Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Adaptive optics (12)
- Photoluminescence (8)
- Computational Fluid Dynamics (7)
- Electron paramagnetic resonance spectroscopy (6)
- Lasers (6)
-
- #antcenter (5)
- Micromechanics (5)
- Thin films (5)
- Fluid Dynamics (4)
- Hyperfine structure (4)
- Laser communication systems (4)
- Nonlinear optics (4)
- Optical detectors (4)
- Optical fibers (4)
- Optical radar (4)
- Optics (4)
- Quantum wells (4)
- Semiconductors (4)
- Atmospheric turbulence (3)
- Boundary Layer (3)
- Coherence (Optics) (3)
- Dielectrics (3)
- Electric fields (3)
- Image processing (3)
- LIBS (3)
- Laser beams (3)
- Light guides (3)
- Metamaterials (3)
- Mirrors (3)
- Optical communications (3)
- Publication Year
- Publication Type
Articles 31 - 60 of 253
Full-Text Articles in Engineering
Twisted Spatiotemporal Optical Vortex Random Fields, Milo W. Hyde Iv
Twisted Spatiotemporal Optical Vortex Random Fields, Milo W. Hyde Iv
Faculty Publications
We present twisted spatiotemporal optical vortex (STOV) beams, which are partially coherent light sources that possess a coherent optical vortex and a random twist coupling their space and time dimensions. These beams have controllable partial coherence and transverse orbital angular momentum (OAM), which distinguishes them from the more common spatial vortex and twisted beams (known to carry longitudinal OAM) in the literature and should ultimately make them useful in applications such as optical communications and optical tweezing. We present the mathematical analysis of twisted STOV beams, deriving the mutual coherence function and linear and angular momentum densities. We simulate the …
Temperature-Immune Self-Referencing Fabry–Pérot Cavity Sensors, Hengky Chandrahalim, Jonathan W. Smith
Temperature-Immune Self-Referencing Fabry–Pérot Cavity Sensors, Hengky Chandrahalim, Jonathan W. Smith
AFIT Patents
A passive microscopic Fabry-Pérot Interferometer (FPI) sensor an optical fiber a three-dimensional microscopic optical structure formed on a cleaved tip of an optical fighter that reflects a light signal back through the optical fiber. The reflected light is altered by refractive index changes in the three-dimensional structure that is subject to at least one of: (i) thermal radiation; and (ii) volatile organic compounds.
Error Reduction For The Determination Of Transverse Moduli Of Single-Strand Carbon Fibers Via Atomic Force Microscopy, Joshua D. Frey
Error Reduction For The Determination Of Transverse Moduli Of Single-Strand Carbon Fibers Via Atomic Force Microscopy, Joshua D. Frey
Theses and Dissertations
The transverse modulus of single strand carbon fibers is measured using PeakForce Atomic Force Microscopy - Quantitative Nanomechanical Measurement to less than 5 percent error for 11 types of carbon fiber with longitudinal moduli between 924-231 GPA, including export-controlled fibers. Statistical methods are employed to improve the quality of data to exclude outliers within an measurement and within the sample set. A positive linear correlation between the longitudinal and transverse modulus with an R2=0.76 is found. Pitch-based fibers exhibit lower measurement error than PAN-based fibers, while PAN fibers exhibited no apparent modulus correlation when the Pitch fibers are …
Impendance Probe Payload Development For Space-Based Joint Service Collaboration, Brian T. Kay
Impendance Probe Payload Development For Space-Based Joint Service Collaboration, Brian T. Kay
Theses and Dissertations
