33 Matching Results

Search Results

Results: 1 - 24 next

Brownian Movement and Quantum Computers

Description: This problem in lieu of thesis is a discussion of two topics: Brownian movement and quantum computers. Brownian movement is a physical phenomenon in which the particle velocity is constantly undergoing random fluctuations. Chapters 2, 3 and 4, describe Brownian motion from three different perspectives. The next four chapters are devoted to the subject of quantum computers, which are the signal of a new era of technology and science combined together. In the first chapter I present to a reader … more
Access: Restricted to UNT Community Members. Login required if off-campus.
Date: December 2004
Creator: Habel, Agnieszka
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Development of a Hybrid Molecular Ultraviolet Photodetector based on Guanosine Derivatives

Description: Modern studies on charge transfer reaction and conductivity measurements of DNA have shown that the electrical behavior of DNA ranges from that of an insulator to that of a wide bandgap semiconductor. Based on this property of DNA, a metal-semiconductor-metal photodetector is fabricated using a self-assembled layer of deoxyguanosine derivative (DNA base) deposited between gold electrodes. The electrodes are lithographically designed on a GaN substrate separated by a distance L (50nm < L < 100nm… more
Access: Restricted to the UNT Community Members at a UNT Libraries Location.
Date: December 2005
Creator: Liddar, Harsheetal
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Surface Plasmon Based Nanophotonic Optical Emitters

Description: Group- III nitride based semiconductors have emerged as the leading material for short wavelength optoelectronic devices. The InGaN alloy system forms a continuous and direct bandgap semiconductor spanning ultraviolet (UV) to blue/green wavelengths. An ideal and highly efficient light-emitting device can be designed by enhancing the spontaneous emission rate. This thesis deals with the design and fabrication of a visible light-emitting device using GaN/InGaN single quantum well (SQW) system wit… more
Access: Restricted to the UNT Community Members at a UNT Libraries Location.
Date: December 2005
Creator: Vemuri, Padma Rekha
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Investigation of Selected Optically-Active Nanosystems Fashioned using Ion Implantation

Description: 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 ma… more
Date: May 2006
Creator: Mitchell, Lee
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Anderson Localization in Two-Channel Wires with Correlated Disorder: DNA as an Application

Description: This research studied the Anderson localization of electrons in two-channel wires with correlated disorder and in DNA molecules. It involved an analytical calculation part where the formula for the inverse localization length for electron states in a two-channel wire is derived. It also involved a computational part where the localization length is calculated for some DNA molecules. Electron localization in two-channel wires with correlated disorder was studied using a single-electron tight-bi… more
Date: December 2007
Creator: Bagci, V. M. Kemal
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Multifunctional Organic-Inorganic Hybrid Nanophotonic Devices

Description: The emergence of optical applications, such as lasers, fiber optics, and semiconductor based sources and detectors, has created a drive for smaller and more specialized devices. Nanophotonics is an emerging field of study that encompasses the disciplines of physics, engineering, chemistry, biology, applied sciences and biomedical technology. In particular, nanophotonics explores optical processes on a nanoscale. This dissertation presents nanophotonic applications that incorporate various fo… more
Date: May 2008
Creator: Garner, Brett William
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Oligonucleotide guanosine conjugated to gallium nitride nano-structures for photonics.

Description: In this work, I studied the hybrid system based on self-assembled guanosine crystal (SAGC) conjugated to wide-bandgap semiconductor gallium nitride (GaN). Guanosine is one of the four bases of DNA and has the lowest oxidation energy, which favors carrier transport. It also has large dipole moment. Guanosine molecules self-assemble to ribbon-like structure in confined space. GaN surface can have positive or negative polarity depending on whether the surface is Ga- or N-terminated. I studied… more
Date: August 2008
Creator: Li, Jianyou
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

A Study of the Synthesis and Surface Modification of UV Emitting Zinc Oxide for Bio-Medical Applications

Description: This thesis presents a novel ZnO-hydrogel based fluorescent colloidal semiconductor nanomaterial system for potential bio-medical applications such as bio-imaging, cancer detection and therapy. The preparation of ZnO nanoparticles and their surface modification to make a biocompatible material with enhanced optical properties is discussed. High quality ZnO nanoparticles with UV band edge emission are prepared using gas evaporation method. Semiconductor materials including ZnO are insoluble in w… more
Date: May 2009
Creator: John, Sween
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Growth and Characterization of β-Iron Disilicide, β-Iron Silicon Germanide, and Osmium Silicides

