Peculiarities of the electrontransport properties of polyimide films implanted with copper and cobalt ions

Thin polyimide foils were implanted with 40 keV Co+ and Cu+ ions at fluencies of 2,5·1016-1,251017 cm2 and at ion current densities of 4, 8 and 12 mA cm2. Surface dc electric resistance of the implanted polymer samples have been measured in the temperature range 40-300 K. Metal implantation results in decreasing polymer resistance with the dose and current density increasing for the both kinds of metal ions. The decrease of dc electric resistance is caused by radiation-induced carbonization and metal nanoparticle formation in the implanted region of polymer. The transition from the insulating to metallic regime of conductivity is observed in cobalt implanted samples for critical doses above Dc = 1,25?1017 cm2 at an ion current density of 8 mA cm2. In the contrary, high-fluence implantation in the polymer with Cu+ ions for the same regimes does not result in the transition. The dominating mechanisms of charge carrier transport and the origin of insulator-to-metal transition in the metal implanted polymer are discussed. (authors)