Materials Science and Engineering Commons^™

Improving The Figure Of Merit In Iron-Vanadium-Aluminium Thermoelectric Alloy System Guided By Computational Modeling, Tao Fang

Dartmouth College Ph.D Dissertations

Thermoelectric materials can convert a thermal gradient to electricity. Currently, commercialized Bi₂Te₃ is brittle and expensive, which restricts the usage of this material. Compared to other thermoelectric materials, Fe₂VAl is cost-effective, stable and more robust mechanically. However, the figure of merit (zT) had been much lower than Bi₂Te₃. In this thesis, our main goal is to improve the figure of merit in Fe₂VAl system guided by computational modeling. We will start the discussion by presenting the Ge doped Fe₂VAl sample with record thermoelectric figure of merit value. …

Investigating The Roles Of Intrinsic Point Defects And Transition Metal Doping In Monolayer And Bulk Tis2, Patrick J. Keeney

UNF Graduate Theses and Dissertations

Within this thesis, the magnetic and electronic properties of various 1T-TiS₂ systems are thoroughly examined using density functional theory (DFT) and scanning tunneling microscopy (STM). Formation energies and electronic implications of intrinsic point defects in bulk TiS₂ and monolayer TiS₂ are analyzed by approximating a computational monolayer of TiS₂ as the surface layer of a bulk sample. This approximation is validated given that intralayer covalent bonding dominates interlayer van der Waals interactions. We conclude that the most energetically favorable intrinsic defects are Ti atoms settling above the outermost S plane and S vacancies. In addition, the …

Contributions To Journal Of Electrochemistry, The Flagship Journal Of Chinese Chemical Society Electrochemical Committee, Will Be Listed As A New Recommendation Policy For China Youth Awards Of Electrochemist, Editorial Office Of J.Electrochem.

Journal of Electrochemistry

No abstract provided.

Ge/Sige Quantum Wells: Material For The Post-Moore Era, Troy Alexander Hutchins-Delgado

Optical Science and Engineering ETDs

This dissertation demonstrates high-quality germanium quantum wells on a 200 mm silicon wafer platform, enabling novel device possibilities. Partnering with a commercial silicon-germanium epitaxy supplier, we obtained shallow, undoped germanium quantum wells with high-crystalline quality, confirmed through x-ray diffraction, secondary ion mass spectroscopy, high-resolution scanning transmission electron microscopy, and energy dispersive x-ray spectroscopy. Hall bar devices fabricated on single quantum wells revealed that surface preparation can tune transport properties while maintaining peak mobilities around 10⁵ cm²V⁻¹s⁻¹. Manganese-germanide spintronic contacts were integrated via solid-state reaction, with contact quality assessed through Schottky diodes, transfer length …

Laser Processing Of Multi-Phase Ceramics, Siddhartha Sarkar

All Dissertations

This research explores laser-based processing for multi-phase ceramics, offering a faster, more energy-efficient alternative to conventional ceramic fabrication. Four material systems are explored: silica-titania, alumina-iron, polymer-derived ceramic SiC-gadolinium zirconate, and polymer-derived ceramic SiC-yttrium silicate.

The silica-titania study presents a novel direct CO₂ laser writing approach to fabricating pure silica and silica-titania glasses with exceptional dimensional control and optical transparency, enabling fine spatial resolution, instantaneous consolidation, and eliminating post-heat treatment. Notably, the TiO₂ solubility in the silica network achieved is higher than previously reported, with structures remaining crack-free and transparent up to a specific TiO₂ percentage.

The alumina-iron …

Nanostructured Silicon Meta-Waveguides And Surfaces For Enhanced Light-Matter Interaction, Saddam Gafsi

All Dissertations

In this study, we tackle the challenge of light-matter interaction engineering and local field enhancement using various silicon photonic platforms based on three different approaches. (i) The first approach is based on boundary condition engineering where we present and show through simulation and experimental results, a silicon nanodisk “diabolo” configuration able to support significant local field enhancement levels in the range ~102 to 104 in the high index medium through proper structural modifications at the nanoscale. We show that the presented optical behavior is consistent with the anapole modes characterized by the observed near-field enhancement and coinciding with far-field suppression. …

Ellipticity-Controlled Exceptional Points From Nanoscale Metasurfaces, Benjamin Goldberg

McKelvey School of Engineering Graduate Student Theses & Dissertations

Precise control over light polarization is critical for advancing technologies in telecommunica- tions, quantum computing, and image sensing. However, existing methods for manipulating polarization around exceptional points in non-Hermitian systems, have exclusively focused on circular polarization and work with reflected light. To address this limitation, we de- velop a novel metasurface platform with high-Q resonators that enables tunable control of polarization exceptional points across arbitrary ellipticity for transmitted light. Our design uses orthogonally polarized guided mode resonators in a two-layer silicon metasurface, where careful tuning of the dipolar guided mode resonances (DGMRs) and layer spacing allows us to control the …

