Strain gradient induced vortex-like domain evolution in freestanding ferroelectric membranes

Ferroelectric vortex domains in strained ferroelectric membranes have recently garnered significant scientific interest. However, understanding domain evolution under varying strain conditions has been challenging due to experimental limitations in generating precise strain gradients. Our research introduces a novel approach to strain gradient manipulation in single-layer ferroelectric membranes. By experimentally investigating freestanding bent PbTiO₃ membranes, we directly observed ferroelectric vortex-like domains. As bending strain increases, c-domains progressively transition to c- and a-mixed domains, with vortex-like structures emerging at a critical bending strain of 5.2%. Complementary atomistic simulations confirm that strain gradients trigger domain formation through continuous dipole rotation at the domain boundaries. This work unveils a strategy for generating sophisticated ferroelectric domain architectures and its mechanism, offering promising pathways for engineering novel polar textures in next-generation electronic devices.