Atomic origin of Ti-deficient dislocation in SrTiO3 bicrystals and their electronic structures.

Dislocations in perovskite oxides have important impacts on their physical and chemical properties, which are determined by their unique atomic environments. In the present study, the structure of dislocations in a 10° low-angle grain boundary of SrTiO3 that was fabricated in an N2 annealing atmosphere is characterized by spherical aberration-corrected scanning transmission electron microscopy and spectroscopy. We find that the dislocation cores are deficient in titanium (Ti) due to Sr substitution and under Ti occupancy. This differs from previously reported dislocation cores fabricated in an air annealing atmosphere, which show Ti enrichment. The presence of oxygen vacancies and partially reduced Ti are also detected in these Ti-deficient dislocation cores. These findings indicate that atomic structures of dislocations can be very different even when they have the same Burgers vectors. Controllable element segregation in the dislocations and grain boundaries via bicrystal engineering should be very useful for designing devices with novel functions. [ABSTRACT FROM AUTHOR]