Tunable Schottky barriers and electronic properties in van der Waals heterostructures of semiconducting monolayer gold sulfides and graphene

Two-dimensional metal-semiconductor heterostructures with tunable Schottky barriers are currently attracting extensive interests, owing to their novel properties and potential applications in nanodevices. Here, heterostructures of semiconducting monolayer gold sulfides and graphene (Gr) with tunable Schottky barriers and contact types are reported based on first-principles calculations. α-, β-Au₂S/Gr are n-type Schottky contacts with Φ_n = 0.14 eV and 1.24 eV, respectively. They could be transformed into p-type Schottky contacts via applying vertically compressive strain. α-, β-, γ-AuS/Gr are ohmic, p-type and n-type Schottky contacts with Φ_n = -0.34 eV, Φ_p = 0.22 eV, Φ_n = 0.22 eV, respectively. The ohmic contact of α-AuS/Gr evolves to a n-type Schottky contact with increasing vertically compressive strain, while the p-type Schottky contact of β-AuS/Gr changes to an ohmic contact. Furthermore, the mechanism of Schottky-barrier modulation via vertical strain underlies that the relative Dirac-cone position of Gr in heterostructures can be tuned by adjusting interfacial charge rearrangement. Benefitting from the tunable Schottky barriers and contact types, heterostructures of semiconducting monolayer gold sulfides and Gr are promising candidates for future-generation nano-devices.