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Articles 1 - 30 of 56
Full-Text Articles in Engineering Physics
Effect Of Fabrication Parameters On The Ferroelectricity Of Hafnium Zirconium Oxide Films: A Statistical Study, Guillermo A. Salcedo, Ahmad E. Islam, Elizabeth Reichley, Michael Dietz, Christine M. Schubert Kabban, Kevin D. Leedy, Tyson C. Back, Weison Wang, Andrew Green, Timothy S. Wolfe, James M. Sattler
Effect Of Fabrication Parameters On The Ferroelectricity Of Hafnium Zirconium Oxide Films: A Statistical Study, Guillermo A. Salcedo, Ahmad E. Islam, Elizabeth Reichley, Michael Dietz, Christine M. Schubert Kabban, Kevin D. Leedy, Tyson C. Back, Weison Wang, Andrew Green, Timothy S. Wolfe, James M. Sattler
Faculty Publications
Ferroelectricity in hafnium zirconium oxide (Hf1−xZrxO2) and the factors that impact it have been a popular research topic since its discovery in 2011. Although the general trends are known, the interactions between fabrication parameters and their effect on the ferroelectricity of Hf1−xZrxO2 require further investigation. In this paper, we present a statistical study and a model that relates Zr concentration (x), film thickness (tf), and annealing temperature (Ta) with the remanent polarization (Pr) in tungsten (W)-capped Hf1−xZrxO2. …
The Behavior Of ½⟨111⟩ Screw Dislocations In W–Mo Alloys Analyzed Through Atomistic Simulations, Lucas A. Heaton, Kevin Chu, Adib J. Samin
The Behavior Of ½⟨111⟩ Screw Dislocations In W–Mo Alloys Analyzed Through Atomistic Simulations, Lucas A. Heaton, Kevin Chu, Adib J. Samin
Faculty Publications
Analyzing plastic flow in refractory alloys is relevant to many different commercial and technological applications. In this study, screw dislocation statics and dynamics were studied for various compositions of the body-centered cubic binary alloy tungsten–molybdenum (W–Mo). The core structure did not appear to change for different alloy compositions, consistent with the literature. The pure tungsten and pure molybdenum samples had the lowest plastic flow, while the highest dislocation velocities were observed for equiatomic, W0.5Mo0.5 alloys. In general, dislocation velocities were found to largely align with a well-established dislocation mobility phenomenological model supporting two discrete dislocation mobility regimes, …
Directional Microwave Emission From Femtosecond-Laser Illuminated Linear Arrays Of Superconducting Rings, Thomas J. Bullard, Kyle Frische, Charlie Ebbing, Stephen J. Hageman, John Morrison, John Bulmer, Enam A. Chowdury, Michael L. Dexter, Timothy J. Haugan, Anil K. Patniak
Directional Microwave Emission From Femtosecond-Laser Illuminated Linear Arrays Of Superconducting Rings, Thomas J. Bullard, Kyle Frische, Charlie Ebbing, Stephen J. Hageman, John Morrison, John Bulmer, Enam A. Chowdury, Michael L. Dexter, Timothy J. Haugan, Anil K. Patniak
Faculty Publications
We examine the electromagnetic emission from two photo-illuminated linear arrays composed of inductively charged superconducting ring elements. The arrays are illuminated by an ultrafast infrared laser that triggers microwave broadband emission detected in the 1–26 GHz range. Based on constructive interference from the arrays a narrowing of the forward radiation lobe is observed with increasing element count and frequency demonstrating directed GHz emission. Results suggest that higher frequencies and a larger number of elements are achievable leading to a unique pulsed array emitter concept that can span frequencies from the microwave to the terahertz (THz) regime.
