Controlling Schottky Barriers and Tunneling Resistances in Metal/Cu₂Se Contacts via van der Waals Interlayers

Electrode contact properties with two-dimensional (2D) channel materials decisively determine the nanodevice's overall performance. A recently synthesized semiconducting Cu₂Se monolayer has emerged as a promising candidate for high-performance device channels due to its high carrier mobility, excellent environmental stability, and a reversible thermal-driven phase transition accompanied by a direct-to-indirect band-gap variation. Herein, to identify promising high-quality electrodes for Cu₂Se, the contact properties with various metals (Al, Ag, Au, Ni, and Co), as well as the modulation effects of graphene and h-BN interlayers, are systematically investigated based on first-principles calculations. The results demonstrate Ohmic contact formation between Cu₂Se and all metals (Al, Ag, Au, Ni, and Co), with tunneling probabilities of 42.84%, 91.67%, 79.89%, 66.89%, and 100%, respectively. Strong interfacial hybridization induces metal-induced gap states (MIGSs), rendering the contact type nontunable with metal work function variations. Intercalating van der Waals interlayers (graphene/h-BN) suppresses MIGSs and enables Schottky barrier tuning. Crucially, at ≥3 interlayers, both metals/Gra/Cu₂Se and metals/BN/Cu₂Se contacts become independent of the bulk metallic electrodes as interlayer work functions dominate the practical work functions of metals/Gra (BN). Concurrently, tunneling barriers increase with additional interlayers. This work provides theoretical insights into interface engineering strategies for the development of high-performance Cu₂Se-based nanodevices.