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  • 1. Shafer, Sally Exploratory studies of infrared emission spectra.

    Master of Science, The Ohio State University, 1975, Graduate School

    Committee: Not Provided (Other) Subjects:

  • 2. Wickramasinghe, Thushan Growth Techniques and Optical and Electrical Characterization of Quantum Confined Zero-Dimensional and Two-Dimensional Device Structures

    Doctor of Philosophy (PhD), Ohio University, 2019, Physics and Astronomy (Arts and Sciences)

    Quantum confinement of charge carriers in semiconductor nanostructures have garnered considerable attention in the past few decades. With new materials being discovered and advanced growth techniques allowing them to be engineered into nanoscale devices with atomic precision, the localization of charge carriers is becoming easier to control. The focus of this dissertation is to highlight the employed growth techniques and the characterization of the device structures studied in our lab.In the first project of the dissertation we examined the temporal dynamics of the Optically Generated Electric Field (OGEF) within a CQD device. We demonstrated the potential of using the interdot transition as a sensitive probe to measure electric fields by using photovoltaic band flattening in a Schottky diode structure. A modulated high energy laser was used to create the OGEF leading to photovoltaic band flattening. A CW laser with energy required to create the interdot transition was used to monitor the electric field in the device and characterize the temporal behavior of the field to determine rise time and decay time as well as to show how they depend on different variables.In the Second project we report on monolayer TMD metal semiconductor metal photodetectors produced using a CVD process. The photodetectors showed maximum responsivity of up to 15 A/W. The response time of the devices is found to be on the order of 1 µs, an order of magnitude faster than previous reports. The main project in this dissertation involved using the CVD growth technique employed in developing TMD devices to create deterministic single photon emitters (SPEs) by carrying out the growth on etched substrates. While we have seen successful growth with TMDs growing over perturbations, SPEs are yet to be found. However, in the process of developing these devices we were able to address several challenges in our technique.As highlighted in previous work in the group while the growth technique employed do (open full item for complete abstract)
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    Committee: Eric Stinaff Ph.D. (Advisor); Sergio Ulloa Ph.D. (Committee Member); David Tees Ph.D. (Committee Member); Wojciech Jadwisienczak Ph.D. (Committee Member) Subjects: Condensed Matter Physics; Physics; Solid State Physics

  • 3. Zheng, Lina Studies on the Elemental Measurement of Aerosols Using Microplasma Spectroscopy

    PhD, University of Cincinnati, 2016, Engineering and Applied Science: Environmental Engineering

    Chemical characterization of aerosols is essential to understand their health effects in environmental and occupational health studies. There has been a great interest in developing low cost, compact, hand-portable and direct-reading instruments for aerosol monitoring. Microplasma spectroscopy methods, such as laser induced breakdown spectroscopy (LIBS), spark emission spectroscopy (SES) and glow discharge optical emission spectroscopy (GD-OES), have been intensively studied and proved as practical technologies for detecting elemental composition of aerosols. The main focus of this dissertation is to develop a low cost and hand-portable methods for near real-time measurement of elemental concentration of aerosol using microplasma spectroscopy. The dissertation is divided into three parts. In the first part, a corona-based aerosol microconcentrator is designed for efficient concentrating aerosols to a substrate for subsequent analysis using microscale optical spectroscopies. Performance of this corona microconcentrator is determined experimentally by measuring collection efficiency, wall losses, and particle deposition density. An intrinsic spectroscopic sensitivity is determined for the aerosol microconcentrator using SES. Using this intrinsic sensitivity, it is shown that the corona-based microconcentration method provides the best measurement sensitivity compared to alternative particle collection methods, such as filtration, focused impaction using aerodynamic lens, and spot collection using condensational growth. This method has been demonstrated to be very suitable for compact hand-held analytical instrumentation. The second part of the dissertation focuses on the development of various methods for aerosol measurement using corona microconentration method coupled with microscale optical spectroscopies. First, a sensitive method has been developed for real-time measurement of carbonaceous aerosol using LIBS or SES. The measurement system is calibrated an (open full item for complete abstract)
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    Committee: Dionysios Dionysiou Ph.D. (Committee Chair); Soryong Chae Ph.D. (Committee Member); Pramod Kulkarni D.Sc. (Committee Member); George Sorial Ph.D. (Committee Member) Subjects: Environmental Engineering

