Growth Of Low Disorder Gaas/Algaas Heterostructures By Molecular Beam Epitaxy For The Study Of Correlated Electron Phases In Two Dimensions,
2015
Purdue University
Growth Of Low Disorder Gaas/Algaas Heterostructures By Molecular Beam Epitaxy For The Study Of Correlated Electron Phases In Two Dimensions, John D. Watson
Open Access Dissertations
The unparalleled quality of GaAs/AlGaAs heterostructures grown by molecular beam epitaxy has enabled a wide range of experiments probing interaction effects in two-dimensional electron and hole gases. This dissertation presents work aimed at further understanding the key material-related issues currently limiting the quality of these 2D systems, particularly in relation to the fractional quantum Hall effect in the 2nd Landau level and spin-based implementations of quantum computation.^ The manuscript begins with a theoretical introduction to the quantum Hall effect which outlines the experimental conditions necessary to study the physics of interest and motivates the use of the semiconductor growth …
Observation Of Antiferromagnetic Correlations In The Hubbard Model With Ultracold Atoms,
2015
Rice University
Observation Of Antiferromagnetic Correlations In The Hubbard Model With Ultracold Atoms, Russell Hart, Pedro Duarte, Tsung-Lin Yang, Xinxing Liu, Thereza Paiva, Ehsan Khatami, Richard Scalettar, Nandini Trivedi, David Huse, Randall Hulet
Faculty Publications
Ultracold atoms in optical lattices have great potential to contribute to a better understanding of some of the most important issues in many-body physics, such as high-temperature superconductivity. The Hubbard model—a simplified representation of fermions moving on a periodic lattice—is thought to describe the essential details of copper oxide superconductivity. This model describes many of the features shared by the copper oxides, including an interaction-driven Mott insulating state and an antiferromagnetic (AFM) state. Optical lattices filled with a two-spin-component Fermi gas of ultracold atoms can faithfully realize the Hubbard model with readily tunable parameters, and thus provide a platform for …
Impact Of Homogeneous Strain On Uranium Vacancy Diffusion In Uranium Dioxide,
2015
University of Florida
Impact Of Homogeneous Strain On Uranium Vacancy Diffusion In Uranium Dioxide, Anuj Goyal, Simon R. Phillpot, Gopinath Subramanian, David A. Andersson, Chris R. Stanek, Blas P. Uberuaga
Faculty Publications
We present a detailed mechanism of, and the effect of homogeneous strains on, the migration of uranium vacancies in UO2. Vacancy migration pathways and barriers are identified using density functional theory and the effect of uniform strain fields are accounted for using the dipole tensor approach. We report complex migration pathways and noncubic symmetry associated with the uranium vacancy in UO2 and show that these complexities need to be carefully accounted for to predict the correct diffusion behavior of uranium vacancies. We show that under homogeneous strain fields, only the dipole tensor of the saddle with respect …
Model For Charge Injection With Electron Beams Into Highly Disordered Insulating Materials,
2015
Utah State Univesity
Model For Charge Injection With Electron Beams Into Highly Disordered Insulating Materials, Jr Dennison, Alec M. Sim, Gregory Wilson
Presentations
The Walden-Wintle model for charge injection and transport through highly disordered insulating materials has been extended to include charge injection with a charged particle beam. The original model is applicable to charge injection in a dielectric material from a pair of electrodes in a parallel-plate geometry. It provides a versatile approach to predict the time-dependent current at a rear grounded electrode and the incident surface voltage, as the injection current density evolves over time with the development of a space charge barrier near the injection electrode. The Walden-Wintle model has been applied to many standard cases including Fowler-Nordheim injection, Schottky …
Simulation Of Uv Radiation Degradation Of Polymers On Misse-6 In The Low Earth Orbit Environment,
2015
Utah State University
