Condensed Matter Physics Commons^™

Synthesis And Characterization Of Cage-Structured Compounds As Promising Thermoelectric Materials, Nusrat Yasmin

Graduate Theses/Dissertations

The development of new thermoelectric materials is of great interest due to their potential to convert waste heat into useful electricity. The primary problem is that the physical factors that are utilized to assess thermoelectric performance conflict with one another. One way to improve their performance is to hinder the lattice from conducting heat through its vibrations while maintaining the heat conduction via the electrons. This can be done by creating cage structures that allow heavy atoms to jiggle. In this study, we report the synthesis of a group of such compounds, using the self-flux method. They all belong to …

Discovering And Understanding High Performance Materials Using Density Functional Theory: Quantum Mechanical Simulations And The Consequences Of Symmetry, Olivia M. Pavlic

Graduate Theses, Dissertations, and Problem Reports (ETD)

There are two primary ways that atomic level modeling data is used: materials prediction and understanding materials properties. This dissertation work encom- passes two studies, each of which explore one application. Both studies rely on the highly successful density functional theory (DFT) formalism but differ in that two different implementations of DFT are used on two different high performance materials. The first study on bulk magnesium (Mg) metal alloys explores materials prediction and relies on VASP, a commercially maintained plane-wave DFT code which has been used extensively to successfully study a wide range of materials. [1] The approach used in …

Emission Spectroscopy Of Ingaas Quantum Dots Via High-Resolution Fabry-Perot Interferometer, Raju Bhai Kc

Graduate Theses, Dissertations, and Problem Reports (ETD)

Single photons emitted from self-assembled quantum dots have been widely studied to use as a promising qubit for quantum information processing. Therefore, it is critical to fully understand the emission spectra from the quantum dot's excitation if we want to use a single photon as a quantum bit. It is almost impossible to produce rotationally symmetric quantum dots due to various growth conditions and restrictions. So the real quantum dots do not have a perfectly symmetric structure. A broken rotational symmetry causes an asymmetric exchange interaction between electron and hole, leading to a fine structure splitting between two excited states. …

Development Of High Kinetic Inductance Superconducting Nanowire Devices On High Permittivity Strontium Titanate Substrates, Jamie Timmons

UNF Graduate Theses and Dissertations

This thesis involves the fabrication and characterization of devices made from two different superconducting materials: yttrium barium copper oxide (YBCO), a high-TC complex oxide, and niobium nitride (NbN), a low-TC transition metal nitride. Both types of devices are fabricated on strontium titanate substrates, which provides a good lattice match to YBCO and also an extremely large permittivity at low temperature. We demonstrate that wet etching of YBCO thin films via bromine can be a viable microfrabriation technique for the material. Using approximately 35 nm thick epitaxially grown YBCO on an STO substrate, we were able to fabricate YBCO “microwires” with …

Using Superatomic Clusters And Charge Transfer Ligands To Control Electronic Characteristics Of Phosphorene Nanoribbons And Phosphorene Monolayer, Ryan Lambert

Theses and Dissertations

Phosphorene is a two-dimensional electron poor p-type semiconductor with high carrier mobility and great promise for applications in electronics and optoelectronics. As the main theme in this dissertation, the following work represents different investigations of various electronic properties associated with phosphorene. Most notable are the findings on charge transfer doping with metal-chalcogenide superatoms which displays novel control of the two most important properties of a semiconductor – the band gap energy and the nature of carriers. By tuning the width of the gap and p-/n-type character of conduction, we gain control over a material’s capacity to play a certain role …

Development Of Sustainable Radiation-Shielding Blend Using Natural Rubber/Nbr, And Bismuth Filler, Elsayed Salama, Ola Aziz, Doaa E. El-Nashar, Assem Bakry

Basic Science Engineering

This research entailed the production of composite materials through the combination of natural rubber and acrylonitrile butadiene rubber, along with nano-silica-loaded bismuth (III) oxide, in varying concentrations ranging from 0 to 45 parts per hundred parts of rubber (phr). The gamma attenuation properties of the composites at different concentrations of Bi2O3 were measured. Additionally, the mechanical properties of the resulting composites, including hardness, tensile strength, and elongation, were tested. The composites with a concentration of 20 phr exhibited the highest tensile strength and elongation at break, followed by a subsequent decrease as the concentration of Bi2O3 increased. The gamma mass-attenuation …

