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Classical Simulations of the Drift of Magnetobound States of Positronium

Description: The production and control of antihydrogen at very low temperatures provided a key tool to test the validity for the antimaterial of the fundamental principles of the interactions of nature such as the weak principle of equivalence (WEP), and CPT symmetry (Charge, Parity, and Time reversal). The work presented in this dissertation studies the collisions of electrons and positrons in strong magnetic fields that generate magnetobound positronium (positron-electron system temporarily bound due to … more
Date: August 2021
Creator: Aguirre Farro, Franz
Item Type: Refine your search to only Thesis or Dissertation
open access

The Electrochemical Etching Process of a Tungsten Wire

Description: This study produced and analyzed shaped tungsten wire tips formed through electrochemical etching. Specifically, the cone length and the radius of curvature of the tip were analyzed. Having the tips move dynamically through an electrolytic solution, such as potassium hydroxide, and tuning the initial starting depth of the tungsten wire along with the dynamic speed of the tungsten wire as it passed throughout the solution allowed various types of tip profiles to be produced. The tip's radius of … more
Date: August 2021
Creator: Richardson, Aaron Michael
Item Type: Refine your search to only Thesis or Dissertation

Low-Energy Electron Irradiation of 2D Graphene and Stability Investigations of 2D MoS2

Description: In this work, we demonstrate the mechanism for etching exfoliated graphene on SiO2 and other technological important substrates (Si, SiC and ITO), using low-energy electron sources. Our mechanism is based on helium ion sputtering and vacancy formation. Helium ions instead of incident electrons cause the defects that oxygen reacts with and etches graphene. We found that etching does not occur on low-resistivity Si and ITO. Etching occurs on higher resistivity Si and SiC, although much less than … more
Date: August 2021
Creator: Femi Oyetoro, John Dideoluwa
Item Type: Refine your search to only Thesis or Dissertation
open access

A Study of Anomalous Conduction in n-Type Amorphous Silicon and Correlations in Conductivity and Noise in Gold Nanoparticle-Ligand Arrays

Description: This work explores two very different structural systems: n-type hydrogenated amorphous silicon (a-Si:H) and gold nanoparticles (AuNPs) suspended in a matrix of organic ligands. For a-Si:H, examination of the gas-phase concentration of dopant (1-6% PH3/SiH4) and argon diluent effects includes the temperature dependent conductivity, low-frequency electronic noise, and Raman spectroscopy to examine structure. It is found that a-Si:H samples grown with high dopant concentration or with argon dilut… more
Date: August 2021
Creator: Western, Brianna J
Item Type: Refine your search to only Thesis or Dissertation
open access

Deep Minima and Vortices for Positronium Formation in Positron-Hydrogen and Positron-Helium Collisions

Description: This dissertation work is a study of positronium formation for positron-hydrogen and positron-helium collisions in the Ore gap (the energy region between the threshold for ground-state positronium formation and the first excitation level of the target atom) using variational K-matrices. We have fitted the K-matrices using multichannel effective range theories and using polynomials. Using the variational K-matrices and their fits, we have located zeros in the positronium-formation scattering amp… more
Date: May 2021
Creator: Alrowaily, Albandari Wanes
Item Type: Refine your search to only Thesis or Dissertation

Investigation of Room Temperature Soft Ferromagnetism in Indium Phosphide Substrate Synthesized via Low Energy Nickel Ion Implantation

Description: In this work, we have utilized an ion beam process known as gettering to migrate implanted Ni ions much deeper into the bulk substrate than their initial projected end of the range. The projected mean depth is known as Rp. The gettering effect is the most crucial part of the fabrication and we have found that for an H fluence of 3x 1016 cm-2 there is a threshold fluence of approximately 7.5 x 1015 cm-2 that cannot be surpassed if the gettering process is to be completed along with the substrat… more
Date: May 2021
Creator: Jones, Daniel C.
Item Type: Refine your search to only Thesis or Dissertation

Modeling, Characterization, and Magnetic Behavior of Transition Metal Nanosystems Synthesized in Silicon Using Low Energy Ion Implantation

Description: Magnetic nano-clusters in silicon involving iron and cobalt were synthesized using low energy (50 keV) ion implantation technique and post-implantation thermal annealing. Before the irradiation, multiple ion-solid interaction simulations were carried out to estimate optimal ion energy and fluence for each experiment. For high-fluence low-energy irradiation of heavy ions in a relatively lighter substrate, modeling the ion irradiation process using dynamic code SDTrimSP showed better agreement w… more
Date: May 2021
Creator: Singh, Satyabrata
Item Type: Refine your search to only Thesis or Dissertation

Synthesis, Modification, and Analysis of Silicate Cosmic Dust Analogues Using Ion-Beam Techniques

Description: Silicates analogous to cosmic dust were synthesized, modified, and analyzed utilizing ion-beam techniques with Rutherford backscattering spectrometry (RBS) and x-ray diffraction (XRD). Silicate dust is a common constituent in interstellar space, with an estimated 50% of dust produced in the stellar winds of M class Asymptotic Giant Branch (AGB) stars. Silicate dust acts as a surface upon which other chemicals may form (water ice for example), increasing significance in the cosmochemistry field,… more
Date: August 2020
Creator: Young, Joshua Michael
Item Type: Refine your search to only Thesis or Dissertation

