changed by less than 5% and 10%, respectively, by
the presence of water. This indicates that theoretical adsorption studies
at the solid-vacuum interface might also be relevant for the solid-liquid
interface.

Oberflächenphysik Montag
O 14.6 Mo 18:00 Bereich C
Physisorption systems with moderate lattice mismatch: The
structure of CO2/KCl(100) — Milica Hadnadev 1 , J.-Peter
Toennies 2 , Franziska Traeger 2 , •Jochen Vogt 1 , and Helmut
Weiss 1 — 1 Chemisches Institut, Universität Magdeburg, Universitätsplatz
2, 39106 Magdeburg, Germany — 2 Max-Planck-Institut für
Strömungsforschung, Bunsenstr. 10, 37073 Göttingen, Germany
Weakly bound adsorbates with a moderate lattice mismatch between
the solid adsorptive and the substrate are examples of self-organizing
systems in which short-range forces may induce complicated long-range
order. The lattice constant of solid CO2 is 12 % smaller than that of
KCl(100). On the latter CO2 initially adsorbs in an unsaturated phase
with (2 √ 2× √ 2)R45 ◦ symmetry which is barely visible at 80 K and wellordered
at 20 K. The saturated 2D phase forms a (6 √ 2× √ 2)R45 ◦ lattice,
verified both with helium atom scattering (HAS) and low-energy electron
diffraction (LEED). Moreover, we use polarization infrared spectroscopy
(PIRS) and show that dense phase IR spectra in the region of the CO2
asymmetric stretch vibration are consistent with dynamic dipole-dipole
coupling of 12 molecules in the corresponding unit cell. The spectra reveal
an aging of the freshly prepared layer within short time. This is attributed
to the heat of adsorption (25±1 kJ/mol) being slightly lower than the
heat of sublimation of solid CO2 (27 kJ/mol). Hence the 2D layer should
be metastable and form 3D clusters. The 2D phase collapses immediately
to the latter upon exposure to acetylene, which has no lattice mismatch
to KCl(100) and a heat of adsorption of 27 kJ/mol.
O 14.7 Mo 18:00 Bereich C
Manipulation of ultrafast surface processes by means of fs-pulse
shaping — •Felix Steeb, Marlies Wessendorf, Jörg Lange,
Alexander Mönnich, Michael Bauer, and Martin Aeschlimann
— FB Physik, TU Kaiserslautern, Erwin-Schrödinger-Str. 46, 67663
Kaiserslautern
In the last years, coherent control of chemical reactions in the gas
phase [1], or in the liquid phase [2] by means of adaptive femtosecond
pulse shaping has been demonstrated.
In this paper, we present application of the pulse shaping technique to
the optimization / manipulation of ultrafast surface processes, such as
surface chemical reactions.
The apparatus used to shape 20 fs pulses consists of an all-reflective
zero-dispersion compressor in combination with a programmable 640stripe
liquid crystal spatial light modulator (SLM). A closed loop setup,
controlled by an evolutionary algorithm [3], iteratively achieves optimization
of an experimental signal which is used as feedback. We find that
the Two-Photon-Photoemission Yield, e.g. measured from an adsorbate
resonance on the system Cs/Cu(111), is a possible detection scheme that
enables us to control specific surface-related properties. The experimental
setup, preliminary results and future prospects will be discussed.
[1] A. Assion et al.: Science 282, 919 (1998)
[2] T. Brixner et al: Nature 414, 57 (2001)
[3] D. Zeidler et al.: Phys. Rev. A 64, 023420 (2001)
O 14.8 Mo 18:00 Bereich C
Growth and thermal stability of Ni adsorption layers on
the (111) Mo crystal surface — •Cezary Tomas 1,2 , Jan
Kolaczkiewicz 1 , and Herbert Pfnür 2 — 1 Institute of Experimental
Physics, University of Wroclaw, Poland — 2 Institut Für
Festkörperphysik, Universität Hannover, Germany
The low-density (111) surfaces of bcc metals have a high surface free
energy and undergo faceting at sufficiently high temperatures, when covered
with a chemisorbed layer. However, not all chemisorbed adsorbates
lead to this process. Madey and coworkers have studied the reconstruction
of the W(111) surface. They found that faceting occurs in the presence of
metals with electronegativity 2 or more on the Pauling scale. Our results
do not support this classification. We suggest that the major cause of
faceting is the adsorbate-substrate and adsorbate-adsorbate interaction
and the magnitude of the atomic radii of the adsorbate and substrate.
The goal of this study was to investigate the growth mechanism and the
thermal stability of Ni layers adsorbed on the (111) Mo surface. AES,
LEED, ∆φ and STM has been used in this work. We find that Ni does
not cause faceting. Only for coverages Θ > 3ML 3D crystallites appear
on the surface and pass into 2D forms with increasing temperature.
O 14.9 Mo 18:00 Bereich C
CO adsorption and desorption processes on Pt(355) investigated
by in-situ high resolution XPS — •B. Tränkenschuh, T.
Fuhrmann, C. Papp, J. F. Zhu, R. Denecke, and H.-P. Steinrück
— Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr.
3, 91058 Erlangen
The adsorption and thermal desorption of CO on a Pt(355) surface
was studied by the combination of a supersonic molecular beam and
in-situ high resolution XPS. This surface contains five atom wide (111)
terraces separated by monatomic steps with (111) orientation. By using
synchrotron radiation we are able to clearly distinguish between adsorption
sites at steps and at terraces in O 1s and C 1s spectra, even at
fast measuring times (about 4 s per spectrum). The terrace adsorption
sites are comparable to those on a Pt(111) surface, namely bridge and
on-top bound species which are well known in literature [1]. Our measurements
show that first the step sites and than the on-top and bridge sites
on the terraces are occupied. The desorption is studied by temperatureprogrammed
XPS and TPD. Supported by the DFG (STE 620/4-2).
[1] M. Kinne et al., J. Chem. Phys. 117, 23 (2002).
O 14.10 Mo 18:00 Bereich C
Influence of Surface Roughness on the Wetting Behaviour of
Liquid Helium on Alkali Metal Surfaces — •Martin Zech, Armin
Fubel, Jürgen Klier, and Paul Leiderer — University of Konstanz,
Department of Physics, 78457 Konstanz, Germany
For many times wetting transitions have been observed for helium and
hydrogen on certain alkali metal surfaces. However, there exist discrepancies
in the measured contact angles and accompanying hysteresis, in
the movement of the helium contact lines, and sometimes even in the
wetting temperature. Surface roughness is expected to have a significant
influence on the wetting properties, but the working mechanism is not
clearly understood yet. For this reason we have developed a special low
temperature setup. This allows simultaneously an in situ evaporation of
the alkali metals, an investigation of the substrate surface using a scanning
tunnelling microscope (STM), and an investigation of the wetting
behaviour of liquid helium on those surfaces. A coherence between different
surface nanostructuring and emerging wetting phenomena is aimed
to be obtained.
O 14.11 Mo 18:00 Bereich C
Adsorption and decompostion of prenal on Pt(111) — •Jan
Haubrich, Alexander Krupski, Conrad Becker, and Klaus
Wandelt — Institut für Physikalische und Theoretische Chemie, Wegelerstrasse
12, D-53115 Bonn, Germany
The adsorption of prenal on Pt(111) is investigated with HREELS,
TPD and LEED. After adsorption of prenal on Pt(111) at 100K the
desorption of fragments between 1 and 100 amu has been studied with
TPD for series of a increasing exposures. Only signals of the masses 2,
28 and 84 (prenal) have been detected. The TPD results indicate that
molecular prenal desorbs from a monolayer, a 2nd adsorption state and
multilayer at 199K, 177K and 160 K, respectively. For the mass 28, a signal
is observed around 420K, saturating below the monolayer exposure
and pointing towards the decarbonylation of an irreversibly adsorbed
submonolayer species. Several signals are detected for molecular hydrogen
desorption between 285K and 480K. HREELS experiments carried
out between 100K and 500K show only small shifts for the reversibly adsorbed
species, while the species remainig above 199K shows some shifts
and sizeable changes in scattering intensities. Above 420K only traces of
hydrocarbon species can be observed by HREELS.
O 14.12 Mo 18:00 Bereich C
HR-XPS study of furan and pyrrole on Ni(111): reactions of
unsaturated hetero ring systems — •C. Papp, R. Denecke, and
H.-P. Steinrück — Physikalische Chemie II, Universität Erlangen-
Nürnberg, Egerlandstr. 3, 91058 Erlangen
The examination of the two hetero-cycles, furan (C4H4O) and pyrrole
(C4H5N) on the Ni(111) surface with temperature programmed XPS
(TP-XPS) and temperature programmed desorption (TPD) was conducted
in a larger effort to understand the adsorption and reaction of
aromatic molecules on single crystal surfaces. The XP spectra of C 1s,
O 1s and N 1s core levels were recorded with the high resolution and
high flux of the third generation synchrotron source MAX II. In both
hetero-cycles the inequivalent C atoms can be clearly resolved. The two
molecules show significant differences in their reaction behavior. Furan
decomposes at 200 K by forming CO, which is desorbing at 430 K, and

Oberflächenphysik Montag
hydrocarbon fragments. Pyrrole dissociates at 290 K, but shows no desorption
of any nitrogen containing species up to 600 K, and even at 1000
K some nitrogen is left on the surface. For both molecules the thermal
evolution of the hydrocarbon fragments is analysed. This work was supported
by a European Community ARI Program (HPRI-CT-1999-00058).
O 14.13 Mo 18:00 Bereich C
DFT study of Li adsorption on TiSe2 (0001) — •C. Ramírez 1 ,
W. Schattke 1 , and R. Adelung 2 — 1 Institut für Theoretische Physik
und Astrophysik, CAU, Kiel — 2 Technische Fakultät der CAU, Kiel
Alkali adsorption on a transition metal dichalcogenide substrate has
attracted many investigations, however a theoretical description of its
coverage dependence is still missing. In a first attempt we considered Li
as an alkali prototype at a specified selection of coverages, Θ = 0.06, 0.11,
0.25, 0.33, 0.5, and 1 ML, adsorbed on TiSe2 (0001).
By means of density-functional theory we obtained through structural
optimisation the coverage dependence of the physical properties adsorption
energy, work function, and valence electron distribution. A preference
of the hcp adsorption sites combines with an optimum coverage of
0.33 ML for the most stable structure. The work function curve shows
a behaviour similar to that found for alkali adsorption on metals. The
redistribution of the charge density at adsorption and the partial density
of states for the constituents of the compound are presented.
This work was supported by the Deutsche Forschungsgemeinschaft
(DFG), Forschergruppe FOR 353.
O 14.14 Mo 18:00 Bereich C
Electronic and optical properties of Au(111) and C60 on Au(111)
— •Elizabeta Ćavar, Marie-Christine Blüm, Marina Pivetta,
François Patthey, and Wolf-Dieter Schneider — Institut de
Physique des Nanostructures, Ecole Polytechniqe Fédérale de Lausanne
(EPFL), CH-1015 Lausanne, Switzerland
We have performed scanning probe investigations of the system C60
on Au(111) with a UHV STM operating at 50K using Pt/Ir tips. Topographic
images with molecular orbital resolution reveal different orientations
of C60 molecules in monolayer islands of C60 on Au(111). STS
measurements show energy resolved LDOS of monolayer islands of C60
on Au(111) exhibiting states derived from HOMO, LUMO and LUMO+1
as well as the surface state of Au(111). We employed spatially resolved
STM induced light emission spectroscopy on clean Au(111) surface areas
and C60 monolayer islands on Au(111) on the same sample. On the
clean Au(111) areas we observed the decay of excited localized surface
plasmons at ≈ 710 nm. For the C60 islands photon emission appears at
similar wavelengths, however, at strongly reduced photon intensity.[1]
[1] R. Berndt, R. Gaisch, J. K. Gimzewski, B. Reihl, R.R. Schlittler,
W. D. Schneider and M. Tschudy, Science 262, 1425-1427 (1993).
O 14.15 Mo 18:00 Bereich C
Adsorption and Dissociation of Methanol on Pd(111) — •A.
Bayer, J. Pantförder, S. Pöllmann, D. Borgmann, R. Denecke,
and H.-P. Steinrück — Physikalische Chemie II, Universität
Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen
Methanol adsorbed on a Pd(111) surface at 100 K dissociates upon
annealing mainly to CO and H, with methoxy as an intermediate. The
investigation of this reaction by high resolution X-ray photoelectron spectroscopy
(XPS) with monochromized Al Kα radiation is complicated because
of two reasons: First, the C 1s binding energy differences between
methanol, methoxy, and CO are too small to discriminate between different
species [1]. Second, the O 1s binding energy region is superposed
by the broad substrate Pd 3p3/2 peak. To overcome the latter problem,
the Pd 3p3/2 peak of the clean surface was subtracted from the measured
spectra after intensity correction via the Pd 3p1/2 peak. In addition, the
surface sensitivity was enhanced by choosing a grazing emission angle.
The resulting difference spectra show discrete O 1s peaks with binding
energy differences of 0.2-1.4 eV for the different species. Additional measurements
by ultraviolet photoelectron spectroscopy (UPS) and temperature
programmed desorption (TPD) allow the assignment to methanol,
methoxy, and CO.
Supported by the DFG (Schwerpunktsprogramm 1091, Ste620/3-3).
[1] M. Rebholz and N. Kruse, J. Chem. Physics 95 (1991) 7745.
O 14.16 Mo 18:00 Bereich C
Excited potential energy surface from spin-restricted densityfunctional
calculations: H/Al(111) — •Michael Lindenblatt
and Eckhard Pehlke — Institut für Theoretische Physik und Astrophysik,
Universität Kiel
Excited-state potential-energy surfaces are needed for the description
of non-adiabatic processes during chemisorption, such as the loss of spinpolarization
of an atom which is approaching a metal surface. A process
of this type has been discussed as a possible explanation for the chemicurrents
observed experimentally by H. Nienhaus et al.[1],[2].
To compute potential-energy surfaces of spin-polarized configurations
away from the Born-Oppenheimer ground state we have carried out spinrestricted
(fixed moment) density-functional calculations with the code
fhi96spin (from M. Bockstedte et al.[3]). To prevent the spin-polarization
from spreading over the whole metal slab at small atom-surface separation,
we apply an additional potential. As an example, we present
potential-energy surfaces for H/Al(111).
[1] H. Nienhaus, Surf. Sci. Rep. 45, 1 (2002).
[2] J. R. Trail et al. , J. Chem. Phys. 119, 4539 (2003).
[3] M. Bockstedte, A. Kley, J. Neugebauer, M. Scheffler, Comp. Phys.
Commun. 107, 187 (1997).
O 14.17 Mo 18:00 Bereich C
STM-Untersuchungen von C64-Picoröhren auf Au(111) —
•Belinda Baisch 1 , Jens Walther 2 , Rainer Herges 2 und Olaf
Magnussen 1 — 1 Institut für experimentelle und Angewandte Physik,
Christian-Albrechts-Universität, Leibnizstraße 19, 24118 Kiel —
2 Institut für Organische Chemie der Christian-Albrechts-Universität
Kiel, Otto-Hahn-Platz 3, 24098 Kiel
Die Bildung ultradünner Filme und Monoschichten von fullerenartigen
Molekülen auf Oberflächen ist von hoher Aktualität. Hier
wurde das Adsorptionsverhalten und die molekulare Ordnung von
5,24:6,11:12,17:18,23-Tetra[1,2]benzenotetrabenzo[a,e,i,m]cyclohexadecen
(”C64-Picoröhren”) auf Au(111) mittels Rastertunnelmikroskopie (STM)
untersucht. Bei den untersuchten Adsorbaten handelt es sich um
einen vollständig konjugierten röhrenförmigen Kohlenwasserstoff, bestehend
aus vier Anthracen-Einheiten. Durch Adsorption aus 1 mM
Lösungen in Benzol oder Toluol wurden auf flammengetemperten
Au(111)-Einkristallen molekulare Adschichten mit Bedeckungen im
(Sub-)Monolagenbereich präpariert. STM-Untersuchungen dieser Adschichten
zeigen, ähnlich wie für C60-Adschichten, eine hexagonale Ordnung
und Abstände zwischen nächsten Nachbarn von 10 ˚A.
O 14.18 Mo 18:00 Bereich C
Step Decoration of Gold Single Crystal Electrode Surfaces with
Pd — •Fernando Hernandez Ramirez and Michael Nielinger
— Institut fuer physikalische u. theor. Chemie, Universitaet Bonn, Roemerstrasse
164, 53117 Bonn, Germany
Surfaces of regularly stepped single crystals can be decorated with foreign
metals in order to change their physicochemical properties.
Step decoration of vicinally stepped platinum single crystals was
achieved for many metals and can be easily monitored in cyclic voltammetry
due to the suppression of the corresponding hydrogen adsorption
at step sites. By using the system Au(hkl)/Pd reactive bonding sites shall
be introduced at regular spacings. Here step decoration is more difficult
to prove. Cyclic voltammetry shows two Pd-oxidation peaks, the first one
being almost independent of Pd coverage. Hydrogen adsorption on the
modified stepped surfaces, but not on Au(111)/Pd, takes place only when
more than a critical amount of Pd, corresponding to a monoatomic row of
Pd at step sites, has been deposited. These facts support the assumption
of step decoration and show that hydrogen only adsorbs at 3-fold hollow
sites of Pd.
O 14.19 Mo 18:00 Bereich C
Influence of adsorbed rare gas on the Au(111) surface state:
combined UPS and STS studies — •T. Andreev, I. Barke, and
H. Hövel — Universität Dortmund, Experimentelle Physik I, D-44221
Dortmund
The Au(111) Shockley surface state is compared before and after adsorbing
different rare gas layers (Ar, Kr and Xe). We used ultraviolet
photoelectron spectroscopy (UPS) and scanning tunneling spectroscopy
(STS) in combination to get comprehensive information by using the advantages
of both methods. The energetic position of the surface state in
UPS is determined using an analytic model, which takes the finite angular
resolution of the electron energy analyzer into account. STS was mea-

Oberflächenphysik Montag
sured for pure Au(111) as well as for the surface covered with a monolayer
Kr and Xe and it is analyzed with an extended Kronig-Penney model for
the 23 × √ 3 reconstruction. The first rare gas monolayer induces energetic
shifts of 50 to 150 meV increasing with the gas atomic number,
whereas a second monolayer results only in small additional shifts of 3
to 18 meV. Using an image potential model it is possible to characterize
these shifts qualitatively. For a semiquantitative analysis we use the
phase accumulation model.
O 14.20 Mo 18:00 Bereich C
Diffusion pathways of hydrogen across Si(001) double-height
steps — •M. Lawrenz, C. Schwalb, M. Dürr, and U. Höfer —
Fachbereich Physik, Philipps-Universität, D-35032 Marburg
Steps can play an important role for macroscopic diffusion processes
at surfaces. An interesting system to study diffusion across steps at the
atomic scale is hydrogen on vicinal Si(001). At room temperature, molecular
hydrogen dissociates selectively at the threefold coordinated DB-step
sites. The adsorption takes place on adjacent Si atoms aligned with the
dimer rows of the upper terrace. Surfaces consisting of long hydrogen
chains at steps and of clean terraces can be prepared easily in this way.
They provide a well-defined starting configuration for imaging hydrogen
diffusion with a variable-temperature STM in real time.
Hydrogen was found to diffuse across the steps and along the dimer
rows at temperatures in excess of 550 K. The hopping rates for different
pathways could be determined from successive scans of the same
300˚A×300˚A region. At 570 K, the rate for diffusion from the steps
sites to the dimers of the upper terrace is 2.2 × 10 −3 s −1 which is comparable
to the rate of intra-row diffusion on the terraces. In contrast,
the diffusion rate to the lower terrace is only 1 × 10 −4 s −1 . At the first
dimer of the upper terraces hydrogen has a preference to diffuse back
to the step sites. The overall step depletion rate could also be determined.
Its value of 1.25 × 10 −4 s −1 at 570 K is in good agreement with
Rdiff = 10 11 s −1 exp(−1.7 eV/kT) as measured previously with optical
second-harmonic generation [1].
[1] M. B. Raschke and U. Höfer, Phys. Rev. B 59, 2783 (1999)
O 14.21 Mo 18:00 Bereich C
Supramolecular solid-solid wetting: A locally guidable selfassembly
of organic semiconductor molecules — •Frank
Trixler 1 , Thomas Markert 1,2 , Ferdinand Jamitzky 1,3 , Axel
Gross 2 , and Wolfgang M. Heckl 1 — 1 Department für Geo- und
Umweltwissenschaften & Center for NanoScience, Ludwig-Maximilians-
Universität, 80333 München, Germany — 2 Physik-Department T30,
Technische Universität München, 85747 Garching, Germany —
3 Centre for Interdisciplinary Plasma Science, Max-Planck-Institut für
extraterrestrische Physik, 85748 Garching, Germany
An easy way to deposit unmodified organic semiconductor molecules
onto substrates and the local control of supramolecular self-assembly
for the realization of designed nanoscopic structures should be important
factors in a future supramolecular nanoelectronics. We show that
these requirements can easily be achieved by a process which we describe
as ” supramolecular solid/solid wetting“: Solid nanocrystals of organic
semiconductors behave similiar to liquid droplets when they get contact
to a crystal surface; this results in an one-dimensional self-assembly of
supramolecular nanowires driven by wetting. We demonstrate that this
self-assembly process is locally guidable at the nanometre scale and allows
to tap the full potential of supramolecular chemistry such as reversibility
and self-healing for organic nanoelectronics.
O 14.22 Mo 18:00 Bereich C
Self-assembly on Surfaces: Supramolecular [60]Fullerene/Porphyrin
Assemblies on Metals — •Hannes Spillmann 1 , Andreas
Kiebele 1 , H.-J. Güntherodt 1 , Thomas Jung 1,2 , Davide Bonifazi
3 , and Francois Diederich 3 — 1 Department of Physics, University
of Basel, Klingelbergstr. 82, CH-4056 Basel, Switzerland — 2 Paul
Scherrer Institute, CH-5232 Villigen, Switzerland — 3 Laboratory of Organic
Chemistry, ETH Zürich, Wolgang-Pauli-Str. 10, CH-8093 Zürich,
Switzerland
The unique electrochemical and photophysical properties of porphyrin
and [60]fullerene compounds makes them promising candidates for the
construction of two- and three-dimensional organic-based materials. An
important question is how pristine C60 (and C70) and self-assembled
monolayer of porphyrin arrays will organize on surfaces. Self-assemblies of
electron-rich flat aromatic molecules such as porphyrins shall enable the
selective formation of electron donating monolayer, which can be covered
by pristine C60. The chromophore interaction between the electron donor
(porphyrin) and acceptor (C60) should enhance a supramolecular multilayer
structure. Herein, we report first Scanning-Tunneling-Microscopy
investigations of the behaviour of several porphyrin derivatives on metal
surfaces wherein single porphyrin molecules are forcefully arranged in
self-assembled monolayer. The specific properties of the single porphyrin
derivatives make such molecularly modified surfaces suitable candidates
for patterned surfaces to allocate fullerenes. Consequently, first observations
of the interaction of the fabricated porphyrin-based assemblies with
fullerene molecules will be presented.
O 14.23 Mo 18:00 Bereich C
Tunnelling voltage dependent submolecular contrast and degenerate
LUMO of Naphthalocynines (Nc) on natural graphite
— •T. G. Gopakumar, M. Lackinger, F. Müller, and M. Hietschold
— Chemnitz University of Technology, Institute of Physics,
Solid Surfaces Analysis Group, D-09107, Chemnitz, Germany
Phthalocyanines (Pc) are an interesting family of organic dye molecules
due to their structural analogy with important bio-molecules like porphyrin,
and also their applications in optoelectronic devices. We studied
the tunneling voltage dependancy of images of Nc monolayer deposited on
freshly cleaved natural graphite (0001) substrate using Organic Molecular
Beam Epitaxy (OMBE) under UHV conditions. The planar Nc molecules
formed monolayers with their molecular plane parallel to the substrate.
For the submolecular contrast we have observed a clear dependency on
tunnelling voltage especially at the centre of molecule. Parallel theoretical
calculations using Restricted Hartree-Fock (RHF) and Density Functional
Theory (DFT) reveal that this effect is due to the difference in
symmetry of molecular orbitals near the Fermi level of molecule. From
some single molecule STM images taken at a positive sample bias, we
have seen the fine structures of unfilled orbitals, which could be explained
only by the superposition of degenerate LUMO and LUMO+1 from the
calculation, which are mainly comprised of pi-electrons.
O 14.24 Mo 18:00 Bereich C
Aufbau von supramolekularen Ensembles an fest/flüssig Grenzflächen
— •Caroline Safarowsky 1 , Alexander Rang 2 , Christoph
Schalley 2 , Klaus Wandelt 1 und Peter Broekmann 1 —
1 Institut für Physikalische und Theoretische Chemie, Universität Bonn,
Wegelerstr. 12, 53115 Bonn — 2 Institut für Organische Chemie und Biochemie,
Universität Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn
Vorgestellt werden in-situ STM-Ergebnisse zum Phasenverhalten von
kationischen, organischen Molekülen auf einer chloridbedeckten Cu(100)-
Elektrodenoberfläche. Befindet sich die Kupferprobe im Kontakt mit einem
salzsauren Elektrolyten, so bildet sich eine c(2×2)-Cl Struktur, die
als anionisches Templat für die kationischen Moleküle dienen kann. Die
supramolekularen Aggregate können dabei entweder durch Selbstorganisation
kleiner Monomere (Dibenzylviologen) oder durch die Adsorption
großer metallorganischer Komplexe (Fujita-Square) gebildet werden.
Es entstehen molekulare Kavitäten, in die prinzipiell Gastmoleküle eingeschlossen
werden können. Die supramolekularen Quadrate sowie das
Dibenzylviologen ordnen sich quadratisch an und folgen damit der Symmetrie
der c(2×2)-Cl Struktur.
O 14.25 Mo 18:00 Bereich C
Investigation of perylene derivatives with STM — •Markus
Wahl 1 , Meike Stöhr 1 , Michael De Wild 1 , Hans-Joachim
Güntherodt 1 , Christian Galka 2 , Lutz Gade 2 , and Thomas
Andreas Jung 1,3 for the collaboration — 1 Institute of Physics,
University of Basel, Klingelbergstr. 82, 4056 Basel, Switzerland —
2 Laboratoire de Chimie Organometallique et de Catalyse, Institut Le
Bel, Universite Louis Pasteur, 4, rue Blaise Pascal, 67070 Strasbourg,
France — 3 Laboratory for Micro- and Nanostructures, Paul Scherrer
Institut, 5232 Villigen, Switzerland
In the last years perylene derivatives have attracted much attention
because of possible and already existing applications in electronic and
optoelectronic devices. The derivative (4,9-diaminoperylenequinone-3,10diimine
= DAPQDI) we investigated belongs to a class of compounds
which is cited very often in the patent literature for photovoltaic devices.
From differential thermoanalysis and gravimetry it is known that the
DAPQDI can polymerize. With UHV-STM experiments we tried to figure
out if this polymerization can also take place on surfaces. Therefore,
thin films in the monolayer regime were prepared by OMBE (Organic
Molecular Beam Epitaxy) on Ag(111) and Cu(111) substrates. Additionally,
the samples could be annealed. In a first step, the arrangement of

Oberflächenphysik Montag
DAPQDI on the surface was examined. Ordered arrangements of stripes
running parallel to the step edges of the substrate were found. In a next
step, the influence of annealing temperatures on the molecular arrangement
will be examined in order to be able to initiate the polymerization.
O 14.26 Mo 18:00 Bereich C
One- and two-dimensional chiral assemblies of lander molecules
— •Jens Kuntze, Xin Ge, and Richard Berndt — Institut
für Experimentelle und Angewandte Physik der Christian-Albrechts-
Universität zu Kiel
Supramolecular assemblies of lander molecules (C90H98) on Cu(100)
and Cu(111) are investigated with low-temperature scanning tunneling
microscopy. The energetically most favourable conformation of the adsorbed
molecule is found to exist in two mirror symmetric enantiomers or
conformers. At low coverage, the molecules align in enantiomerically pure
chains along chiral directions. The arrangement is proposed to be mainly
governed by intermolecular van-der-Waals interaction. At higher coverages,
the molecular chains arrange to chiral domains, for which structural
models are presented.
O 14.27 Mo 18:00 Bereich C
STM, ATR-IRAS und elektrochemische Untersuchungen von
NbSe2 und TaS2-Elektroden in hexylaminhaltigen Elektrolytlösungen
— •Ulrich Jung 1 , Sujit Dora 1 , Martha Poissot 2 ,
Wolfgang Bensch 2 und Olaf Magnussen 1 — 1 Institut für experimentelle
und Angewandte Physik, Christian-Albrechts-Universität,
Leibnizstraße 19, 24118 Kiel — 2 Institut für Anorganische Chemie,
Christian-Albrechts-Universität, Olshausenstraße 40, 24098 Kiel
Übergangsmetalldichalkogenide stellen hochinteressante Modellsysteme
für die Untersuchung elektrochemischer Interkalationsprozesse dar,
da sich selbst große Moleküle in die van-der-Waals Lücken zwischen
den Dichalkogenidschichten einlagern können. Solche elektrochemischen
Adsorptions- und Interkalationsprozesse wurden am Beispiel von NbSe2
und TaS2 in hexylaminhaltigen Lösungen durch in-situ Rastertunnelmikroskopie
(STM), in-situ Infrarotspektroskopie nach der Methode
der verminderten Totalreflektion (ATR-IRAS) und zyklovoltammetrische
Messungen untersucht. Dabei wurden sowohl einkristalline
Proben als auch dünne, über ein Phasentransferverfahren präparierte
Übergangsmetalldichalkogenidschichten auf Siliziumelektroden verwendet.
Letztere erlauben erstmalig ATR-IRAS-Untersuchungen dieser Substanzklasse.
Die erhaltenen Daten zur Struktur und Morphologie dieser
Proben und zum Adsorptionsverhalten weisen auf potentialabhängige
Interkalationsprozesse bei Potentialen negativ von -0.4 V gegen eine
Ag/AgCl-Elektrode hin.
O 14.28 Mo 18:00 Bereich C
Rate equation approach to stacking-fault nucleation in epitaxial
growth — •Celia Polop, Carsten Busse, Andreas Gödecke,
and Thomas Michely — I. Physikalisches Institut, RWTH Aachen,
52056 Aachen
One of the most important defects for thin film growth is the stackingfault.
Growth in the presence of stacking-faults leads to twin crystallite
formation and incoherent twin boundaries. Therefore the density of
stacking-faults is decisive for the film quality.
Here, we present an atomistic model for the nucleation of stacking-fault
islands on dense packed surfaces based on rate equations. Mean-field rate
equations taking into account two kinds of adsorption sites (fcc and hcp)
are able to reproduce the temperature and flux dependence of the formation
probability of stacking-fault islands on Ir(111) as determined by our
STM experiments [1]. The rate analysis of the atomistic processes that
take place during growth provides a kinetic model for the stacking-fault
island formation: for a given temperature, the distribution of large and
metastable stacking-fault islands is governed by the equilibrium distribution
of the largest mobile cluster.
[1] C. Busse, C. Polop, M. Müller, K. Albe, U. Linke, T. Michely, Phys.
Rev. Lett. 91, 56103-1/4 (2003).
O 14.29 Mo 18:00 Bereich C
Eine Rastertunnelmikroskop-Anlage zum Studium des Wachstums
Mn-dotierter III-V-Halbleiter — •Felix Marczinowski 1 ,
Jacques Dumont 2 , Jens Wiebe 1 , Markus Morgenstern 1 und
Roland Wiesendanger 1 — 1 Institut für Angewandte Physik, Universität
Hamburg — 2 Facultes Universitaires Notre-Dame de la Paix,
Namur
Mit dem Ziel, ferromagnetische III-V-Halbleiter für Rastertunnelspektroskopie
(RTS) in-situ herzustellen, wurde eine UHV-Kammer mit einem
Rastertunnelmikroskop (RTM) aufgebaut, welche Verdampfer für
Mangan und Indium-Arsenid enthält, sowie eine Ionenkanone und eine
LEED-/Auger-Einheit. Eine Substratheizung erlaubt das Aufdampfen
bei Substrattemperaturen von bis zu 400 ◦ C. Insbesondere sollen
InxMn1−xAs-Schichten mit variablem Mn-Anteil auf InAs(110) deponiert
werden und die Oberflächenmorphologie mittels RTM charakterisiert
werden. Das Rastertunnelmikroskop wurde speziell für Wachstumsuntersuchungen
konzipiert und ist Teil einer 300mK-UHV-RTM-Anlage, in
der die RTS-Messungen durchgeführt werden.
O 14.30 Mo 18:00 Bereich C
Rastertunnelspektroskopie an ultra-dünnen Co-Filmen auf
W(110) — •Marco Pratzer und Hans-Joachim Elmers —
Institut für Physik, Universität Mainz, Staudingerweg 7, D-55099 Mainz
Die Untersuchung der elektronischen Struktur von ultradünnen
ferromagnetischen Filmen, insbesondere der elektronischen Interface-
Zustände ist von entscheidender Bedeutung für zukünftige Anwendungen
im Spintronik Bereich. Wir haben daher Co-Filme mit einer Bedeckung
von 1-3 ML auf einem W(110) Einkristall präpariert und die elektronische
Struktur mittels Rastertunnelspektroskopie (STS) untersucht. Wie
schon bekannt wächst Co bis zu einer Bedeckung von 0,7 ML pseudomorph
auf W(110). Größere Bedeckungen führen zu dicht gepacktem
Wachstum. Für die dichtgepackten Bereiche können wir mit Hilfe von
atomar aufgelöster Rastertunnelmikroskopie und STS zwei verschiedene
Wachstumsmodi beobachten, die dieselbe 8×1 Überstruktur im LEED-
Bild zeigen und durch eine Umordnung der Atome erklärt werden können.
Höhere Bedeckungen führen zum gleichzeitigen Wachstum von Doppelund
Trippellageninseln. Das STS-Bild der DL-Inseln zeigt kontrastreiche
Linien entlang der [1¯10]-Richtung, die mit der beobachteten Überstruktur
korreliert sind und durch eine stehende Elektronenoberflächenwelle beschrieben
werden können. Bei den TL-Inseln finden wir zwei verschiedene
Inseltypen, die sich durch zwei resonante Peaks bei 0,3 eV und -0,4 eV
im differentiellen Tunnelstromspektrum unterscheiden. Wir ordnen die
Inseltypen einem hcp bzw. fcc Wachstum zu.
O 14.31 Mo 18:00 Bereich C
Simulation of self-assembled nanostructure formation during
heteroepitaxy of immiscible metals — •T. Volkmann 1 , F.
Much 1 , M. Biehl 1 , and M. Kotrla 2 — 1 Institut für Theoretische
Physik, Universität Würzburg, Am Hubland, 97074 Würzburg —
2 Institute of Physics, Academy of Sciences of the Czech Republic, Na
Slovance 2, 182 21 Prague 8, Czech Republic
A variety of material systems, though immiscible in the bulk, form stable
alloy layers at the surface. This surface confined alloying presumably
serves as mechanism for strain relief but the real microscopic mechanism
for formation of multi-component structures and the impact of kinetics
are still unclear. We perform Kinetic Monte Carlo simulations of multicomponent
growth with both lattice and off-lattice models. This allows
for the separate treatment of kinetic and strain effects. The key ingredient
of the lattice model are effective particle interactions of different
strength leading to enhanced step edge diffusion barriers at interfaces of
different adsorbate types. In the off-lattice model particles interact via
pair-potentials with potential depths and equilibrium distances of the
particles as parameters. Our simulations show that surface confined alloying
is indeed a possible strain relaxation mechanism. The competition
between strain and binding energy is found to yield regular stripe patterns,
similar to experimentally observed ones. The edge diffusion barrier
between regions of different particles alone already causes a stripe-like
separation. This confirmes former conjectures, but strain effects have to
be taken into account to achieve a restriction of the stripe width and a
pronounced asymmetry in the behavior of the different particle types.
O 14.32 Mo 18:00 Bereich C
Electrochemical synthesis of CdS-Films on Cu(111) — •S.
Hümann, A. Spänig, P. Broekmann, and K. Wandelt — Institut
für Physikalische Chemie; Wegelerstr.12; 53115 Bonn
Electrochemical Atomic Layer Epitaxy (ECALE) has been found to
be a useful method to grow thin layers of semiconductor compounds at
solid/liquid interfaces. In this contribution we present STM data dealing
with the epitaxial growth of ultrathin CdS-films on a Cu(111) electrode
surface.
It will be shown that the atomic structure and the morphology of the
resulting 2 layers thick CdS film strongly depend on the first layer ad-

Oberflächenphysik Montag
sorbed on the copper substrate.
We present CdS-films prepared by starting up with a sulfide covered
copper surface as a template. Depending on the applied electrode potential
two different sulfide layers can be observed by STM, on top of a
Cu(111) surface exposed to a 10 mM S 2− electrolyte:
1. an incommensurate moiré pattern
2. a commensurate ( √ 7 × √ 7)R19.1 o adlayer
Cd deposition on the ( √ 7 × √ 7)R19.1 o phase at a potential of -375
mV with respect to the RHE results in the formation of a CdS-phase revealing
a complex dislocation network which also shows a √ 7 strukture
with respect to the Cu(111)-substrate. Subsequent termination with S 2−
leads to the loss, of this highly ordered dislocation network.
O 14.33 Mo 18:00 Bereich C
Growth and morphology of titanium dioxide on a Re(10-10)
surface — •Dirk Rosenthal and Klaus Christmann — FU Berlin,
Inst. f. Chemie
Titaniumdioxide films were prepared in UHV by co-adsorption of titanium
and oxygen on a Re(10-10) surface. The films were characterized
by means of LEED, XPS and LEIS. The oxygen partial pressure and
substrate temperature, rather than the titanium flux, are crucial parameters
that influence the resulting titaniumdioxide structure. Thin films
of a few monolayers prepared at 500K exhibit at least three different
LEED structures, one of which indicates an epitaxial phase. Preparation
at 700K on the other hand (after formation of several transient LEED
phases in the sub- and monolayer regime), leads to a (2x2) structure with
missing reflexes in (0, k ± 1/2) positions. The latter are characteristic of
a glide mirror plane in [1-210]-direction (parallel to the troughs of the
Re-surface). A prerequisite for this behavior is a non-primitive unit mesh.
XP-spectra of ultrathin titania films (around 1ML) suggest a stoichiometric
structure that could be attributed to TiO2. We present a structure
model to explain the (2x2) phase.
O 14.34 Mo 18:00 Bereich C
SPA-LEED- und Leitfähigkeitsuntersuchungen an dünnen epitaktischen
Silberfilmen auf Silizium — •Alexandra Goehlich
und Michael Horn-von Hoegen — Institut für Laser- und Plasmaphysik,
Universität Duisburg-Essen, 45117 Essen
Bei der weiterschreitenden Miniaturisierung von Halbleiterbauelementen
und der Entwicklung von Nanostrukturen gewinnt neben Streuphänomenen
im Volumen die Streuung von Leitungselektronen an Oberflächen
immer mehr an Bedeutung. Beispielhaft soll am Modellsystem quasi freitragender
dünnster epitaktischer Ag(111)-Filme auf Si(100) die Änderung
der elektrischen Leitfähigkeit in Abhängigkeit von der Oberflächenmorphologie
des Films studiert werden. Dazu werden bei 80K 20ML dicke
Ag-Filme deponiert. Nach Tempern bei 300K bildet sich ein glatter,
defektarmer Ag(111)-Film [1]. Sowohl die Rauigkeit des Films, die
durch weiteres Aufdampfen bei tieferen Temperaturen gezielt von einzelnen
Adatomen bis zu großen Inseln eingestellt werden kann, als auch die
Bedeckung mit verschiedenen Adsorbaten beeinflußt die elektronischen
Streuprozesse und wirkt sich damit auf die Leitfähigkeit des Films aus.
[1] M. Horn-von Hoegen, T. Schmidt, M. Henzler, G. Meyer, D. Winau
and K.H. Rieder, Phys. Rev. B, Brief Reports 52, 10764-10767 (1995)
O 14.35 Mo 18:00 Bereich C
Epitaxial Ag-films grown on silicon-on-insulator substrates
— •Marcin Czubanowski, Christoph Tegenkamp, and Herbert
Pfnür — Institut Für Festkörperphysik, Appelstr.2 D-30167
Hannover,Germany
Studies of the conductivity of ultrathin metallic films that are only a
few monolayers thick is physically interesting and technically challenging.
In order to make the system simple, the influence of the underlying
substrate should be reduced to a minimum. Therefore, we performed adsorption
experiments of Ag grown under ultra–high vacuum conditions
on silicon on insulator (SOI) substrates. The morphology and chemistry
of the surface was checked by means of LEED and Auger spectroscopy.
To obtain clean and smooth SOI(100) surfaces, the native oxide layer
was removed first by adsorption of Si forming volatile SiO. Because the
temperatures used for cleaning the surface are lower than 1050 K, the
buried oxide layers remain intact and the topmost SOI-film remains undamaged
[1]. For (100)–orientated silicon surfaces, Ag grows at low temperatures
layer–by–layer in (111)–orientation [2]. An important epitaxy
parameter is the growth temperature, which allows to control the defect
concentrations within the Ag–films. Best results with respect to large Ag
islands were obtained for substrate temperatures of 130 K. The conduc-
tivity measurements are done in–situ in a Van der Pauw geometry. First
conductivity measurements for different Ag coverages an adsorption temperatures
will be presented.
(1) M. Czubanowski et.al., submitted to APL. (2) Horn von Hoegen et.al.,
Surface Science vol.331-333 (1995) 575.
O 14.36 Mo 18:00 Bereich C
Influence of selenium and steps on the Si(111)-(1 × 1):GaSe
van der Waals — •Bengt Jaeckel, Rainer Fritsche, Andreas
Klein, and Wolfram Jaegermann — Darmstadt University of Technology,
Surface Science Division, Department of Materials Science, Petersenstr.
23, 64287 Darmstadt
Evaporation of GaSe onto heated Si(111) surfaces leads to the chemically
and electronically passivated Si(111):GaSe surface termination. Before
completion of the termination the Si(111) surface passes through
several Se-free Si:Ga surface terminations, which require considerable rearrangement
of the Si surface atoms. To suppress the intermediate Se-free
Si:Ga surface terminations, we have added additional Se during the formation
of the surface termination. However, the electronic passivation is
less good with additional Se, although the surface shows a clear Si(111)-
(1×1):GaSe structure in LEED and SXPS. UHV-STM studies have been
conducted to analyze the details of the surface termination process in dependence
on Se vapor pressure. The number and orientation of steps on
the Si(111)-surface is strongly modified by additional Se-flux.
O 14.37 Mo 18:00 Bereich C
Experimental and ab initio studies of ultrathin Ag films on
V(100) — •Marko Kralj 1,2 , Predrag Lazic 3 , Jörg Schneider 1 ,
Axel Rosenhahn 1 , Petar Pervan 2 , Milorad Milun 2 , Zeljko
Crljen 3 , Radovan Brako 3 , and Klaus Wandelt 1 — 1 Institut für
Physikalische Chemie, Bonn — 2 Institute of Physics, Zagreb — 3 Rudjer
Boskovic Institute, Zagreb
The growth and structure of ultrathin silver films (1-5 ML) deposited
on a reconstructed V(100)-(5x1) surface are studied by use of STM, AES,
and ARPES. To model the structure of the system we have also performed
first principles calculations.
It has been established that due to the annealing of deposited silver
uniform films are formed and that the vanadium reconstruction is completely
removed. As found from STM measurements and supported by ab
initio calculations in the in-plane direction silver follows the structure of
the V(100)-(1x1) lattice and is tetragonally distorted in the direction perpendicular
to the surface. The ab initio results predicted the adsorption
energies of individual silver layers and the work function of Ag/V(100)
in accordance with experiments.
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Spot Profile Analysis-LEED and AFM Investigations of
Ge/CaF2/Si(111) Multilayers — •Eddy Patrick Rugeramigabo
1 , Carsten Deiter 1 , and Joachim Wollschläger 2 —
1 Institut für Festkörperphysik, Universität Hannover, D-30167 Hannover
— 2 Institut für Angewandte und Physikalische Chemie, Universität
Bremen, D-28359 Bremen
Nanoelectronic devices like resonant tunneling diodes offer very interesting
features and quantum effects. Therefore it is necessary to fabricate
high quality semiconductor insulator multilayers with few nanometer
thick films.
We have investigated the growth and crystallization of thin Ge films
(thickness 1-2 nm) deposited on CaF2 at several temperatures between
RT and by means of SPA-LEED (Spot Profile Analysis Low Energy Electron
Diffraction) and AFM.
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Wachstumsstufen auf CaF2 (111) — •Michael Schick 1 , Heinz
Dabringhaus 2 und Klaus Wandelt 1 — 1 Inst. f. Phys. und Theor.
Chem. der Universität Bonn — 2 Mineral. - Petrol. Inst. der Universität
Bonn
Das Wachstum von CaF2(111) wurde mit Molekularstrahlmethoden
und AFM bei T = 1055 − 1099 K sowie Sättigungsverhältnissen S =
4 − 354 untersucht. Die Oberflächen sind charakterisiert durch Wachstumshügel
mit konzentrischen Anordnungen von Stufen (Höhe: eine Tripellage
F − -Ca 2+ -F − �=0.32 nm), die vorwiegend in -Richtungen
verlaufen, wobei der Typ I überwiegt. Die Abstände der Tripelstufen in
den Wachstumshügeln nimmt proportional zu 1/ ln(S) zu. Hieraus lässt
sich ein Wert für die Randenergie der Tripelstufen von ǫ = 0.7 nJ/m
bestimmen, der mit den theoretisch Werten 0.24 und 0.37 nJ/m für Typ

Oberflächenphysik Montag
I bzw. Typ II-Stufen [1] verglichen werden kann.
Neben Tripelstufen werden auch Makrostufen gefunden. Diese Makrostufen
verlaufen ebenfalls in -Richtungen. Makrostufen, die aus
Tripelstufen des Typs I entstanden sind, sind erheblich steiler als solche,
die von Stufen des Typs II herrühren. Dies lässt sich durch eine attraktive
Wechselwirkung zwischen Tripelstufen des Typs I bei Stufenabständen <
1 nm erklären [1].
[1] Puchin et al., J. Phys.: Cond. Matt. 13 (2001) 2081
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Au/Si(111): Local ordering of the (5 × 2) reconstruction — •C.
Seifert, F.-J. Meyer-zu Heringdorf, and M. Horn-von Hoegen
— Inst. für Laser- und Plasmaphysik, Universität Duisburg-Essen
(Campus Essen)
At Au coverages ΘAu < 1/3ML and substrate temperatures above
300 ◦ C, Si(111) surfaces exhibit a striped (5×2) reconstruction, consisting
of three different domains with an angle of 60 ◦ between them. Upon deposition
of Au, each of the domains forms needles that grow predominantly
in the 2-fold direction of the reconstruction. The resulting anisotropy is
so dominating, that if one domain encounters another one with a different
rotational orientation, the needle-like domain keeps growing, and can
erode the other domains (1) or even completely intersect them (2). Here
we discuss a combined High Resolution Low Energy Electron Diffraction
(SPA-LEED) and Scanning Tunneling Microscopy (STM) experiment to
understand the details of the (5 × 2) reconstruction. The (5 × 2) LEED
pattern can be understood as a (5 × 1) pattern with elongated (5 × 2)
spots that form stripes located at 50% Brillouin-Zone (BZ). The detailed
shape of the stripes depends on the sample preparation temperature.
Room temperature STM measurements combined with fourier analysis
and simple simulations of the adatom arrangement indicate a local ordering
of the gold adatoms.
[1] T. Hasegawa, S. Hosaka, S. Hosoki Surf. Sc. 357-358 (1996), 858-862
[2] F.-J. Meyer zu Heringdorf, R.M. Tromp, unpublished
O 14.41 Mo 18:00 Bereich C
GIXRD-measurements and -simulation of CaF2 on Si(111)
— •Andreas Gerdes 1 , Carsten Deiter 1 , Eddy Patrick
Rugeramigabo 1 , and Joachim Wollschläger 2 — 1 Institut für
Festkörperphysik, Universität Hannover, Appelstr. 2 — 2 Institut für
physikalische Chemie und Festkörperphysik, Universität Bremen, im
Nord-Westen-Bremens NW2
Due to the small lattice mismatch at room temperature CaF2 is a
good candidate to study growth processes on Si(111). Further the system
semiconductor/insulator promises interesting features for electronic
devices on the nanoscale. We grew CaF2 films of different thickness at
T = 500 ◦ C - 600 ◦ C and investigated them by means of GIXRD. Intensity
oscillations due to the finite CaF2 films thickness show that the films
are very homogeneous.
O 14.42 Mo 18:00 Bereich C
GIXRD and AFM Investigations of CaF2/Si Multilayers —
•Carsten Deiter 1 , Andreas Gerdes 1 , Eddy Patrick Rugeramigabo
1 , Joachim Wollschläger 2 , Cunrang Wang 3 , Bernd
Müller 3 , and Karl Hofmann 3 — 1 Institut für Festkörperphysik,
Universität Hannover, D-30167 Hannover — 2 Institut für Angewandte
und Physikalische Chemie, Universität Bremen, D-28359 Bremen
— 3 Institut für Halbleiterbauelemente und Werkstoffe, Universität
Hannover, D-30167 Hannover
Semiconductor/insulator multilayers with few nanometer thick films
offer the opportunity to fabricate nanoelectronic devices with very interesting
features. Due to small lattice mismatch the system CaF2/Si(111)
is a good combination for growth of films with high morphological and
electronical quality.
We have investigated Si/CaF2/Si(111) structures by means of GIXRD
and AFM. Si films (thickness 4nm) and clusters are deposited on CaF2
(thickness 3nm) at temperatures between 800K and 1000K with and
whithout deposition of additional Sb as a surfactant.
O 14.43 Mo 18:00 Bereich C
Growth and morphology of Co films on Pd(111) — •M. Przybylski,
M. Wasniowska, W. Wulfhekel, and J. Kirschner —
Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle
Ultrathin Co films were grown on an atomically clean and flat surfaces
of Pd(111). Scanning Tunneling Microscopy (STM) shows that at 300K
the growth starts by a formation of double-layer patches of a hexagonal
shape. The Moiré pattern due to the 8.7% lattice mismatch of Co and
Pd was clearly seen. At 170K, mobility of Co atoms is strongly reduced
resulting in a more dense packing of the double-layer patches. At the coverage
of ≈2ML of Co grown at 170K almost the whole surface (95%) is
covered with the double-layer patches, in comparison to only 70% if the
growth proceeds at 300K. In the latter case higher layers nucleate when
the patches approach the size of 50nm. After annealing at 420K, the STM
image shows drastically changed morphology of the film. A monolayer of
Co appears which is continuous and covers 98% of the sample area. This
is associated with changes of the LEED pattern: after annealing only
single spots of hexagonal symmetry, typical for Pd(111), are seen with
no superstructure spots, which were clearly visible before annealing.
O 14.44 Mo 18:00 Bereich C
X-ray study of the surface dynamics at the charge density
wave transition in NbSe2 — •Bridget Murphy 1 , Jochim Stettner
1 , Martin Müller 1 , Ingo Grotkopp 1 , Peter Boesecke 2 ,
Till H. Metzger 2 , Michael Krisch 2 , Herwig Requardt 2 , and
Werner Press 1,3 — 1 Institut für Experimentelle und Angewandte
Physik, Christian-Albrechts-Universität Kiel, Leibnizstraße 19, 24098
Kiel — 2 ESRF, BP 220, 38043 Grenoble Cedex 9, France — 3 Institut
Laue-Langevin, BP 156, 38043 Grenoble Cedex 9, France
2H-NbSe2 is a van der Waals bonded layered structure and displays a
Peierls distortion resulting in a charge density wave transition at 33K.
We investigated this transition using grazing incidence X-ray diffraction
and inelastic X-ray scattering. The elastically scattered intensity of the
satellite reflection, which is proportional to the square of the amplitude
of the modulation, as well as the respective diffuse scattering have been
measured for different incidence angles in order to carry out a direct comparison
between the surface and bulk behaviour. We found that the temperature
dependence of the surface charge density wave satellite clearly
varies from that in the bulk and that the surface transition appears to be
continuous. Moreover, the surface CDW transition occurs 1.4 K above
that of the bulk. We conclude that we likely observe the unusual case
of a ’surface transition’. In order to improve the understanding of the
dynamics phonon dispersion curves at room temperature and around the
phase transition have been determined by inelastic X-ray scattering.
O 14.45 Mo 18:00 Bereich C
Die Allotropie von Antimon und die Ostwaldsche Stufenregel —
•B. Stegemann 1,2 , T. M. Bernhardt 2 , B. Kaiser 1 und K. Rademann
1 — 1 Institut für Chemie, Humboldt-Universität zu Berlin, Brook-
Taylor-Str. 2, D-12489 Berlin — 2 Institut für Experimentalphysik, Freie
Universität Berlin, Arnimallee 14, D-14195 Berlin
Das Element Antimon existiert in mehreren festen Modifikationen (Allotropie).
Eine bisher unbekannte, feste Antimonmodifikation, bestehend
aus periodisch angeordneten, undissoziierten Sb4-Clustern, konnte durch
kontrollierte Abscheidung von Sb4-Clustern aus der Gasphase auf geeigneten
Substraten erzeugt und mittels Rastertunnelmikroskopie nachgewiesen
werden. Diese Modifikation weist einen metastabilen Charakter
auf und wandelt sich bei Erreichen einer kritischen Größe in die amorphe
Phase um. In Abhängigkeit von der Bedeckung und der Temperatur
führt dann ein weiterer Phasenübergang zur Ausbildung der energetisch
günstigsten, kristallinen Antimonmodifikation.
Die stufenweisen Umwandlungen dieser allotropen Modifikationen sind
irreversibel (monotrop) und können mit der Ostwaldschen Stufenregel
erklärt werden, gemäß der ein in mehreren energetischen Zuständen vorkommendes
chemisches System nicht direkt in den thermodynamisch stabilen
Gleichgewichtszustand übergeht, sondern stufenweise über metastabile
Zwischenzustände dorthin gelangt.
O 14.46 Mo 18:00 Bereich C
Orientational and positional phase transitions in geometric confined
systems of alkanes - a numerical study — •Frank Oliver
Pfeiffer und Heiko Rieger — Theoretische Physik, Universität des
Saarlandes, 66041 Saarbrücken, Deutschland
A classical phenomenological atom-atom potential is used to study alkane
chains in a single 2D hexagonal pore via the Monte Carlo method.
We find different phases characterized by orientational and positional order
and discuss the influence of (1) the surface structure of the pore wall
and (2) the pore diameter on the correlation functions. Our calculations
for the confinement are compared to the bulk scenario and to recent
experiments on n-alkanes in nano-pores by Huber and Knorr.

Oberflächenphysik Montag
O 14.47 Mo 18:00 Bereich C
Desorption of Atoms from Optically Excited Alkali Halides —
•M. Rohlfing 1 , N.-P. Wang 2 , P. Krüger 2 , and J. Pollmann 2 —
1 School of Engineering and Science, International University Bremen,
P.O. Box 750761, 28725 Bremen — 2 Institut für Festkörpertheorie, Universität
Münster, Wilhelm-Klemm-Str. 10, 48149 Münster
We investigate the emission of halogen atoms from optically excited
alkali halides (e.g., KI). To this end we employ an ab-initio approach
to the excited states and the corresponding total-energy surfaces. Based
on density-functional theory, the electronic correlation effects are treated
within many-body perturbation theory (i.e., the GW method and the
Bethe-Salpeter equation). This yields the total energy of the system,
both in its ground state and in the excited state, as a function of the
geometry. As prototype materials KI and KBr are discussed. Our results
indicate that at the KI(001) surface, a surface exciton can be excited leading
to direct emission of a neutral iodine atom without any desorption
barrier. The emission occurs on a sub-picosecond time scale and leads to
kinetic energies of the iodine atoms of several 100 meV, in accordance
with recent time-of-flight experiments.
O 14.48 Mo 18:00 Bereich C
Surface dynamics of water-glycerol mixtures investigated
by XPCS — •Michael Sprung 1 , Simone Streit 1 , Christian
Gutt 1 , Anders Madsen 2 , Tilo Seydel 3 , and Metin Tolan 1 —
1 Experimentelle Physik I, Universität Dortmund, 44221 Dortmund —
2 ESRF, Grenoble, France — 3 ILL, Grenoble, France
The structure and dynamics of the surface of water / glycerol-mixtures
has been investigated by X-ray photon correlation spectroscopy (XPCS)
and by means of specular x-ray reflectivity.
The aim of the experiments was to investigate (a) the dynamics of the
crossover from propagating to overdamped capillary waves by XPCS, (b)
the temperature dependence of the capillary wave induced surface roughness
and (c) the detailed electron density profile of the surface structure.
Experiments were performed in a broad temperature range and with different
water/glycerol mixtures. We could for the first time observe the
transition from overdamped to propagating waves on the surface. Of special
interest was also the surface dynamics and structure of supercooled
mixtures.
O 14.49 Mo 18:00 Bereich C
Scanning Probe Microscopy of Antimony Single Crystals: Periodic
and Non-periodic Features of the (0001) Cleavage Surface
— •B. Stegemann 1,2 , C. Ritter 1 , B. Kaiser 1 , and K. Rademann 1
— 1 Institut für Chemie, Humboldt-Universität zu Berlin — 2 Institut für
Experimentalphysik, Freie Universität Berlin
Morphology, atomic structure and irregular features of the Sb(0001)
cleavage plane of antimony single crystals are investigated in detail by
STM and AFM. Atomically resolved STM images of the hexagonal structure
of surface atoms on Sb(0001) are presented, extending the base of
STM data available on elemental surfaces. Lateral and vertical lattice
parameters are determined. As the observed lattice spacing of 4.31 ˚A on
Sb(0001) agrees well with the known bulk data, surface reconstruction
can be excluded. Cleavage is found to occur always between adjacent
double layers yielding at least diatomic cleavage steps of 3.75 ˚A height.
Crystal imperfections such as vacancies (0D defects) and step edges (1D
defects) are elucidated and imaged with atomic resolution. Moreover,
twinned interlayers (2D defects) formed upon cleavage of Sb at room
temperature are revealed, confirming the twinning angle of 2.45 degrees,
which has been predicted by the model of twinning in Sb crystals. Results
are discussed in comparison with other layered materials and with regard
to their relevance for the use of Sb(0001) as support for nanostructures.
O 14.50 Mo 18:00 Bereich C
Surface dynamics of gold clusters on thin polymer films investigated
by XPCS — •Virginie Chamard 1 , Markus Krämer 1 ,
Christian Gutt 1 , Anders Madsen 2 , and Metin Tolan 1 —
1 Experimentelle Physik I, Universität Dortmund, 44221 Dortmund —
2 ESRF, Grenbole, France
Using the technique of X-Ray Photon Correlation Spectroscopy
(XPCS) it is possible to observe dynamics at low frequencies (from 10 6
s −1 to 10 −3 s −1 ) and small lengthscales of micro- to nanometers, which
are not or hardly accessible to other techniques.
In the present work we examined the dynamics of thin polymer films
covered with nanometer sized gold clusters. We performed intensity-
intensity autocorrelation measurements of the samples at different temperatures.
If the sample is heated to temperatures higher than the glass
transition temperature of the polymer, the clusters sink inside to a position
a few ˚A below the surface. There they act as markers for the capillary
wave movement of the surrounding polystyrene. Furthermore the clusters
perform a Brownian Motion inside the polymer which can, as well as the
capillary waves, be characterized by correlation measurements. The resulting
viscosity is several orders of magnitude higher than the viscosity
of pure polymer systems without gold. In addition it has been found that
the viscosity of the gold/polymer system is less temperature dependent
than that of the polymer.
O 14.51 Mo 18:00 Bereich C
Kinetische Prozesse an Oberflächen in metallischen Gläsern
unter Einfluß von Teilchendeposition — •Sebastian Vauth
und Stefan G. Mayr — I. Physikalisches Institut, Georg-August-
Universität Göttingen, Tammannstr.1, 37077 Göttingen
In MD-Simulationen wird das Diffusionsverhalten von amorphen Cu-
Ti Schichten unterhalb der Glastemperatur untersucht. Um Oberflächen
mit einzubeziehen, werden in einer Richtung die sonst geltenden periodischen
Randbedingungen aufgehoben. Es werden die Diffusionskonstanten
der Elemente diskutiert in Abhängigkeit von der Entfernung zur Oberfläche,
der Atomsorte und der Zusammensetzung der Probe. Verteilungsfunktionen
von Sprungweiten sowie das Verhalten einzelner Atome liefern
Informationen über den zugrundeliegenden Diffusionsmechanismus.
Weiterhin wird der Einfluß der Deposition von Atomen mit thermischer
Energie und auch von Ionenbestrahlung der Oberfläche auf die atomare
Kinetik untersucht - auch im Hinblick auf Strukturbildung. Entsprechende
experimentelle Untersuchungen an dünnen Schichten metallischer
Gläser werden im Vergleich diskutiert. Diese Arbeit wird vom SFB 602
TP B3 der DFG gefördert.
O 14.52 Mo 18:00 Bereich C
Ultrafast dynamics of the Si(001) surface after electronic excitation
— •Jan van Heys and Eckhard Pehlke — Institut für
Theoretische Physik und Astrophysik, Universität Kiel
Due to the strong Jahn-Teller coupling between the buckling angle and
the electronic structure of the dimers on the Si(001) surface, this surface
represents a promising model system for studying ultrafast surface
atomic motion in response to electronic excitation. Depending on excitation
density, due to the creation of electron-hole pairs in the danglingbond
surface-states the energy preference for buckled dimers as opposed
to symmetric dimers can be nearly lost.
We present first results from ab initio molecular dynamics simulations
of the non-adiabatic motion of the electrons and ions at the Si(001) surface
after strong electronic excitation. Electrons are described within the
time-dependent density functional theory while the motion of the ions
follows from classical Ehrenfest dynamics.
We find that, provided the excitation exceeds order of 1/2 electron per
dimer, the buckling angle flips on a timescale of about 150 fs.
O 14.53 Mo 18:00 Bereich C
Chiral adenine rows on Cu(110) – a theoretical contribution
— •Martin Preuß, Wolf G. Schmidt, and Friedhelm Bechstedt
— Institut für Festkörpertheorie und Theoretische Optik, Friedrich-
Schiller-Universität, Max-Wien-Platz 1, 07743 Jena, Germany
The adsorption of adenine on copper allows for studying the concepts of
self-assembly, adsorbate-induced chirality and low-dimensionality. Both
LEED and STM [1] reveal a long-range ordering of adenine on Cu(110)
in one-dimensional chains in the ±�a1 +�a2 direction. The sign depends on
the way of adsorption: mediated by the substrate, the formerly prochiral
adenine molecules lose their mirror-plane symmetry and, after dimerization,
form chiral chains. We study the process of adenine adsorption
on Cu(110) in detail by means of a first principles approach. The calculations
are carried out in the framework of density-functional theory
using PAW potentials in the generalized gradient approximation. Possible
molecular dimer chain models are presented and interpreted in terms of
stability and chemistry. We especially address the problem of discrimination
between different geometries and the bonding mechanism of adenine
to the substrate.
[1] Q. Chen, D. J. Frankel, N. V. Richardson, Langmuir 2002, 18, 3219

Oberflächenphysik Montag
O 14.54 Mo 18:00 Bereich C
A prove of the spreader-bar approach: Fabrication and characterization
of heterogeneous monomolecular films — •Andrey
Shaporenko 1 , Thomas Hirsch 2 , Vladimir Mirsky 2 , and Michael
Zharnikov 1 — 1 Angewandte Physikalische Chemie, Universität Heidelberg,
69120 Heidelberg — 2 Institut für Analytische Chemie, Chemo- und
Biosensorik, Universität Regensburg, 93040 Regensburg
The aim of the work is a development of a new technology for simple
formation of nanostructures with controlled shape and distribution in
monomolecular films. The technology is based on combination of a selfassembly
of thiol compounds on metals and an approach of molecular
spreader-bars. Through such a combination, mixed monomolecular films
with a defined size of structural elements can be formed and subsequently
used as a platform for biological and chemical research and sensor fabrication.
At an initial stage of the project, several combinations of relevant
molecular constituents have been tested, including simple aliphatic and
aromatic thiols and large conjugated molecules with and without specific
anchor groups. The resulting monomolecular films have been characterized
by several complementary experimental techniques, such as X-ray
photoelectron spectroscopy, near-edge X-ray absorption fine structure
spectroscopy, X-ray absorption spectromicroscopy, and infrared reflection
absorption spectroscopy. Conclusions on the chemical composition,
orientation, and lateral distribution of the molecular constituents were
driven. Based on these conclusions, both the film fabrication procedure
and the selection of the molecular building blocks have been optimized.
O 14.55 Mo 18:00 Bereich C
UV-photoinduced modification and surface anisotropy of
polyimide studied by X-ray absorption spectroscopy and
spectromicroscopy — •Michael Zharnikov 1 , Yukio Ouchi 2 ,
Masaki Hasegawa 3 , and Andreas Scholl 4 — 1 Angewandte
Physikalische Chemie, Universität Heidelberg, 69120 Heidelberg,
Germany — 2 Department of Chemistry, Nagoya University, Nagoya,
464-8602 Japan — 3 IBM Research, Tokyo Research Laboratory, Yamato,
Kanagawa 242-8502, Japan — 4 Advanced Light Source, Lawrence
Berkeley National Lab, Berkeley, CA 94720 USA
An alignment of liquid crystal (LC) molecules in a flat panel display
is mediated by the anisotropic polyimide (PI) substrate. Whereas a conventional
way to fabricate such a substrate is a mechanical rubbing of a
PI, an alternative approach utilizes the irradiation of PI by linearly polarized
UV-light. To get a basic understanding of the phenomenon of UVlight-induced
anisotropy, we have performed NEXAFS spectromicroscopy
measurements at the C, N, and O K-edges on a series of the polyimide
films treated by linearly polarized UV-light through a mask. Fabricated
patterns could be easily distinguished and imaged both for the parallel
and perpendicular orientation of the electric field vectors of the UV- and
synchrotron light. The UV-induced intensity changes of the characteristic
absorption resonances at all probed absorption edges were monitored
and related to the chemical modification of PI. From the analysis of the
NEXAFS microspectra, the extent of the UV-induced anisotropy could
be estimated in good agreement with our previous spectroscopic results.
O 14.56 Mo 18:00 Bereich C
The Interaction of Benzene Derivatives with Amorphous Solid
Water — •O. Höfft 1 , A. Borodin 1 , U. Kahnert 1 , M. O. Abou-
Helal 1 , S. Krischok 2 , and V. Kempter 1 — 1 Institut für Physik
und Physikalische Technologien, TU Clausthal, Leibnizstr. 4, D–38678
Clausthal–Zellerfeld — 2 Institut für Physik und Zentrum für Mikro– und
Nanotechnologien der TU Ilmenau, P.O. Box 100565, D–98684 Ilmenau
Interfaces between films of benzene derivatives (C6H6; C6H5Cl; ortho–
C6H4OHCl; C5H5N) and solid H2O were studied between 90 and 200K
with metastable impact electron spectroscopy (MIES) and ultraviolet
photoelectron spectroscopy (UPS(HeI and II)): (i) adsorption of the benzene
derivatives on solid water in order to simulate their interaction with
ice particles, and (ii) deposition of water on the organic films in order
to simulate the process of water precipitation. The different behaviour
found for the four studied cases is traced back to the different mobilities
of the molecules with respect to that of water. The interaction between
H2O and the benzene dervatives at the interfaces is discussed on the basis
of qualitative profiles for the free energy for the systems.
O 14.57 Mo 18:00 Bereich C
Electron Dynamics in Alkanethiol Self-Assembled Monolayers
on Ultraflat Gold Films — •S. Dantscher, C. Kennerknecht, S.
Schramm, D. Wolpert, and W. Pfeiffer — Physikalisches Institut,
Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
For the self-assembly process of organic molecules like alkanethiols a
very flat surface is necessary. The roughness on the atomic scale has
to be minimized in order to create atomically flat terraces as large as
possible. In this work thin gold films with a thickness from 500 to 700˚A
were evaporated under UHV conditions on freshly cleaved, heated (650K)
mica sheets. After the evaporation process the surface only showed weak
LEED spots which could be improved by sputtering and heating cycles.
The enlargement of the terrace width up to 200nm was also confirmed
by STM topographies. Adsorption of the alkanethiols took place in an
inert gas atmosphere in order to prevent contamination of the gold surface.
The technique of Time Resolved Two Photon Photo Emission was
used to investigate the influence of the adsorbed SAM layer on electronic
properties of the gold surface like work function and lifetime of excited
states.
O 14.58 Mo 18:00 Bereich C
Normal Incidence X-ray Standing Waves (NIXSW) study of
PTCDA on Ag(111) — •A. Hauschild 1 , M. Sokolowski 1 , and F.
S. Tautz 2 — 1 Institut für Physikalische und Theoretische Chemie , Universität
Bonn, Wegelerstr. 12, 53115 Bonn, Germany — 2 School of Engineering
and Science, International University Bremen, PO Box 750561,
28725 Bremen, Germany
Whereas the adsorption geometries of small molecules on surfaces are
already rather well understood up to now, only little information has
been gained for larger aromatic molecules so far, partly because of experimental
reasons.
PTCDA (3,4,9,10-perylene-tetracarboxylicacid-dianhydrid)
chemisorbs on Ag(111) substrate, forming a commensurate monolayer
with flat lying molecules arranged in a so-called ”herringbone-pattern”.
We have investigated the atomic bonding distances of PTCDA relative
to the Ag(111) by NIXSW measurements performed on the O1s and
C1s level. Since oxygen and carbon are light atoms, the analysis requires
taking into account non-dipolar contributions to the photoemission
yield. First results indicate an averaged bonding distance for the oxygen
atoms of 2.84 ˚A and for the carbon atoms of 2.90 ˚A.
This work was performed in cooperation with C. Stadler, C. Kumpf
and E. Umbach (Universität Würzburg) and supported by the ESRF
(Grenoble, France).
O 14.59 Mo 18:00 Bereich C
Reflexions-Anisotropie-Spektroskopie zur Untersuchung von
adsorbatmodifizierten vizinalen Si(001) Oberflächen — •R.
Passmann 1,2 , M. Wahl 1,2 , M. Gensch 1 , K. Hinrichs 1 , W. Richter
2 und N. Esser 1 — 1 Institut für Spektrochemie und Angewandte
Spektroskopie - Institutsteil Berlin, Albert-Einstein-Str. 9, D-12489
Berlin-Adlershof — 2 TU Berlin, Institut für Festkörperphysik, PN6-1,
Hardenbergstr. 36, D-10623 Berlin
Bestimmte organische Moleküle bilden geordnete Monolagen auf
Si(001) Substraten. Durch geeignet gewählte vizinale Substrate kann
zudem eine Vorzugsrichtung dieser Moleküle entlang bestimmter
Richtungen in der Substratebene erreicht werden. Die damit einhergehende
Modifizierung der anisotropen optischen Eigenschaften kann mit
Reflexions-Anisotropie-Spektroskopie (RAS) untersucht werden.
Optisch anisotrope Cyclopenten/Si(001) sowie Ethylen/Si(001) Grenzflächen
wurden auf vizinalen Si(001) Substraten (4 ◦ offcut in 〈111〉
Richtung) im Ultrahochvakuum präpariert und mit RAS und verschiedenen
komplementären Methoden (LEED, Auger) charakterisiert.
Durch Vergleich der optischen Spektren mit entsprechenden ab-initio
Rechnungen [1] werden Bindungsmodelle für die adsorbatmodifizierten
Si(001) Grenzflächen diskutiert.
[1] W. C. Lu, W. G. Schmidt, J. Bernholc, Phys. Rev. B 68 (11), 115327
(2003)

Oberflächenphysik Montag
O 14.60 Mo 18:00 Bereich C
Intermolecular Interactions in Thin Films of SubphthalocyaninatoChloroBoron
(SubPc) and its Fluorinated Derivative
(F12SubPc) — •Christine Mattheus 1 , Dieter Wöhrle 2 ,
William Durfee 3 , and Derck Schlettwein 1 — 1 Physical
Chemistry 1, University of Oldenburg, Germany — 2 Institute of Organic
and Macromolecular Chemistry, University of Bremen, Germany —
3 Department of Chemistry, Buffalo State College, NY, USA
Thin films of unsusbstituted SubPc and perfluorinated F12SubPc were
prepared by PVD on various single crystalline and amorphous insulators.
The intermolecular coupling was studied by in situ UV- vis absorption
spectroscopy, the morphology was analysed by atomic force microscopy
(AFM) and the structure of the films was studied by X-ray diffraction
(XRD). For SubPc, a rather small influence of the substrate structure
was observed, whereas F12SubPc showed significantly different spectra
on KBr and KCl when compared to NaCl, mica or glass. For both materials,
spectral characteristics were observed that point at changing interactions
of the molecules in the solid films. In the AFM analysis larger
and more oriented grains were found for films grown at elevated temperature.
These films were characterized by well- defined chromophores
coupling as seen in UV-vis spectroscopy and were crystalline as observed
in XRD. Relative intensities in XRD were used to discuss a preferential
orientation of crystals and hence the molecules relative to the surface.
O 14.61 Mo 18:00 Bereich C
Surface photovoltage of thin organic layers on single-crystal
metal and semiconductor surfaces — •Sebastian Teich, Stefan
Grafström, Christian Loppacher, Ulrich Zerweck, and
Lukas Eng — Institute of Applied Photophysics, University of Technology
Dresden
Surface photovoltage (SPV) investigations of ultrathin organic films
on metal and semiconductor substrates with a unique sensitivity of
< 1 mV are reported. This is achieved with a novel phase-sensitive
method based on an accurate measurement of the light-induced shift
of the ultraviolet (UPS) or x-ray (XPS) photoemission spectrum under
power-modulated illumination of the sample. Furthermore, in order
to derive local SPV information with high spatial resolution, we
use similar modulation methods, however involving scanning tunneling
and atomic force microscopy rather than XPS/UPS. Our SPV
studies provide access to electronic properties of semiconductor surfaces
and interfaces, including in particular organic-inorganic interfaces.
We demonstrate the versatility of our SPV techniques for thin films
of perylene-tetracarboxylic dianhydride (PTCDA) and Cu-tetra-3,5 ditertiary-butyl-phenyl
porphyrin (Cu-TBPP) on various substrates, including
Cu(100) and Ge(100).
O 14.62 Mo 18:00 Bereich C
Deposition of ordered TiOPc thin films by Supersonic Molecular
Beam Epitaxy (SuMBE) — •Karsten Walzer 1 , Tullio
Toccoli 2 , Alessia Pallaoro 2 , Roberto Verucchi 2 , Salvatore
Iannotta 2 , Torsten Fritz 1 , and Karl Leo 1 — 1 Institut für Angewandte
Photophysik, TU Dresden, 01062 Dresden, Germany — 2 Institute
for Photonics and Nanotechnology, Trento, Italy
The deposition of organic thin films for device applications requires a
reliable method for the deposition of well-ordered molecular films significantly
above the monolayer level. Searching for an alternative method to
conventional organic molecular beam deposition (OMBD), we used Supersonic
Molecular Beam Epitaxy (SuMBE) for the deposition of ordered
organic films. The method uses the expansion of an inert carrier gas into
vacuum with organic molecules seeded into the beam, which allows to
control both energy and momentum of the molecules.
We present the SuMBE growth of titanyl phthalocyanine (TiOPc),
which is of interest for organic solar cells. Substrates were glass and mica.
Depending on substrate and substrate temperature we could adjust the
growth of different crystal phases and surface morphologies. Especially
the TiOPc phase II was grown at significantly lower substrate temperatures
than usually needed in OMBD.
O 14.63 Mo 18:00 Bereich C
Inital growth of PTCDA on Cu(100) investigated by STM —
•Thorsten Wagner, Christian Bobisch, Amin Bannani, Hatice
Karacuban und Rolf Möller — Universtität Duisburg-Essen,
Institut für Experimentelle Physik, Universitätsstr. 3-5, 45141 Essen
The organic semiconductor 3,4,9,10-perylene-tetracarboxylic-
dianhydrid (PTCDA) has been subject of many investigations. In this
work we will discuss the initial growth of PTCDA on a Cu(100) single
crystal surface. The investigations have been carried out with a self
build STM under UHV conditions. The films with a thickness of about
one monolayer have been grown by means of thermal evaporation from a
heated crucible. A structure comparable to the square phase also found
by Chizhov et al. on Au(111. The growth of PTCDA on Cu(100) will be
compared to results on other copper surfaces.
[1] I. Chizhov et al., Journal of Crystal Growth 208 (2000) 449-458
O 14.64 Mo 18:00 Bereich C
STM investigations of very large macrocycles adsorbed on
surfaces — •Iordan Kossev and Moritz Sokolowski — Institut
für Physikalische und Theoretische Chemie, Universität Bonn, Wegelerstr.
12, 53115 Bonn, Germany
Rotaxanes and catenanes are of interest for the investigation on mechanically
interlocked molecules [1]. A large tetralactam - macrocycle
(961.3 amu), used as a building block for rotaxanes and catenanes, was
deposited onto the Au(111) surface from a thermal evaporation cell. STM
images were taken for different coverages at room temperature. At a coverage
of less than one monolayer, it was found that the macrocycles form
small clusters at step edges and surface defects, leaving large terraces
uncovered. At a coverage around one monolayer, the molecules form disordered
structures, which remain disordered after annealing to 423 K.
Presumably, the reason for these observations is the week interaction between
the Au surface and the molecules, in combination with a strong
hydrogen – bonding between the molecules. Further investigations on the
ordering of these molecules on more reactive surfaces like Ag(111) and
Cu(111) are under progress. The macrocycles were kindly supplied by
C. Schalley and F. Vögtle. This work was supported by the DFG (SFB
624). [1] J.-P. Sauvage, Acc. Chem. Res. 31, (1998) 611.
O 14.65 Mo 18:00 Bereich C
Untersuchung von Punkt- und Liniendefekten auf der
NiO(001)-Spaltfläche mittels Rasterkraftmikroskopie — •Nico
Plock, U. Kaiser, A. Schwarz und R. Wiesendanger — IAP,
Mikrostrukturzentrum, Universität Hamburg
Die Übergangsmetalloxide, zu denen auch NiO gehört, waren vor allem
aufgrund ihrer katalytischen Eigenschaften in der Vergangenheit bereits
Gegenstand zahlreicher Untersuchungen. NiO zeigt bei defektfreien
Oberflächen kaum reaktives Verhalten, während z.B. durch Punkt- und
Liniendefekte die Reaktivität stark gesteigert wird. Wir haben mittels eines
Rasterkraftmikroskops (RKM) im Ultrahochvakuum Untersuchungen
an in situ-präparierten (001)-Oberflächen von NiO durchgeführt. Dazu
wurden verschiedene Proben nach dem in situ-Spalten mit dem RKM
abgebildet und anschließend für acht bis zwölf Stunden auf Temperaturen
zwischen 200 ◦ C und 720 ◦ C geheizt. Anschließend wurden die Proben
mit LEED und Augerspektroskopie, sowie dem RKM untersucht. Neben
Ladungen und Adsorbaten auf der Oberfläche wurden sowohl Fehlstellen
als auch Linien- und Punktdefekte gefunden.
O 14.66 Mo 18:00 Bereich C
First-principles study of Cu interacting with polar ZnO surfaces
— •Bernd Meyer and Dominik Marx — Lehrstuhl für Theoretische
Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany
The structure and electronic properties of single Cu atoms, copper
monolayers and thin copper films on the polar oxygen and zinc terminated
surfaces of ZnO are studied using periodic density–functional
calculations. We find that the binding energy of Cu atoms sensitively depends
on how charge neutrality of the polar surfaces is achieved. Bonding
is very strong if the surfaces are stabilized by an electronic mechanism
which leads to partially filled surface bands. As soon as the surface bands
are filled (either by partial Cu coverage, by coadsorbates, or by the formation
of defects), the binding energy decreases significantly. In this case,
values very similar to those found for nonpolar surfaces and for copper
on finite ZnO clusters are obtained. Possible implications of these observations
concerning the growth mode of copper on polar ZnO surfaces and
their importance in catalysis are discussed.
O 14.67 Mo 18:00 Bereich C
Valence Band Spectroscopy on CoO Surfaces: A Comparison of
MIES and UPS(HeI) Results — •F. Schweiger, S. Rudenkiy,
M. Frerichs, W. Maus-Friedrichs, and V. Kempter — Institut
für Physik und Physikalische Technologien, Technische Universität
Clausthal, D–38678 Clausthal–Zellerfeld, Germany

Oberflächenphysik Montag
We report the growth of CoO–films on Si substrates. The characterization
of the electronic and geometrical structure took place by MIES/UPS
and STM/AFM, respectively. Two strategies were pursued for the preparation
of the CoO films: (1) Co films (10 layers) were prepared by thermal
evaporation of Co onto Si substrates. The films were characterized
by XPS, and MIES/UPS(HeI). The Co film was then exposed to oxygen
(2000L) at 500K under ”in situ” control of MIES and UPS(HeI). (2) Co
and O2 (10ML in 7min at 10 −6 mbar) were co–deposited at 400K, and
were characterized by XPS, and MIES/UPS. Although both procedures
give films that display the electronic structure of bulk CoO, procedure
(2), according to STM, produced a superior geometric structure. Both
MIES and UPS display 5 spectral features. However, characteristic differences
are seen. The same behaviour has been seen before for LaCoO3
and NiO. By recalling that the He ∗ probe atom, employed for MIES, interacts
far more efficiently with the diffuse O2p states of the O 2− anions
than with the rather compact Co3d states of the Co 2+ cations, the qualitatively
different behaviour, seen in MIES and UPS, can be explained on
the basis of a Co2O11 cluster model (S. Masuda et al: P.R.L. 71 (1993)
4214).
O 14.68 Mo 18:00 Bereich C
Elektronen-Energieverlust-Spektroskopie am Schichtsystem
Fe/NiO — •V. Bocatius, B. Fromme und E. Kisker — Institut
für Angewandte Physik, Heinrich-Heine Universität Düsseldorf, 40225
Düsseldorf
Dünne ferromagnetische Schichten (Fe) auf einem antiferromagnetischen
Substrat (NiO) sind Grundbausteine für Magnetfeldsensoren.
Ein solches Schichtsystem wird z.B. in Spin-Valve-Strukturen eingesetzt.
Wir haben dünne Fe-Filme (0.5 bis 60ML) auf in-situ gespaltene
NiO-Einkristalle aufgedampft. Mit Hilfe der Elektronen-Energieverlust-
Spektroskopie (EELS) konnte gezeigt werden, dass in der Grenzfläche von
NiO und Fe sowohl oxidiertes Eisen als auch reduziertes Nickel entsteht.
O 14.69 Mo 18:00 Bereich C
Modellversuch zum Design eines non contact lateral force cantilevers
— •Tobias Kunstmann, Lukas Spickermann, Andreas
Schlarb und Rolf Möller — Universtität Duisburg-Essen, Institut
für Experimentelle Physik, Universitätsstr. 3-5, 45141 Essen
Zur Messung von Reibung mit einem non-contact AFM benötigt man
lateral schwingende Spitzen. Durch die Modifikation eines kommerziellen
Cantilevers mittels Ionenstrahlätzens soll dies erreicht werden. Ein
Teil des Cantilevers soll hierzu so abgetragen werden, dass ein weiterer
Schwingungsmode ermöglicht wird, bei dem die Spitze sich parallel zur
Oberfläche bewegt. Die Resonanzfrequenz dieser Bewegung soll separat
angeregt werden können. Die hier gezeigten Vorexperimente wurden an
einem makroskopischen Modell (1000:1) durchgeführt. Zuerst wurde die
Übertragbarkeit des Modells auf die Originalgröße mittels eines einfachen
Cantilevers überprüft. Danach wurde das Schwingungsverhalten und die
Resonanzfrequenzen für das modifizierte makroskopisches Modell experimentell
bestimmt. Ein Vergleich mit finite elements Rechnungen zeigt
qualitativ das gleiche Verhalten. Wir können zeigen, dass sich bei geeigneter
Geometrie die Spitze überwiegend lateral zur Oberfläche bewegt.
Diese Bewegung lässt sich selektiv anregen.
O 14.70 Mo 18:00 Bereich C
Hochauflösende Rasterkapazitätsspektroskopie an Halbleitermikrostrukturen
— •Martin von Sprekelsen, Volker Hagen,
Theophilos Maltezopoulos und Roland Wiesendanger — Universität
Hamburg, Institut für Angewandte Physik, Zentrum für Mikrostrukturforschung,
Jungiusstrasse 11, 20355 Hamburg
Rasterkapazitätsmikroskopie (SCM) ist ein etabliertes Verfahren zur
Analyse zweidimensionaler Dotierungsprofile von Halbleiterbauelementen.
In der Entwicklung, Kontrolle und Fehleranalyse hat es sich als
leistungsfähig und zuverlässig erwiesen. Mit diesem üblichen Messverfahren
lassen sich Ladungsträgerkonzentrationen bei konstanter Probenbiasspannung
abbilden und daraus Rückschlüsse auf die zugrundeliegenden
Dotierungsprofile ziehen.
Bei fester Biasspannung treten unvermeidbare Effekte wie Aufladung
der Probenoberfläche, spannungsabhängige Orts- und Dotierungsauflösung
etc. auf, die dabei jedoch die Interpretation der gewonnenen
Messdaten erschweren. Diese Probleme lassen sich mittels der
Rasterkapazitätsspektroskopie (SCS) dadurch umgehen, dass für jeden
Messpunkt eine vollständige Kapazitäts-Spannungs-Kurve aufgenommen
wird. So werden für den gesamten technologisch relevanten Bereich
vollständige und genaue Ergebnisse über Dotierungskonzentrationen und
die räumliche Lage von Dotierungsübergängen ermöglicht. Über die technische
Umsetzung des Konzeptes (sog. High-Speed-SCS) wird berichtet.
Spektroskopische Messergebnisse an heterogenen Dotierungsprofilen zeigen
Ortsauflösungen bis hinab zu 6 nm.
O 14.71 Mo 18:00 Bereich C
Aufbau eines Tieftemperatur-Hochmagnetfeld-Rastertunnelmikroskops
mit X-Y-Verschiebetisch und Spitzenwechsel —
•Torge Mashoff, Daniel Haude, Markus Morgenstern
und Roland Wiesendanger — Institut für Angewandte Physik,
Jungiusstraße 11, 20355 Hamburg
Für UHV-Rastertunnelmikroskopie bei T=6 K in Magnetfeldern bis
zu 6 T wurde ein sehr kleines (⊘=26 mm) Mikroskop mit X-Y-
Verschiebetisch und Spitzenwechselmechanismus aufgebaut. Die X-Y-
Verschiebung wird durch einen Piezo-Stack, der im Slip-Stick-Modus arbeitet,
realisiert und erlaubt Verfahrwege bis zu 1.5 mm. Der Spitzenwechsel
nutzt den implementierten Grobannäherungsmechanismus nach
dem Walker-Prinzip und basiert auf einer mechanischen Halterung der
Spitze. Erste Testmessungen bei tiefen Temperaturen werden präsentiert.
O 14.72 Mo 18:00 Bereich C
Design of a scanning tunneling microscope for variable temperatures
in an ultra-high-vacuum environment — •Stefan Kuck,
Germar Hoffmann, and Roland Wiesendanger — Institut für
Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität
Hamburg, Jungiusstr. 11, 20355 Hamburg
To study the temperature dependence of the growth and the local
electronic/magnetic properties of molecular systems, we designed a variable
temperature scanning tunneling microscope (VT-STM). The whole
compact and rigid microscope body is connected to a liquid helium flow
cryostat and rests on a commercially available damping stage. The STM
is installed in an ultra-high-vacuum system for insitu preparation of substrates
free of contamination. Molecules are sublimated from mobile evaporators,
whereby deposition onto substrates mounted and cooled in the
STM is possible. We will discuss the design concept of the system and
present first results.
O 14.73 Mo 18:00 Bereich C
Temperature dependence of atomic friction on graphite —
•Lars Jansen 1,2 , Andre Schirmeisen 1,2 , Hendrik Hölscher 1,2 ,
and Harald Fuchs 1,2 — 1 Westfälische Wilhelms Universität,
Physikalisches Institut, Wilhelm-Klemm Str. 10, 48149 Münster —
2 CeNTech, Center for Nanotechnology, Gievenbecker Weg 11, 48149
Münster
One fundamental mechanism of atomic scale friction is believed to be
the so-called sick-slip mechanism, mathematically described by the Tomlinson
model [1]. Previous investigations have shown that the temperature
plays a crucial role for the velocity dependence of atomic scale friction
[2]. The reason is that for finite temperatures the underlying frictional
forces follow a statistical distribution.
The aim of our work is to extract these distributions from data acquired
with an atomic force microscope (AFM) under ultra-high-vacuum
conditions. Comparison with the ’ramped creep’ model [3] indicates good
agreement with our experiments. Furthermore, we measure the temperature
dependence of these distributions. As the main sample serves a vacuum
cleaved HOPG-surface on which we can demonstrate the stick-slip
mechanism with high resolution and good reproducibility. Measurements
are performed in a temperature range from 100 K - 300 K.
[1] Tomlinson, Phil. Mag. 7, 905 (1929)
[2] Gnecco et al., Phys. Rev. Lett. 84, 1172 (2000)
[3] Sang et al., Phys. Rev. Lett. 84, 174301 (2001)
O 14.74 Mo 18:00 Bereich C
Chemical Reactivity Properties of Thiol Self-Assembled Monolayers
on Au(111) observed by STM/ AFM — •Till Hagedorn,
Andre Schirmeisen, Lifeng Chi, and Harald Fuchs
— Physikalisches Institut & CeNTech, University of Muenster,Wilhelm-
Klemm-Str. 10, 48149 Muenster, Germany
In this work self-assembled monolayers of thiols on Au(111) were investigated
with STM/ AFM methods under UHV conditions p≈ 10 −10
mbar) at room temperature. The preparation is done by chemisorbtion
in a 3 mM ethanolic solution of 11-Mercapto-1-undecanol (SH-(CH2)11-
OH) outside the UHV chamber. Heating at approximately 120 ◦ C under

Oberflächenphysik Montag
UHV conditions lowers the density of thiole molecules at the Au(111)
surface which results in an alignment of the thiole molecules parallel to
the Au surface. The focus is on the properties of the line-structure phase
with the lowest surface density [1][2]. Al clusters are evaporated on the
regions of the thiol line-structure in order to investigate where the Al
atoms adsorb. With the STM we find that the Al clusters preferably
adsorb onto the sulphur head of the thiol. Additionally, we investigate
in AFM measurements with Al functionalized tips the forces acting on
different parts of the thiol chain.
[1] Poirer G.E. Langmuir 1999, 15, 1167-1175
[2] Staub R., Toerker M., Fritz T., Schmitz-Hübsch T., Sellam F., Leo
K. Langmuir 1998, 14, 6693-6698
O 14.75 Mo 18:00 Bereich C
Nanoscale Conductivity Spectroscopy on Solid Electrolytes using
an Atomic Force Microscope — •Ahmet Taskiran, Andre
Schirmeisen, Harald Fuchs, Frank Natrup, and Harmut
Bracht — Physikalisches Institut and CeNTech, University of Muenster,
Wilhelm-Klemm-Str.10, 48149 Muenster, Germany
Ion conducting solid materials play an important role as electrolytes
in energy conversion systems, such as batteries and fuel cells, and also in
electrochemical sensors. An important prerequisite for further progress
in this field is a better understanding of the ion transport mechanisms
on microscopic and nanoscopic length scales.
We are using atomic force microscopy (AFM) to measure the ionic
conductivity in nanoscale volumes of dielectric glasses. The AFM is operated
in the non-contact mode in vacuum. After a sudden change of the
tip voltage, the relaxation of the electrostatic force between tip and sample
is measured as a function of time. We measure these relaxation curves
as a function of sample temperatures ranging from 100K to 675K. The
observed relaxation curves are fitted well with a stretched exponential
function and we can determine the activation energy of the conduction
processes of the ions. First results indicate a good agreement of the activation
energies for several prototype ionic glas conductors with values
from macroscopic measurements. This method allows us to study fundamental
processes of ionic transport and is in particular interesting for the
investigation of nanostructured solid electrolytes.
O 14.76 Mo 18:00 Bereich C
Optical phase effects and resonance shift in scattering-type
near-field infrared microscopy — •Thomas Taubner 1 , Fritz
Keilmann 1 , and Rainer Hillenbrand 2 — 1 Max-Planck-Institut für
Biochemie, Am Klopferspitz 18a, 82152 Martinsried — 2 Nano-Photonics
Group, Max-Planck-Institut für Biochemie, Am Klopferspitz 18a, 82152
Martinsried
A scattering-type near-field optical microscope (s-SNOM) detects light
scattered at the sharp tip of a probing needle and allows imaging with
subwavelength resolution, independent of the wavelength used for illumination[1].
We now study amplitude and phase of light scattered from a s-
SNOM’s tip probing a flat SiC sample, at mid-infrared frequencies where
surface phonon polaritons resonantly enhance the tip-sample near-field
interaction [2]. A nanometer-scale variation of the gap width between tip
and sample causes the optical phase to change dramatically and the resonance
to shift. Both effects can be explained by theory that treats the
system as a point dipole (tip) interacting with its image dipole (sample),
in electrostatic approximation. The phase effects and resonance shifts are
not restricted to phonon polariton excitation in polar dielectrics like SiC,
but should be observable also for resonances related to plasmons and
excitons.
[1] T. Taubner, R. Hillenbrand and F. Keilmann, Journal of Microscopy
210, 311 (2003)
[2] R. Hillenbrand, T. Taubner and F. Keilmann, Nature 418, 159
(2002)
O 14.77 Mo 18:00 Bereich C
Investigations on nanocrystals in silicondioxide by atomic force
microscopy — •E. Beyreuther 1 , R. Beyer 1 , K. Walzer 1 , S.
Behrendt 1 , V. Beyer 2 , J. von Borany 2 , J. Weber 1 , and L. Eng 1
— 1 Technische Universität Dresden, Institut für Angewandte Physik, D-
01062 Dresden — 2 Forschungszentrum Rossendorf, Institut für Ionenstrahlphysik
und Materialforschung, PF 510119, D-01314 Dresden
Nanocrystals in SiO2 are promising structures for future optoelectronic
and memory devices. Optimization of the synthesis process needs detailed
information about structure and morphology.
Within the present work SiO2 layers of 100 nm thickness were ther-
mally grown on Si(100). Subsequently Si or Ge nanocrystals were fabricated
within those oxide films by ion implantation and rapid thermal
annealing. Etching in buffered HF-solution with a low rate of 12nm/min
removed the top oxide layer and uncovered the nanocrystals to a certain
depth. The surfaces of several samples, which had undergone varied
implantation and annealing conditions as well as different etching times
were imaged by tapping-mode AFM down to scan sizes of 200x200 µm 2 .
The apparent nanocrystal size and density were found to be dependent
on the synthesis parameters and the position within the oxide layer.
In comparison to TEM investigations of the same structures we discuss
critically the determination of the cluster size.
O 14.78 Mo 18:00 Bereich C
Detection of dopant profiles in silicon by scanning capacitance
microscopy and related techniques: the role of the passivation
layer — •Reinhard Beyer 1 , Elke Beyreuther 1 , Bernd
Schmidt 2 , Stefan Polzin 3 , and Jörg Weber 1 — 1 Technische Universität
Dresden, Institut für Angewandte Physik, D-01062 Dresden —
2 Forschungszentrum Rossendorf, Institut für Ionenstrahlphysik und Materialforschung,
PF 510119, D-01314 Dresden — 3 Fraunhofer-Institut für
Photonische Mikrosysteme, Grenzstrasse 28, D-01109 Dresden
Scanning capacitance microscopy (SCM) was employed for the study
of dopant profiles in silicon test structures. The samples were fabricated
by implantation of boron and phosphorous into n-type silicon. The oxide
mask for the implantation was shaped by photolithography. Hence,
stripe patterns with a size of 2 µm of the implanted region and different
widths of the interregion were obtained. The implantation dose was
5 × 10 12 , 5 × 10 13 and 5 × 10 14 cm −2 for both implanted ions. Samples
with native oxide coverage and with a 7 nm thick silicondioxide layer
were compared in this study. SCM measurements were performed in the
contact-mode. We show, that the contrast of the SCM signal between
differently doped regions depends not only on the dc bias applied during
the scan, but also on charge instabilities and trapping effects. The latter
appeared mostly for samples with native oxide and resulted in hysteresis
effects which could be observed with local dC/dV vs. V spectroscopy.
The charge instabilities are discussed in a MOS-model. The results are
compared with scanning spreading resistance measurements and with
non-contact SCM.
O 14.79 Mo 18:00 Bereich C
Study of particle-substrate interaction by nanomanipulation experiments
with dynamic scanning force microscopy — •Claudia
Ritter 1 , Markus Heyde 2 , and Klaus Rademann 1 — 1 Humboldt-
Universität zu Berlin, Institute of Chemistry, Brook-Taylor-Str. 2, D-
12489 Berlin, Germany — 2 Fritz-Haber-Institute of the Max-Planck-
Society, Faradayweg 4-6, D-14195 Berlin, Germany
We utilise an advanced homebuilt SFM in the dynamic mode, in
conjunction with a special homebuilt software, to perform precise
nanomanipulation experiments. The corresponding experimental technique
should be denoted as Dynamic Surface Modification (DSM), comprising
both the dynamic technique of the SFM, as well as the manipulation
(translation, in-plane rotation, cutting) of structurally unchanged
particles on a given substrate surface. It is easily possible to switch between
imaging mode and DSM mode, enabling the direct manipulation
of nanoparticles under ambient conditions with high precision and simultaneously
studying particle-substrate interaction to give evidence about
motion and tribological values of the sample system. We have successfully
manipulated miscellaneous nanoparticles on surfaces, e.g. antimony
islands, gold islands, tin islands, nanotubes, small latex spheres as well
as cells.
O 14.80 Mo 18:00 Bereich C
In-situ SPM usage at MOVPE-conditions — •Markus
Breusing, Bert Rähmer, Raimund Kremzow, and Wolfgang
Richter — TU-Berlin, Institut für Festkörperphysik, Hardenbergstr.
36, 10623 Berlin
In-situ scanning probe techniques which are applicable in an MOVPE
growth environment to directly give quantitative information about the
nano-scale topography of the sample do not exist up to now.
Developing a SPM for in-situ MOVPE measurements requires a completely
new setup. In comparison to the commercially available SPMsolutions,
a number of additional problems have to be solved. The limited
space in the MOVPE reactors and the high temperature caused by the
thermal conductivity of the carrier gas during growth near the suszeptor
requires a special design of the components of the SPM. On the other

Oberflächenphysik Montag
hand the influence of the SPM components on all growth relevant parameters
should be minimized. Therefore the tip has to be quite long than
(2 cm) in order to bridge the distance between linertube and susceptor.
Nevertheless the construction has to be stable to achieve a good resolution,
especially because of the disturbing influence of vibrations, caused
by pumping systems, gas-flow, etc. in MOVPE.
The new achievements will be demonstrated.
O 14.81 Mo 18:00 Bereich C
Reduktion der Oberflächenrauhigkeit isolierender und metallischer
Schichten mittels niederenergetischem Plasmastrahl —
•D. Hoffmann, P.A. Beck, S.O. Demokritov und B. Hillebrands
— Fachbereich Physik und Forschungsschwerpunkt MINAS,
Technische Universität Kaiserslautern, Erwin-Schrödinger-Str. 56, 67663
Kaiserslautern
Am Beispiel von metallischen Schichten (Cu, CoFe, NiFe) und MgO
Substrate wird der Effekt der Glättung von Oberflächen untersucht. Dazu
wird eine induktiv gekoppelte HF-Plasmastrahlquelle eingesetzt, die
Ionen verschiedener Arbeitsgase (z.B. Ar, O2) mit exakt einstellbaren
Energien von 20-100eV erzeugt. Als Analysemethode wird AFM; insitu
STM, LEED und Auger-Elektronen-Spektroskopie verwendet. Dabei
zeigt sich, dass mittels O2-Ionen nicht nur die Rauhigkeit von MgO stark
reduziert werden kann (RMS < 0.1nm), sondern auch die durch den Herstellungsprozess
bedingte Kontamination der Oberfläche mit Kohlenstoff
vollständig entfernt wird. Einen vergleichbaren Glättungseffekt erzielt
man beim Beschuss von metallischen Schichten mit Ar-Ionen. Die Rauhigkeiten
werden dabei um mehr als 40% verringert. Der Effekt zeigt eine
Selektivität bezüglich des lateralen Maßstabes. Die Rauhigkeit wird mit
einer typischen Skala von 5-50nm am besten reduziert.
O 14.82 Mo 18:00 Bereich C
Micromechanical properties of Tobacco Mosaic Virus studied by
AFM — •Nicola Maghelli, Schmatulla Alexander, and Othmar
Marti — Abteilung Experimentelle Physik Universitaet Ulm
The morphology of the Tobacco Mosaic Virus (TMV) is well known in
spite of its very simple structure, consisting of an helix-arranged protein
capside (pitch 2.3 nm, radius 9 nm) for a total length of 282 nm. However,
very few is still known about its mechanical properties: by means
of a self made atomic force microscope we were able to investigate some
basic properties, such as stiffness and E modulus, at single virion level.
Measurements of the viruses (LGC Promochem ATCC PV-135P) were
both carried on in air and in liquid environment employing various techniques
(tapping mode, pulse force mode). Different substrates (cleaved
mica, glass, polycarbonate, gold Fisher pattern) and probe preparations
methods (spin coating, critical point drying) have been employed as well
O 15 Hauptvortrag M. A. Schneider
as different solvents (DMSO, alcohol, water) when working in liquid environment.
The results give a lower limit to the single virion elasticity and E modulus’s
values.
O 14.83 Mo 18:00 Bereich C
Cantilever characterization by noise measurements in an
Atomic Force Microscope — •T.D. Long, F. Müller, A.-D.
Müller, and M. Hietschold — Chemnitz University of Technology,
Institute of Physics, Solid Surface Analysis Group, 09107 Chemnitz
This contribution presents an instrumentation for low signal analysis
based on the lock-in amplifier principle. The device has been developed
for enhanced signal analysis of multiple cantilever devices for the Atomic
Force Microscopy, where the individual elongations of the cantilevers are
separated by frequency selection. Here, its application is demonstrated
at the example of cantilever noise measurements. Resonance spectra are
detected for various cantilever types in dependence on the excitation amplitude
and the pressure. The quality factor is derived and its dependency
on several parameters is presented.
O 14.84 Mo 18:00 Bereich C
Digital Pulsed Force Mode and Dynamical Friction Measurements
— •Alexander Gigler 1 , Peter Spizig 2 , Stefan Walheim
3 , Othmar Marti 1 , and Thomas Schimmel 3 — 1 Experimental
Physics, University of Ulm, D-89069 Ulm, Germany — 2 WITec GmbH,
www.WITec.de — 3 Institute for Nanotechnology, Forschungszentrum-
Karlsruhe GmbH, D-76021 Karlsruhe, Germany
As a standard technique force vs. distance plots (FD-plots) allow to
acquire local mechanical properties, but they are at least two orders of
magnitude too slow when used in a surface imaging mode. In order to
measure an entire image at the same scanning speed, the Pulsed-Force-
Mode was developed. A recent development is the Digital Pulsed Force
Mode, that acquires each force curve for every pixel during a single run
of the experiment. Therefore, postprocessing algorithms, i.e. for the calculation
of the energy dissipated in each cylce, can be used to analyze
the sample in various ways without scanning the sample more often and
possibly destroying it.
To access friction parameters and the properties accessible by PFM
at thesame time, the system has been extended to the COmbined-
DYnamical-Mode and is now also capable of dynamical friction measurements.
The concurrent measurement of both friction and adhesion is
especially important, since both seem to be closely related.
In this poster, the principles of this measurement system, the implementation
on our WITec α-SNOM setup and results on a SAM based on
a lift-off technique using µ-contact printing will be shown.
Zeit: Dienstag 09:30–10:15 Raum: H36
Hauptvortrag O 15.1 Di 09:30 H36
Electron Spectroscopy of Many-Body Interaction using
Scanning Tunneling Microscopy — •M. Alexander Schneider,
Lucia Vitali, Peter Wahl, Lars Diekhöner, Gero Wittich,
Michael Vogelgesang, and Klaus Kern — Max-Planck-Institut
für Festkörperforschung, Heisenbergstr. 1, 70569 Stuttgart
Electron spectroscopy is pivotal to solid state physics. When traditional
spectroscopy methods like photoelectron spectroscopy, Auger electron
spectroscopy, electron energy loss spectroscopy, etc. reach their limits
to study electronic states in nanostructures, molecules or atoms,
O 16 Hauptvortrag Schäfer
microscopy is the method of choice. Scanning Tunneling Spectroscopy
(STS), is a microscopy method that can provide the wanted spectroscopical
information in many cases with atomic scale resolution.
In this talk I will discuss the possibilities of STS with regard to
many-body interaction in nanostructures. Among these are electronelectron
processes that limit the life time of hot electrons in surface or
image-potential states. But also the interaction of a magnetic adatom or
molecule with a non-magnetic substrate can lead to the formation of a
correlated many-body state, the Kondo state. The spectroscopy of single
impurity Kondo systems provides insight into this interaction of a
magnetic impurity with the electrons at the surface of metals.
Zeit: Dienstag 10:15–11:00 Raum: H36
Hauptvortrag O 16.1 Di 10:15 H36
Electronic Interactions and Phase Transitions at Surfaces and
in Low Dimensions — •Jörg Schäfer — Institut für Physik, Universität
Augsburg, 86135 Augsburg
Low-dimensional and magnetic systems provide particularly clear-cut
cases for the study of modified electron states that result from coupling
with elementary excitations. Electronic quasiparticles of enhanced mass
have been observed on the energy scale of phonons, and very recently on
that of spin waves. Such mechanisms play a role in superconducting pair
formation, with spin fluctuations being considered for high-temperature
superconductivity.
These interactions together with a nesting condition in the Fermi surface
can lead to charge or spin density waves. The phase transition is
characterized by the opening of an energy gap and is accompanied by a

Oberflächenphysik Dienstag
structural distortion. It can be affected by thermal fluctuations and other
metallic states in the system.
Recent progress in photoelectron spectroscopy and synchrotron radi-
ation instrumentation allow to study these effects directly and k-space
resolved. Various examples on surfaces, in quasi-one dimensional crystals,
and in magnetic materials will be shown.
O 17 Elektronische Struktur (Experiment und Theorie) II
Zeit: Dienstag 11:15–13:15 Raum: H36
O 17.1 Di 11:15 H36
Stark Effect for Shockley Surface States of Au(111) and Cu(111)
— •J. Kröger 1 , L. Limot 1 , R. Berndt 1 , and P. Johansson 2
— 1 Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany —
2 University of Örebro, S-70182 Örebro, Sweden
We present scanning tunneling spectroscopy data of Au(111) and
Cu(111) acquired at 9 K. Increasing the electric field between tip and
sample surface leads to a gradual downward shift of the surface state
binding energies for both surfaces. The observed shift is attributed to
the Stark effect as was previously observed for Ag(111) by Limot et al.
[1]. Experimental data are compared with calculations performed within
a one-dimensional model. In the limit of infinitely large tip-surface
distances the photoemission binding energy values are obtained.
[1] L. Limot, T. Maroutian, R. Berndt, and P. Johansson, Phys. Rev.
Lett. 91, 196801 (2003).
O 17.2 Di 11:30 H36
Temperaturabhängige Untersuchung des Cr(001)-Oberflächenzustands
mittels SP-STM/STS — •Torben Hänke, Stefan
Krause, Robert Ravlić, Matthias Bode und Roland Wiesendanger
— Institut für Angewandte Physik, Universität Hamburg,
Jungiusstraße 11, 20355 Hamburg
Die magnetische Struktur der Cr(001)-Oberfläche läßt sich durch
den topologischen Antiferromagnetismus beschreiben, d.h. Terrassen,
die durch monoatomare Stufen getrennt sind, weisen eine alternierende
Magnetisierung auf. Typisch für eine solche bcc(001)-Oberfläche
ist ein spinpolarisierter d z 2-artiger Oberflächenzustand nahe der
Fermi-Kante [1]. Bei Raumtemperatur zeigt spinpolarisierte Rastertunnelspektroskopie
auf benachbarten Terrassen gemäß dieser Interpretation
eine alternierende Peak-Höhe dieses Zustands [2]. Demgegenüber steht
eine STS-Untersuchung bei 4,2 K [3], in der eine scharfe Resonanz
26meV oberhalb der Fermi-Kante beobachtet wird. Diese Resonanz des
Spektrums wird als orbitale Kondo-Resonanz (TK = 180K), hervorgerufen
durch die Bildung eines orbitalen Singlet-Zustandes, erklärt.
Dieser Zustand entsteht aus dem virtuellen Übergang zwischen dxy und
dyz Oberflächenzuständen über Hybridisierung mit dem sp-Band. In
diesem Beitrag wurde der Oberflächenzustand mittels SP-STM/STS bei
Temperaturen von 20-300 K untersucht, und die Ergebnisse werden im
Hinblick auf die verschiedenen Interpretationen diskutiert.
[1] J. A. Stroscio et al., Phys. Rev. Lett. 75 2960 (1995).
[2] M. Kleiber et al., Phys. Rev. Lett. 85 4606 (2000).
[3] O. Yu. Kolesnychenko et al., Nature 415 507 (2002).
O 17.3 Di 11:45 H36
STM-Thermovoltage measurements of surface electronic states
on Ag/Au(111) — •Winfried Langenkamp, Bastian Weyers,
and Rolf Möller — Universität Duisburg-Essen, Institut für Experimentelle
Physik, Universitätsstr. 3-5, 45141 Essen
Submonolayer films of silver on Gold(111) have been examined with
a thermovoltage-STM to determine the shift in the fermi wavelength of
surface state electrons.
If tip and sample of an STM are at different temperatures, a thermovoltage
arises which is correlated to the derivative of the sample’s density
of electronic states at the fermi level.
This voltage is measured by a feedback loop for a bias voltage tuning
the average current to zero. Simultaneously the tip-sample separation is
adjusted by the current resulting from a small alternating bias voltage.
The thermovoltage can be used to analyze atoms of different chemical
nature and standing waves of surface state electrons. [1]
In the experiments discussed the equivalent of less then a monolayer
of Ag was evaporated on Au(111) leading to the formation of silver islands
of monoatomic height. The thermovoltage provides information to
distinguish gold and silver areas below the tip as well as on the standing
waves of surface states on Au(111) and on 1 ML Ag/Au(111).
[1] D. Hoffmann et al., Thermovoltage in scanning tunnelling microscopy,
J. Electron Spectroscopy, 109 (2000) 117
O 17.4 Di 12:00 H36
Shockley surface states at close-packed surfaces — •Frederik
Schiller 1,2 , Vito Servedio 3 , and Clemens Laubschat 1 —
1 Institut für Festkörperphysik, TU Dresden, D-01062 Dresden, Germany
— 2 Donostia International Physics Center, E-20018 Donostia/San
Sebastian, Spain — 3 Sezione INFM and Dip. di Fisica, Università “La
Sapienza”, P. le A. Moro 2, I-00185 Roma, Italy
Valence-band photoemission spectra of close-packed surfaces of the divalent
alkali-earth metals Be and Mg reveal huge peaks due to Shockley
surface states with a free-electron like dispersion parallel to the surface.
Similar states have been observed for close-packed surfaces of the noble
metals Cu, Ag, Au, and the trivalent metal Al. Surprisingly, for the divalent
metals Ca, Sr, Eu, and Yb as well as for all trivalent rare-earth
metals such Shockley states are missing. Instead, rare-earth metals exhibit
a d-like Tamm state that reveals almost no dispersion. On the basis
of band-structure calculations, we show that this different behavior is
caused by the d bands that convert the Shockley-inverted energy gaps at
the close-packed surfaces of Be, Mg, Cu, Ag, Au, and Al into conventional
gaps in the latter group of metals.
Supported by DFG, project La 655/7-2 and SFB 463, TP B4.
O 17.5 Di 12:15 H36
Quantum-well states in thin films of Yb/W(110) studied by
scanning tunnelling spectroscopy — •Daniel Wegner, Andreas
Bauer, and Günter Kaindl — Freie Universität Berlin, Institut für
Experimentalphysik, Arnimallee 14, 14195 Berlin-Dahlem
We have studied the electronic structure of thin films of Yb/W(110)
by low-temperature scanning tunnelling spectroscopy at 10 Kelvin.
Quantum-well states around the Fermi energy, with small dispersion
parallel to the film plane, result in a series of sharp, well resolved peaks
in the tunnelling spectra. Due to the high lateral resolution of STS, the
quantum-well states and their film-thickness dependence can be nicely
observed on films with variations of the local thickness over a range
of 10 monolayers. Close to the Fermi level, the electronic structure is
complex.
This work was supported by the DFG, Sfb-290.
O 17.6 Di 12:30 H36
Confinement and quantization of the Ag(111) surface state in
hexagonal vacancy islands — •Henning Jensen, Jörg Kröger,
and Richard Berndt — Institut für Experimentelle und Angewandte
Physik, Universität Kiel, D-24098 Kiel, Germany
The Shockley surface state of the noble metal (111) faces provides an
experimentally accessible model system for a two-dimensional free electron
gas. We report on the scattering and confinement of the Ag(111) surface
state by hexagonal sputtering-induced surface defects of monatomic
depth. Low-temperature STS measurements of the local density of states
inside these defects reveal a series of resonance peaks, which are compared
with potential well calculations and related experimental results.
Examination of the line width vs. binding energy relation provides an
estimate of surface state electron life time.
O 17.7 Di 12:45 H36
Electronic properties of a 2D-Superlattice of Ce Adatoms on
Ag(111) — •M. Ternes 1 , C. Weber 2 , M. Pivetta 1 , F. Patthey 1 ,
J. Pelz 3 , T. Giamarchi 4 , F. Mila 2 , and W.-D. Schneider 1 —
1 Institut de Physique des Nanostructures, EPFL, CH-1015 Lausanne
— 2 Institut de Physique Théorique, EPFL, CH-1015 Lausanne —
3 Departement of Physics, The Ohio State University, Columbus, Ohio
43210, USA — 4 DPMC, Université de Genève, CH-1211 Genève
Recently we have shown that Ce adatoms on a clean Ag(111) surface
form a hexagonal superlattice at liquid He temperatures [1]. This
superlattice is created by long-range Ag(111) surface state mediated interactions
between the Ce adatoms. We present here local STS measure-

Oberflächenphysik Dienstag
ments and spectroscopic images (dI/dV maps) taken at T = 3.9 K on
this superlattice showing site-dependent characteristic features very different
from the clean Ag(111) surface. Calculations within a nearly free
electron model and tight binding simulations show good agreement with
our data. Furthermore, spectra obtained on compressed and slightly disordered
lattices were successfully simulated and show the dependence of
the LDOS on the local environment. Specifically, we identify the observed
spectroscopic structures with singularities at the high-symmetry points
of the mini-Brillouin zone created by the hexagonal Ce adatom superlattice.
The stability of this superlattice results from the energy gain of
the system manifesting itself by the opening of gaps at the mini-Brillouin
zone boundery.
[1] F. Silly, M. Pivetta, M. Ternes, F. Patthey, J. Pelz, and W.-D.
Schneider, Phys. Rev. Lett., in press.
O 17.8 Di 13:00 H36
Probing of bulk band edges with STM: An ab initio analysis
— •A. Dick 1,2 , M. Hansmann 2 , J.I. Pascual 2,3 , G. Geballos 2,4 ,
H.-P. Rust 2 , K. Horn 2 , and J. Neugebauer 1 — 1 Universität Paderborn,
Dekanat Physik, Warburger Straße 100, D-33098 Paderborn —
2 Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-
14195 Berlin — 3 Institut de Ciència de Materials de Barcelona - CSIC,
08193 Bellaterra, Spain — 4 Laboratorio Nazionale TASC-INFM, 34012
Trieste, Italy
O 18 Adsorption an Oberflächen I
The analysis of standing electronic waves at noble metal surfaces by
scanning tunneling microscopy/spectroscopy (STM/STS) has given valuable
insight into different surface properties such as, e.g., surface state
lifetimes on free surfaces as well as artificial atomic structures. These
studies, however, were mainly limited to surface states. We have therefore
studied the electronic structure of the Ag(110) surface employing
low temperature STS and density-functional theory. In the calculations
atomic relaxation has been fully taken into account and the convergence
of the slab thickness has been carefully checked. Based on these results
a generalized Tersoff-Hamann theory [1] has been used to simulate STS
spectra. A comparison of the experimental and theoretical spectra showed
excellent agreement and clearly demonstrate that bulk states can be
probed in STS.
[1] A.Selloni et al., Phys. Rev. B 31, 2602 (1985)
Zeit: Dienstag 11:15–13:15 Raum: H38
O 18.1 Di 11:15 H38
Composition of the surface oxide on Pd(100) in an O2 and CO
environment — •Jutta Rogal, Karsten Reuter, and Matthias
Scheffler — Fritz-Haber-Institut der MPG, Berlin,Germany
The oxidation of the Pd(100) surface leads to a ( √ 5 × √ 5)R27 ◦ surface
oxide structure, which was recently identified to be essentially a
PdO(101) overlayer on Pd(100)[1]. In thermodynamic equilibrium with
an O2 gas phase this surface oxide represents the most stable phase over
a wide range of environmental conditions, suggesting that the surface oxide
may play some role in the catalytic oxidation of CO on the Pd(100)
surface.
To get a first insight into this catalytic reaction we investigate the
structure and composition of the surface oxide in equilibrium with an
arbitrary O2 and CO gas environment using density-functional theory
and ”constrained” atomistic thermodynamics[2]. Studying the simultaneous
adsorption of CO and O we arrive at a (T, p)-phase diagram of the
stable structures, and discuss possible kinetic effects due to the ongoing
reaction.
[1] M. Todorova et al., Surf. Sci. 541, 101-112 (2003)
[2] K. Reuter and M. Scheffler, Phys. Rev. B 68, 045407 (2003)
O 18.2 Di 11:30 H38
In-situ XPS studies of CO adsorption on Pd(111) in the pressure
range from 10 −8 to 1 mbar — •J. Pantförder, S. Pöllmann,
D. Borgmann, R. Denecke, and H.-P. Steinrück — Physikalische
Chemie II, Universitaet Erlangen-Nuernberg, Egerlandstr. 3, 91058 Erlangen
In an effort to extend the usable pressure range for electron based spectroscopies
from UHV into the so-called pressure gap region, we have built
a new experimental setup for in-situ XPS up to 1 mbar. The principle of
the high pressure cell is based on several stages of differentially pumping
between sample and electron detection, similar to earlier experimental
setups [1]. In our apparatus the measurements can be performed either
by using an ambient pressure in the cell or by application of a directed
gas beam yielding a considerably lower background pressure. The performance
of the high pressure setup will be discussed by the pressure
dependence of CO adsorption on Pd(111), which can be compared to
SFG and XP measurements [2].
Supported by the DFG (Schwerpunktsprogramm 1091, Ste620/3-3).
[1] H.J. Ruppender et al., Surf. Interface Anal. 15 (1990) 245; R.W.
Joyner et al., Surf. Sci. 87 (1979) 501.
[2] V. V. Kaichev et al., J. Phys. Chem. B 107 (2003) 3522.
O 18.3 Di 11:45 H38
Adsorption of water on Pd(111) — •Ari P Seitsonen 1 , Bako
Imre 2 , Gabor Palinkas 2 , and Jürg Hutter 1 — 1 Physikalisch
Chemisches Institut der Universität Zürich — 2 Chemical Research
Centre of the Hungarian Academy
The adsoprtion of water on transition metal surfaces has recently received
wealth of interest. Our studies are motivated by the STM experiments
by Salmeron and co-workers [Mitsui et al, Science 297 (2002)
1850]. They were able to follow the initial adsorption and diffusion of
small water molecules on Pd(111). We have performed density functional
theory (DFT) calculations on water monomer and dimer on the same surface,
using periodic plane wave/pseudo potential method. We find that
the water dimer adsorbs with only one of the molecules adsorbed directly
on the surface, the second one being bound mainly by the hydrogen bond
between the molecules. Our diffusion barrier for the monomer agrees excellently
with the experimental one, however our diffusion barrier for
the dimer is higher than for the monomer, contradicting the conclusions
achieved in the experiments.
O 18.4 Di 12:00 H38
Angular dependence of H2 dissociation at DB steps of Si(001)
— •C. Stanciu and U. Höfer — Fachbereich Physik, Philipps-
Universität Marburg, D-35032 Marburg
The dynamics of dissociative adsorption of molecular hydrogen at the
DB steps of Si(001) was investigated by performing angular dependent
measurements of the initial sticking coefficient for different kinetic energies
of H2 from a supersonic molecular beam. Optical second-harmonic
generation (SHG) was used as a sensitive monitor of hydrogen coverage
at the steps sites. For Ekin = 350 meV, a kinetic energy that considerably
exceeds the mean barrier height of Ea = 80 meV, the polar distribution
is strongly forward-peaked (∼ cos 7.8 θ) whereas for Ekin < Ea,
H2-momentum parallel to the step edges was found to enhance dissociation,
giving rise, e.g., to a broad polar distribution (∼ cos 1.2 θ) for
Ekin = 30 meV. This behaviour contrasts the one previously observed for
H2 adsorption on the terraces [1]. A sharp angular distribution, directed
along the direction of the dangling bonds, was observed in that case for
Ekin < Ea, indicating a strong lateral corrugation of the barrier height
due to the high directionality of the dangling bonds. The behaviour at
the steps, however, suggests the dominant influence of a geometric corrugation.
Possible origins of such a lateral variation of the barrier position
parallel to the step edges, and effects the steering of low energetic
molecules will be discussed.
[1] M. Dürr and U. Höfer, Phys. Rev. Lett. 88, 076107 (2002)

Oberflächenphysik Dienstag
O 18.5 Di 12:15 H38
Re-oxidation of MoO3 and V2O5 systems: Cluster DFT calculations.
— •Malgorzata Witko 1 , Renata Tokarz-Sobieraj 1 ,
Robert Grybos 1 , and Klaus Hermann 2 — 1 Institute of Catalysis
and Surface Chemistry, PAS, ul. Niezapominajek 8, 30-239 Krakow,
Poland — 2 Fritz-Haber-Institut der MPG, Faradayweg 4-6, D-14195
Berlin, Germany
Vanadia and molybdena based systems represent important classes of
materials due to their role in technology, catalysis and environmental
protection. The goal of the present theoretical research is to examine
re-oxidation of V2O5(010) and MoO3(010) surfaces reduced in processes
where surface oxygen vacancies are created. All electronic and energetic
parameters are obtained by the DFT method using embedded clusters
V10O30H12 and Mo15O56H22 clusters as surface models. It is shown that
re-oxidation proceeding via O2 adsorption is a very localized process.
Oxygen adsorbs at any surface vacancy with binding energies EB(O2)
depending on the specific vacancy site (O(1-3)) where the calculations
yield an energetic order O(1) < O(2) < O(3) for MoO3 and O(2) < O(1)
< O(3) for V2O5. Molecular oxygen becomes adsorbed at the surface and
can replace the surface O occupying a specific lattice site with almost no
change in the electron distribution of its vicinity. Thus, the reduced oxide
surface is able to incorporate large amounts of (weakly bound) oxygen
species. The activated oxygen molecule can undergo dissociation yielding
reactive products.
O 18.6 Di 12:30 H38
Surface Strain versus Substrate Interaction in Heteroepitaxial
Metal Layers: Pt on Ru(0001) — •Peter Jakob 1,2 , Andreas
Schlapka 2 , Ulrich Käsberger 2 , Markus Lischka 2 , and
Axel Groß 2 — 1 Fachbereich Physik, Philipps Universität Marburg,
35032 Marburg, Germany — 2 Physik-Department, Technische Universität
München, 85747 Garching, Germany
Using STM, FT-IRAS and TDS, the effect of strain at an epitaxially
grown Pt/Ru(0001) overlayer on the adsorption of various adsorbates
has been studied. These effects are of strong current interest since they
might provide a means of manipulating adsorption properties quite significantly.
For pseudomorphic bimetallic layers the residual influence of
the substrate and of the lattice strain within the deposited film produce
a combined effect on the adsorbed species and it is difficult to uniquely
separate their consequences. By studying the adsorption of CO on increasingly
thicker layers of Pt deposited on Ru(0001), the influence of
surface strain on the adsorption energy has now been disentangled from
the residual chemical interaction with the substrate: whereas the electronic
influence of the substrate dominates for thin films (1-2 layers) and
vanishes for >3 Pt layers, strain related effects due to the 2.5% lattice
mismatch of Pt and Ru remain active for thicker pseudomorphic overlayers
and are only gradually released for n ≥ 5 Pt layers by means of
formation of dislocation networks. Electronic structure calculations confirm
the experimental observations, in particular, the dramatic decrease
of the CO adsorption energy on a single Pt layer which is caused by the
strong Pt-Ru interlayer coupling.
O 19 Teilchen und Cluster II
O 18.7 Di 12:45 H38
Circular dichroism in core-level photoemission from butanediol
on Si(100) — •JeongWon Kim 1 , Massimo Tallarida 1 ,
Hugo Dil 1 , Karsten Horn 1 , Marilena Carbone 2 , Maria
Pia Casaletto 3 , Roberto Flammini 4 , and Maria Novella
Piancastelli 2 — 1 Fritz-Haber-Institut der MPG, 14195 Berlin —
2 Dip. Di Scienze e Tecnologie Chimiche, Universita Tor Vegata, 00133
Roma, Italia — 3 Istituto per lo Studio di Materiali Nanostrutturati,
CNR, I-90146 Palermo — 4 Istituto di Metod. Inorganiche, 00016
Monterotondo
Molecules which possess a chiral center are of great importance in
chemistry and biology. In search of a method to control enantioselectivity
in chemical reactions, recent interest has turned to adsorbed chiral
molecules. The detection of chirality in adsorbed molecules is difficult,
however, having so far been mostly demonstrated in scanning tunnelling
microscopy. Here we report on a study of an adsorbed chiral molecule,
i.e. 2,3 butanediol on Si(100), using circular dichroism in core level photoemission.
Butanediol is well suited for such studies since it contains
two chemically different sets of carbon atoms, only one of which is in a
chiral center. We observe clear dichroism in the carbon 1s emission signal
from R,R and S,S butanediol. In our analysis of the results we aim at distinguishing
between circular dichroism from the chiral center itself, and
that induced by the chiral nature of the experimental geometry, through
a comparison of dichroism observed under different experimental geometries,
as well as by a comparison with data from the achiral enantiomer
of butanediol.
O 18.8 Di 13:00 H38
SERS and infrared spectra of NO on cold-deposited Cu —
•Matthias Lust 1 , Andreas Priebe 1 , Andreas Otto 2 , and Annemarie
Pucci 1 — 1 Kirchhoff-Institut für Physik, Universität Heidelberg,
Im Neuenheimer Feld 227, D-69120 Heidelberg, Germany —
2 Lehrstuhl für Oberflächenwissenschaft, Universität Düsseldorf, Universitätsstr.
1, D-40225 Düsseldorf, Germany
SERS-spectra of nitric oxide (NO) on cold-deposited (

Oberflächenphysik Dienstag
Variation of both the I − and the I2 concentrations enables the identification
of the respective emission features (by their electron binding
energies), and hence allows us to quantitatively follow the evolution of
the relative intensities in accordance with the equilibrium of complex
formation: I − + I2 ⇀↽ I − 3 . The experiments were performed at the MBI
undulator beamline at BESSY in the 50-120 eV photon energy range,
using a 6 µm diameter liquid jet.
O 19.3 Di 11:45 H39
Magnetism of mass selected, deposited, small Gadolinium and
Gadolinium oxide clusters — •Matthias Reif, Leif Glaser,
Michael Martins, and Wilfried Wurth — Institut für Experimentalphysik,
Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg
Results of XMCD (X-Ray Circular Magnetic Dichroism) measurements
of small deposited Gadolinium- and Gadolinium oxide clusters are presented.
The clusters are supported by a magnetized ultrathin iron film
epitaxially grown on Cu(100) and showing an easy magnetization axis
perpendicular to the crystal surface. The clusters are generated by high
energy sputtering of a Gd-target with Xe-ions. After mass selection using
a dipole magnet, the clusters are deposited on the iron surface. In
order to prevent fragmentation of the clusters, the process of softlanding
is applied. Here, some multilayers of Argon consume the kinetic energy
during deposition of the clusters.
Focusing on the 3d→4f and 4d→4f excitations, dichroism spectra measured
at beamline UE56/1PGM at BESSYII are shown and different
contributions to the dichroism signal are discussed. The different Gdn
clusters show similar dichroism patterns as Gd thin films, whereas for
the oxidized GdnOm clusters different features are found in the spectra.
This project is supported by BMBF under contract KS1 GUB/5.
O 19.4 Di 12:00 H39
Lasergestützte Methode zur Einengung der Größen- und Formverteilung
von Gold-Nanoteilchen — •C. Hendrich, H. Ouacha,
T. Vartanyan, F. Hubenthal und F. Träger — Experimentalphysik
I, Institut für Physik und Center for Interdisciplinary Nanostructure
Science and Technology - CINSaT, Universität Kassel, Heinrich-Plett-
Straße 40, D-34132 Kassel
Auf dielektrischen Oberflächen können durch selbstorganisiertes
Wachstum metallische Nanoteilchen (NT) hergestellt werden. Die Teilchenensembles
weisen in der Regel eine gewisse Größen- und Formverteilung
auf. Durch den Wachstumsprozess ist außerdem die Teilchenform
fest mit der Teilchengröße verknüpft. Wir haben diese Parameter nach
dem Wachstum künstlich durch Laserbestrahlung verändert. Ausgenutzt
wurde hierbei die Interaktion des Laserlichts mit den für metallische
NT typischen Oberflächen-Plasmon-Resonanzen (OPR). Ensembles von
Gold-NT wurden in systematischen Untersuchungen mit Nanosekunden-
Laserpulsen bestrahlt. Die resonanten NT wurden durch das resultierende
selektive Heizen kugelähnlicher, die OPR wurde entsprechend zu höheren
Plasmonenergien verschoben. Auf diese Weise wird die durch das Wachstum
vorgegebene Abhängigkeit zwischen Form und Größe verhindert.
Durch sukzessive Bestrahlung bei verschiedenen Laser-Wellenlängen ist
es außerdem möglich, die Größen- und Formverteilung einzuengen. Die
so veränderten NT-Ensembles wurden mit Rasterkraftmikroskopie und
optischer Spektroskopie untersucht.
O 19.5 Di 12:15 H39
Spectroscopy of gold clusters on graphite for a broad range of
cluster sizes — •I. Barke, T. Irawan, and H. Hövel — Universität
Dortmund, Experimentelle Physik I, D-44221 Dortmund
Gold clusters grown on nanostructured highly oriented pyrolytic
graphite (HOPG) have been investigated by Scanning Tunneling
Spectroscopy (STS) and Ultraviolet Photoelectron Spectroscopy (UPS).
The evolution of the d electron UPS spectra for increasing cluster size
is consistent with corresponding Scanning Tunneling Microscopy (STM)
results. The combination of these methods allows a semi quantitative
analysis of the cluster growth process. The main emphasis lies on the
change of the cluster morphology from small clusters without facets to
large faceted clusters. In addition, we present STS results for a wide
variety of cluster sizes. On the (111) facets of large Au clusters (N ≈ 10 4
atoms) STS and UPS spectra revealed a two dimensional cluster surface
state confined to the cluster facet [1, 2]. Further on, we measured dI/dV
spectra for about 70 different smaller clusters (N ≈ 10 1 . . . 10 3 atoms).
Though these series of STS curves look more complicated, we observed
spectral features changing systematically with the cluster size.
[1] I. Barke, H. Hövel, Phys. Rev. Lett. 90, 166801 (2003).
[2] H. Hövel, I. Barke, New J. Phys. 5, 31 (2003).
O 19.6 Di 12:30 H39
Luminescence from gold nanoparticles mediated by plasmon
emission — •T. A. Klar 1 , E. Dulkeith 1 , T. Niedereichholz 1 ,
J. Feldmann 1 , G. von Plessen 2 , D. I. Gittins 3 , S. Mayya 3 ,
and F. Caruso 3,4 — 1 Photonics and Optoelectronics Group, Department
of Physics and CeNS, Ludwig-Maximilians-Universität München
— 2 1. Physikalisches Institut, RWTH Aachen — 3 Max-Planck-Institut
für Kolloid- und Grenzflächenforschung — 4 Department of Chemical and
Biomolecular Engineering, The University of Melbourne, Australia
We observe photoluminescence emission at the particle plasmon frequency
from gold nanoparticles when the nanoparticles are excited above
the d-sp interband transition threshold. Estimates of quantum yields for
direct emission from d-sp interband recombination in bulk metals have
given quantum efficiencies of 10 −10 [1]. In contrast, here we observe a
quantum efficiency of 10 −6 , which is essentially independent of the particle
size. This increased quantum efficiency is explained by a two step
process: Instead of a direct emission of a photon, the d-sp band recombination
excites a particle plasmon which in turn decays radiatively,
emitting a photon.
[1] Mooradian, Phys. Rev. Lett. 5, 185 (1969)
O 19.7 Di 12:45 H39
TEM and STM Study of Gold Nanoparticles — •M. Smetanin 1 ,
S. Schulze 1 , F. Müller 1 , D. Piasta 2 , S. Spange 2 , and M.
Hietschold 1 — 1 Chemnitz University of Technology, Institute of
Physics, Solid Surfaces Analysis Group, D-09107, Chemnitz, Germany
— 2 Chemnitz University of Technology,Institute of Chemistry, D-09107
Chemnitz, Germany
Metal nanoclusters are interesting candidates for nanostructured materials
and nanoelectronic digital circuits. We have investigated the structure
of chemicaly synthesized gold nanoparticles of different sizes with
and without thiol coating. Gold nanoparticles with a diameter of 3 nm
and 10 nm were studied using transmission electron microscopy (TEM)
and scanning tunneling microscopy (STM). TEM investigations show the
crystalline structure of gold nanoparticles in all cases. High energy electron
difraction (HEED) shows that the lattice structure of nanoparticles
of 10 nm average diameter corresponds to fcc independently from
coating. But for smaller clusters with an average diameter of 3 nm the
coexistence of bcc and fcc seems to be possible. Moreovere we have observed
a dependency of the thiol coating for these phases. Furthermore
we have investigated the shapes of gold clusters by STM for comparison
with TEM experiment.
O 19.8 Di 13:00 H39
Shaping silver nanoparticles with cw laser light — •M.
Alschinger, N. Borg, F. Hubenthal, and F. Träger — Institut
für Physik and Center for Interdisciplinary Nanostructure Science and
Technology - CINSaT, Universität Kassel, Heinrich-Plett-Str. 40, 34132
Kassel
Nanoparticles and systems in the nanometer size regime have been
studied intensively in recent years. These systems have e.g. electronic,
optical and catalytic properties which differ considerably from those of
the corresponding bulk material and depend strongly on the size and
morphology of the structures under investigation. For many applications
it is very important to prepare nanoparticles on surfaces with well-defined
sizes and shapes, e.g. for optical filters which selectively block radiation in
narrow wavelength intervals. A widely used method to prepare nanoparticles
on surfaces is to deposit metal atoms on substrates followed by
Volmer-Weber growth. However, this usually produces nanoparticle ensembles
with a broad distribution of sizes and shapes. To overcome this
disadvantage our group has developed a laser-based method to tailor
nanoparticles with well defined dimensions. We showed that, irradiating
the particles with ns pulsed laser light during growth systems of reduced
dimensions can be prepared with a predetermined axial ratio independent
of size [1]. This method has been extended to the use of cw laser
irradiation of different wavelength. For silver particles on quartz we have
observed a strong dependence of the process of nanoparticles shaping on
the intensity of the cw laser light.
[1] T. Wenzel et al., Appl. Phys. B. 69, 513 (1999)

Oberflächenphysik Dienstag
O 20 Oberflächenreaktionen I
Zeit: Dienstag 11:15–13:15 Raum: H45
O 20.1 Di 11:15 H45
Adsorption and Oxidation of NH3 on RuO2(110) — •Yuemin
Wang, Ursula A. Paulus, Karl Jacobi, and Gerhard Ertl —
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-
14195 Berlin
The epitaxially grown RuO2(110) surface was found to exhibit high
catalytic activity for CO oxidation [1, 2]. In the present work the interaction
of NH3 with the stoichiometric and O-enriched RuO2(110) surfaces,
which the latter exposes a weakly bound atomic oxygen species on-top of
the unsaturated Ru atom (Ru-cus), is studied using high-resolution electron
energy-loss spectroscopy (HREELS) and thermal desorption spectroscopy
(TDS). At the stoichiometric RuO2(110) surface we observed
only the molecular adsorption of NH3 on Ru-cus at 85 K, whereas on
the O-enriched surface NH3 oxidation occurs with annealing to higher
temperature. The reaction products depend on the coverage of O-cus.
At low O2 exposures (below 0.3 L) NH3 reacts with O-cus to give rise
to N2 and H2O. With increasing oxygen exposure NO is produced and
becomes the main product at saturation of O-cus. The formation of other
N-containing species such as N2O and NO2 were not observed. Reaction
mechanisms for NH3 oxidation will be discussed in detail. [1] C. Y. Fan,
J. Wang, K. Jacobi, G. Ertl, J. Phys. Chem. B 106, 10058(2002). [2] J.
Wang, C. Y. Fan, K. Jacobi, G. Ertl, Surf. Sci. 481, 113 (2001).
O 20.2 Di 11:30 H45
Austrittsarbeitsänderungen während elektrochemischen Pumpens
von Festelektrolyt/Metall-Systemen am Beispiel YSZ/Pt
— •Tobias Neubrand, Sebastian Günther und Ronald Imbihl
— Institut für Physikalische Chemie und Elektrochemie, Universität
Hannover, Callinstr. 3-3a, 30167 Hannover
Bei der Erklärung des sogenannten NEMCA (Non-faradayic Electrochemical
Modification Catalytic Activity)-Effektes nimmt die durch elektrochemisches
Pumpen hervorgerufene Änderung der Austrittsarbeit eine
entscheidende Rolle ein. Allerdings finden sich hierzu experimentelle und
theoretische Arbeiten mit widersprüchlichen Ergebnissen. Aus diesem
Grund wurden Messungen mit einer Pt-YSZ-Pt Gasreferenzzelle durchgeführt,
bei der Arbeits-, Gegen- und Referenzelektrode durch Aufpinseln
und anschließendem Einsintern einer Pt-Paste aufgebracht wurden. Für
die Arbeitselektrode wurden verschiedene Pt-Pasten (Firma Engelhard
bzw. Demetron) verwendet, die unterschiedliches Verhalten beim elektrochemischen
Pumpen zeigten. Die Änderung der Austrittsarbeit wurde
mittels Kelvin-Sonde und PEEM (Photo Electron Emission Microscopy)
an Luft und unter UHV-Bedingungen untersucht. Die Kombination von
PEEM und Kelvin-Sonde erlaubt es, zwischen elektrostatischen Effekten
und adsorbatbedingter Änderung der Dipolbarriere an einer Oberfläche
zu unterscheiden. Die Ergebnisse zeigen, daß unter Reaktionsbedingungen
der elektrische Kontakt der Pt-Körner zum Teil verloren geht, was
zu elektrostatischen Aufladungen und einer Verfälschung der Austrittsarbeitsmessung
mit einer Kelvin-Sonde führt.
O 20.3 Di 11:45 H45
Adsorption and Interaction of Ethylene on stoichiometric and
oxygen rich RuO2(110) — •Ursula A. Paulus 1 , Yuemin Wang 1 ,
Hans P. Bonzel 2 , Karl Jacobi 1 , and Gerhard Ertl 1 — 1 Fritz-
Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195
Berlin — 2 Forschungszentrum Jülich, ISG3, D-52425 Jülich
The nature of the oxygen species responsible for ethylene (C2H4) oxidation
on Ag particles is still under discussion. Here we prepare stoichiometric
and oxygen rich RuO2(110) surfaces exposing either coordinatively
unsaturated Ru (Ru-cus) and oxygen (O-bridge) atoms or O-bridge
and O-cus atoms. We study the adsorption and interaction of C2H4 on
those surfaces applying high-resolution electron energy loss spectroscopy
(HREELS) and thermal desorption spectroscopy (TDS).
Under the applied conditions (ultra-high vacuum, no continuous reactant
supply) C2H4 adsorbs molecularly on the stoichiometric RuO2(110)
surface at 85 K and desorbs again molecularly at 320 K. Warming up the
sample to 260 K leads to changes in the bond strength. A rearrangement
from π-bonded to σ-bonded is suggested.
On the oxygen rich RuO2(110) surface a complete oxidation of C2H4
to CO2 and water is observed. Warming up the sample between 85 K and
500 K HREEL spectra indicate the presence of several reaction intermediates,
which are discussed here.
[1] J. Wang et al., J. Phys. Chem. B. 106 (2002) 3422.
O 20.4 Di 12:00 H45
CO oxidation at RuO2(110) studied by first-principles kinetic
Monte-Carlo simulations — •Karsten Reuter 1,2 , Daan
Frenkel 2 , and Matthias Scheffler 1 — 1 Fritz-Haber-Institut,
Berlin — 2 AMOLF, Amsterdam
A quantitative modeling of catalytic activity requires a high accuracy
in the description of each of the manifold of involved elementary processes,
as well as a correct statistical mechanics treatment of the interplay
between them. We attempt such a modeling by first-principles kinetic
Monte-Carlo simulations, i.e. using rates derived from density-functional
theory as input. Modeling the CO oxidation over RuO2(110) we obtain
a full (T, pO2 , pCO) turnover frequency diagram, which agrees with available
experimental data. The surface configurations actuating catalysis
are found to be strongly influenced by kinetic effects, most prominently
under gas phase conditions where the system is close to a surface phase
transition. The highest steady-state turnover rates are obtained for the
resulting phase coexistence at the surface, which enables specific reaction
mechanisms that do not operate at other temperature and pressure
conditions including ultra-high vacuum.
O 20.5 Di 12:15 H45
Depolarisation of the rotational alignment. — •M. Rutkowski
and H. Zacharias — Physikalisches Institut, Westfälische Wilhelm-
Universität, Wilhelm-Klemm Str. 10, 48149 Münster, Germany
Up to now experimental investigations of the rotational alignment of
molecules both in the gas phase and desorbing from surfaces are performed
under the assumption that the rotational alignment is nonvarying
with time. However, early theoretical investigations for atoms [1]
predict a strong time dependence, caused by the interaction of the nuclear
spin with the electronic angular momentum. In this talk a corresponding
model for the rotational angular momentum of molecules is applied to
D2, H2 and NO molecules. The calculations of the rotational alignment
of these molecules yield strong periodic oscillations, which significantly
change both in amplitude and periodicity with the rotational quantum
number.
[1] U. Fano, J.H. Macek, Rev. mod. Phys., 45, 553 (1973).
O 20.6 Di 12:30 H45
Dehydrogenation of Methanol on Rhodium/Vanadium Surface
Alloys and the influence of preadsorbed oxygen — •Georg
Krenn, Klaus D. Rendulic, and Robert Schennach — Institute
of Solid State Physics, Graz University of Technology, Austria
The dehydrogenation of methanol on metal surfaces has regained interest
recently due to the development of methanol powered fuel cells.
Dehydrogenation of methanol on Rh(111) leads to the formation of carbon
monoxide and hydrogen only. The reaction products are the same
on the Rh(111)/V alloy surfaces, but the reaction kinetics differ significantly.
On a Rh(111)/V subsurface alloy and on a Rh(111)/V islands
surface the reaction probabilities stay high up to about 400 K and 550
K, respectively, in contrast to about 200 K on Rh(111). On the Rh(111)
surface with V islands a decrease in the reaction probability occurs due
to buildup of carbon layers on the V islands. Preadsorption of oxygen
on the three surfaces reverses the trend from the oxygen free surfaces, so
that the Rh(111) surface shows the highest activity. With preadsorbed
oxygen water and carbon dioxide are found as additional reaction products.
The difference between the oxygen covered surfaces and the oxygen
free surfaces is discussed in terms of two different initial reaction steps
on the surface. With preadsorbed oxygen a proton transfer reaction from
the OH group of methanol to adsorbed oxygen seems to be the first reaction
step, while on the oxygen free surface conventional dehydrogenation
takes place.
O 20.7 Di 12:45 H45
Mixed quantum classical simulation of DIET processes —
•Christian Bach and Axel Groß — Physik-Department T30,
Technische Universität München, 85747 Garching
We present a mixed quantum-classical method for the simulation of
laser-induced desorption processes at surfaces. In this method, the nuclear
motion is described classically while the electrons are treated quan-

Oberflächenphysik Dienstag
tum mechanically while taking the feedback between nuclei and electrons
is into account self-consistently. The computational efficiency of
this method allows a more realistic multi-dimensional treatment of the
desorption processes. We have applied this method to the laser-induced
desorption of NO from NiO(100) using a two-state two-dimensional potential
energy surface derived from ab initio quantum chemistry calculations;
we have extended this potential energy surface to seven dimensions
employing a physically reasonable model potential. We focus on
the velocity, rotational and vibrational distributions of the desorbing NO
molecules and compare our results to the experiment and wave packet
simulations. Furthermore, we added a surface oscillator to model the energy
transfer to the substrate. Including recoil processes in the simulation
has a decisive influence on the desorption dynamics, as far as the velocity
and rotational distribution is concerned. In particular, the bimodality in
the velocity distribution observed in low dimensions and in the experiment
disappears in a high-dimensional treatment.
O 20.8 Di 13:00 H45
Influence of Mn and Co on the Properties of Active Sites in
Molybdena Based Catalysts; DFT Cluster Model Studies —
•Renata Tokarz-Sobieraj and Malgorzata Witko — Institute of
Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek
8, 30-239 Krakow, Poland
O 21 Hauptvortrag Moresco
Molybdenum oxide (VI) in combination with other elements such as
Bi, V, Co, or Mn forms a large group of materials (molybdates, molybdenum
bronzes, heteropolyacids) that are used as catalysts in many reactions
of very different types. In the present work the local electronic
and geometric structure of the clean and reduced manganese molybdate
(MnMoO4) as well as cobalt molybdate (CoMoO4) is discussed and compare
with pure MoO3 to examine the influence of the additional atoms
(Mn, Co) on chemical properties of active sites. In all studied systems
the nucleophilicity of surface oxygen (measured by its charge) scales with
the coordination number. Replacement of Mo atom by Mn or Co atoms
decreases the charge (nucleophilicity) of oxygen sites. The surface Mn
and Co ions form Lewis centers, which are less strong than the Mo ions;
in molybdates the presence of Mn and Co atoms increase the acidity of
Mo centers. In all studied systems metal-oxygen bonds are characterized
by mixed ionic-covalent character, where the Mn/Co-O bonds are more
covalent than Mo-O bonds.
Zeit: Dienstag 14:00–14:45 Raum: H36
Hauptvortrag O 21.1 Di 14:00 H36
Manipulation of large molecules by low temperature STM:
model systems for molecular electronics — •Francesca
Moresco — Institut für Experimentalphysik, FU Berlin, Arnimallee
14, 14195 Berlin
The ability of Low Temperature Scanning Tunneling Microscope to
manipulate atoms and to build nanostructures with atomic precision can
be extended to the manipulation of larger molecules and to selectively
modify their internal degrees of freedom. Manipulation experiments on
individual molecules show an exciting diversity of physical, chemical,
O 22 Hauptvortrag Hövel
and electronic phenomena. They permit a deeper insight into the quantum
electronics of molecular systems and provide important information
on the conformational and mechanical properties of single complex
molecules.
In this talk, some examples of recent manipulation experiments performed
on single molecules will be presented: The principle of a conformational
molecular switch have been realized under the action of the
STM-tip, the small intramolecular changes inside a complex molecule
have be recorded giving information on the internal mechanics of the
molecule, and the electronic contact between a molecular wire and a
metallic nanoelectrode have been investigated with atomic precision.
Zeit: Dienstag 14:45–15:30 Raum: H36
Hauptvortrag O 22.1 Di 14:45 H36
Electronic structure and morphology of supported clusters as
observed by photoemission and STM/STS — •Heinz Hövel —
Universität Dortmund, Experimentelle Physik I, D-44221 Dortmund
The investigation of clusters, i.e. small particles with nanometer dimensions,
in contact with surfaces is a presently very active new direction of
research after many years of successful work on free clusters in vacuum.
Understanding their electronic structure and answering the question of
how it is changed by the interaction with a surface is not only of fundamental
interest but has also several important applications, for example
in the fields of nano-electronics and catalysis. In general, the contact with
the surface also influences the morphology of the clusters. With scanning
tunneling microscopy (STM) one can measure the cluster height and the
O 23 Rastersondentechniken II
shape of facets on top of them. Scanning tunneling spectroscopy (STS)
is able to probe the electronic structure of individual clusters, while photoemission
averages over different sizes, isomers and orientations on the
surface. Metal clusters grown in preformed nanometer sized pits on a
graphite surface proved to be well suited for a combination of these different
techniques on one and the same sample in ultrahigh vacuum [1].
Recently, the combination of STM/STS and photoemission, both measured
at low temperatures, was used to reveal the existence of confined
Shockley surface states on the (111) facets on top of gold clusters with
about 10 4 atoms [2].
[1] H. Hövel, Appl. Phys. A 72, 295 (2001).
[2] I. Barke, H. Hövel, Phys. Rev. Lett. 90, 166801 (2003).
Zeit: Dienstag 15:45–18:15 Raum: H36
O 23.1 Di 15:45 H36
Near-field optical imaging of single molecules by means of
a triangular aperture probe — •D. Molenda 1 , G. Colas
des Francs 1 , U. C. Fischer 1 , H. Fuchs 1 , and A. Naber 2 —
1 Westfälische Wilhelms-Universität, 48149 Münster — 2 Institut für
Angewandte Physik, 76131 Karlsruhe
Recently we have introduced a triangular aperture probe for scanning
near-field optical microscopy (SNOM) that combines a high optical resolution
capability with a high transmission [1]. It turned out that the field
pattern of such a probe is highly confined to only one side of the trian-
gular aperture which is in strong contrast to a circular aperture. In order
to further investigate the field pattern, we performed measurements of
single dye molecules (TDI) embedded in a thin PMMA film. The aim was
to map the electrical field components of the aperture in 3 dimensions
by imaging a large number of randomly oriented molecular dipoles. The
measured fluorescence patterns are compared with theoretical calculations
which are based on a field-susceptibility technique. The calculated
field patterns are in good agreement with the experiments and thus allow
us to infer the dipole orientation of a molecule from the measured image.
Due to the highly confined field of the triangular aperture probe we are

Oberflächenphysik Dienstag
able to demonstrate an optical resolution of 30 nm.
[1] A. Naber et al., Phys. Rev. Lett. 89, 210801 (2002).
O 23.2 Di 16:00 H36
Energy dissipation in non-contact AFM — •Domenique Weiner,
Andre Schirmeisen, and Harald Fuchs — Physikalisches Institut
and CeNTech, University of Muenster, Wilhelm-Klemm-Str. 10, 48149
Muenster, Germany
The atomic force microscope (AFM) driven in the non-contact mode
offers the possibility to measure long-range and short-range forces. Furthermore,
energy dissipation mechanisms can be studied which are up
to now not well-understood and are subject of current research [1]. One
important step towards a better understanding of the energy dissipation
is to study the temperature dependence of the effect [2].
We measure the damping signal on a Au (111) surface which is prepared
under ultra-high vacuum (UHV) conditions by sputtering and annealing.
The commercial silicon cantilevers are covered with a PtIr-layer
of about 30 nm thickness to ensure the measurement of a true metal contact.
We use an UHV-VT-AFM (Omicron) which is integrated in a two
chamber-apparatus. We investigate the frequency shift and the damping
simultaneously as a function of tip-sample separation for different sample
temperatures. Therefore we are able to gain quantitative values of
the dissipation which are compared to current dissipation models like
van der Waals friction [1], electrical dissipation [3] or dissipation induced
by inhomogeneous tip-sample electric fields [2].
[1] Volokitin, Persson, Phys. Rev. Lett. 91, 06101, 2003
[2] B. C. Stipe, H. J. Mamin, T. D. Stowe, T. W. Kenny, D. Rugar,
Phys. Rev. Lett. 87, 096801, 2001.
[3] W. Denk, D. W. Pohl, Appl. Phys. Lett., Vol. 59, No. 17, 1991
O 23.3 Di 16:15 H36
Local interfacial dipoles of alkali chloride thin films on Au(111)
investigated with Kelvin probe force microscopy — •Ulrich
Zerweck, Christian Loppacher, Stefan Grafström, and
Lukas M. Eng — Institute of Applied Photophysics, University of
Technology, D-01062 Dresden
Interface dipole formation of alkali chloride thin films on Au(111) is
investigated under ultrahigh vacuum conditions at room temperature by
noncontact atomic force microscopy in combination with Kelvin-probe
force microscopy (KPFM). Sample preparation is carried out in-situ and
optimized in order to achieve a sub-monolayer coverage on Au(111) with
extended alkali chloride islands.
The local surface potential for LiCl, NaCl, KCl, and RbCl thin films
on Au(111) was determined by KPFM, with the bare Au(111) substrate
serving as a reference. We thus directly probe the local and absolute
change in the work function ∆Φ which is found to vary linearly as a
function of the radius of the alkali ion. Furthermore, good agreement
was obtained when checking our KPFM measurements with ultraviolet
photoemission spectroscopy on a larger scale.
O 23.4 Di 16:30 H36
Scattering-type near-field microscopy for optical nanoanalytics
— •Rainer Hillenbrand — Nano-Photonics Group, Max-Planck Institut
für Biochemie, 82152 Martinsried
We present a scattering-type scanning near-field optical microscope
(s-SNOM) that allows optical imaging at 10nm spatial resolution [1] independent
of the wavelength. In our s-SNOMs the tip apex of an atomic
force microscope (AFM) is illuminated either by a HeNe laser at 633nm
or a CO2 laser at about 10um wavelength. Interferometric detection [2]
of the scattered light allows us to visualize the optical eigenfield patterns
of 91 diameter, plasmon resonant nanoparticles at 633nm wavelength
[3]. When operating the microscope at mid-infrared frequencies we find
a strongly resonant near-field coupling between tip and a SiC sample
due to local excitation of phonon polaritons in SiC [4]. Such phononenhanced
near-field interaction is not only sensitive to the local chemical
composition but also to the local crystal structure of the surface and
thus allows besides chemical imaging also mapping of crystal quality at
nanoscale resolution. Altogether, we envisage optical nanospectroscopy
and imaging of physical, chemical and biological nanocomposites.
[1] R. Hillenbrand, F. Keilmann, Appl. Phys. Lett. 80, 25 (2002)
[2] R. Hillenbrand, F. Keilmann, Phys. Rev. Lett. 85, 3029 (2000)
[3] R. Hillenbrand et.al., Appl. Phys. Lett. 83, 368 (2003)
[4] R. Hillenbrand, T. Taubner, F. Keilmann, Nature 418, 159 (2002)
O 23.5 Di 16:45 H36
NanoSAM: Instrument characterisation at ultimate SAM resolution
— •Jörg Westermann, Ulrich Roll, and Georg Schäfer
— OMICRON NanoTechnology GmbH, 65232 Taunusstein
During the last few years, we have developed a new electron source
as an excitation source for UHV applications such as low voltage SEM,
SAM / small spot Auger, cathodoluminescense and others (BMBF FKZ
13N7486/7). Finally, we now report about the first results in small spot
Auger and Scanning Auger Microscopy utilising this source. We present
images and spectra demonstrating the ultimate lateral resolution and
energy resolution of the setup on various samples. These include gold
nanoparticles on HOPG, silver islands on silicon, and semiconductor heterostructures.
Furthermore, we compare the achieved results with theoretical
calculations and Monte Carlo simulations at different beam energies.
O 23.6 Di 17:00 H36
An Ultra High Vacuum Scanning Tunneling Microscope system
operating at 300 mK and 14 T — •Focko Meier 1 , Jens
Wiebe 1 , Andre Wachowiak 2 , Daniel Haude 1 , Markus Morgenstern
1 , and Roland Wiesendanger 1 — 1 Institute of Applied
Physics, Hamburg University, Jungiusstr. 11, D-20355 Hamburg, Germany
— 2 University of California at Berkeley, Department of Physics,
366 Le Conte Hall, 7300 Berkeley, CA 94720-7300, USA
For scanning tunneling spectroscopy (STS) on low dimensional electron
systems, an ultra high vacuum (UHV) scanning tunneling microscope
(STM) operating at T=300 mK and in magnetic fields up to B=14
T has been built up.
The STM sitting in a bakeable UHV-insert within the 3 He-cryostat
can be operated continuously for about 30 hours witout any refill of the
cryogenic liquid. It achieves a z-noise level below 5 pm. Using superconducting
tips and samples first experimental STS results show that the
energy resolution reached is close to the predicted theoretical limit of 75
µ V. For exchanging tips and samples the insert with STM can be moved
to a UHV chamber. Further connected UHV chambers contain different
equipment for tip and sample preparation and characterisation, i.e.
a RT-STM , a LEED/Auger system, several evaporators and a variable
temperature system to detect the magnetooptical Kerr-effect (MOKE).
O 23.7 Di 17:15 H36
SPM goes video rate and beyond — •M.J. Rost, T.H. Oosterkamp,
J.W.M. Frenken, and et al. — Kamerlingh Onnes Laboratory,
Leiden University, P.O. Box 9504, 2300 RA Leiden
The low imaging rates of conventional scanning probe microscopes
(SPMs) makes these instruments impractical for many applications. We
have developed a novel, flexible SPM control system that can be easily
connected to any SPM, which allows up to 50 Hz imaging rates with 256
x 256 pixels per image. Since fast scanning is impossible without fast
feedback electronics, we have also developed a low-noise STM-feedback
system with a total bandwidth of 600 kHz (including the preamp). We
present high-speed STM movies (images) with 25 Hz frame rate and tip
speeds up to 0.3 mm/s while keeping atomic step resolution on Cu(001),
obtained with a conventional STM. With a new, compact scanner we
have even reached 200 Hz frame rate on graphite while still obtaining
atomic resolution.
O 23.8 Di 17:30 H36
Apertureless SNOM with vibrating AFM probes — •Ralf Vogelgesang,
Ruben Esteban, Alpan Bek, and Klaus Kern — MPI
für Festkörperforschung, 70569 Stuttgart
In the so called apertureless Scanning Near Field Optical Microscopy
(a-SNOM), strongly localized enhancement of the near fields at the apex
of a conical tip probe excited by external radiation is used to achieve
spatial resolution of optical surface properties in the range ∼ 10 nm at
infrared or visible frequencies.
We use Multiple Multipole (MMP) simulations to quantitatively understand
the interaction between the tip and substrate. We study the
variations due to changing tip sample distance in the near field and consequently
in the scattered far field, i.e., the measurable physical magnitude.
For a better understanding of the level of sophistication necessary,
different models are considered, ranging from a point dipole in the static
case to spheres or a conical tip with spherical apex including retardation.
In general two different regions are observed, slowly varying field
strengths for distances of several hundred nm or more and rapid increases
in field strengths for less than 10 nm. This strongly nonlinear dependence

Oberflächenphysik Dienstag
translates into generation of higher harmonics in the scattered far field
intensity when the tip-sample distance is varied sinusoidally. Detecting
the intensity and phase of these harmonics allows to obtain images of the
localized near field interactions essentially free of parasitic linear scattering
signatures from the surrounding area. The consideration of different
tip and substrate materials is important to interpret and optimize experiments.
O 23.9 Di 17:45 H36
Molecular Resolution Imaging of C60 on Au(111) by Dynamic
Force Microscopy — •R. Hoffmann 1,2 , J.M. Mativetsky 1 , S.A.
Burke 1 , Y. Sun 1 , and P. Grütter 1 — 1 Department of Physics,
McGill University, Montreal, Canada, H3A 2T8 — 2 Physikalisches Institut,
Universität Karlsruhe, 76128 Karlsruhe
Dynamic Force Microscopy (DFM) was used to study thin films and
clusters of C60 on Au(111). After observing the Au(111) 23 x √ 3 reconstruction,
2-3 molecular monolayers of C60 were deposited onto the Au
surface. The close-packed C60 surface was imaged by DFM with molecular
resolution. Enhanced corrugation contrast and an apparent contrast
inversion were observed at step edges. Based on a rough spring model
calculation, it is proposed that this may be the result of a tip-induced
displacement of edge molecules. While imaging small clusters of C60,
some molecules were removed by interaction with the tip, leading to
O 24 Nanostrukturen II
structural rearrangements in the clusters.
O 23.10 Di 18:00 H36
Manifestations of slow hysteretic atomic jumps in dynamic force
microscopy — •R. Hoffmann 1,2 , A. Baratoff 1 , H.J. Hug 1 und
H.-J. Güntherodt 1 — 1 Institut für Physik, Universität Basel, Klingelbergstr.82,
CH-4056Basel, Schweiz — 2 Physikalisches Institut, Universität
Karlsruhe, 76128 Karlsruhe
In dynamic force microscopy, the frequency shift and the excitation amplitude
necessary to keep the cantilever oscillation at a constant amplitude
can be measured simultaneously. The mechanisms leading to atomicscale
contrast in the excitation amplitude are currently the subject of
controversies. Several authors suggested that the energy dissipated into
hysteretic motion of atoms induced by the tip in every oscillation cycle
could cause the observed effects [1]. Site-specific force-distance measurements[2]
performed on KBr(001) provide insight into the relation between
the excitation amplitude and the force. Below a certain critical tip-sample
distance, the frequency jumps between two limiting curves on the timescales
of the order of seconds. The fact that these tip instabilities begin to
occur at the same tip-sample distance as the energy dissipation suggests
that the two are related.
[1] N. Sasaki and M. Tsukada, Jap. J. Appl. Phys. 39, L1334 (2000)
[2] M.A. Lantz et al., Science 291, 2580 (2001)
Zeit: Dienstag 15:45–18:30 Raum: H38
O 24.1 Di 15:45 H38
A Method to Generate Aligned Nanowires on Various Substrates
— •Rainer Adelung, O.C. Aktas, A. Biswas, R. Kunz,
J. Kanzow, U. Schürmann, M. Elbahri, U. Saeed, J. Kruse, and
F. Faupel — Lehrstuhl für Materialverbunde, Technische Fakultät der
CAU Kiel
New methods to prepare nanowires like shown in [1] are still of substantial
interest, as no general solution is found to produce nanowires in
arbitrary form on arbitrary substrates. Here we introduce a method that
allows us to produce aligned nanowires on almost any solid surface. The
method is based on the generation of cracks in thin films as template,
large sticking coefficient differences and long diffusion length. Examples
will be given in which metal deposition in vacuum is used to provide the
material for the nanowires. Those include magnetic nanowires on glass,
gold nanowires on polyimide and platinum nanowire networks on Nafion
surfaces. It will be shown how a precise control over the alignment, the
form of nanowire intersections or the type of nanowire (solid or ”dashed”)
is achieved. In addition, applications for the nanowire networks formed
in this manner will be discussed.
[1] N. A. Melosh, A. Boukai, F. Diana, B. Gerardot, A. Badolato, P.
M. Petroff and J. R. Heath, Science 300,112 (2003)
O 24.2 Di 16:00 H38
Low Electron Energy Microscopy and X-ray Photoemission
Electron Microscopy studies of Conducting Atomic-Force Microscopy
induced surface modifications on thermally grown
SiO2 — •Sascha Kremmer 1 , Stefan Heun 2 , Harald Wurmbauer
1 , Sven Peißl 1 , and Christian Teichert 1 — 1 Department
of Physics, University of Leoben, A-8700 Leoben — 2 Nanospectroscopy
Beamline, Synchrotron ELETTRA, I-34012 Trieste
The process of local anodic oxidation, where positive voltages are applied
between a conductive AFM tip and a silicon sample is well understood.
Here, C-AFM induced surface modification of thermally grown oxides
for opposite sample voltage is investigated. To obtain information on
the nature of the protrusions observed after C-AFM experiments, LEEM
and XPEEM experiments are performed. With LEEM it is found that
the protrusions are heavily charged after their formation. This charge
within the protrusions is annihilated after the exposure of the sample to
short pulses of synchrotron radiation. However, these short x-ray pulses
do not change the topography of the protrusions. After prolonged xray
exposure, a radiation induced desorption of the structures as well
as a desorption of the thermal oxide is observed. The spectra obtained
from XPEEM images at different kinetic electron energies reveal that the
structures formed by C-AFM consist of SiO2.
O 24.3 Di 16:15 H38
Imaging of self-assembled organic adsorbates, STMmeasurements
under UHV conditions — •Christian Gerl,
Lorenz Kampschulte, Stefan Griessl, and Wolfgang M.
Heckl — LMU Muenchen, Dept. Geo.- u. Umweltwissenschaften,
Theresienstr. 41, 80333 Muenchen
The adsorption of Trimesic acid (TMA) on single crystal surfaces
has been studied under Ultra High Vacuum conditions. For this purpose
Trimesic acid was evaporated on different substrates using an effusion
cell. For the UHV preparation of TMA monolayers additional TDS
(Thermal Desorption Spectroscopy) and LEED (Low Energy Electron
Diffraction) investigations were necessary. The structure is characterized
by periodic non-dense-packing of the molecules. Two coexisting phases
could be imaged by STM with sub-molecular resolution. Induced by directed
hydrogen bonding, in both cases the organic molecules built a
two-dimensional grid architecture with molecular caves, both able to
store guest molecules. As a first step TMA molecules themselves were
inserted as guest molecules into the host structure. The guest molecules
could be identified in different adsorption sites.
O 24.4 Di 16:30 H38
Behavior of quantum-well and surface states of Ag/Ni(111) —
•A. Varykhalov 1 , O. Rader 1 , C. Di Giacomo 1 , A. M. Shikin 1,2 ,
W. Gudat 1,3 , C. Grazioli 4 , and C. Carbone 4 — 1 BESSY, 12489
Berlin — 2 Institute of Physics, St. Petersburg State University, 198504
Russia — 3 Insitut für Physik, Universität Potsdam, 14415 Potsdam —
4 CNR-ISM, I-34012 Trieste
Ag films on Ni(111) are known to lead to quantum-well states in angleresolved
photoemission experiments [1]. We have improved the growth of
Ag/Ni(111) by low-temperature deposition and post-annealing. The dispersion
of quantum well states parallel to the film plane has been measured,
and the influence of the substrate on the dispersion is compared
for low (∼ 5 atomic layers) and high thickness (∼ 20 layers). Moreover,
a decrease of the intensity of the L-gap centered surface state of Ag(111)
with increasing Ag coverage is observed. The results are discussed in
connection to our recent data obtained from Ag films on W(110) and
Ge(111).
[1] T. Miller, A. Samsavar, and T.-C. Chiang, Phys. Rev. B 50, 17686
(1994).
O 24.5 Di 16:45 H38
Quantum effects in atom-sized contacts — •A.L. Klavsyuk 1 ,
A.N. Baranov 1 , V.S. Stepanyuk 2 , W. Hergert 1 , P. Bruno 2 , and
I. Mertig 1 — 1 Fachbereich Physik, Martin-Luther-Universität, Von-
Seckendorff-Platz 1, 06120 Halle, Germany — 2 Max-Planck-Institut für
Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany

Oberflächenphysik Dienstag
The interplay between structure and quantum effects in atomic
nanocontacts is investigated. Our approach is based on density functional
theory and the Korringa-Kohn-Rostoker Green’s function method.
Atomic relaxations of nanocontacts and electrodes are calculated with ab
initio based many body potentials for low-dimensional systems. We concentrate
on Cu, Fe, Co, Rh and Pd atomic bridges. The quantum size
effect is found to be dominated by unoccupied electronic states and leads
to an enhancement of the LDOS at the Fermi level as the number of atoms
in the contact increases. We show that the atomic bridges constructed
from non-magnetic in bulk Rh and Pd can be magnetic.
O 24.6 Di 17:00 H38
Nanostructuring by Erosion Sputtering: transition from dots
to ripples — •Tobias Allmers, Georgi Rangelov, and Markus
Donath — Physikalisches Institut, Westfälische Wilhelms-Universität
Münster, Wilhelm-Klemm-Str. 10, 48149 Münster
Self-organization plays an important role for massive parallel production
of nanostructures. One way of producing self-organized structures is
erosion sputtering.
The generation of ripples by oblique ion impact on certain material
surfaces has been known since the seventies [1]. In recent studies, selforganized
patterns of hexagonal ordered quantum dots have been found
after ion bombardment perpendicular to the sample surface [2].
For this contribution, we investigated the transition from dots to ripples
for GaSb as a function of the incidence angle of the argon ions. The
structures obtained were characterized by microscopic and spectroscopic
methods.
Dots appeared up to an incidence angle of 10 ◦ relative to the surface
normal. We observed that the transition between dots and ripples is not
abrupt - first the hexagonal order is lost and then ripples begin to appear.
[1] Bradley and Harper, J. Vac. Sci. Technol. A 6, 2390 (1988)
[2] Facsko et al., Science 285, 1551 (1999)
O 24.7 Di 17:15 H38
STM-based nanolithography in diamond-like carbon layers —
•Thomas Mühl — IFW Dresden, Helmholtzstr. 20, D-01069 Dresden
The spatially localized emission current of a scanning tunneling microscope
tip leads to a local graphitization of diamond-like carbon thin
films. Using this technique, lines and dots smaller than 10 nm in size
can be written. Due to the widely different properties of diamond-like
and graphite-like carbon, there are a lot of possible applications of these
graphite nanostructures on the diamond film. Systematic investigations
of the current, voltage, and charge dependence combined with analytical
methods like tunneling spectroscopy lead to some preliminary conclusions
about the underlying modification mechanism on the atomic scale.
O 24.8 Di 17:30 H38
Gold clusters in nanopits: growth process and morphology —
•T. Irawan, I. Barke, and H. Hövel — Universität Dortmund, Experimentelle
Physik I, D-44221 Dortmund
The geometric structure and the growth process of gold clusters on
graphite was investigated with scanning tunneling microscopy and transmission
electron microscopy. Gold was evaporated on the surface with
preformed nanometer sized pits at a temperature of 350 ◦ C with rates of
3 × 10 −3 . . .1.4 × 10 −2 ML/s. Here we present a study for a broad range
of cluster sizes; starting from small clusters (N ≈ 10 2 atoms) without
facets [1] up to large clusters (N ≈ 10 4 atoms) with (111) facets on top of
the clusters [2]. The cluster shape is described with different geometric
models. The position of the clusters at the edge of the pits is determined
using STM images before and after a tip induced cluster displacement.
O 25 Epitaxie und Wachstum II
[1] H. Hövel, Appl. Phys. A 72, 295 (2001).
[2] H. Hövel, I. Barke, New J. Phys. 5, 31 (2003).
O 24.9 Di 17:45 H38
Stability of Au nanoparticles on fully oxidized TiO2 substrates.
An AFM/XPS study of Au/TiO2 model systems — •Stefan
Kielbassa, Markus Kinne, and Rolf-Jürgen Behm — Abt.
Oberflächenchemie und Katalyse, Univ. Ulm, 89069 Ulm
The stability of nm-sized gold particles deposited on fully oxidized
TiO2(110) substrates under ultra-high vacuum (UHV) conditions, in an
O2 atmosphere and in air was examined with atomic force microscopy
(AFM) and x-ray photoelectron spectroscopy (XPS). Au/TiO2 model
systems were prepared by evaporating submonolayers of gold on fully
stoichiometric and atomically smooth TiO2 rutile (110) substrates. The
thermal stability of the particles is found to strongly depend on the reaction
atmosphere. Under UHV conditions, the particles are stable even
after annealing at 400 ◦ C and only minor changes are detected after annealing
at 500 ◦ C. In an O2 atmosphere, the particles are stable at room
temperature, but grow dramatically after annealing to 400 ◦ C. In air, particle
growth is observed already at RT, accompanied by the formation
of Au-OH species. Possible mechanisms underlying these effects are discussed.
O 24.10 Di 18:00 H38
Ferroelectric Nano-Rods Grown in Porous Alumina Template
— •Dung Le Quang Tien 1 , J. Yekecheva 2 , F. Müller 1 , A.-D.
Müller 1 , V.D. Dan 3 , and H. Hietschold 1 — 1 Chemnitz University
of Technology, Institute of Physics, Solid Surfaces Analysis Group, D-
09107 Chemnitz, Germany — 2 On leave from Nowosibirsk State Technical
University-Russia — 3 Physics Department, Hue University,77 Nguyen
Hue street, Hue City - Vietnam
We have investigated the structural and electrical properties of ferroelectric
nano-rods of lead zirconate-titanate PbZr1-xTixO3 (PZT) grown
in a porous alumina template. Porous alumina membranes with pores
ranging from 50 to 400 nm were obtained by an electrochemical etching.
We have seen a clear dependency of the voltage and the electrolyte on the
size and shape of these pores. The morphology was characterized using
SEM and AFM. The perfect cylindrical porous alumina samples were
used to grow the PZT nanotubes by dipping in PZT precursor using
vacuum to promote penetration into the pores.
O 24.11 Di 18:15 H38
Imaging of self-assembled organic adsorbates - STM and
STS measurements under ambient conditions — •Sebastian
Hohenstein, Florian Buchner, Stefan Griessl, and Wolfgang
M. Heckl — LMU Muenchen, Department fuer Geo- und
Umweltwissenschaften, Theresienstr. 41, 80333 Munich
A host-guest structure of trimesic acid molecules (TMA) was investigated
under ambient conditions at the liquid-solid interface.
The organic TMA molecules self assemble into two different, nondense-packaged
phases induced by directed hydrogen bonding on a crystalline
surface. In this way a two-dimensional grid architecture with
molecular caves is formed in both cases. These two structure variants
have been imaged by STM with sub-molecular resolution.
It was found that the preparation method is crucial for the resulting
structure of the TMA-grid-network. Therefore further investigation of
the preparation method specifics is in progress.
Furthermore this grid network is now being used as a host system to
store guest molecules. Different molecules are introduced into the solution
to investigate their interaction with the network and to find new
applications and technological uses for such a system.
Zeit: Dienstag 15:45–18:15 Raum: H39
O 25.1 Di 15:45 H39
Influence of cluster mobility and fault energy on stacking-fault
formation — •Andreas Lammerschop 1 , Carsten Busse 1,2 , Celia
Polop 1 , and Thomas Michely 1 — 1 I. Physikalisches Institut, RWTH
Aachen — 2 Present Address: Institute of Physics and Astronomy, University
of Aarhus, 8000 Aarhus C, Denmark
We have applied a mean field rate equation approach to the formation
of stacking faults in thin film growth. Here, we discuss the influence of
cluster mobility and stacking-fault energy on the probability for the formation
of a fault is found. As expected, the fault energy has a strong
influence on the formation probability. The higher the fault energy, the
lower the probability to find an island in the wrong stacking. Our key
finding is, however, the unexpected importance of cluster mobility on
the stacking fault probability. For a fixed fault energy, cluster mobility
may change the nucleation probability for fault islands by several orders
of magnitude; the formation of stacking faults is favored for low clus-

Oberflächenphysik Dienstag
ter mobility. The results of our calculations are discussed in comparison
with experimental observations for materials like Platinum, Silver and
Copper.
O 25.2 Di 16:00 H39
Nucleation of Sub-monolayer YBa2Cu3O7−δ Films on
SrTiO3(001) Probed by X-ray Standing Waves and XPS —
•Sebastian Thiess, Tien-Lin Lee, Bruce C. C. Cowie, and Jörg
Zegenhagen — ESRF, Grenoble, France
Before epitaxial film growth commences, nucleation of complex materials
such as YBCO is necessary. The first layer then acts as a seed for the
growth of the epitaxial film. Investigating the nucleation can shed some
light on the relationship between the growth mode and the structure of
such epitaxial systems.
Scanning tunneling microscopy (STM) and spectroscopy (STS) have
suggested that submonolayers of YBCO deposited on STO(001) surfaces
first nucleate as a cubic, semiconducting phase of a mixed perovskite
composition, which in a second step transforms into the orthorhombic,
metallic YBCO phase when the film thickness exceeds one monolayer.
We obtained complementary real space information by the x-ray standing
wave technique that uses an interference field typically generated by
the superposition of two x-ray waves during Bragg reflection. By monitoring
the photoabsorption process via photoemission and fluorescence, we
measured the atomic structure of two YBCO films, 0.5 and 1.0 monolayers
thick, grown in situ onto STO(001) surfaces by PLD. Measurements
were carried out in UHV at beamline ID32 at the ESRF for a variety
of different STO(hkl) reflections at photon energies between 2.7 and 5.5
keV. Element-specific crystallograhic distributions were obtained for the
constituent atoms of the films by direct Fourier transform.
O 25.3 Di 16:15 H39
Beobachtung mesoskopischer Strukturen bei Mn-Schichten auf
Si(111) mittels STM und LEED — •K. Schwinge, J.J. Paggel
und P. Fumagalli — Institut für Experimentalphysik, Freie Universität
Berlin, Arnimallee 14, 14195 Berlin
Vorgestellt werden Strukturuntersuchungen von unterschiedlich dicken
Mn-Schichten auf Si(111)-Substraten. Die Schichten mit Dicken von
2-100 ˚A werden unter UHV-Bedingungen bei Raumtemperatur aufgedampft
und anschließend auf verschiedene Temperaturen aufgeheizt. Die
Struktur der Oberfläche wird mittels Rastertunnelmikroskopie (STM)
betrachtet. Weitere Charakterisierungen der Proben erfolgt mittels SPA-
LEED, RHEED, AES und AFM.
Beim Erwärmen der Proben bildet sich Mangansilizid mit einer Struktur
an der Oberfläche, die einer ( √ 3× √ 3)-Überstruktur auf dem Si(111)
entspricht. Sie ist bei Schichtdicken von ca. 10 ˚A mesoskopisch strukturiert
mit einer Periodizität von ca. 20 nm, was auf Verspannungen
zurückzuführen ist. Dieses ist mittels STM, AFM und auch LEED zu
beobachten. Weiterhin existieren Löcher, die tiefer sind als es der aufgedampften
Mn-Schichtdicke entspricht.
Diese Arbeit wurde unterstützt durch die Deutsche Forschungsgemeinschaft
im Rahmen des SFB 290.
O 25.4 Di 16:30 H39
Bare surface structures and quantum dots growth on the
GaAs(315)B surface — •Takayuki Suzuki, Yevgeniy Temko,
Mingchun Xu, and Karl Jacobi — Fritz-Haber-Institut der
Max-Planch-Gesellshaft, Faradayweg 4-6, 14195 Berlin
Surface structures of the GaAs(315)B surface were investigated under
Ga- and As-rich conditions. The Ga-rich surface is not flat on atomic
scale, but exhibits a very anisotropic surface morphology. Narrow stripes
of 1×1 structure extend along [12-1]. The steps between the stripes often
bunch together thus creating {101} facets. The As-rich surface is also not
flat, but facets into vicinal (5 2 11)B surfaces with steps along the [13-
1]proj. and [-321]proj.. {101} facets form on the sidewall of the steps along
the [13-1]proj.. The GaAs(315)B surface becomes flat by adsorbing InAs
with molecular beam epitaxy, and exhibits a c(2×2) reconstruction. Further
adsorption induces quantum dots (QDs) formation. The QDs shape
is given by {101}, {111}, and {2 5 11}A bounding facets. The size distribution
of the QDs is quite broad, with the length at the foot ranging from
15 to 80 nm. Many QDs exhibit signs of coalescence. Stacking-faults and
screw dislocations penetrating the QDs are directly detected with atomic
resolution. Correlation between broad size distribution and incorporation
of lattice defects are demonstrated experimentally for the first time.
O 25.5 Di 16:45 H39
Epitaxial growth of Ag on W(110) studied by Reflectance Difference
Spectroscopy — •L. D. Sun 1 , M. Hohage 1 , P. Zeppenfeld
1 , C. Deisl 2 , and E. Bertel 2 — 1 Institute of Experimental
Physics, Johannes-Kepler University Linz — 2 Institute of Physical Chemistry,
University of Innsbruck
The epitaxial growth of Ag on W(110) at room temperature has been
studied by Reflectance Difference Spectroscopy (RDS). The first two Ag
layers follow a layer-by-layer growth and show a distorted Ag(111) structure.
The anisotropic electronic transitions in the Ag film contribute substantially
to the optical anisotropy and can thus be used to monitor the
growth process. The evolution of the RDS spectrum strongly depends
on the Ag coverage. In particular, the RDS intensity at 4.7 eV increases
monotonically during the formation of the first Ag layer, whereas the
signal at 4.2 eV responds to the growth of the second layer. When the
thickness of the Ag film exceeds 3 monolayers, the RDS spectrum shows
a derivative like feature around a photon energy of 4 eV which can be
attributed to the onset of the bulk d-band transition of Ag. This observation
suggests the formation of a Ag bulk band structure at this growth
stage and thus is consistent with the growth of 3D islands on top of the
bilayer. These results are in good agreement with previous studies on
the crystallographic [1, 2] and electronic structure [3] of the Ag/W(110)
system. [1] E. Bauer et al., J. Appl. Phys. 48 (1977) 3773 [2] Y. Yang et
al., Surf. Sci. 276 (1992) 341. [3] A. Elbe et al., Surf. Sci. 397 (1998) 346
O 25.6 Di 17:00 H39
Thin TiO2 films and Au/TiO2 on Ru (0001) studied by XPS
and CO-TPD — •Zhong Zhao, H. Rauscher, and R.J. Behm —
University of Ulm
The chemical composition and adsorption behavior of welldefined
TiO2 films on Ru (0001) of up to 20 ML thickness and
Au/TiO2/Ru(0001) model catalysts are characterized by XPS and CO-
TPD. The TiO2 films were grown under UHV conditions, Au was deposited
by evaporation (Tsub =300K). XPS shows that titania grows on
Ru (0001) as either well oxidized TiO2 or reduced TiO2 (mixture of TiO2
and Ti2O3), depending on the preparation method. Neither CO2 production,
nor CO dissociation is observed when CO desorbs from surfaces on
the Au/TiO2/Ru model catalyst (dAu =2-3 nm). CO desorbs completely
at around 275 K from nanometer-sized Au clusters supported on reduced
TiO2. As the Au coverage is increased from 0.3 ML to 2 ML, the peak
temperature shifts from around 219 K to 197 K, equivalent to a decrease
in CO adsorption energy from 60 to 54 kJ/mol (v = 10 14 s −1 ). After
annealing the catalyst to 770 K, the amount of adsorbed CO decreases
significantly; corresponding STM measurements indicate a significant increase
of the Au cluster size. Neither encapsulation of the Au clusters by
reduced titanium oxides nor Au oxidation were observed after annealing.
CO adsorption on the titania film itself does not change significantly in
the presence of Au clusters.
O 25.7 Di 17:15 H39
Elementspezifische Oberflächenrekonstruktion auf Inseln bei
der surfactant-modifizierten Homoepitaxie auf Si(111):As,Sb
— •K. Schroeder 1 , A. Antons 1 , B. Voigtländer 2 , V. Cherepanov
2 und S. Blügel 1 — 1 Institut für Festkörperforschung, —
2 Institut für Schichten und Grenzflächen, Forschungszentrum Jülich, D-
52425 Jülich, Germany
Wir haben das frühe Stadium des surfactant(As, Sb)-modifizierten homoepitaktischen
Wachstums auf Si(111) mit STM und ab initio Rechnungen
untersucht. Die Ergebnisse zeigen ein unterschiedliches mikroskopisches
Verhalten für die beiden surfactants: Auf der As-bedeckten
Si(111)-Oberfläche findet man nur Inseln mit der Höhe einer Doppellage,
die die (1×1) Terrassenstruktur zeigen. Auf Sb-bedecktem Si(111) zeigen
die Inseln 2 verschiedene Oberflächenstrukturen. Am Rand der Inseln
erscheint die (1×1)-Struktur, während in der Mitte die ( √ 3 × √ 3) Terrassenstruktur
gefunden wird. Aus den Rechnungen ergibt sich, dass das
Doppellagenwachstum auf Si(111):As (1×1) schon bei Si-Clustergrößen
von 4 beginnt. Auf Si(111):Sb (1×1) sind Doppellagen energetisch instabil,
während auf Si(111):Sb ( √ 3 × √ 3) eine große kinetische Barriere
von 1 eV für die Nukleation neuer Sb-Trimere in der zweiten Lage das
Doppellagenwachstum kinetisch unterdrückt.

Oberflächenphysik Dienstag
O 25.8 Di 17:30 H39
Continuous Phase Transition of Surface Reconstructions
Investigated by X-ray Scattering: Theory and Experiment
— •Frank Grosse 1 , Bernd Jenichen 2 , Wolfgang Braun 2 ,
Vladimir M. Kaganer 2 , Dilip K. Satapathy 2 , X. Guo 2 , and
Klaus H. Ploog 2 — 1 Institut für Physik der Humboldt-Universität zu
Berlin, Newtonstr. 15, 12489 Berlin, Germany — 2 Paul-Drude-Institut
für Festkörperelektronik Hausvogteiplatz 5-7, 10117 Berlin, Germany
Atomistic simulations for the reconstruction transition on the
InAs(001) surface are performed on the basis of ab initio density functional
calculations [1]. A continuous surface phase transition of the Asrich
β2(2×4) reconstruction to the α2(2×4) reconstruction is predicted
leading to a mixture of both reconstructions. The atomic coordinates of
the simulation cells are used to calculate the X-ray diffraction intensity
employing kinematic theory. The equilibrium properties and kinetic effects
due to change in temperature as well as As-pressure are discussed.
Experiments performed at BESSY (Berlin) allow an in situ measurement
and structure analysis of the reconstruction phase transition and are in
agreement with the theoretical predictions. [1] F. Grosse, W. Barvosa-
Carter, J.J. Zinck, M. Wheeler, and M.F. Gyure. Phys. Rev. Lett. 89,
116102 (2002); F. Grosse and M. Gyure. Phys. Rev. B. 66, 075320 (2002).
O 25.9 Di 17:45 H39
Growth and morphology of ultrathin nickel films on Cu (001)
— •Leif Glaser 1 , Robert Nietubyć 1 , Alexander Föhlisch 1 ,
Julian Tobias Lau 1,2 , Michael Martins 1 , Matthias Reif 1 , and
Wilfried Wurth 1 — 1 Institut für Experimentalphysik, Universität
Hamburg, Luruper Chaussee 149, 22761 Hamburg — 2 EPFL, Lausanne,
Switzerland
We have studied the Ni L-X-ray Adsorption Fine Structure (XAFS)
for thin Nickel films that were evaporated on a Cu(001) substrate. The
measurements were made at the Beamline BW3 of the DORIS storage
O 26 Adsorption an Oberflächen II
ring at HASYLAB. The coverages ranged from 0.08 to 3.0 layers of Ni
and were calibrated by the ratio of Ni L3 to Cu L3 jump height and verified
by thermal desorption spectroscopy (TDS). We have found a clear
evolution of the XAFS with coverage. Furthermore we observed layer by
layer growth of the Nickel thin films. The changes in the x-ray adsorption
spectra are in very good agreement with the multiple scattering simulations
that were performed alongside the experiment. Surface alloying did
not take place upon annealing to 400K while at 450K clear evidence for
alloying was observed. Funding for this project by BMBF under contract
KS1 GUB/5 is gratefully acknowledged.
O 25.10 Di 18:00 H39
Growth of Cr on Ru(0001) studied by STM — M.P. Engelhardt
1 , M. Schmid 2 , A. Biedermann 2 , P. Varga 2 , •R.
Denecke 1 , and H.-P. Steinrück 1 — 1 Physikalische Chemie II,
Universität Erlangen-Nbg., Egerlandstr. 3, 91058 Erlangen, Germany
— 2 Inst. f. Allgemeine Physik, Technische Universität Wien, Wiedner
Hauptstr. 8- 10/134, 1040 Wien, Austria
We give an insight into the temperature dependent growth of Cr on
Ru(0001) using scanning tunnelling microscopy (STM). At room temperature
the growth is not purely layer-by-layer. Annealing of the resulting
Cr layers to 500 and 700 K leads to the formation of Cr islands with a
bcc(110)-like structure. A complete pseudomorphic Cr monolayer could
be prepared for evaporation at 700 K. By applying a countervoltage at
the end of the electron beam evaporator to suppress the Cr ions leaving
the evaporator smoother Cr layers are obtained. The formation of a Cr-
Ru surface alloy with a Cr:Ru ratio of 1:2 at 1000 K was observed; on this
alloy CO molecules adsorb predominately at Ru sites in on top geometry.
The conclusions are discussed in the light of Auger electron spectroscopy
and temperature- programmed desorption results [1]. Supported by the
Max-Buchner-Stiftung.
[1] M.P. Engelhardt et al., Surf. Sci. 512 (2002) 107.
Zeit: Dienstag 15:45–18:00 Raum: H45
O 26.1 Di 15:45 H45
STM and STS study of Cu(111)-Cs — •Thomas von Hofe, Jörg
Kröger, and Richard Berndt — Institut für Experimentelle und
Angewandte Physik, Universität Kiel, D-24098 Kiel, Germany
Alkali-covered noble metal surfaces have been of theoretical and experimental
interest for a long time since these are the simplest of metal-metal
systems. Here we present first results of Cs-covered Cu(111) obtained by
STM and STS experiments at 9K for coverages between approximately
0.3 and 0.9 ML. Cs does not grow in homogeneous films as one would
expect, but a kind of island growth takes place. These islands reveal a
p(2x2) LEED pattern and show a quantum well state whose lifetime has
been measured.
O 26.2 Di 16:00 H45
Rastertunnelmikroskopie und -spektroskopie an einzelnen
Kobalt-Carbonylen auf Cu(100) — •Peter Wahl 1 , Ari P.
Seitsonen 2 , Lars Diekhöner 1 , M. Alexander Schneider 1 ,
Gero Wittich 1 und Klaus Kern 1 — 1 MPI für Festkörperforschung,
Heisenbergstr. 1, 70569 Stuttgart — 2 Phys. Chem. Institut, Universität
Zürich, Schweiz
Der Einfluß von Adsorbaten auf die magnetischen Eigenschaften von
einzelnen Adatomen auf der Cu(100) Oberfläche wird untersucht. Als
magnetische Sonde benutzen wir die Kondo-Resonanz in der Nähe der
Fermi-Energie. Die Moleküle werden durch Reaktion von Kobalt mit
Kohlenmonoxid im UHV auf der Oberfläche präpariert und dann im
Rastertunnelmikroskop (STM) bei 6K untersucht. Die Moleküle können
durch kontrollierte Dissoziation analysiert und identifiziert werden. Die
auf den Molekülen gemessenen Spektren werden mit denen von einzelnen
Kobaltadatomen verglichen. Die Ergebnisse werden mit Hilfe von
DFT-Rechnungen interpretiert.
O 26.3 Di 16:15 H45
Non-adiabatic spin effects in O2 dissociation at Al(111) — •Jörg
Behler 1 , Sönke Lorenz 1 , Bernard Delley 2 , Karsten Reuter 1 ,
and Matthias Scheffler 1 — 1 Fritz-Haber-Institut, Faradayweg 4-6,
D-14195 Berlin — 2 Paul Scherrer Institut, CH-5232 Villigen PSI
The experimentally well established low initial sticking coefficient of
thermal oxygen molecules impinging on an Al(111) surface is still lacking
a physical explanation. The calculation of the six-dimensional potential
energy surface using density functional theory (DFT) followed by
extensive molecular dynamics (MD) simulations results in a far too high
sticking probability due to the absence of energy barriers in this adiabatic
description. By including a constrained DFT method we extend
this standard approach to describe the spin triplet state of the oxygen
molecule and the singlet state of the metal surface. This is a generalization
of the fixed spin moment approach, and it enables us to investigate
the effect of non-adiabatic processes in the dissociative adsorption. For
the total energy surface of the spin triplet O2 we find energy barriers up
to 0.5 eV for most molecular orientations agreeing well with the experimental
data. MD simulations on this surface yield a significantly lower
sticking probability than obtained in the adiabatic case.
O 26.4 Di 16:30 H45
CO-H interaction and H-dissolution probed by SFG and TDS:
Specific differences between Pd nanoparticles and Pd(111) —
•Günther Rupprechter, Matthias Morkel, and Hans-Joachim
Freund — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg
4-6, 14195 Berlin, Germany
CO hydrogenation and H bulk dissolution on Pd model catalysts were
studied by sum frequency generation (SFG) vibrational spectroscopy and
thermal desorption spectroscopy (TDS) at pressures ranging from ultrahigh
vacuum (UHV) to 1 bar. Well-facetted Pd nanoparticles (ca. 5
nm), grown on Al2O3/NiAl(110), as well as Pd(111) were employed as
model surfaces and examined using a UHV-compatible high-pressure cell.
Although the Pd nanoparticles mostly exhibt (111) faces, their adsorption/reaction
behaviour is quite different from Pd(111).
Strong differences with respect to the adsorption of the individual
molecules were observed, e.g. an easier formation of a hydride phase on
Pd nanoparticles. Even more pronounced differences occurred for CO-H
coadsorbate structures under UHV and mbar pressure which are strongly
related to the formation of bulk H. It is demonstrated that the dynamic
adsorbate structure of a high-pressure reaction can not be mimicked un-

Oberflächenphysik Dienstag
der the static conditions of a UHV experiment.
O 26.5 Di 16:45 H45
Photodesorption of small molecules adsorbed on ultrathin Ag
— •Olaf Weisse, Claudia Wesenberg, and Eckart Hasselbrink
— FB Chemie, Universitaet Duisburg-Essen, Universitaetstr. 5, 45117
Essen, Germany
Since the early 1990, Ag is known to grow on the Si(100) surface in a
layer-by-layer fashion. The resulting surface forms an epitaxial Ag(111)
layer. These ultrathin Ag films(20-100ML) are ideally suited to study the
elektron dynamics in such films and the influence of the film thickness
on charge transfer to the adsorbate and subsequent photodesorption. In
our experiments, NO2 is chosen as the probe molecule. Its adsorbtion is
performed at 95 K on the Ag-covered Si(100) surface. Photodesorption
is induced using a Nd:YAG laser (2.3eV/3.5eV/4.6eV) and the desorbed
molecules are detected by QMS. The film thickness is varied in order
to obtain information about the charge transfer dynamics between the
ultrathin Ag film and the NO2 adsorbate. The photodesorption crosssection
of NO2 is expected to decrease with increasing film thickness.
We belive that the photodesorption cross-section will increase due to hot
electrons generated in the semiconductor.
O 26.6 Di 17:00 H45
Surface plasmons of metal islands and their influence on the infrared
absorption of adsorbates — •A. Priebe, G. Fahsold, and
A. Pucci — Kirchhoff-Institut für Physik, Universität Heidelberg,
The surface enhanced infrared absorption (SEIRA) of adsorbates on
nano-structured metal films are widely used in chemistry and biology. For
the first monolayer the typical asymmetric SEIRA line shape can be explained
by an interaction of the adsorbate with electron-hole pairs of the
metal film. But asymmetric SEIRA lines are observed also for vibrations
in multilayers. From experimental results it is known that the asymmetry
and the enhancement of SEIRA lines show a strong dependency on
the filling factor of the metal in the island film. In this work we show
how both, the asymmetry and the enhancement could be explained with
respect to their change with filling factor. Experimental SEIRA spectra
from adsorbates on nanoparticle arrays with ordered facets can be
described by a theory that only considers the interaction of adsorbate
vibrations with surface plasmons of the metal film.
A. Priebe, M. Sinther, G. Fahsold, and A. Pucci J. Chem. Phys. 119
(2003), 4887
O 26.7 Di 17:15 H45
Adsorption of CO on the (10¯10) surface of Rhenium — •C.
Pauls, D. Przyrembel, and K. Christmann — Inst. f. Chemie, FU
Berlin, Takustr. 3, 14195 Berlin
We have performed LEED, thermal desorption (TD), and work function
change (∆Φ) measurements of CO interacting with the ’open’
Re(10¯10) surface. Upon exposure at 200 K, negatively polarised (∆Φ ≈
780 meV) molecular α states are populated. TD spectra reveal these
states between 250 and 400 K (Edes= 95...118 kJ/Mol) and, in addition,
pronounced β states due to dissociated CO between 600 and 800 K. Direct
CO exposure at 500 K exclusively yields dissociated CO as evidenced by
i) 2 nd order desorption kinetics at low coverages (Edes= 207 kJ/Mol) and
O 27 Gaedepreisvortrag Sander
ii) the formation of a p(1x2) LEED phase at a CO coverage of Θ= 0.25.
carbon]. Between 0.125 and 0.16 ML an additional c(2x4) phase appears.
During desorption, both phases undergo an order-disorder transition. In
the coverage range of the p(1x2) phase the respective TD spectra show a
common leading edge (zero-order kinetics) until the critical temperatur
of ∼ 660 K is reached.
O 26.8 Di 17:30 H45
Electronic properties and hydrogen absorption of Pd and Ni:O
nano-clusters — •Andreas Borgschulte, Ruud J. Westerwal,
Sven de Man, Bernard Dam, Jan H. Rector, and Ronald
Griessen — Vrije Universiteit, FEW - Vaste-stoffysica, De Boelelaan
1081, 1081 HV Amsterdam
We studied by scanning tunneling microscopy the electronic and geometric
structure of Pd and Ni nano-clusters grown on oxidized yttrium
surfaces. The catalytic activity of Pd and Ni nano-clusters is estimated
from the optically monitored switching kinetics of the underlying yttrium
layer. The electronic structure depends strongly on the cluster
size and changes after hydrogenation. Small Pd clusters are insulating as
evidenced by tunneling spectroscopy. The critical thickness of the metalinsulator
transition coincidences with the minimal thickness for a significant
catalytic Pd activity. Below the critical thickness nano-clusters have
lost the special catalytic properties of (bulk) Pd. In contrast to Pd, Nisurfaces
oxidize in normal environment (air). In that case the interplay
between hydrogen and oxygen chemisorbed on Ni clusters as well on crystalline
surfaces is studied. Surfaces with a partially reduced oxide show
the catalytically highest activity. The results are compared with X-ray
diffraction studies on the interaction of hydrogen with NiO. We discuss
the relevance of the results for a search of novel catalysts for hydrogen
storage and fuel cells, in particular the role of oxides as catalysts.
O 26.9 Di 17:45 H45
Coadsorption of H and CO on Pd(210) — •Christian Mosch,
Markus Lischka, and Axel Groß — Physics-Department, Technical
University of Munich, D-85747 Garching, Germany
The study of the interaction of molecules with stepped surfaces is of
importance in order to close the structure gap between surface science
and heterogeneous catalysis. We have focused on the adsorption of hydrogen
[1,2] and CO on Pd(210) by performing density functional theory
(DFT) calculations within the generalized gradient approximation. The
(210) surface can be regarded as being built up by small (100) terraces.
CO is known to adsorb on Pd(100) in an upright fashion at the bridge
position [3,4]. On Pd(210), there are two inequivalent bridge positions.
And indeed, we find a relatively small corrugation in the CO adsorption
energies with the two bridge sites being energetically almost degenerate.
CO is furthermore known as a strong poison in heterogeneous catalysis.
We have therefore also addressed the coadsorption of CO with atomic
hydrogen. There is a strong inhibition of the hydrogen adsorption due to
the presence of CO which is analyzed in terms of the electronic structure
of the adsorbate system.
[1] P.K. Schmidt et al., Phys. Rev. Lett. 87, 096103 (2001).
[2] M. Lischka and A. Groß, Phys. Rev. B 65, 075420 (2002)
[3] A. M. Bradshaw and F. M. Hoffmann, Surf. Sci. 72, 513 (1978).
[4] A. Eichler and J. Hafner, Phys. Rev. B 57, 10110 (1998).
Zeit: Mittwoch 15:15–16:00 Raum: H1
Hauptvortrag O 27.1 Mi 15:15 H1
Stress on the atomic scale: From surface reconstruction to stress
oscillations and magnetostriction of atomic layers — •Dirk
Sander — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2,
D-06120 Halle
Mechanical stress is an important factor, which governs a number
of fundamental aspects in surface science, film growth, and magnetic
anisotropy. Examples are e.g. the surface reconstruction of clean and
adsorbate-covered surfaces, oscillatory stress relaxation in nanosize islands,
and the magnetoelastic coupling in ferromagnetic monolayers.
Stress measurements by the cantilever bending technique are presented
for each example. Film stress in the GPa range, in excess of the tensile
strength of high-strength materials, is measured for epitaxially strained
layers. Structural relaxation due to island growth and coalescence, and
surface alloy formation are comparatively subtle effects, which are detected
by the respective stress signature. The in situ combination of
stress measurements during film growth with magnetoelastic stress measurements
upon magnetization reversal identifies a strain-induced change
of the magnetoelastic coupling constants from the respective bulk value.
The impact on the peculiar magnetic anisotropy of ferromagnetic layers
is discussed.

Oberflächenphysik Mittwoch
O 28 Postersitzung (Elektronische Struktur, Grenzfläche fest-flüssig,
Halbleiteroberflächen und -grenzflächen, Magnetismus und Symposium SYXM,
Methodisches, Nanostrukturen, Oberflächenreaktionen, Teilchen und Cluster,
Zeitaufgelöste Spektroskopie)
Zeit: Mittwoch 16:00–19:00 Raum: Bereich C
O 28.1 Mi 16:00 Bereich C
Bulk and surface sensitive photoemission on 1T-TiS2 — •M.
Garbrecht, O. Seifarth, M. Skibowski, and L. Kipp — Institut
für Experimentelle und Angewandte Physik, Universität Kiel, D-24098
Kiel, Germany
The bulk and surface sensitive electronic structure of the layered transition
metal dichalcogenide 1T-TiS2 is investigated by means of angle
resolved photoemission spectroscopy with VUV and XUV photons. At
photon energies around 50 eV where ARPES is extremely surface sensitive
we observe a semiconducting band structure. This is contrasted
by more bulk sensitive photoemission data obtained at 150 eV where a
semimetallic behavior is found. The results are discussed in the context
of recent band structure calculations performed within the density functional
theory. The experiments have been performed with the ASPHERE
spectrometer at the HASYLAB beamlines W3.2 and BW3. Work supported
by the BMBF project no. 05 KS1 FKB and DFG Forschergruppe
FOR 353
O 28.2 Mi 16:00 Bereich C
Excited state UPS of C60 — •Arne Rosenfeldt, Klaus Finsterbusch,
and Helmut Zacharias — AG Zacharias, Physikalisches
Institut, Westfälische Wilhelms-Universität
A 200 layer C60 film is prepard by growth on an annealed C60 monolayer
on Cu(111). This system is pumped with tunable 351 to 415nm radiation
of 100ps pulse duration and probed with delayed 263, 211 and 150nm
photons. Using the time-of-flight technique photo-electrons are observed
from LUMO+1, LUMO, and singlet exciton states. The excitation probability
of these states as a function of photon energy is measured. A
maximum is found for hν = 3.16eV (λ ∼ 392nm). Further, the electron
dynamic is analyzed and will be discussed.
O 28.3 Mi 16:00 Bereich C
Geometric and electronic structure of epitaxial PbS on HfS2 —
•J. Iwicki, A. Kamenz, O. Seifarth, S. Habouti, M. Kalläne,
and L. Kipp — Institut für Experimentelle und Angewandte Physik,
Universität Kiel, D-24098 Kiel, Germany
Misfit layer compounds like (PbS)NbS2 form a special class of layered
heterostructures. Due to 4-fold symmetries of the PbS layers which contrast
the 6-fold symmetry of the NbS2 layers a misfit is constituted. Up to
now, bulk crystals of misfit compounds could only be grown with metallic
hexagonal layers like e.g. NbS2 or TiS2. Here we show first steps of epitaxial
growth of PbS on semiconducting HfS2 with corresponding STM
images and angle resolved photoemission spectra for different coverages
of PbS on HfS2. The photoemission results are compared with data of
clean HfS2 and PbS bulk crystals. The experiments have been performed
with the ASPHERE spectrometer at HASYLAB.
Work supported by the BMBF proj. 05 KS1 FKB and DFG Forschergruppe
FOR 353
O 28.4 Mi 16:00 Bereich C
High energy conduction band states in layered materials — •M.
Marczynski, K. Rossnagel, M. Kalläne, E. E. Krasovskii, M.
Skibowski, W. Schattke, and L. Kipp — Institut für Experimentelle
und Angewandte Physik, Universität Kiel, D-24098 Kiel, Germany
Employing angle resolved photoemission in the constant initial state
mode we investigate the conduction band states of layered materials up
to about 100 eV above the Fermi level. The layered materials HfS2 and
TiTe2 serve as model systems showing distinct features even for higher
conduction bands. The experimentally observed structures are discussed
in the context of theoretical results obtained by ab initio calculations. In
particular, photoemission final states are treated within ELAPW based
scattering theory.
The experiments have been performed at HASYLAB (BW3 beamline)
and the Advanced Light Source (beamline 7).
Work supported by the BMBF project no. 05 KS1 FKB and DFG
Forschergruppe FOR 353.
O 28.5 Mi 16:00 Bereich C
Angle resolved measurement of the (1π) 1 photoemission cross
section of CO adsorbed on Pt(111) — •Sebastian Wegner,
Grigorios Tsilimis, Jörg Kutzner, and Helmut Zacharias —
Physikalisches Institut, Westfälische Wilhelms Universität Münster,
Wilhelm-Klemm-Straße 10, D-48149 Münster
High order harmonic radiation is generated by focussing femtosecond
Ti:sapphire pulses into a noble gas. The pulsed radiation is tunable in
the range of 20 − 110 eV in steps of 3.1 eV. At an energy of 32.4 eV we
measured the CO(1π) −1 photoemission of the c(4 ×2)-2CO/Pt(111) surface.
In contrast to experiments on oriented molecules in the gas phase
we observe emission parallel as well as perpendicular to the axes of the
adsorbed CO. We fitted the angular distribution by Legendre polynomials
Pl(cosθ). It is best fitted by l = 3 and l = 4 polynomials indicating a
large contribution of d and f partial waves.
O 28.6 Mi 16:00 Bereich C
Fermi-Surface-Mapping an Übergangsmetallen — •M. Krause,
S. Dreiner, M. Schürmann, U. Berges und C. Westphal — Universität
Dortmund, Experimentelle Physik I, 44221 Dortmund
Die Kenntnis der elektronischen Struktur von Metallen ist grundlegend
für das Verständnis vieler physikalischer Phänomene. Die elektronischen
Zustände an der Fermikante bedingen z.B. die elektrische
Leitfähigkeit, die Temperaturabhängigkeit des Ferromagnetismus, die Supraleitung
und die Hochtemperatursupraleitung. Durch Aufnahme winkelaufgelöster
Photoemissionsspektren über dem Halbraum der Probe
mit HeI Strahlung wurden Schnitte durch die Fermiflächen gemessen. Zur
Interpretation wurden Vergleichsrechnungen der Dichtefunktionaltheorie
(LKKR) durchgeführt.
Die Meßergebnisse für Cu, Ni, Pd und Rh werden gezeigt und mit den
jeweiligen Rechnungen verglichen. Diese Ergebnisse bilden die Grundlage
für zukünftige Experimente.
O 28.7 Mi 16:00 Bereich C
Surface state as local sensor for single magnetic impurities —
•Daniel Wegner, Andreas Bauer, and Günter Kaindl — Freie
Universität Berlin, Institut für Experimentalphysik, Arnimallee 14, 14195
Berlin-Dahlem
The (0001)-surface of Lu metal exhibits a highly localized surface state
directly at the Fermi energy, EF [1]. It appears as a sharp peak in the tunnelling
spectra measured by low-temperature scanning tunnelling spectroscopy
(STS) at 10 K. We have used this surface-state peak as a sensor
for single magnetic impurities of Gd and Ho atoms embedded in the
film surface. Within a radius of about 15 ˚A around such an impurity,
the surface-state appears as a double-peaked structure in the tunnelling
spectra with a narrow dip in between; this dip is only a few meV wide
and is located within less than 1 meV at EF. The results are discussed
on the basis of the Kondo effect.
This work was supported by the DFG, Sfb-290.
[1] A. Bauer, A. Mühlig, D. Wegner, and G. Kaindl, Phys. Rev. B 65,
75421 (2002).
O 28.8 Mi 16:00 Bereich C
Correlation of electronic transport and structural properties of
Cs layers on Si(001) — •Hong Liu, A.A. Shklyaev, V. Zielasek,
and H. Pfnür — Universität Hannover, Institut für Festkörperphysik,
Appelstr. 2, 30167 Hannover
Combining LEED, EELS, and conductivity measurements we have
studied the correlation of electronic transport with structural properties
of Cs layers on Si(001). Depending on the substrate temperature T
during Cs deposition we find three different growth regimes. Only for
T

Oberflächenphysik Mittwoch
For Cs deposition at around 160 K we observe discontinuities of the
surface conductivity at 0.5, 1, and 1.5 monolayer coverage, respectively.
Those at 0.5 and 1 ML can be associated with transitions of the surface
reconstruction from 3 × 4 to 3 × 2 and 3 × 2 to 2 × 1, respectively.
Based on EELS data, electrical phase transitions (metal - semiconductor
- metal) in the submonolayer coverage range have been reported by others
[1]. While according to EELS the wetting layer should be metallic,
conductivity measurements show that the electrical transport in the layer
is activated. Refined models of the surface structure will be presented.
[1] Ki-Dong Lee and Jinwook Chung, Phys. Rev. B 55 (1997) 12906.
O 28.9 Mi 16:00 Bereich C
STM-Simulation der Selbstassemblierung von Adenin auf
Graphit in Abhängigkeit der Scanrichtung — •Thomas
Markert 1 , Thomas Markert 1 , Ferdinand Jamitzky 2 , Frank
Trixler 3 , Axel Groß 1 , Wolfgang Heckl 3 , Ferdinand Jam
itzky 2 , Frank Trixler 3 und Axel Groß 1 — 1 Physik-Department,
TU München, D-85747 Garching — 2 MPI für extraterrestrische Physik,
D-85740 Garching — 3 Department für Geo- und Umweltwissenschaften,
LMU München, D-80333 München
STM-Bilder von Molekülnetzwerken, die über Wasserstoff-Brückenbindungen
stabilisiert sind, zeigen i.a. eine deutliche Abhängigkeit von
der Scanrichtung, da kleine Verschiebungen der Moleküle, die während
des Scanvorgangs durch die Spitze verursacht werden, abhängig von der
Orientierung der Wasserstoff-Brückenbindungen sind. Bei gleicher Auslenkung
sind die Rückstellkräfte parallel zur Wasserstoff-Brückenbindung
größer als senkrecht zu ihr. Mit Hilfe von LDOS-Bildern, die aus DFT-
Rechnungen erstellt wurden, wird am Beispiel der Selbstassemblierung
von Adenin auf Graphit versucht die experimentell gewonnenen Bilder
einer Drehserie zu simulieren.
O 28.10 Mi 16:00 Bereich C
Elctronic structure of MgSO4 crystals — •V.V. Maslyuk 1,2 ,
C. Tegenkamp 1 , T. Bredow 3 , and H. Pfnür 1 — 1 Institut für
Festkörperphysik, Appelstr.2 D-30167 Hannover, Germany — 2 Uzhhorod
National University, Pidgirna St.2 88000 Uzhhorod, Ukraine — 3 Institut
für Theoretische Chemie, Am Kleinen Felde 30 D-30167 Hannover, Germany
Typically, the crystallographic structures of minerals are quite well investigated,
but there is not much knowledge about their electronic structures.
As one candidate of an insulator consisting chemically of more than
two different elements, we investigated the crystallographic and electronic
structure of MgSO4 and kieserite (MgSO4 ·H2O), respectively. Starting
with kieserite with 36 atoms per unit cell, we determined the electronic
structure by ab–initio calculations. Using CRYSTAL03 the lattice parameters
were calculated within an accuracy better than 0.01 ˚A by choosing
basis sets for magnesium and oxygen taken from MgO and for sulfur
taken from CaSO4 including also d–orbitals. In order to calculate the
band gap of kieserite, the method of hybrid mixing of Hartree–Fock and
DFT hamiltonians was used. The band gap at the Γ–point was detemined
to be 7.4 eV. To support the theoretical calculations, first photoelectron–
and electron energy loss spectroscopy experiments have been performed.
Thereby, bulk kieserite crystals have been used. Obviously, the effect of
surface relaxation effects and defects are small, because the measured
band gap agrees quite well with the theoretical findings. Nevertheless,
our calculations will be further refined.
O 28.11 Mi 16:00 Bereich C
Valence band photoemission spectroscopy of chemically
disordered ultrathin NixPd1−x films on Cu3Au(100) — •Frank
Matthes 1 , Liu-Niu Tong 1 , Alexej Rzhevskii 2 , and C.M. Schneider
2 — 1 Leibniz Institut für Festkörper- und Werkstoffforschung
Dresden, PF 27 01 16, D-01171 Dresden — 2 Institut für Elektronische
Eigenschaften, Forschungszentrum Jülich, 52425 Jülich
We have studied the valence band structure of ultrathin NixPd1−x
alloys on a single crystalline Cu3Au(100) substrate. Ni and Pd are isoelectronic,
but while Ni is ferromagnetic with an average exchange splitting
of 0.3 eV along the ∆ direction, Pd exhibits a higher spin orbit
coupling (band splitting 0.3 eV). Via the alloy concentration one can
conveniently vary the relative weight of these two spin-dependent interactions
with profound effects for the electronic structure. We will present
first results of our high-resolution photoemission measurements for 15
monolayer thick NixPd1−x films with different compositions. The measurements
were performed along the ∆ direction for excitation energies
from 16 eV to 40 eV. As a main spectral feature, we observed contri-
butions from bands originating from 3d Ni and 4d Pd electrons near
the Fermi energy. This feature only disperses weakly with the excitation
energy. Starting with pure Ni films, we observed a broadening of
the spectra while increasing the Pd concentration up to 30%. This may
be caused by the chemically induced disorder. To distinguish the spin
dependent contributions and thus arrive a more detailed interpretation
of the photoemission data, we performed for three different Ni rich alloy
compositions also spin-resolved photoemission experiments.
O 28.12 Mi 16:00 Bereich C
Site-specific Valence-electronic Structure of SrTiO3 by X-ray
Standing Waves and XPS — •Sebastian Thiess 1 , Tien-Lin Lee 1 ,
Bruce C. C. Cowie 1 , Joe C. Woicik 2 , and Jörg Zegenhagen 1
— 1 ESRF, Grenoble, France — 2 NIST, Gaithersburg, USA
We used the x-ray standing waves (XSW) technique and x-ray photoelectron
spectroscopy (XPS) to determine the contribution of the constituent
elements Sr, Ti and O of a SrTiO3 (STO) crystal to the STO
valence band, thus deriving their partial density of states.
Lattice site-specific electronic information - which is not available from
standard XPS - is obtained by utilising the spatial intensity modulation
of an x-ray standing wave (XSW) interference field, generated by the coherent
superposition of an incident and a Bragg-reflected x-ray beam. By
proper positioning the antinodes of the XSW within the STO unit cell,
photoemission from specific lattice sites can be preferentially excited and
their valence electronic contribution identified.
XSW fields were generated by the STO(111) and STO(112) reflections
at photon energies of 2.7 and 3.9 keV. XSW modulated, high-resolution
core and valence-electron emission spectra were recorded from an in-situ
UHV annealed STO single crystal at beamline ID32 at the ESRF.
O 28.13 Mi 16:00 Bereich C
Mechanisms and capability of Steam Laser Cleaning — •F.
Lang 1 , M. Mosbacher 1 , S. Georgiou 2 , and P. Leiderer 1 —
1 University of Konstanz, Fach M676, 78457 Konstanz, Germany —
2 FORTH - IESL, P.O. Box 1527, 71110 Heraklion, Greece
Steam Laser Cleaning is a powerful approach to remove submicron
particles from surfaces. In the first step a liquid is applied onto the contaminated
surface. Afterwards a laser pulse heats part of the fluid to
a superheated state resulting in bubble nucleation and growth. Thereby
strong forces are exerted on the contaminants, which are able to overcome
the adhesion of the particles to the surface.
Our measurements covering a broad range of particle sizes demonstrated
the existence of a universal cleaning threshold for the laser fluence.
In addition the influence of different liquid layer thicknesses was
explored. Investigations of the surfaces after cleaning verified for the first
time that damage free removal can be achieved, if the experimental parameters
are chosen properly. Moreover fundamental studies of the bubble
nucleation and growth in the superheated liquid were conducted to
gain a more detailed understanding of the phase transition dynamics.
O 28.14 Mi 16:00 Bereich C
In-situ Video-STM Untersuchung der Dynamik von Sulfidadsorbaten
auf Cu(100)-Elektroden — •Tunay Tansel und Olaf
Magnussen — Institut für Experimentelle und Angewandte Physik
Christian-Albrechts-Universität Kiel
Die Diffusion und Wechselwirkung von Adsorbaten an Elektrodenoberflächen
ist von großer Bedeutung für das Verständnis der elektrochemischen
Phasengrenze. Solche dynamischen Prozesse wurden hier am Beispiel
von Sulfidadsorbaten (Bedeckungen 0,01 bis 0,03ML) auf Cu(100) in
0,01M HCl mittels elektrochemischer Hochgeschwindigkeits- Rastertunnelmikroskopie
(Video-STM) direkt auf der atomaren Skala untersucht.
Eine statistische Analyse der Diffusion isolierter Sad ergab Sprungfrequenzen
im Bereich von ≈ 2 · 10 −1 Hz. An den Domänengrenzen c(2x2)-
Phase ist die Sad Mobilität jedoch stark erhöht. Dies zeigt, dass die
Gegenwart des c(2x2)-Cl Koadsorbatgitters die effektive Diffusionsbarriere
von Sad deutlich vergrößert. Weiterhin weisen die Beobachtungen
auf attraktive Sad-Sad Wechselwirkungen und eine erhöhte Mobilität von
Clustern an mehreren, benachbarten Sad hin.

Oberflächenphysik Mittwoch
O 28.15 Mi 16:00 Bereich C
In-situ-Video-STM-Untersuchungen des (1x1) →”hex” - Phasenüberganges
an Au(100)-Elektrodenoberflächen — •Klaus
Krug 1 , Miguel Labayen 1 , Claudia Ramirez 2 , Wolfgang
Schattke 2 und Olaf Magnussen 1 — 1 Institut für Experimentelle
und Angewandte Physik Christian-Albrechts-Universität zu Kiel —
2 Institut für Theoretische Physik und Astrophysik Christian-Albrechts-
Universität zu Kiel
Die Dynamik des elektrochemisch induzierten (1x1) →”hex”
Übergangs an Au(100)-Elektroden wurde in 0.01 M Na2SO4 + 1 mM
HCl mittels in-situ Video-STM untersucht. Der Phasenübergang erfolgt
über Nukleation und Wachstum elementarer Einheiten der Oberflächenrekonstruktion,
5 Atomreihen breiten, hexagonal geordneten Streifen
in der obersten Atomlage. Wachstum, kollektive Bewegung und Wechselwirkung
der Streifen konnten mit hoher Zeitauflösung als Funktion von
Potential und Temperatur beobachtet werden. Diese Beobachtungen weisen
unter anderem auf einen schnellen eindimensionalen Massentransport
von Goldatomen entlang der Streifen hin, der sowohl über Verzerrungen
im Streifen selbst als auch über Adatome auf dem Streifen erfolgen kann.
Diese Interpretation wird durch Dichtefunktionalrechnungen gestützt.
O 28.16 Mi 16:00 Bereich C
In-situ Video-STM-Untersuchungen der lateralen Bewegung
von ”hex”-Streifen auf Au(100)-Elektrodenoberflächen —
•Christian Haak, Miguel Labayen und Olaf Magnussen
— Institut für experimentelle und Angewandte Physik, Christian-
Albrechts-Universität, Leibnizstraße 19, 24118 Kiel
Die Dynamik von fünf Atomreihen breiten, hexagonal geordneten
Streifen auf Au(100)-Oberflächen wurde mittels Video-STM in 0.01 M
Na2SO4 + 1 mM HCl untersucht. Diese Streifen existieren transient
während des potentialinduzierten Übergangs von der Au(100) (1×1) zur
”hex” rekonstruierten Oberfläche und weisen eine überraschend hohe Mobilität
senkrecht zur Streifenrichtung auf (Sprungraten von ca. 40 s −1 ).
Die Bewegung dieser nanoskaligen Streifen wurde mit automatischen Bilderkennungsverfahren
analysiert und statistisch ausgewertet. Dabei erhaltene
Sprungverteilungsfunktionen weisen auf die Existenz zweier elementarer
Prozesse hin (Sprünge um einen bzw. zwei Atomabstände), welche
simultan ablaufen. Diese Sprünge können über die Bewegung versetzungsähnlicher
Verzerrungen in den Streifen erklärt werden.
O 28.17 Mi 16:00 Bereich C
Copper sulfidation at the solid/liquid interface — •A. Spänig,
T. Mangen, P. Broekmann und K. Wandelt — Institut für Physikalische
Chemie; Wegelerstr. 12; 53115 Bonn
The initial stage of the sulfidation process of a Cu(100) electrode surface
has been studied under electrochemical conditions by means of insitu
Scanning Tunneling Microscopy (STM). At negative electrode potential
sulfide anions form a regular c(2 × 6) adsorbate layer which transforms
irreversibly into two-dimensional copper sulfide phases at more
positive potentials. Depending on the applied electrode potential different
sulfide induced reconstruction phases could be generated which can
be seen as precursor phases for the formation of bulk copper sulfide. The
reconstruction process is accompanied by a massive mass transport out
of the topmost copper layer pointing to a sulfide induced expansion of
the topmost substrate layer.
O 28.18 Mi 16:00 Bereich C
Katalytische und elektrochemische Oxidation von Ameisensäure
auf einer Pd(111)-Elektrode — •Katrin Brandt,
Marco Steinhausen, Thomas Schmidt und Klaus Wandelt —
Institut für Physikalische und Theoretische Chemie, Universität Bonn,
53115 Bonn
Mit dem Ziel kleine, organische Moleküle als ” Sonden“ auf die Oberflächenreaktivität
elektrokatalytisch aktiver, binärer Elektroden einzusetzen,
werden potentielle organische Säuren zunächst auf den Oberflächen
der einzelnen Metallkomponenten untersucht.
Dazu wurde das Reaktionsverhalten von Ameisensäure (HCOOH) bei
Kontakt mit einer Pd(111)-Elektrode im UHV mittels TDS, UPS und
IRRAS sowie in Lösung mit IRRAS untersucht.
Die spektroskopische Charakterisierung der chemisorbierten HCOOH
im UHV zeigt die Desorption des intakten Moleküls aus der Multilage
bei 160 K und in geringen Mengen aus der Monolage bei 186 K. In der
Monolage überwiegt der Zerfall zu CO2 und H2. Zahlreiche Intermediate
des katalytischen Zerfalls können anhand ihrer IR-Absorptionsfrequenzen
zwischen 1800cm −1 und 1900cm −1 nachgewiesen werden.
In situ IR-Untersuchungen in reiner HCOOH zeigen sowohl die katalytische
Freisetzung von CO2 als auch die beschleunigte elektrochemische
Oxidation (> 0.4 V vs. NHE) der Säure.
O 28.19 Mi 16:00 Bereich C
Ab-Initio-Investigation of Static and Magnetic Properties of
Fe|GaAs(001) — •Harald Dobler and Dieter Strauch — Institut
für Theoretische Physik, Universität Regensburg, 93040 Regensburg
We determine the structure and magnetic properties of the (001)surface
of GaAs covered by iron. Encouraged by our former investigations
of the system Fe|ZnSe, where we have obtained dramatic deviations from
the ideal structure as well as sensitivity of the magnetic properties to
structural changes, we consider another example for the compound semiconductor.
Again, the lattice constant of GaAs and the doubled value
of α-Fe agree very well. Nevertheless, we find significant variations of
the ideal behavior. We present our results for one, two, three, and four
monolayers of iron. Similar to the case of Fe|ZnSe the effects are most
interesting for a single monolayer. Therefore, we show the structures and
the profiles of the density of valence electrons and the magnetization in
the direction perpendicular to the interface.
The computations are carried out in the framework of spin polarized
density functional theory implemented in the program package VASP
[1,2]. Further, we use expansion in plane waves, ultrasoft pseudopotentials,
and generalized gradient corrections (GGA). The relaxations of the
structures are realized using a conjugate-gradient method.
[1] G. Kresse and J. Hafner, Phys. Rev. B 47, 558 (1993)
[2] G. Kresse and J. Furthmüller, Phys. Rev. B 54, 11169 (1996)
O 28.20 Mi 16:00 Bereich C
Si(001) surface optical properties modified by organic functionalization
and oxidation — •Andreas Hermann, Frank Groth,
Wolf G. Schmidt, Kaori Seino, Martin Preuss, Patrick H.
Hahn, and Friedhelm Bechstedt — Institut für Festkörpertheorie
und Theoretische Optik, Friedrich-Schiller-Universität, Max-Wien-Platz
1, 07743 Jena, Germany
Tremendous efforts have been devoted to investigate the optical properties
of clean Si(001) surfaces. Their reflectance anisotropy spectra (RAS)
are now well understood in terms of defects and transitions between
surface states as well as surface-modified bulk wave functions [1]. Far
less is known about the modifications of the surface optical response by
chemical reactions. Inspired by recent experiments [2] we study numerically
the influence of organic functionalization with phenanthrenequinone
and layer-by-layer oxidation on the RAS spectrum of Si(001). The calculations
are performed using the gradient-corrected density functional
theory (DFT-GGA) in conjunction with non-normconserving ultrasoft
pseudopotentials and a plane-wave basis. The optical spectra are determined
in the independent-particle approximation from all-electron wave
functions obtained by the projector-augmented wave (PAW) method.
[1] T. Yasuda et al., Phys. Rev. Lett. 74, 1995, 3431; R. Shioda, J. van
der Weide, Phys. Rev. B 57, 1998, R6823; W.G. Schmidt, F. Bechstedt,
J. Bernholc, Phys. Rev. B 2001, 63, 5322.
[2] C.A. Hacker, R.J. Hamers, J. Phys. Chem. B 107, 2003, 7689; T.
Yasuda et al., Phys. Rev. Lett. 87, 2001, 037403.
O 28.21 Mi 16:00 Bereich C
Rauheit und Schädigung einer GaAs-Oberfläche nach dem chemisch
unterstützten Ionenstrahlätzen mit Cl2/Ar + — •Jens Dienelt,
Klaus Zimmer, Justus von Sonntag und Bernd Rauschenbach
— Leibniz-Institut für Oberflächenmodifizierung (IOM), Permoserstr.
15, 04318 Leipzig
Die chemische und die physikalische Abtragskomponente während
des chemisch unterstützten Ionenstrahlätzens (CAIBE) von GaAs mit
Cl2/Ar + bewirkt sehr unterschiedliche Einflüsse auf die Rauheit und
die Schädigung des oberflächennahen Bereiches. Die Charakteristik
der Einzelprozesse spiegelt sich direkt in der Oberflächenrauheit wieder.
Der starke chemische Ätzangriff von Chlorgas auf die GaAs-
Oberfläche zeigt eine ausgeprägte Anisotropie der Ätzprofilentwicklung,
wobei die {111}-Ebenen durch deren geringe Ätzrate den Abtragsprozess
maßgeblich beeinflussen. Neben der Temperatur oder dem Chlordruck
hat demnach auch die Kristallorientierung einen großen Einfluss
auf die Oberflächenrauheit. Beim reinen Zerstäubungsprozess ergeben
sich aufgrund der Impuls- und Energieübertragung des gerichteten
Ionenbeschusses die glattesten Oberflächen. Im Gegensatz
zur geringen Oberflächenrauheit wird bei der Zerstäubung der oberflächennahe
Bereich jedoch am stärksten geschädigt. Hierzu werden orts-

Oberflächenphysik Mittwoch
aufgelöste Photolumineszenz-Untersuchungen an Mehrfach-Quantentrog-
Strukturen aus Al0,35Ga0,65As/GaAs gezeigt, die unter Anwendung der
Schrägschlifftechnik präpariert wurden.
O 28.22 Mi 16:00 Bereich C
Structural, electronic and spin properties of In nanowires
on Si(111) surface — •Xóchitl López 1,2 , Anna Krivosheeva 1 ,
Friedhelm Bechstedt 1 , Jürgen Furtmüller 1 , and Andrey
Stekolnikov 1 — 1 Institut für Festkörpertheorie und Theoretische
Optik, FSU Jena, Max-Wien-Platz 1, 07743 Jena — 2 Instituto de Física,
Universidad Autónoma de Puebla, Apartado Postal J-48, Puebla 72570,
México
In the last years the electronic and structural properties of the indiuminduced
(4×1), (4×2) and (8×2) surface reconstructions on Si(111) have
been intensively studied due to the potential applications on novel optoelectronics
devices. In this work the electronic structure calculations are
performed using density functional theory in the generalized-gradient approximation
and ultrasoft pseudopotentials. The atomic positions were
taken from a previous calculations [1], which are consistent with experimental
data. The electronic band structures with and without spin
polarization are calculated and discussed with respect to the metallic/insulating
character of the chains. Because the spin density distribution
on these systems might be important for their electronic properties,
we study the influence of the spin polarization on the atomic structure
and electronic states of the In nanowires on Si(111). Several initial spin
configurations are taken into account for all the surface reconstructions
in order to observe a magnetic ordering. We acknowledge the partial financial
support from CONACyT grants No.36651-E and 36764-E. [1] F.
Bechstedt et al., Phys Rev B 68, 1934XX (2003).
O 28.23 Mi 16:00 Bereich C
Ultrathin layers of Ag deposited on 4H-SiC(0001) — •Serguei
Soubatch and Ulrich Starke — Max-Planck-Institut für
Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart
Despite the significance of SiC for high-temperature and high-power
electronic devices based on metal/semiconductor interfaces, the initial
stages of metal layer formation on SiC surfaces still remain insufficiently
explored in comparison to well known metal/silicon heterointerfaces, such
as Ag on Si. We investigated the deposition of Ag on 4H-SiC(0001) using
quantitative low-energy electron diffraction (LEED). Ag layers of 0.2, 0.5
and 1 ML coverage were deposited on the clean (3×3) and ( √ 3× √ 3)R30 ◦
SiC(0001) surface phases. The structural development after room temperature
deposition as well as after annealing was studied. The (3×3)
phase is only marginally influenced by Ag deposition at room temperature.
Annealing leads to Ag diffusion and subsequent desorption without
a significant phase transformation. In case of the ( √ 3× √ 3)R30 ◦ phase
considerable changes can be monitored in the LEED intensities spectra
immediately after deposition. Here, structural changes are found during
annealing also, possibly caused by Ag diffusion. In both cases the original
surface phases reappear after Ag desorption.
O 28.24 Mi 16:00 Bereich C
High temperature stable silicide contacts on the nanometer
scale — •G. Gardinowski, C. Tegenkamp, T. Block, S. Vagt, V.
Zielasek, and H. Pfnür — Institut für Festkörperphysik, Universität
Hannover, Appelstrasse 2, 30167 Hannover
In order to characterize nanostructure electrically contacts are essential
to build a bridge between the macrospic and the mesoscopic world.
High temperature experiments with nanostructures on silicon substrates
are particularly interesting, but require contacts which can withstand
temperatures up to 1100 ◦ C without changes in their chemical composition
and without interdiffusion at the contact area of the silicide and
the silicon. Using electron beam lithography different silicide contacts on
both Si(111) and Si(100) surfaces have been fabricated and tested. With
regard to the specific formation temperatures for silicides, mainly Mo,
Ta and Ti have been tested. All three silicides are stable up to at least
800 ◦ C. The metallic character of the silicides was tested by masurements
of the conductivity. However, for higher temperatures the decomposition
of MoSi2 and TaSi2 sets in leaving behind rough contact areas. Only the
TiSi2 silicide remains intact, as checked by µ–Auger spectroscopy. Furthermore,
after optimization of the lithography parameters, TiSi2 contact
pads with separation lengths of 200 nm were fabricated successfully, i.e.
after removing the native oxide from the silicon surface (with pads) by
a high temperature annealing step, perfect silicon was found in between
the contacts as seen by STM/SEM. The edges of the contacts are rather
sharp and well–defined. The transition area was determined to be around
1nm.
O 28.25 Mi 16:00 Bereich C
Direct evidence from FTIR for hydrogen incorporation into
the MOCVD-grown P-rich reconstructed InP(100) surface —
•Tobias Letzig, H.J. Schimper, Thomas Hannappel, and Frank
Willig — Hahn-Meitner-Institute, Glienicker Str. 100, 14109 Berlin,
Germany
Recently, the groups of Schmidt and Bechstedt have discussed several
different surface reconstructions for InP(100). Three of those have
been assigned to actually prepared surface reconstructions. In the case
of MOCVD growth the P-rich (2x1/2x2) surface is postulated to contain
hydrogen bonds that stabilize buckled P-P dimers. A P-rich surface with
a different reconstruction is formed via MBE growth in the absence of
hydrogen. The In-rich (2x4) reconstruction also does not contain any hydrogen
atoms. We present here experimental support for the postulated
hydrogen bonds on the surface of MOCVD grown P-rich (2x1/2x2) reconstructed
InP(100) in the form of FTIR spectra that were measured
in UHV. We made use of a patented contamination free transfer of the
sample from the MOCVD reactor into a mobile UHV chamber. FTIR
spectra will be presented for the as-grown surface and for the surface
after further exposure to hydrogen and deuterium.
O 28.26 Mi 16:00 Bereich C
RMS-roughness of Si from nm to mesoscopic scale — •Stefan
Schröder, Herbert Pfnür, and Martin Henzler — Institut für
Festkörperphysik, Appelstr.2 D-30167 Hannover,Germany
The International Technology Roadmap for Semiconductors (ITRS)
defines a decrease in surface roughness and an increase of the site planarity
on a nm scale as two of the requirements for starting materials
for industrial fabrication of next generations of silicon based micro- and
nanodevices. The rms-roughness on different length scales is the principal
property examined to verify the accomplishment of the goals set. We calculate
Power Spectral Densities to examine the decay of rms-roughness
on the length scales open to STM-measurements (nm to µm) and light
scattering methods (µm to mm) on standard wafers after annealing in
a hydrogen environment. The light scattering method allows the detection
and counting of numbers of particles per area, as demanded by the
ITRS, to make sure that improved flatness is not accompanied by an increase
in defect-density. In further experiments profiles of etched steps are
monitored to determine diffusion behaviour. We gratefully acknowledge
financial support by Wacker Siltronic GmbH.
O 28.27 Mi 16:00 Bereich C
Photoelektronenbeugung an der oxidierten 4H-SiC(0001) Oberfläche
— •M. Schürmann, S. Dreiner, U. Berges, M. Krause und
C. Westphal — Universität Dortmund, Experimentelle Physik I, 44221
Dortmund
SiC ist ein Halbleitermaterial mit großer Bandlücke. Aufgrund seiner
Eigenschaften ist es hervorragend geeignet zur Herstellung von Halbleiterbauelementen,
die bei hohen Temperaturen, mit hohen Strömen
und hohen Frequenzen betrieben werden können. In diesem Zusammenhang
gewinnt auch die Kenntnis über die Struktur an der SiO2/SiC-
Grenzfläche an Bedeutung. In einer Photoelektronenbeugungsuntersuchung
wurden Beugungsmuster an einer oxidierten 4H-SiC(0001) Oberfläche
aufgenommen. Am U41-PGM Meßplatz bei BESSY II stand Synchrotonstrahlung
mit hohem Photonenfluß und guter Energieauflösung
zur Verfügung. Dadurch war es möglich die einzelnen, chemisch verschobenen
Komponenten in den XPS-Spektren aufzulösen und unterschiedliche
Beugungsmuster aufgrund der unterschiedlichen lokalen Umgebung
der Emitter zu erhalten. Ein Vergleich mit Simulationsrechnungen
gibt Aufschluß über ihren Ursprung und die atomare Struktur in der
SiO2/SiC-Grenzfläche.
O 28.28 Mi 16:00 Bereich C
Si2p-Photoemissionsspektroskopie an der SiO2/Si(100)-
Grenzfläche — •S. Dreiner, M. Schürmann, M. Krause, U.
Berges und C. Westphal — Universität Dortmund, Experimentelle
Physik I, 44221 Dortmund
Die SiO2/Si Grenzfläche spielt eine wichtige Rolle in der modernen
Halbleiterindustrie. Ein genaues Verständnis der Grenzschichtstruktur
kann zur Verbesserung der Qualität von Halbleiterbauelementen beitragen.
Die untersuchten SiO2/Si(100) Schichten mit einer Dicke von weni-

Oberflächenphysik Mittwoch
gen ˚Angström wurden durch thermische Oxidation erzeugt. Mit Synchrotronstrahlung
(BESSY II, U41 PGM) wurden hochaufgelöste Si2p-
Photoemissionsspektren über dem gesamten Halbraum bei einer Photonenenergie
von hν = 180 eV aufgenommen. Diese Spektren ermöglichen
durch Anpassungsroutinen die Trennung der Si-Oxidationszustände
(Si 1+ , Si 2+ , Si 3+ , Si 4+ ) vom Volumensignal (Si B ). Dabei zeigt sich, dass
zwei weitere Komponenten (Si α , Si β ) für eine verbesserte Anpassung
nötig sind. Um den Ursprung dieser Komponenten zu ermitteln wird die
Winkelabhängigkeit dieser Signale analysiert. Dazu werden die gemessenen
Photoelektronenbeugungsmuster mit Vielfachstreusimulationen verglichen.
O 28.29 Mi 16:00 Bereich C
Indium- und Indiumselenid-terminierte Si(111)-Oberflächen
als neuartige Pufferschichten in der Heteroepitaxie — •Stefan
Andres, Wolfram Calvet, Tilo Plake und Christian Pettenkofer
— Hahn-Meitner-Institut Berlin, Glienicker Strasse 100, 14109
Berlin
Zur Passivierung von Silizium-Substraten für die Heteroepitaxie sind
III-VI terminierte Oberflächen von grossem Interesse. Wir präsentieren
erste Ergebnisse dünner In- bzw. InSe-Schichten auf Si(111). Die
Präparation der Proben erfolgte mittels Molekularstrahlepitaxie (MBE)
auf H-Si(111)1x1-, Si(111)7x7- und definiert nasschemisch oxidierten
Si(111)-Substraten. Die Schichten wurden in situ mittels Photoelektronenspektroskopie
(PES), niederenergetischer Elektronenbeugung
(LEED) und Rastertunnelmikroskopie (STM) bezüglich ihrer Morphologie
und elektronischen Struktur analysiert. Es wurde zunächst der Einfluss
von elementarem Indium auf Si(111) untersucht. Im weiteren Prozess
erfolgte durch sukzessives Koverdampfen von In und Se die Herstellung
einer InSe-terminierten 1x1-Oberfläche. Es zeigt sich, dass InSe in
einer sogenannten Halblage aufwächst, wobei die In-Atome direkt an die
Si-Oberfläche gebunden sind. Eine Selenisierung der Si-Oberfläche findet
nicht statt. Die Energetik der Grenzfläche wird bezüglich Bandversatz
und Grenzflächendipolen bestimmt.
O 28.30 Mi 16:00 Bereich C
Electrospray Deposition of Sensitive Analytes — •Frank
Stadler 1 , Sergei Koltsov 2 , Eugenio Lunedei 1 , Giovanni
Costantini 1 , and Klaus Kern 1 — 1 Max-Planck-Institut für
Festörperforschung, D-70569 Stuttgart — 2 Institute for Analytical
Instrumentation, Russian Academy of Sciences, 19813 Saint Petersburg
Electrospray ionization is well-known as a means to solve the
volatilization and ionization problem of sensitive analytes such as large
biomolecules [1]. Recently Ouyang et al. [2] reported that electrosprayed
protein ions remain intact, after ionization, in vacuo transfer, massselection
and soft landing. We present a novel electrospray deposition
source, whose objective is the non-destructive deposition of large
sensitive (e.g. organic and biological) analytes under UHV conditions.
Aim of this project is to overcome the limitations of size and mass of the
deposited sample material that are intrinsic to the organic molecular
beam epitaxy techniques based on sublimation. Besides the explanation
of the underlying working principle of this novel experimental setup,
the relevant technological aspects will be discussed. In addition, AFM
images of electrosprayed metal colloid- and protein-containing analyte
solutions (deposited on highly oriented pyrolytic graphite) will be
presented.
[1] J. B. Fenn et al., Science, 246 (1989), 64-71
[2] Z. Ouyang et al., Science, 301 (2003), 1351-1354
O 28.31 Mi 16:00 Bereich C
VUV photon detector with improved resolution for inverse photoemission
— •R. Stiepel, R. Ostendorf, C. Benesch, H. Merz,
and H. Zacharias — Physikalisches Institut, Universität Münster, D-
48149 Münster, Germany
We have significantly improved the energy resolution of a VUV isochromat
spectrometer for inverse photoemission. The detector used is a
Geiger-Müller counter with acetone as filling gas and a CaF2 entrance
window. With this detector we achieve an optical energy resolution of
330meV (FWHM) at a mean energy of 9.9eV for the optical bandpass.
With an additional gas absorption filter arranged between two CaF2 windows
at the entrance of the counting tube we enhance the resolution to
90meV (FWHM) at a slightly decreased mean energy of 9.8eV. The
higher resolution decreases the counting rate to approximately 20%, but
by filling or evacuating the gas chamber we can switch between the two
modes high resolution and high counting rate within seconds.
O 28.32 Mi 16:00 Bereich C
Konventionelle und positroneninduzierte Auger-Elektronenspektroskopie
am System Kupfer-Gold — •Benno Straßer,
Christoph Hugenschmidt und Klaus Schreckenbach —
Technische Universität München, Lichtenbergstraße 1, D-85748
Garching
Bei positroneninduzierter Auger-Elektronenspektroskopie (PAES) erfolgt
die Anregung der untersuchten Probe durch Annihilation von niederenergetischen
Positronen mit Rumpfelektronen des Probenmaterials.
Die Energie der eingestrahlten Positronen kann dabei so klein gewählt
werden, dass sie keinen Sekundärelektronen-Untergrund im Energiebereich
der Auger-Peaks erzeugen. PAES besitzt deshalb ein wesentlich
besseres Signal-zu-Untergrund-Verhältnis als konventionelle AES und
verfügt außerdem über eine höhere Oberflächensensitivität.
Die an der Technischen Universität München bestehende PAES-
Apparatur wurde mit einer Effusionszelle und einem Elektronenstrahlverdampfer
zur Probenbeschichtung im Sub-Monolayer-Bereich erweitert.
Daneben wurden eine Argonkanone zur in situ Probenreinigung,
eine Probenheizung sowie einen Probenschleuse installiert. Die Beschichtungsanlage
wurde an mit Gold bedampften, polykristallinen Kupferproben
getestet und Vergleichsmessungen zur Oberflächensensitivität von
elektronen- und positroneninduzierter AES durchgeführt.
O 28.33 Mi 16:00 Bereich C
Focussing XUV photons with high contrast — •J. Buck 1 , M.
Kalläne 1 , S. Harm 1 , M. Skibowski 1 , R. L. Johnson 2 , and L. Kipp 1
— 1 Institut für Experimentelle und Angewandte Physik, Universität Kiel,
D-24098 Kiel, Germany — 2 Institut für Experimentalphysik, Universität
Hamburg, D-22761 Hamburg, Germany
Photon sieves consisting of a large number of pinholes appropriately
distributed over the Fresnel zones focus electromagnetic radiation [1]. As
part of the program to develop photon sieves for VUV FEL radiation [2]
we present first experimental results on the focussing properties of reflective
photon sieves, which allow to enhance the image contrast efficiently.
The experiments have been performed with visible light (hν = 1.96 eV)
and XUV radiation (hν = 100 eV) supplied from the BW3 beamline at
HASYLAB.
[1] L. Kipp, M. Skibowski, R.L. Johnson, R. Berndt, R. Adelung, S. Harm
and R. Seemann, Nature 414, 184 (2001)
[2] A free-elecron laser (FEL) delivering transversal coherent radiation in
the vacuum ultraviolet regime with photon energies up to several 100 eV
is currently under construction at the Hamburg Synchrotron Radiation
Laboratory HASYLAB/DESY.
Work supported by the BMBF proj. 05 KS1 FK1
O 28.34 Mi 16:00 Bereich C
TOF-PEEM für zeitaufgelöste Mikrospektroskopie von Oberflächen
basierend auf einer fs-Laser EUV-Lichtquelle — •G. H.
Fecher 1,2 , A. Oelsner 1 , G. Schönhense 1 , J. Kutzner 2 , G. Tsimilis
2 und H. Zacharias 2 — 1 Johannes Gutenberg - Universität, 55099
Mainz — 2 Westfälische Wilhelms - Universität, 48149 Münster
Die Kombination eines Photoemissions Elektronen Mikroskops
(PEEM) mit einer Femtosekunden Laser gepumpten EUV Lichtquelle
wird präsentiert. Das PEEM ist für simultane Bildaufnahme und Flugzeitanalyse
(TOF) mit einem 3D (x, y, t) Detektor ausgestattet. Dies
erlaubt neuartige Anwendungen in der Mikrospektroskopie von Oberflächen.
Die Lichtpulse im extremen ultraviolett Bereich werden in Edelgasen
durch ein 30fs Ti:Saphir Lasersystem generiert. Intensive IR Pulse erzeugen
im Konversionsgas hohe Harmonische bis 120eV. Ein Toroidgitter
wird zur Auswahl der Harmonischen eingesetzt. Al-Filter und Au-Spiegel
beschränkten den Energiebereich auf 15-72eV. Die herkömmliche Bildeinheit
de PEEM wurde durch einen 3D-Delayline Detektor ersetzt. Dieser
registriert die Elektronen in 2 räumlichen und einer zeitlichen Koordinate.
Die rückwärtige Mikroskopsäule wird als Flugzeitstrecke betrieben.
Die Zeitauflösung des Detektors beträgt 125ps. Erste Ergebisse zeigen,
daß der Bildkontrast empfindlich von der ausgewählten Energie der Elektronen
abhängt. Die derzeitige Begrenzung der räumlichen (160nm) und
zeitlichen Auflösung der Methode ist durch die Repetitionsrate (1kHz)
des anregenden Lasers bedingt.
O 28.35 Mi 16:00 Bereich C
Growth of Platin Nanowire Networks on Nafion — •M. Elbahri,
J. Franc, O.C. Aktas, R. Adelung, and F. Faupel —
Lehrstuhl für Materialverbunde, Technische Fakultät der CAU Kiel

Oberflächenphysik Mittwoch
The Nafion polymer, produced by the Dupont company, is still the
most prominent membrane material for the commercial polymer electrolyte
fuel cell (PMFC). Usually, the Nafion membrane is sandwiched
by two catalytic layers, consisting of a metal-Nafion-carbon mixture in
order to provide catalytic activity as well as electrical and proton conductivity.
It turns out that most of the Platinum doesn’t contribute to
the catalytic efficiency, which increases the total cost for the PMFCfuel
cell. An alternative approach might be a catalytic layer formed by
a Pt-nanowire network. We present here a strategy to deposit Pt in the
form of a nanowire networks. Therefore we used sputter deposited Pt on
a vacuum deposited amorphous carbon mask layer. We show different
Pt-nanowire networks generated on the Nafion surface and discuss the
mechanisms that tune the network parameters like nanowire dimensions
and mesh width.
The authors thank the Technologiestiftung Schleswig-Holstein for supporting
the project.
O 28.36 Mi 16:00 Bereich C
Imaging of optical near fields of nanostructures with fs laser
pulses — •Juliane Birk, Johannes Boneberg, and Paul Leiderer
— Universität Konstanz, FB Physik, LS Leiderer, SFB 513, 78457
Konstanz
The optical properties of nanostructures are a topic of interesting investigations.
In analogy to the near fields around a Hertz dipole we expect
near fields in the surrounding of all nanostructures. Up to now they were
analysed with the scanning near field optical microscope (SNOM). We
want to introduce an alternative method to image near fields with intensive
short laser pulses. The intensity is adjusted to values where the
substrate far from the particle is not affected. Nevertheless, the surface
around and below the particle can be ablated, due to the local intensity
enhancement in the optical near field. After the laser pulse the modified
surface is imaged with atomic force microscopy (AFM) and thus
the optical near fields of different nanostructures on several substrates,
for example silicon, can be studied. A few examples of the near fields of
various nanostructures are shown.
O 28.37 Mi 16:00 Bereich C
Infrared-optical properties of Cu nanoparticles on CaF2(111)
— •Birgit Gehring, Andreas Priebe, and Annemarie Pucci —
Kirchhoff-Institut für Physik, Im Neuenheimer Feld 227, D - 69120 Heidelberg
Using IR spectroscopy the growth of Cu nanoparticles on UHV-cleaved
CaF2(111) was investigated in situ. Relative transmission spectra informed
about the dynamic conductivity of the nanoparticle film and
about the influence of the substrate temperature on the percolation
threshold.
In the range from about 1000 cm −1 up to about 2500 cm −1 a relative
transmission > 100 % was observed for Cu coverage below percolation,
which corresponds to an anti-reflection effect. The magnitude of this effect
depends on the growth temperature.
For certain average Cu thicknesses we exposed CO at a sample temperature
of about 100 K. The CO adsorption on different Cu facets was
studied by IR transmission spectroscopy. The morphology of the nanoparticle
layer was verified with atomic force microscopy (AFM) ex situ. From
the AFM pictures the particle density was estimated and the filling factor
could be evaluated.
O 28.38 Mi 16:00 Bereich C
Steering host-guest interactions at surfaces using tailormade
two-dimensional nanoporous coordination systems —
•Sebastian Stepanow 1 , Magalí Lingenfelder 1 , Alexandre
Dmitriev 1 , Hannes Spillmann 1 , Erik Delvigne 2 , Nian Lin 1 ,
Xiaobin Deng 3 , Chengzhi Cai 3 , Johannes V. Barth 2 , and
Klaus Kern 1,2 — 1 Max-Planck-Institut für Festkörperforschung,
Heisenbergstraße 1, D-70569 Stuttgart — 2 Institut de Physique des
Nanostructures, Ecole Polytechnique Fédérale de Lausanne, CH-1015
Lausanne, Switzerland — 3 Department of Chemistry and Center for
Materials Chemistry, University of Houston, Houston, TX 77204-5003,
USA
The so-called rational design principle, i.e., synthesis of materials with
predictable structures and properties from appropriate organic molecular
linkers connecting to metal nodes, has recently been explored to control
pore size and functionality of open three-dimensional networks. Here we
demonstrate the fabrication of surface-supported metal-organic coordination
networks (MOCNs) comprising tailored pore sizes and chemical
functionality by the modular assembly of polytopic organic carboxylate
linker molecules and iron atoms on a Cu(100) surface under ultra-high
vacuum conditions. The nanocavity arrays provided can be employed to
host C60 guest molecules. Temperature-controlled studies reveal at the
single-molecule level how pore size and chemical functionality determine
the host-guest interactions.
O 28.39 Mi 16:00 Bereich C
Dynamic Mode Force Microscopy Studies of Individual Single
Wall Nanotubes on HOPG — •Timo Behnke 1 , Makoto
Ashino 1 , Alexander Schwarz 1 , Roland Wiesendanger 1 , Keith
A. Williams 2 , and Cees Dekker 2 — 1 Institute of Applied Physics,
University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
— 2 Department of Applied Physics and DIMES, Delft University of Technology,
Lorentzweg 1, 2628 CJ Delft, The Netherlands
The growing interest in single wall carbon nanotubes (SWNT) is related
to their prospected applications of their unique possibilities in upcoming
nanotechnology (1). To study structural properties of SWNTs
down to the atomic scale dynamic mode force microscopy is well suited.
In a first step, we developed a technique to prepare SWNTs on HOPG.
Tapping Mode Imaging in ambient conditions showed a homogeneous
SWNT distribution on atomically flat and well defined graphite (HOPG)
with only negligible small amounts of contamination. Although most of
SWNTs appeared as bundles or ropes, we found a sufficient density of
individual SWNTs. In a second step, we took advantage of the increased
resolution of dynamic mode force microscopy and spectroscopy in ultrahigh
vacuum and used a home-built low noise and very stable lowtemperature
force microscope to resolve the atomic structure of individual
tubes.
[1] Baughman, Zakhidov, de Heer, Science 296, 787 (2002)
O 28.40 Mi 16:00 Bereich C
Dynamik von selbstorganisierten Nanopartikeln auf Oberflächen
— •Anton plech 1 , Vassilios Kotaidis 1 , Samuel
Gr’esillion 2 und Gero von Plessen 3 — 1 Fachbereich Physik der
Universität Konstanz, Universitätsstr. 10, 78457 Konstanz — 2 ESPCI
10, rue Vauquelin, F-75005 Paris — 3 RWTH Aachen, I. Physikalisches
Institut A, D-52074 Aachen
Naßchemisch hergestellte Nanopartikel können über Selbstaggregationsverfahren
auf Oberflächen abgelagert werden. Es werden so definiert
Submonolagenbedeckungen erreicht. Diese Systeme erlauben das Studium
der strukturellen Eigenschaften von quasifreien Partikeln, wie thermische
Expansion oder strukturelle Dynamik.
Es werden die strukturellen Relaxationen der Partikel auf die ultraschnelle
Laseranregung der Plasmonenresonanz untersucht. Als Sonde
dient ultraschnelle zeitaufgelöste Röntgenbeugung (Meßplatz ID09,
ESRF, Frankreich). Neben der thermischen Anregung und Kühlung des
Kristallgitters werden auch Nichtgleichgewichtsprozesse beobachtet und
im Rahmen von Partikeleigenschwingungen gedeutet.
O 28.41 Mi 16:00 Bereich C
Gold Nanoteilchen auf Al2O3/Nb(110): Eine STM Studie dynamischer
Umladungeffekte bei Raumtemperatur — •Christof
Dietrich, Berndt Koslowski und Paul Ziemann — Abt.
Festkörperphysik, Universität Ulm
Um ein System zu präparieren, das Coulomb-Blockade bei Raumtemperatur
zeigt, wurden epitaktische Niob(110)-Filme auf Saphir(0001)
durch dc-magnetron-Sputtern bei einer Substrattemperatur von 1200K
hergestellt. Diese Metallschichten haben eine extrem glatte Oberfläche
(RMS:2nm auf 500nm 2 ) und mit dem STM konnte atomare Auflösung
erzielt werden. Auf diese Schichten wurde eine 1nm dicke Aluminiumschicht
aufgedampft und anschließend in einem Sauerstoffplasma oder in
Sauerstoffatmosphäre oxidiert. Bei geeigneter Prozessführung kann auch
ein epitaktisches Oxid hergestellt werden. Auf diese Tunnelbarriere wurden
Gold Nanoteilchen mit Größen von 1nm-15nm mittels einer mizellaren
Technik aufgebracht.
I-V-Spektroskopien auf den Teilchen zeigen eine klare Coulomb-
Blockade, die sich sehr gut mit Hilfe der “orthodoxen“Theorie der
Coulomb-Blockade anpassen lassen. Durch Präparation verschiedener
Teilchengrößen konnten die Parameter der Coulomb-Blockade
größenabhängig bestimmt werden. Um die laterale Variation der Parameter
der Coulomb-Blockade auf den Teilchen zu bestimmen, wurden
zusätzlich I-V-Karten angefertigt. Demnach sind die Parameter stark von
der Position auf dem Teichen abhängig.

