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Graphene necessary skills layer number and quality of Raman identification!

wallpapers News 2021-05-14

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The excellent properties and importance of graphene as well as its broad application prospects, this omits N words. Let's cut to the chase and talk about the Raman characterization of graphene.
Raman spectroscopy, as a fingerprint-sensitive vibrational spectroscopy technique, is highly sensitive to molecular bonding and material structure. Even small structural changes are evident in the molecular Raman spectra.
The allotropes of carbon (diamonds, carbon nanotubes, graphene, graphite, fullerenes, etc.) are very similar in structure, and the only differences are the relative positions of the carbon atoms and the way they bond with their neighbors. This sensitivity of Raman spectroscopy provides an excellent convenience for the study of carbon allotrope.
Both G and 2D peaks are very obvious in the Raman spectra of graphite and monolayer graphene. It is worth noting that for graphene with defects in the carbon lattice, a relatively obvious D-peak also tends to appear. Although the differences between the graphite and graphene spectra are very small, the positions and shapes of the G and 2D peaks give us very important information.

In the graphene Raman spectra, G peak is generally located at 1587 cm-1, and the peak shape is very sharp. This peak represents the in-plane vibration mode of SP2 hybrid carbon atoms in graphene. The position of G peak is very sensitive to the number of graphene layers, and the position of G peak can be used to determine the number of layers of a specific graphene sample. With the increase of the number of layers, the G peak moves towards the direction of low displacement, that is, towards the direction of low energy, indicating the weakening of the bond energy between graphene layers. Here is an empirical formula for calculating the number of graphene layers:
Omega G = 1581.6 + 11 / (1 + n1.6)
Where, ωG represents the peak position and n represents the number of graphene layers.
It is important to note that the peak position of graphene is affected by temperature, doping, and very weak stress, so when Raman is needed for graphene layer calculations, the operation needs to be very careful.
 
G-peak can be used not only to calculate the number of graphene layers, but also to determine the thickness of graphene using its strength. As shown in Fig. 3, the peak strength of graphene G with different layers is linearly correlated. G-peak strength is less affected by temperature, doping and stress, and provides a more accurate calculation of the number of graphene layers when environmental factors are unavoidable.
 


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