Electron beam probing of silica surface layers on alumina

The electron beam induced self-consistent charge injection and transport in a layered insulator SiO2-Al2O3 is described by means of an electron-hole flight-drift model FDM and an iterative computer simulation. Thermal and field-enhanced detrapping are included by the Poole-Frenkel effect. The surface layer with a modified electric surface conductivity is included which describes the surface leakage currents. Furthermore, it will lead to particular charge incorporation at the interface between the surface layer and the bulk substrate. As a main result the time-dependent spatial distributions of currents j(x,t), charges ρ(x,t), field F(x,t), and potential V(x,t) are obtained. The spatial charge distribution with depth shows a quadro-polar plus-minus-plus-minus structure in nanometer dimension.