Band edge identification and carrier dynamics of CVD MoS2 monolayer measured by broadband Femtosecond Transient Absorption Spectroscopy

Carrier dynamics in monolayer MoS2 have been investigated using broadband femtosecond transient absorption spectroscopy (FTAS). A tunable pump pulse was used while a broadband probe pulse revealed ground and excited state carrier dynamics. Interestingly, for pump wavelengths both resonant and non-resonant with the A and B excitons, we observe a ground state bleach around 2.9 eV, with decay components similar to A and B. We associate this bleach with the quasi-particle direct gap. Comparison of mono-, few-, and multi-layer regions is consistent with this identification, indicating a binding energy for the exciton states of ~1 eV.