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Ultralow Thermal Conductivity of Single-Crystalline Porous Silicon Nanowires

机译：单晶多孔硅纳米线的超低导热性

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摘要

Porous materials provide a large surface-to-volume ratio, thereby providing a knob to alter fundamental properties in unprecedented ways. In thermal transport, porous nanomaterials can reduce thermal conductivity by not only enhancing phonon scattering from the boundaries of the pores and therefore decreasing the phonon mean free path, but also by reducing the phonon group velocity. Herein, a structure-property relationship is established by measuring the porosity and thermal conductivity of individual electrolessly etched single-crystalline silicon nanowires using a novel electron-beam heating technique. Such porous silicon nanowires exhibit extremely low diffusive thermal conductivity (as low as 0.33 W m(-1) K-1 at 300 K for 43% porosity), even lower than that of amorphous silicon. The origin of such ultralow thermal conductivity is understood as a reduction in the phonon group velocity, experimentally verified by measuring the Young's modulus, as well as the smallest structural size ever reported in crystalline silicon (<5 nm). Molecular dynamics simulations support the observation of a drastic reduction in thermal conductivity of silicon nanowires as a function of porosity. Such porous materials provide an intriguing platform to tune phonon transport, which can be useful in the design of functional materials toward electronics and nanoelectromechanical systems.
机译：多孔材料提供了很大的表面积与体积之比，从而提供了一种以前所未有的方式改变基本特性的旋钮。在热传输中，多孔纳米材料不仅可以通过增强声子从孔边界的散射来降低导热率，从而降低声子的平均自由程，还可以通过降低声子基团速度来降低导热率。在本文中，通过使用新颖的电子束加热技术测量单独的化学蚀刻的单晶硅纳米线的孔隙率和导热率来建立结构-特性关系。这样的多孔硅纳米线表现出极低的扩散热导率（对于300％的孔隙率，在300 K时低至0.33 W m（-1）K-1），甚至低于非晶硅。这种超低导热系数的起因是声子基团速度的降低，通过测量杨氏模量以及晶体硅中最小的结构尺寸（<5 nm）进行了实验验证。分子动力学模拟支持观察到硅纳米线的热导率随孔隙率的急剧下降。此类多孔材料提供了一个有趣的平台，可调节声子的传输，这对于设计功能材料朝电子学和纳米机电系统很有用。

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  • 来源
    《Advanced Functional Materials》 |2017年第40期|1702824.1-1702824.8|共8页
  • 作者

    Zhao Yunshan; Yang Lina; Kong Lingyu; Nai Mui Hoon; Liu Dan; Wu Jing; Liu Yi; Chiam Sing Yang; Chim Wai Kin; Lim Chwee Teck; Li Baowen; Thong John T. L.; Hippalgaonkar Kedar;

  • 作者单位

    Natl Univ Singapore, Dept Elect & Comp Engn, Singapore 117583, Singapore;

    CALTECH, Dept Mech Engn, Pasadena, CA 91125 USA;

    Natl Univ Singapore, Dept Elect & Comp Engn, Singapore 117583, Singapore|Natl Univ Singapore, Grad Sch Integrat Sci & Engn, Singapore 117456, Singapore;

    Natl Univ Singapore, Mechanobiol Inst, Singapore 117411, Singapore;

    Natl Univ Singapore, Dept Elect & Comp Engn, Singapore 117583, Singapore|Natl Univ Singapore, Grad Sch Integrat Sci & Engn, Singapore 117456, Singapore;

    Agcy Sci Technol & Res, Inst Mat Res & Engn, 08-03,2 Fusionopolis Way, Singapore 138634, Singapore;

    Agcy Sci Technol & Res, Inst Mat Res & Engn, 08-03,2 Fusionopolis Way, Singapore 138634, Singapore;

    Natl Univ Singapore, Dept Elect & Comp Engn, Singapore 117583, Singapore;

    Natl Univ Singapore, Mechanobiol Inst, Singapore 117411, Singapore|Natl Univ Singapore, Dept Biomed Engn, Singapore 117576, Singapore;

    Univ Colorado, Dept Mech Engn, Boulder, CO 80309 USA;

    Natl Univ Singapore, Dept Elect & Comp Engn, Singapore 117583, Singapore;

    Agcy Sci Technol & Res, Inst Mat Res & Engn, 08-03,2 Fusionopolis Way, Singapore 138634, Singapore;

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  • 正文语种 eng
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  • 关键词

    electron-beam technique; molecular dynamics; porous silicon nanowires; thermal conductivity; Young's modulus;

    机译：电子束技术分子动力学多孔硅纳米线导热系数杨氏模量;

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