Molecular dynamics simulations of gold-catalyzed growth of silicon bulk crystals and nanowires

Abstract

The growth kinetics of Si bulk crystals and nanowires (NWs) in contact with Au-Si liquids is studied by molecular dynamics simulations using an empirical potential fitted to the Au-Si binary phase diagram. The growth speed nu is predicted as a function of Si concentration x(Si) in the Au-Si liquid at temperature T = 1100 K and as a function of T at x(Si) = 75%. For both bulk crystals and NWs, the {111} surface grows by the nucleation and expansion of a single two-dimensional island at small supersaturations, whereas the {110} surface grows simultaneously at multiple sites. The top surfaces of the NWs are found to be curved near the edges. The difference in the growth velocity between NWs and bulk crystals can be explained by the shift of the liquidus curve for NWs. For both bulk crystals and NWs, the growth speed diminishes in the low temperature limit because of reduced diffusivity.