Vacancy effects in the x-ray photoelectron spectra ofTiNx

Abstract

The electronic structures of titanium nitrides $\mathrm{Ti}{\mathrm{N}}_x$ have been investigated by x-ray photoelectron spectroscopy over the entire composition range of the rocksalt structure ($0.5\lesssim x\lesssim 1$). The valence-region spectrum of stoichiometric TiN is consistent with results of band-structure calculations. The filling of a defect state at about 2-eV binding energy with decreasing $x$ is explicitly demonstrated. Experimental results are compared with different models for calculation of the electronic structure of anion-deficient rocksalt transition-metal compounds. Variation of the core-level binding energies indicates a decrease of the ionicity in $\mathrm{Ti}{\mathrm{N}}_x$ with decreasing $x$. The Ti $2p$ satellite structure found for nearly stoichiometric samples is discussed in terms of screening of the core hole by the conduction electrons.