Auger Electron Spectroscopy

Different energetic beams can be used for excitation of solids with the creation of holes in electronic levels: photons, ions, electrons. In this chapter only the electron impact excitation will be taken into account, but many of the conclusions can easily be extended to other excitation modes. Incident electrons with primary energy (E p ) larger than the energy of a core electronic level (E x ) of the impacted material can generate a core hole by ionization. The excited atom then relaxes by filling the hole via a transition from an outer level E y . The excess energy released can be accommodated by the atom in either of two ways: by emitting an X-ray photon at that energy or by giving this excess energy to another electron which is ejected from the atom. A schematic representation of the electron impact Auger process is given in Figure 9.1. The kinetic energy of the ejected electron is characteristic of the electronic levels involved and therefore of the analyzed material. This process was first discovered by Auger(1,2) and the ejected electrons are called (XYZ) Auger electrons, where X indicates the deep level (K, L 1,...) on which has been created the hole which is then filled by an electron coming from the Y level (L 1, L 2,..., V), the Auger electron being ejected from an outer level Z (L 2 ,..., V); the Auger transition therefore is written as XYZ.