Electron-Beam-Induced Conduction in Polystyrene

Abstract

The carrier mobilities of PS were studied using a short-pulsed electron-beam. Even in the polymer with a π-electron system, no clear knee was observed in the induced charge signals at low applied fields. A logarithmic plot of the induced current versus time gives a knee at time Tr, which is thought to be the transit time of the carrier front between electrodes. Simple calculation by the formula µ=L/TrE gives an apparent carrier mobility µ of 2.5×10-5 for electrons and 1.2×10-5 cm2/Vsec for holes, at 293 K. These apparent mobilities are a little smaller than those (10-4–10-5 cm2/Vsec) estimated from the knee point of the induced charge signal at higher fields in previous reports. Thus the measured mobility is field-independent and increases with temperature with an activation energy of about 0.4 eV for both electrons and holes.