Probing the effect of doped F and N on the structures and properties of fullerene-like hydrogenated carbon films.

Richer fullerene-like (FL) structure interface layers with sp 2 ‑carbon rich are observed in the sliding contacts of ultra-low friction fullerene-like hydrogenated carbon (FL-C:H) films, which can offer a new design possibility to further optimize these films' tribological performances by element doping such as hydrogen, fluorine and nitrogen. In this paper, we provide an understanding about the structure-performance relationship such as the effects of FL structures and incorporated elements such as fluorine and nitrogen. Meanwhile, the detailed structure, mechanical and frictional behaviors and surface properties of the doped films have been investigated. The results indicate that N atoms promote the formation of more cross-linked FL structure, while F atoms terminate sp 2 bond linking state of curved graphitic similar to hydrogen, and thus destroy the FL continuous network structure. Moreover, the N-6 FL-C:H film exhibits higher hardness (~ 18.6 GPa), better elasticity recovery (~ 83%) and a very smooth morphology (rms ~ 0.242 nm), lower friction (0.017) and wear (1.25 × 10 − 9 mm 3 /Nm). [ABSTRACT FROM AUTHOR]