Tribological behavior of plasma-enhanced CVD a-C:H films. Part I: effect of processing parameters

A systematic study was conducted on the effect of plasma-enhanced CVD processing parameters, namely bias voltage, pressure and CH4/Ar flow ratio, on the characteristics and tribological response of amorphous hydrogenated carbon (a-C:H) films. Film hardness, intrinsic stress, structure, composition and tribological response were characterized. Variation of processing parameters was found to produce a-C:H films with a range of characteristics with the CH4/Ar ratio exercising a dominant effect. A low ratio produced harder films with more sp3 bonding, low hydrogen content and low wear rate; whereas a high ratio produced softer films, with more sp2 bonding, higher hydrogen content and low friction. Film characteristics were found to affect the wear mechanism with softer films showing a layer-by-layer removal and harder films involving formation of fine debris. These two diverse types of films offer the opportunity to synthesize multilayered films combining desirable properties from each component.