Impact Of Silicon Ion Irradiation On Aluminum Nitride-Transduced Microelectromechanical Resonators, David D. Lynes, Joshua Young, Eric Lang, Hengky Chandrahalim
Impact Of Silicon Ion Irradiation On Aluminum Nitride-Transduced Microelectromechanical Resonators, David D. Lynes, Joshua Young, Eric Lang, Hengky Chandrahalim
Faculty Publications
Microelectromechanical systems (MEMS) resonators use is widespread, from electronic filters and oscillators to physical sensors such as accelerometers and gyroscopes. These devices' ubiquity, small size, and low power consumption make them ideal for use in systems such as CubeSats, micro aerial vehicles, autonomous underwater vehicles, and micro-robots operating in radiation environments. Radiation's interaction with materials manifests as atomic displacement and ionization, resulting in mechanical and electronic property changes, photocurrents, and charge buildup. This study examines silicon (Si) ion irradiation's interaction with piezoelectrically transduced MEMS resonators. Furthermore, the effect of adding a dielectric silicon oxide (SiO2) thin film is …
Interband Transitions And Critical Points Of Single-Crystal Thoria Compared With Urania, Christina Dugan, Lu Wang, Kai Zhang, James M. Mann, Martin M. Kimani, Wai-Ning Mei, Peter A. Dowben, James C. Petrosky
Interband Transitions And Critical Points Of Single-Crystal Thoria Compared With Urania, Christina Dugan, Lu Wang, Kai Zhang, James M. Mann, Martin M. Kimani, Wai-Ning Mei, Peter A. Dowben, James C. Petrosky
Faculty Publications
The interband transitions of UO2 are validated independently through cathode luminescence. A picture emerges consistent with density functional theory. While theory is generally consistent with experiment, it is evident from the comparison of UO2 and ThO2 that the choice of functional can significantly alter the bandgap and some details of the band structure, in particular at the conduction band minimum. Strictly ab initio predictions of the optical properties of the actinide compounds, based on density functional theory alone, continue to be somewhat elusive.
Electron Traps In Ag-Doped Li2B4O7 Crystals: The Role Of Ag Interstitial Ions, Timothy D. Gustafson, Brant E. Kananen, Nancy C. Giles, Brian C. Holloway, Volodymyr T. Adamiv, Ihor M. Teslyuk, Yaroslav V. Burak, Larry E. Halliburton
Electron Traps In Ag-Doped Li2B4O7 Crystals: The Role Of Ag Interstitial Ions, Timothy D. Gustafson, Brant E. Kananen, Nancy C. Giles, Brian C. Holloway, Volodymyr T. Adamiv, Ihor M. Teslyuk, Yaroslav V. Burak, Larry E. Halliburton
Faculty Publications
Electron paramagnetic resonance (EPR) is used to establish models for electron traps in Ag-doped lithium tetraborate (Li2B4O7) crystals. When exposed at room temperature to ionizing radiation, electrons are trapped at interstitial Ag+ ions and holes are trapped at Ag+ ions on Li+ sites. The trapped electrons occupy a 5s1 orbital on the interstitial Ag ions (some of the unpaired spin density is also on neighboring ions). Three EPR spectra are assigned to electrons trapped at interstitial Ag ions. Their g values are near 1.99 and they have resolved hyperfine structure …
Development Of Advanced Machine Learning Models For Analysis Of Plutonium Surrogate Optical Emission Spectra, Ashwin P. Rao, Phillip R. Jenkins, John D. Auxier Ii, Michael B. Shattan, Anil Patnaik
Development Of Advanced Machine Learning Models For Analysis Of Plutonium Surrogate Optical Emission Spectra, Ashwin P. Rao, Phillip R. Jenkins, John D. Auxier Ii, Michael B. Shattan, Anil Patnaik
Faculty Publications
This work investigates and applies machine learning paradigms seldom seen in analytical spectroscopy for quantification of gallium in cerium matrices via processing of laser-plasma spectra. Ensemble regressions, support vector machine regressions, Gaussian kernel regressions, and artificial neural network techniques are trained and tested on cerium-gallium pellet spectra. A thorough hyperparameter optimization experiment is conducted initially to determine the best design features for each model. The optimized models are evaluated for sensitivity and precision using the limit of detection (LoD) and root mean-squared error of prediction (RMSEP) metrics, respectively. Gaussian kernel regression yields the superlative predictive model with an RMSEP of …
Studying The Conditions For Magnetic Reconnection In Solar Flares With And Without Precursor Flares, Seth H. Garland, Daniel J. Emmons, Robert D. Loper
Studying The Conditions For Magnetic Reconnection In Solar Flares With And Without Precursor Flares, Seth H. Garland, Daniel J. Emmons, Robert D. Loper
Faculty Publications
