An X-ray photoelectron spectroscopy sputter profile study of the native air-formed oxide film on titanium

The incipient air-formed oxide film on titanium is approximately 80 A° in thickness and consists of TiO2. Sputtering the oxide film in vacuum with 3 keV argon ions changes the composition of the oxide film. XPS depth profiles obtained by sputtering with 3 keV argon ions show that after sputtering, the outermost portion of the film consists of TiO2 and that the inner portion consists of Ti2O3 and TiO. Mathematical analysis of the sputtered oxide film as a three-layer structure shows that with increased time of sputtering, the calculated thickness of TiO2 and its mole fraction in the oxide film decreases faster than that due solely to thinning of the outermost layer. In addition, the mole fraction of the TiO layer increases, while that of the Ti2O3 remains relatively unchanged during sputtering. These observations suggest that the ion beam reduces part of the TiO2layer to Ti2O3, which in turn is then reduced to TiO. q1999 Elsevier Science B.V. All rights reserved