The effect of residual stresses in the ZnO buffer layer on the density of a ZnO nanowire array

Density control is a valuable concern in the research of ZnO nanowire arrays. In this study, unannealed and annealed ZnO thin films were used as substrates to fabricate ZnO nanowire arrays. In the unannealed thin film, an inhomogeneous distribution of the nanowire array was found: the density of nanowires decreases with the increase of distance to the edge. In the annealed thin film, the density of nanowire array becomes larger and more homogeneous. Moreover, nanowires are found in high density along microcracks. It is proposed that the residual stresses in the thin film and the density of the nanowire array are in inverse proportion, leading to the results mentioned above. The relationship between residual stresses and the density of nanowires will have potential applications in modifying the density of ZnO nanowire arrays.