Morphological evolution of ZnO thin films deposited by reactive sputtering

The morphological evolution of ZnO thin films deposited by magnetron sputtering has been investigated on two types of substrates, (111) textured Pt and (100) Si possessing a native oxide. The ZnO films are oriented with the c-axis [0001] normal to the substrate and possess varying degrees of crystallinity. The films have a columnar structure with column diameters in the range of 40-300 nm. As observed by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray diffraction, the film microstructure is strongly dependent on substrate temperature during deposition in the range from near room temperature up to 700 degreesC and is also dependent on substrate type. A textured film of platinum promotes nucleation thereby improving the crystallinity and texture of sputtered ZnO films. A mechanism for morphological evolution of the films via surface diffusion is proposed based on atom mobilities.