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Synthesis and Characterization of Ⅱ-Ⅵ Group One-dimensional Semiconductor Nanomaterials and Nanoarrays

Author: CaoBaiLai
Tutor: JiangYang；QianYiTai
School: Hefei University of Technology
Course: Materials Science
Keywords: Ⅱ-Ⅵgroup semiconductors Solvothermal Nanowire arrays Photoluminescence Core/sheath structure Laser
CLC: TB383.1
Type: Master's thesis
Year: 2007
Downloads: 249
Quote: 1
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Abstract


Recently, one-dimensional nanoscale materials, such as nanotubes, nanowires, nanorods and nanobelts, have been received considerable attentions,it is because that these nanoscale materials have novel physical and chemical properties compared with those of their bulk counterparts, which have shown the potential applications in the fields of electronic, optoelectronic, magnetic recording et al. In this dissertation, various solvothermal approaches to synthesis of one-dimensional metal chalcogenide semiconductors, such as CdS nanowire arrays, CdS/CdSe nanowires and ZnS nanorods, were introduced. The control of morphology and sizes of those semiconductors and their optical properties were investigated. The significant results are introduced as following:1. Large-area and highly-ordered wurtzite CdS nanowire arrays were synthesized uniformly on Cd foil substrate via a simple liquid reaction route adopting thiosemicarbazide and Cd foil as starting materials. The CdS nanowires were identified to be single crystals growing along the [001] direction and perpendicular to the substrate surface. Asymmetrical broadening and red-shift of the characteristic CdS Raman signature were observed, and ascribed to phonon confinement due to the nanoscale dimension in the diameter direction of nanowires. Significantly, the uniform CdS nanowire arrays can act as laser cavities in the visible light range, which lead to band gap lasing at -515 nm with obvious modes. The high-density nuclei and the preferential orientation growth induced the formation of aligned CdS nanowires on the metal substrate.2. The uniform CdS/CdSe core/sheath nanowires were prepared by two steps simple solvothermal method using two solvents of ethylenediamine (the first step) and tributylphosphine (the second step). Each nanowire has rough surface with diameter about 50nm and length about 1-5μm. For the second step reaction, the possible formation mechanism of uniform CdS/CdSe core/sheath nanowires was suggested as chemical transportation of selenium by tributylphosphine. Sulphur atoms on the CdS nanowires surface are substituted by selenium atoms, and then, CdS nanowires convertted into CdS/CdSe core/sheath nanowires. Photoluminescence (PL) measurement revealed that CdS/CdSe core/sheath nanowires exhibitted stronger emission than that of CdS nanowires. 3. Large-area and uniform ZnS nanorods were prepared on zinc foil substrate via a simple solvothermal rout adopting thiosemicarbazide and cadmium foil as starting materials. Most of the as-synthesized ZnS products are single crystalline with a hexagonal wurtzite structure and grow along the c axial of (001) direction. The individual ZnS nanorod on zinc foil has square cross-section with the side of about 30nm and length range from 2m to 3m. The reaction temperature, time and the solvent kind are the three key factors to control the morphologies and the sizes of ZnS nanocrystals in our experiments. Meanwhile, the possible growth mechanism of ZnS nanorods has been discussed. Photoluminescence (PL) measurement revealed that the as-prepared ZnS nanorods exhibit strong emission caused by crystalline defects.

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