Control of preferred orientation for ZnO films: control of self-texture

We tried to control preferred orientation of ZnOx films deposited by radio frequency (RF) magnetron sputtering, and to make the growth mechanisms clear. Zinc oxide has tetrahedral coordinates caused by sp3 hybridized orbits, and the (0001) plane has the lowest surface free energy. Therefore, the film grows with strong (0001) preferred orientation even on glass. Considering the formation of tetrahedral coordination in the vapor phase and the deposition rate, however, we succeeded to control the preferred orientation of ZnOx films on glass. The (112̄0) textured film was obtained under sputtering gas composition which deteriorates the formation of tetrahedral coordination in the vapor phase and the high deposition rate. Formation of each texture is strongly related to the formation of tetrahedral coordination in the vapor phase and on the substrate during sputtering. Therefore, (112̄0) textured film had higher carrier concentration than that of the (0001) textured film caused by existing excess Zn atoms. Moreover, the growth mechanism with considering the density of surface energy, and the applications of the control for the epitaxial growth, are discussed.