X-ray-emission-spectroscopy study of vacancy-induced electronic states in substoichiometricTiNx

The Ti K emission band from TiN and substoichiometric ${\mathrm{TiN}}_{\mathrm{x}}$ (0.35≤x<1) has been investigated. The Ti p–like states are very strongly hybridized with the N 2p states located ∼6 eV below the Fermi level ($E_F$) in TiN. In the presence of nitrogen vacancies, p-like nonbonding states are detected ∼2 eV below $E_F$. As x decreases, the intensity of the nonbonding structure increases, that of the ∼6 eV peak decreases, and the valence-band states move closer to $E_F$ reflecting the decrease in cohesion. Theoretical x-ray spectra have been obtained with use of the Korringa-Kohn-Rostoker coherent-potential-approximation densities of states and appropriate transition-matrix elements. The theory is shown to account for all the trends observed experimentally.