Effect of nitrate concentration on the electrochemical growth and properties of ZnO nanostructures

Zinc oxide (ZnO) nanostructures were deposited under potentiostatic control on indium tin oxide coated glass substrate from an aqueous solution containing zinc nitrates. Voltammograms were recorded to determine the optimal potential region for the deposition of ZnO. The deposition was carried out at various concentrations of Zn+2 and constant bath temperature (65 degrees C). The nucleation and growth kinetics at the initial stages of ZnO studied by current transients indicated a 3D island growth (Volmer-Weber). It is characterized by an instantaneous nucleation mechanism followed by diffusion-limited growth. The Mott-Schottky measurements, the flat band potential and the donor density for the ZnO nanostructures were determined. The morphological, structural, and optical properties of the nanostructures have been investigated. Scanning electron microscopy images showed different sizes and morphologies of the nanostructures which depends on the concentrations of Zn+2. X-ray diffraction study confirms the wurtzite phase of the ZnO nanostructures with high crystallinity. UV-visible spectra showed a significant optical transmission (up to 90 %), which decreased with Zn2+ concentrations. The energy band gap values have been estimated to be in the range 3.36-3.54 eV