Auger Electron Spectroscopy (AES)

 Auger electron spectroscopy

Auger electron spectroscopy (AES) utilizes a high-energy electron beam to excite surface layers of the test sample and by detecting the energy and quantities of the resulting Auger electrons, the elemental composition of the sampled surface can be inferred. 

While the beam’s excitation volume within the sample may extend upto 5 microns, the emission of Auger electrons occurs only within the first 2 to 10 atomic layers, corresponding to a depth of 1 nm to 5 nm. An AES spectrum is obtained by plotting auger electron numbers against their respective kinetic energies, which are characteristic of the elements from which the electrons were released. The intensity of an AES peak depends on the amount of element present, while the peak position is element dependent. Since auger electrons carry information from depth of just a few nanometres, it is a good technique for surface sensitive analysis. Further, the electron beam diameter is typically less than 10 nm and hence small surface features can be analysed at this resolution. 

Important elements of an Auger spectrometer include a vacuum system, an electron source, and a detector. AES must be performed at ultra-high vacuum to ensure residual gases are nor adsorbed on the test surface. AES, in combination with surface sputtering by helium or argon ions, provides a means for depth profiling, giving elemental distributions upto 1 micron thickness.

 AES is a valuable tool for research, development and quality control in advanced technologies based on surface chemistry and nanotechnology.

Video 01: Auger electron spectroscopy (AES)

Common Uses of Auger Electron Spectroscopy (AES)

• Research and development in the surface chemistry of thin films and coatings
• Analysis of nanoparticle ensembles and chemical mapping of individual nanoparticles
• Study of grain boundaries in metals and ceramics
• Quality control in applications such as catalysis, magnetic media, adhesives, display technologies and integrated circuits.

Advantages of Auger Electron Spectroscopy (AES)

• High surface sensitivity (within 10 atomic layers)
• Relatively low detection limit (~0.1 atomic percent)
• Wide range of elemental coverage from Lithium to beyond Uranium
• Rapid data acquisition

 Limitations of Auger Electron Spectroscopy (AES)

• Elements with less than 3 electrons (Hydrogen and Helium) cannot be detected by AES
• Typical detection limits of AES are 0.1 – 1% of a monolayer, 10 ^-16 to  10 ^-15 g of material, and 10¹² to 10¹³  atoms/cm²
• Challenging to use on insulating samples 

Industrial Applications of Auger Electron Spectroscopy (AES)

• Metallurgical Industry
• Ceramics
• Semiconductor industry
• Catalysis
• Speciality chemicals
• Electronics