SCANNING ELECTROCHEMICAL MICROSCOPY - A NEW SCANNING-MODE BASED ON CONVECTIVE EFFECTS

A new measuring technique for the scanning electrochemical microscope (SECM) is presented, which we call picking mode. The influence of the tip-surface distance on the current signal is separated from the current due to the electrochemical properties of the surface by this new method. Based on convective effects, the fast approach of the tip towards samples revealed a sharp increase of the tip current close to the samples' surface. During this strongly instationary stage, the current is dominated by convective flows and the influence of the electrochemical surface properties is negligible. Using this convective current, the tip-surface distance can be adjusted within a few microns. In a second step after reaching the steady-state transport conditions again, the electrochemical processes are characterised by the current at this position. The capability of the new mode is proven by scanning a bended platinum sheet and a PVC sample. The new method enables the separate acquisition of the height profile due to the surface's morphology and of the topology due to local variations of electrochemical properties.