Presence and spatial distribution of interfacial electronic states in LaMnO3-SrMnO3 superlattices

We report direct evidence of interfacial states at the onset of O K edge confined to a spatial distance of 1 unit-cell full-width at half maximum at the sharp interfaces between epitaxial films of LaMnO3 and SrMnO3 from electron energy-loss spectroscopy (EELS) measurements. The interfacial states are sensitive to interface sharpness; at rough interfaces with interfacial steps of 1-2 unit cells in height, experimental data shows a reduction, or suppression, of the interfacial states. The EELS measurements were performed using a fine electron probe obtained by electron lens aberration correction. By scanning the electron probe across the interface, we are able to map the spatial distribution of the interfacial states across interfaces at high resolution.