GaAs nanowires grown by Au-catalyst-assisted MOVPE using tertiarybutylarsine as group-V precursor

The morphology, structure and phonon properties of well-aligned and kink-free GaAs nanowires grown on (1¯ 1¯ 1¯)B GaAs are reported. The nanowires were grown at temperatures down to 400°C by Au-catalysed MOVPE using tBuAsH2 and Me3Ga in H2 ambient. Colloidal Au nanoparticles (NPs) with average size of 60–70nm were used as catalyst. Below 425°C the nanowires consist of almost cylindrical segments, their average diameter closely matching that of the original Au NPs. At higher temperatures, the nanowires show a large tapering. The structural analysis of nanowire samples grown at 450°C evidences that residual catalyst droplets at the nanowire tips consist of crystalline fcc Au, with a preferred (1 1 1) crystallographic orientation, and orthorhombic GaAu2 alloy (gamma phase). Non-resonant Raman scattering experiments carried out on GaAs nanowires showed no evidence of phonon confinement effects. However, new strong LO phonon contributions arise in the Raman spectra with respect to bulk GaAs, likely due to the nanowire large surface-to-volume ratio.