Sensing Behavior of Atomically Thin-Layered MoS₂ Transistors

Abstract

Most of recent research on layered chalcogenides is understandably focused on single atomic layers. However, it is unclear if single-layer units are the most ideal structures for enhanced gas-solid interactions. To probe this issue further, we have prepared large-area MoS2 sheets ranging from single to multiple layers on 300 nm SiO2/Si substrates using the micromechanical exfoliation method. The thickness and layering of the sheets were identified by optical microscope, invoking recently reported specific optical color contrast, and further confirmed by AFM and Raman spectroscopy. The MoS2 transistors with different thicknesses were assessed for gas-sensing performances with exposure to NO2, NH3, and humidity in different conditions such as gate bias and light irradiation. The results show that, compared to the single-layer counterpart, transistors of few MoS2 layers exhibit excellent sensitivity, recovery, and ability to be manipulated by gate bias and green light. Further, our ab initio DFT calculations on single-layer and bilayer MoS2 show that the charge transfer is the reason for the decrease in resistance in the presence of applied field.

Two-dimensional inorganic analogues of graphene: transition metal dichalcogenides

“…Devices made of electrochemically reduced MoS 2 thin films showed good conductivity and rapid electron transfer and were used for the selective detection of glucose and dopamine [107]. Transistors made of few-layer MoS 2 are shown to sense humidity and gases such as NH 3 and NO 2 (figure 10) [108]. The sensing is based on the change in deviceresistivity in the presence of these gases, which occurs due to charge transfer to MoS 2 at different applied fields.…”

Identifying different stacking sequences in few-layer CVD-grownMoS2by low-energy atomic-resolution scanning transmission electron microscopy

“…The number of layers not only provides tunability of the band gap of MoS 2 for photonic applications [8], but also performance enhancements that may not be directly gap related. For instance, the gas sensing behavior of few-layer thick MoS 2 has been found to be better than that of single-layer MoS 2 due to the instability of the single-layer form in reactive gas environments [9,10]. Another example is that few-layer MoS 2 usually displays higher carrier mobility than that of single-layer MoS 2 in various heterostructured FET configurations [11][12][13].…”

Visibility of two-dimensional layered materials on various substrates

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In addition to graphene, several other 2D layered materials, such as transition-metal dichalcogenides (TMDCs, also for use as channel materials) and hexagonal boron nitride (h-BN, as gate insulator), have been studied in detail. Due to the fact that 2D materials offer a large variety of different band gaps, heterostructures are particularly appealing since band-gap engineering becomes feasible while maintaining the ultrathin channel layer thickness.…”