First-principles Raman spectra of MoS2, WS2 and their heterostructures.

Raman spectra of MoS2, WS2, and their heterostructures are studied by density functional theory. We quantitatively reproduce existing experimental data and present evidence that the apparent discrepancy between intensity ratios observed experimentally can be explained by the high sensitivity of the Raman-active modes to laser polarization. Furthermore, MoS2/WS2 heterostructures up to four layers are considered in every possible combination and stacking order. Each heterostructure configuration possesses a unique Raman spectrum in both frequency and intensity that can be explained by changes in dielectric screening and interlayer interaction. The results establish a set of guidelines for the practical experimental identification of heterostructure configurations.