Scanning Electron Microscopy


In Auger Electron Spectroscopy (AES) the characteristic Auger peaks are superimposed on a relatively high continuum of back-scattered electrons. In the commonly used differential mode of recording Auger spectra, the influence of the background appears through its contribution to the noise and the enhancement of the Auger signal that makes a backscattering correction necessary in quantitative AES. With the increased use of low incident beam currents to achieve high spatial resolution, the direct spectrum is increasingly used, so that a better understanding of the background is desirable. In this paper the variations of the background with atomic number, incident beam energy and angle of beam incidence are reviewed and some new experimental measurements are presented to augment existing data. The relative contributions of back-scattered primary electrons, secondary electrons and inelastically scattered Auger electrons to the background are discussed. Measurements were also made on the variation of the Auger peak height to background ratio with beam energy from which it is possible to comment on the optimum incident beam voltage for AES. Various approaches to extracting quantitative information from the peaks in the direct spectrum are discussed and a new approach to quantitative analysis based on the ratio of the magnitude of the Auger peak to a background measured in the region of 2 keV is proposed.

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