Monolayer WSe₂ Field-Effect Transistor Performance Enhancement by Atomic Defect Engineering and Passivation

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Monolayer two-dimensional (2D) transition metal dichalcogenides (TMDs) show promise for next-generation electronics due to their unique properties.
• Integration challenges arise from lattice defects and difficulties in stable doping, hindering industrial application of 2D materials like WSe2.
• Existing passivation and doping techniques often fall short in achieving both high performance and stability for 2D electronic devices.

Purpose of the Study:

• To develop and present an effective passivation and doping technique for monolayer tungsten diselenide (WSe2) field-effect transistors (p-FETs).
• To significantly recover and enhance the electrical properties of WSe2, focusing on improving both on-state and off-state performance.
• To establish a correlation between device characteristics and material properties using Raman spectroscopy for better defect understanding.

Main Methods:

• Employed a defect-facilitated surface passivation using ammonium sulfide ((NH4)2S) at room temperature.
• Fabricated and characterized monolayer WSe2 p-type field-effect transistors (p-FETs) to evaluate the treatment's impact.
• Utilized Raman spectroscopy to analyze material properties and correlate the full width at half-maximum (fwhm) of peaks with device performance.

Main Results:

• Achieved robust enhancements in both on-state and off-state performance of WSe2 p-FETs.
• Demonstrated a 3-fold increase in channel mobility, a subthreshold slope (SSmin) of 70 mV/dec, on-currents of 110 μA/μm, and an Ion/Ioff ratio exceeding 10^9.
• Established a strong correlation between off-state performance and the fwhm of Raman peaks, indicating successful defect engineering.

Conclusions:

• The (NH4)2S surface passivation technique effectively addresses defects and enhances electrical properties of monolayer WSe2.
• This defect engineering approach offers a viable pathway for stable passivation and substitutional doping, crucial for 2D electronics.
• The study advances the potential for improved charge transport in future 2D TMD-based electronic devices, overcoming key integration hurdles.