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Suppression Of Magnetostructural Transition On Gdsige Thin Film After Thermal Cyclings, A. L. Pires, J. H. Belo, I. T. Gomes, Ravi L. Hadimani, Deborah L. Schlagel, Thomas A. Lograsso, David C. Jiles, A. M. L. Lopes, J. P. Araújo, A. M. Pereira 2018 Universidade do Porto

Suppression Of Magnetostructural Transition On Gdsige Thin Film After Thermal Cyclings, A. L. Pires, J. H. Belo, I. T. Gomes, Ravi L. Hadimani, Deborah L. Schlagel, Thomas A. Lograsso, David C. Jiles, A. M. L. Lopes, J. P. Araújo, A. M. Pereira

Ravi L Hadimani

The influence of thermal cycling on the microstructure, magnetic phase transition and magnetic entropy change of a Gd5Si1.3Ge2.7 thin film up to 1000 cycles is investigated. The authors found that after 1000 cycles a strong reduction of the crystallographic phase responsible for the magnetostructural transition (Orthorhombic II phase) occurs. This is attributed to chemical disorder, caused by the large number of expansion/compression cycles that the Orthorhombic II phase undergoes across the magnetostructural transition. The suppression of the magnetostructural transition corresponds to a drastic decrease of the thin film magnetic entropy change. These results reveal the importance of ...


Structural, Transport, And Topological Properties Induced At Complex-Oxide Hetero-Interfaces, Justin K. Thompson 2018 University of Kentucky

Structural, Transport, And Topological Properties Induced At Complex-Oxide Hetero-Interfaces, Justin K. Thompson

Theses and Dissertations--Physics and Astronomy

Complex-oxides have seen an enormous amount of attention in the realm of Condensed Matter Physics and Materials Science/Engineering over the last several decades. Their ability to host a wide variety of novel physical properties has even caused them to be exploited commercially as dielectric, metallic and magnetic materials. Indeed, since the discovery of high temperature superconductivity in the “Cuprates” in the late 1980’s there has been an explosion of activity involving complex-oxides. Further, as the experimental techniques and equipment for fabricating thin films and heterostructures of these materials has improved over the last several decades, the search for ...


Generalized Ellipsometry On Complex Nanostructures And Low-Symmetry Materials, Alyssa Mock 2017 University of Nebraska-Lincoln

Generalized Ellipsometry On Complex Nanostructures And Low-Symmetry Materials, Alyssa Mock

Theses, Dissertations, and Student Research from Electrical & Computer Engineering

In this thesis, complex anisotropic materials are investigated and characterized by generalized ellipsometry. In recent years, anisotropic materials have gained considerable interest for novel applications in electronic and optoelectronic devices, mostly due to unique properties that originate from reduced crystal symmetry. Examples include white solid-state lighting devices which have become ubiquitous just recently, and the emergence of high-power, high-voltage electronic transistors and switches in all-electric vehicles. The incorporation of single crystalline material with low crystal symmetry into novel device structures requires reconsideration of existing optical characterization approaches. Here, the generalized ellipsometry concept is extended to include applications for materials with ...


Modeling And Simulation Of Iii-Nitride-Based Solar Cells Using Nextnano®, Malak Refaei 2017 University of Arkansas, Fayetteville

Modeling And Simulation Of Iii-Nitride-Based Solar Cells Using Nextnano®, Malak Refaei

Theses and Dissertations

Nextnano³ software is a well-known package for simulating semiconductor band-structures at the nanoscale and predicting the general electronic structure. In this work, it is further demonstrated as a viable tool for the simulation of III-nitride solar cells. In order to prove this feasibility, the generally accepted solar cell simulation package, PC1D, was chosen for comparison. To critique the results from both PC1D and Nextnano3, the fundamental drift-diffusion equations were used to calculate the performance of a simple p-n homojunction solar cell device analytically. Silicon was picked as the material for this comparison between the outputs of the two simulators as ...


Structural And Elastic Properties Of Degenerate Sno Monolayers At Finite Temperature, Afsana Sharmin 2017 University of Arkansas, Fayetteville

Structural And Elastic Properties Of Degenerate Sno Monolayers At Finite Temperature, Afsana Sharmin

Theses and Dissertations

Chalcogen-based layered superconductors with a litharge structure such as FeS and FeSe mono-layers undergo structural and superconducting phase transitions that are tunable by doping. Representing another material platform with a litharge structure but without valence d-electrons, SnO monolayers also display a structural ground state with a degenerate rectangular unit cell at zero temperature and a charge-tunable energy barrier that leads to a thermally-controllable structural phase change. Doped SnO monolayers with rectangular degenerate unit cells give rise to two-dimensional multiferroicity. Their two-dimensional elastic energy landscape adopts a basic analytic expression that is employed to discuss this structural transition. The results contained ...