Oberflächenphysik Mittwoch
O 28.42 Mi 16:00 Bereich C
Kombination mizellarer und lithographischer Techniken – ein
unkonventioneller Strukturierungsansatz — •Oliver Dubbers 1 ,
S. Fricker 1 , A. Klimmer 1 , H.-G. Boyen 1 , A. Plettl 1 , P. Ziemann
1 , M. Ott 2 und M. Möller 2 — 1 Abt. Festkörperphysik, Universität
Ulm, D-89069 Ulm — 2 Abt. Organische Chemie 3, Universität Ulm,
D-89069 Ulm
Inverse P2VP-PS-Mizellen in Lösung können mit verschiedenen Metallsalzen
beladen werden. Selbstorganisationsprozesse führen bei Abscheidung
auf glatten Oberflächen zu einer hexagonalen Anordnung.
Nach Entfernung des Polymers in einem H2- oder O2-Plasma erhält
man schließlich Nanoteilchen, deren Größe und Abstand durch die Polymerkettenlängen
bestimmt werden. Die Teilchen lassen sich auch noch
nachträglich in einer HAuCl4/NH2OH-Lösung elektrodenfrei weiter vergrößern.
Dieser mizellare Ansatz läßt sich mit lithographischen Methoden
kombinieren. In lithographisch definierte Fenster von Lack- oder Metallmasken
lassen sich Mizellen einfüllen und anschließend veraschen. Beim
Lift-off der Maske werden die darauf liegenden Teilchen mit entfernt, so
dass sich nur noch die Teilchen auf der Oberfläche befinden, die direkt
auf dem Substrat aufgebracht wurden. Derart deponierte Nanoteilchen
lassen sich beim anisotropen Plasmaätzen als Maske verwenden, um zum
Beispiel Nanosäulen in Silizium und Titan herzustellen.
O 28.43 Mi 16:00 Bereich C
Nanostructures as a result of the thermal instability of metal
thin films on insulators — •Torsten Kolb, Dominik Enders,
Annemarie Pucci, and Gerhard Fahsold — Kirchhoff-Institut für
Physik, Universität Heidelberg, Im Neuenheimer Feld 227, D-69120 Heidelberg
We investigate the possibility of structuring metal thin films on a
nanoscale by exploiting their thermal instability. Various metal thin films
(Cu, Au, Fe) were deposited on different substrates (MgO, SiO2) and
subsequent annealing processes were applied for fractioning these films.
For in-situ and online analysis of this fractioning we use infrared spectroscopy,
which we perform during annealing in UHV. Measuring IR
transmission enables investigation of both dynamics and energetics (critical
temperatures) of the processes caused by the thermal instability of
metal thin films. Their morphological properties were characterized exsitu
by atomic force microscopy (AFM). The dependence of the resulting
morphology on annealing temperature and crystalline structure will be
demonstrated.
O 28.44 Mi 16:00 Bereich C
Metal-on-insulator nanostructures via surface color centers —
•Svend Vagt, Tammo Block, Volkmar Zielasek, and Herbert
Pfnür — Institut für Festkörperphysik, Universität Hannover, Appelstr.
2, 30167 Hannover
We present first experimental results obtained in a pursuit of a new
type of electron beam nanolithography in UHV that is based on the generation
of surface color center patterns on epitaxial insulator films and
the selective nucleation of metal islands. Experiments were performed in
a combined system of an SEM (1-25 keV, resol. 4 nm) and a confocal
variable temperature STM (80-900 K). Epitaxial NaCl layers on Ge(100)
(up to 6 ML thick) were irradiated by the electron beam of the SEM
under varying doses. EELS and scanning Auger microscopy showed the
generation of color centers and Na clusters and colloids associated with
electron-induced desorption of Cl in the irradiated areas. The NaCl films
turned out to be extremely sensitive to a 3 keV electron beam and due
to high surface mobility of Na metal clusters formed easily. After high
e-beam exposure STM at 2 monolayer thick NaCl layers revealed the
formation of beam-induced line-shaped gaps in the film down to the substrate.
Depending on the electron dose, a width down to 35 nm was observed,
probably limited by secondary electrons. Deposition of Ag on the
surface leads to metal aggregation in the center of the gaps, presently being
investigated by STM and SEM. The underlying physical mechanisms
as well as the potential use of this type of nanostructuring technique and
possible refinements will be discussed.
O 28.45 Mi 16:00 Bereich C
Pb on Si(557) - Steps towards a one-dimensional conductivity
— •Ziad Kallassy, Martin Henzler, Heinz-Lorenz Günter, and
Herbert Pfnür — Institut für Festkörperphysik,Applestrasse 2,30167
Hannover
The conductivity of ultrathin Pb films evaporated onto a highly
stepped Si(557) surface was investigated by modified macroscopic 4-point
measurements in UHV. After annealing 4 to 10 ML of Pb, evaporated
at a sample temperature of 80K, to temperatures of 990K we obtained a
strongly anisotropic conductivity at temperatures below 100K, with up
to a factor of 20 higher conductance in the direction parallel to the step
edges compared with the direction normal to them. While conductivity
in this direction was found to be thermally activated and close to the
conductivity of 1 ML of Pb on Si(111), it strongly decreases with increasing
temperature in directions parallel to steps. The measurements
will be correlated with LEED and STM results.
O 28.46 Mi 16:00 Bereich C
Dependency of the scattering of light by small planar particles
on the direction of incidence and polarization — •Manuel
Gonçalves and Othmar Marti — Department of Experimental
Physics, University of Ulm, D-89069 Ulm, Germany
The scattering of light by small particles has been intensively researched
in the last decades. The well known dependencies of the scattering
of light on the size, shape, material and environment of the particles
reveals the complexity of the problem. Several publications have
shown numerical simulations and experimental results demonstrating resonances
and local field-enhancements on sub-wavelength particles.
Particles of size comparable to the wavelength and of sub-wavelength
size, of planar geometry i.e. where the thickness is much smaller than
their linear dimensions, are of great interest in photonics.
We have investigated planar particles of different shapes by confocal
and SNOM microscopy. These particles show interesting dependencies
on the direction of the incidence of light, on polarization and on the
dielectric constant of the material.
We have observed important differences in the scattering patterns for
each material, and each relative orientation of the particles with the direction
of incidence of the light.
O 28.47 Mi 16:00 Bereich C
Self-imaging observed on colloid crystals and Fischer projection
patterns — •Manuel Gonçalves and Othmar Marti — Department
of Experimental Physics, University of Ulm, D-89069 Ulm, Germany
The self-imaging phenomenon in optical systems is known since the
Talbot effect was discovered in the 19th century. The Talbot effect is
generated by the interference of the incoming light from a diffraction array
of apertures of size a that takes place near the array (Fresnel zone).
In general, a ≫ λ.
Apertures separated by a distance d, when illuminated by a coherent
and plane wave of wavelength λ produce self-images at distances
dT = ν 2d 2 /λ, for ν = 1, 2, . . . [1],[2].
We have observed that arrays of colloidal crystals of polystyrene
spheres with diameter of few µm produce self-images, at distances of
several tenths of µm. The theoretical Talbot length is compared with the
measured distances for self-images, for different illumination modes of
coherent light.
A discussion of the multiple scattering and diffraction of light by a
regular array of colloidal particles is introduced and analyzed.
[1] K. Patorski, in Prog. Opt. XXVII, Elsevier, 1989.
[2] A. Lohmann and J. A. Thomas, Appl. Opt., 29 29, 4337–4340.
O 28.48 Mi 16:00 Bereich C
Plasma CVD-grown carbon nanotubes studied by field emission
— •Daniell Malsch 1 , Martin Sveningsson 2 , Eleanor Campbell
2 , and Juergen A. Schaefer 1 — 1 Institut für Physik und Zentrum
für Mikro- und Nanotechnologien, TU Ilmenau, P.O. Box 100565,
98684 Ilmenau, Germany — 2 Department of Experimental Physics,
Gothenburg University and Chalmers University of Technology, 41296
Gothenburg, Sweden
Films of carbon nanotubes show an excellent field emission behaviour
that allows a wide range of application in field emitting devices. The
influence of the different emission parameters has to be investigated in
order to improve their performance. We study the field emission of vertically
aligned PCVD-grown multiwall carbon nanotubes. A systematic
influence of the tube length on the emission current, the light emission,
and the surface temperature of the film is found. We also examine blackbody
radiation from resistive heating during field emission. This leads,
in agreement with light emission behaviour and long-time stability measurements,
to a stepwise degradation of the carbon nanotube films.

Oberflächenphysik Mittwoch
O 28.49 Mi 16:00 Bereich C
Generation of metal nanodroplets and experiments on their velocity
and landing — •Anja Habenicht, Michael Olapinski, Johannes
Boneberg, and Paul Leiderer — Universität Konstanz, FB
Physik SFB 513, 78457 Konstanz
An interesting observation can be made when gold nanostructures
placed on a substrate are illuminated with an intensive short laser pulse:
Just above the melting threshold all particles leave the surface. The reason
for this effect is the wetting behaviour: Gold does not wet the glass
substrate, thus the liquid nanostructures can reduce their surface energy
by reforming to spheres. If this transformation is sufficiently fast the
liquid spheres take off from the surface. The velocity of the flying nanodroplets
can be determined by analyzing the time dependent scattering
signal which arises when the droplets cross a sheet of light. This signal
can be converted into a velocity dependent particle density. The particles
cool down during the flight due to thermal radiation. By catching the
nanodroplets on a further substrate at different distances, the droplets
can be landed either in liquid or in solid state. First results of velocity
measurements and the impact experiments are shown.
O 28.50 Mi 16:00 Bereich C
Nanostructuring using colloid crystals and dry and wet etching
techniques — •Manuel Gonçalves 1 , Moritz Trautvetter 2 ,
Oliver Dubbers 2 , Sebastian Fricker 2 , Alfred Plettl 2 , Paul
Ziemann 2 , and Othmar Marti 1 — 1 Department of Experimental
Physics, University of Ulm, D-89069 Ulm, Germany — 2 Department of
Solid State Physics, University of Ulm, D-89069 Ulm, Germany
Sub-wavelength structures produced using latex colloidal crystals have
been intensively investigated in the last years, namely to produce photonic
crystals. One of most known techniques to produce nanoparticles
using monolayers of latex spheres as lithographic masks, has been developed
by U. Ch. Fischer et al. in 1981 (Fischer projection patterns or
FPP). This method, however, is restricted to few possible particle shapes.
We have developed two techniques to extend the number the possible
shapes and geometrical configurations, using colloidal crystals and FPPs
combined with dry and wet etching techniques.
Inverse projection pattens have been produced using the common FPPs
combined with wet chemical etching.
We have also developed a technique to produce sub-wavelength structures
using monolayers of latex spheres etched by a plasma. The size and
the separation of the particles can be controlled by the etching level and
by selecting the size of the latex spheres.
Several nanostructures using these techniques have been produced and
characterized by scanning probe microscopy and scanning electron microscopy.
The optical properties of some samples produced using metallic
thin films are also presented.
O 28.51 Mi 16:00 Bereich C
Application of imaging XPS for chemical analysis and mapping
of magnetic domains — •S. Schmidt 1 , M. Escher 2 , F. Forster 1 ,
D. Funnemann 3 , B. Krömker 3 , M. Merkel 2 , F. Reinert 1 , and N.
Weber 2 — 1 Universität des Saarlandes, FR 7.2 Experimentalphysik,
Postfach 151150, 66041 Saarbrücken — 2 Focus GmbH — 3 Omicron Nanotechnology
GmbH
We present first scientific applications of a new NanoESCA [1] spectrometer:
we have used the good spatial resolution to investigate the
chemical structure of plain and decorated grain boundaries in two reference
materials Al0.98Sn0.02 and Cu0.98Bi0.02 [2]. The data measured at the
high-intensity small-spot beamlines of BESSY II also exhibit detailed information
about the oxidation processes in such materials. In Al0.98Sn0.02
we have detected small differences in the binding energy of the Al 2p XPS
peak of 30–50 meV that could be related to different grain orientations.
We also present data taken on the nanowire prototype system Cu/ZnSe2
[3] where the Cu-nanowires are effectively protected against oxidation
even during air-exposure. Using cicular polarization at the undulator we
were able to map magnetic domains [4] in a Fe single crystal at the Fe
2p XPS core-level with high contrast.
[1] D. Funnemann et al., Bessy Annual Report, 2002
[2] S. Schmidt et al., Bessy Annual Report, 2002
[3] R. Adelung et. al, Adv. Mater. 14, 15, p. 1056-1061, 2002
[4] C. Schneider et al., Rep. Prog. Phys, 65, R1785-R1839, 2002
O 28.52 Mi 16:00 Bereich C
Lead on hydrogen terminated Si(111): A comparison of two
different deposition techniques — •C. Rettig 1,2 , H. Hövel 1 , V.
Chamard 1 , S. Warren 2 , T. H. Metzger 2 , and J. Zegenhagen 2
— 1 Universität Dortmund, Experimentelle Physik I, D-44221 Dortmund
(Germany) — 2 European Synchrotron Radiation Facility (ESRF), B.P.
220, F-38043 Grenoble (France)
We studied the epitaxy of electrochemically deposited Pb clusters on
Si(111):H dependent on the applied overpotential. The former measurements
[1] and the present investigations are carried out in-situ using
Cyclic Voltammograms and Surface X-ray Diffraction (SXRD). The specular
measurements show a predominant alignment of the Pb(111) plane
parallel to the Si(111) plane. In the sample plane the Pb Clusters are
aligned along the high symmetry direction of Si confirmed by Grazing
Incidence Diffraction (GID). New results indicate a dependency of the
Pb clusters alignment in the sample plane on the applied overpotential.
Presently we extend our measurements to Ultra High Vacuum (UHV)
environment with in-situ deposition of Pb on Si(111):H. This system is
studied by Scanning Tunneling Microscopy/Spectroscopy (STM/STS),
Low Energy Electron Diffraction (LEED) and Ultraviolet Photoelectron
Spectroscopy (UPS).
[1] J. C. Ziegler et al., Surf. Sci. 452, 150 (2000).
O 28.53 Mi 16:00 Bereich C
Lifetime of particle plasmon excitation in Ag-Nanoparticles —
•Daniela Bayer, Alexander Mönnich, Jörg Lange, Michael
Bauer, and Martin Aeschlimann — Dep. of Physics, University of
Kaiserslautern
The dynamics of photoexcited hot electrons are of special interest for
a large variety of modern fields such as fs-photochemistry and (magneto)electronics.
These specific applications depend critically on the inelastic
lifetime T1 of these hot electrons. Hence, the question arises if
it would be possible to manipulate T1 in a specific way. In this poster,
we will demonstrate that the specific structuring of the material on a
nanometer scale can govern the effective electron dynamics. Our interest
is focused on localized collective oszillations of the electron gas in metal
particles of nanometer size, the so-called particle plasmons. A. Liebsch
predicts that under certain conditions the plasmon dephasing time at
off-resonance excitation can be longer than on resonance due to the
wavelength dependence of radiation damping. Making use of the Time-
Resolved Two-Photon-Photoemission (TR-2PPE), our investigation concentrates
on elliptically shaped silver nano-particles under resonant and
off-resonant conditions. Experimental results confirming Liebschs theory
will be shown.
O 28.54 Mi 16:00 Bereich C
Surface Plasmon Propagation In Metallic Nanostructures —
•Phillip Olk 1 , Jan Seidel 1 , Stefan Grafström 1 , Eng Lukas 1 ,
Fadi Baida 2 , Daniel Van Labeke 2 , Marcell Ott 3 , and Lothar
Bischoff 4 — 1 Institut für Angewandte Photophysik, TU Dresden,
01062 Dresden — 2 Laboratoire d’Optique P.M. Duffieux, CentreNational
de La Recherche Scientifique, Unité Mixte deRecherche 6603, Université
de Franche–Comté, F-25030Besançon Cedex, France — 3 Organic Chemistry
III / Macromolecular Chemistry, Universität Ulm, 89081 Ulm —
4 Research Center Rossendorf, Institute of Ion BeamPhysics and Materials
Research, 01314 Dresden
Propagation of surface plasmons in metallic nanostructures and their
interaction with defined surface features are presented. We use near-field
optical methods in order to reveal various properties of such travelling
surface waves, like optical transmission across barriers or coupling to
free space electromagnetic waves. These characteristics are directly determined
using an attenuated-total-reflection (ATR) excitation scheme
together with dielectric fiber probes for near-field optical detection. We
show results on plasmon propagation in self-assembled cluster films, discussing
propagation lengths and resonance conditions. Furthermore, we
present an experimental and theoretical analysis of plasmon mode coupling
in continuous metallic films mediated by a single groove structure
produced by focused ion beam (FIB) writing.

Oberflächenphysik Mittwoch
O 28.55 Mi 16:00 Bereich C
Optical anisotropy of Cs nanostructure formation on
GaAs(110), InP(110) and InAs(110) — •Karsten Fleischer
1,2 , Gianlorenzo Bussetti 2 , Claudio Goletti 2 , Pierro
Chiaradia 2 , and Wolfgang Richter 1,2 — 1 TU-Berlin, Institut
für Festkörperphysik, Hardenbergstr. 36, 10623 Berlin, Germany
— 2 Universitá “Tor Vergata”, Dipartimento di Fisica, Via Ricerca
Scientifica 1, 00133 Roma, Italy
We present reflectance anisotropy spectra (RAS) of Cs covered GaAs,
InP and InAs cleaved (110) surfaces. In such systems Cs forms one dimensional
wirelike structures at low coverages. For the first time we studied
the formation of these wires in situ with optical and therefore nondestructive
techniques. Wire formation is accompanied with characteristic
minima in the RAS spectra between the E0 + ∆0 and E1 bulk critical
point. With growing coverages (θ > 0.3ML) and formation of the two
dimensional closed Cs layer (θ ≈ 0.5ML), changes in the Cs related minima
occur. Different wire types and also the transition into the disordered
Cs double layers at saturation coverage (θ ≈ 1ML) can be monitored
optically.
O 28.56 Mi 16:00 Bereich C
Methanol oxidation on clean and oxygen-covered copper surfaces
— •Sung Sakong and Axel Groß — Physik-Department T30,
Technische Universität München, 85747 Garching, Germany
We have studied methanol oxidation steps over clean and oxygencovered
copper surfaces by density functional theory (DFT) calculations.
The reaction pathways are determined by the nudged elastic band (NEB)
method [1] which in particularly also yields the intermediate states and
the reaction barriers. We find that on clean copper surfaces, methanol
is only weakly bound. The decomposition into methoxy and hydrogen
is activated. Upon heating, methanol rather desorbs than dissociates.
The further decomposition of adsorbed methoxy into formaldehyde and
hydrogen is hindered by large barriers (≥ 1.5eV).
The surface intermediate states in the methanol oxidation are significantly
stabilised by co-adsorbed oxygen. The DFT calculations show that
on oxygen-covered Cu(110), methanol dissociates spontaneously because
of the strong attraction between the methanol hydroxyl hydrogen and
the surface oxygen. The reaction steps are analysed in terms of the underlying
electronic structure. Our calculations confirm the importance of
co-exposed oxygen in the methanol oxidation on copper surfaces found
in experiments (see, e.g., [2]).
[1] G. Henkelman and H. Jónsson, J. Chem. Phys. 113, 9978 (2000).
[2] Ch. Ammon et al., Surf. Sci. 507, 845 (2002).
O 28.57 Mi 16:00 Bereich C
Electron Solvation during the Interaction of Na Atoms with
Polar Molecules — •A. Borodin 1 , O. Höfft 1 , U. Kahnert 1 ,
V. Kempter 1 , Y. Ferro 2 , and A. Allouche 2 — 1 Institut für
Physik und Physikalische Technologien, TU Clausthal, Leibnizstr. 4,
D–38678 Clausthal–Zellerfeld — 2 Physique des Interactions Ioniques et
Moléculaires, CNRS–UMR6633 Campus Universitaire de Saint Jérôme,
Marseille France
The interaction of Na atoms with molecular films (H2O; CH3OH; NH3)
was studied with metastable impact electron spectroscopy (MIES) under
UHV conditions. The films were grown at 90K, and exposed to Na.
The spectral feature from 3sNa ionization occurs at an energetic position
different from that found for metals or semiconductors. The results
are compared with DFT calculations. Experiment and theory agree in
the energetic positions of the main spectral features from the molecular
and sodium ionization. The calculations suggest that the 3sNa emission
observed experimentally originates from solvated 3s electrons which are
located far from the Na–core and become stabilized by solvent molecules.
The simultaneous emergence of emission from OH (or CH3O) and from
solvated 3s electrons suggests that the delocalization and, consequently,
the solvation play an important role in the Na–induced formation of
CH3O and OH species from methanol and water, respectively.
O 28.58 Mi 16:00 Bereich C
Spectral evidence for oxide free incorporation of oxygen into
Ru(0001) — •Raoul Blume 1 , Artur Böttcher 2 , Horst Conrad
3 , and Horst Niehus 1 — 1 Institut für Physik, HU-Berlin, Newtonstr.
15, 12489 Berlin — 2 Institut für Physikalische Chemie, Universität
Karlsruhe, Kaiserstr. 12, 76131 Karlsruhe — 3 Fritz-Haber-Institut der
Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin
The capability of a smooth and defected Ru(0001) surface towards the
oxygen accumulation has been studied by the means of thermal desorption
spectroscopy (TDS) and the high resolution scanning XPS (Elettra,
Trieste). By applying a soft Ar + -sputtering procedure individual surface
defects confined to the two outermost Ru layers were created. The oxidation
procedure applied here assures an incorporation of oxygen atoms
in the subsurface region up to 4 monolayer equivalents (MLE) without
any traces of RuO2-domains (high-pressure and low-temperature surface
oxidation). By measuring the temperature and exposure dependence of
the oxygen incorporation and analyzing the corresponding evolution of
the Ru 3d5/2 band we found characteristic electronic signatures allowing
to distinguish oxygen atoms occupying the Ru(I)-Ru(II) interlayer space
and oxygen species associated with surface defects. This assignment is
supported by mesoscopic-scale surface images as well as the quantitative
O2-TD analysis.
O 28.59 Mi 16:00 Bereich C
Investigation of Au electrodeposition processes on metal single
crystal surfaces — •Ahmed Ayyad, Jochim Stettner, and Olaf
Magnussen — Institut für Experimentelle und Angewandte Physik,
Christian-Albrechts-Universität Kiel, Leibnizstraße 19, 24098 Kiel
Metal electrodeposition processes have been a subject of substantial
basic research during the last years, motivated by current technologies
as well as future applications, such as the electrochemical formation of
ultrathin layers and nanostructures. A major, largely unsettled question
is how the electrode surface structure and adsorbates, such as anions or
organic additives, influence the growth process. We studied the homoepitaxial
electrodeposition of Au on Au(111) electrode surfaces (deposition
rates 0.05 to 0.23 ML/min.) by in-situ x-ray diffraction under real time
conditions using a hanging-meniscus transmission cell (reduced cell resistance,
unrestricted mass transport), where the Au(111) electrode surface
is completely covered by an electrolyte droplet. Parallel to the X-ray
measurements cyclic voltammograms were recorded, which confirm that
the hanging-meniscus cell allows high quality electrochemical measurements
combined with in-situ surface X-ray diffraction studies. The X-ray
diffraction data and complementary in-situ ellipsometric measurements
indicate that the deposition process is accompanied by substantial surface
roughening.
O 28.60 Mi 16:00 Bereich C
State selective detection of D2 after femtosecond-laser induced
desorption from Ru(001) — •S. Wagner 1 , M. Rutkowski 2 , R.
Dudek 3 , C. Frischkorn 1 , H. Zacharias 2 , and M. Wolf 1 — 1 Freie
Universtät, Berlin — 2 Westfälische Wilhems-Universität, Münster —
3 Fritz–Haber–Institut der MPG, Berlin
The energy transfer into different degrees of freedom in the fs-laser
induced recombinative desorption of deuterium from Ru(001) has been
investigated with (1+1’)-REMPI and time-of-flight measurements. It has
been shown that hot substrate electrons mediate this reaction within
a few hundred femtoseconds [1]. The rovibrational distributions of the
desorbing D2 molecules are detected via various B 1 Σ + u ← X 1 Σ + g Lyman
bands using tunable vacuum ultraviolet (VUV) laser radiation for
the resonant excitation step [2]. Populations of the rotational quantum
states in the vibrational ground and the first excited state are
measured. The rotational energy of D2 in the vibrational ground state
(Erot/kB = 800 ± 200K) is much lower than the rotational energy in
the excited state (Erot/kB = 1500 ± 300K). Assuming a Boltzmann-like
energy distribution, these results indicate a vibrational temperature of
Evib/kB = 1200 ± 150K. The amount of energy coupled to the translation
is Etrans/kB = 1700 ± 300K. Possible reasons for the incomplete
thermalization will be discussed.
[1] D. N. Denzler, C. Frischkorn, C. Hess, M. Wolf, and G. Ertl, Phys.
Rev. Lett., in press
[2] D. Wetzig, M. Rutkowski, H. Zacharias, and A. Groß; Phys. Rev. B
63, 205412 (2001)
O 28.61 Mi 16:00 Bereich C
Characterisation of Pd/Zn/ZnO real catalysts for methanol
steam reforming — •S. Pöllmann 1 , J. Pantförder 1 , A. Kölbl 2 ,
P. Pfeifer 2 , M. Fichtner 3 , D. Borgmann 1 , R. Denecke 1 , and
H.-P. Steinrück 1 — 1 Physikalische Chemie II, Universität Erlangen,
Egerlandstr. 3, 91058 Erlangen. — 2 FZ Karlsruhe GmbH, Institut für
Mikroverfahrenstechnik -IMVT-, Postfach 3640, 76021 Karlsruhe. — 3 FZ
Karlsruhe GmbH, Institut für Nanotechnologie -INT-, Postfach 3640,
76021 Karlsruhe.

Oberflächenphysik Mittwoch
We studied the chemical composition and the temperature dependent
behavior of Pd/Zn/ZnO catalysts that are used for methanol steam reforming.
Real catalysts coated on microstructured foils have been used
and their performance has been characterised in a high pressure flow apparatus
under realistic reaction conditions. We investigated these samples
by means of X-ray photoelectron spectroscopy (XPS) with Al Kα
radiation. Utilizing a high pressure XPS system the experiments were
performed in-situ and in the presence of methanol and water vapour in
a pressure range up to 1 mbar, at different temperatures. These measurements
allow to establish a correlation between the different activities
for the methanol steam reforming and the chemical composition of the
catalysts surface. Supported by the DFG (Schwerpunktsprogramm 1091,
Ste 620/3-3, Fi 816/1-1,2)
O 28.62 Mi 16:00 Bereich C
Drei unterschiedliche Ursachen für beim maschinellen Geschirrspülen
auftretende Glasoberflächenschäden — •Chun Wang 1 ,
Klaus-Peter Martinek 2 , Edda Rädlein 3 und Georg Krausch 1
— 1 Physikalische Chemie II, Universität Bayreuth — 2 Nachtmann GmbH
— 3 IMA, Universität Bayreuth
1. Glasstruktur: Nach einigen hundert Spülgängen ist die glatte ” Glashaut“
abgetragen und es bilden sich Kornmuster in der Größe von 30
nm. Bei mehr als tausend Spülgängen sind diese Körner verschwunden
und Waffelmuster mit Löchern in der Größe bis zu einem µm haben sich
gebildet. Damit erscheinen die Gläser getrübt. Dieses Phänomen kann
mit der Theorie der Ionen-Kanäle im Glasnetzwerk von Greaves und mit
unserem Vorschlag einer Glashaut gut erklärt werden.
2. Feuerpolitur: An manchen Gläsern konnten bereits nach wenigen
Spülzyklen wolkige Oberflächenschäden beobachtet werden. Die Schäden
haben ihre Ursache im industriellen Prozess der Feuerpolitur. Die auf die
Glasoberfläche treffende Flamme hat einen großen Temperaturgradienten.
So treten je nach Position der Flamme unterschiedliche Muster der
Phasentrennung in Erscheinung.
3. Organische Komplexbildung durch Getränke: An der Innenseite einzelner,
über lange Zeit verwendeter Gläser ist ein goldfarbiger Belag zu
beobachten. Die Reaktionsschicht ist nicht dicht und das Glas unterhalb
dieser Schicht zeigt eine weitere Korrosion. Die Schicht ist auf eine Komplexbildung
von organischen Komponenten aus den Getränken mit dem
Glas zurückzuführen.
O 28.63 Mi 16:00 Bereich C
Deposition massenselektierter Metallclusterionen unter Verwendung
einer Magnetronsputterquelle — •Nils Bertram, Tim
Fischer, Rainer Dietsche, Felix v.Gynz-Rekowski, Young
Dok Kim und Gerd Ganteför — Fachbereich Physik, Universität
Konstanz, 78547 Konstanz.
Das ”weiche” Landen von massenselektierten Clusterionen erlaubt
die Präparation von nanostrukturierten Oberflächen im extrem kleinen
Größenbereich unterhalb von 3 nm und mit atomarer Präzision: die Zahl
der Atome in der Nanostruktur ist exakt bekannt. Das Problem bei dieser
Art von Experimenten ist die niedrige Intensität der üblichen Clusterionenquellen.
Wir präsentieren erste Studien mit einer neu aufgebauten
Magnetron-Sputterquelle (Haberland-Typ). Die deponierten Cluster werden
mittels Elektron-Energieverlust-Spektroskopie untersucht.
O 28.64 Mi 16:00 Bereich C
Katalytische Reaktionen massenselektierter Edelmetallcluster
— •T. M. Bernhardt, L. D. Socaciu, J. Hagen, D. Popolan,
J. Le Roux, T. Gleitsmann, M. Vaida, B. Stegemann und L.
Wöste — Institut für Experimentalphysik, Freie Universität Berlin
Kleine Gold- und Silbercluster mit bis zu 13 Atomen zeigen eine starke
Größenabhängigkeit in ihrer chemischen Reaktivität. Für bestimmte
Clustergrößen kann in der Gasphase die katalytische Konvertierung von
Kohlenmonoxid zu Kohlendioxid nachgewiesen werden. Studien zur temperaturabhängigen
Kinetik geben Aufschluß über den Reaktionsmechanismus.
Strukturinformationen der Zwischenprodukte können aus theoretischen
Berechnungen und laserspektroskopischen Untersuchungen gewonnen
werden. Aus dem Vergleich zu auf definierten Oberflächen massenselektiv
deponierten Clustern können Informationen über den Einfluß
des Trägers auf die katalytische Aktivität gewonnen werden. Besondere
Aufmerksamkeit gilt dem Einfluß der elektronischen Struktur der Cluster
auf die Reaktivität und der Modifikation der elektronischen Struktur
durch den Kontakt mit verschiedenen Substraten.
O 28.65 Mi 16:00 Bereich C
Einfluss der Brechzahl des dielektrischen Substrats auf die optischen
Eigenschaften einzelner Goldnanopartikel — •Katharina
Schätzler, Benjamin Schmidt, Christian Dahmen und Gero
von Plessen — I. Physikalisches Institut (IA), RWTH Aachen
In Berechnungen auf dem Gebiet der optischen Eigenschaften von
Metallnanopartikeln wird die inhomogene dielektrische Umgebung des
Partikels oft durch einfache Mittelwertbildung über die Umgebungsbrechzahlen
berücksichtigt. In unserer Arbeit wird der Einfluss der
Brechzahl des dielektrischen Substrats auf die optischen Eigenschaften
sphärischer Goldnanopartikel mit Hilfe der Dunkelfeld-Mikroskopie sowie
-Spektroskopie untersucht. Diese Methode macht es möglich, einzelne Nanopartikel
zu spektroskopieren und so inhomogene Verbreiterungseffekte
zu vermeiden.
O 28.66 Mi 16:00 Bereich C
Optische Eigenschaften kleiner Aggregate aus Goldnanopartikeln
— •Benjamin Schmidt, Katharina Schätzler, Christian
Dahmen und Gero von Plessen — I.Physikalisches Institut A, RW-
TH Aachen
Liegen Edelmetall-Nanopartikel nah genug beieinander, um elektromagnetisch
miteinander zu koppeln, bilden sich ausgedehnte Plasmonen-
Moden aus. Hier untersuchen wir mit Dunkelfeldmikroskopie kleine Aggregate
aus gekoppelten, kugelförmigen Goldnanopartikeln, insbesondere
Partikelpaare. Um eine Korrelation der Aggregat-Topographie und
der optischen Eigenschaften herzustellen und um inhomogene Verbreiterungseffekte
zu vermeiden, wird polarisationsselektive Spektroskopie an
einzelnen Aggregaten durchgeführt. Die nötigen topographischen Informationen
werden aus elektronenmikroskopischen Aufnahmen gewonnen.
Die experimentellen Ergebnisse werden mit Resultaten aus der Verallgemeinerten
Mie-Theorie verglichen, und es wird der Versuch unternommen,
die Beiträge bestimmter Moden zu den Spektren zu identifizieren.
O 28.67 Mi 16:00 Bereich C
Homogeneous linewidth of gold nanoshells — •S. Brogl, G.
Raschke, A. Susha, A. L. Rogach, T. A. Klar, and J. Feldmann
— Photonics and Optoelectronics Group, Physics Department and CeNS,
University of Munich, Amalienstr. 54, D-80799 Munich, Germany
Nanoshells composed of a few nanometer thin gold layer coated on
Au2S nanoparticles show a pronounced resonance in their scattering spectra
for visible light. Similar to solid noble metal nanoparticles the origin of
the resonance is a collective oscillation of the conduction band electrons,
which is known as the nanoparticle plasmon (NPP). The NPP resonance
position of a gold nanoshell can be tuned over a large spectral range by
varying the relative size of the nanoparticle core and the thickness of the
gold shell.
Experiments carried out on ensembles of nanoshells show a broad absorption
linewidth (FWHM) of about 600meV. This is by far exceeding
what is expected by Mie-theory calculations which yield a NPP resonance
line width of less than 100meV. We investigate this discrepancy by measuring
the homogeneous scattering spectrum of a single gold nanoshell
using dark field microscopy. The results show a homogeneous linewidth
narrowed by 50% compared to ensemble measurements. This indicates
that inhomogeneities e.g. distribution of shell thicknesses and/or core
diameters are one important parameter for line broadening.
O 28.68 Mi 16:00 Bereich C
STM/STS on large silver clusters at germanium (001) —
•Karl-Ludwig Jonas, Armin Kleibert, Fanny Geisler, Ralf-
Peter Methling, Joachim Bansmann, Viola von Oeynhausen
und Karl Heinz Meiwes-Broer — Fachbereich Physik, Universität
Rostock, Universitätsplatz 3, D-18051 Rostock
Cluster deposition is used to create metal-nanodots with a high aspect
ratio. We present scanning tunneling spectroscopy (STS) measurements
on isolated silver clusters at germanium (001). The clusters are generated
using an arc cluster ion source (ACIS), mass selected and deposited
under soft landing conditions (Ekin/atom < 0.5eV). Before performing
STM experiments the cluster structure has been investigated using TEM,
electron diffraction and EDX. Particle diameters between 5 and 14 nm
have been used for the present studies. Scanning tunnelling microscopy
images of large clusters always contain considerable tip folding at the
steep cluster edges. Beside the accurately measured cluster height the
imaging of particles of this height is therefore restricted to cluster facets
at the top. Using STM and STS on deposited silver clusters structural

Oberflächenphysik Mittwoch
and electronic properties are observed. In contrast to silver islands grown
on germanium (001) the orientation of the crystal lattice is not fixed if
cluster melting is neglected. However, some of the clusters show hexagonal
facets at the top. STS is sensitive to occupied and unoccupied states
near the Fermi level and reveals the existence of distinct states in the
tunneling conductivity of the substrate as well as on the clusters. Thus,
the richly structured density of states of the germanium (001) surface
has been discovered and serves as STM/STS condition test.
O 28.69 Mi 16:00 Bereich C
Application of the variable phase theory to the systems with
quasistationary states. — •Oleg Kidun 1 , Jamal Berakdar 1 ,
and Natasha Fominykh 2 — 1 Max-Planck Institut fuer Mikrostrukturphysik,
Halle, Germany — 2 Institute of Physics, St. Petersburg State
University, St. Petersburg, Russia
We develop a method of investigation of the quasistationary (QS)
states of different physical systems based on the variable phase approach
[1-3]. We consider the modification of the physical properties of the QS
states (energy position and resonance width) under the spatial transformation
of the potential field as well as its asymptotical behavior. The
role of the possible nonlocality of the potential in the observability of
the QS states is also estimated. The realization of our approach in the
studies of molecules and nanostructures is discussed.
[1] F. Calogero, Variable Phase Approach in Potential Scattering, AP,
NY (1967)
[2] V. Babikov, Method of the Phase Functions in Quantum Mechanics,
Nauka, Moscow (1969)
[3] O. Kidun, N. Fominykh, J. Berakdar, J. Phys. A 35, 9413 (2001)
O 28.70 Mi 16:00 Bereich C
Electron dynamics of buried interface states in Ar/Cu(100)
probed by time-resolved two-photon photoemission — •M.
Rohleder, W. Berthold, K. Duncker, J. Güdde, and U.
Höfer — Fachbereich Physik und Zentrum für Materialwissenschaften,
Philipps-Universtät, D-35032 Marburg
We demonstrate for the system Ar/Cu(100) how in favourable cases the
dynamics of electronic states located at the interface between a metal and
an insulator can be investigated by means of time-resolved two-photon
photoemission (2PPE). The interface states of Ar/Cu are located above
the vacuum level in the band gaps of both the Cu(100) surface and the
Ar films which were as thick as 70 monolayers (ML). With increasing
layer thickness the states evolve from quantum-well-like resonances into
well-defined bound states which arise from the screened image-potential
of the metal. Electrons excited into these states decay on timescales between
100 fs and 250 fs by electron-hole pair excitation in the metal and
– for thin Ar layers (

Oberflächenphysik Mittwoch
Cs-pads appear blurred. Subsequent reduction of the laser peak power
leads to sharper edges as are also observed when the 80MHz oscillator is
used for illumination.
O 28.75 Mi 16:00 Bereich C
Time-of-Flight Two-Photon Photoemission Spectromicroscopy
of Noble metal cluster films with Femtosecond Laser Radiation.
— •M. Cinchetti, A. Gloskovskii, D. A. Valdaitsev, S.
A. Nepijko, and G. Schönhense — Johannes Gutenberg-Universität,
Institut für Physik, 55099 Mainz, Deutschland
Time-of-Flight Two-Photon Photoemission Spectromicroscopy [1] was
used to investigate the photoemission properties of some Nobel metal
surfaces under femtosecond laser irradiation (photon energy 3.1eV, pulse
width < 200fs, laser fluence 6.4µJcm −2 ).In particular, we present the results
of investigations of Cu surface inhomogeneities and Ag nanoparticle
films deposited on a Si(111) substrate. The photoemission yield resulted
to be enhanced in presence of surface inhomogeneities with dimensions in
the nanometer range. The energy distribution curves obtained from regions
characterized by a strongly enhanced photoemission yield are shown
to have the same qualitative behaviour. They differ significantly from the
energy distribution curves from the homogeneous and clean metal surfaces.
The differences are explained in terms of (i) a reduction of surface
potential barrier connected with the appearance of local fields between
the nanoparticles and the substrate; (ii) the excitation of Localized Surface
Plasmons in the nanoparticles and the consequent modification of
the near field [2], that influences the photoemission. [1] M. Cinchetti, A.
Oelsner, G. H. Fecher, H. J. Elmers, and G.Schönhense, Appl. Phys. Lett.
83, 1503 (2003). [2] V.M. Shalaev, C. Douketis, T. Haslett, T. Stuckless,
and M. Moskovitis, Phys. Rev. B 53, 11193 (1996).
O 28.76 Mi 16:00 Bereich C
Time-Resolved Photoemission Electron Microscopy at nanostructured
surfaces — •Carsten Wiemann, Michael Bauer,
Michael Munzinger, Daniela Bayer, and Martin Aeschlimann
— TU Kaiserslautern
TR-2PPE (Time-Resolved 2-Photon-Photoemission) is a wellestablished
technique to investigate electron dynamics at surfaces on a
femtosecond time-scale. A combination of TR-2PPE with a spatially resolving
electron detection scheme such as Photoemission Electron Microscopy
(PEEM) allows in addition to analyze the precise local origin of
the emitted electrons. In this way a ’lifetime mapping’ of heterogeneous
samples is - in principle - possible. [O. Schmidt et al. Appl. Phys. B 74
(2002) 223-227] Recent time-resolved PEEM results on nanostructured
surfaces demonstrating the capabilities and limits of this setup in extending
time-resolved spectroscopy to the nanoscale will be presented.
O 28.77 Mi 16:00 Bereich C
Surface Recombination Dynamics of SiO2/Si(100) - A Combined
Laser and Synchro Radiation Study — •David Bröcker 1 ,
Tatjana Gießel 1 , and Wolf Widdra 2 — 1 Max-Born-Institut,
Max-Born-Strasse 2a, 12489 Berlin — 2 Martin-Lutter-Universtität
Halle-Wittenberg, Fachbereich Physik, Fachgruppe Experimentelle
Physik III
The charge carrier dynamics at the silicon surface has been studies by
probing the surface photovoltage. Upon excitation of electron hole pairs
in the surface-near region by picosecond laser pulses, the dynamics of the
charge carrier recombination has been determined by time-resolved Si 2p
core level photoemission. We compared several sample preparations, the
clean Si(100) surface, the hydrogen monohydride, and thin oxide layers.
The decay process could be described by a model based on thermionic
emission. The influence of the laser fluence and the temperature on the
decay process has been studied in detail.
O 28.78 Mi 16:00 Bereich C
X-ray longitudinal Kerr rotation and ellipticity spectra measured
at the 2p edges of Fe, Co, and Ni — •Sergio Valencia 1 ,
Hans-Christoph Mertins 1 , Peter M. Oppeneer 2 , Dirk Abramsohn
1 , Andreas Gaupp 1 , and Wolfgang Gudat 1 — 1 BESSY, Berlin
— 2 IFW Dresden
The first measurements of the X-ray longitudinal magneto-optical Kerr
effect (L-MOKE) at the 2p absorption edges of amorphous Fe, Co, and
Ni films are reported. The L-MOKE rotation and ellipticity spectra are
recorded by a complete polarization analysis of the X-rays reflected from
the ferromagnetic surface. At the edges large Kerr rotations of up to ±24 ◦
are detected, which are more than two orders of magnitude larger than
those in the visible energy range. Using a numerical simulation package
based on the magneto-optical refractive indices, the spectral contributions
stemming from magneto-optically active atomic transitions could
be seperated from layer interference effects. Both theoretically and experimentally
it is shown that at grazing incidence the longitudinal Kerr
rotation and Kerr ellipticity are proportional to the transversal MOKE
and the XMCD reflection spectrum, respectively.
O 28.79 Mi 16:00 Bereich C
Magnetische Röntgenstreuung an lateralen Strukturen —
•Arndt Remhof, Johannes Grabis, Alexei Nefedov,
Erik Verduijn und Hartmut Zabel — Experimentalphysik/Festkörperphysik,
Ruhr-Univeristät Bochum, 44780 Bochum
Nano- und Mikrostrukturierung von dünnen magnetischen Systemen
ermöglicht das Ummagnetisierungsverhalten, d. h. die Hystereseschleife,
gezielt zu verändern. Wir haben ein quadratisches Muster aus Co/CoO
Inseln mittels Elektronenstrahl-Lithographie hergestellt. Die Inseln haben
einen Durchmesser von 1mm und eine Periode von 2,5 mm. Die
magnetische Hysterese wurde mit Bragg-MOKE und mit resonanter magnetischer
Röntgenstreuung (XRMS) an der Co L2,3 bei verschiedener
Ordnung der Interferenz bestimmt. Bragg-MOKE liefert eine Fourieranalyse
des Magnetisierungsprofils während des Ummagnetisierungsprozesses.
Analog dazu liefern auch Hysteresen, die mit XRMS an verschiedenen
Ordnungen von Bragg-Reflexen gemessen werden, eine Fourieranalyse
der Ummagnetisierung. Im Vergleich zu Bragg-MOKE zeichnet
sich XRMS durch Elementspezifität und durch höhere Eindringtiefen aus.
Wir präsentieren erste Ergebnisse, die mit Bragg-MOKE und XRMS an
strukturierten Co/CoO Proben gewonnen wurden, und vergleichen die
Ergebnisse.
Gefördert durch SFB 491.
O 28.80 Mi 16:00 Bereich C
Faraday rotation spectrum at shallow core levels: 3p edges
of Fe, Co, and Ni — •Sergio Valencia 1 , Hans-Christoph
Mertins 2 , Peter M. Oppeneer 3 , Dirk Abramsohn 1 , Andreas
Gaupp 1 , Claus M. Schneider 4 , and Wolfgang Gudat 1 —
1 BESSY, Berlin — 2 FH Münster — 3 IFW Dresden — 4 IFF, FZ Jülich
We report measurements of the Faraday effect at the 3p edges of thin
Fe, Co, and Ni films. The Faraday rotation and ellipticity are determined
by a complete polarization analysis of the synchrotron radiation transmitted
across the samples. Surprisingly, the rotation constants k attain
large values comparable to those observed at the 2p edges. Maximal rotation
constants of 2.2 · 10 5 , 1.5 · 10 5 , and 0.8 · 10 5 deg/mm are found
for Fe, Co, and Ni, respectively. While at the 2p edges the spin-orbit
splitting of the 2p levels is considered to be mainly responsible for the
magneto-optical effects, the unexpected similarity underlines the role of
the exchange-splitting of the 3p core levels in the extreme ultra-violet
region (EUV). A full set of optical and magneto-optical constants, which
were determined from the measured rotation and ellipticity, are presented
for the three elements in the energy range of the 3p edges.
O 28.81 Mi 16:00 Bereich C
Anomalous ferromagnetism of monatomic Co wire at the
Pt(111) surface step edge — •Peter M. Oppeneer 1 , Alexander
B. Shick 2 , and Franti˘sek Máca 2 — 1 IFW Dresden — 2 Inst. of
Physics, ASCR, Prague
We report a first-principles investigation of the anomalous ferromagnetism
of a quasi-one-dimensional Co chain decorating the Pt(111) step
edge. Our calculations demonstrate that the symmetry breaking at the Pt
step leads to an easy magnetization axis at an anomalous angle of ∼ 20 ◦
towards the Pt step, in semi-quantitative agreement with the experimentally
observed peculiar easy axis at an angle of ∼ 40 ◦ [P. Gambardella
et al., Nature 416, 301 (2002)]. The computed hard magnetization axis
direction also corresponds well to the experimentally observed hard axis.
A (T = 0) magnetocrystalline anisotropy energy of 3 meV/Co is calculated
in good agreement with the experimental value of ∼ 2 meV/Co at
T = 45 K. On account of the symmetry breaking the Co spin and orbital
moments become noncollinear, even in the case of a collinear ferromagnetic
spin arrangement. We also performed LSDA+U calculations, with
which a significant enhancement of the Co orbital magnetic moment is
achieved already when modest electron correlations (small U) are taken
into account.

Oberflächenphysik Mittwoch
O 28.82 Mi 16:00 Bereich C
Transverse magneto-optical Kerr effect at the 3p edges of Fe and
Co — •Armin Kleibert 1 , Sergio Valencia 2 , Hans-Christoph
Mertins 2 , and Joachim Bansmann 1 — 1 Universität Rostock, Fachbereich
Physik, Universitätsplatz 3, 18051 Rostock — 2 BESSY GmbH,
Albert-Einstein-Str. 15, 12489 Berlin, Germany
Soft x-ray based experimental techniques are powerful and very sensitive
methods to investigate the magnetism of systems with low dimensions
like ultrathin films or clusters, respectively. In particular, the
magneto-optical Kerr-effect (MOKE) at the 2p edges of Fe, Co, and Ni
has attracted much attention. In the transverse geometry (T-MOKE)
huge intensity changes in the resonantly enhanced reflectivity upon reversal
of the magnetization direction have been found. While effects near
the 2p core levels were extensively studied in the last years, only a few
experiments were reported concerning the vicinity of the 3p threshold.
In this contribution, we present angular dependent measurements of
the T-MOKE in the energy range of the 3p edges of thin Fe and Co
films, respectively, revealing surprisingly large asymmetries up to 40%
near the Brewster angle. From these reflectivity measurements it is possible
to obtain information about the energy dependent refractive indices
and magneto-optical Voigt constants. In order to simulate the measured
reflectivity including the influence of capping layers we applied a multilayer
formalism describing magneto-optics. A good agreement of calculation
and experiment was achieved using tabulated values of the index
of refraction and independently obtained Voigt constants.
O 28.83 Mi 16:00 Bereich C
Resonant X-Ray scattering from TbBaCo2O5.5 — •N.V.
Kasper 1 , P. Wochner 1 , G. Carbone 1 , A. Vigliante 2 , D. Mannix
3 , and G. Jakob 4 — 1 Max-Planck-Institut für Metallforschung,
Stuttgart, Germany — 2 Bruker AXS, Karlsruhe, Germany — 3 European
Synchrotron Radiation Facility, Grenoble, France — 4 Institut für
Physik, Universität Mainz, Mainz, Germany
Resonant X-ray scattering at the Co K-edge from epitaxial films and
single crystals of TbBaCo2O5.5 cobaltite with perovskite structure has
been studied in insulating and metallic states. Polarization, energy and
azimuthal dependences of the intensity of (016), (116), and (310) Bragg
peaks were measured. Strong oscillations of the resonantly scattered intensity
were observed both in σ’ and π’ channels. The scattered signal
changes very weakly during the metal-insulator phase transition.
The azimuthal oscillations of the scattered signal are attributed to
the tensor character of the anomalous scattering factor of Co. Using
this concept we have developed a model, describing very well the measured
azimuthal oscillations. On the basis of the obtained experimental
results and literature data it is argued that this anisotropy of the anomalous
scattering factor of Co is caused mainly by distortions of the local
surrounding of cobalt ions and not by anisotropies due to ordering of
electronic orbitals of Co.
O 28.84 Mi 16:00 Bereich C
X-ray magneto-optical sum rules in small Co clusters —
•Kai Fauth 1,2 , Markus Heßler 1,2 und Gisela Schütz 2 —
1 Physikalisches Institut der Universität Würzburg, Am Hubland, 97074
Würzburg — 2 MPI für Metallforschung, Heisenbergstraße 3, 70569
Stuttgart
The so-called spin and orbital sum rules [1,2] in x-ray magnetic circular
dichroism (XMCD) spectroscopy are often believed to apply with
reasonable accuracy in the case of the late 3d transition metals and their
compounds, if the magnetic dipole term Tz can be neglected. Strong deviations
can occur due to symmetry breaking such as given at surfaces,
O 29 Hauptvortrag Pentcheva
causing the magnetic dipole term to contribute significantly to the spin
sum rule, while not contributing to the magnetization. Much less is known
in the case of small clusters. We have derived magnetic moments of superparamagnetic
Co55 clusters from XMCD at various applied magnetic
fields. We find that the moments thus obtained from the magnetization
curve and those determined separately from the sum rules agree to within
10%. This result sets an upper limit for the importance of Tz in these
clusters.
[1] B. T. Thole et al. , Phys. Rev. Lett. 68, 1943 (1992)
[2] P. Carra et al. , Phys. Rev. Lett. 70, 694 (1993)
O 28.85 Mi 16:00 Bereich C
X-ray resonant magnetic scattering of Fe/Cr superlattices
— •Alexei Nefedov, Johannes Grabis, Andre Bergmann,
Florin Radu, and Hartmut Zabel — Institut für Experimentalphysik/Festkörperphysik,
Ruhr-Universität Bochum, D-44780 Bochum,
Germany
We have studied the magnetic and structural properties of an antiferromagnetically
(AF) coupled Fe/Cr(001) superlattice by soft X-ray
resonant magnetic scattering. Strong magnetic Bragg peaks are observed
at the half order positions in reciprocal space parallel to the [001] growth
direction and in between the structural Bragg reflections from the superlattice
periodicity. The magnetic hysteresis loops measured at the structural
Bragg peak and at the half-order peak clearly demonstrate the
AF coupling of the Fe/Cr multilayer. Transverse scans and off-specular
reflectivity measurements confirm an AF domain structure of the superlattice
in remanence with large perpendicular correlation. In addition,
the transverse scan of the half-order Bragg peak exhibits a Lorentzian
line shape at zero field, which diminishes in higher fields, indicative for
a remanent multidomain state which approaches a single domain state
towards saturation.
This work was supported by the German Federal Ministry of Education
and Research (BMBF) under Contract No.03ZAE7BO.
O 28.86 Mi 16:00 Bereich C
Inducing spin crossover in metallo-supramolecular polyelectrolytes
through an amphiphilic phase transition — •Yves
Bodenthin 1 , U. Pietsch 1 , D. Kurth 2 , and H. Möhwald 2 —
1 University of Potsdam, Institute of Physics, Am Neuen Palais 10,
14469 Potsdam, Germany — 2 MPI-KG Golm, Am Mühlenberg 1, 14476
Potsdam-Golm
In the last years resonant magnetic X-ray reflectivity experiments
(XMCD) become important for the investigation of molecular magnetism
in thin films.
In the present work we report a novel approach to affect spin crossover
by introducing mechanical strain through an amphiphilic phase transition
in a metallo-supramolecular polyelectrolyte-amphiphile complex
(PAC). The investigated system consists of thin layers deposited in Yconformation
on a silicon substrate by means of Langmuir-Blodgett technique.
It was observed by EXAFS, x-ray reflectivity and in-plane diffraction
experiments that the structural phase transition in the amphiphilic
mesophase is responsible for the distortion of the coordination geometry
of the tightly coupled transition metal centres. Consequently, the energetic
separation of the subsets of the iron d-orbitals changes and gives
rise to spin crossover. Using temperature resolved SQUID and XMCD
measurements we observe a diamagnetic to paramagnetic phase transition
above room temperature which is connected to a structural phase
transition between two liquid crystalline phases.
Zeit: Donnerstag 09:30–10:15 Raum: H36
Hauptvortrag O 29.1 Do 09:30 H36
Beyond the (p=0 Pa, T=0 K) limit: Surface Phase Diagrams and
Growth Kinetics from First Principles — •Rossitza Pentcheva
— Section Crystallography, Dept. for Earth and Environmental Sciences,
LMU München — Fritz-Haber-Institut der MPG, Berlin
Combining density functional theory (DFT) with methods from statistical
mechanics (ab initio kinetic Monte Carlo (kMC)) or thermodynamics
(ab initio atomistic thermodynamics, see e.g. [1]) enables us to extend
the predictive power of DFT to meso- and macroscopic length scales
and/or to finite pressures and temperatures. Two examples for their application
are presented: In the initial growth of Co on Cu(001) DFT-kMC
simulations reveal that the activation of atomic exchange leads to substantial
deviations from the predictions of standard nucleation theory,
namely a bimodal growth mode and a nonmonotonic scaling behavior of
island density [2]. Using ab initio atomistic thermodynamics we construct
a phase diagram of Fe3O4(001), a promising material for the development
of spintronic devices. A hitherto ignored termination with octahedral
iron and oxygen forming a wave-like structure along the [110]-direction

Oberflächenphysik Donnerstag
is identified as the lowest energy configuration over a broad range of oxygen
pressures. The stabilization of the Fe3O4(001)-surface goes together
with significant changes in the electronic and magnetic properties, e.g. a
halfmetal-to-metal transition. [1] K. Reuter and M. Scheffler, Phys. Rev.
O 30 Hauptvortrag Denecke
B 65, 035406, (2002). [2] R. Pentcheva et al., Phys. Rev. Lett. 90, 076101
(2003). (in collab. with M. Scheffler and W. Moritz; DFG support, PE
883)
Zeit: Donnerstag 10:15–11:00 Raum: H36
Hauptvortrag O 30.1 Do 10:15 H36
Surface chemistry studied by in-situ x-ray photoelectron spectroscopy
— •Reinhard Denecke — Physikalische Chemie II, Universität
Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen
Important aspects of surface science are the dynamics of adsorption
and reaction processes. Using high-resolution x-ray photoelectron spectroscopy
together with high flux synchrotron radiation and in combination
with a molecular beam, such time-dependent processes can be
followed on a time scale of seconds. Spectroscopic information about the
O 31 Oberflächenreaktionen II
species involved can be obtained from the binding energy shifts of adsorbate
and substrate core levels. In the case of hydrocarbons, the vibrational
fine structure can additionally be used to identify surface species.
From quantitative information obtained by intensity analysis, kinetic parameters
can be derived. Examples are discussed for bimolecular reactions
(CO oxidation), activated adsorption (dissociative adsorption of methane
and ethane) and thermal dehydrogenation of hydrocarbons.
Supported by the DFG (Ste 620/4-2).
Zeit: Donnerstag 11:15–13:00 Raum: H36
O 31.1 Do 11:15 H36
Rastertunnelmikroskopische Untersuchung elektroneninduzierter
Prozesse an D2O-Molekülen und -Clustern auf fcc(111)-
Metalloberflächen — •Heiko Gawronski, K. Morgenstern, K.-
F. Braun und K.-H. Rieder — Freie Universität Berlin, Institut für
Experimentalphysik, Arnimallee 14, 14195 Berlin
Diffusion von D2O-Molekülen und kleinen Clustern auf Ag(111)
und Au(111) wird bei 5,5K mittels des Elektronenstroms eines
Tieftemperatur-Rastertunnelmikroskops(RTM) induziert. Hierbei wird
die Abhängigkeit der Diffusion von der Anregungsenergie und der Anregungsdauer
untersucht. Dies erlaubt es, Aussagen über die Abhängigkeit
der Oberflächenreaktionen vom Adsorptionsplatz, der Clustergröße sowie
der angeregten molekularen Schwingung zu treffen. Zunächst werden
die Adsorbate über ihre scheinbaren Höhen identifiziert. Anschließend
induziert man eine diffusive Bewegung durch Injektion von Tunnelelektronen
verschiedener Energie und bestimmt so die Anregungsenergien
der D2O-Moleküle auf den beiden Substraten. Für einzelne Moleküle liegen
diese bei (400±10)mV auf Ag(111) bzw. (440±10)mV auf Au(111)
wobei die Diffusion nach durchschnittlich 0,5ms erfolgt. Die Anregung
der Diffusion eines D2O-Clusters mit der RTM-Spitze direkt über einem
Cluster benötigt auf Au(111) eine Anregungsenergie von (250±10)mV,
während eine Anregung mit der Spitze im Abstand einiger nm erst bei
(480±10)mV stattfindet. Diese Ergebnisse werden mit Ergebnissen von
H2O auf Cu(111) und auf Ag(111) verglichen.
O 31.2 Do 11:30 H36
Interaction of He, Ne and Ar metastable atom beams
with multilayer tunnel systems — •Domokos Kovacs 1 , Johannes
Berndt 1 , Jörg Winter 1 , and Detlef Diesing 2 —
1 Experimentalphysik 2, Ruhr-Universität Bochum — 2 Institut für
Schichten und Grenzflächen 3, Forschungszentrum Jülich
The collision of metastable rare gas atoms He, Ne and Ar with a metal
surface is a well investigated process in surface science. The process leads
with an efficient rate to a relaxation of the atoms and a simultaneous electron
emission from the metal surface. The energy spectrum of the emitted
electrons is a wide distribution with a maximal energy of 4 eV. Due to the
significant width of the emitted electron spectrum one can think about
a distribution of excited defect electrons in the electron emitting metal
surface. This kind of electronic excitation is difficult to detect in a bulk
metal. In a 15 nm thick silver film however the defect electrons may reach
the opposite interface of the metal film. In a multilayer tunnel system,
separating the thin silver film from an aluminium film by a 2 nm thick
oxide spacer one can detect an electron current from the base electrode
to the silver electrode which is exposed to the metastable beam. Competing
processes with deexcitation are discussed. By the application of
a grid filter in the transport tube between the discharge and the vacuum
chamber one can seperate between ion neutralization reactions and
metastable deexcitation. By an asymmetric chopping unit which allows
the exposition of the samples to alternating particle-photon and photon
fluxes we discuss the contribution of the photon induced tunnel current
to the total tunnel current.
O 31.3 Do 11:45 H36
Molecular scattering and adsorption at metallic surfaces studied
by ab initio molecular dynamics simulations — •Axel Groß —
Physik-Department T30, Technische Universität München, 85747 Garching
Molecular dynamics simulations based on density functional theory
(DFT) calculations have been performed to study the interaction of simple
molecules with metallic surfaces. In the simulations, the surface atoms
have been treated dynamically thus allowing a realistic description of the
energy transfer from the impinging molecules to the substrate. In particular,
we focus on the systems O2/Pt(111) [1] and H2/Pd(100). The
energy transfer and dissociation process of O2 which can adsorb both
molecularly as well as dissociatively on Pt(111) is analysed in detail. In
the simulation of H2 adsorption on metallic surfaces, the substrate atoms
are usually kept fixed because of the large mass mismatch between H2
and the metal atoms [2]. This approximation will be critically questioned
by examining the influence of the recoil of the metal atoms on the H2
adsorption dynamics.
[1] A. Groß, A. Eichler, J. Hafner, M.J. Mehl, and D.A. Papaconstantopoulos,
Surf. Sci. 539, L542 (2003).
[2] A. Groß, Surf. Sci. Rep. 32, 291 (1998).
O 31.4 Do 12:00 H36
First-principles Investigation of Structural and Chemical
Properties of Nanoporous Carbon — •Suljo Linic, Johan M.
Carlsson, and Matthias Scheffler — Fritz-Haber-Institut der
Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin
Production of styrene by dehydrogenation of ethylbenzene(ET) is one
of the most important processes in chemical industry. Iron oxide is used
as catalyst, but it has been observed that ET decomposes during an induction
period leaving nanoporous carbon (NPC) on the oxide support.
NPC are curved, defective, graphitic sheets and experiments have shown
that such materials are active catalysts for oxidative dehydrogenation of
ET.[1] Recently, it was therefore suggested that the actual catalyst under
reaction conditions is NPC.[2] This motivates a theoretical study of
NPC. Our results indicate on the one hand that flat and curved basal
planes of graphitic sheets are chemically inert. Vacancies on the other
hand leave dangling bonds and increase the density of state close to the
Fermi level. This gives the vacancies a much higher reactivity, which is
examplified by a large exothermal energy for dissociative adsorption of
O2. We have then studied oxidation of the defects as function of pressure
and temperature. The resulting oxygenated vacancies show interesting
properties as active sites in the dehydrogenation process. [1] M. S. Kane
et al., Ind. Eng. Chem. Res. 35, 3319 (1996). [2] G. Mestl et al., Angew.
Chem. Int. Ed. 40, 2066 (2001).

Oberflächenphysik Donnerstag
O 31.5 Do 12:15 H36
Selective methanol oxidation on a Cu (110) surface — •Ling
Zhou, Sebastian Guenther, and Ronald Imbihl — Institut fuer
Physikalische Chemie und Elektrochemie,Universitaet Hannover
The oxidation of methanol with oxygen to formaldehyde, CO2, H2 and
H2O on a Cu (110) surface was studied under stationary reaction conditions
in the 10 −7 - 10 −3 mbar range with rate measurements, AES,
LEED and PEEM. The catalytic activity of the surface exhibits a pronounced
peak at low temperature (≈ 480 K) and a second peak at high
temperature (≈ 850 K). The selectivity of the stationary reaction was
carefully analyzed and related the adsorbates present on the surface. A
pronounced hysteresis of the reactivity during temperature ramping can
be observed. It was shown that this hysteresis as well as the H2-formation
rate is entirely determined by structural effects. All products are formed
with first order kinetics with respect to oxygen partial pressure up to a
certain ratio. Above this ratio with an oxygen rich gas feed, high oxygen
coverage phases form inhibiting the reaction. By varying the total pressure
from 10 −7 mbar up to 10 −3 mbar a pressure dependent temperature
shift of the first reaction peak of about 20 K / decade was detected. This
finding is in agreement with experiments in the range above 0.01 mbar.
This result can be regarded as a first and successful step in bridging the
pressure gap between UHV- and high-pressure experiments.
O 31.6 Do 12:30 H36
Vibrational Analysis of the V2O5(010) Surface with and without
Oxygen Vacancies: ab-initio DFT Cluster Studies — •Christoph
Friedrich and Klaus Hermann — Fritz-Haber-Institut der Max-
Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin
While the catalytic behavior of vanadium oxide has been known and
utilized for a long time many microscopic details of oxidation reactions
at vanadium oxide surfaces are still not fully understood. V2O5 reduces
quickly when exposed to X-ray and LEED beams. It has been shown that
O 32 Nanostrukturen III
under catalytic reaction conditions oxygen vacancies are always present
on the surface and may act as active sites. From vibrational spectra obtained
e.g. from Infrared and Raman-spectroscopy as well as HREELS
measurements information about the geometry and bond strengths of
the different vibrating species can be gained. Vibrational frequencies are
particularly sensitive to changes in the local geometric and chemical environment.
This work focuses on how the vibrational spectra are modified
by the presence of different types of oxygen vacancies at the surface. In
addition, the influence of adsorbed CO on surface vibrations is discussed.
This work is supported by SFB 546 “Structure, Dynamics, and Reactivity
of Transition Metal Oxide Aggregates”.
O 31.7 Do 12:45 H36
SFG and TDS studies of methanol adsorption and decomposition
on Pd model catalysts — •Matthias Morkel, Günther
Rupprechter und Hans-Joachim Freund — Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Abt. Chemische Physik, Faradayweg 4-6,
14195 Berlin
Methanol adsorption and decomposition on Pd(111) and Al2O3supported
Pd-nanoparticles were studied by sum frequency generation
(SFG) vibrational spectroscopy from ultrahigh vacuum (UHV) to 100
mbar, at temperatures up to 400 K. Under UHV, these processes were
also followed by thermal desorption spectroscopy (TDS).
The decomposition of methanol can be seperated in two reaction pathways.
A fast reaction pathway leads to formation of CO and hydrogen.
The second pathway produces carboneacious species (CHx or C) by scission
of the CO-bond of methanol. Although the reaction rate of the latter
pathway is much lower, it cannot be negelected under high-pressure. Depending
on the temperature the carbon poisoning leads to a partial or
complete deactivation of the catalyst. The binding sites of the carbon
species were characterized by SFG using CO as probe molecule. Regeneration
with oxygen was able to (partly) remove the carbon deposits.
Zeit: Donnerstag 11:15–13:15 Raum: H38
O 32.1 Do 11:15 H38
STM, TDS and LEED examinations of trimesic acid on single
crystal surfaces — •Lorenz Kampschulte, Robert Kraus,
Stefan Griessl, and Wolfgang Heckl — Department für Geound
Umweltwissenschaften, LMU München, Theresienstr. 41, 80333
München, www.nano.geo.uni-muenchen.de
The adsorption of trimesic acid (TMA) on single crystal surfaces was
studied by STM (Scanning Tunnelling Microscopy), TDS (Thermal Desorption
Spectroscopy) and LEED (Low Energy Electron Diffraction).
Trimesic acid consists of a benzene ring with three carboxylic groups
in symmetric 1,3,5-positions. Three different single crystals were used as
substrates: graphite(0001), silver(111) and gold(111).
The measurements were done under Ultra High Vacuum (UHV) conditions,
the trimesic acid was evaporated on different substrates using an
effusion cell. The preparation of a TMA monolayer was observed and adjusted
with thermal desorption spectroscopy. From these measurements
it was possible to deduce the binding conditions. In all cases characteristic
periodically arranged structures could be demonstrated. In the
monolayer regime the structure is characterized by non-dense-packing of
molecules on the surface. It was shown that, depending on the substrate
material and the preparation method, different network structures could
be assembled. These networks are induced by directed hydrogen bonding
(self assembly), forcing the organic molecules to build a two-dimensional
grid architecture with small cavities.
O 32.2 Do 11:30 H38
Self-organization of Au-nanowires on two-dimensional tungsten
carbide — •A. Varykhalov, O. Rader, and W. Gudat — BESSY,
12489 Berlin
A thermally induced formation of well-ordered arrays of Au nanowires
on top of the carbon-induced 15 × 3 reconstruction of W(110) has been
discovered with STM and LEED. STM measurements reveal the formation
of pairs of nanowires showing a continuous, dense character of
the first nanowire and a cluster-like periodic assembly in the internal
structure of the second one. Band mapping with angle-resolved photoemission
confirmes one-dimensional anisotropy of the electronic structure
of the system. Based on quantum size effects observed in photoemission
from the valence band of the clean 15 × 3 surface carbide, a crystallographic
model of the substrate relaxation is proposed as explanation for
the nanowire geometry. In addition, large chemical shifts in the W4f
line permit an element-specific analysis of the self-organized nanowire
formation and reveal the possible role of Au-W surface alloying.
O 32.3 Do 11:45 H38
Epitaxial growth of transition metals on the Ir (100) - (5 ×
1) surface — •Chiara Giovanardi, Andreas Klein, Andreas
Schmidt, Lutz Hammer, and Klaus Heinz — Lehrstuhl für
Festkörperphysik, Universität Erlangen- Nürnberg, Staudtstr. 7,
D-91058 Erlangen
The early growth stages of transition metals (Fe, Ni, Co) on the quasihexagonally
reconstructed Ir(100)-(5×1) surface have been studied by
Scanning Tunnelling Microscopy (STM) and quantitative Low Energy
Electron Diffraction (LEED). The periodic corrugation of the reconstructed
Ir surface rules the growth of the metal by promoting the diffusion
of atoms within the one dimensional troughs of the surface layer.
At sub-monolayer coverage, linear chains are therefore formed with their
length increasing with increasing substrate temperature during deposition.
Laterally, the chains are mostly diatomic, but for Ni and Co also
triple and quadruple chains are observed. Recently published DFT calculations
[1] claim that Fe atoms reside in short bridge sites, while our
experimentally based LEED analisys favours the long bridge position, as
directly imaged by STM in the case of Ni chains, too. With increasing
coverage, the hexagonal reconstruction is locally lifted. This is prior to
the chain phase covering the whole surface and a surface compound (e.
g. Fe4Ir ) forms.
[1] D. Spiˇsák and J. Hafner, Surf. Sci. 546 (2003) 47
O 32.4 Do 12:00 H38
Temperature dependence of surface morphology at grazing
incidence ion bombardement on Pt(111) — Henri Hansen,
•Sebastian Messlinger, Celia Polop, and Thomas Michely —
I. physikalisches Institut, RWTH-Aachen, Postfach, 52056 Aachen

Oberflächenphysik Donnerstag
A Pt(111) surface is bombarded with 5 keV Ar + ions under an incident
angle of 83 ◦ to the surface normal. The projection of the ion beam on the
surface is orientated along the [¯1¯12] direction, so that the ions impinge
onto {111} microfacetted dense packed steps. After bombardement the
surface is investigated by STM.
Using temperatures between 350 K and 720 K the experiments are carried
out both in the submonolayer regime and in the multilayer regime
(fluences up to 20 ML). For submonolayer fluences there are three temperature
regimes with different kinds of damage patterns: for high temperatures
(630 K - 720 K) the remaining vacancy islands have the energetically
favoured hexagonal equilibrium shape. Going to intermediate
temperatures of 450 K - 600 K long, elongated vacancy islands can be
observed, which are orientated along the ion beam projection. For temperatures
lower than 400 K long, branched vacancy islands appear.
Increasing the fluence to 20 ML (multilayer regime) for temperatures
lower than 500 K the ion beam forms deep ripple structures with a good
lateral periodicity, whereas for higher temperatures layer-by-layer erosion
can be observed. The temperature dependency of the damage patterns
can be understood by taking into account that the damage each
ion impact produces can anneal with different rates due to the different
thermally activated diffusion processes.
O 32.5 Do 12:15 H38
Preparation and Characterization of regularly arranged
diamond field emitters using gold nanomasks — •Frank
Weigl 1 , Oliver Pursche 1 , Christof Dietrich 1 , Berndt
Koslowski 1 , Alfred Plettl 1 , Hans-Gerd Boyen 1 , Paul
Ziemann 1 , Silke Riethmüller 2 , Christoph Hartmann 2 und
Martin Möller 2 — 1 Abteilung Festkörperphysik, Universität Ulm,
D-89069 Ulm — 2 Abteilung Organische Chemie III, Universität Ulm,
D-89069 Ulm
Small structures showing field emission are of great importance for new
electron sources, e. g. for flat panel displays. We present a novel method
to produce regularly arranged uniform diamond field emitters exploiting
gold nanoparticles as etching masks. Inverse diblock copolymer micelles
loaded with gold salt are deposited onto boron doped (001)-oriented diamond
substrates resulting in a hexagonally ordered monomicellar film. In
a subsequent plasma step the polymer is removed and pure gold particles
are obtained while maintaining the hexagonal order of the micellar array
[1]. In a subsequent anisotropic etching step uniform diamond tips with
a height of 45nm and a diameter of 10nm (FWHM) are prepared. Their
emission properties are investigated using a standard diode setup as well
as scanning tunnelling microscopy and spectroscopy.
[1] G. Kästle et al., Adv. Func. Mat., 13, 853 (2003)
O 32.6 Do 12:30 H38
Fs laser activated fluorescence from silver oxide nanoparticles
— •T. Gleitsmann, B. Stegemann, T. M. Bernhardt, and L.
Wöste — Freie Universität Berlin, Institut für Experimentalphysik,
Arnimallee 14, D-14195 Berlin, Germany
O 33 Organische Dünnschichten II
Fluorescence from silver oxid nanoparticles was investigated by means
of confocal scanning laser microscopy. This setup allowed us to perform
very fast photo activation by scanning focused 800 nm fs-pulses from a
Ti: Saphire laser over the thin particle film. Fluorescence of the nanoparticles
was excited by subsequent scanning over the sample with an Ar/Kr
- laser. Depending on excitation wavelengths (488 nm or 576 nm) strong
fluorescence in the green or red domain was observed. The writing efficiencies
were examined both as functions of excitation intensity and
exposure time.
O 32.7 Do 12:45 H38
Nanowires and Nanorings at the Atomic Level — •Bert
Voigtländer, Midori Kawamura, Neelima Paul, and Vasily
Cherepanov — ISG 3 Forschungszentrum Jülich
The step-flow growth mode is used to fabricate Si and Ge nanowires
with a width of 3.5nm and a thickness of one atomic layer (0.3nm) by
self-assembly. Alternating deposition of Ge and Si results in the formation
of a nanowire superlattice covering the whole surface. One atomic
layer of Bi terminating the surface is used to distinguish between the elements
Si and Ge. A difference in apparent height is measured in scanning
tunnelling microscopy (STM) images for Si and Ge, respectively. Also different
kinds of two-dimensional Si/Ge nanostructures like alternating Si
and Ge nanorings having a width of 5-10nm were grown.
O 32.8 Do 13:00 H38
Chiral one-dimensional structure formation of di-L-Phenylalanine
(Phe-Phe) on Cu(110) — •Thomas Classen, Frank Stadler,
Giovanni Costantini und Klaus Kern — Max-Planck-Institut
für Festkörperforschung Stuttgart, Heisenbergstr 1, 70569 Stuttgart
Amino acids are at the heart of many biological processes. Furthermore,
they also represent some of the most basic chiral molecules. An
investigation of amino acids on metal single crystal surfaces therefore allows
not only a linking of surface science to elemental biological building
blocks but also opens perspectives for enantioselective catalysis on metal
surfaces.
While the adsorption of simple amino acids on various metal surfaces
has already been studied, only few investigations exist on the deposition
of larger amino acid based compounds under the highly controlled
conditions allowed by an ultra high vacuum environment. The next step
in an increasing hierarchy of complexity are dipeptides consisting of two
amino acids with two chiral centers. In the presented work we have investigated
sub-monolayer coverages of di-L-Phenylalanine (Phe-Phe) on
Cu(110). The chiral adhesion geometry of the resulting 1-dimensional nanostructures
could be proven by means of variable temperature scanning
tunnelling microscopy (VT-STM). Chirality is shown to be reflected not
only in the individual molecule adhesion geometry but also in the intermolecular
binding and the 1D-structure formation.
Zeit: Donnerstag 11:15–13:00 Raum: H39
O 33.1 Do 11:15 H39
Differentielle Reflexionsspektroskopie an hochgeordneten organischen
Schichten: PtOEP auf Kaliumbromid — •Thomas Dienel
1 , Holger Proehl 1 , Yong-Young Noh 2 , Torsten Fritz 1 und
Karl Leo 1 — 1 Institut für Angewandte Photophysik, Technische Universität
Dresden, 01062 Dresden, Germany — 2 Department of Materials
Science and Engineering, Kwangju Institute of Science and Technologie
(K-JIST), Gwangju, South Korea
In elektronischen Bauelementen aus organischen Molekülen ist die
Beweglichkeit der Ladungsträger, die durch die Anordnung der Moleküle
beeinflusst werden kann [1], von entscheidender Bedeutung. Ausgehend
von dieser Veröffentlichung, in der die Molekülorientierung in
PTOEP (Platin-2,3,7,8,12,13,17,18-Oktaethyl-21H,23H-Porphyrin) Filmen
auf Kaliumbromidkristallen in Abhängigkeit von der Präparation
des Substrats beschrieben wird, wurde dieses Materialsystem im UHV
untersucht.
Die Verwendung von organischer Molekularstrahlepitaxie (OMBE) in
Kombination mit Differentieller in situ Reflexionsspektroskopie (DRS)
ermöglicht dabei, durch die Korrelation von optischen Eigenschaften und
Schichtstruktur, das Schichtwachstum zu untersuchen. Für dünne Schichten
auf transparenten Substraten spiegelt das DRS-Signal die Absorption
der adsorbierten Schicht wider. Die Unterschiede beim Übergang
von der Monomerabsorption des Einzelmoleküls zur Kristallabsorption
in der wachsenden PtOEP-Schicht, konnte auf die Substratpräparation
zurückgeführt werden.
[1] Y.-Y. Noh et al., Adv. Mater., 2003, 15, 699
O 33.2 Do 11:30 H39
Self-assembled monolayers of terphenyl-substituted alkanethiolates
on Au(111) and Ag(111) — •Andrey Shaporenko 1 ,
Markus Brunnbauer 2 , Andreas Terfort 2 , Lars Johansson 3 ,
and Michael Zharnikov 1 — 1 Angewandte Physikalische Chemie,
Universität Heidelberg, 69120 Heidelberg — 2 Anorganische und Angewandte
Chemie, Universität Hamburg, 20146 Hamburg — 3 Department
of Physics, Karlstad University, S-65188 Karlstad, Sweden
The packing density and exact arrangement of the molecular constituents
in monomolecular films result from the interplay of the
headgroup-substrate and intermolecular interactions. To get an insight

Oberflächenphysik Donnerstag
into the respective phenomena, we have studied self-assembled monolayers
(SAMs) formed from terphenyl-substituted alkanethiols with varying
length of the alkyl part on (111) Au and Ag substrates. We used several
complementary experimental techniques such as X-ray photoelectron
spectroscopy (XPS), high-resolution XPS, near edge X-ray absorption
fine structure spectroscopy, infrared reflection absorption spectroscopy,
ellipsometry, and water contact angle measurements to characterize the
SAMs. Odd-even changes in the packing density and orientation of the
terphenyl moieties, etc have been observed and considered in detail. The
results imply a predominant role of the headgroup-substrate interaction
in the balance of structure-building forces in the aliphatic SAMs.
O 33.3 Do 11:45 H39
Using a focused soft X-ray beam for the characterization
and fabrication of monomolecular patterns — •Michael
Zharnikov 1 , Ruth Klauser 2 , Anne Paul 1 , Armin Gölzhäuser 1 ,
S.-C. Wang 2 , I.-H. Hong 2 , and Michael Grunze 1 — 1 Angewandte
Physikalische Chemie, Universität Heidelberg, 69120 Heidelberg, Germany
— 2 National Synchrotron Radiation Research Center, Hsinchu
30077, Taiwan (ROC)
We have utilized scanning soft X-ray photoelectron spectromicroscopy
to image and characterize different electron-beam patterned selfassembled
monolayers (SAMs) on gold substrates. The lateral structures
in all SAM-based patterns could be clearly distinguished. The irradiated
areas generally revealed a smaller Au 4f intensity and a higher C1s intensity
than non-irradiated ones due to the adsorption of airborne carboncontaining
molecules on more hydrophilic and rough irradiated areas.
Also, chemical changes in some of the resists could be directly monitored
as soon as the respective emissions were intense enough as compared to
the inelastic background. In addition, we found that the highly intense
zone-plate-focused soft X-ray beam can cause non-intentional irradiationinduced
modification of the SAMs during the SPEM image acquisition.
Taking advantage of this phenomenon, we demonstrate that the X-ray microprobe
can be utilized for in-situ surface patterning of the monomolecular
SAM resist with subsequent imaging of the fabricated patterns.
O 33.4 Do 12:00 H39
Electron-vibron coupling in the NEXAFS spectra of large organic
molecules — •Dominique Hübner 1 , A. Schöll 1 , R. Fink 2 ,
K.C. Prince 3 , R. Richter 3 , S. Stranges 4 , and E. Umbach 1 —
1 Univ. Würzburg, Exp. Phys. II — 2 Univ. Erlangen, Phys. Chem. II —
3 Sincrotrone Trieste — 4 CNR-Istituto di Metodologie Inorganiche e dei
Plasmi
High-resolution NEXAFS spectroscopy is ideally suited to investigate
the electronic structure of large organic molecules in both, the
condensed and the gas phase. In ideal cases one observes distinct fine
structures which are attributed to the electron vibron coupling. Astonishingly,
the electronic excitations significantly couple to few vibronic
states. We present NEXAFS data on the heteroaromatic molecule acenaphthenequinone
(ANQ). ANQ is at present the largest molecule for
which vibronic fine structure has been observed for O K-edge excitations.
Remarkably, the O K-edge spectra of the condensed and gas phase
hardly differ. The well-resolved data furthermore allow to describe the
anharmonicity of the excited state potential. Whereas there are no differences
for O 1s excitations, the comparison for the C K-edge for the
condensed and gas phase gives clear hints that the π-interactions between
neighboring molecules mostly involves the aromatic core. The project is
financed by BMBF under contract 05 KS1 WWA/5.
O 33.5 Do 12:15 H39
Effects of the molecular electric dipole on the HOMO-band
fine structure: metal-phthalocyanine on graphite — •Satoshi
Kera 1,2 , Hiroyuki Yamane 3 , and Nobuo Ueno 3 — 1 Exp. Phys. II,
Univ. Würzburg, Am Hubland, 97074 Würzburg — 2 Institute for Molecular
Science, Okazaki 444-8585, Japan — 3 Chiba Univ., Inage-ku, Chiba
263-8522, Japan
Photoelectron fine structures were observed for metal-phthalocyanine
(Pb-, and OTiPc) ultrathin films on HOPG. They have an electric dipole
perpendicular to the π-conjugated plane, hence a well-defined dipole layer
could be intentionally produced by preparing an oriented monolayer. For
the OTiPc film with asgrown island, in which staggered doublelayers are
formed, we observed two prominent peaks for the HOMO band (single
π state) originating from different molecular orientations in the islands.
Upon annealing, they form a uniform monolayer with the O atom protruding
into the vacuum, and give an unusually sharp HOMO band [1].
The EB difference of the HOMO bands between the staggered doublelayer
and the oriented monolayer was found to agree with the Evac shift, leading
to the conclusion that the relative position of the molecular energy
level with respect to the substrate EF can be changed due to the dipole
layer. These results suggest that we can tailor device interface properties
by controlling the direction and/or the magnitude of the molecular electric
dipole. Moreover it is also interesting to discuss the origins of the
HOMO-bandwidth at the organic/inorganic interfaces. [1] S. Kera et al,
Chem. Phys. Lett. 364, 93 (2002).
O 33.6 Do 12:30 H39
Preparation of submicron-structured alkylsiloxane monolayers
using prepatterned silicon substrates by laser direct writing —
•Nils Hartmann, Thorsten Balgar, and Eckart Hasselbrink
— Universität Duisburg-Essen, Fachbereich Chemie, Universitätsstr. 5,
45141 Essen
A new constructive method for the preparation of laterally structured
alkylsiloxane monolayers is demonstrated. Laser direct writing has been
used to create oxide patterns on H-terminated Si(100) samples under
ambient conditions. Depending on the laser power and the writing speed
oxide structures with a lateral resolution below 500 nm can be prepared
routinely. The patterned samples are suitable as temporary templates
for the preparation of laterally structured octadecylsiloxane monolayers.
Prior to immersion in an octadecyltrichlorosilane (OTS) solution,
however, a hydration of the samples in water is essential to facilitate a
selective coating of the oxidized areas. After coating, atomic force microscopy
(AFM) reveals the formation of octadecylsiloxane islands exclusively
along the oxide lines.
O 33.7 Do 12:45 H39
Epitaxy of titanyl phthalocyanine on Au(111) surfaces —
•Karsten Walzer, Stefan Mannsfeld, Holger Pröhl, Thomas
Dienel, Torsten Fritz, and Karl Leo — Institut für Angewandte
Photophysik, TU Dresden, 01062 Dresden
Organic molecular beam epitaxy (OMBE) was applied to grow titanyl
phthalocyanine (TiOPc) thin films on a Au(111) single crystalline surface
in UHV. The growth was monitored by differential reflection spectroscopy
(DRS) in situ, yielding data for submonolayer up to multilayer coverage.
Using STM and LEED, we studied the epitaxial growth behaviour. We
observed both well-ordered 2d structures and the formation of 3d densely
packed crystals. The dimension of the unit mesh in the monolayer regime
was obtained from LEED measurements. From the structural data and
subsequently performed simulations we conclude that the orientation of
the domains in the first monolayer is determined by the substrate lattice.
In some cases also the intramolecular structure was resolved by STM.
We found that especially in small vacancies of the monolayer often one
molecule is confined, which appears rotated (in-plane) with respect to
the surrounding phthalocyanine molecules.

Oberflächenphysik Donnerstag
O 34 Oxide und Isolatoren
Zeit: Donnerstag 11:15–13:00 Raum: H45
O 34.1 Do 11:15 H45
Investigations of SrO and BaO on the Si(001) surface — •J.
Zachariae and H. Pfnür — Institut für Festkörperphysik, Universität
Hannover, Appelstr. 2, 30167 Hannover
In an attempt to generate epitaxial medium k (ǫr ≈ 30) BaO/SrO
films we investigated the growth conditions, crystalline quality and stoichiometry
using high resolution LEED, UPS, XPS and EELS. Epitaxial
SrO and lattice matched Ba1−xSrxO layers were grown on a Sr/Si(001)
interface in UHV by evaporation of the metals in a ambient oxygen pressure.
The quality of oxide layers strongly depends on two conditions: The
kind of interface e.g. a (5 × 1)-reconstructed Sr-layer and the accurate
oxygen dose, which was determined by mass accumulation on a quartz
crystal micro balance. A correct fraction of Ba and Sr in the mixed oxide
layers leads to well ordered and lattice matched oxide films from a few
monolayers up to 20 nm and more, as seen by the sharper (1 ×1)-LEEDpattern
of the Ba1−xSrxO layers compared to the pattern of the SrO
layers. The electronic structure as a function of the interface properties
and the layer thickness will be discussed.
O 34.2 Do 11:30 H45
Ab initio embedded cluster study of optical second harmonic
generation below the gap of the NiO(001) surface — •Khompat
Satitkovitchai and Wolfgang Hübner — FB Physik, Technische
Universität Kaiserslautern, Erwin-Schrödinger-Straße, D-67663 Kaiserslautern
An embedded cluster approach is applied to study the electronic excitations
on the NiO(001) surface. Using a quantum chemistry calculation, a
small (NiO5) 8− cluster is embedded in a set of point charges to model the
NiO(001) surface. Starting on the unrestricted Hartree-Fock (UHF) level
of theory we calculate ground-state properties to provide some insight of
electronic structure and excitation. We estimate the excitation energies
using the single excitation configuration interaction (CIS) technique. We
then demonstrate the electron correlation effects on the d–d transitions
at several levels of ab initio correlated theory (CID, CISD, QCISD and
QCISD(T)). The electron correlation tends to decrease the magnitude of
d–electron excitation energies. Using the many-body wave-functions and
energies resulting from QCISD(T) calculation we compute the second
harmonic generation (SHG) tensor for the NiO(001) surface. From that,
the intensity of the non-linear optical response at different polarizations
is obtained. This quantity can be directly measured in experiment, and
we suggest possible conditions in order to detect it.
O 34.3 Do 11:45 H45
Ligand Field Approach to Optical Second Harmonic Generation
on NiO(001) and CoO(001) surfaces — •Oleksandr Ney and
Wolfgang Hübner — Department of Physics, Kaiserslautern University
of Technology, Box 3049, 67653 Kaiserslautern
Surfaces and interfaces of transition-metal oxides (TMO) play an important
role in technological applications. The strongly correlated 3delectrons
induce interesting effects, however making such materials difficult
to describe theoretically. To explore the interfacial properties the
optical Second Harmonic Generation (SHG) technique as a nondestructive,
easy to implement, and powerful tool may be applied.
In this work we compute the SHG response from the metal ion on
the (001) surfaces of NiO and CoO. Calculation of states, active in optical
SHG, is performed by using the Hubbard model, Clebsch-Gordan
technique, and parametrized ligand field approach. This combination is
capable of describing the higher lying states in transition metal oxides.
Ionic bonding between metal and oxygen ions is assumed.
As a result, the static dependences of prototypic nonmagnetic and antiferromagnetic
(AF) nonlinear susceptibility tensor elements are calculated.
Comparison of those spectra gives the energies for which the interference
of magnetic and crystallographic contributions may be detected
in the SHG experiment, thus allowing to detect the magnetic structure of
the interface. Although there are more states within the gap for CoO(001)
than for NiO(001), the former one might be as useful for technological
applications, which also stimulates further investigations in FeO(001).
O 34.4 Do 12:00 H45
Oxidation von Ag(100) bei atmosphärennahen Drücken —
•Ioan Costina 1 , Hannes Schiechl 2 , Andreas Stierle 1 , Michael
Schmid 2 , Peter Varga 2 und Helmut Dosch 1 — 1 Max-Planck
Institut für Metallforschung, Heisenbergstrasse 3, 70569 Stuttgart,
Deutschland — 2 Institut für Allgemeine Physik, Technische Universität,
Wien, Österreich
Sauerstoff ist ein Schlüsselschritt in der katalytischen Anwendung von
Silber für die selektive Oxidationen von Ethylen und der Oxydehydrogenierung
von Methanol. Hierbei ist vor allem die Adsorption und Dissoziation
von Sauerstoff auf Silberoberflächen von großem Interesse, da
man je nach Reaktionsbedingungen unterschiedliche Reaktionsprodukte
erhält. Dafür werden unterschiedliche Oberflächenspezies verantwortlich
gemacht. Die Oxidation der Ag(100) Oberfläche bei einem Sauerstoffpartialdruck
von 10 mbar und bei einer Temperatur von 470 K führt
zur Bildung einer wohlgeordneten Oxidschicht. Die Struktur dieses Oxids
wurde mittels Rastertunnelmikroskopie (RTM), Beugung niederenergetischen
Elektronen (LEED), Augerelektronspektroskopie (AES) und oberflächensensitiver
Röntgenbeugung (SXRD) untersucht. Das LEED Bild
der Oxidschicht zeigt eine c(4×6) Überstruktur mit 2 Domänen die gegeneinander
um 90 ◦ gedreht sind. Aus den LEED, STM und SXRD-
Messungen wurde ein Strukturmodel für die Silberoxidschicht abgeleitet.
O 34.5 Do 12:15 H45
In situ Oberflächenröntgenbeugung an Sauerstoff auf Ag(111)
— •Alexander Reicho, Andreas Stierle, Ioan Costina und
Helmut Dosch — Max-Planck Institut für Metallforschung, Heisenbergstrasse
3, 70569 Stuttgart, Deutschland
Silber spielt eine wichtige Rolle als Katalysator bei der Epoxidation
von Ethylen und der partiellen Oxidation von Methanol zu Formaldehyd.
Es ist unklar, ob die katalytische Wirkung des Silbers durch ein
Oberflächenoxid hervorgerufen wird. Wir haben daher in situ Oberflächenröntgenbeugungsuntersuchungen
bei verschiedenen Sauerstoffpartialdrücken
und Temperaturen durchgeführt. Auf der Ag(111) Oberfläche
bildet sich bei einem Sauerstoffpartialdruck von 100 mbar und einer Temperatur
von 500 K eine geschlossene Oxidschicht mit p(4×4) Rekonstruktion.
Im Vortrag wird ein Strukturmodell der Oxidschicht vorgestellt
und dieses mit einem Modell basierend auf STM-Messungen verglichen.
Des weiteren wird ein Phasendiagramm des O/Ag(111)-Systems in
Abhängigkeit von Druck und Temperatur präsentiert und ein Vergleich
mit Dichtefunktionaltheorie-Berechnungen vorgenommen.
O 34.6 Do 12:30 H45
High-resolution core-level spectroscopy and LEED investigations
of Ga2O3 on CoGa(100) surface — •Alina Vlad 1 , I.
Costina 1 , A. Stierle 1 , H. Dosch 1 , E. Lundgren 2 , and J. Anderson
2 — 1 Max-Planck Institut für Metallforschung, Heisenbergstraße 1,
70569 Stuttgart — 2 Department of Synchrotron Radiation Research,
Institute of Physics, University of Lund, Box 118, SE-221 00 Lund,
Sweden
Ultra-thin oxide films are of interest for fundamental studies, as well
as for industrial applications in sectors like heterogeneous catalysis, microelectronics,
high-density data storage technologies. As an example, we
investigated the thermally controlled oxidation of CoGa(100) using High
Resolution Core Level Spectroscopy (HRCLS) and Low Energy Electron
Diffraction (LEED) techniques. HRCLS measurements have been performed
after oxidation at different temperatures up to 750 o C and pressures
between 10 −8 and 5 · 10 −5 mbar O2 on the beamline I 311 at the
Max-lab II, Sweden. After the oxidation at 450 o C an ordered ultra-thin
oxide layer is formed, which shows in LEED a (2 x 1) reconstruction.
After the oxidation at 750 o C and 5 · 10 −5 mbar O2, the LEED patterns
indicate the change in the surface orientation of the oxide layer accompanied
by surface faceting. Also, an additional component shifted to higher
binding energy was observed both in Ga 3d and O 1s spectra.
O 34.7 Do 12:45 H45
SPA-LEED Studies of CoO Thin Films on Ag(100) —
•Jian Wang, Ina Sebastian, Karl-Michael Schindler,
Klaus Meinel, Henning Neddermeyer, and Wolf Widdra —
Martin-Luther-Universität Halle-Wittenberg, FB Physik, D-06099 Halle

Oberflächenphysik Donnerstag
The growth morphology of CoO films deposited in the temperature
range of 300-500 K has been studied by Spot Profile Analysis of Low
Energy Electron Diffraction (SPA-LEED). At a coverage of 3 ML the
growth is pseudomorphic to the Ag(100) substrate with a compression of
4% in the CoO film. Relaxation to the bulk lattice of CoO occurs at a
O 35 Hauptvortrag Bauer
coverage of 6 ML. At 10 ML, splitting of the (00) spot indicates the presence
of terraces which we relate to the carpet growth mode of the film.
Upon annealing in O2 at 500 K, both CoO(100) and CoO(111) structures
were found, whereby the (111) structure shows a ( √ 3 × √ 3)R30 ◦
reconstruction. The corresponding structural model will be presented.
Zeit: Donnerstag 14:00–14:45 Raum: H36
Hauptvortrag O 35.1 Do 14:00 H36
Femtosecond ultraviolet photoelectron spectroscopy for the
study of ultrafast surface processes — •Michael Bauer — Fachbereich
Physik, TU Kaiserslautern, 67663 Kaiserslautern, Deutschland
The technique of ultraviolet photoelectron spectroscopy allows detailed
insights into static properties of molecular adsorption such as bond character,
adsorption geometry or intermolecular interaction.
In combination with an optical pump-probe scheme this technique can
in principle also be used to monitor changes in the adsorbate state on a
femtosecond time-scale and, in consequence, the evolution of the chemical
O 36 Hauptvortrag Weinelt
surface state during the course of a chemical reaction. This has become
possible by the development of laser-driven short-pulse EUV sources delivering
sub-10 fs pulses at photon energies of up to 500 eV.
Recent experimental results will be presented that show the potential
of time-resolved UPS for such studies. In particular it is possible to
identify and follow different steps within a surface chemical reaction at
a time-resolution < 50 fs. This includes the electronic excitation of the
system under investigation, the consequent change in the chemical state
of an adsorbed molecule and the real-time observation of a vibrational
excitation of the adsorbate.
Zeit: Donnerstag 14:45–15:30 Raum: H36
Hauptvortrag O 36.1 Do 14:45 H36
Dynamics of electron relaxation and exciton formation on
Si(001) — •Martin Weinelt — Lehrstuhl für Festkörperphysik,
Universität Erlangen-Nürnberg, Staudtstr. 7, 91058 Erlangen, Germany
Carrier dynamics in silicon is of both fundamental and technological
importance. Equally relevant as the knowledge of the bulk electronic
properties is the understanding of electron dynamics at interfaces. Coupling
of bulk electrons to surface or interface states can dominate electron
recombination and affects device performance. The underlying electrontransfer
processes occur on (sub-)picosecond timescale and can be studied
O 37 Zeitaufgelöste Spektroskopie I
following the electron dynamics after femtosecond-pulse laser excitation.
Identification of the individual processes of carrier scattering, trapping
and recombination requires a detailed knowledge of the surface electronic
structure. The necessary comprehensive information of momentum, energy
and lifetime of excited electrons is obtained by means of angle-,
energy-, and time-resolved two-photon photoelectron spectroscopy. Combining
this experimental approach with many-body perturbation theory
the dynamics of excited electronic states at the Si(100) surface is elucidated.
The recombination of hot carriers at the surface is ruled by
picosecond relaxation of excited electron-hole pairs, resulting in the formation
of an exciton which lives for nanoseconds.
Zeit: Donnerstag 15:45–17:30 Raum: H36
O 37.1 Do 15:45 H36
Electron-phonon coupling for surface states on Pd(111) —
•Andrea Melzer, Martin Weinelt, and Thomas Fauster —
Lehrstuhl für Festkörperphysik, Staudtstraße 7, D-91058 Erlangen
Electrons in surface states can be scattered by phonons to bulk states
or to states within the surface band at different parallel momentum. The
first process usually requires phonons with large momentum compared
to the second process. On the Pd(111) surface an unoccupied sp-like
surface state exists and can be studied by time-resolved two-photon photoemission.
Scattering to bulk states reduces the population in contrast
to scattering within the surface band. The first process shows up in a
reduced lifetime while both processes increase the linewidth. We have
measured the change of lifetime and linewidth for the surface state on
Pd(111) for variable temperatures up to 900 K. For the electron-phonon
mass enhancement parameter a value of 0.36 is found which is significantly
larger than for the occupied surface states on other fcc(111) surfaces.
The time-resolved data indicate large contributions from intraband
scattering in contrast to theoretical expectations.
O 37.2 Do 16:00 H36
Break junctions under femtosecond laser illumination:
steps towards time-resolved photocurrent spectroscopy on
the nanoscale — •W. Pfeiffer 1 , S. Dantscher 1 , C. Kennerknecht
1 , S. Schramm 1 , H.B. Weber 2 , and J.U. Würfel 2 —
1 Physikalisches Institut EP1, Universität Würzburg, 97074 Würzburg
— 2 Forschungszentrum Karlsruhe, Institut für Nanotechnologie,
D-76021 Karlsruhe
Microscopic break junctions provide fascinating possibilities to investigate
microscopic charge transport phenomena. Up to now the studies
are restricted to DC current measurements. Consequently, the illumination
of the contact and the investigation of the resulting photocurrents
opens a new field of research. Especially, ultrashort laser pulses combined
with time-resolved spectroscopy could then reveal details of the charge
transfer dynamics that are of utmost importance for the understanding
of the conductivity in nanoscale contacts. We present first experiments
on the illumination of tunnel junctions and single molecule contacts with
ultrashort laser pulses (800 nm and 400 nm, 50 fs). The junctions are
stable up to intensities of 10 8 Wcm −2 and thus allow the investigation of
microscopic transport in intense laser fields. The mechanisms leading to
a light induced modulation of the conductance are discussed for tunnel
junctions and single molecule contacts.
O 37.3 Do 16:15 H36
Lifetimes of quasiparticle excitations in 4d transition metals
Mo and Rh — •Alexander Mönnich, Daniela Bayer, Michael
Bauer, and Martin Aeschlimann — Dep. of Physics, University of
Kaiserslautern, D-67663 Kaiserslautern
The dynamics of excited electrons in metals are crucial for a detailed
understanding of various chemical and physical phenomena on metal surfaces.
It is already known that noble metals show a longer lifetime of
quasiparticle excitations than transition metals due to the higher densityof-states
around the Fermi level. But also the electron dynamics between
different transition metals can exhibit significant divergences.
With the time resolved two-photon photoelectron spectroscopy (TR-
2PPE) method we investigated the electron dynamics of Mo and Rh in an
energy range up to 3eV above the Fermi level. LMTO-RPG-GW calculations
predict a surprising large difference between the averaged lifetimes
of electron quasiparticles in the 4d transition metals Mo and Rh [1] that
were confirmed in our experiment. The characteristics of electronic structure
responsible for energy dissipation processes of hot electrons will be
discussed.
[1] V. P. Zhukov, F. Aryasetiawan, E. V. Chulkov, P. M. Enchenique
PRB 65 11511 (2002)

Oberflächenphysik Donnerstag
O 37.4 Do 16:30 H36
Image-potential states on stepped Cu(11l) surfaces —
•Manfred Roth, Martin Weinelt, and Thomas Fauster
— Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg,
Staudtstr. 7/A3, 91058 Erlangen
The dynamics of image-potential states on stepped Cu(11l) surfaces
has been studied with time- and angle-resolved two-photon photoemission.
In comparison to the Cu(001) surface the image-potential states
on the stepped surfaces show increased decay and dephasing rates [1].
A direction-dependent resonant scattering process with large momentum
transfer was observed [2], which leads to strong interband scattering from
the n = 2 to the n = 1 image-potential state band. The intensity of this
scattering depends on the regularity and the mean terrace width of the
step arrangement [3]. Further the anisotropic scattering leads to an asymmetric
behavior of the lifetime in the n = 1 image-potential-state band.
This can be explained by a direction-dependent reflection at the step
edges, found by scanning tunneling spectroscopy [4]. The dependence of
the mentioned effects on the step density will be discussed.
[1] M. Roth, M. Pickel, J. Wang, M. Weinelt, and Th. Fauster, Appl.
Phys. B 74, 661 (2002)
[2] M. Roth, M. Pickel, J. Wang, M. Weinelt, and Th. Fauster, Phys.
Rev. Lett. 88, 096802 (2002)
[3] M. Roth, M. Pickel, M. Weinelt, and Th. Fauster, Appl. Phys. A 78,
149 (2004)
[4] M. Roth, M. Weinelt, Th. Fauster, P. Wahl, M. A. Schneider, L.
Diekhöner, and K. Kern, Appl. Phys. A 78, 155 (2004)
O 37.5 Do 16:45 H36
Treatment of many-body effects in sodium clusters by means of
GW theory — •Yaroslav Pavlyukh and Wolfgang Hübner —
FB Physik, TU Kaiserslautern, D-67663 Kaiserslautern, Germany
The GW approximation for the calculation of electronic properties
of systems without translational invariance like clusters or molecules is
presented. In our implementation of the GW approximation we use the
expansion of all quantities in gaussian type basis functions. The Green
function, screened interaction, and self-energy are represented on the real
axis of the frequency domain. The dielectric function is treated without
any simplifications, such as the plasmon pole approximation. Convolutions
are performed using fast Fourier transforms to the real time and
back. We apply our approach to the range of Nan clusters (n=9-25).
We present ionization potentials, electron affinities, band-gaps, plasmon
energies, and life-times of quasiparticle states and collective excitations,
which shows exellent agreement with experiments and other theories,
such as TDLDA. A partially self-consistent GW calculation on Na + 9 cluster
enables us to improve the HOMO-LUMO gap (4.5 eV – HF, 3.7 eV
– G0W0, 3.37 eV GW) and to determine the plasmon width and lifetime
(2 eV and 4.1 fs, respectively).
O 38 Adsorption an Oberflächen III
O 37.6 Do 17:00 H36
Fs-Laserpulspropagation in Single-Mode Glasfasern —
•Georgios Ctistis, Jan Podsiadly, Jens J. Paggel und Paul
Fumagalli — Institut für Experimentalphysik, Freie Universität
Berlin, Arnimallee 14, 14195 Berlin
Die Ausbreitung von Kurzzeitpulsen in dispersiven Medien ist ein nicht
nur für die Telekommunikation wichtiges Gebiet. Bisher wurde intensiv
an ps-Laserpulsen experimentell wie theoretisch geforscht. Der Übergang
zu fs-Pulsen führt nun zu noch größeren Übertragungsraten in der Telekommunikation,
jedoch scheint das Verhalten von fs-Pulsen in den dispersiven
Medien erst jetzt in das Interesse der Forschung zu rücken.
Es werden erste Experimente zum Durchgang von fs-Laserpulsen durch
SM-Glasfasern bei einer Wellenlänge von 820 nm gezeigt. Der Einfluss
der Faserlänge auf die Pulsverbreiterung wurde ebenso geprüft wie die
Abhängigkeit von der eingestrahlten Leistung des benutzten Ti:Sa-Lasers
bei einer Pulsbreite von etwa 150 fs. Die beobachtete Pulsbreite hängt dabei
nichtlinear von der Laserleistung ab und ist um ein vielfaches größer
als theoretisch erwartet.
Gefördert durch die DFG über SPP 1133.
O 37.7 Do 17:15 H36
Femtosecond electron dynamics in amorphous and crystalline
ice layers on Ru(001) — •Martin Wolf, Cornelius Gahl, Julia
Stähler, Panagiotis Loukakos, and Uwe Bovensiepen — Freie
Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin
The ultrafast electron transfer and solvation dynamics in D2O layers on
Ru(001) have been studied by time-resolved two-photon-photoemission
(2PPE) spectroscopy. Structural characterization of the ice layers were
carried out by simultaneous measurements of the electronic structure,
work function and the D2O desorption rate as a function of temperature.
Hereby, amorphous and crystalline multilayers as well as the bilayer can
be prepared with high accuracy. We find that the electron dynamics differ
significantly for amorphous and crystalline ice. In amorphous layers,
electron solvation, characterized by a time-dependent shift of the electron
binding energy by 1 eV/ps, as well as the population decay, occurs much
faster compared to the dynamics observed previously in amorphous D2O
layers on Cu(111) [1]. This is attributed to structural differences of the
first bilayer and more efficient electron backtransfer to the Ru substrate.
Moreover, the binding energy of the solvated state increases at a higher
rate on the Ru substrate suggesting a more mobile hydrogen bonded network
than on Cu. In the crystalline ice layers electron solvation is not
been observed, however, trapping of extremly long-lived electrons into
structural defects formed by thermal activation.
[1] Phys. Rev. Lett. 89, 107402 (2002); J. Phys. Chem. B 107, 8706
(2003).
Zeit: Donnerstag 15:45–18:15 Raum: H38
O 38.1 Do 15:45 H38
Electronic and geometrical structure of adsorbed small organic
molecules: formate, 3-thiophene carboxylate and glycinate on
Cu(110) surface — •Nicolae Atodiresei, Kurt Schroeder, and
Stefan Blügel — Institut für Festkörperforschung, Forschungszentrum
Jülich, D-52425 Jülich, Germany
The attachment of carboxylic acids and biological molecules to metal
surfaces has very important applications like molecular recognition and
biosensor development. One interest is focused in the property of chirality
which can be induced by the absorption of organic molecules on surfaces.
We performed ’ab initio’ calculations based on density functional theory
(DFT) using a projector augmented plane wave (PAW) method to
obtain the equilibrium geometry of formate, 3-thiophene carboxylate and
glycinate adsorbed on the Cu(110) surface. All molecules contain a carboxylate
functional group (COO-) which binds to Cu atoms of the first
layer via the oxygen atoms. In the case of formate and 3-thiophene carboxylate
the functional group is sitting perpendicular to the Cu(110)
surface. The relative energies of formate on Cu(110) with different coverages
in (2x2) unit cell are discussed. For the saturation coverage of
3-thiophene carboxylate on Cu(110) ((2x1) unit cell) the thiophene ring
is sitting perpendicular to the metal surface but rotated with 23 0 relative
to the [110] direction. The glycinate molecules form a (3x2) unit cell
with 2 flat-lying molecules. They bind to the Cu surface also via amino
group ( H2N-). The heterochiral arrangement is found to be energetically
more stable than the homochiral one because two hydrogen bonds per
molecule can be formed.
O 38.2 Do 16:00 H38
Atomically resolved diffusion processes of hydrogen on Si(001)
induced by nanosecond heating pulses — •C. Schwalb, M.
Lawrenz, M. Dürr, and U. Höfer — Fachbereich Physik, Philipps-
Universität, D-35032 Marburg
The rearrangement of silicon dangling bonds following pulsed laser
heating of monohydride-covered Si(001) surfaces has been studied with
scanning tunneling microscopy (STM). Laser-induced thermal desorption
(LITD) of small amounts of H2 via the so-called interdimer pathway
leads to the creation of isolated pairs of dangling bonds at two adjacent
dimers [1]. Hydrogen diffusion causes this arrangement of dangling bonds
- which represents an excited state of the surface - to change quickly into
the equilibrium configuration consisting of dangling bonds paired up at a
single dimer. By using multiple nanosecond heating pulses we were able
to freeze the surface at various stages of the equilibration process and
take snapshots with the STM. In this way we were able to monitor hydrogen
diffusion processes with atomic resolution which are associated

Oberflächenphysik Donnerstag
with rates as high as 10 8 s −1 .
[1] M. Dürr et al., Science 296, 1838 (2002).
O 38.3 Do 16:15 H38
Simulation der Desorption von Wasserstoff von bimetallischen
PtRu-Oberflächen — •Thomas Diemant, Hubert Rauscher und
R. J. Behm — Abt. Oberflächenchemie und Katalyse, Universität Ulm,
D-89069 Ulm
Bimetallische PtRu-Systeme finden großen Einsatz als Anodenmaterial
in Niedertemperatur-Brennstoffzellen. Die Untersuchung der Adsorption
und Desorption von Wasserstoff von PtRu-Oberflächen ist deshalb
von besonderem Interesse. Wir haben hier die Desorption von Ptmodifizierten
Ru(0001)-Oberflächen untersucht, die mit pseudomorphen
Pt-Monolagen-Inseln bedeckt waren. Die Filme werden durch die Deposition
von bis zu einer Monolage Platin auf einem Ru(0001)-Einkristall
bei Raumtemperatur und anschließendem Erhitzen auf 900 K erzeugt.
Die Morphologie und Zusammensetzung dieser PtRu-Oberflächen ist aus
früheren STM-Studien bekannt. Durch Vergleich experimenteller TPD-
Daten mit Simulationen auf der Basis verschiedener Modelle wird versucht,
ein genaueres Szenario des Desorptionsverhaltens von diesen bimetallischen
Oberflächen zu entwickeln.
O 38.4 Do 16:30 H38
Nitrile-functionalized molecules adsorbed on Si(001)-2x1
— •Ralf Funke 1 , Stefan Kubsky 1 , Francois Rochet 2 ,
Sylvie Rangan 2 , Holger Stein 1 , and Ulrich Köhler 1 —
1 Experimentalphysik / Oberflächenphysik, Ruhr-Universität Bochum,
44780 Bochum, Germany — 2 Laboratoire de Chimie Physique Matière
et Rayonnement, Université Pierre et Marie Curie, Paris, France
A controlled adsorption behaviour of organic molecules on silicon is
essential for the deposition of organic layers as a first step for molecular
electronics. The adsorption of acrylonitrile and allylnitrile was studied
using STM at 300K and at 90K. These results were correlated with X-ray
photoemission and absorption spectroscopy data. Both molecules adsorb
in a non-dissociative mode. For low coverage a single adsorption site was
found. In the case of acrylonitrile the molecule bridges two adjacent silicon
dimer rows inducing a strong local dimer buckling in one of the rows.
Bias dependent images and MO calculations are used to determine the
adsorption geometry. Time resolved STM images at 90K show a flipping
between local configurations of the molecule on a time scale of seconds.
The four C-atoms of allylnitrile bond in a semicircle-like configuration
to the silicon atoms of two neighbouring dimers in one dimer row.
Whereas in the case of acrylonitrile no long range order in the adsorbate
layer was found, the allylnitrile layer shows a (2x2) periodicity. The above
results show that despite an identical functional CN-group in a molecule
the local bonding to the silicon surface can be completely different.
O 38.5 Do 16:45 H38
Compression of a silver adlayer on Pt single crystal electrode
— •Katrin F. Domke, Helmut Baltruschat , and Xaioyin
Xaio — Institut für Physikalische Chemie, Abteilung Elektrochemie,
Römerstrasse 164, 53117 Bonn
The effect of coadsorption of CO on an underpotentially deposited
(UPD) silver monolayer on Pt(111) and Pt(665) single crystals is investigated
by means of electrochemical scanning tunneling microscopy
(EC-STM) and cyclic voltammetry (CV) in 0.05 M sulfuric acid. Pure
electrochemical experiments suggest that coadsorbing CO onto Pt(111)
covered by a monolayer of Ag forces Ag atoms of the first UPD monolayer
into a second adlayer. The present STM studies reveal the formation of
Ag islands on Pt(111) and Pt(665) after coadsorption of CO. These small
clusters have a narrow size distribution centered around 10 nm diameter
and are of approximately 0.5 nm height. The desorption of the newly
formed second Ag UPD, the oxidation of CO, and the desorption of the
first Ag UPD can be detected in the corresponding CVs in three different
oxidation peaks. STM images recorded afterwards show the unchanged
Pt surfaces.
O 38.6 Do 17:00 H38
Metal diffusion on transition metal dichalcogenide surfaces —
•R. Kunz und R. Adelung — Chair for Multicomponent Materials, Faculty
of Engineering, Christian-Albrechts University, Kaiserstr. 2, 24143
Kiel
The large difference in condensation coefficient is an immanent property
of layered crystals like the transition metal dichalcogenide crystals
(TMDC) for many different adsorbates. It is well documented that after
metal evaporation on such surfaces in UHV, various structures can
be formed in a self organized processes. In order to understand why
the different structures occur, a systematic study of the growth parameters,
(nucleation, diffusion length, evaporated metal, influence of the
substrate-crystal), is necessary. We could show that in extreme cases (Cu
on metallic TaS2) diffusion length of more than 50 µm could be observed
combined with a nucleation probability of almost zero. In contrast, metal
diffusion (Cu) on the geometrically similar surfaces on the semiconducting
(WSe2) surface show much shorter diffusion length and no diffusion
limited aggregation (DLA) growth. We suggest a model to explain the
different diffusion behavior as a key to understand the growth of different
self organized structures on TMDC-crystals.
O 38.7 Do 17:15 H38
Adsorption geometry of Palladium Phthalocyanine (PdPc) on
Graphite: STM and LEED investigations — •T. G. Gopakumar,
M. Lackinger, F. Müller, and M. Hietschold — Chemnitz
University of Technology, Institute of Physics, Solid Surfaces Analysis
Group, D-09107, Chemnitz, Germany
Adsorption geometry of planar Palladium Phthalocyanine (PdPc)
molecules on natural graphite was studied using a variable temperature
STM and LEED. PdPc films were prepared on a freshly cleaved natural
graphite (0001) surface using Organic Molecular Beam Epitaxy (OMBE)
under UHV conditions at room temperature. It was observed that PdPc
molecules were adsorbed with their molecular planes parallel to the substrate
and forming highly ordered phases with quadratic lattices. Further
analysis to find the orientation of molecular super-lattice with respect to
the graphite lattice vectors shows a rotation of 10 degree. For a better
understanding of the submolecular contrast, the software package Gaussian
98 was used to calculate the electronic structure of isolated PdPc
molecules. The different STM contrast could be explained and electronic
analogies were found.
O 38.8 Do 17:30 H38
Stability of Pd Surface Oxides at Ambient Pressures — •M.
Todorova 1 , J. Rogal 1 , K. Reuter 1 , M. Scheffler 1 , E. Lundgren
2 , J. Gustafson 2 , J.N. Andersen 2 , and A. Stierle 3 — 1 Fritz-
Haber-Institut, Berlin — 2 Departement of Synchrotron Radiation Research,
University of Lund, Sweden — 3 Max-Planck-Institut für Metallforschung,
Stuttgart
Using density-functional theory we study and compare the oxide formation
at the Pd(111) and Pd(100) surfaces. We identify the stable
phases and determine their (T, p) stability range using the concept of
first-principles atomistic thermodynamics. The observed surface oxides,
which only vaguely resemble their bulk counterparts, represent the most
stable phase for a wide range of environmental conditions exceeding the
stability range of bulk PdO by far. The corresponding overall structure
of the surface phase diagram for the Pd(100) surface is in good agreement
with surface X-ray diffraction (SXRD) measurements in the pressure
range up to 1 bar. For T < 600K the comparison with the experimental
data additionally discerns a kinetic hindrance to the formation
of the bulk oxide, stabilizing the ( √ 5 × √ 5)R27 ◦ surface oxide even up
to ambient pressures.
O 38.9 Do 17:45 H38
Adsorption and interaction of methane and ethane on the stoichiometric
and oxygen rich RuO2(110) surface — •Undine Erlekam,
Ursula A. Paulus, Yuemin Wang, Peter Geng, Karl
Jacobi, and Gerhard Ertl — Fritz-Haber-Institut der Max-Planck-
Gesellschaft, Faradayweg 4-6, D-14195 Berlin
The RuO2(110) single crystal surface exposing coordinatively unsaturated
Ru (Ru-cus) and oxygen (O-bridge) atoms, have been proven to
be an efficient catalyst, e.g. for the oxidation of CO [1]. An O-enriched
RuO2(110) surface is obtained by dissociative adsorption of O2 on the
stoichiometric surface giving rise to weakly bonded O-cus atoms on top
of Ru-cus.
In this study we investigated the adsorption and interaction of low hydrocarbons
such as methane and ethane on the RuO2(110) surfaces both
the stoichiometric and the O-rich ones in order to determine whether
or not low hydrocarbons can be oxidized under UHV-conditions. Due
to the weak adsorption of low hydrocarbons (physisorption) the sample
was cooled with liquid nitrogen. The techniques applied are highresolution
electron energy-loss spectroscopy (HREELS) and thermal desorption
spectroscopy (TDS) in combination with isotopic labeling exper-

Oberflächenphysik Donnerstag
iments.
[1] J. Wang et al., J. Phys Chem. B. 106 (2002) 3422.
O 38.10 Do 18:00 H38
Untersuchung der Adsorption von Chlor auf Si(113) — •J. I.
Flege 1,2 , Th. Schmidt 2 , M. Siebert 2 , G. Materlik 3 und J. Falta
2 — 1 HASYLAB am DESY, Notkestr. 85, D-22603 Hamburg — 2 Inst.
f. Festkörperphysik, Universität Bremen, Postfach 330440, D-28334 Bremen
— 3 Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11
0QX, UK
Aufgrund ihrer vielversprechenden Eigenschaften für die Halbleitertechnologie
und die Nanostrukturierung selbstorganisierender Systeme
stellt die Si(113)-Oberfläche ein attraktives Forschungsobjekt dar. Trotzdem
sind ihre Wechselwirkung mit Halogenen, den grundlegenden Komponenten
der Prozeßgase, und ihr Trockenätzverhalten bislang gänzlich
O 39 Epitaxie und Wachstum III
unbekannt.
Wir präsentieren eine umfangreiche Studie des Adsorptionsverhaltens
von Chlor auf Si(113) mit stehenden Röntgenwellenfeldern (XSW), Rastertunnelmikroskopie
(STM) und Dichtefunktionaltheorie (DFT). Nach
Bedampfen bei einer Substrattemperatur von 600 ◦ C ist ein Charakteristikum
dieses Systems die gleichzeitige Existenz von (2×n)-rekonstruierten
Phasen, die im STM-Bild als Formierung von Reihen mit 2-facher Periodizität
in [1¯10]-Richtung nachgewiesen werden können. Dies induziert
eine deutliche Vorzugsrichtung der nunmehr glatten Stufenkanten in derselben
Richtung. XSW-Untersuchungen für verschiedene Cl-Bedeckungen
zeigen, daß die einzelnen (2×n)-Domänen aus der lokalen, periodischen
Anordnung nur weniger Adsorptionsplätze aufgebaut sind. Strukturmodelle
aus ab initio-DFT-Berechnungen werden mit den XSW-Ergebnissen
verglichen und diskutiert.
Zeit: Donnerstag 15:45–18:15 Raum: H39
O 39.1 Do 15:45 H39
A Novel Local Free Energy Minimum on the Cu(001)-Surface
— •Herbert Wormeester, Michail Ovsyanko, Georgiana
Stoyan, and Bene Poelsema — MESA+ Research Institute,
University of Twente, The Netherlands
Glancing incidence Ar+ ion bombardment of the Cu(001) surface leads
to the formation of two atom layer deep nanogrooves parallel to the incident
ion beam. High resolution LEED patterns show that sputtering
along [110] and [100] leads to an intergroove distance that depends on
temperature, ionfluence and -energy. Suprisingly, prolonged sputtering
along [100] leads at various temperatures (175 to 235 K) to a persistent
feature located at 1.0% BZ of the Brillouin Zone (BZ). Annealing
at temperatures between 250 and 290 K of nanogrooves prepared after
a much shorter sputtertime leads to an increase of their separation distance.
Here too, the appearance of this persistent feature at 1.0% BZ is
observed. These various preparation routes are indicative of a thermodynamic
origin of this 1.0% feature, i.e. a local free energy minimum.
Mild annealing above 400K transfers the surface to the global free energy
minimum: It suffices to remove both the nanogroove structure and
the feature at 1.0% BZ. The occurrence of the 1.0% BZ feature is attributed
to the relieve of tensile strain, generally present at (001) fcc
metal surfaces, leading to a contraction of the in-plane lattice constant
of the (001) surface along the [010] azimuth. The energy balance between
gain by stress relieve and cost due to lattice mismatch will be discussed.
The presence of the nanogrooves along a ¡100¿ azimuth turns out to be
essential for the relieve of this strain.
O 39.2 Do 16:00 H39
Spectroscopic signature of stacking faults and dislocation
lines on Co(0001) — •Jens Wiebe 1 , Lilli Sacharow 1 , André
Wachowiak 1,2 , Markus Morgenstern 1 , and Roland Wiesendanger
1 — 1 Institute of Applied Physics, Hamburg University,
Jungiusstr. 11, D-20355 Hamburg, Germany — 2 University of California
at Berkeley, Department of Physics, 366 Le Conte Hall #7300, Berkeley,
CA 94720-7300, USA
Growth morphology and electronic structure of Co films grown on
W(110) were studied using scanning tunneling microscopy and spectroscopy
(STS) at T = 6 K. Depending on growth conditions continuous
films or islands are found. Within the continuous films dislocation lines
partly appear while in both islands and continuous films stacking fault
areas could be identified. STS revealed that the d-like surface-related
state of minority-spin character at 0.3 eV below the Fermi energy is extremely
sensitive to stacking faults at the surface as well as to dislocation
lines located several layers below the surface. The exact character of the
state was determined by comparison to first principle electronic structure
calculations.
O 39.3 Do 16:15 H39
Growth of CoSi2 islands on Si(111) — •M. Löffler 1 , J.
Cordon 2 , E. Ortega 2 , M. Weinelt 1 , and Th. Fauster 1 —
1 Lehrstuhl für Festkörperphysik, Staudtstraße 7, 91058 Erlangen,
Germany — 2 Donostia International Physics Center, Apto. 1072 , 20080
San Sebastian, Spain
Ultrathin cobalt silicide films deposited at room temperature on
Si(111) grow as flat films for annealing temperatures below 500 ◦ C,
but agglomerate for higher annealing temperatures [1]. With scanning
tunneling microscopy we investigated this agglomeration process on
flat and stepped Si(111) samples. For annealing temperatures higher
than 700 ◦ C triangular islands grow on the flat surface, while on
the stepped surface the growth of the islands perpendicular to the
step edges is suppressed: For deposition at room temperature and
subsequent annealing the aspect ratio (width parallel divided by width
perpendicular to step edges) reaches a value around 3 at an annealing
temperature of 900 ◦ C.
The growth of the cobalt silicide islands can be influenced by the
mobility of the different species during the growth process. Deposition at
800 ◦ C sample temperature on the flat surface produces bigger triangular
islands, while on the stepped sample we can enlarge the aspect ratio to
9.
[1] B. Ilge et al., Surf. Sci. 414 (1998), 279
O 39.4 Do 16:30 H39
Formation of a faceted MoO2 epilayer on Mo(112) studied by
XPS, UPS and STM — •Thomas Schroeder 1 , Tien Lin Lee 1 ,
Jörg Zegenhagen 1 , Norbert Magg 2 , Boonchuan Immaraporn 2 ,
and Hans-Joachim Freund 2 — 1 E.S.R.F, Beamline ID32, 6, Rue Jules
Horowitz, 38043 Grenoble, France — 2 Fritz-Haber-Institut, Abt. CP,
Faradayweg 4 - 6, 14195 Berlin, Germany
The open trough and row Mo(112) surface serves as substrate for the
epitaxial growth of MoO2. XPS, UPS and STM studies of the oxygen
adsorption allow to monitor step-by-step the transformation of the electronic
and morphological properties during this process. XPS and UPS
spectra reveal that a stable oxygen chemisorbed state precedes the formation
of MoO2. STM topographs identify this oxygen chemisorbed phase
as an oxygen-induced p(2x3) reconstruction of the missing row type. This
precursor state evolves into a flat p(1x3) reconstructed (010) MoO2 layer
which roughens by the formation of (110) facets under further oxygen
exposure.
O 39.5 Do 16:45 H39
Wachstum, thermische Stabilität und magnetische Eigenschaften
von Co auf einem ultradünnen Al2O3 Film auf CoAl(100)
— •Volker Rose, Vitali Podgursky, Stella M. Van Eek und
René Franchy — Institut für Schichten und Grenzflächen (ISG3), Forschungszentrum
Jülich, D-52425 Jülich, Germany
Das Wachstum und die magnetischen Eigenschaften von Co bei Raumtemperatur
auf θ-Al2O3/CoAl(100) wurden mittels Augerelektronenspektroskopie
(AES), Beugung niederenergetischer Elektronen (LEED),
Rastertunnelmikroskopie (STM) und dem Magnetooptischen Kerr-Effekt
(MOKE) untersucht. Zur Steigerung der AES Oberflächensensitivität
wurde die Probe zusätzlich zum senkrechten Einfall streifend mit
Primärelektronen beschossen. Verursacht durch die stark unterschiedlichen
freien Oberflächenenergien von Co (2709 mJ/m 2 ) und dem Oxid
(690 mJ/m 2 ) kommt es zum Wachstum von Co 3D Clustern (Volmer-
Weber Wachstum). Bereits nach einer nominellen Deposition von 0,05
˚A Co werden Cluster einer maximalen Höhe von 4 ˚A und einem mittleren
Durchmesser von 35 ˚A gefunden. Die Größe der Cluster nimmt mit
steigender Deposition weiter zu, sodass nach 25 ˚A Co der mittlere Durch-

Oberflächenphysik Donnerstag
messer 100 ˚A beträgt und ein geschlossener Co Film gewachsen ist. Nach
Deposition von 7 ˚A zeigt der Co Film erstmals ein magnetisches Verhalten.
Anlassen der Probe über 500 K führt zur Koaleszenz der Cluster und
einer fortschreitenden Diffusion von Co Atomen durch das Oxid in das
Substrat, wobei nach dem Anlassen auf 1000 K Co vollständig diffundiert
ist.
O 39.6 Do 17:00 H39
Kinetic lattice Monte-Carlo simulations of stacking fault nucleation
on Ir(111) — •Michael Müller and Karsten Albe — TU
Darmstadt, FB Materialwissenschaft, Petersenstraße 23, 64289 Darmstadt
A prominent fault during epitaxial growth of face-centered-cubic (111)
metal surfaces is the formation of adatom islands that nucleate and
grow in the hexagonal-close-packed stacking. For sub-monolyer growth
on Ir(111) detailed experimental data on the temperature dependence of
the probability of stacking fault island formation is available from scanning
tunneling microscopy. Here, we present kinetic lattice Monte-Carlo
(KLMC) simulations of homoepitaxial island growth on Ir(111) that are
able to reproduce the experimentally observed shape and distribution of
stacking fault islands over a wide temperature range. In our simulations,
atomic positions are not restricted to perfect fcc lattice sites, as it is the
case in conventional KLMC. Therefore, an effective method to implement
a refined lattice that includes fcc as well as hcp sites is presented. Also,
the diffusion behavior of small adatom clusters plays a central role for
the formation of stacking fault islands on Ir(111). Our KLMC simulations
identify adatom clusters on the surface. In addition to single adatoms,
these clusters are also treated as mobile species.
O 39.7 Do 17:15 H39
Epitaxial growth of thin Alumina on a Cr2O3(0001) substrate
— •Karifala Dumbuya 1 , Sven L. M Schroeder 2 , and Klaus
Christmann 1 — 1 Freie Universität Berlin, Institut für Chemie, Takustrasse
3, 14195 Berlin, Germany — 2 Molecular Materials Centre, Department
of Chemical Engineering, UMIST, PO Box 88, Manchester, M60
1QD, UK
The growth of vapour-deposited Al and aluminium oxide on chromia
Cr2O3(0001) has been studied by auger electron spectroscopy (AES), low
energy electron diffraction (LEED), ion scattering spectroscopy (LEIS),
and x-ray photoelectron spectroscopy (XPS). If aluminium is deposited
in the absence of oxygen, aluminium LVV auger signals are found in the
40-56 eV region, indicative of aluminium in the oxidised state (Metallic
Al appears at 67 eV). This led us to conclude that the phenomenon of aluminothermy
must have occured. Controlled evaporation of aluminium in
an oxygen milieu, however, resulted in the growth of well ordered Al2O3
films up to a thickness of 30 ˚A, whereby the epitactic growth could be
monitored by LEED. These films were conducting enough to be subjected
to electron spectroscopy. A gradual attenuation of the XP signals
of Cr indicates layer-by-layer growth. A parallel and recently concluded
investigation of the Cr2O3/Al2O3 system using LEIS and XPS has corroborated
our assumption that alumina grows on the Cr2O3 substrate
in an oriented manner. In addition, LEIS indicated that the uppermost
Al2O3 layers are Cr-free, and from XPS we deduced that Al actually
exists in the Al 3+ valence state.
O 39.8 Do 17:30 H39
Atomic structure of ultrathin Fe films on Cu(100) and Cu(111)
prepared by pulsed laser deposition (PLD) — •Hannes
Schiechl, Albert Biedermann, Michael Schmid, and Peter
Varga — Institut für Allgemeine Physik, Technische Universität Wien,
Wiedner Hauptstrasse 8-10/134, A-1040 Vienna, Austria
O 40 Halbleiteroberflächen und -grenzflächen
Ultrathin Fe films up to 10 ML were grown on Cu(100) and Cu(111)
using pulsed laser deposition (PLD) and analyzed by scanning tunneling
microscopy (STM). We present a survey of the local atomic structure
of these films, which show enhanced layer-by-layer growth compared to
films grown by thermal deposition (TD). At laser intensities near the ablation
threshold we observe a bcc-like Fe phase between 2 and 5 ML film
thickness on Cu(100), similar to our previous results on TD-films, where
this structure can be correlated to the interesting magnetic properties
of these films. Regarding Fe films grown on the Cu(111) surface using a
laser wavelength of 532 nm, we observe a transition of the growth mode
by increasing the laser fluence per pulse. The bilayer growth mode, which
we find on TD-films, changes to layer-by-layer growth.
O 39.9 Do 17:45 H39
Growth and structure of pulsed laser deposited Pd films on
Cu(100) — •Y. Lu, H.L. Meyerheim, W. Wang, J. Barthel,
M. Przybylski, and J. Kirschner — MPI für Mikrostrukturphysik,
Weinberg 2, 06120 Halle
Pd films in the coverage regime between 0.2 to 8 monolayers
(ML, 1ML=1.53×10 15 atoms/cm 2 ) were grown at room temperature on
Cu(001) using pulsed laser deposition (PLD) and studied by scanning
tunneling microscopy (STM), low energy electron diffraction (LEED) and
Auger-electron spectroscopy (AES). Up to a Pd coverage of θ = 4 ML a
well defined layer-by-layer growth mode is observed, at higher coverage
the strain due to the large mismatch (7.6 %) relaxes by formation of
a two-dimensional ordered array of dislocations running parallel to the
〈100〉 directions of the Cu-substrate. In the coverage regime below 4ML,
LEED images do not indicate the formation of any ordered superstructure
such as the c(2x2), which was previously observed at 0.5 ML for
thermally deposited Pd [1]. The two-dimensional misfit dislocation network
formed at θ > 4ML gives rise to the appearance of diffuse lines of
satellite reflections between the (1x1) substrate reflections. For deposition
at 500 K, Pd-growth proceeds by the step flow mode and a better
ordering of the dislocation network is observed. [1] P.W. Murray et al.,
PRB 52, R14404 (1995)
O 39.10 Do 18:00 H39
Self-healing of stacking faults in homoepitaxial growth on
Ir(111) — Carsten Busse 1,2 , •Arne Thoma 1 , and Thomas
Michely 1 — 1 I. Physikalisches Institut der RWTH Aachen, 52056
Aachen, Germany — 2 Present address: Institute of Physics and
Astronomy, University of Aarhus, 8000 Aarhus C, Denmark
The growth of a thin film is studied from the nucleation phase to the
closure of the first monolayer in the face-centered cubic (fcc) system
Ir/Ir(111) using temperature-variable scanning tunneling microscopy.
The island that nucleate in the hexagonal close-packed (hcp) stacking
cannot coalesce with regular islands. Instead, an assimilation process is
observed, where material is transported from the metastable hcp to the
energetically favourable fcc sites. The atomic mechanisms governing this
transfer are identified. Furthermore, the influence of adsorbates on nucleation
of stacking-faults is investigated by exposing the surface to different
gases prior to evaporation.
Zeit: Donnerstag 15:45–18:45 Raum: H45
O 40.1 Do 15:45 H45
Optische Charakterisierung ultradünner Siliziumoxid-Filme mit
der Brewster-Winkel Analyse (BWA) — •Michael Lublow
und H. J. Lewerenz — Hahn-Meitner-Institut Berlin Abteilung Solare
Energetik (SE5) Glienicker Str. 100 14109 Berlin
Die optische Charakterisierung ultradünner Filme mit Schichtdicken
d < 8 nm wird durch den Einfluß rauher Grenzflächen erschwert: die
ermittelten Werte weichen von denen anderer oberflächensensitiver Me-
thoden wie Auger Elektronenspektroskopie oder Photoelektronenspektroskopie
ab. Für das natürliche Oxid auf Si(111) wird die Oberflächeninformation
mittels dynamischer Anpassung des Einfallswinkels
durch eine symmetrische Messung des Reflektivitätssignals um den
Brewster-Winkel des SiOx/Si-Systems herum erfaßt. Charakteristische
Unterschiede gegenüber phasenoptimierter Ellipsometrie werden für naßchemische
Ätzungen des Oxids untersucht. Es wird gezeigt, daß die BWA
die einzelnen Stufen der Oxidabtragung sowie die anschließende Rauhig-

Oberflächenphysik Donnerstag
keitszunahme optisch trennt. Demgegenüber erweist sich selbst die phasenoptimierte
Ellipsometrie als unempfindlicher. Die größere Empfindlichkeit
der BWA gegenüber Spurrauhigkeiten wird anhand von AFM
Messungen diskutiert.
O 40.2 Do 16:00 H45
On the origin of the STM induced Si(001)c(4×2) – p(2×2) phase
transition — •Kaori Seino, Wolf G. Schmidt, Frank Groth,
and Friedhelm Bechstedt — Institut für Festkörpertheorie und Theoretische
Optik, Friedrich-Schiller-Universität, Max-Wien-Platz 1, 07743
Jena, German
There has been a longstanding interest in the atomic and electronic
structure of the Si(001) surface, related to its industrial applications and
its model character for surface science. Recently the true atomic configuration
of the Si(001) surface at very low temperatures has again become
a very interesting subject. In particular the question whether the surface
ground state reconstructs c(4×2) or p(2×2) is controversially discussed.
A very recent STM study even demonstrates phase manipulation between
c(4 × 2) and p(2 × 2) at 4.2 K [1]. We study the energetics of
the Si(001) surface in an electric field using gradient-corrected densityfunctional
theory (DFT-GGA) and ultrasoft pseudopotentials. The influence
of the preparation conditions and experimental setup on the surface
reconstruction is discussed in detail.
[1] K. Sagisaka, D. Fujita, G. Kido, Phys. Rev. Lett. 91, 146103 (2003)
O 40.3 Do 16:15 H45
Initial and advanced stages of Si dissolution in alkaline media
using photoelectron spectroscopy — •Katarzyna Skorupska
1 , Mohammed Aggour 1 , Eder Goncalves 1 , Ralf Hunger 2 ,
Helmut Jungblut 1 , Michael Kanis 1 , Michael Lublow 1 , Elmar
Rüther 1 , Thomas Wilhelm 1 , and Hans-Joachim Lewerenz 1
— 1 Hahn-Meitner-Institut, Glienicker Str. 100, D-14109 Berlin — 2 TU
Darmstadt, Petersenstr. 23, D-64287 Darmstadt
Silicon dissolution in aqueous alkaline media is of ubiquitous importance
in micro- and nanostructuring. Never the less detailed surface analytical
investigations on the dissolution steps are lacking. The presented
study applies synchrotron radiation spectroscopy using a specifically designed
in-system electrochemistry vessel attached to the SoLiAS apparatus
at the U49/2 beamline at Bessy II. Initial and advanced oxide layers
are analysed in electrode potential-, current- and charge-controlled experiments.
Besides chemical surface changes also surface electronic effects
were monitored using ultraviolet photoelectron spectroscopy. The results
are compared with several recently proposed dissolution mechanisms.
O 40.4 Do 16:30 H45
In-Situ- and UHV-Investigation of MOCVD-Grown GaAsSb-
Interfaces — •Zadig Kollonitsch, Matthias Neges, Kristof
Möller, Frank Willig, and Thomas Hannappel — Hahn-Meitner-
Institut, SE4, Glienicker Strasse 100, D-14109 Berlin, Germany
The effect of antimony segregation at surfaces and interfaces complicates
the application of such layers in semiconductor devices. To improve
interface abruptness various protocols may be employed and investigated
at the atomic scale. Lattice matched GaAs0.51Sb0.49/InP(100)-layers were
grown by MOVPE at 770K. The surface and interface reconstruction
was monitored with reflectance anisotropy/difference (RAS/RDS) spectroscopy.
The RA-Spectrum of the As-rich GaAsSb(100) surface showed
different features compared to that of the Sb-rich surface. The in-situ
signals indicated that the surface was Sb-rich during growth and turned
preferably into an As-rich surface after growth. Contamination free
sample transfer into ultrahigh vacuum (UHV) allowed the correlation
of the in-situ signals with LEED and UV-photoelectron spectroscopy
(UPS). The LEED pattern of As-rich GaAsSb(100) showed a c(4 × 4)
reconstruction with bright spots, whereas the LEED pattern of Sb-rich
GaAsSb(100) showed a (1 × 3)-like reconstruction with weak spots. Possible
models for the surface reconstructions are discussed. Results are
presented for the growth of InP/GaAsSb heterojunctions on As- and Sbrich
GaAsSb(100) surfaces.
O 40.5 Do 16:45 H45
Importance of carrier dynamics and conservation of momentum
in atom-selective STM imaging of semiconductor surfaces
— •Philipp Ebert 1 , Nikos Jäger 1 , Eicke Weber 2 , and Knut Urban
1 — 1 Institut für Festkörperforschung, Forschungszentrum Jülich,
52425 Jülich — 2 University of California and Lawrence Berkeley National
Laboratory
Scanning tunneling microscopy and spectroscopy measurements on the
GaAs(110) surface with complementary theoretical calculations are performed
to clarify the effects involved in the tunneling of unpinned semiconductor
surfaces. We show that the flatband and tip-induced band
bending as well as equilibrium conditions are insufficient to describe the
effects involved. Instead, carrier dynamics and conservation of momentum
of the tunneling electrons need to be taken into account for a complete
description of the contributions of the valence or conduction band
states. The results allow us to understand the unique properties needed
to achieve the atom-selective imaging on semiconductor surfaces as well
as the determination of the band gap energy.
O 40.6 Do 17:00 H45
First-principles calculations for initial adsorption of manganese
on Si(001) — •Mahbube Hortaman, Hua Wu, Peter Kratzer,
and Matthias Scheffler — Fritz-Haber-Institut der MPG, Faradayweg
4-6, 14195, Berlin
Heterojunctions between a semiconductor and a ferromagnetic metal
have attracted attention in the context of spintronics. In this work, we
choose the Mn on Si(001) system as a possible candidate for the growth
of magnetic thin films, and investigated the adsorption behavior of Mn
(coverage θ < 0.5 monolayer) by first-principles total-energy calculations
using density functional theory and the FP-APW+lo method. For one
Mn atom in the Si(001)(2x2) unit cell, the sub-surface site is 0.9 eV lower
in energy than the on-surface position due to the strong Mn-Si covalent
bonding. Moreover, we find a pathway to the subsurface region that exhibits
a practically zero energy barrier. As seen from the potential-energy
surface of Mn in different adsorption geometries, the most stable site on
the surface is the hollow site where Mn is placed between two Si dimers
in the same row. Diffusion barriers both along and perpendicular to the
dimer row are about 0.7 eV, which indicates isotropic diffusion. For onsurface
Mn adatoms we find a strong tendency towards the formation of
Mn islands on the surface. The resulting structure resembles that of a
next Si layer. If the sub-surface site is reached by Mn adatoms before the
on-surface islands are formed, a mixed on-surface/sub-surface structure
will result. We discuss the above sketched results in a simple physical
picture and propose ideas how these different structures may be grown
experimentally.
O 40.7 Do 17:15 H45
Si addimer nanowires on SiC(001) surfaces — P. Krüger and
•J. Pollmann — Institut für Festkörpertheorie, Universität Münster,
Wilhelm-Klemm-Str. 10, 48149 Münster
In recent years it has been observed by scanning tunneling microscopy
that particular reconstructions of the SiC(001) surface show Si addimer
nanowires. Their occurrence depends crucially on preparation conditions.
To explain the physical origin of such nanowires we scrutinize current reconstruction
models of various SiC(001) surfaces. Analysing the energetics
of the c(4×2), 3×2, 5×2 and 7×2 reconstructions, as resulting from
our first-principles DFT-LDA calculations of the formation energy, we
find that the higher N×2 reconstructions can be formed by two basic
building blocks, the c(4×2) and the (3×2) unit. This finding allows us
to set up a simple model which extrapolates to all possible N×2 reconstructions.
First, the model reveals in excellent agreement with experiment
that neither a 4×2 nor a 6×2 reconstruction should occur. Second,
it predicts that all higher reconstructions with N ≥ 7 are possible. This
is in contrast to an earlier notion that only odd reconstructions (with N
odd) were to be expected. In fact, the more recent observations of the
above mentioned Si nanowires have been made at a SiC(001)-(8×2) surface.
This structure directly derives from our model as consisting of one
c(4×2) and two 3×2 units per 8×2 unit cell revealing the origin of the
experimentally observed Si addimer nanowires. In general, all kinds of
Si nanowire arrangements can be achieved depending sensitively on the
distribution of the two structural building blocks at the SiC(001) surface.
O 40.8 Do 17:30 H45
Einfluss photoinduzierter Effekte auf die Photoemissionsspektren
gesputterter ZnO-Schichten auf Si(111)-H — •Henning
Wolf, Ulrich Meier, Tilo Plake und Christian Pettenkofer
— Hahn-Meitner-Institut Berlin, Glienicker Strasse 100, 14109 Berlin
Durch Magnetronsputtern abgeschiedenes ZnO enthält H-Konzentrationen
bis zu 10 21 cm −3 im Volumenmaterial. Tempern in Sauerstoffatmosphäre
bei 400 ◦ C reduziert den Anteil des Wasserstoffs um etwa 2
Grössenordnungen. Bei der Untersuchung gesputterter ZnO-Schichten

Oberflächenphysik Donnerstag
auf Si(111)-H mittels Photoelektronenspektroskopie (UPS/XPS) ist ein
Einfluss photoinduzierter Effekte auf die Intensität und energetische Lage
der Linien in den Spektren zu beobachten. Diese Veränderungen sind
nicht abängig von der Energie des anregenden Lichtes, jedoch von der
Intensität und der Bestrahlungsdauer. Wir diskutieren die Effekte anhand
von Diffusionsprozessen des Sauerstoffs aus dem Volumenmaterial
sowie des auf der Probenoberfläche und in den Korngrenzen in Form von
Hydroxid enthaltenen Wasserstoffs. Im Ergebnis stellen wir ein Modell
vor, das die Photolyse von Oberflächenhydroxid einerseits und von ZnO
bzw. Volumen-Zn(OH)x andererseits berücksichtigt.
O 40.9 Do 17:45 H45
Epitaxial Pr2O3 layers on Si (111) studied with LEED and surface
XRD — •Nicole Jeutter, Zarife Özer, and Wolfgang
Moritz — Section Crystallography, Department of Earth and Environmental
Sciences, University of Munich
Pr2O3 is one of the few oxides which are stable in contact with Si at
temperatures up to 1000 C. It has as high dielectric constant and a small
lattice mismatch (under 0.3 %) to the Si (111) substrate lattice. We have
grown Pr2O3 on the Si (111) surface by evaporation from a tungsten
crucible loaded with Pr6O11. Measurements with LEED and XRD show
that an epitaxial layer is formed at a substrate temperature of about
770 K with the (0001) plane of Pr2O3 parallel to the Si (111) surface.
Subsequent annealing up to 1030 K for less than 2 minutes leads to a
p(2x2) reconstruction of the Pr2O3 layer. Very weak reflections from a
( √ 3x √ 3) structure appear after slow cooling to room temperature. A
disordered (5x1) phase appears after desorption at temperatures above
1050 K. After further desorption the (7x7) structure of the Si (111) surface
is recovered. First x-ray measurements show the orientation relative
to the substrate. The interface consists of a Si-O-Pr bond with Pr above
the T4 site. No indication was found for an intermediate oxide layer. The
thickness of the layer was 0.6 nm, corresponding to one unit cell of Pr2O3.
O 40.10 Do 18:00 H45
Potential Energy Retention of Slow Highly Charged Ar-Ions in
Chemical Clean Silicon Surfaces — •Daniel Kost, Stefan Facsko,
and Wolfhard Möller — Institut für Ionenstrahlphysik und
Materialforschung, Forschungszentrum Rossendorf, 01028 Dresden
A UHV device with a base pressure of p < 10 −9 mbar was connected to
the ECR ion source of the Forschungszentrum Rossendorf for improved
calorimetric measurements of the retention of the potential energy of
highly charged ions. The chemical state of the target surface is controlled
by AES using LEED optics. With a clean silicon surface prepared
by sputtering using Ar + ions, the retained energy of Ar q+ (q = 1 up
to 9) ions was determined at kinetic energies between 60 eV ·q and 200
eV ·q. By extrapolation to zero kinetic energy, the retained fraction of
the potential energy is obtained, which is related to the full potential
energy given by the ionization potentials. The potential energy reten-
O 42 Hauptvortrag Hohage
tion coefficient results as 0.8 ± 0.2 and decreases weakly with increasing
charge state. This is about three times larger than earlier results with
contaminated copper surfaces.
O 40.11 Do 18:15 H45
Angle-resolved photoelectron spectroscopy of CuInSe2(001) —
•Ralf Hunger 1 , Wolfram Jaegermann 1 , Wolfram Calvet 2 ,
Carstan Lehmann 2 , Christian Pettenkofer 2 , Keiichiro Sakurai
3 , and Shigeru Niki 3 — 1 Surface Science Division, TU Darmstadt,
64287 Darmstadt — 2 Abt. Heterogrenzflächen, HMI, 14109 Berlin —
3 Thin Film Solar Cells Group, AIST, Tsukuba 805-8568, Japan
We have investigated the valence band structure of CuInSe2 by
angle-resolved photoelectron spectroscopy (ARPES). Heteroepitaxial
CuInSe2(001)/GaAs films were prepared by molecular beam epitaxy
which and covered by a protective selenium cap. In the UHV analysis
system, clean and ordered CuInSe2(001) surfaces were prepared by
thermal desorption of the Se cap layer. This surfaces exhibited a
(1 × 1)-LEED pattern and MgKα-ecited XPS proved the surface to be
free of oxygen and hydrocarbon contamination. ARPES experiments
were conducted at the TGM7 beamline at Bessy2 using a VG ADES500
analyser.
The final state bands were investigated by EDCs in normal emission
(ΓT direction in the tetragonal chalcopyrite lattice) using excitation energies
from hν = 9.6eV to hν = 40eV . A transition from the top of the
valence band (VBM) at Γ to a free-electron like final state band was observed
for hν = 11.3eV . Thereby, the inner potential V0 was determined
to −6.9eV and the VBM lies at 0.4 eV. Angular scans were performed
along the ΓX ([110]) and ΓM ([010]) directions with hν = 21.2eV . The
resulting experimental band structure will be presented and compared to
calculations by Jaffe&Zunger (PRB 28 (1983) p. 5822).
O 40.12 Do 18:30 H45
Oxide and Carbon contamination removal from semiconductor
surfaces using low-energy hydrogen ion beam etching —
•Nasser Razek, Axel Schindler, Dietmar Hirsch, and Bernd
Rauschenbach — Leibniz-Institut für Oberflächenmodifizierung e. V.,
Permoserstrasse 15, 04318 Leipzig, Germany
A new cleaning technology for semiconductor surfaces to remove oxide
layers and carbon contamination has been applied to GaAs and Ge
surfaces. The cleaning is performed at surface temperatures lower then
300 ◦ C using low energy bombardment of mass separated hydrogen (H + 2 )
ion beam of 300 eV ion energy and of about 4.5 µA cm −2 ion current
density from a broad beam ion source. In comparison to conventional
cleaning, this technique leads to surfaces which are free of contamination
and are characterized by an improved roughness. Surfaces have been
investigated by the X-ray photoelectron spectroscopy and atomic force
microscopy. This work focuses on the development of a room temperature
bonding technique for semiconductors of different chemical nature.
Zeit: Freitag 10:15–11:00 Raum: H36
Hauptvortrag O 42.1 Fr 10:15 H36
Reflectance Difference Spectroscopy : a powerful tool for surface
analysis — •Michael Hohage — Institute of Experimental Physics,
Johannes Kepler University Linz, A-4040 Linz, Austria
Reflectance Difference Spectroscopy (RDS) measures the in plane optical
anisotropy of a surface or a thin film by analysing the reflection of
linearly polarised light under normal incidence. Only recently, the scope
of this method has been extended to study anisotropic metal surfaces.
Since the bulk of cubic crystals is optically isotropic, the RDS signal
from such crystals arises exclusively from symmetry breaking surfaces
(e.g. Cu(110)) and interfaces. Indeed, RDS turned out to be a versatile
and surface sensitive in-situ tool to analyse the electronic structure
of anisotropic metal surfaces as well as to study growth and adsorption
on such surfaces. The RDS signal is extremely sensitive to surface state
transitions, surface modified bulk transitions and adsorbate specific transitions,
each located at characteristic transition energies. These different
and spectroscopically separable contributions can be utilised to monitor
adsorption and growth processes in real time as well as to identify surface
phase transitions simultaneously.

Oberflächenphysik Freitag
O 43 Adsorption an Oberflächen IV
Zeit: Freitag 11:15–13:15 Raum: H36
O 43.1 Fr 11:15 H36
Multilayer Adsorption and Wetting of Acetone on Graphite —
•Frank Kruchten — Universität des Saarlandes, Technische Physik
7.3, 66123 Saarbrücken
Adsorption/desorption isotherms of acetone on highly oriented pyrolytic
graphite have been measured by ellipsometry for temperatures
above the bulk triple point. The behavior in the monolayer and submonolayer
regime is conventional, with 2D gas-liquid and 2D liquid-solid
coexistence regions. Further liquid monolayers grow on top of the completed
monolayer. The growth is basically layer-by-layer. For temperatures
between 190 K and the triple point a prewetting-type transition
occurs with a thin-thick jump of the layer thickness on adsorption but a
layer-wise removal of the film on desorption. In this temperature regime
the first monolayer is solid and its molecules are oriented perpendicular
to the substrate whereas the higher layers are orientationally disordered
polar liquid.
This work has been supported by the Deutsche Forschungsgemeinschaft
(Project No. Kn 234/9).
F.Kruchten and K.Knorr, Phys. Rev. Lett. 91, 085502 (2003)
O 43.2 Fr 11:30 H36
The on-surface ordering behavior of O/Rh(111) and H/Pd(111)
studied from first-principles — •Cesar Lazo 1 , Frerich Keil 1 ,
Karsten Reuter 2 , and Matthias Scheffler 2 — 1 TU Hamburg-
Harburg, Eissendorfer Str. 38, 21071 Hamburg — 2 Fritz-Haber-Institut,
Faradayweg 4-6, 14195 Berlin
We study the mesoscopic ordering behavior of simple adsorbates from
first-principles by parametrizing a lattice gas hamiltonian (LGH) with
density-functional theory (DFT) data. Based on this LGH, subsequent
Monte-Carlo Simulations provide the (T,p)-surface phase diagram, which
enables us to systematically discuss the potential and limitations of
this approach by comparing with corresponding experimental data. For
O/Rh(111) the rather large binding energy variations with coverage lead
to a rapid convergence of the LGH expansion. The subtle energy differences
involved in the hydrogen bonding at surfaces on the other hand
provide a critical test case. Only after including more than 15 lateral,
up to quattro interactions we obtain very good overall agreement with
the experimental phase diagram for H/Pd(111), reproducing the critical
temperatures of the two ordered overlayers within 20K.
O 43.3 Fr 11:45 H36
Activated adsorption of ethane on Pt(111) studied by in-situ
high resolution XPS — •T. Fuhrmann, M. Kinne, J.F. Zhu, B.
Tränkenschuh, R. Denecke, and H.-P. Steinrück — Physikalische
Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen
As less reactive basic materials used in chemical industries, alkanes
need in general catalysts to reduce the activation energies for dissociation.
The first elementary step is the adsorption on the catalysts surface.
Under UHV conditions, alkanes show a strong kinetic energy dependence
of their sticking probability on metal surfaces. Using the combination of
a molecular beam and high resolution XPS at the synchrotron facility
BESSY II, we study the species evolving during the adsorption process.
Time resolved measurements allow to determine the adsorption kinetics.
Depending on the surface temperature and the parameters of the
impinging molecules, both molecular as well as dissociative adsorption
channels are observed. For direct dissociation the same surface species is
observed for all beam parameters used. Using temperature programmed
XPS (TPXPS), the thermal evolution of the adsorbed species is studied.
Before reaching pure carbon by complete dehydrogenation, different
intermediates are identified by their C1s binding energies and their vibrational
fine structure. Supported by the DFG (STE 620/4-2).
O 43.4 Fr 12:00 H36
Nitriding a Gold(110)(1x2) Surface — •P. Schulz 1 , M. Gottfried
2 , and K. Christmann 1 — 1 Inst. f. Chemie, FU Berlin, Takustr.
3, 14195 Berlin — 2 Dept. of Chem. Eng., Univ. of Washington at Seatle
USA
Molecular N2 does not adsorb dissociatively on Au surfaces. Nevertheless,
a study of possible N-Au bonding situations appears to be interesting
(in view of e.g. de-NOX catalysis and semiconducter contacting). So far,
the only known research to produce N atoms on Au sufaces at 300 K used
N + ion bombardment techniques; the N species formed was characterized
by XPS (N 1s core level shifts) [L. Siller et al., Surf. Sci. 513 (2002) 78].
In our combined LEED, UPS, TDS and ∆Φ study we physisorbed N2
on a Au(110) surface at ∼ 30 K and exposed it to 500 eV electrons. We
succeeded in activating the molecules to dissociate into N atoms which
are strongly held on Au(110), desorbing around 450 K (physisorbed N2
desorbs below 50 K). We will communicate data on the energetics and
kinetics of the various Nad species on the Au(110) surface.
O 43.5 Fr 12:15 H36
A HREELS, TPD and LEED investigation of crotonaldehyde
on Pt(111). — •Alexander Krupski, Jan Haubrich, Conrad
Becker, and Klaus Wandelt — Institut für Physikalische und Theoretische
Chemie, Wegelerstrasse 12, D-53115 Bonn, Germany
TPD studies of crotonaldehyde adsorbed on Pt(111) at 100K were performed
for masses between 1 and 100 amu as a function of exposure. Only
fragments of the masses 2, 28, 39, 41 and 70 were detected up to 800K.
The results show the desorption of molecular crotonaldehyde at 175K
(monolayer), 164K (2nd ads. state) and 143K (multilayer). A very weak
signal is observed for propylene fragments (39, 41) around 335K. A signal
at 28 amu is seen around 395K, saturating already below the monolayer
exposure. Two signals are detected for molecular hydrogen desorption
around 291K and 425K. The HREEL spectra measured between 100K
and 175K show a close relationship to the gasphase data. By contrast, the
irreversibly adsorbed species, remainig above 175K, shows besides some
shifts sizeable changes in scattering intensities. Vibrations of molecular
CO evolve between 300K and 350K in the HREEL spectra, indicating
the decarbonylation of the surface species. Above 375K only traces of
hydrocarbon species can be observed by HREELS.
O 43.6 Fr 12:30 H36
Water on Ru(001): Interfacial structure investigated by vibrational
spectroscopy — •C. Frischkorn 1 , D.N. Denzler 2 , R.
Dudek 2 , S. Wagner 2 , M. Wolf 1 , and G. Ertl 2 — 1 Freie Universtät
Berlin, Fachbereich Physik, Arnimallee 14–16, 14195 Berlin — 2 Fritz–
Haber–Institut der MPG, Faradayweg 4–6, 14195 Berlin
Vibrational spectroscopy with sum-frequency generation (SFG) is intrinsically
surface/interface sensitive and thus can provide information
on the local binding structure in adsorbate layers. In this contribution,
we present results on the water structure on ruthenium (D2O/Ru(001))
obtained from SFG spectroscopy. The molecular structure of the first
bilayer of this system has been controversially discussed. LEED (low
energy electron diffraction) studies revealed an almost coplanar arrangement
of the oxygen atoms leading to a vertically compressed bilayer [1].
Recent DFT (density functional theory) calculations found that only a
half-dissociated bilayer wets the surface [2] resulting in a coplanar O
geometry which consequently explains the LEED results. Our SFG vibrational
spectra on D2O/Ru(001) taken at various thicknesses, however,
clearly disagree with both structures proposed. Therefore, we suggest a
D2O bilayer of intact water molecules whereby every second molecule
undergoes a hydrogen-metal bond giving rise to a so-called ”hydrogendown”structure
[3].
[1] G. Held, D. Menzel, Surf. Sci. 327, 301 (1995).
[2] P. J. Feibelman, Science 295, 99 (2002).
[3] D. N. Denzler, C. Hess, R. Dudek, S. Wagner, C. Frischkorn, M. Wolf,
G. Ertl, Chem. Phys. Lett. 376, 618 (2003).
O 43.7 Fr 12:45 H36
Semi-Empirical Potentials for Studying Catalytic Processes ?
— •Bernhard Lehner, Karsten Reuter, and Matthias Scheffler
— Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg
4-6, D-14195 Berlin
Ab initio electronic structure calculations like density functional theory
(DFT) significantly contribute to the understanding of catalytic processes
at solid surfaces, but are currently limited to microscopic system sizes
and time scales. A promising approach to reach mesoscopic and macroscopic
regimes is to use semi-empiric potentials, parameterised from ab
initio calculations. The main challenges in the development of such an
intermediate potential are high accuracy and reliability.
We check the suitability of Modified Embedded Atom Method

Oberflächenphysik Freitag
(MEAM) potentials for interpolating (and the possibility of extrapolating)
DFT data for a description of oxidation reactions on metal surfaces
(Al, Pd, ..). Possible extentions of the MEAM promising higher accuracy
and flexibility are also discussed. The potential-energy surfaces of atomic
oxygen adsorbed at low index facets, calculated by DFT, are used to determine
the free parameters of the semi-empiric potential. The MEAM
is found to be perfectly suitable for interpolating between the DFT data
points. The extrapolation capabilities of the semi-empiric potential are
discussed by examining the adsorption and desorption features predicted
for surfaces not included in the construction of the potential. In particular,
the capability of MEAM to reproduce the preferred adsorption of
oxygen at step edges of vicinal surfaces is discussed.
O 43.8 Fr 13:00 H36
Ab-initio investigation of the adsorption of H on the Ir(100)−1×1
surface — •Daniel Lerch, Stefan Müller, and Klaus Heinz —
Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr.7, D-91058
Erlangen
The adsorption of H on the metastable Ir(100)−1×1 surface was studied
via first-principles calculations, which reveal total energies as well as
vibrational and electronic properties.
Since thermal desorption spectra give no hint that H does occupy subsurface
sites, we focus on the site- and concentraction-dependence of the
adsorption energy of H on the Ir(100) top layer. Our ab-initio DFT calculations
(including vibrational zero-point energies) indicate that for all
considered H-concentrations (0.25 – 2 monolayer) the bridge position is
the energetically favoured adsorption site. At one monolayer coverage an
adsorption energy of 610meV per H-atom results. The energetic hierarchy
of H-adsorbate sites considered is bridge, top and hollow position
with the latter being less favoured by 160meV and 353meV , respectively.
These unexpected results for the adsorption site are discussed, also
with respect to the electronic properties of the Ir(100)−1×1 surface.
This work is supported by Deutsche Forschungsgemeinschaft.
O 44 Elektronische Struktur (Experiment und Theorie) III
Zeit: Freitag 11:15–13:15 Raum: H38
O 44.1 Fr 11:15 H38
Spectroscopy of ion beam induced electronic excitations at
surfaces — •Stefan Meyer 1 , Detlef Diesing 2 , and Andreas
Wucher 1 — 1 Institut für experimentelle Physik, Universität Duisburg-
Essen, 45117 Essen — 2 Institut für Schichten und Grenzflächen 3,
Forschungszentrum Jülich, 52425 Jülich
We investigate the electronic excitation of a solid surface that is generated
by the introduction of kinetic energy in form of fast ion bombardment.
In particular, hot electrons are detected which are excited to
energies below the work function and therefore cannot leave the surface.
The ballistic mean free path of these weakly excited electrons is of the
order of 10 nm. The sample is therefore prepared as a 20 nm thin film constituting
the front electrode of a metal- insulator- metal tunnel junction.
The hot electrons reaching the junction lead to a tunneling current that
can be measured. By applying a variable DC- voltage across the junction
it is possible to measure the energy distribution of excited electrons,
depending on ion beam parameters such as ion energy or ion species.
O 44.2 Fr 11:30 H38
Electronic structure of Pt3 cluster from GW theory —
•Wolfgang Hübner and Yaroslav Pavlyukh — FB Physik, TU
Kaiserslautern, D-67663 Kaiserslautern, Germany
The GW approximation is a powerful class of Green function approaches
that allows for the improved treatment of electronic correlations.
The self-consistent calculation in the framework of localized basis
functions allows for the ab initio treatment of time-resolved experiments,
provides corrections to the HOMO-LUMO gap, gives detailed information
about the density of quasiparticle states, and describes collective excitations
– plasmons. We apply our theory to a Pt3 cluster, a system with
complicated electronic structure due to the open shell (d 9 s 1 ) configuration
of the platinum atom, the importance of the spin-orbit coupling and
correlation effects. The large discrepancy between the HOMO-LUMO
gap from the HF (6.3 eV) and LDA (0.48 eV) approaches indicates the
necessity of using the many-body perturbation technique. Our main results
for this metallic cluster are: corrections of the HOMO-LUMO gap
(5.16 eV), energy resolved self-energy, and density of states. The G0W0
calculations reveal an extremely short life-time of the HOMO (70 fs) and
LUMO (20 fs) states in striking agreement with the experimental observation
(TR2PPE) and shows the capability of the method to treat large
systems.
O 44.3 Fr 11:45 H38
Banddispersion und Fermifläche von MoO2 — •Judith
Moosburger-Will 1 , Matthias Klemm 1 , Philip Hofmann 2 und
Sigfried Horn 1 — 1 Institut für Physik, Universtität Augsburg,
D-86159 Augsburg — 2 Institute for Storage Ring Facilities, University
of Aarhus, DK-8000 Aarhus C
VO2 ist ein korreliertes Elektronensystem, das einen strukturellen und
einen Metall-Isolator-Übergang zeigt. Zur Untersuchung der elektronischen
Struktur bietet sich winkelabhängige Photoemissionsspektroskopie
(ARUPS) an, da die hierbei gemessene Spektralfunktion auch theore-
tisch berechnet werden kann. Jedoch konnte mittels ARUPS an VO2
keine Banddispersion nachgewiesen werden, entgegen theoretischer Vorhersagen.
Um den Einfluss der elektronischen Korrelationen auf ARUPS
zu untersuchen, wurden Messungen an MoO2 durchgeführt. MoO2 ist
isostrukturell zur monoklinen Tieftemperaturphase von VO2, metallisch
und nicht elektronisch korreliert.
Es wurde ARUPS an der (100)-Oberfläche von MoO2 durchgeführt und
die Banddispersion entlang einer Hochsymmetrierichtung vermessen. Eine
deutliche Dispersion ist zu beobachten, die Lage der Bänder ist konsistent
mit der theoretischen Bandstruktur aus LDA-Rechnungen. Des
weiteren wurde die Fermifläche von MoO2 mittels ARUPS bestimmt. An
VO2 war dies auf Grund der nicht vorhandenen Dispersion unmöglich,
an MoO2 konnten sehr gute Ergebnisse erzielt werden. Die vermessene
Fermifläche stimmt sowohl mit de Haas-van Alphen-Messungen als auch
mit LDA-Rechnungen überein.
O 44.4 Fr 12:00 H38
Simulation von XPS-Daten am Beispiel des 2p Niveaus im
Schwefelatom — •Walter Langel — Institut für Chemie und Biochemie,
Universität Greifswald, 17489 Greifswald
Die Charakterisierung der chemischen Umgebung von Adsorbaten auf
Oberflächen geschieht routinemä¨sig mit elektronenspektroskopischen Methoden,
insbesondere XPS.Bei schwefelhaltigen Adsorbaten wird dazu
die Verschiebung der 2p-Orbitale bestimmt.Deshalb ist es von gro¨sem
Interesse, diese Daten mit Hilfe von Berechnungen der Elektronenstruktur
nachzuvollziehen.Schwefel und schwefelhaltige Adsorbate aus Titandioxid
sind von speziellem Interesse sowohl für katalytische als auch biochemische
Anwendungen
Dichtefunktionalprogramme verwenden gewöhnlich Pseudopotenziale,
die die 2p-Elektronen nicht als Valenz- sondern als Kernelektronen behandeln.
Hier werden Car-Parrinello Rechnungen unter Verwendung eines
Pseudopotenzials vorgestellt, das diese Orbitale nicht in den Kern
einbezieht. Damit können Verschiebungen dieser Energien berechnet werden,die
gut mit experimentellen Daten korrelieren.Die Car-Parrinello Methode
bietet dabei den Vorteil gegenüber anderen Rechnungen zur Elektronenstruktur,dass
das System zunächst durch thermische Relaxation
eine stabilen Konfiguration erreichen kann.
O 44.5 Fr 12:15 H38
Resonant photoemission spectra and electronic structure of
RT2 compounds (R = Ce, Pr, Nd; T = Co, Rh, Ir) — •Yuri
Kucherenko, Serguei Molodtsov, and Clemens Laubschat —
Institut für Festkörperphysik, TU Dresden, D-01062 Dresden
Resonant 4f photoemission spectra of RT2 Laves-phase compounds (R
= Ce, Pr, Nd; T = Co, Rh, Ir) taken at the 4d → 4f excitation threshold
are analysed in the framework of the single-impurity Anderson model.
The theoretical simulation of the shape of the photoemission spectra is
performed taking into account both surface and bulk contributions to
the spectral intensity. For a given T element the hybridization strength
is found to decrease in going from Ce to Nd as one would expect, but
the decrease is fairly slow (by about 20%). For given R it increases in

Oberflächenphysik Freitag
going from Co to Ir reflecting the spatial extension of the 3d, 4d and 5d
orbitals. The observed trends are in good agreement with calculated d−f
hybridization matrix elements and, consequently, d − f hybridization is
governed by the spatial overlap of the respective orbitals.
O 44.6 Fr 12:30 H38
Characterisation of the chemical composition and electronic
structure of LiCoO2 thin films using photoelectron
spectroscopy — •Andreas Thissen, David Ensling, Javier
Fernandez-Madrigal, and Wolfram Jaegermann — FB
Materialwissenschaften-Oberflaechenforschung, TU Darmstadt,
Petersenstr. 23, D-64287 Darmstadt
LiCoO2 is used as cathode materials for Li intercalation batteries.
Polycrystalline thin films have been prepared by magnetron sputtering
in an UHV chamber connected to an analysis system. Chemical analysis
using (S)XPS shows that a variation of the sputtering parameters
strongly influences the stoichiometry of the films, leading to different Co
oxidation states (2+, 3+, 4+). Depending on the chemical composition
changes in the electronic structure have been studied by UPS, ResPES
and XAS. The results are in good agreement with DFT band structure
calculations reported in literature. From ResPES measurements the separation
of the O2p- and Co3d-like valence band contributions was possible,
giving the occupation numbers as well. It has been shown by AFM,
REM, XRD, Raman spectroscopy and EXAFS, that also the morphology
and crystal structure of the samples depends on preparation conditions.
(Dis)charging experiments have been carried out in an in-situ battery
device in order to perform XPS and UPS measurements of the cathode
during battery operation. Changes in the electronic structure of the Li1xCoO2
host can clearly be correlated to the charging state of the battery.
O 44.7 Fr 12:45 H38
Second Harmonic Generation on NiO — •Georgios Lefkidis,
Khompat Satitkovitchai, and Wolfgang Hübner — TU Kaiserslautern,
PO Box 3409, D-67653, Germany
The second order susceptibility tensors, which are important for Optical
Second Harmonic Generation (SHG) are studied for NiO starting
from ab-initio calculations. To represent the (001) surface of the rock-
salt NiO lattice we embed a NiO −8
5 cluster in a charge point field which
accounts for the Madelung potential due to the neighboring ions. Sim-
O 45 Zeitaufgelöste Spektroskopie II
ilarly, an embedded NiO −10
6 cluster is used to represent the bulk. The
quantum chemical calculation is performed at various levels, where the
effect of the basis set is studied, and the energy correction due to electron
correlations. A Complete Active Space Configuration Interaction is
performed, while the excited states are studied with Single Excitation
Configuration Interaction (CIS) with energy contribution from double
and triple excitations. The electric and magnetic dipole transitions are
used to calculate the χ (2ω)
eee and χ (2ω)
mee tensors.
While inversion symmetry of the bcc lattice leads to zero tensor elements
for the bulk, the breaking of the symmetry on the surface gives
non-zero elements within the electric-dipole approximation. On the other
hand some χ (2ω)
mee elements exist for both bulk and surface. The effect of
spin-orbit coupling on both tensors is discussed.
O 44.8 Fr 13:00 H38
An X-ray absorption (NEXAFS) and resonant inelastic X-ray
scattering (RIXS) study of liquid water and aqueous solutions
— •O. Fuchs 1 , L. Weinhardt 1 , F. Maier 1 , C. Heske 1 , E. Umbach
1 , Y. Zubavichus 2 , M. Grunze 2 , M. Odelius 3 , L.G.M. Pettersson
3 , A. Nilsson 4 , J.D. Denlinger 5 , Z. Hussain 5 , and R. Follath
6 — 1 Exp. Physik II, Uni Würzburg — 2 Angew. Physikal. Chemie,
Uni Heidelberg — 3 Fysikum, Stockholm University — 4 Stanford Synchrotron
Radiation Lab — 5 ALS, Berkeley — 6 BESSY, Berlin
The electronic and geometric structure of liquids and, in particular, of
water and aqueous solutions is currently strongly discussed and investigated.
Until recently, most experimental results were obtained with neutron
and hard X-ray scattering experiments. Recently, soft X-ray spectroscopic
methods such as fluorescence-yield NEXAFS (near-edge X-ray
absorption fine structure) and RIXS were applied and compared with
theoretical DFT calculations and Car-Parinello molecular dynamics simulations.
This combination yields complementary information especially
about the dynamic hydrogen bond network and the molecular dynamics.
A third-generation synchrotron, a highly efficient spectrometer for soft
x-rays, and suitably designed wet cells are essential for RIXS experiments
on solutions. This talk presents a new spectrometer design consisting of
a spherical mirror and a plane variable line spacing grating for the sulfur
L2,3, carbon K, nitrogen K, and oxygen K edges, dedicated to the study of
biologically relevant molecules. Furthermore, RIXS and NEXAFS measurements
for water, heavy water, NaOH solutions (pH 15), and various
other aqueous solutions are discussed.
Zeit: Freitag 11:15–13:00 Raum: H39
O 45.1 Fr 11:15 H39
Two-pulse correlation of femtosecond laser-induced diffusion of
oxygen on Pt(111) — •K. Stépán, J. Güdde, and U. Höfer —
Fachbereich Physik, Philipps-Universität Marburg, D-35032 Marburg
We have studied the mechanism of oxygen diffusion on Pt(111) induced
by femtosecond laser pulses. The dissociative adsorption of O2 on a vicinal
surface was used to selectively decorate the step sites with atomic
oxygen [1]. Diffusion from the step edges onto the terraces was induced
at a substrate temperature of T = 80 K by 100-fs, 800-nm pump pulses
with absorbed fluences of 8-16 mJ/cm 2 . It was monitored in situ with
optical second-harmonic generation (SHG) by exploiting the sensitivity
of SHG to surface symmetry. The diffusion mechanism was explored in
the time domain by performing measurements of the diffusion efficiency
as a function of the delay time between two cross-polarized pump pulses.
The two-pulse correlation has a width of about 1 ps. This indicates a
diffusion process induced by multiple excitations from the hot electron
gas of the metal, similar to the meanwhile well-studied phenomenon of
desorption induced by multiple electronic excitations (DIMET) [2].
[1] P. Gambardella et al. Phys. Rev. Lett. 87, 056103 (2001)
[2] J. A. Misewich et al. Phys. Rev. Lett. 68, 3737 (1992)
O 45.2 Fr 11:30 H39
Electron Dynamics of C6F6/Cu(111) studied by time-resolved
photoelectron and resonant Auger-Raman spectroscopy —
•Patrick Kirchmann 1 , Panagiotis Loukakos 1 , Uwe Bovensiepen
1 , Martin Wolf 1 , Vijayalakshmi Sethuraman 2 , Franz
Hennies 2 , Alexander Föhlisch 2 und Wilfried Wurth 2 — 1 Freie
Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin
— 2 Universität Hamburg, Institut für Experimentalphysik, Luruper
Chaussee 149, 22761 Hamburg
Ultrafast charge transfer times in molecular resonances at metal substrates
can be obtained in the frequency domain by the ”atomic-clock”
method, i.e. where the ratio between ”Raman” type and ”Auger” type
decay channels of a resonant core hole excitation is evaluated [1]. On
the other hand, the temporal evolution of the population of photoinjected
electrons into an adsorbate resonance by a femtosecond laser pulse
can be probed directly in the time-domain by two-photon-photoemission
(2PPE)[2]. To compare these two approaches quantitatively, we performed
systematic experiments on C6F6/Cu(111) employing resonant X-ray
photoelectron spectroscopy at BESSY II and time-resolved 2PPE using
sub 30 fs laser pulses in the laboratory. Respective procedures of data
analysis and coverage dependent electron lifetimes will presented.
[1] W. Wurth and D. Menzel, Chem. Phys. 251, 141 (2000).
[2] C. Gahl, K. Ishioka, Q. Zhong, A. Hotzel, and M. Wolf; Faraday
Discussion 117, 191 (2000).

Oberflächenphysik Freitag
O 45.3 Fr 11:45 H39
Reflexions-Flugzeitspektrometer für Elektronen-
Koinzidenzspektroskopie — •Carsten Winkler, Gwilherm
Kerherve und Jürgen Kirschner — Max-Planck-Institut für
Mikrostrukturphysik, Weinberg 2, 06120 Halle
Ein Reflexions-Flugzeitspektrometer für die Elektronen-
Koinzidenzspektroskopie (e2e) an Oberflächen wird vorgestellt.
Das Gerät zeichnet sich durch seinen kompakten Aufbau und die
einfache Betriebsweise aus. Abhängig von dem Abstand zwischen Probe
und Spektrometer können entweder die Flugzeitauflösung oder der
erfassbare Raumwinkel optimiert werden.
Für die folgenden Experimente wurde das Spektrometer mit einer
Misch-Optimierung betrieben: die von der Oberfläche gestreuten Elektronen
driften zunächst über eine Strecke von ca. 190 mm in Richtung Spektrometer
(Raumwinkel: 0.3 sterad), wo sie dann eine rotationssymmetrische
Beschleunigungs- (ca. 190 mm) sowie die Reflexionseinheit (20 mm)
durchlaufen. Der Nachweis der reflektierten Elektronen erfolgt mittels eines
Multichannelplates (∅ 20 mm). Mit der verwendeten Elektronenquelle
können so typischerweise Flugzeitauflösungen von 2.7 ns und 1.9 ns bei
kinetischen Energien von 40 eV bzw. 10 eV erreicht werden. Dies entspricht
Energieauflösungen von 1.8 und 0.6 eV. Die Spektrometergeometrie,
die optimalen Betriebsparameter und die charakteristischen Grössen
wie Zeit- und Energieauflösung werden diskutiert. Darüberhinaus werden
erste Flugzeitspektren von Koinzidenzmessungen an Cu(110) und
Co/Cu(110) vorgestellt.
O 45.4 Fr 12:00 H39
Modification of adsorbate substrate coupling by means
of metallic-thin-film overlayers — •Marlies Wessendorf,
Carsten Wiemann, Michael Bauer, and Martin Aeschlimann
— Department of Physics, University of Kaiserslautern, D-67663
Kaiserslautern
We investigated the lifetime of Caesium atoms adsorbed on thin Ag
film overlayers on Cu(111) by means of time-resolved two-photon photoemission
spectroscopy (TR-2PPE). Direct and indirect interaction with
the silver overlayer gives rise to significant changes in the lifetime of the
adsorbate excitation. The electronic band structure of the Ag / Cu(111)
substrate can be controlled by variation of the Ag interface layer thickness
in a distinct way. Tuning the layer thickness allows to adjust the
excited states lifetimes of the adsorbate and, hence, gives the possibility
to control specific properties of chemical surface reactions such as efficiency
and reaction channel. In this paper we report our recent results
for Cs adsorption on Ag / Cu(111) overlayer systems. The experimental
results contain information about the dynamics of the decay of the investigated
intermediate adsorbed state as well as of the motion of the alkali
atoms perpendicular to the surface after excitation.
O 45.5 Fr 12:15 H39
Time-Resolved Laser-Synchrotron 2 Photon Photoemission —
•Annette Pietzsch, Franz Hennies, Vijayalakshmi Sethuraman,
Alexander Föhlisch, and Wilfried Wurth — Institut für
Experimentalphysik, Universität Hamburg, Luruper Chaussee 149, 22761
Hamburg
Time-resolved two-Photon Photoemission (2PPE) allows the investigation
of unoccupied electronic states by populating them with a pump
pulse and probing them with a delayed probe pulse. There, the intensity
from a certain intermediate state is measured as a function of the variable
delay time between the two pulses. Since optical lasers have a limited
energy range, excitation with a laser pulse followed by subsequent probing
of a synchrotron pulse offers the great advantage of being tunable
O 46 Grenzfläche fest-flüssig
in energy. This technique of time-resolved laser-synchrotron 2PPE has
been performed in a proof-of-principle experiment at the MBI-Beamline
at BESSY.
The ns-electron dynamics at the BaF2/Si(001) interface has been investigated
revealing the relaxation time scale of silicon band bending at
the interface. The excitation and decay processes of excited states in C60
films have been studied leading to an estimation of the life time of the
laser excited states.
This project is funded by the DFG in the framework of the priority
program ”Dynamics of Electron Transfer Processes at Interfaces”.
O 45.6 Fr 12:30 H39
Electron relaxation dynamics in Ag nanoparticles on Graphite
— •C. Kennerknecht, M. Merschdorf, and W. Pfeiffer —
Physikalisches Institut, Universität Würzburg, Am Hubland, 97074
Würzburg, Germany
The properties of supported nanoparticles differ substantially from homogeneous
films or bulk material. This makes them interesting for applications,
like for example in catalysis [1] or for single electron tunneling
devices [2]. We show that 2-photon-photoemission spectroscopy can be
used as local time-resolved probe for both relaxation dynamics in the
nanoparticles as well as local transient potential shifts that are directly
related to the charge transfer between particle and substrat.
Resonant multiphoton photoemission spectra map the transient electron
energy distribution in the nanoparticles and reveal the internal thermalization
and cooling of the electron gas. A phenomenological model
based on the Boltzmann equations that includes the charge transfer between
substrate and nanoparticle is used to simulate the transient electron
energy distribution. Optimization of the model parameters shows
that the injection of excited electrons into the nanoparticle accounts for
almost half of the total deposited energy in the nanoparticle strongly
influencing the transient electron distribution in the nanoparticles. In
agreement with results from tunneling spectroscopy [2] our measurements
reveal a rather weak electronic coupling between nanoparticle and substrate.
[1] M. Valden, et al., Science 281, 1647 (1998)
[2] T. Ohgi, et al., Appl. Phys. Lett. 79, 2453 (2001)
O 45.7 Fr 12:45 H39
Scattering by Cu adatoms between image-potential bands
on Cu(001) — •Klaus Boger, Martin Weinelt, and Thomas
Fauster — Lehrstuhl für Festkörperphysik, Universität Erlangen-
Nürnberg, Staudtstr. 7, 91058 Erlangen
With increasing resolution and sensitivity of photoelectron spectroscopy
the influence of defects is becoming more and more obvious.
The scattering processes induced by adsorbate atoms can be studied by
time- and angle-resolved two-photon photoemission. We have examined
the dynamics of electrons in image-potential states on the Cu(001)
surface for different coverages of statistically distributed Cu adatoms.
The following scattering mechanisms were distinguished [1]: Scattering
into the bulk, elastic and inelastic intraband scattering, resonant and
inelastic interband scattering. The rates for these different processes
were estimated by modeling the time-resolved measurements with
optical Bloch equations. By varying the defect density the source of the
various processes can be identified: The Cu adatoms mainly provoke
elastic scattering. Inelastic scattering is due to interaction with electrons
in the bulk.
[1] K. Boger, M. Weinelt, J. Wang, Th. Fauster, Appl. Phys. A 78, 161
(2004)
Zeit: Freitag 11:15–12:45 Raum: H45
O 46.1 Fr 11:15 H45
In-situ Electrochemical Corrosion studied with Synchrotron
Radiation — •Frank Uwe Renner 1,2 , Andreas Stierle 2 , Helmut
Dosch 2 , and Jörg Zegenhagen 1 — 1 ESRF, BP 220, 38043
Grenoble Cedex, France — 2 Max-Planck-Institut für Metallforschung,
70569 Stuttgart, Germany
In our humid atmosphere, most corrosion processes are electrochemical
in nature, driven by contact potentials, e.g., forming between dissimilar
metals. For the basic understanding of corrosion and similar technical
processes, in-situ structural methods capable of atomic resolution, such
as scanning probe or hard X-ray techniques are necessary. Binary metal
alloys serve as model systems for more complicated technically used metal
alloys. We used in-situ methods, like X-ray diffraction and anomalous
X-ray scattering and ex-situ AFM, to study Cu3Au(111) single crystal
surfaces in 0.1MH2SO4 electrolyte as a function of electrode potential.
During the initial electrochemical corrosion Cu atoms are dissolved and
a passivating layer is formed. The experiments show the formation of an
epitaxial ultra-thin CuxAu1−x(111) phase on the surface at a potential

Oberflächenphysik Freitag
where Cu dissolution starts. At higher potentials thicker and still epitaxial
Au islands are emerging on the surface. The applied potential range
is although always well below the so-called critical potential, where the
passivation breaks down and massive Cu dissolution starts. AFM images
reveal a surface that is densely packed with Au islands of a homogeneous
size distribution. Only with longer timescales a more porous morphology
of the surface evolves.
O 46.2 Fr 11:30 H45
X-ray reflectivity of thin liquid films — •Robert Fendt 1 , Christian
Gutt 1 , Michael Sprung 1 , Tuana Ghaderi 1 , Oliver Seeck 2 ,
and Metin Tolan 1 — 1 Experimentelle Physik I, Universität Dortmund,
44221 Dortmund — 2 IFF, Forschungszentrum Jülich, 52425 Jülich
Physical properties of confined liquids may differ significantly from
those of the corresponding bulk liquids. The confinement of a liquid between
a hard wall and the liquid-gas interface on a nanometer thick region
is expected to alter the liquid structure drastically.
We investigated the structure of thin liquid heptane and heptanol films
(thickness of 2-12 nm) adsorbed on silicon substrates by means of x-ray
reflectivity. The aim of the experiment was to study (i) the liquid-solid
interface, (ii) the influence of substrate-adsorbate interaction and (iii)
the capillary wave spectrum of the films. The experiments were carried
out using a newly constructed sample cell which allows to cover a substrate
by a liquid film via gas adsorption. Experiments were carried out
at the W1 diffractometer at Hasylab, Hamburg and at Dortmund using
a laboratory diffractometer.
The results show that the density of thin liquid heptane films is well
described by a homogenous electron density and a capillary wave broadened
interface to the gas phase. In contrast thin films of the corresponding
alcohol heptanol show pronounced oscillations in the electron density
profile, indicating a layering of the molecules close to the hard wall.
O 46.3 Fr 11:45 H45
Nanofluidics: Viscous Dissipation in Layered Liquid Films —
•Thomas Becker and Frieder Mugele — Angewandte Physik, Universität
Ulm, Albert Einstein Allee 11, 89081 Ulm
Using a temperature-controlled 2D-imaging Surface Forces Apparatus
(SFA) we investigated the layer-by-layer collapse of molecularly thin films
of a model liquid between two atomically smooth substrates as a function
of temperature. The dynamics of the consecutive expulsion of four
molecular layers were found to slow down with decreasing film thickness
but showed no evidence for confinement introduced solidification. Using a
new hydrodynamic model, we show that the sliding friction of the liquid
layers on top of the solid substrates is approximately 35 times higher than
the mutual friction between adjacent liquid layers. The latter was independent
of film thickness and in close agreement with the bulk viscosity
[1]. [1] T. Becker and F. Mugele, Phys. Rev. Lett. 91 , p. 166104/1-4
(2003)
O 46.4 Fr 12:00 H45
Interactions Between Seeds and Silicon Nanorods Grown by
Thermal CVD — •Vladislav Spassov, Alan Savan, and Henry
Haefke — CSEM Swiss Center for Electronics and Microtechnology,
Inc., Rue Jaquet-Droz 1, CH 2000, Neuchatel, Switzerland
Growth of silicon nanorods or whiskers by thermal chemical vapor deposition
(CVD) often takes place by the vapor-liquid-solid (VLS) mechanism.
A catalytic seed, for example gold, liquefies on the surface of a
supporting substrate, decomposing the source material in the gas phase
and increasing the epitaxial growth rate of a crystal below it. In the case
of gold, the metal cap remains at the top surface, with the pure, crystalline
silicon nanorod growing up from below. While silicon is the most
widely-used semiconductor material used for the fabrication of electronic
devices to date, gold is normally avoided during device processing, because
it migrates rapidly into silicon and creates deep levels which can
degrade device performance. In this investigation, we use high resolution
transmission electron microscopy (HR-TEM) to examine the interface between
the seed and the Si nanorod. Further studies look for the presence
and placement of catalyst or catalyst-silicon alloy or eutectic mixtures in
or along the nanorod.
O 46.5 Fr 12:15 H45
Structural and electronic effects in the electrochemical properties
of UHV prepared bimetallic Pt/Ru(0001) electrodes
— •H.E. Hoster, E. Filonenko, and R.J. Behm — Abteilung
Oberflächenchemie und Katalyse, Universität Ulm, 89069 Ulm
Combining UHV-STM with cyclic voltammetry in an electrochemical
prechamber, we have investigated the adsorption of H and OH in HClO4
solution on two different, well-defined types of bimetallic Pt/Ru(0001)
surfaces. On pure Ru(0001) the removal of OHad in the cathodic scan,
together with the simultaneous adsorption of Hupd, and its counterpart
in the reverse scan direction exhibit a significant hysteresis. In the presence
of vapor deposited Pt monolayer islands, these processes proceed
much more rapidly in a couple of sharp peaks around 100 mV RHE,
with no apparent hysteresis. We explain the enhanced H adsorption by
a kinetic promotion effect, including facile hydrogen adsorption on the
Pt islands and subsequent spill-over to the Ru areas, where the adsorbed
hydrogen can react with OHad. In the anodic scan, the Pt sites in turn
allow for a faster oxidation of H adsorbed at Ru. On atomically smooth
PtxRuy/Ru(0001) surface alloys, which are formed by subsequent annealing
of the Pt covered substrate to higher temperatures, adsorption of OH
and H are again modified significantly. Comparing results for different Pt
surface contents, where the concentration and ensemble size distribution
of the Pt surface atoms are determined by atomically resolved STM images
with chemical contrast, allows conclusions on the effect of specific
adsorption ensembles and adsorption sites.
O 46.6 Fr 12:30 H45
Adsorption of lead on copper surfaces — •Ari P Seitsonen
und Jürg Hutter — Physikalisch Chemisches Institut der Universität
Zürich
Adsorption of Pb on Cu(100) and Cu(111) leads to a variety of interesting
phenomena. We use molecular dynamics methods to simulate
the Pb monolayer on the copper surfaces, employing both density functional
theory (DFT) to describe the electronic wave functions explicitly,
and embedded atom method (EAM) for an empirical, fitted interaction
between the atoms. We study the melting of the overlayer, and perform
simulations at various different temperature regions.

Tiefe Temperaturen Tagesübersichten
Hauptvorträge
TIEFE TEMPERATUREN (TT)
Prof. Dr. Gerd Schön
Institut für Theoretische Festkörperphysik
Universität Karlsruhe
Wolfgang-Gaede-Str. 1
76131 Karlsruhe
E-Mail: gerd.schoen@phys.uni-karlsruhe.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsäle H18, H19, H20 und Poster A)
TT 2.1 Mo 11:15 (H20) Neutron scattering investigations of high Tc compounds: what have we
learned so far?, Lothar Pintschovius
TT 4.1 Mo 10:00 (H19) Kalte Atome in optischen Gittern, Wilhelm Zwerger
TT 9.1 Di 09:30 (H20) Wavefunction Imaging Studies of Cuprate Superconductivity,
Séamus Davis, K. McElroy, E. W. Hudson, J. E. Hoffman, D.-H. Lee, H. Eisaki,
S. Uchida
TT 10.1 Di 10:00 (H18) Local quantum criticality and non-Fermi liquid properties, Qimiao Si
TT 13.1 Di 15:45 (H20) Anwendung supraleitender Quanteninterferenzdetektoren in der Messtechnik,
Hans-Georg Meyer
TT 14.1 Di 14:30 (H18) Lattice instability of frustrated orbital and spin systems, Maxim Mostovoy
TT 14.8 Di 16:50 (H18) Resonant Soft Energy X-ray Diffraction of Charge, Spin and Orbital Ordering,
Peter Hatton
TT 19.1 Mi 16:45 (H20) Triplet correlations in superconductor-ferromagnet hybrid structures,
Matthias Eschrig, Juha Kopu, Juan-Carlos Cuevas, A. Konstandin, Gerd Schön
TT 25.3 Do 10:30 (H20) Quantum dynamics of persistent current qubits, Kees Harmans
TT 25.4 Do 11:15 (H20) Superconducting Structures for Quantum Computing, Gianni Blatter, Vadim
Geshkenbein, Mikhail Feigelman, Lev Ioffe
TT 25.6 Do 12:15 (H20) π-superconductivity in S/F nano-structures, Marco Aprili, T. Kontos, W.
Guichard, ML. Della Rocca, J. Lesueur, P. Gandit
TT 27.1 Do 09:30 (H19) Molecular wires in electromagnetic fields, Sigmund Kohler, Jörg Lehmann,
Sébastien Camalet, Peter Hänggi
TT 28.1 Do 14:00 (H20) Opportunities and challenges from electron spectroscopy for realistic correlated
electron theory, J. W. Allen
TT 28.2 Do 14:25 (H20) Dynamical Mean Field Theory (DMFT) and Electronic Structure Calculation,
G. Kotliar
TT 28.4 Do 15:15 (H20) Wannier functions formalism and DMFT, V. I. Anisimov

Tiefe Temperaturen Tagesübersichten
Fachsitzungen
TT 1 Supraleitung: Herstellung und Charakterisierung Mo 09:30–11:00 H20 TT 1.1–1.6
TT 2 Supraleitung: Mechanismen, Phasendiagramm, konkurrierende
Ordnungen
Mo 11:15–12:45 H20 TT 2.1–2.5
TT 3 Spin-Systeme und itinerante Magnete Mo 09:30–13:00 H18 TT 3.1–3.14
TT 4 Quantenflüssigkeiten, Bose-Einstein Kondensate, ultrakalte
Atome, ...
Mo 10:00–12:15 H19 TT 4.1–4.8
TT 6 Niederdimensionale Systeme (incl. Peierls-Übergang,
organische Leiter, ...)
Mo 14:15–17:45 H18 TT 6.1–6.14
TT 7 Korrelierte Elektronen: Schwere Fermionen Mo 14:30–17:00 H19 TT 7.1–7.9
TT 8 Postersitzung I: Supraleitung Mo 14:30–19:00 Poster A TT 8.1–8.54
TT 9 Supraleitung: Eigenschaften, elektronische Struktur,
Ordnungsparameter
Di 09:30–13:00 H20 TT 9.1–9.12
TT 10 FV-internes Symposium ”Quantum Phase Transitions”
Di 10:00–12:55 H18 TT 10.1–10.5
TT 11 Nanoelektronik I: Quantenpunkte, -drähte, -punktkontakte
Di 09:30–13:00 H19 TT 11.1–11.14
TT 12 Supraleitung: Anwendungen, Materialien, technische
Supraleiter, Bauelemente
Di 14:30–15:30 H20 TT 12.1–12.4
TT 13 Messgeräte, Kryotechnik Di 15:45–18:45 H20 TT 13.1–13.10
TT 14 FV-internes Symposium ”Orbital Physics” Di 14:30–18:55 H18 TT 14.1–14.14
TT 15 Korrelierte Elektronen: Theorie I Di 14:30–16:30 H19 TT 15.1–15.8
TT 16 Korrelierte Elektronen: Quantenstörstellen, Kondo-
Physik
Di 16:45–19:00 H19 TT 16.1–16.9
TT 17 Postersitzung II: Transport, Quantenkohärenz, Quantenflüssigkeiten
Di 14:30–19:00 Poster A TT 17.1–17.32
TT 18 Supraleitung: Tunneln, Josephson-Kontakte, SQUIDs Mi 14:30–16:30 H20 TT 18.1–18.8
TT 19 Supraleitung: Heterostrukturen, Andreev-Streuung,
Proximity-Effekt, Koexistenz
Mi 16:45–18:45 H20 TT 19.1–19.7
TT 20 Metall-Isolator-Übergänge Mi 14:30–16:30 H18 TT 20.1–20.8
TT 21 Quantenkritische Phänomene Mi 16:45–18:00 H18 TT 21.1–21.5
TT 22 Quantenkohärenz und Quanteninformationssysteme I Mi 14:30–17:15 H19 TT 22.1–22.11
TT 23 Nanoelektronik II: Spin-Elektronik Mi 17:30–18:30 H19 TT 23.1–23.4
TT 24 Postersitzung III: Korrelierte Elektronen, ”Orbital
Physics”
Mi 14:30–19:00 Poster A TT 24.1–24.56
TT 25 FV-internes Symposium ”Superconducting Qubits
and π-junctions”
Do 09:30–12:45 H20 TT 25.1–25.6
TT 26 Korrelierte Elektronen: Theorie II Do 09:30–13:00 H18 TT 26.1–26.13
TT 27 Nanoelektronik III: Molekulare Elektronik Do 09:30–12:45 H19 TT 27.1–27.11
TT 28 FV-internes Symposium ”Theoretical Modeling of
Materials with Correlated Electrons”
Do 14:00–18:10 H20 TT 28.1–28.9
TT 29 Quantenkohärenz und Quanteninformationssysteme
II
Do 14:30–18:00 H19 TT 29.1–29.13
TT 30 Postersitzung IV: Kritische Phänomene, Quantenstörstellen,
niederdimensionale Systeme
Do 14:30–19:00 Poster A TT 30.1–30.41
TT 31 Supraleitung: Vortexdynamik, Vortexphasen, Pinning Fr 10:15–12:45 H20 TT 31.1–31.10
TT 32 Theoretische Modelierung von Materialien mit korrelierten
Elektronen
Fr 10:15–13:00 H18 TT 32.1–32.11
TT 33 Amorphe- und Tunnelsysteme, Gläser Fr 10:15–11:30 H19 TT 33.1–33.5

Tiefe Temperaturen Tagesübersichten
Fachverbands-übergreifende Symposien
SYSN Symposium ”Quantum Shot Noise in Nanostructures” (TT+DY+HL) Mo 13:30-17:45 H1
Organisation: Wolfgang Belzig (Universität Basel) Christoph Strunk (Universität Regensburg)
Hauptvorträge
SYSN 1.1 Mo 13:30 (H1) Quantum Shot Noise in Nanostructures: From Schottky to Bell,
Markus Büttiker
SYSN 1.2 Mo 14:00 (H1) Mesoscopic transition in the shot noise of diffusive SNS junctions,
Francois Lefloch, Christian Hoffmann, Marc Sanquer, Bernard Pannetier
SYSN 1.3 Mo 14:30 (H1) Quantum Noise: Challenge and Prospect, Yuli V. Nazarov
SYSN 2.1 Mo 16:00 (H1) Environmental effects in the third moment of voltage fluctuations in a
tunnel junction, Bertrand Reulet, J. Senzier, Daniel E. Prober
SYSN 2.2 Mo 16:30 (H1) Full Counting Statistics of Multiple Andreev Reflections,
Juan Carlos Cuevas
Weitere Beiträge siehe Programm SYSN
SYNF Symposium ”Non-Fermi Liquids in Quantum Structures” (HL+TT+MA) Do 15:00-18:30 H1
Organisation: M. Sassetti (Universita di Genova) R. Haug (Universität Hannover)
Hauptvorträge
SYNF 1.1 Do 15:00 (H 1) Coulomb Drag Between Quantum Wires: Beyond Tomonaga-Luttinger
Model, Leonid Glazman
SYNF 1.2 Do 15:35 (H 1) Spin and Charge Separation and Localization in One - Dimension Measured
Using Momentum Resolved Tunneling, Amir Yacoby
SYNF 1.3 Do 16:10 (H 1) Probing spin-charge separation in tunnel-coupled parallel quantum wires,
M. Governale, U. Zülicke
SYNF 1.4 Do 16:45 (H 1) A carbon nanotube quantum dot coupled to superconductors,
Mark Buitelaar, Bakir Babic, Wolfgang Belzig, Christoph Bruder, Thomas Nussbaumer,
Christian Schönenberger
SYNF 1.5 Do 17:20 (H 1) Dimensional crossover and deconfinement in Bechgaard salts,
Thierry Giamarchi
SYNF 1.6 Do 17:55 (H 1) Spectroscopic signatures of spin-charge separation in a quasi-onedimensional
organic conductor, Ralph Claessen
Fachverbands-interne Symposien
TT 10 Symposium ”Quantum Phase Transitions” Di 10:00-12:55 H18
Organisation: Matthias Vojta (Universität Karlsruhe)
Haupt- und Fachvorträge
TT 10.1 Di 10:00 (H18) Local quantum criticality and non-Fermi liquid properties, Qimiao Si
TT 10.2 Di 10:35 (H18) Singular behavior near a quantum critical point: YbRh2(Si,Ge)2,
P. Gegenwart
TT 10.3 Di 11:05 (H18) Non-Fermi liquid phase of a pure itinerant-electron magnet, C. Pfleiderer
TT 10.4 Di 11:50 (H18) Monte Carlo simulations of quantum phase transitions in dissipative systems
and ultra-cold atoms, Matthias Troyer, Philipp Werner, Klaus Völker, Fabien
Alet, Stefan Wessel, George G. Batrouni
TT 10.5 Di 12:25 (H18) Numerical renormalization group for bosons and fermions: Impurity
quantum phase transitions, Ralf Bulla

Tiefe Temperaturen Tagesübersichten
TT 14 Symposium ”Orbital Physics” Di 14:30-18:50 H18
Organisation: A. Freimuth (Universität zu Köln) B. Keimer (MPI für Festkörperforschung, Stuttgart)
Haupt- und Fachvorträge
TT 14.1 Di 14:30 (H18) Lattice instability of frustrated orbital and spin systems, Maxim Mostovoy
TT 14.2 Di 15:00 (H18) Magnetism, Charge Order and Giant Magnetoresistance in SrFeO3−δ,
C. Ulrich, A. Lebon, P. Adler, C. Bernhard, A. Boris, A. Pimenov, A. Maljuk, C.T.
Lin, B. Keimer
TT 14.8 Di 16:50 (H18) Resonant Soft Energy X-ray Diffraction of Charge, Spin and Orbital Ordering,
Peter Hatton
TT 14.9 Di 17:20 (H18) The interplay of orbital and lattice degrees of freedom in titanates,
M. Grüninger, R. Rückamp, A. Gössling, M. Cwik, H. Roth, J. Baier, M. Kriener,
T. Lorenz, M. Braden, A. Freimuth
TT 25 Symposium ”Superconducting Qubits and π-junctions” Do 9:30-12:45 H20
Organisation: R. Gross (Walther-Meissner-Institut, Garching)
J. Mannhart (Universität Augsburg)
R. Kleiner (Universität Tübingen)
Haupt- und Fachvorträge
TT 25.1 Do 9:30 (H20) Charge-phase Josephson qubit with radio frequency readout,
Alexander Zorin
TT 25.2 Do 10:00 (H20) Exploring quantum dynamics of Josephson vortices, A.V. Ustinov, A. Wallraff,
M.V. Fistul, A. Kemp, A. Lukashenko, J. Lisenfeld, Y. Koval
TT 25.3 Do 10:30 (H20) Quantum dynamics of persistent current qubits, Kees Harmans
TT 25.4 Do 11:15 (H20) Superconducting structures for quantum computing, Gianni Blatter, Vadim
Geshkenbein, Mikhail Feigelman, Lev Ioffe
TT 25.5 Do 11:45 (H20) Semifluxons as a base for classical and quantum digital circuits?,
Edward Goldobin , Tobias Gaber, Albert Sterck, Dieter Koelle, Reinhold Kleiner
TT 25.6 Do 12:15 (H20) π-superconductivity in S/F nano-structures, Marco Aprili, T. Kontos, W.
Guichard, ML. Della Rocca, J. Lesueur, P. Gandit
TT28 Symposium ”Theoretical Modeling of Materials with Correlated Electrons” Do 14:00-18:10 H20
Organisation: K. Held (MPI für Festkörperforschung, Stuttgart) D. Vollhardt (Universität Augsburg)
Haupt- und Fachvorträge
TT 28.1 Do 14:00 (H20) Opportunities and challenges from electron spectroscopy for realistic correlated
electron theory, J. W. Allen
TT 28.2 Do 14:25 (H20) Dynamical Mean Field Theory (DMFT) and Electronic Structure Calculation,
G. Kotliar
TT 28.3 Do 14:50 (H20) How Chemistry Controls Electron Localization in 3d 1 Perovskites,
O. K. Andersen
TT 28.4 Do 15:15 (H20) Wannier functions formalism and DMFT, V. I. Anisimov
TT 28.5 Do 15:40 (H20) Multi-Band Gutzwiller Method for Transition metals and Compounds:
Magnetism, Fermi Surfaces and Spin-Orbit Coupling, Werner Weber, Jörg
Bünemann, Florian Gebhard
TT 28.6 Do 16:30 (H20) Partial localization, dual nature of 5f electrons and heavy fermions in U
compounds, G. Zwicknagl
TT 28.7 Do 16:55 (H20) Realistic Description of Strongly Correlated Materials, A. I. Lichtenstein
TT 28.8 Do 17:20 (H20) The orbital state and magnetic properties of LiV2O4: Recent insight from
LDA+DMFT, Th. Pruschke
TT 28.9 Do 17:45 (H20) Coulomb Correlations in Multi-Orbital Materials, A. Liebsch

Tiefe Temperaturen Tagesübersichten
Mitgliederversammlung des Fachverbands Tiefe Temperaturen
Do 18:30–19:30 H19
Tagesordnung
1) Frühjahrstagung 2004, Statistik
2) Bericht: DPG und AKF Sitzungen, Frühjahrstagung 2005
3) Themenkreise
4) FV-übergreifende Symposien
5) Verschiedenes

Tiefe Temperaturen Tagesübersichten
Montag, 8.3.04
8:30-9:15 Plenarvortrag Ketterle
9:30-11:00 TT 1 H20
Supraleitung: Herstellung und
Charakterisierung
11:15-12:45 TT 2 H20
Supraleitung: Mechanismen,
Phasendiagramm,
konkurrierende Ordnungen
11:15 HV Pintschovius
13:30-17:45 SYSN H1
Symposium ”Quantum shot noise
in nanostructures”
13:30 HV Büttiker
14:00 HV Lefloch
14:30 HV Nazarov
16:00 HV Reulet
16:30 HV Cuevas
Übersicht über die Sitzungen des Fachverbands Tiefe Temperaturen
9:30-13:00 TT 3 H18
Spin-Systeme und
itinerante Magnete
14:30-18:00 TT 6 H18
Niederdimensionale Systeme
14:30-19:00 TT 8 Postersitzung I: Supraleitung Poster A
18:00-18:45 Plenarvortrag Braeuchle
Dienstag, 9.3.04
8:30-9:15 Plenarvortrag Martin-Moreno
9:30-13:00 TT 9 H20
Supraleitung: Eigenschaften,
elektronische Struktur,
Ordnungsparameter
9:30 HV Davis
10:00-12:55 TT 10 H18
FV-internes Symposium
”Quantum Phase Transitions”
10:00 HV Si
10:35 FV Gegenwart
11:05 FV Pfleiderer
11:50 HV Troyer
12:25 FV Bulla
13:30-14:15 Young physicists special plenary lecture: Nelson
14:30-15:30 TT 12 H20
Supraleitung: Anwendungen,
Materialien, technische Supraleiter,
Bauelemente
15:45-18:30 TT 13 H20
Messgeräte, Kryotechnik
15:45 HV Meyer
14:30-18:55 TT 14 H18
FV-internes Symposium
”Orbital Physics”
14:30 HV Mostovoy
15:00 FV Ulrich
16:50 HV Hatton
17:20 FV Grüninger
10:00-12:15 TT 4 H19
Quantenflüssigkeiten,
BE-Kondensate
ultrakalte Atome, ...
10:00 HV Zwerger
14:30-17:00 TT 7 H19
Korrelierte Elektronen:
Schwere Fermionen
9:30-13:00 TT 11 H19
Nanoelektronik I:
Quantenpunkte, -drähte,
-punktkontakte
14:30-17:00 TT 15 H19
Korrelierte Elektronen:
Theorie I
16:45-19:00 TT 16 H19
Korrelierte Elektronen:
Quantenstörstellen,
Kondo-Physik
14:30-19:00 TT 17 Postersitzung II: Transport, Quantenkohärenz, Quantenflüssigkeiten Poster A

Tiefe Temperaturen Tagesübersichten
Mittwoch, 10.3.04
8:30-10:00 Plenarvorträge Theis, Stoehr
10:00-13:00 Festsitzung Preisträgervortrag Morgenstern, Festvortrag Mlynek
14:30-16:00 Preisträgervorträge Steglich, Sander
14:30-16:30 TT 18 H20
Supraleitung: Tunneln,
Josephson-Kontakte, SQUIDs
16:45-18:45 TT 19 H20
Supraleitung: Heterostrukturen,
Andreev-Streuung, Proximity-Effekt,
Koexistenz
16:45 HV Eschrig
14:30-16:30 TT 20 H18
Metall-Isolator-Übergänge
16:45-18:00 TT 21 H18
Quantenkritische Phänomene
14:30-19:00 TT 24 Postersitzung III: Korrelierte Elektronen, ”Orbital Physics” Poster A
Abendvortrag Wlitschko
Donnerstag, 11.3.04
8:30-9:15 Plenarvortrag Abrikosov
9:30-12:45 TT 25 H20
FV-internes Symposium
”Superconducting Qubits
and π-junctions”
9:30 FV Zorin
10:00 FV Ustinov
10:30 HV Harmans
11:15 HV Blatter
11:45 FV Goldobin
12:15 HV Aprili
15:00-17:45 SYNF H1
Symposium
”Non-Fermi Liquids
in Quantum Structures”
15:00 HV Glazman
15:35 HV Yacoby
16:10 HV Governale
16:45 HV Buitelaar
17:20 HV Giamarchi
17:55 HV Claessen
9:30-13:00 TT 26 H18
Korrelierte Elektronen:
Theorie II
14:00-18:10 TT 28 H20
FV-internes Symposium
”Theoretical Modeling of
Materials with Correlated Electrons”
14:00 HV Allen
14:25 HV Kotliar
14:50 FV Andersen
15:15 HV Anisimov
15:40 FV Weber
16:30 FV Zwicknagel
16:55 FV Lichtenstein
17:20 FV Pruschke
17:45 FV Liebsch
14:30-17:15 TT 22 H19
Quantenkohärenz und
Quanteninformationssysteme
17:30-18:30 TT 23 H19
Nanoelektronik II:
Spin-Elektronik
9:30-12:45 TT 27 H19
Nanoelektronik III:
Molekulare Elektronik
9:30 HV Kohler
14:30-18:00 TT 29 H19
Quantenkohärenz und
Quanteninformationssysteme II
14:30-19:00 TT 30 Postersitzung IV: Kritische Phänomene, Quantenstörstellen, niederdimensionale Systeme Poster A
18:30 Mitgliederversammlung H19
Abendvortrag Lesch
Freitag, 12.3.04
8:30-10:00 Plenarvorträge Chaikin, Weller
10:15-12:45 TT 31 H20
Supraleitung: Vortexdynamik,
Vortexphasen, Pinning
10:15-13:00 TT 32 H18
Theoretische Modelierung
von Materialien
mit korrelierten Elektronen
10:15-11:30 TT 33 H19
Amorphe- und Tunnelsysteme,
Gläser

Tiefe Temperaturen Montag
Fachsitzungen
– Haupt-, Fach-, Kurzvorträge und Posterbeiträge –
TT 1 Supraleitung: Herstellung und Charakterisierung
Zeit: Montag 09:30–11:00 Raum: H20
TT 1.1 Mo 09:30 H20
Molecular beam epitaxy of electron doped high-temperature
superconductors — •Yoshiharu Krockenberger 1 , Michio
Naito 1 , Akio Tsukada 1 , Hideki Yamamoto 1 , Lambert Alff 2 ,
and Rudolf Gross 2 — 1 NTT Basic Research Laboratories, NTT Corporation,
3-1 Morinosato-Wakamiya, Atsugi-shi, Kanagawa 243-0198,
Japan — 2 Walter-Meissner-Institut, 85748 Garching, Germany
The field of high temperature superconductors has been investigated
intensively. Among the studied materials, electron doped high temperature
superconductors are a minority class and only two families are
known: The T ′ and infinite-layer compounds. The superconducting transition
temperatures (Tc) are moderate even for optimum doping: 30K for
T ′ -compounds. Furthermore, sample preparation is very difficult. Nevertheless,
n-type cuprates are of high interest and essential from the basic
physics point of view, especially as to whether or not electron-hole symmetry
holds in the high-Tc superconductors. As reported recently by Alff
et al.[1] tunneling spectroscopy on thin film electron doped cuprates pinpointed
detailed features of the pseudogap behavior. Therefore, we have
investigated the growth and especially the reduction conditions (removal
of apical oxygen) of T ′ -RE2−xCexCuO4+δ thin films for a wide doping
variation.
[1] L. Alff et al., Nature 422, 698 (2003)
TT 1.2 Mo 09:45 H20
Thickness dependence of superconducting properties of ultrathin
Nb and NbN films — •Konstantin Il’in 1 , Michael Siegel 1 ,
Alexei Semenov 2 , Andreas Engel 2 , Heinz-Wilhelm Hübers 2 ,
Eugen Hollmann 3 , Gregory Gol’tsman 4 , and Boris Voronov 4
— 1 Institut für Mikro- und Nanoelektronische Systeme, Universität Karlsruhe,
Karlsruhe — 2 DLR Institut für Planetenforschung, Berlin —
3 Forschungszentrum Jülich GmbH, Jülich — 4 MSPU, Moscow, Russia
We studied systematically superconducting properties of Nb and NbN
films widely used in modern detector technology. The films with a thickness
from 3.5 to 100 nm were deposited by reactive magnetron sputtering.
The Ginzburg-Landau coherence length and the electron diffusion constant
have been obtained from the temperature dependence of the second
critical magnetic field, HC2. We have found that diffusivity in ultra-thin
films reduces with thickness. The non-linear temperature dependence of
HC2 of NbN films at temperatures close to TC was attributed to the
granular structure of the films. At low temperatures, where the normal
core of a magnetic vortex is smaller than the grain size, HC2 depends
linear on temperature. The grain size of 40-80 nm was estimated from
the crossover temperature, where the dependence of HC2 on temperature
changes from linear to non-linear behaviour. We found that grain size and
its dependence on film thickness is determined by sputtering conditions.
TT 1.3 Mo 10:00 H20
Superconducting thin films of the heavy fermion compound
UNi2Al3
— •M. Jourdan, A. Zakharov, M. Foerster, and H. Adrian —
Institut für Physik, Johannes Gutenberg Universität, 55099 Mainz
Thin films of the presumably unconventional superconductor UNi2Al3
were prepared to obtain dedicated samples for novel experiments on the
superconducting order parameter (e.g.tunnelling spectroscopy). UNi2Al3
was deposited by coevaporation of the elementary components in an MBE
system. The preparation on various substrates was studied and epitaxial
growth in (100)-direction was observed. With optimized deposition
parameters thin films showing the typical properties known from bulk
samples were obtained. The best films up to now show a superconducting
transition with Tc ≃ 0.75K. Measurements of the angular dependence
of the upper critical field Bc2(θ) will be presented.
TT 1.4 Mo 10:15 H20
Transition metal, boride and oxide doped Fe/MgB2 tapes and
wires — •Bing Liu, S. Schlachter, and W. Goldacker —
Forschungszentrum Karlsruhe ITP 76021 Karlsruhe,P.O. Box 3640
Transition metal, boride and oxide doped mono- and multifilamentary
Fe/MgB2 tapes and wires have been prepared by the powder-intube
technique at ambient pressure from different precursors. For each
composition, the heating process has been optimized to the full extent
according to DTA measurements. We determined Tc and the transport
critical current density in magnetic fields up to 9T and investigated the
microstructure with high-resolution SEM and quantitative EDX analysis.
Compared with undoped samples, Jc and Hirr of doped samples have
been enhanced significantly in high fields by effective pinning centers and
improved grain connection due to sintering aid effect from the additives,
with the highest Jc value over 5000A/cm2 at 4.2K/9T and insignificant
Tc suppression. However, the improvement of thermal and mechanical
stability of Fe/MgB2 tapes and wires remains a challenge for the future.
TT 1.5 Mo 10:30 H20
Mechanisms of current improvement at grain boundaries in
High-Tc superconductors: Magneto-optic and electron-optic results
— •Christian Jooss 1 , Karsten Guth 1 , Volker Born 1 , Eva
Brinkmeier 1 , Harald Jarzina 1 , Wilko Westhäuser 1 , Marvin
Schofield 2 , Marco Beleggia 2 , and Yimei Zhu 2 — 1 Institut für Materialphysik,
Universität Göttingen, Tammannstr. 1, 37077 Göttingen —
2 Brookhaven National Laboratory, Upton, NY 11973 USA
Grain boundaries in high-temperature superconductors represent the
major factor limiting high current applications. We apply a full quantitative
magneto-optical imaging technique to the investigation of local
transport properties of low angle grain boundaries in YBaCuO and Cadoped
YBaCuO thin films. In order to analyse microscopic mechanisms of
current suppression, the local transport measurements grain boundaries
are combined with the determination of electrostatic potentials by electron
holography. By developing quantitative phase retrieval procedures
for electron holography, we obtained for the first time direct evidence of
a negative potential at the grain boundary dislocations which is significantly
reduced in its spatial extend as well as in its value in Ca-doped
samples. Our results nicely explain the observed enhancement of the intergranular
current densities by Ca-doping and shed light onto the puzzling
electronic properties of high-temperature superconducting oxides at
grain boundaries. We find evidence for the presence of a new insulating
electronic phase at the grain boundary in the strongly overdoped region.
This work is partially supported by the Deutsche Forschungsgemeinschaft
(DFG).
TT 1.6 Mo 10:45 H20
Transport properties of Ca doped superconducting epitaxial
YBCO films — •Jürgen Halbritter 1 , Ermile Gaganidze 1 , Holger
Hochmuth 2 , and Michael Lorenz 2 — 1 FZK, IMF I, Postfach
3640, 76021 Karlsruhe, Germany — 2 Universität Leipzig, Fakultät für
Physik und Geowissenschaften, Linnéstr. 5, D-04103 Leipzig, Germany
O doping enhancing the CuO plane density of states nm is well
known to improve normal conducting and superconducting dc, ac and
rf transport properties of YBCO by orders of magnitude. By Ca doping
Y1−xCaxBa2Cu3O7−δ enhancing nm similarely transport improvements
by factors below 2 to 10 have been found for bicrystal junctions and single
crystals, only. To study the effect of Ca doping on epitaxial PLD films
on CeO2/Al2O3 we performed systematic transport studies for nominal
x = 0.1, 0.15 and 0.2. The resulting superconducting rf properties, and
therewith the mean values of the weak link critical current density jcJ,
degraded with Ca content confirming trends found by dc measurements
of PLD films on STO and on LAO and by rf measurements of doped
films on Al2O3 and on LAO. The normal conducting weak link resistance

Tiefe Temperaturen Montag
Rbn decreased with x in line with nm enhancements but jcJRbn decreased
also. Reasons for the jcJ and jcJRbn degradations and for the differences
between Ca doped YBCO bicrystal junction and natural junctions in
epitaxial films will be given.
11:00 Pause
TT 2 Supraleitung: Mechanismen, Phasendiagramm, konkurrierende Ordnungen
Zeit: Montag 11:15–12:45 Raum: H20
Hauptvortrag TT 2.1 Mo 11:15 H20
Neutron scattering investigations of high Tc compounds: what
have we learned so far? — •Lothar Pintschovius — Forschungszentrum
Karlsruhe, Institut für Festkörperphysik
High Tc compounds have been very extensively studied by neutron
scattering. The focus has been on elucidating the spin fluctuations because
they are widely considered to mediate high Tc superconductivity.
Nevertheless, the experimental characterization of the magnetic fluctuations
is still full of gaps for important materials. The available data show
that the magnetic excitation spectrum differs profoundly between different
classes of materials. Present theories are usually tailored to explain
the essential features in only one particular class of compounds.
The phonons were found to change not much from the insulating parent
compounds to optimally doped superconductors, with the exception
of the plane polarized Cu-O bond-stretching vibrations. It will be
discussed in how far the electron-phonon coupling effects seen in the
bond-stretching phonons can be linked to anomalies in ARPES spectra
or might be associated with dynamic charge order.
TT 2.2 Mo 11:45 H20
Local Fluctuating Charge Order in the Stripe Ground State
of La1.8−xEu0.2SrxCuO4 — •Hans-Joachim Grafe 1,2 , Nicholas
J. Curro 2 , Markus Hücker 3 , and Bernd Büchner 1 — 1 Leibniz-
Institut für Festkörper- und Werkstoffforschung Dresden, 01171 Dresden,
Germany — 2 Los Alamos National Laboratory, Los Alamos, NM 87545,
USA — 3 Brookhaven National Laboratory, Upton, NY 11973, USA
Nuclear Magnetic Resonance (NMR) studies of the planar oxygen sites
in the cuprate superconductors provides information about both local
spin and charge excitations. Here we report the striking observation of a
strongly temperature dependent electric field gradient (EFG) at the planar
oxygen site in antiferromagnetic stripe ordered La1.8−xEu0.2SrxCuO4,
which stands in stark contrast to the temperature independent result in
superconducting La2−xSrxCuO4materials. Furthermore, measurements of
the spin lattice relaxation rate of the planar oxygen suggest the presence
of glassy charge fluctuations. We interpret these results as the consequence
of inhomogeneously fluctuating charge order associated with the
onset of static stripes.
TT 2.3 Mo 12:00 H20
Dimensionality of magnetic excitations in untwinned YBCO
- an inelastic neutron scattering study — •Vladimir Hinkov 1 ,
Bernhard Keimer 1 , Pailhes Stephane 2 , Bourges Philippe 2 ,
Sidis Yvan 2 , Lin CT 1 , and Kulakov Andrej 1 — 1 MPI für
Festkörperforschung, Stuttgart, Germany — 2 Laboratoire Leon
Brillouin, Saclay, France
Theories trying to describe superconductivity in the high-Tc cuprates
are based on 2D-scenarios of strongly correlated charge carriers. The
CuO2-planes in the LSCO family are unstable against the formation of
1D ”stripes” of antiferromagnetically ordered Cu spins separated by periodically
spaced hole domain walls which should result in an 1D response
TT 3 Spin-Systeme und itinerante Magnete
in inelastic neutron scattering (INS). It is of great significance for theory,
if stripe phases are common for all high-Tc cuprates. Investigation
in YBCO is complicated by twinning - the fact that equal proportions
of twin domains with mutually perpendicular directions of the a*- and
b*-axes exist in the crystal. This automatically leads to a overall 2D response,
even if the separate domains show a 1D response. We present the
world-wide first INS-study of fully twin-free optimally doped YBCO and
demonstrate that the response is still 2D, although a strong anisotropy
between the a*- and b*-axes exist. We give a precise mapping of the
relevant (E,q) space allowing to discriminate between different theories.
TT 2.4 Mo 12:15 H20
Possible isotope effect on the resonance peak formation in high-
Tc cuprates — •Ilya Eremin 1 , Mikhail Eremin 2 , and Oleg Kamaev
2 — 1 Institut für Theoretische Physik, Freie Universität Berlin,
Arnimallee 14, D-14195 Berlin — 2 Physics Department, Kazan State
University, 420008 Kazan, Russian Federation
Within effective t−J Hamiltonian we analyze the influence of electronic
correlations and electron-phonon interaction on the dynamical spin susceptibility
in layered cuprates. We find an isotope effect on the resonance
peak in the magnetic spin susceptibility, Im χ(q, ω), seen by inelastic
neutron scattering. It results from both the electron-phonon coupling
and the electronic correlation effects taken into account beyond random
phase approximation(RPA) scheme. We find at optimal doping the isotope
coeffiecient αres ≈ 0.4 which can be further tested experimentally.
TT 2.5 Mo 12:30 H20
Precursor effects above Tc of the ”ideal” superconducting state
within a phase fluctuation model for the underdoped cuprates
— •Thomas Eckl 1 , Werner Hanke 1 , Enrico Arrigoni 1 , and
Douglas J. Scalapino 2 — 1 Institut für Theoretische Physik und Astrophysik,
Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
— 2 Department of Physics, University of California, Santa Barbara,
CA 93106-9530 USA
The phase fluctuation scenario for the underdoped (UD) cuprates is
based on the idea that the pseudogap originates from phase fluctuations
of a d x 2 −y 2 pairing gap, whose amplitude forms at T MF
c , well above the
actual superconducting (SC) transition at Tc. Recently, we have shown
that a phenomenological model for phase fluctuations can account for different
single-particle properties of the pseudogap state. Here we discuss
precursor effects of the ideal SC state above Tc within our phenomenological
phase fluctuation model. In particular, the paraconductivity and
the fluctuating diamagnetism above Tc in the pseudogap state are analyzed
and the temperature scale at which these effects become visible in
experiment discussed.
[1] T. Eckl, D. J. Scalapino, E. Arrigoni, and W. Hanke, Phys. Rev. B
66, 140510(R) (2002)
[2] T. Eckl, W. Hanke and E. Arrigoni, Phys. Rev. B 68, 014505 (2003)
Zeit: Montag 09:30–13:00 Raum: H18
TT 3.1 Mo 09:30 H18
Is there a spinon-spinon interaction in the Haldane–Shastry
model? — •Dirk Schuricht and Martin Greiter — Institut für
Theorie der Kondensierten Materie, Universität Karlsruhe, 76128 Karlsruhe
Recently, there has been great interest in the dynamics of spinons in
the Haldane–Shastry model, a paradigm for antiferromagnetic spin systems.
Bernevig, Giuliano, and Laughlin [1] have presented arguments for
the existence of a short-ranged, attractive interaction between the spinon
excitations in this model. We reexamine their analysis and conclude that
their interpretation is not correct; the spinon excitations in the Haldane–
Shastry model do not interact. The spinons rather represent an ideal gas
of half-fermions.
[1] B. A. Bernevig et al., Phys. Rev. Lett. 86, 3392 (2001).

Tiefe Temperaturen Montag
TT 3.2 Mo 09:45 H18
Spectral Properties of One-Dimensional Heisenberg Antiferromagnets
— •Kai P. Schmidt, Alexander Reischl, Sébastien
Dusuel, and Götz S. Uhrig — Zülpicherstr. 77, D-50937 Köln, Germany
Spectral properties of the dimerized and frustrated S = 1/2 spin chain
are calculated by particle-conserving continuous unitary transformations
(P-CUT’s). A detailed analysis of spectral weights and spectral densities
for various excitation processes will be given. The results are relevant
for inelastic neutron scattering (INS), Raman spectroscopy and infrared
(IR) spectroscopy. The use of triplons (elementary triplets) as elementary
excitations gives a new perspective for the description of low dimensional
quantum spin liquids.
[1] K.P. Schmidt and G.S. Uhrig, Phys. Rev. Lett. 90, 227204 (2003)
[2] K.P. Schmidt, C. Knetter and G.S. Uhrig, cond-mat/0307678
TT 3.3 Mo 10:00 H18
Dimer Korrelationen im dimerisierten eindimensionalen S = 1/2
Heisenberg-Modell — •Carsten Aits und Ute Löw — Universität
zu Köln, Institut für Theoretische Physik, Zülpicher Str. 77, 50937 Köln
Wir untersuchen das Verhalten der Dimer-Korrelationen im eindimensionalen
S = 1/2 Heisenberg-Modell mit und ohne statische Dimerisierung.
Dazu werden numerische Resultate aus exakter Diagonalisierung
und Quanten-Monte-Carlo analysiert. Im nicht dimerisierten Fall werden
die Ergebnisse mit Aussagen aus der konformen Feldtheorie verglichen.
Darüberhinaus wird in dimerisierten Ketten der Zusammenhang
zwischen dem statischen Strukturfaktor und dem Skalenverhalten von
Grundzustandsenergie bzw. Anregungslücke diskutiert.
TT 3.4 Mo 10:15 H18
Theory of spin waves in diluted-magnetic-semiconductor quantum
wells — •Diego Frustaglia 1,2 , Jürgen König 3,2 , and Allan
MacDonald 4 — 1 Scuola Normale Superiore, Pisa, Italy — 2 Institut
für Theoretische Festkörperphysik, Universität Karlsruhe, Germany —
3 Institut für Theoretische Physik III, Ruhr-Universität Bochum, Germany
— 4 Department of Physics, University of Texas, Austin, USA
We present a theory of collective spin excitations in diluted magnetic
semiconductor quantum wells, in which local magnetic moments are magnetically
coupled via a quasi-two-dimensional electron or hole gas. In
contrast to bulk systems, a multiplet of spin-wave branches is predicted.
We discuss the dispersion of these collective excitations and the profiles
of the corresponding modes for different magnetic-ion doping concentrations
and free-carrier densities. In the case of a ferromagnetic state with
a partially spin-polarized two-dimensional electron gas, we find that the
Goldstone collective mode has anomalous k 4 dispersion and that for symmetric
quantum wells odd parity modes do not disperse at all. Moreover,
we further discuss the gap in the collective excitation spectrum which
appears when spin-orbit interactions are included.
TT 3.5 Mo 10:30 H18
Magnetocaloric effect in one-dimensional quantum spin models
— •A. Honecker 1 and M.E. Zhitomirsky 2 — 1 Universität Hannover,
Institut für Theoretische Physik, Appelstraße 2, 30167 Hannover
— 2 Commissariat à l’Énergie Atomique, DMS/DRFMC/SPSMS, 38054
Grenoble, Cedex 9 France
An external magnetic field induces changes in the entropy of a quantum
spin system at finite temperatures which can be rather large in
particular if the spin system is geometrically frustrated. This implies
a magnetocaloric effect, i.e. a change in temperature during an adiabatic
(de)magnetization process. Here we study several examples of onedimensional
spin models with low spin quantum number (S = 1/2 and 1)
employing exact diagonalization and the Jordan-Wigner transformation.
During an adiabatic (de)magnetization process the temperature drops
in the vicinity of a field-induced zero-temperature quantum phase transition.
Comparing different levels of frustration, we find that more frustrated
systems cool down to lower temperatures. Our study demonstrates
that frustrated quantum spin systems are promisimng alternative refrigerant
materials for low-temperature magnetic refrigeration.
TT 3.6 Mo 10:45 H18
Non-dissipative thermal transport and crossover phenomena in
the gapped spin-1/2 XXZ chain — •Andreas Klümper 1 and
Kazumitsu Sakai 2 — 1 Universität Wuppertal, Theoretische Physik,
Gauß-Straße 20 — 2 Institute for solid state physics, University of Tokyo
We present exact results on the thermal conductivity of the onedimensional
spin-1/2 XXZ model in the gapless and the massive antiferromagnetic
as well as ferromagnetic regimes. The thermal Drude weight
is calculated by a lattice path integral formulation. Numerical results for
wide ranges of temperature and anisotropy as well as analytical results
in the low and high temperature limits are presented. At finite temperature,
the thermal Drude weight is finite and hence there is non-dissipative
thermal transport even in the massive regimes.
At low temperature, the thermal Drude weight behaves as Dth(T) ∼ T
in the gapless regime, and as Dth(T) ∼ e −δ/T / √ T in the gapped
regimes where δ is the one-spinon/one-magnon excitation gap in the
antiferromagnetic/ferromagnetic case. In the ferromagnetic regime we
observe a crossover in the low-temperature behaviour of the ratio of the
thermal Drude weight and the specific heat from Dth(T)/C(T) ≃ T to
Dth(T)/C(T) ≃ T 3/2 e −β(δm−δs) when changing from ∆ < 5/3 to ∆ > 5/3
(δm and δs are the magnon and the spinon gap).
TT 3.7 Mo 11:00 H18
Integral representations of correlation functions for the
anisotropic Heisenberg chain at finite temperatures — •Frank
Göhmann and Alexander Seel — Fachbereich C, Physik, Bergische
Universität Wuppertal, 42097 Wuppertal
We derived novel integral representations for correlation functions of
the anisotropic Heisenberg chain at finite values of the temperature and
the applied magnetic field. Our work is based on a combination of Bethe
ansatz techniques for the calculation of matrix elements with the quantum
transfer matrix approach.
TT 3.8 Mo 11:15 H18
Spin dynamics of 1D supersymmetric t-J model with 1/r2 interaction
— •Mitsuhiro Arikawa — Institut fuer Theoretische Physik
III, Universitaet Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart
We report on analytic results on dynamical spin structure factor
S(q, ω) for 1D supersymmetric t-J model with 1/r2 interaction. In this
model, the elementary excitations, spinons and holons appear as free
particle obeying fractional statistics. we presented that interpretation
of S(q, ω) requires both fractionalized and non-fractionalized electrons.
Our results constitutes the first analytical knowledge for S(q, ω) of lattice
electrons with no restriction on the density and the momentum-frequency
range. We discuss how these excitations appear in the dynamics in wide
range energy region.
TT 3.9 Mo 11:30 H18
Effects of proper crystal embedding for low dimensional spin
systems — •H. Rosner 1 , S.-L. Drechsler 2 , M. Knupfer 2 , J.
Málek 2 , H. Eschrig 2 , J. Richter 3 , A. Moskvin 4 , W. Ku 5 , and
W.E. Pickett 5 — 1 Max Planck Institut für Chemische Physik fester
Stoffe — 2 Institut für Festkörper- und Werkstoffforschung Dresden —
3 Universität Magdeburg — 4 Ural State University Ekatarinenburg, Russia
— 5 University of California Davis, USA
Many approaches for the description of low dimensional spin systems
consider their isolated structural units only. Here, we emphasize the importance
of the proper embedding of these structural units in the crystal.
Effects resulting from the crystal field and the inter-unit interaction
are studied in detail for several selected model compounds as Li2CuO2,
LiCu2O2, Cu(Si)GeO3 or CaCu2O3. Band structure calculation, exact
diagonalization and various spectroscopic, magnetic and thermodynamic
data are joined to suggest a novel consistent picture.
TT 3.10 Mo 11:45 H18
Thermal conductivity of spin-1/2 chains — •Achim Rosch 1 ,
Efrat Shimshoni 2 , and Natan Andrei 3 — 1 Institut für Theoretische
Physik, Universität zu Köln — 2 University of Haifa, Israel — 3 Rutgers
University, USA
We study [1] the low-temperature transport properties of clean onedimensional
spin-1/2 chains coupled to phonons. Due to the presence
of approximate conservation laws, the heat current decays very slowly
giving rise to an exponentially large heat conductivity, κ ∼ e T ∗ /T . As a
result of an interplay of Umklapp scattering and spinon-phonon coupling,
the characteristic energy scale T ∗ turns out to be of order ΘD/2, where
ΘD is the Debye energy, rather than the magnetic exchange interaction
J in agreement with recent measurements in SrCuO compounds. A large
magnetic field h strongly affects the heat transport by two distinct mechanisms.
First, it induces a linear spinon-phonon coupling, which alters the
nature of the T → 0 fixed point: the elementary excitations of the system

Tiefe Temperaturen Montag
are composite spinon-phonon objects. Second, the change of the magnetization
and the corresponding change of the wave vector of the spinons
strongly affects the way in which various umklapp processes can relax
the heat current, leading to a characteristic fractal-like spiky behavior of
κ(T, h) as a function of h.
[1] E. Shimshoni, N. Andrei and A. Rosch, Phys. Rev. B 68, 104401
(2003).
TT 3.11 Mo 12:00 H18
ESR study of the low-dimensional quantum spin system TiOCl
— •V. Kataev 1,2 , J. Baier 2 , A. Möller 3 , L. Jongen 3 , G. Meyer 3
und A. Freimuth 2 — 1 Leibniz-Institut für Festkörper- und Werkstoffforschung
PF D-01171 Dresden — 2 II. Physikalisches Institut, Universität
zu Köln, D-50937 Köln — 3 Institut für Anorganische Chemie, Universität
zu Köln, D-50939 Köln
We present electron spin resonance (ESR) measurements of Ti 3+ (3d 1 )
ions in single crystals of the novel layered quantum spin magnet TiOCl
[1]. The ESR data give evidence that the single electron in the d-shell occupies
predominantly the dxy orbital which lies in the bc crystallographic
plane. This result suggests a formation of a spin-1/2 chain along the b
direction, owing to the overlap of the orbital states, and supports recent
LDA+U calculations of the band structure [2]. The ESR signal vanishes
at Tc=67 K signalling the transition to a non-magnetic, possibly a spin-
Peierls state, as proposed in Ref. [2]. Our x-ray powder diffraction data
give however no evidence for the structural transition associated with the
spin-gap transition. A pronounced dependence of the linewidth and the
g factor on temperature suggests a strong coupling of spins to the lattice
which may be decisive for the magnetic properties of TiOCl. In connection
with the peculiar temperature dependence of the ESR parameters
we discuss the role of spin and probably also orbital fluctuations above
Tc for the opening of the spin gap.
[1] For details see, V. Kataev et al., Phys. Rev. B 68, 140405(R) (2003).
[2] A. Seidel et al., Phys. Rev. B 67, 020405(R) (2003).
supported by DFG through SFB 608
TT 3.12 Mo 12:15 H18
Thermodynamic Properties of Layered Ruthenates — •J.
Baier 1 , T. Zabel 1 , M. Kriener 1 , M. Reuther 1 , T. Lorenz 1 ,
A. Freimuth 1 , P. Steffens 1 , O. Friedt 1 , M. Braden 1 , A.
Revcolevschi 2 , S. Nakatsuji 3 , and Y. Maeno 3 — 1 II. Physikalisches
Institut, Universität zu Köln, Germany — 2 Laboratoire de
Physico-Chimie de l‘Etat Solide, Universite Paris-Sud, Orsay, France —
3 Department of Physics, Kyoto University, Japan
The phase diagram of Ca2−xSrxRuO4 presents a rich spectrum of distinct
structural distortions, which are accompanied by drastic changes of
the magnetic and electronic properties [1]. Ca-Doping drives the system
from the spin-triplet superconductor Sr2RuO4 to the antiferromagnetic
Mott-insulator Ca2RuO4. At x = 0.5, the low-temperature magnetic susceptibility
is considerably increased and an unusually large Cp/T-value
due to the evolution of a nearly ferromagnetic heavy-mass Fermi liquid
is observed [2]. We find an anomalous, anisotropic thermal expansion for
this compound. In a magnetic field, the anomalous thermal expansion
and the large Cp/T-value are suppressed with an anisotropic field dependence.
For lower x, an additional tilting of the RuO6 octahedra sets in and
at x = 0.2 the susceptibility is again strongly reduced [2]. In high magnetic
fields this compound is driven through a metamagnetic transition
and the large susceptibility recovers. We observe a large magnetostriction
during this metamagnetic transition.
[1] O. Friedt et al., Phys. Rev. B 63 (2001)
[2] S. Nakatsuji et al., Phys. Rev. Lett. 90 (2003)
Supported by the DFG through SFB 608
TT 3.13 Mo 12:30 H18
Heat Transport in Low Dimensional Spin Systems — •C. Hess 1 ,
H. ElHaes 2 , P. Ribeiro 3 , B. Büchner 3 , F. Heidrich-Meisner 4 ,
W. Brenig 4 , M. Hücker 5 , U. Ammerahl 5 , and A. Revcolevschi 5
— 1 Department of Condensed Matter Physics, University of Geneva,
Switzerland — 2 II. Physikalisches Institut, RWTH Aachen, Germany
— 3 IFW Dresden, Germany — 4 Institut für Theoretische Physik, TU-
Braunschweig, Germany — 5 Laboratoire de Physico-Chimie des Solides,
Université Paris-Sud, France
We present experimental results for the magnon thermal conductivity
κmag of several low dimensional spin systems, like antiferromagnetic
planes, ladders and chains. We focus on the quasi two dimensional antiferromagnet
La2CuO4 and the spin ladder system (Sr, Ca, La)14Cu24O41,
where scattering of the magnetic excitations on static defects, phonons,
magnons and holes is analyzed on basis of a kinetic model. The analysis
yields for example an intimate relation of magnetic and electronic transport
channels in the spin ladders and in both systems a strict limitation
of the magnon mean free path lmag by artificially induced non magnetic
defects, i.e., lmag ≈ dZn−Zn at low temperatures, where dZn−Zn is the
mean distance of doped Zn-ions in the low dimensional structures. The
latter result is in stark contrast to recent model calculations for the heat
transport in the spin ladders.
TT 3.14 Mo 12:45 H18
Magnetic excitations in the low-dimensional quantum spin systems
CaCu2O3 and Ba2Cu3O4Cl2 — •Eva Benckiser 1 , Markus
Grüninger 1 , Tamara Nunner 2 , Thilo Kopp 2 , Chinnathambi
Sekar 3 , and Gernot Krabbes 3 — 1 II. Physikalisches Institut,
Universität zu Köln, Germany — 2 Experimentalphysik VI, Universität
Augsburg, Germany — 3 IFW Dresden, Germany
The magnetic excitations of CaCu2O3 and Ba2Cu3O4Cl2 are studied
by means of phonon-assisted infrared absorption. CaCu2O3 has been discussed
as a two-leg S=1/2 ladder with J⊥ ≪ J�. An analysis of the
optical conductivity σleg(ω) for polarization parallel to the legs at 4K indeed
yields J� ≈ 165 meV and a much smaller J⊥. However, comparison
of σ(ω) for polarization parallel to the rungs and perpendicular to the
ladders with the result of a DMRG calculation shows that the coupling
perpendicular to the ladders is comparable to J⊥, i.e. that CaCu2O3 is
not a ladder but rather a 3D system of weakly coupled chains.
In the 2D cuprates, the large spectral weight in σ(ω) above the bimagnon-plus-phonon
peak and the nature of the high-energy excitations
are still under discussion. The 2D Cu3O4 layers in Ba2Cu3O4Cl2 contain
the CuO2 square lattice plus a second Cu square lattice with a much
weaker coupling constant J2. The spins of the two subsystems are decoupled
from each other on the mean-field level. For ω ≫ J2 the compound
represents a clean realization of an undoped CuO2 layer. We find that the
high-energy spectral weight is larger than assumed previously. The temperature
dependence of σ(ω) and a comparison with 1D systems strongly
indicate a strong contribution from local, incoherent excitations.
TT 4 Quantenflüssigkeiten, Bose-Einstein Kondensate, ultrakalte Atome, ...
Zeit: Montag 10:00–12:15 Raum: H19
Hauptvortrag TT 4.1 Mo 10:00 H19
Kalte Atome in optischen Gittern — •Wilhelm Zwerger — Institut
für Theoretische Physik, Universität Innsbruck, Technikerstr. 25,
A-6020 Innsbruck,
Kalte Atome in optischen Gittern stellen eine neue Klasse von Vielteilchensystemen
dar, in denen die Stärke der Wechselwirkung durch Variation
der Gittertiefe oder der Streulängen über einen weiten Bereich abstimmbar
ist. Paradigmatische Modelle der Vielteilchenphysik, wie das
Hubbard-Modell oder Luttinger-Flüssigkeiten sind daher experimentell
realisierbar und geben Zugang zu komplexen Vielteilchenzuständen und
den damit verbundenen Quantenphasenübergängen. Aufbauend auf dem
Beispiel eines Mott-Hubbard Übergangs für Bosonen von Greiner et.al.
wird ein Überblick über aktuelle Entwicklungen in diesem Gebiet ge-
geben, insbesondere eindimensionale Systeme und die Perspektiven für
Vielteilchenphysik mit Fermionischen kalten Atomen.
TT 4.2 Mo 10:30 H19
Fluctuations and stability of superfluid turbulence in He-4 at
mK temperatures — •Wilfried Schoepe — Fakultaet fuer Physik,
Universitaet Regensburg
Turbulent flow of superfluid helium-4 at mK temperatures around an
oscillating microsphere is known to be unstable at low driving forces,
switching intermittently between turbulent and laminar phases. The lifetimes
of the turbulent phases are exponentially distributed and the mean
lifetimes grow exponentially with the square of the driving force. These
experimental results are attributed to statistical fluctuations of the vor-

Tiefe Temperaturen Montag
ticity. As a model it is suggested that the turbulent state breaks down
when a fluctuation crosses a threshold level. Applying Rice’s formula for
the average level crossing per unit time of a stationary normal process
gives information on the probability density function and the spectral
bandwidth of the fluctuations. As a result a normal distribution is found
and the standard deviation as well as the spectral bandwidth are determined
quantitatively. In addition to superfluid turbulence this model
may be applicable also to other instabilities which result from random
fluctuations exceeding a certain threshold.
TT 4.3 Mo 10:45 H19
Ground state properties and non-equilibrium dynamics of
hard-core bosons confined on optical lattices — •Marcos
Rigol Madrazo and Alejandro Muramatsu — Institut fuer
Theoretische Physik III, Universitaet Stuttgart, Pfaffenwaldring 57,
D-70550 Stuttgart, Germany
We study by means of an exact numerical approach, a gas of hard core
bosons (HCB) confined on optical lattices. The ground state properties
of such systems are analyzed. Local incompressible phases appear in the
system, like in the case of interacting soft-core bosons [1] and fermions
[2,3]. The changes in momentum distribution function and in the natural
orbitals (effective single particle states) introduced by the formation
of such phases are analyzed. We also study non-equilibrium properties
for those systems, which within our numerical approach can be obtained
exactly for systems with ∼ 200 particles on lattices with ∼ 3000 sites.
In particular we analyze the free expansion of the gas when it is released
from the trap turning off the confining potential. We show that the expansion
is non-trivial (as opposed to the fermionic case) and new features
to be observed in the experiments are analyzed.
[1] G. G. Batrouni, V. Rousseau, R. T. Scalettar, M. Rigol, A. Muramatsu,P.
J. H. Denteneer, and M. Troyer, Phys. Rev. Lett. 89, 117203
(2002).
[2] M. Rigol, A. Muramatsu, G. G. Batrouni, and R. T. Scalettar, Phys.
Rev. Lett. 91, 130403 (2003).
[3] M. Rigol and A. Muramatsu, cond-mat/0309670 (2003).
TT 4.4 Mo 11:00 H19
Ultracold fermions and the SU(N) Hubbard model — •Carsten
Honerkamp 1 and Walter Hofstetter 2 — 1 MPI Solid State Research,
Stuttgart — 2 MIT, Cambridge, USA
We investigate the fermionic SU(N) Hubbard model on the twodimensional
square lattice for weak to moderate interaction strengths
using one-loop renormalization group and mean-field methods. For the
repulsive case U > 0 at half filling and small N the dominant tendency
is towards breaking of the SU(N) symmetry. For N > 6 staggered flux
order takes over as the dominant instability, in agreement with the large-
N limit. Away from half filling for N = 3 the system rearranges the
particle densities such that two flavors remain half filled by cannibalizing
the third flavor. In the attractive case and odd N a full Fermi surface
coexists with a superconductor in the ground state. These results may
be relevant to future experiments with cold fermionic atoms in optical
lattices.
TT 4.5 Mo 11:15 H19
Self-energy and critical temperature of weakly interacting
bosons — •Peter Kopietz, Sascha Ledowski, and Nils Hasselmann
— Institut für Theoretische Physik, Universität Frankfurt,
Robert-Mayer-Str. 8, 60054 Frankfurt/Main
Using the exact renormalization group we calculate the momentumdependent
self-energy Σ(k) at zero frequency of weakly interacting bosons
at the critical temperature Tc of Bose-Einstein condensation in dimensions
3 ≤ D < 4. We obtain the complete crossover function interpolating
between the critical regime k ≪ kc, where Σ(k) ∝ k 2−η , and the
short-wavelength regime k ≫ kc, where Σ(k) ∝ k 2(D−3) in D > 3 and
Σ(k) ∝ ln(k/kc) in D = 3. From our Σ(k) we find for the interaction-
induced shift of Tc in three dimensions ∆Tc/Tc ≈ 1.23 an 1/3 , where a is
the s-wave scattering length and n is the density [1].
[1] S. Ledowski, N. Hasselmann, and P. Kopietz, cond-mat/0311043.
TT 4.6 Mo 11:30 H19
Reflectionless dynamics of 1D charge and spin modes in atomic
traps — •Lars Kecke, Wolfgang Häusler, and Hermann
Grabert — Physikalisches Institut, Albert- Ludwigs Univerität,
Freiburg
Gases of Fermionic atoms in cigar shaped, one-dimensional traps provide
an ideal means to study the dynamics of correlated Fermi systems
in the Tonks gas limit of repulsive contact interactions. The interaction
strength can be tuned experimentally [1].
Based on the Tomonaga-Luttinger (TL) model we present calculations
on the dynamics of charge and spin density waves. Particularly at the
edge both modes show features that are strikingly different from the
non-interacting case as well as from conventional TL dynamics. For example
we find a suppression of reflections that should be experimentally
observable.
[1] T. Loftus et al PRL 88, 173201 (2002)
TT 4.7 Mo 11:45 H19
Audio Demonstration of Quantum Oscillations: Phase Locking
of Josephson Oscillations in superfluid 3He-B — •S.V.
Pereverzev and G. Eska — Physikalisches Institut, Universität
Bayreuth
We report on a family of dynamic effects which were observed in superfluid
3He flow through a weak link (array of 65x65 holes of 150 nm dia.
in a 50 nm SiN membrane). The flow was driven by a time dependent
pressure difference (∆p(t)) to which an ac-modulation (paccos(ωt + θ))
was added. A self-trapping phase-locked state could be observed when the
Josephson frequency (ωJ(t) = ∆p(t)
) and the ac-drive frequency ω merged
ρκ0
(reverse AC-Josephson effect). This trapped state is a zero net current
state with a nonzero pressure difference across the weak link. Close to
this resonance the observed beat frequency ωJ − ω clearly indicates the
presence of Josephson oscillations which can be heared. Low frequency oscillations
around this quasi-equilibrium state were also observed, as well
as Helmholtz oscillations around the zero pressure-difference equilibrium
state. The frequencies of both of these oscillatory modes depended on
amplitude and frequency of the ac-drive. For the pressure driven flow we
measured unexpected high losses. The origin of these losses is unclear.
TT 4.8 Mo 12:00 H19
Resonant Transport of Bose-Einstein Condensates — •Tobias
Paul, Peter Schlagheck, and Klaus Richter — Institut für theoretische
Physik, Universität Regensburg
Due to the rapid progress of “atomic chip” technology [1], the implementation
of experiments probing the propagation of Bose-Einstein
condensates in mesoscopic waveguides becomes feasible. A particular interesting
waveguide geometry is the double barrier structure created by
a sequence of two constrictions, which can serve as a Fabry-Perot-like
interferometer for the condensate [2]. In this context the question arises
how the presence of repulsive interactions between the condensed atoms
influences the transmission through this double barrier structure. Our numerical
approach is based on the Gross–Pitaevskii equation and employs
absorbing boundary conditions as well as an inhomogeneous source term
in order to obtain a stationary flow of condensate through the guide. We
show that the nonlinear interaction between the atoms leads to a significant
modification of the positions and shapes of the resonance peaks as
compared to the noninteracting case.
[1] H. Ott et al., Phys. Rev. Lett. 87, 230401 (2001); J. Schmiedmayer et
al., J. Mod. Optics 47, 2789 (2000); W. Hänsel et al., Nature 413, 498
(1999).
[2] J. Fortagh and C. Zimmermann, Physik Journal, Juni 2003

Tiefe Temperaturen Montag
TT 6 Niederdimensionale Systeme (incl. Peierls-Übergang, organische Leiter, ...)
Zeit: Montag 14:15–17:45 Raum: H18
TT 6.1 Mo 14:15 H18
Competing phases in one-dimensional interacting spinless
fermion systems — •Ralph Werner and Peter Schmitteckert
— Institut f”ur Theorie der Kondensierten Materie, Universit”at
Karlsruhe, 76128 Karlsruhe
It has been shown that umklapp-scattering driven instabilities in onedimensional
systems can be generalized to arbitrary multiple umklappscattering
processes at commensurate fillings given that the system has
sufficiently longer range interaction [1]. At commensurate fillings the competition
of interaction of different ranges leads to various phases such as
charge density waves, bond order, and Luttinger liquids which are in
part related to frustration effects. The phenomena are discussed for the
example of half filled chains with nearest- and next-nearest-neighbor interaction.
[1] Peter Schmitteckert and Ralph Werner, cond-mat/0311280
TT 6.2 Mo 14:30 H18
Is the Quantum Hall Effect influenced by the gravitational
field? — •Bernd Rosenow 1 , Friedrich W. Hehl 1,2 , and Yuri
N. Obukhov 1,3 — 1 Institut für Theoretische Physik, Universität zu
Köln, 50923 Köln, Germany — 2 Department of Physics and Astronomy,
University of Missouri-Columbia, Columbia, MO 65211, USA —
3 Department of Theoretical Physics, Moscow State University, 117234
Moscow, Russia
Most of the experiments on the quantum Hall effect (QHE) were made
at approximately the same height above sea level. A future international
comparison will determine whether the gravitational field g(x) influences
the QHE. In the realm of (1 + 2)-dimensional phenomenological macroscopic
electrodynamics, the Ohm-Hall law is metric independent (‘topological’).
This suggests that it does not couple to g(x) [1]. We corroborate
this result by a microscopic calculation of the Hall conductance in the
presence of a post-Newtonian gravitational field. The linear Hall resistance
is not influenced by a gravitational field to order O(g/c 2 ). However,
for a field orientation parallel to the 2DEG, we find both a constant background
current and a nonlinear contribution to the Hall current.
[1] H.W. Hehl, Y.N. Obukhov, and B. Rosenow, eprint cond-mat/0310281
TT 6.3 Mo 14:45 H18
Optical studies of charge ordering in quasi-1D organic conductors
— •Michael Dumm, Mohamed Abaker, and Martin Dressel
— 1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart
Interactions between charge, spin, or lattice degrees of freedom result
in the extraordinary rich phase diagram of the quasi-1D (TMTTF)2X
and (TMTSF)2X charge-transfer salts with ground states like charge order,
spin order, anion order, and superconductivity. The focus of this
contribution is on the charge-order transition in (TMTTF)2AsF6 and
(TMTTF)2PF6 which is related to charge disproportionation along the
molecular stacks at moderate temperatures TCO. We investigated this
phase transition into a ferroelectric state by infrared spectroscopy. For
the first time, the lattice dynamics was explored in the vicinity of TCO.
We observed a splitting of the electron-molecular-vibration coupled totally
symmetric intramolecular ag(ν3) mode in the charge-ordered state.
From this result a charge disproportionation on the TMTTF molecular
stacks of about 2:1 in (TMTTF)2AsF6 and 1.25:1 in (TMTTF)2PF6
can be estimated. In the very far infrared spectral range, we found new
absorption modes in the optical conductivity below TCO.
TT 6.4 Mo 15:00 H18
Die Leiterverbindungen La2(Cu,Zn)2O5 und La8(Cu,Zn)7O19
– ihre magnetischen Eigenschaften — •K.-H. Müller, C.
Sekar, D. Eckert, B. Schüpp, M. Wolf und G. Krabbes
— Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden,
Postfach 270116, 01171 Dresden
Obwohl La2(Cu1−xZnx)2O5 eine 4-Bein-Leiter- und La8(Cu1−xZnx)7O19
eine 5-Bein-Leiter-Verbindung ist, zeigt die magnetische Suszeptibilität
χ beider Verbindungen eine unerwartet ähnliche Abhängigkeit sowohl
von der Temperatur T als auch vom Grad der Zinkdotierung x. Ursache
dafür ist, dass die Cu-O Koordination in beiden Verbindungen sehr
ähnlich ist, sich aber deutlich von der in den klassischen Spinleitern vorliegenden
unterscheidet. Für geringe Zn-Dotierung (x ≤ 0, 04) zeigen die
χ(T)-Kurven ein flaches Maximum (Tmax ≈ 180K), ein Verhalten wie
es auch bei Spinketten beobachtet wird. In diesem Dotierungsbereich
nehmen die effektiven Austauschintegrale und die Curie-Konstante C
(bestimmt mit einem fit aus dem asymptotischen Verhalten von χ(T)
für T → ∞) mit wachsender Zn-Dotierung ab, C aber stärker als nach
einem Verdünnungsgesetz. In beiden Verbindungsreihen verschwindet
das Maximum in den χ(T)-Kurven für x ≥ 0, 04 und χ(T) fällt monoton
mit wachsender Temperatur, d.h. das beschriebene quasieindimensionale
Verhalten wird vollkommen unterdrückt. Es ist offen, ob diese durch
Zinkdotierung verursachte drastische Änderung der magnetischen Eigenschaften
beider Verbindungen auf einen Quantenphasenübergang hinweisen,
oder mit kleinen Änderungen der Gitterstruktur zusammenhängen,
die in diesem Dotierungsbereich beobachtet werden.
TT 6.5 Mo 15:15 H18
ESR investigations of spin and charge ordering in quasi onedimensional
organic conductors — •Belal Salameh, Michael
Dumm, Dieter Schweitzer, and Martin Dressel — Physikalisches
Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart
Electron spin resonance (ESR) and SQUID measurements were performed
on single crystals of the quasi one-dimensional organic chargetransfer
salts (TMTTF)2X (X = BF4 and AsF6) to investigate the
low temperature electronic state. At high temperatures, the magnetic
susceptibility of these compounds can be described by a spin 1/2 antiferromagnetic
Heisenberg chain. Below the spin-Peierls transition in
(TMTTF)2AsF6 (TSP = 13K) and the anion-ordering (AO) transition in
(TMTTF)2BF4 (TAO = 41K) the magnetic susceptibility decreases exponentially
indicating the non-magnetic nature of both ground states.
We observed significant changes in the anisotropy of the ESR linewidth
∆Hpp below the charge-ordering transition in the AsF6 salt (TCO = 103
K) and the AO transition in the BF4 compound. From these results the
possible charge-ordering patterns at low temperatures can be estimated.
TT 6.6 Mo 15:30 H18
Elektrischer Widerstand von dünnen Pd-Filmen auf Eu1−xSrxS
— •A. Cosceev1 , C. Sürgers1 und H. v. Löhneysen1,2 —
1Physikalisches Institut und DFG Center for Functional Nanostructures
(CFN), Universität Karlsruhe, D-76128 Karlsruhe —
2Forschungszentrum Karlsruhe, Institut für Festkörperphysik, D-76021
Karlsruhe
Wir berichten über Messungen des elektrischen Widerstands von
dünnen Pd-Filmen auf isolierenden, magnetischen Eu1−xSrxS-Schichten
für Temperaturen T = 1.5 − 300 K und in Magnetfeldern bis B = 5 T.
Dazu werden 50-nm dicke Eu1−xSrxS-Schichten mit 0.5 ≤ x ≤ 0.7 durch
Elektronenstrahlverdampfung im UHV auf Si(111)-Substraten bei Temperaturen
TS = 800◦C hergestellt, die anschließend in-situ bei Raumtemperatur
mit 7 nm Pd beschichtet werden. Die Charakterisierung der magnetischen
Eigenschaften der Eu1−xSrxS-Schichten geschieht durch Messung
der Magnetisierung und der magnetischen Suszeptibilität. Der elektrische
Widerstand R steigt unterhalb von etwa T = 10 K an und zeigt
ein ausgeprägtes Maximum, dessen Lage sich mit zunehmender Magnetfeldstärke
zu tieferen Temperaturen verschiebt. Der Vergleich mit den
magnetischen Eigenschaften zeigt, dass das Auftreten dieses Maximums
verbunden ist mit der Änderung der magnetischen Ordnung im isolierenden
Eu1−xSrxS. Die unterschiedlichen Streuprozesse werden durch Messung
des Magnetowiderstands und dessen Analyse mit Hilfe der Theorie
der schwachen Lokalisierung ermittelt.
TT 6.7 Mo 15:45 H18
TiOCl and TiOBr: a new inorganic spin-Peierls systems? — •R.
Rückamp 1 , J. Baier 1 , M. Kriener 1 , M. Grüninger 1 , T. Lorenz 1 ,
A. Freimuth 1 , L. Jongen 2 , A. Möller 2 , and G. Meyer 2 — 1 II.
Physikalisches Institut, Universität zu Köln — 2 Institut für anorganis-
che Chemie, Universität zu Köln
In TiOCl and TiOBr antiferromagnetic spin-1 chains are formed along
2
the a axis. Currently, TiOCl attracts much interest due to a transition
to a non-magnetic phase at 67 K which is discussed as the second inorganic
example of a spin-Peierls transition [1]. However, the associated
structural distortions have not been observed so far. Moreover, there are
clear indications for a second phase transition at 92 K.

