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- Gregory Wilson (4)
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- Electrical & Computer Engineering Theses & Dissertations (2)
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- All Graduate Theses and Dissertations, Spring 1920 to Summer 2023 (1)
- Browse all Theses and Dissertations (1)
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Articles 1 - 28 of 28
Full-Text Articles in Physical Sciences and Mathematics
Exploring Cathodoluminescence Evident Features Of Tungsten Disulfide, Molybdenum Disulfide, And Tungsten-Sulfide-Selenide, Nathan Mayer
Exploring Cathodoluminescence Evident Features Of Tungsten Disulfide, Molybdenum Disulfide, And Tungsten-Sulfide-Selenide, Nathan Mayer
Undergraduate Theses
Cathodoluminescence (CL) microscopy can be used to characterize the quantum optical behaviors of two-dimensional nanostructures. To investigate this behavior, we mounted flakes of tungsten disulfide (WS2), molybdenum disulfide (MoS2), and tungsten-sulfide-selenide Janus structures (WSSe) on a SiO2 substrate and analyzed these samples under both high vacuum and low H2O vacuum conditions using a scanning electron microscope. We then captured CL and secondary-electron images of the samples at multiple electron-beam energies and currents (5 keV to 30 keV, and 0.5 nA to 5 nA, respectively). We used a range of beam currents and …
Cathodoluminescence Studies Of Defects In Coated Boron Nitride, Kévin Guerch, Justin Dekany, Jr Dennison, Thierry Paulmier, Sophie Guillemet-Fritsch, Pascal Lenormand
Cathodoluminescence Studies Of Defects In Coated Boron Nitride, Kévin Guerch, Justin Dekany, Jr Dennison, Thierry Paulmier, Sophie Guillemet-Fritsch, Pascal Lenormand
Journal Articles
Optical emission properties of Boron Nitride (BN) substrates, BN with alumina (Al2O3) coating, and thermally-annealed alumina-coated boron nitride (an-BN/Al2O3) were investigated under electron irradiation using cathodoluminescence (CL) measurements. Tests were performed temperatures ranging from ~100 K to ~300 K, with monoenergetic beams from 5 keV to 30 keV, and electron flux densities from 1 nA.cm-2 to 500 nA.cm-2. These experiments were conducted to identify the effects of coating and thermal annealing on the nature and occupation of defect states in different samples with BN substrates. Previous studies have shown that these treatments can limit the charging of BN substrates. Consequently, …
Beyond Conventional C-Plane Gan-Based Light Emitting Diodes: A Systematic Exploration Of Leds On Semi-Polar Orientations, Morteza Monavarian
Beyond Conventional C-Plane Gan-Based Light Emitting Diodes: A Systematic Exploration Of Leds On Semi-Polar Orientations, Morteza Monavarian
Theses and Dissertations
Despite enormous efforts and investments, the efficiency of InGaN-based green and yellow-green light emitters remains relatively low, and that limits progress in developing full color display, laser diodes, and bright light sources for general lighting. The low efficiency of light emitting devices in the green-to-yellow spectral range, also known as the “Green Gap”, is considered a global concern in the LED industry. The polar c-plane orientation of GaN, which is the mainstay in the LED industry, suffers from polarization-induced separation of electrons and hole wavefunctions (also known as the “quantum confined Stark effect”) and low indium incorporation efficiency that …
Defects Density Of States Model Of Cathodoluminescent Intensity And Spectra Of Disordered Sio2, Amberly Evans Jensen, Jr Dennison
Defects Density Of States Model Of Cathodoluminescent Intensity And Spectra Of Disordered Sio2, Amberly Evans Jensen, Jr Dennison
Journal Articles
Electron beam measurements show that disordered SiO2 exhibits electron-induced luminescence, and that it varies with incident beam energy and current density, sample temperature, and wavelength. A simple model based on the electronic band structure and defect density of states—initially used to explain electron transport in highly disordered insulating materials—has been extended to predict the relative cathodoluminescent intensity and spectral radiance for disordered SiO2 as a function of these variables. Due to the large band gap of insulating SiO2, thermal excitation from the valence to conduction band is highly improbable; excitation is through collisions of the incident …
Variations In Cathodoluminescent Intensity Of Spacecraft Materials Exposed To Energetic Electron Bombardment, Justin Dekany, Justin Christensen, Jr Dennison, Amberly Evans Jensen, Gregory Wilson, Todd Schneider, Charles W. Bowers, Robert Meloy
