Multi-Terraced Stacking Engineering in Moiré Ferroelectric Superlattice

Emergent moiré ferroelectricity, capable of realizing ferroelectricity down to the atomic scale, holds transformative promise for ultracompact electronics. However, directly visualizing the stacking-engineered interfacial ferroelectric phase is inherently difficult due to the intricate domain network involving overlapping lattice structures and complex polarization evolution. Moreover, the topological nature of the network inherently restricts nonvolatile switching, posing a fundamental barrier to practical implementation. In this work, a controlled boundary confinement engineering is proposed to disrupt topological constraints and enable precise domain engineering in moiré superlattices. Utilizing scanning probe microscopy and spherical aberration-corrected transmission electron microscopy, atomic-resolution observation of the WSe₂ stacking configuration is achieved, including R- (sliding ferroelectricity), H-stacking, and domain walls with broken C₃ symmetry, from a cross-sectional perspective. Nonvolatile polarization switching is observed due to the elimination of nodes' pinning effects and the freedom of domain wall motion. The findings clarify the relationship between atomic structure and polarization distribution in the moiré system, providing crucial insights for the design and manipulation of moiré ferroelectrics in functional devices.