Phase-engineered low-resistance contacts for ultrathin MoS2 transistors

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Ultrathin molybdenum disulfide (MoS2) is a promising layered semiconductor with a bandgap and no dangling bonds.
• High contact resistance (0.7–10 kΩ μm) between metals and the semiconducting 2H phase of MoS2 limits device performance due to Schottky-limited transport.

Purpose of the Study:

• To demonstrate the local induction of the metallic 1T phase of MoS2 on 2H phase nanosheets.
• To reduce contact resistances and improve the performance of MoS2-based field-effect transistors (FETs).

Main Methods:

• Local phase engineering of MoS2 nanosheets to create 1T phase MoS2.
• Fabrication and characterization of FETs utilizing 1T phase MoS2 electrodes.
• Electrical testing of FETs in ambient conditions.

Main Results:

• Achieved significantly reduced contact resistances in the range of 200–300 Ω μm at zero gate bias.
• Demonstrated FETs with excellent performance: mobility ~50 cm² V⁻¹ s⁻¹, subthreshold swing <100 mV/decade, on/off ratios >10⁷, and drive currents ~100 μA μm⁻¹.
• Observed that FET performance is largely independent of the deposited metal, indicating the 1T/2H interface governs carrier injection.

Conclusions:

• Phase engineering of MoS2 by inducing the 1T phase is an effective strategy to overcome high contact resistance issues.
• The 1T/2H interface plays a crucial role in carrier injection, leading to improved and reproducible electrical characteristics in MoS2 FETs.
• This approach offers a pathway to enhance the performance and reliability of MoS2-based electronic devices.