Coupling Effects of CH4/H2/Ar Gas Ratios and Hot Filament-Substrate Distance on the Growth of Nanocrystalline Diamond

Due to the special shape of cutting or grinding tools used nowadays, hot filament (HF)-substrate distance is usually unavoidable during the process of diamond deposition by hot filament chemical vapor deposition (HFCVD), which will lead to difficult deposition process for nanocrystalline diamond (NCD). Based on this problem, the coupling effects of different CH4/H2/Ar gas ratios and HF-substrate distances on the growth of NCD films are systematically studied. SEM and Raman are used to analyze the surface morphology and sp3/sp2 contents of the diamond films deposited on different areas of each specimen. The results indicate that the proper increase of HF-substrate distance and concentration of CH4 or Ar encourage the growth of NCD. Under the condition of lower concentration of CH4 or Ar, NCD with uniform grain size can also be realized at a certain range of HF-substrate distance. A graph that shows the growth conditions of MCD, MCD/NCD and NCD is creatively presented by summarizing the deposition parameters and experimental results. This work provides a path to coat NCD onto the special-shaped cutting or grinding tools by HFCVD.