Morphological and Crystallographic Transformation of ZnO in Solution

This paper reports the investigation of the aging effects on the preparation of ZnO crystals and films. We have found that the morphology of ZnO films can be optimized by selecting appropriate chemical environments including the types of chemical species and their concentrations, which can regulate the dissolution−recrystallization process during soaking. Several unique morphologies of ZnO have been obtained from an aqueous solution containing ZnCl2 and a mixture complex agent (amine and ammonia). From this simple solution system, dense, transparent, thick ZnO films with thicknesses up to 20 μm can be grown at about 90 °C under atmospheric pressure. The components of the film were single-crystalline ZnO lamellas that were self-organized mainly with their c axis parallel to the substrate surface. The current findings reveal that one can purposely optimize morphology, crystallography, and organization to pursue special properties by kinetically controlling the nucleation and crystallization processes.