Preparation And Properties Of SnE(E=S、Se、Te) Nanomaterials

Tin chalcogenides SnE（E=S,Se,Te）semiconductors have excellent optical,electrical,thermal and other properties,making them have a wide range of applications in photo-detection,thermoelectric and photovoltaic devices.It has been demonstrated that the properties and performances of the materials can be tuned through the decrease for the dimensions and sizes,and the modifications for the morphologies and microstructures.Hence the preparation and structure modifications for the semiconducting nanomaterials is of importance for science and technology.This thesis prepared Sn S_1-xSe_xternary alloy nanobelts,SnSe/Bi₂Se₃nanosheet heterojunctions and highly-oriented Bi-doped SnTe nanopillar array films by solvothermal and vacuum thermal evaporation techniques,and characterized the phases,morphologies,microstructures and properties of the materials.The main results are as follows:（1）.The ternary Sn S_1-xSe_x（x=0,0.1,0.2,0.4,nominal composition）alloy nanobelts were prepared by hydrothermal technique.The phases,chemical compositions,morphologies,microstructures,phonons and optical property of the prepared samples were characterized and analyzed by XRD,XPS,Raman,FESEM,FETEM,and UV-vis-NIR.The results show that single-crystalline nanobelts with smooth surfaces were synthesized and Se was doped into the Sn S lattice as substitution for S to form ternary alloy.The length of nanobelts is in micron scale and can be over ten microns.With the increase for doping concentration of Se,the optical band gap of the nanobelts gradually decreases from 1.15 e V to 1.01 e V,indicating that the optical band gap of nanobelts was tuned by doping Se.（2）.SnSe/Bi₂Se₃nanosheet heterojunctions were prepared by a two-step route combining the vacuum thermal evaporation method and solvothermal method.The uniform Bi₂Se₃nanosheets were prepared by solvothermal technique,and then were used as the substrates for the subsequent deposition of SnSe nanoparticles by vacuum thermal evaporation technique to form SnSe/Bi₂Se₃nanosheet heterojunctions using SnSe powder as the evaporation source.The phase and morphology of the samples were characterized and analyzed by XRD and FESEM.The results showed that the uniformly distributed orthorhombic SnSe nanoparticles were deposited on the trigonal Bi₂Se₃nanosheets,and the thickness and density of the nanoparticles were controlled by thermal evaporation parameters.（3）.The Bi-doped SnTe high orientation array films were prepared by vacuum thermal evaporation technology,and the phase,composition and morphology of the samples were characterized and analyzed by XRD and FESEM.The results show that Bi is successfully doped into cubic phase SnTe lattice,and the sampless are the highly oriented nanopillar array films.The diameters of the nanopillars and thickness of the films can be controlled by thermal evaporation parameters.The high orientation array structure and Bi doping improve the room-temperature electrical transport properties of SnTe thermoelectric materials.In summary,the Se-doped Sn S nanobelts,SnSe/Bi₂Se₃nanosheet heterojunctions and highly-oriented Bi-doped SnTe nanopillar array films were prepared here by different techniques.The modifications for the morphologies and microstructures of the nanomaterials were achieved,and their properties can be tuned.The results would lay a research foundation for expanding their applications in the future.