Research progress of low-dimensional ferroelectric materials

Abstract

Ferroelectricity, which exhibits a spontaneous electrical polarization under Curie temperature, is of potential value for sensors, photonics and energy-efficient memories, solar cell, and photoelectrochemical applications. With the rapid development of high-density electronic devices, miniaturized and integrated ferroelectric devices have been a development tendency for ferroelectric materials. However, the size effect and surface effect restrict the applications of traditional bulk ferroelectric materials on a nanometer scale. Therefore the ferroelectric properties of low-dimensional nanomaterials have become an extensively studying subject in the field of material science. In this article, we review the theoretical and experimental researches of low-dimensional ferroelectric materials in recent years, including two-dimensional van der Waals layered ferroelectric materials, covalent functionalized ferroelectric materials, low-dimensional perovskite materials, external regulation and two-dimensional hyperferroelectric metal. We first give a concise outline of the basic theory, which relates to the existence of ferroelectricity. And then, we introduce the intrinsic ferroelectricity into two-dimensional materials. Many samples have been predicted, and the origin of ferroelectricity can be attributed to the soft modes of phonon, which leads to the ion displacements. Further, we discuss the ferroelectricity in covalent-modified two-dimensional materials. In such structures, the modified groups produce spontaneous electric dipoles, and lead to the macroscopical ferroelectricity. Therefore, we focus on how to design such structures, and the consequent ferreoelectricity. Considering the big potential of perovskite structures in ferroelectric family, we also discuss the recently reported low-dimensional perovskite structures, indicating several competitive mechanisms in such complex compounds. Additionally, we also introduce the research progress of other aspects in this field, including charge-polar induced ferroelectricity, two-dimensional ferromagnetic ferroelectrics, and hyperferroelectric metal. The reported new physical mechanisms are also provided to explain the low-dimensional ferroelectrics. Thus, such results not only mark the research of low-dimensional materials entering into a new stage, but also provide abundant physics in this area. Finally, the development prospects for low-dimensional ferroelectrics are also discussed.