Crystalline-phase-dependent photoluminescence and photoconductivity of roughened ZnO nanostructure grown by self-electrochemical transformation
Journal
Journal of the Electrochemical Society
Journal Volume
158
Journal Issue
8
Pages
E88-E92
Date Issued
2011
Author(s)
Pai, Y.-H.
Abstract
Large-scale hexagonal Znic oxide (ZnO) with a surface-roughened nanostructure on Zn-electrodes is synthesized via a self-electrochemical transformation in sodium chloride gel without employing an annealing process. By tuning the discharged current down to 6.9 mA during self-electrochemical oxidation, a large amount of Zn(OH)2 composites can be effectively transformed into [Zn(OH)4]2− to cause isotropic ZnO growth, which ascribes to the spontaneous electrochemical oxidation induced stable electromigration with minimized Gibbs free energy. With decreasing discharged current to improve the crystallinity, the wurtzite-type hexagonal ZnO crystal with (101) preferred orientation and a lattice spacing of 2.46 Å exhibit an optimized optical responsivity of 350 mA/W under illumination at 35 mW/cm2. Nevertheless, increasing the discharged current up to 49.4 mA inevitably enhances the oxygen-defect related photoluminescence by 1 order of magnitude and red shifts the wavelength to 552 nm. Our results show that the significantly decreased oxygen-defect radiation and oppositely improved bandgap UV emissions are controllable through a reduction of the discharged current in order to decelerate the electrochemical oxidation as regards crystallinity optimization.
Type
journal article