Ultrafast relaxation of electrons and selfconsistent electrical charging in insulators

Low energy electron scattering in insulators is described by a Monte Carlo program based on acoustic and optical phonon scattering as well as on impact ionization of valence band electrons, especially aimed to the scattering of ballistic and drifting electrons in wide gap dielectrics. There is a rapid relaxation of excited electrons within the conduction band of wide gap insulators like SiO2 and Al2O3 over femto-seconds. The field-dependent transport and trapping parameters allow us to model the selfconsistent charge transport and charging-up of insulating samples during electron irradiation. The resulting spatial and time-dependent distributions of all currents j(x,t), charges rho(x,t), the electric field F(x,t) and the potential V(x,t) are obtained and compared with experimental measurements. (C) 2009 Elsevier Ltd. All rights reserved.