Optical properties investigation of reactively sputtered tantalum oxynitride films

Abstract

The coalescent behavior of metal oxide and metal nitride in metal oxynitride (MON) is making the material more conspicuous. Along with tunable optical properties, enhances mechanical properties, better chemical stability can be derived for MONs, which are of prime importance in the fields, such as photovoltaic, photo-chromatics, photocatalytic, protective and aesthetic coatings. In this paper, the optical properties of tantalum oxynitride thin film deposited through a reactive magnetron sputtering method were explored. Pure tantalum target was sputtered with argon gas in the presence of an optimized O2/N2 gas ratio. The chemical and physical properties of the film were investigated by X-ray diffraction technique, Scanning Electron Microscopy and AFM. Optical properties were explored with UV–visible spectroscopy and Spectroscopic Ellipsometry (SE). Transmittance and reflectance of the films show that the optical properties of the films have transparency (70–90%) and an absorption edge near 350 nm. For the analysis of SE data, the Tauc-Lorentz optical model with an additional Lorentz oscillator for semiconductor or insulator material were used. Here, the Ellipsometry technique has provided detailed optical nature of the film in terms of refractive index (n) ranging from 1.82 to 2.62, Energy Bandgap (Eg) 3.6 eV along with film thickness (∼200 nm) and surface roughness (∼6 nm).All these optical properties make the material a suitable candidate for antireflective coating, preparation of optical filters, photocatalytic agent, transparent coating for optical devices.