Texture development of non-epitaxial polycrystalline ZnO films

Preferred orientation and related film morphology of ZnO films have been extensively studied over the last decades. The aim of this paper is conducting a comprehensive survey to organize the information of previous works and to summarize the current status of research. We first collected reported experimental results concerning the relation between operating conditions and preferred orientation. Ion flux, gas composition, and substrate temperature were main factors to control preferred orientation. Then, we collected proposed models. Preferential nucleation, sticking, surface diffusion, grain growth were considered as major phenomena determining preferred orientation. Finally, we discussed the origin of preferred orientation of polycrystalline ZnO films. Unfortunately, the lack of kinetic data such as sticking probability of precursors onto each crystallographic plane and uncertainty of data such as surface energy hampers us to draw a determinate conclusion. But this survey is expected to play a starting point for further elucidation of the mechanism underlying preferred orientation.