Figure 5.

Panel (a) shows the HAADF image of an LSMO/BFO interface. Dashed white lines are guides to the eye, indicating the interface region. A red box indicates a unit cell template, representative of “pure” BFO (far enough away from the interface that chemical interdiffusion is not detected in the EELS data: see Figure S5). This template was used for real-space averaging. Panel (b) shows the EELS spectra for the O K-edge as it develops across the interface, clearly showing the 2-peak structure of LSMO at the bottom, the 3-peak structure of BFO at the top and a flatter region of overlap between them. Panel (c) shows the template-matched average across the pure BFO region, obtained using the red box in panel (a) as the template. Panel (d) shows the (real-space) averaged O K EELS map for pure BFO, obtained by integrating the O K intensity over a 50 eV window above the edge onset after template matching all pure BFO unit cells away from the interface. Panel (f) shows two sets of spectra; the spectrum in the upper panel (black) is the unit cell wide average O K-edge (after template-averaging over the entire pure BFO region), whereas the three spectra in the lower panel are spatially resolved spectra extracted from the template average unit cell from the Bi, FeO, and O₂ positions in the average unit cell, illustrated in the ball model in panel (e). The cyan (top) spectrum is averaged over the pixels corresponding to the Bi environment, the middle (gray) spectrum corresponds to the FeO (longitudinal) environment, and the bottom (red) spectrum corresponds to the O₂ (equatorial) environment.