In situ XPS study of the interactions of evaporated copper atoms with neutral and protonated polyaniline films

Abstract

X-ray photoelectron spectroscopy was employed for the interactions between thermally evaporated copper atoms and neutral polyaniline (PANI) films of various intrinsic oxidation states ([= N-Ee Cyrillic sign-N-] ratios), as well as with the HClO4-protonated PANI film. Quantitative changes in the N 1s core-level spectra, evolution of the Cu 2p core-level signals and the Cu LMM Auger line shapes, and angle-resolved changes in surface stoichiometry of these films with the progreeeive deposition of Cu atoms were carefully monitored. For the neutral films, the incoming Cu atoms appear to affect predominantly the nitrogen sites, resulting in a decrease in the intrinsic oxidation state of the polymer Nevertheless, the effect was observed to be rather weak, possibily through a slight disruption of the π-electron conjugation of the polymer backbone. However, for the protonated film, interactions with incoming copper atoms resulted in the decomposition of the perchlorate dopant and the formation of copper chloride species. Diffusion of Cu atoms into the bulk of the polymer was observed for all types of films studied. The interactions of the Cu atoms with the PANI surfaces were also compared with those of the Al atoms.