Effects of Ligands on Electroless Ni-Fe-P thin Films from Sulphate Bath

Ni-Fe-P thin film was prepared by electroless deposition from sulphate bath. The effects of ligands, such as tri-sodium citrate(NaCit) and/or tri-ammonium citrate(NHCit), on the deposition process, deposition rate, composition, and structure of Ni-Fe-P thin film were investigated. It is found that adding NHCit to the electroless deposition systems made them more polarized, shifted the deposition potential to positive direction and decreased the deposition rate. When the total concentration of NaCit and NHCit is fixed in bath, the increasing of the ratio of [NHCit]/[NaCit+NHCit] in bath increases the amorphous degree of thin films corresponding to the increase of phosphorus content resulted from the competitive reduction of several ions. The work is helpful for the structure optimization and performance improvement of electroless thin films.