Optimization of parameters for the growth of defect free ZnO nanorod arrays with intense UV emission capacity by electrochemcial route

We present the fabrication of highly oriented, well faceted and defect free ZnO nanorods by electrodeposition using ZnCl2 and KCl as the electrolyte. The ZnO nanostructures were prepared on high purity Cu foil, commercial Cu foil, ITO coated glass and Cu (100 nm)/Ti (30 nm)/Si substrates. We have studied in detail the effects of various growth parameters such as bath temperature, deposition time, precursor concentration and applied potential on the morphology, structural and optical properties of ZnO nanorods. A detailed mechanism and the effects of various process parameters on the formation of defect free (with controlled microstructure of) ZnO nanorods are reported. Our studies confirmed that the bath temperature and the deposition time critically influenced the aspect ratio of ZnO nanorods. For instance, the growth of ZnO nanorods along the lateral direction affected marginally, whereas, along the c-axis, the growth affected significantly with bath temperature as well as with the deposition time. At higher deposition time the shape of ZnO nanostructures got distorted because of reduction in the bulk pH value of the solution. Similarly, at bath temperature greater than 80 °C, the ZnO nanorods were misoriented with cauliflower-like microstructure mainly because of reduction in Zn2+ ion concentration. The ZnO nanostructures prepared under the optimized growth conditions showed an intense UV emission without spreading in the visible region as confirmed by photoluminescence spectroscopy, thus demonstrating the formation of defect free structure