Review on Recent Developments in 2D Ferroelectrics: Theories and Applications

Abstract

Although only a few 2D materials have been predicted to possess ferroelectricity, 2D ferroelectrics are expected to play a dominant role in the upcoming nano era as important functional materials. The ferroelectric properties of 2D ferroelectrics are significantly different than those of traditional bulk ferroelectrics owing to their intrinsic size and surface effects. To date, 2D ferroelectrics have been reported to exhibit diverse properties ranging from bulk photovoltaic and piezoelectric/pyroelectric effects to the spontaneous valley and spin polarization. These properties are either dependent on ferroelectric polarization or coupled with it for easy electric control, thus making 2D ferroelectrics applicable to multifunctional nanodevices. At present, cumulative efforts are being made to explore 2D ferroelectrics in theories, experiments, and applications. Herein, such theories and methods are briefly introduced. Subsequently, intrinsic and extrinsic origins of 2D ferroelectricity are separately summarized. In addition, invented or laboratory-validated 2D ferroelectric-based applications are listed. Finally, the existing challenges and prospects of 2D ferroelectrics are discussed.

Recent Progress on Two-Dimensional Materials

“…A distinctive feature of 2D materials is their atomic-thin thickness, which endows them unique physical and chemical properties [1690][1691][1692] . However, the atomic-thin thickness also leads to the relatively high surface reactivity of 2D materials, leading to their environmental instability, as they may be corroded, decomposed, oxidized, segregated and so forth 1693 .…”

Memristive Devices Based on Two-Dimensional Transition Metal Chalcogenides for Neuromorphic Computing

“…In recent reports, several 2D ferroelectric materials have been theoretically predicted and experimentally verified. 2D ferroelectrics can be classified as in-plane ferroelectric semiconductors (group IV monochalcogenides; SnS, SnSe, GeS, and GeSe), out-of-plane ferroelectric semiconductors ( d 1T-MoTe 2 , WTe 2 , and CuInP 2 S 6 ), and intercorrelated ferroelectrics (III 2 -VI 3 compounds, e.g., In 2 Se 3 ) [ 94 , 99 , 100 ]. The ability of layered materials to retain ferroelectric properties to the nanometer range, in contrast to 3D perovskite oxides, is due to their weak interlayer coupling, which stabilizes individual layers from out-of-plane perturbations.…”

Efficient and Anisotropic Second Harmonic Generation in Few‐Layer SnS Film

“…[1][2][3] Recently, ferroelectricity property of 2D ultrathin materials attracts substantial research interest. [4][5][6] Compared with traditional perovskite oxides ferroelectric materials, which cannot sustain its ferroelectricity with single layer thickness, [7] 2D materials offer a new route to maintain the robust ferroelectricity and overcome the thickness limitation giant second harmonic generation (SHG) due to its structural inversion symmetry breaking and large residual of two opposite intraband contributions based on first-principle electronic structure theory. [33] However, second-order NLO property of SnS was rarely reported.…”

“…[ 1–3 ] Recently, ferroelectricity property of 2D ultrathin materials attracts substantial research interest. [ 4–6 ] Compared with traditional perovskite oxides ferroelectric materials, which cannot sustain its ferroelectricity with single layer thickness, [ 7 ] 2D materials offer a new route to maintain the robust ferroelectricity and overcome the thickness limitation due to its atomically thin layered structure, [ 6,8 ] which are technologically important for the miniaturization of nonvolatile memories, [ 9 ] sensors, [ 10 ] and optoelectronic devices. [ 11,12 ] The spontaneous polarization of ferroelectricity can be controlled by external electrical field, which has been experimentally investigated in a range of 2D layered materials such as WTe 2 , [ 13 ] MoTe 2 , [ 14 ] In 2 Se 3 , [ 15–18 ] and SnTe.…”