Growth And Properties Research Of ZnO And ZnS One-dimensional Nanostructures

Zinc oxide (ZnO) and zinc sulfide (ZnS) one-dimensional (1D) nanomaterials were studied in this article. Based on the insight into the research status at home and abroad, chemical vapor deposition (CVD) method was used to synthesize the1D nanomaterials. We mainly focused on the influence of experimental conditions such as heating temperature, position of the substrate, precursor type and proportion on the synthesis products. The morphologies and microstructures of the products were characterized using X-ray powder diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the growth mechanisms of the corresponding products were also discussed. Additionally, the optical property of the products was tested by cathodoluminescence (CL) measurement.Series of growth experiments have proved that the products on the Si substrate were mainly ZnO nanowires with various nanostructures by heating the precursors of ZnS powders and controlling the reaction conditions. The results clearly showed that ZnO nanowires are terminated with catalyst particles, which confirms that the growth of ZnO nanowires is based on typical VLS mechanism. The CL measurements displayed that ZnO nanowires have strong ultraviolet (UV) peak centered at387nm and strong green peak centered at517nm. When P2O5dopants with different contents were added into the ZnS precursor the morphology of products tends to evolve from ZnO nanowires to ZnS nanobelts. With an optimized ratio of P:Zn:ZnS=6:1:10, the yield of ZnS nanobelts reaches to the highest, and the crystallinity of ZnS nanobelts is perfect. The TEM analyses showed that the typical VS mechanism could be used to illustrate the growth process, and the growth directions of the length and width of the belt are along [0001] and [01-10] in a wurtzite-type hexagonal structure, respectively. Optical property measurements indicated that ZnS nanobelts exhibit a strong NBE UV peak centered at341nm and a weak green peak centered at530nm.Based on the above experiments, ZnO nanosheets with triangular morphology have been synthesized on an Au-coated silicon substrate that placed nearby the precursors through a facile thermal evaporation of ZnS powders in1000℃. The results showed that the ZnO nanosheets possess an average bottom width of2-3μm and a length up to5-7μm. HRTEM analyses indicated the formation mechanism of triangular ZnO nanosheet could be assigned to a combination of a vapor-liquid-solid (VLS) process that is believed to be responsible for its initial nucleation and subsequent crystallization along the growth direction, and a vapor-solid (VS) process that is responsible for (0001) and (-2110) lattice planes for radial growth. The cathodoluminescence (CL) spectra revealed a sharp strong near-band-edge (NBE) UV emission centered at387nm which may be described as a result of the recombination of free excitons through an exciton-exciton collection process, whereas the visible green emission attributed to the defect-induced emissions is so weak, implying the low concentrations of oxygen vacancies and zinc interstitials in ZnO nanosheets and their high crystal quality.