Transition metal doped ZnO micro/nanostructures for dilute magnetic semiconductor (DMS) materials
Tan, Yin Mei.
Date of Issue2010
School of Mechanical and Aerospace Engineering
Cobalt-doped Zinc Oxide nanowire arrays were desired to fabricate using the electrochemical deposition method by varying the potentials, and the temperature, while parameters such as concentration of the chemicals, deposition time were held constant. However, though after varying potential and temperature and changes to the 24 experiments were made, nanowires arrays are still not achieved. Instead, Cobalt-doped Zinc Oxide microrods arrays were fabricated. The microrods arrays were found to possess different orientation order and density level which may be due to variation in potential and temperature. The nucleation, growth process and morphology of the nanorods reflect strong dependencies on the potential, temperature applied and silicon wafer used in the fabrication. Characterization of microrods was done using scanning electron microscope (SEM) and X-ray energy dispersive spectroscopy (EDS). It was shown that an appropriate potential is needed for the growth of hexagonal crystal shaped microrods due to the high free energy barrier of activation hindering its nucleation on bare silicon wafer. Growth and morphology of the microrods were also found out to be dependent on the temperature. In addition, by enhancing on the heating effect to the electrolyte and using a lower resistivity of silicon wafer, increasing density of Cobalt-doped Zinc Oxide was also achieved which will be illustrated with SEM micrograph. It was investigated that it was difficult for cobalt to dope in the structure of zinc oxide when analysed through EDS. Last but not least, failure to fabricate Cobalt-doped Zinc Oxide nanowires was also analysed and possible solutions were proposed. The fabrication of the nanotubes from the grown nanowires using past year samples was carried out by varying the duration of etching time from 24 hours to 10 days. The depth of etching from the tips of the nanowires was found to be etched when 2.0 mmol of methenamine solution was used in room temperature with increasing duration. The effect of etching can be illustrated through the surface morphology of the nanowires as shown in the respective SEM micrographs.
DRNTU::Engineering::Materials::Microelectronics and semiconductor materials
Final Year Project (FYP)
Nanyang Technological University
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