Ferromagnetic GaAs/GaMnAs Core−Shell Nanowires Grown by Molecular Beam Epitaxy

Abstract

GaAs/GaMnAs core-shell nanowires were grown by molecular beam epitaxy. The core GaAs nanowires were synthesized under typical nanowire growth conditions using gold as catalyst. For the GaMnAs shell the temperature was drastically reduced to achieve low-temperature growth conditions known to be crucial for high-quality GaMnAs. The GaMnAs shell grows epitaxially on the side facets of the core GaAs nanowires. A ferromagnetic transition temperature of 20 K is obtained. Magnetic anisotropy studies indicate a magnetic easy axis parallel to the nanowire axis.

Direct observation of doping incorporation pathways in self-catalytic GaMnAs nanowires

“…For example, the formation of ferromagnetic precipitates or clusters such as MnAs should be considered as a possible source of magnetism. 11,16,17 Recently, core-shell structured NWs consisting of GaAs/GaMnAs, 18 GaAs/MnAs, 19,20 and InGaAs/GaMnAs 21 have been considered as well. Some of these studies showed that low temperature grown GaMnAs shells can contain high Mn concentrations up to $5% and have ferromagnetic phase transitions above 20 K. 18,21 We have demonstrated previously 11,13 that it is possible to grow GaMnAs NWs by MBE at low temperatures (300-350 C) and if the growth temperature is slightly too high, the formation of MnAs nanoclusters occurs on the surface.…”

“…11,16,17 Recently, core-shell structured NWs consisting of GaAs/GaMnAs, 18 GaAs/MnAs, 19,20 and InGaAs/GaMnAs 21 have been considered as well. Some of these studies showed that low temperature grown GaMnAs shells can contain high Mn concentrations up to $5% and have ferromagnetic phase transitions above 20 K. 18,21 We have demonstrated previously 11,13 that it is possible to grow GaMnAs NWs by MBE at low temperatures (300-350 C) and if the growth temperature is slightly too high, the formation of MnAs nanoclusters occurs on the surface. However, due to high disorder in terms of NW orientation, crystallographic defects, and morphology, other growth regimes of Mn-doped GaAs NWs have been exploited: (i) Ga catalyzed NWs grown at high temperature on Si(100), 13 (ii) Ga catalyzed NWs grown at high temperature on Si(111), 22 and (iii) low-temperature grown GaMnAs shells on high-temperature grown Au-catalyzed GaAs NWs on GaAs(111)B.…”

Magnetic properties of GaAs-Fe3Si core-shell nanowires—A comparison of ensemble and single nanowire investigation

“…[1][2][3][4][5][6][7][8][9][10][11][12] To fabricate SFCSNws, commonly first semiconductor Nws are fabricated by epitaxial methods such as molecular beam epitaxy or metal oxide chemical vapor deposition and are in a second growth step coated with the ferromagnetic material. Thereby the magnetic material does not necessarily stick to the Nw shells exclusively.…”

“…Thus, the insight of ensemble measurements on the Nws themselves that were reported recently by using superconducting quantum interference device magnetometry (SQUID), small angle neutron scattering and ferromagnetic resonance techniques are quite equivocal. [1][2][3][4][5][6][7] Single Nw magnetic investigation on the other hand gives precise information about only the selected structure (one Nw shell) but thus it reflects only the information obtained from one single event of measurement (from one Nw). To draw conclusions from such measurements over all other Nws is hence quite limited.…”

Diffraction at GaAs/Fe3Si core/shell nanowires: The formation of nanofacets

“…[1][2][3][4][5][6][7][8] The cylindrical shape of the ferromagnet in such core/shell NWs causes a magnetization along the wire axis, i.e. perpendicular to the substrate surface.…”