Microstructural evolution and preferred orientation change of radio-frequency-magnetron sputtered ZnO thin films

Abstract

Crystallographic orientation and microstructural changes of ZnO thin films deposited by rf-magnetron sputtering were investigated with changing deposition parameters. Positional dependence of texture orientation and microstructural features, which might be attributed primarily to bombardment of high energetic oxygen species on the film in the region of the target erosion area, were observed. The films deposited at low temperature and/or using pure argon had (002) preferred orientation and a smooth columnar structure. At increasing substrate temperature and/or oxygen partial pressure, c-axis orientation of the film was severely degraded and abnormal elongated crystallites were also developed. As the films became thicker, c-axis orientation changed from normal to the substrate to parallel to the substrate. In this case, the microstructure was altered from a smooth fine columnar structure to abnormally grown elongated crystallites that were developed to a faceted texture structure.