Electron microscopy of GaAs/MnAs core/shell nanowires

GaAs/MnAs core/shell nanowire heterostructures were synthesized by catalyst-free molecular beam epitaxy. Transmission electron microscopy (TEM) reveals that the GaAs core predominantly grows with the zinc-blende crystal structure with a [111] growth direction. In a small population of wires, the crystal structure transitions from zinc blende to wurtzite with a [001] growth direction. Cross-sectional TEM shows that the MnAs grows epitaxially on the GaAs core in the NiAs prototype structure with an epitaxial relation of [202¯1] MnAs∥[111]GaAs and (011¯0) MnAs∥GaAs (1¯10). When the GaAs core is in the wurtzite structure, the epitaxial relation between the GaAs and MnAs changes to [0001] MnAs∥[0001]GaAs and (1¯21¯0) MnAs∥(1¯21¯0)GaAs.