Frictional properties of fluorinated diamond-like carbon films prepared by radio frequency reactive magnetron sputtering

The fluorinated diamond-like carbon (F-DLC) films are prepared by radio frequency reactive magnetron sputtering with different flow ratios of CHF 3 and Ar as a source gas and pure graphite as a target. Surface morphology, hardness, bonding configuration and tribological properties are investigated by atomic force microscope, nanoindenter, Raman spectra, Fourier transform infrared (FTIR) spectra and a ball-on-disk test rig, respectively. The results show that the F-DLC films are distributed compactly and homogeneously and exhibit good friction-reducing behaviors. The minimum of friction coefficient reaches about 0.42 at r =1 ∶6 while the hardness of films is highest. Raman spectra and FTIR spectra reveal that with the increase of r , the fluorine content gradually increases. However, the intensity ratio I D / I G of Raman bands of disordered graphite (D-band) and graphite (G-band) of F-DLC films decreases, which is indicative of the decrease of the fraction of aromatic ring. The results also show that the F content is another significant factor which affects the friction coefficient. The weakening of —CF 2 asymmetric stretch vibration intensity and the formation of CFH in C C chains may result in a lower friction coefficient of F-DLC films.