Plasmonic properties of nonstoichiometric zirconium nitride, oxynitride thin films, and their bilayer structures

Nonstoichiometric ZrNx (ZrN) thin films, ZrOxNy (ZrON) thin films, and bilayer ZrN/ZrON structures were prepared, and the effects of stoichiometry and interface on their plasmonic properties were investigated. We find that the samples are all B1 structured with similar lattice constants. Higher nitrogen and oxygen content can reduce the screened plasma frequency ωc. Interestingly, the bilayer ZrN/ZrON structures with some ZrON thickness are more metallic than ZrN films, which should be reasonable since the mutual diffusion through the ZrN/ZrON interface may cause a ZrON buffer zone with substitute oxygen atoms generating more free carriers. The postulation is further confirmed by the calculations about the band structure, which indicates that substitute oxygen atoms can depress the interband transition level and cause more carriers in conduction band. This work implies that oxygen substitution is an effective method to enhance the performances of nitride-based plasmonic materials and devices.