Understanding the ultra-low friction behavior of hydrogenated fullerene-like carbon films grown with different flow rates of hydrogen gas

Fullerene-like hydrogenated carbon (FL-C:H) films that exhibit ultra-low friction and wear in humid conditions have been the subject of extensive researches, but the structure–performance relationship such as the evolution of FL structures under friction is not well understood. We have prepared FL-C:H films with different FL content, and have addressed a detailed investigation on the relationship. It is found that with the increase in FL content, the friction and wear of FL-C:H films can reach as low as 0.011 and 1.48 × 10−8 mm3/Nm, respectively. Examination of the corresponding wear tracks by Raman spectroscopy reveals that not graphitization but friction-induced promotion of FL structures causes the ultra-low friction and wear of FL-C:H films. We therefore claim that FL structures are in close positive relations with the excellent tribological performance of FL-C:H films.