Nanoscience and Nanotechnology Commons^™

Doping Plasmon-Enhanced Tio2 With Zirconia To Improve Solar Energy Harvesting In Dye-Sensitized Solar Cells, Anastasia Pasche

Electronic Thesis and Dissertation Repository

Solar energy is a promising solution towards meeting the world’s ever-growing energy demand. Dye-sensitized solar cells (DSSCs) are hybrid organic-inorganic solar cells with potential for commercial application, but are plagued by inefficiency due to their poor sunlight absorption. Silver nanoparticles have been shown to enhance the absorptive properties of DSSCs, but their plasmonic resonance causes local hot spots, resulting in cell deterioration. This thesis studies the mitigation of thermal energy loss of plasmon-enhanced DSSCs by the co-incorporation of zirconia, a well-known thermostabilizer, into the cell’s photoactive material. TiO2 was also synthesized using green bio-sourced solvents in supercritical CO2 to compare …

Solution And Surface Properties Of Architecturally- And Compositionally-Complex Block Copolymers And Their Binary Mixtures, Jesse Lawrence Davis

Doctoral Dissertations

The spontaneous generation of complex structures from polymeric building blocks provides a simple yet effective route to create useful soft matter structures having potential application in a variety of nanotechnologies. The topology, chemical structure, block composition, and sequence of the constituent building blocks of polymers are tunable through synthetic chemistry. This tunability offers attractive opportunities to generate complex, yet well-defined structures with control over the geometry, packing symmetry, and microdomain structure. This thesis work involves the study of the self-assembly behaviors of architecturally complex amphiphilic block copolymers (ABCs). ABCs are composed of two or more chemically distinct blocks that are …

Failure Simulations At Multiple Length Scales In High Temperature Structural Alloys, Chao Pu

Doctoral Dissertations

A number of computational methodologies have been developed to investigate the deformation and damage mechanism of various structural materials at different length scale and under extreme loading conditions, and also to provide insights in the development of high-performance materials.

In microscopic material behavior and failure modes, polycrystalline metals of interest include heterogeneous deformation field due to crystalline anisotropy, inter/intra grain or phase and grain boundary interactions. Crystal plasticity model is utilized to simulate microstructure based polycrystalline materials, and micro-deformation information, such as lattice strain evolution, can be captured based on crystal plasticity finite element modeling (CPFEM) in ABAQUS. The comparison …

Ion Irradiation-Induced Microstructural Change In Sic, Chien-Hung Chen

Doctoral Dissertations

The high temperature radiation resistance of nuclear materials has become a key issue in developing future nuclear reactors. Because of its mechanical stability under high-energy neutron irradiation and high temperature, silicon carbide (SiC) has great potential as a structural material in advanced nuclear energy systems.

A newly developed nano-engineered (NE) 3C SiC with a nano-layered stacking fault (SFs) structure has been recently considered as a prospective choice due to enhanced point defect annihilation between layer-type structures, leading to outstanding radiation durability.

The objective of this project was to advance the understanding of gas bubble formation mechanisms under irradiation conditions in …

Incorporation Of High-K Hfo2 Thin Films In A-Igzo Thin Film Transistor Devices, Aaron Hamilton Bales

Masters Theses

In this study, HfO2 [hafnium oxide] thin films are investigated extensively as part of indium gallium zinc oxide (IGZO) thin film transistor (TFT) devices. They are incorporated into the TFTs, both as a gate insulator and a passivation layer. First, the HfO2 [hafnium oxide] films themselves are investigated through an annealing study and through I-V and C-V measurements. Then, HfO2 [hafnium oxide] is suggested as a replacement for commonly used SiO2 [silicon dioxide] gate insulator, as it has a dielectric constant that is 4 – 6 times higher. This higher dielectric constant allows for comparable TFT performance at a lower …

In Vacuo Fabrication And Electronic Structure Characterization Of Atomic Layer Deposition Thin Films, Michael Schaefer

USF Tampa Graduate Theses and Dissertations

Improvement of novel electronic devices is possible by tailor-designing the electronic structure at device interfaces. Common problems observed at interfaces are related to unwanted band alignment caused by the chemical diversity of interface partners, influencing device performance negatively. One way to address this problem is by introducing ultra-thin interfacial dipole layers, steering the band alignment in a desired direction. The requirements are strict in terms of thickness, conformity and low density of defects, making sophisticated deposition techniques necessary. Atomic layer deposition (ALD) with its Ångstrom-precise thickness control can fulfill those requirements.

