Influence of magnetic fields on cobalt electrodeposition

Magnetic fields parallel to electrodes were introduced during plating process to prepare cobalt films from baths without additives. Effects of magnetic intensities on the nucleation process, electrochemical mechanism and surface morphology were investigated. It was found that limiting current and deposition mass increased gradually with the rise in magnetic intensities. Magnetohydrodynamic phenomenon (magnetic fields can induce currents in a moving conductive fluid, which in turn creates forces on the fluid and also changes the magnetic field itself) caused by Lorentz forces could agitate to decrease thickness of diffusion layers, which contribute to the increase in deposition rate. Reduction of cobalt on copper substrates without magnetic fields showed instantaneous nucleation process. However, cobalt reduction with 1 T magnetic intensity deviated from instantaneous nucleation process as a result of micromagnetohydrodynamic (micro-MHD) flows. Films of smaller grain size and compact surface could be obtained under 1 T magnetic intensity as a result of MHD effects.