X-ray photoelectron and Auger spectroscopy study of some vanadium oxides

A detailed investigation of V₂O₅, VO₂, V₂O₃, and V metal is presented. The vanadium core lines in the x-ray photoelectron spectra are anomalously wide for V₂O₃ and VO₂. It is shown that this is a consequence of the narrow 3d band in these materials and the relatively strong core-hole 3d Coulomb interaction. The influence of electron correlation effects in the 3d band on the core linewidths is discussed. The valence bands are compared to band-structure calculations and the difference in the band structure above and below the semiconductor-metal transition is discussed. The Auger results are discussed in terms of the 3d partial density of states. It is found that there is a large amount of d character in the O-2p region of the valence band. Also the average "on-site" Coulomb interaction of 3d electrons is obtained from the Auger spectra and is discussed in terms of electron correlation effects.