Atom vacancies at a screw dislocation core in SrTiO3

A screw dislocation in strontium titanate has been studied taking benefit of negative spherical aberration-imaging in a spherical aberration- corrected transmission electron microscope. The core structure of the dislocation is atomically resolved with respect to both cation and oxygen columns by the inclusion of the central core area. The dislocation core is characterized by a helical distortion of the lattice planes, which leads, in particular, to azimuthally elongated image dots associated with individual atomic columns close to the core centre. The atomic coordination in the dislocation core is identified and a high density of atom vacancies is revealed for a Ti-O column at the core.