Energy Loss of Incident Electrons Depending on Sample Thickness
- Practical Electron Microscopy and Database -
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This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.



As we know that in TEM observation, the transmission of unscattered incident electrons is inversely proportional to the TEM specimen thickness. On the other hand, the increase of the specimen thickness enhances the energy loss of the transmitted electrons. Therefore, the spatial resolution degrades with the increase of specimen thickness because of the chromatic aberration effects. Table 4625 lists examples of the energy loss of incident electrons passing through the specimen. The use of thinner specimen can generally improve spatial resolution because it minimizes the energy loss.

Table 4625. Examples of the energy loss of electrons passing through the TEM specimen.

  Accelerating voltage of incident electrons Penetrated electrons (%) Penetrated electron with energy loss higher than 50 eV (%) Unscattered electrons (%) Elastically scattered electrons (%)
Thin metal foil
50 nm thick carbon film
50 kV

Electrons lose only a small fraction of their energy in electron-transparent thin films, about 5 eV/nm.

Even though there is an energy spread (ΔE, 0.3 ~ 1.5 eV) in the electron sources, the major factor to the chromatic aberration (Cs) is the large energy loss ΔE (normally < 2 keV) induced by inelastic scattering when electrons pass through the specimen.



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