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