Effects of temperature on the chemistry and tribology of co-sputtered MoSx-Ti composite thin films

Co-sputtered thin films of MoSx with Ti were deposited in order to investigate the film's tribological behaviour under various conditions. The mechanical properties of the composite films were investigated by pin-on-disk wear testing in air with 50% relative humidity, indicating improved performance compared to pure MoSx thin films. Additional pin-on-disk measurements on films tested at increasing temperature reveal a sharp drop-off in performance between 250 °C and 350 °C. High resolution X-ray photoelectron spectroscopy, field-emission gun scanning electron microscopy, Raman microscopy and X-ray diffraction measurements have been used to follow the oxidation behaviour of the films as a function of temperature and correlate it to film performance. Results indicate that whereas significant surface oxidation occurs at relatively low temperatures, significant degradation in tribological performance is observed only when bulk oxidation takes place.