Gate-Tuned Gas Molecule Sensitivity of a Two-Dimensional Semiconductor

Abstract

In this work, we develop a gate-tunable gas sensor based on a MoS2/hBN heterostructure field effect transistor. Through experimental measurements and numerical simulations, we systematically reveal a principle that relates the concentration of the target gas and sensing signals (ΔI/I 0) as a function of gate bias. Because a linear relationship between ΔI/I 0 and the gas concentration guarantees reliable sensor operation, the optimal gate bias condition for linearity was investigated. Taking NO2 and NH3 as target molecules, it is clarified that the bias condition greatly depends on the electron accepting/donating nature of the gas. The effects of the bandgap and polarity of the transition metal dichalcogenides (TMDC) channel are also discussed. In order to achieve linearly increasing signals that are stable with respect to the gas concentration, a sufficiently large V BG within V BG > 0 is required. We expect this work will shed light on a way to precisely design reliable semiconducting gas sensors based on the characteristics of TMDC and target gas molecules.

A New Design Rule for Developing SiO with High Performance: Controlling Short‐Range Ordering of SiO2 Phase

“…The Pristine SiO shows four different characteristics in Si─O─Si bond vibrational modes of SiO 4 tetrahedron (Figure 3); Symmetric stretching mode at ≈1200 cm −1 , asymmetric stretching mode at 1100–950 cm −1 , bending mode at 700–800 cm −1 , and rocking mode at 450–400 cm −1 . [ 9 ] For the d ─SiO, overall spectra are very similar to that of the Pristine SiO, but the spectra are slightly shifted to a higher wavenumber range. This shift in FTIR spectra is also observed in the SiO─Li and the SiO─Li─C.…”

“…Additionally, crystalline Si also formed in the SiO─Li sample, therefore, the SiO─Li sample consists of crystalline Si with crystallized SiO 2 phases (Figure 1c), which supports the idea that LiOH∙H 2 O could accelerate the crystallization of SiO 2 and disproportionation of Si, as already shown in our previous work. [ 9 ] Surprisingly, when the citric acid (10 wt%) as a carbon source with 3.51 wt% LiOH∙H 2 O is added during the heat treatment at 850 °C, SiO─Li─C in Figure 1d did not show any crystallized SiO 2 phases or crystallized Li─Si─O phases even though the same amount of Li is added. Only crystalline Si phase is observed with a broad hump at ≈ 20 ≈25°.…”

“…Recently, our group reported on a new potential strategy for improving ICE in SiO by controlling the crystallinity of SiO 2 matrix. [ 9 ] By heating SiO with a small amount of Li source, the crystallization of SiO 2 matrix in the SiO was accelerated, which highly suppressed the irreversible reaction of the SiO 2 matrix in SiO. This resulted in a significant improvement in ICE.…”

Electron Tunneling Enhancement in MoS2/Hexagonal Boron Nitride/Multilayer Graphene Heterostructures by Bubble Formation

“…Figure 1 shows the fabrication steps of the MoS 2 /hBN/MLG heterostructure on a SiO 2 substrate using a micro-transfer system [25][26][27][28]. A 40-nm-thick hBN dielectric layer was stacked on MLG (22 nm in thickness), which was initially prepared on a 280-nm-thick SiO 2 substrate by mechanical exfoliation.…”

Tungsten-Doped Indium Tin Oxide Thin-Film Transistors for Dual-mode Proximity Sensing Application

“…Three-terminal transistors are quite versatile in detecting and amplifying weak sensing signals, 8 which benefits from current amplification characteristics and are utilized for the sensing of, for example, proximity, 9,10 pressure, 11 and gases. 12 Configuration of transistor sensors usually includes an extended-gate configuration with the extended gate as sensing end 13 and compact configuration which is based on the original structure of transistors with the channel 14 or the dielectric 15 as a sensitive component. The extended-gate one enables devices to be more flexible in detecting external stimuli and protects the transistor from the environment, while the compact one presents high integration capability.…”