Understanding Defect Dynamics In Black Phosphorene Under Noble Gas Ion Irradiation., Saransh Gupta

Electronic Theses and Dissertations

Controlled introduction of defects in phosphorene using high-energy ion beams offers a promising route to design novel high-performance materials for energy technologies. However, this potential remains underexplored due to a lack of fundamental understanding of the atomic-scale mechanisms governing the production, accumulation, and temporal evolution of defects during ion irradiation. Here, we employ a combination of classical and ab initio molecular dynamics simulations to elucidate the effects of ion energy, angle of incidence, noble gas ion size/mass, and fluence on (a) defect generation (i.e., point defects, topological imperfections, voids), (b) atomic-scale mechanisms of defect formation and re-arrangement, and (c) defect …

Investigation Of Conductive Die-Top Thermal Capacitors During Short Circuit Operation Of Silicon Carbide Devices, Youssef Abotaleb

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Silicon carbide (SiC) power devices have garnered significant attention in recent years due to their superior thermal and electrical properties compared to traditional silicon devices. However, SiC power devices suffer from severe reliability issues arising from their mechanical properties. This is because the Young's modulus of SiC is about three times larger than that of silicon, which correspondingly raises the mechanical stresses acting on the bonding structure, often leading to device failure under power shock events.

Traditional packaging materials and designs tend to constrain SiC performance, as hot-spot temperature resulting from a power shock is one of the key factors …

Journal Of Electrochemistry, The Flagship Journal Of Chinese Chemical Society Electrochemical Committee, Made A Public Appearance At The 22nd National Electrochemical Congress, Editorial Office Of J.Electrochem.

Journal of Electrochemistry

No abstract provided.

The Award Ceremony Of The 2nd Xiamen University Short Video Abstract Contest For Science And Technology Journal Papers Came To A Successful Conclusion, Editorial Office Of J.Electrochem.

Journal of Electrochemistry

No abstract provided.

The Adviser Of Journal Of Electrochemistry Professor Christian Amatore Received The Chinese Government Friendship Award, Editorial Office Of J.Electrochem.

Journal of Electrochemistry

No abstract provided.

Goodbye With Tears! Deep Condolences To Academician Zhao-Wu Tian!, Editorial Office Of J.Electrochem.

Journal of Electrochemistry

No abstract provided.

Journal Of Electrochemistry Is Selected To Entering Ici Journals Master List, Editorial Office Of J.Electrochem.

Journal of Electrochemistry

No abstract provided.

Zhong-Qun Tian, Academician And Honorary Member Of Electrochemistry Committee Chinese Chemical Society, Achieved "Raman Lifetime Award", Editorial Office Of J.Electrochem.

Journal of Electrochemistry

No abstract provided.

Chinese Chemical Society: First Young Scholars' Symposium On Electrosynthesis Held Successfully, Chinese Society Of Electrochemistry (Cse)

Journal of Electrochemistry

No abstract provided.

2024 Tianmulake Advanced Anode Materials Innovation Forum And Sixth National Conference Of Advanced Battery Failure Analysis And Testing Technology Concluded Successfully, Editorial Office Of J.Electrochem.

Journal of Electrochemistry

No abstract provided.

2024 "Electrochemical Research Paradigms" Summer School Successfully Held, Editorial Office Of J.Electrochem.

Journal of Electrochemistry

No abstract provided.

Upcoming Meeting-The 1St Young Investigator Symposium On Electrosynthesis, Chinese Chemical Society, Chinese Society Of Electrochemistry (Cse)

Journal of Electrochemistry

No abstract provided.

Rate Law For Photoelectrochemical Water Splitting Over Cuo, Bo-Yuan Gao, Wen-Hua Leng

Journal of Electrochemistry

Photocatalytic splitting of water over p-type semiconductors is a promising strategy for production of hydrogen. However, the determination of rate law is rarely reported. To this purpose, copper oxide (CuO) is selected as a model photocathode in this study, and the photogenerated surface charge density, interfacial charge transfer rate constant and their relation to the water reduction rate (in terms of photocurrent) were investigated by a combination of (photo)electrochemical techniques. The results showed that the charge transfer rate constant is exponential-dependent on the surface charge density, and that the photocurrent equals to the product of the charge transfer rate constant …

Winning Results Of The 2Nd Xiamen University Short Video Abstract Contest For Science And Technology Papers, Editorial Office Of J.Electrochem.

Journal of Electrochemistry

No abstract provided.

Winning Works From Journal Of Electrochemistry: The 2Nd Xiamen University Short Video Abstract Contest For Science And Technology Journal Papers, Editorial Office Of J.Electrochem.

Journal of Electrochemistry

No abstract provided.

2024 World Fuel Cell Conference Held In Ningbo, Zhejiang, Editorial Office Of J.Electrochem.

Journal of Electrochemistry

No abstract provided.