Tiefe Temperaturen Montag
We present optical data in the frequency range of 6 meV - 2 eV and
measurements of the magnetic susceptibility, thermal expansion and specific
heat. In the optical data of TiOCl we observe new phonon modes
in the low-temperature phase, in agreement with a spin-Peierls scenario.
An additional new phonon mode occurs below 92 K, which disappears
again in the low-temperature phase. In the literature, the importance of
orbital fluctuations has been discussed. We observe d-d transitions at 0.7
and 1.6 eV, in agreement with the results of a point-charge model. Such
a large splitting of the d-levels shows that orbital fluctuations are not
important in these systems. Qualitatively, the data of TiOBr and TiOCl
are very similar. Again, two transitions are observed, namely at 28 K and
50 K.
[1] A. Seidel et al., Phys. Rev. B 67, 020405 (2003).
TT 6.8 Mo 16:00 H18
Ladungsordnung in β-Na0.33V2O5 — •Monika Heinrich 1 , Hans-
Albrecht Krug von Nidda 1 , Rushana Eremina 1 , Alois Loidl 1 ,
Günter Obermeier 2 und Siegfried Horn 2 — 1 Lehrstuhl für Experimentalphysik
V, Elektronische Korrelationen und Magnetismus, Institut
für Physik, Universität Augsburg — 2 Lehrstuhl für Experimentalphysik
II, Institut für Physik, Universität Augsburg
Die quasi-eindimensionale Vanadiumbronze β-Na0.33V2O5 besitzt drei
inäquivalente Vanadiumplätze, die in Form von Zickzackketten bzw. Leitern
angeordnet sind. Erst 1999 wurde der Metall-Isolator-Übergang
(MIT) bei 130 K entdeckt und eindimensionale elektrische Leitfähigkeit
entlang der Ketten nachgewiesen [1]. Als Ursache des MIT wurde Ladungsordnung
vorgeschlagen [1], jedoch ist die Verteilung der Elektronen
auf den unterschiedlichen Vanadium-Plätzen bislang ungeklärt. Der Elektronenspinresonanz
(ESR) stehen in β-Na0.33V2O5 die V 4+ -Ionen mit ihrer
3d1-Elektronenkonfiguration als mikroskopische Sonden des Spinsystems
zur Verfügung. Orientierungsabhängige Messungen an Einkristallen
bei Temperaturen oberhalb und unterhalb des MIT wurden durchgeführt.
Der Verlauf des g-Faktors und der ESR-Linienbreite in den untersuchten
Kristallebenen wird für unterschiedliche Arten der Ladungsordnung
simuliert und mit den experimentellen Ergebnisse verglichen. Dabei werden
die Resultate von Röntgendiffraktionsmessungen [2] berücksichtigt.
[1] H. Yamada et al., J. Phys. Soc. Jpn. 68, 2735 (1999).
[2] J. Yamaura et al., J. Phys. Chem. Solids 63, 957 (2002).
TT 6.9 Mo 16:15 H18
Zn2VO(PO4)2: An unfrustrated, s = 1/2 Heisenberg antiferromagnetic
square lattice system. — •N.S. Kini, E.E. Kaul, and C.
Geibel — Max Planck Institute for Chemical Physics of Solids, Dresden
Antiferromagnetic frustrated square lattices consisiting of s = 1/2
Heisenberg spins have been reported to give rise to unusual ground states
depending on the magnitude of nearest neighbour (J1) and next nearest
neighbour (J2) interactions. As a part of a study on new frustrated systems,
we have investigated the compound Zn2VO(PO4)2, in which V 4+
(s = 1/2) ions are located on a perfect square lattice.
Polycrystalline samples were synthesised by solid state reaction and characterised
by magnetic susceptibility and specific heat measurements. This
compound has been found to be made up of a nearly perfect, unfrustrated,
s = 1/2 Heisenberg antiferromagnetic square lattice with J1 ≈ 6.8 K and
J2 ≈ 0.1 K. Anomalies in the specific heat and in the suscptibility point
to a transition to an antiferromagnetic state at 3.2 K. Results of magnetic
susceptibility and specific heat measurements will be discussed in
the light of various theoretical models.
TT 6.10 Mo 16:30 H18
Optical and magneto-optical properties of (Sr,Ca,La)14Cu24O41
— •Philipp Haas 1 , B. Gorshunov 1 , M. Dumm 1 , M. Dressel 1 ,
T. Vuletic 2 , B Korin-Hamzic 2 , S. Tomic 2 , and J. Akimitsu 3
— 1 1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart.
— 2 Institut za fiziku, HR-10001 Zagreb, Croatia — 3 Dep. of Physics,
Aoyama-Gakuin University, Tokyo, Japan
The anisotropic optical conductivity of the spin 1/2 2-leg ladder compounds
Sr14−xCaxCu24O41 was measured in the frequency range 1 Hz -
300 THz and at temperatures 5 K - 300 K for Ca dopings x=0, 3, and
9. In the undoped sample we discovered a charge-density wave (CDW)
along the c direction. Calcium doping suppresses the CDW phase with
the transition temperature decreasing from 210K for x=0 to 10 K for x=9.
The transport in the chains subsystem was studied in the La-doped compound
La3Sr3Ca8Cu24O41. We show that the chain array behaves like a
one-dimensional disordered system revealing variable-range-hopping conductivity.
In addition the influence of magnetic fields up to 7T on the
optical spectra of (Sr,Ca,La)14Cu24O41 at low temperatures was investigated.
TT 6.11 Mo 16:45 H18
31 P NMR in the S=1/2 one–dimensional chain Sr2Cu(PO4)2 —
•A. Mahajan 1 , R. Nath 1 , Ch. Kegler 1 , N. Büttgen 1 , A. Loidl 1 ,
J. Bobroff 2 , and H. Alloul 2 — 1 Experimentalphysik V, EKM, Institut
für Physik, Universität Augsburg — 2 Laboratoire de Physique des
Solides, Orsay, France
We present 31 P NMR and bulk susceptibility χ measurements on
a new S = 1/2 Heisenberg antiferromagnetic (HAF) chain compound
Sr2Cu(PO4)2. The susceptibility χ(T) is found to vary according to
the Bonner-Fisher formalism expected for S = 1/2 one–dimensional
(1D) HAF chains [1]. The intra-chain exchange interaction between the
nearest–neighbour Cu spins is found to be J/kB = 150 K. The 31 P NMR
shift K(T) is proportional to χ(T) and no magnetic long–range order is
found down to 1.5 K. The decay of the transverse magnetisation following
a π/2 − τ − π pulse sequence is found to be Gaussian as in other 2D and
1D S = 1/2 HAF systems [2]. The spin–spin relaxation rate 1/T2 is temperature
independent while the spin–lattice relaxation rate 1/T1 varies
linearly with T between 10 K and 250 K. These two results suggest a
dominant contribution to the relaxation from fluctuations of the uniform
susceptibility rather than the staggered susceptibility in this temperature
range [3].
[1] J. C. Bonner and M. E. Fisher, Phys. Rev. 135, A640 (1964)
[2] C.H. Pennington and C.P. Slichter, Phys. Rev. Lett. 66, 381 (1991);
M. Takigawa et al., Phys. Rev. Lett. 76, 4612 (1996)
[3] S. Sachdev, Phys. Rev. B 50, 13006 (1994)
TT 6.12 Mo 17:00 H18
Kopplungskonstanten für Elektron-Elektron Wechselwirkung in
granularen PdxC1−x Schichten — •A. Carl und G. Dumpich —
Universität Duisburg-Essen, Institut für Physik, AG Farle, 47048 Duisburg
Es wird über Magnetowiderstandsmessungen (4.2K ≤ T ≤ 20K)
an granularen metallischen PdxC1−x Schichten mit variablem Metall-
Volumenanteil zwischen 0.35 ≤ x ≤ 1 berichtet. Alle Schichten zeigen
einen positiven Magnetowiderstand (MR) aufgrund starker Spin-Bahn
Wechselwirkung, der vollständig im Rahmen der Theorien zur schwachen
Lokalisierung (WL) und erhöhten Elektron-Elektron Wechselwirkung
(EEI) in 2D beschrieben wird. In kleinen Magnetfeldern wird der
MR hauptsächlich durch WL hervorgerufen und die Analyse liefert die
Temperaturabhängigkeit der Phasenkohärenzlänge Lφ. Die Analyse des
MR in hohen Magnetfeldern liefert sowohl die Kopplungskonstanten λCC
und λDC für Elektron-Elektron Wechselwirkung im Cooper-channel (CC)
und im Diffusion-channel (DC) als auch die Abschirmkonstante F für
Schichten mit unterschiedlichem Metall-Volumenanteil x. λCC und λDC
zeigen unterschiedliche Abhängigkeiten von x und damit vom Grad der
Unordnung des Systems. Es wird gezeigt, dass der MR für EEI im Falle
starker Spin-Bahn Wechselwirkung nicht nur durch EEI im Cooperchannel
hervorgerufen wird - wie von der Theorie erwartet - sondern auch
durch EEI im Diffusion channel.
TT 6.13 Mo 17:15 H18
Dynamics of density waves in the incommensurate high field
phase of CuGeO3. — •Klaus Kiefer 1 and Mechthild Enderle 2
— 1 Technische Physik, Universität des Saarlandes, 66123 Saarbrücken —
2 Institut Laue-Langevin, BP 156, Grenoble, 38042, France
The non magnetic, uniformly dimerized spin-Peierls ground state of a
one-dimensional spin 1/2 Heisenberg antiferromagnet becomes instable
at high magnetic fields. Above a critical magnetic field, incommensurate
quantum fluctuations condensate into a ground state and form a static
modulation pattern with both structural and magnetic components. The
periodicity of this combined structural and spin density wave changes on
variation of the external magnetic field, forcing the density wave to travel
through the crystal lattice. However, the motion of the density wave is
hindered by crystal defects. This leads to non-equilibrium states and in
consequence to heat dissipation. The dynamics of the density wave in
the presence of pinning centers can therefore be determined by the measurement
of the dissipated heat. In the high field phase of CuGeO3 we
observe the complete dynamic phase diagram of densitiy waves in dependence
of driving force and temperature, including the solid pinned, the
fluid drifting and the solid drifting state.

Tiefe Temperaturen Montag
TT 6.14 Mo 17:30 H18
Signal transport in one-dimensional interacting Fermi systems
— •Peter Schmitteckert — Institut für Theorie derKondensierten
Materie, Universität Karlsruhe, 76128 Karlsruhe, Germany
We have extented the density matrix renormalization group method
(DMRG) to calculate the time evolution of a short wave paket in an
one-dimensional system of interacting fermions at zero temperature.
In particular we demonstrate that it is not sufficient to target for the
low energy sector (a few low lying states) of the system to simulate the
dynamic of short pulses, although the overlap between the perturbed
system and the low energy sector of the unperturbed system is close to
one. Therefore, special care has to be taken in the selection of the target
states within the DMRG.
TT 7 Korrelierte Elektronen: Schwere Fermionen
Zeit: Montag 14:30–17:00 Raum: H19
TT 7.1 Mo 14:30 H19
Leitfähigkeit von Systemen schwerer Fermionen mit nichtmagnetischen
Störstellen — •Claas Grenzebach und Gerd Czycholl
— Institut für Theoretische Physik, Universität Bremen
Systeme schwerer Fermionen werden durch das periodische Andersonmodell
(PAM) beschrieben, nichtmagnetische Störstellen jeweils durch
energetisch sehr hoch liegende (ǫf → ∞) und damit unbesetzte f-
Niveaus.
Das PAM wird mittels der dynamischen Molekularfeldtheorie
(DMFT) auf ein effektives SIAM abgebildet. Dieses wird mit modifizierter
Störungsrechnung (MPT) behandelt, einer Näherung, die exakt bis
zu 2. Ordnung in U ist und den atomaren Limes reproduziert. Dabei wird
für die Störstellen-(Unordnungs-)Streuung durch die Kondo- ” Löcher“
die CPA (coherent potential approximation) verwendet, was konsistent
mit der DMFT-Abbildung ist.
Für verschiedene Störstellenkonzentrationen werden in diesem Rahmen
statische und dynamische Leitfähigkeiten berechnet.
TT 7.2 Mo 14:45 H19
Renormalization of the periodic Anderson model: an alternative
analytical approach to heavy Fermion behavior — •Klaus
Becker 1 and Arnd Hübsch 1,2 — 1 Institut für Theoretische Physik,
Technische Universität Dresden, D-01062 Dresden — 2 Department of
Physics, University of California, Davis, CA 95616, USA
A recently developed projector-based renormalization method (PRM)
for many-particle Hamiltonians is applied to the periodic Anderson model
with the aim to describe heavy Fermion behavior. In this method highenergetic
excitation operators instead of high energetic states are eliminated.
We arrive at an effective Hamiltonian for a quasi-free system which
consists of two heavy-quasiparticle bands. In contrast to the usual slave
boson mean-field (SB) treatment one of the bands describes a subsystem
of renormalized but still correlated f electrons whereas the second band
stands for renormalized conduction electrons. The resulting renormalization
equations for the parameters of the Hamiltonian are valid for large
as well as small degeneracy νf of the angular momentum. An expansion
in 1/νf is avoided. Within an additional approximation which adapts the
idea of a fixed renormalized f level ˜εf, we obtain coupled equations for ˜εf
and the averaged f occupation 〈nf 〉. These equations resemble to a certain
extent those of the SB theory. In particular, for large νf the results
for the PRM and the SB approach agree quite well whereas considerable
differences are found for small νf.
TT 7.3 Mo 15:00 H19
Theory for Coexistence of Superconductivity and A-phase in
CeCu2Si2 — •Matthias Neef and Gertrud Zwicknagl — Institut
für Mathematische Physik, TU Braunschweig, Mendelsonstr.3, 38106
Braunschweig
We study the interplay between superconductivity and spin density
waves in CeCu2Si2. We adopt realistic quasiparticle bands as calculated
by means of Renormalized band method. The experimental data concerning
the magnetic structure are confirmed. In addition we investigate
the superconductivity states, which can either coexist with or expel the
A-phase. Results are reported for magnetic susceptibility and thermodynamic
properties. The phase diagram is discussed.
TT 7.4 Mo 15:15 H19
Heavy fermion properties in filled skutterudites — •Tanja
Westerkamp and Gertrud Zwicknagl — Institut für Mathematische
Physik, TU Braunschweig, Mendelssohnstr.3, 38106 Braunschweig
We calculate the temperature-dependence of the effective mass of the
heavy quasiparticles in the filled skutterudites. The latter is assumed
to arise from the low lying Γ1 − Γ5 exitations in the CEF level scheme
suggested by Aoki et al.[1] and Tayama et al.[2].
In addition, we discuss the behavior of the quadropole susceptibility.
[1] Y.Aoki, T.Namiki, S.Ohsaki, S.R.Saha, H.Sugawara, H.Sato 2002
cond-mat/0206193
[2] T.Tayama, T.Sakakibara, H.Sugawara, Y.Aoki, and H.Sato 2003
cond-mat/0303542
15:30 Pause
TT 7.5 Mo 15:45 H19
Microwave Conductivity Spectra of Heavy-Fermion UPd2Al3
— •Marc Scheffler 1 , Martin Dressel 1 , M. Jourdan 2 , and H.
Adrian 2 — 1 1. Physikalisches Institut, Universität Stuttgart, 70550
Stuttgart — 2 Institut für Physik, Johannes Gutenberg Universität, 55099
Mainz
UPd2Al3 is a well-known heavy-fermion system that undergoes antiferromagnetic
and superconducting phase transitions at TN = 14 K and
Tc = 2 K, respectively. Previous optical spectroscopy studies [1] of the
heavy-fermion nature of this system down to frequencies of about 1 cm −1
(= 30 GHz) showed the influence of heavy-fermion as well as magnetic
characteristics and in particular revealed a well-pronounced pseudogap
at low frequencies (below 3 cm −1 ) that was attributed to magnetic correlations.
Thus the optical conductivity at even lower frequencies is of
notable interest because there the Drude roll-off (the high-frequency characteristic
of a metal) remained hidden at extremely low frequencies.
Using a recently developed cryogenic broadband microwave spectrometer
employing the Corbino geometry we have studied the complex optical
conductivity of UPd2Al3 thin films in the frequency range from 45 MHz
to 20 GHz at temperatures from 1.65 K to 300 K. We present spectra
revealing the emergence of a strong Drude-like conductivity roll-off at
frequencies of only a few GHz as the temperature is decreased (in agreement
with the increase of dc conductivity) and discuss the microwave
conductivity of UPd2Al3 in the framework of the optical properties determined
by previous experiments.
[1] M. Dressel et al., Phys. Rev. Lett. 88, 186404 (2002)
TT 7.6 Mo 16:00 H19
Quantum Critical Behavior in Yb1−xLaxRh2Si2 Studied by
Low Temperature Resistivity and Specific Heat — •Franziska
Weickert, Teodora Rus, Julia Ferstl, Philipp Gegenwart,
Christoph Geibel, and Frank Steglich — Max-Planck-Institute
for Chemical Physics of Solids, Nöthnitzer Str.40, 01187 Dresden
The Heavy Fermion System YbRh2Si2 is a very suitable compound
to study non Fermi liquid properties near a Quantum Critical Point
(QCP). At zero magnetic field very weak antiferromagnetic order occurs
at 70 mK. A tiny 0.15% volume expansion due to a substitution of
nominally 5% of Si by larger Ge reduces TN to 20 mK. Difficulties in
sample preperation prevent a complete suppression of TN by Ge-doping.
An alternative and successful route to tune the system through
the zero-field QCP is the partial substitution of Yb by larger La in
Yb1−xLaxRh2Si2.
Here we report low temperature resistivity and specific heat measurements
on x = 0.05 and 0.1 single crystals, which show the complete
suppression of AF order.
TT 7.7 Mo 16:15 H19
YbIr2Si2− A new Yb−based Heavy Fermion System situated
close to Quantum Critical Point — •Z. Hossain, C. Geibel,
H. Jeevan, F. Weickert, P. Gegenwart, T. Lühmann, and F.
Steglich — Max Planck Institute for Chemical Physics of Solids, 01187
Dresden, Germany
While YbRh2Si2 is presently subject of thorough investigation moti-

Tiefe Temperaturen Montag
vated by its proximity to a quantum phase transition, the isoelectronic
compound YbIr2Si2 has not yet been investigated. We have synthesized
polycrystalline and single crystalline samples of YbIr2Si2 and investigated
their physical properties. Depending on synthesis conditions the
samples take either body-centred (ThCr2Si2 structure- I-type) or primitive
tetragonal (CaBe2Ge2 structure- P-type) structure. P-type sample
shows AF order below 700 mK. I-type sample does not show any signature
of magnetic order down to 100 mK. The magnetic susceptibility for
this sample is highly anisotropic with effective moment close to that expected
for Yb 3+ ions. The resistivity is nearly temperature independent
at high temperature followed by a rapid decrease below 100 K similar to
Kondo lattice/heavy fermion system. The resistivity does not show any
anomaly due to either magnetic or superconducting transition down to
20 mK. Further, the resistivity at low temperature follows ρ(T) = ρ0 +
AT n with n =1.3 instead of n = 2 expected from Fermi Liquid theory.
The specific heat is also Non-Fermi-Liquid (NFL) type as C/T continues
to increase with decreasing T down to 350 mK where C/T = 0.6 J/(mol
K 2 ). Thus, I-type YbIr2Si2 is a new heavy fermion compound situated
close to the quantum critical point and exhibits NFL behaviour.
TT 7.8 Mo 16:30 H19
Investigation of the magnetic and the superconducting states of
CeCu2Si2 using large single crystal. — •H.S. Jeevan 1 , M. Deppe 1 ,
O. Stockert 1 , R. Borth 1 , E. Faulhaber 2 , C. Geibel 1 , and F.
Steglich 1 — 1 Max Planck Institute for Chemical Physics of Solids,
Dresden — 2 TU Dresden, IAPD, D-01062 Dresden, Germany.
The discovery of superconductivity in CeCu2Si2 in 1979 opened the
field of unconventional superconductivity in strongly correlated systems.
Later on, another unconventional phase, the A-phase, of presumably
magnetic character was found to compete with the superconducting phase
in CeCu2Si2. Despite more than 20 years of intensive research, the nature
of the superconducting phase and of the A-phase as well as the interac-
TT 8 Postersitzung I: Supraleitung
tion between both are very far from being understood. A major problem
is the lack of large single crystals with well defined physical properties.
This prevents e.g. a study of the magnetic structure and magnetic excitations
of this compound with neutron scattering, which would allow
a much deeper insight into the nature of these unconventional phases.
We have developed a self-flux growth method, which allows the growth
of large CeCu2Si2 single crystal with well defined properties. The ground
state can be tuned by changing growth parameters. We have investigated
the magnetic and the superconducting ground state using specific
heat, resistivity and susceptibility measurements. The preliminary neutron
scattering measurements allow us to determine for the first time
the magnetic structure of the A-phase. We shall analyse and discuss the
physical properties of these single crystals and their relation to growth
parameters.
TT 7.9 Mo 16:45 H19
Weak itinerant metamagnetism at the quantum phase transition
of ZrZn2 — •M. Uhlarz 1 , C. Pfleiderer 1 , and S. M. Hayden
2 — 1 Physikalisches Institut, Universität Karlsruhe, D-76128 Karlsuhe,
Germany — 2 H. H. Wills Physics Laboratory, University of Bristol,
Bristol, BS8 1TL, UK
It is generally assumed that the coexistence of band-ferromagnetism
with superconductivity, recently discovered in ZrZn2 [1], is connected
with the proximity of ZrZn2 to a quantum critical point. We have revisited
the question of quantum criticality in ZrZn2 in a detailed study of
the pressure dependence of the magnetisation of single crystals of ZrZn2
up to 21kbar at temperatures down to 1.5K and magnetic field up to
12T. In the vicinity of the critical pressure we observe evidence for weak
first order behaviour and itinerant metamagnetism. The evolution of the
magnetic state in ZrZn2 is compared with that observed in the superconducting
ferromagnets UGe2 and URhGe.
[1] C. Pfleiderer et al., Nature 412 (2001) 58.
Zeit: Montag 14:30–19:00 Raum: Poster A
TT 8.1 Mo 14:30 Poster A
In-situ deposition of MgB2 thin films by magnetron sputtering
and thermal evaporation — •R. Schneider, A.G. Zaitsev, J.
Geerk, G. Linker, and F. Ratzel — Forschungszentrum Karlsruhe,
Institut für Festkörperphysik
We report on two approaches to the in-situ synthesis of superconducting
MgB2 thin films. In the first approach, Mg and B were simultaneously
sputtered from two separate planar targets. The substrate temperature
Ts was limited to a small range of 290 to 320 ◦ C. The resulting films on
sapphire substrates were c-axis textured with low growth quality. Their
transition temperature Tc reached a maximum of 24 K with a transition
width of 0.6 K. A short-time in-situ annealing at 600 ◦ C improved Tc to
28 K. In the second approach, the Mg sputter source was replaced by
a specially designed Mg evaporator. Due to this intense Mg source Ts
could be increased to 440 ◦ C, and Tc of the ”as-grown” films rose to 33
K. Short-time in-situ annealing after the film deposition enhanced Tc to
36 K. For these films we also measured a high critical current density of
15 MA/cm 2 at 6 K.
TT 8.2 Mo 14:30 Poster A
Preparation, Structure, and Properties of Hg,Re-Containing
High-Temperature Superconductor Thin Films — •Abouelwafa
Salem, Gerhard Jakob und Hermann Adrian — Institut für Physik,
Johannes Gutenberg–Universität, 55099
Fully textured (Hg0.9Re0.1)Ba2CaCu2O6+δ (HgRe-1212) thin films have
been prepared by pulsed laser deposition (PLD) and post-annealing.
The films exhibit sharp superconducting transitions at Tc= 124 K with
transition widths of ∆Tc ≃ 2 K. Conditions for reproducible film preparation
have been found. The resistive transitions have been investigated in
magnetic fields up to 8 T (parallel to the c-axis) and 10 T (perpendicular
to the c-axis). The activation energy of thermally activated flux-motion
has been determined for both magnetic field orientations. The Hall resistivity
(ρxy) has been measured in the ab-plane at 8 T. In the mixed state
a power-law behavior is observed, where ρxy scales to ρxx: ρxy = Aρ β xx,
with β = 1.4 ±0.1. Above 130 K the T 2 dependence of the cotangent of
the Hall angle is observed. Magnetization loops were measured at various
temperatures in a SQUID magnetometer. The corresponding critical cur-
rent densities Jc were calculated. The anisotropic properties of the vortex
state and the depinning field Bdp(θ) have been studied by varying the angle
θ between the field direction and the c-axis of the film. The measured
angular dependence Bdp(θ) shows a cusp for θ = 90 ◦ . The films exhibit
a rather low critical field anisotropy of 7.7. Under the same conditions
(Hg0.9Re0.1)Ba2Ca2Cu3O8+δ (HgRe-1223) thin film (Tc= 130 K) have been
prepared.
TT 8.3 Mo 14:30 Poster A
Novel consideration of the phase diagram of electron doped
high-temperature superductors — •Yoshiharu Krockenberger
1 , Michio Naito 1 , Akio Tsukada 1 , Hideki Yamamoto 1 ,
Lambert Alff 2 , and Rudolf Gross 2 — 1 NTT Basic Research
Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi-shi,
Kanagawa 243-0198, Japan — 2 Walther-Meissner-Institut, 85748
Garching, Germany
The common phase diagram of high-temperature superconductors
(HTS) including electron doped HTS was published first by Luke et al.[1].
Improved sample quality of hole doped cuprates supported and extended
this phase diagram. Using molecular beam epitaxy it is possible to grow
high quality single phase thin films of electron doped high-temperature
superconductors. Usually, for doping the T ′ -structure tetravalent Ce (e.g.
La2−xCexCuO4+δ) is used. Using trivalent ions instead of Ce 4+ , e.g. Tb 3+ ,
one would expect a Mott insulating and antiferromagnetic state. The caxis
dependence of the doping level as well as XPS measurements clearly
show that the Tb-cation is in the trivalent state. Furthermore, other
trivalent dopants such as Lu, Y, Dy, Eu, and Sm have been investigated
and all of them show the same result: superconductivity below about
20K. This result may shed new light on the usually used phase diagram
of electron doped high temperature superconductors.
[1] G. M. Luke et al., Phys. Rev. B 42, 7981 (1990)
TT 8.4 Mo 14:30 Poster A
Growth and superconducting properties of ternary rare earth
(Gd, Eu, Nd)Ba2Cu3Oy thin films — •C. Cai, J. Hänisch, L.
Fernandez, and B. Holzapfel — IFW Dresden, D-01171 Dresden,
Germany

Tiefe Temperaturen Montag
Ternary rare earth (Gd1/3Eu1/3Nd1/3)Ba2Cu3Oy (GEN123) thin films
are prepared with off-axis laser ablation technique. Compared with monorare
earth 123 films, GEN123 films show higher critical current density
(Jc) and improved irreversibility field (Hirr), but no increase in the characteristic
field corresponding to a crossover from low-field plateau to a
linear region in logJc-logH plot. At intermediate fields, Jc vs. H scales
as H −0.5 for GEN123, in contrast to H −0.73 for mono-rare earth samples
such as Gd123. The slow power decay of Jc vs. H together with the improved
Jc and Hirr strongly imply the extra flux pinning centres existing
in GEN123, which are suggested to be non-correlated stress field induced
by lattice mismatch.
TT 8.5 Mo 14:30 Poster A
High magnetic field test facilities at the Forschungszentrum
Karlsruhe — •Hanno Leibrock, Frank Hornung, Marion
Kläser, Hans Müller, Astrid Rimikis, and Theo Schneider —
Institut für Technische Physik, Forschungszentrum Karlsruhe GmbH,
Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen
Since more than 20 years the high-field laboratory (HFL) of the Institute
for Technical Physics at the Forschungszentrum Karlsruhe develops,
constructs and operates superconducting high-field magnets. During this
period we achieved, inter alia, the world record of 20.1 Tesla for a superconducting
magnet system (HOMER 1, 1987) and introduced the world’s
first commercial 750 MHz, 800 MHz and 900 MHz NMR-spectrometer,
together with our industrial partner Bruker Biospin.
Current tasks of the HFL-group is the construction of the HOMER II
test facility with magnetic fields up to 25 Tesla and a national
BMBF-project for the development of a 1000 MHz NMR-spectrometer
(23.5 Tesla) together with Bruker Biospin.
Two experimental facilities, JUMBO (max. 15 Tesla) and HOMER I
(max. 20.1 Tesla) exist in the high field laboratory for the required investigations
in high magnetic fields. The first construction stage of the
third facility, HOMER II, with a magnetic field of 20 Tesla in a bore
of 180 mm diameter will start up soon. All setups, based on advanced
superconducting magnets, are presented in this contribution.
TT 8.6 Mo 14:30 Poster A
Characterisation of advanced technical superconductors —
•Marion Kläser, Frank Hornung, Hanno Leibrock, Hans
Müller, and Theo Schneider — Institut für Technische Physik,
Forschungszentrum Karlsruhe GmbH, Hermann-von-Helmholtz-Platz 1,
76344 Eggenstein-Leopoldshafen
By means of the high magnetic field test facilities in the high-field laboratory
(HFL) at the Forschungszentrum Karlsruhe the superconducting
properties of low (NbTi, Nb3Sn) and high (Bi2212, Bi2223) temperature
superconductors were investigated at 1.8, 2.2 and 4.2 Kelvin in magnetic
fields up to 20 Tesla. The electric field-current relation, E(I), is examined
resistively using a high resolution four-point measurement technique.
Detailed error analysis ensure the significance of the E(I)-characteristics
and of the resultant critical current Ic and n-value. The outcomes are
used e.g. to compare commercial conductors and to optimise the heat
treatment of binary and ternary A15-superconductors.
These investigations are the base for the development and construction
of superconducting high-field magnets for experimental high-field
test facilities and new generations of NMR spectrometers.
TT 8.7 Mo 14:30 Poster A
Herstellung und Charakterisierung von supraleitenden Zuleitungen
aus Niob auf flexibler Polyimide-Folie — •Thomas
Schneider 1 , Cornelia Assmann 2 , Jörn Beyer 2 und Thomas
Schurig 2 — 1 FHTW Berlin — 2 PTB Berlin
Bei experimentellen Aufbauten im Tieftemperaturbereich, insbesondere
unterhalb 1 K, existieren bezüglich der mechanischen, elektrischen
und thermischen Eigenschaften der eingesetzten Verdrahtung oftmals besondere
Anforderungen. In vielen Fällen sind eine geringe thermische
Leitfähigkeit, hohe elektrische Leitfähigkeit, Kompaktheit und mechanische
Robustheit erforderlich. Darüber hinaus können zusätzliche Eigenschaften,
wie z.B. definierter Wellenwiderstand oder niedrige Induktivität,
notwendig sein. Streifenleiter basierend auf Dünnschichtstrukturen
auf flexiblen Kunststoff-Folien können bei geeigneter Wahl der verwendeten
Materialien viele dieser Eigenschaften kombinieren. In diesem Beitrag
berichten wir über die Herstellung von Verdrahtungselementen bestehend
aus supraleitenden Leitungen aus Niob auf Polyimide-Substraten. Dazu
wird Polyimide-Folie mit einer Dicke von 0.125 mm beidseitig mit Niob-
Dünnfilmen beschichtet. Nach Strukturierung des Niobs in Streifenlei-
tergeometrie entstehen niederinduktive Verbindungsleitungen mit hoher
Packungsdichte. Es werden technologische Aspekte sowie die supraleitenden
Eigenschaften und die mechanische Zuverlässigkeit der Proben
diskutiert.
TT 8.8 Mo 14:30 Poster A
Understanding grain boundary critical currents in high-Tc superconductors
— •Karsten Guth, V. Born, S. Sievers, H. C.
Freyhardt, and Ch. Jooss — Institut für Materialsphysik, Universität
Göttingen, Tammannstr. 1, 37077 Göttingen
Even more than 15 years after the discovery of high Tc superconductivity
current suppression at grain boundary (GB) interfaces is one of the
major problems for high current applications.
Therefore, a detailed understanding of current transport across GBs
is of great physical and technical interest. We performed a comparative
study with thin films of the RE-123 (RE=Y, Y0.8Ca0.2, Yb, Er) system
containing small angle GBs. By the manipulation of transport properties
via Ca doping, rare earth ion size and the underlying substrate, we were
able to directly influence GB properties such as the intergranular critical
current.
We used magneto-optical imaging (MOI) to map the magnetic fieldand
current distribution across thin film GBs. With this space resolved
characterisation technique it is further possible to study effects of the
magnetic history on the inhomogeneous current distribution of wide current
bridges. Additionally, via time resolved MOI the electric field distribution
for magnetisation experiments could be calculated from the
time-decay of the magentic field distribution, showing electric fields as
small as 10 −8 V/m in these samples. Our measurements present different
routes how to tailor GB properties in the future.
TT 8.9 Mo 14:30 Poster A
Magneto-optic imaging of superconducting transport currents
in magnetic environments — •Harald Jarzina, Volker Born,
Christian Jooss, Eva Brinkmeier, Karsten Guth, Wilko
Westhäuser, and H. C. Freyhardt — Institut für Materialphysik,
Tammannstrasse 1, 37073 Göttingen
Magneto optic (MOI) imaging provides a valuable tool for space and
time resolved measurements of the flux density distribution of superconducting
films. For technological applications such as coated conductors,
the investigation of transport currents is of special interest. In coated
conductors, grain boundaries are the main reason for current suppression.
In this work, we present flux and current-density distributions of
YBa2Cu3O7 strips on single and bicrystalline substrates with an applied
transport current. We discuss the change in the flux density distribution
if a soft magnetic material is brought into the vicinity of the film. In
the case of magnetization currents, the presence of soft magnetic material
at the edges of the superconductor can prevent flux entry into the
superconductor, thus stabilizing the Meissner phase up to higher external
fields. Thereby current densities larger than the pinning determined
critical current density jc can be obtained.
TT 8.10 Mo 14:30 Poster A
Modifying the current distribution of grain boundaries — •Eva
Brinkmeier, Harald Jarzina, Karsten Guth, Volker Born,
and Christian Jooss — Institut fuer Materialphysik, Universitaet
Goettingen, Tammanstrasse 1, 37077 Goettingen
The current distribution in thin superconducting films can be tailored
by field conditioning via magnetic surroundings [1]. A soft magnet put
parallel to a thin film edge can reduce or prevent the flux entry and
therfor stabilise Meissner screening currents in the film. This is particularly
interesting for the investigations of transport currents across grain
boundaries in high temperature superconductors, where the critical current
density sometimes strongly depends on the flux which penetrates
into the grain boundary. Furthermore using special magnetic arrangements,
asymmetric flux and current distributions can be tailored. We
show, that flux penetration into grain boundary can be suppressed up to
a certain external field H ∗ , which depends on the temperature and on
the angle of the grain boundary.
All investigations were done by magneto-optical imaging and the inversion
of Biot and Savart.
[1] H.Jarzina, Ch. Jooss and H.C. Freyhardt, J. Appl. Phys. 91 (2002)
3775

Tiefe Temperaturen Montag
TT 8.11 Mo 14:30 Poster A
Finite size effects and JC simulations in high-JC coated conductors
— •J. Hänisch, L. Fernández, C. Cai, V.S. Sarma, L.
Schultz und B. Holzapfel — IFW Dresden, Helmholtzstr. 20, 01069
Dresden, Germany
The superconducting layer in coated conductors consists a network
of small angle grain boundaries. Due to the limitation of JC on grain
boundaries in high-TC superconductors, the current flow through this
network is of percolative nature and depends on misorientation angle
distribution, width and length of the tape and grain shape. The current
flow through grain boundary networks had been simulated widely with
purely statistical models on artificial networks. Recent investigations of
biaxially textured orthorhombic materials (as YBCO on coated conductors
is) showed a nonrandom distribution of misorientation angles in this
materials.
JC simulations using a fast and simple limiting-path algorithm were used
to investigate the influence of the grain boundary misorientation statistics
on JC in realistic networks. Input of the simulation program are
large EBSD (electron back scattering diffraction) maps and the misorientation
angle dependence of JC. We found a strong dependence of JC on
the bridge width for bridges smaller then 20 grains (in comparisson to
purely statistical models), whereas JC is not strongly varying for wider
bridges. In rotating the whole EBSD map, we could simulate the influence
of the grain aspect ratio on JC. In current direction elongated grains
show significantly higher JC values. Both these results are promissing for
the performance of coated conductors.
TT 8.12 Mo 14:30 Poster A
Coated Conductors by Inclined Substrate Deposition — •A.
Lümkemann 1 , J. Handke 1 , H. Kinder 1 , R. Nemetschek 2 , C.
Hoffmann 2 , G. Sigl 2 , and W. Prusseit 2 — 1 TU München, Physik
Department E10, 85748 Garching — 2 THEVA Dünnschicht GmbH,
Rote-Kreuz-Str. 8, 85727 Ismaning
Thermal evaporation is one of the most promising techniques for economic
industrial scale production of second generation HTS wire. The
in-plane alignment of the RBCO film necessary for high critical current
densities can be achieved by depositing biaxially textured buffer layers
by inclined substrate deposition (ISD).
The MgO buffer layer is grown at room temperature on electropolished
Hastelloy tape by ISD using electron beam evaporation at roughly
3nm/s and inclination angle of 25 ◦ with respect to the substrate normal.
This results in an in-plane alignment of 11 ◦ − 12 ◦ (FWHM). Meanwhile
33m long buffered Hastelloy tape has been fabricated using a 15 loop
tape winder. HTS deposition is currently performed on 20m long and
1cm wide tape. Average critical current densities over several meters of
tape are about 1.0MA/cm 2 at 77K, i.e. 100A/cm of transport current in
a 1µm DyBCO film.
We also present results on samples up to 20cm optained by HTSdeposition
in static mode which can be summarized as follows: Dy-
BCO on IBAD buffered tape exhibit critical current densities jc (77K)
>2.0MA/cm 2 whereas MgO-ISD-buffer sustain jc in the range of
1.6MA/cm 2 . Ni5%W-RABiTS tape can carry up to 0.8 - 1.2MA/cm 2 .
TT 8.13 Mo 14:30 Poster A
YBCO thin films prepared by a Fluorine-free sol-gel method
— •C. Apetrii 1 , I. v. Lampe 2 , M. Falter 1 , H. Schlörb 1 , B.
Holzapfel 1 , and L. Schultz 1 — 1 IFW Dresden, Helmholtzstr. 20,
01069 Dresden — 2 TU Berlin, Institut für Werkstoffwissenschaften und
-technologien, Englische Str. 20, 10587 Berlin
The chemical solution deposition procedure is a low cost method due
to non-vacuum approach for growing longer YBCO tapes. The polymer
metal precursor technique, a fluorine-free sol-gel method, leads to a stable
and non-aggressive precursor solution and also HF does not form during
the process. HF is difficult to remove in precursor films prepared by the
Trifluoracetates (TFA-method). Y, Ba, and Cu nitrates were chosen as
a starting substances for the preparation of the polymer metal precursor
to avoid the formation of BaCO3. The polymer metal precursor films
were produced by spin coating of a stoichiometric solution onto SrTiO3
single crystal substrate and then dried at 170 ◦ C. The heat treatment
was performed in a tube furnace with reaction temperature of 775 ◦ C. We
obtained epitaxially grown 240 nm thick YBCO films on single crystal
SrTiO3 with a resistively measured Tc of 89.9 K and ∆T of 2.0 K. The
temperature dependence of the critical current density was measured using
the standard 4 point geometry on 20 µm wide bridges and values of
10 5 A/cm 2 (at 77 K) were received.
TT 8.14 Mo 14:30 Poster A
Preparation of perovskite buffer layers on surface oxidized
Ni tapes for coated conductor applications — •R. Hühne 1 , B.
Holzapfel 1 , A. Kursumovic 2 , B. A. Glowacki 2 , J. E. Evetts 2 ,
A. Cavallaro 3 , F. Sandiumenge 3 , A. Pomar 3 , T. Puig 3 , and X.
Obradors 3 — 1 IFW Dresden, Germany — 2 Department of Materials
Science, University of Cambridge, UK — 3 Institut de Ciencia de Materials
de Barcelona, Spain
The preparation of cube textured NiO buffer layers on biaxially textured
Ni tapes (RABiTS) using surface oxidation epitaxy (SOE) offers a
cheap and scalable route for the production of long-length YBCO coated
conductors. A second buffer layer is necessary to ensure epitaxial growth
of the YBCO as well as to prevent Ni contamination of the superconducting
layer. Therefore, different perovskite buffer were grown on SOE-NiO
using pulsed laser deposition (PLD) and metal-organic decomposition
(MOD). Ca0.6Sr0.4TiO3, BaZrO3 and SrZrO3 buffers were successfully deposited
on NiO showing a high quality epitaxial growth with an in-plane
orientation similar to the underlying NiO. The subsequent deposition of
YBCO on top of these buffers using different methods resulted in epitaxial
layers with a Tc0 above 83 K and jc up to 1 MA/cm −2 . Microstructural
investigations showed that in all cases the roughness and the surface topography
of the buffer layers is mainly determined by the quality of the
NiO layer.
TT 8.15 Mo 14:30 Poster A
Ca- und Ag-dotierte YBCO-Filme aus Polymer-Metall-
Precursoren auf STO und Ni-YSZ-Substrat — •Frank
Zygalsky und Irene von Lampe — TU-Berlin, Inst. f. Werkstoffwissenschaften
u. -technologien, Englische Str. 20, 10587 Berlin
Die thermische Zersetzung von durch Spincoating erzeugten Polymer-
Metall-Precursorschichten stellt ein verfahrenstechnisch unkompliziertes
Schichtdepositionsverfahren zur epitaktischen Abscheidung von hochtemperatursupraleitenden
Phasen dar. Ziel der Forschungsarbeit ist die
Weiterentwicklung dieses kostengünstigen Nicht-Vakuum-Verfahrens hinsichtlich
Epitaxiequalität und kritischer Stromdichte der erzeugten
HTSL-Schichten. Dabei wird die Schichtabscheidung sowohl auf einkristallinen
STO-Substraten als auch auf technisch relevanten biaxial texturierten
Ni-Metallbändern mit YSZ-Pufferschicht betrachtet, sowie der
Einfluß von Ca- und Ag-Dotierungen auf die supraleitenden Eigenschaften
untersucht.
TT 8.16 Mo 14:30 Poster A
Superstructure on hightemperature superconductors (N=1,2,3)
affirmed with STM — •Torsten Stemmler, Hendrik
Glowatzki, and Recardo Manzke — Humboldt-Universität,
Institut für Physik
We present new pictures on HTCs from STM.
TT 8.17 Mo 14:30 Poster A
Oxygen superstructures throughout the phase diagram
of (Y,Ca)Ba2Cu3O6+x — •Joerg Strempfer 1 , Ioannis
Zegkinoglou 1 , Uta Ruett 1 , Martin von Zimmermann 2 ,
Christian Bernhard 1 , Chengtian Lin 1 , Thomas Wolf 3 ,
and Bernhard Keimer 1 — 1 Max-Planck-Institut fuer Festkoerperforschung,
Heisenbergstr. 1, 70569 Stuttgart — 2 Hamburger
Synchrotronstrahlungslabor HASYLAB at DESY, Notkestr. 85, 22603
Hamburg — 3 Forschungszentrum Karlsruhe, ITP, 76021 Karlsruhe
Short-range lattice superstructures have been studied with high-energy
x-ray diffuse scattering in underdoped, optimally doped, and overdoped
(Y, Ca)Ba2Cu3O6+x. A new four-unit-cell superstructure was observed
in compounds with x=0.92. The great similarity of the diffuse
scattering pattern of the YBa2Cu3O6.92 compound with the one of
Y0.8Ca0.2Ba2Cu3O6.95, which has approximately the same oxygen-content
but different charge carrier concentration due to the Ca- substitution,
clearly indicates that the origin of these superstructures lies in shortrange
oxygen vacancy ordering rather than in electronic instabilities in
the CuO2 layers. This is further supported by the absolute absence of
any significant diffuse scattering in YBa2Cu4O8, a compound that contains
no oxygen vacancies. The persistence of the diffuse reflections up
to temperatures well above room temperature is also not in favour of the
stripe-related scenario for their origin.

Tiefe Temperaturen Montag
TT 8.18 Mo 14:30 Poster A
Proximity-Effekt in supraleitenden Nb/Ag- und Nb/Ag/Fe-
Schichtpaketen — •H. Stalzer 1 , A. Cosceev 1 , C. Sürgers 1 ,
H. v. Löhneysen 1,2 , J.-M. Brosi 3 , G.-A. Chakam 3 und W.
Freude 3 — 1 Physikalisches Institut und DFG Center for Functional
Nanostructures (CFN), Universität Karlsruhe, D-76128 Karlsruhe —
2 Forschungszentrum Karlsruhe, Institut für Festkörperphysik, D-76021
Karlsruhe — 3 Institut für Hochfrequenztechnik und Quantenelektronik
und DFG Center for Functional Nanostructures (CFN), Universität
Karlsruhe, D-76128 Karlsruhe
Der Proximity-Effekt in supraleitenden Nb/Ag- und Nb/Ag/Fe-
Schichten (Schichtdicken dNb0 nm, dAgU0−800 nm, dFe = 2−20 nm) wird
durch Messung der Magnetisierung M in einem parallelen Magnetfeld B
im Temperaturbereich T = 0.07 − 10 K untersucht. Für die Nb/Ag-
Doppelschichten zeigt M(T) unterhalb von T Nb
c = 9.1 K einen weiteren
diamagnetischen Übergang bei T ∗ durch den Einsatz der Supraleitung
in der Ag-Schicht. Die Verläufe des Breakdown“-Feldes Bc(T, dAg) und
”
der charakteristischen Temperatur T ∗ (dAg) zeigen Abweichungen vom
” schmutzigen“ Grenzfall aufgrund der großen mittleren freien Weglängen
in der Ag-Schicht. In den Nb/Ag/Fe-Schichtpaketen wird der Übergang
bei T ∗ durch die Fe-Schicht unterdrückt. Ausserdem beobachten wir eine
Abhängigkeit des Signals von der Position der Probe zwischen den Pickup-Spulen
des Magnetometers durch Entmagnetisierungseffekte. Diese
ist für den Übergang der Ag-Schicht verschieden vom Übergang in der
Nb-Schicht aufgrund unterschiedlicher Abschirmströme.
TT 8.19 Mo 14:30 Poster A
Tunneling spectra of high-temperature superconductor - manganite
junctions — •Mitja Schonecke, Bettina Welter, Lambert
Alff, and Rudolf Gross — Walther-Meißner-Institut, Walther-
Meißner-Str. 8, 85748 Garching
We use YBa2Cu3O7−δ ramp-type junctions to investigate the
conductance spectra of superconductor-normal metal (S/N) and
superconductor-ferromagnet (S/F) interfaces. The geometry of ramptype
junctions takes advantage of the larger coherence length of the
superconductor in the ab-plane by coupling the two electrodes in this
direction. With our fabrication process it is possible to obtain samples
either in the tunneling limit or in the highly transparent Andreev-regime.
While the S/N samples in the tunneling limit show splitting of the zero
bias conductance peak at zero magnetic fields, the Andreev-spectra of
S/F junctions are dominated by multiple sharp features. The origin of
theses features has not yet been clarified.
TT 8.20 Mo 14:30 Poster A
Andreev reflection and nonequilibrium Josephson effect in
(quasi)ballistic S-N-S junctions — •Dmitri Ryndyk — Institut
für Theoretische Physik, Universität Regensburg, 93040 Regensburg
Josephson effect in mesoscopic S-N-S junctions is possible due to the
phase coherent Andreev reflection even in the absence of a pairing interaction
inside normal region. Recently both stationary and nonstationary
Josephson effects were investigated experimentally in ballistic (or close
to ballistic) structures, and a number of expected as well as unexpected
features were observed. We consider the theory in the case of ballistic
and quasiballistic normal regions. Both stationary and nonstationary
Josephson effects are very sensitive to nonequilibrium effects in a normal
channel.
TT 8.21 Mo 14:30 Poster A
Andreev reflection at superconducting contacts to InGaAs/InP
heterostructures — •I. E. Batov 1 , Th. Schäpers 2 , A. A. Golubov
3 , and A. V. Ustinov 1 — 1 Physikalisches Institut III, Universität
Erlangen-Nürnberg, 91058 Erlangen — 2 Institut für Schichten und Grenzflächen,
Forschungszentrum Jülich, 52425 Jülich — 3 Faculty of Applied
Physics, University of Twente, The Netherlands
Transport in hybrid devices consisting of superconductors (S) in contact
with a two-dimensional electron gas (2DEG) is a subject of increasing
interest in recent years. Novel transport phenomena arising due to Andreev
reflection at the S/2DEG interface were predicted recently in such
devices, such as magnetoconductance oscillations in the Quantum Hall
regime, suppression of the Hall resistance near the S/2DEG interface, etc.
To access the novel transport regime of interest, in most cases the high
transparency of the S/2DEG contacts is essential. In this work, we report
on the fabrication of highly transmissive contacts to the two-dimensional
electron gas in InGaAs/InP heterostructures. As a superconductor NbN
is used. High junction transmissivity was achieved by exploiting a pro-
cess of sputtering a thin (10nm) Au interlayer followed by the deposition
of the NbN electrode and rapid annealing at 400 ◦ C. We observed
a decrease in the differential resistance of the junction with pronounced
double-dip structure within superconducting energy gap. The effect of a
magnetic field perpendicular to the plane of the 2DEG on the differential
resistance of the interface was studied. Experimental data are analyzed
within a model of ballistic SN-2DEG contact, based on the quasiclassical
Green-function approach.
TT 8.22 Mo 14:30 Poster A
Supraleiter-Normalleiter-Supraleiter-Kontakte als Schalter für
die Anwendung in supraleitenden Multiplexern — •Oliver
Lindner 1 , Margret Peters 2 , Jörn Beyer 2 und Thomas
Schurig 2 — 1 FHTW Berlin — 2 PTB Berlin
In komplexen kryoelektronischen Schaltungen, wie z.B. in mehrkanaligen
Tieftemperaturdetektor-Anordnungen mit SQUID-basierter Auslese,
können zur Begrenzung der Schaltungskomplexität Multiplexer eingesetzt
werden. In diesem Beitrag wird ein neues Konzept eines supraleitenden
Multiplexers vorgestellt, das auf Supraleiter-Normalleiter-
Supraleiter-(SNS)-Schaltern ähnlich SNS-Josephson-Transistoren [1] beruht.
Hierbei wird durch Erhöhung der Elektronentemperatur im N-
Bereich des Kontakts eine Beeinflussung des Suprastroms durch den SNS-
Kontakt erreicht. Die SNS-Schalter werden in supraleitende Transformatorstrukturen
integriert und vom supraleitenden Zustand in den normalleitenden
geschaltet. Dadurch lassen sich Signalmodulations- und Multiplexfunktionen
realisieren. Es wird die Herstellung von lateralen Nb-Au-
Nb-Kontakten mit Abständen der supraleitenden Elektroden von unter
1 Mikrometer präsentiert. Die Charakterisierung der supraleitenden und
normalleitenden Eigenschaften der SNS-Kontakte und ihr Schaltverhalten
bei Arbeitstemperaturen von 4.2 K und darunter werden dargestellt
und Rückschlüsse auf die Integration der SNS-Schalter in die Multiplexerschaltung
diskutiert.
[1] A.F.Morpurgo, T.M.Klapwijk, B.J.van Wees, Appl.Phys.Lett. 72, 966
(1998)
TT 8.23 Mo 14:30 Poster A
Pulse driven arrays of HTS bicrystal Josephson junctions —
•Andriy Rebikov 1,2 , Alexander Klushin 1 , and Norbert Klein 1
— 1 Forschungszentrum Juelich GmbH, Institut fuer Schichten und Grenzflaechen,
52425, Juelich, Germany — 2 Department of Radiophysics,
Kiev Taras Shevchenko University, Kiev, the Ukraine
For appropriate pulse driven arrays of shunted HTS bicrystal Josephson
junctions parameters of junctions such as critical current Ic, normal
resistance Rn and characteristic voltage were optimised to guarantee a
large first voltage step comparable with Ic. A new shunting concepts were
developed and tested. With a critical current of 1 mA, the product IcRn
of 20 uV matches a convenient input frequency of approximately 12 GHz.
HTS arrays with 100 junctions were driven with both a broadband twolevel
digital code and sine wave and have shown a full frequency locking
at liquid nitrogen temperature. Pulse-driven Josephson arrays are being
developed for ac quantum voltage standards, for a new temperature
standards and generation of arbitrary waveforms.
TT 8.24 Mo 14:30 Poster A
Design considerations for large area magnetic calorimeters and
detector arrays — •T. Daniyarov 1 , A. Burck 1 , M. Linck 1 , H.
Rotzinger 1 , A. Fleischmann 1 , and C. Enss 2 — 1 Kirchhoff-Institut
für Physik, Universität Heidelberg, INF 227, 69120 Heidelberg —
2 Department of Physics, Brown University, Providence, RI 02912, USA
Only recently it was demonstrated that energy dispersive x-ray detectors
based on the concept of metallic magnetic calorimeters can achieve
resolving powers close to E/δE = 2000. Due to the calorimetric detection
scheme magnetic calorimeters are not limited to ionizing radiation and
do not suffer from dead layers at the surface. This combination of properties
is attractive for a large number of applications, provided that the
active area of the detector is large enough. We present sensor geometries,
which allow for the fabrication of large area magnetic calorimeters and
discuss the optimization of flux coupling to the dc-SQUID magnetometer
used for the inductive readout of such detectors. Additionally, an array of
detectors can be used to increase the total cross section, but this option
also adds complexity to the device. We address the problem of thermal
and magnetic crosstalk between the sensors of a detector array and propose
promising sensor and pickup loop designs to meet the requirements
for high resolution particle detection.

Tiefe Temperaturen Montag
TT 8.25 Mo 14:30 Poster A
Microwave absorption of BSCCO based intrinsic Josephson
junctions — •Denis Vassioukov, Huabing Wang, Vyacheslav
Dremov, Yury Koval, and Paul Müller — Friedrich-Alexander
Universität Erlangen-Nürnberg
Recently, Wang et al. introduced a new sample fabrication method -
the so called double side technique. This sample geometry has unique
properties. It is possible to perform 4-point measurements and also to
avoid a big pedestal of BSCCO single crystal which usually occurs in
mesa-like structures. Using a combination of electron beam lithography
and photolithography, we were able to prepare stacks with minimum cross
sections down to 0.5 µ x 0.5 µ. These structures were imbedded into bowtie
antennas equipped with low pass filters for DC supply. We present
experimental data on microwave absorption in the step-like structures
at frequencies from 760 GHz to 2.5 THz. It is shown that the choice of
structure design is very crucial to the absorption properties of junctions
in the stack. Clear Shapiro steps were observed at positions according to
the Josephson relation.
TT 8.26 Mo 14:30 Poster A
Kollektives und statistisches Schaltverhalten von intrinsischen
Josephsonkontakten an TBCCO-Mikrobrücken auf
20 ◦ vicinal geschnittenem LaAlO3 — •Michael Mans, Jens
Scherbel und Paul Seidel — Institut für Festkörperphysik,
Friedrich-Schiller-Universität Jena, Helmholtzweg 5, 07743 Jena
In einem 2-stufigen Prozeß wurden TBCCO(2212)-Schichten hergestellt.
Ein amorpher Ba-Ca-Cu-O Precurser wird mittels RF-Sputtern bereitgestellt,
um ihn im Anschluß durch Oxythallination zu TBCCO umzukristallisieren.
Auf 20 ◦ vicinal geschnittenen LaAlO3-Substraten kristallisiert
das TBCCO so, daß seine CuO-Ebenen geneigt zur Substratnormalen
aufwachsen. Somit können planare Mikrobrücken gefertigt werden,
die intrinsische Josephsoneffekte zeigen und gut in Mikrowellenstrukturen
integrierbar sind. Die Strom-Spannungs-Kennlinien zeigten bis 70K
multiple Aststrukturen mit IC-Werten weniger µA und Normalleitungswiderständen
einiger kΩ. Das Schalten vom supraleitenden in den resistiven
Zustand wurde für die ersten resistiven Äste statistisch untersucht. In
bestimmten Fällen wurde ein kollektives Schaltverhalten mehrerer intrinsischer
Josephsonkontakte beobachtet. Die Standardabweichung der IC-
Verteilung ist um so geringer je mehr Kontakte zum jeweiligen Übergang
beitragen. Untersuchen zur Mikrowellenabsorption bei 100 GHz zeigten
ein mit wachsender Mikrowellenleistung sukzessives Aufspalten des kollektiven
Übergangs vom supraleitenden zum resistiven Zustand in multiple
Aststrukturen. Diese Dynamik läßt auf eine Kopplung der einzelnen
Josephsonkontakte mit ihren nächsten Nachbarn schließen.
TT 8.27 Mo 14:30 Poster A
Low Tc Josephson Junction response to an ultrafast laser pulse
— •Procolo Lucignano 1,2 , Arturo Tagliacozzo 1,2 , and Giacomo
Rotoli 1,3 — 1 Dipartimento di Scienza Fisiche, Universitá Federico
II Napoli, via Cinthia 80126 Napoli, Italy — 2 Coherentia INFM,
Italy — 3 Dipartimento di Energetica, Universitá di L’Aquila, Localitá
Monteluco, 67040 L’Aquila, Italy
We study the perturbation on the Josephson current induced when one
of the superconducting contacts is exposed to a single ultrafast laser pulse
radiation. Released energy is so small and the pulse duration so short
that coherence is not degradated. Relaxation properties and nonequilibrium
effect of the irradiated contact are taken into account within the
framework of a quasiclassical time dependent Keldysh formalism [1]. The
classical dynamics of a Josephson irradiated junction is simulated numerically
using our analytical results as source term. The switching out of
the zero voltage state can be easily controlled by tuning the laser light
intensity [2].
[1] W. Belzig, F.K. Wilhelm, G. Schön, C. Bruder, and A.D. Zaikin, Superlattices
and Microstructures 25, 1251-1288 (1999) and J. Rammer,H.
Smith, Rev. Mod. Phys., 58, 323,(1986)
[2] P. Lucignano, F.J. Hekking, A. Tagliacozzo in Proceedings of MQC2
ed. A. Legget, P. Silvestrini, B. Ruggiero, and preprints
TT 8.28 Mo 14:30 Poster A
Spectroscopic Measurements on Discrete Breathers in Josephson
ladders — •M. Schuster and A.V. Ustinov — Physikalisches
Institut III, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erwin-
Rommel-Straße 1, 91058 Erlangen
We experimentally study the transmission of electromagnetic radiation
through time-periodic localized excitations (discrete breathers, DB)
in one-dimensional arrays of Josephson junctions (Josephson ladders).
The experiments are motivated by the recent theoretical prediction of
Fano resonances with discrete breathers [1]. In experiment, we create
radiation by forcing one of the array junctions to a rotation frequency
(corresponding to a finite voltage) which is in resonance with the electromagnetic
modes of the lattice. Radiation is detected by a tunnel junction
detector at the opposite boundary of the array. We create the DB states
by local currents and study the radiation transmission through the ladder
as a function of DB frequency. We compare experimental data to
numerical simulations of the DB transmission properties.
[1] S. Flach, A. E. Miroshnichenko, V. Fleurov, and M. V. Fistul,
Phys. Rev. Lett. 90, 084101 (2003).
TT 8.29 Mo 14:30 Poster A
Guided vortex motion in Nb films on facetted substrate surfaces
— •Oleksiy K. Soroka1 , Michael Huth2 , Valerij A.
Shklovskij3 , Jens Oster1 , and Hermann Adrian1 — 1Institute of Physics, Johannes Gutenberg-University, Staudinger Weg 7, D-55099
Mainz, Germany — 2Institute of Physics, Johann Wolfgang Goethe-
University, Robert-Mayer-Str. 2-4, D-60054 Frankfurt/M., Germany —
3Kharkov State University, Physical Department, 4 Svobody Sq.,61077,
Kharkov, Ukraine
In the case of anisotropy of the viscous damping force in superconductors
a guided motion of vortices can take place. This means there exists
a preferred direction for the vortices to move in such superconductors.
Guided vortex motion leads to the appearance of new components in
the galvanomagnetic properties of the sample. One can observe an additional
odd magnetoresistive component with respect to magnetic field
reversal. Furthermore, an even contribution to the transverse (Hall) voltage
emerges.
Guided motion of vortices in Nb films on facetted α-Al2O3 (10¯10) was
observed by measuring the longitudinal and transversal resistivities of
the sample. The thin film sample consisted of five microbridges oriented
at the angles 0◦ , 30◦ , 45◦ , 60◦ and 90◦ with respect to the facet ridges.
Field inversion was used to separate the even and odd components of the
measured magnetoresistivities to obtain the contributions caused by the
guided vortex motion. The guiding angle was measured for the different
current orientations. Anomalous Hall effect, i.e. the sign reversal of the
Hall resistivity was found.
TT 8.30 Mo 14:30 Poster A
Ultra fast magneto-optics on BSCCO single crystals — •Björn
Biehler, Bernd-Uwe Runge, and Paul Leiderer — Universität
Konstanz, Universitätsstr. 10, 78457 Konstanz, Germany
We used the Faraday effect together with ultra short laser pulses to
investigate the dynamics in superconductors down to the nanosecond
regime. The lateral resolution is better than 10µm. Using this technique
we investigated flux penetration into various materials upon sudden heating
with a fs-laser pulse.
Under certain conditions thin superconducting films show a dendritic
instability when heated locally by a laser pulse [1]. Since BSCCO single
crystals have less pinning centers than typical thin films we chose this material
to compare its behaviour with different thin film systems (YBCO,
MgB2). Systematic variation of the experimental parameters did not lead
to dendrite nucleation, which makes it a unique system not showing this
instability.
[1] U. Bolz, B. Biehler, D. Schmidt, B.-U. Runge, P. Leiderer, Europhys.
Lett. 64(4) 517 (2003)
TT 8.31 Mo 14:30 Poster A
Magnetooptische Untersuchung des radiofrequenzinduzierten
Übergangs in die Normalleitung eines YBa2Cu3O7−x-Films
— •Simon Che’Rose 1 , Andreas Heinrich 1 , Bernd Stritzker
1 , Alois Hiebl 2 , Kai Numssen 2 und Helmut Kinder 2 —
1 Experimentalphysik IV, Universität Augsburg, 86135 Augsburg — 2 TU
München, Physik-Department E10, 85747 Garching
YBCO-Filme bieten ideale Eigenschaften für den Einsatz als passive
oder aktive Schalter. Das Schalten, also der Übergang in die Normalleitung,
kann dabei z.B. durch Erhöhung des anliegenden Stroms (passives
Schalten) oder aktiv durch einen thermischen Puls bzw., wie kürzlich gezeigt
werden konnte, durch Einkopplung eines radiofrequenten (RF) Pulses
(10-100MHz) erreicht werden. Im Gegensatz zum thermisch gepulsten
Schalten ist die physikalische Ursache des RF-induzierten Übergangs
noch nicht geklärt. Wir präsentieren in dieser Arbeit Ergebnisse der magnetooptischen
Untersuchungen zum RF-induzierten Schalten diverser

Tiefe Temperaturen Montag
YBCO-Filme der Dimension 10mm x 42mm x 300nm. Unterhalb des
Films befand sich eine supraleitende Pfannkuchenspule an welche RF-
Pulse angelegt wurden. War der an der Probe angelegte Bias-Strom ausreichend
hoch, konnte damit der Übergang in die Normalleitung ausgelöst
werden. Mittels des magnetooptischen Verfahrens war es möglich
die Flussdichteverteilung in dem YBCO-Streifen vor, während und nach
dem Schaltvorgang zu beobachten und somit Rückschlüsse auf die jeweiligen
Stromverteilungen zu ziehen. Als Ergebnis werden magnetooptische
Aufnahmen und ein theoretisches Modell des RF-induzierten Schaltvorgangs
vorgestellt.
TT 8.32 Mo 14:30 Poster A
Magnetic Properties of YBa2Cu3O7 Ring Structures —
•K. Schindler 1 , M. Ziese 1 , P. Esquinazi 1 , H. Hochmuth 2 ,
M. Lorenz 2 , E. Salamatin 3 , and K. Zimmer 3 — 1 Division of
Superconductivity and Magnetism, University of Leipzig, 04103 Leipzig.
— 2 Semiconductor Physics Group, University of Leipzig, 04103 Leipzig.
— 3 IOM, Institute for Surface Modification, 04318 Leipzig.
YBa2Cu3O7 (YBCO) films were grown by pulsed laser deposition on
CeO2-buffered r-plane sapphire substrates. Film thickness was 260 nm;
the films were covered with a gold layer of 220 nm. From a single 3 inch
wafer various ring structures were fabricated using photolithographical
techniques and subsequent etching with either an Excimer laser or an
ultrafast Ti:sapphire laser, respectively. The magnetic properties of the
YBCO ring structures were investigated by ac-susceptibility and SQUID
magnetometry. In order to quantify and assess the material damage introduced
by the different etching techniques, the critical current density
of 12 single rings with 2 mm outer diameter and ring widths between 15
and 110 µm was determined by magnetic field dependent ac-susceptibility
measurements. The complex susceptibility of the rings at least up to the
13th harmonic could be accurately modelled within a critical state model.
The values of the critical current density extracted did not show a systematic
dependence on the patterning technique. Furthermore, structures
with 1024 rings of outer diameter 20 µm and ring width 1 and 2 µm were
investigated. FC-, ZFC- and remanent magnetization measurements were
used to determine the volume of shielded material. The data will be further
discussed within a critical state model.
TT 8.33 Mo 14:30 Poster A
Frequency dependence up to microwave frequencies of the abplane
conductivity peak near Tc of YBa2Cu2O7−δ — •D. Görlitz
and J. Kötzler — Institut f. Angewandte Physik, Univ. Hamburg, D-
20355 Hamburg
The linear suceptibility χ ′ − iχ ′′ of d=50-600 nm thin films has been
measured between 30mHz and 22GHz in ac-fields perpendicular to the
CuO2-planes. For frequencies up to 800 kHz mutual induction techniques
were employed, while between 0.45 and 22 GHz the complex resonance
frequency, ˜ fr = fr + i∆f, of helical resonators and of cylindrical cavities
was determined. The complex shifts δ ˜ fr = ˜ fr(T) − ˜ fr(0) are proportional
to the dynamic susceptibility χ(ω), and DC-susceptibilities were
employed to calibrate δfr. The ab-plane conductivity σ(ω) = σ ′ − iσ ′′
is determined from χ(ω) by means of an exact inversion routine [1].
The loss component σ ′ shows a peak at a temperature Tω near Tc, and
the peak temperatures Tω exhibit an Arrhenius behaviour. Using the inverse
kinetic inductivity determined from σ ′′ ,(µ0Lk(T)) −1 = ωσ ′′ (T, ω),
the Arrhenius barriers are related to the nucleation energy of vortex
cores threading the film. These barriers are found to disappear at T0,
which is distinctly above the true critical temperature Tc, also extracted
from L −1
k (T)[2]. At the largest frequency, 21.3 GHz, the σ ′ -peak becomes
strongly suppressed since Tω approaches T0.
[1] J. Kötzler et al., Phys.Rev. B 50, 3384 (1994)
[2] J. Kötzler et al., Phys.Rev.Lett. 87, 127005 (2001) and 89,149704
(2002)
TT 8.34 Mo 14:30 Poster A
Evidence for a percolation-driven transition to coherent surface
superconductivity — •Lars von Sawilski, Sara Casalbuoni, and
Jürgen Kötzler — Institut für Angewandte Physik und Zentrum
für Mikrostrukturforschung, Universität Hamburg, Jungiusstrasse 11, D-
20355 Hamburg, Germany
Above the upper critical field Hc2 we have investigated the field dependences
of the surface conductance, G ′ − iG ′′ , and the critical current
Jc of different treated Niobium cylinders: as grown, chemically and electrolytically
polished. The low frequency limits of G ′ (H) and G ′′ (H) and
of Jc(H) display power-law singularities, defining a transition to coherent
surface superconductivity at H c c3 > Hc2. The critical exponents as well as
the dynamical scaling of G ′ − iG ′′ studied between 0.1 Hz and 1 MHz are
consistent with predictions for a two-dimensional percolation transition.
Relating H c c3 to the conventional onset field for surface superconductivity
Hc3, we find H c c3 /Hc3 = 0.81. Surprisingly, this ratio turns out to
be independent of significant variations of Hc3 due to differently treated
surfaces. This points to a new universal relation between the nucleation
and the onset of long-range coherent surface superconductivity.
TT 8.35 Mo 14:30 Poster A
Influence of Fermi surface topology on the quasiparticle spectrum
in the vortex state — •Siegfried Graser, Thomas Dahm,
and Nils Schopohl — Institut für Theoretische Physik, Universität
Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen
We study the influence of Fermi surface topology on the quasiparticle
density of states in the vortex state of type II superconductors. We
observe that the field dependence and the shape of the momentum and
spatially averaged density of states is affected significantly by the topology
of the Fermi surface. We show that this behavior can be understood
in terms of characteristic Fermi surface functions and that an important
role is played by the number of points on the Fermi surface at which the
Fermi velocity is directed parallel to the magnetic field. A critical comparison
is made with a broadened BCS type density of states, that has been
used frequently in analysis of tunneling data. We suggest a new formula
as a replacement for the broadened BCS model for the special case of a
cylindrical Fermi surface. We apply our results to the two gap superconductor
MgB2 and show that in this particular case the field dependence
of the partial densities of states of the two gaps behaves very differently
due to the different topologies of the corresponding Fermi surfaces, in
qualitative agreement with recent tunneling experiments.
TT 8.36 Mo 14:30 Poster A
Local Quasiparticle Density of States in unconventional Type-
II Superconductors — •Christian Iniotakis and Nils Schopohl
— Institut für Theoretische Physik, Universität Tübingen, Auf der Morgenstelle
14, D-72076 Tübingen
Our aim is to calculate the quasiclassical propagator in unconventional
(d-wave) superconductors in the vortex state. We assume a clean and
homogeneous superconductor. Near the phase transition at Hc2 the spacial
variation of the gap function is given by the well-known Abrikosov
solution. Concentrating on the quadratic and hexagonal vortex lattice
we present calculations of the local quasiparticle density of states. Our
results have been achieved by using the Riccati-parametrization of the
quasiclassical Eilenberger theory. Additionally, basic symmetry relations
of the vortex lattice have been taken into account.
TT 8.37 Mo 14:30 Poster A
Mirage phenomena in quantum corrals of s-wave superconductors
— •Markus Schmid and Arno P. Kampf — Theortical
Physics III, Center for Electronic Correlations and Magnetism, Institute
of Physics, University of Augsburg, 86135 Augsburg
We investigate the local pairing amplitude and the local density of
states (LDOS) for an s-wave superconductor in an elliptic quantum corral.
Using a T-matrix analysis we explore the spatial structure of the
LDOS in the presence of a single non-magnetic impurity and observe a
variety of quantum mirage phenomena. In particular, we discuss mirage
effects for localized impurity bound states and analyze the interference
patterns for the scattering processes from two impurities in the quantum
corral.
TT 8.38 Mo 14:30 Poster A
Extraction of the nonlinear response function from intermodulation
distortion experiments and application to
high-temperature superconductor resonators — •Roland
Hott, Alexander Zaitsev, and Rudolf Schneider —
Forschungszentrum Karlsruhe, Institut für Festkörperphysik, P.O.B.
3640, D-76021 Karlsruhe, Germany
We present a general scheme how to extract the response function
Z(H) = �
m ZmHm for a nonlinear reaction of a quantity
E(H) = Z(H)H on an input H from two-tone intermodulation distortion
(IMD) experiments using a time-dependent excitation H(t) =
h cos(ω0t) cos(δ0t). We applied this method with success to hightemperature
superconductor (HTS) rf resonators to identify here the
mechanism of nonlinear signal distortions. Comparison of the experimental
3rd-order IMD I3(pcirc) measured as function of rf power pcirc

Tiefe Temperaturen Montag
with the theoretical I3(h) given in terms of the excitation amplitude
h gives direct access to h(pcirc). We derived very similar characteristic
parameters from HTS resonators with extremely different geometries.
They suggest a divergence of Z(H) which can be identified with the critical
magnetic field Hc2 of the superconductor. From comparison of the
theoretical function Z(pcirc) with the experimental surface impedance
ZS(pcirc) = RS(pcirc) + iXS(pcirc) of a HTS disk resonator we deduce
Z(pcirc) ∝ RS(pcirc) identifying the rf power induced dissipation increase
as dominant IMD source.
TT 8.39 Mo 14:30 Poster A
Unusual electronic and magnetic properties of intermetallic antiperovskites
— •Claire Loison and Helge Rosner — Max Planck
Institut für Chemische Physik fester Stoffe
In the last years, antiperovskites XYT3 (X=Mg,Cu,La..., Y=B,C,N...
and T a transition metal) have received considerable attention because
of many unusual physical properties caused by different competing
interactions. Examples are the recently discovered superconductor
MgCNi3 (superconductivity vs. ferromagnetism) or the non-collinear
magnet CuNMn3. Here, we present a systematic study for a series of antiperovskites
using density functional theory (DFT) electronic structure
calculations within the local spin density approximation (LSDA). To investigate
the role of possible strong Coulomb repulsion we applied as well
LSDA +U. The focus of our study are the effects of pressure and doping
on the electronic properties and magnetism and the search for possible
instabilities and phase transitions.
TT 8.40 Mo 14:30 Poster A
Photo-induced Excitation of Cooper Pairs in Superconductors
— •Jamal Berakdar and Konstantin Kouzakov — Max-Planck-
Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
In this work we study the photoinduced Cooper pair excitation in a superconductor.
It is shown [1] that the spectra of the excited electron pair
carry direct information on the energy and angular pair correlation. We
suggest an experimental set-up for the verification of the theoretical predictions
and provide, on the basis of the Bardeen-Cooper-Schrieffer theory
for superconductivity, numerical illustrations of electron-pair spectra.
[1] K. Kouzakov, J. Berakdar, Phys. Rev. Lett (2003) in press.
TT 8.41 Mo 14:30 Poster A
Optical conductivity and approximate conservation laws in dwave
superconductors — •Philip Howell 1 and Achim Rosch 2
— 1 Institut für Theorie der Kondensierten Materie, Universität Karlsruhe,
76128 Karlsruhe — 2 Institut für Theoretische Physik, Universität
zu Köln, 50937 Köln
Recent measurements on high-temperature superconductors show that
the optical conductivity depends strongly on temperature. It has been
pointed out [1] that inelastic quasiparticle–quasiparticle scattering in a
d-wave superconductor suffers kinematical constraints: momentum conservation
leads to an ‘Umklapp gap’ and hence exponential behaviour
of the conductivity. Here we argue that there are additional generalised
momenta [2] which are almost conserved. The decay of the resulting slow
modes determines the optical conductivity at low temperatures, and we
investigate their influence via a memory matrix approach.
[1] M. B. Walker and M. F. Smith, Phys. Rev. B 61, 11285 (2000)
[2] A. Rosch and N. Andrei, Phys. Rev. Lett. 85, 1092 (2000)
TT 8.42 Mo 14:30 Poster A
Raman study of charge ordering instabilities in La2−xSrxCuO4
— •Leonardo Tassini 1 , Francesca Venturini 1 , Rudi Hackl 1 ,
Qing-ming Zhang 2 , N. Kikugawa 3 , and Tojitsu Fujita 3 —
1 Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften,
D-85748 Garching — 2 Department of Physics, Nanjing University,
Nanjing 210093, P.R. China — 3 ADSM, Hiroshima University,
Higashi-Hiroshima 739-8526, Japan
The electronic Raman effect has been studied in differently doped single
crystals of La2−xSrxCuO4 (LSCO). At low energies and temperatures
new structures indicating a very high conductivity are found for which
there is no evidence in Bi2212 and Y123. In the same temperature range
a related low-energy mode is found in the optical conductivity. For the
selection rules and for similarities with ladder compounds we conclude
that the features are an indication of incipient charge ordering and 1D
conduction. The correlation length of these stripes is at least of the order
of the electronic mean free path in LSCO. The direction of the 1D
structures is along the diagonals and the principle axes for x = 0.02 and
x = 0.10, respectively.
TT 8.43 Mo 14:30 Poster A
Photoemission and X-ray absorption study of La and Pb doped
Bi-2201 — •M. Schneider, R. Mitdank, R.-St. Unger, T.
Stemmler, R. Müller, H. Dwelk, C. Janowitz, A. Krapf, and
R. Manzke — Institut für Physik, Humboldt-Universität zu Berlin,
Newtonstr. 15, 12489 Berlin
Besides to investigate the almost undisturbed CuO2-plane of the
cuprates, the additional advantage of the superconducting system
Bi2Sr2−xLaxCuO6+δ and Bi2−yPbySr2−xLaxCuO6+δ is to cover the total
doping range from the insulating up to the metallic phase by adjusting
the La content. By additional substitution of some percentage of Bi by
Pb in these samples also the structural about (5x1) superstructure of the
BiO-planes is almost suppressed. We present a systematic photoemission
(PES) and X-ray absorption (XAS) study of ceramic Bi-2201 samples
for the entire doping range. Due to the determination of the density of
states of both sides of the Fermi energy by PES and XAS, respectively, a
model for the doping mechanism of the CuO2-plane of the cuprates can
be discussed.
TT 8.44 Mo 14:30 Poster A
In-plane infrared conductivity of untwinned La2−xSrxCuO4 crystals
in the regime of stripe order. — •Michael Dumm 1,2 , Dimitri
Basov 2 , Seiki Komiya 3 , and Yoichi Ando 3 — 1 1. Physikalisches Institut,
Universität Stuttgart, 70550 Stuttgart — 2 Department of Physics,
University of California at San Diego, La Jolla, CA, USA — 3 Central Research
Institute of Electric Power Industry, Tokyo, Japan
Using infrared spectroscopy, we show that spin self-organization in
untwinned La1.97Sr0.03CuO4 and La1.96Sr0.04CuO4 single crystals has profound
consequences for the dynamical conductivity σ(ω). The electronic
response of CuO2 planes acquires significant anisotropy in the spinordered
state with enhancement of the conductivity along the direction
of the diagonal spin stripes by up to a factor of two. An examination
of the anisotropic response indicates that the diagonal spin texture in
weakly doped La2−xSrxCuO4 is also accompanied by the modulation of
charge density. The electronic response of the charge stripes is found to be
gapless consistent with the hypothesis of the metallic ground state. Our
experiments directly show that the striped ordered systems reveal new
degrees of freedom not present in ordinary one-dimensional conductors.
TT 8.45 Mo 14:30 Poster A
Nernst effect of stripe ordering La1.8−xEu0.2SrxCuO4 —
•E. Ahmed 1 , C. Hess 2 , B. Büchner 3 , U. Ammeral 4 , A.
Revcolevschi 4 , and B. Keimer 5 — 1 II. Physikalisches Institut,
RWTH Aachen, D-52056 Aachen — 2 Department of Condensed Matter
Physics, University of Geneva, Switzerland — 3 IFW Dresden, D-01171
Dresden — 4 Laboratoire de Physico-Chimie des Solides, Université
Paris-Sud, France — 5 MPI für Festkörperforschung, D-70506 Stuttgart
Nernst effect has been measured for a wide range of stripe ordering
La1.8−xEu0.2SrxCuO4 single crystals. We observe that compared to superconducting
La2−xSrxCuO4, the Nernst signal in the non-superconducting
stripe phase is suppressed. Nevertheless, at higher temperatures we find
a relatively large Nernst signal for a wide temperature range, similar to
the findings in La2−xSrxCuO4. We discuss possible origins of this unusual
large Nernst signal.
TT 8.46 Mo 14:30 Poster A
Temperature dependence of Bismuth-based HTSC as seen in
ARPES — •B. Müller 1 , L. Dudy 1 , H. Dwelk 1 , A. Krapf 1 , C.
Janowitz 1 , H. Höchst 2 , and R. Manzke 1 — 1 Humboldt Universität
zu Berlin, Institut für Physik, Newtonstr. 15, 12489 Berlin —
2 Synchrotron Radiation Center (SRC), Madison/Wisconsin (USA)
Our current investigations focus on the single-, double-, and triple-layer
cuprates Bi2201, Bi2223 and Bi2212, respectively. In ARPES measurements
of Bi2201 a two-peak structure can be observed, which is dependent
on the polarization of the incident light [1,2]. It persists above Tc
and vanishes at a higher temperature. There are hints that this temperature
corresponds to T ∗ , the temperature where the pseudogap closes.
Interestingly this two-peak structure is only visible along one CuO-bond
direction. The comparison with a pseudo-1d-model directs interpretations
of this feature towards a pseudo-1d-effect. The question is, if this
can also be shown for double- and triple-layer compounds.
[1] C. Janowitz, R. Müller, L. Dudy, A. Krapf, R. Manzke, C. Ast, H.

Tiefe Temperaturen Montag
Höchst, Europhysics Letters 60 (2002) 615
[2] R. Manzke, R. Müller, C. Janowitz, M. Schneider, A. Krapf, H. Dwelk,
Phys. Rev. B 63 (2001) R 100504
TT 8.47 Mo 14:30 Poster A
Superconductivity and weak electron-phonon coupling in transition
metal diborides — •H. Rosner 1 , S.-L. Drechsler 2 , G.
Fuchs 2 , K.-H. Müller 2 , G. Behr 2 , H. Eschrig 2 , R. Heid 3 , E.
Forzani 4 , K. Winzer 4 , Y. Naidyuk 5 , and O. Otani 6 — 1 Max Planck
Institut für Chemische Physik fester Stoffe — 2 Institut für Festkörper und
Werkstoffforschung Dresden — 3 FZ Karlsruhe — 4 Universität Göttingen
— 5 NAS Kharkiv, Ukraine — 6 NIMS Tsukuba, Japan
After the surprising discovery of superconductivity at 40K in MgB2 an
intense search for other superconducting diborides was started. Several
contradicting reports about the superconductivity in TB2 (T = transition
metal) have been published so far, and the discussion is not settled
yet. Combining extensive electronic structure and model calculations
with various experiments (specific heat, resistivity, susceptibility,
de-Haas-van-Alphen oscillations, point contacts) we investigate the electronic
structure and the electron-phonon coupling λ in various TB2 with
focus on ZrB2. Based on our calculations, we provide a clear microscopic
picture for the rather weak electron-phonon coupling in these systems
and the absence of conventional superconductivity in agreement with
the empirically determined values from thermodynamic and transport
measurements. Open problems are briefly discussed.
TT 8.48 Mo 14:30 Poster A
”Supraleitende” und ”magnetische” Energiebänder bestimmter
Symmetrie als Voraussetzung für Supraleitung bzw. Magnetismus
— •Ekkehard Krüger — Kraussweg 5, 70597 Stuttgart
Beobachtungen an den Bandstrukturen der elementaren Metalle lassen
vermuten, dass zur Bildung stabiler Cooper-Paare sowie stabiler magnetischer
Strukturen gewisse Symmetriebedingungen im Leitungsband eines
Metalles erfüllt sein müssen, die sich im Rahmen der Gruppentheorie optimal
lokalisierter Wannier-Funktionen behandeln lassen. Zur Erklärung
der Beobachtungen wird ein nichtadiabatisches Modell atomartiger Leitungselektronen
vorgeschlagen.
TT 8.49 Mo 14:30 Poster A
Budd-Vannimenus theorem for superconductors — P. Lipavsk´y
1 , •K. Morawetz 2,3 , Jan Koláček 1 , J.J. Mares 1 , E.H.
Brandt 3 , and M. Schreiber 2 — 1 Institute of Physics, Academy of
Sciences, Cukrovarnická 10, 16258 Praha 6, Czech Republic — 2 Istitute
of Physics, Chemnitz University of Technology, 09107 Chemnitz,
Germany — 3 Max-Planck-Institute for the Physics of Complex Systems,
Nöthnitzer Str. 38, 01187 Dresden, Germany
The Budd-Vannimenus theorem is generalized to apply to superconductors
in the Meissner state. This identity links the surface value of the
electrostatic potential to the free energy in the bulk which allows one
to evaluate the observed potential without the explicit solution of the
charge profile at the surface.
[1] P. Lipavsk´y, K. Morawetz, J. Koláček, J. J. Mareˇs, E. H. Brandt, M.
Schreiber, Phys. Rev. B in press (2003), cond-mat/0311166
[2] P. Lipavsk´y, K. Morawetz, J. Koláček, J. J. Mareˇs, E. H. Brandt, M.
Schreiber, Phys. Rev. B submitted, cond-mat/0311167
TT 8.50 Mo 14:30 Poster A
Pressure and Doping Dependence of the Super Exchange of
2D-Cuprates — •Helge Rosner 1 , Ulrike Nitzsche 2 , and Stefan-
Ludwig Drechsler 2 — 1 Max-Planck-Institute for Chemical Physics of
Solids, Noethnitzer Str. 40, D-01187 Dresden, Germany — 2 Leibniz Institute
for Solid State and Materials Research Dresden, P.O.B. 270016,
01171 Dresden, Germany
The dependence of superconducting Tc from the exchange integrals J
is investigated within many models devoted to HTSC. However, most of
these models ignore the dependence of the exchange integrals on both
the lattice parameters and the doping level because of lacking reliable
data. Here we present a systematic study for the two-dimensional model
compound CaCuO2. Based on LDA and LDA+U band structure calculations
and subsequently derived tight-binding models we calculate
the magnitude of the most relevant exchange integrals and their dependence
on doping and uniaxial pressure. We compare the results of
total energy calculations with those of various tight-binding models (oneband
and multi-band approaches) and the parameters obtained by microscopic
models analyzing the experimental data for the superconducting
HgBaCuO-family.
TT 8.51 Mo 14:30 Poster A
Crystal growth, perfection and selected physical properties
of RENi2B2C (RE=Y, Tb, Ho) — •Dmitri Souptel 1 , Günter
Behr 1 , Wolfgang Löser 1 , Günter Fuchs 1 , Konstantin
Nenkov 1 , and Andreas Kreyssig 2 — 1 IFW Dresden, Helmholtzstr.
20, 01171 Dresden — 2 IAPD, TU Dresden, 01062 Dresden
Single crystals of HoNi2B2C, YNi2B2C and TbNi2B2C intermetallic
compounds have been grown by a floating zone technique with optical
heating. Crystals are crack free, without traces of 2nd phases and single
crystalline in the volumes of 6 mm in diameter and 25-40 mm in length.
YNi2B2C shows superconducting transition temperature Tc=15.5 K
with the width ∆Tc=0.1-0.2 K and RRR=35-39. HoNi2B2C single crystals
exhibit a variety of physical properties. For the first time, macroscopic
single crystalline samples with zero-field re-entrant superconductivity
were prepared. Origins of variations of superconducting properties
have been related to composition, lattice parameters and local resistance
ratio measurements of crystal sections. The results corroborate the existence
of a finite homogeneity range of the HoNi2B2C intermetallic compound.
TT 8.52 Mo 14:30 Poster A
Tieftemperaturverhalten von CeNi2B2C — •Dmitrij Bogdanov,
Klaus Winzer und Eugenio Forzani — I. Physikalisches Institut,
Universität Göttingen, Tammannstr. 1, 37077 Göttingen
Die bisher vorliegenden Untersuchungen an CeNi2B2C lassen die Frage
nach dem Grundzustand des Systems bei tiefen Temperaturen offen.
Die Möglichkeit eines supraleitenden Grundzustandes bei T = 0,1 K [1]
konnte bisher nicht bestätigt werden. Für die Charakterisierung des Systems
wurden sowohl polykristalline Proben als auch Einkristalle hergestellt,
deren Phasenreinheit und Qualität durch Röntgendiffraktometrie
und Messungen des Restwiderstandsverhältnisses bestimmt wurden. Die
Temperatur- und Magnetfeldabhängigkeit des spezifischen Widerstandes
und der magnetischen Suszeptibilität wurden für Temperaturen bis 40
mK bestimmt. Mit einem SQUID-System wurden zusätzlich Messungen
des magnetischen Moments und der Suszeptibilität bis 1,8 K durchgeführt.
Der elektrische Widerstand zeigt im Temperaturbereich um 2
K einen stufenförmigen Verlauf, der auf eine geringe Aufspaltung des
Kristallfeld-Grundzustandes hindeutet. Bei tiefen Temperaturen wird ein
sehr steiler Anstieg der paramagnetischen Suszeptibilität mit einem Maximum
bei T = 100 mK beobachtet, das als Signatur einer magnetischen
Ordnung gedeutet wird. Messungen des spezifischen Widerstandes zeigen
keinerlei Anzeichen für das Auftreten von Supraleitung.
[1] M. El Massalami et al., Physica C 304 , 184 (1998)
TT 8.53 Mo 14:30 Poster A
The effect of noble-gas preplating on quench-condensed hydrogen
films — •Stefan Tibus, Jürgen Klier, and Paul Leiderer
— Universität Konstanz, Universitätsstraße 10, 78464 Konstanz
Triple-point dewetting of H2 on e.g. Au is a well-known phenomenon
and prevents the forming of a thick (i.e. more than a few monolayers)
solid equilibrium film on such surfaces. It was theoretically shown that
a modification of the substrate-adsorbate interaction by means of preplating
should lead to complete wetting and thus to a thick solid film at
saturated vapor pressure (provided that the substrate surface is ideally
smooth). Ne and Ar were found to be appropriate candidates as intermediate
layers, but investigations found no significant change in the film
thickness upon preplating, which was attributed to the roughness of the
substrate.
However, preliminary experiments with quench-condensed hydrogen
showed an effect of the preplating on the film’s structure. This is to be
investigated in more detail by means of a new experimental setup allowing
for both surface-plasmon microscopy (at a higher resolution than
before) as well as surface-plasmon spectroscopy.
TT 8.54 Mo 14:30 Poster A
Josephson coupling in Nb/Al 2 O3/Cu 1 Ni1−x/Nb tunnel junctions
— •Martin Weides 1 , Edward Goldobin 2 , Reinhold Kleiner 2 ,
and Hermann Kohlstedt 1 — 1 Institut für Festkörperforschung,
Forschungszentrum Jülich, D-52425 Jülich — 2 Physikalisches Institut-
Experimentalphysik II, Universität Tübingen, D-72076 Tübingen
The realization of qubits for quantum computation attracts considerable
interest. One of the approaches is to use π Josephson junctions (JJs)
which can be realized as hybrids of superconducting (S) tunnel junction

Tiefe Temperaturen Montag
with a ferromagnetic inter-layer (F) on one side of the tunnel barrier (I),
i.e. having SIFS structure. The magnetic film thickness determines the
Josephson coupling and sets the phase coherence to either 0 or π.
SIFS multilayers consisting of Nb(140 nm)/Al (4) −
Al2O3 (1)/CuNi (0 − 30)/Nb (40) were fabricated. The process
parameters were derived from Josephson junctions with critical currents
of about 0.1 − 1 kA cm 2 . The junction areas are ranged from 20.000 µm 2
down to 10 µm 2 .
The first transport measurements of the junctions showed a monotonic
decrease of IcRn for increasing FM-thickness. The generation of a semifluxon
(cf. 1) pinned at the discontinuity of the magnetic layer thickness
will be discussed. Since the semifluxon is a degenerated two state systems,
it can be used as a qubit when the JJ is in the quantum limit.
[E. Goldobin et al., PRB 66, 100508 (2002)]
0pt
TT 9 Supraleitung: Eigenschaften, elektronische Struktur, Ordnungsparameter
Zeit: Dienstag 09:30–13:00 Raum: H20
Hauptvortrag TT 9.1 Di 09:30 H20
Wavefunction Imaging Studies of Cuprate Superconductivity —
•Séamus Davis 1 , K. McElroy 1 , E. W. Hudson 2 , J. E. Hoffman 3 ,
D.-H. Lee 3 , H. Eisaki 4 , and S. Uchida 5 — 1 Department of Physics,
LASSP, Cornell University, Ithaca, NY — 2 MIT — 3 UC Berkeley —
4 AIST-Tsukuba — 5 Tokyo University
High temperature superconductivity in the cuprates emerges when the
localized electrons of a Mott-insulator become itinerant due to carrierdoping.
Since cuprate superconductivity develops from atomically localized
electrons and exhibits nanoscale disorder, simultaneous information
on electronic structure in both the real-space and momentum-space is
required. I will describe a combination of novel scanning tunneling microscopy
(STM) techniques which achieves these apparently contradictory
aims.
The first technique, atomic-resolution spectroscopic mapping, allows
imaging of interactions between quasiparticle wavefunctions and the realspace
environment at the atomic-scale.
A second technique, Fourier-transform scanning tunneling spectroscopy
(FT-STS), is used to study interference patterns of the
delocalized wavelike electronic states. For optimally doped samples,
analysis of these patterns as due to quasiparticle interference , yields the
Fermi surface and the d-wave superconducting energy gap, in excellent
agreement with ARPES.
Finally I will describe FTSTS experiments designed to detect and identify
the electronic ground state in other regions of the cuprate phase diagram
including studies of the vortex core and of strongly underdoped
samples.
TT 9.2 Di 10:00 H20
The LDA band structure of Bi2Sr2CaCu2O8 revisited. — •Denis
Mertz, Helmut Eschrig, and Klauss Koepernik — IFW Dresden,
P.O.B. 27 0016, D-01171 Dresden, Germany
We study the effects of structural optimizations on the electronic properties
of Bi2Sr2CaCu2O8 high-Tc superconductor by means of the LDA
approach to the density functional theory. The LDA calculations are done
using the FPLO method [1]. Oxygen and Bismuth position optimizations
in a √ 2 × √ 2 supercell with A2aa symmetry yield important changes in
the band structure near the Fermi energy. The effects of buckling in the
CuO planes are also considered.
[1] K. Koepernik and H. Eschrig, Phys. Rev. B 59, 1743 (1999)
TT 9.3 Di 10:15 H20
Anomalous enhancement of the coupling strength upon underdoping
in Pb-Bi2212. — •Sergey Borisenko, Alexander Kordyuk,
Andreas Koitzsch, Martin Knupfer, and Joerg Fink —
Institute for Solid State Research, IFW-Dresden
Angle-resolved photoemission spectroscopy is used to study the mass
renormalization of the charge carriers in the high-Tc superconductor
(Pb,Bi)2Sr2CaCu2O8+δ (Pb-Bi2212) in the vicinity of the (π, 0)-point in
the superconducting and the normal states. Using matrix element effects
at different photon energies and due to a high momentum and energy
resolution the bonding and the antibonding bands could be separated in
the whole dopant range. A huge coupling to a bosonic collective mode
is observed below Tc for both bands, in particular, for the underdoped
case. Above Tc , a weaker coupling to a continuous spectrum of modes
is detected.
TT 9.4 Di 10:30 H20
Electronic structure of doped Bi-cuprates — •R.-S. Unger, M.
Schneider, T. Stemmler, L. Lasogga, H. Dwelk, A. Krapf,
C. Janowitz und R. Manzke — Institut für Physik, Humboldt-
Universität zu Berlin, Newtonstr.15, 12489 Berlin
We present angle-resolved photoemission data from La-doped n=1
and Y-doped n=2 Bi2Sr2−y(Lay)Ca1−n−x(Yx)CunO2n+4+δ single crystals.
The crystal quality is proved by Laue and LEED, the superconducting
properties by susceptibility measurements. So we have the
opportunity to investigate the electronic structure of a high-Tc superconductor
and its parent compound over the entire hole doping range.
We discuss our measured spectra series of the metallic/superconducting
and insulating state of the Bi-cuprate single crystals along high symmetric
directions of the Brillouin zone. This work was supported by the
BMBF project no. MA2371/1-3
TT 9.5 Di 10:45 H20
The bulge in the basal CuO2 area of cuprate superconductors
— •Jürgen Röhler — Universität zu Köln, D-50937 Köln, Germany
Hole doping of the superconducting cuprates not only shrinks their
basal area B (square of the basal lattice parameter) – to be expected
if electrons are removed from the antibonding Cu3d x 2 +y 2O2pxy states –,
but creates also a strong bulge around optimum doping, nopt ≃ 0.16.
The bulge starts growing in the lightly underdoped, and collapses in the
overdoped regime near critical doping, ncrit ≃ 0.19 [1]. We show that
the observed expansion of the basal lattice around nopt and its collapse
at ncrit results from the Aufbau of the strongly correlated many electron
state in the CuO2 sheets with “self-protecting” singlets (SPS) [2].
In them not only the Cu sites are protected against occupation with more
than one hole, but also the oxygen cages of the Zhang-Rice (ZR) singlets.
This additional non-double occupant constraint favours the formation of
non magnetic (S= 0), bond centered molecular pairs. The paired SPS exchange
two oxygen holes across antiferromagnetic chains of 4 Cu spins,
thereby flipping them, and create a delocalized singlet of oxygen holes.
Most closest packing of paired SPS occurs at 1/6 = 0.166 ≃ nopt in a
tweed-like mesoscopic pattern. At higher hole densities, n ≥ 0.2 ≃ ncrit,
the non-double-occupant constraint for the oxygen cage collapses. We
show that the exchange of two oxygen holes in a paired SPS is connected
with the local half-breathing (LO) mode of planar oxygen vibrations
found up to nopt, and that it expands the basal CuO2 area as observed.
[1] J. Röhler, Physica C (2003), cond-mat/0304628.
[2] J. Röhler, J. Supercond. (2003), cond-mat/0307310.
TT 9.6 Di 11:00 H20
Electronic structure and aspects of unconventional superconductivity
in NaxCoO2 . yH2O — •S.-L. Drechsler 1 , H. Rosner
2 , G. Fuchs 1 , A. Wälte 1 , G. Krabbes 1 , K.-H. Müller 1 , H.
Eschrig 1 , and A. Handstein 1 — 1 IFW-Dresden, D-01171, P.O. Box
270116, Dresden, Germany — 2 MPI-CPfS Dresden, Germany
We examine the electronic structure of NaxCoO2 . yH2O within the local
density approximation. The parametrization of the band which forms
the largest hole-Fermi surface centered at Γ shows significant deviations
from what is frequently assumed in recent sophisticated theoretical studies.
In particular, the commonly used nearest neighbor approaches in the
framework of single band pictures are found to be unrealistic. The special
role of H2O in screening the disorder in the charge reservoir is briefly
discussed and compared with the case of Y1−xCaxCu3O6+δ. We report
strucural, magnetic susceptibility, and specific heat measurements of the
unhydrated nonsuperconducting compounds. The results are compared
with our findings for the superconducting perovskite MgCNi3 which is
close to a ferromagnetic instability.

Tiefe Temperaturen Dienstag
TT 9.7 Di 11:15 H20
Spectroscopic investigations of the electronic structure of
NaxCoO2 — •Thomas Kroll 1 , Martin Knupfer 1 , Thomas
Pichler 1 , Bernd Büchner 1 , Chengtian Lin 2 und Bernhard
Keimer 2 — 1 Leibniz Institute for Solid State and Materials Research
Dresden, 01171 Dresden, Germany — 2 Max Planck Institute for Solid
State Research, 70569 Stuttgart, Germany
The discovery of superconductivity in Na0.35CoO2 · 1.3H2O by Takada
et al. at a Tc of about 5K initiated an increasing interest in those
compounds. This superconducting compound consists of two-dimensional
CoO2 layers separated by a thick insulating layer of Na + ions and H2O.
Based on the analogy to the known high Tc cuprates, it has been speculated
that there is a similar underlying mechanism. In this contribution we
present measurements of the electronic structure (using methods such as
Electron Energy Loss Spectroscopy (EELS) and X-ray Absorption Spectroscopy
(XAS)) of the mother compound NaxCoO2 which may provide
an important contribution to understand the physics of cobalt superconductors.
11:30 Pause
TT 9.8 Di 11:45 H20
Phonons and electron-phonon coupling in nickel borocarbides
— •R. Heid, W. Reichardt, and K.-P. Bohnen — Institut für
Festkörperphysik, Forschungszentrum Karlsruhe, D-76021 Karlsruhe
Superconductivity in nickel borocarbides exhibits various unusual
properties [1], which raises the question if electron-phonon coupling
is the main source of pairing in this class of materials. This subject
can be elucidated by modern first principles methods based on
density-functional theory which provide a detailed microscopic picture
of the electron-phonon interaction. We present calculations of the
bandstructure, the phonon dispersion, and the electron-phonon coupling
for superconducting YNi2B2C (Tc=15.5K) and compare them with
results for the non-superconducting reference compounds LaNi2B2C and
Y(Ni.75Co.25)2B2C. The calculations reproduce a pronounced phonon
anomaly in the vicinity of the wave vector (0.6,0,0) in a low frequency
branch of ∆4 symmetry that has been observed experimentally both in
YNi2B2C and LuNi2B2C [2]. We find that the magnitude of the anomaly
and of the electron-phonon coupling depend very sensitively on the
chosen structural parameters (volume, c/a ratio). Another pronounced
anomaly is predicted in an optic branch of the same symmetry with
predominant B and C elongations. Although the low frequency phonon
spectrum is strongly dominated by the vibrations of the heavy metal ions
we find that B and C contribute more than 50% to the electron-phonon
coupling constant λ.
[1] K. Izawa et al., Phys. Rev. Lett. 89, 137006 (2002)
[2] C. Stassis et al., Physica C 317-318, 127 (1999)
TT 9.9 Di 12:00 H20
Strong electron–phonon coupling in the superconducting
perovskite MgCNi3 — •Andreas Wälte 1 , G. Fuchs 1 , K.-H.
Müller 1 , A. Handstein 1 , K. Nenkov 1 , V.N. Narozhnyi 1 , H.
Rosner 2 , S.-L. Drechsler 1 , S.V. Shulga 1 , and L. Schultz 1 —
1 Institut für Festkörper- und Werkstoffforschung Dresden, Helmholtzstr.
20, D-01171 Dresden — 2 MPI CPFS Dresden, Nöthnitzer Str. 40,
D-01187 Dresden
The superconducting state of MgCxNi3, a recently discovered perovskite
superconductor [1], was characterized by measurements of the
specific heat in a temperature range between 2 and 300 K and the resistivity.
Analyzing the upper critical field Hc2(0) = 11 T and the London
penetration depth in terms of impurity scattering rates, evidence
for strong electron–phonon coupling was found. From the characteristic
phonon frequency ωln ≈ 140 K derived from the specific heat data, a
superconducting transition temperature of Tc ≈ 15 K is expected. The
reduced experimental value of Tc ≈ 7 K implies considerable pair break-
ing contribution, which is ascribed to ferromagnetic spin fluctuations.
Our results are discussed in comparison with related borocarbide superconductors.
[1] T. He et al. Superconductivity in the non-oxide perovskite MgCNi3.
Nature, Vol. 411, May 2001.
TT 9.10 Di 12:15 H20
Renormalization of the electron-phonon coupling in the oneband
Hubbard model — •Roland Zeyher and Erik Koch —
Max-Planck-Institut für Festkörperforschung, Stuttgart
We investigate the effect of electronic correlations on the coupling of
electrons to Holstein phonons in the one-band Hubbard model. We calculate
the static electron-phonon vertex within linear response of Kotliar-
Ruckenstein slave-bosons in the paramagnetic saddle-point approximation.
Within this approach the on-site Coulomb interaction U strongly
suppresses the coupling to Holstein phonons at low temperatures. Moreover
the vertex function does not show particularly strong forward scattering.
Going to larger temperatures kT ∼ t we find that after an initial
decrease with U, the electron-phonon coupling starts to increase with U.
We show that this behavior is related to an unusual reentrant behavior
from a phase separated to a paramagnetic state upon decreasing the
temperature.
TT 9.11 Di 12:30 H20
Analytisches Zwei-Flüssigkeitsmodell für unkonventionelle Supraleiter
— •Dietrich Einzel — Walther-Meissner-Institut, Bayerische
Akademie der Wissenschaften, 85748 Garching
Dieser Beitrag untersucht die Möglichkeit, einfache analytische Ausdrücke
für thermodynamische und Responsefunktionen im Rahmen einer
Theorie schwach koppelnder unkonventioneller Supraleiter bei allen
Temperaturen (0 ≤ T ≤ Tc) zu finden. Es werden sehr präzise Interpolationsformeln
abgeleitet, insbesondere für Entropie, Wärmekapazität,
Spinsuszeptibilität und normalfluide Dichte eines Gases aus thermischen
Anregungen (Bogoliubov-Quasiteilchen), sowie für die superfluide Dichte,
welche die Magnetfeld-Eindringtiefe, und damit den Response des Kondensats
bestimmt. Die Resultate können auf alle bekannten unkonventionellen
Supraleiter wie auch auf Fermi–Supraflüssigkeiten wie 3 He–A
und –B angewendet werden und etablieren somit eine analytische Zwei–
Flüssigkeits–Beschreibung für diese Systeme.
TT 9.12 Di 12:45 H20
Bernoulli potential in type-I and weak type-II superconductors
— •K. Morawetz 1,2 , P. Lipavsk´y 3 , Jan Koláček 3 , J.J. Mares 3 ,
E.H. Brandt 2 , and M. Schreiber 1 — 1 Istitute of Physics, Chemnitz
University of Technology, 09107 Chemnitz, Germany — 2 Max-
Planck-Institute for the Physics of Complex Systems, Nöthnitzer Str. 38,
01187 Dresden, Germany — 3 Institute of Physics, Academy of Sciences,
Cukrovarnická 10, 16258 Praha 6, Czech Republic
The electrostatic potential close to the surface of superconductors in
the Meissner state is discussed. We show that beside the Bernoulli potential,
the quasiparticle screening, and the thermodynamic contribution
due to Rickayzen, there is a non-local contribution which is large for
both type-I and weak type-II superconductors [1]. A generalization of
the Budd-Vannimenus theorem is found which allows one to evaluate the
observed potential without the explicit solution of the charge profile at
the surface [2]. The electrostatic potential above the Abrikosov vortex
lattice is evaluated numerically. We propose an experimental measurement
by NMR [3] to access this field which can yield informations about
material parameters.
[1] P. Lipavsk´y, K. Morawetz, J. Koláček, J. J. Mareˇs, E. H. Brandt, M.
Schreiber, Phys. Rev. B in press (2003), cond-mat/0311166
[2] P. Lipavsk´y, K. Morawetz, J. Koláček, J. J. Mareˇs, E. H. Brandt, M.
Schreiber, Phys. Rev. B submitted, cond-mat/0311167
[3] P. Lipavsk´y, J. Kolacek, K. Morawetz, E. H. Brandt, Phys. Rev. B 66
(2002) 134525

Tiefe Temperaturen Dienstag
TT 10 FV-internes Symposium ”Quantum Phase Transitions”
Zeit: Dienstag 10:00–12:55 Raum: H18
Hauptvortrag TT 10.1 Di 10:00 H18
Local quantum criticality and non-Fermi liquid properties —
•Qimiao Si — Dept of Physics and Astronomy, Rice University, Houston,
USA
Quantum criticality not only provides a mechanism for non-Fermi liquid
behavior, it also seems to control large regions of the phase diagram
in strongly correlated electrons. This talk will be devoted to issues that
have originated from quantum critical heavy fermions.I will describe some
recent developments on local quantum criticality. Recent progresses have
been made, within a Kondo lattice model that is amenable to controlled
calculations. Extensive experimental results that pertain to this picture
have also been emerging, including inelastic neutron scattering, NMR,
Hall coefficient, and Grueneisen ratio. The summary of these results will
be followed by some discussions about their broader implications.
Fachvortrag TT 10.2 Di 10:35 H18
Singular Behavior Near a Quantum Critical Point:
YbRh2(Si,Ge)2 — •P. Gegenwart — Max-Planck-Institut
für Chemische Physik fester Stoffe, 01187 Dresden
By discussing resistive, calorimetric, dilatometric and ESR data on
YbRh2(Si1−xGex)2 with 0 ≤ x < 0.05 we argue that these materials represent
systems exhibiting a qualitatively new class of quantum critical
point that cannot be described by the frequently adopted itinerant (3D
or 2D) spin-density-wave scenario. Upon approaching the quantum critical
point we observe large (“unscreened”, i.e., not reduced by the Kondo
effect) magnetic Yb 3+ moments in the static bulk susceptibility and recently
in ESR, disparate behavior in the T-dependences of the electrical
resistivity and the electronic specific heat as well as a fractional scaling
exponent in the T-dependence of the thermal expansion. These findings
seem to be compatible with a local-moment scenario for the quantum
critical point.
In collaboration with J. Custers, J. Ferstl, C. Geibel, R. Küchler,
T. Lühmann, K. Neumaier, S. Paschen, J. Sichelschmidt, G. Sparn, F.
Steglich, Y. Tokiwa, H. Wilhelm, S. Wirth, P. Coleman, C. Pepin, and
Q. Si.
Fachvortrag TT 10.3 Di 11:05 H18
Non-Fermi-Liquid Phase of a Pure Itinerant-Electron Magnet
— •C. Pfleiderer — Physikalisches Institut, Universität Karlsruhe,
D-76128 Karlsuhe
Extensive studies of the itinerant-electron magnetism in the cubic transition
metal compound MnSi as function of pressure are reviewed, that
suggest a distinct transition from a weakly spin polarized Fermi liquid
ground state to a non-Fermi liquid (NFL) phase of exceptional stability
above pc = 14.6kbar [1,2]. In a recent neutron diffraction experiment [3]
sizable quasi-static magnetic moments have been found to exist far into
this NFL phase. These moments are organized in a highly unusual pattern
never seen before, yielding Bragg intensity on the surface of a tiny
sphere in reciprocal space implying partial order. The properties of MnSi
shed new light on the possible nature of inconsistencies of the metallic
state near magnetic quantum phase transitions observed in numerous
itinerant-electron magnets. In particular, they support the genuine
existence of metallic phases with partial order of the conduction elec-
trons, that are reminiscent of liquid crystals, as proposed for the high-Tc
cuprates and heavy-fermion compounds.
[1] C. Pfleiderer et al., Nature 414 (2001) 427.
[2] N. Doiron-Leyraud et al. Nature 425 (2003) 595.
[3] C. Pfleiderer et al., Nature in print.
*in collaboration with J. Flouquet, M. Garst, S. R. Julian, H. v.
Löhneysen, G. G. Lonzarich, L. Pintschovius, D. Reznik, A. Rosch, A.
N. Stepanov, C. Thessieu and M. Uhlarz.
11:35 Pause
Fachvortrag TT 10.4 Di 11:50 H18
Monte Carlo simulations of quantum phase transitions in dissipative
systems and ultra-cold atoms — •Matthias Troyer 1,2 ,
Philipp Werner 1 , Klaus Völker 3 , Fabien Alet 1,2 , Stefan Wessel
1 , and George G. Batrouni 4 — 1 Theoretische Physik, ETH zürich
— 2 Computational Laboratory, ETH Zürich — 3 University of Toronto
— 4 Université de Nice
The past decade has seen tremendous progress in quantum Monte
Carlo algorithms. Advanced classical simulation techniques have been
generalized to quantum system and further refined. This enables simulations
with an unprecedented accuracy, allowing precise investigations
of quantum phase transitions. Here we will focus on some recent results.
The first part of the talk will be about the effect of dissipation on
quantum phase transitions. While in classical simulations dynamics and
thermodynamics are decoupled and dissipation thus has no influence on
the universality class, the dynamics and thermodynamics are intrinsically
coupled in a quantum system and can change the nature of the phase
transition. We will present recent results on the phase diagrams and the
critical behavior of dissipative quantum Ising models in a transverse field
and preliminary results on quantum XY models. The second part of the
talk will be on effects of constrained geometries, as they are created by
an optical or magnetic trap on an ultra-cold atomic gas. We will demonstrate,
that, the constrained geometry and the inhomogeneity of the trap
lead to an absence of quantum critical behavior at the quantum phase
transition in these systems. This explains the absence of critical slowing
down in recent experiments,
Fachvortrag TT 10.5 Di 12:25 H18
Numerical Renormalization Group for Bosons and Fermions:
Impurity Quantum Phase Transitions — •Ralf Bulla — Theoretische
Physik III, Universität Augsburg
Wilson’s numerical renormalization group (NRG) has been very successful
in describing magnetic impurities in a fermionic bath. Here we
review some recent results on quantum phase transitions of impurity
models in a general environment, including examples of local criticality.
In this context, we present the generalization of the NRG to models
where the impurity couples to a bosonic bath. Application of the bosonic
NRG to the subohmic spin-boson model reveals a line of quantum critical
points terminating in the Kosterlitz-Thouless transition for the ohmic
case. Further extensions of this approach (such as the investigation of the
Bose-Fermi Kondo model within the extended DMFT) are discussed.
TT 11 Nanoelektronik I: Quantenpunkte, -drähte, -punktkontakte
Zeit: Dienstag 09:30–13:00 Raum: H19
TT 11.1 Di 09:30 H19
Single-electron effects and quantum fluctuations in metallic
multi-island geometries — •Björn Kubala 1,2 , Göran Johansson
2 , and Jürgen König 1 — 1 Institut für Theoretische Physik III,
Ruhr-Universität Bochum, D-44780 Bochum — 2 Institut für Theoretische
Festkörperphysik, Universität Karlsruhe, D-76128 Karlsruhe
We have developed a method to model electron transport through a
complex network of single-electron transistors.
Based on a real-time transport theory [1], we automatically generate
all diagrams up to second order in tunnel coupling and calculate their
contributions to the current. This captures quantum fluctuations and
multi-channel Kondo physics for each island as well as the mutual influence
of tunneling effects on two neighbouring islands. The latter is
essential for a detailed analysis of recent experiments [2], where an SET,
capacitively coupled to a single electron box, was used as a sensitive
electrometer, measuring the charge state of the box. Here the backaction
between measurement device (SET) and system (box) is fully included
in our approach.
We will discuss the applicability of our method to different experimental
setups of metallic islands, coupled capacitively and/or by tunneling
barriers, and possible generalizations to the case of magnetic or superconducting
leads.
[1] H. Schoeller and G. Schön, Phys. Rev. B 50, 18 436 (1994); J. König,

Tiefe Temperaturen Dienstag
H. Schoeller, and G. Schön, Phys. Rev. Lett. 78, 4482 (1997)
[2] R. Schäfer et al., cond-mat/0205223; K. W. Lehnert et al., Phys. Rev.
Lett. 91, 106801 (2003).
TT 11.2 Di 09:45 H19
The Coulomb blockade in two island systems with high conductive
junctions — •Roland Schäfer, Bernhard Limbach, Peter
vom Stein, and Christoph Wallisser — Forschungszentrum Karlsruhe,
Institut für Festkörperphysik, Postfach 3640, 76021 Karlsruhe
We report measurements on single electron pumps consisting of two
metallic islands formed by three tunnel junctions in a row. We focus
on the linear response conductance as a function of gate voltages
and temperature of three samples with varying system parameters. In
all cases strong quantum fluctuation phenomena are observed by a
log (kBT/(2Eco))-reduction of the maximal conductance where Eco measures
the coupling strength between the islands. The samples display
a rich phenomenology culminating in a non-monotonic behavior of the
maximal conductance as a function of temperature.
TT 11.3 Di 10:00 H19
Coulomb blockade and Non-Fermi-liquid behavior in quantum
dots — •Frithjof Anders 1 , Eran Lebanon 2 , and Avraham
Schiller 2 — 1 Insititut für Theoretische Physik, Universität Bremen,
Postfach 330 440, D-28334 Bremen — 2 Racah Institute of Physics, The
Hebrew University, Jerusalem 91904, Israel
The non-Fermi-liquid properties of an ultrasmall quantum dot coupled
to a lead and to a quantum box are investigated using a new variant of
Wilson’s numerical renormalization group. Below the charging energy of
the quantum box, a second screening channel is dynamically generated.
Tuning the ratio of the tunneling amplitudes to the lead and box, we
find a two-channel Kondo fixed point for arbitrary Coulomb repulsion on
the dot, proving that the two-channel Kondo effect is far more generic
to this setting than the original scenario of Oreg and Goldhaber-Gordon.
At T = 0, a step-like structure is found in the conductance of a twolead
setting, the height of which depends on the dot occupancy. The
temperature scale below which the two-channel Kondo effect sets in is
greatly enhanced away from the local-moment regime, making this effect
accessible in realistic devices.
TT 11.4 Di 10:15 H19
Thermopower of metallic single electron devices — •Marko
Turek, Jens Siewert, and Klaus Richter — Institut für theoretische
Physik, Universität Regensburg, D-93040 Regensburg
While charge transport in single-electron devices has been thoroughly
investigated during the past decade, heat transport did not attract much
attention, apart from basic considerations, e.g. [1 − 3]. This is surprising
since heat transport exhibits interesting behavior as a function of
external gate voltages and, in particular, renders transport regimes accessible
which are difficult to study by means of charge transport. Here
we present new results for the linear thermopower as a function of the
applied gate voltage in single-electron transistors with normal leads and
normal-conducting islands, as well as for devices with superconducting
islands.
[1] C. W. J. Beenakker and A. A. M. Staring, Phys. Rev. B 46, 9667
(1992)
[2] Y. M. Blanter, C. Bruder, R. Fazio and H. Schoeller, Phys. Rev. B 55,
4069 (1997)
[3] D. Boese and R. Fazio, Europhys. Lett. 56, 576 (2001)
TT 11.5 Di 10:30 H19
Weak charge quantization and full current statistics — •Dmitry
Bagrets 1 and Yuli Nazarov 2 — 1 Institut für Theoretische
Festkörperphysik, Universität Karlsruhe, D-76128 Karlsruhe, Germany
— 2 Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The
Netherlands
We evaluate the full statistics of the current via a Coulomb island that
is strongly coupled to the leads [1]. This strong coupling weakens the
Coulomb interaction. We show that at voltages below the inverse RCtime
in the circuit all effects of interaction can be incorporated into the
energy renormalization of transmission eigenvalues of the arbitrary scatterers
that connect the island and the leads. At moderate conductance
G of the island below some critical value Gc the above renormalization
results in the onset of an effective Coulomb blockade gap in the currentvoltage
dependence, the value of this gap being exponentially suppressed
as compared to the classical charging energy E = e 2 /2C of the island.
In the opposite case, G > Gc, the Coulomb blockade does not develop
and the interaction correction to transport saturates at low voltages below
the Thouless energy of the island. Remarkably, our renormalization
group approach agrees with the previous equilibrium instanton calculations
[2], i.e. both methods give the same energy scale for the effective
charging energy.
[1] D.A. Bagrets and Yu. V. Nazarov, cond-matt/0304347
[2] Yuli V. Nazarov, Phys. Rev. Lett. 82, 1245 (1999).
TT 11.6 Di 10:45 H19
Negative differential resistance due to the resonance coupling of
a quantum-dot dimer — •Shidong Wang 1,2 , Zouzou Sun 1 , Nelson
Cue 1 , and Xiangrong Wang 1 — 1 Department of Physics, Hong
Kong University of science and technolgy, HKSAR, China — 2 Institut
für Theoretische Physik, Universität Regensburg, 93040 Regensburg
We investigate the electron tunneling through a coupled quantum-dot
dimer (a two quantum-dot system) under a dc bias. We find a new mechanism
for the negative differential resistance (NDR) in a system with more
than one quantum dots. We show that a peak in the I-V curves, that is,
a NDR, occurs at low temperature when two discrete electronic states in
the two quantum dots are aligned with each other. We call this coupling
of two states the resonance coupling. We study also the dependence of
the height and width of the I-V peak on the dot-dot coupling, e-e interaction,
and the temperature. We find that the peak disappears due to
thermal smearing effects at high temperature. We expect that this new
NDR is useful in STM experiments. We hope that a better understanding
of this resonance coupling effect may enhance the STM as a powerful
probe not just for a regular surface, but also for a cluster structure.
TT 11.7 Di 11:00 H19
Nonlinear Transport through Quantum Wires: Functional
Renormalization Group in Nonequilibrium — •Severin
Jakobs 1 , Volker Meden 2 , Herbert Schoeller 1 , and Kurt
Schönhammer 2 — 1 Institut für theoretische Physik A, RWTH Aachen,
D-52056 Aachen, Germany — 2 Institut für Theoretische Physik,
Universität Göttingen, Bunsenstr. 9, D-37073 Göttingen, Germany
We study nonlinear transport at finite temperature through a quantum
wire with impurities. The wire is modelled by a one-dimensional
quantum lattice including nearest neighbour interaction. It is coupled
via tunneling barriers to two reservoirs to which a finite bias voltage is
applied. For calculating the nonequilibrium properties we generalize a
functional renormalization group method (applied recently to the equilibrium
case [1]) to the nonequilibrium situation by utilizing real-time
Feynman diagrams. This enables us to handle weak as well as strong tunneling
and arbitrary potentials on the wire. The coulomb interaction is
treated within perturbative renormalization group, i.e. only the Hartree-
Fock type of diagrams are included. For a single impurity in an infinite
quantum wire we recover the exponents for the current vs. temperature
and for the current vs. bias voltage predicted from bosonization [2]. For
a finite wire however, the interplay of tunneling barriers and impurity
produces exponents depending on the position of the impurity.
[1] V.Meden et al., Phys.Rev.B 65, 045318 (2002)
[2] C.L.Kane, M.P.A.Fisher, Phys.Rev.B 46, 15233 (1992)
TT 11.8 Di 11:15 H19
Electron transport through interacting quantum dots —
•Andrei Zaikin 1 and Dmitri Golubev 1,2 — 1 Institut ür Nanotechnologie,
Forschungszentrum Karlsruhe, 76021 Karlsruhe — 2 Institut für
Theoretische Festkörperphysik, Universität Karlsruhe, 76128 Karlsruhe
We present a detailed theoretical investigation of the effect of Coulomb
interactions on electron transport through quantum dots and double
barrier structures connected to a voltage source via an arbitrary linear
impedance. Combining real-time path integral techniques with the scattering
matrix approach we derive the effective action and evaluate the
current-voltage characteristics of quantum dots with large conductances.
Our analysis reveals a reach variety of different regimes which we specify
in detail for the case of chaotic quantum dots. At sufficiently low energies
the interaction correction to the current depends logarithmically on
temperature and voltage. We identify two different logarithmic regimes
with the crossover between them occurring at energies of order of the
inverse dwell time of electrons in the dot. We also analyze the frequencydependent
shot noise in chaotic quantum dots and elucidate its direct
relation to interaction effects in mesoscopic electron transport.

Tiefe Temperaturen Dienstag
TT 11.9 Di 11:30 H19
Inelastic quantum transport through a mesoscopic region —
•Dmitri Ryndyk — Institut für Theoretische Physik, Universität Regensburg,
93040 Regensburg
We consider quantum transport through a (nonequilibrium) mesoscopic
region at finite voltage with inelastic scattering inside a region. In
this case the standard Landauer-Buttiker approach can not be used anymore.
We use the Nonequilibrium Green Function method and develop
quasi-classical kinetic theory. We show that, due to a nonequilibrium distribution
function in the mesoscopic region, inelastic scattering rate is a
function of voltage and can be significantly enhanced. This effect can be
used for investigation of an inelastic scattering at low energies, e.g. in the
resonant tunneling devices.
TT 11.10 Di 11:45 H19
Evidence for fractional quasiparticles in the persistent current
in clean one-dimensional rings — •Janine Splettstoesser 1 , Ulrich
Zülicke 2 , and Michele Governale 1 — 1 Scuola Normale Superiore,
Piazza dei Cavalieri 7, I - 56126 Pisa, Italy — 2 Institute of Fundamental
Sciences, Massey University, Private Bag 11 222, Palmerston
North, New Zealand
The presence of electron-electron interaction affects the persistent currents
flowing in mesoscopic rings threaded by a magnetic flux. We study
an interacting one-dimensional clean ring. It is known that the groundstate
of such a one-dimensional conductor is a Luttinger liquid. We derive
the zero-mode Hamiltonian for the system, and subsequently the average
value of the persistent current. In particular, we find that the persistent
current has a universal form as a function of T/T ∗ , Φ/Φ ∗ , where both
the temperature scale T ∗ and the flux period Φ ∗ are renormalized by the
interaction strength. Certain formal analogies with the noninteracting
case suggest that the interaction-dependent flux period can be seen as a
manifestation of electron fractionalization in a Luttinger liquid [1].
[1] K. V. Pham, M. Gabay, and P. Lederer, Phys. Rev. B 61, 16397
(2000).
TT 11.11 Di 12:00 H19
Interaction-induced damping of Aharonov-Bohm oscillations —
•Thomas Ludwig 1,2 and Alexander Mirlin 1,2 — 1 Institut für Nanotechnologie,
Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany
— 2 Institut für Theorie der Kondensierten Materie, Universität Karlsruhe,
76128 Karlsruhe, Germany
We study the amplitudes of mesoscopic Aharonov-Bohm oscillations
in diffusive metallic rings in the presence of electron-electron interaction.
In the limit of strong dephasing we derive an analytical expression for
the damping of the oscillations. The dephasing behaviour is qualitatively
different from other situations because although Lϕ is much shorter than
the system size the dephasing mechanism is governed by energy transfers
determined by the system size.
TT 11.12 Di 12:15 H19
Schwache Lokalisierung und erhöhte Elektron-Elektron Wechselwirkung
in nanostrukturierten magnetischen Leiterbahnen
— •Mario Brands, Axel Carl und Günter Dumpich — Experimentalphysik,
AG Farle, Institut für Physik, Fakultät IV, Universität
Duisburg-Essen, Standort Duisburg, Lotharstrasse 1, 47048 Duisburg
Es wurden Widerstandsmessungen an dünnen Kobalt-Leiterbahnen
in Abhängigkeit der Temperatur (T = 1, 5K bis T = 30K) und
eines senkrecht zur Leiterbahn angelegten Magnetfeldes (bis B =
4, 5T) durchgeführt. Die Leiterbahnen wurden mittels eines Drei-Schritt-
Elektronenstrahllithografie (EBL)-Prozesses auf GaAs Substraten hergestellt
und haben eine konstante Länge von l = 400µm wohingegen ihre
Breite (w = 100nm bis w = 2000nm) und ihre Schichtdicke (t = 7nm
bis t = 32nm) systematisch variiert wurde. Zum Schutz vor Oxidation
wurden die Leiterbahnen mit verschiedenen Abdeckschichten versehen.
Der Magnetowiderstand ist negativ und kann im wesentlichen auf
den Anisotropen Magnetowiderstand (AMR) zurückgeführt werden. In
der Temperaturabhängigkeit des Widerstands zeigt sich zu tiefen Temperaturen
hin der charakteristische logarithmische Widerstandsanstieg,
aus dessen Steigung in Abhängigkeit des äußeren Magnetfeldes die respektiven
Anteile resultierend aus Schwacher Lokalisierung (WEL) und
Elektron-Elektron Wechselwirkung (EEI) bestimmt werden können. Diese
Arbeit wird gefördert von der DFG im Rahmen des SFB 491.
TT 11.13 Di 12:30 H19
Non-equilibrium quasiparticle distribution in diffusive quantum
wires in a magnetic field — •J. Kroha 1 , J. Paaske 2 , A. Rosch 2 ,
O. Uhsaghy 3 , P. Wölfle 2 und A. Zawadowski 3 — 1 PI, Univ. Bonn
— 2 TKM, Univ. Karlsruhe — 3 Dept. of Physics, TU Budapest
The non-equilibrium distribution function f(E, V ) of quasiparticles
with energy E in a diffusive quantum wire at bias V has a doublestep
shape due to the different chemical potentials in the leads [1]. The Fermi
steps display an anomalous rounding whose origin has been identified
with a tiny concentration of Kondo impurities (Kondo temperature TK)
present in the wire [2]. The magnetic field B dependence of f(E, V ),
in particular its non-monotonic behavior as B crosses from B < V to
B > V , suggests qualitatively the Kondo impurities to be of magnetic
origin. However, there is a strong quantitative discrepancy between
experiments and theory [3] both concerning the B dependence and the
expected Kondo impurity concentration. We generalize the perturbative
RG method [4], which was recently developed for a Kondo impurity at
finite V and B, to the case of a variable f(E, V ) along the wire. We use
this method to solve the quantum Boltzmann equation for f(E/eV ) in
the presence of Kondo impurities in a diffusive quantum wire at large
bias V ≫ TK and arbitrary B and compare with experiments.
[1] A. Anthore et al. PRL 90, 076806 (2003).
[2] A. Kaminski, L.I. Glazman, PRL 86, 2400 (2001);
J. Kroha, A. Zawadowski, PRL 88, 176803 (2002).
[3] G. Göppert et al., PRB 66, 195328 (2002).
[4] A. Rosch, J. Paaske, J. Kroha, P. Wölfle, PRL 90, 076804 (2003).
TT 11.14 Di 12:45 H19
Nanoelectronic transport through a spin-polaron system —
•Frank Reininghaus, Thomas Korb, and Herbert Schoeller
— Institut für Theoretische Physik A, RWTH Aachen, Germany
We consider non-equilibrium transport of electrons through a polarised
quantum spin chain of finite length. We model the chain by an itinerant
electron system exchange-coupled to the spins of the chain locally. This
model has been previously considered for several types of magnetic semiconductors.
The spins are treated within the spin-wave approximation.
This enables us to use the Keldysh technique. In equilibrium the elementary
excitations of this system are spin-polarons. We are interested
in the effect of the spin-polaron on the electronic transport through the
chain. We expect that the transport strongly depends on the spin of the
injected electrons.
TT 12 Supraleitung: Anwendungen, Materialien, technische Supraleiter, Bauelemente
Zeit: Dienstag 14:30–15:30 Raum: H20
TT 12.1 Di 14:30 H20
Chemisch unterstützte Oberflächenepitaxie: Orientiertes (001)
NiO, Puffer und YBCO Wachstum auf Ni 5at%W RABiTS —
•Andreas Heinrich, Bernhard Woerz und Bernd Stritzker —
Unversität Augsburg, Experimentalphysik IV
Für die Deposition von YBCO auf metallische Substrate sind Pufferschichten
notwendig. Verwendet man oxidische Puffer kommt es bei der
Deposition auf Ni zu einer unerwünschten (111) NiO Bildung. Durch eine
Voroxidation des Ni-Bandes bei hohen Temperaturen (ca. 1200C / Surface
Oxidation Epitaxie / SOE) kann dies vermieden werden. Dabei bildet
sich die erwünschte (001) NiO Orientierung aus. Diese Methode ist prak-
tikabel im Falle von NiCr od. NiV Legierungen. Werden hochlegierte NiW
Verbindungen (ab 3%W) verwendet, bildet sich keine (001)NiO-Schicht.
Wir haben ein Verfahren entwickelt, mit der ein (001)NiO Wachstum
während der SOE bei tiefen Temperaturen (350C) auf NiW möglich ist.
Damit kann eine (001) NiO Schicht während des Heizvorganges zur Pufferdepositionstemperatur
erzeugt werden. Es wird über den Einfluss der
chemischen Vorbehandlung und der SOE auf das Ni berichtet. Ausserdem
wird gezeigt, dass (001)NiO/La0.7Ca0.3MnO3/YBCO biaxial texturiert
auf Ni5W wächst.

Tiefe Temperaturen Dienstag
TT 12.2 Di 14:45 H20
Fast active high power switches on YBCO thin films — •Alois
Hiebl 1 , Kai Nummsen 1 , Helmut Kinder 1 , Werner Weck 2 , Anton
Müller 2 , and Hermann Schölderle 2 — 1 TU München, Physik
Department E10, 85748 Garching — 2 Fa. Magnet Motor, Petersbrunner
Str. 2, 82139 Starnberg
YBCO thin films have excellent switching properties at high power
levels and within microsecond time scale. We have studied the possibility
of using YBCO thin films not only as passive switches, as in the case
of resistive fault current limiters (FCL), but also as actively switchable
devices. We have investigated a new switching method with a radio frequency
(RF) trigger pulse directly applied to the superconducting strip
itself. The RF magnetic field is applied by various types of coils at frequencies
in the MHz - kHz range. The samples were prepared by thermal
co-evaporation on sapphire substrates in the form of strips with dimensions
10 mm x 42 mm and a thickness of 300 nm. No normal conducting
topcoat was used to retain higher switching powers. They were submerged
in liquid nitrogen and biased by a dc current. We observe the onset of a
dc voltage drop along the superconductor simultaneously with the leading
edge of the RF pulse. This voltage drop continues to increase over
several microseconds until the YBCO film switches into the normal state.
We present measurements for the frequency dependence of the switching
time, which decreases from 10 kHz to 45 MHz. For the RF induced
heating we present a theoretical explanation which we proved with a new
experimental setup. With the new setup short switching times are also
achievable, using a trigger pulse in the kHz range.
TT 12.3 Di 15:00 H20
Superconductively levitated transport system - the Supra-
Trans project — •O. de Haas, L. Schultz, C. Beyer, P. Verges
und G. Fuchs — Leibniz-Instistut für Festkörper und Werkstoffforschung
Dresden, Helmholtzstr. 20, 01069 Dresden
The development and creation of a full working prototype of a superconductively
levitated train is the aim of the SupraTrans project. It is
a joint venture between research institutes (IFW Dresden), universities
(Dresden University of Technology, University of Applied Sciences Dresden),
industrial companies (ELBAS GmbH-railway consulting and engineering,
Baumüller Kamenz-linear drives, CIDEON Bautzen-technical
engineering) and the Dresden Transportation Company (DVB). In our
contribution we will give a detailed insight into technology and physics
of the levitation system and surrounding parts.
The SupraTrans technology uses the flux pinning in melt textured
massive YBCO to stabilize the lateral and the vertical position of
the vehicle on top of the magnetic track. This self-stabilization is the
main advantage of the superconductive levitation in comparison to the
already used Transrapid-technology, which needs an electronic control
system to keep a constant distance between the train and the track. In
a first step, permanent magnets will be used for the prototype rail. In
further steps the permanent magnets will be replaced by electromagnets
that provide the magnetic field for levitation and guidance. Supported
by Sächsische Aufbaubank (SAB) and Sächsisches Staatsministerium für
Wirtschaft und Arbeit (SMWA).
TT 12.4 Di 15:15 H20
A new track for a superconductively levitated transport system
— •Christoph Beyer, Zongyou Ren, Oliver de Haas, Peter
Verges, Günter Fuchs, and Ludwig Schultz — Leibniz-Instistut
für Festkörper und Werkstoffforschung Dresden, Helmholtzstr. 20, 01069
Dresden
Based on investigations on a toy sized model levitation train[1], we have
constructed a new permanent magnetic track for a superconductively levitated
transport system, which will be the base of the demonstrator in
our SupraTrans project. First results exhibit similar levitation forces
compared to existing systems [2] with a three times lower material outlay.
The track is made out of a combination of Nd-Fe-B permanent magnets
and soft magnetic steel as flux collector. In the experimental setup we
used a rectangular bulk melt-textured YBCO block with the dimension of
30 ×90 ×15 mm. We achieved a maximum levitation force of around 200
N at 77 K and a vertical stiffness of 10 N/mm in zero-field-cooled mode.
Supported by Sächsische Aufbaubank (SAB) and Sächsisches Staatsministerium
für Wirtschaft und Arbeit (SMWA)
[1]L. Schultz et al.; Z. Metallkd. 93, 1057
[2]J. Wang et al.; Physica C 378-381, 809
15:30 Pause
TT 13 Messgeräte, Kryotechnik
Zeit: Dienstag 15:45–18:45 Raum: H20
Hauptvortrag TT 13.1 Di 15:45 H20
Anwendung supraleitender Quanteninterferenzdetektoren
in der Messtechnik — •Hans-Georg Meyer — Institut für
Physikalische Hochtechnologie e.V., Albert-Einstein-Straße 9, 07745
Jena
Supraleitende Quanteninterferenzdetektoren (SQUID) realisieren ein
schon lange bekanntes quantenelektronisches Meßprinzip, mit dem empfindlichste
magnetische Messungen durchgeführt werden können. Die bei
der SQUID-Fertigung erreichten Fortschritte und die Anwendung neuer
Techniken bei der Signalanalyse haben in den letzten Jahren zu einer
deutlichen Verbesserung der anwenderspezifischen SQUID-Technologie
geführt. Entsprechend rasch hat die SQUID-Meßtechnik immer neue Anwendungsfelder
besetzt. Der Bogen spannt sich von den traditionellen
Einsatzgebieten im Biomagnetismus (Magnetoenzephalogramm, Magnetokardiogramm)
über Zerstörungsfreies Testen, Geophysik (hier insbesondere
Lagerstättenerkundung), Altlastenerkundung, Archäometrie und
Röntgenspektroskopie bis hin zu neuen Feldern wie SQUID-Mikroskopie,
Astronomie und Niedrig-Feld-NMR. Ausgehend vom Meßprinzip wird der
Ausbau des SQUID als Magnetfeld-, Magnetfeldgradienten- und Stromsensor
diskutiert. An ausgewählten Beispielen werden der Weg zum kompletten
System und dessen meßtechnische Anwendung vorgestellt. Es
wird ein Ausblick auf neue Sensorkonzepte gegeben, die auf der SQUID-
Technologie aufbauen.
TT 13.2 Di 16:15 H20
Anwendung supraleitender Tunneldioden als hochauflösende
Röntgendetektoren — •Michael Huber, Klemens Rottler, Josef
Jochum und Franz von Feilitzsch — Physik-Department E15,
TU München, James-Franck-Str., 85748 Garching
Ein an der Technischen Universität München entwickelter
Tieftemperatur-Röntgendetektor, basierend auf einer supraleitenden
Tunneldiode mit phononisch gekoppeltem Pb-Absorber, erreichte bei
Bestrahlung mit 55 Mn-Röntgenstrahlung eine Energieauflösung von 10.8
eV bei 5.9 keV. Dies stellt die beste, bisher mit einer supraleitenden
Tunneldiode gemessene Energieauflösung in diesem Energiebereich dar.
Vorteile dieses Detektorsystems gegenüber anderen Tieftemperaturdetektoren
sind die hohe Zählratenfestigkeit und die Unempfindlichkeit
gegenüber Schwankungen der Arbeitstemperatur.
Im Vortrag werden Analysen zum Verständnis physikalischer
Energietransport- und -verlustprozesse im Detektor vorgestellt. Dies erlaubt
die Verbesserung anwendungsrelevanter Detektorcharakteristika
wie Signallinearität und Artefaktunterdrückung.
TT 13.3 Di 16:30 H20
Nano-scaled superconducting meanders as single-photon detectors
— •Andreas Engel 1 , Alexei Semenov 1 , Heinz-Wilhelm
Hübers 1 , Konstantin Il’in 2 , and Michael Siegel 2 — 1 Deutsches
Zentrum für Luft- und Raumfahrt, Rutherfordstr. 2, 12489 Berlin —
2 Institut für Mikro- und Nanoelektronische Systeme, Universität Karlsruhe,
Hertzstr. 16, 76187 Karlsruhe
There is great need for sensitive, fast, and energy-dispersive photon
detectors in such diverse areas as far-infrared astronomy or x-ray spectroscopy.
Nano-scaled superconducting meanders biased with a direct
current slightly less than the critical current Ic(T) are promising candidates
to close some of the gaps. Depending on the desired application and
spectral range the thin (down to a few nm) and narrow (of the order of
100 nm or less) superconducting strips have to be fabricated from superconducting
materials with varying critical temperature and thus varying
energy gap ∆. An absorbed photon creates a hot spot with a normal
conducting core. The bias current is expelled from the normal conducting
core thereby increasing the current density in the side-walks until

Tiefe Temperaturen Dienstag
eventually the critical current density is exceeded. Information about the
photon’s energy is contained in the height and duration of the resulting
voltage transient.
We will present the latest theoretical models we use to describe experimental
results and discuss some aspects with regard to detector performance.
Examples are geometrical effects and dark count rates caused by
superconducting fluctuations.
TT 13.4 Di 16:45 H20
Entwicklung magnetischer Mikrokalorimeter für die hochauflösende
Teilchendetektion — •H. Rotzinger 1 , T. Daniyarov
1 , M. Linck 1 , A. Burck 1 , A. Fleischmann 1 und C. Enss 2
— 1 Kirchhoff-Institut für Physik, INF 227, 69120 Heidelberg — 2 Physics
Department, Brown University, Providence, RI 02912, USA
Metallische magnetische Kalorimeter (MMC) sind energiedispersive
Tieftemperatur-Teilchendetektoren, mit denen das Anwendungsspektrum
konventioneller energiedispersiver Detektoren in vielerlei Hinsicht
erweitert werden kann. Von besonderem Interesse ist dabei die um
nahezu zwei Größenordnungen bessere Energieauflösung, und das
kalorimetrische Detektionsprinzip, das große Freiheiten bei der Wahl des
Absorbermaterials und der Absorbergeometrie erlaubt. MMCs bestehen
aus einem Absorber und einem paramagnetischen Temperatursensor
in einem schwachen Magnetfeld. Ein Energieeintrag in den Absorber
bewirkt daher neben einer Erwärmung des Sensors auch eine kurzzeitige
Änderung dessen Magnetisierung, die mit einem SQUID-Magnetometer
nachgewiesen wird und ein Maß für die eingetragene Energie darstellt.
Wir diskutieren das Detektionsprinzip und den Aufbau magnetischer
Kalorimeter und stellen zwei Prototypdetektoren vor. Der erste
wurde für die Bestimmung absoluter Aktivitäten in der Metrologie
optimiert und besitzt einen Absorber, der den gesamten Raumwinkel
4π um die radioaktive Quelle mit einer Quanteneffizienz von 99,9%
abdeckt.Der zweite Prototyp wurde für die hochauflösende Röntgenfluoreszenz-
Spektroskopie entwickelt und besitzt im Energiebereich bis
6 keV eine Quanteneffizienz von 98% und eine Energieauflösung von
∆EFWHM = 3,4 eV.
17:00 Pause
TT 13.5 Di 17:15 H20
Development of a cryogenic detection concept for GNO
— •Tobias Lachenmaier, Jean-Côme Lanfranchi, Walter
Potzel, and Franz von Feilitzsch — Technische Universität
München, James-Franck-Str, 85748 Garching
The Gallium-Neutrino-Experiment GNO measures solar neutrinos radiochemically
via the reaction 71 Ga(ν,e) 71 Ge. In order to reduce statistical
and systematic uncertainties in detecting the decay of 71 Ge to 71 Ga,
a favourable way could be the use of high-resolution cryogenic detectors
instead of the presently integrated miniaturized proportional counters.
After the successful development of a highly efficient 4π-detector, optimization
of thermal Ge-deposition, decoupling of deposition and detection,
present activity concentrates on low background considerations,
enhancement of external and internal shielding of the cryostat and a
longterm run with artificially activated 71 Ge to prove the feasibility of
’cryo-GNO’ in our Underground Laboratory in Garching.
TT 13.6 Di 17:30 H20
Detector developement for calibration measurements in
CRESST — •Wolfgang Westphal, Franz von Feilitzsch,
Thomas Jagemann, Josef Jochum, Walter Potzel, Wolfgang
Rau, Marco Razeti, Michael Stark, and Hesti Wulandari
— Technische Universität München, Physik-Department E15,
James-Franck-Strasse, D-85748 Garching
CRESST searches for Dark Matter Particles (WIMPs) by means of
elastic scattering on nuclei in cryogenic detectors. The main background
are electron recoils iduced by radioactivity. Our target (CaWO4) is a
scintillator, which has lower light output for nuclear recoils than for electron
recoils allowing us to discriminate this background. The detectors
consist of a 300 g crystal with a Tungsten Transition Edge Sensor (TES)
to measure the thermally deposited energy, enclosed in a reflecting housing
together with a light detector. These detectors are designed for low
count rates as expected for the experiment.
To understand the detector response to nuclear recoils we plan a calibration
experiment with a neutron beam, requiring high count rates.
The same holds for an experiment studying recoiling nuclei from alphadecays,
one of the remaining backgrounds. Therefore we have developed
faster detectors, using Ir/Au TES operated in the electro thermal feedback
mode. We will discuss the latest results of this developement.
TT 13.7 Di 17:45 H20
EDS with Microcalorimeters — •Christian Hollerith 1 , M.
Bühler 2 , F. von Feilitzsch 1 , J. Höhne 2 , M. Huber 1 , J. Jochum 1 ,
K. Phelan 2 , B. Simmnacher 3 , R. Weiland 3 und D. Wernicke 1
— 1 Physikdepartment der TU München, E15, 85748 Garching —
2 Vericold technologies GmbH, 85737 Ismaning — 3 Infineon technologies
AG, 81739 München Perlach
Energy dispersive X-ray spectroscopy (EDS) of samples mounted in
scanning electron microscopes (SEM) is a standard technique for elemental
material analysis. Today Si(Li)-detectors are used in this field
with a maximum energy resolution of about 130eV at a X-ray energy
of 6keV. This energy resolution is unsatisfactory for the separation of
the low energetic lines like M-lines of heavy elements, L-lines of medium
heavy elements and K-lines of light elements. But for excitation of small
volumes like particles in samples with the electron beam in the SEM only
low acceleration voltages may be used and therefore only low energetic
lines are excited. A high resolution spectrometer with a microcalorimeter
detector cooled by a pulse tube refrigerator with an ADR unit has been
installed on a SEM for this purpose. It shows an average energy resolution
of better than 10eV at 1.5keV. The low countrate in comparison to
Si(Li) detectors due to the small area of the microcalorimeter has been
increased by the application of a polycapillary X-ray optics. This way the
microcalorimeter is a promising tool for material analysis of thin layers
and small samples.
TT 13.8 Di 18:00 H20
Industrielle Anwendungen von Tieftemperaturdetektoren —
•Jens Höhne — VeriCold Technologies GmbH, Bahnhofstr. 21, 85737
Ismaning
Tieftemperaturdetektoren, wie sie seit Jahren für astrophysikalische
Fragestellungen entwickelt werden, haben eine gute Energieauflösung
im niederenergetischen Röntgenbereich. Sie werden daher seit kurzer
Zeit auch im Bereich der Materialanalytik eingesetzt. Ein weit verbreitetes
Verfahren ist die sogenannte Mikroanalyse, welche durch Elektronenbestrahlung
einer Probe die dadurch erzeugte charakteristische
Röntgenstrahlung nachweist. Die in konventionellen Röntgendetektoren
auftretenden Linienüberlappungen können mit Tieftemperaturdetektoren
aufgelöst werden und es wird damit die hochortsaufgelöste Untersuchung
von Oberflächen und sub-um-Partikeln möglich. Der Vortrag
diskutiert die industriellen Anforderungen an die Kühl- und Sensortechnologie,
Anwendungsbeispiele sowie zukünftige Anforderungen und Entwicklungen.
TT 13.9 Di 18:15 H20
Charakterisierung von Tieftemperaturdetektoren in einem
ADR (Adiabatic Demagnetisation Refrigerator) — •Doreen
Wernicke 1 , Jens Höhne 1 , Theo Hertrich 1 , Kevin Phelan 1 ,
Mathias Bühler 1 , Christian Hollerith 2 , Franz v. Feilitzsch 2 ,
Josef Jochum 2 , Michael Stark 2 und Wolfgang Westphal 2 —
1 VeriCold Technologies GmbH, Bahnhofstrasse 21, D-85737 Ismaning —
2 Physik-Department E15, TU München, James-Franck-Strasse, D-85748
Garching
In den letzten Jahren gewann die ADR Technologie zur Erzeugung
tiefer Temperaturen zunehmend an Bedeutung. Der Einsatz von Tieftemperatursensoren
zur Strahlungsdetektion auf Satellitenmissionen und
auch in der industriellen Anwendung verlangte nach transportablen und
robusten Kühlsystemen zur Erzeugung von Temperaturen unter 100mK.
Im Gegensatz zu Entmischungskryostaten überzeugen ADRs durch eine
einfache Bedienung und eine kompakte Bauweise.
Die Firma VeriCold Technologies GmbH beschäftigt sich u. a. mit der
Weiterentwicklung und Optimierung der ADR Technologie und nutzt
diese auch selbst in einem auf Tieftemperatursensoren basierenden hochauflösenden
Röntgenspektrometer (Polaris).
In dem Vortrag sollen die wichtigsten Aspekte von ADRs und die Charakterisierung
von Phasenübergangsthermometern für die Anwendung in
der Materialanalyse diskutiert werden.

Tiefe Temperaturen Dienstag
TT 13.10 Di 18:30 H20
Measurements of coherent transition radiation by Hilberttransform
spectroscopy with Josephson junctions — •Andre
Kaestner 1 , Frank Ludwig 2 , Frank Ludwig 1 , and Meinhard
Schilling 1 — 1 Institut für elektrische Messtechnik und Grundlagen
der Elektrotechnik, TU Braunschweig, Hans-Sommer-Straße 66,
D-38106 Braunschweig — 2 Deutsches-Elektronen-Synchrotron DESY,
Notkestraße 85, D-22603 Hamburg
We present measurements of coherent transition radiation from 50
to 500 GHz using the method of Hilbert-transform spectroscopy. The
Josephson junctions out of YBa2Cu3O7 (YBCO) used for Hilberttransform
spectroscopy are prepared on symmetric 24 o LaAlO3 bicrystal
substrates. For better coupling of high frequency radiation they are
equiped with integrated wideband antennas out of YBCO. We obtain for
a 6 micrometer wide junction an ICRN-product of 170 microvolt at 77 K
and 2.0 millivolt at 10 K. The set-up is optimized for low insertion loss
over a wide frequency range from 50 GHz to 2 THz. The measurements
of coherent transition radiation are compared with similar measurements
done at the Tesla Test Facility for the same set-up.
TT 14 FV-internes Symposium ”Orbital Physics”
Zeit: Dienstag 14:30–18:55 Raum: H18
Hauptvortrag TT 14.1 Di 14:30 H18
Lattice instability of frustrated orbital and spin systems —
•Maxim Mostovoy — Materials Science Center, University of Groningen,
The Netherlands
In materials with strong exchange interactions between electrons occupying
degenerate orbitals the cooperative Jahn-Teller effect may be suppressed,
as it is often impossible to order orbitals on all pairs of neighboring
transition metal ions in a unique optimal way. This frustration
may be relieved by several competing mechanisms, e.g., quantum orbital
fluctuations or ‘Peierls-like’ lattice distortions. I will discuss similarities
and differences between frustrated Jahn-Teller materials and frustrated
spin systems, such as antiferromagnets with a pyrocholore and triangular
lattice.
Fachvortrag TT 14.2 Di 15:00 H18
Magnetism, Charge Order and Giant Magnetoresistance in
SrFeO3−δ — •C. Ulrich 1 , A. Lebon 1 , P. Adler 2 , C. Bernhard 1 ,
A. Boris 1 , A. Pimenov 1 , A. Maljuk 1 , C.T. Lin 1 , and B. Keimer 1
— 1 Max-Planck-Institut FKF, Stuttgart — 2 Institut für Anorganische
Chemie, Universität Karlsruhe
The relationship between spin ordering, charge ordering, and magneto–
transport effects has recently received much attention in the context of
the colossal magnetoresistance (CMR) phenomenon in manganites. In the
3D perovskite SrFeO3, Fe 4+ is isoelectric to the Jahn–Teller ion Mn 3+ in
the manganite system. However, while the parent compound of the CMR
manganites, LaMnO3, is insulating and shows a cooperative Jahn–Teller
effect, its analogue SrFeO3 remains metallic at all temperatures and exhibits
a helical antiferromagnetic spin structure below 130 K. Therefore,
SrFeO3 is right at the borderline between an itinerant and a strongly
localized electron system.
We have studies three single crystals of SrFeO3−δ with different oxygen
content. Cubic SrFeO3.00 is metallic in the entire temperature range
and shows a large negative magnetoresistance effect at 55 K. Tetragonal
SrFeO2.87 shows semiconducting behavior below a second magnetic phase
transition at 75 K. Our Mössbauer studies reveal that this phase transition
is accompanied by a charge ordering of Fe 3.5+ into Fe 3+ and Fe 4+ . An
orthorhombic sample SrFeO2.81 on the other side showed semiconducting
behavior and a pronounced positive MR effect at 70 K.
TT 14.3 Di 15:20 H18
Frustrated orbital ground state in thiospinels — •J. Hemberger,
H.-A. Krug von Nidda, V. Fritsch, N. Büttgen, E.-W. Scheidt,
P. Lunkenheimer, R. Fichtl, V. Tsurkan, and A. Loidl — Center
for Electronic Correlations and Magnetism, Institute of Physics, University
of Augsburg
We studied the ground state properties of the normal cubic spinel compounds
AB2S4 (A = Fe, Mn and B = Sc, Cr) by means of specific heat,
magnetization and susceptibility measurements, as well as dielectric and
optical spectroscopy. In all compounds frustration strongly influences the
interplay of orbital and magnetic degrees of freedom and corresponding
order phenomena. Our results indicate the existence of distinguished spinorbital
scenarios: In the case of nonmagnetic B-sites (Sc) we find strong
magnetic coupling (Curie-Weiss temperature θCW = −45 K for A = Fe)
without any indications of order down to 50 mK. The ground states of
these compounds have to be characterized as a spin liquid in MnSc2S4
and a spin-orbital liquid in FeSc2S4, where Fe 2+ is Jahn-Teller active but
orbitally frustrated. In the case of magnetic B-sites (Cr) spin-order is
induced and the low-temperature states have to be described as orbital
liquid, orbital glass, or finally orbital order.
TT 14.4 Di 15:35 H18
Isotropic spin waves in the paramagnetic spin liquid state of
FeSc2S4 — •Alexander Krimmel 1 , Vladimir Tsurkan 1 , Alois
Loidl 1 , Michael Mücksch 1,2 , and Marek Koza 2 — 1 Institut für
Physik, Univ. Augsburg, D-86159 Augsburg, Germany — 2 Institut Laue
Langevin, BP156, 38042 Grenoble Cedex 9, France
FeSc2S4 crystallizes in the normal cubic spinel structure with magnetic
Fe 2+ ions (3d 6 , high spin configuration, µeff = 5.12µB) on the A-site. The
Jahn-Teller ions Fe 2+ are orbitally frustrated. Specific heat and magnetic
measurements showed no signs of long range magnetic order down to 50
mK. The ground state properties of FeSc2S4 can be described by a spinorbit
liquid. Here we report on inelastic neutron scattering experiments
on polycrystalline FeSc2S4. Even at 80 K, the paramagnetic spectral response
is centered around 0.6 ˚A −1 corresponding to the antiferromagnetic
Bragg position. On cooling, a well defined isotropic magnon dispersion
evolves but the system remains in a cooperative paramagnetic state without
magnetic Bragg peaks. These results are discussed within a scenario
of collective magnetic excitations in an orbital liquid state.
TT 14.5 Di 15:50 H18
Orbital degree of freedom in manganites determined by O1s
and Mn2p NEXAFS: crystal field versus orbital coupling in
single-layered La1−xSr1+xMnO4 — •Michael Merz 1 , P. Reutler
2 , B. Büchner 2 , Y. U. Idzerda 3 , S. Tokumitsu 4 , N. Nücker 4 ,
and S. Schuppler 4 — 1 Institut für Kristallographie, RWTH Aachen
— 2 Institut für Festkörper- und Werkstoffforschung, Dresden — 3 Naval
Research Laboratory, Washington — 4 Forschungszentrum Karlsruhe, Institut
für Festkörperphysik
Manganites exhibit a manifold of highly interesting magnetic and electronic
phases, with charge- and orbital-ordered states being at the center
of interest. Especially single-layered La1−xSr1+xMnO4 is a prototypical
example for such ordering effects. For this compound a ferro-orbital ordering
of |3z2 − r2 > states is expected from the strong crystal field, yet
anti-ferro type orbital coupling might lead to an admixture of |x2 −y2 >
states.
Using polarization-dependent O1s and Mn2p near-edge x-ray absorption
spectroscopy on untwinned La1−xSr1+xMnO4 single crystals (0 ≤
x ≤ 0.5), the doping- and temperature-dependent occupancies of the
O2p and Mn3d orbitals were studied. According to the spectra, Sr doping
not only provides holes to the system but also induces a continuous
transfer of electrons from out-of-plane |3z2−r2 > to in-plane |3x2−r2 >
and |3y2 − r2 > states. The data clearly demonstrate that electrons reside
for all doping levels on mixed α|3z2 − r2 > +β|x2 − y2 > states, i.
e., antiferro-coupled canted orbitals where α and β strongly depend on
the Sr content.
TT 14.6 Di 16:05 H18
Magnetische Polaronen: Magnetismus der dotierten Schichtmanganate
La1−xSr1+xMnO4 (x=1/8) — Davide Cattani 1 ,
Christoph Baumann 2,1 , Pascal Reutler 2 , •Rüdiger Klingeler
2 , Alexandre Revcolevschi 3 und Bernd Büchner 2 —
1 Università di Parma, I-43100 Parma — 2 Leibniz-Institut für Festkörperund
Werkstoffforschung Dresden, PF 270116, D-01171 Dresden —
3 Laboratoire de Chimie des Solides, Université Paris-Sud, F-91405
Orsay Cedex
In den einfach geschichteten Manganaten La1−xSr1+xMnO4 zeigen Messungen
der thermischen Ausdehnung im Fall lochfreier (x=0) oder gering
dotierter Systeme (x=1/8) eine grosse, stark anisotrope magnetoelastische
Kopplung beim Einsetzen der langreichweitig antiferromagne-

Tiefe Temperaturen Dienstag
tisch geordneten Tieftemperaturphase. Darüber hinaus ergeben sich Belege
für eine temperaturabhängige Umbesetzung der Orbitale. Eine geringe
Dotierung (x=1/8) mit Löchern, d.h. das Einschalten von konkurrierenden
ferromagnetischen Doppelaustauschwechselwirkungen, verringert die
Stabilität der antiferromagnetischen Tieftemperaturphase. Dabei zeigen
Messungen der Magnetisierung das Auftreten zusätzlicher xy-artiger magnetischer
Momente in der geordneten Phase, die als stark anisotrope
magnetische Polaronen verstanden werden können.
TT 14.7 Di 16:20 H18
Bond centered vs. site-centered charge ordering and ferroelectricity
in oxides. — •Dmitry Efremov 1 , Jeroen van den Brink 2 ,
and Daniel Khomskii 3 — 1 Technische Universität Dresden, Institut
für Theoretische Physik, 01062 Dresden — 2 Institut-Lorentz for Theoretical
Physics, Universiteit Leiden, 2300 RA Leiden, The Netherlands
— 3 Universität zu Köln, 50937 Köln
Many transition metal oxides show charge ordering, which up to now
was always treated as alternation of valency of transition metal ions. We
show that besides this site-centered charge ordering there may exist another
type of charge and orbital ordering, namely bond-centered ordering.
We demonstrate that such type of ordering should exist in manganites
close to half-filling. Moreover we show that these two types of ordering
may coexist making the system ferroelectric.
16:35 Pause
Hauptvortrag TT 14.8 Di 16:50 H18
Resonant Soft Energy X-ray Diffraction of Charge, Spin and
Orbital Ordering — •Peter Hatton — Dept. of Physics, University
of Durham, UK
Soft x-ray resonant diffraction is a new technique pioneered by our
group. We have published examples of the huge resonant enhancements
of charge and magnetic scattering that can be obtained at the L-edges
of 3d transition metal oxides as well as the first direct observation of
orbital ordering. In this talk we will review the technique of soft x-ray
diffraction as well as giving recent examples of results In particular we
will report the first resonant soft x-ray scattering observations of orbital
ordering from a bulk single crystal. We have studied the low temperature
phase of La1.5Sr0.5MnO4 that displays charge, spin and orbital ordering.
Previous claims of orbital ordering in such materials have relied on observations
at the K edge. These claims have attracted a barrage of controversy
from theoretical studies. Instead we have employed resonant soft
x-ray scattering at the manganese LIII and LII edges which provides
a direct measurement of the orbital ordering. Energy scans at constant
wavevector have been compared to theoretical predictions and show that
at all temperatures there are two separate contributions to the observed
scattering, direct Goodenough orbital ordering and strong cooperative
Jahn-Teller distortions of the Mn 3+ ions.
Fachvortrag TT 14.9 Di 17:20 H18
The interplay of orbital and lattice degrees of freedom in titanates
— •M. Grüninger, R. Rückamp, A. Gößling, M. Cwik,
H. Roth, J. Baier, M. Kriener, T. Lorenz, M. Braden, and A.
Freimuth — II. Physikalisches Institut, Universität zu Köln, Germany
Recently, several interesting phenomena have been proposed in which
orbitals play a key role, e.g. orbital order, dispersing orbital waves or
orbital liquids. However, the driving force in most theoretical treatments
is based on electronic interactions, the possible role of the lattice is often
neglected.
One interesting phenomenon which still has to be confirmed experimentally
is the existence of orbital liquids. The pseudo-“cubic” d 1 antiferromagnet
LaTiO3 seemed a promising candidate. We discuss the structure,
the thermal expansion and the optical conductivity of LaTiO3 and of
orbitally ordered YTiO3. A consistent description of the data of both
compounds is obtained within a Jahn-Teller scenario. Orbital excitations
are observed in the optical conductivity spectra of both LaTiO3 and
YTiO3 at about 0.25eV, which is difficult to reconcile with an orbital
liquid ground state of LaTiO3. On contrary, the data suggest that the
coupling to the lattice is of dominant importance not only for eg systems,
but also for t2g electrons. This point of view is corroborated by the optical
conductivity data of TiOCl. There, the splitting of the t2g levels is
larger than 0.5eV.
TT 14.10 Di 17:40 H18
Spin-orbital physics in Raman and optical spectra of Mott
insulators — •Giniyat Khaliullin — a:Max-Planck-Institut FKF,
Heisenbergstr.1, 70569 Stuttgart
We review our recent work which focuses on Raman [1] and optical
[2] spectroscopy in Mott insulators. First, we discuss different Raman
scattering channels involving orbital excitations in titanates. Next, we
consider the spectral weights of optical transitions in titanates and cubic
vanadates. We show that the temperature and polarization dependences
of the Raman and optical spectra are directly determined by the underlying
spin and orbital correlations, and discuss the role played by orbital
quantum fluctuations.
[1] G. Khaliullin, (unpublished).
[2] G. Khaliullin, P. Horsch, and A.M. Ole´s, (unpublished).
TT 14.11 Di 17:55 H18
Direct observation of charge order in La1.8Sr0.2NiO4 —
•C. Schüßler-Langeheine 1 , J. Schlappa 1 , Z. Hu 1 , M. W.
Haverkort 1 , M. Benomar 1 , O. Friedt 1 , E. Schierle 2 , H. Ott 2 ,
E. Weschke 2 , G. Kaindl 2 , G. A. Sawatsky 3 , A. Tanaka 4 , M.
Braden 1 , and L. H. Tjeng 1 — 1 II. Physikalisches Institut, Universität
zu Köln — 2 Institut für Experimentalphysik, Freie Universität Berlin —
3 Department of Physics and Astronomy, University of British Columbia,
Vancouver, Canada — 4 ADSM, Hiroshima University, Japan
We report on the direct observation of charge order in Sr-doped
La2NiO4 using resonant soft x-ray scattering at the Ni L2,3 and La
M4,5 resonances. Unlike conventional scattering techniques, which are
essentially probing lattice modulations, resonant soft x-ray scattering is
very sensitive to the oxidation state and hence particularly suited to
study charge-order phenomena. The charge-order superstructure peak
from La1.8Sr0.2NiO4 shows a resonant enhancement predominantly at Ni
L2,3 edges, in contrast to the x-ray absorption signal, which is dominated
by the La absorption. The details of this energy dependence agree
well with charge order in the Ni system, providing a direct experimental
observation of this ordered phase. Furthermore, the superstructure peak
observed with resonant soft x-ray scattering is much narrower in momentum
space than known from conventional scattering techniques, because
the comparably short penetration depth of soft x-rays together with the
availability of well focused x-ray beams makes this technique sensitive to
slight local inhomogeneities of the doping level, which cannot be probed
by other techniques.
TT 14.12 Di 18:10 H18
Extended moment formation and magnetic ordering in the trigonal
chain compound Ca3Co2O6 — •Volker Eyert 1 , Christian
Laschinger 1 , Thilo Kopp 1 , and Raymond Frésard 2 — 1 Institut für
Physik, Universität Augsburg, Germany — 2 Laboratoire Crismat, UMR
CNRS-ENSICAEN (ISMRA) 6508, Caen, France
The results of electronic structure calculations for the one-dimensional
magnetic chain compound Ca3Co2O6 are presented. The calculations are
based on density functional theory and the local density approximation
and used the augmented spherical wave (ASW) method. Our results allow
for deeper understanding of recent experimental findings. In particular,
alternation of Co 3d low- and high-spin states along the characteristic
chains is related to differences in the oxygen coordination at the inequivalent
cobalt sites. Strong hybridization of the d states with the O 2p
states lays ground for polarization of the latter and the formation of extended
localized magnetic moments centered at the high-spin sites. In
contrast, strong metal-metal overlap along the chains gives rise to intrachain
ferromagnetic exchange coupling of the extended moments via the
d 3z 2 −r 2 orbitals of the low-spin cobalt atoms.
TT 14.13 Di 18:25 H18
Excitation spectrum of the cobaltite NaxCoO2 yH2O as function
of Na content and hydration — •P. Lemmens 1,2 , K.-Y. Choi 2 ,
V. Gnezdilov 3 , N.N. Kovaleva 1 , H. Sakurai 4 , K. Takada 4 , T.
Sasaki 4 , E. Takayama-Muromachi 4 , F.C. Chou 5 , C.T. Lin 1 , and
B. Keimer 1 — 1 MPI for Solid State Research, D-70569 Stuttgart — 2 2.
Phys. Inst., RWTH Aachen, D-52056 Aachen — 3 B.I. Verkin Inst. for Low
Temp. Phys., NASU, 61164 Kharkov — 4 Superconducting Mat. Center
and Advanced Mat. Lab., NIMS, Tsukuba, Ibaraki 305-0044 — 5 Center
for Material Science and Engineering, MIT, Cambridge, MA 02139
We report on a Raman scattering study on the superconducting
cobaltite NaxCoO2 yH2O as function of Na content and hydration

Tiefe Temperaturen Dienstag
(x≈1/3, 3/4 and y≈0, 2/3, 4/3). The observed phonon scattering is analyzed
in terms of lattice strain due to the structural misfit and disorder.
Hydration, due to the intercalation of H2O layers, releases a part of this
strain. We will show experimental evidence for a pseudo gap formation in
the electronic scattering continuum. Furthermore, our Raman data suggest
a connection between disorder on the partly occupied Na sites, the
split off of the a1g level from the other t2g states of Co 4+ and superconductivity.
Work supported by DFG SPP1073, NATO PST.CLG.9777766,
INTAS 01-278, CREST of JST (Japanese Science and Technology Corporation)
and MRSEC Program of NSF under award number DMR 02-
13282.
TT 14.14 Di 18:40 H18
Beziehung zwischen orbitaler Besetzung und Magnetismus in
Ca2−xSrxRuO4 — P. Steffens, O. Friedt, O. Schumann, R.
Müller, J. Baier, M. Kriener, T. Zabel, S. Nakatsuji, Y. Maeno,
T. Lorenz, A. Freimuth, M. Braden, •P. Steffens, O.
Friedt, O. Schumann, R. Müller, J. Baier, M. Kriener, T.
Zabel, S. Nakatsuji, Y. Maeno, T. Lorenz, A. Freimuth und
M. Braden — II. Physikalisches Institut, Universität zu Köln
TT 15 Korrelierte Elektronen: Theorie I
Das Phasendiagram von Ca2−xSrxRuO4 ist sehr vielfältig, obwohl sich
Ca und Sr nur durch ihre Ionengröße unterscheiden[1-3]. Es reicht von
dem Spin-triplet Supraleiter Sr2RuO4 bis hin zum antiferromagnetisch
geordneten Mott-Isolator Ca2RuO4. Insbesondere in dem noch metallischen
Konzentrationsbereich nahe der elektronischen Lokalisierung beobachtet
man verschiedene konkurrierende magnetische Instabilitäten, die
durch nur kleine strukturelle Verzerrungen bestimmt zu sein scheinen.
So kann man sowohl mittels eines Magnetfeldes als auch mit äußerem
Druck zwischen verschiedenen magnetischen Phasen schalten, und dabei
immer strukturelle Änderungen induzieren. Wir diskutieren das Wechselspiel
zwischen orbitaler Besetzung und magnetischen Eigenschaften
anhand von Neutronen-Streuuntersuchungen und Messungen von thermischer
Ausdehnung, spezifischer Wärme und Magnetostriktion.
[1] S. Nakatsuji et al., PRL 84, 2666 (2000) [2] M. Braden et al., PRB
58, 847 (1998); O. Friedt et al., PRB 63, 174432 (2001) [3] S. Nakatsuji
et al., PRL 90, 137202 (2003)
Zeit: Dienstag 14:30–16:30 Raum: H19
TT 15.1 Di 14:30 H19
The coherence scale of the two-dimensional Kondo Lattice
model. — •Fakher F. Assaad — Institut für Theoretische
Physik und Astrophysik, Universität Würzburg, Am Hubland D-97074
Würzburg
A doped hole in the two-dimensional half-filled Kondo lattice model
with exchange J and hopping t has momentum (π, π) irrespective of the
coupling J/t. The quasiparticle residue of the doped hole, Z(π,π), tracks
the Kondo scale, TK, of the corresponding single impurity model. Those
results stem from high precision quantum Monte Carlo simulations on
lattices up to 12 × 12. Accounting for small dopings away from halffilling
within a rigid band approximation, this result implies that the
effective mass of the charge carriers at the Fermi level tracks 1/TK or
equivalently that the coherence temperature Tcoh ∝ TK. This results is
consistent with the large-N saddle point of the SU(N) symmetric Kondo
lattice model.
TT 15.2 Di 14:45 H19
Quasi-particle structure and ferromagnetism in the Kondolattice
model — •Tilmann Hickel and Wolfgang Nolting —
Humboldt-Universität, Institut für Physik, Newtonstr. 15, 12489 Berlin
The Kondo-lattice model (KLM) describes an indirect exchange interaction
of localized magnetic moments, mediated by itinerant conduction
electrons. The quantum-mechanical character of these local spins,
which has an substantial impact on the magnetic properties of the concerned
materials, prohibits a straight-forward application of standard
many-body approaches to the model Hamiltonian. We shall show that
the projection-operator method (POM) is instead a valuable analytical
technique to obtain substantial statements on one-particle properties of
the KLM. It allows the derivation of perturbational results of the same
quality as obtained for fermionic models as the Hubbard model. We will
use the POM to study the ferromagnetic phase of the KLM and its dependence
on material parameters self-consistently. In each step we make
sure, that the subsystems of conduction electrons and localized moments
are approximated on the same level.
TT 15.3 Di 15:00 H19
Spectral Densities of Single Impurity Models by Density-
Matrix Renormalization — •Götz S. Uhrig 1 , Carsten Raas 1 ,
and Frithjof B. Anders 2 — 1 Institut für Theoretische Physik,
Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany —
2 Institut für Theoretische Physik, Universität Bremen, 28334 Bremen,
Germany
The quantitative control of the dynamic correlations of single impurity
models is essential in many active fields. We analyze the local propagator
with a constant energy resolution by dynamical density-matrix renormalization
(D-DMRG). This approach is particularly useful for higher-lying
excitations. In contrast to other approaches, sharp dominant resonances
at high energies are found. We analyze their line shapes and discuss their
origin and importance. An analysis of the Kondo energy scale is also
presented.
The D-DMRG provides the density of states convolved with a
Lorentzian of width η. Choosing η is a trade-off between run-time
and energy resolution. Thus, accurate deconvolution strategies are
essential. We analyze several deconvolution methods to calculate
continuous spectral densities and propose a novel non-linear algorithm,
the least-bias algorithm.
Our findings provide a well-controlled numerical approach to impurity
problems which can serve as the impurity solver in dynamical mean
field theory (DMFT) calculations as well as in calculations of more complex
impurities like quantum dots, molecules, or the effective problems
of extended DMFT schemes.
TT 15.4 Di 15:15 H19
Elektronische Eigenschaften des Anderson-Gitters - ein Zugang
durch Flussgleichungen — •Karsten Meyer und Klaus W. Becker
— Insitut für Theoretische Physik, TU Dresden
Die von Wegner [1] vorgeschlagene Flussgleichungsmethode wird zur
Untersuchung des Anderson-Gitters verwendet. Die elektronische Struktur
ist dabei durch zwei Quasiteilchenbänder gekennzeichnet, die durch
eine Lücke voneinander getrennt sind. Die Ergebnisse werden mit den
Resultaten aus anderen theoretischen Zugängen verglichen.
Für das System lässt sich eine charakteristische Temperatur T ∗ definieren,
die für kleine Hybridisierungsstärken exponentiell klein wird. T ∗ ist
tendenziell gegenüber der Kondo-Temperatur des Störstellen-Anderson-
Modells abgesenkt. Ein solcher Effekt ist mit dem von Nozières [2] diskutierten
Exhaustion-Szenarium konsistent.
[1] F. Wegner, Ann. Phys. 3, 77 (1994)
[2] P. Noziéres, Eur. Phys. J. B 3, 447 (1998)
TT 15.5 Di 15:30 H19
Low-energy charge excitations on frustrated lattices — •Erich
Runge — Max Planck Institute for the Physics of Complex Systems,
Dresden, Germany
We study strongly interacting electrons on frustrated lattices of complex
topology. Often, these systems have a huge phase space for low-lying
excitations. In the case of LiV2O4, this leads to heavy-fermion behavior.
However, the nature of the low-energy excitations is generally not well
understood. It has even been predicted that fractionally charged quasiparticles
exist in two and three dimensions [1].
We discuss in detail the interplay of the frustrated kinetic energy
and the Coulomb repulsion between nearest-neighbor sites. An effective
Hamiltonian for the low-energy excitations is derived, which involves ring
exchanges and shows a huge density of states of non-magnetic excitations.
It can serve as a prototype for a new class of effective interactions and
quasi-particles.
Large-scale numerical results for the spectral function and related
quantities are presented as well.
[1] Peter Fulde, Karlo Penc, and Nic Shannon, Fractional charges in py-

Tiefe Temperaturen Dienstag
rochlore lattices, Annalen der Physik 11, 892 (2002)
TT 15.6 Di 15:45 H19
Periodic Anderson Model in the Charge Transfer Regime —
•Konrad Matho — CRTBT CNRS, 38042 GRENOBLE CEDEX 9,
FRANCE
We have proposed a fast track to calculate correlated fermionic
Green functions in momentum representation as Padé approximants,
with the aim of data analysis in ARPES experiments
(J.Electr.Spectr.Rel.Phen.117,13 (2001)). A stringent test is the comparison
to microscopic results beyond the one band Hubbard model. Therefore,
we have implemented spectra of the periodic Anderson model. In
this talk, we focus on the generics of charge transfer phenomena in a
range of metallic densities above and below one hole per site and discuss
the following properties: (i) Position of the chemical potential (ii)
Position and width of charge gap and Hubbard satellites (iii) Existence
of quasiparticle bands and their dependence on charge transfer and hybridisation
strength (iv) Differences in the spectra upon electron doping
versus hole doping (v) Spin correlations of the Zhang-Rice type.
TT 15.7 Di 16:00 H19
Continuous Unitary Transformations: Dynamic Structure Factors
at Zero and Finite Temperatures — •Christian Knetter 1 ,
Götz S. Uhrig 2 , and Hans Kroha 1 — 1 Physikalisches Institut, Universität
Bonn, Nussallee 12, D-53115 Bonn — 2 Institut für Theoretische
Physik, Universität Köln, Zülpicher Str. 77, D-50937 Köln
Continuous Unitary Transformations (CUTs) have been successfully
used to quantitatively calculate the zero temperature spectral densities
of various experimentally relevant observables for spin systems in one and
two dimensions. Here we present results for the dynamic structure factor
of the two-dimensional S = 1/2 Shastry-Sutherland model. Our theoretical
findings are in excellent agreement with recently obtained inelastic
neutron scattering data.
The CUTs are constructed such that the resulting effective Hamiltonians
conserve suitably defined quasi-particles. This property is exploited
to extend the method to finite temperatures. We present results for the
temperature dependent spectral densities of a one-dimensional model including
two-particle interactions.
TT 15.8 Di 16:15 H19
Well-defined quasiparticles in interacting metallic grains —
•Dominique Gobert, Ulrich Schollwöck, and Jan von Delft
— CeNS und Sektion Physik, LMU München
We analyze spectral functions of the reduced BCS Hamiltionian and of
the “universal Hamiltonian” of mesoscopic systems with large dimensionless
conductance. We show that an important class of spectral functions is
dominated by one single eigenstate only, which implies an infinite lifetime
of the quasiparticles. Furthermore, this property allows us to calculate
zero-temperature spectral functions with high accuracy using the densitymatrix
renormalization group. We illustrate the use of this method by
calculating various physically relevant quantities.
16:30 Pause
TT 16 Korrelierte Elektronen: Quantenstörstellen, Kondo-Physik
Zeit: Dienstag 16:45–19:00 Raum: H19
TT 16.1 Di 16:45 H19
Flowing uphill: From single- to multi-channel Kondo effect in
quantum dots due to weak charging energies in the leads —
•Serge Florens 1 and Achim Rosch 2 — 1 Institut für Theorie der
Kondensierten Materie,Universität Karlsruhe, Postfach 6980, 76128 Karlsruhe
— 2 Institut für Theoretische Physik, Zülpicher Str.77, D-50937
Köln
We have studied a model for quantum dots which takes into account
Coulomb blockade in the electrodes, a setup proposed recently by Oreg
and Goldhaber-Gordon as a way to observe exotic transport in nanostructures.
Even if the charging energy in the leads Ec is much smaller than
the Kondo temperature TK, we find surprisingly that the long-ranged interactions
destabilize the single-channel Kondo effect and induce a flow
towards a multi-channel Kondo fixed point associated with a rise of the
impurity entropy with decreasing temperature. Such an “uphill flow”
implies a negative impurity specific heat, in contrast to all systems with
local interactions. An exact solution found for a large number of channels
allows us to capture this physics and to predict transport properties
through the device.
TT 16.2 Di 17:00 H19
Quantum Phase Transitions in the Fermi-Bose-Kondo and
Pseudogap Kondo Models — •Matthias Vojta, Lars Fritz,
and Marijana Kircan — Institut für Theorie der Kondensierten
Materie,Universität Karlsruhe, D-76128 Karlsruhe
We discuss aspects of zero-temperature phase transitions in variations
of the Kondo model, where fermionic Kondo screening can be suppressed
due to the coupling to a bosonic bath or due to a gap in the fermionic
density of states. In particular, we identify the lower and upper critical
“dimensions” for the pseudogap Kondo model and present the field theories
describing the critical behavior. We determine a number of universal
properties near the impurity phase transitions and discuss applications
to magnetic impurities in strongly correlated systems and to scenarios of
local criticality in heavy-fermion compounds.
TT 16.3 Di 17:15 H19
Quantum Phase Transitions in Models of Magnetic Impurities
— •Hyun Jung Lee 1 , Ralf Bulla 1 , Ning-Hua Tong 1 , and
Matthias Vojta 2 — 1 Theoretische Physik III, Universität Augsburg —
2 Institut für Theorie der Kondensierten Materie, Universität Karlsruhe
The numerical renormalization group method is used to investigate
zero temperature phase transitions in single-impurity models, where an
impurity couples to a non-trivial fermionic bath (Pseudogap Anderson
model) or to a (sub)ohmic bosonic bath (Spin-Boson Model). In both
cases, zero temperature phase transitions occur between two different
phases whose fixed points can be built up of non-interacting singleparticle
states. However the quantum critical point cannot be described
by non-interacting fermionic or bosonic excitation. To understand the
quantum critical behavior, we study the character of the different fixed
points as well as thermodynamic quantities such as entropy and specific
heat.
TT 16.4 Di 17:30 H19
Lattice path integral approach to the Kondo problem —
•Michael Bortz 1 und Andreas Klümper 2 — 1 Universität
Dortmund, Fachbereich Physik, Lehrstuhl T1, 44221 Dortmund —
2 Bergische Universität Wuppertal, Fachbereich Physik, 42097 Wuppertal
We propose a lattice regularization of the one-dimensional isotropic single
channel spin-1/2 Kondo model, including the host and the impurity.
From symmetry arguments, effective models for the more general anisotropic
m-channel spin-S case are given. By application of the Quantum
Transfer Matrix formalism, we obtain the free energy and other thermodynamic
equilibrium response functions exactly by a set of max(2S, m)+1
non-linear integral equations. These are studied analytically in certain
limiting ranges of the external parameters (temperature and magnetic
field) and numerically over wide parameter ranges. Both high- and lowtemperature
scales (Wilson ratios) are calculated; especially, the ratios
relating the regimes of high- and low-temperatures are derived for the
first time in the framework of an exact solution.
TT 16.5 Di 17:45 H19
Dynamics of a 3-level quantum impurity with orbital degeneracy
in a fermionic bath — •Michael Arnold 1 , Johann Kroha 1 ,
and Alfred Zawadowski 2 — 1 Physikalisches Institut, Universität
Bonn — 2 Department of Physics, TU Budapest
We consider a model of an atom moving in a mexican hat-like potential
with 3-fold rotational symmetry, corresponding to a small atom localized
in the interstitial space of, e.g., an fcc lattice. The atom is coupled to the
conduction electron sea via angular momentum scattering. The local impurity
spectrum consists of the ground state and two Kramers degenerate
excited states. We investigate the possibility of 2-channel Kondo correlations
developing in the Kramers doublet in an intermediate energy region,
in competition to the relaxation to the ground state. The two channels

Tiefe Temperaturen Dienstag
of the system are represented by the conduction electron spin conserved
by the electron-impurity coupling. A perturbative RG scheme is used to
investigate the intermediate energy region of the model. We show that,
in analogy to previous work on Kondo impurities out of equilibrium [1],
the running coupling constants acquire a parametric dependence on the
energy of the scattering electrons, induced by the thermal excitations of
the impurity system.
[1] A. Rosch, J. Paaske, J. Kroha, and P Wölfle, Phys. Rev. Lett. 90,
076804 (2003).
TT 16.6 Di 18:00 H19
Optical fingerprints of Kondo-correlations — •Rolf Helmes,
Michael Sindel, Laszlo Borda, and Jan von Delft — Sektion
Physik und CeNS, LMU, Theresienstr. 37, 80333 Muenchen
We calculate the recombination spectra of trapped excitons in selfassembled,
optically excited, charge-tunable quantum dots of the type
recently investigated experimentally by R. J. Warburton et al. (Nature
405, 926). If the experimental situation is such that the initial state decays
via exciton recombination into a final state which is a Kondo-state
with strong correlations between the electrons in the dot and those in the
semiconductor, the Kondo-effect should be visible in the recombination
spectrum. We use Wilson’s numerical renormalization group method to
calculate this spectrum. Depending on the numbers of electrons in the
charge-tunable quantum dot, we find an unusual dip in the Kondo-peak
of the spectrum.
TT 16.7 Di 18:15 H19
NRG study of the Kondo effect in the presence of itinerantelectron
ferromagnetism — •M. Sindel 1 , J. Martinek 2 , L.
Borda 1 , J. Barnas 3 , J. König 2 , G. Schön 2 , and J. von Delft 1
— 1 LMU Muenchen — 2 U Karlsruhe — 3 U Poznan, Polen
The successful observation of the Kondo effect in molecular quantum
dots (QDs) like carbon nanotubes and single molecules attached to metallic
electrodes opened the possibility to study the influence of many-body
correlations in the leads (superconductivity or ferromagnetism) on the
Kondo effect. The Kondo effect in QDs - artificial magnetic impurities
- attached to ferromagnetic leads is studied with the numerical renormalization
group (NRG) method. Here we adapt this method to the
case of a QD coupled to ferromagnetic leads with parallel magnetization
directions. It is shown that the QD level is spin-split due to presence
of ferromagnetic electrodes, leading to a suppression of the Kondo effect.
The resulting splitting of the Kondo resonance is similar to the
usual magnetic-field-induced splitting. We find that this splitting can
be fully compensated by an appropriately tuned external magnetic field
and thus the Kondo effect can be restored, confirming a recent prediction.
Although the resulting Kondo resonance then has an unusual spin
asymmetry with a reduced Kondo temperature, the ground state is still
a locally-screened state, describable by Fermi liquid theory and a generalized
Friedel sum rule, and transport in the unitary limit is not spin
dependent.
TT 16.8 Di 18:30 H19
Exact ground states of Anderson models with assisted hopping
— •Marcus Kollar and Florian Schütz — Institut für Theoretische
Physik, Universität Frankfurt, Robert-Mayer-Str. 8, 60054 Frankfurt/Main
Due to the Coulomb interaction the hopping amplitude for an electron
into and out of a quantum dot depends on the presence of an oppositespin
electron in the dot, leading to a description in terms of an Anderson
impurity model with assisted hopping [1]. Here we show that the application
of a local correlator to an uncorrelated state yields the exact ground
state for certain parametrizations of this model. We discuss possible valence
regimes and calculate the impurity spectral function using a set of
variational excited states.
[1] F. Guinea, Phys. Rev. B 67, 195104 (2003).
TT 16.9 Di 18:45 H19
Finite-size effects in an ultrasmall Kondo quantum box —
•Thomas Hand, Hans Kroha, and Hartmut Monien — Physikalisches
Institut, Universität Bonn
We investigate the correlation effects induced by a Kondo impurity
embedded in such a quantum box, using as a model a one-dimensional
tight-binding band with a finite number of lattice sites which is coupled
to an Anderson impurity. The model is solved by means of the density
matrix renormalization group (DMRG) including the Lanczos method as
well as the correction vector method. We examined systems with more
than 500 sites and kept 2600 states. We define the Kondo temperature
TK for the case of a discrete conduction electron density of states (level
spacing ∆E). The strength of the correlations, indicated by the weight of
the Kondo resonance, W, is determined by the local conduction density
of states at the impurity site, x0. Hence, in addition to the even/odd
effect predicted in [1], W depends both on the symmetry of the conduction
electron wave function at the Fermi edge, Ψ0(x), and on the impurity
position x0. We also investigate the crossover to the continuum limit.
[1] W. B. Thimm, J. Kroha, and J. v. Delft, Phys. Rev. Lett. 82, 2143
(1999).
TT 17 Postersitzung II: Transport, Quantenkohärenz, Quantenflüssigkeiten
Zeit: Dienstag 14:30–19:00 Raum: Poster A
TT 17.1 Di 14:30 Poster A
Charge transport through a two-site system driven by a highfrequency
field — •Michael Straß, Jörg Lehmann, Sébastien
Camalet, Sigmund Kohler, Gerd-Ludwig Ingold, and Peter
Hänggi — Institut für Physik, Universität Augsburg
We study the transport properties of a two-site system driven by an
external oscillating field. Possible experimental realizations are molecular
wires in laser fields or coupled quantum dots exposed to microwave
radiation. The current and the associated noise are computed within
a high-frequency approximation in which the time-dependent system is
mapped to a static one described by renormalized, effective parameters
that depend on the driving frequency and amplitude [1]. This allows for
an illustrative explanation of the characteristic dips in the noise characterized
by the Fano factor.
We compare our analytic results of the Fano factor with an exact numeric
solution obtained by a Floquet approach [2]. The external field
allows to switch between three qualitatively different situations: either
transport through a tunnel contact, a two-barrier setup or a open channel.
Therefore tunning the field permits a control of the transport properties
of two-site systems in molecular electronic devices.
[1] S. Kohler, S. Camalet, M. Strass, J. Lehmann, G.-L. Ingold, and
P. Hänggi, Chem. Phys. (in press), cond-mat/0306704.
[2] S. Camalet, J. Lehmann, S. Kohler, and P. Hänggi,
Phys. Rev. Lett. 90, 210602 (2003).
TT 17.2 Di 14:30 Poster A
Laser driven electronic transport through molecular wires
in the presence of electron-phonon interaction — •Jörg
Lehmann 1 , Sigmund Kohler 1 , Volkhard May 2 , and Peter
Hänggi 1 — 1 Institut für Physik, Universität Augsburg — 2 Institut für
Physik, Humboldt Universität zu Berlin
Recently, possibilities of laser control of electric currents through
molecular wires have been investigated [1-2]. So far, these theoretical
studies have neglected the influence of a coupling of the wire electrons
to vibrational modes of the molecule itself and its surroundings, thereby
assuming a fully coherent transport through the molecular wire.
Here, we put forward a quantum Boltzmann equation approach in the
Floquet basis. This approach allows to take into account exactly the coherent
dynamics in the presence of an arbitrarily strong time-periodic
field, while describing the influence of a weak coupling of the wire to
its environment comprised of electronic leads and phononic degrees of
freedom within a mean-field approximation.
As exemplary application of our formalism, we study the influence of
electron-phonon interaction on the generation of a directed current in the
absence of a mean external bias, i.e. a molecular electron pump.
[1] J. Lehmann, S. Kohler, P. Hänggi, and A. Nitzan, Phys. Rev. Lett. 88,
228305 (2002).
[2] J. Lehmann, S. Camalet, S. Kohler und P. Hänggi, Chem. Phys.
Lett. 368, 282 (2003).

Tiefe Temperaturen Dienstag
TT 17.3 Di 14:30 Poster A
Green’s functions method for modelling the interplay between
Coulomb blockade and Andreev reflection — •Ursula Schröter
— FB Physik, Universität Konstanz, Universitätsstraße 10, 78457 Konstanz
We want to investigate charge transport across a superconducting island
which is coupled to two superconducting reservoirs and whose potential
is adjustable via a gate. In single-electron-transistor structures
with weak coupling single electron tunneling is the dominant process
and Coulomb blockade occurs. For superconducting materials multiple
Andreev reflection (MAR) is also possible resulting in the transfer of
several elementary charges in one process. With transmissions for the
junctions no longer much smaller than one, as are found in mechanically
controllable break junctions [1], these higher order processes give subgap
contributions to the IV-characteristics. We regard two junctions in
series, at least one of which has a fairly high transmission. The question
is whether or not the MAR contribution to the current will be suppressed
because of Coulomb blockade. Based upon an algorithm for a single junction
[2] in a first ansatz we regard the two junctions as decoupled from
one another but for the charging state of the island. A second ansatz
shall include possible coherence over the entire structure. The two contacts
are treated as two ’perturbations’ by folding Green’s functions into
one another [3].
[1] E.Scheer et al., Nature 394, 154 (1998).
[2] J.C.Cuevas et al., Phys.Rev.B 54, 7366 (1996).
[3] U.Schröter, EPJ B 33, 297 (2003).
TT 17.4 Di 14:30 Poster A
Superconducting SETs in a Dissipative Environment: the JQP-
Cycle — •Konstanze Jähne and Frank Wilhelm — Lehrstuhl für
Theoretische Festkörperphysik, Sektion Physik der Universität München,
Theresienstr. 37, 80333 München
The properties of a mesoscopic device in the quantum limit are strongly
influenced by its electromagnetic environment, which destroys quantum
coherence and induces energy relaxation. We investigate the Josephsonquasiparticle
(JQP) process in a superconducting single-electron transistor
(SET), which is coupled to a controllable electromagnetic environment.
By using the P(E)-theory, we calculate transition rates for the
tunneling electrons and Cooper pairs and investigate the impact of the
environment on the transport through the device. This will be compared
with an experiment by A. Rimberg et al. The JQP process has an important
application in the read out of charge quantum bits.
TT 17.5 Di 14:30 Poster A
Preparation and Characterization of Magnetic Single Electron
Transistors — •Jürgen Schuler, Heribert Knoglinger, Josef
Höß, Christian Probst, Karl Neumaier, Achim Marx, and
Rudolf Gross — Walther-Meissner-Institut, Bayerische Akademie der
Wissenschaften, Walther-Meissner Straße 8, 85748 Garching
We have developed a process to fabricate ferromagnetic single electron
transistors (SET) based on the Al/Al2O3-tunnel junction technique and
the shadow evaporation technique. With this process we were able to fabricate
SETs with either the island or the leads made of nickel. The goal
of this work is to realize a device, which gives access to both controllable
single charging and magnetoresistive effects.
Apart from a short overview on the preparation and the measurement
setup developed in this work, we will show the characterization of the
devices in magnetic field up to 2 T in the normal conducting state. We
will compare several methods to determine the key parameters of the
device in the normal conducting state including numerical simulations in
the framework of the orthodox theory.
Based on our measurements in the superconducting regime at low magnetic
fields we will discuss the potential of these devices. Furthermore,
we discuss the abilities and the limits of the preparation techniques used
in this work.
TT 17.6 Di 14:30 Poster A
Coulomb blockade in benzol-dithiol: DFT calculations — •M.
Koentopp, F. Evers, and F. Weigend — Institut für Nanotechnologie,
Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany
For the development of future molecular-electronics devices an important
prerequisite is the ability to realize molecular switches, i.e. changing
the conductance properties of a molecule in a controlled fashion. A major
recent achievement has been the observation of Coulomb blockade in
single organic molecules by applying a gate voltage (S. Kubatkin et al.,
Nature 425, 698-701 (2003)).
Here, we report theoretical calculations on the Coulomb blockade for a
paradigmatic system, namely the molecule 1,4 benzol-dithiol. We use the
nonequilibrium Green’s function formalism in combination with density
functional calculations with the program package TURBOMOLE. The
number of atoms in the simulated electrodes is large enough to ensure
that Fermi level mismatch does not occur. The gate is realized by point
charges distributed homogenously on a square grid in a plane parallel to
the C-atoms. Charging effects are included in a manner that in principle
is exact. Screening of the gate by the electrodes (charge neutrality) is
thereby taken fully into account.
We observe the expected shift of the transmission resonances with increasing
gate voltage. These shifting levels lead to spikes in the transmission
when they cross the Fermi energy.
TT 17.7 Di 14:30 Poster A
Computersimulations of electronic charge transport in
nanowires — •Markus Dreher and Peter Nielaba — Lehrstuhl
für Theoretische Physik, Fachbereich Physik, Universität Konstanz,
D-78457 Konstanz, collaboration with Jan Heurich and Carlos Cuevas
(Universität Karlsruhe)
With a molecular dynamic simulation we calculated the structure of
gold nanocontacts which were pulled apart [1]. In order to prevent heating
up the system during the stretching process we established a Nosé-Hoover
thermostat. The gold atoms are interacting via an effective-mediumtheory-potential
incorporating many body effects [2]. The formation of
single atom chains was observed.
In cooperation with Heurich and Cuevas, who developed -by using a
tight-binding-model and Green function techniques- a program for the
current through a nanocontact, conductivity curves (in different channels)
have been determined and are in good agreement with the experimental
data [1].
The conductance is not totally determined by the atoms of the constriction,
but also by atom rearrangements in the vicinity of the constriction.
[1] M. Dreher, Diplomarbeit, Konstanz, 2002
[2] K. Jacobsen et al., A semi-empirical effective medium theory for metals
and alloys, Surface Science, 366, 394 (1996)
TT 17.8 Di 14:30 Poster A
Transport properties of single-atom contacts of zinc — •P.
Konrad 1 , P. Brenner 2 , A. Mayer-Gindner 2 , H. v. Löhneysen 2 ,
and E. Scheer 1 — 1 Physics Department, University of Konstanz —
2 Institute of Physics, Physics Department, University of Karlsruhe
We report low-temperature measurements of the electrical transport
properties of single-atom zinc contacts fabricated by different variations
of the mechanically-controllable breakjunction technique, including the
notched-wire method [1], the lithographic method [2], and using whiskers.
From investigations of the statistical behavior in the normalconducting
state as well as from the analysis of individual contacts in the superconducting
state we find indications for the presence of preferred atomic
configurations. In particular there exist contacts with a single, well transmitted
transport channel.
In lithographic breakjunctions made of thin films we find nonlinearities
in the current-voltage characteristics that we attribute to Coulomb
blockade due to the granular structure of the film. These latter findings
are in qualitative agreement with a recent prediction by Avishai et al.
[3].
[1] C. Muller, J. M. van Ruitenbeek and J. L. de Jongh, Physica C191,
485 (1992)
[2] J. M. van Ruitenbeek et al., Rev. Sci. Instrum. 67, 108 (1996)
[3] Y. Avishai, A. Golub and A. D. Zaikin, Europhys. Lett. 54, 640 (2001)
TT 17.9 Di 14:30 Poster A
Wechselwirkungseffekte in kleinen Quantenpunkten —
•Stephan Weiß, Boris Reusch und Reinhold Egger — Institut
für Theoretische Physik IV, Heinrich-Heine-Universität Düsseldorf,
40225 Düsseldorf
Wir untersuchen Wechelwirkungseffekte in kleinen Quantenpunkten
(ne ≤ 10) mit Hilfe der Pfad-Integral-Monte-Carlo-Methode (PIMC).
Das Verhalten der Elektronen im Quantenpunkt wird wesentlich
durch Kopplungsparameter, z.B. den Brücknerparameters rs, sowie
die Spin-Bahn-Wechselwirkung αr, bestimmt. Bei festem Gesamtspin
des Systems, ist es möglich den Übergang von Fermi-Flüssigkeit zur
Wigner-Kristallisation zu verstehen [1][2]. Spin-Bahn-Effekte werden
durch Berücksichtigung des Rashba-Kopplungsterms beschrieben [3].

Tiefe Temperaturen Dienstag
[1] R. Egger, W. Häusler, C.H. Mak and H. Grabert, Phys. Rev. Lett 82,
3320 (1998)
[2] B. Reusch, R. Egger, Europhysics Letters, 64, 84 (2003)
[3] M. Governale, Phys. Rev. Lett 89, 206802 (2002)
TT 17.10 Di 14:30 Poster A
Conductance Measurements on Ferromagnetic Breakjunctions
— •C. Bacca , R. Arnold, and E. Scheer — Department of Physics,
University of Konstanz
We investigate lithographically fabricated breakjunctions of ferromagnetic
(Co,Ni) nanobridges with or without superconducting leads (Al).
With the help of a three-point bending mechanism, the bridges can be
opened to a single-atom contact, broken to a vacuum-tunnel contact and
closed again repeatedly at low temperatures. As reported for nonmagnetic
materials [1] we observe steps in the conductance that are due to
atomic rearrangements in the contact region. From the opening and closing
curves with and without magnetic field we calculate conductance
histograms in order to determine the preferred conductance values. We
do not find indications of maxima at half-integer conductance quanta
e 2 /h. The latter is often assumed to give indications for the existence of
spin-polarized conductance channels.
We observe very high magnetoconductance effects up to 150% for
single-atom or 500% tunnel contacts in magnetic fields up to 5 T. However
the details of the magnetoconductance curves are not very reproducible.
[1] J.M. Krans et al. Nature 375, 767 (1995)
TT 17.11 Di 14:30 Poster A
Aharonov-Bohm-Oszillationen in mesoskopischen metallischen
Ringen: Einfluss magnetischer Verunreinigungen
und eines inhomogenen Magnetfelds — R. Häussler 1 , H. v.
Löhneysen 1,2 , C. Paschke 1 , H. B. Weber 3 und E. Scheer 4 —
1 Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe —
2 Forschungszentrum Karlsruhe, Institut für Festkörperphysik, 76344
Karlsruhe — 3 Forschungszentrum Karlsruhe, Institut für Nanotechnologie,
76344 Karlsruhe — 4 Fachbereich Physik, Universität Konstanz,
78457 Konstanz
Wir berichten über Oszillationen des Magnetleitwerts als Funktion eines
äußeren Magnetfelds (Aharonov-Bohm-Oszillationen) in Cu-Ringen
mit Durchmesser von etwa 1µm und Stegbreite von etwa 80nm. Eine
mit 640pm Mn dotierte Probe zeigt eine klare Signatur von h/e-
Oszillationen, die jedoch einer Leitwertänderung von nur etwa ∆G =
2 · 10 −4 e 2 /h entsprechen gegenüber ∆G = 5 · 10 −2 e 2 /h für reine Cu-
Proben ähnlicher Geometrie. Aufbringen eines ferromagnetischen Kerns
aus Dy (Durchmesser 1µm) direkt oberhalb des Cu-Rings (durch eine
30nm dicke SiO2- Schicht von diesem separiert) erzeugt ein inhomogenes
radiales Magnetfeld in der Ebene des Cu-Rings. Wir diskutieren
die Möglichkeit einer dadurch hervorgerufenen Berry-Phase in den
Aharonov-Bohm-Oszillationen.
TT 17.12 Di 14:30 Poster A
Transmission Coefficients for Oscillating Barriers — •Mario Fischer,
Frank Grossmann und Thomas Kunert — Techn. Univ.
Dresden, Inst. f. Theor. Physik, 01062 Dresden
Hamiltonians with localized oscillating potentials serve as model systems
for break junctions and lead-molecule-lead systems in laser fields.
Because for this class of Hamiltonians energy is not conserved and absorption
resp. emission of photons occurs, the definition of transmission
coefficients is not straightforward. For those Hamiltonians a new numerical
approach to define and calculate transmission coefficients is presented.
By perfoming a limited amount of wave packet propagations the
transmission coefficients for all interesting energies and photon exchange
numbers can be obtained. Using this approach basic phenoma as the rectification
of current through molecules [ 1 ] can be examined.
[ 1 ] J. Lehmann, S. Kohler, P. Hänggi, J. Chem. Phys. 118, 3283 (2002)
TT 17.13 Di 14:30 Poster A
Einfluss von Laserlicht auf den Stromtransport zwischen zwei
Metallspitzen — •Daniel Schmidt, Paul Leiderer und Elke
Scheer — Universität Konstanz, Universitätsstraße 10, 78457 Konstanz
Wir untersuchen die Auswirkungen von Laserlicht verschiedener Wellenlängen
auf den elektronischen Transport in mechanisch kontrollierten
Bruchkontakten. Dabei soll der Einfluss der Polarisation des Lichts
berücksichtigt, sowie Effekte der Gleichrichtung untersucht werden.
Auf Grund ihrer Abmessungen sind die Metallspitzen des Bruchkontakts
auch optische Antennen. Diese Eigenschaft besser zu verstehen, ist ein
weiteres Ziel unseres Experiments.
TT 17.14 Di 14:30 Poster A
Conductance properties of single-molecule junctions under
pulsed laser illumination — •J. U. Würfel 1 , S. Dantscher 2 , C.
Kennerknecht 2 , W. Pfeiffer 2 , S. Schramm 2 , and H. B. Weber 1
— 1 Forschungszentrum Karlsruhe, Institut für Nanotechnologie, PO-Box
3640, D-76021 Karlsruhe — 2 Physikalisches Institut EP1, Universität
Würzburg, Am Hubland, D-97074 Würzburg
We investigate electron transport properties of single-molecule junctions,
formed by the mechanically-controlled break-junction technique.
Recent experiments demonstrated that we are able to contact single
molecules [1]. Here, we report on measurements carried out under illumination
with a femtosecond TiSa laser system. We observe a photoinduced
enlargement of the conductance. As possible mechanism a thermally
induced diminishment of the contact distance is discussed and contrasted
to a picture of photo-excited electrons in the leads. When diodelike
molecules are used, different photo-induced conductance changes for
positive and negative bias voltage are observed.
[1] Phys. Rev. Lett., 88, 176804 (2002)
TT 17.15 Di 14:30 Poster A
Conductance fluctuations in nonequilibrium — •Thomas Ludwig
1,2 , Alexander Mirlin 1,2 , and Yaroslav Blanter 3 — 1 Institut
für Nanotechnologie, Forschungszentrum Karlsruhe, 76021 Karlsruhe,
Germany — 2 Institut für Theorie der Kondensierten Materie, Universität
Karlsruhe, 76128 Karlsruhe, Germany — 3 Department of NanoScience,
Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
We investigate the amplitude of mesoscopic fluctuations of the differential
conductance of a metallic wire at arbitrary bias voltage. We identify
the parameter regime where inelastic scattering is important. In the
noninteracting case we show quantitative results for T = 0, in the interacting
case we qualitatively identify the asymptotic behaviour. We show
that, due to inelastic scattering, conductance fluctuations cannot grow
with increasing voltage in a way that would lead to negative differential
resistance.
TT 17.16 Di 14:30 Poster A
Spin Hall Effect in paramagnetic Metal — •Christian Debuschewitz,
Sergio O. Valenzuela, and Michael Tinkham —
Department of Physics Gordon McKay Laboratory, Harvard University
When a current is circulating in a paramagnetic metal, electrons with
spin up and spin down are predicted to separate due to skew scattering
[1]. The generated spin imbalance results in a spin Hall voltage which
can be measured by attaching a ferromagnet, perependicular to the current
on one side of a gold wire [2]. By changing the magnetization of the
ferromagnet, we observed a voltage difference of ≈ 100 nV.
[1] J. E. Hirsch PRL 83, 1834 (1999)
[2] S. Zhang PRL 85, 393 (2000)
TT 17.17 Di 14:30 Poster A
Quantum holonomies with Josephson-junction devices
— •Mateusz Cholascinski — Institut für Theoretische
Festkörperphysik, Universität Karlsruhe, D-76128 Karlsruhe, Germany
— Nonlinear Optics Division, Adam Mickiewicz University, 61614
Poznan, Poland
We examine properties of a Josephson-junction system composed of
two coupled Cooper-pair boxes (charge qubits) as a candidate for observation
of quantum holonomies. We construct a universal set of transformations
in a two-fold degenerate ground state, and discuss the effects of
noise in the system. The cheme can be applied to any system of two coupled
qubits (independently of physical realization) provided the number
of tunable parameters is sufficiently large.
TT 17.18 Di 14:30 Poster A
Compensation of telegraph noise decoherence by means of
bang-bang control — •Henryk Gutmann 1 , William Kaminsky 2 ,
Seth Lloyd 3 , and Frank Wilhelm 1 — 1 Sektion Physik and CeNS,
LMU, 80333 München — 2 Department of Physics, MIT, Cambridge,
Mass. 02139 — 3 Department of Mechanical Engineering, MIT, Cambridge,
Mass. 02139
With growing success in isolating solid-state qubits from external noise
sources the origins of decoherence inherent to the material start to play a

Tiefe Temperaturen Dienstag
relevant role. Prominent examples were charged impurities in the disordered
substrate of a Josephson qubit which produce typically telegraph
noise. In order to demonstrate the possibility of the active suppression
of the disturbance from a single fluctuator, we theoretically implement
an elementary bang-bang control protocol. We numerically simulate the
appearing random walk on the Bloch sphere with and without bang-bang
control and compare it with analytical results found by use of appropriate
Langevin equations in the long-time limit. Hereby we find out, that
the bang-bang control mechanism mostly compensates the slow noise,
which indicates, how the influence of 1/f-noise ubiquitous to the solidstate
world could be reduced. We also derive two generic and analytically
solvable random walk models to describe imperfect pulses and evaluate
the impact of these aberrations on the qubit.
TT 17.19 Di 14:30 Poster A
Periodically controlled qubit system coupled to an environment
— •Marcus Stollsteimer und Günter Mahler — Universität
Stuttgart, Institut für Theoretische Physik 1, Pfaffenwaldring 57,
D-70550 Stuttgart
We study the Schrödinger dynamics of a small system of coupled spin-
1/2 particles (qubits) which is subject to periodic external parameter
control (Floquet-type system). This system proper is coupled to another
quantum system that acts as environment or ”bath” (no bath approximations
are made).
When the control is switched off, the system relaxes into an equilibrium
state (except for finite size effects); for non-zero control the system
reaches a different ”quasi-equilibrium” state. We are interested on properties
of this new equilibrium state, and how they can be manipulated
by the external control.
TT 17.20 Di 14:30 Poster A
Superconducting flux qubits — •Heribert Knoglinger, Jürgen
Schuler, Chiara Coppi, Matteo Mariantoni, Georg Wild,
Christian Probst, Achim Marx, and Rudolf Gross — Walther-
Meissner-Institut für Tieftemperaturforschung der Bayerische Akademie
der Wissenschaften, 85748 Garching
Superconducting quantum bits (qubits) based on Josephson junctions
where the Josephson coupling energy is larger than the charging energy
are usually called flux qubits. Starting from our well-established technology
used for fabricating single charge transistors based on Al/Al2O3
tunnel junctions we have developed a modified process for fabricating
Josephson junctions and superconducting qubit structures. We have used
this process to produce and characterize different flux qubit structures.
We discuss different design variants for flux qubits and give a short
overview of the process technology. Measurements on various test structures
(Josephson junctions, SQUIDs, qubits) are used to analyze and further
optimize the system parameters and to compare the different qubit
variants. The measurement results and the limits of our technology are
the basis for a discussion of the usefulness of the individual elements to
realize superconducting qubits.
TT 17.21 Di 14:30 Poster A
Superconducting Qubits: Experimental setup for electrical
characterization — •Chiara Coppi, Georg Wild, Heribert
Knoglinger, Matteo Mariantoni, Jürgen Schuler, Christian
Probst, Achim Marx, and Rudolf Gross — Walther-Meissner-
Institut für Tieftemperaturforschung der Bayerischen Akademie der
Wissenschaften, 85748 Garching, Germany
An experimental setup for electrical characterization of superconducting
flux Qubits has been established. The setup consists of a 3 He/ 4 He
dilution refrigerator and a specially designed sample housing which provides
shielding against environmental electromagnetic radiation. Special
attention has been paid on filtering the wiring of the sample (wire-inpowder
filters at base temperature, low-pass filters at room temperature).
Magnetic shielding of the samples is obtained using cryoperm and double
µ- metal shields. The whole setup is placed in a high frequency shielded
room.
The setup has been used for measurements of switching current distributions
on low-TC Josephson junctions to evaluate the measurement
setup, the filtering, and the shielding. The temperature dependence of
the escape temperature, determined from the switching current distributions,
is compared to the theoretical predictions of thermal escape and
macroscopic quantum tunneling.
TT 17.22 Di 14:30 Poster A
Scaleable single-spin based quantum processor — •Michael
Domhan, Torsten Gaebel, Iulian Popa, Achim Gruber, Fedor
Jelezko, and Jörg Wrachtrup — Universität Stuttgart, 3.
Physikalisches Institut, Pfaffenwaldring 57, 70550 Stuttgart
Readout and manipulation of the single spin states are crucial basics
for spin-based quantum information processing. As formerly shown optically
detected magnetic resonance (ODMR) techniques can be used to
investigate single paramagnetic nitrogen-vacancy (N-V) defect centers
in diamonds. As two-qubit operations on single NV-defect centers have
also been performed, the effort will now be concentrated on coupling single
spins between NV-centers. Potential scemes for scaling-up single-spin
based quantum processor are presented.
TT 17.23 Di 14:30 Poster A
Characterization of qubits based on current-biased Josephson
junctions — •J. Lisenfeld 1 , C. Coqui 1 , A. Kemp 1 ,
A. Lukashenko 1 , A. Wallraff 2 , and A.V. Ustinov 1 —
1 Physikalisches Institut III, Universität Erlangen-Nürnberg, 91058
Erlangen, Germany — 2 Dept. Applied Physics, Yale University, New
Haven, CT 06520, USA
The discrete energy levels of small current-biased Josephson junctions
can be used as logical states for quantum computation [1]. Using microwave
spectroscopy, we characterize both the level spacing and their
dissipation-limited lifetimes. We report the observation of multi-photon
transitions [2] between levels at photon energies being integer fractions of
the transition energy, as it is expected for an anharmonic oscillator. For a
capacitively coupled two-junction system, which we currently study, entangled
macroscopic quantum states should be observable using the same
technique. Our experimental results available to date will be presented.
[1] J.M. Martinis et. al., Phys. Rev. Lett. 89, 117901 (2002)
[2] A. Wallraff et. al., Phys. Rev. Lett. 90, 037003 (2003)
TT 17.24 Di 14:30 Poster A
Coherent and incoherent motion in spin-boson systems —
•Wolfgang Pfersich and Walter T. Strunz — Albert-Ludwigs-
Universität Freiburg, Physikalisches Institut, Hermann-Herder-St. 3,
79104 Freiburg, Germany
We investigate the non-Markovian dynamics of the spin-boson system.
Our approach is based on ’quantum paths’ widely used in quantum optics.
We use an expansion in the coupling strength for the non-Markovian
stochastic Schrödinger equation based on Heisenberg’s equation of motion.
We have a special interest in the evolution of the reduced system for
short times compared to the correlation time of the bath and the decay
of the coherence.
Therefore we solve numerically the second and fourth order equation
of motion for the stochastic wave function of the reduced system.
TT 17.25 Di 14:30 Poster A
Microwave spectroscopy of long Josephson junctions in the
quantum regime — •A. Kemp 1 , A. Lukashenko 1 , Y. Koval 1 , J.
Lisenfeld 1 , M.V. Fistul 1 , A. Wallraff 2 , and A.V. Ustinov 1 —
1 Physikalisches Institut III, Universität Erlangen-Nürnberg, 91058 Erlangen,
Germany — 2 Dept. Applied Physics, Yale University, New Haven,
CT 06520, USA
We experimentally investigate the quantum escape of the phase in fluxfree
narrow annular Josephson junctions under influence of microwaves.
A measurement technique developed earlier [1] based on ramp-type measurements
enables us to resolve the populations of the ground state and
the first excited state. We probe the level structure of the junction with
small magnetic fields applied and at currents close to the fluctuation-free
critical current. The data obtained are compared to the theory [2] describing
the escape as dissociation of a vortex-antivortex pair and predicting
the specific scaling of the energy level spacing with the bias current. A
rather good agreement is found, while the detailed behavior of the observed
resonances leaves few open questions.
[1] A. Wallraff et al., Rev. Sci. Inst. 74, 3740 (2003)
[2] M.V. Fistul et al., to appear in Phys.Rev.Lett. (cond-mat/0307705)
TT 17.26 Di 14:30 Poster A
2-Qubit quantum gate with single spins in a solid state system —
•Achim Gruber, Michael Domhan, Thorsten Gaebel, Iulian
Popa, Fedor Jelezko, and Jög Wrachtrup — 3. Physikalische Institut,
Universität Stuttgart, 70550 Stuttgart, Germany

Tiefe Temperaturen Dienstag
The preparation, manipulation and detection of single spin states are
the essential prerequisites for spin based quantum computation. The coupling
of a single C13 spin (I=1/2) to the ground state triplet spin (S=1)
of a single nitrogen-vacancy defect center (NV-center)in diamond forms a
single 2-qubit system. The joint approach of single molecule spectroscopy
and optically detected magnetic resonance (ODMR) allows to detect optically
individual NV-centers and to manipulate the spin subsystem of
the defect.
Coherent oscillations of the triplet spin in a single NV-Center have
been detected. Further pulsed ODMR sequences, derived from optical
detected electron nuclear double resonance experiments, allows the coherent
control of the coupled spin states. As a first quantum computation
operation the conditional rotation gate (CROT) has been implemented.
The poster presents the measurements and discusses the limitations due
to coherence decay.
TT 17.27 Di 14:30 Poster A
Towards an Autonomous Quantum Thermodyamic Machine —
•Friedemann Tonner und Günter Mahler — Institut für Theoretische
Physik 1, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart
On a fundamental level thermodynamic machines necessarily consist of
quantum mechanical parts. Here we address quantum mechanical analogs
to each functional part of a thermodynamic machine. Thus we construct
time-independent Hamiltonians for the gas system, the work variable and
the control system responsible for driving the thermodynamic process,
normally controlled from the outside. Baths are dealt with in Markov
approximation.
We are interested not in quantum mechanical modeling of existing
(classical) machines, but rather in exploring the small system (quantum)
limit: how small can a machine be made to still exhibit machine functions?
TT 17.28 Di 14:30 Poster A
Schrödinger-dynamics of a spin-chain in contact with a quantum
environment — •Markus Henrich, Michael Hartmann, Mathias
Michel, and Günter Mahler — Institut für Theoretische Physik
1, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart
We study the exact Schrödinger-dynamics of a spin-chain with nearestneighbour
interaction coupled to a finite quantum environment. The relaxation
behavior of the spin-chain is analyzed for two coupling topologies;
1. all spins are directly coupled to the environment, 2. only one
edge of the spin-chain is coupled to the environment. Various coupling
strengths between the spins as well as various initial states are considered.
We then analyze the conditions under which a thermodynamical
description should become appropriate for the entire spin-system or even
for the induvidual spins.
TT 17.29 Di 14:30 Poster A
Viscous Transport in Dirty Fermi Superfluids — •Dietrich
Einzel 1 and Jeevak M. Parpia 2 — 1 Walther-Meissner-Institut, Bayerische
Akademie der Wissenschaften, 85748 Garching — 2 Dept. of
Physics, Cornell University, Ithaca, NY 14853, USA
The transport theory of clean Fermi superfluids like 3 He–A,B is generalized
to include strong elastic scattering from impurities represented by
a system of low density silica arogel strands. The dynamics of the aerogel
system is taken into account within a collision–drag model. In particular,
we calculate for the first time the viscosity of superfluid 3 He–B in the
presence of impurity scattering both in the Born and the unitary limit.
The shear viscosity dominates the attenuation of transverse sound, the
general dispersion relation of which is also provided by our theory. The
observability of the shear viscosity is discussed in context with recent
torsional oscillator experiments.
TT 17.30 Di 14:30 Poster A
Pressure Driven 3 He Flow Through Submicron Sized Apertures
— •S.V. Pereverzev and G. Eska — Physikalisches Institut, Universität
Bayreuth
The flow of liquid 3 He through two different weak link structures was
investigated at temperatures of T< 1 mK to 1 K by measuring the characteristic
time τ which was needed for pressure equilibration between
two volumes connected by the weak links. For the flow through a regular
structure of 65x65 holes of 150 nm dia. in a 50 nm thick SiN membrane
we observed the expected T-dependence and the transition from Knudsen
to viscous flow behavior. To the contrary, no T-dependence was found for
normal fluid 3 He-flow through 10 5 holes of 15 nm diameter, statistically
distributed over a 14 nm thick nitrocellulose film. Below the superfluid
transition the relaxation rate (1/τ ∼flow-channel conductance) increased
by orders of magnitude for both types of weak links. Our data are in qualitative
agreement with experiments by other groups. We present a model
which describes our normal flow results quantitatively for the 150 nm
aperture, but which does not explain the flow through the 15 nm holes.
TT 17.31 Di 14:30 Poster A
Light propagation and random lasing — •Andreas Lubatsch
and Hans Kroha — Physikalisches Institut, Universitaet Bonn
We present caculations and numerical results for light propagation in
disordered media. We consider vector waves passing through a system
of randomly distributed Mie - scatterers. The scaterers themselves can
consist of optical active media. We present as well results for such systems,
which are known as random lasers. In order to find the results,
we calculated the necessary transport properties including e.g. the exact
Ward Identity and the diffusion constant.
TT 17.32 Di 14:30 Poster A
Channel analysis of electrical conductance through a Zn
single-atom contact — •Michael Häfner, Jan Heurich,
Juan-Carlos Cuevas und Gerd Schön — Institut für Theoretische
Festkörperphysik, Universität Karlsruhe, 76128 Karlsruhe
Today it is possible to manipulate atomic-sized structures in a controlled
way. Special attention is payed to the electronic transport properties
of single-atom contacts. For noble and s-p like metals the conduction is
carried by the s-band (one channel) and the s- and p-bands (up to four
channels) respectively. Scheer et al. have recently measured the conductance
of Zn single-atom contacts. As Zn is intermediate between noble
and s-p like metals it constitutes an excellent testbed for the detailed
study of the interplay between electronic configuration and conduction
properties in this regime.
In this work we present a theoretical analysis of the experiment using
tight binding transport calculations. This approach allows us to show
how the conduction channels arise from the atomic orbitals and elucidate
which specific properties of the individual orbitals determine their
contribution to the current. For the case of Zn single-atom contacts we
find a typical total transmission of ∼ 0.6 in good agreement with the
experiment. In contrast to the noble or s-p like metals, the current is
predominantly carried by two channels which can be related to a combination
of the s and p valence bands of Zn.
TT 18 Supraleitung: Tunneln, Josephson-Kontakte, SQUIDs
Zeit: Mittwoch 14:30–16:30 Raum: H20
TT 18.1 Mi 14:30 H20
Electron tunneling into superconducting MgB2 — •J. Geerk, R.
Schneider, A. Zaitsev, R. Heid, and G. Linker — Forschungszentrum
Karlsruhe, Institut für Festkörperphysik
We have prepared tunnel junctions of the sandwich-type on superconducting
thin films of MgB2. The films were prepared by physical vapor
deposition from an evaporation source for magnesium and a sputtering
source for boron with Tc values near 33 K. The tunnel junctions showed
an energy gap between 2.5 and 3.0 meV and phonon structures in the
reduced density of states with a strength of about 0.8%. The inversion of
the tunnel data using standard single-band Eliashberg equations revealed
an Eliashberg function with 3 distinct peaks at 40, 60 and 90 meV. It can
be deduced that the boron-like phonons (60 and 90 meV) couple about 3
times stronger than the magnesium like phonons (40 meV). The strong
peak due to the E2g-mode near 70 meV which is predicted by several
theoretical calculations could not be detected in the tunnel data.

Tiefe Temperaturen Mittwoch
TT 18.2 Mi 14:45 H20
Experimental Realization of all High-Tc dc π/2-SQUIDs —
•Christof Schneider, German Hammerl, Rainer Held, Klaus
Wiedenmann, and Jochen Mannhart — Experimentalphysik VI,
Universität Augsburg
In the presentation, we will report on the realization of all high-Tc
π/2-SQUIDs. The characteristics of the π/2-SQUIDs, which were fabricated
using YBa2Cu3O7−δ thin films grown on tetracrystalline substrates
will be presented and compared with the properties of standard high-Tc
SQUIDs.
TT 18.3 Mi 15:00 H20
Imaging of Josephson Current Distribution in YBa2Cu3O7-Nb
Zigzag Junctions — •D. Dönitz 1 , E. Goldobin 1 , R. Straub 1 ,
R. Kleiner 1 , D. Koelle 1 , H.J.H. Smilde 2 , Ariando 2 , H.
Hilgenkamp 2 , and H. Rogalla 2 — 1 Universität Tübingen, Physikalisches
Institut – Experimentalphysik II, Auf der Morgenstelle 14,
D-72076 Tübingen, Germany — 2 Low Temperature Division, Faculty of
Science and Technolgoy and MESA+ Research Institute, University of
Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
We used low temperature scanning electron microscopy (LTSEM) to
image the supercurrent distribution in zigzag YBa2Cu3O7 (YBCO)–Nb
ramp edge Josephson junctions. These junctions consist of several artificial
facets of length a ≤ λJ and alternating orientation along the in-plane
crystallographic axes of the YBCO film. At zero applied magnetic field
we clearly observed the reversal of the direction of the Josephson current
flowing through neighboring facets. This is a direct visualization of
the opposite sign of the critical current in neighboring facets, i.e. they
can be considered as 0 and π junctions. This constitutes direct imaging
of the sign change in the phase of the d x 2 −y 2 order parameter symmetry
in YBCO. We performed numerical simulations of the sine–Gordon
model which showed that for our particular geometry the phase profile
along the zigzag junctions corresponds to a compressed chain of antiferromagnetically
ordered semifluxons. At the matching field, for which
the critical current is maximum, the simulations predict a supercurrent
distribution which has the same sign and an arc–like profile in all facets.
This prediction is directly confirmed by LTSEM.
TT 18.4 Mi 15:15 H20
Doping dependence of pseudogap and superconductivity in
electron doped high-temperature-superconductors: results from
tunneling spectroscopy — •B. Welter 1 , L. Alff 1 , Y. Krockenberger
1 , M. Naito 2 , and R. Gross 1 — 1 Walther-Meissner-Institut,
Bayerische Akademie der Wissenschaften, Walther-Meissner-Str. 8, 85748
Garching, Germany — 2 NTT Basic Research Laboratories, Atsugi, Japan
Studying the influence of doping on the characteristics of oxide superconductors
is essential to both the understanding of the underlying
physics and the development of new applications. Here, we report
on tunneling spectroscopy measurements on grain boundary junctions
of electron doped high-temperature superconductors La2−xCexCuO4,
Pr2−xCexCuO4 and Nd2−xCexCuO4 with different Ce concentrations
around optimal doping. We focus on the pronounced depletion in the
density of states near EF observed in the normal state above Bc2 and its
evolution with temperature, magnetic field and doping [1]. Considerations
concerning the conservation of states rule even indicate a coexistence of
this pseudogap regime and the superconducting state.[2]
[1] L. Alff, Y. Krockenberger, B. Welter, M. Schonecke, R. Gross, D.
Manske and M. Naito, Nature 422, 698 (2003)
[2] B. Welter, Y. Krockenberger, L. Alff, M. Naito und R. Gross, to appear
in Physica C
TT 18.5 Mi 15:30 H20
STM structure analysis of bismuth high-TC crystals depending
on the bias voltage — •Hendrik Glowatzki, Torsten Stemmler,
Johannes Zeggel, Alicia Krapf, Christoph Janowitz, and Recardo
Manzke — Institut f. Physik, Humboldt-Universität zu Berlin,
Newtonstr. 15, 12489 Berlin
A detailed structural analysis of single and double layered bismuth
single crystals (BSCCO) has been performed by Scanning Tunneling
Microscopy (STM). Because of the special layered configuration of these
superconductors, containing semiconducting, insulating and the superconducting
metallic layers, we obtain different atomic images depending
on the applied tunneling voltage. In particular, semiconducting layers
will be invisible for bias voltages below its gap energy /1/. So it has
become possible to observe not only the surface layer but also deeper
CuO2-layers which cause high-TC superconductivity. The results can be
understood from the particular crystal structure of BSCCO.
[1] Oda, M. et al. Phys. Rev. B 53, 2253 (1995)
TT 18.6 Mi 15:45 H20
Cavity resonances in Bi2Sr2CaCu2O8 intrinsic Josephson
junction stacks under low frequency microwave irradiation —
•Tobias Clauss, Takashi Uchida, Michael Mößle, Dieter
Koelle, and Reinhold Kleiner — Universität Tübingen, Physikalisches
Institut - Experimentalphysik II, Auf der Morgenstelle 14, 72076
Tübingen
One important problem towards the realization of THz oscillators from
intrinsic Josephson junction stacks is to make the junctions in the stack
to oscillate in-phase. One possibility to generate such oscillations is to
excite cavity resonances by collective motion of Josephson fluxons in the
stack.
So far, cavity resonances have only been observed for Bi2Sr2CaCu2O8
stacks at high external magnetic fields. We have investigated single crystal
Bi2Sr2CaCu2O8 stacks at zero magnetic field under microwave irradiation
with frequencies between 2 and 25 GHz. Measured current voltage
characteristics show structures which can be attributed to cavity resonances.
Using low temperature scanning electron microscopy to image
the current distribution in the stack we find clear cavity resonances with
wavelengths of some µm. We believe that the resonances are excited by
the collective motion of vortex-antivortex pairs generated by the external
microwave field.
TT 18.7 Mi 16:00 H20
Intrinsic Josephson Effects in RuSr2GdCu2O8 — •Timo Nachtrab
1 , D. Koelle 1 , R. Kleiner 1 , C. T. Lin 2 , and C. Bernhard 2
— 1 Universität Tübingen, Physikalisches Institut -Experimentalphysik
II, Auf der Morgenstelle 14, 72076 Tübingen, Germany — 2 Max-Planck-
Institut für Festkörperforschung, Heisenbergstrasse 1, 70569 Stuttgart,
Germany
We report on electrical transport measurements on single crystals of
RuSr2GdCu2O8(Ru1212). The material shows coexistence of magnetic
ordering (Tm ≈ 130 K) and superconductivity (Tc ≈ 55 K) at low temperatures.
The crystal structure consists of alternating RuO2 layers (with
a weak ferromagnetic (F) component in-plane) and superconducting (S)
CuO2 layers, separated by insulating (I) layers of SrO. Ru1212 thus forms
an intrinsic SIFIS multilayer structure. For transport perpendicular to
the planes an intrinsic Josephson effect as, e.g., in Bi2Sr2CaCu2O8+δ
(Bi2212) has been predicted. In addition, the magnetic component inside
the barrier might provoke interesting phenomena like π-phases in
the superconducting order parameter.
We measured the interlayer current transport in micron-sized Ru1212
single crystals in magnetic fields up to 7T and temperatures between
4.2K and 300K. The system shows a clear intrinsic Josephson effect, e.g.
the typical multi-branched current-voltage characteristics known from
high-Tc cuprates. Our magnetic field measurements reveal that fluxon
motion takes place in a very similar fashion as in Bi2212. So far, however,
we did not observe any unconventional behavior due to the magnetism
of the RuO2 layers.
TT 18.8 Mi 16:15 H20
Charge-imbalance relaxation rate in layered d-wave superconductors
— •Joachim Keller and Dmitri Ryndyk — Institut für
Theoretische Physik, Universität Regensburg, 93040 Regensburg
Intrinsic (inter-layer) Josephson effect in layered d-wave superconductors
is accompanied by static and oscillating charge fluctuations on the
layers. In a system of weakly coupled very thin atomic layers, such charge
fluctuations may lead to non-equilibrium effects described by a shift of
the chemical potential of the condensate and a charge imbalance between
electron- and hole-like quasiparticles. We have developed the microscopic
theory based on the nonequilibrium Green function method and calculated
static and high-frequency charge imbalance relaxation rates in dwave
superconductors (which are determined at low temperatures by
elastic scattering).
16:30 Pause

Tiefe Temperaturen Mittwoch
TT 19 Supraleitung: Heterostrukturen, Andreev-Streuung, Proximity-Effekt, Koexistenz
Zeit: Mittwoch 16:45–18:45 Raum: H20
Hauptvortrag TT 19.1 Mi 16:45 H20
Triplet correlations in superconductor-ferromagnet hybrid
structures — •Matthias Eschrig, Juha Kopu, Juan-Carlos
Cuevas, A. Konstandin, and Gerd Schön — Institut für
theoretische Festkörperphysik, Universität Karlsruhe
Based on the technique of quasiclassical Green’s functions, we construct
a theoretical framework for describing heterostructures consisting
of superconductors and ferromagnets. We show, that singlet-triplet
mixing near such interfaces is important and affects strongly the proximity
of superconductivity into strong ferromagnets. We suggest a new
mechanism for the penetration of superconducting correlations into halfmetallic
materials via an indirect proximity effect, which involves equal
spin pairing correlations. We discuss the influence of magnetic domain
walls on the superconducting proximity effect.
TT 19.2 Mi 17:15 H20
Ferromagnetic/Superconducting Bilayer Structure: A Model
For Spin Diffusion Length Estimation — •Soltan Soltan,
Joachim Albrecht, and Hanss-U. Habermeier — Max Planck
Institut für Festkörperforschung, Heisenbergstr.1, D 70569 Stuttgart,
Germany
Epitaxial bilayer structures of La2/3Ca1/3MnO3 (LCMO) and
YBa2Cu3O7−δ (YBCO) are grown on single crystalline SrTiO3 substrates
by pulsed laser deposition. The microstructure is analyzed by XRD and
exhibits c-axis oriented growth. The properties of these samples are investigated
by current transport and magnetization measurements. We
find that the transition temperature of the superconductor strongly depends
on the thickness of the YBCO film which can be explained by the
tunnelling of spin polarized quasiparticles from the magnetic film into
the superconductor. A theoretical model has been developed that fits the
experimental data quite well and allows us to determine the spin diffusion
length to be in the order of 10 nm. Furthermore we observe a shift
of the Kosterlitz-Thouless transition temperature close to Tc in case of
the injection of an additional transport into the bilayers.
TT 19.3 Mi 17:30 H20
Measurement of nonlocal conductance in superconductorferromagnet
hybrid structures — •Detlef Beckmann 1 , Heiko
B. Weber 1 , and Hilbert v. Löhneysen 2,3 — 1 Forschungszentrum
Karlsruhe, Institut für Nanotechnologie — 2 Forschungszentrum
Karlsruhe, Institut für Festkörperphysik — 3 Physikalisches Institut,
Universität Karlsruhe
We have measured the conductance of nonlocal aluminum-iron spinvalve
structures fabricated by e-beam lithography and shadow evaporation.
The sample geometry consists of an aluminum wire with two or more
ferromagnetic wires forming diffusive point contacts to the aluminum at
varying distances from each other. In the normal state of aluminum,
we observe a spin-valve signal which allows us to control the relative
orientation of the magnetizations of the ferromagnetic contacts. In the
superconducting state, at low temperatures and excitation voltages well
below the gap, we observe a spin-dependent non-local conductance which
decays on a smaller length scale than the normal-state spin-valve signal.
The sign, magnitude and decay length of this signal is consistent with
predictions made for crossed Andreev reflections [1] (CARE) in a diffusive
superconductor.
[1] G. Deutscher and D. Feinberg, Appl. Phys. Lett. 76 (2000) 487, D.
Feinberg, cond-mat/0307099.
TT 19.4 Mi 17:45 H20
Spontaneous Current in a Superconducting Loop with Ferromagnetic
Josephson Junction — •Andreas Bauer 1 , Johannes
Bentner 1 , Marco Aprili 2,3 , Maria-Luisa Della Rocca 2,3 ,
Matthias Reinwald 1 , Werner Wegscheider 1 , and Christoph
Strunk 1 — 1 Institut für Experimentelle und Angewandt Physik,
Universität Regensburg, Germany — 2 CSNSM-CNRS, Université
Paris-Sud, Orsay, France — 3 LPQ-ESPCI, 75005 Paris, France
Recently it has been shown that Cooper pairs can be transferred coherently
across a very thin ferromagnetic interlayer sandwiched between
two superconducting reservoirs. Thereby an exchange field acts upon the
spins of the paired electrons, resulting in a spatially oscillating pair amplitude.
For proper values of the ferromagnetic layer thickness and exchange
field, this oscillation allows the construction of Josephson-junctions with
a built-in phase difference of π. Niobium loops interrupted by a PdNi
π-junction are fabricated by means of shadow evaporation using a high
temperature stable shadow mask made of Polyethersulfone and Germanium.
A single loop is placed on top of the active area of a micro-Hall
sensor made of a modulation doped GaAs/AlGaAs heterostructure. By
varying the applied magnetic field, the phase difference across the weak
link is tuned. When comparing the magnetic response of loops with and
without π-junction, the π-loop is found to be asymmetric when reversing
the applied magnetic field. Upon cooling down the loop below the critical
temperature in zero field, a spontaneous current is detected which
provides half-integer flux quantization in the π-loop. Both effects can be
understood in terms of the intrinsic phase bias of the π-junction.
TT 19.5 Mi 18:00 H20
Experimental detection of the current phase relation in SNS
Josephson contacts — •Johannes Bentner, Andreas Bauer,
Matthias Reinwald, Werner Wegscheider, and Christoph
Strunk — Institut für experimentelle und angewandte Physik,
Universität Regensburg, Universitätsstrasse 31, 93053 Regensburg
Short superconductor/normalconductor weak links (SNS) are expected
to show a non-sinusodial current phase relation. This is due to a relativ
high transmission probability, and hence the Cooper pairs are not transfered
uncorrelated, but in Clusters of n correlated pairs. We present direct
measurements of the current phase relation of Al/Au/Al and Al/Ag/Al
SNS weak links prepared by shadow evaporation. Micropatterned GaAs-
AlGaAs Hall-sensors are used to measure the flux which is generated by
the circulating supercurrent in Al loops containing a single SNS junction.
The supercurrent is generated by the phase difference across the
junction which is controlled by applying an external magnetic flux to
the loop. In highly transparent Al/Ag junctions we find a non-sinusoidal
current phase relation. In contrast to that, in Al/Au junctions with lower
transparency the standard sinusoidal behavior is found. The critical current
extracted from the measured current phase relations agrees well with
transport measurements of simliar control samples.
TT 19.6 Mi 18:15 H20
Parity Effect in SN-Proximity-Systems — •Harald Kloos and
Andrei Zaikin — Forschungszentrum Karlsruhe, Institut für Nanotechnologie,
76021 Karlsruhe, Germany
A normal metal layer in good electric contact to a superconductor exhibits
properties sumarized under the term proximity effect, i.e. Andreev
reflection and the formation of a gap in the density of states which is
much smaller than the superconducting order parameter ∆. At low temperatures
thermodynamic properties of small isolated superconducting
grains depend on the parity of the number of electrons they carry, because
pairs of electrons can form Cooper pairs and enter the condensate,
whereas the lowest available state for an unpaired electron is given by
∆. We investigate the parity effect in an SN layer structure within the
quasiclassical Green’s functions formalism for arbitrary concentrations of
nonmagnetic impurities. The temperature T ∗ is estimated, below which
parity effects dominate the physical properties of the sample due to the
proximity induced features of the N-layer. It is shown that the free energy
difference between ensembles with even and odd numbers of particles at
zero temperature coincides with the proximity gap of the normal metal
layer. At finite temperatures the entropy factor is related to the density
of states of the sample.
TT 19.7 Mi 18:30 H20
Parity-Affected Supercurrents in Hybrid Nanorings —
•Sergei Sharov 1 and Andrei Zaikin 2 — 1 Institut für Theoretische
Festkörperphysik, Universität Karlsruhe, 76128 Karlsruhe, Germany
— 2 Forschungszentrum Karlsruhe, Institut für Nanotechnologie, 76021,
Karlsruhe, Germany
It has been established both experimentally and theoretically that
thermodynamic properties of small isolated superconducting islands and
grains may strongly depend on the electron parity number. In the present
work we investigate the influence of the parity effect on supercurrents in
isolated superconducting nanorings interrupted by a quantum point contact(QPC)
and threaded by the Aharonov-Bohm magnetic flux.
In order to evaluate superurrents in rings with even and odd total

Tiefe Temperaturen Mittwoch
number of electrons we employ the parity projected partition function
formalism. Our main results and observations are as follows: (a) the dependence
of the supercurrent on the external flux and temperature in
both even and odd canonical ensembles derived here may strongly deviate
from that established for the grand canonical ensemble, (b) at sufficiently
low temperatures supercurrents in rings with odd number of electrons are
TT 20 Metall-Isolator-Übergänge
totally blocked provided QPC has only one conducting mode and (c) this
blocking effect gets partially lifted in structures with several or many conducting
modes. We also discuss possible realizations of the above effects
and demonstrate that our predictions can be directly tested in modern
experiments.
Zeit: Mittwoch 14:30–16:30 Raum: H18
TT 20.1 Mi 14:30 H18
Projektor-basiertes Renormierungsverfahren für das spinlose
Holstein-Modell — •Steffen Sykora 1 , Arnd Hübsch 1,2 und
Klaus W. Becker 1 — 1 Institut für Theoretische Physik, Technische
Universität Dresden, D-01062 Dresden — 2 Department of Physics,
University of California, Davis, CA 95616, USA
Mit Hilfe eines kürzlich vorgestellten Renormierungsverfahrens wird
der Metall-Nichtmetall-Übergang im eindimensionalen Holstein-Modell
bei Halbfüllung untersucht. In dieser Methode werden mit Hilfe einer
unitären Transformation sukzessiv Anregungsoperatoren der Elektron-
Phonon-Wechselwirkung von höheren zu tieferen Energien herausintegriert.
Als Ergebnis erhält man einen effektiven Hamiltonoperator für ein
quasifreies System aus renormierten ungekoppelten Elektronen und Phononen.
Für kleine Werte der Elektron-Phonon-Kopplung g findet man ein
stetiges Verhalten der elektronischen Einteilchenenergie ˜εk an der Fermikante
und somit eine metallische Phase. Dagegen öffnet sich für g größer
als ein kritischer Wert gc eine Lücke an der Fermikante, so daß eine isolierende
Phase entsteht. Gleichzeitig mit dem Auftreten der Lücke in ˜εk
wird die renormierte Phononenfrequenz ˜ωq am Rand der Brillouin-Zone
weich, was auf das Entstehen einer Peierls-Phase schließen läßt.
TT 20.2 Mi 14:45 H18
Weak ferromagnetism of the charge stripes in La5/3Sr1/3NiO4 —
•Rüdiger Klingeler 1 , Bernd Büchner 1 , Sang-Wook Cheong 2 ,
and Markus Hücker 3 — 1 Leibniz-Institut für Festkörper- und Werkstoffforschung
Dresden, PF 27 01 16, 01171 Dresden — 2 Department
of Physics and Astronomy, Rutgers University, Piscataway, New Jersey
08854 — 3 Physics Department, Brookhaven National Laboratory, Upton,
New York 11973
In doped nickelates the interplay of charge and spin degrees of freedom
results a long range charge order where static charge stripes and
spin stripes are present. We present measurements of the high field magnetization
and the specific heat of a La5/3Sr1/3NiO4 single crystal in order
to elucidate the thermodynamic properties of the stripe phase. The data
provide the magnetic phase diagram. The charge ordering temperature
TCO is nearly independent of the magnetic field and there is a significant
and highly anisotropic field dependence of the long range spin ordering
temperature TSO. High field magnetization data reveals a weak ferromagnetism
in the entire stripe ordered phase. We analyze these data in terms
of weak moments which are long range correlated. Double exchange interactions
are discussed as a possible origin of the weak ferromagnetism.
TT 20.3 Mi 15:00 H18
Magnetothermal Conductivity of Highly Oriented Pyrolytic
Graphite — •Konstantin Ulrich, Pablo Esquinazi,
Roberto Ocaña, and Heiko Kempa — Abteilung Supraleitung und
Magnetismus, Universität Leipzig, Linnestrasse 5, D-04103 Leipzig
The magnetic field (0T≤ B ≤ 9T) dependence of the longitudinal
thermal conductivity κ(T, B) of highly oriented pyrolytic graphite samples
was measured in the temperature range 0.2 K ≤ T ≤ 20 K for fields
parallel to the c−axis. With the measured longitudinal electrical resistivity
we show that the Wiedemann-Franz law is violated in the high-field
(quantum-Hall) regime, where large oscillations in the thermal conductivity
are measured at B > 2 T, as well as near the Metal-Insulator
transition (MIT) at B ∼ 0.1 T. For a strong anisotropic graphite sample
κ(B) reveals a kink-behavior at the MIT that looks similar to that predicted
by the magnetic-field induced gap theory due to the phenomenon
of magnetic catalysis. We discuss our results taking into account recently
published models for the behavior of Dirac-like Fermi quasiparticles.
TT 20.4 Mi 15:15 H18
X-ray magnetic and natural circular dichroism at the vicinity
of the Co low-spin to high-spin transition in REBaCo2O5.5
(RE= Dy; Gd) system — •S. Gold 1 , E. Goering 1 , P. Lemmens 2 ,
A. Podlesnyak 3 , G. Bychkov 4 , J. Deisenhofer 5 , A. Loidl 5
und G. Schütz 1 — 1 MPI für Metallforschung, Stuttgart — 2 MPI für
Festkörperforschung, Stuttgart — 3 PSI, ETHZ&PSI, Villingen — 4 Inst.
of Solid State & Semicond. Phys., Nat. Acad. Sci. Minsk — 5 EP5,
Universität Augsburg
The magnetic perovskite REBaCo2O5.5 (RE= Dy; Gd) system shows
a rich magnetic and electronic phase diagram, with a MI transition at
higher temperatures and ferromagnetic ordering just below room temperature.
With a further reduction of temperature the ferromagnetic magnetization
is strongly reduced. This has been discussed in terms of a
Co spin state transition and/or antiferromagnetism. A double peak like
structure could be observed in the Co L2,3 XMCD. We interpret this double
peak by spectroscopic distinguishable octahedral and pyramidal Co
sites. The Co L2,3 XMCD has been separated from the overlapping Ba
M4,5 spectra by a recently developed XMCD analysis tool called moment
analysis. This analysis exhibits an unusual large orbital/spin-moment ratio.
In addition, we could observe an extreme large X-ray natural circular
dichroism (XNCD) signal, which is about two orders of magnitude larger
compared to other published results and about 20% of the corresponding
white line intensity. This suggests a large non centrosymmetric charge
distribution at the Co site. Nevertheless, the orgin of this extreme large
XNCD effect is not clear up to now.
TT 20.5 Mi 15:30 H18
Pressure-induced metal-insulator transition in rare earth nickelates
RNiO3 — •R. Lengsdorf 1 , J.A. Alonso 2 , M.J. Martinez-
Lope 2 , M. Amboage Castro 2 , and M.M. Abd-Elmeguid 1 — 1 II.
Physikalisches Institut Universität zu Köln, Zülpicherstr. 77, 50937 Köln,
Germany — 2 Instituto de Ciencia de Materiales de Madrid, Consejo
Superior de Investigaciones Cientificas, Cantoblanco, E-28049 Madrid,
Spain
We report on the effect of pressure up to 25 GPa on the electronic
and structural properties (electrical resistance and x-ray diffraction) of
two selected antiferromagnetic charge transfer insulators EuNiO3 (orthorhombic,
TN = 220 K) and LuNiO3 (monoclinic, TN = 130 K) which
undergo a thermal-induced insulator-metal transition (IMT) at TIM =
460 K and 599 K, respectively. The IMT in LuNiO3 is connected with
a monoclinic-to-orthorhombic structural phase transition, whereas the
orthorhombic structure of EuNiO3 remains unchanged.
In both systems we find a pressure-induced IMT at a critical pressure
of about 6 GPa, while the crystal structure remains unchanged. Structural
phase transitions are observed at much higher pressures: EuNiO3
orthorhombic to rhombohedral at 12 GPa and LuNiO3 at 16 GPa. The
experimental results are explained in terms of a pressure-induced increase
of the 3d-2p-3d orbital hybridization as a result of increasing the Ni-O-
Ni bonding angle with increasing pressure. The influence of the charge
transfer between localized Ni and O states on the pressure-induced IMT
in LuNiO3 is also discussed.
TT 20.6 Mi 15:45 H18
Low temperature instability and magnetic entropy in
La7/8Sr1/8MnO3 — •Jochen Geck 1 , Peter Wochner 2 , Sven
Kiele 3 , Rüdiger Klingeler 4 , Pascal Reutler 4 , and Bernd
Büchner 4 — 1 II. Physikalisches Institut der RWTH Aachen —
2 Max-Planck-Institut für Metallforschung, Stuttgart — 3 HASYLAB
am DESY, Hamburg — 4 Leibniz-Institut für Festkörper- und
Werkstoffforschung, Dresden
Specific heat and magnetization measurements reveal that the entropy
changes at the metal-insulator transition of La1−xSrxMnO3 with x ∼ 1/8

Tiefe Temperaturen Mittwoch
are mainly of magnetic origin. This intriguing feature necessarily implies
a low temperature instability of the ferromagnetic insulating (FMI) phase
in La1−xSrxMnO3. Indeed, such an instability is observed: The FMI-phase
decays upon x-ray irradiation at temperatures below 30K. Moreover, the
doping dependence of short range correlations above the metal-insulator
transition can be consistently interpreted in terms of magnetic entropy
changes.
TT 20.7 Mi 16:00 H18
Einfluß globaler und lokaler Verzerrungen auf Magnetismus und
Leitfähigkeit in La1−xMxCoO3 (M = Ca, Sr, Ba) — •M. Kriener,
J. Baier, H. Kierspel, T. Lorenz, A. Reichl, C. Zobel und A.
Freimuth — II. Physikalisches Institut, Universität zu Köln, Zülpicher
Str. 77, 50937 Köln
LaCoO3 ist ein Isolator mit ungewöhnlichen magnetischen Eigenschaften,
der einen thermisch getriebenen Spinübergang durchläuft. Bei Lochdotierung
mit Sr beobachtet man als Funktion der Konzentration einen
Übergang von paramagnetisch über eine Spinglasphase (x > 4 %) bis
hin zu einem ferromagnetischen Metall (x > 18 %) [1]. Weit weniger
untersucht sind bisher die Dotierungsreihen mit Ca bzw. Ba. Wir
präsentieren eine Analyse des Einflusses der unterschiedlichen Ionen im
System La1−xMxCoO3 auf Struktur, Magnetismus und Leitfähigkeit. Das
Sr- bzw. Ba-dotierte System kristallisiert in einer rhomboedrisch verzerrten
Struktur, wobei die Verzerrung mit zunehmender Dotierung abnimmt.
Ca-Dotierung führt zu einem strukturellen Phasenübergang von
rhomboedrischer hin zu orthorhombischer Verzerrung (x ≃ 20%). Dotierung
mit Sr führt zu höheren Übergangstemperaturen als analoge Dotierung
mit Ca bzw. Ba. Zur Erklärung des nicht monotonen Verhaltens
bzgl. der Ionenradien diskutieren wir einerseits den Einfluß von chemi-
schem Druck (globale Verzerrung; Toleranzfaktor) und andererseits die
durch die unterschiedlichen Ionenradien von La 3+ und M 2+ verursachte
lokale Unordnung. [1] M.Itoh et al., J.Phys.Soc. Japan 63, 1486 (1994)
Gefördert von der DFG durch den SFB 608.
TT 20.8 Mi 16:15 H18
Crossover from Coulomb to Fermi Glass in Si:P studied by high
frequency conductivity measurements — •Marco Hering 1,2 ,
Marc Scheffler 1 , M. Dressel 1 und Hilbert v. Löhneysen 2
— 1 1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart,
Germany — 2 Physikalisches Institut, Universität Karlsruhe, 76128
Karlsruhe, Germany
In highly doped but still insulating Si:P various transport mechanisms
are possible. At very low energies hopping processes between disordered,
localized electronic states dominate the transport and hence Si:P can be
considered as a model system for so called insulating electron glasses.
We studied the electrodynamics of these systems in a frequency range
between 50 GHz and 1200 GHz using a coherent source cw THz spectrometer.
At liquid helium temperatures the influence of electron-electron
interactions play an important role and a transition from the so called
Coulomb Glass at lower frequencies to the Fermi Glass at higher frequencies
could be observed. We also studied the influence of different
doping concentrations and temperature on the frequency dependant conductivity
and the dielectric constant. We compare the results of these
measurements with the well established theory of A. L. Efros and B. I.
Shklovskii.
16:30 Pause
TT 21 Quantenkritische Phänomene
Zeit: Mittwoch 16:45–18:00 Raum: H18
TT 21.1 Mi 16:45 H18
Hall-Effekt am Quantenphasenübergang von CeCu6−xAux
— •H. Bartolf 1 , C. Pfleiderer 1 , O. Stockert 1,2 und H. v.
Löhneysen 1,3 — 1 Physikalisches Institut, Universität Karlsruhe,
D-76128 Karlsruhe — 2 Max-Planck-Institut für chemische Physik fester
Stoffe, D-01187 Dresden — 3 Forschungszentrum Karlsruhe, Institut für
Festkörperphysik, D-76021 Karlsruhe
Einer der am besten untersuchten magnetischen Quantenphasenübergänge
befindet sich im Au-substituierten Schwer-Fermion-
System CeCu6. Dabei beoabachtet man in CeCu6−xAux für xc > 0.1
antiferromagnetische Ordnung. Die Dynamik der Spinanregungen
zeigt Charakteristiken, die einerseits als niedrigdimensionale Spinfluktuationen
und andererseits als lokal kritisches Verhalten der
Spinfluktuationen am Quantenphasenübergang interpretiert werden [1].
Theoretische Vorhersagen [2] legen nahe, dass sich diese Szenarien mit
Hilfe des Hall-Effekts unterscheiden lassen. Wir berichten Messungen
des Hall-Effekts von CeCu6−xAux im Limit tiefer Temperaturen und
niedriger Felder. Die Ergebnisse werden mit den Erwartungen der
Modelle des Quantenphasenübergangs von CeCu6−xAux verglichen.
[1] A. Schröder et al., Nature 407, 6802 (2000).
[2] P. Coleman et al., J. Phys. Cond. Matt. 13, R723 (2001).
TT 21.2 Mi 17:00 H18
Weak magnetism and non-Fermi liquids near heavy-fermion
critical points — •Matthias Vojta 1 , T. Senthil 2 , and Subir
Sachdev 3 — 1 Institut für Theorie der Kondensierten Materie, Universität
Karlsruhe, D-76128 Karlsruhe — 2 Department of Physics, Massachusetts
Institute of Technology, Cambridge, USA — 3 Department of
Physics, Yale University, New Haven, USA
This contribution discusses weak-moment magnetism in heavy-fermion
materials and its relation to the non-Fermi liquid physics observed near
the transition to the Fermi liquid. We explore the hypothesis that the primary
fluctuations responsible for the non-Fermi liquid physics are those
associated with the destruction of the large Fermi surface of the Fermi liquid.
A concrete realization of this picture is provided by a fractionalized
Fermi liquid state which has a small Fermi surface of conduction electrons,
but also has other exotic excitations with interactions described by
a gauge theory in its deconfined phase. Of particular interest is a threedimensional
fractionalized Fermi liquid with a spinon Fermi surface and
a U(1) gauge structure. A direct second-order transition from this state
to the conventional Fermi liquid is possible and involves a jump in the
electron Fermi surface volume. The critical point displays non-Fermi liquid
behavior. A magnetic phase may develop from a spin density wave
instability of the spinon Fermi surface. Experimental signatures of this
phase and implications for heavy-fermion systems are discussed.
TT 21.3 Mi 17:15 H18
Numerical Renormalization Group for Quantum Two-Level
Systems in a Dissipative Environment — •Ralf Bulla 1 ,
Matthias Vojta 2 , and Ning-Hua Tong 1 — 1 Theoretische Physik
III, Universität Augsburg — 2 Institut für Theorie der Kondensierten
Materie, Universität Karlsruhe
The dynamics of quantum two-level systems has recently attracted a
lot of interest in the context of quantum computing. The coupling to the
environment strongly influences the phase coherence necessary to perform
elementary quantum computing steps. A suitable description of the coupling
of the qubit to the environment is given by the spin-boson model for
which a reliable and (in particular) non-perturbative method is required;
such a method should be applicable to general bath spectral functions
(such as the sub-ohmic case with exponents of the bath spectral function
s < 1). Here we present the recently developed bosonic numerical renormalization
group approach [R. Bulla, N. Tong, and M. Vojta, Phys. Rev.
Lett. 91, 170601 (2003)]. In particular, we discuss the phase diagram of
the spin-boson model for arbitrary exponents s and couplings α, as well
as the dynamics across the whole phase diagram. Further applications of
this approach (two coupled qubits, qubits coupling to a structured bath)
are discussed.
TT 21.4 Mi 17:30 H18
Dynamical CPA approach to an itinerant fermionic spin glass
model — •Michael Bechmann and Reinhold Oppermann — Institut
für Theoretische Physik und Astrophysik, Universität Würzburg,
Am Hubland, 97074 Würzburg
We study a fermionic version of the Sherrington-Kirkpatrick model including
nearest-neighbor hopping on a ∞-dimensional simple cubic lattices.
The problem is reduced to one of free fermions moving in a dynamical
effective random medium. By means of a CPA method we derive a
set of self-consistency equations for the spin glass order parameter and
for the Fourier components of the local spin susceptibility. In order to
solve these equations numerically we employ an approximation scheme

Tiefe Temperaturen Mittwoch
which restricts the dynamics to a feasible number of the leading Fourier
components. From a sequence of systematically improved dynamical approximations
we estimate the location of the quantum critical point.
TT 21.5 Mi 17:45 H18
On the quantum critical point in Sr2Ru1−xTixO4 — •Ralph
Werner 1 and Sam T. Carr 2 — 1 Institut f”ur Theorie der Kondensierten
Materie, Universit”at Karlsruhe, 76128 Karlsruhe — 2 Condensed
Matter Section, The Abdus Salam ICTP, Strada Costiera 11, 34014 Trieste,
Italy
Upon doping with 2.5% of Ti on the Ru site Sr2RuO4 develops incommensurate
static magnetic order which has been attributed to the nesting
of the bands that form the α and β Fermi surfaces [1]. We argue that a
standard Stoner mechanism modeled by RPA is insufficient to describe
the transition. Instead it is proposed that the quantum critical point is
driven by a weak-coupling to strong-coupling crossover which in turn
is modeled in a non-perturbative manner [2]. The expected dynamical
magnetic response is calculated.
[1] M. Braden et al., Phys. Rev. Lett. 88 (2002) 197002
[2] R. Werner and V. J. Emery, Phys. Rev. B 67 (2003) 014504
TT 22 Quantenkohärenz und Quanteninformationssysteme I
Zeit: Mittwoch 14:30–17:15 Raum: H19
TT 22.1 Mi 14:30 H19
Coherent oscillations in a single electron spin — •Iulian Popa,
Fedor Jelezko, Torsten Gaebel, Achim Gruber, Michael
Domhan, and Jörg Wrachtrup — 3.Phys. Institut Universität
Stuttgart 70563
Rabi nutations of a single electron spin in a single defect center in diamond
have been detected,at room temperature. The N-V defect center in
diamond is a defect consisting of a substitutional nitrogen atom adjacent
to a carbon-atom vacancy. The optical transition between 3A ground
state and 3E excited state has a very high quantum efficiency allowing
single defect spectroscopy. Because of paramagnetic nature of the ground
electronic state, single N-V defects are believed to be promising candidates
for the solid state quantum computation. The coherent evolution of
the spin quantum state is followed via optical detection of the spin state.
Coherence times up to several microseconds at room temperature have
been measured. The influence of the optical excitation on the coherence
time is analyzed.
TT 22.2 Mi 14:45 H19
Solid-state 2-qubit gate based on a single defect center in diamond
— •Torsten Gaebel, Michael Domhan, Iulian Popa,
Achim Gruber, Fedor Jelezko, and Jörg Wrachtrup — 3.
Physikalisches Institut, Universität Stuttgart
For spin-based quantum information processing, the readout and manipulation
of the single spin states are of an outmost importance. Recently,
single paramagnetic nitrogen vacancy (N-V)defects in diamond
have been investigated by the optically detected magnetic resonance
(ODMR)technique. Single spin ODMR approach is based on the optical
selection of a single paramagnetic defect by confocal optical microscopy.
Photon antibunching proves that ODMR signal is originating from the
single quantum system.
Pulsed ODMR experiments have been performed in order to demonstrate
the ability of the coherent manipulation of single spin states.
Coupling to the spin of a 13C nucleus provides a 2-qubit system, on
which the conditional rotation gate (CROT) was performed.
TT 22.3 Mi 15:00 H19
Open systems dynamics in a spin star — •Daniel Burgarth 1 ,
Heinz-Peter Breuer 1 , and Francesco Petruccione 1,2 —
1 Physikalisches Institut, Universitaet Freiburg, Germany — 2 Istituto
Italiano per gli Studi Filosofici, Naples, Italy
The study of strongly coupled spin systems is important for various
applications in quantum computation and quantum communication. The
dynamics of a spin coupled to a spin bath is strongly influenced by dissipation
and decoherence. Within the theory of open quantum systems
the dynamics is described in terms of a master equation for the density
matrix of the reduced spin degree of freedom.
A very simple, exactly solvable spin star system will be discussed and
the reduced non-Markovian dynamics of the spin will be derived using
different strategies of approximation. Particular attention will be devoted
to the comparison of the non-Markovian approximations obtained by the
Nakajima-Zwanzig and by the time-convolutionless projection operator
technique.
TT 22.4 Mi 15:15 H19
Quantum impurity approach to a two qubit problem — •Josef
Schriefl 1,2 , Sebastien Camamet 2 , Pascal Degiovanni 2 , and
Francois Delduc 2 — 1 Institut für theoretische Festkörperphysik,
Universität Karlsruhe, 76128 Karlsruhe, Germany — 2 Laboratoire de
Physique de l’Ecole Normale Supérieure de Lyon, UMR 5672, 69007
Lyon, France
We study the mutual influence of two qubits via a common environment.
By mapping our model on a system with two Kondo type interactions
we show its equivalence with the problem of a quantum wire
coupled at its boundaries to two resonant levels. Using non perturbative
techniques we obtain exact expressions for the equilibrium populations
and correlation of the qubits at a special point of the interaction strength.
The nontrivial behavior of both quantities can be explained within a simple
Kondo cloud picture. Depending on control-parameters each qubit
generates a Kondo cloud of a characteristic size in the environment. The
conditions for a non-zero correlation are found to be not only spatial
overlap of the clouds but also their action on the same environmental
modes. Furthermore, perturbation calculations suggest that this picture
is qualitatively valid nearby the exactly solvable point.
TT 22.5 Mi 15:30 H19
Quantum trajectory approach to the dynamics of spin qubits in
quantum dots — •Holger Schaefers and Walter T. Strunz —
Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-
Herder-Str. 3, 79104 Freiburg, Germany
We investigate continuous measurement of a single electron spin qubit
in a quantum dot as described in [1]. The dot is coupled to two leads
and we choose the sequential tunneling regime. Our approach is based
on ‘quantum trajectories’, widely used in quantum optics, here adapted
to describe conditional quantum dot dynamics in a fermionic environment.
We use the quantum trajectory approach to simulate the quantum
dynamics conditioned on the continuous measurement outcome, here the
electron current through the dot. We simulate so called ‘shelving’ experiments
and show that it is possible to measure directly the relaxation time
T1, in the time domain. In a modified parameter regime the decoherence
time T2 can be obtained as well. Further, using realistic parameters, we
calculate counting statistics of electrons tunneling through the dot and
show, that this device can be used to measure initial coherences of the
qubit state.
[1] H.-A. Engel, D. Loss, Phys. Rev. Lett. 86, 4648 (2001)
TT 22.6 Mi 15:45 H19
Dynamics of the spin-boson model with a structured environment
— •Michael Thorwart 1 , Elisabetta Paladino 2 , and
Milena Grifoni 3 — 1 Institut für Theoretische Physik IV, Heinrich-
Heine-Universität Düsseldorf — 2 Dipartimento Metodologie Fisiche e
Chimiche per L’ingegneria, Universitá di Catania, Italy — 3 Institut für
Theoretische Physik, Universität Regensburg
We investigate the dynamics of the spin-boson model when the spectral
density of the bath shows a resonance at a characteristic frequency
Ω but behaves Ohmically at small frequencies. A useful exact mapping
of this system to a system composed of a quantum two-state system
(TSS) coupled to an Ohmically damped harmonic oscillator (HO) with
frequency Ω is invoked. The dynamics is calculated by employing the
numerically exact quasiadiabatic path-integral technique. We find significant
new properties compared to the Ohmic spin-boson model. By
reducing the combined TSS+HO-system in the dressed states picture to
a three-level system, we calculate analytically the dephasing rates for

Tiefe Temperaturen Mittwoch
the special case at resonance. Finally, we apply our model to experimentally
realized superconducting flux qubits coupled to an underdamped
ds-SQUID-detector.
TT 22.7 Mi 16:00 H19
Coherence control for qubits — •Karen M. Fonseca Romero,
Sigmund Kohler, and Peter Hänggi — Institut für Physik, Universität
Augsburg, Universitätstr. 1, D-86135, Augsburg
We examine the possibility of coherence stabilization of qubits, weakly
coupled to a bath, by the application of periodic driving. For the description
of the qubit dynamics we derive a master equation, which makes use
of the periodicity of the driving force. The so-called Floquet-Born-Markov
master equation is valid for frequencies much larger than the inverse of
the typical qubit evolution and allows us to determine the decoherence
rates of the qubit system, under the influence of the driving. As a first
example we consider a single qubit under the influence of bit-flip noise
in two types of external harmonic driving fields (i) one that commutes
with the qubit-bath coupling Hamiltonian, in the coherent destruction of
tunnelling regime, and (ii) one that anticommutes with the qubit-bath
coupling Hamiltonian, which dynamically decouples the qubit from the
noise source. As a second example we consider two qubits performing a
CNOT gate operation using the Heisenberg exchange interaction, with a
decoherence source which couples to one spin component of the qubits.
We show that the influence of a high-frequency field leads to coherence
stabilized gate operation in the regime of low temperatures.
[1] K. M. Fonseca Romero, S. Kohler, and P. Hänggi, arxiv: quantph/0307136,
Chem. Phys. (in press).
TT 22.8 Mi 16:15 H19
Decoherence without T2 — •Frank Wilhelm — Sektion Physik
und CeNS, Ludwig-Maximilians-Universität, Theresienstr. 37, 80333
München
In order to achieve coherent manipulation of quantum states in solidstate
systems, it is crucial to analyze and engineer the decoherence of the
system. Traditionally, its impact is parameterized using the relaxation
and dephasing times T1 and T2. In particular, T2 is the time constant of
the exponential decay of quantum coherent oscillations at times longer
than the bath correlation time. Recent experiments on well-controlled superconducting
quantum bits show however, that T2 does not account for
the complete supression of the oscillations: The overall amplitude (visibility)
appears to be further reduced. In order to explain this effect, I
propose a consistent model invoking an environment whose spectrum is
gapped or at least supressed at low frequencies. It is shown from the exact
solution of the pure dephasing case, that the coherent oscillation amplitude
decays up to times of the order of the inverse infrared cutoff and
then remains constant, i.e. the system quickly decoheres to a constant
level although T2 defined from the long-time limit is infinite. Such baths
are ubiquitous in the experiments in question, e.g. in the quasiparticle
channel parallel to the Josephson junctions.
TT 22.9 Mi 16:30 H19
Quantum Dissipative Dynamics of the Magnetic Resonance
Force Microscope in the Single-Spin Detection Limit — •Hanno
Gassmann 1 , Mahn-Soo Choi 2 , Hangmo Yi 3 , and Christoph
Bruder 1 — 1 Department of Physics and Astronomy, University of
Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland — 2 Department of
Physics, Korea University, Seoul 136-701, Korea — 3 Korea Institute for
Advanced Study, 207-43 Cheongryang 2-dong, Seoul 130-722, Korea
We study a model of a magnetic resonance force microscope (MRFM)
based on the cyclic adiabatic inversion technique as a high-resolution tool
to detect single electron spins. We investigate the quantum dynamics of
spin and cantilever in the presence of coupling to an environment. To
obtain the reduced dynamics of the combined system of spin and cantilever,
we use the Feynman-Vernon influence functional and get results
valid at any temperature as well as at arbitrary system-bath coupling
strength. We propose that the MRFM can be used as a quantum measurement
device, i.e., not only to detect the modulus of the spin but also
its direction.
TT 22.10 Mi 16:45 H19
Towards mechanical entanglement in nano-electromechanical
devices — •Jens Eisert 1 , Martin B. Plenio 2 , and Sougato
Bose 3,4 — 1 Institut für Physik, Universität Potsdam, Am Neuen Palais
10, D-14469 Potsdam, Germany — 2 QOLS, Blackett Laboratory, Imperial
College London, Prince Consort Road, London SW7 2BW, UK
— 3 Department of Physics and Astronomy, University College London,
Gower Street, London, WC1E 6BT, UK — 4 Institute for Quantum Information,
California Institute of Technology, Pasadena, CA 91125, USA
We study arrays of mechanical oscillators in the quantum domain and
demonstrate how the motions of distant oscillators can be entangled
without the need for control of individual oscillators and without a direct
interaction between them. These oscillators are thought of as being
members of an array of nano-electromechanical resonators with a voltage
being applicable between neighbouring resonators. Sudden switching
of the interaction results in a squeezing of the states of the mechanical
oscillators, leading to an entanglement transport in chains of mechanical
oscillators. We discuss the spatial dimensions, Q-factors, and temperatures
that would be necessary to achieve entanglement in the canonical
coordinates in such a scheme, and discuss decoherence mechanisms in
some detail, and find a distinct robustness of the scheme under decoherence.
We also briefly discuss the challenging aspect of detection of the
generated entanglement.
TT 22.11 Mi 17:00 H19
Macroscopic quantum effects in driven nanomechanical wires
— •Vittorio Peano and Michael Thorwart — Institut für Theoretische
Physik IV, Heinrich-Heine-Universität Düsseldorf
We investigate the nonlinear response of a vibrating doubly clamped
suspended nanomechanical wire on an externally applied periodic driving.
The setup can be mapped onto the dynamics of a quantum particle moving
in a monostable quartic potential which is driven by an ac-field. The
quantum system is weakly damped due to interaction with a harmonic
bath. By solving the corresponding Born-Markovian master equation for
the reduced density operator, we calculate the response of the system
for varying driving frequencies. For strong driving, we observe characteristic
resonances which are absent in the corresponding classical model.
The resonances are explained in terms of tunneling transitions in the
dynamically induced effectively bistable system which is obtained within
the Floquet theory. Applications of the model to nanowires as well as to
driven SQUIDs are discussed.
17:15 Pause
TT 23 Nanoelektronik II: Spin-Elektronik
Zeit: Mittwoch 17:30–18:30 Raum: H19
TT 23.1 Mi 17:30 H19
Aharonov-Bohm Oscillations with Rashba Spin-Orbit Coupling:
Influence of Electron-Electron Interactions — •Maxim Trushin
and Alexander Chudnovskiy — 1.Institute of Theoretical Physics,
University of Hamburg, Jungiusstrasse 9, D-20355 Hamburg, Germany
We report a study of the Aharonov-Bohm effect, the oscillations of
the current through a one-dimensional quantum ring connected to two
reservoirs as a function of a perpendicular magnetic field, in presence of
Rashba spin-orbit coupling and Zeeman spin-splitting. In such a system
the geometric (Berry) phase is different for two chiral states and depends
on the parameters of the system such as the spin-orbit coupling constant
and Zeeman splitting. We discuss the quantum interference pattern arising
in the Aharonov-Bohm oscillations from the superposition of that
two chiral states. In the framework of the Tomonaga-Luttinger liquid approach
we derive an analytic formulae for the current and show that in
contrast to the usual situation without Rashba spin-orbit coupling the
electron-electron interactions can play a role here.

