A combined scanning electrochemical microscope (SECM) - atomic force microscope (AFM) is described. This instrument permits the first simultaneous topographical and electrochemical measurements of substrates both in air and under aqueous solution, at high spatial resolution. For in-air measurements, the amperometric response of a Pt-coated AFM tip connected as a working electrode is monitored as the probe is scanned over the surface of interest. For work under fluid, probe tips have been constructed by coating flattened and etched Pt microwires with insulating, electrophoretically-deposited paint. The flattened portion of the probe provides a flexible cantilever (force sensor), while the coating insulates the probe such that only the tip end (electrode) is exposed to solution. In both cases, the SECM-AFM technique is illustrated with simultaneous topographical and electrochemical imaging studies of track-etched polycarbonate membranes. The possible use of the technique for targeting surface structural features for subsequent electrochemical-topographical investigations is highlighted with preliminary studies on the local etching of crystal surfaces
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