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arXiv 1805.00564cond-mat.mes-hall
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块体六方氮化硼的各向异性热输运

Anisotropic thermal transport in bulk hexagonal boron nitride

Puqing Jiang, Xin Qian, Ronggui Yang, Lucas Lindsay

摘要:

六方氮化硼(h-BN)作为石墨烯衍生体系的宽带隙类似物近年来受到极大关注。然而,h-BN的热输运性质,这可能是关键的设备的可靠性和功能,很少在实验和理论上研究。h-BN各向异性热导率的实验测量的主要挑战是通常h-BN单晶的样品尺寸对于传统测量技术来说太小,因为最先进的技术合成的h-BN单晶的横向尺寸仅高达2.5 mm,厚度高达200 μm。最近发展的时域热反射(TDTR)技术适合于测量这样小样品的各向异性热导率,因为它只需要50 × 50 μm2的小面积进行测量。由于高度各向异性的层状结构,本体h-BN中的热传输的精确原子建模也是具有挑战性的。在这里,我们利用多个调制频率的TDTR测量和声子Boltzmann输运方程的全尺度数值计算,对100 K至500 K温度范围内块状h-BN单晶的各向异性热导率进行了综合的实验和理论研究。从第一性原理开始。我们的实验和数值计算结果比较有利的面内和通过平面的热导率。我们观察到不寻常的温度依赖性和声子同位素散射的h-BN的通过平面的热导率,并阐明其起源。这项工作不仅提供了h-BN的各向异性热导率的重要基准,而且还开发了对这种高度各向异性层状材料中声子输运性质的基本见解。

英文摘要:

Hexagonal boron nitride (h-BN) has received great interest in recent years as a wide bandgap analog of graphene-derived systems. However, the thermal transport properties of h-BN, which can be critical for device reliability and functionality, are little studied both experimentally and theoretically. The primary challenge in the experimental measurements of the anisotropic thermal conductivity of h-BN is that typically sample size of h-BN single crystals is too small for conventional measurement techniques, as state-of-the-art technologies synthesize h-BN single crystals with lateral sizes only up to 2.5 mm and thickness up to 200 μm. Recently developed time-domain thermoreflectance (TDTR) techniques are suitable to measure the anisotropic thermal conductivity of such small samples, as it only requires a small area of 50x50 μm2 for the measurements. Accurate atomistic modeling of thermal transport in bulk h-BN is also challenging due to the highly anisotropic layered structure. Here we conduct an integrated experimental and theoretical study on the anisotropic thermal conductivity of bulk h-BN single crystals over the temperature range of 100 K to 500 K, using TDTR measurements with multiple modulation frequencies and a full-scale numerical calculation of the phonon Boltzmann transport equation starting from the first principles. Our experimental and numerical results compare favorably for both the in-plane and through-plane thermal conductivities. We observe unusual temperature-dependence and phonon-isotope scattering in the through-plane thermal conductivity of h-BN and elucidate their origins. This work not only provides an important benchmark of the anisotropic thermal conductivity of h-BN but also develops fundamental insights into the nature of phonon transport in this highly anisotropic layered material.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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