Journal of Applied Physics vol:92 issue:9 pages:5543-5549
During electrochemical atomic force microscopy (AFM) measurements that involve metal deposition or dissolution, the photodiode voltage changes when the electrode potential changes. These changes in photodiode voltage are caused by deflection of the laser beam due to concentration gradients near the electrode. In this work, the changes in photodiode voltage versus polarization time were studied using a commercial AFM. For an anodically polarized electrode, the concentration increases near the electrode due to metal dissolution. This causes a steady decrease in photodiode voltage. For a cathodically polarized electrode, oscillations in the photodiode voltage are observed. These oscillations are caused by Rayleigh-Benard instabilities due to the fact that the concentration, and hence the density of the electrolyte near the electrode, is lower than the bulk electrolyte. A mathematical model was constructed that calculates the changes in photodiode voltage with polarization time. (C) 2002 American Institute of Physics.