标题： 金薄膜的温度依赖性光学性质 显示英文标题

标题： Temperature-dependent optical properties of gold thin films

摘要： 理解薄金属膜的光学性质随温度变化的特性对于设计在多种研究领域中高温应用的实际器件至关重要，包括等离激元和近场辐射传热。尽管已经对高温下块体金属的光学性质进行了研究，但厚度从几十纳米到几百纳米的薄金属膜的温度依赖数据却大多缺失。在本工作中，我们报告了在370至2000纳米波长范围内，单晶和多晶金薄膜在高温下的光学常数。我们的结果表明，虽然介电函数的实部随着温度升高仅有微小变化，但虚部却发生了显著变化。对于200纳米厚的单晶和多晶金薄膜，在500 0C时介电函数的虚部几乎比室温时大一倍。相反，在较薄的薄膜（50纳米和30纳米）中，虚部在同一温度范围内可能表现出增加或减少的行为，并且最终在500 0C时几乎比室温时大3-4倍。高温下虚部的增加显著降低了表面等离激元极化子的传播长度以及球形粒子局域表面等离激元共振的品质因数。我们提供了实验拟合模型，以描述温度依赖的金介电函数，该模型由一个德鲁德项和两个临界点振荡器组成。这些因果分析模型可以实现对基于金的纳米光子和等离激元元件在频域和时域中的准确多物理场建模。 显示英文摘要

摘要： Understanding the temperature dependence of the optical properties of thin metal films is critical for designing practical devices for high temperature applications in a variety of research areas, including plasmonics and near-field radiative heat transfer. Even though the optical properties of bulk metals at elevated temperatures have been studied, the temperature-dependent data for thin metal films, with thicknesses ranging from few tens to few hundreds of nanometers, is largely missing. In this work we report on the optical constants of single- and polycrystalline gold thin films at elevated temperatures in the wavelength range from 370 to 2000 nm. Our results show that while the real part of the dielectric function changes marginally with increasing temperature, the imaginary part changes drastically. For 200-nm-thick single- and polycrystalline gold films the imaginary part of the dielectric function at 500 0C becomes nearly twice larger than that at room temperature. In contrast, in thinner films (50-nm and 30-nm) the imaginary part can show either increasing or decreasing behavior within the same temperature range and eventually at 500 0C it becomes nearly 3-4 times larger than that at room temperature. The increase in the imaginary part at elevated temperatures significantly reduces the surface plasmon polariton propagation length and the quality factor of the localized surface plasmon resonance for a spherical particle. We provide experiment-fitted models to describe the temperature-dependent gold dielectric function as a sum of one Drude and two Critical Point oscillators. These causal analytical models could enable accurate multiphysics modelling of gold-based nanophotonic and plasmonic elements in both frequency and time domains.