二维铁电材料的第一性原理研究

FIRST-PRINCIPLES STUDY OF FERROELECTRICITY IN TWO-DIMENSIONAL MATERIALS

陈立春

11749038

硕士

物理学

徐虎

2019-05-14

2019-07-10

哈尔滨工业大学

深圳

近年来，铁电材料一直是凝聚态物理以及材料科学研究重点关注的领域之一。 从原来的压电陶瓷材料到后来的钙钛矿铁电材料，再从钙钛矿铁电材料到现在的 铁电薄膜材料，铁电材料朝着更小易集成器件的方向的发展，并且具有广泛的应用 前景。寻找具有自发极化，并且极化可以由外电场调控反转的铁电材料，对于研发 新型的信息存储材料具有至关重要的意义。传统的三维铁电材料由于表面净电荷 的存在而产生退极化场，使得三维铁电材料薄膜在小于一定的厚度时自发极化被 抑制。这严重制约了器件的小型化，高集成度方向的应用。所以寻找并研究具有稳 定自发极化的二维铁电材料至关重要。在我们的研究中将通过第一性原理方法重 点研究具有二维单层结构的铁电材料。 我们从体系对称性观点出发，寻找和筛选可能出现自发极化的二维铁电材料， 特别是具有垂直材料平面的面外极化行为。在研究中，我们发现应变可以调控一些 二维材料中的极化行为，使 这些材料在铁电相和顺电相之间发生转换。我们通过第 一性原理的方法研究了这些行为，包括极化反转以及相关晶格序耦合行为。基于第 一性原理计算的数据，构建了相应的唯象朗道模型，初步展示了这些材料中面内应 变与垂直平面的极化之间的耦合关系。我们的研究揭示了一部分二维铁电行为的 基本规律，同时为寻找新的二维铁电、多铁材料提供了新的思路和方法。

In recent years, Ferroelectric materials have been one of the intensively studied field in condensed matter physics and materials science. Ferroelectric materials have been from the original piezoelectric ceramic materials to the perovskite ferroelectric materials, and they’re ferroelectric thin film materials at present. Ferroelectric materials are improved in the direction of smaller and easier to integrate devices, and they have a wide range of applications. It is necessary to find ferroelectric materials which have spontaneous polarization and whose polarization can be artificially modulated and reversed. That has great significance for the development of new information storage materials. Due to the net charge on the surface, depolarization field is generated inside the traditional 3D ferroelectric material. That inhibits the spontaneous polarization of the 3D ferroelectric material whose film is less than a certain thickness, it seriously restricts the device miniaturization and the application of high integration direction. Therefore, it is very important to find and study two-dimensional ferroelectric materials with stable spontaneous polarization. In our study, we will focus on two-dimensional single-layer ferroelectric materials through the DFT calculation. Based on the system symmetry analysis, we explored two-dimensional materials with spontaneous polarization, especially the ones with out-of-plane polarization. In our study, we notice that in-plane strain is able to tune the ferroelectric behaviors of twodimensional materials, induce the transition between ferroelectric phase and paraelectric phase. We investigated some related behavior such as the inversion of polarization and the coupling between lattice modes via our first-principles calculations. Based on which, the phenomenological Landau model was built as well in order to better show the coupling between in-plane and out-of-plane polarization. Our research reveals some fundamental rules of two-dimensional ferroelectric behavior, and provides new pathway of exploring novel two-dimensional ferroelectric and multi-ferro materials.

铁电材料 二维材料 第一性原理 自发极化 朗道模型

Ferroelectric material Two-dimensional material First principles calculation Spontaneous polarization Landau model

中文

联合培养

陈立春. 二维铁电材料的第一性原理研究[D]. 深圳. 哈尔滨工业大学,2019.