Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 32: Epitaxie und Wachstum II
O 32.5: Vortrag
Donnerstag, 27. März 2003, 16:00–16:15, FOE/ANOR
Structure and thermal stability of TiOx films on Ru(0001) and Au/TiOx/Ru(0001) model catalysts — •Zhong Zhao1, A. Männig1, D. Rosenthal2, J. Osswald2, S.L.M. Schroeder3, K. Christmann2, H. Rauscher1, and R.J. Behm1 — 1Oberflächenchemie und Katalyse, Universität Ulm — 2Bereich Physikalische und Theoretische Chemie, Freie Universität Berlin — 3Department of Chemical Engineering, University of Manchester, UK
Titanium oxide films with a thickness of up to 20 ML were deposited on Ru(0001) at temperatures between 500 K and 700 K by evaporation of titanium in oxygen at a pressure of 1.0×10−7mbar. As deposited, the films are rather rough. Subsequent annealing to different temperatures up to 1200 K, either in UHV or in oxygen atmosphere (p=1.0×10−7mbar), leads to considerable smoothing and to the formation of large terraces and screw dislocation structures. On the atomic scale, the terraces show relatively ordered structures with considerable differences between films annealed in UHV or in oxygen. For the latter, we find a large number of straight chains of spherical units arranged along rows of the TiOx substrate. AES shows that the ratios of TiLMV/TiLMM and OKLL/TiLMM after annealing in oxygen are in close agreement with literature values for TiO2 single crystals, whereas after annealing in UHV an oxygen deficiency is found. Model catalysts were prepared by evaporating Au on the UHV-annealed TiOx film. Nanometer-size Au clusters can be found preferentially along row-like structures of the TiOx substrate. The Au clusters are stable up to 780 K, no encapsulation indicative of strong metal support interaction effects (SMSI) was observed.