This method is based on the Auger effect, discovered by French physicist Pierre Victor Auger in the 1920s. In this phenomenon, when a sample is exposed to a beam of high-energy emitted electrons, the example shown in Fig. a, the binding energy of levels involved can be estimated as follows , where is the work function of material. It is worth noting that the equation gives a rough estimate, since it does not take into account that electrons are emitted from an ion, and not from a neutral atom. Ionisation of atoms leads to a shift of electronic levels down, which naturally affects the energy of the emitted Auger electrons. The Auger spectroscopy method is widely used in R&D labs, as well as in the chemical and metal industries and microelectronics due to the high surface sensitivity, the obtainability of quantitative information, and the usability of the method.