Charge transport in Teflon and Kapton

Teflon and Kapton films of 25 μm thickness are charged with 30 keV and 20 keV electron beams, respectively, to charge densities of 100 nC/cm². Thereafter, the charge distribution in the depth direction and its change with time at 120°C are measured with the laser-induced pressure-pulse (LIPP) method. A theoretical model of charge buildup during electron-beam irradiation and charge transport thereafter, considering the charge deposition and dose profiles, the radiation-induced conductivity and the carrier mobility is used to interpret the experimental data. While the charge transport at room temperature is mostly due to the direct and delayed radiation-induced conductivity and is therefore limited to the volume penetrated by the electron beam, charge motion at elevated temperatures is also caused by increased carrier mobility in the nonirradiated volume. Evaluations yield numerical values for the charge transport parameters, such as Schubweg, mobility-lifetime product, and trap density