Electrically Tunable and Negative Schottky Barriers in Multi-layered Graphene/MoS(2) Heterostructured Transistors

We fabricated multi-layered graphene/MoS(2) heterostructured devices by positioning mechanically exfoliated bulk graphite and single-crystalline 2H-MoS(2) onto Au metal pads on a SiO(2)/Si substrate via a contamination-free dry transfer technique. We also studied the electrical transport properties of Au/MoS(2) junction devices for systematic comparison. A previous work has demonstrated the existence of a positive Schottky barrier height (SBH) in the metal/MoS(2) system. However, analysis of the SBH indicates that the contacts of the multi-layered graphene/MoS(2) have tunable negative barriers in the range of 300 to −46 meV as a function of gate voltage. It is hypothesized that this tunable SBH is responsible for the modulation of the work function of the thick graphene in these devices. Despite the large number of graphene layers, it is possible to form ohmic contacts, which will provide new opportunities for the engineering of highly efficient contacts in flexible electronics and photonics.