Tweaking the mechanical stability of Al1−xWxN ternary nitride alloys for hard coating applications, and study on their structural, photoluminescence and surface chemical analysis

Abstract

This study focuses on the synthesis and achievement of ternary Al1−xWxN nitride films as hard coating materials. A dual-target DC reactive magnetron sputtering process was used to coat Al1−xWxN thin films on Si (100), glass, and transparent quartz substrates. The elemental analysis of the films was calculated by energy dispersion spectroscopy and the corresponding value of x changes from 0 to 1. The X-ray diffraction data showed a-axis orientation of the AlN films with hexagonal phase and amorphous nature for Al0.78W0.22N and Al0.58W0.42N films. Atomic force microscopy analysis showed that the surface morphology of Al0.78W0.22N films was better than that of AlN and Al0.3W0.7N films, as evidenced by the significantly lower root-mean-square roughness value of 1.79 nm compared to 5.78 and 13.9 nm, respectively. The resistivity of Al1−xWxN films was determined by a four-probe method and resulted in a record low value of 4.08 × 10−5 Ω-m for WN films. The photoluminescence emission spectra showed distinct peaks in the visible region at different wavelengths, and the deconvoluted blue emission peak was attributed to the native defects in the Al1−xWxN films. X-ray absorption spectroscopy data showed an increase in feature-a from Al0.78W0.22N to Al0.58W0.42N films, indicating stronger hybridization of N 2p with Al 3p and W 5d orbitals due to π * -resonance. The oxygen content calculated by X-ray photoelectron spectroscopy was 34.6, 35.39, and 19.74 at% on the surface of AlN, Al0.58W0.42N, and WN films, respectively. The surface oxidation of AlN films triggered the transfer of charge from nitrogen to oxygen on the surface of AlN films. The nanoindentation results showed that the Al0.3W0.7N films have hardness and elastic modulus of 17.84 GPa and 196.96 GPa, which are higher than those of the other Al1−xWxN films, while the AlN films have higher fracture toughness due to the reduction of contact pressure.