Probing Local Structural and Chemical Properties of Atomically Thin Two-Dimensional Materials by Optical Scanning Tunneling Microscopy

新技术应用的发展需要具有适当性能的新材料。二维（2D）材料吸引了巨大的兴趣，因为它们具有广泛的材料特性，可以创建复杂的人工结构，并具有天然块状材料中不可用的新功能。通过利用其独特的特性，二维材料可以用于许多应用，例如柔性电子产品，小型化设备以及为可穿戴电子产品提供电力。本项目由伊利诺伊大学芝加哥分校固态与材料化学项目资助，江南教授和他的研究小组将重点研究具有独特结构和物理性质的硼单层（硼苯）相关二维材料的合成。该项目包括开发复杂的硼苯基结构，并以前所未有的空间分辨率测量其局部特性。这种先进的理解对于微调电子、光子学、传感和能量收集应用的二维结构的特性是必不可少的。该项目将从代表性不足的群体中招收和培训本科生和研究生，并将纳入一系列广泛的推广工作，包括在小学开展项目和示范活动。该项目由材料研究部固态与材料化学计划支持，开发了一种精确控制和从根本上了解新型二维材料（如硼罗芬）的晶格，缺陷和电子结构之间相互作用的新方法。这些研究包括使用最先进的技术，结合扫描隧道显微镜（STM）和尖端增强拉曼光谱（TERS），直接观察硼罗芬基结构的振动模式。该方法以大约5埃的空间分辨率和5波数的光谱分辨率，促进了纳米和原子尺度非均匀性的局部振动和电子-声子耦合特性的成像和表征。除了检测形貌和电子特性外，STM-TERS方法还阐明了局部界面特征，包括应变、缺陷和原子厚度极限下的掺杂。基于这些突破性的技术进步，该项目研究了通过氧对硼罗芬进行化学修饰，定义了硼罗芬与有机分子的杂交，并构建了与硼罗芬相关的二维范德华异质结构。总的来说，这些研究为在原子厚度极限下电荷和晶格之间的关系提供了前所未有的见解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARYThe development of new technological applications requires new materials with appropriate properties. Two-dimensional (2D) materials attract tremendous interest because they have a broad range of material properties for creating complex artificial structures with novel functionalities unavailable in natural bulk materials. By harnessing their unique properties, 2D materials can be used for many applications, such as flexible electronics, miniaturized devices, and providing electricity for wearable electronics. In this project, funded by the Solid State and Materials Chemistry Program of the Division of Materials Research, Prof. Nan Jiang and his research group at the University of Illinois, Chicago, will focus on the synthesis of boron monolayer (borophene) related 2D materials, which have unique structural and physical properties. The project encompasses the development of complex borophene-based structures and the measurement of their local properties with an unprecedented spatial resolution. Such advanced understanding is essential for fine-tuning the properties of 2D structures for electronics, photonics, sensing, and energy-harvesting applications. This project will recruit and train undergraduate and graduate students from underrepresented groups and will be integrated into a broad set of outreach efforts, including programs and demonstrations in elementary schools. TECHNICAL SUMMARYThis project, supported by the Solid State and Materials Chemistry Program of the Division of Materials Research, develops a new approach to precisely control and fundamentally understand the interplay among lattice, defects, and the electronic structure of novel 2D materials, such as borophene. The studies involve the direct observation of vibrational modes of borophene-based structures using a state-of-the-art technique that combines scanning tunneling microscopy (STM) with tip-enhanced Raman spectroscopy (TERS). This method facilitates the imaging and characterization of local vibrational and electron-phonon coupling properties of nano- and atomic-scale heterogeneity with approximately 5-Angstrom spatial resolution and 5-wavenumber spectroscopic resolution. In addition to detecting topographical and electronic properties, the STM-TERS approach elucidates localized interfacial features, including strain, defects, and doping at the atomic-thickness limit. Building on these groundbreaking technological advances, the project investigates the chemical modification of borophene via oxygen, defines the hybridization of borophene with organic molecules, and constructs borophene-related 2D van der Waals heterostructures. Collectively, these studies provide unprecedented insights into the relationship between charge and lattice at the atomic-thickness limit.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.