The Role of Argon Metastables in an Inductively Coupled Plasma for Treatment of PET

Metastable states play an important role in many plasmas because they are often one of the main ionization channels and therefore essential for the discharge dynamics. Because of their high population, density fluxes of metastable states on surfaces are not negligible compared to fluxes of reactive species or ions. If the energy of argon metastable states (Ar-m) is high enough to cause bond breakage or other surface reactions, they can be an alternative component to treat substrates. In view of the role of Ar-m in an inductively coupled PECVD reactor for the deposition of barrier films on PET, the densities, lifetimes, and fluxes of Ar-m are quantified by means of tuneable diode laser absorption (TDLAS) and compared to the ion flux.