SIMULATION OF REACTIVE FLOW IN FILAMENT-ASSISTED DIAMOND GROWTH INCLUDING HYDROGEN SURFACE-CHEMISTRY

One-dimensional reactive-flow simulations of a hot-filament chemical v apor deposition-system including surface reactions of H atoms and H-2 molecules are reported. The corresponding governing equations of mass, momentum, chemical species, and energy are solved assuming a stagnati on-point flow. In the model, the filament is catalytically active to d issociate H-2 molecules, and the net surface reaction is the recombina tion of H atoms to H-2 molecules. It is shown that the surface chemist ry strongly influences the H and CH4 concentration profiles, whereas o nly a minor influence on CH3 and C2H2 concentrations-possible candidat es as precursors for diamond growth-is observed. The influence of the surface temperature on gas-phase species concentration is discussed. A t surface temperatures below 1000 K, the CH3-concentration dependence on the substrate temperature can be characterized by an activation ene rgy of 14 kJ/mol which is in good agreement with experiment. The simul ations show that this activation energy is a pure gas-phase effect due to recombination of methyl radicals and H atoms to methane in the coo l gas layer near the substrate. (C) 1996 American Institute of Physics .