Fig. 3: Elucidating the microstructure of mixed phases in NaNbO3/SrTiO3 heterostructures.
Synchrotron X-ray reciprocal space map (RSM) near the 002-diffraction condition for an 80 nm NaNbO3/SrTiO3 heterostructure, revealing two distinct peaks corresponding to the MB and MC phases, along with surrounding satellite peaks from the triclinic phase in the a HL-plane, b HK-plane at L = 2.013, and c HK-plane at L = 1.995. Zoomed-in RSMs near the 103-diffraction condition for the d MB and e MC phases of an 80 nm NaNbO3 film show peak splitting, as highlighted in Supplementary Fig. 10. f Scanning diffraction X-ray microscopy (SDXM) dark-field imaging depicts the coexistence of MB (blue), MC (red), and bridging Triclinic 1 (Tri-1, orange) phases. g Schematic illustration of the polarization rotation pathway between the MC and MB phases, facilitated by intermediate triclinic phases. h HAADF-STEM image of the NaNbO3/SrTiO3 heterostructure. i Nanoscale spatial distribution of two distinct phases in the NaNbO3 film, identified in red and blue via segmentation of nanobeam electron diffraction data. j, k Average diffraction patterns from the two segmented regions, showing the presence (j) or absence (k) of half-order diffraction spots indicative of in-phase and anti-phase octahedral tilts, respectively. l, m Ptychographic images of a 2 × 2 pseudo-cubic unit-cell region of the two phases, illustrating (l) in-phase and (m) anti-phase octahedral tilting. These tilt modes are distinguished by singular or split oxygen sites, highlighted with yellow ovals.
