Biomedical Engineering Reference
In-Depth Information
a
b
Incident Beam
Incident Beam
Crystal
Annular
Detector
Z-Contrast
Image
Spectrometer
Annular Detectors
Fig. 3.8
(
a
) Different detectors in STEM mode and (
b
) STEM mode of elastic and inelastic
transmitted electrons: ADF or HAADF detector
obtaining a very narrow beam on a thin specimen and the high-energy resolution for
EELS analyses. The spatial resolution reached is of the same size as the probe used.
In a “dedicated STEM,” as well as in the latest generations of analytical micro-
scopes (TEM/STEM) equipped with field emission guns (FEGs), the electron beam
makes high resolution possible because of the very small probe size it can attain
(
∼
0.14 nm). It is then possible to analyze and characterize very small areas a
Electron Beam
EDS Detector
Analyzer
EELS or PEELS
Detector
Fig. 3.9
Different types of detection in a TEM/STEM microscope: analysis of X-rays and elastic
and inelastic electrons transmitted constituted by a PEELS energy-loss filter outside the column
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