Electrodeposition of template free hierarchical ZnO nanorod arrays via a chloride medium

Abstract

We have successfully grown template and buffer free ZnO nanorod films via chloride medium by controlling bath temperature in a simple and cost effective electrochemical deposition method. Thin films of ZnO nano-rods were obtained by applying a potential of −0.75 V by employing Ag/AgCl reference electrode for 4 h of deposition time. The CV measurements were carried out to determine potential required to deposit ZnO nanorod films whereas chronoamperometry studies were carried out to investigate current and time required to deposit ZnO nanorod films. The formation of ZnO nanorod has been confirmed by scanning electron microscopy (SEM) and Raman spectroscopy. Low angle XRD analysis confirms that ZnO nanorod films have preferred orientation along (101) direction with hexagonal wurtzite crystal structure. The SEM micrographs show nice surface morphology with uniform, dense and highly crystalline hexagonal ZnO nanorods formation. Bath temperature has a little influence on the orientation of nanorods but has a great impact on their aspect ratio. Increase in bath temperature show improvement in crystallinity, increase in diameter and uniform distribution of nanorods. Compositional analysis shows that the amount of oxygen is ~49.35 % and that of Zn is ~50.65 %. The optical band gap values were found to be 3.19 and 3.26 eV for ZnO nanorods prepared at bath temperature 70 and 80 °C respectively. These results indicate that by controlling the bath temperature band gap of ZnO nanorods can be tailored. The obtained results suggest that it is possible to synthesize ZnO nanorod films by a simple, cost effective electrodeposition process which can be useful for opto-electronic devices fabrication.