Wide spectral range optical characterization of niobium pentoxide (Nb2O5) films by universal dispersion model

Abstract

In this work, the optical properties of niobium pentoxide (${\text{Nb}}_2{\text{O}}_5$) films were extensively studied across a wide spectral range using heterogeneous data-processing methods, combining ellipsometric and spectrophotometric measurements for five samples with thicknesses between 20 and 250 nm. This study primarily determined the optical constants of ${\text{Nb}}_2{\text{O}}_5$ from the far infrared to the vacuum ultraviolet, presenting these constants as dispersion parameters using the universal dispersion model to describe valence electron excitations in ultraviolet region as well as phonon vibrations in infrared region. These comprehensive and reliable data across such a broad spectral range are unprecedented. Secondly, presented optical characterization proofs that ${\text{Nb}}_2{\text{O}}_5$ films can be grown without defects such as surface roughness, porosity, or inhomogeneity. This fact, together with its high refractive index, makes ${\text{Nb}}_2{\text{O}}_5$ a promising material for optical applications.