Fig. 1

a XRD pattern of the BLFO film. The inset shows the cross-sectional SEM image. b M-H hysteresis loop of the BLFO film. The inset gives the expanded area of the red dotted circle. c Surface AFM image of the BLFO film with the area of 3 × 3 μm². d The corresponding c-AFM image at a bias voltage of 6 V. e, f The typical 10 × 10 μm² out-of-plane PFM phase and amplitude images, respectively