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Articles 1 - 14 of 14
Full-Text Articles in Physics
Laser-Induced Modifications In Two-Dimensional Materials, Tariq Afaneh
Laser-Induced Modifications In Two-Dimensional Materials, Tariq Afaneh
USF Tampa Graduate Theses and Dissertations
Atomically thin two-dimensional (2D) materials have attracted a growing interest in the lastdecade from the fundamental point of view as well as their potential applications in functional devices. Due to their high surface-to-volume ratio, the physical properties of 2D materials are very sensitive to the environmental factor such as surrounding media and illumination conditions (e.g. light-mater interaction). In the first part of this dissertation I will present recent advances in developing laser-assisted methods to tune the physical properties of 2D transition metal dichalcogenides (TMDs). We demonstrate laser-assisted chemical modification ultrathin TMDs, locally replacing selenium by sulfur atoms. The photo-conversion process …
Deep Donors And Acceptors In Β-Ga2O3 Crystals: Determination Of The Fe2+/3+ Level By A Noncontact Method, Christopher A. Lenyk, Trevor A . Gustafson, Larry E. Halliburton, Nancy C. Giles
Deep Donors And Acceptors In Β-Ga2O3 Crystals: Determination Of The Fe2+/3+ Level By A Noncontact Method, Christopher A. Lenyk, Trevor A . Gustafson, Larry E. Halliburton, Nancy C. Giles
Faculty Publications
Electron paramagnetic resonance (EPR), infrared absorption, and thermoluminescence (TL) are used to determine the Fe2+/3+ level in Fe-doped β-Ga2O3 crystals. With these noncontact spectroscopy methods, a value of 0.84 ± 0.05 eV below the conduction band is obtained for this level. Our results clearly establish that the E2 level observed in deep level transient spectroscopy (DLTS) experiments is due to the thermal release of electrons from Fe2+ ions. The crystals used in this investigation were grown by the Czochralski method and contained large concentrations of Fe acceptors and Ir donors, and trace amounts of Cr …
Probing Quantized Excitations And Many-Body Correlations In Transition Metal Dichalcogenides With Optical Spectroscopy, Shao-Yu Chen
Probing Quantized Excitations And Many-Body Correlations In Transition Metal Dichalcogenides With Optical Spectroscopy, Shao-Yu Chen
Doctoral Dissertations
Layered transition metal dichalcogenides (TMDCs) have attracted great interests in recent years due to their physical properties manifested in different polytypes: Hexagonal(H)-TMDC,which is semiconducting, exhibits strong Coulomb interaction and intriguing valleytronic properties; distorted octahedral(T’)-TMDC,which is semi-metallic, is predicted to exhibit rich nontrivial topological physics. In this dissertation,we employ the polarization-resolved micron-Raman/PL spectroscopy to investigate the optical properties of the atomic layer of several polytypes of TMDC. In the first part for polarization-resolved Raman spectroscopy, we study the lattice vibration of both H and T’-TMDC, providing a thorough understanding of the polymorphism of TMDCs. We demonstrate that Raman spectroscopy is a …
Near Bandgap Two-Photon Excited Luminescence Of Inas Quantum Dots, Xian Hu
Near Bandgap Two-Photon Excited Luminescence Of Inas Quantum Dots, Xian Hu
Graduate Theses and Dissertations
Semiconductor quantum dots (QDs) confine carriers in three dimensions, resulting in atomic-like energy levels as well as size-dependent electrical and optical properties. Self-assembled III-V QD is one of the most studied semiconductor QDs thanks to their well-established fabrication techniques and versatile optical properties. This dissertation presents the photoluminescence (PL) study of the InAs/GaAs QDs with both above bandgap continuous-wave excitation (one-photon excitation) and below-bandgap pulse excitation (two-photon excitation). Samples of ensemble QDs, single QD (SQD), and QDs in a micro-cavity, all grown by molecular beam epitaxy, are used in this study. Morphology of these samples was examined using atomic force …
