Fabrication of diamond films at low temperature by pulse-modulated magneto-active microwave plasma CVD

A magneto-active microwave plasma chemical vapour deposition technique was developed by pulse modulation of the discharge to reduce the time-averaged microwave power for diamond film synthesis at low temperature. Due to a threshold power being required to start growth, the practical growth rate obtained by using the pulse-modulated plasma became three times larger than that obtained by using a continuous plasma of time-averaged power near the threshold. The methyl (CH3) radical density was measured in continuous or pulse-modulated plasma by infrared laser absorption spectroscopy and compared to the growth rate. The time-averaged CH3 radical density was also enhanced by pulse modulation; it was up to 1.3 times larger than that in the continuous plasma. Though the correlation between CH3 density and diamond growth rate was not clear, the number of carbon atoms supplied as CH3 radicals was larger than the actual growth rate by almost two orders of magnitude.