Twin boundaries in ZnO sintered with small additions of Ga2O3 were characterized with advanced methods of transmission electron microscopy. The twin boundaries and accompanying inversion domain boundaries were on {01▪3} planes of ZnO. The Ga content of the twin boundaries corresponds to an effectively half occupied {01▪3} plane determined from compositional maps calculated from electron spectroscopic images by using electron filtering transmission electron microscopy. The structure of the twin boundaries were investigated by high-resolution transmission electron microscopy, and images of focus series were used to reconstruct the complex electron wave. Simulated electron waves based on structure models of the twin boundary were quantitatively compared with the reconstructed wave to identify and to refine atom positions. The twins could be considered to be created by a mirror operation on a {01▪3} plane of ZnO, and two alternating closed-packed polyhedral clusters of O ions could be identified as building units of the twin boundary structure. Unit 1 was occupied with Zn2+ by simply continuing ZnO4 tetrahedra of the same type from both crystals to the twin boundary. Using arguments of local charge balance unit 2 could only be occupied with the trivalent Ga3+ ion. The Ga3+ position was refined with high precision (±5pm), and the resulting polyhedron was a GaO5 square pyramid. The pyramids form densely occupied columns parallel to the twin axis [2¯1▪0]. The analysis of the twin boundary structure yields a fractional occupancy of the boundary plane by Ga of 0.5, which was in good agreement with the result of the chemical composition measurement with energy filtered transmission electron microscopy.

Twin Boundaries in Zinc Oxide with Additions of Gallium Oxide. Barf, J., Walther, T., Mader, W.: Interface Science, 2004, 12[2-3], 213-26