Electric field-induced defect redistribution along a near 23° (100) tilt grain boundary in SrTiO3

An electrostatic field strength of 11.6 V/mm was applied during thermal annealing along the grain boundary plane of a near 23 degrees (100) tilt grain boundary in SrTiO3. Electron microscopy characterization revealed the development of an increased number of pores located at the grain boundary plane near the positive electrode. Toward the negative electrode a lower physical density at the interface and a wider grain boundary core structure was observed compared to areas close to the positive electrode. Atomic resolution scanning transmission electron microscopy identified different structure units for the grain boundary core in the proximity of the two electrodes and a higher density of interfacial steps close to the negative electrode. Electron energy-loss spectroscopy confirms modifications of the local interfacial bonding, stronger reduction of Ti cations, and distorted Ti & horbar;O octahedra close to the negative electrode. The experimental observations demonstrate field-induced redistribution of oxygen vacancies along the interface plane accommodated by disconnection movement.