Atomically thin, single-crystalline 2D electronic materials have recently emerged, offering a remarkably wide range of building blocks of nanostructures, ranging from metals (e.g. graphene), large gap insulators (BN), to semiconductors (transition metal dichalcogenides and black phosphorous). One key advantage of these van der Waals materials lies in the flexibility of stacking different types of materials to form heterostructures, providing a design platform for achieving novel device functionality. In vdW hetero-bilayers, the interface encompasses the whole heterostructure, and interlayer interactions become the controlling parameter for the electronic structure.
In this talk, I will first discuss probing the inter-layer interactions using scanning tunneling microscopy and spectroscopy (STM/S). I will first revisit the issue of how to accurately probe the quasi-particle band structure and corroborate with the newly available k-resolved data using time-resolved angle-resolved photoemission. I will then briefly touch upon our earlier effort in probing the electronic structure of moiré superlattice formed in MoS2/WSe2 vdW heterobilayer.
I will then switch gear to show a new approach to tailor the lateral energy profile of a monolayer transition metal dichalcogenide (TMD) without using heterobilayers. This new approach harnesses a close proximity effect of a 2D monolayer to an hBN substrate with a nanoscale engineered electrostatic field and Coulomb screening by tuning the interface between the hBN monolayer and the supporting transition metal. Using this new approach, one can create a lateral p-n heterojunction with a built-in potential of 1eV within 6 nm, and a change of bandgap by 0.35 eV, all on the same TMD monolayer.