Condensed Matter Physics Commons^™

Density Functional Theory Study On The Electronic Structure Of N- And P-Type Doped Srtio3 At Anodic Solid Oxide Fuel Cell Conditions, S. Suthirakun, Salai Cheettu Ammal, G. Xiao, Fanglin Chen, Hans-Conrad Zur Loye, Andreas Heyden

Faculty Publications

The electronic conductivity and thermodynamic stability of mixed n-type and p-type doped SrTiO3 have been investigated at anodic solid oxide fuel cell (SOFC) conditions using density functional theory (DFT) calculations. In particular, constrained ab initio thermodynamic calculations have been performed to evaluate the phase stability and reducibility of various Nb- and Ga-doped SrTiO3 at synthesized and anodic SOFC conditions. The density of states (DOS) of these materials was analyzed to study the effects of n- and p-doping on the electronic conductivity. In agreement with experimental observations, we find that the transformation from 20% Nb-doped Sr-deficient SrTiO3 to a non-Sr-deficient phase …

Superplastic Boronizing On Duplex Stainless Steel (Dss) Using Compression Method., Yong Siu Fung

Student Works (2010-2019)

The formation and growth of boride phases on duplex stainless steel (DSS) during superplastic boronizing (SPB) were studied in comparison with conventional boronizing (CB) from previous research. SPB is a surface hardening technique that combines boronizing with superplastic deformation. It utilizes the ultra high plasticity phenomenon in metal while carrying out boronizing in which boron atoms are diffused into the metal substrate to form hard boronized layer. The SPB process was conducted under compression mode at a strain rate of 2 × 10-4 s-1, at three different temperature conditions (1223 K, 1273 K, 1373 K) and strains (0.2 to 0.6). …

Chemical And Electronic Structure Of Surfaces And Interfaces In Compound Semiconductors, Sujitra Pookpanratana

UNLV Theses, Dissertations, Professional Papers, and Capstones

The interface formation between two different materials is important in applications for optoelectronic devices. Often, the success or performance of these devices is dependent on the formation of these heterojunctions. In this work, the surface and interfaces in such materials for optoelectronic devices are investigated by a suite of X-ray analytical techniques including X-ray photoelectron (XPS), X-ray excited Auger electron (XAES), and X-ray emission (XES) spectroscopies to provide novel insight.

For the group III-nitrides (e.g., AlxGa1-xN) used in many light emitting devices, a significant challenge exists to form an Ohmic contact. The electron affinities and band gaps of GaN and …

Boron Carbide Based Solid State Neutron Detectors: The Effects Of Bias And Time Constant On Detection Efficiency, Nina Hong, John Mullins, Keith Foreman, Shireen Adenwalla

Shireen Adenwalla Papers

Neutron detection in thick boron carbide(BC)/n-type Si heterojunction diodes shows a threefold increase in efficiency with applied bias and longer time constants. The improved efficiencies resulting from long time constants have been conclusively linked to the much longer charge collection times in the BC layer. Neutron detection signals from both the p-type BC layer and the n-type Si side of the heterojunction diode are observed, with comparable efficiencies. Collectively, these provide strong evidence that the semiconducting BC layer plays an active role in neutron detection, both in neutron capture and in charge generation and collection.

Vibrational Frequencies Of Magnetic Random Access Memory Materials., Lee Li Ling

Student Works (2010-2019)

The advantages of MRAM are so overwhelming which acts as motivation for scientist in further investigation for better read and write operation. The types of materials used are closely related to the cell performance in forming the ferromagnetic layers. Thus,the vibrational frequencies of the MRAM materials are of interest. Clusters for the two types of combinations, FexNiy and FexCoyBz are built. Subsequently, vibrational frequencies of each cluster are calculated theoretically from the first principles. The secular determinant is large when the number of electrons in a cluster is large. For the simplest combination of Fe-Ni cluster, (atomic number of an …

The Thermoluminescence Properties Of Manganese Doped Zns Nanophosphor., Khalid Humaid Zahir Al-Hinai

Student Works (2010-2019)

The thermoluminescence (TL) properties of Manganese (Mn) doped ZnS nanophosphors were investigated after gamma irradiation at room temperature. The ZnS:Mn nanophosphors were prepared by chemical precipitation method by using Zinc sulfate, Sodium sulfide and Manganese sulfate. 1 mole, 2 moles and 3 moles of Manganese sulfate were used to have different concentrations of Mn in doped ZnS. The formation of the nanophosphors was characterized by high resolution scanning electron microscopy FESEM, XRD and EDX. The obtained products consist of particles with the dimension about 85–150nm. Comparison between ZnS nanophosphors and commercial ZnS powder glow curves was studied. It was observed …

