Electrical Properties Of Annealed And Coated Boron Nitride Under Electron Beam Irradiation,
2015
Utah State Univesity
Electrical Properties Of Annealed And Coated Boron Nitride Under Electron Beam Irradiation, Kevin Guerch, Thierry Paulmier, Jr Dennison, Justin Dekany, Sophia Guillemet-Fritsch, Pascal Lenormand
Presentations
Technical dielectric materials and ceramics are used in many different high technology industrial areas and especially for spacecraft applications. On satellites, these materials are subjected to extreme conditions due to the space plasma environment. To survive, these ceramic insulators must have exceptional electrical and thermal properties. Boron Nitride (BN) and Aluminum Oxide (Al2O3) are used in particular because they combine good electrical insulation and high thermal conductivity. However, BN and Al2O3 used in spacecraft interiors are exposed to critical radiation demands, where these insulators are irradiated by electrons with high energies and flux. Charged particles are trapped in the ceramics, …
Critical Point Pairs For Smectic-A* - Smectic-C* Phase Transitions.,
2015
California Polytechnic State University - San Luis Obispo
Critical Point Pairs For Smectic-A* - Smectic-C* Phase Transitions., Ted Cassirer
Physics
Liquid crystals is a class of materials possessing properties from both solids and fluids. Similar to solids the molecules arrange themselves in some sort of order. In the liquid crystal state there are multiple phases, smectic being one of them. In a smectic liquid crystal the molecules are aranged (along $z$) in layers. Of the smectic liquid crystals there exists different phases. In the smectic-A (Sm-A) phase the avarage tilt is $0$ relative to $z$ and in the Smectic-C (Sm-A) phase the avarage tilt is non-zero relative to $z$. Normally the liquid crystal will transition between the two phases by …
Titanium Trisulfide Monolayer: Theoretical Prediction Of A New Direct-Gap Semiconductor With High And Anisotropic Carrier Mobility,
2015
University of Nebraska-Lincoln
Titanium Trisulfide Monolayer: Theoretical Prediction Of A New Direct-Gap Semiconductor With High And Anisotropic Carrier Mobility, Jun Dai, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
A new two-dimensional (2D) layered material, namely, titanium trisulfide (TiS3) monolayer, is predicted to possess novel electronic properties. Ab initio calculations show that the perfect TiS3 monolayer is a direct-gap semiconductor with a bandgap of 1.02 eV, close to that of bulk silicon, and with high carrier mobility. More remarkably, the in-plane electron mobility of the 2D TiS3 is highly anisotropic, amounting to about 10,000 cm2 V−1 s−1 in the b direction, which is higher than that of the MoS2 monolayer, whereas the hole mobility is about two orders of magnitude lower. …
Capacitance Measurements Of Defects In Solar Cells: Checking The Model Assumptions,
2015
Linfield College
Capacitance Measurements Of Defects In Solar Cells: Checking The Model Assumptions, Justin R. Davis
Senior Theses
Capacitance measurements of solar cells are sensitive to minute changes in charge in the material. For that reason, capacitance is used in several methods to electrically characterize defects in the solar cell. Standard interpretations of capacitance rely on many assumptions, which, if wrong can skew the results. We explore possible alternative explanations for capacitance transitions, such as a non-ideal back contact and series resistance. Using Drive Level Capacitance Profiling measurements, a capacitance step is linked to a defect between the energy bands of a solar cell.
