2009 Volume 125 Issue 2 Pages 62-67
The effect of thiourea on copper electrodeposition has been investigated by measuring the cathodic polarization curves for aqueous H2SO4-CuSO4 solutions and observing the surface morphology of deposited Cu. The cathode potential for Cu deposition was depolarized by the addition of thiourea less than 0.1 mmol/L, whereas it was significantly polarized with increasing the concentration of thiourea above 0.1 mmol/L. The thiourea showed both effects of depolarization and polarization on Cu deposition depending on its concentration. The grain size of deposited Cu decreased monotonously by the addition of thiourea. In the presence of both thiourea and gelatin, the polarization effect due to gelatin decreased with addition of thiourea less than 0.1 mmol/L. The grain size of deposited Cu looks smaller in the presence of both thiourea and polymer additive such as gelatin or PEG than thiourea alone. On the other hand, in solution containing both thiourea and Cl- ions, the synergistic effect of thiourea and Cl- ions on the polarization for Cu deposition was observed only in the case that the concentration of thiourea was increased to 10 mmol/L. However, at 0.1 mmol/L of thiourea, the cathode potential was depolarized irrespective of coexistence of Cl- ions.
