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首页> 外文期刊>Physical review >Effects of vacancy defects on thermal conductivity in crystalline silicon: A nonequilibrium molecular dynamics study
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Effects of vacancy defects on thermal conductivity in crystalline silicon: A nonequilibrium molecular dynamics study

机译：空位缺陷对晶体硅热导率的影响：非平衡分子动力学研究

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摘要

We examine the effects of vacancy defects on thermal conductivity in bulk crystalline silicon (c-Si) using nonequilibrium molecular dynamics simulations. While most vacancies are thought to remain in the form of clusters in bulk c-Si, recent theoretical studies have predicted that small vacancy clusters energetically prefer to be fourfold coordinated by nullifying dangling bonds. Hence, in this work, we consider three different-sized fourfold vacancy clusters, tetra-(V_4), hexa- (V_6), and dodeca-vacancy (V_12), with particular interest in studying how phonon transport is affected by vacancy concentration and cluster size in association with fourfold coordination-induced lattice distortions. Our simulations show that thermal conductivity (k) rapidly drops with vacancy concentration (n_ν) with an inverse power-law relation (k ∝nν_ν~(-α), with α ≈ 0.7-1.1 depending on cluster size); the presence of 1.5% vacancies leads to a 95% reduction in k as compared to the defect free c-Si. When n_v is low (<1%), the reduction of k with n_v appears to be a function of cluster size, and the size effect becomes unimportant as n_v increases above 1%. We discuss the correlation between phone scattering and cluster size, based on the relative rates of phonon-vacancy scattering associated with defect-induced strain fields. We also estimate the dependence of phonon mean free path on vacancy concentration and cluster size.
机译：我们使用非平衡分子动力学模拟研究了空位缺陷对体晶硅（c-Si）导热系数的影响。尽管大多数空位被认为以块状c-Si的簇的形式存在，但是最近的理论研究预测，小的空位簇在能量上更倾向于通过消除悬空键来进行四重协调。因此，在这项工作中，我们考虑了三个不同大小的四倍空位簇，四-（V_4），六-（V_6）和十二空位（V_12），特别关注研究声子迁移如何受空位浓度和团簇大小与四重配位引起的晶格畸变有关。我们的模拟表明，导热系数（k）随着空位浓度（n_ν）迅速下降，且与幂律关系成反比（k ∝nν_ν〜（-α），α≈0.7-1.1，取决于簇的大小）；与无缺陷的c-Si相比，1.5％的空位的存在会导致k降低95％。当n_v低（<1％）时，k随n_v的减少似乎是簇大小的函数，并且当n_v增加到1％以上时，大小效应变得不重要。我们基于与缺陷诱导的应变场相关的声子空位散射的相对速率，讨论了电话散射与簇大小之间的相关性。我们还估计了声子平均自由程对空位浓度和簇大小的依赖性。

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  • 来源
    《Physical review》 |2011年第12期|p.125202.1-125202.7|共7页
  • 作者

    Yongjin Lee; Sangheon Lee; Gyeong S. Hwang;

  • 作者单位

    Department of Chemical Engineering, University of Texas, Austin, Texas 78712, USA;

    Department of Chemical Engineering, University of Texas, Austin, Texas 78712, USA;

    Department of Chemical Engineering, University of Texas, Austin, Texas 78712, USA;

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  • 正文语种 eng
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  • 关键词

    thermal properties of crystalline solids;

    机译：结晶固体的热性质;

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