Variations In Cathodoluminescent Intensity Of Spacecraft Materials Exposed To Energetic Electron Bombardment, Justin Dekany, Justin Christensen, Jr Dennison, Amberly Evans Jensen, Gregory Wilson, Todd Schneider, Charles W. Bowers, Robert Meloy
Journal Articles
Many contemporary spacecraft materials exhibit cathodoluminescence when exposed to electron flux from the space plasma environment. A quantitative, physics-based model has been developed to predict the intensity of the total glow as a function of incident electron current density and energy, temperature, and intrinsic material properties. We present a comparative study of the absolute spectral radiance for more than 20 types of dielectric and composite materials based on this model which spans more than three orders of magnitude. Variations in intensity are contrasted for different electron environments, different sizes of samples and sample sets, different testing and analysis methods, and …
Modeling The Defect Density Of States Of Disordered Sio2 Through Cathodoluminescence, Amberly Evans Jensen
Modeling The Defect Density Of States Of Disordered Sio2 Through Cathodoluminescence, Amberly Evans Jensen
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Spacecraft charging is the accumulation of an electrical charge on orbiting spacecraft induced by the space plasma environment and has harmful effects on the electrical functionality of a spacecraft. This is studied extensively, particularly in the Materials Physics Group (MPG) at Utah State University (USU). During charging studies performed by the MPG, another potentially problematic effect of the space plasma environment on spacecraft was observed: light emanating from the sample undergoing electron beam bombardment. Space-based observatories are one type of spacecraft on which this luminescence may occur. If the luminescence from the material caused by the space plasma is within …
Extended Defects In Gan Nanocolumns Characterized By Cathodoluminescence Directly Performed In A Transmission Electron Microscope, Frank Bertram, Marcus Müller, Gordon Schmidt, Peter Veit, Jürgen Christen, Arne Urban, Joerg Malindretos, Angela Rizzi
Extended Defects In Gan Nanocolumns Characterized By Cathodoluminescence Directly Performed In A Transmission Electron Microscope, Frank Bertram, Marcus Müller, Gordon Schmidt, Peter Veit, Jürgen Christen, Arne Urban, Joerg Malindretos, Angela Rizzi
Turkish Journal of Physics
Using cathodoluminescence spectroscopy directly performed in a scanning transmission electron microscope at liquid helium temperature, the structural and optical properties of GaN nanocolumns, in particular extended defects like stacking faults and dislocations, have been characterized. The influence of the crystalline real structure on the emission properties using the capability of addressing individual stacking faults is comprehensively examined.
Diverse Electron-Induced Optical Emissions From Space Observatory Materials At Low Temperatures, Jr Dennison, Amberly Evans Jensen, Gregory Wilson, Justin Dekany, Charles W. Bowers, Robert H. Meloy
Diverse Electron-Induced Optical Emissions From Space Observatory Materials At Low Temperatures, Jr Dennison, Amberly Evans Jensen, Gregory Wilson, Justin Dekany, Charles W. Bowers, Robert H. Meloy
Conference Proceedings
Electron irradiation experiments have investigated the diverse electron-induced optical and electrical signatures observed in ground-based tests of various space observatory materials at low temperature. Three types of light emission were observed: (i); long-duration cathodoluminescence which persisted as long as the electron beam was on (ii) short-duration (<1 s) arcing, resulting from electrostatic discharge; and (iii) intermediate-duration (~100 s) glow—termed “flares”. We discuss how the electron currents and arcing—as well as light emission absolute intensity and frequency—depend on electron beam energy, power, and flux and the temperature and thickness of different bulk (polyimides, epoxy resins, and silica glasses) and composite dielectric materials (disordered SiO2 thin films, carbon- and fiberglass-epoxy composites, and macroscopically-conductive carbon-loaded polyimides). We conclude that electron-induced optical emissions resulting from interactions between observatory materials and the space environment electron flux can, in specific circumstances, make significant contributions to the stray light background that could possibly adversely affect the performance of space-based observatories.
