Abstract: Conducting polythiophene films electrochemically polymerized in aqueous perchloric solu-tion have been characterized by means of reflecting FT-IR spectra, UV-Vis spectra and XPS spectra.The XPS spectra with etching technique were used to obtain the informationin depth.Water seems to participate in the polymerization process of thiopheene and intro-duce oxygen atom into the PTh structure as carbonyl group.ClO₄^- content varied withthe depth of the film.No ClO₄^- was found in the bulk, but at the surface it gave a concen-tration of 8～10mol%, lower than the concentration of PTh in organic solvents.C-Cl bonds were formed during the oligomerization of thiophene in concentrated HClO₄ solutionand uniformlly distributed in the PTh film.The conductivity of PTh film is about 1S/cm.

Key words: polythiophene, characterization, XPS, FTIR