Local rotations due to mixed-type misfit dislocation at α-Fe 2 O 3 /α-Al 2 O 3 heterostructure interface.

The misfit dislocations at α-Fe2 O3 /α-Al2 O3 heterostructure interfaces were investigated by high-resolution transmission electron microscopy (HRTEM), geometric phase analysis (GPA) and dislocation density tensor analysis. When imaged along the [112¯0] direction, the misfit dislocation core is a mixed-type, which can be characterised by one extra (11¯02) plane and one extra (1¯104) plane of α-Al2 O3 . Dislocation density tensor analysis gave a very high accuracy in determining the corresponding Burgers vectors of two extra half-planes. By comparing the measured Burgers vectors with theoretical ones, we are able to determine local rotations in the dislocation core region: the (11¯02) plane is rotated clockwise 6.25° and the (1¯104) plane is rotated anticlockwise 4.81°. Such a local rotation is favourable from the viewpoint of both energy and function to relax lattice misfit.