Plenarvorträge - DPG-Tagungen

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