09.12.2012 Views

Plenarvorträge - DPG-Tagungen

Plenarvorträge - DPG-Tagungen

Plenarvorträge - DPG-Tagungen

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

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

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!