The images produced by Scanning Electron Microscopy typically have hills and craters. Both of these features have a contrast that is different from that on the surface. So how do I identify if a feature is a hill or a crater or say, if it is a pillar or a hole ? What's the principle behind this?
Vladimir is correct, It can be very confusing. I have seen images where in one orientation I have craters, and if I rotate the image they become hills. You can however, try to take a stereo-pair image of your sample, by using two images with different tilts then recombining as a red-green anaglyph. This will then become very obvious which way your topography is pointing. I have a lot of success with this method have many stereo-images published. Here is an example.
Dear Siddharth,
if this is not clear from the secondary electron images, you might use the additional information of backscattered electron images. Holes usually appear dark at BSD images.
Another way might be to focus on the ground of a hole or the top of a hill at high magnification by adjusting the electron beam focus distance and to compare the resulting working distances.
I think that this information could be well deduced from images collected with secondary electrons, that are the most suitable to detect morphological features. The craters usually appear black while the pillars white due to the different number of electrons that reach the detector
The answer from Marcella has probably already solved your problem. However, if you are still not sure, you can tilt your sample in the SEM and it will be even easier to identify the hills.
In many cases it is obvious. But for novice operator quite often it is rather difficult task.
Suppose you can tell what is "hill" and what is "crater". Rotate image (on a screen) 180 degrees and "hills" now will be seen as craters...
If there is a trouble with determination, you can "wobble" specimen, tilt it back and forth to some degree. It is very helpful and makes things clear.
Vladimir is correct, It can be very confusing. I have seen images where in one orientation I have craters, and if I rotate the image they become hills. You can however, try to take a stereo-pair image of your sample, by using two images with different tilts then recombining as a red-green anaglyph. This will then become very obvious which way your topography is pointing. I have a lot of success with this method have many stereo-images published. Here is an example.
Thanks a lot, Dr. Slipper. That is a very intelligent method indeed and seems to have a 3D effect which considerably simplifies the analysis.
You are welcome. It does become a little more tricky at higher magnifications, but is well worth the effort. At lower mags I use -5 and +5 degree tilt, and with increasing magnifications, reduce the angles to -3 and +3. Stage calibration is important in order to ensure you are using a perfectly centred eucentric tilt. Also the centre of rotation should be calibrated if possible. If your pit/hill features are deep/high, you may need to increase the WD in order to get it in focus , but beware of image rotation with increasing WD. It may take a bit of experimentation. Good luck.
Dear Dr. Slipper,
How to make green-red colour in SEM image?
Thank you
- Badges
- Science method