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Table 3418. Comparison between background and edge onset in EEL spectra.
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Edge onset |
Background |
Mechanism |
Ionization edges |
From plural-scattering events associated with outer-shell interactions, single-scattering contributions from the tails of preceding (lower) ionization edges and valence electron excitations
|
Information |
Provide elemental information |
Provide sample thickness information |
In the cases that very thick TEM samples are used in EELS or EFTEM measurements, the increase of plural scattering effects induces two main problems:
i) The background models, e.g. the form of power law, are not convenient to represent the actual background;
ii) The low energy edge onsets are embedded in the background, meaning some edge becomes invisible.
Furthermore, plural inelastic scattering by plasmon excitation is a special concern when measuring the low energy loss (e.g. Li K-edge) because it is close to the low-energy plasmon region. For instance, double plasmon scattering distorts the pre-edge background and can mask the Li K-edge.
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