3 Product and Functional Description | 3.5 Optional Components and Accessories
ZEISS
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Printed circuit boards
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Semiconductors
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Bond pads
Life sciences:
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Mineral deposits in plant structures
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Biological sections
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Bone structures
Another type of BSD detector is the YAG BSD. For more information on this detector, refer to
YAG BSD Detector.
Function
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 BSD detector. If the energy of the
backscattered electrons is high enough, then the electrons pass through the very thin dead layer
of the diode and create electron-hole pairs in the silicon segments.
In each individual segment, the charge separation due to the electron-hole pairs is measured as a
current, which is used as a signal for image generation. Only electrons that have an energy high
enough to create electron-hole pairs can contribute to image generation. Electrons that have a
lower energy (e.g. secondary electrons) are not detected by the BSD detector.
The emission of backscattered electrons from a specimen is related to the atomic number of the
involved material: Elements with high atomic numbers generate more backscattered electrons (i.e.
the backscatter coefficient is higher). When imaging, regions that contain elements with higher
atomic numbers appear brighter. Regions that contain elements with lower atomic numbers ap-
pear darker.
Since the detector has a limited speed, it is recommended to use scan speed 6 or higher (slower),
especially at small magnifications. The lower the gain is, the faster is the detector.
3.5.1.4 YAG BSD Detector
Purpose
The YAG BSD detector is a scintillation type detector for backscattered electrons.
The YAG BSD detector has a high sensitivity and is specifically designed for high speed imaging.
It can be used in HV mode and in VP mode.
Function
The YAG BSD detector uses yttrium aluminum garnet (YAG) as a fast scintillation material that is
mechanically and chemically resistant. Since it is a scintillation type detector, the YAG BSD detec-
tor does not have segments with changeable polarity and you can only use this detector for com-
position imaging. In comparison to segment based BSD detectors, the YAG BSD detector has a
faster response time.
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Instruction Manual ZEISS EVO | en-US | Rev. 10 | 354706-0780-006
Содержание EVO
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