Understanding Domain Walls in a Two-Dimensional Ferroelectric Material

非技术摘要：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，而且通常还具有周围区域不存在的异常物理特性。这个项目研究了一种独特的二维材料中的界面，该材料由正负电荷的不同空间分隔区域组成。对这些接口行为的了解为使用具有大存储密度和超低功耗的高速逻辑和存储设备实现更快的计算奠定了基础，并为探索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组成部分。除了为学生提供研究培训外，该项目还包括开发课堂演示和实验，并将其整合到本科物理课程中。首席调查员为当地初中生和高中生举办了为期一周的年度科学夏令营，并通过普尔曼市的公园和娱乐部提供服务。首席调查员还与当地组织合作，将开展的活动纳入向公众开放的科学展览和科学博览会。技术综述：二维铟硒是一种独特的铁电材料，其极化由共价键维持，面外和面内极化相互关联。强烈的共价键导致了非常强健的铁电性，这种铁电性一直持续到单层极限。相互关联的面外和面内极化允许使用局部电场来定义和操纵带电磁区壁。这些域壁具有独特的晶格结构，有望显示出许多有趣和新颖的特征。这个项目的目的是发展基本的域壁属性知识，具体目的是了解局域极化、晶格结构和电荷载流子之间的复杂耦合如何影响域壁的电子和声子属性。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基于原子力显微镜的高空间和时间分辨率测量，来探测单个磁区壁上的局部性质。作为对这些实验研究的补充，密度泛函理论计算被用来确定晶格、电子和声子结构，以及域壁中的载流子输运性质和动力学。实验和理论研究之间的相关性使我们能够获得机械性的洞察力，并为在电子应用中开发独特的域壁属性提供了基本基础。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.