XPS study of TiOx thin films prepared by d.c. magnetron sputtering in Ar-O-2 gas mixtures

Titanium oxide films have been deposited, at a pressure of 5 mTorr and a di scharge current of 500 mA, on borosilicate glass substrates, We have studie d in situ by XPS the dependence of film composition on oxygen partial press ure. All the experiments have been performed under high vacuum; there is no air contamination of film surfaces before XPS analysis. The ions produced in the plasma have been analysed by glow discharge mass spectrometry (GDMS) , The stoichiometry of the films is compared to the plasma composition. The XPS results show that for an increasing oxygen partial pressure four re gimes are observed, At very low oxygen concentration (<2%), the film is mai nly metallic (zone I). For an oxygen concentration between 2% and 6%, a mix ture of Ti, TiO, Ti2O3 and TiO2 is observed (zone II). In this zone the con centration of Ti decreases but the concentration of the three titanium oxid es grows. In zone III (6% < O-2 < 15%) the TiO2 concentration in the film i ncreases. Finally, for O-2 > 15% (zone IV) a pure TiO2 film is obtained, Wh en zone IV starts, the Ti+ mass spectrometric signal is still higher than t he TiO+ signal, showing that a pure TiO2 phase is occurring at the substrat e while the sputtering mode is still partially metallic. Copyright (C) 2000 John Wiley & Sons, Ltd.