Flexible polarization rotation at the ferroelectric/metal interface as a seed for domain nucleation

The absence of a realistic polarization screening scenario at the pivotal ferroelectric-metal interface impedes the widespread application of low-dimensional ferroelectric heterostructures. Employing quantitative atom-resolved (scanning) transmission electron microscopy and first-principles calculations, we report that structural and chemical reconstruction universally lowers symmetry of the ferroelectric-metal interface. Irrespective of structural and strain mismatch, chemical termination and diffusion, polar catastrophe, and electrode type, the polarization screening is executed by a flexible polarization rotation at several-unit-cell-thick interfaces. By combining nanoscale and atomic-scale microscopy investigations, our ex situ electric-field biasing experiments reveal that the monoclinically distorted interfaces may act as seeds to nucleate new domains during the polarization switching process. These findings suggest that the long-standing fatigue issue is expected to be overcome by interface modification engineering at the monolayer scale.