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*Auger electron spectroscopy(AES)*uses electrons as primary radiation. The analyze electrons are not the emitted core electrons, but the Auger electrons that are ejected as a consequence of the return of the ionized atom to its ground state. The process is illustrated in the figures below


                                                                                                                                                             fig 1.Auger electron emission process
                                                                                                                                                              fig2. X-ray fluorescence process

A hole is created on the K level in the initial ionization step. This requires a primary energy greater than the binding energy of the electron in that shell. The hole can be produced by either the primary beam, or the backscattered secondary electrons. The atom relaxes by filling the hole with an electron coming from an outer level as a result excess energy is available which can be used in two ways. Either emission of an X-ray occurs or the energy may be given to another electron, either in the same level or in a shallower one. The first process produces X-ray florescence and the second one produces Auger electrons but the probability for Auger emission is much higher for core levels with binding energies below about 2 keV.

The Auger electrons are analyzed and since these electrons are independent of the type of primary beam (i.e. electrons or X-rays) and its energy AES spectra are always plotted on a kinetic energy scale.

Common Applications of AES

• Qualitative analysis through fingerprinting spectral analysis

• Identification of different chemical states of elements

• Determination of atomic concentration of elements

• Depth profiling

• Adsorption and chemisorption of gases on metal surfaces

• Interface analysis of materials deposited in situ on surfaces