X-ray Generation by Scattering of Incident Electrons
- Practical Electron Microscopy and Database -
- An Online Book -



This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.



In EM measurements, after a core electron has been emitted from an ionized atom, this atom quickly decays from its excited state to its ground state and thus may produce a characteristic X-ray (“radiative”) or an Auger electron (“nonradiative”). Therefore, these processes of inner-shell ionization loss are different aspects of the same phenomenon. Both processes compete for the decay.

Table 3815 shows that electrons interact with 1 electron, many electrons, 1 nucleus, and many nuclei in solids.

Table 3815. 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

In EDS measurements, the path of X-ray absorption mainly depends on two factors:
         i) The depth of x-ray generation in the specimen.
         ii) The take-off angle.

In addition to the specimen itself, the X-ray generation process is also affected by the probe size, current, and convergence angle. Fortunately, elemental concentration quantification can be done with reasonable accuracy by comparing the peak intensities with k-factors in EDS spectra.



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