Fabrication of Nano-Channel Templates and a Study of the Electrical and Magnetic Properties of Nanowires Grown in Template Pores

Description: This thesis is a study of the structural, electrical and magnetic properties of indium antimonide (InSb) nanowires (NWs), that were synthesized by a template-assisted ordered growth technique via electrochemical deposition. InSb was chosen for this study because of its intrinsic properties that make it a material of choice for applications in high channel mobility, infrared (IR) sensing, thermoelectrics, and magnetoresistive sensing martials. This work has four main components: (i) Growth in co… more
Date: May 2020
Creator: Singh, Abhay Pratap
Item Type: Refine your search to only Thesis or Dissertation
open access

Investigation of Specialized Laser and Optical Techniques to Improve Precision Atomic Spectroscopy of Helium

Description: The aim of this thesis is to develop both Yb and Tm fiber laser sources with all fiber cavities. Both wavelength ranges provide useful laser sources for optical pumping of helium. The goal is to develop Tm laser sources operating at 2058 nm to optically quench 3He (2058.63 nm) and 4He (2058.69 nm) singlets (21S0). We also have developed Yb laser sources at 1083 nm to optical pump the triplet states of helium and laser cool an atomic beam of helium.
Date: May 2020
Creator: Currey, Ronnie
Item Type: Refine your search to only Thesis or Dissertation

Optical Property Study of 2D Graded Photonic Super-Crystals for Photon Management

Description: In this dissertation, we study the optical property of 2D graded photonic super-crystals (GPSCs) for photon management. We focused primarily on manipulation and control of light by using the newly discovered GPSCs which present great opportunity for electromagnetic wave control in photonic devices. The GPSC has been used to explore the superior capability of improving the light extraction efficiency of OLEDs. The enhancement of extraction efficiency has been explained in term of destructive int… more
Date: May 2020
Creator: Hassan, Safaa
Item Type: Refine your search to only Thesis or Dissertation

Manipulation of Light-Matter Interactions in Molybdenum Disulfide (MoS2) Monolayer through Dressed Phonons (DP) and Plasmons

Description: The performance of electrical and optical devices based on two-dimensional semiconductors (2D) such as molybdenum disulfide is critically influenced due to very poor light absorption in the atomically thin layers. In this study, the phonon mediated optical absorption and emission properties in single atomic layers of MoS2 have been investigated. The electronic transitions in MoS2 due to near-field optical interaction and the influence of interface phonons due to the dielectric substrate GaN on … more
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Date: December 2019
Creator: Poudel, Yuba R
Item Type: Refine your search to only Thesis or Dissertation

PAOFLOW-Aided Computational Materials Design

Description: Functional materials are essential to human welfare and to provide foundations for emerging industries. As an alternative route to experimental materials discovery, computational materials designs are playing an increasingly significant role in the whole discovery process. In this work, we use an in-house developed python utility: PAOFLOW, which generates finite basis Hamiltonians from the projection of first principles plane-wave pseudopotential wavefunctions on pseudo atomic orbitals(PAO) for… more
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Date: December 2019
Creator: Wang, Haihang
Item Type: Refine your search to only Thesis or Dissertation
open access

Renewal and Memory Approaches to Study Biological and Physiological Processes

Description: In nature we find many instances of complex behavior for example the dynamics of stock markets, power grids, internet networks, highway traffic, social networks, heartbeat dynamics, neural dynamics, dynamics of living organisms, etc. The study of these complex systems involves the use of tools of non-linear dynamics and non-equilibrium statistical physics. This dissertation is devoted to understanding two different sources of complex behavior – non-poissonian renewal events also called crucial… more
Date: May 2019
Creator: Tuladhar, Rohisha
Item Type: Refine your search to only Thesis or Dissertation

UV Magnetic Plasmons in Cobalt Nanoparticles

Description: The main goals of this research were to fabricate magnetic cobalt nanoparticles and study their structural, crystal structure, optical, and magnetic properties. Cobalt nanoparticles with average particle size 8.7 nm were fabricated by the method of high temperature reduction of cobalt salt utilizing trioctylphosphine as a surfactant, oleic acid as a stabilizer, and lithium triethylborohydride as a reducing reagent. Energy-dispersive X-ray spectroscopy (EDX) analysis confirmed the formation of c… more
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Date: May 2019
Creator: Bhatta, Hari Lal
Item Type: Refine your search to only Thesis or Dissertation
open access

Electrically Tunable Absorption and Perfect Absorption Using Aluminum-Doped Zinc Oxide and Graphene Sandwiched in Oxides

Description: Understanding the fundamental physics in light absorption and perfect light absorption is vital for device applications in detector, sensor, solar energy harvesting and imaging. In this research study, a large area fabrication of Al-doped ZnO/Al2O3/graphene/Al2O3/gold/silicon device was enabled by a spin-processable hydrophilic mono-layer graphene oxide. In contrast to the optical properties of noble metals, which cannot be tuned or changed, the permittivity of transparent metal oxides, such a… more
Date: December 2018
Creator: Adewole, Murthada Oladele
Item Type: Refine your search to only Thesis or Dissertation
open access

