Auger spectroscopy - Principles and performances in fixed probe

Electron-induced Auger electron spectroscopy (AES) is a surface analysis technique that can identify the elements (except H and He) making up the very first atomic layers (a few nanometers) on the surface of solids, with a lateral resolution of up to a few nanometers and a detection limit of a few dozen or fewer identical atoms. Its principle is based on the Auger effect mechanism, with the emission of electrons having kinetic energies characteristic of the elements from which they originate, and independent of the energy of the incident exciter particles. For microanalysis of surfaces, the Auger process is generally induced by a finely focused beam of incident electrons of a few kiloelectronvolts (5 to 25 keV) in specific equipment with a structure similar to that of a scanning electron microscope equipped with ultra-high vacuum and an electron analyzer. In local microanalysis, the incident electron probe is focused on the detail to be analyzed, and the spectrum of electrons emitted between 50 eV and 2.5 keV is acquired. The energetic position of the Auger lines is used to determine the nature of the constituent elements, while measurement of the intensity of the lines provides access to their concentration (dosage or quantification). Concentration accuracy can be as high as 5% at/at, especially when the protocols suggested by ISO standards (the result of international cooperation, the VAMAS program) are followed.

The technique's limitations are linked to the disruptive effects of the incident electron beam, which make it tricky to use on insulating materials (charge effects) and on fragile materials such as polymers (thermal effects).

Detailed in the following file , developments in the technique concern the possibility of acquiring x, y maps of the distribution of surface elements (in scanning mode of the incident probe) or depth profiles of these same elements (in fixed probe mode combined with ion erosion). Its performance means that it is ideally suited to applications in the microelectronics industry (analysis and control of highly-integrated circuits), metallurgy (for grain boundary composition), mechanics and surface treatment, and even catalysis (for spot analysis of dispersed catalysts), as well as in research and application laboratories for metal multilayers, pending its foreseeable development in the various fields of nanotechnology.