Synthesis, Characterization And Photoluminescence Properties Of Quasi-one-dimensional Semiconductor Nanomaterials

Research on one-dimensional (1D) nanostructure, including nanowires (rods), nanotubes, nanobelts, nanocables, heterojunction and supperlattice nanowirws, has been one of the most important fields and focus of nanomaterials because of their contribution to the understanding of the basic concepts and potential technological applications. 1D nanostructures are ideal systems for investigating the dependence of electrical transport, optical properties and mechanical properties on size and dimensionality. They are expected to play an important role as both interconnects and functional components in "bottom up" design and the fabrication of nanoscale electronic and optoelectronical devices. The successful synthesis of 1D nanomaterials is the foundation to research on the properties of 1 D nanomaterials.Based on the comprehensive analysis of fabrication methods of 1D nanostructures and combined with the present conditions in our laboratory, we focused on the flowing aspects: synthesis, characterization and photoluminescence properties of oxide and sulfide nanostructures by thermal evaporation method according to VLS or VS growth mechanism. The content and result of this thesis listing as follows:1. Synthesis and photoluminescence properties of novel SnO₂ asterisk-like nanostructures with vertical branched multi-arm.Further more, synthesis of Mn-doped SnO₂ nanowires is also studied..The novel SnO₂ asterisk-like nanostructures with multi-armed nanoribbons and nanowires have been prepared without any catalysts by thermal evaporation of the mixture of SnO and Sn powders at 1000℃ for very short time about 5 minutes. It was observed that there are some vertical branches stemming from arms. The products were characterized and analyzed with field emission scanning electron microscope (FE-SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectroscopy. A room temperature photoluminescence spectrum of as-synthesized products shows two peaks: one at 319nm (3.89ev), which was seldom observed and discussed previously, and the other at 583nm (2.13ev).The possible growth mechanism of the products was discussed. Further more, the synthesis of Mn-doped SnO₂ nanowires is also studied.2. Synthesis and photoluminescence properties of the doorframe-like nanostructures of tin-doped indium oxide (Sn:In₂O₃, ITO).ITO doorframe-like nanostructure and nanowires were successfully synthesized by direct thermal evaporation of a mixture of In, Sn and SnO powders in air at 1000℃. Such nanodoorframe and nanowires have a uniform shape and single crystalline cubic bixbite structure. The growth process of these ternary oxide doorframe-like and nanowires can be interpreted by Self-catalytic VLS and epitaxial growth mechanism concurrently. The RT PL spectra shows that there is a peak at 580 nm, and the luminescence mechanism has been studied.3. Synthesis and photoluminescence of CdS nanobelts without any catalysts and template.Large-scale CdS nanobelts were synthesized using a simple physical thermal evaporation of CdS particles without a metal catalyst and a template. X-ray diffraction analysis, scanning electron microscopy and high-resolution transmission electron microscopy observations show that the CdS nanostructures consist of nanobelts with a hexagonal wurtzite structure, growing along the [100] direction and the growth process follows a vapor-solid mechanism. Two emission bands around 512nm and 713nm of the nanobelts are observed, and the luminescence mechanism has been discussed.