Growth And Characterization Of Hexagonal Lu-Fe-O Multiferroic Thin Films, 2012 University of Tennessee, Knoxville
Growth And Characterization Of Hexagonal Lu-Fe-O Multiferroic Thin Films, Wenbin Wang
Doctoral Dissertations
In the quest for new types of information processing and storage, complex oxides stand out as one of the most promising material classes. The multiple functionalities of complex oxides naturally arise from the delicate energy balance between the various forms of order (structural, electronic, magnetic). In particular, multiferroic and magnetoelectric oxides which simultaneously exhibit more than one type of ferroic orders have many advantages over existing materials. Widespread practical applications will require a single-phase multiferroic material with a transition temperature that lies considerably above room temperature, large electric and magnetic polarizations, and strong coupling between ferroic orders.
Recently, multiferroic LuFe …
Structure And Dynamics Of High Temperature Superconductors, 2012 University of Tennessee, Knoxville
Structure And Dynamics Of High Temperature Superconductors, Jennifer Lynn Niedziela
Doctoral Dissertations
High temperature superconductivity in iron based compounds has presented a series of complex problems to condensed matter physics since being discovered in 2008. The stalwart basis of condensed matter physics is the “strength in numbers" aspect of crystalline periodicity. Perfect crystalline periodicity has made possible the reduction of the questions of structural and electronic properties to single dimensions, increasing the tractability of these problems. Nevertheless, modern complex materials stretch these assumptions to their limits, and it is at this point where our work starts. Using neutron and x-ray scattering, we have conducted a series of studies on the structural disorder …
Pulse Sharpening Effects Of Thin Film Ferroelectric Transmission Lines, 2012 University of Arkansas, Fayetteville
Pulse Sharpening Effects Of Thin Film Ferroelectric Transmission Lines, Robert J. Sleezer
Graduate Theses and Dissertations
Advances in material science have resulted in the development of electrically nonlinear high dielectric thin film ferroelectrics, which have led to new opportunities for the creation of novel devices. This dissertation investigated one such device: a low voltage nonlinear transmission line (NLTL). A finite element simulation of ferroelectric transmission lines showed that NLTLs are capable of creating shockwaves. Additionally, if the losses are kept sufficiently low, it was shown that voltage gain should be possible. Furthermore, a method of accounting for material dispersion was developed. Results from simulations including material dispersion showed that temporal solitons might be possible from a …
Electron-Phonon Coupling And Structural Phase Transitions On Au/Mo(112), 2012 University of Nebraska-Lincoln
Electron-Phonon Coupling And Structural Phase Transitions On Au/Mo(112), Keisuke Fukutani
Department of Physics and Astronomy: Dissertations, Theses, and Student Research
The electronic structures, many-body interactions and Fermi surface topologies of Au/Mo(112) were investigated in detail and were found to play important roles in the newly discovered order-disorder structural phase transition of the system. First, the high-resolution angle-resolved photoemission spectroscopy was utilized to characterize the electronic band structure of Mo(112) in far greater details than before. This elucidated the existence of several surface-derived states and their dispersion relations in high precisions near the Fermi level, as well as the symmetries of the bulk and surface electronic states, which are in good quantitative agreement with the ab-initio calculations. Such thorough understanding of …
Ultra-Thin Perfect Absorber Employing A Tunable Phase Change Material, 2012 William & Mary
Ultra-Thin Perfect Absorber Employing A Tunable Phase Change Material, Mikhail A. Kats, Deepika Sharma, (...), M. M. Qazilbash, Et Al.
Arts & Sciences Articles
We show that perfect absorption can be achieved in a system comprising a single lossy dielectric layer of thickness much smaller than the incident wavelength on an opaque substrate by utilizing the nontrivial phase shifts at interfaces between lossy media. This design is implemented with an ultra-thin (∼λ/65) vanadium dioxide (VO2) layer on sapphire, temperature tuned in the vicinity of the VO2 insulator-to-metal phase transition, leading to 99.75% absorption at λ = 11.6 μm. The structural simplicity and large tuning range (from ∼80% to 0.25% in reflectivity) are promising for thermal emitters, modulators, and bolometers.
