Gamma-ray-induced conduction in polyethylene-terephthalate under high electric fields

Radiation-induced conduction in polyethylene-terephthalate under high electric field (1×106 to 1.6×108 V/m) has been studied. At field strengths below 1×108 V/m, the induced current reaches its initial steady-state value (primary component) soon after irradiation is initiated, then monotonically decreases with time thereafter. This decrease of current is due to a ’’polarization’’ effect. Above 1×108 V/m, the induced current decreases for a while then increases again to reach the equilibrium value (secondary component). This secondary component is due to the electron injection, enhanced by the fixed positive space-charge accumulation near the cathode. The radiation-induced conductivity of the primary component increases with electric field strength between 1×106 and 1×108 V/m and then shows a saturation tendency above 1×108 V/m. This may be due to geminate recombination in the carrier generation process. The primary component in the 50-μm-thick specimen is deduced to be dominated by a deep-trapping-limited process. The primary component of the induced current in a 6-μm-thick specimen is demonstrated to attain saturation above 1.2×108 V/m.