Reversible Spin Texture In Ferroelectric Hfo2,
2017
University of Nebraska-Lincoln
Reversible Spin Texture In Ferroelectric Hfo2, L. L. Tao, Tula R. Paudel, Alexey Kovalev, Evgeny Tsymbal
Department of Physics and Astronomy: Faculty Publications
Spin-orbit coupling effects occurring in noncentrosymmetric materials are known to be responsible for nontrivial spin configurations and a number of emergent physical phenomena. Ferroelectric materials may be especially interesting in this regard due to reversible spontaneous polarization making possible a nonvolatile electrical control of the spin degrees of freedom. Here, we explore a technologically relevant oxide material, HfO2, which has been shown to exhibit robust ferroelectricity in a noncentrosymmetric orthorhombic phase. Using theoretical modelling based on density-functional theory, we investigate the spin-dependent electronic structure of the ferroelectric HfO2 and demonstrate the appearance of chiral spin textures driven by spin-orbit coupling. …
Ferroelectric-Domain-Patterning-Controlled Schottky Junction State In Monolayer Mos2,
2017
University of Nebraska-Lincoln
Ferroelectric-Domain-Patterning-Controlled Schottky Junction State In Monolayer Mos2, Zhiyong Xiao, Jingfeng Song, David K. Ferry, Stephen Ducharme, Xia Hong
Stephen Ducharme Publications
We exploit scanning-probe-controlled domain patterning in a ferroelectric top layer to induce nonvolatile modulation of the conduction characteristic of monolayer MoS2 between a transistor and a junction state. In the presence of a domain wall, MoS2 exhibits rectified I-V characteristics that are well described by the thermionic emission model. The induced Schottky barrier height ΦeffB varies from 0.38 to 0.57 eV and is tunable by a SiO2 global back gate, while the tuning range of ΦeffB depends sensitively on the conduction-band-tail trapping states. Our work points to a new route to achieving programmable …
Effects Of Temperature And Radiation Dose On Radiation Induced Conductivity,
2017
Utah State Univesity
Effects Of Temperature And Radiation Dose On Radiation Induced Conductivity, Jr Dennison
Presentations
Radiation induced conductivity (RIC) is an important conduction mechanism in highly disordered insulating materials exposed to ionizing radiation. Measurements of RIC as a function of dose rate and exposure time of polymeric and glassy insulators will be presented. RIC results from excitation of carriers into conduction states by the ionizing radiation. The measurements will be discussed in terms of models for the distribution of localized disordered states. The effects of temperature and radiation damage from ionizing radiation on the density and occupation of trap states, and how this affects RIC, will also be discussed.
Effects Of Temperature And Radiation Dose On Radiation Induced Conductivity,
2017
Utah State Univesity
Effects Of Temperature And Radiation Dose On Radiation Induced Conductivity, Jr Dennison
Presentations
No abstract provided.
Enhanced Test Facility For Survivability And Characterization Of Evolving Multiscale Materials In Extreme Plasma Environments,
2017
Utah State Univesity
Enhanced Test Facility For Survivability And Characterization Of Evolving Multiscale Materials In Extreme Plasma Environments, Jr Dennison
Posters
No abstract provided.
Universal Disorder In Organic Semiconductors Due To Fluctuations In Space Charge,
2017
University of New Mexico
Universal Disorder In Organic Semiconductors Due To Fluctuations In Space Charge, Tzucheng Wu
Physics & Astronomy ETDs
This thesis concerns the study of charge transport in organic semiconductors. These materials are widely used as thin-film photoconductors in copiers and laser printers, and for their electroluminescent properties in organic light-emitting diodes. Much contemporary research is directed towards improving the efficiency of organic photovoltaic devices, which is limited to a large extent by the spatial and energetic disorder that hinders the charge mobility. One contribution to energetic disorder arises from the strong Coulomb interactions between injected charges with one another, but to date this has been largely ignored. We present a mean-field model for the effect of mutual interactions …
Intervalley Scattering Rates In Tellurium Observed Via Time-Resolved Terahertz Spectroscopy,
2017
Macalester College
Intervalley Scattering Rates In Tellurium Observed Via Time-Resolved Terahertz Spectroscopy, Joshua R. Rollag
Macalester Journal of Physics and Astronomy
We conducted time-resolved terahertz spectroscopy measurements on the elemental semiconductor tellurium. Pump-probe measurements were used to find the conductivity as a function of time in single crystalline tellurium samples. It was found that the excitation dynamics in tellurium changes for photon energies of 1.03 eV and 1.55 eV. The change in these excitation dynamics was attributed to intervalley scattering effects. A model using intervalley scattering and Auger recombination was fit to the data, giving a value of 2.28 ps for the intervalley scattering time constant in tellurium.
