3 Product and Functional Description | 3.3 Optional Components and Accessories
ZEISS
1
2
3
4
1
2
3
4
detector
1
Incident electron beam (primary elec-
trons)
2
Thin specimen
3
Dark-field STEM detector;
detector-to-specimen distance (2 to
4 mm recommended)
4
Bright-field STEM detector
Info
Risk of malfunction: The diode segments are sensitive to the light that is used for illumination
in TV mode (infrared and white).
When you use a diode detector, always make sure that the TV illumination is switched off. If
the CCD Mode is set to
Auto Detect
, then the TV illumination is automatically switched off
when a diode detector is used.
Function
The STEM detector is a pneumatically retractable multi-mode detector with a 12-stub specimen
holder for bright-field and dark-field detection. The STEM unit is equipped with semiconductor
diodes that are switched on or off in order to allow dark-field and bright-field imaging. The diode
area consists of four quadrants for the dark-field (DF) and one diode for the bright field (BF) imag-
ing.
The “cone angles” of the BF and DF signals depend on the specimen as well as the illumination
aperture. The center hole separates the DF and the BF signals, and the arrangement of the diodes
allows simultaneous detection of the bright-field and dark-field signals without the need for re-
alignment. Moving the detector in the Z-axis and changing the working distance makes it possible
to obtain optimum separation of the signal. A detector-to-specimen distance in the range of 2
mm to 4 mm is recommended for optimum imaging results.
The STEM detector is used in cases where the thickness of a specimen is similar to or less than the
dimensions of the interaction volume. The specimen must be mounted on a TEM grid with a thin
carbon-film support (approximately 10 nm thick). Electrons that pass through the target can then
be collected by the detector and used to form an image. The SmartSEM user interface allows to
select different imaging modes (DF or BF). It is also possible to mix the DF and BF signals.
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Instruction Manual ZEISS SIGMA series | en-US | Rev. 7 | 352102-9344-006