Elastic Scattering of Electrons
- Practical Electron Microscopy and Database -
- An Online Book -

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Elastic scattering means that the electron energy lost by the primary electron is too small to be detected. Simply speaking, the elastic scattering of electrons occurs mainly from electron interaction with the atomic nuclei or the whole electrostatic field of the atoms. The elastic scattering is responsible for electron diffraction from the specimens in TEM.

Elastic scattering is represented by the peak at zero energy loss, illustrated in EELS profiles, and and is often described in terms of Rutherford scattering from atoms or ions. For single scattering, elastic scattering can be treated as independent atomic scattering events and the cross-section of the scattering can be extracted by the relation,
         1/λ = Nσ -------------------------- [4108]
where,
         N = ρ/(Am)
         N -- The atomic density,
         ρ -- The mass density,
         A -- The dimensionless atomic mass,
         m -- The proton mass.

Thermal diffuse scattering (TDS) can also be described by elastic scattering modified by the atomic vibrations.

Table 4108 shows that electrons interact with 1 electron, many electrons, 1 nucleus, and many nuclei in solids.

Table 4108. Effects of interactions of electrons in solids.
  Interaction with electron(s) Interaction with nucleus/nuclei
  1 electron Many electrons 1 nucleus Many nuclei
Scattering type Inelastic Inelastic Quasi-elastic Elastic Inelastic
Scattering effect Electron Compton effect; electron excitation (from 50 eV to a few keV: EDS and EELS) Plasmon excitation (< 50 eV, ~100 nm TEM specimen); Cerenkov effect Rutherford scattering; phonon scattering (< 1 eV, heat) Bragg scattering Bremsstrahlung

Kikuchi lines are more pronounced in CBED patterns than in SAD patterns because:
        i) CBED patterns arise from a smaller, and thus more uniform region than SAD patterns,
        ii) The enhancement of coherent and elastic scattering in CBED.


 

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