A 2D Van Der Waals Molecular Ferroelectric

Abstract

2D van der Waals (vdW) ferroelectrics have aroused great interest for their novel structures and functionalities in many applications such as in‐memory computing and ferroelectric detectors. However, the documented 2D ferroelectrics remain very rare, mainly limited to inorganic ones represented by transition metal thio/selenophosphates. Constructing new 2D vdW ferroelectric categories may bring interesting phenomena, but it has always been a challenge. Here, a molecular 2D vdW ferroelectric sodium 2,2,3,3‐tetrafluoropropionate (2,2,3,3‐TFPS) is successfully designed through H/F substitution, which adopts a unique stable layered structure where each coordination bonded molecule‐based 2,2,3,3‐TFPS monolayers knitted together by weak vdW forces between protruding (−CHF2) cantilevers in the adjacent two monolayers. More strikingly, it can show robust room‐temperature ferroelectricity even in a mechanically exfoliated ultrathin flake as thin as 9 nm, which has never been achieved in traditional molecular ferroelectrics with ferroelectricity mainly in the bulk form and micron‐scale thin film. To the best of the knowledge, 2,2,3,3‐TFPS is the first molecular 2D vdWs ferroelectric showing robust ferroelectricity in sub‐10 nm thickness. This work expands the diversity of 2D vdW ferroelectrics and sheds light on the exploration of molecular 2D vdW ferroelectrics with promising low‐dimensional ferroelectricity for applications in nanoscale devices.