Understanding Domain Walls in a Two-Dimensional Ferroelectric Material

在包含具有不同结构和特性的区域的材料中，分隔这些区域的界面不仅影响整体材料特性，而且通常具有周围区域不存在的不寻常的物理特性。该项目研究由正负电荷不同空间分离区域组成的独特二维材料中的界面。这些接口的行为知识为使用具有大存储密度和超低功耗的高速逻辑和存储器设备实现更快的计算奠定了基础，也为探索其功能可以动态修改以适应不同需求和应用的下一代设备奠定了基础。教育和外联活动是该项目的一个组成部分。除了为学生提供研究培训外，该项目还涉及课堂演示和实验的开发，这些演示和实验被纳入本科物理课程。为期一周的年度科学营为当地初中和高中学生开发的主要研究者和提供通过公园和娱乐部在普尔曼市。首席研究员还与当地组织合作，将已开发的活动纳入向公众开放的科学展览和科学博览会。技术概述：二维硒化铟是一种独特的铁电材料，其极化由共价键维持，并具有互连的面外和面内极化。强共价键导致高度稳健的铁电性，其持续到单层极限。互连的面外和面内极化允许使用局部电场来限定和操纵带电畴壁。这些畴壁具有独特的晶格结构，并有望表现出许多有趣的和新颖的特性。该项目旨在发展畴壁性质的基础知识，具体目标是了解局部极化，晶格结构和电荷载流子之间的复杂耦合如何影响畴壁电子和声子性质。实验工作利用先进的电子显微镜和多功能扫描探针显微镜技术，如尖端增强拉曼光谱和各种原子力显微镜为基础的测量与高的空间和时间分辨率，探测局部属性在个别域壁。补充这些实验研究，密度泛函理论计算被用来确定晶格，电子和声子结构，以及载流子输运性质和动态域壁。实验和理论研究之间的相关性使机理的见解，并提供了一个基本的基础，利用独特的磁畴壁性质在电子应用中。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

Nontechnical Summary:In materials that contain regions with different structures and properties, the interfaces that separate these regions not only influence the overall material characteristics, but also often feature unusual physical properties not present in the surrounding regions. This project investigates interfaces in a unique two-dimensional material consisting of regions characterized by different spatial separations of positive and negative electric charges. Knowledge of the behaviors of these interfaces lays the groundwork for realizing faster computing using high-speed logic and memory devices with large storage density and ultra-low power consumption, as well as for exploring next-generation devices whose functions can be modified on the fly to adapt to different demands and applications. Education and outreach activities are an integral part of this project. In addition to providing research training for students, this project involves the development of classroom demonstrations and experiments that are integrated into an undergraduate physics course. A week-long annual science camp for local middle and high school students is developed by the principal investigator and offered through the Parks and Recreation Department in the City of Pullman. The principal investigator also works with local organizations to integrate the developed activities into science exhibitions and science fairs that are open to the general public. Technical Summary:Two-dimensional indium selenide is a unique ferroelectric material, with the polarization sustained by covalent bonding and with interlinked out-of-plane and in-plane polarizations. The strong covalent bonding leads to highly robust ferroelectricity that persists down to the monolayer limit. The interlinked out-of-plane and in-plane polarizations allow for defining and manipulating charged domain walls using a local electric field. These domain walls have distinctive lattice structures and are expected to exhibit many interesting and novel characteristics. This project aims to develop a fundamental knowledge of the domain wall properties, with the specific objective to understand how the intricate coupling between the local polarization, lattice structure, and charge carriers affects the domain wall electronic and phonon properties. The experimental efforts utilize advanced electron microscopy and multi-functional scanning probe microscopy techniques, such as tip-enhanced Raman spectroscopy and various atomic force microscopy-based measurements with high spatial and temporal resolutions, to probe local properties in individual domain walls. Complementing these experimental investigations, density-functional-theory calculations are used to determine the crystal lattices, electronic and phonon structures, as well as charge carrier transport properties and dynamics in domain walls. The correlation between experimental and theoretical studies enables mechanistic insights and provides a fundamental basis for exploiting unique domain wall properties in electronic applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.