Characterization of functionally graded zinc oxide film prepared from aqueous solution by controlling cathode potential

Wurtzite zinc oxide (ZnO) film was cathodically deposited on a conductive glass substrate from a simple aqueous zinc nitrate solution kept at 335 K. ZnO films with changing resistivity in the thickness direction was prepared at increased deposition rate by controlling potential method composed of Ist-step electrolysis at the cathode potentials ranging from -0.9 to -1.2 V referred to Ag/AgCl electrode for electric charge of 60 C m(-2) and of following End-step electrolysis at -0.7 V up to 200 C m(-2). The sheet resistivity of the ZnO films decreased by about three orders of magnitude with the increase in the film thickness from 0.3 to 0.9 mu m. Defect-free and 0.9 mu m-thick ZnO film with smooth surface was obtained by using controlling potential method with Ist-step electrolysis of -1.2 V for approximately Ih and showed optical transmission of 74% at visible wave length.