Tiefe Temperaturen Mittwoch
TT 23.2 Mi 17:45 H19
Persistent spin currents in mesoscopic Heisenberg rings —
•Florian Schütz, Marcus Kollar, and Peter Kopietz — Institut
für Theoretische Physik, Universität Frankfurt, Robert-Mayer-Str.
8, 60054 Frankfurt/Main
We discuss spin transport in magnetic insulators and show that a spatially
inhomogeneous magnetic field gives rise to a persistent spin current
around a mesoscopic Heisenberg ring [1]. This is a mesoscopic quantum
interference effect and is analogous to persistent charge currents in normal
metal rings threaded by a magnetic flux. The spin current is carried
by magnons and is driven by a geometric flux. For a ferromagnetic ring
spin waves are thermally activated while for an antiferromagnetic ring
quantum fluctuations lead to a magnetization current even in the ground
state. Since moving magnetic dipoles produce electric fields, the magnetization
current leads to an electric dipole moment perpendicular to the
ring plane, which may allow the experimental detection of this effect.
[1] F. Schütz, M. Kollar, and P. Kopietz, Phys. Rev. Lett. 91, 017205
(2003); cond-mat/0308230.
TT 23.3 Mi 18:00 H19
Spin-dependent transport through quantum dots attached to
ferromagnetic leads — •Jürgen König 1,2 , Jan Martinek 1 , and
Gerd Schön 1 — 1 Institut für Theoretische Festkörperphysik, Universität
Karlsruhe — 2 Institut für Theoretische Physik III, Ruhr-Universität
Bochum
We study spin-dependent transport through quantum dots coupled to
ferromagnetic leads. First, we consider strong dot-lead coupling and ana-
lyze how the spin polarization of the leads affects the Kondo effect. Based
on a scaling approach we predict [1] that an effective Zeeman splitting
and hence a splitting of the zero-bias anomaly is induced. With an additional
magnetic field, this splitting can be compensated, and the strongcoupling
limit of the Kondo effect is recovered. These results are backed
up by rigorous numerical-renormalization-group calculations [2]. Second,
weak dot-lead coupling is considered. We determine the linear conductance
as a function of the relative angle between the leads’ magnetization
directions [3]. An interaction-induced rotation of the quantum-dot spin
is found, which yields a reduction of the spin-valve effect.
[1] J. Martinek et al., Phys. Rev. Lett. 91, 127203 (2003).
[2] J. Martinek, M. Sindel, L. Borda, J. Barnas, J. König, G. Schön, and
J. v. Delft, accepted for Phys. Rev. Lett.
[3] J. König and J. Martinek, Phys. Rev. Lett. 90, 166602 (2003).
TT 23.4 Mi 18:15 H19
Semiclassical theory of weak antilocalization in chaotic systems.
— •Oleg Zaitsev 1 , Diego Frustaglia 2 , and Klaus Richter 1 —
1 Universität Regensburg, Theoretische Physik, D-93040 Regensburg —
2 Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
We propose a semiclassical theory of weak antilocalization in clean
ballistic systems with chaotic dynamics. Our approach is based on the
semiclassical Landauer formula that we extended to include spin-orbit interaction.
The general theory is applied to a chaotic billiard with Rashba
interaction. We find that the spin relaxation in chaotic systems is considerably
slower than in the diffusive systems. As a consequence, one expects
different scales of the weak antilocalization in these cases.
TT 24 Postersitzung III: Korrelierte Elektronen, ”Orbital Physics”
Zeit: Mittwoch 14:30–19:00 Raum: Poster A
TT 24.1 Mi 14:30 Poster A
LDA+DMFT results for ARPES spectra of SrVO3 — V.
I. Anisimov 1 , K. Held 2 , •G. Keller 3 , D. E. Kondakov 1 , I.
Nekrasov 1 , T. Pruschke 4 , and D. Vollhardt 3 — 1 Institut für
Metallphysik, Ekaterinburg GSP-170, Russland — 2 Max Planck Institut
für Festkörperforschung, 70569 Stuttgart — 3 Theoretische Physik III,
Universität Augsburg, 86135 Augsburg — 4 Institut für Theoretische
Physik, Universität Göttingen, 37077 Göttingen
We report angle resolved photoemission spectra of SrVO3 calculated
by LDA+DMFT(QMC). Starting from LDA band structure calculations
in the LMTO basis set [1], we use a projection method [2,3] to extract a
Hamiltonian for the three-fold degenerate t2g bands from the total band
structure. With this reduced LDA-Hamiltonian as input to DMFT(QMC)
calculations [4], we obtain (via maximum entropy) angle resolved spectral
functions A(k, ω) on the real axis. The spectra exhibit featureless upper
and lower Hubbard bands with a quasi-particle peak which is narrowed
by correlations. In view of the good agreement of our previous (not angle
resolved) LDA+DMFT results [5] with high-resolution PES for SrVO3
[6], it will be interesting to see how our predictions compare with future
ARPES experiments.
[1] O. K. Andersen, Phys. Rev. B 12, 3060 (1975)
[2] N. Marzari and D. Vanderbilt, Phys. Rev. B 56, 12847 (1997)
[3] W. Ku et al., Phys. Rev. Lett. 89, 167204 (2002)
[4] K. Held et al., Psi-k Newsletter #56 (April 2003), p. 65-103
[5] I. Nekrasov et al., cond-mat/0211508
[6] A. Sekiyama et al., cond-mat/0206471
TT 24.2 Mi 14:30 Poster A
Charge and orbital order in Fe3O4 — •I. Leonov 1,2 , A. N
Yaresko 3 , V. N. Antonov 4 , M. A. Korotin 2 , V. I. Anisimov 2 ,
and D. Vollhardt 1 — 1 Theoretical Physics III, University of
Augsburg, 86135 Augsburg — 2 Institute of Metal Physics, Ekaterinburg
GSP-170, Russia — 3 Max Planck Institute for Physics of Complex
Systems, 01187 Dresden — 4 Institute of Metal Physics, 03142 Kiev,
Ukraine
The issue of charge and orbital ordering in the low-temperature monoclinic
(P2/c) structure of magnetite (Fe3O4)[1] is investigated using
LSDA+U. The ground state is found to display both charge order (CO)
and orbital order (OO) [2]. The CO is described by a [001] charge density
wave with a minor [001 ] modulation, and is incompatible with the An-
2
derson criterion. The OO agrees with the Kugel-Khomskii theory. The
system is described by two order parameters: (i) the difference between
the t2g minority occupancies of 2+ and 3+ Fe cations, and (ii) the total
3d charge difference. While the former is large (0.5), the screening of
charge disproportion is so effective that the latter is rather small (0.23).
This agrees well with the results of bond valence sum analysis (0.2).
The LSDA+U results are also in reasonably good with measured optical
spectra.
[1] J. P. Wright, J. P. Attfield and P. G. Radaelli, Phys. Rev. Let. 87,
266401 (2001)
[2] I. Leonov, A. N. Yaresko, V. N. Antonov, M. A. Korotin, V. I. Anisimov
and D. Vollhardt (preprint)
TT 24.3 Mi 14:30 Poster A
DFT-Gutzwiller Calculations for ferromagnetic bcc Nickel
— •Torsten Ohm 1 , Stefan Weiser 1 , Werner Weber 1 , and
Jörg Bünemann 2 — 1 Institut für Physik, Universität Dortmund —
2 Fachbereich Physik, Phillips Universität Marburg
Thin films of bcc Nickel can be produced on appropriate substrates and
can be studied experimentally; e.g., by photoemission spectroscopy. This
has stimulated us to carry out a multi-band Gutzwiller calculation for
the quasi-particle energy bands. Our single particle Hamiltonian is based
on results of spin-density functional theory ground state calculations using
the LAPW-Wien2k code. In the DFT calculations, some problems
with the k-mesh integration had to be overcome in order to establish
well converged total energy values. The spin-only magnetic moment is
found to be about 20 percent smaller than in fcc Nickel. For the multiband
Gutzwiller calculations we use the DFT lattice constant and the
same atomic Racah interaction parameters A,B, and C as in our previous
calculations for fcc Nickel. The Gutzwiller quasi-particle bands and the
Fermi surfaces are compared with the corresponding DFT results.
TT 24.4 Mi 14:30 Poster A
Quantum Monte Carlo approach to the Holstein model —
•Martin Hohenadler, Hans Gerd Evertz, and Wolfgang von
der Linden — Institute for Theoretical and Computational Physics,
Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
Based on the canonical Lang-Firsov transformation of the Hamiltonian,
we develop a novel quantum Monte Carlo algorithm for the Holstein
model with one electron. Separation of the fermionic degrees of freedom
by a reweighting of the probability distribution leads to a dramatic reduction
in computational effort. A principle component representation
of the phonon degrees of freedom allows us to sample completely uncorrelated
phonon configurations. Despite a minus-sign problem, which

Tiefe Temperaturen Mittwoch
is a consequence of the Lang-Firsov transformation, the combination of
these elements enables us to perform efficient simulations for a wide range
of temperature, phonon frequency and electron-phonon coupling in one
to three dimensions, and on clusters large enough to avoid significant
finite-size effects. The algorithm is employed to investigate the problem
of small polaron formation in the Holstein model, and comparison with
exact results and with existing work is made. Moreover, the new ideas
presented here can also be applied to the many-electron case.
TT 24.5 Mi 14:30 Poster A
Variational cluster approach to extended Hubbard models at
half filling — •Markus Aichhorn 1 , Hans Gerd Evertz 1 , Wolfgang
von der Linden 1 , and Michael Potthoff 2 — 1 Institut für
Theoretische Physik und Computational Physics, Technische Universität
Graz, Petersgasse 16, A-8010 Graz, Austria — 2 Institut für Theoretische
Physik und Astrophysik, Universität Würzburg, Am Hubland, D-97074
Würzburg, Germany
We present an extension of the recently proposed variational cluster
perturbation theory to extended Hubbard models at half filling with
repulsive nearest neighbor interaction. The method takes into account
short-range correlations exactly by the exact treatment of clusters of finite
size via exact diagonalization, whereas long-range order beyond the
size of the clusters is treated on a mean-field level. We show that for one
dimension results known from Quantum Monte Carlo and Density Matrix
Renormalization Group can be reproduced with very good accuracy.
Moreover we apply the method to the two-dimensional extended Hubbard
model on a square lattice. Different from one dimension, we find a first order
phase transition between spin density wave phase and charge density
wave phase down to onsite interaction U = 3t. In addition, the singleparticle
spectral function is calculated for both the one-dimensional and
the two-dimensional system.
TT 24.6 Mi 14:30 Poster A
Influence of long-range Coulomb interaction and on-site
Hubbard repulsion on the formation of d-wave Copper-pairing
in high-Tc cuprates — •Dirk Manske 1 , Ernst Pashitskii 2 ,
Vsevolod Pentegov 2 , and Ilya Eremin 1 — 1 Institut für Theoretische
Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin
— 2 Institute of Physics NAS of Ukraine, 46 Nauki str., Kiev, 03028,
Ukraine
We develop a diagram technique for the self-consistent treatment of
the long-range Coulomb interaction and on-site Hubbard repulsion in
the normal and superconducting state of high-Tc cuprates. The resultant
analytical expression for the screened matrix elements taking into
account long-range and on-site repulsion has been derived. In particular,
it accounts for processes with and without spin-flip due to an exchange
of spin and charge density fluctuations. Furthermore, we derive the expressions
for the normal and anomalous self-energy parts near the superconducting
transition temperature Tc that takes into account the vertex
corrections including crossing diagrams. The contribution of the crossing
parts is taken within the ladder approximation (similar to Fluctuations
Exchange approximation) where the role of Hubbard on-site interaction
is replaced by the Coulomb matrix element with a spin-flip averaged
over the momentum. Finally, the developed scheme allows to analyze
the formation of d-wave superconductivity and its stability in presence
of the long-range Coulomb repulsion within a self-consistent anisotropic
Eliashberg-like approach.
TT 24.7 Mi 14:30 Poster A
Electronic structure of quasi-one-dimensional metals: Theory vs
Experiment — •Holger Benthien 1 , Eric Jeckelmann 2 , Florian
Gebhard 1 , Michael Sing 3 , and Ralph Claessen 3 — 1 Fachbereich
Physik, Universität Marburg, 35032 Marburg — 2 Institut für Physik,
Universität Mainz, 55099 Mainz — 3 Experimental Physik II, Universität
Augsburg, 86135 Augsburg
We compare theoretical and experimental results for the electronic
structure of quasi-one-dimensional correlated metals. On the one hand
the one-particle Green’s function is calculated numerically in the onedimensional
Hubbard model away from half filling using the dynamical
density-matrix renormalization group method [1]. On the other hand the
angle-resolved photoemission spectrum has been measured in the quasione-dimensional
organic charge transfer salt TTF-TCNQ [2]. We show
that the experimental spectrum at intermediate to high energy (up to
about 1eV) can be explained consistently in the framework of the onedimensional
Hubbard model. In particular, our results show clear evi-
dence for spin-charge separation in the excitation spectrum (and thus for
a non-Fermi liquid) up to the energy scale of the bandwidth.
[1] E. Jeckelmann, Phys. Rev. B 66, 045114 (2002).
[2] R. Claessen et al., Phys. Rev. Lett. 88, 096402 (2002).
TT 24.8 Mi 14:30 Poster A
Thermodynamic properties of ferromagnetic mixed-spin chain
systems — •Noboru Fukushima 1 , Andreas Honecker 1 , Stefan
Wessel 2 , and Wolfram Brenig 1 — 1 Institut für Theoretische Physik,
Technische Universität Braunschweig, Germany — 2 Theoretische Physik,
ETH Zürich, Switzerland
Using a combination of high-temperature series expansion, exact diagonalization
and quantum Monte Carlo, we perform a complementary
analysis of the thermodynamic properties of one-dimensional mixed-spin
systems with alternating magnetic moments. In particular, we focus on
the difference between ferromagnetic (FM) and antiferromagnetic (AFM)
exchange. Not only the peak structure of the specific heat is more pronounced
in the FM case, but also the number of the peaks appears different.
Namely, the FM case seems to have some additional energy scale(s).
The origin of these differences will be discussed. In addition, the impact
of interchain exchange will be also investigated.
TT 24.9 Mi 14:30 Poster A
Scaling of the conductance in interacting quantum wires —
•Tilman Enss 1 , Sabine Andergassen 1 , Volker Meden 2 , Walter
Metzner 1 , Ulrich Schollwöck 3 , and Kurt Schönhammer 2
— 1 Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart
— 2 Institut für Theoretische Physik, Universität Göttingen, D-37073
Göttingen — 3 Sektion Physik, Universität München, Theresienstr. 37,
D-80333 München
The conductance through an interacting nanowire containing impurities
and coupled to non-interacting leads is studied at zero and finite temperature.
Our functional RG method starts from the microscopical model
and arrives at an effective low-energy model correctly showing Luttinger
liquid behavior. For a single impurity we observe one-parameter scaling
of the conductance. Using several impurities, we study resonances of the
conductance and temperature-dependent transport through a quantum
dot.
TT 24.10 Mi 14:30 Poster A
Functional RG for Luttinger liquids with impurities — •Sabine
Andergassen 1 , Tilman Enss 1 , Volker Meden 2 , Walter Metzner
1 , Ulrich Schollwöck 3 , and Kurt Schönhammer 2 — 1 Max-
Planck-Institut für Festkörperforschung, D-70569 Stuttgart — 2 Institut
für Theoretische Physik, Universität Göttingen, D-37073 Göttingen —
3 Sektion Physik, Universität München, D-80333 München
Using a functional RG we compute the flow of the renormalized impurity
potential for a single impurity in a Luttinger liquid over the entire
energy range from the microscopic scale of a lattice-fermion model
down to the low-energy limit. The non-perturbative method provides a
complete real-space picture of the effective impurity potential. Further
developments of the functional RG approach including 2-particle vertex
renormalization considerably improve the quantitative accuracy of the
results in particular at moderate interaction strenghts, which are compared
to exact DMRG results. Focusing on the spectral properties of the
single-particle excitations near an impurity or boundary and on the density
profile, we confirm the universality of the open chain fixed point, but
it turns out that very large systems are required to reach the asymptotic
regime for realistic choices of the impurity and interaction parameters.
TT 24.11 Mi 14:30 Poster A
Coexistence of s-wave Superconductivity and Antiferromagnetism
— •Martin Feldbacher 1 , Fakher Assaad 2 , Frederic
Hébert 3 , and George Batrouni 3 — 1 Max-Planck-Institut für
Festkörperforschung, Heisenbergstraße 1, D-70569 Stuttgart —
2 Universität Würzburg, Institut für Theoretische Physik I, Am Hubland,
97074 Würzburg — 3 Institut Non-Linéaire de Nice, Université de
Nice-Sophia Antipolis, France
We study the phase diagram of a new model that exhibits a first order
transition between s-wave superconducting and antiferromagnetic phases.
The model, a generalized Hubbard model augmented with competing
spin-spin and pair-pair interactions, was investigated using the projector
Quantum Monte Carlo method. Upon varying the Hubbard U from
attractive to repulsive we find a first order phase transition between superconducting
and antiferromagnetic states. Phys. Rev. Lett., 91:056401,

Tiefe Temperaturen Mittwoch
2003
TT 24.12 Mi 14:30 Poster A
Hubbard model in a magnetic field at weak coupling —
•Carsten L. Knecht and P.G.J. van Dongen — Institut für
Physik, Johannes Gutenberg-Universität, Staudinger Weg 7, 55099
Mainz, Germany
The phase diagram of the half-filled Hubbard model is studied at weak
coupling in two spatial dimensions. A homogeneous magnetization in
the z-direction and a staggered magnetization in the x-direction are assumed.
We apply perturbation theory at fixed order parameter (PTFO)
to this system. The results are compared with the well know Hartree-Fock
solutions that usually overestimate the order parameters. This calculation
is also relevant for superconductivity in the doped two-dimensional
negative-U Hubbard model.
TT 24.13 Mi 14:30 Poster A
Self-energy-functional approach: New results and developments
— •Michael Potthoff — Institut für Theoretische Physik und Astrophysik,
Universität Würzburg
The self-energy-functional approach [1-3] is a general variational framework
to construct non-perturbative and thermodynamically consistent
approximations for lattice models of correlated electrons. The main idea
is to shift the problem to a more simple reference system with the same
(two-particle) interaction which is exactly solved for different one-particle
parameters. The parameters are fixed by evaluation of a fundamental variational
principle for the self-energy.
This contribution gives an overview over the recent developments in
the extension of the approach to Bose systems, two-particle excitations or
disordered systems and discusses efficient numerical methods to evaluate
the variational principle.
[1] M.P., EPJB 32, 429 (2003)
[2] M.P., M. Aichhorn and C. Dahnken, PRL 91, 206402 (2003)
[3] M.P., EPJB in press, cond-mat/0306278
TT 24.14 Mi 14:30 Poster A
Crossover from Non-equilibrium to Equilibrium Behavior in the
Time–DependentKondo Model — •Stefan Kehrein and Dmitry
Lobaskin — Insitut für Physik – Elektronische Korrelationen und Magnetismus,
Universität Augsburg
We investigate the equilibration of a Kondo model that is initially
prepared in a non–equilibrium state towards its equilibrium behavior
for large times. Such initial non–equilibrium states can e.g. be realized
in quantum dot experiments with time–dependent gate voltages or
in rf SQUIDS. We evaluate the spin–spin correlation function at the
Toulouse point of the Kondo model exactly and show that there is a
smooth crossover between non–equilibrium and equilibrium behavior as
the non–equilibrium initial state decays as a function of the waiting time.
In particular, we demonstrate that the decaying non–equilibrium state
cannot be thought of as an equilibrium state with an effective temperature
that depends on the waiting time.
TT 24.15 Mi 14:30 Poster A
Finite temperature Drude weight of strongly correlated 1d systems
— •Stefan Glocke and Andreas Klümper — Universität
Wuppertal, Theoretische Physik, Gauß-Straße 20
We present results for the Drude weight Ds of the spin conductivity
σ of the integrable spin-1/2 XXZ chain at arbitrary temperature (σ =
electrical conductivity in the spinless fermion language of the model). The
results are obtained by a combination of linear response theory (Kubo
formula) and solution techniques of Bethe ansatz type. Unlike the case
of thermal conductivity, the state of investigation of the spin conductivity
of the XXZ chain is less complete if not controversial. The reason
for this lies in the non-conservation of the spin (charge) current. Despite
this, there is a delta-function peak at zero frequency in the dynamical
conductivity σ(ω) = Ds · δ(ω) + σreg(ω). The controversies of [1],[2]
and more recent treatments arise about the anisotropy (interaction) and
temperature dependence of Ds. Some of the controversies are resolved by
the observation of a strong variation of the energy level curvatures even
within a microcanonical ensemble between “very similar states”.
[1] B.N. Narozhny, A.J. Millis, N. Andrei: Phys. Rev. B 58, R2921 (1998)
[1] X. Zotos: Phys. Rev. Lett. 82, 1764 (1999)
TT 24.16 Mi 14:30 Poster A
General susceptibilities of highly correlated electron systems
from a local point of view — •Sebastian Schmitt and Norbert
Grewe — Institut für Festkörperphysik, Hochschulstraße 6, 64289
Darmstadt
Starting from a cumulant expansion in terms of the transfer between
lattice sites in the presence of large local Coulomb matrix elements,
Bethe-Salpeter equations are derived. Using only local particle-hole or
particle-particle irreducible vertices, as in the dynamical mean field theory,
general susceptibilities can be approximated. Employing a decoupling
scheme for the energy summations, a typical Stoner-form is obtained,
where the local interaction part is explicitly known.
In the case of the Hubbard model the magnetic susceptibility is studied
in detail.
TT 24.17 Mi 14:30 Poster A
Charge Fluctuations in the t-U-V1-V2 Model — •Satoshi Ejima 1 ,
Florian Gebhard 1 , Satoshi Nishimoto 1 , and Yukinori Ohta 2 —
1 Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg —
2 Department of Physics, Chiba University, Chiba 263-8522, Japan
Recently, charge dynamics has attracted much interest in the
transition-metal oxide PrBa2Cu3O7 and in the organic conductor
(TYMTSF)2. In the low-energy physics of these materials, charge
fluctuations play a crucial role, due to the frustration of the long-range
Coulomb interactions.
The minimal model for these systems is the one-dimensional
quarter-filled Hubbard model with nearest-neighbor (V1) and nextnearest-neighbor
(V2) Coulomb interactions. We investigate the ground
state and some excited states using the (dynamical) density-matrix
renormalization group technique. We present an accurate phase diagram
and discuss the possible emergence of a metallic (or superconducting)
phase induced by charge fluctuations. Moreover, we compare our
single-chain results with calculations for double-chain systems such as
PrBa2Cu4O8 [1].
[1] S. Nishimoto and Y. Ohta, cond-mat/0305610
TT 24.18 Mi 14:30 Poster A
Analytical and numerical treatment of the Mott–Hubbard
insulator in infinite dimensions — •Satoshi Nishimoto 1 ,
Satoshi Ejima 1 , Florian Gebhard 1 , Eva Kalinowski 1 , Reinhard
M. Noack 1 , and Eric Jeckelmann 2 — 1 Fachbereich Physik,
Philipps-Universität Marburg, 35032 Marburg — 2 Institut für Physik,
Johannes-Gutenberg Universität Mainz, 55099 Mainz
The half-filled Hubbard model on a Bethe-lattice with infinite coordination
number describes a Mott-Hubbard insulator above a critical
interaction strength. We extend our previous study [1] by using the Dynamical
Density-Matrix Renormalization Group method (DDMRG) [2,3]
to solve the Dynamical Mean-Field equations. To this end, we analyze a
single-impurity Anderson model with up to ns = 64 levels in the bath.
We refine our results in [1] which were limited to ns = 14 in exact diagonalization.
Furthermore, we extend our analytical results on the groundstate
energy of the Mott-Hubbard insulator, to ninth-order in the inverse
coupling strength.
[1] M.P. Eastwood, F. Gebhard, E. Kalinowski, S. Nishimoto, and R.M.
Noack, Eur. Phys. J. B 35, 155 (2003).
[2] E. Jeckelmann, Phys. Rev. B 66, 045114 (2002).
[3] F. Gebhard, E. Jeckelmann, S. Mahlert, S. Nishimoto, and R.M.
Noack, cond-mat/0306438.
TT 24.19 Mi 14:30 Poster A
Quartic Oscillator: Diagonalization by Continuous Unitary
Transformations — •Sébastien Dusuel und Götz S. Uhrig —
Zülpicherstr. 77, D-50937 Köln, Germany
The method of Continuous Unitary Transformations (CUTs) has been
applied successfully to various many-body Hamiltonians. We here consider
a simple model, namely a single quartic oscillator. Our aim is two-fold:
First, it can be used as a pedagogical and illustrative introduction to the
CUTs. Second, thanks to its simplicity, the quartic oscillator allows to
gain an intuition about the CUTs. Various generators of the transformations
are tested and their efficiency is compared. Various high-order
truncation schemes are equally analyzed. The results are also compared
to results from the functional renormalization group.

Tiefe Temperaturen Mittwoch
TT 24.20 Mi 14:30 Poster A
The physics of chiral helices in a metal — •Inga Fischer and
Achim Rosch — Institut für Theoretische Physik, Universität zu Köln
At high pressures, MnSi exhibits non-Fermi liquid behaviour over a
wide temperature and pressure range [1,2]. This may point to the existence
of a genuine non-Fermi liquid phase in an extremely pure cubic
system. Recent neutron scattering measurements [3] suggest the presence
of partial helical order in this phase, motivating us to study the physics
of chiral helices theoretically.
Helical order with a large pitch is stabilized by weak spin-orbit
(Dzyaloshinskii–Moriya) interactions in the non-centrosymmetric
crystal structure of MnSi. The interplay of static helical order and
further spin-orbit interactions in the conduction electron bands leads
to the formation of surprisingly large band-gaps in certain regions of
the Brillouin zone. We discuss their experimental consequences and
furthermore investigate the nature of magnetic fluctuations in MnSi.
[1] C. Pfleiderer et al., Nature 414 427–430 (2001).
[2] N. Doiron-Leyraud et al., Nature 425 595–599 (2003).
[3] C. Pfleiderer et al., to be published.
TT 24.21 Mi 14:30 Poster A
Die stark-Kopplungs-Phase des ionischen Hubbard Modells —
•Salvatore Manmana 1,2 , Volker Meden 3 , Reinhard Noack 2
und Kurt Schönhammer 3 — 1 Institut f. Theoretische Physik III,
Universität Stuttgart, Pfaffenwaldring 57/V, 70550 Stuttgart — 2 AG
Vielteilchennumerik, Philipps-Universität Marburg, Renthof 6, 35032
Marburg — 3 Institut f. Theoretische Physik, Georg-August-Universität
Göttingen, Tammannstr. 1, 37077 Göttingen
Das Phasendiagramm des ionischen Hubbard-Modells war ein in der
Literatur viel diskutiertes Thema. In einer numerischen Arbeit mit
Hilfe der DMRG-Methode (Dichtematrix-Renormierungsgruppe) ist es
uns gelungen, ein konsistentes Bild des Phasendiagramms zu erstellen.
Bei der Untersuchung der Eigenschaften der Phasen findet man
überraschenderweise eine Korrelierte-Isolator-Phase mit einer divergierenden
elektrischen Suszeptibilität und einem Potenzgesetzabfall in der
Dichte-Dichte-Korrelationsfunktion. In diesem Poster sollen diese ungewoehnlichen
Eigenschaften und die bisherigen Erklärungsversuche vorgestellt
werden.
TT 24.22 Mi 14:30 Poster A
Incommensurate charge-density wave in the stripe phase of
the two-dimensional Hubbard-Holstein model — •Serguei Varlamov
and Götz Seibold — Institut für Physik, BTU Cottbus, PBox
101344, 03013 Cottbus, Germany
We investigate the structure of the stripe phase in the two-dimensional
infinite-U Hubbard-Holstein model by means of the slave-boson technique.
We find in the mean-field approximation that the incommensurate
charge density waves (ICDW) appear in the region of the g vs δ phase
diagram where an ICDW is expected to form in the frustrated phaseseparation
scenario. Our main finding is that due to the competition
between strong on-site correlations and CDW ordering instability the incommensurability
of CDW depends from the number of carriers leading
to the reduction of the incommensurability with increasing of hole doping.
The influence of long-range Coulomb interaction on the structure of
ICDW is discussed.
TT 24.23 Mi 14:30 Poster A
Electronic structure, magnetism, and superconductivity in
pseudo-ladder compounds — •S.-L. Drechsler 1 , H. Rosner 1 ,
N.M. Plakida 2 , A. Vladimirov 3 , H. Eschrig 1 , and M. Knupfer 1
— 1 IFW-Dresden, P.O. Box 270116, 01171 Dresden, Germany —
2 MPI-CPfS Dresden, Germany — 3 J. Inst. f. Nuclear Res., Dubna,
Russia
The electronic structure of ACu2O3 compounds [A=Ca,Mg] has been
calculated within the local density approximation and compared with
x-ray absorption spectroscopy and magnetic neutron scattering data [1].
Both compounds deviate markedly from the usual pdσ cuprate picture.
Significant interlayer exchange in the stacking c-direction is found to be
responsible for the missing spin gap (generic for ideal two-leg ladders)
and the finite Néel-temperature. Hence, they can be modelled as weakly
coupled anisotropic Heisenberg (Hubbard) bi-layers. Within a derived effective
t-J-model in mean-field approximation nodeless superconductivity
below 50 K is predicted for Ca0.88Na0.12Cu2O3 (optimal hole doping).
[1]V. Kiryukhin et al., PRB 64, 1444418 (2001).
TT 24.24 Mi 14:30 Poster A
Time-dependent Gutzwiller theory of magnetic excitations in
the Hubbard model — •Goetz Seibold 1 , Federico Becca 2 , and
Jose Lorenzana 3 — 1 Lehrstuhl Theoretische Physik, BTU Cottbus,
03013 Cottbus, Germany — 2 SISSA, 34014 Trieste, Italy — 3 Dip. di
Fisica, Universita di Roma ’La Sapienza’, 00185 Roma, Italy
We use a spin-rotational invariant Gutzwiller energy functional to compute
random-phase-approximation-like (RPA) fluctuations on top of the
Gutzwiller approximation (GA). Since no restrictions are imposed on
the symmetry of the underlying saddle-point solution, our approach is
suitable for the evaluation of the magnetic susceptibility and dynamical
structure factor in strongly correlated inhomogeneous systems. We
present a detailed study of the quality of our approach by comparing
with exact diagonalization results and show its much higher accuracy
compared to the conventional Hartree-Fock+RPA theory. In infinite dimensions,
where the GA becomes exact for the Gutzwiller variational energy,
we evaluate ferromagnetic and antiferromagnetic instabilities from
the transverse magnetic susceptibility. The resulting phase diagram is in
complete agreement with previous variational computations.
TT 24.25 Mi 14:30 Poster A
Stability of metallic stripes in the extended one-band Hubbard
model — •Goetz Seibold 1 and Jose Lorenzana 2 — 1 Lehrstuhl
Theoretische Physik, BTU Cottbus, 03013 Cottbus, Germany — 2 Dip.
di Fisica, Universita di Roma ’La Sapienza’, 00185 Roma, Italy
Based on an unrestricted Gutzwiller approximation (GA) we investigate
the stripe orientation and periodicity in an extended one-band Hubbard
model. A negative ratio between next-nearest and nearest neighbor
hopping t ′ /t, as appropriate for cuprates, favors partially filled (metallic)
stripes for both vertical and diagonal configurations. At around optimal
doping diagonal stripes, site centered (SC) and bond centered (BC) vertical
stripes become degenerate suggesting strong lateral and orientational
fluctuations. We find that within the GA the resulting phase diagram
is in agreement with experiment whereas it is not in the Hartree-Fock
approximation due to a strong overestimation of the stripe filling. Results
are in agreement with previous calculations within the three-band
Hubbard model but with the role of SC and BC stripes interchanged.
TT 24.26 Mi 14:30 Poster A
Ionic Hubbard Model in High Dimension — •Krunoslav Pozgajcic
and Claudius Gros — Universität des Saarlandes, Fakultät 7,
Theoretische Physik, Postfach 15 11 50, D-66041 Saarbrücken
Ionic Hubbard model was proposed for the description of organic
mixed-stack charge-transfer crystals and also for the description of the
ferroelectric transition in perovskite materials. Theoretical efforts have
mostly been directed to the one dimensional case, which has be thoroughly
investigated by various methods on disposal for the one dimensional
systems. Recently, the self-energy functional approximation (SFA)
has been proposed (M. Potthoff, Eur. Phys. J. B 32, 429(2003)) as a
unifying scheme for a few cluster methods. We will present results for
the one dimensional and the higher dimensional ionic Hubbard model
calculated in the SFA framework.
TT 24.27 Mi 14:30 Poster A
Self-energy effects in the two-dimensional Hubbard-Model from
Functional Renormalisation
— •Daniel Rohe — Max-Planck-Institut FKF, Heisenbergstr. 1, 70569
Stuttgart
We present a numerical study of the two-dimensional Hubbard Model
in the normal state at low temperatures by means of a functional renormalisation
group scheme. It is found that anomalous features arise in
the self-energy slightly above a mean-field transition temperature T*.
This offers information on possible mechanisms responsible for unusual
properties of the model in the normal (non-symmetry-broken) state.
TT 24.28 Mi 14:30 Poster A
Druckeinfluss auf die magnetische Ordnung in CeNiGa2 —
•Andreas Eichler 1 , Ernst Bauer 2 , Robert Hauser 2 , Heinrich
Weiss 1 und Torsten Burghardt 1 — 1 Institut für Technische Physik,
TU Braunschweig, Mendelssohnstr. 2, D-38106 Braunschweig — 2 Institut
für Festkörperphysik, TU Wien, A-1040 Wien
Die Verbindung CeNiGa2 ist bekannt als antiferromagnetisches Kondogitter
mit einer Néel-Temperatur von ca. 4 K und relativ hoher elektronischer
spezifischer Wärme von 490 mJ/molK 2 . Messungen des elektrischen
Widerstandes unter Druck hatten ergeben, dass TN schnell abnimmt und

Tiefe Temperaturen Mittwoch
nahe 0,4 GPa verschwindet.
Wir präsentieren hier Ergebnisse aus Messungen der magnetischen
Suszeptibilität und spezifischen Wärme unter Druck. Danach sind noch
schwache Kennzeichen für einen magnetischen Ordnungsübergang jenseits
der 0,4 GPa zu finden, die nahe 0,5 GPa definitiv verschwinden.
Dabei bildet sich sukzessive ein Verlauf von χ heraus, der mit abnehmender
Temperatur ungefähr logarithmisch ansteigt.
TT 24.29 Mi 14:30 Poster A
Specific heat of PrOs4Sb12 at high magnetic fields — •K.
Grube 1 , S. Drobnik 2 , C. Pfleiderer 2 , A. Faisst 2 , R. Vollmer 2 ,
H. v. Löhneysen 1,2 , E.D. Bauer 3 , and M.B. Maple 3 —
1 Forschungszentrum Karlsruhe, Institut für Festkörperphysik, D-76021
Karlsuhe — 2 Physikalisches Institut, Universität Karlsruhe, D-76128
Karlsuhe — 3 Department of Physics and Institute of Pure and
Applied Physical Sciences, University of California San Diego, La Jolla,
California 92093-0319
PrOs4Sb12 is the first Pr based heavy-fermion superconductor. Detailed
measurements of the low temperature specific heat [1] have helped
identify the superconductivity in PrOs4Sb12 as a strong contender for
quadrupolar pairing, i.e., superconductivity that is neither electronphonon
nor magnetically mediated. Here we focus on a related issue,
the formation of an ordered phase at low temperatures and high magnetic
fields, that appears to be connected with the Zeeman splitting of
the crystal electric field ground state. We have revisited this high field
phase in a detailed study of the specific heat up to 14T at temperatures
down to 0.4K. The possible nature of the high-field phase is discussed in
the context of the crystal field ground state and the evidence for several
superconducting phases.
[1] R. Vollmer et al., Phys. Rev. Lett. 90 (2003) 057001
.
TT 24.30 Mi 14:30 Poster A
Thermische Ausdehnung von CeCu6−xAux — •K. Grube 1 , P.
Estrela 2 , A. de Visser 2 , O. Stockert 3 und H. v. Löhneysen 1,4 —
1 Forschungszentrum Karlsruhe, Institut für Festkörperphysik, D-76021
Karlsruhe — 2 Van der Waals-Zeeman Institute, Universiteit van Amsterdam,
1018XE Amsterdam — 3 Max-Planck-Institut für chemische Physik
fester Stoffe, D-01187 Dresden — 4 Physikalisches Institut, Universität
Karlsruhe, D-76128 Karlsruhe
CeCu6−xAux ordnet oberhalb von x > 0.1 antiferromagnetisch.
Während der magnetische Ordnungsvektor sich drastisch zwischen x =
0.4 und 0.5 ändert, steigt die Néeltemperatur zwischen x = 0.1 und 1.0
linear an. Am Übergang zur magnetischen Ordnung zeigen die linearen
thermischen Ausdehnungskoeffizeinten für x = 0.3 positive Sprünge in a
und b Richtung und einen negativen Sprung in c Richtung. Für x = 0.5
wechseln die Sprünge entlang der a und b Achse ihr Vorzeichen. Dieses
Verhalten scheint die drastische Änderung des Ordnungsvektors widerzuspiegeln.
Mit Hilfe der elastischen Konstanten lassen sich die resultierenden
uniaxialen Druckabhängigkeiten der Néeltemperatur in Dehnungsabhängigkeiten
umrechnen und mit der Dotierungs- und Druckabhängigkeit
der magnetischen Struktur vergleichen.
TT 24.31 Mi 14:30 Poster A
Ferromagnetic to paramagnetic quantum phase transition of
single crystal CeSi1.81 at high pressure — •S. Drotziger 1 , C.
Pfleiderer 1 , M. Uhlarz 1 , H. v. Löhneysen 1,2 , D. Souptel 3 , W.
Löser 3 , and G. Behr 3 — 1 Physikalisches Institut, Universität Karlsruhe,
D-76128 Karlsuhe — 2 Forschungszentrum Karlsruhe, Institut für
Festkörperphysik, D-76021 Karlsuhe — 3 Institut of Solid State and Materials
Research Dresden, Postfach 270116, D-01171 Dresden
Silicon deficient CeSi2−x crystallizes over a large range of compositions
in the orthorhombic α-GdSi2 structure. Below a critical Si content,
easy-plane ferromagnetism is observed. Being one of the rare examples
of a ferromagnetic Ce compound, the nature of this ferromagnetic state
has been studied intensively in the past. Here we report a high pressure
study of the magnetisation of a new generation of CeSi2−x single crystals
grown with an optical floating zone furnace under ultrapure conditions. In
CeSi1.81 where TC = 9.5K, moderate pressures are sufficient to suppress
ferromagnetism. The easy-plane ferromagnetic to paramagnetic quantum
phase transition is compared with the predictions of weak-coupling spin
fluctuation theory.
TT 24.32 Mi 14:30 Poster A
Investigation of the Low Ordered Moment in CeBiPt —
•G. Goll 1 , O. Stockert 2 , M. Prager 3 , N. Stüßer 4 , and T.
Takabatake 5 — 1 Physikalisches Institut, Universität Karlsruhe, 76128
Karlsruhe — 2 Max-Planck-Institut CPfS, 01187 Dresden — 3 Institut
für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich —
4 Hahn-Meitner-Institut, 14109 Berlin — 5 Department of Quantum
Matter ASDM, Hiroshima University, Higashi Hiroshima, 739-8526,
Japan
The electronic properties of CeBiPt show semimetallic behavior with
low charge carrier concentration nh = 7.7 ·10 17 cm −3 . Shubnikov-de Haas
experiments reveal a Fermi surface consisting mainly of a small hole
pocket around the Γ point with a volume of 1.5 · 10 −4 of the volume
of the first Brillouin zone [1]. To explain these result by band-structure
calculation a local character of the 4f electrons is required. The magnetic
behavior supports a local character as well. The magnetic susceptibility
follows a Curie-Weiss law above T = 100K with the full moment of free
Ce 3+ ions and magnetic order was found below TN = 1.1K by specificheat
measurements [2]. However, previous neutron-diffraction data suggested
an ordered moment well below 1µB. Crystal-electric fields (CEF)
in the cubic crystal symmetry can only partly account for the reduced
moment. Inelastic neutron scattering as well as neutron diffraction on
powder were used to investigate the CEF ground state and the magnetically
ordered moment. The measurements suggest additional magnetic
excitations with a characteristic temperature of 10 - 20K being responsible
for the low ordered moment.
[1] G. Goll et al., Europhys. Lett. 57, 233 (2002).
[2] T. Pietrus et al., Physica B 281 & 282, 745 (2000).
TT 24.33 Mi 14:30 Poster A
Successful growth of the intermetallic compound CeCu2(Si,Ge)2
by high-temperature solution — •M. Deppe, H. S. Jeevan, R.
Borth, C. Geibel, and F. Steglich — Max-Planck-Institute for
Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dreden, Germany
Among the intermetallic compounds the system CeCu2(Si,Ge)2 is of
high interest because of the interplay between heavy-fermion superconductivity
and magnetism. For an intensive microscopic study large single
crystals of high quality are necessary. Large single crystals of this
compound were not available because of the incongruent formation of
CeCu2Si2 and substantial loss of copper during the typical growing process.
To overcome this difficulty the typical procedure is to use an offstochiometric
starting melt with an excess of copper. Four different
ground states exist for CeCu2Si2 which are very sensitiv to the exact
Cu/Si ratio. This makes it difficult to grow single crystals with a predetermind
ground state. To overcome this problem we started the growth
process with higher amount of Germanium because this reduced the
variety of physical ground states to only one. Later on we reduce the
Germanium content. We will discuss the optimal growth conditions for
our modified Bridgman technique using copper as flux. For the physical
characterisation we used resistivity and specific heat measurements.
These measurements show that our crystal growth method gives reproducible
results and evidence a systematic development of the magnetic
state with increasing Germanium content in the concentration range x
≤ (0 - 0.5). The discussion will focus on the future optimization of our
growth methods and the comparison with other crystal grow techniques.
TT 24.34 Mi 14:30 Poster A
Transferred hyperfine fields in the heavy fermion compounds
CeCu6−xAux — •Max Winkelmann, Gerda Fischer, and Elmar
Dormann — Physikalisches Institut, Universitaet Karlsruhe, D-76128
Karlsruhe
CeCu6 is one of the best known heavy-fermion paramagnets, CeCu5Au1
is a heavy-fermion antiferromagnet with TN = 2.3 K, and for x ≈
0.1 signatures of non-Fermi-liquid behaviour were reported. We present
temperature dependent studies of 63 Cu- and 65 Cu-NMR line shifts for
CeCu6−xAux (x=0;0.1;1) single-crystal powder samples. These are different
to the earlier[1] presented line shifts for polycrystalline powder
samples. Via the correlation with the temperature dependence of the
static magnetic susceptibility, Cu-site dependent Knight shift and transferred
hyperfine field coupling constants are derived. Local polarization
varies in sign and is larger by a factor of 10 than indicated by the earlier
published[2] high-temperature average value.
[1] M. Winkelmann, et al. Eur. Phys. J. B 26, (2002) 199
[2] I. Pop, et al. Czech. J. Phys. B 24 (1974) 1398

Tiefe Temperaturen Mittwoch
TT 24.35 Mi 14:30 Poster A
Heavy Fermion CePd3: Coherent State Versus Kondo Holes
— •Philipp Haas, Peter Weber, Konstantin Petukhov, Oleg
Ushakov, Boris Gorshunov, and Martin Dressel — 1. Physikalisches
Institut, Universität Stuttgart, 70550 Stuttgart
The formation of the coherent heavy-fermion state in CePd3 is studied
when doped with non-magnetic La. The La atoms act as Kondo-holes.
Low-energy excitations are studied by dc, microwave, THz, and infrared
measurements at temperatures from 5 K to 300 K. Pure CePd3 shows
typical features for heavy-fermion systems in the conductivity spectra: A
hybridization gap opens at around 1000 cm −1 ; below 50 cm −1 the optical
conductivity increases. In addition, at microwave frequency a feature is
detected which resembles an extremely small energy gap (≈ 2 cm −1 ).
TT 24.36 Mi 14:30 Poster A
Calculated de Haas-van Alphen quantities of CeMIn5 (M =Co,
Rh, and Ir) compounds — •Saad Elgazzar, Ingo Opahle,
Roland Hayn, and Peter M. Oppeneer — Leibniz-Institute of Solid
State and Materials Research, P.O. Box 270016, 01171 Dresden
We report a critical analysis of the electronic structures and de Haasvan
Alphen (dHvA) quantities of the heavy-fermion superconductors
CeCoIn5, CeRhIn5, and CeIrIn5. The electronic structures are investigated
ab initio on the basis of full-potential band-structure calculations,
adopting both the scalar and fully relativistic formulations within the
framework of the local spin-density approximation (LSDA). In contrast
to another recent study, in which a pronounced change of the Fermi surface
due to relativistic effects and therefore the importance of relativistic
interactions for the superconductivity was claimed, we find only minor
relativistic modifications of the band structure in our calculations. The
ab initio calculated dHvA quantities are in good agreement with experimental
data for CeCoIn5 and CeInIn5, when we adopt the delocalized
LSDA description for the Ce 4f states. For CeRhIn5, however, a better
agreement with experiment is obtained when the Ce 4f electron is
treated as a localized core electron. The implications for an emerging picture
of the localization behavior of the 4f electron in these materials are
discussed. We furthermore compare our calculated dHvA quantities with
other recent relativistic calculations and discuss the differences between
them.
TT 24.37 Mi 14:30 Poster A
Transport Properties of LaTiO3+x Films and Heterostructures
— •Andreas Schmehl 1 , Frank Lichtenberg 1 , Darrell
Schlom 2 , Hartmut Bielefeldt 1 , and Jochen Mannhart 1 —
1 Experimentalphysik VI, Elektronische Korrelationen und Magnetismus,
Institut für Physik, Universität Augsburg, Universitätsstr. 1, D-86135
Augsburg, Deutschland — 2 Department of Materials Science and
Engineering, The Pennsylvania State University, University Park,
Pennsylvania 16802-5505, USA
We report on the transport properties of LaTiO3+δ and LaTiO3.5 films.
The LaTiO3+δ samples show metallic transport and several samples exhibit
a hysteretic drop of resistance during cooldown at ∼240K. The ferroelectric
LaTiO3.5 samples, grown in capacitor structures, have nonlinear,
diode-like and hysteretic V(I)-characteristics. Two charge-controlled
transport regimes are found, which can be utilized for switching the devices
between two voltage states.
TT 24.38 Mi 14:30 Poster A
Eigenschaften von YbAl2 bei tiefen Temperaturen —
•T. Görlach 1 , C. Pfleiderer 1 und H. v. Löhneysen 1,2 —
1 Physikalisches Institut, Universität Karlsruhe, D-76128 Karlsruhe —
2 Forschungszentrum Karlsruhe, Institut für Festkörperphysik, D-76021
Karlsruhe
Die zwischenvalente Legierung YbAl2 hat bei tiefen Temperaturen eine
Reihe interessanter Eigenschaften. So wurde bei Messungen oberhalb
100 K festgestellt, dass die Magnetisierung nur schwach temperaturabhängig
ist und das für zwischenvalente Verbindungen typische Verhalten
zeigt [1]. Wir präsentieren Messungen der Magnetisierung, des Widerstandes
und der spezifischen Wärme im Temperaturbereich zwischen
1,5 und 300 K. Der elektrische Widerstand ist bei tiefen Temperaturen
(T ≤ 20 K) proportional zu T 3 – ein auch bei anderen zwischenvalenten
Verbindungen beobachtetes Verhalten. Die spezifische Wärme wird
durch den Gitterbeitrag dominiert, weicht aber von der Debye-Funktion
ab, was auf zusätzliche Anregungen hinweist. Die Magnetisierungsmessungen
sind qualitativ konsistent mit älteren Messungen für T > 100 K
und zeigen bei tieferen Temperaturen Curie-Verhalten.
[1] A. Iandelli, A. Palenzona, Journal of the Less-Common Metals
29 (1972), 293
TT 24.39 Mi 14:30 Poster A
Single crystal studies of a new ternary Europium pnictide
EuZn2Sb2 — •F. Weber 1 , A. Cosceev 1 , A. Nateprov 1,2 , M. Uhlarz
1 , C. Pfleiderer 1 , and H. v. Löhneysen 1,3 — 1 Physikalisches
Institut, Universität Karlsruhe, D-76128 Karlsuhe, Germany —
2 Institute of Applied Physics, Academei 5, MD-2028 Kishinev, Moldova
— 3 Forschungszentrum Karlsruhe, Institut für Festkörperphysik,
D-76021 Karlsruhe, Germany
We report the synthesis and characterisation of a new ternary Europium
pnictide EuZn2Sb2. Single crystals were grown by a solid state
reaction of high-purity starting materials in carbon glass crucibles. The
crystal structure was determined using powder x-ray diffraction. Single
crystals were oriented using Laue x-ray diffraction. EuZn2Sb2 is isostructural
with the hexagonal Yb compound YbZn2Sb2. The bulk properties
were characterised in terms of measurements of the resistivity, magnetoresistance,
Hall effect, specific heat and magnetisation. Pronounced
features characteristic of antiferromagnetic order with TN = 13.3K are
observed. For field parallel to the c-axis the antiferromagnetism is suppressed
above 2.7T while it persists up to ∼ 4.7T for field in the basal
plane. An analysis of the nature of the antiferromagnetic state as inferred
from the bulk properties is presented.
TT 24.40 Mi 14:30 Poster A
Orbital and spin exchange in LiNiO2 — •Roland Hayn 1 , Daré
Anne-Marie 1 , and Richard Jean-Louis 2 — 1 L2MP, Université Aix-
Marseille, Fac. St. Jerôme, 13397 Marseille Cedex 20, France — 2 Centre
de Physique Theorique, Luminy Case 907, 13288 Marseille Cedex 9,
France
We derive an effective orbital and spin exchange Hamiltonian using a
perturbative approach to study the compound LiNiO2. We show that the
inclusion of the trigonal crystal field splitting at the oxygen sites leads to
the appearance of antiferromagnetic exchange integrals in deviation from
the Goodenough-Kanamori-Anderson rules for this 90 degree bond. That
gives a microscopic foundation for the recently observed coexistence of
ferromagnetic and antiferromagnetic couplings in the orbitally frustrated
state of LiNiO2.
TT 24.41 Mi 14:30 Poster A
High energy photoemission study on the Verwey transition in
Fe3O4 — •David Schrupp 1 , Michael Sing 1,2 , Sigemasa Suga 2 , and
Ralph Claessen 1 — 1 Institut für Physik, Universität Augsburg, 86135
Augsburg, Germany — 2 Department of Material Physics, Osaka University,
Osaka 560-8531, Japan
Magnetite (Fe3O4) undergoes a first-order phase transition called the
Verwey transition (VWT). Although known for a long time the VWT
is currently a matter of intensive debate questioning fundamental issues
such as the charge ordering of Fe 2+ and Fe 3+ ions which is widely believed
to be the driving mechanism of the VWT.
We present a study of the VWT by valence band high energy photoemission.
Compared to VUV PES this enhances the probing depth by
at least a factor of 2 with surface effects greatly reduced. Nonetheless,
we still observe subtle differences in the valence band spectra between
differently prepared surfaces. While the spectra of sputtered, annealed,
and post-oxidized (111) and (100) single crystal surfaces display a continuous
temperature evolution through the Verwey temperature (TV ), a
first order VWT is observed on surfaces obtained by fracturing a crystal
at 40 K. The non-equilibrium atomic configuration of these surfaces is
thus apparently rather bulk-like, whereas the annealed samples display
strong surface relaxations. The spectra at T < TV of the fractured samples
are identified as those of a correlated insulator with a gap of at least
150 meV, which at TV closes into a pseudogap situation. The absence
of clear quasiparticle signatures characterizes the T > TV phase as an
incoherent metal, consistent with transport and optical data.
TT 24.42 Mi 14:30 Poster A
Metal-Insulator transitions driven by magnetic field in halfdoped
manganites — •Horacio Aliaga and Dieter Vollhardt
— Institut fuer Physik, Universitaet Augsburg D-86135, Germany
We study the first order transition between an antiferromagnetic (AF)
charge-ordered (CO) insulator to a ferromagnetic (FM) metal under external
applied magnetic field. The temperature variation of the charge
gap and magnetization as a function of temperature for different magnetic

Tiefe Temperaturen Mittwoch
fields are calculated using a model that considers the competition between
double exchange (DE), super exchange (SE) and electron-phonon
interactions. We show a comparison to transport and magnetization experiments
in related compounds.
TT 24.43 Mi 14:30 Poster A
Comparison of LSDA+U calculations and photo emission
data of Fe3O4 — •David Schrupp 1 , Ivan Leonov 1 , Alexander
Yaresko 2 , Shigemasa Suga 3 , Vladimir Anisimov 4 , and Ralph
Claessen 1 — 1 Institut für Physik, Universität Augsburg, 86135
Augsburg, Germany — 2 Max Planck Institute for Physics of Complex
Systems, 01187 Dresden, Germany — 3 Department of Material Physics,
Osaka University, Osaka 560-8531, Japan — 4 Institute of Metal Physics,
Ekaterinburg GSP-170, Russia
Magnetite, undergoes a first-order phase transition, reflected by an
increase of electrical resistivity by two orders of magnitude, called the
Verwey transition. Although known for a long time the Verwey transition
is currently a matter of intensive debate questioning fundamental
issues such as the charge ordering of Fe 2+ ions which is widely believed
to be the driving mechanism of the Verwey transition.
The LSDA+U calculations based on new structure refinements in the
low temperature phase of magnetite result in a charge and orbitally ordered
insulator. The self-consistent solution corresponding to charge order
does not satisfy the widely-accepted Anderson condition of minimum
electrostatic repulsion, but agrees with photoemission spectra, taken below
the Verwey transition temperature.
These spectra where obtained by using polished, sputtered, annealed
and post-oxidized single crystals. The correct stoichiometry and longrange
order of the thus prepared surfaces were proven by LEED, STM,
and XPS. The samples were measured with high energy photoemission
(¯hω ≈ 700 eV), which means an enhanced information depth.
TT 24.44 Mi 14:30 Poster A
Dimerization versus Orbital Moment Ordering in the Mott insulator
YVO3 — •Peter Horsch1 , Giniyat Khaliullin1 und Andrzej
M. Oles2 — 1Max-Planck-Institut f. Festkoerperforschung, D-
70569 Stuttgart, Germany. — 2Smoluchowski Institute of Physics, PL-
30059 Krakow, Poland.
We investigate the magnetic and orbital ordering within the spinorbital
model [1] for cubic vanadates using exact diagonalization in combination
with mean-field theory [2]. Increasing Hund’s exchange JH triggers
a crossover from the valence-bond orbital states to C-type antiferromagnetic
(AF) phase, while a finite spin-orbit coupling induces the
staggered component of magnetization which couples to the t2g orbital
moments. Our results provide a qualitative explanation of the observed
spin canting and large reduction of magnetization in the C-AF phase
of YVO3 [3]. At finite temperature an orbital instability in the C-type
antiferromagnetic phase induces modulation of magnetic exchange constants
even in the absence of lattice distortions. This dimerization should
be distinguished from a usual Peierls instability, as it emerges at finite
temperatures (and vanishes at zero temperature) due to an interplay of
quantum effects and thermal fluctuations, which open the way towards
dimerized orbital- and spin-correlations. The calculated spin structure
factor shows a magnon splitting at �q = (0, 0, π)
due to the orbital di-
2
merization, similar to the spinwave dispersions measured by Ulrich et
al.
[1] G. Khaliullin, P. Horsch, A.M. Oles, Phys. Rev. Lett. 86,3879 (2001).
[2] P. Horsch, G. Khaliullin, A.M. Oles, Phys. Rev. Lett. in print (2003).
[3] C. Ulrich et al., Phys. Rev. Lett. in print (2003).
TT 24.45 Mi 14:30 Poster A
Orbital assisted metal insulator transition in VO2 — •L.H.
Tjeng 1 , T. Koethe 1 , M.W. Haverkort 1 , Z. Hu 1 , A. Tanaka 2 ,
S. Streltsov 3 , M. Korotin 3 , V. Anisimov 3 , W. Reichelt 4 , H.H.
Hsieh 5 , H.-J. Lin 5 , and C.T. Chen 5 — 1 II. Physikalisches Institut,
Universität zu Köln — 2 ADSM, Hiroshima University, Japan — 3 IMP,
Ekaterinburg, Russia — 4 Institut für Anorganische Chemie, Dresden —
5 NSRRC, Hsinchu, Taiwan
VO2 is a non-magnetic oxide that undergoes a metal-to-insulator transition
at 340 Kelvin. Above this temperature, VO2 is metallic and has a
rutile (TiO2) structure (R-phase). At low temperatures, it is an insulator
with a monoclinic structure (M1-phase), in which V-V pairs are formed.
The long-standing debate about this compound concerns the nature of
the metal-to-insulator transition. The issue is whether the non-magnetic
insulating state would be regarded as a Peierls-insulator with the char-
acter of a band insulator (one-electron picture), or whether it should be
viewed as a Mott-insulator (many-body picture).
We have used polarization dependent soft-X-ray absorbtion at the V
L2,3 edges to investigate the local electronic structure of VO2, and have
found that the V 3d orbital occupation symmetry changes dramatically
across the metal-insulator transition. From a comparison with LDA and
LDA+U calculations we infer that this phase transition is assisted by
the orbital degrees of freedom, i.e. requiring an explanation beyond the
classical Peierls mechanism.
TT 24.46 Mi 14:30 Poster A
Orbital occupation and momentum in LaTiO3 — •M.W.
Haverkort 1 , Z. Hu 1 , H. Roth 1 , T. Lorenz 1 , C. de Nadai 2 , N.B.
Brookes 2 , A. Tanaka 3 , H.H. Hsieh 4 , H.-J. Lin 4 , C.T. Chen 4 , and
L.H. Tjeng 1 — 1 II. Physikalisches Institut, Universität zu Köln —
2 ESRF, Grenoble, France — 3 ADSM, Hiroshima, Japan — 4 NSRRC,
Hsinchu, Taiwan
LaTiO3 is an antiferromagnetic insulator with a magnetic ordering
temperature of TN ≈ 145 K. Neutron measurements reveal a magnetic
moment of 0.45 ∼ 0.57 µB, significantly less than the 1 µB expected for
a S = 1
2 system (Ti = 3d1 ). One may envision that this discrepancy can
be ascribed to the presence of an anti-parallel aligned orbital momentum
in this quasi cubic material. However, neutron data also found an almost
perfect isotropic spin wave spectrum with an extremely low spin gap,
indicative for the absence of an orbital moment. An orbital liquid model
is then proposed to explain these data. We have carried out detailed temperature
dependent soft-x-ray absorption and circularly-polarized/spinresolved
photoemission experiments. We find that the orbital moment
is practically quenched, in agreement with the neutron spin wave data.
Using the results from LDA and LDA+U calculations, we infer that this
quenching is caused by non-cubic crystal fields associated with the small
but non-negligible non-cubic distortions in LaTiO3. These crystal fields
are much stronger than the spin-orbit interaction, and crucial for the
explanation of the lineshape and the lack of temperature dependence of
the spectra. It seems that these conditions do not favor the formation of
an orbital liquid.
TT 24.47 Mi 14:30 Poster A
Orbital excitations in LaTiO3 and YTiO3 investigated by infrared
and Raman spectroscopy — •A. Gössling 1 , R. Rückamp 1 ,
M. Grüninger 1 , M. Cwik 1 , H Roth 1 , T. Lorenz 1 , A. Freimuth 1 ,
B. Keimer 2 und C. Ulrich 2 — 1 II.Physikalisches Institut, Universität
zu Köln — 2 Max-Planck-Institut FKF, Stuttgart
There is still discussion about the puzzling compound LaTiO3 [1,2,3].
We compare LaTiO3 with orbitally ordered YTiO3 using IR and Raman
spectroscopy. With IR we observe broad peaks at approximately 0.30 eV
in both compounds, with Raman at 0.25 eV. The difference in energy
is due to the simultaneous excitation of a phonon in IR spectroscopy,
breaking the parity selection rule. This clearly reveals the even parity of
the excitation, typical for orbital excitations. We discuss the origin of the
peaks within the framework of different theoretical models. Supported by
the DFG through SFB 608.
[1] B.Keimer et al., Phys.Rev.Lett.85, 3946 (2000).
[2] G.Khaliullin et al., Phys.Rev.Lett.85, 3950 (2000).
[3] M.Cwik et al., Phys.Rev.B 68, 060401 (2003).
TT 24.48 Mi 14:30 Poster A
Search for orbital excitations in YTiO3: calculation of phonon
dispersion relations — •M. Guennou 1 , C. Ulrich 1 , C. Frost 2 ,
S. Miyasaka 3 , Y. Taguchi 3 , Y. Tokura 3 , and B. Keimer 1 —
1 Max-Planck-Institut FKF, Stuttgart — 2 ISIS, Oxford, England —
3 Departement of Applied Physics, University of Tokyo, Japan
The purpose of our study was to search for elementary excitations of
the orbital magnetization, the so-called orbitons, in YTiO3. We have performed
single crystal inelastic neutron scattering experiments up to high
energies (350 meV) at the spectrometer MAPS at the ISIS facility in Oxford.
In order to give an interpretation of the features observed at high
energies, we have calculated the phonon dispersion relations and the first
and higher order density of states. There is a good agreement between
the calculated phonon dispersion relations and the first order phonon
modes measured by neutron and Raman scattering. These results will
be compared with the theoretical predictions for the orbital dispersion
relations given by G. Khaliullin [1].
[1] G. Khaliullin et al., Phys.Rev.Lett. 89, 167201 (2002).

Tiefe Temperaturen Mittwoch
TT 24.49 Mi 14:30 Poster A
Giant phonon anomalies in the pseudo-gap phase of TiOCl —
•P. Lemmens 1,2 , K.-Y. Choi 2 , G. Caimi 3 , L. Degiorgi 3,4 , A. Seidel
5 , and F.C. Chou 5 — 1 MPI for Solid State Research, D-70569
Stuttgart — 2 2. Physikalisches Institut, D-52056 RWTH Aachen —
3 Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zürich —
4 Paul Scherrer Institute, CH-5232 Villigen — 5 Center for Material Science
and Engineering, MIT, Cambridge, MA 02139
We report infrared and Raman spectroscopy results of the spin-1/2
quantum magnet TiOCl. Giant anomalies are found in the temperature
dependence of the phonon spectrum, which hint to unusual coupling of
the electronic degrees of freedom to the lattice. These anomalies develop
over a broad temperature interval, suggesting the presence of an extended
fluctuation regime. This defines a pseudo-gap phase, characterized by a
local spin-gap. Below 100 K a dimensionality cross-over leads to a dimerized
ground state with a global spin-gap of about 2∆spin ≈ 430 K. Work
supported by the DFG SPP1073, MRSEC Program of NSF under award
number DMR 02-13282, NATO PST.CLG.9777766, INTAS 01-278, and
the Swiss National Foundation for the Scientific Research.
TT 24.50 Mi 14:30 Poster A
Orbital-spin coupling in La1−xSr1+xMnO4 observed by Raman
spectroscopy — •K.-Y. Choi 1 , D. Heydhausen 1 , T. Sahaoui 1 , P.
Reutler 2 , B. Büchner 2 , P. Lemmens 1,3 , and G. Güntherodt 1 —
1 2. Physikalisches Institut, RWTH Aachen — 2 Institute for Solid State
Research, IFW Dresden — 3 MPI for Solid State Research, Stuttgart
We present an inelastic light scattering study of the layered manganites
La1−xSr1+xMnO4 (x = 0 and 1/8). The samples have the K2NiF4-type
tetragonal structure (symmetry group I4/mmm ) and show a C-type
antiferromagnetic ordering at TN ≈ 125 K for x = 0 as well as of an
orbital ordering with a dominant character of the d 3z 2 −r 2 orbital. The
undoped sample shows a pronounced two-magnon spectrum (2MS) in
the ab plane. The 2MS undergoes a strong damping already above 1.5
TN and evolves into quasielastic scattering consisting of two components.
The latter implies the rapid suppression of short-range antiferromagnetic
correlations while there appear other magnetic correlations. In addition,
a symmetry-forbidden phonon mode is observed around 700 cm −1 in
the high-temperature region for in-plane polarizations. Surprisingly, new
modes appear upon cooling below TN. This is due to zone-folded modes
induced by the formation of a superstructure. This provides evidence for
induced orbital ordering through spin-orbital coupling in the plane. As
to x = 1/8 the 2MS is totally suppressed while activated phonon modes
develop which are not Raman-active for x = 0. This feature is discussed
in terms of the mixture of d x 2 −y 2 with d 3z 2 −r 2 orbitals as well as of the
motion of holes. Work supported by DFG SPP1073
TT 24.51 Mi 14:30 Poster A
Orbital-induced phonon anomalies in (La1−yPry)1−xSrxMnO3
and LaMnO3+δ — •K.-Y. Choi 1 , P. Lemmens 1,2 , G. Güntherodt 1 ,
Yu. Pashkevich 3 , V. Gnezdilov 4 , P. Reutler 5 , B. Büchner 5 ,
and A. Revcolevschi 6 — 1 2. Physikalisches Institut, RWTH Aachen
— 2 MPI for Solid State Research, Stuttgart — 3 A. A. Galkin Donetsk
Phystech NASU, Ukraine — 4 B. I. Verkin Inst. for Low Temp. Physics
NASU, Ukraine — 5 Institute for Solid State Research, IFW Dresden —
6 Laboratoire de Physico-Chimie, Université Paris-Sud, France
We present an inelastic light scattering study of single crystalline
(La1−yPry)1−xSrxMnO3 (0 ≤ x ≤ 0.14, y = 0 and x = 1/8, 0 ≤ y ≤ 0.5)
and LaMnO3+δ (0.071 ≤ δ ≤ 0.125). The studied samples range from
canted antiferromagnetic insulating (CAF) to ferromagnetic insulating
(FMI) phase. A giant softening up to 20 -30 cm −1 of the Mn-O
breathing mode around 610 cm −1 is observed only for the FMI samples
(0.11 ≤ x ≤ 0.14 and 0.085 ≤ δ ≤ 0.125) upon cooling below the
Curie temperature. Moreover, Pr-doping leads to the gradual suppression
of the softening. This is attributed to a coupling of the breathing
mode to orbital polarons, giving evidence for their presence in the FMI
phase. No obvious saturation of the softening signals the instability of an
orbital polaron state. In addition, the CAF samples (0 ≤ x ≤ 0.1 and
δ = 0.071) exhibit pronounced multi-phonon features at 1000-1300 cm −1 .
Unexpectedly, they undergo a strong softening of the peak energy and a
damping as a function of temperature and doping. This odd behavior is
interpreted in terms of the change of orbital forms. Work supported by
DFG SPP1073
TT 24.52 Mi 14:30 Poster A
Electron Spin Resonance in charge and orbitally ordered manganites
— •J. Deisenhofer 1 , H.-A. Krug von Nidda 1 , A. Loidl 1 ,
T. Nakajima 2 , and Y. Ueda 2 — 1 EP V, Center for Electronic Correlations
and Magnetism, Institute for Physics, Augsburg University, D-
86135 — 2 Material Design and Characterization Laboratory,Institute for
Solid State Physics, University of Tokyo, 5-1-5
Both the paramagnetic and the magnetically ordered regime have been
investigated for La1−xSrxMnO3 (0 ≤ x ≤ 0.2) single crystals by ESR: For
x=0.05 the analysis of the temperature dependence and the anisotropy
of ESR linewidth and g-value in the orbitally ordered phase allows to
determine unambiguously the orbital mixing parameter above TN, indicating
that also in pure LaMnO3 orbital ordering is stabilized to a
large extent by superexchange processes in the ferromagnetic bonds. For
0.075 ≤ x < 0.15 we observe anisotropic quasi-ferromagnetic resonance
signals persisting far into the paramagnetic regime, indicating the existence
of a Griffiths-like phase above long-range magnetic order on crossing
from the canted antiferromagnetic state at x=0.075 to a purely ferromagnetic
ground state at x=0.175. Moreover, we report on correlations
between the ESR linewidth and resistivity at the charge-ordering transition
in the layered manganites RBaMn2O6 (R=Y,Dy).
TT 24.53 Mi 14:30 Poster A
Magnetic and orbital correlations in single layered manganates
— •D. Senff 1 , O. Friedt 1 , M. Ben Omar 1 , Y. Sidis 2 , P. Reutler
3,4 , A. Revcolevschi 4 , and M. Braden 1 — 1 II. Physikalisches
Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln —
2 Laboratoire Léon Brillouin,CE-Saclay, F-91191 Gif-sur-Yvette —
3 IfW Dresden, Helmholtzstr. 20, D-01069 Dresden — 4 Laboratoire de
Physico-Chimie de l’Etat Solide, Université Paris Sud, F-91405 Orsay
Cedex
We have studied the magnetic and charge/orbital order in
La1−xSr1+xMnO4 by elastic and inelastic neutron scattering. The
antiferromagnetic transition and the spinwave dispersion of the parent
compound LaSrMnO4 show a typical 2D behavior. There is a large
anisotropy gap of 9meV, but we find additional localized magnetic
scattering below this spin-wave gap whose intensities increase upon
minor Sr-content enhancement. For higher Sr-concentrations, x>0.4,
the system exhibits at low temperatures charge-orbital ordering, best
established for the concentration of x=0.5. In La0.4Sr1.6MnO4 (x=0.6)
we find incommensurate ordering most likely induced by the additional
number of Mn 4+ -ions. The resulting orbital and magnetic structure may
be interpreted in a stripe picture similar to the nickelates.
supported by DFG through SFB 608
TT 24.54 Mi 14:30 Poster A
Orbital ordering in single-crystal and thin-film La7/8Sr1/8MnO3
— •Y. Su 1 , D. Wermeille 2 , O.H. Seeck 1 , A. Fattah 1 , J. Persson
1 , P. Foucart 1 , K. Istomin 1 , D. Hupfeld 1 , Th. Brueckel 1 ,
Zhi-Hong Wang 3 , G. Cristiani 3 , H.-U. Habermeier 3 , F. Wu 4 und
R.L. Johnson 4 — 1 Institut fuer Festkoerperforschung, Forschungszentrum
Juelich GmbH, D-52425 Juelich, Germany — 2 MuCAT, Advanced
Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne,
IL 60439, USA — 3 Max-Planck-Institut fuer Festkoerperforschung,
Heisenbergstrasse 1, D-70569 Stuttgart, Germany — 4 II Institut fuer Experimentalphysik,
Universitaet Hamburg, D-22761 Hamburg, Germany
The orbital ordering (OO) is believed to be a key ingredient for the
metal-to-insulator transition in the ferromagnetic regime of lightly doped
manganites. By utilising the resonant X-ray scattering (RXS) technique,
a novel OO was identified in the ferromagnetic insulating (FI) regime
of single-crystal La7/8Sr1/8MnO3. Meanwhile, Templeton scattering due
to anisotropic structural effects was systematically measured at a set of
forbidden Bragg reflections in the full temperature range, enabling us to
quantitatively determine the atomic scattering tensor in both orbital ordered
and disordered states. The complex structural phase transition and
lattice modulations associated with this novel OO were also comprehensively
examined by high-energy X-ray diffraction. A definite model on the
OO in the FI regime will be proposed based on these new X-ray scattering
results. In addition, latest results on the RXS investigations of orbital ordering
and related structural modulation in thin-film La7/8Sr1/8MnO3
will also be presented

Tiefe Temperaturen Mittwoch
TT 24.55 Mi 14:30 Poster A
Orbital ordering in manganites on the band approach. —
•Dmitry Efremov 1 and Daniel Khomskii 2 — 1 Technische
Universität Dresden, Institut für Theoretische Physik, 01062 Dresden
— 2 Universität zu Köln, 50937 Köln
We consider the orbital ordering in LaMnO3 and similar systems, proceeding
from the band picture. We show that for the realistic magnetic
structure of A-type there exists a complete nesting between two eg-bands.
As a result there occurs an instability towards Q = (π, π) an excitonic insulator
like state – an electron-hole pairing with the wave vector, which
opens a gap in the spectrum and makes the system insulating. In the
resulting state there appear an orbital ordering – orbital density wave
(ODW), the type of which coincides with these existing in LaMnO3.
TT 24.56 Mi 14:30 Poster A
Magnetic ordering in the trigonal chain compounds Ca3CoRhO6
and Ca3FeRhO6 — •Udo Schwingenschlögl, Volker Eyert, and
Ulrich Eckern — Theoretische Physik II, Institut für Physik, Universität
Augsburg, 86135 Augsburg
Low-dimensionality and frustration effects in compounds containing
magnetic ions have attracted a lot of attention since long owing to the
expectation of a variety of fascinating properties. Much interest has focused
on systems, where the chains are arranged in a triangular lattice.
Continuing recent work on the prototypical compound Ca3Co2O6
[1] we present the results of augmented spherical wave (ASW) electronic
structure calculations for the closely related compounds Ca3CoRhO6 and
Ca3FeRhO6. In accordance with experimental data we find strong intrachain
magnetic coupling of high-spin 3d-metal sites via the d-states of
the interjacent low-spin rhodium sites resulting in the observed ferromagnetic
and antiferromagnetic order in Ca3CoRhO6 and Ca3FeRhO6,
respectively. Considerable hybridization with the O 2p states leads to polarization
of the latter and the formation of extended magnetic moments,
which are well localized at the high-spin sites.
[1] V. Eyert. C. Laschinger, T. Kopp, and R. Frésard, submitted to
Chem. Phys. Lett.
TT 25 FV-internes Symposium ”Superconducting Qubits and π-junctions”
Zeit: Donnerstag 09:30–12:45 Raum: H20
Fachvortrag TT 25.1 Do 09:30 H20
Charge-phase Josephson qubit with radio frequency readout —
•Alexander Zorin — PTB, Bundesallee 100, 38116 Braunschweig
A solid state qubit presenting a macroscopic superconducting ring including
two small tunnel Josephson junctions is considered. A pulsed gate
voltage polarizing a small island between the junctions and a variable
magnetic flux applied to the ring make it possible quantum manipulations
of the system state. Readout of the state is performed by probing the
effective Josephson inductance of the qubit. This is done by inducing lowfrequency
harmonic oscillations in inductively coupled tank circuit and
measuring the resonance frequency shift. On one hand, this narrow-band
readout system requires sufficiently long time for a single measurement.
On the other hand, due to the qubit symmetry and its disconnection from
dc bias lines and, presumably, from microwave-frequency noise sources
it should be safely decoupled from environment and exhibit rather long
coherence and relaxation times. The issues related to optimization of the
qubit characteristics and regime of its operation will be addressed in the
talk. The results of first experiments will be also reported.
Fachvortrag TT 25.2 Do 10:00 H20
Exploring quantum dynamics of Josephson vortices —
•A.V. Ustinov 1 , A. Wallraff 2 , M.V. Fistul 1 , A. Kemp 1 , A.
Lukashenko 1 , J. Lisenfeld 1 , and Y. Koval 1 — 1 Physikalisches
Institut III, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany
— 2 Dept. Applied Physics, Yale University, New Haven, CT 06520, USA
Engineering of an energy profile for a vortex in a Josephson junction
opens an opportunity for designing superconducting qubits based
on spatially distinct quantum states. The energy profile for the vortex
can be created, e.g., by making the junction of a particular geometrical
shape and applying an external magnetic field. In our first experiments
we have demonstrated novel vortex states in long Josephson junctions
with complex engineered potentials [1]. Recently, for the first time, we
have observed quantum tunneling of a single vortex in a long junction at
temperatures below 100 mK and performed microwave spectroscopy of
the vortex energy levels within a potential well [2]. The vortex behaves as
a macroscopic quantum particle (with a spatial extent of several micrometers)
which tunnels through a potential barrier created by a magnetic
field applied to the junction. In agreement with theory, the separation
between vortex energy levels is controlled by the field. We have also measured
quantum dissociation of a vortex ”molecule”, consisting of a bound
state of vortex and antivortex [3].
[1] A. Kemp et al. Phys.Stat.Sol.(b) 233, 472 (2002)
[2] A. Wallraff et al., Nature 425, 155 (2003)
[3] M.V. Fistul et al., to appear in Phys.Rev.Lett. (cond-mat/0307705)
Hauptvortrag TT 25.3 Do 10:30 H20
Quantum dynamics of persistent current qubits — •Kees Harmans
— Quantum Transport Group, Department of NanoScience/TNW,
Delft University of Technology,Delft, The Netherlands
Quantum bits employing superconductivity come in a few varieties,
comprising (Cooperpair) charge, (condensate) phase, and persistent current
or flux. In a flux-based qubit the loop-shape topology allows a persistent
current to circulate in opposite directions, leading to two quantum
states that are well separated from a higher lying manifold of states. The
properties of these two states can be fully engineered during the fabrication,
and largely controlled during the experiment. Employing flux-flux
coupling in addition allows a flexible qubit-qubit interaction scheme towards
multi-qubit systems. Using burst microwave magnetic excitation
resonant between the levels and pulsed fluxes, both of well controlled amplitude
and duration/interval, allows full quantum control of the qubit(s).
We will present a series of experiments demonstrating the quantum behavior
of a single qubit, comprising Rabi, Ramsey and echo-type oscillations.
In addition some results on a coupled two-qubit experiment will
be discussed. The role of decoherence in our quantum experiments will
be highlighted, including the effect of the qubit state detection.
11:00 Pause
Hauptvortrag TT 25.4 Do 11:15 H20
Superconducting Structures for Quantum Computing —
•Gianni Blatter 1 , Vadim Geshkenbein 1 , Mikhail Feigelman 2 ,
and Lev Ioffe 3 — 1 Theoretische Physik, ETH-Hönggerberg, CH-8093
Zürich — 2 Landau Institute, RAS, Moskow, Russia — 3 Department of
Physics and Astronomy, Rutgers University, Piscataway, USA
In a quantum computer the information is stored in arrays of quantum
two-level systems or ‘qubits’. Execution of a quantum algorithm involves
quantum gates, unitary operations rotating individual qubits and entangling
them pairwise. Superconducting solid-state qubits are promising
candidates for the hardware implementation of scalable quantum information
processors; quantum fluctuations are introduced through samllcapacitance
Josephson junctions and the frustrating drive is introduced
through a gate potential (charge-qubit) or a magnetic flux (phase- or flux
qubit). Recent experiments have achieved a breakthrough with quality
factors of the order of 10 4 . Upscaling to a real quantum computer will
require further improvements in noise reduction, manipulation, fault tolerance,
and simplifications in design/fabrication. Superconductors with
d-wave symmetry bear a number of benefits, such as the possibility to
construct π- or double-periodic 2φ-junctions providing a quiet driving
force and allowing for manipulation through switches. Further geometric
frustration can be used to enhance quantum fluctuations in a new
qubit design with tetrahedral symmetry, reducing charge noise and the
demands on the fabrication of ultra-small junctions.
Fachvortrag TT 25.5 Do 11:45 H20
Semifluxons as a base for classical and quantum digital circuits?
— •Edward Goldobin, Tobias Gaber, Albert Sterck, Dieter
Koelle, and Reinhold Kleiner — Physicalische Institut II, Universität
Tübingen

Tiefe Temperaturen Donnerstag
In a long Josephson junction (LJJ) made of alternating regions with
positive and negative critical currents (so-called 0 and π regions) halfinteger
vortices (semifluxons) may spontaneously appear at the boundaries
between 0 and π parts.
The semifluxons have unique properties: they are pinned at the 0-πboundary
but may have two different polarities corresponding to the half
integer flux +Φ0/2 and −Φ0/2. In comparison with the freely moving
fluxon, the semifluxon represents the ground state of the system and
therefore is extremely stable. Semifluxons may be obtained and investigated
in 0-π-junctions made of d-wave superconductors, in junctions with
ferromagnetic barrier or in conventional LJJs with specially designed injectors.
In this talk I discuss the properties of semifluxons and their interaction
with integer fluxons (solitons) in view of possible applications for
information storage and processing in classical and quantum domains.
Hauptvortrag TT 25.6 Do 12:15 H20
π-superconductivity in S/F nano-structures — •Marco
Aprili 1,2 , T. Kontos 1 , W. Guichard 3 , ML. Della Rocca 1,2 , J.
Lesueur 2 , and P. Gandit 3 — 1 CSNSM-CNRS, Bat.108 Université
Paris-Sud, 91400 Orsay, France — 2 Laboratoire de Physique Quantique
ESPCI, 10 rue Vauquelin, 75005 Paris, France — 3 CRTBT-CNRS, 25
Avenue des Martyrs, 38000 Grenoble, France
TT 26 Korrelierte Elektronen: Theorie II
Hybrid nanostructures not only open new routes for studying the coexistence
between superconductivity and ferromagnetism, but they also
provide new insights to fundamentals of quantum electronics. We have
investigated the change in the superconducting wavefunction resulting
from the interaction between the spins of a Cooper pair and the exchange
field. Tunnelling spectroscopy reveals an inhomogeneous superconducting
state induced in a ferromagnetic thin film by the proximity effect.
As a consequence, critical current and macroscopic quantum interference
experiments show π-coupling when the ferromagnetic thin film is coupled
with a second superconductor. π-coupling originates a spontaneous half
quantum flux in a superconducting ring. This phase transition has been
recently observed by SQUID and Hall magnetometry (Regensburg-Orsay
experiment).
Zeit: Donnerstag 09:30–13:00 Raum: H18
TT 26.1 Do 09:30 H18
Itineranzeffekte in Spinkorrelationen eindimensionaler Mott
Isolatoren — •Anja Grage 1 , M. Joseph Bhaseen 2 , Fabian H. L.
Essler 2 und Florian Gebhard 1 — 1 Fachbereich Physik, Philipps-
Universität Marburg, 35032 Marburg, Germany — 2 Department of
Physics, Brookhaven National Laboratory, Upton, NY 11973-5000
Mott-Isolatoren werden häufig mit Hilfe des Spin-1/2 Heisenberg-
Modells analysiert, das die Spinfreiheitsgrade im Hubbard-Modell bei
starker lokaler Coulomb-Abstoßung U/t charakterisiert. Neutronenstreuexperimente
[1,2] an zweidimensionalen Spin-1/2 Antiferromagneten zeigen
jedoch, daß die Dispersion erheblich von der des Heisenberg-Modells
abweicht. Dies unterstreicht die Bedeutung der Itineranz der Elektronen
auch in Mott Isolatoren.
Wir untersuchen magnetische Eigenschaften quasi-eindimensionaler
Mott-Isolatoren, zum Beispiel von Strontium-Kupraten oder Bechgaard-
Salzen. Wir berechnen den dynamischen magnetischen Strukturfaktor in
der Nähe der antiferromagnetischen Wellenzahl k = π fuer kleines U/t
im Rahmen der Feldtheorie exakt und diskutieren dessen Verhalten als
Funktion von U/t. Wir finden signifikante Effekte für U/t ≈ 2-3.
[1] R. Coldea et al., Phys. Rev. Lett. 86, 5377 (2001).
[2] H.M. Rønnow et al., Phys. Rev. Lett. 87, 037202 (2001).
TT 26.2 Do 09:45 H18
Phase diagram of the one-dimensional t − J model — •Jochen
Hub, Catia Lavalle, and Alejandro Muramatsu — Universität
Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart
Using a recently developed hybrid-loop algorithm [1] we determine the
phase diagram of the t − J model in one-dimension, where a Luttingerliquid
phase (with Kρ < 1 and Kρ > 1), a spin-gap phase and a region
of phase-separation are determined on the basis of a detailed finite-size
scaling.
[1] C. Lavalle, M. Arikawa, S. Capponi, F. F. Assaad and M. Muramatsu
Phys. Rev. Lett. 90, 216401 (2003)
TT 26.3 Do 10:00 H18
Electron-phonon interaction in the t-J model — •Oliver
Rösch and Olle Gunnarsson — Max-Planck-Institut für
Festkörperforschung, 70569 Stuttgart
Starting from the three-band model of a CuO2 layer we derive a t − J
model with electron-phonon interaction taking into account the modulation
of both hopping and Coulomb integrals by phonons. The former
is found to be dominant, but the modulation of the Coulomb integrals
cannot be neglected.
The model is studied on finite clusters using exact diagonalization. It
explains the anomalous softening of the half-breathing mode upon doping
and a weaker renormalization of the breathing mode as observed exper-
imentally in many cuprates. The coupling to other modes is not strong
in this model.
TT 26.4 Do 10:15 H18
Effective Models by Self–Similar Continuous Unitary Transformations:
the Hubbard Model at Strong Coupling —
•Alexander Reischl, Erwin Müller-Hartmann, and Götz
Silvester Uhrig — Institut für theoretische Physik, Universität zu
Köln, Zülpicher Str. 77, D-50937 Köln, Germany
An effective model conserving the number of double occupancies is
derived for the half–filled Hubbard model at strong coupling.
The mapping to the effective model is performed by a self–similar continuous
unitary transformation (CUT). The sectors of different double
occupancy are decoupled. Therefore the effective model is a generalized
t–J–model. A truncation scheme that selects operators according to their
locality is used to close the flow equations.
The convergence and accuracy of the method are discussed in the light
of the developing itinerant character of the system for increasing bandwidth.
The apparent energy–gap for a single hole or a double occupancy
is calculated within the effective model.
Our main result is that the mapping of the Hubbard–Model to the
t–J–model is possible and very robust as long as the apparent gap is
positive. In this regime relatively small clusters suffice to determine the
parameters of the effective model reliably. Besides correlated hopping and
interaction of charges the most prominent interactions are the two–spin
nearest neighbor exchange and the four–spin ring–exchange.
TT 26.5 Do 10:30 H18
Ferroelektrische Phasen im erweiterten Falicov-Kimball-Modell
— •Claudia Schneider und Gerd Czycholl — Institut für Theoretische
Physik, Universität Bremen
Ferroelektrische Phasenübergänge und Ordnungs-Unordnungs-
Übergänge in der Ladungsdichte stellen zwei konkurrierende Phänomene
dar, die in der Behandlung des Falicov-Kimball-Modells (FKM) auftreten.
Damit läßt sich das FKM nicht nur auf Systeme anwenden, in denen
Valenzübergänge eine Rolle spielen (z.B. YbInCu4), sondern auch auf
Ferroelektrika wie SmB6 und vergleichbare Verbindungen. In der vorliegenden
Untersuchung wird das Modell um eine lokale Hybridisierung
zwischen Leitungsband und Valenzband sowie um eine endliche Valenzbandbreite
erweitert. Es werden Ergebnisse zu der Frage vorgestellt,
in welchen Parameter- und Temperaturbereichen spontane Polarisation
und Ladungsdichtewellen (CDW-Lösungen) auftreten, wenn man den
Grenzfall schwacher Wechselwirkung in Hartree-Fock-Näherung betrachtet.
Ferner wird geprüft, inwieweit die gefundenen Lösungen in höheren
Ordnungen Störungsrechnung stabil bleiben.

Tiefe Temperaturen Donnerstag
TT 26.6 Do 10:45 H18
Optische Leitfähigkeit eines Hubbard-Rings mit Störstelle —
•Cosima Schuster und Philipp Brune — Institut für Physik, Universität
Augsburg, 86135 Augsburg
Wir untersuchen mittels exakter Diagonalisierung (Lanzcos-Verfahren)
die optische Leitfähigkeit eines Hubbard-Rings in Anwesenheit einer Potentialstörstelle.
Wir konzentrieren uns dabei auf den ersten angeregten,
stromtragenden Zustand, d.h. auf verdrehte Randbedingungen. In der
metallischen Phase liegt ein wesentlicher Teil des spektralen Gewichts
im Drude-Peak σ(ω) = Dcδ(ω) + σreg. Im Fall U = 0 lässt sich dieser
Drude-Peak in unseren Rechnungen bei ω = 0 darstellen, da hier auch
für endliche Kettenlängen der Sprung im chemischen Potential verschwindet.
Bei Addition von einer Störstelle ist dieser Sprung im chemischen
Potential endlich und damit der Haupt-Peak verschoben zu endlichen Frequenzen.
Für repulsive Wechselwirkung wird dieser störstelleninduzierte
Peak allerdings erst sichtbar, wenn eine gewisse Störstellenstärke, bei der
die Grösse des Sprungs im chemischen Potential mit und ohne Störstelle
übereinstimmt, überschritten wird. Wir können also in der optischen
Leitfähigkeit für endliche metallische Systeme anhand den Sprung im
chemischen Potential verfolgen.
TT 26.7 Do 11:00 H18
Electron-spin Vertex in the Two-dimensional One-band Hubbard
Model — •Zhongbing Huang, Werner Hanke, and Enrico
Arrigoni — Institut für Theoretische Physik, Universität Würzburg,
am Hubland, 97074 Würzburg, Germany
Using Quantum Monte Carlo techniques, we study the renormalization
of the electron-spin (el-sp) interaction or vertex due to Coulomb
correlations in a two-dimensional one-band Hubbard model with spinfluctuation
momentum transfer q = (π, π). In the physically relevant
strong-correlation regime, we find that the renormalized el-sp vertex decreases
monotonically and rather dramatically with increasing doping
from the underdoped to the overdoped region. In the underdoped region
the spin susceptibility increases very quickly with decreasing temperature,
leading to a substantial increase of the effective pairing interaction.
In the overdoped case, the temperature dependence of the effective
pairing interaction is rather weak. Our findings imply that antiferromagnetic
spin fluctuations play an important role in the transport and
superconducting properties of the underdoped high-temperature superconductors.
This will further be substantiated with similar calculations
for the electron-phonon vertex.
11:15 Pause
TT 26.8 Do 11:30 H18
Variational cluster extension approach to the doped Hubbard
model — •Björn Michaelis, Michael Potthoff, and Werner
Hanke — Institut für theoretische Physik und Astrophysik, Universität
Würzburg, Am Hubland, D-97074 Würzburg
Thermodynamic properties and single particle excitations of the oneband
Hubbard model are calculated in the one and two dimensional
case on the basis of the recently proposed selfenergy-functional theory
(”SFT”, Eur. Phys. J. B 32 (429) ,2003). We use exact diagonalization
to get the selfenergy of finite systems and then obtain the Greensfunction
of the infinite lattice by means of SFT. A particle reservoir is included and
determined selfconsistently to achieve continuous doping. Results about
the filling and bandwith controlled Mott metal-insulator transition are
presented.
TT 26.9 Do 11:45 H18
Gossamer metals — •Marcus Kollar — Institut für Theoretische
Physik, Universität Frankfurt, Robert-Mayer-Str. 8, 60054 Frankfurt/Main
Using Laughlin’s gossamer method we construct a class of extended
Hubbard models with long-range correlated hopping that have exact
metallic Gutzwiller ground states, with arbitrary particle density, noninteracting
dispersion, and lattice dimensionality [1]. The susceptibility
and magnetization curves are obtained, showing that the Pauli susceptibility
is enhanced by correlations. The elementary quasiparticle excitations
of this correlated “gossamer metal” are gapless, except for a halffilled
band, where a Mott metal-insulator transition of Brinkman-Rice
type occurs.
[1] M. Kollar, cond-mat/0308513.
TT 26.10 Do 12:00 H18
Contractor Renormalization Group Calculation for the
Hubbard model including Fermionic and Bosonic excitations.
— •Sascha Brehm 1 , Enrico Arrigoni 1,2 , and Werner Hanke 1
— 1 Institut für Theoretische Physik und Astrophysik, Universität
Würzburg, Am Hubland, D-97074 Würzburg, Germany — 2 Institut
für Theoretische Physik, Technische Universität Graz, Petersgasse 16,
A-8010 Graz, Austria
We apply the contractor renormalization group technique (CORE) to
extract a low-energy effective Hamiltonian for the 2-D Hubbard model.
In contrast to earlier studies1 we explicitly incorporate both bosonic
and fermionic low-energy excitations. It is shown that one basic effect
of the latter is to effectively enhance the hopping probability of the
charge-(pair-)excitations with increasing Hubbard U interactions. The
low-energy Hamiltonian is then solved with slave-boson techniques.
[1] E.Altman and A.Auerbach, Phys.Rev.B 65, 104508 (2002)
TT 26.11 Do 12:15 H18
First-order Mott transition at finite doping and temperature
— •Theo Costi, Achim Rosch, Matthias Vojta, and Peter
Woelfle — Institut fuer Theorie der Kondensierten Materie, Universitaet
Karlsruhe, 76128 Karlsruhe
The dynamical mean field theory in combination with the numerical
renormalization group is used to compute the phase diagram of the Hubbard
model away from half-filling in the (T,U) plane. We find coexistance
of two solutions with the same doping at finite temperature, as for half
filling. We also discuss the effect of a small doping on the single-particle
spectra of a Mott insulator.
TT 26.12 Do 12:30 H18
Anomalous self-energy and pseudogap formation in the 2D
Hubbard model — •Andrey Katanin 1,2,3 and Arno Kampf 1
— 1 Institut fuer Physik, Theoretische Physik III, Elektronische
Korrelationen und Magnetismus, Universitaet Augsburg, 86135
Augsburg, Germany — 2 Max Planck Institute for Solid State Research,
Heisenbergstrasse 1, D-70569 Stuttgart, Germany — 3 Institute of Metal
Physics, 620219 Ekaterinburg, Russia
We calculate [1] the self-energy in the weak-coupling regime of the t-t ′
Hubbard model using the functional RG approach. The flow of the vertices
is truncated at one-loop order. At this order and at van Hove (vH)
band fillings the quasiparticle concept is not valid at kF = (π, 0) due to
either thermal excitations of electrons at the vH singularities (vHs) or
pseudogap formation. At low temperature the quasiparticle weight along
the Fermi surface continuously vanishes from a finite value at the zone
diagonal towards the (π, 0) point. Away from vH band fillings the quasiparticle
peak is formed inside a pseudogap of size ∆, and within a finite
frequency window |ω| ≪ ∆ around the Fermi energy the electronic selfenergy
has the conventional Fermi-liquid characteristics. With increasing
separation between Fermi level and vHs the spectral anomalies gradually
disappear.
[1] A. A. Katanin and A. P. Kampf, cond-mat/0310112.
TT 26.13 Do 12:45 H18
Low-energy physics of cuprates beyond the standard pdσ-model
— •S.-L. Drechsler 1 , J. Málek 1 , H. Rosner 2 , A.S. Moskvin 3 ,
H. Eschrig 1 , M. Knupfer 1 und A. Kordyuk 1 — 1 IFW-Dresden,
P.O. Box 270116, D-01171 Dresden, Germany — 2 MPI-CPfS Dresden,
Germany — 3 Ural St.ate University, 620083 Ekaterinburg, Russia
The role of orbitals beyond the Cu 3dO2p set employed in the widely
used standard pdσ extended Hubbard model is considered with respect
to the low-energy physics of several cuprates and different experiments.
Special attention is paid to the theoretical description of the loss function
and optical conductivity data of the 1D compound Sr2CuO3 and the 2D
system Sr2CuO2Cl2 with respect to excited O 2π states. Consequences
for the orbital character of doped holes are considered. Effects of Cu 4s
orbitals and states derived from cations outside the CuO2 planes are discussed
with respect to the observed bi-layer splitting in Bi2212 [1], the
Néel state ordering in CaCuO2, and NMR data of La2CuO4 [2].
[1] A.A. Kordyuk et al., cond-mat/0311137
[2] E.P. Stoll et al., Int. J. of Mod. Phys. 17, 3329 (2003).

Tiefe Temperaturen Donnerstag
TT 27 Nanoelektronik III: Molekulare Elektronik
Zeit: Donnerstag 09:30–12:45 Raum: H19
Hauptvortrag TT 27.1 Do 09:30 H19
Molecular wires in electromagnetic fields — •Sigmund Kohler 1 ,
Jörg Lehmann 1 , Sébastien Camalet 1,2 , and Peter Hänggi 1
— 1 Institut für Physik, Universität Augsburg, 86135 Augsburg —
2 Laboratoire de Physique, ENS Lyon, Frankreich
Electromagnetic ac fields can alter significantly the transport properties
of mesoscopic systems like molecular wires. Resonant excitations
of electrons can e.g. enhance drastically the currents through molecules.
The opposite phenomenon also exists: a proper off-resonant driving field
reduces the coherent transport across the molecule resulting in a strong
current suppression. Moreover, near such current suppressions, we find
characteristic minima and maxima of the shot noise [1]. This effect allows
to manipulate current fluctuations by external fields. Molecular wires in
laser fields may also be used to study the so-called ratchet effect: in asymmetric
molecules, an ac field induces a dc current even in the absence of
any bias voltage [2].
The external field is modelled by a periodic time-dependence of the
Hamiltonian. This requires a generalization of established transport theories
like, e.g., the Landauer formula. Such a generalization, which is
based on the Floquet theorem, will be presented and the main differences
to the static situation will be discussed.
[1] S. Camalet et al., Phys. Rev. Lett. 90, 210602 (2003).
[2] J. Lehmann et al., Phys. Rev. Lett. 88, 228305 (2002).
TT 27.2 Do 10:00 H19
Electronic transport through single molecules — •H. v.
Löhneysen 1,2 , F. Hennrich 3 , M.M. Kappes 3 , R. Krupke 3 ,
M. Mayor 3 , J. Reichert 3 und H.B. Weber 3 — 1 Physikalisches
Institut, Universität Karlsruhe, 76128 Karlsruhe — 2 Forschungszentrum
Karlsruhe, Institut für Festkörperphysik, 76344 Karlsruhe —
3 Forschungszentrum Karlsruhe, Institut für Nanotechnologie, 76344
Karlsruhe
Electronic transport measurements through single π-conjugated molecules
can be realized using mechanically controlled break junctions to
couple thiol end groups of the molecules to two gold electrodes. We have
investigated transport through π-conjugated molecules which differ
by their spatial symmetry and π-conjugated connectivity. The current
voltage characteristics (IV s) of the metal-molecule-metal system reflect
the spatial symmetry and topology of the molecules with respect to the
direction of current flow indicating that transport occurs indeed through
single molecules [1]. Fluctuations in the IV s are a manifestation of the
variation of level spacings of the system, which depend crucially on the
bonding between thiol end groups and Au electrodes.
For the future electronics, carbon nanotubes are the prime candidates.
Recent progress in the controlled deposition of nanotubes between
electrodes and separation of metallic and semiconducting nanotubes [2]
is reported.
[1] J. Reichert et al., Phys. Rev. Lett. 88, 176804 (2002)
[2] R. Krupke et al., Science 301, 344 (2003)
TT 27.3 Do 10:15 H19
Electronic Transport through C60 — •Tobias Böhler, Jochen
Gebing, and Elke Scheer — FB Physik - Universität Konstanz
We present an experiment to measure the differential conductance of a
single or few C60 molecules embedded in between the single atom tips of a
mechanically controllable break junction (MCB). The C60 is evaporated
onto an opened break junction under high vacuum conditions. Then I-
V-curves are taken at room temperature. The tip electrodes of the MCB
are fabricated of aluminium or gold.
The I-V-curves are linear for voltages |U| ≤ 0.2V and show slowly
increasing conductance for higher voltages with time dependent fluctuations.
After the evaporation of C60 the fluctuations are suppressed, but
the nonlinearities of the I-V-curves remain unaffected. Thus, it appears
that the C60 molecules stabilize the gold contact across which a maximum
voltage of 1V can be applied.
Another method is the fabrication of a MCB made of C60 without
metallic electrodes by evaporating the molecules onto a lithographic
mask. The conductance of the junction is much smaller (≈ 150MΩ) with
similar nonlinear I-V-curves for larger voltages.
TT 27.4 Do 10:30 H19
Electron tunneling through a single Co-complex — •Maarten
Wegewijs 1 , Christian Romeike 1 , Wolfgang Wenzel 2 und Herbert
Schoeller 1 — 1 Institut für Theoretische Physik - Lehrstuhl A ,
RWTH Aachen , 52056 Aachen , Germany — 2 Forschungszentrum Karlsruhe
, Institut für Nanotechnologie , 76021 Karlsruhe , Germany
We theoretically consider electron tunneling through a transition-metal
complex coupled to metallic electrodes. A single Co 2+/3+ ion is fixed between
a left and right terpyridine ligand, each of which is in turn coupled
to a linker molecule with a functionalized end group to connect to one of
the electrodes. It was found experimentally [1] that by varying the type
of linker molecules, a strong Kondo effect in the current appears at low
temperatures in Coulomb blocked transport regimes due to a stronger
coupling to the electrodes.
We have investigated the conjecture that the tunneling is dominated
by single atom-like d-orbitals of the ion by electronic structure calculations.
We show that microscopically the ligands of this particular complex
function as a tunnel barrier due to the different character (symmetry)
of the highest ligand (π) and two Co 2+/3+ -ion orbitals (σ). The role of
the linker molecules connecting the ligands to the electrodes is therefore
crucial. We discuss the simplest phenomenological tunneling model
consistent with our findings (molecular states, addition energy, tunneling
matrix elements).
[1] J. Park et al, Nature 417, 722 (2002)
TT 27.5 Do 10:45 H19
Shot noise in tunneling transport through molecules and quantum
dots — •Axel Thielmann 1 , Matthias H. Hettler 1 , Jürgen
König 2 , and Gerd Schön 1,3 — 1 Forschungszentrum Karlsruhe, Institut
für Nanotechnologie, 76021 Karlsruhe, Germany — 2 Institut für Theoretische
Physik III, Ruhr-Universität Bochum, 44780 Bochum, Germany
— 3 Institut für Theoretische Festkörperphysik , Universtität Karlsruhe,
76128 Karlsruhe, Germany
We consider charge transport through single molecules coupled weakly
to metal electrodes via tunneling barriers. The molecule is represented
by the Anderson impurity model which is the simplest model that includes
Coulomb interactions U. We calculate the current and current
noise within a first-order perturbation expansion in the coupling strength
using a diagrammatic technique. Analytical results for current, noise and
the Fano factor, F,(depending on the ratio of the couplings to the left
and right electrodes) are presented and discussed for all transport regimes
involving a single interacting (molecular) level (Phys. Rev. B 68, 115105
(2003)). Furthermore an extended model with two levels will be considered,
where the effects of asymmetric coupling and photon-relaxation can
be studied. Negative differential conductance (NDC) behavior leading to
super-poissonian noise (F > 1) can be observed in the case of asymmetric
coupling to the leads and is distroyed by strong relaxation rates. In
addition to the numerical evaluation analytical expressions for several
transport regimes will be presented.
11:00 Pause
TT 27.6 Do 11:15 H19
Vibrational Effects in the Conductance through a Molecular
Bridge — •Michael Hartung, Klaus Richter, and Gianaurelio
Cuniberti — Institute for Theoretical Physics, University of Regensburg,
93040 Regensburg , Germany
We study the conductance of a single molecule sandwiched between
two electrodes and taking into account the center of mass motion of the
molecule.
The starting point is a tight-binding model Hamiltonian, which includes
a linear coupling between the electronic degrees of freedom and
the bosonic motion. The conductance is calculated within the scattering
matrix formalism. The coupling to the electronic degrees of freedom
shows the interesting effect such as enhancing the off resonant conductance.
TT 27.7 Do 11:30 H19
Role of vibrational modes in the transport through single
molecules — •Juan Carlos Cuevas, Fabian Pauly, and Gerd
Schön — Institut für Theoretische Festkörperphysik, Universität Karlsruhe,
D-76128 Karlsruhe

Tiefe Temperaturen Donnerstag
With the recent advances in nanofabrication techniques it has become
possible to manipulate and explore the electronic transport through
individual molecules. This has posed an exciting theoretical challenge,
namely the understanding of the conduction mechanisms at the molecular
scale. So far, the effort has been concentrated in the analysis of the
role of the electronic structure, but little has been done on the role of
the internal degree of freedom of molecules. In this talk I will present our
efforts to understand what are the effects of the vibrational modes in the
molecular conduction. Making use of the density functional theory, we
have developed an ab inito approach to describe the influence in the electrical
current of the inelastic electron-phonon processes. This approach
allows us to address many different questions such as (i) what makes
that in some experimental situations the vibrational modes enhance the
current and some others they reduce it? (ii) What are the possible signatures
of these modes in the current-voltage characteristics? (iii) What
are the selection rules that explain why some vibrational modes do not
show up in the transport experiments?
TT 27.8 Do 11:45 H19
Controlled contacting of single-walled carbon nanotubes
— •Daniel Secker 1 , Ralph Krupke 1 , Heiko B. Weber 1 ,
and Hilbert v. Löhneysen 2,3 — 1 Forschungszentrum Karlsruhe,
Institut für Nanotechnologie, PO-Box 3640, D-76021 Karlsruhe —
2 Forschungszentrum Karlsruhe, Institut für Festkörperphysik, PO-Box
3640, D-76021 Karlsruhe — 3 Physikalisches Institut, Universität
Karlsruhe, D-76128 Karlsruhe
We present a method to encapsulate the ends of single-walled carbon
nanotubes (SWNT) in metallic leads. For this purpose we employed an
inorganic shadow mask of Si3N4 patterned by e-beam lithography on a
PMMA/Si3N4/SiO2/Si substrate [1]. The SWNTs are deposited between
the contacts after a first evaporation step by applying an ac electric field
making use of the dielectrophoretic force [2]. A second evaporation step
encapsulates the ends of the SWNTs by the metallic leads. Therefore
in contrast to marker-assisted e-beam lithography any exposure of the
SWNTs to organic substances like PMMA is avoided. We present lowtemperature
electrical transport measurements with samples thus prepared.
[1] T. Hoss et al., Microel. Engin. 46 (1999) 149-152
[2] R. Krupke et al., Appl. Phys. A 76 (2003) 397-400
TT 27.9 Do 12:00 H19
Parallel and Perpendicular Magnetoresistance of Multiwall
Carbon Nanotubes — •Bernhard Stojetz 1 , Christoph
Hendlmeier 1 , Christian Hagen 1 , Edina Ljubović 2 , Lazlo
Forró 2 , and Christoph Strunk 1 — 1 Institut für Experimentelle und
Angewandte Physik, Universität Regensburg — 2 Institute of Physics of
Complex Matter, FBS Swiss Federal Institute of Technology (EPFL),
Lausanne, Switzerland
We report resistance measurements for single multiwall carbon nanotubes
in magnetic fields both parallel and perpendicular to the tube axis.
The tubes were trapped onto pre-patterned Al gate electrodes by means
of an ac electric field. The strong electrostatic coupling of the nanotube
to the gate allows a considerable variation of the doping level of the
tube. Magnetoresistance traces were measured for many values of the
gate voltage, which allows an ensemble averaging of the conductance
fluctuations induced by quantum interference. The ensemble averaging
reduces the conductance fluctuations while leaving the weak localization
contribution to the resistance unchanged. The data can be consistently
interpreted in terms of quantum transport in presence of weak disorder.
TT 27.10 Do 12:15 H19
Scaling of the Performance of Schottky barrier Carbon Nanotube
Transistors — •Stefan Heinze 1 , Marko Radosavljević 2 ,
Jerry Tersoff 3 , and Phaedon Avouris 3 — 1 Institute of Applied
Physics, University of Hamburg, Jungiusstr. 11, 20355 Hamburg, Germany
— 2 Novel Device Group, Intel Corporation, Hillsboro, OR 97124,
USA — 3 IBM Research Division, T. J. Watson Research Center, Yorktown
Heights, NY 10598, USA
Today, the performance of carbon nanotube field-effect transistors
(CNFETs) is already competitive with that of state-of-the-art silicon
transistors [1]. However, a metal-semiconductor junction as in CNFETs
fabricated to date necessitates a Schottky type contact which may present
a significant barrier for transport. Most CNFETs thus behave as Schottky
barrier transistors [2]. This leads to an unexpected scaling of CNFET
performance as the device size is reduced [3]. Using an analytic model, we
derive explicit scaling laws in the turn-on regime and for the transistor
OFF state – in excellent agreement with experimental data [3]. An important
consequence of the scaling behavior is an exponential increase of
the OFF current with drain voltage for ultra-thin oxide CNFETs which
limits the usable drain voltage and thus the achievable ON currents [4].
[1] S. J. Wind et al., Appl. Phys. Lett. 80, 3817 (2002).
[2] S. Heinze et al., Phys. Rev. Lett. 89, 106801 (2002).
[3] S. Heinze et al., cond-mat/0302175 and Phys. Rev. B (in press).
[4] M. Radosavljević et al., Appl. Phys. Lett. 83, 2435 (2003).
TT 27.11 Do 12:30 H19
Transport through a Carbon Nanotube with Superconducting
Contacts — •Wolfgang Belzig, Mark Buitelaar, Thomas
Nussbaumer, Christoph Bruder, and Christian Schöneberger
— Universität Basel, Klingelbergstr. 82, 4056 Basel, Schweiz
We report on experimental and theoretical studies of transport through
multi-walled carbon nanotubes strongly coupled to superconducting
leads. In the normal state of the leads the conductance displays a Kondo
behaviour for odd numbers of electrons on the nanotube dot. If superconductivity
is turned on, the transport characteristic changes dramatically.
A large zero bias conductance (with G ≫ 2e 2 /h) and a strongly nonlinear
differential conductance are observed. Both effects depend on the
gate voltage. We explain the experimental observations theoretically by a
subtle interplay between Kondo physics and proximity effect on the dot.
Multiple Andreev reflections play a key-role to explain the features seen
in the differential conductance.
TT 28 FV-internes Symposium ”Theoretical Modeling of Materials with Correlated
Electrons”
Zeit: Donnerstag 14:00–18:10 Raum: H20
Hauptvortrag TT 28.1 Do 14:00 H20
Opportunities and challenges from electron spectroscopy for
realistic correlated electron theory — •J. W. Allen — Randall
Laboratory of Physics, University of Michigan, Ann Arbor, MI 48109,
USA
In the past 25 years electron spectroscopy has developed steadily to
take its place with optical and Raman spectroscopy and with neutron
scattering as an established general technique for studying the electronic
structure of condensed matter systems. Already the current quality
of available data on strongly correlated electron systems calls for theory
beyond that of the model Hamiltonian and the need is expected to increase
with further improvements in the experimental technique. I will
give current examples in the context of the elucidation of Landau Fermi
liquid theory quasi-particles and their absence in photoemission spectra.
Hauptvortrag TT 28.2 Do 14:25 H20
Dynamical Mean Field Theory (DMFT) and Electronic Structure
Calculation — •G. Kotliar — Department of Physics and
Astronomy, Rutgers University, Piscataway, NJ 08854-8019, USA
We will discuss how a many body technique, DMFT is interfaced with
band structure methods so as to obtain quantitative system specific information
about correlated materials. Our talk will cover, computation
of total energies, photoemission spectra, thermodynamical quantities
transport properties phonon spectra, and optical conductivity. We will
illustrate the method drawing examples from a simple system d electron
system undergoing a density driven Mott transition (LaSrTiO3) and from
lanthanide and actinide materials.
Fachvortrag TT 28.3 Do 14:50 H20
How Chemistry Controls Electron Localization in 3d 1 Perovskites
— •O. K. Andersen — Max-Planck Institute for Solid State
Research, D-70506 Stuttgart

Tiefe Temperaturen Donnerstag
A current route to describing the physical properties of real materials
with strongly correlated electrons, is to derive a low-energy Hubbard
Hamiltonian using Wannier-functions obtained by a density-functional
calculation, and to solve it using the dynamical mean-field approximation.
As an example, we consider the series of 3d 1 orthorhombic perovskites
SrVO3, CaVO3, LaTiO3, and YTiO3, in which an increasing tilting and
rotation of the oxygen octahedron is accompanied by an increasing localization
of the t2g electron; the vanadates are mass-enhanced metals
and the titanates Mott insulators. We show that cation covalency, rather
than ion-sizes and JT-distortions, is the controlling mechanism.
Hauptvortrag TT 28.4 Do 15:15 H20
Wannier functions formalism and DMFT — •V. I. Anisimov —
Institute of Metal Physics, Russian Academy of Science - Ural Division,
620219 Ekaterinburg, GSP-170, Russia
The Hubbard model is expressed in a site-centered, atomic-like orbital
basis set which is usually not explicitly defined. We propose a method for
calculating the explicit form of the Wannier functions and also a procedure
of projecting the full-orbital Hamiltonian on the Wannier function
subspace defined for the partially filled bands of interest. The few (Wannier)
orbital Hamiltonian calculated in this way is used for DMFT(QMC)
calculations. The self-energy operator defined in Wannier function basis
obtained in such calculations is converted back into the full-orbital Hilbert
space and is used for the calculation of the total and partial densities
of states of real materials. Results obtained by this method for SrVO3
and V2O3 are reported.
Fachvortrag TT 28.5 Do 15:40 H20
Multi-Band Gutzwiller Method for Transition metals and Compounds:
Magnetism, Fermi Surfaces and Spin-Orbit Coupling —
•Werner Weber1 , Jörg Bünemann2 , and Florian Gebhard2 — 1Institu für Physik, Universität Dortmund — 2Fachbereich Physik,
Philipps Universität Marburg
The multi-band Gutzwiller method is used to calculate ground state
properties and quasi-particle energy bands of magnetic transition metals
and compounds. Our scheme utilizes single-particle model Hamiltonians
with an s, p, and d spin orbital basis, obtained from density functional
theory studies. For cubic, ferromagnetic Nickel our results even correctly
reproduce details of the quasi particle bands near the Fermi surface. In
the case of low crystal symmetry and/or of a large orbital basis, the hopping
reduction factors q(σ, σ ′
)of the effective single particle Hamiltonian
have a matrix form in the space of the spin orbitals σ. Furthermore,
additional variational parameters appear, which act on the eigenvectors
of the atomic multiplet states. Incorporation of spin-orbit coupling for
Nickel results, via the off-diagonal q(σ, σ ′
), in spin-flip hopping terms of
the effective Hamiltonian. These terms considerably enhance the value of
the orbital magnetic moment over the Hartree-Fock limit, so that good
agreement with experiment is achieved.
16:05 Pause
Fachvortrag TT 28.6 Do 16:30 H20
Partial localization, dual nature of 5f electrons and heavy fermions
in U compounds — •G. Zwicknagl — Institut fuer Mathematische
Physik, TU Braunschweig, D-38106 Braunschweig
There is growing evidence that actinide ions may have localized as well
as delocalized 5f electrons. These observations form the basis of the dual
model which provides a microscopic theory for the heavy quasiparticles
in U compounds. In the present talk, I shall present results for the Fermi
surface and effective masses in U-based heavy fermion compounds.
In addition, I shall show how the dual character of the 5f electrons may
arise from the interplay between (effective) hopping and Hund’s rule correlations.
Fachvortrag TT 28.7 Do 16:55 H20
Realistic Description of Strongly Correlated Materials — •A. I.
Lichtenstein — University of Nijmegen, The Netherlands
Local density approximation (LDA) of density functional theory has
been highly successful for electronic structure calculations of different
non-correlated ystems. The LDA scheme quite often failed for strongly
correlated materials containing transition metals and rare-earth elements
with complicated charge, spin and orbital fluctuations. Dynamical
mean field theory (DMFT) in combination with the first-principle LDA
scheme can be a starting point for a realistic description of various correlated
electron materials. We discuss a competition between the local
Coulomb interaction and chemical bonding as well as effects of of nonlocal
Coulomb interactions for transiton metal oxides within a cluster
LDA+DMFT scheme.
Fachvortrag TT 28.8 Do 17:20 H20
The orbital state and magnetic properties of LiV2O4: Recent insight
from LDA+DMFT — •Th. Pruschke — Institute for Theoretical
Physics, University of Goettingen, D-37077 Goettingen
LiV2O4 is considered to be the first system showing heavy fermion
physics without f electrons. This behaviour is even more surprising if one
takes into account that the average occupancy of the Vanadium d-states
is 1.5 electrons/V, i.e. the system seems to be rather in the mixed-valence
than in the classical Kondo regime typically required for heavy-fermions.
Within the framework of DMFT+LDA we show that this part of the
puzzle can be resolved in a rather surprising manner, namely by localizing
one of the d-electrons in the non-degenerate A1g level of the t2g
manifold, while 0.5 electrons/V in the twofold degenerate Eg level remain
itinerant. The existence of precisley one localized and 0.5 delocalized electrons
per Vanadium leads to very specific theoretical predictions about
the magnetic properties of LiV2O4, which can be compared to experiment.
In particular, the effective magnetic moment deduced from the
high-temperature Curie behavior and inelastic, spin-polarized neutron
scattering support our conjecture.
Fachvortrag TT 28.9 Do 17:45 H20
Coulomb Correlations in Multi-Orbital Materials — •A. Liebsch
— Forschungszentrum Juelich, D-52425 Juelich
The influence of local Coulomb interactions on the electronic properties
of transition metal oxides is investigated within the Dynamical Mean
Field Theory and multi-orbital Quantum Monte Carlo method. In materials
such as VO2, SrVO3, and Sr2RuO4 the quasi-particle spectra exhibit
correlation features which cannot be understood within density functional
theory. In particular, we discuss the enhancement of correlation effects
due to orbital polarization induced by Peierls distortion, the enhancement
of correlations at surfaces due to band narrowing, and the possibility of
observing multi-gapped Mott insulators.
TT 29 Quantenkohärenz und Quanteninformationssysteme II
Zeit: Donnerstag 14:30–18:00 Raum: H19
TT 29.1 Do 14:30 H19
Experimental investigations of superconducting qubits using a
resonant tank circuit. — •Il’ichev Evgeni — IPHT, A. Einstein
Str. 9, 07745 Jena, Germany
On-chip LC tank circuits with a high quality factor 2000 can be effective
probes of superconducting qubits, to which they are coupled inductively.
Resonant properties of the circuits are strongly dependent on the
qubit’s effective susceptibility that allows to measure the qubit’s tunneling
amplitude and decoherence rate. This setup trades off time control
for sensitivity at the LC-resonance frequency. As a result, a weak coupling
to the qubit suffices, which helps to reduce measurement-induced
decoherence in the system. Weak continuous measurements of Rabi os-
cillations and a detection of Landau-Zener transitions will be discussed
together with low-frequency measurements of the energy splitting in the
flux qubit.
TT 29.2 Do 14:45 H19
Quantum dissociation of a vortex-antivortex pair in a long
Josephson junction — •M.V. Fistul 1 , A. Wallraff 2 , Y. Koval
1 , A. Lukashenko 1 , B.A. Malomed 3 , and A.V. Ustinov 1 —
1 Physikalisches Institut III, Universität Erlangen-Nürnberg, 91058 Erlangen,
Germany — 2 Dept. Applied Physics, Yale University, New Haven,
CT 06520 USA — 3 Tel Aviv University, Tel-Aviv, 69978 Israel
Thermal and quantum dissociation of a single vortex-antivortex (VAV)

Tiefe Temperaturen Donnerstag
pair in an annular Josephson junction is experimentally observed and
theoretically analyzed [1]. VAV pair is confined in a pinning potential
controlled by external magnetic field and bias current. The dissociation
of the pinned VAV pair manifests itself by a switching of the Josephson
junction from the superconducting to the resistive state. The observed
temperature and field dependence of the switching current distribution is
in agreement with our analysis. In an extremely narrow long JJs (a small
width of a JJ allows to decrease the ”electromagnetic” effective mass of
a VAV pair) the crossover from the thermal to the macroscopic quantum
tunneling mechanism of dissociation occurs at a temperature of about
100 mK. We also predict the specific magnetic field dependence of the oscillatory
energy levels of the pinned VAV state. The quantum-mechanical
dynamics of a VAV pair can be used for quantum information processing.
[1] M.V. Fistul et al., to appear in Phys.Rev.Lett. (cond-mat/0307705)
TT 29.3 Do 15:00 H19
Multi-photon transitions and subharmonic-like resonances in
a superconducting flux qubit device — •M. Thorwart 1,2 , S.
Saito 2 , H. Tanaka 2 , H. Nakano 2 , M. Ueda 2 , K. Semba 2 , and H.
Takayanagi 2 — 1 Institut für Theoretische Physik IV, Heinrich-Heine-
Universität Düsseldorf — 2 NTT Basic Research Laboratories, Atsugi-shi,
Japan
We investigate both experimentally and theoretically the quantum mechanical
dynamics of superposition states of a superconducting loop with
three Josephson junctions in the presence of an external RF-field. Readout
of the state of this driven macroscopic quantum two-state system
is performed by an additional dc-SQUID. For strong enough driving,
we find up to three-photon transitions in spectroscopy measurements.
The width of the n-photon resonance scales with the n-th Bessel function.
This is in agreement with theoretical predictions starting from the
driven spin-boson model and applying real-time path integral methods.
In addition, we report on subharmonic-like resonances in spectroscopy
measurements. They are related to excitations in the combined driven
flux-qubit-SQUID system and are explained in terms of avoided level
crossings in the Floquet spectrum.
TT 29.4 Do 15:15 H19
Dynamic Features of a Superconducting Ring-Type Charge
Qubit — •Detlef Born 1 , Wolfram Krech 1 , Vladimir
Shnyrkov 1 , Thomas Wagner 2 , Evgeni Il’ichev 2 , Uwe Hübner 2 ,
and Hans-Georg Meyer 2 — 1 FSU, Institut für Festkörperphysik,
07743 Jena — 2 IPHT e.V., 07702 Jena
We study dynamic properties of a special Josephson charge qubit consisting
of a single-Cooper-pair transistor with capacitive gate closed by
a superconducting loop.
Within the framework of a two-band model we consider analytically
the features of the oppositely circulating ring currents corresponding to
ground and upper quantum state, respectively, in terms of gate charge
and total Josephson phase across the transistor. We determine basic device
characteristics, e.g. the critical current, current-phase relationships
as well as the critical loop parameter and the oppositely acting Josephson
inductances belonging to the separate bands.
We observed experimentally dynamic features of the described quantum
object. For this purpose, we investigated the total impedance of a
configuration consisting of the ring qubit inductively coupled to the coil
of a high-quality tank circuit. Measuring the phase shift between tank
current and voltage (MHz range), we demonstrated the modulation of
the qubit ground state impedance with respect to both electric gate voltage
and magnetic flux bias. Illuminating the qubit by means of an UHF
source (GHz range), we detected the effect of the (negative) inductance
of the upper state.
TT 29.5 Do 15:30 H19
Investigation of a superconducting flux qubit with SQUID readout
— •S. Linzen 1 , B.L.T. Plourde 1 , T.L. Robertson 1 , T. Hime 1 ,
P.A. Reichardt 1 , C.E. Wu 1 , F. Wilhelm 2 , and John Clarke 1
— 1 Department of Physics, University of California, Berkeley, USA —
2 Sektion Physik, Ludwig-Maximilians-Universität, München, Germany
We have studied large inductance flux qubits based on submicron
Al/AlOx/Al tunnel junctions. A dc SQUID is used to distinguish the
two fundamental states of the three-junction qubit by measuring the
switching probability with a pulsed bias current. We have optimized the
qubit flux signal and the coupling to the SQUID to minimize decoherence.
Single-shot readout has been reached by on-chip shunting of each of the
two SQUID junctions with a resistor and capacitor in series. We can still
resolve the qubit state with 60% fidelity with a single measurement without
the RC shunts. We measure the qubit energy levels spectroscopically
using microwave pulses in the wide frequency range 100 MHz to 20 GHz
while adjusting the fluxes in the SQUID and qubit by means of static
currents in two inductively coupled lines on-chip. The repetition rate of
the readout pulses is limited by hot electron generation in the SQUID
tunnel junctions when the SQUID switches out of the supercurrent state.
The influence of the repetition rate on the resonance peak widths and
the relaxation time will be discussed. We observe long relaxation times,
more than 20 µs, and dephasing times of about 5 ns when the repetition
rate is lower than 2 kHz.
This work was supported by Alexander von Humboldt-Foundation,
AFOSR, ARO, and ARDA.
TT 29.6 Do 15:45 H19
Decoherence of superconducting qubits due to phonons —
•Christian Helm 1 , L.B. Ioffe 2 , V.B. Geshkenbein 1 , and G.
Blatter 1 — 1 ETH Hönggerberg, Institut fuer theoretische Physik,
Zürich — 2 Department of Physics and Astronomy, Rutgers University,
Piscataway, USA
Decoherence is the main adversary of the unitary time evolution governing
the quantum systems, which provide the hardware for a future
quantum information technology based on solid state devices. Here, we
discuss a fundamental limitation for the coherent operation of superconducting
quantum bits based on Josephson junctions due to phonon
radiation (Such an effect was observed e.g. in C. Helm at al. PRL 79
(1997),737). We find that recently reported quality factors may be explained
in terms of decoherence from phonon radiation, which therefore
might be the limiting factor in current experiments. We show the way to
reduce the impact of this source of decoherence, e.g. by a choice of materials
with appropriate elastic properties or by comparing various qubit
designs.
16:00 Pause
TT 29.7 Do 16:15 H19
Controllable coupling of two charge qubits — •C. Bruder 1 and
D.V. Averin 2 — 1 Department of Physics and Astronomy, University of
Basel, Klingelbergstrasse 82, CH-4056 Basel — 2 Department of Physics
and Astronomy, University of Stony Brook, SUNY, Stony Brook, NY
11794-3800
We propose and investigate a novel method for the controlled coupling
of two Josephson charge qubits by means of a variable electrostatic transformer.
The value of the coupling capacitance is given by the discretized
curvature of the lowest energy band of a Josephson junction, which can
be positive, negative, or zero. We calculate the charging diagram of the
two-qubit system that reflects the transition from positive to negative
through vanishing coupling. We also discuss how to implement a phase
gate making use of the controllable coupling.
[1] D.V. Averin and C. Bruder, Phys. Rev. Lett. 91, 057003 (2003).
TT 29.8 Do 16:30 H19
Enhancing the Gate Performance of Superconducting Qubits
by DFS Encoding — •Markus J. Storcz 1 , Frank K. Wilhelm 1 ,
Jiri Vala 2 , Kenneth R. Brown 2 , Julia Kempe 2 , and K. Birgitta
Whaley 2 — 1 Sektion Physik und CeNS, Ludwig-Maximilians-
Universität, Theresienstr. 37, 80333 München — 2 Department of Chemistry
and Pitzer Center for Theoretical Chemistry, University of California,
Berkeley, California 94720
Solid state qubits such as superconducting qubits are potentially extremely
scalable. However, strong decoherence may be caused or transferred
to the qubits by various elements of the circuit that couples individual
qubits, in particular when couplings over long physical distance
are implemented. We propose encoding into a subspace protected against
collective phase errors for a chain of superconducting qubits that are
coupled to nearest neighbors with ˆσ (i)
x ˆσ (i+1)
x + ˆσ (i)
y ˆσ (i+1)
y -type of interaction.
We show by numerical simulation of the encoded operations for an
ohmic environment that, even if the mathematical preconditions for full
DFS-protection are not fully satisfied, the encoding results in significant
improvement of the gate performance on the logical qubits at low temperatures.
Moreover, for a super-ohmic environment perfect protection
and gate performance of the logical qubits can be achieved.

Tiefe Temperaturen Donnerstag
TT 29.9 Do 16:45 H19
Influence of Pulse Shape for Josephson Junction Quantum
Computation — •Carsten Hutter, Yuriy Makhlin, and Gerd
Schön — Institut für Theoretische Festkörperphysik, Universität Karlsruhe,
D–76128 Karlsruhe, Germany
Recently, a controlled NOT quantum gate employing coupled charge
qubits was demonstrated for the first time [1]. A pulse technique with
ideally steplike pulses was used to switch the field parameters. In reality,
the pulses have finite rise- and falltimes, which influence the time evolution
of the qubits. While most studies on this problem consider a single
qubit, we focus on the effects of the pulse shape on two coupled qubits.
Analytical and numerical results are presented, and based on them a
qualitative understanding of the suppression of oscillations in an earlier
experiment [2] is given.
[1] T. Yamamoto et al, Nature 425, 941 (2003)
[2] Yu.A. Pashkin et al, Nature 421, 823 (2003)
TT 29.10 Do 17:00 H19
Cavity QED using superconducting qubits - intermediate
temperatures — •Göran Johansson, Alexander Shnirman, and
Ileana Rau — Institut für Theoretische Festkörperphysik
Inspired by recent experiments we investigate the dynamics of a
Josephson qubit resonantly coupled to a damped harmonic oscillator.
We specifaclly investigate the temperature dependence of the cavity susceptebility,
which in solid state devices corresponds to the impedance
of the LC-circuit. At zero temperature the uncoupled resonant peak is
Rabi splitted by the qubit. At temperatures comparable to the oscillator
frequency we find an intricate multiple peak structure, while at high
temperatures the uncoupled single peak is recovered. We treat the dynamics
of the system numerically by exact diagonalizing of the qubit plus
up to 100 states in the oscillator. We then include the bath within the
Bloch-Redfield formalism, without making the secular approximation.
Specifically we investigate the break-down of the secular approximation
at finite temperatures, caused by the Liouvillian degeneray, i.e. two or
more transitions with approximately equal energy. In the impedance this
is seen as the overlap of nearby peaks, which cannot be calculated as the
sum of the two peaks.
TT 29.11 Do 17:15 H19
Bath assisted adiabatic following — •Christos Kostoglou,
Mathias Michel, and Günter Mahler — Institut für Theoretische
Physik 1, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart
We regard quantum systems for which adiabatic following is ”not
generic”, i.e. not only the eigenvalues but also the eigenstates of the
Hamiltonian are time dependent. A simple, pertinent model is a spin-
1/2-system in a rotating magnetic field, the adiabatic following of which
fades away with increasing rotation frequency. Here we test if the dephasing
influence of a microcanonically coupled environment supports
adiabatic following. The environment is modeled as a n-level system randomly
coupled to the spin without allowing for energy exchange. The
environment can be interpreted as an ubiquitous container of thermodynamic
machines; such a combination of spin-1/2-system and container
leads us to an analog to thermodynamic processes on quantum scale.
Time evolution is given by the time-dependent Schrödinger equation.
TT 29.12 Do 17:30 H19
Quantum Control: Mechanical Versus Thermodynamical
Aspects — •Harry Schmidt und Günter Mahler — Universität
Stuttgart, Institut für Theoretische Physik 1, Pfaffenwaldring 57,
D-70550 Stuttgart
External quantum control is usually taken to mean that certain classical
parameters entering the Hamiltonian of the controlled quantum system
can be changed from the outside. To exert such a control one may
be tempted to use another (mesoscopic) quantum system.
We investigate the conditions under which such a mesoscopic system
may, indeed, act like a classical (mechanical) control on the one hand or
as a bath on the other hand with respect to the state evolution of the
controlled microscopic system. Both control features can be used as working
parts of quantum thermodynamical machines. The actual control
mode depends on the state of the system as a whole, the state of the mesoscopic
object, in particular, and parameters of the interaction that are
easily accessible and adjustable in an experimental setup. These parameters
thus provide an external control of the behavior of the mesoscopic
system.
TT 29.13 Do 17:45 H19
Quantum versus classical temperature profiles — •Michael
Hartmann 1,2 , Günter Mahler 2 und Ortwin Hess 3 — 1 Institut
für Technische Physik, DLR Stuttgart, Pfaffenwaldring 38 - 40, D-70569
Stuttgart — 2 Institut für Theoretische Physik I, Universität Stuttgart,
Pfaffenwaldring 57, D-70550 Stuttgart — 3 School of Electronics & Physical
Sciences, University of Surrey, GU2 7XH, UK
We consider a quantum system consisting of a regular chain
of elementary subsystems with nearest neighbour interactions and
form groups of N subsystems each. Assuming that the total system
is in a canonical state ρ = exp(H/kT)/Z with temperature
T we analyse under what condition the state may be decompo-
sed into a product of canonical density matrices of the subgroups,
ρ ′ = �
i exp(Hi/kT)/Zi, with the same temperature T. We then compare
the classical and the quantum regime and apply our analysis to a
harmonic chain as an example.
TT 30 Postersitzung IV: Kritische Phänomene, Quantenstörstellen, niederdimensionale
Systeme
Zeit: Donnerstag 14:30–19:00 Raum: Poster A
TT 30.1 Do 14:30 Poster A
Lattice dynamics and electron-phonon interaction in carbon
nanotube — •K.-P. Bohnen 1 , R. Heid 1 , H.J. Liu 2 , and C.T. Chan 2
— 1 Institut für Festkörperphysik, Forschungszentrum Karlsruhe, P.O.B.
3640, D-76021 Karlsruhe, Germany — 2 Dept. of Physics, University of
Science and Technology, Clear Water Bay, Kowloon, Hongkong, China
Over the past decade the interest in understanding the physical properties
of carbon nanotubes has grown enormously. This is based not only
on their potential for applications but also due to their role as model systems
for studying properties in one dimension. Especially the electronphonon
interaction is of interest with respect to Peierls transition [1],
Kohn anomalies and superconductivity [2]. Using density functional perturbation
theory we have calculated the complete phonon dispersion for
(3,3) and (5,0) tubes. Both tubes show instabilities at q=2kF which can
be seen in certain phonon modes. Due to the special topology of the
Fermi surface for (n,n) tubes we find also phonon anomalies at q=0 for
the (3,3) tube. Part of these have already been seen in other studies
[3]. Since the instabilities at q=2kF show up usually at q vectors incommensurable
with the lattice periodicity it is exceptionally difficult to see
these effects in frozen-phonon calculations. We will present comparison
with Raman measurements and approximate theoretical treatments [4].
[1] M. Th. Figge et al., Phys. Rev. Lett 86, 4572 (2001)
[2] Z. K. Tang et al., Science 292, 2462 (2001)
[3] O. Dubay et al., Phys. Rev. B 67, 035401 (2003)
[4] R. Barnett at al., cond-mat/0305006v2 (2003)
TT 30.2 Do 14:30 Poster A
Numerical Renormalization Group Study for Bosonic Systems
— •Ninghua Tong 1 , Ralf Bulla 1 , and Matthias Vojta 2 —
1 Theoretische Physik III, Universität Augsburg — 2 Institut für Theorie
der Kondensierten Materie, Universität Karlsruhe
The physics of an impurity imbedded in a metallic fermionic bath is one
of the best studied fields in condensed matter physics. Wilson’s numerical
renormalization group (NRG) method has been very successfully applied
to such problems due to its non-perturbative nature and the ability to
access exponentially small energy scales. In recent years, the physics of
impurities in a bosonic bath has attracted much interest. Such systems
include impurities imbedded in a magnetic environment and qubits in
a dissipative environment. A non-perturbative and accurate method for
handling these problems is highly desirable. We propose to generalize
Wilson’s NRG method to bosonic systems [R. Bulla, N.-H. Tong, and
M. Vojta, Phys. Rev. Lett. 91, 170601 (2003)]. As a first application, we
study the spin-boson model, which describes a two-level system coupled

Tiefe Temperaturen Donnerstag
linearly to a bath of harmonic oscillators with power law spectral density.
We find that the NRG technique works well for this bosonic systems, despite
the fact that we have to limit the number of bosons on each site. For
the sub-Ohmic bath with exponents 0 < S < 1, we find clear evidence for
a line of continuous quantum phase transitions between localized and delocalized
phases. The line terminates in a Kosterlitz-Thouless transition
at S = 1. Further application to other bosonic impurity problems and
the combination with the dynamical mean-field theory for lattice bosonic
systems are to be explored.
TT 30.3 Do 14:30 Poster A
Numerical Renormalization Group for the Bose-Fermi Kondo
Model — •Tae-Hyoung Gimm and Ralf Bulla — Theoretische
Physik III, Universität Augsburg
Wilson’s numerical renormalization group (NRG) method is a powerful
tool for the investigations of quantum impurity systems. It was originally
developed for the Kondo problem to study the physics of a magnetic impurity
in a fermionic bath. Recently, the NRG was successfully applied
to a simple two state system with a bosonic bath, that is, the spin-boson
model. Here we consider the Ising Bose-Fermi Kondo model, which describes
a magnetic impurity simultaneously coupled to both a fermionic
and a bosonic bath. When the Kondo lattice system is analyzed within
an extended dynamical mean field theory, the Kondo lattice Hamiltonian
is mapped onto an effective single-site problem and represented by
the Bose-Fermi Kondo Hamiltonian. We present a progress report of our
NRG investigation of the Bose-Fermi Kondo model with Ising anisotropy
for the boson field.
TT 30.4 Do 14:30 Poster A
Magnetic response of the non-Fermi-liquid YbRh2Si2 — •O.
Stockert 1 , N. Bernhoeft 2 , M. Koza 3 , J. Ferstl 1 , A. Murani 3 ,
C. Geibel 1 , and F. Steglich 1 — 1 Max-Planck-Institut CPfS,
Nöthnitzer Straße 40, D-01187 Dresden — 2 CEA Grenoble, DRFMC,
F-38054 Grenoble, France — 3 Institut Laue-Langevin, BP 156, F-38042
Grenoble, France
Deviations from the usual Landau-Fermi-liquid theory are observed in
an increasing number of correlated electron system which are close to a
magnetic instability where a transition from a nonmagnetic ground state
to a magnetically ordered state occurs. YbRh2Si2 is the first Yb-based
compound which obeys non-Fermi-liquid behavior as seen in unusual
temperature dependences of thermodynamic and transport properties at
temperatures above the very low ordering temperature TN = 65mK. In
the vicinity of the magnetic instability in YbRh2Si2 one expects critical
spin fluctuations which are the origin of the non-Fermi-liquid behavior.
Inelastic neutron scattering on YbRh2Si2 powder has been performed to
investigate the magnetic response. The high energy response is dominated
by crystalline electric field excitations, found at ≈ 27, and 42meV.
In contrast, the low energy response is quasielastic and shows a critical
slowing down as the temperature is reduced. However, the quasielastic
response seems to be non-Lorentzian like, but could be fitted by a phenomenological
model for the susceptibility using a distribution of relaxation
rates with an upper, temperature independent bound and a lower
bound varying roughly linearly with T.
TT 30.5 Do 14:30 Poster A
Anderson localization in disordered electron-phonon systems —
•Andreas Alvermann, Franz X. Bronold, and Holger Fehske
— Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, 17489
Greifswald
In order to study the competition between Anderson localization and
polaron formation we adopt the statistical dynamic mean field theory to a
generic model for a strongly coupled disordered electron-phonon system.
The localization properties of a single polaron are discussed in detail.
TT 30.6 Do 14:30 Poster A
Comparative numerical study of localization in disordered electron
systems — •Gerald Schubert 1 , Alexander Weiße 2 , and
Holger Fehske 1 — 1 Institut für Physik, Ernst-Moritz-Arndt Universität
Greifswald, 17487 Greifswald, Germany — 2 School of Physics, The
University of New South Wales, Sydney, NSW 2052, Australia
Taking into account that a proper description of disordered systems
should focus on distribution functions, the authors develop a powerful
numerical scheme for the determination of the probability distribution
of the local density of states (LDOS), which is based on a Chebyshev
expansion with kernel polynomial refinement and allows the study of
large finite clusters (up to 100 3 ). As the distribution of the LDOS shows
a significant change at the disorder induced delocalization-localization
transition, the so-called typical density of states, defined as the geometric
mean of the LDOS, emerges as a natural order parameter. Using this
method, we calculate the phase diagram for the three dimensional Anderson
model, treat correlated disorder in one dimension and consider
the quantum percolation problem on a simple cubic lattice.
TT 30.7 Do 14:30 Poster A
The extended-Harris criterion and scale-free disorder in the
3D Anderson model of localization — •Macleans L. Ndawana 1 ,
Rudolf A. Römer 1 , and Michael Schreiber 2 — 1 University of
Warwick, Department of Physics and Center for Scientific Computing,
CV4 7AL, Coventry, United Kingdom — 2 Institut für Physik, Technische
Universität, D-09107 Chemnitz
We investigate the 3D Anderson model of localization [1] in the presence
of scale-free [2] diagonal disorder via a modified transfer matrix
method. The diagonal disorder is characterized by a correlation function
that decays as r −α for separation r in the limit r → ∞ and α is
the correlation-strength exponent. The extended-Harris criterion [3] is
investigated by analyzing the dependence of the correlation-length critical
exponent ν on α. We observe that for fixed W, there is a critical
value αc below which, i.e. for α < αc, the universality class of the system
changes. For α > αc, ν remains unchanged. This value of αc separates
two regions, a region where correlations in disorder are relevant (α < αc)
and a region where they are irrelevant (α > αc). Furthermore, we observe
that at E = 0, ν is independent of α. This might suggest that the
metal-insulator transition at E = 0 exhibits strong universality.
[1] P. W. Anderson, Phys. Rev. 109, 1492 (1958)
[2] H. A. Makse, et. al Phys. Rev. B 53, 5443 (1996)
[3] A. Weinrib and B. I. Halperin, Phys. Rev. B 27, 413 (1983)
TT 30.8 Do 14:30 Poster A
Mott Transition on the Surface of 1T-TaSe2 studied by Angle-
Resolved Photoemission — •Markus Hoinkis, Hidenori Fujiwara,
Benjamin Schmid, Matthias Klemm, David Schrupp,
Jörg Schäfer, Michael Sing, and Ralph Claessen — Institut
für Physik, Universität Augsburg, 86135 Augsburg
The layered transition metal dichalcogenide 1T-TaSe2 is known to be
in a charge density wave phase below T1 = 475K. Recently, an additional
phase transition occurring only at the surface has been discovered
at T2 = 260K [1]. Below this temperature the density of states is strongly
depressed at the Fermi energy. The authors of [1] have interpreted this
as a bandwidth-controlled Mott transition: The temperature-dependent
modulation of the atomic positions leads to a smaller bandwidth W of
the Ta 5d-Band. While this modification of the ratio U/W (U is the onsite
Coulomb interaction) does not suffice to trigger a Mott transition
in the bulk, the effective bandwidth at the surface could be sufficiently
small for this effect.
By angle-resolved photoemission we have studied the spectral evolution
through the transition, with particular focus on the identification
and dispersion of the quasiparticle and lower Hubbard band peaks.
[1] L. Perfetti et al., Phys. Rev. Lett. 90, 166401 (2003)
TT 30.9 Do 14:30 Poster A
Characterisation of the Polaron Energy Spectrum in the Molecular
Holstein Model — •Daniela Schneider and Karl-Heinz
Höck — Theoretische Physik II, Institut für Physik, Universität Augsburg,
D-86135 Augsburg
The polaron energy spectrum of the molecular Holstein and E × β
Jahn-Teller model includes some frequently discussed aspects, which are
related to the crossover from itinerant to localized polarons. We studied
in particular the crossing and anticrossing effect of the energy branches.
We are also interested in the consequence of electron-phonon-coupling
on various physical quantities such as the absorption spectrum and optical
conductivity. The associated calculations are based on a closed form
for the matrix elements. Considerations from a group theoretical and
symmetry point of view are used to classify the eigenstates and give information
about both the possible transitions in the energy spectrum and
the correct analytical treatment of the model. The results are discussed
and compared with those of a numerical recurrence method.
This work is supported by DFG (SFB 484).

Tiefe Temperaturen Donnerstag
TT 30.10 Do 14:30 Poster A
Ferromagnetic Polarons in the 2D Kondo Model — •Maria
Daghofer 1 , Winfried Koller 2 , Hans Gerd Evertz 1 , and Wolfgang
von der Linden 1 — 1 Institut für Theoretische Physik, TU Graz,
Petersgasse 16, 8010 Graz, Österreich — 2 Department of Mathematics,
Imperial College London, London SW7 2BZ , GB
The 2D ferromagnetic Kondo model with classical corespins is studied
via unbiased Monte-Carlo simulations. A canonical algorithm for finite
temperatures is developed.
We show that with realistic parameters for the manganites and at low
temperatures, the double-exchange mechanism does not lead to phase
separation on a two-dimensional lattice but rather stabilizes individual
ferromagnetic polarons. Within the ferromagnetic polaron picture, the
pseudogap in the one-particle spectral function Ak(ω) can easily be explained.
Further, we explore the influence of the AFM superexchange coupling
J ′ . We find that larger J ′ stabilizes the polarons, while it destroys the ferromagnetism
at very large doping and leads to the so called ”flux phase”
around half filling of the lower Kondo band. We also find that lower
temperatures further enhance polaronic behavior at realistic parameters
J ′ > 0.01.Detailed phase diagrams for β = 50 and β = 80 are given, in
which a narrow window in parameter space exists for phase separation.
TT 30.11 Do 14:30 Poster A
UV-Photoemissions-Spektroskopie zur Deutung der magnetischen
Eigenschaften von Fe1−xCoxSi-Einkristallen — •D. Menzel,
D. Zur und J. Schoenes — Institut für Halbleiterphysik und
Optik, Technische Universität Braunschweig, Mendelssohnstr. 3, 38106
Braunschweig
Das System FeSi mit seinen ungewöhnlichen paramagnetischen Eigenschaften
hat seit kürzerer Zeit wegen seines Verhaltens als Kondo-Isolator
großes Interesse hervorgerufen. Dotiert man FeSi mit Co, so erhält man
ab einer Co-Konzentration von 5 at.% einen Übergang zu einem ferromagnetischen
Metall. Die Oberflächen von Fe1−xCoxSi-Einkristallen mit
unterschiedlicher Co-Konzentration, die mit Tri-Arc-Czochralski-Technik
hergestellt worden sind, wurden im Ultrahochvakuum zunächst durch Ar-
Sputtern gereinigt und anschließend in einem Temperschritt ausgeheilt.
In-situ-UV-Photoemissions-Untersuchungen zeigen ein scharfes Valenzbandmaximum,
das sich mit wachsender Co-Konzentration in Richtung
der Fermikante verschiebt. Auf diese Weise vergrößert sich die elektronische
Zustandsdichte am Ferminiveau, so dass das Stoner-Kriterium für
ferromagnetischen Austausch erfüllt wird. Magnetische Untersuchungen,
die mit einem SQUID-Magnetometer durchgeführt wurden, zeigen ein
nahezu reines Spinmoment von 1 Elektron pro Co-Atom.
TT 30.12 Do 14:30 Poster A
Obtaining optical constants for resonant soft x-ray scattering
— •J. Schlappa 1 , C. Schüßler-Langeheine 1 , Z. Hu 1 , M. W.
Haverkort 1 , E. Schierle 2 , H. Ott 2 , E. Weschke 2 , G. Kaindl 2 ,
P. Abbamonte 3 , M. Huijben 4 , G. Rijnders 4 , D. H. A. Blank 4 ,
A. Tanaka 5 , and L. H. Tjeng 1 — 1 II. Physikalisches Institut, Universität
zu Köln — 2 Institut für Experimentalphysik, Freie Universität
Berlin — 3 NSLS, Brookhaven National Laboratory, USA — 4 Faculty of
Science and Technology, University of Twente, Enschede, Netherlands —
5 ADSM, Hiroshima University, Japan
The new technique of resonant soft x-ray scattering at the transition
metal L2,3 and lanthanide M4,5 absorption edges is uniquely suited to
study order phenomena like spin, charge and orbital order in correlated
solids. A quantitative data analysis, however, requires the precise determination
of optical constants across the resonance. While these constants
are quite well known for energies far off resonance, reliable data on resonance,
where the index of refraction shows a strong energy dependence,
are missing. As a model system, we studied different surfaces of SrTiO3
at the Ti L2,3 resonance and obtained the optical parameters either indirectly
from a Kramers-Kronig transform of the absorption signal or
directly by measuring reflectivity and from that determined the critical
angle of total reflection. These results will be compared to theoretical
values. We demonstrate how much a proper data interpretation depends
on the precise knowledge of optical constants and discuss the suitability
and accuracy of either exprimental techniqe for their determination.
TT 30.13 Do 14:30 Poster A
Gitterdynamik von LaCoO3: Wechselspiel von Gitter- und Spinfreiheitsgraden
— •M. Cwik, M. Kriener, C. Zobel, T. Taetz, T.
Lorenz, A. Freimuth und M. Braden — II. Physikalisches Institut,
Universität zu Köln, Zülpicher Str. 77, 50937 Köln
Die Natur des thermisch induzierten Spinübergangs von LaCoO3 von
einem unmagnetischen Isolator zu einem paramagnetischen Isolator bei
100 K und des Isolator-Metall-Übergangs bei 500 K ist Gegenstand
kontroverser Diskussionen. Vom Grundzustand t6 2ge0g (S=0) des Co3+ -
Ions ist in Abhängigkeit von den relativen Energieskalen der Kristallfeldaufspaltung
und der Hund’schen Kopplung ein Übergang in einen
Intermediate-Spin- (IS) t5 2ge1 g (S=1) und in einen Highspin-Zustand (HS)
t 4 2g e2 g
(S=2) möglich. Untersuchungen der thermischen Ausdehnung und
der magnetischen Suszeptibilität deuten auf ein Einsetzen orbitaler Ordnung
beim Spinübergang und auf ein Verschwinden dieser beim Isolator-
Metall-Übergang hin [1]. Diese Ergebnisse favorisieren einen starken Einfluss
des Jahn-Teller-aktiven IS. Eine strukturelle Symmetrieerniedriegung
durch eine kollektive Jahn-Teller-Verzerrung wurde anhand von
Röntgendiffraktionsexperimenten beobachtet [2]. Wir präsentieren die
Ergebnisse detaillierter Untersuchungen der Gitterdynamik von LaCoO3-
Einkristallen mittels inelastischer Neutronenstreuung. Die Bindungsstreckschwingungen
entlang der drei Hauptsymmetrierichtungen zeigen
eine im Vergleich zu vielen anderen 3d Oxidperovskiten flache Dispersion.
gefördert von der DFG durch den SFB 608
[1] C. Zobel et al. Phys. Rev. B 66, 020402(R) (2002)
[2] G. Maris et al. Phys. Rev. B 67, 224423 (2003)
TT 30.14 Do 14:30 Poster A
Spin- und Metall-Isolator-Übergang in La1−xEuxCoO3 — •M.
Kriener, J. Baier, H. Kierspel, T. Lorenz, A. Reichl, C. Zobel,
S. Jodlauk und A. Freimuth — II. Physikalisches Institut, Universität
zu Köln, Zülpicher Str. 77, 50937 Köln
LaCoO3 ist ein Isolator mit ungewöhnlichen magnetischen Eigenschaften.
Im Grundzustand befindet sich das System in einem unmagnetischen
Low-Spin-Zustand (S = 0), in dem alle sechs d-Elektronen die
t2g-Zustände besetzen. Mit steigender Temperatur (T > 30K) wird
auch das eg-Orbital mit Elektronen thermisch besetzt, und es entwickelt
sich ein magnetisches Moment. Bei etwa 500K durchläuft die
Substanz einen Metall-Isolator-Übergang. Die Dotierung mit isovalentem
Eu bietet die Möglichkeit der gezielten Einstellung von Spin- und
Ladungsträgerlücke sowie Metall-Isolator-Übergangstemperatur. Unverstanden
ist bislang, warum die Größe der Spinanregungslücke so stark
von der der Ladungsanregungslücke abweicht. Wir diskutieren Suszeptibilität,
Widerstand, thermische Ausdehnung, spezifische Wärme und
Wärmeleitfähigkeit von La1−xEuxCoO3 innerhalb eines Modells, das eine
Jahn-Teller-Aufspaltung des magnetischen Zustandes miteinbezieht.
Wir führen den starken Anstieg beider Lücken auf eine systematische
Zunahme des Kristallfeldes auf Grund der La-Substitution durch das
kleinere Eu zurück. Die Ladungslücke wächst dabei stärker, da wegen
der strukturellen Verzerrung die Leitungsbandbreite kleiner wird. Obiges
Modell erklärt auch, daß im Bereich des Spinübergangs die thermische
Ausdehnung stark erhöht und die Wärmeleitfähigkeit unterdrückt wird.
Gefördert von der DFG durch den SFB 608.
TT 30.15 Do 14:30 Poster A
Observation of non-Gaussian conductance fluctuations at low
temperatures in Si:P(B) at the metal-insulator transition —
•Swastik Kar 1 , A. K. Raychaudhuri 1 , Arindam Ghosh 2 , H. v.
Löhneysen 3 , and G. Weiss 3 — 1 Department of Physics, Indian Institute
of Science, Banaglore 560012, India — 2 Cavendish Laboratory,
University of Cambridge, Cambridge CB3 0HE, United Kingdom —
3 Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe, Ger-
many
Conductance fluctuation(noise) has been one of the most studied areas
in condensed matter. Of considerable interest is the behavior of noise near
the the Anderson-Mott metal-insulator transition (MIT). In this report
we present the results of the first extensive experimental investigations
of non-Gaussian conductance fluctuations in a bulk (3-D) system (single
crystals of P-doped Si) as it is driven through the MIT at low temperatures
(T< 20K). As T → 0 and the system crosses over to the insulating
regime, the scaled magnitude of noise, γH, increases with decrease in temperature
following an approximate power-law γH ∼ T −β . At low temperatures,
γH diverges as n decreases through the critical concentration nc,
accompanied by a growth of low-frequency spectral weight. The second
spectrum and the Probability Density of the fluctuations show strong

Tiefe Temperaturen Donnerstag
non-Gaussian behavior below 20K as n/nc decreases through 1. This has
been interpreted as the onset of a glassy freezing of the electronic system
across the transition.
TT 30.16 Do 14:30 Poster A
Structure, Magnetism and Transport in Titanates — •H. Roth,
N. Schittner, A. Elfilali, K. Kordonis, M. Cwik, A. Komarek,
M. Reuther, R. Müller, T. Lorenz, M. Braden und A. Freimuth
— II. Physikalisches Institut, Universität zu Köln, Zülpicher str.
77, 50939 Köln
The RTiO3 compounds (R = Rare Earth) are typical Mott-insulators
with ferro- or antiferromagnetic order depending on the radius of the
R 3+ -ion. These Mott-insulators can be driven to a metal by hole doping.
We have prepared single crystals of the systems La1−xSrxTiO3, LaTiO3+δ
and Y1−xCaxTiO3 and studied the magnetization and resistivity. The resistivity
of La1−xSrxTiO3 with 0.07 < x ≤ 0.2 show a T 2 behaviour
over an unusually large temperature range up to 300K. In contrast to
La1−xSrxTiO3, where the transition from antiferromagnetic to paramagnetic
behaviour occurs around a hole concentration of 6%/Ti, the antiferromagnetic
order in LaTiO3+δ is stable up to δ = 0.1, which formally
corresponds to a hole concentration of 20%/Ti. Both, oxygen- as well
as Sr-doping causes a systematic decrease of the unusual orthorhombic
splitting observed in the pure LaTiO3. YTiO3, the other end compound
of the RTiO3 series, is a ferromagnet with a magnetic moment of 0.9µB.
In Y1−xCaxTiO3 the ferromagnetic order is strongly suppressed with increasing
x and we find some indication for a sign change of the effective
magnetic coupling, which could lead to a canted ferromagnetic ground
state for 0.1 < x < 0.4. gefördert von der DFG durch den SFB 608
TT 30.17 Do 14:30 Poster A
Metal-insulator transition in quasi 2D systems — •K.
Morawetz — Institute of Physics, Chemnitz University of Technology,
09107 Chemnitz, Germany — Max-Planck-Institute for the Physics of
Complex Systems, Nöthnitzer Str. 38, 01187 Dresden, Germany
The conductivity in quasi two-dimensional systems is calculated using
the quantum kinetic equation. Weak localization correction as an
interference effect appears from the field dependence of the collision integral.
The approximation is applied to a system of quasi two-dimensional
electrons in hetero-junctions which interact with charged and neutral
impurities and the low temperature correction to the conductivity is calculated
analytically. It turns out that the dynamical screening due to
charged impurities leads to a linear temperature dependence, while the
scattering from neutral impurities leads to the usual Fermi-liquid behavior.
The experimental metal-insulator transition at low temperatures are
reproduced [1]. The effective mass of quasiparticle excitations in quasi
two-dimensional systems is calculated analytically. It is shown that the
effective mass increases sharply when the density approaches the critical
one of metal-insulator transition. This suggests a Mott-type of transition
rather than an Anderson-like transition [2].
[1] K. Morawetz, Phys. Rev. B 67 (2003) 115125
[2] K. Morawetz, cond-mat/0210168
TT 30.18 Do 14:30 Poster A
Electrical conductivity of pure and doped K0.3MoO3 single crystals
grown by various preparation methods — •S. Yue 1 , M.
Dressel 1 , C. Kuntscher 1 , S. van Smaalen 2 , F. Ritter 3 , and
W. Assmus 3 — 1 1. Physikalisches Institut, Universität Stuttgart, 70550
Stuttgart, Germany — 2 Laboratory of Crystallography, University of
Bayreuth, 95440 Bayreuth, Germany — 3 Physikalisches Institut, Universität
Frankfurt, 60054 Frankfurt, Germany
We have studied the temperature dependence of the nonlinear electrical
conductivity in a series of pure and doped K0.3MoO3 single crystals
obtained by different preparation methods (i.e., electrochemistry and
temperature-gradient flux techniques). All the pure samples reveal the resistivity
anomaly near 180 K and the nonlinear transport, resulting from
the Peierls transition and the sliding of the charge-density wave (CDW),
respectively. Doping with Rb and W smears out the sharp transition,
with the transition temperature decreased. Furthermore, the doping introduces
pinning centers which enhance the threshold field for CDW depinning.
We will also discuss the temperature dependence of the threshold
field for the various samples.
TT 30.19 Do 14:30 Poster A
One-dimensional fermions with static dimerisation: Zero-mode
bosonisation and self consistent harmonic approximation —
•Carmen Mocanu, Peter Schwab, Michael Dzierzawa, and Ulrich
Eckern — Universität Augsburg, Theoretische Physik II, 86135
Augsburg
We investigate one-dimensional fermions with static dimerisation,
where the static dimerisation is introduced as a modulation of the hopping
amplitude. As theoretical tools we use bosonisation in connection
with the self consistent harmonic approximation (SCHA), which is based
on a variational principle. The conventional SCHA Hamiltonian is constructed
by replacing the non linear terms by quadratic forms. The Klein
factors and zero-modes are ignored. Here, we develop an improved SCHA,
including the Klein factors and zero-modes and compare the results with
the conventional procedure.
TT 30.20 Do 14:30 Poster A
Magnetische Beiträge zum Wärmetransport in den quasi-1D
Spinketten von SrCuO2 — •Patrick Ribeiro 1 , Christian Hess 2 ,
Pascal Reutler 1 , Rudiger Klingeler 1 , Bernd Büchner 1 und
Georg Roth 3 — 1 IFW-Dresden, D-01171 Dresden — 2 Department of
Condensed Matter Physics, CH-1211 Geneva — 3 Institut für Kristallographie
der RWTH-Aachen, D-52056 Aachen
Wir präsentieren Ergebnisse der Wärmeleitfähigkeit des Spinkettensystems
Sr1−xCaxCuO2 . Diese Verbindung enthält in ihrer Struktur zwei
parallel laufende Cu-Ketten, die um einen halben Cu-Cu Abstand versetzt
sind. Wegen der dadurch entstehenden magnetischen Frustration
zwischen jeweils drei Cu-Spins bilden sich magnetisch nahezu isolierte
antiferromagnetische S=1/2 Spinketten, deren Intrakettenkopplung
J=2100K beträgt. Unsere Ergebnisse zeigen eine starke anisotropie der
thermischen Leitfähigkeit, die wir auf einen zusätzlichen magnonischen
Beitrag zur Wärmeleitfähigkeit entlang der Ketten zurückführen. Eine
Bestätigung dieser Interpretation ergibt sich aus Messungen der thermischen
Leitfähigkeit an Systemen, in denen Sr isovalent durch Ca substituiert
wurde, da diese Messungen eine genauere Separation von phononischen
und magnonischen Beiträgen zum Wärmetransport erlauben.
TT 30.21 Do 14:30 Poster A
Studies of a CDW system under hydrostatic pressure and high
magnetic fields: from field-induced CDW transitions to superconductivity
— •Dieter Andres, Mark Kartsovnik, Werner
Biberacher, and Karl Neumaier — Walther-Meissner-Institut, Bayerische
Akademie der Wissenschaften, Walther-Meissner-Str.8, 85748
Garching
In α-(BEDT-TTF)2KHg(SCN)4 a charge density wave (CDW) is
formed below about 8 K. This extremely low transition temperature
gives the unique possibility to study the B-T phase diagram in an
extended range. Moreover, hydrostatic pressure is known to easily tune
the nesting conditions of the CDW system.
We show how orbital and Pauli effects of magnetic field compete within
the CDW state leading to new quantization phenomena of successive
field-induced CDW transitions. Furthermore, a coexistence of superconductivity
and CDW in a certain pressure range will be discussed.
TT 30.22 Do 14:30 Poster A
Quantum Monte Carlo simulation for the conductance of onedimensional
quantum spin systems — •Kim Louis und Claudius
Gros — Universität des Saarlandes
Recently, the stochastic series expansion (SSE) has been proposed as
a powerful MC-method, which allows simulations at low T for quantumspin
systems. We show that the SSE allows to compute the magnetic
conductance for various one-dimensional spin systems without further
approximations. We consider various modifications of the anisotropic Heisenberg
chain. We recover the Kane-Fisher scaling for one impurity in a
Luttinger-liquid and study the influence of non-interacting leads for the
conductance of an interacting system.
TT 30.23 Do 14:30 Poster A
Thermal conductivity of the layered cuprates R2CuO4 with R =
Pr, Nd, Sm, Eu and Gd — •H. Anapa 1 , K. Berggold 1 , K. Kordonis
1 , M. Kriener 1 , J. Baier 1 , T. Lorenz 1 , A. Freimuth 1 , and
S. Barilo 2 — 1 II. Physikalisches Institut, Universität zu Köln, 50937
Köln — 2 Inst. of Sol. St. & Semicond. Phys., National Academy of Sciences,
Minsk

Tiefe Temperaturen Donnerstag
La2CuO4, well known as parent compound for high temperature superconductors,
is an anti-ferromagnetic insulator with a large exchange
constant J ≈ 1400K. The thermal conductivity shows an unusual double
peak structure for a heat current in the Cu-O planes, whereas perpendicular
to the planes only one low-temperature maximum is present. It was
proposed [1], that this double-peak structure is caused by a structural
instability. However, we found this feature also in the related compound
SrCuO2Cl2, which has no structural instability, and concluded, that the
second maximum arises from additional heat transport by magnetic excitations
[2]. To investigate, whether magnetic heat transport is a common
feature of single-layer cuprates, we performed thermal conductivity measurements
on R2CuO4 with R=Pr, Nd, Sm, Eu and Gd. A structural
instability occurs only for R=Eu, Gd, but all R2CuO4 samples show a
high-temperature maximum (shoulder) of the in-plane thermal conductivity.
This is further evidence, that considerable magnetic heat transport
is an intrinsic feature of these cuprates.
[1] J. L. Cohn et al., Phys. Rev. B 52, R13134 (1995)
[2] M. Hofmann et al., Phys. Rev. B 67, 184502 (2003).
TT 30.24 Do 14:30 Poster A
Elektronischer Transport in dünnen Goldfilmen auf Si (111)
— •Svenja Klages 1 , Christoph Sürgers 1 und Hilbert v.
Löhneysen 1,2 — 1 Physikalisches Institut und DFG Center for Functional
Nanostructures (CFN), Universität Karlsruhe, D-76128 Karlsruhe —
2 Forschungszentrum Karlsruhe, Institut für Festkörperphysik, D-76021
Karlsruhe
Wir untersuchen den elektronischen Transport in dünnen Goldfilmen
auf Si(111). Dazu werden bei Raumtemperatur 1-5 Monolagen (ML)
Au auf die rekonstruierte Si(111)-7x7-Oberfläche im UHV aufgedampft
und mittels Rastertunnelmikroskopie charakterisiert. Der elektronische
Transport wird durch in-situ-Messungen des elektrischen Widerstands R
im Temperaturbereich T = 3 − 300 K untersucht. Unterhalb 30 K wird
R durch den Beitrag des Goldfilms dominiert wobei R mit zunehmender
Schichtdicke abnimmt. In diesem Bereich wird R(T) durch Effekte der
schwachen Lokalisierung bestimmt. Für T > 30 K überwiegt der Beitrag
des Si-Substrats. Eine Schicht mit 5 ML zeigt nach kurzzeitigem Tempern
im UHV bei 600 ◦ C eine Rekonstruktion der Oberfläche, deren Symmetrie
möglicherweise durch die Si(111)-7x7-Rekonstruktion des Substrats
bestimmt wird. Für diese Schicht zeigt R(T) ein Verhalten ähnlich einem
reinen Si(111) Substrat. Mögliche Ursachen wie Si-Au-Legierungsbildung
werden diskutiert.
TT 30.25 Do 14:30 Poster A
κ-(BEDT-TTF)2Cu(SCN)2: Comparative Analysis of Tc and
Magnetotransport Measurements under Pressure — •A.-K.
Klehe 1 , T. Biggs 1 , C.A. Kuntscher 1,2 , A.M. Kini 3 , and J.A.
Schlueter 3 — 1 Clarendon Laboratory, Dept. of Physics, Oxford
University, Parks Road, Oxford OX1 3PU, U.K. — 2 1. Physikalische
Institut, Universitaet Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart
— 3 Materials Science Division, Argonne National Laboratory, 9700
Magnetotransport measurements under pressure on the organic superconductor
κ-(d8−BEDT-TTF)2Cu(SCN)2 with Helium as a pressure
medium are compared to other measurements of the superconducting
transition temperature, Tc, with the same pressure medium as well as
magnetotransport measurements using other quasi-hydrostatic pressure
media. The exact pressure dependence of the physical properties in κ-
(BEDT-TTF)2Cu(SCN)2 depends on the pressure medium used, indicating
that small degrees of non-hydrostaticity can strongly affect the
results. A strong correlation between Tc and the quasi 2-dimensional
carrier density in κ-(BEDT-TTF)2Cu(SCN)2 is seen, when comparing
measurements of Tc to Fermi surface parameters. The suppression of Tc
with pressure can be correlated to the transfer of carriers from the quasi
1-dimensional to the quasi 2-dimensional Fermi surface sections, thus
revealing a mechanism reminiscent of Cuprate superconductors, where
pressure is known to transfer carriers from the insulating charge reservoir
layers into the conducting cuprate sheets.
TT 30.26 Do 14:30 Poster A
Magnetic and transport properties of the new organic conductor
(BEDT-TTF)2(B12H12)(CH2Cl2) — •Belal Salameh 1 ,
Dieter Schweitzer 1 , Christof Schneck 2 , Ioannis Tiritiris 2 ,
and Thomas Schleid 2 — 1 3.Physikalisches Institut, Universität
Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart — 2 Institut für Anorganische
Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70550
Stuttgart
We performed detailed electrical transport, SQUID and ESR measurements
on three new synthesized organic conductors based on the
(BEDT-TTF) donor and (B12H12) −2 anions. From the ESR line width
(1.7, 13, 45 Gauss) and the conductivity measurements it is clear that
three different phases were obtained by electrochemical crystallization.
The structure of one phase could be solved yet giving a stoichiometry of
(BEDT-TTF)2(B12H12)(CH2Cl2). The unit cell is triclinic with P-1 symmetry
and the lattice constants are: 8.296˚A, 11.498˚A, 12.386˚A, 72.73 ◦ ,
85.93 ◦ , 82.09 ◦ . Electronically this material is 1:1 salt (donor (+2) acceptor
(-2) ratio),the dc conductivity at room temperature equlas 0.004 (Ω
cm) −1 . The three phases show semiconducting behaviour with relatively
small energy gaps. ESR, SQUID and dc resistivity measurements will be
discussed.
TT 30.27 Do 14:30 Poster A
AMRO-Messungen am Organischen Leiter (BEDT-
TTF)4[Ni(dto)2] — •Wolfgang Schmidt 1 , Jochen Hagel 2 ,
Eduard Balthes 1 , Jochen Wosnitza 2 und Dieter Schweitzer 1
— 1 3. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring
57, 70569 Stuttgart, Germany — 2 Institut für Angewandte Physik und
Didaktik der Physik, TU Dresden, 01069 Dresden, Germany
Das organische Metall (BEDT-TTF)4[Ni(dto)2] besitzt eine hohe Anisotropie
des elektrischen Widerstandes ρc/ρ(a,b) = 100 (bei RT), wobei
(a,b) die hochleitfähige Ebene repräsentiert. Die Substanz zeigt oberhalb
von 1.2T starke Quantenoszillationen mit den zwei Frequenzen
Fα = 634T und Fβ = 4245T (bei T = 20mK).
In diesem Beitrag stellen wir AMRO (angular dependent magnetoresistance
oscillation) Messungen an diesem Material vor, die durch Drehung
eines Einkristalls um verschiedene Achsen, die alle innerhalb der
(a,b)-Ebene lagen, bei verschiedenen konstanten Magnetfeldern (bis zu
13T) gewonnen wurden. Die Ergebnisse bestätigen die Größe, Lage und
auch die ungefähre Form des schwach gewellten α-Orbits, wie wir sie aus
der Bandstrukturrechnung und auch aus Shubnikov-de Haas (SdH) und
de Haas-van Alphen (dHvA) Messungen bereits erhalten haben.
Zusätzlich wurde, wenn das Magnetfeld parallel zur (a,b)-Ebene anliegt,
ein starkes, scharfes Maximum beobachtet, was auf kohärenten Ladungstransport
zwischen den einzelnen Moleküllagen hindeutet. Um dieses
Maximum sind Schultern angeordnet, die durch das eindimensionale
Band des Materials hervorgerufen sein könnten.
TT 30.28 Do 14:30 Poster A
Quantenoszillationsexperimente an θ-(BEDT-TTF)2I3 — •Axel
Nothardt 1 , Eduart Balthes 1 , Anja Much 1 , Belal Salameh 1 ,
Wolfgang Schmidt 1 , Dieter Schweitzer 1 und Duncan Maud 2
— 1 3.Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57,
D-70550 Stuttgart Deutschland — 2 MPI/CNRS Hochmagnetfeldlabor
Grenoble, Avenue des Martyrs 25, B.P. 166, F-38042 Grenoble cedex 9
Frankreich
Der organische Supraleiter θ-(BEDT-TTF)2(I3)1−x(AuI2)x (x

Tiefe Temperaturen Donnerstag
sowie mehrere thermodynamische Größen, wie die spezifische Wärme und
die magnetische Suszeptibilität von vielen niedrigdimensionalen Spinsystemen
wurden in den letzten Jahren intensiv untersucht. Im Gegensatz
dazu, ist über die Dynamik der magnetischen Anregungen und ihre
Kopplung zu den Phononen bisher nur wenig bekannt. Eine hilfreiche
Methode um sie zu untersuchen sind Messungen der Wärmeleitfähigkeit.
Wir präsentieren Messungen der Wärmeleitfähigkeit der Spinleitersysteme
LiCu2O2, NaV2O5, der Spinkettensysteme β-Na0.33V2O5, LiV2O5,
sowie Messungen der Wärmeleitfähigkeit, des spezifischen Widerstandes
und der thermischen Ausdehnung des Haldanesystems Y2BaNiO5. Bei
fast allen Systemen zeigt die Wärmeleitfähigkeit Doppelmaximastrukturen
in Abhängigkeit der Temperatur an. Dies kann auf zusätzliche magnetische
Beiträge zur Wärmeleitfähigkeit hinweisen, insbesondere dann,
wenn diese nur entlang der eindimensionalen magnetischen Richtungen
auftreten, wie z.B. bei der S=1 Spinkette (Haldanesystem) Y2BaNiO5.
gefördert von der DFG durch den SFB 608
TT 30.30 Do 14:30 Poster A
Exactly solvable model of three interacting particles in an external
magnetic field — E. P. Nakhmedov 1,2 , •K. Morawetz 1,2 , M.
Ameduri 3 , A. Yurtsever 4 , and C. Radehaus 1 — 1 Chemnitz University
of Technology, 09107 Chemnitz, Germany — 2 Max Planck Institute
for the Physics of Complex Systems, Nöthnitzer Str. 38, 01187 Dresden,
Germany — 3 Weill Cornell Medical College in Qatar, Qatar Foundation,
Doha, Qatar — 4 Azerbaijan Academy of Sciences, Institute of Physics,
H. Cavid 33, 370143 Baku, Azerbaijan
The quantum mechanical problem of three identical particles, moving
in a plane and interacting pairwise via a spring potential, is solved exactly
in the presence of a magnetic field. Calculations of the pair–correlation
function, mean distance and the cluster area show a quantization of these
parameters. Especially the pair-correlation function exhibits a certain
number of maxima given by a quantum number. We obtain Jastrow prefactors
which lead to an exchange correlation hole of liquid type, even in
the presence of the attractive interaction between the identical electrons.
[1] E. P. Nakhmedov, K. Morawetz, M. Ameduri, A. Yurtsever, C. Radehaus,
Phys. Rev. B 67 (2003) 205106
TT 30.31 Do 14:30 Poster A
Magneto-Elastische Kopplung in dem Spin-Dimer System
TlCuCl3 — •N. Johannsen 1 , T. Lorenz 1 , M. Kriener 1 , A.
Freimuth 1 , T. Zabel 1 , A. Vasiliev 2 , A. Oosawa 3 und H.
Tanaka 3 — 1 II. Physikalisches Institut, Universität zu Köln — 2 Low
Temperature Physics Department, Moscow State University, Russland
— 3 Department of Physics, Tokyo Institut of Technology, Japan
In TlCuCl3 bilden Cu 2+ -Ionen Spin-Dimere mit antiferromagnetischer
Kopplung. Die Energielücke zwischen dem Singulett-Grundzustand und
dem ersten angeregten Triplett-Zustand beträgt etwa 0.6meV. Ein Magnetfeld
H >5.6T induziert eine antiferromagnetische Ordnung, die aktuell
als Bose-Einstein-Kondensat aus S=1 Magnonen diskutiert wird.
Wir präsentieren hochaufgelöste Messungen der thermischen Ausdehnung,
der Magnetostriktion und der spezifischen Wärme an einkristallinem
TlCuCl3. Die Daten zeigen, daß die feldinduzierte magnetische Ordnung
deutliche Anomalien in der Feld - und Temperaturabhängigkeit der
Längenänderung (senkrecht zu den Flächen (010) und (102)) der Probe
hervorruft. Aus diesen Anomalien lässt sich die Temperaturabhängigkeit
des Übergangsfeldes bestimmen. Weiterhin lassen sich uniaxiale Druckabhängigkeiten
der Übergangstemperaturen und - felder bestimmen. Wir
finden sehr große und stark anisotrope Werte für ∂ lnTc/∂ lnpi und
∂ lnHc/∂ lnpi in der Größenordnung von ±100%/GPa, abhängig von
der Richtung des uniaxialen Drucks pi. Dies zeigt eine starke magnetoelastische
Kopplung in TlCuCl3 und eine große Empfindlichkeit der feldinduzierten
magnetischen Ordnung auf geringe strukturelle Änderungen.
TT 30.32 Do 14:30 Poster A
Thermal transport of one-dimensional spin systems in the presence
of a magnetic field — •Fabian Heidrich-Meisner, Andreas
Honecker, and Wolfram Brenig — Technische Universität Braunschweig,
Institut für Theoretische Physik, Mendelssohnstraße 3, 38106
Braunschweig
Transport properties of one-dimensional spin-1/2 systems have attracted
strong theoretical interest during the last years. Many studies
have focussed on the question of possible dissipationless transport in
nonintegrable models and recent results indicate that the thermal conductivity
is nondiverging in dimerized and frustrated systems. In the
integrable XXZ model, the thermal conductivity is divergent, characterized
by a finite thermal Drude weight, due to the relation of the thermal
current operator to conserved quantities. In particular, the temperature
dependence of the thermal Drude weight at zero magnetic field has been
studied in great detail. It is the purpose of this work to extent these results
in two directions. First, we consider the influence of a magnetic field
on the thermal Drude weight of the XXZ model. Second, we analyze the
frequency dependence of the thermal conductivity of spin ladders and
frustrated chains both at zero and finite magnetic field. In addition, we
discuss possible implications of our results for the mean lifetime of the
thermal current in the case of nonintegrable models.
TT 30.33 Do 14:30 Poster A
Optical measurements of two-dimensional electron systems
on helium films — •Andreas Faustein, Jörg Angrik, Jürgen
Klier, and Paul Leiderer — Fachbereich Physik, Universität
Konstanz, Postfach M676, D-78457 Konstanz
We measure, with optical methods, the two-dimensional electron system
on helium films which are adsorbed on metallic substrates as van-der-
Waals films. Using plasmon spectroscopy and ellipsometry we are able
to measure the helium film thickness with a resolution of approximately
one Angström. The electrostatic pressure of the electrons decreases the
film thickness which allows us to determine the electron density in the
range from about 10 13 to 10 15 m −2 . Our experiments show a surprisingly
high stability of the electrons on thin helium films of about 30nm thickness
adsorbed on evaporated gold films. Therefore not only static, but
also transport and mobility measurements become possible. We show first
measurements to determine electron densities on a source, split-gate, and
drain electrode structure, where a quasi-one-dimensional electron transport
through a confining channel is realized.
TT 30.34 Do 14:30 Poster A
Electron Mass Enhancement on the Spin Wave Energy Scale —
•Jörg Schäfer, David Schrupp, and Ralph Claessen — Institut
für Physik, Universität Augsburg, 86135 Augsburg
High-resolution photoelectron spectroscopy is used to explore metallic
states localized at the Fe(110) surface which provide an opportunity to
study quasiparticle renormalization effects in a magnetic system. Modifications
from a conventional parabolic dispersion are observed up to
rather high binding energies, exceeding the phonon energy scale by an
order of magnitude. Analysis of the spectral function in terms of the
real and imaginary part of the self energy yield the typical signature of
coupling of the electrons to an excitation spectrum. The characteristic energy
scale of ∼ 160 meV is in striking agreement with spin waves detected
by neutron scattering and therefore points at electron-magnon coupling.
Comparison to spin wave dispersions and related features in electron energy
loss spectra is made. A model for spin-wave-induced quasiparticle
renormalization which describes the spectroscopic behavior of the data
is presented.
TT 30.35 Do 14:30 Poster A
Domain Walls in 1D Systems - QM and Finite Size Corrections
— •Markus Lippert, Hans-Joachim Elmers, and Peter G. J.
van Dongen — Institut für Physik, Johannes Gutenberg-Universität,
Staudinger Weg 7, D-55099 Mainz, Germany
We consider 1D domain walls in order to describe 1D nanoscale magnetic
systems, in which such walls can be realized experimentally. Due
to the discrete structure of these walls, a phase transition between an
Ising-type and an extended wall is found. In order to evaluate quantum
corrections, we use a systematic 1/S expansion in combination with a new
numerical method to evaluate these corrections. We compare to results
already known in literature and extend our theory to the calculation of
shape corrections and quantum critical behaviour.
TT 30.36 Do 14:30 Poster A
Magnetische und Kristallstruktur von Ca2−xSrxRuO4 — •O.
Schumann 1 , O. Friedt 1 , P. Steffens 1 , R. Müller 1 , G. Andre 2 ,
P. Adelmann 3 , S. Nakatsuji 4 , Y. Maeno 4 und M. Braden 1 für
die -Kollaboration — 1 II. Physikalisches Institut, Universität zu Köln —
2 Laboratoire Léon Brillouin — 3 Forschungszentrum Karlsruhe, IFP —
4 Department of Physics, Kyoto University
Die Ersetzung von Sr durch das isovalente und kleinere Ca führt
zu dem sehr vielfältigen Phasendiagramm von Ca2−xSrxRuO4 [1-4],
das den Spin-triplet Supraleiter Sr2RuO4 mit dem antiferromagnetisch
geordneten Mott-Isolator Ca2RuO4 verknüpft. Mittels verschiedener

Tiefe Temperaturen Donnerstag
Neutronendiffraktionstechniken haben wir sowohl die Kristall- als
auch die magnetische Struktur eingehend untersucht. Strukturelle
Verzerrungen sind zunächst durch Verdrehungen der RuO6-Oktaeder
charakterisiert, wobei eine unterschiedliche Kopplung zwischen den
Ebenen zu 5 verschiedenen Strukturtypen führt. Zusätzlich zu den
Oktaeder-Drehungen beoabachtet man Stauchungen oder Dehnungen
der Oktaeder, die eng mit unterschiedlichen physikalischen Eigenschaften
(Metamagnetismus, heavy-Fermion-Verhalten, verschiedene
Ordnungsschema, Metall-Isolator-Übergang) verbunden sind.
[1] S.Nakatsuji et al., Phys. Rev. Lett. 84, 2666 (2000)
[2] M.Braden et al., Phys. Rev. B 58, 847 (1998)
[3] O.Friedt et al., Phys. Rev. B 63 174432 (2001)
[4] S.Nakatsuji et al., Phys. Rev. Lett. 90, 137202 (2003)
TT 30.37 Do 14:30 Poster A
Magnon heat transport of 2-leg spin ladders: Scattering on holes
and static defects — •H. ElHaes 1 , C. Hess 2 , P. Ribeiro 3 , B.
Büchner 3 , M. Hücker 4 , U. Ammerahl 4 , A. Revcolevschi 4 , F.
Heidrich-Meisner 5 , and W. Brenig 5 — 1 II. Physikalisches Institut,
RWTH-Aachen, D-52056 Aachen, Germany — 2 DPMC, University of
Geneva, Switzerland — 3 IFW-Dresden, D-01171 Dresden, Germany —
4 Université Paris-Sud, France — 5 Institut für Theoretische Physik, TU-
Braunschweig D-38106 Braunschweig, Germany
We investigate scattering processes relevant for the magnon thermal
conductivity κmag of the spin ladders in (Sr/Ca)14Cu24O41. Based on a
kinetic model we find that scattering is dominated by static defects and
scattering on holes in the ladders. Our analysis reveals that the magnon
mean free path lmag can reach values up to 3000 ˚A. This value is confirmed
by results obtained from Zn-doped materials where lmag is approximately
equal to the mean distance of Zn-ions in the ladders. The mean free path
related to scattering on holes, lh, is strongly doping and temperature
dependent and is intimately related to the electrical resistivity. In particular,
magnon-hole scattering becomes unimportant upon charge ordering
in the ladders.
TT 30.38 Do 14:30 Poster A
Magnetische Anregungen in reinem und dotierten Sr2RuO4 —
•P. Steffens, P. Steffens, O. Friedt, O. Schumann, A. Komarek,
Y. Sidis, J. Kulda, P. Bourges, S. Hayden, S. Nakatsuji,
Y. Maeno, M. Braden, O. Friedt, O. Schumann, A. Komarek,
Y. Sidis, J. Kulda, P. Bourges, S. Hayden, S. Nakatsuji, Y.
Maeno und M. Braden — II. Physikalisches Institut, Universität zu
Köln
Der Mechanismus der Spin-triplet Supraleitung in Sr2RuO4 bleibt
ungeklärt : die Symmetrie des Ordnungsparameters könnte durch eine
Wechselwirkung mit ferromagnetischen Fluktuationen erklärt werden,
aber im Neutronenstreuexperiment findet man eine klare Dominanz
von inkommensurablen Fluktuationen [1,2]. Wir haben diese Fluktuationen
weiter mittels polarisierter Neutronen-Streuung charakterisiert, um
Theorien zu überprüfen [3], die eine Lösung dieses Problems vorschlugen.
Wir finden eine starke Anisotropie der inkommensurablen Fluktuationen
[6]; allerdings bleibt diese weit unter dem Wert, der in Referenz
[3] angenommen werden musste. Dotierungen entweder auf dem Ru- oder
auf dem Sr-Platz induzieren unterschiedliche magnetische Instabilitäten
[4,5]. Wir haben deren Einfluss auf das magnetische Anregungsspektrum
analysiert.
[1] Y. Sidis et al., PRL 83, 3320 (1999)
[2] M. Braden et al., PRB 66, 064522 (2002)
[3] T. Kuwabara et al., PRL 85, 4586 (2000)
[4] M. Braden et al., PRL 88, 197002 (2002)
[5] S. Nakatsuji et al., PRL 90, 137202 (2003)
[6] M. Braden et al., condmat 0307662 (2003)
TT 30.39 Do 14:30 Poster A
Optical study of the doped spin-ladder Sr14−xCaxCu24O41 — •C.
Hilgers 1 , M. Grüninger 1 , A. Freimuth 1 , U. Ammerahl 1,2 , P.
Ribeiro 3 , B. Büchner 4 , and A. Revcolevschi 2 — 1 II. Physikalisches
Institut, Universität zu Köln — 2 Laboratoire de Physico-Chimie
de l’ Etat Solides, Université Paris-Sud, France — 3 II. Physikalisches
Institut, RWTH-Aachen — 4 IFW Dresden
The phase-diagram of intrinsically hole-doped Sr14−xCaxCu24O41
shows e.g. superconductivity, charge order and magnetism, and the system
offers a fascinating playground to study the interplay of spin and
charge degrees of freedom. A key question is how the holes are distributed
among the two subsystems, chains and ladders. We present the infrared
reflectivity of Sr14−xCaxCu24O41 for x = 3, 5, 6 and 8 between 5meV
and 1.5eV as a function of temperature for polarization along the legs
(E||c) and along the rungs (E||a). The optical conductivity σ(ω) is derived
via a Kramers-Kronig analysis and shows both a strong anisotropy
and a strong temperature dependence. Between x = 6 and 8 we observe a
qualitative change of σ(ω) for both polarization directions, and two additional
strongly temperature dependent peaks develop in the far-infrared
region, one in σa(ω) at about 400cm −1 and one in σc(ω) below 100cm −1 .
We discuss different scenarios, e.g. the suppression of charge order in
the chains, the evolution of a charge-density wave in the ladders, magnetic
excitations, the formation of hole pairs or a bonding-antibonding
transition.
TT 30.40 Do 14:30 Poster A
Vibrating reed-Messungen an polykristallinem Aluminium bei
tiefen Temperaturen — •J. Haust, M. Burst und G. Weiss —
Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe
Wie in anderen strukturell ungeordneten Festkörpern, werden auch
in polykristallinem Aluminium die akustischen Eigenschaften bei tiefen
Temperaturen durch atomare Tunnelsysteme bestimmt. Deren Zustandsdichte
und damit auch die Details im Temperaturverlauf von Schallgeschwindigkeit
und Dämpfung hängen vom Grad der Unordnung ab [1].
In früheren Messungen [2] an Aluminiumdrähten wurde allerdings im
Gegensatz zu Messungen an metallischen Gläsern kein signifikanter Unterschied
zwischen dem Verhalten im supraleitenden und dem Verhalten
im normalleitenden Zustand festgestellt. In unseren neuen Messungen
an Aluminiumproben mit einer für vibrating reed-Messungen günstigen
Geometrie können wir dies nicht bestätigen. Unsere Resultate beweisen,
dass die Tunnelsysteme in Aluminium in ähnlicher Weise mit den Leitungselektronen
wechselwirken wie in metallischen Gläsern.
[1] B.Kübler et al, Physica B 316-317, 558 (2002)
[2] R.König et al, Phys.Rev.B 51, 11424 (1995)
TT 30.41 Do 14:30 Poster A
Measurements of the low-frequency elastic properties of glasses
with double paddle oscillators and SQUID based readout —
•X. Cao 1 , M. Layer 1 , A. Fleischmann 1 , C. Enss 2 , and S. Hunklinger
1 — 1 Kirchhoff-Institut fuer Physik, Heidelberg University, Im
Neuenheimer Feld 227, D-69120 Heidelberg — 2 Brown University, Providence,
RI 02912, USA
The double paddle resonator is a common tool for investigating the
low-frequency elastic properties of solids. With the special oscillator geometry
the background damping due to clamping is very small compared
with the vibrating reed method. At low temperatures, the changes in the
sound velocity and the internal friction of amorphous solids are dominated
by the interaction between the phonons and the tunnelling systems.
In order to avoid nonlinear response from the system, the deformation
amplitude used in the measurements has to be very small. To achieve
high sensitivity we incorporated an inductively complied readout based
on a DC-SQUID, whose performance has been shown to exceed that of
the conventional capacitive method in the vibrating reed measurements.
With this combination, it is possible to study the acoustic properties of
glasses at ultralow temperatures (T < 5 mK). The technique and first
measurements are presented.

Tiefe Temperaturen Freitag
TT 31 Supraleitung: Vortexdynamik, Vortexphasen, Pinning
Zeit: Freitag 10:15–12:45 Raum: H20
TT 31.1 Fr 10:15 H20
Vortex radiation in long Josephson nanojunctions — •A.A. Abdumalikov
Jr. 1 , M.V. Fistul 1 , V.V. Kurin 2 , and A.V. Ustinov 1
— 1 Physikalisches Institut III, Universität Erlangen-Nürnberg, Erwin-
Rommel-str.1, 91058 Erlangen, Germany — 2 Institute for Physics of Microstructure
(RAS), Nizhniy Novgorod, Russia
We theoretically, numerically and experimentally investigate the dynamics
of vortices in long submicron-wide Josephson junctions. Using a
variational approach, the current voltage characteristics are calculated
for various junction width and number of vortices trapped in the junction.
The theoretical and numerically calculated current-voltage characteristics
show good agreement. The maximum velocity of vortices is
increasing with decreasing the junction width. Due to interaction with
stray magnetic fields outside the junction, the vortices radiate Cherenkov
waves as they move in the junction. Locking of the vortex oscillation frequency
to that of the Cherenkov radiation leads to strong resonances on
the current-voltage characteristics. We observe such resonances in experiment
in qualitative agreement with our theoretical analysis.
TT 31.2 Fr 10:30 H20
Study of semifluxons in artificial long Josephson 0-π-junctions
— •Tobias Gaber1 , Edward Goldobin1,2 , Albert Sterck1 , Dieter
Koelle1 , and Reinhold Kleiner1 — 1Physikalisches Institut,
Experimentalphysik II, Universität Tübingen, Auf der Morgenstelle 14,
72076 Tübingen — 2Institut für Mikro- und Nanoelektronische Systeme,
Universität Karlsruhe (TH), Hertzstr. 16, D-76187 Karlsruhe
In long Josephson junctions (LJJ) consisting of two parts with positive
and negative critical current (0 and π parts) half-integer vortices (semifluxons)
can spontaneously appear at the boundary between these parts.
Such a boundary formally corresponds to a π-discontinuity of the Josephson
phase. In our experiments we artificially create such a discontinuity
in conventional Nb-AlOx-Nb LJJs using a pair of current injectors. Such
JJs allow one to study arbitrary fractional vortices and their dynamics.
In the 0-π-state the Ic(H) dependence shows a minimum at H = 0 as
in natural 0-π-LJJs. We investigate the dynamics of the magnetic flux
in such junctions for various lengths and observe half-integer zero-field
steps (ZFS) with n = 1
3 5 , , 2 2 2
on the IV -characteristics which appear due
to the motion of semi-integer flux. We also show that semi-integer ZFS
quantisation persists even when arbitrary fractional vortices (other that
Φ0/2) are participating in the motion.
TT 31.3 Fr 10:45 H20
Rasche Relaxation der irreversiblen Ströme durch Vortex
Schütteln in dünnen Supraleitern — •Ernst Helmut Brandt 1
und Grigorii P. Mikitik 1,2 — 1 Max-Planck-Institut für Metallforschung,
D-705069 Stuttgart — 2 Verkin Institute for Low Temperature
Physics, Kharkov 61103, Ukraine
Beim Auftreten von Vortex-Pinning zeigen Supraleiter 2. Art stark irreversibles
Verhalten. Durch Anlegen eines schwachen magnetischen Wechselfeldes
senkrecht zum angelegten konstanten Magnetfeld relaxieren die
irreversiblen Supraströme rasch, etwa exponentiell mit der Zeit. Dieses
Vortex-Schütteln wird quantitativ erklärt zuerst für lange dünne Streifen
in senkrechtem Gleichfeld (Hdc�z) und dazu senkrechtem Wechselfeld
quer (Hac�y) [1] oder parallel (Hac�x) [2] zum Streifen (transversales und
longitudinales Schütteln) und dann fuer dünne rechteckige Platten oder
Filme, in denen beide Schüttelarten auftreten und damit zwei Relaxationszeiten
[3]. Die irreversiblen Abschirmströme kreisen in der Platte
zuerst in einer einfachen Schleife. Während der Relaxation treten dann
aber mehrere neue Stromschleifen auf, da die Stromkomponente ⊥ Hac
schneller relaxiert als die � Hac. Nach einiger Zeit bleiben nur noch die
reversiblen Ströme übrig, die so trotz Pinning gemessen werden können.
[1] E.H. Brandt and G.P. Mikitik, Phys.Rev.Lett. 89, 027002 (2002).
[2] G.P. Mikitik and E.H. Brandt, Phys.Rev. B 67, 104511 (2003).
[3] G.P. Mikitik and E.H. Brandt, Phys.Rev. B, submitted
TT 31.4 Fr 11:00 H20
Observation of Abrikosov Lattice Melting in Real Space by
Magnetic Force Microscopy — •Alexander Schwarz, Marcus
Liebmann, and Roland Wiesendanger — IAP, University of Hamburg,
Hamburg, Germany
In this study, we use low temperature magnetic force microscopy to
visualize the melting of a regular Abrikosov vortex lattice frozen into a
Bi2Sr2CaCu2O8 single crystal by field cooling. Due to the high sensitivity
and spatial resolution of our instrument (below 50 nm [1]), individual flux
lines (perpendicular bound pancake vortices) are easily resolved. Upon
increasing the temperature towards TC, the flux lines appear broader,
because (i) the penetration depth increases, and (ii) they become more
mobile within their lattice position. However, the regular hexagonal arrangement
stays intact, until a certain temperature (T ≈ 50 K) is reached
beyond which the contrast vanishes. Strongly pinned individual vortices
can remain visible and act as scattering centers for the now unbound
pancake vortices, which are in the liquid state. After recondensation,
the regular hexagonal arrangement is restored, but somewhat tilted with
respect to the original configuration.
[1] M. Liebmann et al., Rev. Sci. Instrum. 73, 3508 (2002).
TT 31.5 Fr 11:15 H20
Magnetic flux pinning in bilayers of high-temperature superconductors
and ferromagnets — •J. Albrecht, S. Soltan, and
H.–U. Habermeier — Max–Planck–Institut für Festkörperforschung,
Heisenbergstr. 1, 70569 Stuttgart
Epitaxial bilayers of YBCO and ferromagnetic perowskites such as
doped lanthanum manganites or strontium ruthenate are grown on single
crystalline substrates by pulsed laser deposition. From quantitative
magnetooptical investigations we find that the critical current density in
these bilayers strongly depend on the magnetization state of the ferromagnet
[1]. This leads to a hysteretic behaviour of the critical currents
in these structures which is absent if the ferromagnet is replaced by an
oxidic metal. The observed effect can be explained by pinning of flux
lines at the magnetic domain walls in the ferromagnet.
[1] J. Albrecht, S. Soltan and H.–U. Habermeier, Europhys. Lett. 63,
881 (2003).
TT 31.6 Fr 11:30 H20
Vortex matter phase diagram of pure and Zn-doped
YBa2Cu3O7−x in magnetic fields up to 50 T — •Yurii Skourski
1,2 , Günter Fuchs 1 , Nadezhda Kozlova 1 , Konstantin
Nenkov 1 , Gernot Krabbes 1 , and Karl-Hartmut Müller 1 —
1 Leibniz Institut für Festkörper- und Werkstoffforschung Dresden, P.O.
Box 270016, D-01171 — 2 Max-Planck-Institut für Physik komplexer
Systeme, Nöthnitzer Strasse 38, 01187 Dresden
The vortex matter phase diagram of melt textured YBa2Cu3O7−x
(YBCO) and of Zn doped YBCO was investigated by magnetization and
resistance measurements in magnetic fields up to 50 T. Data for the irreversibility
field Hirr(T) and the upper critical field Hc2(T) obtained in
pulsed and static fields show a good agreement. A strong suppression
of the superconducting transition temperature by about 15 K was observed
for a YBCO sample doped with 1.2%Zn. In addition, the shape
of Hirr(T) and Hc2(T) was found to be strongly affected by Zn doping.
Consequently, the transition from the vortex glass to the vortex liquid
phase found for undoped YBCO is shifted to lower magnetic fields for Zn
doped YBCO. The experimental data are compared with the predictions
of existing models.
TT 31.7 Fr 11:45 H20
Oberflächenbarriere und Vortex Matching in YBa2Cu3O7−δ Nanobrücken
— •Johannes Eisenmenger, Frank-Michael Kamm,
Alfred Plettl und Paul Ziemann — Abteilung Festkörperphysik,
Universität Ulm, 89069 Ulm
Dünne Typ-II Supraleiter-Schichten im parallelen Magnetfeld bilden
bei bestimmten Magnetfeldern besonders stabile Flussschlauchanordnungen,
was sich u.a. in einer erhöhten kritischen Stromdichte äußert. Der
Wert dieser sogenannten Matching-Felder hängt u.a. vom angelegten Feld
und der Dicke der Schicht ab. Eine wesentliche Rolle spielt dabei die
Oberflächenbarriere, die das Eindringen und Verlassen der Flussschläuche
aus der Schicht behindert. In unseren Messungen werden erstmalig solche
Matching-Effekte auch an supraleitenden Brücken beobachtet. Die
YBa2Cu3Oδ−7 Brücken mit der Länge von 240 nm und einer Breite und
Dicke von 100 nm wurden mittels Elektronenstrahllithograhie strukturiert
und nasschemisch geätzt. Die erhöhte Stabilität spiegelt sich in der
Magnetfeldabhängigkeit der kritischen Stromdichte wieder. Vergleichbare
Matching-Felder werden auch bei der Feldabhängigkeit der Stromstärke

Tiefe Temperaturen Freitag
beobachtet, bei der Spannungssprünge in den I-U-Kennlinien aufgrund
von Larkin-Ovchinikov-Vortex Instabilitäten auftreten. Die experimentell
bestimmten Matching-Felder werden im Zusammenhang mit bestehenden
Theorien für dünne Schichten diskutiert.
TT 31.8 Fr 12:00 H20
Advanced manipulation of substrates for growth induced pinning
in YBCO thin films — •S. Brück 1 , J. Albrecht 1,2 , S. Leonhardt
2 , R. Spolenak 1 , G. Cristiani 2 , H.–U. Habermeier 2 , and G.
Schütz 1 — 1 Max-Planck-Institut für Metallforschung, Heisenbergstr.
3, D-70569 Stuttgart — 2 Max-Planck-Institut für Festkörperforschung,
Heisenbergstr. 1, D-70569 Stuttgart
One way to enhance flux pinning and thus the critical current density
in YBCO thin films is by modifying the substrates’ surface topography
[1,2]. Irradiation with a focused beam of gallium ions (FIB) creates dotlike
structures which induce pinning sites in the superconductor during
film growth. To enhance the density of these structures it is necessary to
prevent surface charging, which can be achieved by using substrates with
a higher conductivity. We show AFM images of the microstructures and
quantitative magnetooptical measurements of YBCO thin films grown on
such sophisticated substrates. It is found, that the critical current density
can be enhanced substantially by lateral size reduction of the created
structures.
[1] S. Leonhardt, J. Albrecht, R. Warthmann, H.-U. Habermeier and
H. Kronmüller, Physica C 341-348, 1979-1980 (2000)
[2] J. Albrecht, S. Leonhardt, H.-U. Habermeier, S. Brück, R. Spolenak
and H. Kronmüller, Physica C, in Press
TT 31.9 Fr 12:15 H20
Competitive localization of vortex lines or interacting bosons
by a defect — •Jan Kierfeld 1 and Valerii Vinokur 2 — 1 MPI
für Kolloid- und Grenzflächenforschung, 14424 Potsdam — 2 Materials
Science Division, Argonne National Laboratory
We present a theory describing the localization of N three-dimensional
vortex lines or two-dimensional bosons with short-ranged repulsive interaction
which are competing for a single columnar defect or potential
well. For N=2 we use a necklace model formulation to find a delocalization
transition between two different states with a single bound particle.
The transition is characterized by the onset of particle exchange on the
defect. For strong repulsive interaction between vortex lines a permutation
symmetry is broken and the potential well is occupied by the same
particle at all times. For decreasing repulsion or increasing temperature
a transition into a different bound state takes place in which the particles
occupy the potential well alternately. A generalization of this transition
to arbitrary vortex number N is proposed.
TT 31.10 Fr 12:30 H20
Enhanced Magnetic Flux Pinning of Nanocrystalline Mechanically
Alloyed Bulk MgB2 by Stoichiometry Variation and Doping
— •Olaf Perner 1 , Jürgen Eckert 2 , Günter Fuchs 1 , Konstantin
Nenkov 1 , Bernhard Holzapfel 1 , and Ludwig Schultz 1
— 1 Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, PF
270116, D-01171 Dresden — 2 TU Darmstadt, Petersenstr. 23, D-64287
Darmstadt
In order to overcome the poor intrinsic properties of MgB2 concerning
the low upper critical field and to obtain an enhancement of the magnetic
flux pinning a combination of microstructure optimization as well
as chemical variation of the pure MgB2 compound were chosen.
Starting from the elements Mg and B, the phase formation was realized
by the mechanical alloying technique receiving a partially reacted
MgB2 powder with grain sizes of about 10 nm. Short uniaxial hot pressing
under vacuum led to phase pure highly densified nanocrystalline bulk
samples with low impurity content. The variation of the stoichiometry by
increasing and reducing the Mg content by up to 10 wt.% as well as the
doping with various concentrations of SiO2 and MgO leads to increased
pinning forces Fp compared to the stoichiometric composition.
The MgB2 bulk sample with a Mg excess of 10 wt.% shows an improved
critical temperature Tc of 36.0 K and a critical current density jc
of about 10 6 A/cm 2 at 7.5 K in self field whereas Mg deficit of 10 wt.%
enhances the upper critical field Hc2 (9 T at 20 K). Doping with SiO2
which improves significantly Hc2 and jc reveals more effective than with
MgO. Microstructure investigations will be presented.
TT 32 Theoretische Modelierung von Materialien mit korrelierten Elektronen
Zeit: Freitag 10:15–13:00 Raum: H18
TT 32.1 Fr 10:15 H18
Quasiparticles from quantum Monte Carlo: Effective mass and
Wilson ratio for K3C60 — •Erik Koch and Olle Gunnarsson —
Max-Planck-Institut für Festkörperforschung, Stuttgart
Taking advantage of the fixed-node approximation to stabilize excited
states, we calculate quasiparticle energies by quantum Monte Carlo. We
apply this approach to a model describing K3C60 and show that it works
surprisingly well. We determine how the quasiparticle dispersion changes
with increasing correlation and compare to the many-body enhancement
of the Pauli susceptibility. While the self-energies for our model seem
to depend only weakly on the momentum (and band-index), we find a
Wilson ration that appears to behave qualitatively different from what
is expected from dynamical mean-field theory.
TT 32.2 Fr 10:30 H18
A wavefunction-based quantum chemical method for infinite
systems — •Beate Paulus — Max-Planck-Institut für Physik komplexer
Systeme, Nöthnitzer Straße 38, D-01187 Dresden
Wave-function based quantum chemical methods are applied to the
infinite system using an incremental scheme to partitioning the correlation
energy. After the success for a wide range of semiconductors [1] and
insulators even such weakly bound as rare gas crystals [2], the method
is extended to strongly correlated metallic systems [3]. As example we
present the cohesive energy of mercury, where the binding is entirely due
to correlations. [1] B. Paulus, P. Fulde and H. Stoll,Phys. Rev. B 54
(1996) 2556 [2] K. Rosciszewski, B. Paulus, P. Fulde, and H. Stoll,Phys.
Rev. B 60 (1999) 7905 [3] B. Paulus, Chem. Phys. Lett. 371 (2003) 7
TT 32.3 Fr 10:45 H18
TiOCl, an orbital-ordered system? — •Roser Valenti 1 , T. Saha-
Dasgupta 2 , Helge Rosner 3 , and Claudius Gros 4 — 1 Institut für
Theoretische Physik, Universität Frankfurt, D-60054 Frankfurt — 2 S.N.
Bose National Centre for Basic Sciences, Kolkata 700098, India — 3 Max-
Planck Institute for Chemical Physics of Solids, D-01187 Dresden —
4 Theoretische Physik, Universität des Saarlandes, D-66041 Saarbrücken
We present first principles density functional calculations and downfolding
studies of the electronic and magnetic properties of the layered
quantum spin system TiOCl. We attempt to clarify the concept of orbital
ordering in this material and discuss existing studies. An analysis
of the electronic structure of slightly distorted structures according to
the phononic modes allowed in this material suggests that this system is
subject to large orbital fluctuations driven by the electron-phonon coupling.
Based on these results, we propose a microscopic explanation of
the behavior of TiOCl at lower temperatures.
TT 32.4 Fr 11:00 H18
Hartree-Fock-Approximation und Berücksichtigung von
Abschirm-Effekten in Ab-Initio-Bandstruktur-Berechnungen
— •Olaf Peschel 1 , Ilan Schnell 2 und Gerd Czycholl 1 —
1 Universität Bremen, Institut für Theoretische Physik — 2 Los Alamos
National Laboratory, Theoretical Division
Wir gehen von den Bloch-Wellenfunktionen einer DFT-Hartree-
Rechnung (ohne Austausch-Korrelationspotential) aus, die wir zu
maximal lokalisierten Wannier-Funktionen Transformieren. Bezüglich
dieser Basis berechnen wir die Hopping- und Coulomb-Matrixelemente
des Hamilton-Operators in Zweiter Quantisierung und führen eine
selbstkonsistente Hartree-Fock-Rechnung durch. Alternativ können
wir eine Hartree-Fock-(HFA)-Rechnung mit bezüglich der Bloch-Basis
berechneten Matrixelementen durchführen.
Um über die HFA hinauszugehen und Abschirmeffekte zu berücksichtigen,
berechnen wir die Suszeptibilität in verallgemeinerter Lindhard-

Tiefe Temperaturen Freitag
Näherung. Dies erlaubt die Berechnung von abgeschirmten Coulomb-
Matrixelementen und ist Grundlage für die Anwendung einer firstprinciples
”random phase approximation” (RPA) bzw. GW-Näherung.
Konkrete Rechnungen wurden für Li als denkbar einfachstes Metall
durchgeführt.
TT 32.5 Fr 11:15 H18
Spectral functions for systems with Hund’s rule correlated 5f
electrons — •Frank Pollmann and Gertrud Zwicknagl — Institut
für Mathematische Physik, TU-Braunschweig, Mendelssohnstraße
3, 38106 Braunschweig
We calculate the spectral functions for systems with 5f electrons by
performing exact diagonalization of small clusters and treating the intercluster
hopping as a perturbation. The perturbation is treated in the
formalism of the Strong Coupling Theory. In the calculated spectra well
defined quasiparticles and partial localization are observed.
The obtained results are compared with data from exact diagonalization
of finite clusters and measurements by angle resolved-photoemission
spectroscopy (ARPES).
TT 32.6 Fr 11:30 H18
The spin-state puzzle in cobaltates — •Z. Hu 1 , H. Wu 2 , D.
Madenci 1 , J. Baier 1 , T. Lorenz 1 , I. Bonn 3 , C. F e lser 3 , A.
Tanaka 4 , H.H. Hsieh 5 , H.-J. Lin 5 , C.T. C h en 5 , and L.H. Tjeng 1
— 1 II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77,
50937 Köln, Germany — 2 Max-Plank-Institut für Physik komplexer
Systeme, Nöthnitzer Str.38, 01187 Dresden, Germany — 3 Johannes
Gutenberg-Universität Mainz, Becher Wege 24, 55099 Mainz, Germany
472 — 4 Department of Materials Science, Faculty of Science, Hiroshima
University, Higaschi-Hiroschima, Japan — 5 Synchrotron Radiation Research
Center, No. 1 R&D Road VI, Science Based Industrial Park,
Hsinchu 300, Taiwan
We have carried out an experimental and theoretical study on the spinstate
of the Co 3+ ion in the layered Sr2CoO3Cl material. Using soft-x-ray
absorption spectroscopy at the Co L2,3 and O K edges, in combination
atomic multiplet cluster and LDA+U calculations, we found that the
Co 3+ ion is in the high spin-state, thereby falsifying all claims reported
so far in the literature which were based mostly on neutron, magnetic, or
crystallographic measurements. Detailed full-potential LDA+U calculations
reveal that the persistent high spin state and insulating behavior of
Sr2CoO3Cl are caused by the CoO5 pyramidal coordination and, particularly,
by the large plane corrugation of the basal CoO2 layer. Our finding
has far reaching implications for other layered cobalt oxides currently
under intense debat, e.g., RBaCo2O5+x, the layered double perovskites
showing metal-insulator transitions and colossal magneto-resistance.
TT 32.7 Fr 11:45 H18
Mott transition and suppression of orbital fluctuations in orthorhombic
3d 1 perovskites — •E. Pavarini 1 , S. Biermann 2,3 ,
A. Poteryaev 4 , A.I. Lichtenstein 4 , A. Georges 3 , and O.K.
Andersen 5 — 1 INFM and Dipartimento di Fisica ”A.Volta”, Pavia,
Italy — 2 Laboratoire de Physique des Solides, CNRS-UMR 8502, UPS
Bat. 510, 91405 Orsay France — 3 LPT-ENS CNRS-UMR 8549, 24 Rue
Lhomond, 75231 Paris Cedex 05, France — 4 NSRIM, UNSRIM, University
of Nijmegen, NL-6525 ED Nijmegen, The Netherlands — 5 Max-
Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569
Stuttgart, Germany
Using the first-principles downfolding technique, a low-energy Hamiltonian
is derived for several 3d 1 transition metal oxides. Electronic correlations
are included by combining this approach with an implementation
of dynamical mean-field theory appropriate for non-cubic systems. Good
agreement with photoemission data is obtained. The interplay of correlation
effects and structural distortions is found to strongly suppress orbital
fluctuations in both YTiO3 and LaTiO3 (in the latter less strongly), and
to favor the transition to the insulating state.
TT 32.8 Fr 12:00 H18
Zero Temperature Quantum Monte Carlo for Dynamical Mean
Field Theory — •Martin Feldbacher 1 , Karsten Held 1 und Fakher
Assaad 2 — 1 Max-Planck-Institut für Festkörperforschung, Heisenbergstraße
1, D-70569 Stuttgart — 2 Universität Würzburg, Institut für
Theoretische Physik I, Am Hubland, 97074 Würzburg
In recent years there has been a revival of interest in Kondo-like physics,
in particular in quantum dot systems and in connection with the
dynamical mean field theory (DMFT). The numerical solution of the
underlying Anderson impurity models is, however, limited: In the Numerical
Renormalization Group treatment the effort grows exponentially
with the number of orbitals, allowing not more than two interacting orbitals;
the Hirsch-Fye Quantum Monte Carlo (QMC) algorithm on the
other hand scales like T −3 (T: temperature) and quickly becomes too expensive
in CPU time. This limitation is especially severe when DMFT is
used to model materials with strong electron correlations where, in order
to observe the physics of interest, low temperatures need to be achieved.
We propose a projective QMC algorithm for the Anderson impurity
model which converges rapidly to the ground state. With this new impurity
solver we study the Mott-Hubbard metal-insulator transition in
the Hubbard model, demonstrating that it gives reliable “T = 0” DMFT
results.
TT 32.9 Fr 12:15 H18
Energy of the Mott insulator - 10th order perturbation theory
extended to infinite order using QMC — •Nils Blümer 1 and Eva
Kalinowski 2 — 1 Institut für Physik, Johannes-Gutenberg-Universität,
55099 Mainz — 2 FB Physik, Philipps Universität, 35032 Marburg
Of fundamental interest in solid state theory is the correlation induced
Mott-Hubbard metal-insulator transition (MIT) between a paramagnetic
metal and a paramagnetic insulator. Much progress has been made within
the last decade by application of the nonperturbative dynamical meanfield
theory to the frustrated one-band Hubbard model with semielliptic
density of states. In particular, a coexistence region of metallic and insulating
solutions has been established at low temperatures.
Only recently, numerical energy estimates have been obtained with
high enough precision for reliably pinpointing the first order MIT line.
Even higher accuracy is reached in this work for the ground state insulator
using 10 th order perturbation theory (PT) and an improved quantum
Monte Carlo (QMC) scheme which treats the high-frequency part of the
self-energy exactly. Extrapolating the PT coefficients, we obtain a continuous
estimate of the energy of the insulating phase with precision
O(10 −5 ) throughout its stability region. Analyzing the critical behavior,
we determine the (lower) stability edge as Uc1 ≈ 1.19 ×bandwidth.
TT 32.10 Fr 12:30 H18
Charge ordering in quarter filled ladder systems coupled to the
lattice — •H.G. Evertz 1 , M. Aichhorn 1 , M. Hohenadler 1 , C.
Gabriel 1 , J. Spitaler 2 , C. Ambrosch-Draxl 2 , and E.Ya. Sherman
1 — 1 Theor. Physik, TU Graz, Austria — 2 Theor. Physik, KFU
Graz, Austria
Using DMRG, Exact Diagonalization, and QMC, we investigate charge
ordering in the presence of electron-phonon coupling for quarter-filled ladder
systems. Parameters of a corresponding extended Hubbard model are
obtained from first-principles band-structure calculations for NaV2O5.
We show that dynamical Holstein phonons, which are strong in
NaV2O5, together with the nearest-neighbor Coulomb repulsion V result
in a static zig-zag lattice distortion. Such a distortion, as also measured
in NaV2O5, causes the system to order already at small values of V . We
calculate dynamical susceptibilities, including spin and charge spectra
and examine the effective Heisenberg model along the ladder in the
ordered state. Energy and length of kink-like excitations of the ordered
state are determined.
On finite systems, charge ordering also takes place as an effective finite
temperature transition because of a rapidly growing correlation length.
In a grand canonical ensemble, the charge order manifests itself as a
plateau in the density as a function of chemical potential. In ongoing
calculations, we are investigating Raman spectra and the effects of interladder
coupling.
TT 32.11 Fr 12:45 H18
Finite-temperature analysis of 2D spin frustrated Vanadium
compounds — •Burkhard Schmidt 1 , Nic Shannon 1,2 , Karlo
Penc 3 , and Peter Thalmeier 1 — 1 MPI für Chemische Physik fester
Stoffe, 01187 Dresden, Germany — 2 SPEC, CEA Saclay, Orme des
Merisiers, F-91191 Gif sur Yvette CEDEX, France — 3 Research Institute
of Solid State Physics and Optics, H-1525 Budapest, P.O. Box 49,
Hungary
We present an analysis of the finite-temperature properties of the J1-J2
Heisenberg model on a square-lattice based on the exact diagonalisation
of 8, 16, and 20 site clusters. Our method provides a possibility to determine
the exchange constants of recent experimental realisations of the
model in a unique way. In particular, the two-dimensional compounds
Li2VO(Si,Ge)O4 and Pb2VO(PO4)2 will be discussed.

Tiefe Temperaturen Freitag
We propose that diffuse neutron scattering can be used to resolve the
inherent ambiguity in determining the ratio and sign of J1 and J2 from
thermodynamic properties alone, and use a finite temperature Lanczos
algorithm to make predictions for the relevant high temperature spin-spin
correlation functions.
TT 33 Amorphe- und Tunnelsysteme, Gläser
We investigate the crossover between the various magnetic and spinliquid
phases for both ferromagnetic and antiferromagnetic couplings J1
and J2. We also analyse the nonlinear magnetic susceptibility to resolve
the ambiguity of the frustration ratio J2/J1.
Zeit: Freitag 10:15–11:30 Raum: H19
TT 33.1 Fr 10:15 H19
Isotopeneffekt der Magnetfeldabhängigkeit von dielektrischen
Polarisationsechos in amorphem Glycerin — •Maximilian
Brandt 1 , Peter Nagel 2 , Andreas Fleischmann 1 , Christian
Enss 3 und Siegfried Hunklinger 1 — 1 Kirchhoff Institut für Physik,
Universität Heidelberg,D- 69120 Heidelberg — 2 Forschungszentrum
Karlsruhe, D- 76021 Karlsruhe — 3 Brown University, Providence, RI
02912, USA
Die physikalischen Eigenschaften von amorphen Festkörpern werden
unterhalb einiger Kelvin durch atomare Tunnelsysteme bestimmt. In
diesem Temperaturbereich zeigen dielektrische Multikomponentengläser
mit Ausnahme von Quarzglas magnetfeldabhängige Eigenschaften. Zur
Erklärung dieser unerwarteten Magnetfeldeffekte in nominell unmagnetischen
amorphen Systemen wurden in den letzten Jahren verschiedene
Modelle entwickelt. Eines dieser Modelle setzt voraus, dass die Atomkerne
der tunnelnden Teilchen ein elektrisches Kernquadrupolmoment besitzen.
Mit dielektrischen Polarisationsechoexperimenten haben wir an amorphem
Glycerin den Zerfall der Echoamplitude in Abhängigkeit des Magnetfeldes
untersucht. Durch partielles Deuterieren wurden gezielt Atome
mit Kernquadrupolmoment und bekannter Quadrupolaufspaltung in
das System eingebracht. Der beobachtete Isotopeneffekt stützt die Erklärung
der Magnetfeldeffekte basierend auf einem Kernquadrupolmement.
Auch das in Glycerin beobachtete Quantum-Beating im Zerfall von
Zweipulsechos kann im Rahmen dieses Modells semiquantitativ erkärt
werden.
TT 33.2 Fr 10:30 H19
Dielektrische Eigenschaften von Glyzerin bei tiefen Temperaturen
im Magnetfeld — •Marek Bartkowiak 1 , Andreas Fleischmann
1 , Christian Enss 2 und Siegfried Hunklinger 1 — 1 Kirchhoff
Institut für Physik, Universität Heidelberg — 2 Brown University, Providence,
USA
Bei tiefen Temperaturen werden die thermischen, akustischen und dielektrischen
Eigenschaften von amorphen Festkörpern durch atomare
Tunnelsysteme bestimmt. Völlig unerwartet wurde vor wenigen Jahren
gefunden, dass die dielektrischen Eigenschaften von bestimmten Multikomponentengläsern
bei sehr tiefen Temperaturen vom Magnetfeld
abhängen. Eine derartige Abhängigkeit wurde nicht nur in der dielektrischen
Suszeptibilität sondern auch bei Polarizationsechos beobachtet.
Letztere Messungen deuten darauf hin, dass tunnelnde Atome mit Kernquadrupolmoment
für die Magnetfeldabhängigkeit verantwortlich sind.
Um den Einfluss des Kernquadrupolmoments zu untersuchen haben wir
Messungen der dielektrischen Suszeptibilität bei verschiedenen Frequenzen
an natürlichem und vollständig deuteriertem Glyzerin in Magnetfeldern
durchgeführt. Wir stellen die Messungen vor und diskutieren die
Isotopenabhängigkeit.
TT 33.3 Fr 10:45 H19
Low-temperature investigation on thermal conductivity of
glasses — •H.-Y. Hao 1 , M. Neumann 1 , A. Rost 1 , A. Fleischamnn
1 , C. Enss 2 , and S. Hunklinger 1 — 1 Kirchhoff-Institut fuer
Physik, Universitaet Heidelberg — 2 Department of Physics, Brown
University
The thermal conductivity of glasses at temperatures below 1 K is generally
described through the resonant scattering between the heat-carrying
phonons and the tunnuling systems in the glasses. At further low temperature,
it is evident that the interactions between the tunneling systems
themselves could be responsible for describing the anomalies observed in
certain properties of glasses. It is therefore conceivable that such interactions
could also contribute to the heat transport and become visible
when the phonons are frozen out at very low temperatures or suppressed
by some additional scattering mechanism introduced to the system. For
measuring thermal conductivity of such diminutive magnitude, our recently
developed contact-free technique is proved to be ideal owing to its
surpassingly small parasitic heating to the system. Measurements on bulk
BK7 glass and synthetic quartz glass have been successfully preformed
down to 5 mK. For reducing the phonon mean-free-path, a glass capillary
array is used to introduce extra scattering of the thermal phonons. For
such a sample, an advanced design of the setup is developed to improve
the precision of the measurements. Preliminary findings will be presented
and discussed.
TT 33.4 Fr 11:00 H19
Systematic Location and Description of Two Level Tunneling
States in Simulated Lennard-Jones and Silicate Glasses. —
•Jens Reinisch and Andreas Heuer — Institut für Physikalische
Chemie and International Graduate School of Chemistry, Westfälische
Wilhelms-Universität, Corrensstraße 30, 48149 Münster
Though the existence of Two Level Tunneling States (TLS) is widely
accepted to explain low temperature anomalies in the sound absorption,
heat capacity, thermal conductivity and other quantities, an exact description
of their microscopic nature is still lacking. We performed computer
simulations on a binary Lennard-Jones and a silicate system, using
a newly developed algorithm to find TLS on a systematic basis. A detailed
microscopic description of the Tunneling States in the simulated
systems is thus available. Beyond structure we are also interested in general
movement schemes for the participating particles. We found local
density anomalies at the TLS, which are connected to the movement of
the participating particles and we suggest that these anomalies are important
for the TLS formation. For the LJ-system we will show strong
evidence that only one particle is dominant in TLS, although several
particles are moving. Furthermore, semi-quantitative estimations for the
density of states of TLS are presented.
TT 33.5 Fr 11:15 H19
Four level tunneling systems and electronic structure in
clathrates — •Ivica Zerec 1 , Alexander Yaresko 2 , and Peter
Thalmeier 1 — 1 Max-Planck-Institut fuer Chemische Physik fester
Stoffe, Noethnitzer Str. 40, 01187 Dresden — 2 Max-Planck-Institut fuer
Physik komplexer Systeme, Noethnitzer Str. 38, 01187 Dresden
The clathrates are cage compounds, interesting because of their structural
and thermoelectrical properties. In the oversized cages formed by
Si, Ge, Ga, etc. atoms, the ”guest” atoms rattle and strongly scatter
phonons, reducing the phonon dominated thermal conductivity.
The elastic response of the Eu clathrate provides clear evidence for the
existence of a new type of four-well tunneling states, described by two
nearly degenerate four level systems (FLS). The FLS’s are closely linked
with the fourfold split positions of Eu known from neutron diffraction
density profiles. Using a realistic potential we estimate the tunneling frequencies
and show that the energy gap between the two FLS’s is of the
same order as the Einstein oscillator frequency. This explains why the observed
harmonic oscillator type specific heat is not modified by tunneling
states. The quadrupolar interaction of FLS’s with elastic strains explains
the pronounced dip observed in the elastic constant measurements.
We present also the electronic band structure of Ba6Ge25 clathratelike
compound and investigate the modifications due to the structural
phase transitions, reflected in the shifting of some Ba and Ge atoms to
the split sites. The corresponding modifications in optical conductivity
is calculated. It agrees well with experiment.

Vakuumphysik und Vakuumtechnik Tagesübersichten
Hauptvorträge
VAKUUMPHYSIK UND VAKUUMTECHNIK (VA)
Dr. Karl Jousten
Physikalisch-Technische Bundesanstalt
Labor für Vakuummetrologie
Abbestraße 2-12
10587 Berlin
E-Mail: karl.jousten@ptb.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsaal H47)
VA 1.1 Mo 09:30 (H47) Nano-fabrication with Focused Ion Beams, Jacques Gierak, Ralf Jede, Lars
Bruchhaus, Toralf Kliem, Peter Hawkes
VA 3.1 Mo 14:30 (H47) 350 Jahre Otto von Guerickes Regensburger Experimente - Beginn
der Vakuumphysik und Begründung der Lehre vom Luftdruck,
Peter Streitenberger, Ditmar Schneider
Fachsitzungen
VA 1 Vakuumverfahrenstechnik Mo 09:30–10:50 H47 VA 1.1–1.3
VA 2 Vakuummessung Mo 10:50–12:30 H47 VA 2.1–2.5
VA 3 Geschichte und Entwicklung der Vakuumphysik Mo 14:30–15:40 H47 VA 3.1–3.2
Mitgliederversammlung des Fachverbands Vakuumphysik und Vakuumtechnik
Mo 15:40–16:30 H47
1. Bericht des FV-Leiters
2. Wahl des neuen FV-Leiters
3. Wahl des Stellvertreters
4. Folgende Tagungen
5. Verschiedenes

Vakuumphysik und Vakuumtechnik Montag
Fachsitzungen
– Haupt-, Fach- und Kurzvorträge –
VA 1 Vakuumverfahrenstechnik
Zeit: Montag 09:30–10:50 Raum: H47
Hauptvortrag VA 1.1 Mo 09:30 H47
Nano-fabrication with Focused Ion Beams — •Jacques Gierak 1 ,
Ralf Jede 2 , Lars Bruchhaus 2 , Toralf Kliem 2 , and Peter
Hawkes 3 — 1 LPN-CNRS, Route de Nozay, 91460 Marcoussis, France
— 2 RAITH GmbH, Hauert 18, Technologiepark, 44227 Dortmund,
Germany — 3 CEMES/CNRS, 29 rue Jeanne Marvig, 31055 Toulouse,
France
Focused Ion Beam (FIB) technology today plays an important role
in IC manufacturing processes, but it is also a challenging technique
for nanotechnology. We will present a Nano-FIB system that was developed
specifically for sub-10nm FIB patterning. This instrument combines
the advantages of a very high resolution FIB system with the accuracy
of a high precision laser interferometer stage and 10MHz digital pattern
generator. For FIB patterning of devices at the nanometer scale,
the appropriate level of interaction between ions and solids shifts towards
much lower dose effects. Most target materials involved exhibit
very high ion sensitivity, which can reach the 10 12 ions/cm 2 range. As a
direct consequence, chemical or crystal modification of a surface by local
ion bombardment offers new possibilities for selective epitaxial growth
of materials or selective deposition of nano grains for example. Applications
such as organizing gold nanoclusters (nanoelectronics), changing
magnetic properties (data storage), defect injection in III/V nano devices
and localized epitaxial growth of semiconductor dots, the possibility to
place high quality orientated CNT’s at chosen sites, and inorganic lithography
experiments will be presented.
VA 1.2 Mo 10:10 H47
Vakuum am Bau: Mit Vakuum-Isolations-Paneelen Energie sparen
und Platz schaffen — •Gregor Erbenich und Hans-Frieder
Eberhardt — Heisinger Str. 8 , 87437 Kempten
In vielen Bereichen der Industrie ist ein kontinuierlicher Prozess hin
zu besseren Dämmstandards zu beobachten. Die klassischen Dämmstoffe
VA 2 Vakuummessung
können einer solchen Entwicklung jedoch kaum noch folgen. Die Nachfrage
nach effizienteren Systemen nimmt deshalb stetig zu. Ausserdem
gibt es immer wieder Situationen, in denen Platz entweder teuer, oder
schlichtweg nicht vorhanden ist, um eine den geltenden Dämmstandards
entsprechende Wärmedämmung zu erzielen. Mit Vakuum Isolation Paneelen
(VIP‘s) erreicht man Wärmeleitfähigkeiten, die um einen Faktor
5 bis 10 geringer sind als bei konventionellen Dämmstoffen. Der Vortrag
gibt einen Überblick über das Wirkprinzip von VIP‘s, illustriert das
Energieeinspar- und Raumgewinnpotential anhand einer Simulation fuer
ein Kühlgeraet und stellt weiter bereits realisierte Anwendungen dar.
Mögliche Verbesserungs- und Weiterentwicklungsmoeglichkeiten, werden
anhand eines Massnahmenkatalogs definiert.
VA 1.3 Mo 10:30 H47
Barrier films for vacuum insulation panels (VIP) — •Dirk
Kaczmarek — Wipak Walsrode GmbH & Co. KG, Postfach 1661, 29656
Walsrode
Barrier films for vacuum insulation panels were used since a long time
in the market of refrigerator. On one side the energy-efficiency-class will
be extend to A+ and A++ in the next year and on the other side the
energy saving in the field of buildings will become more and more important.
These applications require a higher insulation like the VIPs. The
VIPs based on multi layer films which surround a core that can consist
of different materials. To realize a high level of insulation the VIP need
an internal pressure of 1 mbar. From there, the main focus of the barrier
films is, to keep this pressure as low as possible over years but the heat
conductivity has to be low as well. The company Wipak offers since several
years films for the production of vacuum insulation panels. In this
paper the requirements (e.g. influence of oxygen permeation) to a barrier
film will be discussed as well as the different solutions will be presented
(e.g. thickness of the metallization).
Zeit: Montag 10:50–12:30 Raum: H47
VA 2.1 Mo 10:50 H47
Geometrical characterization of primary vacuum standard
based on digital non-rotating piston manometer with conical
gap in Czech metrology institute — •Jiri Tesar 1 , Dominik
Prazak 1 , Zdenek Krajicek 1 , and Petr Repa 2 — 1 Czech Metrology
Institute, department of the primary pressure metrology; Okruzni
31, 638 00 Brno, Czech Republic — 2 Charles University, Faculty of
Mathematics and Physics; V Holesovickach 2, 180 00 Praha 8, Czech
Republic
The pressure and vacuum department of CMI performed geometrical
traceability of its conical piston-cylinder unit of the vacuum standard
DHI FPG 8601. At first the profile of the conical cylinder was measured.
From those measurements five parts of the cylinder were selected:
strain part above top maximum A, conical part between top maximum
A and top minimum B, lubrication section, conical part between bottom
minimum C and bottom maximum D, strain part under bottom maximum
D. The shape and mean diameter of the cylinder in points A, B, C
and D were measured and the same parameters of the piston in equivalent
points. The effective area calculated from geometrical data is AG =
980.5297 mm2. The effective area got by cross-floating with a CMI classical
rotating piston-cylinder unit is APG = 980.5271 mm2. The original
DHI effective area is ADHI = 980.511 mm2. The results show very good
agreement with CMI traceability to classical piston-cylinder unit. The
DHI effective area is very close to the geometrical area of the piston only.
VA 2.2 Mo 11:10 H47
Dynamisches Pirani-Vakummessgerät — •Simone Ludwig und
Wolfgang Jitschin — Fachbereich MNI, Fachhochschule Gießen,
35390 Gießen
Das nach Pirani benannte, weit verbreitete Vakuummeter besitzt einen
einfach aufgebauten Sensor, nämlich einen dünnen Metalldraht. Der
Draht wird durch direkten Stromdurchfluss geheizt und die Wärme durch
das umgebende Gas nach außen abgeführt. Üblicherweise wird der Sensor
stationär betrieben und das Messsignal aus der abgeführte Wärme,
also aus der Wärmeleitung des Gases erhalten. Nachteile dieses Prinzips
sind, dass die Wärmeleitung im Bereich des Atmosphärendrucks nahezu
gesättigt ist und dass die Wärmeleitung stark von der Gasart abhängt.
Diese Nachteile können vermieden werden, wenn man das Messsignal aus
der Wärmekapazität des Gases herleitet. Hierzu muss im gepulsten Betrieb
gearbeitet werden, bei dem die Drahtheizung ein- und ausgeschaltet
wird. In der vorliegenden Arbeit wird über Messungen des Aufheizvorganges
und des Abkühlvorganges berichtet. Als Temperatursensor dient
der Metalldraht selbst, dessen Widerstand mit steigender Temperatur zunimmt.
Die Messergebnisse werden mit Modellrechnungen verglichen. Bei
Atmosphärendruck ist die Wärmekapazität des Gases wesentlich höher
als die des Drahtes. Allerdings ist die mittlere Übertemperatur des Gases
gering, was die Gewinnung eines druckabhängigen Messsignals erschwert.

Vakuumphysik und Vakuumtechnik Montag
VA 2.3 Mo 11:30 H47
A new dynamic-flow-high-vacuum-standard designed in CR —
•Ladislav Peksa 1 , Petr Repa 1 , Tomas Gronych 1 und Jiri Tesar
2 — 1 Charles University Prague, V Holesovickach 8, CZ18000 Praha
8, Czech Republic — 2 Czech Institute of Metrology (CMI), Okruzni 31,
CZ63800 Brno, Czech Republic
A new high vacuum standard based on the dynamic flow principle is
designed in Common Laboratory of the Czech Institute of Metrology
and Charles University, CR. A classic one-step-expansion arrangement
with a cylindrical chamber divided by the orifice plate into two chambers
was chosen. The orifice has the spherical-geometry-channel but with one
sphere only in contrast to the most common NPL orifice. A stable turbomolecular
pump of medium pumping speed was used; its pumping speed
was measured by the AVS recommended orifice method and its value is
involved in the Seff-calculation. The flowmeter based on constant pressure
principle is a part of the standard. An electronically driven ”dry”
welded bellows is used as the volume varying element. Its parameters
were tested.
VA 2.4 Mo 11:50 H47
Reduzierung der Offsetschwankung eines Gasreibungsvakuummeters
mittels Schwingungsisolierung — •Thomas Bock und
Karl Jousten — Physikalisch-Technische Bundesanstalt, Abbestr. 2–
12, D-10587 Berlin
Die Restabbremsung (Offset) eines Gasreibungsvakuummeters ist in
drei Anteile zerlegbar. Veränderungen des Offsets durch Temperatureffekte
besitzen Zeitkonstanten im Minutenbereich. Streuungen des Offsets
die durch Coulomb-Kräfte und Wirbelströme erzeugt werden, liegen
auf kürzeren Zeitskalen. Es kann analytisch gezeigt werden, dass
bei der Einkopplung von zufallsverteilten Schwingungen in das Messsystem,
Coulomb-Kräfte und Wirbelströme stochastischen Charakters entstehen.
Daraus resultiert eine stochastische Energiedissipation die zu einer
zusätzlichen Offsetstreuung führt. Zur Reduzierung der Vibrationen
am Messsystem wurde eine Schwingungsisolierung konstruiert. Es wurden
diverse Konfigurationen (z.B. Messkopf schwingungsisoliert, Rotor
nicht schwingungsisoliert: C1, Messkopf und Rotor schwingungsisoliert:
C2) getestet und Datensätze generiert, die Zeit, Rotorfrequenz, ˙ω/ω und
Temperatur des Messfingers mit einer Messzeit von 30s beinhalten. Weiterhin
wurden Geräte mit verschiedenen Messparametern (z.B. Rotorund
Messfingerdurchmesser, Einzelstreuung (SSC)) auf die Reduzierbarkeit
der Offsetstreuung untersucht. Die Konfiguration C2 weist eine signifikant
kleinere Offsetstreuung als C1 auf. Durch die Schwingungsisolierung
konnte die Varianz der Streuung der Restabbremsung um bis zu
einem Faktor 4 verringert werden.
VA 2.5 Mo 12:10 H47
Stetige Präzisions-Vakuumregelung, lautlos, komfortabel und
preiswert — •Plöchinger — Thyracont Elektronik GmbH, Max-
Emanuel-Str. 10, D-94036 Passau
Steigende Anforderungen an Produktqualität und die damit verbundene
Optimierung von Vakuumprozessen erfordern zunehmend den Einsatz
moderner, stetig arbeitender Regelsysteme. Diese ermöglichen gegenüber
klassischen Auf/Zu-Ventilen eine weiche und präzise Kontrolle des Prozessdrucks
bei minimaler Regelabweichung und vernachlässigbarer Regelschwankung.
Mit dem neuen Regelsystem VD9CV von Thyracont steht
nun hierfür eine kostengünstige und leistungsfähige Komplettlösung zur
Verfügung, die mit nahezu jedem Pumpentyp oder auch an Zentralvakuumanlagen
einsetzbar ist. Der in einem störsicheren 19Gehäuse untergebrachte
Controller regelt den benötigten Prozessdruck kontinuierlich
über stetige Proportionalventile für Evakuierung und Belüftung, die direkt
vom Regler versorgt werden. Er ist erhältlich als Set mit Vakuum-
Transmitter(n), Ventilen und Anschlusskabeln. Die serielle Schnittstelle
erlaubt eine externe Steuerung des Geräts, beispielsweise zur Regelung
komplexer Druck-Profile. Die hohe Zuverlässigkeit des VD9CV, einfache
Bedienbarkeit und seine feinfühlige Fuzzy-3Punkt-Regelung mit PI-
Charakteristik stehen dabei für einen optimalen Anwender-Nutzen.
VA 3 Geschichte und Entwicklung der Vakuumphysik
Zeit: Montag 14:30–15:40 Raum: H47
Hauptvortrag VA 3.1 Mo 14:30 H47
350 Jahre Otto von Guerickes Regensburger Experimente - Beginn
der Vakuumphysik und Begründung der Lehre vom Luftdruck
— •Peter Streitenberger 1 und Ditmar Schneider 2 —
1 Otto-von-Guericke-Universität Magdeburg, Institut für Experimentelle
Physik, PF 4120, D-39016 Magdeburg — 2 Guericke-Forschungsarchiv,
Otto-von-Guericke-Gesellschaft e. V. Magdeburg, Zschokkestrasse 32, D-
39104 Magdeburg
Aus Anlass des 350jährigen Jubiläums der ersten öffentlichen Demonstration
der Vakuumexperimente Otto von Guerickes während des
Reichstages zu Regensburg 1654 würdigt der vorliegende Beitrag die
überragende Bedeutung Guerickes für die Herausbildung der auf der experimentellen
Methode basierenden Neuen Wissenschaft im 17. Jahrhundert.
Guericke gilt unbestritten als Erfinder der Vakuum-Luftpumpe und
hervorragender Experimentator, der durch seine publikumswirksamen
Experimente eindrucksvoll die Wirkungen des atmosphärischen Luftdrucks
demonstrierte. Weniger bekannt sind dagegen seine physikalischinterpretatorischen
Leistungen, ohne die er nicht unabhängig zur Lehre
vom Luftdruck gelangt wäre. Im Beitrag wird daher gezeigt, dass Guericke
durch eine Reihe subtiler Vakuumexperimente und deren physikalische
Deutung sowie nicht zuletzt durch seine Berechnung der Druckkräfte
der Luft wichtige Beiträge zum physikalischen und begrifflichen
Verständnis der Hydrostatik der Gase und damit auch zur Ideen- und
Begriffsentwicklung der Physik insgesamt erbracht hat.
Fachvortrag VA 3.2 Mo 15:10 H47
Entwicklung der Oberflächen- und Schichttechnologien aus
Sicht des VDI — •Ralph Jürgen Peters und Karin Wey —
VDI-Technologiezentrum; Graf-Recke-Strasse 84; 40239 Duesseldorf
Oberflächen- und Schichttechnologien haben sich in den letzten
Jahrzehnten zu einer der unbestrittensten Schlüsseltechnologien entwickelt,
die massgeblich eine Vielzahl von Funktionalitäten von hochwertigen
technischen Produkten beeinflusst. Die Geschichte der Oberflächentechnik
reicht bis in die Antike zurück, als Menschen anfingen,
Keramik zu glasieren. Beflügelt durch die Vakuumtechnik, die moderne
Beschichtungsverfahren erst möglich machte, hat sich die Oberflächentechnik
zu einer wahren Querschnittstechnologie entwickelt, deren
Anwendungen aus unserem täglichen Leben nicht mehr wegzudenken
sind. Mit modernen Verfahren werden funktionstragende Oberflächen erzeugt,
verändert und charakterisiert. Der Vortrag unternimmt eine Reise
durch die Geschichte der Oberflächentechnik und zeigt die Vielfalt an modernen
Anwendungen auf, die von dekorativen Beschichtungen, über den
Verschleiss- und Korrosionsschutz bis hin zu biokompatiblen Schichten
für Implantate reicht.

Ausschuss Industrie und Wirtschaft Tagesübersichten
AUSSCHUSS INDUSTRIE UND WIRTSCHAFT (AIW)
Mittwoch, 10.03.2004: SITZUNG DES AIW (14:00 - 18:00) (Raum M 101)
Donnerstag, 11.03.2004: INDUSTRIETAG (10:00 - 19:00) (Hörsaal H 17)
10:00 Dr. Udo Weigelt, Grünecker & Koll., Begrüßung
1. Übersicht
THEMA DES INDUSTRIETAGS:
PHOTONIK
Leitung des Industrietags
Dr. Udo V. Weigelt (Vorsitzender des AIW)
Anwaltssozietät Grünecker & Koll.
Gewerblicher Rechtsschutz
Maximilianstraße 58
80538 München
E-Mail: weigelt@grunecker.de
Dr. Lutz Schröter
AutoVision GmbH
Venture
Major-Hirst-Str. 11
38442 Wolfsburg
E-Mail: lutz.schroeter@autovision-gmbh.com
10:15 Dr. Stefan Altmeyer, VDI Technologiezentrum Düsseldorf, Optische Technologien
2. Anwendungen
10:45 Sven Ederer, TRUMPF GmbH & Co. KG, Lasermaterialbearbeitung - Photonen in der Fertigungstechnik
11:15 Dr. Robert Brunner, Carl Zeiss Jena GmbH, Diffraktive Optik: Neue Chancen mit Micro- u. nanostrukturierter Optik
3. Optik im Automobil
13:45 Dr. Bernd Stoffregen,Volkswagen AG, Messtechnik in der Fahrzeugentwicklung
14:15 Dr. Joachim Massen, ADC GmbH, Optische Sensorik in Fahrerassistenzsystemen
14:45 Dr. Eberhard Zeeb, DaimlerChrysler AG, Optische Datenbusse für Automobilanwendungen
4. Strahlquellen
15:15 Dr. Norbert Stath, Osram Opto Semiconductors GmbH & Co., Opto-Halbleiter - Lichtquellen der Zukunft
15:45 Andrea Sigl, P.A.L.M. Microlaser-Technologies AG, Lasermicromanipulation u. optische Pinzette in Biologie u. Medizin
5. Ausblick
16:15 Dr. Frank Bitte, PhotonAix e.V., Optische Technologien - Potenziale und Perspektiven
6. Podiumsdiskussion: Photonik Quo Vadis?
17:00 Teilnehmer: Frank Bitte, Lutz Schröter, Horst Sickinger, Udo Weigelt, u.a.
18:00 Geselliges Beisammensein
19:00 Ende der Veranstaltung

Ausschuss Industrie und Wirtschaft Donnerstag
Fachsitzungen
– Hauptvorträge und Veranstaltungen –
AIW 1 Übersicht
Zeit: Donnerstag 10:15–10:45 Raum: H 17
AIW 1.1 Do 10:15 H 17
Optische Technologien — •Stefan Altmeyer — VDI Technologiezentrum,
Düsseldorf
Optische Technologien sind eine der Schlüsseltechnologien für dieses
Jahrhundert. Sie beeinflussen in direkter Weise alle gesellschaftlich relevanten
Bereiche. Anhand von Beispielen wird die essenzielle Bedeutung
für die Information & Kommunikation, die Beleuchtung & den
AIW 2 Anwendungen
Umweltschutz, die Medizin & Biotechnologie, sowie die Produktion und
die Mobilität verdeutlicht. Dabei ist der Innovationsgehalt und die Treiberfunktion
der Optische Technologien für dieses Jahrhundert vergleichbar
mit dem des Elektrons für das vergangene Jahrhundert. Sowohl die
Unternehmens- als auch die Forschungslandschaft in Deutschland bieten
die besten Voraussetzungen dafür, die mit den Optischen Technologien
verbundenen Chancen aufzugreifen und effektiv zu nutzen.
Zeit: Donnerstag 10:45–11:45 Raum: H 17
AIW 2.1 Do 10:45 H 17
Lasermaterialbearbeitung - Photonen in der Fertigungstechnik
— •Sven Ederer — TRUMPF GmbH & Co. KG
Die Lasertechnik findet breite Anwendung in der Fertigungstechnik,
denn die Eigenschaften des Laserlichtes erlauben präzise, berührungsund
kräftefrei Bearbeitung unterschiedlichster Werkstoffe.
Dabei ist der Laser ist auch ein sehr flexibles Werkzeug. Dies ermöglicht
einerseits die wirtschaftliche Darstellung kleiner Serien und andererseits
sehr hohe Flexibilität der Fertigung. So kann sich die Fertigung sehr
schnell auf wechselnde Anforderung und Revisionen einstellen.
In der Industrie werden Laser für klassische Fertigungsaufgaben wie
Fügen, Trennen, Beschriften und Generieren vor allem im Maschinen-,
Automobil-, Schiffs- und Flugzeugbau eingesetzt. Auch in der Fertigung
von neuen Werkstoffen wie Nanoteilchen, Mikroelektronik sowie in der
Mikrostrukturierung wird Laserlicht eingesetzt.
.
AIW 3 Optik im Automobil
AIW 2.2 Do 11:15 H 17
Diffraktive Optik: Neue Chancen mit mikro- und nanostrukturierter
Optik — •Robert Brunner — Carl Zeiss Jena GmbH
Hybride optische Systeme in der Kombination aus diffraktiv und refraktiv
wirkenden Elementen weisen ein enormes Potential auf, klassische
Design-Ansätze stark zu vereinfachen und Abbildungsleistungen zu
ermöglichen, die durch einen konventionellen Ansatz nicht realisierbar
wären. Die Stärken dieses hybriden Ansatzes werden anhand verschiedener
optischer Systeme, wie z.B. einem speziellen UV-Mikroskop-Objektiv
diskutiert. Effizient beugende diffraktive Elemente bilden die Basis zur erfolgreichen
Umsetzung des hybriden Konzeptes. Als Basistechnologie zur
Realisierung dieser Elemente eignen sich besonders holografische Strukturierungsprozesse.
Durch die Verwendung von Wellenlängen im tiefen
UV-Bereich sind Strukturbreiten unter 100 nm auf holografischem Wege
erzielbar. Diese nanooptischen Elemente ( ” Zero-Order-Gratings“) lassen
sich durch Anpassung der Profilgeometrie in ihrer polarisierenden oder
antireflektierenden Wirkung optimieren.
Zeit: Donnerstag 13:45–15:15 Raum: H 17
AIW 3.1 Do 13:45 H 17
Messtechnik in der Fahrzeugentwicklung — •Bernd Stoffregen
— Volkswagen AG, Wolfsburg
Optische Technologien nehmen auch in der Automobilindustrie ständig
an Bedeutung zu. In der Produktion sind es vor allem die Laser als
Werkzeuge zum Schneiden, Schweißen und Härten und die optischen
Sensoren zur Geometrie-Überwachung. Bei der Entwicklung von Automobilen
werden optische Verfahren für unterschiedliche Messaufgaben
eingesetzt. Die eingesetzten Techniken sind dabei genauso vielfältig wie
die Problemstellungen. Zum Beispiel erfolgt die 3-D-Geometrieerfassung
an Designmodellen mittels Fotogrammetrie- und Streifenprojektionsverfahren.
Zur Untersuchung von Schwingungsvorgängen werden Holografie
und Laser-Doppler-Vibrometrie eingesetzt. Die optischen Verfahren zur
Untersuchung von Strömung, Gemischbildung und Verbrennung in Motoren
tragen entscheidend zur Entwicklung neuer direkteinspritzender
Otto- und Dieselmotoren bei. Im Vortrag werden eine Reihe von optischen
Messtechniken und ihre Einbindung in die Automobilentwicklung
dargestellt.
AIW 3.2 Do 14:15 H 17
Optische Sensorik in Fahrerassistenzsystemen — •Joachim
Massen — ADC GmbH
Fahrerassistenzsysteme sind ein wichtiger Schritt auf dem Weg zum
unfallvermeidenden Fahrzeug. Sie erhöhen die Sicherheit entweder durch
direkten Eingriff, oder durch Entlastung des Fahrers in Komfortsystemen.
Hierzu benötigen sie Informationen aus der Umgebung, in der
sich das Kraftfahrzeug bewegt. Die Abstände und Winkel auftretender
Objekten werden von RADAR oder LIDAR-Sensoren erfasst. Durch
die wellenlängenbedingte hohe Winkelauflösung sind optische Sensoren,
ergänzt durch Kamerasysteme, auch in der Lage, die Ausdehnung
von Objekten zu vermessen und sie zu klassifizieren. Die einzigartige
Möglichkeit mit den 2D-Kamerabildern gleichzeitig 3D-Entfernungsbilder
zu liefern, bietet der Photomischdetektor (PMD). Typische Anwendungen
optischer Umfeldsensoren sind ACC, Stauassistenten, Einparkhilfen,
Spurführungssysteme, Nachtsichtsysteme, Spurwechselassistenten,
Precrash-Sensoren, oder Systeme zum Fußgängerschutz. Besondere Herausforderungen
stellen die Signaldynamik, das Umgebungslicht und das
Mensch Maschine Interface.
AIW 3.3 Do 14:45 H 17
Optische Datenbusse für Automobilanwendungen — •Eberhard
Zeeb — DaimlerChrysler AG
Optische Datenbusse werden seit 1998 in Serienfahrzeuge eingebaut
und haben sich als Standardnetze für Insasseninformations- und entertainmentsysteme
durchgesetzt. Zur Zeit werden Punkt-zu-Punkt Datennetze
auf Basis von Polymerfasern mit Datenraten bis zu 22.5 MBit/s
eingesetzt, die in ihren mechanischen und thermischen Eigenschaften
auf den Fahrzeuginnenraum beschränkt bleiben. Zukünftig werden auch
hochbitratige, passiv verzweigte Datennetze benötigt, die im Temperaturbereich
bis zu 125 ◦ C einsetzbar sind. Dazu werden zur Zeit intensiv
Dickkernglasfasersysteme in Kombination mit vertikal-emittierenden IR-
Laserdioden untersucht und entwickelt. Der Vortrag gibt einen Überblick
über die Systemanforderungen im Automobil, zeigt den Stand der Technik
optischer Datenübertragungssysteme und deren Komponenten auf
und stellt neuartige skalierbare optische Datennetze für zukünftige Automobilanwendungen
vor.

