Detailed peak fitting analysis of the Ni 2p photoemission spectrum for metallic nickel and an initial oxidation

A quantitative study of the surface composition of clean metallic and partially oxidized nickel exposed to oxygen was carried out employing X-ray photoelectron spectroscopy (XPS). By fitting both branches of the metallic Ni 2p spectrum, it was possible to resolve two previously unreported satellite peaks in the Ni 2p1/2 portion of the spectrum. For the partial oxidation of the nickel surface, we analyzed the Ni 2p, O 1s, and C 1s angle-resolved XPS spectra. Using state-of-the-art peak-fitting (including the block approach) and background modeling methods (including the active approach) it was possible to discriminate the peaks of Ni2O3 from those of metallic nickel for both branches of the Ni 2p spectra from partially oxidized nickel. The oxidation of metallic nickel is through the formation of a Ni+3 oxide layer together with deep protrusions. The uncertainties are calculated with the covariance matrix method. The strong overlap and shape similarity of the Ni0 L3M45M45 Auger structure with that of the Ni+3 strongly suggests that the modified Auger Parameter does not provide direct additional insight about the chemical state to that provided by the photoemission spectra.