First principles prediction of gas-phase composition and substrate temperature for diamond film growth

A model consisting of ten hydrocarbon species and eight reactions is propos ed to describe the gas-phase chemistry of diamond film growth. Based on the model, the gas-phase compositions of the chemical species were computed as suming thermodynamic equilibrium using molecular and transition-state data predicted by ab initio molecular orbital theory, and thermodynamic quantiti es calculated by statistical mechanics. Although the absolute compositions predicted by the model are in fair agreement with experimental data availab le in the literature, the model qualitatively accounts for experimentally o bserved changes in the concentrations of various gasphase species with incr easing addition of methane to the feed gas. The calculations also predict t he pattern of temperature variance in the gas-phase close to the substrate with changes in methane concentration in the feed gas, leading to first-pri nciples predictions of favorable conditions for diamond growth.