Enhanced Exciton-to-Trion Conversion by Proton Irradiation of Atomically Thin WS₂

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Defect engineering in van der Waals semiconductors is key for device control.
• Understanding defect evolution's impact on physical properties is crucial but underexplored.

Purpose of the Study:

• To investigate the effects of proton irradiation on the excitonic properties of atomically thin WS2.
• To establish correlations between induced defects and changes in electronic states.

Main Methods:

• Proton irradiation of WS2.
• Scanning transmission electron microscopy (STEM) for structural analysis.
• Photoluminescence (PL) and Raman spectroscopy for optical characterization.
• Density functional theory (DFT) calculations.
• Ion energy loss simulations.

Main Results:

• Proton irradiation enhanced exciton-to-trion conversion in WS2.
• Observed defects include nanopores, W nanoclusters, and zigzag edge terminations.
• DFT revealed in-gap states formed by nanopores, facilitating electron-exciton coupling.
• Ionization was the dominant energy loss mechanism, causing band perturbations and nanopores without significant crystallinity loss.

Conclusions:

• Proton irradiation effectively engineers defects in WS2, altering its excitonic properties.
• Nanopore formation and associated in-gap states are critical for enhanced exciton-to-trion conversion.
• This study offers a viable method for tuning van der Waals semiconductor properties via irradiation-induced defects.