The Auger electron is generated during an excited atoms relaxation process, where excess energy is transfered to an outer shell electron, which leaves the atom and becomes the Auger electron. The energy of this electron depends on the binding energies of the participating electrons and is unique to the element where it occurs. As the Auger electrons energy is very low, it can escape the material from only near the surface (few nanometers). This means that this signal is highly surface sensitive and can be used to obtain information from only the surface, not from the bulk material as it is common with other material characterization methods.