- Auger Electron Spectroscopy
Auger Effect was named after its discoverer Pierro Auger. The phenominon is initiated by the creation of a vacancy at subshells of atom.With this vacancy, the atom will be ionized and unstable as shown in Figure 1. The unstability will cause the atom to loose overall energy and will transfer outer shell eletron to fill the vacancy. During this process, higher than required energy drop occurs and the access energy will push out Auger Electron, which is usually located in outer shells. Overall, the atom will be short of two electrons at the end - One that was removed by high energy in the begining and also by Auger electron at the end.
AES consists of the three main steps as shown in Figure 2 and they are atom ionization by removing core electron, electron emission (Auger effect), analysis of the emitted electons. Two well known processes for the first step are a beam of high energy electron ranging from 2-10 KeV and soft X-ray ranging from 1000 to 2000 eV and eletron emission will be followed. These emitted eletrons will be collected by the detector, which will measure the kinetic energies. The characteristic of material will be identified by the location of initial hole and the location of the two final holes. Also keep in mind that Auger transitions are possible for all elements except H, He and Li. For solids containing Li an intra-atomic Auger line is also observed.
Figure 1 - Auger Effect illustration
Figure 2 - Simplified Schematics of AES