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Conventional and reverse depth profile analysis of electrodeposited Fe–Co–Ni alloys was performed by secondary neutral mass spectrometry (SNMS). It was found that the reverse sputtering method gave a much better depth resolution at the vicinity of the substrate. The reverse SNMS spectra showed that the deposition of Fe–Co–Ni alloys starts with the formation of an Fe-rich zone followed by an increase in Co concentration, then the nickel content increases and a steady-state alloy composition is achieved. At high current density, the initial depth pattern reproduces itself twice before the composition becomes stable. It was concluded that the varying depth profile is a consequence of the anomalous nature of the codeposition of the alloy components, the depletion of the electrolyte with respect to the metal salts, and the dependence of the intensity of the hydrogen evolution on the deposit surface composition. Keywords: Electrodeposition, Fe–Co–Ni alloys, Anomalous codeposition, Depth profile analysis, Secondary neutral mass spectrometry (SNMS)

The overall quality of multilayer thin films prepared by electrodeposition could strongly be influenced by the surface and interface roughness. The roughness, however, may increase with the number of layers. For that very reason the reliable analysis of the first few layers is essential. However, in depth profiling methods based on sputtering techniques the first layer is always found at the bottom of the sputter crater. Since the depth resolution might decrease during sputtering, the analysis of the first few layers is often very difficult. In order to circumvent this problem, we performed SNMS depth profiling in the direction from the substrate. We prepared thin film samples in two ways. First, Co/Cu multilayer stacks were electrodeposited on Si/Cr/Cu substrates and SNMS depth profiling was carried out from the direction of the topmost layer. Secondly, electrodeposited Co/Cu multilayer stacks were coated with a few microns thick Ni layer and detached from the Si substrate in order to study the film structure from the side of the substrate. Using this latter method, which we denote as “reverse depth profiling”, we were able to analyze the first and, probably, the most even layers of the thin film structure with high resolution.