Resonant Raman scattering characterization of thermally annealed HiPIMS deposited MoSx coatings

Raman spectroscopy is used to investigate the structural and tribological properties of HiPIMS sputtered MoSx thin films which were post-growth-annealed at different temperatures. The Raman scattering combined with X-ray diffraction determines a reduction in the residual strain within the MoSx layers with increasing annealing temperature. In the high-temperature annealed coatings a Raman signature at 40 cm−1 emerges, which results from a strengthening of the inter-layer van-der-Waals interaction. This observation indicates that the thermally annealed MoSx thin films become more resistant against shear forces, which is manifested in an increase of the coefficient of friction measured with a ball-on-disc tribometer. The coefficient of friction moreover decreases with lowering the sulfur/molybdenum ratio which, in turn, depends on the substrate and annealing temperatures. Furthermore, a Raman forbidden mode may be exploited to detect stacking faults within the sputtered coatings. Its observation is realized through resonant excitation of an MoS2 exciton at about 633 nm. •Raman scattering combined with XRD determines a reduction in the residual strain within the annealed MoSx layers.•Thermally annealed MoSx films become more resistant against shear forces due to enhanced inter-layer van-der-Waals forces.•A Raman forbidden mode may be exploited to detect stacking faults within the sputtered coatings.•Weak MoO3 bondings are detected due to the resonant Raman scattering.•Coefficient of friction decreases with lower sulfur/molybdenum ratio.