Hemispherical Grid Retarding Field Analyzer Redesign For Secondary Electron Emission Studies,
2017
Utah State University
Hemispherical Grid Retarding Field Analyzer Redesign For Secondary Electron Emission Studies, Greg Wilson, Jr Dennison
Presentations
A redesign of the Hemispherical Grid Retarding Field Analyzer is discussed in relationship to multilayer charging models. In order to accurately extend single layer charging models to dynamic multilayer scenarios, precise measurements of electron emission as well as the net surface potential must be made. By learning from the previous design and thinking of future applications, the new instrument will greatly enhance our ability to precisely measure materials undergoing energetic electron bombardment.
Of Mice And Materials: Payoffs Of Unsgc Research Infrastructure Awards,
2017
Utah State Univesity
Of Mice And Materials: Payoffs Of Unsgc Research Infrastructure Awards, Jr Dennison, Kent Hartley, Lisa Phillipps, Justin Dekany, Robert H. Johnson, James S. Dyer
Presentations
A versatile test facility has been designed and built to study space environments effects on small satellites and system components. Testing for potentially environmental-induced modifications of small satellites is critical to avoid possible deleterious or catastrophic effects over the duration of space mission. This is increasingly more important as small satellite programs have longer mission lifetimes, expand to more harsh environments (such as polar or geosynchronous orbits), make more diverse and sensitive measurements, minimize shielding to reduce mass, and utilize more compact and sensitive electronics (often including untested off-the-shelf components). The vacuum chamber described here is particularly well suited for …
Of Mice And Materials: Payoffs Of Unsgc Research Infrastructure Awards,
2017
Utah State Univesity
Of Mice And Materials: Payoffs Of Unsgc Research Infrastructure Awards, Jr Dennison
Presentations
No abstract provided.
Hemispherical Grid Retarding Field Analyzer Redesign For Secondary Electron Emission Studies,
2017
Utah State University
Hemispherical Grid Retarding Field Analyzer Redesign For Secondary Electron Emission Studies, Greg Wilson, Jr Dennison
Conference Proceedings
A redesign of the Hemispherical Grid Retarding Field Analyzer is discussed in relationship to multilayer charging models. In order to accurately extend single layer charging models to dynamic multilayer scenarios, precise measurements of electron emission as well as the net surface potential must be made. By learning from the previous design and thinking of future applications, the new instrument will greatly enhance our ability to precisely measure materials undergoing energetic electron bombardment.
New Easy-Plane CpN−1 Fixed Points,
2017
University of Kentucky
New Easy-Plane CpN−1 Fixed Points, Jonathan D'Emidio, Ribhu K. Kaul
Physics and Astronomy Faculty Publications
We study fixed points of the easy-plane CPN−1 field theory by combining quantum Monte Carlo simulations of lattice models of easy-plane SU(N) superfluids with field theoretic renormalization group calculations, by using ideas of deconfined criticality. From our simulations, we present evidence that at small N our lattice model has a first-order phase transition which progressively weakens as N increases, eventually becoming continuous for large values of N. Renormalization group calculations in 4−ε dimensions provide an explanation of these results as arising due to the existence of an Nep that separates the fate of …
Kinetic Theory Of Dark Solitons With Tunable Friction,
2017
University of Maryland
Kinetic Theory Of Dark Solitons With Tunable Friction, Hilary M. Hurst, Dimitry K. Efimkin, I. B. Spielman, Victor Galitski
Faculty Research, Scholarly, and Creative Activity
We study controllable friction in a system consisting of a dark soliton in a one-dimensional Bose-Einstein condensate coupled to a non-interacting Fermi gas. The fermions act as impurity atoms, not part of the original condensate, that scatter off of the soliton. We study semi-classical dynamics of the dark soliton, a particle-like object with negative mass, and calculate its friction coefficient. Surprisingly, it depends periodically on the ratio of interspecies (impurity-condensate) to intraspecies (condensate-condensate) interaction strengths. By tuning this ratio, one can access a regime where the friction coefficient vanishes. We develop a general theory of stochastic dynamics for negative mass …
