Surface analysis of plasma deposited polymer films, 7 - In situ characterization of plasma deposited allylamine films by ToF-SSIMS, XPS and NEXAFS spectroscopy

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 power, and plasma parameters such as duty cycle. 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 crosslinked 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 nitrites 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.