Studies On Synthesis And Performance Improvement Of Two-Dimensional SnS Photodetector

Photodetector is a device that converts optical signals into electrical signals which plays an irreplaceable role in social life and production.With the advancement of the times,photodetectors will develop toward wide detecting band,high sensitivity,tiny imaging units,and high integration.Photodetectors which are built based on materials like Si,PbS,Hg_1-xCd_xTe are difficult to meet the above mentioned development needs.In recent years,two-dimensional（2D）layered materials have been extensively studied by researchers because of their ultra-thin nanostructure and excellent photoelectric properties.Among all kinds of 2D materials,the Group IV metal monosulfide compounds which are represented by tin sulfide（2D SnS）,have an appropriate optical band gap and strong light absorption characteristics.Based on the progress of 2D SnS research,the controllable synthesis of 2D SnS is not so good,and the light absorption effect is weaker than the three-dimensional SnS.This work first optimizes the process parameters of 2D SnS in physical vapor deposition method,improving its growth controllability.The method of modifying 2D SnS surface by gold nanoparticles（AuNPs）is used to enhance the light absorption effect of it,which finally improve the performance of the two-dimensional SnS photodetector.The specific research contents and results are as follows:（1）Controllable preparation of two-dimensional SnS nanomaterial.The physical vapor deposition（PVD）method was used to realize the controllable growth of two-dimensional SnS by adjusting the growth temperature and time as well as other process parameters.Ultrathin two-dimensional SnS nanosheets were successfully prepared under a seriers of process parameters with a growth temperature of 580°C,growth time of 10 min,protecting gas flow rate of 70 sccm and tube furnace pressure of 100 Torr.（2）Preparation of two-dimensional SnS photodetectors and visible-near-infrared light response tests.Two-terminal 2D SnS photodetector was fabricated by UV lithography.Under the illumination of 450 nm laser with a power of 2.1 mW,the photoresponsivity and response time as well as the specific detectivity of the device were 161 A·W^-1,0.18 s,1.6×10⁹ Jones respectively.Under illumination of 808 nm near-infrared light,the photoresponsivity of device reached 45.6 A·W^-1.The cycling test of device exhibits its good cycling stability in the wavelength range of 450-808 nm.The photocurrent along the[010]crystal orientation of the two-dimensional SnS is 1.7 times that of the[001]crystal orientation,and the anisotropic light response characteristic of the device is outstanding.（3）Gold nanoparticles（AuNPs）modified the surface of two-dimensional SnS to enhance the light absorption,improving the photoresponsivity and external quantum efficiency of 2D SnS devices.After modification by AuNPs,the 2D SnS photodetector has a photocurrent of 1.53μA with an optical power of 2.1 mW and a photoresponsivity of 507 A·W^-1,an external quantum efficiency of 1.42×10⁵%,and a specific detectivity of 3.65×10⁹ Jones.The photoresponsivity and the specific detectivity are three times to that of the unmodified 2D SnS photodetector,and the external quantum efficiency is also significantly improved.The experimental results show that the local light field formed by the surface modification of the AuNPs and the two-dimensional SnS photogating effect are independent of each other.