Electrochemical Deposition Of Zno Thin Films

ZnO, which has a wurtzite structure, is a wide bandgap, low dielectric constant and high chemical stability semiconductor. In recent years, zinc oxide (ZnO) has attracted intense attention due to its interesting properties, such as transparency in the visible, acoustic characteristics, high electrochemical stability, large electromechanical coupling coefficient, direct band gap and so on. At first, we overviewed functional properties, recent development and preparation techniques of ZnO thin film. Then we have systematically described elementary principle and technical equipment of electrochemical deposition method. Electrochemical deposition method is a simple and convenient method, has been extensively used in the synthesis of many different types of materials. It has several advantages such as low processing temperature, possibility of large-scale deposition, low cost, higher deposition rate, controllable film thickness and morphology. This paper was focused on the growth of ZnO films in two different solutions. The mechanism, preparation and characterization of ZnO thin films'electrodeposition were studied in detail.Experiments are performed in a conventional three electrodes electrochemical cell. The ITO-coated glass, a platinum sheet and an Ag/AgCl electrode were used as the working, counter and reference electrodes. Firstly, the mechanism of electrochemical reaction and the range of technical parameters, such as the solution concentration, pH value, deposition potential and temperature, were roughly determined from the cyclic voltammetry experiment. The effects of different electrodeposition conditions on the microstructures of ZnO thin films were investigated in detail. X-ray diffraction measurement showed that the as-grown films were of hexagonal wurtzite structure. The film morpHology was observed with a scanning electron microscope (SEM) and atomic force microscope (AFM). The XPS analysis presents a Zn/O composition close to stoichiometric. The results indicated that in aqueous solution the films obtained at 0.05M-0.1M Zn(NO3)2, -0.8V~-0.9V potential and 65-70℃were compact , homogeneous and (002) oriented, the transmission values in the visible wavelength was upto 70%. In non-aqueous solution, the best technical parameters were 0.05 mol.L-1, 70℃and -0.9V. High optical transmission values upto 80% was obtained. The microstructures of the ZnO thin films could be improved after annealing treatment.