High-Performance Chemical Sensing Using Schottky-Contacted Chemical Vapor Deposition Grown Monolayer MoS₂ Transistors

Abstract

Trace chemical detection is important for a wide range of practical applications. Recently emerged two-dimensional (2D) crystals offer unique advantages as potential sensing materials with high sensitivity, owing to their very high surface-to-bulk atom ratios and semiconducting properties. Here, we report the first use of Schottky-contacted chemical vapor deposition grown monolayer MoS2 as high-performance room temperature chemical sensors. The Schottky-contacted MoS2 transistors show current changes by 2-3 orders of magnitude upon exposure to very low concentrations of NO2 and NH3. Specifically, the MoS2 sensors show clear detection of NO2 and NH3 down to 20 ppb and 1 ppm, respectively. We attribute the observed high sensitivity to both well-known charger transfer mechanism and, more importantly, the Schottky barrier modulation upon analyte molecule adsorption, the latter of which is made possible by the Schottky contacts in the transistors and is not reported previously for MoS2 sensors. This study shows the potential of 2D semiconductors as high-performance sensors and also benefits the fundamental studies of interfacial phenomena and interactions between chemical species and monolayer 2D semiconductors.

Molecular detection on a defective MoS2 monolayer by simultaneous conductance and force simulations

“…For example, this weak interaction has been very recently confirmed in a study involving CO 2 molecules deposited on a MoS 2 monolayer [17]. Some molecules, such as NO or NO 2 , experienced a stronger interaction with the monolayer [18], in good agreement with experimental evidence obtained in gas-sensing studies [12][13][14].…”

“…Two-dimensional (2D) materials are generally known as poorly reactive and, following this idea, many authors have fabricated transistors using MoS 2 monolayers in order to validate their potential application as gas-sensor devices [12][13][14]. Indeed, physisorbed molecules on a MoS 2 monolayer can modify its electronic properties and consequently the electronic current in the transistor is altered, leading to the molecular detection.…”

Thin 2D: The New Dimensionality in Gas Sensing

“…Obviously, high operation temperatures (usually above 200 • C) are needed to obtain this. The sensing mechanism of TMDs layered nanomaterials is instead typically based on physisorption-charge transfer processes [25]. Physical adsorption dominates at relatively low operating temperatures, so this approach is an advantage for minimizing power consumption of sensors and increasing their life-time [26].…”

Ultrafast, Broadband Photodetector Based on MoSe2/Silicon Heterojunction with Vertically Standing Layered Structure Using Graphene as Transparent Electrode

“…Although the gapless band structure of graphene offers the capability of ultrawide band detection, the short lifetimes of the photogenerated carriers in graphene (in the ps range) hinder the improvement of photocurrent 36, 39, 40. In comparison to graphene, TMDs such as MoS 2 and MoSe 2 possess large bandgap and thus higher carrier lifetimes, making them as promising candidates for high‐sensitivity photodetectors 34, 41, 42. For a practical photodetector, fast response speed is particularly important for the applications such as imaging and optical communication.…”