Scanning electrochemical microscopy (SECM) is a versatile scanning probe technique that allows monitoring of a plethora of electrochemical reactions on a highly resolved local scale. SECM in combination with atomic force microscopy (AFM) is particularly well suited to acquire electrochemical data correlated to sample topography, elasticity, and adhesion, respectively. The resolution achievable in SECM depends critically on the properties of the probe acting as an electrochemical sensor, i.e., the working electrode, which is scanned over the sample. Hence, the development of SECM probes received much attention in recent years. However, for the operation and performance of SECM, the fluid cell and the three-electrode setup are also of paramount importance. These two aspects received much less attention so far. Here, we present a novel approach to the universal implementation of a three-electrode setup for SECM in practically any fluid cell. The integration of all three electrodes (working, counter, and reference) near the cantilever provides many advantages, such as the usage of conventional AFM fluid cells also for SECM or enables the measurement in liquid drops. Moreover, the other electrodes become easily exchangeable as they are combined with the cantilever substrate. Thereby, the handling is improved significantly. We demonstrated that high-resolution SECM, i.e., resolving features smaller than 250 nm in the electrochemical signal, could be achieved with the new setup and that the electrochemical performance was equivalent to the one obtained with macroscopic electrodes.
Keywords: atomic force microscopy; electrochemical sensors; scanning electrochemical microscopy.