Investigation of misfit dislocations in α-Fe2O3/α-Al2O3 interface by geometric phase analysis and dislocation density tensor analysis

The misfit dislocations in α-Fe2O3/α-Al2O3 heterostructure interfaces were investigated by high-resolution transmission electron microscopy (HRTEM), geometric phase analysis (GPA) and dislocation density tensor analysis. The misfit dislocations form a two-dimensional network structure at the interface. We characterized the atomic configurations and strain distribution of misfit dislocations by HRTEM and GPA. The observation indicates that one and two extra half planes/strain fields exist in the dislocation cores imaged along the [1¯100] and [112¯0] direction, respectively. Dislocation density tensor analysis gave a very high accuracy in determining the Burgers vectors and proved useful in accurately localizing the dislocation distribution in the core region. The results show that all the dislocations have the same Burgers vector, however the different space distributions of dislocation density, which may be attributed to the differences of atomic configuration in dislocation cores. Classical elasticity theory was found to be in agreement with the 3D visualizations of dislocation density tensor. The relationships between atomic configuration, dislocation density distributions, and strain distributions in dislocation cores were investigated, which can be described briefly as: one/two extra half planes induce one/two Burgers vectors in dislocation density distributions; one/two Burgers vectors induce one/two strain fields around dislocation core. Finally by comparing the experimental strain distributions with dislocation models (Peierls-Nabarro model and Foreman model), we found that all the dislocations follow the Foreman model (a = 2), which indicates that they have the same spatial extension of strain field. This work demonstrates the superiority of dislocation density tensor analysis in the investigation of misfit dislocations, particularly the dislocations with complicated core structure.