Characterization of ZnO nanowires grown on Ga-doped ZnO transparent conductive thin films: Effect of deposition temperature of Ga-doped ZnO thin films

Abstract

ZnO nanowires on Ga-doped ZnO (GZO) transparent conductive thin films deposited at different substrate temperatures were demonstrated and characterized. The GZO thin films were deposited at various substrate temperatures ranging from 200 to 600°C in order to study the influence of deposition temperature of the GZO on the characteristics of the ZnO nanowires. The resistivity of the GZO thin films decreased from 5.11×10−4 (200°C) to 4.83×10−4Ωcm (400°C) and then increased to 6.12×10−4Ωcm (600°C). The ZnO nanowires were grown vertically and were highly c-axis oriented on the GZO thin films at every deposition temperature without any seed layers. The crystallinity of the ZnO nanowires was improved with increasing deposition temperature of the GZO thin films. In addition, as deposition temperature increased, the diameter of the ZnO nanowires increased, while the density decreased. Photoluminescence (PL) measurement and energy-dispersive X-ray spectroscopy (EDX) proved that the ZnO nanowires on the GZO thin films deposited at higher substrate temperature had less defects and were closer to stoichiometric ZnO. After the growth of the ZnO nanowires on the GZO thin films, the transmittance decreased with respect to that of the GZO only thin films, but the sample was still transparent with an average optical transmittance higher than 70%.