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. By 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 E _m. This energy is related to elapsed time since charge injection via the equation E_m=kT1n(vt ). Time dependence of charge decay is thus related to the energy distribution of traps in the polymer