  Vapor-liquid-solid (VLS) route and its variants are routinely used for
scalable synthesis of semiconducting nanowires yet the fundamental growth
processes remain unknown. Here, we employ atomic-scale computations based on
model potentials to study the stability and growth of gold-catalyzed silicon
nanowires (SiNWs). Equilibrium studies uncover segregation at the solid-like
surface of the catalyst particle, a liquid AuSi droplet, and a silicon-rich
droplet-nanowire interface enveloped by heterogeneous truncating facets.
Supersaturation of the droplets leads to rapid 1D growth on the truncating
facets and much slower nucleation-controlled 2D growth on the main facet.
Surface diffusion is suppressed and the excess Si flux occurs through the
droplet bulk which, together with the Si-rich interface and contact line,
lowers the nucleation barrier on the main facet. The ensuing step flow is
modified by Au diffusion away from the step edges. Our study highlights key
interfacial characteristics for morphological and compositional control of
semiconducting nanowire arrays.
