The efficient conversion of solar energy to heat is a prime challenge for solar thermal absorbers, and various material classes and device concepts are discussed. One exciting class of solar thermal absorbers are plasmonic broadband absorbers that rely on light absorption thanks to plasmonic resonances sustained in metallic nanoparticles. This work focuses on Cu/Al₂O₃ plasmonic absorbers, which consist of a thin film stack of a metallic Cu-mirror, a dielectric Al₂O₃ spacer, and an Al₂O₃/Cu-nanoparticle nanocomposite. This work explores two preparation routes for the Al₂O₃/Cu-nanoparticle nanocomposite, which rely on the self-organization of Cu nanoparticles from sputtered atoms, either in the gas phase (i.e., via gas aggregation source) or on the thin film surface (i.e., via simultaneous co-sputtering). While in either case, Cu-Al₂O₃-Al₂O₃/Cu absorbers with a low reflectivity over a broad wavelength regime are obtained, the simultaneous co-sputtering approach enabled better control over the film roughness and showed excellent agreement with dedicated simulations of the optical properties of the plasmonic absorber using a multi-scale modeling approach. Upon variation of the thickness and filling factor of the Al₂O₃/Cu nanocomposite layer, the optical properties of the plasmonic absorbers are tailored, reaching an integrated reflectance down to 0.17 (from 250 to 1600 nm).

中文翻译：

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基于自组织等离子体铜纳米粒子的薄膜宽带吸收体的共溅射

将太阳能有效转化为热量是太阳能吸热器面临的主要挑战，本文讨论了各种材料类别和设备概念。一类令人兴奋的太阳能吸热器是等离子体宽带吸收器，由于金属纳米颗粒中维持的等离子体共振，它依赖于光吸收。这项工作的重点是Cu/Al ₂ O _{3等离子体吸收体，它由金属Cu镜、电介质Al 2} O ₃间隔物和Al ₂ O ₃ /Cu纳米粒子纳米复合材料的薄膜堆叠组成。这项工作探索了 Al ₂ O ₃ /Cu 纳米粒子纳米复合材料的两种制备路线，它们依赖于溅射原子的 Cu 纳米粒子的自组织，无论是在气相中（即通过气体聚集源）还是在薄膜上表面（即通过同时共溅射）。虽然在任何一种情况下，都获得了在宽波长范围内具有低反射率的 Cu-Al ₂ O ₃ -Al ₂ O ₃ /Cu 吸收体，但同步共溅射方法能够更好地控制薄膜粗糙度，并与专用材料表现出良好的一致性。使用多尺度建模方法模拟等离子体吸收体的光学特性。_{根据Al 2} O ₃ /Cu纳米复合层的厚度和填充因子的变化，等离子体吸收体的光学特性被定制，达到低至0.17的积分反射率（从250到1600 nm）。