Raman Spectroscopy in Graphene-Based Systems: Prototypes for Nanoscience and Nanometrology

Table 1

Assignments and frequency behavior for the Raman modes from sp² carbon materials [2].

Name^(1)	𝜔 (cm^−1)^(2)	Res.^(3)	𝜕𝜔/𝜕𝐸^(4)	Notes^(5)
iTA	288	DRd1	129	Intra-V (𝑞 ~ 2𝑘 near Γ)
LA	453	DRd1	216	Intra-V (𝑞 ~ 2𝑘 near Γ)
RBM^(6)	227/𝑑𝑡	SR	0	SWNT vibration of radius
IFM^− (oTO − LA)	750	DR2	−220	Intra-V + Intra-V (𝑞 ~ 2𝑘 near Γ)
oTO	860	DRd1	0	Intra-V (𝑞 ~ 0 near Γ), IR active
IFM^+ (oTO + LA)	960	DR2	180	Intra-V + Intra-V (𝑞 ~ 2𝑘 near Γ)
D (iTO)	1350	DRd1	53	Inter-V (𝑞 ~ 2𝑘 near K)
G (iTO·LO)^(7)	1585	SR	0	𝑞=0, that is, at Γ
D′ (LO)	1620	DRd1	10	Intra-V (𝑞 ~ 2𝑘 near Γ)
M^− (2oTO)	1732	DR2	−26	Intra-V + Intra-V (𝑞 ~ 2𝑘 near Γ)
M^+ (2oTO)	1755	DR2	0	Intra-V + Intra-V (𝑞 ~ 0 near Γ)
iTOLA (iTO + LA)	1950	DR2	230	Intra-V + Intra-V (𝑞 ~ 2𝑘 near Γ)
G* (LA + iTO)	2450	DR2	−10	Inter-V + Inter-V (𝑞 ~ 2𝑘 near K)^(8)
G′ (2iTO)^(9)	2700	DR2	100	Inter-V + Inter-V (𝑞 ~ 2𝑘 near K)
G + D	2935	DRd2	50	Intra-V + Inter-V^(10)
D′ + D	2970	DRd2	60	Intra-V + Inter-V^(10)
2G	3170	DR2	0	Overtone of G mode
2D′	3240	DR2	20	Overtone of D′ mode

⁽¹⁾Usually the respective graphene phonon branch labels the Raman peaks. When other names are given in the literature, the respective phonon branch appears between parentheses.
⁽²⁾The frequencies quoted in the table are observed at 𝐸_laser=2.41 eV.
⁽³⁾The notation for resonances is as follows: SR: single resonance, 1-phonon Raman allowed; DR2: double resonance, 2-phonon Raman allowed; DRd1: double resonance Raman activated by disorder, 1 phonon; DRd2: double resonance Raman activated by disorder, 2 phonons.
⁽⁴⁾The change of phonon frequency in cm⁻¹ obtained by changing the laser excitation energy by 1 eV.
⁽⁵⁾Intra-V: intravalley scattering; Inter-V: intervalley scattering.
⁽⁶⁾The radial breathing mode (RBM) only occurs for carbon nanotubes.
⁽⁷⁾The iTO and LO phonons are degenerated at the Γ point for graphene. For nanoribbons and SWNTs, the G band splits into several peaks due to symmetry, and differs for metallic and semiconducting nanotubes. The G band frequency depends strongly on doping and strain.
⁽⁸⁾There is another assignment of 2iTO (𝑞 ~ 0 near K) with 𝜕𝜔/𝜕𝐸∼0.
⁽⁹⁾Some groups use the nomenclature “2D band” for the G′ band.
⁽¹⁰⁾This combination mode consists of intra-valley + inter-valley scattering, and thus, the elastic scattering process also exists for some combination modes.