Interlayer charge transfer in ReS 2 / WS 2 van der Waals heterostructures

Abstract

We observed ultrafast charge transfer between distorted 1T−ReS2 with anisotropic in-plane electronic and optical properties and 2H−WS2 that is in-plane isotropic. Heterostructures of monolayer ReS2/monolayer WS2 and bilayer ReS2/monolayer WS2 were fabricated by mechanical exfoliation and dry transfer techniques. Significant photoluminescence quenching of WS2 in the heterostructures indicates efficient charge transfer. In femtosecond transient absorption measurements, it was found that holes injected in monolayer or bilayer ReS2 transfer to WS2 on a timescale that is shorter than the time resolution of the measurement. This observation provides evidence that the holes are delocalized in bilayer ReS2, revealing strong van der Waals interlayer couplings. These results also show that ReS2 and WS2 form type-II heterostructures with excellent charge transfer properties.