Electron dynamics in MoS ₂ -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.