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Optical Properties and Wave Propagation in Semiconductor-Based Two-Dimensional Photonic Crystals

Description: This work is a theoretical investigation on the physical properties of semiconductor-based two-dimensional photonic crystals, in particular for what concerns systems embedded in planar dielectric waveguides (GaAs/AlGaAs, GaInAsP/InP heterostructures, and self-standing membranes) or based on macro-porous silicon. The photonic-band structure of photonic crystals and photonic-crystal slabs is numerically computed and the associated light-line problem is discussed, which points to the issue of intr… more
Date: December 31, 2002
Creator: Agio, Mario
Partner: UNT Libraries Government Documents Department
open access

Scalable Computational Chemistry: New Developments and Applications

Description: The computational part of the thesis is the investigation of titanium chloride (II) as a potential catalyst for the bis-silylation reaction of ethylene with hexaclorodisilane at different levels of theory. Bis-silylation is an important reaction for producing bis(silyl) compounds and new C-Si bonds, which can serve as monomers for silicon containing polymers and silicon carbides. Ab initio calculations on the steps involved in a proposed mechanism are presented. This choice of reactants allows … more
Date: December 31, 2002
Creator: Alexeev, Yuri
Partner: UNT Libraries Government Documents Department
open access

Design of Surface Micromachined Compliant MEMS

Description: The consideration of compliant mechanisms as Microelectromechanical Systems (MEMS) is the focus of this research endeavor. MEMS are micron to millimeter devices that combine electrical, mechanical, and information processing capabilities on the same device. These MEMS need some mechanical motion or parts that move relative to each other. This relative motion, using multiple parts, is not desired because of the assembly requirement and the friction introduced. Compliant devices limits or elimina… more
Date: December 31, 2002
Creator: Bradley, Joe Anthony
Partner: UNT Libraries Government Documents Department
open access

Scanning Tunneling Microscopy Studies of Surface Structures of Icosahedral Al-Cu-Fe Quasicrystals

Description: Three papers are included in this dissertation. The first paper: ''Structural aspects of the fivefold quasicrystalline Al-Cu-Fe surface from STM and dynamical LEED studies'', is in press with ''Surface Science''. The second paper: ''An STM study of the atomic structure of the icosahedral Al-Cu-Fe fivefold surface'' is submitted to ''Physical Review B, Rapid Communication''. The third paper: ''Pseudomorphic starfish: arrangement of extrinsic metal atoms on a quasicrystalline substrate'' is submi… more
Date: December 31, 2002
Creator: Cai, Tanhong
Partner: UNT Libraries Government Documents Department
open access

Implementation of MP{_}Lite for the VI Architecture

Description: MP{_}Lite is a light weight message-passing library designed to deliver the maximum performance to applications in a portable and user friendly manner. The Virtual Interface (VI) architecture is a user-level communication protocol that bypasses the operating system to provide much better performance than traditional network architectures. By combining the high efficiency of MP{_}Lite and high performance of the VI architecture, they are able to implement a high performance message-passing libra… more
Date: December 31, 2002
Creator: Chen, Weiyi
Partner: UNT Libraries Government Documents Department
open access

Synthesis and Gas Phase Thermochemistry of Germanium-Containing Compounds

Description: The driving force behind much of the work in this dissertation was to gain further understanding of the unique olefin to carbene isomerization observed in the thermolysis of 1,1-dimethyl-2-methylenesilacyclobutane by finding new examples of it in other silicon and germanium compounds. This lead to the examination of a novel phenylmethylenesilacyclobut-2-ene, which did not undergo olefin to carbene rearrangement. A synthetic route to methylenegermacyclobutanes was developed, but the methyleneger… more
Date: December 31, 2002
Creator: Classen, Nathan Robert
Partner: UNT Libraries Government Documents Department
open access

The Zintl Chemistry of the Heavy Tetrel Elements

Description: Exploration of the alkali metal/alkaline-earth metal/heavy tetrel (Sn or Pb) systems has revealed a vast array of new chemistry and novel structure types. The structures and properties of these new materials have been studied in an attempt to understand the chemistry of these and other related systems. The first phase reported is Rb{sub 4}Pb{sub 9} (K{sub 4}Pb{sub 9} type). The compound contains two different types of Pb{sub 9}{sup 4-} deltahedra, a monocapped square pyramid and a distorted tri… more
Date: December 31, 2002
Creator: Corbett, John D.
Partner: UNT Libraries Government Documents Department
open access