Collaborations utilizing small spacecraft in near earth orbit between the U. S. Coast Guard Academy (CGA), Naval Research Lab (NRL), the U. S. Naval Academy (USNA), and the Air Force Institute of Technology (AFIT) have initiated scientific and engineering space-based experiments. Sourced opportunities like the VaSpace ThinSat missions have provided a platform for payload, sensor, and experiment development that would have otherwise been resource prohibitive. We have constructed an impedance probe payload derived from the existing ‘Space PlasmA Diagnostic suitE’ (SPADE) mission operating from NASA’s International Space Station. Currently both space and laboratory plasmas are investigated with AC impedance measurements …
Lithium Compound Characterization Via Laser Induced Breakdown Spectroscopy And Raman Spectroscopy, James T. Stofel
Lithium Compound Characterization Via Laser Induced Breakdown Spectroscopy And Raman Spectroscopy, James T. Stofel
Theses and Dissertations
Industries such as lithium-ion battery producers and the nuclear industry community seek to produce and store lithium in pure chemical forms. However, these lithium compounds are reactive with the atmosphere and quickly degrade into less desirable forms. Therefore, industry desires a fast and effective quality control approach to quantify the ingrowth of these secondary lithium chemical forms. This research presents a novel approach using Laser-Induced Breakdown Spectroscopy (LIBS) and Raman spectroscopy in tandem to enhance lithium compound characterization beyond what is achieved by either technique alone. The resulting spectral data are aggregated using data fusion and analyzed using chemometrics for …
Optical Study Of 2-D Detonation Wave Stability, Eulaine T. Grodner
Optical Study Of 2-D Detonation Wave Stability, Eulaine T. Grodner
Theses and Dissertations
Fundamental optical detonation study of detonations constricted to a 2-d plane propagation, and detonations propagating around a curve. All images were processed using modern image processing techniques. The optical techniques used were shadowgraph, Schlieren, and chemiluminescence. In the 2-Dstraight channels, it was determined wave stability was a factor of cell size. It was also determined the detonation wave thickness (area between the combustion and shockwave) was a factor of how much heat available for the detonation. For the detonations propagating around a curve, it was determined the three main classifications of wave stability were stable, unstable, and detonation wave restart. …
Computational Electromagnetic Modeling Of Metasurface Optical Devices With Defect Study, Carlos D. Diaz
Computational Electromagnetic Modeling Of Metasurface Optical Devices With Defect Study, Carlos D. Diaz
Theses and Dissertations
One of the first fabricated metasurface optical devices, the in-plane V-antenna lenses, were plagued by a fundamental transmission limit (<25 >). Two distinct sets of Out-of-Plane phase elements were designed with improved transmission (~60 ). These were fabricated as beamsteerers and characterized in terms of their Bidirectional Transmittance Distribution Function measured as a function of scatter angle. Experimental data from the beamsteerers was analyzed via simulations using a finite element method (FEM). The measurements showed the designed beamsteering, but also a strong zero-order diffraction not present in the simulations, which motivated this study to understand what was causing these differences. …
Photoinduced Trapping Of Charge At Sulfur Vacancies And Copper Ions In Photorefractive Sn2P2S6 Crystals, Timothy D. Gustafson, Eric M. Golden, Elizabeth M. Scherrer, Nancy C. Giles, A. A. Grabar, Sergey A. Basun, Jonathan E. Slagle, Larry E. Halliburton
