Spectroscopic Signatures for Interlayer Coupling in MoS2-WSe2 van der Waals Stacking
OSTP Journal Article
William Marsh Rice University Houston United States
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Stacking of MoS2 and WSe2 monolayers is conducted by transferring triangular MoS2 monolayers on top of WSe2 monolayers, all grown by chemical vapor deposition CVD. Raman spectroscopy and photoluminescence PL studies reveal that these mechanically stacked monolayers are not closely coupled, but after a thermal treatment at 300 deg C, it is possible to produce van der Waals solids consisting of two interacting transition metal dichalcogenide TMD monolayers. The layer-number sensitive Raman out-of-plane mode Aexpn 2 sub 1g for WSe2 309 cmexpn -1 is found sensitive to the coupling between two TMD monolayers. The presence of interlayer excitonic emissions and the changes in other intrinsic Raman modes such as E for MoS2 at 286 cmexpn -1 and Aexpn 2 sub 1g for MoS2 at around 463 cmexpn -1 confirm the enhancement of the interlayer coupling.