Condensed Matter Physics Commons^™

Multiferroicity In Iron Vanadate, Magnetite And Polyvinylidene Fluoride Nanocomposite Films, Ehab Hamdy Abdelmonaim Abdelhamid

Wayne State University Dissertations

With the increasing demand on cheaper and better performance multifunctional materials for different applications, it is becoming more crucial to have a better understanding of the physics needed to tailor more devices and materials to fit better in every day’s technological needs. Materials which show more than one ferroic order simultaneously –namely, multiferroics– are of particular importance for their potential applications as multiple state memory elements, transducers and electrically tunable microwave devices.

In this work, we studied FeVO4 single crystals as an example on low symmetry multiferroics. We focused on the anisotropy in those crystals in an attempt to nail …

Understanding Electrical Conduction In Lithium Ion Batteries Through Multi-Scale Modeling, Jie Pan

Theses and Dissertations--Chemical and Materials Engineering

Silicon (Si) has been considered as a promising negative electrode material for lithium ion batteries (LIBs) because of its high theoretical capacity, low discharge voltage, and low cost. However, the utilization of Si electrode has been hampered by problems such as slow ionic transport, large stress/strain generation, and unstable solid electrolyte interphase (SEI). These problems severely influence the performance and cycle life of Si electrodes. In general, ionic conduction determines the rate performance of the electrode, while electron leakage through the SEI causes electrolyte decomposition and, thus, causes capacity loss. The goal of this thesis research is to design Si …

Anisotropy, Phonon Modes, And Free Charge Carrier Parameters In Monoclinic Β-Gallium Oxide Single Crystals, Mathias Schubert, Rafal Korlacki, Sean Knight, Tino Hofmann, Stefan Schöche, Vanya Darakchieva, Erik Janzén, Bo Monemar, Daniela Gogova, Q.-T. Thieu, R. Togashi, H. Murakami, Yoshinao Kumagai, Ken Goto, Akito Kuramata, S. Yamakoshi, Masataka Higashiwaki

Department of Electrical and Computer Engineering: Faculty Publications

We derive a dielectric function tensor model approach to render the optical response of monoclinic and triclinic symmetry materials with multiple uncoupled infrared and far-infrared active modes. We apply our model approach to monoclinic β-Ga₂O₃ single-crystal samples. Surfaces cut under different angles from a bulk crystal, (010) and (2̅01), are investigated by generalized spectroscopic ellipsometry within infrared and far-infrared spectral regions. We determine the frequency dependence of 4 independent β-Ga₂O₃ Cartesian dielectric function tensor elements by matching large sets of experimental data using a point-by-point data inversion approach. From matching our monoclinic …

The Metal/Organic Interface In Cobalt/Vinylidene Fluoride Heterostructures, Keith Foreman, E Echeverria, Mark A. Koten, R. M. Lindsay, N. Hong, Jeffrey E. Shield, Shireen Adenwalla

Shireen Adenwalla Papers

Organic-based electronic devices are rapidly increasing in popularity, making it essential to understand and characterize the interface between organic materials and metallic electrodes. This work reports on the characterization of the interface between thin films of an emerging organic ferroelectric, vinylidene fluoride (VDF) oligomer, and Co, an important high Curie temperature ferromagnet. Using a wide battery of experimental techniques, it is shown that VDF oligomer thin films as thin as 15 nm can halt, or prevent, Co oxidization in atmospheric conditions, a necessary condition for device applications. Selectivity of magnetic properties, such as remanent magnetization, is enabled by the clarification …

Ferroelectric Characterization And Growth Optimization Of Thermally Evaporated Vinylidene Fluoride Thin Films, Keith Foreman, N. Hong, C. Labedz, C. Shearer, Stephen Ducharme, Shireen Adenwalla

Shireen Adenwalla Papers

Organic thin films have numerous advantages over inorganics in device processing and price. The large polarization of the organic ferroelectric oligomer vinylidene fluoride (VDF) could prove useful for both device applications and the investigation of fundamental physical phenomena. A VDF oligomer thin film vacuum deposition process, such as thermal evaporation, preserves film and interface cleanliness, but is challenging, with successful deposition occurring only within a narrow parameter space. We report on the optimal deposition parameters for VDF oligomer thin films, refining the parameter space for successful deposition, resulting in a high yield of robust ferroelectric films. In particular, we investigate …