Photoinduced Trapping Of Charge At Sulfur Vacancies And Copper Ions In Photorefractive Sn2P2S6 Crystals, Timothy D. Gustafson, Eric M. Golden, Elizabeth M. Scherrer, Nancy C. Giles, A. A. Grabar, Sergey A. Basun, Jonathan E. Slagle, Larry E. Halliburton
Faculty Publications
Electron paramagnetic resonance (EPR) is used to monitor photoinduced changes in the charge states of sulfur vacancies and Cu ions in tin hypothiodiphosphate. A Sn2P2S6 crystal containing Cu+ (3d10) ions at Sn2+ sites was grown by the chemical vapor transport method. Doubly ionized sulfur vacancies (V2+S) are also present in the as-grown crystal (where they serve as charge compensators for the Cu+ ions). For temperatures below 70 K, exposure to 532 or 633 nm laser light produces stable Cu2+ (3d9) ions, as electrons move from Cu+ ions to …
On-Chip Silicon Photonic Controllable 2 × 2 Four-Mode Waveguide Switch, Cao Dung Truong, Duy Nguyen Thi Hang, Hengky Chandrahalim, Minh Tuan Trinh
On-Chip Silicon Photonic Controllable 2 × 2 Four-Mode Waveguide Switch, Cao Dung Truong, Duy Nguyen Thi Hang, Hengky Chandrahalim, Minh Tuan Trinh
Faculty Publications
Multimode optical switch is a key component of mode division multiplexing in modern high-speed optical signal processing. In this paper, we introduce for the first time a novel 2 × 2 multimode switch design and demonstrate in the proof-of-concept. The device composes of four Y-multijunctions and 2 × 2 multimode interference coupler using silicon-on-insulator material with four controllable phase shifters. The shifters operate using thermo-optic effects utilizing Ti heaters enabling simultaneous switching of the optical signal between the output ports on four quasi-transverse electric modes with the electric power consumption is in order of 22.5 mW and the switching time …
3-D Fabry–Pérot Cavities Sculpted On Fiber Tips Using A Multiphoton Polymerization Process, Jonathan W. Smith, Jeremiah C. Williams, Joseph S. Suelzer, Nicholas G. Usechak, Hengky Chandrahalim
3-D Fabry–Pérot Cavities Sculpted On Fiber Tips Using A Multiphoton Polymerization Process, Jonathan W. Smith, Jeremiah C. Williams, Joseph S. Suelzer, Nicholas G. Usechak, Hengky Chandrahalim
Faculty Publications
This paper presents 3-D Fabry–Pérot (FP) cavities fabricated directly onto cleaved ends of low-loss optical fibers by a two-photon polymerization (2PP) process. This fabrication technique is quick, simple, and inexpensive compared to planar microfabrication processes, which enables rapid prototyping and the ability to adapt to new requirements. These devices also utilize true 3-D design freedom, facilitating the realization of microscale optical elements with challenging geometries. Three different device types were fabricated and evaluated: an unreleased single-cavity device, a released dual-cavity device, and a released hemispherical mirror dual-cavity device. Each iteration improved the quality of the FP cavity's reflection spectrum. The …
Applications Of Portable Libs For Actinide Analysis, Ashwin P. Rao, John D. Auxier Ii, Dung Vu, Michael B. Shattan
Applications Of Portable Libs For Actinide Analysis, Ashwin P. Rao, John D. Auxier Ii, Dung Vu, Michael B. Shattan
Faculty Publications
A portable LIBS device was used for rapid elemental impurity analysis of plutonium alloys. This device demonstrates the potential for fast, accurate in-situ chemical analysis and could significantly reduce the fabrication time of plutonium alloys.