Description: The semiconducting silicides offer significant potential for use in optoelectronic devices. Full implementation of the materials, however, requires the ability to tailor the energy gap and band structure to permit the synthesis of heterojunctions. One promising approach is to alloy the silicides with Ge. As part of an investigation into the synthesis of semiconducting silicide heterostructures, a series of β-Fe(Si1−xGex)2 epilayer samples, with nominal alloy content in the range 0 < x < 0.15, h… more
Date: August 2009
Creator: Cottier, Ryan James
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

High Efficiency High Power Blue Laser by Resonant Doubling in PPKTP

Description: I developed a high power blue laser for use in scientific and technical applications (eg. precision spectroscopy, semiconductor inspection, flow cytometry, etc). It is linearly polarized, single longitudinal and single transverse mode, and a convenient fiber coupled continuous wave (cw) laser source. My technique employs external cavity frequency doubling and provides better power and beam quality than commercially available blue diode lasers. I use a fiber Bragg grating (FBG) stabilized infr… more
Date: August 2011
Creator: Danekar, Koustubh
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Nanoscale Materials Applications: Thermoelectrical, Biological, and Optical Applications with Nanomanipulation Technology

Description: In a sub-wavelength scale, even approaching to the atomic scale, nanoscale physics shows various novel phenomena. Since it has been named, nanoscience and nanotechnology has been employed to explore and exploit this small scale world. For example, with various functionalized features, nanowire (NW) has been making its leading position in the researches of physics, chemistry, biology, and engineering as a miniaturized building block. Its individual characteristic shows superior and unique featur… more
Date: August 2011
Creator: Lee, Kyung-Min
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Development of Indium Oxide Nanowires as Efficient Gas Sensors

Description: Crystalline indium oxide nanowires were synthesized following optimization of growth parameters. Oxygen vacancies were found to impact the optical and electronic properties of the as-grown nanowires. Photoluminescence measurements showed a strong U.V emission peak at 3.18 eV and defect peaks in the visible region at 2.85 eV, 2.66 eV and 2.5 eV. The defect peaks are attributed to neutral and charged states of oxygen vacancies. Post-growth annealing in oxygen environment and passivation with sulp… more
Date: December 2011
Creator: Gali, Pradeep
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Effects of Dissipation on Propagation of Surface Electromagnetic and Acoustic Waves

Description: With the recent emergence of the field of metamaterials, the study of subwavelength propagation of plane waves and the dissipation of their energy either in the form of Joule losses in the case of electomagnetic waves or in the form of viscous dissipation in the case of acoustic waves in different interfaced media assumes great importance. with this motivation, I have worked on problems in two different areas, viz., plasmonics and surface acoustics. the first part (chapters 2 & 3) of the disser… more
Date: May 2012
Creator: Nagaraj, Nagaraj
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Electrostatic Effects in III-V Semiconductor Based Metal-optical Nanostructures

Description: The modification of the band edge or emission energy of semiconductor quantum well light emitters due to image charge induced phenomenon is an emerging field of study. This effect observed in quantum well light emitters is critical for all metal-optics based light emitters including plasmonics, or nanometallic electrode based light emitters. This dissertation presents, for the first time, a systematic study of the image charge effect on semiconductor–metal systems. the necessity of introducing … more
Date: May 2012
Creator: Gryczynski, Karol Grzegorz
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Electrostatic Mechanism of Emission Enhancement in Hybrid Metal-semiconductor Light-emitting Heterostructures

Description: III-V nitrides have been put to use in a variety of applications including laser diodes for modern DVD devices and for solid-state white lighting. Plasmonics has come to the foreground over the past decade as a means for increasing the internal quantum efficiency (IQE) of devices through resonant interaction with surface plasmons which exist at metal/dielectric interfaces. Increases in emission intensity of an order of magnitude have been previously reported using silver thin-films on InGaN/GaN… more
Date: May 2012
Creator: Llopis, Antonio
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Ultrafast Spectroscopy of Hybrid Ingan/gan Quantum Wells

Description: Group III nitrides are efficient light emitters. The modification of internal optoelectronic properties of these materials due to strain, external or internal electric field are an area of interest. Insertion of metal nanoparticles (MNPs) (Ag, Au etc) inside the V-shaped inverted hexagonal pits (IHP) of InGaN/GaN quantum wells (QWs) offers the potential of improving the light emission efficiencies. We have observed redshift and blueshift due to the Au MNPs and Ag MNPs respectively. This sh… more
Date: August 2012
Creator: Mahat, Meg Bahadur
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Broad-band Light Emission From Ion Implanted Silicon Nanocrystals Via Plasmonic and Non-plasmonic Effects for Optoelectronics

