HETEROGENEOUS FORMATION OF ATOMIC-HYDROGEN IN HOT-FILAMENT DIAMOND DEPOSITION

A two-dimensional finite element model has been developed for the reactor of W. L. Hsu [Appl. Phys. Lett. 59, 1427 (1991)], focusing on the relative importance of heterogeneous and homogeneous chemistry in the production of atomic hydrogen. Although hot-filament reactors have been the subject of extensive modeling efforts, most previous work has neglected the impact of the filament on both chemistry and fluid flow. Our calculations show that catalytic activity is responsible for at least 95% of the atomic hydrogen production. In addition, the concentration of atomic hydrogen at the filament is far below thermal equilibrium values. An analysis of experimental data reveals an activation energy of 150 kJ/mol for the filament-catalyzed reaction. From these measurements, a kinetic expression is developed to explain catalytic production of atomic hydrogen at the surface. Finally, the effect of recombination of hydrogen atoms at the growing surface was examined.