Regensburg 2013 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 9: Ion and Electron Beam Induced Processes

DS 9.2: Vortrag

Montag, 11. März 2013, 16:30–16:45, H8

Bombardment induced ion transport (BIIT) through thin polymer films — •Susanne Schulze, Julia Zakel, Martin Schäfer, Andreas Greiner, and Karl-Michael Weitzel — Philipps-Universität Marburg, FB Chemie, 35032 Marburg

We report on the transport of potassium ions (K⁺) through Poly(para-xylylene) (PPX) films (thickness 100 nm to 2720 nm) induced by ion bombardment. The films were formed by plasma chemical vapor deposition onto a metal electrode. The experiments were performed in an UHV apparatus where an ion beam is generated by thermionic emission of potassium ions from aluminosilicates. By bombarding the PPX films with an ion beam of low kinetic energy (10 eV to 500 eV) we generate a potential gradient and a concentration gradient inducing transport of the ions through the material. The ion transport is detected as a current on the backside electrode of the film. By measuring this current as a function of the kinetic energy of the impinging ions, we are able to determine the ionic conductivity of the material. In a second experiment PPX is bombarded with an ion beam of constant kinetic energy for several days. This experiment leads to the formation of an electro-diffusion profile of potassium in the film as shown by time-of-flight secondary ion mass spectrometry. The potassium diffusion profiles, which reach through the entire film, can be quantitatively described by theoretical calculations based on the numerical solution of the Nernst-Planck-Poisson equations. From this analysis we conclude that the effective diffusion coefficient of K⁺ in PPX decreases with increasing incorporation of the K⁺ ions into the film.