Second harmonic generation spectroscopy of MoS₂/WSe₂ heterostructure

Recently, heterostructures of transition metal dichalcogenides (TMDs) have attracted much interest owing to their unique physical properties. One of the most interesting characteristics is the large exciton energy of TMDs. As the electronic band structures of TMD materials are highly dependent on the number of layers, the interlayer interaction between constituent layers in the heterostructure also affects the band structure [1]. Therefore, understanding the changes of exciton states is important to revealing the band structure of the TMD heterostructure. We fabricated MoS₂/WSe₂ heterostructures by the stamping methods using exfoliated monolayer MoS₂ and WSe₂. The PL and Raman measurements were carried out to determine the quality of interface in the heterostructures. Finally, using the second harmonic generation spectroscopy, which is a useful experimental method to measure the exciton states in TMD materials [2], we observed a shift of the exciton energy in the heterostructure compare to those in individual constituent layers.

[1] M. M. Ugeda et al., Nat. Mater. 13, 1091 (2014).
[2] G. Wang et al, Phys. Rev. Lett. 114, 097403 (2015).