Solid Au nanoparticles as a catalyst for growing aligned ZnO nanowires: a new understanding of the vapour--liquid--solid process

X-ray diffraction techniques have been applied to characterize the Au-catalysed growth of aligned ZnO nanowire arrays on an AlGaN/AlN/Al2O3 substrate. The orientation relationships between the AlN layer, AlGaN layer, ZnO nanowires and Au particles were determined using x-ray texture analysis. Two orientations of the Au nanoparticles, related by a 30◦ rotation about the sample normal, were observed. The gold lattice parameter of the ZnO nanowire sample was determined to be the same as that of a control sample never exposed to vaporized ZnO, indicating the absence of Zn in the Au catalyst particles. Our results indicate that the Au catalyst particles were solid during growth, and that growth proceeded by a surface diffusion process, rather than a bulk diffusion process.