Gamma Attenuation And Mechanical Characteristics Of A Lead/Nbr/Sbr Rubber Composite With Black Nanocarbon Reinforcement, Elsayed Salama, Romisaa Gamal, Hassan Elshimy, Doaa E. El-Nashar, Assem Bakry, Mohamed Ehab

Basic Science Engineering

In this work, black nanocarbon-loaded 0–100 parts-per-hundred (phr) PbO-filled acrylonitrile butadiene rubber (NBR)/styrene-butadiene rubber (SBR) blend composites were prepared by using an ordinary standard rubber mixer. Both mechanical and gamma attenuation properties of the prepared samples were investigated. Maximum tensile strength and elongation at break were obtained at 40 phr PbO concentration. The obtained values for the mass attenuation coefficient with the increased PbO concentration from 0–100 phr ranged from 0.12–0.22 cm2/g at 0.239 MeV. Scanning electron microscope (SEM) with the elemental mapping analysis results showed high homogeneity at 40 phr of the prepared rubber composites, with some areas of …

Diffuse Scattering And 3d-∆Pdf Analyses: Order-Disorder Phase Transitions In (Sr1−Xcax)3rh4sn13 And Nano2, Puspa Upreti

Graduate Research Theses & Dissertations

Classification of structural phase transitions as being of the displacive or order-disorder types is usually done based on spectroscopic measurements performed above the transition. Transitions of the displacive type typically occur when soft phonon modes condense upon approaching the phase transition, whereas those of the order-disorder type are characterized by structures in which the atoms are located randomly above the phase transition at T* at the minima of a multiwell potential. In the ordered state, i.e., when T

We have performed single crystal x-ray scattering experiments and three-dimensional pair distribution functions (3D-∆PDF) analyses to understand the nature of phase transitions …

Mechanical And Morphological Characterization Of Energy Materials By Nanoindentation And Scanning Probe Microscopy, Jacob Hempel

Theses and Dissertations--Physics and Astronomy

The demand for robust materials in energy-based applications such as solid electrolytes for batteries, piezoelectric composites for mechanical energy harvesting, or new polymer materials for polymer binders in composite electrodes is on the rise. Mechanical degradation is the most common way for devices to fail in operation, thus a thorough understanding of a material’s mechanical properties is essential for application purposes.

In this dissertation, the mechanical characterization of novel boron cluster solid electrolytes is presented. Therein, we determine the elastic modulus and hardness of these compounds using instrumented indentation. A comparison is made against other solid electrolytes. It is found …

Aspects Of Topology In Moiré Graphene, Ahmed Khalifa

Theses and Dissertations--Physics and Astronomy

Moiré materials, such as twisted bilayer graphene, have provided a rich platform for fundamental physics and potential technological applications. Superconductivity,
correlated insulators, and Chern insulators are examples of phenomena that have been found experimentally in moiré systems. The interplay of strong electron-electron interactions and topology lies at the heart of the mechanism driving these phenomena. In this work, we study the topological aspects of moiré graphene materials, such as the valley Chern and Chern insulating phases. To study the topological response of these phases, we construct models to describe the edge states which are the telltale signs of nontrivial topology. …

Investigations Of Epitaxial Heterostructures Of Layered Iridates With Resonant X-Ray Techniques, Sujan Shrestha

Theses and Dissertations--Physics and Astronomy

In layered 5d transition metal oxides, like Sr₂IrO₄, strong spin-orbit interaction comparable to the relevant interactions such as electron correlation and crystal field splitting provides fertile ground for emergent non-trivial phenomena. Some of these phenomena include metal-insulator transition, high-temperature superconductivity, and spin-orbit Mott insulator. The ground state is governed by the spin-orbit-entangled pseudospins J_eff =1/2, which have a significant orbital contribution. Therefore, magnetic exchange interactions and anisotropies are highly susceptible to external stimuli such as strain and heterointerface. As a result, it has a significant impact on the magnetic properties of the system. However, …

Collective Relaxation Processes In Nonchiral Nematics, Neelam Yadav, Yuri Panarin, Wanhe Jiang, Georg H. Mehl, Jagdish Vij

