ZnO films with varied surface morphologies and microstructures were synthesized from acidic precursor colloids by varying the pH of the precursor colloids. The aim of the present work is to further clarify whether the pH of the film’s precursor colloid is one of the most important factors that could influence the morphology of the ZnO films. The effects of acid nature and concentration on the pH of the precursor colloids were also investigated. The results of the X-ray diffraction, field-emission-scanning electron microscopy, atomic force microscopy, and transmission electron microscopy analyses reveal that the surface microstructure of the films can be tailored by adjusting the acid colloids at the optimum pH values. The morphology of the films indicates the presence of small polycrystallites with a size of ∼20nm when the pH of their acid colloids was adjusted to a pH domain of 5.9–2.0. However, the pH of the precursor colloids can further decrease to a pH domain below 1.0 by using the strong mineral acid HCl or the HCOOH agent in high concentration, and numbers of large crystallites with a size of about 500–1000 nm appear on top of a ZnO fine crystallite layer; the surface root-mean-square of the coatings is over 71.3 nm.
JOURNAL OF THE ELECTROCHEMICAL SOCIETY,157(5),K103-K108.