Reactive Magnetron Sputter Deposition of Titanium Oxynitride TiNxOy Coatings: Influence of Substrate Bias Voltage on the Structure, Composition, and Properties

TiOxNy films were grown onto 316L stainless steel substrate using radiofrequency (rf) magnetron sputtering from a pure titanium nitride target in Ar–O2 gas mixture with various substrate bias voltages. The aim of this work is to investigate the effect of applied substrate bias Vs, varied from 0 to –100 V, on the deposition rate, structure, hardness and optical properties of the TiNxOy films. The characterization of the coatings by grazing incidence X-ray diffraction exhibited a crystalline structure of a mixture of TiN, rutile and anatase. The indirect and direct bad gap were found to decrease for unbiased substrate voltage to Vs = −100 V from 3.84 to 3.20 eV. In addition, the coatings exhibit high transparency (transmittance over 80%). The hardness of the coatings were found in the range of 6.2 to 12.5GPa.