Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/36147
Title: SYNTHESIS AND STUDY OF ZINC OXIDE NANOSTRUCTURES AND FILMS.
Authors: WEE RUI QI
Keywords: Zinc Oxide, Nanostructure, Film, Synthesis, Chemical, Characterization
Issue Date: 10-Aug-2012
Source: WEE RUI QI (2012-08-10). SYNTHESIS AND STUDY OF ZINC OXIDE NANOSTRUCTURES AND FILMS.. ScholarBank@NUS Repository.
Abstract: Zinc oxide (ZnO) is a promising candidate for many applications. Nanostructured ZnO has been gaining a strong foothold as they vastly improve ZnO properties. In this project, nanostructured ZnO and its related compounds are synthesized with sputtering, furnace and hydrothermal methods. Characterization is done with X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), photoluminescence (PL), and vibrating sample magnetometer (VSM). The film thickness is done with surface profilometer. This M. Eng work determines if black ZnO (pure ZnO) exists while investigating properties of the resultant annealed zinc films. The findings disputed this claim. TEM suggested a Zn/ZnO layered structure. The enhanced ultraviolet (UV) emission in ZnO films is attributed to a low annealing temperature of 100 oC as its structure is retained. Zn is able to enhance UV emissions for ZnO film annealed at 200 oC. Zn is also responsible for ferromagnetism in annealed ZnO films. In addition, the synthesis of ZnO by a new method with aqueous sodium chloride is succeeded. Films with network of circular pores to a film with nanowire-like network with bigger pores were obtained. The rise and subsequent decline in green emission could be related to the morphology change over time since ZnO films are obtained within 3 hours of heating. Further investigation demonstrates the importance of nanostructured Zn films in oxidation by aqueous NaCl solution. The model behind pitting corrosion is responsible for nanostructured ZnO films in this study. Finally, this work studied the effect of substrates, heating durations and Ga addition on ZnO by hydrothermal methods. The substrates did not have much significant role in affecting morphologies or optical properties. The thickness of as-synthesized powder grown on substrates can be tuned with heating durations from 4 to 24 hours. It is found that GZO is obtained when 10 and 20 at % of Ga was added in, while ZnGa2O4 is obtained with 30 to 50 at % of Ga introduced. The amount of Ga used for GZO is much larger than typical chemical methods as usually GZO can only tolerate less than 10 at % Ga. Without any Ga introduction, rods with diameter 1-1.5 um and length 10-12 um were grown and arranged in a neat floral arrangement. With 10 at % Ga, hexagonal discs littered with vertically protruding spike-like rods were formed. This is a unique morphology which has not yet been reported. PL spectra showed that the visible emission centers shifted to shorter wavelengths from 2.11 to 2.57 eV with 0, 10 and 20 at % Ga in GZO, suggesting that the Ga dopants contributed to the defects in ZnO. With ZnGa2O4, blue emissions emerged as well though they were blue-shifted drastically to 2.66-2.73 eV. In summary, these studies have sprouted interesting ideas towards nanostructured ZnO, and provided room for further investigations. However, this will be left to the other group members to explore these prospects.
URI: http://scholarbank.nus.edu.sg/handle/10635/36147
Appears in Collections:Master's Theses (Open)

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