In-Situ Switching of van der Waals Ferroelectrics with In-Plane Electric Biasing

Two-dimensional van der Waals (vdW) ferroelectrics offer the enticing opportunity of both stabilizing ferroelectricity down to atomic thickness while seamlessly integrating with current complementary metal-oxide-semiconductor (CMOS) technologies [1-3]. Here, we perform in-situ in-plane biasing scanning transmission electron microscopy (STEM) imaging to investigate the switching dynamics in SnSe (anti)ferroelectrics. By visualizing the metastable intermediate states during switching processes at atomic scale, we reveal the pivotal role of stacking-polarization coupling in governing the switching pathways of SnSe. Upon applying in-plane electric field to pristine AFE-order SnSe, both AFE-to-FE polarization order transition and AB-to-AC stacking order transition were observed through a 180° switching pathway. To quantify localized strain, we performed strain mapping derived from the atomic-scale images to understand the switching mechanisms. In summary, we reveal the intrinsic coupling between stacking and polarization order and highlight the strain-mediated switching pathways in vdW ferroelectrics.