Low-Defect-Density Monolayer MoS₂ Wafer by Oxygen-Assisted Growth-Repair Strategy

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Atomic chalcogen vacancies are common defects in 2D transition-metal dichalcogenides, negatively impacting material properties and device performance.
• Developing methods to reduce these defects is crucial for advancing 2D material applications.

Purpose of the Study:

• To develop and demonstrate a wafer-scale epitaxial technology for producing low-defect density, high-uniformity 2D transition-metal dichalcogenides.
• To quantitatively evaluate the efficiency of an in situ oxygen-incorporated
• growth-repair
• strategy in reducing sulfur vacancies in molybdenum disulfide (MoS2) monolayers.

Main Methods:

• Utilized an in situ oxygen-incorporated
• growth-repair
• strategy for wafer-scale single crystal epitaxial growth of MoS2.
• Employed first-principle calculations to investigate the atomic-scale mechanisms of oxygen substitution and sulfur vacancy formation energy.
• Quantitatively evaluated oxygen-repairing efficiency using atomic-scale analysis and photoluminescence spectroscopy.

Main Results:

• Achieved a significant reduction in sulfur defect density in MoS2 monolayers, from (2.71 ± 0.65) × 10^13 cm^-2 to (4.28 ± 0.27) × 10^12 cm^-2.
• Demonstrated that oxygen substitution is kinetically favorable and increases sulfur vacancy formation energy, effectively suppressing defects.
• Observed elimination of sulfur vacancy-induced donor defect states, confirmed by quenched defect-related emission.
• Engineered MoS2 devices with over three times improved carrier mobility (up to 65.2 cm^2 V^-1 s^-1) and reduced Schottky barrier height (< 20 meV).

Conclusions:

• The oxygen-incorporated
• growth-repair
• strategy is highly effective in reducing intrinsic defect density in 2D materials.
• This method significantly suppresses Fermi-level pinning effects, leading to enhanced electronic device performance.
• Provides a viable route for engineering the quality and electronic properties of 2D materials for future applications.