3 Product and Functional Description | 3.3 Optional Components and Accessories
ZEISS
Fig. 47: The effects of working distance:
too short (right)
Parameter
Description
Acceleration voltage
1 kV to 30 kV
Use of very low and very high acceleration voltages is possible
Working distance
7 mm to 12 mm
If the working distance is too short or too long, the solid angle avail-
able for detection deteriorates away from the optimum
Aperture
30 μm
The standard aperture is recommended for many applications
7.0 μm to 20 μm
With these apertures, the probe current is frequently too low to ob-
tain a sufficient signal-to-noise ratio and the required contrast
60 μm
Higher probe currents frequently improve the contrast
120 μm
Often only recommended for analytical applications
Specimen tilt
Avoid large angles of tilt, if possible
Operation mode
Use of the BSE detector is possible in high vacuum and VP mode
3.3.1.2.2 BSE Detector Segments
The HDBSD detector has five silicon diode segments:
detector with five segments
The HDAsB detector has four diode segments.
On the surface of the specimen, some of the primary electrons are backscattered. The backscat-
tered electrons then move towards the silicon segments of the detector, which are covered by a
thin layer of additional material. If the energy of the backscattered electrons is high enough, then
they can pass through the thin layer of material and create electron-hole pairs in the silicon seg-
ments.
60
Instruction Manual ZEISS SIGMA series | en-US | Rev. 7 | 352102-9344-006