Juhyoun Kwak and Allen J. Bard, "Scanning Electrochemical Microscopy. Apparatus and Two-Dimensional Scans of Conductive and Insulating Substrates," Anal. Chem., 61 (17), 1794 - 1799 (1989.09.01.)

Abstract
The application of scanning electrochemical microscopy (SECM) in the feedback mode to two-dimensional scans over conductive and insulating substrates to obtain topographic information at the micrometer-level is described. In the feedback mode the effect of the conductivity of the substrate and distance of the substrate from a scanning ultramicroelectrode tip on the current flowing at the tip caused by an electrode reaction is recorded as a function of the tip x-y position. Experiments with a 50-mm Pt wire on glass, a ca. 50-mm  glass fiber on glass, a gold minigrid, a Pt foil, and a KCl crystal in both aqueos and acetonitrile solutions are presented. The construction of the SECM and the hardware and software that control three-dimensional tip movement and data acquisition are also described.