Diamond growth chemistry during atmospheric-pressure plasma CVD

Diamond films were deposited by chemical vapor deposition using a radio-frequency induction plasma operating at 130 torr. Linear growth rates of polycrystalline diamond films ranged from 18 to 37 μm h^-1. For a fixed substrate temperature of 1000°C the input methane-hydrogen ratio was varied from 2% to 10%. Over this range the resulting film morpologies changed from faceted ball-like structures to well-faceted diamond, then to non-faceted balls, and for the well-faceted films increases in methane-hydrogen ratio caused the film texture to shift toward the 〈100〉 direction. During these experiments gas sampled through an orifice in the center of the substrate was delivered to a gas chromatograph for measurement of stable hydrocarbon species. As the input methane-hydrogen ratio was increased the measured methane-acetylene ratio decreased. The gas chromatograph measurements showed marked differences from measurements made for an RF reactor with somewhat different flow geometry operating at atmospheric pressure.