1. How SECM works

The principle of SECM is based on measuring the current flowing through the EMU (an electrode with a radius r ranging from a few nanometers to 25 μm) as it sweeps over the surface of a sample from a short distance. The sample, also known as the "substrate", can be solid or liquid (although we'll confine ourselves to the case of solid substrates). The presence of the sample at a short distance from the EMU will perturb the electrochemical response of the probe, providing information on the nature and properties of the substrate. The EMU thus constitutes the SECM probe: SECM resolution will thus be limited by the size of the EMU, and its sensitivity by the minimum current that can be precisely measured at it.

Figure 1 shows the complete system required for SECM manipulations: a system for...