OPTICAL-EMISSION CHARACTERIZATION OF CH4+H2 DISCHARGES FOR DIAMOND DEPOSITION

Methane and hydrogen discharges has been studied at different discharge frequencies (35 kHz, 13.56 MHz, and 2.45 GHz) and feeding gas ratios (up to 100% of methane) during diamond and diamond-like deposition by plasma chemical vapor deposition techniques. Optical emission spectroscopy shows that the intensity of atomic hydrogen line (H(alpha)) is the highest at the microwave frequency (2.45 GHz). In addition, at this frequency and low methane concentrations (< 7.5%) the emission of CH+ species is also detected, which has been associated to the presence of the diamond phase in the films. On the contrary, at the lower frequencies (35 kHz and 13.56 MHz), the emission spectra are dominated by neutral CH species that are supposed to be the precursor species in the diamond-like films deposited at these frequencies.