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2.4 X-ray Photoelectron Spectroscopy task. In order to obtain meaningful information, usually, the multiplet Ni2p spec- tra are analyzed, which contain the spin-orbit coupled components from originat- ing from 2p3/2 and 2 p1/ 2 levels, - satellites assigned to excitations within the valence band and/or plasmon excitations - plasmon loss satellites. Clean oxygen- free metallic nickel has its main Ni2p line at about 852.6 eV et al.(43). It is accompanied by two satellites at about 3.7 and 6 eV higher BEs. In RNiO3 the nickel line is split into two components - the Ni 2p3/2 and 2p1/2. This multiplet splitting occurs due to presence of unpaired electrons in nickel 3+ ions. In the early 1970s Matienzo studied by XPS almost seventy nickel compounds and no- ticed that binding energy of nickel in its compounds can have a wide range of values (73). Especially for the octahedrally coordinated nickel ions. The binding energy is correlated with ligand electronegativity and their ability to remove elec- tron from metal ion. For oxygen it is larger than for fluorine or bromine. The binding energy itself was said to have no confirmation in the oxidation state of nickel in the different compounds. It is because the differences in binding energy - in for example compounds with Ni2+ ions - were noticed to be as large as 4 eV. The nickel structure is rather complicated and its analysis requires a careful deconvolution. The shake-up satellites that appear in the spectra were discussed to follow some rules depending on the coordinated ligand as well (73). In paramagnetic compounds where nickel is octahedrally coordinated with oxygen, the satellites usually appear one for each of the Ni2p main line components (C type satellites). In diamagnetic compounds these should not appear. The stereochemistry was not seen to play a major role in the qualitative character of the nickel spectra. However the shake-up satellite separation from the main line might comply with the degree of covalency of a bonding, with the bonding being more covalent for satellites further apart (73). For the qualitative information on the bonding, the binding energy should be also considered. As calculated by Veenendaal and Sawatzky, a main xps line of nickel ion surrounded by NiO6 clusters reflects well spectrum shown by nickel oxide (94). The structure of 2p3/2 line is complex. It consists of main line, additional high BE line resulting from screening by an electron originating from oxygen orbitals from a neighbouring NiO6 unit rather than from around the Ni atom with a core hole. For a polycrystalline NiO, the main multiplet line could only be fitted with at least four components from 853 up to 857 eV. This creates a large difficulty in fitting and differentiation of specific oxidation states of nickel. The calculations 47PDF Image | Investigation of metal-insulator transition in magnetron sputtered samarium nickelate thin films
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