Bidirectional doping of two-dimensional thin-layer transition metal dichalcogenides using soft ammonia plasma

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional transition metal dichalcogenides (TMDs) exhibit promising electronic properties for microelectronics.
• Controllable p-type and n-type doping remains a significant challenge for TMD materials.
• Existing doping methods often lack precision or are incompatible with industrial processes.

Purpose of the Study:

• To develop a novel soft plasma doping technique for achieving controllable p-type and n-type doping in TMDs.
• To investigate the effects of varying plasma parameters (RF power, processing time) on doping characteristics.
• To demonstrate the efficacy of this method on MoS2 and WS2 materials.

Main Methods:

• A soft plasma doping approach was employed, adjusting radio frequency (RF) power and processing time.
• Doping effects were analyzed by measuring changes in off-state current, threshold voltage, and carrier mobility.
• Material characterization was performed using Raman spectroscopy, photoluminescence (PL), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM).

Main Results:

• p-type doping in MoS2 was achieved with low RF power and short processing times, increasing off-state current and mobility while shifting threshold voltage positively.
• n-type doping in MoS2 was realized with high RF power and long processing times, resulting in a negative shift in threshold voltage and reduced mobility.
• Plasma treatment was shown to influence sulfur vacancies and nitrogen substitution, correlating with observed doping types and material properties.

Conclusions:

• The soft plasma doping method offers a controllable and versatile approach for both p-type and n-type doping of TMDs.
• This technique is non-destructive, scalable, and compatible with existing microelectronics fabrication.
• The developed method holds potential for advancing the development of diverse and functional TMD-based electronic devices.