Chemical Processes of Ions

Formation - Transport - Reactivity

Transport of ions through ultra-thin deposited fims

The bombardment induced ion transport (BIIT) approach developed in our group not only allows to measure ionic conductivities of solid electrolytes, which are ionic conductors in the first place, but also of polymer films. Many polymer films are considered “electrically insulating”, which more precisely should read “electronically insulating”. We can easily demonstrate that ultra-thin PPX (poly-para-xylylene) films are capable of transporting alkali ions.

Recently, we have reported on the first investigation of bombardment induced ion transport of potassium ions through a thin PPX film deposited on a metal electrode. We demonstrate that the current scales quadratically with the ion beam energy. Analysis of these current-voltage curves yields the diffusion coefficient. The measurement of the diffusion coefficient as a function of the film temperature yields the activation energy for potassium ion hopping through PPX-films to be 2.74 eV ± 0.18 eV [1].

In a separate experiment we have demonstrated that BIIT of potassium ions in PPX leads to a concentration profile of potassium reaching through the entire film [2]. For further details see nanoionics at interfaces.

[1]        Susanne Schulze, Martin Schäfer, Andreas Greiner and Karl-Michael Weitzel
Bombardment induced ion transport – Part III: Experimental potassium ion conductivities in poly(para-xylylene)         
PCCP, 15, 1481-1487, (2013)

[2]        Susanne Schulze, Julia Zakel, Martin Schäfer and Karl-Michael Weitzel
Potassium ion transport through poly-para-xylylene films  
IEEE-TDEI, 19, 1167-1174 (2012)