Articles

Nematic–nematic transitions in a highly polar nematic compound are studied, in thick cells in which the molecules are aligned parallel to the substrates but perpendicular to the applied electric field, using dielectric spectroscopy in the frequency range 1 Hz to 10 MHz over a wide temperature range. The studied compound displays three nematic phases under cooling from the isotropic phase: ubiquitous nematic N; high polarizability NX; and ferroelectric nematic NF. Two collective processes were observed. The dielectric strength and relaxation frequency of one of the processes P2 showed a dependence on the thickness of the cell. The process P1 is …

Investigations Into The Electronic And Magnetic Properties Of (Crps4)N Layers, Alexandria R. Alcantara

UNF Graduate Theses and Dissertations

2D magnetic semiconductors have become of interest due to their magneto-optical effects in lower dimensionality. More specifically, CrPS4 has gained renewed attention due to its A-type AFM order and air stability prompting analysis and stability studies in its layered forms for use in scalable technology such as spintronic and optoelectronic devices. In this study, we benchmark our approach using the SCAN meta-GGA functional used without U-parameterization on bulk CrPS4 to demonstrate the accuracy of our methodology to use as tools to go beyond current CrPS4 theoretical studies. We examine the 2D electronic nature and optical spectrum for use in experimental …

Exploring Mottness And Electronic Order In Strongly Correlated Vanadate Thin Films, Nathan Bairen

UNF Graduate Theses and Dissertations

Mott insulators provide a window into some of the most intensely investigated phenomena in physics. Recent discoveries—including the emergence of high-temperature superconductivity in doped Mott insulators not from the cuprate family of superconductors—have inspired investigation into systems with strong electron-electron interactions. One of these systems is La_1-xSr_xVO₃, in which one end-member, LaVO₃, is a Mott insulator and the other, SrVO_3, is a strongly correlated metal.

Herein, we detail two studies regarding this system. In our oxidation study, we optimized the growth parameters for LaVO_3, finding that the ultra-high vacuum technique …

Surface Reconstruction In Iron Garnets, Sushree Dash

Dissertations, Master's Theses and Master's Reports

This dissertation presents the results of a study investigating the physical mechanisms underlying an unexpectedly large increase in magneto-optic efficiency observed in iron garnet. Such materials are technologically important for telecommunications due to their nonreciprocal optical action. In the past, our group had found evidence of an enhanced Faraday rotation in bismuth-substituted iron garnet films less than 50 nm thick. Subsequent investigation revealed that this enhancement could be traced to surface effects. This is significant because understanding these phenomena could be used to formulate engineering solutions for device miniaturization. In this dissertation, we present the result of a research project …

Structural And Magnetic Study Of Epitaxial Ni/Nio Thin Films On Various Single Crystalline Substrates Using Pulsed Laser Deposition, Md Shaihan Bin Iqbal

Graduate Theses/Dissertations

In recent years, magnetic thin films have gained significant attention in the field of spintronics, which is a branch of electronics that utilizes the spin of electrons in addition to their charge. The applications in the spintronic sector rely on the magnetic properties of the thin films. To address this, Ni (FM)/NiO (AFM) thin films on single crystalline sapphire and lithium niobate substrates have been investigated using pulsed laser deposition (PLD) technique prior to hydrogen-reduction annealing to explore new functionalities. The manufactured films were extensively analyzed by state-of-the-art characterization techniques. X-ray diffraction (XRD) and X-ray reflectometry (XRR) show the structural …

Growth And Characterization Of Sm3hfbi5, Patrick Lambdin

Graduate Theses/Dissertations

First found experimentally in 2015, topological Weyl materials are desirable compounds that have garnered much interest due to their ability to conduct electricity via their surface states even though the bulk material is a semimetal. Such a candidate, Sm3HfBi5, was discovered with a flux crystal growth method, following an extensive amount of reaction syntheses. This thesis reports on the discovery, growth, structural characterization via x-ray diffraction, and magnetization measurements on Sm3HfBi5.

