Formation of functional metallic patterns in downflow of argon-diluted ammonia microplasmas at atmospheric pressure

Summary form only given. Microplasmas at or near the atmospheric pressure play novel roles in photonic devices,¹ electromagnetic wave media,² and underwater reactive fields,³ which cannot be achieved by low-pressure large-volume plasmas. In this study, we report another promising scheme in which novel gas reformation and successive material synthesis processes take place in a glass capillary compatible to a conventional gas tubing system. The main and important output species of these microplasmas in Ar/NH₃ mixture gases is hydrazine (N₂H₄),⁴ which is a strong reducing agent; we used it to make functional metallic patterns for transparent conductive films and optical layers with extraordinary properties.We developed a fairly simple electrode system for coaxial dielectric barrier discharges in a glass capillary with outer diameter was 6 mm. We installed it just after Ar and NH3 gas containers and the successive small reaction chamber which was followed by a NH3 abatement system. The total system is quite compact and can be installed in one closed gas cabinet at the atmospheric pressure throughout the system. When we replaced the reaction chamber by ultraviolet-ray absorption cell, we detected N2H4 in the order of 1015 cm-3.4 In the similar parameter set for the N2H4 generation, we confirmed formation of Ag nano-particles after drying the AgNO3 solutions in the reaction chamber. Furthermore, after optimization of the discharge and the solution parameters, we successfully observed fractal-like Ag patterns composed of the nano-particles, and they showed a feature of partiallyconductive transparent films and extraordinary responses to infrared rays; the spectra include a few absorption peaks, similar to designed optical metamaterials with abnormal permittivity and permeability.