Effect of ultrasonic field on the mechanism of electrodeposited Cu nucleation and growth

Electrodeposition technology is widely used in the surface treatment of copper foil. The unique "mechanical disturbance effect" and "cavitation effect" of ultrasonic field can effectively control the electrodeposition process of Cu and improve the quality of electrodeposited layer. In this paper, Linear Sweep Voltammetry (LSV), Cyclic Voltammetry (CV), Chronoamperometry (CA) and Chronocoulometry (CC) were used to study the electrochemical behavior of electrodeposited Cu in ultra-high acidity sulfate systems under different ultrasonic field powers. The nucleation and growth mechanism of Cu were discussed, and the surface morphology of electrodeposited layer was analyzed. The results show that the electrodeposition of Cu under the static condition (0 W) follows the diffusion controlled progressive nucleation and 3D growth mechanism, and the deposits are in the cylindrical shape with spherically agglomerated. The ultrasonic field significantly improves the mass transfer rate in the electrodeposition process, and the fine dispersion effect is obvious. The uniform and dense micro-nano layers are formed, following the 3D growth mechanism. With the increasing of ultrasonic field power, the nucleation mechanism gradually changes from the diffusion controlled progressive nucleation to the electrochemistry controlled instantaneous nucleation. In addition, there appear peeling, grooving and local microcracks on the electrodeposited layer under higher ultrasonic power condition, and it is easier to form a smooth and uniform electrodeposited layer with the ultrasonic power of 60 W compared to that with the ultrasonic power of 100 W.