PARAMETRIC STUDY OF ATMOSPHERIC-PRESSURE DIAMOND SYNTHESIS WITH AN INDUCTIVELY-COUPLED PLASMA TORCH

Polycrystalline diamond coatings have been deposited on molybdenum and silicon substrates using an inductively coupled, atmospheric-pressure plasma torch. Growth rates are on the order of 10 mum/hr. The inducti vely coupled plasma reactor is found to produce a uniform, well-charac terized growth environment for experimental and computational study of the atmospheric-pressure diamond growth regime. Growth morphology is found to be sensitive to reactor conditions such as substrate surface temperature and methane-to-hydrogen feed ratio. An experimental parame tric study of these variables is performed and the resultant growth an alyzed by scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. Spectroscopic analysis of the gas phase is also performed Results indicate that the substrate temperature range over which diam ond growth occurs shifts toward higher temperatures as the methane-to- hydrogen feed ratio is increased The growth rate is observed to reach a maximum with varying methane-to-hydrogen feed ratio at constant subs trate temperature. Raman analysis of the deposits indicates that highe r-quality diamond is achieved at the highest limits of substrate tempe rature for a given methane-to-hydrogen ratio. Higher-quality diamond i s also observed to be formed al lower methane-to-hydrogen feed ratios.