Domain‐Wall‐Free Sliding Ferroelectricity in Fully Commensurate 3R Transition Metal Dichalcogenide Bilayers

Abstract Stacked bilayers of transition metal dichalcogenides (TMDs) with the rhombohedral (3R) domains exhibit robust room‐temperature sliding ferroelectricity with exceptional stability even at the ultrathin limit. Polarization switching in stacked 3R‐TMD bilayers is typically mediated by the lateral migration of domain walls (DWs). However, the random formation and pinning of DWs during stacking reduce reliability and uniformity in 2D ferroelectric devices. Here, DW‐free sliding ferroelectric switching in fully commensurate (FC) 3R‐TMD bilayers is demonstrated. Using encapsulation annealing or promoter‐assisted chemical vapor deposition (CVD), single‐domain 3R‐TMD bilayers (SD‐TMDs) are realized. These SD‐TMDs show pinning‐free ferroelectric switching, resulting in a larger remanent polarization, long retention, and improved thermal stability compared to artificially stacked poly‐domain 3R‐TMD bilayers (PD‐TMDs), ensuring complete polarization switching and addressing a key limitation of PD‐TMDs with short retention and lower polarization. Rectangular polarization–electric field ( P–E ) hysteresis loops in SD‐TMDs highlight their stable switching behavior with well‐defined coercive‐field‐dependence, in contrast to the gradual, incomplete transitions in PD‐TMDs. The DW‐free SD‐TMDs also show minimal device‐to‐device variation, making them suitable for large‐scale and reliable ferroelectric device applications. This work provides a reproducible pathway to obtain high‐quality DW‐free 3R‐TMD bilayers, offering a scalable platform for robust and high‐performance 2D ferroelectric devices.