  • 4. Winner, Taryn FURTHERING THE DEVELOPMENT OF SPECTROSCOPY FOR EDUCATION AND UNIQUE SAMPLING SITUATIONS

    Doctor of Philosophy, Miami University, 2015, Chemistry and Biochemistry

    This dissertation describes five unique projects which advance spectroscopy in terms of education, technology and applications. Project goals were designed so the end results would assist with solving educational, military and industrial challenges through the use of spectroscopy. These goals were accomplished through the use of new, existing and adaptations of existing spectroscopic instrumentation. New spectroscopic instruments were developed and built for use in educational teaching laboratories at Miami University. These instruments included a low-cost Raman spectrograph and a low-cost flame atomic emission spectrometer. Both instruments have economic and educational benefits over commercial instruments and the flame emission instrument has already demonstrated its value in the classroom. The next project, driven by military interest, involved using near-infrared diffuse reflectance spectroscopy for the standoff detection of explosive materials on common surfaces. Projects included coating substrates with high energy materials and acquiring spectra from those coated substrates. Results showed differences in the detection limits for ammonium nitrate on various substrates, and these limits were directly dependent on the characteristics of the substrate. Another project was completed in collaboration with the United States Food and Drug Administration's Forensic Chemistry Center. This project's goal was to identify counterfeit goods based on their packaging materials. By taking a cross section of a packaging material and acquiring a high resolution attenuated total internal reflection (ATR) Fourier transform infrared (FTIR) image, differences could be revealed which showed variances between the authentic and counterfeit packaging materials. Finally, an adaptation of an ATR-FTIR microscope was used in an attempt to improve the spatial resolution of an ATR-FTIR image by working in a non-contact type sampling configuration. Improvements in spatial resolution have n (open full item for complete abstract)
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    Committee: Andre Sommer (Advisor); Neil Danielson (Committee Chair); Jonathan Scaffidi (Committee Member); Tom Cambron (Committee Member); Paul Urayama (Committee Member) Subjects: Chemistry

  • 5. Pulcini, Annie Nitric Oxide and Other Characterizations of an Atmospheric Pressure Plasma Jet

    Master of Science, The Ohio State University, 2015, Chemistry

    This thesis presents the characteristics of an atmospheric pressure plasma jet (APPJ) that was used for surface chemistry at the University of Maryland. Recently, APPJs have gained popularity in the medical field to decontaminate surfaces, heal wounds, and cancer treatment. The motivation for this study is that many APPJs lack NO measurements. Characteristics done on this jet include charge-voltage (QV) measurements, time resolved spectroscopy, optical emission spectroscopy (OES) and NO-PLIF. QV measurements were done in order to find the energy of the plasma throughout the jet which was on the order of magnitude of 10-4-10-5 Joules/period. The time resolved spectroscopy showed that the plume of the plasma changes with time. The use of optical emission spectroscopy revealed that oxygen, nitrogen and NO were present in the plasma even if there was none being pumped through the jet. NO number density was calculated from taking PLIF measurements. It was found that helium mixtures create more NO than the argon mixtures.
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    Committee: Walter Lempert Ph.D (Advisor); Anne McCoy Ph.D (Committee Member) Subjects: Chemistry; Mechanical Engineering

  • 6. Kunati, Sandeep Trace Measurements of Tellurium, Tin and Other Metals by Atomic and Laser Spectroscopy Techniques

    Master of Science in Chemistry, Youngstown State University, 2008, Department of Chemistry

