Interlayer charge transfer in supported and suspended MoS.sub.2/Graphene/MoS.sub.2 vertical heterostructures

In this letter, we report on the optical and structural properties of supported and suspended MoS.sub.2 /Graphene/MoS.sub.2 vertical heterostructures using Raman and photoluminescence (PL) spectroscopies. Vertical heterostructures (VH) are formed by multiple wet transfers on micro-sized holes in SiO.sub.2 /Si substrates, resulting in VH with different configurations. The strong interlayer coupling is confirmed by Raman spectroscopy. Additionally, we observe an enhancement of the PL emission in the three-layer VH (either support or suspended) compared with bare MoS.sub.2 or MoS.sub.2 /Graphene. This suggests the formation of a spatial type-II band alignment assisted by the graphene layer and thus, the operation of the VH as a n++/metal/n junction.