Exploring the Interplay between Charge, Strain and Polarization in Ferroelectric Nanostructures

非技术描述：铁电材料的特征在于自发的电极化，其可以随着施加的电场而重新取向。形成和操纵均匀极化的纳米级区域（畴）的能力使铁电体成为未来低功率电子器件，特别是计算机存储器的有希望的候选者。当铁电体与其他材料集成时，新的和独特的特性可以从两种材料连接的界面中出现。为了理解这些涌现的性质，关键是要表征原子结构，化学键，电场，界面电荷分布。现代电子显微镜能够直接成像原子结构，但其他性质通常必须从这些图像中推断。该项目旨在开发新的成像方法，能够同时确定所有这些属性。这将全面了解界面处如何以及为什么会出现独特的特性，并将为未来电子设备的设计和制造提供信息。虽然研究重点是铁电体，但在此项目期间开发的显微镜技术和从该项目中获得的科学知识广泛适用于许多不同类型的材料。该研究与教育和推广活动相结合，以吸引不同的年轻科学家，包括妇女和代表性不足的少数群体，并将有助于培养未来的领导者，以解决关键的社会挑战。技术装备：该项目利用独特的电子显微镜设施在欧文材料研究所，PI担任主任。本项目旨在开发一种新的四维扫描透射电子显微镜（4D STEM）方法，该方法能够以原子分辨率测量不同边界条件下纳米结构和界面中的原子尺度结构、局部电场、电荷密度、价态和极化配置。4D STEM还将与电子能量损失谱和扫描探针显微镜以独特的多模态方法相结合，以探测界面的原子尺度结构和性质，并对铁电极化，束缚电荷，外延应变，电荷屏蔽，以及不同条件下铁电界面或掺杂铁电薄膜中拓扑缺陷周围的结构重构。铁电界面的详细表征需要深入了解界面处涌现现象的原子机制，并为工程铁电纳米结构提供指导。这项研究与学生的教育和培训相结合，使该项目的结果能够通过课程和本科生的独立研究传播给校园内的不同学生群体，以及通过暑期学校课程传播给来自不同背景的高中生，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准。

NON-TECHNICAL DESCRIPTION: Ferroelectric materials are characterized by a spontaneous electric polarization, which can be reoriented with an applied electric field. The ability to form and manipulate nanoscale regions of uniform polarization (domains) makes ferroelectrics a promising candidate for future low-power electronic devices, particularly computer memories. When ferroelectrics is integrated with other materials, new and unique properties can emerge from interfaces where the two materials join. To understand these emergent properties, it is critical to characterize the atomic structure, chemical bonding, electric field, charge distribution at interfaces. Modern electron microscopy is capable of directly imaging the atomic structure, but the other properties must generally be inferred from these images. This project aims to develop new imaging methods that enable to determine all of these properties simultaneously. This will give a full picture of how and why unique properties can emerge at the interface and will inform the design and fabrication of future electronic devices. Although the research focuses on ferroelectrics, the microscopy techniques developed during and scientific knowledge gained from this project are broadly applicable to many different types of materials. The research is integrated with education and outreach activities to attract diverse junior scientists, including women and underrepresented minority groups, and will help train future leaders to address critical societal challenges.TECHNICAL DETAILS: This project leverages unique electron microscopy facilities at the Irvine Materials Research Institute where the PI serves as the director. This project aims to develop a novel four-dimensional scanning transmission electron microscopy (4D STEM) method that enables the measurement of atomic scale structure, local electric field, charge density, valence states, and polarization configuration in nanostructures and interfaces under different boundary conditions with atomic resolution. 4D STEM will also be combined with electron energy-loss spectroscopy and scanning probe microscopy in a unique multimodal approach to probe the atomic scale structure and properties of interfaces and to gain a fundamental understanding of the interaction between ferroelectric polarization, bound charge, epitaxial strain, charge screening, and structure reconstruction in ferroelectric interfaces under different conditions or surrounding topological defects in doped ferroelectric thin films. The detailed characterization of ferroelectric interfaces is required to gain deep insights into the atomic mechanisms of emergent phenomena at interfaces and provide guidance for engineering ferroelectric nanostructures with novel functionalities. The integration of this research with the education and training of students allows the results from this project to be disseminated to the diverse student populations on campus through coursework and independent studies for undergraduate students, as well as to high school students from diverse backgrounds through summer school programs, which promotes their interest in scientific research and education.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.