Optical Characterization of Nanoscale Thermal Transport

0854118克罗宁本研究的目的是测量和发展的理解纳米级的热传输现象，使用光学，非接触式测量技术。在这项研究中，显微拉曼光谱将用于测量纳米线，纳米管和石墨烯中的热流。将从拉曼光谱中的校准下移以亚微米空间分辨率确定沿沿着单个悬浮纳米结构的温度分布。温度梯度将通过激光照射、微制造加热器以及通过纳米结构本身运行高电流来产生。这些光学的、非接触的方法1.）消除热接触电阻和通过衬底的热短路的影响，2.）区分扩散声子输运和弹道声子输运，以及3.）能够以纳秒分辨率执行时间分辨测量。通过测量悬浮纳米结构的加热和冷却时间，将获得它们的热扩散率。这些测量将以前所未有的精度和准确度为纳米结构的接触热阻和热导率提供可靠的值。用于测量热传输的常规方法不能提供微米和纳米尺度上的可靠结果，因为跨接触的大的温度降，这不能从测量中确定或排除。因此，建议的光学方法，更适合于测量纳米尺度的热输运比传统的技术。此外，这些技术的非接触、非破坏性性质使得能够通过其他手段（例如透射电子显微镜（TEM）和电子传输测量）进一步表征相同的单个纳米结构。智力优势：新的测量技术将量化的几个热参数，迄今为止，逃避目前的最先进的纳米级热传输测量，如激光的每个入射光子产生的热量。这些技术也使我们能够研究几个纳米级的热传输现象，仍然知之甚少，只有理论上的研究。更广泛的影响：了解纳米结构中的热传输对于设计和优化高速电子产品非常重要。这对于在未来5至10年内推广摩尔定律至关重要。从拟议的工作的结果将使热工程在纳米尺度上提供现实的热管理解决方案，极高的功率密度电路。利用低维度的改进热电材料可以通过从废热中回收电力来显着影响我们依赖能源的经济。这项提案中开发的新技术可以很容易地被该领域的许多其他科学家和工程师应用，并可能导致其他科学和技术领域的创新。对洛杉矶地区高中教师的推广计划将向代表性不足的学生介绍结果，更重要的是，这项研究和洛杉矶地区大学的其他前沿研究的兴奋。本科生的研究项目和新课程，将创造力融入科学课程，将培养出能够应对纳米技术下一代挑战的熟练和知识渊博的学生。

0854118Cronin The objective of this research is to measure and develop an understanding of nanoscale thermal transport phenomena using optical, non-contact measurement techniques. In this study, micro-Raman spectroscopy will be used to measure heat flow in nanowires, nanotubes, and graphene. The temperature profile along individual suspended nanostructures will be determined with sub micron spatial resolution from the calibrated downshifts in the Raman spectra. Temperature gradients will be created by laser irradiation, micro-fabricated heaters, and by running high electric currents through the nanostructures themselves. These optical, non-contact methods 1.) eliminate the effect of thermal contact resistance and thermal shorting through the substrate, 2.) differentiate between diffusive and ballistic phonon transport, and 3.) enable time resolved measurements to be performed with nanosecond resolution. By measuring the heating and cooling times of suspended nanostructures, their thermal diffusivity will be obtained. These measurements will provide reliable values for the thermal contact resistance and the thermal conductivity of nanostructures with unprecedented precision and accuracy. Conventional approaches for measuring thermal transport do not provide reliable results on the micron and nanometer scales because of the large temperature drops across the contacts, which cannot be determined or excluded from the measurement. The proposed optical methods are, therefore, more suitable for measuring nanometer scale thermal transport than conventional techniques. Furthermore, the non contact, non destructive nature of these techniques enables further characterization of the same individual nanostructure by other means, such as transmission electron microscopy (TEM) and electron transport measurements. Intellectual Merit: The novel measurement techniques will quantify several thermal parameters that have, so far, eluded current state of the art nanoscale thermal transport measurements, such as heat generated per incident photon of laser light. These techniques also allow us to investigate several nanoscale thermal transport phenomena that remain poorly understood and have only been theoretically investigated. Broader Impacts: Understanding thermal transport in nanostructures is important for designing and optimizing high speed electronics. This is essential for extending Moore's law over the next 5 to 10 years. Results from the proposed work will enable thermal engineering on the nanometer scale to provide realistic thermal management solutions for extremely high power density circuits. Improved thermoelectric materials that exploit the low dimensionality could significantly impact our energy dependent economy by recovering electricity from waste heat. The novel techniques developed in this proposal can be readily applied by many other scientists and engineers working in the field and will likely lead to innovations in other fields of science and technology. The outreach program to Los Angeles area high school teachers will introduce underrepresented students to the results and, more importantly, the excitement of this research and other cutting edge research at universities in the Los Angeles area. Research projects for undergraduate students and the new curriculum, which integrates creativity into a science based course, will produce skilled and knowledgeable students able to address the next generation of challenges in nanotechnology.