Substrate Lattice-induced Orientation Controls The Growth Of Metal Chalcogenides

In recent years,the universality of using chemical vapor deposition(CVD)growth technology to prepare low-dimensional(LD)nanomaterials has been confirmed by more and more research results.It is exactly due to the advantages of CVD growth technology that the intrinsic research of LD nanomaterials has become more and more accessible.However,there are still many challenges for the research of one-dimensional Sb2Se3 nanomaterials.On the one hand,the research of near-infared devices based on high-quality 1D Sb2Se3 nano wires is still in blank.On the other hand,it is difficult to obtain 1D Sb2Se3 nano wires with controllable orientation based on the current solution method,which severely limits the exploration of intrinsic electrical and optoelectronic properties.Meanwhile,for the most concerned member of two-dimensional transition metal dichalcogenides(TMDs)family,although the research on MoS2 has achieved significant achievements,the problems of random orientation,poor grain boundaries and thin film continuity during the preparation of MoS2 using CVD growth technology still exists as well as the controllable preparation of large-area,large-domain,high-quality single-layer thin films has become one of the major breakthroughs for this material.Therefore,in order to solve above problems,we have successively achieved successful preparation of high-quality 1D Sb2Se3 nanowires and orientation-controlled 2D MoS2 single-crystal films by using CVD growth technology,which lays a solid foundation for the the intrinsic research of Sb2Se3 nanomaterials and the controllable preparation of large-area and single-crystal MoS2 thin films.The specific research contents of this paper are as follows:(1)Chemical Vapor Deposition Growth of High Crystallinity Sb2Se3 Nanowire with Strong Anisotropy for Near-Infrared PhotodetectorsTo solve the problems of low crystalline quality,random orientation and long time-consuming preparation of 1D Sb2Se3 nanowires based on the solution method,we developed a CVD growth method that directly uses Sb powder and Se powder as reaction precursors and achieved successfully the large-area,high-quality and uniform preparation of 1D Sb2Se3 nanowires on the mica substrate.By exploring the influence of different growth substrates on material preparation,we found that compared with SiO2/Si substrates,the surface-level atomic mica substrates are more conducive to the epitaxial growth of materials,thereby effectively improving the efficiency of material preparation.Meanwhile,the sixfold symmetry structure of the mica substrate has a good induction effect on the orientation of the material,which builds a solid foundation for further exploration of the material in the later period.In addition,we used a series of instruments to characterize the morphology,structural composition and optical properties of the prepared materials.As a result,the materials we have synthesized have a high and reliable crystal quality.On this basis,a photodetector based on Sb2Se3 nanowires was designed and constructed,and its electrical and photoelectric properties were studied.It was found that the material exhibits a wide light response range from visible light to near-infrared(400-900 nm),and has strong anisotropic photoelectric performance.In addition,the high crystal quality of the material itself gives the photodetector an excellent light response rate and a large on/off ratio.Our work not only enriches the preparation method of Sb2Se3 nanowires,but also provides a new perspective for the construction of versatile low-dimensional optoelectronic devices.(2)Epitaxial Growth of Rectangle Shape MoS2 with Highly Aligned Orientation on Twofold Symmetry a-Plane SapphireIn view of the current MoS2 prepared via CVD approaches,which has the problems of random domain orientation and a large number of grain boundaries.We have achieved efficient preparation of rectangular MoS2 with uniform orientation by utilizing the twofold symmetric A-plane sapphire as growth substrate and precise control of growth conditions.During the experimental investigation,we found that the morphological evolution and orientation of MoS2 have a strong dependence on the growth temperature.On this basis,with the help of DFT simulation calculation,the adsorption energy of MoS2 arranged at different angles on the substrate surface is used as a breakthrough,which explains the effect of growth temperature on the MoS2 orientation arrangement as well as clarifies the evolution process of MoS2 morphology anisotropy due to anisotropy growth.In addition,directional MoS2 almost achieves seamless and natural splicing during the growth process,thereby well avoiding the degradation of carrier transfer performance of field effect transistor devices.The work in this chapter highlights the importance of growth substrate selection in the process of expecting to realize large-area and orientation-controlled MoS2,and provides reference idea and route for the controllable synthesis of large-area 2D TMDs single-crystal films in the future.