Vapor-phase Synthesis, Characterization And Photoluminescence Properties Of Quasi-one-dimensional Metal Oxide Semiconductor Nanomaterials

Quasi-one dimensional (1D) nanomaterials, including nanowires (rods), nanotubes, nanobelts, nanocables, heterojunction and superlatice nanowires, are ideal systems for investigating the dependence of electrical transport, optical properties, magnetic properties, and mechanical properties on size and dimensionality. In addition, they are expected to play an important role as interconnects and functional components in the "botom up" design and fabrication of new electronic and optoelectronic devices. Now the research of the 1D nanomaterials has already become one of the centre subjects of nanomaterial science.Though the research of 1D nanomaterials already has been got considerable progresses, it still remains a significant challenge to achieve controlled synthesis of 1D nanomaterials with desired morphologies, components, and structures, which is a foundation and prerequisite for the applications of nanomaterials. Focusing on the research of controlled synthesis of 1D nanomaterials and relative physical properties, we have done a series of work, and the main contents and conclusion can be summarized as following: 1. Synthesis and characterization of In-doped ZnO nanowires with periodical single-twin structureThe In-doped ZnO (IZO) nanowires has been synthesized by a thermal evaporation method. The morphology and microstructure of the IZO nanowires has been extensively investigated using scanning electron microscopy (SEM) and x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM). The products in general contain several kinds of nanowires. In the present work, a remarkable type of IZO zigzag nanowires with a periodical twinning structure has been investigated by transmission electron microscopy (TEM). HRTEM observation reveals that this type of IZO nanowires has an uncommonly observed zinc blende crystal structure. These nanowires, with a diameter about 100 nm, grow along [111] direction with well-defined twinning relationship and the well-coherent lattice cross the boundary. In addition, IZO nanodendrities structure was also observed in our work. A growth model based on the vapor-liquid-solid mechanism is proposed for interpreting the growth of zigzag nanowires in our work. Due to the heavy doping of In, the emission peak in photoluminescence spectra has red-shifted as well as broadened seriously.2. Self-Catalyst selective growth and optical properties of single-crystalline nanowiresUniform zinc gallate (ZnGa2C>4) nanowires are successfully synthesized by one-step simple thermal evaporation of a mixture of ZnO and Ga2C>3 powders under controlled conditions. Its morphology and microstructures were determined by X-ray powder diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy. The observations reveal that the as-synthesized ZnGa2O4 nanowires are single-crystalline with cubic spinel structure, usually several tens of microns in length. The typical diameters of ZnGa2C>4 nanowires range from 100 to200 nm. The room-temperature photoluminescence spectrum of ZnGa2O4 nanowires features four luminescence peaks around 400, 503, and 686 nm, which are attributed to self-activation center of the octahedral Ga-O, electronic transitions of localized Ga3+ ion in the octahedral Ga-O, single oxygen vacancies (Vo*), respectively. A self-catalytic vapor-liquid-solid (VLS) formation mechanism is also proposed to interpret the growth of ZnGa2O4 nanowires in our work.3. Synthesis and photoluminescence properties of single-crystalline Ga-doped SnC>2 nanowiresSingle-crystalline Ga-doped SnC>2 nanowires were synthesized by a simple one-step thermal evaporation and condensation method. They were characterized by means of X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). FE-SEM images showed that the products consisted of nanowires and microcombs that represent a novel morphology. XRD, SAED and EDS indicated that they were single-crystalline tetragonal SnC>2. The influence of experimental conditions on the morphologies of the products is discussed. Due to the heavy doping of Ga, the emission peak in photoluminescence spectra has red-shifted as well as broadened seriously.