Fabrication Of Tin Dioxide Nanomaterials By Chemical Vapour Deposition

SnO₂ is an n-type semiconductor with a wide band gap (Eg = 3.6 eV, at 300 K) and well-known for its potential applications in optoelectronic devices, gas sensors, photocataiysts, nanofiltration membranes, glasscoatings, transparent electrodes in solar cells and anode materials in lithium batteries.One-dimensional undoped and Sb doped SnO₂ nanomaterials with different morphographies have been synthesized using a lot of growth processes. The structure, morphology and character of the nanomaterials were employed by the X-ray diffraction (XRD), transmission election microscopy(TEM), field emission scanning electron microscope (FE-SEM), photoluminescence apparatus(PL) and so on. The main contents are as follows:1. Porous adonic aluminum oxide templates are widely used to fabricate nanowires or nanotubes of many materials. We have prepared porous alumina templates using oxalic acid as electrolyte. The membrane prepared through a two-step oxidation process has regular-arranged nanopores. The channels of the template are parallel and the diameters of the nanopores are uniform, which could be altered in the range of 30-100 nm by enlarging treatment.2. Intriguing one-dimensional (1D) nanostructures of SnO₂, including nanowires, dendritic nanorods and falchion-like nanosheets, have been prepared by chemical vapor deposition (CVD) method. To meet the needs of large-scale, controllable, and designable synthesis of nanostructures, it is crucial to systematically study the experimental conditions under which the desired nanostructures can be synthesized reproducibly in large quantity and with controllable morphology. The most important factors that influence the morphology of the product are temperature and template. The effects of temperature and anodic aluminum oxide (AAO) template with or without Au catalyst particles on the morphology of the final product were studied in our work. The growth mechanism is also tried to explain.3. The Sb doped ladder-shaped SnO₂ nanostructure have been prepared by thermal evaporation of tin grains and antimony powders on gold filled anode aluminum oxide (AAO). Here the gold nanoparticles embedded in AAO act as catalyst. The as-synthesized Sb doped SnO₂ appeares to be single crystals. Room temperature photoluminescence (PL) spectra of the undoped SnO₂ display green emission band. But the peaks of the Sb doped SnO₂ red shift a lot compared with the undoped SnO₂, which should be caused by the doped of Sb. The doped content of Sb influences the morphology of samples. And the redundant Sb makes the dopping invalid.4. Carbon nanotubes have the defects of easily bending and entangling with each other. Many organic or inorganic materials could be coated on the surface of carbon nanotube. However, most of the coatings are amorphous or poly-crystalline.The single-crystals have been attempted to coat on the surfaces of carbon nanotubes to form nanotube-monocrystalline-coating composite tubes. In our experiment, single-crystalline SnO₂ coating is successfully overgrown onto the surfaces of carbon nanotubes. Bearded crystal SnO₂ are found, which can be caused by nanoparticles attaching to carbon nanotuble or be arosed by Au which may be introduced by the decomposed of HAuCl.