Fabrication And Property Analysis Of Two-Dimensional SnS₂/SnS Heterostructure

As new members of two-dimensional materials,SnS₂ and SnS belonging group IV metal chalcogenides（GIVMCs）,have the advantages of abundant reserves,environmentally friendly,unique physical-chemical properties and excellent photoelectronic properties,which have become one of the hot spots of current research.Their photoelectric performance has a very attractive development prospect in the new optoelectronic devices.However,compared with transition metal dichalcogenides,the research on SnS₂ and SnS started relatively late and lacked certain depth and systematicness.The p-n heterostructures based on SnS₂ and SnS are only obtained by CVD method and hydrothermal method.The heterostructures prepared have small size and large thickness,which limiting its application in photoelectric devices.In addition,due to the difficulty in preparing two-dimensional SnS samples,the SnS₂/SnS heterostructure prepared by mechanical transfer method has not been reported.Therefore,the preparation,basic properties and applications of SnS₂,SnS and SnS₂/SnS heterostructure are systematically studied in this paper.The main contents are as follows:1.Preparation and characterization of SnS₂ and SnS:SnS₂ and SnS were prepared by mechanical exfoliation method and hydrothermal method.Firstly,single crystal and layers samples of SnS₂ and SnS were prepared by chemical vapor transport method and micro-mechanical exfoliation method.And they were characterized using an optical microscope,an X-ray diffractometer,a Raman spectrometer,an X-ray photoelectron spectroscopy and an atomic force microscope.The as-prepared SnS₂ and SnS samples have a high purity and crystallinity.The maximum size of the samples can reach 50μm,the thinnest thickness is about 2 nm.In addition,SnS₂ nanosheets and SnS nanobelts were also prepared by a hydrothermal method.SnS₂ nanosheets show a typical hexangular shape with a thickness of as 20 nm.SnS nanobelts show a typical belt shape with a maximum size up to 15μm.2.Preparation and characterization of SnS₂ and SnS devices:SnS₂and SnS optoelectronic devices are prepared by a lithographic pattern transfer method.The surface of the device is smooth,and the electrodes have good contacts.The electronic mobility of the SnS₂ device is 0.59 cm²v^-1s^-1,and the current on/off ratio is about 9.26,showing a good control effect.Under illuminations of a visible light,the responsivity of the device is 3278AW^-1,and the detectivity is 7.56×10¹¹Jones.The device based on SnS exhibits excellent visible light detection performance,with a high responsivity of 4382 AW^-1 and a high detectivity of 1.3×10¹¹Jones.3.Preparation and characterization of SnS₂/SnS heterostructure:Two-dimensional SnS₂/SnS p-n heterostructures are prepared by mechanical transfer method.The phototransistor based on SnS₂/SnS heterostructure shows a unique bipolar behavior and rectification characteristics.Because of the construction of p-n junction and the typeⅡheterostructure,the effective separation of electron-hole pair is realized.The responsivity of the device is 7070 AW^-1,the detectivity of 7.22×10¹³Jones,which are superior to that of the single materials.4.Preparation and characterization of SnS₂/SnSe₂ heterostructure:Two-dimensional SnS₂/SnSe₂ n-n heterostructures are prepared by mechanical transfer method.The device based on the heterostructure shows a typical n-type behavior,with an electron mobility of about 3.78 cm²v^-1s^-1,and an on/off ratio of 10⁵.The device has an excellent performance for visible light,inheriting the high photoresponse of SnS₂ and the fast response speed of SnSe₂.The responsivity is as high as 1793 AW^-1,and the external quantum efficiency is as high as5.49×10⁵%,and shows an ultra-fast response rate of 2.1 ms to a 650 nm light.