Effects Of Temperature On The Crystal Structure Of Lithium-Lanthanum Zirconate,
2015
DePaul University
Effects Of Temperature On The Crystal Structure Of Lithium-Lanthanum Zirconate, Mir Iqbal
DePaul Discoveries
ABSTRACT Lithium-lanthanum zirconate (LLZ) can potentially be used as a solid electrolyte in lithium-metal batteries. Li-metal batteries offer superior charge capacities and higher energy densi-ties compared to currently used Li-ion batteries. Lithium is highly reactive, which can be dangerous in consumer electronics, but a layer of LLZ electrolyte inserted alongside the Li-metal electrode greatly stabilizes its reactivity. The cubic phase structure of LLZ (Li7La3Zr2O12) has the highest conductivity of its crystalline phases, making it the most promising crystal form of LLZ for this application. Samples of LLZ were doped with different amounts …
A Static And Dynamic Investigation Of Quantum Nonlinear Transport In Highly Dense And Mobile 2d Electron Systems,
2015
CUNY Graduate Center
A Static And Dynamic Investigation Of Quantum Nonlinear Transport In Highly Dense And Mobile 2d Electron Systems, Scott A. Dietrich
Dissertations, Theses, and Capstone Projects
Heterostructures made of semiconductor materials may be one of most versatile environments for the study of the physics of electron transport in two dimensions. These systems are highly customizable and demonstrate a wide range of interesting physical phenomena. In response to both microwave radiation and DC excitations, strongly nonlinear transport that gives rise to non-equilibrium electron states has been reported and investigated. We have studied GaAs quantum wells with a high density of high mobility two-dimensional electrons placed in a quantizing magnetic field. This study presents the observation of several nonlinear transport mechanisms produced by the quantum nature of these …
Measuring Charge Carrier Mobility In Graphene,
2015
Linfield College
Measuring Charge Carrier Mobility In Graphene, Christina A. Harmon
Senior Theses
This research reports measurements of electron mobility in Graphene Field Effect Transistors (GFET), gated with liquid. Mobility is a quantity describing how easily charge carriers move through a material. GFET biosensors have the greatest sensitivity when the mobility is high; therefore, increasing mobility should improve sensitivity of these and similar devices. An optimal method was established for preparing samples and taking measurements of a liquid-gate device. Sheet conductivity was measured using van der Pauw geometry and carrier density was determined from measurements of the liquid-gate capacitance. It is shown that mobility improves after the graphene surface is cleaned by an …
Modification Of Electronic Surface States By Graphene Islands On Cu(111),
2015
University of New Hampshire - Main Campus
Modification Of Electronic Surface States By Graphene Islands On Cu(111), Shawna M. Hollen, G A. Gambrel, S J. Tjung, N M. Santagata, Ezekiel Johnston-Halperin, Jay A. Gupta
Physics & Astronomy
We present a study of graphene/substrate interactions on ultrahigh-vacuum-grown graphene islands with minimal surface contamination using in situ low-temperature scanning tunneling microscopy. We compare the physical and electronic structure of the sample surface with atomic spatial resolution on graphene islands versus regions of bare Cu(111) substrate. We find that the Rydberg-like series of image potential states is shifted toward lower energy over the graphene islands relative to Cu(111), indicating a decrease in the local work function, and the resonances have a much smaller linewidth, indicating reduced coupling to the bulk. In addition, we show the dispersion of the occupied Cu(111) …
Transverse Thermoelectric Properties Of Cu/Mg2si And Ni/Mg2si Artificially Anisotropic Materials,
2015
University of New Orleans
Transverse Thermoelectric Properties Of Cu/Mg2si And Ni/Mg2si Artificially Anisotropic Materials, David J N Esch
LSU New Orleans Theses and Dissertations
In this thesis the spark plasma sintering process (SPS) was used to press Mg2Si powder with Ni and Cu slices into alternating layer stacks. These stacks, once cut at an angle, are an artificially anisotropic material. This anisotropy provides transverse thermoelectric properties to the sample. The transverse transport properties were measured along with the individual component transport properties. The SPS process provided malleable samples that gave a power factors of for the Ni/Mg2Si stack and for the Cu/Mg2Si stack. These fall short of the theoretical calculations which would give the power factors as .0254 …
Analysis Of Spin Polarization In Half-Metallic Heusler Alloys,
2015
Macalester College
Analysis Of Spin Polarization In Half-Metallic Heusler Alloys, Alexandra Mcnichol Boldin
Macalester Journal of Physics and Astronomy
