Titanium Oxynitrideby TiO2 Nitridation:A Comparative Study of Film, Nanoparticle, and Metasurface NanostructureProperties

Abstract

Abstract Titanium oxynitride (TiOxNy) is a unique plasmonic material bridging dielectric TiO2 and metallic TiN. In this study, the properties of TiOxNy films, film-derived metasurfaces, and colloidal nanoparticles, all synthesized by the temperature-controlled ammonia nitridation of TiO2, are investigated. In all cases, nanoscale heterogeneity and vacancy formation are responsible for the distinct optical responses of each of these nanomaterials. TiOxNy nanoparticles exhibit dielectric behavior at the single-particle level dominated by interband transitions and impurity states. In contrast, TiOxNy nanodisk metasurfaces fabricated by the nitridation of TiO2 thin films display pronounced plasmonic behavior with a metallic permittivity. These observations establish a direct relationship between synthesis-dependent structure and optical and plasmonic responses, providing key insights for the rational design of TiOxNy-based nanophotonic and metasurface devices by the choice of starting material and synthesis route.