Experimental Design And Construction For Critical Velocity Measurement In Spin-Orbit Coupled Bose-Einstein Condensates, Ting-Wei Hsu, Yong P. Chen

The Summer Undergraduate Research Fellowship (SURF) Symposium

Quantum simulation using ultra-cold atoms, such as Bose-Einstein Condensates (BECs), offers a very flexible and well controlled environment to simulate physics in different systems. For example, to simulate the effects of spin orbit coupling (SOC) on electrons in solid state systems, we can make a SOC BEC which mimics the behavior of SOC electrons. The goal of this project is to see how the superfluid property of BECs change in the presence of SOC. In particular, we plan to measure the critical velocity of an 87Rb BEC with and without SOC by stirring it with a laser. This laser needs …

The Effects Of Strain And Vacancies On The Electric And Vibrational Properties Of Ferroelectric Batio3 From First-Principles, Aldo Serge Michael Raeliarijaona

Graduate Theses and Dissertations

The studies of ferroelectricity (FE) are of technological significance because of the multitude of applicable properties that ferroelectric materials exhibit. The mastery, and control of these properties necessitate the knowledge of the fundamental physics governing these insulating materials.

In this dissertation I present the results of first-principles investigations of the behavior of the fundamental ferroelectric properties under strain, and in the presence of vacancies. In the first part I introduce the important FE properties, their common behavior, and their numerous valuable applications. Following this background on FEs, a review of theoretical methods is presented with topics such as: Density Functional …

Engineering The Ground State Of Complex Oxides, Derek Joseph Meyers

Graduate Theses and Dissertations

Transition metal oxides featuring strong electron-electron interactions have been at the forefront of condensed matter physics research in the past few decades due to the myriad of novel and exciting phases derived from their competing interactions. Beyond their numerous intriguing properties displayed in the bulk they have also shown to be quite susceptible to externally applied perturbation in various forms. The dominant theme of this work is the exploration of three emerging methods for engineering the ground states of these materials to access both their applicability and their deficiencies.

The first of the three methods involves a relatively new set …

Temperature Dependent Surface Reconstruction Of Freely Suspended Films Of 4-N-Heptyloxybenzylidene-4-N-Heptylaniline, Daniel E. Martinez Zambrano

Lawrence University Honors Projects

Surfaces of freely suspended thick films of 4-n-heptyloxybenzylidene-4-n-heptylaniline (7O.7) in the crystalline-B phase have been imaged using non-contact mode atomic force microscopy. Steps are observed on the surface of the film with a height of 3.0 +/- 0.1 nm corresponding to the upright molecular length of 7O.7. In addition, we find that the step width varies with temperature between 56 and 59 degrees C. The steps are many times wider than the molecular length, suggesting that the steps are not on the surface but instead originate from edge dislocations in the interior. Using a strain model for liquid crystalline layers …

Capacitance Measurements Of Defects In Solar Cells: Checking The Model Assumptions, Justin R. Davis

Senior Theses

Capacitance measurements of solar cells are sensitive to minute changes in charge in the material. For that reason, capacitance is used in several methods to electrically characterize defects in the solar cell. Standard interpretations of capacitance rely on many assumptions, which, if wrong can skew the results. We explore possible alternative explanations for capacitance transitions, such as a non-ideal back contact and series resistance. Using Drive Level Capacitance Profiling measurements, a capacitance step is linked to a defect between the energy bands of a solar cell.

