基于声子局域共振机制调控分支型纳米带热输运性质的研究

The study of thermal transport properties in nanostructures is crucial for their applications in electronic devices for information and new energy-conversion devices. There are normally two approaches to manipulate the thermal transport properties of nanostructures: one is changing anharmonic phonon scattering (particle-like) and the other is realizing coherent phonon transport (wave-like). However, both of them have obvious limitations, therefore it is urgent to explore new physical mechanisms and regulation schemes. In this project, the influence of phonon local resonance on heat conduction in branched nanoribbons will be systematically studied by nonequilibrium Green's-function method and molecular dynamics simulations, as well as lattice kinetic theory. We will focus on: (1) investigating the effects of geometry size, branch configuration and ambient temperature etc. on thermal conductivity in branched nanoribbons to ascertain the best parameters of the resonance intensity; (2) understanding the intrinsic relevance between various phonon scattering mechanisms such as vacancy scattering, impurity scattering, stress scattering etc. and phonon local resonance mechanism, exploring the novel phenomenon of thermal transport in branched nanoribbons under the synergism of phonon scattering—local resonance, and establishing a physical model for quantitatively distinguishing the contribution from two kinds of mechanisms to thermal conductivity; (3) designing thermoelectric devices and thermal management devices on the base of branched nanoribbons. This project will be helpful for improving the theory of phonon transport, and will provide the scientific evidence for regulating thermal transport properties in nanostructures.

研究热输运性质对纳米结构在电子信息和新能源器件方面的应用至关重要。通过控制声子的非谐散射(粒子性)或实现相干声子输运（波动性)可以调控纳米结构的热输运性质，但两者都存在明显的局限性，亟需探索新的物理机制和调控方案。本项目拟采用非平衡格林函数方法、分子动力学模拟，结合晶格动力学理论，系统地研究声子局域共振机制对分支型纳米带热传导的影响，重点探索：(1)几何尺寸、分支构型、环境温度等因素对体系热导率的影响，以确定声子共振强弱的最佳参数范围；(2)分析空位散射、杂质散射、应力场散射等散射机制与声子局域共振机制的内在关联，研究在声子散射—局域共振协同作用下分支型纳米带体系中的新奇热输运现象，并建立定量区分两类机制对热导率贡献的物理模型，实现对全频域声子输运调控的目的；(3)基于分支型纳米带的热电和热管理器件的理论设计。本项目的开展有助于完善声子输运理论，为调控纳米结构热输运性质提供科学依据。

通过声子粒子性（散射）或声子波动性（干涉和共振）可实现微纳结构热输运性质的调控，但两者都存在局限性，亟需探索新的物理机制和调控思路。本项目以分子动力学模拟和基于第一性原理的非平衡格林函数方法为基础，(1)研究了分支构型对graphenylene纳米带声子输运的影响规律，并探索了如何利用这种分支构型引入的声子局域共振增强体系的热电优值；(2)研究了空位缺陷及外界应力对三维graphene中各向异性热输运的调控，并基于声子态密度分析揭示热导率各向异性系数与声子模式耦合程度的本构关系；(3)依据实验上自组装graphene/BN范德华异质结，通过引入声子过滤效应设计出性能优良的热整流器与负微分热阻器，并给出了性能参数和物理模型；(4)鉴于第三代半导体优异物性与广泛应用前景，探究了GaN基器件中高热导率基底材料与界面热输运的调控机制；(5)对碳纳米材料及其异质结构中热输运机理与声子调控总结。我们的研究为全频域声子输运调控提供了重要的思路，对热电/热器件性设计具有理论参考价值。