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

摘要

Semiconductor nanowires have been shown to exhibit novel optoelectronicproperties with respect to bulk specimens made of the same material. However,if a semiconductor alloy has a miscibility gap in its phase diagram, atequilibrium it will phase separate, leading to deterioration of theaforementioned properties. One way to prevent this separation is to grow thematerial at low temperatures and therefore to suppress kinetics. Such growthoften needs to be followed by high-temperature annealing in order to rid thesystem of undesirable growth-induced defects. In this study, we propose amethod to control phase separation in core-shell nanowires during hightemperature annealing by tailoring geometry and strain. Using a phase fieldmodel we determined that phase separation in nanowires begins at the freesurface and propagates into the bulk. We discovered that including a thin shellaround the core delays the phase separation whereas a thick shell suppressesthe separation almost entirely.