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

•The aim of the work is the characterization of GaAs-Fe3Si core-shell nanowires (NWs).•GaAs NWs grow epitaxially on the Si(111) surface via the vapor-liquid-solid growth mechanism.•The surfaces of the original GaAs NWs are completely covered by magnetic Fe3Si.•The substrate temperature during Fe3Si deposition has influence on the quality of the NW structures.•Poly-crystalline Fe3Si shells are the result of the Volmer-Weber growth.

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.