Electrochemical deposition of ZnO thin films from acidic solutions

We deposited ZnO thin films on Sn-doped In2O3-coated glass substrate using three-step pulsed electrochemical deposition from aqueous solutions with two different compositions, the first solution containing ZnSO4 with pH lowered using H2SO4 and the second solution containing ZnCl2 with pH lowered using HCl. We found that addition of small amount of Na2S2O3 (about 1.2 mM) and use of the three-step pulse for deposition highly improved the film composition and the deposition rate. Using Auger electron spectroscopy we found that the as-deposited films grown from the two solutions have a nearly stoichiometric composition. The X-ray diffraction pattern showed polycrystalline nature of the ZnO films. The photoelectrochemical measurements showed n-type conduction of the film and increase in the photosensitivity by annealing.