Simultaneous visualization of surface topography and concentration field by means of scanning electrochemical...

Scanning electrochemical microscopy visualizes concentration profiles. To determine the location of the probe relative to topographical features of the substrate, knowledge of the probe-to-sample distance at each probe position is required. The use of electrochemical impedance spectroscopy for obtaining information on the substrate-to-probe distance and on the concentration of interest using the electrochemical probe alone is suggested. By tuning the frequencies of interrogation, the probe-to-substrate distance can be derived followed by interrogation of processes that carry information on concentration at lower frequencies. These processes may include charge-transfer relaxation, diffusional relaxation at the electrode, and open-circuit potential at zero frequency. A potentiometric chloride sensing microprobe is used herein to reconstruct both topography and the concentration field at a microscopic diffusional source of chloride.