Forecasting of solar flares remains a challenge due to the limited understanding of the triggering mechanisms associated with magnetic reconnection, the primary physical phenomenon connected to these events. Studies have indicated that changes to the photospheric magnetic fields associated with magnetic reconnection – particularly in relation to the field helicity – occur during solar flare events. This study utilized data from the Solar Dynamics Observatory (SDO) Helioseismic and Magnetic Imager (HMI) and SpaceWeather HMI Active Region Patches (SHARPs) to analyze full vector-field component data of the photospheric magnetic field during solar flare events within a near decade long HMI dataset. …
Zn Acceptors In Β-Ga2O3 Crystals, Timothy D. Gustafson, J. Jesenovec, Christopher A. Lenyk, Nancy C. Giles, J. S. Mccloy, M. Mccluskey, Larry E. Halliburton
Zn Acceptors In Β-Ga2O3 Crystals, Timothy D. Gustafson, J. Jesenovec, Christopher A. Lenyk, Nancy C. Giles, J. S. Mccloy, M. Mccluskey, Larry E. Halliburton
Faculty Publications
Electron paramagnetic resonance (EPR) is used to identify and characterize neutral zinc acceptors in Zn-doped β-Ga2O3 crystals. Two EPR spectra are observed at low temperatures, one from Zn ions at tetrahedral Ga(1) sites (the Zn0Ga1 acceptor) and one from Zn ions at octahedral Ga(2) sites (the Zn0Ga2 acceptor). These Zn acceptors are small polarons, with the unpaired spin localized in each case on a threefold coordinated oxygen O(I) ion adjacent to the Zn ion. Resolved hyperfine interactions with neighboring 69Ga and 71Ga nuclei allow the EPR spectra from the two acceptors …
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 …
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 …
Fast And Effective Techniques For Lwir Radiative Transfer Modeling: A Dimension-Reduction Approach, Nicholas M. Westing [*], Brett J. Borghetti, Kevin C. Gross
Fast And Effective Techniques For Lwir Radiative Transfer Modeling: A Dimension-Reduction Approach, Nicholas M. Westing [*], Brett J. Borghetti, Kevin C. Gross
Faculty Publications
The increasing spatial and spectral resolution of hyperspectral imagers yields detailed spectroscopy measurements from both space-based and airborne platforms. These detailed measurements allow for material classification, with many recent advancements from the fields of machine learning and deep learning. In many scenarios, the hyperspectral image must first be corrected or compensated for atmospheric effects. Radiative Transfer (RT) computations can provide look up tables (LUTs) to support these corrections. This research investigates a dimension-reduction approach using machine learning methods to create an effective sensor-specific long-wave infrared (LWIR) RT model.
M2 Factor Of A Vector Schell-Model Beam, Milo W. Hyde Iv, Mark F. Spencer
M2 Factor Of A Vector Schell-Model Beam, Milo W. Hyde Iv, Mark F. Spencer
Faculty Publications
Extending existing scalar Schell-model source work, we derive the M2 factor for a general electromagnetic or vector Schell-model source to assess beam quality. In particular, we compute the M2 factors for two vector Schell-model sources found in the literature. We then describe how to synthesize vector Schell-model beams in terms of specified, desired M2 and present Monte Carlo simulation results to validate our analysis.
Estimation Of Atmospheric Turbulence Using Differential Motion Of Extended Features In Time-Lapse Imagery, Santasri Bose-Pillai, Jack E. Mccrae, Christopher A. Rice, Ryan A. Wood, Conner E. Murphy, Steven T. Fiorino
Estimation Of Atmospheric Turbulence Using Differential Motion Of Extended Features In Time-Lapse Imagery, Santasri Bose-Pillai, Jack E. Mccrae, Christopher A. Rice, Ryan A. Wood, Conner E. Murphy, Steven T. Fiorino
Faculty Publications
We address the design, development, and testing of a pointer/tracker as a probe beam for the purpose of making high-speed, aero-optical measurements of the flow over a scaled beam director turret. The tracker uses retro-reflection of the probe beam off of a Reflexite annulus surrounding the turret. The constraints of the design required a near-total-commercial off the shelf system that could be quickly installed and removed in a rented aircraft. Baseline measurements of environmental vibrations are used to predict pointing performance; mitigation of line-of-sight jitter on the probe beam is achieved through passive isolation and the design of relay optics. …
Arrhenius Rate Chemistry-Informed Inter-Phase Source Terms (Arciist), Matthew J. Schwaab, Robert B. Greendyke, Bryan J. Steward
Arrhenius Rate Chemistry-Informed Inter-Phase Source Terms (Arciist), Matthew J. Schwaab, Robert B. Greendyke, Bryan J. Steward
Faculty Publications
