Real-space observation of polarization induced charges at nanoscale ferroelectric interfaces.

Unique electrical properties emerging at nanoscale ferroelectric interfaces originate from the polarization induced charges. However, real-space characterization of polarization induced charges at nanoscale ferroelectric interfaces has been extremely challenging. Here, directly observing the nanoscale electric field by tilt-scan averaged differential phase contrast scanning transmission electron microscopy enables us to measure the spatially varying total charge density profiles across both head-to-head and tail-to-tail domain walls in a ferroelectric crystal. Combined with atomic column displacement measurements, the spatial distribution of polarization bound charges and screening charges across the domain walls can be disentangled. Our results reveal the true charge states of the nanoscale ferroelectric interfaces, providing an opportunity for experimentally exploring the interplay between atomic-scale local polarization structures and their charge states in ferroelectric interfaces.