The work presented here encompasses the implementation of an …

Application Of 3d Printing Technology In Porous Anode Fabrication For Enhanced Power Output Of Microbial Fuel Cells, Bin Bian

Electronic Thesis and Dissertation Repository

Microbial fuel cells (MFCs) are widely researched for application in wastewater treatment. However, the current anodes used in MFCs often suffer from high fabrication cost and uncontrollable pore sizes. In this thesis, three-dimensional printing technique was utilized to fabricate anodes with different micro pore sizes for MFCs. Copper coating and carbonization were applied to the printed polymer anodes to increase the conductivity and specific surface area. Voltages of MFCs with various anodes were measured as well as other electrochemical tests such as linear sweep voltammetry and electrochemical impedance spectroscopy. 3D copper porous anode produced higher maximum voltages and power densities …

Tunable Photonic Multilayers From Stimulus-Responsive, Photo-Crosslinkable Polymers, Maria C. Chiappelli

Doctoral Dissertations

This dissertation describes the synthesis of photo-crosslinkable copolymers and their utilization for the fabrication and testing of tunable and responsive one-dimensional (1D) photonic multilayers. Photonic multilayers exhibit structural color due to the interference of incident light at layer interfaces, providing a convenient route towards optically responsive materials that do not rely on potentially light- or oxygen-sensitive chromophore-containing pigments and dyes. A fabrication technique based on sequential spin-coating and crosslinking of photo-crosslinkable polymers is used to assemble tunable and responsive photonic multilayers. Chapter One introduces the fundamental underlying principles of 1D photonic structures and explores their importance in a variety of …

Thermal Kinetics Of Ion Irradiation Hardening In Selected Alloys For The Canadian Gen. Iv Nuclear Reactor Concept, Heygaan Rajakumar

Electronic Thesis and Dissertation Repository

Canada is designing supercritical water fission reactors (SCWR) to increase the thermal efficiency of nuclear power generation from ~34% to ~48%. The temperature and pressure of a supercritical water reactor core is very high compared to a CANDU reactor. This thesis examines irradiation hardening and thermal recovery of two candidate alloys, AISI 310 and Inconel 800H, for the Canadian SCWR.

Samples of both alloys are mechanically ground and polished, then irradiated using 8.0 MeV Fe ions. The use of ion irradiation safely and quickly simulates neutron damage. The change in the hardness of the samples is then studied during a …

Nanoscaled Cellulose And Its Carbonaceous Material: Application And Local Structure Investigation, Yujie Meng

Doctoral Dissertations

In this dissertation, cellulose nanocrystals three-dimensional morphology, size distribution, and the crystal structure were statistically and quantitatively investigated. Lognormal distribution was identified as the most likely for cellulose nanocrystals’ size distribution. Height and width dimensions were shown to decrease toward the ends from the midpoint of individual CNCs, implying a spindle-like shape. XRD analysis of crystallite size accompanied with TEM and AFM measurements revealed that the cross-sectional dimensions of individual switchgrass CNC were either rectangular or elliptical shape, with an approximately 3~5 nm [nanometer] lateral element length range. A sponge-like carbon aerogel from microfibril cellulose with high porosity, ultra-low density, …

Minimizing Sheet Resistance Of Organic Photovoltaic Cell Top Contact Electrode Layer: Silver Nanowire Concentration Vs. Conductive Polymer Doping Concentration, Caitlyn Cook

Materials Engineering

The top contact electrode layers of nine organic photovoltaic cells were prepared with two varying factors: three Silver nanowire (AgNW) densities deposited on a conductive polymer doped with three concentrations. Silver’s low sheet resistance of 20-Ω/sq is hypothesized to lower the sheet resistance of the anode layer and thus enhance the overall efficiency of the cell. Four-point probe measurements indicated that increasing AgNW density in the top contact electrode layer of an organic photovoltaic cell significantly reduces sheet resistance from 52.2k-Ω/sq to 18.0 Ω/sq. Although an increase in doping concentration of the conductive polymer reduced sheet resistance in low AgNW …

Large-Scale Graphene Film Deposition For Monolithic Device Fabrication, Khaled Al-Shurman

Graduate Theses and Dissertations

Since 1958, the concept of integrated circuit (IC) has achieved great technological developments and helped in shrinking electronic devices. Nowadays, an IC consists of more than a million of compacted transistors.

