Effect of backscattered electrons on the analysis area in scanning Auger microscopy

A simple analytical model has been used to determine the effects of backscattered electrons on the analysis area in scanning Auger microscopy. For normally incident electrons, the radius ra of the analysis area is calculated corresponding to detection of 80, 90, and 95% of the total Auger-electron signal as a function of two sample parameters, the backscattering factor R and the Gaussian parameter σb describing the radial distribution of the backscattered electrons. For a reasonable range of these parameters, ra depends linearly on σb and to a lesser extent on R. Values of ra can also be appreciably larger, by more than a factor of 100, than the widths of the incident beam in modern instruments, and need to be considered in quantitative analyses of particles and inclusions. Monte-Carlo calculations are needed for more realistic evaluations of the analysis area and to determine this area for non-normal incidence of the electron beam.