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Photoexcitation in Superconductors

Description: Dissertation discussing the results of experiments to study the behavior of superconductors under light illumination.
Date: June 1976
Creator: Schuller, Ivan
Partner: UNT Libraries Government Documents Department
open access

Structural and Photoelectron Emission Properties of Chemical Vapor Deposition Grown Diamond Films

Description: The effects of methane (CH4), diborone (B2H6) and nitrogen (N2) concentrations on the structure and photoelectron emission properties of chemical vapor deposition (CVD) polycrystalline diamond films were studied. The diamond films were grown on single-crystal Si substrates using the hot-tungsten filament CVD technique. Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) were used to characterize the different forms of carbon in the films, and the fraction of sp3 carbon to sp3 plus sp2… more
Date: August 1998
Creator: Akwani, Ikerionwu Asiegbu
Partner: UNT Libraries
open access

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

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.
Date: May 1998
Creator: Lim, Seong-Chu
Partner: UNT Libraries
open access

Influence of design and coatings on the mechanical reliability of semiconductor wafers.

Description: We investigate some of the mechanical design factors of wafers and the effect on strength. Thin, solid, pre-stressed films are proposed as a means to improve the bulk mechanical properties of a wafer. Three-point bending was used to evaluate the laser scribe density and chemical processing effect on wafer strength. Drop and strike tests were employed to investigate the edge bevel profile effect on the mechanical properties of the wafer. To characterize the effect of thin films on stren… more
Date: August 2002
Creator: Yoder, Karl J.
Partner: UNT Libraries
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The Effect of Average Grain Size on Polycrystalline Diamond Films

Description: The work function of hydrogen-terminated, polycrystalline diamond was studied using ultraviolet photoelectron spectroscopy. Polycrystalline diamond films were deposited onto molybdenum substrates by electrophoresis for grain sizes ranging from 0.3 to 108 microns. The work function and electron affinity were measured using 21.2 eV photons from a helium plasma source. The films were characterized by x-ray photoelectron spectroscopy to determine elemental composition and the sp2/sp3 carbon fractio… more
Date: May 2002
Creator: Abbott, Patrick Roland
Partner: UNT Libraries
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Device Engineering for Enhanced Efficiency from Platinum(II) Phosphorescent OLEDs

Description: Phosphorescent organic light emitting diodes (PHOLEDs) based on efficient electrophosphorescent dopant, platinum(II)-pyridyltriazolate complex, bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) (Pt(ptp)2) have been studied and improved with respect to power efficiency, external efficiency, chromacity and efficiency roll-off. By studying the electrical and optical behavior of the doped devices and functionality of the various constituent layers, devices with a maximum EQE of 20.8±0.2 % and p… more
Date: August 2010
Creator: Li, Minghang
Partner: UNT Libraries
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Carrier Mobility, Charge Trapping Effects on the Efficiency of Heavily Doped Organic Light-Emitting Diodes, and EU(lll) Based Red OLEDs

Description: Transient electroluminescence (EL) was used to measure the onset of emission delay in OLEDs based on transition metal, phosphorescent bis[3,5-bis(2-pyridyl)-1,2,4-triazolato] platinum(ΙΙ) and rare earth, phosphorescent Eu(hfa)3 with 4'-(p-tolyl)-2,2":6',2" terpyridine (ttrpy) doped into 4,4'-bis(carbazol-9-yl) triphenylamine (CBP), from which the carrier mobility was determined. For the Pt(ptp)2 doped CBP films in OLEDs with the structure: ITO/NPB (40nm)/mcp (10nm)/65% Pt(ptp)2:CBP (2… more
Date: August 2010
Creator: Lin, Ming-Te
Partner: UNT Libraries
open access

Amorphization and De-vitrification in Immiscible Copper-Niobium Alloy Thin Films

Description: While amorphous phases have been reported in immiscible alloy systems, there is still some controversy regarding the reason for the stabilization of these unusual amorphous phases. Direct evidence of nanoscale phase separation within the amorphous phase forming in immiscible Cu-Nb alloy thin films using 3D atom probe tomography has been presented. This evidence clearly indicates that the nanoscale phase separation is responsible for the stabilization of the amorphous phase in such immiscible sy… more
Date: May 2007
Creator: Puthucode Balakrishnan, Anantharamakrishnan
Partner: UNT Libraries
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Growth, Structure and Tribological Properties of Atomic Layer Deposited Lubricious Oxide Nanolaminates

