Determination of optimum imaging conditions in AC-SECM using the mathematical distance between approach curves displayed in the impedance domain

Scanning electrochemical microscopy (SECM) in its alternating current mode (AC-SECM) has been of growing importance to detect and interpret local variations of electrochemical surface properties with high spatial resolution. The sensitivity of AC-SECM and hence the quality of imaging was found to be highly dependent on the experimental conditions. It was commonly judged using approach curves in the distance domain. As an alternative to current–distance approach curves, the coordinate system based on real and imaginary part of impedance is suggested for their display. In this framework, the difference between the impedance vector magnitude, real or imaginary part of impedance over neighboring surfaces is considered as a measure of imaging contrast. The variable which grants maximum difference is selected for imaging while measurement conditions associated with this maximum indicate optimum scanning conditions. The methodology of determining these optimized parameters is laid out in this contribution and examples are given. Since the optimum parameters are identified before the actual lateral imaging, this time-saving method facilitates the visualization of local electrochemical properties at the highest possible quality.