Emission Excitation Spectroscopy in WS2 Monolayer Encapsulated in Hexagonal BN

Resonant conditions of the Raman scattering in monolayer WS2encapsulated in hexagonal BN are investigatedusing the Raman scattering excitation technique at low temperature (T= 5K). The resonance of the detectedsignal with the neutral exciton leads to an extremely rich Raman scattering excitation spectrum, which displaysalso the Raman scattering features not reported so far. Moreover, the intensities of the observed phonon modes arestrongly enhanced when the energy difference between the excitation laser and the neutral exciton emission (X0)is equal to the corresponding phonon energy. The intensity profile of the out-of-plane A′1phonon mode reflectsthe Lorentzian lineshape of the X0line with the linewidth of about 4 meV, which underlines the outgoing resonanceconditions with the X0complex.