TiS₃ sheet based van der Waals heterostructures with a tunable Schottky barrier

Monolayer titanium trisulfide (TiS₃), synthesized recently through exfoliation [Adv. Mater., 2015, 27, 2595], has emerged as a new 2D material with outstanding electronic and optical properties. Here, using first-principles calculations we show for the first time the great potential of the TiS₃ monolayer as a channel material when in contact with graphene and other 2D metallic materials to form van der Waals (vdW) heterostructures, where the intrinsic properties of both the TiS₃ monolayer and the 2D materials are preserved, different from the conventional 3D metal/TiS₃ semiconductor heterojunction [Nanoscale, 2017, 9, 2068]. Moreover, the TiS₃ monolayer forms an n-type Schottky barrier (Φ_e) when in contact with graphene, exhibiting a tunneling barrier and a negative band bending at the lateral interface; the Schottky barrier character can also be changed from n-type to p-type by doping graphene with boron atoms or replacing graphene with other high-work-function 2D metals, while a Schottky-barrier-free contact can be realized by doping graphene with nitrogen atoms, thus providing a solution to the contact-resistance problem in 2D electronics.