Structure and tribological properties of Si/a-C:H(Ag) multilayer film in stimulated body fluid*

Abstract

Si/a-C:H(Ag) multilayer films with different modulation periods are prepared to test their potential applications in human body. The composition, microstructure, mechanical and tribological properties in the simulated body fluid are investigated. The results show the concentration of Ag first decreases and then increases with the modulation period decreasing from 984 nm to 250 nm. Whereas the C content has an opposite variation trend. Notably, the concentration of Ag plays a more important role than the modulation period in the properties of the multilayer film. The a-C:H sublayer of the film with an appropriate Ag concentration (8.97 at.%) (modulation period of 512 nm) maintains the highest sp3/sp2 ratio, surface roughness and hardness, and excellent tribological property in the stimulated body fluid. An appropriate number of Ag atoms and size of Ag atom allow the Ag atoms to easily enter into the contact interface for load bearing and lubricating. This work proves that the Ag nanoparticles in the a-C:H sublayer plays a more important role in the tribological properties of the composite-multilayer film in stimulated body fluid condition.