Microscopic Investigations of Point Defect Interactions in WS₂ Monolayers

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Atomic point defects are key to engineering 2D transition metal dichalcogenides (TMDs).
• Understanding defect electronic structure is vital for device applications.
• Sulfur vacancies (V_S) and oxygen substituents (O_S) are common in monolayer WS₂, but their interaction is unstudied.

Purpose of the Study:

• Investigate the interaction between sulfur vacancies and oxygen substituents in monolayer WS₂.
• Characterize the electronic structure modifications induced by these interacting defects.

Main Methods:

• Scanning tunneling microscopy/spectroscopy (STM/STS) was employed to study defect interactions.
• First-principles (ab initio) calculations were used to understand the electronic origins of observed phenomena.

Main Results:

• An occupied in-gap state (OIGS) was observed at sulfur vacancy sites interacting with oxygen substituents.
• The energy of the OIGS is dependent on the local density of oxygen substituents.
• Ab initio calculations revealed the OIGS arises from modified hybridization between tungsten (W) d-orbitals and sulfur (S) p-orbitals at the Γ-valley.

Conclusions:

• The interaction between V_S and O_S in WS₂ creates a tunable electronic state.
• This finding offers a new pathway for defect engineering in 2D materials for electronic applications.