Growth kinetics of electroless NixCo1 − x deposition

Various electroless Ni-Co-P films were deposited on silicon substrates in electroless baths using sodium hypophosphite as reducing agent and nickel and cobalt sulfates as ion source at pH value of 9 and temperature from 55 to 85 °C. The effect of the atomic ratio of Co to Ni + Co in baths on the growth behavior of the electroless Ni-Co-P films was studied. The various electroless Ni-Co-P films were characterized by scanning electron microscopy for the morphology, transmission electron microscopy for the microstructure and thickness, and energy dispersion spectroscopy for the composition. The results showed that the growth rate of the electroless Ni-Co-P films is generally increased with increase of the bath temperature and is decreased with atomic ratio of Co to Ni + Co in baths. The reduction of the Co2+ ion is easier than the Ni2+ ion in various baths, except for the bath with 0.9 atomic ratio of Co to Co + Ni.