Statistical Photo-Calibration Of Photo-Detectors For Radiometry Without Calibrated Light Sources Comprising An Arithmetic Unit To Determine A Gain And A Bias From Mean Values And Variance Values, Adrian M. Catarius, Nicholas Yielding, Stephen C. Cain, Michael D. Seal
Statistical Photo-Calibration Of Photo-Detectors For Radiometry Without Calibrated Light Sources Comprising An Arithmetic Unit To Determine A Gain And A Bias From Mean Values And Variance Values, Adrian M. Catarius, Nicholas Yielding, Stephen C. Cain, Michael D. Seal
AFIT Patents
Calibration of a radiometry system uses a readout circuit of a photo-detector to provide first and second measurements collected over first and second integration times, respectively, where the first and second measurements are related to a photonic input to the photo-detector by a gain and a bias. First mean and variance values are computed for a plurality of first measurements. Second mean and variance values are computed for a plurality of second measurements. The gain and bias are determined from the first and second mean values and the first and second variance values without the use of a calibrated source. …
A Physics-Based Machine Learning Study Of The Behavior Of Interstitial Helium In Single Crystal W–Mo Binary Alloys, Adib J. Samin
A Physics-Based Machine Learning Study Of The Behavior Of Interstitial Helium In Single Crystal W–Mo Binary Alloys, Adib J. Samin
Faculty Publications
In this work, the behavior of dilute interstitial helium in W–Mo binary alloys was explored through the application of a first principles-informed neural network (NN) in order to study the early stages of helium-induced damage and inform the design of next generation materials for fusion reactors. The neural network (NN) was trained using a database of 120 density functional theory (DFT) calculations on the alloy. The DFT database of computed solution energies showed a linear dependence on the composition of the first nearest neighbor metallic shell. This NN was then employed in a kinetic Monte Carlo simulation, which took into …
Single-Pulse, Kerr-Effect Mueller Matrix Lidar Polarimeter, Keyser, Christian K., Richard K. Martin, Helena Lopez-Aviles, Khanh Nguyen, Arielle M. Adams, Demetrios Christodoulides
Single-Pulse, Kerr-Effect Mueller Matrix Lidar Polarimeter, Keyser, Christian K., Richard K. Martin, Helena Lopez-Aviles, Khanh Nguyen, Arielle M. Adams, Demetrios Christodoulides
Faculty Publications
We present a novel light detection and ranging (LiDAR) polarimeter that enables measurement of 12 of 16 sample Mueller matrix elements in a single, 10 ns pulse. The new polarization state generator (PSG) leverages Kerr phase modulation in a birefringent optical fiber, creating a probe pulse characterized by temporally varying polarization. Theoretical expressions for the Polarization State Generator (PSG) Stokes vector are derived for birefringent walk-off and no walk-off and incorporated into a time-dependent polarimeter signal model employing multiple polarization state analyzers (PSA). Polarimeter modeling compares the Kerr effect and electro-optic phase modulator–based PSG using a single Polarization State Analyzer …
Experimental Determination Of The (0/−) Level For Mg Acceptors In Β-Ga2O3 Crystals, Christopher A. Lenyk, Trevor A . Gustafson, Sergey A. Basun, Larry E. Halliburton, Nancy C. Giles
Experimental Determination Of The (0/−) Level For Mg Acceptors In Β-Ga2O3 Crystals, Christopher A. Lenyk, Trevor A . Gustafson, Sergey A. Basun, Larry E. Halliburton, Nancy C. Giles
Faculty Publications
Electron paramagnetic resonance (EPR) is used to experimentally determine the (0/−) level of the Mg acceptor in an Mg-doped β-Ga2O3 crystal. Our results place this level 0.65 eV (±0.05 eV) above the valence band, a position closer to the valence band than the predictions of several recent computational studies. The crystal used in this investigation was grown by the Czochralski method and contains large concentrations of Mg acceptors and Ir donors, as well as a small concentration of Fe ions and an even smaller concentration of Cr ions. Below room temperature, illumination with 325 nm laser light …
One-Dimensional Multi-Frame Blind Deconvolution Using Astronomical Data For Spatially Separable Objects, Marc R. Brown
One-Dimensional Multi-Frame Blind Deconvolution Using Astronomical Data For Spatially Separable Objects, Marc R. Brown
Theses and Dissertations
Blind deconvolution is used to complete missions to detect adversary assets in space and to defend the nation's assets. A new algorithm was developed to perform blind deconvolution for objects that are spatially separable using multiple frames of data. This new one-dimensional approach uses the expectation-maximization algorithm to blindly deconvolve spatially separable objects. This object separation reduces the size of the object matrix from an NxN matrix to two singular vectors of length N. With limited knowledge of the object and point spread function the one-dimensional algorithm successfully deconvolved the objects in both simulated and laboratory data.
