Dissertation
Infrared spectroscopy of zinc oxide and magnesium nanostructures
Washington State University
Doctor of Philosophy (PhD), Washington State University
12/2007
DOI:
https://doi.org/10.7273/000005693
Abstract
Impurities in ZnO nanoparticles andMg nanorods were investigated. ZnO nanopar-
ticles were prepared by a reaction of zinc acetate and sodium hydrogen carbonate. The
presence and source of CO2 impurities in ZnO nanoparticles were studied by infrared
(IR) spectroscopy. Isotopic substitution was used to verify the vibrational frequency
assignment. Isochronal annealing experiments were performed to study the formation
and stability of molecular impurities. The results indicate that the molecules are much
more stable than CO2 adsorbed on bulk ZnO surfaces. IR reflectance spectra of as-grown and hydrogen-annealed ZnO nanoparticles were measured at near-normal incidence. The as-grown particles were semi-insulating and showed reflectance spectra characteristic of insulating ionic crystals. Samples annealed in hydrogen showed a significant increase in electrical conductivity and free-carrier ab-sorption. A difference was observed in the reststrahlen line shape of the conductive sample compared to that of the as-grown sample. The effective medium approximation was applied to model the reflectance and absorption spectra. The agreement between the experimental results and the model suggests that the nanoparticles have inhomogeneous carrier concentrations. Exposure to oxygen for several hours led to a significant decrease in carrier concentration, possibly due to the adsorption of negative oxygen molecules on the nanoparticle surfaces. Cu doped ZnO nanoparticles were prepared by using a zinc acetate/copper acetate precursor. The electronic transitions of Cu2+ ions were observed in the IR absorption spectrum at low temperatures. The high resistivity property of ZnO:Cu nanoparticles was observed. Magnesium hydroxide thin layers were formed by a chemical reaction between magnesium nanorods and water. IR spectroscopy showed hydroxide (OH) vibrational modes. The assignment was verified by reactions with heavy water which produced the expected OD vibrational frequency. A Fano interference was detected for hydroxide layers formed on metallic magnesium. For hydroxide layers on insulating magnesium hydride, however, the line shape was symmetric and no Fano resonance was observed. The results show that the hydroxide layer is thin such that the vibrational motion couples to the free electron continuum of the magnesium metal.
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Details
- Title
- Infrared spectroscopy of zinc oxide and magnesium nanostructures
- Creators
- Win Maw Hlaing Oo
- Contributors
- Matthew D. McCluskey (Chair) - Washington State University, Department of Physics and AstronomySusan L Dexheimer (Committee Member)M Grant Norton (Committee Member) - Washington State University, Honors College
- Awarding Institution
- Washington State University
- Academic Unit
- Materials Science and Engineering Program
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 134
- Identifiers
- 99901054941401842
- Language
- English
- Resource Type
- Dissertation