Role of inert gas in the low-temperature nano-diamond chemical vapour deposition process

We report a systematic investigation of the effect of different inert gases on chemical vapour deposition (CVD) of nano-crystalline diamond. The surface morphology and growth rate of the nano-structure CVD films were characterized by Raman spectroscopy and different microscopic techniques. In situ optical emission measurement was employed to monitor the plasma chemistry, which possibly influences the film growth. Our result indicates that C2 is not necessarily the key growth species for nano-crystalline diamond and we demonstrate here that the nano-crystalline diamond film can be grown under conditions where the C2 concentration is very small. Modelling results support the trend in number density changes for intermediate radicals with the volume percentage of argon variation for CH4/H2/Ar plasma.