Auger electron spectroscopy (AES) is an analytical technique used to determine the composition of surface layers of a sample. It involves three steps: (1) removing a core electron from an atom via ionization, typically using a 2-10 keV electron beam; (2) an electron dropping to fill the vacancy, releasing energy; (3) this energy causes the emission of an Auger electron. AES collects these low-energy (20-2000 eV) Auger electrons that escape from within 50 angstroms of the surface, allowing it to provide compositional information about just the sample's surface.
2. What is AES?
AES is an analytical techniques for
determining the composition of the
surface layers of a sample.
Auger spectroscopy can be considered
as involving three basic steps :
(1) Atomic ionization (by removal of a
core electron)
(2) Electron emission (the Auger process)
(3) Analysis of the emitted Auger
electrons
3. 1) Excitation of the atom
causing emission of an
electron
2) An electron drops down to fill
the vacancy created in step 1
3) The energy released in step 2
causes the emission of an Auger
electron.
4.
5. i-ionization
The Auger process is initiated by creation of a core hole - this is
typically carried out by exposing the sample to a beam of
high energy electrons (typically having a primary energy in
the range 2 - 10 keV). Such electrons have sufficient energy to
ionise all levels of the lighter elements, and higher core levels
of the heavier elements.
6. ii- Electron
Emission
The ionized atom that remains after the removal of
the core hole electron is, of course, in a highly
excited state and will rapidly relax back to a lower
energy state by one of two routes :
X-ray fluorescence
Auger emission
7. iii- Emitted Auger
Electron
The energy of Auger electrons is usually
between 20 and 2000 eV.
The depths from which Auger electrons
are able to escape from the sample
without losing too much energy are low,
usually less than 50 angstroms.
Thus, Auger electrons collected by the
AES come from the surface or just
beneath the surface.
AES can only provide compositional
information about the surface of the
sample.