Scanning Electron Microscopy


The effects of the sample to incident electron beam angle and of the detector. angle on the Auger electron signal are important for quantitative Auger analysis, particularly for Auger mapping and line scans. A first approximation, single scattering, mean free path model is employed to simulate the Auger signal resulting from a range of sample and detector angles. The model is single scattering in the sense that the excitation path is taken to be a straight line into the solid. A second model approximates multiple scattering by a normal distribution of ionizing flux angles about the incident beam direction.

Since spherical particles exhibit all possible surface angles, they are useful for testing the theoretical models. A coaxial electron gun/cylindrical mirror analyzer (CMA) instrument with an "angle-resolved drum" is employed to analyze 200μm diameter Ti spheres on a Sn substrate. The observations compare favorably with predictions of the model for Ti and O Auger signals, and the multiple scattering approximation is seen describe the results.

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