Fabrication And Characterization Of ZnO Nanostructured Materials By Chemical Vapor Deposition Method

The synthesis and the application of semiconducting materials have aroused people's enormous interest because of their unique and novel application in the domains of optics, electrooptic, catalysis, piezoelectricity, and so on. ZnO is a promising material with extensive applications in fabricating electronic and luminescent devices due to its wide direct bandgap (3.37eV) and large exciton binding energy (60meV). But nanometer ZnO displays many properties of electricity, magnetism, optics, chemistry, which is obviously different from body materials. With the presentation of ZnO nanomaterials preparation method, we have synthesized many kinds of ZnO structured nanomaterials in chemical vapor deposition (CVD) method. The structural, componential, and optical properties of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) spectroscopy, and photoluminescence (PL) spectroscopy. Based on the reaction conditions, the growth mechanism of the the ZnO nanostructured materials is also discussed. The main results obtains are as follows,1. ZnO nanorodsZnO nanorods were synthesized over NiCl2-coated Si substrates via a CVD process. The NiCl2 buffer layer was deposited on Si subtrates with dropping method. The as-fabricated nanorods with diameters ranging from 150 nm to 200nm and lengths up to several tens ofmicrometers were ZnO with hexagonal wurtzite structure. The growth of the nanorods does not undergo a conventional VLS mechanism. And the Ni metal particles that were deposited by the simple way of dropping the NiCl2 solution onto the Si substrate can subsequently be used as potential nucleation sites for the ZnO nanorods. 2. ZnO nanoprismsZnO nanoprisms were synthesized on Ce(NO3)3-coated Si(111) substrates via a carbon-thermal evaporation process. The Ce(NO3)3 buffer layer was deposited on Si subtrates with dropping method. In the contract experiment, nanoprisms without pyramids on their tops were prepared. Electron microscopy analyses show that the as-grown hexagonal prism-like platforms, with hexagonal nanopyramids on the tops of them, are pure hexagonal wurtzite single-crystals. Finally, the growth mechanism of the nanostructures was discussed in brief.3. Sn-doped ZnO nanoneedlesWe synthesized Sn-doped ZnO nanoneedles on Si(111) substrates in two steps: sputtering and thermal oxidation. First, a thin layer of the Sn:Zn films was deposited onto the Si(111) substrates in a JCK-500A radio-frequency magnetron sputtering system. Sn-doped ZnO nanoneedles were then grown by simple thermal oxidation of the as-deposited films at 650°C in Ar atmosphere. Based on the reaction conditions, the growth mechanism of the Sn-doped ZnO nanoneedles was also discussed.4. ZnO brush-like nanostructuresZnO brush-like nanostructures were fabricated on polished Si substrates by the simple carbon-thermal reduction method. The brush-like ZnO nanostructures randomly distribute on the substrate. The majority of the brush-like nanostructures are straight but rough, with uniform feature consisting of sets of central axial nanorods, surrounded by radial oriented"nail-like"nanostructures. And the sizes of the nanonails are uniform, composed of a cap and a shaft with a smaller diameter neck, and the average diameter of the shaft is about 100 nm. Based on the testing results, the growth mechanism of the ZnO brush-like nanostructures was discussed.