Growth of ZnO nanowire arrays on Ga-doped ZnO transparent conductive layers

Vertically well-aligned ZnO nanowire arrays were successfully grown on Ga-doped ZnO (GZO) transparent conductive layers. In this study, not only do the GZO thin films play a role as transparent electrodes but also a role as seed layers simultaneously, so that any additional seed layers are not needed. The GZO thin films with various thicknesses (50, 100, and 200 mm) were deposited to investigate the effect of the thickness on the growth behavior of ZnO nanowire arrays. The resistivities of the GZO thin films of 50, 100, and 200 mm thickness were measured to be 8.47 x 10(-4), 7.30 x 10(-4), and 6.51 x 10(-4) Omega cm, respectively. The degree of alignment and the crystalline quality of the ZnO nanowires were improved with increasing the thickness of the GZO thin films. Photoluminescence (PL) measurement, which detected a UV near band edge (NBE) emission peak and a visible deep-level (DL) emission peak on each sample, revealed that the ZnO nanowires were grown with higher crystalline quality and less defects as the thickness of the GZO thin films increased. These may be ascribed to the improved degree of orientation of the (0002) plane and crystallinity of the GZO thin films, which were confirmed by XRD analysis. The grain size of the GZO films, which was observed to increase with increasing the thickness, also influenced the diameter and the density of the ZnO nanowires. With the increase in the grain size of the GZO thin films, the diameter of the ZnO nanowires tended to increase, while the density decreased. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.