CAREER: Structurally and Chemically Ordered States in Low Dimensional Crystals

非技术描述：该项目旨在探索合成策略，通过这种策略，可以在包含两个以上不同化学元素的原子的材料的亚纳米薄层中创建有序原子链，这些元素通常被称为合金。通过控制原子在合金中的准确位置，材料的性质可以在不同的方向上进行调节。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化的机制。这项研究有可能在很大范围内设计具有可控热、电、光电和磁性的材料，并为正确设计散热、储能、电子学、光电子学和热电学器件提供关键。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，首席调查员通过向高中、本科生和研究生提供研究经验，特别是关注服务不足社区中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。由此得到的合金结构是无序的还是有序的，都会对材料的宏观电子、光电子、振动和传输特性产生深远的影响。超晶格和异质结中的结构和化学有序已经被证明，并导致声子反常和热和电输运中的显著各向异性。然而，在二维(2D)晶体家族中，结构自由度，即晶格中给定结晶学位置上不同元素之间的空间相关性仍然很大程度上是未知的。这项研究探索了化学有序作为一种机制来设计2D晶体合金及其以外的各向异性。通过动力学驱动的合成机制，在原子薄的2D晶体合金中引入了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以及空位-掺杂复合体如何调节2D材料中的宏观电荷和声子输运各向异性。此外，这项研究还有可能确定由此产生的化学和结构自由度如何适应2D晶体合金的宏观光电子、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.