A Secondary Emission Analog for Improved Auger Spectroscopy with Retarding Potential Analyzers

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Abstract
An objectionable feature of electron spectra taken with a retarding potential analyzer, for example, as in Auger electron spectroscopy, is the large background that is characteristic of the general shape of the secondary electron distribution function. It is shown that an electron analog of the secondary electron emission from a specimen can be injected at the signal source of a retarding potential analyzer so as to cancel the secondary emission function. The result is that the annoying background that characterizes Auger electron spectra taken with retarding potential analyzers is removed, the error in the magnitude of Auger peaks due to secondary emission background is eliminated, ``washed‐out'' fine structure accompanying large Auger signals may be recovered, and uniform amplifier gain is useful throughout the energy range of the detector circuit. The technique employs one of two analog functions for an approximation to the secondary electron emission and does not attempt an exact fit. The mathematical properties of these functions are described as well as criteria for choosing the appropriate function for the best approximation. It has been found that the functional behavior of the major component of the secondary electron energy spectrum from Ni (110) (i.e., ignoring superimposed Auger electron contributions) is essentially constant from 10 to 1000 eV. Consequently, there is no experimentally observed demarcation between true secondary emission and rediffused primaries. The general energy distribution function can be represented as N(E)=A(E+E0)−m.