Optical signatures of states bound to vacancy defects in monolayer MoS${}_2$

Abstract

We show that pristine MoS${}_2$ single layer (SL) exhibits two bandgaps $E_{g\parallel }=1.9$ eV and $E_{g\perp }=3.2$ eV for the optical in-plane and out-of-plane susceptibilities ${\chi }_{\parallel }$ and ${\chi }_{\perp }$, respectively. In particular, we show that odd states bound to vacancy defects (VDs) lead to resonances in ${\chi }_{\perp }$ inside $E_{g\perp }$ in MoS${}_2$ SL with VDs. We use density functional theory, the tight-binding model, and the Dirac equation to study MoS${}_2$ SL with three types of VDs: (i) Mo-vacancy, (ii) S${}_2$-vacancy, and (iii) 3$\times$MoS${}_2$ quantum antidot. The resulting optical spectra identify and characterize the VDs.

5 pages, 5 figures