Ultrasound-assisted pulse electrodeposition of cobalt films

Pulse electrodeposition of cobalt was conducted in a sodium saccharin contained sulfate bath under silent or insonated conditions. The effects of pulse duty cycle, pulse frequency and ultrasonic agitation on the crystallographic structure and surface morphology of cobalt deposits were studied. All deposits obtained have a hexagonal close-packed structure, with its basal plane preferentially aligned parallel to the substrate surface. With the increase in duty cycle, texture coefficient for (100) plane increased whether ultrasonic agitation was imposed or not, while the imposition of ultrasonic agitation clearly decreased the texture coefficient for (100) plane. A finer-grained and smoother cobalt electrodeposit was obtained at 62.5 Hz and 25% duty cycle under insonated condition. To understand the roles that these operating parameters played in the electrodeposition, chronopotentiometry and linear sweep voltammetry were used to record the cathodic potential in cobalt deposition and hydrogen evolution current, respectively, which were associated with the morphological and structural change of cobalt deposits. Transmission electron microscopy was also employed to investigate the microstructure and crystal defect of cobalt films. A high density of stacking faults was detected in the cobalt films by high-resolution transmission electron microscopy.