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

Methods of surface analysis and micromodification using the scanning electrochemical 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 conductivity and reactivity can be imaged in the feedback and collector/generator mode. The same set-up allows micromodification processes as well. The degree of doping of polyaniline deposited on a PETG film was increased locally. The generated structure formed an interdigital array consisting of doped and undoped polyaniline. Its local conductivity was successfully analysed in a second step. To fabricate a polymer microstructure the monomer 2,5-bis(1-methyl-pyrrol-2yl)-thiophene was deposited by evaporation on an ITO substrate. Polymerisation was induced by the tip via an oxidation reaction. The remaining monomer was easily removed by organic solvents. A new method for the microdeposition of silver on a gold substrate is described. Silver cations were complexated in an aqueous solution of ammonia. Protons locally generated by the tip shifted the complexation equilibrium to create free silver cations. When the sample is held on an adequate potential they were deposited on the gold surface.