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• W68851788 abstract "Zinc oxide (ZnO) is one of the most important low dimensional semiconducting oxides owing to the amazing variety of the nanostructures it can form by means of various synthesis routes. The most important methods are the vapor deposition and the chemical bath deposition. ZnO nanostructures have attracted considerable attention in view of several applications they encounter such as optics – optoelectronics, sensors, energy production, biomedical sciences, etc.Despite systematic research concerning the rational growth of ZnO nanostructures for over a decade, the establishment of an experimental methodology capable of providing specific morphologies of ZnO nanostructures in a reproducible way is still an open question. This is also one of the current research challenges because the resulting morphologies are characterized by different physical properties and are quite sensitive to small changes in experimental conditions.The current work is aimed at providing a systematic study of the role of various growth parameters on the morphological features and the optical properties of ZnO nanostructures. Growth was achieved by catalyst-assisted (Au) vapor transport at high temperature (VLS) and by solution chemistry (CBD). It is important to gain understanding about how certain parameters affect the morphology of the nanostructures, the size distributions of the diameters and their orientation relative to the substrate.High temperature evaporation methods, such as the vapor-liquid-solid mechanism, have been exploited for the controlled growth of ZnO nanostructures on various substrates. While Au is the most frequently used catalyst for growing ZnO nanowires, its morphological features on the substrate, which determine the size and shape of the nanostructures grown, are not yet methodically explored. In the current work, we investigated the details of thermal dewetting of Au films into nanoparticles on Si substrates. Au films of various thicknesses, h, ranging from 2 to 15 nm, were annealed under slow and fast rates at various temperatures and the morphological details of the nanoparticles formed were investigated. The vapor-liquid-solid method was employed to investigate the role of the Au nanoparticles on the growth details of ZnO nanowires. Efficient and high throughput growth of ZnO nanowires, for a given growth time, is realized in cases of thin Au films, i.e. when the thickness is lower than 10 nm.In the second case, the influence of a number of parameters such as the thickness of the seed layer, the reactants concentration, the existence of organic compounds, the growth time, etc. on the growth of ZnO nanowires on conducting glass substrates (FTO) was examined. After parameter optimization it was found that ZnO nanowires grown have excellent orientation, perpendicular to the substrate, while their diameter and length were found to be ~30 nm and ~7 μm, respectively. The best growth conditions were achieved using 0.04 Μ ZnAc, 0.02 M HMTA, 0.16 M PEI and 0.04 M NH4OH. The reaction temperature was kept at 95 οC for 1 h to 24 h. The pH value was ~ 7. The alignment of ZnO nanowires deteriorates when their length increases; therefore neighboring nanowires bend forming bundles. This shortcoming has been overcome by employing the renewal of the solution every 2.30 h.The structure of ZnO nanowires was investigated by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Raman scattering was used to study defects of ZnO nanostructures. New Raman modes, in comparison to the bulk crystal, have been assigned to finite size effects and phonon confinement in the nanostructures. Photoluminescence spectroscopy provides evidence for the type of the defects such as oxygen vacancies, zinc interstitials etc." @default.
• W68851788 created "2016-06-24" @default.
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• W68851788 date "2013-09-26" @default.
• W68851788 modified "2023-09-27" @default.
• W68851788 title "Σύνθεση και χαρακτηρισμός της δομής και των οπτικών ιδιοτήτων νανοδομών του ZnO" @default.
• W68851788 hasPublicationYear "2013" @default.
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