Half-metals have recently gained great interest in the field of spintronics because their 100% spin polarization may make them an ideal current source for spintronic devices. This project examines four Heusler Alloys of the form Co2FexMn1−xSi that are expected to be half-metallic. Two magnetic properties of these alloys were examined, the Anisotropic Magnetoresistance (AMR) and the Anomalous Hall Effect (AHE). These properties have the potential to be used as simple and fast ways to identify materials as half-metallic or non-half-metallic. The results of these measurements were also used to examine the spin …
Modelling Transient Terahertz Magneto-Spectroscopy Measurements Of P-Type Cvd Graphene Leading To A Negative Photoconductivity.,
2015
Macalester College
Modelling Transient Terahertz Magneto-Spectroscopy Measurements Of P-Type Cvd Graphene Leading To A Negative Photoconductivity., Rhyan Foo Kune
Macalester Journal of Physics and Astronomy
Ultrafast Terahertz (THz) Magneto-Spectroscopy (UTMS) measurements were performed on p-type CVD graphene sample to investigate the intrinsic carrier dynamics of the material. We investigated static and time-resolved THz transmission measurements, in which the sample was photo-excited by a near infrared (NIR) pump pulse, in order to study its behavior in a magnetic field. In these measurements the free carriers were probed to independently measure the carrier density and scattering rate in this film. We observed, in our graphene sample, an increase in transmission related to a negative photoconductivity (decrease in conductivity after photoexcitation) consistent with previous research. This decrease is …
Thermoelectric Properties Of Nano-Meso-Micro Β-Mno2 Powders As A Function Of Electrical Resistance: Experiment And Theory,
2015
James Madison University
Thermoelectric Properties Of Nano-Meso-Micro Β-Mno2 Powders As A Function Of Electrical Resistance: Experiment And Theory, Morgan Hedden
Senior Honors Projects, 2010-2019
In this work, the thermoelectric properties of Beta-MnO2 powders as a function of electrical resistance are measured and compared to theoretical models. The discovery of a giant Seebeck coefficient by Song et al. in these powders rejuvenated interest in understanding the physical mechanism behind it. A simple pestle and mortar method was used to modify the MnO2 powder sizes. We and the largest S coefficient, power factor, and thermal conductivity values were found to be S=-316 uV/K, (sigma)S2 =5.8x10-7 W/mK2 and k=0.2096 W/(mK), all observed at a particle electrical resistance of R=9.8 Ohms. From these …
Surface Microstructure Evolution Of Metallic Specimens Using The Large Chamber Scanning Electron Microscope,
2015
Western Kentucky University
Surface Microstructure Evolution Of Metallic Specimens Using The Large Chamber Scanning Electron Microscope, Grace Egbujor
Masters Theses & Specialist Projects
An initial study into the use of the large chamber scanning electron microscope (LCSEM) to interrogate the surface microstructure evolution of metallic specimens has been carried out. The LC-SEM located at Western Kentucky University is the largest instrument of its type at any university in the world. As such, unique measurements can be performed due to the size of its chamber and extended view of its optic system. Strain was varied for each individual specimen, and imaged using Secondary Electrons within the gauge length as well as near the grip position. Results will show progression of surface microstructures and nickel …
Mirror Buckling Transitions In Freestanding Graphene Membranes Induced Through Scanning Tunneling Microscopy,
2015
University of Arkansas, Fayetteville
Mirror Buckling Transitions In Freestanding Graphene Membranes Induced Through Scanning Tunneling Microscopy, James Kevin Schoelz
Graduate Theses and Dissertations
Graphene has the ability to provide for a technological revolution. First isolated and characterized in 2004, this material shows promise in the field of flexible electronics. The electronic properties of graphene can be tuned by controlling the shape of the membrane. Of particular interest in this endeavor are the thermal ripples in graphene membranes. Years of theoretical work by such luminaries as Lev Landau, Rudolf Peierls, David Mermin and Herbert Wagner have established that 2D crystals should not be thermodynamically stable. Experimental research on thin films has supported this finding. Yet graphene exists, and freestanding graphene films have been grown …
Epitaxial Growth Of Silicon On Poly-Crystalline Si Seed Layer At Low Temperature By Using Hot Wire Chemical Vapor Deposition,
2015
University of Arkansas, Fayetteville
Epitaxial Growth Of Silicon On Poly-Crystalline Si Seed Layer At Low Temperature By Using Hot Wire Chemical Vapor Deposition, Manal Abdullah Aldawsari
Graduate Theses and Dissertations
There has been a growing interest in using low cost material as a substrate for the large grained polycrystalline silicon photovoltaic devices. The main property of those devices is the potential of obtaining high efficiency similar to crystalline Si devices efficiency yet at much lower cost because of the thin film techniques. Epitaxial growth of Si at low temperatures on low cost large grained seed layers, prepared by aluminum induced crystallization method (AIC), using hot wire chemical vapor deposition (HWCVD) system is investigated in this thesis. In this work, different parameters have been studied in order to optimize the growth …
