Probing Highly Non-equilibrium Thermal Transport in Nanostructures and Devices

CBET-1336968 PI：Li Shi（U Texas，Austin）在纳米电子器件、激光材料加工和热输运测量中，不同的电子和声子群可以被驱动出局部热平衡。更好地理解高度非平衡输运现象对于设计具有增强性能和可靠性的下一代器件和材料结构是必要的。然而，目前的实验能力不足以探测这些不同能量激发的局部温度。尽管最近在扫描热显微镜（SThM），红外光谱和显微拉曼光谱的进展，有一个缺乏的实验方法来解决的局部温度的声学声子占主导地位的热传导，以及低频声学声子，可能在弹道输运制度的纳米结构。本研究的目的是探讨新的实验方法，探测在纳米结构和设备的高度非平衡输运过程中的声学声子的局部温度。待研究的技术包括一种新的方法，基于微布里渊光散射（BLS）探测局部温度的低频（0.5 GHz至100？s GHz）的声学声子，具有亚微米的空间分辨率。基于玻璃中局部声学声子温度的初步BLS测量，将进一步研究这种技术用于探测电偏置或光激发的硅纳米结构中的局部声学声子温度。所获得的声学声子温度将与那些测量的显微拉曼光谱，红外光谱，和SThM量化电子，声学和光学声子之间的局部非平衡。演示的微BLS技术作为一个热显微镜工具，低频声子将是有价值的实验热输运研究社区。同时，测量数据可以被理论和计算热输运研究人员用来更好地理解几个有趣的和重要的非平衡输运现象。这种理解可以影响纳米电子器件，激光材料加工和热测量技术的进一步发展。此外，这项研究将为学生提供最先进的实验技术培训机会，并为本科生和研究生课程提供新的示例材料。它还将产生新的演示材料，用于外展活动，吸引来自代表性不足群体的学生从事工程和科学专业，并将大学研究成果展示给德克萨斯州的K-12学生，家长和教师。

CBET-1336968PI: Li Shi (U Texas, Austin)Different electron and phonon populations can be driven out of local thermal equilibrium in nanoelectronic devices, laser materials processing, and thermal transport measurements. A better understanding of the highly non-equilibrium transport phenomena is necessary for the design of next-generation devices and material structures with enhanced performance and reliability. However, current experimental capabilities are inadequate for probing local temperatures of these different energy excitations. Despite the recent progresses in scanning thermal microscopy (SThM), infrared spectroscopy, and micro-Raman spectroscopy, there is a lack of experimental methods for resolving the local temperature of the acoustic phonons that dominate heat conduction, as well as low-frequency acoustic phonons that may be in the ballistic transport regime in nanostructures. The objective of this research is to investigate new experimental methods for probing the local temperature of acoustic phonons during highly non-equilibrium transport processes in nanostructures and devices. The techniques to be investigated include a new method based on micro-Brillouin light scattering (BLS) for probing the local temperature of low-frequency (0.5 GHz to 100?s GHz) acoustic phonons with sub-micron spatial resolution. Based on preliminary BLS measurements of local acoustic phonon temperatures in glass, this technique will be investigated further for probing the local acoustic phonon temperature in silicon nanostructures that are either electrically biased or optically excited. The obtained acoustic phonon temperature will be correlated with those measured by micro-Raman spectroscopy, infrared spectroscopy, and SThM to quantify local non-equilibrium between electrons, acoustic and optical phonons.The demonstration of the micro-BLS technique as a thermal microscopy tool for low-frequency phonons will be of value for the experimental thermal transport research community. Meanwhile, the measurement data can be used by theoretical and computational thermal transport researchers to establish a better understanding of several intriguing and important non-equilibrium transport phenomena. Such understanding can impact further advances in nanoelectronic devices, laser materials processing, and thermal measurement techniques. In addition, this research will provide student training opportunities in state-of-the-art experimental techniques, and result in new example materials for undergraduate and graduate courses. It will also generate new demonstration materials to be used in outreach activities for attracting students from underrepresented groups to engineering and science professions, and for exposing university research to K-12 students, parents, and teachers in Texas.