Power And Charge Deposition In Multilayer Dielectrics From Monoenergetic Electron Bombardment, Gregory Wilson, Amberly Evans, Justin Dekany, Jr Dennison
Power And Charge Deposition In Multilayer Dielectrics From Monoenergetic Electron Bombardment, Gregory Wilson, Amberly Evans, Justin Dekany, Jr Dennison
Gregory Wilson
Power and charge deposition in multilayer dielectrics from electron bombardment is dependent upon the flux and electron range of the electron beam, where the range,--a lso known as the penetration depth—is dependent upon the incident beam energy. Using the Continuous Slow Down Approximation (CSDA), a composite analytical formula has been developed to relate the electron range to the dose rate and subsequently to the deposited power in each subsequent layer. Based on the constituent layer geometry and material , the deposited charge can also be inferred. To validate these models two separate experiments were conducted, one based on the net …
Temperature Dependence Of Sio2 Electron-Induced Cathodoluminescence, Amberly Evans, Gregory Wilson, Jr Dennison
Temperature Dependence Of Sio2 Electron-Induced Cathodoluminescence, Amberly Evans, Gregory Wilson, Jr Dennison
Gregory Wilson
No abstract provided.
Low Temperature Cathodoluminescence Of Space Observatory Materials, Amberly Evans, Gregory Wilson, Justin Dekany, Alec Sim, Jr Dennison
Low Temperature Cathodoluminescence Of Space Observatory Materials, Amberly Evans, Gregory Wilson, Justin Dekany, Alec Sim, Jr Dennison
Gregory Wilson
In recent charging studies, a discernable glow was detected emanating from sample surfaces undergoing electron beam bombardment that resulted from a luminescent effect termed cathodoluminescence. This suggests that some of the materials used as optical elements, structural components, and thermal control surfaces in the construction of space-based observatories might luminesce when exposed to sufficiently energetic charged particle fluxes from the space plasma environment. If these visible, infrared and ultraviolet emissions are intense enough, they can potentially produce optical contamination detrimental to the performance of the observatory optical elements and sensors, and act to limit their sensitivity and performance windows. As …
Low Temperature Cathodoluminescence In Disordered Sio2, Amberly Evans, Gregory Wilson, Jr Dennison
Low Temperature Cathodoluminescence In Disordered Sio2, Amberly Evans, Gregory Wilson, Jr Dennison
Gregory Wilson
Disordered SiO2 is commonly used for optical instrumentation and coatings. In space telescope applications, these materials can be exposed to low temperature (particularly for IR telescopes) and simultaneous electron fluxes from the space plasma environment. During recent charging tests of this dielectric material, a discernable glow was detected emanating from the surface of the SiO2, indicating that the incident electron beam induced a luminescent effect, termed cathodoluminescence. As the sample cooled from 300 K to 120 K, a change in the intensity and energy spectrum of the glow was observed between 250 nm and 1700 nm, demonstrating that the SiO2 …
Low Temperature Cathodoluminescence Of Space Observatory Materials, Amberly Evans, Gregory Wilson, Justin Dekany, Alec Sim, Jr Dennison
Low Temperature Cathodoluminescence Of Space Observatory Materials, Amberly Evans, Gregory Wilson, Justin Dekany, Alec Sim, Jr Dennison
Justin Dekany
In recent charging studies, a discernable glow was detected emanating from sample surfaces undergoing electron beam bombardment that resulted from a luminescent effect termed cathodoluminescence. This suggests that some of the materials used as optical elements, structural components, and thermal control surfaces in the construction of space-based observatories might luminesce when exposed to sufficiently energetic charged particle fluxes from the space plasma environment. If these visible, infrared and ultraviolet emissions are intense enough, they can potentially produce optical contamination detrimental to the performance of the observatory optical elements and sensors, and act to limit their sensitivity and performance windows. As …
