Research On Preparation, Characterization And Growth Mechanism And Spectroscopic Of Based-Zn Nanomaterials

Based-Zn nanomaterials, an important wide band gap semiconductor material, exhibit excellent optical and electrical properties. In this thesis, the thermal evaporation method, the hydrothermal synthesis method and two-steps synthesis method were respectively used to preparing ZnO, ZnS, and the heterogeneous structure of ZnO/ZnS nanomaterials. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The proper growth mechanism is proposed based on results of SEM and TEM. Their optical properties are studied by Raman and photoluminescence (PL) spectra. The main contents are as follows:(1) Research on controlled synthesis of multiforms ZnO nanostructures, the influence of substrate temperature on the growth of nanostructures and growth mechanismMultiforms ZnO nanostructures were successfully synthesized by a thermal evaporation method. A series of experiments were carried on by only to change the distance between the substrate and the evaporation source (ZnS powder as raw material), while other conditions were unchanged. Multiforms ZnO nanostructures, such as nanofiber, flake, spike the ball, needle nanorods, nanocombs, nanoribbons, spiral microstructres, obsearved by SEM and TEM. The oxygen content of ZnO samples decreases when the substrate temperature decreased. And then the different morphologies of ZnO structures were synthesized.(2) The microstructure and spectroscopy of needle-like ZnO nanorod arraysNeedle-like ZnO nanorod arrays were first synthesized by thermal evaporation ZnS power at certain conditions. The products were characterized in detail by XRD, SEM and TEM. The needle-like ZnO nanorods with a regular hexagonal cross-section are single-crystalline. The diameter of nanorods is between200-300nm with a tip about50nm, while the length is more than10um. Based on results of HRTEM, ZnO nanorods grow along [0001] crystal direction. The Needle-like ZnO nanoarrays can be used as a good field-emission device in the fulter.(3) ZnO/ZnS nanobelts At first, ZnS nanoparticles were synthersized by hydrothermal method in different solution concentrations. It is obsearved that the lower the concentration of solution, the smaller the particle by TEM. Then, ZnO/ZnS nanobelts were preprared by a two-steps synthesis method. ZnS grows on the surface of ZnO nanobelts in ZnS precursor solutions of different concentrations. As the solution concentration increasing, more ZnS particles were wrapped on ZnO nanobelts. ZnS particles epitaxially grow on the surface of ZnO nanobelts at the condition of0.2mol/L solution concentration. It is worth noticed that ZnO/ZnS nanobelts are single-crystalline. The optical properties are studied by Raman and PL spectra. The Raman shifts at348and697cm-1are belong to A1/E1(LO) and SO vibrational modes. The two vibrational modes shift to lower wave number as the solution concentration increasing.