X-ray photoelectron spectroscopy and ellipsometry studies of the electrochemically controlled adsorption of benzotriazole on copper surfaces

Adsorption of the corrosion inhibitor benzotriazole (BTA) from solution has been studied on well-characterized electrochemically prepared Cu surfaces. In situ ellipsometry and ex situ x-ray photoelectron spectroscopy (XPS) have been used to probe both the nature of the Cu surfaces prior to BTA adsorption and to determine the stoichiometry, thickness, and chemical composition of the Cu–BTA overlayer films. The films grown on Cu2O and on Cu0 under oxidizing conditions are generally 5–40 Å thick and best described as Cu+1 BTA. Uptake of BTA is also observed on CuO and reduced Cu0 surfaces where the adsorbed film is limited at close to a monolayer. Therefore, Cu2O does not appear to be a prerequisite for uptake of BTA. The thickness of the inhibitor overlayer was calculated from the N 1s/ Cu 3p core level XPS data and was in good agreement with independent ellipsometric measurements on similar samples. Roughening of the Cu surface is observed for samples treated at low pH. Differing amounts of oxygen are found in the Cu+1 BTA films depending upon the preparation environment.