Epitaxial Growth Of Silicon On Poly-Crystalline Si Seed Layer At Low Temperature By Using Hot Wire Chemical Vapor Deposition, Manal Abdullah Aldawsari

Graduate Theses and Dissertations

There has been a growing interest in using low cost material as a substrate for the large grained polycrystalline silicon photovoltaic devices. The main property of those devices is the potential of obtaining high efficiency similar to crystalline Si devices efficiency yet at much lower cost because of the thin film techniques. Epitaxial growth of Si at low temperatures on low cost large grained seed layers, prepared by aluminum induced crystallization method (AIC), using hot wire chemical vapor deposition (HWCVD) system is investigated in this thesis. In this work, different parameters have been studied in order to optimize the growth …

High Pressure Behavior Of Mullite-Type Oxides: Phase Transitions, Amorphization, Negative Linear Compressibility And Microstructural Implications, Patricia Kalita

UNLV Theses, Dissertations, Professional Papers, and Capstones

Even though mullite occurs rarely in nature, it is perhaps one of the most important phases in both traditional and advanced ceramics. Existing and emerging applications of mullite and mullite-type materials include: high-temperature composites, aerospace materials, ballistic shielding for military applications and even non-linear optical materials. There are many uncertainties regarding the basic physical properties of mullite-type materials, particularly in terms of their high-pressure structural stability and mechanical behavior that are important to address for emerging applications of mullites as engineering materials. This work is the first reported comprehensive investigation of the high –pressure structural behavior of several different mullites …

Transport Studies In Graphene-Based Materials And Structures, Jiuning Hu

Open Access Dissertations

Graphene, a single atomic layer of graphite, has emerged as one of the most attractive materials in recent years for its many unique and excellent properties, inviting a broad area of fundamental studies and applications. In this thesis, we present some theoretical/experimental studies about the thermal, electronic and thermoelectric transport properties in graphene-based systems. We employ the molecular dynamic simulations to study the thermal transport in graphene nanoribbons (GNRs) exhibiting various properties, including chirality dependent thermal conductivity, thermal rectification in asymmetric GNRs, defects and isotopic engineering of the thermal conductivity and negative differential thermal conductance (NDTC) at large temperature biases. …

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 2^nd 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 …

Computing And The Electrical Transport Properties Of Coupled Quantum Networks, Casey Andrew Cain

Doctoral Dissertations

In this dissertation a number of investigations were conducted on ballistic quantum networks in the mesoscopic range. In this regime, the wave nature of electron transport under the influence of transverse magnetic fields leads to interesting applications for digital logic and computing circuits. The work specifically looks at characterizing a few main areas that would be of interest to experimentalists who are working in nanostructure devices, and is organized as a series of papers. The first paper analyzes scaling relations and normal mode charge distributions for such circuits in both isolated and open (terminals attached) form. The second paper compares …

Multiscale Examination And Modeling Of Electron Transport In Nanoscale Materials And Devices, Douglas R. Banyai

Dissertations, Master's Theses and Master's Reports - Open

For half a century the integrated circuits (ICs) that make up the heart of electronic devices have been steadily improving by shrinking at an exponential rate. However, as the current crop of ICs get smaller and the insulating layers involved become thinner, electrons leak through due to quantum mechanical tunneling. This is one of several issues which will bring an end to this incredible streak of exponential improvement of this type of transistor device, after which future improvements will have to come from employing fundamentally different transistor architecture rather than fine tuning and miniaturizing the metal-oxide-semiconductor field effect transistors (MOSFETs) …

Understanding Electronic Structure And Transport Properties In Nanoscale Junctions, Kamal B. Dhungana

Dissertations, Master's Theses and Master's Reports - Open

Understanding the electronic structure and the transport properties of nanoscale materials are pivotal for designing future nano-scale electronic devices. Nanoscale materials could be individual or groups of molecules, nanotubes, semiconducting quantum dots, and biomolecules. Among these several alternatives, organic molecules are very promising and the field of molecular electronics has progressed significantly over the past few decades. Despite these progresses, it has not yet been possible to achieve atomic level control at the metal-molecule interface during a conductance measurement, which hinders the progress in this field. The lack of atomic level information of the interface also makes it much harder …

