采用弯曲加热器几何结构的三欧米茄热导率测量
Three-Omega Thermal-Conductivity Measurements with Curved Heater Geometries
AI总结：
针对三欧米茄测量中直导线难以避开样品障碍的问题，本文在SiO2/Si上对比弯曲与直线加热器，证明曲率对热导率和约65 nm SiO2热阻测定影响极小，并给出设计界限。
摘要：
三欧米茄法是测量纳米厚度薄膜及其界面热导率的一种强大技术，历史上一直采用直导线同时充当加热器和温度计。在研究二维材料和纳米膜等随机制备的样品时，残留物和多余材料会使所需毫米级直导线难以安置在样品表面。目前，关于绕开障碍物使三欧米茄加热导线改向会如何影响热测量有效性，尚无可资利用的判据。在本Letter中，我们通过在SiO2/Si样品上采用弯曲和直线两种加热器几何结构进行宽频率范围的三欧米茄实验，量化了导线曲率的影响。当加热导线弯曲时，我们发现测得的Si衬底热导率仅变化0.2%。类似地，我们发现导线曲率对约65 nm厚SiO2层热阻的测定没有显著影响，即使对于此处考虑的最尖锐转角也是如此；在该情形下，所施加热波的热穿透深度与加热导线曲率半径之间测得的最大比值为4.3。该结果通过设定热穿透深度与导线曲率半径最大比值的下界，为三欧米茄实验提供了有用的设计判据。
英文摘要：
The three-omega method, a powerful technique to measure the thermal conductivity of nanometer-thick films and the interfaces between them, has historically employed straight conductive wires to act as both heaters and thermometers. When investigating stochastically prepared samples such as two-dimensional materials and nanomembranes, residue and excess material can make it difficult to fit the required millimeter-long straight wire on the sample surface. There are currently no available criteria for how diverting three-omega heater wires around obstacles affects the validity of the thermal measurement. In this Letter, we quantify the effect of wire curvature by performing three-omega experiments with a wide range of frequencies using both curved and straight heater geometries on SiO$_2$/Si samples. When the heating wire is curved, we find that the measured Si substrate thermal conductivity changes by only 0.2%. Similarly, we find that wire curvature has no significant effect on the determination of the thermal resistance of a $\sim$65 nm SiO$_2$ layer, even for the sharpest corners considered here, for which the largest measured ratio of the thermal penetration depth of the applied thermal wave to radius of curvature of the heating wire is 4.3. This result provides useful design criteria for three-omega experiments by setting a lower bound for the maximum ratio of thermal penetration depth to wire radius of curvature.
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