ZEISS
5 Commissioning and First Operating Steps | 5.8 Working with Variable Pressure
When VPSE/C2D collector bias is on, gas cascade electrons are guided to the VPSE/C2D detector
and can therefore not be detected by InLens SE detector or EsB detector. Additionally changing
VPSE/C2D collector bias may result in a beam shift because of the side mounted VPSE/C2D detec-
tor. VPSE/C2D collector bias may limit your InLens SE detector or EsB detector efficiency.
In case you would like to optimize InLens efficiency, set VPSE/C2D collector bias to zero.
All bias voltage supplies have protective circuits to prevent serious damage to the system.
However, when you see arcing (bright stripes in electron image, light flickering in chamberscope),
reduce VPSE/C2D collector bias or beamsleeve bias.
Beamsleeve bias acts as an additional lens and influences the focus of the objective lens. This is
automatically corrected by the SmartSEM software.
At low voltages and not perfectly flat and horizontally aligned specimens this correction may need
refinement by adapting the focus of the objective lens with the focus knob.
Every time the beamsleeve aperture is inserted, a leak test is done automatically. In case the leak
test fails because the beamsleeve aperture is not vacuum tight fitted to the objective lens for
some reason, the system is going back to High Vacuum mode and an error message occurs in
SmartSEM: “Beam sleeve is not vacuum tight. System is going back to HV mode”.
In Nano and XVP mode, the vacuum system permanently monitors the pressures in the micro-
scope. If a leak at the beamsleeve aperture occurs it is immediately detected and the EHT will be
shut down automatically, the system is going back to High Vacuum mode and an error message
occurs in SmartSEM: “Beamsleeve is no longer vacuum tight. System is going back to HV mode”.
In case you get the error message “Beamsleeve is no longer vacuum tight. System is going back to
HV mode”:
§
Check if the slide can freely move to insert the beamsleeve completely and inspect the O-ring
at the beamsleeve.
§
If the error still exists, contact your local ZEISS service representative.
The following settings are recommended for the Nano VP/XVP Mode:
Parameter
Ideal
Ultimate
Limits
EHT
3 kV – 20 kV
1 kV – 30 kV
Maximum WD at
1 kV is 7.5 mm
Skirt effect increases
with lower accelera-
tion voltage
Primary probe cur-
rent
100 pA – 200 pA
10 pA – 100 nA
Signal-to-noise ratio
decreases with low
currents
Image resolution de-
creases with high
current
WD
7.2 mm – 9.2 mm
6.5 mm – Z
max
At WD > 12 mm In-
Lens efficiency de-
creases
Beam Gas Path
Length (BGPL)
1 mm – 3 mm
0.3 mm – Z
max
Below BGPL of
1 mm incomplete
charge compensa-
tion
BGPL > 2 mm in-
creasing skirt effect
Instruction Manual ZEISS GeminiSEM series | en-US | Rev. 2 | 349500-8138-000
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