Ausschuss Industrie und Wirtschaft Donnerstag
AIW 4 Strahlquellen
Zeit: Donnerstag 15:15–16:15 Raum: H 17
AIW 4.1 Do 15:15 H 17
Opto-Halbleiter - Lichtquellen der Zukunft — •Norbert Stath
— OSRAM Opto Semiconductors GmbH, Regensburg
Durch die Erforschung neuer Materialien und den Einsatz modernster
Fertigungstechniken haben die Opto-Halbleiter in den letzten
zehn Jahren mit zahllosen Innovationen eine stürmische Entwicklung
zurückgelegt. Leuchtdioden (LED) und Halbleiterlaser haben sich mittlerweile
zu beachtlichen Lichtquellen entwickelt, die durch ihre Systemvorteile
zunehmend neue Anwendungsfelder erobern. Die Potentiale zur
Steigerung der Lichtausbeute und zur Erhöhung der Lichtmengen sind
bei weitem nicht ausgeschöpft, so dass sich dieser Trend auch über die
nächsten Jahre bei zweistelligen Zuwachsraten fortsetzen wird. Anhand
von Innovationsbeispielen werden die technologischen Fortschritte bei
den Opto-Halbleitern erläutert und die Verbesserungsmöglichkeiten diskutiert.
Es werden aktuelle und zukünftige Anwendungsbeispiele für LED
und Laser zur Beleuchtung und zur Visualisierung von Informationen in
den Bereichen Automobil und Kommunikation dargestellt.
AIW 4.2 Do 15:45 H 17
Lasermikromanipulation und optische Pinzette in Biologie und
Medizin — •Andrea Sigl — P.A.L.M Microlaser-Technologies AG
Laser, die in ein Mikroskop eingekoppelt werden, verändern das rein
AIW 5 Ausblick
zur Beobachtung geeignete Gerät in ein einzigartiges Werkzeug für die
Mikromanipulation. Probenvorbereitung in reinster Form ist eine der
spannendsten Aufgaben in der modernen molekularen Biologie und Medizin.
Die einzigartige Technik der Laser-Mikrodissektion und des ” Laser
Pressure Catapulting“ (LMPC) ermöglicht ein zuverlässiges Gewinnen
von ausgewählten Zellen ohne mechanischen Kontakt und ohne die Gefahr
einer Kontamination mit unerwünschtem Probenmaterial. Es wird
ausschließlich die Kraft des fokussierten Laserstrahls benützt, um ausgewählte
Proben von einem Objektträger oder von einer lebenden Zellkultur
auszuwählen, auszuschneiden und direkt in eine geeignete Auffangvorrichtung
zu katapultieren. Diese kontaktfreie Methode garantiert
reinstes und homogenes Probenmaterial, eine Voraussetzung für aussagekräftige
genomische oder proteomische Untersuchungen. Bei dieser Technik
findet weder ein Hitze-Übertrag in das Probenmaterial statt, noch
wirkt sich die eingesetzte Laserwellenlänge auf die biologische Information
der Bio-Moleküle, wie DNA, RNA oder Proteine negativ aus. LMPC
ist eine einzigartige Methode, um Proben aus morphologisch definierter
Herkunft für weitere molekularbiologische Untersuchungen zu gewinnen
oder sogar einzelne lebende Zellen zu entnehmen, weiter zu kultivieren
und zu klonieren. Zusätzlich ermöglicht der PALM r○ MicroBeam die Microinjektion
von Wirkstoffen oder genetischem Material in lebende Zellen,
die nach diesem Prozess mittels der LMPC einzeln entnommen werden
können.
Zeit: Donnerstag 16:15–16:55 Raum: H 17
AIW 5.1 Do 16:15 H 17
Optische Technologien - Potenziale und Perspektiven — •Frank
Bitte — PhotonAix e.V. Aachen
Optische Technologien sind bereits heute wichtige Querschnitts- und
Schlüsseltechnologien, die mit dem Photon als Innovationstreiber ein
erhebliches und z. T. noch ungenutztes Potential zum Nutzen der
Wirtschaft und der Gesellschaft haben. Optische Technologien finden
sich heute in einer Vielzahl verschiedener Fachdisziplinen und Spezialgebiete
(z.B. in den Bereichen Medizin, Fertigungstechnik, Kommu-
AIW 6 Podiumsdiskussion
nikation, Beleuchtung). Sie bieten enorme Chancen für weitere innovative
Anwendungen in den unterschiedlichsten Wirtschaftsbranchen und
gesellschaftlichen Bereichen. Die Erwartungen an diese Technologie sind
so hoch, dass schon jetzt von dem gerade begonnenen 21. Jahrhundert
vielfach als ” Jahrhundert des Photons“ gesprochen wird. Woran das liegt,
welche atemberaubenden Anwendungen vorstellbar sind und welche Perspektiven
sich ergeben wird ebenso beleuchtet wie ein Rückblick und die
wirtschaftliche Bedeutung dieser wichtigen Technologie.
Zeit: Donnerstag 17:00–18:00 Raum: H 17
Gruppenbericht AIW 6.1 Do 17:00 H 17
Podiumsdiskussion — •Frank Bitte 1 , Lutz Schröter 2 , Horst
Sickinger 3 , Udo Weigelt 4 und andere 5 — 1 PhotonAix, Aachen —
2 AutoVision GmbH, Wolfsburg — 3 Bayern-Photonics — 4 Grünecker &
Koll., München — 5 (steht noch nicht fest)
Photonik Quo Vadis ?

Arbeitskreis Biologische Physik Tagesübersichten
BIOLOGISCHE PHYSIK (AKB)
Der 2003 ins Leben gerufene Arbeitskreis Biologische Physik versteht sich als Diskussionsforum und Fachvertretung der
Biophysik, der Physik weicher kondensierter Materie und der biophysikalischen Chemie innerhalb der DPG. Durch den
Zusammenschluss der in diesen Fachgebieten arbeitenden Wissenschaftlern/innen sollen Diskussion und Kooperation untereinander,
sowie eine einheitliche Vertretung nach außen gefördert werden. Alle auf diesen Gebieten arbeitenden Forscher/innen
sowie interessierte Studenten/innen sind aufgerufen, durch Beitritt und Mitwirkung im Arbeitskreis Biologische Physik zur
Weiterentwicklung und Stärkung der biologischen Physik als eigenständiger Fachbereich der physikalischen Wissenschaften
beizutragen. (http://www.biologische-physik.de/)
Hauptvorträge
Prof. Dr. Erich Sackmann
Physik-Department E 22
Technische Universität
James-Franck-Str. 1
85748 Garching
E-Mail: sackmann@ph.tum.de
Prof. Dr. Erwin Frey
Abteilung Theorie
Hahn-Meitner-Institut
Glienicker Strasse 100
14109 Berlin
E-Mail: frey@hmi.de
Prof. Dr. Axel Haase
Universität Würzburg
Experimentelle Physik V
Am Hubland
97074 Würzburg
E-Mail: Haase@physik.uni-wuerzburg.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsaal H40)
AKB 10.1 Mo 09:30 (H40) Micromechanics of Biopolymer Networks and Shells , Christoph F. Schmidt,
Maryam Atakhorrami, Gijsberta H. Koenderink, Pedro J. de Pablo, Iwan A.T.
Schaap, Irena L. Ivanovska, Gijs J.L. Wuite, Frederick C. MacKintosh
AKB 10.2 Mo 10:00 (H40) Microrheology of Actin Networks, Andreas Bausch
AKB 10.3 Mo 10:30 (H40) The Cytoskeleton: A Model System for Stiff Polymers, Erwin Frey
AKB 10.4 Mo 11:00 (H40) Models of Biological Fiber Systems, Camilla Mohrdieck, Eduard Arzt
AKB 11.1 Mo 12:00 (H40) Active Biomimetic Systems, Reinhard Lipowsky
AKB 11.2 Mo 12:30 (H40) Membranes and Active Gels, Hans-Günther Döbereiner
AKB 12.1 Mo 14:30 (H40) Active Polymer Networks in Biological Cells, Josef Käs, Claudia Brunner,
Jochen Guck, Falk Wottawah, Stefan Schinkinger, Karla Mueller, Timo Betz, Bjoern
Stuhrmann, Daniel Koch, Allen Ehrlicher, Michael Goegler, David Smith

Arbeitskreis Biologische Physik Tagesübersichten
AKB 12.2 Mo 15:00 (H40) Dynamic Phenomena and Force Generation in Cells, Frank Jülicher
AKB 12.3 Mo 15:30 (H40) Symmetriebrechung in einem mulitzellulären System am Besipiel der Hydra,
Albrecht Ott, Jordi Soriano, Cyril Colombo
AKB 12.4 Mo 16:00 (H40) Investigating Cell Division and Cell Protrusion by AFM,
Manfred Radmacher
AKB 13.1 Mo 17:00 (H40) Membranes with Rotating Motors, Peter Lenz
AKB 13.2 Mo 17:30 (H40) Models for Pattern Formation in Cell Biology, Walter Zimmermann
AKB 20.1 Di 09:30 (H40) Physics of DNA Compaction into Chromatin, Helmut Schiessel
AKB 20.2 Di 10:00 (H40) Structure and Dynamics of DNA Nanoparticles, Joachim Rädler
AKB 20.3 Di 10:30 (H40) Electronic Detection of DNA on Transistor Arrays, Ulrich Bockelmann,
François Pouthas, Cedric Gentil, Denis Cote
AKB 21.1 Di 11:30 (H40) Chemische Kinetik einzelner spezifischer Bindungen, Rudolf Merkel, Melanie
Nguyen-Duong
AKB 21.2 Di 12:00 (H40) Forces acting on Biological Model Systems, Udo Seifert
AKB 21.3 Di 12:30 (H40) Cell Organization in Soft Media due to Active Mechanosensing,
Ulrich Schwarz
AKB 22.1 Di 14:00 (H40) A Biophysical View of Molecular Recognition, Dario Anselmetti
AKB 22.2 Di 14:30 (H40) Mechanical Single Molecule Experiments in the Thermal Energy Regime,
Ernst-Ludwig Florin
AKB 22.3 Di 15:00 (H40) Labeling of Cells with Quantum Dots, Wolfgang Parak
AKB 22.4 Di 15:30 (H40) Detecting and Manipulating Single Molecules in the Fluid Phase,
Petra Schwille
AKB 23.1 Di 16:30 (H40) Microscopy and Spectroscopy on Single Membrane Proteins,
Jörg Wrachtrup, Carsten Tietz, Margarita Khazarchyan, Thews Elmar
AKB 23.2 Di 17:00 (H40) X-ray Scattering Studies of self-assembled Lipid Protein Membranes,
Tim Salditt
AKB 23.3 Di 17:30 (H40) Protein Micropatterns in Supported Lipid Membranes, Motomu Tanaka
AKB 30.1 Mi 14:30 (H40) Hierarchical Structure and Mechanical Function of Biological Materials,
Peter Fratzl
AKB 30.2 Mi 15:00 (H40) Bioelektronische Hybride, Andreas Offenhäusser
AKB 30.3 Mi 15:30 (H40) Micro- and Nanolithographic Tools for Designing Biophysical Models of
Cell Adhesion and Mechanics, Joachim Spatz
AKB 30.4 Mi 16:00 (H40) Feeling for Cells with Light, Jochen Guck, Falk Wottawah, Kort Travis, Stefan
Schinkinger, Frank Sauer, Bryan Lincoln, Susanne Ebert
AKB 31.1 Mi 16:30 (H40) NMR Tomography, Peter Jakob
AKB 40.1 Do 14:30 (H40) Structure and Evolution of bio-molecular Networks, Michael Lässig
AKB 40.2 Do 15:00 (H40) Dynamics and Evolution of Networks: From the Genome to Ecosystems,
Barbara Drossel
AKB 40.3 Do 15:30 (H40) Evolution of a Genetic Switch in a Fluctuating Environment,
Ulrich Gerland, Terence Hwa
AKB 40.4 Do 16:00 (H40) Proteins: Structure, Function, and Evolution, Markus Porto, Ugo Bastolla,
H. Eduardo Roman, Michele Vendruscolo
AKB 41.1 Do 17:00 (H40) Identification of Sensory Transduction Chains in vivo, Andreas Herz, Tim
Gollisch
AKB 41.2 Do 17:30 (H40) Intracellular Ca 2+ Dynamics , Martin Falcke
Fachsitzungen
AKB 10 Cytoskeleton and Polymer Networks Mo 09:30–11:30 H40 AKB 10.1–10.4
AKB 11 Active Biomimetic Systems and Gels Mo 12:00–13:00 H40 AKB 11.1–11.2
AKB 12 Active Systems: Complex Cellular Processes Mo 14:30–16:30 H40 AKB 12.1–12.4
AKB 13 Active Systems: Structure and Pattern Formation Mo 17:00–18:00 H40 AKB 13.1–13.2
AKB 20 Physics of DNA Di 09:30–11:00 H40 AKB 20.1–20.3
AKB 21 Bioadhesion and Molecular Forces Di 11:30–13:00 H40 AKB 21.1–21.3
AKB 22 Single Molecule Methods Di 14:00–16:00 H40 AKB 22.1–22.4
AKB 23 Membranes Di 16:30–18:00 H40 AKB 23.1–23.3
AKB 30 Biomaterials and Bioengineering Mi 14:30–16:30 H40 AKB 30.1–30.4
AKB 31 Investigations of Biological Structures Mi 16:30–17:00 H40 AKB 31.1–31.1

Arbeitskreis Biologische Physik Tagesübersichten
AKB 32 Post-deadline Talks Mi 17:00–19:00 H40 AKB 32.1–32.1
AKB 40 Evolution and Complex Systems Do 14:30–16:30 H40 AKB 40.1–40.4
AKB 41 Cell Signaling Do 17:00–18:00 H40 AKB 41.1–41.2
AKB 50 Poster Session ”Biological Physics” Fr 10:30–13:00 B AKB 50.1–50.132
Mitgliederversammlung des Fachverbands Arbeitskreis Biologische Physik
Do 19:00–20:00 H40
Allgemeine Diskussion
Planung 2004 und 2005

Arbeitskreis Biologische Physik Montag
Fachsitzungen
– Hauptvorträge und Posterbeiträge –
AKB 10 Cytoskeleton and Polymer Networks
Zeit: Montag 09:30–11:30 Raum: H40
Hauptvortrag AKB 10.1 Mo 09:30 H40
Micromechanics of Biopolymer Networks and Shells —
•Christoph F. Schmidt 1 , Maryam Atakhorrami 1 , Gijsberta
H. Koenderink 1 , Pedro J. de Pablo 2 , Iwan A.T. Schaap 1 ,
Irena L. Ivanovska 1 , Gijs J.L. Wuite 1 , and Frederick C.
MacKintosh 1 — 1 Vrije Universiteit Amsterdam, Dept. Physics, De
Boelelaan 1081, — 2 Universidad Autonoma de Madrid, Departamento
de Fisica de la
Polymeric macromolecular assemblies play crucial roles in biology, from
DNA to the cytoskeleton or the cell membrane. We are generally interested
in the mechanical physical properties of such structures and in
their interactions with force generating motor proteins. I will report here
on measurements of the viscoelastic properties of model 3D actin networks
by microrheology and on measurements of the elastic properties
of two types of 2D-crystalline protein shells, microtubules and bacteriophage
capsids, probed by indentation with a scanning force microscope.
Actin networks are determining cell elastic response and we have probed
their complex viscoelastic response over a large range of length and time
scales, under a variety of conditions approaching those found in cells.
Both, microtubules and viral capsids are 2D protein shells and we found
linear elastic regimes that can be described by thin-shell theory and finite
element methods. We also found non-linear regimes and catastrophic collapse
under large loads. The mechanical response of these protein shells
at the nanometer scale shows simultaneously aspects of continuum elasticity,
as well as molecular graininess, particularly in their non-linear
behavior.
Hauptvortrag AKB 10.2 Mo 10:00 H40
Microrheology of Actin Networks — •Andreas Bausch — Lehrstuhl
fuer Biophysik E22, TU Muenchen
The actin cytoskeleton is of outstanding importance for the proper
functioning of cells. In order to study the underlying physical properties
of the actin polymer networks it is important to determine the mechanical
properties of these semiflexible polymer networks in vitro. Here, we measure
the viscoelasticity of entangled F-actin over length scales between
1 and 100 µm using one- and two-particle microrheology and directly
identify two distinct microscopic contributions to the elasticity. Filament
entanglements lead to a frequency-independent elastic modulus over an
extended frequency range of 0.01 to 30 rad/sec; this is probed only with
one-particle microrheology. Longitudinal fluctuations of the filaments increase
the elastic modulus between 0.1 and 30 rad/sec at length scales
larger than the filament persistence length; this is probed by two particle
microrheology.
AKB 11 Active Biomimetic Systems and Gels
Hauptvortrag AKB 10.3 Mo 10:30 H40
The Cytoskeleton: A Model System for Stiff Polymers — •Erwin
Frey — Abteilung Theorie, Hahn-Meitner-Institut, Glienicker Strasse
100, D-14109 Berlin
The structure responsible for the extraordinary mechanical properties
of cells is the cytoskeleton, a rigid yet flexible and dynamic network
of protein fibers, combined with a variety of associated regulatory proteins,
whose tasks range from passive cross-linking and active transport
to the regulation of biochemical processes. Due to their enormous stiffness,
the physics of cytoskeletal filaments is fundamentally different from
the physics of synthetic polymers like polyethylene. It is determined by
a subtle interplay between entropic and energetic contributions. Over
the past years novel interesting concepts of polymer physics have been
established. We will discuss the statistical mechanics and dynamics of
single filaments and show how the theoretical predictions can be confirmed
by fluorescence microscopy on single F-actin filaments. Building
on the physics of single filaments we will give a detailed theoretical model
for the viscoelasticity of solutions and the complex micro-mechanics of
crosslinked networks.
Hauptvortrag AKB 10.4 Mo 11:00 H40
Models of Biological Fiber Systems — •Camilla Mohrdieck
and Eduard Arzt — Max-Planck-Institut für Metallforschung, Heisenbergstr.
3, 70569 Stuttgart
Biological fiber systems have to be able to sustain large loads but they
must also be capable of undergoing large deformations, depending on
which environmental conditions they are subject to. Many fiber systems
meet these needs by responding in a nonlinear way to external loads.
Key to this nonlinearity is the crosslinking of fibers into a meshwork
and in some cases also a prestress in the fibers. To relate the influence
of topology and prestress to the mechanical stability and flexibility of
a fiber system, we perform computer simulations in which fiber systems
are iteratively deformed by applying forces to their nodal points. To this
end, we construct fiber sytems that reflect characteristic features of their
biological counterparts as for example the icosahedral capsids of some
viruses or the spherical actin cortex as it can be observed in quiescent
cells. In our study we combine large deflection analysis with a determination
of the topological properties such as the connectivity of the
meshwork, states of self stress and inextensional modes of deformation.
This allows to evaluate the mechanical properties of the fiber system as
well as to follow the evolution of its intrinsic structural properties as the
whole system deforms under a given load.
Zeit: Montag 12:00–13:00 Raum: H40
Hauptvortrag AKB 11.1 Mo 12:00 H40
Active Biomimetic Systems — •Reinhard Lipowsky — MPI für
Kolloid und Grenzflächenforschung, 14424 Potsdam
Biological systems have the ability to reorganize and to reconstruct
their spatial structure on the nano- and microscale. This capability is
based on molecular assemblies which can transform chemical (free) energy
into mechanical work. The simplest nanomachines of this type are filaments,
which grow by self-assembly, and molecular motors, which move
along such filaments. These active nanostructures generate force, provide
transport of cargo, and form biomimetic scaffolds. The talk will discuss
the basic phasics of these processes and their potential applications.
Hauptvortrag AKB 11.2 Mo 12:30 H40
Membranes and Active Gels — •Hans-Günther Döbereiner —
Departments of Biology & Physics, Columbia University, New York, NY
10027, USA
During the last decade, Biological Physics has become a major research
field. Especially, the fascinating physics of membranes continues to drive
forward our quantitative understanding of cellular behavior. Giant vesicles
[1] are an important tool to monitor the properties of biomembranes
[2,3] and soft matter in general [4]. Recently, active gels have drawn a lot
of attention. Combining the physics of polymers and molecular motors
to model biological phenotype [5] will require new concepts. We propose
to view cell spreading and migration as a sequence of dynamic phase
transitions of active gels and their regulatory networks.
[1] H.-G. Döbereiner, in Giant Vesicles, Perspectives in Supramolecular
Chemistry 6, 150, Eds. P.L. Luisi and P. Walde, Wiley & Sons (2000).

Arbeitskreis Biologische Physik Montag
[2] H.-G. Döbereiner et al., Phys. Rev. Lett. 91, 048301 (2003).
[3] K.A. Riske and H.-G. Döbereiner, Biophys. J. 85 2352-2362 (2003).
[4] C.K. Haluska, W. Gó´zd´z, H.-G. Döbereiner, S. Förster, G. Gompper,
Phys. Rev. Lett. 89, 238302 (2002).
[5] B.J. Dubin-Thaler, G. Giannone, H.-G. Döbereiner, M.P Sheetz, Bio-
phys. J. (2004), in press.
AKB 12 Active Systems: Complex Cellular Processes
Zeit: Montag 14:30–16:30 Raum: H40
Hauptvortrag AKB 12.1 Mo 14:30 H40
Active Polymer Networks in Biological Cells — •Josef Käs,
Claudia Brunner, Jochen Guck, Falk Wottawah, Stefan
Schinkinger, Karla Mueller, Timo Betz, Bjoern Stuhrmann,
Daniel Koch, Allen Ehrlicher, Michael Goegler, and David
Smith — Fakultaet fuer Physik und Geowissenschaften, Universitaet
Leipzig
Cells signify the next fundamental challenge to soft matter physics
since they require establishing the physics of networks of active nanoelements.
All eukaryotic cells depend in their internal structure and organization
on a highly dynamic and active polymer network, the cytoskeleton.
Our results demonstrate that switchable nano-sized motors
can regulate the structural strength and assembly of such polymer networks.
These active mechano-sensitive networks generate motion driven
by nano-muscles and polymerization. Scanning force microscopy allows
us a precise spatial characterization of the resulting active forces. Lasers
provide optomolecular control over these active motions. In neurons weak
optical gradient forces can determine the growing nerve’s leading edge’s
direction, speed, branching, and contact to other neurons. Moreover,
these intracellular networks are closely related to cellular differentiation
and thus, cell elasticity measurements with our new laser trap, the optical
cell stretcher, provide an unparalleled cell marker distinguishing
malignant cells as well as stem cells from other cells.
Hauptvortrag AKB 12.2 Mo 15:00 H40
Dynamic Phenomena and Force Generation in Cells — •Frank
Jülicher — Max-Planck Institut für Physik komplexer Systeme,
Nöthnitzerstr. 38, 01187 Dresden
Living cells exhibit a remarkable variety of active behaviors. Material
is transported within the cell, cells divide and a lot of cells can swim or
crawl along substrates. The molecular basis of such behaviors are highly
specialized protein molecules which transduce the chemical energy of a
fuel molecule, ATP, to mechanical work and motion. A prototype system
are molecular motors of the cytoskeleton which generate forces and motion
along linear filaments. The activity on the molecular level leads to
complex dynamic behaviors as a result of the interaction of many interacting
components. The cytoskeleton on larger scales thus represents a
gel-like soft material which is far from thermal equiligrium due to internal
active processes. The physical properties and the dynamics of such
active gels can be described by a hydrodynamic theory. These concepts
can be used to obtain a phenomenological descriptoin of dynamic cellular
phenomena such as cell locomotion.
Hauptvortrag AKB 12.3 Mo 15:30 H40
Symmetriebrechung in einem mulitzellulären System am Besipiel
der Hydra — •Albrecht Ott 1 , Jordi Soriano 1 und Cyril
Colombo 2 — 1 Universität Bayreuth, EP1, NW1, 95440 Bayreuth, Germany
— 2 Institut Curie, Paris, France
Die Hydra hat erstaunliche Regenerationsfähigkeiten. Sie kann sich
nach Dissoziation in einzelne Zellen aus einem ungeordneten Zellball neu
formieren. Dabei bildet sie zunächst einen Zellball, dann wird die Achse
des Tieres festgelegt. Wir untersuchen diesen Prozess der Achsenfindung.
Wir zeigen das eine wohlregulierte mechanische Pumpbewegung des Balles
offenbar Information über die Achsenfindung überträgt. Unsere Beobachtung
ergänzt molekularbiologische Studien, die auf die Wichtigkeit
der Adhesionsregulierung hinweisen. Sie erklärt ebenfalls, wie eine kleine
Gruppe von fünf bis zehn irreversibel differenzierten Zellen den Prozess
der Achsenfindung entscheiden und mitteilen kann. Wir untersuchen
die Expression des Gens ks1 durch insitu Hybridisierung. Ks1 wird als
repräsentativ für das genetische Kopfprogramm der Hydra angesehen.
Erste Ergebnisse weisen auf ein fluktuierendes Expressionsmuster dieses
Gens auf dem Zellball hin, die Grössenverteilung skaliert. Wir etablieren
einen Zusammenhang mit der kürzlich in der Hydra nachgewiesenen
WNT-Signalkaskade her. Wir schlagen vor das genetische Fluktuationen
die Symmetrie brechen.
Hauptvortrag AKB 12.4 Mo 16:00 H40
Investigating Cell Division and Cell Protrusion by AFM —
•Manfred Radmacher — Institut für Biophysik, Universität Bremen
We have used an AFM to investigate the mechanical properties of
the cells cytoskeleton during dynamical processes like cell migration and
division. Actin is in the case of fibroblasts cells the major cellular components
responsible for the cellular stiffness. Stiffness is increased further by
myosin II creating cortical tension. When myosin function is diminished
by inhibiting the myosin light chain kinase a decrease in stiffness can be
observed. This is congruent with importance of both actin and myosin in
processes like cell migration and cell division. In cell division for instance
a rapid and large increase in stiffness is observed in the region where the
cleavage furrow will form. This is congruent with results from cellular
biology and supports the equatorial stiffening model of cytokinesis which
has been one out of several models suggested.
AKB 13 Active Systems: Structure and Pattern Formation
Zeit: Montag 17:00–18:00 Raum: H40
Hauptvortrag AKB 13.1 Mo 17:00 H40
Membranes with Rotating Motors — •Peter Lenz — Fachbereich
Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
We study collections of rotatory motors confined to 2-dimensional manifolds.
These systems show a non-trivial collective behavior since the rotational
motion leads to a repulsive hydrodynamic interaction between
motors. While for high rotation speed motors might exhibit crystalline
order, they form at low speed a disordered phase where diffusion is enhanced
by velocity fluctuations. These effects should be experimentally
observable for motors driven by external fields and for dipolar biological
motors embedded into lipid membranes in a viscoelastic solvent.
Hauptvortrag AKB 13.2 Mo 17:30 H40
Models for Pattern Formation in Cell Biology — •Walter Zimmermann
— Theoretische Physik Universität des Saarlandes, 66041
Saarbrücken
During polymerization of the biological filaments microtubules or
actin, during filament transport by motor proteins or for interacting ionchannels
in biomembranes various types of spatiotemporal patterns occur.
Compared to the huge variety of patterns occuring in the unanimate
world, for these examples often conservation laws lead to new universality
classes of patterns und with rather surprising patterns. The effects of the
excluded volume interaction between filaments and the related nematic
ordering lead also additional pattern formation processes. An overview
about these effects and models will be given.

Arbeitskreis Biologische Physik Dienstag
AKB 20 Physics of DNA
Zeit: Dienstag 09:30–11:00 Raum: H40
Hauptvortrag AKB 20.1 Di 09:30 H40
Physics of DNA Compaction into Chromatin — •Helmut
Schiessel — Max-Planck-Institute for Polymer Research, Theory
Group, D 55021 Mainz
Chromatin is the dense complex between DNA and histone proteins
that occupies the nuclei of plant and animal cells. At the lowest level the
DNA is wrapped around protein spools forming so-called nucleosomes.
The resulting string of nucleosomes is folded into the chromatin fiber. I
will present theoretical models that allow to interpret recent experiments
on the stretching of single nucleosomes and of chromatin fibers.
Our findings on single nucleosomes suggest a mechanism by which the
nucleosome combines two seemingly contradictory features: being very
stable and having its wrapped DNA highly accessible at the same time.
Our results on fiber stretching show the delicate interplay between soft
elasticity due to the DNA linker backbone and stiffening due to internucleosomal
contacts – directing the folding of fibers at the next level of
DNA compaction.
cf. also the review: H. Schiessel, J. Phys.: Condens. Matter 15 (2003)
R699-R774
AKB 21 Bioadhesion and Molecular Forces
Hauptvortrag AKB 20.2 Di 10:00 H40
Structure and Dynamics of DNA Nanoparticles — •Joachim
Rädler — Geschwister-Scholl-Platz 1, D-80539 München
e report on various strategies to assemble cationic lipid-DNA and
polypeptide DNA nanocomplexes. For application in gene therapy wellcontrolled
single- plasmid particles are formed from dilute solutions of
DNA and oppositely charged macromolecules. The internal structure,
size and transport properties of the complexes are characterized using
small angle X-ray scattering, fluorescence microscopy and fluorescence
correlation spectroscopy.
Hauptvortrag AKB 20.3 Di 10:30 H40
Electronic Detection of DNA on Transistor Arrays — •Ulrich
Bockelmann, François Pouthas, Cedric Gentil, and Denis
Cote — LPMC Ecole Normale Supérieure, Paris, France
This talk will focus on our research on electronic detection of unlabeled
biomolecules. Field effect measurements, based on integrated silicon transistor
arrays, are used to detect DNA bound to a solid/liquid interface.
The planar configuration is compatible with DNA chip technology and
with microfluidics approaches.
Zeit: Dienstag 11:30–13:00 Raum: H40
Hauptvortrag AKB 21.1 Di 11:30 H40
Chemische Kinetik einzelner spezifischer Bindungen — •Rudolf
Merkel 1 und Melanie Nguyen-Duong 2 — 1 Institut für Schichten
und Grenzflächen, Forschungszentrum Jülich — 2 Lehrstuhl für Biophysik
E22 der Technischen Universität München
Bioadhäsion ist ein physiologischer Prozess von großer Bedeutung. Der
zugrunde liegende Mechanismus ist die spezifische Erkennung und Bindung
zwischen komplementären Zelladhäsionsmolekülen, welche biologische
Strukturen (z.B. zwei Zellen) mechanisch verbinden. Erst in den
letzten Jahren wurden mechanische Experimente an einzelnen solchen
Bindungen möglich. Hierbei zeigte sich überraschenderweise, dass die Dissoziationsrate
einzelner Bindungen, welche mikroskopische Körper verbinden,
ungefähr 100 mal größer ist im Vergleich zu Bindungen zwischen
denselben Molekülen in Lösung. Wir präsentieren hier eine mögliche Erklärung
dieses Phänomens sowie entsprechende experimentelle Befunde.
Hauptvortrag AKB 21.2 Di 12:00 H40
Forces acting on Biological Model Systems — •Udo Seifert — II.
Institut für Theoretische Physik, Universität Stuttgart, 70550 Stuttgart
An overview on our recent theoretical work about the effects of forces
on three biological model systems will be given. (i) Forces acting on adhering
vesicles lead to significant shape changes thereby inducing detachment
of bound vesicles either by smooth deformations for weak adhesion
or tether formation for strong adhesion [1]. (ii) Time-dependent forces
AKB 22 Single Molecule Methods
acting on surfaces hold together by receptor/ligand pairs lead to rupture
depending on the loading rate. For slow loading rebinding events
become crucial [2]. (iii) For forces acting on a single biopolymer with two
equilibrium configurations (like folded/ unfolded) the equilibrium energy
landscape along the pulling co-ordinate can be reconstructed even from
non-equilibrium experiment data by using the Jarzynksi relation.
[1] A. Smith, E. Sackmann and U. Seifert, Europhys. Lett. 64, 281,
2003.
[2] U. Seifert, Phys. Rev. Lett. 84, 2750, 2000; Europhys. Lett. 58, 792,
2002.
[3] O. Braun, A. Hanke and U. Seifert, in preparation.
Hauptvortrag AKB 21.3 Di 12:30 H40
Cell Organization in Soft Media due to Active Mechanosensing
— •Ulrich Schwarz — Max Planck Institute of Colloids and Interfaces,
Golm
Adhering cells actively probe the mechanical properties of their environment
in order to position and orient themselves. In an elastically
anisotropic environment, cells prefer to orient in the direction of maximal
effective stiffness. By converting this observation into an extremum
principle in linear elasticity theory, we can predict cell organization in
soft media in excellent agreement with experiments with fibroblasts on
elastic substrates and in hydrogels. We also discuss how effective cell behaviour
might follow from the stochastic dynamics of cell-matrix contacts
under force.
Zeit: Dienstag 14:00–16:00 Raum: H40
Hauptvortrag AKB 22.1 Di 14:00 H40
A Biophysical View of Molecular Recognition — •Dario Anselmetti
—
Mechanical unbinding experiments with single molecules give insights
into the physico-chemical fundamentals and mechanisms of biomolecular
recognition and specific interaction. In biology, this is often associated
with complex processes such as replication, transcription/translation, or
gene regulation. After an introduction, which briefly explains our experimental
methods (single molecule force spectroscopy with AFM and
optical tweezers), key findings between mechanical single-molecule experiments
and biomolecular ensemble experiments are summarized. Latest
results on transcriptional proteins and DNA, synthetically produced
peptide analoga and DNA, as well as on artificial recognition elements
(supramolecular guest-host systems) will be presented and discussed
within the framework of our Nanobiology activities.
Hauptvortrag AKB 22.2 Di 14:30 H40
Mechanical Single Molecule Experiments in the Thermal Energy
Regime — •Ernst-Ludwig Florin — EMBL, Cell Biology and
Biophysics Programme, Meyerhofstrasse 1, D-69117 Heidelberg
Hauptvortrag AKB 22.3 Di 15:00 H40
Labeling of Cells with Quantum Dots — •Wolfgang Parak —
Center for Nanoscience, LMU Muenchen, Muenchen, Germany
Colloidal quantum dots are semiconductor nanocrystals well dispersed
in a solvent. The optical properties of quantum dots, in particular the

Arbeitskreis Biologische Physik Dienstag
wavelength of their fluorescence, depend strongly on their size. Because
of their reduced tendency to photobleach, colloidal quantum dots are interesting
fluorescence probes for all types of labeling studies. We will give
an overview on how quantum dots so far have been used in cell biology.
In particular we will discuss the biological relevant properties of quantum
dots and focus on three topics: Labeling of cellular structures and receptors
with quantum dots, incorporation of quantum dots by living cells,
and the tracking of the path and the fate of individual cells by quantum
dot labels.
Hauptvortrag AKB 22.4 Di 15:30 H40
Detecting and Manipulating Single Molecules in the Fluid
Phase — •Petra Schwille — TU Dresden, Institut f. Biophysik
Single molecule research has within the past ten years become a fascinating
new approach in nearly all branches of physical sciences, but
for the biosciences it bears particular relevance: The ”key players” on
AKB 23 Membranes
a molecular scale - proteins - are remarkably complex and variable
molecules, their functionality in cells and organelles is so subtle that they
are often referred to as ”molecular machines”. To study these elaborate
molecular systems, traditional methods that analyze a certain function by
averaging over large ensembles are sometimes not appropriate: Especially
in the living cell, where a multitude of complex processes are continuously
occurring on a molecular scale, ensemble methods are unable to
capture the underlying mechanisms in a satisfactory manner. Techniques
that allow to study the distribution, translocation, interactions and internal
dynamics of single biological working units, in many cases single
protein molecules or complexes, are therefore of particular importance to
the biosciences. We discuss novel developments and applications of single
molecule-based dynamic analysis of proteins and nucleic acids in the living
cell, and give perspectives for possible strategies to manipulate, sort
and select single molecules in the fluid phase.
Zeit: Dienstag 16:30–18:00 Raum: H40
Hauptvortrag AKB 23.1 Di 16:30 H40
Microscopy and Spectroscopy on Single Membrane Proteins —
•Jörg Wrachtrup, Carsten Tietz, Margarita Khazarchyan,
and Thews Elmar — Universität Stuttgart, 3. Physikalisches Institut
The membrane environment is of vital importance for the function
of most cellular receptors. Either stability requires the lipid bilayer or
receptor function is related to oligomerisation in the membrane. The
contribution will describe single-molecule studies of photoreceptors in
membranes under ambient conditions as well as low temperature. Life
cell studies with fluorescence correlation sprectroscopy and burst width
analysis reveals clustering of TNF receptors as well as details of the diffusion
behaviour of second messengers in the apoptotic signalling pathway.
Hauptvortrag AKB 23.2 Di 17:00 H40
X-ray Scattering Studies of self-assembled Lipid Protein Membranes
— •Tim Salditt — Experimentalphysik, Universität des Saarlandes,
D-66041 Saarbrücken
AKB 30 Biomaterials and Bioengineering
Hauptvortrag AKB 23.3 Di 17:30 H40
Protein Micropatterns in Supported Lipid Membranes —
•Motomu Tanaka — Biophysics Lab, Tech. Univ. Munich
The design of soft, compatible interfaces between solids and biological
materials is an interdisciplinary challenge for scientific and biotechnological
applications. Planar cell surface models can be designed by deposition
of lipid membranes on ultrathin polymer supports that play the role of
extracellular matrix and glycocalix. As physical models of cell surfaces,
several methods have been developed to fabricate micropatterns of proteins
in supported membranes, such as (i) accumulation of membraneassociated
proteins by electrophoresis and (ii) confinement of proteins
in membrane micropatterns. The first method utilizes fluid supported
membranes as a quasi-2D matrix to separate membrane proteins under
lateral electrical fields, while the second includes the micropatterning of
biocompatible polymer supports. Such strategies are promising for complimentary
coupling of bioorganic functional systems and semiconductor
devices by matching of the lateral dimensions of biofunctional micropatterns
and device arrays.
Zeit: Mittwoch 14:30–16:30 Raum: H40
Hauptvortrag AKB 30.1 Mi 14:30 H40
Hierarchical Structure and Mechanical Function of Biological
Materials — •Peter Fratzl — Max Planck Institute of Colloids and
Interfaces, Department of Biomaterials, D-14424 Potsdam
Natural materials, such as tendon, bone, dentin, wood or mollusc shell
are hierachically structured and functional adaptation occurs at all size
levels. The aim of the newly created Department of Biomaterials at the
Max-Planck-Institute of Colloids and Interfaces is, first, to study structure
- function relations and the principles of mechanical deformation
and adaptation at all the hierarchical levels in natural materials. The
major approaches are in-situ deformation experiments with synchrotron
radiation or environmental scanning electron microscopy, scanning probe
techniques to obtain simultaneous structural and mechanical information
at several size levels, as well as numerical simulation. Second, different
approaches (”biomimetics” and ”biotemplating”) are being pursued in
order to transfer the principles of hierachical structuring to the development
of new materials for various applications. Third, research on bone
and connective tissue is carried out with the objective to characterize
the effect of diseases (such as the ”brittle bone disease”, for instance) as
well as to study the consequence of osteoporosis treatments on the bone
material quality.
Hauptvortrag AKB 30.2 Mi 15:00 H40
Bioelektronische Hybride — •Andreas Offenhäusser — Institut
f. Schichten und Grenzflächen (ISG-2), Forschungszentrum Jülich, 52425
Jülich
Unsere Forschungsaktivitäten konzentrieren sich auf die funktionelle
Kopplung biologischer Signalprozesse und Erkennungsreaktionen mit
mikro- und nanoelektronischen Halbleiterbauelementen. Hierbei werden
insbesondere folgende Systeme vorgestellt:
- Verwendung von Feldeffekt-Transistoren bei der Entwicklung eines
elektronischen DNA-Chips.
- Entwicklung von Ganzzell-Sensoren auf der Basis der Zell-Transistor-
Kopplung.
- Erzeugung lebender Nervenzell-Netzwerke zur Untersuchung der neuronalen
Informationverarbeitung.
Hauptvortrag AKB 30.3 Mi 15:30 H40
Micro- and Nanolithographic Tools for Designing Biophysical
Models of Cell Adhesion and Mechanics — •Joachim Spatz —
University of Heidelberg, Inst. Physical Chemistry, Biophysical Chemistry,
INF 253, 69120 Heidelberg
We investigate the dynamic regulation of adhesive contacts and of the
cytoskeleton architecture of cells in contact with novel nano- and microlithographic
materials, and its resultant influence on cellular activities
as well as clinical malfunctions in organism. In this context, we apply
new optical and mechanical techniques and develop new micro- and
nanostructured materials to perform experiments on living cells. We also
construct biomimetic models of protein networks with tuneable complexity
on nano- or microstructured platforms to untangle chemo-mechanical
properties of the cytoskeleton and the adhesion protein complex. In detail,
we will discuss (i) the development of nano- and microlithographic
interfaces by self-assembly and its biofunctionlisation, (ii) the activation
control of single integrin function of adherent cells by nanopatterned
adhesive interfaces, (iii) the biomimetic model design of the actin cortex
based on microfabricated pillar surfaces and dynamic holographic
optical tweezers, and (iv) a chemo-mechanical approach to understand
regulation of metastases formation of human cancer cells by cytoskeleton

Arbeitskreis Biologische Physik Mittwoch
architecture.
Hauptvortrag AKB 30.4 Mi 16:00 H40
Feeling for Cells with Light — •Jochen Guck, Falk Wottawah,
Kort Travis, Stefan Schinkinger, Frank Sauer, Bryan
Lincoln, and Susanne Ebert — Fakultät für Physik und Geowissenschaften,
Univeristät Leipzig
The relationship between the mechanical properties of cells and their
molecular architecture has been the focus of extensive research for
decades. Especially the cytoskeleton, an internal polymer network, determines
a cell’s mechanical strength and morphology. This cytoskeleton
evolves during the normal differentiation of cells, is involved in many
cellular functions, and is characteristically altered in many diseases, including
cancer. We can exploit this link between function and elasticity
to distinguish between different cells using an optical stretcher, a new
laser tool optimized to deform hundreds of single cells per hour by optically
induced surface forces. Optical deformability is sensitive enough
to monitor the subtle changes during the progression of individual human
breast epithelial cells from normal to cancerous and even metastatic
state. The surprisingly low numbers of cells required for this distinction
reflects the tight regulation of the cytoskeleton by the cell. This suggests
using optical deformability as an inherent cell marker for basic cell
biological investigation and diagnosis of disease.
AKB 31 Investigations of Biological Structures
Zeit: Mittwoch 16:30–17:00 Raum: H40
Hauptvortrag AKB 31.1 Mi 16:30 H40
NMR Tomography — •Peter Jakob — Julius-Maximilians-
Universität Würzburg, Lehrstuhl für Experimentelle Physik 5, Am
Hubland, D-97074 Würzburg
AKB 32 Post-deadline Talks
Zeit: Mittwoch 17:00–19:00 Raum: H40
AKB 32.1 Mi 17:00 H40
Platzhakter für post-deadline Vorträge — • —
AKB 40 Evolution and Complex Systems
Zeit: Donnerstag 14:30–16:30 Raum: H40
Hauptvortrag AKB 40.1 Do 14:30 H40
Structure and Evolution of bio-molecular Networks — •Michael
Lässig — Institut für theoretische Physik, Universität zu Köln, 50937
Köln
The genomes of higher organisms are highly collective systems with
multiple interactions between genes. These genetic networks are linked
to other levels of molecular information processing such as protein interaction
maps or metabolic networks. Their combinatorial complexity is
an essential characteristic of higher organisms, allowing a large number
of functional tasks to be performed by a limited number of genes. This
talk describes our current understanding of the structure and evolution
of molecular networks. How do we recognize modules related to specific
functions in large networks? How does nature evolve complex interaction
patterns and adapts them to fluctuating environments? These questions
lead to the statistical physics of bio-molecular networks and their nonequilibrium
dynamics.
Hauptvortrag AKB 40.2 Do 15:00 H40
Dynamics and Evolution of Networks: From the Genome to
Ecosystems — •Barbara Drossel — Institut für Festkörperphysik,
TU Darmstadt, Hochschulstr. 6, 64289 Darmstadt
This talk presents an overview of my research projects in the field of
genetic networks and foodwebs. The study of genetic network models
begins with Kauffman networks and aims at understanding the relation
between the structural network properties and the properties of its attractors.
The long-term goal is to model network evolution by including
biologically realistic features such as mutator genes, transpositions and
duplications. The main question addressed in the study of foodweb models
is the relation between the population dynamics and the structural
properties of foodwebs under long-term evolution. Our recent research
shows that only certain types of population dynamics allow the formation
and long-term persistence of complex webs.
Hauptvortrag AKB 40.3 Do 15:30 H40
Evolution of a Genetic Switch in a Fluctuating Environment
— •Ulrich Gerland 1 and Terence Hwa 2 — 1 Sektion Physik, Uni
München — 2 Department of Physics, UC San Diego
Gene regulation encompasses a variety of molecular processes which determine
the protein concentrations in cells and their signal dependence.
Perhaps the simplest regulatory unit (or ‘node’ in a genetic network) is
a genetic switch, which sets the transcription rate of a gene either to
‘high’ or ‘low’. Many genetic switches in bacteria respond to a chemical
‘inducer’ signaling the present state of a fluctuating environment.
Mechanically, there are two basic designs, which are both realized in
bacteria: either the transcription level is low by default and the inducer
activates a DNA-binding protein stimulating transcription, or the inducer
deactivates a DNA-binding protein repressing a high default level.
We formulate a theory to quantitate an old evolutionary argument that
attempts to rationalize the observed choice between these two designs
in bacteria. To this end, we are forced to consider explicitly the effects
of environmental fluctuations, which are usually neglected in standard
evolutionary models.
Hauptvortrag AKB 40.4 Do 16:00 H40
Proteins: Structure, Function, and Evolution — •Markus
Porto 1 , Ugo Bastolla 2 , H. Eduardo Roman 3 , and Michele
Vendruscolo 4 — 1 Institut für Theoretische Physik, Technische Universität
Dresden, 01062 Dresden, Germany — 2 Centro de Astrobiología
(INTA-CSIC), 28850 Torrejon de Ardoz, Spain — 3 Dipartimento di
Fisica and INFN, Università di Milano, Via Celoria 16, 20133 Milano,
Italy — 4 Department of Chemistry, University of Cambridge, Lensfield
Road, Cambridge CB2 1EW, UK
In my talk I will discuss very recent theoretical work related to the
evolution of proteins. The starting point is to understand the statistical
properties of neutral evolution of protein sequences under the requirement
that the native state remains thermodynamically stable. As a first
result, such study yields the rigidity profile (the amount of local conservation)
of a given protein fold, which indicates structural and functional
important places. The second central result is the observation of strongly
correlated fluctuations in the substitution rate and the resulting lack of
self-averaging for certain observables, which is important for instance for
bioinformatics applications. Thirdly, a relation between sequence based
quantities and protein structure is established, which might provide a
different route to protein structure prediction.

Arbeitskreis Biologische Physik Donnerstag
AKB 41 Cell Signaling
Zeit: Donnerstag 17:00–18:00 Raum: H40
Hauptvortrag AKB 41.1 Do 17:00 H40
Identification of Sensory Transduction Chains in vivo —
•Andreas Herz and Tim Gollisch — Institute for Theoretical
Biology, Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin
Every sensation begins with the conversion of a sensory stimulus into
the response of a receptor neuron. Typically, this involves a multi-step
sequence of multiple biophysical processes that cannot all be monitored
directly. Here we present a method that makes it possible to extract their
dynamical features by comparing different stimuli that cause the same
output, the only signal to be measured. Applied to auditory receptor
cells, this novel technique reveals sub-millisecond details of mechanosensory
signal processing and yields a quantitative four-step signal transduction
model. Owing to its simplicity and generality, the method is readily
applicable to a large variety of signal-processing systems.
Hauptvortrag AKB 41.2 Do 17:30 H40
Intracellular Ca 2+ Dynamics — •Martin Falcke — Hahn Meitner
Institut, SF5, Glienicker Str. 100, 14109 Berlin
AKB 50 Poster Session ”Biological Physics”
Ca 2+ is an important messenger in living cells. Intracellular Ca 2+ dynamics
is a pattern forming system showing a rich variety of phenomena.
The transition from a regime dominated by random local events to global
events like waves and oscillations can be observed. Fluorescent dyes
allow for observation of elemental events underlying global patterns at
the same time as the global pattern itself. That opens the unique possibility
to study the built up of global events from elemental random local
events. The transition from a fluctuation dominated regime to a more
deterministic behavior is accompanied by a transition from behavior determined
by spatial discreteness to a continuous medium. As a continuous
medium, intracellular Ca 2+ dynamics shows novel phenomena like e.g. a
gap of forbidden velocities in the dispersion relation. The talk gives an
introduction to Ca 2+ dynamics and its theoretical desription.
Zeit: Freitag 10:30–13:00 Raum: B
AKB 50.1 Fr 10:30 B
Spatial discreteness and stability of reaction-diffusion systems
— •Rüdiger Thul and Martin Falcke — Hahn-Meitner Institut,
Abteilung Theorie, Glienicker Strasse 100, 14109 Berlin
We present a novel approach to the dynamics of spatially discrete
reaction-diffusion equations. The approach addresses systems with active
regions on the submicrometer length scale arranged with distances
of a few micrometers. The size of the active region is determined by the
production of the diffusing substance. The linear stability analysis reveals
that due to spatial discreteness, diffusion becomes one of the major
determinants of the stability of the reaction dynamics. We illustrate this
new approach with Ca 2+ dynamics.
AKB 50.2 Fr 10:30 B
Modelling regulatory genetic system as random boolean network
— •Viktor Kaufman — AG Drossel, Hochschulstraße 6, 64289
Darmstadt
Recent results on the dynamical behaviour of critical random boolean
networks (RBN) have superseded those obtained more than 30 years ago.
There is now evidence that the mean attractor number and length grow
exponentially with the network size. This work contributes to the understanding
of those findings by means of examining the size and topology
of the relevant part of the network, using analytical arguments and computer
simulations.
AKB 50.3 Fr 10:30 B
Elektrische Stimulation von neuronalen Netzwerken über ein
strukturiertes Elektrodeninterface — •A. Reiher 1 , A. Krtschil 1 ,
S. Günther 1 , H. Witte 1 , A. Krost 1 , A. de Lima 2 , T. Opitz 2 ,
T. Voigt 2 , K. Kube 3 , V. Spravedlyvyy 3 , A. Herzog 3 und B.
Michaelis 3 — 1 Institut für Experimentelle Physik, OvG-Universität
Magdeburg — 2 Institut für Physiologie, OvG-Universität Magdeburg —
3 Institut für Elektronik, Signalverarbeitung und Kommunikationstechnik
(IESK), OvG-Universität Magdeburg, PF 4120, 39016 Magdeburg
Es ist bekannt, dass Nervenzellen aus dem Cortex von embryonalen
Ratten in vitro komplexe, neuronale Netzwerke ausbilden. Für dieses
System wurde ein in die Kultur integriertes Interface entwickelt, um eine
Kommunikation mit den Neuronen zu ermöglichen.
Dieses besteht aus einer planaren Fingerstruktur von Mikro-Gold-
Elektroden auf einer Titanhaftschicht, über die eine elektrische Stimulation
von Nervenzellen, d.h. eine induzierte Generation von Aktionspotenzialen,
realisiert wird. Um Aussagen über die erforderlichen Grössen
der Anregungen zu erhalten, wurden elektrische Stimuli systematisch hinsichtlich
Pulsdauer, -höhe und -anzahl variiert. Die Analyse der stimulierten
Netzwerkaktivität er-folgte global mit Ca 2+ -Fluoreszenz-Aufnahmen
bzw. lokal durch Patch-Clamp-Messungen. Parallel dazu wurde der Neu-
ronenresponse über das Elektrodenarray elektrisch ausgelesen. Der Einfluss
der einzelnen Stimulationsparameter auf die Netzwerkaktivität wird
im Detail vorgestellt und mit den Ergebnissen von Simulationsrechnungen
an biologisch realistischen neuronalen Netzwerken verglichen.
AKB 50.4 Fr 10:30 B
Modelling long-term evolution of food webs — •Satoshi Uchida
and Barbara Drossel — Institut für Festkörperphysik, TU Darmstadt,
Hochschulstr. 6, D-64289 Darmstadt, Germany
The relation between the stability and complexity of ecosystems is
much debated in the recent literature. An important theoretical approach
to this issue consists in exploring mathematical models of food webs,
which are networks constructed by prey-predator relationships in ecosystems.
Using computer simulations, we study a model that does not only
include Lotka-Volterra type population dynamics, but also a long-term
change in the linkage pattern and composition of the foodweb due to
species invasions and evolutionary change. We find that the foodweb becomes
unstable and collapses after some time. We explain this finding and
propose modified (and more realistic) population dynamics, for which the
complex foodweb structure persists in time.
AKB 50.5 Fr 10:30 B
Elasticity of Two-Dimensional Stiff Polymer Networks —
•Claus Heussinger and Erwin Frey — Hahn-Meitner Institut,
Berlin
We study the elasticity of two-dimensional networks of semiflexible
polymers (”Mikado model”). The essential features incorporated into the
model are the random geometry of the network and the anisotropic elasticity
of its constituents.
In a first study, the elements are modeled as purely mechanical Euler
beams [1,2]. We show that there are three distinct scaling regimes,
characterized by two characteristic length scales. In addition to a critical
rigidity percolation region and a homogeneous elastic regime (dominated
by beam compression) we find a novel intermediate scaling regime, where
the elasticity of the network is dominated by bending deformations. The
observations for the shear modulus can be rationalized by a crossover
scaling ansatz that permits to collapse the data over eight orders of magnitude
in the scaling variable.
In a second step, effective elastic properties of semiflexible polymers
are implemented to study the entropic contributions to the polymer compliance
and its effects on the scaling behaviour.
To get further insight into the nature of the force propagation, more
complicated modes of deformation can be explored. As an example, we
visualize force chains induced by the action of a microrheological probe.
[1] J. Wilhelm and E. Frey PRL 91, 108103 (2003)
[2] E. Frey, K. Kroy, J. Wilhelm and E. Sackmann, in Dynamical Net-

Arbeitskreis Biologische Physik Freitag
works in Physics and Biology (Springer Verlag Berlin, 1998)
AKB 50.6 Fr 10:30 B
Using Spins to Find Functional Modules of Bio-Molecular Networks
— •Sabine Tornow — Theoretische Physik III, Universitaet
Augsburg, D-86135 Augsburg
Genes and proteins are organized on the basis of their particular mutual
relation, or according to their interaction, in cellular and genetic
networks. These include metabolic or signaling pathways, protein interaction,
regulatory or coexpression networks. Integrating the information
from the different types of networks may lead to the notion of a functional
network and functional modules. To find these modules, we propose
a new technique which is based on collective, multi–body correlations in
a genetic network (a). We calculate the correlation strength of a group of
genes (e.g., in the coexpression network) which were identified as members
of a module in a different network (e.g., in the protein interaction
network) and estimate the probability that this correlation strength was
found by chance. Groups of genes with a significant correlation strength
in different networks have a high probability that they perform the same
function. Here, we propose to evaluate the multi–body correlations applying
the Superparamagnetic approach (b). We compare our method
to the presently applied mean Pearson correlations and show that our
method is more sensitive in revealing functional relationships.
(a)Tornow,S. ,Mewes, H.: Functional modules by relating protein interaction
networks and gene expression, Nucleic Acids Research 31, 6283
(2003)
(b) Blatt, M, Wiseman, M., and Domany, E.: Superparamagnetic clustering
of data. (1996) Phys. Rev. Lett., 76, 3251-5.
AKB 50.7 Fr 10:30 B
Mechanics and Force Generation of a Single Cell in Presence
of Cytoskeleton Structure Modifying Bioactive Lipids. —
•alexandre Micoulet 1 , Joachim P. Spatz 1 , and Thomas Seufferlein
2 — 1 Biophysical Chemistry, University of Heidelberg, 69120
Heidelberg, Germany — 2 Department of Internal Medecin I, University
of Ulm, 89081 Ulm, Germany
In tissues, constantly regulated processes, such as biochemical and mechanical
interactions between a cell and its environment play a major role
in differentiation and gene expression of cells. In contrast, cancer cells
are able to escape to these regulations and migrate through tissues since
their mechanical and adhesion properties change drastically than those
of non-tumor cells. Under physiological conditions, we applied a uniaxial
deformation to a single cell adhering between two parallel glass plates
(microplates). A precise feedback control allowed for measurements at
constant force or constant deformation. Both microplates were functionalized
in order to control cell adhesion. Thus, we manipulated a single
living cell by controlled adhesion and defined external mechanical stress.
We evaluated elasticity and viscosity of different cell types, such as fibroblasts,
human pancreatic cancer cells. In presence of two bioactive lipids,
lysophosphalitidic acid (LPA) and sphingosylphosphorylcholine (SPC),
we analysed the mechanical response of Panc-1 cells. LPA and SPC influenced
the organisation of actin- or keratin-cytoskeleton. E.g., elasticity
of Panc-1 cells decreased in presence of SPC consolidating biological
studies which predicted that SPC could facilitate metastasis.
AKB 50.8 Fr 10:30 B
Fibronectin fiber formation by surface tension on microfabricated
pillar interfaces — •Jens Ulmer, Stefan Graeter,
Wouter Roos, and Joachim Spatz — University of Heidelberg, Institute
for Physical Chemistry, Biophysical Chemistry,
The extracellular matrix (ECM) provides positional and environmental
information for cells which are essential for tissue function. ECM proteins
such as fibronectin (FN), laminin or collagen form distinct protein
networks in vivo that show tissue-specific variation in composition and
architecture. In vivo, FN-matrix assembly is mediated through integrins
which bind FN for forming cell-ECM contacts. FN molecules are then
stretched by cell generated forces. This causes conformational change in
FN molecules and enables FN from solution to bind. Thus, fibrillogenesis
of FN is stimulated and directed by force. We mimicked this force
induced FN assembly into fibers in vitro by stretching surface bound FN
molecules through water surface tension appearing between the surface
of a water drop and the tops of microfabricated pillars. Microfabricated
pillar arrays offer binding points to the ECM molecules which then bridge
the pillars tops by fibre network formation. In addition, micropillar interfaces
are sensitive force sensors which allow quantitative access to
the fiber formation process. The architecture of the resultant structure
showed to depend on concentration of the FN-solution and to be mediated
by forces generated from water surface tensions. Subsequently, the
defined FN-networks offers guiding cues for cell-ECM interactions.
AKB 50.9 Fr 10:30 B
Substrate Dependent Fibronectin Fibrillogenesis of Adherent
Cells — •Tilo Pompe 1,2 , Manfred Bobeth 3 , and Wolfgang
Pompe 3,2 — 1 Institut für Polymerforschung Dresden e.V. — 2 Max-
Bergmann-Zentrum für Biomaterialien Dresden — 3 Institut für
Werkstoffwissenschaft, TU Dresden
Cell-cell and cell-substrate binding is supported by extracellular matrix
proteins like fibronectin. The formation of fibrils from single fibronectin
molecules is a complex process which includes binding of cell
receptors, like integrins, conformational changes of fibronectin by mechanical
forces exerted from the cell, and polymerisation of fibronectin
molecules at newly exposed binding sites. The dependence of fibrillogenesis
on the fibronectin bond strength to the substrate was investigated
on different copolymer surfaces in respect to the characteristic pattern
of the fibronectin fibrils. Additionally, the process of fibrillogenesis was
modelled by Monte-Carlo simulations of the diffusion and aggregation
of integrin-fibronectin complexes, including cytoskeletal forces acting on
the focal adhesions. The resulting pattern was analysed in dependence
on the fibronection-substrate bond strength and compared with the experimental
observations.
AKB 50.10 Fr 10:30 B
Rod-Coil Multiblock Copolymers as a Simple Protein Model:
Some Scaling Arguments — •Christian Nowak and Thomas
Vilgis — MPI f”ur Polymerforschung, Postfach 3148, 55021 Mainz
We consider the behaviour of rod-coil multiblock copolymers by means
of scaling arguments. A rich phase behaviour is found depending on the
quality of the solvent and the strenght of the intermolecular interactions.
The phase behavior is essentially driven by strong attractive interactions
of the rodlike parts which stabilize the rod micelles and the entropy loss
and confinement of the flexible joints. Such systems could serve as a
very simple model for proteins like myoglobin where the helical parts are
modelled by stiff rods which are joined by flexible (chainlike) elements.
AKB 50.11 Fr 10:30 B
First-Passage and Residence Times in a Periodically Driven
Integrate-and-Fire Model — •Michael Schindler, Peter
Talkner, and Peter Hänggi — Institut für Physik, Universität
Augsburg
The stochastic integrate-and-fire model presents a simple model for
the spiking behavior of neurons. In this model a neuron ”fires” if an
Ornstein-Uhlenbeck process crosses a prescibed threshold. After the firing
the process is assumed to be in a refractory state, and from there it
is put back into its initial, active, state.
For short refractory times this process can be characterized by the distribution
of either the first-passage times of the threshold or the residence
times in the active state. We determined the distributions of these times
for the integrate-and-fire model in the presence of a periodic signal. This
is done by solving numerically both the respective Langevin equation
and the equivalent Fokker-Planck equation. The results are compared
with an approximate analytic theory. If the period of the signal is large
compared to the relaxation time of the Ornstein-Uhlenbeck signal and if
the threshold is higher than a few times the noise strength we find theory
and numerics to be in excellent agreement.
AKB 50.12 Fr 10:30 B
Fluorescence intermittency of single CdSe/ZnS quantum
dots: A comparison between organic and water soluble ligand
shells. — •Andrei Yu. Kobitski 1 , Colin D. Heyes 1 , Vladimir
V. Breus 1 , Kirill V. Anikin 1 , and G. Ulrich Nienhaus 1,2 —
1 Department of Biophysics, University of Ulm, D - 89069 Ulm, Germany
— 2 Department of Physics, University of Illinois Urbana-Champaign,
Urbana, IL 61801, USA
Recently, chemically synthesized quantum dots (QDs) are becoming
widely used as fluorescent labels in biophysical and life-science research.
The procedure of preparing organic soluble CdSe/ZnS core/shell QDs
has become well established over the last 10 years and reproducibly
gives monodisperse nanocrystals with high emission quantum yields of
up to 50%. However, the procedure of water solubilization of the particles,
which is needed for bio-related experiments, is not so well deter-

Arbeitskreis Biologische Physik Freitag
mined. Moreover, the blinking mechanism of water soluble QDs has not
yet been systematically studied. In this work we present the study of single
CdSe/ZnS QDs by means of Total Internal Reflection Fluorescence
Microscopy (TIRFM). A comparison in blinking behavior of QDs with
organic soluble Tri-n-octylphosphine oxide (TOPO) and water soluble
mercaptoundecanoic acid (MUA) shells is performed.
AKB 50.13 Fr 10:30 B
Artificial actin cortices on microfabricated pillar arrays —
•Wouter Roos 1 , Alexander Roth 2 , Roman Glass 1 , Erich
Sackmann 2 , and Joachim P. Spatz 1 — 1 Universitaet Heidelberg,
Institut fuer physikalische Chemie, Biophysikalische Chemie, 69120
Heidelberg — 2 Technische Universitaet Muenchen, Physik-Department
E22, 85747 Garching
Arrays of microfabricated pillars are constructed to serve as a template
for mimicking the actin cortex. Different methods to fabricate pillar arrays
will be discussed, these involve top-down and bottom-up approaches
using photolithographic techniques, plasma etching processes and epitaxial
ZnO growth. A two-dimensional network of actin filaments, that
is pending from the pillar tops, is fabricated. Due to the 3-dimensional
template surface interaction of the filaments hanging in between the pillars
with substrate surfaces is prevented. This opens new possibilities
to study the mechanics of 2-dimensional actin networks as a function of
actin-crosslinkers, and the active diffusion of molecular motors operating
on pending networks. The behaviour of this artificial actin cortex will be
compared to models of networks and to cortices in living cells.
AKB 50.14 Fr 10:30 B
Dynamics of cell adhesion contacts and forces on rigid nanoadhesive
templates — •Christine Selhuber 1 , Marco Arnold 1 ,
Roman Glass 1 , Jacques Blümmel 1 , Horst Kessler 2 , and
Joachim Spatz 1 — 1 Universität Heidelberg, Biophysikalische Chemie,
INF 253, 69120 Heidelberg — 2 TU München, Institut für Organische
Chemie und Biochemie, Lichtenbergstrasse 4 , 85747 Garching
Cooperative processes in cell adhesion are one of the most fundamental
issues in cell sciences which control many cell functions. Nanometer
sized RGD based adhesive dots of an extension smaller 8 nm are applied
as bindin g sites for the activation of a single integrin per dot. The dots
assemble with high precision on interfaces where the pattern geometry
and the separation of single dots can be controlled in a flexible way. Thus,
the pattern resembles a rigid adhesive template on which cell or vesicle
adhesion can be probed with single receptor resolution. If adhesive dots
are separated by more than 73 nm cell adhesion fails due to extended
singl e integrin-integrin separation, as well as cell spreading, formation
of foca l contact clusters and actin stress fibre formation is constricted.
The adhesion forces generated on such substrates are measured as a function
of nanopattern geometry and adhesion time. The dynamic change of
the cell adhesive area is determined using reflection interference contrast
microscopy.
AKB 50.15 Fr 10:30 B
Probing a Biomimetic Model of the Actin Cortex with Dynamic
Holographic Optical Tweezers — •Christian Schmitz, Jennifer
Curtis, and Joachim Spatz — Biophysikalische Chemie, Institut für
Physikalische Chemie, Universität Heidelberg
The actin cortex is an adaptive chemo-mechanical polymer network
located beneath the cell membrane. A thin, quasi two-dimensional (2D)
network, the actin cortex plays a leading role in controlling cellular viscoelasticity,
shape, and motility. Regulated by internal and external stimuli,
the actin cortex varies its properties with controlled reversible polymerisation
of actin. We construct a freely-floating 2D biomimetic actin
network to address key questions such as what are the viscoelastic properties
of a 2D actin network, and how are these mechanical properties
modified by active, biochemical components like molecular motors. The
actin network is arranged and probed using holographic optical tweezers,
which produce and independently steer one to hundreds of optical traps.
Using a bed of optical traps, microspheres are arranged into a geometric
array onto which actin is deposited or grown. The tweezers coordinatively
exert distorting forces on the network and when calibrated, they measure
the response of the network at each microsphere.
AKB 50.16 Fr 10:30 B
Optical Control of Neuronal Growth — •Björn Stuhrmann,
Josef Käs, Allen Ehrlicher, Michael Gögler, Daniel Koch,
and Timo Betz — Lehrstuhl für die Physik weicher Materie, Universität
Leipzig, Fakultät für Physik und Geowissenschaften, Linnéstr. 5,
D-04103 Leipzig, Germany
The control of neuronal growth is an essential tool in neuroscience,
cell biology, biophysics, biomedicine, and is particularly important for
the formation of neural circuits in vitro, as well as nerve regeneration in
vivo. We have shown experimentally that we can use weak optical forces
to influence the motility of a growth cone by biasing the polymerizationdriven
intracellular machinery. In actively extending growth cones, a laser
spot placed at specific areas of the nerve’s leading edge affects the following
three potentially important elements of controlled neuronal network
formation: the growth speed, the direction taken by a growth cone, and
the splitting of a growth cone [Ehrlicher et al. ”Guiding neuronal growth
with light” PNAS (2002)]. We have also succeeded to establish transient
cell-cell contacts between growth cones and cell bodies of other nerve
cells. Our results open a new venue to control neuronal growth with a
simple, noncontact technique with potential applications in the formation
of neural networks and in understanding the cytoskeleton driven
morphological changes in growth cones.
AKB 50.17 Fr 10:30 B
Elektrische Charakterisierung von Metall-Glas-
Elektrodenstrukturen zur Stimulation von Neuronen —
•S. Günther 1 , A. Krtschil 1 , A. Reiher 1 , H. Witte 1 , A. Krost 1 ,
A. de Lima 2 , T. Opitz 2 und T. Voigt 2 — 1 Institut für Experimentelle
Physik, Otto-von-Guericke-Universität Magdeburg, PF 4120, D-39016
Magdeburg — 2 Institut für Physiologie, Otto-von-Guericke-Universität
Magdeburg, Leipziger Str. 44, D-39120 Magdeburg
Durch in vitro-Kultivierung von Neuronen aus dem Kortex embryonaler
Ratten ist es möglich, 2-dimensionale neuronale Netzwerke zu erzeugen,
in die planare Elektrodenstrukturen zur elektrischen Kommunikation
mit den Neuronen integriert werden können. Die Stimulation
und das Auslesen von Aktionspotentialen wird dabei maßgeblich von den
elektrischen Eigenschaften des Systems Elektrodenstruktur, Nährlösung
und neuronales Netzwerk bestimmt. Die Untersuchungen wurden an
Streifen- und Fingerstrukturen von Ti/Au-Schichten durchgeführt. Auf
der Grundlage von elektrischen Untersuchungen der Einzelkomponenten,
sowie der vollständigen Anordnung wurde ein Ersatzschaltbild zur Beschreibung
der DC/AC-Eigenschaften erstellt. Als ein kritischer Parameter
des Interfaces erwies sich das elektrische Verhalten der Nährlösung,
verbunden mit elektrolytischen Effekten. Aufgrund dieser Analysen wurde
ein geeignetes Parameterfeld gefunden und optimiert, so dass neuronale
Netzwerke stimuliert werden konnten.
AKB 50.18 Fr 10:30 B
Mechanism of Model Membrane Fusion Determined from
Monte Carlo Simulation — •Marcus Mueller 1 , Kirill
Katsov 2 , and Michael Schick 2 — 1 Institut fuer Physik, WA331,
Johannes Gutenberg Universitaet, D55099 Mainz, Germany — 2 Dept.
of Physics, University of Washington, Seattle, WA 98195-1560, USA
Fusion of membranes is essential to living systems, but its mechanism
is not well understood. We have carried out extensive Monte Carlo simulations
of the fusion of tense apposed bilayers formed by amphiphilic
molecules within the framework of a coarse grained lattice model. Our
model exhibits a phase diagram which is similar to that of biological
lipids. The fusion pathway, however, differs from the “hemifusion hypothesis”.
First stalks form between the apposed bilayers, but rather than expanding
radially to form an axial-symmetric hemifusion diaphragm of
the cis leaves of both bilayers, they promote hole nucleation of the bilayers
in their vicinity. Two subsequent paths are observed: (i) A second
hole is formed in the opposite bilayer, and the stalk aligns both hole as
it encircles them and forms the fusion pore. (ii) The stalk encircles the
hole completely before a second hole is formed in the opposite bilayer.
A diphragm is formed out of both leaves of the intact bilayer. The rupture
of this diaphragm completes fusion. Both pathways give rise to an
increase in mixing between the cis and trans leaves of the bilayer and
allow for leakage.

Arbeitskreis Biologische Physik Freitag
AKB 50.19 Fr 10:30 B
Far-infrared spectroscopy of α amino acids — •Adriana Matei,
Natalia Drichko, Bruno Gompf, and Martin Dressel —
1.Physikalisches Institut, Universität Stuttgart
In contrast to covalent bonds, which leads to intramolecular vibrations
in mid-infrared, low energy interactions such as hydrogen bonds and van
der Waals forces can lead to intermolecular vibrations in far-infrared
(THz-range).
We report on FTIR measurements of a large number of amino acids
prepared as pellets in a polyethylene matrix in the region 50-650 cm −1 .
The observed absorption peaks can be related to five regions: the region
around 600 cm −1 (CO2 wagging), around 540 cm −1 (NH3 torsion and
CO2 rocking/wagging/bending), the one at 320 cm −1 (CC α N deformation),
and the one at 200 cm −1 (CO2 torsion and CC α N deformation).
The features between 50 and 200 cm −1 are intermolecular vibrations due
to hydrogen bonds. Starting from previous normal mode calculations, an
assignment of the observed vibration frequencies is possible.
AKB 50.20 Fr 10:30 B
Transverse fluctuations of grafted polymers — •Gianluca Lattanzi
1 , Tobias Munk 2 , and Erwin Frey 1,2 — 1 Abteilung Theoretische
Physik SF5, Hahn-Meitner Institut Berlin — 2 Fachbereich Physik,
Freie Universität Berlin
We explore the mechanical properties of a single polymer filament with
arbitrary stiffness in a two dimensional embedding space with Monte
Carlo simulations. Clamping one end of the filament induces non trivial
effects on the distribution of the second end, supposed free. The reduced
distribution in the transverse direction shows an anomalous double
peak structure that hallmarks the semiflexible parameter range. This
phenomenon represents a challenge for analytical theories of semiflexible
polymers and should be easily detectable for a number of experimental
situations involving F-Actin, Microtubules, DNA or coiled-coils in the
dimerization domain of kinesin and in myosin V. In addition, we explore
the response of the filament to a transverse force applied at its free end.
AKB 50.21 Fr 10:30 B
Structure control in living bone — •Markus A. Hartmann 1 ,
Richard Weinkamer 1 , Yves Brechet 2 , and Peter Fratzl 1 —
1 Max-Planck-Institute of Colloids and Interfaces, Dept. of Biomaterials,
14476 Potsdam, Germany — 2 Laboratory of Thermodynamics and Metallurgical
Physico-Chemistry/ENSEEG, Grenoble, France
Living bone is an example of a biological system, where the structure is
reacting to mechanical load and controlled by a biological feedback loop.
Specialised cells form new bone where the mechanical stimulus is high
and others dissolve it, where the stimulus is low (Wolff-Roux law). We
use a lattice model and a simple mechanical procedure to evaluate local
stresses to study trabecular bone remodelling in a human vertebra. Starting
from a homogenous, isotropic configuration, a network-like structure
emerges, with struts mainly in vertical and horizontal directions resembling
natural bone. With time, the bone volume fraction reaches a steady
state value independent of initial conditions, while some struts thicken
at the expense of others (coarsening) favouring the vertical main loading
direction. Our simulations provide a mechanistic explanation for some
features typically observed in ageing and disease.
AKB 50.22 Fr 10:30 B
Stability of adhesion clusters under constant force: a stochastic
analysis — •Thorsten Erdmann and Ulrich S. Schwarz —
Max Planck Institute of Colloids and Interfaces, Theory Division, 14424
Potsdam
Cells in multicellular organisms adhere to the extracellular matrix and
to other cells through two-dimensional clusters of transmembrane adhesion
receptors, which usually have to operate under mechanical load.
We present a theoretical model which allows to study the stability of
multiple parallel bonds under shared constant loading. The dynamics of
thermally activated bond rupture and rebinding is modelled by a one-step
Master equation with an absorbing boundary for the completely dissociated
state. For small forces and weak rebinding, mean cluster lifetime
grows only logarithmically with bond number. For strong rebinding, this
dependence becomes exponential, thus rebinding is a very efficient way
to stabilise adhesion clusters. For intermediate forces, a small increase in
force leads to a large reduction in mean cluster lifetime. This allows cells
to switch the stability of cell-matrix adhesions by loading through the
cytoskeleton.
AKB 50.23 Fr 10:30 B
Probing molecular free energy landscapes by periodic loading
— •Oliver Braun 1 , Andreas Hanke 1,2 , and Udo Seifert 1 —
1 Institute for Theoretical Physics II, University of Stuttgart, Pfaffenwaldring
57, D-70550 Stuttgart, Germany — 2 Theoretical Physics Department,
University of Oxford, 1 Keble Road, OX1 3NP Oxford, United
Kingdom
Recent experimental developments of highly sensitive force probes such
as atomic force microscopy, optical or magnetic tweezers and biomembrane
force probes allow one to manipulate a single biological macromolecule.
The free energy landscape along its end-to-end distance, which
is governed by molecular forces and self-interactions, may be recovered by
applying time-dependent forces. Previous experiments have mostly used
a linear force ramp.
Using periodically modulated forces we show how to reconstruct this
free energy landscape more efficiently. A central tool is Jarzynski’s identity,
which allows us to recover equilibrium quantities from the statistics
of non-equilibrium experimental data. As a main advantage, our method
also yields the convex unstable part of the free energy surface, where
the linear ramp protocol provides poor results. The quality of the reconstruction
depends crucially on the frequency of the periodic forcing. Best
results were obtained at frequencies of the order of the transition rates
between adjacent meta-stable configurations.
AKB 50.24 Fr 10:30 B
Dynamics of Eukaryotic Flagella — •Andreas Hilfinger 1 ,
Ingmar Riedel 2 , Amit Chattopadhyay 1 , Karsten Kruse 1 ,
Jonathon Howard 2 , and Frank Jülicher 1 — 1 Max-Planck-
Institute for Physics of Complex Systems, D-01187 Dresden, Germany
— 2 Max-Planck-Institute of Molecular Cell Biology and Genetics,
D-01307 Dresden, Germany
Many types of sperm swim in a viscous environment by beating a
whiplike appendage called the flagellum. The flagellum contains a highly
conserved structure called the axoneme, whose characteristic architecture
is based on a cylindrical arrangement of long elastic filaments composed
of microtubules. The microtubules in adjacent filaments are coupled by
the molecular motor dynein. In the presence of ATP these motor proteins
exert shear forces on neighbouring microtubules. The shear forces lead
to bending of the axoneme because microtubule sliding near the sperm
head is constrained by additional crosslinking proteins. Here we discuss
how regular beating patterns can emerge as nonlinear waves due to internal
stresses that are generated by a large ensemble of molecular motors
working within such an elastic structure. We compare our results with
experimentally observed beating patterns and analyse dynamic force distributions
in active bull sperm flagella.
AKB 50.25 Fr 10:30 B
Ab initio - Berechnungen von elektrischen Feldgradienten in
biologischen Molekülen — •Frank Heinrich und Wolfgang
Tröger — Institut für Experimentelle Physik II, Universität Leipzig
Die Messung des elektrischen Feldgradienten (EFG) am Ort einer
nuklearen Sonde ist über die Kernquadrupolwechselwirkung
mit verschiedenen Verfahren möglich, wie z.B. NMR oder γ-γ-
Winkelkorrelationsspektroskopie (TDPAC). Die Interpretation von Daten
des elektrischen Feldgradienten erfolgt in der Regel durch die Verwendung
von bekannten EFGs einiger Modellverbindungen mit bekannter
atomarer Struktur. Ab initio-Berechnungen des EFG sind eine Alternative,
um mutmaßliche chemische Strukturen zu überprüfen. Moderne
Dichte-Funktional-Programme, wie ADF (Amsterdam Density Functional
Code), ermöglichen auch quantenmechanische Berechnungen von
großen biologischen Molekülen. Es wurden für verschiedene Klassen von
Molekülen (Mercaptide, Thiokronenether) mit bis zu etwa 100 Atomen
die mit TDPAC ermittelten EFGs reproduziert. Damit wurde die Grundlage
geschaffen, um EFGs in Makromolekülen zu berechnen und offene
Probleme der Ligandierung von Metallzentren in Proteinen zu klären.
AKB 50.26 Fr 10:30 B
204m Pb: Eine ” neue“ isomere TDPAC-Sonde — •Frank Heinrich
1 , Wolfgang Tröger 1 und Heinz Haas 2 — 1 Institut für Experimentelle
Physik II, Universität Leipzig — 2 Hahn-Meitner-Institut,
Berlin
Am Massenseparator ISOLDE/CERN steht seit kurzer Zeit das Bleiisotop
204m Pb (t1/2 = 67 min) für TDPAC-Messungen (zeitdifferentielle
gestörte γ-γ-Winkelkorrelation) zur Verfügung. In ersten Experimenten
konnten einige 204m Pb(II)-Komplexe aus wässrigen Lösungen präpariert

Arbeitskreis Biologische Physik Freitag
und gemessen werden, die als Modellverbindungen für den Einsatz dieser
Sonde in den ” Life Sciences“ dienen werden. Im Vergleich zu anderen
TDPAC-Isotopen verfügt diese Sonde über eine sehr lange Lebensdauer
des Zwischenzustandes (tN = 382 ns) und damit über eine exzellente Frequenzauflösung,
die sie für Dynamik-Studien prädestinieren. Die 204m Pb-
Aktiviät wurde auch mit einem 204 Bi/ 204m Pb-Generator hergestellt. Mit
dieser Sonde sind zum ersten Mal TDPAC-Experimente mit einem Isomer
im ” Heimlabor“ möglich. Die Ergebnisse der 204m Pb-TDPAC-Messungen
am ISOLDE/CERN und an der Uni Leipzig werden vorgestellt.
AKB 50.27 Fr 10:30 B
A model for pathfinding and targeting in mixed populations
of axons — •Peter Borowski and Martin Zapotocky — Max-
Planck-Institut für Physik komplexer Systeme; Nöthnitzer Str. 38; 01187
Dresden
We present a model for the development of a neural map involving
multiple axon species. The model is motivated by the neural connectivity
scheme of the olfactory system, where axons start in a spatially disordered
configuration in the sensory epithelium, yet converge to specific
points on the olfactory bulb depending on which type of odorant receptor
they express. An important ingredient of our model is the presence
of axon-axon interactions which lead to preferential bundling of axons of
the same species. We classify the connectivity patterns that develop in
such a system in the presence and absence of spatially graded guidance
cues, and discuss the robustness of the corresponding neural maps.
AKB 50.28 Fr 10:30 B
Minkowski Functionals of high-dimensional data sets: application
to protein analysis — •Boris Breidenbach 1,2 , Hubert
Mantz 1 , and Klaus Mecke 1,2 — 1 MPI für Metallforschung, Heisenbergstr.3,
70569 Stuttgart — 2 Universität Stuttgart, Institut für theoretische
und angewandte Physik, Pfaffenwaldring 57, 70569 Stuttgart
The Minkowski functionals are a well established tool for the analysis
of various types of spatial experimental data such as tomographic images
of porous materials and atomic force measurements of thin polymer
films where they have proven their ability to extract physically relevant
information. Here, we present the first application of integral geometry in
spaces with more than three dimensions: data is taken from microarray
experiments of gene expression profiles in cells. Each protein is assigned
a point in the high-dimensional concentration space. The functionals can
be calculated exactly and efficiently for such decorated point distributions.
The method is fast and statistically robust. We illustrate it by
analyzing the gene-expression timecourse during the development of the
Drosophila life cycle with respect to its clustering behaviour, i.e., its
protein-protein interactions. The results are subsequently compared to
standard techniques in bioinformatics such as hierarchical clustering and
self-organising maps.
AKB 50.29 Fr 10:30 B
Filament depolimerization by motor molecules — •Gernot
Klein 1 , Giovanni Cuniberti 2 , Karsten Kruse 1 , and Frank
Jülicher 1 — 1 Max-Planck-Institut fuer Physik komplexer Systeme,
Dresden — 2 Universitaet Regensburg, Regensburg
Motor proteins are specialized molecules which bind to filaments of the
cytoskeleton and are able to generate forces. An unusual protein, closely
related to kinesin motors is MCAK, which binds to microtubule ends and
depolymerizes them (1),(2).
We study the process of MCAK binding to microtubules and subsequent
depolymerization using stochastic models.Computer simulations
of a one-dimensional hopping model are compared to the mean-field theory
of the adopted discrete model.Our theory can explain how molecules
accumulate at depolymerizing ends.
(1) A.W. Hunter, M.Caplow, D.L. Coy, W.O. Hancock, S. Diez,
L.Wordeman, J. Howard; Mol. Cell, Vol 11, 445-457, 2003.
(2) R. Ohi, M.L. Coughlin, W.S. Lane, T. Mitchison; Dev. Cell, Vol.5,
309-321, 2003.
AKB 50.30 Fr 10:30 B
In-situ investigation of wood pyrolysis with synchrotron radiation
— •Gerald Andreas Zickler 1 , Cordt Zollfrank 2 , Manfred
Burghammer 3 , and Oskar Paris 1 — 1 Max Planck Institute
of Colloids and Interfaces, Dept. Biomaterials, Am Mühlenberg 1, D-
14476 Potsdam, Germany — 2 Friedrich Alexander University Erlangen-
Nuremberg, Dept. Materials Science - Glass and Ceramics, Martensstr.
5, D-91058 Erlangen, Germany — 3 European Synchrotron Radiation Facility
(ESRF), 6 Rue Jules Horowitz, F-38043 Grenoble, France
Advanced cellular ceramics from biologically derived pre-forms have
gained considerable interest over the last years. Aim of biomimetic materials
synthesis is the transformation of biological tissue into anorganic
structures for the production of biomorphous ceramics and composite
materials with advanced properties. The present study is focusing on
structural aspects of non oxidising pyrolysis of native spruce wood, with
the aim to transform the hierarchical structure of wood into oriented Biocarbon.
Microfocus synchrotron radiation is used in combination with a
custom made furnace to study wood pyrolysis in situ. Scanning the specimens
provides further information on the micrometre scale. Detailed
time resolved diffraction data from single wood slices give deeper insight
into the kinetics of cellulose degradation, nano pore formation and development
of turbostratic carbon at different pyrolysis temperatures. The
results are presented and discussed with respect to existing structural
models of cellulose degradation from literature.
AKB 50.31 Fr 10:30 B
Modelling of Rhodopsin Chromophore — •Minoru Sugihara 1 ,
Ana-Nicoleta Bondar 2 , Peter Entel 1 , Volker Buss 3 , and Marcus
Elstner 4 — 1 Institute of Physics, University of Duisburg-Essen —
2 IWR, University of Heidelberg — 3 Institute of Chemistry, University of
Duisburg-Essen — 4 Institute of Physics, University of Paderborn
Bovine retinal photoreceptor rhodopsin is the only one visual pigment
whose three-dimensional atomic coordinates are available now [1,2]. It
is composed of the 40-kDa apoprotein opsin (348 amino acids) and its
chromophore. The chromophore of rhodopsin is 11-it cis-retinal which
is covalently attached to Lys296 via a Schiff base. The Schiff base nitrogen
atom is protonated and there is a salt-bridge between the protonated
Schiff base and its counterion, Glu113. Illumination of light of ∼
500nm leads to photoisomerization from 11-cis retinal to all-trans within
200fs, which is the primary event in visual system and is the only lightdependent
step. This is followed by a conformational change in the protein
and after a series of intermediates, the pigment reaches the signaling
state, the so-called meta-II. In the present work we focus on the modelling
of the chromophore in the dark state (rhodopsin state) and the
first intermediate state (batho state) based on the crystal structure of
rhodopsin state [2]. We use the recently developed quantum mechanical
/ molecular mechanical (QM/MM) method [3]. [1] K. Palczewski, et al.
Science 2000, 289, 739. [2] T. Okada, et al. Proc. Natl. Acad. Sci, U.S.A.
2002, 99, 5982. [3] Q. Cui, et al. J. Phys. Chem. B 2001, 20, 569.
AKB 50.32 Fr 10:30 B
Unbinding Transitions of Filament Bundles — •Jan Kierfeld,
Torsten Kühne, and Reinhard Lipowsky — MPI für Kolloid- und
Grenzflächenforschung, 14424 Potsdam
Filament bundles are an important structural element of the cytoskeleton.
We study the unbinding transition bundles of semiflexible filaments
such as F-actin. The interaction between the filaments is mediated by
crosslinking stickers. It is shown that the formation of a filament bundle
requires a threshold concentration of stickers. We find that the corresponding
unbinding transition of the filament bundle happens in a single,
discontinuous transition.
AKB 50.33 Fr 10:30 B
Application of micron and nano scale metal island patterns as
coordinative system for quantifying intracellular diffusion —
•Tamas Haraszti and Joachim P. Spatz — University of Heidelberg,
INF 253, 69120 Heidelberg
Quantitative determination of intracellular diffusion in adhering cells
allows access to evaluate dynamics important in cell functions. On very
small length scales we face the problem that the absolute localisation of
a diffusive probe such as fluorescent molecules or quantum dots in cells
relative to the adhering substrate might fail. In our studies we correlate
cellular diffusion to an absolute coordinative system made of micro and
nano scale metal islands. Either e-beam or micellar diblock copolymer
lithography applied to form the desired patterns. The patterns are iden-

Arbeitskreis Biologische Physik Freitag
tified by statistically distributed or alternating gold and silver islands. A
microscope with ATR capability allows to evaluated both, the coordinate
system and the diffusion of molecular probes in cells.
AKB 50.34 Fr 10:30 B
Elastic interactions of cells with soft materials — •Ilka Bischofs
and Ulrich Schwarz — Max Planck Institut für Kolloid- und Grenzflächenforschung,
Theorie, 14424 Potsdam
Mechanically active cells sense the mechanical properties of their environment
and respond by strenghtening their cytoskeleton in the direction
of maximal effective stiffness. Rigidity gradients, prestrain induced
by external forces, traction by other cells, and the presence of sample
boundaries locally alter the effective stiffness encountered by contractile
cells. We model cells as anisotropic force contraction dipoles and use linear
elasticity theory to calculate optimal cell organization in soft media.
Our predictions for single cells agree nicely with experiments for fibroblasts:
cells orient toward clamped and away from free surfaces and along
the direction of tensile strain. The elastic interaction between cells shows
a similar angular dependence as electrical dipoles. At low cell density,
this leads to strings of cells, while at high cell density, branching into
ring-like structures occurs.
AKB 50.35 Fr 10:30 B
Active forces of motile cells — •Claudia Brunner, Michael
Gögler, Allen Ehrlicher, and Josef Käs — a
Cellular motility is a ubiquitous component of prokaryotic and eukaryotic
cells, spanning varied functions from the immune system, to the
developing brain, to the grave invasiveness of cancer.
Various individual components, such as molecular motors and actin
filament polymerization have been explored to explain cell movement,
but the cell as a whole system is not well understood. Experiments on
living cells are necessary to understand the properties and abilities of
their polymer networks functioning together as one system.
The atomic force microscope is an excellent tool to determine the
mechanical forces which are responsible for cell movement. With a
polystyrene bead glued on a commercial AFM-tip, living cells can be
safely measured. We have probed fast moving keratocytes and directly
measured the cell extension forces, allowing us to compare extension
forces with the cells velocities and other properties.
AKB 50.36 Fr 10:30 B
Functionalization and Passivation of a Silicon-on-Insulator
based Sensor Device — •Petra A. Neff, Michael G. Nikolaides,
Stefan Rauschenbach, Simon Q. Lud, and Andreas
R. Bausch — Lehrstuhl für Biophysik - E22, Technische Universität
München, 85747 Garching
The sensitive and specific detection of biomolecular interactions relies
on the functionalization and passivation of the detecting surfaces.
Recently, a new Silicon-on-Insulator (SOI) based thin film resistor device
for chemical and biological sensor applications was introduced. It
has been shown that this sensor is highly sensitive to variations of the
surface potential evoked by the adsorption of small amounts of charged
molecules. Whereas most of the conventional detection techniques require
the labeling of molecules, the SOI based sensor allows a label-free
detection of interactions.
Here we discuss the passivation and functionalization of the bare silicon
oxide surface by physical adsorption of polyelectrolytes and the covalent
binding of silanes. Results of the adsorption of PAH/PSS multilayers are
presented and their interpretation will be discussed. First results of the
application of the sensor device towards the label-free detection of DNA
hybridization will be presented.
AKB 50.37 Fr 10:30 B
Activation of Integrin Function by Nanopatterned Adhesive Interfaces
— •Marco Arnold 1 , Elisabetta Ada Cavalcanti 1 ,
Roman Glass 1 , Jacques Blümmel 1 , Wolfgang Eck 2 , Martin
Kantlehner 3 , Horst Kessler 3 , and Joachim P. Spatz 1
— 1 University of Heidelberg, Institute for Physical Chemistry, Biophysical
Chemistry, INF 253, D-69120 Heidelberg — 2 University of Heidelberg,
Institute for Physical Chemistry, Applied Physical Chemistry, INF
253, D-69120 Heidelberg — 3 Technical University of Munich, Institute
for Organic Chemistry and Biochemistry, Lichtenbergstrasse 4, D-85747
Garching
To study the function behind molecular arrangement of single integrins
in cell adhesion, we designed a hexagonally closepacked rigid template of
cell adhesive gold nanodots by lithographic means of diblock copolymer
selfassembly. The diameter of the adhesive dots are smaller than 8nm,
which allows the binding of one integrin per dot. These dots are positioned
with high precision at 28, 58, 73 and 85nm spacing at interfaces.
A separation of more than 73nm between the dots results in limited cell
attachment and spreading and reduces the formation of focal adhesion
and actin stress fibers. We attribute these cellular responses to restricted
integrin clustering rather than insufficient number of ligand molecules
in cellmatrix interface since micronanopatterned substrates consisting of
alternating fields with dense and no nanodots support cell adhesion. We
propose that the range between 58 and 73nm is a universal length scale
for integrin clustering and activation.
AKB 50.38 Fr 10:30 B
Coherent Scatter Computed Tomography — •Johannes Delfs 1 ,
Jens-Peter Schlomka 1 , and Robert L. Johnson 2 — 1 Philips Research
Laboratories Hamburg, Röntgenstrasse 24-26, 22335 Hamburg,
Germany — 2 Institut für Experimentalphysik, Universität Hamburg, Luruper
Chaussee 149, 22761 Hamburg, Germany
The dominant component of low-angle scatter in the energy regime
of diagnostic radiology ( 60 keV) is coherent scatter. This leads to the
phenomenon of x-ray diffraction, which is widely used for determining
atomic structure in material science.
A reconstructive tomographic imaging technique (”Coherent Scatter
Computed Tomography (CSCT) ”) is presented for the spatially-resolved
measurement of the coherent scatter cross-section in extended objects.
These diffraction patterns supplement conventional CT images in material
discrimination.The technique is based on the energy analysis, at
known angle, of coherent x-ray scatter by polychromatic radiation employing
a novel energy-resolving CdZnTe detector array. Images of test
objects are shown to illustrate the feasibility of the technique and potential
applications in medicine and industrial material inspection.
AKB 50.39 Fr 10:30 B
An individual-based Model to Tumor Growth in Vitro —
•Drasdo Dirk 1 and Hoehme Stefan 2 — 1 MPI fuer Mathematik in
den Naturwissenschaften, Inselstr. 22-26,Leipzig — 2 Interdisciplinary
Inst. for Bioinformatics, Kreuzstr. 7b, Leipzig
We present a mathematical model to study the spatio-temporal growth
dynamics of two-dimensional tumor monolayers and three-dimensional
tumor spheroids as a complementary tool to in-vitro experiments. Within
our model each cell is represented as an individual object and parameterized
by cell-biophysical and cell-kinetic parameters that can all be experimentally
determined. Hence our modeling strategy in principle provides
a link between mechanisms on the microscopic level of individual cells
and the macroscopic properties of a growing tumor. We find a remarkable
robustness of the growth kinetics and patterns in early growth stages
although their mechanistic origin can be different. Quantitative comparisons
of computer simulations with our model to published experimental
observations on monolayer cultures suggest a biomechanically-mediated
form of growth inhibition during the experimentally observed transition
from exponential to sub-exponential growth at sufficiently large tumor
sizes. Our simulations show that for avascular tumor spheroids this transition
can usually be explained by a nutrient or oxygen depletion, and
predict that it becomes biomechanically triggered at a sufficiently large
nutrient and oxygen supply.
AKB 50.40 Fr 10:30 B
Dynamics of Tension in Semiflexible Polymers — •Oskar Hallatschek
1 , Erwin Frey 1,2 , and Klaus Kroy 1 — 1 Abteilung Theorie,
Hahn-Meitner Institut, Glienicker Str. 100, 14109 Berlin, Germany
— 2 Fachbereich Physik, Freie Universität,14195 Berlin, Germany
We present a general discussion of non-equilibrium tension propagation
through a semiflexible polymer in various situations of experimental
interest. Typical situations include the response of the polymer’s conformation
to a given longitudinal force at one end, or the relaxation of the
polymer after it has been equilibrated under a certain applied tension.
In both cases the propagation of tension exhibits power law behavior,
but with distinct dynamic exponents. Whereas the initial exponent always
equals 1/8, the exponent for late time propagation depends on the
experimental situation. Based on a set of coarse-grained equations of motion
we give a unified theoretical explanation of the various scenarios. In
addition, we discuss the behavior of end grafted chains in an external
field, and analyze the problem of a polymer that undergoes a sudden
temperature change.

Arbeitskreis Biologische Physik Freitag
AKB 50.41 Fr 10:30 B
Overdamped Buckling Dynamics — •Oskar Hallatschek 1 , Erwin
Frey 1,2 , and Klaus Kroy 1 — 1 Abteilung Theorie, Hahn-Meitner
Institut, Glienicker Str. 100, 14109 Berlin, Germany — 2 Fachbereich
Physik, Freie Universität,14195 Berlin, Germany
We discuss the generic relaxation dynamics of a weakly bending incompressible
rod in a viscous environment. We show that the decay of the
initially imposed transverse undulations creates two expanding boundary
layers that grow at the cost of a longitudinally inert bulk. In the bulk,
longitudinal expansion is completely suppressed by the viscous friction
on the boundary regions. We have calculated tension profiles based on
coarse grained equations of motion for the position dependent tension,
from which all other relevant observables can be calculated. We find that
the different scenarios of tension release can conveniently be classified
in terms of a roughness exponent β as a measure for the type of initial
excitation.
AKB 50.42 Fr 10:30 B
Linear response of a grafted semiflexible polymer to a uniform
field — •Panayotis Benetatos 1 and Erwin Frey 1,2 — 1 Hahn-
Meitner-Institut, Abteilung Theorie, Berlin — 2 Fachbereich Physik, Freie
Universitaet, Berlin
We study the linear response of a semiflexible polymer to a uniform
force field. We use the worm-like chain model and we consider a polymer
which has one end grafted and the other free. In contrast to a force
applied at the free end, the field introduces a nonlocal interaction along
the polymer contour. Because of this nonlocality, using the free chain
propagator (two-point orientational probability density) for the calculation
of the linear response of the polymer extension in the direction of
the field fails. We can apply the propagator method, however, in order to
calculate the linear response of the end-point tangent vector orientation
where locality is restored. We then use this result and make an Ansatz
to obtain the linear response of the extension. Our analytic results are
functions of the total contour length, the persistence length, and the orientation
of the field. We discuss how the response to a field differs from
that to a force.
AKB 50.43 Fr 10:30 B
Depinning of weakly bending semiflexible polymers —
•Panayotis Benetatos 1 and Erwin Frey 1,2 — 1 Hahn-Meitner-
Institut, Abteilung Theorie, Berlin — 2 Fachbereich Physik, Freie
Universitaet, Berlin
We present a simple theoretical model for the thermal depinning of a
weakly bending semiflexible polymer in 1+1 dimensions. We consider a
discrete sequence of pinning sites along the polymer contour. Each pinning
site is characterized by a binding energy, a transverse width, and
an angular width. We use the necklace model of phase transitions in
quasi-one-dimensional systems and we obtain a phase transition in the
thermodynamic limit where the density of pinning sites goes to infinity
and the widths of a pinning site go to zero. This novel way to take
the thermodynamic limit is consistent with the weakly bending approximation
which is valid when the total contour length of the polymer is
smaller than its persistence length. We also consider the depinning in
1+d dimensions.
AKB 50.44 Fr 10:30 B
Random walks of molecular motors — •Stefan Klumpp 1 ,
Theo M. Nieuwenhuizen 1,2 , and Reinhard Lipowsky 1 —
1 Max-Planck-Institut für Kolloid- und Grenzflächenforschung, 14424
Potsdam — 2 Instituut voor Theoretische Fysica, Valckenierstraat 65,
1018 XE Amsterdam
Processive molecular motors perform directed walks along cytoskeletal
filaments. Upon unbinding from the filaments, they undergo non-directed
Brownian motion until they rebind to the same or another filament. The
random walks that result from the interplay of bound and unbound motors
movements are studied theoretically. These random walks exhibit
anomalous drift behaviour in open compartments and stationary concentration
profiles characterized by a balance of bound and unbound motor
currents in closed compartments [1]. Mutual exclusion of motors from
the binding sites of the filaments leads to traffic jams and a maximal
motor current at an intermediate motor concentration. These transport
phenomena mimic transport phenomena in cells and are accessible to in
vitro experiments.
[1] R. Lipowsky, S. Klumpp, and T. M. Nieuwenhuizen,
Phys. Rev. Lett. 87, 108101 (2001).
AKB 50.45 Fr 10:30 B
Gating charge effects for nerve excitation — •Gerhard Schmid,
Igor Goychuk, and Peter Hänggi — Institut für Physik, Universität
Augsburg
Voltage dependent ion channels mainly determine the electric properties
of axonal cell membranes. The ion channels thereby do not only allow
passage of ions trough the cell membrane, but they also contribute to the
membrane capacity, since the switching of the channel gates between an
open and a closed configuration is always connected with movement of
charge within the cell membrane. Especially, in case of moderately large
densities of ion channels, which are found, for example, in the nodes of
Ranvier, this may play a crucial role for nerve excitation. Our model system
is a modified Hodgkin-Huxley model which takes into account the
change in the membrane capacity. Additional terms, which are proportional
to the number of ion channels resp. the number of gates, extend the
original Hodgkin-Huxley model and allow the consideration of a – due
to the gating charges – time-dependent membrane capacity. Surprisingly,
the gating charge do not dramatically change the excitation behavior
even for extreme dense ion channel assemblies, instead, the membrane
capacity at rest exhibits a bell-shaped dependence on the ion channel
density. This work is supported by DFG (SFB 486).
AKB 50.46 Fr 10:30 B
Membrane mechanics and polymer decoration — •Thorsten
Auth and Gerhard Gompper — Institut für Festkörperforschung,
Forschungszentrum Jülich, 52425 Jülich
Polymers embedded into or attached to lipid bilayer membranes modify
the membrane’s mechanical properties. A prominent example of a
polymer-membrane system is the red blood cell [1]. The lipid bilayer
membrane can be modeled by a mathematical surface and a set of material
constants: bending rigidity, saddle-splay modulus, spontaneous curvature.
In many cases the effect of attached, adsorbed or free polymers
can be described by effective curvature elastic constants (see e. g. [2]).
The excluded-volume interaction is well known to strongly affect the
scaling behaviour of polymer chains. We have therefore developed a
Monte Carlo simulation method to investigate the effects of self-avoidance
and different polymer architectures on the curvature elastic constants for
low polymer coverage [3]. The method will be introduced, results for the
effective curvature constants will be presented and discussed together
with implications on the behaviour of membrane systems.
[1] N. Gov, A. G. Zilman and S. Safran; Phys. Rev. Lett. 90, 228101
(2003)
[2] C. Hiergeist and R. Lipowsky; J. Phys. II (France) 6, 1465 (1996)
[3] T. Auth and G. Gompper; Phys. Rev. E 68, 051801 (2003)
AKB 50.47 Fr 10:30 B
Elastic and caloric properties of model membranes at the chain
melting transition — •Wolfgang Manglkammer and Jan K.
Krüger — Universität des Saarlandes, Experimentalphysik, Postfach
151150, D-66041 Saarbrücken, GERMANY
One remarkable feature of lipid membranes, which often serve as a
model for ’real’ biological membranes, is the so-called main transition,
but its nature is not yet clear. When the hydrocarbon chains are melting,
the lipid bilayer transforms from the gel phase into the fluid Lα phase.
We investigated the hypersonic properties of oriented, solid supported
Phosphatidylcholine bilayer stacks of different chain length by Brillouin
spectroscopy as a function of hydration and temperature. The elastic
moduli show huge steps which accompany several phase transitions.
Therefore the transition points can easily be defined, what allows us
to draw a temperature-composition phase diagram.
The elastic behaviour near the main transition is related to the specific
heat as obtained from multi-lamellar vesicles by quasi-isothermal Temperature
Modulated DSC. The heat capacity shows critical behaviour on
both sides of the transition. Such pre-critical features were not found
for the high frequency elastic moduli, although they were reported in
literature for low frequency elastic experiments.
AKB 50.48 Fr 10:30 B
Vesicle adhesion and cohesion at finite temperature — •Thomas
Gruhn and Reinhard Lipowsky — MPI for Colloids and Interfaces
14424 Potsdam
Biological cells are the fundamental building blocks of living organisms.
They are surrounded by a closed membrane surface that serves as
an interface to the outside world. In many cases cells act very similar

Arbeitskreis Biologische Physik Freitag
to vesicles, which are homogenously filled membrane shells. The bending
rigidity κ of the membrane and the molecular interaction with external
substances have an important influence on the cell morphology and
the cell’s adhesion behavior. Rather few attention has been paid in the
past to the influence of thermal fluctuations on the adhesion behavior.
With the help of Monte Carlo simulations we study the behavior of a
one-component vesicle adhered to a substrate at finite temperature. The
adhesion behavior of vesicles was studied systematically as a function of
temperature, potential depth and potential width. For high enough adhesion
strength the contact area of the vesicle goes linear with T/κ. This
behavior can be justified by an analytic approach. Further, a master equation
has been derived which describes all our simulation results. Thus, by
measuring the adhesion area one can derive the adhesion strength from
κ or vice versa.
AKB 50.49 Fr 10:30 B
Morphogen transport by planar transcytosis — •Tobias
Bollenbach 1 , Karsten Kruse 1 , Periklis Pantazis 2 , Marcos
González-Gaitán 2 , and Frank Jülicher 1 — 1 MPI for Physics
of Complex Systems, Nöthnitzerstr. 38, 01187 Dresden — 2 MPI for
Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307
Dresden
Morphogens are signaling molecules that play a key role in development.
They spread from a restricted source into an adjacent target tissue
forming a concentration gradient therein. The fate of cells in the target
tissue is determined by the local concentration of such morphogens.
So far, the dominant mechanism by which morphogens are transported
through the tissue has not been clearly identifed. While diffusion through
the extracellular space is a possibility, recent in vivo experiments on the
morphogen Dpp in the fruit fly Drosophila provide evidence for an active
transport mechanism that was termed “planar transcytosis”. Here,
a theoretical description of this transport mechanism is presented. As a
consequence of nonlinearities in the current, this transport phenomenon
exhibits rich behavior. We compare our description to experimental observations
and aim at a quantitative description of morphogen transport.
AKB 50.50 Fr 10:30 B
Kinetics of salivary protein adsorption — •Anthony Quinn, Hubert
Mantz, and Karin Jacobs — Experimental Physics, Saarland
University, POB 151 150, 66041 Saarbrücken
Exposure to saliva in the oral cavity results in the formation of a layer
of proteins and related biopolymers on all solid surfaces, known as an
acquired salivary pellicle. Pellicle formation occurs immediately and is
considered to be complete within 1-2 hours, with a thickness of approximately
1 micron. Bacteria in the saliva then selectively attaches to the
pellicle (dependent on the surface characteristics of the bacteria and the
specific proteins), marking the onset of plaque formation. Observations
of plaque, which is known to play a crucial role in the development of
oral diseases, reveal an enhanced or diminished growth dependent on the
supporting substrate. This research therefore aims to identify the mechanisms
for salivary protein adsorption at solid-liquid interfaces, with the
intention of optimising the biocompatibility of dental replacement materials,
and reduce the incidence of disease inducing plaque formation.
In-situ ellipsometry is utilized to follow the adsorption kinetics of purified
protein solutions, and the competitive adsorption from mixed protein
solutions on a series of tailored substrates. The physicochemical composition
of these tailored surfaces is carefully controlled and fully characterised
via AFM and wettability analysis, enabling the structural and
interfacial tension components to be identified respectively.
AKB 50.51 Fr 10:30 B
Studying cell adhesion with holographic optical tweezers —
•Jennifer E. Curtis and Joachim P. Spatz — Biophysical Chemistry,
Institiute for Physical Chemistry, University of Heidelberg
Most cells must adhere to a surface if they are to survive. Cell adhesion
involves the orchestration of a stunning number of proteins to form focal
complexes, the physical link between the surface, plasma membrane, and
the stabilizing cytoskeleton. Despite this complexity, simple mechanical
force plays a unique role in the initiation of cell adhesion. The activities
of cells depend sensitively on the mechanical nature of their adhesion
substrate. When too soft, a cell cannot adhere and focal contacts fail to
form. When too hard, unphysiological actin stress fibers plague the cell.
Using holographic optical tweezers, we present dozens of microspheres
directly above the surface of a fibroblast to study the dynamics of focal
adhesion formation. We also study how the initial position and the force
exerted by the optical traps influences the final binding strength, the total
time for full binding, and the subsequent motion of the bead. Lastly,
we hope to elucidate the role of the hylauronic acid layer in focal adhesion
by studying binding dynamics with and without this sticky sugar
matrix.
AKB 50.52 Fr 10:30 B
Electronic Transport in DNA — •Daphne Klotsa, Rudolf A.
Römer, and Matthew S. Turner — Department of Physics, University
of Warwick, CV4 7AL, Coventry, United Kingdom
Based on a theoretical model proposed by Cuniberti et al. [1] we are focusing
on electron localisation along the Deoxyribose Nucleic Acid (DNA)
double helix, using a tight-binding Hamiltonian. The possibility that this
organic super molecule might facilitate electron transfer, along the overlapping
π-orbitals [2], as a means of signalling other biomolecules, has
led us to perform calculations varying the DNA sequences. We have performed
simulations on random sequence, λ- and telomeric DNA. For the
first two the resulting localisation lengths as functions of energy and
disorder show similar behaviour whereas the latter — specific sequence
DNA — gives significantly larger localisation lengths. In all cases an energy
bandgap, indicating semiconducting behaviour, has been observed.
Counter intuitively, for random absorption of Sodium (Na) atoms onto
the backbone, preliminary results have shown localisation lengths to increase
with increasing disorder. A “moving window”technique will be
used in order to assess whether particular shorter fragments of a sequence
behave differently, whose contribution would inevitably be smoothed out
when the whole sequence is considered. Finally, we are looking at another
theoretical way of modelling DNA’s complex structure and properties,
the “ladder model”— an extension of the aforementioned model.
[1] G. Cuniberti, et al., Phys. Rev. B 65, 241314 (2002)
[2] P. J. de Pablo, et al. Phys. Rev. Letters 85, 4992 (2000)
AKB 50.53 Fr 10:30 B
Interlamellar variation of the 3D bone nanostructure
— •Wolfgang Wagermaier 1 , Himadri S. Gupta 1 , Paul
Roschger 2 , Manfred Burghammer 3 , Klaus Klaushofer 2 , and
Peter Fratzl 1 — 1 MPI-KGF, Biomaterials, Potsdam, Germany —
2 LBIO, 4th Med. Dept., Hanusch Hospital and UKH Meidling, Vienna,
Austria — 3 ESRF, Grenoble, France
Bone is a biomineralised tissue structurally optimised for its biological
function. Diverse fibrillar array types - at the 0.1 - 10 micrometer range,
adapted to their local load bearing requirements - bring about this optimisation.
We used a novel combination of synchrotron scanning small
angle X-ray scattering combined with sample rotation to see how the 3D
mineralised nanostructure varied in bone with inter-lamellar resolution.
Several osteons around blood vessels in compact bone were scanned over
a total area of typically (100 x 100 micrometer) and a simple physical
model was developed to reconstruct the 3D orientation. Our results show
mineral crystallite orientation has a fiber texture within single lamellae,
but shows a smooth spatial variation around the cylindrical core of the
osteon. Biomechanically the variation may be explained in terms of the
in-vivo stresses developed around osteonal channels, requiring a composite
structure able to resist large deformation and bending stresses. Our
results provide insights into how bone is designed at the lamellar level
for its biophysical function.
AKB 50.54 Fr 10:30 B
Fusion of giant vesicles observed with time resolution below
a millisecond — •Rumiana Dimova 1 , Christopher Haluska 1 ,
Karin A. Riske 1 , Valerie Marchi-Arztner 1 , and Reinhard
Lipowsky 2 — 1 Max Planck Institute of Colloids and Interfaces, Am
Muehlenberg 1, 14476 Golm, Germany — 2 Universite de Rennes, Rennes
France
Using optical microscopy and a high speed camera, we are able to
record the fusion process with a high temporal resolution of 100us. We
consider two model membrane systems: functionalized giant unilamellar
vesicles (GUVs) in the presence of multivalent ions, and lipid or polymer
GUVs subjected to electrical pulses.
In the first case, we functionalize lecithin membranes with synthetic
molecules bearing a ligand, which form complexes with Eu3+ (2:1). Micropipettes
are used to manipulate GUV’s and inject Eu3+ solution in
the contact zone between two vesicles. The injections induce adhesion
and formation of intermembrane complexes, followed by fusion. This system
has the potential to mimic the action of fusogenic SNARE proteins

Arbeitskreis Biologische Physik Freitag
and give us a better understanding about fusion in biological membranes.
In the second case, we study the fusion of GUVs made of neutral lipid
or diblock copolymer when subjected to electric pulses. We estimate the
characteristic times related to the evolution of the fusion neck. In comparison
to lipid GUVs, polymer vesicles show much slower relaxation due
to the high surface viscosity of their membrane.
In both cases, we detect that the fusion process takes place on the time
scale less than half a millisecond.
AKB 50.55 Fr 10:30 B
Bestimmung der intra- und extraneuronalen Eisenkonzentration
im Gehirn mittels Ionenstrahlanalytik — •Christoph
Meinecke 1 , Tilo Reinert 1 , Markus Morawski 2 , Thomas
Arendt 2 und Tilman Butz 1 — 1 Universität Leipzig; Abteilung
Nukleare Festkörperphysik, Linnestr. 5 , 04103 Leipzig — 2 Paul-Flechsig-
Institut für Hirnforschung, Abteilung Neuroanatomie, Jahnallee 59 ,
04109 Leipzig
”The gain in brain is mainly in the stain” galt lange Zeit für die
Untersuchung neurodegenerativer Krankheiten. Allerdings sind die
Färbemethoden für quantitative Aussagen nur bedingt brauchbar.
Hingegen erlauben neue physikalische Methoden quantitative Analysen
biologischer Materialien. Zum Beispiel bietet die moderne Ionenstrahlanalytik
quantitative ortsaufgelöste Konzentrationsanalysen auf
zellulärer und subzellulärer Ebene.
Bei der Untersuchung von Gehirnschnitten mittels Ionenstrahlanalytik
wurde erstmals die Eisenkonzentration intra- und extraneuronal in
der Substantia nigra Pars compacta und Pars reticulata bei Menschen
quantitativ bestimmt, die an Parkinson erkrankt waren, und mit der Eisenkonzentration
in Hirnschnitten von gesunden Menschen verglichen.
Die Vorteile der Ionenstrahlanalytik (hier PIXE und RBS) sind dabei
die hohe Ortsauflösung von circa 1 µm und die geringe Nachweisgrenze
für Eisen im Bereich von circa 0,05 mmol/l (entspricht 3,7 µg/g des
eingebetteten Gehirnschnittes).
AKB 50.56 Fr 10:30 B
Diffusion in Inhomogeneous Monolayers as Biomimetic
Membranes — •Carsten Selle 1 , Florian Rückerl 1 , Douglas
S. Martin 2 , Martin B. Forstner 2 , Natalie Bordag 1 ,
Marlis Wilke 1 , and Josef Käs 1,2 — 1 Fakultaet fuer Physik und
Geowissenschaften, Universitaet Leipzig — 2 University of Texas at
Austin
Lateral diffusion within membranes plays an important role for essential
cellular processes as, e.g., membrane formation and inter- / intracellular
signalling. We model the diffusion of a protein represented by a
charged polystyrene latex within a lipid monolayer at the air-water interface
mimicking a cell membrane with spatial inhomogeneities - e.g. lipid
rafts - on an expanded scale. For this purpose, the motion of carboxylated
polystyrene latexes diffusing in simple lipid monolayers (pure a)
dimyristoyl phosphatidylethanolamine, DMPE and b) methyl palmitate)
on aqueous subphases has been tracked. We observed that the diffusion
of the particles is apparently influenced by the presence of liquid condensed
domains. Presumably, dipolar interactions between the domains
and the charged particles induce this behavior. This motion was qualitatively
modeled by Monte Carlo simulations.
Furthermore, we study the effect of the antimicrobial peptide Gramicidin
S on the phase behavior and the diffusion properties of the model
systems mentioned above.
AKB 50.57 Fr 10:30 B
Production and Mechanical Properties of Designed Porous
Ceramic Scaffolds — •Alexander Woesz 1,2 , Monika Rumpler 3 ,
Juergen Stampfl 4 , Franz Varga 3 , Nadja Fratzl-Zelman 3 ,
Paul Roschger 3 , Klaus Klaushofer 3 , and Peter Fratzl 1,2 —
1 Max Planck Institute of Colloids and Interfaces, Dept. of Biomaterials,
Germany — 2 Erich Schmid Institute of Materials Science, Austrian
Academy of Sciences, Austria — 3 Ludwig Boltzmann Institute of
Osteology, 4th med. Dept., Hanusch Hospital and UKH Meidling,
Austria — 4 Institute of Materials Science and Testing, Vienna University
of Technology, Austria
Scaffolds made of porous calcium phosphates are potentially interesting
as bone replacement materials. We use a rapid prototyping method based
on microstereolithography and ceramic gelcasting to fabricate highly
porous hydroxylapatite scaffolds suited as substrate for bone cells, whose
strength and stiffness can be adjusted within a certain range. Generally
mechanical properties of cellular solids depend on the apparent density,
the architecture and the properties of the dense material. We showed in
compression tests of cellular structures produced by selective laser sintering
that the strength and stiffness as well as the defect tolerance can
be varied independently from each other by a factor of three, just by
changing the architecture. The scaffolds have been investigated in cell
culture experiments, they were found to support the growth of mouse osteoblasts.
The osteoblasts covered the whole external and internal surface
of the scaffold, they were embedded in an extra cellular matrix consisting
of collagen.
AKB 50.58 Fr 10:30 B
The History of Mutation Pattern along the Human Genome
— •Peter Arndt — Max-Planck Institute for Molecular Genetics,
Ihnestr. 73, 14195 Berlin
Long-ranged correlations of base composition along the chromosomes
have been observed in the human genome. Although this so-called human
isochore structure is known for a long time, we still do not know
its origin or functional consequence. Here we utilize the vast amount of
repetitive sequence deposited in the human genome over the past 250
Myr to investigate differences in the regional mutation patterns. Comparing
substitutional patterns in repetitive elements of various ages, we
reconstruct the history of the base-substitutional process in the different
isochores. At around the time of the mammalian radiation, we find an
abrupt 4- to 8-fold increase of the cytosine transition rate in CpG pairs
compared to that of the reptilian ancestor. Further analysis of nucleotide
substitutions in regions with different GC-content reveals that concurrently
the substitutional pattern changed. We conclude that isochores
have been established before the radiation of the eutherian mammals.
AKB 50.59 Fr 10:30 B
Microfabricated label-free biosensors — •Jürgen Fritz — School
of Engineering and Science, International University Bremen
Label-free microfabricated biosensors offer the advantage of real-time
and highly parallel detection of biomolecules. Two recent examples of
label-free silicon biosensors are presented: nanomechanical cantilever sensors
which detect biomolecules by surface stress and electronic field-effect
sensors, which detect biomolecules by their intrinsic charge. We will discuss
applications, advantages, and limits of both sensors for real-time
detection of nucleic acids and proteins.
J. Fritz et al., Translating biomolecular recognition into nanomechanics,
Science 288 (2000) 316.
J. Fritz et al., Electronic detection of DNA by its intrinsic molecular
charge, PNAS 99 (2002) 14142.
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The emergence of a torus-like attractor in a hemin containing
pH oscillator — •Ronny Straube 1 , Dietrich Flockerzi 2 , Marcus
J.B. Hauser 1 , and Stefan C. Müller 1 — 1 Abteilung Biophysik,
Institut für Experimentelle Physik, Otto-von-Guericke Universität, Universitätsplatz
2, D-39106 Magdeburg — 2 Max-Planck-Institut für komplexe
technische Systeme, Sandtorstr. 1, D-39106 Magdeburg
We investigate the bifurcations leading to burst-like oscillations in the
hemin – hydrogen peroxide – sulfite System [1], where hemin can be considered
as a mimick for heme-containing enzymes. For parameter regions
where these kind of oscillations occur, we find an attractor with the topology
of a torus which does not bifurcate locally from a Hopf bifurcation.
Instead it can be described as the union of several quasi stationary manifolds.
The phase flow on the attractor is governed by the dynamics of a
slow variable which triggers the switching between the different parts of
the attractor. Similar behaviour is known from neural systems [2].
[1] R. Straube, S.C. Müller, and M.J.B. Hauser, Z. Phys. Chem. 217,
1427-1442 (2003)
[2] E.M. Izhikevich, Int. J. Bifurcat. Chaos 10, 1171-1266 (2000)
AKB 50.61 Fr 10:30 B
Pressure-Induced Unfolding of Myoglobin: Neutron Diffraction
and Dynamic Scattering Experiments — •Wolfgang Doster 1 ,
Ronald Gebhardt 1 , and Alan Soper 2 — 1 Technische Universität
München, Physik E 13, 85748 Garching — 2 ISIS, Rutherford Appleton
National Laboratory, England
Pressure, as opposed to temperature, probes the role of volume fluctuations
in biophysical reactions without affecting the thermal energy.
This feature can provide new insight into the folding problem. Globular
proteins tend to unfold in response to the application of hydrostatic
pressure typically exceeding 3 kbar. Unfolding is driven by a volume de-

Arbeitskreis Biologische Physik Freitag
crease, which may occur either by releasing intra-molecular voids or by
contraction of the solvent near the newly exposed protein surface. The
latter involves changes in structure of the protein-solvent network. By
dynamic neutron scattering we probe the pressure evolution of proteinsolvent
bonds. At the unfolding transition, we observe a reduction of the
structural inter-conversion rates and of water fluctuational amplitudes,
related to a compressibility change. This result suggests that stronger
protein-solvent interactions in the unfolded form destabilize the native
state at high pressure. Neutron diffraction experiments reveal a reorganisation
in the hydration shell upon unfolding in parallel with a decrease in
helix content. About 40 intact in the pressure-unfolded state indicative
of a molten globular conformation.
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Collective dynamics of lipid membranes studied by inelastic
neutron scattering — •Maikel C. Rheinstädter 1,2 , Christoph
Ollinger 3 , Giovanna Fragneto 1 , and Tim Salditt 3 — 1 Institut
Laue-Langevin, 6 rue Jules Horowitz, 38042 Grenoble, France — 2 IFF,
FZ-Jülich, 52425 Jülich, Germany — 3 Institut für Röntgenphysik, Georg-
August-Universität Göttingen, Geiststr. 11, 37073 Göttingen, Germany
The collective dynamics of lipid molecules are believed to affect significantly
the physical properties of phospholipid membranes. In the context
of more complex biological membranes, collective molecular motions may
play a significant role for different biological functions [1]. We present a
first time inelastic neutron scattering study on the collective dynamics of
the lipid acyl chains in the model system DMPC -d54. We have measured
the dynamical structure factor S(Qr, ω) in the gel (Lβ) and the fluid (Lα)
phase of the lipid bilayer. The dispersion relation we find is similar to
those found in liquids, with a distinct minimum at Q0, the maximum of
the static structure factor S(Qr), and can be compared to recent Molecular
Dynamics simulations [2]. Furthermore, we investigated the temperature
dependence of the excitations in the minimum in the vicinity of
the main phase transition. Our discussion may shed light on the gel-fluid
phase transition and coexistence of the two phases. By combining neutron
diffraction and inelastic measurements, we gain information about
structure and (collective) dynamics of model membranes on a molecular
length scale. [1] R. Lipowsky and E. Sackmann, Handbook of Biological
Physics, vol. 1, Elsevier (1995); [2] M. Tarek et al., Phys. Rev. Lett. 87,
238101 (2001).
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Investigation of the N-terminal domain of LHCII using single
molecule techniques — •Felix Neugart 1 , Sebastian Schuler 1 ,
Carsten Tietz 1 , Jörg Wrachtrup 1 , Stephanie Boggasch 2 , and
Manuel Lion 2 — 1 3. Physikalisches Institut, Universität Stuttgart —
2 Institut für Allgemeine Botanik, Universität Mainz
The light-harvesting complex II (LHCII) is the most abundant
chlorophyll-binding complex in photosynthesis of green plants. The
native LHCII trimer is responsible for the absorption of half the photons
involved in photosynthesis of algae and higher plants.
The structure of the transmembrane part of the protein of the LHCII
is well known (Kühlbrandt et al. 1994, Nature 367, 614-621) whereas the
N-terminal region of the LHCII complex is not resolved and its function,
orientation and dynamic is still under debate.
One possibility to gather information about the motion of the Nterminal
domain is to attach an artificial fluorophor to the N-terminus
and observe the energy transfer to the Chlorophylls of the LHCII. Different
conformations of the N-terminal domain lead to different energy
transfer rates. Hence, the observation of single labeled LHCII-Monomers
in a confocal setup monitors the dynamics of the N-terminal region and
reveal subensembles of different conformations.
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Continuum theory of filamental self-organization —
•Alexander Zumdieck, Karsten Kruse, and Frank Jülicher
— Max-Planck-Institut für Physik komplexer Systeme
The cytoskeleton is a dynamic complex network of protein filaments
which is involved in many active cellular processes. The polymerization
and depolymerization of filaments as well as the interaction with other
proteins such as molecular motors induce mechanical stresses and dynamic
processes in these structures.Linear filament bundles are important
substructures of the cytoskeleton.
We discuss a general continuum description of the dynamics of such
active networks[1] and focus on one-dimensional bundle geometries. We
show that polymerization and depolymerization play a key role for the
dynamic properties of a bundle, they for example introduce a new length
scale in the system which governs instabilities leading to inhomogenous
states. We relate this continuum theory to a more microscopic description
of active filament systems and show that de-/polymerization could play
a similar role as motors for bundle dynamics. The continuum description
can also be applied to higher dimensional filament geometries that are
for example relevant to the formation of filament rings on cell surfaces.
[1] K. Kruse, A. Zumdieck and F. Jülicher, Europhys. Lett. 64, 716
(2003)
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Spontaneous Oscillations by hair bundles from the vertebrate
inner ear — •Björn Nadrowski 1 , Pascal Martin 2 , and Frank
Jülicher 1 — 1 Max-Planck-Institut für Physik komplexer Systeme,
Nöthnitzer Straße 38, D-01187 Dresden, Germany — 2 Laboratoire
Physico-Chimie Curie, Unité Mixte de Recherche 168, Institut Curie, 26
rue d’Ulm, F-75248 Paris Cedex 05, France
Hearing relies on active filtering to achieve exquisite sensitivity and
sharp frequency selectivity. In a quiet environment, the ears of many
vertebrates emit one to several tones. These spontaneous otoacoustic
emissions, the most striking manifestation of the inner ear’s active process,
must result from self-sustained mechanical oscillations of aural constituents.
As early as 1948, Thomas Gold proposed that the ear contains
an active amplifier, and predicted oto-acoustic emissions for malfunctioning,
i.e. over-amplified ears. It has recently been shown that the
mechanosensitive hair bundles of vestibular cells from the frog ear have
the ability to oscillate spontaneously. This spontaneous oscillation leads
to frequency-selective amplification and nonlinearity in the bundles mechanical
response. We discuss the physical principles behind detection
based on critical oscillation as well as specific mechanisms that can lead
to oscillations and active behaviors by hair bundles. A simple theoretical
description of the hair bundle is presented, and its implications are
studied. The hair bundles non-linear response to mechanical stimuli is
described. We pay special attention to the role of noise in the system.
AKB 50.66 Fr 10:30 B
Structure and Fluctuations of Highly Oriented and Charged
Membranes Under Osmotic Stress. — •Guillaume Brotons, Ulrike
Mennicke, and Tim Salditt — Institut fuer Roentgenphysik,
Universitaet Goettingen
Imposing osmotic pressure to multilamellar membranes is a unique
method for studing lipid bilayer interactions [1]. We have extended this
approach to charged lamellar phases oriented on flat solid support, which
are then probed by interface sensitive X-ray scattering. In this first study
we used the anionic phospholipid POPS [2] and synthetic cationic surfactant
DDABr [3], at controlled osmotic stress corresponding to water
layer thicknesses in the range of a few water molecules up to more than
15 times the bilayer thickness. High-pressures (deshydrated) are obtained
by controlled water vapour, while lower pressures (full hydration) are imposed
by direct contact with a polyelectrolyte solution of same sign as
the lamellar phase under investigation. Under these conditions, specular
and non-specular reflectivity can be carried out within the different symmetry
axes of the oriented membranes (Fig.1) which opens new routes
for establishing the Equations Of State (Pressure-Distance diagram) of
bio-molecular assemblies and studing bilayer undulations or compressibility
fluctuations as a function of pressure. [1] Parsegian,V.A. et all,
Methods in Enzymology; Academic-Press 1986; Vol.127. [2] Mennicke,U.,
PhD-Dissertation, Göttingen-Universität, 08/2003. [3] Brotons,G. et all,
Langmuir 2003, 19, 8235-8244.
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X-ray and neutron reflectivity analysis of peptide-lipid model
systems — •Chenghao Li und Tim Salditt — Institut fuer Roentgenphysik,
Universitaet Goettingen
Using x-ray and neutron reflectivity, we have investigated the structure
of solid-supported, multilamellar lipid membranes with and without
membrane active, antimicrobial peptides. To analyse the measured
reflectivity curve we fit the curves to a model bilayer profile
of adjustable resolution and deduce detailed structural parameters
of the bilayers on an absolute scale of the scattering length
density. The model is implemented in the framework of a semikinematical
scattering theory. We have analysed reflectivity curves
for lipids POPC (1-Palmitoyl-2-Oleoyl-sn-Glycero-3-Phosphocholine),
DMPC (1,2-Dimyristoyl-sn-Glycero-3-Phosphatidylcholin, mixture of
POPC/POPS (1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine]) )

Arbeitskreis Biologische Physik Freitag
in 3:1 mol ratio, and mixture of DMPC/DMPG (1,2-Dimyristoyl-sn-
Glycero-3-[Phospho-rac-(1-glycerol)]) also in 3:1 mol ratio with and without
the antibiotic peptide magainin 2. For the pure OPPC lipid, the
resulting bilayer electron density profile agrees well with previously published
data of a molecular dynamics (MD) simulation.
AKB 50.68 Fr 10:30 B
Investigation of Lipid Multilayers under Electric Field Using
X-Ray Reflectivity — •Doru Constantin, Christoph Ollinger,
and Tim Salditt — Institut fuer Roentgenphysik, Universitaet Goettingen
The influence of an external electric field upon lipid bilayers is of
paramount importance, both from a practical and a fundamental point
of view. Cell electroporation has been long employed for introducing exogenous
molecules into cells, while electroformation is the best method to
date for obtaining giant unilamellar vesicles. Although very important,
these phenomena are still in need of a clear-cut explanation.
We studied the behaviour of solid-supported multilayers of the zwitterionic
lipid DMPC under an applied transverse electric field, using specular
and non-specular X-ray scattering. As a first step, we determined the kinetics
of unbinding under field for various applied voltages, both for thin
(tens of bilayers) and thick (thousands of bilayers) samples. Surprising
similarities with the previously characterized thermal unbinding kinetics
were revealed.
No changes were detected in the diffuse scattering signal, hinting that
the unbinding could be a surface phenomenon, not related to instabilities
in the bulk, but rather affecting only a few layers at the top of the stack.
This hypothesis is reinforced by the fact that the time correlation function
of the reflectivity signal from thin samples exhibits a peak at the
frequency of the applied field, which does not appear for thick samples.
AKB 50.69 Fr 10:30 B
A cluster mode–coupling approach to weak gelation in colloids
and proteins — •Klaus Kroy — Hahn-Meitner Institut, Berlin
Mode–coupling theory (MCT) predicts arrest of colloids in terms of
their volume fraction, and the range and depth of the interparticle attraction.
We discuss how effective values of these parameters evolve under
cluster aggregation. We argue that weak gelation in colloids and proteins
can be idealized as a two–stage ergodicity breaking: first at short scales
(approximated by the bare MCT) and then at larger scales (governed
by MCT applied to clusters). The competition between arrest and phase
separation is considered in relation to recent experiments with colloids
and proteins. Among other things we predict a long–lived ‘semi–ergodic’
phase of mobile clusters, a ‘kinked’ gel line, and strong stretching of the
relaxation even at low volume fractions.
(Work done in collaboration with the soft condensed matter group of
the University of Edinburgh, see cond-mat/0310566,0309616)
AKB 50.70 Fr 10:30 B
Strain hardening of biological tissue — •Klaus Kroy and
Thomas Franosch — Hahn-Meitner Institut, Berlin
It is an everyday experience that our tissue can easily be stretched to
a certain (substantial) extent before dramatic strain hardening painfully
prevents any further elongation. Our toy model for the non–linear elasticity
of stiff polymer networks rationalizes this general phenomenology
in terms of non–affine local deformations of the individual polymers that
are attributed to their highly anisotropic elastic response. We analyze
a particularly simple schematic ansatz for this non–affinity guided by
an analogy to dilatancy in granular media, which leads to analytic results
for the non–linear modulus and the yield strain as a function of the
concentration and stiffness of the polymers.
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Small Angle X-ray Scattering (SAXS) of Novel Pd Bionanocatalysts
— •Barbara Aichmayer 1,2 , Ingomar Jäger 2 , Michael
Mertig 3 , Oskar Paris 4 , and Peter Fratzl 4 — 1 Erich Schmid Institute
of Material Science, Austrian Academy of Sciences, Leoben, Austria
— 2 Institute of Metal Physics, University of Leoben, Austria — 3 IfWW,
University of Technology, Dresden, Germany — 4 Max-Planck-Institute of
Colloids and Interfaces, Department of Biomaterials, Potsdam, Germany
We investigate two types of new bionanocatalysts which are produced
using biotechnology: the cell surface of bacteria as well as twodimensional
S-layer protein crystals serve as templates for the deposition
of Pd crystals. Structural investigations of the Pd particles were carried
out in order to optimise the catalysts and to find out how the biological
templates affect the precipitation of Pd. By means of SAXS the specific
surface and size of the Pd particles were evaluated. Correlations between
the specific surface and the catalytic activity were proven. Indications
for a change of the S-layer protein structure caused by the metal loading
were observed. Furthermore, it was shown that the particle formation
is affected by synchrotron radiation (SR). Pd clusters with a diameter
of 2-3 nm were built in the synchrotron beam. Although the amount of
these particles increased with increasing exposure time to SR, no coarsening
of the particles occurred. From this behaviour we conclude that the
nanoclusters are stabilized by the protein which prevents further growth
of the Pd particles.
This work is supported by the European Union Grant number GRD1-
2001-40424.
AKB 50.72 Fr 10:30 B
NEURON-SEMICONDUCTOR CHIP WITH CHEMICAL
SYNAPSES BETWEEN PAIRS OF IDENTIFIED NEURONS
— •Alexander Kaul 1 , Naweed Syed 2 , and Peter Fromherz 1
— 1 MPI für Biochemie, Membran- und Neurophysik — 2 University of
Calgary, Respiratory and Neuroscience Research Group
We here report on a first integration of a basic biological element of
learning with a silicon chip. We interfaced the pre- and postsynaptic
neuron of an excitatory chemical synapse by non-invasive contacts for
capacitive stimulation and transistor recording. Using the identified respiratory
neurons visceral dorsal 4 (VD4) and left pedal dorsal 1 (LPeD1)
from the mollusk Lymnaea stagnalis, we successfully stimulated presynaptic
neuron VD4 by a chip capacitor and recorded postsynaptic action
potentials in LPeD1 by a transistor. With the soma-soma paired neurons
the strength of the cholinergic synapse was potentiated by tetanic
capacitive stimulation from the chip. The non-invasive interfacing of a
synapse by a semiconductor is a fundamental step towards the development
of hybrid neurocomputing devices and also for long-term studies of
synaptic plasticity in complex neuronal nets [1].
1. Kaul, R.A., Syed N.I., Fromherz P. PRL in press.
AKB 50.73 Fr 10:30 B
Fast and Slow Transistor Records of Recombinant Voltage-
Gated K + Channels — •Matthias Brittinger and Peter
Fromherz — MPI für Biochemie, Abt. Membran und Neurophysik,
Martinsried
To understand transistor recording of neuronal excitation it is necessary
to study the response to defined voltage-gated ion channels under
voltage-clamp.
HEK 293 cells were stable transfected with Kv1.3 potassium channels
and cultured on field effect transistors with an exposed silica gate. We
observed two kinds of transistor signals on a time scale of one microsecond
and ten milliseconds when the Kv1.3 channels opened and closed.
The relative amplitudes depended on the extracellular concentrations of
sodium and potassium.
The fast signal is due to a change of the gate voltage as caused by
charge diffusion in a core-coat conductor. The slow signal is related with
a change of extracellular ion concentration (electrodiffusion) which affects
the transistor threshold. It is rationalized in all details by a Stern
model of the electrical double layer with binding dynamics of potassium
ions.
AKB 50.74 Fr 10:30 B
Capacitive Opening of Ion Channels in Cell Membranes on Silicon
Chips — •Maximilian H. Ulbrich und Peter Fromherz —
Max Planck Institute for Biochemistry, Dept. Membrane and Neurophysics,
Am Klopferspitz 18 a, 82152 Martinsried
In order to understand and optimize capacitive excitation of neurons
from silicon microstructures, it is necessary to study the response of defined
voltage-gated ion channels to voltage transients applied to a chip.
/par HEK 293 cells were stably transfected with Kv1.3 potassium channels.
The cells were cultured on silicon chips insulated with a thin dielectric
and coated with fibronectin. Voltage transients were applied to the
chip. They were chosen such that capacitive coupling gave rise to a stationary
voltage in the narrow extracellular space between chip and cell.
The resulting changes of potassium current through the attached membrane
were recorded at constant intracellular voltage using whole-cell
patch clamp. /par We succeeded in capacitive gating of Kv1.3 channels
through negative extracellular voltages elicited from silicon. Extracellular
voltage-clamp with sufficient amplitude and sufficient duration required,
however, an enhanced time constant of high pass coupling that was

Arbeitskreis Biologische Physik Freitag
achieved with a high-k dielectric on silicon and a high resistance of the
electrolyte.
AKB 50.75 Fr 10:30 B
Electrical Imaging of Neuronal Activity with CMOS Chip at
8 Micrometer Resolution — •A. Lambacher 1 , M. Jenkner 2 , B.
Eversmann 2 , M. Merz 1 , A. Kaul 1 , F. Hofmann 2 , R. Thewes 2 , and
P. Fromherz 1 — 1 Max Planck Institute for Biochemistry, Martinsried
— 2 Infineon Technologies, München
Transistors with open gates on silicon chips are able to record the extracellular
voltage beneath cultured neurons and brain slices. To achieve
electrical imaging in two dimensions at high spatial resolution a CMOS
chip with integrated multiplexing circuits was developed. The sensitive
area of 1 mm 2 contains an array of 128 x 128 individually addressable
transistors at a pitch of 8 µm. We report on experiments with individual
neurons from Lymnaea stagnalis. The extracellular voltage beneath a single
neuron can be recorded with a spatial resolution of 8 µm and a time
resolution of at least 2 kHz. Adhesion regions with different shapes of
signals are observed that are assigned to an inhomogeneous distribution
of ion conductances in the cell membrane. The proof-of-principle experiment
opens the door for high resolution electrical imaging of complex
neuronal systems on a chip.
AKB 50.76 Fr 10:30 B
Electrical Coupling of Lipid Vesicles to Silicon Chips —
•Christian Figger and Peter Fromherz — Max-Planck-Institute
for Biochemistry, Department of Membrane- and Neurophysics, Am
Klopferspitz 18a, 82152 Martinsried
We developed a method to contact giant vesicles with microelectrodes
and studied their electrical coupling to silicon chips.
Electrophysiological recordings were achieved by a combination of
three techniques: (i) Fixation of the vesicles by plastic cages. (ii) Coating
of the microelectrodes. (iii) Verifying the contacts by fluorescein injection.
The contacts originated mostly from rolling membranes. Seal resistances
reached the gigaohmic range and declined during a maximum period of
half an hour.
The novel method was applied to measure the signal transmission from
the vesicle into an array of field-effect-transistors. An electrolyte with a
very high resistance was used to improve the transmission between vesicle
and chip. Two results were obtained: (i) The conductance of the adherent
membrane was much higher than expected. This may result from the
membrane tension or the albumin coating of the chips. (ii) The resistance
of the electrolyte in the gap between vesicle and chip was much
lower than in the bath. The diffuse double layer on the chip surface may
account for this.
AKB 50.77 Fr 10:30 B
High-K Coatings on Silicon Chips for Capacitive Stimulation of
Cells. — •Frank Wallrapp and Peter Fromherz — Max Planck
Institut für Biochemie, Abt. Membran- und Neurophysik, Martinsried,
Germany
So far leech and snail neurons were capacitively stimulated with silicon
chips that were insulated from electrolyte by a thin layer of SiO2. To
enhance capacitance we replaced SiO2 by the high-k materials HfO2 and
TiO2. Capacitance and leakage current were measured in an electrolyteinsulator-silicon
(EIS) configuration. Considering leakage current and
biocompatibility, HfO2 and TiO2 both proved to be suitable for neuronal
stimulation. Due to the higher capacitance, however, TiO2 is superior
in applications. We cultured nerve cells from rat hippocampi on TiO2coated
chips and recorded the intracellular voltage by patch-clamp techniques.
Applying bursts of positive voltage pulses to stimulation areas,
we could reliably elicit action potentials in the neurons. The new high-k
coated chips open up the way to new applications, e.g. opening voltagegated
potassium channels in stably transfected HEK293 cells (Ulbrich
& Fromherz, in preparation) and stimulating rat brain slices (Hutzler &
Fromherz, in preparation).
AKB 50.78 Fr 10:30 B
ENZYME INDUCED STAINING OF BIOMEMBRANE
WITH VOLTAGE SENSITIVE FLUORESCENT DYE —
•Marlon Hinner, Gerd Hübener, and Peter Fromherz —
Max-Planck-Institut für Biochemie, Dept. Membran- und Neurophysik,
82152 Martinsried
The application of fast voltage sensitive fluorescent dyes in brain is limited
due to non-selective staining of the tissue. Here we describe a model
experiment that may eventually lead to a selective staining of individual
nerve cells by enzymatic activation of a water soluble dye precursor.
Three steps were considered: (i) An amphiphilic hemicyanine dye with
an alcohol headgroup and its phosphoric acid ester were synthesized. The
partition coefficient of the phosphorylated dye between water and membrane
is lower by a factor of about 16. (ii) The phosphorylated dye is
converted to the corresponding alcohol by a phosphatase. (iii) Individual
giant lipid vesicles and human erythrocytes are incubated with the
phosporylated hemicyanine. Hydrolysis by added enzyme induces an increase
of membrane fluorescence by a factor of 9 to 13 (vesicles) and 15-25
(erythrocytes). The model experiment forms the physicochemical basis
for development of enzyme induced staining with genetically targeted
cells.
AKB 50.79 Fr 10:30 B
Topologically Defined Networks of Mollusc Neurons Electrically
Interfaced to Silicon Chips. — •Matthias Merz and Peter
Fromherz — MPI für Biochemie, Abteilung Membran- und Neurophysik,
D-82152 Martinsried
A detailed investigation of neuronal networks requires a defined topology
of the synaptic connections and a stimulation and recording technique
that allows long-term supervision of the neurons involved.
We fabricated silicon chips with arrays of two-way contacts of capacitive
stimulators and field-effect transistors. On top of these chips, novel
topographic polyester structures were processed, consisting of pits aligned
with the two-way contacts and of narrow connecting grooves. Neurons
from Lymnaea stagnalis were placed into the pits. The grooves guided the
outgrowth of neurites and held them in their grown geometry, with the
somata being immobilized by the pits. Electrical synapses formed when
the growing neurites encountered in the grooves. Individual neurons of
small nets were capacitively stimulated by voltage pulses applied to the
chip. Signals propagated along the neurites, passed the synapses and triggered
action potentials in postsynaptic neurons, which were recorded by
the respective transistors.
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Extracellular Recording of Individual Mammalian Neurons
with Low Noise Field Effect Transistors — •Moritz Voelker
and Peter Fromherz — MPI für Biochemie, Abt. Membran und
Neurophysik, Martinsried
Noninvasive recording of electrical activity of individual nerve cells
in culture is a prerequisite for the study of designed neuronal networks
and neuron-based pharmacological sensors. We employ open field effect
transistors to record the extracellular signals beneath the cells. While
invertebrate neurons yield large signals, the smaller rat neurons could be
recorded previously only by signal averaging. Here we report on extracellular
recording of individual neurons from rat hippocampus as well as
of dense cultures. By using buried channel field effect transistors built
with a low noise process, we detect extracellular signals from individual
neurons with an amplitude of about 100 µV and from dense cultures
with signals up to 4 mV, considerably more than with planar metal electrodes.
The extracellular voltages with individual neurons and dense cell
cultures are discussed in terms of capacitive and ionic currents in the
planar core-coat conductor of cell-silicon junctions.
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Small Cantilever AFM for Single Molecule Force Spectroscopy
— •Joerg Martini 1 , Volker Walhorn 1 , Jeroen Steen 2 , Tobias
Kramer 2 , Gyuman Kim 3 , Juergen Brugger 2 , Robert Ros 1 ,
and Dario Anselmetti 1 — 1 Experimental Biophysics, Physics Department,
Bielefeld University, Germany — 2 Inst. de Microsystèmes, EPFL,
Lausanne, Switzerland — 3 Kyungpook National University, Korea
AFM-based single molecule force spectroscopy has developed into a
standard method to gain information about molecular elasticities, internal
structural transitions and binding forces and kinetics of single
(bio-)+molecules. The sensitivity and the resolution of these force spectroscopy
measurements are inherently connected to the properties of the
cantilevers used in these experiments. The spring constant of the cantilever
determines its sensitivity, due to Hooke’s law. The coefficient of
viscous damping and the resonance frequency of the cantilever determine
the resolution of the measurement. In case of the coefficient of viscous
damping this is due to the fact, that the Nyquist theorem is valid for the
thermal white noise of the cantilever. In case of high resonance frequencies,
bandpassfiltering between 1/f-noise and the resonance peak reduces
noise without loss of information about the force-distance-dependency of

Arbeitskreis Biologische Physik Freitag
the molecule. Small cantilevers (length: < 30µm, width: < 10µm, thickness:
< 200nm) show all necessary properties for force spectroscopy:
small spring constants, low viscous damping and high resonance frequencies.
We present an AFM that is capable of using small cantilevers for force
spectroscopy experiments of single biomolecules and our current results.
AKB 50.82 Fr 10:30 B
X-ray scattering and microscopy on spider silk fibers — •Anja
Glisovic, Juergen Thieme, Peter Guttmann, and Tim Salditt
— Institut fuer Roentgenphysik, Universitaet Goettingen
We report on the structural characterization of different types of spider
silk. Spider silk is a high performance biomaterial with a unique combination
of elastic properties consisting of only one to two proteins. The
structural basis for these properties on the molecular and mesoscopic
scale of the silk fiber is a matter of intensive scientific debate [1]. We
have used synchrotron based x-ray diffraction as well as x-ray microscopy
to investigate single as well as bundle of fibers. Some technical aspects
(beam collimation, background to noise, analysis of crystalline domains)
and first results of these experiments will be discussed. [1] F. Vollrath,
Knight DP, Nature 410, 541 (2001), and references therein.
AKB 50.83 Fr 10:30 B
Transistor Array probes Release of Vesicles of Chromaffin Cells
— •Janosch Lichtenberger and Peter Fromherz — Membran
and Neurophysics,MPI for Biohemistry
We monitored the release of large dense core vesicles from bovine chromaffin
cells using a linear array of open field effect transistors with a pitch
of 3.6 µm. When secretion was induced by barium, brief spikes in the
transistor current were observed. The events were well localized on the
transistor array with an amplitude of effective gate voltage up to 17 mV.
We assign the events to the local drop of pH in the narrow cleft between
cell and chip that is caused by the release of ATP by individual vesicles.
The pH change affects the threshold of the transistor by proton binding
to the exposed gate oxide. We found good agreement for amplitude,
duration and localization of the signals with the change of the electrical
surface potential that is computed with a model that takes into account
(i) local release of ATP from a vesicle at pH 5.5 into the cleft with an extracellular
buffer at pH 7.2, (ii) diffusion of protons, buffer and ions along
the cleft and (iii) binding of protons to the negatively charged oxide. The
investigation establishes the first chemical neuron-silicon synapse.
AKB 50.84 Fr 10:30 B
Effective pair–potential approach to entangled stiff polymers —
•Sven van Teeffelen, Erwin Frey, and Klaus Kroy — Hahn-
Meitner Institut, Berlin
The entanglement of stiff polymers in solution is remarkably well described
by an effective tube model, in complete analogy to the well–known
blob model for flexible polymers. We extend the scope of this (so far homogeneous)
model to account for spatial density fluctuations by reformulating
it in terms of a microscopically motivated effective pair potential.
This allows us to straightforwardly include additional interactions (depletion,
van der Waals, electrostatic...), and thus turns the model into
a versatile tool for predicting the static structure factor and the equilibrium
phase behavior of stiff polymer solutions. Non–equilibrium (kinetic
arrest) scenarios are also considered. Finally we discuss applications to
biopolymer solutions.
AKB 50.85 Fr 10:30 B
Silicon chip with cultured rat hippocampus slice interfaced with
arrays of capacitors and transistors — •Michael Hutzler and
Peter Fromherz — Max Planck Institute of Biochemistry, Martinsried,
Germany
In the past, field potentials of cultured hippocampal slices evoked by
tungsten electrode stimulation could be recorded by electrolyte-oxidesilicon
field effect transistors. We developed a new silicon chip with a
TiO2-coated surface, containing capacitor arrays for eliciting as well as
transistor arrays for detecting neuronal activity. After cultivating the
brain slices on the silicon chips for one week, we were able to capacitively
stimulate the slices in CA3 by application of defined voltage pulses. The
resulting field potential in CA1 could be recorded with the transistors.
By combining a row of capacitors with a row of transistors we also determined
a simple transfer matrix from CA3 to CA1. This novel type
of purely capacitive interfacing allows a mechanically noninvasive and
electrically minimally interfering contact compared to traditional electrophysiological
methods.
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Growth of the Mineral Particles in Bone - Combined Study of
Small Angle X-ray Scattering (SAXS) and Electron Backscattering
(qBEI) — •A. Valenta 1,2 , P. Roschger 2 , B.M. Misof 2 ,
O. Paris 3 , W. Tesch 1,2 , S. Bernstorff 4 , H. Amenitsch 5 , K.
Klaushofer 2 , and P. Fratzl 3 — 1 Erich Schmid Inst. of Material Science,
Austrian Academy of Sciences and Inst. of Metal Physics, University
of Leoben, Leoben, Austria — 2 L. Boltzmann Inst. of Osteology,
4th Med. Dept., Hanusch Hospital & UKH-Meidling, Vienna, Austria
— 3 Max Planck Inst. of Colloids and Interfaces, Dept. of Biomaterials,
Potsdam, Germany — 4 Sincrotrone Trieste S.C.p.A., Basovizza, Trieste,
Italy — 5 IBR, Austrian Academy of Sciences, Graz, Austria
Bone is a nanofiber composite formed by mineralized collagen fibrils.
In this study bone areas from human biopsies with different degree of
mineralization were investigated. The mineral volume fraction (φ) was
assessed by qBEI, and then the particle surface per volume (σ) was determined
by scanning-SAXS using a micro focus (20 micron) synchrotron
x-ray beam. A biphasic correlation between φ and σ was found: In the
φ-range of 0-27 vol% mineral σ showed a monotone increase, whereas
in the range of 27-40 vol% σ remained constant. This finding suggests,
that after nucleation, mineralization proceeds by a rapid predominant-
2-dimensional growth of the mineral particles, followed by a slow increase
in thickness.
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SARS membrane protein E in model membranes: structural
— •Ziad Khattari 1 , Guillaume Brotons 1 , Tim Salditt 1 , and
Shy Arkin 2 — 1 Institut fuer Roentgenphysik, Universitaet Goettingen,
Goettingen — 2 Department of Biological Chemistry, Hebrew University,
Jerusalm
We present a structural investigation of the SARS membrane protein
E in model membranes by x-ray reflectivity. After the recent publication
of the SARS coronavirus genome [1], structural characterization of its
membrane active proteins is of great importance. The SARS membrane
protein E is believed to be a viral ion channel, but it may also exhibit
fusiogenic functions. The structure and interaction of the membrane active
part of the protein is therefore investigated in model membranes.
Using x-ray reflectivity on highly aligned stacks of membranes on silicon
surfaces in the fluid La phase [2,3], we can determine the electron
density profile of the lipid bilayer as a function of peptide-lipid (P/L)
ratio. Structural properties of the peptide can be determined, as well as
changes in lipid bilayer properties as a function of protein concentration
may be assessed, ranging from bilayer thickness to acyl chain ordering
and head-group hydration. In addition we use site-specific iodination as
a marker in the density profile. Measurements have been performed at
the D4 bending magnet station of HASYLAB/DESY. The results are
complemented by spatial restraints from FTIR spectroscopy on samples
containing site-specific isotopic labels (peptidic 13C=18O). [1] Marra et
al. Science 300, 1399 (2003). [2] T. Salditt et al, Eur. Phys. J. E 7, 105
(2002). [3] Li, C. et al, accepted in J. Phys. D.
AKB 50.88 Fr 10:30 B
Dynamics of Lipid and Protein Domains in Biomembranes
— •Karin John and Markus Bär — Max-Planck-Institute für die
Physik komplexer Systeme, Nöthnitzer Strasse 38, D-01187 Dresden
Acidic lipids such as PIP2 and PIP3 are thought to elicit localized responses,
e.g. for remodeling the cytoskeleton in response to external stimuli.
We consider a mechanism that accounts for a nonrandom distribution
of acidic lipids in the plasma membrane: electrostatic sequestration by
basic proteins such as GMC (MARCKS, CAP23, GAP43) proteins. Our
strategy is to incorporate the different properties of GMC proteins into
a reaction-diffusion model:
1. GMC proteins are cytosolic proteins. Membrane association depends
on a basic effector domain, which interacts with acidic lipids in the membrane
and can lead to the formation of domains enriched in acidic lipids
and GMC.
2. GMC proteins are probably integrators of PKC and Ca 2+ signalling
pathways. Upon phosphorylation of residues within the basic effector domain
by a protein kinase C or interaction with Ca ++ /calmodulin GMC
proteins translocate from the membrane into the cytosol. Upon dephosphorylation
or a decrease in cytosolic Ca ++ GMC proteins reassociates
with the membrane. This cycle is called myristoyl-electrostatic switch

Arbeitskreis Biologische Physik Freitag
(ME-switch).
The resulting model reveals different mechanism of phase separation acting
on different length scales, namely phase separation driven by proteinlipid
interaction as well as phase separation due to enzymatic activity. In
addition, we find also oscillatory behavior and traveling domains.
AKB 50.89 Fr 10:30 B
Complex Crystal Growth of CaCO3 controlled by Diblock-
Copolymer Solutions — •Antje Reinecke 1 , Helmut Cölfen 1 ,
and Hans-Günther Döbereiner 1,2 — 1 Max-Planck-Institut für
Kolloid- und Grenzflächenforschung, D-14424 Potsdam — 2 Department
of Biology, Columbia University, New York, NY 10027
The morphology of CaCO3 crystals grown from Na2CO3 and CaCl2
solutions in a double jet reactor is extensively modified in the presence
of Poly(ethyleneoxide)-block-Poly(methacrylic acid). We observe growth
via rod, dumbell and final sphere morphologies using electron and phasecontrast
microscopy. It is well known that diblock-copolymer additives
influence strongly crystal shapes. However, so far, detailed morphological
sequences during crystal growth have not been reported. For the first
time, we present a quantitative characterization of crystal shapes and
their growth dynamics. Extensive phase-contrast microscopy studies are
statistically analyzed to provide the dynamics of shape distributions over
time. Electron microscopy gives high resolution images of faceted crystal
shapes. We correlate crystal morphology to dynamic free ion concentration
measurements using Ca ++ sensitive electrodes.
AKB 50.90 Fr 10:30 B
Giant Hexagonal Superstructures in Diblock-Copolymer
Membranes — •Wojciech Gó´zd´z 1 , Christopher Haluska 2 ,
Hans-Günther Döbereiner 2,3 , Stephan Förster 4 , and Gerhard
Gompper 3 — 1 Institute of Physical Chemistry, PAS, Warsaw —
2 Max-Planck-Institut für Kolloid- und Grenzflächenforschung, Potsdam
— 3 Department of Biology, Columbia University, New York — 4 Institut
für Physikalische Chemie, Universität Hamburg
In aqueous solutions, amphiphilic diblock copolymers self-assemble into
bilayer membranes similar to phospholipid membranes. Such membranes
can form spherical vesicles called polymersomes in analogy to liposomes,
vesicles built from lipid molecules. We have discovered a new type of
polymersomes, characterized by a genus of the order of one hundred.
The genus describes the number of holes or handles in a vesicle. We have
studied the properties of the high-genus polymersomes both experimentally
and theoretically. We are particularly interested in the structure
of the polymersome walls, which resemble locally a hexagonal network
of passages. The structure of the walls can be altered by applying thermodynamic
stimuli, for example temperature. A few types of ordered
structures which form the wall of polymersomes have been observed experimentally,
such as connected spheres, connected spindles, narrow and
wide passages. The transition between different structures is predicted
and the phase diagram is calculated [1]. The theoretical calculations are
in good agreement with the experiments.
1. C. Haluska et al. , Phys. Rev. Lett., 89(2002), 238302
AKB 50.91 Fr 10:30 B
Slow Relaxation Dynamics of Tubular Polymersomes after
Thermal Quench — •Antje Reinecke 1 and Hans-Günther
Döbereiner 1,2 — 1 Max-Planck-Institut für Kolloid- und Grenzflächenforschung,
D-14424 Potsdam — 2 Department of Biology,
Columbia University, New York, NY 10027
Morphological shape changes of giant tubular vesicles prepared from
the diblock copolymer polybutadiene- (32)-b-polyethylene oxide(20)
(PB-PEO) in aqueous solution after thermal quenches between 10 and
50K were monitored via quantitative phase-contrast microscopy [1].
Reducing the temperature leads to extremely slow sequential beading
of the tubes where the formation of necks starts symmetrically at
the two ends. We characterize the neck diameters and find that the
necks close one by one with effective velocities on the order of a few
tens of nanometers per minute. The necks do not close continuously,
but rather their radii decrease in time in a sequence of exponential
decays between intermediate plateaus. The slow dynamics is a result of
the high membrane surface viscosity of PB-PEO. Sequential beading
is rationalized via a cascade of metastable shapes determined by the
bending elastic energy of the tubular polymersomes.
[1] A. Reinecke, H.-G. Döbereiner, Langmuir 19, 605-608 (2003)
AKB 50.92 Fr 10:30 B
Advanced Flicker Spectroscopy of Fluid Membranes — •Hans-
Günther Döbereiner 1,2 , Gerhard Gompper 3 , Christopher K.
Haluska 1 , Daniel M. Kroll 4 , Peter G. Petrov 1,5 , and Karin A.
Riske 1 — 1 Max-Planck-Institut für Kolloid- und Grenzflächenforschung,
14424 Potsdam — 2 Dept. of Biology, Columbia University, New York,
NY 10027, USA — 3 IFF, Forschungszentrum Jülich, 52425 Jülich, —
4 Dept. of Medicinal Chemistry, University of Minnesota, Minneapolis,
Minnesota 55455, USA — 5 School of Physics, University of Exeter, EX4
4QL, UK
The bending elasticity of a fluid membrane is characterized by its modulus
and spontaneous curvature. We present a new method, advanced
flicker spectroscopy of giant nonspherical vesicles, which makes it possible
to simultaneously measure both parameters for the first time [1]. Our
analysis is based on the generation of a large set of reference data from
Monte Carlo simulations of randomly triangulated surfaces. As an example
of the potential of the procedure, we monitor thermal trajectories
of vesicle shapes and discuss the elastic response of zwitterionic membranes
to transmembrane pH gradients. Our technique makes it possible
to easily characterize membrane curvature as a function of environmental
conditions.
[1] Phys. Rev. Lett. 91, 048301-4 (2003)
AKB 50.93 Fr 10:30 B
Mechanisms of pattern formation during T cell adhesion
— •Thomas Weikl — Max-Planck-Institut für Kolloid- und
Grenzflächenforschung, 14424 Potsdam
T cells form intriguing patterns during adhesion to antigen-presenting
cells. The patterns at the cell-cell contact zone are composed of two types
of domains, which either contain short TCR/MHCp receptor-ligand complexes
or the longer LFA-1/ICAM-1 complexes. The final pattern consists
of a central TCR/MHCp domain surrounded by a ring-shaped LFA-
1/ICAM-1 domain, while the characteristic pattern formed at intermediate
times is inverted with TCR/MHCp complexes at the periphery of
the contact zone and LFA-1/ICAM-1 complexes in the center. We have
developed a statistical-mechanical model of cell adhesion and propose a
novel mechanism for the T cell pattern formation. Our mechanism for
the formation of the intermediate inverted pattern is based (i) on the initial
nucleation of numerous TCR/MHCp microdomains, and (ii) on the
diffusion of free receptors and ligands into the contact zone. Due to this
inward diffusion, TCR/MHCp microdomains at the rim of the contact
zone grow faster and form an intermediate peripheral ring for sufficiently
large TCR/MHCp concentrations. According to our model, the formation
of the final pattern with a central TCR/MHCp domain requires
active cytoskeletal transport processes, which agrees with experimental
findings.
AKB 50.94 Fr 10:30 B
DNA in situ hybridization detection by gold conjugated
nanoparticles and Atomic Force Microscopy — •Gabriella
Teti 1 , Konstantin Agelopoulos 2 , Burkhard Brandt 2 , Stefan
Thalhammer 1 , and Wolfgang Heckl 1 — 1 Department Geo- und
Umweltwissenschaften, Ludwig Maximilians Universitaet-Muenchen —
2 Institut klinische Chemie und Laboratoriumsmedizin, Westf*lische
Wilhelms-Universitaet Muenster
The localization of specific molecules in biological samples continues
to be important for the basic and applied biological research. Immunocytochemistry
and in situ hybridization of nucleic acids are key methods.
For high resolution localization of specific DNA sequences in situ
on biological samples, a study based on the combination of atomic force
microscope (AFM) and DNA in situ hybridization technique has been
proposed. The DNA probes were labelled with digoxigenin and the detection
system was based on antibodies against digoxigenin conjugated
with gold particles. In some cases the gold labelling was amplified by a
colloidal silver enhancement. Compared to high resolution electron microscopy,
AFM generates topographic and three-dimensional images on a
nanometre scale in ambient and liquid conditions without destroying the
sample morphology. The experimental approach was demonstrated on
specific probes against human leukaemia, epidermal growth factor receptor
on human metaphase chromosomes and specific oligonucleotides on
stretched plasmid DNA. Finally, we suggest potential applications based
on our results for high-resolution physical mapping of human genes and
disease correlated genes.

Arbeitskreis Biologische Physik Freitag
AKB 50.95 Fr 10:30 B
Global pattern formation from local cell-to-cell communication
— •Thimo Rohlf and Stefan Bornholdt — IZBI, University of
Leipzig, Kreuzstr. 7b, 04103 Leipzig, Germany
A central observation in developmental biology is the self-organization
of spatial gene expression patterns on scales much larger than cell size. In
existing models, this is often explained by morphogen gradients, which
are established by Turing instability of activator-inhibitor systems [1].
However, pattern formation in these models depends on parameter tuning
of, e.g., diffusion constants. The role of gene regulation in development
is neglected. Here we sketch a new process of global pattern formation
from local information transfer without the need for parameter tuning.
We study a three-state cellular automaton which reproduces two basic
experimental observations at the polyp Hydra: de novo pattern regeneration
and regulation of expression domain size proportional to system
size.
The model shows remarkable robustness with respect to noise and cell
movement. Similar mechanisms could in principle occur in biological organisms
where direct contact induction is present.
[1] Gierer, A. and Meinhardt, H., Kybernetik 12, 30 (1972)
AKB 50.96 Fr 10:30 B
A biological solar energy generator — •Dieter F. Ihrig 1 , H.
Michael Heise 2 , Alexander Moor 2 , Manuel Gemuend 1 , Darius
Wilczek 1 , Ruediger Kuckuk 2 , and Martin Poschmann 1 —
1 FH Suedwestfalen Iserlohn, Germany — 2 Institut fuer Spektrochemie
und angewandte Spektrometrie, Dortmund, Germany
Biomass production by micro algae is by a factor of 10 more efficient
then plants. This gives the chance to create an economic process of solar
energy harvesting. In view of the very low dry mass content of algal
suspensions the most promising way of conversion to a high exoergic and
transportable form of energy is the anearobic production of biogas.
We are actually developing such processes especially micro algal reactors,
a method to separate micro algal cells, a method to treat the micro
algal biomass and a two stage anaerobic process. First results of these
project sections are shown. The developed anaerobic process is very efficient
but also very unstable. To get a better process management it is
necessary to understand the influences between the parameters of process
engineering and biochemical parameters like the concentration of
carboxylic acids. Goal of this part of the project is the development of
an inline sensor. The project was funded by the German Federal Ministry
for Education and Research (BMBF).
AKB 50.97 Fr 10:30 B
FCS used to study translational mobilities in plasma membranes
of living cells — •Margarita Khazarchyan 1 , Elmar
Thews 1 , Carsten Tietz 1 , Jörg Wrachtrup 1 , Sylvia Willi 2 ,
Anja Krippner-Heidenreich 2 , and Peter Scheurich 2 —
1 3.Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring
57, 70569 Stuttgart — 2 Institut für Zellbiologie und Immunologie,
Universität Stuttgart, Allmandring 31, 70569 Stuttgart
Fluorescence correlation spectroscopy (FCS) is an attractivce method
of measuring molecular concentrations, chemical kinetics and diffusion
processes in living cells. We use one- and two-photon excitation for the
investigation of translational mobility in cytoplasm and in plasma membranes
using different fluorophores for intracellular applications of FCS.
Measurements in living cells and in plasma membranes are feasible with
reasonable signal-to-noise ratios, even with fluorophore concentrations on
a single molecule level in the detection volume.
We present an application of this method to study TNF(Tumor Necrosis
Factor)-R1, TNF-R2 in plasma membranes and TRAF2-protein in
cytoplasm of living cells. Other investigations demonstrated that TNF-R
and TRAF-proteins involved in the cells apoptotic pathway. Apoptosis is
the specific controlled mechanism of cell death which is distinct from uncontrolled
necrotic cell death. Apoptosis requires tight regulation. Lack of
such regulation leads to either too much or too little apoptosis, resulting
in pathological conseqeunces, such as Alzheimer disease or cancer.
Diffusion coefficients of the signal TNF-R and TRAF2-protein were
determined before and after stimulation with TNF ligand.
AKB 50.98 Fr 10:30 B
Stepwise rotation of the epsilon-subunit of EFoF1-ATP synthase
during ATP synthesis and hydrolysis - a single-molecule
FRET approach — •Michael Börsch 1 , Boris Zimmermann 2 ,
Nawid Zarrabi 1 , Manuel Diez 2 , and Peter Gräber 2 —
1 3. Physikalisches Institut, Universität Stuttgart — 2 Institut für
Physikalische Chemie, Universität Freiburg
F-type ATP synthases catalyze the formation of ATP by coupling
two rotary motions of subunits within the enzyme. We attached
tetramethylrhodamine-maleimide at the rotating epsilon-subunit and
Cy5-bismaleimide crosslinking the two b-subunits, and reconstituted the
enzymes fully functional into liposomes. Fluorescence resonance energy
transfer (FRET) was monitored in photon bursts of freely diffusing ATP
synthases with a confocal setup for single-molecule detection. Incubation
with non-hydrolysable AMPPNP resulted in stable intensity ratios
within a burst and three different FRET efficiencies corresponding to
the three possible orientations of the epsilon-subunit.
Upon addition of ATP at mM concentrations, a consecutive order of
three distinguishable FRET efficiencies was observed indicating a stepwise
movement of the epsilon-subunit, comparable to the stepwise rotation
of the gamma-subunit in EFoF1 [1,2]. Under the conditions for ATP
synthesis stepwise rotation of the epsilon-subunit was observed in opposite
direction. Dwell-time analysis revealed heterogeneity of the three
catalytic binding sites.
[1] M. Borsch et al. (2002) FEBS lett. 527, 147-152.
[2] M. Diez et al. (2004) Nat. Struct. Mol. Biol., in press.
AKB 50.99 Fr 10:30 B
DNA translocation through a biological nanopore — •Ulrich F.
Keyser 1 , N. Wennersbusch 1 , D. J. Bonthuis 1 , N. H. Dekker 1 ,
X. S. Ling 2 , and Cees Dekker 1 — 1 Molecular Biophysics, Delft University
of Technology, Lorentzweg , 2628 CJ Delft, The Netherlands1 —
2 Brown University, Providence, USA
We study the translocation of single-stranded DNA (ss-DNA)
molecules through a single biological nanopore, viz., an alpha-Hemolysin
pore from Staphylococcus aureus assembled within a lipid membrane.
The inner diameter of this nanopore is only 1.5 nm and ss-DNA molecules
can be transferred one by one. Applying a bias voltage at high salt concentrations
gives rise to an ionic current through the nanopore. If a ss-DNA
molecule enters the pore the current is partly blocked and the passage
of a molecule is detected. We are investigating different types of ss-DNA
with various lengths and sequences to study the influence on the translocation
speed and current. The experimental results will be compared to
recent theoretical models.
AKB 50.100 Fr 10:30 B
Immobilisation of the Light harvesting complex LH1 of
Rhodospirillum rubrum on nanostructured surfaces — •Britta
Götze, Carsten Tietz, and Jörg Wrachtrup — 3. Physikalisches
Institut, Universität Stuttgart, Germany
Sunlight is the driving force on this planet. To make it useable plants
and bacteria have created a sofisticated system- the photosynthetic apparatus
-.The final product of this system is ATP - the most common
transporter of energy in every living thing.
The first step in this apparatus is to capture sunlight as excitation
energy and transfer it to the reaction center. Here a charge seperation
takes place as a initializing step in photosynthesis.
In this work the light harvesting complex LH1, a pigment protein complex
of the purple bacterium Rhodospirillum rubrum is investigated. The
studies have been performed on nanostructured as well as on modified
surfaces. The aim of this work is to investigate the possibility of long
range 1d energy transfer between light harvesting complexes on nanostructured
surfaces.
The structures are made using electron beam lithography and consist
of gold/titanium on SiO2. A self assembled monolayer is formed on top
of them using different types of mercaptanes.
First step was to figure out what kind of mercaptane offers the best adsorbance
properties for the light harvesting complexes./par Second step
was to proof a specific binding / adsorbance of the proteins on the modified
surface./par Third step will be to get a densly package of proteins
on these structures.

Arbeitskreis Biologische Physik Freitag
AKB 50.101 Fr 10:30 B
Biomechanical investigations of collagen fibrils — •Stefan
Strasser, Wolfgang M. Heckl, and Stefan Thalhammer —
Department for Geo und Environmental Sciences, GeoBioCenter and
Center for Nanoscience, Ludwig Maximilians University, Theresienstr.
41, 80333 Munich, Germany
Collagen fibrils, type I and II with various periodicities were investigated,
using the Atomic Force Microscope both as tool for imaging and
nanomanipulation. Native and fibrous long spacing (FLS) collagen fibrils
were formed by self assembling in vitro, using a special setup for
dialysing. Depending on the conditions of assembly, collagen may form a
variety of different structures. The received collagen fibrils of type I had
a bending pattern of 67nm for the native fibrils, and 200nm to 300nm
for the FLS fibrils. Collagen is a system which shows a large degree of
polymorphism. All fibrils with a periodicity greater than 67nm can be
considered as FLS collagen. The collagen fibrils were imaged in air and
in liquids. To determine the elastic properties of collagen fibrils the tip of
the AFM was used as a nano-indentor. Force displacement curves were
recorded in liquids at different hights of collagen clusters as well as on
single fibrils and the youngs modulus has been calculated utilizing the
Hertzian theory. Results will be shown and discussed on single fibrils and
on multilayer stacks.
AKB 50.102 Fr 10:30 B
Contact Resistance of Cell Silicon Junctions Measured with
Voltage-Sensitive Dye — •Raimund Gleixner and Peter
Fromherz — MPI für Biochemie, Abt. Membran und Neurophysik,
Martinsried
The electrical sheet resistance between a cell and a solid substrate is
a crucial parameter for bioelectronic coupling. It can be determined by
applying transient voltages to a silicon chip, observing the response of
the membrane with a voltage-sensitive dye (Braun:PRL86,2905,2002).
We used the novel dye ANNINE-5 (Hübener:JPC,107,7896,2003) to
study the contact between HEK293 cells and fibronectin-coated oxidized
silicon. We determined the sheet resistance as a function of salt concentration
in the bath. A train of voltage transients was applied to the
chip and the fluorescence in the attached membrane was averaged in a
confocal microscope over several periods. For sinusoidal stimulation, the
frequency dependent spatially resolved transfer function was fitted with
a core-coat conductor model of the junction.
We found that the sheet resistance was proportional to the bulk specific
resistance. This indicated a cleft of 80nm filled with bulk electrolyte.
¿From fluorescence interference contrast (FLIC)microscopy we obtained
a distance of 70nm between membrane and chip, independent of salt
concentration. We conclude: (i)The narrow extracellular space of cell
adhesion is filled with bulk electrolyte. (ii)The sheet resistance can be
enhanced by enhancing the resistance of the bath.
AKB 50.103 Fr 10:30 B
Correlation functions and Boltzmann Langevin approach for
driven one dimensional lattices gases — •Paolo Pierobon 1,2 , Felix
Von Oppen 2 , Andrea Parmeggiani 1 , and Erwin Frey 1,2 for the
collaboration — 1 Hahn-Meitner Institut, Abteilung Theorie, Glienicker
Str.100, D-14109 Berlin, Germany — 2 Fachbereich Physik, Freie Universitaet
Berlin, Arnimallee 14, D-14195 Berlin, Germany
The Totally Asymmetric Simple Exclusion Process (TASEP) is a simple
one dimensional driven lattice gas model. It may serve as a simplified
model highlighting some aspects of traffic flow and biological transport
phenomena, e.g. motion of molecular motors on microtubules. At the
same time it has become a paradigm of non-equilibrium systems which
exhibit dynamic phase transitions driven by the boundaries. Although
the stationary density profile has been understood for long time, the time
dependent properties are still under investigation. We study the dynamic
correlation function of the particle density in such a system using real
time Monte Carlo simulations. In certain regimes the results can be rationalized
using a Boltzmann-Langevin approach i.e. adding a fluctuating
current to the mean field equation in a phenomenological way. We also
analyze our results within the ”domain wall”picture, where a “shock”
separates two phases and fluctuates as a Brownian walker with reflective
boundary conditions. Critical exponents are measured with great accuracy
from the properties of autocorrelation function at the critical point
(where three phases coexist), and in the maximal current phase. The
results corroborate that the system, in such conditions, belongs to the
KPZ universality class.
AKB 50.104 Fr 10:30 B
An off-lattice model for multicellular tumor spheroid growth —
•Gernot Schaller and Michael Meyer-Hermann — Institut für
Theoretische Physik, Zellescher Weg 17, 01062 Dresden
We model three-dimensional multicellular tumor spheroids using an
agent-based Delaunay/Voronoi-model which relies on experimentally accesible
cellular properties.
For the detection of natural neighbors we use three-dimensional
weighted dynamic and kinetic Delaunay/Voronoi tessellations. The
resulting bidirectional graph can be dynamically updated with in
average linear complexity versus the number of cells. Cells are assumed
to be elastically deformable spheres with varying radii. The growth of
cells is modeled by coupling the cells to a reaction-diffusion-equation for
nutrients. The dynamics is then calculated using the Langevin equation
in the overdamped limit.
We study the emergence of typical avascular tumor morphologies starting
with a single tumor cell. The influence of several mechanisms such
as nutrient limitation, external tissue pressure and intercellular adhesion
on growth and morphology is studied.
This work has been financially supported by the SMWK.
AKB 50.105 Fr 10:30 B
Molecular dynamics of intramyocellular metabolites from highresolution
in vivo 1 H NMR spectroscopy — •Leif Schröder 1 ,
Christian Schmitz 2 , and Peter Bachert 1 — 1 Dept. of Medical
Physics in Radiology, Deutsches Krebsforschungszentrum, Heidelberg,
Germany — 2 Biophysikalische Chemie, Physikalisch-Chemisches Institut,
Universität Heidelberg, Germany
Residual dipolar couplings affecting resonances in 1 H NMR spectra of
living tissue have been discovered 10 years ago (Kreis et. al.). Our purpose
was to explore molecular dynamics of creatine (Cr), taurine (Tau),
and carnosine (Cs) in human calf muscle (m. gastrocnemius) in vivo by
analyzing dipolar-coupled multiplets in localized high-resolution 1 H NMR
spectra (STEAM and PRESS technique). Measurements were performed
in healthy volunteers on a whole-body MR tomograph at B0 = 1.5T. The
residual coupling strength SD0 derived from the spectra was compared
to the coupling constant D0 calculated using the internuclear distance
under the assumption of completely frozen molecular libration. The order
parameter S is a measure of molecular mobility. We found a large
S (1.2 × 10 −2 ) for the detectable Cs spin system, i.e. the imidazole ring
protons, which indicates restricted reorientational motion of this compound
in contrast to high mobilities of the CH2 and CH3 groups of Tau
and Cr (S = 1.4 − 3 × 10 −4 ). The observed motional restriction of Cs is
explained by interaction of the metabolite with phospholipids in muscle
cell membranes. These results demonstrate that 1 H NMR spectroscopy
permits noninvasive studies of intermolecular processes in vivo.
AKB 50.106 Fr 10:30 B
Are there lipid rafts? — •Heiko Heerklotz — Biozentrum Basel,
Klingelbergstr. 70, CH-4056 Basel
Functional domains in biological membranes and the role of lipids in
the formation of such structures are still not unequivocally clarified. A
classical definition of the term lipid rafts refers to large, long-lived domains
in native cellular membranes that are formed by a spontaneous demixing
of a liquid ordered phase rich in sphingomyelin (SM) and cholesterol
(Cho) from the fluid, phosphatidylcholine (PC)-rich matrix. Rafts
have been believed to accumulate large numbers of proteins and it has
been assumed that rafts can be isolated from membranes as so-called detergent
resistant membrane fragments (DRMs). Our investigations have
revealed however that these common assumptions are inconsistent. Putative
lipid rafts having stability properties similar to liquid ordered domains
in a PC-SM-Cho mixture cannot be isolated by detergent without
changing their properties substantially. We came to this conclusion on
the basis of studies of the stability of domains and intermolecular interactions
between lipids (POPC-SM-Cho) and detergents (Triton X-100
and others) by various microcalorimetric techniques (isothermal titration
calorimetry, differential scanning calorimetry, pressure perturbation
calorimetry) and solid-state NMR. A simple thermodynamic model based
on the enthalpy and entropy of the interactions of different lipids with
the detergent explains the phenomena.
AKB 50.107 Fr 10:30 B
Contact mechanics of bioinspired fibrillar structures — •Ralph
Spolenak, Stanislav Gorb, and Eduard Arzt — Max-Planck-
Institut für Metallforschung, Heisenbergstr. 3, D- 70569 Stuttgart

Arbeitskreis Biologische Physik Freitag
Animals like beetles, flies, spiders and geckos rely on hairy (fibrillar)
structures to adhere to natural surfaces enabling them to walk on vertical
surfaces or on the ceiling. Recently, experimental evidence has been
provided by Autumn et al. that the adhesion between single fibers and
the natural surfaces is caused by van der Waals interaction. Modeling
the adhesion of fibrillar structures by contact mechanics reveals that the
total adhesion of the system can be enhanced by contact splitting. In
effect the size of fibers in animals scales inversely with their body mass.
Derived from contact mechanics we present the effects of contact shape,
fiber material and fiber geometry on the total adhesion of the system.
Design rules are devised that can serve as guidelines for the fabrication
of artificial adhesion systems.
AKB 50.108 Fr 10:30 B
Geometrical parameters of periodical structures by 1 H NMR —
•Stefan Kirsch and Peter Bachert — Dept. of Medical Physics in
Radiology, Deutsches Krebsforschungszentrum, Heidelberg, Germany
Some biological tissue, e.g., muscle and trabecular bone, contains periodical
structures at different levels of organisation. Assessment of the
corresponding geometrical parameters is possible on the basis of intermolecular
dipole-dipole couplings. In liquid-state 1 H NMR the distant
dipolar field generated by the bulk of water protons can have a significant
effect on the evolution of the magnetization. Application of the
CRAZED sequence (two rf pulses, delay τ, gradient G) yields a train
of echo signals at times nτ (n = 1, 2, ...) which are explained by intermolecular
multiple-quantum coherences of the order n (Warren et al.)
and which are generated by dipolar-coupled spins of mutual distance
d = π/(γGτ). In periodical structures echo formation for n �= 2 is only
expected when d is a linear combination of the characteristic length scale
λs of the structure: d = Σi li · (λs/2); li = ±1, ±2,... . With the purpose
of possible application in vivo, we performed CRAZED experiments with
tightly packed microcapillaries immersed in water in a 1.5-T whole-body
MR tomograph (MAGNETOM Vision; Siemens). We demonstrate, that
for n = 1 and 3 information on λs of the structure can be obtained.
AKB 50.109 Fr 10:30 B
Asynchronous networks of switches and the reliability of gene
regulation — •Konstantin Klemm and Stefan Bornholdt — Interdiszplinäres
Zentrum für Bioinformatik, Universität Leipzig, Kreuzstr.
7b, 04103 Leipzig
How do networks of regulatory genes function in a near deterministic
way, although they consist of mostly autonomous non-synchronized
switches? This is studied using a network of asymmetrically coupled binary
threshold units with asynchronous serial update in random order.
Motivated by the biochemical processes during gene regulation involving
mRNA and protein, each unit updates its state according to an individual
clock that is subject to noise. In general, this asynchronous mode leads
to stochastic, non-deterministic system behavior. However, considering
a transmission delay between the nodes leads to synchronization and
ordering of the dynamics: On a coarse grained time scale, units switch
simultaneously. These results suggest that transmission delay may contribute
to the robustness of genetic regulation. Further, as some topological
features are more favorable than others for this effect, it hints at a
possible explanation of why some topological motifs, in particular loops,
are suppressed in the wiring of genetic networks.
[1] Konstantin Klemm and Stefan Bornholdt, preprint
http://www.arXiv.org/abs/q-bio/0309013
AKB 50.110 Fr 10:30 B
Spatially periodic patterns in nematic and biopolymer-motor
systems — •Falko Ziebert and Walter Zimmermann — FR Theoretische
Physik, Universität des Saarlandes, 66041 Saarbrücken
We present two possible mechanisms of pattern formation in rigid
biopolymer systems like actin filaments and microtubules. The first one
is the competition between diffusion and the finite lifetime of the filaments,
which are in vivo continuously assembled and disassembled. This
kinetics transforms the phase separation close to the isotropic-nematictransition
into the formation of spatially periodic patterns, as predicted
on the basis of a phenomenological model.
In the second scenario, motor proteins are added to a solution of filaments.
Because the motors walk on a filament only in one specified
direction defined by the structure of the filament and the motor species,
the �n ↔ −�n symmetry of the filament solution is broken which leads to
new patterns. This scenario can be described microscopically by means
of a Smoluchowski-equation.
AKB 50.111 Fr 10:30 B
Entropic Forces between Biopolymers — •Azam Gholami 1 and
Erwin Frey 1,2 — 1 Hahn-Meitner-Institut, Abteilung Theoretische
Physik, Glienicker Strasse 100, D-14109 Berlin, Germany — 2 Fachbereich
Physik, Freie Universitat Berlin, Arnimallee 4, D-14195 Berlin, Germany
The interaction between biopolymers in the cytoskeleton is characterized
by the interplay of energy and entropy. There are electrostatic forces,
interactions mediated by crosslinking proteins, and steric interactions induced
by thermal fluctuations. We study these steric interactions in various
geometries using Monte Carlo methods. The Monte Carlo data give
clear evidence for the existence of repulsive interaction between biopolymers
at short distances. The form of the repulsive interaction is in good
agreement with the analytical results obtained from scaling arguments.
AKB 50.112 Fr 10:30 B
Electrophoretic Accumulation of Membrane Bound Proteins on
Polymer Supports — •Joachim Hermann 1 , Markus Fischer 2 ,
Steven Boxer 3 , and Motomu Tanaka 1 — 1 Physik Department,
Lehrstuhl f”ur Biophysik E22, TU M”unchen, James-Franck-Str., D-
85748 Garching — 2 Fakult”at f”ur Chemie, TU M”unchen, James-
Franck-Str., D-85748 Garching — 3 Department of Chemistry, Stanford
University, CA 94305-5080, USA
The presented work deals with the local biofunctionalization of solid
surfaces by means of electrophoretic accumulation of genetically engineered
recombinant proteins docking onto membranes deposited on polymer
supports. His-tagged fluorescent proteins (GFP and DsRed) were
firstly coupled homogeneously to lipid monolayers doped with chelator
(NTA) lipids, then a DC electric field was applied for accumulation of
the proteins. The resulting concentration gradient of proteins at equilibrium
could empirically be analyzed by a simple differential equation.
As a result, the mean velocities and mobilties of the two proteins were
obtained.
The proteins on the membrane surface experienced not only electrophoretic
forces but also electroosmosis in the opposite direction. The
counter balance between these two opposing forces was further studied
by shifting the surface charge densities, namely, the difference in zeta
potentials between the membrane and the proteins. In fact, incorporation
of oppositely charged lipids into the membrane led to larger mean
velocities for both proteins, which supports the proposed scenario semiquantitatively.
AKB 50.113 Fr 10:30 B
Vesicles in the Optical Stretcher - Shape changes induced
by stress-dependent flip-flop processes — •Frank Sauer, Stefan
Schinkinger, Falk Wottawah, Bryan Lincoln, and Jochen
Guck — Fakultät für Physik und Geowissenschaften, Univeristät Leipzig
We have investigated giant unilamellar vesicles (DLPC and C12E4)
with an optical stretcher. This laser-based micromanipulation tool induces
optical surface stresses that can trap vesicles and deform them
from spherical into a prolate shape. The observed deformation increased
linearly with applied stresses ranging from 1-20 Pa. This deformation
was reversible upon immediate removal of the stress. Surprisingly, under
continued stress for more than 1s, the vesicle returned to its spherical
shape with the return rate increasing with stress. When the stress was
then removed, the vesicle became oblate and recovered its equilibrium
spherical shape only after a very long time (10-20 min). This effect could
be repeated several times with the same vesicle, excluding damage to
the vesicle as possible cause. The most likely explanation of this phenomenon
is a stress dependent flip-flop rate between outer and inner
leaflets. This leads to a stress dependent spontaneous curvature, which
changes the equilibrium shape of the vesicle. Further experiments to test
this hypothesis are underway.
AKB 50.114 Fr 10:30 B
Pattern formation in systems with conservation laws — •Ronny
Peter and Walter Zimmermann — Theoretische Physik, Universität
des Saarlandes, 66041 Saarbrücken
Pattern formation in dissipative systems, especially in systems with
unconserved order parameters, were intensively explored during the recent
decade. Pattern formation in systems with conservation laws, that
recently emerged in models for biological systems, however exhibit new
aspects. For both, stationary and spatially periodic pattern as well as for
traveling and standing waves, in systems with conservation laws largescale
neutral modes must be included in the asymptotic analysis for pattern
formation near onset. Various consequences are related to these slow

Arbeitskreis Biologische Physik Freitag
modes. As a microscopic example a model of ion-channels with openclosing
kinetics embedded in a biomembrane is presented. This model
leads to generic amplitude equations occuring in systems with conserved
order parameter and are furthermore studied in the general case of a
simple reaction-diffusion system.
AKB 50.115 Fr 10:30 B
Hopf-bifurcations in systems with conserved quantities —
•Markus Hilt and Walter Zimmermann — Theoretische Physik,
Universität des Saarlandes, 66041 Saarbrücken
A cubic Ginzburg–Landau equation is presented, which describes for
the first time the universal properties of a Hopf-bifurcation in a system
with conserved quantities. This bifurcation occurs for instance in a model
describing the dynamics of two interacting ion-channels in a membrane.
It is a universal feature of this bifurcation that all nonlinear traveling
wave solutions are linear unstable in general, besides the smallest possible
wavenumber in a finite system with periodic boundary conditions.
Spatio-temporal chaos occurs either due to boundary effects or due to
an extension of the destabilizing wavenumber band. This scenario is different
from other cases, where spatio-temporal chaos often occurs, as for
instance for one of the most studied nonlinear equations in physics, the
Ginzburg–Landau equation for unconserved systems (see e.g. I. Aranson
and L. Kramer, Rev. Mod. Phys. 74, 99 (2002)).
AKB 50.116 Fr 10:30 B
Fluorescence Excitation Spectroscopy on Single Light-
Harvesting Complexes of Higher Plants — •Carsten Tietz 1 ,
Sebastian Schuler 1 , Fedor Jelezko 1 , Heiko Lokstein 2 ,
and Jörg Wrachtrup 1 — 1 3. Physikalisches Institut, Universität
Stuttgart, 70550 Stuttgart, Germany — 2 Institut für Pflanzenphysiologie,
Humboldt-Universität Berlin, 10099 Berlin, Germany
Photosynthesis of higher plants and green algae is the most important
metabolic process on earth. The absorption of light in higher plants is
carried out by pigment-protein complexes. Besides the well known major
Light-Harvesting Complex II (LHCII) that exists in a trimeric form
there are several minor chlorophyll (Chl) a and b binding complexes to
be found in Photosystem 2.
Single molecule spectroscopy has been used to investigate the photophysics
of the minor plant antenna CP29 in its native monomeric form.
This complex binds 8 chlorophylls of which 2 are supposed to be Chl
b and 6 Chl a. Although the structure is not known, sequence analysis
showed a strong resemblance between LHCII monomers and CP29.
Therefore it was possible to construct a structural model of CP29 on the
basis of LHCII.
With combined excitation and emission spectra of single CP29 complexes
at low temperatures (2 K), we can gather information about the
energy levels of the bound Chl molecules, the relative orientation of their
transition dipole moments and the energy transfer rate. Here we report
on the first fluorescence excitation spectra of single CP29 complexes.
AKB 50.117 Fr 10:30 B
Cell Adhesion onto Highly Curved Particle Surfaces - One-
Step Immobilization of Cell Membranes — •Motomu Tanaka
und Stefan Kaufmann — Biophysics Lab, Tech. Univ. Munich
We report single-step, orientation selective immobilization of human
erythrocyte membranes on bare silica beads with different topographies:
1) solid (nonporous) silica beads with a diameter of 3 microns and 2) porous
silica beads with a diameter of 5 microns. Erythrocyte membranes
were immobilized onto beads simply by incubation, without sonication or
osmotic lysis. Membrane orientation before and after the immobilization
was identified with a first monoclonal antibody and a second fluorescent
polyclonal antibody. Adherent erythrocytes on the beads all ruptured,
inverted the asymmetric orientation of the membrane, and selectively
exposed their cytoplasmic domain. The surface topography did not influence
orientation or the amount of immobilized membranes. On the other
hand, the fact that no adsorption or rupture of erythrocytes could be
observed on planar quartz substrates suggests a significant influence of
contact curvatures on the adhesion free energy.
AKB 50.118 Fr 10:30 B
Analysis of Spatiotemporal Data Sets in Dictyostelium —
•Christiane Hilgardt 1 , Marc-Thorsten Hütt 2 , and Stefan C.
Müller 1 — 1 Otto-von-Guericke Universität Magdeburg, Institut für
Experimentelle Physik, Abteilung Biophysik, Universitätsplatz 2, 39106
Magdeburg — 2 Technische Universität Darmstadt, Institut für Botanik,
Arbeitsgruppe Theoretische Biologie und Bioinformatik, Schnittspahnstraße
3, 64287 Darmstadt
We investigate reaction-diffusion waves in the slime mould Dictyostelium
with spatiotemporal analysis filters, [1, 2, 3]. Our hypothesis
is that the spatial distribution of cell properties determines the architecture
of structures in later morphogenetic stages, e.g. aggregation
streams. Our investigations address the constructive role of variability
in biological structure formation. To this goal we visualize local inhomogeneities
in fluctuations, which allow to distinguish between fast and
directed dynamics. We correlate extremal behavior with later structures.
In particular, we focus on the borders between the different states of
an excitable medium (excitable, excited and refractory) to evaluate biological
variability as the ”roughness” of these border lines. First results
support our hypothesis. The spatial distribution of our observable shows
an elevated correlation with the position of later aggregation streams.
Furthermore, methods of information theory and estimation theory from
sequence analysis are developed and applied to the spatiotemporal data
sets. [1] Müller S. C. et al. (1998) Biophys. Chem. 72: 37-47. [2] Hütt
M.-Th., Neff R. (2001) Physica A 289: 498-516. [3] Hütt M.-Th. et al.
(2002) Phys. Rev. E. 66: 26117.
AKB 50.119 Fr 10:30 B
Functional Micro-Domains of Glycolipids with Partially Fluorinated
Membrane Anchors - Impact on Cell Adhesion —
•Motomu Tanaka 1 , Matthias Schneider 1 , Laurent Limozin 1 ,
Doris Heinrich 1 , Gabriele Schumacher 2 , Gerd Bendas 2 , Ulrich
Rothe 3 , Christian Gege 4 , and Richard Schmidt 4 — 1 Dept.
Physics E22, Tech. Univ. Munich — 2 Dept. Pharmacy, Univ. Bonn —
3 Dept. Physiol. Chem., Univ. Halle — 4 Dept. Chem., Univ. Konstanz
Functional micro-domains of glycolipids were designed by mixing neoglycolipids
with partially fluorinated (F-alkyl) chains and matrix lipids
with alkyl chains. Fluorescence images of the mixed lipid monolayers
at air/water interface demonstrated that it is possible to control both
size and distribution of the micro-domains according to the strong demixing
of alkyl and F-alkyl membrane anchors, while the correlation
between carbohydrate head groups seemed to play rather minor roles.
These micro-domains in monolayers could be transferred onto hydrophobized
substrates, and subjected to dynamic flow chamber experiments.
The results obtained here clearly indicated that the dynamic adhesion of
Chinese hamster ovarial cells expressing E-selectin (CHO-E cells) onto
the lipid monolayer containing micro-domains of sialyl LewisX (sLeX)
can be both enhanced and reduced by controlled de-mixing of ligands
and matrices. Moreover, the same clusters of sLeX could also be formed
in giant lipid vesicles, which can be used as a model cell that locally
expresses bio-specific functions.
AKB 50.120 Fr 10:30 B
Functional Micro-Domains of Glycolipids with Partially Fluorinated
Membrane Anchors - Impact on Cell Adhesion —
•Motomu Tanaka 1 , Matthias Schneider 1 , Laurent Limozin 1 ,
Doris Heinrich 1 , Gabriele Schumacher 2 , Gerd Bendas 2 , Ulrich
Rothe 3 , Christian Gege 4 , and Richard Schmidt 4 — 1 Dept.
Physics E22, Tech. Univ. Munich — 2 Dept. Pharmacy, Univ. Bonn —
3 Dept. Physiol. Chem., Univ. Halle — 4 Dept. Chem., Univ. Konstanz
Functional micro-domains of glycolipids were designed by mixing neoglycolipids
with partially fluorinated (F-alkyl) chains and matrix lipids
with alkyl chains. Fluorescence images of the mixed lipid monolayers
at air/water interface demonstrated that it is possible to control both
size and distribution of the micro-domains according to the strong demixing
of alkyl and F-alkyl membrane anchors, while the correlation
between carbohydrate head groups seemed to play rather minor roles.
These micro-domains in monolayers could be transferred onto hydrophobized
substrates, and subjected to dynamic flow chamber experiments.
The results obtained here clearly indicated that the dynamic adhesion of
Chinese hamster ovarial cells expressing E-selectin (CHO-E cells) onto
the lipid monolayer containing micro-domains of sialyl LewisX (sLeX)
can be both enhanced and reduced by controlled de-mixing of ligands
and matrices. Moreover, the same clusters of sLeX could also be formed
in giant lipid vesicles, which can be used as a model cell that locally

Arbeitskreis Biologische Physik Freitag
expresses bio-specific functions.
AKB 50.121 Fr 10:30 B
Hydration limits of synthetic glycolipids under controlled osmotic
pressure - a small angle neutron scattering (SANS)
study — •Florian Rehfeldt 1 , Bruno Demé 2 , Christian Gege 3 ,
Richard R. Schmidt 3 , and Motomu Tanaka 1 — 1 Lehrstuhl für
Biophysik E22, Technische Universität München, James-Franck-Str. 1,
85748 Garching, Germany — 2 Institut Laue-Langevin, BP 156, F-38042
Grenoble Cedex 09, France — 3 Fachbereich Chemie, Universität Konstanz,
Fach M-725, D-78457 Konstanz, Germany
In animal cells, oligo- and polysaccharide chains form complexes with
glycolipids, glycoproteins, and proteoglycans (called glycocalix), and are
mostly expressed on cellular surfaces. Complex interplays of various physical
forces (electrostatic interaction, hydrogen bonding, etc.) enable them
to keep distinct conformation to serve not only as a hydrophilic cushion to
maintain intercellular spacing but also as a selective ligand against complimentary
receptors. To date, however, only a few studies have been conducted
to clarify the impact of molecular structures on their in-plane and
inter-plane correlation. In this study we investigated the hydration limits
and morphology of synthetic glycolipids under controlled osmotic pressure.
Multilayers of synthetic deuterated and protonated glycolipids with
different sugar head groups were deposited on silicon wafers by solvent
casting, and the quantative force-distance relationships were measured
in a humidity chamber using small angle neutron scattering (SANS).
AKB 50.122 Fr 10:30 B
Deposition of Supported Membranes with F1F0-ATP-Synthase
on Cellulose Thin Films — •Murat Tutus 1 , Thomas Nawroth 2 ,
and Motomu Tanaka 1 — 1 Biophysics Lab, Tech. Univ. Munich —
2 Dept. Phys. E17, Tech. Univ. Munich
A new method for the reconstitution of proteins (F1F0-ATP-Synthase
of Micrococcus luteus) into lipid vesicles without causing membrane disruption
is developed. To verify non-disruptive, orientation selective reconstitution
of ATP-Synthase in lipid vesicles, the vesicle size before and
after insertion is quantitatively compared by dynamic light scattering
experiments. To determine the side selectivity the proteoliposomes were
spread onto biocompatible ultra thin (thickness of 5 to 10 nm) polymer
supports where the homogeneity and the lateral mobility are characterized
with fluorescence microscopy and fluorescence recovery after photobleaching.
The protein distribution is checked by covalent coupling of
synthetic dyes as well as by immunofluorescence labeling with antibodies.
The glass slides coated with ultra thin cellulose films serve as interlayer
to achieve homogeneous distribution over macroscopically large (cm2 order)
surfaces. Moreover, immuno-labeling of F1 head group verifies the
reconstitution of the entire protein into the supported membrane.
AKB 50.123 Fr 10:30 B
Structure and Elasticity of DNA and Chromatin — •Ralf Everaers
1 and Boris Mergell 2 — 1 Max-Planck-Institut für Physik komplexer
Systeme, Nöthnitzerstr. 38, 01187 Dresden, Germany — 2 Max-
Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz,
Germany
We use computer simulations to study structure formation and response
to mechanical forces in generic linked rigid body models of DNA
and chromatin. In the case of DNA we use a variant of the Gay-Berne
potential to represent the stacking interactions between neighboring basepairs.
The sugar-phosphate backbones are taken into account by semirigid
harmonic springs with a non-zero spring length. The competition of
these two interactions and the introduction of a simple geometrical constraint
lead to a stacked right-handed B-DNA-like conformation. Beyond
a critical stretching force we observe a transition to an overstretched S-
DNA conformation with highly inclined bases that partially preserves the
stacking of successive base-pairs. The geometry of the chromatin fiber is
based on the two-angle crossed-linker model. In this case the Gay-Berne
potential is used to model the excluded volume and short-range attraction
between nucleosomes. We find that the elastic properties such as
the bending and stretching moduli of condensed fibers are dominated
by the internucleosomal interactions. They can lead to the formation of
hairpin conformations whose tension induced opening manifests itself in
a quasi-plateau in the force-extension curve.
AKB 50.124 Fr 10:30 B
Towards folding and assembly of single light-harvesting
complexes from plants — •Peter Schwaderer 1 , Sebastian
Schuler 1 , Carsten Tietz 1 , Ulrich Gerlach 2 , Harald
Paulsen 2 , and Jörg Wrachtrup 1 — 1 3. Physikalisches Institut,
Universität Stuttgart — 2 Institut für Allg. Botanik, Universität Mainz
Individual light-harvesting chlorophyll a b protein complexes (LHCII)
from higher plants are investigated in vitro at room temperature. The
LHCII apoprotein binds about 15 pigments, chlorophylls (Chl) a and b
and carotenoids, and probably is the most abundant membrane protein
on earth.
The advantages of TIR microscopy are applied to investigate the properties
of single LHCII proteins in detergent solution that have been immobilized
on a quartz coverslip by different techniques. TIR excitation
via a prism as well as total reflection within a high numerical aperture
microscope objective are tested to find the best signal to background ratio.
Thus, the time resolved Chl fluorescence of single LHCII molecules
can be observed.
This experiment is a first step towards immobilizing the LHCII apoprotein
which is known to fold in the presents of Chl a, Chl a, and carotenoid
pigments. As the fluorescence of unbound pigments is not observable on
single molecule level because the molecules are trapped in the long-lived
triplet states, the fluorescence of correctly folded complexes, where the
triplet states of the Chl molecules are quenched by the carotenoids, can
be used as a monitor for the folding process.
AKB 50.125 Fr 10:30 B
Optical Microheology on Biological Cells — •Falk Wottawah,
Stefan Schinkinger, Bryan Lincoln, Maren Romeyke, Revathi
Ananthakrishnan, Josef Käs, and Jochen Guck — Fakultät für
Physik und Geowissenschaften, Universität Leipzig
Biological cells, such as fibroblasts, can be described as a polymeric
compound material. Their passive rheological response to optically applied
step stresses on the time scale of seconds suggests a hybrid between
a crosslinked and an entangled actin network, a transiently crosslinked
actin cortex, as the main contributor. Their frequency dependent shear
modulus reveals elastic to viscous transitions, requiring stress relaxation
beyond reptation-based mechanisms. This viscoelastic response is defining
for cells within the same cell line, and distinguishes between different
cell lines. Strain on the time scale of a minute additionally triggers an
active response, exceeding the mere relaxation of applied stresses.
AKB 50.126 Fr 10:30 B
Molecular motors in cells: an analogue for thermotropic ordering
— •David Smith and Josef Käs — Linne Str 5, 04103, Leipzig
All eukaryotic cells rely on the self-assembly of protein filaments to
form an intracellular cytoskeleton. The need for motility and reaction additionally
requires pathways that restructure and disassemble cytoskeletal
structures. Temperature-driven increases in disorder are the most obvious
method, thermodynamically, for dissolving complex structures, yet
could denature cellular components. This is exemplified in the unfolding
of double-stranded DNA for duplication. While de-hybridization of
the strands by a temperature increase represents the simplest pathway,
molecular motors are present to perform the same function in the nucleus
without heat-induced damage to the cell. We report another fundamental
mechanism whereby changes in the activity of the molecular motor
myosin II induce order-disorder transitions in actin networks. In nearchemical-rest
states, aggregates of myosin II motors acting as crosslinkers
induce a compounded state of aligned actin filaments and motors. This
results in the self-assembly of various macro-molecular structures such as
asters, neuron-like networks, and condensed super-precipitates. However,
when the molecular motors are turned on and the system assumes an active
nonequilibrium state, the myosin II-induced filament motility maintains
a disordered high-entropy state. Experiments with photo-activated
motors show the rapid dynamics of disassembly of actomyosin structures
and the reversibility of the changes. This ability for rapid transitions of
the entropic state by motor activity indicates that molecular motors, in
general, may substantially contribute to dynamic cellular organization.

Arbeitskreis Biologische Physik Freitag
AKB 50.127 Fr 10:30 B
Induced changes in comformation and charge density of thin
polymer films at the interface - a neutron and x-ray reflectivity
study towards controlled protein-surface interaction —
•Florian Rehfeldt 1 , Roland Steitz 2 , Regine v. Klitzing 2 , and
Motomu Tanaka 1 — 1 Lehrstuhl für Biophysik E22, Technische Universität
München, James-Franck-Str. 1, 85748 Garching, Germany —
2 Stranski-Laboratorium, TU Berlin, Straße d. 17. Juni 112, D-10623
Berlin, Germany
The switching of physical properties of thin polymer films (charge density,
conformation, etc.) under physiological conditions draws increasing
attention to control cell-surface/protein-surface interaction by means of
external stimulation. For this purpose, one of the attractive candidates is
a relatively ”weak” polyelectrolyte, whose degree of ionisation (D.I.) can
be controlled by pH titration. We chose a diblock-copolymer that possesses
a hydrophobic MMA block and a hydrophilic DMAEMA block.
The D.I. of DMAEMA block is 0.6 at pH = 5.5, and 0.2 at pH=8.5,
respectively. When the block ratio is 1:1, this type of diblock forms an
insoluble monolayer at air/water interface. Recently, we demonstrated
the adsorption and desorption of weakly charged DMAEMA chains at
air/water interface by pH titration. Such insoluble monolayers can be
transferred from air/water interface onto hydrophobized silicon blocks,
where distinct changes in the layer thickness as well as in the scattering
length density were monitored with neutron reflectivity. Furthermore,
adsorption of water-soluble proteins on charged- and uncharged brushes
can be detected by ex-situ x-ray reflectivity and fluorescence microscopy.
AKB 50.128 Fr 10:30 B
Solid domains in fluid vesicles — •Erwin Gutlederer, Thomas
Gruhn und Reinhard Lipowsky — MPI Kolloid- und Grenzflaechenforschung
14424 Potsdam
Recent experiments have shown the existence of solid domains in multicomponent
fluid vesicles when they are cooled below a certain temperature.
In our theoretical approach we analyse thermodynamic properties
of this domain formation. With the help of free energy minimisation techniques
we estimate the curvature energy of vesicles with a solid domain
as a function of the domain size. This allows us to investigate the temperature
dependence of domain formation for various values of bending
rigidities and molecular composition of the vesicle membrane.
AKB 50.129 Fr 10:30 B
Functional Incorporation of Cell Receptors into Polymer
Tethered Membranes - Influence of Spacer Length and Density
— •Oliver Purrucker 1 , Stephanie Gönnenwein 1 , Monika
Rusp 1 , Anton Förtig 2 , Rainer Jordan 2 , and Motomu Tanaka 1
— 1 Technische Universität München, Lehrstuhl für Biophysik E22,
James-Franck-Str., D-85748 Garching — 2 Technische Universität
München, Lehrstuhl für Makromolekulare Stoffe, Lichtenbergstr. 4,
D-85748 Garching
To study physical principles of cell-cell interactions, supported lipid
membranes with cell surface receptors have been intensively and widely
investigated as a general model of plasma membranes. The close proximity
of the artificial membrane to the solid support (0.5-2 nm) does not
provide a sufficient water reservoir that even causes nonspecific adsorption
and denaturing of proteins. This problem can be overcome by introduction
of hydrophilic polymer spacers, which can provide more ”fluid”
environments for proteins. In our recent study, we designed a new type
of polymer-tethered membrane with defined poly(2-methyl-2-oxazoline)
lipopolymer spacers and could demonstrate the incorporation of transmembrane
cell receptors 1 .
Measurements of adhesion free energy of a ligand-doped lipid vesicle
on the supported membrane with integrin αIIbβ3 receptors, we found
that the functionality of incorporated integrin receptors systematically
depends on the density and length of the lipopolymer tethers.
[1] O. Purrucker, A. Förtig, R. Jordan, M. Tanaka, ChemPhysChem
in print
AKB 50.130 Fr 10:30 B
Dissipative Micro-Domain Formation in Transferred Lipid
/ Lipopolymer Monolayers — •Oliver Purrucker 1 , Anton
Förtig 2 , Rainer Jordan 2 , and Motomu Tanaka 1 — 1 Technische
Universität München, Lehrstuhl für Biophysik E22, James-Franck-Str.,
D-85748 Garching — 2 Technische Universität München, Lehrstuhl für
Makromolekulare Stoffe, Lichtenbergstr. 4, D-85748 Garching
Ultra-thin (d < 10 nm) liquid films that ”wet” solid surfaces can be
stabilized by surfactant films covering the air/liquid interface. E.g., single
chain surfactants can increase the thickness of a glucose solution by two
orders of magnitude 1 . Langmuir monolayers of lipid/lipopolymer mixtures
can be treated as models of cell surfaces, where hydrated polymer
films create high osmotic pressures to stabilize membrane structures 2 .
Here, we observed that Langmuir-Blodgett lipid/lipopolymer monolayers
form stripe-like microscopic domains that align parallel to the
transfer direction. Systematic characterization before and after transfer
demonstrated that formation of such micro-domains is not caused
by thermodynamic phase separation. Width and spacing of stripes are
clearly dependent on transfer velocity, suggesting a formation due to hydrodynamic
forces operating within ultra-thin liquid films between lipids
and substrates.
(1) G. Elender, E. Sackmann, J. Phys. II France 4 (1994) 455
(2) E. Sackmann, M. Tanaka, Trends Biotechnol. 18 (2000) 58
AKB 50.131 Fr 10:30 B
Biophysical applications of chemically engineered GaAs-based
semiconductors — •Klaus Adlkofer 1 , Daniel Gassul 1 , Andrey
Shaporenko 2 , Michael Zharnikov 2 , Michael Grunze 2 , Abraham
Ulman 3 , and Motomu Tanaka 1 — 1 Lehrstuhl für Biophysik
E22, Technische Universität München — 2 Lehrstuhl für Angewandte
Physikalische Chemie, Universität Heidelberg — 3 Polytechnic University
Brooklyn, New York, USA
Stable chemical engineering of stoichiometric GaAs [100] surfaces was
achieved by deposition of 4-′-substituted-4-mercaptobiphenyl terminated
with −H, −CH3 and −OH. Topography of the engineered surface was
studied by atomic force microscopy (AFM). Orientation of the molecules
was evaluated by near edge x-ray fine structure (NEXAFS) spectroscopy
and Fourier transformed infrared spectroscopy (FTIR), and the covalent
binding between the thiolate and surface arsenide was confirmed
by high-resolution x-ray photoelectron spectroscopy (HRXPS). Surface
free energies of the engineered surfaces were calculated from contact angle
measurements. Current-voltage scans showed the drastic suppression
of oxidation and reduction by coating of GaAs. Electrochemical properties
of the engineered GaAs in aqueous electrolytes were measured by
impedance spectroscopy, demonstrating that all three types of mercaptobiphenyls
can form stable monolayers with high electric resistances,
R > 2MΩcm 2 . The surface engineering method established here allows
for control of surface free energies towards deposition of model biomembranes
on GaAs-based device surfaces.
AKB 50.132 Fr 10:30 B
Thermal fluctuation analysis of grafted microtubules —
•Francesco Pampaloni 1 , Gianluca Lattanzi 2 , A. Jonas 1 ,
Erwin Frey 2 , Ernst-Ludwig Florin 1 , and 3 for the collaboration
— 1 EMBL, Meyerhofstrasse 1, D-69117 Heidelberg — 2 Abteilung
Theorie, Hahn-Meitner Institut, Glienicker Strasse 100, D-14109 Berlin
— 3
Cytoskeletal filaments play a fundamental role in imparting polarity
to the cell, determining the plane of symmetry in cell division, and regulating
cell movements and shape. Unlike most of the synthetic organic
polymers, cytoskeletal filaments are semiflexible polymers, with a typical
stiffness that is intermediate between that of a random coil and that of a
rigid rod. A basic parameter for characterizing the stiffness of polymeric
fibres is the persistence length, which is defined as the typical length over
which correlations of the tangent vectors of the filament contour decay. A
persistence length comparable to the filaments contour length, defined as
the maximum end-to-end distance, is a characteristic property of semiflexible
polymers. Whereas an established theoretical framework already
exists for flexible polymers, the static and dynamic properties of single
semiflexible filaments are still the object of intense and challenging theoretical
investigations [1]. Semiflexible chains have many interesting features
that disappear in the flexible and stiff limits. For example, the distribution
function of the end-to-end distances has a typical non-Gaussian
shape with the weight of the distribution shifting toward full stretching
[2, 3]. In this work, we present a novel method to measure the predicted
end-to-end distributions for grafted microtubules in three-dimensions using
a recently developed method for high-resolution particle tracking [4]
and without any disturbance by surface effects that affects earlier work.
In our assay, one end of the microtubules is grafted to a gold substrate
while the other end is freely fluctuating in solution. The thermally-driven
motion of the microtubules is measured by tracking the positions of single
200 nm fluorescent beads attached to them. Since the supporting

Arbeitskreis Biologische Physik Freitag
substrate is placed tens of micrometers apart from the top and bottom
boundaries of the measuring chambers, every influence due to surface effects
is negligible. This is an improvement with respect to the alternative
assays previously developed for measuring the mechanical properties of
microtubules [5, 6, 7, 8] or actin [9], where surface effects could not be
completely excluded. Our experimental results show a non-Gaussian distribution
of longitudinal fluctuations for microtubules of length 5 micron.
The measured half-width of the longitudinal and transverse fluctuations
is typically about 50 nm and 400 nm, respectively. The non-Gaussian
longitudinal distribution indicates that taxol-treated microtubules show
the typical behaviour of semiflexible polymers also on the typical length
scale of a cell.
[1] E. Frey, K. Kroy, J. Wilhelm, Adv. Struct. Biol. 5, 135-168 (1998)
[2] J. Wilhelm, E. Frey, Phys. Rev. Lett. 77, 2581-2584 (1996) [3] G. Lattanzi,
T. Munk, E. Frey, Phys. Rev. E, in press. [4] M. Speidel, A. Jonas,
E.-L. Florin, Opt. Lett. 28, 69-71 (2003) [5] H. Felgner1, R. Frank, M.
Schliwa, J. Cell Sci. 109, 509-516 (1996) [6] R. B. Dye, S. P. Fink, R. C.
Williams, J. Biol. Chem. 268, 6848-6850 (1993) [7] F. Gittes, B. Mickey,
J. Nettleton, J. Howard J. Cell Biol. 120, 923-934 (1993) [8] B. Mickey, J.
Howard, J. Cell Biol. 130, 909-917 (1995) [9] L. Le Goff, O. Hallatschek,
E. Frey, F. Amblard, Phys. Rev. Lett. 89, 258101 (2002)

Arbeitskreis Physik sozio-ökonomischer Systeme Tagesübersichten
Hauptvorträge
PHYSIK SOZIO-ÖKONOMISCHER SYSTEME (AKSOE)
Vorsitzender: Priv.-Doz. Dr. Dr. Frank Schweitzer
Fraunhofer Institut für Autonome Intelligente Systeme
Schloß Birlinghoven
53754 Sankt Augustin
E-Mail: schweitzer@ais.fraunhofer.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsäle H8 und H10)
AKSOE 1.1 Mo 09:30 (H8) Toward an Understanding of Market Behavior: A Physics Perspective,
Neil Johnson
AKSOE 4.1 Di 09:30 (H8) Stochastic Games: Theory and Simulation, Kristian Lindgren
AKSOE 6.1 Di 16:00 (H10) The Dynamics of Information, Bernardo Huberman
AKSOE 10.1 Do 14:00 (H8) Physicists’ Insights into Wealth Distributions, Frantiˇsek Slanina
Fachsitzungen
AKSOE 1 Finanzmärkte und Risikomanagement Mo 09:30–12:30 H8 AKSOE 1.1–1.5
AKSOE 2 Urbane Systeme und Verkehrsdynamik Mo 14:00–15:30 H8 AKSOE 2.1–2.3
AKSOE 3 Postersitzung Mo 16:00–18:00 Poster D AKSOE 3.1–3.13
AKSOE 4 Soziale Systeme und Entscheidungsmodelle I Di 09:30–12:30 H8 AKSOE 4.1–4.5
AKSOE 5 Soziale Systeme und Entscheidungsmodelle II Di 14:00–15:30 H8 AKSOE 5.1–5.3
AKSOE 6 Sondersitzung: Verleihung des Young-Scientist-
Award for Socio- and Econophysics
Di 16:00–18:00 H10 AKSOE 6.1–6.2
AKSOE 7 Makro-ökonomische Modelle und Wirtschaftswachtum
I
Mi 14:00–15:30 H8 AKSOE 7.1–7.3
AKSOE 8 Makro-ökonomische Modelle und Wirtschaftswachtum
II
Mi 16:00–18:00 H8 AKSOE 8.1–8.4
AKSOE 9 Symposium: Fat Tail Distributions – Applicati- Do 09:30–12:30 H1 AKSOE 9.1–9.1
on from Physics to Finance
AKSOE 10 Mikro-ökonomische Modelle und Multi-
Agenten-Systeme
Sondersitzung:
Verleihung des Young-Scientist Award
for Socio- and Econophysics
Di 16:00–18:00, H10
1. Hauptvortrag: Bernardo Huberman
2. Preisverleihung
3. Vortrag der Preisträgerin / des Preisträgers
Do 14:00–17:30 H8 AKSOE 10.1–10.6
Mitgliederversammlung des Fachverbands Arbeitskreis Physik sozio-ökonomischer Systeme
Mi 18:00–19:00 H8
1. Bericht des Vorsitzenden des AKSOE
2. Diskussion über geplante Aktivitäten
3. Verschiedenes
gez. Frank Schweitzer

Arbeitskreis Physik sozio-ökonomischer Systeme Montag
Fachsitzungen
– Haupt-, Kurzvorträge und Posterbeiträge –
AKSOE 1 Finanzmärkte und Risikomanagement
Zeit: Montag 09:30–12:30 Raum: H8
Hauptvortrag AKSOE 1.1 Mo 09:30 H8
Toward an Understanding of Market Behavior: A Physics Perspective
— •Neil Johnson — Physics Department, Oxford University
U.K.
There is growing interest in agent-based market models within the
physics community. In light of this, we give an overview of such physicsbased
approaches to self-consistent market modelling. We will focus on
the physics community’s search for a minimal market model, and examine
the trade-off between the desire for simplicity, yet consistency with
the known ’stylized facts’ of markets. [For further details, see ’Financial
Market Complexity’ (Oxford University Press, 2003).]
We will then briefly explore related applications of these models in sociological
and biological domains.
15 min. Pause
AKSOE 1.2 Mo 10:30 H8
Modeling Correlations in Portfolio Credit Risk — •Bernd
Rosenow 1 , Rafael Weißbach 2 , and Frank Altrock 2 — 1 Institut
für Theoretische Physik, Universität zu Köln, 50923 Köln, Germany
— 2 Risk Management Support & Control, WestLB AG, Düsseldorf,
Germany
The risk of a credit portfolio depends crucially on correlations between
the probability of default (PD) in different economic sectors. Often, PD
correlations have to be estimated from relatively short time series of default
rates, and the resulting estimation error hinders the detection of
a signal. We present statistical evidence that PD correlations are well
described by a (one-)factorial model. However, when using the model to
generate short time series and calculating their correlation matrix, one
typically observes large statistical fluctuations in the correlation structure.
Due to these fluctuations, the parameter estimation for a one–factor
model is plagued by large uncertainties. When estimating the model parameters
in such a way that the empirically observed ones appear as a
worst case scenario, the reliability of the estimate is increased in a systematic
way, leading to a moderately increased CreditVaR.
AKSOE 1.3 Mo 11:00 H8
Tackling Mutual Funds Style Analysis with Medoid Clustering
and Differential Evolution — •Thiemo Krink 1 , Sandra Paterlini
2 , Tommaso Minerva 2 , and Francesco Pattarin 2 — 1 EVALife
Group, Dept. of Computer Science, Univ. of Aarhus, Denmark — 2 Dept.
of Political Economics, Univ. of Modena and Reggio Emilia, Italy
Mutual funds style analysis requires objective, representative, consistent
and empirically testable classification schemes in order to give reliable
information to investors and fund managers who are interested in
evaluating and comparing different financial products. Institutional classification
schemes, when available, do not always provide consistent and
representative peer groups of funds. In this study, we introduce a classification
algorithm, which identifies mutual funds styles by analysing the
time series of past returns. The proposed classification procedure consists
of three steps: (a) dimensionality reduction based on principal component
analysis, (b) clustering by a novel medoid evolution approach utilizing
differential evolution, and (c) style identification by a constrained regression
model. We tested the algorithm regarding Italian mutual funds data
and achieved satisfactory results with respect to the agreement with the
existing institutional classification and the explanatory power of out of
sample variability in the cross-section of returns.
AKSOE 1.4 Mo 11:30 H8
Significance of log-periodic signatures in cumulative noise —
•Hans-Christian Graf v. Bothmer — Universität Hannover, Institut
für Mathematik (C), Welfengarten 1, 30167 Hannover
Using methods introduced by Scargle we derive a cumulative version
of the Lomb periodogram that exhibits frequency independent statistics
when applied to cumulative noise. We show how this cumulative Lomb
periodogram allows us to estimate the significance of log-periodic signatures
in the S&P 500 anti-bubble that started in August 2000.
AKSOE 1.5 Mo 12:00 H8
Application of Heston and Hull-White model to German DAX
data — •Ralf Remer and Reinhard Mahnke — University of Rostock,
Department of Physics, 18051 Rostock
We concentrate on the stock price dynamics described by the Heston
and the Hull -White model [1]. We apply the model to the German tickby-tick
DAX data [2]. The data are from May 1996 to December 2001.
We compare the short and the long time solution of the Heston model
[3] with the DAX data and with numerical simulations of the Heston
model. Therefore we use the probability density distributions of the logarithmic
returns, calculated out of the data, and fit these distributions
with the theoretical distribution.
Finally we compare the short-time solution of the Heston model and of
the Hull-White model as another example of the models with stochastic
volatility.
[1] Fouque, J P, Papanicolaou G and Sircar K R 2000 Derivatives in Financial
Markets with Stochastic Volatility (Cambridge: Cambridge University
Press)
[2] Karlsruher Kapitalmarktdatenbank 2002 DAX and its stock prices
(Universität Karlsruhe)
[3] Drăgulescu A A and Yakovenko V M 2002 Quant. Finance 2 443
AKSOE 2 Urbane Systeme und Verkehrsdynamik
Zeit: Montag 14:00–15:30 Raum: H8
AKSOE 2.1 Mo 14:00 H8
New experimental results concerning the car-following dynamics
— •Peter Wagner 1 , Georg Hertkorn 1 , and Ihor Lubashevsky
2 — 1 Institut für Verkehrsforschung, Deutsches Zentrum für
Luft- und Raumfahrt, Rutherfordstrasse 2, 12489 Berlin — 2 General
Physics Institute, Russian Academy of Sciences, Vavilov Str. 38, Moscow,
119991, RUSSIA
Car-following experiments conducted recently with cars equipped with
DGPS (differential GPS) deliver fairly accurate and highly interesting
data. The distances ∆x, the speeds v(t) and the accelerations can be
measured (or computed) making it possible to draw solid conclusion related
to the car-following dynamic.
In contrast to almost all of the car-following models currently in use
the data demonstrate that the behaviour of the drivers is described by
fairly old (but rarely used) ”action-point” models. These models claim
that the acceleration is constant most of the time but is changing very
fast at the action-points. The time between subsequent action-points is
distributed exponentially, compatible with the assumption that the decision
to change acceleration is drawn randomly.
It follows, that there is no fixed-point of the car-following dynamic.
It can be hypothesized that this is due to driver’s inability to regulate
speed difference ∆v and acceleration exactly to zero. Nevertheless, there
is a strong attraction toward these values, as can be seen by the cusp in
the frequency distribution of ∆v = 0.
From these results, important consequences might be drawn for the
modeling of the car-following process.

Arbeitskreis Physik sozio-ökonomischer Systeme Montag
AKSOE 2.2 Mo 14:30 H8
Phase diagram of a traffic flow model with a non-unique flowdensity
relation with open boundaries — •Michael Spahn and
Peter Wagner — Institute of Transport Research, German Aerospace
Center (DLR) in the Helmholtz Association, Rutherfordstrasse 2, 12489
Berlin, Germany
The phase diagram of a traffic flow model with a non-unique flowdensity
relation [1] in the case of open boundaries is presented. It exhibits
the typical phases corresponding to free flow and jams. Additionally there
is a region in the flow-density plane with a plateau in the mean velocity.
This corresponds to a model rule introducing synchronized flow.
Furthermore results will be presented concerning the applicability of a
general principle [2] connecting the phase diagram of a model in the case
of open boundaries with the fundamental diagram in the case of periodic
boundary conditions.
[1] B.S. Kerner et. al., Cellular automata approach to three-phase traffic
theory, J. Phys. A: Math. Gen. 35 (2002)
[2] V. Popkov and G.M. Schütz, Europhys. Lett. 48, 257 (1999)
AKSOE 3 Postersitzung
AKSOE 2.3 Mo 15:00 H8
MOBIL – A Realistic Lane Change Strategy for Microscopic
Traffic Modelling — •Arne Kesting, Martin Treiber und Dirk
Helbing — Institute for Economics and Traffic, Dresden University of
Technology
An adequate description of multi-lane traffic and lane changes is a key
ingredient for a realistic modeling of traffic dynamics on freeways. With
MOBIL (“Minimizing Overvall Braking Induced by Lane-Changes”), we
propose a general strategy for lane changes that is based on the acceleration
function of the used longitudinal model. To cope with situations
with forced lane changes, e.g. at on-ramps or at lane closings, one has
to model the occuring complex cooperative human behaviour. We model
this longitudinal-transversal coupling in terms of physical repulsive nextneigbour
interactions on neigbouring lanes. The resulting lane change
behaviour is demonstrated for typical situations such as lane closings
and merging at on-ramps.
Zeit: Montag 16:00–18:00 Raum: Poster D
AKSOE 3.1 Mo 16:00 Poster D
Order book approach to price impact — •Philipp Weber and
Bernd Rosenow — Institut für Theoretische Physik der Universität
zu Köln, Zülpicher Straße 77, 50937 Köln
Stock price changes due to an imbalance of supply and demand are
described by the price impact function. We compare the actual price
impact of market orders with the virtual price impact calculated from
the limit order book. The latter one would be caused by a market order
matched with limit orders from the order book. This impact is found to
be four times stronger than the actual price impact of market orders.
We explain this difference with a dynamical feedback mechanism related
to strong anticorrelations between returns and limit orders. Including
this dynamical effect, we present a quantitative explanation of the price
impact function using order book information.
AKSOE 3.2 Mo 16:00 Poster D
Evidence of Markov properties of high frequency exchange rate
data — •A. P. Nawroth 1 , Ch. Renner 1 , J. Peinke 1 , and R.
Friedrich 2 — 1 Institut für Physik, Universität Oldenburg, D-26111
Oldenburg, Germany — 2 Institut für Theoretische Physik, Universität
Münster, D-48149 Münster, Germany
We present a stochastic analysis of a data set consisting of 10 6 quotes
of the US Dollar-German Mark exchange rate. Evidence is given that the
price changes x(τ) upon different delay times τ can be described as a
Markov process evolving in τ. Thus, the τ-dependence of the probability
density function (pdf) p(x, τ) on the delay time τ can be described
by a Fokker-Planck equation, a generalised diffusion equation for p(x, τ).
This equation is completely determined by two coefficients D1(x, τ) and
D2(x, τ) (drift- and diffusion coefficient, respectively). We demonstrate
how these coefficients can be estimated directly from the data without
using any assumptions or models for the underlying stochastic process.
Furthermore, it is shown that the solutions of the resulting Fokker-Planck
equation describe the empirical pdfs correctly, including the pronounced
tails.
AKSOE 3.3 Mo 16:00 Poster D
No profit in spite of a perfect prediction? How interaction destroy
arbitrage. — •Roland Rothenstein and Klaus Pawelzik
— University Bremen, Institute for Theoretical Physics,
Otto-Hahn-Allee 1, D-28359 Bremen, Germany
The efficient market hypothesis stated, that -because markets anticipate
future returns of stock markets- nobody is able to make a profit
using past (public) informations. However not all markets are all the
time efficient. Under the assumption that markets are not efficient, many
traders try to find inefficiencies in the market and use them to build
forecast systems. But every order has an influence to the market, which
changes the price and contradicts the original prediction. Can a trader
neglect its own influence to the market or is this influence so important
that it has to be considered in the prediction of the future? Can interaction
destoy arbitrage opportunities? We study a evolutionary stock
market model with a trader (super agent), that is able to make a perfect
prediction. In this market, we determine how the transactions of this superagent
affects his ability to use his perfect knowledge to make a profit
in this market. We measure this influence under different conditions in
our market model like different number of agents, different memory of
the agents or different evolutionary strategies.
AKSOE 3.4 Mo 16:00 Poster D
An Indication for Qualitative Change of Economic Relations
at about 1985 for the USA — •Karl-Friedrich Albrecht 1 ,
Werner Mende 2 , and Dirk Orlamuender 3 — 1 TU Dresden, Inst. f.
Allg. Oekologie und Umweltschutz, Dozentur fuer Umweltsystemanalyse,
Pienner Str. 8 , 01737 Tharandt — 2 Berlin-Brandenburgische Akademie
der Wissenschaften, Jaegerstr. 22-23, 10117 Berlin — 3 TU Dresden,
Lehrstuhl fuer Volkswirtschaftslehre insbes. Allokationstheorie, Mommsenstr.
13, 01062 Dresden
Because of the 2-nd law of thermodynamics the electricity consumption
(EC) should be an important indicator for the economic growth
of an industrialised country. Comparing the results on EC-growth with
the GDP-growth (Gross Domestic Product) two remarkable facts have
been found: (1) a linear relation between the EC and the GDP holds
from 1955 to 1985 for the countries considered, (2) in 1973 when the
growth of primary energy consumption decoupled from GDP growth the
EC-growth started a strong coupling to the GDP growth. This has been
reported earlier. The present question is: What is the reason for the two
mentioned facts. To solve the question why the linear relation ends up
at about 1985 the data for the USA have been analysed more in detail.
The growth trend was determined by fitting the EC-data (up to 1981) by
a growth model. In about 1985 both EC- and BIP-data leave this trend
and indicate a qualitative new behavior. An other but connect fact is
the approximate proportionality between EC and GDP starting in 1973.
This leads to the question: What is the reason for a coupling between
EC and GDP since the First World Energy Crisis?
AKSOE 3.5 Mo 16:00 Poster D
Interaction of heterogeneous socio-economic cycles — •Andreas
Bohn — TU Darmstadt, FB Biologie - Graduiertenkolleg, Schnittspahnstr.
10, 64287 Darmstadt
Oscillatory dynamics are a fundamental phenomenon in physics, biology
as well as sociology and economics. Over the past 20 years, a number
of models describing socio-economical periodic phenomena such as, e.g.,
dynastic or business cycles, have been developed using methods from
nonlinear dynamics. The present work investigates the aggregated dynamics
of a multitude of such oscillating systems being coupled to each
other. A focus is on the effects of parametric heterogeneity in the oscillator
ensemble, i.e assuming that the amplitude and frequency of the
individual systems are non-identical.

Arbeitskreis Physik sozio-ökonomischer Systeme Montag
AKSOE 3.6 Mo 16:00 Poster D
Investors’ Game Strategies using Genetic Algorithms — •J.
Emeterio Navarro B. 1 and Frank Schweitzer 2,3 — 1 Institute
for Informatics, Humboldt University, Berlin — 2 Institute for Physics,
Humboldt University, Berlin — 3 Fraunhofer Institute for Autonomous
Intelligent Systems, Schloss Birlinghoven, Sankt Augustin
We use an Investors’ Game model to study two kind of strategies investors
can use: the first one is based on feedback information or previous
experience and the second one is based on genetic algorithms. We compare
these two approaches within a multi-agent system where agents play
the role of investors and they interact with each other in order to establish
projects. We investigate (i) the competition between these two different
strategies, (ii) the formation of coalitions and (iii) how the learning process
of agents depends on the genetic algorithm parameters.
AKSOE 3.7 Mo 16:00 Poster D
Evolution of Investor Coalitions in a Multi-Agent Market Simulation
— •Adrian Marcelo Seufert 1 and Frank Schweitzer 2
— 1 Technische Universität Berlin — 2 Fraunhofer Institut für Autonome
Intelligente Systeme
We analyze the evolution of investor’s preference networks by means of
a multi-agent market simulation. In our model, N investors interact with
I initiators over several periods of time. In each period, a randomly chosen
initiator i proposes a project into which investors k decide to invest
a proportion of their budget or not, depending on their “trust” in the
initiator. That trust is quantified by a number wki, that depends on past
experience with that initiator. The return on investment is then randomly
picked from a distribution ri(t) that characterizes the particular initiator.
A positive return boosts the trust of the investors in that initiator, a
negative return diminishes it. Over time we observe the development of
preference networks, that is, of investors interacting with certain initiators
on a preferential basis, while largely ignoring others. Particular emphasis
is placed on the analytical understanding of the Network dynamics using
methods from statistical physics and the theory of stochastic processes.
AKSOE 3.8 Mo 16:00 Poster D
Fairness – The Paradise State in a Network of Trading Agents
— •Juan G. Diaz O., Elena Ramirez Barrios, and Johannes
J. Schneider — Institute for Physics, Johannes Gutenberg University,
Staudinger Weg 7, D-55099 Mainz, Germany
The definition of fairness in economy is based on the comparison of
the agents’ goods, taking into account the preferences of each agent. The
first ingredient is the exchange of goods in a space where there are only
finite numbers of goods. The second ingredient is the possibility that each
agent gets some goods from some markets as well as from the exchange
with other agents. The third ingredient is the expression of the revealed
agents’ preferences. With this three ingredients, we developed a simulation
of a net trade of agents in order to show that there is an equilibrium
in the distribution of goods and eventually to demonstrate that we can
define fairness in a multi-agent system.
AKSOE 3.9 Mo 16:00 Poster D
Networks in a simple freight transport demand model —
•Michael Spahn und Peter Wagner — Institute of Transport Research,
German Aerospace Center (DLR) in the Helmholtz Association,
Rutherfordstrasse 2, 12489 Berlin, Germany
A simplistic model of freight transport demand and the resulting networks
of producers and buyers is presented. Transport costs are initially
determined stochastically from a given range and define a distance network.
Agents representing buyers of a single good repeatedly try to optimize
their supplier network minimizing transport costs while also trying
to stick to trusted suppliers. Trust is built up over time in an unchanged
supplier-buyer relationship. Producers have a limited inventory of
the good and don’t accept further buyers when sold out. Stochastical
fluctuations prevent the system from reaching a completely static state.
The resulting transport networks are analyzed in regimes of low and
high transport costs. The dynamics of the transport network evolution
towards the static distance network are described.
AKSOE 3.10 Mo 16:00 Poster D
Characterization of networks from nondiagonal elements of
node-node link cross-distribution — •Jens Christian Claussen
— Institut für Theoretische Physik und Astrophysik, Universität Kiel
A vast variety of biological, social, and economical networks shows
topologies drastically differing from random graphs; yet the quantitative
characterization remains unsatisfactory from a conceptual point of view.
Motivated from the discussion of small scale-free networks, a biased
link distribution entropy is defined, which takes an extremum for a power
law distribution. This approach is extended to the node-node link crossdistribution,
whose nondiagonal elements characterize the graph structure
beyond link distribution, cluster coefficient and average path length.
From here a simple (and computationally cheap) complexity measure
can be defined. This complexity measure is compared with alternative
approaches to complexity measures, entropies and hierarchy estimators.
AKSOE 3.11 Mo 16:00 Poster D
Food-web representation of agent interaction in a spatial IPD
— •Robert Mach 1,2 and Frank Schweitzer 1,3 — 1 Fraunhofer Institute
for Autonomous Intelligent Systems, Schloss Birlinghoven, D-53754
Sankt Augustin, Germany — 2 Institute for Theoretical Physics, Cologne
University, D-50923 Koeln, Germany — 3 Institute of Physics, Humboldt
University Berlin, D-10099 Berlin, Germany
We use a two-dimensional cellular automaton to investigate an iterated
Prisoner’s Dilemma (IPD) game with 8 different strategies and one-step
memory. The agents are distributed on a 2D grid and are assumed to
interact a number of ng times with their four nearest neighbors during
each generation. The agents try to increase their individual payoff by
adopting the strategy of their most successful neighbor at the end of each
generation. This adaptation process leads to a global pattern formation
of strategy distribution. For ng = 2 and an initial population consisting
of three strategies, a food-web representation can be found by means of a
local configurations analysis, describing the relationship between agents.
This food-web representation is suitable to explain a crossover dynamics,
in which a strategy after an initially strong decline becomes the majority
in the end. Dependent on the local frequencies of the strategies,
two consecutive stages can be distinguished until the dynamics become
stationary.
AKSOE 3.12 Mo 16:00 Poster D
The Probability of Traffic Violations and Criminal Acts: a
Model of Agent Behavior — •Jürgen Mimkes — Physik Department
Universität Paderborn
Traffic is a system of traffic agents under constraints of traffic laws. The
system corresponds to atomic systems under constraint of energy laws.
The Lagrange LeChatelier principle of statistics corresponds to Gibbs
free energy and leads to a model of agent behavior. We always find three
different kinds of agent behavior, corresponding to the solid, liquid and
gas states of materials.
1.For a few rich, individual agents the probability of traffic violations
is a Boltzmann distribution and depends on the punishment (in money)
compared to income.
2.Most agents are less affluent individuals and the probability of traffic
violations depends on the punishment and the risk of being caught.
3. For poor hierarchic agents the probability depends only on the hierarchic
pressure.
In contrast to traffic violators criminal agents make a profit in criminal
acts like bribing. This leads to a modified behavior of the second state:
nearly every agent may be bribed, if the risk is low and the bribe is high
enough compared to the punishment. However, no data are available, yet.
AKSOE 3.13 Mo 16:00 Poster D
Stochastic Description of Traffic Breakdown: Langevin Approach
— •Julia Tolmacheva 1,2 , Reinhard Mahnke 2 , Hans Weber
3 , and Jevgenijs Kaupuˇzs 4 — 1 Res. Inst., Nat. Acad. Sci., 61001
Kharkov, Ukraine — 2 FB Physik, Univ. Rostock, D–18051 Rostock —
3 Physics Dept., Lule˚a Univ., Sweden — 4 Univ. Latvia, LV–1459 Riga,
Latvia
We analyze the characteristic features of jam formation on a circular
one–lane road. We have applied an optimal velocity model including
stochastic noise, where cars are treated as moving and interacting particles.
The motion of N cars is described by the system of 2N stochastic
differential equations with multiplicative white noise. Our system of cars
behaves in qualitatively different ways depending on the values of control
parameters c (dimensionless density), b (sensitivity parameter characterising
the fastness of relaxation), and a (dimensionless noise intensity).
In analogy to the gas–liquid phase transition in supersaturated vapour
at low enough temperatures, we observe three different regimes of traffic
flow at small enough values of b < bcr. There is the free flow regime (like

Arbeitskreis Physik sozio-ökonomischer Systeme Montag
gaseous phase) at small densities of cars, the coexistence of a jam and
free flow (like liquid and gas) at intermediate densities, and homogeneous
dense traffic (like liquid phase) at large densities.
The stochastic noise allows us to calculate the distribution of headway
distances and time headways between the successive cars, as well as the
distribution of jam (car cluster) sizes in a congested traffic.
AKSOE 4 Soziale Systeme und Entscheidungsmodelle I
Zeit: Dienstag 09:30–12:30 Raum: H8
Hauptvortrag AKSOE 4.1 Di 09:30 H8
Stochastic Games: Theory and Simulation — •Kristian Lindgren
— Physical Resource Theory, Chalmers University of Technology,
Gothenburg, Sweden
Recent results regarding games in an evolutionary context is presented.
The main part of the talk deals with the evolution of cooperative behaviour
in a random environment, using evolution of finite state strategies.
The interaction between agents is modelled by a repeated game with
random observable payoffs. The agents are thus faced with a more complex
situation, compared to the Prisoner’s Dilemma that has been widely
used for investigating the conditions for cooperation in evolving populations.
Still, there is a robust cooperating strategy that usually evolves
in a population of agents. In the cooperative mode, this strategy selects
an action that allows for maximizing the payoff sum of both players in
each round, regardless of the own payoff. Two such players maximize
the expected total long-term payoff. If the opponent deviates from this
scheme, the strategy invokes a punishment action, which may be to aim
for minimising the opponent’s score for the rest of the (possibly infinitely)
repeated game.
15 min. Pause
AKSOE 4.2 Di 10:30 H8
Inter-Party-Movements in Bavaria and Germany — •Christian
Hirtreiter 1 and Johannes J. Schneider 2 — 1 Institute of Organic
Chemistry, University of Regensburg, D-93040 Regensburg —
2 Department of Physics, Johannes Gutenberg University of Mainz,
Staudinger Weg 7, D-55122 Mainz
The major parties in Germany lose or gain party members depending
on the results of their current policies. Many people join or leave a
party often immediately after a scandal or a won/lost election. This results
in inter-party-movements: parties losing members can be considered
as the providers for other parties which get additional members. However,
in real life, only seldomly people change directly from their current
membership-book to another one. This is due to the fact that because of
a ” diffusion barrier“ a conservative party member is seldomly tempted
to join a left-wing party and vice versa. Thus, new party members are
mostly recruited from formerly not in parties organized but not apolitical
persons. We will present historical and recent movements based on data
both from Bavaria and from the Federal Republic of Germany and will
discuss these movements from a physical point of view. Furthermore, we
will present computational results for a model simulating these movements.
AKSOE 4.3 Di 11:00 H8
Invasion of Cooperation in Heterogeneous Populations —
•Frank Schweitzer 1,2 and Laxmidhar Behera 1,3 — 1 Fraunhofer
Institut for Autonomous Intelligent Systems, Schloss Birlinghoven,
D-53754 Sankt Augustin — 2 Institute of Physics, Humboldt University,
Newtonstraße 15, D-12489 Berlin — 3 Department of Electrical
Engineering Indian Institute of Technology, Kanpur, 208 016, India
We consider a population of agents interacting in an iterated prisoner’s
dilemma (IPD) game. Using a one-step memory agents can play differ-
ent strategies, thus the population becomes heterogeneous. Further it is
assumed that after each generation agents adopt another strategy proportional
to the relative performance (average payoff) of the respective
strategy. We investigate under which conditions a stable coexistence of
subpopulations playing different strategies can be found and how this
depends on the number of interactions within each generation. We further
discuss a model where agents are spatially separated on different
“islands” and are allowed to migrate after each generation. Here we
find a critical migration rate at which e.g. an island dominated by noncooperating
agents can be transformed into a cooperative one. Thus,
optimal (im)migration may enhance cooperation!
AKSOE 4.4 Di 11:30 H8
Cooperation in a Dynamic Route Choice Experiment —
•Martin Schönhof 1,2 , Dirk Helbing 1 , Hans-Ulrich Stark 1 , and
Janusz Holyst 2 — 1 Institute for Economics and Traffic, Dresden
University of Technology, Andreas-Schubert-Str. 23, D-01062 Dresden,
Germany — 2 Faculty of Physics, Warsaw University of Technology,
Koszykowa 75, Pl-00-662 Warsaw, Poland
The efficient usage of road infrastructures requires an optimal distribution
of vehicles on alternative roads. The corresponding route decision
problem for drivers relates to the minority game. Recent decision experiments
have shown that drivers tend to establish a user equilibrium
characterized by equal travel times on alternative roads (according to
the Wardrop equilibrium). We will present fair strategies that allow road
users to establish even the system optimum, i.e. significantly better results
with reduced travel times.
[1] D. Helbing, M. Schönhof, and D. Kern, New J. Phys. 4 (2002) 33
AKSOE 4.5 Di 12:00 H8
Modelling the role of competencies in a complex problem solving
process - a new model for flexibility — •Andrea Scharnhorst
1 and Werner Ebeling 2 — 1 KNAW, NIWI, Joan Muyskenweg
25, 1090HC Amsterdam — 2 HUB, Inst. f. Physik, Newtonstrasse 15,
12489 Berlin
Learning is both a process which takes place in individuals and in
groups. In this paper we explore to which extend evolutionary models
about the collective search of groups (or populations) in a multidimensional
abstract problem space can be used to describe the role of
individual competencies. In the model the formation of a group of individuals
sharing a similar problem representation can be understood
as effort of a collective search process. Additional to earlier models of
search processes in complex fitness landscapes we assume that the group
formation process (the occupation density) now also depends on the coordinates
and the velocity in the problem space. The new model makes
use of the formalism of active Brownian particles developed recently. The
velocity-dependence means that the fitness of the individuals depends on
the speed with which problem representations can be changed individually.
We call this feature the flexibility of the individuals to develop
alternative problem representations. We discuss the application of such
types of models for learning and decision making processes in social systems.
AKSOE 5 Soziale Systeme und Entscheidungsmodelle II
Zeit: Dienstag 14:00–15:30 Raum: H8
AKSOE 5.1 Di 14:00 H8
Emissions Trading Between Multiple Regions and Firms —
•Jürgen Scheffran — Potsdam Institute for Climate Impact Research,
Telegrafenberg A31, 14412 Potsdam
Emissions trading is an instrument to achieve emission reductions in regions
and business sectors where they are least costly. Emission paths and
emission trading flows are analysed in a multi-agent framework of multi-
level decisionmaking in climate policy and market interaction among
firms. The price mechanism depends on individual threshold prices, the
level of required emission reduction and the capacity of economies to
shift to a low-carbon mode of production. The model discusses the role of
climate guardrails, equity principles on the allocation of emission rights,
conditions for switching to low-emission goods and technologies, and benefits
of cooperation between developing and industrialized regions.

Arbeitskreis Physik sozio-ökonomischer Systeme Dienstag
AKSOE 5.2 Di 14:30 H8
Epidemics in hierarchical social networks — •Marian Brandau
and Steffen Trimper — Fachbereich Physik, Friedmann-Bach-Platz,
06108 Halle
Epidemiological processes in hierarchical social networks are studied
within a so called susceptible–infected–refractory model (SIR). Within
the network model, a population of individuals may be characterized by
certain independent hierarchies H (or dimension) to which they belong it
(family, the acquaintance, job etc.). The degree of homophily (relationship)
in the hierarchy is determined by a parameter α. Detailed numerical
simulations reveal that for H > 1, global spreading results regardless
of the degree of homophily α. For H = 1, a transition from global to
local spread occurs as the population becomes decomposed into increasingly
homophilous groups. Multiple dimensions in classifying individuals
(nodes) thus make a society (computer network) highly susceptible to
large scale outbreaks of infectious diseases (viruses). The SIR–model is
extended to an SIRS–model, where already infected persons may enter
the dynamical process after a finite waiting time.
AKSOE 5.3 Di 15:00 H8
About a new algorithm of the measurment of user interests
in the Internet search — •Andreas Schaale — Mulackstrasse 6,
10119 Berlin
The main idea of this algorithm is to extend the existing algorithms by
a component, reflecting the interests of the users more than already existing
methods. The VoxPopuli Algorithm creates a feedback of the users to
the content of the search index. The information, derived from the users
query analysis is used to modify the existing crawling algorithms. The
VPA controls the distribution of the resources of the Internet crawler.
AKSOE 6 Sondersitzung: Verleihung des Young-Scientist-Award for Socio- and
Econophysics
Zeit: Dienstag 16:00–18:00 Raum: H10
Hauptvortrag AKSOE 6.1 Di 16:00 H10
The Dynamics of Information — •Bernardo Huberman — hp
labs, palo alto, ca 94304
The dynamics of information within social organizations is relevant to
issues of productivity, innovation and the sorting out of useful ideas from
the general chatter of a community. How information spreads and is aggregated
determines the speed with which individuals and organizations
can act and plan their future activities.
This talk will describe new mechanisms for automatically identifying
communities of practice within organizations and for elucidating the
spread of information spreads within those communities. In addition, a
new method for forecasting uncertain events using small groups of people
will be presented, along with empirical results that show its efficacy at
making predictions in the laboratory and in the real world.
Di 17:00 H10
Verleihung des Young-Scientist Award for Socio- and Econophysics
AKSOE 6.2 Di 17:15 H10
Vortrag der Preisträgerin / des Preisträgers — • —
AKSOE 7 Makro-ökonomische Modelle und Wirtschaftswachtum I
Zeit: Mittwoch 14:00–15:30 Raum: H8
AKSOE 7.1 Mi 14:00 H8
Stability and Dynamics of Regular and Random Supply Networks
— •Dirk Helbing and Stefan Lämmer — TU Dresden, Institute
for Economics and Traffic, Andreas-Schubert-Str. 23, 01062 Dresden
We investigate the stability and dynamic behavior of linear supply
chains and supply networks of different topologies, including “supply circles”,
“supply ladders”, and “supply hierarchies”. When the desired production
rate is adapted to forecasted inventories rather than actual stock
levels, the resulting equations turn out to be coupled sets of (damped)
oscillator equations similar to those of electrical networks. Longer forcast
time horizons τ have a stabilization effect. However, for a given supply
matrix C, one normally cannot tune between unstable, damped, and
overdamped behavior. Moreover, even in the damped case, one may face
the “bull-whip effect”, according to which the oscillation amplitude is increased
compared to the perturbations in the consumption rate. We will
provide analytical solutions and discuss resonance phenomena in supply
networks.
AKSOE 7.2 Mi 14:30 H8
The German Powermarkets - Timeseries Analysis and Pricing
— •Magda Schiegl — Versicherungskammer Bayern, Abt. 8MS02,
Maximilianstr. 53, 80530 Muenchen
After the liberalisation of the German power market in 2000 a new
market structure has developed which is determined by two major parts:
The OTC- forward market and the exchange spot market (day ahead,
equilibrium price by bilateral auctions)
There is no analytic formula that links the spot price to the forward
price as it is the case in financial markets (”cost-of-carry” relationship).
The reason for this is the inability of storing electricity in an efficient way
therefore the no-arbitrage approach of pricing derivative securities cannot
be applied in the usual manner. On the spot market energy volumes
arising from misfits in hedges between short term electricity consumption
on the one hand and long term, highly standardized forward products on
the other are dealt. We analyse the structure of spot prices and find it
to be a combination of deterministic, time periodic motion and stochastic
movements (f.i.weather dependent). The time periodic effects can be
observed on different time scales. We use factor model, Fourier method
and extreme value theory for our analyses.
As an application of your results we discuss a pricing formula for special
products of the OTC non-standard power markets, so called ”shaped
deals”. This is of course the basis of an efficient risk management of power
portfolios containing such contracts.
AKSOE 7.3 Mi 15:00 H8
A socio-economic model of the German energy market —
•Dieter Ihrig — FH Suedwestfalen, Iserlohn, Germany
Last year a socio-economic model of the German energy market was
presented. This model is improved: Depreciation of power plants is realized
in a bookkeeper sense. The loss of jobs in the classic energy sector
is calculated more realistic. The data base is actualized.
The model is based on data of the study-group of energy balances at
the VDEW (Organization of German energy supplier). The end energy
consumption will be recorded in 4 sectors (households, low consumer,
industries, traffic) and 4 service arrays (room heating, process heat, mechanical
energy and light) specified for primary energy sources. To assess
the primary energy requirement it is necessary to deal with more than 125
end primary energy consumption data each year. It is possible to define
over 40 years objectives on higher energy saving in the most service arrays
of each end energy consumption sector. The effects on CO2-emission of
several strategies of energy saving will be calculated including commercial
data and socioeconomic aspects (investment, foreign trade, energy
prizes, jobs etc.). The model is build by 45 EXCEL files including more
than 400 corresponding work sheets.
A overview of the results of the model is given. A more detailed look
of the ways of realization of the energy model is given.

