Characterization of nickel phosphorus surface by ToF-SIMS

ToF-SIMS was used to characterize the surface of nickel phosphorus (NiP) layers that were electrolessly plated on aluminum substrates of magnetic recording disks. X-ray photoelectron spectroscopy (XPS) was also used to study the bonding nature of phosphorus and nickel. ToF-SIMS and XPS results showed that the NiP surface is oxidized and composed of nickel oxide, nickel hydroxide, nickel phosphate, and nickel phosphite. It was also shown that the oxidized NiP surface is about 10 Å thick and has a dual layer structure. In the dual layer structure, nickel oxide and hydroxide form the top layer while nickel phosphate and phosphite make the bottom layer. It was concluded that the oxidation of NiP surface is electrochemical in nature.