Potassium ion transport through poly-para-xylylene films

Bombardment of poly-para-xylylene films by a beam of potassium ions induces ion transport through the polymer material, which originally is an electrical insulator. The ion transport can easily be detected as neutralization current on an electrode at the back side of the film. The transport is accompanied by the formation of an electrodiffusion profile of potassium in the film as shown by time-of-flight secondary ion mass spectrometry. The potassium depth profiles can be rationalized by theoretical calculations based on numerical solving the Nernst-Planck-Poisson equations. The results may shed new light on the formation and dynamics of space charge zones in polymers and is thus potentially relevant for electret research.