ELECTRONIC-STRUCTURE OF TITANIUM MONOXIDE

The electronic structure of the monoclinic phase of titanium monoxide and a vacancy-free rock-salt phase have been investigated using x-ray photoelectron spectroscopy and ?c-ray emission spectroscopy techniques . For the investigation of the monoclinic structure type, polycrystall ine samples of titanium monoxide were used The samples of the vacancy- free rock-salt structure have been obtained by annealing monoclinic ti tanium monoxide at high temperature and pressure. The x-ray powder dif fraction pattern of both types of samples revealed single-phase crysta ls without any substructures. The x-ray photoelectron valence band spe ctra reveal that the upper, mainly Ti 3d-derived, part of the valence band is split and that the lower, mostly O 2p-derived, band exhibits t hree features. A combined representation of the photoelectron valence band spectrum of the monoclinic phase and O K-alpha, Ti L-alpha, and T i K-beta 5 x-ray emission spectra shows that titanium and oxygen state s are hybridized over almost the full valence band region, without a g ap. The valence band of the vacancy-free rock-salt phase was found to be wider than that of the monoclinic phase. The experimentally obtaine d valence band density of states are compared with recent band structu re calculations. In addition, we present spectra of the O 1s and Ti 2p core levels and show the effects of a gradual oxidation of the sample on these spectra. [S0163-1829(97)08639-6].