Mechanical And Thermodynamic Properties Of Bacteriorhodopsin Langmuir Film., Vijayandren Kuppusamy

Student Works (2010-2019)

Bacteriorhodopsin is a photoactive protein found in the purple membranes of the highly halophilic bacterium Halobacterium Salinarium. Due to highly efficient and simple in its function, Bacteriorhodopsin has been extensively researched and successfully incorporated into many practical applications. In this regard, the fabrication of compactly packed and functionally active Bacteriorhodopsin thin film is crucial in realizing a highly efficient device. The aim of this thesis is to analyze the mechanical and thermodynamic properties of the Bacteriorhodopsin-Langmuir monolayer film from the surface pressure-area per molecule isotherm to produce a compactly pact and functionally active monolayer film. For this, we have proposed …

Electro-Optic And Magneto-Dielectric Properties Of Multifunctional Nitride And Oxide Materials, Ambesh Dixit

Wayne State University Dissertations

ABSTRACT

Materials that simultaneously exhibit different physical properties provide a rich area of research leading to the development of new devices. For example, materials having a strong coupling between charge and spin degrees of freedom are essential to realizing a new class of devices referred to generally as spintronics. However, these multifunctional systems pose new scientific challenges in understanding the origin and mechanisms for cross-control of different functionalities. The core of this Ph.D. dissertation deals with multifunctional nitride and oxide compound semiconductors as well as multiferroic magnetic oxide systems by investigating structural, optical, electrical, magnetic, magnetodielectric and magnetoelectric properties.

Thin …

Quantum Dot Quantum Computation In Iii-V Type Semiconductor, Sanjay K. Prabhakar

Legacy Theses & Dissertations (2009 - 2024)

Among recent proposals for next-generation, non-charge-based logic is the notion that a single electron can be trapped and spin of the electron can be manipulated through the application of gate potentials. In the thesis, there are two major contributions of the manipulation of electron spin. In regard to the first contribution, we present numerical simulations of such a spin in single electron devices for realistic asymmetric potentials in electrostatically confined quantum dot. Using analytical and numerical techniques we show that breaking in-plane rotational symmetry of the confining potential by applied gate voltage leads to a significant effect on the tuning …

Suppression Of Octahedral Tilts And Associated Changes In Electronic Properties At Epitaxial Oxide Heterostructure Interfaces, A. Y. Borisevich, H. Y. Chang, Mark Huijben, M. P. Oxley, S. Okamoto, Manish K. Niranjan, John D. Burton, Evgeny Y. Tsymbal, Y. H. Chu, P. Yu, R. Ramesh, Sergei V. Kalinin, S. J. Pennycook

Materials Research Science and Engineering Center: Faculty Publications

Epitaxial oxide interfaces with broken translational symmetry have emerged as a central paradigm behind the novel behaviors of oxide superlattices. Here, we use scanning transmission electron microscopy to demonstrate a direct, quantitative unit-cell-by-unit-cell mapping of lattice parameters and oxygen octahedral rotations across the BiFeO₃ -La_0:7 Sr_0:3MnO₃ interface to elucidate how the change of crystal symmetry is accommodated. Combined with low-loss electron energy loss spectroscopy imaging, we demonstrate a mesoscopic antiferrodistortive phase transition near the interface in BiFeO₃ and elucidate associated changes in electronic properties in a thin layer directly adjacent to the interface.

Band Structure Of Fe Based Superconductors., Teh Yee Lin

Student Works (2010-2019)

Several iron containing superconductors are discovered in 2008. The discovery introduced a new class of high-temperature superconductors, which are iron-based. The iron-based superconductors do not resemble conventional superconductors and have properties on their own which differ from the cuprates. We have studied the iron selenium, FeSe compound by removing some Se atoms from the lattice forming Fe:Se = 2:1 and 8:6 and also by replacing the Se vacancy with tellurium, samarium and oxygen atoms forming Fe:Se:Te = 2:1:1 and 8:6:2, Fe:Se:O = 8:6:2 and 8:4:2, FeSeSmO, FeSeTeO, Fe2SeSm2O2, FeSeTeSmO and FeTeSmO. The band structures for each lattice are calculated by …

Robust Isothermal Electric Control Of Exchange Bias At Room Temperature, Xi He, Ning Wu, Anthony N. Caruso, Elio Vescovo, Kirill D. Belashchenko, Peter A. Dowben, Christian Binek

