Secondary electron emission of an insulating target induced by a well-focused electron beam -: Monte Carlo simulation study

The secondary electron emission of an insulating target bombarded by an electronic beam varies as the sample charges up. This evolution is most often described via the conventional approach. However this latter is far from being entirely satisfactory and several observations obviously take it at fault. One can then wonder which parameters play the leading role in the emission. To study this, we have developed a Monte Carlo simulation of the electron trajectories where the trace of all the charge carriers implied in the interaction of the electronic beam with the insulator can be followed. These moving charges can trap in the material after they have lost most part of their energy or they can be emitted at the surface. The simulations carried out in cases where the sample charges either positively or negatively indicate that the in-charge secondary emission curve does not generally follow that deduced from the conventional approach. We explain this difference by the influence of the internal electric field developed in the target during the charge and, consequently, by the physical characteristics of the trapping sites present in the sample. So, the characteristics of the secondary emission are mainly governed by the ability of the material to trap charges of and by the probability of relaxation of part of these charges under the influence of the internal field. (C) 2004 WILEY-VCH Vertag GmbH & Co. KGaA, Weinheim.