ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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- Creators: Palais, Joseph C.
Another design is a hexagonal checkerboard surface that achieves the same RCS reduction bandwidth because it combines the same EBG designs. The hexagonal checkerboard design further reduce the RCS than square checkerboard designs because the reflected energy is re-directed toward six directions and a null remains in the normal direction.
A dual frequency band checkerboard surface with 10-dB RCS reduction bandwidths of 61% and 24% is realized by utilizing two dual-band EBG structures, while the surfaces maintain scattering in four quadrants. The first RCS reduction bandwidth of the dual band is basically the same as in the square checkerboard design; however, the present surface exhibits a second frequency band of 10-dB RCS reduction.
Finally, cylindrically curved checkerboard surfaces are designed and examined for three different radii of curvature. Both narrow and wide band curved checkerboard surfaces are evaluated under normal incidence for both horizontal and vertical polarizations. Simulated bistatic RCS patterns of the cylindrical checkerboard surfaces are presented.
For all designs, bistatic and monostatic RCS of each checkerboard surface design are compared to that of the corresponding PEC surface. The monostatic simulations are also compared with measurements as a function of frequency and polarization. A very good agreement has been attained throughout.
In the first part of my research, I selected chalcogenides (such as CdS and CdSe) for a comprehensive study in growing two-segment axial nanowires and radial nanobelts/sheets using the ternary CdSxSe1-x alloys. I demonstrated simultaneous red (from CdSe-rich) and green (from CdS-rich) light emission from a single monolithic heterostructure with a maximum wavelength separation of 160 nm. I also demonstrated the first simultaneous two-color lasing from a single nanosheet heterostructure with a wavelength separation of 91 nm under sufficiently strong pumping power.
In the second part, I considered several combinations of source materials with different growth methods in order to extend the spectral coverage of previously demonstrated structures towards shorter wavelengths to achieve full-color emissions. I achieved this with the growth of multisegment heterostructure nanosheets (MSHNs), using ZnS and CdSe chalcogenides, via our novel growth method. By utilizing this method, I demonstrated the first growth of ZnCdSSe MSHNs with an overall lattice mismatch of 6.6%, emitting red, green and blue light simultaneously, in a single furnace run using a simple CVD system. The key to this growth method is the dual ion exchange process which converts nanosheets rich in CdSe to nanosheets rich in ZnS, demonstrated for the first time in this work. Tri-chromatic white light emission with different correlated color temperature values was achieved under different growth conditions. We demonstrated multicolor (191 nm total wavelength separation) laser from a single monolithic semiconductor nanostructure for the first time. Due to the difficulties associated with growing semiconductor materials of differing composition on a given substrate using traditional planar epitaxial technology, our nanostructures and growth method are very promising for various device applications, including but not limited to: illumination, multicolor displays, photodetectors, spectrometers and monolithic multicolor lasers.