CAREER: Structurally and Chemically Ordered States in Low Dimensional Crystals

非技术性描述：该项目旨在探索合成策略，通过该策略，可以在含有两种以上不同化学元素原子的亚纳米薄层材料（通常称为合金）中创建有序的原子链。通过控制合金中原子的确切位置，可以在不同方向上调整材料的性能。这项工作利用先进的电子显微镜成像和光谱技术来了解这些材料的化学和结构有序的机制。该研究有可能设计具有可控的热，电子，光电子和磁性能的材料，并提供正确设计散热应用，储能，电子，光电子和热电器件的关键。该项目还通过各种教育模块促进新兴技术的科学基础。此外，首席研究员通过向高中生，本科生和研究生提供研究经验，特别关注服务不足社区内的妇女和其他少数群体，与特定的目标受众接触。技术描述：合金化和掺杂被认为是调节纳米结构中电荷和热传输的通用策略。无论所得合金结构是随机的还是有序的，都会对材料的宏观电子、光电、振动和输运性质产生深远的影响。超晶格和异质结构中的结构和化学有序性已经得到证实，并导致声子异常和热输运和电输运的显著各向异性。然而，在二维（2D）晶体家族中，结构自由度，即晶格中给定晶体学位点上的不同元素之间的空间相关性在很大程度上仍然未知。本研究探讨了化学有序化作为设计2D晶体合金及其他各向异性的机制。通过动力学驱动的合成机制，在原子薄的2D晶体合金中引入化学和结构有序状态。利用原子分辨率成像和光谱学的最新进展，这项研究阐明了原子水平上的化学和结构有序态和空位掺杂复合物如何调节2D材料中的宏观电荷和声子输运各向异性。此外，该研究有可能确定所产生的化学和结构自由度如何能够定制2D晶体合金中的宏观光电、电子和热输运各向异性。这种理解有助于设计结构各向异性，以改善低维晶体中的电子学、光电子学和热电响应。

Nontechnical description: This project aims to explore synthesis strategies by which ordered atomic chains can be created in sub-nanometer thin layers of materials containing atoms of more than two different chemical elements, often called alloys. By controlling the exact positions of the atoms in an alloy, the properties of the material can be tuned in different directions. The work utilizes advanced electron microscopy imaging and spectroscopy techniques to understand the mechanisms of chemical and structural ordering of these materials. The research has a potential to design materials with controllable thermal, electronic, optoelectronic, and magnetic properties in wide ranges and to provide the key to properly design devices for heat dissipation applications, energy storage, electronics, optoelectronics, and thermoelectrics. This project also promotes the scientific fundamentals of emerging technologies through various educational modules. In addition, the principal investigator engages with specific target audiences by providing research experience to high school, undergraduate, and graduate students, in particular focusing on women and other minority groups within under-served communities. Technical description: Alloying and doping are considered versatile strategies for tuning charge and heat transport in nanostructures. Whether the resulting alloy structure is random or ordered can have a profound impact on the macroscale electronic, optoelectronic, vibrational, and transport properties of the material. Structural and chemical ordering in superlattices and heterostructures have already been demonstrated and led to phonon anomalies and significant anisotropy in thermal and electrical transport. In the family of two-dimensional (2D) crystals, however, the structural degree of freedom, i.e. the spatial correlation between dissimilar elements on a given crystallographic site in the lattice remains largely unknown. This research explores chemical ordering as a mechanism to design anisotropy in 2D crystal alloys and beyond. Through a kinetically-driven synthesis mechanism, chemically and structurally ordered states are introduced in atomically thin 2D crystal alloys. Leveraging recent advancements in atomic resolution imaging and spectroscopy, this research elucidates how chemically and structurally ordered states and vacancy-dopant complexes at the atomic level can tune the macroscale charge and phonon transport anisotropy in 2D materials. Furthermore, the research has a potential to determine how the resulting chemical and structural degrees of freedom can tailor the macroscale optoelectronic, electronic, and thermal transport anisotropy in 2D crystal alloys. This understanding helps design structural anisotropy towards improved electronics, optoelectronics and thermoelectric response in low dimensional crystals.