Auger Electron Spectroscopy (AES):
Auger electron spectroscopy is a surface analytical method revealing the chemical composition. Surface atoms or molecules are core-ionised by an electron beam (~5 keV) or photon. An electron is emitted from an core-ionised atom via a two step process. Generally an ionised atom will emit light, when an electron fills the empty place, but under certain conditions the energy will be transferred onto another electron which is emitted with a characteristic energy. This is a competing process to x-ray emissions and can be observed for lighter atoms predominantly. Auger electrons are named after the three atomic shells involved (e.g. KLM). The energy of the emitted Auger electrons is recorded providing surface sensitive chemical information.
By electron beam:
By photon beam:
X-ray Photoemission Spectroscopy (XPS):
X-ray photoemission spectroscopy is another surface analytical technique that reveals the chemical composition. Surface atoms or molecules are ionised by a beam of photons (~1486 eV) and electrons are emitted from the surface of the sample (by the photoelectric effect). X-ray photoemission spectroscopy provides chemical information through the kinetic energy of the detected electrons and information about the chemical bond which was involved.