Figure 1: Influence of graphene on the electronic bandgap of MoS2 monolayer.
From: Slow cooling and efficient extraction of C-exciton hot carriers in MoS2 monolayer
(a) Optical microscope and AFM images of MoS2 monolayer/graphene heterostructure. In the bottom, the scale bar is 2 μm. (b) Theoretically predicted energy band structure corresponding to the direct transitions in the momentum space of MoS2 monolayers considering the spin-orbit coupling. Eg, energy gap; Eb, exciton binding energy. The green area is the band nesting region. The vertical brown, pink and purple arrows in b represent the optical transitions of A/B/C-exciton, respectively. (c) Steady-state absorption spectra of graphene, MoS2 monolayer and MoS2 monolayer/graphene heterostructure. O.D., optical density. The orange solid line is the PL spectrum of MoS2 monolayer under 532 nm excitation. (d) STS spectra for MoS2 monolayer and MoS2 monolayer/graphene heterostructure. (e) Sketch of electronic and optical bandgaps for MoS2 monolayer (bottom figure). The top image illustrates the MoS2 monolayer (sky blue solid sphere represents the Mo atom, and yellow solid sphere represents the S atom); brown, pink and purple spheres represent the A/B/C-exciton, respectively; the orange curves represent the hot-carrier cooling and diffusion processes. (f) Sketch of electronic and optical bandgaps for MoS2 monolayer/graphene heterostructure (bottom figure). The top illustration schematizes the MoS2 monolayer/graphene heterostructure (black solid sphere represents the C atom); the red arrows indicate the vertical electron extraction processes. Eopt, optical bandgap.
