Effects of metal silicide inclusion interface and shape on thermal transport in silicon nanocomposites
Effects of metal silicide inclusion interface and shape on thermal transport in silicon nanocomposites
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DOI：
10.1063/1.5099507
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发表时间：
2019-07
影响因子：
3.2
通讯作者：
Laia Ferrer-Argemi;Ziqi Yu;Jaeho Lee
中科院分区：
文献类型：
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作者：
Laia Ferrer-Argemi;Ziqi Yu;Jaeho Lee
虽然各种具有低导热率的硅纳米复合材料在热电应用中受到了广泛关注，但夹杂物界面和形状对热传输的影响仍不清楚。在这里，我们研究了硅纳米复合材料的热传输特性，其中金属硅化物夹杂物在硅内周期性排列。利用已知的声子色散关系和扩散失配模型，我们探索了不同硅化物-硅界面的影响，并使用蒙特卡罗射线追踪模拟，我们探索了硅化物夹杂物形状的影响。我们的研究表明，硅纳米复合材料的热导率可以降低到相同几何形状的纳米多孔硅的范围，具体取决于界面密度、晶体取向和声学失配。例如，当夹杂物密度高达12.5%且界面密度为7.5 μm−1时，[111]取向的CoSi2夹杂物比具有较低本征热导率的夹杂物材料（例如NiSi2）更有效地降低纳米复合材料的热导率。在本工作研究的硅化物夹杂材料中，Mn4Si7 由于低本征热导率和高声学失配的结合而导致纳米复合材料热导率最低。与宽间隔和对称的夹杂物（例如圆形）相比，窄间隔和不对称的夹杂物（例如三角形）在限制声子平均自由程和降低纳米复合材料热导率方面更有效。这些关于硅纳米复合材料中夹杂物界面和形状的热传输的发现将指导热电冷却和发电的最佳材料设计。
While various silicon nanocomposites with their low thermal conductivity have received much attention for thermoelectric applications, the effects of inclusion interface and shape on thermal transport remain unclear. Here, we investigate thermal transport properties of silicon nanocomposites, in which metal silicide inclusions are periodically arranged within silicon. Using the known phonon dispersion relations and the diffuse mismatch model, we explore the effects of different silicide-silicon interfaces, and using Monte Carlo ray tracing simulations, we explore the effects of silicide inclusion shapes. Our investigations show that the thermal conductivity of silicon nanocomposites can be reduced to the range of nanoporous silicon of the same geometry, depending on the interface density, crystal orientation, and acoustic mismatch. For instance, CoSi2 inclusions of [111] orientation can reduce the nanocomposite thermal conductivity more effectively than inclusion materials with lower intrinsic thermal conductivity, such as NiSi2, when the inclusion density is up to 12.5% with an interface density of 7.5 μm−1. Among the silicide inclusion materials investigated in this work, Mn4Si7 leads to the lowest nanocomposite thermal conductivity due to a combination of low intrinsic thermal conductivity and high acoustic mismatch. Compared to widely spaced and symmetric inclusions such as a circular shape, narrowly spaced and asymmetric inclusions such as a triangular shape are more effective in limiting the phonon mean free path and reducing the nanocomposite thermal conductivity. These findings regarding thermal transport in silicon nanocomposites with respect to inclusion interface and shape will guide optimal material designs for thermoelectric cooling and power generation.