Effect of butanedione oxime, 3-mercapto-2-propanesulfonate, and histidine on growth and magnetic properties of electrodeposited cobalt on copper substrate

Shorter electron mean free path, lower thermal expansion coefficient, and higher melting point compared to copper have made cobalt a promising alternative to copper in the post-Moore era. It has been extensively explored as a magnetic alloy material for downsized magnetic electronic components, storage devices, and specialized devices. Nevertheless, a lack of research on additives for cobalt plating solutions and unclear mechanism of the electroplating process, pose challenges in achieving cobalt plating layers with desired specifications. Electrodeposition with organic additives was employed to successfully producing cobalt plating layers. Electrochemical tests were performed to investigate the polarization effects of butanedione oxime (DMG), sodium 3-mercapto-2-propanesulfonate (SPS), and histidine (HIS) during cobalt electrodeposition to find out the inhibitory capacities of these additives. The adsorption behavior of the additives and interactions of the functional groups were analyzed by electron density and energy distribution of the additives based on quantum chemical calculations. The findings suggested that during the electrodeposition of cobalt, adsorption sites for molecules varied from the imine group of DMG to sulfonic acid group of SPS, and to imidazole group of HIS. HIS-assisted electrodeposition generated cobalt layer with pronounced soft magnetic properties of the lowest coercivity of 27.3 Oe and highest saturation magnetization intensity of 0.958 emu/g.