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

The contact resistance formed between MoS and metal electrodes plays a key role in MoS-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 MoS-metal interfaces. Here, we investigate the FLP effect and the contact types of monolayer and multilayer MoS-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 MoS-metal close interfaces, the FLP effect can be significantly reduced in monolayer MoS-metal vdW interfaces. Furthermore, as the layer number of MoS increases from 1L to 4L, the FLP effect is first weakened and then increased, which can be attributed to the charge redistribution at the MoS-metal and MoS-MoS interfaces. In addition, the p-type Schottky contact can be achieved in 1L-4L MoS-Pt, 3L MoS-Au, and 2L-3L MoS-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 MoS-metal vdW interfaces by selecting the layer number of MoS.