Electrical transport properties of single-layer WS2

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Transition Metal Dichalcogenides (TMDs) like WS2 are promising 2D semiconductors.
• Understanding their electronic transport properties is crucial for device applications.

Purpose of the Study:

• Fabricate and characterize field-effect transistors (FETs) using single-layer and bilayer WS2.
• Investigate the electronic transport properties of WS2 FETs.
• Explore the influence of device environment and annealing on WS2 properties.

Main Methods:

• Fabrication of WS2-based field-effect transistors (FETs).
• In situ annealing for improved contact transparency.
• Four-terminal and two-terminal electrical transport measurements.
• Analysis of device behavior across different charge carrier densities and temperatures.

Main Results:

• WS2 FETs exhibit n-type behavior with high room-temperature on/off current ratios (~10^6).
• High mobilities were observed (~140 cm^2/(V·s) for monolayers, >300 cm^2/(V·s) for bilayers at low temperatures).
• Metallic behavior at high carrier densities and variable-range hopping in the insulating regime were identified.

Conclusions:

• WS2 demonstrates excellent electronic properties comparable to MoS2 and WSe2.
• Strong spin-orbit coupling in WS2 enhances its potential for electronic, optical, and valleytronic devices.
• Optimized fabrication and annealing are key to realizing the intrinsic properties of WS2 for future applications.