Vapor-phase Synthesis, Characterization And Photoluminescence Of Quasi-one-dimensional Inorganic Nanomaterials

In this paper, quasi-one-dimensional nanostructured ZnO, ZnS/Zn, doped Ga₂O₃ (ISGO) have been synthesized by thermal evaporation. The morphology, structure, chemical composition and physical properties of these quasi-one-dimensional nanostructures are characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) and photoluminescence (PL) spectroscopy. Some novel methods to synthesize quasi-one-dimensional nanostructures have been developed. The growth mechanisms of one-dimensional nanostructures of different morphologies are further investigated. The relationship between photoluminescence properties and the morphologies is discussed. The following are the main contents and conclusions:1. Growth mechanism and optical properities of ZnO nanostructures synthesized by thermal evaporationMass production of uniform wurtzite ZnO nanowires and wurtzite ZnO nanoscumbs has been achieved by a H₂-assisted thermal evaporation technique. Neither a metal catalyst nor a template was introduced in the synthesis process. X-ray diffraction analysis, scanning electron microscopy and high-resolution transmission electron microscopy observations show that the ZnO nanostructures consist of nanowires, nanosaws with a hexagonal wurtzite structure. The as-synthesized nanowires' diameters are about 100nm. The ZnO nanosaws consist of nanoribbons and nanowires(or nanorod) which are on nanoribbons by self-catalyzed VLS growth. Room-temperature photoluminescence measurement shows that the synthesized structures have a strong broadened emission band at a wavelength of 509nm(2.44eV).2. Bulk-quantity synthesis and photoluminescence properties of ZnS/Zn nanostructuresBulk-quantity of ZnS/Zn structures containing nanoribbon and nanorod have been achieved by a thermal evaporation of a ZnS in Ar+5%H2 ambience. X-raydiffraction analysis indicates the product is mainly composed of hexagonal a-ZnS. By EDS it indicates that there are a few of Zn nanobelts in the as-synthesis. Scanning electron microscopy characterization shows that the structures consist of nanoribbon whose widths are from 200nm to 500nm and lengths are several tens of micronmeters appearing in higher temperature place of the silicon substrate and nanorod whose diameters are from 80nm to 150nm and lengths are from lum to 2um appearing in lower temperature place of the silicon substrate. The HR-TEM and SAED indicate that the growth direction of the nanoribbon is [001]. Room-temperature photoluminescence measurement shows that the synthesized structures have a strong broadened emission band at a wavelength of 495nm(2.51eV).3. Synthesis and optical properties of quaternary oxide In,Sn doped Ga2C>3 (ISGO) nanowiresUniform quaternary oxide ISGO nanowires are successfully synthesized by simple thermal evaporation method using Ga , In metals and SnO powder as the raw materias. The morphology and microstructure of the as-prepared nanowires has been extensively investigated using field-emission scanning electron microscopy (SEM), X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED). XRD, SAED and EDS indicated that synthesized products are single-crystalline with monoclinic /?-Ga2O3 structure doped with In and Sn. A self-catalytic vapor-liquid-solid (VLS) mechanism is proposed for interpreting the growth of quarternary oxide ISGO nanowires. Due to the doping of In and Zn, the emission peak in photoluminescence spectra has red-shifted as well as broadened seriously.