Synthesis and Characterization of MoS2/WS2 Heterostructures by Second Harmonic Generation

Monolayers of MoS
₂
and WS
₂
, as well as their vertical heterostructures, were synthesized via chemical vapor deposition. The samples were then characterized via microRaman and micro-photoluminescence spectroscopies, and by second harmonic generation (SHG). SHG confirms that the layers in bilayers and heterostructures grow with ~0
^o
(or ~60
^o
) relative twist angle. Interestingly, SHG is observed in MoS
₂
bilayers, indicating a deviation from the centrosymmetric 2H phase.