Junction-configuration-dependent interfacial electronic states of a monolayer MoS₂/metal contact

Electrical contacts are crucial to the high performances of electronic devices, and they become more prominent for the popular two-dimensional (2D) semiconductors because they commonly have high contact resistances and are sensitive to the interfacial states. In this paper, taking monolayer MoS₂ as an example, first-principles calculations are done to study and predict the influences of the contact mode on the interfacial electronic states of monolayer MoS₂/metal (metal = Mg, Al, In, Cu, Ag, Au, Pd, Sc, and Ti). It is found that the interfacial properties are determined by the matching degree between the electronic states of the monolayer MoS₂ and metal electrodes. The top contact configuration is preferred for the monolayer MoS₂/Sc system as a result of an extremely low Schottky barrier (0.086 eV) as compared to that (0.439 eV) in the edge contact configuration, however, the edge contact configuration is preferred for Ag, Cu, Au, and Pd electrodes. Furthermore, metal electrodes in the top contact configuration might usually result in n-type doping of monolayer MoS₂, but lead to p-type doping in the edge contact configuration. The pinning factor S (0.257, −0.009, −0.132, and −0.172) of monolayer MoS₂ in both contact modes is close to zero, suggesting a strong electronic pinning effect. The findings provide theoretical guidance for the selection of electrodes for high-performance 2D material based devices.