Scanning Electrochemical Microscopy
The basic idea of SECM is the visualization of local electrochemical activity of a sample surface. To achieve this, a microelectrode is scanned over the sample surface in close proximity. The nearfield regime in SECM is about three to five times the diameter of the active area of the used microelectrode. Close to the surface, the microelectrode interacts with the surface depending on the surface properties. Microelectrodes with active electrode radii below 100 µm are chosen as tips because of their unique electrochemical properties. The most important electrochemical property of microelectrodes making them for SECM is the hemispherical diffusion field at a microelectrode assuring fast mass transport towards the microelectrode and a steady-state behaviour. This current as measured at the microelectrode is modulated according to the electrochemical properties of the surface.