Synthesis And Photoluminescence Properties Of Particular Nanostructures

Rencently, Quasi-one-dimensional (1D) nanomaterials have considerableattentions due to their novel physical and chemical properties compared with thoseof their bulk counterparts. It still remains a significant challenge to achievecontrolled synthesis of quais-one-dimensional (1D) nanomaterials with peculiarstructures. These peculiar structures are ideal systems for investigating thedependence of electrical transport, optical properties, magnetic properties, andmechanical properties on size and dimensionality. In addition, they are expected toplay an important role as interconnects and functional components in the the"Botom-up" design and fabrication of new electronic and optoelectronic devices.This paper is mainly focused on the controllable synthesis and optical properties ofultrafine hierarchical ZnS treelike nanoarchitectures, zigzag SnO₂ and SnOnanowires and kinds of ZnO peculiar nanostructures. We have done a series ofwork, and the main contents and conclusion can be summarized as following:1.Self-assembled Ultrafine Hierarchical ZnS Treelike NanoarchitecturesUltrafine hierarchical tree-shaped nanoarchitectures of ZnS were synthesized bya H₂-assisted thermal evaporation and condensation technique. Using the scanningelectron microscopy and high-resolution transmission electron microscopy, themorphologies and microstructures of nanotrees were investigated. Treelikenanostructures grow epitaxially from the microsheets and rock-bottom well-alignedsubmicrowires, and the growth of the novel nanostructures is a Spontaneous andself-assembled process. Vapor-solid (VS) growth mechanism is proposed for theformation of the treelike nanostructures because catalyst was not introduced duringthe synthesis process. The simultaneous control of nanocrystal size and shapetogether with the possibility of growing hierarchical nanostructures on certainnanocrystal facets opens up novel routes to the synthesis of more sophisticatednanostructures as building blocks for a high efficient spatial resolved photondetector.2. Growth mechanism and photoluminescence properties of zigzag SnO₂ and SnOnanowiresZigzag SnO₂ and SnO nanowires were synthesized by thermal evaporation andcondensation technique. The products were characterized with field emissionscanning electron microscope (FE-SEM), X-ray powder diffraction (XRD),transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectroscopy. The all productsare with the same tetragonal structure. The SnO₂ nanowire has anomalous zigzagmorphology, the length and angle of the two segments are not exactly the same. Thediameter and angle of SnO nanowire are almost invariable in the whole structure. A roomtemperature photoluminescence spectrum of as-synthesized products shows twopeaks: one at 380 nm (3.26 eV), and the other strong peak at 580 nm (2.14 eV). Thegrowth of the nanostructures is a spontaneous and self-assembled process. Thepossible growth mechanism of the products was discussed. This novel zigzag SnO₂nanowire may offer great potential for applications in chemical, optical, electronic,and mechanical fields.3. Temperature dependence of ZnO nanostructures and photoluminescence propertiesIn this paper, different morphologies of ZnO nanostructures are achieved bysimple thermal evaporation of mixed powders of ZnO, In₂O₃ and C at 1100℃onsilicon substrates, the molar ratio of the powders is about 3:1:1. Kinds ofnanostructures are nanosheet arrays, nanocone arrays, nanorod arrays, hexangularnanostructures and nanopin arrays. Moreover, using the XRD, FE-SEM, EDS andPL, the structure, morphologies, chemical compositions, and photoluminescence ofnanostructures were investigated. The influence of the temperature on thenanostructures has been studied. The analysis shows that the high temperature zonehas the high vapor pressure. The self-assembled ZnO buffer layer was first obtainedon the Si substrate, the size of grains of the buffer layer decide the size ofnanostructures. The homoepitaxial growth on the buffer layer make thenanostructures have the same growth direction, which lead to array easily. The lowtemperature zone has the lower vapor pressure, which only caused some Zn droplet.The size of droplets decide the diameter of nanorods. The growth conditions, suchas the carrier gas, the size and the location of catalysts droplet, were considered toimpact the morphology mostly, which need to be confirmed by further research.The room-temperature photoluminescence spectrum indicate there are a UVemission at 380nm, a green emission around 496nm and 492nm. The strong defectemission may due to oxygen vacancy, oxygen antiposition and surface defect.