The Construction And Gas Sensing Properties Of MoS₂ Nanocomposite Interface

Constructing the nanocomposite interface can modulate the surface morphology of the material,and increase the specific surface area of the composite structure,so that more gas molecules diffuse into the surface and interior of the material to improve the gas-sensing performance;at the same time,the movement of the Fermi level leads to the appearance of a barrier,which can adjust the width of the depletion layer and the structure of the band gap.It improves the gas sensing properties of the nanocomposite structure.As a typical two-dimensional material,it is a natural n-type semiconductor with a large number of dangling bonds and contact sites?sulfur defects,vacancies,and edge contacts?.Therefore,three different structures of MoS₂ nanocomposite interfaces were constructed to improve the gas sensing properties of NO₂,namely MoS₂-ZnONWs interface,MoS₂-PSiNWs interface and Si-MoS₂-Si interface.The parameter of MoS₂ nanosheets in chemical vapor deposition process was at770°C for 90 minutes.In this work,the core-shell molybdenum disulfide/ZnO nanowires?MoS₂/ZnONWs?have been designed.MoS₂/ZnONWs exhibited the highest detection limit was 200 ppb NO₂ at 200°C and the greatest response was 31.2%to 50 ppm NO₂.The enhancement mechanism of this phenomenon was mainly attributed to the recombination of the electron-hole and the modulation of the depletion layer width at the interface.In order to decrease the working temperature further,three kinds of molybdenum disulfide/porous silicon nanowire?MoS₂/PSiNWs?heterojunctions with different thicknesses were designed.It was measured at room temperature with the highest limit detection of 1 ppm to NO₂.The MoS₂/PSiNWs?with a thickness of 60 nm for MoS₂?exhibited a maximum response of 28.4%to 50 ppm NO₂.Compared with gas sensors based on different MoS₂ nanostructures and similar MoS₂ nanostructures reported in the previous literature,MoS₂/PSiNWs heterojunction has exhibited superior gas sensing properties at room temperature.This enhancement of sensitivity was mainly attributed to the effects of morphology and the modulation of the depletion layer width at the interface.At the same time,the deposition temperature during chemical vapor deposition?CVD?was also discussed.The results showed that the annealing temperature of 770°C was optimum for the vulcanization process in this paper.This can be explained by the rapid transfer of charge in MoS₂ and the high density of electron accumulation at the interface during annealing.In order to design the gas-sensing device to be simpler and more practical,the gas-sensing performance is improved without a large specific surface area.This article constructed the Si-MoS₂-Si sandwich nanostructure with a simple and easy method.The highest detection limit of NO₂ was 500 ppb at room temperature,while the sandwich structure of Si-MoS₂-Si?120 nm thickness for MoS₂?exhibited the greatest response of13.7%to 50 ppm NO₂.Compared with pure Si-MoS₂?response value was 0.5%?,the Si-MoS₂-Si sandwich nanosturcture exhibited superior gas sensitivity at room temperature,and a high response enhancement factor of 27.4.In addition,the gas-sensing behavior of the comparison of Si-MoS₂-Si and PSiNWs to NO₂ at room temperature was also discussed in detail.The results show that compared with the gas-sensing response of PSiNWs?12.7%to 50 ppm NO₂?,the construction of Si-MoS₂-Si sandwich structure?13.6%to 50 ppm NO₂?exhibited a comparable gas-sensing performance to that of PSiNWs nanostructures,achieving a device from the structure to performance optimization.