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

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Elemental doping is vital for tuning the electronic and optical properties of 2D semiconductors.
• Existing doping methods like ion implantation and chemical vapor deposition yield variable results based on the chemical environment.

Purpose of the Study:

• To systematically investigate elemental doping in monolayer molybdenum disulfide (MoS2).
• To identify stable doping sites, formation energies, and charge transition levels for 27 elements.
• To understand the impact of doping on electronic states and carrier conduction mechanisms.

Main Methods:

• Density-functional theory (DFT) calculations were employed for systematic analysis.
• Koopmans-compliant hybrid functionals were utilized to accurately predict electronic states.
• Formation energies and charge transition levels were computed for various doping configurations.

Main Results:

• Thermally stable sites for 27 elemental dopants were identified, including atomic substitutions, surface adsorption, and lattice interstitials.
• Hydrogenic states predicted by semilocal functionals transformed into localized polaronic states using hybrid functionals.
• These polaronic states consistently exhibited deep transitions approximately 1.0 eV from the band edges.

Conclusions:

• The study provides fundamental insights into elemental doping of MoS2.
• Polaronic behavior and impurity conduction are identified as dominant mechanisms in doped MoS2, persisting even in bulk form.
• These findings are crucial for advancing the doping strategies in transition metal dichalcogenides and other 2D semiconductors.