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
||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)
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.