Theoretical Insights to Niobium-Doped Monolayer MoS2–Gold Contact

We report a first principles study of the electronic properties for a contact formed between Nb-doped monolayer MoS ₂ and gold for different doping concentrations. We first focus on the shift of energy levels in band structure and the density of states with respect to the Fermi level for a geometrically optimized 5 × 5 MoS ₂ supercell for both pristine and Nb-doped structures. The doping is achieved by substituting Mo atoms with Nb atoms at random positions. It is observed that for an experimentally reported sheet hole doping concentration of (ρ _2D ) 1.8 × 10 ¹⁴ cm ^-2 , the pristine MoS ₂ converts to degenerate p-type semiconductor. Next, we interface this supercell with six layers of (111) cleaved surface of gold to investigate the contact nature of MoS ₂ -Au system. By careful examination of projected band structure, projected density of states, effective potential and charge density difference, we demonstrate that the Schottky barrier nature observed for pure MoS ₂ -Au contact can be converted from n-type to p-type by efficient Nb doping.