Effect of phosphorus concentration on the electronic structure of nanocrystalline electrodeposited Ni-P alloys: an XPS and XAES investigation

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 cl-type core-hole screening is less pronounced and the binding energy of the satellite for the final state with a filled Ni4s shell increases. Copyright (C) 2008 John Wiley & Sons, Ltd.