Each atomic layer in van der Waals heterostructures possesses a distinct electronic band structure that can be manipulated for unique device operations. In the precise device architecture, the subtle but critical band coupling between the atomic layers, varied by the momentum of electrons and external electric fields in device operation, has not yet been presented or applied to designing original devices with the full potential of van der Waals heterostructures. I will introduce interlayer coupling spectroscopy at the device-scale based on the negligible quantum capacitance of two-dimensional semiconductors in lattice-orientation-tuned, resonant tunneling transistors. The effective band structures of the mono-, bi-, and quadrilayer of MoS2 and WSe2, modulated by the orientation- and external electric field-dependent interlayer coupling in device operations, could be demonstrated by the new conceptual spectroscopy overcoming the limitations of the former optical, photoemission, and tunneling spectroscopy . Based on the vertical heterojunction, novel orbital-gating based phototransistors and self-selective memristors [2,3] could be developed.
 Adv. Mater. (2020)  Nat. Commun. (2019)  Sci. Adv. (2021)