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8 Operation | 8.3 Modifying Gun Parameters
Purpose
Prerequisites ¢
Procedure 1
Purpose
112
8.3 Modifying Gun Parameters
|
8.3
Modifying Gun Parameters
8.3.1 Selecting the Gun Mode
In the Imaging gun mode, the temperature of the Schottky emitter and the
extraction voltage are reduced. This leads to a reduction of the energy spread of
the primary electrons. The Imaging gun mode is especially useful at low kV to
reduce chromatic error and achieve a better resolution. The probe current in
Imaging gun mode is about half the probe current in Normal gun mode.
In the Analytic gun mode, the temperature of the Schottky emitter and the
extraction voltage are increased. This leads to a higher probe current. The Analytic
gun mode is especially useful for applications which require high intensities (e.g.
WDX). The probe current in Analytic gun mode is about twice the probe current in
Normal gun mode.
INFO
After switching the gun mode, you can immediately work with the selected gun
mode. For applications, which require a high probe current stability, wait
24 hours until a stability of 0.2 %/h is reached.
The GeminiSEM Control panel is closed.
From the Menu Bar, select Tools > User Preferences.
The User Preferences dialog is displayed.
2
Select User > Expert Gun Mode.
3
Click in the Value field and select Yes.
4
In the Panel Configuration Bar, double-click GeminiSEM Control.
5
In the GeminiSEM Control panel, select the Control tab.
6
In the Beam section, click one of the following buttons:
– To switch to Imaging gun mode, click Imaging.
– To switch to Normal gun mode, click Normal.
– To switch to Analytic gun mode, click Analytic.
INFO
If you use the Analytic gun mode, then the lifetime of the
emitter is reduced.
8.3.2 Measuring the Probe Current
Measuring the probe current using the Faraday cup ensures that the current
displayed in the software 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 electrons and no backscattered
electrons leave the Faraday cup.
Instruction Manual ZEISS GeminiSEM Series | en02 | 349500-8038-000
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