  In this study,we combined time-resolved terahertz spectroscopy along with
transient absorption spectroscopy to revisit the interlayer non-equilibrium
carrier dynamics in largely lateral size Gr/MoS2 heterostructure fabricated
with chemical vapor deposition method. Our experimental results reveal that,
with photon-energy below the A-exciton of MoS2 monolayer, hot electrons
transfer from graphene to MoS2 takes place in time scale of less than 0.5 ps,
resulting in ultrafast formation of interfacial exciton in the heterostructure,
subsequently, recombination relaxation of the interfacial exciton occurs in
time scale of ~18 ps. A new model considering carrier heating and photogating
effect in graphene is proposed to estimate the amount of carrier transfer in
the heterostructure, which shows a good agreement with experimental result.
Moreover, when the photon-energy is on-resonance with the A-exciton of MoS2,
photogenerated holes in MoS2 are transferred to graphene layer within 0.5 ps,
leading to the formation of interfacial exciton, the subsequent
photoconductivity (PC) relaxation of graphene and bleaching recovery of
A-exciton in MoS2 take place around ~10 ps time scale, ascribing to the
interfacial exciton recombination. The faster recombination time of interfacial
exciton with on-resonance excitation could come from the reduced interface
barrier caused by bandgap renormalization effect. Our study provides deep
insight into the understanding of interfacial charge transfer as well as the
relaxation dynamics in graphene-based heterostructures, which are promising for
the applications of graphene-based optoelectronic devices.
