Mechanical and optical properties of composite TiOxNy films prepared by pulsed bias arc ion plating

Composite TiOxNy films were synthesized with pulsed bias arc ion plating from two Ti target evaporators in a gaseous mixture of Ar, N2 and O2. With the substrate bias varying from 0 to −700 V, the structural, compositional, mechanical and optical properties of the films were characterized with X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), wear tests and UV–VIS absorption spectra. XRD and XPS results show that deposited at a substrate bias of −100 V, the film crystallized in a mixture of Anatase and Rutile TiO2 phases with O locations partly substituted by N atoms. The threshold wavelength of optical absorption shifts from 367 to 400 nm after N doped, which is related with band gap narrowing cased by N doping. The wear tests indicate that friction efficient first decreases, then increases as the substrate bias goes up. The films deposited at a bias of −300 V exhibit the lowest friction efficient, less than 0.15. For the films on steel substrates, the TiOxNy films deposited at −300 and −500 V exhibit the highest adhesion strength and nano-hardness, respectively.