Abstract
Achieving a low contact resistance has been an important issue in the design of two-dimensional (2D) semiconductor-metal interfaces. The metal contact resistance is dominated by interfacial interactions. Here, we systematically investigate 2D semiconductor-metal interfaces formed by transferring monolayer MoS(2) onto prefabricated metal surfaces, such as Au and Pd, using X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and Raman spectroscopy. In contrast to the MoS(2)/HOPG interface, the interfaces of MoS(2)/Au and MoS(2)/Pd feature the formation of weak covalent bonds. The XPS spectra reveal distinct peak positions for S-Au and S-Pd, indicating a higher doping concentration at the S-Au interface. This difference is a key factor in understanding the electronic interactions at the metal-MoS(2) interfaces. Additionally, we observe that the metal surface roughness is a critical determinant of the adhesion behavior of transferred monolayer MoS(2), resulting in different strains and doping concentrations. The strain on transferred MoS(2) increases with an increase in substrate roughness. However, the strain is released when the roughness of metal surface surpasses a certain threshold. The dependence of the contact material and the influence of the substrate roughness on the contact interface provide critical information for improving 2D semiconductor-metal contacts and device performance.