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Surface Analysis of Plasma Deposited Polymer Films, 7

“In situ” Characterization of Plasma Deposited Allylamine Films by ToF-SSIMS, XPS and NEXAFS Spectroscopy



Summary: Plasma deposited allylamine films were studied by “in situ” ToF-SSIMS, XPS and NEXAFS Spectroscopy before exposure to ambient air. The influence of external plasma parameters such as duty cycle, plasma power, and monomer flow rate on (i) unsaturation, (ii) branching and cross-linking, (iii) nitrogen surface concentration and (iv) retention of amino groups was investigated. Harder plasma conditions, which can be obtained when high duty cycles, high plasma power, and low monomer flow rates are employed, increase the unsaturated, branched and cross-linked character of the plasma deposited films, while the surface concentration of N as well as the retention of the monomer's amino group decrease. As proven by NEXAFS findings and cross-checked by ToF-SSIMS results, the allylamine monomer's primary amino groups are partially transformed into other nitrogen functionalities during its plasma polymerization. Amongst them imines and nitriles are the conversion products with the highest probabilities of formation. Another conversion channel is the formation of nitrogen species not participating in the film growth. This is the reason for an increased N loss in plasma deposited allylamine films as observed independently by XPS and ToF-SSIMS when the plasma parameters are changed from mild to hard.

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Summations of π*(C[DOUBLE BOND]N) and π*(C[TRIPLE BOND]N) resonance intensities for NEXAFS N K-edge spectra measured with plasma deposited allylamine films vs. variation of duty cycle, or power.