| Two-dimensional transition metal sulfide（TMDs）have excellent mechanical properties,good optical absorption and electron mobility.It not only make up for the shortcomings of graphene with zero band gap,but also it have adjustable band gap,so it has become an ideal material for the preparation of the next generation of high sensitivity,high response,small volume,wide spectrum photodetectors.Two-dimensional TMDs van der Waals heterostructures have no hanging bonds.It is not affected by lattice mismatches,so they show great potential in the field of next-generation functional electronic and optoelectronic devices.In this paper,In this paper,different transition metal sulfide films（Mo S2,Sn S2,Mo S2/Sn S2）were developed by chemical vapor deposition on sapphire substrates.And the photodetectors of the Mo S2/Sn S2 heterojunctions and their single-component materials were studied under different conditions,and photodetectors were prepared by localization transfer.Secondly,heterojunction photodetectors based on Mo S2/Sn S2 was prepared by mechanical peeling method,and the responsivity of each part to different wavelengths of optical signals was studied,and the influence of optical power density on the net photocurrent,photoresponsivity,detection rate and external quantum efficiency of photodetectors was explored under laser excitation with a wavelength of 385 nm.The following research results have been achieved:（1）The chemical vapor deposition method was used to successfully grow a uniformly distributed thin film material on the sapphire substrate.The monolayer Mo S2prepared was well crystallied,and its morphology was a triangle with a side length of about 20μm and the band gap is about 1.88 e V.The size of the grown Sn S2 is about 20μm and the band gap is about 2.22 e V,which is a film with a multilayer thickness and an uneven surface distribution,which is related to the spiral growth of Sn S2,which seriously affects the preparation of Sn S2 with a monolayer thickness.Mo S2/Sn S2 was grown in two steps,and it was found that the second deposited Sn S2 was based on Mo S2as the optimal growth substrate,and a film was deposited on its surface to construct a heterojunction with a vertical structure.（2）Photodetectors based on different thin film materials（such as Mo S2、Sn S2、Mo S2/Sn S2）were prepared,and the effects of excitation wavelength,optical power density and bias voltage on photoelectric performance were systematically studied.The results show that the Mo S2/Sn S2 heterojunction photodetector has different degrees of response between 250～850 nm,and the response current is greater than that of the single material detector.The heterojunction photodetector has the best response to green light with a wavelength of 520 nm,and the weakest light intensity that can be detected by the detector at this wavelength is 0.0008 m W/cm2,which realizes the detection of weak light signals,and under these conditions,the photoresponsivity,detection rate and external quantum efficiency of the heterojunction photodetector reach the highest values,which are 3.25 A/W,6.25×1012 Jones,8.40,respectively.In addition to the visible light band,the detection ability of the heterojunction photodetector in the near-infrared light band with a wavelength of 1064 nm is significantly enhanced,and the weakest light intensity that can be detected is 0.3m W/cm2,indicating that its own detectable spectral range is greatly enhanced by constructing a heterogeneous structure.At the same time,its response speed is significantly improved,with response time and recovery time of 102 ms and 85 ms,respectively.（3）Mo S2/Sn S2-based heterojunction photodetectors were constructed by mechanical stripping method,and the photoelectric characteristics of Mo S2、Sn S2 and Mo S2/Sn S2 were studied.The results show that the line type of the photocurrent-wavelength relationship diagram of the heterojunction part has a similar line type as Mo S2,because Mo S2 plays a decisive role in the improvement of the photocurrent of the constructed heterojunction photodetector.When the wavelength is 385 nm,the bias voltage is 0.9 V and the optical power density is 1 m W/cm2,the photoresponsivity and external quantum efficiency of the device are the highest,8.71 A/W and 28.1,respectively. |
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