Gas phase equilibrium limitations on the vapor-liquid-solid growth of epitaxial silicon nanowires using SiCl₄

Epitaxially oriented silicon nanowires (SiNWs) were grown on (111) Si substrates by the vapor-liquid-solid technique in an atmospheric-pressure chemical vapor deposition (APCVD) system using Au as the catalyst and SiCl4 as the source gas. The dependencies of SiNW growth rate on the growth temperature and SiCl₄ partial pressure (PSiCl₄) were investigated, and the experimental results were compared with calculated supersaturation curves for Si obtained from a gas phase equilibrium model of the SiCl ₄-H₂ system. The SiNW growth rate was found to be weakly dependent on temperature but strongly dependent on the PSiCl₄, exhibiting a maximum value qualitatively similar to that predicted from the equilibrium model. The results indicate that SiNW growth from SiCl4 is limited by gas phase chemistry and transport of reactant species to the growth surface under APCVD conditions. The experimental results are discussed within the context of a gas phase mass transport model that takes into account changes in equilibrium partial pressure due to curvature-related Gibbs-Thomson effects.