THE SPATIAL-DISTRIBUTION OF BACKSCATTERED ELECTRONS REVISITED WITH A NEW MONTE-CARLO SIMULATION

A Monte Carlo simulation program including the discrete energy loss process has been developed, based on the Mott cross section for elastic scattering and the Vriens cross section for inelastic scattering. A deficiency of the previous model which is based on the screened Rutherford cross section and the Bethe law is made clear, from comparison between the new and old results such as the energy distribution of backscattered electrons for a Cu target. With the new Monte Carlo model, the radial spreading and penetration depth of both all and low-loss backscattered electrons have been studied for the Cu target at electron energies of 5.10 and 20 keV. From these studies, it is found that the electron exit angle dependence of the spatial spreading is more significant with the low-loss backscattered electrons and a very high resolution of 2 to 3 nm can be obtained even with backscattered electrons.