Figure 3.

a) The Raman spectra of the 2H phase (black) and the 1T′ phase (red) of MoTe₂. The Raman spectra of from mono‐ to few‐layers of the TMDs in the 1T′ (or Td) phase. Reproduced with permission.105 Copyright 2015, American Association for the Advancement of Science. b) WTe₂. Reproduced with permission.99 Copyright 2016, the authors, published under CC‐BY‐4.0 license. c) ReS_2. Reproduced with permission.108 Copyright 2016, American Chemical Society. d) ReSe₂. e) Scatter plot of the vibrational frequencies of the ReSe₂ unit cell at the Γ point. d,e) Reproduced with permission.97 Copyright 2014, the authors, published under CC‐BY‐4.0 license. f) Optical absorption spectra of monolayer ReS₂ and ReSe₂ for the incident light polarized along the Γ‐K₂ direction and the Γ‐M₃ direction. g) Polarization‐dependent oscillator strength of excitons in monolayer ReS₂, the exciton E_Γ, the exciton E_Λ and their combined oscillator strength in monolayer ReSe₂ with a 50 meV smearing to mimic the absorption spectrum. Reproduced with permission.65 Copyright 2015, American Physical Society.