Subdiffraction‐Limited Motheye‐Like Metastructures Fabrication by Dual‐Beam Overexposure Methodology Enhancing Broadband Infrared Antireflective Application

Abstract Materials possessing broadband antireflective properties benefit applications of military camouflage, photovoltaic devices, and highly transparent windows. In this work, large area, high throughput subdiffraction‐limited motheye‐like metastructures featuring broadband infrared (3–12 µm) antireflectivity are realized through dual‐beam overexposure shrinking strategy and subsequent controllable anisotropic reactive‐ion‐etching process. Both overexposure and overdevelopment processes severely controlled in conventional lithography processes, attribute significantly to improving linewidth resolution to <150 nm when photoresist thickness exceeding 500 nm, even to one micron. For antireflective application, the motheye profiles with customized anisotropic ratio (>3.27) and tunable taper‐angle range (>12.2°) are also realized by regulating the competition of directional ion bombardment and isotropic chemical etching in sulfur hexafluoride (SF6) plasma. The corresponding reflectivity is theoretically well‐simulated and experimentally validated after accounting for the tunable profiles and fractional volume coverage of motheye‐like structures. A low reflectivity <2.0% with the uniformity of ±4.8% and averaged to 1.2% across the overall spectrum of 3–12 µm are achieved. Implementing such efficient shrinking approach can possess huge potential in applications of military camouflage, photovoltaic devices, and highly transparent windows.