Troubleshooting Guide

Every sample interacts with the electron beam differently. Consider:

• What part of the sample do I want to see?

• Is the sample charging?

You may need to change the beam voltage, probe current or spot size. There will always be a balance between beam energy, sample damage, charging, and image quality. Try different combinations of settings if you are uncertain and observe how your sample responds.

There are three steps to alignment.

1. The focal plane should be on your sample surface

2. The beam should emerge straight from the pole piece

3. The beam should be round

If you are having trouble focusing, the number 1 reason is that the stigmators are not aligned. Try aligning them at a higher magnification and slightly out of focus where you can see the image stretching, then return to focus and repeat until you cannot see stretching on either side of focus.

We collect signal with a single-point detector, not an array like the detector in a camera. Because of this, we must consider: 

• How the beam generates signal

• How signal reaches the detector 

• How images are formed

In some cases, slowing the scan speed or integrating more frames can improve the signal-to-noise ratio in response to different types of charging. In others, the sample may need to be moved to a shorter working distance to maximize the contrast between similar features. Be careful if moving the stage closer to the pole piece: use the chamberscope, ask for help, and be aware of stage limits.

Sample preparation can help or impede signal generation. Consider:

• How the sample itself is prepared

• How the sample is secured to the stub.

Ensure there is a conductive pathway between the sample surface and the stub. This may mean coating, adding copper tape or clips, pressing your sample better to the carbon tape, using a conductive substrate, or ensuring powders or fibers are not stacked in large piles (large to the SEM may seem small to us.) Failure to ground the sample well may result in charging or drift.