Low temperature cathodic electrodeposition of nanocrystalline zinc oxide thin films

This paper investigates electrochemical behavior of ZnO thin films deposition on transparent conducting optically glass from a simple aqueous zinc nitrate solution. At low temperature, ZnO films with grain sizes between 10 and 15 nm are obtained by controlling growth rate. The X-ray diffraction pattern shows that ZnO film has a hexagonal wurtzite structure and the preferred growth orientation is the (002) direction. Detailed X-ray photoelectron spectroscopy analysis indicates the presence of metallic Zn, OH and H2O species in the as prepared ZnO films. In addition, ZnO thin film changes from Zn-rich to O-rich after being annealed in air. Optical characterizations show that the films as prepared and annealed at 250 °C have high optical transmittance (> 90%) in the visible wavelength range and the band gap of the nanocrystalline ZnO films is 3.37 eV.