Electron-Induced Conduction in Plastics. I. Determination of Carrier Mobility

Samples of commercial plastics have been bombarded by short pulses of nonpenetrating electrons. Observations of charge transients representing the long-lived component of the induced current lead to the following conclusions: (i) One carrier species is rapidly and strongly localized; (ii) the mobile excess carriers decay by bimolecular recombination; (iii) although such carriers cannot in practice complete transits through the thickness of the samples, they can be swept out of the excited layer into the bombarded electrode. This paper fully explains how the sweep-out time, and from it the effective carrier mobility and generation efficiency, are deduced. The mobilities, with the sign of the mobile carrier, are polystyrene (20°C), μ+=1.0×10−6 cm2/V sec; polyethylene terephthalate (20°C), μ−=1.5×10−6 cm2/V sec; linear polyethylene (80°C), μ+=4.5×10−10 cm2/V sec. The temperature dependence of mobility is studied in the first two materials.