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O: Oberflächenphysik

O 21: Oberfl
ächenreaktionen (II)

O 21.1: Vortrag

Dienstag, 27. März 2001, 16:15–16:30, B

High-Pressure Oxidation of Ru(0001) — •D.I. Sayago¹, M. Polcik¹, R. Blume², H. Niehus², H. Conrad¹, and A. Böttcher¹ — ¹Fritz-Haber-Institut der MPG in Berlin, Faradayweg 4-6, 14195 Berlin — ²Institut für Physik der Humboldt-Universität, Invalidenstr. 110, 10115 Berlin

The modifications of the Ru(0001) surface induced by high-pressure oxidation were investigated by XPS and TDS. The appearance of spectral features characteristic for the RuO₂ phase (O1s, Ru3d, valence band) depends strongly on the applied oxygen pressure and the oxidation temperature. RuO₂ phase starts to dominate the surface for temperatures above 600K and pressures higher than 1mbar. For instance the XP spectra characteristic for the RuO₂ bulk phase appear after exposing the sample kept at 750K to oxygen pressure of 1bar. The O/Ru ratio as determined by taking the O1s and Ru3d intensities, increases continuously with oxidation temperature and oxygen dose. Within the whole range of applied oxidation conditions the shape of the O1s spectrum can be reproduced by using only three single gaussian components. In addition to the known components representing the bulk RuO₂ and the O-1x1 adsorbed phase, a third component appears at the high binding energy side and it reflects the presence of the non-stochiometric oxygen species. The depletion of the oxygen load as induced by exposing the oxidized surface kept at 600K to CO reveals clearly that within the initial reaction stage the RuO₂ dominates the reaction kinetics.