Synthesis of Allylamine Plasma Polymer Films: Correlation between Plasma Diagnostic and Film Characteristics

Primary amine-based plasma polymer films (NH2-PPF) were synthesized using plasma polymerization of allylamine in continuous wave (CW) and pulsed radio-frequency (RF) modes. Plasma chemistry, studied by residual gas analysis mass spectrometry, revealed that the precursor fragmentation is a function of the equivalent power (P-eq) dissipated in the discharge, independently of the plasma mode used. X-ray photoelectron spectroscopy combined with time-of-flight secondary ion mass spectrometry suggests as the precursor fragmentation in the plasma increases: (i) a decrease of the primary amine concentration in the NH2-PPF (%NH2) and (ii) an increase of the cross-linking degree. For a given P-eq, similar to the precursor fragmentation in the plasma, the NH2-PPF characteristics were found to be independent of the plasma mode used. Therefore, the main advantage of using pulsed RF processes over CW ones is the possibility to work at very low Peq which enables low precursor fragmentation, optimization of %NH2, and reduction of the film cross-linking degree. The chemical composition and the cross-linking degree of the NH2-PPF synthesized by allylamine plasma polymerization can thus be tailored by adjusting the equivalent RF power injected in the plasma.