The introduction of a scavenger that reacted with the tip-generated species produced a significant focusing effect on the diffusion field. We investigated the basic principles of this new scanning electrochemical microscope operating mode, called a chemical lens. This focusing effect was demonstrated by silver deposition from solution, which enabled direct monitoring of the turnover at the sample's surface by measuring the current. In the electrolyte solution, silver cations were complexed by an excess of ammonia to avoid initial silver deposition at the gold substrate. Using this tip electrode, locally electrogenerated protons shifted the complex formation equilibrium back to produce higher concentrations of free silver ions, which were subsequently discharged at the goldcovered sample electrode. The free silver cations in the outer part of the diffusion field were recomplexed by the excess of ammonia, which as it acted as a scavenger, did not take part in the deposition. The resolution reached values as low as less than one-third of the active tip diameter. The introduction of a scavenger which itself does not take part in electrochemical reactions represents a general method for downscaling in microelectrochemistry. The improvement in resolution is not restricted to surface modifications but has been observed in surface analysis as well.

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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 inter‐digital 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.