Quantitative Analysis of Scanning Conductance Microscopy

We present a quantitative model for phase shifts observed in scanning conductance microscopy and show excellent agreement with data on samples of (conducting) single wall carbon nanotubes and insulating poly(ethylene oxide) (PEO) nanofibers. The model takes into account phase shifts due to the electrostatic (capacitive) forces exerted on the tip by sample and substrate, using simple approximate geometries. Data for large diameter, conducting doped polyaniline/PEO nanofibers are qualitatively explained. This quantitative approach is used to determine the dielectric constant of PEO nanofiber, a general method that can be extended to other dielectric nanowires.