Uniaxial strain in graphene by Raman spectroscopy:Gpeak splitting, Grüneisen parameters, and sample orientation

Abstract

We uncover the constitutive relation of graphene and probe the physics of its optical phonons by studying its Raman spectrum as a function of uniaxial strain. We find that the doubly degenerate E 2g optical mode splits in two components: one polarized along the strain and the other perpendicular. This splits the G peak into two bands, which we call G + and G − , by analogy with the effect of curvature on the nanotube G peak. Both peaks redshift with increasing strain and their splitting increases, in excellent agreement with first-principles calculations. Their relative intensities are found to depend on light polarization, which provides a useful tool to probe the graphene crystallographic orientation with respect to the strain. The 2D and 2DЈ bands also redshift but do not split for small strains. We study the Grüneisen parameters for the phonons responsible for the G, D, and DЈ peaks. These can be used to measure the amount of uniaxial or biaxial strain, providing a fundamental tool for nanoelectronics, where strain monitoring is of paramount importance

Resonant Raman spectroscopy of twisted multilayer graphene

“…We also note that FWHM(G) of our t (1 þ 3)LG is B18 cm À 1 , broader than the B12 cm À 1 intrinsic in pristine SLG 30,31 . Closer inspection shows that the G band consists of two sub-bands, which we call G À and G þ , using a similar terminology to that used in strained graphene 32 . However, the G peak of t(1 þ 3)LG measured at 1.58 eV has a single Lorentzian lineshape, with identical width and position to the G À peak of t(1+3)LG measured at 1.9 eV.…”

“…As the EPC of C 41 in 4LG is B15 times larger than the other Raman-active C 43 mode at 17 cm À 1 , the other C modes are challenging to detect 18 . The observation of different resonant profiles for C 31 and C 32 indicates that, in addition to differences in the EPC strength, the EPC is also anisotropic in the k space, thus removing the contribution from some optically allowed transitions to the resonant Raman process of some vibration modes. This results in the significant difference between the resonant profiles of C 31 and C 32 , although their phonon energy is smaller than 5 meV.…”

Electronic properties of embedded graphene: doped amorphous silicon/CVD graphene heterostructures

“…Moreover, for the (p)-aSi:H/Gr heterostructure, the 2D/G ratio decreases. This trend could result from mechanical strain induced by the boron or phosphorus doped a-Si:H layers [40,41], or from field effect doping from the charges at the interface.…”

Nanoscale Strainability of Graphene by Laser Shock-Induced Three-Dimensional Shaping

“…It is a sign of splitting of G peak, which is also a strain effect. 21 The Raman spectrum of fractured graphene film is plotted in Figure 4d, in which the graphene film is deformed into 250 nm wide and 60 nm deep circular mold (aspect ratio = 0.24). No obvious downshifts of G peak and 2D peak are observed.…”