Zeiss GeminiSEM Series, Instruction Manual

Page: 87 / 164

ZEISS 5 Commissioning and First Operating Steps | 5.5 Modifying Gun Parameters
Info
After cathode replacement or after re-alignment of the electron optical column, OptiProbe has
to be calibrated.
Prerequisite ü Requires the licenses OPTIPROBE and HIGH VOLTAGE
ü Particular hardware and the specimen current amplifier are installed.
Procedure 1. In the GeminiSEM Control panel, select the Gun tab.
2. Activate the OptiProbe checkbox.
3. Use the I Probe slider to set the desired probe current.
à
As soon as the probe current adjustment is finished, the OptiProbe Status readout
changes from Busy to Ready .
à The probe current displayed in the I Probe readout corresponds to the actual probe cur-
rent (± 15 %).
4. To deactivate the function, deactivate the OptiProbe checkbox.
INFO: If OptiProbe is deactivated, the I Probe readout continues to indicate the actual
probe current (± 15 %).
5.5.4 Measuring the Probe Current
Measuring the probe current using the Faraday cup ensures that the current displayed in the soft-
ware equals the incident probe current. The Faraday cup consists of a strongly absorbing material
with a cavity covered by a small aperture. If the beam is focused in this cavity, no secondary elec-
trons and no backscattered electrons leave the Faraday cup.
Info
The specimen current (absorbed current) is the fraction of the incident probe current (beam
current) that hits the specimen and is not emitted as secondary electrons, backscattered elec-
trons, or transmitted electrons. In case there is no other signal emission from the specimen,
the specimen current equals the incident probe current that hits the specimen.
Parts and Tools
Designation Part no.
Faraday cup 348342-8055-000
Prerequisite
ü
You have successfully carried out the steps described in Acquiring an Image [
}
74]
Procedure 1. Load the Faraday cup into the specimen chamber. Refer to Loading the Specimen Chamber
[
}
76] .
2. Evacuate the specimen chamber.
3. Switch on the gun. Refer to
Switching on the Gun [
}
80] .
4. Switch on the EHT. Refer to Switching on the EHT [
}
80] .
5. From the Panel Configuration Bar , select Specimen Current Monitor .
à
The Specimen Current Monitor window is displayed.
6. Activate the Stage Bias checkbox.
INFO: If the Stage Bias checkbox is activated, a small negative bias voltage is applied to
the specimen stage. This enhances the sensitivity for touch alarm, especially for weakly con-
ducting specimens. In some special cases (e.g. very low EHT values), it may be necessary to
deactivate the Stage Bias option and set the stage potential close to zero.
Instruction Manual ZEISS GeminiSEM series | en-US | Rev. 2 | 349500-8138-000 87