THE GROWTH-KINETICS OF DIAMOND FILMS DEPOSITED BY HOT-FILAMENT CHEMICAL VAPOR-DEPOSITION

The growth kinetics of diamond film has been studied, grown by a hot-filament chemical vapor deposition method, to obtain a fundamental information for the growth process of diamond from the gas phase. In order to study the growth kinetics of a pure diamond, the deposition conditions for high-quality diamond are first determined and the kinetics study is carried out under these deposition conditions. Diamond film thickness is directly proportional to the deposition time. This indicates that diamond films are deposited in the steady state under these experimental conditions. The variation of growth rate with substrate temperature shows a distinct maximum. The maximum temperature is shifted somewhat to the higher temperature side with increasing methane concentrations. It is found that this behavior is due to the decrease of supersaturation with increasing substrate temperature. However, the growth rate of diamond film increases linearly with methane concentrations. Therefore, the growth rate of diamond film can be described by the rate constant for a first-order reaction. From the kinetic data of diamond deposition, the deposition rate is controlled by the surface reaction (activation energy of 11 kcal/mol) at the lower temperature range, while the deposition rate is gas phase diffusion controlled (activation energy of 3.8 kcal/mol) at the higher temperature range.