Auger Electron Spectroscopy

Auger electron spectroscopy (AES) is a method that uses an electron beam (or X-ray) with a certain energy to excite the Auger effect of the sample, and obtains information about the chemical composition and structure of the surface of the material by detecting the energy and intensity of the Auger electron.

Learn about T,C&A's Auger Electron Spectroscopy Laboratory services or contact us to talk to one of our highly skilled analysts.

History

• In 1925, French physicist P. Auger discovered Auger electrons when he used X-rays to study the photoelectric effect and gave a correct explanation for the phenomenon.
• In 1968, L.A. Harris adopted a differential electronic circuit, which made the Auger electron spectrum enter the practical stage.
• In 1969, Palmberg, Bohn and Tracey introduced the tube-lens energy analyzer, which improved the sensitivity and analysis speed, and made Auger electron spectroscopy widely used.

Basic principle

The basic principle of Auger electron spectroscopy is that the incident electron beam or X-ray ionizes the electrons in the inner layer of the atom, and the outer electrons produce non-radiative Auger transitions, emit Auger electrons, and detect them in vacuum with an electron spectrometer.

Strengths

• The surface sensitivity is high, and it can give the composition information of 0.1~3 nm on the solid surface.
• A wide range of element analysis, which can analyze all elements on the periodic table except H and He, especially low atomic number elements.
• The micro area analysis ability is high, and it can give the one-dimensional or two-dimensional distribution image of the element on the surface. The lateral resolution can reach 15 nm.
• Combined with ion sputtering, deep analysis of components can be carried out, with the ability of three-dimensional analysis of solid components.
• In-depth analysis of components or thin film and interface analysis can be performed.
• Rich chemical state information, using high-resolution Auger spectroscopy to obtain surface chemical state information from energy shifts and linear changes.

Limitations

• Low sensitivity: Not sensitive to elements H and He, for most elements, the quantitative detection sensitivity is 0.1%~1.0%.
• Quantitative difficulties: When using the published element sensitivity coefficient calculation, the accuracy of quantitative analysis is limited to ±30%. When using standard samples of similar samples, it is possible to improve the quantitative results (±10%).
• Surface damage: The electron beam damage will be serious, which limits the effective analysis of organic matter, living organisms and a few ceramic materials.
• High requirements for samples, the surface must be clean (preferably smooth), etc.
• Surface charge: Electron beam charging will limit the inspection and analysis of highly insulating materials, and incident electrons will cause changes in the surface state to induce adsorption or desorption, etc.
• Analysis time: For the full spectrum identification work from 0~2000 eV, the analysis time is usually less than 5 minutes. The study of chemical effects, Auger element imaging and depth-component analysis of selective peak analysis generally takes a long time.

Applications & industries

• Study the effect of material surface components (including surface contamination or surface segregation of multiple systems) on problems such as corrosion, oxidation, adhesion, catalysis, friction and wear or secondary electron emission.
• Study the influence of grain boundary desolubilization or solute grain boundary segregation on material corrosion, stress corrosion cracking and mechanical properties. It involves material strength, brittleness, fracture, fatigue, creep, welding, adhesion, plating or coating, etc.
• Study the composition changes in the ~50 nm region of the material.
• Study the three-position micro-domain distribution and interface characteristics of elements in various surface modification layers and films.
• Study surface chemical processes, including the study of reaction products and reaction kinetics. It involves adsorption, heterogeneous catalysis, corrosion, passivation, oxidation, etc.

Sample requirements

• Form: Solids with low vapor pressure (<10^-8 Torr at room temperature), such as metals, ceramics and organic materials. Materials with high vapor pressure can be processed with sample cooling. Similarly, many liquid samples can also be treated with sample cooling or as a thin film coated on conductive materials.
• Size: The diameter of a single powder particle that can be analyzed is as small as 1 µm. The maximum sample size depends on the specific instrument, usually 1.5 cm in diameter and 0.5 cm in height.
• Surface: Flat surface is best, but rough surface can be analyzed on a small local area (about 1 µm) or averaged on a large area (diameter 0.5 mm).
• Preparation: Usually no preparation is required, and the sample must not have fingerprints, oils and other high vapor pressure substances.

Note: this service is for Research Use Only and Not intended for clinical use.

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