Laser Shock Peening Pressure Impulse Determination Via Empirical Data-Matching With Optimization Software, Colin C. Engebretsen
Laser Shock Peening Pressure Impulse Determination Via Empirical Data-Matching With Optimization Software, Colin C. Engebretsen
Theses and Dissertations
Laser shock peening (LSP) is a form of work hardening by means of laser induced pressure impulse. LSP imparts compressive residual stresses which can improve fatigue life of metallic alloys for structural use. The finite element modeling (FEM) of LSP is typically done by applying an assumed pressure impulse, as useful experimental measurement of this pressure impulse has not been adequately accomplished. This shortfall in the field is a current limitation to the accuracy of FE modeling, and was addressed in the current work. A novel method was tested to determine the pressure impulse shape in time and space by …
Laser Induced Thermal Degradation Of Carbon Fiber-Carbon Nanotube Hybrid Laminates, Joshua A. Key
Laser Induced Thermal Degradation Of Carbon Fiber-Carbon Nanotube Hybrid Laminates, Joshua A. Key
Theses and Dissertations
Recent advancements in fiber laser technology have increased interest in target material interactions and the development of thermal protection layers for tactical laser defense. A significant material of interest is carbon fiber reinforced polymers due to their increased use in aircraft construction. In this work, the thermal response of carbon fiber-carbon nanotube (CNT) hybrid composites exposed to average irradiances of 0.87-6.8 W/cm2 were observed using a FLIR sc6900 thermal camera. The camera had a pixel resolution of 640x512 which resulted in a spatial resolution of 0.394x0.383 mm/pixel for the front and 0.463x0.491 mm/pixel for the back. The hybrid samples …
Measurement Of The 160Gd(P,N)160Tb Excitation Function From 4 18 Mev, Using A Stacked Foil Technique, Ryan K. Chapman
Measurement Of The 160Gd(P,N)160Tb Excitation Function From 4 18 Mev, Using A Stacked Foil Technique, Ryan K. Chapman
Theses and Dissertations
A stack of thin Gd, Ti, and Cu foils were irradiated with an 18 MeV proton beam at Lawrence-Berkeley National Laboratory's 88-Inch Cyclotron to investigate the 160Gd(p,n)160Tb nuclear reaction for nuclear forensics applications. This experiment will improve knowledge of 160Tb production rates, allowing 160Tb to be efficiently created in a foil stack consisting of other proton induced isotopes for forensics applications. A set of 15 measured cross sections between 4-18 MeV for 160Gd(p,n)160Tb were obtained using a stacked foil technique. The foil stack consisted of one stainless steel, one iron, fifteen gadolinium, …
Rapid Analysis Of Plutonium Surrogate Material Via Hand-Held Laser-Induced Breakdown Spectroscopy, Ashwin P. Rao
Rapid Analysis Of Plutonium Surrogate Material Via Hand-Held Laser-Induced Breakdown Spectroscopy, Ashwin P. Rao
Theses and Dissertations
This work investigated the capability of a portable LIBS device to detect and quantify dopants in plutonium surrogate alloys, specifically gallium, which is a common stabilizer used in plutonium alloys. The SciAps Z500-ER was utilized to collect spectral data from cerium-gallium alloys of varying gallium concentrations. Calibration models were built to process spectra from the Ce-Ga alloys and calculate gallium concentration from spectral emission intensities. Univariate and multivariate analysis techniques were used to determine limits of detection of different emission line ratios. Spatial mapping measurements were conducted to determine the device's ability to detect variations in gallium concentration on the …
Conduction Mapping For Quality Control Of Laser Powder Bed Fusion Additive Manufacturing, Chance M. Baxter
Conduction Mapping For Quality Control Of Laser Powder Bed Fusion Additive Manufacturing, Chance M. Baxter
Theses and Dissertations
A process was developed to identify potential defects in previous layers of Selective Laser Melting (SLM) Powder Bed Fusion (PBF) 3D printed metal parts using a mid-IR thermal camera to track infrared 3.8-4 m band emission over time as the part cooled to ambient temperature. Efforts focused on identifying anomalies in thermal conduction. To simplify the approach and reduce the need for significant computation, no attempts were made to calibrate measured intensity, extract surface temperature, apply machine learning, or compare measured cool-down behavior to computer model predictions. Raw intensity cool-down curves were fit to a simplified functional form designed to …
