Defect Coupling and Sub-Angstrom Structural Distortions in W_1-xMo_xS₂ Monolayers

Area of Science:

• Materials Science
• Atomic Physics
• Condensed Matter Physics

Background:

• Two-dimensional (2D) materials possess unique properties tunable by doping.
• Local atomic structure around dopants critically influences material behavior.
• Understanding dopant-defect interactions is key for tailoring 2D material properties.

Purpose of the Study:

• Investigate the coupling between Molybdenum (Mo) dopants and defects in tungsten disulfide (WS₂) monolayers.
• Determine the local atomic structure around Mo dopants and its effect on WS₂.
• Explore the potential for controlling defect distribution in 2D materials.

Main Methods:

• Aberration-corrected scanning transmission electron microscopy (STEM) with sub-Ångstrom resolution.
• First-principles density functional theory (DFT) calculations.
• Analysis of dopant-defect colocalization and lattice distortions.

Main Results:

• Mo dopants show a strong affinity for sulfur monovacancies in WS₂ monolayers (~80% colocalization).
• Mo dopants facilitate the charging and induce lattice deformation around paired sulfur vacancies.
• A partially occupied midgap defect state enhances the Mo-vacancy affinity.

Conclusions:

• Mo is not an ideal substitutional dopant in WS₂, exhibiting significant coupling with vacancies.
• This dopant-vacancy coupling can be leveraged to control chalcogenide vacancy distribution in transition metal dichalcogenides (TMDs).
• Strategic placement of Mo can segregate vacancies away from active device regions in TMDs.