Nanowires of GaAs were grown on single-crystal (001) Si and GaAs substrates by using the vapour-liquid-solid mechanism in a metal-organic chemical vapour deposition chamber. These nanowires typically exhibited a circular cross-section with diameters in the range of 10 to 40nm. They contained a high density of growth twins that were investigated in detail here using transmission electron microscopy and high-resolution electron microscopy. The results indicated that the wires usually had a zincblende diamond-cubic structure with their growth-axis parallel to [111] and with twins perpendicular to the growth axis. In many cases, multiple twins tended to cluster in groups along the length of the nanowires; either in a near-periodic fashion or on consecutive {111} planes, resulting in the formation of local regions which exhibited the hexagonal wurtzite structure of GaAs. The small difference in energy between these two forms of GaAs was suggested to be the reason for the coexistence of both zincblende and wurtzite structures within the same nanowire.

Structure of Twins in GaAs Nanowires Grown by the Vapour-Liquid-Solid Process. R.Banerjee, A.Bhattacharya, A.Genc, B.M.Arora: Philosophical Magazine Letters, 2006, 86[12], 807-16