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ABSTRACT: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°Cand 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.

The morphological evolution of zinc oxide (ZnO) thin films deposited by magnetron sputtering is described by the use of a Structure Zone Model. A modified Structure Zone Model was revealed, in which the boundaries between zones with specific features are shifted toward lower homologous temperatures (T/T m ) than in the classical models. The range of homologous temperatures for this study were 0.13 < T/T m < 0.43. The promotion of the formation of high temperature structures at relatively low temperatures is a consequence of the energetic species generated during the sputtering process that bombard the growing film. The reduction of the shadowing effect, along with the substrate heating that increases the surface diffusion, led to the suppression of zone T. Two new subzones of zone II were identified, IIa and IIb. The film in subzone IIa displays pronounced faceting. The film in subzone IIb has a characteristic smooth surface due to enhanced surface diffusion at higher substrate temperatures during deposition, although pitted due to still incomplete surface diffusion.