Abstract: In macroscopic tribological applications, graphene-based carbon films exhibit low friction coefficient but weak mechanical strength and short wear life. Aimed at these problems, a fluorine plasma etching technology is proposed to promote the tribological property of a graphene nanocrystallites embedded carbon (GNEC) film. By characterizing the influences of the fluorine plasma etching on the morphology and structure of the GNEC film, it is found that the etching has two functions: atom removal and ion implantation. On the one hand, the etching can remove the carbon atoms in surface asperities through physical bombardment or chemical reaction to effectively reduce the film surface roughness. On the other hand, the etching induced subplantation can restructure the film top-surface to make its sp³ bonds and fluorine atoms increase. Then the effects of the fluorine plasma etching on the film properties are measured. The results show that after the etching, the film surface energy decreases because the introduced fluorine atoms would passivate the dangling bonds on the film surface, and the film hardness is enhanced due to the increased sp³ bonds. Therefore, compared with the GNEC film, the restructured film after the fluorine plasma etching exhibits the excellent tribological property. Under the normal load of 2 N, the friction coefficient decreases from 0.22 to 0.08, and the wear life increases from 120 cycles to more than 15 000 cycles. The reasons for the improved tribological property after the fluorine plasma etching are the reduced surface roughness, the passivation of surface dangling bonds, and the enhanced mechanical property.

Key words: fluorine plasma etching, graphene-based carbon film, top-surface restructuring, passivation of surface dangling bonds, tribological property