IDR: Molecular engineering of thermal interfaces

avik Ghosh, Patrick E. Hopkins & Lloyd R. Harriott固体材料的导热工程对于广泛的应用至关重要，从电子产品的热管理到发电，再到信息技术。许多这些现代系统包括材料和结构的特征长度尺度在几十到几百纳米的顺序。在这些长度尺度上，主要的热阻出现在两种材料之间的界面上，导致纳米系统的热性能在很大程度上取决于这些固体界面。因此，为了能够准确地控制纳米系统的热性能，开发控制和调节界面间热传递的机制至关重要。为了实现这一目标，该项目将探索两个固体层之间的热传输，由在其界面生长的有机分子的特性控制。通过宽频带、空间局域的分子振动与窄频带、空间局域的衬底声子之间的相互作用，在分子尺度上对材料界面的组成、形态和声子带结构进行系统、有针对性的工程设计，以实现界面热导的高度可调性。一个结合和紧密耦合的理论和实验研究将启动探索各种类型的自组装单层有机分子（SAM）作为热界面材料，作为SAM和衬底质量和材料等变量的函数，利用自组装和最重要的是丰富多样的功能化学。热输运将通过时域热反射来测量。实验结果将与利用非平衡格林函数形式的从头算建模工作紧密结合。在这个项目中发现的科学也将广泛应用于通用金属和半导体界面系统的热工。这项工作的智力价值在于发展了对纳米级界面热性质的新理解。这将证明对热流的原子控制至关重要。通过理论和实验之间的紧密协同，本研究将结合分子热流背后的原子概念和固体体热流概念，从最基本的微观极限增强对热流和耗散的理解。它将跨越学科、材料，并最终跨越基础科学和技术应用之间的界限。准确，良好的基准模拟将解决带对准和固体分子界面化学的关键作用。实验将侧重于制造定义良好的基于sam的界面结构，通过分子化学，表征和热边界电阻测量来修改它们，目标是创建高质量的可调热边界。这个项目更广泛的影响包括工程相关性和教育/推广组件。所获得的知识将引入纳米尺度科学的新概念：热界面控制和通过分子化学工程。纳米级热管理和控制将给科学、技术和经济带来颠覆性的变化，从卓越的质量和量身定制的热涂层和热电冰箱，到数十亿美元的半导体行业更好的热管理。教育和推广活动将包括在弗吉尼亚大学开设纳米课程，在thermalHUB上创建教程，通过pi教授的课程中的热传输实验室将研究和教育结合起来，组织有本科生参与的分子传热会议，通过REU项目吸引少数民族本科生参加暑期项目，并利用弗吉尼亚大学工程多样性中心培训中学教师进行课程开发。

IDR: Molecular Engineering of Thermal Interfaces 1134311Avik Ghosh, Patrick E. Hopkins & Lloyd R. Harriott Engineering the conduction of heat in solid materials is essential for a wide array of applications, ranging from thermal management of electronics, to power generation, to information technology. Many of these modern systems include materials and structures with characteristic length scales on the order of tens to hundreds of nanometers. At these length scales, the major thermal resistances arise at the interfaces between two materials, leading to thermal properties of nanosystems that are strongly dictated by these solid interfaces. Therefore, it is of utmost importance to develop mechanisms of controlling and tuning the thermal transport across interfaces to be able to accurately manage the thermal properties of nanosystems. To achieve this, this project will explore thermal transport between two solid layers, controlled by properties of organic molecules grown at their interface. Through the interplay between the wide-band, spatially localized molecular vibrons and the narrow-band, spatially delocalized substrate phonons, the project will aim for the systematic and targeted engineering of the composition, morphology and phonon bandstructures of material interfaces at the molecular scale in order to achieve a high degree of tunability of the interfacial thermal conductance. A combined and closely coupled theoretical and experimental study will be launched exploring various classes of self-assembled monolayers (SAMs) of organic molecules as thermal interfacial materials, as a function of variables such as the SAM and substrate quality and material, utilizing self-assembly and most importantly a rich variety of functional chemistry. The thermal transport across the wide array of SAM-based interfaces will be measured with time domain thermoreflectance. The experimental results will be strongly coupled with ab initio modeling efforts utilizing Nonequilibrium Green's Functions formalisms. The science discovered in this project will also be widely applicable to thermal engineering of generic metal and semiconductor interfacial systems.The intellectual merit of this proposed work is in the development of a new understanding of nanoscale interfacial thermal properties. This will prove critical for the atomistic control of heat flow. Through the close synergy between theory and experiment, the study will enhance the understanding of heat flow and dissipation at their most fundamental, microscopic limits, combining atomistic concepts behind molecular heat flow with solid state concepts of bulk heat flow. It will bridge disciplines, materials, and ultimately the boundary between fundamental science and technological applications. Accurate, well benchmarked simulations will address the critical role of band-alignment and chemistry at the solid-molecular interface. Experiments will focus on fabrication of well-defined SAM-based interfacial structures, modifying them through molecular chemistry, characterization and measurement of thermal boundary resistances with a goal towards creating high quality tunable thermal boundaries. The broader impacts of this project include both engineering relevance and education/outreach components. The knowledge gained will introduce a new concept in nanoscale science: thermal interface control and engineering via molecular chemistry. Nanoscale thermal management and control will bring about disruptive changes to science, technology and economics, ranging from superior quality and tailor-made thermal coatings and thermoelectric refrigerators, to better heat management in the multi-billion dollar semiconductor industry. Educational and outreach activities will involve creation of a nano-curriculum at UVa, tutorial creation on the thermalHUB, integration of research and education through thermal transport labs in courses taught by the PIs, conference organization of session on molecular heat transfer with undergraduate involvement, engaging minority undergraduate students for summer projects through the REU program and training middle school teachers for curriculum development utilizing UVA's Center for Diversity in Engineering.