The trapping of electrons in polystyrene

The trapping of electrons in localized states in polystyrene has been studied by means of an electron beam technique. A 2.2 kV beam is used to inject a short pulse of charge into the free surface of a thin film of the polymer, and a second electron beam monitors the surface potential of the film. The surface potential is related to trapped charge density and to the depth of charge penetration. Defining a trapping parameter α (=1/μτE), one can relate the incremental buildup of surface potential to the injected charge density and carrier range. The release of electrons from traps is analyzed in terms of a time and temperature dependent demarcation energy. The time dependence of charge decay is related to the energy distribution of traps in the polymer