Modulated wafer-scale WS₂ films based on atomic-layer-deposition for various device applications

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Tungsten disulfide (WS₂) exhibits excellent electronic properties, making it suitable for transistors and gas sensors.
• Controlling WS₂ film quality is crucial for optimizing device performance.

Purpose of the Study:

• To develop a controllable atomic layer deposition (ALD) process for high-quality N- and P-type WS₂ films.
• To investigate the effects of deposition temperature, growth mechanism, annealing, and Nb doping on WS₂ properties.
• To fabricate and characterize field-effect transistors (FETs) and gas sensors using the prepared WS₂ films.

Main Methods:

• Comprehensive study of WS₂ deposition temperature, growth mechanism, and annealing conditions.
• Controlled N- and P-type doping of WS₂ films using Nb doping via ALD.
• Fabrication of WS₂-based FETs and gas sensors.
• Characterization of electronic properties, crystallinity, and device performance.

Main Results:

• Deposition and annealing temperatures significantly impact WS₂ electronic properties and crystallinity.
• Insufficient annealing degrades FET performance (switch ratio and on-state current).
• ALD process control allows tuning of WS₂ film morphology and carrier type.
• Achieved high on/off ratios for N-type (10⁵) and P-type (10²) WS₂ FETs.
• Demonstrated gas sensing capabilities with 14% (N-type) and 42% (P-type) response to 50 ppm NH₃.

Conclusions:

• A controllable ALD process for WS₂ film fabrication with tunable morphology and doping was successfully demonstrated.
• The developed process enables the creation of WS₂-based devices with diverse functionalities.
• Optimized WS₂ films are promising for high-performance transistors and sensitive gas sensors.