Black Phosphorus Gas Sensors

TLDR

Black phosphorus and its few‑layer forms have attracted attention for field‑effect transistors, PN junctions, photodetectors, and other devices, yet experimental evidence of its chemical sensing capabilities remains unreported. This study reports chemical sensing of nitrogen dioxide using multilayer black‑phosphorus field‑effect transistors. The authors fabricated multilayer black‑phosphorus FETs and measured their conductance response to NO₂ exposure. The sensors showed conductance increases upon NO₂ exposure, detecting as low as 5 ppb, with relative changes following a Langmuir isotherm and adsorption/desorption rate constants between 130–840 s, demonstrating high sensitivity and providing insight for future applications.

Abstract

The utilization of black phosphorus and its monolayer (phosphorene) and few-layers in field-effect transistors has attracted a lot of attention to this elemental two-dimensional material. Various studies on optimization of black phosphorus field-effect transistors, PN junctions, photodetectors, and other applications have been demonstrated. Although chemical sensing based on black phosphorus devices was theoretically predicted, there is still no experimental verification of such an important study of this material. In this article, we report on chemical sensing of nitrogen dioxide (NO2) using field-effect transistors based on multilayer black phosphorus. Black phosphorus sensors exhibited increased conduction upon NO2 exposure and excellent sensitivity for detection of NO2 down to 5 ppb. Moreover, when the multilayer black phosphorus field-effect transistor was exposed to NO2 concentrations of 5, 10, 20, and 40 ppb, its relative conduction change followed the Langmuir isotherm for molecules adsorbed on a surface. Additionally, on the basis of an exponential conductance change, the rate constants for adsorption and desorption of NO2 on black phosphorus were extracted for different NO2 concentrations, and they were in the range of 130-840 s. These results shed light on important electronic and sensing characteristics of black phosphorus, which can be utilized in future studies and applications.