The role of image charges in solid electrolyte capacitors

Thin films of ion conducting polyethylene oxide (PEO) were prepared to produce plane parallel capacitance structures. The samples exhibit a Kohlrausch behaviour of the polarisation current in the long time range after application of an electrical field: j ∝t^-α. This can be explained by image charges in the electrodes which attract the mobile ions. The attraction of charges influences the dynamic and the static properties of the system. These charges can be observed experimentally by a modified CV-measurement in the static case. The remanent polarisation in hysteresis measurements confirms the presence of these charges. To describe the experimental results a three-dimensional hopping model is developed. Computer simulations yield the attraction of ions to the electrodes due to the image charges as well as the experimentally determined t^-α currents.