Metal-induced growth of graphene/a-C: H composite films and tribological properties

In this work, the metal Ni-induced graphene/hydrogenated amorphous carbon (a-C: H) composite films were prepared by a direct current (DC) magnetron sputter deposition system using argon and acetylene to sputtering a single nickel target. By adjusting the content of the C2H2 in the gas mixture, the composite films with different microstructures and constituents were prepared. The surface morphology, microstructure, carbon bonding status, hardness, toughness, and tribological properties of the deposited films were systematically analyzed to explore the relationship between structure and properties with C2H2 gas flow ratio. The results indicated that the films were composite films consisting of graphene embedded in hydrogenated amorphous carbon film. The hardness of the films increased significantly with increasing C2H2 gas flow ratio due to the decrease in metallic Ni content in the films. And the decrease in friction coefficient was related to the generation of graphene induced by Ni in the films and the passivation of suspension bonds. Especially, the films deposited at 30 % C2H2 exhibited low friction coefficient and outstanding wear resistance, which provides guidance for further designing carbon-based solid lubricating films with excellent performances.