HRTEM and EELS study of screw dislocation cores in SrTiO3 -: art. no. 144103

A [100] twist low-angle grain boundary in SrTiO3 was systemically studied by means of conventional transmission electron microscopy, high-resolution transmission electron microscopy (HRTEM), lattice distortion analysis, and electron energy-loss spectroscopy (EELS). A dislocation network is formed in the grain boundary by two sets of a<100> screw dislocations. HRTEM images show that the image contrast in the core region is different from that in the surrounding bulk. Image analysis reveals that compared with an ideal screw dislocation the dislocation core is expanded, probably due to both surface relaxation and a reconstruction of the core. The EELS spectra show a small increase of the Ti/O ratio but no significant change of the Sr/Ti ratio in the core region. From the increase of the Ti/O ratio it is concluded that the dislocation cores are oxygen deficient, which may be responsible for the expansion of the core. Ti L-2,L-3 EELS spectra show a reduction of Ti in the screw dislocation cores as well as a reduced crystal field splitting, both of which are in accordance with a loss of oxygen.