Position controlled self-catalyzed growth of GaAs nanowires by molecular beam epitaxy.

GaAs nanowires are grown by molecular beam epitaxy using a self-catalyzed, Ga-assisted growth technique. Position control is achieved by nano-patterning a SiO(2) layer with arrays of holes with a hole diameter of 85 nm and a hole pitch varying between 200 nm and 2 µm. Gallium droplets form preferentially at the etched holes acting as catalyst for the nanowire growth. The nanowires have hexagonal cross-sections with {110} side facets and crystallize predominantly in zincblende. The interdistance dependence of the nanowire growth rate indicates a change of the III/V ratio towards As-rich conditions for large hole distances inhibiting NW growth.

Ferromagnetic GaAs/GaMnAs core-shell nanowires grown by molecular beam epitaxy.

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.