Element-sensitive electron energy loss

Reflected Electron Energy-Loss Spectroscopy (REELS) has elemental sensitivities on the order of a few tenths of a percent, phase discrimination at the few-percent level, operator controllable depth resolution from several nm to 0.07 nm, and a lateral resolution as low as 100 nm. 

In order to increase the sensitivity toward the detection of light elements, a technique known as electron energy-loss spectroscopy (EELS) may be utilized. This method may be carried out within a (S)TEM, and consists of monitoring the loss in energy (due to inelastic scattering) of the beam electrons as they pass through the sample. Since it is more difficult to focus X-rays relative to electrons with appropriate lenses,... 

Electron energy loss spectroscopy EELS 50 A All elements 0.1 at. -% e excitation in Low sensitivity 17... 

Analytical electron microscopy (AEM) permits the determination of the elemental composition of a solid catalyst at the microscopic level by energy-dispersive detection of the electron-induced X-ray emission (EDX). Energy dispersive spectroscopy (EDS) is sensitive for elements with atomic numbers Z > 11. For lighter elements (Z < 11), electron energy loss spectroscopy (EELS) is applied. An example is shown in Figure 7 (bottom), which exhibits the elemental composition by EDX of two individual Pt/Rh particles on a carbon film. This analysis clearly demonstrates the heterogeneous composition of the alloy particles. 

REELS provides information concerning higher energy loss mechanisms than HREELS such as plasmons, interband transitions and characteristic energy losses. EXELES is a technique used in TEM (transmission electron microscopes). It provides information similar to EXAFS (X-ray absorption fine structure), (i.e. data regarding the immediate neighbourhood of atoms of certain elements in the sample). EXELES is bulk sensitive. 

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