Revealing atomistic mechanisms of gold-catalyzed germanium growth using molecular dynamics simulations

TL;DR

This study uses molecular dynamics simulations with a fitted interatomic potential to explore the atomistic mechanisms of gold-catalyzed germanium nanowire growth via the vapor-liquid-solid method, revealing how growth conditions influence morphology and growth modes.

Contribution

It provides detailed atomistic insights into Ge crystal growth mechanisms during VLS synthesis, linking interface properties to growth conditions and morphologies, which was previously limited by experimental resolution.

Findings

Growth rate depends on substrate orientation, temperature, and supersaturation.

Atom surface stability and exchange rates influence growth modes.

Orientation-dependent morphologies are explained by interface dynamics.

Abstract

The vapor-liquid-solid (VLS) method is considered a plausible technique for synthesizing germanium (Ge) nanostructures (e.g. nanowires), which have a broad range of applications due to their unique electronic properties and intrinsic compatibility with silicon. However, crystallization failures and material defects are still frequently observed in VLS processes, with insufficient understanding of their underlying mechanisms due to instrumental limitations for high-resolution in-situ characterizations. Employing an accurate interatomic potential well fitted to the gold-germanium (Au-Ge) phase diagram, we performed molecular dynamics simulations for a systematic investigation on the Au-catalyzed growth process of Ge crystals. From the simulations, relationships were established between the overall Ge growth rate and several main synthesis conditions, including substrate crystallographic orientation, temperature and Ge supersaturation in liquid. The dynamical behaviors of Ge atoms near the liquid-solid growing interface were captured, from which the atom surface stability and exchange rate were estimated for quantifying the atomistic details of the growth. These interface properties were further linked to the surface morphologies, to explain the observed orientation-dependent growing modes. This study sheds new lights into the understanding of the VLS growth mechanisms of Ge crystals, and provides scientific guidelines for designing innovative synthesis methods for similar nanomaterials.