THERMAL TRANSPORT IN TWO-DIMENSIONAL SEMICONDUCTOR MATERIALS

半导体薄膜是所有现代电子设备的基本材料。近年来，由晶体单层原子或由几个晶体原子层堆叠而成的新型半导体薄膜被发现具有非凡的性能。这些新材料有望在信息技术、能源和医疗保健领域，甚至可能在量子技术领域创造新的设备。了解这些新材料中的热传输是很重要的，因为散热对器件性能有很大的影响。热输运也与能量转换过程密切相关，如热电和光伏。该项目将研究半导体材料中热传输的基本和重要问题，以实现这些材料和器件的热设计和热管理。拟议的项目是建立在研究者在热输运过程的广泛专业知识，特别是在热输运研究的实验方法的发展。该项目将采用先进的实验工具来研究以下基本问题：(1)半导体薄膜中电子和声子对热输运的单独贡献；(2)半导体中电子的电输运和热输运之间的关系；(3)半导体中热输运的双极扩散，特别是在低带隙二维半导体材料中。总的来说，这些研究将允许测量电热导率，声子电导率和总热导率，确定洛伦兹数的值，评估双极扩散的影响，并研究超快能量散射过程，这是能量传输过程的基础。实验工作将由计算研究补充，以提供对实验结果的见解。该研究成果将为微纳米材料和器件的热输运研究做出贡献，有助于提高对半导体中不同能量载体的热输运的基本认识，并为控制半导体器件中的热输运提供可能的手段。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。

Semiconductor thin films are building blocks for all modern electronics devices. In recent years, new semiconductor thin films consisting of crystalline single layer of atoms or stacks of a few crystalline atomic layers have been found to possess extraordinary properties. These new materials promise new devices in information technology, energy, and health care, and possibly in quantum technology. Understanding thermal transport in these new materials is important as heat dissipation has a large influence on the device performance. Thermal transport is also closely related to energy conversion processes such as thermoelectrics and photovoltaics. This project will investigate the fundamental and important issues of thermal transport in semiconductor materials to enable thermal design and thermal management in these materials and devices.The proposed project is built upon investigator’s extensive expertise in thermal transport processes, especially in the development of experimental methods for thermal transport research. The proposed project will employ advanced experimental tools to investigate the following fundamental problems: (1) the individual contributions of electrons and phonons to thermal transport in semiconductor thin films, (2) the relation between electrical and thermal transport by electrons in semiconductors, and (3) the bipolar diffusion which contributes to thermal transport in semiconductors, especially in low-bandgap two-dimensional semiconductor materials. Collectively, these studies will allow for measuring electric thermal conductivity, phonon conductivity, and total thermal conductivity, determining the value of the Lorenz number, evaluating the effect of bipolar diffusion, and investigating ultrafast energy scattering processes that are fundamental to the energy transport processes. The experimental work will be supplemented by computational studies to provide insights to the experimental results. The research outcome will contribute to many on-going studies in thermal transport in micro and nanoscale materials and devices, lead to much improved fundamental understandings of thermal transport by different energy carriers in semiconductors, and provide possible means to control thermal transport in semiconductor devices.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.