Copper-Doped Lithium Triborate (Lib3o5) Crystals: A Photoluminescence, Thermoluminescence, And Electron Paramagnetic Resonance Study, Brant E. Kananen, John W. Mcclory, Nancy C. Giles, Larry E. Halliburton
Copper-Doped Lithium Triborate (Lib3o5) Crystals: A Photoluminescence, Thermoluminescence, And Electron Paramagnetic Resonance Study, Brant E. Kananen, John W. Mcclory, Nancy C. Giles, Larry E. Halliburton
Faculty Publications
When doped with copper ions, lithium borate materials are candidates for use in radiation dosimeters. Copper-doped lithium tetraborate (Li2B4O7) crystals have been widely studied, but little is known thus far about copper ions in lithium triborate (LiB3O5) crystals. In the present investigation, Cu+ ions (3d10) were diffused into an undoped LiB3O5 crystal at high temperature. These ions occupy both Li+ and interstitial positions in the crystal. A photoluminescence (PL) band peaking near 387 nm and a photoluminescence excitation (PLE) band peaking near 273 nm verify that a portion of these Cu+ ions are located at regular Li+ sites. After an …
Photoluminescence From Gan Co-Doped With C And Si, Mykhailo Vorobiov
Photoluminescence From Gan Co-Doped With C And Si, Mykhailo Vorobiov
Theses and Dissertations
This thesis devoted to the experimental studies of yellow and blue luminescence (YL and BL relatively) bands in Gallium Nitride samples doped with C and Si. The band BLC was at first observed in the steady-state photoluminescence spectrum under high excitation intensities and discerned from BL1 and BL2 bands appearing in the same region of the spectrum. Using the time-resolved photoluminescence spectrum, we were able to determine the shape of the BLC and its position at 2.87 eV. Internal quantum efficiency of the YL band was estimated to be 90\%. The hole capture coefficient of the BLC …
Light Soaking Phenomena In Organic-Inorganic Mixed Halide Perovskite Single Crystals, Hye Ryung Byun, Dae Young Park, Hye Min Oh, Gon Namkoong, Mun Seok Jeong
Light Soaking Phenomena In Organic-Inorganic Mixed Halide Perovskite Single Crystals, Hye Ryung Byun, Dae Young Park, Hye Min Oh, Gon Namkoong, Mun Seok Jeong
Electrical & Computer Engineering Faculty Publications
Recently, organic inorganic mixed halide perovskite (MAPbX3; MA = CH3NH3+, X = Cl-, Br-, or I-) single crystals with low defect densities have been highlighted as candidate materials for high-efficiency photovoltaics and optoelectronics. Here we report the optical and structural investigations of mixed halide perovskite (MAPbBr3-xIx) single crystals. Mixed halide perovskite single crystals showed strong light soaking phenomena with light illumination conditions that were correlated to the trapping and detrapping events from defect sites. By systematic investigation with optical analysis, we found that the …
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 …
Electron-Phonon Interactions And Quantum Confinement Effects On Optical Transitions In Nanoscale Silicon Films, Vimal Kumar Kamineni
Electron-Phonon Interactions And Quantum Confinement Effects On Optical Transitions In Nanoscale Silicon Films, Vimal Kumar Kamineni
Legacy Theses & Dissertations (2009 - 2024)
Theoretical studies have attributed the temperature dependence of the linear optical response (dielectric function) of bulk semiconductors to electron-phonon interactions and thermal expansion of the lattice. However, the role of phonons in the optical properties of nanoscale structures is often overlooked. This thesis systematically investigates the impact of both carrier confinement and electron-phonon interactions using nanoscale films of silicon in crystalline silicon quantum wells (c-Si QW). Spectroscopic ellipsometry (SE) is a linear optical technique used to of extract the dielectric function and thickness of very thin films. X-ray reflectivity (XRR) was used as the complementary thickness metrology method. The dielectric …
Optical Characterization And Modeling Of Compositionally Matched Indium Arsenide-Antimonide Bulk And Multiple Quantum Well Semiconductors, Scott C. Phillips
Optical Characterization And Modeling Of Compositionally Matched Indium Arsenide-Antimonide Bulk And Multiple Quantum Well Semiconductors, Scott C. Phillips
