On the relationship between the Raman scattering features and the Ti-related chemical states of TixOyNz films

Owing to its singular and (to some extend) adaptable characteristics, titanium oxynitride (TixOyNz) represents an exceptional choice in the realm of new materials aiming at the development of practical devices. However, the effective use of TixOyNz in photovoltaic and (photo)catalysis applications, for example, relies on a refined production−properties balance. Accordingly, this paper reports on the physico-chemical properties of TixOyNz films as investigated by means of the Raman scattering and X-ray photoelectron spectroscopy (XPS) techniques – the former shedding light on the structural characteristics of the films, and the latter providing the state of oxidation of the film's constituents. The films were prepared by sputtering TiO2 and Ti targets in a plasma comprising different mixtures of Ar and N2. Because of the deposition method and conditions, the films exhibit Raman spectra that are consistent with a combination of TiO2 and TiN or, more properly, TixOyNz under the amorphous and (nano/micro-)crystalline structures. In fact, the experimental data indicate the presence of four TiO2- and two TiN-related phonon modes, whose relative scattering features scale with the oxygen and nitrogen contents of the films. A similar concentration dependence was verified with the percentage of Ti4+, Ti3+, and Ti2+ chemical states of oxidation. This mutual concentration dependence was explored thoroughly and the results clearly indicate the suitability of the Raman data to estimate the typical atom composition and distribution of the Ti-related chemical states of TixOyNz