Charge transfer between the epitaxial monolayer WSe2 films and graphene substrates

Abstract

Monolayer WSe2 with a direct bandgap shows great application potential in photon–electronic devices. Using in situ angle-resolved photoemission spectroscopy, we investigate the interfacial charge transfer between the grown WSe2 films and the graphene with different numbers of layers. For the WSe2 grown on the monolayer graphene (MLG) substrate, its band structure shifts downward by ∼140 meV compared to that grown on the bilayer graphene (BLG) substrate and by ∼230 meV compared to that grown on trilayer graphene (TLG), revealing that the MLG substrate transfers more electrons to the grown WSe2 than what the BLG and TLG do. Our results provide significant information for understanding the charge transfer behaviors and energy-level alignments in the two-dimensional (2D) stacking-heterostructures as well as the designation of future nano-devices based on 2D materials.