Self-organized and self-catalyst growth of semiconductor and metal wires by vapour phase epitaxy: GaN rods versus Cu whiskers

Wires represent a new class of nanostructures that offer unprecedented freedom in materials design and new physical properties. Amongst the very different growth mechanisms reported in literature, the vapour-phase growth of self-catalyzed wires has the advantages of simplicity and rapidity with a low level of contaminants. The elaborations of semiconducting and metallic wires are usually considered as very distinct fields and no significant analogies have been noticed yet. This paper illustrates significant similarities of the mechanisms involved in the GaN and Cu wire growths that highlight firstly the role of the substrate surface preparation (with the deposition of an intermediate layer on the substrate surface impacting the nucleation seeds) and secondly the role of the different diffusion paths contributing to the one-dimensional growth in particular the influence of the surrounding gas phase and respective diffusion lengths on the substrate surface and wire sidewall. Experimental data describing the evolution of the wire diameter and length as a function of the growth time are quantitatively analyzed to evidence different growth regimes.