Single-Step, Atmospheric Pressure Chemical Vapor Deposition Of Methylammonium Bismuth Iodide Thin Films, Xiao Chen 2017 Washington University in St. Louis

Single-Step, Atmospheric Pressure Chemical Vapor Deposition Of Methylammonium Bismuth Iodide Thin Films, Xiao Chen

Engineering and Applied Science Theses & Dissertations

Lead halide perovskites (CH3NH3PbI3 and its variants) are promising solar cell absorber materials. Though the reported power conversion efficiencies of lead halide perovskite solar cells (up to 21%) are competitive with commercial silicon solar cells, lead toxicity in these perovskites present a challenge to further scale-up and eventual commercialization. Recently, bismuth (Bi3+) based organic halide perovskite has drawn attention as a substitution for lead-free perovskites, since it is a non-toxic 6p-block element, isoelectronic with Pb2+. Methylammonium bismuth iodide ((CH3NH3)3Bi2I9) is reported for its non-toxic constituents ...


Atomistic Simulations Of Novel Nanoscale Semiconductor Devices: Resistance Switches And Two-Dimensional Transistors, Joseph P. Anderson, Mahbubul Islam, David Guzman, Alejandro Strachan 2017 Texas A & M University - College Station

Atomistic Simulations Of Novel Nanoscale Semiconductor Devices: Resistance Switches And Two-Dimensional Transistors, Joseph P. Anderson, Mahbubul Islam, David Guzman, Alejandro Strachan

The Summer Undergraduate Research Fellowship (SURF) Symposium

As transistors get smaller, we are achieving record levels of memory density. However, there is a limit to how small transistors can be made before their functionality breaks down. Thus alternatives to traditional transistor technology are needed. The two such technologies we examined are: resistance switching devices, which reversibly grow metal filaments through a dielectric, and two-dimensional transistors, which are capable of breaking through the scalability limit of traditional transistors. In order to design resistance switching devices which create filaments with some level of consistency, the dynamics of the filament formation need to be explored. Herein we model this process ...


Improving Methods Of Doping On Black Phosphorus, Yuqin Duan, Adam Charnas, Jingkai Qin, Peide Ye 2017 Electrocal and Computer Engineering

Improving Methods Of Doping On Black Phosphorus, Yuqin Duan, Adam Charnas, Jingkai Qin, Peide Ye

The Summer Undergraduate Research Fellowship (SURF) Symposium

Black phosphorus (BP) is a 2D semiconducting material with high carrier mobility. It is usually p-type due to oxidation states near its valence band. Although achieved through other growth methods, n-type doping has not yet been accomplished through the modern chemical vapor transport (CVT) growth method. To address this issue, small amounts of tellurium were added to Red Phosphorus to act as a dopant during the CVT growth process in addition to tin(Sn) and tin(IV) iodide, which facilitate growth. The chemicals are heated up to 600°C and precisely cooled in a 21-hour process, during which BP crystals ...


Fabrication And Characterization Of Hybrid Nanocomposites By Matrix Assisted Pulsed Laser Evaporation, Songlin Yang 2017 The University of Western Ontario

Fabrication And Characterization Of Hybrid Nanocomposites By Matrix Assisted Pulsed Laser Evaporation, Songlin Yang

Electronic Thesis and Dissertation Repository

Different methods have been applied to deposit hybrid nanocomposites which can be applied in various fields due to their light weight and multifunctional properties. Here, matrix assisted pulsed laser evaporation (MAPLE) equipment with 532 nm Nd:YAG laser is applied to fabricate three types of hybrid nanocomposites on different substrates.

Chemical synthesized FeCo nanoparticles were deposited on graphene sheets by MAPLE technique (laser fluence: 300 mJ/cm2). The effects of deposition time (t) on particle amount, shape and size have been investigated. Yttrium barium copper oxide (YBCO) materials are one type of high-temperature superconductive materials and could be applied ...


