Delayed radiation-induced conductivity in nickel polymethacrylate: II

Abstract Generation and transport of charge carriers in nickel polymethacrylate (NiPMA) in the post-irradiation phase have been investigated by means of DC conductivity as a function of temperature, exposure rate and electric field strength. The delayed radiation-induced conductivity due to the temperature- and field-assisted dissociation of electron-holes excitation of the chain segment is appropriately described within the framework of the one-dimensional Onsager theory of geminate-pair dissociation. At high temperatures the conductivity is dominated by the local, liquid-like motion of the heterocharges moving in an amorphous or locally disordered environment. After a certain radiation dose the transition from increasing to decreasing conductivity with increase of exposure rate is due to the radiation-hardening of the material. It is concluded that prolonged irradiation of the material produces new trap-centres which cause a decrease in conductivity.