Orientation control of ZnO thin film prepared by CVD

The orientations of ZnO films parallel and perpendicular to the surface of the substrate were investigated as functions of the deposition temperature and substrate material. The degree of orientation increased with increasing deposition temperature and became perfectly oriented at a characteristic temperature. At a deposition temperature of 620 °C, polycrystalline films were obtained on polycrystalline Al₂O₃; substrates. (001) oriented films were obtained on fused silica and (100) rutile substrates. Epitaxially grown (110) and (001) oriented films were obtained on various kinds of single crystal substrates. The difference between the (110) and (001) orientations was explained by the lattice mismatch between the films and the substrates. Epitaxial growth of films exhibiting two directions was observed when the two equivalent directions of lattice mismatch existed. These results show the possible formation of various types of the crystallographic relationships between the grains in the film.