Kirill Belashchenko Publications

Voltage-controlled spin electronics is crucial for continued progress in information technology. It aims at reduced power consumption, increased integration density and enhanced functionality where non-volatile memory is combined with highspeed logical processing. Promising spintronic device concepts use the electric control of interface and surface magnetization. From the combination of magnetometry, spin-polarized photoemission spectroscopy, symmetry arguments and first-principles calculations, we show that the (0001) surface of magnetoelectric Cr₂O₃ has a roughness-insensitive, electrically switchable magnetization. Using a ferromagnetic Pd/Co multilayer deposited on the (0001) surface of a Cr₂O₃ single crystal, we achieve reversible, room-temperature isothermal switching …

Modeling Of Metal-Ferroelectric-Insulator-Semiconductor Structures Based On Langmuir–Blodgett Copolymer Films, Timothy J. Reece, Stephen Ducharme

Stephen Ducharme Publications

Among the ferroelectric thin films used in field-effect transistor devices; the ferroelectric copolymer of polyvinylidene fluoride PVDF –CH2–CF2–, with trifluoroethylene TrFE –CHF–CF2–, has distinct advantages, including low dielectric constant, low processing temperature, low cost, and compatibility with organic semiconductors. The operation of a metal-ferroelectric insulatorsemiconductor structure with PVDF-TrFE as the ferroelectric layer was analyzed and optimized by numerical solution of the Miller and McWhorter model. A model device consisting of 20 nm PVDF/TrFE on a 10-nm-thick high-k dielectric buffer exhibits a memory window of 5 V with an operating voltage of 15 V. The operating voltage can be reduced to …

Nanoscale Domain Patterns In Ultrathin Polymer Ferroelectric Films, Pankaj Sharma, Timothy J. Reece, Daniel W. Wu, Vladimir M. Fridkin, Stephen Ducharme, Alexei Gruverman

Stephen Ducharme Publications

High-resolution studies of domain configurations in Langmuir–Blodgett films of ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), have been carried out by means of piezoresponse force microscopy (PFM). Changes in film thickness and morphology cause significant variations in polarization patterns. In continuous films and nanomesas with relatively low thickness/grain aspect ratio (<1/10), the relationship between the average domain size and thickness follows the Kittel law. Nanomesas with high aspect ratio (>1/5) exhibit significant deviations from this law, suggesting additional surface-energy-related mechanisms affecting the domain patterns. Polarization reversal within a single crystallite has been demonstrated and local switching parameters (coercive voltage and remnant piezoresponse) have been measured by monitoring the local hysteresis loops. Reliable control of polarization at the sub-grain level demonstrates …

Dielectric Nanocomposites: An Inside-Out Approach To Storing Electrostatic Energy, Stephen Ducharme

Stephen Ducharme Publications

The ability to achieve high-energy densities is the central challenge in energy storage and recovery. A promising strategy for increasing energy storage is to use highperformance dielectric materials, such as highly polarizable nanoparticles or polymers, or nanocomposites of the two. In this issue, Kim et al. use a molecular coating and clever chemistry to combine oxide nanoparticles with a polymer matrix, thereby producing an improved nanocomposite dielectric. Some advantages and challenges of using nanocomposites as improved dielectric materials are presented in this Perspective.

Polarization Switching Kinetics Of Ferroelectric Nanomesas Of Vinylidene Fluoride-Trifluoroethylene Copolymer, R. V. Gaynutdinov, O. A. Lysova, S. G. Yudin, A. L. Tolstikhina, A. L. Kholkin, V. M. Fridkin, Stephen Ducharme

Stephen Ducharme Publications

The polarization switching kinetics of ferroelectric polymer nanomesas was investigated using piezoresponse force microscopy. The nanomesas were made by self-organization from Langmuir–Blodgett films of a 70% vinylidene fluoride and 30% trifluoroethylene copolymer. The polarization switching time exhibits an exponential dependence on reciprocal voltage that is consistent with nucleation-type switching dynamics.

Nanometrology Device Standards For Scanning Probe Mmicroscopes And Processes For Their Fabrication And Use, Peter Moeck

Physics Faculty Publications and Presentations

Nanometrology device standards and methods for fabricating and using such devices in conjunction With scanning probe microscopes are described. The fabrication methods comprise: (1) epitaxial growth that produces nanometer sized islands of knoWn morphology, structural, morphological and chemical stability in typical nanometrology environments, and large height-to-width nano-island aspect ratios, and (2) marking suitable crystallographic directions on the device for alignment With a scanning direction.

