=================================================================================
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. Artifacts due to plural scattering can be reduced by increasing the inelastic mean-free-path with the increase of the accelerating voltage of the electron beam or by restricting analyses to thin regions of the sample.
In conventional TEMs working at accelerating voltages of 200 to 400 keV, in the interpretation of the low energy loss from EFTEM and EELS data, several effects have to be kept in mind. For instance, because of the difficulties of multiple scattering corrections, it is necessary to take EFTEM and EELS data from thin specimens.
In EFTEM imaging, an important contribution for low-loss imaging is the delocalization of the inelastic scattering process itself, while at much higher energy-losses the resolution-limiting parameter is usually the chromatic aberration. For instance, to lower the effect of the chromatic aberration, the accelerating voltage needs to be 300 kV if one expects a resolution better than 0.3 nm for >100 eV energy-loss [1].
[1] R.F. Egerton, Electron Energy-Loss Spectroscopy in the
Electron Microscope, 2nd Edition, Plenum Press, New
York, 1996.
|
