Auger electron spectroscopy (AES) is used to determine the elemental composition and, in many cases, the chemical state of the atoms in the surface region of a solid, vacuum stable, not insulating material. AES has found widespread use in an extensive variety of materials applications, especially those requiring surface specificity and high spatial resolution. The method is based on the Auger effect which is resulting from inter- and intrastate transitions of electrons in an excited atom. Because of the relatively low kinetic energy of the Auger electrons they can only escape from the uppermost few monolayers of a specimen surface. This is the reason why this technique is such surface sensitive. In combination with Argon ion sputtering depth profiles to 1000 nm are available without prior sample preparation. In many cases there is no complex and time-consuming sample preparation needed.