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A surface analysis has been conducted on a series of electrodeposited nickel-phosphorus (Ni-P) alloys containing from 6 to 29 at.% phosphorus, using X-ray photoelectron spectroscopy (XPS) and X-ray excited Auger electron spectroscopy (XAES). No changes in core-level binding energies, Ni2p3/2 and Ni2p1/2, P2p, P2s, or X-ray excited NiLMM and PKLL Auger lines were observed regardless of phosphorus concentration. The only systematic differences observed concerned: (i) the binding energy of the Ni2p satellite peak, (ii) the fine structure of the NiLMM Auger lines, (iii) the percentage of the satellite in the total Ni2p3/2 spectrum and (iv) the valence band density of states in the Ni3d electrons region, all related to the electronic structure of the Ni-P alloys. For the first time, it has been possible to describe and rationalise the influence of (phosphorus) ligand concentration on the electronic structure of nickel-based alloys, using a screening model proposed in the literature for clarifying the role of substituents on the electronic structure of conductor compounds of nickel. As the phosphorus content increases, the number of non-bonding Ni3d electrons decreases. Thus the d-type core-hole screening is less pronounced and the binding energy of the satellite for the final state with a filled Ni4s shell increases.

Amorphous electrodeposited nickel−phosphorus alloys with 22 at. % of phosphorus (Ni22P) have been analyzed in the amorphous and re-crystallized state by EDXD and XPS surface analysis. The re-crystallization kinetics have been determined following in situ structural changes by EDXD. Distinct diffraction patterns indicating the presence of Ni3P confirm alloy re-crystallization at 645 °C. The XPS results show that all the core level binding energies of nickel such as Ni2p3/2 and Ni2p1/2 and phosphorus (P2p, P2s) remained constant after the change from X-ray amorphous to crystalline structure of the NiP alloy. Differences observed were as follows:  (a) the binding energy difference between the Ni2p main lines and the satellite, (b) the fine structure of the NiLMM Auger lines, and (c) the density of states in the valence band in the region of the Ni3d electrons. On the basis of these results from EDXD and XPS, it can be concluded that the change in alloy structure from X-ray amorphous to crystalline influences the electronic structure of the NiP alloy but not the chemical state of phosphorus. An explanation based on the screening model proposed in the literature is discussed.