Contact Effect of ReS₂/Metal Interface

Rhenium disulfide (ReS₂) has attracted immense interest as a promising two-dimensional material for optoelectronic devices owing to its outstanding photonic response based on its energy band gap's insensitivity to the layer thickness. Here, we theoretically calculated the electrical band structure of mono-, bi-, and trilayer ReS₂ and experimentally found the work function to be 4.8 eV, which was shown to be independent of the layer thickness. We also evaluated the contact resistance of a ReS₂ field-effect transistor using a Y-function method with various metal electrodes, including graphene. The ReS₂ channel is a strong n-type semiconductor, thus a lower work function than that of metals tends to lead to a lower contact resistance. Moreover, the graphene electrodes, which were not chemically or physically bonded to ReS₂, showed the lowest contact resistance, regardless of the work function, suggesting a significant Fermi-level pinning effect at the ReS₂/metal interface. In addition, an asymmetric Schottky diode device was demonstrated using Ti or graphene for ohmic contacts and Pt or Pd for Schottky contacts. The ReS₂-based transistor used in this study on the work function of ReS₂ achieved the possibility of designing the next-generation nanologic devices.