Atomistics of vapor-liquid-solid nanowire growth

TL;DR

This study uses atomic-scale simulations to uncover the fundamental growth mechanisms of gold-catalyzed silicon nanowires in vapor-liquid-solid synthesis, revealing key interfacial processes that influence nanowire morphology.

Contribution

It provides the first atomic-scale insights into VLS nanowire growth, detailing the roles of segregation, supersaturation, and diffusion in the process.

Findings

Segregation occurs at the catalyst surface and interface.

Supersaturation drives rapid 1D growth on truncating facets.

Surface diffusion is suppressed, and Si flux occurs through the droplet bulk.

Abstract

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.