Regensburg 2007 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 17: Poster Session I (Nanostructures at Surfaces; Metal Substrates: Epitaxy and Growth; Methods: Scanning Probe Techniques; Phase Transitions)

O 17.30: Poster

Montag, 26. März 2007, 17:30–20:30, Poster C

UPS investigations of ultrathin Au films deposited on Pt(111) — •Tomasz Kobiela¹, Marco Moors¹, Wojciech Linhart², Iza Cebula², Aleksander Krupski², Conrad Becker¹, and Klaus Wandelt¹ — ¹Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115 Bonn, Germany — ²Institute of Experimental Physics, University of Wroclaw, pl. Maxa Borna 9, 50-204 Wroclaw, Poland

The structure and the local electronic properties of ultrathin Au films deposited on Pt(111) under UHV conditions have been studied by UPS and LEED. Investigations of bimetallic systems concerning morphology and adsorption properties are of great interest for the development of new catalysts with higher efficiency and durability. LEED measurements indicated an initial pseudomorphic growth of the Au films. UPS and PAX experiments showed a strong temperature dependence of the surface morphology. The Au-Pt surface prepared at 150 K is quite rough and smoothens significantly only above RT. At a temperature of 900 K gold starts to diffuse into the bulk forming a surface alloy with platinum and gold sites. The electronic properties of the resulting Au-Pt surface alloy seem to be nearly independent from the deposited Au amount in the investigated range of 1 - 10 monolayers. The removal of Au from the surface regions has been verified by STM. Adsorption experiments with various probe molecules showed a significant lower affinity of the Au-Pt surface alloy towards e.g. CO, but similar adsorption properties concerning butadiene in comparison to the clean Pt surface.