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

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 × 10 10 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 (10 11 -10 15 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 T was 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).