Doping Experiments on Low-Dimensional Oxides and a Search for Unusual Magnetic Properties of MgAlB14

Description: Doping experiments on La{sub 2}CuO{sub 4}, Sr{sub 2}CuO{sub 3} and SrCu{sub 2}(BO{sub 3}){sub 2} were performed with the intent of synthesizing new metallic low-=dimensional cuprate oxide compounds. Magnetic susceptibility {chi}(T) measurements on a polycrystalline La{sub 2}CuO{sub 4} sample chemically oxidized at room temperature in aqueous NaClO showed superconductivity with a superconducting transition temperature T{sub c} of 42.6 K and a Meissner fraction of 26%. They were unable to electro… more
Date: December 31, 2002
Creator: Hill, Julienne Marie
Partner: UNT Libraries Government Documents Department
open access

The Dopants and Doping Level Dependence of the Structure and Magnetic Properties of the Eu (BA1-xLRx)2Cu3O7+Theta

Description: Eu(Ba{sub 1-x}Nd{sub x}){sub 2}Cu{sub 3}O{sub 7+{delta}} were systematically studied in order to understand how the valence of the rear earth elements, ionic sizes and magnetic moment affect the crystal structure and magnetic and electrical properties. Differential thermal analyses were carried out to check the phase purity, X-ray data were least-squares fitted to determine the lattice parameters, and DC-SQUID magnetometry was used to characterize the superconducting properties. These results s… more
Date: December 31, 2002
Creator: Lin, Yu
Partner: UNT Libraries Government Documents Department
open access

High Growth Rate Deposition of Hydrogenated Amorphous Silicon-Germanium Films and Devices Using ECR-PECVD

Description: Hydrogenated amorphous silicon germanium films (a-SiGe:H) and devices have been extensively studied because of the tunable band gap for matching the solar spectrum and mature the fabrication techniques. a-SiGe:H thin film solar cells have great potential for commercial manufacture because of very low cost and adaptability to large-scale manufacturing. Although it has been demonstrated that a-SiGe:H thin films and devices with good quality can be produced successfully, some issues regarding grow… more
Date: May 31, 2002
Creator: Liu, Yong
Partner: UNT Libraries Government Documents Department
open access

Critical Phenomena of the Disorder Driven Localization-Delocalization Transition

Description: Metal-to-insulator transitions are generally linked to two phenomena: electron-electron correlations and disorder. Although real systems are usually responding to a mixture of both, they can be classified as undergoing a Mott-transition, if the former process dominates, or an Anderson-transition, if the latter dominates. High-T{sub c} superconductors, e.g., are a candidate for the first class. Materials in which disorder drives the metal-to-insulator transition include doped semiconductors and … more
Date: December 31, 2002
Creator: Ruhlander, Marc
Partner: UNT Libraries Government Documents Department
open access

CMOS Interface Circuits for Spin Tunneling Junction Based Magnetic Random Access Memories

Description: Magneto resistive memories (MRAM) are non-volatile memories which use magnetic instead of electrical structures to store data. These memories, apart from being non-volatile, offer a possibility to achieve densities better than DRAMs and speeds faster than SRAMs. MRAMs could potentially replace all computer memory RAM technologies in use today, leading to future applications like instan-on computers and longer battery life for pervasive devices. Such rapid development was made possible due to th… more
Date: December 31, 2002
Creator: Saripalli, Ganesh
Partner: UNT Libraries Government Documents Department
open access

Microstructural evolution of eutectic Au-Sn solder joints

Description: Current trends toward miniaturization and the use of lead(Pb)-free solder in electronic packaging present new problems in the reliability of solder joints. This study was performed in order to understand the microstructure and microstructural evolution of small volumes of nominally eutectic Au-Sn solder joints (80Au-20Sn by weight), which gives insight into properties and reliability.
Date: May 31, 2002
Creator: Song, Ho Geon
Partner: UNT Libraries Government Documents Department
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