Scanning Electron Microscopy of Graphene

[stefan741]

Hi Everyone,

I have recently made some graphene on copper via a chemical vapour deposition process. I have also managed to have a peep under an SEM at this. I do see what I believe to be monolayer graphene. I am very sure the contrast I see is graphene due to the growth patterns, ranging from hexagonal to star shaped, very commonly reported in literature. The contrast I see (between Cu and graphene) is simply one shade, and does not show any layering (if you imagine different contrasts for more or less layers) which could indicate several layers. I do expect monolayer graphene simply from the nature of CVD of graphene on Copper but really would like to understand this further. I have attached an image for you to see.

The questions I have are:

Under an SEM is it possible to tell if you have monolayer graphene? And if yes, how?

Using an SEM what is the smallest separation between two objects that can be resolved with secondary electrons?

I'm very new to SEM and any help or guidance with these questions will be greatly appreciated. THANKS!

 

[ZapperZ]

Did you use EDS to determine which was the graphene and which was the Cu?

When you look at the graphene's EDS, do you also see signatures of Cu? If you do, then maybe one can estimate the thickness of the graphene's layer from the intensity of the Cu signal (when compared to the bare Cu). That should tell you if you have only a monolayer of graphene or not.

Zz.

 

[f95toli]

Under an SEM is it possible to tell if you have monolayer graphene? And if yes, how?

I doubt it. AFAIK you need to use Raman to be 100% sure. There are also various SPM technques (Kelvin etc) that give you contrast between one and two layers.

 

[stefan741]

Thanks for your responses, I really appreciate them :)

I have been very sceptical that it was possible to determine number of layers of graphene by simply looking at picture contrast from the SEM and believe that even if it is possible it is more than likely very unreliable, however I thought I would ask just in case somebody came up with a fantastic answer here.

Zapperz I think this may be a solution for me as from what I understand it is possible to determine the graphene thickness using electron diffraction form the ratio of intensities from the graphene and underlying substrate. I just have not used diffraction methods before and will need to be trained. But this will be good for me as I should be able to get an image of the sample and determine it's thickness with EDS both using the SEM I believe.

f95toli from what I understand Raman is the best technique to determine number of graphene layers, however unfortunately I still need training in Raman spectroscopy.

Thanks again for your answers.