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

Recently, quasi-one dimensional nanoscale materials, such as nanotube, nanowire and nanobelt, have received considerable attentions due to not only their novel physical and chemical properties compared with those of their bulk counterparts, but also their potential applications in the fields of electronic, magnetic recording, optoelectronic and so on, therefore, it become the frontier and focus of nano-materials In this paper, several quasi-one dimensional nanoscale materials (silica nanotube, gallium oxide nanostructures and gallium nitride nanowire arrays) have been prepared and their physics properties and growth mechanism had also been studied. The main results and conclusions can be summarized as following: 1. Research on synthesis and photoluminescence properties of silica nanotubeWith liquid Ga as medium, large quantities of silica nanotube are synthesized by thermal evaporation. The average diameter of these nanotubes is about 70-100nm with smooth surface and even diameter. Through the analysis of EDS, Si/O occupies 2/3 in the product. Further SEM and TEM test shows that the inner diameter of these tubes is very small but the tube wall is thick. It is assumed that due to the concentration gradient of Si in liquid Ga, no silica precipitate in the top of liquid Ga surface, resulting in the formation of tube structure. Room temperature photoluminescence measurements under excitation at 260nm show that the SiOx nanotubes had a strong blue emission at 453nm with two shoulders at 410nm and 480nm respectively, which may be related to oxygen defects.2. Research on Ga₂O₃ nanostructure with thermal evaporationIn the atmosphere of NH3, different morphology of gallium oxide mico/nanostructure is successfully synthesized. After carrying on XRD, SEM, HRTEM tests on these products, we found that the synthesized nanostructure owns good single crystallite structure, and also the morphology in different temperature zones changes in regular. In high-temperature zone, blocky structure observed while in low-temperature zone, it is relatively fine nanowire and nanosheet that are generated. Therefore, we considered that in the growing process of those mico/nanostructure, it is the temperature field that plays decisive role. Some novelspiral nanobelts and tree-like nanotube are also found in our synthesized product. The formation of these is probably relative with the defects in the growing process and secondary nucleation of the crystal. The PL spectrum shows a broad and strong emission band around 510nm, which is probably attributed to O vacancies and Ga-0 vacancy pairs in3. Self-catalytic and Ni-catalytic synthesis of gallium nitride nanowires and the effect on product of different conditionsWe have synthesized high-quality GaN nanowires via two different nucleation and growth mechanisms on the LaAlC>3 substrate. On no Ni distribution area, GaN nanowires nuclear and grow via liquid-phase epitaxy process in which the diameters of the GaN nanowires are determined by the small GaN crystal nuclei. On Ni distribution area, GaN nanowires nuclear and grow via Ni-catalytic VLS process in which the diameters of the GaN nanowires are determined by the Ni-Ga alloy droplets. It is much easier to synthesize GaN nanowires by Ni-catalytic VLS mechanism than by liquid-phase epitaxy mechanism. In addition, we still analysis the effect on GaN nanowire growth process of different parameters, including catalyst, airtightness of reaction chamber, temperature, chamber pressure, carrying gas capacity, substrate, etc.