Identification of individual and few layers of WS2 using Raman Spectroscopy

The Raman scattering of single- and few-layered WS2 is studied as a function of the number of S-W-S layers and the excitation wavelength in the visible range (488, 514 and 647 nm). For the three excitation wavelengths used in this study, the frequency of the A1g(Γ) phonon mode monotonically decreases with the number of layers. For single-layer WS2, the 514.5 nm laser excitation generates a second-order Raman resonance involving the longitudinal acoustic mode (LA(M)). This resonance results from a coupling between the electronic band structure and lattice vibrations. First-principles calculations were used to determine the electronic and phonon band structures of single-layer and bulk WS2. The reduced intensity…

• MU
  Multidisciplinary University Research Initiative
• DO
  Division of Materials Research
• AR
  Army Research Office

  Awards: W911NF-11-1-0362, MURI grant W911NF-11-1-0362, W911NF, W911NF-11