纳米多孔硅热导率降低的热流密度关系效应
Heat current anticorrelation effects leading to thermal conductivity reduction in nanoporous Si
摘要：
当前的纳米结构化策略集中在增加声子散射和减少整个光谱的声子的平均自由程。例如，在纳米多孔硅材料中，边界散射显著降低了热导率。在这项工作中，我们确定了一个不寻常的反射相关的镜面声子散射效应，这可能会导致额外的减少高达80%的特定纳米多孔几何形状的热导率。我们进一步发现的证据表明，这种效果有其起源于热捕获之间的大孔与狭窄的脖子。当热量被捕获在孔隙之间时，声子经历多次镜面反射，使得它们对热导率的贡献部分地被取消。我们发现这种效应在低温下取决于波矢。我们使用大规模的分子动力学模拟，波包分析，以及一个分析模型，以说明的关系效应，评估其对热导率的影响，并详细说明如何可以控制操纵纳米多孔材料中的声子输运。
英文摘要：
Prevailing nanostructuring strategies focus on increasing phonon scattering and reducing the mean-free-path of phonons across the spectrum. In nanoporous Si materials, for example, boundary scattering reduces thermal conductivity drastically. In this work, we identify an unusual anticorrelated specular phonon scattering effect which can result in additional reductions in thermal conductivity of up to ~ 80% for specific nanoporous geometries. We further find evidence that this effect has its origin in heat trapping between large pores with narrow necks. As the heat becomes trapped between the pores, phonons undergo multiple specular reflections such that their contribution to the thermal conductivity is partly undone. We find this effect to be wave-vector dependent at low temperatures. We use large-scale molecular dynamics simulations, wave packet analysis, as well as an analytical model to illustrate the anticorrelation effect, evaluate its impact on thermal conductivity, and detail how it can be controlled to manipulate phonon transport in nanoporous materials.
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