How is the chemical bonding of W–Si–N sputtered coatings?

Thin films of W–Si–N, deposited by reactive magnetron sputtering, were investigated using X-ray photoelectron spectroscopy (XPS). The objective of this research work was to study the chemical binding state of these coatings. During the sputtering process, the established atomic bonds may possibly not agree to the elemental bonding preview using the values of chemical affinity, which decrease for SiN, SiW to WN bonds. XPS data show that in W-based films which have simultaneous additions of Si and N, a SiN type is the preferential bond established. This behaviour is confirmed either by the evolution of the Si/W atomic ratio of the as-deposited coatings, which increase with the N content, or the variation of the lattice parameters of the b.c.c. α-W phase for W–N, W–Si and W–Si–N systems. However, since no compound of silicon nitride was detected, it was concluded that this phase, formed by specific contents of Si and N must have been present in the W–Si–N films in the amorphous state.