Effects of assisting ions on the structural and plasmonic properties of ZrN_x thin films

Plasmonic ZrN_x thin films were prepared by ion beam assisted deposition (IBAD). The effects of the assisting ion current (I _a), assisting ion energy (E _a) and the partial flow rate ratio of N₂/Ar (r) on the structure and dielectric properties of the films were investigated. The results show that all the films are fcc-structured, and the IBAD films exhibit a preferred fcc-(1 1 1) orientation. Nitrogen content of the films can be improved by higher E _a and r, and reduced by higher I _a. Higher I _a, E _a or r can reduce the crossover frequency at which the films turn from dielectric to metallic phase, and reduce the loss function of the films. Moreover, the plasmonic quality factor can also be modulated by these parameters. The main mechanism of the modulation is the variation of the carrier concentration in the films. Our study demonstrates that the IBAD-ZrN_x thin films have considerable plasmonic performances, and their dielectric and plasmonic properties can be modulated from visible to near infrared region by assisting ion beam.