First-Principles Calculations of Electronic Properties of Defective Armchair MoS2 Nanoribbons

We investigated the electronic properties of armchair MoS2 nanoribbons with vacancy defects using a first-principles method based on density functional theory. It was found that defects reduced the stability of armchair MoS2 nanoribbons. Mo vacancies and MoS2 triple vacancies can both change the band structures of nanoribbons from semiconductor to metallic, whereas S vacancies, 2S divacancies, and MoS divacancies only decrease the bandgap. The densities of states and eigenstates of the nanoribbons indicated that impurity bands near the Fermi level basically contributed to the defect states. The relationships between the bandgap and width of four types of semiconducting nanoribbons were simulated. Nanoribbons with no defects have a bandgap that oscillates with width in a period of three, but the bandgap changes nonperiodically for nanoribbons with S vacancies, 2S divacancies, and MoS divacancies. We also found that when the concentration of defects decreased, the vacancy defects did not destroy the nanoribbon semiconducting behavior but only decreased the bandgap. These results open up possibilities for MoS2 nanoribbon applications in novel nanoelectronic devices.