Electrical Characterization Of Irradiated Semiconducting Amorphous Hydrogenated Boron Carbide, George Glen Peterson 2017 University of Nebraska-Lincoln

Electrical Characterization Of Irradiated Semiconducting Amorphous Hydrogenated Boron Carbide, George Glen Peterson

Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

Semiconducting amorphous partially dehydrogenated boron carbide has been explored as a neutron voltaic for operation in radiation harsh environments, such as on deep space satellites/probes. A neutron voltaic device could also be used as a solid state neutron radiation detector to provide immediate alerts for radiation workers/students, as opposed to the passive dosimetry badges utilized today. Understanding how the irradiation environment effects the electrical properties of semiconducting amorphous partially dehydrogenated boron carbide is important to predicting the stability of these devices in operation. p-n heterojunction diodes were formed from the synthesis of semiconducting amorphous partially dehydrogenated boron carbide ...


Advanced Purification And Direct-Write 3d Nanoprinting Via Focused Electron Beam Induced Deposition, Brett Bloxton Lewis 2017 University of Tennessee, Knoxville

Advanced Purification And Direct-Write 3d Nanoprinting Via Focused Electron Beam Induced Deposition, Brett Bloxton Lewis

Doctoral Dissertations

This dissertation addresses three difficulties with focused electron beam induced deposition preventing broader application; purity, spatial control, and mechanical characterization.

Focused electron beam induced deposition (FEBID) has many advantages as a nanoscale fabrication tool. It is compatible for implementation into current lithographic techniques and has the potential to direct-write in a single step nanostructures of a high degree of complexity. FEBID is a very versatile tool capable of fabricating structures of many different compositions ranging from insulating oxides to conducting metals.

Due to the complexity of the technique and the difficulty in directly measuring many important variables, FEBID has remained ...


Dewetting Properties Of Ag-Ni Alloy Thin Films, Benjamin Scott Wolf 2017 University of Tennessee, Knoxville

Dewetting Properties Of Ag-Ni Alloy Thin Films, Benjamin Scott Wolf

Masters Theses

In this study, pulsed laser induced dewetting of both patterned and continuous Nickel (Ni)-Silver(Ag) thin films was investigated extensively as a novel way to perform directed assembly of nano-particles. First, continuous Ni-Ag thin film dewetting was studied on both bulk and TEM (Transmission electron microscope) membrane substrates at a variety of compositions to better understand the dewetting dynamics of the Ni-Ag system. Then, patterned Ni-Ag thin film dewetting was studied on both bulk and TEM membrane substrates to understand how different patterns and thin film configurations effect nano-particle distribution and formation. All of this work was done in ...


Electronic And Magnetic Properties Of Two-Dimensional Nanomaterials Beyond Graphene And Their Gas Sensing Applications: Silicene, Germanene, And Boron Carbide, Sadegh Mehdi Aghaei 2017 Florida International University

Electronic And Magnetic Properties Of Two-Dimensional Nanomaterials Beyond Graphene And Their Gas Sensing Applications: Silicene, Germanene, And Boron Carbide, Sadegh Mehdi Aghaei

FIU Electronic Theses and Dissertations

The popularity of graphene owing to its unique properties has triggered huge interest in other two-dimensional (2D) nanomaterials. Among them, silicene shows considerable promise for electronic devices due to the expected compatibility with silicon electronics. However, the high-end potential application of silicene in electronic devices is limited owing to the lack of an energy band gap. Hence, the principal objective of this research is to tune the electronic and magnetic properties of silicene related nanomaterials through first-principles models.

I first explored the impact of edge functionalization and doping on the stabilities, electronic, and magnetic properties of silicene nanoribbons (SiNRs) and ...


Are Solar Panels A Viable Power Source For A Green Energy Vehicle?, Mason C. Adams 2017 Linfield College

Are Solar Panels A Viable Power Source For A Green Energy Vehicle?, Mason C. Adams

Senior Theses

A solar cell powered go-kart has been built and tested. The result shows using solar energy alone cannot meet the requirement of running a regular passenger car. This is due to the limited surface area of the passenger car. This thesis also discusses the operating principles of solar panels, the physics of P type and N type semiconductors, and the formation of the PN junction, as well as the solar current. Modifications of an existing go-kart are described in detail in this thesis. Suggestions for making green vehicles are discussed as well.


Operating Temperature Of A Solar Thermal Stirling Engine, Spencer Beck 2017 Linfield College

Operating Temperature Of A Solar Thermal Stirling Engine, Spencer Beck

Senior Theses

This paper explores the relationship between the operating temperature and electricity production of a simple heat engine. A Stirling engine was designed and constructed which runs on solar thermal energy collected by a Fresnel lens. The surface area of the solar collector was varied. This manipulated the operating temperature of the Stirling engine in order to measure power output. The mechanical energy from the engine was converted to electricity using a DC motor running in reverse, acting like a generator, in conjunction with an Arduino for data collection. Although adjustments must be made in order to improve the efficiency of ...


