Universal Polaronic Behavior in Elemental Doping of MoS2 from First-Principles

Elemental doping of two-dimensional (2D) semiconductors is crucial for manipulating their electrical and optical properties and enhancing the performance of advanced 2D devices. However, doping methods, such as ion implantation and chemical vapor deposition, can produce various outcomes extensively, depending on the chemical environment. We systematically study the elemental doping of the monolayer MoS2 by using density-functional theory calculations, which identify thermally stable sites among atomic substitutions, surface adsorption, and lattice interstitials of 27 elemental dopants, along with their formation energies and charge transition levels. By adopting the Koopmans-compliant hybrid functionals, the hydrogenic states predicted by semilocal functionals transform into localized polaronic states, which universally exhibit deep transitions located 1.0 eV away from the band edges. This polaronic behavior persists even in bulk MoS2, which suggests impurity conduction as the predominant carrier conduction mechanism. Our study offers fundamental insights into elemental doping in MoS2, which could be essential for doping transition metal dichalcogenides and similar 2D semiconductors.