Impurity-Induced Emission in Re-Doped WS₂ Monolayers.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Impurity doping is crucial for tuning semiconductor optical properties.
• Two-dimensional (2D) semiconductors like transition metal dichalcogenides (TMDs) are highly excitonic.
• Doped TMDs typically show broad, featureless emission, hindering material design.

Purpose of the Study:

• To investigate impurity-induced optical emission in doped two-dimensional (2D) semiconductors.
• To characterize the nature of impurity states in monolayer tungsten disulfide (WS2).
• To enable strategic engineering of optical responses in 2D materials.

Main Methods:

• Substitutional doping of monolayer WS2 with rhenium (Re) as an electron donor.
• Photoluminescence spectroscopy to observe impurity-induced emission.
• Temperature-dependent measurements and gate-field-effect studies.
• First-principles GW-Bethe-Salpeter equation (GW-BSE) calculations.

Main Results:

• Observation of well-defined, impurity-induced emission in Re-doped WS2.
• Emission characteristics consistent with localized states, dominating up to 200 K.
• Gate dependence confirmed the role of neutral impurity centers.
• Calculations attributed emission to Re-band to valence band transitions.

Conclusions:

• Rhenium doping in monolayer WS2 creates well-defined localized states.
• This controlled emission provides a pathway for engineering optical properties of 2D semiconductors.
• The findings advance the understanding of impurity physics in TMDs.