ZnO Etch-Feature Control via Concentration and Temperature of Various Acids

Separating the dependence of ZnO:Al thin-film texturization from deposition conditions is an important aspect for optimization of ZnO as light scattering, transparent contact in solar cells. The crater density and shape for a given polycrystalline ZnO:Al thin-film are shown to be controllable by altering the temperature and concentration of various acids. The crater densities generally increase with increasing temperature, decreasing concentration, or by etching in a weak acid with small molecular size. The etching trends observed for polycrystalline ZnO:Al films are confirmed on ZnO single crystals. We discuss in detail the etch process in terms of etch rates and crater formation statistics. Results are explained in accordance with a recently proposed ZnO etch model, and possible physical explanations are given.