Cation intermixing and electronic deviations at the insulating LaCrO ₃/SrTiO₃(001) interface

The interface between polar perovskite LaCrO₃ and nonpolar SrTiO₃(001) grown by molecular beam epitaxy is examined using a combination of electron microscopy, spectroscopy, and Rutherford backscattering spectrometry. The A-site cations of these ABO₃ perovskites are found to diffuse across the interface to a greater extent than the B-site cations, based on high-angle annular dark-field scanning transmission electron microscopy, energy-dispersive x-ray spectroscopy, and electron-energy-loss spectroscopy (EELS). The B-site cation valences are shown to be partially reduced near the interface by analysis of EELS near-edge structures. The location and direction of these electronic modifications do not intuitively compensate the charge imbalance imposed by uneven cation interdiffusion, and yet both the film and interface are insulating. These results highlight the importance of considering both the physical and electronic structure of such complex interfaces in determining their characteristics.