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ZEISS 5 First Operating Steps | 5.7 Working with Specific Specimen Types
5.7.2 Non-conductive Specimen
Non-conductive specimens can be imaged in one of the following vacuum modes:
HV mode If possible, coat non-conductors to prevent charging.
Observation of the specimen at low kV (start at 1 kV) is another good option to obtain a “charge
balance”.
VP Mode (optional)
You can use variable pressure modes (VP mode), where a gas can be introduced into the speci-
men chamber. The gas molecules are ionized by collisions with secondary, backscattered, and pri-
mary electrons. The positively charged ions neutralize the negative charge that builds up on the
specimen surface due to the impact of high-energy primary electrons. This enables you to image
the specimen without the necessity to coat.
For VP mode, the 100 μm VP aperture is fitted under the objective lens and the 750 μm mid-col-
umn aperture is used.
Refer to Installing and Deinstalling the VP or EasyVP Apertures [
}
93] .
EasyVP Mode
(optional)
EasyVP is the recommended configuration for EVO series systems. EasyVP enables the use of all
Optibeam modes and switching between the HV and VP conditions, allowing a maximum cham-
ber pressure of 133 Pa. If higher chamber pressures are required for the charge compensation of
non-conductive specimen, the VP mode needs to be used.
For EasyVP mode, the 400 μm EasyVP aperture is fitted under the objective lens and the 20 μm
mid-column aperture is used.
Refer to Installing and Deinstalling the VP or EasyVP Apertures [
}
93] and Aligning the Gun and
Mid-column Aperture for EasyVP Mode [
}
96] .
Recommended
Parameters
The following parameters are recommended for non-conductive specimens. The values given are
only suggestions and the operator may find that different values will give better information for
the types of specimens that are being investigated.
Parameter HV mode EasyVP mode
EHT 1 kV 25 kV
I Probe 10 pA 250 pA
WD 5 mm 8.5 mm
Filament Fil I set to second peak Fil I set to second peak
Mid-column aperture 20 μm 20 μm
Pressure-limiting aperture – 400 μm EasyVP aperture
Detector SE with collector bias +400 V BSD or VPSE
Scaning parameters Scan speed = 3 with frames
to average = 30 to reduce
noise Cycle time ≥ 20 s
Chamber pressure HV 10 Pa for BSD detector,
40 Pa for VPSE detector or
adjust to eliminate charge
disturbances
5.7.2.1 Installing and Deinstalling the VP or EasyVP Apertures
To use the optional VP mode or EasyVP mode, you need to install the VP or the EasyVP pressure-
limiting aperture under the objective lens.
Additionally, you need to select the mid-column aperture according to the pressure mode and the
pressure-limiting aperture and adjust some settings in SmartSEM.
Instruction Manual ZEISS EVO | en-US | Rev. 10 | 354706-0780-006 93