Numerical microwave plasma discharge study for the growth of large single-crystal diamond

• Numerical microwave plasma discharge simulation based on a reactive fluid model was conducted in a 2/3-dimensional system.
• Two-dimensional distribution of the electron number density and several radicals were predicted under an actual experimental setup, which was realized in the calculation domain.
• Dependence of uniformity and growth rate on several discharge parameters was determined.
• Comparison with experimental results suggests the importance of substrate temperature uniformity and a possible contribution of CHx (x < 3) radicals to growth.

A microwave plasma discharge simulation was conducted to determine the spatial concentrations of hydrocarbon radicals and their uniformity over areas over 25 mm2. Dependences of these on controllable growth parameters were also determined. Parameters included the absorbed microwave power, the methane concentration in the feed gas mixture and the gas pressure. The radical concentrations that were obtained using simplified chemistry for the source gas species are consistent with those specified in other reports. The radical concentrations were consistent with the experimental growth rates but not with their distributions. This suggests the importance of substrate temperature uniformity and a contribution from CHx(x < 3) in addition to CH3.