    Sample introduction by using hydride generation (HG) technique enhances the sensitivity of certain hydride forming elements. In this study, methods have been investigated for the quantitative detection of Tellurium (Te), Tin (Sn), and other elements using HG coupled to Laser Induced Fluorescence (LIF), Laser Induced Breakdown Spectroscopy (LIBS), and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) detection techniques. In these studies, samples were subjected to HG and the resulting hydrides were carried to the flame atomizer in LIF, inductively coupled plasma in ICP-AES, and laser induced plasma in LIBS. The analytical figures of merit of these studies were evaluated to show the relative performance of each technique. The limits of detections (LOD) of Te and Sn were found to be 0.008 ppb and 0.07 ppb using HG-LIF, 1 ppm and 1 ppm using HG-LIBS and 2 ppm and 1 ppm using ICP-AES techniques. The results demonstrate that the combination of HG with LIF technique provides greater sensitivity as compared to the LIBS and ICP-AES techniques.
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    Committee: Josef B. Simeonsson PhD (Advisor); Larry S. Curtin PhD (Committee Member); Roland Reisen PhD (Committee Member) Subjects: Chemistry

  • 7. Chen, Ming-Wei Laser Spectroscopy Studying Organic and Inorganic Intermediates in The Atmospheric Oxidation Process

    Doctor of Philosophy, The Ohio State University, 2011, Chemical Physics

    Laser spectroscopy is a powerful tool to study the structure and photochemistry of molecules at selected electronic states. Under jet-cooled conditions, the rotational spectrum can be simplified with less congestion on the rotational contour owing to the low J population on the ground electronic state. Laser induced fluorescence (LIF), stimulated emission pumping (SEP), and cavity ringdown spectroscopy (CRDS) apparatuses are used to measure the methoxy(CH3O·), β-hydroxyethylperoxy (HOC2H4OO·) and nitrate (NO3·) radicals. The novel laser spectroscopy apparatuses are designed for the direct measurement to the forbidden electronic state attributed to the selection rules or low absorption cross section. The spectroscopic analysis applies the least-square fitting to determine the molecular parameters in Hamiltonians as well as the vibronic coupling induced distortion of molecular structure. Furthermore, in the collaboration with Dr. W. Leo Meerts (Radboud University, The Netherlands), the quantum mechanical model is also adapted to the evolutionary algorithm to investigate the biological evaluation on spectrum simulation.The ~A2A1-~X2E3/2 and ~X2E1/2-~A2A1 electronic transitions of methoxy and all four deuterium isotopologues are measured with a LIF/SEP apparatus that is both high-resolution (Δν ∼ 250 MHz) and and high-accuracy (Δσ ∼ 50 MHz). Since the ~X2E1/2 state is not thermally populated in a jet-cooled environment, the complementary SEP experiment directly interrogates the ~X2E1/2 level of methoxy by depleting the fluorescence from the ~A2A1 state. The global analysis of the microwave, LIF, and SEP data breaks correlations in the microwave data and provides better determinations for the ~X and ~A states′ parameters. The jet-cooled ~A-~X origin band spectra of 1G2G3 conformer of β-hydroxyethylperoxy have been recorded by a CRDS appratus with a laser source linewidth  ∼ 70 MHz in the near IR region. The spectra of four deuterium-substituted isotopologues have been (open full item for complete abstract)
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    Committee: Terry Miller A. (Advisor); Frank DeLucia (Committee Member); Walter Lempert (Committee Member); Guanglong He (Committee Member) Subjects: Physical Chemistry

  • 8. Bender, Edward Spectroscopic Characterization of Metal Oxide Nanofibers

    Master of Science, University of Akron, 2006, Physics

    Metal oxide nanofibers have potential applications in filtration, catalysis, energy conversion, and other areas. The most popular techniques for the characterization of nanofibers are X-ray diffraction (XRD) and scanning electron microscopy (SEM). However, these methods need to be supplemented with surface sensitive spectroscopies for more complete characterization. In several metal oxide nanofiber systems, unexpected impurities were found which may have a significant influence on the structure and surface chemistry. These impurities are not usually detectable with XRD and SEM. The main spectroscopic methods used here for materials characterization are X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Additionally, two relatively uncommon yet powerful techniques, photoacoustic FTIR and infrared emission spectroscopy are also used. These spectroscopic methods have provided insight into some of the unusual properties of metal oxide nanofibers. With the aid of surface sensitive spectroscopies, further development of these interesting materials will be enabled.
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    Committee: Rex Ramsier (Advisor) Subjects:

  • 9. Smith, Bryan Exploring the Anisotropic Ion Emission and Nano-plasma Resonance Conditions in the Mid-Infrared Spectral Range

    Doctor of Philosophy, The Ohio State University, 2023, Physics

    This study considers the interaction between noble gas nano-clusters under intense femtosecond laser fields. Charged ion emission is investigated for various driving laser wavelengths and intensities. We previously assumed that the resonance-absorption condition in laser-nano-plasma interactions followed the same wavelength dependence as the critical plasma density. However, our experimental results show that this is not true for the middle-infrared spectral range, though it is still valid for visible and near-infrared wavelengths. Here I discuss non-equilibrium transition dynamics of nano-plasmas formed by laser-ionized van der Waals argon nano-clusters. My experiment utilizes a novel probe wavelength scanning technique in a pump probe scheme. I conducted a thorough analysis, along with comparison to molecular dynamic simulations, and found that the change in resonance condition is due to a reduction in electron scattering rate and an increase in outer-ionization contribution from clusters. Using experimental data and MD-simulations, I present a new expression for the nano-plasma resonance density. These findings are important for a wide range of plasma experiments and applications, as studies on laser-plasma interactions at longer wavelengths are becoming increasingly significant. This is especially true for ongoing plasma experiments, diagnostics, and applications with optical probes for example imaging of plasma density and generation of high-energy charged particles and X-ray radiation.
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    Committee: Louis DiMauro Ph. D. (Advisor); Leonard Brillson Ph. D. (Committee Member); Gregory Lafyatis Ph. D. (Committee Member); Richard Furnstahl Ph. D. (Committee Member) Subjects: Physics

  • 10. Olivier, Grace Pre-Supernova Stellar Feedback: from the Milky Way to Reionization

    Doctor of Philosophy, The Ohio State University, 2022, Astronomy

    Galaxy formation and evolution are driven by stars and star formation. Star formation is fundamental for shaping the universe as we see it today as part of the cosmic ecosystems encompassing galaxies, yet half of the physics that determines how much gas forms into stars – the stellar feedback (injection of energy and momentum to the surrounding material) half of the tug-of-war between gravity and stellar feedback – have only recently become a focus for observational astronomers. Theoretical explorations of stellar feedback have been extensive for the past four decades and our current understanding of star-forming galaxies comes primarily through extensive modeling and simulations with sub-grid physics prescriptions based on a handful of observations. In order to secure the basis for these sub-grid physics models and expand our understanding of star-formation and the effects of massive stars during all epochs of the universe, more observations of these processes are needed. Observations of star forming regions provide the foundation to anchor simulations and observations of analogues to high-redshift galaxies help determine the sources that reionized the universe and the role stars played in during the Epoch of Reionization. With multiwavelength observations of H ii regions in the Milky Way, I have probed the effects of stellar feedback in dynamics of H ii regions, providing the necessary basis for defining the sub-grid physics in simulations. With multiwavelength observations of nearby galaxies with properties similar to galaxies in the EoR (low mass: < 107 M⊙; low metallicity: < 0.15 Z⊙; and high star-formation rates: > 10−1.2 M⊙/yr), I have determined the properties of sources that produce the photoionization feedback we observe and which sources ionized the universe in the Reionization Era. With X-ray observations of a massive colliding wind binary I have explored the effects of stellar wind feedback on small spatial scales and found that wind prescriptions assum (open full item for complete abstract)
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    Committee: Laura Lopez (Advisor); Todd Thompson (Committee Member); Adam Leroy (Committee Member) Subjects: Astronomy; Astrophysics

