Optical characterization and modeling of nanoporous gold absorbers fabricated by thin-film dealloying
Optical characterization and modeling of nanoporous gold absorbers fabricated by thin-film dealloying
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DOI：
10.1088/1361-6528/ab9cf4
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发表时间：
2020-06
期刊：
影响因子：
3.5
通讯作者：
R. Ramesh;S. Niauzorau;Q. Ni;B. Azeredo;Liping Wang
中科院分区：
文献类型：
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作者：
R. Ramesh;S. Niauzorau;Q. Ni;B. Azeredo;Liping Wang
本文研究了由Ag-Au合金前驱体化学脱合金法制备的不同孔体积分数（PVF）的纳米多孔金（NPG）薄膜的光学反射特性。用扫描电子显微镜对制备的样品进行表征，并用积分球测量光谱半球反射率。利用Bruggeman有效介质理论，模拟了NPG在0.4 ~ 1.6 μm波长范围内随PVF变化的有效各向同性光学常数。由于NPG薄膜的厚度大于有效穿透深度的十倍以上，因此可以用不同入射角和偏振的空气和半无限NPG界面处的菲涅耳系数来简单地模拟光谱反射率。与模拟结果相一致，光学测量数据表明，在近红外区域，NPG的光谱法向反射率随着PVF值的增大而显著减小。在另一方面，反射率大大增加，只有在可见光范围内，在较大的倾斜角的横向电偏振波相比，横向磁波。此外，NPG样品表现出良好的热稳定性，从室温到100 °C的温度依赖的光谱半球反射率的变化很小。
This work studies the optical reflectance of nanoporous gold (NPG) thin films of varying pore volume fraction (PVF) synthesized by chemical dealloying of Ag-Au alloy precursors. The fabricated samples are characterized by scanning electron microscopy, and spectral hemispherical reflectance is measured with an integrating sphere. The effective isotropic optical constants of NPG with varying PVF are modeled for the wavelength range from 0.4 to 1.6 μm using the Bruggeman effective medium theory. As the thickness of the NPG thin films is more than ten times larger than the effective penetration depth, the spectral reflectance is simply modeled with the Fresnel coefficients at the interface of air and semi-infinite NPG with different incident angles and polarizations. Consistent with the modeling results, the optical measurement data shows that the spectral normal reflectance of NPG significantly decreases with larger PVF values in the near-infrared regime. On the other hand, the reflectance increases greatly only within visible range at larger oblique angles for transverse-electric polarized waves compared to transverse-magnetic waves. Moreover, the NPG samples demonstrate good thermal stability from room temperature up to 100 °C with little changes in the temperature-dependent spectral hemispherical reflectance.