Ion implanted poly(paraphenylene) electrical property modifications induced by cobalt 60 γ ray irradiation

Abstract

Electroactive polymers become conducting or semiconducting materials by ion implantation process and can act as electrode of polymer electrooptic modulators. Their semiconducting properties depend on the defects occurring during this process. In this study, we have observed conductivity and thermopower behavior of low energy ( E=30 keV) alkali ion implanted polyparaphenylene (n doping) before and after Cobalt 60 γ irradiation. No significant conductivity change is observed when high doses are used (from 6 to 100 kGy). The infrared spectra show a decay of the C–H bonds in the irradiated material. Hydrogen atoms are diffused outside the non implanted sample or stopped by the implanted layer in the case of alkali implanted samples. If low irradiation doses are used (less than 1 kGy) the conductivity is enhanced for an optimal dose which increases with the implantation parameters (ion fluence and ion mass). This conductivity increase associated with a constant thermopower value indicates a charge carrier mobility increase after γ irradiation for non degenerated samples (low fluence sodium implanted samples). In this case, implantation defects are assumed to be passivated by γ irradiation.