The effect of plasma treatment on the permeability of PET substrates

Poly ethylene terephthalate (PET) is a favorite polymer for applications in flexible electronics such as flexible displays and solar cells. Also it has extensive applications in food and packaging industries. A considerable decrease in permeability of polyethylene terephthalate (PET) films by means of surface plasma treatment in a reactive ion etching system is reported. The effects of hydrogen, oxygen and SF6 radio frequency plasma on the surface properties of PET polymers are investigated by SEM, AFM and X-ray photon spectroscopy (XPS) and optical spectroscopy. Also the penetration of air through the treated substrates was investigated using a vacuum test. The creation of new C-O bonds and C-F bonds are believed to be improving the physical properties of the substrate without significantly degrading its optical behavior. It is found that hydrogen and oxygen plasmas lead to about two-fold and four-fold reduction in the penetration of air through the PET films, respectively.