Simulation Of Uv Radiation Degradation Of Polymers On Misse-6 In The Low Earth Orbit Environment, Kelby T. Peterson, Jr Dennison
Senior Theses and Projects
Materials International Space Station Experiment 6 (MISSE-6) was an experiment designed to examine the consequences of the space environment on various materials used in space-component design. USU’s contribution was comprised of approximately 180 samples that were suspended from the side of the International Space Station (ISS) for 18 months and returned to allow for pre- and post-flight comparisons. The sample with the most evident changes was a thin film of polyethylene terephthalate (PET) MylarTM coated with Vapor Deposited Aluminum (VDA). The post-flight analysis showed evidence of atomic oxygen erosion of the VDA layer, UV-induced discoloration of the polymer, and …
Charged Skyrmions On The Surface Of A Topological Insulator,
2015
University of Maryland
Charged Skyrmions On The Surface Of A Topological Insulator, Hilary M. Hurst, Dimitry K. Efimkin, Jiadong Zang, Victor Galitski
Faculty Research, Scholarly, and Creative Activity
We consider the interplay between magnetic skyrmions in an insulating thin film and the Dirac surface states of a 3D topological insulator (TI), coupled by proximity effect. The magnetic texture of skyrmions can lead to confinement of Dirac states at the skyrmion radius, where out of plane magnetization vanishes. This confinement can result in charging of the skyrmion texture. The presence of bound states is robust in an external magnetic field, which is needed to stabilize skyrmions. It is expected that for relevant experimental parameters skyrmions will have a few bound states that can be tuned using an external magnetic …
Enhancement Of Local Piezoresponse
In Polymer Ferroelectrics Via Nanoscale
Control Of Microstructure,
2015
Argonne National Laboratory
Enhancement Of Local Piezoresponse In Polymer Ferroelectrics Via Nanoscale Control Of Microstructure, Yoon-Young Choi, Pankaj Sharma, Charudatta Phatak, David J. Gosztola, Yunya Liu, Joonseok Lee, Byeongdu Lee, Jiangyu Li, Alexei Gruverman, Stephen Ducharme, Seungbum Hong
Stephen Ducharme Publications
Polymer ferroelectrics are flexible and lightweight electromechanical materials that are widely studied due to their potential application as sensors, actuators, and energy harvesters. However, one of the biggest challenges is their low piezoelectric coefficient. Here, we report a mechanical annealing effect based on local pressure induced by a nanoscale tip that enhances the local piezoresponse. This process can control the nanoscale material properties over a microscale area at room temperature. We attribute this improvement to the formation and growth of β-phase extended chain crystals via sliding diffusion and crystal alignment along the scan axis under high mechanical stress. We believe …
Electric Control Of Spin Injection Into A Ferroelectric Semiconductor,
2015
University of Nebraska-Lincoln
Electric Control Of Spin Injection Into A Ferroelectric Semiconductor, Xiaohui Liu, John D. Burton, M. Ye. Zhuravlev, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
Electric-field control of spin-dependent properties has become one of the most attractive phenomena in modern materials research due to the promise of new device functionalities. One of the paradigms in this approach is to electrically toggle the spin polarization of carriers injected into a semiconductor using ferroelectric polarization as a control parameter. Using first-principles density-functional calculations, we explore the effect of ferroelectric polarization of electron-doped BaTiO3 (n-BaTiO3) on the spin-polarized transmission across the SrRuO3/n-BaTiO3(001) interface. Our study reveals that, in this system, the interface transmission is negatively spin polarized …
Statistical Variation Of Diverse Light Emission Measurements From Bisphenol/Amine Epoxy Under Energetic Electron Bombardment,
2015
Utah State University
Statistical Variation Of Diverse Light Emission Measurements From Bisphenol/Amine Epoxy Under Energetic Electron Bombardment, Justin Christensen
Senior Theses and Projects
No abstract provided.
