Introduction

Of all the techniques that have been developed to analyze surfaces, Auger electron spectroscopy has had the most widespread application. In the field of materials science, it has joined such analytical methods as X-ray diffraction and transmission electron microscopy as a staple of any well-equipped laboratory. It is used in chemistry and materials science to study the composition of solid surfaces and the chemical states of atoms and molecules on those surfaces. Chemists and physicists study the basic Auger transition to help learn about electronic processes in solids. Those interested in developing electronic equipment have been concerned with providing spectrometers with ever-decreasing incident beam diameters that will allow the chemical analysis of a surface on a microscopic scale. It is hoped that this article plus the bibliography will provide the interested reader with a start in this field.

An obvious question that must be answered is why Auger electron spectroscopy has achieved this place in the surface analytical field. First of all, it is a relatively straightforward technique to use, and high-quality commercial spectrometers are available. The data are easily interpretable, at least on a qualitative level, and it is also possible to use an incident beam that is well under 1 ¡m in diameter. This diameter is several orders of magnitude smaller than what is possible for most other surface analytical techniques, and this fact means that Auger spec-troscopy can be used to probe changes in composition across a surface at a microscopic scale. Finally, Auger electron spectroscopy can detect every element except hydrogen and helium, so it useful for studying both light and heavy element. We now wish to consider Auger electron spectroscopy and the process on which it is based.

FIGURE 1 Energy level diagram representing de-excitations by (a) Auger electron emissions and (b) X-ray fluorescence. In the particular Auger process that is shown, a K-shell hole is first created and an electron in the LI shell drops down to fill it. In so doing, it gives off enough energy to knock an electron out of the LIII shell, which becomes the Auger electron.

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