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

Abstract

Fluorinated ethylene propylene (FEP) and tetrafluoroethylene-perfluoro(alkoxy vinyl ether) (PFA) copolymer films were irradiated in vacuum with 60keV C4+ and N4+ ions to fluences ranging from 1.0×1012 to 5.0×1015cm-2. Changes in optical and dielectric properties were analyzed by spectroscopic ellipsometry and ultraviolet-visible (UV-vis), Raman and dielectric relaxation spectroscopies. Direct and indirect energy band gap values were determined from the absorption edge in the 200-800nm region using Tauc's relation. The values of the direct energy gap have been found to be greater than the corresponding values of the indirect energy gap. Significant changes in the index of refraction, and Β and γ dielectric relaxations were observed in the case of N4+ irradiated FEP and PFA samples. © 2011 Elsevier Ltd.