SURFACE CHARACTERIZATION AND MODIFICATION BY THE SCANNING ELECTROCHEMICAL MICROSCOPE (SECM)

Methods of surface analysis and micromodification using the scanning e lectrochemical microscope (SECM) are described. An ultramicroelectrode (UME) is scanned in a liquid electrolyte a few microns above a sample 's surface. The principles of SECM are explained. Local surface conduc tivity and reactivity can be imaged in the feedback and collector/gene rator mode. The same set-up allows micromodification processes as well . The degree of doping of polyaniline deposited on a PETG film was inc reased locally. The generated structure formed an interdigital array c onsisting of doped and undoped polyaniline. Its local conductivity was successfully analysed in a second step. To fabricate a polymer micros tructure the monomer 2,5-bis(1-methyl-pyrrol-2yl)-thiophene was deposi ted by evaporation on an ITO substrate. Polymerisation was induced by the tip via an oxidation reaction. The remaining monomer was easily re moved by organic solvents. A new method for the microdeposition of sil ver on a gold substrate is described. Silver cations were complexated in an aqueous solution of ammonia. Protons locally generated by the ti p shifted the complexation equilibrium to create free silver cations. When the sample is held on an adequate potential they were deposited o n the gold surface.