Fig. 2: Geometric phase analysis (GPA) and octahedral distortions of the LNMO/LCMO superlattice films.
a Low magnification TEM image of the SL30 at the interface and the FFT image of the films. b, c Corresponding GPA analysis of (a) along in-plane direction εxx (b) and out-of-plane direction εyy (c), respectively. d HAADF STEM image of the SL60 near the surface and the inset of the FFT image. e, f Corresponding GPA analysis of εxx (e) and εyy (f) on the local atomic image (d), respectively. The insets attached to εxx and εyy are corresponding phase images with normalized phase variation from -π to π (black to white). White circles in FFT images mark the non-collinear reciprocal lattice vectors g1 and g2 for GPA. Yellow squares show the reference region for GPA. The color scale indicates the relative difference of local strain in the films. g Average intensity profiles of the red and green lines in the grayscale images of εxx (e) and εyy (f), respectively. h Local annular bright-field (ABF) STEM images of the SL60 films and STO. The schematic shows the corresponding BO6 octahedral distortions. i The ABF-STEM image of the cross-sectional interface of SL60 on STO and the tilting angle (B-O-B’) of oxygen octahedrons by collecting 19 layers of perovskite unit cells. The average and median are marked by the blue and red lines in the data boxes, respectively. The error bar represents the standard deviation of the tilting angles counted from the ABF image.
