Direct monitoring of CH3 in a filament-assisted diamond chemical vapor deposition reactor

Abstract

The technique of resonance-enhanced multiphoton ionization (REMPI) was used to determine relative density distributions of gas-phase methyl radical (CH3) in a filament-assisted diamond chemical vapor deposition reactor. The dependences of CH3 concentration on input CH4/H2 ratio, filament temperature, and distance from the filament were determined. We also report similar REMPI data for excited-state C(1D) atoms, which were produced photolytically from an unknown gas-phase parent. Arrhenius parameters show that the CH3 is not the parent of the C( 1D) atoms. The CH3 density saturates at high filament temperature. We compare the REMPI measurements with other determinations and models of CH3 concentrations.