Stamping colors with solid-state superionic stamping (S4)

Traditional top-down approaches to producing metallic nanostructures are usually indirect; involve ultra-high vacuum processing steps and deep sub-micron lithography such as electron-beam lithography (EBL). Therefore, such pathways are difficult to scale up to high production rates. Additionally, they are too expensive to deploy in the production of single-use, low-cost products like plasmonic biological or chemical sensors, security tags or decorative patterns, all of which involve metallic nanopatterns. Hence, there is a need for more scalable and affordable manufacturing pathways for producing metallic nanostructures. In this work, we demonstrate a scalable manufacturing pathway for patterning silver nanostructures for plasmonic color generation. The pathway begins with the production of a single master pattern. We use commercially available Two-Photon Lithography (TPL) to direct-write a mask on a silicon substrate. Shallow etching of the silicon substrate with this mask by the Reactive Ion Etching (RIE) process (or Deep Reactive-Ion Etching for deeper patterns) produces a silicon master mold with the desired pattern. This master is used for hot embossing AgI-AgPO₃ glass, a chemically stable, pure Ag-ion conductor with a low glass transition temperature (of about 100 °C, depending on its stoichiometry), into a stamp. This glass stamp, in turn, is used in the Solid-State Superionic Stamping (S4) process to electrochemically imprint the desired pattern into several substrates. Here, with this direct, facile, and efficient process, we report that a single nano-patterned stamp is capable of producing several high-fidelity replicas of the master.