Structure of thin Alumina films on atomic Scale

Abstract

The properties and structure of small metal particles deposited on oxide surfaces attract much interest due to their applications in catalysis. Thin alumina films grown on metallic substrates have proved to be a suitable support for studies on heterogeneous catalysis.<br />Oxidation of the (110) surface of NiAl and of Cu-9at.%Al(111) at elevated temperatures leads to the formation of an alumina film of uniform thickness and structure. The alumina films exhibit a network of domain boundaries, which act as nucleation centres for metal clusters.<br />Within this thesis we succeeded in determining the atomic arrangement of the oxide films and of the structure of the straight antiphase domain boundaries vibible in the oxide/NiAl(110) by combining atomically resolved STM (scanning tunneling microscopy) images and density-functional theory calculations. Furthermore we investigated the morphology and the morphological changes upon annealing and upon deposition at different temperatures and nucleation sites of Co, Pd and mixed Co-Pd clusters grown on the thin alumina films by STM, AES (Auger electron spectroscopy), LEED (low energy electron diffraction) and LEIS (low energy ion scattering). The evaluation of the nucleation sites of Pt clusters showed that that there are no periodical point defects within the domains of the alumina films.