Investigation of Interface Interactions Between Monolayer MoS₂and Metals: Implications on Strain and Surface Roughness

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.