Electron Energy Loss Spectroscopy (EELS)

Electron Energy Loss Spectroscopy (EELS)

Electron Energy Loss Spectroscopy (EELS) is based on the principle that high energy electrons passing through a material can lose energy by various mechanisms due to interactions with atomic nuclei or their surrounding electrons. In the EELs technique, a thin sample of the specimen is investigated in a Transmission Electron Microscope (TEM) or Scanning Transmission Electron Microscope (STEM). The energy loss of transmitted electrons is measured and analysed by electron spectroscopy. The energy loss spectra yields information for atomic-level chemical and structural characterization. The EELS technique can identify atomic species, their chemical bonding, oxidation states, electronic properties in valence and conduction bands, as well material surface properties. It is also used with electron tomography, to provide nano-scale, spatial mapping of elements and oxidation states.

Common Uses of Electron Energy Loss Spectroscopy (EELS)

• Analysis of surface morphology and study of atomic composition, bonding, oxidation states and electronic properties
• By combining EELS with electron tomography, a reconstructed image of that volume element can be obtained
• Nano-scale structures in semiconductor applications such as thin deposited layers,  quantum well and dot structures, can be investigated
• EELS can be used to conduct studies of compositional effects in micro-alloying of metals

 Advantages of Electron Energy Loss Spectroscopy (EELS)

• EELS has been found to be better than comparable methods (e,g EDX) for elements of lower atomic number, especially from carbon through 3D transition metals
• Direct quantitative estimation is obtained, without the need for a calibration standard
• EELS can identify different structural forms and oxidation states of the same element.