Despite the progress made in the past decades, the mechanism of the CVD diamond growth process has remained somewhat a mystery. Considering the two growth techniques just mentioned, the hot-filament system is a thermal system, while the microwave plasma involves processes such as excitation, ionization, dissociation, and ion-neutral reactions. It has always been perplexing that these two techniques, being so different in nature, require nearly identical conditions for diamond growth and produce fairly similar results. When using a microwave source (800 W), with the process pressure at ~20 Torr, a feed gas with methane/hydrogen ?0.5%, and a substrate temperature of 1073 K, high quality poly-crystalline diamond films can be produced like in hot-filament (2600 K) operated under the same conditions. The only significant difference being that the growth rate is approximately a factor higher in the microwave plasma [141]. However, that the two techniques would produce nearly identical results appears to suggest that under the conditions necessary for diamond deposition the gas phase kinetics existing in a microwave plasma system are not that dissimilar to those in a hot-filament system. This implies that there must be a uniform dominating mechanism for diamond growth.
The physical properties of diamond films grown using CVD techniques have been shown to be sensitive to the changes in the growth environment. As a result, most studies of diamond CVD attempt to optimize film growth properties by either probing different regions of the reactor parameter space or by changing...
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