  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{\deg}
low-angle grain boundary of SrTiO3 (STO) is characterized by spherical
aberration corrected scanning transmission electron microscopy (Cs-STEM) and
spectroscopy. In contrast to previous studies, the deficiency instead of
enrichment of titanium (Ti) is observed at the dislocation cores mainly due to
the Sr substitution and under occupancy of Ti. The presence of oxygen vacancies
and partially reduced Ti are also detected at the Ti deficient dislocations
cores. These findings indicate the atomic structure of dislocations can be very
different even they have the same Burges vectors. Controllable elemental
segregation in the dislocations and grain boundaries via bicrystal engineering
should be very useful for design of devices with novel functions.
