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ZEISS
3 Product and Functional Description | 3.3 Detectors
at long working distances. This is particularly important for low magnification imaging that is nec-
essary for adjusting the orientation of the specimen holder or locating a specific area on the speci-
men.
Optimal Initial
Settings
The following settings provide a good field of view for navigating on the specimen at low magni-
fications:
§
Initial working distance in the range of 10 mm to 20 mm.
§
Acceleration voltage of approximately 10 kV.
The imaging conditions can be readjusted for a desired application after identifying the area of in-
terest on the specimen.
Fig. 19: 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. 20: 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-
Instruction Manual ZEISS EVO | en-US | Rev. 10 | 354706-0780-006
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Summary of Contents for EVO
Page 1: ...Instruction Manual ZEISS EVO Scanning Electron Microscope...
Page 179: ......