Optical and dielectric properties of fluorinated ethylene propylene and tetrafluoroethylene-perfluoro(alkoxy vinyl ether) copolymer films modified by low energy N4+ and C4+ ion beams

► Effect of N4+ and C4+ irradiation on properties of FEP and PFA copolymers. ► Changes in index of refraction and β and γ relaxations in N4+ irradiated PFA. ► Optical energy gaps of FEP and PFA copolymers decrease with increasing fluence of ions. ► Direct energy gap found to be greater than indirect energy gap. ► Increase in Raman D-band intensity observed in irradiated FEP and PFA samples.