Space charge measurements with the scanning Kelvin probe

Using the scanning Kelvin probe the potential distribution on the surface of an ion-conducting polymer (polyethylene oxide) can be determined. Due to space charge accumulations a voltage applied between two electrodes causes a strongly nonlinear potential distribution in the samples. The curvature of the potential distribution indicates negative mobile ions in the samples. During the measurement the dc currents in the samples are observed to verify the steady state of the potential distribution. Additionally the measurement results are compared to simulations performed with a three-dimensional hopping model. These simulations show qualitatively the same results as the experiments.