ABSTRACT We develop a nanosecond grating imaging (NGI) technique to measure in-plane thermal transport properties in bulk and thin-film samples. Based on nanosecond time-domain thermoreflectance (ns-TDTR), NGI incorporates a photomask with periodic metal strips patterned on a transparent dielectric substrate to generate grating images of pump and probe lasers on the sample surface, which induces heat conduction along both cross- and in-plane directions. Analytical and numerical models have been developed to extract thermal conductivities in both bulk and thin-film samples from NGI measurements. This newly developed technique is used to determine thickness-dependent in-plane thermal conductivities (κx) in Cu nano-films, which agree well with the electron thermal conductivity values converted from four-point electrical conductivity measurements using the Wiedemamn–Franz law, as well as previously reported experimental values. The κx measured with NGI in an 8 nm x 8 nm GaAs/AlAs superlattice (SL) is about 10.2 W/m⋅K, larger than the cross-plane thermal conductivity (8.8 W/m⋅K), indicating the anisotropic thermal transport in the SL structure. The uncertainty of the measured κx is about 25% in the Cu film and less than 5% in SL. Sensitivity analysis suggests that, with the careful selection of proper substrate and interface resistance, the uncertainty of κx in Cu nano-films can be as low as 5%, showing the potential of the NGI technique to determine κx in thin films with improved accuracy. By simply installing a photomask into ns-TDTR, NGI provides a convenient, fast, and cost-effective method to measure the in-plane thermal conductivities in a wide range of structures and materials.

中文翻译：

---

使用纳秒光栅成像技术进行面内热导率测量

摘要 我们开发了一种纳秒光栅成像 (NGI) 技术来测量块状和薄膜样品的面内热传输特性。基于纳秒时域热反射 (ns-TDTR)，NGI 将光掩模与在透明介电基板上图案化的周期性金属条结合在一起，以在样品表面生成泵浦激光器和探针激光器的光栅图像，从而引起沿交叉和交叉方向的热传导。平面方向。已经开发了分析和数值模型来从 NGI 测量中提取大块和薄膜样品的热导率。这种新开发的技术用于确定 Cu 纳米薄膜中与厚度相关的面内热导率 (κx)，这与使用 Wiedemamn-Franz 定律从四点电导率测量转换而来的电子热导率值以及先前报告的实验值非常吻合。在 8 nm x 8 nm GaAs/AlAs 超晶格 (SL) 中使用 NGI 测量的 κx 约为 10.2 W/m⋅K，大于跨平面热导率 (8.8 W/m⋅K)，表明各向异性热传输在 SL 结构中。测量的 κx 的不确定性在 Cu 膜中约为 25%，在 SL 中小于 5%。灵敏度分析表明，通过仔细选择合适的衬底和界面电阻，Cu 纳米薄膜中 κx 的不确定性可低至 5%，显示了 NGI 技术在提高精度确定薄膜中 κx 的潜力。通过简单地将光掩模安装到 ns-TDTR 中，NGI 提供了一个方便的、