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Auger electron spectroscopy (AES) identifies the chemical composition of a surface layer using electrons or X-rays. The energy of emitted particles is unique to the element, and peaks on a graph identify compounds. The technique is used in physical and chemical applications, but can damage the surface.
Auger electron spectroscopy (AES) is often used to determine the chemical composition of a thin, microscopic layer of a surface. Particles called electrons typically target the material, triggering the Auger effect, in which an electron is removed from the inner shell of an atom, a higher-level particle takes its place, and another electron is emitted. Conducted in an ultra-high vacuum, the test is usually done with an electron gun, analyzer, detector, and data logger. Information is typically analyzed graphically; the nature of the peaks usually helps identify which compounds are present in the sample.
Electron beams are often used, although X-rays are sometimes released. The type of material tested determines which one is used; oxides, for example, can degrade when exposed to high levels of electrons. Substances can be identified because the energy of an Auger electron is typically unique to the element. In Auger electron spectroscopy, the particles that escape are generally not as energetic as the others. They typically need to be very close to the surface for them to escape, and any gas present during the AES can prevent the particle from reaching the detector.
An electron gun used in Auger electron spectroscopy usually consists of a source for the particles and a lens that focuses the beam. The target can be electrostatic or electromagnetic; which one is used depends on the required resolution. An electron energy analyzer that is part of an Auger electron spectroscopy technique can sort out the emitted particles based on their energy levels. The analyzer can be designed as a cylindrical mirror or two concentric hemispherical shells.
Single-channel or multi-channel detectors are often used for Auger electron spectroscopy. The data is then analyzed by sets of peaks on a graph. Scans typically take a few minutes to complete, while high-resolution measurements can take up to 25 minutes. A survey scan typically identifies which elements are present, while another scan can tell how concentrated certain atoms are. If the beam is scanned through the sample, a map of the measured surface can be produced.
The science of Auger electron spectroscopy is often used in many physical and chemical applications. In addition to identifying elements on surfaces, it can also be used to detect oxidation and corrosion. Temperature response and related fatigue can be analyzed using AES. The technique can also be used to inspect integrated circuits for contaminants, but one limitation of the process is that damage to the surface of the tested material often occurs.
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