TiO2 thin films grown onto (11•0) sapphire at 800C by using the metallo-organic chemical vapour deposition technique were characterized by transmission electron microscopy. The TiO2 thin films were single-crystal rutile. The epitaxial orientation relationship between the rutile thin films (R) and the sapphire substrates (S) was (101)[010]R||(11•0)[00•1]S. Growth twins were commonly observed in the films with (101) twin planes and [101]-type twinning directions. The atomic structure of the twin boundaries and TiO2-α-Al2O3 interfaces were investigated by means of high-resolution electron microscopy. When the interfaces were viewed in the direction of [010]R-[0001]S, the interfaces appeared to be structurally coherent along the direction of [10¯1]R-[1¯1•0]S. The small misfit (0.5%) was accommodated at interface steps. In contrast, in the direction of [10¯1]R-[1¯1•0]S, the interfaces were semi-coherent.

Study of Defects and Interfaces on the Atomic Scale in Epitaxial TiO2 Thin Films on Sapphire. Gao, Y., Merkle, K.L., Chang, H.L., Zhang, T.J., Lam, D.J.: Philosophical Magazine A, 1992, 65[5], 1103-25