Utilized
signals: inelastically scattered
electrons (energy-loss electrons) and X-rays
| Methods |
Information |
| EDXS |
qualitative
and quantitative element analysis |
| EELS |
qualitative
and quantitative element analysis.
Bonding situation (energy-loss near-edge structure ELNES), coordination and interatomic
distances (extended energy-loss fine structure EXELFS) |
| ESI |
element
distribution |
| STEM + EDXS/EELS |
element
distribution |
Comparison
of EELS and EDXS
EELS |
EDXS |
high detection efficiency for low Z elements |
high detection efficiency for high Z elements
|
elemental, chemical and dielectric information
|
elemental information only |
excellent
energy resolution (0.3-2 eV) results in few peak overlaps;
fine structures of the ionization edges can be analyzed (ELNES, EXELFS) |
low
energy resolution (> 100 eV) causes frequent overlaps |
very
efficient and high sensitivity to most elements => fast
and efficient mapping technique |
inefficient
signal collection and detection
=> X-ray mapping is time-consuming |
fast
technique; complex processing required
|
slow
technique; only simple data processing required |
Restrictions:
Since electron-matter interactions are mostly elastic,
high electron doses are necessary for all methods of analytical
electron microscopy. A long recording time may be required for a
good signal/noise ratio which is only possible if the sample is
stable under the intense electron beam and if no specimen drift
occurs.
Since ionization edges occur at characteristic energies and have different
shapes, not all methods are equally suitable for all elements.
|