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 …

Structural Characterization Of Multimetallic Nanoparticles, Vineetha Mukundan

Open Access Dissertations

Bimetallic and trimetallic alloy nanoparticles have enhanced catalytic activities due to their unique structural properties. Using in situ time-resolved synchrotron based x-ray diffraction, we investigated the structural properties of nanoscale catalysts undergoing various heat treatments. Thermal treatment brings about changes in particle size, morphology, dispersion of metals on support, alloying, surface electronic properties, etc. First, the mechanisms of coalescence and grain growth in PtNiCo nanoparticles supported on planar silica on silicon were examined in detail in the temperature range 400-900°C. The sintering process in PtNiCo nanoparticles was found to be accompanied by lattice contraction and L1₀chemical ordering. …

Transport And Optical Properties Of Low-Dimensional Complex Systems, Andrii Iurov

Dissertations, Theses, and Capstone Projects

Over the last five years of my research work, I, my research was mainly concerned with certain crucial tunneling, transport and optical properties of novel low-dimensional graphitic and carbon-based materials as well as topological insulators. Both single-electron and many-body problems were addressed. We investigated the Dirac electrons transmission through a potential barrier in the presence of circularly polarized light. An anomalous photon-assisted enhanced transmission is predicted and explained in a comparison with the well-known Klein paradox. It is demonstrated that the perfect transmission for nearly-head-on collision in an infinite graphene is suppressed in gapped dressed states of electrons, which is …

Nanoscale Manipulation Of Pristine And Functionalized Freestanding Graphene Using Scanning Tunneling Microscopy, Matthew Ackerman

Graduate Theses and Dissertations

Over the past ten years the 2D material graphene has attracted an enourmous amount of attention from researchers from across diciplines and all over the world. Many of its outstanding electronic properties are present only when it is not interacting with a substrate but is instead freestanding. In this work I demonstrate that pristine and functionalized freestanding graphene can be imaged using a scanning tunneling microscope (STM) and that imaging a flexible 2D surface is fundamentally different from imaging a bulk material due to the attraction between the STM tip and the sample. This attraction can be used to manipulate …

A Soft Condensed Matter Approach Towards Mathematical Modelling Of Mass Transport And Swelling In Food Grains, Michael Chapwanya, N. Misra

Articles

Soft condensed matter (SCM) physics has recently gained importance for a large class of engineering materials. The treatment of food materials from a soft matter perspective, however, is only at the surface and is gaining importance for understanding the complex phenomena and structure of foods. In this work, we present a theoretical treatment of navy beans from a SCM perspective to describe the hydration kinetics. We solve the transport equations within a porous matrix and employ the Flory–Huggin’s equation for polymer–solvent mixture to balance the osmotic pressure. The swelling of the legume seed is modelled as a moving boundary with …

Quantum Levitation Using Metamaterials, Venkatesh K. Pappakrishnan

Doctoral Dissertations

The emergence of an attractive vacuum force (Casimir force) between two purely dielectric materials can lead to an increase in the friction and the stiction effects in nanoscale devices, resulting in degradation or decreased performance. Thus, it is of high practical importance that the conditions for the reversal of the Casimir force from attractive to repulsive are identified. Although the repulsive Casimir force has been considered for high dielectric materials as an intermediate (between the plates) medium, so far no realistic system has been proposed that can demonstrate quantum levitation with air/vacuum as a host medium. Since air is the …

The Soft Mode Driven Dynamics Of Ferroelectric Perovskites At The Nanoscale: An Atomistic Study, Kevin Mccash

USF Tampa Graduate Theses and Dissertations

The discovery of ferroelectricity at the nanoscale has incited a lot of interest in perovskite ferroelectrics not only for their potential in device application but also for their potential to expand fundamental understanding of complex phenomena at very small size scales. Unfortunately, not much is known about the dynamics of ferroelectrics at this scale. Many of the widely held theories for ferroelectric materials are based on bulk dynamics which break down when applied to smaller scales. In an effort to increase understanding of nanoscale ferroelectric materials we use atomistic resolution computational simulations to investigate the dynamics of polar perovskites. Within …

Properties Of Multiferroic Bifeo3 From First Principles, Dovran Rahmedov

Graduate Theses and Dissertations

In this dissertation, a first-principle-based approach is developed to study magnetoelectric effect in multiferoic materials. Such approach has a significant predictive power and might serve as a guide to new experimental works. As we will discuss in the course of this work, it also gives an important insight to the underlying physics behind the experimentally observed phenomena.

