Thickness-dependent optical properties of low-loss transdimensional plasmonic Sr_0.82NbO₃ thin films

To develop alternative plasmonic materials for nanophotonic applications, the thickness-dependent optical properties of ultrathin plasmonic Sr_0.82NbO₃ (SNO) films deposited on MgO are investigated. As the thickness decreases from 10 to 2 nm, the film exhibits less metallic, epsilon-near-zero (ENZ) wavelength redshift and higher optical loss due to increased scattering. Nevertheless, the thinnest film still has a high carrier concentration of 10²²cm^-3, and the real part of the dielectric functions of all films is less than zero in the near-infrared (NIR) wavelength region, indicating that the samples possess relatively high metallicity and plasmonic characteristics in the NIR. It is found that the carrier concentration dominates the electron effective mass and Drude plasma frequency. Although Au is a commonly used plasmonic material, at a wavelength of 1550 nm, the loss of SNO is 85.8% lower than that of Au, and its plasmonic performance metrics is significantly higher than TiN, Al:ZnO and Sn:In₂O₃, demonstrating the great potential of SNO in NIR plasmonic device applications.