Zeiss GeminiSEM Series, Instruction Manual

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3 Product and Functional Description | 3.2 Main Components ZEISS
Optional Detectors Detected Signals Typical Application Vacuum Mode
* These detectors are available either with one video output channel or with four video output
channels.
For more information about optional detectors, refer to Optional Detectors [
}
46] . For more in-
formation about the aSTEM detector, refer to the corresponding Instruction Manual.
3.2.7.3 InLens SE Detector
Purpose
The InLens SE detector is a high-efficiency detector for high resolution SE imaging and detects
secondary electrons directly in the beam path. The very high detection efficiency of this detector
results from its geometric position in the beam path and from the combination with the electro-
static/electromagnetic lens.
Position The annular shaped in-column detector is located above the objective lens.
1
2
3
4
Fig. 17: Schematics of the InLens SE detector
1 InLens SE detector 2 Beam path
3 Objective lens 4 Specimen
Function The primary electrons are accelerated by the acceleration voltage at the anode and, up to an ac-
celeration voltage of 20 kV, by an additional beam booster voltage of 8 kV at the liner tube. To
ensure that the electrons reach the specimen surface with the energy set as acceleration voltage,
an opposing electrostatic field of the same magnitude as the beam booster voltage (8 kV) is gen-
erated at the end of the objective lens by the electrostatic lens. This electrostatic field acts as ac-
celeration field for the SEs generated on the specimen surface.
At the InLens SE detector, the electrons hit a scintillator. This generates a flash of light that is led
out of the beam path and onto a photomultiplier by means of a lightguide. The photomultiplier
converts the light information into an electronic signal, which can be displayed on the monitor.
The efficiency of the InLens SE detector is mainly determined by the electric field of the electro-
static lens, which decreases exponentially with the distance.
Thus, the working distance (WD) is one of the most important factors affecting the signal-to-noise
ratio of the InLens SE detector.
As the tilt angle of the specimen surface affects the emission angle of the electrons, you should
avoid strong specimen tilting.
42 Instruction Manual ZEISS GeminiSEM series | en-US | Rev. 2 | 349500-8138-000