Variations In Cathodoluminescent Intensity Of Spacecraft Materials Exposed To Energetic Electron Bombardment,
2015
Utah State University
Variations In Cathodoluminescent Intensity Of Spacecraft Materials Exposed To Energetic Electron Bombardment, Justin Dekany, Justin Christensen, Jr Dennison, Amberly Evans Jensen, Gregory Wilson, Todd Schneider, Charles W. Bowers, Robert Meloy
Journal Articles
Many contemporary spacecraft materials exhibit cathodoluminescence when exposed to electron flux from the space plasma environment. A quantitative, physics-based model has been developed to predict the intensity of the total glow as a function of incident electron current density and energy, temperature, and intrinsic material properties. We present a comparative study of the absolute spectral radiance for more than 20 types of dielectric and composite materials based on this model which spans more than three orders of magnitude. Variations in intensity are contrasted for different electron environments, different sizes of samples and sample sets, different testing and analysis methods, and …
Dynamic Interplay Between Spacecraft Charging, Space Environment Interactions And Evolving Materials,
2015
Utah State Univesity
Dynamic Interplay Between Spacecraft Charging, Space Environment Interactions And Evolving Materials, Jr Dennison
Journal Articles
While the effects on spacecraft charging from varying environmental conditions and from the selection of different construction materials have been studied extensively, modification of materials properties by exposure to the space plasma environment can also have profound effects on spacecraft charging. Given the increasingly demanding nature of space missions, there is a clear need to extend our understanding of the dynamic nature of material properties that affect spacecraft charging and to expand our knowledgebase of materials’ responses to specific environmental conditions so that we can more reliably predict the long term response of spacecraft to their environment. This paper focuses …
Electrical Properties Of Annealed And Coated Boron Nitride Under Electron Beam Irradiation,
2015
The French Aerospace Lab, Utah State University, & Université Paul Sabatier
Electrical Properties Of Annealed And Coated Boron Nitride Under Electron Beam Irradiation, Kevin Guerch, Theirry Paulmier, Jr Dennison, Justin Dekany, Pascal Lenormand, Sophie Guillemet-Fritsch
Journal Articles
The charging and relaxation kinetics of pyrolytic boron nitride (BN) substrates, BN with an aluminium oxide (BN/Al2O3) coating, and thermally-annealed alumina-coated boron nitride (an-BN/Al2O3) were investigated under low power electron irradiation (5 < E0 < 20 keV, Ji = 10 nA.cm-2 at room temperature) in the CEDRE facility at ONERA (Toulouse, France). Surface potentials of each ceramics configuration were measured over time using the Kelvin probe method. The influence of coating and annealing treatments to limit charging is discussed in this paper. A thorough study of a an–BN/Al2O3 sample was carried out …
The Adsorption Of Polyatomic Molecules On Carbon Surfaces,
2015
University of Denver
The Adsorption Of Polyatomic Molecules On Carbon Surfaces, Jared T. Burde
Electronic Theses and Dissertations
Carbon nanotubes exhibit the structure and chemical properties that make them apt substrates for many adsorption applications. Of particular interest are carbon nanotube bundles, whose unique geometry is conducive to the formation of pseudo-one-dimensional phases of matter, and graphite, whose simple planar structure allows ordered phases to form in the absence of surface effects. Although both of these structures have been the focus of many research studies, knowledge gaps still remain. Much of the work with carbon nanotubes has used simple adsorbates1-43, and there is little kinetic data available. On the other hand, there are many studies of …
Electrostatic Discharge And Endurance Time Measurements Of Spacecraft Materials: A Defect-Driven Dynamic Model,
2015
Utah State University
Electrostatic Discharge And Endurance Time Measurements Of Spacecraft Materials: A Defect-Driven Dynamic Model, Allen Andersen, Jr Dennison, Alec Sim, Charles Sim
Journal Articles
Electrostatic breakdown leads to the majority of anomalies and failures attributed to spacecraft interactions with the plasma space environment. It is therefore critical to understand how electrostatic field strength (FESD) of spacecraft materials varies due to environmental conditions such as duration of applied electric field, rate of field change, history of exposure to high fields, and temperature. We have developed a dual-defect, thermodynamic, mean-field trapping model in terms of recoverable and irrecoverable defect modes to predict probabilities of breakdown. Fits to a variety of measurements of the dependence of FESD of insulating polymers on endurance time, voltage …
Multiferroic Tunnel Junctions And Ferroelectric Control Of Magnetic State At Interface,
2015
Pennsylvania State University
