Plenarvorträge - DPG-Tagungen

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.