Inhibition of Copper Deposition by Polyethylene Glycol and Chloride

A comprehensive model for the effect of polyethylene glycol (PEG) and Cl − on Cu 2 + reduction developed in Part I of this study [ Huerta Garrido and Pritzker , J. Electrochem. Soc. , 156 , D36 (2009) ] is further analyzed in Part II. On the basis of the model, the sharp loss of inhibition at a critical potential during cathodic scans occurs whenever the PEG adsorption density decreases below the minimum amount required to completely cover the electrode. When high additive concentrations are used, the electrode remains completely covered by the inhibiting film throughout the scan and, thus, the current for Cu 2 + reduction rises more gradually with overpotential. Excellent agreement between the computed and measured current-potential curves during both forward and reverse directions of cyclic scans is obtained for each solution investigated in this study. Furthermore, analysis of the model reveals that hysteresis in these cyclic scans occurs whenever the electrode goes from a state where it is completely covered by PEG to one where it is only partially covered during the forward scan.