Copper Deposition in the Presence of Polyethylene Glycol I. Quartz Crystal Microbalance Study

The addition of polyethylene glycol (PEG) and Cl - to an acid copper electrolyte inhibits the deposition reaction for cathodic overpotentials of up to about 150 mV. Adding Cl - only promotes the deposition reaction, while adding PEG alone has a relatively small effect on electrode kinetics. Frequency shifts of an electrochemical quartz crystal microbalance suggest the adsorption of a monolayer of PEG molecules that are collapsed into spheres provided chloride ions are present, with little adsorption occurring when Cl - is absent. This behavior is the same for gold and copper surfaces. Transient current measurements suggest that chloride ions affect the PEG adsorption equilibrium rather than adsorption kinetics alone.