1. How SECM Works

The SECM principle is based on measuring the current flowing through the UME (radius electrode) $r$ ranging from a few nanometers to 25 μm) as it scans the surface of a sample by hovering over it at a short distance. The sample, also known as the substrate, can be solid or liquid (however, we will limit ourselves to the case of solid substrates). The presence of the sample at a short distance from the UME causes a disturbance in the probe’s electrochemical response, which provides information about the nature and properties of the substrate. The UME thus constitutes the SECM probe: the resolution of the SECM is therefore limited by the size of the UME, and its sensitivity is limited by the minimum current that can be accurately measured at the UME.

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