Microstructure of high c-axis oriented stand-alone ZnO self-assembled film

Stand-alone ZnO films were fabricated at air-liquid interfaces. The Microstructures of the films were observed precisely using a transmission electron microscope (TEM) in this study. They were assemblies of nano-sheets having uniform film thickness. The nano-sheets grew down toward the bottom of solutions by the supply of Zn ions from the solutions. X-ray diffraction patterns indicated high c-axis orientation of the films perpendicular to the air-liquid interface. An area of the nano-sheets was magnified for further observation. Electron diffraction patterns and lattice images indicated that the nano-sheets consisted of ZnO crystals. A slight amount of co-precipitated zinc carbonate hydroxide (Zn5(CO3)2(OH)6) was also observed. Their morphologies were drastically changed by electron beam irradiation because of dehydration and crystallization to ZnO.