Ferroelectric-Semiconductor Systems For New Generation Of Solar Cells, Rahmatollah Eskandari 2017 University of New Orleans, New Orleans

Ferroelectric-Semiconductor Systems For New Generation Of Solar Cells, Rahmatollah Eskandari

University of New Orleans Theses and Dissertations

This dissertation includes two parts. In the first part the study is focused on the fabrication of multifunctional thin films for photovoltaic applications. There is no doubt about the importance of transforming world reliance from traditional energy resources, mainly fossil fuel, into renewable energies. Photovoltaic section still owns very small portion of the production, despite its fast growth and vast research investments. New methods and concepts are proposed in order to improve the efficiency of traditional solar cells or introduce new platforms. Recently, ferroelectric photovoltaics have gained interest among researchers. First objective in application of ferroelectric material is to utilize ...


Understanding Photovoltaic Properties Of Pbs Quantum Dot Solids Via Solution Contacting, Vitalii Dereviankin, Erik Johansson 2017 Portland State University

Understanding Photovoltaic Properties Of Pbs Quantum Dot Solids Via Solution Contacting, Vitalii Dereviankin, Erik Johansson

Student Research Symposium

Photovoltaic (PV) devices based on PbS quantum dot (QD) solids demonstrate high photontoelectron conversion yields. However, record power conversion efficiency remain low, in part due to small photovoltages, which in turn are affected by both bulk and interfacial defects. Their relative impacts on limiting the photovoltaic performance of QD solids are not known. Interfacial defects can be formed when contacting a semiconductor and may dominate the semiconductor/metal or metaloxide junction properties. The objective of this study is to explore whether electrochemical contacting using liquid electrolytes provides means of contacting QD solids without introducing interfacial defects. We have initially focused ...


Investigating The Classical And Non-Classical Mechanical Properties Of Gan Nanowires, Mohammad Reza Zamani Kouhpanji 2017 University of New Mexico

Investigating The Classical And Non-Classical Mechanical Properties Of Gan Nanowires, Mohammad Reza Zamani Kouhpanji

Electrical and Computer Engineering ETDs

Study and prediction of classical and non-classical mechanical properties of GaN is crucial due to the potential application of GaN nanowires (NWs) in piezoelectric, probe-based nanometrology, and nanolithography areas. GaN is mainly grown on sapphire substrates whose lattice constant and thermal expansion coefficient are significantly different from GaN. These discrepancies cause mechanical defects and high residual stresses and strains in GaN, which reduce its quantum efficiency.

Specifically, for nanoscale applications, the mechanical properties of materials differ significantly compared to the bulk properties due to size-effects. Therefore, it is essential to investigate the mechanical properties of GaN NWs using the non-classical ...


A Novel Technique For Designing High Power Semiconductor Optical Amplifier (Soa)-Based Tunable Fiber Compound-Ring Lasers Using Low Power Optical Components, Muhammad A. Ummy, Simeon Bikorimana, Roger Dorsinville 2017 CUNY New York City College of Technology

A Novel Technique For Designing High Power Semiconductor Optical Amplifier (Soa)-Based Tunable Fiber Compound-Ring Lasers Using Low Power Optical Components, Muhammad A. Ummy, Simeon Bikorimana, Roger Dorsinville

Publications and Research

A simple, stable and inexpensive dual-output port widely tunable semiconductor optical amplifier (SOA)-based fiber compound-ring laser structure is demonstrated. This unique nested ring cavity enables high optical power to split into different branches where amplification and wavelength selection are achieved by using low-power SOAs and a tunable filter. Furthermore, two Sagnac loop mirrors, which are spliced at the two ends of the compound-ring cavity not only serve as variable reflectors but also channel the optical energy back to the same port without using any high optical power combiner. We propose and discuss how the demonstrated fiber compound-ring laser structure ...


Compositionally Graded Indium Gallium Nitride Solar Cells, Christopher Matthews 2017 University of Arkansas, Fayetteville

Compositionally Graded Indium Gallium Nitride Solar Cells, Christopher Matthews

Electrical Engineering Undergraduate Honors Theses

For the past several decades, methods to harvest solar energy have been investigated intensively. A majority of the work done in this field has been on solar cells made with silicon – the most mature semiconductor material. Recent developments in material fabrication and processing techniques have enabled other semiconductor materials to attract practical interest and research effort as well. Indium gallium nitride (InGaN) is one such material. The material properties of InGaN indicate that solar cells made with it have the potential to achieve much higher power density than a standard silicon solar cell. High power density InGaN solar cells could ...


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