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O: Oberflächenphysik

O 36: Structure and dynamics

O 36.5: Vortrag

Donnerstag, 30. März 2006, 12:15–12:30, WIL C207

Preparation and characterization of bimetallic AuPt/Pt(111) surface alloys - a quantitative STM study — •Andreas Bergbreiter, Harry E. Hoster, Eleonora Filonenko, and Rolf J. Behm — Department of Surface Chemistry and Catalysis, University of Ulm, D-89069 Ulm

Structures of atomically smooth and laterally equilibrated AuPt/Pt(111) surface alloys have been studied by UHV-STM. The alloys were prepared by Au island deposition onto a Pt(111) single crystal followed by annealing at 1000K. The Au fraction visible by atomically resolved STM images with chemical contrast is correlated to the respective amount of Au deposited on the Pt(111) single crystal prior to annealing. The known bulk immiscibility of AuPt is reflected in a tendency towards phase separation also in two dimensions. Across the whole concentration range, homoatomic bonds dominate the structure and cause the formation of larger homoatomic ensembles. For comparison with other systems, the short range order (SRO) was quantified by Warren-Cowley-parameters. In order to correlate the atomic distribution with adsorption properties and catalytic behaviour in further studies, the surface density of selected homoatomic adsorption sites were calculated.