Untersuchungen zum strukturkorrelierten Ionentransport mittels BIIT und ToF-SIMS durch ultradünne Polymerfilme

The central aspect of this thesis is the investigation of ultra-thin deposited polymer films in the range between 4 nm to 400 nm and its influence on the ion transport by varying the thickness of the polymer film, the material of the backside electrode and the species of the emitted ions. Explicitly, the thermoplastic, surface conform and semi crystalline polymer poly-para-xylylene (PPX) and the polyelectrolyte multilayer (PAH/PSS)n consisting of layers of poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) are investigated extensively. The measurement techniques applied in this work are on the one hand the bombardment induced ion transport (BIIT) which has been established in the working group of Prof. Dr. Weitzel and results in a homogeneous, low-energetic alkaline ion beam hitting the polymer surface. On the other hand, ex-situ measurements of the bombarded polymer samples are performed via time-of-flight secondary ion mass spectrometry (ToF-SIMS) in order to obtain space-dependent concentration profiles. BIIT technique enables the generation of current-time- and current-voltage-curves structural characteristics of the samples can be derived from. Time constants τ and the amount of inserted charge Q into the PPX-Films can be obtained from current-time-curves as a function of the PPX structure and of the underlying metallic substrate. In this work the differences of samples with non-intermittent pathways (NIPs) and samples with no NIPs can be distinguished by different behavior of the current-voltage-curves and are visualized by ToF-SIMS depth profiling. A linear current-voltage-characteristic is obtained if NIPs are dominating the sample. If the bulk material of the polymer is dominating, a quadratic current-voltage curve can be fitted. Furthermore the diffusion constant and the activation energy of temperature dependent measurements can be derived from the current-voltage-characteristics as a function of the used alkaline ion and the used substrate. Ex-situ depth profiling with ToF-SIMS on BIIT long-time bombarded samples allows to get insight in the concentration distribution within the samples. Due to the low extend of the polymer layers the formation of an alkali ion interphase, analogous to the solid electrolyte interphase (SEI) in batteries, can be observed via ToF-SIMS depth profiling for the first time. The interphase is formed between the polymer film and the metal substrate as a consequence of the alkaline ion neutralization at the backside electrode. Further investigations consider the behavior of current-voltage-curves as a function of the underlying substrate material and the type of emitted ion in comparison to the electrochemical description of BIIT experiment and the different diffusion coefficients. The interconnection of BIIT and ToF-SIMS measurements allows to obtain information about miscibility and immiscibility of metal-metal-systems. For (PAH/PSS)n systems thickness- and temperature-dependent conductivity studies are performed by BIIT and discussed as a function of their preparation method.