Illustrating the pertinacious interlayer charge compression effect in van der Waals heterointerfaces

Heterojunctions of two-dimensional (2D) van der Waals (vdW) nanomaterials often exhibit unusual, “non-textbook” bonding mechanism that involves distinct orbital coupling within the compressed vdW gap. To unravel this atypical bonding mechanism for 2D heterointerfaces, using density-functional theory calculations, we examine the compressed charge redistribution and interface dipoles for the heterostructures of ReSe2/graphene, ReSe2/h-BN, and a triply-stacked ReSe2/h-BN/graphene heterointerface. Here, we report the optimized atomic structures, electronic density-of-states, (integrated) planar-averaged electron density differences, and tip-inclusive scanning tunneling microscopy simulations for these heterostructures, while focusing on the explicit contributions of the conductive graphene and insulating h-BN substrates to the interlayer confined charges and dipoles. Using other 2D heterosystems, we also demonstrate that this charge compression effect within the vdW gap is ubiquitous and general regardless of the nature of the substrates and supports. Upon applying an external electric field, we clearly demonstrate a tunable control (in both magnitude and sign of these interface dipoles) in 2D vdW heterostructures and advance the precise engineering of pertinacious interlayer compressed charges/interface dipoles for the next-generation ambipolar field-effect (nano)transistor (FET) applications.