High Pressure Behavior Of Mullite-Type Oxides: Phase Transitions, Amorphization, Negative Linear Compressibility And Microstructural Implications,
2015
University of Nevada, Las Vegas
High Pressure Behavior Of Mullite-Type Oxides: Phase Transitions, Amorphization, Negative Linear Compressibility And Microstructural Implications, Patricia Kalita
UNLV Theses, Dissertations, Professional Papers, and Capstones
Even though mullite occurs rarely in nature, it is perhaps one of the most important phases in both traditional and advanced ceramics. Existing and emerging applications of mullite and mullite-type materials include: high-temperature composites, aerospace materials, ballistic shielding for military applications and even non-linear optical materials. There are many uncertainties regarding the basic physical properties of mullite-type materials, particularly in terms of their high-pressure structural stability and mechanical behavior that are important to address for emerging applications of mullites as engineering materials. This work is the first reported comprehensive investigation of the high –pressure structural behavior of several different mullites …
Calibration Of Muon Detector For Coincidence Cathodoluminescence Experiments,
2015
Utah State University
Calibration Of Muon Detector For Coincidence Cathodoluminescence Experiments, Kenneth Zia, Jr Dennison
Presentations
A muon scintillation detector has been calibrated by measuring the magnitude and angular dependence of high energy cosmic background radiation events. Optimizing dark current as a function of voltage across the photomultiplier tube (PMT) detector was essential for accurate counting of current pulses as narrow as the counts in the PMT. Measurements of the crosssection zenith angle were also optimized by sweeping the detector across the horizon and from the zenith to nadir angle. The detector is now operating within proper Poisson distribution statistics for counting particle experiments, and is ready for the next step in determining coincidence between the …
Electron Penetration Range For Every Body,
2015
Utah State University
Electron Penetration Range For Every Body, Anne Starley, Lisa Montierth Phillipps, Jr Dennison
Presentations
The penetration range of an electron into diverse materials can be estimated using an approximation fit as a function of a single parameter, N y, which describes the effective number of valence electrons. This fit is found using the Continuous-Slow Down-Approximation (CSDA), which simplifies the process of estimating an expected penetration range of a given material by applying some of the material’s key characteristics. Using the CSDA, a simple composite analytical formula is created which estimates the range or maximum penetration depth of incident electrons. This formula generates an approximation to the range using the parameter, Nv . The range …
Degradation Of Space Polymers: A Case Study,
2015
Utah State University
Degradation Of Space Polymers: A Case Study, Kelby T. Peterson
Senior Theses and Projects
Materials International Space Station Experiment 6 (MISSE-6) was an experiment designed to examine the consequences of the space environment on various materials used in space-component design. USU’s contribution was comprised of approximately 180 samples that were suspended from the side of the International Space Station (ISS) for 18 months and returned to allow for pre- and post-flight comparisons. The sample with the most evident changes was a thin film of polyethylene terephthalate (PET) MylarTM coated with Vapor Deposited Aluminum (VDA). The post-flight analysis showed evidence of atomic oxygen erosion of the VDA layer, UV-induced discoloration of the polymer, and a …
Transport Studies In Graphene-Based Materials And Structures,
2015
Birck Nanotechnology Center, Purdue University
Transport Studies In Graphene-Based Materials And Structures, Jiuning Hu
Open Access Dissertations
Graphene, a single atomic layer of graphite, has emerged as one of the most attractive materials in recent years for its many unique and excellent properties, inviting a broad area of fundamental studies and applications. In this thesis, we present some theoretical/experimental studies about the thermal, electronic and thermoelectric transport properties in graphene-based systems. We employ the molecular dynamic simulations to study the thermal transport in graphene nanoribbons (GNRs) exhibiting various properties, including chirality dependent thermal conductivity, thermal rectification in asymmetric GNRs, defects and isotopic engineering of the thermal conductivity and negative differential thermal conductance (NDTC) at large temperature biases. …