The majority of current ICs use silicon as a semiconductor material. According to Moore's law, the number of transistors built-in on a microchip can be double every two years. However, silicon device manufacturing reaches its physical limits. To explain, there is a new trend to shrinking circuitry to seven nanometers where a lot of unknown quantum effects such as tunneling effect can not be controlled. Hence, there is an …

Resonant Spectra Of Metal Nanotoroids Of Various Sizes, Huong Quynh Tran

Electrical Engineering Undergraduate Honors Theses

Nowadays, the manipulation of light by using metallic nanostructures has wide applications in photonics, optoelectronics and energy conversion. Along with other universities all over the world, the University of Arkansas is researching on nano-antennas’ design, fabrication and applications. Current research in Dr. El-Shenawee’s Terahertz Imaging and Spectroscopy Computational Electromagnetics Group, has computationally investigated the behaviors of plasmonic nanostructures by using the commercial finite element electromagnetic solver Ansys® HFSS. This work reproduced the previous work of spectral absorption enhancement of infinite and finite arrays of silver and gold nanotoroids with sizes of the inner radii: 13nm – 21nm, while outer radius …

Investigations Of Carbon Nanotube Catalyst Morphology And Behavior With Transmission Electron Microscopy, Sammy M. Saber

Open Access Dissertations

Carbon nanotubes (CNTs) are materials with significant potential applications due to their desirable mechanical and electronic properties, which can both vary based on their structure. Electronic applications for CNTs are still few and not widely available, mainly due to the difficulty in the control of fabrication. Carbon nanotubes are grown in batches, but despite many years of research from their first discovery in 1991, there are still many unanswered questions regarding how to control the structure of CNTs. This work attempts to bridge some of the gap between question and answer by focusing on the catalyst particle used in common …

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 …

Functional Nanostructures From Nanoparticle Building Blocks, Jimmy Lawrence

Doctoral Dissertations

Advances in the synthetic strategies of engineered nanomaterials, multifunctional molecules and polymers have opened pathways for the development of functional nanomaterials having unique optoelectronic, mechanical, and biological properties. By designing the chemistry of surface ligands, the organic interface of nanoparticles, one can further the versatility and utilization of engineered nanomaterials, opening pathways for breakthroughs in sensing, catalysis, and delivery using nanomaterials. This thesis describes the synthesis and characterization of small molecule and polymer ligand functionalized inorganic nanoparticles (e.g., metal, semiconducting). Embedding specific chemical functionality into the ligand periphery of nanoparticles enables the resulting functional nanoparticles to react selectively …

Structures, Properties And Functionalities Of Magnetic Domain Walls In Thin Films, Nanowires And Atomic Chains: Micromagnetic And Ab Initio Studies, Liwei D. Geng

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

Structures, properties and functionalities of magnetic domain walls in thin film, nanowires and atomic chains are studied by micromagnetic simulations and ab initio calculations in this dissertation. For magnetic domain walls in thin films, we computationally investigated the dynamics of one-dimensional domain wall line in ultrathin ferromagnetic film, and the exponent α = 1.24 ± 0.05 is obtained in the creep regime near depinning force, indicating the washboard potential model is supported by our simulations. Furthermore, the roughness, creep, depinning and flow of domain wall line with commonly existed substructures driven by magnetic field are also studied. Our simulation results …

On Thermal Aging Prevention In Polymer Core Composite Conductor Rods, Joe D. Hoffman

