SEIRAS Study of Chloride Mediated Polyether Adsorption on Cu
Thomas P. Moffat, Daniel Josell, Lee J. Richter
Surface enhanced infrared absorption spectroscopy (SEIRAS) was used to examine the co- adsorption of a selection of polyethers with Cl- under conditions relevant to superconformal Cu electrodeposition in CuSO4-H2SO4 electrolytes. In 0.1 mol/L H2SO4 a potential dependent mixed SO42--H3O+/H2O layer forms on weakly textured (111) Cu thin film surfaces. With the addition of 1 mmol/L NaCl the SO42--H3O+/H2O adlayer is displaced and rapidly replaced by an ordered halide layer that disrupts the adjacent solvent network leading to an increase in non-hydrogen bonded water that makes the interface more hydrophobic. The altered wetting behavior facilitates co- adsorption of polyethers, such as poly(ethylene glycols), polyoxamers, or polyoxamines. Interfacial water is displaced by co-adsorption of the hydrophobic polymer segments on the Cl- terminated surface while the hydrophilic ether oxygens are available for hydrogen bond formation with the solvent. The combined polyether-Cl- layer serves as an effective suppressor of the Cu electrodeposition reaction by limiting access of Cu2+aq to the underlying metal surface. This insight differs from previous efforts that suggest polymer binding is mediated by Cu+ species.
, Josell, D.
and Richter, L.
SEIRAS Study of Chloride Mediated Polyether Adsorption on Cu, Journal of Physical Chemistry C, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=926260
(Accessed June 3, 2023)