Fig. 3: Composition analysis of SiOC-WOx films.
a XPS survey spectra underscore the dominance of O, W, Si, and C elements on the film surface. b XPS survey assisted with etching techniques is employed to characterize the sample in different depths (h = 0, −20, −40, and −60 nm). Aside from the external surface (h = 0), the oxidation of Si almost does not change with depth in the tested conditions. However, the oxidation of W decreases with an increase in depth. c SIMS characterization results (throughout 0 to −750 nm) show that the Si and W components change drastically in the very thin layer (around 20 nm beneath the surface) which is consistent with the XPS results. In the deeper region (−20 nm > h > −750 nm), the degree of oxidation of Si is almost constant while the oxidation of W decreases gradually. d TEM characterization of a sample slice at h = −6500 nm. Aside from the external surface, the “rock-embedded" morphology is also observed in the deep region of the sintered layer. e, f HRTEM and SAED images reveal that the W-abundant spherical phase is either W monocrystalline or polycrystalline W-composition. g Intensity unfolding treatment of a polycrystalline ring clarifies that the polycrystalline W-composition consists of W and WO3.
