Nanocrystalline diamond formation by using an inductively coupled radio-frequency CH4/H2/Ar plasma

Effect of gas-mixing ratio on the formation of nanocrystalline diamond has been investigated in a low electron temperature CH4/H2/Ar plasma produced by inductively coupled rf discharge. The gas-mixing ratio is controlled by introducing an orifice between the plasma production region and the deposition region. When the diameter of the orifice is 6 mm, the Raman spectrum indicating a deposition of nanocrystalline diamond is observed when the gas-mixing ratio is less than ∼0.03. The reduction of CH4 gas-mixing ratio is important for the formation of nanocrystalline diamonds.