Optical detection of CH_3 during diamond chemical vapor deposition

Measurements of CH_3 have been made using resonance-enhanced multiphoton ionization (REMPI) in two different diamond growth environments. Spatial profiles of methyl above the substrate have been measured in a filament- assisted reactor, which show that the CH_3 concentration is depleted near the substrate. The CH_3 concentration at the substrate shows an approximate Arrhenius dependence on substrate temperature below 1000 K, characterized by an activation energy of 4 kcal/mole. Methyl measurements were also made in 35 Torr hydrogen/oxygen flame into which methane is injected near the substrate. Radial profiles of methyl, acquired using REMPI, and of CH_4, acquired using sampling mass spectroscopy, are in good qualitative agreement with the results of numerical simulations