Description: Friction and wear mitigation is typically accomplished by introducing a shear accommodating layer (e.g., a thin film of liquid) between surfaces in sliding and/or rolling contacts. When the operating conditions are beyond the liquid realm, attention turns to solid coatings. Solid lubricants have been widely used in governmental and industrial applications for mitigation of wear and friction (tribological properties). Conventional examples of solid lubricants are MoS2, WS2, h-BN, and graphite;… more
Date: December 2010
Creator: Mensah, Benedict Anyamesem
Partner: UNT Libraries
open access

Electrodeposition of Diamond-like Carbon Films

Description: Electrodeposition of diamond-like carbon (DLC) films was studied on different substrates using two different electrochemical methods. The first electrochemical method using a three-electrode system was studied to successfully deposit hydrogenated DLC films on Nickel, Copper and Brass substrates. The as-deposited films were characterized by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR) and cyclic vol… more
Date: August 2002
Creator: Chen, Minhua
Partner: UNT Libraries

Scanning Tunneling Microscopy of Homo-Epitaxial Chemical Vapor Deposited Diamond (100) Films

Description: Atomic resolution images of hot-tungsten filament chemical-vapor-deposition (CVD) grown epitaxial diamond (100) films obtained in ultrahigh vacuum (UHV) with a scanning tunneling microscope (STM) are reported. A (2x1) dimer surface reconstruction and amorphous atomic regions were observed on the hydrogen terminated (100) surface. The (2x1) unit cell was measured to be 0.51"0.01 x 0.25"0.01 nm2. The amorphous regions were identified as amorphous carbon. After CVD growth, the surface of the epita… more
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Date: May 2000
Creator: Stallcup, Richard E.
Partner: UNT Libraries
open access

Processing and Protection of Rare Earth Permanent Magnet Particulate for Bonded Magnet Applications

Description: Rapid solidification of novel mixed rare earth-iron-boron, MRE{sub 2}Fe{sub 14}B (MRE = Nd, Y, Dy; currently), magnet alloys via high pressure gas atomization (HPGA) have produced similar properties and structures as closely related alloys produced by melt spinning (MS) at low wheel speeds. Recent additions of titanium carbide and zirconium to the permanent magnet (PM) alloy design in HPGA powder (using He atomization gas) have made it possible to achieve highly refined microstructures with mag… more
Date: December 1, 2007
Creator: Sokolowski, Peter Kelly
Partner: UNT Libraries Government Documents Department
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Two-photon Photoemission of Organic Semiconductor Molecules on Ag(111)

Description: Angle- and time-resolved two-photon photoemission (2PPE) was used to study systems of organic semiconductors on Ag(111). The 2PPE studies focused on electronic behavior specific to interfaces and ultrathin films. Electron time dynamics and band dispersions were characterized for ultrathin films of a prototypical n-type planar aromatic hydrocarbon, PTCDA, and representatives from a family of p-type oligothiophenes.In PTCDA, electronic behavior was correlated with film morphology and growth modes… more
Date: May 15, 2008
Creator: Yang, Aram & Yang, Aram
Partner: UNT Libraries Government Documents Department
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Nanoscale chemical and mechanical characterization of thin films:sum frequency generation (SFG) vibrational spectroscopy at buriedinterfaces

Description: Sum frequency generation (SFG) surface vibrational spectroscopy was used to characterize interfaces pertinent to current surface engineering applications, such as thin film polymers and novel catalysts. An array of advanced surface science techniques like scanning probe microscopy (SPM), x-ray photoelectron spectroscopy (XPS), gas chromatography (GC) and electron microscopy were used to obtain experimental measurements complementary to SFG data elucidating polymer and catalyst surface compositi… more
Date: May 19, 2006
Creator: Kweskin, S.J.
Partner: UNT Libraries Government Documents Department
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The Role of Defects in the Quantum Size Effect

Description: This investigation is a theoretical study of the influence of defects of finite volume on the electrical conductivity in the quantum size effect regime. Correction terms to existing equations are derived, and a physical explanation of the results is given. Many macroscopic properties of films exhibit an oscillatory dependence on thickness when the thickness is comparable to the de Broglie wavelength of an electron at the Fermi surface. This behavior is called the quantum size effect. In very th… more
Date: December 1974
Creator: Malone, Farris D.
Partner: UNT Libraries
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Plasma enhanced chemical vapor deposition of ZrO{sub 2} thin films

Description: Amorphous ZrO{sub 2} thin films were deposited in an inductively coupled PECVD system using a Zr {beta}-diketonate, Zr(C{sub 11}H{sub 19}O{sub 2}){sub 4}, as the precursor. The deposits were air annealed at 900C for 5 min to get pure, single phase, oriented, polycrystalline {alpha}-ZrO{sub 2}. Feasibility of using 2 different types of reactors was investigated. The inductively heated horizontal reactor depositions at 600C had a lower deposition rate and the films were non-uniform in thickness w… more
Date: December 9, 1993
Creator: Saravanan, Kolandaivelu
Partner: UNT Libraries Government Documents Department
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Resonant holographic measurements of laser ablation plume expansion in vacuum and argon gas backgrounds