  • 11. Das, Sanskriti Feeding and Feedback in the Circumgalactic Medium (CGM) of Low-redshift Spiral Galaxies: a gastronomical tale in X-ray, 21-cm, and Sunyaev-Zel'dovich Effect

    Doctor of Philosophy, The Ohio State University, 2022, Astronomy

    The composition and evolution of galaxies have been an elemental but long-standing mystery in Astronomy. In the last century, the advent of telescopes across the electromagnetic spectrum has revolutionized our perception of galaxies from a mere assembly of stars to a complex ecosystem. Both observational and theoretical studies have pointed towards the existence of a gaseous medium beyond the stellar component of galaxies, aka, the circumgalactic medium (CGM). The CGM is a multi-phase gas surrounding the stellar disk of a galaxy, filling up its dark-matter halo. The CGM is simultaneously the fuel tank, waste dump, and recycle hub of galaxies. It is expected to harbor the baryons, metals, and feedback that are missing from the stellar disk. I have studied the two extreme phases of the CGM to investigate how the feeding (accretion) and the feedback (outflow) at the galactic scale govern the evolution of the Milky Way and similar nearby galaxies. The ≥106 K hot CGM, despite being challenging to detect, is a treasure trove of galaxy evolution. By probing the hot CGM of the Milky Way (MW) using X-ray absorption lines of multiple metal ions, I have discovered a super-virial 107 K phase coexisting with the well-known virialized 106 K phase, featuring non-solar abundance ratios of light elements, α-enhancement, and non-thermal line broadening. I have also detected this super-virial phase of MW CGM in X-ray emission analyses. Detection of these surprising properties of the CGM along multiple directions in the sky suggests a strong connection between the hot CGM and past Galactic outflow(s). Observations of MW-like galaxies complement our observations of the Milky Way. I have discovered the hot CGM emission of an MW-mass galaxy NGC 3221 that is extended (~150-200 kpc) and is massive enough to account for its missing baryons. The CGM is not isothermal, with the CGM within 100 kpc of NGC 3221 being super-virial, and fainter along the minor axis than the global a (open full item for complete abstract)
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    Committee: Smita Mathur (Advisor); Paul Martini (Committee Member); Annika Peter (Committee Member); Adam Leroy (Committee Member) Subjects: Astronomy; Astrophysics

  • 12. Mahbub, Shahrea Synthesis and photophysical property investigation of beads on a chain (BoC) silsesquioxane hybrid oligomers: probable pseudo conjugation

    Doctor of Philosophy (Ph.D.), Bowling Green State University, 2022, Photochemical Sciences

    Our overall goal here in this dissertation is to develop silicon-based hybrid materials that are potential high stability materials replacements for those in current electronics systems. To design the hybrid structures, a unique class of silicon-based compounds, silsesquioxanes (SQ) was used as the building block. SQs are three dimensionally compact Si-O bonded, cage-type compounds that can be synthesized to contain a variety of functional groups on each of the cage vertices. They offer useful properties such as thermal and photo stability, a high degree of functionalization, solution processability, and facile synthesis. The works in this dissertation focus on mixed functional (vinyl/phenyl) SQs of different sized cages containing 8, 10, and 12 silicon atoms. They are synthesized by fluoride catalyzed rearrangement reaction in a statistically controlled manner to achieve the desired vinyl groups for oligomerization. Spectroscopic measurements in picosecond/subpicosecond timeframes were performed before evaluating their potential applications. In chapter 2, vinyl/phenylSQs are cross-coupled by 4-di-bromo-aromatic linkers: Benzothiadiazole (BT), Phenanthrenequinone (PQ), Ethyl-carbazole (EC) and Phenyl-carbazole (PC). To compare photophysical properties between caged and non-caged structures, bis-tri-alkoxysilyl (linker) model compounds are synthesized. Luminescence quantum yields for oligomers are generally lower than the corresponding model compounds (except for PQ) which denotes non-radiative energy transfer possibility in oligomer. In addition, rapid transient absorption anisotropy decay (10's ps in oligomers) provide signatures for excitation energy transfer between linker chromophores in oligomers. In chapter 3, we have designed hybrid oligomers with a vinyl/phenylSQ cage backbone linked with cross-linkers including 2,7-dibromo-9-fluorenone, 2,7-dibromo-9,9-dimethylfluorene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-dibromopyridine, 2,6-dibromopyridine, 2, (open full item for complete abstract)
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    Committee: Joseph Furgal Ph.D. (Committee Chair); Robyn Miller Ph.D. (Other); H. Peter Lu Ph.D. (Committee Member); Xiaohong Tan Ph.D. (Committee Member) Subjects: Organic Chemistry; Physical Chemistry

