Electronic structure of TiO_x (0.8 < x < 1.3) with disordered and ordered vacancies

Abstract

We report x-ray photoemission, UV photoemission, and bremsstrahlung isochromat spectra of TiO with ordered vacancies in both Ti and O sublattices and of the series TiO_x (0.8 < x < 1.3) containing disordered Ti and O vacancies. The details of the electronic structure are discussed in comparsion to band-structure calculations for the ordered structures performed in this work as well as to density of states obtained for the disordered systems within different approximate methods reported earlier in the literature. Our results in the valence-band regions indicate the need for a better theoretical approach to describe the effect of disordered vacancies on the electronic structure than has been attempted to date. Ti 2p core-level spectra indicate the existence of vacancy-induced local environments with the formal charge on the Ti atom ranging from 2+ to 4+.