Exploring Growth Kinematics and Tuning Optical and Electronic Properties of Indium Antimonide Nanowires

Description: This dissertation work is a study of the growth kinematics, synthesis strategies and intrinsic properties of InSb nanowires (NWs). The highlights of this work include a study of the effect of the growth parameters on the composition and crystallinity of NWs. A change in the temperature ramp-up rate as the substrate was heated to reach the NW growth temperature resulted in NWs that were either crystalline or amorphous. The as-grown NWs were found to have very different optical and electrical pro… more
Date: December 2018
Creator: Algarni, Zaina Sluman
Item Type: Refine your search to only Thesis or Dissertation
open access

Fabrication and Study of the Optical Properties of 3D Photonic Crystals and 2D Graded Photonic Super-Crystals

Description: In this dissertation, I am presenting my research on the fabrication and simulation of the optical properties of 3D photonic crystals and 2D graded photonic super-crystals. The 3D photonic crystals were fabricated using holographic lithography with a single, custom-built reflective optical element (ROE) and single exposure from a visible light laser. Fully 3D photonic crystals with 4-fold, 5- fold, and 6-fold symmetries were fabricated using the flexible, 3D printed ROE. In addition, novel 2D g… more
Date: December 2018
Creator: Lowell, David
Item Type: Refine your search to only Thesis or Dissertation
open access

Physical Boundary as a Source of Anomalies in Transport Processes in Acoustics and Electrodynamics

Description: Various anomalous effects that emerge when the interfaces between media are involved in sound-matter or light-matter interactions are studied. The three specific systems examined are a fluid channel between elastic metal plates, a linear chain of metallic perforated cylindrical shells in air, and a metal-dielectric slab with the interfaces treated as finite regions of smoothly changing material properties. The scattering of acoustic signals on the first two is predicted to be accompanied by the… more
Date: December 2018
Creator: Bozhko, Andrii
Item Type: Refine your search to only Thesis or Dissertation
open access

Quantum Coherence Effects Coupled via Plasmons

Description: This thesis is an attempt at studying quantum coherence effects coupled via plasmons. After introducing the quantum coherence in atomic systems in Chapter 1, we utilize it in Chapter 2 to demonstrate a new technique of detection of motion of single atoms or irons inside an optical cavity. By taking into account the interaction of coherences with surface plasmonic waves excited in metal nanoparticles, we provide a theoretical model along with experimental data in Chapter 3 to describe the modifi… more
Date: December 2018
Creator: Moazzezi, Mojtaba
Item Type: Refine your search to only Thesis or Dissertation
open access

Application of Statistical Physics in Human Physiology: Heart-Brain Dynamics

Description: This dissertation is devoted to study of complex systems in human physiology particularly heartbeats and brain dynamics. We have studied the dynamics of heartbeats that has been a subject of investigation of two independent groups. The first group emphasized the multifractal nature of the heartbeat dynamics of healthy subjects, whereas the second group had established a close connection between healthy subjects and the occurrence of crucial events. We have analyzed the same set of data and esta… more
Date: August 2018
Creator: Bohara, Gyanendra
Item Type: Refine your search to only Thesis or Dissertation
open access

Emergence of Cooperation and Homeodynamics as a Result of Self Organized Temporal Criticality: From Biology to Physics

Description: This dissertation is an attempt at establishing a bridge between biology and physics leading naturally from the field of phase transitions in physics to the cooperative nature of living systems. We show that this aim can be realized by supplementing the current field of evolutionary game theory with a new form of self-organized temporal criticality. In the case of ordinary criticality, the units of a system choosing either cooperation or defection under the influence of the choices done by thei… more
Date: August 2018
Creator: Mahmoodi, Korosh
Item Type: Refine your search to only Thesis or Dissertation
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Nanophotonics of Plasmonic and Two-Dimensional Metamaterials

Description: Various nanostructured materials display unique and interesting optical properties. Specific nanoscale objects discussed in an experimental perspective in this dissertation include optical metamaterials, surface plasmon sensors, and two-dimensional materials. These nanoscale objects were fabricated, investigated optically, and their applications are assessed. First, one-dimensional magnetic gratings were studied, followed by their two-dimensional analog, the so-called "fishnet." Both were fabri… more
Date: August 2018
Creator: Roccapriore, Kevin M
Item Type: Refine your search to only Thesis or Dissertation
open access

Artificially Structured Boundary for Control and Confinement of Beams and Plasmas

Description: An artificially structured boundary (ASB) produces a short-range, static electromagnetic field that can reflect charged particles. In the work presented, an ASB is considered to consist of a spatially periodic arrangement of electrostatically plugged magnetic cusps. When used to create an enclosed volume, an ASB may confine a non-neutral plasma that is effectively free of applied electromagnetic fields, provided the spatial period of the ASB-applied field is much smaller than any one dimension … more
Date: May 2018
Creator: Hedlof, Ryan
Item Type: Refine your search to only Thesis or Dissertation
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