Collaborative Research: Spectroscopy of Phonon Scattering Cross-Sections in Nanomaterials from Time-Resolved Surface Wave Fields

热量从一个物体到另一个物体的传递在当代技术中具有基础性的作用。在能源、运输、制造、生物医疗设备、信息处理和通信方面的进步往往依赖于系统与环境之间工程热传递的改善。例如，提高数据中心的能效，在一定程度上需要改善其电子元件的热管理。热传递技术的影响虽然不经常可见，但在现代社会中却无处不在。当热流在三维存在的(典型的)材料和只跨越两维空间的新型材料之间流动时，一个重要的新问题就出现了。最近成功地制备了这种二维材料，为研究这一重要系统铺平了道路。然而，目前用于研究热传输的工具在探索这种复杂的传输现象时遇到了问题。这个项目开发了专门的实验工具，结合模拟来探索这种连接三维和二维材料的热传递。此外，运输过程的简化模型有助于未来电子、传感器和能源技术的设计和开发。该项目还培训未来的本科生和研究生工程师，包括那些在技术劳动力中比例较低的工程师，学习先进的计量和模拟技术，并帮助保持美国工业劳动力的技术优势。该项目开发的数据和模型通过同行评议的出版物、技术会议和专门的在线数据库传播。与这项研究相关的基本概念在对K-12学校的外联工作中以及通过大学对普通公众的开放活动中得到了展示。该项目的科学目标是阐明声子在成分和维度不同的材料之间通过结间传输的微观物理，并开发用于设计的简化模型。具体地说，该项目开发了一种半经验方法，用于直接测量二维材料(如石墨烯)和三维材料(如硅或氧化硅)交界处的声子散射截面，而不需要解释导电性或导电性。这推动了实验纳米级热传输的技术水平超越了流行的热导/电导测量方法。

The transfer of heat from one body to another has a fundamental role in contemporary technology. Advancements in energy, transportation, manufacturing, biomedical devices, information processing and communication often rely on improvements in engineering heat transfer between a system and its environment. For instance, increasing the energy efficiency of data centers, in part requires improved heat management of their electronic components. The impact of heat transfer technology, though not often visible is nevertheless ubiquitous in modern society. An important new problem arises when the heat flow is between a (typical) material that exists in three dimensions and a novel material that spans space in only two dimensions. Recent success in fabricating such two-dimensional materials paves the way for investigating this important system. However, current tools for investigating heat transport run into problems when probing such complex transport phenomena. This project develops specialized experimental tools in conjunction with simulations to probe such heat transfer that bridges three- and two-dimensional materials. Further, simplified models of the transport process aid the design and development of future electronics, sensors and energy technologies. The project also trains future undergraduate and graduate engineers, including those underrepresented in the technical workforce, in advanced metrology and simulations and helps maintain the technical edge of the US industrial workforce. Data and models developed in the project are disseminated through peer-reviewed publications, technical conferences, and specialized online databases. Elementary concepts associated with the research are demonstrated in outreach efforts to K-12 schools and through university open houses to the general public. The scientific goal of the project is to elucidate the microscopic physics of phonon transport across junctions between materials of dissimilar composition and dimensionality and develop simplified models to be used in design. Specifically, the project develops a semi-empirical approach for directly measuring the phonon scattering cross-section at the junction between a two-dimensional material such as graphene and a three-dimensional material such as silicon or silicon oxide, without any requirement for interpreting conductivity or conductance. This advances the state of art of experimental nanoscale thermal transport beyond the prevalent thermal conductivity/conductance measurement approaches.