Development And Structural Origin Of Stretchable Semiconducting Polymers And Composites, Yunfei Wang

Dissertations

Stretchable semiconductors are pivotal in advancing wearable and implantable electronics, with those boasting both high stretchability and self-healing capabilities being especially significant for a myriad of wearable applications. In this dissertation, we developed an extremely soft, highly stretchable, and self-healing elastomer based on H-bonding crosslinked amide-functionalized polyisobutylene (PIB-amide). When blended with a high-performance conjugated diketopyrrolopyrrole (DPP-T) polymer, the composite exhibits unprecedented stretchability, exceptionally low elastic modulus, and an innate ability to self-heal at room temperature.

The morphology of conjugated polymer/elastomer semiconducting composites have significant impacts on electrical and mechanical properties Further investigations focused on manipulating the phase separation size in …

Synthesis Of Selenium Nanostructures: Rods, Wires, And Fibers By Pulsed Laser Ablation In Liquids, Atikur Rahman

Theses and Dissertations

Selenium is a semiconductor that has a bulk energy bandgap of 1.74 eV, is mainly used in sensors, rectifiers, and advanced photovoltaic solar cells. Selenium is very important for the energy applications and was declared as Energy Critical Element (ECE) by the American Physical Society (APS) and the Materials Research Society (MRS). The goal of this dissertation was to control the growth of selenium when being irradiated by a pulsed laser within a liquid environment. The method called “Pulsed Laser Ablation in Liquids” is a green synthesis technique that allows for ligand-free nanoparticles to be created. Laser repetition rates were …

Molecular Beam Epitaxy Of Gesn On Iii-V Substrates For Photonic Applications, Calbi Gunder

Graduate Theses and Dissertations

This dissertation explores the advancement of germanium-tin (GeSn) as a tuneable narrow bandgap material, crucial for the development of high-efficiency photodetectors and laser devices in near- and mid-infrared technologies. We investigate the synthesis challenges, particularly the lattice mismatch between GeSn alloys and substrates, which significantly affects their crystalline and optical qualities. Through molecular beam epitaxy, we examine the growth of Ge and GeSn on GaAs (001) substrates, employing Ge/GaAs and Ge/AlAs buffer layers to investigate these challenges. Our findings, characterized by X-ray diffraction, atomic force microscopy, reflection high-energy electron diffraction, and photoluminescence, demonstrate the production of high-quality Ge layers, achieving …

Fabrication And Characterization Of A Monolithic Photonic Integrated Circuit With High-Aspect Ratio Photonic Device Structures, Sami A. Nazib

Optical Science and Engineering ETDs

The focus of this work was to create a process to fabricate an InP-based Photonic Integrated Circuit (PIC). The design of the PIC required the photonic components of this device to be created by deep etching of an epitaxially-grown multilayer structure. Therefore, a novel dry etching process was developed to produce very high aspect- ratio (HAR) features. This process not only involved the development of dry etch chemistry but also the engineering of a metal mask structure. The next step of the challenge was to use a polymer-based material that would have two functions: cladding for the etched photonic components …

Secondary Electron Yield Of Metals, Alloys, And Metal Oxides From First Principles Based Monte Carlo Simulations, Raul E. Gutierrez

Electrical and Computer Engineering ETDs

Density Functional Theory (DFT) based Monte Carlo (MC) simulations of the Sec-
ondary Electron Yield (SEY) of metals, alloys, and metal oxides are performed to
find material properties that could help reduce or influence the multipactor effect.
In order to accurately model the SEY of materials, knowledge of the frequency- and
momentum-dependent Energy Loss Function (qDepELF) is required. The qDepELF
is difficult to determine from experiment; however, it can be calculated from first
principles. The DFT-MC approach for simulating the secondary electron genera-
tion, propagation, and emission processes is described herein. Material properties,
which are calculated using DFT and used …

First Announcement Of 76th Annual Meeting Of The International Society Of Electrochemistry, International Society Of Electrochemistry (Ise)

Journal of Electrochemistry

No abstract provided.

Optical Responses Of Hybrid Electromagnetic Nanostructures, Dominic Bosomtwi

Optical Science and Engineering ETDs

Fano resonances result from the interference between a broad background and a narrow state, producing asymmetric scattering profiles. Under specific conditions, destructive interference collapses the Fano resonance width, leading to bound states in the continuum (BICs) that localize light within a nanostructure while maintaining an infinitely high-quality factor (Q-factor).

This dissertation explores the design of nanostructures with multilayer hybrid plasmonic-dielectric metasurfaces using full-wave numerical simulations, facilitating multiple Fano resonances and BICs. By adjusting nanoantenna dimensions, multiple modes are excited at plasmonic-dielectric interfaces, leading to strong interactions and hybridization of energy levels, manifested as Rabi splitting.

These findings enable advancements in …