Application And Extension Of Glauber Ising-Spin Dynamics In The Context Of A Single Chain Magnet System, Ryan Tucker Kristensen

Legacy Theses & Dissertations (2009 - 2024)

The Glauber Ising-spin dynamic with a local equilibrium approximation is applied to infinite and finite one-dimensional (anti-)ferromagnetic Ising chains with classic nearest neighbor interactions. The application of the Glauber dynamic and local equilibrium approximation is then extended to the one-dimensional ferrimagnetic chain with nearest neighbor interactions. Time dependant behavior and equilibrium states of the one-dimensional ferrimagnetic chain are then discussed in terms of the single chain magnet referred to as CoPhOMe, whose behavior empirical data to date suggest is consistent with a one-dimensional Ising ferrimagnet.

Precession Electron Diffraction And Its Advantages For Structural Fingerprinting In The Transmission Electron Microscope, Peter Moeck, Sergei Rouvimov

Physics Faculty Publications and Presentations

The foundations of precession electron diffraction in a transmission electron microscope are outlined. A brief illustration of the fact that laboratory-based powder X-ray diffraction fingerprinting is not feasible for nanocrystals is given. A procedure for structural fingerprinting of nanocrystals on the basis of structural data that can be extracted from precession electron diffraction spot patterns is proposed.

Start The Presses, Stephen V. Ducharme, Alexei Gruverman

Stephen Ducharme Publications

A simple nanoimprinting method creates arrays of ferroelectric polymer structures suitable for low-cost, non-volatile memories. With the development of nanoimprinted high-quality ferroelectric nanomesa arrays, it seems that we now have all the necessary ingredients to print inexpensive, disposable organic memory chips.

Observed Superspin-Glass Behavior In Ni0.5zn0.5fe2o4 Nanoparticles, Antony Adair

Open Access Theses & Dissertations

In this investigation we seek to identify the magnetic behavior of Ni0.5Zn0.5Fe2O4 nanoparticles though AC-susceptibility and DC-magnetization measurements. Powder x-ray diffraction was performed to determine the purity and average diameter ( ~ 9nm) of the particles. Aditionally, structure was confirmed by comparison through the International Centre for Diffraction Data's Powder Diffraction File [52] (PDF # 08-0234).

Zero-field cooled and field cooled DC magnetization measurements (bifurcation and blocking temperature), as well as M(H) hysteresis (below and above the blocking temperature) lead us to initially suggest that the material may in fact be superparamagnetic. However, further investigation of the real AC susceptibility …

Intergranular Phases In Cyclically Annealed Yba2cu3o7-X And Their Implications For Critical Current Densities, Andrew Peter Clarke

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

We report changes in the intergranular material and grain morphology of YBa₂Cu₃O_7-x during cyclic anneals between 780 and 980 ºC in oxygen at atmospheric pressure. Two endothermic reactions were detected: (a) the eutectic reaction of YBa₂Cu₃O_7-x with CuO and BaCuO₂ at 900 ºC (enthalpy ∆H_a) and (b) the peritectic reaction of YBa₂Cu₃O_7-x with CuO at 950 ºC (∆H_b). During the first anneal, only reaction (b) is detected, and although it should only occur if there is an excess of CuO, …

Regulating Self-Organizing Nanostructures Via External Mechanism, Jiangyu Li, Q. G. Du, Stephen Ducharme

Stephen Ducharme Publications

Self-organizing nanostructures are ubiquitous in both natural and synthetic materials. They are not only appealing scientifically, by revealing the intrinsic atomic and molecular interactions that might be difficult to detect otherwise, but may also hold the key for the development of novel functional structures and devices. For their technological potential to be fully realized, the size, morphology, and distribution of the self-organizing nanostructures must be regulated. In this paper, we investigate the principles under which the self-organizing nanostructures can be regulated via external mechanisms. Using nanomesa and nanowell formation in polyvinylidene fluoride trifluoroethylene copolymer film as an example, we demonstrate …

A Finite Difference Method For Studying Thermal Deformation In Three-Dimensional Thin Films Exposed To Ultrashort Pulsed Lasers, Suyang Zhang

Doctoral Dissertations

Thermal analysis related to ultrashort-pulsed lasers has been intensely studied in science and engineering communities in recent years, because the pulse duration of ultrashort-pulsed lasers is only the order of sub-picoseconds to femtoseconds, and the lasers have exclusive capabilities in limiting the undesirable spread of the thermal process zone in the heated sample. Studying the thermal deformation induced by ultrashort-pulsed lasers is essential for preventing thermal damage. For the ultrashort-pulsed laser, the thermal damage is different from that caused by the long pulsed lasers and cracks occur after heating.

