The reliability of XPS spectra interpretation of heterogeneous materials exhibiting compositionally-driven phase transformations is shown to improve by a comprehensive sample analysis including characterization of microstructure, elemental composition, impurity level, and phase constitution. This approach is demonstrated here for a series of W 1-x N x films with N content varying in the range 0 ≤ x ≤ 0.65, which results in a complex evolution of W 4f spectra. The reliability of peak models is further enhanced by performing self-consistent XPS analysis from all major core level spectra (W 4f, N 1s, O 1s, and C 1s) in liaison with XRD (for crystalline phase content, lattice parameters, preferred orientation), ToF-ERDA (elemental composition, impurity levels), SEM and TEM (micro- and nano-structural analysis), and SAED (crystalline content down to the nm-level). It is thus found that a phase transformation occurs as x increases from bcc α -W(N) with x = 0.06 to bcc α -W(N) + cubic β -W y N (0.08 ≲ x ≲ 0.27), cubic β -W y N + hexagonal W 2 N 3 (0.36 ≲ x ≲ 0.56), and finally to cubic β -W y N + amorphous WN 2 (0.62 ≲ x ≲0.65). The comparison of spectra recorded before and after Ar + etching reveals that sensitivity to sputter damage varies greatly between different phases. This integrated methodology is particularly valuable for transition metal nitrides, carbides, and related compounds exhibiting continuous structural evolution with overlapping XPS signatures.
Rogoz et al. (2026) studied this question.