First-principles investigation of charged dopants and dopant-vacancy defect complexes in monolayer MoS2

Substitutional doping of two-dimensional semiconducting transition metal dichalcogenides such as $\mathrm{Mo}{\mathrm{S}}_{2}$ offers a stable and promising route for tailoring their electrical, optical, and magnetic properties. We perform density functional theory calculations for two promising transition metal dopants, Re and Nb, and their defect complexes with intrinsic S vacancies in $\mathrm{Mo}{\mathrm{S}}_{2}$. We compute the formation energy of each dopant and complex in different charge states utilizing a charge correction scheme that enables us to accurately predict the charge transition levels and complex binding energies, as well as characterize their electronic properties. We predict remarkably different behavior between Re and Nb dopants and their defect complexes: Re dopants can form complexes with S vacancies which quench the $n$-type doping of ${\mathrm{Re}}_{\mathrm{Mo}}$, while Nb dopants are unlikely to form such complexes and their $p$-type doping properties appear to be less sensitive to the presence of S vacancies.