This dissertation presents a new finite difference method for studying thermal …

Reflection High-Energy Electron Diffraction Studies Of Indium Phosphide (100) And Growth On Indium And Indium Nitride On Silicon (100), Mohamed Abd-Elsattar Hafez

Electrical & Computer Engineering Theses & Dissertations

Study of the effects of atomic hydrogen exposure on structure and morphology of semiconductor surfaces is important for fundamental properties and applications. In this dissertation, the electron yield of a hydrogen-cleaned indium phosphide (InP) surface was measured and correlated to the development of the surface morphology, which was monitored by in situ reflection high-energy electron diffraction (RHEED). Atomic hydrogen treatment produced a clean, well-ordered, and (2x4)-reconstructed InP(100) surface. The quantum efficiency, after activation to negative electron affinity, and the secondary electron emission were shown to increase with hydrogen cleaning time. RHEED patterns of low-index InP(100) surface were modified by the …

Structural Identification Of Cubic Iron-Oxide Nanocrystal Mixtures: X-Ray Powder Diffraction Versus Quasi-Kinematic Transmission Electron Microscopy, Peter Moeck

Physics Faculty Publications and Presentations

Two novel (and proprietary) strategies for the structural identification of a nanocrystal from either a single high-resolution (HR) transmission electron microscopy (TEM) image or a single precession electron diffraction pattern are proposed and their advantages discussed in comparison to structural fingerprinting from powder X-ray diffraction patterns. Simulations for cubic magnetite and maghemite nanocrystals are used as examples.

Performance Comparison Of Pb(Zr0.52Ti0.48)O3-Only And Pb(Zr0.52Ti0.48)O3-On-Silicon Resonators, Hengky Chandrahalim, Sunil A. Bhave, Ronald G. Polcawich, Jeff Pulskamp, Dan Judy, Roger Kaul, Madan Dubey

Faculty Publications

This paper provides a quantitative comparison and explores the design space of lead zirconium titanate (PZT)–only and PZT-on-silicon length-extensional mode resonators for incorporation into radio frequency microelectromechanical system filters and oscillators. We experimentally measured the correlation of motional impedance (R_X) and quality factor (Q) with the resonators’ silicon layer thickness (t_Si). For identical lateral dimensions and PZT-layer thicknesses (t_PZT), the PZT-on-silicon resonator has higher resonant frequency (f_C), higher Q (5100 versus 140), lower R_X (51 Ω versus 205 Ω), and better linearity [third-order input intercept …

Oligo(Vinylidene Fluoride) Langmuir-Blodgett Films Studied By Spectroscopic, Rafal Korlacki, J. Travis Johnston, Jihee Kim, Stephen Ducharme, Daniel W. Thompson, Vladimir M. Fridkin, Zhongxin Ge, James M. Takacs

Stephen Ducharme Publications

Thin films of amphiphilic vinylidene fluoride oligomers prepared by Langmuir–Blodgett deposition on silicone substrates were investigated by comparing experimental and theoretical mid-infrared (IR) spectra. The experimental spectra were obtained using infrared spectroscopic ellipsometry. Theoretical spectra were calculated using density functional theory. Excellent correspondence of major IR bands in both data sets shows that the molecular backbone is oriented with the long axis normal to the substrate plane. This is in contrast to poly vinylidene fluoride[1] LB films, in which the polymer chains are parallel to the substrate.

Plasma Medicine, Mounir Laroussi, Alexander Fridman

Electrical & Computer Engineering Faculty Publications

Recent demonstrations of plasma technology in the treatment of living cells, tissues, and organs are creating a newfield at the intersection of plasma science and technology with biology and medicine - Plasma Medicine.

Effect Of Tip Resonances On Tunnelling Anisotropic Magnetoresistance In Ferromagnetic Break Junctions: A First-Principles Study, John D. Burton, Renat F. Sabirianov, Julian P. Velev, O. N. Mryasov, Evgeny Y. Tsymbal

Materials Research Science and Engineering Center: Faculty Publications

First-principles calculations of electron tunneling transport in nanoscale Ni and Co break-junctions reveal strong dependence of the conductance on the magnetization direction, an effect known as tunneling anisotropic magnetoresistance TAMR. An important aspect of this phenomenon stems from resonant states localized in the electrodes near the junction break. The energy and broadening of these states is strongly affected by the magnetization orientation due to spin-orbit coupling, causing TAMR to be sensitive to bias voltage on a scale of a few millivolts. Our results bear a resemblance to recent experimental data and suggest that TAMR driven by resonant states is a …