Curvature-Controlled Polar-Dislocation Coupling in Freestanding Ferroelectric Oxide Heterostructures

Curvature couples polarization, crystalline defects, and interfacial electrostatics in freestanding ferroelectric oxides. Here, we examine bent epitaxial Pb(Zr0.2Ti0.8)O3/SrTiO3/Pb(Zr0.2Ti0.8)O3 (PZT/STO/PZT) membranes using atomic-resolution electron microscopy, strain and polarization mapping, relative projected-potential reconstruction, and molecular dynamics simulations. The tensile-side PZT remains comparatively lattice-continuous and accommodates bending mainly through polarization rotation and domain reorganization. The compressive-side PZT exhibits dislocations, slip-related lattice offsets, surface steps, and localized strain concentration. Curvature-series observations and images across U-shaped and N-shaped regions indicate that the defect-rich region follows the local compressive stress state. Bending also breaks the approximate electrostatic symmetry of the two PZT/STO interfaces: the tensile side shows weakened negative interfacial contrast, whereas the compressive side shows a dislocation-associated increase in relative projected potential. These results identify curvature as a variable for selecting polar versus plastic relaxation pathways and modulating interfacial electrostatic landscapes in flexible ferroelectric heterostructures.