The chemistry of organophosphate thin film coatings from low pressure plasma and the effect of the substrate on adhesion

Abstract

Plasma polymers incorporating phosphate ions have been produced using triethyl phosphate as the precursor. Plasma phase analysis showed that the phosphate ion is highly stable in the plasma, while neutral species are more likely to be hydrocarbon precursor fragments. Increasing the RF power input increases the contribution of ions to the deposition. Surface analysis by XPS showed that the plasma polymer surfaces were a mixture of hydrocarbon species, retained PO groups, with only minor loss of PO groups. The stability of the plasma polymers in water on different substrates showed that applied RF power only had a minor effect on film solubility. The nature of the substrate − plasma species interaction is critical in being able to form insoluble structures.

Rational approaches for optimizing chemical functionality of plasma polymers: A case study with ethyl trimethylacetate

“…[ 12 ] However, although plasma polymerization has been most often discussed in terms of radical reactions and combinations, it is also well‐established by now that ions can also play important roles in the plasma gas phase and in the build‐up of coatings. [ 13‐15 ] The acceleration of ions across the plasma sheath versus the diffusion‐controlled transport of radical species means that ions can play a role in plasma polymer build‐up that substantially exceeds their relative abundance in the bulk. Moreover, ions may be much less susceptible to rapid reactions in the plasma phase.…”