Pérez Escudero, José ManuelBuldain, IbanBeruete Díaz, MiguelGoicoechea Fernández, JavierLiberal Olleta, Íñigo2021-06-142021-06-1420201094-408710.1364/OE.402397https://academica-e.unavarra.es/handle/2454/39904The absorption of infrared radiation within ultra-thin metallic films is technologically relevant for different thermal engineering applications and optoelectronic devices, as well as for fundamental research on sub-nanometer and atomically-thin materials. However, the maximal attainable absorption within an ultra-thin metallic film is intrinsically limited by both its geometry and material properties. Here, we demonstrate that material-based high-impedance surfaces enhance the absorptivity of the films, potentially leading to perfect absorption for optimal resistive layers, and a fourfold enhancement for films at deep nanometer scales. Moreover, material-based high-impedance surfaces do not suffer from spatial dispersion and the geometrical restrictions of their metamaterial counterparts. We provide a proof-of-concept experimental demonstration by using titanium nanofilms on top of a silicon carbide substrate.13 p.application/pdfeng© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved.Ultra-thin metallic filmsAbsorptivitySilicon carbide substratesInfrarred radiationMaterial-based high-impedance surfacesinfo:eu-repo/semantics/articleinfo:eu-repo/semantics/openAccess