Currently, in macro-scale hydrocodes designed to simulate explosive material undergoing shock-induced ignition, the state of the art is to use one of numerous reaction burn rate models. These burn models are designed to estimate the bulk chemical reaction rate. Unfortunately, these burn rate models are largely based on empirical data and must be recalibrated for every new material being simulated. We propose that the use of Arrhenius Rate Chemistry-Informed Interphase Source Terms (ARCIIST) in place of empirically derived burn models will improve the accuracy for these computational codes. A reacting chemistry model of this form was developed for the cyclic …
Comparison Of Plume Dynamics For Laser Ablated Metals: Al And Ti, William A. Bauer, Glen P. Perram, Timothy Haugan
Comparison Of Plume Dynamics For Laser Ablated Metals: Al And Ti, William A. Bauer, Glen P. Perram, Timothy Haugan
Faculty Publications
Emissive plumes from pulsed laser ablation of bulk Ti and Al from KrF laser irradiation at laser fluence up to 3.5 J/cm2 and argon background pressures of 0–1 Torr have been observed using gated intensified charged-coupled device imagery. Mass loss for Ti increases from 0.1 to 0.8 μg/pulse as pulse energy increase from 174 to 282 mJ/pulse (35–170 photons/atom) and decreases by ∼30% as pressure increases from vacuum to 1 Torr. Early plume energies are described by the free expansion velocities of 1.57 ± 0.02 and of 1.81 ± 0.07 cm/μs for Ti and Al, respectively, …
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 …
Statistical Photocalibration Of Photodetectors For Radiometry Without Calibrated Light Sources, Nicholas J. Yielding, Stephen C. Cain, Michael D. Seal
Statistical Photocalibration Of Photodetectors For Radiometry Without Calibrated Light Sources, Nicholas J. Yielding, Stephen C. Cain, Michael D. Seal
Faculty Publications
Calibration of CCD arrays for identifying bad pixels and achieving nonuniformity correction is commonly accomplished using dark frames. This kind of calibration technique does not achieve radiometric calibration of the array since only the relative response of the detectors is computed. For this, a second calibration is sometimes utilized by looking at sources with known radiances. This process can be used to calibrate photodetectors as long as a calibration source is available and is well-characterized. A previous attempt at creating a procedure for calibrating a photodetector using the underlying Poisson nature of the photodetection required calculations of the skewness of …
Spin-Imbalance In A 2d Fermi-Hubbard System, Peter Brown, Debayan Mitra, Elmer Guardado-Sanchez, Peter Schauß, Stanimir Kondov, Ehsan Khatami, Thereza Paiva, Nandini Trivedi, David Huse, Waseem Bakr
Spin-Imbalance In A 2d Fermi-Hubbard System, Peter Brown, Debayan Mitra, Elmer Guardado-Sanchez, Peter Schauß, Stanimir Kondov, Ehsan Khatami, Thereza Paiva, Nandini Trivedi, David Huse, Waseem Bakr
Faculty Publications
The interplay of strong interactions and magnetic fields gives rise to unusual forms of superconductivity and magnetism in quantum many-body systems. Here, we present an experimental study of the two-dimensional Fermi-Hubbard model—a paradigm for strongly correlated fermions on a lattice—in the presence of a Zeeman field and varying doping. Using site-resolved measurements, we revealed anisotropic antiferromagnetic correlations, a precursor to long-range canted order. We observed nonmonotonic behavior of the local polarization with doping for strong interactions, which we attribute to the evolution from an antiferromagnetic insulator to a metallic phase. Our results pave the way to experimentally mapping the low-temperature …
Estimating Index Of Refraction For Specular Reflectors Using Passive Polarimetric Hyperspectral Radiance Measurements, Jacob A. Martin, Kevin C. Gross
Estimating Index Of Refraction For Specular Reflectors Using Passive Polarimetric Hyperspectral Radiance Measurements, Jacob A. Martin, Kevin C. Gross
Faculty Publications
Results of a method of estimating index of refraction from passive, polarimetric hyperspectral imaging radiance measurements are presented. As off-nadir viewing hyperspectral imaging platforms gain prominence, estimating index of refraction, which is invariant to viewing angle, may prove advantageous to estimating the emissivity, which is not. Results show that index of refraction can be retrieved to within 8% rms error for fused silica and sapphire glass targets, while simultaneously estimating object temperature. The accuracy and self-consistency of this technique for estimating index of refraction are shown to compare favorably to the maximum smoothness temperature–emissivity separation algorithm. Additionally, the results show …
Relaxation Of Microwave Nonlinearity In A Cuprate Superconducting Resonator, Richard A. Huizen, Sean L. Hamilton, Geoffrey T. Lenters, Stephen K. Remillard
