DIAMOND GROWTH-RATES VS ACETYLENE CONCENTRATIONS

Previous measurements and analyses have pointed to either methyl CH3 or acetylene C2H2 as the primary growth species for diamond films grown from chemical vapor deposition. In this work we used a quartz microprobe and a mass spectrometer to measure how the concentration of C2H2 varied with pressure and with the ratio of methane to hydrogen in the input gas. We compared these variations with variations in the growth rate, as measured with a microbalance. We found no consistent correlation between the growth rate and the C2H2 concentration. This contrasts with a linear relationship that we found previously between the growth rate and the calculated concentration of the methyl radical CH3.