Dislocations are one of the most common one-dimensional crystalline defects and are frequently observed in thin film forms of materials. When a material is doped with impurities for electronic applications, dislocations can strongly interact with the impurities, as long been recognized in a wide range of thin film semiconductors, and can result in modulation of physical and chemical properties of the material. Despite its significance, direct study of the interplay between dislocations and dopants has remained challenging due to the atomic-scale defect size and low concentration of dopants. Here, aberration-corrected scanning transmission electron microscopy (STEM) and ab initio calculations are employed to investigate the dislocation-dopant interactions in promising perovskite oxides, La-doped BaSnO₃, at the atomic level. The atomic and chemical configurations of two types of dislocations, single- and dissociated- edge dislocations, in La:BaSnO₃ thin films are investigated; along with a substantial amount of dopant segregation inside and outside dislocation cores, dopant-driven atomic re-arrangement is observed via STEM imaging and spectroscopy, and explained via structure optimization simulations. By employing STEM-electron energy-loss spectroscopy combined with electronic band structure calculations, the local electronic structures at/around dislocations are probed at sub-angstrom resolution.

[ref] H. Yun^*, A. Prakash, T. Birol, B. Jalan, K.A. Mkhoyan^*, “Dopant segregation inside and outside dislocation cores in perovskite BaSnO₃ and reconstruction of the local atomic and electronic structures”, Nano Lett. 21, 43357 (2021).