Electronic Theses and Dissertations

Increased energy usage in the United States and worldwide is driving the demand for new technologies to transmit electrical power in greater quantities and with reliable, safe, and more efficient methods. One recent innovation is to replace the standard Aluminum Conductor Steel Reinforced electrical transmission conductor with a new conductor design that utilizes a fiber reinforced polymer core rod to support a fully annealed aluminum conductor. This new technology that includes a hybrid carbon fiber/epoxy and glass fiber/epoxy support core allows for better efficiency and for greater current to be transmitted in the same size and weight line. These new …

Systems Approach To Producing Electrospun Polyvinylidene Difluoride Fiber Webs With Controlled Fiber Structure And Functionality, Brian D. Bell

USF Tampa Graduate Theses and Dissertations

Polyvinylidene difluoride (PVDF) is a functional polymeric material that can be used for a wide variety of applications. There are many new future applications that were recently suggested for electrospun PVDF fibers. Electrospinning is a process capable of producing nano to micro sized PVDF fibers in a web. It is important to control the structure of the web during electrospinning because by controlling the structure of the web it is possible for the PVDF fiber web to have increased performance in comparison to other common forms of PVDF.

While past scientific literature focused on applications of PVDF fibers, little was …

Biomimetic Oral Mucin From Polymer Micelle Networks, Sundar Prasanth Authimoolam

Theses and Dissertations--Chemical and Materials Engineering

Mucin networks are formed by the complexation of bottlebrush-like mucin glycoprotein with other small molecule glycoproteins. These glycoproteins create nanoscale strands that then arrange into a nanoporous mesh. These networks play an important role in ensuring surface hydration, lubricity and barrier protection. In order to understand the functional behavior in mucin networks, it is important to decouple their chemical and physical effects responsible for generating the fundamental property-function relationship. To achieve this goal, we propose to develop a synthetic biomimetic mucin using a layer-by-layer (LBL) deposition approach. In this work, a hierarchical 3-dimensional structures resembling natural mucin networks was generated …

Designed Synthesis Of Nanoporous Organic Polymers For Selective Gas Uptake And Catalytic Applications, Pezhman Arab

Theses and Dissertations

Design and synthesis of porous organic polymers have attracted considerable attentions during the past decade due to their wide range of applications in gas storage, gas separation, energy conversion, and catalysis. Porous organic polymers can be pre-synthetically and post-synthetically functionalized with a wide variety of functionalities for desirable applications. Along these pursuits, we introduced new synthetic strategies for preparation of porous organic polymers for selective CO₂ capture.

Porous azo-linked polymers (ALPs) were synthesized by an oxidative reaction of amine-based monomers using copper(I) as a catalyst which leads to azo-linkage formation. ALPs exhibit high surface areas of up to 1200 …

Novel Engineered Nanomaterials For Water Remediation And Gas Adsorption: Graphene Oxide And Carbon Nanotubes Decorated With Metal-Organic Frameworks And Magnetic Nanoparticles, Vahid Jabbari

Open Access Theses & Dissertations

In the current study, a series of novel magnetic and non-magnetic hybrid nanocomposites based on metal-organic frameworks (MOFs) of M3(BTC)2 (M: Ni, Cu, Zn, and Cd), graphene oxide (GrO), and carbon nanotubes (CNTs), and Fe3O4 magnetic nanoparticles (MNPs) were developed via a green, simple and versatile solvothermal method at which GrO and CNT were used as platform to grow the MOFs and Fe3O4 MNPs over them. The as-synthesized nanocomposites were characterized by XRD, SEM, TEM, XPS, IR, Raman, TGA, and N2 adsorption/desorption isotherms. Morphological analysis confirmed successful growth of nano-size Fe3O4 MNPs and M3(BTC)2 MOFs over GrO and CNT platforms. …

Initiated Chemical Vapor Deposition (Icvd) Polymer Thin Films : Structure-Property Effects On Thermal Degradation And Adhesion, Vijay Jain Bharamaiah Jeevendrakumar

Legacy Theses & Dissertations (2009 - 2024)

Opportunities and challenges for chemical vapor deposition (CVD) of polymer thin films stems from their applications in electronics, sensors, and adhesives with demands for control over film composition, conformity and stability. Initiated chemical vapor deposition (iCVD) is a subset of the CVD technique that conjoins bulk free-radical polymerization chemistry with gas-phase processing. The novelty of iCVD technique stems from the use of an initiator that can be activated at low energies (150 – 300 °C) to react with surface adsorbed monomer to form a polymer film. This reduces risk for potential unwarranted side-reactions.

