Two-Dimensional MoS₂ Field-Effect-Transistors with Graphene and Titanium Source-Drain Contacts

Based on the first principles calculation, we investigate the electronic band structures of graphene-MoS₂ and Ti-MoS₂ heterojunctions under gate-voltages [1]. By simultaneous control of external electric fields and carrier charging concentrations, we show that the graphene’s Dirac point position inside the MoS₂ bandgap is easily modulated with respect to the co-varying Fermi level, while keeping the graphene’s linear band structure around the Dirac point. The easy modulation of graphene bands is not confined to the special cases where the conduction-band-minimum point of MoS₂ and the Dirac point of graphene are matched up in reciprocal space, but is generalized to their dislocated cases. This flexibility caused by the strong decoupling between graphene and MoS₂ bands enhances the gate-controlled switching performance in MoS₂-graphene hybrid stacking-device. [1] S. S. Baik et al, Scientific Reports. 7, 45546 (2017).