Arbeitskreis Physik sozio-ökonomischer Systeme Mittwoch
AKSOE 8 Makro-ökonomische Modelle und Wirtschaftswachtum II
Zeit: Mittwoch 16:00–18:00 Raum: H8
AKSOE 8.1 Mi 16:00 H8
Thermodynamics of Economic Growth — •Jürgen Mimkes —
Physik Department Universität Paderborn
Thermodynamics is a statistical theory, that applies to all large systems
with constraints (E). In liquids atoms are under constraints of energy (E).
In economies people are under constraint of capital (E). According to the
second law of thermodynamics,
dW = d E - T dS
Work (W) in atomic systems increases the amount of energy (E) and
reduces the energy distribution (S). T is ordering parameter, in liquids
T is the temperature or mean kin. energy. In Carnot cycles work may
be applied to raise (heat pump) or reduce (refrigerator) the temperature
(T).
Work (W) in economic systems increases the amount of capital (E)
and reduces the capital distribution (S). The economic temperature T
is the mean capital or standard of living. The economic cycle of goods
and capital corresponds to the Carnot cycle. Production cycles lead to
exponential economic growth, to saturation or reduction of the standard
of living (T). The results are compared to data of East-West Germany
and US-Japan.
AKSOE 8.2 Mi 16:30 H8
An Inquiry into the Nature of the Economy — •Hans G.
Danielmeyer — Mozartstr. 69, 85521 Ottobrunn
After a brief review of macroeconomic theory a new, closed theory is
presented that includes social order as input besides human ability and
physical capital. As the lifetimes of the inputs are natural constants of the
human species, they lend the economy an intrinsic dynamical behavior
beyond economic control. Strong growth periods cause inevitably long
range economic problems. The classical advice to invest physical capital
is counterproductive. The correct production function is discovered.
Former functions can be obtained as mathematical approximations for
perfect social order. The development of the industrial society in general
is as slow as it is because it requires the interactive removal of barriers to
technical, educational, and social advances. Below that benchmark level,
the development of a real nation can be dramatic, depending on the level
of destruction afflicted to physical and social capital per capita. The latter
has an inherited component and a direction. For the first time the
global mixed social order economy is tractable. The quantitative agreement
between the real long-term input and output trajectories for Germany,
Japan and the USA is excellent although their input dynamics
differ considerably.
AKSOE 8.3 Mi 17:00 H8
Konsumverhalten und die Dynamik der Mode — •Thomas
Brenner — Max-Planck-Institut zur Erforschung von Wirtschaftssystemen,
Kahlaische Str. 10, 07745 Jena
Dieses Papier untersucht die Wechselwirkung zwischen Konsumenten
und die daraus entstehende Modedynamik. Ziel ist es dabei zu prüfen,
welche Aspekte eine wiederkehrende Veränderung von Mode zu erklären.
Dazu wird ein Modell des Konsumverhaltens entwickelt, das auf dem
Verstärkungslernen basiert. Es wird davon ausgegangen, dass der Konsum
von Gütern verstärkt wird, die entweder ebenfalls von anderen Konsumenten
gewählt werden oder neu sind. Den Konsumenten wird damit
eine Präferenz für Konformität und Neuigkeit unterstellt. Eine Modellierung
der entstehenden Interaktion zwischen Konsumenten zeigt,
dass diese beiden Präferenzen nicht ausreichen, um eine wiederholte
Veränderung der Mode zu erklären. Deshalb wird mit Hilfe eines Simulationsmodells
untersucht, welche zusätzlichen Umstände die wiederkehrende
Veränderung von Mode erklären. Es werden verschiedene Modelle
untersucht, die eine Veränderung der Konsumentenpopulation, eine Wiedererlangung
der Attraktivität durch Güter bei ausbleibendem Konsum
oder eine Veränderung der angebotenen Güter beinhalten. Es zeigt sich,
dass nur bestimmte Modellvarianten die wiederkehrende Veränderung der
Mode erklären, und dass die Produzenten maßgeblich and der Dynamik
der Mode beteiligt sind.
AKSOE 8.4 Mi 17:30 H8
Complexity and Evolutionary Economics — •Carl Henning
Reschke — Mainzer Str. 80, 50678 Koeln, affiliation: Universitaet Witten/Herdecke
The aim of this paper is to sketch a strategic map of some of the relevant
issues at the intersection of economics, sociology and evolutionary
theories. Methodologically a successful integration of these areas requires
a transfer of complexity methods and development of further methods in
the complexity area. The paper therefore poses challenges to complexity
researchers as well as discusses how these areas intersect conceptually.
I review approaches to complexity from physics, computer science and
biology.
Each of these disciplines offers a specific way of dealing with complex
phenomena, with distinctive advantages and disadvantages. Physics measures
potentially relevant characteristics. Computer science aims at algorithmic
accounts of how complex systems can be artificially constructed.
Evolutionary thinking asks for the adaptive value of specific characteristics.
It shifts attention from a generalized standard optimality criterion
to a differentiated account of selection criteria and selection conditions
in specific circumstances. Hypotheses and are illustrated with examples
from the pharmaceuticals market.
AKSOE 9 Symposium: Fat Tail Distributions – Application from Physics to Finance
Zeit: Donnerstag 09:30–12:30 Raum: H1
AKSOE 9.1 Do 09:30 H1
Symposium: Fat Tail Distributions – Applications from Physics
to Finance — • —
AKSOE 10 Mikro-ökonomische Modelle und Multi-Agenten-Systeme
Zeit: Donnerstag 14:00–17:30 Raum: H8
Hauptvortrag AKSOE 10.1 Do 14:00 H8
Physicists’ Insights into Wealth Distributions — •Frantiˇsek
Slanina — Institute of Physics, Academy of Sciences of the Czech Republic,
Na Slovance 2, CZ-18221 Praha, Czech Republic
Distribution of wealth in human society was one of first features of
socio-economic systems which was attempted to approach scientifically.
Empirical analysis performed by Vilfredo Pareto lay down the foudation
of the quantitative analysis of social inequality which was of first concern
throughout the 19th century. The famous Pareto law, claiming power-law
distribution of wealth, robust in time and valid in all diverse societies,
was re-examined many times since then. Several other functional dependencies
were suggested, but the essential message that the tail of the
distribution follows a power-law passed all tests.
However, the explanation of the Pareto tail was less straightforward
than it might have seemed. In our talk we summarise several approaches,
including Lotka-Volterra equations, random directed polymers and idealgas
analogies. We will present a new model of wealth exchange which
yields exact analytical solution for the wealth distribution.
We will be stressing that the essence of all these approaches can be

Arbeitskreis Physik sozio-ökonomischer Systeme Donnerstag
boiled down to random multiplicative processes with appropriate boundary
conditions. In so doing we indirectly argue against the presence of
self-organized criticality in economic systems and suggest the triviality
of ubiquitous power-law distributions.
15 min. Pause
AKSOE 10.2 Do 15:00 H8
Finite Size Effects in Herding Models — •Friedrich Wagner 1 ,
Simone Alfarano 2 , and Thomas Lux 2 — 1 Institut für theoretische
Physik, Universität Kiel — 2 Institut für Volkswirtschaft, Universität Kiel
Agent models to describe stock indices are usually applied at fixed
number N of agents, as f.e. the Lux-Marchesi model (LMM) [1]. As
shown in [2] LMM exhibits only gaussean fluctuations and no herding
if N → ∞. As a paradigma for herding we treat the ant model of [3]. In
this model the herding parameters in the transition probability for one
agent to change his oppinion have to scale with N and do not depend
only on the concentration as in LMM. If this N-dependence is omitted
as one could do for fixed N, also this model becomes trivial for N → ∞.
This motivates our believe that the independence on N of the herding
term in LMM is responsible for the triviality at large number of agents.
[1] T.Lux, M.Marchesi, Nature 397(1999)498
[2] E.Egenter, T.Lux, D.Stauffer Physica A 268(1999)250
[3] A.Kirman Quant. Journ. Econ. 108(1993) 137
AKSOE 10.3 Do 15:30 H8
Tobin tax and market depth — •Gudrun Ehrenstein 1 , Dietrich
Stauffer 1 , and Frank Westerhoff 2 — 1 Institute for Theoretical
Physics, Cologne University, Zülpicherstr. 77, 50937 Köln —
2 Department of Economics, University of Osnabrück, Rolandstrasse 8,
49069 Osnabrück
This paper investigates - on the basis of the Cont-Bouchaud model -
whether a Tobin tax may stabilize foreign exchange markets. Compared
to earlier studies, this paper explicitly recognizes that a transaction-taxinduced
reduction in market depth may increase the price responsiveness
of a given order. We find that the imposition of a transaction tax may
still achieve a triple dividend: (1) exchange rate fluctuations decrease, (2)
currencies are less mispriced, and (3) central authorities raise substantial
tax revenues. However, if the price impact function is too sensitive with
respect to the market depth, stabilization may turn into destabilization.
AKSOE 10.4 Do 16:00 H8
Knowledge agents represented by knowledge functions —
•Hans-Diedrich Kreft — 21521 Dassendorf, Ecksweg 4
Specific knowledge characteristics can be described mathematically by
the use of knowledge functions. In this sense we can speak of the operability
of knowledge. The operability of knowledge enables us to combine
the agent concept with knowledge functions. Thereby we get ”knowledge
agents” which can operate in an extended economic space. In this
socio-economic space we can mathematically derive for the first time new
micro and macro economic features like comepetence,rationalisation potential,innovation.
These extension of the space of economic description
seems to be essential for explaining complex economic dependencies on
an unique mathematical concept.
AKSOE 10.5 Do 16:30 H8
Fair or not fair? That is the question! – An Investigation based
on a System of a Network of Trading Agents — •Elena Ramirez
Barrios, Juan G. Diaz O. und Johannes J. Schneider —
Institute for Physics, Johannes Gutenberg University, Staudinger Weg 7,
D-55099 Mainz, Germany
Imagine an economy with a finite number of agents, each owning an
initial allocation of a finite number of commodities. There is no production,
and a price system is given. The agents choose the best net trades
according to their preferences, which are maximal in the limited budget
sets the agents have. This results in an equilibrium under optimal conditions.
In this equilibrium, we can find properties such as fairness, following
the fact that all agents have the same trading possibilities and the same
access to the entire set of commodities. A net trade is fair for any agent
i, if no other agent j can perform a better net trade than possible for
agent i, according to the preference list of agent i and according to his
budget set. Usually, only a normative meaning and a low measurability
of fairness are considered, as the concept of fairness is very difficult to
describe in an exact mathematical way. On the other hand, the concept
of fairness has occupied a good place in the political decisions trying to
improve the social welfare. However, with mathematical methods, we try
to simulate the economical agents’ behaviors and measure the fairness in
this system, finding a trend behavior such that their improved actions
result in a justice horizon as suggested by the first and second welfare
theorems.
AKSOE 10.6 Do 17:00 H8
Simulated Trading and Working — •Johannes J. Schneider —
Department of Physics, Johannes Gutenberg University, Staudinger Weg
7, D-55122 Mainz
Simulated Trading is a multi agent approach to solve combinatorial
optimization problems: the overall system shall be optimized by a set
of agents who buy and sell parts of the problem, which are currently in
their possessions, from or to each other [1,2]. The agents try to solve
their system parts in a rather optimum way – but this way is only locally
optimum. The results achieved with this approach depend strongly
on the overall number N of agents and on the fraction q of agents taking
part in a trading move. In order to improve results, the agents shall
not only trade but also work in this new approach. This means that
improvements are not only achieved with inter-agent trading moves but
also with intra-agent local moves. I will show results for an application
to the Traveling Salesman Problem and will compare this new approach
to the original approach and also to global optimization algorithms like
Simulated Annealing.
[1] A. Bachem, W. Hochstättler, M. Malich (1993), The Simulated Trading
Heuristic for Solving Vehicle Routing Problems, Report No. 93.139,
Institute of Mathematics, University of Cologne, Germany
[2] A. Bachem, W. Hochstättler, M. Malich (1994), Simulated Trading –
A New Parallel Approach for Solving Vehicle Routing Problems, Parallel
Computing: Trends and Applications: Proceedings of the International
Conference ParCo93, Grenoble, France, 7–10 September 1993

Symposium Fat-Tail Distributions - Applications from Physics to Finance Tagesübersichten
FAT-TAIL DISTRIBUTIONS - APPLICATIONS FROM PHYSICS TO FINANCE (SYFT)
Prof. Dr. Wolfgang Paul
Institut für Physik
Johannes Gutenberg Universität
55099 Mainz
PD Dr. Bernd Rosenow
Institut für Theoretische Physik
Universität zu Köln
Zülpicher Str. 77
50937 Köln
E-Mail: wolfgang.paul@uni-mainz.de rosenow@thp.uni-koeln.de
Since the pioneering work of Bachelier and Einstein at the beginning of the 20th century Gaussian fluctuations and Brownian
motion have been pervasive in physics as well as in financial theory. Itô not only mathematically formalized the concept of
Brownian motion but in 1944 also introduced geometric Brownian motion which still is the accepted model for stock-price
dynamics in applied finance. Mandelbrot in 1963 realized that actual data on price dynamics might be better described by
fat-tailed Lévy distributions than by the log-normal distribution of geometric Brownian motion, although today we would
rather use a truncated Lévy distribution or a power law with exponent outside the Lévy regime for the tail of the distribution.
In the last 15 years many physicists have found applications of Lévy stable distributions in ”classical”physics areas as well as
in socio-economic areas and it is therefore timely to bring together researchers from statistical physics as well as the physics
of socio-economic phenomena for a symposium on the applications of non-Gaussian fluctuations.
Hauptvorträge
SYFT 1.1 Do 09:30 (H1) Fat Tail Statistics and Beyond, Joachim Peinke
SYFT 1.2 Do 10:00 (H1) Use and Abuse of Ito vs. non-Ito Stochastic Calculus, Peter Hänggi
SYFT 1.3 Do 10:30 (H1) Non-Gaussian option pricing, Hagen Kleinert
SYFT 2.1 Do 11:30 (H1) Credit Risk in Banking - Methods, Problems, Implications,
Axel Müller-Groeling, Jan-Hendrik Schmidt
SYFT 2.2 Do 12:00 (H1) Understanding large fluctuations in stock market activity using methods
of statistical physics, H. Eugene Stanley
Fachsitzungen
SYFT 1 Fat-Tail Distributions - Applications from Physics to
Finance
SYFT 2 Fat-Tail Distributions - Applications from Physics to
Finance
SYFT 3 Fat-Tail Distributions - Applications from Physics to
Finance
Do 09:30–11:00 H1 SYFT 1.1–1.3
Do 11:30–13:00 H1 SYFT 2.1–2.4
Mo 16:00–18:00 Poster D SYFT 3.1–3.3

Symposium Fat-Tail Distributions - Applications from Physics to Finance Donnerstag
Fachsitzungen
– Haupt-, Fachvorträge und Posterbeiträge –
SYFT 1 Fat-Tail Distributions - Applications from Physics to Finance
Zeit: Donnerstag 09:30–11:00 Raum: H1
Hauptvortrag SYFT 1.1 Do 09:30 H1
Fat Tail Statistics and Beyond — •Joachim Peinke — Hydrodynamics
Group , Faculty of Physics, Carl v. Ossietzky University, D -
26111 Oldenburg
Many complex systems are characterized by non-Gaussian statistics,
which show pronounced fat tails. For risk analysis these fat tails play a
very important role. Analyzing different systems with respect to their fat
tail statistics, the question arises whether there are common or universal
features behind this stochastic phenomenon or not. In this talk data from
different systems are presented together with their fat tail statistics. In
particular we present results from environmental systems, from turbulent
flows and from the financial exchange market. Besides the comparison of
the statistics, we present a method to reconstruct from the data stochastic
processes which model the heavy tail statistics accurately. These reconstructed
stochastic systems are given as a specific Fokker-Planck equation,
which provides a statistically more complete characterization of the
system’s complexity. Even for similar fat tail statistics we find that different
underlying stochastic processes are present.
Hauptvortrag SYFT 1.2 Do 10:00 H1
Use and Abuse of Ito vs. non-Ito Stochastic Calculus — •Peter
Hänggi — Universität Augsburg, Institut für Physik
Brownian motion dynamics, discovered first in 1789 by Jan Ingen-
Housz on charcoal particles under his microscope and by Robert Brown
in 1828 in his observations of pollen, inspired many physicists to develop
guiding contributions to the theory of fluctuation phenomena and
statistical mechanics of irreversible processes per se. The list includes distinguished
names such as Langevin, Einstein, Smoluchowski, Ornstein,
Uhlenbeck, to name but a few. The use of stochastic differential equations
plays a key role in most phenomena involving noisy perturbations.
The paper by K. Ito (Proc. Imp. Acad. Tokyo, 20: 519 (1944)) gave the
corresponding stochastic integral a mathematical precise meaning while
Stratonovich in his works introduced a different notion that is appealing
for many from a physics point of view. In this talk I will survey the use –
and abuse – of actually infinite many differing stochastic integral definitions
for Gaussian white noise and, as well as, for white Poisson shot noise
[1]. With this talk I elaborate on various pitfalls and comment on the use
of colored noise (or correlated) driven flows. Moreover, I will clarify the
connection with a path integral representation of the stochastic dynamics
and clear up some confusion of Ito vs. Stratonovitch discretization rules.
Finally, I present results of multiplicative Langevin equations to describe
long time tail phenomena and anomalous diffusion.
[1] P. Hänggi and H. Thomas, Phys. Rep. 88: 207 (1982); sec. 2.4; P.
Hänggi, Helv. Phys. Acta 51: 183 (1978).
Hauptvortrag SYFT 1.3 Do 10:30 H1
Non-Gaussian option pricing — •Hagen Kleinert — Institut
für Theoretische Physik, Freie Universität Berlin, Arnimallee 14, 14195
Berlin
A new option pricing formula is derived which takes into account the
risk of rare dramatic price changes by using non-Gaussian distributions
with heavy tails. The derivation is based on a solvable path integral corresponding
to a Gaussian process in which the width fluctuates with
Gaussian noise. The resulting returns fit the Dow Jones data over many
times scales.
[1] H. Kleinert, Physica A 311, 536 (2002) (cond-mat/0203157)
[2] H. Kleinert, Physica A 312, 217 (2002) (cond-mat/0202311)
[3] See Chapter 20 in the textbook Path Integrals in Quantum Mechanics,
Statistics, Polymer Physics, and Financial Markets, World Scientific,
Singapore, 2003.
SYFT 2 Fat-Tail Distributions - Applications from Physics to Finance
Zeit: Donnerstag 11:30–13:00 Raum: H1
Hauptvortrag SYFT 2.1 Do 11:30 H1
Credit Risk in Banking - Methods, Problems, Implications —
•Axel Müller-Groeling and Jan-Hendrik Schmidt — McKinsey
Company, Inc.
We give a short introduction into credit risk and its fundamental importance
for the banking sector. We compare the main methods currently
in use for measuring the loss distribution originating from loan portfolios
and highlight some of the practical and methodological problems
involved. The main observable used by banks, credit value-at-risk, depends
sensitively on the tails of the distribution. It plays an important
role in the overall steering model of banks, as it characterizes the economic
capital required to run the credit business safely. We conclude with
a discussion of value-based steering and the optimal capital allocation to
credit-risk taking business units.
Hauptvortrag SYFT 2.2 Do 12:00 H1
Understanding large fluctuations in stock market activity using
methods of statistical physics — •H. Eugene Stanley — Department
of Physics, Boston University, Boston, Massachusetts 02215, USA
After a very short introduction to some of the most recent results
obtained in the field of econophysics we consider the problem of “rare
events” of the stock market price dynamics. It is becoming widely appreciated
that even extremely large movements in stock market activity may
not be “outliers” but rather may conform to newly-uncovered empirical
laws, such as the (i) power law distribution of returns with exponent
3, outside the Levy-stable regime, (ii) power law distribution of trading
volume with exponent 1.5 [1]. We discuss these new empirical laws, and
also discuss how one interdisciplinary “economist/physicist” collaboration
is beginning to gain theoretical insight and understanding of these
new empirical laws using concepts drawn from both the economics and
physical sciences [2-6].
The research reported was done primarily in collaboration with X.
Gabaix MIT Economics Dept), P. Gopikrishnan (now at Goldman Sachs),
and V. Plerou (Boston University) and has been supported by NSF.
[1] R. N. Mantegna and H. E. Stanley, Introduction to Econophysics:
Correlations and Complexity in Finance (Cambridge University Press,
Cambridge, 2000).
[2] V. Plerou, P. Gopikrishnan, X. Gabaix, and H. E. Stanley, “Quantifying
Stock Price Response to Demand Fluctuations,” Phys. Rev. E
66, 027104-1 – 027104-4 (2002) cond-mat 0106657; B. Rosenow, “Fluctuations
and market friction in financial trading” Int J Mod Phys C 13,
419-425 (2002).
[3] V. Plerou, P. Gopikrishnan, and H. E. Stanley, “Two-Phase
Behaviour of Financial Markets” Nature 421, 130 (2003). condmat/0111349.
[4] X. Gabaix, P. Gopikrishnan, V. Plerou, and H. E. Stanley, “A Theory
of Power-Law Distributions in Financial Market Fluctuations,” Nature
423, 267–270 (2003).
[5] X. Gabaix, P. Gopikrishnan, V. Plerou, and H. E. Stanley, “A Simple
Theory of Asset Market Fluctuations, Motivated by the Cubic and
Half Cubic Laws of Trading Activity in the Stock Market” Quarterly
Journal of Economics (submitted).
[6] V. Plerou, P. Gopikrishnan, B. Rosenow, L.A.N. Amaral, T. Guhr,
and H. E. Stanley, “A Random Matrix approach to Financial Cross-
Correlations” Phys. Rev. E 65, 066126 (2002) cond-mat/0108023.

Symposium Fat-Tail Distributions - Applications from Physics to Finance Donnerstag
Fachvortrag SYFT 2.3 Do 12:30 H1
The Sierpinski signal: 1/f α noise in a simple 1D automaton
model of pattern formation — •Jens Christian Claussen 1 , Jan
Nagler 2 , and Heinz Georg Schuster 1 — 1 Theoretische Physik, Universität
Kiel — 2 Theoretische Physik, Universität Bremen
Cellular automata have been considered widely as a model for complexity
and self-organized criticality: In classic models (Game of Life,
Bak-Sneppen, BTW, OFC), power law spectra and avalanche distributions
have been observed and compared with neural oscillators, extinction
dynamics, and earthquakes [1]. An even more simplified model, yet
exhibiting complex patterns, is the Sierpinski automaton xi(t + 1) =
(xi+1(t) + xi−1(t)) mod 2. Sierpinski patterns appear quite generically
in 1D reaction-diffusion pattern formation and have been observed in
catalytic reactions and in molluscs (Olivia porphyria).
In [2] we investigate the spectral properties of the time dependence
of total activity X(t) = �
i xi(t) of the Sierpinski automaton with initial
condition of one single seed. The spectrum is derived analytically and
shows a power-law decay with exponent 1.15. The relation to the paradigmatic
Thue-Morse sequence is discussed. While in our model the strict
lattice topology is crucial for the analytic result and seems to prevent
a direct mapping on economic agent networks, cellular (and stochastic)
automata may serve as candidates for modelling of fat-tailed observables
resulting from an underlying complex spatio-temporal dynamics.
[1] P. Bak, How nature works; H. J. Jensen, Self-organized criticality.
[2] J. C. Claussen, J. Nagler, and H. G. Schuster, cond-mat/0308277.
Fachvortrag SYFT 2.4 Do 12:45 H1
Robust estimation of correlation matrices and principal component
analysis for fat-tailed elliptical distributions — •Uwe
Jaekel 1 und Gabriel Frahm 2 — 1 NEC Europe Ltd., C&C Research
Laboratories, Rathausallee 10, 53757 St. Augustin — 2 Research Center
CAESAR, Project Group Financial Engineering, Ludwig-Erhard-Allee 2,
53175 Bonn
Many problems in physics and finance require the estimation of covariance
and correlation matrices. We present a maximum likelihood method
for the estimation of these matrices that, unlike the commonly used
moment estimator, is robust for the large class of elliptically contoured
distributions, thus leading to substantially better estimates in the presence
of fat tails. We try to reduce the complexity of the estimation
problem using Bayes or Akaike information criteria, and compare this to
attempts based on random matrix theory. The methods are applied to
high-dimensional simulated and observed equity market data sets. Finally,
we sketch some applications to the analysis of financial markets and
to practical problems like portfolio risk minimisation.
SYFT 3 Fat-Tail Distributions - Applications from Physics to Finance
Zeit: Montag 16:00–18:00 Raum: Poster D
SYFT 3.1 Mo 16:00 Poster D
Extreme value distributions for processes with Gaussian, Lévy
and truncated Lévy distributed increments: A computer simulation
study — •Thomas Schwiertz and Wolfgang Paul —
Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz
For many applications it is not so much of interest what the average
behavior of a stochastic process is but what its extremal excursions in
a time interval are. Examples are material failure, portfolio risk and the
pricing of barrier options. For sequences of identically distributed random
numbers there exists an exact classification of limiting distributions for
their extremal values. For sum variables (the time-dependent stock price
for instance) no general solution is known. Specifically it is of interest to
contrast Gaussian distributed increments to Lévy distributed ones and
to analyze the crossover between the two for truncated Lévy distributed
increments known to describe stock price fluctuations on the time scale
of a few minutes.
SYFT 3.2 Mo 16:00 Poster D
Pricing of Fire Insurance Contracts — •Magda Schiegl —
Versicherungskammer Bayern, Abt. 8MS02, Maximilianstr. 53, 80530
Muenchen
For pricing of insurance contracts the distribution of the annual claims
losses has to be calculated. We have given empirical data for number of
claims’ occurrence days distribution as well as single claim size distribution
data.
We find a stochastic model describing the number of claims process.
The single claim sizes in fire insurance possess a clearly fat-tailed distribution
function. We combine these two components to obtain the distribution
of annual claims losses We investigate the impact of those two
stochastic components (claim number and size) on the distribution of
annual claims losses, especially the behaviour of the tail.
SYFT 3.3 Mo 16:00 Poster D
Simple stochastic modeling for financial markets — •Hans-
Georg Matuttis — Department of mechanical engineering and intelligent
systems, The University of Electrocommunications, Chofu Chofugaoka
1-5-1,Tokyo 182-8585, Japan
A simple model using a stochastic differential euqation is proposed
which allows to extrapolate from random-walk type distributions to fat
tail distributions. To transcend the purely qualititative aggrement, an attempt
is made to derive the assumption in the model from contemporary
stock market practices in a quantitative way.

Symposium Life Sciences on the Nanometer Scale - Physics Meets Biology Tagesübersichten
Hauptvorträge
LIFE SCIENCES ON THE NANOMETER SCALE - PHYSICS MEETS BIOLOGY (SYLS)
Prof. Dr. Jürgen Köhler
Lehrstuhl für Experimentalphysik IV
Universität Bayreuth
Universitätsstr. 30
95447 Bayreuth
E-Mail: DPG.BioSymp@uni-bayreuth.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsaal H37)
SYLS 1.1 Mi 14:00 (H 37) Aquaporin Proteins: Perfect filters, Helmut Grubmüller, Bert L. de Groot
SYLS 1.2 Mi 14:30 (H 37) Single-Molecule Cellular Signaling, Thomas Schmidt
SYLS 4.1 Do 09:30 (H 37) Single Molecule Mechanics of Cytoskeletal Proteins, Matthias Rief
SYLS 5.1 Do 11:15 (H 37) Mechano-Chemical Coupling in F1-ATPase , Kazuhiko Kinosita
Fachsitzungen
SYLS 1 Symposium ”Life Sciences on the Nanometer Scale -
Physics Meets Biology”
SYLS 2 Symposium ”Life Sciences on the Nanometer Scale -
Physics Meets Biology”
SYLS 3 Symposium ”Life Sciences on the Nanometer Scale -
Physics Meets Biology”
SYLS 4 Symposium ”Life Sciences on the Nanometer Scale -
Physics Meets Biology”
SYLS 5 Symposium ”Life Sciences on the Nanometer Scale -
Physics Meets Biology”
Mi 14:00–15:00 H 37 SYLS 1.1–1.2
Mi 15:15–16:00 H 37 SYLS 2.1–2.3
Mi 16:00–18:30 B SYLS 3.1–3.58
Do 09:30–11:00 H 37 SYLS 4.1–4.5
Do 11:15–12:30 H 37 SYLS 5.1–5.4

Symposium Life Sciences on the Nanometer Scale - Physics Meets Biology Mittwoch
Fachsitzungen
– Haupt-, Kurzvorträge und Posterbeiträge –
SYLS 1 Symposium ”Life Sciences on the Nanometer Scale - Physics Meets Biology”
Zeit: Mittwoch 14:00–15:00 Raum: H 37
Hauptvortrag SYLS 1.1 Mi 14:00 H 37
Aquaporin Proteins: Perfect filters — •Helmut Grubmüller and
Bert L. de Groot — Theoretische und computergestützte Biophysik
MPI für biophysikalische Chemie, 37075 Göttingen
Aquaporins are highly selective water channels. Molecular dynamics
simulations of water permeation correctly predict the permeation rate,
explain why these channels are so efficient, and suggest that protons are
blocked by an electrostatic barrier.
Hauptvortrag SYLS 1.2 Mi 14:30 H 37
Single-Molecule Cellular Signaling — •Thomas Schmidt —
Physics of Life Processes, Leiden Institute of Physics, Leiden University
Recent studies showed that several types of membrane microdomains
are involved in H-Ras signal transduction. However, our knowledge about
the in vivo dynamics of these domains is still in its infancy. In this study,
the effect of plasma membrane organization on the activation of the small
GTPase H-Ras was studied by single-molecule fluorescence microscopy.
Diffusion analysis revealed a major, fast diffusing population and a minor,
slow diffusion population for both inactive and active H-Ras. Activation
of H-Ras resulted in a transfer from free diffusion to confinement into
200 nm-sized domains for the minor, slowly diffusing fraction. This is a
first indication for the relevance of membrane ultrastructure on cellular
signalling.
SYLS 2 Symposium ”Life Sciences on the Nanometer Scale - Physics Meets Biology”
Zeit: Mittwoch 15:15–16:00 Raum: H 37
SYLS 2.1 Mi 15:15 H 37
Nucleo-Cytoplasmic Transport of Single Molecules — •Ulrich
Kubitscheck, Andreas Hoekstra, David Grünwald, Jan Peter
Siebrasse, and Reiner Peters — Institute of Medical Physics
and Biophysics, Westfälische Wilhelms-Universität, D-48149 Münster
Understanding the intracellular exchange of matter and information
across the envelopes of cell nuclei presents a central biophysical problem.
Single-molecule microscopy was used to examine the topography and
transport properties of the large pore complexes (NPCs) in the nuclear
envelopes of digitonin-permeabilized cells. The nucleoporins POM121,
Nup358 and Nup153 could be localized along the NPC axis with a precision
of ±25 nm. Binding sites of NTF2 were detected on cytoplasmic
filaments and in the central framework of the NPC. Binding sites of an
import complex containing karyopherin β, however, were localized to the
central framework, and extended up to 200 nm into the nuclear basket.
In order to monitor the interaction of the transport substrates with the
NPC in real-time, we used an electron-multiplying CCD for fast kinetic
measurements. The dwell times of NTF2 and import complex at their
NPC binding sites were determined as 8.2±0.4 and 16±0.6 ms, respectively.
Together with the known transport rates these data suggest that
nucleocytoplasmic transport occurs via multiple parallel pathways within
single NPCs.
SYLS 2.2 Mi 15:30 H 37
Biophysical Applications of Quantum Dots: Labeling of Single
Biomolecules — •Colin D. Heyes 1 , Andrei Yu. Kobitski 1 , Elza
V. Amirgoulova 1 , Vladimir V. Breus 1 , Kirill V. Anikin 1 , and
G. Ulrich Nienhaus 1,2 — 1 Department of Biophysics, University of
Ulm, D - 89069 Ulm, Germany — 2 Department of Physics, University of
Illinois Urbana-Champaign, Urbana, IL 61801, USA
Fluorescent quantum dots (QDs) have several important properties,
which render them extremely useful in ultrasensitive studies of biomolecular
dynamics. They are bright, easily tunable in emission color, can be
chemically modified at the surface to recognize specific biomolecules without
changing the color, and are extremely stable against photobleaching.
We have studied the single particle photophysics, such as fluorescence
blinking and brightness, under various conditions to evaluate their usefulness
in single biomolecular experiments. We then present examples
in which they can be used to evaluate ultrasensitive and long timescale
biophysical processes as well as, or better than, conventional fluorescent
dyes. In the first example, we have studied the lateral diffusion of labeled
lipid molecules. This allows us to track lipid molecules for long periods of
time without significantly affecting the diffusion kinetics, as has been observed
with latex bead tracking. In the second example, we have studied
enzyme-substrate interactions of single enzyme molecules. Both examples
highlight the fact that QDs will continue to increase in importance for
biophysical applications, and the photophysics of such species needs to
be thoroughly understood.
SYLS 2.3 Mi 15:45 H 37
Detection and spectroscopy of 5 nm gold particles using
white-light confocal microscopy — •Patrick Stoller 1 , Klas
Lindfors 2 , Thomas Kalkbrenner 3 , and Vahid Sandoghdar 1 —
1 Physical Chemistry Laboratory; Swiss Federal Institute of Technology
(ETH); CH-8093, Zurich; Switzerland — 2 Department of Physics;
Helsinki University of Technology; P. O. Box 1000; FIN-02015 HUT;
Finland — 3 FOM Institute for Atomic and Molecular Physics (AMOLF);
Kruislaan 407; 1098 SJ Amsterdam; The Netherlands
The interaction of fluorescently labeled biological molecules can be
observed dynamically using optical microscopy. Gold nanoparticles can
also be used to optically label biological molecules because of their welldefined
plasmon resonance spectrum. Gold nanoparticles are biocompatible
and, unlike fluorophores, they do not bleach. To avoid interference
with the molecular interaction, it is important to minimize the size of
the labels. Recently, Boyer et. al. succeeded in detecting 2.5 nm gold
nanoparticles using photothermal imaging [Science. 297. 1160-1163]. In
our work, we used white light confocal microscopy not only to detect but
also to observe the plasmon resonance spectrum of single gold nanoparticles
with diameters as small as 5 nm [submitted]. An ultra-short pulse
laser and a photonic crystal fiber were used to generate a collimated beam
of quasi-continuum white light, which was tightly focused onto the sample
using a high numerical aperture microscope objective; the scattered
light was collected confocally and detected using an imaging spectrometer.
Our goal is to apply this technique to studying the interaction of
biological molecules at the single molecule level.

Symposium Life Sciences on the Nanometer Scale - Physics Meets Biology Mittwoch
SYLS 3 Symposium ”Life Sciences on the Nanometer Scale - Physics Meets Biology”
Zeit: Mittwoch 16:00–18:30 Raum: B
SYLS 3.1 Mi 16:00 B
Accumulation and Replication of DNA driven by temperature
gradients — •Dieter Braun — Emmy Noether Gruppe, Experimentalphysik,
Universitaet Muenchen, Amalienstr. 54, 80799 Muenchen
The influence of temperature gradients on DNA is investigated. For the
first time, the thermophoresis of DNA from hot to cold was measured.
Under conditions which also allow for convection, thermophoresis accumulates
DNA thousandfold into microscopic pots [1]. R. Piazza showed
that thermophoresis of ions such as DNA in water is probably driven and
dominated by a gradient of interfacial tension at the nanoscopic interface
between molecule and water [2].
In a similar geometry, the laminar convection can be used to drive the
DNA amplifying reaction of PCR. Such a laminar convective PCR amplifies
DNA specifically and quantitatively at a speed faster than standard
PCR machines [3].
Both studies of mesoscopic open system far away from thermodynamic
equilibrium revealed new effects. Besides biotechnological applications,
the experiments suggests a convective origin of life in porous rock near
submarine hydrothermal vents [4].
[1] D. Braun and A. Libchaber, PRL 89:188103 (2002)
[2] R. Piazza and A. Guarino, PRL 88:208302 (2002)
[3] D. Braun, N.L. Goddard and A. Libchaber, PRL 91:158103 (2003)
[4] D. Braun and A. Libchaber, Physical Biology, submitted
SYLS 3.2 Mi 16:00 B
Modulation of the Nanoscale-Structure of Fibronectin Fibrils —
•Tilo Pompe — Institut für Polymerforschung Dresden e.V. & Max-
Bergmann-Zentrum für Biomaterialien Dresden
The protein fibronectin is a major component of the extracellular matrix
providing cells with binding sites to the surrounding tissue. The
formation of fibrils from single fibronectin molecules is a complex process
which includes binding of cell receptors, like integrins, conformational
changes of fibronectin by mechanical forces exerted from the cell,
and polymerisation of fibronectin molecules at newly exposed binding
sites. Scanning force microscopy analysis revealed that early stages of
fibronectin fibrillogenesis are controlled by the binding strength of fibronectin
molecules to the underlying polymer substrate. Furthermore,
the nano-structure of the fibrils exhibits characteristic distances between
small fibrils with a distinct periodicity of 73 nm. The periodic spacing
implies a mechanism of the fibrillogenesis process directly related to the
force applied to the protein via the cytoskeleton of the cell.
SYLS 3.3 Mi 16:00 B
Interactions of Thionin with DNA-Strands: Intercalation vs
External Stacking — •Christoph Hecht 1 , Josef Friedrich 1 ,
and Ta-Chau Chang 2 — 1 TU München, Physik-Department E14,
Lehrstuhl für Physik Weihenstephan, 85350 Freising — 2 Institute of
Atomic and Molecular Science, Academia Sinica, Taiwan
The interaction of dye-molecules with DNA-strands plays an important
role in anti-cancer drug research. We investigated the binding modes of
thionin with various structures of short stranded DNA-molecules by measuring
the response of a spectral hole to pressure variations. Thionin binds
through Coulomb-interaction via external stacking to DNA-quadruplex
structures. The binding to DNA-duplex structures, however, is different:
One of the two possible isomers of thionin intercalates into the DNAstrands.
SYLS 3.4 Mi 16:00 B
SINGLE VIRUS TRACING: VISUALIZATION OF THE IN-
FECTION PATHWAY OF A VIRUS INTO A LIVING CELL
— •T. Endreß, S. Mugrauer, A. Zumbusch, and C. Bräuchle
— Department Chemie, Universität München, Butenandtstr. 11, 81377
München, Germany
Viruses play a major role in biology and medicine. A detailed analysis
of the different steps of a viral infection is not only necessary to understand
viral biology, but also for the development of efficient antiviral
drugs and save viral gene therapy vectors. Single Virus Tracing allows
visualization of the infection pathway of an individual virus labeled with
fluorescent dye molecules (even in the case of labeling with a single dye
molecule). The fluorescence of the marker molecule is imaged and used
to follow the pathway of the virus with high spatial (≥ 40 nm) and time
(≥ 10 ms) resolution. As a first model system we have investigated the
infection pathway of Adeno-associated viruses (AAV) into HeLa cells.
AAV shows promising results for the use in gene therapy applications.
A sequence of events can be tracked starting with a virus approaching
the cell surface, successive receptor binding, membrane penetration, endosome
formation and trafficking, virus release from the endosome and
virus trafficking in the cytoplasm as well as penetration into the nuclear
area.
Besides AAV the studies have been extended to other viral particles like
HIV. HIV is an enveloped virus, which was labeled at its matrix protein
(MA) and its viral protein (Vpr) with GFP and GFP mutants. First
results from these studies will also be presented.
SYLS 3.5 Mi 16:00 B
Interactions of biopolymers of fixed topology with thermal fluctuations
— •Ralf Metzler 1 and Andreas Hanke 2 — 1 NORDITA,
Blegdamsvej 17, DK-2100 Copenhagen OE — 2 Theoretical Physics, University
of Oxford, Oxford OX1 3NP, United Kingdom
DNA knots of different complexity effect different mobility of the chain,
and they pose an intricate problem to a biological cell in respect to transcription
or replication. Specific enzymes remove knots very efficiently
despite having access to local information, only. I will discuss ideas on
how interaction of thermal fluctuations with the fixed topology of the
chain may assist the enzymes in their task, and under which conditions
this may actually work in vivo.
Double-stranded DNA even at physiological temperatures undergoes
fluctuations, during which single-stranded bubbles open up along the
strand. Increasing the temperature, dsDNA eventually undergoes a melting
transition. Starting from a microscopic model for the Free energy, we
derive a Fokker-Planck equation to the bubble fluctuations, whose predictions
close to physiological temperatures reproduce recent experimental
results on single bubble fluctuations.
References: R. Metzler, A. Hanke, P. G. Dommersnes, Y. Kantor, and
M. Kardar, Phys. Rev. Lett. 88 (2002) 188101; Phys. Rev. E 65 (2002)
061103. A. Hanke and R. Metzler, Phys. Rev. Lett. 90 (2003) 159801, A.
Hanke and R. Metzler, J. Phys. A (Lett.) 36 (2003) L473.
SYLS 3.6 Mi 16:00 B
Tuning of microcapsule adhesion by varying capsule stiffness —
•Nils Elsner and Andreas Fery — MPI for Colloids and Interfaces
14424 Potsdam
We have been studying the adhesion polyelectrolyte (PE) capsules
composed from Polyallylamine (PAH) and Polystyrenesulfonate (PSS).
These PE capsule can be produced in sizes up to 20 mm, while the thickness
remains tunable on the nanometer scale. This makes it possible to
vary the elastic properties by changing the wall thickness, which has been
shown by us recently [1].
The interaction of these capsules with a glass surface was studied by
Reflective Interference Contrast Microscopy measurements. It was found,
that negatively charged capsules adhere to glass, which was coated with
positively charged polyelectrolyte, whereas these capsules do not adhere
to bare glass. We found that the adhesion area increases with decreasing
shell thickness for shells with identical surface interactions. The data for
the adhesion area for different thicknesses and different radii could be
fitted with a simple model based on [2], having the surface energy as the
only fitting parameter.
In pH-experiments, the stiffness of the capsules is found to decrease
upon increasing pH as revealed by force spectroscopy measurements.
Consequently, we observe an increase of the adhesion areas although the
surface interactions are not strongly changed in this pH range.
[1] F. Dubreil, N. Elsner, and A. Fery, Eur. Phys. J. E in press (2003).
[2] L. D. Landau and E. M. Lifschitz, Elastizitätstheorie (Akademie
Verlag, Berlin, 1991).
SYLS 3.7 Mi 16:00 B
Persistent Spectral Labeling of Proteins via UV-
Photochemistry of their Aromatic Amino Acids — •Christoph
Schnell, Christoph Hecht, Markus Stübner, and Josef
Friedrich — Physik-Department E14, Lehrstuhl für Physik
Weihenstephan, Technische Universität Müenchen, 85350 Freising
We used hole burning techniques for high resolution frequency label-

Symposium Life Sciences on the Nanometer Scale - Physics Meets Biology Mittwoch
ing of proteins in the absorption range of their aromatic amino acids.
Tyrosine is most effective as a hole burning probe most probably due
to light-induced hydrogen abstraction at the hydroxy-group. We applied
the technique to BPTI, insuline and ribonuclease. We performed Starkeffect
and pressure tuning experiments with the holes to shed light on
the electrostatic and elastic properties of the proteins.
SYLS 3.8 Mi 16:00 B
Spectal diffusion experiment with a denatured protein
— •Vladimir Ponkratov and Josef Friedrich — Physik-
Department E14, Lehrstuhl fuer Physik Weihenstephan, TU Muenchen
Spectral diffusion broadening of a persistent spectral hole burnt into
the absorption of a cytochrome c-type protein in its unfolded state is investigated
and compared to the corresponding broadening in the native
state. Spectral diffusion broadening is much larger in the unfolded state.
We found that the time law which governs spectral diffusion changes
from a power law to a seemingly logarithmic law as the aging time of the
protein encreases.
SYLS 3.9 Mi 16:00 B
Direct Observation of Tiers in the Energy Landscape of a Chromoprotein:
A Single-Molecule Study — •Martin Richter 1 ,
C. Hofmann 1 , T.J. Aartsma 2 , H. Michel 3 , and J. Köhler 1 —
1 Experimental Physics IV, University of Bayreuth — 2 Department of
Biophysics, Leiden University — 3 Department of Molecular Membrane
Biology, Max-Planck Institute of Biophysics, Frankfurt
We report the observation of spectral fluctuations in the B800 band of
light harvesting 2 (LH2) complexes from Rhodospirillium molischianum.
The electronically excited states of these chromophores are mainly localized
on individual BChl a molecules and can serve as local probes to
monitor changes in the protein envirornment. The data provide information
about the organization of the energy landscape of the protein in
tiers that can be characterized by an average barrier height. In addition
a clear correlation for the transition rates between those states and the
energy separation of the levels involved is uncovered.
SYLS 3.10 Mi 16:00 B
High-Resolution Near-Field Fluorescence Microscopy of Single
Nuclear Pore Complexes in an Intact Nuclear Envelope — •C.
Höppener 1 , J.-P. Siebrasse 2 , U. Kubitscheck 2 , R. Peters 2 ,
H. Fuchs 1 , and A. Naber 3 — 1 Physikalisches Institut, Westfälische
Wilhelms-Universität, 48149 Münster — 2 Institut für Medizinische
Physik und Biophysik, Westfälische Wilhelms-Universität, 48149
Münster — 3 Institut für Angewandte Physik, Universität Karlsruhe
(TH), 76131 Karlsruhe
The nuclear pore complex (NPC) is a large macromolecular protein
assembly embedded in the nuclear envelope (NE) of a eukaryotic cell
and mediates the highly selective, bi-directional exchange of all kinds of
molecules between cytoplasm and nucleus. So far single NPCs could not
be resolved by optical means since the NPCs are densely packed in the
membrane. We present high-resolution near-field optical images of a fluorescently
labelled NE [1] performed in a buffer solution. These images
represent the first example of a high-resolution scanning near-field optical
measurement of a functionally intact biomembrane. A super-resolution
of 60nm enables us to optically identify for the first time single, closely
neighboured NPCs. Furthermore, the appearance of the NPCs markedly
varies with the primary antibody used for fluorescence labelling, thus revealing
information about the location of a specific nucleoporin within
the NPC.
[1] C. Höppener, D. Molenda, H. Fuchs, and A. Naber, J. Microsc. 210,
288 (2003)
SYLS 3.11 Mi 16:00 B
Time-resolved Fluorescence Resonance Energy Transfer on
DNA duplexes — •Petra Müller, Jürgen Köhler, and Dagmar
Klostermeier — Experimental Physics IV, University of Bayreuth,
Bayreuth
Fluorescence resonance energy transfer (FRET) is an established technique
to determine intramolecular distances between 1 and 10 nm. In
time-resolved FRET experiments, inter-fluorophore distance information
is retrieved from the analysis of fluorescence emission decays of the donor
fluorophore in the absence and presence of the acceptor fluorophore.
Here we report distance measurements using our home-built timeresolved
FRET setup. Excitation is performed using the frequencydoubled
output of a pulsed titanium:sapphire laser, and the nanosecond
decay profile of the donor is measured via time-correlated single photon
counting. Calibration with a series of donor-acceptor labelled DNA
molecules yields inter-fluorophore distances in good agreement with calculated
values based on standard DNA B-form geometry and the chemistry
of fluorophore attachment. Furthermore, multiple distance distributions
for various mixtures of DNA molecules of different lengths can be
extracted correctly from the donor decays.
Having established the possibilities and limitations of our time-resolved
FRET set-up we will now employ this technique to identify functional
conformers of proteins that modulate nucleic acid structures, such as
helicases and topoisomerases.
SYLS 3.12 Mi 16:00 B
A fluorescence anisotropy-based activity assay for the RNA-
Helicase DbpA — •Niklas Nachtmann and Dagmar Klostermeier
— Experimental Physics IV, University of Bayreuth, Bayreuth
The Escherichia coli protein DbpA is an RNA-helicase involved in ribosome
biogenesis. It comprises conserved helicase motifs, such as a Walker
A motif and a DEAD box involved in ATP binding and hydrolysis, an
arginine-rich motif that mediates RNA binding, and a SAT motif responsible
for coupling of ATPase and RNA unwinding activities.
We have developed a DbpA helicase activity assay using a fluoresceinlabeled
model substrate and fluorescence anisotropy. The fluorescently
labeled substrate binds to DbpA with high affinity, and the unwinding
of its short double-stranded region can be followed via a concomitant
decrease in fluorescein anisotropy. This anisotropy decrease is only observed
in the presence of ATP, not ADP, consistent with ATP-dependent
helix unwinding. Furthermore, a mutant of DbpA in which the conserved
SAT motif has been converted to AAA does not exhibit helicase activity
towards this substrate, as monitored by fluorescence anisotropy.
Despite minor sequence differences in the corresponding ribosomal
RNA region, this activity test is applicable to the homologous RNA helicase
YxiN from Bacillus subtilis. This anisotropy-based activity test
will be an invaluable means to assay helicase constructs manipulated for
single molecule FRET experiments for wild-type like activity.
SYLS 3.13 Mi 16:00 B
Multivariate Statistical Analysis applied to Single-Molecule
Spectra — •Jürgen Baier 1 , C. Hofmann 1 , M. Richter 1 ,
M. Schatz 2 , H. Michel 3 , M. van Heel 4 , and J. Köhler 1 —
1 Experimental Physics IV, University of Bayreuth — 2 Image Science
Software GmbH, Berlin — 3 Department of Membrane Biology, MPI of
Biophysics, Frankfurt — 4 Department of Biological Sciences, Imperial
College, London
The spectral width of an optical transition from an ensemble of
molecules reflects the statistical distribution of local environments and
is commonly termed inhomogeneous linewidth. As is well known, singlemolecule
spectroscopy allows to supass this phenomenon and to obtain
the homogeneous linewidth of the optical transition. However, the observed
linewidth corresponds to the temporal average and the above mentioned
argument holds true only if the experimental observation time for
the single-molecule transition is short with respect to the timescale of
the fluctuations in the sample.
Here we demonstrate that the combination of fast data acquisition
and pattern recognition algorithms which are ususally employed in cryoelectron
microscopy allows us to elucidate further information from
single-molecule lineshapes if this perequisite is not fulfilled.
SYLS 3.14 Mi 16:00 B
Optimizing Water-Soluble Quantum Dots for Biological Application
— •Vladimir V. Breus 1 , Colin D. Heyes 1 , Andrei Yu.
Kobitski 1 , Kirill V. Anikin 1 , and G. Ulrich Nienhaus 1,2 —
1 Department of Biophysics, University of Ulm, D - 89069 Ulm, Germany
— 2 Department of Physics, University of Illinois Urbana-Champaign,
Urbana, IL 61801, USA
The use of quantum dots has several advantages over fluorescent dyes
for biological application. They are bright, easy tunable in color, and
extremely stable against photo bleaching (> 10 8 emitted photons). Various
bifunctional ligands were used to obtain water-soluble, biocompatible
ZnS coated CdSe quantum dots. The chemical stability, photoluminescence
efficiency and fluorescent blinking of the different samples were
compared. The optimized water-soluble quantum dots were used in longtimescale
single-molecule imaging of lipid diffusion in membranes.

Symposium Life Sciences on the Nanometer Scale - Physics Meets Biology Mittwoch
SYLS 3.15 Mi 16:00 B
Acid-attack on Dental Enamel Investigated by Scanning Force
Microscopy — •N. Schwender 1 , F. Al Marrawi 2 , K. Huber 2 , M.
Hannig 2 , and C. Ziegler 1 — 1 Department of Physics, University of
Kaiserslautern — 2 Department of Operative Dentistry and Periodontology,
Saarland University
As food or drinks always contain acids knowledge about the interaction
of acids with dental enamel is important in preventive dentistry.
Using the possibilities of Scanning Force Microscopy (SFM), the influence
of acids on enamel surfaces was therefore investigated here. For
this purpose, bovine enamel samples were ground flat, polished or cut
by a diamond knife. Samples were treated with different acids such as
phosphoric, citric, or hydrochloride acid, systematically changing the exposure
time and the pH-value. Typical etch-patterns with a variation
of height from the nano- to the micrometer scale as a result of mineral
loss was observed. Distinct differences between the different acids could
be observed which will be discussed taking into account the different reactivity
of the components of enamel. Furthermore, the etched enamel
shows a loss in stability and hardness noted by the erosion induced by
the cantilever. In a further step the adsorption of saliva proteins such
as BSA and lysozym on the etched surface compared to the undestroyed
surface was investigated.
SYLS 3.16 Mi 16:00 B
Towards a near-field optical observation of single particle
transport through an unsupported cell membrane — •Simone
Johnas 1 , Christiane Höppener 2 , and Andreas Naber 1 —
1 Institut für Angewandte Physik, Wolfgang-Gaede-Str. 1, Universität
Karlsruhe (TH), 76131 Karlsruhe — 2 Physikalisches Institut,
Wilhelm-Klemm-Str. 10, Universität Münster, 48149 Münster
Highly differentiated macromolecular protein assemblies, so-called nuclear
pore complexes (NPC), are embedded in the nuclear envelope (NE)
of a eukaryotic cell and tightly control the exchange of all kinds of
molecules between cytoplasm and nucleus. Since the NPCs are densely
packed in the membrane, conventional optical microscopy is not able to
distinguish between neighboring NPCs. By means of scanning near-field
optical microscopy (SNOM) we have recently attained an optically resolved
fluorescence image of dye-labeled NPCs in a functionally intact
NE for the first time [1, 2]. Since SNOM enables us to address single
NPCs, we are now aiming at a time-resolved observation of single transport
events. A major obstacle towards this goal is the need of two compartments
below and above the NE that mimics its natural environment.
We will discuss possible preparation techniques and ways to image a freestanding
membrane in a buffer solution with a SNOM. [1] C. Höppener,
D. Molenda, H. Fuchs, and A. Naber, J. Microsc. 210, 288 (2002). [2]
Contribution of C. Höppener et al. in this symposium.
SYLS 3.17 Mi 16:00 B
Biological photonic crystals — •Thomas Fuhrmann, Melanie El
Rharbi-Kucki, and Stefan Landwehr — Makromolekulare Chemie
und Molekulare Materialien, Fachbereich Naturwissenschaften und Center
for Interdisciplinary Nanostructure Science and Technology, Universität
Kassel
Active and passive photonic crystals are interesting for a wide range
of applications. We show that photonic crystal structures for visible light
can be found in centric diatoms which exhibit a very efficient photosynthesis.
We present electromagnetic wave calculations addressing the
photonic structure of the algae cells and experimental results about the
light distribution in the cell.
SYLS 3.18 Mi 16:00 B
Density functional theory study of alpha-helical polypeptides
under tensile strain — •Joel Ireta 1 , Jörg Neugebauer 1,2 ,
and Matthias Scheffler 1 — 1 Fritz-Haber-Institut der Max-
Planck-Gesellschaft, Berlin — 2 Theoretische Physik, Universität
Padeborn
Recent experimental techniques employing e. g. optical tweezers or
atomic force microscopes make it possible to monitor the behavior of
biopolymers under tensile strain. Using this technique force-driven phase
transitions occurring at single molecule level have been observed. While
such studies give important information they are (presently) not able
to provide insight into the atomistic details of such processes. We have
therefore studied the mechanical response of infinite polyalanine and
polyglicine chains in alpha-helical conformation since these structures
represent the smallest but still realistic models of a protein. We employ
density functional theory, ab initio pseudopotentials and the Perdew-
Burke-Ernzerhof formulation for the exchange and correlation functional.
Calculating the response force along the helix axis as function of strain,
we have identified a plateau region at forces of about 25 pN. The presence
of a plateau is characteristic for a first order phase transition. An analysis
of the helical structures shows that sizeable changes in the covalent bonds
of the peptide unit (particularly carbon and nitrogen pyramidalization)
are the driving force causing the phase transition.
SYLS 3.19 Mi 16:00 B
Carbon nanotube-assisted microwave absorption of gold
nanoparticles across bacterial membranes — •Jose Rojas-
Chapana 1 , Miguel Correa-Duarte 1 , Neli Sobal 1 , Krzysztof
Kempa 2 , and Michael Giersig 1 — 1 Caesar Research Center,
Ludwig-Erhard Allee 2, 53175 Bonn — 2 Boston College, Boston, MA,
USA
Acidothiobacillus ferrooxidans an acid tolerant bacterium was used as
a tool to study intracellular incorporation and storage of gold nanoparticles
(GN) induced by carbon nanotubes (CNTs). The microwave (MW)
irradiation induced an electrostatic charge in the CNTs. Under this condition
all the single CNTs work as an electric dipole. The addition of a
small concentration of CNTs to a medium containing both bacteria and
GN, and subsequent MW-irradiation leads to intracellular transport of
gold without altering the viability of bacterial cells. As is shown by the
transmission electron microscopy (TEM) examination, CNT tip heads are
very close to the cell wall of bacteria. This CNTs-cell electrical contact
is a prerequisite for the onset of temporary channels. One of the possible
mechanisms during the MW-irradiation is a local electrical dipole
induced in CNTs which leads to cell-wall destabilization, having the dimension
of the CNTs tip heads (ca.30 nm diameter), which in turn act as
a channel for the transport of gold. The occurrence of this phenomenon,
as documented by TEM images, constitutes the most important factor
facilitating MW-induced transport of GN across the cells.
SYLS 3.20 Mi 16:00 B
Quantum Monte Carlo study of small molecules and hydrogen
bonded model systems - benchmarking density functionals —
•M. Fuchs 1 , A. Badinski 1 , J. Ireta 1 , P. Kratzer 1 , C. Filippi
2 und M. Scheffler 1 — 1 Fritz-Haber-Institut der MPG, Berlin —
2 Instituut Lorentz, Univ. Leiden
Diffusion Monte Carlo (DMC) calculations can be useful to validate
(and correct) results from density-functional theory (DFT) where manyelectron
correlations must be approximated. DMC is not yet a routine
tool however, partly because experience to corroborate its robustness is
still scarce. Here we apply the pseudopotential fixed-node DMC method
to (i) selected small molecules and (ii) model systems for hydrogen bonds,
the latter playing a key role for the structure and functionality of, e.g.,
biomolecules. We carefully monitor how DMC performs dependent on
(nonlocal) pseudopotentials and on the optimization of the initial trial
wavefunction. We find that both aspects can be nontrivial, even for the
simple N2 diatomic. For finite formamide chains our DMC data show
that the cooperative increase of the H-bond strength in longer chains is
best reproduced in DFT using the PBE gradient corrected functional.
Our findings support a recent DFT study of the stabilization of α helical
polyalanine which found an unusually large cooperativity of the H-bonds
[J. Ireta et al., J. Phys. Chem. B 107, 1432 (2003)].
SYLS 3.21 Mi 16:00 B
Conformational flexibility of pigment-protein complexes
studied by optical single-molecule spectroscopy — •Silke
Oellerich 1 , Martijn Ketelaars 1 , Jean-Manuel Segura 1 ,
Ward P.F. de Ruijter 1 , Richard J. Cogdell 2 , and Thijs J.
Aartsma 1 — 1 Dept. of Biophysics, Leiden University, Niels Bohrweg 2,
2333 CA Leiden, The Netherlands — 2 Dept. of Biochemistry, University
of Glasgow, Scotland
Low temperature, optical single-molecule spectroscopy was employed
to study the conformational flexibility and its effect on the electronic
properties of individual pigment-protein complexes. We studied the bacterial
light-harvesting complex 3 (LH3), which consists of 27 bacteriochlorophyll
a (BChl a) pigments and exhibits a heterogeneous spectral
behaviour at the single-molecule level. The applied technique provides
information about both the interaction between the pigments within a
complex as well as the effect of the local environment on an individual pigment.
We show that the spectral heterogeneity is caused by light-induced
conformational changes of individual BChl a pigments which affect the

Symposium Life Sciences on the Nanometer Scale - Physics Meets Biology Mittwoch
optical properties of the whole complex.
SYLS 3.22 Mi 16:00 B
Ab-initio vibrational analysis of the secondary structure of proteins
— •Lars Ismer 1 , Joel Ireta 1 und Jörg Neugebauer 2 —
1 FHI Berlin — 2 Universität Paderborn
For a detailed understanding of protein functionality an accurate description
of their dynamical properties is crucial. However, so far ab-initio
based studies on realistic structures going beyond the primary structure
are rare, particularly with respect to vibrational properties. We have therefore
performed a full ab-initio DFT-PBE based harmonic vibrational
analysis of infinite poly-alanine and -glycine chains in two different secondary
conformations: the infinite α-helical conformation, as model for the
most ubiquitous native secondary conformation stabilized by hydrogen
bonds (hb) and the fully extended conformation (FES), as a reference
system where hb’s are absent. By comparing the phonon dispersion relation
of α-helix and FES we were able to extract a direct ”fingerprint”
of the hb’s and their cooperativity in specific high frequent vibrational
branches. We also observed that constraining the peptide chain to the
helical conformation leads to significant blue-shifts in the low frequent
backbone vibrations. A thermodynamic analysis based on these results
revealed that the vibrational contributions of the free energy significantly
lower the stability of the α-helix with respect to the FES by about 0.8
kcal/mol at 300K.
SYLS 3.23 Mi 16:00 B
Optical characterisation of artifical confinements for protein
folding — •Johannes Hohlbein 1 , Ulrike Rehn 1 , and Ralf B.
Wehrspohn 2 — 1 Max-Planck-Institute of Microstructure Physics,
Weinberg 2, 06120 Halle, Germany — 2 Department of Physics,
University of Paderborn, Warburger Str. 100, 33098 Paderborn,
Germany
We present a new method to characterize in-situ the optical thickness
of porous alumina films by the use of photoluminescence-induced Fabry-
Pèrot-interferences. Additionally we show, that the use of different electrolytes
yields different photoluminescence pattern. A second experiment
allows to determine the degree of filling of the pores by a liquid which is
of importance when using the pores as templates for protein folding. First
studies of the influence of geometrical confinement on protein folding will
be presented.
Porous oxide growth on aluminium under anodic bias in various electrolytes
has been studied for nearly 50 years. Recently, porous anodic
alumina (PAA) films have been used to prepare nanostructures for a
wide range of applications. In order to use porous alumina as template
for protein folding in-situ optical measurements of their thickness as well
as the degree of filling are required. It has been shown, that porous alumina
exhibits a photoluminescence (PL) signal. We will use the PL pattern
to determine the thickness and the degree of filling by Fabry-Pèrotinterferences.
SYLS 3.24 Mi 16:00 B
Neuronale Synchronität in biologisch plausiblen exzitatorischen
Netzwerken: Entstehung und Modulation — •K. Kube 1 , V.
Spravedlyvyy 1 , A. Herzog 1 , B. Michaelis 1 , A. de Lima 2 , T.
Opitz 2 , T. Voigt 2 , A. Reiher 3 , A. Krtschil 3 , S. Günther 3 , H.
Witte 3 und A. Krost 3 — 1 Institut für Elektronik, Signalverarbeitung
und Kommunikationstechnik, Otto-von-Guericke-Universität Magdeburg
— 2 Institut für Physiologie, Otto-von-Guericke-Universität Magdeburg
— 3 Institut für Experimentelle Physik, Otto-von-Guericke-Universität
Magdeburg
Detaillierte Kompartimentmodelle von Einzelneuronen sind oft benutzt
worden, um das Gehirn als modulare elektrische Apparatur darzustellen.
Wir präsentieren eine biologisch realistische Simulation von
Netzwerk-Eigendynamik, wie sie in Zellkulturen des frühen zerebralen
Kortex von Wirbeltieren abläuft. Dabei wird die Entwicklung der
natürlichen Vernetzungstruktur nachgebildet, in der verschiedene funktionelle
Neuronentypen interagieren. Ausgehend von spontaner elektrischer
Aktivität einzelner Neurone werden in massiven Simulationen Eigenarten
der elektrischen Dynamik des Netzwerks und deren gezielte
Beeinflussung gezeigt sowie mit der in-vitro-gemessenen Aktivität verglichen,
die in Verbindung mit zellulären Lernmechanismen (Hebb-LTP)
wechselwirken können, um sich an Muster äußerer Reize anzupassen. Abschließend
wird diskutiert, auf welche Art man in spontan feuernden Zellen,
die über zufällige, rekurrente Strukturen von Netzwerken verbunden
werden, von Organisation sprechen kann.
SYLS 3.25 Mi 16:00 B
Protein adsorption on tailored substrates — •Hubert Mantz,
Anthony W. Quinn, and Karin Jacobs — Experimental Physics,
Saarland University, POB 151 150, 66041 Saarbrücken
It has long been established that bacterial plaque plays an essential role
in the development of oral diseases such as dental caries. Dental plaque
consists of a diversity of different components, which makes it difficult to
determine the mechanism for their formation and growth. Understanding
them would enhance the field of preventative dentistry enabling restorative
materials to be tailored to resist bacterial attachment or have some
antibacterial effect.
We try to get an insight in these mechanisms by using ellipsometry, a
non-destructive optical method for determining film thickness and optical
properties of the sample to be studied. These experiments can measure
the adsorption kinetics of purified salivary proteins on tailored substrates.
By using AFM and wettability analysis, the composition of the surfaces
can be controlled and described.
SYLS 3.26 Mi 16:00 B
Picosecond dynamics of bacterial porins investigated by
quasi-elastic neutron scattering — •Marie Plazanet 1 , Cecile
Bon 2 , Franck Gabel 3 , Sylviane Julien 2 , Peter Timmins 1 ,
and Guiseppe Zaccai 3 — 1 Institut Laue Langevin, 6 rue Jules
Horowitz, 38042 Grenoble Cedex 9, France — 2 CNRS/IPBS, 205 route
de Narbonnes, 31077 Toulouse cedex, France — 3 IBS, 41, rue Jules
Horowitz, 38027 Grenoble Cedex 1, France
The survival of bacteria requires a continuous exchange of molecules
across the cell wall. Porins, a large class of membrane proteins, are involved
in the transport of small hydrophilic molecules across the outer
membrane. Porins have peculiar structural features; they fold in a multistranded,
closed beta-sheet, exposed to the hydrophobic membrane core
on one side and an aqueous channel on the other. Dynamics of these extremely
stable proteins clearly modulate the pore activity (i.e. biological
activity of the porin), and there is good evidence that this dynamics is
modulated by the dynamics of the lipids surrounding the porins.
Experiments have been undertaken on outer membrane fractions of
E.Coli, with the natural asymmetric lipid distribution (lipopolysaccharides
in the outer leaflet and various phospholipids in the inner leaflet).
Samples enriched in porins and samples depleted in porins have been investigated
to probe both lipid and porin contribution. While data are still
under study, preliminary results show that both systems clearly exhibit
very different dynamics on the pico-second timescale. A brief comparison
with corresponding results on the bacteriorhodospsin, a representative of
the membrane proteins folded in an helix-bundle, will be done.
SYLS 3.27 Mi 16:00 B
Controlled proliferation of living cells on UV-light modified polymers
— •Thomas Gumpenberger 1 , Johannes Heitz 1 , Dieter
Baeuerle 1 und Christoph Romanin 2 — 1 Angewandte Physik, Universitaet
Linz, Austria — 2 Biophysik, Universitaet Linz, Austria
We demonstrated the controlled proliferation of human umbilical endothelial
cells (HUVEC) on UV-light modified polymer samples. The polymers
under investigation were either polytetrafluoroethylene (PTFE)
or polyethyleneterephtalate (PET), which are among the most frequently
employed biomaterials in reconstructive medicine. The PTFE surfaces
were modified by exposure to the ultraviolet (UV) light of a Xe2*-excimer
lamp at a wavelength of 172 nm in an ammonia atmosphere. The irradiation
led to an efficient exchange of the F-atoms in the surface by other
chemical moieties. In-vitro, this resulted in a significant increase in the
number of adhering cells 1 day after seeding and in the formation of a
confluent cell layer after 3 to 8 days. The results were comparable or even
better than those obtained on standard polystyrene petri-dishes used in
cell cultivation. Similar studies were performed on PET.
SYLS 3.28 Mi 16:00 B
Electrolytic fabrication of SNOM aperture-sensors — •Carola
Haumann, Christoph Pelargus, Robert Ros, and Dario Anselmetti
— Experimental Biophysics and Applied Nanosciences, Faculty
of Physics, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld,
Germany
The resolution achievable with scanning near-field optical microscopy
(SNOM) is determined by the optical quality of the near-field sensors.
We present a method to fabricate reproducibly aperture probes with diameters
in the sub 100nm range by solid state electrolysis. The method,
originally invented by A. Bouhelier et al., was further developed by in-

Symposium Life Sciences on the Nanometer Scale - Physics Meets Biology Mittwoch
tegrating a STM distance control in order to form nanoapertures with
sizes from 50nm to 100nm.
The electrolytic cell consists of the probe tip as the first electrode, a
thin platelet of a solid electrolyte, and a silver counterelectrode evaporated
onto the electrolyte. The electrolyte consists of amorphous silver
metaphosphate-iodide, because it has to fulfil some conditions like high
conductivity, transparency and ease of fabrication. As a probe we use
tube-etched optical fibers coated with a silver layer of about 500nm.
Fluorescently labeled DNA and antibodies were measured by using a
home-built SNOM integrated into an inverted optical microscope.
SYLS 3.29 Mi 16:00 B
Density-Functional Study of Left handed Helices — •Franziska
Grzegorzewski, Joel Ireta, and Matthias Scheffler — Fritz-
Haber-Institut Berlin
Knowledge of the factors influencing the stability of protein structures
is crucial to understand their biological function and the regulatory
mechanisms that enable the protein to adapt to changing conditions
in cells. The most ubiquitous conformation in globular proteins is the
right-handed α-helix. Considering the polypeptide backbone alone, each
helix has an energetically equivalent mirror image. However, left-handed
helices seldomly appear in protein structures. The common explanation
is that side groups disfavor the left-handed enantiomer. In order to gain
a deeper understanding of how the handedness affects the helical stability
we performed a density functional theory study on the behavior of
infinite polyalanine in a left-, right-handed 310- helical conformation and
fully extended structure as a reference system. The study was carried out
exploiting periodic boundary conditions and ab initio pseudopotentials,
together with the generalized gradient approximation of the exchangecorrelation
energy functional. A vibrational analysis of the studied structures
shows that vibrational entropic contributions are of the same order
of magnitude as the side group effect for the destabilization of the lefthanded
conformation.
SYLS 3.30 Mi 16:00 B
SILICON-ON-INSULATOR NANOWIRE TRANSISTORS
FOR BIOSENSOR APPLICATIONS — •Pagra Truman 1 ,
Karin Buchholz 1 , Andreas Kress 1 , Dominik Scheible 2 , Marc
Tornow 1 , and Gerhard Abstreiter 1 — 1 Walter Schottky Institut,
TU Muenchen, 85748 Garching, Germany — 2 Center for Nanoscience
and Sektion Physik, LMU, 80539 Muenchen
Planar semiconductor field effect devices have potential for applications
in biosensing such as the label-free detection of DNA or proteins
due to their high sensitivity to surface potential changes. Lateral patterning
into nanowire-like structures largely increases the surface-to-volume
ratio and opens up applications with high spatial resolution.
We present electrical transport measurements on sub-micron transistor
structures based on Silicon-on-Insulator (SOI) technology in aqueous solutions.
Silicon wires with lateral dimensions of few 100 nm were laterally
patterned out of the 30 nm thick top Silicon layer by high resolution electron
beam lithography and reactive ion etching. After encapsulation into
a fluidic chamber setup the transistor device is operated in an inverted
MOSFET mode with an in-plane-gate controlled sensitivity.
Device characterization in aqueous electrolytes of different ionic
strength and pH will be presented. We discuss perspectives for the detection
of biomolecular interactions at the functionalized Si surface.
SYLS 3.31 Mi 16:00 B
Specific Binding of a Single Peptide to DNA investigated
by AFM Force Spectroscopy — •Rainer Eckel 1 , Sven David
Wilking 2 , Alexandra Ros 1 , Norbert Sewald 2 , Robert
Ros 1 , and Dario Anselmetti 1 — 1 Experimental Biophysics and
Applied Nanosciences, Bielefeld University, Universitätsstr. 25, 33615
Bielefeld — 2 Organic and Bioorganic Chemistry, Bielefeld University,
Universitätsstr. 25, 33615 Bielefeld
Peptides mimicking protein epitopes serve as excellent model systems
for the investigation of the specific molecular recognition between DNA
and transcriptional regulators. Our studies focus on the functional characterization
of synthetic peptide segments taken from the sequence of the
transcriptional activator E. coli PhoB by means of single molecule techniques.
AFM dynamic force spectroscopy and fluorescence correlation
spectroscopy investigations proove the specifity of the binding, yielding
force-related properties and kinetic data such as thermal rate constants.
Further studies involve variation of the recognizing peptide sequence in
order to taylor and indentify the optimal structure that ensures binding
specificity.
SYLS 3.32 Mi 16:00 B
SILICON-ON-INSULATOR BASED THIN FILM RESISTOR
FOR CHEMICAL AND BIOLOGICAL SENSOR APPLICA-
TIONS — •Michael G. Nikolaides, Simon Q. Lud, Petra Neff,
Stephan Rauschenbach, and Andreas R. Bausch — Lehrstuhl für
Biophysik - E 22, TU München, 85747 Garching, Germany
The understanding of the dynamics of biomolecular interactions is one
of the main challenges for future biophysical research. Recently, there
have been several approaches emerging for label-free detection techniques.
Very promising surface sensitive techniques, which are envisioned,
are impedance spectroscopy, ellipsometry or force spectroscopy.
We present a novel surface sensitive technique based on commercially
available silicon on insulator (SOI) substrates. By very sensitive electrical
transport measurements we are able to detect the change of the surface
potential which results in a change of the conductance parallel to the surface.
An applied back gate voltage enables us to control the sensitivity
of the sensor layer.
We present the detection of pH and electrolyte concentration with the
bare silicon oxide surface. We get good agreement with the theoretical
predictions of the Grahame equation and the site binding theory. The adsorption
of polyelectrolytes on the oxide surface can be used to estimate
the sensitivity of the device to be 1e-/40nm2.
Furtheron, we discuss first results of a lipid membrane based charge
sensor on the SOI device and discuss the aplication of the developed
system towards the specific recognition of poteins.
SYLS 3.33 Mi 16:00 B
Intrinsic Conductivity of DNA and Polythiophenes —
•Hermann Kleine 1 , Ralf Wilke 1 , Karsten Rott 2 , Jörg
Schotter 2 , Katja Tönsing 1 , Günter Reiss 2 , Rober Ross 1 ,
and Dario Anselmetti 1 — 1 Experimentelle Biophysik, Fakultät
für Physik, Universität Bielefeld — 2 Experimentelle Festkörperphysik,
Fakultät für Physik, Universität Bielefeld
Charge transfer and transport play an important role in many biological
processes and are potentially very interesting for technical applications.
Single DNA and poly(3-octylthiophenes) (P3OTs) were stretched
over metal-isolator-metal gap structures with 20 - 1 500 nm. The
long-range transport of electric charge through single DNA and P3OT
molecules were investigated at well-defined experimental conditions in
I/V spectroscopy experiments down to a level of attoamperès. The highly
debated intrinsic conductance of DNA was found to be very low and
mostly dominated by humidity phenomena. The effects of doping and
intercalating on the conductivity of DNA and P3OT will be discussed.
In addition to the room temperature experiments, the conductivity of
P3OT molecules was also investigated in the temperature range of 10 -
300 K.
SYLS 3.34 Mi 16:00 B
Gel-Free Electrophoresis of λ and T2-DNA in structured PDMS
Microfluidic Devices — •Thanh Tu Duong 1 , Martin Streek 2 ,
Alexandra Ros 1 , Friederike Schmid 2 , and Dario Anselmetti 1
— 1 Experimental Biophysics, Physics Department, Bielefeld University,
Germany — 2 Condensed Matter Theory, Physics Department, Bielefeld
University, Germany
Electrophoresis has been established as a standard method for DNA
and protein analysis which is often carried out in gels or entangled polymer
solutions. With the miniaturization today’s analyses are carried out
in capillaries whereas the incorporation of gels is not trivial.
In contrast to alternative methods based on artificial gel structures
or entropic traps we report the successful separation of DNA in free solution
in structured microfluidic channels. Single DNA molecules were
stained with the bisintercalator YOYO-1 and detected with sensitive fluorescence
video microscopy in 1.5, 3 and 5 µm structured microchannels.
Topographical structuring of our microchannels was achieved through
rapid prototyping i.e. moulding of PDMS from a master structure made
of the negative photoresist SU-8 by contact lithography.
Additionally MD-simulations are in very good agreement to experimental
data resulting in the possibility of optimizing channel geometries
in advance. For higher throughput parallelized separation channels are
planned.

Symposium Life Sciences on the Nanometer Scale - Physics Meets Biology Mittwoch
SYLS 3.35 Mi 16:00 B
Translocation of structured RNA molecules through nanopores
— •Ulrich Gerland 1 , Ralf Bundschuh 2 , and Terence Hwa 3 —
1 Sektion Physik, Universität München — 2 Department of Physics, The
Ohio State University — 3 Department of Physics, University of California
at San Diego
We investigate theoretically the translocation of structured RNA/DNA
molecules through narrow pores which allow single but not double
strands to pass. The unzipping of basepaired regions within the molecules
presents significant kinetic barriers for the translocation process. We show
that this circumstance may be exploited to determine the full basepairing
pattern of polynucleotides, including RNA pseudoknots. The crucial
requirement is that the translocation dynamics (i.e., the length of the
translocated molecular segment) needs to be recorded as a function of
time with a spatial resolution of a few nucleotides. This could be achieved,
for instance, by applying a mechanical driving force for translocation and
recording force-extension curves (FEC’s) with a device such as an atomic
force microscope or optical tweezers. Our analysis suggests that with this
added spatial resolution, nanopores could be transformed into a powerful
experimental tool to study the folding of nucleic acids.
SYLS 3.36 Mi 16:00 B
UV-Laser Induced Fluorescence Detection of Proteins in PDMS
Microfluidic Devices — •Wibke Hellmich, Alexandra Ros, and
Dario Anselmetti — Experimental Biophysics, Physics Department,
Bielefeld University, Bielefeld, Germany
Since the complete mapping of the human genome growing interest
in the field of proteomics requires new techniques for protein analysis.
Especially efficient and sensitive methods for separation, detection and
analysis of unlabeled protein solutions are of great importance. This work
focuses on the separation and label free fluorescence detection of proteins
in the UV range in uncoated polydimethylsiloxane (PDMS) microfluidic
devices.
In the visible range we determined a detection limit of 100fM for fluorescein,
a fluorescent dye, and in the UV-range 50µM for tryptophane
(Trp), an aromatic amino acid. In a first test experiment the separation
of a protein mixture, avidin (four Trp) and lysocyme C (six Trp), in a
microfluidic system with UV detection was successfully realized.
Further investigation will include the optimization of the detection system
to enhance the sensitivity of this label free protein analysis method.
SYLS 3.37 Mi 16:00 B
Attraction of similarly-charged macroions — •Ali Naji and
Roland Netz — Sektion Physik, Ludwig-Maximilians-Universitaet
Muenchen, Theresienstr. 37, 80333 Muenchen
We investigate effective electrostatic interaction between similarlycharged
rod-like and spherical macroions in the regime of strong electrostatic
correlations using the asymptotic strong-coupling theory. We examine
the regime of charge parameters, in which dominant electrostatic
attraction is predicted between charged rods and charged spheres. For
highly-charged macroions, such an attraction gives rise to the formation
of closely-packed macroion-macroion bound states with finite surface-tosurface
separation. In this regime, the predictions of the strong-coupling
theory for the equilibrium separation of macroions is found to be in quantitative
agreement with recent numerical simulations both on charged
rods and charged spheres. We study finite size effects (due to confinement)
on the effective interaction: rod-like macroions are found to attract
each other both in confined and unconfined geometries; specifically,
unconfined rods show attraction when the single-rod Manning parameter
becomes larger than 2/3. By contrast, spherical macroions exhibit
attraction only in confinement, and the onset of attraction (the threshold
charge strength) in this case depends on the size of the confining box,
and weakly (logarithmically) increases with the box size. By decreasing
the charge parameter, attracting macroions undergo an unbinding transition
from a closely-packed bound state to a repulsion-dominated state.
This transition occurs continuously for charged rods displaying a scaling
relation, while charged spheres exhibit a discontinuous transition.
SYLS 3.38 Mi 16:00 B
DNA-histone complexes: interaction and conformation —
•Hoda Boroudjerdi and Roland Netz — Sektion Physik,
Ludwig-Maximilians-Universitaet Muenchen, Theresienstr. 37, 80333
Muenchen
We investigate effective interaction between two complexes of semiflex-
ible charged polymers with oppositely-charged spheres with parameters
appropriate for the DNA-histone system. We determine the ground state
of the system numerically by minimizing a free energy expression, which
includes electrostatic effects on a linear level. We obtain the effective
interaction potential between two complexes for various system parameters,
namely, the charge valency of the spheres and the salt concentration.
It is shown that within this model, complexes can attract each other at
short distances depending on the system parameters, which arises from an
interplay between electrostatic interactions, bending rigidity and conformational
behavior of the charged polymers. We examine different phases
of the system based on symmetry arguments, which include bridging and
binding phases. Finally, we present the behavior of the second virial coefficient
of this system in terms of the salt concentration, which exhibits
a non-monotonic behavior with a minimum at moderate salt concentrations.
SYLS 3.39 Mi 16:00 B
Dynamics of Driven Polymers — •Xaver Schlagberger and
Roland Netz — Department of Physics, LMU Munich
A semiflexible charged bead-spring chain in solution under the influence
of an external field is investigated using Brownian Dynamics simulation.
Counterions are explicitly added. Hydrodynamic interactions are
included via an approximate mobility tensor (Rotne-Prager tensor). By
choosing strong stretching and bending moduli we also cover stiff rodlike
objects of the nanometer/micrometer scale. While, in low Reynolds
number flow, highly symmetric rigid objects like cylinders and ellipsoids
are not oriented in an homogeneous flow or by a homogeneous external
force, a slight coupling between flexibility and hydrodynamic interactions
leads to a torque the direction of which depends on the ratio between the
stretching and bending moduli. Polarization effects compete with this
mechanism. We extrapolate the results to experimentally accessible regions.
SYLS 3.40 Mi 16:00 B
Single cell manipulation in microfluidic networks by optical
tweezers — •Kai Leffhalm 1 , Andy Sischka 1 , Wibke Hellmich 1 ,
Thanh Tu Duong 1 , Annika Grabbe 2 , Jürgen Wienands 2 , Katja
Tönsing 1 , Robert Ros 1 , Alexandra Ros 1 , and Dario Anselmetti
1 — 1 Experimental Biophysics, Physics Department, Bielefeld University,
Germany — 2 Biochemistry, Department of Chemistry, Bielefeld
University, Germany
Experiments with single cells gain importance as a tool to better understand
the behaviour of living cells in vivo. Microfluidic networks provide
dimensions small enough to navigate a single cell with optical tweezers
to different areas of the artificial network where the flow properties can
be controlled by electrophoresis and electroosmosis.
The expression of special proteins in a cell can be stimulated or suppressed
by changing the velocity of the flow or the concentration of substances,
e.g. cytokines or (cytostatic) drugs, in the culture medium.
We will present our experimental setup and our first test experiments
for future applications in monitoring the expression level of individuell
cells and microproteomics.
SYLS 3.41 Mi 16:00 B
Untersuchungen der DNS des Bakteriums Streptomyces violaceoruber
mit dem Rasterkraftmikroskop — •A. Kronenberger 1 ,
A. Ehlers 1 , D. Engel 1 , H. Schmoranzer 1 , A. Ehresmann 1 , K.
Kropp 2 , K. Spatz 2 und M. Redenbach 2 — 1 Technische Universität
Kaiserslautern, Fachbereich Physik, Erwin-Schrödinger-Str., 67663 Kaiserslautern
— 2 Technische Universität Kaiserslautern, Fachbereich Biologie,
Erwin-Schrödinger-Str., 67663 Kaiserslautern
Das lineare Plasmid pSV2 des Bakteriums Streptomyces violaceoruber
wurde mit dem Rasterkraftmikroskop untersucht. Ziel war es, das an den
DNS-Strang gebundene Endprotein eindeutig zu bestimmen. Dazu war
es notwendig alle Reagenzien des biologischen Isolationsprozesses zu betrachten,
um mittels Ausschluss die Identifikation des Endproteins zu
ermöglichen. Weiterhin wurden die Messergebnisse für das Endprotein
über Vergleiche mit anderen schon bekannten Proteinen bestätigt. Somit
konnte eine mögliche Lage des Endproteins relativ zum DNS-Strang
ermittelt werden.

Symposium Life Sciences on the Nanometer Scale - Physics Meets Biology Mittwoch
SYLS 3.42 Mi 16:00 B
Diffusion in live cells: A combined optical sectioning and single
particle tracking approach — •Ralf Bausinger 1 , Christoph
Bräuchle 1 , Sabine Boeckle 2 , Katharina von Gersdorff 2 ,
Ernst Wagner 2 , and Andreas Zumbusch 1 — 1 Department Chemie -
LMU München - Butenandtstr. 5-13 - D-81377 München — 2 Department
Pharmazie - LMU München - Butenandtstr. 5-13 - D-81377 München
Single particle tracking methods with sensitivities down to the single
molecule detection limit have become important tools for the study of
diffusion processes. For their application to studies of trafficking in live
cells, the trajectories have to be analyzed in the context of the complex
cellular structures. In order to visualize these structures in three dimensions,
confocal fluorescence microscopy is commonly applied because of
its high axial resolution. This raster scanning method however contradicts
the simultaneous usage of wide-field microscopy usually employed
for particle tracking. Classical wide-field microscopy in turn does not offer
sufficient axial resolution in order to reconstruct the three dimensional
image of the cell.
For this reason we use structured wide-field illumination in order to
achieve high axial resolution. Like this, fast switching between high resolution
cellular imaging and tracking with single molecule sensitivity becomes
possible. The application of this setup to studies of artificial virus
diffusion in live cells is demonstrated.
SYLS 3.43 Mi 16:00 B
Investigating structure and function of single citrate transport
proteins — •Michael Prummer 1 , Horst Vogel 1 , Beate Sick 2 ,
Alois Renn 3 , Urs P. Wild 3 , Christopher N. Kästner 4 , and Peter
Dimroth 4 — 1 Institute of Biomolecular Sciences, EPFL, CH-1015
Lausanne — 2 DNA-Array Facility, University of Lausanne, CH-1015 Lausanne
— 3 Physical Chemistry Laboratory, ETH-Hönggerberg, CH-8093
Zürich — 4 Institute of Microbiology, ETH-Zentrum, CH-8092 Zürich
We have utilized fluorescence quenching to study functional conformational
changes in single membrane transport proteins upon substrate
binding. The fluorescence of a fluorophore, specifically attached to the citrate
carrier CitS, was completely quenched upon addition of citrate, but
not DL-isocitrate. After exclusion of other possible reasons we attribute
the quenching to conformational changes of CitS in the citrate transport
cycle. Many membrane proteins are thought to obtain their functional
state upon dimerization. To test the hypothesis in a very direct way,
whether or not also CitS occurs as a dimer, we conducted a dual-color
colocalization experiment and found strong evidence for a homo-dimeric
arrangement of CitS.
SYLS 3.44 Mi 16:00 B
Single-molecule microscopy of the rotary motor F0F1 ATP
synthase at work — •Michael Prummer 1 , Horst Vogel 1 ,
Beate Sick 2 , Alois Renn 3 , Gert Zumofen 3 , Urs P. Wild 3 ,
Georg Kaim 4 , and Peter Dimroth 4 — 1 Institute of Biomolecular
Sciences, EPFL, CH-1015 Lausanne — 2 DNA-Array Facility, University
of Lausanne, CH-1015 Lausanne — 3 Physical Chemistry Laboratory,
ETH-Hönggerberg, CH-8093 Zürich — 4 Institute of Microbiology,
ETH-Zentrum, CH-8092 Zürich
The universal ATP factory F0F1 ATP synthase is the smallest rotary
motor in nature. The driving force for rotation during ATP production
is a trans-membrane potential together with a H + /Na + gradient. Vice
versa, F0F1 can act as an ion pump by consuming ATP and is thus a
completely reversible rotor. We have investigated the rotation of individual
immobilized and functionally coupled F0F1 rotary motors during ATP
synthesis and hydrolysis by single-fluorophore multi-parameter confocal
microscopy. Simultaneously, a number of parameters have been recorded,
like the emission polarization, the fluorescence lifetime, the anisotropy decay
time, and the spectral relaxation time. These fluorescence quantities
can be correlated with structural and functional features of the protein
being part of the nano-environment of the fluorophore.
SYLS 3.45 Mi 16:00 B
Optical Tweezers: A Single Molecule Biosensor for molecular
DNA manipulation and detection of individual receptors on
cells — •A. Sischka 1 , K. Toensing 1 , A. Grabbe 2 , K. Leffhalm 1 ,
R. Eckel 1 , S.D. Wilking 3 , N. Sewald 3 , J. Wienands 2 , R. Ros 1 ,
and D. Anselmetti 1 — 1 Experimental Biophysics and Applied
Nanosciences, Faculty of Physics, Bielefeld University, Germany —
2 Organic and Bioorganic Chemistry, Faculty of Chemistry, Bielefeld
University, 33615 Bielefeld, Germany — 3 Biochemistry, Faculty of
Chemistry, Bielefeld University, 33615 Bielefeld, Germany
We used a compact, single beam optical tweezers system to investigate
mechanical properties of double stranded DNA in the presence of different
binding ligands. Individual binding modes could be distinguished by
analyzing the mechanic response of a lambda-DNA molecule to an applied
external force. We compared the effects of the minor groove binder
distamycin-A, a major groove binding a-helical peptide, the intercalators
ethidium bromide, YO-1 and daunomycin as well as the bisintercalator
YOYO-1 on lambda-DNA.
Significant force hysteresis effects occurring during stretching/relaxation
cycles with velocities in the range between 100 nm/s
and 12,000 nm/s were found for daunomycin and YOYO-1. These time
dependent mechanical properties were found to directly reflect the
kinetics of the binding and unbinding behaviour.
Futhermore, specific interactions and rupture force properties of an
antibody against a receptor on a living chicken-B-cell were successfully
measured.
SYLS 3.46 Mi 16:00 B
Modulation of protein exchange by the physicochemical characteristics
of copolymer substrates — •Tilo Pompe, Lars Renner,
Katrin Salchert, and Carsten Werner — Institut für Polymerforschung
Dresden e.V. & Max-Bergmann-Zentrum für Biomaterialien
Dresden
The kinetics of adsorption, desorption, and exchange of the proteins
fibronectin and human serum albumin were studied in their dependency
on the physicochemical surface characteristics of different maleic anhydride
copolymer films. The analysis of the kinetics indicates two kinds
of populations - a fast desorbing species and a species with a slow exchange
rate. By a multivariate regression analysis the variation of the
surface energy of the substrate was identified as an important parameter
for the description of the desorption and exchange characteristics. The
exchange was further shown to depend significantly on the kind of the
pre-adsorbed protein and the protein competing for adsorption sites in
a size dependent manner related to the diffusion constant and the area
of exclusion on the surface. A higher exchange efficiency is observed for
fibronectin on hydrophobic and for human serum albumin on hydrophilic
surfaces.
SYLS 3.47 Mi 16:00 B
Influence of water on the mechanical properties of wood —
•Ingo Grotkopp 1 , Klaas Kölln 1 , Sergio S. Funari 2 , Martin
Dommach 2 , and Martin Müller 1 — 1 IEAP, Uni Kiel, 24098 Kiel —
2 MPIKG Golm c/o HASYLAB, Hamburg
The unique mechanical properties of the biological material wood
strongly depend on the water content. Water is not only present in the
lumina of the wood cells but is adsorbed to the cell walls. These are a
composite of nanocrystalline cellulose microfibrils embedded in a disordered
matrix. We investigated dry and wet wood using X–ray diffraction
techniques using synchrotron radiation. Tensile tests were carried out in
situ. The changes in the fibre diffraction diagrams upon stretching enable
us to conclude on the microscopic mechanisms responsible for the dependence
of wood properties on water content. Implications for the use of
wood as a biomaterial in trees (wet) and construction material (variable
moisture content) are discussed.
SYLS 3.48 Mi 16:00 B
Exact Enumeration of 3D Lattice Proteins — •Reinhard Schiemann,
Michael Bachmann, and Wolfhard Janke — Institut für
Theoretische Physik, Universität Leipzig, Augustusplatz 10/11, 04109
Leipzig (Germany)
We investigate the properties of native, i.e. non–degenerate, ground
states of lattice proteins in the HP model[1] on the three–dimensional
simple cubic lattice. In order to do so, the complete sets of sequences
and conformations were enumerated exhaustively for chains of up to 19
monomers. The identification of native ground states was accelerated by

Symposium Life Sciences on the Nanometer Scale - Physics Meets Biology Mittwoch
generating the set of contact matrices from the set of conformations of a
given length.
In a statistical analysis, we compared characteristic properties of HP
proteins that have a unique ground state to those of proteins with a
degenerate ground state. Such properties are the compactness and designability
of conformations, and the content and distribution of hydrophobic
monomers. Furthermore, the complete density of states as a
function of energy was exactly enumerated for a variety of HP sequences.
This information could be used to show that the temperature dependences
of the energy and specific heat have a peculiar shape for those HP
sequences that have a low ground–state degeneracy and in particular for
sequences with non–degenerate ground states.
[1] K.F. Lau and K.A. Dill, Macromolecules 22 (1989) 3986.
SYLS 3.49 Mi 16:00 B
Infrared ellipsometry for studying membrane protein films —
•M. Gensch 1 , K. Hinrichs 1 , J. Heberle 2 , N. Esser 1 , E.H. Korte
1 , and A. Röseler 1 — 1 Institut für Spectrochemie und Angewandte
Spektroskopie - Institutsteil Berlin, Albert-Einstein-Str. 9, D-
12489 Berlin — 2 Forschungszentrum Jülich, IBI-2: Structural Biology,
D-52425 Jülich
Infrared ellipsometry is a standard method for the determination of
the thickness and the optical constants of thin films in the mid infrared
spectral range [1]. In the case of anisotropic films (e.g. membrane protein
films) iterative best-fit calculations based on layer models and classical
electromagnetic theory are applied to derive the anisotropic optical
constants. The macroscopic properties of membrane protein films (e.g.
roughness, varying thickness) generally do not meet the idealized conditions
assumed in the layer models, which makes the determination of
absolute values for the optical constants particulary difficult. Different
approaches are presented for the determination of the anisotropic optical
constants of membrane protein films using infrared ellipsometry and
cooperative methods. [1] A. Röseler, E.H. Korte, ”Infrared spectroscopic
ellipsometry”in: P.R. Griffiths, J. Chalmers (eds), Handbook of vibrational
spectroscopy, Wiley. Chichester (2001) , chap 2.8
SYLS 3.50 Mi 16:00 B
Composition and Decomposition of DNA-Containing Polyelectrolyte
Multilayers — •Rolf Dootz 1 , Jingjing Nie 1 ,
Binyang Du 1 , Alexander Otten 1 , Wolfgang Schnitzler 1 ,
Stephan Herminghaus 1,2 und Thomas Pfohl 1 — 1 Angewandte
Physik, Universität Ulm, Albert-Einstein-Allee 11, 89081 Ulm —
2 Max-Planck-Institut für Strömungsforschung, Bunsenstrasse 10, 37073
Göttingen
The layer-by-layer technique provides a convenient and controllable
way of forming functional and organised polyelectrolyte multilayer films.
In this study multilayers consisting of DNA and polypropyleneimine dotriacontaamine
dendrimer, generation 4.0 (G4), which are discussed for
nonviral gene delivery systems, have been investigated. A nonlinear growth
of film thickness with increasing layer number has been observed. A
growth mechanism of polyelectrolyte multilayer based on charge overcompensation
during the buildup process is proposed, which is able to
explain the nonlinear growth. Furthermore, combined addition of monoand
multivalent ions leads to a controlled decomposition of the layers.
The release of embedded DNA-molecules may be tuned by varying the
concentration of the salts.
SYLS 3.51 Mi 16:00 B
Fluoreszenzspektroskopie an Einzelmolekuelen — •Johannes
Zaepfel und Torsten Gaebel — Spemannstr. 9, 70186 Stuttgart
Ziel dieser Arbeit ist es, Erkenntnisse über die Weitergabe von Signalen
in lebenden Zellen zu gewinnen. Dabei steht die Untersuchung
des Proteins TNF (Tumor Necrosis Factor) im Mittelpunkt, da es eine
wichtige Rolle bei programmiertem Zelltod (Apoptose) spielt und somit
interessant für die Erforschung der Krebsentstehung und -bekaempfung
beim Menschen ist. Mit der Floureszenzspektroskopie kann man Molekuele
in sehr niedriger Konzentration auf Oberflaechen, in Loesungen und
in lebenden Zellen untersuchen. Vorrangiges Interesse gilt dabei nicht der
Emissionsintensität, des von der Probe ausgehenden Lichts, sondern zeitlichen
Intensitaetsfluktuationen, die durch kleine Abweichungen des Systems
vom thermischen Gleichgewicht zustande kommen. Mit Hilfe einer
mathematischen Korrelationsanalyse erhält man unterschiedliche physikalische
Parameter: Konzentrationen, Mobilitaetskoeffizienten, Umwandlungsraten.
Bedingung dabei ist allerdings, daß die zu untersuchenden
Molekuele mit einem fluoreszierenden Farbstoff gekennzeichnet sind.
SYLS 3.52 Mi 16:00 B
Charge Transfer Kinetics of Individual Photosystem I Reaction
Centers — •Alexandra Elli, Fedor Jelezko, and Joerg
Wrachtrup — 3. Physikalisches Institut, Universitaet Stuttgart, Pfaffenwaldring
57, D-70550 Stuttgart
The charge separation in single reaction center Photosystem I has been
investigated. The fluorescence of the red-most group of antenna chlorophylls
has been used as a sensor of the redox state of reaction center.
Cyclic electron recombination from iron-sulfur cluster Fx and reaction
center P700 has been observed. Recombination kinetics has been analyzed
using fluorescence autocorrelation approach.
SYLS 3.53 Mi 16:00 B
Mechanical properties of cellulose fibres — •Klaas Kölln 1 ,
Claas Behrend 1 , Ingo Grotkopp 1 , Sergio S. Funari 2 , Martin
Dommach 2 , Stephan V. Roth 3 , Manfred Burghammer 3 , and
Martin Müller 1 — 1 IEAP, Uni Kiel, 24098 Kiel — 2 MPIKG Golm
c/o HASYLAB, Hamburg — 3 ESRF, Grenoble, France
The structural biomaterial cellulose is a composite of nanocrystalline
cellulose microfibrils embedded in a disordered matrix of cellulose and
other polysaccharides. The viscoelastic mechanical properties reflect this
morphology. In order to understand the structure–properties relation of
cellulose fibres, we carried out tensile tests in situ while taking X–ray
diffraction patterns using synchrotron radiation. Fibre bundles were investigated
at HASYLAB, single fibres at ESRF. Two mechanisms on the
microscopic scale could be identified: A rotation of the microfibrils and
a stretching of the individual microfibrils.
SYLS 3.54 Mi 16:00 B
Zeitabhängige Schwingungsspektroskopie von Polypeptiden —
•Jens Antony, Burkhard Schmidt, and Christof Schütte —
Freie Universität Berlin, Institut für Mathematik II, Arnimallee 2-6, D-
14195 Berlin
Eine interessante Eigenschaft biochemischer Moleküle ist das Vorliegen
verschiedener Konformationen, d. h. verschiedener geometrischer
Anordnungen, aufgrund von sehr “weichen” inneren Freiheitsgraden.
Das wohl prominenteste Beispiel dieses Verhaltens ist die Möglichkeit
von Proteinen zur Ausbildung so unterschiedlicher Anordnungen wie
Faltblättern oder Helices. Im vorliegenden Projekt wird die Fragestellung
der Korrelation von Struktur und Spektrum modellhaft am kleinen
Polypeptid Glycin-Dipeptid theoretisch untersucht. Hier ist das Vorliegen
verschiedener Konformationen durch die hohe Flexibilität der Torsion
der verschiedenen Peptid–Einheiten um das gemeinsame Rückgrat
begründet.
Einen direkten Zugang zur Struktur des Kerngerüstes von Molekülen
stellt die Schwingungsspektroskopie dar. Neben konventioneller Infrarot–
oder Raman–Spektroskopie mit kontinuierlichen Lasern erlauben moderne
Methoden mit ultrakurzen Lichtpulsen im Bereich von fs bis ps auch
die Beobachtung der Dynamik in Echtzeit. Daher können diese Methoden
nicht nur zur Untersuchung der Struktur von verschiedenen Konformationen,
sondern auch zur Charakterisierung des Übergangs zwischen diesen
eingesetzt werden.
Ein für diese Fragestellungen besonders aussagekräftiger Spektralbereich
ist die Amid I–Bande kleiner Polypeptide. So koppeln die C=O
Streckschwingungen benachbarter Peptideinheiten (oder übernächster
Nachbarn) und ermöglichen einen experimentellen Zugriff auf die Konformation.
Entsprechende erste Messungen sind am Max–Born–Institut
in Berlin vorgenommen worden (S. Woutersen and P. Hamm. J. Phys.:
Condens. Matter 14 (2002) R1035-R1062).
SYLS 3.55 Mi 16:00 B
Polarised proton spin domains in catalase from bovine liver —
•Heinrich Stuhrmann 1,2 , B. van den Brandt 3 , J. Gaillard 4 , H.
Glättli 5 , I. Grillo 6 , H. Jouve 1 , R. Kahn 1 , J. Kohlbrecher 3 ,
J.A. Konter 3 , E. Leymarie 5 , S. Mango 3 , R.P. May 6 , O.
Zimmer 7 , and P. Hautle 3 — 1 Institut de Biologie Structurale
Jean Pierre Ebel, F-38027 Grenoble cedex 1, France — 2 GKSS
Forschungszentrum, D-21502 Geesthacht, Germany — 3 Paul Scherrer
Institute, CH-5232 Villingen PSI, Switzerland — 4 Commissariat à
l’Energie Antomique, CEA Grenoble, CEA/DSM/DRFMC/SCIB,
F-38054 Grenoble, France — 5 Commissariat à l’Energie Atomique, CE
Saclay/DSM/DRECAM/SPEC and LLB, F-91191 Gif-sur Yvette cedex,
France — 6 Institut Laue Langevin, BP 156, F-38042 Grenoble cedex 1,
France — 7 Physics Department E18, Technische Universität München,
D-85748 Garching, Germany

Symposium Life Sciences on the Nanometer Scale - Physics Meets Biology Mittwoch
In very dilute paramagnets selective dynamic nuclear polarisation of
proton spins close to paramagnetic centres provides an amplitude of polarised
neutron scattering which is considerably stronger than that of
magnetic neutron scattering. This is shown for bovine liver catalase,
which is a homotetramer of 506 amino acids (MW=230 kD) with tyrosin-
369 and possibly other tyrosins in a radical state. From comparison of
time-resolved polarised neutron small-angle scattering with simultaneous
NMR measurements it appears that at the onset of dynamic nuclear
polarisation a large majority of the polarised protons are close to the
unpaired electron of the tyrosyl radicals. Polarised proton spin domains
are built up in less than 10 s, while the polarisation of the bulk proton
remains low. Comparison of the time-resolved neutron scattering data
with model calculations confirms the existence of tyrosyl-369
SYLS 3.56 Mi 16:00 B
Plasmon-enhanced Ramanspectroscopy in the Near-field of
Dynamically Tuneable Nanostructured Gratings — •Dominic
Zerulla, Gereon Isfort, Frank Katzenberg, Micha Kölbach,
and Klaus Schierbaum — Heinrich-Heine Universität Düsseldorf,
IPkM, AG Physikalische Methoden für Biologie und Medizin,
Universitätsstr. 1, D-40225 Düsseldorf
Ramanspectroscopy has proven to be a powerful tool in the investigation
of biological molecules. However, additional enhancements are often
needed. As a first enhancement we use the resonance effect by tuning the
laser wavelength onto a certain electronic excitation.
Apart from Surface Enhanced Raman Scattering (SERS) as a second
enhancement technique which is ill-suited to the problem, one solution
to the problem is given by exciting a surface-plasmon-wave on a surface
which is specifically tailored to the system. Confining the enhancement
to its electromagnetic part by means of smooth surfaces or a regular
metallic grating leads to predictable electromagnetic field strengths with
decay lengths of about 100 nm. In order to meet the requirements of a
specific plasmon excitation and the resonance conditions simultaneously,
it is extremely helpful to tune the grating properties. This is done by
using specific gratings which consist of quantum wire-like structures of
metals on a polymer base whose spacings can be changed dynamically
from 0 nm to several hundredth of nm. Such systems can be optimized to
yield high sensitivity and selectivity along with decay length appropriate
for detection of macromolecular mechanisms at membranes.
SYLS 3.57 Mi 16:00 B
Investigation of the range of electromagnetic Raman-
Enhancement in biological Films by means of SAMs —
•Gereon Isfort, Micha Kölbach, Dominic Zerulla, and
Klaus Schierbaum — Heinrich-Heine-Universität Düsseldorf, IPkM,
Materialwissenschaften, AG Physikalische Methoden für Biologie und
Medizin, Universitätsstr. 1, D-40225 Düsseldorf, Germany
Raman-Spectroscopy is a powerful tool for probing the structure and
conformation of proteins. Biological environments produce a large number
of signals, not easily to assign. A selected enhancement might help
to exclude the environmental signals.
The ATR-SPP (Attenuated Total Reflection - Surface Plasmon-
Polariton) technique enhances the electromagnetic field at thin metal
interfaces. The exponential decrease of the evanescent field confines the
range of the enhancement. The Raman activity of the molecules inside
this field is strongly accentuated compared to the molecules outside. To
prove this theoretically trivial statement under real conditions (not perfect
plane metallic layer, unclear microscopic dielectric constants) and to
get quantitative results of the decay lengths, we have made a systematic
approach by using specific self-assembled monolayers of definitive thickness
as spacers in order to vary the distance between the metallic layer
and the Raman-active sample deposited on the SAMs.
SYLS 3.58 Mi 16:00 B
Evaluation of Laser Scanning Microscopic Methods on
Biological Molecules in Membranes — •Micha Kölbach,
Dominic Zerulla, Kerstin Elfrink, Gereon Isfort, and
Klaus Schierbaum — Heinrich-Heine-Universität Düsseldorf, IPkM,
Materialwissenschaften, AG Physikalische Methoden für Biologie und
Medizin, Universitätsstr. 1, D-40225 Düsseldorf, Germany
As of today the infection mechanisms of the prion proteins are still not
completely understood.
In order to investigate these infectious biological molecules in membranes,
we have tested a multitude of different microscopic approaches, basing on
fluorescence as well as Raman spectroscopy. We have decided to pursue
this goal by building two different high sensitive microscopes for low light
detection.
The first one uses only reflecting light and offers, through the use of a
high precision xyz micropositioning table, a scanning mode. This system
is able to supply a large quantity of information from each single sample
by providing a full spectrum for each scanned point. Since the scanning
mode is a long lasting process, the second microscope makes use of a multichannel
detector in conjunction with dispersive components or optical
filters, and therefore offers a faster recording of fluorescence or Raman
images. It also features the use of both reflecting light and see-through
mode. In connection with the use of photoncounting equipment we strive
to detect single molecule fluorescence of labelled Acetylcholinesterase
molecules bound via GPI-anchors in a lipid bilayer, a system already
close to prion proteins in the same membrane.
SYLS 4 Symposium ”Life Sciences on the Nanometer Scale - Physics Meets Biology”
Zeit: Donnerstag 09:30–11:00 Raum: H 37
Hauptvortrag SYLS 4.1 Do 09:30 H 37
Single Molecule Mechanics of Cytoskeletal Proteins —
•Matthias Rief — Lehrstuhl fuer Biophysik E22 der TU Muenchen,
James-Franck-Str., 85748 Garching
The mechanical properties of cytoskeletal proteins and molecular motors
are important for their function in vivo. However, this information
has become accessible only recently through the invention of single
molecule techniques like atomic force microscopy. We have used AFM
based force spectroscopy to investigate the mechanical response of the
coiled-coil domains of myosin II and the actin cross-linking protein Ddfilamin.
We find that the myosin coiled-coil is a highly elastic protein structure
that undergoes an unfolding/refolding transition at 25 pN. Unlike
all other proteins investigated so far this transition occurs in equilibrium.
These measurements show that a coiled-cloil is able to produce
forces during folding. Ddfilamin is an actin crosslinking protein from dictyostelium
discoideum. Using single molecule unfolding experiments we
show that one of the immunoglobulin domains of this protein unfolds at
low forces via a stable intermediate. We have used amino-acid inserts into
the loops of this domain to map the structure of this intermediate. We
show evidence that the intermediate is also populated during folding of
this domain which increases the refolding rates drastically. Low unfolding
forces together with fast refolding kinetics suggest an in-vivo role for this
domain as a reversibly extensible element under mechanical strain.
SYLS 4.2 Do 10:00 H 37
Atomic Force Microscopy and Spectroscopy of Specific Protein-
DNA Interaction — •F. Bartels 1 , B. Baumgarth 2 , A. Becker 2 ,
R. Ros 1 , and D. Anselmetti 1 — 1 Experimental Biophysics, Faculty of
Physics, Bielefeld University — 2 Genetics, Faculty of Biology, Bielefeld
University
Specific protein-DNA interaction is fundamental for all aspects of gene
expression. In the soil bacterium Sinorhizobium meliloti 2011, the protein
ExpG controls the biosynthesis of polysaccharide polymers, which
promote the bacterium‘s symbiosis with alfalfa plants for means of fixing
molecular nitrogen. We investigated the molecular mechanism of
binding of ExpG to three associated DNA target sequences both with
standard biochemical methods and single molecule force spectroscopy
based on the atomic force microscope (AFM). AFM imaging was used
in addition to obtain topographical information regarding the process of
binding. We demonstrated binding in a sequence specific manner, with
unbinding forces ranging from 50 to 165 pN in a logarithmic dependence
from the loading rates of 70 to 79,000 pN/s. Two different regimes

Symposium Life Sciences on the Nanometer Scale - Physics Meets Biology Donnerstag
of loading rate-dependent behaviour were identified. A thermal off-rate
koff = (1.2 ± 1.0) × 10 −3 s −1 was derived from the lower loading rate
regime for all DNA fragments. In the upper loading rate regime, however,
these fragments exhibited distinct differences which are attributed
to sequence specific details of the binding mechanism.
SYLS 4.3 Do 10:15 H 37
Fast Folding Dynamics of α-Helical Peptides — •Martin Volk,
Angela Pozo Ramajo, Edmund Leary, and Sarah A. Petty —
Department of Chemistry, University of Liverpool, UK
The dynamics of secondary structure formation, which is generally believed
to be the first phase of protein folding, has attracted much attention
recently, particularly since the application of the temperature jump
technique. Using nanosecond lasers, a sudden temperature increase is
induced; the ensuing (un)folding can then be observed by suitable timeresolved
methods, such as IR-spectroscopy. Previous studies on α-helical
model peptides investigated alanine-based peptides containing a repeat
motif of the type -(AAAXA)n- (X: hydrophilic amino acid, n = 2-4),
which show helix-coil relaxation on the time scale of 150-300 ns.
Here, we report results on longer and more complex helical peptides.
We found that the helix-coil relaxation in Poly-N 5 -(3-hydroxypropyl)-Lglutamine
(DP 230) occurs on the same time scale as in alanine-based
peptides, in spite of the peptide length and the complex and bulky side
chain. On the other hand, the helix-coil relaxation in the random copolymer
Poly(Ala, Lys, Glu, Tyr) 6:5:2:1 (DP 180) is much more complex. At
high concentrations, it occurs on the µs-time scale and seems to be limited
by strong interpeptide interactions of the abundant charged residues,
whereas at lower concentrations it shows major deviations from monoexponentiality
due to sequence heterogeneity.
SYLS 4.4 Do 10:30 H 37
Photomodulation of conformational states — •Christian
Renner, Alexander Milbradt, Markus Schütt, Raymond
Behrend, Simone Krupka, Eva-Karthin Sinner, Ciara
Cabrele, and Luis Moroder — Max-Planck-Institut für Biochemie
Every living cell, be it bacterial or human, contains a variety of proteins
that turn the static information encoded in the genes into the densely
packed activity of life. Although protein functions are built on well-known
fundamental physical laws the sheer complexity of such macromolecules
due to their size and variability renders experimental as well as theoretical
investigations a difficult challenge. A productive and helpful approach
has been the reduction to simpler albeit artificial model systems. We
have constructed peptide models that combine small functional protein
fragments of a few amino acid residues with a light-switch allowing for
photomodulation of properties like spatial structure, redox potential or
affinity for ligands. The light induced changes could be exploited for a
limited photo-control of peptide structure (1), protein binding (2) and
oxidative protein refolding (3). The consequences observed upon applying
well-defined changes to the system through the photoisomerization
process should allow for a better understanding of the functional protein
parts that are contained in our model systems.
(1) Biopolymers 63 (2002), 382-393.; (2) Angew. Chem. Int. Ed. 41
(2002), 289-292.; (3) Chem. Biol. 10, 487-490.
SYLS 4.5 Do 10:45 H 37
Electro-Manipulation of Oligonucleotides Tethered to Au-
Surfaces — •Ulrich Rant 1 , Kenji Arinaga 1,2 , Shozo Fujita 2 ,
Naoki Yokoyama 2 , Gerhard Abstreiter 1 , and Marc Tornow 1
— 1 Walter Schottky Institut, Technische Universitaet Muenchen,
85748 Garching, Germany — 2 Fujitsu Laboratories Ltd., 10-1
Morinosato-Wakamiya, Atsugi 243-0197, Japan
We present electro-optical investigations of short DNA strands, tethered
to Au-electrodes in aqueous solutions. By controlling the bias potential
at the supporting electrodes, we are able to study multiple phenomena
related to electrostatic interactions between polyelectrolytes and
metal interfaces in electrolyte environment:
DNA-desorption at highly negative electrode potentials can be utilized
to study the electrostatic nature of DNA, revealing a new regime of excessive
counterion condensation in solutions of high salt concentrations.
In contrast, by employing moderate AC-potentials with respect to the
potential of zero charge, we are able to attain persistent conformational
switching with formidable long term stability of the DNA layer on the Au-
surface, alternating the orientation of the strands between a lying‘ and a
’
’ standing‘ state. We elucidate the capability of the presented modulation
experiments to provide information on collective monolayer properties
such as steric interactions between adsorbed molecules, as well as the
possibilities to study molecular dynamics of tethered DNA subjected to
electric fields at the metal/solution interface.
SYLS 5 Symposium ”Life Sciences on the Nanometer Scale - Physics Meets Biology”
Zeit: Donnerstag 11:15–12:30 Raum: H 37
Hauptvortrag SYLS 5.1 Do 11:15 H 37
Mechano-Chemical Coupling in F1-ATPase — •Kazuhiko Kinosita
— Center for Integrative Bioscience, Okazaki National Research
Institutes
The protein F1-ATPase is a rotary motor made of a single molecule.
Its central γ subunit rotates against a surrounding cylinder made of α3β3
subunits. This rotary motor is powered by sequential ATP hydrolysis in
the three β subunits, and reverse rotation of the motor is expected to
drive ATP synthesis. We have shown, by single-molecule imaging, that
(i) the rotary torque is nearly independent of the rotation angle, (ii) 80-
90 pN nm of mechanical work can be done per ATP hydrolyzed, (iii)
binding of ATP causes ∼90 o rotation, and (iv) release of the last hydrolysis
product causes further ∼30 o rotation. Point ii implies that the
efficiency of chemo-mechanical conversion may reach ∼100 %. Points i-iv
allowed us to infer the angle-dependent potential energies for γ rotation
for each of chemical intermediates that appear during rotation. Details
of the coupling scheme between chemical reactions on the three catalytic
sites and mechanical rotation of the rotor are beginning to unravel.
SYLS 5.2 Do 11:45 H 37
Probing individual F0F1 ATP synthases by multi-parameter
fluorescence spectroscopy — •Michael Prummer 1 , Horst Vogel
1 , Beate Sick 2 , Alois Renn 3 , Gert Zumofen 3 , Urs P. Wild 3 ,
Georg Kaim 4 und Peter Dimroth 4 — 1 Institute of Biomolecular
Sciences, EPFL, CH-1015 Lausanne — 2 DNA-Array Facility, University
of Lausanne, CH-1015 Lausanne — 3 Physical Chemistry Laboratory,
ETH-Hönggerberg, CH-8093 Zürich — 4 Institute of Microbiology, ETH-
Zentrum, CH-8092 Zürich
The rotary motor F0F1 ATP synthase is the universal ATP factory
in most cells from bacteria to plants and animals. The driving force for
ATP production is a trans-membrane potential plus a H + /Na + gradient.
Vice versa, F0F1 can act as an ion pump by consuming ATP and is thus
a completely reversible rotor. We have simultaneously measured several
fluorescence quantities from individual immobilized and functionally coupled
F0F1 rotary motors by single-fluorophore multi-parameter confocal
microscopy. By analyzing these quantities we could monitor the rotation
of F0F1 during ATP synthesis and hydrolysis. We could further correlate
for example the different distributions of the fluorescence lifetime or
the emission spectral ratio with structural and functional features of the
protein.
SYLS 5.3 Do 12:00 H 37
Molecular dynamics simulations of isolated β-subunits of F1-
ATPase — •U. Kleinekathöfer 1 , B. Isralewitz 2 , M. Dittrich 2 ,
and K. Schulten 2 — 1 International University Bremen, 28725 Bremen
— 2 Beckman Institute, University of Illinois, Urbana-Champaign, USA.
The F1 unit of ATPase has three-fold symmetry and consists of three
noncatalytic α and three catalytic β-subunits. The β-subunits furnish
the binding sites where ADP is transformed into ATP. We have investigated
the properties of isolated β-subunits as a step towards explaining
the function of the integral F1 unit. The β-subunits exist in different
conformations at any moment of the F1 unit reaction cycle.
The open conformation of the AlF3-inhibited β-subunit of bovine
ATPase had been equilibrated for about 10 ns and a spontaneous change
in conformation was observed. The change can be decomposed into two
rotations: one around an axis parallel to the pseudo-symmetry axis of F1-
ATPase and one around an axis perpendicular to the first axis . In several
runs the equilibrated subunit was in a conformation about half-way between
the open and the closed conformation. This partially confirms the

Symposium Life Sciences on the Nanometer Scale - Physics Meets Biology Donnerstag
assumption that elastic energy is stored in the open confirmation. It is
unclear if there is a further spontaneous closing motion on longer time
scales. To test the effect of the adjacent alpha subunit we performed
simulations of the joined units and found only a negligible effect. We
also equilibrated isolated β-subunits for the AlF − 4 -inhibited F1-ATPase
starting from the the half-closed state with ADP bound and from modified
half-closed states with bound ATP. The simulations again revealed
spontaneous motion towards the closed conformation.
SYLS 5.4 Do 12:15 H 37
A molecular machine based on a DNA aptamer — •Friedrich
Simmel, Wendy Huynh, and Andreas Reuter — Sektion Physik
and Center for Nanoscience, LMU Muenchen, Geschwister-Scholl-Platz
1, 80539 Muenchen
A functional nanomechanical DNA switch based on the anti-thrombin
aptamer structure is presented. Utilizing DNA strand displacement by
branch migration, thrombin can be selectively bound or released by the
DNA machine. The operation of the machine is demonstrated by electrophoretic
mobility shift assays and fluorescence resonance energy transfer
experiments.

Symposium Non-Fermi Liquids in Quantum Structures Tagesübersichten
Hauptvorträge
NON-FERMI LIQUIDS IN QUANTUM STRUCTURES (SYNF)
Organisiert von den Fachverbänden HL, MA und TT
Prof. Dr. M. Sassetti
Dipartimento di Fisica
Universita di Genova
Via Dodecaneso 33
16146 Genova
Italy
E-Mail: sassetti@fisica.unige.it
Prof. Dr. R. Haug
Institut für Festkörperphysik
Universität Hannover
Appelstraße 2
30167 Hannover
Germany
E-Mail: haug@nano.uni-hannover.de
ÜBERSICHT DER HAUPTVORTRÄGE
(Hörsaal H 1)
SYNF 1.1 Do 15:00 (H 1) Coulomb Drag Between Quantum Wires: Beyond Tomonaga-Luttinger
Model, Leonid Glazman
SYNF 1.2 Do 15:35 (H 1) Spin and Charge Separation and Localization in One - Dimension Measured
Using Momentum Resolved Tunneling, Amir Yacoby
SYNF 1.3 Do 16:10 (H 1) Probing spin-charge separation in tunnel-coupled parallel quantum wires,
M. Governale, U. Zülicke
SYNF 1.4 Do 16:45 (H 1) A carbon nanotube quantum dot coupled to superconductors,
Mark Buitelaar, Bakir Babic, Wolfgang Belzig, Christoph Bruder, Thomas Nussbaumer,
Christian Schönenberger
SYNF 1.5 Do 17:20 (H 1) Dimensional crossover and deconfinement in Bechgaard salts,
Thierry Giamarchi
SYNF 1.6 Do 17:55 (H 1) Spectroscopic signatures of spin-charge separation in a quasi-onedimensional
organic conductor, Ralph Claessen
Fachsitzungen
SYNF 1 Non-Fermi Liquids in Quantum Structures Do 15:00–18:30 H 1 SYNF 1.1–1.6
HL 47 Quantendrähte und Korrelationseffekte Fr 11:00–13:00 H 15 HL 47.1–47.8
Die Kurzfassungen der gemeinsamen Fachsitzung Quantendrähte und Korrelationseffekte am Freitag Morgen (Sitzung HL 47)
sind in dem Programm des Fachverbands HL aufgeführt.

Symposium Non-Fermi Liquids in Quantum Structures Donnerstag
Fachsitzungen
– Hauptvorträge –
SYNF 1 Non-Fermi Liquids in Quantum Structures
Zeit: Donnerstag 15:00–18:30 Raum: H 1
Hauptvortrag SYNF 1.1 Do 15:00 H 1
Coulomb Drag Between Quantum Wires: Beyond Tomonaga-
Luttinger Model — •Leonid Glazman — Theoretical Physics Institute,
University of Minnesota, Minneapolis, Minnesota 55455, USA
We demonstrate that in a wide range of temperatures, Coulomb drag
between two weakly coupled quantum wires is dominated by processes
with a small interwire momentum transfer. Such processes, not accounted
for in the conventional Luttinger liquid theory, contribute to drag only
because the electron dispersion relation is not linear. The corresponding
contribution to the drag resistance scales with temperature as T 2 if the
wires are identical, and as T 5 if the wires are different.
Hauptvortrag SYNF 1.2 Do 15:35 H 1
Spin and Charge Separation and Localization in One - Dimension
Measured Using Momentum Resolved Tunneling — •Amir
Yacoby — Department of Condensed Matter Physics, Weizmann Institute
of Science, Rehovot 76100, Israel
We have measured the collective excitation spectrum of interacting
electrons in one-dimension. The experiment consists of controlling the
energy and momentum of electrons tunneling between two clean and
closely situated, parallel quantum wires in a GaAs/AlGaAs heterostructure
while measuring the resulting conductance. At high elelctron densities
the measured excitation spectrum clearly deviates from the noninteracting
spectrum, attesting to the importance of Coulomb interactions.
Notable is the observation of two excitation branches corresponding
to spin - charge separation. In short wires, 6 microns and 2 microns long,
finite size effects, resulting from breaking of translational invariance, are
observed. Here spin and charge separation is manifested through Moire
patterns generated from the spin and charge excitation velocities. At low
electron densities the system abruptly looses translation invariance and
becomes localized. We find that the localization length corresponds to
the inter-electron spacing determined by the 1D electron density.
Hauptvortrag SYNF 1.3 Do 16:10 H 1
Probing spin-charge separation in tunnel-coupled parallel quantum
wires — •M. Governale 1 and U. Zülicke 2 — 1 Scuola Normale
Superiore, piazza dei Cavalieri 7, I-56100 Pisa, Italy — 2 Institute of Fundamental
Sciences, Massey University, Private Bag 11222, Palmerston
North, New Zealand
Interactions in one-dimensional electron systems are expected to cause
a dynamical separation of electronic spin and charge degrees of freedom.
This non-Fermi liquid phenomenon, called spin-charge separation,
manifests itself as a double peak structure in the single-electron spectral
function, and can be detected by momentum-resolved tunneling spectroscopy.
A promising setup consists of two quantum wires coupled by
an extended uniform tunnel barrier[1].
We consider a minimal model for one-dimensional interacting electrons
exhibiting spin-charge separation, where we neglect interactions between
electrons with opposite chirality. We present results for the differential
tunneling conductance and we discuss the features arising from spincharge
separation. Furthermore, we provide a theoretical framework to
go beyond the perturbative treatment of tunneling, and we calculate the
density-density response function[2].
[1] O. M. Auslander, A. Yacoby, R. de Picciotto, K. W. Baldwin, L. N.
Pfeiffer, and K. W. West, Science 295, 825 (2002).
[2] U. Zülicke, and M. Governale, Phys. Rev. B 65, 205304 (2002).
Hauptvortrag SYNF 1.4 Do 16:45 H 1
A carbon nanotube quantum dot coupled to superconductors
— •Mark Buitelaar 1,2 , Bakir Babic 2 , Wolfgang Belzig 2 ,
Christoph Bruder 2 , Thomas Nussbaumer 2 , and Christian
Schönenberger 2 — 1 Cavendish Laboratory, Madingley Road, CB3
0HE, Cambridge, United Kingdom — 2 Institut für Physik, Universität
Basel, Klingelbergstrasse 82, CH 4056 Basel, Switzerland
The electron spin is of central importance in two of the most widely
studied many-body phenomena in solid-state physics: the Kondo effect
and superconductivity. We have investigated their mutual interplay at
the level of a single spin in a carbon nanotube quantum dot. The quantum
dot can be changed from a non-Kondo to a Kondo system as the
number of electrons on the dot is changed from even to odd. We demonstrate
that the Kondo correlations on the dot are not destroyed by the
superconductivity if the Kondo temperature, which varies for different
single-electron states, exceeds the superconducting gap energy.
We observe multiple Andreev reflection peaks in the differential conductance.
The position and magnitude of the subharmonic gap structure
is found to depend strongly on the level positions of the single-electron
states which are adjusted with a gate electrode. A theoretical model of
the device reproduces some of the key features of the experimental data.
Hauptvortrag SYNF 1.5 Do 17:20 H 1
Dimensional crossover and deconfinement in Bechgaard salts
— •Thierry Giamarchi — DPMC, University of Geneva, 24 Quai
Ernest-Ansermet, CH-1211 Geneva, Switzerland
The Bechgaard salts are made of weakly coupled one dimensional
chains. This particular structure gives the possibility to observe in these
systems a dimensional crossover between a high temperature (or high
energy) one dimensional phase and a two or three dimensional system.
Since the filling of the chains is commensurate the system thus undergoes
a deconfinement transition from a one dimensional Mott insulator
to a two (or three) dimensional metal. Such a transition has of course
a strong impact on the physical properties of these compounds, and is
directly seen in transport measurements.
In order to describe such a transition a dynamical mean field method
has been introduced (chain-DMFT). Using this method we investigate
a system of coupled Hubbard chains and show that we can indeed reproduce
the deconfinement transition. This allows to determine physical
quantities such as the transport transverse to the chains and the shape
of the Fermi surface and quasiparticle residues in the low temperature
phase. The consequences for the Bechgaard salts are discussed.
Hauptvortrag SYNF 1.6 Do 17:55 H 1
Spectroscopic signatures of spin-charge separation in a quasione-dimensional
organic conductor — •Ralph Claessen — Experimentalphysik
II, Universität Augsburg, D-86135 Augsburg
In interacting one-dimensional (1D) metals conventional Fermi liquid
behavior is expected to break down due to a dynamical decoupling of
charge and spin degrees of freedom. Angle-resolved photoelectron spectroscopy
(ARPES) on the electronic structure of the quasi-1D organic
conductor TTF-TCNQ [1] indeed reveals significant discrepancies to
band theory. Instead, the experimental spectra can be well explained
by the 1D Hubbard model [2], which accounts for the intramolecular
Coulomb interaction and predicts signatures of spin-charge separation
over the entire conduction band width. The model description can even
be made quantitative, if one accounts for an enhanced hopping integral
at the surface related to a relaxation of the topmost molecular layer.
The importance of strong 1D correlation effects is further supported by
a remarkable temperature dependence of the ARPES data. These results
provide strong spectroscopic evidence for the occurence of spin-charge
separation in the finite energy physics of TTF-TCNQ. Deviations of the
Hubbard model description for the low-energy spectral behavior is attributed
to the neglect of interchain coupling, long-range Coulomb interaction
and/or electron-phonon coupling.
[1] R. Claessen et al., Phys. Rev. Lett. 88, 096402 (2002).
[2] M. Sing et al., Phys. Rev. B 68, 125111 (2003).

Symposium Functional Nanoparticles Tagesübersichten
FUNCTIONAL NANOPARTICLES (SYNP)
gemeinsam veranstaltet mit den Fachverbänden
Chemische Physik und Polymerphysik (CPP)
Dielektrische Festkörper (DF)
Halbleiterphysik (HL)
Magnetismus (MA)
Oberflächenphysik (O)
Prof. Dr. Thomas Schimmel Dr. Bernd Rellinghaus
Institut für Angewandte Physik Sonderforschungsbereich 445
Universität Karlsruhe Institut für Verbrennung und Gasdynamik
Wolfgang-Gaede-Straße 1 Universität Duisburg-Essen
Physikhochhaus 5.-8.OG Lotharstraße 1
D-76131 Karlsruhe D-47048 Duisburg
E-Mail: thomas.schimmel@physik.uni-karlsruhe.de E-Mail: brell@ivg.uni-duisburg.de
Functional nanoparticles are of great scientific interest, since on the nanometer scale, many physical properties become size
dependent. The variation of size, shape, composition, and chemical functionality of the particles and their surfaces provides a
high potential for the engineering of novel physical and chemical properties. Nanoparticles can be tailored not only to optical,
magnetic, dielectric, and semiconducting properties, but also to meet specific catalytic and biological functions. A broad
range of examples for the use of such particles includes coatings, medical applications, cosmetics, catalysis, novel ferroelectric
systems, magnetic storage media, etc. The symposium highlights current key areas of nanoparticle research and emphasizes
its technological impact.
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsaal H1)
Hauptvorträge
SYNP 1.1 Di 09:30 (H1) Semiconductor Nanocrystals: Science and Applications, Moungi Bawendi
SYNP 1.2 Di 10:15 (H1) Nano-Optics with Chemically Functionalized Metal Nanoparticles,
Jochen Feldmann
SYNP 1.3 Di 10:45 (H1) Biomedical Applications of Magnetic Nanoparticles, Lutz Trahms
SYNP 2.1 Di 11:30 (H1) Deposited Nanoparticles: Models for Heterogeneus Catalysts,
Hans-Joachim Freund
SYNP 2.2 Di 12:00 (H1) Nanoscale Ferroelectrics, Marin Alexe
SYNP 2.3 Di 12:30 (H1) Synthesis and Application of Functional Nanomaterials, Andreas Gutsch,
Peter Ottersbach
SYNP 2.4 Di 12:50 (H1) Nanomaterials in Industrial Applications, Ralf Anselmann, V. Hilarius, G.
Pfaff, M. Kursawe, H. Winkler
Fachsitzungen
SYNP 1 Functional Nanoparticles - I Di 09:30–11:15 H1 SYNP 1.1–1.3
SYNP 2 Functional Nanoparticles - II Di 11:30–13:10 H1 SYNP 2.1–2.4

Symposium Functional Nanoparticles Dienstag
Fachsitzungen
– Hauptvorträge –
SYNP 1 Functional Nanoparticles - I
Zeit: Dienstag 09:30–11:15 Raum: H1
Hauptvortrag SYNP 1.1 Di 09:30 H1
Semiconductor Nanocrystals: Science and Applications —
•Moungi Bawendi — Department of Chemistry, Massachusetts
Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139,
USA
Semiconductor nanocrystal quantum dots that are of high crystal quality
and have high fluorescence quantum yields have spurred detailed studies
of their electronic and optical properties. Their color range with size
as a result of quantum confinement has motivated applications in fields
ranging from biology to optical devices. This talk will review the chemistry
of nanocrystal quantum dots, the study of the fluorescence properties
of single nanocrystal dots and the insights that have been obtained,
the incorporation of nanocrystal dots in organic light emitting devices,
the observation of stimulated emission and lasing from nanocrystal dots
under optical pumping and the application of nanocrystal dots in biological
and biomedical imaging.
Hauptvortrag SYNP 1.2 Di 10:15 H1
Nano-Optics with Chemically Functionalized Metal Nanoparticles
— •Jochen Feldmann — Photonics and Optoelectronics
Group, Physics Department and CeNS, Ludwig-Maximilians-Universität
München, Amalienstrasse 54, D-80799 München, Germany
Hybrid systems comprising (bio-)molecules with specific functions and
metal nanoparticles of variable geometry and size offer unique and novel
possibilities in nano-optics and optical bio-sensing. When molecules and
metal nanoparticles approach each other, their mutual interaction leads
to characteristic changes in the fluorescent [1] and light scattering properties
[2]. Time-resolved fluorescence spectroscopy and single particle light
SYNP 2 Functional Nanoparticles - II
scattering techniques are well suited to study such processes in detail.
Potential applications in bio-photonics and medical diagnostics are discussed.
[1] E. Dulkeith, A.C. Morteani, T. Niedereichholz, T.A. Klar, J. Feldmann,
S. Levi, F.C. van Veggel, D.N. Reinhoudt, and M. Möller,
Phys. Rev. Lett. 89, 203002 (2002)
[2] G. Raschke, S. Kowarik, T. Franzl, C. Sönnichsen, T.A. Klar, J. Feldmann,
A. Nichtl, K. Kürzinger, Nano Letters 3, 935 (2003)
Hauptvortrag SYNP 1.3 Di 10:45 H1
Biomedical Applications of Magnetic Nanoparticles —
•Lutz Trahms — Laboratory for Bioelectricity and Biomagnetism,
Physikalisch-Technische Bundesanstalt Berlin, D-10587 Berlin, Germany
Magnetic nanoparticles (MNP) having dimensions ranging from a few
nanometers up to a few hundred nanometers may be employed as smart
in-vivo probes, which develop their activity only after external stimulation.
Taking advantage of their particular interaction with externally
applied homogeneous or inhomogeneous constant or time dependent magnetic
fields, MNP can be utilised for a variety of biomedical applications.
Magnetic drug targeting and MNP-coupled hyperthermia are promising
new therapies, which may improve the prognosis for cancer patients. A
couple of years ago MNP were introduced into radiological diagnostics as
a new contrast agent for magnetic resonance imaging. Yet little attention
has been given to the applicability of SQUIDs for localising and quantifying
the amount of MNP accumulated in human tissue. With their high
sensitivity to the magnetic relaxation of MNP, SQUID relaxometry of
MNP could become another useful diagnostic method, in particular for
monitoring MNP-based therapies.
Zeit: Dienstag 11:30–13:10 Raum: H1
Hauptvortrag SYNP 2.1 Di 11:30 H1
Deposited Nanoparticles: Models for Heterogeneus Catalysts
— •Hans-Joachim Freund — Fritz-Haber-Institut der Max-Planck-
Gesellschaft, Department of Chemical Physics, Faradayweg 4-6, D-14195
Berlin, Germany
In an attempt to model heterogeneous and heterogenized homogeneous
catalysts, well-ordered thin oxide films of alumina and silica have been
prepared onto which metal nanoparticles have been deposited via evaporation
of metal from an oven. By controlling the flux of the metal and
the surface temperature nanoparticle ensembles with a rather narrow size
distribution and well-defined morphology may be grown. These systems
are well suited to be investigated applying surface science tools. We report
on a variety of properties of such systems including the electronic
structure, the adsorption as well as the reactive properties. In particular,
size and morphology dependences are studied, both under ultrahigh vacuum
as well as under ambient conditions. We show that such systems, to
a certain extent, allow us to bridge the gaps between catalysis and surface
science. Sum Frequency generation is employed to study vibrational
spectra of surfaces species under ambient pressures.
Hauptvortrag SYNP 2.2 Di 12:00 H1
Nanoscale Ferroelectrics — •Marin Alexe — Max-Planck Institute
of Microstructure Physics, D-06120 Halle, Germany
Nanotechnology is expected soon to have a big impact on most of our
life. Sustained effort will be necessary to transform the nowadays dreams
into reality, and the only way to do it is to acquire a good knowledge
on phenomena at nanoscale. The science of atoms and molecules, on
one end, and the science of matter from microstructure to larger scale,
on the other, are generally established. The remaining size spectrum,
roughly from 1 nm to 100 nm, represents the nanoscale at which properties
of materials are clearly size dependent and can be engineered or
tailored. Among all materials, functional materials are expected to play
an important role in the establishing of nanotechnology. Moreover, among
nanoscale functional materials ferroelectrics are expected to have a major
involvement in fields such as sensors and actuators, memory devices, and
optics.
The present lecture will give the last achievements in the nanofabrication
of ferroelectric materials with both top-down and bottom-up approaches.
Preparation and characterization of ultrathin films, nano-rods
and -tubes, and nanostructures will be presented. Special emphasis will
be put on nanoscale ferroelectric crystals fabricated by self-pattering and
nano-shell ferroelectric tubes fabricated using template-mediated methods.
Hauptvortrag SYNP 2.3 Di 12:30 H1
Synthesis and Application of Functional Nanomaterials —
•Andreas Gutsch and Peter Ottersbach — Degussa AG,
Creavis Technologies & Innovation, Paul-Baumann-Str.1, D-45764 Marl,
Germany
Nanomaterials and ultra-thin functional coatings of nanoparticles will
determine the utility of many products in the future. Degussa possesses
many years of experience in the manufacture and marketing of fine powders.
Fumed silica is used in particular as a reinforcing filler in silicone
rubber and to control the rheology of coatings and colorants. Industrial
carbon black is used particularly in the tire industry and as a
pigment in printing inks, coatings and plastics. Nanoscale titanium dioxide
and zinc oxide ensure effective ultraviolet-filter formulations. The
nanoscale character of such pigments enables easy processing and combines
high sun protection factors with transparency and nice skin feel-

Symposium Functional Nanoparticles Dienstag
ing. Other nanoscale dispersions are useful for highly polished surfaces
as, e.g., microchips. The combination of electrical conductivity and optical
transparency is a great challenge in further developments of plastics.
Nanoscaled indium-tin-oxide is being developed for use as a raw material
for these applications. In cancer therapy, nanomaterials are of great
interest. Superparamagnetic nanoparticles of iron oxide could be helpful
to destroy tumors when using fast changing magnetic fields.
Hauptvortrag SYNP 2.4 Di 12:50 H1
Nanomaterials in Industrial Applications — •Ralf Anselmann,
V. Hilarius, G. Pfaff, M. Kursawe, and H. Winkler — Merck
KGaA, D-64271 Darmstadt, Germany
The lecture gives an overview on materials with nanostructures in at
least one dimension. It describes the results of many years of research
done in the Chemicals divisions of Merck. Most of the materials are com-
mercially very successful products. Included are examples of materials
such as:
1. Platelets: Uncoated mica platelets as fillers for cosmetics to improve
the skin feeling of formulations. Mica platelets, which are coated with
metal oxides (pearlescent pigments), where the interaction of the metal
oxide layers with light yields interference colours. Multilayer coatings of
metal oxides on mica with tunable optical and electrical characteristics.
Silica and alumina flakes coated with metal oxides for special optical
effects.
2. Silica spheres: Uncoated as fillers for cosmetics to influence skin feeling
and viscosity of formulations. Coated with inorganic nano materials
to impart colour and good skin feel or hide wrinkles by controlled light
scattering. Monodisperse silica spheres.
3. Ordered structures made from spheres, photonic materials.

Symposium Organic and Hybrid Systems for Future Electronics Tagesübersichten
Hauptvorträge
ORGANIC AND HYBRID SYSTEMS FOR FUTURE ELECTRONICS (SYOH)
gemeinsam veranstaltet von den Fachverbänden
Chemische Physik und Polymerphysik (CPP),
Oberflächenphysik (O) und
Halbleiterphysik (HL)
Organisation
D. Neher (Potsdam), M. Sokolowski (Bonn) und K. Leo (Dresden)
Kontakt
Prof. Dr. D. Neher, Institut für Physik, Universität Potsdam, Am Neuen Palais 10, 14469 Potsdam
E-Mail: neher@rz.uni-potsdam.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsaal H37, Poster B, Hörsaal H1)
SYOH I Fr 10:15 (H1) Growth Control and Optics of Organic Nanoaggregates, H.-G. Rubahn
SYOH II Fr 10:45 (H1) Electronic Transport through Single Molecules, H. v. Löhneysen, F. Heinrich,
M. M. Kappes, R. Krupke, M. Major, J. Reichert, H. B. Weber
SYOH III Fr 12:10 (H1) Inorganic Nanorods: Synthesis, Properties, Photovoltaic Applications, D.
Milliron, I. Gur, P. Alivisatos
SYOH IV Fr 12:40 (H1) Understanding Donor-Acceptor Photovoltaic Devices, N. Greenham, B.
Sun, H. Snaith, J. Barker, R. Friend, C. Ramsdale
Fachsitzungen
SYOH 1 Geometric Organic Structures on Surfaces Do 14:00–14:45 H37 SYOH 1.1–1.3
SYOH 2 Spectroscopy Do 14:45–15:45 H37 SYOH 2.1–2.4
SYOH 3 Electronic Structure and Transport Properties Do 16:00–16:45 H37 SYOH 3.1–3.3
SYOH 4 Hybrid Systems and Devices Do 16:45–17:45 H37 SYOH 4.1–4.4
SYOH 5 Poster Do 18:00–21:00 B SYOH 5.1–5.90
SYOH 6 Hauptvorträge I-II Fr 10:15–11:15 H1 SYOH 6.1–6.2
SYOH 7 Molecular Systems and Applications Fr 11:15–11:55 H1 SYOH 7.1–7.2
SYOH 8 Hauptvorträge III-IV Fr 12:10–13:10 H1 SYOH 8.1–8.2

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
Fachsitzungen
– Haupt-, Fach-, Kurzvorträge und Posterbeiträge –
SYOH 1 Geometric Organic Structures on Surfaces
Zeit: Donnerstag 14:00–14:45 Raum: H37
SYOH 1.1 Do 14:00 H37
Self-assembled molecular architectures — •Elena Mena-
Osteritz and Peter Baeuerle — Organic Chemistry II. University
of Ulm. Albert-Einstein-allee 11 89081 ULM
Well-defined pi-conjugated macrocycles are of interest as modular
building blocks for the assembly of new materials and supramolecular
chemistry. They will play an essential role as key components for coming
nanoelectronic devices. However, the assembly of molecular materials
in nanoscale architectures will be a crucial step for the future molecular
scale electronics. On the other side due to their toroidal structure,
p-conjugated macrocycles could represent intriguing molecular circuits
which would additionally include sites for recognition and selective complexation.
Two years ago our group successfully achieved the synthesis of the first
class of fully conjugated macrocycles: the cyclo[n]thiophene. In this contribution
we will present the different 2D-arrangements of the macrocycles
at the liquid/HOPG interface re-vealed by in-situ scanning tunnelling
macroscopy (STM). The data will be analysed with the help of theoretical
conformational and MO analyses. By means of STM, we also investigated
epitaxy and interactions of C60-fullerenes with 2D crystalline monolayers
of cyclo[12]thiophene resulting in perfectly ordered 1:1 complexes.
STM-analyses of the nature, specificity and dynamics of the processes
taking place at the surface, supported by theoretical calculations, will be
discussed.
SYOH 1.2 Do 14:15 H37
Growth of perylene films on Cu(110) — •Kathrin Hänel, Sandra
Söhnchen, Thomas Strunskus, Gregor Witte, Alexander
Birkner, and Christof Wöll — Lehrstuhl für Physikalische Chemie
I, Ruhr Universität Bochum, Universitätstr. 150, 44780 Bochum
Organic semiconductors such as polycyclic hydrocarbons have attracted
a considerable amount of attention because of their promising
potential for electronic and optoelectronic devices. Of particular interest
for the fabrication of such devices is the molecular microstructure in het-
SYOH 2 Spectroscopy
erostructures of thin organic films deposited on inorganic substrates. Here
we present a comprehensive study of perylene (C20H12) films grown under
UHV conditions on Cu(110). The growth and structure of the films
were characterized by means of STM, LEED, HAS, TDS, XPS, NEX-
AFS. While the perylene molecules form an ordered monolayer with an
almost planar orientation, they continue to grow in an upright orientation
without a preferential azimuthal ordering. The multilayer films
reveal a pronounced tendency for dewetting leading to the formation of
descrete islands. The terrace structure of such islands could be imaged
by non contact AFM measurements under ambient condition and reveals
the presence of molecular steps.
SYOH 1.3 Do 14:30 H37
Spectro-microscopic study of organic film growth: PTCDA/
Ag(111) — •Th. Schmidt 1 , U. Groh 1 , H. Marchetto 2 , R. Fink 3 ,
and E. Umbach 1 for the SMART collaboration — 1 Exp. Physik II,
Universität Würzburg, 97074 Würzburg — 2 Fritz-Haber-Institut, 14195
Berlin — 3 Phys. Chemie II, Univ. Erlangen, 91058 Erlangen
We report on first dynamic growth studies of PTCDA on Ag(111) using
a PEEM with photon excitation by either UV-light or polarized monoenergetic
synchrotron radiation. The PEEM instrument is the SMART
spectro-microscope in the actual version, an energy-filtered, but not yet
aberration-corrected microscope. At elevated temperatures between 350
and 450 K we observe the layer-by-layer growth of two to three layers, followed
by the growth of three-dimensional islands (Stranski-Krastanov).
At room temperature a transition from Stranski-Krastanov to layer-bylayer
growth (Franck-van der Merwe) occurs. By laterally resolved NEX-
AFS spectroscopy and by switching the linear polarization of the light
one can clearly derive the molecular orientation as flat-lying in both, the
islands and the bilayer. Additionally, the circular polarization reveals a
natural circular dichroism for the PTCDA crystallites, which is unique
and unexpectedly large for these planar and non-chiral molecules. Funded
by BMBF under contract no. 05-KS1WW2-0.
Zeit: Donnerstag 14:45–15:45 Raum: H37
SYOH 2.1 Do 14:45 H37
Relation between optical transition energies and the transport
gap in α-PTCDA — •Reinhard Scholz and Thorsten U Kampen
— Institut für Physik, Technische Universität Chemnitz
Recently, the slowest photoluminescence (PL) channels in α-PTCDA
were assigned to pairs of oppositely charged molecules [1]. Based on detailed
model calculations of molecular dimers with time-dependent density
functional theory, we can determine the Stokes shift arising from the
internal deformation of the ionized molecules, resulting in an improved estimate
for the energy of the charge transfer states in the periodic crystal.
These findings are compared with the results of high-resolution photoemission
spectroscopy and electrical characterization techniques applied
to PTCDA films grown on n-doped GaAs(100) substrates. Depending
on the substrate treatment, the ionization potential of the GaAs surfaces
varies by more than 1 eV, resulting in a sign change of the interface dipole
within this interval. From a linear fit of the interface dipole vs. the electron
affinity of the substrate, an electron affinity of 4.12 ± 0.10 eV can
be deduced for the organic layer. This procedure allows for an estimate
of the energy offset between the LUMO of PTCDA and the conduction
band minimum of the substrate, and the resulting HOMO-LUMO gap of
2.44 - 2.55 eV is in agreement with the lower limit estimated from the
electrical measurements. The energetic difference between the observed
PL energy and the transport gap can be related to the energy required
for the separation of the two opposite charges to infinite distance.
[1] A. Yu. Kobitski, R. Scholz, H. P. Wagner, and D. R. T. Zahn, Phys.
Rev. B 68, 155201 (2003).
SYOH 2.2 Do 15:00 H37
Femtosecond near-field spectroscopy of semiconducting polymers
— •Kerstin Müller 1 , Christoph Lienau 1 , Dario Polli 2 ,
Giulio Cerullo 2 , and Guglielmo Lanzani 2 — 1 Max-Born-Institut
für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin —
2 Politecnico di Milano, Dipartimento di Fisica, 20133 Milano, Italy
During recent years, ultrafast spectroscopy has provided a wealth of
new insight into the dynamics of optical excitations of semiconducting
polymers and thus into the function of polymer-based optoelectronic devices.
So far from these studies little is known about spatial inhomogeneities
of optical nonlinearities in such systems. Such information is
crucial, however, for a detailed microscopic understanding of the optolectronic
properties of polymers, which are strongly influenced by effects
of disorder, e.g, fluctuations in size and orientation of polymer chains
on nanoscopic and mesoscopic length scales. Here, we introduce a novel
technique, femtosecond near-field pump-probe spectroscopy, for spatially
mapping the temporal dynamics of polymer optical nonlinearities on a
100 nm length scale with sub-picosecond resolution. We report first experimental
studies of the time- and space-resolved photo-induced absorption
of thin films of methyl-substituted poly(para-phenylene) ladder-type
polymers (m-LPPP) and of mixed phase segregated polyfluorene/dye

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
blends. Even on nominally homogeneous m-LPPP films, we observe pronounced
spatial fluctuations in both magnitude and dynamics of the ultrafast
picosecond decay of the photoinduced absorption on sub-micron
length scales. In this paper, we introduce our novel experimental technique
and discuss the implications of our findings.
SYOH 2.3 Do 15:15 H37
Morphology-dependent energy transfer within polyfluorene
thin films — •Anna Köhler, Amena L.T. Khan, Paiboon
Sreearunothai, Laura M. Herz, and Michael J. Banach —
Cavendish Laboratory, University of Cambridge, Cambridge CB3 OHE,
U.K.
Polyflourenes are a class of blue luminescent organic semiconductors
with photophysical properties that vary strongly with the morphology of
the film. In Poly (9,9-dioctylfluorene) (PFO), distinct phases of molecular
order have been identified such as the disordered glassy phase and
crystalline alpha and beta-phases where the PFO chains are considered
to be planar. We present a detailed study of the interrelationship between
morphology and photophysics in thin films of PFO. Small amounts of the
crystalline beta-phase dominate the emission characteristics. We demonstrate
that the formation of the two phases during spin-coating can be
controlled reliably through the choice of the boiling point and solubility
parameter of the solvent. A Franck-Condon analysis shows that the planar
chains are characterized by a low Huang-Rhys parameter, consistent
with well delocalised excited states, while the non-planar chains of the
glassy phase show high values for the Huang-Rhys parameter. The close
intermixing of the two phases and the large spectral overlap of emission
from the glassy phase and absorption from the b-phase leads to efficient
transfer on a sub-picosecond timescale with a large Förster radius of
about 8 nm. As a result, the steady state emission spectra show a significant
fraction of emission from the beta-phase if only a few percent of
the chains are planarized.
SYOH 2.4 Do 15:30 H37
Up-conversion Fluorescence in Polyfluorenes doped with
Metallated Macrocycles — •Stanislav Baluschev 1 , Panagiotis
Keivanidis 1 , Tzenka Miteva 2 , Gabriele Nelles 2 , Ulrich
Scherf 3 , Akio Yasuda 2 , and Gerhard Wegner 1 — 1 Max-Planck-
Institute for Polymer Research, Ackermannweg 10, 55128 Mainz —
2 Sony International (Europe), MSL, Hedelfinger Str. 61, 70327 Stuttgart
— 3 Bergische Universität Wuppertal, Fach. Chemie, Gauss Str. 20,
42119 Wuppertal
In our research towards polymer lasers we achieved for the first time
quasi-cw up-conversion in doped polyfluorenes (PFs). Metallated macrocycles
as porphyrins and phthalocyanines were used as dopands (sensitisers).
Upon excitation with 532 nm the characteristic emission of the
PF (420-480 nm) was detected together with the sensitisers emission.
The system was optimised for dopands type, doping level and for the
side-chain pattern of the PFs. The macroscopic temperature was controlled
and the efficiency of the sensitiser excitation was optimised. As a
result, up-conversion at pumping densities as low as a few kWcm −2 were
achieved to be compared very favourably with the GWcm −2 necessary
for similar magnitude two-photon excited fluorescence in PFs.
From our results it is evident that the up-converted PF emission is
a consequence of an energy transfer process from the sensitisers to the
PF. We suggest that a mechanism involving a sequential multiphoton
absorption in the macrocycles may govern this energy transfer process.
SYOH 3 Electronic Structure and Transport Properties
Zeit: Donnerstag 16:00–16:45 Raum: H37
SYOH 3.1 Do 16:00 H37
Electronic transport in tetracene single crystals: A benchmark
for thin film devices — •J. Pflaum, J. Niemax, A.K. Tripathi,
Chr. Herb, and Chr. Ender — 3. Phys. Inst., Universität Stuttgart,
70550 Stuttgart
Although a major contribution in the field of molecular electronics is
attributed to organic thin film devices, the intrinsic electronic properties
of organic materials without the influence of structural disorder or contact
effects can be studied only for single crystals. We have carried out transport
studies on tetracene single crystals prepared by different growth
techniques in combination with chemical analysis by gas chromatography.
Comparing the charge carrier transport, different temperature dependences
of the hole mobility together with different mobility values at
room temperature (RT) were observed. For crystals grown by a modified
Bridgman setup the hole mobility of ∼ 0.1cm 2 /Vs at RT is much smaller
than that of ∼ 1cm 2 /Vs obtained for crystals grown by sublimation in an
H2 vapor stream. The result can be explained by different concentrations
and energies of the occurring traps related to the respective preparation
method. Supported by the DFG (OFET-Schwerpunktprogramm).
SYOH 3.2 Do 16:15 H37
Dynamics of Hot Electrons in PTCDA Thin Films — •Steffen
Berger, Alexander Mönnich, Jens Wüsten, Martin Aeschlimann,
and Christiane Ziegler — University of Kaiserslautern, Department
of Physics,
Charge carrier dynamics are of importance for many applications of organic
semiconductors. We therefore studied the electron dynamics in 100
nm thin 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) films
without and with dopants by means of time-resolved two-photon photoelectron
spectroscopy (TR-2PPE) on a femtosecond scale.
As light source a titanium-sapphire laser system with a repetition rate
of 80 MHz and a pulse length of 20 fs was used. Frequency doubling
gives a photon energy of 3.1 eV, which allows to examine the life time of
electrons in PTCDA with energies of 1.3-3.0 eV above the Fermi level.
By deposition of alkali-metals such as Na the conductivity of the
n-type organic semiconductor 3,4,9,10-perylene-tetracarboxylic dianhydride
(PTCDA) can be increased by several orders of magnitude. In TR-
2PPE we observed an increase in the life time of electrons with energies
> 1.2 eV above EF after Na reaction. This can be explained by results
from inverse photoemission spectroscopy which reveals that the density
of states at 1.2 eV above EF is reduced by the same process, i.e. there
are less unoccupied states in which the hot electrons can relax.
SYOH 3.3 Do 16:30 H37
Influence of Defect States on the Electronic Transport of Pentacene
Thin Film Transistors — •Pravesh Kumar 1 , Dietmar
Knipp 1,2 , Armin R. Volkel 2 , and Veit Wagner 1 — 1 International
University Bremen, School of Science and Engineering, Germany — 2 Palo
Alto Research Center, Palo Alto, USA
The influence of acceptor and donor like defect states on the current
voltage characteristics of polycrystalline pentacene thin film transistors
(TFTs) were explored. The thermally evaporated pentacene films
were prepared on organic and inorganic dielectrics. Careful control of
the preparation conditions leads to TFTs with very similar mobility of
0.4 cm 2 /Vs and on/off ratio > 10 8 on thermal oxide, silicon nitride and
poly-vinyl phenol (PVP) dielectrics. To gain insides in the electronic
transport behavior of the organic TFTs we used a one-dimensional transistors
model. The model assumes an exponential distribution of defect
states in the bandgap [1]. The experimental data can be described by a
steep exponential distribution of donors close to the valence band and a
shallower distribution of acceptors deeper in the bandgap. The influence
of different preparation conditions of the pentacene film and the organic
dielectric PVP will be discussed in greater detail by a comparison of
experimental and simulation data. Dihexylquaterthiophene (DH4T) was
also used to fabricate the thin film transistors. The mobility and the on/
off ratios for pentacene and DH4T thin film transistors were compared.
[1] A.R. Volkel, R.A. Street, D. Knipp, Phys. Rev. B66, 195336 (2002).

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
SYOH 4 Hybrid Systems and Devices
Zeit: Donnerstag 16:45–17:45 Raum: H37
SYOH 4.1 Do 16:45 H37
Fast integrated plastic circuits — •Robert Blache, Andreas
Ullmann, Jürgen Ficker, Dietmar Zipperer, Walt e r Fix, and
Wolfgang Clemens — PolyIC GmbH & Co. KG, Paul-Gossen-Str.
100, 91052 Erlangen, Germany
Using soluble polymers as active and insulating layers we report on
fast and stable integrated circuits based on p-type organic transistors.
On flexible polyester film substrates single field-effect transistors and ring
oscillators with frequencies above 190 kHz and propagation stage delays
below 0.4 µs were fabricated with regioregular poly(3-alkylthiophene).
Even without encapsulation the devices show a very stable performance
while stored and measured under ambient and extreme conditions
[1]. Furthermore we report on organic rectifiers based on polymer
rectifier diodes and polymer capacitors. Our results show the potential
of integrated plastic circuits based on soluble polymers to be suitable
for inexpensive high volume electronic applications (e.g. RFID-tags).
[1] J. Ficker, et al., JAP 2003, Vol.94, p. 2638
SYOH 4.2 Do 17:00 H37
Submicron Polymer Field-Effect Transistors — •Susanne
Scheinert 1 , Axel Scherer 2 , Theodor Doll 1 , Gernot Paasch 3 ,
and Ingo Hörselmann 1 — 1 TU Ilmenau — 2 CALTECH, Pasadena,
USA — 3 IFW Dresden
Application-relevant speed of polymerelectronics requires transistors
with submicrometer channel length. At present appropriate low-cost
patterning does not exist. We prepared such transistors using a nonlithographic
technique for the definition of the channel length in the
submicron range. To avoid short-channel effects a hybrid design with
silicon dioxide as gate insulator is used. As active layer different poly(3alkythiophene)
(P3AT) has been used. The transistors feature (i) controlled
defined channel length between 0.75µm and 1µm, (ii) an operation
at voltages lower than 5V , (iii) well pronounced saturation of
the output characteristics with (iv) only marginal short channel effects,
(v) a high on-off ratio (> 10 4 ), (vi) rather small inverse subthreshold
slope S ≈ 0.5V/dec, and (vii) negligible contact resistances. Since
the used P3AT were not especially treated, the mobility is still low
(≈ 2...3cm 2 /V s). The hysteresis is negligible for the drain voltage sweep
for a given gate voltage, but as usual there is a hysteresis for the gate voltage
sweep at given drain voltage. However, the corresponding threshold
voltage shift is with ≈ 1V relatively small.
SYOH 5 Poster
SYOH 4.3 Do 17:15 H37
Cascade energy transfer in bandgap modulated multilayer
structures of CdTe quantum dots — •Thomas Franzl, Stefan
Schietinger, Thomas A. Klar, Andrey L. Rogach, and
Jochen Feldmann — Photonics and Optoelectronics Group, Physics
Department and CeNS, Ludwig-Maximilians-Universität München,
Amalienstr. 54, D-80799 Munich, Germany
We report on very fast and directed energy transfer leading to
strongly increased excitonic densities in cascaded energy transfer structures
(CET) made of CdTe quantum dots capped by short chain thiols.
A systematic bandgap variation in one spatial direction is realized by
a layer-by-layer technique using CdTe nanocrystals of stepwise increasing
sizes in subsequent layers. We observe an efficient energy transfer
towards the layer of largest quantum dots. In this layer the excitonic
density increases by an order of magnitude in comparison to a layered system
containing only one size of CdTe nanocrystals. These high excitonic
densities in CET structures are especially interesting for optoelectronic
devices such as nanocrystal LEDs or lasers.
SYOH 4.4 Do 17:30 H37
Optical modeling of CuPc/C60 photovoltaic devices — •T.
Stübinger 1 and W. Brütting 2 — 1 Experimentalphysik II, Universität
Bayreuth, D-95440 Bayreuth — 2 Experimentalphysik IV,
Universität Augsburg, D-86135 Augsburg
Photovoltaic devices with Cu-phthalocy anine (CuPc) as electron
donor and Buckminsterfullerene (C60) as electron acceptor exhibit high
incident photon-to-current conversion efficiencies (IPCE) in bilayer devices
and composite systems. Optical interference effects significantly influence
photocurrent spectra and quantum efficiencies, which arises from
the strong dependence of layer thicknesses on the spatial distribution of
the photon density. By optical modelling using transfer-matrix-methods
the experimental photocurrent spectra of bilayer systems with various
layer thicknesses (organic layers, buffer layers, electrodes) could be explained.
Blend systems of CuPc and C60 show high quantum efficiencies
of almost 60% (IPCE) due to an effectively enhanced dissociation volume
in these composite systems. These high IPCE values demonstrate a
very efficient photocarrier generation and charge transport in these low
molecular weight composite systems, which is comparable to the most
efficient polymer-fullerene composite systems after post-annealing treatments.
The mixing ratio and total layer thickness of the blend system
are varied to achieve optimum photovoltaic performance.
Zeit: Donnerstag 18:00–21:00 Raum: B
SYOH 5.1 Do 18:00 B
Normal Incidence X-ray Standing Waves on Light Elements:
The Limits of the Dipole Approximation — •Christian Kumpf,
Jörg Stanzel, Christoph Stadler, Wolfgang Weigand, and
Eberhard Umbach — Experimentelle Physik II, Univ. Würzburg
The normal incidence x-ray standing wave (NIXSW) technique is a
powerful tool for obtaining detailed structural information on surfaces,
e.g., exact atomic coordinates which enable quantum chemical calculations.
In most XSW experiments either the photoelectron or the Augerelectron
yield is used to measure the absorption of a specific atomic
species adsorbed on a surface. For the analysis of organic adsorbates,
which contain low-Z elements only, this is a difficult issue since the dipoleapproximation
is no longer sufficient to describe the photoemission process.
Using the Auger yield is also problematic since the Auger process is
not only stimulated by the x-ray standing wave field but also by (photo-)
electrons emerging from the bulk. Therefore, significant effort was put in
finding a proper way to correct the photoemission yield for non-dipolar
contributions as well as the Auger-yield for its electron-induced portion.
We report on a NIXSW experiment performed on a coherent monolayer
of NTCDA on Ag(111) for which this correction was successfully
performed and consistent results were obtained from the O1s photo electron
yield as well as from the OKLL Auger electron yield. The electroninduced
portion of the Auger yield was found to be as large as 50%.
Furthermore, a significant covalent character was found for the bonding
between the NTCDA molecules and the substrate. The bonding distance
is 3.08(3)˚A, considerably smaller than a Van der Waals distance.
SYOH 5.2 Do 18:00 B
Template guided self-assembly of nanoclusters — •Li Zhang,
Lifeng Chi, and Harald Fuchs — Physikalisches Institut,
Westfälische Wilhelms-Universität, Wilhelm-Klemm-Str. 10, 48149
Münster, Germany
Surface patterning with microscopically small structures has attracted
increasing scientific and technological interest over the past decade. In
our work, variable surface patterns of chiral molecule C11-CO-(L)-Cys-
(L)-Cys-NH-C18 are obtained by changing the subphase conditions. At
the air- water (pure) interface, it forms a kind of chiral pattern. Due
to the potential complex ability of the sulfur atom in the molecule, this
kind of surface aggregate could be used as a template to trap the metal
ions or nanoparticles during its interfacial assembly process, which may
provide a method to assemble the metal or semi-conductor particles into
a designed way.
Using the metal ions as subphase, the chiral pattern size is smaller compared
with the result without metal ions. The size of this kind of aggregate
decreases with increased concentration of metal ions. For the subtle
structure inside the circle domain, the stripe like structure is found. At
the air-CdTe nanoparticle aqueous interface, a kind of branched nanostripes
appears. The furcation point appears at the end of some branches.

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
The preliminary results of SEM and confocal fluorescence microscopy
show that the nanoparticle are trapped in the nanowires during the process
of interfacial assembly.
SYOH 5.3 Do 18:00 B
STM Investigation of the Adsorption of C60 Molecules on Vicinal
Si(111)-7x7 Surfaces — •Yu Suzuki, Falk Müller, Thorsten
Kampen, Michael Hietschold, and Dietrich Zahn — Institute of
physics, University of Technology Chemnitz, 09126 Chemnitz, Germany
Vicinal silicon surfaces have attracted much attention as promising
candidates for templates of self-assembled organic nano-structures. The
step edges on vicinal surfaces might serve as preferential adsorption sites
for the molecules, which may result in the self-assembly of molecular
nano-wires.
In this study the adsorption of high symmetrical C60 on vicinal Si(111)-
7x7 surfaces was investigated using scanning tunnelling microscopy under
UHV conditions. The vicinal silicon substrates were first chemically
cleaned by hydrogen peroxide and followed by direct current heating in
UHV. STM showed stepped surface on vicinal silicon after this preparation
procedure. A 7x7 reconstruction was confirmed by LEED and STM.
However, the morphology of the vicinal surfaces were strongly affected
by details of the preparation procedure. The C60 molecule at the edges
showed more stability and less mobility against the manipulation by STM
tip, compared to the ones on terraces of silicon steps.
SYOH 5.4 Do 18:00 B
Self-assembly of highly rigid redox-active nanostructures monitored
by optical second harmonic generation — •Tobias Weidner
1 , Jens Vor der Brüggen 2 , Andreas Krämer 2 , Ulrich
Siemeling 2 , and Frank Träger 1 — 1 Institut für Physik and Center
for Interdisciplinary Nanostructure Science and Technology - CINSaT,
Universität Kassel, Heinrich-Plett-Str. 40, D-34132 Kassel — 2 Institut für
Chemie and Center for Interdisciplinary Nanostructure Science and Technology
- CINSaT, Universität Kassel, Heinrich-Plett-Str. 40, D-34132
Kassel
We have used self-assembly techniques for the preparation of highly
ordered electronically active monolayers on gold substrates. Many compounds
used for self assembly at present are intrinsically flexible due to
flexible spacer units thus limiting the overall film ordering. To resolve this
problem we have synthesized compounds bearing highly rigid π-spacers
and 2, 2 ′ : 6 ′ , 2 ′′ -terpyridin-4 ′ -yl or tripodal tris[(methylthio)methyl]silyl
headgroups, adding to the rigidity of the obtained films. These molecules
have been functionalised with phenyl and ferrocenyl groups. Ferrocene is
a redox-active organometallic unit which is widely used for sensoric and
electronic applications. Adsorption from solution was studied in situ by
optical second harmonic generation (SHG) with submonolayer resolution.
SHG was also used to examine film ordering in real time. The results have
been compared to ellipsometric measurements. The data show that adsorption
leads to the formation of monomolecular films at the interface.
We found that film growth is followed by self-assembly of highly ordered
redox-active ferrocenyl nanostructures.
SYOH 5.5 Do 18:00 B
Luminescence quenching of tetracene molecules adsorbed
on the sapphir surface — •Andreas Langner and Moritz
Sokolowski — Institut für Physikalische und Theoretische Chemie,
Universität Bonn, Wegelerstr. 12, D-53115 Bonn
A surface usually affects the photolumenescence (PL) of adsorbed
molecules. Our aim is to understand the mechanisms which modify the
PL, in order to apply PL spectroscopy to learn something about the
dynamic processes of molecules on surfaces (e.g., mobility, diffusion, rotation
of molecules). So far PL investigations of isolated molecules on well
defined surfaces are missing, partly because on metallic surfaces ultrafast
quenching occurs and no fluorescence is observable.
However, on surfaces of wide gap insulator materials we expect to
obtain PL signal from adsorbed molecules. In particular, we have investigated
tetracene evaporated at 100K on Al2O3(0001). The substrate
was prepared in UHV by Ar + sputtering and annealing in O2 at 1200K.
We control the number of adsorbed molecules very accurately by thermal
desorption. Contrary to our expectation, no fluorescence is observed
for a 0.2 monolayer thick film of presumably isolated molecules. After
annealing to 240K we can measure an increase of the PL signal of the
order of three magnitudes, which is probably due to the growth of 3Dtetracene-crystallites.
We report the evolution of the PL in dependence
of the film thickness and the annealing temperature.
SYOH 5.6 Do 18:00 B
Langmuir-Blodgett monolayer behavior of dinuclear ruthenium(II)trisbipyridine
complexes — •Xiaodong Chen 1 , Frank
Vergeer 2 , Steve Welter 2 , Luisa de Cola 2 , Lifeng Chi 1 , and
Harald Fuchs 1 — 1 Physikalisches Institut, Wilhelm-Klemm-Str. 10,
48149, Muenster, Germany — 2 Molecular Photonics Group, Institute of
Molecular Chemistry, University of Amsterdam, 1018 WV Amsterdam,
The Netherlands
Dinuclear ruthenium complexes have been generating interest as a
class of electroluminescent materials [1]. Langmuir-Blodgett (LB) technique
is a powerful tool for assembling different molecules to build ultrathin
organic films with well-controlled structure and thickness. In the
present report, we used the LB technique to prepare dinuclear ruthe-
nium(II)trisbipyridine complexes monolayers. The complexes contain two
Ru(bpy) 2+
3 moieties and four phenylene units as spacers between the two
ruthenium centers. From the surface pressure-molecular area isotherms
and morphologies, it was found that the complexes possessing long alkyl
chains on one of the Ru(bpy) 2+
3 centers and those without long alkyl
chains show different behaviors. It seems that the introduction of the
alkyl chains in the complexes is indeed necessary to obtain a more homogeneous
film. In addition, the effect of pressure on the morphologies
of monolayers was considered. The results provide basic clues for future
monomolecular layers electroluminescent device preparation.
[1] S. Welter et al. Nature 421, 54 (2003)
SYOH 5.7 Do 18:00 B
Synthese von molekularskaligen Drähten auf DNA-Basis —
•Patrick Nickels, Wendy Huynh und Friedrich Simmel —
Sektion Physik und Center for Nanoscience, Universität München,
Geschwister-Scholl-Platz 1, 80539 München
Die herausragenden molekularen Erkennungseigenschaften von DNA-
Molekülen können für den Aufbau komplexer supramolekularer Netzwerke
genutzt werden. Solche Netzwerke könnten die Grundlage selbstorganisierter
Schaltkreise bilden. Die unzureichenden elektronischen Eigenschaften
von DNA-Molekülen verhindern allerdings ihren unmittelbaren
Einsatz als molekularskalige Komponenten. Ein wesentlicher Schritt
ist daher die Funktionalisierung von DNA-Strängen mit halbleitenden
oder metallischen Materialien. Hier präsentieren wir verschiedene Methoden
zur DNA-gesteuerten Synthese von Metallen, leitfähigen Polymeren
und anorganischen Halbleitern sowie deren rasterkraftmikroskopische
und elektronische Charakterisierung.
SYOH 5.8 Do 18:00 B
Self-Organized Nanocomposites of CdSe Nanocrystals and Porphyrins
— •Abey Issac 1 , Thomas Blaudeck 2 , Frank Cichos 2 ,
Edward Zenkevich 3 , Alexander Shulga 3 , and Christian von
Borczyskowski 1 — 1 Institut für Physik 122501, TU Chemnitz, 09107
Chemnitz — 2 Institut für Physik 123705, TU Chemnitz, 09107 Chemnitz
— 3 Institute of Molecular and Atomic Physics and B.I. Stepanov Institute
of Physics National Academy of Sciences, 70 F. Skaryna Avenue,
220072 Minsk, Belarus
Composites of semiconductor nanocrystals (NC) and organic compounds
open a road to new functional units for optoelectronic applications.
Such composites may be prepared by self-organization of functionalized
organic chromophores on semiconductor NCs. We present results
of spectroscopic studies, where we investigate composites of pyridyl containing
porphyrin molecules and CdSe NCs in solution. The experiments
show a strong quenching of the emission of CdSe NCs even at ratios of the
porphyrin to NC concentration much smaller than one. This is ascribed
to the self-organization of porphyrin molecules on the NC surface by ligation
interactions. The close proximity of NC and porphyrin and their
electronic interaction opens nonradiative channels, which we tentatively
ascribe to an electron transfer process from the NC to the porphyrin.
With increasing number of porphyrin molecules per NC the NC emission
is quenched almost completely. This points to an electron transfer, that
occurs on a much shorter timescale than the emission decay of the NC
which is confirmed by time resolved measurements. The dependence of
the observed emission quenching on the NC size will be discussed.
SYOH 5.9 Do 18:00 B
Nanopatterning of Organically Modified Semiconductor Surfaces
— •Thierry Djenizian, Eugen Balaur, Yan Zhang, and
Patrik Schmuki — Chair for Surface Science and Corrosion, WW4,
University of Erlangen-Nuremberg, Martensstrasse 7, 91058, Erlangen
The preparation, development and integration of practical electronic

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
or bionic devices require a high degree of functionality as well as a good
stability of surfaces against degradation. In this context, the nanopatterning
of organically modified surfaces has attracted great attention
because such functionalized surfaces offer an excellent passivation and
at the same time the possibility to attach different biological species
(including DNA, proteins and complex systems). In the present work,
strategies for the nanopatterning of chemically modified silicon surfaces
using different lithographic approaches will be presented. It will be shown
that organic monolayers can be used as a new class of organic-based resists
for direct electron-beam writing as well as atomic force microscope
nanoscratching. The use of organic monolayers as positive or negative
resists will be highlighted by exploiting the contrast in reactivity via
chemical deposition (electroless technique) and plating of metals. The
high resolution achieved through the use of such organic-based resists
will be discussed.The processes presented here open new perspectives for
selective deposition and direct patterning of Si surfaces and can be used
not only for chemical and electrochemical nanogrowth but also for the
nanopatterning of chemical and relevant biological species on semiconductor
surfaces.
SYOH 5.10 Do 18:00 B
Blinking and Emission Quenching of CdSe Nanocrystals in Organic
Environments — •Thomas Blaudeck 1 , Abey Issac 2 , Frank
Cichos 1 , Edward Zenkevich 3 , Alexander Shulga 3 , and Christian
von Borczyskowski 2 — 1 Institut für Physik 123705, TU Chemnitz,
09107 Chemnitz — 2 Institut für Physik 121501, TU Chemnitz,
09107 Chemnitz — 3 Institute of Molecular and Atomic Physics and
B.I. Stepanov Institute of Physics National Academy of Sciences, 70 F.
Skaryna Avenue, 220072 Minsk, Belarus
The interaction of ZnS capped CdSe nanocrystals with their environment
is studied on an ensemble and single nanocrystal (NC) level. Individual
CdSe NC’s show an emission intermittency (blinking), which
is commonly related to an NC photo-ionization by electron tunneling.
The statistics of this blinking is found to be independent of the studied
NC even though NCs may differ in size and local structure of the
surrounding polymer matrix. We analyze the obtained blinking statistics
in terms of charge diffusion through trap states in the NCs vicinity and
further compare this to current blinking model. Despite the insensitivity
of the blinking process to the surrounding polymer matrix a strong interaction
between CdSe NCs and pyridyl containing porphyrin molecules
is found. The porphyrin molecules self-organize on the NC surface by
ligation effects. The interaction of porphyrin and NC introduces a fast
non-radiative decay of the NC emission, which is ascribed to an electron
transfer process by electron tunneling. The dependence of this tunneling
process on the NC size is discussed.
SYOH 5.11 Do 18:00 B
Temperature-Dependent Growth of Porphyrin and Phthalocyanine
Thin Films on Modified Silicon Surfaces — •Christian
Kelting 1 , Ossamah Abdallah 2 , Marinus Kunst 2 , Natalia
Bazyakina 3 , Dieter Wöhrle 3 , and Derck Schlettwein 1 —
1 Physical Chemistry 1, University of Oldenburg, Germany — 2 Hahn-
Meitner- Institute, Berlin, Germany — 3 Institute of Organic and
Macromolecular Chemistry, University of Bremen, Germany
Films of phthalocyaninatozinc (PcZn) and Tetraphenylporphyrinatozinc
(TPPZn) were evaporated on thin films of microcrystalline Si and
on hydrogen-terminated Si-wafers (111) as a model surface for microcrystalline
Si under conditions of its preparation. The goal is to embed
molecular sensitizers into microcrystalline Si as a new concept for thin
film solar cells. The maximum substrate temperature for a successful deposition
of PcZn and TPPZn was determined to 523 K for PcZn and 423
K for TPPZn on H-Si (111). UV-Vis differential reflection spectroscopy
was measured in situ. At 300 K, a 50 nm PcZn film survived for 5h, but
slowly evaporated during this time. The morphology of the deposited
films was investigated by atomic force microscopy. Larger particles with
well- defined shape indicating crystallinity of the films were detected at
these higher substrate temperatures. Changes in the crystal structure
of PcZn were also observed on the silicon substrates. The alpha- modification
of PcZn was found in depositions at 298 K whereas the betamodification
was formed at 523 K.
SYOH 5.12 Do 18:00 B
The influence of carbon on the mono- and multilayer growth of
p-quaterphenyl on Au(111) — •Adolf Winkler, Stefan Muellegger,
Thomas Haber, and Roland Resel — Solid State Physics,
Graz University of Technology
The tailoring of the growth mode of ultra-thin organic films is of utmost
importance for the application of electronic and optoelectronic devices.
As a model system we have studied the monolayer adsorption and the
multilayer growth of p-quaterphenyl on clean and carbon covered gold
(111) surfaces. TDS, XPS, LEED and XRD-pole figure technique have
been applied for these investigations. In TDS, the monolayer peaks are
quite different for the Au(111) and Au(111)+C surface. Also LEED shows
pronounced differences. The evaluation of the LEED patterns, in combination
with quantitative TDS, suggests a monolayer structure with flat
lying and side tilted 4P molecules on the clean, but with only side tilted
molecules on the C-covered surface. These different monolayer structures
lead to different multilayer film structures, as verified by XRD-pole figure
technique and XPS. In the former case island growth is preferred,
whereas in the latter case layer-like growth dominates.
SYOH 5.13 Do 18:00 B
Morpholoy and growth of organic semiconductor films on metal
surfaces — •S. Söhnchen, S. Lukas, G. Beernink, K. Hänel, A.
Birkner, G. Witte, and C. Wöll — Physikalische Chemie I, Ruhr-
Universitaet Bochum
Organic semiconducting materials have experienced a tremendous
amount of attention because of the recent breakthrough in using such
materials as active components in electronic or optoelectronic devices.
Of particular interest for an optimization of such devices is a detailed
understanding of the crystalline structure and growth properties of thin
organic semiconductor films deposited on inorganic substrates.
In this talk we compare the growth properties observed for pentacene
and perylene films grown by OMBE on copper and gold
single crystal surfaces as well as on a SAM modified gold surface.
Although some of these films are well ordered and partly reveal even
an epitaxial growth relation with respect to the substrate [1] they all
have a large tendency for dewetting which causes the formation of islands.
[1] Lukas et al. Chem. Phys. Chem (in press)
SYOH 5.14 Do 18:00 B
The Growth of Pentacene on Gold — •F.-J. Meyer zu Heringdorf
1,2 , M.C. Reuter 1 , and R.M. Tromp 1 — 1 IBM T.J. Watson
Research Center, Yorktown Heights, USA — 2 present address:Inst. für
Laser- und Plasmaphysik, Universität Duisburg-Essen (Campus Essen)
We used Low Energy Electron Microscopy and Atomic Force Microscopy
to compare the growth of pentacene on Si(111) with the growth
of pentacene on Au. In the LEEM Au films are prepared on Si(111)
at elevated temperatures and their formation is monitored using quasisimultaneous
imaging at different dark field conditions. At low coverages,
Au forms a (5 × 2) reconstruction on the Si(111) substrate, and pentacene
is observed to grow in the thin film phase, similar to growth on
clean silicon. At coverages beyond 3/4 ML of Au, however, a ( √ 3 × √ 3)
reconstruction is formed that causes the orientation of the pentacene
film to rotate by almost 90 ◦ . The same result is found for pentacene on
thick polycrystalline Au films. The adsorption of organic self-assembled
monolayers (SAMs) prior to deposition of pentacene has been reported
to improve the electrical contact between Au and pentacene. Here we
show that thiol based SAMs on Au can restore the growth direction of
pentacene to a crystal orientation as seen on Si. This demonstrates that
carefully chosen organic substrate termination layers are likely to play a
key role in the development of organic thin film semiconductor technology.
SYOH 5.15 Do 18:00 B
Dislocation Arrangements in Pentacene Films — •Bert Nickel
— Ludwig-Maximilians-Universität München
Organic molecules are currently at the focus of many research programms
due to their applications in molecular electronics. Among the
various materials under investigation, pentacene (C22H14), a long, flat,
aromatic molecule is particularly promising, in part because pentacene
easily forms layered crystals if deposited onto flat, inert surfaces, resulting
in highly anisotropic transport properties. We have studied the
growth of pentacene films (2-8 monolayers) on modified Si-wafer surfaces
by means of synchrotron x-ray diffraction. A quantitative analysis of the

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
Bragg and diffuse scattering allows us to identify screw- and edge dislocations
as the main defects on the molecular scale. We quantify dislocation
densities obtained for different substrate preparations and discuss their
potential relation to transport properties.
SYOH 5.16 Do 18:00 B
Morphology of Pentacene and Tetraazapentacene grown on
SiO2 and vacuum deposited Polytetrafluoroethylene substrates.
— •Paul Quinn 1 , S Schrader 1 , L Brehmer 1 , G Jarosz 1 , V
Failla 1 , and K Gritsenko 2 — 1 Condensed Matter Physics, Institute
of Physics, University of Potsdam, Germany — 2 Institute of Semiconductor
Physics NASU, Kiev, Ukraine
The growth and morphology of the pentacene based thin films, grown
under ultra high vacuum, on SiO2 and vacuum deposited polytetrafluoroethylene
was studied using AFM/STM, ellipsometry and polarisation
dependent second harmonic generation. The films were grown under a
wide range of experimental conditions with variations in the depositions
rates, substrate temperatures, and geometries employed to optimise the
structural ordering. Polytetrafluoroethylene, of particular interest due to
the demand for low-k dielectric materials in semiconductor devices, is
shown to form highly ordered films. It was found that the ordering of
the pentacene and tetraazapentacene is greatly increased on the polytetrafluoroethylene
surface. The ordering of the polytetrafluoroethylene
and the ability of this film to promote ordering of the pentacene films
is discussed. Acknowledgement: The work was supported by Marie-Curie
Host Fellowships: Project MODERN No.HPMD-CT-2001-00083 and by
the RTN EUROFET HPRN-CT-2002-00327
SYOH 5.17 Do 18:00 B
Substrate and temperature dependent lateral order in N,N’dibutyl-substituted
quinacridone monolayer studied by MBD-
LEED — •Feng Lin, Dingyong Zhong, Lifeng Chi, and Harald
Fuchs — Physikalisches Institut, Universität Münster, D-48149
Münster, Germany
Ordered monolayers of N,N’-dibutyl-substituted quinacridone (QA4C)
were prepared by vacuum sublimation on Cu(110),Ag(110), and Ag(111)
surfaces. Using Low energy electron diffraction that was designed specially
to follow the growth processes and thus obtain the kinetics of
growth phenomena, the nucleation, grwoth, and superstructures of QA4C
monolayers were investigated and compared. The strong interlayer interaction
between the QA4C molecules and Cu(110) surface results in very
low surface diffusivity at room temperature. Consequently, the commensurate
monolayer structure of QA4C was only obtained when annealing
the substrate up to 420 K and its crstallographic parameters were determined
by the substrate lattice rather than the bulk structure of QA4C
itself. While for Ag(110) surface, the QA4C monolayer tended to arrange
the molecules in accordance with its bulk crystallography. The
microscopic mechanism might be the intralayer interaction of H-bond
between molecules which becomes significant since the interlayer interaction
is weaker than the case of Cu(110). Temperature induced structural
transition was observed on Ag(111), where the six symmetry-equivalent
domains at room temperature was changed to a single domain that was
more similar to its bulk crystallography at about 200 K.
SYOH 5.18 Do 18:00 B
Structure and growth morphology of CuPc thin films — •S.
Kowarik 1 , A. Gerlach 1 , N. Kishimoto 1,2 , R. Jacobs 1 , and F.
Schreiber 1 — 1 Physical and Theoretical Chemistry Laboratory, Oxford
University, South Parks Road, Oxford OX1 3QZ, UK — 2 Department
of Chemistry, Tohoku University, Aoba-ku, Sendai 980-8578, JAPAN
We present a study of the growth and structure of thin films of the
organic semiconductor copper-phthalocyanine (CuPc) on SiO2. Films up
to a thickness of 2000 ˚A have been studied as a function of the growth
parameters (temperature and growth rate) by x-ray diffraction, spectroscopic
ellipsometry and atomic force microscopy. The films exhibit a
change in morphology from smooth films to needle-shaped crystallites
depending on growth temperature. This transition is associated with a
change from low crystallinity in smooth films to high crystallinity in
rough films. Measurements of the geometric film parameters (thickness
and roughness) with spectroscopic ellipsometry and x-ray diffraction allow
for a comparison of the two techniques. The results are compared to
measurements on thin films of the fluorinated version F16CuPc (1, 2).
1. J. O. Osso et al., Advanced Functional Materials 12, 455-460 (2002).
2. M. I. Alonso et al., Journal of Chemical Physics 119, 6335-6340
(2003).
SYOH 5.19 Do 18:00 B
Structural and Morphological Properties of N,N´-DiMethyl-
3,4,9,10-PeryleneTetraCarboxylic DiImide Films on Passivated
GaAs(100) Substrates — •G. Salvan, S. Silaghi, G. Baumann,
T.U. Kampen, R. Scholz, and D.R.T. Zahn — Institut für Physik,
Technische Universität Chemnitz, 09107 Chemnitz, Germany
Amongst the many-fold applications of organic thin films the use as active
interlayers in metal/inorganic semiconductor junctions for the highfrequency
and microwave technology is very promising. A route to achieve
better device performance is to control the morphology of the organic film
by changing the substrate temperature for the film growth. Raman spectroscopy
was employed to investigate in situ the structural properties
and the morphology of N,N´-DiMethyl-3,4,9,10-PeryleneTetraCarboxylic
DiImide films deposited onto S-passivated GaAs(100) substrates in ultrahigh
vacuum at various temperatures. Complementary scanning electron
microscopy studies revealed that all the films consist of islands. The crystalline
nature of these islands was proven by the observation of libronic
phonon-like modes of the molecular crystal in the Raman spectra. The
decrease in the phonon band widths observed at elevated substrate temperatures
is related to an increase in the size of the crystalline domains
and improvement of crystallinity.
SYOH 5.20 Do 18:00 B
Structural investigation of the low temperature order-disorder
phase transition of NTCDA on Ag(111) using NIXSW — •C.
Stadler, J. Stanzel, M. Scheuermann, S. Hansen, C. Kumpf
und E. Umbach — Exp. Physik II, Uni Würzburg
The properties of organic thin films largely depend on their interaction
with the underlying substrate. For NTCDA on Ag(111) the bonding is
regarded as chemisorption as revealed e. g., by photoemission or thermal
desorption spectroscopy. Recently an unusual phase transition upon
cooling of NTCDA (sub)monolayers on Ag(111) has been observed by
electron diffraction studies and other techniques. Upon cooling the long
range order disappears below 180 K. Normal Incident X-Ray Standing
Waves (NIXSW) measurements were performed using the wiggler beamline
ID32 at the ESRF. We report on detailed structural results of different
room temperature and low temperature phases, especially on the precise
bonding distance between the NTCDA molecules and the Ag substrate.
A comparison of the NIXSW results obtained from photoemissionand
Auger-yield measurements enables a reasonable correction for nondipolar
contributions to the photoeletron yield as well as for electron
induced Auger processes. Both effects cannot be neglected for small atomic
species.
SYOH 5.21 Do 18:00 B
Doping and Diffusion Properties of Na in PTCDA Thin Films
— •Jens Wüsten, Steffen Berger, Stefan Lach, and Christiane
Ziegler — University of Kaiserslautern, Department of Physics,
Erwin-Schrödinger-Straße 56, D-67663 Kaiserslautern
In order to investigate the electronic and vibronic properties of n-doped
PTCDA (perylene-3,4,9,10-tetracarboxylic-dianhydride), thin films were
grown under UHV conditions. The n-doping was performed by subsequently
evaporating sodium (Na) from a dispenser source, followed by
one or several annealing steps to reach a homogeneous distribution of
the dopant throughout the layer.
Experimental results from electronic (XPS/UPS/IPE), conductivity,
Seebeck, vibration (FT-IR), angle resolved XPS and SIMS measurements
of Na doped PTCDA before and after annealing will be presented. The
changes in the elctronic structure and the electrical properties show that
doping is already established after Na evaporation. However, the results
suggest that the model of an initially built doped surface layer and a
subsequent diffusion of Na into the PTCDA bulk during the annealing
step is incorrect. In fact evidences could be found, that the deposited
dopant initially establishes a homogeneous distribution in the PTCDA
layer and is partially removed during the annealing step.
SYOH 5.22 Do 18:00 B
Radiotracer diffusion measurements of noble metal atoms
in crystalline organic films — •Michael Scharnberg 1 , Jörn
Kanzow 1 , Rainer Adelung 1 , Klaus Rätzke 1 , Franz Faupel 1 ,
Christoph Pannemann 2 , Ulrich Hilleringmann 2 , and Jens
Pflaum 3 — 1 Technische Fakultät, CAU Kiel, Kaiserstr. 2, 24143 Kiel
— 2 Department EIM-E/Sensorik, Univ. Paderborn — 3 3. Physikalisches
Institut, Univ. Stuttgart
The application of organic field effect transistors (OFETs) for large

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
scale low-cost electronic devices has lead to intensive research. Pentacene
and Diindenoperylene (DIP) thin films on SiO2 are two prominent systems
due to their high structural order out-of-plane. While bottom contact
FET structures can be realized easily, preparation of top contacts
may involve diffusion of metal atoms (typically Au) deep into the organic
film changing its electronic properties. For a better understanding of the
growth process and the diffusion of noble metal atoms in crystalline organic
films, a radiotracer technique has been used to obtain diffusion
profiles and the condensation coefficient of noble metals for these films.
The results for Pentacene and DIP films will be presented with respect
to their structural properties and will be compared to polymer films.
SYOH 5.23 Do 18:00 B
Electronic Structure and Morphology of 7.8-Dimethylalloxazin
on Ag, Au, and HOPG — •Stefan Lach and Christiane Ziegler
— Erwin-Schrödinger-Str. 33 67663-Kaiserslautern
Our main emphasis was put on the investigation of the electronic and
structural behavior of thin films of the redox-active model substance
7.8-dimethylalloxazin (DMA) on several inorganic surfaces as a prerequisite
to construct organic/inorganic molecular electron transfer devices.
Alloxazines are capable of building up intermolecular hydrogen-bonded
complexes. The optimized structures of the monomer and several dimers
were calculated (DFT). The calculated eigenvalues were used to simulate
the theoretical photoelectron spectra of the monomer and the dimers.
Comparison of the calculations and simulations with the measured data
exhibit a small preference for a dimerization. Photoelectron spectroscopy
and morphology studies of ultra thin films from DMA on polycrystalline
silver and gold as well as on HOPG show distinct differences for these
substrates. On HOPG and Au there is no chemical interaction. On HOPG
a homogeneous, unstructured layer is formed, but on Au DMA shows island
growth with large islands and deep crevices in between. On Ag a
new state appears 1.2 eV below the Fermi level and smaller islands are
built on the substrate. A calculation and simulation of the photoelectron
spectra of a DMA/Ag-complex shows a good correspondence with the
experimental results.
SYOH 5.24 Do 18:00 B
Orientation of phthalocyanine thin films on disordered
substrates — •Heiko Peisert 1,2 , Indro Biswas 1 , Torsten
Schwieger 2 , Martin Knupfer 2 , Andreas Petr 2 , Lothar
Dunsch 2 , Danilo Dini 3 , Michael Hanack 3 , and Thomas Chasse 1
— 1 University of Tuebingen, IPC, Auf der Morgenstelle 8, 72076
Tuebingen, Germany — 2 Leibniz Institute for Solid State Research
Dresden, P.O. Box 270116, D-01171 Dresden, Germany — 3 University
of Tuebingen, Inst. Organ. Chem., Auf der Morgenstelle 18, D-72076
Tuebingen, Germany
We have studied the molecular orientation of fluorinated metallophthalocyanines
(CuPCFx with x = 0, 4, 16), and of tetra tert-butyl magnesium
phthalocyanine (MgPC(t-bu)4) on technically relevant organic
and inorganic substrates using polarisation-dependent x-ray absorption
spectroscopy. As organic substrate a mixture of poly-3,4-ethylenedioxythiophene
(PEDOT) and polystyrenesulfonate (PSS) was chosen, often
applied as electrode material in (all-)organic semiconductor devices. Although
we observe a chemical interaction at the PC/PEDOT:PSS interface
and a diffusion of Pc molecules into the polymer film [1], CuPcFx
grows in an ordered, ”standing” geometry on this substrate.
The tert-butyl metallophthalocyanines are highly soluble and thus they
are especially suitable for solution processed organic semiconductor thin
films. On polycrystalline gold evaporated MgPc(t-bu)4 molecules are as
highly ordered as CuPC. However, on Au(100) we observe a very high
orientation (the molecules lie) only for (sub-) monolayer coverages.
[1] H. Peisert et al. Appl. Phys. Lett. 83 (2003) 3930
SYOH 5.25 Do 18:00 B
Intermolecular Interactions in Thin Films of Subphthalocyanines
— •Christine Mattheus 1 , Wilfried Michaelis 1,2 , Dieter
Wöhrle 2 , and Derck Schlettwein 1 — 1 Physical Chemistry 1, University
of Oldenburg, Germany — 2 Institute of Organic and Macromolecular
Chemistry, University of Bremen, Germany
Thin films of SubphthalocyaninatoChloroBoron (SubPc) and its Fluorinated
Derivative (F12SubPc) have been prepared by physical vapour
deposition on NaCl, KBr, mica and glass. The intermolecular coupling
was studied in situ by UV- vis absorption spectroscopy and the structure
of the films was studied by X- ray diffraction (XRD). During deposition
of SubPc at 298 K optical spectra were obtained that were quite simi-
lar to spectra of the molecules in solution indicating negligible specific
intermolecular coupling in the films. After heating or during deposition
on heated substrates a spectral change was observed speaking for an
increased coupling in the films. The increased coupling of molecules in
annealed films led to an X- ray diffraction pattern of the films consistent
with the bulk crystal structure. The relative intensity in XRD shows
a preferential orientation of crystals with the ab-plane parallel to the
surface caused by an orientation of the molecules with their B-Cl axis
perpendicular to the surface and with their aromatic cone parallel to it.
As an additional parameter, the influence of fluorination on the growth
characteristics was also studied.
SYOH 5.26 Do 18:00 B
VUV-Spectroscopic Ellipsometry Investigations of DNA Base
Layers Deposited onto H-Si(111) Surfaces — •S. D. Silaghi 1 ,
Yu J. Suzuki 1 , O. D. Gordan 1 , C. Himcinschi 1 , G. Salvan 1 ,
M. Friedrich 1 , T. U. Kampen 1 , D. R. T. Zahn 1 , C. Cobet 2 , N.
Esser 2 , W. Richter 2 , and W. Braun 3 — 1 Institut für Physik, TU
Chemnitz, 09107 Chemnitz, Germany — 2 Institut für Festkörperphysik,
TU Berlin, 10623 Berlin, Germany — 3 BESSY GmbH, 12489 Berlin-
Adlerhof, Germany
DNA bases (adenine, guanine, thymine, cytosine) have electronic properties
comparable to wide-gap semiconductors thus being promising candidates
for hybrid organic/silicon electronics. Vacuum Ultraviolet Spectroscopic
Ellipsometry (VUV-SE) was applied for the in situ optical characterization
of DNA base layers grown by organic molecular beam deposition
onto H-Si(111) under ultra-high vacuum conditions. VUV-SE
measurements were performed with a rotating analyzer-type ellipsometer
using synchrotron radiation as a light source. The spectra were recorded
at an incidence angle of about 68 o in the energy range from 2.5 to 10
eV. Additionally the samples were investigated ex situ using a variable
angle spectroscopic ellipsometer in the energy range from 0.8 to 5 eV.
The dielectric functions of the DNA base layers were determined in the
whole energy range.
SYOH 5.27 Do 18:00 B
Spectroscopic ellipsometric characterization of organic films deposited
via Organic Vapor Phase Deposition — •C. Himcinschi 1 ,
N. Meyer 2 , S. Hartmann 3 , M. Friedrich 1 , G. Strauch 2 , W.
Kowalsky 3 , M. Heuken 2 , and D.R.T. Zahn 1 — 1 Halbleiterphysik,
Technische Universität Chemnitz, Reichenhainerstr. 70, D-09107 Chemnitz,
Germany — 2 AIXTRON AG, Kackertstr. 15-17, D-52072 Aachen,
Germany — 3 Institut für Hochfrequenztechnik, Technische Universität
Braunschweig, Schleinitzstr. 22, D-38106 Braunschweig, Germany
Thin films of Tris-(8-hydroxyquinoline)-aluminum(III) (Alq3) and
N,N ′ -[Di-(1-naphthyl)-N,N ′ -diphenyl]-(1,1 ′ -biphenyl )-4,4 ′ -diamine
(α-NPD) were deposited onto 8” Si substrate by Organic Vapor Phase
Deposition. The thickness analysis by Variable Angle Spectroscopic
Ellipsometry revealed very uniform films with minor edge effects that
originate from the distortion of the flow profile in the vicinity of the
wafer edges. However, even including these effects the standard deviation
for the thickness considering 21 points along one sample diameter is
below 1 nm in all cases.
The refractive indices and extinction coefficients of Alq3 and α-NPD
were determined from ellipsometry in the spectral range from 0.8 eV
up to 5 eV. These optical constants were derived using a multi-sample
analysis approach that employs simultaneous point-by-point fitting of ellipsometric
spectra recorded for samples with different thicknesses of the
organic layer.
SYOH 5.28 Do 18:00 B
Determination of the Anisotropic Optical Properties for Perfluorinated
Vanadyl Phthalocyanine Thin Films — •O. D. Gordan
1 , M. Friedrich 1 , W. Michaelis 2 , R. Kr öger 3 , T. Kampen 1 ,
D. Schlettwein 2 , and D. R. T. Zahn 1 — 1 Institute of Physics, University
of Technology Chemnitz, — 2 Physical Chemistry 1, Institute of
Pure and Applied Chemistry, — 3 Institute of Solid State Physics, University
of Bremen, D-28334
Thin films of perfluorinated vanadyl phthalocyanine F16PcVO were
prepared by physical vapor deposition (PVD) in high vacuum on fused silica
and KBr substrates. The absorption spectra in the visible region show
that the films on different substrates have different structure. The optical
constants for F16PcVO films were obtained in the spectral range of 0.7
- 4.5 eV from the simulation of ellipsometry spectra with an anisotropic
uniaxial model. From the difference between the in-plane and out-of-

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
plane components of the dielectric function the average tilt angle of the
F16PcVO molecular planes with respect to the substrate plane was found
to be 56 0 for fused silica substrates and between 0 0 and 3 0 for KBr substrates.
SYOH 5.29 Do 18:00 B
Strongly Enhanced Thermal Stability of Organic Semiconductor
Thin Films Induced by Aluminum Oxide Capping Layers
— •S. Sellner 1,2 , A. Gerlach 3 , F. Schreiber 3 , M. Kelsch 1 , N.
Kasper 1 , H. Dosch 1,2 , S. Meyer 4 , J. Pflaum 4 , M. Fischer 5 , and B.
Gompf 5 — 1 MPI für Metallforschung, Stuttgart, Germany — 2 Institut
für Theoretische und Angewandte Physik, Universität Stuttgart, Germany
— 3 Physical Chemistry Laboratory, Oxford University, UK — 4 III.
Physikalisches Institut, Universität Stuttgart, Germany — 5 I. Physikalisches
Institut, Universität Stuttgart, Germany
We show that the thermal stability of thin films of the organic semiconductor
diindenoperylene (DIP) can be substantially increased by an
aluminium oxide capping layer (50 nm). The DIP films do not only stay
on the substrate (oxidized silicon), but even remain crystalline on a time
scale of ≥ 1 hour more than 250 K above the desorption temperature
for uncapped films. The results of in-situ X-ray diffraction are supported
by thermal desorption spectroscopy. We argue that this very effective
enhancement of the thermal stability compared to uncapped and also
metal-capped organic layers is related to the low mobility of aluminum
oxide and the relatively well-defined as-grown interfaces with limited interdiffusion.
We discuss possible mechanisms for the eventual breakdown
at high temperatures.
SYOH 5.30 Do 18:00 B
Direct and inverse photoemission spectroscopy on organic
semiconductors in the pristine and reduced state — •Torsten
Schwieger 1 , Martin Knupfer 1 , Weiying Gao 2 , and Antoine
Kahn 2 — 1 Leibniz Institute for Solid State and Materials Research
Dresden, D-01069 Dresden, Germany — 2 Department of Electrical
Engineering, Princeton University, Princeton, NJ 08544, USA
Phthalocyanines and α-NPD are organic semiconductors which are
commonly used in organic electronic devices like transistors and diodes.
We intercalated the organic semiconducting film with potassium in order
to investigate the impact of negative charge to the electronic structure
of the organic system. A combined direct and inverse photoemission
spectroscopy study of the occupied and unoccupied states of the organic
semiconductors ZnPc and α-NPD in the pristine and K-intercalated state
is presented. A combination of PES and IPES allows the determination
of the transport gap in organic materials both in the undoped and doped
state. The observed splitting of the lowest unoccupied molecular orbitals
upon potassium intercalation leads to an evaluation of the size of correlation
effects in both molecular systems. These effects are discussed in
detail.
As expected, the Fermi level is found to shift towards the vacuum level
upon intercalation. However, the results clearly demonstrate that the
Fermi level in potassium intercalated organic semiconductors cannot a
priori be assumed to be pinned at the onset of the lowest unoccupied
molecular orbital in all cases.
SYOH 5.31 Do 18:00 B
Band gap engineering of insulating films due to defects and adsorption
of organic molecules — •C. Tegenkamp and H. Pfnür —
Institut Für Festkörperphysik, Appelstr.2 D-30167 Hannover,Germany
For possible applications of organic molecules in electronic circuits,
the functionality of a chemically designed molecule can be significantly
changed due to fundamental interactions of the molecule with a surface
after adsorption. Generally, the strength of the chemical bond should depend
on serveral parameters like substrate, orientation of the surface and
defects.
As an example of functional organic molecules, we will present results
about the problem of contact charging between insulators. Therefore, we
have studied the adsorption of OH-substituted benzoic acids on insulating
films like NaCl(100) and KCl(100) in the multilayer, monolayer
and submonolayer regime using photoelectron- and electron energy loss
spectroscopy. The experiments were performed on both defect–free surfaces
and on surfaces decorated with anion vancancies. In accordance
with DFT claculations, there are specific molecular orbitals which are
in resonance with the valence band structure of the alkali halides. Interestingly,
defects like anion vancancies only strengthen the bond by
polarization effects. A reactivity of these centers in form of a dissoci-
ation of the molecules as for water has not been found. Although the
molecules are chemisorbed in presence of defects, this is not reflected in
energetic shifts of molecular orbitals of the functional acid- and phenoli
OH–groups, which are most important for our model of contact charging.
Our experimental results are supported by simple DFT calculations.
SYOH 5.32 Do 18:00 B
Electronic properties of organic/organic semiconductor interfaces
CuPC/C60 — •Olga Molodtsova, Torsten Schwieger,
and Martin Knupfer — Leibniz Institute for Solid State and Materials
Research Dresden, D-01069 Dresden, Germany
Phthalocyanines and C60 are typical organic materials which are often
used in organic electronic devices such as diodes, transistors or solar
cells. Especially the electronic structure of their interface in solar cells is
of great interest for the functionality of these devices.
In this contribution we present a study of the interface properties of the
molecular organic semiconductor copper Phthalocyanine (CuPc) on C60
using photoemission (PES) and near-edge X-ray absorption spectroscopy
(NEXAFS). As well we present a study of C60/CuPc-interfaces with different
orientation of the molecules (standing on polycrystalline gold and
lying on gold single crystals). We discuss important electronic parameters
like electron and hole injection barriers and chemical interactions at this
organic/organic interface. Further we will adress the electronic properties
of mixed C60/CuPc-films.
SYOH 5.33 Do 18:00 B
Photo Electron Spectroscopy of Silicon-Organic Pigment Interfaces
— •Ulrich Weiler 1 , Thomas Mayer 1 , Ralf Hunger 1 ,
Wolfram Jaegermann 1 , Christian Kelting 2 , and Derck
Schlettwein 2 — 1 Technische Universität Darmstadt, FB Materialund
Geowissenschaften, FG Oberflächenforschung — 2 Universität
Oldengurg, Physikalische Chemie 1
One of the prerequisites to obtain a photovoltaically active composite
material uniting high light absorption of an organic dye with good charge
separation and transport properties of Si is the specific alignment of the
dye frontier orbitals versus the Si bands: in order to inject both, the
photo excited electrons from the dye LUMO into the Si conduction band
and the holes from the dye HOMO into the Si valence band, the LUMO
should energetically be situated just above the CB and the HOMO just
below the VB. According to the Anderson model, ZnPc should match
perfectly this requirement. As model systems for the composite, the interface
properties of ZnPc and related organics adsorbed on different Si
surfaces have been characterized with photoelectron spectroscopy. Experimental
results of ZnPc on H-terminated Si are in good agreement
to the Anderson model implying that no additional dipoles are formed
at the interface. In addition, the experimental set-up of our deposition
system for silicon organic compounds will be explained on our poster. In
order to conserve the organic dyes during growth of the compound, Si
will be deposited from a remote hot wire source by CVD and the dyes
will be co-sublimated from a second source.
SYOH 5.34 Do 18:00 B
Energy level alignment at organic interfaces: Interface induced
gap states and charge neutrality levels — •Thorsten U. Kampen
and Dietrich R. T. Zahn — Institut für Physik, TU Chemnitz,
D-09107 Chemnitz
The energy level alignment at organic interfaces determines the efficiency
of charge injection into organic films. Quite often the vacuum
level alignment rule has been used to determine the energy level alignment
at organic interfaces. Here, barrier heights can simply be calculated
using the ionisation potentials or electron affinities of semiconductors materials
and work functions of metals. For organic interfaces a conclusion
has been reached that in general the vacuum levels do not align. At intimate,
abrupt, and defect free interfaces of inorganic semiconductors
interface induced gap states are the primary mechanism determining the
energy level alignment. These interface states derive from the bulk states
and their character changes across the band gap from more acceptorlike
closer to the conduction band to predominantly donor-like nearer
to the valence band. The branch point where the character changes has
the significance of a charge neutrality level. This work shows that the
concept of interface induced gap states may also be applied to organic
interfaces. The charge neutrality levels of PTCDA, DiMe-PTCDI, and
CuPc are found to be 1.96 eV, 1.93 eV and 0.51 eV above the HOMO,
respectively.

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
SYOH 5.35 Do 18:00 B
Energy Shifts in Copper Phthalocyanine Grown on Hydrogen
Passivated Si(111) — •M. Gorgoi, T. U. Kampen, and D. R. T.
Zahn — Insitut f”ur Physik, TU Chemnitz, 09107 Chemnitz, Germany
Being a major component in organic light emitting devices and solar
cells, copper phthalocyanine (CuPc) owes its increasingly attractive application
potential to its optical and electronic properties. In this contribution
ultraviolet photoemission spectroscopy (UPS) and inverse photoemission
spectroscopy (IPES) were employed to study the electronic density
of states of CuPc layers deposited onto hydrogen passivated Si(111)
substrates as a function of film thickness. The highest occupied molecular
orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)
features are found to shift gradually in the same direction with increasing
film thickness. HOMO and LUMO shift away from and towards the
Fermi level, respectively. Saturation occurs at approximately 10 nm coverage,
when the shifts amount to about 0.4 eV. In spite of this shift, the
HOMO – LUMO peak to peak difference is found to be constant at (2.95
– 0.25) eV in agreement to previous studies [1]. The 0.4 eV shifts of the
HOMO and LUMO are proposed to originate from the growth morphology
of CuPc. [1] I.G.Hill, A. Kahn, Z.G. Soos, R.A. Pascal, Jr., Chem.
Phys. Lett. 327, 181, (2000)
SYOH 5.36 Do 18:00 B
Electrical Properties of a Hybrid Ag / DiMe-PTCDI / GaAs
(100) device — •Henry Mendez, Ilja Thurzo, Thorsten Kampen,
and Dietrich R.T. Zahn — Institut für Physik, Technische Universität
Chemnitz
The perylene derivative dimethyl-3,4,9,10-perylenetetracarboxylic diimide
(DiMe-PTCDI) was used for the organic modification of Ag Schottky
contacts on n-type GaAs(100) surfaces. The transport electronic
properties were investigated recording in situ current-voltage (IV) and
capacitance-voltage (CV) characteristics, as well as ex situ characterisation
by Deep Level Transient Spectroscopy (DLTS). Additionally, an
examination of the unoccupied states of DiMe-PTCDI / GaAs(100) interface
was performed by Ultraviolet Photoemission Spectroscopy (UPS).
Modification of the Schottky diodes was obtained by growing an organic
DiMe-PTCDI layer on GaAs(100) prior to the preparation of silver
dots. Examination of the in situ IV characteristics of the organic modified
Schottky contacts shows a decrease in effective barrier height as a
function of organic film thickness. This suggests that the transport level
band in the organic DiMe-PTCDI layer, lies below the conduction band
minimum of GaAs(100). The transport level in the organic layer is further
evaluated by DLTS measurements. With UPS an energy level alignment
for the GaAs(100) / DiMe-PTCDI / Ag interface is deduced.
SYOH 5.37 Do 18:00 B
Interface Formation Between Mg and DiMe-PTCDI Studied
by Raman Spectroscopy — •Beynor Antonio Paez Sierra, Georgeta
Salvan, Reinhard Scholz, Thorsten U. Kampen und
Dietrich R. T. Zahn — Institut für Physik, Technische Universität
Chemnitz, 09107, Germany
The metal / organic interface plays an important role in the performance
of devices with organic active layers. In particular the N,N ′ -DiMethyl-
3,4,9,10-Perylene Tetra Carboxylic DiImide (DiMe-PTCDI) is a promising
candidate in organic field effect transistors. Previous studies revealed
that the interaction of Ag and In with DiMe-PTCDI is weak [1].
In this work the interface formation between Mg and DiMe-PTCDI
films with different thicknesses grown on S-passivated GaAs (100) substrates
is investigated in situ by Raman spectroscopy. When Mg is deposited
onto a 15 nm DiMePTCDI film the external molecular modes
are preserved even up to 15 nm Mg coverage, indicates a low diffusion
of Mg into the DiMePTCDI film. Concerning the internal molecular modes,
the Mg deposition induces a break down of selection rules reflecting
a dynamical charge transfer between the DiMe-PTCDI molecules and the
metal. This is in contrast to the Mg / PTCDA interface where strong
reaction was observed.
[1] B.A. Paez, G. Salvan, R. Scholz, T. U. Kampen, and D.R.T. Zahn,
SPIE USE, V 1 5217-13, (2003).
SYOH 5.38 Do 18:00 B
Chemistry and Electronic Properties of Mg/PTCDA Interface
— •G. Gavrila 1 , H. Mendez 1 , T. Kampen 1 , D. Vyalikh 2 , W.
Braun 2 , and D.R.T Zahn 1 — 1 Institut für Physik, TU Chemnitz,
09107 Chemnitz, Germany — 2 BESSY GmbH, 12489 Berlin, Germany
The chemical and electronic properties of interfaces formed between
an organic semiconductor, i.e. 3,4,9,10-perylene-tetracarboxylic dianhydride
(PTCDA), and the low electron affinity metal Mg were investigated
using Near Edge X-ray Absorption Fine Structure (NEXAFS) and PhotoEmission
Spectroscopy (PES). NEXAFS spectra taken for C K-edge
and O K-edge of PTCDA show that the intensity in the π*-resonance
decreases after deposition of Mg. This is interpreted as a partial occupation
of the lowest unoccupied molecular orbital. Since Mg possesses a
smaller electronegativity than PTCDA, a negative charge transfer from
Mg to PTCDA can be expected. Changes in C1s and O1s core levels and
the valence band structures corroborate this interpretation. Moreover,
changes in the C=O component of core levels indicate a strong chemical
reaction of Mg with the organic material. Previous work based on
Raman Spectroscopy and NEXAFS revealed considerable differences between
Mg/PTCDA and Ag/PTCDA interfaces. Here, it was found that
the Ag atoms do not disrupt the chemical structure of the PTCDA and
do not diffuse into the organic film.
SYOH 5.39 Do 18:00 B
Organic pn-homojunction using a new class of organic donors —
•K. Harada 1 , A.G. Werner 1 , M. Pfeiffer 1 , K. Leo 1 , C. Bloom 2 ,
and C.M. Elliott 2 — 1 Institut für Angewandte Photophysik, TU Dresden,
D-01062 Dresden — 2 Dep. of Chemistry, Colorado State University,
Fort Collins, CO 80523
Organic devices with p-type doped hole transport layers are now well
established. So far, n-type doped electron transport materials have been
realized with alkali metals as dopants only, because the common matrices
are rather weak electron acceptors. This demands for donor compounds
with a very low ionization potential, which are generally difficult to handle.
This limitation seemingly prevented n-type doping using very strong
organic donors.
We present a study of n-type doping of phthalocyanine zinc (ZnPc)
using metalorganic complexes as donors. ZnPc is generally considered as
a p-type semiconductor. However, using the transition metal complexes
as donors, we are able to achieve n-type conduction in this material. Conductivies
in the order of 10 −6 S/cm are observed and the conduction type
was confirmed by field effect measurements.
This enabled us to realize the first stable organic p-n junctions constisting
of p- and n-type doped layers of the same material (homo-junctions).
They have very high built-in potentials. This does not only reflect the
versatility of doping in organic devices, but pave a way to increase the
open circuit voltage of organic solar cells and to use n-type doped electron
transport layers in OLEDs.
SYOH 5.40 Do 18:00 B
Leuco bases as dopants for n-type doping of organic thin films
— •Fenghong Li, Ansgar Werner, Martin Pfeiffer und Karl
Leo — Institut fuer Angewandte Photophysik, TU Dresden, 01062
Doping of organic thin films by insertion of electron donating (n dopant)
or electron accepting (p dopant) atoms or moleculars has been
shown to be efficient and to increase film conductivity by several orders
of magnitude. N-type doping of electron transport materials with alkali
metal atoms has also been extensively reported, but these metals may
not be suitable for controlled doping. Now, organic molecules as dopants
for n-type doping are also investigated for device applications.
We demonstrated that the cationic dye pyronin B (pyB) greatly increased
the conductivity of electron transporting materials /1/. Based on
this finding, we further studied other triphenylmethane dyes as dopants
for fullerene C60 used in solar cells. For instance, conductivities up to
7.9·10 −3 S/cm were achieved when C60 was doped with Crystal Violet.
Such high conductivities render the ohmic losses in the electron transport
layers of organic solar cells neglectable.
As in the case of pyronin B, the leuco bases of the corresponding dyes
are formed by during sublimation. We found that these leuco bases become
re-oxidized to the cation in the layer by electron transfer to electron
accepting matrices, leading to the doping effect.
/1/ A.G. Werner, F. Li et al Appl. Phys. Lett., 82, 4495
SYOH 5.41 Do 18:00 B
A photoelectron spectroscopy study of transparent electrodes
in organic solar cells — •Mirko Vogel, Boyan Johnev, and
Konstantinos Fostiropoulos — Hahn-Meitner-Institut Berlin,
Glienicker Str. 100, 14109 Berlin
The interface of indium-tin oxide (ITO) electrodes with organic layers
has been shown to play an important role for the collection of charge

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
carriers in organic solar cells. In this study photoelectron spectroscopy
is applied to determine the electronic properties of the ITO surface. By
treating the ITO substrates with phosphoric or periodic acid these properties
are adjusted to those of the following organic layer. Evidence of adsorbed
acid ions on the electrode surface is found in x-ray photoelectron
spectra. Their inelastic cutoff was determined to calculate work functions.
The work function values are correlated with the performance of
Zn-Phthalocyanine-C60 solar cells. The influence of acid treatments on
the solar cell parameters is compared to the effect of a conventional PE-
DOT:PSS buffer layer.
SYOH 5.42 Do 18:00 B
High efficiency vacuum deposited solar cells using single or multiple
p-i-n architecture. — •Steffen Grundmann, Jens Drechsel,
Bert Männig, Wenge Guo, Karl Leo, and Martin Pfeiffer
— Insitut für Angewandte Photophysik, TU Dresden, D-01062 Dresden,
Germany
We introduce a p-i-n type heterojunction architecture for organic solar
cells where the active region (i) is sandwiched between two doped widegap
layers (p and n). The photoactive layer is formed by a mixture of
zinc phthalocyanine (ZnPc) and the fullerene C60. In the blend layer, the
ZnPc is found in an amorphous morphology while C60 forms nanocrystallites
of less than 10nm size. The solar cells exhibit an external quantum
efficiency of around 40% between 630nm and 700nm wavelength. With
the help of an optical multilayer model, we optimize the optical properties
of the solar cells by placing the active region at the maximum of the
optical field distribution. The results of the model are largely confirmed
by the experimental findings. For an optically optimized device, we find
an internal quantum efficiency of around 85% at short-circuit conditions.
Adding 10nm thick layer of the red material PTCBI to the active region,
a power conversion efficiency of 2% is obtained. Such optically thin cells
with high internal quantum efficiency are an important step towards high
efficiency tandem cells. First tandem cells, which are not yet optimized,
already show 2.4% power conversion efficiency. Moreover, we present first
promising results on device lifetime under simulated AM 1.5 conditions.
SYOH 5.43 Do 18:00 B
Numerical simulation of photovoltaic devices based on organic
materials — •Fryderyk Kozlowski, Wenge Guo, Bert Maennig,
Jens Drechsel, Martin Pfeiffer, and Karl Leo for the H.
Hope collaboration — Institut für Angewandte Photophysik,01069 Dresden,
Germany
We have modelled the optical and electrical behaviours of organic (pi-n)
and (p-i-i-n) solar cells fabricated in our laboratory by numerical
simulations. In the cells with structure (p-i-n), the dissociation of exitons
and free carrier creation occurrs in a photoactive mixed layer (i) e.g. zinc
phthalocyanine mixed with fullerene (ZnPc:C60). The photovoltaic devices
based on a photoactive donor-acceptor heterojunction with a p-i-i-n
architecture consist of the same organic materials. Here however, exitons
are formed in bulk materials and the dissociation of the excitons takes
place at the interface of neat ZnPc and C60 layers. In the numerical model
describing the electrical properties, we took into account effects like bipolar
charge carrier drift and diffusion, bulk and interface recombination,
trapping, creation, diffusion and quenching of exitons. The distribution
of generated free carriers in the mixed layer or the generation profile of
exitons in heterojunctions, respectively, is calculated from optical simulations.
By including trap-mediated recombination for (p-i-n) solar cells,
we are able to simulate the linear dependence of the short circuit current
on light intensity. Furthermore, we study the optimum thickness of the
active layer and compare it with experimental data. Finally, we show the
temperature dependence of short circuit current and open circuit voltage.
SYOH 5.44 Do 18:00 B
Photocurrent action spectra and X-ray diffraction on diindenoperylene/pentacene
heterostructures — •D. Kurrle,
S. Hirschmann, and J. Pflaum — III. Physikalisches Institut,
Universität Stuttgart, Germany
As a new candidate for photovoltaic applications, thin films of the
organic semiconductors diindenoperylene (DIP, C32H16) and pentacene
(C22H14) were prepared and examined by measuring the absorption and
photocurrent action spectra.
Samples of different structures were grown by thermal evaporation, using
ITO and silver as electrode materials. DIP/pentacene double layers
as well as co-evaporated mixed layers were studied (both 100-250 nm
in total thickness), both yielding considerable photocurrents up to 50
nA/cm 2 under the applied conditions.
Furthermore, X-ray diffraction and AFM were carried out to obtain
additional information on the structure of the films. The growth of the
DIP/pentacene bilayers showed a pronounced structural dependence on
the substrate temperature (140-400 K) and the underlying electrode material,
whereas the impact on the photocurrent emerged to be minor.
SYOH 5.45 Do 18:00 B
Optical and Electronic Contributions in Thin Film Organic Solar
Cells — •Helmut Hänsel 1 , Heiko Zettl 1 , Georg Krausch 1 ,
Roman Kisselev 2 , Mukundan Thelakkat 2 , and Hans-Werner
Schmidt 2 — 1 Universität Bayreuth, Physikalische Chemie II —
2 Universität Bayreuth, Makromolekulare Chemie I,D-95447 Bayreuth
We investigate the photocurrent of a (ITO/CuPc/perylene dye/Al)
cell and a (ITO/CuPc/perylene dye/TiO2/Al) cell as a function of the
perylene dye layer thickness. In addition to the experimental data, we
present a model that describes the short circuit current of these cells.
The charge generation probability is estimated from the intensity profile
that is calculated via a matrix transfer algorithm taking into account the
full illumination spectrum. We find that the TiO2 layer modifies the short
circuit current by two effects: Optically, by shifting the charge transfer
interface with respect to the light intensity profile, and electronically, by
introducing a second heterojunction where additional charge transfer can
occur. Thickness dependent studies can clearly separate these two effects
and can yield an estimate of the ratio of the exciton diffusion lengths
in the absorbing media. The high accuracy in thickness variation that is
necessary for such study is achieved by the combinatorial fabrication and
testing of the devices. We can furthermore show that the introduction of
the TiO2 layer leads to a faster and stronger degradation.
SYOH 5.46 Do 18:00 B
Multilayer solar cells based on polymer nanoparticles —
•Thomas Kietzke 1 , Katharina Landfester 2 , and Dieter
Neher 2 — 1 University of Potdam, Institute of Physics, Am Neuen
Palais 10, D-14469 Potsdam — 2 University of Ulm, Institute of
Macromolecular Chemistry, Albert-Einstein-Allee 11, D-89069 Ulm
Recently, we have demonstrated that polymer nanospheres with diameters
in the range of 30 to 250 nm dispersed in water can be prepared
with the miniemulsion process. First solar cells based on layers of
these nanoparticles have shown efficiencies comparable to solvent processed
layers. Formation of films from polymer nanoparticles opens up
new strategies for the deposition of multilayer assemblies, since the semiconducting
polymer nanospheres are dispersed in water. Preparing multilayer
structures of polymers from organic solvents is often difficult if the
polymers of e.g. the second layer is deposited from a solvent, which is also
a good solvent for the underlying polymer. Utilizing dispersions of polymer
nanospheres can help to circumvent this problem. After preparing the
first nanoparticle layer, the sample is thoroughly dried to completely remove
residual water. Then, a second nanosphere layer is deposited on top,
resulting in a multilayer assembly with a well-defined polymer-polymer
interface and no interdiffusion of the polymers in the separate layers. We
show the results on double layer polymer solar cells with ITO and Ca
electrodes as well as devices including a thin TiO2 electron-accepting
layer. Reference: [1] T.Kietzke, D. Neher et. al. Nature Materials, June
2003, 408-412
SYOH 5.47 Do 18:00 B
Organic Photovoltaic Elements - Influence of 100 nm scale
electrode spacing on morphology and efficiency for PF/PANI
conjugated block copolymer — •Jörg Seekamp 1 , R. Güntner 2 ,
V.G. Solovyev 1 , A.P. Kam 1 , A. Goldschmidt 1 , T. Farrell 2 , U.
Scherf 2 , and C.M. Sotomayor Torres 1 — 1 Institute of Materials
Science and Department of Electrical and Information Engineering, University
of Wuppertal, Gauß Straße 20, 42097 Wuppertal, Germany —
2 Fachbereich Chemie, Makromolekulare Chemie, University of Wuppertal,
Gauß Straße 20, 42097 Wuppertal, Germany
The transport properties of organic semiconductors in solar cells are
the object of intense research. The efficiency of these devices crucially
depends on the charge separation and effective transport to metal electrodes.
This work combines closely spaced electrodes and the intrinsically
nanostructured morphology of a block copolymer to improve the
efficiency. The idea is to direct the intrinsic nanostructuring along the

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
electrodes sorting the acceptor and donor block to the respective electrode.
The experimental results discussed in terms of spectrally resolved
external quantum efficiency with respect to electrode spacings between
100 nm and 10 um were obtained from interdigitated electrodes patterned
by electron beam lithography and nanoimprint lithography. They were
covered with the conjugated block copolymer polyfluorene/polyaniline
(PF/PANI) as a model system for photovoltaic applications. This work
is supported by the Volkswagen Stiftung (I/77 721).
SYOH 5.48 Do 18:00 B
Silicon - organic pigment material hybrids for photovoltaic
application — •Thomas Mayer 1 , Ulrich Weiler 1 , Wolfram
Jaegermann 1 , Derck Schlettwein 2 , Dieter Wöhrle 3 , and Marinus
Kunst 4 — 1 Technische Universität Darmstadt, FB Material-und
Geowissenschaften, FG Oberfächenforschung — 2 Universität Oldenburg,
Physikalische Chemie 1 — 3 Universität Bremen, Institut für Organische
und Makromolekulare Chemie — 4 Hahn-Meitner Institut Berlin, Abt.
Solare Energetik
We are running a project that is focussed on the development of siliconorganic
pigment hybrid materials for thin film solar cell application. High
conversion efficiency is expected from a combination of the advantages
of organic dyes for light absorption and of silicon for charge carrier separation
and transport. The project team, wants to find suitable dyes
and deposition conditions for the preparation of photovoltaic hybrid materials.
The composite will be prepared by (remote) hot wire chemical
vapour deposition of silicon and co-sublimation of organic dye molecules.
Pigments are synthesized and specifically modified to allow for injection
of photo-excited charge carriers from dye orbitals to silicon bands. The
basic idea of the concept of bulk hybrid materials for photovoltaic application
will be introduced. As model experiments dye-Si and Si-dye
layers have been grown and characterized by photoelectron spectroscopy,
Raman spectroscopy and Time Resolved Microwave Conductivity. The
results will exemplify the strategy to challenge the task of producing a
new inorganic-organic functional composite material in view of photovoltaic
applications.
SYOH 5.49 Do 18:00 B
Photophysical properties of annealed polyhexylthiophen:fullerene
composites — •Michael Pientka, Dana
Chirvase, and Vladimir Dyakonov — Institute of Physics,
University of Oldenburg, 26111 Oldenburg, Germany
Composites of polyhexylthiophen and methanofullerene (PCBM) are
promising for polymer photovoltaics. External quantum efficiences above
70% and power conversion efficiences above 3% were demonstated recently.
Decisive step to achieve such high values is a thermal annealing,
strongly improving the electrical performance. The exact nature of this
effect is still under discussion. We apply photoinduced absorption, light
induced electron spin resonance and photoluminescence spectroscopy for
the investigation of the photogenerated states and their transformation
upon annealing. The heat treatment leads to a number of effects: increase
of the photoluminescence previously suppressed, energy shift of polaronic
absorption band together with a strong increase in the density of charge
separated states. The changes observed are discussed in terms of variation
of nanomorphology in polymer-fullerene blends, as supported by
AFM, and are related to device performance.
SYOH 5.50 Do 18:00 B
High efficiency charge carrier generation and recombination
free charge carrier transport in polymer-fullerene bulk heterojunction
devices — •Vladimir Dyakonov 1 , Ingo Riedel 1 , Pavel
Schilinsky 1,2 , Christoph Waldauf 1,2 , and Christoph Brabec 2 —
1 Energy- and Semiconductor Research Laboratory, Institute of Physics,
University of Oldenburg, D-26111 Oldenburg, Germany — 2 Siemens AG,
Innovative Electronics,CTMM1-L2P, Paul-Gossen-Strasse 100, D-91052
Erlangen, Germany
We present experimental evidences for the efficient photogeneration
of charge carriers in photovoltaic conjugated polymer-fullerene blends
followed by the recombination-free charge carrier transport through the
semiconductor layer. From the incident photon conversion efficiency exceeding
70%, an internal quantum efficiency of close to 100% was calculated,
indicating high potential of these materials for solar cell applications.
We demonstrate that by increasing the active layer thickness (up to
350 nm) without significant decrease of internal quantum efficiency, high
short-circuit photocurrent densities (JSC) of 15 mA/cm 2 can be achieved.
The temperature dependence of the photocurrent generally reflects the
charge carrier transport losses in the device under test. Being thermally
activated at low temperatures, the JSC saturates and becomes nearly
temperature independent above T=260 K, indicating that the charge
carriers traverse the active layer without being influenced by the semiconductor’s
transport properties. The corresponding high value of the
mobility-lifetime product µτ provides therefore a basis to design solar
cells with thick absorber layers able to overcome transport limitations.
SYOH 5.51 Do 18:00 B
Bulk heterojunction solar cells from low bandgap polymer and
PCBM — •Martin Knipper 1 , Anja Henckens 2 , Laurence Lutsen
2 , Jean Manca 2 , and Dirk Vanderzande 2 — 1 Energy- and Semiconductor
Research Laboratory, Institut of Physics, University of Oldenburg,
D26111 Oldenburg, Germany — 2 Limburgs Universitair Centrum,
Department SBG/SCH universitaire campus D, B3590 Diepenbeek, Belgium
Low bandgap bulk heterojunction solar cells were made from a precursor
polymer mixed with [6,6]-phenyl C61-butyric acid methyl ester
(PCBM). This mixture is spincoated onto an indiumtinoxid (ITO) substrate
covered with PEDOT:PSS. The conversion in film to the conducting
low band gap (1.4 eV) polymer polythienylenevinylene (PTV) is made
by heat treatment. Finally lithiumfluoride (LiF) and aluminum contacts
were thermally evaporated. JV-characteristics under 1.5 AM illumination
(100mW/cm 2 ) are taken at room temperature after the evaporation
and several times after post production heat treatments. We see an high
increase in solar cell performance with the post production treatment.
All main solar cell parameters (open-circuit voltage, short-circuit current
density and fillig factor) increase. By varying the weight concentration
of PCBM with respect to the precursor PTV we found an optimal ratio
around 1:1. With these conditions and without further optimisation we
get a solar cell efficiency of 0.63%.
SYOH 5.52 Do 18:00 B
Photodegradation of organic films and organic solar cells —
•O. Schulz 1 , M. Spode 1 , G. Ecke 1 , J. Uziel 1 , W. Schliefke 1 , M.
Al-Ibrahim 1 , O. Ambacher 1 , D. Raabe 2 , M. Helbig 2 , L. Carta-
Abelmann 3 , P. Scharff 3 , U. Zhokhavets 4 , T. Erb 4 , and G. Gobsch
4 — 1 TU Ilmenau, Center for Micro- und Nanotechnologies, D-98693
Ilmenau, Germany — 2 SurA Chemicals GmbH, D-07745 Jena, Germany
— 3 TU Ilmenau, Chemistry, D-98693 Ilmenau, Germany — 4 TU Ilmenau,
Experimental Physics I, D-98693 Ilmenau, Germany
For the application of organic solar cells a high electronic and structural
stability is of fundamental importance in addition to a high conversion
efficiency. Photovoltaic devices with active layers based on polymers
as poly-3 hexylthiophene(P3HT) and tetraphenyl-biphenyldiamindiphenylxylylene(TPD-DPX)
show a significant degradation of optoelectronic
properties under AM1.5 illumination. For instance the short circuit
current density of a P3HT based solar cell decreases under the influence
of light(60 mW/cm 2 ) within 2 minutes by 50 %.
Polymer films of 30 - 200 nm thickness are produced by spin-coating.
The electrical, optical and structural parameters of the generated organic
devices are investigated with regard to the dependency of the
photodegradation effects on ambient parameters. These parameters are
oxygen pressure, temperature and light intensity. The photodegradation
process is analysed by measurements of current-voltage curves, spectral
resolved photoconductivity, spectral resolved ellipsometry, atomic force
microscopy and Auger electron spectroscopy.
SYOH 5.53 Do 18:00 B
Dielectric spectroscopy of the photovoltaic cell formed by
di-(pyridyl)-perylenetetracarboxylic diimide and copper
phthalocyanine — •Grazyna Jarosz 1 , Ryszard Signerski 2 , Jan
Godlewski 2 , Paul David Quinn 1 , Niels Stephan 1 , and Ludwig
Brehmer 1 — 1 Condensed Matter Physics, Institute of Physics,
University — 2 Department of Applied Physics and Mathematics,
Gdansk
Dielectric spectroscopy is one of the major techniques applied in the
investigation of Schottky barriers or p-n junctions due to dielectric phenomena
which arise between metal-semiconductor and semiconductorsemiconductor
interfaces. Indeed, it provides us with important information
such as the depletion-layer capacitance, the diffusion capacitance
and the series and parallel resistance which are particularly important in
the investigation of the various processes determining the DC response
of a device. However, in the case of organic solar cells this method has
been not widely applied despite the increasing interest in these types of

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
devices. Our work will present dielectric spectra of organic heterojunctions
formed by di-(pyridyl)-perylenetetracarboxylic diimide (Py-PTC)
and copper phthalocyanine (CuPc). This organic junction exhibits a photovoltaic
effect with effective photogeneration of charge carriers occuring
near the Py-PTC/CuPc interface. The main processes determining
the heterojunction performance will be discussed. Acknowledgement: The
work was supported by Marie-Curie Host Fellowships: Project MODERN
No.HPMD-CT-2001-00083 and by KBN: Project No.4T11B 057 22.
SYOH 5.54 Do 18:00 B
An impedance spectroscopy study of Ag/PTCDA/n-GaAs(100)
heterostructures — •A. Bekkali, I. Thurzo, T. U. Kampen und
D. R. T. Zahn — Insitut für Physik, TU Chemnitz, D-09107 Chemnitz
In this work impedance spectroscopy (IS) was applied to investigate
Ag/PTCDA/n-GaAs(100) heterostructures. Describing the samples
using an equivalent circuit consisting of resistors and capacitors, the potential
drop across each relevant area of the sample, that is, the GaAs and
PTCDA bulk as well as the Ag/PTCDA and PTCDA/GaAs interface,
can be determined. The IS characteristics can be simulated by modeling
the Ag/PTCDA interface using a parallel RoCo circuit connected in series
with a bulk resistance Rb for the PTCDA layer. All the elements are
found to be nonlinear with respect to the applied bias and frequency independent.
The depletion layer in GaAs is correctly characterized by its
parallel resistance Rd and capacitance Cd. The most important feature
of the Ag/PTCDA interface is the capacitance Co, which consists of a
geometric capacitance and an excess capacitance δC, the latter originating
from recharging a Gaussian density of states (DOS). This Gaussian
DOS is attributed to surface states Nss(E), their respective capacitance
δCss(E) = q 2 Nss(E) peaking for an applied bias of 0.2 V. This value
agrees with the thermal activation energy for carrier transport in the
PTCDA layer.
SYOH 5.55 Do 18:00 B
Characterization of polymeric metal-insulator-semiconductor
diodes — •Silviu Grecu, Markus Bronner, Andreas Opitz, and
Wolfgang Brütting — Experimentalphysik IV, Universität Augsburg,
86135 Augsburg, Germany
Metal-insulator-semiconductor (MIS) diodes are the two-terminal pendants
of thin film transistors sharing the same basic layer structure. However,
instead of the current-voltage characteristics one has to study the
capacitance-frequency and capacitance-voltage behavior, which can give
information about mobile charges and trapping processes in these devices.
We have investigated MIS structures based on poly(alkyl-thiophene) as
semiconductor which were fabricated on glass substrates with polymeric
insulator layers and compared their response to devices fabricated on
Si/SiO2 substrates. From capacitance-voltage measurements the acceptor
dopant concentration is determined for different preparation conditions.
Typically these measurements show hysteresis between forward and reverse
bias sweeps. We have investigated this behavior as a function of
external parameters like sweep speed and temperature and discuss their
possible origin. The analysis of the frequency response using appropriate
equivalent circuits allows the extraction of material parameters, like
conductivity and charge carrier mobility, which are compared to data
obtained on thin film transistor structures.
SYOH 5.56 Do 18:00 B
Charge injection into thin fullerene films — •Elizabeth von
Hauff, Vladimir Dyakonov, Jürgen Parisi, and Zivayi Chiguvare
— Energy and Semiconductor Research Laboratory, Institute of
Physics, University of Oldenburg, D-26129, Oldenburg, Germany
In this study, charge injection currents into thin film fullerene diodes
composed of a thin film of PCBM sandwiched between a metal and an
ITO (indium tin oxide) electrode. Decreasing the thickness of the semiconductor
layer in the diodes results in a transition from bulk limited to
injection limited currents. From the injection limited currents through the
thin film fullerene diodes, parameters describing the energy barrier between
metal and semiconductor, the transport level within the bulk, and
the activation energy could be calculated according to an already existing
hopping model. The model describes charge carriers being injected from
the metal into energy sites in the semiconductor medium distributed in a
Gaussian density of states. The barrier height experienced by the charge
carriers described by the above model was compared to a value calculated
earlier from the Fowler-Nordheim model for quantum mechanical
tunneling. In an attempt to shed more light on the metal/semiconductor
interface, the fullerene diodes were futher investigated via capacitance-
voltage measurements.
SYOH 5.57 Do 18:00 B
Quantum transport through carbon-based nanojunctions —
•Miriam del Valle 1,2 , Carlos Tejedor 1 , and Gianaurelio Cuniberti
2 — 1 Dpto. Física Teórica de la Materia Condensada, UAM,
Spain — 2 Institut für Theoretische Physik, Universität Regensburg
We present a quantum transport study of two- and three-terminal carbon
nanotube (CNT) based junctions. We concentrate our analysis on
functionalized and recapped zig-zag CNTs exhibiting peculiar surface
electronic states localized at the zig-zag cut and at the cap defect atoms
respectively. We calculate the linear conductance by means of the Green
function technique, within a π-orbital description of the carbon network,
and show the interplay between these peculiar localized states and the
open transport channels through the device. In correspondence of the
energies of the localized states, the conductance behavior shows a Fanolike
resonance. Possible experimental conditions and setup in which such
effect could be detected are also discussed.
SYOH 5.58 Do 18:00 B
Electron Transport in Carbon Nanotube-Metal Systems: Contact
Effects — •Rafael Gutierrez 1 , Nitesh Ranjan 2 , Stefan
Krompiewski 3 , and Gianaurelio Cuniberti 1 — 1 Institute for Theoretical
Physics, University of Regensburg, D-93040 Regensburg, Germany
— 2 Institute for Physical-Chemistry and Electrochemistry,Technical University
Dresden, 01062 Dresden, Germany — 3 Institute of Molecular
Physics, Polish Academy of Sciences,PL-60179 Poznan, Poland
Carbon nanotubes (CNT) posses a very large application potential in
the rapid developing field of molecular electronics. Infinite single-wall
metallic CNTs have theoretically a conductance of 2×G0, (G0 = 2e2)
be- h
cause of the two electronic bands crossing the Fermi level. For finite size
CNTs experiments have shown that other values are also possible, indicating
a very strong influence of the contacts. We study electron transport
in single- and double-wall CNTs contacted to metallic electrodes with a
fcc(111) surface within the Landauer transport formalism combined with
Green function techniques. The electronic structure of the CNTs is described
with a simple π-orbital model.We show that the symmetry of the
contact region may lead in some cases to blocking of one of the transport
channels reducing the conductance to 1×G0 for single-wall CNTs. In the
case of double-wall systems with both inner and outer shells being metallic,
non-diagonal selfenergy contributions from the electrodes may induce
mixing of the CNT’s channels, again reducing the conductance from the
theoretically expected value (4×G0). Finally, we discuss the influence of
inter-wall interactions on the conductance.
SYOH 5.59 Do 18:00 B
Nonequilibrium-Transport through Metallic Point Contacts
and Single-Molecule Junctions — •Fabian Pauly 1 , J. Heurich 1 ,
J.C. Cuevas 1 , W. Wenzel 2 , and Gerd Schön 1,2 — 1 Institut für
Theoretische Festkörperphysik, Universität Karlsruhe, 76128 Karlsruhe,
Germany — 2 Institut für Nanotechnologie, Forschungszentrum
Karlsruhe, 76021 Karlsruhe, Germany
The future of molecular electronics depends crucially on our understanding
of the transport mechanism in single-molecule junctions. From
the theoretical point of view an important problem, not yet fully solved,
is the way of dealing with the high voltage applied in the experiments.
Building upon traditional quantum-chemistry density functional calculations,
we extend our method [1,2] to compute ab initio current-voltage
characteristics of molecular devices. We show our first results on the
bias-dependent conductance of metallic point contacts, illustrating the
predictive power of the developed method.
[1] J. Heurich, J.C. Cuevas, W. Wenzel, G. Schön, Phys. Rev. Lett. 88,
256803 (2002)
[2] J.C. Cuevas, J. Heurich, F. Pauly, W. Wenzel, G. Schön, Nanotechnology
14 (2003)
SYOH 5.60 Do 18:00 B
Transport properties of [2,2]-paracyclophane thin films
— •Bruno Gompf 1 , Wenping Hu 1 , Martin Dressel 1 , Jens
Pflaum 2 , and Dieter Schweitzer 2 — 1 1. Physikalisches Institut,
Universität Stuttgart — 2 3. Physikalisches Institut, Universität
Stuttgart
The transport properties of [2,2]-paracyclophane thin films prepared by
molecular beam epitaxy were studied by space charged limited current
measurements. This organic semiconductor, which has a three dimen-

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
sional π-system comparable to that of C60 is an interesting new material
for molecular electronics applications due to its remarkably high mobility
and its insensitivity against photo-oxidation. The I-V characteristics
were recorded using a coplanar electrode geometry. This geometry has
the advantage, that after deposition no further processing of the organic
semiconducting layer is necessary. In polycrystalline films hole mobilities
up to 10 −2 cm 2 V −1 s −1 were observed at room temperature.
SYOH 5.61 Do 18:00 B
Single crystalline organic field effect transistors — M. Fischer
1 , •J. Niemax 2 , B. Gompf 1 , M. Dressel 1 , and J. Pflaum 2
— 1 1.Physikalisches Institut, Universität Stuttgart — 2 3.Physikalisches
Institut, Universität Stuttgart
Organic field effect transistors are receiving increased attention during
the last few years due to their potential application in low cost electronics.
It has been proven that grain boundaries significantly influence
charge transport in these devices. In order to evaluate the maximum
performance that can be achieved for a certain type of organic molecule,
it is thus necessary to investigate the charge carrier transport in single
crystalline devices.
We have studied the field effect in organic single crystals. The crystals
were grown by a sublimation technique in a stream of vapor. We have
investigated the influence of different organic materials (Tetracene, Anthracene),
different gate insulators (Mylar, PPX) and different electrode
materials (silver paste, colloidal graphite) on the field effect.
SYOH 5.62 Do 18:00 B
Downscaling of thiophene based organic field-effect transistors
to the nanometer regime — •M. Leufgen 1 , U. Bass 1 , T.
Borzenko 1 , G. Schmidt 1 , J. Geurts 1 , T. Muck 2 , and V. Wagner 2
— 1 Physikalisches Institut der Universität Würzburg, EP III, Am Hubland,
D-97074 Würzburg — 2 International University Bremen, School of
Engineering and Science, Campus Ring 8, D-28759 Bremen
For future electronics high-performing organic field-effect transistors
(OFETs) are required. Downscaling to channel lengths L in the nanometer
regime means higher accessible frequency, integration and current of
transistors. To vary L from 2 µm down to 50 nm, we use an assembly
of n-type silicon wafer as common gate with thermally grown oxide
as insulator layer and Au/Ti source and drain interdigitated electrodes,
defined by electron beam lithography. In order to keep good characteristics
downscaling the channel requires a thinner insulator layer because
of the ratio of horizontal and transversal electrical field in the device.
The thickness of the SiO2 investigated ranges from 200 nm down to 30
nm. The active material is the soluble hexyl substituted quaterthiophene
(DH4T). For the 30 nm oxide layers our results show high mobility of
about 2 × 10 −2 cm 2 /Vs for a 200 nm channel DH4T-device with ratio
W/L of 800. Moreover, the linear and saturation regime are proven and
on/off-ratios for devices with L down to 200nm are as high as 10 5 . Below
200nm field-effect is still observed, but the transistor performance
decreases.
SYOH 5.63 Do 18:00 B
Organic phototransistors based on intramolecular charge transfer
— •Tobat Saragi, Robert Pudzich, Thomas Fuhrmann, and
Josef Salbeck — Makromolekulare Chemie und Molekulare Materialien,
Fachbereich Naturwissenschaften und Center for Interdisciplinary
Nanostructure Science and Technology, Universität Kassel
The conductivity of organic field effect transistors is based on the
generation of radical ions as additional charge carriers by the field effect.
Similarly, charge carriers can be produced by intramolecular charge
transfer reactions in an organic photoconductor. Using an asymmetric
spiro compound, 2,7-bis-(N,N’-diphenylamino)-2’,7’-bis(biphenyl-4- yl)-
9,9’-spirobifluorene (Spiro-DPSP), which consists of a hole transport moiety
in one molecular half and an electron-accepting chromophore in the
other, we demonstrate an one-component organic phototransistor. The
sensitivity of the photosensing device is better than 1 A/W for UV light.
SYOH 5.64 Do 18:00 B
Influence of contact metal on the serial resistance in organic
field effect transistors — •U. Bass 1 , M. Leufgen 1 , T. Muck 2 , J.
Geurts 1 , and V. Wagner 2 — 1 Physikalisches Institut der Universität
Würzburg, EP III, Am Hubland, D-97074 Würzburg — 2 International
University Bremen, School of Engineering and Science, Campus Ring 8,
D-28759 Bremen
The performance of organic field effect transistors (OFETs) depends
essentially on the channel resistance of the organic material and the resistance
between the organic material and the metal contacts. With improving
film morphology and reducing channel lengths the relative influence
of the contact resistance increases and becomes the dominating factor
of the OFETs performance. We present a systematic study of various
noble metals as source and drain contact materials for OFETs, based on
DH4T. We applied gold and platinum, which both required a titanium
adhesion layer, and palladium, which we could deposit directly on the
SiO2 substrate. The smallest contact resistance was obtained when using
Pd. However, these contacts turned out to be rather vulnerable during
the chemical processing prior to the deposition of the organic active layer.
From the contacts with Ti adhesion layers, the Au results were superior
to those of Pt. For a more detailed study of the Au/Ti system, we varied
the Ti adhesion layer thickness from 10 nm down to 1 nm, yielding an
increasing performance with decreasing Ti thickness. Finally, a reduction
of the channel resistance of the DH4T film was achieved by employing a
pretreatment of the SiO2 substrate with octadecyltrichlorosilane (OTS)
instead of hexamethyldisilane (HMDS).
SYOH 5.65 Do 18:00 B
In situ electrical characterization of DH4T transistors — •T.
Muck 1 , V. Wagner 1 , M. Leufgen 2 , J. Geurts 2 , E. Bentes 3 , and
H. L. Gomes 3 — 1 International University Bremen, School of Engineering
and Science, Campus Ring 8, D-28759 Bremen — 2 Experimentelle
Physik II, Universität Würzburg, Am Hubland, D-97074 Würzburg —
3 University of the Algarve, Campus de Gambelas, FCT, 8000, Portugal
The performance of organic field effect transistors (OFETs) was
improved over the last years enormously, e.g., dihexyl-quaterthiohene
(DH4T) has proven high mobility values and is compatible with cheap
solution processing, which is of high interest due to low cost production.
The transport properties of OFETs are influenced by different parameters,
e.g., temperature, film morphology, and the ambient atmosphere.
For a systematic analysis we performed in situ electrical measurements on
DH4T thin film transistors during the deposition of the active layer onto
prepatterned templates by organic molecular beam deposition (OMBD).
Here we get information about the charge transport in the first monolayers
and the dependence of the mobility values on film thickness. Results
for different substrate temperatures will be discussed, including the phase
transition of the active layer at elevated temperatures.
Applying a gate voltage leads to filling of traps (bias stress). This effect is
influenced by the ambient atmosphere. Performing these measurements
in situ as well as in air enables us to systematically analyze these stress
effects.
SYOH 5.66 Do 18:00 B
Transparent organic field effect transistors based on rf magnetron
sputtered alumina films — •Michael Voigt and Moritz
Sokolowski — Institut für Physikalische und Theoretische Chemie,
Universität Bonn, Wegelerstrasse 12, 53115 Bonn
Organic field effect transistors (OFETs) were fabricated by evaporation
of pentacene (Pc) onto alumina insulator films (d = 160–320 nm).
The alumina films were prepared on ITO covered glass (gate–electrode)
by rf magnetron sputtering and show under optimized sputter conditions
breakdown fields of 1.2 MV/cm and a dielectric constant of ∼7. AFM
investigations reveal that their surface is rather rough (rms = 3.6 nm).
Source and drain contacts (Au; d = 50 nm) were prepared by shadow
mask technique either on top of the Pc films or on top of the alumina.
The channel length L was 50 µm. In the first case, a charge mobility of
0.01 cm 2 /Vs was observed, a value of the same order as we obtained for
comparable OFETs on SiO2. In the second case, no field effect mobility
was observed, which we relate to a detrimental influence of Au clusters on
the alumina surface on the Pc film formation. Since the OFET–channel
is transparent, we can control growth of the Pc films by polarization microscopy.
Supported through the DFG-priority program ”Organic field
effect transistors”.
SYOH 5.67 Do 18:00 B
Field Effect Transistor and Space Charge Limited Current Measurements
on Tetracene and Perylene Single Crystals — •G.
Ulbricht 1 , J. H. Smet 1 , J. Niemax 2 , Ch. Herb 2 , and K. von Klitzing
1 — 1 MPI-FKF, Stuttgart — 2 3. Phys. Inst. Uni Stuttgart
The study of charge carrier transport in organic single crystals is an
experimental challenge. Among other things, the intrinsic carrier concentration
is very low and doping quite difficult. Increasing the amount of

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
charge carriers using a field effect geometry instead offers improved access
to the intrinsic charge transport properties of these materials. We are
investigating single crystals of tetracene and perylene. In order to get a
working FET, the gate isolation has to fulfil some stringent requirements.
We have screened several materials suitable as gate dielectrics. With the
polymer PPX (poly-para-xylylene or parylene), field effect transistors
on tetracene single crystals can be prepared reliably without significant
damage to the delicate crystal surface. The properties of these FET’s
were examined down to liquid helium temperatures, and the influence of
different sample preparation techniques will be discussed. To understand
the pronounced influence of different metals for the source-electrode, we
have measured space charge limited currents (SCLC) on tetracene and
perylene. Trap concentrations as low as 1·10 13 cm −3 in Bridgman-grown
perylene attest the high quality of the crystals used. These SCLC measurements
also show deficient charge carrier injection for many contact
metals, especially in perylene. Therefore, carrier injection was systematically
evaluated, both in the SCLC as well as in the FET geometry.
Supported by the DFG (Sm64/4-1, Ka 427/8).
SYOH 5.68 Do 18:00 B
Morphology-performance relationship in pentacene-based thin
film transistors — •Wolfgang Kalb 1 , Philippe Lang 2 , Mohammad
Motaghi 2 , Matthias Wuttig 1 , and Gilles Horowitz 2 — 1 1.
Physikalisches Institut der RWTH Aachen, Germany — 2 ITODYS / Universite
Paris 7, France
Pentacene-based thin film transistors were fabricated on Si/alumina
substrates with gold top-contact source and drain electrodes. On some
devices, the alumina surface was modified with fatty acid self-assembled
monolayers prior to pentacene deposition. Pentacene layers were grown
by vacuum evaporation at various deposition rates ranging from 0.003A/s
to 3A/s and various film thicknesses. The gate voltage dependent mobility
was extracted from the transfer characteristics with correction for contact
resistance. We find that treating the alumina with fatty acid leads
to a substancial increase in the mobility. The mobility furthermore depends
upon the film thickness. An intermediate deposition rate of 0.1A/s
is found to lead to optimal transistor performance. The growth mechanism
of the pentacene layers was followed by atomic force microscopy.
It is found that the primary growth-stage of pentacene-films leading to
transistors of best performance is characterised by a high nucleation rate.
The size of the grains tends to drastically increase during the deposition
process.
SYOH 5.69 Do 18:00 B
Simulation-Optimization of Ambipolar Organic Field-Effect
Transistors — •Gernot Paasch 1 , Thomas Lindner 1 , and
Susanne Scheinert 2 — 1 IFW Dresden — 2 TU Ilmenau
Ambipolar or double-injection field effect transistors based on amorphous
silicon have been investigated almost two decades ago, but they
did not find significant application. With organic materials as active layer
such devices become of interest due to direct recombination with light
emission. Even advanced existing models based on the Pao-Sah description
neglect both the actual contact properties and the recombination
process. Hence, for analyzing experimental data or optimizing the device
performance detailed numerical simulations have been carried out. Comparison
with experimental data allows for the determination of important
material parameters. Moreover, the simulation reveals the subtle interplay
between the properties of the source and gate contacts, interface
charges, the ratio of the electron and hole mobilities, doping, and recombination
(and the heterojunction in the case of a double layer system).
Operation modes are clarified by inspection of the internal concentration
and field distributions. Further, the simulations result in rules for possible
simple analytical examination of experimental data and for device
optimization.
SYOH 5.70 Do 18:00 B
Effect of Annealing on Characteristic Hole Traps in
Poly(3hexyl-thiophene) Thin Films — •Zivayi Chiguvare,
Jürgen Parisi, and Vladimir Dyakonov — University of
Oldenburg, Faculty of Physics (EHF), 26111 Oldenburg
Bulk transport properties of poly(3hexylthiophene) (P3HT) were studied
by analysing temperature dependent current-voltage characteristics
of the polymer thin films sandwiched between ITO/PEDOT and aluminium
electrodes. It was found that the contacts limit charge injection
under reverse bias, but under forward bias the current is limited by space
charge that accumulates near the hole injecting electrode (ITO/PEDOT)
due to the poor transport properties of P3HT. The forward current density
obeys a power law of the form J ∼ V m , characteristic of SCLC in
the presence of exponentially distributed traps within the band gap. The
energy that characterises the exponential distribution of hole traps increases
with temperature. Hole trap density was found to decrease on
annealing the devices, resulting in more than 2 orders of magnitude increase
in SCLC hole mobility. We attribute this to better chain packing
and thus a large increase in the degree of interchain interactions as compared
to as-cast films.
SYOH 5.71 Do 18:00 B
Influences on the mobility in poly-(3-hexylthiophene) based
organic field effect transistors — •Holger Heil, Roland
Schmechel, and Heinz von Seggern — Insitute of Material Science,
Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt,
Germany
Regioregular head-to-tail coupled poly-(3-hexylthiophene) polymers
(P3HT) are one of the most promising candidates for application in organic
field effect transistors (OFETs) due to their self-ordering properties.
The effect of surface treatment as well as mechanical rubbing of
the polymer layer on the morphology, texture and orientation of the
molecules were investigated by means of optical and x-ray diffraction
methods and were correlated to the obtained field effect mobility. It could
be demonstrated that mechanical rubbing along the transport direction
results in an orientation of the polymer chains and enhances the field
effect mobility. But an enhanced crystallinity due to surface treatment
of the insulator surface or drop casting of the polymer results in an even
more increased mobility. The results are discussed with respect to the importance
of inter- and intra-chain charge transfer processes to the overall
charge transport.
SYOH 5.72 Do 18:00 B
Effect of Molecular Weight and Annealing of Poly(3hexylthiophene)s
on the Performance of Organic Field
Effect Transistors — •Achmad Zen 1 , Frank Jaiser 1 , Dieter
Neher 1 , Jens Pflaum 2 , Stephan Hirschmann 2 , Jürgen Rabe 3 ,
Wei Zhuang 3 , Ullrich Scherf 4 , and Udom Asawapirom 4 —
1 University of Potsdam, Institute of Physics, Am Neuen Palais 10,
D-14469 Potsdam — 2 University of Stuttgart, Institute of Physics,
Pfaffenwaldring 57, D-70569 Stuttgart — 3 Humboldt University,
Department of Physics, Newtonstr. 15, D-12489 Berlin — 4 University
of Wuppertal, Macromolecular Chemistry, Gauss-Str.20, D-42097
Wuppertal
Details on the performance of polymer OFETs prepared from P3HT
with different molecular weights are presented. Lowering the molecular
weight of P3HTs dramatically decreases the mobility of the transistors.
This is mainly explained by the ability of the high-molecular weight fractions
to form well-ordered domains with planar backbone conformation
at room temperature and its low density of defects. On the other hand,
we observe a larger degree of crystallization for the low molecular weight
fractions, in accordance to recent publications by others. Based on experiments
performed at elevated temperatures and on annealed samples, we,
however, conclude that crystallinity is not the major factor controlling
the performance of these OFETs.
SYOH 5.73 Do 18:00 B
Dynamic measurements on organic FETs — •I. Hörselmann 1 ,
P. Kornetzky 2 , A. Herasimovich 1 , and S. Scheinert 1 — 1 TU Ilmenau
— 2 IMMS Ilmenau
The application of organic field effect transistors in electronic circuits
requires transistors with frequencies up to 100kHz. One possibility to investigate
the frequency response of the transistors is the measurement of
the transconductance.
For this purpose, we prepared organic FETs using an interdigital pattern
for the source/drain contacts to obtain high w/L ratios. The active
layer made from polyalkylthionphen (P3AT) was spin coated on top of a
silicon wafer with SiO2 as gate insulator.
The measured static current characteristics of the transistor allow an
estimation of the transconductance. At different operating points we
measured the frequency response of these quantity. The results show
the strong influence of the overlap capacities between the gate and
source/drain contacts resulting in a low cut-off frequency. Consequently,
a design using an organic insulator is necessary to realize higher cut-off
frequencies. Additionally, the accuracy was limited by hysteresis effects
already observed during the static measurements.

