INFLUENCE OF THE ANGULAR-DISTRIBUTION OF BACKSCATTERED ELECTRONS ON SIGNALS AT DIFFERENT TAKE-OFF ANGLES IN LOW-VOLTAGE SCANNING ELECTRON-MICROSCOPY (LVSEM)

It is well known that the differential Mott cross section for large-an gle elastic scattering shows maxima and minima at angles depending on material and electron energy. For electron energies of 10-30 keV, the averaging by frequent elastic scattering processes results in approxim ate Lambert angular distributions of backscattered electrons (BSE). Ho wever, the present Monte Carlo calculations for electron energies E = 1-5 keV and different angles of incidence show strong deviations from a Lambert distribution which increases with decreasing energy. The sig nals of the BSE detector with five annular segments for different take -off directions show good agreement with the calculations for normal e lectron incidence.