Phase-field investigation of the stages in radial growth of core–shell Ge/Ge1−xSnx nanowires

Abstract

Core–shell Ge/Ge1−x Snxnanowires are considered promising silicon-compatible nanomaterials with thepotential to achieve a direct band-gap for optoelectronic applications. In this study, we systematicallyinvestigated the formation of this heterostructure in the radial direction by the phasefield methodcoupled with elasticity. Our model simulated the shell growth of the wire, capturing the evolution of boththe sidewall morphology and the strain distribution. We predicted the minimum chemical potential drivingforces required for initiating the Ge1−xSnx shell growth at given tin concentrations. In addition, we studiedthe dependences of the shell growth rate on the chemical potential, the tin concentration, the sidewallinterface kinetics and the mass transport rate respectively. From these analyses, we identified threesequential stages of the growth: the Stage 1 growth at an accelerated rate, the Stage 2 growth at a con-stant rate, andfinally the Stage 3 growth at a reduced rate scaling with 1/[square root]t. This research improves ourcurrent understanding on the growth mechanisms of heterogeneous core–shell nanowires, and providesuseful guidelines for optimizing nanowire synthesis pathways.