低维铁电材料研究进展

铁电材料是一类重要的功能材料,铁电元件的小型化、集成化是当今铁电材料发展的一大趋势.但是尺寸效应、表面效应等的存在制约了传统块体铁电材料在纳米尺度下的应用,因而低维度纳米材料中的铁电性能研究成为当前材料科学领域的研究热点之一.本文综述了近年来理论和实验上关于低维铁电材料的探索,包括二维范德瓦耳斯层状铁电材料、共价功能化低维铁电材料、低维钙钛矿材料、外界调控以及二维"铁电金属"等材料的理论预言与实验铁电性的观测;也提出一些物理新机制来解释低维下的铁电性;最后对该领域今后的发展进行了展望.

Research progress of low-dimensional ferroelectric materials

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.