Silicon nanowires (SiNWs) have attracted much attention owing to their potential applications in electronics and photonics, while remaining as a cost-effective material platform. Key material properties in engineering SiNWs for different applications include their length, density, and presence of oxides or other chemicals on the surface. However, monitoring these properties is challenging, as scanning electron microscopy and atomic force microscopy (AFM), which directly image the wires, require destructive cleaving of the sample. This paper uses polarized, variable-angle Fourier Transform IR reflectance spectroscopy as a nondestructive technique to characterize the areal density and length of metal-assisted chemically etched SiNW arrays. In addition to the ability to characterize “as-etched” wires, we show that IR spectroscopy can also measure few-nanometer thick layers of aluminum oxide (AlOx) grown radially around the length of the SiNWs utilizing atomic layer deposition. Despite sample inhomogeneities, an effective medium theory (EMT) model can determine the length and density of the NWs for a range of lengths between 3 and 14 μm. The EMT can also reproduce the experimentally measured vibrational bands for coated NWs, demonstrating that IR spectroscopy can also evaluate the presence of molecular contaminants on the wires.

中文翻译：

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使用中红外光谱对硅纳米线和纳米线涂层进行无损表征

硅纳米线（SiNW）因其在电子和光子学方面的潜在应用而备受关注，同时仍然是一种具有成本效益的材料平台。用于不同应用的 SiNW 工程的关键材料特性包括它们的长度、密度以及表面上氧化物或其他化学物质的存在。然而，监测这些特性具有挑战性，因为直接对电线进行成像的扫描电子显微镜和原子力显微镜 (AFM) 需要对样品进行破坏性切割。本文使用偏振、可变角度傅里叶变换红外反射光谱作为一种无损技术来表征金属辅助化学蚀刻 SiNW 阵列的面密度和长度。除了能够表征“蚀刻”线的能力之外，我们还表明，红外光谱还可以利用原子层沉积来测量沿 SiNW 长度径向生长的几纳米厚的氧化铝 (AlOx) 层。尽管样本不均匀，有效介质理论 (EMT) 模型可以确定 3 至 14 μm 长度范围内纳米线的长度和密度。 EMT 还可以重现实验测量的涂层纳米线的振动带，这表明红外光谱也可以评估导线上分子污染物的存在。