Revealing Atomic-Scale Switching Pathways in van der Waals Ferroelectrics

TL;DR

This study combines atomic-resolution imaging and first-principles calculations to uncover atomic-scale switching pathways in van der Waals ferroelectrics, revealing complex mechanisms involving interlayer sliding and strain in SnSe.

Contribution

It provides the first detailed atomic-scale understanding of ferroelectric switching pathways in vdW materials, highlighting coexistence of different switching modes and their associated atomic movements.

Findings

Identified coexistence of 90° and 180° switching pathways in SnSe.

Revealed interlayer sliding and strain as key mechanisms during switching.

Demonstrated atomic coherence despite multidomain structures.

Abstract

Two-dimensional van der Waals (vdW) materials hold the potential for ultra-scaled ferroelectric (FE) devices due to their silicon compatibility and robust polarization down to atomic scale. However, the inherently weak vdW interactions enable facile sliding between layers, introducing complexities beyond those encountered in conventional ferroelectric materials and presenting significant challenges in uncovering intricate switching pathways. Here, we combine atomic-resolution imaging under in-situ electrical biasing conditions with first-principles calculations to unravel the atomic-scale switching mechanisms in SnSe, a vdW group-IV monochalcogenide. Our results uncover the coexistence of a consecutive 90 degrees switching pathway and a direct 180 degrees switching pathway from antiferroelectric (AFE) to FE order in this vdW system. Atomic-scale investigations and strain analysis reveal that the switching processes simultaneously induce interlayer sliding and compressive strain, while the lattice remains coherent despite the presence of multidomain structures. These findings elucidate vdW ferroelectric switching dynamics at atomic scale and lay the foundation for the rational design of 2D ferroelectric nanodevices.