Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 48: Oxide und Isolatoren II

O 48.1: Vortrag

Dienstag, 8. März 2005, 15:45–16:00, TU EB107

Ordered alumina film on NiAl(110): Structure and nucleation centers — •E. Napetschnig¹, G. Kresse², L. Köhler², M. Schmid¹, and P. Varga¹ — ¹Institut f. Allgemeine Physik, Vienna University of Technology, Austria — ²Institut fuer Materialphysik, University of Vienna, Austria

Transition metal clusters on alumina support are one of the most frequently used model systems for investigations of heterogenous catalysis. Oxidation of the (110) surface of NiAl at elevated temperatures leads to the formation of an alumina film of uniform thickness and structure [1]. In spite of many attempts of structural analysis, the atomic structure of the unit cell was unknown until now. Unexpectedly our atomically resolved STM images of the topmost oxygen layer show squares with oxygen atoms at the edges in addition to areas with hexagonal structure. The unit cell has a p2g symmetry. This is an atomic arrangement not found in the known bulk structures of alumina. Based on these STM images the complete determination of the oxide film structure was possible by ab-initio calculations [2]. This was the starting point to determine the nucleation centers of platinum clusters on the alumina film.

[1] M. Bäumer et al., Prog. Surf. Sci. 61 (1999) 127

[2] G. Kresse et al, to be published