Tunable double epsilon-near-zero behavior in niobium oxynitride thin films

• DOI: 10.1016/j.apsusc.2021.150912
• Publication Date: 2021-08-26T02:44:34Z
• Authors: Ryan Bower; Matthew P. Wells; Freya Johnson; Rebecca Kilmurray; Brock Doiron; Eleonora Calì; Giuseppe Mallia; Bin Zou; Andrei P. Mihai; Nicholas M. Harrison; Sarah Fearn; Rupert Oulton; Neil McN. Alford; Lesley F. Cohen; Peter K. Petrov
• Keywords: 02 engineering and technology; Plasmonics; Epsilon-near-zero; Transition metal nitrides; Sputtering; 0210 nano-technology

Abstract Refractory transition metal nitrides and oxynitrides are of interest for plasmonic applications due to their increased thermal stability, tunability and comparatively low loss. Presented here is an experimental investigation of reactively sputtered niobium oxynitride thin films, demonstrating screened plasma wavelengths tunable over a ~90 nm spectral range. The optical response is correlated with resistivity and Hall measurements. Additionally, an explanation is provided for the double epsilon-near-zero (2ENZ) behavior observed and it is compared with other material systems. Experimental analysis of film composition and structure are combined with computational modelling, based on density functional theory, to explain the dispersion behavior observed and indicate that 2ENZ behavior arises due to the incorporation of oxygen within the films during deposition.