Preparation and tribological properties of Ni/DLC multilayer film

Ni was selected as a transition layer and sublayer in the diamondlike carbon-based multilayered film with varied bilayer periods (from 228 to 970 nm) prepared by magnetron sputtering. The reaction between Ni- and C-containing particles was discussed, and the influences of bilayer periods on the structure and morphology, accompanied with the frictional behaviors at different loading forces (2 and 5 N), as well as the field emission properties were investigated. The results showed that Ni grew in the (111) plane, and there was no Ni–C bond or graphene formed in the film because of the relatively lower energy during deposition. Moreover, the content of sp2C in the film, the hardness, and the field emission performance exhibited an initial increase followed by a subsequent decrease with increasing bilayer periods. However, the frictional coefficient decreased owing to more graphitization with an increase of the applied load. Particularly noteworthy was that the film possessed a bilayer period of 710 nm, displayed a compact structure with a smaller grain size, and showed reduced sp2C content in the role of Ni. This resulted in sustained lower surface roughness, heightened hardness, decreased coefficient of friction, and a smaller opening electric field.