1. Alignment. Your microscope is SEM S3400, made by Hitachi. Its highest obtainable resolution is 3 nm, much better than your images show. You should have a specimen for checking SEM performance, for example gold on carbon. You may want to get a picture from such a specimen and determine whether your microscope needs alignments (including stigmator compensation).

2. Your oxides are semiconductors and I do not see any charging effects on your pictures. So, observation without coating is possible. However, I’d recommend to apply coating for better secondary electron generation (oxides are not really good in this department). With better SE generation you can decrease your beam intensity significantly (very important when working with high magnifications). Au coating could be visible at your magnifications, so Pt or Au-Pd coatings are preferred ones.

3. I do not know how good performance of your SEM is at low accelerating voltages, but generally speaking you can see more details at lower voltages (but you will lose in resolution).

We are using Carbon tape and we  used powder directly once and in another trying  we dispersed the samples in ethanol  , methanol, etc.. and dropped on the carbon tape but the images still not clear.

I'm not personally acquainted with Thermo machines, but assuming it works in a similar manner to the Zeiss machines, there are a few things you can try.

Firstly, 20-25kV should be fine for most applications, and SE mode will give you better resolution than BSE. If your sample is very thin, or you only want to examine the surface, you will need to lower this value. 10-15kV should work, but for nanotubes you might need to go even lower.

The other things to bear in mind is the probe current (Sometimes called I-probe) and the spot size (These are linked. A higher current leads to a larger spot size). A smaller spot size will allow you to resolve finer detail, but the consequent lower probe current will lead to a worse signal-to-noise, resulting in grainier images. You'll need to find a happy medium.

Focussing can be done in a number of ways, but adjusting either the working distance or the sample height are the simplest by far. The simplest way to keep focus is to focus at minimum zoom, and then zoom in, refocus, zoom in, refocus, etc.

When you are resolving smaller details, you will need a smaller spot size, but this will cause grainier images. Assuming everything is correctly focussed, you should be able to eliminate this by lowering the scan speed.

Astigmatism can be a factor. The easiest way to test if you have it is to use a series of Sn spheres, which you can usually buy as a standard. They should be extremely spherical. If they aren't, adjust your astigmatism until they are.

Another possible factor is charging of a sample by the electron beam. This will cause the sample to 'glow' as far as the detector is concerned, and your resolution will be shot to hell. Conductive tape is one method for getting around it, and gold sputtering is another. The sputtering is better, but often more expensive and time consuming.

Hope that helps.

Dear Abdo,

Your samples are oxides (TiO2 and ZnO) which are not conductor samples. You will probably have the charge up problem. If you only want to observe and take some pictures, you have to use the lowest acceleration potential possible (2-5 keV). In BSE mode the charge up has less effects on your observations.

You can also metallize your sample if you have the metallization facilities. It consist of to put a few layers of metal who permit to eliminate the charge up problem.     

1. Could you attach your pictures? Without them it is almost impossible to give you sound advise.

2. Please tell us what SEM you use. You have written it is from "Thermo scientific", but I doubt it very much: as far as I know Thermo Scientific does not make SEMs. Is your microscope field emission?

3.  What does it mean: "even at 1 micro"? 

4. You should check whether you specimens need coating. Make suspension in water/ethanol/etc, place a drop on well polished conductive surface, let it dry out and check in SEM for charging. If charging is a problem, coat them. If coating does needed, you can use any (including non-conductive) substrate, such as glass or plastic.

These are some  images of Our SEM

I was thinking about pictures of your specimens...

Anyway, you have an EDS system manufactured by Themro Scientific. It is separate system from SEM itself. Still it is known what microscope you do have. I can see it is not an old one and it is not a FE SEM. So, I do not expect you can work with really low voltages (preferred) but you can still try to go as low as you can, maybe 5kV. 

Images of your specimens still could be helpful.

these are Examples of gotten images Where TNT (TiO2 nanotubes) and ZnR (nanoflowers)

Dear Abdo,

Someone mentioned that it might be necessary to cover the surface of your samples with nanometer thick layer of conducting metal (e.g. gold). You should try it, since your sample do not conduct electricity. This is the simplest way to increase the quality of your images. We use gold sputter from Emitech, but any gold sputtering aparatus will do the trick. However, then you will have this metal in your EDS results (if you want to use it).

Best regards,

Michał W.

1. Alignment. Your microscope is SEM S3400, made by Hitachi. Its highest obtainable resolution is 3 nm, much better than your images show. You should have a specimen for checking SEM performance, for example gold on carbon. You may want to get a picture from such a specimen and determine whether your microscope needs alignments (including stigmator compensation).

2. Your oxides are semiconductors and I do not see any charging effects on your pictures. So, observation without coating is possible. However, I’d recommend to apply coating for better secondary electron generation (oxides are not really good in this department). With better SE generation you can decrease your beam intensity significantly (very important when working with high magnifications). Au coating could be visible at your magnifications, so Pt or Au-Pd coatings are preferred ones.

3. I do not know how good performance of your SEM is at low accelerating voltages, but generally speaking you can see more details at lower voltages (but you will lose in resolution).

Thank you all of you for answers

Thank you Vladimir Dusevich