Preparation And Performance Of Humidity Sensor Based On Two-dimensional ?-In₂Se₃ Nanosheet

Humidity sensors play a vital role in many fields such as industry,agriculture,medicine,and aerospace.Generally,an ideal humidity sensor must meet the requirements of high sensitivity,fast response,wide humidity detection range,and long life.In order to achieve this goal,people are committed to researching moisture-sensitive materials.In recent years,two-dimensional materials with high specific surface area have been favored by researchers for their excellent moisture-sensing ability,but there are still problems such as slow response speed.Two-dimensional(2D)?-In₂Se₃is an emerging semiconductor material with high specific surface area.There is a charge transfer between Se atoms and water molecules on the surface.Especially 2D?-In₂Se₃is also an interesting ferroelectric material with in-plane(IP)and out-of-plane(OOP)polarization simultaneously.Here,a single large-size two-dimensional?-In₂Se₃nanosheet was selected as the humidity sensitive material.A humidity sensor based on a single piece of?-In₂Se₃nanosheet was prepared and its humidity sensing performance was studied.In order to optimize the performance of the device,the hydrophilic Li Cl material and?-In₂Se₃nanosheet was combined to construct a humidity sensor.The specific research content and results are as follows:(1)Preparation and characterization of two-dimensional?-In₂Se₃nanosheet.Firstly,two-dimensional?-In₂Se₃nanosheet were prepared on silicon substrate and PET flexible substrate by mechanical exfoliation.Subsequently,the morphology,structure and composition of?-In₂Se₃nanosheet were characterized by scanning electron microscopy,atomic force microscopy,transmission electron microscopy,Raman spectroscopy and energy spectrometer.The results indicate that the large-area,high-quality?-In₂Se₃nanosheets were successfully prepared.(2)Preparation and performance test of humidity sensor based on single?-In₂Se₃nanosheet.Humidity sensors based on two different substrates were fabricated on silicon substrate and PET flexible substrate.Humidity sensors based on single?-In₂Se₃nanosheet were prepared on silicon substrates and PET flexible substrates,and the humidity sensing properties of the devices was tested by impedance analyzer.The results show that the three humidity sensors based on two-dimensional?-In₂Se₃nanosheet have short response recovery time and good repeatability.The impedance values of the silicon-based humidity sensors based on different thickness of?-In₂Se₃nanosheet have no obvious change,indicating that the interaction between water molecules and?-In₂Se₃nanosheet only occurs on the surface of the material.The flexible humidity sensor based on?-In₂Se₃nanosheet with a thickness of 200 nm is 25times more sensitive than a silicon-based humidity sensor with the same thickness.This is mainly due to the tight combination of?-In₂Se₃nanosheet and the PET flexible substrate,which reduces the activation energy of the device.Therefore,the sensitivity of the device to the surrounding environment is improved.(3)Preparation and performance test of humidity sensor based on Li Cl composite?-In₂Se₃nanosheet.The humidity sensor based on Li Cl composite?-In₂Se₃nanosheet was prepared on silicon substrate and PET flexible substrate,and the effect of Li Cl on the humidity sensing properties of?-In₂Se₃nanosheet was studied.The results show that the sensitivity of the humidity sensor composited with saturated Li Cl solution is greatly improved,and the maximum sensitivities of the composited silicon-based and flexible humidity sensors are 1.10×10⁴%and 2.79×10⁵%,respectively.