The Behavior Of A Falling Particle In A Funnel, 2012 The University of Western Ontario
The Behavior Of A Falling Particle In A Funnel, Tahani Hassn Aldahri
Electronic Thesis and Dissertation Repository
Recent theoretical work has suggested that a frictional, inelastic, spherical particle falling under gravity through a symmetric funnel will display interesting behavior as a function of the angle of the funnel walls. We have studied this system experimentally, using high-speed video to record the particle trajectories. By analyzing the video images, we have analyzed the time the ball spends in the funnel and its energy loss as functions of the angle of the walls with respect to the horizontal. The coefficient of restitution was also varied by using different balls and funnel materials. We found some similarities and differences between …
Hohenberg-Kohn Theorem Including Electron Spin, 2012 Ningbo University
Hohenberg-Kohn Theorem Including Electron Spin, Xiao-Yin Pan, Viraht Sahni
Publications and Research
The Hohenberg-Kohn theorem is generalized to the case of a finite system of N electrons in external electrostatic epsilon(r) = -del nu(r) and magnetostatic B(r) = del x A(r) fields in which the interaction of the latter with both the orbital and spin angular momentum is considered. For a nondegenerate ground state a bijective relationship is proved between the gauge invariant density rho(r) and physical current density j(r) and the potentials {nu(r), A(r)}. The possible many-to-one relationship between the potentials {v(r), A(r)} and the wave function is explicitly accounted for in the proof. With the knowledge that the basic variables …
Equilibrium Magnetic States In Individual Hemispherical Permalloy Caps, 2012 Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden
Equilibrium Magnetic States In Individual Hemispherical Permalloy Caps, Robert Streubel, Volodymyr P. Kravchuk, Denis D. Sheka, Denys Makarov, Florian Kronast, Oliver G. Schmidt, Yuri Gaididei
Robert Streubel Papers
The magnetization distributions in individual soft magnetic permalloy caps on non-magnetic spherical particles with sizes ranging from 50 to 800nm are investigated. We experimentally visualize the magnetic structures at the resolution limit of the x-ray magnetic circular dichroism photoelectron emission microscopy (XMCD-PEEM). By analyzing the so-called tail contrast in XMCD-PEEM, the spatial resolution is significantly enhanced, which allowed us to explore magnetic vortices and their displacement on curved surfaces. Furthermore, cap nanostructures are modeled as extruded hemispheres to determine theoretically the phase diagram of equilibrium magnetic states. The calculated phase diagram agrees well with the experimental observations. © 2012 American …
Influence Of Quantum Dot Structure On The Optical Properties Of Group Iv Materials Fabricated By Ion Implantation, 2012 The University of Western Ontario
Influence Of Quantum Dot Structure On The Optical Properties Of Group Iv Materials Fabricated By Ion Implantation, Eric G. Barbagiovanni
Electronic Thesis and Dissertation Repository
In nanostructures (NSs), to acquire a fundamental understanding of the electronic states by studying the optical properties is inherently complicated. A widely used simplification to this problem comes about by developing a model for a small scale representation of types of NSs and applying it to a hierarchy of fabrication methods. However, this methodology fails to account for structural differences incurred by the fabrication method that lead to differences in the optical properties. Proper modelling is realized by first considering the proper range of experimental parameters individually as inputs to a theoretical model and applying the correct parameters to the …
Molecular Dynamics Studies Of Water Flow In Carbon Nanotubes, 2012 The University of Western Ontario
Molecular Dynamics Studies Of Water Flow In Carbon Nanotubes, Alexander D. Marshall
Electronic Thesis and Dissertation Repository
We present classical molecular dynamics (MD) simulations providing insight into the behaviour of water. We focus on confined water, the properties of which are often significantly different from the properties of bulk water.
First, we performed several simulations investigating the handling of long-range interactions in GROMACS [1], a MD simulation package. Selection of simulation protocols such as handling of long-range interactions is often overlooked, sometimes to the significant detriment of the final result [2, 3, 4]. Ensuring that the chosen simulation protocols are appropriate is a critical step in computer simulation.
