Effects of Crystal Defects on the Electronic and Magnetic Properties of Bulk and 2D Monolayer MoS2: A Density Functional Theoretical study

A Theoretical study of the electronic and magnetic properties of monolayer and bulk MoS2 was conducted based on first-principle Density Functional Theoretical methods (DFT), as implemented in Burai version 1.3 and Quantum Espresso version 7.1. Density of states (DOS) and projected density of state (PDOS) calculations reveal an indirect band gap of 1.003 eV for bulk MoS2 but a direct band gap of 1.750 eV for the monolayer. Point defect formation energies are calculated in the range of 1.29 to 27.12 eV where that for sulfur (S) vacancy in Molybdenum (Mo)-rich state and S interstitial in S-rich state are most favorable among native defects. Substitutional defects, including native defect and also that resulting from the incorporation of vanadium, are most stable when a Mo is replaced with V under Mo-rich conditions. Such changes in the lattice composition result in changes in the magnetic properties of both the bulk and monolayer MoS2; that is, the incorporation of certain defects can lead to a “switching on”/ “switchable” magnetic behaviour which can be modulated by defect concentration.