Figure 4
From: Raman fingerprint for semi-metal WTe2 evolving from bulk to monolayer

Raman evolution.
(a) Raman spectra of bulk and few-layer WTe2. (b) Calculated phonon dispersion curve along the Γ-Y-X-Γ direction in the orthorhombic BZ and DOS for the WTe2 monolayer. Blue and green curves are optical and acoustic vibrational branches, respectively. (c) Calculated Raman spectrum for the WTe2 monolayer. (d) Frequencies of the
,
,
and
modes as functions of the layer number.