Positron Annihilation Induced Auger Electron Spectroscopy (PAES)

Magnetic Beam

Electrostatic Beam

Time of Flight System

Experiments performed in our laboratory have led to the development of a unique new surface spectroscopy: Positron Annihilation induced Auger Electron Spectroscopy (PAES), which has significant advantages over conventional Auger methods. PAES makes use of a fundamentally new process in which the core-holes necessary for Auger Electron Spectroscopy (AES) are created by positrons (antimatter electrons) annihilating core electrons and not (as in conventional Auger methods) by collisional ionization (see PAES mechanism).
Our studies have demonstrated that PAES can be used to eliminate the large secondary elelcton background which plagues conventional Auger spectroscopy and to obtain Auger spectra while delivering an extremely low energy dose to the sample. We have demonstrated further, that the PAES signal originates almost exclusively from the topmost atomic layer due to the trapping of positrons in an image potential well at the surface before annihilation. Many important surface properties including those pertaining to catalytic activity, adhesion, and initial stages of corrosion are dependent on details of the elemental content and local electronic structure of the topmost atomic layer.
PAES is unique among surface science techniques in being able to probe both the chemical content and local electronic structure of the topmost atomic layer with an extremely high degree of selectivity.


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