Intense conductivity suppression by edge defects in zigzag MoS2 and WSe2 nanoribbons: a density functional based tight-binding study.

The effects of edge vacancies on the electron transport properties of zigzag MoS2/WSe2 nanoribbons are studied using a density functional theory (DFT)-based tight-binding model with a sp(3)d(5) basis set for the electronic structure calculation and applying the Landauer-Büttiker approach for the electronic transport. Our results show that the presence of a single edge vacancy, with a missing MoS2/WSe2 triplet, is enough to suppress the conductance of the system by almost one half for most energies around the Fermi level. Furthermore, the presence of other single defects along the same edge has little effect on the overall conductance, indicating that the conductance of that particular edge has been strongly suppressed by the first defect. The presence of another defect on the opposite edge further suppresses the quantum conductance, independently of the relative position between the two defects in opposite edges. The introduction of other defects cause the suppression to be energy dependent, leading to conductance peaks which depend on the geometry of the edges. The strong conductance dependence on the presence of edge defects is corroborated by DFT calculations using SIESTA, which show that the electronic bands near the Fermi energy are strongly localized at the edge.