All-Electrical High-Sensitivity, Low-Power Dual-Mode Gas Sensing and Recovery with a WSe₂/MoS₂ pn Heterodiode

Area of Science:

• Materials Science
• Nanoscience
• Chemical Sensing

Background:

• Conventional two-dimensional MoS2 gas sensors rely on FET channel resistance or Schottky barriers.
• Existing methods face limitations in sensitivity, detection limits, and power consumption.

Purpose of the Study:

• To develop a highly sensitive, low-power, and versatile gas sensor platform.
• To investigate the performance of a gate-tunable type-II WSe2(p)/MoS2(n) heterodiode for gas sensing.

Main Methods:

• Fabrication of a WSe2/MoS2 heterodiode gas sensor on the same MoS2 flake as a reference FET.
• Systematic measurements of NO2 sensing performance under varying concentrations, gate biases, and MoS2 thicknesses.
• First-principles calculations to elucidate the sensing mechanisms.

Main Results:

• The WSe2/MoS2 heterodiode exhibited a 6x enhancement in sensitivity and an 8x reduction in detection limit compared to the MoS2 FET.
• Achieved a power consumption as low as sub-100 μW/cm2 due to dual-mode operation (high-bias thermionic current and near-zero-bias interlayer recombination current).
• Demonstrated fast, gate-tunable recovery and detection of trinitrotoluene (TNT) down to 80 ppb.

Conclusions:

• The WSe2/MoS2 pn heterojunction offers a significant improvement over traditional MoS2 FET sensors.
• The dual-mode operation enables high sensitivity and ultra-low power consumption for dynamic, room-temperature gas sensing.
• This platform shows potential for versatile and efficient chemical sensing applications.