Theses and Dissertations
Indium arsenide-antimonide (InAsSb) semiconductors have been determined to emit in the 3-5 micrometer range, the window of interest for countermeasures against infrared electro-optical threats. This experiment set out to cross the bulk to quantum well characterization barrier by optically characterizing two sets of compositionally matched type I quantum well and bulk well material samples. Absorption measurements determined the band gap energy of the bulk samples and the first allowed subband transition for the quantum wells. By collecting absorption spectra at different temperatures, the trend of the energy transitions was described by fitting a Varshni equation to them. The expected result …
Time-Resolved Photoluminescence Of Inas/Gainsb Quantum Well Lasers, Michael R. Mckay
Time-Resolved Photoluminescence Of Inas/Gainsb Quantum Well Lasers, Michael R. Mckay
Theses and Dissertations
In the world of semiconductor photonic device fabrication, one important objective may be to extract as much light as possible from the device. In these devices, photons are created when electrons recombine with holes by transitioning from a high-energy state to a lower one. Unfortunately, electron-hole recombination does not always result in the formation of a photon. There are three basic types of recombination: the first results in the formation of a photon and is called radiative recombination; and the second and third, known as Shockley-Read-Hall and Auger recombination, result in the heating of the device and do not produce …
Photoluminescence Of Single Quantum Well Structures In Gallium Arsenide, Christian A. Bartholomew
Photoluminescence Of Single Quantum Well Structures In Gallium Arsenide, Christian A. Bartholomew
Theses and Dissertations
The continued development of state-of the-art semiconductor technologies and devices by the United States Air Force and the Department of Defense requires accurate and efficient techniques to evaluate and model these new materials. Of particular interest to the Air Force are quantum well structures which can be used for small-scale laser sources in fly-by-light applications, as efficient infrared countermeasures to heat-seeking missiles, or as advanced seekers in optically guided missiles. This thesis provides the initial experimental procedures and data necessary to begin producing accurate yet robust models. Although carrier effective masses could not be evaluated using hot-electron photoluminescence, photoluminescence excitation …
Photoluminescence And Electroluminescence Of Erbium And Neodymium Implanted Semiconductors, James R. Hunter
Photoluminescence And Electroluminescence Of Erbium And Neodymium Implanted Semiconductors, James R. Hunter
Theses and Dissertations
Low temperature photoluminescence (PL) and electroluminescence (EL) measurements were used to study the excitation of erbium- and neodymium-implanted GaAs and AlxGa1-xAs (x=0. 1, 0.3) pn-junctions. The rare-earth (RE) emissions were investigated as a function of ion dose, aluminum mole fraction, laser excitation power, and applied forward bias voltage for the implanted samples. Low temperature PL was also measured from Er doped silicon grown by the metalorganic chemical vapor-phase deposition (MOCVD) method using various growth parameters.. The MOCVD-grown Si samples were studied as a function of metalorganic source temperature, silane (SiH4) flow, growth time, and …
The Excitation Mechanism Of Praseodymium-Doped Semiconductors, Paul L. Thee
The Excitation Mechanism Of Praseodymium-Doped Semiconductors, Paul L. Thee
Theses and Dissertations
This study on praseodymium Pr luminescence in AlxGa1-xAs was conducted to enhance the understanding of the excitation mechanism. Pr was implanted at 390 keV with doses from 5 x 1012 to 5 x 1013 sq cm into AlxGa1-xAs x0.0 to 0.50 wafers which were annealed using the rapid thermal annealing RTA method. Low temperature photoluminescence PL was conducted using an Ar-ion laser and Ge detector. PL emissions of Pr from all hosts include peaks near 1.3 and 1.6 µm which are assigned to the intra-4f transitions of 1G4 yielding 3H5 …