Patterned, Low-Temperature Growth of Transition Metal Dichalcogenides for Low Resistance Raised Contacts

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Physics

Background:

• Transition metal dichalcogenide (TMD) monolayers are key materials for next-generation electronics.
• High contact resistance between TMDs and metal electrodes, particularly for holes, hinders device performance.
• Developing effective raised source/drain contacts at compatible temperatures is a significant challenge.

Purpose of the Study:

• To present a novel, plasma-free method for fabricating raised contacts on TMD monolayers.
• To achieve growth at temperatures compatible with CMOS back-end-of-line processes.
• To demonstrate the effectiveness of these contacts in reducing contact resistance.

Main Methods:

• Plasma-free selenization and sulfurization of metal oxides at substrate temperatures as low as 400 °C.
• Thermal activation of gas-phase chalcogen precursors at 950 °C to enable low-temperature growth.
• Fabrication of raised contacts on WSe2 monolayers and characterization using transmission electron microscopy and contact resistance measurements.

Main Results:

• Achieved high-quality, crystalline films of various TMDs (WS2, MoSe2, MoS2, PtSe2, NbS2) grown on monolayer TMDs.
• Demonstrated successful fabrication of raised contacts on WSe2 monolayers at CMOS-compatible temperatures (down to 400 °C).
• Obtained a low hole contact resistance of 0.3 kΩ·μm on WSe2 monolayers after chemical doping.

Conclusions:

• The developed plasma-free chalcogenization process enables the direct growth of raised contacts on TMD monolayers at low temperatures.
• This method addresses the critical challenge of high contact resistance in TMD-based electronic devices.
• The process is versatile and applicable to a range of important TMD materials, paving the way for advanced flexible and integrated electronics.