Description: This thesis discusses the following on resonant holographic measurements of laser ablation plume expansion: Introduction to laser ablation; applications of laser ablation; The study of plume expansion; holographic interferometry; resonant holographic interferometry; accounting for finite laser bandwidth; The solution for doppler broadening and finite bandwidth; the main optical table; the lumonics laser spot shape; developing and reconstructing the holograms; plume expansion in RF/Plasma Enviro… more
Date: October 1, 1993
Creator: Lindley, R. A.
Partner: UNT Libraries Government Documents Department
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Model heterogeneous acid catalysts and metal-support interactions: A combined surface science and catalysis study

Description: This (<100 {Angstrom}) silica-alumina layers were tested as potential model heterogeneous acid catalysts for combined surface science and catalysis studies. Three preparation methods were used: oxidation of r3 {times} r3 R30 Al/Si(111) structure in UHV; deposition on Si(lll) from aqueous solution; and argon ion beam sputter deposition in UHV. The homogeneous thin layers are amorphous, and the chemical environment of surface atoms is similar to that of Si, Al and oxygen atoms on high surface are… more
Date: May 1, 1991
Creator: Boszormenyi, I.
Partner: UNT Libraries Government Documents Department
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Optical pumping and xenon NMR

Description: Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower … more
Date: November 1, 1991
Creator: Raftery, M. D.
Partner: UNT Libraries Government Documents Department
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Sol-gel preparation of ion-conducting ceramics for use in thin films

Description: A metal alkoxide sol-gel solution suitable for depositing a thin film of La{sub 0.6}Sr{sub 0.4}CoO{sub 3} on a porous substrate has been developed; such films should be useful in fuel cell electrode and oxygen separation membrane manufacture. Crack-free films have been deposited on both dense and porous substrates by dip-coating and spin-coating techniques followed by a heat treatment in air. Fourier transform infrared spectroscopy was used to determine the chemical structure of metal alkoxide … more
Date: December 1, 1992
Creator: Steinhauser, M. I.
Partner: UNT Libraries Government Documents Department
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Sol-gel derived ceramic electrolyte films on porous substrates

Description: A process for the deposition of sol-gel derived thin films on porous substrates has been developed; such films should be useful for solid oxide fuel cells and related applications. Yttria-stabilized zirconia films have been formed from metal alkoxide starting solutions. Dense films have been deposited on metal substrates and ceramic substrates, both dense and porous, through dip-coating and spin-coating techniques, followed by a heat treatment in air. X-ray diffraction has been used to determin… more
Date: May 1, 1992
Creator: Kueper, T. W.
Partner: UNT Libraries Government Documents Department
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Novel Carborane Derived Semiconducting Thin Films for Neutron Detection and Device Applications

Description: Novel carborane (B10C2H12) and aromatic compounds (benzene, pyridine, diaminobenzene) copolymers and composite materials have been fabricated by electron beam induced cross-linking and plasma enhanced chemical vapor deposition (PECVD) respectively. Chemical and electronic structure of these materials were studied using X-ray and ultra-violet photoelectron spectroscopy (XPS and UPS). UPS suggest that the systematic tuning of electronic structure can be achieved by using different aromatic compou… more
Date: August 2015
Creator: James, Robinson
Partner: UNT Libraries
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Microfabrication of an Implantable silicone Microelectrode array for an epiretinal prosthesis

Description: Millions of people suffering from diseases such as retinitis pigmentosa and macular degeneration are legally blind due to the loss of photoreceptor function. Fortunately a large percentage of the neural cells connected to the photoreceptors remain viable, and electrical stimulation of these cells has been shown to result in visual perception. These findings have generated worldwide efforts to develop a retinal prosthesis device, with the hope of restoring vision. Advances in microfabrication, i… more
Date: June 10, 2003
Creator: Maghribi, M
Partner: UNT Libraries Government Documents Department
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Dislocation dynamics simulations of plasticity at small scales

Description: As metallic structures and devices are being created on a dimension comparable to the length scales of the underlying dislocation microstructures, the mechanical properties of them change drastically. Since such small structures are increasingly common in modern technologies, there is an emergent need to understand the critical roles of elasticity, plasticity, and fracture in small structures. Dislocation dynamics (DD) simulations, in which the dislocations are the simulated entities, offer a w… more
Date: December 15, 2010
Creator: Zhou, Caizhi
Partner: UNT Libraries Government Documents Department
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