Optical emission spectroscopy of H2–CO and H2O–CH3OH plasmas for diamond growth

Optical emission spectroscopy (OES) was used as a diagnostic tool to determine diamond growth in our rf plasma chemical vapor deposition systems. Diamond was grown with a conventional H2–CO source gas and in a low pressure system using a water–methanol source. Optical emission spectra were recorded between the wavelengths of 2000 and 8000 Å for both the systems. The OES spectral peak ratios of Hα to certain carbon radicals are an indicator of diamond growth in H2–CO plasmas. In particular, both the growth rate and morphology showed a correlation with Hα to certain carbon radical ratios in H2–CO discharges. The OES spectra in the water–methanol plasma are quite different than in the H2–CO plasma. Different species are represented and the intensity of the common peaks is much higher than in the H2–CO plasma.