I found in a lot of papers showing 3 realizable peaks D,G and 2D. In some works, there usually is a significant small peak (next to the 2D peak, you can google with keyword Graphene Raman), which is mostly appriximate 2435 cm-1. I haven't read any information about it.
I did the raman tests several times but the strange peak is still at the same position. Could it be the new phase/mode of graphene?
PHYSICAL REVIEW B 87, 205435 (2013) states:
"It is also interesting to compare the relative intensity of the two-phonon lines, such as 2D, 2D', and D + D', measured for SLG [single layer graphene] on CaF2 as a function of excitation energy. The D + D' peak lies at ∼2450 cm^−1, and it is a combination between D and the D' peak at ∼1100 cm^−1."
This might me an overtone, rightly suggested by Jason Moscatello in his reply.
You can get the details in the following review-
'Fundamentals, overtones, and combinations in the Raman spectrum of graphite;
PHYSICAL REVIEW B VOLUME 52, NUMBER 14 1 OCTOBER 1995-II'
go through it. Might be of help to you.
Trupti
Yes, Mr. Arranz. I'd seen that question before posting my question. The data were taken from one of the best research centers in Japan and I did avoid the fluorescent wavelength as being mentioned.
Actually, our sample contains not only graphene but also other hybridizing materials, which I believe they somehow enhance the phonon activity of graphene at strange peak but the function of that signal still remains unclear.
Hello Mr. Minh,
I wonder if you have found the answer to your problem. I'm seeing a similar spectra for my graphene samples.
Hi Şenyıldız,
I believe it is the D+D". They have some arguments about it but I prefer this work:
May, P. et al. Signature of the two-dimensional phonon dispersion in graphene probed by double-resonant Raman scattering. Physical Review B 87, doi:10.1103/PhysRevB.87.075402 (2013). .
The band at approximately 2440 cm-1 is assigned to the contribution of a transverse optical phonon D and a longitudinal acoustic phonon D”, usually referred as D+D” or G* mode.
This link is really useful,
http://www.instanano.com/characterization/experimental/raman-graphene/