| Popis: |
The use of in‐situ, optical diagnostics for probing the gaseous chemistry in the chemical vapor deposition (CVD) of diamond is described. Both radical (H, CH3) and stable (CH4, C2H2, C2H4) species have been detected. We report here the resonance‐enhanced multiphoton ionization (REMPI) detection of CH3 and atomic hydrogen under diamond CVD conditions. The H atom concentration, found to be quite sensitive to initial CH4/H2 fraction (F0), decreased with increasing F0 and was severely depleted with F0=30% and filament temperatures below 2200 C. Our present model of the filament‐assisted gas phase environment is one in which thermodynamically‐favored species (e.g., C2H2, CH3) are formed at high temperature near the filament, followed by depletion of the more reactive species during transport to the diamond growth surface. An interference effect due to third harmonic generation in atomic hydrogen was also observed in the REMPI experiments. |
