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3 Product and Functional Description | 3.3 Detectors ZEISS
mation about the topography of the specimen. Surfaces tilted towards the detector provide more
surface detail with brighter edges; specimens tilted away from the detector display shadowing ef-
fects and less surface detail.
Fig. 21: Comparison of topographic contrast – SE / BSE detectors on a fracture surface: SE detector: Image with large
depth of field (left); BSE detector: Good material contrast but with limited topographical detail (right)
Some imaging applications require both, compositional and topographical details. The generation
of mixed SE and BSE images is recommended for such applications. The signal mixing option is
available in the
Detectors tab in the SEM Controls panel.
Tilting the specimen increases the signal in the SE detector and sometimes improves the topo-
graphical information. Tilting the specimen towards the SE detector also results in a change of the
solid angle in which both the backscattered and secondary electrons are emitted from the speci-
men.
Parameter Description
Acceleration voltage
0.02 kV to 30 kV In principle suitable for the entire high-voltage range
1 kV to 5 kV Low-voltage applications for the compensation of charges and for
surface-sensitive imaging
5 kV to 20 kV The average voltage range is suitable for many different applications
20 kV to 30 kV Voltage range frequently used for analytical purposes
Working distance
≥ 4 mm If the working distance is too short, shadowing effects occur which
diminish the efficiency of the detector. Below 20 kV, the SEs are ab-
sorbed by the field of the electrostatic lens
4 mm to 6 mm For low-voltage applications (1 kV to 5 kV)
6 mm to 12 mm Useful for the average voltage range (5 kV to 20 kV)
12 mm to 30 mm Recommended only for low magnifications and to increase the depth
of field
Collector voltage
300 V Standard value of the collector voltage
0 V to 400 V Variation of the collector voltage at high magnifications to obtain the
mixed signal
−150 V to 0 V For pseudo-BSE images
36 Instruction Manual ZEISS EVO | en-US | Rev. 10 | 354706-0780-006