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 x-ray emission spectroscopy techniques. For the investigation of the monoclinic structure type, polycrystalline samples of titanium monoxide were used. The samples of the vacancy-free rock-salt structure have been obtained by annealing monoclinic titanium monoxide at high temperature and pressure. The x-ray powder diffraction pattern of both types of samples revealed single-phase crystals without any substructures. The x-ray photoelectron valence band spectra 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 three features. A combined representation of the photoelectron valence band spectrum of the monoclinic phase and O $K_{\alpha },$ Ti $L_{\alpha },$ and Ti $K_{\beta 5}$ x-ray emission spectra shows that titanium and oxygen states are hybridized over almost the full valence band region, without a gap. The valence band of the vacancy-free rock-salt phase was found to be wider than that of the monoclinic phase. The experimentally obtained valence band density of states are compared with recent band structure 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.

• Received 27 November 1996

DOI:https://doi.org/10.1103/PhysRevB.56.10656