Second, we performed MD simulations where water flowed between …
Nanomechanical Resonator Coupled Linearly Via Its Momentum To A Quantum Point Contact, 2012 Dartmouth College
Nanomechanical Resonator Coupled Linearly Via Its Momentum To A Quantum Point Contact, Latchezar L. Benatov, Miles P. Blencowe
Dartmouth Scholarship
We use a Born-Markov approximated master equation approach to study the symmetrized-in-frequency current noise spectrum and the oscillator steady state of a nanoelectromechanical system where a nanoscale resonator is coupled linearly via its momentum to a quantum point contact (QPC). Our current noise spectra exhibit clear signatures of the quantum correlations between the QPC current and the back-action force on the oscillator at a value of the relative tunneling phase (η=−π/2) where such correlations are expected to be maximized. We also show that the steady state of the oscillator obeys a classical Fokker-Planck equation, but can experience thermomechanical noise squeezing …
Investigation Of Vopcpho As An Acceptor Material For Bulk Heterojunction Solar Cells, 2012 Low Dimensional Material Research Centre, Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia
Investigation Of Vopcpho As An Acceptor Material For Bulk Heterojunction Solar Cells, Shahino Mah Abdullah
Shahino Mah Abdullah
In this study, we have successfully demonstrated a new system of donor–acceptor blend for bulk heterojunction solar cells of poly(3-hexylthiophene) (P3HT) by using vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine (VOPcPhO) as acceptor material. A broad absorption over the whole visible range (450–750 nm) is achieved. Utilizing this blend system in solar cell fabrication, ITO/PEDOT:PSS/P3HT:VOPcPhO/Al solar cells have been fabricated and characterized in open air. A maximum power conversation efficiency up to 1.09% has been recorded. To confirm the charge transport, the electron and hole mobility of VoPcPhO has been measured. The results show that the VoPcPhO has bipolar transport and can act as an …
Ii-Vi Core-Shell Nanowires: Synthesis, Characterizations And Photovoltaic Applications, 2012 kwang1@uno.edu
Ii-Vi Core-Shell Nanowires: Synthesis, Characterizations And Photovoltaic Applications, Kai Wang
University of New Orleans Theses and Dissertations
The emergence of semiconducting nanowires as the new building blocks for photovoltaic (PV) devices has drawn considerable attention because of the great potential of achieving high efficiency and low cost. In special, nanowires with a coaxial structure, namely, core-shell structures have demonstrated significant advantages over other device configurations in terms of radial charge collection and cost reduction. In this dissertation, several core-shell nanowire structures, including ZnO/ZnSe, ZnO/ZnS, and CdSe/ZnTe, have been synthesized and the photovoltaic devices processed from a ZnO/ZnS core-shell nanowire array and a single CdSe/ZnTe core-shell nanowire have been demonstrated.
By combining the chemical vapor deposition and pulsed …
High Frequency Study Of Magnetic Nanostructures, 2012 University of New Orleans
High Frequency Study Of Magnetic Nanostructures, Abhishek Srivastava
University of New Orleans Theses and Dissertations
The work in this thesis is divided in three parts. In part one we developed electrodeposition method of Nickel Nanowire in commercial AAO template in constant current (Galvanostatic) mode, further we tried to estimate the growth rate from theory, from saturation magnetization and direct measurement from SEM image.
In part two we focused on using the Vector Network Analyzer (VNA) to measure the Ferromagnetic Resonance (FMR))of various magnetic Nanowire arrays. We employed different measurement geometries using microstripline and coplanar waveguide as microwave transmission lines.
In part three our aim was to study the magnetic properties of complex ferromagnetic system, especially …
Characterization Of Magnetic Nanostructured Materials By First Order Reversal Curve Method, 2012 University of New Orleans
Characterization Of Magnetic Nanostructured Materials By First Order Reversal Curve Method, Denny R. Lenormand
University of New Orleans Theses and Dissertations
The Interactions and magnetization reversal of Ni nanowire arrays and synthetic anit-ferromagnetic coupled thin film trilayers have been investigated through first order reversal curve (FORC) method. By using a quantitative analysis of the local interaction field profile distributions obtained from FORC, it has proven to be a powerful characterization tool that can reveal subtle features of magnetic interactions.
