Electronic Structure of Rutile Oxides TiO 2 , RuO 2 and IrO 2 Studied by X-ray Photoelectron Spectroscopy

Valence band X-ray photoelectron spectra of the rutile oxides TiO 2 , RuO 2 , and IrO 2 show a distinct evolution as a function of the increasing number of metal d -electrons. The observations are found to be in excellent agreement with recent theoretical models. Intensity analysis and photo-ionization cross sections are used to confirm the nature of the band responsible for conducting properties. The result is in accordance with a crystal field model proposed earlier. The deduced number of "free electrons" in the valence band is used to correlate the asymmetry recorded for the core level lines.