Influence of structure evolution on tribological properties of fluorine-containing diamond-like carbon films: From fullerene-like to amorphous structures

Fluorine incorporation can tune the properties of diamond-like carbon (DLC) films particularly to the tribological behaviors, which is closely related to the film inner structural transformation and ultimately influenced by the fluorine content variation. In order to demonstrate it visually, in this work, a special fullerene-like nanostructure is intentionally designed in F-DLC amorphous matrix and then the fluorine content is adjusted by artificial regulation, eventually the film structure evolution is observed directly by Raman, XPS and TEM. Subsequent mechanical and tribological measurements discover the related performance difference between all films, which reveals that the fluorine-containing fullerene-like carbon (F-FLC) film with lowest fluorine content (4.8 at.%) has the lowest friction coefficient (0.052) and wear rate (0.32 × 10−16 m3/Nm) in ambient environment, due to the special microstructure. In addition, the inert atmosphere is beneficial to the formation of C-phase tribofilms, not the tribo-oxidation, in which all the films and especially the F-FLC film have the lower friction coefficients.