Direct Observation of Nanoscale Polarization Switching in HZO Ferroelectrics Using STEM-EBIC

We report the experimental observation of discrete ferroelectric switching down to 0.475 nm × 0.475 nm in HfO2-based ferroelectrics using correlated STEM electron beam induced current (EBIC) imaging and nanoscale voltage pulsing. These high-resolution measurements reveal single-domain switching events characterized by abrupt, bi-state transitions with no intermediate polarization states. By mapping polarization–voltage behavior and switching kinetics across thousands of domains, we extract spatially resolved switching thresholds (Emin), switching speeds (tsw), and remanent polarization (2Pr), uncovering robust scaling trends. Larger domains exhibit nearly twice the polarization and faster switching despite higher Emin, while smaller domains switch more slowly at the same field. Sub-domain imaging enables quantification of variation scaling: polarization variation increases linearly logarithmically with area, with inter-domain variation dominating intra-domain variation. Importantly, we show that multi-bit operation arises from the statistical distribution of domain-level switching—rather than partial polarization—enabling distinct and reliable states in devices as small as 0.01 μm2. These findings provide a foundational experimental framework for designing scalable, multibit ferroelectric memory based on grain- and domain-level heterogeneity.