Pulsed microwave plasma-assisted chemical vapour deposition of diamond

In a pulsed microwave discharge used for plasma CVD of diamond, operating with a dilute mixture of methane and argon (as actinometer) in hydrogen, emissions of H, Ar, H-2, CH and C-2 were observed by time-resolved optical emission spectroscopy. At constant microwave average power, the influence of repetition rate on the concentration of atomic hydrogen and on the morphology and microstructure of diamond films was studied in detail. At high pulse repetition rates (greater than or equal to 1 kHz), the atomic hydrogen concentration becomes almost time-independent and approaches the continuous wave value. At low repetitition rates, the average concentration of atomic hydrogen is lower in pulsed plasmas compared to continuous wave conditions, but the atomic hydrogen concentration during the pulse-on-time is increased. However, growth rate as well as film quality, as assessed by scanning electron microscopy and Raman spectroscopy, is almost unaffected by pulsed deposition conditions in the range of 50 Hz-20 kHz.