Electron dynamics in MoS2-graphite heterostructures.

The electron dynamics in heterostructures formed by multilayer graphite and monolayer or bulk MoS2 were studied by femtosecond transient absorption measurements. Samples of monolayer MoS2-multilayer graphite and bulk MoS2-multilayer graphite were fabricated by exfoliation and dry transfer techniques. Ultrafast laser pulses were used to inject electron-hole pairs into monolayer or bulk MoS2. The transfer of these photocarriers to the adjacent multilayer graphite was time resolved by measuring the differential reflection of a probe pulse. We found that photocarriers injected into monolayer MoS2 transfer to graphite on an ultrafast time scale shorter than 400 fs. Such an efficient charge transfer is key to the development of high performance optoelectronic devices with MoS2 as the light absorbing layer and graphite as electrodes. The absorption coefficient of monolayer MoS2 can be controlled by the carriers in graphite. This process can be used for interlayer coupling and control. In a bulk MoS2-graphite heterostructure, the photocarrier transfer time is about 220 ps, due to the inefficient interlayer charge transport in bulk MoS2. These results provide useful information for developing optoelectronic devices based on MoS2-graphite heterostructures.