Effect of feed gas composition effects on the nanotribological properties of diamond-like carbon films

Abstract A series of experimental nanoindentation, nanowear and nanoscratch tests was conducted to investigate the relationship between the nanotribological characteristics of diamond-like carbon (DLC) and feed gas composition used for the deposition. The DLC films were deposited on silicon substrates in radio-frequency plasma enhanced chemical vapor deposition system with a mixture of hydrogen and methane gases. Raman spectroscopy results show that the integrated intensity ratios (I D /I G ) of each profile correlate with sp 2 /sp 3 ratios. The result also indicates that the hydrogen content in the source gas has a significant influence upon the sp 2 /sp 3 ratio and hydrogen-to-carbon ratio in DLC films. It is demonstrated that the sp 2 /sp 3 ratio decreases with increasing hydrogen content in the DLC film. Our result also reveals that a significant relationship between the hydrogen content and the nanotribological characterizations of the DLC films, namely lower hydrogen-to-carbon ratio leads to higher hardness, elastic modulus, friction coefficient, and lower wear depth. The surface reinforcement can be attributed to the fact that variation of surface energy arises from the different carbon hybridized states (sp 2 /sp 3 ratio), which improve the surface properties via the hydrogen content in the source gas and associated nanotribological characteristics.