The effects of plasma pre-treatment and post-treatment on diamond-like carbon films synthesized by RF plasma enhanced chemical vapor deposition

Diamond-like carbon (DLC) films were synthesized by RF plasma enhanced chemical vapor deposition and the effects of plasma pre-treatment and post-treatment on the DLC films were investigated. Experimental results show that the surface roughness of the substrate, ranging from 0.2 to 1.2 nm, created by the plasma pre-treatment, will affect the surface roughness of the DLC films deposited using methane as the carbon source. However, the film surface roughness (0.1-0.4 nm) is much smaller than that of the substrate. Raman analysis and hardness measurement by nanoindentation indicate that the structure and the hardness of the DLC films are relatively unchanged for the film surface roughness investigated. For the argon or hydrogen plasma post-treatment of the DLC films deposited using acetylene as the carbon source, it is found that surface roughness decreases with the post-treatment time. Although the hardness decreases after post-treatment, it remains relatively constant with increasing post-treatment time.