Fig. 4: Microstructural characterization of BFMO thin films.
a,b Bright-field TEM images of BFMO on Ni-Cr and LNO/Ni-Cr with yellow-solid square (a1) represents a randomly selected small grain. c Dark-field TEM image of BFMO on LNO/Ni-Cr, where white-dashed (c1) lines marking discontinuous-columnar grains, orange-solid circle (c2) demarcating grain-boundary-adjacent region and inset shows SAED pattern of area (c1) with blue and red circles highlighting two Bravais lattices. d–f HRTEM images of area (a1), (c1) and (c2), respectively. g–i Inverse Fast Fourier Transform (IFFT) (color bar: strain variation scales proportionally with color depth from white to green) corresponding to d, e and white-dashed square in f, where red-dashed line marking a grain boundary. j,k Fast Fourier Transform (FFT images (in the left top) and Geometric Phase Analysis (GPA) in different faces (the other three) corresponding to g and h. In contrast to the randomly-distributed dislocations and a non-uniform strain state in BFMO/Ni-Cr, the BFMO/LNO/Ni-Cr thin film exhibits dislocation self-assembly along grain boundaries with a uniform strain state.
