Synthesis of nanocrystalline diamond films using CH4 concentration modulated plasma

Microcrystalline diamond (MCD) has excellent characteristics, such as high hardness and high wear resistance, but it also has the disadvantage of high surface roughness. On the other hand, nanocrystalline diamond (NCD) film has the advantage of low surface roughness. However, it contains non-diamond phases, resulting in a decrease in wear resistance. In this study, CH4 concentration was modulated from 1% to 10% in MCD and NCD synthesis to synthesize high-quality NCD films with high hardness. Conventional NCD film synthesized with a CH4 concentration of 10% had a hardness of 46 GPa, while that synthesized with CH4 concentration modulation had a hardness of 73 GPa. These observations indicated that CH4 concentration modulation increased the hardness and improved the film quality. CH4 modulation can be used to synthesize NCD film with higher hardness and higher quality than conventional NCD film.