Carrier Transport Properties of MoS2 Asymmetric Gas Sensor Under Charge Transfer-Based Barrier Modulation

Abstract

Over the past few years, two-dimensional materials have gained immense attention for next-generation electric sensing devices because of their unique properties. Here, we report the carrier transport properties of MoS2 Schottky diodes under ambient as well as gas exposure conditions. MoS2 field-effect transistors (FETs) were fabricated using Pt and Al electrodes. The work function of Pt is higher than that of MoS2, while that of Al is lower than that of MoS2. The MoS2 device with Al contacts showed much higher current than that with Pt contacts because of its lower Schottky barrier height (SBH). The electrical characteristics and gas responses of the MoS2 Schottky diodes with Al and Pt contacts were measured electrically and were simulated by density functional theory calculations. The theoretically calculated SBH of the diode (under gas absorption) showed that NOx molecules had strong interaction with the diode and induced a negative charge transfer. However, an opposite trend was observed in the case of NH3 molecules. We also investigated the effect of metal contacts on the gas sensing performance of MoS2 FETs both experimentally and theoretically.Electronic supplementary materialThe online version of this article (10.1186/s11671-018-2652-9) contains supplementary material, which is available to authorized users.

Improved Sensitivity in Schottky Contacted Two-Dimensional MoS2 Gas Sensor

“…Previously, based on SBM, the Schottky-contacted ZnO nanowire sensor showed enhanced sensitivity compared with the ohmic contacted sensor. − This is due to the increase in the charge flow induced by the SBM in the case of the Schottky contact device compared with the ohmic-contact one. Similar characteristics were also observed in other nanomaterials such as carbon nanotubes and 2D InSe. , However, several researches focused primarily on the effect of surface charge transfer in 2D TMD gas sensor, while the SBM property is not investigated in detail. , In particular, the number of studies on gas sensor characteristics based on electrode types with various Schottky barrier heights (SBHs) is limited.…”

“…28,29 However, several researches focused primarily on the effect of surface charge transfer in 2D TMD gas sensor, while the SBM property is not investigated in detail. 30,31 In particular, the number of studies on gas sensor characteristics based on electrode types with various Schottky barrier heights (SBHs) is limited.…”

Nanoscale Heterostructured Materials Based on Metal Oxides for a Chemiresistive Gas Sensor

“…Typically, TMDs do not require any surface functionalization unlike graphene, which is chemically inert in nature, and they have higher gas adsorption capacity. They have layer dependent band gaps and high specific surface area, which makes them suitable candidates for gas sensing applications. − However, the intrinsic shortcomings of pure TMDs nanomaterials like high response time/incomplete recovery and cross selectivity limit their practical application. − Alternative strategies to improve their performance by designing semiconductor heterostructure that are constructed by integrating TMDs with metal oxides have been proposed by many authors with properties which are difficult to achieve in a single system. − Previously, Lee et al presented a comprehensive review on TMDs and metal oxide hybrids for gas sensing applications and their collaborative benefit in terms of geometric, electronic, and chemical effects . Although recent achievements in TMDs have promoted increasing research interest in hybrid nanostructures for sensing applications, significant research effort is necessary to unfold many uncertainties for real life applications.…”