Two-Dimensional High-Quality Monolayered Triangular WS₂ Flakes for Field-Effect Transistors

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Large-area, uniform single-crystal tungsten disulfide (WS₂) is crucial for advanced optoelectronics.
• Controlling growth parameters for two-dimensional (2D) materials like WS₂ remains a significant challenge for device development.

Purpose of the Study:

• To develop a method for synthesizing uniform, single-crystal monolayered WS₂ flakes over large areas.
• To optimize growth conditions by precisely controlling precursor introduction and source-substrate distances to manage nucleation density.

Main Methods:

• Synthesis of triangular monolayered WS₂ flakes using controlled sulfur precursor introduction and optimized source-substrate distances.
• Characterization of morphology and crystal structure via transmission electron microscopy (TEM).
• Analysis of structural properties and crystallinity using Raman spectroscopy.

Main Results:

• Successfully synthesized high-quality triangular monolayered WS₂ flakes (up to 233 μm side length) with uniform crystallinity.
• Fabricated field-effect transistors using the single-crystal WS₂ demonstrated stable charge transport.
• Achieved a field-effect mobility of 50.5 cm²/V·s and a high current on/off ratio (I_on/I_off) of approximately 10⁷.

Conclusions:

• The optimized synthesis method enables the production of large-area, uniform single-crystal WS₂.
• The high-performance transistors indicate the potential of WS₂ for various 2D-material-based electronic and optoelectronic devices.
• This work facilitates the broader application of WS₂ in next-generation technologies.