Recent Progress in Two-Dimensional Ferroelectric Materials

The investigation of two-dimensional (2D) ferroelectrics has attracted significant interest in recent years for applications in functional electronics. Without the limitation of a finite size effect, 2D materials with stable layered structures and reduced surface energy may go beyond the presence of an enhanced depolarization field in ultrathin ferroelectrics, thereby opening a pathway to explore low-dimensional ferroelectricity, making ultra-high-density devices possible and maintaining Moore's Law. Although many theoretical works on potential 2D ferroelectric materials have been conducted, much still needs to be accomplished experimentally, as it is rare for 2D ferroelectric materials to be proven and plenty of 2D ferroelectrics are waiting to be discovered. First, experimental and theoretical progress on 2D ferroelectric materials, including in-plane and out-of-plane, is reviewed, followed by a general introduction to various characterization methods. Intrinsic mechanisms associated with promising 2D ferroelectric materials, together with related applications, are also discussed. Finally, an outlook for future trends and development in 2D ferroelectricity are explored. Researchers can use this to obtain a basic understanding of 2D ferroelectric materials and to build a database of progress of 2D ferroelectrics.