Bottom-Up Formation of Vertical Free-Standing Semiconductor Nanowires Hybridized with Ferromagnetic Nanoclusters

Abstract

The author introduces and summarizes the results on bottom-up formation and structural characterizations obtained so far for the MnAs nanoclusters and MnAs/semiconductor nanowire hybrids. First, MnAs nanoclusters were grown by selective-area metal-organic vapor phase epitaxy. They had a hexagonal NiAs-type crystal structure. Their <00(0)1> direction was parallel to <111>B direction of zinc-blende-type GaAs substrates. Hybrid MnAs/GaAs nanowires, subsequently, were fabricated by combining selective-area metal-organic vapor phase epitaxy of GaAs nanowire templates and endotaxial MnAs nanoclustering on them. MnAs nanoclusters ordered at six ridges of hexagonal GaAs nanowires were formed possibly owing to more atomic steps between {0-11} crystal facets. In the case of hybrid MnA/InAs nanowires, MnAs nanoclusters were not formed only on the {0-11} side-walls, and/or ridges between them, but on the top {111}B crystal facets of hexagonal InAs nanowires. MnAs nanoclusters were formed much deeper into the InAs nanowires than into the GaAs nanowires. These facts are possibly due to the InAs nanowires are thermally less stable than the GaAs nanowires. Some of the hybrid MnA/InAs nanowires were bent at the parts where the MnAs nanoclusters were grown into the host nanowires mainly owing to the strain effects.