2024/04/26 by Lukas Rieland, Julian Wagner, Rieland, Lukas +19
Engineering · Materials Science · #2D Materials and Applications #Chalcogenide Semiconductor Thin Films #FOS: Physical sciences #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Organic and Molecular Conductors Research
paper · pdf · doi:10.48550/arxiv.2404.17416
openalex publication_date 2024/04/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Using heterodyne transient grating spectroscopy, we observe a significant enhancement of exciton diffusion within a monolayer WSe2 stacked on top of graphene. We further demonstrate that the diffusion dynamics can be optically tuned on the ultrafast time scale (i.e. a few picoseconds) by altering the photoexcited charge carrier density in graphene. The results reveal that, on a time scale of a few picoseconds, the effective diffusion constant in the WSe2/graphene heterostructure is approximately 40 cm2 /s, representing a substantial improvement over the 2 cm2 /s typical for an isolated monolayer of WSe2. The enhanced diffusion can be understood in terms of a transient screening of impurities, charge traps, and defect states in WSe2 by photoexcited charge carriers in graphene. Furthermore, we observe that the diffusion within WSe2 is affected by interlayer interactions, like charge transfer, exhibiting different dynamic states depending on the incident excitation fluence. These findings underscore the dynamic nature of screening and diffusion processes in heterostructures of 2D semiconductors and graphene and provide valuable insights for future applications of these systems in ultrafast optoelectronic devices.