Effect of humidity on the friction properties of a-C:H and a-C:H:Si films deposited by PECVD employing microwave sheath-voltage combination plasma

Abstract

Si-doped diamond-like carbon (a-C:H:Si) films can be deposited at an ultra-high rate around 100 μm h−1 by using microwave sheath-voltage combination plasma (MVP), showing a friction coefficient of 0.05–0.1 similar to that of conventional a-C:H:Si films. However, the effect of humidity on the friction property of a-C:H:Si films deposited by MVP has not been studied. Thus, we investigate the frictional characteristics of a-C:H:Si films deposited on different duty ratios of 10, 30, and 50% using MVP, where a steel ball is slid against an a-C:H:Si film under dry conditions with 10%–50%RH. The a-C:H:Si film deposited on the low duty ratio of 10% became a polymeric structure. The friction coefficients of the a-C:H:Si films decreased with a decrease in the relative humidity. At the low relative humidity of 10%, it was shown that low friction below 0.06 is achieved by transfer film with the amorphous carbon structure formed on the mating ball.