Power And Charge Deposition In Multilayer Dielectrics From Monoenergetic Electron Bombardment, Gregory Wilson, Amberly Evans, Justin Dekany, Jr Dennison
Power And Charge Deposition In Multilayer Dielectrics From Monoenergetic Electron Bombardment, Gregory Wilson, Amberly Evans, Justin Dekany, Jr Dennison
Justin Dekany
Power and charge deposition in multilayer dielectrics from electron bombardment is dependent upon the flux and electron range of the electron beam, where the range,--a lso known as the penetration depth—is dependent upon the incident beam energy. Using the Continuous Slow Down Approximation (CSDA), a composite analytical formula has been developed to relate the electron range to the dose rate and subsequently to the deposited power in each subsequent layer. Based on the constituent layer geometry and material , the deposited charge can also be inferred. To validate these models two separate experiments were conducted, one based on the net …
Properties Of Cathodoluminescence For Cryogenic Applications Of Sio2-Based Space Observatory Optics And Coatings, Amberly Evans Jensen, Jr Dennison, Gregory Wilson, Justin Dekany, Charles Bpwers, Robert Meloy, James B. Heaney
Properties Of Cathodoluminescence For Cryogenic Applications Of Sio2-Based Space Observatory Optics And Coatings, Amberly Evans Jensen, Jr Dennison, Gregory Wilson, Justin Dekany, Charles Bpwers, Robert Meloy, James B. Heaney
Conference Proceedings
Disordered thin film SiO2/SiOx coatings undergoing electron-beam bombardment exhibit cathodoluminescence, which can produce deleterious stray background light in cryogenic space-based astronomical observatories exposed to high- energy electron fluxes from space plasmas. As future observatory missions push the envelope into more extreme environments and more complex and sensitive detection, a fundamental understanding of the dependencies of this cathodoluminescence becomes critical to meet performance objectives of these advanced space-based observatories. Measurements of absolute radiance and emission spectra as functions of incident electron energy, flux, and power typical of space environments are presented for thin (~60-200 nm) SiO2/SiOx optical coatings on reflective metal …
Muon Contribution To Cathodoluminescence Tests?, Justin Dekany, Allen Anderson, Jr Dennison
Muon Contribution To Cathodoluminescence Tests?, Justin Dekany, Allen Anderson, Jr Dennison
Posters
Tests of composites incorporating highly disordered insulating materials that were bombarded with low-flux keV electron beams exhibited three distinct forms of light emission: short-duration (<<1 s), high intensity luminous electrostatic discharges between the insulator and ground--termed “arcs”; intermediate-duration (10-100 s), intense surface emissions—termed “flares”; and lower intensity, continuous surface cathodoluminescent “glow”. During long-duration experiments at temperatures <150 K, relatively intense flare events occurred at rates of ~2 per min. Rapid increase in photon emission and electron displacement current were observed, with long exponential decay times >1 min. We propose that the source of the flares is the interactions of high energy muons—of cosmic ray origin—with the highly-charged insulating components of the composite materials, which trigger avalanche electrostatic discharge and subsequent recharging along with concomitant light emission. We review evidence from the insulator conductivity at low temperatures, the rates and magnitude of surface charging, the flare frequency, and the magnitude and time-dependence of currents and light emission with regard to this …
Power And Charge Deposition In Multilayer Dielectrics From Monoenergetic Electron Bombardment, Gregory Wilson, Amberly Evans, Justin Dekany, Jr Dennison
Power And Charge Deposition In Multilayer Dielectrics From Monoenergetic Electron Bombardment, Gregory Wilson, Amberly Evans, Justin Dekany, Jr Dennison
Presentations
Power and charge deposition in multilayer dielectrics from electron bombardment is dependent upon the flux and electron range of the electron beam, where the range,--a lso known as the penetration depth—is dependent upon the incident beam energy. Using the Continuous Slow Down Approximation (CSDA), a composite analytical formula has been developed to relate the electron range to the dose rate and subsequently to the deposited power in each subsequent layer. Based on the constituent layer geometry and material , the deposited charge can also be inferred. To validate these models two separate experiments were conducted, one based on the net …
