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  Partner: UNT Libraries
 Degree Discipline: Physics
 Collection: UNT Theses and Dissertations
Scanning Tunneling Microscopy of Epitaxial Diamond (110) and (111) Films and Field Emission Properties of Diamond Coated Molybdenum Microtips

Scanning Tunneling Microscopy of Epitaxial Diamond (110) and (111) Films and Field Emission Properties of Diamond Coated Molybdenum Microtips

Date: May 1998
Creator: Lim, Seong-Chu
Description: The growth mechanism of chemical vapor deposition (CVD) grown homo-epitaxial diamond (110) and (111) films was studied using ultrahigh vacuum (UHV) scanning tunneling microscopy (STM). In addition, the field emission properties of diamond coated molybdenum microtips were studied as a function of exposure to different gases.
Contributing Partner: UNT Libraries
Scaling Behaviors and Mechanical Properties of Polymer Gels

Scaling Behaviors and Mechanical Properties of Polymer Gels

Date: May 1994
Creator: Li, Chʻun-fang
Description: Polymer gels undergo a volume phase transition in solvent in response to an infinitesimal environmental change. This remarkable phenomenon has resulted in many potential applications of polymer gels. The understanding of its mechanical properties has both scientific and technological importance. For this purpose, we have developed a novel method for measuring Poisson's ratio, which is one of the most important parameters determining the mechanical property of gels. Using this method, Poisson's ratio in N-isopropyacrylamide (NIPA) and polyacrylamide (PAAM) gels has been studied.
Contributing Partner: UNT Libraries
Accelerator Mass Spectrometry Studies of Highly Charged Molecular Ions

Accelerator Mass Spectrometry Studies of Highly Charged Molecular Ions

Date: December 1994
Creator: Kim, Yong-Dal
Description: The existence of singly, doubly, and triply charged diatomic molecular ions was observed by using an Accelerator Mass Spectrometry (AMS) technique. The mean lifetimes of 3 MeV boron diatomic molecular ions were measured. No isotopic effects on the mean lifetimes of boron diatomic molecules were observed for charge state 3+. Also, the mean lifetime of SiF^3+ was measured.
Contributing Partner: UNT Libraries
Experimental Synchronization of Chaotic Attractors Using Control

Experimental Synchronization of Chaotic Attractors Using Control

Date: December 1994
Creator: Newell, Timothy C. (Timothy Charles)
Description: The focus of this thesis is to theoretically and experimentally investigate two new schemes of synchronizing chaotic attractors using chaotically operating diode resonators. The first method, called synchronization using control, is shown for the first time to experimentally synchronize dynamical systems. This method is an economical scheme which can be viably applied to low dimensional dynamical systems. The other, unidirectional coupling, is a straightforward means of synchronization which can be implemented in fast dynamical systems where timing is critical. Techniques developed in this work are of fundamental importance for future problems regarding high dimensional chaotic dynamical systems or arrays of mutually linked chaotically operating elements.
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Charge State Dependence of M-Shell X-Ray Production in 67Ho by 2-12 MeV Carbon Ions

Charge State Dependence of M-Shell X-Ray Production in 67Ho by 2-12 MeV Carbon Ions

Date: August 1994
Creator: Sun, Hsueh-Li
Description: The charge state dependence of M-shell x-ray production cross sections of 67HO bombarded by 2-12 MeV carbon ions with and without K-vacancies are reported. The experiment was performed using an NEC 9SDH-2 tandem accelerator at the Ion Beam Modification and Analysis Laboratory of the University of North Texas. The high charge state carbon ions were produced by a post-accelerator stripping gas cell. Ultra-clean holmium targets were used in ion-atom collision to generate M-shell x rays at energies from 1.05 to 1.58 keV. The x-ray measurements were made with a windowless Si(Li) x-ray detector that was calibrated using radiative sources, particle induced x-ray emission (PIXE), and the atomic field bremsstrahlung (AFB) techniques.
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Deterministic Brownian Motion

Deterministic Brownian Motion

Date: August 1993
Creator: Trefán, György
Description: The goal of this thesis is to contribute to the ambitious program of the foundation of developing statistical physics using chaos. We build a deterministic model of Brownian motion and provide a microscpoic derivation of the Fokker-Planck equation. Since the Brownian motion of a particle is the result of the competing processes of diffusion and dissipation, we create a model where both diffusion and dissipation originate from the same deterministic mechanism - the deterministic interaction of that particle with its environment. We show that standard diffusion which is the basis of the Fokker-Planck equation rests on the Central Limit Theorem, and, consequently, on the possibility of deriving it from a deterministic process with a quickly decaying correlation function. The sensitive dependence on initial conditions, one of the defining properties of chaos insures this rapid decay. We carefully address the problem of deriving dissipation from the interaction of a particle with a fully deterministic nonlinear bath, that we term the booster. We show that the solution of this problem essentially rests on the linear response of a booster to an external perturbation. This raises a long-standing problem concerned with Kubo's Linear Response Theory and the strong criticism against it by van ...
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Linear, Nonlinear Optical and Transport Properties of Quantum Wells Composed of Short Period Strained InAs/GaAs Superlattices

Linear, Nonlinear Optical and Transport Properties of Quantum Wells Composed of Short Period Strained InAs/GaAs Superlattices

Date: December 1993
Creator: Huang, Xuren
Description: In this work, ordered all-binary short-period strained InAs/GaAs superlattice quantum wells were studied as an alternative to strained ternary alloy InGaAs/GaAs quantum wells. InGaAs quantum wells QWs have been of great interest in recent years due to the great potential applications of these materials in future generations of electronic and optoelectronic devices. The all binary structures are expected to have all the advantages of their ternary counterparts, plus several additional benefits related to growth, to the elimination of alloy disorder scattering and to the presence of a higher average indium content.
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Magneto-Optical and Chaotic Electrical Properties of n-InSb

Magneto-Optical and Chaotic Electrical Properties of n-InSb

Date: December 1991
Creator: Song, Xiang-Ning
Description: This thesis investigation concerns the optical and nonlinear electrical properties of n-InSb. Two specific areas have been studied. First is the magneto-optical study of magneto-donors, and second is the nonlinear dynamic study of nonlinear and chaotic oscillations in InSb. The magneto-optical study of InSb provides a physical picture of the magneto-donor levels, which has an important impact on the physical model of nonlinear and chaotic oscillations. Thus, the subjects discussed in this thesis connect the discipline of semiconductor physics with the field of nonlinear dynamics.
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Studies of Particles and Wave Propagation in Periodic and Quasiperiodic Nonlinear Media

Studies of Particles and Wave Propagation in Periodic and Quasiperiodic Nonlinear Media

Date: May 1995
Creator: Sun, Ning, 1963-
Description: This thesis examines the properties of transmission and transport of light and charged particles in periodic or quasiperiodic systems of solid state and optics, especially the nonlinear and external field effects and the dynamic properties of these systems.
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Angular Dependence of the Stopping Processes and the Yields of Ion-induced Electron Emission from Channeled MEV Protons in <100> Silicon Foils

Angular Dependence of the Stopping Processes and the Yields of Ion-induced Electron Emission from Channeled MEV Protons in <100> Silicon Foils

Date: December 1993
Creator: Zhao, Zhiyong
Description: The present work reports the experimental evidence of anomalous energy loss, energy straggling, and the corresponding ion-induced electron emission yields of channeled protons in silicon.
Contributing Partner: UNT Libraries