Three-Dimensional MoS₂ Synthsized By Template-Assisted Method For Photodetection Application

As a new type of two-dimensional layered materials,thin-layered MoS2 has the characteristics of tunable bandgap(1.3-1.8 eV)and high mobility(-500 cm2V-1s-1).Photoelectronic devices based on MoS2 have gained a lot of attention in recent years.However,thin-layered MoS2 absorbs light relatively poorly than bulk MoS2,thus limiting the further applications of MoS2 in optoelectronic field.In view of the above problems,this dissertation proposes a method for improving the light absorption and photoelectronic performance of MoS2 heterojunction photodetector by using a three dimensional(3D)ZnO nanostructure arrays as a trapping template.The main contents are as follows:(1)3D ZnO template.Regular pencil-like ZnO nanorod arrays and clustered ZnO arrays were prepared on sapphire and silicon substrates by electron beam exposure combined with hydrothermal synthesis.At the same time,the formation mechanism of pencil-like structure is discussed in detail.The height and spacing of ZnO nanorod arrays were controlled,and the ZnO nanorod arrays was proved to have high crystalline quality.(2)3D MoS2 assisted by ZnO template.The morphology of thin-film MoS2 can be controlled by changing the sputtering parameters.It is proved that thin-film MoS2 can form layered and vertical standing layered structures respectively under specific sputtering conditions.The same rule applied to the sputtering on ZnO arrays surface.Through the characterization of ZnO-MoS2 core-shell structure with a shell thickness of 6 nm,the high crystalline quality and layered properties of MoS2 film were proved.And with the three steps of spin-coating,sputtering,and gel-removal,a composite structure of ZnO and 3D chessboard wavy MoS2 film with good regioselectivity can be obtained.(3)Optoelectronic applications of 3D ZnO-MoS2 composite structure.The optical simulation of ZnO-MoS2 core-shell structure was performed by finite-difference time-domain(FDTD)method.It was proved that the light trapping effect of ZnO nanorod arrays highly enhances the light-absorbing ability of thin-layered MoS2 shell.ZnO-MoS2 core-shell nanorod arrays-based photodetector shows a broadband response from the ultraviolet(UV)to the near-infrared(NIR)light range.Compare with the planar ZnO-MoS2 heterojunction,the photocurrent of nanorod arrays under illumination of a near-infrared 808 nm laser is improved up to 60 times.This work demonstrates that the light-trapping ZnO-MoS2 heterojunction nanorod arrays structure will have important applications in high-performance optoelectronic devices.This conclusion proves that using 3D structure as a trapping template can effectively enhance the light absorption of the thin layered MoS2 and significantly improve the performance of MoS2 heterojunction photodetector.