surface by approximately 0 25 u2033 the deposition chamber 10 is evacuated to a base pressure of less than 0 01 torr and process gases consisting of hydrogen and methane are admitted to the deposition chamber from gas supply 30 at a mixture ratio of 95 hydrogen 5 methane and the chamber pressure is regulated at 5 torr when 5 torr pressure is reached the 150 mhz source is energized and a plasma is observed to cover both the deposition substrate 14 and the counterelectrode 26 and to fill the space in between these two structures chamber pressure is slowly increased to 150 torr with concurrent increase in the power level of the 150 mhz source and with concurrent adjustments of the impedance matching device not shown to maintain a good electrical match between the power source 20 and the deposition system as pressure increases the plasma is observed to fade from the interelectrode space and to persist as a thin structure on the deposition substrate 14 and on the immediately opposed surface of counterelectrode 26 at a pressure of 150 torr approximately 75 kw of 150 mhz energy is required to maintain a uniform plasma over the deposition substrate 14 after a duration of seven hours the deposition system is shut off and allowed to cool a diamond film is observed to have grown over the silicon deposition substrate to a thickness of approximately 120 microns the power deposition efficiency is calculated to be 1 4 kwhr carat of diamond deposited the raw composite growth efficiency is 0 00832 the normalized composite growth efficiency is calculated to be approximately 17 6 times or 1780 of the efficiency of the 100 reference growth efficiency of the arc.