Temperature effects on the chemical composition of nickel-phosphorus alloy thin films

Electroless Ni-P (EN) alloys are widely used as coating materials. Their properties depend on the level of phosphorus present and the extent of thermal treatment. We report the results of two complimentary electronic structure techniques, X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy (XPS), and the site-specific surface chemistry in EN alloys of different phosphorus compositions and thermal treatments. In XANES experiment, absorption at the Ni L3,2 edge and the P K edge were measured and the P 2p, Ni 2p, and Ni 3p bands were measured by XPS. Heating EN alloys to high temperatures result in a competitive reaction between phosphorus and nickel on the surface for oxygen. There is an increase in the level of phosphates and other forms of phosphorus oxides and a decrease in the oxidized nickel on the surface of the EN alloy thin film. Changes in the electronic structure and chemical composition in the bulk of the EN alloy are not obvious.