Ion beam induced changes in electrical resistivity of polymer films: the case of unplasticized poly(vinyl chloride)

Abstract

Electrical resistivity of the unplasticized poly(vinyl chloride) copolymer (UPVC) films irradiated with high-energy proton beams was studied with reference to a control sample, as a function of both ion energy and ion dose. Upon irradiation with beam energy ranging from 25 up to 37 MeV and at a beam fluence of 0.225×1010 ion cm-2, the room-temperature resistivity of the insulating films decreased by four orders of magnitude from its original value. Furthermore, using 25 MeV proton beams over a wide range of fluence (1011-1015 cm-2), the room-temperature resistivity of the films decreased by only three orders. Then, the dependence of the resistivity ρ(T) on the ion energy and fluence was also observed as the temperature Twas progressively increased up to 373 K. The observed behaviour of ρ(T) agrees with the charge transport model, consistent with a hopping mechanism in the polymer. In addition, the changes in the ac electrical resistivity of the irradiated UPVC films have been measured within the temperature range (293-373 K) and at different frequencies (100 kHz-3 MHz).