Co‐sputtering of A Thin Film Broadband Absorber Based on Self‐Organized Plasmonic Cu Nanoparticles

• Published in: Particle & particle systems characterization Vol. 41; no. 2
• Main Authors: Drewes, Jonas, Perdana, Nanda, Rogall, Kevin, Hartig, Torge, Elis, Marie, Schürmann, Ulrich, Pohl, Felix, Abdelaziz, Moheb, Strunskus, Thomas, Kienle, Lorenz, Elbahri, Mady, Faupel, Franz, Rockstuhl, Carsten, Vahl, Alexander
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.02.2024
• Subjects: Absorbers; Aluminum oxide; black absorber; Broadband; Copper; Electromagnetic absorption; gas aggregation source; magnetron sputtering; Nanocomposites; Nanoparticles; Optical properties; plasmonic particles; Plasmonics; RF sputtering; Solar energy conversion; Solar heating; Sputtering; Thin films; Vapor phases
• ISSN: 0934-0866; 1521-4117
• DOI: 10.1002/ppsc.202300102

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). Cu‐Al2O3‐Al2O3/Cu thin film broadband absorbers rely on plasmonic interaction between photons and metallic (Cu‐)nanoparticles embedded in a dielectric Al2O3 matrix. Thin film absorbers prepared by simultaneous co‐sputtering exhibit a lower roughness than those prepared via a gas aggregation source. By tailoring the thickness and filling factor of the Al2O3/Cu nanocomposite layer, only 0.17 reflectance integrated from 250 to 1600 nm is obtained. An excellent agreement between multi‐scale modeling and experimental results is observed.