Vapor-liquid-solid and vapor-solid growth of self-catalyzed GaAs nanowires

We report on the morphological and structural properties of GaAs nanowires nucleated by self-catalyzed vapor-liquid-solid processes by molecular beam epitaxy on Si-treated GaAs substrates.We found that GaAs nanowires display zincblende and/or wurtzite phase depending on the As/Ga abundance ratio at the growth front, that determines the size and supersaturation of the Ga nanoparticles at the nanowire tip. We also found that even when growth conditions lead to the disappearance of such Ga nanoparticles, preferential one-dimensional growth continues through a vaporsolid mechanism. The nanowire portions grown by vapor solid mechanism display zincblend structure.