The Contact Properties of Monolayer and Multilayer MoS₂-Metal van der Waals Interfaces

The contact resistance formed between MoS₂ and metal electrodes plays a key role in MoS₂-based electronic devices. The Schottky barrier height (SBH) is a crucial parameter for determining the contact resistance. However, the SBH is difficult to modulate because of the strong Fermi-level pinning (FLP) at MoS₂-metal interfaces. Here, we investigate the FLP effect and the contact types of monolayer and multilayer MoS₂-metal van der Waals (vdW) interfaces using density functional theory (DFT) calculations based on Perdew-Burke-Ernzerhof (PBE) level. It has been demonstrated that, compared with monolayer MoS₂-metal close interfaces, the FLP effect can be significantly reduced in monolayer MoS₂-metal vdW interfaces. Furthermore, as the layer number of MoS₂ increases from 1L to 4L, the FLP effect is first weakened and then increased, which can be attributed to the charge redistribution at the MoS₂-metal and MoS₂-MoS₂ interfaces. In addition, the p-type Schottky contact can be achieved in 1L-4L MoS₂-Pt, 3L MoS₂-Au, and 2L-3L MoS₂-Pd vdW interfaces, which is useful for realizing complementary metal oxide semiconductor (CMOS) logic circuits. These findings indicated that the FLP and contact types can be effectively modulated at MoS₂-metal vdW interfaces by selecting the layer number of MoS₂.