Twinning in GaAs nanowires on patterned GaAs(111)B

We have studied twinning in GaAs nanowires grown via holes in a silica mask deposited on GaAs(111)B substrates by metal-organic chemical vapour epitaxy without catalysts. Twins perpendicular to the growth direction form in the nanowires, their {111}-type side facets leading to corrugation of their {110} side walls. The top facets are almost atomically smooth. Aberration corrected annular dark-field scanning transmission electron microscopy reveals all twins are rotational, commencing with layers of Ga and finishing with As atoms. Energy-loss spectroscopic profiling has shown no significant changes in the band-gap or bulk plasmon energy at those twin boundaries, and the observed reduction of the interface plasmon energy by ∼0.13 eV is close to the detection limit of the technique, reflecting the very low energetic electronic changes related to twin formation.