Effect of parametric variation on the surface composition, structure, and tribological properties of zirconium nitride/oxynitride thin films

Abstract

This paper evaluates the effect of parametric variation on the structure, surface composition and tribological properties of reactive RF-magnetron sputter deposited ZrN/ Zr2ON2 thin films. The properties of the films were investigated with respect to Ar: N2 flow rate, and power coupled to the plasma. X-ray photoelectron spectroscopy (XPS) revealed the presence of both the Zr2ON2 and ZrO2 stoichiometric components on the surface. Also, coupled power beyond 100 W promotes the formation of Zr2ON2 on the film surface. That’s why samples having thickness as low as 101–106 nm exhibit lower COF values 0.42–0.46 owing to the dominant presence of lubricating ZrO2 phase in the surface layer. Grazing angle X-ray (GIXRD) diffractogram exhibit that in the bulk, c-ZrN (311) and c-Zr2ON2 (440) phases are dominant. With increased power beyond 100 W, the (222) orientation of the Zr2ON2 phase also becomes significant, owing to enhanced reaction rate between the sputtered Zr and reactive gas atoms. Tribological studies show that the sample with the lowest surface roughness (S5) (∼114 nm) has the highest specific wear rate (∼1.26 ×10−3 mm3/ Nm). Colour of the films changed with applied power from grey at 50 W, to brownish yellow at 100 W, blue at 150 W, and golden yellow at 200 W. The films exhibited long term stability after 18 months of deposition, in terms of adhesion and colour, upon exposure to ambient condition.