“…Nano-size polycrystalline and epitaxial ZnO films have been extensively fabricated by using several methods including pulse laser deposition [8,9], molecular beam epitaxy [10][11][12], magnetron sputtering [13,14], oxidation of metallic zinc films [15], sol-gel method [16], etc. The surface morphology, microstructure, film growth, electrical and optical properties of ZnO films can be affected by the experimental conditions, such as substrates, fabrication methods, oxygen flow rate, and element doping [17][18][19][20][21], which can be ascribed to the change of the defects in the films. It is well known that the sputtering technology is an effective and the most widespread method for fabricating thin films in industry nowadays, and the oxygen flow rate can affect the intrinsic defects in the ZnO films during the film deposition significantly.…”