Growth And Characterization Of Tin Selenide Nanostructures

Two-dimensional nanomaterials have unique physical and chemical properties due to their special structures,which enable them to show excellent performance in the fields of optoelectronic devices,energy storage and conversion,and have important technical applications.Tin selenide is a material of group IV-VI with a layered structure.It has an orthorhombic crystal structure at room temperature.Its band gap matches well with the solar spectrum and has technical application value in the field of optoelectronics.In addition,tin selenide has ultra-low lattice thermal conductivity and exhibits high thermoelectric performance that has received extensive attention in the field of thermoelectric energy conversion.This thesis used chemical vapor deposition technique to prepare high-quality single crystal SnSe nanoplates and SnSe_1-xS_x(x=0-1)ternary alloy nanoplates and characterized the phases,morphologies,compositions,microstructures and optical properties of the nanoplates,and studied the growth mechanism of the materials.The main results are as follows:High-quality single crystal SnSe nanoplates were prepared by chemical vapor deposition using high-purity SnSe powder.Various characterization methods were used to examine the phase,morphology,compositions and microstructure of the synthesized SnSe nanoplates.It was found that the average side length and thickness of SnSe single crystal nanoplates grown on silicon wafer substrates is about 7.7?m,and 120 nm respectively.Similar morphologies of SnSe nanoplates grown on different substrates were observed.It is concluded that the growth of nanoplates is independent on the substrates.By adjusting the growth time of the nanoplates and observing the morphology of the nanoplates volution,it is thought that the growth mechanism of the nanoplates is a spontaneous two-dimensional vapor-solid(VS)growth mode.The UV-vis-NIR spectroscopy of SnSe nanoplates shows a strong absorption in the near-infrared band,corresponding to a direct optical band gap of 1.02 e V and an indirect optical band gap of 0.87 e V.Single crystal SnSe_1-xS_x(x=0-1)ternary alloy nanoplates were prepared by chemical vapor deposition method,and the phase,morphology and microstructure of the nanoplates were analyzed.XRD and Raman spectra show that SnSe_1-xS_xnanoplates are in pure phase,and S atoms are substituted into the SnSe crystal lattice.The composition changes of Se and S have no influence on the morphology of the nanoplates.The UV-vis-NIR test of SnSe_1-xS_x nanoplates showed that with the increase of S atom concentration,the direct band gap and indirect band gap of the nanoplates gradually increase,indicating that the energy gaps of the nanoplates were tuned.In summary,this thesis used chemical vapor deposition to grow single crystal SnSe nanoplates and SnSe_1-xS_x(x=0-1)ternary alloy nanoplates,and perform a variety of characterizations on the materials and studied its optical properties which lays a research foundation for the applications of the materials.