In situ x-ray photoelectron spectroscopy study of evaporated magnesium on chemically synthesized polypyrrole films

The physicochemical interactions of thermally evaporated magnesium atoms wi th the chemically synthesized polypyrrole film in its salt and partially un doped (deprotonated) forms were studied in situ by x-ray photoelectron spec troscopy (XPS). The changes in the N(Is), Mg(2p), and S(2p) core-level spec tra of the films, as well as the changes in the interfacial chemical compos itions, were carefully monitored. It was observed that both types of films underwent an increase in intrinsic oxidation state ([=N-]/[-NH-] ratio) in response to the metal deposition process.. Careful analysis of the Mg(2p) a nd S(2p) spectra revealed that the incoming magnesium atoms reacted with th e dopant to form a salt. The observed increase in the intrinsic oxidation s tate of the films could therefore be attributed to the undoping (deprotonat ion) process. The interactions had also involved oxygen since a surge in ox ygen concentration at the metal/polymer interface was observed with increas ing magnesium coverage. From the results obtained, it could be concluded th at the interfacial layer consisted of magnesium-dopant salts, magnesium oxi des, magnesium cluster, and magnesium metal. (C) 2001 American Vacuum Socie ty.