Influence of exposure to an atmosphere of high relative humidity on tribological properties of diamondlike carbon films

Abstract

‘‘Diamondlike’’ carbon films have potential applications because of their high wear resistances. We have investigated the influence of exposure to an atmosphere of high relative humidity (RH) on tribological properties of carbon films prepared with a radio‐frequency plasma enhanced chemical vapor deposition. Wear characteristics were measured using a pin‐on‐disk wear tester. A friction coefficient of a carbon film as deposited was as low as 0.2. However, the value increased up to 0.3–0.4 after exposure to an atmosphere of 60 °C 90% RH for seven days. Electron spectroscopy for chemical analysis and electron energy‐loss spectroscopy analysis suggested that a very thin (<1 nm) unstable surface layer of the film had suffered a chemical change during the exposure process. We have found that the change can be suppressed by increasing a degree of fragmentation of the hydrocarbon source in the plasma, or by removing the unstable layer with an Ar plasma etching.