Low Temperature Cathodoluminescence Of Space Observatory Materials, Amberly Evans, Gregory Wilson, Justin Dekany, Alec Sim, Jr Dennison
Low Temperature Cathodoluminescence Of Space Observatory Materials, Amberly Evans, Gregory Wilson, Justin Dekany, Alec Sim, Jr Dennison
Posters
In recent charging studies, a discernable glow was detected emanating from sample surfaces undergoing electron beam bombardment that resulted from a luminescent effect termed cathodoluminescence. This suggests that some of the materials used as optical elements, structural components, and thermal control surfaces in the construction of space-based observatories might luminesce when exposed to sufficiently energetic charged particle fluxes from the space plasma environment. If these visible, infrared and ultraviolet emissions are intense enough, they can potentially produce optical contamination detrimental to the performance of the observatory optical elements and sensors, and act to limit their sensitivity and performance windows. As …
Low Temperature Cathodoluminescence In Disordered Sio2, Amberly Evans, Gregory Wilson, John R. Dennison
Low Temperature Cathodoluminescence In Disordered Sio2, Amberly Evans, Gregory Wilson, John R. Dennison
All Physics Faculty Presentations
Disordered SiO2 is commonly used for optical instrumentation and coatings. In space telescope applications, these materials can be exposed to low temperature (particularly for IR telescopes) and simultaneous electron fluxes from the space plasma environment. During recent charging tests of this dielectric material, a discernable glow was detected emanating from the surface of the SiO2, indicating that the incident electron beam induced a luminescent effect, termed cathodoluminescence. As the sample cooled from 300 K to 120 K, a change in the intensity and energy spectrum of the glow was observed between 250 nm and 1700 nm, demonstrating that the SiO2 …
Radiation Effects On Wide Band Gap Semiconductor Transport Properties, Casey Minna Schwarz
Radiation Effects On Wide Band Gap Semiconductor Transport Properties, Casey Minna Schwarz
Electronic Theses and Dissertations
In this research, the transport properties of ZnO were studied through the use of electron and neutron beam irradiation. Acceptor states are known to form deep in the bandgap of doped ZnO material. By subjecting doped ZnO materials to electron and neutron beams we are able to probe, identify and modify transport characteristics relating to these deep accepter states. The impact of irradiation and temperature on minority carrier diffusion length and lifetime were monitored through the use of the Electron Beam Induced Current (EBIC) method and Cathodoluminescence (CL) spectroscopy. The minority carrier diffusion length, L, was shown to increase as …
The Mechanisms Of Luminescence From Zno Under Electron Irradiation, Devin Marlinjames Todd
The Mechanisms Of Luminescence From Zno Under Electron Irradiation, Devin Marlinjames Todd
Browse all Theses and Dissertations
Zinc Oxide has been utilized for centuries in a wide range of applications including medical, food, and materials. It is now that ZnO draws much attention to its potential as a high frequency semiconductor and UV laser. As a result, there has been much investigation into the properties of ZnO and many papers have been published in the area. Despite this fact, there is still much that is unknown about its electronic defect structure. This research investigates the broad region of the Zinc Oxide luminescence spectrum known as the green band, which lies roughly between 480 - 580 nm or …
Temperature Dependence Of Sio2 Electron-Induced Cathodoluminescence, Amberly Evans, Gregory Wilson, John R. Dennison
Temperature Dependence Of Sio2 Electron-Induced Cathodoluminescence, Amberly Evans, Gregory Wilson, John R. Dennison
All Physics Faculty Presentations
No abstract provided.