Relaxation Of Microwave Nonlinearity In A Cuprate Superconducting Resonator, Richard A. Huizen, Sean L. Hamilton, Geoffrey T. Lenters, Stephen K. Remillard
Faculty Publications
The second- and third-order nonlinear microwave response of a superconducting YBa2Cu3O7 thin-film resonator was synchronously measured using three input tones. This technique permits the local measurement, and hence mapping, of intermodulation distortion inside the resonator. Second- and third-order IMD measured with a fixed probe relaxed in remarkably different ways after the removal of a static magnetic field. The second-order IMD relaxed by two different magnetic processes, a fast process that appears related to bulk remanent magnetization and a slow process that fits the description of Bean and Livingston. The third-order IMD relaxes by only one process that is distinct from …
Estimation Of Turbulence From Time-Lapse Imagery, Jack E. Mccrae, Santasri Bose-Pillai, Steven T. Fiorino
Estimation Of Turbulence From Time-Lapse Imagery, Jack E. Mccrae, Santasri Bose-Pillai, Steven T. Fiorino
Faculty Publications
Atmospheric turbulence parameters are estimated for an imaging path based on time-lapse imaging results. Atmospheric turbulence causes frame-to-frame shifts of the entire image as well as parts of the image. The statistics of these shifts encode information about the turbulence strength (as characterized by Cn2, the refractive index structure function constant) along the optical path. The shift variance observed is simply proportional to the variance of the tilt of the optical field averaged over the area being tracked and averaged over the camera aperture. By presuming this turbulence follows the Kolmogorov spectrum, weighting functions, which relate the turbulence strength along …
Simulation Of Anisoplanatic Imaging Through Optical Turbulence Using Numerical Wave Propagation With New Validation Analysis, Russell C. Hardie, Jonathan D. Power, Daniel A. Lemaster, Douglas Droege, Szymon Gladysz, Santasri Bose-Pillai
Simulation Of Anisoplanatic Imaging Through Optical Turbulence Using Numerical Wave Propagation With New Validation Analysis, Russell C. Hardie, Jonathan D. Power, Daniel A. Lemaster, Douglas Droege, Szymon Gladysz, Santasri Bose-Pillai
Faculty Publications
We present a numerical wave propagation method for simulating imaging of an extended scene under anisoplanatic conditions. While isoplanatic simulation is relatively common, few tools are specifically designed for simulating the imaging of extended scenes under anisoplanatic conditions. We provide a complete description of the proposed simulation tool, including the wave propagation method used. Our approach computes an array of point spread functions (PSFs) for a two-dimensional grid on the object plane. The PSFs are then used in a spatially varying weighted sum operation, with an ideal image, to produce a simulated image with realistic optical turbulence degradation. The degradation …
Gallium Vacancies In Β-Ga2O3 Crystals, Brant E. Kananen, Larry E. Halliburton, K. T. Stevens, G. K. Foundos
Gallium Vacancies In Β-Ga2O3 Crystals, Brant E. Kananen, Larry E. Halliburton, K. T. Stevens, G. K. Foundos
Faculty Publications
The gallium vacancy, an intrinsic acceptor, is identified in β-Ga2O3 using electron paramagnetic resonance (EPR). Spectra from doubly ionized (V2−Ga) and singly ionized (V−Ga) gallium vacancies are observed at room temperature, without photoexcitation, after an irradiation with high-energy neutrons. The V2−Ga centers (with S = 1/2) have a slight angular variation due to a small anisotropy in the g matrix (principal values are 2.0034, 2.0097, and 2.0322). The V2−Ga centers also exhibit a resolved hyperfine structure due to equal and nearly isotropic interactions with the …
Direct Bandgap Cross-Over Point Of Ge1-YSnY Grown On Si Estimated Through Temperature-Dependent Photoluminescence Studies, Thomas R. Harris, Mee-Yi Ryu, Yung Kee Yeo, Buguo Wang, C. L. Senaratne
Direct Bandgap Cross-Over Point Of Ge1-YSnY Grown On Si Estimated Through Temperature-Dependent Photoluminescence Studies, Thomas R. Harris, Mee-Yi Ryu, Yung Kee Yeo, Buguo Wang, C. L. Senaratne
Faculty Publications
Epitaxial Ge1-ySny (y = 0%–7.5%) alloys grown on either Si or Ge-buffered Si substrates by chemical vapor deposition were studied as a function of Sn content using temperature-dependent photoluminescence (PL). PL emission peaks from both the direct bandgap (Γ-valley) and the indirect bandgap (L-valley) to the valence band (denoted by ED and EID, respectively) were clearly observed at 125 and 175 K for most Ge1-ySny samples studied. At 300 K, however, all of the samples exhibited dominant ED emission with either very weak or no measureable EID emission. At 10 K, …
Tunable Split-Ring Resonators Using Germanium Telluride, Christopher H. Kodama, Ronald Coutu Jr.
