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Once the machine is under vacuum (indicated by the SEM beeping twice), navigate to the Operation Panel (Figure 7). IMAGE GOES HERE
Select an accelerating voltage (range: 1 to 30 kV; see table 1 for working guide).
1-5 kV
Delicate or uncoated samples (e.g. microfossils)
5-10 kV
Coated biological samples (e.g. Au coated microfossils, recommended)
10-30 kV
Carbon-coated thin section samples
Table 1. Working guide for accelerating voltage
- Select which detector to use:
- the secondary electron (SE) detector, which returns an image of the topography of the sample's surface and is generally used for micropaleontological identification with SEM stubs
- or the back-scattered electron (BSE) detector, which returns a value based on the average atomic number (Z) of a given material and is generally used on thin sections or grain mounts.
- User guide can have a more in-depth explanation of the two different detectors and show samples of SE and BSE images.
- Click the START button to generate an electron beam.
- Monitor the emission current, which should be around 110uA. If it has diverged by more than ±20 uA, please notify a technician as this either means the filament is about to die or the beam is not stable, and image quality will be subpar. how to change the filament
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Align the beam
Recommended settings
| Sample | Sample preparation | SEM settings |
|---|---|---|
| Foraminifera or other large (50 um - 1 mm) particles of geological material | Picked and mounted on an SEM stub, optionally sputter coated |
|
| Diatoms or nannofossils | Smear slide, sputter coated with Au/Pd |
|
| Polished thin section/polished thick section | Polished thin/thick section placed in thin section holder, fastened down using the clips and carbon tape, carbon coated |
|
| Larger amounts of geological material, prepared as a polished grain mount | Grain mount placed in grain mount holder, carbon coated |
|
Additional tips
- Dealing with movement
- Sea state
- Jostling the table
- For high magnification (>5000x; unlikely at sea conditions)
- Change the variable strip aperture
- Increase the Spot Size (higher number)
- Change the accelerating voltage up or down
- Adjust the stigmation
- Focus the microscope/decrease the scan speed
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