Auger Electron Spectroscopy

Abstract

Abstract Auger electron spectroscopy (AES) is a method for determining the elemental composition of the several outermost atomic layers of materials. The surface layers often have a composition that is quite different from the bulk material due to contamination, oxidation, or processing. In AES, a specimen is probed with an energetic electron beam with an energy fixed between 3 and 30 keV, resulting in the ejection of core‐level electrons from atoms. The resulting vacancy in a core level can be filled by an outer‐level electron, with the excess energy being used to emit either an x‐ray (electron probe microanalysis) or another electron from the atom (AES). This emitted electron is called an Auger electron. AES is a surface‐sensitive technique due to the strong inelastic scattering of low‐energy electrons traveling within specimens. Auger electrons from only the outermost several atomic layers are emitted from the specimen without energy loss, and contribute to the Auger peak intensities in a spectrum. The Auger electron kinetic energies are characteristic of the emitting atoms, and the measurement of their energies is used to identify the elements that produce them. The concentrations of elements detected can be determined from the intensities of the Auger peaks. Variation of composition with depth can be determined by depth profiling, which is usually accomplished by removing atomic layers by sputtering with inert gas ions and monitoring the Auger signals from the newly created surfaces. For most elements, the detection limit with AES is between 0.1 and 1 at.%.