Polarization-Controlled Structural Modulation in the Single Atomic Layer at the PbZr_0.2Ti_0.8O₃/LaNiO₃ Interface

Conductivity modulation via ferroelectric polarization coupling with LaNiO₃ (LNO) is demonstrated at an epitaxial ferroelectric-LNO interface. Conductivity measurements, varying the thickness of the LNO channel, show that this phenomenon is confined to a few atomic layers at the interface. Combining in situ biasing and off-axis holography, we mapped out electrostatic potentials at the PbZr0_.2Ti_0.8O₃(PZT)/LNO/SrTiO₃(STO) heterostructure upon polarization switching. Using aberration-corrected STEM, the interfacial atomic structures were investigated for the two different PZT polarization states. Polarization in PZT induces a significant change in the in-plane O-Ni-O bond angles, with a 37° modulation in the topmost 1 or 2 LNO unit cells, driven by strain in the oxygen sublattice for the two opposite polarization directions in PZT. Both oxygen and cation sublattices exhibit strain responses exceeding 10% upon switching. This atomic-layer structural modulation highlights a mechanism for functional oxide heterostructure development, offering pathways for advancements in nonvolatile memory, sensors, and energy-efficient transistors.