Evolution of the optical properties in atomically thin plasmonic titanium nitride

In this study, we present a joint theoretical and experimental study on the dielectric permittivity of ultra-thin TiN films of varying thicknesses. We perform both ex situ and in situ ellipsometry to decouple the effects of thickness and oxidation. Our results indicate a remarkably persistent plasmonic character as the thickness is reduced. The effects of thickness and oxidation on their plasmonic properties are analyzed as fundamental parameters to optimize the optical response. Atomically thin plasmonic materials display great potential for the realization of tailorable and dynamically tunable metasurfaces because of their large sensitivity to structural parameters and external perturbations.