Bilayer MoS2 nanoribbons: observation of an optically inactive “exciton-free” regions and electrical gating of optical response

Due to large anisotropy and tuneable exciton transitions observed in visible light, transitional metal dichalcogenides could become platform materials for on-chip next-generation photonics and nano-optics. For this to happen, one needs to be able to nanostructure transitional metal dichalcogenides without losing their optical properties. However, both our understanding of the physics of such nanostructures and their technology are still at infancy and, therefore, experimental works on optics of transitional metal dichalcogenides nanostructures are urgently required. Here, we study optical characteristics of bilayer MoS2 nanoribbons by measuring reflection and photoluminescence of nanostructured bilayer MoS2 flakes near exciton transitions. We show that there exist optically inactive “exciton-free” regions near the edges of nanoribbons with sizes of around 10 nm. We demonstrate that the “exciton-free” regions can be controlled by external electrical gating. These results are important for nanostructured optoelectronic devices made of MoS2 and other transitional metal dichalcogenides.