Generally, the non-metallic and oily surface samples are first gold-coated for SEM study. Is there any equipment available which can eliminate gold coating and we can get similar results as in gold-coated samples.
1. Low voltage mode. Available on most newer microscopes, but the best results with field emission SEM. Shoosing right voltage (0.5-1.5 kV) for specimen will permit work without any coating.
2. Variable pressure (VP) SEM (sometimes erroneously referred as ESEM). No need for coating also.
The gold coating depends more on your sample not your equipment.
It would be helpful if you could provide some context about what you would like to do.
Depending on your samples and the analyses you plan to do, if you want to avoid gold coating you could try carbon coating instead. I've used it for EDS analysis, since the gold peak in the spectra will usually overlap the peak of other chemical elements of interest.
@Martin & @Sergio
Dear Friends
Thanks for ur concern
Recently, I came to know that some newly developed SEM equipment do not require any type of coating on the samples irrespective of sample material during analysis. Regarding this If you have any idea, plz share.
Thanks
1. Low voltage mode. Available on most newer microscopes, but the best results with field emission SEM. Shoosing right voltage (0.5-1.5 kV) for specimen will permit work without any coating.
2. Variable pressure (VP) SEM (sometimes erroneously referred as ESEM). No need for coating also.
There is an unusual advanced technique. If your specimen is smooth, you can cover it with a grid for TEM or other thin metal non-magnetic foil with small apertures, connected with a stub. Then you can direct the beam in center of an aperture, focus on the specimen's surface and take a picture. Some electrons will be going to grid and the charging of the surface will be not so strong.
Good luck!
@Denis Korneev and @Vladimir Dusevich
Thank you for sharing good piece of information.
I would also recommend using a noncharging electron microscope which is a method used within the frame of Scanning Low Voltage Electron Microscopy (SLEEM). For most of the materials, there is so called "critical energy" of impinging electrons which allows observation of uncoated sample while preventing sample charging.
http://www.formatex.org/microscopy3/pdf/pp795-804.pdf
I have been testing this for graphene oxides and it is really good microscope for low voltage usage and non conductive samples http://cp.literature.agilent.com/litweb/pdf/5990-6183EN.pdf
for good resolution of semiconducting or nonconducting species you need coating. thats all, good luck
While it is correct that VP mode instruments offer a way around having to coat the specimen, the disadvantage is that if you want to carry out EDS analysis on your sample, the spatial resolution is degraded as electrons are scattered by the gas molecules (beam skirting). If EDS (or EDX) analysis is important then use a Carbon coating instead of Au. If you are really not able to coat at all, you can ground your sample locally (e.g. by using a nanoprober that is grounded) and carry out analysis around the area (especially at
@ Dr. Lang thanks for sharing valuable knowledge. Hope it will help my research assignments.
The conductive coatings, such as polypyrrole, no need to Au coating.
Depends on sample. I spent dozens of hours on observations of polymers in low-preasure mode w/o gold or other metal. With ceramics had no problms too. But if we talking about huge magnification, covering sample with conductive material may help.
if the sample is metal and you require huge magnification we need Au coating for that you can contact DMSRDE Kanpur
1. Lower the voltage 600V and current 30pA
2. If sample charges up zoom out field of view to discharge
3. As mentioned above try a PPY polypyrrole coat this is a conductive polymer
@Anthony Davis
Polypyrrole coating for SEM specimens? Can you explain it in a bit more detail. Have you tried it? What is a thickness of coating?
I tried to google, but it looks like Google does not know about use of polypyrrole for SEM specimen preparation.
It depends on your substrate. PPY is often used on electrospun nanofibers that can be used imaged in SEM. There is a lot of literature on that. It is not sputtered on the surface of substrate like Gold, however. Sample is prepped with it.
So, you just confirmed my point. PPY is not suitable for SEM specimen preparation. So, why this advise?
I agree low voltage 500V-600V landing energy would prevent some of the unwanted charging.
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