Scanning Electrochemical Microscopy. Introduction and Principles

The technlque of scannlng electrochemical mlcroscopy (SECM) Is descrlbed. I n thls technlque the electrolysls current that flows as an ultramicroelectrode tlp (diameter ca. 10 gm) Immersed In a soiutlon Is moved above a substrate surface is used to characterize processes and structural features of the substrate. Modes of Operation consldered Include collectlon modes, where products electrogenerated at the substrate are detected at the tip (held at constant potentlal or operated In the cyclic voltammetrlc mode), and feedback modes, where the effect of substrate on the tlp current Is monltored. The feedback mode can be used with both conductive and lnsulatlng substrates and Is less sensithe to electrlcal coupllng between substrate and tlp. An ailernatlng current generatlon/collectlon mode Is also described. Experimental results for the different modes of Operation and proposed extensions of the SECM technlque are presented.