  • 13. Hernandez, Armando Growth and Characterization of Wide Band-Gap Group III Oxide Semiconductors by MOCVD

    Doctor of Philosophy (Ph.D.), Bowling Green State University, 2021, Photochemical Sciences

    This dissertation work is focused on the deposition of gallium oxide (Ga2O3) thin films by metal organic chemical vapor deposition (MOCVD) method. This material belongs to a special group of wide bandgap oxide semiconductors with high optical transmittance and high levels of conductivity. The importance of this material is generated by the wide range of applications of electronic and optoelectronic devices such as MOSFET's, photo diodes, solar cells, LED's, laser diodes, sensors etc. Through MOCVD technique, an implementation of a Si4+ dopant was incorporated in the monoclinic β-Ga2O3 crystal structure on homoepitaxial and heteroepitaxial β-Ga2O3 single crystal wafers. The MOCVD process allowed us to deposit at a growth rate of 1 μm/hour while controlling the electrical transport properties with this dopant. These films were carefully characterized by surface morphology, crystal structure, levels of conductivity and trapping defects. The work shows that the electron density and conductivity of MOCVD Ga2O3 films are mainly governed by the interplay between dopant concentration, C concentration and the presence of trapping defects in the films, which is most likely applicable for other oxide films grown by MOCVD. Conductive films of Ga2O3 with resistivity in the order of 0.07 Ω.cm were successfully grown. The electron density in most of these films was in the range of 1019 cm−3 but the mobility was limited to 1.5 cm2/V⋅s. Higher mobility of 30 cm2/V⋅s was obtained in some films at the expense of carrier concentration by reducing Si doping level resulting in resistivity in the order of 0.3 Ω.cm. This range of conductivity and mobility is relevant for field-effect transistors (FET) and the applications of Ga2O3 as transparent FET in Deep Ultra-Violet (DUV) technology. The second part of this work focuses on investigating the electronic and crystal structure properties of an indium gallium oxide alloy (IGO) doped with Si4+ ions through MOCVD technique on c-sapph (open full item for complete abstract)
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    Committee: Farida Selim Dr. (Advisor); Marco Nardone Dr. (Committee Member); Alexander Tarnovsky Dr. (Committee Member); Ellen Grosevski Dr. (Other) Subjects: Materials Science; Physics

  • 14. Galiano, Kevin Scanning Probe Microscopy Measurements and Simulations of Traps and Schottky Barrier Heights of Gallium Nitride and Gallium Oxide

