Factors in Phase Formation in the Heterogeneous Chain Oxidation of Dichlorosilane at Low Pressures

Dichlorosilane oxidation, a heterogeneous branching-chain reaction, is considered in terms of unsteady-state nucleation theory taking into account the condensation growth of nuclei, and the following observations are interpreted: the crossover between the homogeneous and heterogeneous phase formation; the dependence of the amount of aerosol on the initial temperature, pressure, and admixture concentration; and the kinetics of phase formation and of the disappearance of the original substance. Introducing an inhibitor is found to reduce the mean size of aerosol particles. This result is in qualitative agreement with experimental data. It is found that it is because of the growing equilibrium vapor pressure of the new phase that the amount of aerosol formed decreases with increasing initial temperature, including when an active admixture is present. The reactivity of the silicon dioxide aerosol obtained in the presence of Freon-12 varies reversibly. The role of surface diffusion and surface nucleation in the deposition of thin films is discussed.