Controlling Electron, Magnon, and Phonon States in Quasi-2D Antiferromagnetic Semiconductors for Enabling Novel Device Functionalities

非技术描述本研究解决了一类具有本征磁性质的新型超薄准二维半导体的特性。这种新型半导体的奇异特性使它们在基础科学研究和实际应用中特别有趣。研究人员将探索这些只有几个原子层厚度的独特材料的电子、磁性和热性能。pi还将研究这些材料在具有新功能的器件中使用的潜力，这些器件可以高速低能耗运行。这项研究符合国家对开发和研究新型半导体材料和器件的需求，根据最近的芯片和科学法案。该项目的跨学科性质将促进学生参与拟议的研究，并为本科和研究生STEM教育做出贡献。项目团队制定了详细的“扩大参与计划”，该计划将影响STEM领域代表性不足的少数民族的K-12、本科和研究生教育。过渡金属磷-三硫族化合物涵盖多种具有不同电子、磁性和声子性质的化合物。这些材料是少数具有内在反铁磁性的范德华层状结构之一，即使在单层厚度下也是如此。这些材料的带隙根据其过渡金属元素的类型在~1.3 eV到~3.5 eV之间变化。理论表明，栅极偏置和应变的应用可以引起这些材料的相变，改变它们的性能。虽然具有AFM自旋顺序的电绝缘体和导体已被广泛研究，但在实验上对反铁磁层状半导体知之甚少。该项目旨在研究这些独特材料在单层和多层结构中的电子、声子和磁振子特性，并评估控制其特性以实现新器件功能的可能性。为了实现这些目标，将使用低温微布里渊-拉曼光谱以及电和热输运测量来合成和表征各种类型的这些化合物。这项跨学科研究的结果将增加材料科学和电气工程几个领域的核心知识，从而为反铁磁性层状半导体的应用带来变革性的影响。本项目的智力优势包括：了解声子和磁振子带结构，以及它们随厚度、应变和电偏置的变化；二维反铁磁半导体薄膜中nsamel温度控制的实验数据在栅极和应变作用下调整AFM半导体相变的机制和方法；通过控制二维反铁磁半导体中的电子、声子和磁振子状态来实现新器件功能的创新方法。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 DescriptionThis research addresses the properties of a new class of ultra-thin quasi-two-dimensional semiconductors with intrinsic magnetic properties. The exotic properties of this new class of semiconductors make them particularly interesting for fundamental science research and practical applications. The investigators will explore the electronic, magnetic, and thermal properties of these unique materials with thicknesses of a few-atomic layers only. The PIs will also investigate the potential of these materials for use in devices with novel functionality that operate at high speed with low-energy dissipation. This research aligns with the Nation’s need for the development and research of novel semiconductor materials and devices under the recent CHIPS and Science Act. The interdisciplinary nature of the project will facilitate the involvement of students in the proposed research and contribute to undergraduate and graduate STEM education. The project team has developed a detailed Broadening Participation Plan that will impact the K-12, undergraduate, and graduate education of minorities underrepresented in STEM fields.Technical DescriptionTransition-metal phospho-trichalcogenides span a wide variety of compounds with different electronic, magnetic, and phonon properties. These materials are one of a few van der Waals layered structures which can have intrinsic antiferromagnetism, even at mono-layer thickness. The band gap of these materials varies from ~1.3 eV to ~3.5 eV based on the type of its transition- metal element. Theory suggests that the application of gate bias and strain can induce phase transitions in these materials, changing their properties. While electrical insulators and conductors with AFM spin order have been studied extensively, little is known experimentally about antiferromagnetic layered semiconductors. This project aims to investigate the electron, phonon, and magnon properties of these unique materials at single- and few-layer structures, and to assess the possibilities of controlling their properties for enabling novel device functionalities. To achieve these goals, various types of these compounds will be synthesized and characterized using cryogenic micro – Brillouin – Raman spectroscopy, and electrical and thermal transport measurements. The results of this interdisciplinary research will add to the core knowledge in several areas of material science and electrical engineering, thereby delivering a transformative impact for applications of antiferromagnetic layered semiconductors. The intellectual merit of this project include knowledge of phonon and magnon band structures, and their modification with the thickness, strain, and electric bias; experimental data for controlling the Néel temperature in two- dimensional antiferromagnetic semiconductor films; mechanisms and methods for tuning the phase transitions in AFM semiconductors under the action of gate and strain; innovative approaches for enabling novel device functionalities via control of the electron, phonon, and magnon states in two-dimensional antiferromagnetic semiconductors.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.