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ZEISS
3 Product and Functional Description | 3.2 Main Components
Fig. 31: Field of view at different working distances: The smallest possible magnification depends on the working dis-
tance: Field of view at 30 mm
: Reasonably good signal-to-noise ratio, minimum magnification levels can be set
: Limits exist on the lowest magnification setting possible (right)
Although images produced by the SE detector always include some backscattered electron com-
ponents, most of the signal is generated by the secondary electrons and the fraction of backscat-
tered signal is negligible. The images obtained by the SE detector are therefore primarily sec-
ondary electron images.
Fig. 32: Comparison of material contrast using
/
detectors on a polished specimen:
= 5 mm using
detec-
tor: Material contrast is very poor (left);
detector: Clear image showing good material contrast
(right)
In the previous figure the SE image taken at 5 mm working distance shows relatively poor mate-
rial contrast. In this example the reduced yield of secondary electrons is caused by the specimen
preparation technique of polishing the specimen surface. The ratio of SE to BSE electrons is there-
fore altered in favor of backscattered electrons.
Because the SE detector is mounted on the chamber at a certain angle to the specimen, the speci-
men is always viewed laterally. The SE detector, therefore, provides good surface information. All
other detectors (InLens SE and BSE) view the specimen from above, providing only limited infor-
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.
Instruction Manual ZEISS SIGMA series | en-US | Rev. 7 | 352102-9344-006
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