ON THE OPTIMIZATION OF A DC ARCJET DIAMOND CHEMICAL-VAPOR-DEPOSITION REACTOR

Based on results from chemical kinetic model calculations, a method to improve diamond film growth in a de arcjet chemical vapor deposition reactor has been developed. Introducing the carbon source gas (CH4) in to an Ar/H-2 plasma in close proximity to the substrate produced diamo nd films exhibiting simultaneous improvements in quality and mass depo sition rates. These improvements result from a reduced residence time of the methane in the plasma which inhibits the hydrocarbon chemistry in the gas from proceeding significantly beyond methyl radical product ion prior to encountering the substrate, Improvements in growth rate w ere modest, increasing by only a factor of two. Optical emission actin ometry measurements indicate that the flux of atomic hydrogen across t he stagnation layer to the substrate is mass diffusion limited. Since diamond growth depends upon the flux of atomic H to the substrate, the se results suggest that under the conditions examined here, a low atom ic H flux to the substrate poses an upper limit on the attainable diam ond growth rate.