The low-angle ADF image of ∼250 nm BLT layer epitaxially grown on (a) and (c) SRO/STO(111) substrate and acquired with electron beam parallel to the zone axis (ZA) 〈110〉STO and (b), (d) SRO/STO(001) substrate and acquired with electron beam parallel to the ZA 〈100〉STO. The BLT unit cell on SRO/STO(111) shows the a-axis forming a 57° angle to the interface, while the BLT unit cell on SRO/STO(001) shows the c-axis perpendicular to the interface. (a) and (b) is the low magnification view, (c) and (d) is a detailed view of the interface.
(a) The ADF image (without aberration corrector) of BLT on SRO/STO(111) taken in the direction parallel to the ZA 〈110〉STO || 〈010〉BLT. (b). The probe corrected HAADF image of BLT on SRO/STO(001) taken in the direction parallel to the ZA 〈100〉STO || 〈110〉BLT. The inset in (a) and (b) are the simulated HAADF images of BLT along the ZA 〈010〉 and 〈110〉BLT, respectively, corresponding to the overlaid structural model. In all cases, the images are showing raw and unprocessed data. In (b), the intensity “tails” are indicated by red arrows.
The ADF images (acquired without the use of probe corrector) of BLT films on SRO/STO(111) reveal presence of defects within BLT unit cell, namely (a) the OPBs as marked with a dashed red rectangle (image rotated) and (b) extra row of atoms appear between the (Bi2O2)2+ layer and the perovskite-like layers along the c-axis of BLT unit cell.
(a) Atomic resolution HAADF image of BLT film grown on (100)-STO substrate in the direction parallel to the 〈110〉BLT ZA showing a modulation of the defect-free and defected regions along the lateral direction of the film. The white ellipses indicate the approximate width of brightest first atomic layer located at the SRO/BLT interface. The left inset shows the defect-free unit cells above the first atomic layer with brightest intensity, and the right inset shows the defected unit cells, with extra atomic rows in between the perovskite slabs, above the first atomic layer with lower intensity. (b) and (c) are the Bragg filtered image and amplitude image respectively calculated from (a) by a geometric phase analysis (GPA) software attached to Digital Micrograph software from Gatan. They enhance a specific periodicity (c/3) in BLT unit cell and thus show clear modulation along the interface with regions, where this missing periodicity appear as dark boundaries.
The BLT/SRO interface shows the presence of gradual interface step (highlighted in the blue rectangle) and dislocation (highlighted in the green square). The insert is a masked Fourier filtered image pertaining to the green square, showing the presence of a dislocation.
(a) HAADF image of the SRO-BLT interface with the area from which EELS mapping was carried out highlighted with a green rectangle; (b) HAADF intensity recorded simultaneously during the EELS acquisition in the region of interest (green rectangle in (a)); (c) Sr M edge (133 eV) signal, (d) La M edge (850 eV) signal, (e) Ti L edge (456 eV) signal, (f) Ru M edge (287 eV) signal, (g) the EELS composite map of La (red) and Sr (violet), and (h) the EELS composite map of Ti (green) and Ru (blue). The red cross identified with the “Beam” label in (a) identifies the reference position of the electron beam on the rastered area before and after the map acquisition.
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