Cathodoluminescence And Photoemission Of Doped Lithium Tetraborate, Christina L. Dugan
Cathodoluminescence And Photoemission Of Doped Lithium Tetraborate, Christina L. Dugan
Theses and Dissertations
Lithium tetraborate (Li2B4O7) crystals are being developed for possible use in solid state neutron detectors. The 6Li(n,α)3H and 10B(n,α)7Li reactions are the basis for neutron detection, and a Li2B4O7 crystal enriched with Mn should show improved efficiency for neutron detection. There is a lack of fundamental characterization information regarding this useful material, particularly with regard to its electronic configuration. Photoemission spectroscopy was used to determine the energy level structure of the Mn doped Li2B4O7 crystals. …
The Material Properties Of Cssnbr3 And Csbr:Sn-1% And Their Potential As Scintillator Detector Material, Neal B. Kleinschmidt
The Material Properties Of Cssnbr3 And Csbr:Sn-1% And Their Potential As Scintillator Detector Material, Neal B. Kleinschmidt
Theses and Dissertations
The search for superior nuclear radiation detection materials is ongoing. Current scintillator materials using Thallium doped Sodium Iodide or Cesium Iodide are the benchmarks for ease of use and quick identification of isotope species. This research aims to explore Cesium Bromide doped with 1% molar tin (CsBr:Sn-1%) and Cesium Tin Bromide (CsSnBr3) as candidate materials for a new scintillator. The techniques of Extended X-Ray Absorption Fine Structure (EXAFS), X-Ray Absorption Near Edge Structure (XANES) and Cathodoluminescence are used to determine the suit- ability of CsSnBr3 and CsBr:Sn-1% with Sn4+ as a potential scintillator materials and explore their …
Polarity-Related Asymetry At Zno Surfaces And Metal Interfaces, Y. F. Dong, Z-Q. Fang, David C. Look, Daniel R. Doutt, M. J. Hetzer, L. J. Brillson
Polarity-Related Asymetry At Zno Surfaces And Metal Interfaces, Y. F. Dong, Z-Q. Fang, David C. Look, Daniel R. Doutt, M. J. Hetzer, L. J. Brillson
Physics Faculty Publications
Clean ZnO (0001) Zn- and (000(/1)) O-polar surfaces and metal interfaces have been systematically studied by depth-resolved cathodoluminescence spectroscopy, photoluminescence, current-voltage and capacitance-voltage measurements, and deep level transient spectroscopy. Zn-face shows higher near band edge emission and lower near surface defect emission. Even with remote plasma decreases of the 2.5 eV near surface defect emission, (0001)-Zn face emission quality still exceeds that of (000(/1))-O face. The two polar surfaces and corresponding metal interfaces also present very different luminescence evolution under low-energy electron beam irradiation. Ultrahigh vacuum-deposited Au and Pd diodes on as-received and O2/He plasma-cleaned surfaces display not …
Electron Injection-Induced Effects In Iii-Nitrides: Physics And Applications, William Charles Burdett
Electron Injection-Induced Effects In Iii-Nitrides: Physics And Applications, William Charles Burdett
Electronic Theses and Dissertations
This research investigated the effect of electron injection in III-Nitrides. The combination of electron beam induced current and cathodoluminescence measurements was used to understand the impact of electron injection on the minority carrier transport and optical properties. In addition, the application of the electron injection effect in optoelectronic devices was investigated. The impact of electron injection on the minority carrier diffusion length was studied at various temperatures in Mg-doped p-GaN, p-Al[subscript x]Ga[subscript 1-x]N, and p-Al[subscript x]Ga[subscript 1-x] N/GaN superlattices. It was found that Lsubscript n] experienced a multi-fold linear increase and that the rate of change of L[subscript n] decreased …
Electron Beam Emission From A Ferroelectric Cathode, Crystal Briana Garland
Electron Beam Emission From A Ferroelectric Cathode, Crystal Briana Garland
Electrical & Computer Engineering Theses & Dissertations
The electron beam emission from a LTZ-2 (lead titanate-zirconate) ferroelectric cathode was characterized. The purpose was to determine the operation range for this type of electron emitter. The experimental apparatus consisted of a high voltage driving circuit with a charging voltage up to 30kV. A solid-state SCR switch is used to generate the high voltage pulse which induces a polarization change. Current densities on the order of 80A/cm2 30kV were achieved. The electron beam profile is Guassian. At long anode-cathode distances the measured current densities were found to be above Child-Langmuir space charge limits. The large current densities and …
Study Of Cathodoluminescence In Semiconductors, Mandakini V. Kale
Study Of Cathodoluminescence In Semiconductors, Mandakini V. Kale
Electrical & Computer Engineering Theses & Dissertations
Cathodoluminescence in Zn doped GaAs and ZnSe, the materials of interest for electron-beam controlled semiconductor switches, has been investigated. A new diagnostic technique, using telescopic setup of lenses, was developed to study the spatially resolved cathodoluminescence. The setup eliminated the light, other than rays from the sample, parallel to the optical axis, resulting in an enhanced spatial resolution. At high e-beam energies, light was detected, from the Zn layer region in the GaAs. It is proposed to be due to the radiative recombination of electron-hole pairs, created by the e-beam. For the polycrystalline ZnSe no light emission was detected. This …