Large-Area Broadband Near-Perfect Absorption from a Thin Chalcogenide Film Coupled to Gold Nanoparticles

Perfect absorbers that can efficiently absorb electromagnetic waves over a broad spectral range are crucial for energy harvesting, light detection, and optical camouflage. Recently, perfect absorbers based on a metasurface have attracted intensive attention. However, high-performance metasurface absorbers in the visible spectra require strict fabrication tolerances, and this is a formidable challenge. Moreover, fabricating subwavelength meta-atoms requires a top-down approach, thus limiting their scalability and spectral applicability. Here, we introduce a plasmonic nearly perfect absorber that exhibits a measured polarization-insensitive absorptance of ∼92% across the spectral region from 400 to 1000 nm. The absorber is realized via a one-step self-assembly deposition of 50 nm gold (Au) nanoparticle (NP) clusters onto a 35 nm-thick Ge₂Sb₂Te₅ (GST225) chalcogenide film. An excellent agreement between the measured and theoretically simulated absorptance was found. The coalescence of the lossy GST225 dielectric layer and high density of localized surface plasmon resonance modes induced by the randomly distributed Au NPs play a vital role in obtaining the nearly perfect absorptance. The exceptionally high absorptance together with large-area high-throughput self-assembly fabrication demonstrates their potential for industrial-scale manufacturability and consequential widespread applications in thermophotovoltaics, photodetection, and sensing.