FEI Quanta FEG 250, User'S Operation Manual, Page: 76 / 228

Operating Procedures: Obtaining an Image
5-4
Obtaining an Image
OPERATION PRE-CHECK
To ensure correct operation in any Vacuum mode, check the following
list before continuing. After obtaining a preliminary image, you can
then experiment with your settings.
It is also possible to use Set Default Parameters ( Ctrl + D ) function
found at the Tools menu.
TABLE 5-1 QUANTA FEG SETUP CONDITIONS
Adjustment E-Beam Setting
Vacuum mode HiVac: conductive samples
LoVac: nonconductive, mixed or contaminating
samples
ESEM: wet samples (use H
2
O gas medium)
High Voltage Select voltage relative to specimen type:
- low voltage for surface imaging, beam-sensitive
samples and slightly charging samples
- high voltage for conductors, high resolution,
compound info (BSE, X-ray)
For example:
- biological sample High Voltage = (1–10) kV
- metal sample High Voltage = (10–30) kV
Spot size HiVac and LoVac: 3 or 4
ESEM: 4
Pressure HiVac: the lowest
LoVac: 60 Pa (0.5 Torr)
ESEM: 600 Pa (3.7 Torr)
Scan rate HiVac: fast (dwell time about 0.1 - 0.3 µs)
LoVac and ESEM: slow (dwell time about 1 - 3 µs)
Working
Distance Set the highest specimen point to approximately
10 mm (yellow mark in an optical quad) and press
Ctrl + F to set WD to 10 mm.
Magnification Set to lowest – from 50× to 200×
Standard
Detector HiVac: ETD (SE)
LoVac: LFD
ESEM: GSED
Filtering HiVac: Average (4 frames for fast scans)
LoVac and ESEM: Live
Contrast
and Brightness With contrast at minimum value adjust brightness
to just show a change in intensity to the screen.
Increase the contrast to produce a reasonable
image on screen. Increases in brightness and
decreases in contrast produce softer images and
vice versa.