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Investigation of Selected Optically-Active Nanosystems Fashioned using Ion Implantation (open access)

Investigation of Selected Optically-Active Nanosystems Fashioned using Ion Implantation

Opto-electronic semiconductor technology continues to grow at an accelerated pace, as the industry seeks to perfect devices such as light emitting diodes for purposes of optical processing and communication. A strive for greater efficiency with shrinking device dimensions, continually pushes the technology from both a design and materials aspect. Nanosystems such a quantum dots, also face new material engineering challenges as they enter the realm of quantum mechanics, with each system and material having markedly different electronic properties. Traditionally, the semiconductor industry has focused on materials such Group II-VI and III-V compounds as the basis material for future opto-electronic needs. Unfortunately, these material systems can be expensive and have difficulties integrating into current Si-based technology. The industry is reluctant to leave silicon due in part to silicon's high quality oxide, and the enormous amount of research invested into silicon based circuit fabrication. Although recently materials such as GaN are starting to dominate the electro-optical industry since a Si-based substitute has not been found. The purpose of the dissertation was to examine several promising systems that could be easily integrated into current Si-based technology and also be produced using simple inexpensive fabrication techniques such ion implantation. The development of optically active …
Date: May 2006
Creator: Mitchell, Lee
System: The UNT Digital Library

Characterization, Properties and Applications of Novel Nanostructured Hydrogels.

Access: Use of this item is restricted to the UNT Community
The characterization, properties and applications of the novel nanostructured microgel (nanoparticle network and microgel crystal) composed of poly-N-isopropylacrylanmide-co-allylamine (PNIPAM-co-allylamine) and PNIPAM-co-acrylic acid(AA) have been investigated. For the novel nanostructured hydrogels with the two levels of structure: the primary network inside each individual particle and the secondary network of the crosslinked nanoparticles, the new shear modulus, drug release law from hydrogel with heterogeneous structure have been studied. The successful method for calculating the volume fraction related the phase transition of colloid have been obtained. The kinetics of crystallization in an aqueous dispersion of PNIPAM particles has been explored using UV-visible transmission spectroscopy. This dissertation also includes the initial research on the melting behavior of colloidal crystals composed of PNIPAM microgels. Many new findings in this study area have never been reported before. The theoretical model for the columnar crystal growth from the top to bottom of PNIPAM microgel has been built, which explains the growth mechanism of the novel columnar hydrogel colloidal crystals. Since the unique structure of the novel nanostructured hydrogels, their properties are different with the conventional hydrogels and the hard-sphere-like system. The studies and results in this dissertation have the important significant for theoretical study and valuable application …
Date: December 2006
Creator: Tang, Shijun
System: The UNT Digital Library
Ion-Induced Damage In Si: A Fundamental Study of Basic Mechanisms over a Wide Range of Implantation Conditions (open access)

Ion-Induced Damage In Si: A Fundamental Study of Basic Mechanisms over a Wide Range of Implantation Conditions

A new understanding of the damage formation mechanisms in Si is developed and investigated over an extended range of ion energy, dose, and irradiation temperature. A simple model for dealing with ion-induced damage is proposed, which is shown to be applicable over the range of implantation conditions. In particular the concept of defect "excesses" will be discussed. An excess exists in the lattice when there is a local surplus of one particular type of defect, such as an interstitial, over its complimentary defect (i.e., a vacancy). Mechanisms for producing such excesses by implantation will be discussed. The basis of this model specifies that accumulation of stable lattice damage during implantation depends upon the excess defects and not the total number of defects. The excess defect model is validated by fundamental damage studies involving ion implantation over a range of conditions. Confirmation of the model is provided by comparing damage profiles after implantation with computer simulation results. It will be shown that transport of ions in matter (TRIM) can be used effectively to model the ion-induced damage profile, i.e. excess defect distributions, by a simple subtraction process in which the spatially correlated defects are removed, thereby simulating recombination. Classic defect studies …
Date: May 2006
Creator: Roth, Elaine Grannan
System: The UNT Digital Library
Modeling and Optimization of Deflection Slits for Fast-Pulsing a Low Energy Ion Beam (open access)

Modeling and Optimization of Deflection Slits for Fast-Pulsing a Low Energy Ion Beam

Honors thesis written by a student in the UNT Honors College discussing the deflection of ion beams to simulate ion flight.
Date: Spring 2006
Creator: Bosca, Ryan
System: The UNT Digital Library