Control of surface induced phase separation in immiscible semiconductor alloy core-shell nanowires

TL;DR

This paper presents a method to control phase separation in immiscible semiconductor alloy nanowires during high-temperature annealing by adjusting geometry and strain, using phase field modeling.

Contribution

It introduces a novel approach to suppress phase separation in core-shell nanowires through geometric and strain engineering during annealing.

Findings

Thin shells delay phase separation onset.

Thick shells nearly suppress phase separation.

Phase separation initiates at the free surface and propagates inward.

Abstract

Semiconductor nanowires have been shown to exhibit novel optoelectronic properties with respect to bulk specimens made of the same material. However, if a semiconductor alloy has a miscibility gap in its phase diagram, at equilibrium it will phase separate, leading to deterioration of the aforementioned properties. One way to prevent this separation is to grow the material at low temperatures and therefore to suppress kinetics. Such growth often needs to be followed by high-temperature annealing in order to rid the system of undesirable growth-induced defects. In this study, we propose a method to control phase separation in core-shell nanowires during high temperature annealing by tailoring geometry and strain. Using a phase field model we determined that phase separation in nanowires begins at the free surface and propagates into the bulk. We discovered that including a thin shell around the core delays the phase separation whereas a thick shell suppresses the separation almost entirely.