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

非技术描述本研究旨在研究一类具有本征磁性的新型超薄准二维半导体的性质。这类新半导体的奇特性质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仅有几个原子层厚度的独特材料的电子、磁性和热学性质。PI还将研究这些材料在具有新功能的设备中使用的潜力，这些设备以高速度和低能耗运行。这项研究符合国家根据最近的芯片和科学法开发和研究新型半导体材料和器件的需要。该项目的跨学科性质将促进学生参与拟议的研究，并为本科生和研究生STEM教育做出贡献。项目组已经制定了一项详细的扩大参与计划，该计划将影响STEM领域中代表性较低的少数族裔的K-12、本科和研究生教育。技术说明过渡金属磷三盐基化物跨越具有不同电子、磁性和声子性质的各种化合物。这些材料是少数几种范德华层状结构中的一种，即使在单层厚度的情况下，这些结构也可以具有固有的反铁磁性。根据过渡金属元素的类型不同，这些材料的带隙从~1.3 eV到~3.5 eV不等。理论表明，施加栅极偏压和应变可以在这些材料中诱导相变，从而改变它们的性质。虽然具有AFM自旋有序的电绝缘体和导体已经被广泛研究，但在实验上对反铁磁层状半导体的研究还很少。该项目旨在研究这些独特材料在单层和少层结构中的电子、声子和磁振子性质，并评估控制其性质以实现新器件功能的可能性。为了实现这些目标，将合成不同类型的化合物，并使用低温微布里渊-拉曼光谱以及电学和热输运测量对其进行表征。这一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，从而对反铁磁层状半导体的应用产生革命性的影响。该项目的智力价值包括：声子和磁振子能带结构的知识，以及它们随厚度、应变和电偏压的变化；二维反铁磁半导体薄膜中Néel温度控制的实验数据；AFM半导体在栅极和应变作用下相变的调谐机制和方法；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型器件功能的创新方法。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.