A long-lifetime MoS2/a-C:H nanoscale multilayer film with extremely low internal stress

A series of MoS2/a-C:H multilayer films with different bilayer periods were deposited by medium frequency unbalanced magnetron sputtering. The morphology, microstructure, mechanical and tribological properties of the films were investigated. It was found that all the films have relatively low hardness and internal stress. Furthermore, the nanoscale multilayer film with a bilayer period of 97.8 nm shows highly dense and well defined interfaces. Tribological tests indicated that the MoS2/a-C:H nanoscale multilayer film has low friction coefficient and extremely long sliding distance in vacuum, under high sliding speed and the initial Hertzian contact pressure of the sliding surface closed to its hardness. In addition, the film exhibits excellent tribological properties in both N2 and air, which is associated with the oxidation of MoS2 and the graphitization of a-C:H. The result indicates that the nanoscale multilayer combined soft and hard phase is continuously a design methodology for developing the vacuum solid lubricating materials.