Phonon Transport Near and Across Seminductor Interfaces

该奖项支持与纳米结构材料中声子通过界面传输热能相关的理论和计算研究以及教育活动。 原子建模工具，包括晶格动力学计算，玻尔兹曼输运方程，分子动力学模拟和密度泛函理论计算，以及理论发展将被应用于解决声子传播和散射的条件下非常不同的存在于体相的基本问题。具体而言，PI的目的是：（1）推导出声子界面散射率的表达式。(2)通过预测界面附近的非体声子分布，解决不同边界热阻模型之间的差异。(3)证明密度泛函理论计算可用于为基于晶格动力学的边界热阻模型提供输入。然后，预测将被用来评估电子在金属-半导体界面热传输中的作用。(4)确定Bloch声子模式如何在从孤立界面到多界面到周期性超晶格的过渡中发展，包括界面物种混合的影响。这项研究与包含多层组件的技术重要系统的财富直接相关，例如场效应晶体管中的二氧化硅层，用于热电能量转换应用的硅锗和碲基超晶格，以及由GaAs、AlGaAs和GaN层构建的量子级联激光器和发光二极管。 与Jon Malen教授（卡内基梅隆大学）的互动将允许理论和计算预测与实验测量的直接比较。该项目将促进传热物理学新兴领域的教育：在载流子水平上研究热传输，即通过声子，光子，电子和流体粒子。将开设本科生选修课。 NanoHUB和thermalHUB这两个在线资源将用于传播一般信息和研究结果。 基于发现的讲座将在本科课程中开发和呈现，并通过基于爱丁堡的推广计划。非技术摘要该奖项支持与固-固界面传热相关的理论和计算研究以及教育活动。当这些界面之间的距离只有人类头发丝大小的千分之一到百万分之一时，就像计算机芯片和发光二极管中的界面一样，它们可以控制热阻。 高热阻使得难以去除热量，从而导致不期望的高操作温度。 此外，紧密间隔的接口的行为不同的接口是相距甚远，大多数以前的研究的主题。 PI将进行计算机模拟和理论计算，以考虑原子水平上的界面。将研究单个原子的运动，以确定能量如何流过界面。计算将在不同的精度水平上进行，其中一些基于量子力学，允许与实验结果进行比较。这项工作与包含多层组件的技术重要系统的财富有关，例如场效应晶体管，用于热电能量转换应用的由不同成分的周期性交替区域制成的材料，激光器和发光二极管。该项目将促进原子一级传热研究方面的教育。将开设本科生选修课。 NanoHUB和thermalHUB这两个在线资源将用于传播一般信息和研究结果。基于发现的讲座将在本科课程中开发和呈现，并通过基于爱丁堡的推广计划。

Technical SummaryThis award supports theoretical and computational research and educational activities related to the transport of thermal energy by phonons across interfaces in nanostructured materials. Atomistic modeling tools including lattice dynamics calculations, the Boltzmann transport equation, molecular dynamics simulations, and density functional theory calculations, as well as theoretical development will be applied to address fundamental questions regarding phonon propagation and scattering under conditions very different from what exists in the bulk phase. Specifically, the PIs aim to:(1) Derive an expression for the phonon-interface scattering rate.(2) Resolve the discrepancies between different thermal boundary resistance models by predicting the non-bulk-like phonon distributions that exist near an interface.(3) Demonstrate that density functional theory calculations can be used to provide the input for lattice-dynamics based thermal boundary resistance models. The predictions will then be used to assess the role of electrons in thermal transport across metal-semiconductor interfaces.(4) Identify how Bloch phonon modes develop in the transition from an isolated interface to multiple interfaces to a periodic superlattice, including the effect of interfacial species mixing.This research is immediately relevant to the wealth of technologically important systems that contain multi-layer components, such as the silica layer in a field-effect transistor, silicon-germanium and tellurium-based superlattices for thermoelectric energy conversion applications, and quantum cascade lasers and light emitting diodes built from layers of GaAs, AlGaAs, and GaN. Interactions with Professor Jon Malen (Carnegie Mellon University) will allow for direct comparison of the theoretical and computational predictions to experimental measurements.This project will promote education in the emerging field of heat transfer physics: the study of thermal transport at the carrier-level, i.e. via phonons, photons, electrons, and fluid particles. An undergraduate elective course will be developed. NanoHUB and thermalHUB, two online resources, will be used to disseminate general information and research findings. Discovery-based lectures will be developed and presented in undergraduate classes and through Pittsburgh-based outreach programs.Nontechnical SummaryThis award supports theoretical and computational research and educational activities related to heat transfer across solid-solid interfaces. When such interfaces are separated by distances of the order of one thousandth to one millionth the size of the human hair, as they are in computer chips and light-emitting diodes, they can dominate thermal resistance. High thermal resistance makes it difficult to remove heat, leading to undesirably high operating temperatures. Furthermore, closely spaced interfaces behave differently than interfaces that are far apart, the topic of most previous studies. The PI will perform computer simulations and theoretical calculations to consider interfaces at the atomic level. The motions of individual atoms will be studied so as to determine how energy flows across an interface. Calculations will be performed at different levels of accuracy, with some based on quantum mechanics, allowing for comparison to experimental results.The work is relevant to the wealth of technologically important systems that contain multi-layer components, such as field-effect transistors, materials made of periodically alternating regions of different compositions for thermoelectric energy conversion applications, lasers, and light emitting diodes. This project will promote education in the study of heat transfer at the atomic-level. An undergraduate elective course will be developed. NanoHUB and thermalHUB, two online resources, will be used to disseminate general information and research findings. Discovery-based lectures will be developed and presented in undergraduate classes and through Pittsburgh-based outreach programs.