V2O3(0001) on Au(111) and W(110):: growth, termination and electronic structure

We have prepared well-ordered V2O3(0 0 0 1) films with thicknesses between 60 and 160 Angstrom on W(1 1 0) and Au(1 1 1). These films have been studied with respect to the surface electronic and geometric structure and the interaction with oxygen. We find that after preparation with oxygen the surface is terminated by vanadyl groups. The surface may be reduced by electron bombardment. Oxygen adsorption with subsequent annealing restores the vanadyl groups. The vanadyl groups are thermally stable on the surface until at least 1000 K under UHV conditions. In XPS spectra of the vanadyl terminated surface a V2p induced surface state becomes visible under surface sensitive conditions. The binding energy shift of this state is compatible with a higher oxidation state of the vanadium atoms on the surface as compared to the bulk atoms. The V2p surface state induces additional intensity also in NEXAFS spectra as concluded from a set of spectra recorded with two different methods. (C) 2003 Elsevier B.V. All rights reserved.