Multiferroic Tunnel Junctions And Ferroelectric Control Of Magnetic State At Interface, Y. W. Yin, M. Raju, W. J. Hu, John D. Burton, Y.-M. Kim, A. Y. Borisevich, S. J. Pennycook, S. M. Yang, T. W. Noh, Alexei Gruverman, X. G. Li, Z. D. Zhang, Evgeny Y. Tsymbal, Qi Li
Alexei Gruverman Publications
As semiconductor devices reach ever smaller dimensions, the challenge of power dissipation and quantum effect place a serious limit on the future device scaling. Recently, a multiferroic tunnel junction (MFTJ) with a ferroelectric barrier sandwiched between two ferromagnetic electrodes has drawn enormous interest due to its potential applications not only in multi-level data storage but also in electric field controlled spintronics and nanoferronics. Here, we present our investigations on four-level resistance states, giant tunneling electroresistance (TER) due to interfacial magnetoelectric coupling, and ferroelectric control of spin polarized tunneling in MFTJs. Coexistence of large tunneling magnetoresistance and TER has been observed …
Electrical Properties Study Under Electron Beam Of Annealed And Coated Boron Nitride,
2015
Utah State University
Electrical Properties Study Under Electron Beam Of Annealed And Coated Boron Nitride, Kevin Guerch, Thierry Paulmier, Jr Dennison, Justin Dekany, Sophie Guillemet-Fritsch, Pascal Lenormand
Journal Articles
The charging and relaxation kinetics of pyrolytic boron nitride (BN) substrates, BN with an aluminum oxide (BN/Al2O3) coating, and thermally-annealed alumina-coated boron nitride (an–BN/Al2O3) were investigated under low power electron irradiation (5 < incident energy E0 < 20 keV and incident flux Ji = 10 nA.cm-2 at room temperature) in the CEDRE facility at ONERA (Toulouse, France). Surface potentials of each ceramics configuration were measured over time using the Kelvin probe method. The influence of coating and annealing treatments to limit charging is discussed in this paper. A thorough study of a an–BN/Al2O3 sample was carried out …
Magnetic Force Microscopy Study Of Zr2co11-Based Nanocrystalline Materials: Effect Of Mo Addition,
2015
University of Nebraska - Lincoln
Magnetic Force Microscopy Study Of Zr2co11-Based Nanocrystalline Materials: Effect Of Mo Addition, Lanping Yue, Yunlong Jin, Wenyong Zhang, David J. Sellmyer
Nebraska Center for Materials and Nanoscience: Faculty Publications
The addition of Molybdenum was used to modify the nanostructure and enhance coercivity of rare-earth-free Zr2Co11-based nanocrystalline permanent magnets. The effect of Mo addition on magnetic domain structures of melt spun nanocrystalline Zr16Co84−xMox (𝑥 = 0, 0.5, 1, 1.5, and 2.0) ribbons has been investigated. It was found that magnetic properties and local domain structures are strongly influenced by Mo doping. The coercivity of the samples increases with the increase in Mo content (𝑥 ≤ 1.5). The maximum energy product (𝐵𝐻)max increases with increasing 𝑥 from 0.5 MGOe for 𝑥 …
Investigation Of Temperature Dependent Magnetic Hyperthermia In Fe3o4 Ferrofluids,
2015
Wayne State University
Investigation Of Temperature Dependent Magnetic Hyperthermia In Fe3o4 Ferrofluids, Humeshkar Bhaskar Nemala
Wayne State University Dissertations
Magnetic nanoparticles (MNPs) of Fe3O4 and gamma-Fe2O3 have been exploited in the biomedical fields for imaging, targeted drug delivery and magnetic hyperthermia. Magnetic hyperthermia (MHT), the production of heat using ferrofluids, colloidal suspensions of MNPs, in an external AC magnetic field (amplitude, 100-500 Oe and frequency 50 kHz -1MHz), has been explored by many researchers, both in vitro and in vivo, as an alternative viable option to treat cancer. The heat energy generated by Néel and Brownian relaxation processes of the internal magnetic spins could be used to elevate local tissue temperature to about 46 ˚C to arrest cancerous growth. …
Radar Detection Of Ultra High Energy Cosmic Rays: Searching For Coincident Events With Telescope Array Radar And Surface Detectors,
2015
Utah State University
Radar Detection Of Ultra High Energy Cosmic Rays: Searching For Coincident Events With Telescope Array Radar And Surface Detectors, Zachary Gibson, Rasha Abbasi, John Belz
Presentations
No abstract provided.
Defects Density Of States Model Of Cathodoluminescent Intensity And Spectra Of Disordered Sio2,
2015
Utah State University
Defects Density Of States Model Of Cathodoluminescent Intensity And Spectra Of Disordered Sio2, Amberly Evans Jensen, Jr Dennison
Journal Articles
Electron beam measurements show that disordered SiO2 exhibits electron-induced luminescence, and that it varies with incident beam energy and current density, sample temperature, and wavelength. A simple model based on the electronic band structure and defect density of states—initially used to explain electron transport in highly disordered insulating materials—has been extended to predict the relative cathodoluminescent intensity and spectral radiance for disordered SiO2 as a function of these variables. Due to the large band gap of insulating SiO2, thermal excitation from the valence to conduction band is highly improbable; excitation is through collisions of the incident …