Implementation Of Strategies To Improve The Reliability Of Iii-Nitride Photodetectors Towards The Realization Of Visible And Solar-Blind Imaging Arrays, John Bulmer

Legacy Theses & Dissertations (2009 - 2024)

Ultraviolet (UV) radiation detectors are being heavily researched for applications in non-line-of-sight (NLOS) communication systems, flame monitoring, biological detection, and astronomical studies. These applications are currently being met by the use of Si-based photomultiplier tubes (PMTs), which are bulky, fragile, expensive and require the use of external filters to achieve true visible-blind and solar-blind operation.

Carbon 1d/2d Nanoelectronics : Integration And Device Applications, Zhaoying Hu

Legacy Theses & Dissertations (2009 - 2024)

Graphene is a one-atom thick planar monolayer of sp2-bonded carbon atoms organized in a hexagonal crystal lattice. A single walled carbon nanotube (CNT) can be thought of as a graphene sheet rolled up into a seamless hollow cylinder with extremely high length-to-diameter ratio. Their ultra-thin body, large surface area, and exceptional electronic, optical and mechanical properties make these low-dimensional carbon materials ideal candidates for electronic applications. However, adopting low-dimensional carbon materials into semiconductor industry faces significant material and integration challenges. There is an urgent need for research at fundamental and applicative levels to find a roadmap for carbon nanomaterial to …

Determination Of Current Density Distribution In An Electron Beam, Yudhishthir Prasad Kandel

Legacy Theses & Dissertations (2009 - 2024)

Electron beams are useful in many applications because they can be focused down to a spot far exceeding the physical limit of focusing visible light or x-rays. Additionally, electron beams are useful in transferring concentrated amounts of energy to a very small well defined region of a target for a fixed duration. This has led to the development of both scanning electron microscopes (SEMs) and electron beam lithography. The goal of this work was to develop a general method that accurately and easily yields the best estimate of the electron current density distribution of a focused electron beam, known as …

Design And Development Of Stress Engineering Techniques For Iii-Nitride Epitaxy On Si, Jeff Leathersich

Legacy Theses & Dissertations (2009 - 2024)

III-Nitrides have been a heavily researched material system for decades. Their material properties are favorable for a number of applications, most commonly in the optoelectronic and power device industry. Currently a majority of commercialized devices are fabricated on sapphire and SiC substrates but these are expensive and limit the widespread commercialization of the technology. There is substantial ongoing research geared toward the development of GaN on Si substrates because of the significant cost saving that would be realized through the inexpensive, large wafer and maturity of Si fabrication. Significant challenges with the deposition of GaN on Si have, thus far, …

The Impact Of Seed Layer Structure On The Recrystallization Of Ecd Cu And Its Alloys, Brendan B. O'Brien

Legacy Theses & Dissertations (2009 - 2024)

Despite the significant improvements originally offered by the use of Cu over Al as the interconnect material for semiconductor devices, the continued down-scaling of interconnects has presented significant challenges for semiconductor engineers. As the metal line widths shrink, both the conductivity and reliability of lines decrease due to a stubbornly fine-grained microstructure in narrow lines.

High Frequency Signal Transmission In Through Silicon Via Based 3d Integrated Circuit, Min Xu

Legacy Theses & Dissertations (2009 - 2024)

Through silicon vias (TSVs) enable 3-dimensional (3D) integrated circuits (ICs), which have the potential to reduce the power consumption, interconnect length and overall communication latency in modern nanoelectronics systems. High-speed signal transmission channels through stacked silicon substrates are critical for 3D heterogeneous integration. This work presents systematic analyses of fabricated 3D IC test structures. This includes test structure design, fabrication, experimental characterization, equivalent circuit modeling and full wave simulations for high-speed signal transmission of the TSV based 3D IC channels.