MODEL PREDICTIONS VERSUS EXPERIMENTS: CH_3 RADICAL DENSITY PROFILES IN DIAMOND DEPOSITION MICROWAVE PLASMA REACTOR

摘要

Simulation results based on a one dimensional diffusive CH_4 + H_2 plasma model interacting with a diamond surface are presented. The dependence of axial profiles of H-atom, CH_3 and CH radical densities and temperatures as a function of two reactor variables: microwave power density and percentage of methane is shown. CH_3-radical density profiles are compared to line-of-sight methyl radical density profiles measured by UV absorption spectroscopy. The results suggest that although H-atom density in the near-substrate vicinity is controlled by diffusion process, the near-substrate methyl density is controlled by gas-phase, temperature activated reactions in the near-substrate region. The results also show that measured methyl densities are approximately a factor of ten greater than those predicted by the model. Part of this difference is attributed to limitations of the model, and part to line of sight limitations of the measurements.