Spectroscopic mapping of local structural distortions in ferroelectric PbTiO3/SrTiO3 superlattices at the unit-cell scale

The local structural distortions in polydomain ferroelectric PbTiO3/SrTiO3 superlattices are investigated by means of high spatial and energy resolution electron-energy-loss spectroscopy combined with high-angle annular dark field imaging. Local structural variations across the interfaces have been identified with unit-cell resolution through the analysis of the energy-loss near-edge structure of the Ti L-2,L-3 and O K edges. Ab initio and multiplet calculations of the Ti L-2,L-3 edges provide unambiguous evidence for an inhomogeneous polarization profile associated with the observed structural distortions across the superlattice.