How to avoid the charged bands in FESEM images?

Some solution I have got by imaging it as soon as it is coated, but if we need to search for the better area in heterogeneous sample then the band is re appearing. Please provide me solution for this band formation in SEM and FESEM( imaging

Jibran Khaliq

Try increasing the thickness of your Pt upto 15 nm. probably the thickness is not enough!!

Yashwanth Purushotham

Thanks for the answer, but coating of 15 nm may interfere in the morphology of nano particle. So please share me some detailed information to understand the mechanism better.

Pieter Westerik

Can you upload an example picture?

Yashwanth Purushotham

Please find the attachment

Pieter Westerik

You can try to reduce the spot size/beam current of your electron beam, or reduce the residence/integration time per pixel. This should reduce charging, but also the signal to noise ratio. This can be compensated by averaging/integrating multiple scans, provided that your image is very stable (otherwise you also get a blurry effect).

You can also try to reduce the accelerating voltage, however it might reduce your resolution. On the other hand it reduces the chance that the electrons will penetrate your thin platinum layer.

Yashwanth Purushotham

Thanks for the guidelines but please clarify me the below mentioned since I am in learning stage

to reduce the spot size/beam current of your electron beam, or reduce the residence/integration time per pixel. This should reduce charging, but also the signal to noise ratio. This can be compensated by averaging/integrating multiple scans, provided that your image is very stable (otherwise you also get a blurry effect).

means reducing probe current ?

Please explain

Yashwanth Purushotham

The band problem is with uploaded image taken by JSM 7100F JEOL FESEM (schottky gun)

Pieter Westerik

Yes, I think beam current and probe current are the same.

The fact that you have charging means that more electrons reach the charging surface in a short time than can easily flow away. The platinum layer should help for the conduction, but apparently the thin layer you have is not enough. So it may help to reduce the amount of electrons reaching the surface. I mentioned several ways to do this:

Spot size/beam current directly influences the amount of electrons in the beam. I think it is done by tuning the size of a hole through which the beam is passed.

Residence time per pixel means how long the beam stays at one point, all the time integrating the amount of collected charge to get to an intensity value for that particular pixel. Reducing this time obviously results in less charge buildup, and also in a quicker scanning of your picture. This does not really help if your sample is completely insulating, because in that case the built up charge will just remain in place until the next scan, and for every subsequent scan the charge will increase. However if you have sufficient conduction the charges can flow away before the beam reaches the same spot in the next scan.

When you reduce the accelerating voltage, I think also less electrons reach your sample, and also they penetrate less deep into it. However I am not entirely sure how this is for FESEM because it is supposed to be less sensitive to acceleration voltage. I have no experience with this.

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