The Design Of A Continuous Wave Molecular Nitrogen Stimulated Raman Laser In The Visible Spectrum, Timothy J. Bate
The Design Of A Continuous Wave Molecular Nitrogen Stimulated Raman Laser In The Visible Spectrum, Timothy J. Bate
Theses and Dissertations
Hollow-core photonic crystal fibers (HCPCFs) shows promise as a hybrid laser with higher nonlinear process limits and small beam size over long gain lengths. This work focuses on the design of a CW molecular nitrogen (N2) stimulated Raman laser. N2 offers Raman gains scaling up to 900 amg, scaling higher than H2. The cavity experiment showed the need to include Rayleigh scattering in the high pressure required for N2 Raman lasing. Even at relatively low pressure ssuch as 1,500 psi, high conversion percentages should be found if the fiber length is chosen based on …
Cn And C2 Spectroscopy On The Pulsed Ablation Of Graphite In The Visible Spectrum, Brandon A. Pierce
Cn And C2 Spectroscopy On The Pulsed Ablation Of Graphite In The Visible Spectrum, Brandon A. Pierce
Theses and Dissertations
An experimental study was conducted on the nanosecond pulsed laser ablation of graphite using a KrF laser at a fluence of 3.8 J/cm2 in Air, Ar, He, and N2. Optical emissions spectroscopy revealed the C2 Swan sequences and the CN Violet sequences. A spectroscopic model was developed to extract the molecular rotational and vibrational temperatures of each excited species for t=0.5-10 microseconds after laser irradiation. The rovibrational temperatures were found to vary with background gas for the CN Violet; however, only the vibrational temperature varied between He and the other background gases for C2 Swan. …
Synthesizing General Electromagnetic Partially Coherent Sources From Random, Correlated Complex Screens, Milo W. Hyde Iv
Synthesizing General Electromagnetic Partially Coherent Sources From Random, Correlated Complex Screens, Milo W. Hyde Iv
Faculty Publications
We present a method to generate any genuine electromagnetic partially coherent source (PCS) from correlated, stochastic complex screens. The method described here can be directly implemented on existing spatial-light-modulator-based vector beam generators and can be used in any application which utilizes electromagnetic PCSs. Our method is based on the genuine cross-spectral density matrix criterion. Applying that criterion, we show that stochastic vector field realizations (corresponding to a desired electromagnetic PCS) can be generated by passing correlated Gaussian random numbers through “filters” with space-variant transfer functions. We include step-by-step instructions on how to generate the electromagnetic PCS field realizations. As an …
Superconducting Phase Transition In Inhomogeneous Chains Of Superconducting Islands, Eduard Ilin, Irina Burkova, Xiangyu Song, Michael Pak, Dmitri S. Golubev, Alexey Bezryadin
Superconducting Phase Transition In Inhomogeneous Chains Of Superconducting Islands, Eduard Ilin, Irina Burkova, Xiangyu Song, Michael Pak, Dmitri S. Golubev, Alexey Bezryadin
Faculty Publications
We study one-dimensional chains of superconducting islands with a particular emphasis on the regime in which every second island is switched into its normal state, thus forming a superconductor-insulator-normal metal (S-I-N) repetition pattern. As is known since Giaever tunneling experiments, tunneling charge transport between a superconductor and a normal metal becomes exponentially suppressed, and zero-bias resistance diverges, as the temperature is reduced and the energy gap of the superconductor grows larger than the thermal energy. Here we demonstrate that this physical phenomenon strongly impacts transport properties of inhomogeneous superconductors made of weakly coupled islands with fluctuating values of the critical …
Monte Carlo And Experimental Analysis Of A Novel Directional Rotating Scatter Mask Gamma Detection System, Julie V. Logan, Darren E. Holland, Larry W. Burggraf, Justin A. Clinton, Buckley E. O'Day Iii
Monte Carlo And Experimental Analysis Of A Novel Directional Rotating Scatter Mask Gamma Detection System, Julie V. Logan, Darren E. Holland, Larry W. Burggraf, Justin A. Clinton, Buckley E. O'Day Iii
Faculty Publications
Excerpt: This work demonstrates successful experimental operation of a prototype system to identify source direction which was modeled using a library of signals simulated using GEANT and a novel algorithm....
