Galvanostatic deposition of ZnO thin films

In this study we report on the galvanostatic deposition of zinc oxide (ZnO) thin films from an aqueous chloride based solution. The influence of the deposition conditions (bath temperature, supporting electrolyte (KCl) concentration and current density) on the properties of ZnO 2D layers is studied. It has been found that to obtain good quality films the bath temperature should be above 60 °C. At lower deposition temperatures, porous-like layers formed by small grains of ZnO with poor optical properties are obtained. The supporting electrolyte concentration ([KCl]) influences the film composition, morphology and optical properties due to the change of species reparation in the solution. It is shown that the increased KCl concentration is the main cause for surface defects, which are accounted to the electrode passivation due to the Zn2+ ions complexation. The applied deposition current density is another parameter permitting to prepare 2D layers with desired surface morphology and thickness. ZnO thin films deposited at high temperature (70 °C) and lower [KCl] are homogeneous and compact (without surface defects) which permits their integration in solar cells and other optoelectronic devices. ZnO nanowires were electrodeposited on these thin films. It has been found that the nanowire dimensions could be tailored by the seed layer thickness and morphology.