The conditions have been established for detection and recognition of rotation domains in α–Ga2O3/α–Al2O3 (0001) thin films in the presence of other polymorphs. The domains are visualized by high-resolution transmission electron microscopy. Their structural characteristics are determined by preparing cross-sectional and plan-view specimens, choosing the correct diffraction conditions and proper imaging modes. As a result, the dimensions, the spatial distribution, the volume fraction and area fraction of the inclusions of domains have been determined.

The results of a study by transmission electron microscopy of the structural state of α-Ga2O3 film with a thickness of about 1 micron, grown on the prismatic m-face sapphire by the method of chloride vapor phase epitaxy, are presented. The influence of the substrate orientation on the formation of the dislocation structure is discussed. Threading dislocations, including those with the Burgers vector 1/3<11-20> , and dislocation half-loops are revealed. The inclined propagation of dislocations and the formation of dislocation half-loops result in the reduction of the threading dislocation density near the surface.