Selected effect of the ions and the neutrals in the plasma treatment of PTFE surfaces: An OES-AFM-Contact angle and XPS study

Polytetrafluoroethylene (PTFE) surfaces were treated by oxygen and nitrogen species generated either in a remote (filtered) RF plasma or in an ion gun. In the first case, the majority of the species reaching the surface are neutral molecules, whereas in the second case, ions are the reactive agent. In this paper, we show that ions alone do not lead to a significant grafting of new functions on the PTFE surface. The XPS analysis of the treated surface show identical behaviour with oxygen and nitrogen ion treatment, and the evolution of the C Is peak shape suggest a progressive sputtering, leading to defluorination of the surface. The nitrogen plasma treatment lead to a subsequent grafting that is attributed mostly to the "excited neutrals", but we suggest here that the ions could play a significant role in the activation process of the surface. The exposure of PTFE to an oxygen plasma lead to chemical etching of the surface, different from the physical sputtering induced by the ion treatment, that lead to a super-hydrophobic behavior of the surface attributed to an increase in the surface roughness.