Role of defects in enhanced Fermi level pinning at interfaces between metals and transition metal dichalcogenides

Density functional theory calculations are performed to explore the nature of the contact between metal electrodes and defected monolayer ${\mathrm{MoSe}}_{2}$. Partial Fermi level pinning is observed at perfect ${\mathrm{MoSe}}_{2}$/metal interfaces. Both As- and Br-substituted ${\mathrm{MoSe}}_{2}$ will induce extra bands in valence band and conduction band, respectively, which exerts influence on the Schottky barrier height. An enhanced partial Fermi level pinning occurs when As- and Br-substituted ${\mathrm{MoSe}}_{2}$ make contacts with metal electrodes. Se vacancy in the ${\mathrm{MoSe}}_{2}$ layer can induce a large amount of interfacial states in the band gap of the ${\mathrm{MoSe}}_{2}$ layer. As a result, nearly complete Fermi level pinning is observed in Se-vacancy ${\mathrm{MoSe}}_{2}$/metal contacts. Our work offers insight into the Fermi level pinning at the interfaces between two-dimensional materials and metal electrodes, which is important for the applications of two-dimensional materials in nanoelectronic devices with good performance.