Enhanced gas sensing performance and all-electrical room temperature operation enabled by a WSe2/MoS2 heterojunction

TL;DR

This paper introduces a novel WSe2/MoS2 heterojunction gas sensor that significantly enhances NO2 detection sensitivity and operates effectively at room temperature using all-electrical control, outperforming traditional MoS2 sensors.

Contribution

It demonstrates for the first time that a gate-tunable WSe2/MoS2 heterojunction can greatly improve gas sensing performance and enable room temperature operation with simple electrical control.

Findings

4x increase in sensitivity compared to MoS2 FET sensors

8x lower detection limit for NO2

Effective detection of TNT down to 80PPB

Abstract

Gas sensors built using two-dimensional (2D) MoS2 have conventionally relied on a change in field-effect-transistor (FET) channel resistance or a change in Schottky contact/pn homojunction barrier. This report demonstrates, for the first time, an NO2 gas sensor that leverages a gate tunable type II WSe2 (p)/MoS2 (n) heterojunction to realize a 4x enhancement in sensitivity, 8x lower limit of detection and improved dynamic response when compared to an MoS2 FET sensor on the same flake. Comprehensive sensing measurements over a range of analyte concentrations, gate biases and MoS2 flake thicknesses indicate a novel two-fold electrical response to NO2 exposure underlying the enhanced sensitivity of the heterojunction- (i) a series resistance change that leads to an exponential change in thermionic current at high bias, and, (ii) a carrier concentration change that leads to a linear change in interlayer recombination current near zero bias. The heterojunction diode also exhibits fast and tunable recovery under negative gate biasing. All-electrical (gate controlled) sensing and recovery operation at room temperature makes this a simple, low-overhead sensor. The ability to sense tri-nitro toluene (TNT) molecules down to a concentration of 80PPB highlights its potential as a comprehensive chemical sensing platform.