If we compare a Raman spectrum of monolayer graphene and bilayer or fewlayer graphene, we will see that the 2D peak intensity decreases (relative to the G peak intensity) for the later cases. I have not clear what is the reason. I suppose it could be related to the density of states for the phonons near the K point. Or maybe the what is actually happens is that the intensity of the G peak increases with the number of layers. And this could be related to the splitting of the electron dispersion for bi/few layer graphene. Could you please clarify my ideas? I would appreciate your contributions.
As the layer of graphene increase the properite changed to graphite properities as the layer increase
Ph. D. Amer Al-Taee , thanks very much for your response. I am aware that these materials have different properties depending on the number of layers. As far as I know, the Raman intensity is proportional to the electron-phonon coulplig squared. So, in my opinion, there are two options:
Is it known which is the right one and why? Or maybe there is another explanation that haven't come to my mind.
Pretty interesting question (still seems to be no set answer in publications), so I have been giving it a bit of a read, the reference here seems to be pretty detailed and may help you. https://arxiv.org/pdf/1306.5856.pdf
From looking at other publications it looks like the 2D peak, the overtone of the D peak broadens as well as decreasing in intensity. As more layers are present these must be more available phonons, but the peak seems to show a wider distribution suggesting that the phonon response is spread/split, so coupling would not be reduced (I would say). Another possible answer I read was the splitting of electron bands that give rise to the broadening.
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