Study Of Electronic And Magnetic Properties Of Bilayer Graphene Nanoflakes And Bimetallic Chalcogenides Using First-Principles Density Functional Theory And Machine Learning, Dharmendra Pant

Dissertations, Master's Theses and Master's Reports

Graphene, a one-atom-thick material, has been a wonder material since its discovery because of its superlative electronic, mechanical, and optical properties. When a layer of graphene is rotated over another layer, it exhibits many intriguing behaviors, ranging from superconductivity to the anomalous Hall effect to ferromagnetism at a magic angle of 1°, and hence the twisted bilayer graphene has been the subject of intense research in recent years. The surge in interest in this moiré structure can be attributed to the emergence of electronic flat minibands near the magic angle. Here, we studied the electronic and magnetic properties of twisted …

Fabrication And Optical Properties Of Two-Dimensional Transition Metal Dichalcogenides, Manpreet Boora

Dissertations, Master's Theses and Master's Reports

Two-dimensional layered materials such as graphene and transition metal dichalcogenides have gained a lot of attention because of their distinctive chemical, optical, and electronic properties. Transition metal dichalcogenides can have a tunable bandgap in the range of 1 − 3 eV (visible), which enables their applications in ultrathin field effect transistors, photovoltaics, sensors, and optoelectronic devices. They exhibit an indirect-to-direct band gap transition when thinned down from bulk to a single layer. They show strong photoluminescence, electron–photon interaction, valley pseudospin, nonlinear optical response, and lack of dangling bonds. Many exotic phenomena appear when materials are thinned to nanoscale size because …

Polymeric Nitrogen: Computational Catalysis And Materials Design, Safa Alzaim

Dissertations

The urgent climactic crisis currently endangering all life on earth is largely due to the combustion of fossil fuels as an energy source. This work combines physics, chemistry, mathematics and computer science to develop new ways to harvest, store and use sustainable energy. In particular, this work centers on polymeric nitrogen (PN). PN is highly desirable because the energy density is extremely high. This energy density lends PN to applications such as rocket fuel and energetic materials. Recently, the polymeric phase N₈ was shown to be highly active for oxygen reduction reactions (ORR); the material is an excellent electrocatalyst …

Structural And Magneto Conductivity Studies Of Nio/Smba2cu3o7-Δ Superconducting Composite, Hadi Basma, Sajida Rmeid, Ramadan Awad, Mohammed Said

BAU Journal - Science and Technology

In this work, we investigate the effect of NiO nanoparticles' addition on the structure, superconductivity, and magneto conductivity for the SmBa₂Cu₃O_7-δ phase. Composite nano/superconductor of (NiO)_x/SmBa₂Cu₃O_7-δ (0.00≤x≤0.12 wt.%) were prepared by conventional solid-state reaction technique and characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The orthorhombic structure was maintained whereas the lattice parameters showed unsystematic variations with the NiO nanoparticles addition. The superconducting transition temperature T_c, determined from electrical resistivity measurements, showed an enhancement with x up to 0.04wt.% followed by a reduction …

Perspectives On Determinism In Quantum Mechanics: Born, Bohm, And The “Quantal Newtonian” Laws, Viraht Sahni

Publications and Research

Quantum mechanics has a deterministic Schrödinger equation for the wave function. The Göttingen–Copenhagen statistical interpretation is based on the Born Rule that interprets the wave function as a “probability amplitude.” A precept of this interpretation is the lack of determinism in quantum mechanics. The Bohm interpretation is that the wave function is a source of a field experienced by the electrons, thereby attributing determinism to quantum theory. In this paper, we present a new perspective on such determinism. The ideas are based on the equations of motion or “Quantal Newtonian” Laws obeyed by each electron. These Laws, derived from …

Highly Efficient Photocatalysts For Methylene Blue Degradation Based On A Platform Of Deposited Go-Zno Nanoparticles On Polyurethane Foam, Mohamed Morsy

Nanotechnology Research Centre

No abstract provided.

Spacecraft Charging Test Considerations For Composite Materials, Allen Andersen, Wousik Kim, J. R. Dennison, Brian Wood, Todd A. Schneider, Jason Vaughn, Kenneth H. Wright Jr., Nelson W. Green, Eric Suh, Joel Schwartz, Abdul-Majeed Azad

Journal Articles

Composite materials present a growing challenge for spacecraft charging assessments. We review some recent lessons learned for charging tests of composite materials using both parallel-plate and electron beam test geometries. We also discuss examples of materials that exhibit significant variations between samples, despite them all having the same trade name.

