Phonon transport in the nano-system of Si and SiGe films with Ge nanodots and approach to ultralow thermal conductivity,Nanoscale

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Phonon transport in the nano-system of Si and SiGe films with Ge nanodots and approach to ultralow thermal conductivity
Nanoscale ( IF 5.8 ) Pub Date : 2021-2-25 , DOI: 10.1039/d0nr08499a
Tatsuhiko Taniguchi _{1,

2,

3,

4} , Tsukasa Terada _{1,

2,

3,

4} , Yuki Komatsubara _{1,

2,

3,

4} , Takafumi Ishibe _{1,

2,

3,

4} , Kento Konoike _{1,

2,

3,

4} , Atsushi Sanada _{1,

2,

3,

4} , Nobuyasu Naruse _{4,

5,

6,

7} , Yutaka Mera _{4,

5,

6,

7} , Yoshiaki Nakamura _{1,

2,

3,

4}

Affiliation

Phonon transport in the nano-system has been studied using well-designed nanostructured materials to observe and control the interesting phonon behaviors like ballistic phonon transport. Recently, we observed drastic thermal conductivity reduction in the films containing well-controlled nanodots. Here, we investigate whether this comes from the interference effect in ballistic phonon transport by comparing the thermal properties of the Si or Si_0.75Ge_0.25 films containing Ge nanodots. The experimentally-obtained thermal resistance of the nanodot layer shows peculiar nanodot size dependence in the Si films and a constant value in the SiGe films. From the phonon simulation results, interestingly, it is clearly found that in the nanostructured Si film, phonons travel in a non-diffusive way (ballistic phonon transport). On the other hand, in the nanostructured SiGe film, although simple diffusive phonon transport occurs, extremely-low thermal conductivity (∼0.81 W m⁻¹ K⁻¹) close to that of amorphous Si_0.7Ge_0.3 (∼0.7 W m⁻¹ K⁻¹) is achieved due to the combination of the alloy phonon scattering and Ge nanodot scattering.

中文翻译：

具有Ge纳米点的Si和SiGe薄膜纳米系统中的声子传输及其超低导热性的方法

已经使用精心设计的纳米结构材料研究了纳米系统中的声子传输，以观察和控制有趣的声子行为，例如弹道声子传输。最近，我们观察到含有良好控制的纳米点的薄膜的热导率急剧降低。在这里，我们通过比较Si或Si _0.75 Ge _0.25的热性质，研究这是否来自弹道声子传输中的干扰效应。含有Ge纳米点的薄膜。实验获得的纳米点层的热阻在Si膜中显示出特殊的纳米点尺寸依赖性，而在SiGe膜中显示出恒定值。有趣的是，从声子模拟结果可以清楚地发现，在纳米结构的Si膜中，声子以非扩散方式传播（弹道声子传输）。另一方面，在纳米结构的SiGe膜中，尽管发生了简单的扩散声子传输，但是极低的热导率（〜0.81 W m ^-1 K ^-1）接近非晶硅_0.7 Ge _0.3（〜0.7 W m ^-1）由于合金声子散射和Ge纳米点散射的组合而获得了K ^-1）。

更新日期：2021-02-25

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