We start by applying our method to investigate properties of a generic multiferroic material. We observe how magnetic susceptibility of such materials evolves with temperature and compare this evolution with the characteristic behavior of magnetic susceptibility for pure magnetic systems. Then we focus …

Discrete Strain Engineering In Graphene, Cedric Marcus Horvath

Graduate Theses and Dissertations

Graphene has a number of fascinating mechanical and electrical properties. Strain engineering in graphene is the attempt to control its properties with mechanical strain. Previous research in this area has come up with an approach using a continuum theory to describe the strain induced gauge fields in graphene; however, this approach is only valid for small strains (5% at most). A discrete framework is being developed in Arkansas that can more accurately calculate the deformation (electrical) and (pseudo-)magnetic gauge fields created by large strains. Computational simulations were carried out and used to get discrete atomic positions for strained, suspended graphene …

Large-Scale Solution Synthesis Of Narrow Graphene Nanoribbons, Timothy H. Vo, Mikhail Shekhirev, Donna A. Kunkel, Martha D. Morton, Eric Berglund, Lingmei Kong, Peter M. Wilson, Peter A. Dowben, Axel Enders, Alexander Sinitskii

Nebraska Center for Materials and Nanoscience: Faculty Publications

According to theoretical studies, narrow graphene nanoribbons with atomically precise armchair edges and widths of(1.1 eV), which makes them potentially promising for logic applications. Different top–down fabrication approaches typically yield ribbons with width >10nm and have limited control over their edge structure. Here we demonstrate a novel bottom–up approach that yields gram quantities of high-aspect-ratio graphene nanoribbons, which are only ~1 nm wide and have atomically smooth armchair edges. These ribbons are shown to have a large electronic bandgap of ~1.3 eV, which is significantly higher than any value reported so far in experimental studies of graphene nanoribbons prepared by …

Dynamic Analysis Of Dna Nanoparticle Immobilization To Model Biomaterial Substrates Using Combinatorial Spectroscopic Ellipsometry And Quartz Crystal Microbalance With Dissipation, Tadas Kasputis, Alex Pieper, Mathias Schubert, Angela K. Pannier

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Gene expression within cells can be altered through gene delivery approaches, which have tremendous potential for gene therapy, tissue engineering, and diagnostics. Substrate-mediated gene delivery describes the delivery of plasmid DNA or DNA complexed with nonviral vectors to cells from a surface, with the DNA immobilized to a substrate through specific or nonspecific interactions. In this work, DNA-nanoparticle (DNA–NP) adsorption to substrates is evaluated using combinatorial, in situ spectroscopic ellipsometry and quartz crystal microbalance with dissipation (SE/QCM-D), to evaluate the basic dynamic processes involved in the adsorption and immobilization of DNA–NP complexes to substrates. The concentration of DNA–NP solutions influences …

Plasma Processes And Polymers Special Issue On: Plasma And Cancer, Mounir Laroussi, Michael Keidar

Electrical & Computer Engineering Faculty Publications

During the last two decades, research efforts on the application of low temperature plasmas in biology and medicine have positioned nonequilibrium lowtemperature plasmas as a technology that has the potential of revolutionizing healthcare.[1,2] Low temperature plasmas can be applied in direct contact with living tissues to inactivate bacteria,[3] to disinfect wounds and accelerate wound healing,[4] and to induce damage in some cancer cells.[5–11]

Organic Ferroelectric Evaporator With Substrate Cooling And In Situ Transport Capabilities, Keith Foreman, C. Labedz, M. Shearer, Shireen Adenwalla

Shireen Adenwalla Papers

We report on the design, operation, and performance of a thermal evaporation chamber capable of evaporating organic thin films. Organic thin films are employed in a diverse range of devices and can provide insight into fundamental physical phenomena. However, growing organic thin films is often challenging and requires very specific deposition parameters. The chamber presented here is capable of cooling sample substrates to temperatures below 130 K and allows for the detachment of the sample from the cooling stage and in situ transport. This permits the use of multiple deposition techniques in separate, but connected, deposition chambers without breaking vacuum …