Electron microscopy
Lithium Drifted & Intrinsic Germanium EDS Detectors
- Practical Electron Microscopy and Database -
- An Online Book -
Microanalysis | EM Book                                                                                   http://www.globalsino.com/EM/        

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


The key component of germanium (Ge) EDS detectors is the Ge crystals. The Ge crystals may be either lithium drifted Ge (Ge (Li)) or high-purity intrinsic Ge (HPGe). The HPGe crystal has an advantage that it can be warmed to room temperature if it is not being used, thus no liquid nitrogen is needed at that time. Germanium is much less transparent to high-energy electrons than silicon (Si) because Ge  has a higher stopping power than Si, and thus is able to detect very high energy X rays, e.g. gold (Au) Kα (69 keV). This is an advantage when the elements in the materials have serious peak overlap in the lower energy ranges.

However, such Ge-based detectors have some disadvantages:
        i) K-shell absorption edge at 11.1 keV.
        ii) Complex L-shell absorption edge structure starting at 1.4 keV.
        iii) A series of escape peaks in the energy range 2 to 12 keV.

Therefore, in the energy range that is most frequently used (i.e. 1-10 keV) in EDS measurements, the Ge detectors do not work as well as Si (Li) detectors.





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