Electronic Transport In Thermoelectric Bismuth Telluride, 2012 University of New Orleans
Electronic Transport In Thermoelectric Bismuth Telluride, Westly Nolting
University of New Orleans Theses and Dissertations
An experimental investigation of the electronic transport properties of bismuth telluride nanocomposite materials is presented. The primary transport measurements are electrical conductivity, Seebeck coefficient and Hall effect. An experimental apparatus for measuring Hall effect and electrical conductivity was designed, constructed and tested. Seebeck coefficient measurements were performed on a commercial instrument. The Hall effect and Seebeck coefficient measurements are two of the most important tools for characterizing thermoelectric materials and are widely used in the semiconductor industry for determining carrier types, carrier concentration and mobility. Further, these transport parameters are used to determine the thermal to electrical conversion efficiency of …
Magnetic Excitations In The Iron Based Superconductors, 2012 University of Tennessee, Knoxville
Magnetic Excitations In The Iron Based Superconductors, Leland Weldon Harriger
Doctoral Dissertations
Presented within are neutron scattering studies detailing the spin dynamics of BaNi$_{x}$Fe$_{2-x}$As$_{2}$ for x = 0 (parent), 0.04 (underdoped), and 0.1 (optimal) dopings, and FeSe$_{x}$Te$_{1-x}$ for x = 0 (parent), 0.3 (underdoped), and 0.4 (optimal) dopings. These recently discovered Fe-based superconducting compounds are strikingly similar, in many respects, to the cuprate class of unconventional superconductors and share qualitatively similar phase diagrams consisting of a long range ordered magnetic ground state in the parents which, upon doping, is supplanted in favor of superconductivity. The dopings discussed herein allow us to tune through the phase diagram, beginning with long range ordered parents …
Study Of Local Structure, Stress And Dynamics In Disordered Materials Using Ab-Initio And Molecular Dynamics Simulation, 2012 University of Tennessee, Knoxville
Study Of Local Structure, Stress And Dynamics In Disordered Materials Using Ab-Initio And Molecular Dynamics Simulation, Madhusudan Ojha
Doctoral Dissertations
Understanding the atomic structure and dynamics in structurally disordered systems has been a long-standing and most challenging problem in physics and material science. To begin with, it is difficult to describe disorder quantitatively and to differentiate the degree of disorder from one system to another. The majorities of experimental and theoretical approaches to the study of disordered systems are either transferred directly from the study of crystals or address the problem in the macroscopic scale where the atomic origin of behavior is obscured. First principle atomic level stresses and dynamic pair distribution functions described in this dissertation represent attempts to …
Iron Pnictides: Superconductivity In Multi-Orbital Systems, 2012 University of Tennessee, Knoxville
Iron Pnictides: Superconductivity In Multi-Orbital Systems, Andrew David Nicholson
Doctoral Dissertations
This work focuses on the development and implementation of microscopic models as well as their numerical and analytical study to elucidate the properties of the iron pnictides. There are many first principle and phenomenological studies of these materials, but there is a need for unbiased numerical calculations following an approach similar to the one used in the study of the Hubbard and t-J models for the cuprates.
First a two orbital model for the pnictides, focusing on two hybridized Fe-d orbitals (dxz and dyz) is formulated, including hoppings between nearest and next nearest neighbors as well as on site Coulomb …
Information Content Of Spontaneous Symmetry Breaking, 2012 Dartmouth College
Information Content Of Spontaneous Symmetry Breaking, Marcelo Gleiser, Nikitas Stamatopoulos
Dartmouth Scholarship
We propose a measure of order in the context of nonequilibrium field theory and argue that this measure, which we call relative configurational entropy (RCE), may be used to quantify the emergence of coherent low-entropy configurations, such as time-dependent or time-independent topological and nontopological spatially extended structures. As an illustration, we investigate the nonequilibrium dynamics of spontaneous symmetry breaking in three spatial dimensions. In particular, we focus on a model where a real scalar field, prepared initially in a symmetric thermal state, is quenched to a broken-symmetric state. For a certain range of initial temperatures, spatially localized, long-lived structures known …