Uv Degradation Of Polycarbonate,
2017
Utah State University
Uv Degradation Of Polycarbonate, Katie Gamaunt
Senior Theses and Projects
The decrease in visible and ultraviolet transmission spectra of polymeric and glass spacecraft materials has been measured to determine the extent of degradation due to high-energy UV radiation similar to the solar spectrum (both above and below the stratosphere, which is where most of the UV radiation is absorbed). This project looked at the effects that the atmosphere has in regards to blocking UV radiation and thus, slowing down the UV degradation process. A polycarbonate sample was exposed to radiation from a focused high intensity deuterium lamp source, which generates radiation in the UVA and UVB spectrum. A particularly severe …
Microcontroller And Memory Card Survivability In Space Conditions,
2017
Utah State University
Microcontroller And Memory Card Survivability In Space Conditions, Windy Olsen
Senior Theses and Projects
The Utah State University (USU) Materials Physics Group (MPG) is interested in the performance of Commercial Off the Shelf (COTS) microcontrollers in space conditions. Microcontrollers are commonly used on CubeSats, small relatively inexpensive satellites that are flown in Low Earth Orbit (LEO) at altitudes of ~160 km-2000 km. There is a large area of interest in COTS microcontrollers because they provide a more cost-effective on-board computer for CubeSats. This experiment focused on the functionality of an ATmega328 microcontroller on an Arduino Uno board inside the MPG’s Space Survivability Test (SST) Chamber. A diagnostic program was used to try to detect …
Synthesis And Fundamental Property Studies Of Energy Material Under High Pressure.,
2017
University of Louisville
Synthesis And Fundamental Property Studies Of Energy Material Under High Pressure., Meysam Akhtar
Electronic Theses and Dissertations
Recently, high-pressure science and technology has flourished and rapidly advanced to impact a wide domain of materials and physical sciences. One of the most substantial technological developments is the integration of samples at ultrahigh pressure with a wide range of in-situ probing techniques. Applications of extreme pressure have significantly enriched our understanding of the electronic, phonon, and doping effects on the newly emerged two-dimensional (2D) materials. Under high pressure, materials’ atomic volume radically decreases, and electronic density rises, which will lead to extraordinary chemical reaction kinetic and mechanisms. The promising capability of high pressure combine with the significance of novel …
Microcontroller Survivability In Space Conditions,
2017
Utah State University
Microcontroller Survivability In Space Conditions, Windy Olsen
Senior Theses and Projects
No abstract provided.
Fabrication And Study Of The Structure And Magnetism Of Rare-Earth Free Nanoclusters,
2017
University of Nebraska-Lincoln
Fabrication And Study Of The Structure And Magnetism Of Rare-Earth Free Nanoclusters, Bhaskar Das
Department of Physics and Astronomy: Dissertations, Theses, and Student Research
No abstract provided.
Reduction Of Radiation Effects In Polymers,
2017
Utah State University
Reduction Of Radiation Effects In Polymers, Alexandra Hughlett, Tyler Kippen, Jr Dennison
Posters
No abstract provided.
Dynamic Secondary Electron Emission In Dielectric/Conductor Mixed,
2017
Instituto de Ciencia de Materiales de Madrid
Dynamic Secondary Electron Emission In Dielectric/Conductor Mixed, Leandro Olano, Isabel Montero, María E. Dávila, A. Jacas, M. A. Rodriguez, Jr Dennison
Conference Proceedings
Secondary Emission Yield (SEY) of dielectric materials is of great importance for prediction and testing of the Multipaction discharge in RF components for space applications. An atypical behavior of the SEY of coatings composed by a mixture of conductor and dielectric microparticles was reported and modeled in [1]; in this original model, the interactions between dielectric and conductor particles were not taken into account, but an effective action of the surface voltage generated within the sample was included. The aim of the present contribution is to more accurately model the effect the electric fields between dielectric and conductor particles have …