    Doctor of Philosophy, The Ohio State University, 2020, Physics

    Gallium Nitride (GaN) and Gallium Oxide (Ga2O3) are two semiconductors of significant interest for high power and high frequency electronics. However, the performance of these electronics can be inhibited by the presence of defects which can produce "trap" states in the "forbidden" bandgap of semiconductors. These traps can then degrade the output current of transistors and cause undesireable time-dependent phenomenon. This work investigates the physical origin of the most common trap, EC - 0.57 eV, in Gallium Nitride (which happens to be detrimental for certain transistors) by using Scanning Probe - Deep Level Transient Spectroscopy (SP-DLTS) to probe its spatial distribution. For the first time, this trap species is mapped with high spatial resolution and it is found to exhibit strong spatial localization in the form of "trap clusters". Through a correlative study with Electron Channeling Contrast Imaging (ECCI), this trap is found to be located at pure edge dislocations. In another study, the impact of iron on the spatial distribution of this trap is investigated, and it is found that the iron causes a more spatially-uniform trap distribution. One possible explanation is that the EC - 0.57 eV traps are directly related to iron atoms that are gettered by edge dislocations in Gallium Nitride. To better understand how the SP-DLTS maps relate to the trap concentration, simulations are performed. A comparison between the measurement and simulation shows reasonable agreement for the two GaN samples studied here. In collaboration with fellow graduate student Darryl Gleason, a study is conducted on a different device geometry (AlGaN/GaN heterostructures with semi-insulating GaN layers). This study allows for the characterization of two trap species in the GaN layer (one of which is the EC - 0.57 eV trap), and good agreement is found between macroscopic DLTS and SP-DLTS for both trap species. Finally, the first Ballistic Electron Emission Microscopy (BEEM) measurements on (open full item for complete abstract)
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    Committee: Jonathan Pelz (Advisor); Steven Ringel (Advisor); Nandini Trivedi (Committee Member); Yuri Kovchegov (Committee Member) Subjects: Physics

  • 15. Crenshaw, Daniel An analysis of the broad emmission line profiles of Seyfert 1 galaxies /

    Doctor of Philosophy, The Ohio State University, 1985, Graduate School

    Committee: Not Provided (Other) Subjects: Physics

  • 16. Sheasley, William The electronic emission spectra of H³⁵Cl⁺, H³⁷Cl⁺, D³⁵Cl⁺, and D³⁷Cl⁺ /

    Doctor of Philosophy, The Ohio State University, 1972, Graduate School

    Committee: Not Provided (Other) Subjects: Physics

  • 17. Posavec, Tony An Investigation into the Fluorescence of Polymers

    Master of Science, University of Akron, 2017, Physics

    Fluorescence refers to the emission of light after absorbing short wavelength energy and ceases within 10−6 seconds upon termination of excitation. In this thesis, the effects of low temperature—i.e., liquid nitrogen with a temperature of 77 K—on the emission spectra of industrial grade polymers were studied and compared with their room temperature fluorescence spectra. Multiple excitation energies with wavelengths that range from 250 nm to 450 nm (the ultraviolet spectrum) were used to isolate the most intense emission wavelengths at room temperature (300 K), and then again at 77 K to compare the temperature dependence of fluorescence for select polymer samples against themselves. The intensity of the fluorescence peak increases for cryogenic temperature measurements for all samples, with an acrylic sample displaying the largest intensity difference between the two temperatures. In addition to fluorescence spectroscopy, an analysis to evaluate the amount of light energy absorbed and transmitted through the polymers was implemented using an ultraviolet-visible spectrophotometer; demonstrating the samples absorb ultraviolet energy while permitting visible light to pass through most of them, resulting in the absorbed energy being released through photoluminescence.
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    Committee: Sasa Dordevic Dr. (Advisor); Robert Mallik Dr. (Committee Chair); Alper Buldum Dr. (Committee Member) Subjects: Condensed Matter Physics; Energy; Experiments; Low Temperature Physics; Materials Science; Physical Chemistry; Physics; Plastics; Polymer Chemistry; Polymers; Scientific Imaging; Solid State Physics

  • 18. Kersell, Heath Alternative Excitation Methods in Scanning Tunneling Microscopy

    Doctor of Philosophy (PhD), Ohio University, 2015, Physics and Astronomy (Arts and Sciences)

