Chemical boundary layers in CVD.I. Irreversible reactions

Because of the coupling of the temp. dependence of gas-phase reaction rate consts. with the steep temp. gradient, present inmost CVD (chem. vapor deposition) reactors, a thin chem. reaction boundary layer can be defined in the gas phase just above the susceptor. This boundary layer will be present under all operating conditions, including lower pressures irresp. of the kinetic regime of the deposition reaction or the existence of flow and temp. boundary layers. By using this chem. boundary layer concept, it is possible to derive deposition rate equations not only for the gas-phase transport limited regime but also for the gas-phase kinetic regime, or for the case where surface reactions are rate limiting