FEI Quanta FEG 250, Руководство пользователя

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System Options: Wet STEM
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WET STEM BASIC OPERATIONS
The Wet STEM experiments are very dynamic and proper observation
conditions can be stable for a few minutes only.
Note:
Precise control of sample humidity is essential in Wet STEM
experiments. Therefore, it is highly recommended to execute the
cooling stage calibration procedure (see above).
1. Plug the GSED detector on. Alternatively, the GAD, the Low kV
PLA or the X-Ray PLA can be used.
2. Insert the TEM grid (ideally holey carbon coated grid) into the Wet
STEM Sample holder.
3. Insert the Wet STEM Sample holder with the grid into the Wet
STEM assembly and tighten it by Fixation sleeve.
4. Pre-cool empty grid to 1.5°C for 15 minutes.
5. When it is cold, put a droplet of liquid with specimens on the grid.
6. Use a filter paper to siphon the liquid off the grid until only a thin
liquid layer remains.
7. Add water droplets in the 4 indentations.
8. Set pressure to 750 Pa, set purging to 800-1000 Pa in two cycles
(see
Preferences / ESEM tab), move the stage away of the beam
axis and pump the chamber.
9. When the vacuum status is Pumped (750 Pa), move the stage
back to the observing position and switch the Beam On
(15 – 30 kV, spot size 4 – 5).
10. Set the GSED / LFD for Quad 3, go to a working distance
5 –10 mm (depends on the detector / pole piece cone plugged on)
and optimize the imaging.
11. Set the STEM I detector segment A for Quad 1 and segment B for
Quad 2.
Liquid stays on grid meshes during the observation. If there is no or a
poor STEM detector sample imaging, the liquid layer could be too
thick. Decrease pressure slightly until the liquid layer becomes
correctly thick.