Scanning Electrochemical Microscopy. Apparatus and Two-Dimensional Scans of Conductive and Insulating Substrates

The applicatlon of scannlng electrochemical microscopy (SECM) in the feedback mode to two-dknenslonai scans over conductlve and insuiatlng substrates to obtain topographic information at the micrometer-level Is descrlbed. I n the feedback mode the effect of the conductlvlty of the substrate and dlstance of the substrate from a scanning ultramicroelectrode tlp on the current flowing at the tip caused by an electrode reaction Is recorded as a function of the tlp x-y position. Experiments wlth a 50-pm Pt wlre on glass, a ca. 50-pm glass fiber on glass, a gold mkrlgrkl, a Pt fdl, and a KCI crystal In both aqueous and acetonitrile solutions are presented. The construction of the SECM and the hardware and software that control three-dimensional tip movement and data acqulsltlon are also described.