Optical gradient of the trapezium-shaped NaNb O3 thin films studied by spectroscopic ellipsometry

Ellipsometric studies of the optical gradient of NaNb O3 thin films were performed in the photon energy range of 1.24-4.96 eV. Effective values of the complex refractive index and thickness nonuniformity, roughness, and depth profile of the real part of the refractive index were evaluated. An increase of the refractive index with increasing of the sample thickness was observed and discussed.