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PVD Coatings

Your guide to PVD technology, theory and applications

AES, Auger Electron Spectroscopy

Posted by mark00 On March - 26 - 2010

Electrons of energy in the range 3-20keV are accelerated onto a conducting sample. The incident electrons cause the core electrons from the atoms in the sample to be ejected resulting in the emission of a photoelectron. The atom then relaxes by electrons with a lower binding energy dropping into the atom’s core hole left behind.

The energy that is then released can be converted in the form of an X-ray (see EDX) or the emission of an electron. This electron is called an Auger electron after Pierre Auger who discovered this process.

The energy of the Auger electron is characteristic of the element that emitted it, and can thus be used to identify the element.

AES is a popular technique for determining the composition of the top few layers of a surface. It cannot detect hydrogen or helium, but is sensitive to all other elements, being most sensitive to the low atomic number elements.

AES must be carried out in UHV conditions. A popular method of looking at buried layers with AES is to use the technique in combination with sputter cleaning. Normally, when a sample is brought into the UHV environment from air, it will be coated with carbon and oxygen. This material has to be removed (usually by sputtering) before the clean surface can be investigated. Sputtering involves directing a beam of ions (usually Ar ions) at between 500eV and 5keV at the sample. This process cleans the surface, but can also be used to erode away the sample to reveal structure beneath the surface. Obviously this is a destructive technique.