Impact of nitrogen doping on growth and hydrogen impurity incorporation of thick nanocrystalline diamond films

A much larger amount of bonded hydrogen was found in thick nanocrystalline diamond (NCD) films produced by only adding 0.24% N₂ into 4% CH₄/H₂ plasma, as compared to the high quality transparent microcrystalline diamond (MCD) films, grown using the same growth parameters except for nitrogen. These experimental results clearly evidence that defect formation and impurity incorporation (for example, N and H) impeding diamond grain growth is the main formation mechanism of NCD upon nitrogen doping and strongly support the model proposed in the literature that nitrogen competes with CH_x (x=1,2,3) growth species for adsorption sites.