Microstructure, mechanical properties and optical reflectance of TiNiN films deposited on silicon substrates using cathodic arc evaporation

Abstract

Variations in applied substrate bias during cathodic arc deposition may impose intriguing consequences on the mechanical and optical properties of TiNiN coatings. Here, TiNiN films were fabricated onto Si substrates using a Ti95Ni5 (at.%) alloy target via cathodic arc evaporation employing a range of substrate bias voltages varying from 0 to -150 V. The aim of this study was to investigate the microstructures, mechanical performance, and optical properties of the TiNiN films in terms of the employed substrate potential. A significant enhancement (57%) in hardness for the TiNiN film was attained at -50 V as compared to zero substrate potential. This was principally attributed to the evolution of a fine, equiaxed nanocomposite structure, in association with the induction of a very high compressive residual stress at -50 V. In contrast, a maximum optical reflectance of 73% in the near-infrared range was determined for the coating synthesised at -150 V. It is speculated that incidence of fewer macroparticles on the film surface at elevated negative potentials, due to the induction of a higher repulsive force, may reduce the scattering of light incident on the coating's surface, promoting improved spectral reflectivity.