Ga2Se3 Nanowires via Au-Assisted Heterovalent Exchange Reaction on GaAs

Out-of-plane Ga2Se3nanowires are grown bymolecular beam epitaxy via Au-assisted heterovalent exchangereaction on GaAs substrates in the absence of Ga deposition. It isshown that at a suitable temperature around 560°C the Au-decorated GaAs substrate releases Ga atoms, which react with theincoming Se and feed the nanowire growth. The nanowirecomposition, crystal structure, and morphology are characterizedby Raman spectroscopy and electron microscopy. The growthmechanism is investigated by X-ray photoelectron spectroscopy.We explore the growth parameter window andfind an interestingeffect of shortening of the nanowires after a certain maximumlength. The nanowire growth is described within a diffusiontransport model, which explains the nonmonotonic behavior of thenanowire length versus the growth parameters. Nanowire shortening is explained by the blocking of Ga supply from the GaAssubstrate by thick, in-plane worm-like Ga2Se3structures, which grow concomitantly with the nanowires, followed by backwarddiffusion of Ga atoms from the nanowires down to the substrate surface.