Resonance effects on the Raman spectra of graphene superlattices

Resonant Raman spectroscopy of twisted multilayer graphene

“…1b shows an absorption peak at B2.03 eV, which agrees with that calculated in ref. 39 for (1,9) t (1 þ 1)LG. We thus use a twist vector of (1,9) and y t ¼ 10.4°in our band structure calculations for t(1 þ 1)LG and t (1 þ 3)LG.…”

“…y t can also be expressed in terms of the twist vector 7,37 (p,q). The so-called R and R 0 Raman bands have been suggested as probes of y t in t (1 þ 1)LG 38,39 . As shown in Fig.…”

“…The major contribution to the intensity comes from resonance matching between E ex and the VHSs energies of the JDOS OAT . Therefore, the intensity of Raman modes in t(m þ n)LG as a function of E ex can be evaluated as 39 :…”

Raman modes in transferred bilayer CVD graphene

“…In addition to the resonant G and 2D bands, the spectra also contain weak Raman peaks due to in-plane combination modes and overtones (LOTA, TOLA, LOLA, TOTA, and 2LO) [15][16][17][18]. The tBLG contains, besides the aforementioned spectral bands, out-of-plane modes such as breathing (ZO ′ and ZO [19][20][21]), rotation (R and R ′ [22][23][24][25][26]), and shear (C [27]) modes. Although these modes generally produce only weak Raman peaks compared with the G and 2D bands, they carry important information for characterizing the perfection, stacking order, and carrier transport in graphene samples.…”

“…Among other characterization techniques such as scanning tunneling microscopy (STM), Landau level (LL) spectroscopy [6], high-resolution transmission electron microscopy (HRTEM) [10], optical microscopy and infrared spectroscopy, Raman spectroscopy has also been widely used in the studies of tBLG [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. This is because Raman spectroscopy is a very sensitive and versatile tool to probe the electron-phonon and phononphonon coupling in graphene samples [11].…”