  Oxygen vacancies are increasingly recognized to play a role in phenomena
observed at transition-metal oxide interfaces. Here we report a study of
SrRuO3/La0.7Sr0.3MnO3 (SRO/LSMO) interfaces using a combination of quantitative
aberration-corrected scanning transmission electron microscopy, electron energy
loss spectroscopy, and density-functional calculations. Cation displacements
are observed at the interface, indicative of a dipole-like electric field even
though both materials are nominally metallic. The observed displacements are
reproduced by theory if O vacancies are present in the near-interface LSMO
layers. The results suggest that atomic-scale structural mapping can serve as a
quantitative indicator of the presence of O vacancies at interfaces.
