Compositional and Structural Properties of TiO2−xNx ThinFilms Deposited by Radio-Frequency Magnetron Sputtering

Abstract

TiO2−xNx thin films are deposited ontoSi(100) and quartz substrates by a rf magnetron sputtering method usinga titanium metal disc as a target in Ar, N2, andO2 atmospheres. The substrate temperature is kept at300°C. The O2 and Ar gas flow rates are kept to beconstants and the N gas flow rate is varied. TiO2−xNx filmswith different N contents are characterized by x-ray diffraction andx-ray photoelectron spectroscopy. The results indicate that theTiO2−xNx thin films can be obtained at 13% N and 15% N contentsin the film, and the films with mixed TiO2 and TiN crystalcan be obtained at 13% N and 15% N contents in the film. In terms ofthe results of x-ray photoelectron spectroscopy, N 1s of β-N (396 eV)is the main component in the TiO2−xNx thinfilms. Because the energy level of β-N is positioned above thevalence-band maximum of TiO2, an effectiveoptical-energy gap decreases from 2.8 eV (for pure TiO2film deposited by the same rf sputtering system) to 2.3 eV, which isverified by the optical-absorption spectra.