论文标题
声子的两步修改平均自由路径，用于基于薄膜的纳米结构的热导率预测
Two-Step Modification of Phonon Mean Free Paths for Thermal Conductivity Predictions of Thin-Film-Based Nanostructures
论文作者
论文摘要
作为一种简单的超材料，通常在薄膜上制造纳米模式，以便可以操纵热传输。这些纳米结构的蚀刻侧壁通常由于纳米化过程中引入的表面缺陷而变得粗糙，而顶部和底部膜表面更加顺畅。在现有的分析模型中，尚未解决这些表面之间的对比，并且假定所有边界对于声子反射是扩散的。在本文中，提出了一种新的两步方法来解决此问题，以针对一般基于薄膜的结构的声子传输建模。在这种方法中，有效的平面声子平均自由路径（λ_FILM）首先从散装声子MFP进行修改，以解释顶部/底部膜表面的影响，并且可能会在低温温度下具有镜头声子反射的概率。该λ_FILM经过进一步修改，包括几乎完全扩散的声子散射的蚀刻侧壁散射。这样的两步声子平均自由路径修改几乎与频率依赖性的声子蒙特卡洛模拟蚀刻纳米线和代表性的纳米孔薄膜相同。这个简单而准确的分析模型可以应用于一般的基于薄膜的纳米结构，以结合正交方向的声子大小效应。
As one simple metamaterial, nanopatterns are often fabricated across a thin film so that the thermal transport can be manipulated. The etched sidewalls for these nanostructures are usually rough due to surface defects introduced during the nanofabrication, whereas the top and bottom film surfaces are smoother. In existing analytical models, the contrast between these surfaces has not been addressed and all boundaries are assumed to be diffusive for phonon reflection. In this paper, a new two-step approach to address this issue is proposed for phonon transport modeling of general thin-film-based structures. In this approach, the effective in-plane phonon mean free paths (Λ_Film) are first modified from the bulk phonon MFPs to account for the influence of the top/bottom film surfaces, with possibly enhanced probability of specular phonon reflection at cryogenic temperatures. This Λ_Film is further modified to include the scattering by etched sidewalls with almost completely diffusive phonon scattering. Such a two-step phonon mean free path modification yields almost identical results as frequency-dependent phonon Monte Carlo simulations for etched nanowires and representative nanoporous thin films. This simple yet accurate analytical model can be applied to general thin-film-based nanostructures to combine the phonon size effects along orthogonal directions.
