Interfacial effects during the analysis of multilayer metal coatings by radio-frequency glow discharge optical emission spectroscopy -: Part 2.: Evaluation of depth resolution function and application to thin multilayer coatings

The crater shape effects in GDOES depth profiling of multilayer metal coatings, with an individual thickness layer >500 nm, studied in the foregoing paper, have been extended to the case of thinner layers ( layer thickness <150 nm). The analysis of 10 bilayers of 70 nm chromium and 150 nm titanium showed an increased degradation of the composition depth profiles. The continuous change in shape of the crater after each interface induces a higher mixing of the thin layers. Reducing the thickness of the individual layers added new features to the depth profiles, such as changes on the symmetry of the profiles probably due to a mixing or simultaneous detection of consecutive bilayers. Ultra-thin chromium layers of 2.5 and 5 nm, buried at different depths in a titanium matrix up to a thickness of 3 mm, were properly resolved both near the surface and deeply embedded in the matrix and used to evaluate the depth resolution function of the GDOES technique. The relative depth resolutions of all the interfaces were estimated showing a typical dependence with depth (z) of the type z(-0.6-0.7).