The backscattering factor in Auger-electron spectroscopy: New approach for an old subject

We describe an algorithm for the calculation of backscattering factors in Auger-electron spectroscopy that, unlike most previous analyses, is not based on the assumption of the probability of inner-shell ionization being independent of depth. Illustrative BF results from Monte Carlo simulations are presented for four Auger transitions (Si KL23L23, Cu L3M45M45, Ag M5N45N45, and Au M5N67N67 in the corresponding elemental solids) with primary-electron energies between 0.5 keV and 10 keV, normal incidence of the primary electrons, and Auger electrons emitted at angles between 10° and 80° with respect to the surface normal. Our calculated backscattering factors agree with values obtained from an empirical formula of Shimizu [Jpn. J. Appl. Phys. 22 (1983) 1631] to better than 4% for the Si KL23L23 transition and better than 11% for the other three transitions. This degree of agreement is considered satisfactory on account of the fact that data of higher accuracy are now available for needed parameters. We find that the backscattering factor varies with Auger-electron emission angle. This variation can be up to 6.7% for primary energies between 3 keV and 10 keV.