title: The unusual mechanism of partial Fermi level pinning at metal-MoS2 interfaces.
abstract: Density functional theory calculations are performed to unravel the nature of the contact between metal electrodes and monolayer MoS2. Schottky barriers are shown to be present for a variety of metals with the work functions spanning over 4.2-6.1 eV. Except for the p-type Schottky contact with platinum, the Fermi levels in all of the studied metal-MoS2 complexes are situated above the midgap of MoS2. The mechanism of the Fermi level pinning at metal-MoS2 contact is shown to be unique for metal-2D-semiconductor interfaces, remarkably different from the well-known Bardeen pinning effect, metal-induced gap states, and defect/disorder induced gap states, which are applicable to traditional metal-semiconductor junctions. At metal-MoS2 interfaces, the Fermi level is partially pinned as a result of two interface behaviors: first by a metal work function modification by interface dipole formation due to the charge redistribution, and second by the production of gap states mainly of Mo d-orbitals character by the weakened intralayer S-Mo bonding due to the interface metal-S interaction. This finding would provide guidance to develop approaches to form Ohmic contact to MoS2.
authors.affiliation: Department of Materials Science and Engineering, The University of Texas at Dallas , Richardson, Texas 75080, United States.
authors.forename: Cheng
authors.initials: C
authors.lastname: Gong
authors.forename: Luigi
authors.initials: L
authors.lastname: Colombo
authors.forename: Robert M
authors.initials: RM
authors.lastname: Wallace
authors.forename: Kyeongjae
authors.initials: K
authors.lastname: Cho