Fabrication of Transparent ZnO Thick Film with Unusual Orientation by the Chemical Bath Deposition

We report a fabrication of transparent ZnO thick films by a chemical bath deposition using zinc acetate ethanolic-aqueous solutions with cetyltrimethylammonium chloride (CTAC). In this system, CTAC plays a particular role in nucleation and crystal growth of ZnO, and the micrometer-thick ZnO films formed on ZnO-buffered glass substrates. The resultant ZnO thick films show a high transmittance of around 80% in the visible region. An orientation of ZnO nuclei formed on the substrates in the early stage is different from a c-axis orientation of the ZnO-buffer layer, and the resultant ZnO thick films also show the unusual orientation. The detailed information on the orientation of these ZnO films was analyzed based on X-ray diffraction (XRD) 2θ/θ scan measurements at angles between in-plane and out-of-plane geometries. According to the results, the c-axis of ZnO is tilted at around 40-50° with respect to the film normal, and the micrometer-thick ZnO films exhibit the (112)-plane orientation by adjusting the CTAC concentration of reaction solutions.