Humidity resistant MoSx films prepared by pulsed magnetron sputtering

It is well known that MoS2 is a good lubricant, but the lubricity of MoSx t hin films is greatly affected by the deposition parameters, especially when used under environmental conditions of high relative humidity. In this wor k, MoSx films were prepared by magnetron sputtering using a bipolar pulsed power supply. Several deposition parameters such as argon pressure, substra te temperature, substrate bias voltage, cathode power and deposition time w ere varied. Composition, morphology and structure were investigated by a nu mber of techniques including energy dispersive spectroscopy (EDS), Rutherfo rd back scattering (RBS), scanning electron microscopy(SEM) and X-ray diffr action (XRD). Tribological properties were measured with a ball-on-disk fre tting tester. The results show that MoSx films prepared at low argon pressu re (below 0.4 Pa) and low substrate temperature (room temperature) have a l ow friction coefficient and long wear life. These films have a remarkable l ow sulfur content (x approximate to 1 and even smaller, in contrast to freq uently reported values of x = 1.2 similar to 1.8), a featureless morphology and only a strong basal plane (002) diffraction peak The relative humidity , up to values of 90%, has only a small effect on the friction coefficient and wear life. The structure of the films and the friction and wear mechani sm are discussed in view of the low sulfur content. (C) 2000 Elsevier Scien ce B.V. All rights reserved.