Description: Broad band light emission ranging from the ultraviolet (UV) to the near infrared (NIR) has been observed from silicon nanoparticles fabricated using low energy (30-45 keV) metal and non-metal ion implantation with a fluence of 5*1015 ions/cm2 in crystalline Si(100). It is found from a systematic study of the annealing carried out at certain temperatures that the spectral characteristics remains unchanged except for the enhancement of light emission intensity due to annealing. The annealing resu… more
Date: December 2012
Creator: Singh, Akhilesh K.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Zinc Oxide Nanoparticles for Nonlinear Bioimaging, Cell Detection and Selective Cell Destruction

Description: Light matter interactions have led to a great part of our current understanding of the universe. When light interacts with matter it affects the properties of both the light and the matter. Visible light, being in the region that the human eye can "see," was one of the first natural phenomenon we used to learn about our universe. The application of fundamental physics research has spilled over into other fields that were traditionally separated from physics, being considered two different scien… more
Date: May 2013
Creator: Urban, Ben E.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Development of High Gain Ultraviolet Photo Detectors Based on Zinc Oxide Nanowires

Description: Semiconductor nanowires acts as an emerging class of materials with great potential for applications in future electronic devices. Small size, large surface to volume ratio and high carrier mobility of nanowires make them potentially useful for electronic applications with high integration density. In this thesis, the focus was on the growth of high quality ZnO nanowires, fabrication of field effect transistors and UV- photodetectros based on them. Intrinsic nanowire parameters such as carrier … more
Date: May 2014
Creator: Mallampati, Bhargav
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Electromagnetically Modulated Sonic Structures

Description: Phononic crystals are structures composed of periodically arranged scatterers in a background medium that affect the transmission of elastic waves. They have garnered much interest in recent years for their macro-scale properties that can be modulated by the micro-scale components. The elastic properties of the composite materials, the contrast in the elastic properties of the composite materials, and the material arrangement all directly affect how an elastic wave will behave as it propagates … more
Date: May 2014
Creator: Walker, Ezekiel Lee
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Synthesis Strategies and a Study of Properties of Narrow and Wide Band Gap Nanowires

Description: Various techniques to synthesize nanowires and nanotubes as a function of growth temperature and time were investigated. These include growth of nanowires by a chemical vapor deposition (CVD) system using vapor-liquid-solid (VLS) growth mechanism and electro-chemical synthesis of nanowires and nanotubes. Narrow band gap InSb Eg = 0.17 eV at room temp) nanowires were successively synthesized. Using a phase diagram, the transition of the nanowire from metallic- semiconducting- semi-metallic phase… more
Date: May 2014
Creator: Sapkota, Gopal
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Interaction of Plasmons and Excitons for Low-Dimension Semiconductors

Description: The effects of surface plasmon for InGaN/GaN multi-quantum wells and ZnO nanoparticles optical linear and nonlinear emission efficiency had been experimentally studied. Due to the critical design for InGaN MQWs with inverted hexagonal pits based on GaN, both contribution of surface plasmon effect and image charge effect at resonant and off resonant frequencies were experimentally and theoretically investigated. With off- resonant condition, the InGaN MQWs emission significantly enhanced by meta… more
Date: December 2014
Creator: Lin, Jie (physicist)
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Enhancement of Light Emission from Metal Nanoparticles Embedded Graphene Oxide

Description: A fully oxidized state of graphene behaves as a pure insulating while a pristine graphene behaves as a pure conducting. The in-between oxide state in graphene which is the controlled state of oxide behaves as a semiconducting. This is the key condition for tuning optical band gap for the better light emitting property. The controlling method of oxide in graphene structure is known as reduction which is the mixed state of sp2 and sp3 hybrid state in graphene structure. sp2 hybridized domains cor… more
Date: May 2016
Creator: Karna, Sanjay K.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Elucidation of Photoinduced Energy and Electron Transfer Mechanisms in Multimodular Artificial Photosynthetic Systems

Description: Multimodular designs of electron donor-acceptor systems are the ultimate strategy in fabricating antenna-reaction center mimics for artificial photosynthetic applications. The studied photosystems clearly demonstrated efficient energy transfer from the antenna system to the primary electron donor, and charge stabilization of the radical ion pair achieved with the utilization of secondary electron donors that permits either electron migration or hole transfer. Moreover, the molecular arrangement… more
Date: May 2017
Creator: Lim, Gary Lloyd
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
Back to Top of Screen