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
SYOH 5.74 Do 18:00 B
Spectromicroscopic Characterisation of All Polymer Transistor
Structures — •Klaus Mueller, Yevgen Burkov, and Dieter
Schmeisser — BTU Cottbus, Angewandte Physik-Sensorik, 03013 Cottbus,
P.O.Box 101344
In order to optimize organic field effect transistors, the characterization
of surfaces in terms of their roughness or chemical composition is
very important. We report on high resolution spectromicroscopic mapping
of organic thin film transistors by photoemission electron microscopy
(PEEM). It was shown that PEEM is a useful technique to characterize
the surface morphology (roughness), the chemical homogeneity or
the composition of structures in between the source and drain electrodes.
Mapping of surface potentials, especially at the interface electrode/channel
is possible. We compare different preparation methods and
the characterization at applied voltages is also shown.
The transistors itself were prepared by a new low cost method. The
electrodes for source and drain have been prepared by a plotting method
with colloidal graphite or carbon black as the conducting material. P3HT
was used as active layer and has been prepared by spin coating.
SYOH 5.75 Do 18:00 B
All Polymer Field-Effect-Transistors based on Low-Cost-
Microstructuring — •Klaus Mueller, Ioanna Paloumpa,
Carola Schwiertz, Agnes Jahnke und Dieter Schmeisser —
BTU Cottbus, Angewandte Physik-Sensorik, 03013 Cottbus
Thin film transistors with P3HT as active layer have been prepared by
spin coating. The electrodes for source and drain have been prepared by
a low cost plotting method with colloidal graphite or carbon black as the
conducting material. PEDOT or carbon black was used as gate electrode.
The devices, prepared by different methods and materials have been
characterized by electrical measurements, for example, their transfer and
output characteristics. Furthermore, the influence of different materials
on effects like hysteresis or reproducibility will be compared.
In addition, we describe a project investigating new types of biosensors
with functionalized gate electrodes. Exchanges of dipole moments or
charges by immobilisation of biomolecules will change the electrical characteristic
of the transistor, which leads to a sensing signal proportional
to their amount.
SYOH 5.76 Do 18:00 B
Stability Investigations on Polymer Light Emitting Diodes —
•Dessislava Sainova, Armin Wedel, and Bert Fischer — Fraunhofer
IAP, Geiselberstr. 69, 14 476 Golm
Organic light emitting diodes (LEDs) are an important topic in the
rapidly developing field of flat panel display technologies due to their
application potential as backlights and indicators. Polymer utilization as
emissive LED-layers offers the advantage of low-cost solution processing
on variable substrates.
A significant factor for the successful LED-application is the high operational
stability of the devices. The presentation concerns the stability
investigations of polymer LEDs. The entire LED preparation starting
from the careful substrate cleaning until the encapsulation was made using
clean room and glove box facilities. Optimisation procedures have
been made on different steps of the device preparation e.g. the deposition
conditions of the different layers constituting the devices and the
configuration of the electrodes. The lifetime tests on the encapsulated devices
have been performed in ambient atmosphere under constant current
driving mode of the experimental set up.
SYOH 5.77 Do 18:00 B
Fatigue mechanisms of organic light emitting diodes — •Roland
Schmechel, Frederik Neumann, Yuri A. Genenko, and Heinz
von Seggern — TU-Darmstadt; FB:Material- und Geowissenschaft;
Petersenstr.23; D-64287 Darmstadt
A study on possible electrical fatigue mechanisms in organic light emitting
diodes (OLEDs) is presented. In order to distinguish bulk and interface
properties, electroluminescence (EL) and photoluminescence (PL)
intensities are measured simultaneously during device operation. In addition,
I-V characteristics were recorded before and after fatigue. Unlike an
almost constant PL, a strong decrease in EL is observed indicating an interface
related fatigue mechanism. The I-V characteristics differ strongly
before and after the device operation, especially in the low forward voltage
regime. Whereas the I-V characteristics of the virgin device can be
explained by space charge limited currents and field dependent charge
carrier mobilities, the fatigued, but still operating device has developed
a low Ohmic parallel resistance. At present we conclude that a fatigued
device shows additional conductive pathways through the bulk and a disturbed
charge carrier balance due to reduced injection of charge carriers.
SYOH 5.78 Do 18:00 B
High Efficiency and Low Voltage p-i-n Electrophosphorescent
OLEDs with Double Emission Layer — •Gufeng He, Martin
Pfeiffer, and Karl Leo — Institut fuer Angewandte Photophysik,
Technische Universitaet Dresden, D-01062 Dresden,Germany
We demonstrate high-efficiency and low-voltage organic phosphorescent
light-emitting devices employing a green phosphor,
tris(2-phenylpyridine) iridium [Ir(ppy)3].
The intrinsic emitting layers are sandwiched between two p- and ndoped
layers. The p-i-n structure results in efficient carrier-injection from
both contacts into the doped transport layers and low ohmic losses. Thus,
low operating voltages are obtained compared to conventional undoped
OLEDs.
By doping Ir(ppy)3 into both electron- and hole-transport hosts, a
power efficiency of 70 lm/W and external quantum efficiency of 19.5 at
100 cd/m2 (2.95V). More importantly, the efficiency decays only weakly
with increasing current density (or brightness). A quantum efficiency of
13.5 luminance of around 50,000 cd/m2. This improvement can be attributed
mainly to the confinement of the recombination region to the
interface of the dye doped electron- and hole-transport hosts. Thus, the
influence of electron or blocking layers is reduced as compared to conventional
single-emission-layer structures and charge accumulation at the
interfaces of these blocking layers is avoided.
SYOH 5.79 Do 18:00 B
Dynamics of Charge Carrier Transport and Electroluminescence
in Organic Light-Emitting Diodes — •Anton G. Mückl 1
and Wolfgang Brütting 2 — 1 Experimentalphysik II, Universität
Bayreuth, D-95440 Bayreuth — 2 Experimentalphysik IV, Universität
Augsburg, D-86135 Augsburg
When describing the dynamics of charge carrier transport and recombination
processes in organic light-emitting devices not only the dependence
of the drift mobility of the majority charge carriers on temperature
and applied electric field is important but also the dynamics of the minority
charge carriers should be considered. We have investigated the
mobility of electrons and holes in Alq3 at various temperatures and electric
fields using time resolved electroluminescence measurements on a
specially designed multilayer OLED structure. Both, electron and hole
mobility show a Poole-Frenkel-type dependence on temperature and electric
field, however in contrast to the electron transport the hole transport
is found to be non-dispersive with a temperature independent field enhancement
factor. These results indicate clearly the mechanisms of electron
and hole transport in Alq3 to be of different nature.
We also measured the time-resolved current through unipolar and bipolar
single and double layer OLED structures at various temperatures. The
decay of the current towards the steady-state value will be discussed in
terms of the dynamics of the built-up of space charges and trap filling.
SYOH 5.80 Do 18:00 B
Polymer light-emitting diodes containing dendronized emitters
— •Frank Jaiser 1 , Xiaohui Yang 1 , Dieter Neher 1 , Jianqiang
Qu 2 , and Klaus Müllen 2 — 1 Universität Potsdam, Institut für Physik,
Am Neuen Palais 10, 14469 Potsdam — 2 Max-Planck-Institut für Polymerforschung,
Ackermannweg 10, 55128 Mainz
One approach to the construction of efficient polymer light-emitting
diodes is to dope well-defined emitting dyes into a suitable polymer hosts.
Such dopants can improve LED efficiency by either influencing charge
carrier transport in the material or being a highly-emissive species in the
system. In this respect, various fluorescent and phosphorescent dyes have
been studied in the past. In fact, both types of dyes have been used to
tune the emission color through the visible spectrum.
The understanding of excitation transfer between host and guest
molecules is crucial for the construction of efficient LEDs. Possible transfer
routes are Förster and Dexter transfer or charge trapping on the
guest molecules. Depending on the spatial distance between guest and
host molecules, the different possible transfer mechanisms show vastly
different transfer rates. Dendronization of small molecules is an elegant
way to control this intermolecular distance without changing the electronic
structure of the emitting core. We have studied polymers doped
with different generations of perylene dendrimers. We found that den-

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
dronization does not help to suppress luminescence quenching in thin
films but decreases the probability of direct charge trapping on the dye.
SYOH 5.81 Do 18:00 B
Polymer electrophosphorescence with high power conversion
efficiencies — •Xiaohui Yang 1 , Frank Jaiser 1 , Dieter Neher 1 ,
Dirk Hertel 2 , Thomas Däubler 2 , and Klaus Bonrad 2 —
1 University of Potsdam, Institute of Physics, Am Neuen Palais 10, 14469
Potsdam, Germany — 2 Schott Spezialglas GmbH, Hattenbergstraße 10,
55122 Mainz, Germany
We demonstrate efficient single-layer polymer phosphorescent lightemitting
devices based on a green-emitting iridium-complex blended
into the polymer host poly (N-vinyl carbazole), co-doped with electrontransporting
and hole-transporting molecules. Efficiencies and current
densities of the devices increase with increasing iridium-complex concentration.
The devices with high iridium complex concentration can be
operated at relatively low voltages, resulting in a large power conversion
efficiency of up to 19.2 lm/W at luminance efficiencies exceeding 30 cd/A.
The overall performances of these devices are approaching those of small
molecule multilayer devices, which suggests that efficient electrophosphorescent
devices with acceptable operating voltages can be achieved in very
simple device structure fabricated by spin-coating.
SYOH 5.82 Do 18:00 B
Investigation of electric field in organic thin film devices by
electroabsorption spectroscopy — •Wenge Guo, Jens Drechel,
Michael Hoffmann, Martin Pfeiffer, and Karl Leo — Institut
fuer Angewandt Photophysik, Dresden,Germany
Electroabsorption (EA) spectroscopy is a non-destructive technique
used to study the internal electric field distribution in organic light emitting
diodes and organic solar cells. In EA measurement, an electric field
modulation is applied to the device and a synchronous change in the optical
absorption coefficient is detected. The change in the amplitude of
the optical absorption coefficient at the fundamental frequency ? of the
applied electric field is proportional to the static internal electric field
in the device. As a starting point, we conduct electroabsorption measurements
on polycrystalline MePTCDI and PTCDA thin single layer
devices. EA spectra at 1? and 2? are obtained. In EA measurements at
1?, the EA signal vanishes as applied DC bias compensate the build-in
potential due to the work function difference of the two electrodes. From
this, a reasonable built-in potential (0.5 0.7eV) is observed. Since the
EA response at 1? is linear with the applied DC bias in single layer devices,
this method can be used further for characterization of static field
distribution in multilayer devices.
SYOH 5.83 Do 18:00 B
Linewidth-limited energy transfer in single conjugated polymer
molecules — •John Lupton 1 , Juergen Mueller 1 , Florian
Schindler 1 , Ullrich Scherf 2 , and Jochen Feldmann 1 —
1 Photonics and Optoelectronics Group, Sektion Physik, LMU Muenchen
— 2 FB Chemie, Universitaet Wuppertal
Single molecule fluorescence spectroscopy is a powerful tool, which allows
a direct distinction between homogeneous and inhomogeneous spectral
broadening. We apply this technique to gain fundamental insight into
energy transfer processes in conjugated polymers relevant to molecular
electronics. At low temperatures we are able to identify individual homogeneously
broadened chromophore units on the polymer chain. Using
time resolved and polarisation sensitive fluorescence spectroscopy we image
the intramolecular transfer of excitation energy from higher energy
segments on the chain to lower energy segments. As the temperature is
raised we find that the emission lines of individual chromophore units
are broadened. Concomitantly, the average polarisation anisotropy decreases,
suggesting that excitation energy is distributed across different
chromophore units. Studies of the single chain fluorescence as a function
of time show a pronounced blinking behaviour of the multichromophoric
chain at room temperature, but not at low temperatures, demonstrating
that chromophore coupling is controlled by temperature and spectral
linewidth (Mueller et al., Phys. Rev. Lett. 2003). High resolution fluorescence
spectroscopy also enables us to gain insight into the strength
and nature of vibrational coupling and structural relaxation on a single
molecule level.
SYOH 5.84 Do 18:00 B
Time resolved temperature measurements using molecular
thermometers — •Joachim Stehr, Gunnar Raschke,
Thomas A. Klar, John M. Lupton, and Jochen Feldmann
— Photonics and Optoelectronics Group, Department of Physics and
CeNS, Ludwig-Maximilians-Universität, Amalienstrasse 54, 80799
Munich
Platin octaethyl porphyrin (PtOEP) shows a photoluminescence (PL)
spectrum dominated by a red band at 650 nm and a thermally activatable
band at 540 nm. Therefore, this molecule can be used as a molecular
thermometer by taking the ratio between these two emission bands. A
resolution of 0.25 K has been demonstrated [1]. We want to use these
molecular thermometers to observe heating and cooling dynamics at the
surface of micro and nano objects. Heating is accomplished either by
pulsed electrical excitation of thin wires or by pulsed optical excitation
of nanoparticles. The optical excitation of the PtOEP molecules is delayed
with respect to the heating pulses. Towards the realisation of such
a molecular thermometer we also investigate the internal dynamics of the
PtOEP molecules following excitation.
[1] J. M. Lupton, Appl. Phys. Lett. 81, 2478 (2002)
SYOH 5.85 Do 18:00 B
A Spectroscopic Investigation Using Model Oligofluorenes —
•Chan Im 1 , Chunyan Chi 1 , Panagiotis E. Keivanidis 1 , Andreas
Ziegler 1 , Sigrud Höger 1 , Gerhard Wegner 1 , Jung-Ho Jo 2 , Ji-
Hoon Kang 2 , and Do-Young Yoon 2 — 1 Max-Planck Institute for
Polymer Research, Ackermannweg 10, 55128 Mainz, Germany — 2 Seoul
National University, Department of Chemistry, Seoul, South-Korea
Polyfluorene derivatives are very promising electroluminescent materials
due to their highly effcient electroluminescence with blue emission
color. Unfortunately, there is still a well-known problem that a broad
green emission band appears and grows up during the operating of light
emitting devices. While many groups have shown that ketonic defects on
polymer backbones are mainly responsible for this green band, there are
still many questions which should be answered as for the population of
these green emissive states. To understand the nature of such ketonic defect
states in detail, we have decided to study a model system including
a number of oligofluorenes both with and without an embedded ketone
unit. After synthesis of highly pure oligofluorenes, delayed fluorescence
measurements were performed at various temperatures either as films or
as dilute solutions to estimate photoluminescent properties for long lived
emission bands, e.g. the green band. Additionally, fast spectroscopy using
a streak camera within a time range of nanoseconds was carried out in
order to trace blue singlet emission decay behavior. Those detailed spectroscopic
results show significantly different photoluminescence behavior
between oligofluorenes with various sidechain groups especially in solid
state.
SYOH 5.86 Do 18:00 B
Towards polymer spintronics: Manipulating the triplet state in
conjugated polymers — •M. Reufer 1 , J. M. Lupton 1 , J. Feldmann
1 , and U. Scherf 2 — 1 Photonics and Optoelectronics Group,
Physics Department, University of Munich, Germany — 2 Fachbereich
Chemie, Universität Wuppertal, Gauss-Str. 20, 42097 Wuppertal, Germany
Organic semiconductors are characterised by strong exchange interactions,
which typically lead to a large energetic splitting of the singlet
and triplet states. The presence of both of these levels is crucial to the
photophysics of molecular semiconductors and particularly relevant to
the operation of light-emitting diodes. Lupton et al. recently presented
a novel technique to visualise triplet excitations in conjugated polymers
using a new class of materials exhibiting strong room temperature phosphorescence
due to trace amounts of metallic impurities [1]. Here we
demonstrate that we can manipulate the triplet state by applying external
perturbations in the form of electrical or optical fields. We can
directly monitor and time resolve triplet creation and annihilation due
to electric field induced carrier dissociation and recombination. As the
conjugated polymers used exhibit strong optical gain, we are also able
to use stimulated emission to deplete the singlet state before intersystem
crossing to the triplet state occurs. This allows us to image and
time resolve the process of spin-forbidden intersystem crossing and the
associated spin flip in organic semiconductors directly.
[1] Lupton et al., Phys. Rev. Lett. 89, 167401 (2002)

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
SYOH 5.87 Do 18:00 B
Photophysical properties of core substitution at perylene
derivates — Harald Graaf 1 , Christine Mattheus 2 , Derck
Schlettwein 2 , Gottfried Heinrich Bauer 1 , •Harald Graaf 1 ,
Christine Matth eus 2 , Derck Schlettwein 2 , and Gottfried
Heinrich Bauer 1 — 1 Inst. of Physics, CvO University Oldenburg —
2 Dept. of Pure and Applied Chemistry, CvO University Oldenburg
Chemical substitution in bay-position at perylene tetra carboxylic acid
derivates (PTCD) e.g. by chlorine substitution leads to a twisting of the
aromatic core and as a consequence influences the photophysical properties
especially in the solid state. Unlike the unsubstituted PTCD, however,
thin films (≈ 30nm) of the bay-chlorinated Cl4PTCD showed almost
no chromophore coupling, directly measured by optical absorption
spectroscopy. The formation of excimers is prevented so that an emission
from uncoupled monomers could be found in a quantum efficiency
comparable to that in solution. Also the arrangement of the molecules
in the film is influenced by the hindered coupling which was seen in an
unstructured morphological configuration measured by AFM. In thicker
films (≥ 100nm) a slow ordering process was observed and an excimer
formation could be obtained. More over we have prepared monolayers of
substituted molecules by covalent bounding at a modified glass surface
in order to study two- dimensional intermolecular interactions.
SYOH 5.88 Do 18:00 B
Structural and Optoelectronic Properties of Different Phases
of the Electroluminescent Material Alq3 — •Michael Cölle 1 ,
Christoph Gärditz 1 , Jürgen Gmeiner 1 , Stefan Forero 1 , and
Wolfgang Brütting 1,2 — 1 Experimental Physics II, University of
Bayreuth, 95440 Bayreuth, Germany — 2 Experimental Physics IV, University
of Augsburg, 86135 Augsburg, Germany
Tris(8-hydroxyquinolinato)aluminium(III) (Alq3) stands as one of the
most successful materials used in OLEDs for display applications. Although
the partly nanocrystalline character of evaporated films used in
these applications is known, so far comparatively few investigations have
been devoted to the crystalline state of this material. Another still unresolved
issue concerns the isomery of the Alq3 molecule. From theory
is well-known that Alq3 can occur in two different geometrical isomers:
meridional and facial. However, until recently all existing phases ( α, β
and γ) have been found to consist of the meridional isomer. Recently we
have reported a new crystalline phase of Alq3 (δ-Alq3) exhibiting strongly
blue-shifted fluorescence. Its significantly different optical properties have
been tentatively discussed in terms of the isomery of the Alq3 molecule.
In this contribution we will present an in-depth characterisation of the
different phases of Alq3 by combining thermal, structural and vibrational
analysis. These data provide the first unambigous evidence for the existence
of the facial isomer in the blue-luminescent δ-phase of Alq3. These
results will be correlated to the optoelectronic properties of Alq3 and
Alq3-based thin film electroluminescent devices.
SYOH 5.89 Do 18:00 B
EPR spectroscopy on different phases of electroluminescent
Alq3 — •A. Mirea 1,2 , M. N. Grecu 2 , M. Cölle 1 , and M.
Schwoerer 1 — 1 Experimentalphysik II, Universität Bayreuth,
D-95440 Bayreuth — 2 National Institute for Materials Physics, R-76900
Bucharest, Romania
Tris(8-hydroxyquinolino)aluminum (Alq3) is one of the most extensive
used electron conductor and emitting layer material in organic lightemitting
devices (OLED’s). We report on X- and Q-band temperature
dependence EPR experiments on different crystalline Alq3 phases formed
by using the train sublimation method. The room temperature X-band
EPR spectra show two types of signals centered at g=2 and g=4 whose
relative intensity are dependent on the crystalline phase nature. The g=2
signal is of a very particular nature - its intensity is temperature independent
between 10-300 K for all phases, and increases of 4-6 times under
room temperature e − - or γ-irradiation. By choosing appropriate annealing
conditions (663-673 K temperature range, inert atmosphere) of as
prepared Alq3 phases, new features in the Q-band EPR spectra appear.
Their simulation and analysis based on a spin Hamiltonian appropriate
to a high spin system (S =1, S=3/2) is in good agreement with the existence
of triplet and quartet spin states in annealed Alq3. The D and
E zero field parameters are evaluated. The EPR results, correlated with
others investigation methods, are discussed in terms of different molecular
models.
SYOH 5.90 Do 18:00 B
Origin of delayed fluorescence in conjugated polymers — •Dirk
Hertel 1 and Chan Im 2 — 1 Institute of Physical Chemistry, University
of Cologne, Luxemburger Str. 116, 50939 Cologne, Germany — 2 Max-
Planck Institute for Polymer Research, Ackermannweg 10, 55021 Mainz,
Germany
We report on measurements of phosphorescence (Ph) and delayed
fluorescence (DF) in poly(2,7-(9,9-bis(2-ethylhexyl)fluorene)) (PF2/6)
present as dilute solid solution as well as in bulk films. From combined
experimental investigations of the time and intensity dependence of DF
and Ph as well as the temperature dependence of DF we are able to show
that DF in PF2/6 both in solution and film is dominated by triplet-triplet
annihilation (TTA). As a consequence of the intra-chain diffusion and,
hence, relaxation of triplets, the kinetics of the bimolecular reaction show
a turn-over from dispersive to non-dispersive regime as borne out by the
DF decay. This in accord with theoretical predictions of TTA in disordered
solids.
The dominance of TTA as source of DF in PF2/6 films is in marked
contrast to the DF in MeLPPP, although the chemical structures of the
materials are similar. In MeLPPP geminate pair recombination is responsible
for DF. In order to understand the relation between chemical
structure and routes of DF generation we have investigated the delayed
fluorescence on the electron-accepting poly(9,9-dioctylfluorene-cobenzothiadiazole)
F8BT present as film and solid solution.
SYOH 6 Single Molecules and Molecular Clusters
Zeit: Freitag 10:15–11:15 Raum: H1
Hauptvortrag SYOH 6.1 Fr 10:15 H1
Growth control and optics of organic nanoaggregates — •Horst-
Günter Rubahn — Fysisk Institut, Syddansk Universitet, DK-5230
Odense M, Danmark
Nanoaggregates and ultrathin films made of organic molecules might
become integral parts of new electronic and optoelectronic devices due to
their interesting optical properties as well as their chemical and mechanical
flexibility. We present a new way to generate by a combination of
external control and self assembled growth well ordered, crystalline nanoscaled
structures (nanofibers and rings) of highly luminescent organic
materials (1). It is shown that microscopic growth control results in low
defect densities and thus strongly improved optical properties of these
aggregates. Since the nanofibers possess macroscopic lengths but nanoscaled
widths and heights they are ideal model systems for investigating
limitations and possibilities of optics on the nanoscale. This aspect is
exploited in the present talk via a combination of structural and morphological
sensitive methods such as low energy electron scattering and
atomic force microscopy with optical methods such as epifluorescence
microscopy, scanning near field microscopy and two-photon femtosecond
resolved spectroscopy. 1: F. Balzer and H.-G.Rubahn, Optics and Pho-
tonics News, 14(12), Dec.2003.
Hauptvortrag SYOH 6.2 Fr 10:45 H1
Electronic transport through single molecules — •H. v.
Löhneysen 1,2 , F. Heinrich 3 , M. M. Kappes 3 , R. Krupke 3 , M.
Major 3 , J. Reichert 3 , and H. B. Weber 3 — 1 Physikalisches
Institut, Universität Karlsruhe, 76128 Karlsruhe — 2 Forschungszentrum
Karlsruhe, Institut für Festkörperphysik, 76344 Karlsruhe —
3 Forschungszentrum Karlsruhe, Institut für Nanotechnologie, 76344
Karlsruhe
Electronic transport measurements through single π-conjugated
molecules can be realized using mechanically controlled break junctions
to couple thiol end groups of the molecules to two gold electrodes. We
have investigated transport through π-conjugated molecules which differ
by their spatial symmetry and π-conjugated connectivity. The current
voltage characteristics (IV s) of the metal-molecule-metal system reflect
the spatial symmetry and topology of the molecules with respect to the
direction of current flow indicating that transport occurs indeed through
single molecules [1]. Fluctuations in the IV s are a manifestation of the
variation of level spacings of the system, which depend crucially on the

Symposium Organic and Hybrid Systems for Future Electronics Freitag
bonding between thiol end groups and Au electrodes.
For the future electronics, carbon nanotubes are the prime candidates.
Recent progress in the controlled deposition of nanotubes between electrodes
and separation of metallic and semiconducting nanotubes [2] is
reported.
[1] J. Reichert et al., Phys. Rev. Lett. 88, 176804 (2002)
[2] R. Krupke et al., Science 301, 344 (2003)
SYOH 7 Molecular Systems and Applications
Zeit: Freitag 11:15–11:55 Raum: H1
Fachvortrag SYOH 7.1 Fr 11:15 H1
Geometric and electronic structure of sexiphenyl grown
on metal, oxygen modified metal and oxide — •Michael
Ramsey 1 , Georg Koller 1 , Jan Ivanco 1 , Barbara Winter 1 ,
Steve Berkibile 1 , Roland Resel 2 , and Christian Teichert 3 —
1 Experimental Physics, University of Graz, A-8010 Graz, Austria —
2 Solid State Physics,TU-Graz,A-8010,Austria — 3 Physics, University
Leoben,A-8700 Leoben,Austria
For device relevant organic films the organic films crystal structure,
molecular orientation, film morphology and electronic structure are of
prime importance. It will be demonstrated that all these properties can
be drastically affected by the exact nature of the substrate surface on
which they are grown. Here the results of sexiphenyl (6P) growth on
model substrates ranging from clean and oxygen modified single crystal
metal surfaces through to clear conducting oxide surfaces will be discussed.
For growth on Al(111) at room temperature the ordered monolayer
that forms provides the basis for the highly crystalline, single phase,
epitaxial thick 6P that results. Chemisorbed oxygen at the Al surfaces
leads to the formation of 6P films of near vertically oriented molecules. In
contrast oxygen in the Ni(110)-(2x1)O acts as a template for the formation
of strings of azimuthally oriented molecules parallel to the substrate.
On TiO2(110) no wetting layer can be formed and large needle like 6P
crystallites form. The micrometer long needles are oriented exclusively
perpendicular to the atomic rows of the surface while the molecules within
them are parallel them.
SYOH 8 Hybrid Systems
Fachvortrag SYOH 7.2 Fr 11:35 H1
Ambipolar Organic Field-Effect Transistor based on an Organic
Heterostructure — •Constance Rost 1 , David J. Gundlach 2 ,
Siegfried Karg 1 , and Walter Rieß 1 — 1 IBM Research, Zurich
Research Laboratory, CH-8803 Rüschlikon, Switzerland — 2 Laboratory
for Solid State Physics, Department of Physics, ETH Zurich, CH-8093
Zürich, Switzerland
Ambipolar charge injection and transport are a prerequisite for a lightemitting
organic field-effect transistor (LE-OFET). Organic materials,
however, typically show unipolar charge-carrier transport characteristics.
Consequently, organic thin-film field-effect transistors based on a single
material as active layer can typically either be operated as p- or as nchannel
device. We show that by using a heterostructure with pentacene
as hole-transport and Ditridecylperylene-3,4,9,10-tetracarboxylic diimide
(PTCDI-C13H27) as electron-transport material, ambipolar characteristics,
i.e. simultaneous p- and n-channel formation, can be observed in
a single device. An OFET structure is investigated in which electrons
and holes are injected from Mg top and Au bottom contacts into the
PTCDI-C13H27 and pentacene layers, respectively. This device architecture
serves as a model structure for ambipolar field-effect transistors,
which are a prerequisite for light-emitting field-effect transistors.
Zeit: Freitag 12:10–13:10 Raum: H1
Hauptvortrag SYOH 8.1 Fr 12:10 H1
Inorganic Nanorods: Synthesis, Properties, Photovoltaic Applications
— •Delia Milliron, Ilan Gur, and Paul Alivisatos —
University of California, Berkeley, College of Chemistry, Berkeley, CA
94720, USA
Inorganic nanocrystals with well defined shapes are important for understanding
basic size-dependent scaling laws, and may be useful in a
wide range of applications. Methods for controlling the shapes of inorganic
nanocrystals are evolving rapidly. This talk will focus on a strategy
that involves pyrolysis of organometallic precursors in mixtures of hot
organic surfactants. The surfactant mixtures can be used to control the
growth rates of different facets of the nanocrystals, allowing for wide tunability
of shape. This will be illustrated with CdSe and Co nanocrystals.
Both of these materials show pronounced variation of fundamental properties
with aspect ratio. The semiconductor nanorods can be embedded
in plastic films, and they can be aligned in a variety of ways. This talk will
describe recent work on the production of solar cells based on nanoscale
composites of CdSe nanorods and poly-alkyl thiophene semiconductor
polymers, as well as very recent results on the isolation of liquid crystal
phases of semiconductor nanorods. Finally, we will present recent results
on the synthesis of colloidal semiconductor heterostructures with well-
controlled branch points.
Hauptvortrag SYOH 8.2 Fr 12:40 H1
Understanding Donor-Acceptor Photovoltaic Devices — •Neil
Greenham, Baoquan Sun, Henry Snaith, James Barker,
Richard Friend, and Catherine Ramsdale — Cavendish
Laboratory, Madingley Road, Cambridge CB3 0HE, United Kingdom
The power conversion efficiency of a polymer photovoltaic device is determined
by the short-circuit quantum efficiency, the open-circuit voltage
and the shape of the current-voltage curve. A high short-circuit quantum
efficiency requires efficient charge separation and charge collection, and
I will present photovoltaic devices based on conjugated polymers and
CdSe tetrapods which provide efficient charge transport perpendicular
to the plane of the film and which have solar power conversion efficiencies
in excess of 3 processes which determine the open-circuit voltage
in donor-acceptor devices, and will demonstrate the importance of diffusion
currents in generating an additional intensity-dependent open-circuit
voltage. These ideas will be applied to bilayer and blended photovoltaic
devices, where numerical modelling allows the current-voltage curve to
be calculated under illumination.

Symposium Physics of Foams Tagesübersichten
Hauptvorträge
PHYSICS OF FOAMS (SYPF)
Herr Prof. John Banhart
Hahn-Meitner-Institut
Abteilung SF3
Glienicker Str. 100
14109 Berlin
E-Mail: banhart@hmi.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsaal H16)
SYPF 1.1 Mi 14:00 (H16) The foam/emulsion analogy in structure and drainage, Stefan Hutzler, Nicolas
Peron, Denis Weaire, Wiebke Drenckhan
SYPF 3.1 Mi 16:20 (H16) Die Stabilität metallischer Schäume, Dietmar Leitlmeier
Fachsitzungen
SYPF 1 Foams I Mi 14:00–14:30 H16 SYPF 1.1–1.1
SYPF 2 Foams II Mi 14:30–15:50 H16 SYPF 2.1–2.4
SYPF 3 Metallic Foams I Mi 16:20–16:50 H16 SYPF 3.1–3.1
SYPF 4 Metallic Foams II Mi 16:50–18:30 H16 SYPF 4.1–4.5
SYPF 5 Physics of Foams Di 14:30–16:30 C SYPF 5.1–5.4

Symposium Physics of Foams Mittwoch
Fachsitzungen
– Haupt-, Kurzvorträge und Posterbeiträge –
SYPF 1 Foams I
Zeit: Mittwoch 14:00–14:30 Raum: H16
Hauptvortrag SYPF 1.1 Mi 14:00 H16
The foam/emulsion analogy in structure and drainage —
•Stefan Hutzler, Nicolas Peron, Denis Weaire, and Wiebke
Drenckhan — Physics Department, Trinity College Dublin, Ireland
In recent years the study of the physics of foams has advanced across a
wide front. Often the analysis of a property will begin with the assertion
that the same description applies equally well to an emulsion. However,
this is rarely tested.
We have therefore revisited some of the key experiments, using a watersilicone
oil emulsion system (stabilised by surfactants) of similar scale to
familiar foam systems. Here we present illustrations of several ordered
SYPF 2 Foams II
structures in cylindrical tubes, essentially identical to those observed in
foams.
We have also performed the common foam experiment of “forced
drainage” on these emulsions, i.e. adding surfactant solution from the
top at constant flow rates. These experiments suggest that drainage is of
the Poiseuille type flow of liquid past the drops.
At high flow rates the drops exhibit oscillations within the emulsion,
eventually leading to a break-up of the arrangement. This differs from
the behaviour of foams, where varies types of convective instabilities set
in, once a critical flow rate, dependent on bubble size and geometry, is
exceeded.
Zeit: Mittwoch 14:30–15:50 Raum: H16
SYPF 2.1 Mi 14:30 H16
The role of geometrical optics for light transport in dry foams
— •Holger Stark 1 and MirFaez Miri 2 — 1 Universität Konstanz,
Fachbereich Physik, D-78457 Konstanz, Germany — 2 Institute For Advanced
Studies in Basic Sciences, Zanjan, Iran
Recent light-scattering experiments on foams suggest that the light
transport is diffusive. This means that single photons can be considered
as random walkers. However, there is a debate in literature about the
main mechanism underlying the random walk. One suggestion is that it
is based on light scattering from Plateau borders and/or vertices. On the
other hand, since the cells are much larger than the wavelength of light,
one can employ geometrical optics and follow a light beam or photon as
it is reflected by the liquid films with a probability r called the intensity
reflectance. This naturally leads to a random walk of the photons in
space.
Here we study the second mechanism based on geometrical optics in
two steps using numerical simulations. In a first model, we introduce
topological and geometrical disorder based on a 2D Voronoi foam model
and choose a constant r to investigate the influence of disorder. In a
second model, we use the realistic intensity reflectance r of thin films
and also consider disorder in the film thickness. Comparing our results
to recent experiments, we find that the geometrical optics approach reproduces
experimental features and the right order of magnitude for the
diffusion constant. This convinces us that geometrical optics is an important
mechanism for the diffusive light transport in foams.
SYPF 2.2 Mi 14:50 H16
Effect of colloidal charges on the thickness of foam films —
•Regine v. Klitzing, Branko Kolaric, and Tatjana Mauser
— Stranski-Laboratorium, TU Berlin, Str. d. 17. Juni 112, 10623 Berlin
Polymers can be used as stabilizers of foams. To use polymers in an
efficient way in surfactant systems, it is necessary to control and to manipulate
the building blocks, i.e. the single free-standing surfactant films
of a foam. In our experiments the film thickness is controlled on a mesoscopic
length scale (5-100 nm) by varying the outer pressure in a thin
film pressure balance. The sum of interactions (DLVO, steric, structural
forces) between the film surfaces is determined quantitatively by the disjoining
pressure. The addition of polyelectrolytes affects the (de)stability
of the film due to complexation between polymer and surfactant at the
film surfaces. In dependence on the charge combination of the surfactant
and polyelectrolyte either a Newton Black Film (NBF, stabilized by steric
repulsion) or a Common Black Film (CBF, stabilized by electrostatic repulsion)
occurs at high outer pressure. The influence of polyelectrolytes
on the film stability is compared to the effect of hard colloids.
SYPF 2.3 Mi 15:10 H16
Single foam films and macroscopic foams stabilized by CnTAB:
influence of the chain length — •Cosima Stubenrauch 1 , Judith
Schlarmann 1 , and Khristo Khristov 2 — 1 Institut für Physikalische
Chemie, Universität zu Köln, Luxemburgerstr. 116, D-50939 Köln,
Deutschland — 2 Institute of Physical Chemistry, Bulgarian Academy of
Sciences, u. Acad, G. Bonchev 11, Sofia 1113, Bulgarien
A quantitative comparison of single foam films and the corresponding
macroscopic foams is very difficult. One problem is the fact that investigations
of foam films are usually performed at constant capillary pressures
P, whereas in macroscopic foams P is a function of the height of the
foam column. A way out of this dilemma is to examine films and foams
at the same P. The method of choice for the foam films is the ”thin film
pressure balance ” (TFPB) with which the film thickness is measured as
a function of P. The corresponding investigation of macroscopic foams is
based on the ”foam pressure drop technique” (FPDT). As in the TFPB
a constant P is applied at which the rate of drainage as well as the lifetime
of the foam is determined. In order to study the correlation between
the properties of films and foams we investigated the homologous series
of the cationic alkyl trimethyl ammonium bromides CnTAB with n =
10,12,14, and 16. For this series a strong increase of foam film stability
was observed when the chain length was increased from n = 12 to n =
14. In order to show that this change is also reflected in the properties of
the macroscopic foam we measured the lifetime and the drainage of the
respective CnTAB foams with the FPDT as a function of P. The results
will be compared and discussed.
SYPF 2.4 Mi 15:30 H16
Foam Analysis by the Foam Pressure Drop Technique — •R.
Miller 1 , C. Stubenrauch 2 , Khr. Khristov 3 , L. Christov 3 ,
A.V. Makievski 4 , and D. Exerowa 3 — 1 MPI für Kolloid- und
Grenzfl¨chenforschung, Am Mühlenberg 1, D-14476 Golm, Germany
— 2 Institute Phys. Chem., University Cologne, Luxemburger Str.
116, D-50939 Cologne, Germany — 3 Institute of Physical Chemistry,
Bulgarian Academy of Sciences, Sofia 1113, Bulgaria — 4 SINTERFACE
Technologies, Volmer Str. 5-7, D-12489 Berlin, Germany
Foam is a complex capillary system and the processes of foam drainage
and foam destruction (stability) are important for its properties. These
processes are interrelated in a very peculiar way. The questions on which
would be the predominating mechanism or how would the processes impact
on each other depend entirely on the characteristics of the foam.
The complex relationships make it very hard to assess the different processes
independently. Moreover, for many application the drainage is important,
for example in firefighting, food industry, while for others the
lifetime (stability) plays the major role, such as in foam concentration,
foam separation.
The characterisation of foams by the foam pressure drop technique

Symposium Physics of Foams Mittwoch
gives access to the main properties of aqueous foams in a reasonably
short time even if the foam is very stable. This technique determines the
decrease of the water content W as a function of time t (drainage) and
the lifetime τp of a foam at a definite reduced pressure Pr (pressure drop).
It is found that the rate of drainage is influenced by the type of foam
film, namely Common Thin Film (CTF), Common Black Film (CBF),
Newton Black Film (NBF), and Bilayer Film (BF). The type of film the
foam consists of also plays a role for the lifetime τp. Measuring τp as a
function of ∆P one obtains characteristic curves for foams consisting of
SYPF 3 Metallic Foams I
CTFs, CBFs, NBFs, and BFs, respectively.
Example experiments are given for some surfactant solutions and discussed
with respect to the correlation between single foam films and
macroscopic foams. The properties of selected foam films will also be
discussed with respect to the dynamic and mechanical properties of the
respective adsorption layers. This attempt demonstrates one of the basic
open questions – what are the interrelations between the properties
of adsorption layers and respective isolated liquid foam films with the
properties of the final foam.
Zeit: Mittwoch 16:20–16:50 Raum: H16
Hauptvortrag SYPF 3.1 Mi 16:20 H16
Die Stabilität metallischer Schäume — •Dietmar Leitlmeier —
ARC Leichtmetallkompetenzzentrum Ranshofen (Austria)
Verschiedene Möglichkeiten zur Herstellung metallischer Schäume werden
vorgestellt und ihr Anwendungspotential verglichen. Die wissenschaftlich
interessante Frage der Stabilisierung von Metallschäumen wird
diskutiert und am Beispiel der durch Einblasen von Gasen in partikelverstärkte
Metallschmelzen im Detail behandelt. Bei diesen Schäumen
ist die Rolle der Keramikpartikel ebenso wichtig wie die Oxidschichtbildung
an der Phasengrenze Gasblase/flüssiges Metall und der Einfluss der
SYPF 4 Metallic Foams II
Viskositaet.
Es wurde der Mindestpartikelgehalt zur Erzeugung stabiler Schäume
ebenso bestimmt, wie der Partikelgehalt der erstarrten Schäume in
Abhängigkeit der Blasensteighöhe, der Blasengrösse und der Schmelzezusammensetzung.
Die sich an der Phasengrenze Gasblase/flüssiges Aluminium bildende
Oxidschicht hängt neben anderen Parametern vor allem von der Zusammensetzung
des verwendeten Aufschäumgases ab. Der Einfluss verschiedener
Gase auf die gebildete Oxidschicht wurden neben einem makroskopischen
Vergleich mit dem REM analysiert und Sputter-Tiefenprofile der
Elementzusammensetzung mit Hilfe der Augersonde erstellt.
Zeit: Mittwoch 16:50–18:30 Raum: H16
SYPF 4.1 Mi 16:50 H16
Die Bildung und der Kollaps von Metallschäumen — •Heiko
Stanzick 1 , Frank von Zeppelin 2 , Lukas Helfen 3 , Tilo Baumbach
4 , Michael Hirscher 2 und John Banhart 5 — 1 Fraunhofer Institut
IFAM, 28359 Bremen — 2 Max-Planck-Institut für Metallforschung,
70569 Stuttgart — 3 ESRF Grenoble, F-38000 Grenoble — 4 Fraunhofer
Institut IZFP, Außenstelle EADQ, 01326 Dresden — 5 Hahn-Meitner-
Institut, 14109 Berlin
Details der Schaumbildung und des Kollapses bei Metallen wurden mit
radioskopischen Methoden untersucht.
Es konnten dadurch in-situ Bilder von der inneren Struktur flüssiger, sich
verändernder Metallschäume aufgenommen werden und somit Effekte im
Inneren (z.B. Koaleszenz) eines Metallschaumes beobachtet werden.
Mittels Thermischer Desorptionsspektroskopie wurde das Ausgasverhalten
während des Schäumens mit der Entgasung der Treibmittel verglichen.
Dabei zeigte sich, dass beim Kompaktieren frische, nicht oxidierte
Oberflächen am Treibmittelpulver entstehen.
SYPF 4.2 Mi 17:10 H16
The decomposition behaviour of as-received and oxidized TiH2
foaming-agent powder — •Biljana Matijasevic 1,2 , Sebastian
Fichter 1 , Ivo Zizak 1 , and John Banhart 1,2 — 1 Hahn-Meitner-
Institut Berlin, SF3, SE5, SF4, Glienicker Str. 100, 14109 Berlin, Germany
— 2 Technical University Berlin, Institute of Material Sciences and
Technology, Straße des 17. Juni 135, 10623 Berlin, Germany
Aluminium foam is created by expanding compacted mixtures of aluminium
alloy powders and titanium hydride (TiHX). As there is a mismatch
between the melting point of aluminium alloys and the decomposition
temperature of TiHX, the latter should be subjected to thermal
and / or oxidizing treatments to try to adjust these temperatures. The
influence of various pre-treatments on the release of hydrogen from the
blowing agent TiHX is investigated. For this purpose the decomposition
of TiHX powders is examined by differential scanning calorimetry (DSC),
thermogravimetric analysis (TGA) and mass spectrometry (MS). First
in situ X-ray diffraction experiments at the synchrotron BESSY 2 combined
with scanning electron microscopy (SEM) and energy dispersive
X-ray analysis (EDX) are used to further characterize the effects of the
treatments.
SYPF 4.3 Mi 17:30 H16
Stabilisierung flüssiger metallischer Schäume durch feste Partikel
— •Thomas Wübben 1 , György Kaptay 2 , and Stefan Odenbach
1 — 1 ZARM, Universität Bremen — 2 Universität Miskolc, Ungarn
Metal foams are porous metallic structures. Their advantageous den-
sity to stiffness ratio leads to a variety of applications especially in automotive
industry.
Solid metal foams are usually produced by solidification of a liquid
metallic foam. The latter is generated by the introduction of gas into a
melt analogous to aqueous foams. However, while the mechanisms leading
to stable aqueous foams are well understood, this is not the case for
metallic foams. In contrast for example to soap foams, no surface active
or polar substances are present in liquid metals. It is only known empirically
that solid particles have a major influence on the stability of a
liquid metallic foam.
In our presentation a model describing a possible stabilizing mechanism
in metallic foams will be discussed and compared to experimental
observations. One major result or our investigations is the fact that the
inner surface of a metal foam is proportional to the grain size of the used
powder.
SYPF 4.4 Mi 17:50 H16
Charakterisierung von Metallschäumen mittels Synchrotron-
Tomographie und 3D-Bildanalyse — •A. Rack 1 , A. Haibel 1 , B.
Matijasevic 1,2 , H. Riesemeier 3 , G. Weidemann 3 , J. Goebbels 3
und J. Banhart 1,2 — 1 Hahn-Meitner-Institut Berlin, Abteilung Strukturforschung,
Glienicker Str. 100, 14109 Berlin — 2 Institut für Metallphysik,
Hardenbergstr. 36, 10623 Berlin — 3 Bundesanstalt für Materialforschung
und -prüfung, Unter den Eichen 87, Haus 60, 12205 Berlin
Bei der Untersuchung von Metallschäumen hat sich in den letzten Jahren
zunehmend die Synchrotron-Tomographie als zerstörungsfreie Meßmethode
etabliert. Synchrotron-Tomogramme zeichnen sich sowohl durch
eine hohe Ortsauflösung als auch durch die Möglichkeit aus, die Elementzusammensetzung
eines Prüfkörpers räumlich zu bestimmen. Mittels
aus der Stochastischen Geometrie stammenden Verfahren zur 3D-
Bildanalyse [1] ist es möglich, statistische Informationen wie Größenverteilung
von Poren, Treibmittelpartikel oder Zellwandstärken sowie Korrelationen
zwischen Partikeln und Poren im Metallschaum zu bestimmen.
Wir untersuchen Schaum aus Zink- als auch aus Aluminiumlegierungen,
Treibmittel sind Titanhydrid oder Zirkonhydrid.
[1] J. Ohser and F. Mücklich, Statistical Analysis of Microstructures in
Materials Science, John Wiley & Sons, 2000
SYPF 4.5 Mi 18:10 H16
Methods for the quantitative analysis of high-resolution microtomography
datasets of metallic foams — •Oliver Brunke 1 ,
Stefan Odenbach 1 , and Felix Beckmann 2 — 1 ZARM Universität
Bremen, Am Fallturm, 28359 Bremen — 2 GKSS, Max-Planck-Str. 1,
21502 Geesthacht

Symposium Physics of Foams Mittwoch
Metallic foams are a rather new class of porous and lightweight materials
offering a unique combination of mechanical, thermal and acoustical
properties. Their high stiffness to weight ratio, acoustic damping properties
and thermal resistance provide possible applications in automobile
industry for instance as crash energy absorbers or acoustic dampers, or in
aerospace industry for lightweight parts in rockets or aircrafts. A promising
and versatile tool for the non-destructive investigation of the structure
SYPF 5 Physics of Foams
of metallic foams on a µm scale is X-ray or synchrotron X-ray tomography.
This technique yields 3D-datasets of the whole foam structure.
We will describe quantitative methods for the analysis of the pore and
material space of the µCT foam data and present first results obtained
by analysing foams examined at the W2 Beamline at HASYLAB/DESY
.
Zeit: Dienstag 14:30–16:30 Raum: C
SYPF 5.1 Di 14:30 C
Anordnungsmechanismen porenstabilisierender Partikel im
Metallschaum — •Astrid Haibel, Alexander Rack und John
Banhart — Hahn-Meitner-Institut Berlin, Glienicker Str. 100, 14109
Berlin
Die reproduzierbare Einstellbarkeit makroskopischer Eigenschaften
metallischer Schäume (z.B. Festigkeit, Härte, Energieabsorption) basieren
auf der exakten Kenntnis ihrer Mikrostruktur. Ein Verfahren
zur zerstörungsfreien Charakterisierung von Metallschäumen ist die
Synchrotron-Tomographie. Neben der Bestimmung der Porengrößenund
der Lamellendickenverteilung kann mit Hilfe der gewonnenen 3D-
Datensätze zum Beispiel auch die Anordnung schaumstabilisierender Partikel
im Material und auf den Metallporenoberflächen verfolgt werden.
Die Beobachtung der dreidimensionalen Verteilung solcher schaumstabilisierender
Partikel mittels Synchrotron-Tomographie im festen Ausgangsmaterial,
im flüssigen Metallschaum sowie im anschließend erstarrten
Zustand ist Gegenstand des Beitrags. Das Ziel dabei ist, am Beispiel
einer Aluminiumlegierung mit beigemengten Siliziumkarbidteilchen den
Partikelumordnungsmechanismus im flüssigen Schaum zu erklären. Unter
Verwendung der Dilatation wurden quantitative Korrelationsrechnungen
am System durchgeführt.
SYPF 5.2 Di 14:30 C
Strukturuntersuchungen an Metallschäumen in verschiedenen
Schäumstadien — •A. Bütow 1 , A. Haibel 2 , B. Matijasevic 2,1 ,
H.-M. Helwig 2 , A. Rack 2 und J. Banhart 2,1 — 1 Technische Universität
Berlin, Institut für Metallphysik, Hardenbergstr. 36, 10623 Berlin —
2 Hahn-Meitner-Institut Berlin, Abteilung Strukturforschung, Glienicker
Str. 100, 14109 Berlin
Die reproduzierbare Herstellung von Aluminiumschäumen wird
häufig beeinträchtigt durch die Variation der Porengrößenverteilungen
und Lammellendicken einzelner Produktionsserien. Mit Hilfe von
Temperatur-Zeit-Kurven, die während des Schäumvorgangs im Inneren
der Proben aufgenommen werden, ist es uns jedoch möglich, Metallschäume
in untereinander vergleichbaren Entwicklungsstadien herzustellen.
Wir untersuchen mit Synchrotrontomographie die Abhängigkeit
der Porengrößenverteilung von der Partikelgrößenverteilung des verwendeten
Schäummittels in gleichen Schaumentwicklungsstadien. Verwendet
werden dazu verschiedene Aluminiumlegierungen und unterschiedliche
Titanhydrid-Partikelgrößen. Außerdem werden ergänzende Messungen
mit EDX und Lichtmikroskopie vorgestellt.
SYPF 5.3 Di 14:30 C
Analyse des Schmelzverhaltens von Al-Legierungen während
des Aufschäumprozesses — •H.-M. Helwig 1 und J. Banhart 1,2
— 1 Hahn-Meitner-Institut Berlin, Abteilung Strukturforschung, Glienicker
Str. 100, 14109 Berlin — 2 Technische Universität Berlin, Institut für
Metallphysik, Hardenbergstr. 36, 10623 Berlin
Aluminiumschäume können durch Wärmebehandlung von Pulverpreßlingen
hergestellt werden, welche aus Metallpulver und einem Treibmittel,
i.d.R. TiH2, bestehen. Da diese Treibmittel das Gas bei definierten, treibmittelabhängigen
Temperaturen freisetzen, ist es notwendig, die Schmelztemperaturen
der verwendeten Legierung so zu wählen, daß zum Zeitpunkt
der Gasfreisetzung zum einen genug Schmelze zur Verfügung steht,
zum anderen eine ausreichende Menge fester Al-Kristalle den Schaum
stabilisiert. Zu diesem Zwecke wurden am HMI Schäumversuche mit verschiedenen
Legierungen mit Echtzeit-Temperaturerfassung durchgeführt
und die gewonnenen Temperaturkurven mit Differentialthermoanalyse
der untersuchten Legierungssysteme verglichen. Das Ziel dieser Messungen
ist es eine auf Legierung und Treibmittel angepaßte Temperaturführung
zu entwickeln, die es erlaubt, einen definierten Feststoffgehalt
in der Schmelze während des Aufschäumens einzustellen.
SYPF 5.4 Di 14:30 C
Embedded atom porous structures studied via molecular dynamics
simulations — •Igor Stankovic 1 , Martin Kröger 2 , and
Siegfried Hess 1 — 1 Institute of Theoretical Physics, PN 7-1, Technical
Universityof Berlin, Hardenbergstr. 36, D-10623 Berlin — 2 Polymer
Physics, ETH Zurich, ML H18, Sonneggstr. 3, CH-8092Zurich
We report about a modification of the embedded atoms model (EAM)
used earlier to study bulk metals [1]. The modification concerns the
controlled mismatch between overall number density and preferred embedding
density. Molecular dynamics simulations are used to follow the
phase separation of EAM particles evolving form a homogeneous configuration
into porous structure. Evolution of the structure with the time is
studied using pictures of configurations, structure factor, common neighbor
analysis, and volume and surface analysis [2,3]. We demonstrate an
application of EAM porous structures to study diffusion of a gas of short
range attractive particles in porous media. Simulations of the evolution
and drain in a single wall made of EAM particles with different values
of cohesive and surface energies will be also presented.
1. I. Stankovic, M. Kröger, and S. Hess, Phys. Rev. E, accepted 2003.
2. J. F. M. Lodge and D. M. Heyes, J. Chem. Phys. 109, 7567 (1998).
3. I. Stankovic, M. Kröger, and S. Hess, Comput. Phys. Commun. 145,
371 (2002).

Symposium Quantum Shot Noise in Nanostructures Tagesübersichten
QUANTUM SHOT NOISE IN NANOSTRUCTURES (SYSN)
Gemeinsames Symposium mit den Fachverbänden DY, HL und TT
PD Dr. Wolfgang Belzig
Departement für Physik und Astronomie
Universität Basel
Klingelbergstrasse 82
CH-4056 Basel
E-Mail: Wolfgang.Belzig@unibas.ch
Hauptvorträge
Prof. Dr. Christoph Strunk
Institut für Experimentelle und Angewandte Physik
Universität Regensburg
Universitätsstr. 31
93040 Regensburg
Email: Christoph.Strunk@physik.uni-regensburg.de
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsaal H1)
SYSN 1.1 Mo 13:30 (H1) Quantum Shot Noise in Nanostructures: From Schottky to Bell,
Markus Büttiker
SYSN 1.2 Mo 14:00 (H1) Mesoscopic transition in the shot noise of diffusive SNS junctions,
Francois Lefloch, Christian Hoffmann, Marc Sanquer, Bernard Pannetier
SYSN 1.3 Mo 14:30 (H1) Quantum Noise: Challenge and Prospect, Yuli V. Nazarov
SYSN 2.1 Mo 16:00 (H1) Environmental effects in the third moment of voltage fluctuations in a
tunnel junction, Bertrand Reulet, J. Senzier, Daniel E. Prober
SYSN 2.2 Mo 16:30 (H1) Full Counting Statistics of Multiple Andreev Reflections,
Juan Carlos Cuevas
Fachsitzungen
SYSN 1 Quantum Shot Noise in Nanostructures Mo 13:30–15:30 H1 SYSN 1.1–1.5
SYSN 2 Quantum Shot Noise in Nanostructures Mo 16:00–17:45 H1 SYSN 2.1–2.5

Symposium Quantum Shot Noise in Nanostructures Montag
Fachsitzungen
– Haupt- und Kurzvorträge –
SYSN 1 Quantum Shot Noise in Nanostructures
Zeit: Montag 13:30–15:30 Raum: H1
Hauptvortrag SYSN 1.1 Mo 13:30 H1
Quantum Shot Noise in Nanostructures: From Schottky to Bell
— •Markus Büttiker — Département de Physique Theorique, Université
de Genève, CH-1211 Genéve 4, Switzerland.
For more than a decade, theoretical and experimental investigations
of noise properties have been at the forefront in our quest to understand
the transport properties of small electrical conductors. Initial work
aimed at characterizing shot noise with the help of Fano factors: the ratio
of the shot noise to full Poisson (Schottky) noise. Later the theory
was extended to include not only the second moment (shot noise) but
all higher order current correlations. We contrast fully quantum mechanical
approaches to this problem with semiclassical discussions. Current
fluctuations are often understood as simply a stochastic successive transfer
of particles. But an analysis of current-current fluctuations shows
that it is possible to invent geometries in which there is no Aharonov-
Bohm effect in the conductance (second order interference) but there is
very well an Aharonov-Bohm effect in noise-correlations (fourth order
interference). We demonstrate that this is a consequence of a two particle
Aharonov-Bohm effect: in the tunneling limit it can be connected
to orbitally entangled electron-hole states. We show that zero-frequency
noise-correlation measurements can be used to proof that these states
violate a Bell inequality.
Hauptvortrag SYSN 1.2 Mo 14:00 H1
Mesoscopic transition in the shot noise of diffusive SNS junctions
— •Francois Lefloch 1 , Christian Hoffmann 1 , Marc Sanquer
1 , and Bernard Pannetier 2 — 1 Département de Recherche
Fondamentale sur la Matière Condensée/SPSMS/LCP, CEA/Grenoble,
17 rue des Martyrs, 38054 Grenoble cedex 09, France — 2 Centre de
Recherches sur les Très Basses Températures-C.N.R.S. associated to Université
Joseph Fourier, 25 rue des Martyrs, 38042 Grenoble, France
We experimentally investigated the current noise in short diffusive Superconductor/Normal
metal/Superconductor junctions over a large range
of energy that covers the regimes of coherent and incoherent multiple Andreev
reflections. The transition between these two regimes, occurs at the
Thouless energy where a pronounced minimum in the current noise density
is observed. Above the Thouless energy, in the regime of incoherent
multiple Andreev reflections, the noise is very much enhanced compared
to a normal junction and grows linearly with the bias voltage. Semiclassical
theory describes accurately the experimental results over the
entire temperature range, but only if we take into account the voltage
dependence of the resistance which reflects the proximity effect. Below
the Thouless energy, the shot noise diverge as 1/eV and may indicate
the coherent transfer of multiple charges.
Hauptvortrag SYSN 1.3 Mo 14:30 H1
Quantum Noise: Challenge and Prospect — •Yuli V. Nazarov
— Department of NanoScience, Delft University of Technology,
Lorentzweg 1, 2628 CJ Delft, The Netherlands
The concept of full counting statistics does not just give a new dimension
to studies of electron transport: it gives it infinitely many dimensions.
To enter and conquer this new world is a challenge, better understanding
of nanophysics and quantum mechanics is the prospect.
SYSN 1.4 Mo 15:00 H1
Electron counting statistics and the Clauser-Horne inequality
— •Fabio Taddei 1 , Lara Faoro 2 , and Rosario Fazio 1 — 1 NEST-
INFM & Scuola Normale Superiore, Pisa, Italy — 2 ISI Foundation, Viale
Settimio Severo, 65, I-10133 Torino, Italy
We derive the Clauser-Horne (CH) inequality for the full electron
counting statistics in a mesoscopic multiterminal conductor and we discuss
its properties. We first consider the idealized situation in which a
flux of entangled electrons is generated by an entangler. Given a certain
average number of incoming entangled electrons, the CH inequality can
be evaluated for different numbers of transmitted particles. Strong violations
occur when the number of transmitted charges on the two terminals
is the same (Q1 = Q2), whereas no violation is found for Q1 �= Q2. We
then consider a three terminal normal beam splitter and a hybrid superconducting
structure. Interestingly, we find that the CH inequality is
violated for the three terminal normal device. As expected, we find full
violation of the CH inequality in the case of the superconducting system.
SYSN 1.5 Mo 15:15 H1
Suppression of shot noise by dynamical mechanisms —
•Henning Schomerus — MPIPKS Dresden, Nöthnitzer Str. 38, 01187
Dresden
The investigation of shot noise in mesoscopic systems has many merits,
one of the primary ones being the detection of system-specific details
that help to uncover dynamics and interactions. We identify three dynamical
mechanisms that reduce shot noise in ballistic quantum dots below
the universal prediction of random-matrix theory: a) direct processes, b)
dynamics along stable trajectories, and c) delay of diffraction for very
small wavelength. Mechanisms a) and b) are efficient means in the quest
to suppress shot noise in phase-coherent systems, while mechanism c)
elucidates the particle-wave duality and the correspondence principle in
the quantum-to-classical crossover.
[1] H.-S. Sim and H. Schomerus, Phys. Rev. Lett. 89, 066801 (2002).
[2] R. G. Nazmitdinov, H.-S. Sim, H. Schomerus, and I. Rotter, Phys.
Rev. B 66, 241302(R) (2002).
[3] J. Tworzydlo, A. Tajic, H. Schomerus, and C. W. J. Beenakker, Phys.
Rev. B 68, 115313 (2003).
SYSN 2 Quantum Shot Noise in Nanostructures
Zeit: Montag 16:00–17:45 Raum: H1
Hauptvortrag SYSN 2.1 Mo 16:00 H1
Environmental effects in the third moment of voltage fluctuations
in a tunnel junction — •Bertrand Reulet 1,2 , J. Senzier
1 , and Daniel E. Prober 1 — 1 Departments of Applied Physics
and Physics, Yale University, New Haven CT 06520-8284, USA —
2 Laboratoire de Physique des Solides, associé au CNRS, bâtiment 510,
Université Paris-Sud 91405 Orsay, France
We present the first measurements of the third moment of the voltage
fluctuations in a conductor. This technique can provide a new and complementary
information on the electronic transport in any kind of physical
system. The measurement was performed on non-superconducting
tunnel junctions as a function of voltage bias, for various temperatures
and frequency bandwidths up to 1GHz. The data demonstrate the importance
of the effect of the electromagnetic environment of the sample
on the voltage fluctuations.

Symposium Quantum Shot Noise in Nanostructures Montag
Hauptvortrag SYSN 2.2 Mo 16:30 H1
Full Counting Statistics of Multiple Andreev Reflections
— •Juan Carlos Cuevas — Institut für Theoretische
Festkörperphysik,Universität Karlsruhe, D-76128 Karlsruhe
The complete understanding of the electronic transport in mesoscopic
systems requires information that goes beyond the analysis of the current.
In this sense, the ultimate goal is the determination of the full
current distribution. In the context of superconductivity the basic situation,
in which this full distribution had not been yet investigated, is
a point contact between two superconductors out of equilibrium, where
the transport properties at subgap voltages are dominated by multiple
Andreev reflections (MAR).
In this talk I will present our recent results, which demonstrate that
in superconducting contacts at finite voltage the charge transport is described
by a multinomial distribution of multiple charge transfers. This
proves that in the MAR processes the charge is transmitted in large
quanta. We have obtained analytically the MAR probabilities, from which
all transport properties are easily computed. Our result constitutes the
culmination of the recent progress in the understanding of MARs, which
are a key concept in mesoscopic superconductivity.
SYSN 2.3 Mo 17:00 H1
Shot noise in resonant single electron tunneling through InAs
quantum dots — •Frank Hohls 1 , André Nauen 1 , Niels Maire 1 ,
Rolf Haug 1 , and Klaus Pierz 2 — 1 Institut für Festkörperphysik, Universität
Hannover, D-30167 — 2 Physikalisch-Technische Bundesanstalt,
Bundesallee 100,
We investigate the noise properties of resonant single electron transport
through self-assembled InAs quantum dots which are embedded in
the AlAs barrier of a GaAs-AlAs-GaAs tunneling device. Due to their
small size (diameter 10-15 nm and height 3 nm) these quantum dots
display both strong size quantization and Coulomb blockade. Thus the
tunneling current through our device is given by resonant single electron
tunneling through the ground state of the quantum dot.
The measured noise spectrum of the current is dominated by frequencyindependent
shot noise for frequencies above 1 kHz. As expected for single
electron tunneling the spectral noise power S is suppressed in comparison
to the full Poissonian shot noise 2eI observed for single barrier tunneling.
We observe a linear voltage dependence of the suppression α = S/2eI
which can be related to the dimensionality of the source contacts. At the
onset of the resonant current we observe additional features which are
probably caused by a correlation effect between dot and lead known as
fermi edge singularity.
SYSN 2.4 Mo 17:15 H1
Shot noise of coherent tunneling through Coulomb interacting
quantum dots — •G. Kießlich, A. Wacker, and E. Schöll —
Institut für Theoretische Physik, TU Berlin, Hardenbergstr. 36, 10623
Berlin
The spectral power density of the tunneling current through quantum
dots can help to clarify the transition from sequential (particlelike) to
coherent (wavelike) mesoscopic transport. In the high temperature limit
kBT ≫ Γ (Γ is the linewidth of the resonant quantum dot level) the
noise and the current are well described by sequential tunneling using
a Pauli master equation approach [1] which is in good agreement with
experimental data [2]. For intermediate temperatures kBT ≃ Γ we derive
the noise behavior starting from the Anderson Hamiltonian using a
nonequilibrium Green’s function technique. In this framework we treat
the tunneling coupling to the reservoirs exactly, and the Coulomb interaction
in the quantum dot is included perturbatively beyond the Hartree
approximation. The effect of Coulomb repulsion on the bias dependence
of the noise in the sequential and coherent regime will be shown in detail.
[1] G. Kießlich, A. Wacker, and E. Schöll, Phys. Rev. B 68, 125320 (2003)
[2] G. Kießlich, A. Wacker, E. Schöll, A. Nauen, F. Hohls, and R.J. Haug,
Phys. Status Solidi C 0, 1293 (2003)
SYSN 2.5 Mo 17:30 H1
Frequency Dispersion in Full Counting Statistics — •Sebastian
Pilgram 1 , Kirill Nagaev 2 , and Markus Büttiker 1 —
1 Département de Physique Théorique, Université de Genève, CH-1211,
Genève, Switzerland — 2 Institute of Radioengineering and Electronics,
Russian Academy of Sciences, Mokhovaga ulica 11, 125009 Moscow,
Russia
Transport of electrons through disordered mesoscopic conductors is
considered in the semiclassical regime. We express the full transport
statistics of current in terms of a stochastic path integral. In the semiclassical
limit, this path integral may be evaluated in the saddle point
approximation. The formalism is used to study the frequency dispersion
of higher order correlation functions. Investigating both ballistic cavities
and diffusive wires, we find surprisingly that the third cumulant of
full current statistics shows a low-frequency dispersion which is absent
in noise correlators. This dispersion is associated with charge neutral
fluctuations of the electron occupation function and exists in the regime
of non-interacting electrons as well as in the presence of strong electronelectron
scattering (Reference: K.E. Nagaev, S. Pilgram, and M. Buttiker,
cond-mat/0306465).

Symposium X-RAY Magneto-Optics Tagesübersichten
X-RAY MAGNETO-OPTICS (SYXM)
Priv.-Doz. Dr. Kai Starke
Magnetic Materials Spectroscopy
Freie Universität Berlin
Fachbereich Physik
Arnimallee 14
14195 Berlin
E-Mail: starke@physik.fu-berlin.de
Prof. Dr. Hubert Ebert
Ludwig-Maximilians-Universität München
Department Chemie
Physikalische Chemie
Butenandtstraße 11
81377 München
E-Mail: hubert.ebert@cup.uni-muenchen.de
Intense soft x-ray beams with variable light polarization from synchrotron radiation sources are widely used to investigate
nanoscale heteromagnetic structures. When tuning to inner-shell absorption edges resonant x-ray magnetic scattering gives
rise to magneto-optical signals in transmission, specular reflection, and diffuse reflection. As unique features of x-ray
magneto-optics, (i) the information depth can be varied by orders of magnitude from surface to bulk sensitive, and (ii)
interference becomes significant when the soft x-ray wavelength is comparable with the nanometer dimensions of layered
magnetic structures. – This symposium is jointly held by the sections Magnetism and Surface Science of the Condensed
Matter Division in the German Physical Society. Seven invited speakers highlight various aspects of the field, reaching from
principles of x-ray magneto-optics, its application to magnetometry, the possibility of using coherent scattering to image and
study dynamics of magnetic domains, to recent theoretical and experimental achievements in research on magnetic transition
metal clusters and single atoms deposited on surfaces.
Hauptvorträge
ÜBERSICHT DER HAUPTVORTRÄGE UND FACHSITZUNGEN
(Hörsaal H1)
SYXM 1.1 Di 14:30 (H1) Magneto-optical polarisation spectroscopy with soft x-rays,
Hans-Christoph Mertins, Sergio Valencia, Andreas Gaupp, Wolfgang Gudat,
Peter Oppeneer
SYXM 1.2 Di 15:00 (H1) Magnetization profiling by resonant magnetic x-ray reflectometry,
G. Schütz, J. Geissler, E. Goering
SYXM 1.3 Di 15:30 (H1) X-ray magneto-optics of lanthanide materials: principles and applications,
José Emilio Prieto, Franziskus Heigl, Oleg Krupin, Kristian Döbrich, Günter Kaindl,
Kai Starke
SYXM 1.4 Di 16:00 (H1) Resonant soft x-ray diffuse scattering from magnetic multilayers,
Maurizio Sacchi, Carlo Spezzani, Renaud Delaunay, Coryn F. Hague
SYXM 1.5 Di 16:30 (H1) Ab-initio calculations for adatoms and clusters on surfaces,
Peter H. Dederichs
SYXM 1.6 Di 17:00 (H1) Magnetic properties of mass selected transition metal clusters,
Wilfried Wurth, Leif Glaser, Tobias Lau, Michael Martins, Robert Nietuby`c, Matthias
Reif
SYXM 1.7 Di 17:30 (H1) Coherent x-ray scattering and lensless imaging of magnetic materials,
Stefan Eisebitt, Marcus Lörgen, Wolfgang Eberhardt, Jan Lüning, Joachim Stöhr
Fachsitzungen
SYXM 1 X-Ray Magneto-Optics Di 14:30–18:00 H1 SYXM 1.1–1.7

Symposium X-RAY Magneto-Optics Dienstag
Fachsitzungen
– Hauptvorträge –
SYXM 1 X-Ray Magneto-Optics
Zeit: Dienstag 14:30–18:00 Raum: H1
Hauptvortrag SYXM 1.1 Di 14:30 H1
Magneto-optical polarisation spectroscopy with soft x-rays
— •Hans-Christoph Mertins 1 , Sergio Valencia 2 , Andreas
Gaupp 2 , Wolfgang Gudat 2 , and Peter Oppeneer 3 — 1 University
of Applied Sciences, Münster, Stegerwaldstr. 39, 48565 Steinfurt —
2 BESSY, Berlin, Germany — 3 IFW-Dresden, Germany
Among the x-ray magneto-optical spectroscopy techniques, the polarisation
analysis of light after its interaction with the material gaines
increasing importance since it reveals both, the intensity and the phase.
Thus it directly gives the complete magneto-optical constants, something
that is not possible with a single intensity measurement.
Polarisation effects appear when linearly polarized light interacts with
a sample that has a magnetization component parallel to the light propagation
direction k. Behind the sample the light polarisation plane is
rotated and the polarisation has changed to elliptical. This effect has been
observed in transmission (Faraday effect [1]) and recently in reflection (L-
MOKE [2]). Both effects are even in the magnetization M allowing for
investigations of ferromagnetic materials. Antiferromagnetic ordering can
be probed by second order effects by applying a perpendicular orientation
between k and M (Voigt effect [3]).
The applicability of these effects for the characterization of magnetic
materials and devices is demonstrated with x-ray rotation and ellipticity
spectra across the 3p and 2p edges of Mn, Fe, Co and Ni.
[1] J. Kunes et al., Phys. Rev. B 64, 174417 (2001)
[2] H.-Ch. Mertins et al., Phys. Rev. B, in press (2003)
[3] H.-Ch. Mertins et al., Phys. Rev. Lett. 87, 047401 (2001).
Hauptvortrag SYXM 1.2 Di 15:00 H1
Magnetization profiling by resonant magnetic x-ray reflectometry
— •G. Schütz, J. Geissler, and E. Goering — Max-Planck
Institut für Metallforschung, Stuttgart
The asymmetry ratio of resonant magnetic x-ray reflection shows a
strong variation with the angle of incidence. The maximum value of the
complex magnetic reflection profile is in the order of the corresponding
XMCD signal, from which the main magnetic contribution of the
absorptive scattering amplitude can be deduced while the dispersive
part is calculated via Kramers Kronig relations. If the correlation of
the XMCD effect to the atomic magnetic moment is known, the magnetization
depth profile can be deduced by an artificial slicing method
utilizing the Parratt algorithm [1]. For hard x-rays (e.g. L2,3 edges for 4f
or 5d elements) with scattering vector of less than one degree cross and
scalar products can be simplified. The application of this theoretical
model is much more complicated for soft x-rays and related to large
scattering angles. However, this energy range covers the L2,3 edges of 3d
transition elements, which exhibit large asymmetry ratios amounting to
50 % [2]. The potential of this method especially for technical relevant
GMR/TMR systems, whose magneto-electric properties can strongly
depend on the interphase morphogy, is demonstrated for a Pt/Co/Cu
trilayer. For this composition it was possible to determine the variation
of the magnetic interface depth profile for each layer reaching an
accuracy of about 10 % for Pt and Co with a depth resolution up to 0.1
nm. Even for the Cu component an estimation of the induced magnetic
moment at the Co-Cu interface is possible [3].
[1] J. Geissler et al., Phys. Rev. B 65, 020405 (2001)
[2] J. Geissler et al., Z. Metallkd. 93, 946 (2002)
[3] E. Goering et al., in preparation
Hauptvortrag SYXM 1.3 Di 15:30 H1
X-ray magneto-optics of lanthanide materials: principles and
applications — •José Emilio Prieto, Franziskus Heigl, Oleg
Krupin, Kristian Döbrich, Günter Kaindl, and Kai Starke —
Institut für Experimentalphysik, Freie Universität Berlin, Germany
Lanthanides are frequently employed in technical magnetic systems
to achieve high anisotropies. In contrast to transition metals, magnetic
moments are carried mainly by the localized 4f electrons, and their correlation
energies give rise to rich multiplet structures in optical excitation
spectra whenever the 4f shell is involved. This results in strong magnetic
dichroism in x-ray absorption and, due to the connection between real
and imaginary parts of the refractive index, also in large magneto-optical
effects in resonant reflectivity [1].
Soft x-ray magneto-optics is well suited to study magnetization
reversal processes in external magnetic fields. Yet in order to obtain
quantitative information on the magnetization from reflectivity data,
comparison with model calculations is required. Here we report on
recent progress in determining the soft x-ray magneto-optical constants
of lanthanides [2,3] and show examples of applying specular resonant
reflectivity to analyse the magnetization reversal of thin films and
exchange-coupled trilayer systems in an element specific way.
[1] K. Starke, F. Heigl, A. Vollmer, M. Weiss, G. Reichardt, and
G. Kaindl, Phys. Rev. Lett. 86, 3415 (2001)
[2] J. E. Prieto, F. Heigl, O. Krupin, G. Kaindl, and K. Starke, Phys.
Rev. B 66, 172408 (2002)
[3] J. E. Prieto, F. Heigl, O. Krupin, G. Kaindl, and K. Starke, Phys.
Rev. B 68, 134453 (2003)
Hauptvortrag SYXM 1.4 Di 16:00 H1
Resonant soft x-ray diffuse scattering from magnetic multilayers
— •Maurizio Sacchi 1 , Carlo Spezzani 1 , Renaud Delaunay 2 ,
and Coryn F. Hague 1,2 — 1 LURE, Centre Universitaire Paris Sud, Orsay,
France — 2 LCP–MR, Université P. et M. Curie, Paris, France
We have applied resonant diffuse scattering of polarized soft x-rays
to the investigation of the field dependent magnetic structure in Co/Cu
multilayers. At remanence, and for weak applied fields, Co layers break
up into magnetic domains with a high degree of AF coupling normal
to the stacked layers. We estimate the degree of AF coupling and the
average size of the AF domains as a function of the applied field.
The analysis of the domain size distribution, and of its correlation with
magnetoresistance, after a demagnetization process gives further evidence
that the remanent magnetic structure is influenced by the magnetic history
of the multilayer.
We have compared the field dependence of the sample resistance and of
the scattered intensity at various off-specular angles. Our results suggest
that at high fields non-negligible variations in the resistance may be due
to the persistence of small magnetically hard domains.
Hauptvortrag SYXM 1.5 Di 16:30 H1
Ab-initio calculations for adatoms and clusters on surfaces
— •Peter H. Dederichs — Institut für Festkörperforschung,
Forschungszentrum Jülich, D-52425 Juelich
Adatoms and small clusters on surfaces have a considerably lower coordination
number than in a bulk environment. Therefore one expects
that these nanostructures exhibit considerably larger spin and orbital
moments than in the bulk. Here we review a series of ab-initio results for
adatoms and small clusters on surfaces of the noble metals (Cu, Ag, Au,
Pt) and the ferromagnets Fe and Ni. The calculations were performed
within the density-functional formalism by using the KKR-Green’s function
method. On the noble metal surfaces, we find strongly enhanced
spin moments, and even small clusters of 4d atoms are magnetic. A much
stronger enhancement is found for the orbital moments and anisotropy
energies. Compared to this, the enhancement of the moments on the
surfaces of Fe and Ni are rather moderate, being a result of the much
stronger hybridisation of the adatoms with the substrate d states.

Symposium X-RAY Magneto-Optics Dienstag
Hauptvortrag SYXM 1.6 Di 17:00 H1
Magnetic properties of mass selected transition metal clusters
— •Wilfried Wurth 1 , Leif Glaser 1 , Tobias Lau 1,2 , Michael
Martins 1 , Robert Nietuby`c 1 , and Matthias Reif 1 — 1 Institut
für Experimentalphysik, Universität Hamburg, Hamburg, Germany —
2 EPFL, Lausanne, Switzerland
The magnetism of nanoparticles has attracted a lot of interest recently
due to their promising properties for storage media. From a more fundamental
point of view small clusters allow to study the transition from
the magnetic properties of atoms to those of the respective solids.
We have developed a cluster source which enables us to investigate size
selected transition metal clusters deposited on solid surfaces using x-ray
magnetic circular dichroism. In this talk recent results for iron clusters
[1,2] and chromium clusters deposited on ferromagnetic substrates will
be presented which demonstrate the strong size dependence of the
magnetic properties of the clusters.
[1] J.T. Lau, A. Föhlisch, R. Nietuby`c, M. Reif, and W. Wurth, Phys.
Rev. Lett. 89, 57202 (2002)
[2] J.T. Lau, A. Föhlisch, M. Martins, R. Nietuby`c, M. Reif, and W.
Wurth, New J. of Phys. 4, 98.1 (2002)
Hauptvortrag SYXM 1.7 Di 17:30 H1
Coherent x-ray scattering and lensless imaging of magnetic
materials — •Stefan Eisebitt 1 , Marcus Lörgen 1 , Wolfgang
Eberhardt 1 , Jan Lüning 2 , and Joachim Stöhr 2 — 1 BESSY, Berlin,
Germany — 2 SSRL, SLAC, Stanford, USA
Coherent Scattering is sensitive to the individual sample geometry beyond
statistical averages – this is the reason why the speckle fine structure
in coherent scattering can be exploited for imaging and to track
the dynamics of a sample. The basics of coherent x-ray scattering using
synchrotron radiation sources will be reviewed, including advantages and
limitations of ”lensless” imaging techniques. Magnetic scattering of soft
x-rays and in particular polarization effects in the interference will be
discussed in detail, as they have consequences for both static and dynamic
studies of magnetic samples. Recent progress in magnetic domain
imaging via coherent scattering will be presented. The future perspectives
regarding the application of these techniques at free electron x-ray
lasers, which will deliver a coherent photon flux many orders of magnitude
higher than available today, will be discussed.

Lehrertage Regensburg Tagesübersichten
LEHRERTAGE REGENSBURG (LTR)
Ein Fortbildungsangebot der Deutschen Physikalischen Gesellschaft für Physiklehrer/-innen
Vorträge zu aktuellen Themen der Festkörperphysik und der Fachdidaktik
Akad. Dir. Josef Reisinger
Fachdidaktik Physik der Universität Regensburg
Universität Regensburg
93040 Regensburg
E-Mail: josef.reisinger@physik.uni-regensburg.de
Dr. Christian Hirtreiter
Universität Regensburg
93040 Regensburg
E-Mail: christian.hirtreiter@chemie.uni-regensburg.de

Lehrertage Regensburg Hauptvorträge
Hauptvortrag LTR I Mi 09:15 H36
Physik macht Spaß! — •Norbert Treitz — Universität Essen-
Duisburg
Rätselhafte oder verblüffende Experimente, viele davon mit Requisiten
aus der Spielzeugkiste oder dem Haushalt, entpuppen sich als Schlüssel
zum Verständnis grundlegender Erfolgsrezepte der Physik. So zeigt eine
auf den ersten Blick sehr seltsame Waage, wie man viele Naturgesetze (zu
jeder ” einfachen Maschine“ eins) zu einem einzigen (Energiebilanz beim
Gleichgewicht) zusammen fassen kann: Physik ist eine äußerst elegante
und umfassende Form der Datenkompression! Eine ” Fallstudie“ als Freihandversuch
mit zwei Bällen erweist sich als Analogon zu der Methode,
aus der Begegnung eines Raumschiffs mit einem – im doppelten Sinn des
Wortes – entgegen-kommenden Planeten Energie abzuzapfen, zwar nicht
in dessen Bezugssystem, wohl aber im heliostatischen. Weitere ” Fragen“:
Bewegt sich am Fahrrad irgend etwas rückwärts? Gibt es wirklich roten
und grünen elektrischen Strom? Was hat das überschlagene Parallelogramm
mit der Optik zu tun? Fällt ein Teil einer Falltür mit größerer
Beschleunigung als eine Punktmasse?
Rund um diese und andere Themen: www.eddy.uni-duisburg.de/treitz/
Hauptvortrag LTR II Mi 10:45 H36
Die Interaktive Physik-Show — •physikanten und co. — Dortmund
Hier wird Wissenschaft zur Show! Experimente, die wie Magie erscheinen,
knifflige Versuche zum Mitmachen, Showeinlagen und ein packender
Zuschauerwettstreit: Die Interaktiven Physik Shows fesseln.
Welche verblüffenden Eigenschaften hat Wasser? ” Platsch! Die Interaktive
Wasser-Show“ zeigt es Ihnen. Warum kreist ein Koffer auf der
Kante? Die Interaktive Mechanik-Show bietet Bewegendes von Auftrieb
bis Zentrifugalkraft.
Kein physikalisches Phänomen, zu dem Entertainer Herr Schwupp keine
Showeinlage einfiele; kein Experiment, das Professor Liebermann nicht
leicht verständlich erklären könnte. Unterstützt werden die Physikanten
von ihrem Forscherteam: dem Publikum, das dafür mit einem besonderen
Preis belohnt wird.
Hauptvortrag LTR III Fr 09:00 H4
Physikexperimente mit Blechdosen — •Hans-Joachim Wilke —
TU Dresden
Hauptvortrag LTR IV Fr 10:00 H4
Nanobeben auf dem Chip: Von Handyfiltern, Photonenförderbändern
und Biochips — •Achim Wixforth —
Universität Augsburg
Akustische Oberflächenwellen sind das Nanometer-Analogon zu Erdbeben.
Auf dieser Längenskala jedoch wirken Sie nicht zerstörerisch sondern
können als effiziente, wenn auch ungewöhnliche Werkzeuge der
Nanotechnologie eingesetzt werden. Vom hochempfindlichen Messinstrument
kleinster Leitfähigkeiten z.B. im Bereich des quantisierten Hall-
Effektes über den Einsatz als funkabfragbare Sensoren bis hin zu einem
” Photonenförderband“ leisten akustische Oberflächenwellen Erstaunliches.
Schließlich fanden sie in den letzten Jahren sogar Einzug in das sich
rasch entwickelnde Feld der Biochips. Hier sorgen sie für den Transport
und die Prozessierung kleinster Flüssigkeitsmengen auf einer Chipoberfläche
– ein Labor auf der Fläche eines Daumennagels.
Hauptvortrag LTR V Fr 11:00 H4
Magnetresonanztomographie: Abbildung dreidimensionaler
Details in (Sub)millimeter-Auflösung mit Meterwellen —
•Nikolaus Nestle — TU Darmstadt
Die Kernspintomographie – oder Magnetresonanztomographie (MRT)
– ist mittlerweile zu einem der wichtigsten bildgebenden Verfahren in
der medizinischen Diagnostik geworden. Die physikalische Grundlage
der Kernspintomographie ist die Zeeman-Aufspaltung der Energieniveaus
von Wasserstoffkernen in einem angelegten Magnetfeld. Die in üblichen
Magnetfeldern erreichbaren Energieaufspaltungen sind sehr klein und
entsprechen Quantenenergien im Radiowellenbereich. Trotz der langwelli-
Hauptvorträge
gen Strahlung (die Auflösung optischer Abbildungsverfahren wird durch
die Wellenlänge begrenzt) können hiermit tomographische Abbildungen
mit Auflösung im Submillimeterbereich am Menschen und mit weniger als
10 Mikrometern an kleineren Objekten erreicht werden. Der Vortrag stellt
die physikalischen Grundlagen dieser nichtoptischen Abbildungsmethode
vor und beschreibt verschiedene Anwendungen der Kernspintomographie
in Medizin, Material- und Umweltforschung.
Hauptvortrag LTR VI Fr 14:00 H4
Zur Vorgeschichte und Geschichte des Ohm’schen Gesetzes —
•Jürgen Teichmann — LMU München
Am 7. Juli 1854 – 2004 sind 150 Jahre vergangen – starb Georg Simon
Ohm, der zunächst Mathematiker werden wollte, als Gymnasiallehrer in
Köln 1826 das ” Ohm’sche Gesetz“ entdeckte und erst sehr spät, 1849,
seinen Lebenstraum als Universitätsprofessor verwirklichen durfte. Untersucht
man den langen Weg zum Ohm’schen Gesetz, findet man sehr
überraschende Ergebnisse. Schon um 1775 – lange vor Ohm – lag es
ganz nahe, obwohl es eigentlich noch gar keinen konstanten Strom gab,
sondern v. a. Kondensatorentladungen (von Leidener Flaschen) und das
elektrische Fluidum gerade erst mit einem zusätzlichen Begriff (Spannung)
quantitativ handhabbar gemacht wurde. Kurz nach 1800 wurde es
eigentlich entdeckt, aber von Experimentalphysikern (Volta, Ritter), die
es mathematisch nicht formulieren konnten. Wie wichtig war eigentlich
das genaue Strommessinstrument Ohms? So wesentlich prinzipiell nicht
– aber es sicherte ihm Nachruhm. Beginnende Elektrotechnik, die unbedingt
ein Konzept von Widerstand, Spannung, Stromstärke brauchte,
spielte auch eine Rolle – und Nationalismus (England contra Frankreich).
Hauptvortrag LTR VII Fr 15:00 H4
Robotik für Schulen, ein Weg zum Einstieg in die Naturwissenschaften
— •Martin Bader — Illertal-Gymnasium Vöhringen
Die Robotik bietet eine hervorragende Möglichkeit, Schüler für die Naturwissenschaft
und Technik zu begeistern. Grund dafür ist eine ausgewogene
Mischung zwischen Theorie und Praxis. Als Projektabschluss bieten
sich Wettbewerbe wie der RoboCup Junior an, bei dem Roboter Fußball
spielen, Männchen retten oder tanzen. (robocupjunior.org)
Hauptvortrag LTR VIII Sa 09:00 H4
Erfolgsfaktoren für Schulen: Das Bildungssystem in Finnland
— •Rainer Domisch — Zentralamt für Unterrichtswesen Helsinki
Finnland ist seit der Veröffentlichung der Pisa-Studie der OECD im
Dezember 2001 zum Musterland für erfolgreiche schulische Bildung geworden.
Beste Ergebnisse im Bereich der Lesekompetenz, dritte Position
in den Naturwissenschaften und vierter Rang in Mathematik sprechen für
sich. Für Finnland ist das plötzliche Interesse der Weltöffentlichkeit an
seinen Schulen überraschend gekommen, und die Pisa-Studie hat bis zum
heutigen Tag außer eines kleinen Artikels in der Presse keinerlei Schlagzeilen
verursacht. Ganz im Gegenteil, man versucht verstärkt, bestehende
Defizite im Bildungsbereich mit großen Anstrengungen zu bereinigen. So
sind z. B. die finnischen Jungen in der Lesekompetenz besser als die Jungen
in allen vergleichbaren Ländern, aber der Unterschied zwischen Jungen
und Mädchen beunruhigt die finnische Öffentlichkeit zutiefst. Sieben
Prozent der Neuntklässler erreichen eine nicht genügende Lesekompetenz
(in Deutschland beträgt die entsprechende Zahl über 23 Prozent), aber
diese sieben Prozent sind erschreckend viele und man hat bereits begonnen,
durch landesweite Projekte das Problem anzugehen.
Finnland hat vor über 30 Jahren sein Bildungssystem radikal verändert
und reformiert und seither ununterbrochen und unermüdlich an der Weiterentwicklung
der Einrichtung Schule gearbeitet. Wichtige Stationen in
dieser Entwicklung waren
– Einführung eines integrierten Schulwesens
– Übertragung der Schulträgerschaft auf die Kommunen
– Verzicht auf Schulinspektion und auf Bindung der Finanzmittel
– Einführung einer landesweiten schulischen Evaluation
– Weitgehende Eigenverwaltung und Verantwortung der Schulen
– Ständige Reformen der Rahmenlehrpläne/Standards
und künftige Herausforderungen sind die

Lehrertage Regensburg Hauptvorträge
– Verwirklichung der Informationsgesellschaft
– die Rolle der Schule dabei und
– die Erhaltung gleicher Bildungschancen unabhängig vom Wohnort, vom
Geschlecht und von der sozialen Herkunft.
Hauptvortrag LTR IX Sa 10:00 H4
Wie Physikunterricht in Deutschland aussieht und wie er weiterentwickelt
werden kann — •Reinders Duit — IPN Kiel
Eine Projektgruppe des Leibniz Instituts für die Pädagogik der Naturwissenschaften
(IPN) an der Universität Kiel untersucht die Praxis des
deutschen Physikunterrichts in der Sekundarstufe I. An der ersten Phase
dieser Studie nahmen 13 Lehrkräfte aus Bayern und Schleswig-Holstein
teil. In der zweiten Phase waren es 51 Lehrkräfte – zusätzlich aus Baden-
Württemberg und Brandenburg. Mit diesen Daten ist es möglich, ein
recht zuverlässiges Bild über den Physikunterricht in den Schuljahren 7
bis 9 zu zeichnen. Die Studie gibt darüber hinaus Hinweise zur Verbesserung
des Physikunterricht. Ein wichtiger Aspekt scheint zu sein, das fachdidaktische
Denken der Lehrkräfte über den Unterricht zu entwickeln.
Bislang ist dies vor allem am Inhalt und weniger an den Lernschwierigkeiten
der Schülerinnen und Schüler orientiert. Ergebnisse der Studie
werden vorgestellt und es wird diskutiert, wie Physikunterricht verbessert
werden kann. Dabei spielt ein neues Projekt ” Physik im Kontext“
eine wichtige Rolle, das im Verlaufe des Schuljahres 2003/2004 anlaufen
wird. Es wird vom BMBF und den teilnehmenden Ländern unterstützt.
Das Vorhaben hat drei Schwerpunkte: (1) Entwicklung einer neuen Lehr-
Lern-Kultur; (2) Förderung naturwissenschaftlichen Arbeitens und Anwendens;
(3) Vermittlung von Grundlagen moderner Physik und moderner
Technologien. Wer sich über die Videostudie des IPN und das
Vorhaben ” Physik im Kontext“ informieren möchte, sei eingeladen, die
Homepage des Instituts zu besuchen: http://www.ipn.uni-kiel.de/ (dort
weiter zu: Projekte).
Hauptvortrag LTR X Sa 11:00 H4
Themen oder Kontexte als Strukturelemente für den Physikunterricht?
— •Heinz Muckenfuss — PH Weingarten
” Themenorientierter Unterricht“ wird in der aktuellen Lehrplanarbeit
oft als Gegenentwurf zu einem systematisch an den Fachdisziplinen ausgerichteten
Unterricht gesehen. Dem liegt die Auffassung zugrunde, das
Lernen im Fachunterricht untergrabe die Fähigkeit Zusammenhänge zu
sehen und sei zu abstrakt und lebensfern. Im Vortrag wird die These
expliziert, dass zwischen der Ideenwelt der Naturwissenschaft und der
unbefangenen Weltwahrnehmung eine Kluft liegt, deren Überbrückung
nur gelingt, wenn systematisches Lernen als Aufgabe verstanden wird,
die Fähigkeit zum Abstrahieren und Konkretisieren zu entwickeln. Ein
Verharren in den Fachsystematiken kann dies nicht leisten. Aber auch
eine Themenorientierung ohne den Primat der systematisch geordneten
Ideenwelt der Fächer wird dieser Aufgabe nicht gerecht. Manche aktuellen
Vorschläge zur Strukturierung des naturwissenschaftlichen Unterrichts
orientieren sich an einem wissenschaftstheoretisch problematischen
Organisationsmodell, das die bisherigen Probleme voraussichtlich nicht
lösen sondern verschärfen wird. An Beispielen für den Physikunterricht
wird dargestellt, wie mit interessanten Kontexten systematisches Lernen
organisiert werden kann.
Hauptvortrag LTR XI Sa 14:00 H4
Wie erklärt man das Fliegen in der Schule? — •Rita Wodzinski
— Univ.-Gesamthochschule Kassel
Das Fliegen ist ohne Zweifel ein Thema, das bei Schülerinnen und
Schülern auf großes Interesse stößt. Als Physiklehrer oder -lehrerin ist
man jedoch häufig ratlos, welche Antwort man im Unterricht auf die
Frage geben kann, warum eigentlich ein Flugzeug fliegt. Zu viele verschiedene
Erklärungsmuster kursieren, deren Gültigkeit man nur schwer
abschätzen kann. Der Vortrag möchte ein wenig Klarheit in die fachlichen
Zusammenhänge bringen und zugleich einen Vorschlag unterbreiten, wie
man das Fliegens im Unterricht schülergerecht erklären kann.
Hauptvortrag LTR XII Sa 15:00 H4
Erfinderwettbewerbe an Schulen – Physik durch die Hintertür
— •Toni Widemann — Gymnasium Wolnzach
Baue ein Fahrzeug, das mit einem Liter kalten Wasser als alleinige
Antriebsenergie möglichst weit fährt! Baue ein Flugzeug, das möglichst
weit fliegt! Einzige Antriebsenergie ist eine Mausefalle. Ein rohes Ei fällt
aus großer Höhe und bleibt ganz! Baue dazu eine *Egg-Bag* (deutsch
” Eiertasche“)
Solche und ähnliche Probleme wurden bei schulinternen Veranstaltungen
gestellt und mussten dann möglichst originell gelöst werden. Bei
diesen Wettbewerben sind Kreativität, Eigeninitiative und auch etwas
handwerkliches Geschick erforderlich; Teamarbeit ist erwünscht! Die angemeldeten
Schülerinnen und Schüler bauen passende Modelle und treten
damit in einem Wettkampf gegeneinander an. Dabei passieren natürlich
auch viele lustige Dinge. So ist es nicht verwunderlich, dass sich die am
Schyren-Gymnasium seit dem Schuljahr 1994/95 durchgeführten Erfinderwettbewerbe
nach wie vor großer Beliebtheit erfreuen. Schier unglaubliche
Leistungen wurden bei den einzelnen Aufgabenstellungen erreicht.

A. D., Mirlin .................HL 14.5
A., Ernst .....................MA 4.1
A., Moevs ................ MA 13.109
Aartsma, T. J. ..............SYLS 3.9
Aartsma, Thijs J. ..........SYLS 3.21
Abaker, Mohamed ............ TT 6.3
Abbamonte, P. ............. TT 30.12
Abd-Elmeguid, M. M. ........TT 20.5
Abdallah, Ossamah ....... SYOH 5.11
Abdumalikov Jr., A. A. .......TT 31.1
Abermann, Stephan ..........DS 15.2
Abetz, Volker ............. CPP 15.30
Abicht, Hans-Peter ............DF 7.5
Able, Andreas ..... HL 27.6, HL 44.87
Abou-Helal, M. O. ........... O 14.56
ABRA - Kollaboration ....... MA 6.13
Abramsohn, D. ..............MA 10.6
Abramsohn, Dirk ....O 28.78, O 28.80
Abrikosov, Alexei .............. PV XI
Abstreiter, G. .. HL 12.63, HL 22.4,
HL 37.11, HL 42.5, HL 44.17,
HL 44.18, HL 44.37, HL 47.6
Abstreiter, Gerhard HL 22.7, HL 32.6,
HL 50.3, SYLS 3.30, SYLS 4.5
Acet, M. MA 6.6, MA 6.10, MA 13.77,
MA 13.113
Acet, Mehmet ...............MA 24.1
Adam, R. ................... MA 26.4
Adam, Roman ...............MA 31.8
Adamovsky, Sergey ........CPP 16.25
Ade, G. .................... HL 27.11
Adeagbo, Waheed Adeniyi .. DY 46.98
Adelmann, P. ...............TT 30.36
Adelung, R. .O 14.13, O 28.35, O 38.6
Adelung, Rainer ...O 24.1, SYOH 5.22
Adler, P. .................... TT 14.2
Adlkofer, Klaus .......... AKB 50.131
Adrian, H. ............TT 1.3, TT 7.5
Adrian, Hermann .... TT 8.2, TT 8.29
Advanced Energy Industries ......FB 1
Aeschlimann, Martin O 14.7, O 28.53,
O 28.76, O 37.3, O 45.4, SYOH 3.2
Afanas’ev, Valeri .............HL 52.3
Agarwal, K. C. ....HL 12.17, HL 12.74
Agelopoulos , Konstantin .. AKB 50.94
Agena, Ceno .............. CPP 16.19
Aggour, Mohammed . DS 20.5, O 40.3
Agne, Th. ................... HL 21.5
Ahlers, H. .......MA 13.79, MA 13.80
Ahles, Marcus ............... HL 23.4
Ahmed, E. ...................TT 8.45
Ahmed, Imad .......CPP 8.4, DS 13.1
Ahuja, Rajeev ................ MA 4.4
Aichele, Martin ............CPP 15.49
Aichhorn, M. ............... TT 32.10
Aichhorn, Markus ............TT 24.5
Aichmayer, Barbara ....... AKB 50.71
Aidam, Rolf ................ HL 38.10
Aits, Carsten ................. TT 3.3
AIXTRON ......................FB 2
Akimitsu, J. ................. TT 6.10
Aktas, Cenk ................ DS 22.24
Aktas, O. C. ......... O 24.1, O 28.35
Aktas, Oral Cenk ... CPP 16.8, DS 7.1
al., et .........................O 23.7
Al Marrawi, F. .............SYLS 3.15
Al-Ibrahim, M. ............SYOH 5.52
Al-Ibrahim, Maher . HL 12.96, HL 23.3
Al-Kassab, Talaat .....M 15.4, M 18.3
Al-Kassab, Talaát .............M 24.2
Al-Shamery, Katharina .....CPP 16.23
Albe, Karsten ........ HL 17.7, O 39.6
Albert, Takács ............ MA 13.109
Albrecht, Daniel ............. DF 5.12
Albrecht, F. ..................HL 27.8
Albrecht, Fanny ..............HL 40.3
Albrecht, J. ........ TT 31.5, TT 31.8
Albrecht, Joachim ........... TT 19.2
Albrecht, Karl-Friedrich ... AKSOE 3.4
Albrecht, M. .................HL 27.7
Albrecht, Manfred ........... MA 26.5
Albrecht, Tom R. CPP 2.1, CPP 15.15
Aldo, Romero ............... DY 40.5
Aleiner, I. L. ................. HL 14.2
Alet, Fabien ................. TT 10.4
Alexander, Schmatulla ........O 14.82
Alexe, Gabriela ...............HL 3.11
Alexe, M. .....................DF 6.4
Alexe, Marin ............... SYNP 2.2
Alfa Aesar ...................... FB 3
Alfarano, Simone ........ AKSOE 10.2
Alff, L. ............ MA 13.5, TT 18.4
Alff, Lambert .. HL 44.9, MA 13.27,
MA 13.39, MA 13.116, TT 1.1,
TT 8.3, TT 8.19
Ali, M. ...................... HL 16.1
Aliaga, Horacio .............TT 24.42
Alivisatos, Paul ............ SYOH 8.1
allectra .........................FB 4
Allen, J. W. ................. TT 28.1
Allenstein, F. ............... DS 22.11
Allmers, Tobias ............... O 24.6
Allouche, A. ................. O 28.57
Alloul, H. ....................TT 6.11
Almokhtar, M. .............. MA 20.3
Alnot, Patrick ............... CPP 8.7
Alonso, J. A. ................ TT 20.5
Alonso, M. Isabel ...............O 4.4
Alschinger, M. ................ O 19.8
Alsheimer, Walter ............DF 5.15
Altieri, P. ....................HL 10.1
Altmeyer, Stefan .............AIW 1.1
Altrock, Frank ............AKSOE 1.2
Alvarez, David ............... HL 10.3
Alvermann, Andreas ......... TT 30.5
Alves, H. ................... HL 12.85
Amann, Andreas ............DY 46.32
Amarouchene, Yacine ........ DY 15.4
Ambacher, O. ...HL 16.1, HL 16.2,
HL 16.3, HL 27.4, HL 27.15,
SYOH 5.52
Ambacher, Oliver . DS 22.12, HL 9.1,
HL 40.1, HL 40.2
Amboage Castro, M. .........TT 20.5
Ambrosch-Draxl, C. .........TT 32.10
Ameduri, M. ............... TT 30.30
Amenitsch, H. ............ AKB 50.86
Amirgoulova, Elza V. ....... SYLS 2.2
Amis, E. .................... CPP 6.1
Amman, U. ........ DF 7.6, MA 13.46
Ammerahl, U. ..TT 3.13, TT 30.37,
TT 30.39
Ammeral, U. ................ TT 8.45
Amsel, L. ...................... O 9.3
Amy Y., Liu .............. MA 13.109
Ana Maria, Lakasta .......... DY 40.5
Ananthakrishnan, Revathi AKB 50.125
Anapa, H. ..................TT 30.23
andere ...................... AIW 6.1
Andergassen, Sabine .... TT 24.9,
TT 24.10
Anders, Frithjof .....HL 47.1, TT 11.3
Anders, Frithjof B. ...........TT 15.3
Anders, Rolf .................M 18.22
Andersen, Audree ...........CPP 10.4
Andersen, J. N. ............... O 38.8
Andersen, O. K. .... TT 28.3, TT 32.7
Andersen, Torsten ............ MA 4.4
Anderson Duarte, Helio ..... CPP 16.3
Anderson, J. .................. O 34.6
Ando, Yoichi ................ TT 8.44
Andre, G. .................. TT 30.36
Andreev, T. ..................O 14.19
Andrei, Natan ............... TT 3.10
Andrej, Kulakov .............. TT 2.3
Andres, Dieter ..............TT 30.21
Andres, Stefan ...............O 28.29
Anfatec ........................ FB 5
Angermann, H. .............. HL 31.6
Angrik, Jörg ................TT 30.33
Anikin , Kirill V. AKB 50.12, HL 44.36,
SYLS 2.2, SYLS 3.14
Anil Kumar, P. S. .MA 4.6, MA 13.122
Anisimov, V. ............... TT 24.45
Anisimov, V. I. .. TT 24.1, TT 24.2,
TT 28.4
Anisimov, Vladimir ......... TT 24.43
Ankudinov, A. L. ............. MA 8.4
Anne-Marie, Daré ...........TT 24.40
Anselmann, Ralf ........... SYNP 2.4
Anselmetti, D. .. SYLS 3.45, SYLS 4.2
Anselmetti, Dario .....AKB 22.1,
AKB 50.81, CPP 16.19, SYLS 3.28,
SYLS 3.31, SYLS 3.33, SYLS 3.34,
SYLS 3.36, SYLS 3.40
Anton, Rainer ..............MA 13.92
Antoniak, C. ................. MA 6.4
Antonov, V. N. .............. TT 24.2
Antons, A. ....................O 25.7
Antony, Jens .............. SYLS 3.54
ap. Prof. Neumann, Manfred
CPP 15.39
Apalkov, V. M. .............. HL 14.3
Apetrii, C. ...................TT 8.13
Apetrii, G. ..................HL 37.11
Appelhans, Dietmar ..........CPP 7.6
Aprili, Marco ....... TT 19.4, TT 25.6
Arendt, Thomas .......... AKB 50.55
Ariando ..................... TT 18.3
Arikawa, Mitsuhiro ............TT 3.8
Arinaga, Kenji ..............SYLS 4.5
Arkin, Handan ...............CPP 5.3
Arkin, Shy ................ AKB 50.87
Arndt, Christian ............ HL 12.96
Arndt, Peter .............. AKB 50.58
Arnold, Marco AKB 50.14, AKB 50.37
Arnold, Michael ..............TT 16.5
Arnold, R. ..................TT 17.10
Arnold, Thomas ............ DS 22.17
Arrigoni, Enrico .. TT 2.5, TT 26.7,
TT 26.10
Artemyev, Mikhail V. .........HL 15.6
Arwin, H. ....................HL 23.6
Arzt, Eduard ..AKB 10.4, AKB 50.107
Asawapirom, Udom ....... SYOH 5.72
Ashino, Makoto ....... O 9.1, O 28.39
Ashkenov, N. ... DS 9.7, HL 12.83,
HL 12.86, HL 28.5
Assa, Jacky .................HL 12.95
Assaad, Fakher ....TT 24.11, TT 32.8
Assaad, Fakher F. ............TT 15.1
Assayag, G. Ben .............. HL 3.6
Assmann, Cornelia ............ TT 8.7
Assmann, Walter ..............DS 3.2
Assmus, W. ................ TT 30.18
Ast, Christian ..........M 5.3, O 11.5
Atakhorrami, Maryam ...... AKB 10.1
Atodiresei, Nicolae ............ O 38.1
attocube systems ............... FB 6
Auer, Richard ................DS 19.1
Augustin, Markus ... HL 2.3, HL 15.11
Auth, Nicole ............... MA 20.10
Auth, Thorsten ........... AKB 50.46
Avasthi, D. K. ................ DS 1.7
Avasthi, Devesh Kumar ..... CPP 16.8
Avelino de Abreu, Heitor ....CPP 16.3
Averin, D. V. ................TT 29.7
Avouris, Phaedon ...........TT 27.10
Avrutin, V. .................. HL 37.4
Awschalom, D. D. ........... HL 50.1
Axt, Vollrath Martin ........ HL 44.39
Ayalasomayajula, Phani .. CPP 8.4,
DS 7.3, DS 13.3
Ayyad, Ahmed ............... O 28.59
B.G. Teubner ................... FB 7
B. lum, Carsten ............... HL 8.2
Baberschke, K. ..MA 15.1, MA 20.2,
MA 28.12
Babic, Bakir ............... SYNF 1.4
Babic, Dusan ...............DY 46.18
Bacca , C. ..................TT 17.10
Bach, Christian ............... O 20.7
Bach, Lars ...................HL 38.8
Bach, Markus . CPP 15.39, CPP 16.19
Bach, P. .....................HL 29.3
Bachert, Peter ..... AKB 50.105,
AKB 50.108
Bachmann, Andreas ............ O 3.1
Bachmann, Michael CPP 5.3, CPP 5.4,
DY 46.58, SYLS 3.48
Back, C. ..........HL 43.2, MA 13.76
Back, Christian .MA 13.86, MA 28.7,
MA 28.13
Back, Christian H. ...........MA 28.5
Backen, Elke ................ MA 30.5
Backes, D. .................MA 13.48
Bactavachalou, Ravindrakumar
CPP 2.6
Bactavatchalou, Ravi ....... CPP 15.3
Bactavatchalou, Ravindrakumar
CPP 7.5, CPP 15.36
Bader, A. ....................HL 29.3
Bader, Martin ................LTR VII
Bader, S. ...................HL 44.84
Bader, Samuel .............. MA 12.2
Badinski, A. ...............SYLS 3.20
Badran, Rashad I. ...........HL 44.23
Bähtz, C. ......................M 3.1
Bär, Markus ..AKB 50.88, CPP 6.3,
DY 20.4, DY 20.5, DY 24.3,
DY 46.51
Baer, N. .....................HL 36.7
Baer, Norman ................HL 36.5
Bärmann, M. ..............CPP 15.11
Bärner, K. ................ MA 13.115
Baeuerle, Dieter .. DS 17.3, SYLS 3.27
Baeuerle, Peter ............ SYOH 1.1
Baggio-Saitovitch, Elisa ......MA 6.11
Bagrets, Alexej .............MA 13.30
Bagrets, Dmitry ............. TT 11.5
Baida, Fadi .................. O 28.54
Baier, J. . TT 3.11, TT 3.12, TT 6.7,
TT 14.9, TT 14.14, TT 14.14,
TT 20.7, TT 30.14, TT 30.23,
TT 32.6
Baier, Jürgen ..............SYLS 3.13
Baik, Seung Chul ............. M 20.2
Bailleul, M. ................ MA 13.41
Baisch, Belinda .............. O 14.17
Bakin, A. ....................DS 22.1
Balanetskyy, Sergiy ........... M 31.1
Balanov, Alexander .......... DY 42.2
Balaur, Eugen ............. SYOH 5.9
Baldassarri H. v.H., G. ...... HL 44.34
Baldassarri Höger von Högersthal,
Giorgio ..................HL 28.2
Baldus, Oliver ....... DF 4.5, DY 29.5
Balgar, Thorsten .............. O 33.6
Baller, Jörg ... CPP 8.2, CPP 8.7,
CPP 15.3
Balthes, Eduard ............ TT 30.27
Balthes, Eduart .............TT 30.28
Baltruschat , Helmut .......... O 38.5
Baluschev, Stanislav ....... SYOH 2.4
Balzer, Frank ......... CPP 1.4, O 4.3
Balzer, H. .................... DF 2.2
Autorenverzeichnis
Banach, Michael J. ........ SYOH 2.3
Banhart, F. .................. MA 6.3
Banhart, J. ....M 22.5, SYPF 4.4,
SYPF 5.2, SYPF 5.3
Banhart, John .. M 22.6, SYPF 4.1,
SYPF 4.2, SYPF 5.1
Bannani, Amin ...............O 14.63
Bansmann, J. .............. MA 13.88
Bansmann, Joachim . O 7.1, O 28.68,
O 28.82
Banys, J. ..................... DF 7.4
Baranov, A. N. ................O 24.5
Baranovskii, S. D. ............HL 41.3
Baratoff, A. ..................O 23.10
Bardot, Cedric ..............HL 36.12
Baret, Jean-Christophe ..CPP 16.14,
DY 15.2
Barilo, S. ...................TT 30.23
Barke, I. ..... O 14.19, O 19.5, O 24.8
Barker, James ............. SYOH 8.2
Barkow, U. .. M 18.28, MA 13.103,
MA 13.104
Barnas, J. ................... TT 16.7
Barnes, Richard G. ............. M 3.4
Barrena, Esther ........ DS 7.2, O 4.4
Bartel, Til ................... HL 50.2
Bartels, F. ..................SYLS 4.2
Barth, Dirk .................CPP 13.8
Barth, Johannes V. ...........O 28.38
Barth, Silko ................ HL 12.82
Barth, Stephan .............. DY 40.3
Barthel, J. ... MA 13.13, MA 15.5,
MA 20.7, O 39.9
Barthel, Wolfgang ........... DY 26.3
Barthelmess, Miriam ....... MA 13.25
Barthelmeß, Miriam .......... MA 2.2
Barthold, P. ................ HL 44.28
Bartkowiak, Marek ...........TT 33.2
Bartolf, H. .................. TT 21.1
Bartsch, Alexander .............M 7.1
Bartz, Peter ...............CPP 16.19
Barzola, J. ....................M 14.5
Basov, Dimitri ...............TT 8.44
Bass, U. ..... SYOH 5.62, SYOH 5.64
Bastolla, Ugo .............. AKB 40.4
Bastwöste, K. .................DF 2.4
Basu, Abhik ................. DY 12.3
Batov, I. E. ..................TT 8.21
Batrouni, George ........... TT 24.11
Batrouni, George G. ..........TT 10.4
Bauchspieß, K. R. .............. O 4.2
Baudach, Mandy ..............HL 3.9
Baudelet, François ...........MA 30.1
Bauer, Andreas ...MA 5.2, O 17.5,
O 28.7, TT 19.4, TT 19.5
Bauer, E. .......CPP 15.8, CPP 16.24
Bauer, E. D. ............... TT 24.29
Bauer, Ernst ............... TT 24.28
Bauer, Gottfied Heinrich ......HL 24.5
Bauer, Gottfried H. . DS 14.7, HL 30.4
Bauer, Gottfried Heinrich ..HL 30.3,
SYOH 5.87, SYOH 5.87
Bauer, Günther ............... HL 7.1
Bauer, J. ................... HL 12.63
Bauer, Jens ........DS 22.3, HL 44.58
Bauer, Michael ...O 14.7, O 28.53,
O 28.76, O 35.1, O 37.3, O 45.4
Bauer, R. .....................DF 2.2
Baule, Adrian ................DY 14.4
Baumann, Christoph ......... TT 14.6
Baumann, G. ............. SYOH 5.19
Baumann, P. ..... HL 12.74, HL 12.76
Baumbach, Tilo ............ SYPF 4.1
Baumgarth, B. ............. SYLS 4.2
Baumgartl, Jörg ............ DY 46.83
Baur, Barbara ...... HL 16.5, HL 16.7
Bausch, A. R. ............. CPP 15.11
Bausch, Andreas ........... AKB 10.2
Bausch, Andreas R. ... AKB 50.36,
DY 46.97, SYLS 3.32
Bausinger, Ralf ............SYLS 3.42
Bautista, Rafael ................ O 4.5
Bawendi, Moungi ...........SYNP 1.1
Bayer, A. .................... O 14.15
Bayer, C. .................. MA 13.62
Bayer, Daniela .. O 28.53, O 28.76,
O 37.3
Bayer, M. HL 13.1, HL 36.3, HL 36.12,
HL 44.34
Bayer, Manfred .............. HL 28.2
Bayerl, Thomas .............DS 22.44
Bayon, R. DF 5.3, DS 22.55, DS 22.56
Bayreuther, G. .MA 13.41, MA 13.61,
MA 15.4
Bayreuther, Günther ... MA 13.31,
MA 13.40
Bazyakina, Natalia ........SYOH 5.11
Beaumont, Virginie ..........MA 20.6
Becca, Federico .............TT 24.24
Bechinger, Clemens ....DY 46.18,
DY 46.83, DY 46.84, DY 46.88
Bechmann, Michael ..........TT 21.4

Bechstedt, F. ................ HL 27.4
Bechstedt, Friedhelm ... CPP 16.2,
HL 36.1, HL 36.9, O 14.53,
O 28.20, O 28.22, O 40.2
Bechtel, F. .....................O 9.3
Beck, Markus ...............HL 44.53
Beck, P. A. ........ MA 16.5, O 14.81
Becker, A. ..................SYLS 4.2
Becker, B. ................. MA 13.61
Becker, Conrad ...... O 14.11, O 43.5
Becker, Klaus ........HL 32.2, TT 7.2
Becker, Klaus W. ...TT 15.4, TT 20.1
Becker, Moritz ................. O 6.8
Becker, S. K. ......... HL 3.10, O 9.3
Becker, Sascha ...............HL 32.5
Becker, Sebastian Kai ......... HL 3.9
Becker, Thomas MA 13.22, MA 13.23,
O 46.3
Beckmann, Björn ...........MA 10.10
Beckmann, Detlef ............TT 19.3
Beckmann, Felix ............SYPF 4.5
Bedanta, S. ..... MA 13.83, MA 13.84
Beddies, G. ...DS 22.10, DS 22.11,
DS 22.47
Bednorz, J. Georg .............DF 2.1
Beer, M. ................... HL 44.84
Beernink, G. ..............SYOH 5.13
Begoin, Maik ............... HL 44.52
Behera, Laxmidhar ........AKSOE 4.3
Behler, Jörg .................. O 26.3
Behm, R. J. .. O 5.7, O 6.6, O 25.6,
O 38.3, O 46.5
Behm, Rolf-Jürgen ............ O 24.9
Behnke, Timo .........O 9.1, O 28.39
Behr, G. .......... TT 8.47, TT 24.31
Behr, Günter ... DS 22.41, M 22.2,
TT 8.51
Behrend, Claas ............ SYLS 3.53
Behrend, Raymond ......... SYLS 4.4
Behrendt, S. ................. O 14.77
Behrens, Peter ...............CPP 9.3
Behringer, Hans ............. DY 16.4
Beige, Horst .................. DF 7.5
Bein, Thomas ............... CPP 9.3
Beiner, M. ................ CPP 15.24
Beiner, Mario .............. CPP 14.5
Bek, Alpan ................... O 23.8
Bekkali, A. ............... SYOH 5.54
Bel’kov, V. V. ..... HL 43.2, HL 44.46
Belaidi, A. .DF 5.3, DS 21.3, DS 22.56
Beleggia, Marco .............. TT 1.5
Belenchuk, Alexandr .........MA 22.3
Belger, Andre .................M 31.4
Beljakowa, Svetlana .......... HL 30.6
Belzig, Wolfgang HL 49.4, SYNF 1.4,
TT 27.11
Ben Omar, M. ..............TT 24.53
Benabdallah, Abdelhadi ..... DY 46.13
Benckiser, Eva ...............TT 3.14
Bendas, Gerd ..... AKB 50.119,
AKB 50.120
Bendix, Oliver .................HL 5.8
Benea, Diana ..... M 18.7, MA 13.112
Benesch, C. ..................O 28.31
Benetatos, Panayotis .. AKB 50.42,
AKB 50.43
Benndorf, G. ...DS 22.7, HL 12.73,
HL 12.86, HL 17.12
Benndorf, Gabriele HL 12.68, HL 44.56
Bennemann, Karl Heinz .....MA 13.75
Benner, Hartmut ... DY 36.2, DY 36.4
Bennewitz, K. ....... M 16.4, M 18.15
Benomar, M. ............... TT 14.11
Bensch, Wolfgang MA 13.112, O 14.27
Bente, Klaus ............... DS 22.52
Benten, W. ................... O 10.5
Bentes, E. ................SYOH 5.65
Benthien, Holger .............TT 24.7
Bentner, Johannes ..TT 19.4, TT 19.5
Benyoucef, M. ............... HL 36.7
Berakdar, Jamal . HL 12.20, HL 47.2,
O 28.69, TT 8.40
Berche, Bertrand ........... DY 46.95
Berche, Pierre Emmanuel ... DY 46.95
Bercioux, Dario .............. HL 29.6
Berenguier, Baptiste ......... DS 20.5
Berger, Andreas ............. MA 10.9
Berger, Steffen SYOH 3.2, SYOH 5.21
Berges, U. .. O 28.6, O 28.27, O 28.28
Berggold, K. ............... TT 30.23
Berginski, Michael ..........MA 13.69
Bergmann, Andre MA 16.8, MA 20.8,
MA 30.8, O 28.85
Bergmann, Antje ..CPP 7.4, CPP 16.7
Berkebile, S. .................. DS 7.4
Berkemeier, F. .......DF 4.6, DY 29.6
Berkibile, Steve ............ SYOH 7.1
Berndt, Johannes ............. O 31.2
Berndt, R. .................... O 17.1
Berndt, Richard .. O 14.26, O 17.6,
O 26.1
Berndt, Sven ........ DF 4.1, DY 29.1
Bernhard, C. ....... TT 14.2, TT 18.7
Bernhard, Christian .......... TT 8.17
Bernhard, P .................. DS 9.6
Bernhardt, T. M. ..O 10.6, O 14.45,
O 28.64, O 32.6
Bernhoeft, N. ................TT 30.4
Bernien, M. ................. MA 15.1
Bernstorff, S. ............. AKB 50.86
Bernstorff, Siegrid ............HL 3.11
Bertagnolli, Helmut ..........CPP 4.4
Bertel, E. ..................... O 25.5
Berthold, W. .................O 28.70
Bertram, F. ...... HL 12.18, HL 27.14
Bertram, Frank .... HL 12.78, HL 21.3
Bertram, Nils ................ O 28.63
Bertrand, Francois ...........MA 10.7
Bertschat, H. H. ............ MA 15.6
Beschoten, B. . MA 10.8, MA 28.11,
MA 31.4
Beschoten, Bernd .. HL 35.7, MA 31.1
Best, Margaret E. ........... MA 26.5
BESTEC ....................... FB 8
Bestehorn, Michael CPP 16.5, DY 15.5,
DY 17.1, DY 34.6, DY 46.51
Bethke, C. ...... MA 13.121, MA 18.2
Betsehorn, Michael .......... DY 15.1
Bett, Andreas ...............HL 44.48
Betz, M. .................... HL 4.11
Betz, Timo .... AKB 12.1, AKB 50.16
Beuckert, Guido ...............DS 9.4
Beuttler, Mirjam .............. DS 1.6
Beyer, C. ....................TT 12.3
Beyer, Christoph .............TT 12.4
Beyer, Jörn ..........TT 8.7, TT 8.22
Beyer, R. .................... O 14.77
Beyer, Reinhard ..............O 14.78
Beyer, V. .................... O 14.77
Beyreuther, E. ............... O 14.77
Beyreuther, Elke ............. O 14.78
Bhaseen, M. Joseph ..........TT 26.1
Bhattacharya, Sarbari .........MA 6.7
Bhaumik, Sheila .............. M 20.3
Biberacher, Werner ......... TT 30.21
Biberger, Josef .............. MA 26.7
Bichler, M. ... HL 12.63, HL 14.3,
HL 14.4, HL 22.4, HL 42.5,
HL 44.17, HL 44.18, HL 44.27,
HL 44.37, HL 47.6
Bichler, Max ...HL 12.94, HL 22.7,
HL 32.6, HL 44.52, HL 50.3
Biedermann, A. .............. O 25.10
Biedermann, Albert ........... O 39.8
Biegel, Daniel ..............MA 13.57
Biehl, M. .................... O 14.31
Biehl, Michael ....DY 46.12, DY 46.69
Biehl, Ralf ................. DY 46.66
Biehler, Björn ............... TT 8.30
Biehne, Gisela .... HL 12.84, HL 44.11
Bielefeldt, Hartmut ......... TT 24.37
Bierkandt, M. ...............HL 44.25
Biermann, S. ................ TT 32.7
Bierwisch, Claas ............ HL 12.47
Biggs, T. ...................TT 30.25
Bihler, Christoph .............HL 35.5
Bihlmayer, G. ...MA 4.9, MA 4.10,
MA 13.9, MA 31.2
Bihlmayer, Gustav DS 12.1, MA 11.4,
MA 26.9, O 5.8
Bihr, H. ..................... M 18.15
Bilgram, J. H. ................ M 28.1
Bilgram, Jörg ................DY 25.1
Bilgram, Jörg H. .DY 25.2, DY 46.70,
DY 46.71
Bilzer, C. ...................HL 44.83
Bimberg, D. ....... HL 3.10, HL 50.10
Bimberg, Dieter . HL 16.10, HL 25.3,
HL 36.4, HL 36.10, HL 36.11,
HL 37.3, HL 42.4, HL 44.89,
HL 50.2
Binder, Kurt . CPP 14.8, CPP 15.48,
CPP 15.49, DF 3.5, DF 3.6,
DY 28.5, DY 28.6
Binek, Christian ............MA 13.45
Bird, J. P. ..................DY 46.39
Bird, Jon ...................HL 44.32
Birk, Juliane ................. O 28.36
Birkner, A. ............... SYOH 5.13
Birkner, Alexander ......... SYOH 1.2
Birner, S. ...................HL 44.37
Birringer, R. ..M 20.5, M 21.4, M 32.4
Birringer, Rainer .. M 21.1, M 21.3,
M 26.3
Birringer, Reiner .............. M 26.4
Bischoff, Lothar ..............O 28.54
Bischofs, Ilka ............. AKB 50.34
Biswas, A. ..........DS 22.29, O 24.1
Biswas, Abhijit .. CPP 16.8, DS 7.1,
DS 22.24
Biswas, Indro ............. SYOH 5.24
Bitte, Frank ........AIW 5.1, AIW 6.1
Bittkau, K. ................. HL 12.13
Bittner, Alexander ........... HL 51.1
Bittner, E. ...................DY 10.2
Bittner, Elmar .. DY 16.1, DY 16.2,
DY 46.92
Bitzer, Karl .................HL 44.77
Blache, Robert .............SYOH 4.1
Bläsing, J. .........HL 27.1, HL 27.11
Bläsing, Jürgen ............. HL 12.78
Blanco, A. .................... HL 8.3
Bland, J. A. C. ..............MA 25.2
Blank, D. H. A. ............ TT 30.12
Blanter, Mikhail S. ............M 25.2
Blanter, Yaroslav ........... TT 17.15
Blatter, G. .................. TT 29.6
Blatter, Gianni ...............TT 25.4
Blaudeck, Thomas HL 50.7, SYOH 5.8,
SYOH 5.10
Bleil, Stefan ................DY 46.84
Blochowicz, Thomas .DF 2.6, DF 3.4,
DF 3.7, DY 28.4, DY 28.7
Block, Michael ................HL 3.2
Block, T. ............. O 3.6, O 28.24
Block, Tammo ...............O 28.44
Blomeier, Steffen . MA 10.4, MA 13.47
Bloom, C. ................ SYOH 5.39
Blügel, S. MA 4.9, MA 4.10, MA 13.9,
MA 13.89, MA 31.2, O 8.1, O 25.7
Blügel, Stefan .. DS 12.1, HL 44.12,
MA 11.4, MA 26.9, MA 27.2,
MA 27.9, O 5.8, O 6.2, O 38.1
Blüm, Marie-Christine ........ O 14.14
Blümer, Nils .................TT 32.9
Blümmel, Jacques ....AKB 50.14,
AKB 50.37
Blum, Carsten ................ HL 8.2
Blum, Ralf-Peter ............... O 5.5
Blum, Volker ...................O 6.1
Blume, Raoul ................ O 28.58
Blumen, Alexander . CPP 5.1, CPP 5.2
Bobbert, Peter ...............HL 23.1
Bobek, Thomas ..............DS 15.2
Bobeth, Manfred ...........AKB 50.9
Bobisch, Christian ............O 14.63
Bobroff, J. .................. TT 6.11
Bocatius, V. ....... MA 10.1, O 14.68
Bock, Thomas ................ VA 2.4
Bockelmann, Ulrich .........AKB 20.3
Bode, M. ...................... O 8.1
Bode, Matthias .. MA 4.7, MA 4.8,
MA 17.3, MA 26.12, O 17.2
Bodenthin, Yves ............. O 28.86
Boeck, Torsten ................HL 3.2
Boeckle, Sabine ........... SYLS 3.42
Boedecker, Geesche ......... HL 12.27
Bödeker, Hendrik U. .... DY 14.1,
DY 46.16
Böhler, Tobias ...............TT 27.3
Böhm, Andrea .............. MA 24.2
Böhme, Christoph ............HL 41.5
Böhmer, Roland ...DF 4.1, DF 5.8,
DY 29.1, DY 46.7
Böker, Alexander .... CPP 15.30,
CPP 16.9, CPP 16.32
Böni, Peter .... MA 13.66, MA 13.102
Börger, Volker ..............CPP 10.2
Börner, Uwe .................DY 24.3
Börsch, Michael ...........AKB 50.98
Boese, Markus . DS 22.23, MA 24.5,
MA 24.6
Boesecke, Peter ..............O 14.44
Böttcher, Artur .............. O 28.58
Böttcher, Tim ...HL 16.8, HL 16.9,
HL 44.88
Boettger, Gunnar HL 12.29, HL 12.32,
HL 20.3
Böttger, L. H. .............. HL 12.48
Böttger, T. ................... DS 9.8
Böttger, U. ................... DF 6.3
Bogdanov, A. N. ............ MA 24.4
Bogdanov, Dmitrij ........... TT 8.52
Boger, Klaus ..................O 45.7
Boggasch, Stephanie ...... AKB 50.63
Bogner, Thorsten ..........CPP 15.35
Bogner, U. ....................DF 2.2
Bohn, Andreas ........... AKSOE 3.5
Bohne, Wolfgang .... DS 1.6, DS 21.1
Bohne, Y. .................. DS 22.34
Bohnen, K.-P. ....... TT 9.8, TT 30.1
Bollenbach, Tobias ........ AKB 50.49
Bollero, A. ....... MA 13.3, MA 13.93
Bolse, W. .....................DS 1.7
Bolse, Wolfgang ...DS 1.2, DS 1.3,
DS 1.6, DS 3.5, DS 3.6
Bolte, Markus ................MA 2.2
Bolz, A. .................... HL 44.38
Bolz, Arne ..........HL 3.12, HL 37.2
Bombis, Christian .............. O 3.7
Bommas, Christoph ............ M 3.3
Bon, Cecile ................SYLS 3.26
Bonafos, C. ...................HL 3.6
Bondar, Ana-Nicoleta ..... AKB 50.31
Boneberg, Johannes .O 28.36, O 28.49
Bonfim, M. ................ MA 28.10
Autorenverzeichnis
Bonifazi, Davide ............. O 14.22
Bonn, Daniel ................ DY 15.4
Bonn, I. ......... MA 13.117, TT 32.6
Bonné, Tune B. ........... CPP 16.30
Bonrad, Klaus ............ SYOH 5.81
Bonthuis, D. J. ........... AKB 50.99
Bonzel, Hans P. ...............O 20.3
Bootsmann, M.-T. ........... HL 42.2
Borchers, C. ................... M 3.1
Borcia, Rodica ...............DY 15.5
Borck, Andreas ............. DY 46.22
Borda, L. ....................TT 16.7
Borda, Laszlo ................TT 16.6
Bordag, Natalie ........... AKB 50.56
Borenstain, S. .............. HL 12.73
Borg, N. ......................O 19.8
Borgardt, Nikolai ............HL 44.62
Borgmann, D. ... O 14.15, O 18.2,
O 28.61
Borgschulte, A. ................ M 3.2
Borgschulte, Andreas ..........O 26.8
Boris, A. .................... TT 14.2
Borisenko, Sergey ............. TT 9.3
Borisov, Pavel ..............MA 13.45
Bork, Thorsten .............. DS 22.1
Born, Detlef ................. TT 29.4
Born, Harald ................HL 36.10
Born, V. ......................TT 8.8
Born, Volker TT 1.5, TT 8.9, TT 8.10
Bornemann, S. ............... MA 6.2
Bornholdt, Stefan .... AKB 50.95,
AKB 50.109
Borodin, A. .........O 14.56, O 28.57
Boroudjerdi, Hoda ......... SYLS 3.38
Borowski, Peter ........... AKB 50.27
Borowski, Rene ... DS 22.23, MA 24.5
Borri, P. .....................HL 36.3
Borth, R. .......... TT 7.8, TT 24.33
Bortz, Michael ...............TT 16.4
Boruszczak, Malgorzata ....CPP 16.23
Borzenko, T. ............. SYOH 5.62
Borzenko, Tatjana . HL 29.4, HL 44.20
Boschloo, G. .................HL 30.1
Bose, Sougato ..............TT 22.10
Boshta, M. ............... MA 13.115
Botcharova, E. ................M 13.1
Botcharova, Ekaterina .........M 16.2
Bothe, Karsten ...............HL 24.4
Boucharat, Nancy .............M 24.1
Bourges, P. ...... TT 30.38, TT 30.38
Bovensiepen, Uwe MA 28.14, O 28.73,
O 37.7, O 45.2
Bowen, M. ................... MA 3.2
Boxer, Steven ............AKB 50.112
Boyen, H.-G. ....DS 1.9, DS 22.8,
DS 22.37, MA 6.3, O 28.42
Boyen, Hans-Gerd ..DS 15.5, O 3.2,
O 32.5
Brabec, C. J. ................ HL 19.4
Brabec, Christoph HL 23.3, SYOH 5.50
Bracchi, A. ...........M 18.2, M 24.4
Bracht, Harmut ..............O 14.75
Braden, M. ....TT 3.12, TT 14.9,
TT 14.11, TT 14.14, TT 14.14,
TT 24.53, TT 30.13, TT 30.16,
TT 30.36, TT 30.38, TT 30.38
Bradford, C. ................ HL 12.19
Bräuchle, C. ................SYLS 3.4
Bräuchle, Christoph CPP 9.2, CPP 9.3,
CPP 9.4, PV II, SYLS 3.42
Braggio, Alessandro .......... HL 47.5
Brako, Radovan ..............O 14.37
Brandau, Marian ......... AKSOE 5.2
Brandes, T. ..................HL 44.8
Brands, Mario ... MA 13.60, TT 11.12
Brandt , Burkhard .........AKB 50.94
Brandt, E. H. ...... TT 8.49, TT 9.12
Brandt, Ernst Helmut ........ TT 31.3
Brandt, Katrin ............... O 28.18
Brandt, Martin S. ...HL 25.2, HL 35.5
Brandt, Maximilian .......... TT 33.1
Brandt, O. ..................MA 31.4
Brandt, Sebastian ............DY 26.4
Bratos, Savo ............... CPP 10.5
Braun, A. .....................DS 9.7
Braun, Daniel .................. O 9.8
Braun, Dieter ...............SYLS 3.1
Braun, Jürgen ..... MA 4.12, MA 15.3
Braun, K.-F. .................. O 31.1
Braun, Matthias ............. HL 37.8
Braun, Oliver ............. AKB 50.23
Braun, Petr ........ DY 27.6, DY 27.7
Braun , W. ...SYOH 5.26, SYOH 5.38
Braun, Wolfgang ..............O 25.8
Brechet, Yves .............AKB 50.21
Bredow, T. .................. O 28.10
Bregliozzi, Giuseppe ..DS 6.1, DS 13.1
Brehm, Sascha ............. TT 26.10
Brehme, S. ................. DS 22.54
Brehmer, L ...............SYOH 5.16
Brehmer, Ludwig ......... SYOH 5.53
Breidbach, Michael .......... MA 20.4

Breidenbach, Boris ........ AKB 50.28
Breitling, Achim ... DS 12.4, DS 22.43
Breitzke, Hergen ..............M 31.3
Breliozzi, Guiseppe .......... CPP 8.4
Bremers, H. ..MA 13.74, MA 13.79,
MA 13.80
Bremers, Heiko .... M 25.4, MA 13.78
Brendel, Rolf ................ DS 19.1
Brener, Efim .................DY 25.5
Brenig, W. ....MA 21.2, MA 21.3,
TT 3.13, TT 30.37
Brenig, Wolfram .. TT 24.8, TT 30.32
Brenn, Rüdiger ............CPP 15.44
Brenner, P. ..................TT 17.8
Brenner, Thomas ......... AKSOE 8.3
Bretinger, Helmut ...........HL 12.33
Bretschneider, S. . MA 13.58, MA 14.2
Brett, D. ................... HL 44.70
Breuer, Heinz-Peter ..........TT 22.3
Breunig, H. G. ................ HL 4.5
Breunig, Hans Georg .......... HL 4.2
Breus, Vladimir V. ....AKB 50.12,
HL 44.36, SYLS 2.2, SYLS 3.14
Breusing, Markus ............ O 14.80
Brieler, F. J. .......HL 12.70, HL 35.6
Brillo, Jürgen .................M 18.4
Brinkmann, Dirk ............ MA 27.4
Brinkmeier, Eva ...TT 1.5, TT 8.9,
TT 8.10
Brinzanik, Roman .......... MA 13.75
Brion, Hans-Georg .........CPP 15.17
Brito, Ricardo ............... DY 44.5
Brittinger, Matthias ....... AKB 50.73
Britz, Thomas .. CPP 7.5, CPP 8.2,
CPP 8.7
Brocke, T. .........HL 42.2, HL 44.38
Bröckelmann, M. ............MA 21.5
Bröcker, David ...............O 28.77
Bröking, Kai .................. HL 5.6
Brökmann, Olaf ............ DY 46.74
Broekmann, P. ......O 14.32, O 28.17
Broekmann, Peter ............O 14.24
Brötz, Joachim .............MA 13.38
Brogl, S. .................... O 28.67
Brokmeier, Heinz-G. .......... M 20.2
Brommer, Peter .............. M 29.1
Bronner, Markus ..........SYOH 5.55
Bronold, Franz X. ............TT 30.5
Broocks, K.-B. ...............HL 14.3
Brookes, N. B. ............. TT 24.46
Brosi, J.-M. ................. TT 8.18
Brosińska, Renata ............DY 46.9
Brostowski, Anja ............HL 44.89
Brotons, Guillaume ... AKB 50.66,
AKB 50.87
Brown, Kenneth R. .......... TT 29.8
Bruchhaus, Lars ...............VA 1.1
Bruder, C. ...................TT 29.7
Bruder, Christoph HL 49.4, SYNF 1.4,
TT 22.9, TT 27.11
Brück, S. ....................TT 31.8
Brueckel, Th. ...............TT 24.54
Brückl, Hubert ..MA 2.7, MA 13.37,
MA 13.51, MA 13.72, MA 16.2,
MA 26.13, MA 27.4, MA 27.8
Brückner, J. ................. HL 17.4
Brückner, Jan .............. HL 12.80
Brückner, Klemens ...........HL 40.2
Brückner, Winfried ..........DS 22.31
Brüderl, G. ........ HL 38.3, HL 44.84
Brüderl, Georg ............... HL 38.5
Brüggemann, Rudolf DS 14.7, HL 12.8,
HL 30.3, HL 30.4, HL 44.23
Brueser, Volker .............. DS 22.4
Brütting, W. ...............SYOH 4.4
Brütting, Wolfgang ... SYOH 5.55,
SYOH 5.79, SYOH 5.88
Brugger, Juergen ..........AKB 50.81
Brune, Harald ..................O 5.2
Brune, Philipp ...............TT 26.6
Brunelli, M. .................. M 21.4
Brunke, Oliver ..............SYPF 4.5
Brunkov, P. .................HL 50.10
Brunnbauer, Markus ...........O 33.2
Brunner, Claudia .....AKB 12.1,
AKB 50.35
Brunner, Dieter .......M 23.1, M 30.1
Brunner, Matthias DY 46.83, DY 46.84
Brunner, Robert ............. AIW 2.2
Brunner, Roland ............ HL 44.32
Bruno, P. .............. O 3.3, O 24.5
Bruno, Patrick .MA 13.98, MA 27.14,
O 11.9
Bryllert, T. ................. HL 44.28
Buback, Michael ............. DS 13.2
Buca, D. ..................... DS 1.1
Buchholz, A. .................HL 27.9
Buchholz, Karin ........... SYLS 3.30
Buchler, Ben .................HL 15.9
Buchmeier, Matthias DS 6.3, MA 20.4
Buchner, Florian ............. O 24.11
Buck, J. ..................... O 28.33
Buck, Volker ............... DS 22.38
Budke, Michael ............... O 12.5
Budzinski, Lutz ............. DS 22.10
Büchner, B. ... MA 21.5, TT 3.13,
TT 8.45, TT 14.5, TT 24.50,
TT 24.51, TT 30.37, TT 30.39
Büchner, Bernd ...TT 2.2, TT 9.7,
TT 14.6, TT 20.2, TT 20.6,
TT 30.20
Bühler, M. .................. TT 13.7
Bühler, Mathias ............. TT 13.9
Buehrle, Juergen ... DY 17.2, DY 26.5
Bünemann, Jörg ....TT 24.3, TT 28.5
Bürgler, Daniel E. ... DS 6.3, MA 20.4
Büsgen, Thomas .. DS 22.23, MA 24.6
Buess, Matthias . MA 28.5, MA 28.7,
MA 28.13
Bütow, A. ..................SYPF 5.2
Büttgen, N. ........ TT 6.11, TT 14.3
Büttiker, Markus SYSN 1.1, SYSN 2.5
Büttner, M. .................. MA 6.3
Bugiel, E. .................. HL 44.25
Buhmann, Hartmut ......... HL 44.31
Buitelaar, Mark ..SYNF 1.4, TT 27.11
Bull, Craig L. ................ HL 11.5
Bulla, Ralf TT 10.5, TT 16.3, TT 21.3,
TT 30.2, TT 30.3
Buluschek, Philipp ..............O 5.2
Bulut, F. ...................MA 13.88
Bund, Andreas CPP 15.42, CPP 16.22
Bunde, Armin .. DY 36.6, DY 42.3,
DY 42.5, DY 46.33
Bundesmann, C. . DS 9.7, HL 17.12,
HL 23.6, HL 44.79
Bundesmann, Carsten ....HL 12.4,
HL 12.68, HL 44.51
Bundschuh, Ralf ..DY 23.4, SYLS 3.35
Bunk, Angelika .............. DS 18.5
Bunk, Wolfram .............. DY 20.6
Burck, A. .......... TT 8.24, TT 13.4
Burgarth, Daniel .............TT 22.3
Burger, Hendrik .............HL 12.75
Burghammer, M. ........... CPP 11.3
Burghammer, Manfred ..AKB 50.30,
AKB 50.53, SYLS 3.53
Burghardt, Bernd ............ DY 23.1
Burghardt, Torsten ......... TT 24.28
Burke, S. A. .................. O 23.9
Burkov, Alexander .......... DS 22.41
Burkov, Yevgen ...........SYOH 5.74
Burst, M. .................. TT 30.40
Busch, K. ..HL 1.1, HL 8.3, HL 8.4,
HL 15.8
Busch, Kurt ....HL 8.5, HL 12.30,
HL 12.31, HL 12.37, HL 15.3,
HL 15.7, HL 20.7
Busch, Peter . CPP 15.13, HL 12.77,
HL 44.41
Buschbeck, Jörg ........... MA 15.10
Buschbeck, Michael .......... HL 51.2
Buslaps, Thomas .............HL 11.5
Buss, Volker .............. AKB 50.31
Busse, Carsten ... O 14.28, O 25.1,
O 39.10
Busse, Karsten CPP 15.16, CPP 15.16,
CPP 15.18
Bussetti, Gianlorenzo .........O 28.55
Butz, Tilman ....AKB 50.55, MA 11.1
Buß, Andre .................HL 12.41
Bychkov, G. ................. TT 20.4
Byrne, A. ...................HL 44.70
Bányai, L. .................... HL 4.1
C. h. en, C. T. ...............TT 32.6
Cabrele, Ciara .............. SYLS 4.4
Cabria, I. ..........MA 4.11, MA 6.13
CABURN-MDC .................FB 9
Cai, C. ..............TT 8.4, TT 8.11
Cai, Chengzhi ................O 28.38
Caillard, D. ...................M 30.2
Caimi, G. .................. TT 24.49
Cain, Philipp .................HL 22.2
Calarco, Raffaella ........... HL 44.86
Calvet, Wolfram ..DS 20.4, DS 21.1,
O 28.29, O 40.11
Camacho González, Francisco
CPP 15.47
Camalet, Sébastien . TT 17.1, TT 27.1
Camamet, Sebastien ......... TT 22.4
Camarero, J. ...............MA 28.10
Campbell, C. E. ............MA 13.62
Campbell, Eleanor ............O 28.48
Canzler, T. W. ...............HL 23.7
Cao, Guang-hui .......M 22.3, M 22.3
Cao, J. L. .................... DF 6.3
Cao, X. .................... TT 30.41
Cao, Xinmin ................HL 12.54
Capek, Richard .............. HL 20.4
Cappellini, Giancarlo ......... HL 36.1
Carbone, C. .......... MA 3.1, O 24.4
Carbone, G. ..................O 28.83
Carbone, Marilena .............O 18.7
Cardona, M. ................. HL 51.3
Cardoso, S. ................ MA 13.84
Carl, A. ..................... TT 6.12
Carl, Axel .................. TT 11.12
Carlo, Amoruso ..............DY 26.2
Carlsson, Johan M. ............O 31.4
Carmen R., Kmety ........ MA 13.109
Carpene, E. ....... DS 17.4, DS 22.21
Carr, Sam T. ................ TT 21.5
Carrillo-Cabrera, W. ........ CPP 10.7
Carsteanu, A.-M. ..... M 3.2, M 18.27
Carstens, Anke ..............HL 12.69
Carstensen, Jürgen ..........HL 12.34
Carta-Abelmann, L. .......SYOH 5.52
Caruso, F. .................... O 19.6
Caruso, Frank ................HL 20.6
Casalbuoni, Sara .............TT 8.34
Casaletto, Maria Pia ...........O 18.7
Casper, Frederick ............MA 20.6
Castagnet, Jean-Frederic ...... M 26.2
Castaño, Fernando J. .......MA 13.55
Casu, M. B. ....................O 4.2
Cataudella, Vittorio .......... HL 29.6
Cattani, Davide ..............TT 14.6
Cavalcanti , Elisabetta Ada AKB 50.37
Cavaliere, Fabio ..............HL 47.5
Cavallaro, A. ................ TT 8.14
Cavalleri, A. .................. HL 4.8
Caymax, M. .................. DS 1.1
CEA Grenoble - Kollaboration .MA 6.5
Cercellier, H. ..................O 11.8
Cerovski, Viktor ...............M 29.3
Cerullo, Giulio ............. SYOH 2.2
Chado, I. ................... HL 29.11
Chadov, Stanislav ............ MA 8.3
Chaib, Hassan ................ DF 1.3
Chaikin, Paul .................PV XIII
Chakai, W. ................. HL 12.86
Chakam, G.-A. .............. TT 8.18
Chakraborty, T. ..............HL 14.3
Chamard, V. .................O 28.52
Chamard, Virginie ............O 14.50
Chan, C. T. ................. TT 30.1
Chang, Ta-Chau ............ SYLS 3.3
Chantrell, Roy ...............MA 28.2
Chaplygin, Igor ............... M 18.9
Chapman, John N. MA 10.4, MA 13.47
Chasse, Thomas .......... SYOH 5.24
Chassé, A. ................... MA 4.2
Chatelain, Christophe ....... DY 46.95
Chatterjee, Sangam .......... HL 28.4
Chattopadhyay, Amit ......AKB 50.24
Chauhan, R. S. ............... DS 1.7
Che’Rose, Simon .............TT 8.31
Checco, Antonio ............CPP 12.2
Chelaru, L. ..................MA 20.7
Chelaru, L. I. .....MA 13.53, MA 16.3
Chen, C. T. ......TT 24.45, TT 24.46
Chen, L. ...........HL 12.70, HL 35.6
Chen, Peifeng ................HL 44.3
Chen, Weiye ..........M 15.1, M 22.6
Chen, Xi ... MA 13.45, MA 13.83,
MA 13.84
Chen, Xiaodong ............SYOH 5.6
Cheong, S. ................. TT 30.29
Cheong, Sang-Wook ......... TT 20.2
Cherepanov, V. ............... O 25.7
Cherepanov, Vasily ............ O 32.7
Cherkastinin, G. ..............HL 16.3
Cheung, W. Y. ............. DS 22.13
Chi, Chunyan .............SYOH 5.85
Chi, Lifeng ... O 14.74, SYOH 5.2,
SYOH 5.6, SYOH 5.17
Chiang, Tai-Chang ............ O 11.1
Chiaradia, Pierro .............O 28.55
Chigrin, Dmitry .HL 12.24, HL 12.26,
HL 20.1, HL 20.8
Chiguvare, Zivayi .... SYOH 5.56,
SYOH 5.70
Chilla, G. ...................HL 44.38
Chioncel, Livio ............... MA 8.3
Chirvase, Dana ........... SYOH 5.49
Choi, K.-Y. ...TT 14.13, TT 24.49,
TT 24.50, TT 24.51
Choi, Mahn-Soo ............. TT 22.9
Cholascinski, Mateusz .......TT 17.17
Chong, H. H. ................. HL 4.8
Chou, F. C. ......TT 14.13, TT 24.49
Chow, Weng W. ... HL 32.5, HL 36.13
Christ, A. .....................HL 8.4
Christ, Andre ................. HL 2.5
Christen, J. ...HL 12.18, HL 27.14,
HL 33.5
Christen, Jürgen ... HL 12.78, HL 21.3
Christmann, K. ........O 26.7, O 43.4
Christmann, Klaus ... O 14.33, O 39.7
Christoph, S. ................MA 18.2
Christov, L. ................ SYPF 2.4
Chrobok, Roland .DY 34.1, DY 46.20,
DY 46.21
Chu, M.-W. ...................DF 6.4
Chudnovskiy, Alexander ...... TT 23.1
Chudoba, Thomas .......... DS 22.32
Autorenverzeichnis
Chulia Jordan, Raquel .......DY 46.52
Chumakov, Dmitry .......... MA 28.6
Chuvilin, A. ..................HL 30.5
Cichos, Frank .CPP 14.7, CPP 16.20,
CPP 16.21, CPP 16.28, HL 50.6,
HL 50.7, SYOH 5.8, SYOH 5.10
Cieslak, J. HL 12.6, HL 12.7, HL 24.6,
HL 30.5
Cimalla, V. HL 16.1, HL 16.2, HL 27.4
Cimalla, Volker .............. HL 40.2
Cinchetti, M. ...... DS 22.27, O 28.75
Ciobanu, Florin .............. HL 52.3
Ciunel, Kasia ..............CPP 16.15
Claessen, Ralph .SYNF 1.6, TT 24.7,
TT 24.41, TT 24.43, TT 30.8,
TT 30.34
Clarke, John .................TT 29.5
Classen, Thomas .............. O 32.8
Clausen, Torben ..............HL 3.11
Clauss, Tobias ............... TT 18.6
Claussen, Jens Christian AKSOE 3.10,
DY 46.11, SYFT 2.3
Claverie, A. ...................HL 3.6
Clemens, Daniel ........... CPP 15.32
Clemens, H. ........ DS 22.45, M 22.5
Clemens, Patrick ............DS 22.53
Clemens, Wolfgang .........SYOH 4.1
Cobet, C. ....... HL 27.4, SYOH 5.26
Cobet, Christoph ...HL 27.16, HL 28.9
Cölfen, Helmut . AKB 50.89, CPP 14.2
Cölle, M. .................SYOH 5.89
Cölle, Michael ............ SYOH 5.88
Coffin, H ..................... HL 3.6
Cogdell, Richard J. ........ SYLS 3.21
Cohen, Doron ............... DY 50.7
COHERENT ...................FB 10
Colas des Francs, G. ...........O 23.1
Collaboration, die ISOLDE - MA 11.2,
MA 11.2, MA 13.108
Colliex, C. .................... HL 3.6
Colombo, Cyril .............AKB 12.3
Comins, J. D. .................DS 6.4
Conrad, Erhard ............... DS 4.4
Conrad, Horst ................O 28.58
Constantin, Doru ..........AKB 50.68
Cookson, David ............ CPP 16.9
Coppi, Chiara .... TT 17.20, TT 17.21
Coqui, C. .................. TT 17.23
Cordon, J. .................... O 39.3
Correa-Duarte, Miguel ...CPP 12.4,
SYLS 3.19
Cosceev, A. .... TT 6.6, TT 8.18,
TT 24.39
Costantini, Giovanni HL 51.1, O 28.30,
O 32.8
Costes, M. .................. MA 21.2
Costi, Theo ................ TT 26.11
Costina, I. .................... O 34.6
Costina, Ioan MA 20.1, O 34.4, O 34.5
Cote, Denis ................ AKB 20.3
Cottet, Audrey ...............HL 49.4
Cowie, B. C.C. ................O 14.2
Cowie, Bruce C. C. ...O 25.2, O 28.12
Craciunescu, Corneliu ........MA 24.3
Crecelius, Tristan .............MA 5.2
Creczynski-Pasa, T. B. .......CPP 6.2
Cristiani, G. .......TT 24.54, TT 31.8
Crljen, Zeljko ................ O 14.37
Cronin, Leroy ............... MA 21.1
Crowell, P. .................MA 13.62
Croy, A. .................... HL 44.60
CRYO-TECHNICS .............FB 11
CRYOPHYSICS ............... FB 12
CryoVac .......................FB 13
CrysTec ....................... FB 14
CT, Lin ...................... TT 2.3
Ctistis, G. ......................O 9.6
Ctistis, Georgios ...............O 37.6
Cubitt, R. ....... CPP 14.9, CPP 15.9
Cue, Nelson ................. TT 11.6
Cuevas, J. C. ............. SYOH 5.59
Cuevas, Juan Carlos ... SYSN 2.2,
TT 27.7
Cuevas, Juan-Carlos ....TT 17.32,
TT 19.1
Cuniberti, Gianaurelio ..SYOH 5.57,
SYOH 5.58, TT 27.6
Cuniberti, Giovanni ........AKB 50.29
Cunis, S. ..................CPP 16.24
Curro, Nicholas J. .............TT 2.2
Curtis, Jennifer ........... AKB 50.15
Curtis, Jennifer E. .........AKB 50.51
Cwik, M. .... TT 14.9, TT 24.47,
TT 30.13, TT 30.16
Czerner, Michael ........... MA 13.30
Czubanowski, Marcin .........O 14.35
Czycholl, Gerd ..HL 28.3, HL 44.35,
TT 7.1, TT 26.5, TT 32.4
D. O., Demchenko ........ MA 13.109
D., Sander ...........MA 4.1, MA 4.3
Da Silva, Juarez L. F. .......... O 6.2
Dabringhaus, Heinz .......... O 14.39

Dadgar, A. ....HL 27.1, HL 27.12,
HL 27.14, HL 33.5, HL 44.80
Dadgar, Armin ..HL 12.78, HL 21.3,
HL 26.1, HL 44.81
Dähne, M. ..... HL 3.10, O 3.4, O 9.3
Dähne, Mario HL 3.9, HL 25.3, HL 42.3
Däne, Markus ..............MA 13.98
Däubler, Thomas ......... SYOH 5.81
Däweritz, L. ........ MA 3.2, MA 31.4
Daghofer, Maria ............ TT 30.10
Dahlhaus, Daniel ............... O 4.5
Dahlke, Robert .............. HL 47.4
Dahm, Thomas ..............TT 8.35
Dahmen, A. ................MA 13.96
Dahmen, Christian .. O 28.65, O 28.66
Daillant, Jean .............. CPP 12.2
Daimon, H. .................. MA 4.2
Dais, Christian ................DS 3.6
Dal Don, B. ................ HL 12.19
Dal Don, Bénédicte ......... HL 44.16
Dam, Bernard .................O 26.8
Damaschke, Bernd .... MA 13.22,
MA 13.23
Dambrowski, Jaroslaw .........DF 6.6
Damm, Thorsten ..............DS 6.3
Damm, Timo ............... MA 16.9
Dan, V. D. .................. O 24.10
Daniel, B. ... HL 12.10, HL 12.72,
HL 12.74, HL 12.76
Daniel, Bruno ...............HL 12.75
Danielmeyer, Hans G. .....AKSOE 8.2
Danilov, Denis .........M 4.3, M 18.5
Danilov, Sergey N. ..........HL 44.45
Daniyarov, T. ...... TT 8.24, TT 13.4
Dantscher, S. ....O 14.57, O 37.2,
TT 17.14
Danzenbächer, Steffen ..........O 4.7
Darowski, Nora ............... M 15.1
Das, Subir Kumar ....DF 3.5, DY 28.5
Dasbach, Gregor ............. HL 28.2
Dassow, H. ................. MA 26.4
Dassow, Henning ............MA 20.4
Davis, Séamus ................ TT 9.1
de Cola, Luisa ............. SYOH 5.6
de Groot, Bert L. ........... SYLS 1.1
de Haas, O. ................. TT 12.3
de Haas, Oliver .............. TT 12.4
de Lima, A. . AKB 50.3, AKB 50.17,
SYLS 3.24
de Lima, Jr., M. M. HL 12.23, HL 20.9
de Lozar, Alberto ...........DY 46.81
de Man, Sven ................. O 26.8
de Mello, N. F. .............. CPP 6.2
de Pablo, Pedro J. ......... AKB 10.1
de Ruijter, Ward P. F. ..... SYLS 3.21
de Souza, Melanie M. ....... HL 44.33
de Visser, A. ............... TT 24.30
De Wild, Michael ............ O 14.25
Debald, S. ................... HL 44.8
Deborde, Jean-Laurent ........ HL 5.1
Debuschewitz, Christian .....TT 17.16
Decker, Björn ............. CPP 16.19
Decker, D. ................. DS 22.47
Dederichs, P. ................MA 31.3
Dederichs, P. H. .MA 4.11, MA 6.13,
MA 13.89
Dederichs, Peter .............MA 11.3
Dederichs, Peter H. ....MA 27.10,
SYXM 1.5
Dedkov, Yu. .................MA 13.4
Dedkov, Yu. S. .............. MA 13.1
Dedkov, Yuriy ........ MA 13.2, O 4.7
Deegan, Robert D. ...........DY 15.3
Degenhard, Andreas .... CPP 2.2,
CPP 15.35
Degiorgi, L. ................ TT 24.49
Degiovanni, Pascal ...........TT 22.4
Deicher, M. ...................DF 1.4
Deisenhofer, J. .... TT 20.4, TT 24.52
Deisl, C. ...................... O 25.5
Deiter, Carsten .. O 14.38, O 14.41,
O 14.42
Dekker, Cees ...AKB 50.99, O 9.1,
O 28.39
Dekker, N. H. .............AKB 50.99
Dekorsy, T. ........... HL 4.6, HL 4.8
Dekorsy, Thomas .. HL 4.4, HL 9.2,
HL 28.6
del Valle, Miriam ......... SYOH 5.57
Delaunay, Renaud ..........SYXM 1.4
Delduc, Francois .............TT 22.4
Delfs, Johannes ........... AKB 50.38
Della Rocca, Maria-Luisa .....TT 19.4
Della Rocca, ML. ............ TT 25.6
Delley, Bernard ................O 26.3
Delto, Ralf ................CPP 15.44
Delvigne, Erik ................O 28.38
Demidov, Vladislav E. ........ MA 9.1
Demokritov, S. O. ..MA 16.5, O 14.81
Demokritov, Sergej O. ........ MA 9.1
Dempsey, Nora M. .......... MA 26.3
Demé, Bruno ............ AKB 50.121
Denecke, R. O 14.9, O 14.12, O 14.15,
O 18.2, O 25.10, O 28.61, O 43.3
Denecke, Reinhard ............ O 30.1
Deng , D. W. .................M 31.6
Deng, Xiaobin ............... O 28.38
Deniozou, Thalia .............HL 31.5
Denker, U. ...................HL 37.7
Denker, Ulrich ............... HL 51.1
Denlinger, J. D. ...............O 44.8
Dennemarck, Jens . HL 16.8, HL 44.88
Denzler, D. N. ................ O 43.6
Deppe, M. ......... TT 7.8, TT 24.33
Descas, Radu ................CPP 5.1
DeSimone, A. ............... MA 24.4
Detemple, Ralf ......HL 11.1, HL 11.2
Dethlefsen, A. F. ............HL 44.40
Deubel, M. ................... HL 1.1
Deubert, Stefan .....HL 15.5, HL 38.9
Devyatych, G. G. .............HL 51.3
Dhar, S. .................... MA 31.4
Di Giacomo, C. ............... O 24.4
Diaconescu, Dorina ......... HL 12.49
Dianat, Arezoo ................O 14.3
Diaz O., Juan G. .... AKSOE 3.8,
AKSOE 10.5, CPP 15.49
Diaz-Ortiz, Alejandro ......... M 22.1
Dick, A. ...................... O 17.8
die ISOLDE Collaboration .... HL 27.8
Diederich, Francois ...........O 14.22
Dieker, Henning ... DS 12.4, HL 44.43
Diekhöner, Lars O 11.5, O 15.1, O 26.2
Diekmann, Thomas .......... HL 23.2
Diem, M. ....................HL 15.8
Diem, Marcus .... HL 12.30, HL 12.37
Diemant, Thomas .............O 38.3
Dienel, Thomas O 4.1, O 4.8, O 33.1,
O 33.7
Dienelt, Jens .................O 28.21
Dierke, Hanno ................ M 30.3
Diesing, Detlef .. DS 12.3, O 28.71,
O 31.2, O 44.1
Diesmann, Markus ...........DY 42.1
Dieterich, W. .............. MA 13.87
Dieterich, Wolfgang ....... CPP 15.28
Dietrich, Christian ...........MA 26.6
Dietrich, Christof .. O 9.2, O 28.41,
O 32.5
Dietrich, M. DF 1.4, HL 21.5, HL 27.8,
MA 11.2, MA 11.2, MA 13.108
Dietrich, Mark .............. MA 15.6
Dietsche, Rainer ............. O 28.63
Dietsche, W. .................HL 14.4
Dietz, A. .. HL 12.6, HL 24.6, HL 30.5
Diez, Annette .... HL 12.78, HL 44.81
Diez, Manuel ............. AKB 50.98
Diezemann, Gregor . DF 4.1, DF 5.7,
DY 29.1
Dil, Hugo ..... O 11.4, O 11.6, O 18.7
Dimopoulos, Theodoros .. MA 16.2,
MA 27.7
Dimova, Rumiana ......... AKB 50.54
Dimroth, Peter SYLS 3.43, SYLS 3.44,
SYLS 5.2
Dinda, Guru Prasad ...........M 20.1
Dini, Danilo .............. SYOH 5.24
Dinkel, Markus ............... M 21.2
Dinsmore, A. D. ............CPP 16.9
Dirk, Drasdo ..............AKB 50.39
Distler, G. .................... DS 6.4
Dittmer, Kai ................HL 29.12
Dittrich, M. ................ SYLS 5.3
Dittrich, Th. ....DF 5.3, DS 21.3,
DS 22.55, DS 22.56, HL 30.1
Dittrich, Thomas ........... DS 22.57
Djenizian, Thierry ..........SYOH 5.9
Djordjevic, M. ....MA 13.65, MA 14.2
Dloczik, L. ...................HL 30.1
Dmitriev, Alexandre .......... O 28.38
Dmitriev, I. A. ............... HL 14.2
Dobler, Harald ............... O 28.19
Dobrawa, Rainer .......... CPP 16.10
Döbereiner, Hans-Günther .AKB 11.2,
AKB 50.89, AKB 50.90,
AKB 50.91, AKB 50.92
Döbrich, K. ... MA 4.9, MA 13.56,
MA 31.2
Döbrich, K. M. .... MA 13.9, MA 17.2
Döbrich, Kristian .......... SYXM 1.3
Döhler, G. . HL 9.5, HL 12.92, HL 33.2
Döhler, G. H. ... HL 4.10, HL 4.11,
HL 9.4, HL 12.21, HL 42.1,
HL 43.5, HL 50.4
Döhler, Gottfried ............HL 44.53
Döhrmann, Stefanie ....HL 12.47,
HL 41.2, HL 44.52
Dönitz, D. ...................TT 18.3
Döppe, M. ........ HL 29.5, HL 29.10
Döppe, Matthias .............HL 44.7
Dörfler, U. ....................DF 2.4
Döring, Stefan ..............DS 22.18
Dörr, K. ......... MA 20.11, MA 22.2
Doerr, Mathias ...............MA 3.3
Dohmen, A. .................MA 31.4
Doll, Theodor ..............SYOH 4.2
Domhan, Michael TT 17.22, TT 17.26,
TT 22.1, TT 22.2
Domisch, Rainer ............ LTR VIII
Domke, Katrin F. ............. O 38.5
Dommach, Martin .... SYLS 3.47,
SYLS 3.53
Domokos, Peter ............. DY 50.2
Donath, Markus . MA 4.12, MA 15.3,
O 3.1, O 12.5, O 24.6
Dootz, Rolf ............... SYLS 3.50
Dora, Sujit .................. O 14.27
Dorda, U. .....................DF 1.4
Dormann, Elmar . CPP 3.4, CPP 3.5,
M 18.29, TT 24.34
Dosch, H. .. M 8.4, M 12.1, O 14.2,
O 34.6, SYOH 5.29
Dosch, Helmut ...DS 7.2, DY 25.1,
M 8.3, M 22.1, O 4.4, O 6.8,
O 34.4, O 34.5, O 46.1
Doster, Wolfgang ......... AKB 50.61
Dotzler, C. .................. HL 50.4
Drago, Massimo HL 12.16, HL 27.16,
HL 28.9, HL 28.10, HL 33.3
Drautz, Ralf . M 5.1, M 22.1, MA 28.1
Drautz, Ralph ..................O 6.7
Drechel, Jens ............. SYOH 5.82
Drechsel, Jens SYOH 5.42, SYOH 5.43
Drechsler, Peter .............. M 15.2
Drechsler, S.-L. .. TT 3.9, TT 8.47,
TT 9.6, TT 9.9, TT 24.23,
TT 26.13
Drechsler, Stefan-Ludwig .....TT 8.50
Drechsler, Ute ...............CPP 2.1
Dreher, Markus ..............TT 17.7
Dreiner, S. ..O 28.6, O 28.27, O 28.28
Dremin, Aleksey ............ HL 44.10
Dremov, Vyacheslav ......... TT 8.25
Drenckhan, Wiebke .........SYPF 1.1
Drescher, Malte ............. CPP 3.5
Drescher, Markus ..........CPP 16.19
Dressel, M. .. SYOH 5.61, TT 6.10,
TT 20.8, TT 30.18
Dressel, Martin AKB 50.19, MA 21.8,
SYOH 5.60, TT 6.3, TT 6.5,
TT 7.5, TT 24.35
Drexel, Michael .............. DS 17.6
Dreyer, Jens ................... O 4.6
Dreyhaupt, André ............. HL 9.2
Drichko, Natalia .......... AKB 50.19
Driscoll, D. ........HL 4.10, HL 12.21
Drobniewski, Chr. ...........DS 22.47
Drobnik, S. .................TT 24.29
Drossel, Barbara AKB 40.2, AKB 50.4,
DY 46.27
Drotziger, S. ............... TT 24.31
Du, Binyang ... CPP 15.25, SYLS 3.50
Dubbers, Oliver ..... O 28.42, O 28.50
Dubreuil, Frederic .......... CPP 13.5
Ducommun, Yann ............HL 50.3
Dudek, R. ........... O 28.60, O 43.6
Dudy, L. .................... TT 8.46
Duerig, Urs ......CPP 2.1, CPP 15.15
Dürr, Ferdinand ..............HL 12.4
Dürr, M. .....O 14.1, O 14.20, O 38.2
Duesberg, Georg ............. HL 46.1
Dugaev, Vitalii ............. MA 27.14
Duhm, Steffen ............... HL 24.1
Duit, Reinders ................ LTR IX
Dulkeith, E. ....... CPP 16.34, O 19.6
Dulkeith, Eric ...............HL 44.33
Duman, E. ... MA 6.10, MA 13.77,
MA 13.113
Dumbuya, Karifala ............ O 39.7
Dumitras, Gheorghe ..........HL 25.1
Dumm, M. ........ MA 15.4, TT 6.10
Dumm, Martin .. MA 13.31, MA 13.40
Dumm, Michael ...TT 6.3, TT 6.5,
TT 8.44
Dumont, Jacques ............ O 14.29
Dumpich, G. ......MA 13.85, TT 6.12
Dumpich, Günter DS 12.5, MA 13.60,
MA 27.3, TT 11.12
Duncker, K. ................. O 28.70
Dung, L. Q.T. ............... HL 10.4
Dunger, Thoralf .... DS 4.2, DS 22.42
Dunsch, Lothar ........... SYOH 5.24
Duong, N. P. .............. MA 13.67
Duong, Thanh Tu .... SYLS 3.34,
SYLS 3.40
Durfee, William .............. O 14.60
Dusuel, Sébastien ...TT 3.2, TT 24.19
Duvenbeck, Andreas ...........O 10.7
Dwelk, H. ..TT 8.43, TT 8.46, TT 9.4
Dworzak, Matthias .HL 36.10, HL 50.2
Dyakonov, Vladimir .... CPP 3.3,
CPP 16.6, HL 23.5, SYOH 5.49,
SYOH 5.50, SYOH 5.56,
SYOH 5.70
Dzierzawa, Michael ......... TT 30.19
E. Z., Kurmaev ........... MA 13.109
Autorenverzeichnis
Ebbesen, Thomas W. ..........HL 2.4
Ebbinghaus, S. ..............HL 12.51
Ebbinghaus, S. G. .............DF 1.6
Ebeling, Werner .AKSOE 4.5, DY 22.1
Eberhardt, Hans-Frieder ....... VA 1.2
Eberhardt, J. ... HL 12.6, HL 12.7,
HL 24.6, HL 30.5
Eberhardt, Wolfgang .......SYXM 1.7
Ebert, H. . MA 4.11, MA 6.2, MA 6.13
Ebert, Hubert ... M 18.7, MA 8.1,
MA 8.3, MA 11.3, MA 13.90,
MA 13.112, MA 27.10, MA 30.2
Ebert, Philipp ........M 18.24, O 40.5
Ebert, Susanne .............AKB 30.4
Eck, Wolfgang AKB 50.37, CPP 16.18
Eckardt, M. ....HL 4.10, HL 4.11,
HL 12.21
Ecke, G. ..................SYOH 5.52
Ecke, Gernot ........DS 22.12, HL 9.1
Eckel, R. ..................SYLS 3.45
Eckel, Rainer .............. SYLS 3.31
Eckelt, Peter ............... DY 46.43
Eckerlebe, Helmut .........MA 13.102
Eckern, Ulrich ... M 5.4, TT 24.56,
TT 30.19
Eckert, D. .......... MA 18.3, TT 6.4
Eckert, Dieter .... MA 11.6, MA 11.10
Eckert, J. ......................M 8.5
Eckert, Juergen M 9.2, M 9.4, M 14.2,
M 31.3, MA 26.1, TT 31.10
Eckl, Thomas .................TT 2.5
Ederer, Sven .................AIW 2.1
Efetov, K. B. ................ HL 5.10
Efremov, Dmitry .. TT 14.7, TT 24.55
Efthimiadis, K. G. .......... MA 13.79
Egen, Marc .................HL 15.10
Eggeler, Gunther .............M 18.20
Egger, Holger .............. CPP 14.4
Egger, Reinhold ..............TT 17.9
Egger, Werner ...............CPP 7.3
Eggers, Jens .................DY 15.4
Eggers, Maik .................. M 7.3
Eggersmann, Martin .......... M 10.1
Egry, Ivan ............. M 2.2, M 18.4
Egues, J. Carlos ..............HL 49.1
Ehlers, A. ... MA 10.6, MA 13.48,
MA 13.49, MA 13.50, MA 27.6,
SYLS 3.41
Ehlkes, L. ................... DY 36.5
Ehrenstein, Gudrun ...... AKSOE 10.3
Ehresmann, A. . MA 10.6, MA 13.48,
MA 13.49, MA 13.50, MA 27.6,
SYLS 3.41
Ehrl, Moritz ................. CPP 9.2
Ehrlicher, Allen AKB 12.1, AKB 50.16,
AKB 50.35
Eich, Manfred ..HL 12.29, HL 12.32,
HL 12.33, HL 20.3
Eichhorn, Frank ..............DS 18.2
Eichhorn, K. ................HL 12.76
Eichhorn, K.-J. .. CPP 8.6, CPP 15.45
Eichhorn, Ralf ............... DY 12.2
Eichler, Andreas ............ TT 24.28
Eichler, Hans ................ DS 14.6
Eichler, S. ...................M 18.15
Eichner, Jan F. ............. DY 46.33
Eickhoff, M. ................ HL 27.15
Eickhoff, Martin ..HL 16.5, HL 16.6,
HL 16.7, HL 27.13
Eilers, G. .........MA 13.59, MA 14.2
Einfeldt, S. .................. HL 36.8
Einfeldt, Sven ..... HL 16.9, HL 44.88
Einzel, Dietrich ....TT 9.11, TT 17.29
Eisaki, H. .....................TT 9.1
Eisebitt, Stefan ............ SYXM 1.7
Eisele, H. ............. HL 3.10, O 9.3
Eisele, Holger ........ HL 3.9, HL 25.3
Eiselt, René ................MA 13.68
Eisenmenger, J. .MA 10.8, MA 13.44,
MA 14.1
Eisenmenger, Johannes .......TT 31.7
Eisert, Jens ....... DY 50.3, TT 22.10
Ejima, Satoshi ... TT 24.17, TT 24.18
Ekatarina, Orlova ............ HL 38.7
El Goresy, Tarek .............. DF 5.8
El Ouali, Mehdi ................ O 5.2
El Rharbi-Kucki, Melanie .. HL 15.1,
SYLS 3.17
El-Hossary, F. M. ............ DS 15.6
El-Rahmann, A. M. Abd ......DS 15.6
Elbahri, M. .......... O 24.1, O 28.35
Elefant, Dieter . DS 22.22, DS 22.40,
DS 22.41, MA 13.10, MA 13.107
Elfilali, A. .................. TT 30.16
Elfrink, Kerstin ............ SYLS 3.58
Elgazzar, Saad ..............TT 24.36
ElHaes, H. ........ TT 3.13, TT 30.37
Elhassan, Mohamed .........HL 44.32
Elhor, Hamid ................ DY 44.3
Ell, Claudia ..................HL 28.4
Ellabban, Mostafa .............DF 2.5
Ellerkmann, U. ................DF 6.3

Elli, Alexandra .............SYLS 3.52
Elliott, C. M. ............. SYOH 5.39
Ellmer, Klaus .. DS 19.5, DS 22.51,
DS 22.57, DS 22.58
Ellrich, J. .................... MA 6.3
Ellrich, Jens ................MA 13.82
Elmar, Thews .............. AKB 23.1
Elmers, H. J. ...MA 13.71, MA 13.105
Elmers, H.-J. .....MA 8.5, MA 13.114
Elmers, Hans-Joachim ... MA 15.2,
MA 20.6, O 14.30, TT 30.35
ELS Elektronik Laser System ... FB 15
Elsaesser, Thomas ........... HL 50.8
Elsässer, Wolfgang DY 36.1, HL 32.1,
HL 32.2, HL 38.2
Elsäßer, Wolfgang ............HL 38.6
Elsanousi, Ammar .............DS 3.5
Elsholz, Frank ............... DS 14.6
Elsner, Nils ...... CPP 13.5, SYLS 3.6
Elstner, Marcus ........... AKB 50.31
Eltner, Brigitte ...............O 11.10
Eltschka, Christopher ....... DY 46.37
Embs, Jan ........ DY 11.6, DY 46.76
Emmerling, Monika ......... HL 38.11
Emrick, Todd .............. CPP 16.9
Ender, Chr. ................SYOH 3.1
Enderle, Hans-Friedrich ..... CPP 13.6
Enderle, Mechthild ...........TT 6.13
Enders, A. ................... MA 3.1
Enders, Dominik ............. O 28.43
Endreß, Emil ............... DS 22.44
Endreß, T. ................. SYLS 3.4
Ene, Constantin Buzau ........M 24.3
Eng, L. ...................... O 14.77
Eng, Lukas ....DF 1.3, O 9.5, O 14.61
Eng, Lukas M. ................ O 23.3
Enge, Wolfgang ............. CPP 7.1
Engel, Andreas .. DS 22.25, TT 1.2,
TT 13.3
Engel, D. ....MA 10.6, MA 13.48,
MA 13.49, MA 13.50, MA 27.6,
SYLS 3.41
Engel, E. .................... HL 23.7
Engel, Egbert ................HL 23.8
Engel, Hans-Andreas ......... HL 50.1
Engel, Harald ................DY 20.3
Engel, Ulf Martin ........... DY 46.43
Engelbertz, Andre ..............M 3.3
Engelhardt, M. P. ............ O 25.10
Engelmann, Andreas .......CPP 16.11
Engemann, Simon ........... DY 25.1
Engl, K. ..........HL 44.83, HL 44.84
Engl, Karl HL 27.5, HL 27.6, HL 44.87
Enkovaara, Jussi .............MA 27.9
Enkrich, C. ................... HL 8.3
Ennen, Inga .... MA 6.8, MA 6.9,
MA 13.78
Ensling, David ................ O 44.6
Ensling, J. ................ MA 13.117
Enss, C. TT 8.24, TT 13.4, TT 30.41,
TT 33.3
Enss, Christian ..... TT 33.1, TT 33.2
Enss, Tilman ......TT 24.9, TT 24.10
Entel , Peter . AKB 50.31, DY 46.98,
M 18.1, MA 6.1, MA 23.3,
MA 24.6, MA 27.1
Enz, Thorsten ................ MA 6.7
Epstein, R. J. ................ HL 50.1
Erb, A. ..................... MA 13.5
Erb, Andreas . MA 13.27, MA 13.39,
MA 13.116
Erb, T. ...................SYOH 5.52
Erb, Tobias .................. HL 23.3
Erbe, Andreas .............. CPP 11.6
Erbenich, Gregor .............. VA 1.2
Erdmann, M. ............... HL 12.92
Erdmann, Thorsten ........AKB 50.22
Erdmann, Udo ...............DY 22.1
Eremin, Ilya ......... TT 2.4, TT 24.6
Eremin, Mikhail ...............TT 2.4
Eremina, Rushana .............TT 6.8
Eremtchenko, Maxim ....... DS 22.18
Erhart, Paul ................. HL 17.7
Erichsen, Jörn ............... CPP 7.2
Eriksson, Olle ................ MA 8.2
Erlekam, Undine .............. O 38.9
Ernst, Arthur .......MA 13.98, O 11.9
Ernst, N. ..................... O 10.5
Ertl, G. ....................... O 43.6
Ertl, Gerhard .. O 20.1, O 20.3, O 38.9
Escher, M. ...................O 28.51
Eschrig, H. TT 3.9, TT 8.47, TT 9.6,
TT 24.23, TT 26.13
Eschrig, Helmut .. MA 3.4, MA 8.7,
MA 8.9, MA 13.99, TT 9.2
Eschrig, Matthias ............TT 19.1
Eska, G. ........... TT 4.7, TT 17.30
Esquinazi, P. .. MA 13.3, MA 13.93,
TT 8.32
Esquinazi, Pablo .HL 12.77, HL 22.3,
HL 44.11, MA 11.1, MA 13.106,
TT 20.3
Esser, N. ....CPP 15.45, HL 27.4,
O 14.59, SYLS 3.49, SYOH 5.26
Esser, Norbert ..... HL 27.16, HL 31.5
Essler, Fabian H. L. ..........TT 26.1
Esteban, Ruben ............... O 23.8
Estrela, P. ..................TT 24.30
Estrin, Juri .M 13.4, M 15.3, M 20.2,
M 27.3, M 27.4
Etissa-Debissa, Dereje ......... DS 1.3
Etrich, Christoph ....HL 6.2, HL 15.11
Ettema, Ad ................... O 11.4
Etzkorn, M. ................MA 13.16
Etzkorn, Markus ..MA 4.6, MA 13.122
Eurich, Frank ............. CPP 15.28
Evans, Martin ............... DY 46.5
Everaers, Ralf .AKB 50.123, CPP 8.5,
DY 46.53, DY 51.6
Evers, F. .................... TT 17.6
Eversmann, B. ............ AKB 50.75
Evertz, H. G. ...............TT 32.10
Evertz, Hans Gerd TT 24.4, TT 24.5,
TT 30.10
Evetts, J. E. .................TT 8.14
Evgeni, Il’ichev .............. TT 29.1
Exerowa, D. ................SYPF 2.4
Eychmueller, Alexander .. HL 12.24,
HL 20.1, HL 20.4
Eyert, V. .....................MA 8.8
Eyert, Volker ... M 5.4, TT 14.12,
TT 24.56
F. e. lser, C. .................TT 32.6
Facsko, Stefan ............... O 40.10
Fähler, S. ....DS 18.1, MA 13.18,
MA 15.8, MA 15.9
Fähler, Sebastian .....MA 13.17,
MA 15.10, MA 30.5, MA 30.6
Fähnle, Manfred ... M 5.1, M 22.1,
MA 28.1, O 6.7
Fafard, S. ......... HL 36.3, HL 44.34
Fagot-Revurat, Y. .............O 11.8
Fahsold, G. ........... O 14.4, O 26.6
Fahsold, Gerhard .............O 28.43
Failla, V ..................SYOH 5.16
Faisst, A. .................. TT 24.29
Falcke, Martin ...AKB 41.2, AKB 50.1
Falk, Stefan .................MA 20.6
Fally, Martin ..................DF 2.5
Falta, J. ..................... O 38.10
Falta, Jens ...................HL 3.11
Falter, M. ................... TT 8.13
Falub, Mihaela .............. MA 11.5
Fan, Hongjin ............... HL 12.52
Faoro, Lara ................ SYSN 1.4
Faragis, Baker ............... HL 17.9
Farangis, B. ................ HL 17.10
Farle, M. .....................MA 6.4
Farrell, T. ................ SYOH 5.47
Fasolka, M. ................. CPP 6.1
Fassbender, Jürgen .... DS 22.35,
MA 10.3, MA 10.4, MA 10.5,
MA 13.47, MA 28.9
Fattah, A. ..................TT 24.54
Faubel, Manfred .............. O 19.2
Faulhaber, E. ................. TT 7.8
Faupel, F. . DS 22.29, O 24.1, O 28.35
Faupel , Franz .. CPP 4.3, CPP 7.2,
CPP 7.3, CPP 11.4, CPP 16.8,
DS 7.1, DS 15.7, DS 22.24, M 7.1,
SYOH 5.22
Faupel, Jörg ........DS 14.1, DS 17.2
Faustein, Andreas ...........TT 30.33
Fauster, Th. .................. O 39.3
Fauster, Thomas ...O 37.1, O 37.4,
O 45.7
Fauth, K. ...........MA 6.3, MA 31.5
Fauth, Kai .MA 30.1, O 10.4, O 19.1,
O 28.84
Fazio, Rosario ..............SYSN 1.4
Fecher, G. H. ....M 26.1, MA 8.5,
MA 13.114, O 28.34
Fecher, Gerhard H. ........... MA 8.6
Fecioru, Alin Mihai .HL 12.88, HL 31.2
Fedorenko, Andrei A. ........ DY 46.4
Fedorov, Dimitry .............DS 12.2
Fehse, Karsten ....HL 12.78, HL 44.81
Fehske, Holger ..... TT 30.5, TT 30.6
Feigelman, Mikhail ...........TT 25.4
Feil, T. .....................HL 44.17
Feilitzsch, Franz von ......... TT 13.2
Feldbacher, Martin TT 24.11, TT 32.8
Feldmann, and J. ..........CPP 16.34
Feldmann, J. ... HL 15.12, O 19.6,
O 28.67, SYOH 5.86
Feldmann, Jochen CPP 9.1, HL 12.36,
HL 44.33, SYNP 1.2, SYOH 4.3,
SYOH 5.83, SYOH 5.84
Felix, von Oppen .............HL 14.5
Felner, I. ...................MA 13.44
Felsch, W. ....... MA 13.65, MA 14.2
Felsch, Wolfgang MA 10.7, MA 13.54,
MA 30.1
Felser, C. ....MA 8.5, MA 13.114,
MA 13.117
Felser, Claudia ......MA 8.6, MA 20.6
Fendt, Robert .................O 46.2
Feranchuk, S. .................HL 3.3
Ferkel, Hans .................. M 26.2
Fernandes, F. M.B. .......... DS 14.2
Fernandez, L. .................TT 8.4
Fernandez-Madrigal, Javier .... O 44.6
Fernández, L. ................TT 8.11
Ferrand, David ...............HL 35.2
Ferrand, Patrick ............ HL 15.10
Ferro, Y. .................... O 28.57
Ferstl, J. .................... TT 30.4
Ferstl, Julia ...................TT 7.6
Fery, Andreas .... CPP 13.5, SYLS 3.6
Feuerbacher, M. .. M 30.2, M 30.5,
M 31.6
Feydt, Jürgen ..DS 22.23, MA 24.5,
MA 24.6
Feyerabend, F. ..............DS 22.45
Feyerherm, R. ..... MA 21.2, MA 21.3
FHR Anlagenbau .............. FB 16
Fichter, Sebastian .......... SYPF 4.2
Fichtl, R. ............DF 1.6, TT 14.3
Fichtner, Andreas DY 46.23, DY 46.23
Fichtner, M. ................. O 28.61
Fichtner, P. ...................DS 1.1
Fick, Jörg ..... CPP 16.17, CPP 16.18
Ficker, Jürgen ............. SYOH 4.1
Fidler, Josef ..................MA 1.1
Fiebig, M. .... DF 7.6, MA 13.46,
MA 13.67
Fiederling, R. ............... HL 29.11
Figge, Stephan ...............HL 16.9
Figger, Christian .......... AKB 50.76
Filipov, Oleksiy ............. DS 22.38
Filippi, C. ................. SYLS 3.20
Filonenko, E. ..................O 46.5
Filonenko, Eleonora .............O 6.6
Filonenko, O. .....DS 22.10, DS 22.11
Finckh, E. W. ................ M 26.1
Findenegg, Gerhard .........CPP 14.4
Finger, T. ................... HL 33.5
Fink, Dietmar .............. CPP 16.8
Fink, Joerg ................... TT 9.3
Fink, R. .CPP 12.6, O 33.4, SYOH 1.3
Finkelmann, Heino ........ CPP 16.35
Finley, J. J. .........HL 20.5, HL 42.5
Finley, Jon J .................HL 50.3
Finsterbusch, Klaus ........... O 28.2
Fischer, Bert ............. SYOH 5.76
Fischer, C.-H. .............. DS 22.56
Fischer, Ch.-H. .............. DS 21.3
Fischer, Frank ............... HL 22.7
Fischer, Franz .............CPP 15.30
Fischer, Gerda .....M 18.29, TT 24.34
Fischer, Inga ............... TT 24.20
Fischer, Ingo ... DY 36.1, HL 32.1,
HL 32.2, HL 38.2, HL 38.6
Fischer, M. .. HL 16.2, SYOH 5.29,
SYOH 5.61
Fischer, Marc ...............HL 38.11
Fischer, Mario ..............TT 17.12
Fischer, Markus ..........AKB 50.112
Fischer, Michael ............. HL 40.2
Fischer, S. F. .. HL 37.11, HL 41.1,
HL 44.2, MA 26.11
Fischer, Saskia F. ............. HL 5.1
Fischer, Tim .................O 28.63
Fischer, U. C. .................O 23.1
Fistul, M. V. .. TT 17.25, TT 25.2,
TT 29.2, TT 31.1
Fix, R. ...................... HL 42.1
Fix, Walt e. r .............. SYOH 4.1
Flammini, Roberto ............ O 18.7
Fleck, T. ................... HL 12.17
Flege, J. I. ...................O 38.10
Flege, Stefan ................. M 29.5
Fleischamnn, A. ............. TT 33.3
Fleischer, Karsten ............ O 28.55
Fleischmann, A. .DY 46.91, TT 8.24,
TT 13.4, TT 30.41
Fleischmann, Andreas ... TT 33.1,
TT 33.2
Fleischmann, Ragnar .. HL 5.6, HL 5.8
Flockerzi, Dietrich .........AKB 50.60
Flohrer, Sybille .............. MA 26.2
Florens, Serge ............... TT 16.1
Florin, Ernst-Ludwig ... AKB 22.2,
AKB 50.132
Föhlisch, Alexander . O 25.9, O 45.2,
O 45.5
Föll, Helmut ................HL 12.34
Förster, A. .................MA 13.58
Förster, Christian ............ HL 40.2
Foerster, M. .................. TT 1.3
Förster, Stephan .......... AKB 50.90
Förtig, Anton ..... AKB 50.129,
AKB 50.130
Folk, Reinhard ......DY 10.1, DY 46.6
Follath, R. .................... O 44.8
Folman, Ron ................ DY 50.2
Autorenverzeichnis
Fominykh, Natasha ...........O 28.69
Fonin, M. ......... MA 13.1, MA 13.4
Fonin, Mikhail ...............MA 13.2
Fonseca Romero, Karen M. ...TT 22.7
Fonseca-Romero, Karen M. ...DY 50.5
Fontaine, A. ............... MA 28.10
Forberich, Karen ............HL 12.37
Forchel, Alfred .. DS 22.44, HL 5.5,
HL 15.5, HL 38.8, HL 38.9,
HL 38.11
Forero, Stefan ............ SYOH 5.88
Forró, Lazlo ................. TT 27.9
Forschungszentrum Jülich ...... FB 17
Forster, Daniel .....HL 12.78, HL 21.3
Forster, F. ........... O 11.8, O 28.51
Forster, Frank ................O 11.10
Forstner, Martin B. ........AKB 50.56
Fortuna, Franck ............. MA 10.7
Forzani, E. .................. TT 8.47
Forzani, Eugenio .............TT 8.52
Fostiropoulos, Konstantinos
SYOH 5.41
Foucart, P. ................. TT 24.54
Fouckhardt, H. ...............HL 44.2
Fragneto, Giovanna ....... AKB 50.62
Frahm, Gabriel ............. SYFT 2.4
Franc, J. .................... O 28.35
Franchy, René ....... MA 20.1, O 39.5
Frank, Meikel ...............HL 12.31
Frank, Till ......... DY 14.3, DY 36.3
Frank, Till D. ..... DY 14.1, DY 46.16
Franke, Kerstin ........... MA 13.120
Frankevich, Eugene .......... CPP 3.3
Franosch, Thomas ....AKB 50.70,
DY 14.6, DY 51.4
Franz, Demmel .............. CPP 4.4
Franzka, Steffen ................O 4.5
Franzl, Thomas ............SYOH 4.3
Franzrahe, Kerstin .......... DY 46.48
Fratzl, P. ................. AKB 50.86
Fratzl, Peter . AKB 30.1, AKB 50.21,
AKB 50.53, AKB 50.57,
AKB 50.71, CPP 13.1, DY 26.1
Fratzl-Zelman, Nadja ......AKB 50.57
Frauenheim, Th. ............. HL 40.5
Fraune, M. .................MA 13.35
Freimuth, A. ... TT 3.11, TT 3.12,
TT 6.7, TT 14.9, TT 14.14,
TT 14.14, TT 20.7, TT 24.47,
TT 30.13, TT 30.14, TT 30.16,
TT 30.23, TT 30.29, TT 30.31,
TT 30.39
Freitas, P. P. ...............MA 13.84
Freking, Ansgar .............DY 46.12
Frenkel, Daan .................O 20.4
Frenken, J. W.M. ............. O 23.7
Frenz, Carsten ............ CPP 15.46
Frerichs, M. ................. O 14.67
Freude, W. .................. TT 8.18
Freudenberger, J. ..M 13.1, M 13.3,
M 16.3
Freudenberger, Jens ...........M 16.2
Freund, H.-J. ................. O 10.5
Freund, Hans-Joachim O 9.11, O 26.4,
O 31.7, O 39.4, SYNP 2.1
Frey, Erwin .. AKB 10.3, AKB 50.5,
AKB 50.20, AKB 50.40, AKB 50.41,
AKB 50.42, AKB 50.43,
AKB 50.84, AKB 50.103,
AKB 50.111, AKB 50.132, DY 12.3,
DY 14.6, DY 51.4
Frey, Holger ...............CPP 15.18
Freyer, W. ................ CPP 16.31
Freyer, Wolfgang ..............O 19.2
Freyhardt, H. C. ...... TT 8.8, TT 8.9
Freyhardt, Herbert C. ... DS 22.19,
DS 22.39
Fricke, C. ..........HL 12.56, HL 47.3
Fricke, J. ..................... HL 3.3
Fricker, S. ................... O 28.42
Fricker, Sebastian ............ O 28.50
Friedel, Bettina ....... HL 8.2, HL 8.2
Friedland, K. J. .....MA 3.2, MA 31.4
Friedrich, Christoph ........... O 31.6
Friedrich, Josef .SYLS 3.3, SYLS 3.7,
SYLS 3.8
Friedrich, M. SYOH 5.26, SYOH 5.27,
SYOH 5.28
Friedrich, R. ..............AKSOE 3.2
Friedrich, Rudolf . DY 14.1, DY 17.3,
DY 36.3, DY 46.16
Friedrich, Rudolph ........... DY 20.2
Friedrichs, Rene ............. DY 11.4
Friedt, O. ....TT 3.12, TT 14.11,
TT 14.14, TT 14.14, TT 24.53,
TT 30.36, TT 30.38, TT 30.38
Friend, Richard ............ SYOH 8.2
Frischkorn, C. ........O 28.60, O 43.6
Frischkorn, Christian ........ HL 44.66
Fritsch, Daniel ..HL 12.87, HL 17.1,
HL 17.6
Fritsch, V. ...................TT 14.3

Fritsche, Jochen ............ DS 22.50
Fritsche, Rainer ....... O 5.6, O 14.36
Fritz, Jürgen ..............AKB 50.59
Fritz, Lars ...................TT 16.2
Fritz, Torsten .O 4.1, O 4.8, O 14.62,
O 33.1, O 33.7
Fritzsche, Joachim . HL 44.6, HL 44.53
Friák, Martin ................MA 17.1
Fröb, Hartmut ..............HL 12.95
Fröba, M. ......... HL 12.70, HL 35.6
Fröhlich, Dietmar ............ HL 28.2
Fromherz, P. ..............AKB 50.75
Fromherz, Peter .....AKB 50.72,
AKB 50.73, AKB 50.74, AKB 50.76,
AKB 50.77, AKB 50.78, AKB 50.79,
AKB 50.80, AKB 50.83,
AKB 50.85, AKB 50.102
Frommberger, M. ........... DS 22.29
Fromme, B. ..................O 14.68
Frommert, Matthias ...........M 27.1
Frost, C. ................... TT 24.48
Frost, Frank ...DS 15.1, DS 22.15,
DS 22.46
Fruebing, Peter ............CPP 15.41
Frustaglia, Diego .... TT 3.4, TT 23.4
Frésard, Raymond .......... TT 14.12
Fubel, Armin ................ O 14.10
Fuchs, Dirk ...... MA 13.21, MA 20.9
Fuchs, G. . TT 8.47, TT 9.6, TT 9.9,
TT 12.3
Fuchs, Günter .. TT 8.51, TT 12.4,
TT 31.6, TT 31.10
Fuchs, H. ......... O 23.1, SYLS 3.10
Fuchs, Hans-Jörg ........... HL 15.11
Fuchs, Harald .O 9.8, O 9.9, O 14.73,
O 14.74, O 14.75, O 23.2,
SYOH 5.2, SYOH 5.6, SYOH 5.17
Fuchs, M. ................. SYLS 3.20
Fuchs, O. .....................O 44.8
Fühner, C. ...................HL 37.1
Fuhrmann, D. .. HL 27.9, HL 27.11,
HL 44.82
Fuhrmann, Richard ...........HL 24.5
Fuhrmann, T. ......... O 14.9, O 43.3
Fuhrmann, Thomas .....HL 15.1,
SYLS 3.17, SYOH 5.63
Fuhs, W. ................... DS 22.54
Fuhs, Walther ... DS 4.4, DS 13.4,
DS 20.1, DS 20.2, DS 22.49,
DS 22.53
Fuhse, Christian ............ DS 22.20
Fujara, Franz ...... CPP 3.1, CPP 4.1
Fujita, Shozo ............... SYLS 4.5
Fujita, Tojitsu ............... TT 8.42
Fujiwara, Hidenori ........... TT 30.8
Fukumoto, K. ..............MA 28.10
Fukushima, Noboru .......... TT 24.8
Fukushima, T. ...............DY 27.3
Fullerton, Eric E. ............ MA 10.9
Fumagalli, P. . MA 15.7, O 9.6, O 25.3
Fumagalli, Paul . MA 16.9, MA 18.5,
O 5.3, O 37.6
Funari, Sergio S. SYLS 3.47, SYLS 3.53
Funke, Ralf ................... O 38.4
Funnemann, D. .............. O 28.51
Furdyna, Jacek K. ............HL 35.1
Furitsch, M. ................. HL 38.3
Furitsch, Michael ............ HL 38.5
Furthmüller, J. ...............HL 27.4
Furthmüller, Jürgen . HL 36.1, HL 36.9
Furtmayr, Florian ........... HL 27.13
Furtmüller, Jürgen ........... O 28.22
Gabel, Franck ............. SYLS 3.26
Gaber, Tobias ...... TT 25.5, TT 31.2
Gabriel, C. ................. TT 32.10
Gade, Lutz .................. O 14.25
Gaebel, Thorsten ........... TT 17.26
Gaebel, Torsten SYLS 3.51, TT 17.22,
TT 22.1, TT 22.2
Gähler, Franz .........M 29.1, M 29.2
Gärditz, Christoph ........ SYOH 5.88
Gärtner, Andreas ..............HL 9.3
Gaganidze, Ermile .............TT 1.6
Gaganov, A. ..M 13.1, M 13.3, M 16.3
Gahl, Cornelius .......O 28.73, O 37.7
Gaillard, J. ................ SYLS 3.55
Gainaru, Catalin ...DF 2.6, DF 3.7,
DF 3.8, DY 28.7, DY 28.8
Gajbhiye, N. S. ............... MA 6.3
Gajic, Rados ................. HL 28.8
Galakhov, Vadim ............ MA 11.5
Galbraith, I. ................ HL 12.19
Galenko, Peter ................M 18.5
Galka, Christian ..............O 14.25
Gall, Stefan .... DS 4.4, DS 20.2,
DS 22.49, DS 22.53
Galler, Robert ................ M 29.5
Galluppi, Massimo ........... HL 25.1
Gandit, P. ................... TT 25.6
Ganichev, S. D. . HL 43.2, HL 44.45,
HL 44.46
Ganteför, Gerd ...............O 28.63
Ganzer, S. ................. MA 13.61
Gao, Jianrong ................ M 12.3
Gao, Weiying ............. SYOH 5.30
Gao, Xingyu ..................MA 4.2
Gaponik, Nikolai .HL 12.24, HL 15.2,
HL 20.1, HL 20.4
Garbe, Ulf .................... M 22.4
Garbrecht, M. .................O 28.1
Garcia, Almudena ............DY 44.3
Garcia de Oteyza , Dimas ......DS 7.2
Garcia-Matres, Elvira ........ MA 11.7
Garcocz, M. ...... HL 44.74, HL 44.75
García-Vidal, F. J. ............. PV III
Gardinowski, G. .............. O 28.24
Garleff, J. K. ..................HL 3.8
Garnier, M. G. ................MA 6.3
Garrido, Jose ................ HL 48.1
Garriga, Miquel ................ O 4.4
Gartner, P. .................. HL 36.7
Gartner, Paul ....... HL 36.5, HL 36.6
Gassenbauer, Yvonne .........DS 21.2
Gassmann, Hanno ........... TT 22.9
Gassul, Daniel ........... AKB 50.131
Gaul, Mirko ..................DS 20.5
Gaupp, Andreas ..O 28.78, O 28.80,
SYXM 1.1
Gavrila, G. ............... SYOH 5.38
Gavrilov, S. ...................DF 5.3
Gawronski, Heiko ..............O 31.1
Gaál-Nagy, Katalin ..........HL 44.71
Ge, Xin ......................O 14.26
Geballos, G. ...................O 17.8
Gebert, Annett ..DS 18.4, MA 11.9,
MA 11.11
Gebhard, Florian .TT 24.7, TT 24.17,
TT 24.18, TT 26.1, TT 28.5
Gebhardt, R. K. ............MA 13.88
Gebhardt, Ronald ......... AKB 50.61
Gebhardt, Ulrich .............. DS 9.2
Gebing, Jochen .............. TT 27.3
Geck, Jochen ................TT 20.6
Geelhaar, Lutz ... HL 3.9, HL 25.1,
HL 50.5
Geerk, J. ............TT 8.1, TT 18.1
Gege, Christian .....AKB 50.119,
AKB 50.120, AKB 50.121
Gegenwart, P. ....... TT 7.7, TT 10.2
Gegenwart, Philipp ............TT 7.6
Gegner, Jürgen .. M 17.1, M 18.12,
M 18.13, M 18.14
Gehl, Bernhard ...............DS 17.6
Gehrig, Edeltraud ............ HL 38.6
Gehring, Birgit ...............O 28.37
Geibel, C. . TT 6.9, TT 7.7, TT 7.8,
TT 24.33, TT 30.4
Geibel, Christoph ............. TT 7.6
Geil, Burkhard ..... CPP 3.1, CPP 4.1
Geisel, Theo ... DY 21.1, DY 21.3,
DY 24.4, DY 24.5, DY 27.4,
DY 42.1, DY 50.7, HL 5.8
Geisler, Fanny ............... O 28.68
Geissler, J. ................ SYXM 1.2
Geller, M. .................. HL 50.10
Geller, Martin ................HL 37.3
Gemmer, Jochen .............DY 50.6
Gemming, Sibylle CPP 16.3, DF 5.15,
M 18.9, M 18.17, MA 13.94
Gemuend, Manuel .........AKB 50.96
Genenko, Yuri A. ......... SYOH 5.77
Geng, Peter ...................O 38.9
Gensch, M. . CPP 15.21, CPP 15.45,
O 14.59, SYLS 3.49
Gentil, Cedric .............. AKB 20.3
Georges, A. ..................TT 32.7
Georgii, Robert ........... MA 13.102
Georgiou, S. ................. O 28.13
Geppert, Steffen ............CPP 14.1
Geppert, Torsten M. ........ HL 12.35
Geprägs, Stephan .....MA 13.27,
MA 13.116
Gerber, A. .................... DF 6.7
Gerber, P. .................... DF 6.3
Gerbig, Yvonne ...... DS 7.3, DS 14.5
Gerdes, Andreas .....O 14.41, O 14.42
Gerhard-Multhaupt, Reimund
CPP 13.9, CPP 15.41, CPP 15.47
Gerhardt, Ilja ................CPP 9.5
Gerhardt, N. C. .............. HL 12.1
Gerl, Christian ................ O 24.3
Gerlach, A. ... O 14.2, SYOH 5.18,
SYOH 5.29
Gerlach, J. W. .. DS 22.6, DS 22.7,
DS 22.46
Gerlach, Ulrich ...........AKB 50.124
Gerland, Ulrich . AKB 40.3, SYLS 3.35
Gerlich, Dieter ..............HL 12.82
Gerstermann, U. ............. HL 40.5
Gerth, Gerhard ..............HL 44.69
Gerthsen, D. .. HL 12.10, HL 12.72,
HL 12.74, HL 12.76, HL 43.3
Gerthsen, Dagmar . DY 46.72, HL 42.4
Geshkenbein, V. B. .......... TT 29.6
Geshkenbein, Vadim ......... TT 25.4
Getzlaff, M. ................MA 13.88
Geue, Th. ..................CPP 11.5
Geue, Thomas ..............CPP 10.3
Geurts, J. ... HL 21.1, SYOH 5.62,
SYOH 5.64, SYOH 5.65
Ghaderi, Tuana ............... O 46.2
Ghafari, Mohammad ....MA 6.11,
MA 13.38
Gholami, Azam .......... AKB 50.111
Ghosh, Arindam ............ TT 30.15
Giamarchi, T. ................. O 17.7
Giamarchi, Thierry ......... SYNF 1.5
Gibbs, Hyatt M. ............. HL 28.4
Giemsch, Sören ............. HL 12.18
Gierak, Jacques ............... VA 1.1
Gieres, Guenter ...MA 13.51, MA 27.7
Giersig, M. ...................MA 6.5
Giersig, Michael . CPP 12.4, HL 17.2,
SYLS 3.19
Giesen, Christoph ............ HL 33.4
Giesen, F. ..................MA 13.63
Giesen, Fabian ............. MA 13.64
Giessen, Harald ............... HL 2.5
Giessibl, Franz J. ..............O 9.10
Gießel, Tatjana ...............O 28.77
Giglberger, S. ...............HL 44.46
Gigler, Alexander ... CPP 2.3, O 14.84
Gil, Woosik ................ MA 13.24
Gilet, Ph. ....................HL 43.3
Gimm, Tae-Hyoung .......... TT 30.3
Giorgetti, Christine .......... MA 30.1
Giovanardi, Chiara O 3.5, O 3.8, O 32.3
Gippius, Nikolai ............... HL 2.5
Giske, Arnold . MA 13.22, MA 13.23,
MA 22.3, MA 27.5
Gittins, D. I. .................. O 19.6
Gjukic, Mario ................ HL 51.2
Glättli, H. .................SYLS 3.55
Glaser, Leif O 19.3, O 25.9, SYXM 1.6
Glass, Roman AKB 50.13, AKB 50.14,
AKB 50.37, CPP 15.4
Glatzel, T. ...................HL 30.2
Glazman, Leonid ........... SYNF 1.1
Gleiter, H. ....................M 20.5
Gleitsmann, T. O 10.6, O 28.64, O 32.6
Gleixner, Raimund ....... AKB 50.102
Glisovic, Anja ............. AKB 50.82
Glocke, Stefan ..............TT 24.15
Gloskovskii, A. . DS 22.27, DS 22.28,
O 28.75
Gloskovskij, A. ................M 26.1
Glowacki, B. A. ..............TT 8.14
Glowatzki, Hendrik . TT 8.16, TT 18.5
Gmeiner, Jürgen .......... SYOH 5.88
Gmeinwieser, Nikolaus ........HL 27.5
Gnaser, H. ...................DS 12.6
Gnezdilov, V. .... TT 14.13, TT 24.51
Gnodtke, C. ...................HL 5.2
Gobert, Dominique ...........TT 15.8
Gobsch, G. ... HL 27.12, HL 27.15,
HL 44.67, SYOH 5.52
Gobsch, Gerhard ...HL 12.96, HL 23.3
Godlewski, Jan ........... SYOH 5.53
Gößling ......... .........
Goebbels, J.SYPF 4.4 Goede, Karsten
HL 44.41
Gödecke, Andreas ............ O 14.28
Goedeke, Sven ...............DY 42.1
Goedel, Werner A. .......... HL 12.55
Goegler, Michael ..... AKB 12.1,
AKB 50.16, AKB 50.35
Goehlich, Alexandra ..........O 14.34
Göhmann, Frank ..............TT 3.7
Göken, Mathias ...............M 21.2
Gölzhäuser, Armin .............O 33.3
Goennenwein, Sebastian T. B. HL 25.2,
HL 35.5
Gönnenwein, Stephanie ...AKB 50.129
Goering, E. . MA 13.110, SYXM 1.2,
TT 20.4
Goering, Eberhard .............O 12.4
Goering, Harald ........... CPP 15.41
Göritz, Dietmar . CPP 8.1, CPP 11.2,
CPP 15.14, CPP 15.40, CPP 16.7,
DY 21.5
Görlach, T. .................TT 24.38
Görlitz, D. ...................TT 8.33
Goesele, Ulrich ...DF 5.1, HL 11.3,
HL 12.28, HL 12.52, HL 12.58,
HL 12.88, HL 15.4, HL 31.2,
HL 44.69
Gössling, A. ................ TT 24.47
Götze, Britta ............ AKB 50.100
Götze, Wolfgang .....DF 3.3, DY 28.3
Götzendorfer, Andreas ....... DY 44.3
Gogova, D. ................. HL 44.79
Gokhale, Shubha .............. O 11.6
Gol’tsman, Gregory ........... TT 1.2
Gold, S. .........MA 13.110, TT 20.4
Goldacker, W. ................ TT 1.4
Goldberg, Roy ..............CPP 12.1
Autorenverzeichnis
Goldhahn, R. ... HL 12.7, HL 16.3,
HL 27.4, HL 27.12, HL 30.5
Goldhahn, Rüdiger .......... HL 27.16
Goldman, Daniel I. . DY 15.3, DY 44.2
Goldobin, E. .................TT 18.3
Goldobin, Edward .TT 8.54, TT 25.5,
TT 31.2
Goldschmidt, A. .......... SYOH 5.47
Goletti, Claudio .............. O 28.55
Goll, D. ............. MA 2.3, MA 2.4
Goll, G. .................... TT 24.32
Gollisch, Tim .............. AKB 41.1
Golovin, Igor S. ...M 25.2, M 25.3,
M 25.4
Golovina, Svetlana B. ......... M 25.3
Golub, L. E. ....... HL 43.2, HL 44.46
Golubev, Dmitri ............. TT 11.8
Golubov, A. A. .............. TT 8.21
Gombert, Andreas .......... HL 12.37
Gomes, H. L. ............. SYOH 5.65
Gompf, B. ....SYOH 5.29, SYOH 5.61
Gompf, Bruno AKB 50.19, SYOH 5.60
Gompper, Gerhard ....AKB 50.46,
AKB 50.90, AKB 50.92, DY 51.7
Goncalves, Eder ......DS 20.5, O 40.3
Goncharov, V. K. ........... HL 44.67
González-Gaitán, Marcos .. AKB 50.49
Gonçalves, Manuel O 28.46, O 28.47,
O 28.50
Gopakumar, T. G. ....O 14.23, O 38.7
Gopalakrishnan, Selvi ...........O 5.7
Gorb, Stanislav .......... AKB 50.107
Gordan, O. D. SYOH 5.26, SYOH 5.28
Gorgoi, M. ............... SYOH 5.35
Gorovikov, S. ....... MA 4.9, MA 31.2
Gorshunov, B. ............... TT 6.10
Gorshunov, Boris ..MA 21.8, TT 24.35
Goryachko, Andriy ............ DS 9.4
Goryako, Andrey ............ HL 44.42
Gossard, A. C. .. HL 4.10, HL 4.11,
HL 12.21
Gossla, M. .HL 12.6, HL 24.6, HL 30.5
Gossla, Mario ................ HL 12.3
Gotsmann, Bernd CPP 2.1, CPP 15.15
Gottfried, M. ..................O 43.4
Gottfriedsen, Peter ...........HL 27.5
Gottmann, J. ................ DF 5.10
Gottschalch, Volker DS 22.2, DS 22.3,
HL 12.50, HL 12.89, HL 44.11,
HL 44.55, HL 44.56, HL 44.57,
HL 44.58, HL 44.64
Gottstein, G. ......... M 12.4, M 12.4
Gottstein, Günter ..... M 20.3, M 27.1
Gouder, T. .................MA 13.19
Gould, C. HL 29.3, HL 29.7, HL 29.8,
HL 29.11
Gould, Charles ..HL 29.4, HL 44.20,
HL 49.3
Goulkov, M. .......... DF 2.4, DF 7.3
Governale, M. ..............SYNF 1.3
Governale, Michele HL 29.6, HL 29.9,
HL 49.2, TT 11.10
Goychuk, Igor . AKB 50.45, DY 23.3,
DY 46.60
Gr undmann, M. ............. HL 17.5
Gr’esillion, Samuel ........... O 28.40
Graaf, Harald .SYOH 5.87, SYOH 5.87
Grabbe, A. ................ SYLS 3.45
Grabbe, Annika ............SYLS 3.40
Grabert, Hermann ............ TT 4.6
Grabis, Johannes .MA 10.2, MA 16.8,
MA 20.8, MA 30.8, O 12.1,
O 28.79, O 28.85
Grabovski, Sergey ...........DS 22.17
Grabowski, J. .........MA 16.7, O 9.3
Grabowski, Jan ...HL 3.9, HL 3.10,
HL 25.3
Grabs, P. HL 21.1, HL 29.7, HL 29.8,
HL 29.10, HL 29.11
Grabs, Peter .......HL 44.20, HL 49.3
Gräber, Peter ............. AKB 50.98
Graeter, Stefan .............AKB 50.8
Graf, Herbert .............. MA 13.86
Graf v. Bothmer, Hans-Christian
AKSOE 1.4
Grafe, Hans-Joachim ..........TT 2.2
Graff, Andreas . M 18.8, MA 13.107,
O 10.8
Grafström, Stefan .. O 9.5, O 14.61,
O 23.3, O 28.54
Grage, Anja ................. TT 26.1
Graham, Andrew .............HL 46.1
Granzow, T. .......... DF 7.2, DF 7.3
Graser, Siegfried ............. TT 8.35
Grau, A. .....................HL 43.3
Grayson, M. ................. HL 47.6
Grayson, Matthew .HL 14.6, HL 14.6,
HL 22.7
Grazioli, C. ...........MA 3.1, O 24.4
Grecu, M. N. ............. SYOH 5.89
Grecu, Silviu ..............SYOH 5.55
Greenham, Neil ............ SYOH 8.2

Greer, Lindsay ......... M 9.1, M 14.3
Greiling, Arnd .............. HL 12.78
Greiter, Martin ................TT 3.1
Grenouillet, L. ............... HL 43.3
Grenzebach, Claas ............ TT 7.1
Grenzer, J. .......... CPP 11.5, O 6.5
Grenzer, Jörg ................. HL 3.3
Gresillion, Samuel ...........DY 46.96
Grest, Gary S. ......CPP 8.5, DY 51.6
Greulich-Weber, S. ..HL 6.3, HL 8.1,
HL 40.5
Greulich-Weber, Siegmund ..HL 8.2,
HL 8.2
Greve, H. ...................DS 22.29
Greve, M. .................. HL 27.11
Grewe, Norbert ............. TT 24.16
Griesche, Christian ........... HL 42.3
Griessen, Ronald .............. O 26.8
Griessl, Stefan O 24.3, O 24.11, O 32.1
Grifoni, Milena .... DY 46.14, TT 22.6
Grigalaitis, R. ................. DF 7.4
Grigorian, S. A. ............... HL 3.3
Grigorian, V. ..................O 11.8
Grigoriev, Sergey ..........MA 13.102
Grigorieva, Elena .............DY 34.6
Grigorieva, N. .......DF 5.3, DS 22.55
Grigoryan, Valeri ............. O 11.10
Grille, Hartmut ............. DY 46.10
Grillenberger, J. ..............HL 27.8
Grillo, I. ...................SYLS 3.55
Grimm, Uwe ..................M 29.3
Grin, Y. ....................CPP 10.7
Grinberg, Farida ............... M 3.4
Gritsenko, K ..............SYOH 5.16
Grob, Andreas .............. DS 22.33
Grochol, Michal .............HL 12.14
Grochowski, Rafal ........... DY 44.3
Gröger, A. ................... HL 29.8
Gröger, Andreas ............ HL 44.20
Grössinger, R. ..................M 8.5
Grössinger, Roland ......... MA 11.10
Groh, U. ...................SYOH 1.3
Gronski, Wolfram ...........CPP 14.1
Gronych, Tomas .............. VA 2.3
Gros, Claudius . TT 24.26, TT 30.22,
TT 32.3
Gross, Axel .................. O 14.21
Gross, E. K.U. .............. MA 20.2
Gross, R. .......... MA 13.5, TT 18.4
Gross, Rudolf .. HL 44.9, MA 13.27,
MA 13.39, MA 13.116, MA 22.1,
TT 1.1, TT 8.3, TT 8.19, TT 17.5,
TT 17.20, TT 17.21
Grosse, Frank .. HL 12.14, HL 36.2,
O 25.8
Grossmann, Frank .......... TT 17.12
Groth, Frank .........O 28.20, O 40.2
Groth, Steffen .............. HL 12.11
Grotkopp, Ingo . O 14.44, SYLS 3.47,
SYLS 3.53
Groudeva-Zotova, Stefka .... DS 22.22
Groß, Axel ..O 14.3, O 14.5, O 18.6,
O 20.7, O 26.9, O 28.9, O 28.9,
O 28.56, O 31.3
Grube, K. ........TT 24.29, TT 24.30
Gruber, Achim . TT 17.22, TT 17.26,
TT 22.1, TT 22.2
Gruber, Th. ....... HL 12.18, HL 17.4
Gruber, Thomas ............ HL 12.79
Grubmüller, Helmut .........SYLS 1.1
Grübel, Gerhard ............. DY 26.1
Grün, Günther ...............DY 17.4
Grünberg, Peter ..... DS 6.3, MA 20.4
Grüning, H. ..................HL 25.5
Grüninger, M. ... TT 6.7, TT 14.9,
TT 24.47, TT 30.39
Grüninger, Markus ........... TT 3.14
Grünwald, David ............SYLS 2.1
Grütter, P. ....................O 23.9
Grützun, Verena .............. M 30.4
Gruhn, Thomas ..... AKB 50.48,
AKB 50.128
Grundler, D. .. HL 12.66, HL 44.13,
MA 13.63
Grundler, Dirk . HL 44.15, MA 13.64,
MA 13.69
Grundmann, M. ..DS 9.7, HL 12.71,
HL 12.73, HL 12.83, HL 12.86,
HL 17.5, HL 17.12, HL 28.5
Grundmann, Marius ....HL 12.61,
HL 12.68, HL 12.69, HL 12.77,
HL 12.81, HL 12.84, HL 12.87,
HL 12.89, HL 17.1, HL 17.3,
HL 17.6, HL 44.11, HL 44.41,
HL 44.51
Grundmann, Steffen .......SYOH 5.42
Grunze, M. ................... O 44.8
Grunze, Michael .... AKB 50.131,
CPP 16.16, CPP 16.17, CPP 16.18,
O 33.3
Grupp, Arthur ...............MA 21.6
Grusemann, U. ................DS 1.8
Grusewski, Christa ............ M 25.4
Grushko, Benjamin .M 18.24, M 31.1,
M 31.2
Grybos, Robert ................O 18.5
Grzegorzewski, Franziska ...SYLS 3.29
Gsell, S. ...................... DS 9.6
Guck, Jochen . AKB 12.1, AKB 30.4,
AKB 50.113, AKB 50.125
Gudat, W. MA 10.6, MA 31.5, O 24.4,
O 32.2
Gudat, Wolfgang . O 28.78, O 28.80,
SYXM 1.1
Guderian, P. ......MA 13.65, MA 14.2
Güdde, J. ............O 28.70, O 45.1
Güngerich, M. ..... HL 12.51, HL 43.1
Guennou, M. ............... TT 24.48
Guenoun, Patrick ...........CPP 12.2
Günter, Heinz-Lorenz .........O 28.45
Günther, Guido .............DY 46.85
Günther, S. ..AKB 50.3, AKB 50.17,
SYLS 3.24
Guenther, Sebastian ... O 20.2, O 31.5
Güntherodt, G. . MA 10.8, MA 13.1,
MA 13.4, MA 13.35, MA 28.11,
MA 31.4, TT 24.50, TT 24.51
Guentherodt, Gernot .... MA 7.2,
MA 13.2, MA 31.1
Güntherodt, H.-J. ...O 14.22, O 23.10
Güntherodt, Hans-Joachim ... O 14.25
Güntner, R. .............. SYOH 5.47
Guerdane, M. ........DF 4.4, DY 29.4
Gütay, Levent ................HL 24.5
Güßmann, Martin ............DY 34.5
Guffarth, F. .................HL 50.10
Guffarth, Florian .HL 36.4, HL 36.10,
HL 36.11
Gui, Y. S. .....................HL 5.3
Guichard, W. ................ TT 25.6
Guldbakke, J. M. ........... HL 12.42
Gumbsch, Peter ...............M 29.4
Guminskaya, T. .. DF 5.3, DS 21.3,
DS 22.55
Guminskaya, Tanja ..........DS 22.57
Gumpenberger, Thomas ....SYLS 3.27
Gundel, H. W. ................ DF 1.2
Gundlach, David J. .........SYOH 7.2
Gunnarsson, Olle ... TT 26.3, TT 32.1
Guo, Wenge SYOH 5.42, SYOH 5.43,
SYOH 5.82
Guo, X. .......................O 25.8
Gupta, Himadri S. .........AKB 50.53
Gupta, Mukul ............. CPP 15.32
Gur, Ilan .................. SYOH 8.1
Gurtovenko, Andrei .......... CPP 5.2
Guslienko, Konstantin ....... MA 28.2
Gust, Arne ..........HL 21.2, HL 21.4
Gustafson, J. ..................O 38.8
Gutberlet, Thomas ........ CPP 15.32
Gutfleisch, Oliver .MA 11.6, MA 11.8,
MA 11.9, MA 11.11, MA 26.3
Guth, Karsten .. MA 13.29, TT 1.5,
TT 8.8, TT 8.9, TT 8.10
Gutheim, F. ................. DY 25.4
Gutierrez, Rafael ..........SYOH 5.58
Gutiérrez, Rafael .............DY 34.4
Gutlederer, Erwin ........ AKB 50.128
Gutmann, Henryk ...........TT 17.18
Gutowski, J. ......... HL 4.5, HL 36.8
Gutowski, Jürgen ..............HL 4.2
Gutsch, Andreas ........... SYNP 2.3
Gutt, Christian ... HL 11.5, O 6.3,
O 14.48, O 14.50, O 46.2
Guttenberg, Z ............... DY 40.4
Guttmann, Peter .......... AKB 50.82
Guzenko, V. A. .............MA 13.96
Guzmán, Erick ..............HL 12.77
GVL Cryoengineering ...........FB 18
Györfy, Balas ...............MA 13.98
Gywat, Oliver ................HL 50.1
Gó´zd´z, Wojciech .......... AKB 50.90
H. Hope - Kollaboration ...SYOH 5.43
H. L., Meyerheim .... MA 4.1, MA 4.3
Haak, Christian .............. O 28.16
Haak, Matthias ............ MA 13.12
Haake, Fritz ........DY 27.6, DY 27.7
Haaks, M. ...........M 16.4, M 18.15
Haaks, Matz ......... M 10.2, M 13.2
Haarer, Dietrich ............ CPP 10.1
Haas, H. ......................DF 1.4
Haas, Heinz ...............AKB 50.26
Haas, Philipp ......TT 6.10, TT 24.35
Haase, A. ....................HL 23.6
Haase, W. ..................HL 15.13
Haase, Wolfgang ..............DF 1.1
Habasaki, Junko ............. DY 46.9
Habenicht, Anja ............. O 28.49
Haber, Thomas ...........SYOH 5.12
Habermeier, H. U. ............ DS 9.2
Habermeier, H.-U. TT 24.54, TT 31.5,
TT 31.8
Habermeier, Hanss-U. ........TT 19.2
Habl, M. .................... HL 22.4
Haboeck, U. ................HL 27.14
Haboeck, Ute ................HL 17.9
Habouti, S. ................... O 28.3
Hachenberg, Jörg ...........DY 46.68
Hacia, S. ......... HL 41.1, MA 26.11
Hackbarth, Thomas .........HL 12.64
Hackl, A. ................... MA 18.1
Hackl, Rudi ................. TT 8.42
Hader, Jörg HL 32.3, HL 32.4, HL 32.5
Hadnadev, Milica ..............O 14.6
Häberle, Uli ...................DF 5.7
Häberlen, M. ....... DS 1.4, DS 22.13
Häckel, Michael ........... CPP 15.46
Haefke, Henry ...CPP 8.4, DS 4.3,
DS 6.1, DS 7.3, DS 13.1, DS 13.3,
DS 14.5, O 46.4
Häfner, Michael ............ TT 17.32
Häfner, Wolfgang ......... CPP 16.32
Hägele, D. ...................HL 43.2
Hägele, Daniel .. HL 4.7, HL 12.15,
HL 12.47, HL 41.2, HL 44.6,
HL 44.52, HL 44.53
Haehnel, Marcel ............ DS 22.16
Hähner, Peter ................ M 30.4
Haendel, Kai-Martin ..........HL 37.7
Hänel, K. .................SYOH 5.13
Hänel, Kathrin .............SYOH 1.2
Hänggi, Peter AKB 50.11, AKB 50.45,
DY 23.3, DY 46.15, DY 46.60,
DY 50.5, SYFT 1.2, TT 17.1,
TT 17.2, TT 22.7, TT 27.1
Hänisch, J. ..........TT 8.4, TT 8.11
Hänke, Torben ...... MA 17.3, O 17.2
Haenni, Werner ............... DS 6.1
Hänsel, Helmut CPP 15.30, SYOH 5.45
Härle, V. HL 38.3, HL 44.83, HL 44.84
Härle, Volker ... HL 16.4, HL 27.5,
HL 38.5
Härtl, Andreas ............... HL 48.1
Häusler, Wolfgang ... HL 29.1, TT 4.6
Häussler, P. .................. M 14.5
Häussler, Peter . M 2.3, M 2.4, M 14.4
Häussler, R. ................ TT 17.11
Häußler, Peter ................. M 9.6
Hafner, Jürgen ............. DY 46.98
Hafstein, Sigurdur F. ....DY 34.1,
DY 46.20, DY 46.21
Hagedorn, Till ............... O 14.74
Hagel, Jochen .............. TT 30.27
Hagemann, Felix ..............M 30.4
Hagen, Christian .............TT 27.9
Hagen, J. ....................O 28.64
Hagen, Volker ............... O 14.70
Hager, Jürgen .................O 11.2
Hagfeldt, A. ................. HL 30.1
Hagler, T. ................. MA 13.61
Hagler, Thomas ............MA 13.40
Hagmann, Frank .............. HL 8.5
Hague, Coryn F. ...........SYXM 1.4
Hahn, Eike ......... HL 16.6, HL 42.4
Hahn, H. .....................MA 6.3
Hahn, Horst ...MA 6.7, MA 13.38,
MA 13.82
Hahn, Patrick H. .. CPP 16.2, O 28.20
Hahn, Th. HL 12.6, HL 12.7, HL 24.6,
HL 30.5
Haibel, A. ....... SYPF 4.4, SYPF 5.2
Haibel, Astrid .............. SYPF 5.1
Haider, Ferdinand . M 15.2, M 18.16,
M 18.21, M 18.22
Hajak, H. ...................HL 44.37
Halbritter, Jürgen .............TT 1.6
Hallatschek, Oskar ....AKB 50.40,
AKB 50.41
Hallerberg, Sarah ............ DY 46.1
Halsall, M. P. ................HL 43.1
Haluska, Christopher ...AKB 50.54,
AKB 50.90
Haluska, Christopher K. ... AKB 50.92
Hammer, H. .... MA 13.121, MA 18.2
Hammer, Lutz . O 3.5, O 3.8, O 6.1,
O 6.7, O 32.3
Hammerl, Claus ...............DS 3.2
Hammerl, German ........... TT 18.2
Hammerschmidt, Thomas ... HL 12.59
Han, Kyoo-hyun .............MA 11.1
Hanack, Michael ..........SYOH 5.24
Hand, Thomas ...............TT 16.9
Handge, Ulrich A. ........... CPP 8.3
Handke, J. .................. TT 8.12
Handstein, A. .........TT 9.6, TT 9.9
Handstein, Axel . MA 11.6, MA 11.8,
MA 11.10, MA 11.11, MA 26.3
Hangleiter, A. .. HL 27.9, HL 27.10,
HL 27.11, HL 44.82, HL 44.85
Hanke, Andreas .AKB 50.23, SYLS 3.5
Hanke, Werner ...TT 2.5, TT 26.7,
TT 26.8, TT 26.10
Hanna, G. .......... HL 12.5, HL 30.2
Hannappel, Thomas HL 33.4, O 28.25,
O 40.4
Hannemann, U. ............. MA 15.9
Autorenverzeichnis
Hannemann, Ullrich ....MA 13.17,
MA 15.10
Hannewald, Karsten ..........HL 23.1
Hannig, M. ................SYLS 3.15
Hans-Christian, Weißker ......HL 36.1
Hansch, Walter .............. HL 10.5
Hansen, Henri .................O 32.4
Hansen, S. ............... SYOH 5.20
Hansen, Ulf-Hendrik ........ DY 46.16
Hansen, W. .. HL 3.7, HL 5.4, HL 42.2
Hansen, Wolfgang . HL 3.12, HL 5.9,
HL 12.93, HL 25.4, HL 37.2
Hansmann, M. ................ O 17.8
Hanson, M. ....HL 4.10, HL 4.11,
HL 12.21
Hantke, K ................... HL 25.5
Hao, H.-Y. .................. TT 33.3
Hara, S. ..................... HL 44.5
Harada, K. ............... SYOH 5.39
Haramina, Tatjana ........ CPP 15.17
Haraszti, Tamas ...........AKB 50.33
Harayama, T. ................DY 27.3
Hardtdegen, Hilde ............HL 27.3
Harke, B. ...................HL 12.56
Harm, S. .................... O 28.33
Harmans, Kees .............. TT 25.3
Harmer, P. ...................HL 43.1
Harnagea, C. ................. DF 6.4
Hartmann, Alexander K. .. DS 14.4,
DY 23.1, DY 26.3
Hartmann, Christoph .......... O 32.5
Hartmann, David ..............HL 5.5
Hartmann, Markus ...........DY 26.1
Hartmann, Markus A. ..... AKB 50.21
Hartmann, Michael .... TT 17.28,
TT 29.13
Hartmann, Nils .........O 4.5, O 33.6
Hartmann, S. .............SYOH 5.27
Hartung, Michael ............ TT 27.6
Hasche, T. ...................HL 23.7
Hasegawa, Masaki ........... O 14.55
Haselier, H. ..................DS 14.3
Hassdorf, Ralf ..DS 22.23, MA 24.5,
MA 24.6
Hasselbrink, Eckart .DS 12.3, O 26.5,
O 33.6
Hasselkamp, Dietmar .........HL 17.9
Hasselmann, Nils .... DY 10.5, TT 4.5
Hatton, Peter ................TT 14.8
Haubrich, Jan ........O 14.11, O 43.5
Hauch, J. O. ...............MA 13.35
Haude, Daniel ........O 14.71, O 23.6
Haug, H. ..................... HL 4.1
Haug, R. J. ...HL 12.56, HL 12.60,
HL 22.1, HL 37.1, HL 37.4,
HL 37.7, HL 37.12, HL 44.27,
HL 44.28, HL 47.3
Haug, Rolf .......HL 22.10, SYSN 2.3
Haug, Rolf J. ............... HL 12.41
Haug, Thomas .... MA 26.7, MA 28.5
Haumann, Carola ..........SYLS 3.28
Hauschild, A. ................ O 14.58
Hauschild, Dirk ................ M 9.6
Hauschild, Robert ...........HL 12.79
Hauser, Marcus J. B. .. AKB 50.60,
DY 46.34
Hauser, Robert ............. TT 24.28
Hausfeld, Stephan .............DF 2.5
Hausmanns, Britta MA 13.60, MA 27.3
Haust, J. ...................TT 30.40
Hautle, P. .................SYLS 3.55
Havemann, Markus ..........MA 18.4
Haverkort, M. W. TT 14.11, TT 24.45,
TT 24.46, TT 30.12
Havlin, Shlomo ..DY 36.6, DY 42.3,
DY 46.33
Hawkes, Peter ................ VA 1.1
Hawrylak, P. .......HL 36.3, HL 44.34
Hayden, S. .......TT 30.38, TT 30.38
Hayden, S. M. ................ TT 7.9
Hayn, Roland .... TT 24.36, TT 24.40
Haß, Joachim .............. DY 46.35
He, Gufeng ...............SYOH 5.78
He, Yunbin .................. HL 17.9
Heber, J. D. ................. HL 25.5
Heberle, J. ................ SYLS 3.49
Hebert, Rainer ................M 14.1
Hecht, Bert ................. CPP 9.6
Hecht, Christoph . SYLS 3.3, SYLS 3.7
Heck, Barbera .............CPP 15.29
Heck, Sandra ................M 18.29
Heckl , Wolfgang AKB 50.94, O 28.9,
O 32.1
Heckl, Wolfgang M. .. AKB 50.101,
O 14.21, O 24.3, O 24.11
Hedler, André ................DS 15.4
Heera, Viton .................DS 18.2
Heerklotz, Heiko ......... AKB 50.106
Heggen, M. ...................M 30.5
Hehl, Friedrich W. ............ TT 6.2
Heid, R. . TT 8.47, TT 9.8, TT 18.1,
TT 30.1

Heide, M. ......................O 8.1
Heidkamp, Marcus .......... MA 31.1
Heidrich-Meisner, F. .... TT 3.13,
TT 30.37
Heidrich-Meisner, Fabian ....TT 30.32
Heigl, F. ...................MA 13.56
Heigl, Franziskus .......... SYXM 1.3
Heil, Holger .............. SYOH 5.71
Heiliger, Christian ............DF 5.14
Heim, Erik .................. MA 18.4
Heimbeck, Tobias ............ HL 48.1
Heimbrodt, W. . HL 12.51, HL 12.70,
HL 25.5, HL 35.6, HL 41.3,
HL 43.1, HL 44.5, HL 44.47
Hein, G. ..........HL 12.42, HL 12.43
Hein, Günter ................HL 12.41
Hein, Matthias ...............HL 40.2
Heine, G. .........HL 44.74, HL 44.75
Heine, Thomas ............. CPP 16.3
Heinen, A. ................. DY 46.17
Heinen, Oliver ........ M 12.2, M 12.3
Heiner, Cynthia ................ O 4.6
Heinig, K.-H. ................. HL 3.6
Heinig, Karl-Heinz ........... HL 11.4
Heinrich, Alexander ........... M 15.4
Heinrich, Andreas .. TT 8.31, TT 12.1
Heinrich, B. ................. HL 29.3
Heinrich, Bret ..............MA 28.13
Heinrich, Doris .....AKB 50.119,
AKB 50.120
Heinrich, F. ................SYOH 6.2
Heinrich, Frank AKB 50.25, AKB 50.26
Heinrich, Helge .............. DS 10.2
Heinrich, Monika ..............TT 6.8
Heinrichs, S. ............... MA 13.87
Heinrichs, St. ...............DY 46.17
Heinz, Klaus .. O 3.5, O 3.8, O 6.1,
O 6.7, O 32.3, O 43.8
Heinz, O. ....................O 28.74
Heinze, Stefan ....MA 4.7, O 5.8,
TT 27.10
Heinzmann, Ulrich .........CPP 16.19
Heise, H. M. .............. CPP 15.21
Heise, H. Michael ......... AKB 50.96
Heitjans, Paul ....... DF 5.12, M 10.5
Heitmann, D. ...HL 5.3, HL 12.13,
HL 12.48, HL 12.66, HL 14.3,
HL 28.7, HL 42.2, HL 44.13,
HL 44.38, HL 44.40, MA 13.63
Heitmann, Detlef .HL 12.11, MA 13.69
Heitmann, Johannes ..........HL 18.1
Heitmann, Sonja ...MA 16.6, MA 30.7
Heitsch, S. ................. HL 17.12
Heitsch, Susanne ............HL 12.68
Heitz, Johannes ........... SYLS 3.27
Heitz, R. ................... HL 50.10
Heitz, Robert ................ HL 36.4
Helbig, M. ................SYOH 5.52
Helbing, Dirk AKSOE 2.3, AKSOE 4.4,
AKSOE 7.1
Held, K. .....................TT 24.1
Held, Karsten ................TT 32.8
Held, Rainer .................TT 18.2
Helfen, L. .................... M 32.4
Helfen, Lukas .............. SYPF 4.1
Helge, Riemann ..............HL 38.7
Helias, Moritz .............. HL 12.45
Hellmich, Wibke SYLS 3.36, SYLS 3.40
Hellmig, Ralph J. .. M 13.4, M 20.2,
M 27.3, M 27.4
Hellriegel, Christian CPP 9.3, CPP 9.4
Hellweg, Thomas CPP 14.4, CPP 15.2
Hellwig, Olav ............... MA 10.9
Helm, Christian ..............TT 29.6
Helm, M. ..................... HL 4.6
Helm, Manfred ... HL 4.4, HL 9.2,
HL 28.6
Helmes, Rolf .................TT 16.6
Helwig, H.-M. ... SYPF 5.2, SYPF 5.3
Hembacher, Stefan ............O 9.10
Hemberger, J. ............... TT 14.3
Hemmingsson, C. ........... HL 44.79
Hempel, E. ................CPP 15.24
Hempel, Th. .................HL 33.5
Hempel, Thomas . HL 12.78, HL 44.81
Henckens, Anja ........... SYOH 5.51
Hendlmeier, Christoph ....... TT 27.9
Hendrich, C. .......... O 10.2, O 19.4
Henk, Jürgen ................. O 11.9
Henkel, Carsten . DY 50.2, HL 12.22,
HL 12.27
Henkel, Karsten .............HL 44.42
Henkel, Malte ............... DY 12.5
Henneberg, Oliver .......... CPP 10.3
Henneberger, Klaus .......... HL 4.12
Hennies, Franz ........ O 45.2, O 45.5
Hennig, Th. ................ DY 46.17
Hennrich, F. .................TT 27.2
Hennrich, Frank ..............HL 48.2
Henrich, Markus ............TT 17.28
Henseler, Peter ............. DY 46.49
Hentschel, Martina ......... DY 46.42
Henzler, Martin ..... O 28.26, O 28.45
Herasimovich, A. ......... SYOH 5.73
Herb, Ch. ................ SYOH 5.67
Herb, Chr. .................SYOH 3.1
Herber, U. ...................HL 12.5
Hergert, W. ............ O 3.3, O 24.5
Hergert, Wolfram . DF 5.14, MA 13.98
Herges, Rainer ............... O 14.17
Hering, Marco ............... TT 20.8
Herlach, D. H. ..............HL 44.68
Herlach, Dieter ............... M 12.3
Herlach, Dieter M. ............M 12.2
Hermann, Andreas ........... O 28.20
Hermann, Daniel .............HL 15.3
Hermann, Joachim .......AKB 50.112
Hermann, Klaus .......O 18.5, O 31.6
Hermann, M. ............... HL 27.15
Hermann, Martin . HL 16.5, HL 16.6,
HL 16.7, HL 27.13
Hermatschweiler, M. ......... HL 15.8
Herminghaus, Stephan ...CPP 1.2,
CPP 13.7, CPP 16.13, CPP 16.14,
DY 15.2, DY 17.2, DY 26.5,
SYLS 3.50
Hermsdorf, N. ..............CPP 15.7
Hernandez Ramirez, Fernando O 14.18
Herper, Heike ............... MA 27.1
Herr, Ulrich ................ DS 22.33
Herrle, Thomas ..... HL 32.6, HL 38.1
Herrmann, Michael DY 21.1, DY 46.35
Herrnberger, Helmut DS 22.2, DS 22.3,
HL 12.89, HL 44.55, HL 44.58
Herrwerth, Sascha .........CPP 16.18
Hertel, Dirk .. SYOH 5.81, SYOH 5.90
Hertel, I. V. ........ CPP 16.31, O 4.6
Hertel, Ingolf V. ...............O 19.2
Hertel, R. .................... MA 2.4
Hertel, Riccardo ..MA 2.1, MA 28.3,
MA 28.4
Herth, P. ..................... DF 7.2
Herth, Simone ................ M 10.1
Hertkorn, Georg .......... AKSOE 2.1
Hertrich, Theo ...............TT 13.9
Herweg, Carsten ............ DS 22.39
Herz, Andreas ..............AKB 41.1
Herz, Laura M. ............ SYOH 2.3
Herzer, Giselher ............. MA 26.2
Herzinger, Craig M. .......... HL 17.1
Herzog, A. ..... AKB 50.3, SYLS 3.24
Heske, C. CPP 12.6, HL 12.5, HL 24.2,
HL 24.3, O 4.2, O 44.8
Hess, C. . TT 3.13, TT 8.45, TT 30.37
Hess, Christian ............. TT 30.20
Hess, Ortwin ...... HL 38.6, TT 29.13
Hess, Siegfried ..DY 11.2, DY 46.47,
DY 46.80, SYPF 5.4
Hesse, Anke .................. HL 7.1
Hesse, D. .....................DF 6.4
Hesse, Dietrich ....... DF 5.1, M 18.8
Hesse, J. .... MA 5.1, MA 13.74,
MA 13.79, MA 13.80
Hesse, Jürgen ..............MA 13.78
Hetterich, M. ..HL 12.10, HL 12.72,
HL 12.74, HL 12.76, HL 43.3
Hetterich, Michael .......... HL 12.75
Hettich, Christian ............CPP 9.5
Hettler, Matthias H. ......... TT 27.5
Heuchel, Matthias ........... CPP 4.3
Heuer, Andreas ...DF 3.9, DF 3.10,
DF 4.8, DF 5.9, DY 28.9, DY 28.10,
DY 29.8, TT 33.4
Heuken, M. .... HL 44.79, SYOH 5.27
Heuken, Michael ............. HL 33.4
Heumann, Martin ........... MA 26.8
Heun, Stefan ..................O 24.2
Heurich, J. ............... SYOH 5.59
Heurich, Jan .....MA 27.13, TT 17.32
Heusel, Gerhard ............. CPP 4.4
Heusler, Stefan .....DY 27.6, DY 27.7
Heussinger, Claus .......... AKB 50.5
Heuvingh, Julien ............CPP 13.5
Hey, R. ............HL 12.23, HL 20.9
Heyde, Markus O 9.7, O 9.11, O 14.79
Heyderman, L. J. ............MA 25.2
Heydhausen, D. ............ TT 24.50
Heyes, Colin D. AKB 50.12, HL 44.36,
SYLS 2.2, SYLS 3.14
Heyn, Ch. .HL 3.7, HL 5.4, HL 12.13,
HL 12.48, HL 12.66, HL 14.3,
HL 28.7, HL 42.2, HL 44.13,
HL 44.38, HL 44.40
Heyn, Christian ...HL 3.12, HL 5.9,
HL 12.11, HL 12.93, HL 25.4,
HL 37.2, MA 13.69
Heyroth, Frank ...... DF 5.14, DS 9.1
Hezel, R. .................... HL 19.2
Hezel, Rudolf ................ HL 24.4
Heßler, M. ................... MA 6.3
Heßler, Markus ... O 10.4, O 19.1,
O 28.84
Hickel, Tilmann ..............TT 15.2
Hiden Analytical ............... FB 19
Hiebl, Alois ........ TT 8.31, TT 12.2
Hiester, Thorsten ............ DY 17.6
Hietschold, H. ............... O 24.10
Hietschold, M. .. HL 10.4, HL 31.6,
O 14.23, O 14.83, O 19.7, O 38.7
Hietschold, Michael .....DS 18.5,
SYOH 5.3
High Q Laser .................. FB 20
Hihara, T. ................. MA 13.80
Hilarius, V. ................ SYNP 2.4
Hilbert, S. ................. MA 13.95
Hild, Sabine ... CPP 1.3, CPP 2.1,
CPP 15.12, CPP 15.15
Hildner, Richard ...........CPP 16.29
Hilfer, Rudolf ...DY 46.2, DY 46.3,
DY 46.62
Hilfinger, Andreas .........AKB 50.24
Hilgardt, Christiane ...... AKB 50.118
Hilgendorff, Michael ..........HL 17.2
Hilgenkamp, H. ..............TT 18.3
Hilgers, C. ................. TT 30.39
Hill, John P. .............. MA 13.118
Hillebrand, Reinald ...........HL 15.2
Hillebrands, B. ...DS 6.4, DS 13.5,
MA 16.5, O 14.81
Hillebrands, Burkard MA 9.1, MA 10.4,
MA 10.5, MA 13.47, MA 28.9
Hillenbrand, Rainer .DF 6.5, O 14.76,
O 23.4
Hiller, Martin ............... HL 44.72
Hiller, Moritz ................ DY 50.7
Hiller, S. ..................CPP 15.24
Hillerbrand, Rafaela ..........DY 20.2
Hilleringmann, Ulrich ....HL 23.2,
SYOH 5.22
Hilt, Markus ............. AKB 50.115
Himcinschi, C. SYOH 5.26, SYOH 5.27
Hime, T. .................... TT 29.5
Himmelhaus, Michael .. CPP 16.16,
CPP 16.17, CPP 16.18
Himmerlich, Marcel .............O 5.1
Hinkov, Vladimir ..............TT 2.3
Hinneberg, H.-J. DS 22.10, DS 22.11,
DS 22.47
Hinner, Marlon ............AKB 50.78
Hinrichs, K. .. CPP 8.6, CPP 15.21,
CPP 15.45, O 14.59, SYLS 3.49
Hinz, Dietrich ............... MA 11.8
Hinz, Martin .....CPP 2.1, CPP 15.15
Hinze, Gerald ........DF 4.2, DY 29.2
Hinze, Jan ..................DS 22.51
Hinze, P. ................... HL 27.11
Hippler, Rainer .............. DS 16.1
Hiraoka, Nozomu ............ HL 11.5
Hirsch, A. .................. HL 12.42
Hirsch, Dietmar . DS 22.2, HL 44.56,
O 40.12
Hirsch, Thomas ..............O 14.54
Hirscher, Michael ...........SYPF 4.1
Hirschmann, S. ........... SYOH 5.44
Hirschmann, Stephan ..... SYOH 5.72
Hirtreiter, Christian .......AKSOE 4.2
Hitzel, F. .........HL 27.10, HL 44.85
Hjörvarsson, Björgvin ........MA 20.5
Hlawacek, G. ....... DS 7.4, DS 22.45
Hlushchuk, Yuriy ........... DY 46.38
HMW .........................FB 21
Ho, Wilson .....................O 2.1
Hobbeling, Katharina DF 3.9, DY 28.9
Hoch, Sascha ...............HL 12.49
Hochmuth, H. . HL 12.71, HL 12.73,
HL 12.83, HL 12.86, TT 8.32
Hochmuth, Holger HL 12.69, HL 12.77,
HL 12.81, HL 12.84, TT 1.6
Hochstrat, Andreas .........MA 13.45
Hodeck, K. .................... O 9.3
Hodeck, Kai ................. HL 42.3
HöJos, ß ........ ........
Höche, T.DS 22.6, DS 22.7 Höche,
Thomas ..................DS 9.1
Höchst, H. .................. TT 8.46
Höchst, Hartmut ...............M 5.3
Höck, Karl-Heinz ............ TT 30.9
Höfer, U. . HL 31.1, O 14.20, O 18.4,
O 28.70, O 38.2, O 45.1
Höfft, O. ........... O 14.56, O 28.57
Höfling, Sven ............... HL 38.11
Höger, Sigrud ............ SYOH 5.85
Höhne, J. ................... TT 13.7
Höhne, Jens ........TT 13.8, TT 13.9
Höhne, R. ........MA 13.3, MA 13.93
Höhne, Roland .. MA 11.1, MA 13.106
Höink, V. ................... MA 27.6
Hoekstra, Andreas .......... SYLS 2.1
Höllinger, Rainer MA 13.100, MA 28.5,
MA 28.7
Hölscher, Hendrik ..... O 9.9, O 14.73
Hoener, M. ................. HL 44.13
Hoener, Matthias ........... HL 44.15
Hoenlein, Wolfgang .......... HL 46.1
Höppener, C. ..............SYLS 3.10
Höppener, Christiane ...... SYLS 3.16
Autorenverzeichnis
Höring, Stefan ................M 22.5
Hörselmann, I. ............SYOH 5.73
Hörselmann, Ingo .......... SYOH 4.2
Hövel, H. ..O 14.19, O 19.5, O 24.8,
O 28.52
Hövel, Heinz ..................O 22.1
Hövel, Philipp ............... DY 34.2
Hövel, S. .................... HL 12.1
Hofbauer, F. .................HL 20.5
Hofer, Christian ..............DS 15.2
Hofer, Ferdinand .............DS 10.3
Hoffman, J. E. ................TT 9.1
Hoffmann, A. ...............HL 27.14
Hoffmann, Anke ...........CPP 16.12
Hoffmann, Axel . HL 17.9, HL 36.10,
HL 36.11, HL 50.2
Hoffmann, C. ................TT 8.12
Hoffmann, Christian ........ SYSN 1.2
Hoffmann, D. ................O 14.81
Hoffmann, Dominik M. P. ..CPP 16.27
Hoffmann, Germar ........... O 14.72
Hoffmann, H. .............. MA 13.76
Hoffmann, Horst ........... MA 13.86
Hoffmann, Jens-Uwe ..........MA 3.3
Hoffmann, Jörg ...DS 22.19, DS 22.39
Hoffmann, M. ..... HL 12.97, HL 23.7
Hoffmann, M. J. .............. DF 6.2
Hoffmann, Michael .....HL 23.8,
SYOH 5.82
Hoffmann, Patrick ........... HL 40.4
Hoffmann, R. ........ O 23.9, O 23.10
Hoffmann, Stefan ............ HL 38.4
Hoffmann, Volker ........... DS 22.22
Hofmann, A. .................DS 22.6
Hofmann, C. .... SYLS 3.9, SYLS 3.13
Hofmann, D. M. ............ HL 17.11
Hofmann, Dieter .............CPP 4.3
Hofmann, F. ..............AKB 50.75
Hofmann, K. R. .. HL 44.25, HL 44.73
Hofmann, Karl ...............O 14.42
Hofmann, M. ................ HL 12.1
Hofmann, Martin ............ HL 38.4
Hofmann, Philip ........O 1.1, O 44.3
Hofmann, Richard ......... CPP 15.40
Hofmann, T. .................HL 28.5
Hofmann, Tino . HL 12.50, HL 12.90,
HL 44.57
Hofmeister, C. ............. MA 13.74
Hofmeister, Herbert .HL 11.3, HL 18.1
Hofstetter, Walter ............ TT 4.4
Hohage, M. ...................O 25.5
Hohage, Michael .............. O 42.1
Hohenadler, M. .............TT 32.10
Hohenadler, Martin .......... TT 24.4
Hohenstein, Sebastian ........O 24.11
Hohlbein, Johannes ........SYLS 3.23
Hohls, F. HL 12.56, HL 12.60, HL 22.1,
HL 37.12, HL 44.28, HL 47.3
Hohls, Frank .. HL 12.41, HL 22.10,
SYSN 2.3
Hohlwein, D. .......DF 7.6, MA 13.46
Hoinkis, Markus ............. TT 30.8
Holland, S. ................. HL 12.48
Holland-Moritz, Dirk . M 1.1, M 8.2,
M 12.2, M 12.3
Hollensteiner, S. ... DS 14.3, DS 22.36
Hollerith, Christian . TT 13.7, TT 13.9
Hollmann, Eugen ............. TT 1.2
Hollmann, Frank .............CPP 1.3
Holm, Christian ... DY 23.2, DY 46.53
Holub-Krappe, E. .......... MA 13.88
Holy, Vaclav .................. HL 7.1
Holyst, Janusz ............AKSOE 4.4
Holz, M. ................... HL 44.13
Holz, Matthias ..............HL 44.15
Holz, T. ...................... DS 9.8
Holzapfel, B. .. DS 18.1, MA 13.18,
MA 15.8, TT 8.4, TT 8.11,
TT 8.13, TT 8.14
Holzapfel, Bernhard ....MA 13.17,
MA 15.10, TT 31.10
Holzner, Oliver .............. DY 21.2
Hommel, D. ................. HL 36.8
Hommel, Detlef ..HL 3.11, HL 16.8,
HL 16.9, HL 21.2, HL 21.4,
HL 44.88
Honecker, A. ...MA 21.2, MA 21.3,
TT 3.5
Honecker, Andreas TT 24.8, TT 30.32
Honerkamp, Carsten .......... TT 4.4
Hong, I.-H. ................... O 33.3
Hong, Ke .................. CPP 13.4
Honolka, J. .................. MA 3.1
Hoppe, S. ......................O 9.6
Horbach, Jürgen ...DF 3.5, DF 3.6,
DY 28.5, DY 28.6, M 6.1
Horn, A. .....................DF 5.10
Horn, K. ......................O 17.8
Horn, Karsten . O 11.4, O 11.6, O 18.7
Horn, S. .................. MA 13.101
Horn, Siegfried ................TT 6.8
Horn, Sigfried .................O 44.3

Horn-von Hoegen, M. O 13.2, O 14.40,
O 28.74
Horn-von Hoegen, Michael .. O 5.4,
O 5.4, O 14.34
Hornung, Frank .......TT 8.5, TT 8.6
Horowitz, Gilles ...........SYOH 5.68
Horsch, Peter ...............TT 24.44
Hortaman, Mahbube .......... O 40.6
Hortenbach, H. ............. DS 22.11
Horvat, A. ................ CPP 15.34
Hoser, Andreas ..............MA 20.5
Hositrad Deutschland .......... FB 22
Hossain, Z. ................... TT 7.7
Hoster, H. E. ................. O 46.5
Hoster, Harry .................. O 6.6
Hott, Roland ................ TT 8.38
Houben, L. ................ MA 13.96
Howard, Jonathon .........AKB 50.24
Howell, Philip ................TT 8.41
Hoyer, Walter ................HL 28.4
Hsieh, H. H. .. TT 24.45, TT 24.46,
TT 32.6
Hu, C.-M. HL 5.3, HL 12.13, HL 12.48
Hu, Can-Ming .............. HL 12.11
Hu, Wenping ............. SYOH 5.60
Hu, Z. TT 14.11, TT 24.45, TT 24.46,
TT 30.12, TT 32.6
Huang, Y.-L. .................. M 4.1
Huang, Yue-Lin .............HL 44.63
Huang, Zhong-Le ......... MA 13.112
Huang, Zhongbing ........... TT 26.7
Hub, Jochen .................TT 26.2
Hubenthal, F. . O 10.2, O 19.4, O 19.8
Huber, B. ................... DS 12.6
Huber, K. ......... HL 6.3, SYLS 3.15
Huber, M. ...................TT 13.7
Huber, Michael .... MA 26.7, TT 13.2
Huberman, Bernardo ......AKSOE 6.1
Hudert, F. ................... HL 30.5
Hudson, E. W. ................TT 9.1
Hübener, Gerd ............ AKB 50.78
Hübener, Kati ............... DS 20.2
Hübers, Heinz-Wilhelm .. DS 22.25,
HL 38.7, TT 1.2, TT 13.3
Huebl, Hans ........ HL 25.2, HL 35.5
Hübner, D. .....................O 4.2
Hübner, Dominique ............O 33.4
Hübner, M. C. ............... HL 42.1
Hübner, Silke ................. DS 4.4
Hübner, Uwe .. HL 12.29, HL 12.32,
TT 29.4
Hübner, Wolfgang ..MA 4.4, O 34.2,
O 34.3, O 37.5, O 44.2, O 44.7
Hübsch, Arnd ....... TT 7.2, TT 20.1
Hücker, M. ........TT 3.13, TT 30.37
Hücker, Markus ..... TT 2.2, TT 20.2
Hüfner, S. .................... O 11.8
Hüfner, Stefan ............... O 11.10
Hueging, N. ...................DS 1.1
Hühne, R. ..........DS 18.1, TT 8.14
Hüller, Alfred ...............DY 46.86
Hülsen, Christian .............HL 40.3
Hülser, T. ........MA 6.10, MA 13.77
Hümann, S. ..................O 14.32
Hünsche, Ingwar .............. M 27.2
Hütt, Marc-Thorsten ..... AKB 50.118
Hüttel, Andreas K. ..HL 5.7, HL 37.13
Hütten, A. .................MA 13.83
Hütten, Andreas .. MA 6.8, MA 6.9,
MA 12.1, MA 13.6, MA 13.78,
MA 16.6, MA 30.7
Hug, H. J. ...................O 23.10
Hugenschmidt, Christoph ..M 18.10,
O 28.32
Huijben, M. ................ TT 30.12
Huisken, Friedrich ............DS 14.7
Hulliger, F. ............... MA 13.103
Hund, Markus ............... CPP 2.4
Hunger, Ralf ... DS 22.48, O 40.3,
O 40.11, SYOH 5.33
Hunklinger, S. . DY 46.91, TT 30.41,
TT 33.3
Hunklinger, Siegfried ....DF 4.11,
DY 29.11, TT 33.1, TT 33.2
Hupe, O. .................. MA 13.74
Hupfeld, D. ................ TT 24.54
Hussain, Z. ................... O 44.8
Huth, Heiko ... CPP 15.20, CPP 16.26
huth, michael ....... MA 2.5, TT 8.29
Hutt, Axel ...................DY 22.3
Hutter, Carsten ..............TT 29.9
Hutter, Jürg . CPP 5.5, O 18.3, O 46.6
Hutzler, Michael .......... AKB 50.85
Hutzler, Stefan ............. SYPF 1.1
Huynh, Wendy .. SYLS 5.4, SYOH 5.7
Hwa, Terence ...AKB 40.3, SYLS 3.35
Hwu, Y. .................. MA 13.114
Hébert, Frederic ............ TT 24.11
I. V., Gornyi ................. HL 14.5
Iannaccone, Giuseppe ........ HL 49.2
Iannotta, Salvatore ...........O 14.62
Ibach, H. .... MA 4.6, MA 13.16,
MA 13.122
Ibach, Harald .................. O 3.7
IBM Research Division, Zurich Research
Laboratory, Switzerland -
Kollaboration ........... CPP 2.1
IDB Budzylek ..................FB 23
Idzerda, Y. U. ............... TT 14.5
Iglói, Ferenc ................. DY 12.1
Igor, Sokolov ................ DY 40.5
Ihrig, Dieter .............. AKSOE 7.3
Ihrig, Dieter F. ............AKB 50.96
Ihringer, J. .........DF 7.6, MA 13.46
Il’ichev, Evgeni .............. TT 29.4
Il’in, Konstantin ..... TT 1.2, TT 13.3
Ilegems, Mark ................HL 16.9
Ilg, Patrick ........DY 11.2, DY 46.80
Iliew, Rumen ........HL 6.2, HL 15.11
Im, Chan .....SYOH 5.85, SYOH 5.90
Imada, S. .................... MA 4.2
Imbihl, Ronald ........ O 20.2, O 31.5
Imlau, M. .....DF 2.4, DF 7.2, DF 7.3
Imlau, Mirco CPP 10.6, DF 2.5, DF 5.5
Immaraporn, Boonchuan .......O 39.4
Imre, Bako ....................O 18.3
Imre, Árpád W. ......DF 4.9, DY 29.9
Imre, Á.W. .......... DF 4.6, DY 29.6
Indris, Sylvio .................DF 5.12
Inganäs, O. .................. HL 23.6
Ingo, Rehberg .............. DY 46.82
Ingold, Gerd-Ludwig ......... TT 17.1
Iniotakis, Christian ...........TT 8.36
Ioffe, L. B. .................. TT 29.6
Ioffe, Lev ....................TT 25.4
IOPP ......................... FB 24
Irawan, T. ............ O 19.5, O 24.8
Ireta, J. ................... SYLS 3.20
Ireta, Joel .. SYLS 3.18, SYLS 3.22,
SYLS 3.29
Irmer, Gert ................. HL 44.54
Isfort, Gereon SYLS 3.56, SYLS 3.57,
SYLS 3.58
Ishibashi, Koji .............. HL 44.32
Ishida, Hiroshi ...............MA 27.2
Ismer, Lars ................ SYLS 3.22
Isobe, M. ...................TT 30.29
ISOLDE-Kollaboration, die .... DF 1.4
Isralewitz, B. ............... SYLS 5.3
Issac, Abey ... HL 50.7, SYOH 5.8,
SYOH 5.10
Istomin, K. .................TT 24.54
Ito, Nobuyasu ............... DY 10.6
Ivanco, Jan ................SYOH 7.1
Ivanov, I. ...................HL 44.79
Ivanova, Lena .................HL 3.9
Ivanovska, Irena L. ......... AKB 10.1
Ivchenko, E. L. ............. HL 44.46
Iwicki, J. ......................O 28.3
Iyer, Kartik K. ................ M 22.2
J., Kirschner .........MA 4.1, MA 4.3
Jacob, David ............... HL 44.30
Jacob, T. .................. MA 13.50
Jacobi, Karl .HL 3.5, O 20.1, O 20.3,
O 25.4, O 38.9
Jacobs, Karin AKB 50.50, CPP 15.22,
CPP 15.27, CPP 15.37, CPP 15.38,
SYLS 3.25
Jacobs, R. ................SYOH 5.18
Jaeckel, Bengt ........ O 5.6, O 14.36
Jaeger, A. ................... HL 10.1
Jäger, D. ...................DY 46.17
Jäger, Ingomar ............AKB 50.71
Jäger, Nikos .................. O 40.5
Jäger, W. ......... DS 14.3, DS 22.36
Jaegermann, Wolfram DS 22.50, O 5.6,
O 14.36, O 40.11, O 44.6,
SYOH 5.33, SYOH 5.48
Jähne, Konstanze ............TT 17.4
Jaekel, Uwe ................SYFT 2.4
Jaensch, Stefan .............HL 12.61
Jagemann, Thomas .......... TT 13.6
Jahn, Sandro .......... DF 2.3, M 2.1
Jahnke, Agnes ............ SYOH 5.75
Jahnke, F. ................... HL 36.7
Jahnke, Frank
HL 36.6
...HL 28.3, HL 36.5,
Jaiser, Frank SYOH 5.72, SYOH 5.80,
SYOH 5.81
Jakob, G. ....................O 28.83
Jakob, Gerhard
TT 8.2
.MA 20.6, MA 20.10,
Jakob, Peter ....... AKB 31.1, O 18.6
Jakobs, Severin .............. TT 11.7
Jakopic, G. .................. HL 23.6
Jam itzky, Ferdinand .......... O 28.9
Jamitzky, Ferdinand
O 28.9
DY 20.6, O 14.21,
Jamois, Cecile ............... HL 15.2
Jamois, Cécile ............... HL 15.4
Jancu, Jean-Marc ............ HL 41.4
Janeček, Miloˇs ........M 15.3, M 27.4
Janisch, Rebecca ...........MA 13.94
Janke, W. ................... DY 10.2
Janke, Wolfhard . CPP 5.3, CPP 5.4,
DY 16.1, DY 16.2, DY 16.3,
DY 46.58, DY 46.89, DY 46.90,
DY 46.92, DY 46.93, DY 46.95,
SYLS 3.48
Janke-Gilman, N. ............MA 16.4
Janke-Gilman, Nathaniel ...MA 13.119
Janowitz, C. TT 8.43, TT 8.46, TT 9.4
Janowitz, Christoph .HL 24.1, TT 18.5
Jansen, Lars ................. O 14.73
Janson, Natalia ..............DY 42.2
Jantoß, Wolfgang ............DY 15.6
Janzen, A. .................... O 13.2
Jarosz, G .................SYOH 5.16
Jarosz, Grazyna ...........SYOH 5.53
Jarzina, Harald ..MA 13.29, TT 1.5,
TT 8.9, TT 8.10
Jayakar, A. ................. HL 12.51
JCM Müller ................... FB 25
Jean-Louis, Richard .........TT 24.40
Jeckelmann, Eric .. TT 24.7, TT 24.18
Jede, Ralf .....................VA 1.1
Jeevan, H. ....................TT 7.7
Jeevan, H. S. .......TT 7.8, TT 24.33
Jeffrey, Ken R. .......DF 4.1, DY 29.1
Jelezko, Fedor ..... AKB 50.116,
SYLS 3.52, TT 17.22, TT 17.26,
TT 22.1, TT 22.2
Jeliazova, Yanka ............. DS 12.3
Jenichen, Bernd ...............O 25.8
Jenkner, M. ...............AKB 50.75
Jensen, Henning .............. O 17.6
Jensen, Peter J. ............MA 13.75
Jerman, Martin ............... DS 6.5
Jerome, D. ..................MA 21.3
Jester, Stefan-Sven ......... DY 46.72
Jeutter, Nicole ................ O 40.9
Jia, C. ........................DF 6.7
Jiang, Xiuli ............... CPP 15.32
Jisrawi, N. M. ................. M 3.1
Jitschin, Wolfgang ............ VA 2.2
Jo, Jung-Ho .............. SYOH 5.85
Jochum, J. .................. TT 13.7
Jochum, Josef .. TT 13.2, TT 13.6,
TT 13.9
Jodlauk, S. .................TT 30.14
Jörger, M. ..................HL 12.17
Johannsen, N. ..............TT 30.31
Johannsmann, Diethelm . CPP 15.25,
CPP 15.42, CPP 16.22
Johansson, Göran . TT 11.1, TT 29.10
Johansson, Lars ............... O 33.2
Johansson, P. ................. O 17.1
John, Karin .. AKB 50.88, CPP 6.3,
DY 46.51
John, S. ...................... HL 1.1
Johnas, Christine M. S. .......HL 44.4
Johnas, Simone ............SYLS 3.16
Johnev, Boyan ............SYOH 5.41
Johnson, Neil .............AKSOE 1.1
Johnson, R. L. .....O 28.33, TT 24.54
Johnson, Robert L. ... AKB 50.38,
HL 3.12
Johs, B. .................... HL 12.83
Jonas, A. ................ AKB 50.132
Jonas, Karl-Ludwig ...........O 28.68
Jongen, L. .......... TT 3.11, TT 6.7
Jonsson, Frederik ........... HL 15.10
Jooss, Ch. .................... TT 8.8
Jooss, Christian . MA 13.29, TT 1.5,
TT 8.9, TT 8.10
Jordan, Rainer .....AKB 50.129,
AKB 50.130, CPP 16.30
Jose Maria, Sancho .......... DY 40.5
Joseph, Toby ............... DY 46.62
Joshi, Sanjeev .............. CPP 12.6
Jourdan, M. ..........TT 1.3, TT 7.5
Jousten, Karl ................. VA 2.4
Jouve, H. ................. SYLS 3.55
Jülicher, Frank AKB 12.2, AKB 50.24,
AKB 50.29, AKB 50.49,
AKB 50.64, AKB 50.65, DY 12.4
Juhász, Róbert .............. DY 46.5
Julien, Sylviane ............SYLS 3.26
Jung, A. ..................MA 13.117
Jung, Achim ............... DY 46.63
Jung, Christophe ............ CPP 9.4
Jung, K. .............DS 6.4, DS 13.5
Jung, Thomas ............... O 14.22
Jung, Thomas Andreas ....... O 14.25
Jung, Ulrich ................. O 14.27
Jungblut, Helmut .... DS 20.5, O 40.3
Jungnickel, Bernd-J ....... CPP 15.33
Junk, D. ... MA 13.48, MA 13.49,
MA 27.6
Jursic, I. .......... MA 13.7, MA 13.8
Just, Wolfram .. DY 34.2, DY 36.4,
DY 46.1, DY 46.22, DY 46.23,
DY 46.23
Jutzi, Peter .... MA 6.8, MA 6.9,
MA 13.78
Jérome, D. ..................MA 21.2
Autorenverzeichnis
K. Hartmann, Alexander ..... DY 26.2
Kabiraj, D. ................... DS 1.7
Kaczmarek, Dirk .............. VA 1.3
Kador, Lothar . CPP 15.46, CPP 16.33
Kähler, Goetz .............. DY 46.93
Kämmerer, Sven ............ MA 13.6
Kärtner, F. X. .................HL 4.1
Käs, Josef .. AKB 12.1, AKB 50.16,
AKB 50.35, AKB 50.56,
AKB 50.125, AKB 50.126
Käsberger, Ulrich ..............O 18.6
Kästle, G. ....................MA 6.3
Kästle, Gerd .......... DS 15.5, O 3.2
Kaestner, Andre ............ TT 13.10
Kästner, Christopher N. ....SYLS 3.43
Kaganer, Vladimir M. ......... O 25.8
Kahle, M. .................. DS 22.21
Kahn, Antoine ............SYOH 5.30
Kahn, R. ..................SYLS 3.55
Kahnert, U. .........O 14.56, O 28.57
Kaidashev, E. M. .HL 12.71, HL 17.5,
HL 17.5, HL 17.12
Kaidashev, Evgeni . HL 17.3, HL 44.51
Kaidashev, Evgeni M. ... HL 12.68,
HL 17.1
Kailuweit, P. .................HL 42.1
Kailuweit, Peter ..............HL 37.9
Kaim, Georg .... SYLS 3.44, SYLS 5.2
Kaindl, G. MA 4.9, MA 4.10, MA 13.9,
MA 13.56, MA 13.85, MA 17.2,
MA 31.2, TT 14.11, TT 30.12
Kaindl, Günter ... MA 5.2, O 17.5,
O 28.7, SYXM 1.3
Kaiser, A. .................CPP 16.36
Kaiser, B. ...O 10.6, O 14.45, O 14.49
Kaiser, Joachim ..............HL 38.6
Kaiser, U. .......... HL 30.5, O 14.65
Kaiser, Uwe ...............MA 13.123
Kaiser, W. ...................HL 39.1
Kaiser, Wolfgang .............HL 38.8
Kalafat, Melih ................ DS 1.3
Kalb, Johannes ............. DS 22.30
Kalb, Wolfgang ...........SYOH 5.68
Kalinikos, Boris A. ............MA 9.1
Kalinowski, Eva ... TT 24.18, TT 32.9
Kalkbrenner, Thomas ....... SYLS 2.3
Kalläne, M. .. O 28.3, O 28.4, O 28.33
Kallassy, Ziad ................O 28.45
Kallenbach, Senta ...........HL 38.10
Kalt, H. ........... HL 12.19, HL 17.4
Kalt, Heinz ...HL 12.75, HL 12.79,
HL 12.80, HL 44.16
Kaltofen, Rainer DS 22.31, DS 22.40,
DS 22.41, MA 13.10
Kaltofen, Reiner ............ DS 22.22
Kaluza, N. ................. MA 13.96
Kaluza, Nicoleta ............. HL 27.3
Kam, A. P. ............... SYOH 5.47
Kamaev, Oleg ................ TT 2.4
Kamarou, Andrey ............. DS 1.5
Kamenz, A. ...................O 28.3
Kaminsky, William ..........TT 17.18
Kamm, Frank-Michael ....... TT 31.7
Kamp, Martin ..... DS 22.44, HL 15.5
Kampen, T. ..SYOH 5.28, SYOH 5.38
Kampen, T. U. ..... SYOH 5.19,
SYOH 5.26, SYOH 5.35,
SYOH 5.54
Kampen, Thorsten ....SYOH 5.3,
SYOH 5.36
Kampen, Thorsten U. .. SYOH 2.1,
SYOH 5.34, SYOH 5.37
Kampf, Arno ............... TT 26.12
Kampf, Arno P. ..............TT 8.37
Kampfrath, T. ....MA 13.65, MA 14.2
Kampfrath, Tobias .......... HL 44.66
Kampmann, J. ..............HL 12.70
Kamps, Oliver ............... DY 17.3
Kampschulte, Lorenz .. O 24.3, O 32.1
Kandpal, H. C. .MA 8.5, MA 13.111,
MA 13.114
Kandulski, Witold .............DS 9.5
Kang, Hyungdon ............ MA 15.3
Kang, Ji-Hoon ............SYOH 5.85
Kanis, Michael ....... DS 20.5, O 40.3
Kankate, Laxman ............CPP 1.4
Kantelhardt, Jan W. .... DY 26.1,
DY 36.6, DY 42.3, DY 46.33
Kanter, Ido ..................DY 22.2
Kantlehner, Martin ........AKB 50.37
Kanzow, J. ......... DS 22.29, O 24.1
Kanzow, Jörn .. CPP 4.3, CPP 7.2,
CPP 7.3, CPP 16.8, SYOH 5.22
Kappa, Mathias .....DS 17.1, DS 22.9
Kappertz, Oliver ............. DS 12.4
Kappes, M. M. ... SYOH 6.2, TT 27.2
Kaptay, György .............SYPF 4.3
Kar, Swastik ............... TT 30.15
Karacuban, Hatice ........... O 14.63
Karatchentsev, Alexei ......CPP 15.28
Karbach, Michael .......... MA 13.57
Kardelky, Stefan ............MA 11.11