Towards The Electronic Response Of Carbon-Based Van Der Waals Heterostructures In A Diamond Anvil Cell, George Thomas Foskaris

UNLV Theses, Dissertations, Professional Papers, and Capstones

The nanoscale regime of materials has been at the forefront of research and interest in condensed matter physics for many years. In a merger of the fields of two-dimensional (2D) materials and high pressure physics, we present an investigation of the electronic response of carbon-based, van der Waals (vdW) heterostructures in a diamond anvil cell (DAC). Combining these fields presents us with the ability to study the characteristics of such systems both optically, and through electrical transport. Properties such as conductance, band structure, and layer number are considered. The samples in this study are assembled using exfoliation and stacking techniques …

Characterization Of Losses In Superconducting Radio-Frequency Cavities By Combined Temperature And Magnetic Field Mapping, Ishwari Prasad Parajuli

Physics Theses & Dissertations

Superconducting radio-frequency (SRF) cavities are one of the fundamental building blocks of modern particle accelerators. To achieve the highest quality factors (10¹⁰-10¹¹), SRF cavities are operated at liquid helium temperatures. Magnetic flux trapped on the surface of SRF cavities during cool-down below the critical temperature is one of the leading sources of residual RF losses. Instruments capable of detecting the distribution of trapped flux on the cavity surface are in high demand in order to better understand its relation to the cavity material, surface treatments and environmental conditions. We have designed, developed, and commissioned two novel …

Raman Scattering Measurements And Analyses Of Gan Thin Films Grown On Zno Substrates By Metalorganic Chemical Vapor Deposition, Zane Mcdaniel, Zhe Chuan Feng, Kevin Stokes

Symposium of Student Scholars

Metalorganic chemical vapor deposition (MOCVD) is a popularly used method of growing thin films of GaN on ZnO (GZ) substrates, which pair well due to their structural and characteristic similarities. In this research, optical characterization of the surface quality of GZ sample films is measured by analyzing Raman scattering (RS) using a Renishaw inVia spectrometer fitted with a 532nm laser. Samples were grown in an improved double injection block rotating disc reactor. Multiple samples' spectra show broad peaks that correspond with the E2 (high) and A1 (LO) branches of GaN, and nicely fitted curves are observed for the characteristic E2 …

Exploring Cathodoluminescence Evident Features Of Tungsten Disulfide, Molybdenum Disulfide, And Tungsten-Sulfide-Selenide, Nathan Mayer

Undergraduate Theses

Cathodoluminescence (CL) microscopy can be used to characterize the quantum optical behaviors of two-dimensional nanostructures. To investigate this behavior, we mounted flakes of tungsten disulfide (WS₂), molybdenum disulfide (MoS₂)_, and tungsten-sulfide-selenide Janus structures (WSSe) on a SiO₂ substrate and analyzed these samples under both high vacuum and low H₂O vacuum conditions using a scanning electron microscope. We then captured CL and secondary-electron images of the samples at multiple electron-beam energies and currents (5 keV to 30 keV, and 0.5 nA to 5 nA, respectively). We used a range of beam currents and …

Oil/Water Separation And Functionality Of Smart Carbon Nanotube–Titania Nanotube Composite, Mohamed Morsy

Nanotechnology Research Centre

No abstract provided.

Effects Of Volatile Compounds On Breakdown Field Strength Measurements Of Polymers, Megan Loveland Dewaal, Jr Dennison

Journal Articles

This study investigates the effects of absorbed water and volatile compounds on measurements of the electrostatic breakdown field strength. Comparisons are made between sets of pristine samples, ones that underwent a thorough vacuum bake out, and ones subsequently exposed to humid conditions to determine how quickly the samples reverted to an unbaked state. Specifically, we compared signatures related to an electrostatic breakdown (electrostatic breakdown field strength, frequency of pre-breakdown arcing, and flashover) and images of the arc damage sites. The work reports results for three prototypical polymeric dielectric materials: low density polyethylene (LDPE), polyether-etherketone (PEEK), and Nylon 66, listed in …