Generating Electromagnetic Nonuniformly Correlated Beams, Milo W. Hyde Iv, Xifeng Xiao, David G. Voelz
Generating Electromagnetic Nonuniformly Correlated Beams, Milo W. Hyde Iv, Xifeng Xiao, David G. Voelz
Faculty Publications
We develop a method to generate electromagnetic nonuniformly correlated (ENUC) sources from vector Gaussian Schell-model (GSM) beams. Having spatially varying correlation properties, ENUC sources are more difficult to synthesize than their Schell-model counterparts (which can be generated by filtering circular complex Gaussian random numbers) and, in past work, have only been realized using Cholesky decomposition—a computationally intensive procedure. Here we transform electromagnetic GSM field instances directly into ENUC instances, thereby avoiding computing Cholesky factors resulting in significant savings in time and computing resources. We validate our method by generating (via simulation) an ENUC beam with desired parameters. We find the …
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 …
Gamma-Ray Radiation Effects In Graphene-Based Transistors With H-Bn Nanometer Film Substrates, E. J. Cazalas, Michael R. Hogsed, S. R. Vangala, Michael R. Snure, John W. Mcclory
Gamma-Ray Radiation Effects In Graphene-Based Transistors With H-Bn Nanometer Film Substrates, E. J. Cazalas, Michael R. Hogsed, S. R. Vangala, Michael R. Snure, John W. Mcclory
Faculty Publications
Radiation effects on graphene field effect transistors (GFETs) with hexagonal boron nitride (h-BN) thin film substrates are investigated using 60Co gamma-ray radiation. This study examines the radiation response using many samples with varying h-BN film thicknesses (1.6 and 20 nm thickness) and graphene channel lengths (5 and 10 μm). These samples were exposed to a total ionizing dose of approximately 1 Mrad(Si). I-V measurements were taken at fixed time intervals between irradiations and postirradiation. Dirac point voltage and current are extracted from the I-V measurements, as well as mobility, Dirac voltage hysteresis, and the total number of GFETs that remain …
Measurement Of Electron Density And Temperature From Laser-Induced Nitrogen Plasma At Elevated Pressure (1–6 Bar), Ashwin P. Rao [*], Mark Gragston, Anil K. Patnaik, Paul S. Hsu, Michael B. Shattan
Measurement Of Electron Density And Temperature From Laser-Induced Nitrogen Plasma At Elevated Pressure (1–6 Bar), Ashwin P. Rao [*], Mark Gragston, Anil K. Patnaik, Paul S. Hsu, Michael B. Shattan
Faculty Publications
Laser-induced plasmas experience Stark broadening and shifts of spectral lines carrying spectral signatures of plasma properties. In this paper, we report time-resolved Stark broadening measurements of a nitrogen triplet emission line at 1–6 bar ambient pressure in a pure nitrogen cell. Electron densities are calculated using the Stark broadening for different pressure conditions, which are shown to linearly increase with pressure. Additionally, using a Boltzmann fit for the triplet, the electron temperature is calculated and shown to decrease with increasing pressure. The rate of plasma cooling is observed to increase with pressure. The reported Stark broadening based plasma diagnostics in …