Tunable Split-Ring Resonators Using Germanium Telluride, Christopher H. Kodama, Ronald Coutu Jr.
Faculty Publications
We demonstrate terahertz (THz) split-ring resonator (SRR) designs with incorporated germanium telluride (GeTe) thin films. GeTe is a chalcogenide that undergoes a nonvolatile phase change from the amorphous to crystalline state at approximately 200 °C, depending on the film thickness and stoichiometry. The phase change also causes a drop in the material's resistivity by six orders of magnitude. In this study, two GeTe-incorporated SRR designs were investigated. The first was an SRR made entirely out of GeTe and the second was a gold SRR structure with a GeTe film incorporated into the gap region of the split ring. These devices …
Improved Terahertz Modulation Using Germanium Telluride (Gete) Chalcogenide Thin Films, Alexander H. Gwin, Christopher H. Kodama, Tod V. Laurvick, Ronald Coutu Jr., Philip F. Taday
Improved Terahertz Modulation Using Germanium Telluride (Gete) Chalcogenide Thin Films, Alexander H. Gwin, Christopher H. Kodama, Tod V. Laurvick, Ronald Coutu Jr., Philip F. Taday
Faculty Publications
We demonstrate improved terahertz (THz) modulation using thermally crystallized germanium telluride (GeTe) thin films. GeTe is a chalcogenide material that exhibits a nonvolatile, amorphous to crystalline phase change at approximately 200 °C, as well as six orders of magnitude decreased electrical resistivity. In this study, amorphous GeTe thin films were sputtered on sapphire substrates and then tested using THz time-domain spectroscopy (THz-TDS). The test samples, heated in-situ while collecting THz-TDS measurements, exhibited a gradual absorbance increase, an abrupt nonvolatile reduction at the transition temperature, followed by another gradual increase in absorbance. The transition temperature was verified by conducting similar thermal …
Effect Of Z1/2, Eh5, And Ci1 Deep Defects On The Performance Of N-Type 4h-Sic Epitaxial Layers Schottky Detectors: Alpha Spectroscopy And Deep Level Transient Spectroscopy Studies, M. A. Mannan, S. K. Chaudhuri, K. V. Nguyen, K. C. Mandal
Effect Of Z1/2, Eh5, And Ci1 Deep Defects On The Performance Of N-Type 4h-Sic Epitaxial Layers Schottky Detectors: Alpha Spectroscopy And Deep Level Transient Spectroscopy Studies, M. A. Mannan, S. K. Chaudhuri, K. V. Nguyen, K. C. Mandal
Faculty Publications
No abstract provided.
Sixteen Years Of Collaborative Learning Through Active Sense-Making In Physics (Clasp) At Uc Davis, Wendell Potter, David Webb, Cassandra Paul, Emily West, Mark Bowen, Brenda Weiss, Lawrence Coleman, Charles De Leone
Sixteen Years Of Collaborative Learning Through Active Sense-Making In Physics (Clasp) At Uc Davis, Wendell Potter, David Webb, Cassandra Paul, Emily West, Mark Bowen, Brenda Weiss, Lawrence Coleman, Charles De Leone
Faculty Publications
This paper describes our large reformed introductory physics course at UC Davis, which bioscience students have been taking since 1996. The central feature of this course is a focus on sense-making by the students during the five hours per week discussion/labs in which the students take part in activities emphasizing peer-peer discussions, argumentation, and presentations of ideas. The course differs in many fundamental ways from traditionally taught introductory physics courses. After discussing the unique features of CLASP and its implementation at UC Davis, various student outcome measures are presented showing increased performance by students who took the CLASP course compared …