Duan Luo

SLAC National Accelerator Laboratory

ABSTRACT  

Vertically stacked transition metal dichalcogenides-graphene heterostructures provide a platform for novel optoelectronic applications with high photoresponse speed. Photoinduced non-equilibrium carrier and lattice dynamics in such heterostructures underlie these applications but have not been understood. In particular, the dependence of these photoresponses on the twist angle, a key tuning parameter, remains elusive. Here, using ultrafast electron diffraction, we report the simultaneous visualization of charge transfer and electron-phonon coupling in MoS2-graphene heterostructures with different stacking configurations. We find that the charge transfer time-scale from MoS2 to graphene varies strongly with twist angle, becoming faster for smaller twist angles, and show that the relaxation time-scale is significantly shorter in a heterostructure as compared to monolayer. These findings illustrate that twist angle constitutes an additional tuning knob for interlayer charge transfer in heterobilayers and deepen our understanding of fundamental photophysical processes in heterostructures, of importance for future applications in optoelectronics and light harvesting.

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Email: dluo@slac.stanford.edu