Engineering electrically tunable TiN/SiO₂ epsilon-near-zero metamaterials

Electrically tunable TiN/SiO 2 /TiN epsilon-near-zero photonic structures with various parameters were fabricated using the reactive DC magnetron sputtering approach. Effective medium approximation was used to predict the optical permittivity of a multilayered TiN/SiO 2 metamaterial and guide the design/fabrication. Experimental reflectance measurements for tunable TiN/SiO 2 /TiN structures were obtained using the ellipsometer technique in the visible and near-infrared spectral ranges. Results show that reflectance for biased (12 V) and un-biased bulk TiN/SiO 2 /TiN structure changes up to ∼ 2% with the spectral shift at the ENZ spectral point ∼ 10 nm for samples with an optimal SiO 2 dielectric layer (thickness d=10 nm). Reflectance measurements for multilayered tunable TiN/SiO 2 /TiN structures show strong variation in reflectance change for s- polarized light at epsilon-near-zero wavelengths due to applied voltage (12 V). We expect that the results of this research study of the tunable TiN/SiO 2 /TiN epsilon-near-zero photonic structures will potentially be useful for the photonic density of states engineering, surface sensing, and metamaterial-based super-resolution imaging.