二维反铁电晶体材料的理论设计与高通量预测

With the rapid development of information technology, electronic component tends to miniaturization, and the study of physical properties of low-dimensional materials have attracted a lot of attention. Two-dimensional (2D) crystalline materials with the properties of both low-dimensional and periodic lattices, become a research focus. The recently discovered room-temperature ferroelectricity in inorganic 2D multiple atomic-layer crystalline materials, opens a new direction for the application of 2D materials. 2D antiferroelectric materials could have advantages in interference immunity, reliability, response speed, etc. however, are not well studied yet, and the physical model for the application of 2D antiferroelectric crystals in electronic technology is not clear. In this project, we will start from the symmetry of quasi-2D lattice, systematically study the symmetry relationship of 2D crystal structures, design 2D crystal structures that can realize antiferroelectric switch, then theoretically generate numerous primary 2D antiferroelectric materials via element substitution. We will develop the first-principles calculation methods for 2D antiferroelectric crystalline materials, and select candidate materials with relatively strong antiferroelectricity via high-throughput calculations, then study their antiferroelectric structural phase transition barriers, the modulation effect of external electric field on their electric polarizations, and an new effect in which electric potential difference is generated from perpendicular electric current that is unrelated to magnetic properties, thus provide theoretical methods, physical models, and selectable materials for further research of 2D antiferroelectric materials and their device applications.

随着信息技术的高速发展，电子元器件趋于微型化，低维材料的物性研究备受关注。二维晶体材料兼具低维与周期性晶格的特征，成为研究的热点。最近发现的无机二维多原子层晶体材料中的室温铁电性，为二维材料的应用开辟了新方向。二维反铁电晶体材料可能在抗干扰性、可靠性、响应速度等方面存在优势，但是目前没有得到足够的研究，二维反铁电晶体在电子技术中应用的物理模型也尚不清楚。本项目将从准二维晶格对称性出发，系统研究二维晶体结构之间的对称性关联，设计可以实现反铁电调控的二维晶体结构，利用元素替换方法理论上生成大量二维反铁电预选材料。发展二维反铁电晶体材料的第一性原理计算方法，通过高通量计算筛选出反铁电性较强的备选材料，并研究它们的反铁电结构相变势垒，外电场对其电极化性质的调制效应，以及一种与磁性无关的、电流引起垂直方向电势差的新效应，为二维反铁电材料及其器件应用的进一步研究提供理论方法、物理模型与可选材料。

二维材料在光电、电子、能源、医疗等领域有广阔的应用前景，局域电极化在二维材料中广泛存在。然而，局域电极化对二维材料物理性质的影响目前尚不清楚。具有较低局域电极化翻转能垒的二维反铁电材料在二维反铁电隧道结等电子器件中有重要应用价值。通过第一性原理高通量计算与晶格对称性分析，对二维材料中的局域电极化及相关物理性质开展了深入研究，预言了一系列二维反铁电材料。取得的主要结果如下：1）研究了纤锌矿半导体的机械剥离过程，预测了大量稳定的新型二维纤锌矿反铁电材料，发现新材料具有较低的反铁电相变能垒，并具有铁弹性质和隐藏的自旋极化；2）在基于二维反铁电材料磷烯的混合维度异质结中发现了表面诱导的面内宏观电极化，通过磷烯在表面的微小移动可以实现面内宏观电极化的翻转；3）在IV-VI族二维铁电材料中发现了一种不涉及对称性改变和电子结构显著变化的赝相变，相变过程伴随着泊松比值的翻转，并可以被外电场调控；4）通过晶面特征分析与理论模拟，从非层状三维氧化物中剥离出稳定的二维氧化物，进一步筛选出反铁电相变能垒较低的二维氧化物反铁电材料；5）通过局域对称性分析与理论计算，在Cs3Cu2Cl5中发现了一种伴随着局域电极化改变的局域对称性升高的自陷态激子发光过程。项目执行期间，项目负责人共发表高水平学术论文42篇，其中Advanced Materials 1 篇、Advanced Functional Materials 1 篇、Journal of the American Chemical Society 1篇、Chemistry of Materials 4篇、Journal of Materials Chemistry A 1篇、Journal of Materials Chemistry C 4篇、NPG Asia Materials 1篇、The Journal of Physical Chemistry Letters 2篇、Applied Surface Science 1篇。这些研究增进了我们对二维材料中的局域电极化及相关物理性质的认识和理解。