    Since its inception, scanning tunneling microscopy (STM) has developed into an indispensible tool for surface science. Its sub-nanometer spatial resolution in both real space imaging and tip-sample interactions continue to demonstrate versatility in the study of novel phenomena at materials' surfaces. This dissertation explores the expansion of experimental techniques in STM through application of two uncommonly exploited interactions at the tip-sample junction: X-ray absorption and the electric field between the tip and sample. This study begins by targeting the STM tip-sample junction with X-ray photons tuned to core level electron energies of atomic species on the sample. Interactions of atomic islands with the incident light are employed to introduce elemental sensitivity in STM with a resolution of just 2 nm. Elementally sensitive images are produced simultaneously with conventional STM images, and exploited to probe X-ray cross section behavior for structures measuring just a few tens of nanometers in the lateral directions. Additionally, point spectroscopic measurements of X-ray absorption behavior vs. incident photon energy facilitate the detection of local variations in emitted electron density due to the X-ray interactions. Locally measured electron emission densities measured by specialized SXSTM smart tips demonstrate a clear dependence on incident photon energy. Next, electric field interactions between the tip and sample are used to investigate the behavior of strongly dipolar molecular rotor networks. Symmetry and structure in the molecular networks are found to inhibit rotation of molecular rotors that exhibit thermally induced switching at temperatures as low as 5 K for isolated molecules. Additionally, inelastic electron tunneling is employed to induce controlled directional rotation in a different, single molecule motor system. The directionality is explained through the structure of calculated potentials in the motor system. The mechanis (open full item for complete abstract)
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    Committee: Saw-Wai Hla Dr. (Advisor) Subjects: Condensed Matter Physics; Experiments; Low Temperature Physics; Molecular Physics; Molecules; Nanoscience; Nanotechnology; Physics

  • 19. Caplinger, James ULTRAVIOLET RAYLEIGH SCATTER IMAGING FOR SPATIAL TEMPERATURE PROFILES IN ATMOSPHERIC MICRODISCHARGES

    Master of Science (MS), Wright State University, 2014, Physics

    Spatially resolved temperature measurements within a microdischarge in atmospheric pressure air have been conducted using Rayleigh scattering of a pulsed ultraviolet laser. Scattering intensity images were used to generate a radial profile of translational temperature, with the analysis based on the ideal gas inverse relationship of temperature and gas density. Rayleigh scattering results were compared to standard optical emission spectral analyses of N2(C3Πu - B3Πg) bands, where the calculated rotational temperatures from emission were in reasonable agreement with the Rayleigh translational temperature profiles.
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    Committee: Steven Adams Ph.D. (Advisor); Jerry Clark Ph.D. (Committee Chair); Ivan Medvedev Ph.D. (Committee Member) Subjects: Chemistry; Optics; Physics

  • 20. Gudavalli, Dileep Measurement of selenite reduction to elemental selenium by Stenotrophomonas maltophilia OR02.

    Master of Science in Biological Sciences, Youngstown State University, 2013, Department of Biological Sciences and Chemistry

    Selenium is required by all organisms, but too much can be toxic. Environments that are contaminated with selenium contain large amounts of the oxyanions, selenite and selenate, which are toxic to living organisms. Stenotrophomonas maltophilia OR02 (S. maltophilia 02), which was isolated from a heavy metal contaminated site in Oak Ridge, TN, appears to reduce a clear solution of selenite to non-toxic red elemental selenium when grown in the presence of selenite. To test the ability of this strain to remove selenite from its environment, S. maltophilia02 was grown to early log phase and then exposed to 1 mM selenite. Two control experiments containing 1) cells and growth medium and 2) growth medium and selenite were performed simultaneously. Growth over time was monitored by measuring turbidity in Klett units and viable cell counts. Selenium content in the growth medium and cells was monitored using Inductively Coupled Plasma (ICP) spectroscopy. Selenite affected the log phase of the cell growth, and the mechanism of resistance appeared to be reduction of selenite to elemental selenium. The concentration of selenium decreased in the growth medium and increased in pelleted cells. This reduction process can be a useful tool in bioremediation of selenite in the environment. From our results, when treated with 1 mM of sodium selenite the strain removed 17 % of the selenite.
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    Committee: Jonathan Caguiat Ph.D (Advisor); Josef Simeonsson Ph.D (Committee Member); George Yates Ph.D (Committee Member) Subjects: Analytical Chemistry; Biology; Environmental Studies; Microbiology; Toxicology
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