THEORETICAL AND EXPERIMENTAL INVESTIGATION OF INTERNAL-REFLECTION AT THIN COPPER-FILMS EXPOSED TO AQUEOUS-SOLUTIONS

Research directed toward the adsorption of biopolymers at an aqueous/solid interface is of particular interest due to the prevalence of corrosion influenced by biopolymers and/or microorganisms adsorbed at the interface. A method for depositing continuous copper films (10-12 nm) on a germanium internal reflection element (IRE) by physical vapor deposition is described. The Maxwell and Fresnel equations were used to model reflectance and mean square electric field intensity as function of distance from the Cu/H2O interface for stratified media consisting of Ge/Cu/air and Ge/Cu/H2O. Calculation of the absorption of the H2O bending mode allows an estimate of the feasibility of measuring biofilms at the Cu surface. Results of theoretical calculations were verified by exposing the Cu-coated Ge three-reflection IRE to flowing saline. Initially the intensity and location of the 1640-cm(-1) band was consistent with the theoretical calculations. After -1 min, surface-enhanced infrared absorption was observed leading to anomalous band shifts to 1650 cm(-1) and dispersive band shapes due to the removal of Cu from the IRE surface and the formation of Cu islands that were originally formed during the deposition.