Scaling-up Atomically Thin Coplanar Semiconductor-Metal Circuitry via Phase Engineered Chemical Assembly

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) layered semiconductors offer potential for transistor scaling but suffer from high contact resistance with external metals.
• Existing methods for contacting 2D materials often lack scalability for mass production.
• Coplanar 2D conductors show promise for reducing contact resistance in 2D transistors.

Purpose of the Study:

• To develop a scalable method for fabricating field-effect transistors (FETs) using phase-engineered molybdenum ditelluride (MoTe2).
• To integrate coplanar metallic 1T'-MoTe2 contacts with semiconducting 2H-MoTe2 channels.
• To demonstrate the performance and potential applications of these heterophase FETs in electronics and optoelectronics.

Main Methods:

• Large-scale, spatially controlled chemical assembly of heterophase MoTe2 structures.
• Phase engineering to create integrated 2H-MoTe2 (semiconductor) and 1T'-MoTe2 (metal) components.
• Transmission electron microscopy (TEM) for structural characterization.
• Fabrication of 1T'-MoTe2 gated heterophase FET arrays using patterned growth.
• Transfer of device arrays onto flexible substrates.

Main Results:

• Demonstrated ohmic contact behavior with low contact resistance due to seamless coplanar 2H/1T'-MoTe2 interfaces.
• Achieved an average carrier mobility of 23 cm^2 V^-1 s^-1 in heterophase FETs, attributed to large single-crystalline 2H-MoTe2 domains (486 ± 187 μm).
• Successfully fabricated arrays of 2D-material-only FETs with all components (channel, gate, contacts) made from MoTe2.
• Demonstrated near-infrared photoresponse with high photoresponsivity (∼1.02 A/W) on flexible substrates.

Conclusions:

• Phase-engineered MoTe2 offers a scalable solution for creating low-resistance, coplanar contacts in 2D transistors.
• The developed heterophase approach enables high-performance 2D electronics and optoelectronics on flexible platforms.
• This work provides a foundation for the large-scale application of integrated 2D semiconductor-metal structures.