Karg, Dieter ................. HL 30.6
Karg, F. ...HL 12.5, HL 24.2, HL 24.3
Karg, Siegfried .............SYOH 7.2
Kargl, Florian ..... DF 4.10, DY 29.10
Kargl, Verena .............. MA 13.66
Karim, A. ................... CPP 6.1
Karl, H. ...................... DS 9.6
Karniychuk, Maksim ........ DS 22.32
Karsten, L. ................. HL 44.38
Kartsovnik, Mark ........... TT 30.21
Kasano, M. .................HL 15.13
Kasic, A. .........HL 44.79, HL 44.80
Kaso, A. ......................HL 1.1
Kaspari, Ch. ................. HL 43.4
Kasper, Erich ................ DS 15.2
Kasper, Gernot ....DF 4.11, DY 29.11
Kasper, N. ............... SYOH 5.29
Kasper, N. V. ................O 28.83
Kassner, K. ................ DY 46.29
Kassner, Klaus ..... DY 46.67, M 18.6
Kataev, V. .................. TT 3.11
Katanin, Andrey ............TT 26.12
Katayama-Yoshida, H. ....... MA 31.3
Katja, Lindenberg ............DY 40.5
Katsaros, Georgios ........... HL 51.1
Katsnelson, Michael .......... MA 8.3
Katsnelson, Mikhail I. .........MA 8.2
Katsov, Kirill ............. AKB 50.18
Katzenberg, Frank .........SYLS 3.56
Kaufel, Gudrun ............. HL 38.10
Kaufman, Viktor ........... AKB 50.2
Kaufmann, Stefan ........AKB 50.117
Kaul, A. .................. AKB 50.75
Kaul, Alexander ...........AKB 50.72
Kaul, E. E. ................... TT 6.9
Kaupuˇzs, Jevgenijs ...AKSOE 3.13,
DY 14.5
Kautz, Holger .............CPP 15.18
Kawai, Takahiko ...........CPP 15.19
Kawamura, Midori ............ O 32.7
Kayser, Michael ..............DS 12.3
Kazantseva, Natalia ......... MA 17.4
Kecke, Lars ...................TT 4.6
Keding, Ralf .................. DS 9.1
Kegler, Ch. ..................TT 6.11
Kehrein, Stefan .............TT 24.14
Keil, Frerich .................. O 43.2
Keilhauer, Ilka ...............MA 21.6
Keilmann, Fritz .....CPP 2.5, O 14.76
Keimer, B. .... TT 8.45, TT 14.2,
TT 14.13, TT 24.47, TT 24.48
Keimer, Bernhard MA 13.118, TT 2.3,
TT 8.17, TT 9.7
Keivanidis, Panagiotis ...... SYOH 2.4
Keivanidis, Panagiotis E. .. SYOH 5.85
Kelemen, Marc ............. HL 38.12
Kelemen, Marc Tibor ....... HL 38.10
Keller, D. ...........HL 21.1, HL 29.7
Keller, G. ....................TT 24.1
Keller, J. ....................MA 31.4
Keller, Joachim ....HL 12.91, TT 18.8
Keller, S .................... DY 40.4
Kelsch, M. ....... M 32.1, SYOH 5.29
Kelting, Christian ....SYOH 5.11,
SYOH 5.33
Kemp, A. ... TT 17.23, TT 17.25,
TT 25.2
Kempa, Heiko ...... HL 22.3, TT 20.3
Kempa, Krzysztof ......... SYLS 3.19
Kempe, Julia ................ TT 29.8
Kempter, V. O 14.56, O 14.67, O 28.57
Kennerknecht, C. ..O 14.57, O 37.2,
O 45.6, TT 17.14
Kentsch, Carsten A. G. .......HL 22.9
Kera, Satoshi ................. O 33.5
Kerherve, Gwilherm ........... O 45.3
Kern, Dieter P. .... HL 12.67, HL 22.9
Kern, K. ..................... MA 3.1
Kern, Klaus .. CPP 16.27, HL 51.1,
O 5.2, O 11.5, O 15.1, O 23.8,
O 26.2, O 28.30, O 28.38, O 32.8
Kerschl, Peter ..............MA 11.10
Kersten, Holger ....DS 22.4, DS 22.16
Kessler, Horst .AKB 50.14, AKB 50.37
Kessler, M. ................ MA 13.87
Kesting, Arne ............ AKSOE 2.3
Ketelaars, Martijn ......... SYLS 3.21
Kettemann, Stefan HL 12.40, HL 12.44
Ketterle, Wolfgang .............. PV I
Keune, W. ........DS 17.5, MA 13.44
Keune, Werner . MA 13.11, MA 30.3,
MA 30.4
Keyser, U. F. ...... HL 37.1, HL 44.27
Keyser, Ulrich F. .......... AKB 50.99
Khaliullin, Giniyat TT 14.10, TT 24.44
Khan, Amena L. T. ........ SYOH 2.3
Khattari, Ziad .............AKB 50.87
Khazarchyan, Margarita ..AKB 23.1,
AKB 50.97
Khim, Z. G. .............. MA 13.123
Khitrova, Galina ............. HL 28.4
Khlopkov, Kirill ...MA 11.8, MA 11.10
Khomskii, Daniel .. TT 14.7, TT 24.55
Khonik, V. A. ..................M 7.3
Khristov, Khr. ..............SYPF 2.4
Khristov, Khristo ........... SYPF 2.3
Kidun, Oleg ................. O 28.69
Kiebele, Andreas ............. O 14.22
Kiefer, J. C. .................. HL 4.8
Kiefer, Klaus ................ TT 6.13
Kielbassa, Stefan ..............O 24.9
Kiele, Sven .................. TT 20.6
Kiendl, Fabian ................MA 7.2
Kierfeld, Jan ..AKB 50.32, DY 24.2,
TT 31.9
Kierren, B. ....................O 11.8
Kierspel, H. ....... TT 20.7, TT 30.14
Kiesel, P. .................... HL 43.5
Kieseling, Frank ..............HL 4.12
Kiesslich, G. .................. HL 5.2
Kietzke, Thomas ..........SYOH 5.46
Kießlich, G. ....... HL 37.5, SYSN 2.4
Kijewski, Harald ............. DS 13.2
Kikoin, Konstantin ..........HL 37.10
Kikugawa, N. ................TT 8.42
Kilassonia, Sasa ...............M 26.4
Killinger, Andreas ......... MA 13.100
Kim, D. W. ...............MA 13.123
Kim, Gyuman .............AKB 50.81
Kim, Hyoung Seop ....M 20.2, M 27.3
Kim, JeongWon O 11.4, O 11.6, O 18.7
Kim, T. H. .......MA 13.65, MA 14.2
Kim, T.-Y. ............HL 3.10, O 9.3
Kim, Tai-Yang ....... HL 3.9, HL 25.3
Kim, Y.-H. ................. DY 46.39
Kim, Young Dok ............. O 28.63
Kimura, S. ................. CPP 10.7
Kinder, H. ...................TT 8.12
Kinder, Helmut .....TT 8.31, TT 12.2
Kindrachuk, Vitaliy ........... M 22.6
Kini, A. M. .................TT 30.25
Kini, N. S. ....................TT 6.9
Kinne, M. .....................O 43.3
Kinne, Markus ................ O 24.9
Kinosita, Kazuhiko ..........SYLS 5.1
Kinzel, Wolfgang ... DY 22.2, DY 34.8
Kipferl, W. .......MA 13.61, MA 15.4
Kipp, L. ...O 11.3, O 28.1, O 28.3,
O 28.4, O 28.33
Kipp, T. .....................HL 28.7
Kira, Mackillo ...... HL 28.4, HL 32.3
Kiraz, Alper ................. CPP 9.2
Kircan, Marijana .............TT 16.2
Kirchheim, R. ..........HL 9.5, M 3.1
Kirchheim, Reiner CPP 15.17, M 15.4,
M 17.1, M 18.3, M 18.18, M 18.25,
M 24.2, M 24.3
Kirchmann, Patrick ............O 45.2
Kirchner, Alexander ............ O 4.7
Kirchner, Anke .............. MA 11.9
Kirchner, Ch. ................ HL 17.4
Kirchner, Christoph ......... HL 12.79
Kirchner, Nadeschda .........MA 21.8
Kirsch, Stefan ........... AKB 50.108
Kirschgen, Thomas M. .......CPP 3.1
Kirschner, J. ....MA 4.2, MA 4.6,
MA 13.13, MA 13.14, MA 13.16,
MA 13.53, MA 13.122, MA 15.5,
MA 16.3, MA 16.4, MA 16.7,
MA 20.7, MA 28.10, O 3.3, O 12.2,
O 14.43, O 39.9
Kirschner, Jürgen MA 2.1, MA 13.119,
MA 28.3, MA 28.4, O 45.3
Kirst, Christoph ............. DY 24.4
Kirste, L. .................... HL 27.7
Kirstein, Johanna ............CPP 9.3
Kiselev, Mikhail .............HL 37.10
Kishimoto, N. ............ SYOH 5.18
Kisker, E. ....MA 10.1, MA 13.43,
MA 13.121, MA 18.1, MA 18.2,
O 14.68
Kissel, H. .....................HL 3.3
Kisselev, Roman .......... SYOH 5.45
Kittel, A. ......... DY 36.5, DY 46.64
Kittel, Achim ...............DY 46.74
Kittler, G. ................... HL 16.2
Kittler, Gabriel ................HL 9.1
Kittur, H. ..................MA 13.35
Kläser, Marion ........TT 8.5, TT 8.6
Kläui, Mathias .............. MA 25.2
Klages, Svenja ..............TT 30.24
Klais, M. ..................... DF 1.2
Klapp, Sabine H. L. ....CPP 15.1,
DY 15.7, DY 46.54
Klar, O. ........... HL 4.10, HL 12.21
Klar, P. J. ... HL 12.51, HL 12.70,
HL 25.5, HL 35.6, HL 41.3,
HL 43.1, HL 44.5, HL 44.47
Klar, T. A. CPP 16.34, O 19.6, O 28.67
Klar, Thomas A. HL 44.33, SYOH 4.3,
SYOH 5.84
Klaua, M. .....................O 12.2
Klaumünzer, S. .............. M 18.19
Klaumünzer, Siegfried DS 1.2, DS 1.3,
DS 3.5, DS 15.4
Klauser, R. ............... MA 13.114
Klauser, Ruth .................O 33.3
Klaushofer, K. ............ AKB 50.86
Klaushofer, Klaus .... AKB 50.53,
AKB 50.57
Klauss, H.-H. .. MA 21.2, MA 21.3,
MA 21.5
Klavsyuk, A. L. .........O 3.3, O 24.5
Kleemann, W. ....DF 7.3, DF 7.4,
MA 13.83, MA 13.84
Kleemann, Wolfgang ....... MA 13.45
Klehe, A.-K. ................TT 30.25
Kleibert, A. ................ MA 13.88
Kleibert, Armin ..... O 28.68, O 28.82
Klein, Andreas .. DS 19.2, DS 21.2,
DS 22.48, DS 22.50, O 3.5, O 3.8,
O 5.6, O 14.36, O 32.3
Klein, Gernot ............. AKB 50.29
Klein, Juliane ...............DS 22.49
Klein, Norbert ....... DF 5.4, TT 8.23
Klein, T. ...................MA 13.44
Kleine, Hermann ...........SYLS 3.33
Kleinekathöfer, U. .....CPP 16.1,
DY 46.45, SYLS 5.3
Kleinekathöfer, Ulrich .......DY 46.44
Kleiner, Andreas . CPP 2.1, CPP 15.15
Kleiner, R. ......... TT 18.3, TT 18.7
Kleiner, Reinhold .MA 22.1, TT 8.54,
TT 18.6, TT 25.5, TT 31.2
Kleinert, Hagen ... DY 10.3, SYFT 1.3
Kleinhempel, Ronny .........DS 22.42
Klement, Kai ................ M 18.16
Klemm, Konstantin ...... AKB 50.109
Klemm, M. ............... MA 13.101
Klemm, Matthias .... O 44.3, TT 30.8
Klemradt, U. ........ DF 5.10, DF 6.3
Klenk, Reiner ................ DS 19.4
Klewer, G. ..................HL 44.85
Kley, Ernst-Bernard . HL 2.3, HL 15.11
Klieber, Robert .............. HL 28.2
Kliefoth, Klaus ......DS 13.4, DS 20.3
Kliem, Toralf ..................VA 1.1
Klier, Jürgen ... O 14.10, TT 8.53,
TT 30.33
Klimmer, A. ................. O 28.42
Klingeler, R. ................ MA 21.5
Klingeler, Rudiger .......... TT 30.20
Klingeler, Rüdiger .TT 14.6, TT 20.2,
TT 20.6
Klingelhoeffer, Hellmuth .......M 15.1
Klinger, G. ....... HL 44.74, HL 44.75
Klingner, Anke ...............DY 17.2
Klingshirn, C. ..HL 12.17, HL 12.74,
HL 12.76, HL 17.4
Klingshirn, Claus ..HL 12.79, HL 12.80
Klitzing, Klaus v. ............ HL 37.6
Klöcker, Iris ................ HL 44.43
Klöden, Burghardt ............ M 22.4
Kloos, Harald ................TT 19.6
Klose, Frank ..................M 30.4
Klostermeier, Dagmar .. SYLS 3.11,
SYLS 3.12
Klotsa, Daphne ........... AKB 50.52
Klude, Matthias .....HL 21.2, HL 21.4
Klümper, A. .................MA 21.2
Klümper, Andreas . TT 3.6, TT 16.4,
TT 24.15
Klug, Dennis D. ..............HL 11.5
Klumpp, Stefan ..AKB 50.44, DY 14.7
Klushin, Alexander ...........TT 8.23
Kluth, Patrick ............... HL 10.3
Kluth, Susan .................HL 10.3
Kmiec, Daniel ..........DS 6.2, O 6.4
Knabl, Wolfram ...............M 27.2
Knauer , A. ...................HL 3.3
Knecht, Carsten L. ..........TT 24.12
Kneppe, Martin ............ MA 13.12
Knetter, Christian ............TT 15.7
Knieling, Holger ............ DY 46.78
Knipp, Dietmar ............ SYOH 3.3
Knipper, Martin .......... SYOH 5.51
Knipper, U. .................DS 22.54
Knipping, J. ............... MA 13.77
Knneth L., Stevensson .....MA 13.109
Knobbe, J. ....................HL 5.3
Knoglinger, Heribert .... TT 17.5,
TT 17.20, TT 17.21
Knop, Michael ...... HL 3.1, HL 44.26
Knorr, Klaus ............... DY 46.76
Knorr, Stefan ............... MA 21.6
Knoth, Hans .........DF 3.6, DY 28.6
Knupfer, M. ... TT 3.9, TT 24.23,
TT 26.13
Knupfer, Martin .....SYOH 5.24,
SYOH 5.30, SYOH 5.32, TT 9.3,
TT 9.7
Ko, H. J. .................... HL 17.4
Kobitski, Andrei Yu. ...AKB 50.12,
HL 44.36, SYLS 2.2, SYLS 3.14
Koch, Daniel ...AKB 12.1, AKB 50.16
Koch, Erik ......... TT 9.10, TT 32.1
Autorenverzeichnis
Koch, J. ............HL 25.5, HL 43.1
Koch, S. W. ......... HL 6.1, HL 31.1
Koch, Stephan W. .HL 28.4, HL 32.3,
HL 32.4, HL 32.5
Ködderitzsch, Diemo ....... MA 13.98
Koeder, Achim ...............HL 35.5
Kögel, Gottfried ............. CPP 7.3
Kögerler, Paul ...............MA 21.1
Köhler, A. ..................DS 22.46
Köhler, Anna .............. SYOH 2.3
Köhler, J. .......SYLS 3.9, SYLS 3.13
Köhler, Jürgen CPP 16.10, CPP 16.29,
SYLS 3.11
Köhler, U. ........MA 13.3, MA 13.93
Köhler, Ulrich ...... MA 13.12, O 38.4
Köhler, Werner .............. CPP 7.1
Kölbach, Micha SYLS 3.56, SYLS 3.57,
SYLS 3.58
Kölbl, A. .................... O 28.61
Koelle, D. ..........TT 18.3, TT 18.7
Koelle, Dieter .. MA 22.1, TT 18.6,
TT 25.5, TT 31.2
Kölln, Klaas ... SYLS 3.47, SYLS 3.53
Koelsch, Patrick ............CPP 12.5
Koenderink, Femius .......... HL 15.9
Koenderink, Gijsberta H. ... AKB 10.1
Könemann, Jens ............. HL 37.4
König, C. ................... MA 13.1
König, Christian .............MA 13.2
König, Hans .......DF 4.12, DY 29.12
König, J. .................... TT 16.7
König, Jürgen ...HL 29.9, HL 37.8,
HL 49.2, MA 27.13, TT 3.4,
TT 11.1, TT 23.3, TT 27.5
König, M. .................... DF 2.2
König, Ulf .................. HL 12.64
Köntges, M. ................. HL 12.2
Koentopp, M. ............... TT 17.6
Koepernik, Klaus ..MA 3.4, MA 8.7,
MA 8.9, MA 13.99
Koepernik, Klauss .............TT 9.2
Köpnick, Th. ..............CPP 15.45
Köppl, Michael ............. DY 46.88
Koerfer, Friedel .............. DS 18.3
Köster, Sarah ....CPP 13.7, CPP 14.3
Koethe, T. ................. TT 24.45
Kötzler, J. ...................TT 8.33
Kötzler, Jürgen MA 13.24, MA 13.81,
TT 8.34
Koh, H. ........... MA 13.9, MA 17.2
Kohl, Helmut ................ DS 10.5
Kohlbrecher, J. ............ SYLS 3.55
Kohler, Sigmund . TT 17.1, TT 17.2,
TT 22.7, TT 27.1
Kohlstedt, H. ....... DF 6.7, MA 26.4
Kohlstedt, Hermann MA 31.8, TT 8.54
Kohn, Peter ...............CPP 15.29
Koidl, Peter ...................HL 4.3
Koitzsch, Andreas .............TT 9.3
Kolaczkiewicz, Jan ............ O 14.8
Kolaric, Branko .. CPP 11.1, SYPF 2.2
Kolb, Florian M. .HL 11.3, HL 12.52,
HL 18.1
Kolb, Torsten ................ O 28.43
Kolb, U. ......................M 26.1
Kolberg, D. .... MA 13.19, MA 13.103
Kolev, Hristo ...... MA 4.12, MA 15.3
Kollaboration, die ISOLDE .. HL 44.49
Kollaboration, ISOLDE .......HL 21.5
Kollar, Marcus .. TT 16.8, TT 23.2,
TT 26.9
Koller, Georg .............. SYOH 7.1
Koller, Winfried ............ TT 30.10
Kollonitsch, Zadig ....HL 33.4, O 40.4
Koltsov, Sergei ...............O 28.30
KoláJ, ček ........ ........
Komarek, A.TT 30.16, TT 30.38,
TT 30.38 Komin, Niko .. DY 24.8
Komiya, Seiki ................TT 8.44
Kondakov, D. E. .............TT 24.1
Konjhodzic, Denan ..........HL 12.33
Konle, Johannes ............ HL 12.55
Konrad, P. .................. TT 17.8
Konrad, Renate ........... CPP 15.37
Konstandin, A. .............. TT 19.1
Konter, J. A. ..............SYLS 3.55
Kontos, T. .................. TT 25.6
Kooij, E. Stefan ...............O 10.1
Kopelevich, Yakov ............HL 22.3
Kopietz, Peter ...DY 10.5, TT 4.5,
TT 23.2
Kopp, Thilo .......TT 3.14, TT 14.12
Koppers, E. ................. MA 18.2
Kopu, Juha ..................TT 19.1
Korb, Thomas ..............TT 11.14
Kordonis, K. .. TT 30.16, TT 30.23,
TT 30.29
Kordyuk, A. ................ TT 26.13
Kordyuk, Alexander ........... TT 9.3
Korecki, Jozef ..........DS 6.2, O 6.4
Korin-Hamzic, B .............TT 6.10
Korn, T. ...................MA 13.63

Korn, Tobias ...............MA 13.64
Kornetzky, P. ............. SYOH 5.73
Korotin, M. ................ TT 24.45
Korotin, M. A. ...............TT 24.2
Korte, E. H. .. CPP 8.6, CPP 15.21,
CPP 15.45, SYLS 3.49
Korte, Lars .................. DS 20.3
Kortright, Jeffrey B. ......... MA 10.9
Korytar, D. ................... DS 9.8
Koschella, Ulrich ..............M 29.2
Koschorreck, M. ............. HL 23.7
Koschorreck, Marco .......... HL 23.8
Kosiba, Rastislav ....DS 22.12, HL 9.1
Kosiorek, Adam ...............DS 9.5
Koslowski, Berndt .. O 9.2, O 28.41,
O 32.5
Kossev, Iordan ............... O 14.64
Kost, Daniel ................. O 40.10
Kostoglou, Christos .........TT 29.11
Kostur, Marcin .............. DY 40.4
Kostylev, Michail P. .......... MA 9.1
Kosubek, E. ................MA 28.12
Kosuth, Michal ..............MA 30.2
Kotaidis, Vassilios . DY 46.96, O 28.40
Kotani, Takao .............. HL 44.12
Kotissek, P. ................MA 13.41
Kotliar, G. ...................TT 28.2
Kotrla, M. ................... O 14.31
Kotsugi, M. ... MA 4.2, MA 13.53,
MA 16.3
Kotthaus, J. P. ................HL 9.3
Kotthaus, Jörg ................HL 5.7
Kotthaus, Jörg P. ...........HL 37.13
Kottos, Tsampikos . DY 27.4, DY 50.7
Koudela, Daniela ............. MA 8.7
Kouteva-Arguirova, Simona ...DS 22.9
Kouwenhoven, L. P. ..........HL 34.1
Kouzakov, Konstantin ........TT 8.40
Kovacs, Domokos ............. O 31.2
Koval, Y. TT 17.25, TT 25.2, TT 29.2
Koval, Yury ................. TT 8.25
Kovaleva, N. N. ............ TT 14.13
Kowalsky, W. .............SYOH 5.27
Kowarik, S. ...............SYOH 5.18
Koza, M. ....................TT 30.4
Koza, Marek ................ TT 14.4
Koza, Michael Marek ........ CPP 4.1
Kozhuharova, Radinka .....MA 13.107
Kozlov, M. ........ MA 18.3, MA 22.2
Kozlova, N. ....... MA 18.3, MA 22.2
Kozlova, Nadezhda .......... TT 31.6
Kozlowski, Fryderyk .......SYOH 5.43
Kozubski, Rafal ..............M 18.11
Kr öger, R. ............... SYOH 5.28
Krabbes, G. .......... TT 6.4, TT 9.6
Krabbes, Gernot ....TT 3.14, TT 31.6
Krämer, Andreas ...........SYOH 5.4
Krämer, M. ................. MA 26.4
Krämer, Markus ............. O 14.50
Krämer, S. ....................HL 9.4
Krämer, Thorsten ............ HL 17.9
Kräusslich, J. ....... HL 12.6, HL 30.5
Kraft, Daniel ............... DS 22.50
Krahmer, Claudia ........... HL 44.55
Kraikivski, Pavel .............DY 24.2
Krajicek, Zdenek .............. VA 2.1
Kralj, Marko ................. O 14.37
Kramer, B. .................. HL 44.8
Kramer, Bernhard HL 12.40, HL 12.44,
HL 22.6, HL 29.12, HL 47.5
Kramer, Lorenz .............DY 46.81
Kramer, T. ................... HL 6.3
Kramer, Tobias ........... AKB 50.81
Kramper, Patrick ............ HL 15.9
Krapf, A. .. TT 8.43, TT 8.46, TT 9.4
Krapf, Alicia ........HL 24.1, TT 18.5
Krasia, Theodora ..........CPP 15.43
Krasovskii, E. E. .............. O 28.4
Krasyuk, A. ................. MA 28.8
Krasyuk, Aleksander .........MA 6.12
Kratzer, P. ................ SYLS 3.20
Kratzer, Peter ...HL 3.4, HL 12.59,
O 40.6
Kraus, Robert .......HL 12.36, O 32.1
Kraus, S. .................... HL 14.4
Krausch, G. ................. CPP 6.1
Krausch, Georg CPP 15.5, CPP 15.30,
CPP 16.9, CPP 16.32, O 28.62,
SYOH 5.45
Krause, Andreas ............. DS 18.4
Krause, B. ..................HL 12.62
Krause, M. ..O 28.6, O 28.27, O 28.28
Krause, Stefan ...... MA 17.3, O 17.2
Krauß, Robert ..............DY 46.79
Kravtsov, Evgeny ............MA 20.5
Krawehl, Fabian .............. M 30.3
Krebs, Hans-Ulrich .DF 5.6, DS 13.2,
DS 14.1, DS 17.2, DS 22.20,
DY 46.68
Krebs, Roland ............... HL 38.9
Krech, Wolfram ..............TT 29.4
Kree, Reiner ................. DS 14.4
Kreft, Hans-Diedrich .....AKSOE 10.4
Kreibig, Uwe ..........O 10.3, O 10.8
Kreissig, Ulrich ................DS 1.6
Kreitlow, J. ................. MA 21.5
Kreitmeier, Stefan ..... CPP 8.1,
CPP 15.26, DY 21.5
Kreitmeir, Markus ........... CPP 4.4
Kreitz, Susanne ............ CPP 11.4
Kremer, Friedrich CPP 7.6, CPP 15.10,
CPP 15.23
Kremer, Kurt ..... DY 46.53, DY 51.6
Kremer, R. K. ............... HL 51.3
Kremmer, Alexander .......CPP 15.41
Kremmer, Sascha ..... DF 5.2, O 24.2
Kremzow, Raimund HL 12.16, O 14.80
Krenke, T. ................MA 13.113
Krenke, Thorsten ............MA 24.1
Krenn, Georg ................. O 20.6
Krenner, H. J. ...... HL 20.5, HL 42.5
Krenzer, B. ................... O 13.2
Kress, Andreas ............ SYLS 3.30
Kressler, Jörg CPP 15.16, CPP 15.16,
CPP 15.18
Kreth, Magnus ................M 18.1
Kretz, Johannes ..............HL 10.3
Kreupl, Franz ................ HL 46.1
Kreutz, E. W. ............... DF 5.10
Kreuzer, Stephan ............ HL 44.3
Krey, Uwe ................ MA 13.100
Kreyssig, Andreas ... MA 3.3, TT 8.51
Kreß, A. F. .................. HL 20.5
Krieger, M. ..................DS 22.8
Krieger, Markus G. ............M 27.4
Krieger, Michael ............. HL 52.2
Kriener, M. TT 3.12, TT 6.7, TT 14.9,
TT 14.14, TT 14.14, TT 20.7,
TT 30.13, TT 30.14, TT 30.23,
TT 30.29, TT 30.31
Krill, C. E. ................... M 32.1
Krill III, C. E. .........M 21.4, M 32.4
Krimmel, Alexander ..........TT 14.4
Krink, Thiemo ............AKSOE 1.3
Krinner, Axel ................ DY 16.1
Krippner-Heidenreich , Anja AKB 50.97
Krisch, Michael .............. O 14.44
Krischok, S. ........ HL 16.2, O 14.56
Krischok, Stefan ...DS 22.5, DS 22.12
Krishnakumar, S. R. .......... MA 3.1
Kristukat, Christian .......... DS 21.1
Krivosheeva, Anna ........... O 28.22
Krockenberger, Y. ........... TT 18.4
Krockenberger, Yoshiharu .. TT 1.1,
TT 8.3
Kröger, J. .....................O 17.1
Kröger, Jörg .......... O 17.6, O 26.1
Kröger , Martin . DY 11.2, DY 46.47,
SYPF 5.4
Krömker, B. ................. O 28.51
Kroha, Hans ... TT 15.7, TT 16.9,
TT 17.31
Kroha, J. ...................TT 11.13
Kroha, Johann ...............TT 16.5
Kroll, Daniel M. ...........AKB 50.92
Kroll, Thomas ................ TT 9.7
Krompiewski, Stefan ...... SYOH 5.58
Kronast, F. ................. MA 31.5
Kronenberger, A. .......... SYLS 3.41
Kronenwerth, O. ............HL 44.13
Kronenwerth, Oliver .........HL 44.15
Kronmüller, H. ............... MA 2.4
Kropp, K. ................. SYLS 3.41
Krost, A. ...AKB 50.3, AKB 50.17,
HL 27.1, HL 27.11, HL 27.12,
HL 27.14, HL 33.5, HL 44.80,
SYLS 3.24
Krost, Alois ... HL 12.78, HL 21.3,
HL 27.2, HL 44.81
Kroth, K. .................MA 13.114
Kroutvar, Miro ...............HL 50.3
Kroy, Klaus .AKB 50.40, AKB 50.41,
AKB 50.69, AKB 50.70, AKB 50.84
Krtschil, A. ..AKB 50.3, AKB 50.17,
HL 27.12, SYLS 3.24
Krtschil, Andre .... HL 12.78, HL 27.2
Kruchten, Frank ...............O 43.1
Krüger, Ekkehard ............ TT 8.48
Krüger, Guido ............... DY 36.3
Krüger, Jan K. . AKB 50.47, CPP 15.3
Krueger, Jan Kristian ... CPP 2.6,
CPP 7.5, CPP 8.2, CPP 8.7,
CPP 15.36
Krüger, P. .. O 14.47, O 28.72, O 40.7
Krülle, Christof .....DY 44.1, DY 44.3
Kruelle, Christoph ........... DY 44.5
Krug, Klaus ..................O 28.15
Krug von Nidda, H.-A. ... HL 35.6,
TT 14.3, TT 24.52
Krug von Nidda, Hans-Albrecht TT 6.8
Krupin, O. .... MA 4.9, MA 4.10,
MA 13.56, MA 31.2
Krupin, Oleg ....MA 28.14, SYXM 1.3
Krupka, Simone ............ SYLS 4.4
Krupke, R. ....... SYOH 6.2, TT 27.2
Krupke, Ralph ............... TT 27.8
Krupski, Alexander ... O 14.11, O 43.5
Kruse, J. ......................O 24.1
Kruse, Jan .................. CPP 4.3
Kruse, Karsten AKB 50.24, AKB 50.29,
AKB 50.49, AKB 50.64, DY 24.1
Ksenofontov, V. ...........MA 13.117
Ku, W. .......................TT 3.9
Kubala, Björn ............... TT 11.1
Kube, K. ....... AKB 50.3, SYLS 3.24
Kubetzka, A. ...................O 8.1
Kubetzka, André ..MA 2.6, MA 4.7,
MA 26.12
Kubitscheck, U. ........... SYLS 3.10
Kubitscheck, Ulrich ......... SYLS 2.1
Kubsky, Stefan ................O 38.4
Kuch, W. .... MA 4.2, MA 13.53,
MA 16.3, MA 20.7, MA 28.10
Kuchar, Fridemar ............ HL 28.8
Kuchar, Friedemar .. DF 5.2, HL 44.32
Kuchenbrandt, Kai ........ MA 13.120
Kucherenko, Yuri ..............O 44.5
Kuck, Stefan .................O 14.72
Kuckuk, Ruediger ......... AKB 50.96
Kuduz, Mario ................M 18.18
Kudyk, I. ..................... HL 4.5
Kuehn, Uta .....M 9.2, M 9.4, M 31.3
Kühne, Torsten ........... AKB 50.32
Kümmler, Volker .............HL 16.4
Künzel, H. ..................HL 12.43
Kuepper, Karsten ............MA 11.5
Kuhl, J. ...................... HL 8.4
Kuhl, Jürgen ..................HL 2.5
Kuhl, U. ....DY 46.39, DY 46.40,
DY 46.41, HL 20.2
Kuhl, Ulrich ................ DY 46.38
Kuhn, Marcus .................DS 3.2
Kuhn, Tilmann ............. HL 44.39
Kuhnke, K. ...................MA 3.1
Kuhnke, Klaus ............ CPP 16.27
Kuksov, A. ..................MA 28.8
Kuksov, Andrew .............MA 6.12
Kukunin, A. ....MA 13.71, MA 13.105
Kulawik, Maria ................O 9.11
Kulda, J. ........ TT 30.38, TT 30.38
Kulkarni, S. K. ............. CPP 12.6
Kulyuk, Leonid ..............MA 22.3
Kumar, Ashok .............CPP 15.42
Kumar, G. .....................M 8.5
Kumar, Golden ..............MA 11.7
Kumar, P. S. Anil .......... MA 13.16
Kumar, Pravesh ............SYOH 3.3
Kumpf, C. ..... CPP 12.6, SYOH 5.20
Kumpf, Christian .......... SYOH 5.1
Kuncser, V. ................ MA 13.44
Kuncser, Victor ............ MA 13.11
Kunert, Roland ..... HL 3.2, HL 12.65
Kunert, Thomas ............TT 17.12
Kunow, Magnus ...............DF 5.9
Kunst, Marinus .....SYOH 5.11,
SYOH 5.48
Kunstmann, Tobias .......... O 14.69
Kuntscher, C. .............. TT 30.18
Kuntscher, C. A. ........... TT 30.25
Kuntze, Jens .................O 14.26
Kunz, Ludvik ................. M 13.4
Kunz, R. ..............O 24.1, O 38.6
Kunze, Peter ..............CPP 16.23
Kunze, U. HL 37.11, HL 41.1, HL 44.2,
MA 26.11
Kunze, Ulrich .... HL 3.1, HL 5.1,
HL 12.64, HL 44.26
Kuo, C. C. ....................O 12.2
Kuo, K. H. ................... M 31.6
Kupfer, Hartmut ....DS 4.2, DS 22.42
Kurfiss, Malte ..............MA 13.91
Kurfiß, Malte .............. MA 13.92
Kurin, V. V. .................TT 31.1
Kurrle, D. ................ SYOH 5.44
Kursawe, M. ............... SYNP 2.4
Kursumovic, A. ..............TT 8.14
Kurth, D. ....................O 28.86
Kury, Peter ..............O 5.4, O 5.4
Kurz, Heinrich ............... DS 15.2
Kurz, T. .....................HL 35.6
Kutzner, J. .................. O 28.34
Kutzner, Jörg ................. O 28.5
Kuz’min, Michael D. ....... MA 13.99
Kuzmin, Michael ............. MA 8.7
Kveder, Vitaly .............. HL 44.44
Kvietkova, J. ............... HL 12.10
Kwon, Ah-Ram ..MA 13.17, MA 15.10
Kyarad, Amir ............... HL 44.19
L. D., Filkenstein ..........MA 13.109
L.O.T.-Oriel ................... FB 26
La Rocca, Giuseppe .......... HL 41.4
Laades, Abdelazize ..DS 13.4, DS 20.3
Labayen, Miguel .... O 28.15, O 28.16
Lach, Stefan . SYOH 5.21, SYOH 5.23
Lachenmaier, Tobias ......... TT 13.5
Lackinger, M. ........O 14.23, O 38.7
Autorenverzeichnis
Ladadwa, Imad ...... DF 4.3, DY 29.3
Ladenburger, Andreas ...HL 12.54,
HL 12.55
Läffert, Annette ............ DS 22.12
Lämmer, Stefan .......... AKSOE 7.1
Lässig, Michael .............AKB 40.1
Lahmann, S. ................HL 27.10
Lakemeyer, Ilsemarie .......... M 30.1
Lamago, Daniel ........... MA 13.102
Lamark, Torbjørn ..... M 13.4, M 15.3
Lambacher, A. ............ AKB 50.75
Lambrecht, Armin .......... HL 12.35
Lammerschop, Andreas ........O 25.1
Lammert, Heiko ..... DF 4.8, DY 29.8
Lampalzer, M. ............... HL 44.5
Lampe, I. v. ................. TT 8.13
Lampe, T. .......... M 16.4, M 18.15
Landfester, Katharina ..... SYOH 5.46
Landwehr, Stefan .HL 15.1, SYLS 3.17
Lanfranchi, Jean-Côme .......TT 13.5
Lang, Christian ............... M 21.1
Lang, Erwin ...............CPP 16.10
Lang, F. .....................O 28.13
Lang, Jonathan ........... MA 13.118
Lang, M. ..................... M 14.5
Lang, Michael .. CPP 8.1, DY 21.5,
M 2.4, M 9.6
Lang, Philippe ............SYOH 5.68
Lang, R. ......................DS 1.9
Langa, Sergiu ...............HL 12.34
Langbein, W. ................ HL 36.3
Lange, Jörg ..........O 14.7, O 28.53
Langel, Walter ................ O 44.4
Langenkamp, Winfried .........O 17.3
Langner, Andreas .......... SYOH 5.5
Lanzani, Guglielmo .........SYOH 2.2
Lanzendörfer, Michael ..... CPP 16.32
Lapanik, A. .................HL 44.24
Larionov, A. V. ............. HL 44.34
Larsson, H. ................. HL 44.79
Laschinger, Christian ........TT 14.12
Lasogga, L. ...................TT 9.4
Lassl, Andreas ............... DY 27.5
Last, T. . HL 41.1, HL 44.2, MA 26.11
Lattanzi, Gianluca ....AKB 50.20,
AKB 50.132
Lau, Julian Tobias .............O 25.9
Lau, Tobias ............... SYXM 1.6
Laubschat, C. .................. O 3.4
Laubschat, Clemens O 11.11, O 17.4,
O 44.5
Lauer, Markus ............ MA 13.111
Lavalle, Catia ................TT 26.2
Lavrinenko, Andrei ........... HL 20.8
Lavrov, Edward ............. HL 44.72
Lawrenz, M. ......... O 14.20, O 38.2
Layer, M. ........ DY 46.91, TT 30.41
Lazic, Predrag ............... O 14.37
Lazo, Cesar ................... O 43.2
le Coutre, Andrä. . CPP 8.7, CPP 15.3
Le Quang Tien, Dung ........ O 24.10
Le Roux, J. .................. O 28.64
Leary, Edmund ............. SYLS 4.3
Lebanon, Eran ......HL 47.1, TT 11.3
Lebedev, V. .........HL 16.2, HL 16.3
Leber, A. ..........HL 38.3, HL 44.83
Leber, Andreas ......HL 27.5, HL 38.5
Lebon, A. ................... TT 14.2
Lechner, Rainer T. ............ HL 7.1
Lechner, Robert ..............HL 51.2
Lederer, Falk ....... HL 6.2, HL 15.11
Ledowski, Sascha .... DY 10.5, TT 4.5
Lee, D.-H. ....................TT 9.1
Lee, Hyun Jung ..............TT 16.3
Lee, T. L. .....................O 14.2
Lee, T. Y. ....................MA 3.1
Lee, Tien Lin ......... DS 9.3, O 39.4
Lee, Tien-Lin ........ O 25.2, O 28.12
Leeb, T. ....................HL 29.10
Leffhalm, K. ...............SYLS 3.45
Leffhalm, Kai ..............SYLS 3.40
Lefkidis, Georgios ............. O 44.7
Lefloch, Francois ........... SYSN 1.2
Lehmann, Carstan ............O 40.11
Lehmann, Carsten ............DS 20.4
Lehmann, Frank ... HL 44.20, HL 49.3
Lehmann, Jörg .. TT 17.1, TT 17.2,
TT 27.1
Lehner, Bernhard ..............O 43.7
Leibiger, Gunnar HL 12.50, HL 12.90,
HL 44.55, HL 44.56, HL 44.57
Leibrock, Hanno ...... TT 8.5, TT 8.6
Leiderer, P. .................. O 28.13
Leiderer, Paul .. DY 46.88, O 14.10,
O 28.36, O 28.49, TT 8.30,
TT 8.53, TT 17.13, TT 30.33
Leighton, C. ...MA 10.8, MA 14.1,
MA 28.11
Leiner, Vincent ..............MA 16.8
Leinert, S. ........MA 13.18, MA 15.8
Leistner, Karin .............. MA 30.5
Leitenberger, W. ............... O 6.5

Leitlmeier, Dietmar ......... SYPF 3.1
Leitner, H. ................... M 22.5
Lell, A. ..HL 38.3, HL 44.83, HL 44.84
Lell, Alfred HL 16.4, HL 27.5, HL 38.5
Lemcke, Oliver ............... MA 2.6
Lemmens, P. .. TT 14.13, TT 20.4,
TT 24.49, TT 24.50, TT 24.51
Lemmer, Uli .... CPP 16.29, HL 12.37
Lengfellner, Hans ........... HL 44.19
Lengsdorf, R. ................ TT 20.5
Lentze, M. ...................HL 21.1
Lenz, A. .............. HL 3.10, O 9.3
Lenz, Andrea ........ HL 3.9, HL 25.3
Lenz, K. ................... MA 28.12
Lenz, Peter ................ AKB 13.1
Lenzner, J. ... HL 12.71, HL 12.73,
HL 17.5, HL 17.5
Lenzner, Jörg ......HL 12.81, HL 17.3
Leo, K. HL 12.97, HL 23.7, SYOH 5.39
Leo, Karl . HL 12.95, HL 23.8, O 4.1,
O 14.62, O 33.1, O 33.7,
SYOH 5.40, SYOH 5.42,
SYOH 5.43, SYOH 5.78,
SYOH 5.82
Leon, Carlos .................. DF 2.6
Leonhardt, Albrecht ....... MA 13.107
Leonhardt, S. ................TT 31.8
Leonov, I. ................... TT 24.2
Leonov, Ivan ............... TT 24.43
Leopold, Andre .............CPP 10.1
Leppin, Roland ..............MA 21.7
Lerch, Daniel ................. O 43.8
Lermer, M. ................. HL 44.18
Lermer, Markus .............HL 12.39
Lesch, Harald ................. PV XII
Lesueur, J. .................. TT 25.6
Letz, T. ..................... DY 36.5
Letzig, Tobias ................O 28.25
Leuchs, G. ...................HL 50.4
Leuenberger, F. .. MA 13.65, MA 14.2
Leuenberger, Frank ..........MA 30.1
Leufgen, M. SYOH 5.62, SYOH 5.64,
SYOH 5.65
Leupold, O. ................MA 13.44
Leutloff, Firmin ............. MA 13.6
Levichkova, Marieta .........HL 12.95
Lewenkopf, C. H. ........... DY 46.40
Lewerenz, H. J. ............... O 40.1
Lewerenz, Hans-Joachim .. DS 20.5,
O 40.3
Ley, Lothar .................. HL 31.4
Leyer, Stephan .............. M 18.29
Leymarie, E. ...............SYLS 3.55
Leˇzaić, Marjana ............. MA 11.4
Li, Chenghao ............. AKB 50.67
Li, Fenghong ............. SYOH 5.40
Li, J. .........................M 26.1
Li, Zhipan .................. MA 14.1
Libralesso, Laure .............. DS 9.3
Lichte, Hannes ................DS 8.1
Lichtenberg, Frank ..........TT 24.37
Lichtenberger, Janosch .... AKB 50.83
Lichtenstein, A. I. .. TT 28.7, TT 32.7
Lichtenstein, Alexander ....... MA 8.3
Liebau, Maik ................ HL 46.1
Liebl, Helmut ................. O 12.5
Liebmann, M. .............MA 13.123
Liebmann, Marcus ........... TT 31.4
Liebsch, A. .................. TT 28.9
Liedke, Maciej-Oskar ........DS 22.35
Liedke, Oskar ............... MA 10.5
Liehr, A. W. ...... DY 14.2, DY 46.31
Liehr, Andreas W. .DY 14.1, DY 46.16
Lienau, Christoph . HL 50.8, SYOH 2.2
Lierfeld, Thomas ..............M 12.2
Lilge, Dieter ................CPP 13.6
Limbach, Bernhard ...........TT 11.2
Limbach, Hans Jörg ..........DY 23.2
Limmer, Wolfgang .......... HL 44.77
Limot, L. ..................... O 17.1
Limozin, Laurent ....AKB 50.119,
AKB 50.120
Limpert, Jens ................. HL 2.3
Lin, C. T. TT 14.2, TT 14.13, TT 18.7
Lin, Chengtian .......TT 8.17, TT 9.7
Lin, Feng .................SYOH 5.17
Lin, H.-J. ... TT 24.45, TT 24.46,
TT 32.6
Lin, M. T. .................... O 12.2
Lin, Nian .................... O 28.38
Lin, Yao ................... CPP 16.9
Linck, M. .......... TT 8.24, TT 13.4
Lincoln, Bryan AKB 30.4, AKB 50.113,
AKB 50.125
Linden, S. .................... HL 8.4
Linden, Stefan ................ HL 2.5
Lindenblatt, Michael ......... O 14.16
Linder, N. ................... HL 10.1
Lindfors, Klas ...............SYLS 2.3
Lindgren, Kristian ........ AKSOE 4.1
Lindner, J. .................MA 28.12
Lindner, J. K. N. ....DS 1.4, DS 22.13
Lindner, Jörg K. N. .......... DS 17.6
Lindner, Oliver ...............TT 8.22
Lindner, Thomas HL 10.2, SYOH 5.69
Ling, X. S. ................AKB 50.99
Lingenfelder, Magalí ..........O 28.38
Linic, Suljo ................... O 31.4
Linker, G. ........... TT 8.1, TT 18.1
Linz, Stefan J. ...............DY 44.3
Linzen, S. ................... TT 29.5
Lion, Manuel ............. AKB 50.63
Lipavsk´y, P. ........TT 8.49, TT 9.12
Lipowsky, Peter .............DY 46.97
Lipowsky, Reinhard ....AKB 11.1,
AKB 50.32, AKB 50.44,
AKB 50.48, AKB 50.54,
AKB 50.128, DY 14.7, DY 24.2
Lipperheide, R. .............. HL 44.1
Lippert, Gunther .............. DF 6.6
Lippert, Markus ............ TT 30.35
Lippitz, H. .................. MA 15.7
Lippitz, Holger ................. O 5.3
Lippold, G. ................... DS 9.7
Lippold, Gerd ................DS 21.5
Lips, Klaus .................. DS 20.1
Lischewski, I. ......... M 12.4, M 12.4
Lischka, Markus .......O 18.6, O 26.9
Lisenfeld, J. .. TT 17.23, TT 17.25,
TT 25.2
Lisowski, Martin ............. O 28.73
Liszkay, Laszlo ...............CPP 7.3
Litterst, F. J. .. MA 21.2, MA 21.3,
MA 21.5
Litvinov, D. ...HL 12.10, HL 12.74,
HL 12.76, HL 43.3
Liu, Bing ..................... TT 1.4
Liu, Bo .......................M 18.6
Liu, H. J. ....................TT 30.1
Liu, Hong .....................O 28.8
Liu, Hui Chun .................HL 4.3
Liu, Jianing ................ DY 46.66
Liu, Jieping ............... CPP 15.33
Liu, K. .................... MA 13.44
Liu, K. W. ....................M 20.5
Liu, Kai .....................MA 14.1
Liu, Quincy ................... HL 3.4
Liu, R. P. ...................HL 44.68
Ljubović, Edina ..............TT 27.9
Lloyd, Seth .................TT 17.18
Lo, Fang-Yuh ...............HL 44.10
Loata, G. ..........HL 4.10, HL 12.21
Lobaskin, Dmitry ........... TT 24.14
Löckenhoff, Rüdiger .........HL 44.48
Löcse, Frank .......HL 44.22, HL 47.7
Löffler, M. .................... O 39.3
Löffler, T. ......... HL 4.10, HL 12.21
Löffler, Wolfgang ........... HL 12.75
Löhneysen, H. v. . TT 24.29, TT 30.15
Löhneysen, Hilbert v. ....TT 19.3,
TT 20.8, TT 27.8
Löhr, S. ...................... HL 5.4
Lölkes, Stefan .............. HL 12.34
Lörgen, Marcus ............SYXM 1.7
Lösch, Rainer ...............HL 38.10
Löser, Andre ................HL 44.59
Löser, W. ........... M 8.5, TT 24.31
Löser, Wolfgang ..... M 22.2, TT 8.51
Löw, Ute ..................... TT 3.3
Loewenhaupt, Michael ........ MA 3.3
Lohmann, T. ................MA 13.1
Lohmeyer, H. ................ HL 36.8
Lohöfer, G. ................. HL 44.68
Loi, S. .................... CPP 16.24
Loidl, A. . DF 1.6, HL 35.6, TT 6.11,
TT 14.3, TT 20.4, TT 24.52
Loidl, Alois ..DF 5.6, TT 6.8, TT 14.4
Loison, Claire ................TT 8.39
Lok, Sjoerd .................. HL 14.4
Lokstein, Heiko .......... AKB 50.116
Long, T. D. .........HL 10.4, O 14.83
Lonkai, Th. ........ DF 7.6, MA 13.46
Loo, R. .......................DS 1.1
Loppacher, Christian .O 9.5, O 14.61,
O 23.3
Lorenz, Eric ................ DY 46.89
Lorenz, M. .... DS 9.7, HL 12.71,
HL 12.73, HL 12.83, HL 12.86,
HL 17.5, HL 17.5, HL 17.12,
HL 28.5, TT 8.32
Lorenz, Michael .HL 12.68, HL 12.69,
HL 12.77, HL 12.81, HL 12.84,
HL 17.1, HL 17.3, HL 44.51, TT 1.6
Lorenz, Sönke .................O 26.3
Lorenz, T. TT 3.12, TT 6.7, TT 14.9,
TT 14.14, TT 14.14, TT 20.7,
TT 24.46, TT 24.47, TT 30.13,
TT 30.14, TT 30.16, TT 30.23,
TT 30.29, TT 30.31, TT 32.6
Lorenzana, Jose .. TT 24.24, TT 24.25
Lorke, Axel ........ HL 22.11, HL 50.9
Loss, Daniel ........ HL 49.1, HL 50.1
Loth, S. ..................... HL 33.2
Lott, D. .....................MA 20.3
Lottermoser, Th. .DF 7.6, MA 13.46,
MA 13.67
Louis, Kim ................. TT 30.22
Loukakos, Panagiotis O 28.73, O 37.7,
O 45.2
Lounis, S. ..................MA 13.89
Lu, H. .......................HL 27.4
Lu, Y. MA 13.13, MA 15.5, MA 20.7,
O 39.9
Lubashevsky, Ihor AKSOE 2.1, DY 14.5
Lubatsch, Andreas ..........TT 17.31
Lublow, Michael .......O 40.1, O 40.3
Lucignano, Procolo .......... TT 8.27
Lud, Simon Q. .AKB 50.36, SYLS 3.32
Luding, Stefan ...............DY 44.4
Ludwig, Frank .MA 13.120, MA 18.4,
TT 13.10, TT 13.10
Ludwig, Jöerg .............CPP 15.14
Ludwig, Simone ...............VA 2.2
Ludwig, Stefan ......HL 5.7, HL 37.13
Ludwig, Thomas . TT 11.11, TT 17.15
Ludwigs, S. ................. CPP 6.1
Ludwigs, Sabine ............ CPP 15.5
Lübke, Jens ..................HL 51.2
Lueck, Stephan ..............DY 40.3
Lücke, Manfred .............DY 46.76
Lüders, Klaus .................M 31.3
Lüders, Martin ............. MA 13.98
Lüdtke, Karin ............. CPP 16.30
Lüdtke, T. ..................HL 12.60
Lühmann, T. ................. TT 7.7
Lühn, Ole ................... DS 22.3
Lümkemann, A. ..............TT 8.12
Lüning, Jan ............... SYXM 1.7
Lüth, Hans HL 10.3, HL 27.3, HL 44.86
Lüttich, M. .......MA 13.65, MA 14.2
Lüttjohann, Stephan ......... HL 50.9
Luh, Dah-An ..................O 11.1
Lukas, Eng .................. O 28.54
Lukas, S. .................SYOH 5.13
Lukashenko, A. .TT 17.23, TT 17.25,
TT 25.2, TT 29.2
Luna-Acosta, G. A. DY 46.41, HL 20.2
Lundgren, E. ..........O 34.6, O 38.8
Lunedei, Eugenio .............O 28.30
Lunkenheimer, P. .... DF 1.6, TT 14.3
Lunkenheimer, Peter .......... DF 5.6
Luo, Mengbo ................ HL 12.9
Luo, Yuansu ..MA 13.22, MA 13.23,
MA 27.5
Lupaca-Schomber, J. ........HL 12.72
Lupascu, Doru Constantin ..... DF 1.5
Lupina, Grzegorz ............HL 44.42
Lupton, J. M. .. HL 15.12, SYOH 5.86
Lupton, John ............. SYOH 5.83
Lupton, John M. .CPP 9.1, HL 12.36,
SYOH 5.84
Lusceac, Sorin Adrian DF 3.8, DY 28.8
Lust, M. ......................O 14.4
Lust, Matthias ................ O 18.8
Lutsen, Laurence ......... SYOH 5.51
Lux, Thomas ............AKSOE 10.2
Lux-Steiner, M. C. .......... DS 22.56
Lux-Steiner, Martha ..........DS 21.1
Luysberg, M. .......DS 1.1, MA 13.96
Lymperakis, L. ...............HL 27.7
Lyon, S. A. .................. HL 29.2
Lyubina, Julia ...............MA 26.3
Lyutovich, Klara ............. DS 15.2
López, Xóchitl ............... O 28.22
Ma, Wenhui .................. DF 5.1
Maass, Ph. ...... DY 46.17, MA 13.87
Maass, Philipp .CPP 15.28, DY 46.9,
DY 46.10
Maccarini, Marco ..........CPP 16.17
MacDonald, Allan .............TT 3.4
MacDonald, Allan H. ....... MA 27.13
Macedo, W. A. A. ..........MA 13.44
Mach, Robert ........... AKSOE 3.11
Machnikowski, Pawe̷l ........HL 44.39
Macht, M.-P. ........... M 9.3, M 9.5
Machura, Lukasz ........... DY 46.15
MacKinnon, A. ............. HL 44.60
MacKintosh, Frederick C. ...AKB 10.1
Macutkevic, J. ................ DF 7.4
Madden, Paul A. ..............DF 2.3
Madenci, D. .................TT 32.6
Madge, Shantanu ......M 9.1, M 14.3
Madsen, Anders .....O 14.48, O 14.50
Mändl, Stephan ...............DS 3.3
Maennig, Bert SYOH 5.42, SYOH 5.43
Maeno, Y. ....TT 3.12, TT 14.14,
TT 14.14, TT 30.36, TT 30.38,
TT 30.38
März, Reinhard .............. HL 15.5
Magerle, R. ......CPP 6.1, CPP 15.34
Magerle, Rober ..............CPP 2.4
Magerle, Robert ............ CPP 15.5
Magg, Norbert ................ O 39.4
Maghelli, Nicola ..............O 14.82
Magnoli, Nicodemo .......... HL 22.6
Magnussen, Olaf . O 14.17, O 14.27,
Autorenverzeichnis
O 28.14, O 28.15, O 28.16, O 28.59
Mahajan, A. .................TT 6.11
Mahler, Günter .TT 17.19, TT 17.27,
TT 17.28, TT 29.11, TT 29.12,
TT 29.13
Mahmood, Nasir .....CPP 15.16,
CPP 15.16
Mahnke, Reinhard ....AKSOE 1.5,
AKSOE 3.13, DY 14.5
Mahrov, B. .................. HL 30.1
Maier, F. ..................... O 44.8
Maier, K. ....................M 18.15
Maier, Karl . M 3.3, M 10.2, M 10.3,
M 10.4, M 13.2, M 16.4
Maier, Thomas ................HL 4.3
Maire, N. .........HL 37.12, HL 44.28
Maire, Niels ................SYSN 2.3
Maitz, Manfred ............... DS 3.4
Majer, Günter ................. M 3.4
Majewski, P. ................ MA 13.5
Majewski, Petra .HL 44.9, MA 13.27,
MA 13.39, MA 13.116
Majhofer, A. ............... MA 13.87
Major, M. ................. SYOH 6.2
Major, Zsuzsanna .............M 18.7
Makhlin, Yuriy ...............TT 29.9
Makievski, A. V. ............SYPF 2.4
Maletta, H. ................ MA 13.88
Maleyev, Sergey ...........MA 13.102
Maljuk, A. ...................TT 14.2
Malomed, B. A. ............. TT 29.2
Malsch, Daniell .............. O 28.48
Malterre, D. .................. O 11.8
Maltezopoulos, Theophilos . HL 3.12,
HL 37.2, O 14.70
Malzahn, Dörthe .............DY 21.4
Malzer, S. HL 4.10, HL 9.5, HL 12.21,
HL 12.92, HL 33.2, HL 42.1,
HL 43.5, HL 50.4
Malzer, Stefan ..............HL 44.53
Manca, Jean ..............SYOH 5.51
Mandal, Kalyan ............. MA 11.6
Mandre, Shyam K. ........... HL 32.1
Manfred, Neumann ........MA 13.109
Manfred, W. ................HL 15.12
Mangen, T. ..................O 28.17
Manglkammer, Wolfgang AKB 50.47,
CPP 2.6, CPP 8.2, CPP 15.36
Mango, S. .................SYLS 3.55
Mangold, Konrad ...........DY 46.88
Mani, Ramesh ............... HL 14.1
Mankovskyy, Sergiy ...........MA 8.1
Manmana, Salvatore ........TT 24.21
Mann, Bernward A. .........DY 46.53
Mannarini, Gianandrea ....... HL 28.1
Mannhart, Jochen . O 9.10, TT 18.2,
TT 24.37
Mannix, D. .................. O 28.83
Mannsfeld, Stefan .............O 33.7
Manova, Darina ...............DS 3.3
Mans, Anton ..................O 11.4
Mans, Michael ...............TT 8.26
Manske, Dirk ................ TT 24.6
Mantl, S. ..................... DS 1.1
Mantl, Siegfried ..............HL 10.3
Mantouvalou, I. ................ O 9.3
Mantz, Hubert ..... AKB 50.28,
AKB 50.50, SYLS 3.25
Manz, Niklas ......DY 22.4, DY 46.24
Manzano, Carlos ............. HL 51.1
Manzhur, Y. ................ MA 15.6
Manzke, Günter ..............HL 4.12
Manzke, R. TT 8.43, TT 8.46, TT 9.4
Manzke, Recardo . HL 24.1, TT 8.16,
TT 18.5
Maple, M. B. ...............TT 24.29
Marcano, D. ...................M 3.1
Marchetto, H. ............. SYOH 1.3
Marchi-Arztner, Valerie ....AKB 50.54
Marczinowski, Felix .......... O 14.29
Marczynski, M. ............... O 28.4
Mares, J. J. ........ TT 8.49, TT 9.12
Mariantoni, Matteo ....TT 17.20,
TT 17.21
Marigliano Ramaglia, Vincenzo HL 29.6
Marinov, Danira .............MA 21.6
Markert, Thomas ..O 14.21, O 28.9,
O 28.9
Markina, M. ................TT 30.29
Markmann, J. ................ M 20.5
Markmann, Jürgen ............M 20.4
Marlow, Frank .............. HL 12.33
Marr, Sabine ................ CPP 2.4
Marsmann, Heinrich ... HL 8.2, HL 8.2
Marti, Othmar .. CPP 1.3, CPP 2.1,
CPP 2.3, CPP 15.12, CPP 15.15,
O 14.82, O 14.84, O 28.46,
O 28.47, O 28.50
Martin, C. ................ MA 13.115
Martin, Douglas S. ........ AKB 50.56
Martin, Jörg ................. HL 50.6
Martin, Pascal ............ AKB 50.65

Martin, Tobias ............. MA 13.61
Martinek, J. ................. TT 16.7
Martinek, Jan ...... HL 37.8, TT 23.3
Martinek, Klaus-Peter ........ O 28.62
Martinez-Lope, M. J. ........ TT 20.5
Martini, Joerg ............ AKB 50.81
Martins, Michael ...O 19.3, O 25.9,
SYXM 1.6
Martins, R. M.S. .............DS 14.2
Martín-Moreno, L. ............. PV III
Martínez, Teresa .......... MA 13.106
Marutzky, M. . MA 13.7, MA 13.103,
MA 13.104
Marx, Achim .. TT 17.5, TT 17.20,
TT 17.21
Marx, Dominik ...............O 14.66
Marx, G. .................... DS 13.5
Mashoff, Torge ...............O 14.71
Maslyuk, V. V. ...............O 28.10
Maslyuk, Volodymyr V. ...... DF 5.13
Massen, Joachim ............ AIW 3.2
Masuda, H. ................. MA 14.1
MaTecK .......................FB 27
Matei, Adriana ............AKB 50.19
Materlik, G. ................. O 38.10
Mathiak, Gerhard .............. M 2.2
Matho, Konrad .............. TT 15.6
Mathon, Olivier ............. MA 30.1
Matijasevic, B. ...SYPF 4.4, SYPF 5.2
Matijasevic, Biljana .........SYPF 4.2
Mativetsky, J. M. ............. O 23.9
Matos-Abiague, Alex ... HL 12.20,
HL 47.2
Matsuyama, Toru ............ HL 44.4
Mattay, Jochen ............CPP 16.19
Mattern, Norbert .....M 9.4, MA 24.2
Matteucci, Maurizio ......... MA 11.5
Matth eus, Christine ...... SYOH 5.87
Mattheis, Roland DS 22.22, MA 10.11,
MA 13.52
Matthes, F. ................. MA 13.4
Matthes, Frank ...... O 12.3, O 28.11
Mattheus, Christine ... CPP 16.23,
O 14.60, SYOH 5.25, SYOH 5.87
Matthias, Eckart ........... MA 28.14
Matthias, Sven ...............HL 15.4
Matuttis, Hans-Georg ... DY 10.6,
DY 46.73, SYFT 3.3
Matzdorf, René ............... O 11.2
Mauch, Irene .................MA 5.2
Maud, Duncan ............. TT 30.28
Maude, D. K. ................HL 37.4
Maultzsch, Janina ............HL 48.2
Maurer, E. ..... CPP 15.9, CPP 16.24
Maurer, Edith ............... DY 46.8
Maus-Friedrichs, W. ..........O 14.67
Mauser, Tatjana . CPP 11.1, SYPF 2.2
Mavropoulos, Ph. .......... MA 13.89
Mavropoulos, Phivos ........ MA 11.3
May, R. P. ................ SYLS 3.55
May, Sonia ................. DY 46.76
May, Volkhard ...............TT 17.2
Mayer, Ch. ...................MA 6.6
Mayer, Joachim ..............DS 10.1
Mayer, Norbert ............. DY 46.35
Mayer, Thomas .....SYOH 5.33,
SYOH 5.48
Mayer-Gindner, A. ........... TT 17.8
Mayerhöfer, T. G. ............DS 22.7
Mayor, M. ...................TT 27.2
Mayr, S. G. ............DS 3.1, M 7.5
Mayr, Stefan ............... DS 22.14
Mayr, Stefan G. .DY 25.3, DY 46.68,
O 14.51
Mayya, S. .....................O 19.6
Mazilu, Irina ..................M 22.2
Mazur, Florian ..DY 34.1, DY 46.20,
DY 46.21
Mazzarello, Riccardo ........ HL 12.40
MBE-Komponenten ............FB 28
McCombe, B. D. ............HL 29.11
McCord, Jeff .... MA 10.11, MA 13.72
McCord, Jeffrey . MA 7.1, MA 13.52,
MA 13.73, MA 28.6
McElroy, K. ...................TT 9.1
McGrouther, Damien ....MA 10.4,
MA 13.47
McMillan, Paul F. ............HL 11.5
McVitie, Stephen .MA 10.4, MA 13.47
Mechau, Norman ........... CPP 10.2
Mechler, s. ............. M 9.3, M 9.5
Mechonics .....................FB 29
Mecke, K. R. ..............CPP 15.34
Mecke, Klaus . AKB 50.28, DY 10.4,
DY 17.4, DY 17.6
Meckenstock, Ralf ..........MA 13.12
Medebach, Martin ........... DY 51.2
Meden, Volker .. TT 11.7, TT 24.9,
TT 24.10, TT 24.21
Medick, Peter ....... DF 3.8, DY 28.8
Meduna, Mojmir .............. HL 7.1
Medvedev, Dmitry .......... DY 46.67
Medvedeva, I. .............MA 13.115
Megaides, Rodrigo ..........DY 46.90
Mehaddene, T. ............CPP 16.24
Mehner, J. ...................HL 10.4
Mehrer, H. .......... DF 4.6, DY 29.6
Mehrer, Helmut ...DF 4.7, DF 4.9,
DY 29.7, DY 29.9, M 10.6, M 29.5
Meier, Cedrik ................ HL 50.9
Meier, Focko ..................O 23.6
Meier, Gu ido ................ MA 2.2
Meier, Guido .. HL 44.4, MA 13.25,
MA 13.68, MA 13.91, MA 13.92
Meier, T. ............ HL 6.1, HL 31.1
Meier, Ulrich ..................O 40.8
Meier, Wolfgang ............... O 6.1
Meijers, Ralph .............. HL 44.86
Meinecke, Christoph .......AKB 50.55
Meinel, Klaus ................. O 34.7
Meinert, H. ................. MA 10.1
Meining, C. J. .............. HL 29.11
Meisel, D. C. ................ HL 15.8
Meisel, Daniel C. .............HL 15.7
Meisels, Ronald ....HL 28.8, HL 44.32
Meissner, G. ................HL 12.38
Meiwes-Broer, K.-H. ....... MA 13.88
Meiwes-Broer, Karl Heinz .....O 28.68
Meißner, Daniel .............. MA 6.9
Melcher, S. ................. MA 15.9
Melinte, S. .................. HL 29.2
Mellenthin, Jesper .......... DY 46.36
Mellinger, Axel ............CPP 15.47
Melnikov, Alexander ........ HL 44.21
Melnikov, Alexey ........... MA 28.14
Melzer, Andrea ................O 37.1
Men, Yongfeng ............. CPP 13.6
Mena-Osteritz, Elena .......SYOH 1.1
Mendach, Stefan ....HL 5.9, HL 12.93
Mende, Werner ...........AKSOE 3.4
Mendez, H. ...............SYOH 5.38
Mendez, Henry ........... SYOH 5.36
Mendez-Bermudez, J. A. ....DY 46.41
Mendoza, F. ................. HL 50.1
Menk, Ch. ..................HL 12.13
Mennerich, C. ...............MA 21.5
Mennicke, Ulrike .......... AKB 50.66
Menzel, D. .. MA 13.7, MA 13.103,
TT 30.11
Menzel, Henning ........... CPP 10.2
Merfeld, D. .................. HL 16.1
Mergel, Dieter ................ DS 6.5
Mergell, Boris ............AKB 50.123
Merkel, M. .................. O 28.51
Merkel, Rudolf ............. AKB 21.1
Merkt, Domnic . CPP 16.5, DY 15.1,
DY 17.1
Merkt, Florian S. ............ DY 15.3
Merkt, Ulrich . MA 13.25, MA 13.68,
MA 13.91, MA 13.92
Merlo, Matteo ............... HL 22.6
Merschdorf, M. ............... O 45.6
Mertens, V. ..................HL 12.2
Mertig, I. .............. O 3.3, O 24.5
Mertig, Ingrid ...DF 5.14, DS 12.2,
MA 4.5, MA 13.30, MA 31.7
Mertig, Michael .... AKB 50.71, O 4.7
Mertinat, Markus ............ M 18.21
Mertins, H. C. ...............MA 10.6
Mertins, Hans-Christoph .. O 28.78,
O 28.80, O 28.82, SYXM 1.1
Mertz, Denis .......MA 13.99, TT 9.2
Merz, H. .................... O 28.31
Merz, M. ................. AKB 50.75
Merz, Matthias ........... AKB 50.79
Merz, Michael ............... TT 14.5
Meschede, Andreas ......... DS 22.20
Messlinger, Sebastian ..........O 32.4
Methling, R.-P. .............MA 13.88
Methling, Ralf-Peter ..........O 28.68
Metzger, T. H. .... HL 12.62, O 28.52
Metzger, Till H. ..............O 14.44
Metzler, Ralf ............... SYLS 3.5
Metzner, C. .........HL 42.1, HL 43.5
Metzner, Claus ................HL 4.9
Metzner, H. ....HL 12.6, HL 12.7,
HL 24.6, HL 30.5
Metzner, Walter ...TT 24.9, TT 24.10
Mewe, Agnes A. ...............O 10.1
Meyer, Andreas . DF 4.10, DY 29.10,
M 7.1
Meyer, B. K. .. HL 12.85, HL 17.10,
HL 17.11
Meyer, Bernd ................ O 14.66
Meyer, Bruno K. ...HL 17.9, HL 17.13
Meyer, C. ..................MA 13.85
Meyer, Christian ............. HL 37.2
Meyer, G. ........... TT 3.11, TT 6.7
Meyer, Gereon ................MA 5.2
Meyer, Hans-Georg HL 12.29, TT 13.1,
TT 29.4
Meyer, Karsten .............. TT 15.4
Meyer, N. ................ SYOH 5.27
Meyer, R. ....................HL 20.5
Meyer, S. .................SYOH 5.29
Meyer, Stefan .................O 44.1
Meyer, Thorsten ...........CPP 15.39
Meyer zu Heringdorf, F.-J. . O 28.74,
SYOH 5.14
Meyer-Hermann, Michael .AKB 50.104
Meyer-zu Heringdorf, F.-J. ....O 14.40
Meyerheim, H. ... MA 13.13, MA 15.5
Meyerheim, H. L. ............. O 39.9
Mi, Shaobo ...................M 31.2
Mibu, K. ....................MA 20.3
Michael, Wagenknecht .......MA 22.1
Michaelis, B. ... AKB 50.3, SYLS 3.24
Michaelis, Björn ............. TT 26.8
Michaelis, W. .............SYOH 5.28
Michaelis, Wilfried ........ SYOH 5.25
Michalke, Thordis ............. O 11.2
Michalke, Wolfgang .........DS 22.22
Michel, C. ................... HL 41.3
Michel, H. ...... SYLS 3.9, SYLS 3.13
Michel, Mathias ..TT 17.28, TT 29.11
Michele, O. .. MA 13.74, MA 13.79,
MA 13.80
Michele, Oliver .............MA 13.78
Michels, D. ...................M 21.4
Michelswirth, Martin ...... CPP 16.19
Michely, Thomas ..O 14.28, O 25.1,
O 32.4, O 39.10
Michler, P. ...................HL 36.7
Michutta, Jens .............. M 18.20
Mick, U. ......... MA 10.1, MA 13.43
Micklitz, H. ................MA 13.26
Miclea, Paul ................. HL 20.6
MICOS ........................FB 30
Micoulet, alexandre .........AKB 50.7
Middeke, Jürgen ............... O 5.5
Miehe, Gerhard ............ MA 13.82
Mientus, Rainald ............DS 22.57
Mikhailov, Alexander S. ...... DY 22.1
Mikitik, Grigorii P. ........... TT 31.3
Mikulla, Michael ..HL 38.10, HL 38.12
Mikuszeit, Nikolai MA 13.15, MA 26.10
Mila, F. .......................O 17.7
Milbradt, Alexander ....CPP 13.8,
SYLS 4.4
Mildner, Beate ...............DS 12.3
Miller, R. .................. SYPF 2.4
Miller, S. .......... HL 38.3, HL 44.84
Miller, Stephan ..... HL 27.5, HL 38.5
Miller, Tom ...................O 11.1
Milliron, Delia ............. SYOH 8.1
Miltat, Jacques ..............MA 25.1
Milun, Milorad ...............O 14.37
Mimkes, Jürgen .... AKSOE 3.12,
AKSOE 8.1
Minakov, Alexander .........CPP 13.3
Minar, J. ....................MA 4.11
Minerva, Tommaso ....... AKSOE 1.3
Mingaleev, Sergei ............ HL 15.3
Minár, J. .....................MA 6.2
Minár, Ján ..................MA 6.13
Mirea, A. .................SYOH 5.89
Miri, MirFaez .............. SYPF 2.1
Mirlin, A. D. .................HL 14.2
Mirlin, Alexander .TT 11.11, TT 17.15
Mirloup, Fabien ............ CPP 10.5
Mirmelstein, Alex .......... MA 13.66
Mirsky, Vladimir ............. O 14.54
Mishina, Elena .............. MA 22.3
Misof, B. M. ..............AKB 50.86
Mitdank, R. ................. TT 8.43
Miteva, Tzenka ............ SYOH 2.4
Miyasaka, S. ............... TT 24.48
MKS Instruments ..............FB 31
Mocanu, Carmen ........... TT 30.19
Mocuta, Cristian .............DY 10.4
Modrow, Hartwig ............. M 10.3
Möbius, Arnulf .............. DY 40.6
Möhwald, H. ..........O 6.5, O 28.86
Möller, A. ...........TT 3.11, TT 6.7
Möller, Björn M. .............HL 15.6
Möller, Kristof ....... HL 33.4, O 40.4
Möller, M. ...................O 28.42
Moeller, Martin .....CPP 15.4, O 32.5
Möller, Rolf .O 14.63, O 14.69, O 17.3
Möller, W. ........ DS 15.6, DS 22.34
Möller, Wolfhard .............O 40.10
Mönch, Ingolf . DS 22.40, MA 13.97,
MA 13.107
Mönnich, Alexander O 14.7, O 28.53,
O 37.3, SYOH 3.2
Moers, Jürgen ............... HL 10.3
Möwald, Melmuth .......... CPP 13.5
Mößle, Michael .............. TT 18.6
Mogadalai Pandurangan, Gururajan
M 18.22
Mogilatenko, A. .. DS 22.10, DS 22.11
Mohles, Volker ................M 25.1
Mohn, E. .............M 13.1, M 13.3
Mohr, Martina ..............HL 12.96
Mohrdieck, Camilla .........AKB 10.4
Mokrousov, Yuriy ............MA 26.9
Autorenverzeichnis
Molenda, D. .................. O 23.1
Molenkamp, L. ....HL 29.10, MA 31.5
Molenkamp, L. W. HL 29.3, HL 29.7,
HL 29.8, HL 29.11
Molenkamp, Laurens ......... HL 29.4
Molenkamp, Laurens W. ..HL 37.10,
HL 44.20, HL 44.31, HL 49.3
Molière, Eugène ..... DF 4.7, DY 29.7
Molodtsov, S. ............... MA 13.4
Molodtsov, S. L. ............... O 3.4
Molodtsov, Serguei . MA 13.2, O 4.7,
O 44.5
Molodtsova, Olga .........SYOH 5.32
Moloney, Jerome V. .HL 32.4, HL 32.5
Molony, Jerry V. ............. HL 32.3
Molter, Stephan ...........CPP 16.19
Monecke, Jochen ........... HL 44.54
Monemar, B. ..... HL 44.79, HL 44.80
Monetti, Roberto ............ DY 20.6
Monien, Hartmut ............ TT 16.9
Monroy, Eva .................HL 16.6
Monz, Stefan ................. M 26.3
Moodera, J. S. ... MA 13.65, MA 14.2
Moor, Alexander .......... AKB 50.96
Moosavi, Ali .................DY 46.3
Moosburger-Will, Judith .......O 44.3
Morais, J. ................ MA 13.114
Moran, Oswaldo ..MA 13.21, MA 20.9
Morawetz, K. .. CPP 11.5, DY 14.9,
O 6.5, TT 8.49, TT 9.12, TT 30.17,
TT 30.30
Morawski, Markus .........AKB 50.55
Morchshakov, V. .......... MA 13.115
Mordvintsev, Dmitry .......CPP 15.20
Moresco, Francesca ........... O 21.1
Morfill, Gregor ...............DY 20.6
Morgenstern, K. ...............O 31.1
Morgenstern, Markus ....HL 37.2,
HL 44.61, O 5.8, O 14.29, O 14.71,
O 23.6, O 39.2, PV VII
Morgner, U. .................. HL 4.1
Morita, Shinichi ............ DY 46.73
Moritz, Wolfgang ............. O 40.9
Morkel, Matthias ......O 26.4, O 31.7
Moroder, Luis ....CPP 13.8, SYLS 4.4
Morschbacher, M. .............DS 1.1
Mosbacher, M. ...............O 28.13
Mosch, Christian .............. O 26.9
Moschkau, P. .....MA 13.65, MA 14.2
Moser, Andreas ............. MA 26.5
Moser, Günter ............... DY 46.6
Moser, Jürgen ............... HL 44.3
Moshnyaga, Vasily MA 13.23, MA 22.3
Moske, Michael . DS 22.23, MA 24.5,
MA 24.6
Moskvin, A. .................. TT 3.9
Moskvin, A. S. ............. TT 26.13
Mosor, Sorin .................HL 28.4
Mostovoy, Maxim ............TT 14.1
Motaghi, Mohammad ..... SYOH 5.68
Motschmann, Hubert ... CPP 10.4,
CPP 12.5
Mryasov, Oleg ...............MA 28.2
Much, Anja ................ TT 30.28
Much, F. .................... O 14.31
Muck, T. ..SYOH 5.62, SYOH 5.64,
SYOH 5.65
Muckenfuss, Heinz ............ LTR X
Mücke, O. D. ................. HL 4.1
Mückl, Anton G. ..........SYOH 5.79
Mücksch, Michael ............TT 14.4
Mühl, Thomas .... MA 13.107, O 24.7
Mühle, A. .................. HL 44.27
Müllegger, S. ................. DS 7.4
Muellegger, Stefan ........SYOH 5.12
Müllen, Klaus .............SYOH 5.80
Müller, A.-D. ... HL 10.4, HL 31.6,
O 14.83, O 24.10
Müller, Anne-D. ............. DS 18.5
Müller, Anton ............... TT 12.2
Müller, Axel H. E. .........CPP 16.32
Müller, B. ................... TT 8.46
Müller, B. H. ............... HL 44.25
Müller, Bernd ................O 14.42
Müller, C. ...................MA 15.7
Müller, Christian ............ MA 18.5
Müller, F. HL 10.4, HL 31.6, O 14.23,
O 14.83, O 19.7, O 24.10, O 38.7
Müller, Falk ...... DS 18.5, SYOH 5.3
Müller, Frank ................ HL 15.4
Müller, Gerhard ............ MA 13.57
Müller, Hans ......... TT 8.5, TT 8.6
Müller, I. ....................M 18.15
Müller, Ingo ..M 10.2, M 10.3, M 16.4
Müller, J. DS 4.1, HL 15.12, HL 50.4,
MA 18.2
Mueller, Juergen ..........SYOH 5.83
Müller, K.-H. ..MA 18.3, MA 20.11,
MA 22.2, TT 6.4, TT 8.47, TT 9.6,
TT 9.9
Müller, Karl-Hartmut ... MA 11.6,
MA 11.8, MA 11.10, MA 26.3,

TT 31.6
Mueller, Karla ..............AKB 12.1
Müller, Kerstin ....HL 50.8, SYOH 2.2
Mueller, Klaus HL 44.42, SYOH 5.74,
SYOH 5.75
Müller, L. ................... DF 5.10
Mueller, Marcus AKB 50.18, CPP 14.8
Müller, Martin . O 14.44, SYLS 3.47,
SYLS 3.53
Müller, Martina .............. HL 11.1
Müller, Matthias ............DY 46.77
Müller, Michael ............... O 39.6
Müller, Paul ................. TT 8.25
Müller, Petra ..............SYLS 3.11
Müller, R. ....TT 8.43, TT 14.14,
TT 14.14, TT 30.16, TT 30.36
Müller, S. ...................MA 24.4
Mueller, S. C. .............. DY 46.29
Müller, Sebastian .DY 27.6, DY 27.7,
DY 50.4
Müller, Stefan .M 8.1, M 11.1, O 6.1,
O 6.7, O 43.8
Müller, Stefan C. .... AKB 50.60,
AKB 50.118, DY 15.6, DY 20.4,
DY 20.5, DY 46.24, DY 46.34
Müller, T. .................... HL 3.6
Müller, Thomas .....DS 15.3, DS 15.5
MÜLLER, Uli ............. CPP 15.36
Mueller, Ulrich .. CPP 2.6, CPP 7.5,
CPP 15.3
Müller, Volkmar ...............DF 7.5
Müller, W. .................MA 13.20
Müller-Buschbaum, P. ...CPP 11.3,
CPP 14.9, CPP 15.7, CPP 15.8,
CPP 15.9, CPP 16.24
Müller-Groeling, Axel ....... SYFT 2.1
Müller-Hartmann, Erwin ......TT 26.4
Müller-Kirsch, L. .............HL 3.10
Müller-Krumbhaar, H. ........DY 25.4
Münch, Andreas .....CPP 15.22,
CPP 15.27
Münzenberg, M. MA 13.58, MA 13.59,
MA 13.65, MA 14.2
Müssig, Hans Joachim .........DS 9.3
Muessig, Hans-Joachim ... DF 6.6,
HL 31.3
Muffler, H. ................. DS 22.56
Muffler, H.-J. ................DS 21.3
Mugele, Frieder ..CPP 1.2, DY 15.2,
DY 17.2, DY 26.5, O 46.3
Mugrauer, S. ............... SYLS 3.4
Mukhin, Alexander .......... MA 21.8
Mukhopadhyay, Nilay Krishna . M 31.4
Muljarov, Egor ...............HL 36.2
Munayco, K. E. ............. MA 6.11
Munk, Tobias ............. AKB 50.20
Munoz-Javier, A. ..........CPP 16.34
Munzel, Marco ............. DY 46.64
Munzinger, Michael .......... O 28.76
Muraki, K. ...................HL 14.4
Muramatsu, Alejandro TT 4.3, TT 26.2
Murani, A. .................. TT 30.4
Murphy, Bridget ............. O 14.44
Musiol, Hans-Juergen .......CPP 13.8
Muske, Martin ...DS 4.4, DS 20.2,
DS 22.49
Mussawisade, Kiaresch ....... DY 51.7
Máca, Franti˘sek ..............O 28.81
Málek, J. .......... TT 3.9, TT 26.13
Méndez-Sánchez, R. A. ..... DY 46.40
Naber, A. ......... O 23.1, SYLS 3.10
Naber, Andreas ............SYLS 3.16
Nachtmann, Niklas ........ SYLS 3.12
Nachtrab, Timo ....MA 22.1, TT 18.7
Nachtwei, G. ..... HL 12.42, HL 12.43
Nachtwei, Georg ............ HL 12.41
Nadai, C. de ................TT 24.46
Nadrowski, Björn ..........AKB 50.65
Nagaev, Kirill .............. SYSN 2.5
Nagel, Peter .................TT 33.1
Nagler, Jan ................ SYFT 2.3
Naidyuk, Y. ................. TT 8.47
Naito, M. ................... TT 18.4
Naito, Michio .........TT 1.1, TT 8.3
Naji, Ali ...................SYLS 3.37
Nakabayashi, Seiichiro ....... MA 22.3
Nakajima, T. ............... TT 24.52
Nakano, H. ..................TT 29.3
Nakatani, Yoshinobu .........MA 25.1
Nakatsuji, S. .. TT 3.12, TT 14.14,
TT 14.14, TT 30.36, TT 30.38,
TT 30.38
Nakhmedov, E. P. .......... TT 30.30
Nanofilm ...................... FB 32
nanonic ....................... FB 33
NanOp - Kollaboration ....... HL 43.4
Narozhnyi, V. N. ..............TT 9.9
Natali, Francesca ............ CPP 4.1
Nateprov, A. ............... TT 24.39
Nath, R. .................... TT 6.11
Natrup, Frank ............... O 14.75
Natusch, D. ................ HL 12.71
Nau, Dietmar ................. HL 2.5
Nau, S. ......................HL 25.5
Nauen, A. ........ HL 37.12, HL 44.28
Nauen, André .............. SYSN 2.3
Naundorf, Björn ............. DY 24.5
Navarro B., J. Emeterio ...AKSOE 3.6
Navratil, A. .... MA 13.19, MA 13.103
Nawroth, A. P. ........... AKSOE 3.2
Nawroth, Thomas ........AKB 50.122
Nazarov, Yuli ................TT 11.5
Nazarov, Yuli V. ............SYSN 1.3
Ndawana, Macleans L. ....... TT 30.7
Neddermeyer, Henning ........ O 34.7
Neeb, D. ....................MA 28.8
Neeb, Daniel ................ MA 6.12
Neef, Matthias ................TT 7.3
Nefedov, Alexei . MA 10.2, MA 20.5,
MA 20.8, MA 30.8, O 12.1,
O 28.79, O 28.85
Neff, Petra ................ SYLS 3.32
Neff, Petra A. .............AKB 50.36
Neges, Matthias ..... DS 21.4, O 40.4
Negm, N. Z. .................DS 15.6
Negrini, Christine ............. M 10.2
Neher, Dieter .CPP 10.2, SYOH 5.46,
SYOH 5.72, SYOH 5.80,
SYOH 5.81
Neher, Richard ............. DY 46.87
Neisius, Thomas .............MA 30.1
Nekrasov, I. ................. TT 24.1
Nelke, Dorit ................. DS 13.2
Nelles, G. .....................O 14.1
Nelles, Gabriele ............ SYOH 2.4
Nelson, Christie S. ........ MA 13.118
Nelson, David R. ...............PV IV
Nemanich, Robert J. ........... O 5.1
Nembach, Hans . MA 10.3, MA 10.5,
MA 28.9
Nemetschek, R. ..............TT 8.12
Nenkov, K. ................... TT 9.9
Nenkov, Konstantin MA 11.6, TT 8.51,
TT 31.6, TT 31.10
Nepijko, S. A. . DS 22.27, DS 22.28,
MA 28.8, O 28.75
Nest, Mathias ............... DY 50.2
Nestle, Nikolaus ..... CPP 3.2, LTR V
Nestler, Britta .. M 4.3, M 4.4, M 18.5
Neto, Chiara .. CPP 15.22, CPP 15.27
Netsch, A. ................. DY 46.91
Netz, Roland .SYLS 3.37, SYLS 3.38,
SYLS 3.39
Netzel, C. .................. HL 27.10
Neu, V. MA 13.18, MA 15.8, MA 15.9
Neu, Volker ..... MA 13.17, MA 15.10
Neuberth, U. ..................HL 8.4
Neubrand, Tobias ............. O 20.2
Neudecker, Ingo ............MA 28.13
Neudert, Andreas .............MA 7.1
Neugart, Felix .............AKB 50.63
Neugebauer, J. .......HL 27.7, O 17.8
Neugebauer, Jörg . HL 17.8, HL 53.2,
SYLS 3.18, SYLS 3.22
Neuhäuser, Hartmut . M 7.3, M 25.3,
M 25.4, M 30.3, M 30.4
Neuking, Klaus .............. M 18.20
Neumaier, Karl ....TT 17.5, TT 30.21
Neumann, Christian .........HL 17.13
Neumann, Frederik ........SYOH 5.77
Neumann, H. ....... DS 9.7, DS 22.46
Neumann, Horst .............. DS 3.3
Neumann, M. ................TT 33.3
Neumann, Manfred ... CPP 16.19,
MA 11.5
Neumann, S. ..................HL 9.4
Neumann, Wolfgang .......... M 15.1
Ney, Oleksandr ................O 34.3
Ngaruiya, J. M. .............. DS 18.3
Nguyen-Duong, Melanie .... AKB 21.1
Nickel, Bert .............. SYOH 5.15
Nickels, Patrick ............ SYOH 5.7
Nie, Jingjing .............. SYLS 3.50
Niedereichholz, T. . CPP 16.34, O 19.6
Niegemann, Jens .............HL 20.7
Niehus, H. .................. CPP 6.2
Niehus, Horst CPP 1.4, O 5.5, O 28.58
Nielaba, Peter . DY 46.48, DY 46.49,
DY 46.50, DY 46.85, TT 17.7
Nielinger, Michael ............O 14.18
Niels, Hovenier ...............HL 38.7
Nielsch, Kornelius MA 13.55, MA 29.1
Nielsen, Karl-Wilhelm ........ HL 44.9
Nielsen, Torben Roland .......HL 36.6
Niemax, J. ..SYOH 3.1, SYOH 5.61,
SYOH 5.67
Niemeyer, Andrea ........... MA 27.8
Nienhaus , G. Ulrich ...AKB 50.12,
HL 44.36, SYLS 2.2, SYLS 3.14
Nierlich, Wolfgang ............ M 17.1
Niermann, T. .........M 18.2, M 24.4
Niermann, Tore .............HL 44.62
Niesen, T. P. ... HL 12.5, HL 24.2,
HL 24.3
Niesert, Manfred .............DS 12.1
Nietubyć, Robert ..............O 25.9
Nietuby`c, Robert .......... SYXM 1.6
Nieuwenhuizen, Theo M. .. AKB 50.44
Niki, Shigeru .................O 40.11
Nikitin, Eugen ............... M 18.25
Nikolaides, Michael G. ..AKB 50.36,
DY 46.97, SYLS 3.32
Nikonenko, N. ...............CPP 8.6
Nikopoulos, Renate .......... DY 17.2
Nilius, N. ..................... O 10.5
Nilius, Niklas ...................O 2.1
Nilsson, A. ....................O 44.8
Nirschl, Thomas ............. HL 10.5
Nishimoto, Satoshi .... TT 24.17,
TT 24.18
Nishio, K. ...................MA 14.1
Nitsche, Robert ..........O 4.1, O 4.8
Nitzsche, Ulrike .. MA 3.4, MA 8.7,
MA 8.9, TT 8.50
Njiokep, Tanguep .... DF 4.7, DY 29.7
Noack, Reinhard ............TT 24.21
Noack, Reinhard M. ........ TT 24.18
Nobis, T. ...................HL 12.71
Nobis, Th. ..........HL 17.5, HL 17.5
Nobis, Thomas .... HL 12.89, HL 17.3
Nogues, J. ................. MA 13.44
Nogués, J. ....MA 10.8, MA 14.1,
MA 28.11
Noh, T. W. ...............MA 13.123
Noh, Yong-Young ............. O 33.1
Nojiri, Hiroyuki ..............MA 21.1
Nolte, Markus ............... CPP 3.2
Nolte, Stefan ....... HL 2.3, HL 15.11
Nolting, W. ... MA 8.8, MA 13.20,
MA 13.95
Nolting, Wolfgang ..MA 16.1, TT 15.2
Northrup, J. E. .............. HL 27.7
Nosova, L. ....................DF 5.3
Nothardt, Axel ............. TT 30.28
Nouveau, Corinne ............DS 14.5
Novikov, Alexey ............ DY 46.44
Novikov, Dmitri V. ............ O 13.1
Nowak, Christian ..........AKB 50.10
Nowak, Gregor ... MA 10.2, MA 13.42
Nowak, Ulrich . MA 10.10, MA 17.4,
MA 27.3, MA 28.2
Nowitzki, Tobias ............HL 12.15
Nücker, N. .................. TT 14.5
Nummsen, Kai ...............TT 12.2
Numssen, Kai ............... TT 8.31
Nunner, Tamara ............. TT 3.14
Nussbaumer, Thomas ...SYNF 1.4,
TT 27.11
Nußbaumer, Andreas .........DY 16.2
Nédélec, R. .................HL 44.49
O., Robach .......... MA 4.1, MA 4.3
O’Neill, Robin ...............MA 10.4
Obermeier, Günter ............ TT 6.8
Oberschmid, R. .............. HL 10.1
Obradors, X. .................TT 8.14
Obukhov, Yuri N. ............. TT 6.2
Ocaña, Roberto ..............TT 20.3
Ocelic, Nenad .................DF 6.5
Odelius, M. ................... O 44.8
Odenbach, Stefan DY 11.1, DY 46.75,
SYPF 4.3, SYPF 4.5
Oelhafen, P. ..................MA 6.3
Oellerich, Silke ............ SYLS 3.21
Oelsner, A. .........MA 28.8, O 28.34
Oelsner, Andreas ............ MA 6.12
Oepen, Hans Peter ....MA 13.15,
MA 26.10
Oertel, C.-G. ................ MA 15.8
Oertel, Carl-georg ..M 22.3, M 22.3,
M 22.4, M 27.2
Oertker, S. .......MA 10.8, MA 28.11
Oestreich, M. ................ HL 43.2
Oestreich, Michael .HL 4.7, HL 12.15,
HL 12.47, HL 41.2, HL 44.6,
HL 44.52, HL 44.53
Offenhäusser, Andreas ......AKB 30.2
Offi, F. MA 4.2, MA 13.53, MA 16.3,
MA 28.10
Ohe, Jun-Ichiro ............. HL 29.12
Ohlerich, Martin .............DY 34.6
Ohm, Torsten ............... TT 24.3
Ohresser, Philippe ........... MA 10.7
Ohta, Yukinori ..............TT 24.17
Ohtsuki, Tomi .............. HL 12.44
Okorokov, Alexey ......... MA 13.102
Olapinski, Michael ........... O 28.49
Oldenburg Wissenschaftsverlag . FB 34
Oles, Andrzej M. ........... TT 24.44
Oleynik, Nikolay ... HL 12.78, HL 21.3
Oliverio, Rodriguez-Fernandez
DY 46.82
Olk, Phillip .................. O 28.54
Ollinger, Christoph ... AKB 50.62,
AKB 50.68
Oosawa, A. .................TT 30.31
Oosterkamp, T. H. ............ O 23.7
Autorenverzeichnis
Opahle, Ingo MA 3.4, MA 8.7, MA 8.9,
MA 13.99, TT 24.36
Opel, M. ....................MA 13.5
Opel, Matthias MA 13.27, MA 13.39,
MA 13.116
Opfermann, Th. ...............DS 1.8
Opitz, Andreas .. DS 22.5, SYOH 5.55
Opitz, T. ...AKB 50.3, AKB 50.17,
SYLS 3.24
Oppeneer, Peter ........... SYXM 1.1
Oppeneer, Peter M. O 28.78, O 28.80,
O 28.81, TT 24.36
Opper, Manfred ............. DY 21.4
Oppermann, Reinhold ........TT 21.4
Orendorz, A. .................DS 12.6
Orlamuender, Dirk ........AKSOE 3.4
Orlinski, S. ................. HL 17.11
Ortega, E. .................... O 39.3
Ortner, Gerhard .............HL 44.34
Ossó , J. Oriol ......... DS 7.2, O 4.4
Ostendorf, Frank ............... O 3.1
Ostendorf, R. ................ O 28.31
Oster, Jens .................. TT 8.29
Osterloh, Andreas ............DY 50.1
Ostrauskaite, Jolita .........CPP 10.1
Otani, O. ....................TT 8.47
Ott, Albrecht .............. AKB 12.3
Ott, H. .......... TT 14.11, TT 30.12
Ott, Holger ................ MA 13.85
Ott, M. ......................O 28.42
Ott, Marcell ................. O 28.54
Ott, N. ......................HL 30.2
Otte, Kai ....................HL 21.4
Otte , Karsten ...... DS 21.5, HL 12.4
Otten, Alexander CPP 13.7, CPP 14.3,
SYLS 3.50
Ottersbach, Peter .......... SYNP 2.3
Otto, Andreas .................O 18.8
Otto, F. .................... MA 24.4
Otto, Tobias ..................DF 1.3
Ouacha, H. ................... O 19.4
Ouchi, Yukio .................O 14.55
Ovsyanko, Michail .............O 39.1
Owen, Anthony ..............CPP 7.4
Oxford Applied Research ....... FB 35
Oxford Instruments ............ FB 36
Ozaki, M. .................. HL 15.13
P., Bruno .................... MA 4.1
Paarmann, Alexander ....... HL 36.11
Paasch, Gernot . HL 10.2, SYOH 4.2,
SYOH 5.69
Paaske, J. ..................TT 11.13
Paetzold, A. ............... MA 13.48
Paez Sierra, Beynor Antonio
SYOH 5.37
Paggel, J. J. ..MA 15.7, O 9.6, O 25.3
Paggel, Jens .................. O 11.1
Paggel, Jens J. ......... O 5.3, O 37.6
Pai, Ranith Krishna ........CPP 15.12
Pala, Marco G. ..... HL 29.9, HL 49.2
Paladino, Elisabetta ..........TT 22.6
Palberg, Thomas CPP 12.1, CPP 12.3,
DY 46.46, DY 46.52, DY 46.55,
DY 46.56, DY 46.66, DY 51.2
Palinkas, Gabor ............... O 18.3
Pallaoro, Alessia ............. O 14.62
Paloumpa, Ioanna .........SYOH 5.75
Pamler, Werner .............. HL 46.1
Pampaloni, Francesco .... AKB 50.132
Panagiotou, P. ............. CPP 15.9
Panchenko, Elena ............ DS 13.2
Pankrath, R. ..................DF 7.4
Pannemann, Christoph ... HL 23.2,
SYOH 5.22
Pannetier, Bernard ......... SYSN 1.2
Panofen, C. .................HL 44.68
Pantazis, Periklis ..........AKB 50.49
Pantförder, J. ... O 14.15, O 18.2,
O 28.61
Panzner, Tobias ................ O 6.5
Papadakis, Christine M. .. CPP 1.1,
CPP 15.13, CPP 16.30
Papathanasiou, Olga ......... DS 21.1
Papp, C. .............O 14.9, O 14.12
Paprotta, S. ................ HL 44.25
Parak, W. J. .............. CPP 16.34
Parak, Wolfgang ........... AKB 22.3
Parge, A. ........ MA 13.58, MA 14.2
Parge, Anne .................MA 30.1
Paris, O. ..................AKB 50.86
Paris, Oskar ...AKB 50.30, AKB 50.71
Parisi, Andrea ..................M 4.2
Parisi, J. .....................HL 12.2
Parisi, Jürgen ..CPP 3.3, CPP 16.6,
HL 23.5, SYOH 5.56, SYOH 5.70
Park, C.-M. .......... M 12.4, M 12.4
Park, Icksoon ................ HL 38.2
Park, J. P. ................. MA 13.62
Park, W. G. ...... MA 10.1, MA 13.43
Parmeggiani, Andrea .. AKB 50.103,
DY 14.6
Parpia, Jeevak M. .......... TT 17.29

Partyka, Ewa ................ M 18.11
Pasa, A. A. ..................CPP 6.2
Paschen, S. ................ CPP 10.7
Paschke, C. ................ TT 17.11
Pascual, J. I. ..................O 17.8
Pasenow, B. .................. HL 6.1
Pashitskii, Ernst ............. TT 24.6
Pashkevich, Yu. .............TT 24.51
Pasold, G. ................... HL 27.8
Pasold, Gunnar .............. HL 40.3
Passmann, R. ................ O 14.59
Paterlini, Sandra ..........AKSOE 1.3
Pattarin, Francesco ....... AKSOE 1.3
Patthey, F. ....................O 17.7
Patthey, François ............ O 14.14
Paufler, Peter .................M 31.4
Paul, Anne ....................O 33.3
Paul, Neelima .................O 32.7
Paul, Tobias .................. TT 4.8
Paul, Wolfgang ..... CPP 15.48,
CPP 15.49, SYFT 3.1
Paulose, P. L. .................M 22.2
Pauls, C. ..................... O 26.7
Paulsen, Harald ..........AKB 50.124
Paulus, Beate ........ M 5.2, TT 32.2
Paulus, Hartmut ...DS 1.2, DS 1.3,
DS 3.6
Paulus, Michael ....... HL 11.5, O 6.3
Paulus, Ursula A. .. O 20.1, O 20.3,
O 38.9
Pauly, Fabian ....SYOH 5.59, TT 27.7
Pavarini, E. ..................TT 32.7
Pavlova, Tatjana ......M 25.3, M 25.4
Pavlyukh, Yaroslav .... O 37.5, O 44.2
Pawelzik, Klaus ...........AKSOE 3.3
Peano, Vittorio ............. TT 22.11
Pecz, Bela ...................DS 18.2
Pedarnig, Johannes D. ....... DS 17.3
Peguiron, Joël .............. DY 46.14
Pehlke, Eckhard .....O 14.16, O 14.52
Peibst, Robby .............. DY 46.10
Peil, Michael ................ DY 36.1
Peinke, J. ......AKSOE 3.2, DY 46.64
Peinke, Joachim ...DY 40.3, SYFT 1.1
Peisert, Heiko ............ SYOH 5.24
Peißl, Sven ....................O 24.2
Peksa, Ladislav ................VA 2.3
Pelargus, Christoph ........ SYLS 3.28
Pelekanos, Nikos .............. HL 9.1
Pels, Christian ..MA 2.2, MA 13.25,
MA 13.91, MA 13.92
Pelster, Axel ... DY 10.3, DY 26.4,
DY 34.5
Pelz, J. ....................... O 17.7
Penc, Karlo ................ TT 32.11
Peng, Bin .................CPP 16.33
Peng, D. L. ................ MA 13.80
Pennec, Y. .................MA 28.10
Penner, J. ................... DF 5.11
Pensl, G. ................... HL 17.10
Pensl, Gerhard .. HL 30.6, HL 52.1,
HL 52.2, HL 52.3
Pentcheva, Rossitza ........... O 29.1
Pentegov, Vsevolod .......... TT 24.6
Penzel, Thomas ............. DY 36.6
Pereira, S. ............ HL 1.1, HL 8.4
Pereira, Suresh . HL 12.30, HL 12.31,
HL 12.37
Perepezko, John H. ........... M 14.1
Pereverzev, S. V. ... TT 4.7, TT 17.30
Perez Foullerat, David ....... CPP 1.3
Perfetti, Luca ...............HL 44.66
Perlov, Alexander .............MA 8.3
Perner, Olaf ................TT 31.10
Peron, Nicolas ..............SYPF 1.1
Perroud, Olivier ............. MA 11.7
Persson, J. ................. TT 24.54
Persson, N. C. ............... HL 23.6
Pertsev, N. A. ................ DF 6.7
Peruzzi, Martin .............. DS 17.3
Pervan, Petar ................ O 14.37
Perzlmaier, Korbinian ... MA 28.5,
MA 28.7
Peschel, Olaf ................ TT 32.4
Peschel, Ulf .........HL 6.2, HL 15.11
Pescia, Danilo ...............MA 28.5
Peteline, Serguei ..............M 10.6
Peter, Ronny ............ AKB 50.114
Peters, Margret ..............TT 8.22
Peters, R. ................. SYLS 3.10
Peters, Ralph Jürgen .......... VA 3.2
Peters, Reiner .............. SYLS 2.1
Peters, Robert .............. MA 30.3
Petersen, Jan ...............DS 22.14
Petkov, Nikolay ..............CPP 9.3
Petr, Andreas .............SYOH 5.24
Petracic, O. ...... MA 13.84, MA 14.1
Petrov, Alexander ............ HL 20.3
Petrov, Peter G. .......... AKB 50.92
Petruccione, Francesco .......TT 22.3
Petry, W. .................. CPP 14.9
Pettenkofer, Christian ... DS 20.4,
DS 21.1, O 19.2, O 28.29, O 40.8,
O 40.11
Petter, K. ................... HL 28.7
Petter, Kai .................. DS 20.1
Pettersson, L. G.M. ........... O 44.8
Petty, Sarah A. ............. SYLS 4.3
Petukhov, Konstantin .......TT 24.35
Pezoldt, Jörg ....... HL 40.1, HL 40.2
Pfab, Robert ................ CPP 9.5
Pfaff, G. ...................SYNP 2.4
Pfalz, Stefan ........HL 4.7, HL 12.15
Pfalzer, P. ................ MA 13.101
Pfannkuche, D. .............. HL 42.2
Pfannkuche, Daniela ....HL 12.45,
HL 22.5, HL 44.29, HL 44.30
Pfeifer, P. ................... O 28.61
Pfeiffer, Frank Oliver ......... O 14.46
Pfeiffer, M. ...............SYOH 5.39
Pfeiffer, Martin ..... SYOH 5.40,
SYOH 5.42, SYOH 5.43,
SYOH 5.78, SYOH 5.82
Pfeiffer, W. .O 14.57, O 37.2, O 45.6,
TT 17.14
Pfeiffer, Walter .............. O 28.71
Pfersich, Wolfgang ..........TT 17.24
Pfisterer, D. ................ HL 17.11
Pflaum, J. ..SYOH 3.1, SYOH 5.29,
SYOH 5.44, SYOH 5.61
Pflaum, Jens SYOH 5.22, SYOH 5.60,
SYOH 5.72
Pfleiderer, C. ... TT 7.9, TT 10.3,
TT 21.1, TT 24.29, TT 24.31,
TT 24.38, TT 24.39
Pfnür, H. .. O 3.6, O 28.8, O 28.10,
O 28.24, O 34.1, SYOH 5.31
Pfnür, Herbert ... DF 5.13, O 14.8,
O 14.35, O 28.26, O 28.44, O 28.45
Pfohl, Thomas .CPP 13.7, CPP 14.3,
SYLS 3.50
Pfundstein, P. ..HL 12.72, HL 12.74,
HL 12.76
Phelan, K. ...................TT 13.7
Phelan, Kevin ............... TT 13.9
Philipp, Jan B. .MA 13.27, MA 13.116
Philipp, Jan Boris .. HL 44.9, MA 22.1
Philippe, Bourges ............. TT 2.3
Philippou, Alexander ......... HL 33.1
physikanten und co. ........... LTR II
Pi, U. H. ................. MA 13.123
Piancastelli, Maria Novella .....O 18.7
Piasta, D. .................... O 19.7
Pichler, Thomas .............. TT 9.7
Pickenhain, Rainer HL 12.84, HL 44.11
Pickett, W. E. ................ TT 3.9
Piel, Rainer ...............MA 13.120
Pientka, Michael CPP 3.3, CPP 16.6,
SYOH 5.49
Pierobon, Paolo ..........AKB 50.103
Pierz, K. HL 12.60, HL 37.12, HL 44.28
Pierz, Klaus ................SYSN 2.3
Pietronero, Luciano .......... DY 20.1
Pietsch, U. ....HL 3.3, O 6.5, O 28.86
Pietsch, Ullrich .............CPP 10.3
Pietzsch, Annette ............. O 45.5
Pietzsch, O. ....................O 8.1
Pietzsch, Oswald .. MA 4.7, MA 26.12
piezosystem jena ...............FB 37
Pilawa, Bernd ..... MA 21.6, MA 21.7
Pilgram, Sebastian ......... SYSN 2.5
Pimenov, A. .................TT 14.2
Pindl, Markus ................HL 38.1
Pinheiro, M. V.B. ............ HL 40.5
PINK ......................... FB 38
Pintschovius, Lothar .......... TT 2.1
Pionteck, J. ................. CPP 8.6
Piotrowska, Anna ............ HL 16.8
Pivetta, M. ................... O 17.7
Pivetta, Marina .............. O 14.14
Pizzini, S. ..................MA 28.10
Plaenitz, Philipp ............. M 18.23
Plagwitz, Heiko ..............DS 19.1
Plake, Tilo ...........O 28.29, O 40.8
Plakida, N. M. ............. TT 24.23
Plapp, Mathis ........ DY 25.6, M 4.2
Plazanet, Marie ............SYLS 3.26
plech, Anton ..CPP 10.5, DY 46.96,
O 28.40
Pleimling, Michel ..DY 12.1, DY 46.86
Plenio, Martin B. ........... TT 22.10
Pletea, Mirela .............. DS 22.31
Pletl, Thomas ............... CPP 4.5
Plettl, A. ........... DS 22.8, O 28.42
Plettl, Alfred O 3.2, O 28.50, O 32.5,
TT 31.7
Plikat, Boris ................ HL 44.62
Plock, Nico ..................O 14.65
Plöchinger .................... VA 2.5
Ploog, K. H. ........MA 3.2, MA 31.4
Ploog, Klaus H. ...............O 25.8
Plourde, B. L.T. ............. TT 29.5
Plyushchay, Inna ..............M 14.4
Poberaj, Igor ............... DY 46.18
Pochstein, Christian .........DS 22.24
Podbielski, J. .............. MA 13.63
Podbielski, Jan .............MA 13.64
Podgurski, Vitali ............ MA 20.1
Podgursky, Vitali ..............O 39.5
Podlesnyak, A. ...............TT 20.4
Podloucky, Raimund ........... M 8.1
Podsiadly, Jan .......MA 16.9, O 37.6
Podsiadly, Jan Peter .........MA 18.5
Podzimek, Daniel ..........CPP 15.38
Pöhlmann, Markus ...........DY 46.8
Pöllmann, S. O 14.15, O 18.2, O 28.61
Poelsema, Bene ....... O 10.1, O 39.1
Poenariu, Sorin ............. HL 12.64
Pöpperl, Tobias ............ CPP 16.7
Pötschke, K. .................HL 3.10
Pötschke, Konstantin .........HL 25.3
Pohl, H.-J. ...................HL 51.3
Pohl, U. W. ................. HL 3.10
Pohl, Udo W. .. HL 25.3, HL 28.10,
HL 33.3
Poissot, Martha ..............O 14.27
Polesya, Svitlana ........... MA 13.90
Polity, Angelika .............. HL 17.9
Polli, Dario ................ SYOH 2.2
Pollmann, Frank .............TT 32.5
Pollmann, J. O 14.47, O 28.72, O 40.7
Polop, Celia ..O 14.28, O 25.1, O 32.4
Polotsky, Alexey ............. CPP 2.2
Polyakov, D. G. ..............HL 14.2
Polychroniadis, E. K. ....... MA 13.79
Polzin, Stefan ................O 14.78
Pomar, A. ...................TT 8.14
Pompe, Tilo ..AKB 50.9, SYLS 3.2,
SYLS 3.46
Pompe, Wolfgang ... AKB 50.9, O 4.7
Ponkratov, Vladimir ........ SYLS 3.8
Ponpandian, N. ............. MA 15.1
Pop, D. ...................CPP 16.31
Pop, Loredana ...............DY 11.1
Popa, Iulian .. TT 17.22, TT 17.26,
TT 22.1, TT 22.2
Popescu, V. ....... MA 4.11, MA 6.13
Popescu, Voicu .MA 11.3, MA 27.10,
MA 30.2
Popolan, D. ..................O 28.64
Popov, Mikhail V. ............ M 27.4
Popovic, Dunja .............. O 11.10
Popović, Dunja ............... O 11.8
Poppe, U. .................... DF 6.7
Poprawe, R. ................. DF 5.10
porrati, fabrizio ...............MA 2.5
Porto, Markus ..............AKB 40.4
Posch, Harald A. ............ DY 40.1
Poschmann, Martin ....... AKB 50.96
Poser, F. .................... HL 43.4
Possart, Wulff .. CPP 2.6, CPP 7.3,
CPP 8.2, CPP 8.7
Posselt, Dorthe ............CPP 15.13
Postels, B. ..................HL 44.82
Poteryaev, A. ................TT 32.7
Pototsky, Andreij ............ DY 17.1
Pototsky, Andrey ..CPP 16.5, DY 15.1
Potthoff, Michael TT 24.5, TT 24.13,
TT 26.8
Pottmeier, Andreas .....DY 34.1,
DY 46.20, DY 46.21
Potzel, Walter ......TT 13.5, TT 13.6
Potzger, K. ................. MA 15.6
Pouthas, François .......... AKB 20.3
Pozgajcic, Krunoslav ........TT 24.26
Pozo Ramajo, Angela ....... SYLS 4.3
Prager, M. ................. TT 24.32
Prandolini, M. J. ............ MA 15.6
Pranzas, Klaus ............MA 13.102
Pratzer, M. ............... MA 13.105
Pratzer, Marco ..... MA 15.2, O 14.30
Prazak, Dominik .............. VA 2.1
Preinesberger, C. ...............O 3.4
Preis, Thorsten ............. DY 46.66
Preisinger, M. .............MA 13.101
Press, Werner ................O 14.44
Pressl, D. .................. DS 22.45
Prestel, W. .................. HL 42.5
Prettl, W. .... HL 43.2, HL 44.45,
HL 44.46
Preuss, Martin .... CPP 16.2, O 28.20
Preusser-Mellert, Karolin ..HL 12.29,
HL 12.32, HL 20.3
Preuß, Martin ................O 14.53
Price, D.-J. ................. MA 21.5
Priebe, A. .............O 14.4, O 26.6
Priebe, Andreas ...... O 18.8, O 28.37
Prieto, J. E. ... MA 4.9, MA 4.10,
MA 13.9, MA 13.56, MA 17.2,
MA 31.2
Prieto, José Emilio .........SYXM 1.3
Priller, Heiko .. HL 12.79, HL 12.80,
HL 17.4
Prince, K. C. ..................O 33.4
Prince, Kevin ............... MA 11.5
Prineas, John P. ............. HL 28.4
Autorenverzeichnis
Prior, K. ................... HL 12.19
Pristovsek, Markus ...........HL 33.1
Prober, Daniel E. ...........SYSN 2.1
Probst, Christian TT 17.5, TT 17.20,
TT 17.21
Proehl, Holger .O 4.1, O 4.8, O 33.1,
O 33.7
Prokert, F. ........ DS 15.6, DS 22.34
Prokop, J. ..... MA 13.71, MA 13.105
Prost, Jacques ...............DY 12.4
Prost, W. .....................HL 9.4
Prummer, Michael .....CPP 9.6,
SYLS 3.43, SYLS 3.44, SYLS 5.2
Prunici, Pavel ...............HL 44.54
Pruschke, T. .................TT 24.1
Pruschke, Th. ............... TT 28.8
Pruskil, G. .............. O 3.4, O 9.3
Prusseit, W. .................TT 8.12
Prusty, Manamohan ........ DY 46.28
Przybylski, M. .MA 13.13, MA 13.14,
MA 15.5, MA 16.7, MA 20.7,
O 14.43, O 39.9
Przyrembel, D. ................O 26.7
Pucci, A. ............. O 14.4, O 26.6
Pucci, Annemarie ..O 18.8, O 28.37,
O 28.43
Puchalla, Jochen .............DS 18.6
Pudzich, Robert .......... SYOH 5.63
Pütter, C. ................... DY 25.4
Pütter, Sabine ............. MA 13.15
Puhlmann, Mathias .......... DY 27.4
Puig, T. .....................TT 8.14
Pundt, A. ......................M 3.1
Pundt, Astrid ................M 18.25
Purrucker, Oliver ....AKB 50.129,
AKB 50.130, HL 16.5
Pursche, Oliver ................O 32.5
Purwins, H.-G. .... DY 14.2, DY 46.31
Purwins, Hans-Georg ....DY 14.1,
DY 46.16
Puzyrou, M. V. ............. HL 44.67
Pyczak, Florian ............... M 21.2
Pyragas, K. ..................DY 36.5
Pérez León, Carmen ....... CPP 16.33
Qteish, Abdallah ............. HL 17.8
Qu, Jianqiang ............ SYOH 5.80
Quaas, N. ..............DS 4.1, O 9.4
Quabis, S. ................... HL 50.4
Quandt, E. ................. DS 22.29
Quandt, Eckhard ............ MA 24.3
Quate, Calvin F. .............. O 9.10
Queisser, H. J. ...............HL 19.1
Quester, Wolfram ...........DY 46.50
Quinn, Anthony ...........AKB 50.50
Quinn, Anthony W. ........SYLS 3.25
Quinn, Paul .............. SYOH 5.16
Quinn, Paul David ........ SYOH 5.53
Quirion, David ...............HL 37.6
R., Popescu ......... MA 4.1, MA 4.3
Raabe, D. ................ SYOH 5.52
Raas, Carsten ................TT 15.3
Raasch, Sebastian ............ MA 3.3
Rabe, Jürgen ............. SYOH 5.72
Rack, A. .........SYPF 4.4, SYPF 5.2
Rack, Alexander ............SYPF 5.1
Rada, Mihaela ...............MA 11.9
Radehaus, C. ...............TT 30.30
Rademann, K. ... O 10.6, O 14.45,
O 14.49
Rademann, Klaus ......O 9.7, O 14.79
Rader, O. ... MA 31.5, O 24.4, O 32.2
Radmacher, Manfred ....... AKB 12.4
Radons, Günter ..DY 40.2, DY 46.1,
DY 46.13, DY 46.22, DY 46.23,
DY 46.25, DY 46.26
Radosavljević, Marko ....... TT 27.10
Radovanovic, Jelena ..........HL 28.8
Radtke, Nicolle ......... M 9.2, M 9.4
Radu, Florin .. MA 10.2, MA 13.42,
MA 20.5, O 28.85
Radu, Ilie .................. MA 28.14
Rädlein, Edda ................O 28.62
Rädler , J. O ................ DY 40.4
Rädler, Joachim ............AKB 20.2
Rähmer, Bert ......HL 12.16, O 14.80
Raeth, Christoph .............DY 20.6
Rätzke, Klaus ....CPP 4.3, M 7.1,
SYOH 5.22
Rahm, A. ....HL 12.71, HL 12.73,
HL 17.5, HL 17.5
Rahm, Andreas .HL 12.69, HL 12.81,
HL 17.3
Rahm, Michael .............MA 13.70
Raible, Martin ............... DY 24.6
Rakel, Munise .............. HL 27.16
Rakoto, H. ..................MA 21.2
Raleva, Sofiya ....CPP 15.18, HL 23.3
Ramirez Barrios, Elena . AKSOE 3.8,
AKSOE 10.5
Ramirez, Claudia .............O 28.15
Ramos, Luis ................. HL 36.9
Rampf, Federica ...........CPP 15.48

Rams, M. ................... MA 16.7
Ramsdale, Catherine ....... SYOH 8.2
Ramsey, M. ...................DS 7.4
Ramsey, Michael ...........SYOH 7.1
Ramsteiner, I. ......... M 8.4, M 12.1
Ramsteiner, Ingo ...............M 8.3
Ramírez, C. ..................O 14.13
Rang, Alexander ............. O 14.24
Rangan, Sylvie ................ O 38.4
Range, Gabriel M. .......... CPP 15.1
Rangelov, Georgi .MA 4.12, MA 15.3,
O 3.1, O 12.5, O 24.6
Ranjan, Nitesh ............SYOH 5.58
Rant, Ulrich ................ SYLS 4.5
Raschke, G. ..................O 28.67
Raschke, Gunar ............. HL 44.33
Raschke, Gunnar ..........SYOH 5.84
Rasing, Theo ................. DF 6.1
Rastelli, A. ................. HL 12.62
Rastogi, Ankur ............. CPP 13.4
Rathgen, Helmut ............. MA 8.2
Ratzel, F. .................... TT 8.1
Ratzke, Markus .....DS 17.1, DS 22.9
Rau, B. .................... DS 22.54
Rau, Björn ........ DS 20.1, DS 22.53
Rau, Ileana .................TT 29.10
Rau, N. .......................HL 8.4
Rau, U. ............ HL 12.5, HL 30.2
Rau, Uwe ....................DS 19.3
Rau, Wolfgang .............. TT 13.6
Rauch, Jürgen ...............CPP 7.1
Rauls, E. .................... HL 40.5
Rauschenbach, B. . DS 9.7, DS 22.6,
DS 22.7, DS 22.34, DS 22.46
Rauschenbach, Bernd DS 3.3, DS 15.1,
DS 22.15, HL 44.64, O 28.21,
O 40.12
Rauschenbach, Stefan ..... AKB 50.36
Rauschenbach, Stephan ....SYLS 3.32
Rauscher, H. ........... O 5.7, O 25.6
Rauscher, Hubert .......O 6.6, O 38.3
Rauscher, Markus CPP 15.13, DY 17.4
Raveau, B. ............... MA 13.115
Ravlic, Daniel ..............MA 13.64
Ravlić, Robert ................ O 17.2
Raychaudhuri, A. K. ........ TT 30.15
Razavi, F. .................... DS 9.2
Razek, Nasser ..... HL 44.64, O 40.12
Razeti, Marco ............... TT 13.6
Rebikov, Andriy ..............TT 8.23
Rector, Jan H. ................ O 26.8
Redenbach, M. ............ SYLS 3.41
Reents, Georg .....DY 34.8, DY 46.12
Rega, N. .....................HL 24.6
Regul, J. .................... HL 47.3
Rehberg, Ingo .. DY 44.3, DY 44.5,
DY 46.77, DY 46.78, DY 46.79,
DY 46.81
Rehfeldt, Florian ....AKB 50.121,
AKB 50.127
Rehn, Ulrike ...............SYLS 3.23
Rehr, J. J. ................... MA 8.4
Rehse, Nicolaus ..............CPP 2.4
Reiber, Holger ..............CPP 12.3
Reich, Stephanie ............. HL 48.2
Reichardt, P. A. ............. TT 29.5
Reichardt, W. .................TT 9.8
Reichelt, M. ......... HL 6.1, HL 31.1
Reichelt, W. ................TT 24.45
Reichert, H. ........... M 8.4, M 12.1
Reichert, Harald . DY 10.4, DY 25.1,
M 8.3
Reichert, J. .......SYOH 6.2, TT 27.2
Reichert, Michael ...........DY 46.30
Reichl, A. .........TT 20.7, TT 30.14
Reicho, Alexander ............. O 34.5
Reif, Jürgen ........ DS 17.1, DS 22.9
Reif, Matthias ....O 19.3, O 25.9,
SYXM 1.6
Reiher, A. .. AKB 50.3, AKB 50.17,
SYLS 3.24
Reimann, Peter .....DY 12.2, DY 24.6
Reinecke, Antje AKB 50.89, AKB 50.91
Reineke-Koch, R. ............ HL 12.2
Reineker, Peter .. CPP 4.5, CPP 16.11
Reinert, F. ...........O 11.8, O 28.51
Reinert, Friedrich ............ O 11.10
Reinert, Tilo .............. AKB 50.55
Reinhard, Richte ............DY 46.82
Reinhardt, Helke .......... CPP 15.42
Reinhold, B. ................CPP 11.5
Reinholdt, Alexander .......... O 10.3
Reininghaus, Frank ......... TT 11.14
Reinisch, Jens ............... TT 33.4
Reinwald, E. ................HL 44.18
Reinwald, M. ...HL 29.5, HL 29.10,
HL 44.17, HL 44.18, HL 44.37
Reinwald, Matthias HL 44.7, HL 44.50,
TT 19.4, TT 19.5
Reischl, Alexander ... TT 3.2, TT 26.4
Reiser, Andreas ....DF 4.11, DY 29.11
Reiser, Anton .....HL 12.54, HL 12.55
Reisinger, D. ................ MA 13.5
Reisinger, Daniel .. HL 44.9, MA 13.39
Reislöhner, U. ...HL 12.6, HL 12.7,
HL 24.6, HL 27.8, HL 30.5
Reiss, G. ....................MA 27.6
Reiss, Guenter ... MA 2.7, MA 6.8,
MA 6.9, MA 13.6, MA 13.33,
MA 13.34, MA 13.36, MA 13.37,
MA 13.51, MA 13.78, MA 16.2,
MA 16.6, MA 27.4, MA 27.8,
MA 30.7, SYLS 3.33
Reissmann, Lars .. HL 16.10, HL 44.89
Reiter, Günter ..............CPP 13.2
Reithmaier, Hans-Peter .......HL 15.5
Reithmaier , Johann Peter . HL 38.8,
HL 38.9
Reithmaier, Johann-Peter ... HL 38.11
Reitzenstein, Stephan ......... HL 5.5
Reller, A. ...........DF 1.6, HL 12.51
Rellinghaus, B. .... MA 6.6, MA 13.77
Remer, Ralf .............. AKSOE 1.5
Remhof, Arndt ...MA 20.5, O 12.1,
O 28.79
Ren, Zongyou ............... TT 12.4
Rendulic, Klaus D. ............ O 20.6
Renken, Volker ................O 12.5
Renn, Alois ...CPP 9.5, SYLS 3.43,
SYLS 3.44, SYLS 5.2
Renner, B. ....................DF 1.6
Renner, Ch. .............. AKSOE 3.2
Renner, Christian .CPP 13.8, SYLS 4.4
Renner, Frank H. .. HL 4.10, HL 12.21
Renner, Frank Uwe ............O 46.1
Renner, Johannes ........... DS 22.44
Renner, Lars ...............SYLS 3.46
Repa, Petr ............VA 2.1, VA 2.3
Repetto, D. .................. MA 3.1
Requardt, Herwig ............ O 14.44
Rericha, Erin C. ............. DY 15.3
Reschke, Carl Henning .... AKSOE 8.4
Resel, R. ......................DS 7.4
Resel, Roland ..SYOH 5.12, SYOH 7.1
Rettig, C. ....................O 28.52
Rettner, Charles T. .......... MA 26.5
Reufer, M. ............... SYOH 5.86
Reulet, Bertrand ........... SYSN 2.1
Reusch, Boris ................TT 17.9
Reusch, T. C. G. ....DS 4.1, HL 12.92
Reusch, T. C.G. .. HL 9.5, HL 33.2,
HL 44.65
Reuter, Andreas ............ SYLS 5.4
Reuter, D. ....HL 12.1, HL 12.56,
HL 22.1, HL 36.12, HL 42.1,
HL 44.76, HL 44.76, HL 47.3
Reuter, Dirk HL 3.1, HL 5.1, HL 12.49,
HL 12.57, HL 22.11, HL 37.9,
HL 44.10, HL 44.26, HL 44.78,
HL 50.9
Reuter, K. .................... O 38.8
Reuter, Karsten ... O 18.1, O 20.4,
O 26.3, O 43.2, O 43.7
Reuter, M. C. .............SYOH 5.14
Reuter, Stephan ............ DS 22.38
Reuther, M. .......TT 3.12, TT 30.16
Reutler, P. ... TT 14.5, TT 24.50,
TT 24.51, TT 24.53
Reutler, Pascal .. TT 14.6, TT 20.6,
TT 30.20
Reutzel, Sven .................M 12.2
Revcolevschi, A. . TT 3.12, TT 3.13,
TT 8.45, TT 24.51, TT 24.53,
TT 30.37, TT 30.39
Revcolevschi, Alexandre ...... TT 14.6
Rheinländer, Bernd .... HL 12.69,
HL 12.89, HL 17.1
Rheinstädter, Maikel C. ....AKB 50.62
Ribeiro, P. ....TT 3.13, TT 30.37,
TT 30.39
Ribeiro, Patrick .............TT 30.20
Richter, Andreas ............DY 46.86
Richter, Barbara ................O 6.6
Richter, E. ...................DS 15.6
Richter, Frank .. DS 4.2, DS 22.32,
DS 22.42
Richter, Heiko .............. DS 22.25
Richter, J. ....................TT 3.9
Richter, Klaus .. DY 27.5, DY 50.4,
MA 27.11, TT 4.8, TT 11.4,
TT 23.4, TT 27.6
Richter, M. ................SYLS 3.13
Richter, Manuel .. MA 3.4, MA 8.7,
MA 8.9, MA 13.99
Richter, Martin ............. SYLS 3.9
Richter, Mirja .......HL 3.1, HL 44.26
Richter, R. ....................O 33.4
Richter, Reinhard DY 11.3, DY 46.78,
DY 46.79
Richter, Stefan ...............HL 15.2
Richter, W. ....HL 43.4, O 14.59,
SYOH 5.26
Richter, Wolfgang HL 12.16, HL 27.16,
HL 28.9, HL 28.10, HL 33.1,
HL 33.3, O 14.80, O 28.55
Ricker, Michael ...... DF 3.2, DY 28.2
Ridgway, M. ................ HL 44.70
Riechert, Henning . DS 11.1, HL 3.9,
HL 25.1, HL 50.5
Riedel, Ingmar ............ AKB 50.24
Riedel, Ingo ..... HL 23.5, SYOH 5.50
Riedel, Marc .................HL 31.4
Riedel, N. ........ HL 27.11, HL 44.82
Rieder, Bernhard ............HL 12.91
Rieder, K.-H. ................. O 31.1
Riedesel, Christof ........... HL 44.78
Rief, Matthias .............. SYLS 4.1
Rieger, Bernhard .............CPP 1.3
Rieger, Heiko ......DY 46.94, O 14.46
Rieger, Jens ................CPP 13.6
Riekel, C. .................. CPP 11.3
Riemann, T. ................HL 27.14
Riemann, Till ...............HL 44.81
Riesemeier, H. ..............SYPF 4.4
Riethmüller, Silke ............. O 32.5
Rietz, Frank ................. DY 15.6
Rieß, Walter ...............SYOH 7.2
Rigol Madrazo, Marcos ........TT 4.3
Rijnders, G. ................ TT 30.12
Rimikis, Astrid ................TT 8.5
Ringler, M. ................CPP 16.34
Rinke, Patrick ............... HL 17.8
Ripoll, Marisol ...............DY 51.7
Riske, Karin A. AKB 50.54, AKB 50.92
Risler, Thomas .............. DY 12.4
Ristein, Jürgen ...............HL 31.4
Ritschel, Manfred ......... MA 13.107
Ritter, C. .................... O 14.49
Ritter, Claudia ........ O 9.7, O 14.79
Ritter, F. ...................TT 30.18
Ritze, Hans-Hermann ...........O 4.6
Rivera, Alberto ... DF 2.6, DF 3.7,
DY 28.7
Robertson, T. L. .............TT 29.5
Roch, Tomas ................. HL 7.1
Rochet, Francois .............. O 38.4
Rocker, F. ....................M 26.1
Rode, M. ... M 3.2, M 18.26, M 18.27
Rodina, A. ..................HL 12.85
Rodriguez Neto, Camilo .. DY 20.4,
DY 20.5
Rodriguez-Contreras, J. ....... DF 6.7
Rodriguez-Ponce, Maria Inmaculada
DY 46.59, DY 51.3
Rodt, Sven ......... HL 36.4, HL 42.4
RöU., ßler ........ ........
Röbel, MichaelM 10.3, M 10.4 Roeder,
T. ....................... HL 6.3
Röder, Uwe .................HL 12.54
Röhler, Jürgen ................TT 9.5
Röhlsberger, R. ............ MA 13.44
Röhrich, Jorg ................ DS 21.1
Röll, K. ....................MA 13.48
Römer, R. A. ............... HL 44.60
Römer, Rudolf .............. HL 44.61
Römer, Rudolf A. .... AKB 50.52,
HL 12.46, HL 22.2, TT 30.7
RÖNTEC ......................FB 39
Röntzsch, Lars ...............HL 11.4
Rösch, Frohmut ...............M 29.4
Rösch, Oliver ................TT 26.3
Röseler, A. ...CPP 8.6, CPP 15.21,
CPP 15.45, SYLS 3.49
Röser, Fabian ...............HL 15.11
Rösler, O. .................. HL 12.66
Rösner, H. ....................M 20.5
Roesner, Harald ...M 20.1, M 20.4,
M 24.1
Rösner, Peter .......... DF 5.6, M 7.4
Rössler, Clemens ............HL 37.13
Roessler, Ernst ... DF 2.6, DF 3.4,
DF 4.5, DY 28.4, DY 29.5
Roessler, Ernst A. ..DF 3.7, DF 3.8,
DY 28.7, DY 28.8
Roessli, Bertrand ..........MA 13.102
Röttger, M. C. .... DY 14.2, DY 46.31
Röwer, R. .................... M 32.1
Rößler, Ulrich K. .............DY 40.6
Rogach, A. L. ......HL 15.12, O 28.67
Rogach, Andrei .... HL 12.24, HL 20.1
Rogach, Andrey . CPP 16.6, HL 15.2,
HL 20.4
Rogach, Andrey L. .... HL 12.36,
HL 44.33, SYOH 4.3
Rogal, J. ......................O 38.8
Rogal, Jutta .................. O 18.1
Rogalla, H. ..................TT 18.3
Rogge, M. C. ................ HL 37.1
Rogobete, Lavinia ...........HL 12.22
Rohde, Ingo .................MA 30.7
Rohe, Daniel ............... TT 24.27
Rohleder, M. .................O 28.70
Rohlf, Thimo ............. AKB 50.95
Rohlfing, M. HL 31.1, O 14.47, O 28.72
Rojas-Chapana, Jose .......SYLS 3.19
Rolff, Haiko ................MA 13.69
Autorenverzeichnis
Roll, Ulrich ................... O 23.5
Rollmann, Georg ............. MA 6.1
Roman, H. Eduardo ........ AKB 40.4
Roman, Zhukavin ............ HL 38.7
Romanin, Christoph ........SYLS 3.27
Romanov, Sergei HL 12.24, HL 12.25,
HL 15.10, HL 20.1, HL 20.4,
HL 20.6
Romanus, Henry ...DS 22.12, HL 40.1
Romeike, Christian . MA 21.4, TT 27.4
Romero-Enrique, Jose Manuel DY 51.3
Romeyke, Maren .........AKB 50.125
Roos, B. F.P. ............... MA 16.5
Roos, Wouter .. AKB 50.8, AKB 50.13
Ropers, C. ..................HL 12.92
Ros, Alexandra SYLS 3.31, SYLS 3.34,
SYLS 3.36, SYLS 3.40
Ros, R. ......... SYLS 3.45, SYLS 4.2
Ros, Robert .AKB 50.81, CPP 16.19,
SYLS 3.28, SYLS 3.31, SYLS 3.40
Rosch, A. .................. TT 11.13
Rosch, Achim ...TT 3.10, TT 8.41,
TT 16.1, TT 24.20, TT 26.11
Roschger, P. .............. AKB 50.86
Roschger, Paul AKB 50.53, AKB 50.57
Rosciszewski, Krzysztof .........M 5.2
Rose, Volker .................. O 39.5
Rosenauer, A. ................HL 43.3
Rosenfeld, Arkadi ............ DS 14.6
Rosenfeldt, Arne .............. O 28.2
Rosenhahn, Axel ............. O 14.37
Rosenow, Bernd .... AKSOE 1.2,
AKSOE 3.1, TT 6.2
Rosenthal, Dirk .............. O 14.33
Roshchin, I. V. .............. MA 14.1
Roskos, H. .........HL 4.10, HL 12.21
Rosner, H. .TT 3.9, TT 8.47, TT 9.6,
TT 9.9, TT 24.23, TT 26.13
Rosner, Helge ...MA 8.7, TT 8.39,
TT 8.50, TT 32.3
Ross, Caroline A. ...........MA 13.55
Ross, Rober ............... SYLS 3.33
Rosselli, S. ....................O 14.1
Rossnagel, K. .. MA 13.9, MA 17.2,
O 28.4
Rossnagel, Kai ................ O 11.3
Rossow, U. ... HL 27.9, HL 27.10,
HL 27.11, HL 44.82, HL 44.85
Rost, A. .....................TT 33.3
Rost, Constance ........... SYOH 7.2
Rost, M. J. ................... O 23.7
Rotenberg, E. ..... MA 13.9, MA 17.2
Rotenberg, Eli ................ O 11.3
Roth, Alexander ...........AKB 50.13
Roth, Georg ................TT 30.20
Roth, H. .... TT 14.9, TT 24.46,
TT 24.47, TT 30.16
Roth, Johannes ............... M 29.2
Roth, Manfred ................ O 37.4
Roth, P. ................... MA 13.77
Roth, S. F. .................. HL 47.6
Roth, S. V. .................CPP 11.3
Roth, Stefan ...... MA 24.2, MA 26.1
Roth, Stephan V. ..........SYLS 3.53
Rothe, Ulrich ......AKB 50.119,
AKB 50.120
Rothenstein, Roland ...... AKSOE 3.3
Rotoli, Giacomo ............. TT 8.27
Rott, Karsten .. MA 6.8, MA 13.72,
MA 26.13, SYLS 3.33
Rotter, Martin ................MA 3.3
Rottler, Klemens .............TT 13.2
Rotzinger, H. .......TT 8.24, TT 13.4
Roudgar, Ataollah .............O 14.5
Roussak, Liudmila .......... DS 22.52
Roventa, Elena ...............HL 21.2
Rubahn, Horst-Günter CPP 1.4, O 4.3,
SYOH 6.1
Ruben, Saldivar-Guerrero ....DY 46.82
Rudenkiy, S. ................. O 14.67
Rudhart, Christoph ............M 29.4
Rudolf, Carsten ............. HL 44.63
Rudolph, J. ..................HL 43.2
Rudolph, Jörg ...HL 41.2, HL 44.6,
HL 44.53
Rückamp, R. ....TT 6.7, TT 14.9,
TT 24.47
Rücker, U. ...................DS 17.5
Rückerl, Florian ........... AKB 50.56
Rückmann, I. ................. HL 4.5
Rückmann, Ilja ................HL 4.2
Rüdiger, U. ... MA 13.1, MA 13.4,
MA 13.35, MA 25.2
Rüdiger, Ulrich ..............MA 13.2
Rüffer, R. ..................MA 13.44
Rüffer, Rudolf ..........DS 6.2, O 6.4
Rühle, Manfred ............... M 30.1
Rühle, W. W. ................HL 25.5
Rührig, Manfred .............MA 16.2
Rüster, Christian ....HL 29.4, HL 49.3
Rüther, Elmar .................O 40.3
Ruett, Uta .................. TT 8.17

Rugeramigabo, Eddy Patrick O 14.38,
O 14.41, O 14.42
Rull, Luis F ..................DY 51.3
Rumbolz, C. .................. DS 1.7
Rumpf, Holger .............. MA 24.3
Rumpler, Monika ..........AKB 50.57
Runge, Bernd-Uwe ...........TT 8.30
Runge, Erich ................ TT 15.5
Rupp, Romano A. .............DF 2.5
Rupprechter, Günther ..O 26.4, O 31.7
Rurimo, G. .................. HL 50.4
Rus, Teodora ................. TT 7.6
Ruske, J.-P. ...................DS 1.8
Rusp, Monika ............AKB 50.129
Rusponi, Stefano ............... O 5.2
Russ, Stefanie . DY 46.36, DY 46.38,
HL 53.1
Russell, Thomas P. ......... CPP 16.9
Rust, H.-P. ................... O 17.8
Rust, Hans-Peter ..............O 9.11
Rutkowski, M. ....... O 20.5, O 28.60
Ruttor, Andreas ............. DY 34.8
Ruß, Marco .................HL 22.11
Rybacki, Erik ................. M 22.4
Rybski, Diego ................DY 42.3
Ryndyk, Dmitri ..MA 31.6, TT 8.20,
TT 11.9, TT 18.8
Rzhevskii, Alexej ............. O 28.11
S., Ferrer ............MA 4.1, MA 4.3
S.I.S. ..........................FB 40
Saas, F. .................... HL 15.12
Sabathil, M. ................. HL 42.5
Sabathil, Matthias ........... HL 47.8
Sacca, Barbara ............. CPP 13.8
Sacchi, Maurizio ...........SYXM 1.4
Sacharow, Lilli ..........O 5.8, O 39.2
Sachdev, Subir .............. TT 21.2
Sacher, Marc ....MA 13.34, MA 13.36
Sackmann, Erich .......... AKB 50.13
Sadewasser, S. ...............HL 30.2
Sadowsky, Nana ............ DY 46.80
Saeed, U. ...........DS 22.29, O 24.1
Saeed, Usman ......CPP 16.8, DS 7.1
Säuberlich, Frank ............ DS 21.2
Säuberlich, Thomas .........HL 27.16
Saez de Jauregui, David ......CPP 3.5
Safarowsky, Caroline ......... O 14.24
Sagol, B. Erol .............. HL 12.41
Saha-Dasgupta, T. ...........TT 32.3
Sahaoui, T. ................ TT 24.50
Sahoo, B. ..................MA 13.44
Sahoo, S. ....... MA 13.83, MA 13.84
Sahoo, Sanjubala .............MA 6.1
Sahre, K. ................. CPP 15.45
Sainova, Dessislava ....... SYOH 5.76
Saito, S. .................... TT 29.3
Sakai, Kazumitsu ............. TT 3.6
Sakong, Sung ........ O 14.3, O 28.56
Saksaengwijit, Aimorn ....DF 3.9,
DF 3.10, DY 28.9, DY 28.10
Sakurai, H. .................TT 14.13
Sakurai, Keiichiro ............ O 40.11
Salamatin, E. ................TT 8.32
Salameh, Belal .. TT 6.5, TT 30.26,
TT 30.28
Salbeck, Josef ............ SYOH 5.63
Salchert, Katrin ........... SYLS 3.46
Salditt, T. ................. MA 13.58
Salditt, Tim . AKB 23.2, AKB 50.62,
AKB 50.66, AKB 50.67,
AKB 50.68, AKB 50.82, AKB 50.87
Salem, Abouelwafa ............TT 8.2
Salinga, Christian ........... DS 22.26
Salinga, Martin ............. DS 22.30
Salvan, G. ....SYOH 5.19, SYOH 5.26
Salvan, Georgeta ..........SYOH 5.37
Sameh, A ......................M 3.3
Samokhvalov, V. .MA 11.2, MA 11.2,
MA 13.108
Sampathkumaran, E. V. .......M 22.2
Samwer, K. ... M 4.1, M 18.2, M 24.4
Samwer, Konrad ..DF 5.6, DY 25.3,
DY 46.68, M 7.4, MA 13.22,
MA 13.23, MA 22.3
Samwer, Korand ............ MA 27.5
Sanchez, Diana ............ MA 20.10
Sanchez, Juan M. ..............M 5.1
Sanctuary, Roland CPP 2.6, CPP 7.5,
CPP 8.2, CPP 8.7, CPP 15.36
Sander, Dirk ...........O 27.1, PV IX
Sandiumenge, F. .............TT 8.14
Sandoghdar, Vahid CPP 9.5, HL 12.22,
HL 15.9, SYLS 2.3
Sandoval, Luis ...............DY 34.4
Sandvik, P. .................. HL 16.1
Sann, J. ....................HL 17.10
Sann, Joachim ..............HL 17.13
Sanquer, Marc ............. SYSN 1.2
Santamaria, Jacobo ........... DF 2.6
Santen, Ludger ....DY 46.5, DY 46.94
Santos, C. ................... MA 8.8
Santos, P. V. ...... HL 12.23, HL 20.9
Saphiannikova, M. ..........CPP 11.5
Saphiannikova, Marina ......CPP 10.3
Sapper, Angelika ............DS 22.44
Saragi, Tobat .............SYOH 5.63
Sarlah, Andreja .............. DY 51.4
Sarma, V. S. ................ TT 8.11
Sasaki, T. ..................TT 14.13
Sass, B. ..........MA 13.65, MA 14.2
Sass, Björn .......MA 10.7, MA 13.54
Sassetti, Maura ..... HL 22.6, HL 47.5
Satapathy, Dilip K. ............O 25.8
Satitkovitchai, Khompat ...O 34.2,
O 44.7
Satmarel, Cristian ........... CPP 5.2
Sato, K. .................... MA 31.3
Sato, Kazunori .............. MA 11.3
Sato, R. ....................... M 8.5
Satoh, T. .................. MA 13.67
Sauer, Frank .. AKB 30.4, AKB 50.113
Sauer, H. .................... MA 6.5
Sauer, Rolf ...HL 12.54, HL 12.55,
HL 44.77
Sauerwald, Jan .............MA 13.34
Sautter, Armin ............ CPP 16.10
Savan, Alan ..DS 4.3, DS 13.1, O 46.4
Sawatsky, G. A. ............ TT 14.11
Sayar, Mehmet .............. DY 23.2
Scalapino, Douglas J. ......... TT 2.5
Schaaf, P. .........DS 17.4, DS 22.21
Schaaf, Peter ................ DS 13.2
Schaale, Andreas ......... AKSOE 5.3
Schaap, Iwan A. T. .........AKB 10.1
Schade, U. ................CPP 15.21
Schäfer, Christian ......... CPP 16.19
Schaefer, G. .................. DS 9.6
Schäfer, Georg ................ O 23.5
Schaefer, H.-E. ............... M 32.1
Schaefer, J. A. ...............HL 16.2
Schäfer, Jörg ....O 16.1, TT 30.8,
TT 30.34
Schaefer, Juergen A. .... DS 22.5,
DS 22.12, DS 22.18, O 5.1, O 28.48
Schäfer, R. .................. DY 27.1
Schäfer, Roland ..............TT 11.2
Schäfer, Rudi .............. MA 13.10
Schäfer, Rudolf ..MA 7.1, MA 26.2,
MA 28.6
SCHAEFER TECHNOLOGIE ...FB 41
SCHAEFER-TEC .............. FB 42
Schaefers, Holger ............ TT 22.5
Schäpers, T. .................. HL 5.3
Schäpers, Th. .....MA 13.96, TT 8.21
Schätzler, Katharina .O 28.65, O 28.66
Schaff, W. J. ................ HL 27.4
Schafmeister, Peter .......... HL 37.9
Schafranek, Robert ...........DS 21.2
Schaller, Gernot ..........AKB 50.104
Schalley, Christoph ...........O 14.24
Schaniel, Dominik .......... CPP 10.6
Schanz, Holger ..DY 27.2, DY 27.4,
DY 46.28
Schanze, H. ..................HL 20.2
Schardt, M. ..................HL 50.4
Scharf, Thorsten . DS 13.2, DS 14.1,
DS 17.2
Scharfenorth, Chris ...........DS 14.6
Scharff, P. ................SYOH 5.52
Scharnberg, Michael ...... SYOH 5.22
Scharnhorst, Andrea ...... AKSOE 4.5
Schattat, B. .................. DS 1.7
Schattat, Beate ....... DS 1.2, DS 3.5
Schattke, W. .........O 14.13, O 28.4
Schattke, Wolfgang .......... O 28.15
Schatz, M. ................ SYLS 3.13
Scheer, E. ....TT 17.8, TT 17.10,
TT 17.11
Scheer, Elke .......TT 17.13, TT 27.3
Scheffler, M. ...... O 38.8, SYLS 3.20
Scheffler, Marc ...... TT 7.5, TT 20.8
Scheffler, Matthias HL 17.8, MA 17.1,
O 11.7, O 18.1, O 20.4, O 26.3,
O 31.4, O 40.6, O 43.2, O 43.7,
SYLS 3.18, SYLS 3.29
Scheffran, Jürgen .........AKSOE 5.1
Scheible, Dominik ......... SYLS 3.30
Scheibner, Ralf ............. HL 44.31
Scheidt, E.-W. ...............TT 14.3
Scheinert, S. ..............SYOH 5.73
Scheinert, Susanne .....HL 10.2,
SYOH 4.2, SYOH 5.69
Scheinfein, Michael R. ....... MA 28.5
Schell, N. ....................DS 14.2
Schelle, Detlef .............. HL 15.11
Schelten, J. ................. MA 26.4
Schelten, Jakob ............. MA 31.8
Schenk, Tobias L. ..HL 28.9, HL 28.10
Schennach, Robert ............ O 20.6
Schepper, Willi ............... MA 2.7
Scherbel, Jens ............... TT 8.26
Scherdel, S. ...............CPP 15.34
Scherdel, Sabine .............CPP 2.4
Scherer, Axel .............. SYOH 4.2
Scherer, Helmut ............. HL 15.5
Scherf, U. ....SYOH 5.47, SYOH 5.86
Scherf, Ullrich . CPP 9.1, CPP 16.29,
SYOH 5.72, SYOH 5.83
Scherf, Ulrich ..............SYOH 2.4
Scherz, A. MA 8.4, MA 15.1, MA 20.2
Scheuermann, M. ......... SYOH 5.20
Scheurich, Peter .......... AKB 50.97
Schick, Christoph .....CPP 13.3,
CPP 15.20, CPP 15.31, CPP 16.25
Schick, Michael .. AKB 50.18, O 14.39
Schiechl, Hannes ...... O 34.4, O 39.8
Schiegl, Magda AKSOE 7.2, SYFT 3.2
Schiemann, Reinhard ...... SYLS 3.48
Schierbaum, Klaus ....SYLS 3.56,
SYLS 3.57, SYLS 3.58
Schierle, E. .. MA 13.85, TT 14.11,
TT 30.12
Schiessel, Helmut .......... AKB 20.1
Schietinger, Stefan .........SYOH 4.3
Schilinsky, Pavel . HL 23.3, SYOH 5.50
Schiller, Arwed ............. DY 46.92
Schiller, Avraham ...HL 47.1, TT 11.3
Schiller, F. .....................O 3.4
Schiller, Frederik ..... O 11.11, O 17.4
Schilling, Meinhard ... MA 13.120,
MA 18.4, TT 13.10
Schilling, Rolf ....DF 3.1, DF 3.2,
DY 28.1, DY 28.2
Schillinger, Matthias ......... HL 15.3
Schimansky-Geier, Lutz ...... DY 24.7
Schimmel, Thomas . CPP 2.3, O 14.84
Schimper, H. J. .............. O 28.25
Schindler, Alexandra .......... DS 6.3
Schindler, Axel . DS 22.17, HL 44.64,
O 40.12
Schindler, Florian CPP 9.1, SYOH 5.83
Schindler, K. ................ TT 8.32
Schindler, Karl-Michael ........O 34.7
Schindler, Michael .........AKB 50.11
Schindlmayr, Arno HL 44.12, MA 17.1
Schinkinger, Stefan ....AKB 12.1,
AKB 30.4, AKB 50.113,
AKB 50.125
Schirmacher, Walter ......... DY 46.8
Schirmeisen, Andre ...O 9.8, O 9.9,
O 14.73, O 14.74, O 14.75, O 23.2
Schirmer, Ortwin ..............DF 7.1
Schittner, N. ............... TT 30.16
Schlaad, Helmut .......... CPP 15.43
Schlachter, S. .................TT 1.4
Schlagberger, Xaver ....... SYLS 3.39
Schlagheck, Peter .. DY 46.37, TT 4.8
Schlaphof, Frank ..............DF 1.3
Schlapka, Andreas .............O 18.6
Schlappa, J. ..... TT 14.11, TT 30.12
Schlarb, Andreas .............O 14.69
Schlarmann, Judith .........SYPF 2.3
Schleid, Thomas ............TT 30.26
Schlettwein, D. ........... SYOH 5.28
Schlettwein, Derck ....CPP 16.23,
O 14.60, SYOH 5.11, SYOH 5.25,
SYOH 5.33, SYOH 5.48,
SYOH 5.87, SYOH 5.87
Schlichenmaier, Christoph ..HL 32.3,
HL 32.4
Schlickum, U. ............... MA 16.4
Schliefke, W. ............. SYOH 5.52
Schliemann, John ............ HL 49.1
Schliwa, Andrei .............. HL 36.4
Schlörb, H. ..................TT 8.13
Schlörb, Heike .............. MA 30.5
Schlom, Darrell .............TT 24.37
Schlomka, Jens-Peter ......AKB 50.38
Schlosser, V. ..... HL 44.74, HL 44.75
Schlueter, J. A. .............TT 30.25
Schmalhorst, J. ............. MA 27.6
Schmalhorst, Jan .....MA 13.33,
MA 13.34, MA 13.36, MA 13.51
Schmalz, Holger ...........CPP 16.32
Schmechel, Roland .....HL 23.4,
SYOH 5.71, SYOH 5.77
Schmehl, Andreas .......... TT 24.37
Schmeisser, Dieter .DS 9.4, HL 44.42,
SYOH 5.74, SYOH 5.75
Schmeißer, Dieter ... HL 31.3, HL 40.4
Schmid, A. ....................O 14.1
Schmid, Benjamin ........... TT 30.8
Schmid, Frank ............... HL 52.1
Schmid, Friederike ..... CPP 2.2,
CPP 15.35, SYLS 3.34
Schmid, Gerhard AKB 50.45, DY 46.60
Schmid, J. ..................HL 17.11
Schmid, M. ..................O 25.10
Schmid, Markus ............. TT 8.37
Schmid, Michael ...... O 34.4, O 39.8
Schmidt, Andreas O 3.5, O 3.8, O 32.3
Schmidt, Benjamin ..O 28.65, O 28.66
Schmidt, Bernd ..HL 11.4, HL 28.6,
O 14.78
Schmidt, Burkhard ....SYLS 3.54,
TT 32.11
Autorenverzeichnis
Schmidt, Christian ..............O 6.1
Schmidt, Christoph F. ...... AKB 10.1
Schmidt, Daniel ............ TT 17.13
Schmidt , G. ... HL 29.3, HL 29.7,
HL 29.8, HL 29.10, HL 29.11,
MA 31.5, SYOH 5.62
Schmidt, Georg . HL 29.4, HL 44.20,
HL 49.3
Schmidt, Hans-Werner ..CPP 15.46,
SYOH 5.45
Schmidt, Harry ............. TT 29.12
Schmidt, Heidemarie ... HL 12.61,
HL 12.77, HL 12.87, HL 17.1,
HL 17.6
Schmidt, Jan ....... HL 24.4, HL 30.6
Schmidt, Jan-Hendrik .......SYFT 2.1
Schmidt, K. ................. CPP 6.1
Schmidt, Kai P. ...............TT 3.2
Schmidt, Kristin CPP 15.5, CPP 15.30
Schmidt, Manfred ...DS 13.4, DS 20.3
Schmidt, Markus HL 12.29, HL 12.32,
HL 12.33, HL 20.3
Schmidt, O. ................. HL 4.11
Schmidt, O. G. .... HL 12.62, HL 37.7
Schmidt, Oliver .............. HL 51.1
Schmidt, Philipp Martin ....... O 19.2
Schmidt, R. .........HL 42.1, HL 43.5
Schmidt, Richard ....AKB 50.119,
AKB 50.120
Schmidt, Richard R. ......AKB 50.121
Schmidt, S. ..................O 28.51
Schmidt, Sebastian .......... DY 10.3
Schmidt, Stefan ..............O 11.10
Schmidt, Th. .... O 4.2, O 38.10,
SYOH 1.3
Schmidt, Thomas . HL 3.11, O 28.18,
SYLS 1.2
Schmidt, Torsten ............ M 18.23
Schmidt, Volker .............HL 12.58
Schmidt, W. ................ MA 20.3
Schmidt, Wolf G. CPP 16.2, O 14.53,
O 28.20, O 40.2
Schmidt, Wolfgang .... TT 30.27,
TT 30.28
Schmidt-Grund, Rüdiger ..HL 12.69,
HL 12.77, HL 12.89, HL 17.1,
HL 17.6
Schmidtke, Jürgen .........CPP 16.35
Schmidtling, Thorsten .......HL 27.16
Schmidtling, Torsten .... HL 28.9,
HL 28.10, HL 33.3
Schmitt, Carmen ........... DY 46.18
Schmitt, Holger ............ MA 13.38
Schmitt, Ljubomira .........MA 13.38
Schmitt, Sebastian ..........TT 24.16
Schmitt, U. .................HL 12.38
Schmitt-Landsiedel, Doris .....HL 10.5
Schmitte, Till ............... MA 30.4
Schmitteckert, Peter .TT 6.1, TT 6.14
Schmitz, Christian ....AKB 50.15,
AKB 50.105
Schmitz, D. ................MA 13.88
Schmitz, Guido .. M 18.18, M 24.3,
MA 16.6
Schmoranzer, H. MA 10.6, MA 13.48,
MA 13.49, MA 13.50, SYLS 3.41
Schmuki, Patrik ............SYOH 5.9
Schmult, Stefan .....HL 32.6, HL 38.1
Schnack, Jürgen .............MA 21.1
Schnautz, Tobias ............ DY 44.5
Schneck, Christof ...........TT 30.26
Schneider, C. M. .MA 13.4, MA 28.8,
O 12.3, O 28.11
Schneider, Christof ...........TT 18.2
Schneider, Claudia ........... TT 26.5
Schneider, Claus .. DS 22.22, MA 6.12
Schneider, Claus M. DS 6.3, DS 22.31,
MA 13.107, O 28.80
Schneider, Daniela ........... TT 30.9
Schneider, Ditmar .............VA 3.1
Schneider, F. .. MA 11.2, MA 11.2,
MA 13.108
Schneider, Gerald CPP 11.2, CPP 16.7
Schneider, Hans Christian ... HL 36.13
Schneider, Harald ............. HL 4.3
Schneider, Jens ....DS 20.2, DS 22.49
Schneider, Jörg .............. O 14.37
Schneider, Johannes ..........O 28.71
Schneider, Johannes J. . AKSOE 3.8,
AKSOE 4.2, AKSOE 10.5,
AKSOE 10.6, DY 46.57
Schneider, M. ....... TT 8.43, TT 9.4
Schneider, M. Alexander ...O 11.5,
O 15.1, O 26.2
Schneider, Marc ............ CPP 10.4
Schneider, Matthias .. AKB 50.119,
AKB 50.120
Schneider, Petra ... HL 43.2, HL 44.46
Schneider, R. ........TT 8.1, TT 18.1
Schneider, Rudolf MA 13.21, MA 20.9,
TT 8.38
Schneider, S. .. M 4.1, M 18.2, M 24.4

Schneider, Susanne ......M 7.4, O 9.5
Schneider, Theo ...... TT 8.5, TT 8.6
Schneider, Thomas ............TT 8.7
Schneider, W.-D. ..............O 17.7
Schneider, Wolf-Dieter ....... O 14.14
Schnell, Christoph .......... SYLS 3.7
Schnell, Ilan ................. TT 32.4
Schnell, Ingo .............. CPP 16.12
Schnitzler, Wolfgang .......SYLS 3.50
Schob, Arne ...............CPP 16.20
Schober, Helmut . CPP 4.1, DF 4.10,
DY 29.10
Schoch, Wladimir ............ HL 35.5
Schock, H.-W. ...............HL 30.5
Schoedl, Thomas ............ HL 16.4
Schölderle, Hermann .........TT 12.2
Schöll, A. .............. O 4.2, O 33.4
Schöll, E. . HL 5.2, HL 37.5, SYSN 2.4
Schöll, Eckehard . DS 14.6, DY 14.8,
DY 21.2, DY 34.2, DY 42.2,
DY 46.32, HL 3.2, HL 12.65
Schoeller, Herbert MA 21.4, TT 11.7,
TT 11.14, TT 27.4
Schön, A. .................. HL 12.73
Schön, G. ................... TT 16.7
Schön, Gerd . SYOH 5.59, TT 17.32,
TT 19.1, TT 23.3, TT 27.5,
TT 27.7, TT 29.9
Schoen, Martin .............. DY 17.5
Schöneberger, Christian .....TT 27.11
Schönenberger, Christian ... SYNF 1.4
Schoenes, J. M 3.2, M 18.26, M 18.27,
M 18.28, MA 13.7, MA 13.8,
MA 13.19, MA 13.103, MA 13.104,
TT 30.11
Schönhammer, Kurt TT 11.7, TT 24.9,
TT 24.10, TT 24.21
Schönhense, G. .. DF 1.2, DS 22.27,
DS 22.28, M 26.1, MA 8.5,
MA 13.71, MA 13.105, MA 13.114,
MA 28.8, O 28.34, O 28.75
Schoenhense, Gerd .......... MA 6.12
Schoenhense, S. ...............DS 9.6
Schönhof, Martin ......... AKSOE 4.4
Schoenlein, R. W. .............HL 4.8
Schöpe, Hans Joachim .. DY 46.46,
DY 46.52, DY 46.55, DY 46.56,
DY 46.66
Schoepe, Wilfried ............. TT 4.2
Schoepf, Wolfgang ..........DY 46.81
Schöps, A. ............ M 8.4, M 12.1
Schöps, Andreas ............... M 8.3
Schofield, Marvin ............. TT 1.5
Scholl, Andreas .............. O 14.55
Schollmeyer, Hauke .........CPP 12.2
Schollwöck, Ulrich HL 47.4, TT 15.8,
TT 24.9, TT 24.10
Scholten, Gregor ........... MA 10.10
Scholtyssek, Jan M. ........ MA 13.91
Scholz, R. ........ DF 6.4, SYOH 5.19
Scholz, Reinhard CPP 16.4, HL 12.98,
HL 41.4, SYOH 2.1, SYOH 5.37
Scholz, Roland ...DS 1.2, HL 11.3,
HL 12.52, HL 18.1, HL 31.2
Scholz, Sebastian ............ DS 22.2
Scholz, U. ................... HL 42.1
Schomerus, Henning ... DY 46.42,
SYSN 1.5
Schonecke, M. .............. MA 13.5
Schonecke, Mitja .....MA 13.27,
MA 13.39, TT 8.19
Schopohl, Nils ......TT 8.35, TT 8.36
Schorn, P. J. ..................DF 6.3
Schorr, Roland ............. DY 46.94
Schott, G. .................. MA 31.5
Schott, Stephan ............ DY 46.10
Schotter, Jörg .... MA 2.7, SYLS 3.33
Schrader, S ...............SYOH 5.16
Schramm, S. HL 3.6, O 14.57, O 37.2,
TT 17.14
Schramm, Sven .............. O 28.71
Schreck, M. ...................DS 9.6
Schreckenbach, Klaus ........ O 28.32
Schreckenberg, Michael ...DY 34.1,
DY 46.20, DY 46.21
Schrefl, Thomas ..............MA 1.1
Schreiber, F. .. O 14.2, SYOH 5.18,
SYOH 5.29
Schreiber, Frank ................O 4.4
Schreiber, Lars .............. MA 31.1
Schreiber, M. . CPP 16.1, DY 46.45,
HL 44.60, TT 8.49, TT 9.12
Schreiber, Michael .... CPP 16.3,
CPP 16.4, DY 46.44, HL 12.98,
HL 22.2, M 18.9, M 18.17, M 29.3,
MA 13.94, TT 30.7
Schreiber, Thomas ............ HL 2.3
Schrempel, F. .................DS 1.8
Schreyer, A. .................MA 20.3
Schreyer, Andreas ...........DS 22.35
Schriefl, Josef ............... TT 22.4
Schrobsdorff, Hecke ..........DY 21.1
Schröder, Alexander ... DS 15.5, O 3.2
Schroeder, H. ................DS 14.3
Schroeder, K. ................. O 25.7
Schroeder, Kurt ........ O 6.2, O 38.1
Schröder, Leif ............AKB 50.105
Schröder, M. ............... CPP 16.1
Schröder, Stefan ............. O 28.26
Schroeder, Sven L. M ......... O 39.7
Schroeder, Thomas ....DS 9.3, O 39.4
Schröer, Daniel ............... HL 5.7
Schröter, H. .......... M 3.2, M 18.28
Schröter, K. ...............CPP 15.24
Schröter, Lutz ............... AIW 6.1
Schröter, Matthias ...........DY 44.2
Schröter, P. ..................HL 14.3
Schröter, Patrick ............HL 12.94
Schröter, Ursula ............. TT 17.3
Schröter, Wolfgang ......... HL 44.44
Schropp, Andreas ........... DS 22.30
Schrupp, David .TT 24.41, TT 24.43,
TT 30.8, TT 30.34
Schubert, E. ........DS 9.7, DS 22.46
Schubert, Frank ...........CPP 15.30
Schubert, Gerald .............TT 30.6
Schubert, J. .................. DF 6.7
Schubert, Kai .................HL 2.5
Schubert, Luise ............. HL 44.69
Schubert, M. ... DS 9.7, HL 12.10,
HL 12.83, HL 12.86, HL 17.12,
HL 23.6, HL 28.5, HL 44.79,
HL 44.80
Schubert, Mathias HL 12.4, HL 12.50,
HL 12.68, HL 12.90, HL 17.1,
HL 44.51
Schüller, C. ....HL 14.3, HL 28.7,
HL 42.2, HL 44.38, HL 44.40
Schüller, Christian HL 12.94, MA 13.64
Schüpp, B. ................... TT 6.4
Schüpp, Barbara ............ MA 30.5
Schüppel, R. ................HL 12.97
Schürmann, M. ...O 28.6, O 28.27,
O 28.28
Schürmann, U. ................O 24.1
Schürmann, Ulrich CPP 7.2, CPP 11.4,
CPP 16.8, DS 7.1, DS 15.7,
DS 22.24
Schütt, Markus .............SYLS 4.4
Schütte, Christof .......... SYLS 3.54
Schütz, Florian ..... TT 16.8, TT 23.2
Schütz, G. ... MA 6.3, MA 13.110,
MA 31.5, SYXM 1.2, TT 20.4,
TT 31.8
Schütz, Gisela O 10.4, O 19.1, O 28.84
Schüßler-Langeheine, C. ..TT 14.11,
TT 30.12
Schüßler-Langeheine, C. .... MA 13.85
Schuh , D. HL 9.3, HL 12.63, HL 14.4,
HL 20.5, HL 22.4, HL 37.11,
HL 42.5, HL 44.17, HL 44.18,
HL 44.37, HL 47.6
Schuh, Dieter ...HL 22.7, HL 32.6,
HL 37.13, HL 41.2, HL 44.52
Schuler, J. .................. MA 13.5
Schuler, Jürgen . TT 17.5, TT 17.20,
TT 17.21
Schuler, Sebastian ....AKB 50.63,
AKB 50.116, AKB 50.124
Schuller, I. K. ..MA 10.8, MA 13.44,
MA 28.11
Schuller, Ivan K. ............ MA 14.1
Schulmeyer, Thomas ........DS 22.48
Schulten, K. ................SYLS 5.3
Schultrich, Bernd ............. DS 5.1
Schultz, Franziska ..........MA 13.92
Schultz, L. . DS 18.1, M 8.5, M 13.1,
M 13.3, M 16.3, MA 13.18,
MA 15.8, MA 18.3, MA 20.11,
MA 22.2, TT 8.11, TT 8.13,
TT 9.9, TT 12.3
Schultz, Ludwig ...DS 18.4, M 9.2,
M 9.4, M 14.2, M 16.2, M 22.2,
M 31.3, MA 7.1, MA 11.8,
MA 11.9, MA 11.10, MA 11.11,
MA 13.17, MA 15.10, MA 26.1,
MA 26.2, MA 26.3, MA 28.6,
MA 30.5, MA 30.6, TT 12.4,
TT 31.10
Schulz, B. .................CPP 15.45
Schulz, Michael ..............CPP 4.5
Schulz, O. ................SYOH 5.52
Schulz, P. .....................O 43.4
Schulz, R. .................. HL 12.63
Schulz, Stefan .............. HL 44.35
Schulz, Stephan ..............HL 25.4
Schulze, F. ........ HL 27.1, HL 44.80
Schulze, Fabian .............HL 44.81
Schulze, S. ....................O 19.7
Schulze Wischeler, Fritz .....HL 12.41
Schulze-Wischeler, F. .........HL 22.1
Schumacher, G. ..............M 18.19
Schumacher, Gabriele ..AKB 50.119,
AKB 50.120
Schumacher, Gerhard ......... M 15.1
Schumacher, Olrik .. HL 5.9, HL 12.93
Schumacher, Stefan ..........HL 28.3
Schumann, J. ...............DS 22.47
Schumann, Joachim ....DS 22.40,
DS 22.41, MA 13.97
Schumann, O. . TT 14.14, TT 14.14,
TT 30.36, TT 30.38, TT 30.38
Schumann, Oliver .... HL 3.9, HL 50.5
Schuppler, S. ................ TT 14.5
Schuricht, Dirk ............... TT 3.1
Schurig, Thomas .... TT 8.7, TT 8.22
Schuster, Cosima ............ TT 26.6
Schuster, D. .................. HL 3.7
Schuster, Ellen ....HL 44.10, MA 30.4
Schuster, Heinz Georg ... DY 34.3,
SYFT 2.3
Schuster, Jörg .. CPP 14.7, CPP 16.21
Schuster, M. ................ TT 8.28
Schuster, Michael ............. DF 5.4
Schuster, R. ................ HL 44.37
Schwab, M. ................ HL 36.12
Schwab, Matthias ............HL 36.3
Schwab, Peter ..............TT 30.19
Schwabl, Franz ............. DY 46.59
Schwaderer, Peter ........AKB 50.124
Schwalb, C. ..........O 14.20, O 38.2
Schwanhäusser, A. ........... HL 4.11
Schwanhäußer, A. ............HL 4.10
Schwartz, G. ................HL 12.19
Schwartz, Gregor ........... HL 44.16
Schwartz, Rico ..............HL 12.12
Schwarz, A. ......MA 13.123, O 14.65
Schwarz, Alexander . O 9.1, O 28.39,
TT 31.4
Schwarz, M. P. ............. HL 12.66
Schwarz, Thorsten MA 13.21, MA 20.9
Schwarz, Ulrich AKB 21.3, AKB 50.34,
HL 38.1
Schwarz, Ulrich S. .........AKB 50.22
Schwarz, Ulrich T. .. HL 16.4, HL 27.5
Schwarzburg, Klaus .......... DS 21.4
Schwarzer, Norbert ......... DS 22.32
Schwedt, Daniel ............ HL 12.12
Schweiger, F. ................ O 14.67
Schweitzer, Dieter SYOH 5.60, TT 6.5,
TT 30.26, TT 30.27, TT 30.28
Schweitzer, Frank ....AKSOE 3.6,
AKSOE 3.7, AKSOE 3.11,
AKSOE 4.3
Schweizer, Stefan ............ HL 15.2
Schweizer, Stefan L. ....HL 12.28,
HL 12.35
Schwender, C. ............... HL 44.2
Schwender, N. .............SYLS 3.15
Schwenk, Ulrich ............ CPP 16.7
Schwesinger, Norbert .........DS 22.5
Schwieger, Stephan ..........MA 16.1
Schwieger, Torsten ... SYOH 5.24,
SYOH 5.30, SYOH 5.32
Schwiertz, Carola ......... SYOH 5.75
Schwiertz, Thomas ......... SYFT 3.1
Schwiete, G. .................HL 5.10
Schwille, Petra .............AKB 22.4
Schwinge, K. ..................O 25.3
Schwinge, Kai ..................O 5.3
Schwingenschlögl, Udo .... M 5.4,
TT 24.56
Schwoerer, M. ............SYOH 5.89
Scudino, Sergio ............... M 31.3
Sebald, K. ................... HL 36.8
Sebastian, Ina .................O 34.7
Sebastiani, Daniel ......... CPP 16.12
Secker, Daniel ............... TT 27.8
Seebacher, Christian ......... CPP 9.4
Seeck, O. H. ............... TT 24.54
Seeck, Oliver ..................O 46.2
Seeger, J. ..................MA 13.58
Seeger, Stefan .............. DS 22.57
Seekamp, Joerg HL 15.10, SYOH 5.47
Seel, Alexander ............... TT 3.7
Seemann, Matthias ...........HL 4.12
Seemann, Ralf CPP 16.13, CPP 16.14,
DY 15.2
Seguin, Robert ......HL 36.4, HL 42.4
Segura, Jean-Manuel ...... SYLS 3.21
Seibold, Goetz . TT 24.22, TT 24.24,
TT 24.25
Seibt, M. ......M 4.1, M 18.2, M 24.4
Seibt, Michael . HL 44.44, HL 44.62,
HL 44.63
Seidel, A. .................. TT 24.49
Seidel, Jan ...................O 28.54
Seidel, Paul ................. TT 8.26
Seidel, Robert ............... HL 46.1
Seifarth, O. ... O 11.3, O 28.1, O 28.3
Seifert, C. ................... O 14.40
Seifert, Gotthard .CPP 16.3, DF 5.15,
M 18.17
Seifert, Udo ....AKB 21.2, AKB 50.23
Seino, Kaori ...CPP 16.2, O 28.20,
O 40.2
Autorenverzeichnis
Seip, Markus ............... HL 12.78
Seitsonen, Ari P. ..CPP 5.5, O 18.3,
O 26.2, O 46.6
Sekar, C. ..................... TT 6.4
Sekar, Chinnathambi .........TT 3.14
Selhuber, Christine ........ AKB 50.14
Selinger, Andreas ..........CPP 15.39
Selle, Carsten ............. AKB 50.56
Sellin, Roman ................HL 37.3
Sellner, S. ........ O 14.2, SYOH 5.29
Semba, K. ...................TT 29.3
Semenov, Alexei . DS 22.25, TT 1.2,
TT 13.3
Semmelhack, H. C. ..........MA 13.3
Semmelroth, Kurt ............HL 52.2
Senff, D. ................... TT 24.53
Sennikov, P. G. .............. HL 51.3
Sensfuss, Steffi .... HL 12.96, HL 23.3
SENTECH .................... FB 43
Senthil, T. .................. TT 21.2
Senz, Stephan . HL 12.58, HL 12.88,
HL 31.2, M 18.8
Senzier, J. ................. SYSN 2.1
Seo, Min Hong ............... M 27.3
Sepiol, Bogdan DS 6.2, DY 26.1, O 6.4
Serga, Alexander A. .......... MA 9.1
Sergey, Pavlov ............... HL 38.7
Serghei, Anatoli ........... CPP 15.10
Sernov, S. P. ............... HL 44.67
Servedio, Vito ........O 11.11, O 17.4
Seshadri, Ram ............ MA 13.111
Sethuraman, Vijayalakshmi ..O 45.2,
O 45.5
Setzer, A. ...................MA 13.3
Setzer, Annette ... HL 12.77, MA 11.1
Seufert, Adrian Marcelo ...AKSOE 3.7
Seufert, Jochen ............. HL 38.11
Seufferlein, Thomas ........ AKB 50.7
Severin, D. .................. DS 18.3
Severin, Daniel .... HL 12.9, HL 44.43
Severin, Ralf .................HL 24.1
Sevink, A. ...................CPP 6.1
Sewald, N. ................ SYLS 3.45
Sewald, Norbert ........... SYLS 3.31
Seybold, Hansjörg ........... DY 46.2
Seydel, Tilo ..................O 14.48
Shafarman, William N. ....... HL 12.3
Shannon, Nic ...............TT 32.11
Shaporenko, Andrey .. AKB 50.131,
O 14.54, O 33.2
Shapoval, Oleg ..............MA 22.3
Shapran, Larysa ............ DY 46.46
Shariq, Ahmed ................M 18.3
Sharov, Sergei ............... TT 19.7
Shayegan, M. ................ HL 29.2
Sherman, E. Ya. ............ TT 32.10
Shevchenko, N. ............. DS 22.34
Shevchenko, Natalia ...........DS 3.4
Shick, Alexander B. .......... O 28.81
Shiferaw, Tesfaye ............ CPP 7.2
Shikin, A. M. ................. O 24.4
Shimshoni, Efrat .............TT 3.10
Shinn, M. ................... DS 17.4
Shklovskij, Valerij A. .........TT 8.29
Shklyaev, A. A. ............... O 28.8
Shliomis, Mark .............. DY 11.5
Shnirman, Alexander ........TT 29.10
Shnyrkov, Vladimir ...........TT 29.4
Shokhovets, S. ....HL 27.15, HL 44.67
Shulga, Alexander .... SYOH 5.8,
SYOH 5.10
Shulga, S. V. ................. TT 9.9
Si, Qimiao ...................TT 10.1
Sichelschmidt, J. ........... CPP 10.7
Sick, Beate ...CPP 9.6, SYLS 3.43,
SYLS 3.44, SYLS 5.2
Sickinger, Horst ............. AIW 6.1
Sidis, Y. .... TT 24.53, TT 30.38,
TT 30.38
Sidorenko, A. ................ DS 22.7
Siebentritt, S. .......HL 24.6, HL 30.5
Siebentritt, Susanne .DS 21.1, HL 31.5
Sieber, I. ..................... DF 5.3
Sieber, Ina ..................DS 22.53
Siebert, M. .................. O 38.10
Siebrasse, J.-P. ............ SYLS 3.10
Siebrasse, Jan Peter .........SYLS 2.1
Siegel, Michael .. MA 31.8, TT 1.2,
TT 13.3
Sieger, Johannes ........... CPP 16.6
Sielemann, Rainer ............HL 40.3
Siemeling, Ulrich ...........SYOH 5.4
Sienz, S. .....................DS 22.7
Sievers, S. ....................TT 8.8
Sievers, Sibylle ..............DS 22.19
Siewert, Jens .......DY 50.1, TT 11.4
Siffalovic, Peter ........... CPP 16.19
Sigel, Reinhard . CPP 11.6, CPP 15.43
Sigl, Andrea .................AIW 4.2
Sigl, G. ......................TT 8.12
Sigle, Wilfried ............... DS 10.4
Signerski, Ryszard ........ SYOH 5.53

Sihler, J. .................... DS 22.8
Silaghi, S. ................ SYOH 5.19
Silaghi, S. D. ............. SYOH 5.26
Silbermann, Jörg ............ DY 17.5
Sildos, I. ......................DF 2.2
Silva, R. .....................DS 14.2
Simmel, Friedrich SYLS 5.4, SYOH 5.7
Simmnacher, B. ............. TT 13.7
Simon, Jürgen ............... HL 44.9
Simon, P. .................. DS 22.11
Sindel, M. ...................TT 16.7
Sindel, Michael .............. TT 16.6
Sing, Michael .. TT 24.7, TT 24.41,
TT 30.8
Singer, Herman M. DY 25.2, DY 46.70
Singer, Reinhard .............MA 28.1
Singh, A. ................... MA 15.8
Sinner, Eva-Karthin .........SYLS 4.4
Sinning, Hans-Rainer ..........M 25.2
Sinning, S. ....................HL 4.6
Sintec Keramik ................ FB 44
Sischka, A. ................SYLS 3.45
Sischka, Andy ............. SYLS 3.40
Sivasubramanian, Arvind ..... DY 51.6
Skaff, Habib ................CPP 16.9
Skender, Michael ............HL 12.67
Skibbe, O. .................... O 14.4
Skibowski, M. O 28.1, O 28.4, O 28.33
Skorupa, Wolfgang ..DS 18.2, HL 28.6
Skorupska, Katarzyna ..........O 40.3
Skourski, Yurii ...............TT 31.6
Skripov, Alexander V. .......... M 3.4
Skrotzki, W. ....... DS 18.1, MA 15.8
Skrotzki, Werner .. M 22.3, M 22.3,
M 22.4, M 27.2
Skupin, Alexander ........... DY 34.7
Sladecek, Marcel ....... DS 6.2, O 6.4
Slanina, Frantiˇsek ....... AKSOE 10.1
Slezak, Tomasz .........DS 6.2, O 6.4
Slobodskyy, A. .. HL 29.7, HL 29.8,
HL 29.11
Slobodskyy, T. ......HL 29.7, HL 29.8
Slobodskyy, Taras ...........HL 44.20
Slowik, B. ...................MA 16.4
SMART - Kollaboration .... SYOH 1.3
Smet, J. H. ...............SYOH 5.67
Smetanin, M. ................. O 19.7
Smilde, H. J.H. ..............TT 18.3
Smilgies, Detlef-M. ........ CPP 15.13
Smith, David ..AKB 12.1, AKB 50.126
Smith, Grant ............... CPP 14.6
Smith, N. V. ..................O 11.3
Snaith, Henry ..............SYOH 8.2
Snigirev, Anatoly ........... CPP 14.3
Sobal, Neli ........MA 6.5, SYLS 3.19
Socaciu, L. D. ............... O 28.64
Socolar, Joshua E. S. ........ DY 34.2
Söhnchen, S. ............. SYOH 5.13
Söhnchen, Sandra ..........SYOH 1.2
Sohrmann, Christoph ........HL 12.46
Sokolov, Igor M. .. DY 24.7, DY 46.61
Sokolowski, M. ...............O 14.58
Sokolowski, Moritz ..... O 14.64,
SYOH 5.5, SYOH 5.66
Solbach, A. ................... DF 6.3
Solbrig, Heinrich .............M 18.23
Soliman, Ragab ........... CPP 15.31
Solina, D. ...................MA 20.3
Solina, Danica .............. DS 22.35
Solovyev, V. G. ........... SYOH 5.47
Solovyev, Vladimir ........... HL 20.1
Soltan, S. ................... TT 31.5
Soltan, Soltan ............... TT 19.2
Sommer, Jens-Uwe CPP 5.1, CPP 13.2
Somsen, Christoph ...........M 18.20
Songmuang, R. ............. HL 12.62
Sonneberger, S. ..............M 18.15
Soper, Alan ...............AKB 50.61
SOPRA ....................... FB 45
Sordelet, Daniel ...............M 14.2
Sorg, C. .. MA 8.4, MA 15.1, MA 20.2
Sorge, Roland .................DF 6.6
Soriano, Jordi .............. AKB 12.3
Sorin, Chiuzbăian ......... MA 13.109
Soroka, Oleksiy K. ........... TT 8.29
Sotier, F. .................... HL 4.11
Sotomayor Torres, C. M. .. SYOH 5.47
Sotomayor Torres, Clivia ..HL 12.24,
HL 12.26, HL 15.10, HL 20.1,
HL 20.4, HL 20.6, HL 20.8
Soubatch, Serguei ............O 28.23
Souffi, Nacera ............... HL 12.8
Soukoulis, C. M. .............. HL 1.1
Souptel, D. .................TT 24.31
Souptel, Dmitri ..............TT 8.51
Spänig, A. .......... O 14.32, O 28.17
Spaepen, Frans ................ M 8.2
Späth, Bettina ..............DS 22.50
Spaeth, J.-M. ................HL 40.5
Spahn, Michael .....AKSOE 2.2,
AKSOE 3.9
Spaldin, Nicola .............MA 13.94
Spange, S. ....................O 19.7
Spangenberg, T. .............CPP 6.2
Spassov, Vladislav . DS 4.3, DS 13.1,
O 46.4
Spatschek, Robert ........... DY 25.5
Spatz, Joachim AKB 30.3, AKB 50.8,
AKB 50.14, AKB 50.15, CPP 15.4
Spatz, Joachim P. .... AKB 50.7,
AKB 50.13, AKB 50.33,
AKB 50.37, AKB 50.51
Spatz, K. ................. SYLS 3.41
Speck, James ................ HL 16.9
SPECS ........................FB 46
Spehner, Dominique ......... DY 50.4
Spemann, D. .. HL 12.10, HL 12.76,
HL 17.12
Spemann, Daniel HL 12.68, HL 12.69,
HL 12.77, MA 11.1
Sperl, M. .........MA 13.61, MA 15.4
Sperl, Matthias ...... DF 3.3, DY 28.3
Sperlich, M. .................MA 13.4
Sperlich, Martin .............MA 13.2
Sperr, Peter ................. CPP 7.3
Spezzani, Carlo ............SYXM 1.4
Spickermann, Lukas .......... O 14.69
Spiecker, E. ....... DS 14.3, DS 22.36
Spiess, Hans Wolfgang .....CPP 16.12
Spieß, Lothar ................ HL 40.1
Spillmann, Hannes .. O 14.22, O 28.38
Spitaler, J. ................. TT 32.10
Spitzer, A. .................MA 13.41
Spizig, Peter ....... CPP 2.3, O 14.84
Splettstoesser, Janine .......TT 11.10
Spoddig, Detlef ............ MA 13.12
Spode, M. ................SYOH 5.52
Spöler, Carsten ............. DY 46.54
Spolenak, R. .................TT 31.8
Spolenak, Ralph ......... AKB 50.107
Spravedlyvyy, V. AKB 50.3, SYLS 3.24
Sprekeler, H. .................HL 37.5
Sprengel, W. ..................M 32.1
Springborg, M. ................O 11.8
Springborg, Michael ..........O 11.10
Springborn, J. I. ............ HL 12.66
Sprung, Michael ...O 6.3, O 14.48,
O 46.2
Srajer, George ............ MA 13.118
Sreearunothai, Paiboon .....SYOH 2.3
Staab, T. E. M. ..... M 16.4, M 18.15
Staab, Torsten E. M. M 10.2, M 10.3,
M 10.4
Stabaginski, Andreas ....... MA 13.37
Stadlbauer, Martin ...........M 18.10
Stadler, C. ............... SYOH 5.20
Stadler, Christoph ..........SYOH 5.1
Stadler, Frank ........O 28.30, O 32.8
Stadler, Lorenz-M. ...........DY 26.1
Stähler, Julia .........O 28.73, O 37.7
Stafford, C. ................. CPP 6.1
Stahl, B. .....................MA 6.3
Stahl, Branko .. MA 6.7, MA 13.38,
MA 13.82
Stahlmecke, B. .............MA 13.85
Stahlmecke, Burkhard ........DS 12.5
Stalzer, H. .................. TT 8.18
Stamm, M. .................CPP 15.8
Stampfl, Juergen .AKB 50.57, HL 28.8
Stanciu, C. ................... O 18.4
Staneva, Rosina ............ CPP 14.1
Stangl, Julian ................. HL 7.1
Stangl, Rolf ..................DS 13.4
Stankovic, Igor ...DY 46.47, SYPF 5.4
Stanley, H. Eugene ......... SYFT 2.2
Stanzel, J. ................SYOH 5.20
Stanzel, Jörg .............. SYOH 5.1
Stanzick, Heiko .............SYPF 4.1
Stark, Hans-Ulrich ........ AKSOE 4.4
Stark, Holger .... DY 46.30, SYPF 2.1
Stark, Michael ......TT 13.6, TT 13.9
Starke, K. MA 4.9, MA 4.10, MA 13.9,
MA 13.56, MA 17.2, MA 31.2
Starke, Kai .. MA 13.36, MA 28.14,
SYXM 1.3
Starke, Ulrich ................ O 28.23
Starukhin, Dzmitry ........ CPP 16.28
Stath, Norbert ...............AIW 4.1
Stauden, Thomas ............ HL 40.1
Stauffer, Dietrich ........AKSOE 10.3
Stauss, P. ................... HL 10.1
Stavarache, Victorina ....... HL 12.57
Steeb, Felix ................... O 14.7
Steen, C. .................... HL 43.5
Steen, Jeroen ............. AKB 50.81
Stefan, Hoehme ...........AKB 50.39
Steffens, P. ... TT 3.12, TT 14.14,
TT 14.14, TT 30.36, TT 30.38,
TT 30.38
Stegemann, B. ... O 10.6, O 14.45,
O 14.49, O 28.64, O 32.6
Stegemann, Grischa ..........DY 14.8
Steglich, F. ... CPP 10.7, PV VIII,
TT 7.7, TT 7.8, TT 24.33, TT 30.4
Steglich, Frank ............... TT 7.6
Stehr, Dominik ................HL 4.9
Stehr, Joachim ........... SYOH 5.84
Stein, Holger ..................O 38.4
Steinbauer, F. ..............MA 13.76
Steinbeck, Lutz ............ MA 13.99
Steinbock, Oliver ............ DY 22.4
Steiner, Marcus ............ MA 13.25
Steiner, R. ...................DS 22.8
Steinhausen, Marco .......... O 28.18
Steinhauser, Dagmar .........DY 15.2
Steinhoff, Georg .... HL 16.5, HL 16.7
Steinrück, H.-P. .. O 14.9, O 14.12,
O 14.15, O 18.2, O 25.10, O 28.61,
O 43.3
Steins, Roger ................ HL 27.3
Steitz, Roland AKB 50.127, CPP 15.6,
CPP 16.17
Stekolnikov, Andrey .......... O 28.22
Stellmach, C. ............... HL 12.42
Stemler, Thomas ............ DY 36.2
Stemmler, T. ........TT 8.43, TT 9.4
Stemmler, Torsten ..TT 8.16, TT 18.5
Stepanov, Andrey L. ...........O 10.3
Stepanow, Sebastian ......... O 28.38
Stepanow, Semjon ..DY 46.4, DY 51.1
Stepanyuk, V. S. ....... O 3.3, O 24.5
Stephan, Niels ............ SYOH 5.53
Stephane, Pailhes ............. TT 2.3
Stephany, Jorge .............HL 44.61
Sterck, Albert ...... TT 25.5, TT 31.2
Sternemann, Christian ........HL 11.5
Stettner, Jochim .... O 14.44, O 28.59
Stiepel, R. ................... O 28.31
Stierle, A. .............O 34.6, O 38.8
Stierle, Andreas O 34.4, O 34.5, O 46.1
Stille, Werner ............. CPP 16.35
Stipp, Andreas ............. DY 46.66
Stock, Erik .................. HL 37.3
Stockburger, Juergen .........HL 47.5
Stockert, O. ....TT 7.8, TT 21.1,
TT 24.30, TT 24.32, TT 30.4
Stöckel, S. ...................DS 13.5
Stöcker, Bernhard ........... M 18.16
Stöckmann, H.-J. DY 27.1, DY 46.39,
DY 46.40, DY 46.41, HL 20.2
Stöckmann, Hans-Jürgen ....DY 46.38
Stöhr, Joachim .....PV VI, SYXM 1.7
Stöhr, Meike .................O 14.25
Stoffel, Mathieu ..............HL 51.1
Stoffregen, Bernd ............AIW 3.1
Stoica, Mihai .........M 9.2, MA 26.1
Stojetz, Bernhard ............TT 27.9
Stoller, Patrick ............. SYLS 2.3
Stollsteimer, Marcus ........ TT 17.19
Stolz, Heinrich ..HL 4.12, HL 12.12,
HL 28.2, HL 28.4
Stolz, W. HL 25.5, HL 43.1, HL 44.5,
HL 44.47
Stolz, Wolfgang ..............HL 44.6
Storb, Ulrich ....... DY 20.4, DY 20.5
Storch, G. ................... HL 24.2
Storcz, Markus J. ............TT 29.8
Stotz, J. A. H. ...............HL 20.9
Stoyan, Georgiana .............O 39.1
Stoycheva, Svetlana ....... CPP 16.16
Strahl, Alexander ...M 7.3, M 25.3,
M 25.4
Stranges, S. ...................O 33.4
Strassburg, Martin ........... HL 50.2
Strasser, Stefan ..........AKB 50.101
Straub, R. ...................TT 18.3
Straube, Ekkehard ........... CPP 4.2
Straube, Ronny ........... AKB 50.60
Strauch, Dieter .... HL 44.71, O 28.19
Strauch, G. ...............SYOH 5.27
Straß, Michael ...............TT 17.1
Straßer, Benno ...............O 28.32
Strebel, Oliver ..............DY 46.19
Streek, Martin .............SYLS 3.34
Streicher, F. ................... O 9.3
Streicher, Ferdinand ..HL 3.9, HL 25.3
Streit, Simone ............... O 14.48
Streitenberger, Peter .. M 32.2, VA 3.1
Streltsov, S. ................TT 24.45
Strempfer, Joerg .MA 13.118, TT 8.17
Streng, Christoph DY 25.3, DY 46.68,
MA 13.22
Strepp, Wolfram ............DY 46.50
Streubel, K. ................. HL 10.1
Strittmatter, Andre HL 16.10, HL 42.4,
HL 44.89, HL 50.2
Stritzker, B. ........ DS 1.4, DS 22.13
Stritzker, Bernd .. DS 3.2, DS 17.6,
TT 8.31, TT 12.1
Strobel, Paul ................ HL 31.4
Strobl, Gert ..CPP 13.4, CPP 15.19,
CPP 15.29
Strohmenger, Jörn ....M 12.2, M 12.3
Stroisch, Marc .............. HL 12.37
Stromberg, Frank .......... MA 13.11
Stroucken, T. ................. HL 6.1
Autorenverzeichnis
Strub, Erik .................. DS 21.1
Struck, Alexander ...........HL 12.44
Strunk, Christoph .TT 19.4, TT 19.5,
TT 27.9
Strunk, H. P. ....... HL 27.7, HL 30.2
Strunskus, Thomas .DS 7.1, SYOH 1.2
Strunz, Walter T. . TT 17.24, TT 22.5
Struth, Bernd .............. CPP 14.3
Stubenrauch, C. ............SYPF 2.4
Stubenrauch, Cosima ....... SYPF 2.3
Stübinger, T. .............. SYOH 4.4
Stübner, Markus ............SYLS 3.7
Stühn, Bernd .CPP 14.1, CPP 15.18,
HL 23.3
Stührk, A. ................... HL 42.2
Stüßer, N. ..................TT 24.32
Stufler, S. ................... HL 42.1
Stuhrmann, Bjoern ....AKB 12.1,
AKB 50.16
Stuhrmann, Heinrich .......SYLS 3.55
Stumpf, Wolfgang ............HL 15.9
Stutzmann, Martin HL 16.5, HL 16.6,
HL 16.7, HL 27.13, HL 35.5,
HL 48.1, HL 51.2
Stépán, K. ....................O 45.1
Su, Bertram ................ HL 12.94
Su, Y. ..................... TT 24.54
Suck, Jens-Boie ................M 2.1
Sudfeld, D. ................ MA 13.83
Sudfeld, Daniela .. MA 6.8, MA 6.9,
MA 13.78
Süllow, S. MA 21.2, MA 21.3, MA 21.5
Sürgers, C. .. HL 3.8, TT 6.6, TT 8.18
Sürgers, Christoph ..........TT 30.24
Süske, Erik DF 5.6, DS 13.2, DS 17.2,
DY 46.68
Suga, S. ..................... MA 4.2
Suga, Shigemasa ........... TT 24.43
Suga, Sigemasa .............TT 24.41
Sugihara, Minoru ..........AKB 50.31
Sugiono, Erli .............. CPP 16.12
Sukhodub, Gennadiy ........ HL 22.10
Sukumaran, Sathish K. .......DY 51.6
Suleiman, M. .................. M 3.1
Sumiyama, K. ..............MA 13.80
Sun, Baoquan ............. SYOH 8.2
Sun, Jiaming ................ HL 28.6
Sun, L. D. .................... O 25.5
Sun, Y. .......................O 23.9
Sun, Zouzou .................TT 11.6
Supritz, Christoph ......... CPP 16.11
Susha, A. ....................O 28.67
Susha, Andrei ................HL 20.6
Suter, Dieter .................HL 28.2
Suzuki, Takayuki ...... HL 3.5, O 25.4
Suzuki, Y. ................... HL 31.6
Suzuki, Yu .................SYOH 5.3
Suzuki, Yu J. ............. SYOH 5.26
Svane, Axel ................ MA 13.98
Svaneborg, Carsten .CPP 8.5, DY 51.6
Sveningsson, Martin ..........O 28.48
Swinney, Harry L. .. DY 15.3, DY 44.2
Syed, Naweed .............AKB 50.72
Sykora, Steffen .............. TT 20.1
Syrowatka, Frank ............ DF 5.14
Szafraniak, I. ................. DF 6.4
Szamel, Grzegorz .... DF 3.1, DY 28.1
Szotek, Dzidka .............MA 13.98
Taddei, Fabio .............. SYSN 1.4
Taetz, T. ...................TT 30.13
Tagliacozzo, Arturo .......... TT 8.27
Taguchi, Y. ................ TT 24.48
Taillefumier, Mathieu .......MA 27.14
Takabatake, T. ............. TT 24.32
Takada, K. ................. TT 14.13
Takahashi, K. ................HL 5.10
Takayama-Muromachi, E. ... TT 14.13
Takayanagi, H. .............. TT 29.3
Takele, Haile .....CPP 11.4, DS 22.24
Talalaev, Vadim ............ HL 44.69
Talalaev, Vadim G. ...........HL 18.1
Talapin, D. ................. HL 15.12
Talapin, Dimitri ............ CPP 16.6
Talapin, Dmitry .............HL 12.36
Talkner, P ...................DY 40.4
Talkner, Peter ... AKB 50.11, DY 50.5
Tallarida, Grazia .............. DF 5.2
Tallarida, Massimo ............ O 18.7
Talneau, Anne ................ HL 2.2
Tamm, R. ...................MA 15.8
Tamm, Roland ................M 22.4
Tammer, Michael ..........CPP 15.23
Tamura, Takehisa ........... MA 22.3
Tan, Hong W. .............. HL 12.28
Tanaka, A. ...TT 14.11, TT 24.45,
TT 24.46, TT 30.12, TT 32.6
Tanaka, H. ........TT 29.3, TT 30.31
Tanaka, Motomu .....AKB 23.3,
AKB 50.112, AKB 50.117,
AKB 50.119, AKB 50.120,
AKB 50.121, AKB 50.122,
AKB 50.127, AKB 50.129,

AKB 50.130, AKB 50.131, HL 16.5
Tang, W. .... MA 4.6, MA 13.16,
MA 13.122
Tansel, Tunay ................O 28.14
Tarasenko, V. ... MA 13.121, MA 18.2
Tardon, Saioa ................HL 30.4
Taskiran, Ahmet ............. O 14.75
Tassini, Leonardo ............ TT 8.42
Taubner, Thomas ...CPP 2.5, O 14.76
Tauer, Klaus ............... CPP 11.6
Tausendfreund, Andreas .....HL 44.88
Tautz, F. S. ................. O 14.58
tectra ......................... FB 47
Tegenkamp, C. .. O 28.10, O 28.24,
SYOH 5.31
Tegenkamp, Christoph ........O 14.35
Tegude, T. J. ................. HL 9.4
Teich, Sebastian ............. O 14.61
Teichert, C. .........DS 7.4, DS 22.45
Teichert, Christian . DF 5.2, DS 15.2,
O 24.2, SYOH 7.1
Teichler, H. ..........DF 4.4, DY 29.4
Teichler, Helmar ..... DF 4.3, DY 29.3
Teichmann, Jürgen ........... LTR VI
Tejedor, Carlos ........... SYOH 5.57
Telfah, Ahmad .................M 3.4
Telg, Hagen ................. HL 48.2
Tellez-Blanco, Juan-Carlos ..MA 11.10
Temirov, Ruslan ............ DS 22.18
Temko, Yevgeniy ...... HL 3.5, O 25.4
Temmerman, Walter ....... MA 13.98
Tempus, G. ..................M 18.15
Tence, M. .................... HL 3.6
Terentyev, Alexander ....... CPP 16.4
Terfort, Andreas .............. O 33.2
Terheiden, A. .................MA 6.6
Ternes, M. ....................O 17.7
Terris, Bruce D. ............. MA 26.5
Tersoff, Jerry ...............TT 27.10
Tesar, Jiri .............VA 2.1, VA 2.3
Tesch, W. ................ AKB 50.86
Teti, Gabriella .............AKB 50.94
Tetzlaff, Tom ................DY 42.1
Teubert, J. ................. HL 44.47
Teubner, Thomas ............. HL 3.2
Tews, M. .................... HL 42.2
Thalhammer , Stefan .. AKB 50.94,
AKB 50.101
Thalmeier, Peter .. TT 32.11, TT 33.5
Tharmann, R. .............CPP 15.11
Theis, Thomas N. .............. PV V
Theis-Bröhl, Katharina .. MA 13.72,
MA 26.13, MA 26.14
Thelakkat, Mukundan ...CPP 10.1,
CPP 16.33, SYOH 5.45
Therese, H. A. ................M 26.1
Thewes, R. ............... AKB 50.75
Thews, Elmar .............AKB 50.97
Thiaville, André ............. MA 25.1
Thiel, Karsten .... HL 44.44, HL 44.62
Thiel, Werner .............. CPP 16.3
Thiele, C. ..................MA 20.11
Thiele, Karola .............. DS 22.19
Thiele, Uwe ...CPP 6.3, CPP 16.5,
DY 15.1, DY 17.1, DY 46.51
Thielmann, Axel ............. TT 27.5
Thieme, Alexander ........... MA 2.2
Thieme, Gabi ................ DS 22.4
Thieme, Juergen .......... AKB 50.82
Thien, D. ....................O 28.74
Thienhaus, Sigurd DS 22.23, MA 24.5,
MA 24.6
Thiess, Sebastian .....O 25.2, O 28.12
Thillosen, N. ...............MA 13.96
Thissen, Andreas ..............O 44.6
Thißen, Andreas ............ DS 22.50
Thoma, Arne ................ O 39.10
Thomas, Andy ... MA 13.36, MA 27.4
Thomas, Juergen DS 22.22, MA 13.10
Thomas, P. .......... HL 6.1, HL 41.3
Thomsen, C. ................HL 27.14
Thomsen, Christian .......... HL 48.2
Thonke, Klaus ....HL 12.54, HL 12.55
Thorwart, M. ................TT 29.3
Thorwart, Michael .TT 22.6, TT 22.11
Thorwarth, Götz .............. DS 3.2
Thränhardt, Angela HL 32.3, HL 32.4,
HL 32.5
Thul, Rüdiger .............. AKB 50.1
Thurn-Albrecht, Thomas ...CPP 15.32
Thurzo, I. ................ SYOH 5.54
Thurzo, Ilja ...............SYOH 5.36
Tibus, Stefan ................TT 8.53
Tietz, Carsten AKB 23.1, AKB 50.63,
AKB 50.97, AKB 50.100,
AKB 50.116, AKB 50.124
Tietze, Ursula .............. DS 22.35
Tiginyanu, Ivan ............. HL 44.54
Tikhodeev, Sergei ............. HL 2.5
Tilak, V. .................... HL 16.1
Tilgner, Andreas ............ MA 19.1
Tillmanns, A. .....MA 10.8, MA 28.11
Timm, Carsten ...............HL 35.4
Timm, R. .............HL 3.10, O 9.3
Timm, Rainer ........HL 3.9, HL 25.3
Timme, Marc ...... DY 21.3, DY 24.4
Timmins, Peter ............SYLS 3.26
Timoshenko, V. ...............DF 5.3
Tinkham, Michael .......... TT 17.16
Tiritiris, Ioannis ............ TT 30.26
Titz, T. ....................CPP 15.7
Tjeerd, Klaassen ............. HL 38.7
Tjeng, L. H. .. TT 14.11, TT 24.45,
TT 24.46, TT 30.12, TT 32.6
Tkachov, Grigory ...........MA 27.12
Tkeshelashvili, Lasha ......... HL 20.7
Toccoli, Tullio ............... O 14.62
Todorova, M. ................. O 38.8
Töben, Lars ................. HL 33.4
Toennies, J.-Peter .............O 14.6
Tönshoff, H. .................M 18.15
Tönshoff, Hans ............... M 13.2
Toensing, K. .............. SYLS 3.45
Tönsing, Katja .SYLS 3.33, SYLS 3.40
Tokarz-Sobieraj, Renata O 18.5, O 20.8
Tokumitsu, S. ............... TT 14.5
Tokura, Y. ................. TT 24.48
Tolan, Metin O 6.3, O 14.48, O 14.50,
O 46.2
Toliński, T. ................ MA 28.12
Tolkiehn, Martin .............. O 13.1
Tolmacheva, Julia ....... AKSOE 3.13
Tolstykh, P. V. ..............HL 44.67
Tomas, Cezary ................ O 14.8
Tomic, S. ................... TT 6.10
Tong, L. N. ................. MA 13.4
Tong, Liu-Niu ........O 12.3, O 28.11
Tong, Ning-Hua .... TT 16.3, TT 21.3
Tong, Ninghua .............. TT 30.2
Tonner, Friedemann ........ TT 17.27
Tonnère, J.-M. .............MA 13.85
Toperverg, Boris ........... MA 13.72
TOPTICA Photonics ...........FB 48
Torche, Mohamed ...........HL 44.42
Tornow, Marc ...SYLS 3.30, SYLS 4.5
Tornow, Sabine ............ AKB 50.6
Toth, Lajos .................. DS 18.2
Träger, F. .....O 10.2, O 19.4, O 19.8
Träger, Frank ..............SYOH 5.4
Traeger, Franziska .............O 14.6
Tränkenschuh, B. ......O 14.9, O 43.3
Trahms, Lutz .............. SYNP 1.3
Traian Ionica, Crainic ......MA 13.109
Trampert, A. ................MA 31.4
Tranitz, H.-P. .....HL 29.10, HL 44.17
Tranitz, Hans-Peter ......... HL 44.50
Tranitz, P. ...................HL 29.5
Tranitz, Peter ...............HL 12.47
Traulsen, Arne ...............DY 34.3
Trautvetter, Moritz ...........O 28.50
Travis, Kort ................AKB 30.4
Trebin, Hans-Rainer .M 29.2, M 29.4,
M 31.5
Trebst, Simon ............... DY 16.5
Treiber, Martin ........... AKSOE 2.3
Treitz, Norbert .................LTR I
Trellakis, Alex ............... HL 22.8
Trellenkamp, Stefan ..........HL 10.3
Tremel, W. ....... M 26.1, MA 13.117
Tributsch, Helmut .......... DS 22.57
Trimper, Steffen .AKSOE 5.2, DY 42.4
Tripathi, A. K. .............SYOH 3.1
Tritschler, T. ..................HL 4.1
Trixler, Frank O 14.21, O 28.9, O 28.9
Tröger, Wolfgang .... AKB 50.25,
AKB 50.26
Tröndle, Daniel ............. HL 12.75
Tromborg, Biarne ............ HL 38.8
Tromp, R. M. .............SYOH 5.14
Troyer, Matthias .............TT 10.4
Troć, R. .................. MA 13.104
Truman, Pagra ............ SYLS 3.30
Trumm, S. ...................HL 4.11
Trushin, Maxim ..............TT 23.1
Tsarkova, Larisa ............. CPP 2.4
Tschirner, N. ...................O 9.3
Tschirwitz, Christian .DF 3.7, DY 28.7
Tschöpe, Andreas ..M 21.1, M 26.3,
M 26.4
Tse, John S. .................HL 11.5
Tsilimis, Grigorios ............. O 28.5
Tsimilis, G. .................. O 28.34
Tsitsishvili, Elena ........... HL 12.75
Tsukada, Akio ........TT 1.1, TT 8.3
Tsurkan, V. ................. TT 14.3
Tsurkan, Vladimir .. M 18.21, TT 14.4
Tsuwi, Julius ................ CPP 7.6
Tünnermann, Andreas ....HL 2.3,
HL 15.11
Tuncer, Enis ............... CPP 13.9
Turad, Markus .............. MA 22.1
Turban, P. ................. MA 13.35
Turek, Marko ...DY 27.5, DY 50.4,
TT 11.4
Turner, Matthew S. ....... AKB 50.52
Tusche, Christian .MA 10.7, MA 13.54
Tutuc, E. ....................HL 29.2
Tutus, Murat ............ AKB 50.122
Uccelli, E. .................. HL 12.63
Uchida, S. ....................TT 9.1
Uchida, Satoshi ............ AKB 50.4
Uchida, Takashi ............. TT 18.6
Uecker, Reinhard .............DF 5.12
Ueda, M. ....................TT 29.3
Ueda, Y. .........TT 24.52, TT 30.29
Ueno, Nobuo ..................O 33.5
Ueta, Akio ..........HL 21.2, HL 21.4
Uhlarz, M. .... TT 7.9, TT 24.31,
TT 24.39
Uhlemann, Margitta ..........DS 18.4
Uhlig, Thomas .....MA 26.6, MA 26.7
Uhrich, Christian ........... MA 13.68
Uhrig, Götz S. ...TT 3.2, TT 15.3,
TT 15.7, TT 24.19
Uhrig, Götz Silvester .........TT 26.4
Uhsaghy, O. ................TT 11.13
Ulbrich, Maximilian H. .... AKB 50.74
Ulbrich, R. G. ....HL 3.8, HL 9.5,
HL 12.92, HL 33.2, HL 44.65,
MA 13.65, MA 14.2, O 9.4
Ulbrich, R. G. U. ..............DS 4.1
Ulbricht, G. ...............SYOH 5.67
Ullmann, Andreas ..........SYOH 4.1
Ulman, Abraham ....AKB 50.131,
CPP 16.16
Ulmeanu, M. .................MA 6.4
Ulmer, Jens ................AKB 50.8
Ulrich, C. .... TT 14.2, TT 24.47,
TT 24.48
Ulrich, Konstantin ........... TT 20.3
Ulrich, Marco ................CPP 3.4
Ulrich, S. M. .................HL 36.7
Umansky, Vladimir ......... MA 13.70
Umbach, E. ... CPP 12.6, HL 12.5,
HL 24.2, HL 24.3, O 4.2, O 33.4,
O 44.8, SYOH 1.3, SYOH 5.20
Umbach, Eberhard ......... SYOH 5.1
Unger, Eugen ................ HL 46.1
Unger, R.-S. .................. TT 9.4
Unger, R.-St. ................TT 8.43
Uni Duisburg - Kollaboration ..MA 6.5
Unold, Thomas .... DS 22.51, HL 50.8
Unterricker, S. ..MA 11.2, MA 11.2,
MA 13.108
Urayama, Kenji .............CPP 10.2
Urban, G. .................. DS 22.55
Urban, I. ..................... DF 5.3
Urban, K. .... DS 1.1, M 30.5, M 31.6
Urban, Knut .........M 18.24, O 40.5
Urban, R. ....................HL 29.3
Usadel, K. D. .............. MA 10.10
Usadel, Klaus D. ............ MA 17.4
Ushakov, Oleg ..............TT 24.35
Ustinov, A. V. .. TT 8.21, TT 8.28,
TT 17.23, TT 17.25, TT 25.2,
TT 29.2, TT 31.1
Ustinov, V. M. ..............HL 50.10
Uzdin, V. ................... MA 18.1
Uziel, J. ..................SYOH 5.52
v. Feilitzsch, Franz ...........TT 13.9
v. Gynz-Rekowski, Felix .......O 28.63
v. Klitzing, Regine ... AKB 50.127,
CPP 11.1, CPP 15.6, CPP 16.15,
SYPF 2.2
v. Löhneysen, H. .HL 3.8, SYOH 6.2,
TT 6.6, TT 8.18, TT 17.8,
TT 17.11, TT 21.1, TT 24.30,
TT 24.31, TT 24.38, TT 24.39,
TT 27.2
v. Löhneysen, Hilbert ....... TT 30.24
v. Loewenich, Clemens ....... DY 36.4
V. R., Galakhov ...........MA 13.109
v. Wenckstern, H. ............HL 28.5
VACOM .......................FB 49
Vagt, S. ..................... O 28.24
Vagt, Svend ................. O 28.44
Vaida, M. ....................O 28.64
Vala, Jiri .................... TT 29.8
Valdaitsev, D. A. DS 22.27, DS 22.28,
MA 13.71, MA 13.105, O 28.75
Valencia, Sergio ..O 28.78, O 28.80,
O 28.82, SYXM 1.1
Valenta, A. ............... AKB 50.86
Valenti, Roser ... MA 13.111, TT 32.3
Valenzuela, Sergio O. ....... TT 17.16
Valery, Shastin ...............HL 38.7
Vallaitis, Thomas ............ HL 25.2
van Aken, Peter ...............DS 9.1
van den Brandt, B. ........ SYLS 3.55
van den Brink, Jeroen ........TT 14.7
van der Hart, A. .............MA 26.4
van Dongen, P. G.J. ........ TT 24.12
van Dongen, Peter G. J. .... TT 30.35
van Driel, Henry M. .........HL 12.28
Van Eek, Stella M. ............ O 39.5
Van Eek, Stella Maris ........MA 20.1
Autorenverzeichnis
van Heel, M. .............. SYLS 3.13
van Heys, Jan ................O 14.52
Van Labeke, Daniel .......... O 28.54
van Loyen, Ludwig ......... MA 13.10
van Riesen, Sascha ..........HL 44.48
van Slageren, Joris .......... MA 21.8
van Smaalen, S. ............ TT 30.18
van Staa, Alexander ..........HL 44.4
van Teeffelen, Sven ........AKB 50.84
Vancea, Johann ............ MA 13.86
Vanderzande, Dirk ........ SYOH 5.51
Vanormelingen, Koen ..........DS 6.2
Vantomme, Andre .............DS 6.2
Varga, Franz ..............AKB 50.57
Varga, P. .................... O 25.10
Varga, Peter .......... O 34.4, O 39.8
Vargoz, Emmanuel ............. O 5.2
Varlamov, Serguei .......... TT 24.22
Vartanyan, T. ......... O 10.2, O 19.4
Vartanyants, I. A. ............. O 14.2
Varykhalov, A. ........ O 24.4, O 32.2
Vasil’ev, V. .................TT 30.29
Vasiliev, A. .................TT 30.31
Vassioukov, Denis ............TT 8.25
Vauth, Sebastian .. DY 46.68, O 14.51
Vavilov, M. G. ............... HL 14.2
Vaz, C. A. F. ................MA 25.2
Vedmedenko, Elena ........ MA 26.12
Vedmedenko, Elena Y. ......MA 26.10
Veit, Peter ................. HL 44.81
Velleuer, J. ..................MA 18.1
Vendruscolo, Michele .......AKB 40.4
Venkataraj, S. ............... DS 18.3
Venkataraj, Selvaraj DS 12.4, DS 22.43
Venkataraman, Shankar ....... M 14.2
Venturini, Francesca ......... TT 8.42
Verduijn, Erik .....MA 13.32, O 28.79
Verechtchaguina, Tatiana .... DY 24.7
Vergeer, Frank .............SYOH 5.6
Verges, P. ................... TT 12.3
Verges, Peter ................ TT 12.4
VeriCold Technologies ..........FB 50
Veronese, M. .................MA 3.1
Vertommen, François ....... DS 22.26
Verucchi, Roberto ............O 14.62
Vettiger, Peter .............. CPP 2.1
Vianden, R. ... DF 5.11, HL 44.49,
HL 44.70
Vidrich, Gabriele .............. M 26.2
Vigliante, A. ......... DS 9.2, O 28.83
Vignoli, Stephane ............ HL 30.3
Vilgis, Thomas ............AKB 50.10
Villmann, Thomas .......... DY 46.11
Vinogradov, Alexandr ........MA 13.2
Vinokur, Valerii ..............TT 31.9
Vinzelberg, Hartmut ....DS 22.40,
DS 22.41, MA 13.10, MA 13.97
Visbeck, S. ......... HL 24.2, HL 24.3
Vitali, Lucia ...........O 11.5, O 15.1
Vitzethum, M. ............... HL 42.1
Vlad, Alina ................... O 34.6
Vladimirov, A. ..............TT 24.23
Völker, Klaus ................ TT 10.4
Voelker, Moritz ........... AKB 50.80
Völker, Thomas ............ DY 46.75
Völker, U. .................... DF 2.4
Voelkmann, C. ...............HL 31.1
Voevodin, V. ............... CPP 10.7
Vogel, Horst .. CPP 9.6, SYLS 3.43,
SYLS 3.44, SYLS 5.2
Vogel, J. ...................MA 28.10
Vogel, M. ................... DS 21.3
Vogel, Mirko ............. SYOH 5.41
Vogel, Thomas ....CPP 5.4, DY 46.58
Vogelgesang, Michael ..........O 15.1
Vogelgesang, Ralf ............. O 23.8
Vogl, Gero ....DS 6.2, DY 26.1, O 6.4
Vogl, Peter ......... HL 22.8, HL 47.8
Vogt, F. ....................HL 12.43
Vogt, Jochen ................. O 14.6
Voigt, Felix ..................DS 14.7
Voigt, Michael ............SYOH 5.66
Voigt, T. ...AKB 50.3, AKB 50.17,
SYLS 3.24
Voigtländer, B. ................O 25.7
Voigtländer, Bert ..............O 32.7
Voisin, Paul ..................HL 41.4
Vojta, Matthias ..TT 16.2, TT 16.3,
TT 21.2, TT 21.3, TT 26.11,
TT 30.2
Volbers, N. ................. HL 17.11
Volk, Martin ................SYLS 4.3
Volkel, Armin R. ........... SYOH 3.3
Volkmann, T. ................O 14.31
Volkmann, Thomas ... M 12.2, M 12.3
Vollhardt, D. ....... TT 24.1, TT 24.2
Vollhardt, Dieter ............TT 24.42
Vollmayr-Lee, Ben ........... DY 51.5
Vollmer, R. ... MA 4.6, MA 13.16,
MA 13.122, TT 24.29
Vollweiler, Goetz ............DS 22.58
Volmer, Martin .............. HL 11.5

Volz, K. .................... HL 44.47
vom Stein, Peter .............TT 11.2
von Bergmann, K. ..............O 8.1
von Bergmann, Kirsten ... MA 4.8,
MA 26.12
von Borany, J. .....DS 22.34, O 14.77
von Borczyskowski, Christian
CPP 16.21, CPP 16.28, HL 50.6,
HL 50.7, SYOH 5.8, SYOH 5.10
von Delft, J. .................TT 16.7
von Delft, Jan ......TT 15.8, TT 16.6
von der Heydt, Irmgard ..... DY 46.65
von der Heydt, Nikolaus .....DY 46.65
von der Linde, D. ............ O 28.74
von der Linden, Wolfgang . TT 24.4,
TT 24.5, TT 30.10
von Feilitzsch, F. ............ TT 13.7
von Feilitzsch, Franz TT 13.5, TT 13.6
von Ferber, Christian ........ CPP 5.2
von Freymann, G. ............. HL 1.1
von Gersdorff, Katharina ... SYLS 3.42
von Hauff, Elizabeth ...... SYOH 5.56
von Hofe, Thomas ............ O 26.1
von Klitzing, K. ..HL 14.4, SYOH 5.67
von Lampe, Irene ............ TT 8.15
von Middendorff, Claas .. HL 12.50,
HL 12.90
von Oehsen, Sebastian ......MA 13.91
von Oeynhausen, Viola ....... O 28.68
Von Oppen, Felix ........ AKB 50.103
von Plessen, G. ............... O 19.6
von Plessen, Gero DY 46.96, O 28.40,
O 28.65, O 28.66
von Rhein, A. ................. HL 6.3
von Ribbeck, Hans-Georg ... DY 46.97
von Sawilski, Lars ............TT 8.34
von Seggern, Heinz .....HL 23.4,
SYOH 5.71, SYOH 5.77
von Sonntag, Justus ..........O 28.21
von Sprekelsen, Martin ....... O 14.70
von Wenckstern, H. ....HL 12.73,
HL 17.12
von Wenckstern, Holger ..HL 12.68,
HL 12.77, HL 12.81, HL 12.84,
HL 44.11, HL 44.51
von Zeppelin, Frank ........ SYPF 4.1
von Zimmermann, Martin .... TT 8.17
Vongtragool, Suriyakan ...... MA 21.8
Vor der Brüggen, Jens ......SYOH 5.4
Voronov, Boris ................TT 1.2
Voronv, Andrej ............. CPP 15.5
Voss, Johannes ............. HL 44.29
Voss, S. ............. DF 4.6, DY 29.6
Voss, Stephan ....... DF 4.9, DY 29.9
Voss, T. ...................... HL 4.5
Voss, Tobias .................. HL 4.2
Voß, Oliver ................. HL 44.44
Vragović, Igor ...............HL 12.98
VTS CREATEC ................FB 51
Vu, Q. T. .....................HL 4.1
Vuilleumier, Rodolphe ...... CPP 10.5
Vuletic, T. .................. TT 6.10
Vyalikh, D. ..... MA 13.4, SYOH 5.38
Vyalikh, D. V. ..................O 3.4
Vyalikh, Denis ........MA 13.2, O 4.7
Vyborny, Karel ...............HL 22.5
W. Berg, Tommy ............ HL 38.8
Waag, A. .HL 12.18, HL 17.4, HL 37.4
Waag, Andreas ..HL 12.79, HL 35.3,
HL 35.5
Wacha, Marcus ............CPP 15.26
Wachowiak, Andre ............ O 23.6
Wachowiak, André ............ O 39.2
Wacker, A. HL 5.2, HL 37.5, SYSN 2.4
Wacker, Andreas ........... DY 46.32
Wächter, Markus ............ DS 15.2
Wälte, A. .....................TT 9.6
Wälte, Andreas ............... TT 9.9
Wagenhuber, K. ............. HL 29.5
Wagenhuber, Klaus ......... HL 44.50
Wagermaier, Wolfgang .... AKB 50.53
Wagner, Christian DY 15.4, DY 46.63,
DY 46.76
Wagner, Dieter ................O 10.8
Wagner, Ernst .............SYLS 3.42
Wagner, F. .................. HL 21.6
Wagner, Friedrich ....... AKSOE 10.2
Wagner, G. ........DS 22.46, HL 28.5
Wagner, Gerald .DS 22.52, HL 12.61,
HL 44.58, HL 44.64
Wagner, Guenter .....DS 9.4, HL 52.3
Wagner, Hans-Erich .........DS 22.17
Wagner, Herbert ............DY 46.87
Wagner, Peter ..... AKSOE 2.1,
AKSOE 2.2, AKSOE 3.9
Wagner, R. ......... DF 5.10, HL 16.3
Wagner, Ronny ............. DS 22.12
Wagner, S. .......... O 28.60, O 43.6
Wagner, Stefanie ..HL 44.9, MA 13.39
Wagner, Thomas ............ TT 29.4
Wagner, Thorsten ............O 14.63
Wagner, V. .SYOH 5.62, SYOH 5.64,
SYOH 5.65
Wagner, Veit .............. SYOH 3.3
Wahl, M. .................... O 14.59
Wahl, Markus ................O 14.25
Wahl, Peter ... O 11.5, O 15.1, O 26.2
Wahle, M. ................... HL 44.2
Wahn, Matthias ..............HL 53.2
Walaszek, Bernadeta .........CPP 3.2
Wald, Christian ..............DY 51.5
Waldauf, Christoph ....... SYOH 5.50
Waldmann, W. ... HL 44.74, HL 44.75
Waldmueller, E. ...............HL 8.1
Waldner, Isabella ............ CPP 4.4
Walheim, Stefan ....CPP 2.3, O 14.84
Walhorn, Volker ...........AKB 50.81
Walke, R. ................... DY 14.9
Wallis, Thomas M. ............. O 2.1
Wallisser, Christoph ..........TT 11.2
Wallraff, A. .. TT 17.23, TT 17.25,
TT 25.2, TT 29.2
Wallrapp, Frank ...........AKB 50.77
Walter, H. ................. CPP 11.3
Walter, T. ................. MA 20.11
Waltereit, Patrick ............ HL 16.9
Walterfang, M. .............. DS 17.5
Walther, Jens ................O 14.17
Walther, Markus ............DY 46.69
Walther, Martin ...............HL 4.3
Walz, Christof ................ M 31.5
Walzel, Peter ................DY 44.3
Walzer, K. ...................O 14.77
Walzer, Karsten O 4.1, O 14.62, O 33.7
Wamwangi, Daniel HL 11.2, HL 12.9,
HL 12.53
Wandelt, K. ........ O 14.32, O 28.17
Wandelt, Klaus .. O 14.11, O 14.24,
O 14.37, O 14.39, O 28.18, O 43.5
Wanderka, N. ...M 9.3, M 9.5, M 22.5
Wanderka, Nelia ......M 15.1, M 22.6
Wang, C. R. ................HL 44.25
Wang, Changzhong .......... HL 17.9
Wang, Chun ................. O 28.62
Wang, Cunrang ...... O 13.1, O 14.42
Wang, H. ..................MA 13.62
Wang, Huabing ..............TT 8.25
Wang, J. MA 13.53, MA 16.3, MA 20.7
Wang, Jian ................... O 34.7
Wang, Ke .................. HL 12.53
Wang, N.-P. ........ O 14.47, O 28.72
Wang, Peng-Fei ..............HL 10.5
Wang, Rong-Yao .......... CPP 16.18
Wang, S.-C. .................. O 33.3
Wang, Shidong .............. TT 11.6
Wang, W. ... MA 13.13, MA 15.5,
MA 20.7, O 39.9
Wang, Xiangrong ............ TT 11.6
Wang, Yuemin O 20.1, O 20.3, O 38.9
Wang, Zhi-Hong ............TT 24.54
Wanjek, M. ...................HL 8.1
Wannemacher, Reinhold ......HL 15.6
Wanner, Matthias .......... DY 46.72
Warming, Till .... HL 36.11, HL 50.10
Warren, S. ...................O 28.52
Waser, R. .............DF 6.3, DF 6.7
Wasilewski, Z. ..... HL 36.3, HL 44.34
Wasniowska, M. ...MA 13.14, O 14.43
Wasserman, D. .............. HL 29.2
Wasserman, E. F. ........... MA 6.10
Wassermann, E. F. ... MA 13.113,
MA 23.1
Wassermann, Eberhard F. ....MA 24.1
Wassner, Thomas A. ......... HL 35.5
Wastin, F. ................. MA 13.19
Weaire, Denis .............. SYPF 1.1
Weber, C. .................... O 17.7
Weber, Eicke ..................O 40.5
Weber, F. .................. TT 24.39
Weber, H. B. ...O 37.2, SYOH 6.2,
TT 17.11, TT 17.14, TT 27.2
Weber, Hans ............ AKSOE 3.13
Weber, Heiko B. ....TT 19.3, TT 27.8
Weber, J. ....................O 14.77
Weber, Jörg ....... HL 44.72, O 14.78
Weber, Jürgen ....HL 38.10, HL 38.12
Weber, Markus C. ...........MA 28.9
Weber, Markus Christian .....MA 10.3
Weber, N. ................... O 28.51
Weber, Peter ............... TT 24.35
Weber, Philipp ........... AKSOE 3.1
Weber, Ramona ...............O 19.2
Weber, S. ....... M 18.26, MA 13.104
Weber, Sebastian ...........DY 46.69
Weber, Werner ..... TT 24.3, TT 28.5
Weck, Werner ............... TT 12.2
Wecker, Joachim MA 13.51, MA 16.2,
MA 27.7
Wedel, Armin .............SYOH 5.76
Weeke, S. ................... HL 43.4
Weeke, Stefan ............... HL 33.1
Wegener, M. HL 1.1, HL 4.1, HL 8.3,
HL 8.4, HL 15.8
Wegener, Martin .............HL 15.7
Wegener, Michael .....CPP 13.9,
CPP 15.41
Wegewijs, Maarten .......... TT 27.4
Wegewijs, Maarten R. ....... MA 21.4
Wegner, Daniel ........O 17.5, O 28.7
Wegner, Gerhard .....SYOH 2.4,
SYOH 5.85
Wegner, Sebastian ............ O 28.5
Wegscheider, W. . HL 14.3, HL 14.4,
HL 22.4, HL 29.5, HL 29.10,
HL 43.2, HL 44.17, HL 44.18,
HL 44.27, HL 44.37, HL 44.46
Wegscheider, Werner .... HL 5.7,
HL 12.39, HL 12.47, HL 12.94,
HL 27.5, HL 27.6, HL 32.6,
HL 38.1, HL 44.3, HL 44.7,
HL 44.50, HL 44.87, MA 13.70,
TT 19.4, TT 19.5
Wehlack, Carsten ............CPP 7.3
Wehn, Robert .................DF 5.6
Wehner, Susanne ..........CPP 16.22
Wehrspohn, Ralf ............. HL 15.2
Wehrspohn, Ralf. B. ....HL 12.28,
HL 12.35, HL 15.4, SYLS 3.23
Weickert, F. .................. TT 7.7
Weickert, Franziska ........... TT 7.6
Weidemann, G. .............SYPF 4.4
Weidemann, Olaf ............ HL 16.6
Weidenkaff, A. ..............HL 12.51
Weides, M. ................. MA 26.4
Weides, Martin .............. TT 8.54
Weidner, Tobias ........... SYOH 5.4
Weigand, H. ..................M 32.1
Weigand, Wolfgang ........ SYOH 5.1
Weigel, Martin .... DY 16.3, DY 46.93
Weigelt, Udo ................ AIW 6.1
Weigend, F. ................. TT 17.6
Weigert, Andreas ........... CPP 16.7
Weigl, F. .....................MA 6.3
Weigl, Frank ..................O 32.5
Weih, Petia ..................HL 40.1
Weikl, Thomas ............AKB 50.93
Weiland, R. ................. TT 13.7
Weiler, Ulrich SYOH 5.33, SYOH 5.48
Weimar, A. ................. HL 44.83
Weimar, Andreas ....HL 27.5, HL 38.5
Weinelt, M. ...................O 39.3
Weinelt, Martin ... O 36.1, O 37.1,
O 37.4, O 45.7
Weiner, Domenique ........... O 23.2
Weinhardt, L. .. CPP 12.6, HL 24.2,
HL 24.3, O 44.8
Weinhold, Swen .............HL 12.84
Weinkamer, Richard ...AKB 50.21,
DY 26.1
Weirich, Thomas E. ........... O 10.3
Weis, Juergen ................HL 37.6
Weis, Marcus ................ HL 10.5
Weise, K. ....................DS 13.5
Weiser, Stefan ...............TT 24.3
Weishart, Hannes ............ DS 18.2
Weisheit, Martin ...MA 30.5, MA 30.6
Weismann, A. ..................O 9.4
Weiss, D. .... HL 29.5, HL 29.10,
HL 44.18, HL 44.46
Weiss, Dieter .. HL 12.39, HL 44.3,
HL 44.7, MA 13.70, MA 26.7
Weiss, G. ........ TT 30.15, TT 30.40
Weiss, Heinrich .............TT 24.28
Weiss, Helmut ................ O 14.6
Weiss, Thomas ............CPP 15.30
Weisse, Olaf .................. O 26.5
Weissmüller, J. ............... M 20.5
Weissmüller, Jörg ............. M 20.4
Weißbach, Rafael ......... AKSOE 1.2
Weiß, Stephan ...............TT 17.9
Weiß, Volkmar ..............DS 22.57
Weiße, Alexander ............ TT 30.6
Wejrzanowski, T. ............. M 32.1
Welker, Armin C. ............ HL 37.6
Well Diamantdrahtsägen ....... FB 52
Weller, Dieter ................ PV XIV
Weller, H. .................. HL 15.12
Weller, Horst .....CPP 16.6, HL 12.36
Welsch, Holger ......HL 5.9, HL 12.93
Welter, B. ...................TT 18.4
Welter, Bettina .............. TT 8.19
Welter, Steve .............. SYOH 5.6
Welzel, Thomas .... DS 4.2, DS 22.42
Wen, Gangyao ............ CPP 16.13
Wende, H. MA 8.4, MA 15.1, MA 20.2
Wenderoth, M. DS 4.1, HL 3.8, HL 9.5,
HL 12.92, HL 33.2, HL 44.65, O 9.4
Wendler, Elke .........DS 1.5, DS 2.1
Wendler, Frank ................ M 4.4
Wendrock, Horst ............DS 22.31
Wenger, Christian .....DF 6.6, DS 9.3
Wennersbusch, N. .........AKB 50.99
Wenning, Ludger ........... CPP 14.8
Wenzel, Sandro .............DY 46.92
Wenzel, W. ...............SYOH 5.59
Wenzel, Wolfgang ..MA 21.4, TT 27.4
Autorenverzeichnis
Wermeille, D. .............. TT 24.54
Werner, A. G. ............ SYOH 5.39
Werner, Ansgar ...........SYOH 5.40
Werner, C. ....... HL 44.76, HL 44.76
Werner, Carsten ........... SYLS 3.46
Werner, Christoph HL 12.16, HL 28.10,
HL 33.3
Werner, J. H. .......HL 19.3, HL 30.2
Werner, Jan .................. M 14.4
Werner, Jochen .............DS 22.41
Werner, Johannes ............DY 36.2
Werner, Marcus .... CPP 10.6, DF 5.5
Werner, Peter .............. HL 44.69
Werner, Philipp ..............TT 10.4
Werner, Ralph .. DY 46.72, TT 6.1,
TT 21.5
Wernicke, D. ................ TT 13.7
Wernicke, Doreen ............TT 13.9
Wernsdorfer, W. .............MA 25.2
Wesch, W. ....................DS 1.8
Wesch, Werner ... DS 1.5, DS 2.1,
DS 15.4
Weschke, E. .. MA 13.85, TT 14.11,
TT 30.12
Wesenberg, Claudia ........... O 26.5
Wessel, Stefan ..... TT 10.4, TT 24.8
Wessendorf, Marlies ... O 14.7, O 45.4
Westerhoff, Frank ....... AKSOE 10.3
Westerholt, Kurt MA 13.11, MA 13.32,
MA 13.42, MA 16.8, MA 20.8,
MA 30.8
Westerkamp, Tanja ........... TT 7.4
Westermann, Jörg .............O 23.5
Westerwal, Ruud J. ........... O 26.8
Westhäuser, Wilko MA 13.29, TT 1.5,
TT 8.9
Westphal, C. O 28.6, O 28.27, O 28.28
Westphal, Wolfgang TT 13.6, TT 13.9
Westphalen, Andreas ... MA 26.13,
MA 26.14
Wette, Patrick .CPP 12.1, DY 46.55,
DY 46.56
Wette, Patrik ...............DY 46.46
Wetzel, Bernd ..............CPP 15.3
Wey, Karin ....................VA 3.2
Weyand, K. ................ MA 13.80
Weyers, Bastian ...............O 17.3
Weyers, M. ................... HL 3.3
Weygand, Daniel ..............M 16.1
We̷l. nic, Wojciech .......... HL 44.43
Whaley, K. Birgitta .......... TT 29.8
Wichert, Th. ........HL 21.5, HL 21.6
Widdra, W. ............... CPP 16.31
Widdra, Wolf ..O 4.6, O 28.77, O 34.7
Widemann, Toni ............. LTR XII
Wiebe, Jens .O 5.8, O 14.29, O 23.6,
O 39.2
Wieck, A. ................... HL 42.1
Wieck, A. D. ...HL 12.1, HL 12.56,
HL 22.1, HL 36.12, HL 44.24,
HL 44.76, HL 44.76
Wieck, Andreas .HL 12.15, HL 12.49,
HL 12.57, HL 22.11, HL 44.10
Wieck, Andreas D. ..HL 3.1, HL 5.1,
HL 37.9, HL 44.21, HL 44.26,
HL 44.78, HL 50.8
Wieckhorst, Ole ......... O 6.1, O 6.7
Wiedenmann, Albrecht ...DY 11.1,
MA 11.7
Wiedenmann, Klaus ..........TT 18.2
Wiek, A. D. ................. HL 47.3
Wiekhorst, Frank ...........MA 13.81
Wiele, Klaus ............... MA 13.57
Wiemann, Carsten ....O 28.76, O 45.4
Wienands, J. .............. SYLS 3.45
Wienands, Jürgen ......... SYLS 3.40
Wiersig, J. ......... DY 27.3, HL 36.7
Wiese, Nils ..................MA 16.2
Wiese, Ruben ...............DS 22.16
Wiesendanger, R. .MA 13.123, O 8.1,
O 14.65
Wiesendanger, Roland ... HL 37.2,
MA 2.6, MA 4.7, MA 4.8, MA 17.3,
MA 26.12, O 5.8, O 9.1, O 14.29,
O 14.70, O 14.71, O 14.72, O 17.2,
O 23.6, O 28.39, O 39.2, TT 31.4
Wieser, Robert .............. MA 17.4
Wieser, Ulrich ...HL 3.1, HL 12.64,
HL 44.26
Wietler, T. ....... HL 44.25, HL 44.73
Wiezorek, Jorg ................M 19.1
Wilbrandt, P.-J. ...............HL 9.5
Wilbrandt, Peter-J. ........... M 17.1
Wilczek, Darius ........... AKB 50.96
Wild, Georg ......TT 17.20, TT 17.21
Wild, Urs P. .. CPP 9.6, SYLS 3.43,
SYLS 3.44, SYLS 5.2
Wilde, F. ................... HL 44.38
Wilde, Gerhard M 7.2, M 9.1, M 14.1,
M 14.3, M 20.1, M 24.1
Wilde, M. A. ............... HL 12.66
Wilhelm, F. ..................TT 29.5

Wilhelm, Frank . TT 17.4, TT 17.18,
TT 22.8
Wilhelm, Frank K. ........... TT 29.8
Wilhelm, Thomas .... DS 20.5, O 40.3
Wilke, Hans-Joachim ..........LTR III
Wilke, Marlis ..............AKB 50.56
Wilke, Ralf ................ SYLS 3.33
Wilkening, Martin .............M 10.5
Wilking, S. D. .............SYLS 3.45
Wilking, Sven David ....... SYLS 3.31
Wille, Eric ...................DY 36.1
Wille, Sebastian ..............DS 15.7
Wille, U. .................... HL 44.1
Willeke, G. .................. HL 19.5
Willi, Sylvia ...............AKB 50.97
Williams, Keith A. .....O 9.1, O 28.39
Willig, Frank ... DS 21.4, HL 33.4,
O 28.25, O 40.4
Willumeit, R. ............... DS 22.45
Wilson, Mark ................. DF 2.3
Wiltschko, Wolfgang ............PV X
Wimmer, Michael .......... MA 27.11
Windisch, R. .................HL 10.1
Winkelkemper, Momme ...... DS 20.5
Winkelmann, Max .......... TT 24.34
Winking, L. HL 9.5, HL 12.92, HL 33.2
Winkler, A. ................... DS 7.4
Winkler, Adolf ............SYOH 5.12
Winkler, Carsten .............. O 45.3
Winkler, H. ................ SYNP 2.4
Winkler, R. .................. HL 29.2
Winkler, Roland ............ HL 12.15
Winkler, Roland G. .......... DY 51.7
Winnerl, Stephan ......HL 4.4, HL 9.2
Winning, Myrjam ..... M 20.3, M 32.3
Winter, B. ................ CPP 16.31
Winter, Barbara ............SYOH 7.1
Winter, Bernd ..........O 4.6, O 19.2
Winter, Jörg .................. O 31.2
Winterer, Markus .............MA 6.7
Winterlich, Manfred DF 4.1, DY 29.1,
DY 46.7
Winzer, A. T. ...HL 16.3, HL 27.4,
HL 27.12
Winzer, K. .................. TT 8.47
Winzer, Klaus ............... TT 8.52
Wirges, Werner . CPP 13.9, CPP 15.41
Wirthmann, André ..........HL 12.11
Wirtz, Konrad ............... HL 27.3
Wischmeier, Lars ..............HL 4.2
Wissel, Felix ................DY 46.27
WiTeC ........................ FB 53
Witko, Malgorzata .... O 18.5, O 20.8
Witte, G. .................SYOH 5.13
Witte, Gregor ..............SYOH 1.2
Witte, H. ...AKB 50.3, AKB 50.17,
HL 27.12, SYLS 3.24
Witte, Ulrike ................. MA 3.3
Witthuhn, W. ...HL 12.6, HL 12.7,
HL 24.6, HL 27.8, HL 30.5
Witthuhn, Wolfgang ......... HL 40.3
Wittich, Gero . O 11.5, O 15.1, O 26.2
Wittkowski, T. .......DS 6.4, DS 13.5
Wittwer, Oliver ............. DY 46.71
Wixforth, A ................. DY 40.4
Wixforth, Achim ..............LTR IV
Wochner, P. ......... DS 9.2, O 28.83
Wochner, Peter ..............TT 20.6
Wodzinski, Rita ...............LTR XI
Wöhlecke, M. .DF 2.4, DF 7.2, DF 7.3
Wöhrl, Nicolas ..............DS 22.38
Wöhrle, Dieter .O 14.60, SYOH 5.11,
SYOH 5.25, SYOH 5.48
Wölfle, P. .................. TT 11.13
Woelfle, Peter ...... HL 8.5, TT 26.11
Wöll, C. ..................SYOH 5.13
Wöll, Christof ..............SYOH 1.2
Wöltgens, Han-Willem ....... HL 11.2
Woerz, Bernhard .............TT 12.1
Woess, Alexander ............ HL 28.8
Wöste, L. .... O 10.6, O 28.64, O 32.6
Woesz, Alexander ......... AKB 50.57
Woggon, U. ................. HL 36.3
Woggon, Ulrike .............. HL 15.6
Woicik, Joe C. ............... O 28.12
Woike, Th. ... DF 2.4, DF 7.2, DF 7.3
Woike, Theo CPP 10.6, DF 2.5, DF 5.5
Wojczykowski, K. .......... MA 13.83
Wojczykowski, Klaus MA 6.8, MA 6.9,
MA 13.78
Wolde-Giorgis, Daniel ......... M 24.2
Wolf, Adriana .............. HL 38.11
Wolf, Fred ......... DY 21.3, DY 24.5
Wolf, H. ............HL 21.5, HL 21.6
Wolf, Henning ................ O 40.8
Wolf, M. .... O 28.60, O 43.6, TT 6.4
Wolf, Martin ..HL 44.66, MA 28.14,
O 28.73, O 37.7, O 45.2
Wolf, Thomas ............... TT 8.17
Wolf, Walter ...................M 8.1
Wolfframm, Dirk ....DS 17.1, DS 22.9
Wollgarten, M. .................M 9.5
Wollschläger, Joachim ... O 14.38,
O 14.41, O 14.42
Wollweber, Jürgen .......... HL 44.42
Wolpert, D. ..................O 14.57
Wolter, A. .................. MA 21.5
Wolter, A. U.B. ... MA 21.2, MA 21.3
Woltersdorf, G. .............. HL 29.3
Woltersdorfer, Georg ....... MA 28.13
Wolverson, D. ............... HL 21.1
Wondraczek, Katrin ....... CPP 16.22
Wong, John ................CPP 15.6
Wong, S. P. ................ DS 22.13
Wormeester, Herbert .. O 10.1, O 39.1
Worschech, Lukas ...DS 22.44, HL 5.5
Wortmann, Daniel . MA 27.2, MA 27.9
Wosnitza, Jochen ...........TT 30.27
Wottawah, Falk AKB 12.1, AKB 30.4,
AKB 50.113, AKB 50.125
Woywod, Dirk ............... DY 17.5
Wrachtrup, Jög .............TT 17.26
Wrachtrup, Joerg .....AKB 23.1,
AKB 50.63, AKB 50.97,
AKB 50.100, AKB 50.116,
AKB 50.124, SYLS 3.52, TT 17.22,
TT 22.1, TT 22.2
Wu, C. E. ................... TT 29.5
Wu, F. .....................TT 24.54
Wu, H. ......................TT 32.6
Wu, Hua ..................... O 40.6
Wucher, Andreas ......O 10.7, O 44.1
Wübben, Thomas .......... SYPF 4.3
Würfel, J. U. ....... O 37.2, TT 17.14
Würschum, Roland ............M 10.1
Würthner, Frank .......... CPP 16.10
Wüsten, J. .................. DS 12.6
Wüsten, Jens ..SYOH 3.2, SYOH 5.21
Wuite, Gijs J. L. ........... AKB 10.1
Wulandari, Hesti .............TT 13.6
Wulff, Michael ............. CPP 10.5
Wulfhekel, W. . MA 13.14, MA 16.4,
MA 16.7, O 14.43
Wulfhekel, Wulf MA 13.119, MA 28.3,
O 12.2
Wunderlich, F. ......HL 12.6, HL 30.5
Wunner, Günter ............. DY 34.5
Wunsch, B. ..................HL 42.2
Wunsch, Bernhard .......... HL 44.30
Wurm, Andreas ........... CPP 15.31
Wurmbauer, Harald ... DF 5.2, O 24.2
Wurmehl, S. ......MA 8.5, MA 13.114
Wurmus, Helmut .............DS 22.5
Wurstbauer, U. .............. HL 29.5
Wurstbauer, Ursula .......... HL 44.7
Wurth, Wilfried ... O 19.3, O 25.9,
O 45.2, O 45.5, SYXM 1.6
Wuttig, M. .................. DS 18.3
Wuttig, Manfred ...MA 23.2, MA 24.3
Wuttig, Matthias .DS 12.4, DS 22.26,
DS 22.30, DS 22.43, HL 11.1,
HL 11.2, HL 12.9, HL 12.53,
HL 44.43, SYOH 5.68
Wzietek, P. ................. MA 21.3
Xaio, Xaioyin ................. O 38.5
Xu, Ming Chun ............... HL 3.5
Xu, Mingchun .................O 25.4
Xulvi-Brunet , Ramon .......DY 46.61
Yacoby, Amir ...............SYNF 1.2
Yakabchuk, H. .. MA 13.121, MA 18.2
Yamamoto, Hideki .... TT 1.1, TT 8.3
Yamamuro, S. ..............MA 13.80
Yamane, Hiroyuki ............. O 33.5
Yan, Aru ....................MA 11.6
Yan, Feng .................. HL 12.55
Yan, L. ..................... MA 15.5
Yanev, V. ....................HL 16.2
Yanev, Vasil ....... DS 22.5, DS 22.12
Yang, Hongliu ..DY 40.2, DY 46.25,
DY 46.26
Yang, J. ..................... HL 12.1
Yang, Lisong ................ MA 16.9
Yang, M. .................. MA 13.62
Yang, Woochul .................O 5.1
Yang, Xiaohui SYOH 5.80, SYOH 5.81
Yao, T. ......................HL 17.4
Yaresko, A. N ............... TT 24.2
Yaresko, Alexander TT 24.43, TT 33.5
Yasuda, A. ....................O 14.1
Yasuda, Akio .............. SYOH 2.4
Yavorsky, Bogdan ...MA 4.5, MA 31.7
Yawny, Alejandro ............ M 18.20
Ye, S. ....................... HL 44.5
Yekecheva, J. ................ O 24.10
Yewande, Oluwole E. .........DS 14.4
Yi, Hangmo ................. TT 22.9
Yin, H. .............DS 1.9, DS 22.37
Yokoyama, Naoki ........... SYLS 4.5
Yoon, Do-Young .......... SYOH 5.85
Yoshino, K. .................HL 15.13
Yu, Dengke ................... O 11.7
Yue, S. .....................TT 30.18
Yugova, I. .................. HL 44.34
Yukecheva, J. ................HL 31.6
Yurechko, Mariya ............ M 18.24
Yurtsever, A. ............... TT 30.30
Yvan, Sidis ................... TT 2.3
Zabel, Hartmut .MA 10.2, MA 13.42,
MA 13.72, MA 16.8, MA 20.5,
MA 20.8, MA 26.13, MA 26.14,
MA 30.4, MA 30.8, O 12.1,
O 28.79, O 28.85
Zabel, T. .... TT 3.12, TT 14.14,
TT 14.14, TT 30.31
Zabrocki, Knud ..............DY 42.4
Zaccai, Guiseppe .......... SYLS 3.26
Zachariae, J. ..................O 34.1
Zacharias, H. ....O 20.5, O 28.31,
O 28.34, O 28.60
Zacharias, Helmut .....O 28.2, O 28.5
Zacharias, Margit HL 11.3, HL 12.52,
HL 15.2, HL 18.1
Zaepfel, Johannes ......... SYLS 3.51
Zahn, D. R. T. ..... SYOH 5.26,
SYOH 5.28, SYOH 5.35,
SYOH 5.54
Zahn, D. R.T. ..... SYOH 5.19,
SYOH 5.27, SYOH 5.38
Zahn, Dietrich ............. SYOH 5.3
Zahn, Dietrich R. T. .. SYOH 5.34,
SYOH 5.36, SYOH 5.37
Zahn, Peter ........DS 12.2, MA 31.7
Zaikin, Andrei .. TT 11.8, TT 19.6,
TT 19.7
Zaitsev, A. .................. TT 18.1
Zaitsev, A. G. .................TT 8.1
Zaitsev, Alexander ........... TT 8.38
Zaitsev, Oleg ................ TT 23.4
Zajonz, Hubert .................O 6.8
Zakharov, A. ................. TT 1.3
Zakharov, Nikolai ........... HL 44.69
Zaks, Michael ............... DY 11.5
Zamponi, C. .........M 16.4, M 18.15
Zamponi, Christiane .......... M 10.3
Zanchi, G .....................HL 3.6
Zaporojtchenko, V. ......... DS 22.29
Zaporojtchenko, Vladimir ..CPP 7.2,
CPP 11.4, CPP 16.8, DS 7.1,
DS 15.7
Zaporotchenko, Vladimir .... DS 22.24
Zapotocky, Martin ........ AKB 50.27
Zare-Kolsaraki, H. ..........MA 13.26
Zarrabi, Nawid ............AKB 50.98
Zaumseil, Peter DF 6.6, DS 9.3, DS 9.4
Zaus, Edgar ................. HL 16.6
Zavaliche, F. ..................O 12.2
Zawadowski, A. .............TT 11.13
Zawadowski, Alfred .......... TT 16.5
Zayak, Alexey ..... MA 23.3, MA 24.6
Zech, Martin .................O 14.10
Zeeb, Eberhard .............. AIW 3.3
Zegenhagen, J. .......O 14.2, O 28.52
Zegenhagen, Jörg .. DS 9.3, O 25.2,
O 28.12, O 39.4, O 46.1
Zeggel, Johannes ............ TT 18.5
Zegkinoglou, Ioannis ...MA 13.118,
TT 8.17
Zehnder, C. ...................HL 5.3
Zehnder, Carsten ........... HL 12.11
Zeidler, Manfred D. ..........CPP 3.1
Zeika, Olaf .................. HL 23.9
Zeimer, U. ....................HL 3.3
Zeitler, U. ................... HL 22.1
Zeitz, Wolf Dietrich .......... HL 40.3
Zekonyte, Jurgita ............ DS 15.7
Zeller, R. ..........MA 4.11, MA 6.13
Zeller, Rudi ................. MA 11.3
Zeller, Rudolf .............. MA 27.10
Zellweger, Christoph ......... HL 16.9
Zemskov, E. P. ............. DY 46.29
Zen, Achmad .............SYOH 5.72
Zenger, Marcus .............. HL 44.3
Zengerle, Remigius ............ HL 2.1
Zenkevich, Edward ....SYOH 5.8,
SYOH 5.10
Zentel, Rudolf ...CPP 15.23, HL 15.10
Zentgraf, Thomas .............HL 2.5
Zeppenfeld, P. ................ O 25.5
Zerec, I. ................... CPP 10.7
Zerec, Ivica ..................TT 33.5
Zerulla, Dominic .....SYLS 3.56,
SYLS 3.57, SYLS 3.58
Zerweck, Ulrich O 9.5, O 14.61, O 23.3
Zettl, Heiko ..CPP 15.30, CPP 16.9,
CPP 16.32, SYOH 5.45
Zeuner, Arndt .............. HL 17.13
Zeyher, Roland .............. TT 9.10
Zhang, F. ....................HL 23.6
Zhang, J. ................. CPP 15.11
Zhang, Li ..................SYOH 5.2
Autorenverzeichnis
Zhang, Qing-ming ........... TT 8.42
Zhang, X. W. .......DS 1.9, DS 22.37
Zhang, Yan ................SYOH 5.9
Zhao, Bin ..................MA 13.97
Zhao, H. ................... HL 12.19
Zhao, Zhong ..................O 25.6
Zhaohui, Qiao ................ DS 6.5
Zharnikov, Michael ...AKB 50.131,
O 14.54, O 14.55, O 33.2, O 33.3
Zhitomirsky, M. E. ............ TT 3.5
Zhokhavets, U. ........... SYOH 5.52
Zhokhavets, Uladzimir ...HL 12.96,
HL 23.3
Zhong, Dingyong ......... SYOH 5.17
Zhong, Zhenyang ............. HL 7.1
Zhou, Ling ....................O 31.5
Zhou, P. .....................O 28.74
Zhu, J. F. .............O 14.9, O 43.3
Zhu, Yimei ................... TT 1.5
Zhuang, Wei ............. SYOH 5.72
Zhukov, Sergei ............. CPP 14.1
Zi, Aikaterini ................. M 27.3
Ziberi, Bashkim ....DS 15.1, DS 22.15
Zickler, Gerald Andreas ....AKB 50.30
Ziebert, Falko ............AKB 50.110
Ziegler, Andreas .....CPP 15.12,
SYOH 5.85
Ziegler, C. ....... DS 12.6, SYLS 3.15
Ziegler, Christiane .... SYOH 3.2,
SYOH 5.21, SYOH 5.23
Ziegler, Stefan .....DS 22.30, HL 11.1
Ziegler, T. .................... O 10.2
Ziehmer, M. .................. M 32.4
Zielasek, V. ... O 3.6, O 28.8, O 28.24
Zielasek, Volkmar ............ O 28.44
Ziemann, P. .... DS 1.9, DS 22.8,
DS 22.37, MA 6.3, O 28.42
Ziemann, Paul .. DS 15.3, DS 15.5,
O 3.2, O 9.2, O 28.41, O 28.50,
O 32.5, TT 31.7
Ziese, M. .... HL 44.14, MA 13.3,
MA 13.28, MA 13.93, MA 22.2,
TT 8.32
Ziese, Michael .............. HL 44.11
Ziethen, Ch. .................. DS 9.6
Zillmer, Rüdiger ............. DY 40.7
Zimmer, K. ..................TT 8.32
Zimmer, Klaus ...............O 28.21
Zimmer, O. ............... SYLS 3.55
Zimmer, Patrick ............ HL 36.10
Zimmer, Patrik ............... M 21.3
Zimmermann, Boris ....... AKB 50.98
Zimmermann, J. ............ HL 44.45
Zimmermann, Jan ........... CPP 9.5
Zimmermann, Roland ... HL 12.14,
HL 28.1, HL 36.2
Zimmermann, Walter ...AKB 13.2,
AKB 50.110, AKB 50.114,
AKB 50.115
Zippelius, Annette ........... DY 51.5
Zipperer, Dietmar ..........SYOH 4.1
Zirkelbach, F. .................DS 1.4
Zirwes, R. ...................MA 18.2
Zitzler, Lothar ...............CPP 1.2
Zizak, Ivo ..........M 15.1, SYPF 4.2
Zobel, C. TT 20.7, TT 30.13, TT 30.14
Zöllmer, Volker ................ M 7.1
Zoellner, Dana ................M 32.2
Zollfrank, Cordt ...........AKB 50.30
Zontone, Federico ........... DY 26.1
Zorin, Alexander .............TT 25.1
Zotova, Stefka ............ MA 13.107
Zrenner, A. .................. HL 42.1
Zschiegner, Stephan ......... DY 36.6
Zubavichus, Y. ................O 44.8
Zuberova, Zuzana .............M 13.4
Zülicke, U. .................SYNF 1.3
Zülicke, Ulrich .. HL 29.9, HL 49.2,
TT 11.10
Zumbusch, A. .............. SYLS 3.4
Zumbusch, Andreas .... CPP 9.2,
SYLS 3.42
Zumdieck, Alexander ...... AKB 50.64
Zumkley, Th. ................ M 18.19
Zumofen, Gert .. SYLS 3.44, SYLS 5.2
Zur, D. ..M 3.2, M 18.27, MA 13.7,
MA 13.8, TT 30.11
Zvelindovsky, A. ............. CPP 6.1
Zweck, J. ........ HL 44.83, HL 44.84
Zweck, Josef ... HL 27.5, HL 27.6,
HL 44.87, MA 26.6, MA 26.7,
MA 26.8
Zwerger, Wilhelm ............. TT 4.1
Zwicknagl, G. ....... MA 8.2, TT 28.6
Zwicknagl, Gertrud . TT 7.3, TT 7.4,
TT 32.5
Zygalsky, Frank ..............TT 8.15
Zykov, Vladimir ..............DY 20.3