Time-domain thermoreflectance (TDTR) is a powerful pump-probe technique for measuring thermal properties of materials and interface thermal conductance. However, a diffusive thermal transport model is often used for data analysis, leading to underestimated thermal conductivities for high thermal conductivity materials, for example, single-crystalline semiconductors like Si at low temperatures. In this work, we have developed a theoretical model based on phonon hydrodynamics, an approximation of the phonon Boltzmann transport equation, for TDTR data analysis. We apply this model to process the TDTR signals of Si measured between 80 and 300 K. The extracted thermal conductivities using the phonon hydrodynamic model agree remarkably well with the bulk values measured by the steady-state technique, providing a more appropriate way of TDTR data analysis. The effectiveness of the phonon hydrodynamic model is further verified by analyzing TDTR signals of Ge at room temperature.
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机译：时域热反射 （TDTR） 是一种强大的泵浦探头技术，用于测量材料的热特性和界面热导率。然而，扩散热输运模型通常用于数据分析，导致低估了高导热材料的热导率，例如，低温下的硅等单晶半导体。在这项工作中，我们建立了一个基于声子流体动力学的理论模型，该模型是声子玻尔兹曼输运方程的近似值，用于TDTR数据分析。我们应用该模型来处理在 80 到 300 K 之间测量的 Si 的 TDTR 信号。利用声子流体动力学模型提取的热导率与稳态技术测量的体积值吻合得非常好，为TDTR数据分析提供了更合适的方法。通过分析室温下Ge的TDTR信号，进一步验证了声子流体动力学模型的有效性。
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