Fig. 1: Structural and ferroelectric properties.

a Schematic illustration of Ag/PZT/NSTO FTJ devices. b Cross-sectional HAADF-STEM images of the PZT/NSTO heterostructure at four different areas, with the insets showing the ferroelectric atomic displacements in the PZT. The orange and green spheres denote Pb and Zr/Ti ions, respectively. The arrows in the insets indicate the polarization directions. c PFM phase, d PFM amplitude, and e SKPM surface potential images recorded after writing an area of 3 × 3 μm2 with −6 V and the central area of 1.5 × 1.5 μm2 with +5 V on the (111)-oriented PZT (1.2 nm)/NSTO. f PFM phase and g amplitude loops collected with various AC voltages.