Size-dependent nucleation kinetics at nonplanar nanowire growth interfaces

Abstract

In nanowire growth, kinetic processes at the growth interface can play an important role in governing wire compositions, morphologies, and growth rates. Molecular-dynamics simulations have been undertaken to probe such processes in a system featuring a solid-liquid interface shape characterized by a facet bounded by rough orientations. Simulated growth rates display a dependence on nanowire diameter consistent with a size-dependent barrier for facet nucleation. A theory for the interface mobility is developed, establishing a source for size-dependent growth rates that is an intrinsic feature of systems possessing growth interfaces with faceted and rough orientations.

Atomistics of vapour–liquid–solid nanowire growth

“…At small driving forces, the nucleation and growth dynamics associated with the melting kinetics is completely reversed; the truncating facets melt first as the energy of formation of a vacancy on these facets is lower, and eventually the main facet melts preferentially from the corner edges. The layer-by-layer melting velocities are smaller compared with those during growth due to the different morphological features implicated in the two processes, which by itself is important as the growth is a steady state between crystallization and melting kinetics3346.…”

“…We focus exclusively on a small diameter 2 R =10 nm, 111 silicon nanowire growing isothermally above the eutectic temperature at T =873 K. Both experiments and ab-initio computational techniques are handicapped in accessing the spatio-temporal scales associated with the energetics and three-dimensional (3D) dynamics during growth323334. We capture these processes in their full complexity by employing atomistic simulations based on an angular embedded-atom-method (AEAM) framework for describing the hybrid metallic–covalent interactions35.…”

Atomistic simulation of hillock growth

“…We were particularly interested in initial stages of the growth of hillocks and whiskers, a process in which a protrusion grows by addition of material to its root. We emphasize that this process is different from other growth phenomena that have recently been simulated by MD, such as the nanowire growth by the vapor-liquid-solid mechanism in which the nanowire grows by accretion of material on its top [21].…”

Computational Investigations of Solid-Liquid Interfaces

“…In these contexts crystal growth rates and morphologies are sensitively affected by the thermodynamic and kinetic properties of steps present on vicinal interfaces. In this project we applied MD simulations in detailed studies of crystal-melt interface steps, employing the Stillinger-Weber (SW) model of Si as a model system [6,9,16]. Non-equilibrium molecular-dynamics (NEMD) methods were applied to investigate crystal growth at interfaces with orientations vicinal to the faceted [111] plane.…”

“…The tools developed in the work on SW-Si models were extended in simulation studies of size effects on nucleation kinetics in model systems crystallizing in confined geometries [16]. The work was motivated in the context of catalyst-mediated nanowire growth, where kinetic processes at the growth interface can play an important role in governing wire compositions, morphologies, and growth rates.…”