Growth and electronic structure of vanadium on alpha-Al2O3(0001)

The interaction of metallic vanadium with the alpha-Al2O3(0001) surface was studied in the submonolayer-to-multilayer coverage regime using X-ray phot oemission spectroscopy (SPS) and near-edge X-ray absorption fine structure (NEXAFS). At low coverage the V 2p photoemission spectra reveal a strong in teraction of vanadium with alumina, thus indicating the formation of a vana dium oxide. The NEXAFS data, both the line-shape and the position of the va nadium L-edge, are consistent with the formation of V2O3. A comparison of t he results of both spectroscopies reveals that vanadium seems to be highly dispersed at low coverage, and final state effects on the core level ioniza tion energies, e.g, cluster size effects, have to be considered. At higher amounts of vanadium deposition a metallic vanadium overlayer forms on top o f a vanadia/Al2O3 interface. In an ambient of 5 x 10(-5) Torr oxygen metall ic vanadium oxidizes rapidly, even at 300 K, and the formation of V2O3 is o bserved. (C) 2000 Elsevier Science B.V. All rights reserved.