The atomic structure of a ${\mathrm{SrTiO}}_3$ dislocation is revealed directly by phase-retrieval electron microscopy. In particular, atomic columns of light oxygen are observed simultaneously with the columns of considerably heavier Sr and Ti. A distinct structural modification of the oxygen octahedra at the dislocation core as well as a significant nonstoichiometry, including a deficiency of oxygen, are observed. Deviations from the bulk chemical concentration are quantified column by column by means of structure modeling and quantum-mechanical simulations of the electron scattering process.

• Received 22 July 2005

DOI:https://doi.org/10.1103/PhysRevLett.95.225506