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|Title:||Second-order overtone and combination raman modes of graphene layers in the range of 1690-2150 cm-1|
|Source:||Cong, C., Yu, T., Saito, R., Dresselhaus, G.F., Dresselhaus, M.S. (2011-03-22). Second-order overtone and combination raman modes of graphene layers in the range of 1690-2150 cm-1. ACS Nano 5 (3) : 1600-1605. ScholarBank@NUS Repository. https://doi.org/10.1021/nn200010m|
|Abstract:||Though graphene has been intensively studied by Raman spectroscopy, in this letter, we report a study of the second-order overtone and combination Raman modes in a mostly unexplored frequency range of 1690-2150 cm-1 in nonsuspended commensurate (AB-stacked), incommensurate (folded) and suspended graphene layers. On the basis of the double resonance theory, four dominant modes in this range have been assigned to (i) the second order out-of-plane transverse mode (2oTO or M band), (ii) the combinational modes of in-plane transverse acoustic mode and longitudinal optical mode (iTA+LO), (iii) in-plane transverse optical mode and longitudinal acoustic mode (iTO+LA), and (iv) longitudinal optical mode and longitudinal acoustic mode (LO+LA). Differing from AB-stacked bilayer graphene or few layer graphene, single layer graphene shows the disappearance of the M band. Systematic analysis reveals that interlayer interaction is essential for the presence (or absence) of the M band, whereas the substrate has no effect on the presence (or absence) of the M band. Dispersive behaviors of these new Raman modes in graphene have been probed by laser excitation energy-dependent Raman spectroscopy. It is found that the appearance of the M band strictly depends on the AB stacking, which could be used as a fingerprint for AB-stacked bilayer graphene. This work expands upon the unique and powerful abilities of Raman spectroscopy to study graphene and provides another effective way to probe phonon dispersion, electron-phonon coupling, and to exploit the electronic band structure of graphene layers. © 2011 American Chemical Society.|
|Source Title:||ACS Nano|
|Appears in Collections:||Staff Publications|
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