Real structure of lattice matched GaAs-Fe3Si core-shell nanowires

TL;DR

This study elucidates the detailed structure and growth mechanisms of GaAs-Fe3Si core-shell nanowires grown by molecular-beam epitaxy, revealing their epitaxial growth, grain structure, and shell inhomogeneities.

Contribution

It provides the first detailed structural analysis of GaAs-Fe3Si core-shell nanowires, including growth stages, grain orientation, and shell faceting, using TEM and XRD techniques.

Findings

GaAs nanowires grow epitaxially via vapor-liquid-solid mechanism.

Fe3Si shells are textured with small grains and inhomogeneous thickness.

Two growth stages of GaAs nanowires were identified.

Abstract

GaAs nanowires and GaAs-Fe3Si core-shell nanowire structures were grown by molecular-beam epitaxy on oxidized Si(111) substrates and characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Ga droplets were formed on the oxide surface, and the semiconducting GaAs nanowires grew epitaxially via the vapor-liquid-solid mechanism as single-crystals from holes in the oxide film. We observed two stages of growth of the GaAs nanowires, first the regular growth and second the residual growth after the Ga supply was finished. The magnetic Fe3Si shells were deposited in an As-free chamber. They completely cover the GaAs cores although they consist of small grains. High-resolution TEM micrographs depict the differently oriented grains in the Fe3Si shells. Selected area diffraction of electrons and XRD gave further evidence that the shells are textured and not single crystals. Facetting of the shells was observed, which lead to thickness inhomogeneities of the shells.