Unraveling the Role of Interfacial Interactions in Electrical Contacts of Atomically Thin Transition-Metal Dichalcogenides

Van der Waals (vdW) contact has been widely regarded as one of the most potential strategies for exploiting low-resistance metal-semiconductor junctions (MSJs) based on atomically thin transition-metal dichalcogenides (TMDs), but this method is still not efficient due to weak metal-TMD interfacial interactions. Therefore, an understanding of interfacial interactions between metals and TMDs is essential for achieving low-resistance contacts with weak Fermi level pinning (FLP). Herein, we report how the interfacial interactions between metals and TMDs affect the electrical contacts by considering more than 90 MSJs consisting of a semiconducting TMD channel and different types of metal electrodes, including bulk metals, MXenes, and metallic TMDs. We reveal that the vdW contact scheme cannot ensure the formation of low-resistance metal-TMD contacts. The interfacial coupling between metals and TMDs leads to a delicate competition between the FLP and carrier tunneling efficiency, which explains the broad experimental observations in which the weakly coupled van der Waals contacts usually show high contact resistance, while the strongly coupled metal-TMD contacts suffer from strong FLP. Benefiting from the low Schottky barrier and weak FLP, bulk Ag is a promising electrode for n-type MoS2 devices with a contact resistance of 83 Omega mu m at a carrier concentration of 5.95 x 1013 cm-2, and 1T '-phase MoS2 and Sc2NO2 are identified as superior contact electrodes for p-type WSe2 devices. This work offers a general rule to exploit high-performance MSJs and clarifies the key role of interfacial coupling in the electrical contacts of TMD-based devices.