Quantitative impedance measurement using atomic force microscopy.
Obtaining quantitative electrical information with scanning probe microscopy techniques poses a significant challenge since the nature of the probe/sample contact is frequently unkown. For example, obtaining quantitative kinetic data from the recently developed atomic force microscopy (AFM) impedance technique requires normalization by the probe/sample contact area. In this paper, a methodology is proposed that enables the extraction of quantitative information from the AFM impedance technique. This methodology applies results from nanoindentation experiments and contact mechanics theory to characterize AFM probe contacts. Using these results, probe/sample contact forces (which can be accurately measured in the AFM) may be converted into probe/sample contact area estimates. These contact area estimates, when included in model of the probe/sample contact, enable the extraction of quantitative data. This methodology is applied to the recently developed AFM impedance measurement technique, enabling a quantitative study of the oxygen reduction reaction (ORR) at nanometer length scales. Using the AFM impedance system, kinetic data for the (ORR) at nanoscale Platinum/Nafion contacts is extracted. The kinetic data obtained from the AFM impedance technique match previous bulk measurements-affirming the technique's quantitative potential.
|Main Author:||O'Hayre, Ryan.|
|Other Authors:||Feng, Gang., Nix, William., Prinz, Fritz.|