Physics-Based Design of Efficient Metasurface Temperature-Adaptive Radiative Coatings

Abstract

This work introduces a physics-based model and detailed examination of how efficient VO₂-based, metasurface thermally-adaptive radiative coatings (TARCs) can be designed through careful selection of the dielectric spacer material and thickness as well as tailoring of the tungsten-doped vanadium dioxide (W_xV_1-xO₂ where x = 0 and 0.015) patch dimensions. This study explores how the phase and magnitude of transmission through the nanopatterned layer of the metasurface TARC are impacted by these parameters and subsequently influence the resulting contrast in emissivity between the low- and high-temperature states. When these parameters are optimized, the emissive contrast (8–13 µm) is predicted to be as high as 0.725 and 0.607 respectively for the undoped and doped TARCs. Additionally, this study investigates the use of alumina (Al₂O₃), a dielectric spacer with significant mechanical stability, and experimentally demonstrate the realization of metasurface TARCs with notably high emissive contrast. The findings describe the fundamental limits of emissivity contrast that can be achieved with a metasurface TARC composed of a W_xV_1-xO₂ layer deposited atop an Al₂O₃ coated aluminum ground plane. Ultimately, the study provides a deeper understanding of the underlying physics of TARCs and demonstrates that metasurface engineering can be used to achieve enhanced control in tuning their emissive contrast.