Evaluation Of The Temperature Dependence Of Endurance Models Of Electrostatic Breakdown, 2012 Utah State University
Evaluation Of The Temperature Dependence Of Endurance Models Of Electrostatic Breakdown, Charlie Sim, Jr Dennison
Senior Theses and Projects
The goal of this research was to investigate temperature and time dependent models for the electrostatic breakdown of polymeric spacecraft insulators. Temperature dependent breakdown was found by inducing an electrostatic breakdown in the prototypical polymer Low Density Polyethylene (LDPE) at various temperatures. Time dependent breakdown was found by applying a static voltage to LDPE and measuring the time to electrostatic breakdown. No significant temperature dependence of the electrostatic breakdown of LDPE was observed in a temperature range of 150 K to 300 K. The time dependent results show that the time to electrostatic breakdown is modeled by a negative logarithmic …
The Effects Of Surface Roughness On Diffuse Optical Reflection And Photoyields On Spacecraft Materials, 2012 Utah State University
The Effects Of Surface Roughness On Diffuse Optical Reflection And Photoyields On Spacecraft Materials, Amberly Evans Jensen
Senior Theses and Projects
The goal of this project was to measure the change in the absorbance of spacecraft materials due to changes in the surface of the material. The absorbance was obtained by measuring reflectance and transmittance. We found that modifying the surface of a material did affect the material’s specular reflectance. However, the change may not have been entirely due to an increase in absorbance, but may also imply an increase in the diffuse reflection. To understand the affect on absorbance, diffuse reflectance and transmission will need to be measured. This will lead to a prediction of how surface modification affects the …
Insulator-To-Metal Transition And Correlated Metallic State Of V 2 O 3 Investigated By Optical Spectroscopy, 2012 William & Mary
Insulator-To-Metal Transition And Correlated Metallic State Of V 2 O 3 Investigated By Optical Spectroscopy, M. K. Stewart, D. Brownstead, (...), M. M. Qazilbash, Et Al.
Arts & Sciences Articles
The optical properties of V2O3 thin films are investigated across the insulator-to-metal transition and in the metallic state. The spectral weight transfer observed across the transition, over an energy scale of 5 eV, is consistent with the Mott-Hubbard model for correlated electron systems. In the metallic phase, a strong Drude peak is observed, which exhibits a pronounced temperature dependence related to the transfer of states from the Hubbard bands to the quasiparticle peaks as the temperature is reduced. The analysis of the far-infrared spectra reveals signatures of strong electronic correlations in V2O3. Finally, a comparison to VO2 data is presented.
Mott Transition And Electronic Structure In Complex Oxide Heterostructures, 2012 University of Arkansas, Fayetteville
Mott Transition And Electronic Structure In Complex Oxide Heterostructures, Jian Liu
Graduate Theses and Dissertations
Strongly correlated electron systems, particularly transition metal oxides, have been a focus of condensed matter physics for more than two decades since the discovery of high-temperature superconducting cuprates. Diverse competing phases emerge, spanning from exotic magnetism to unconventional superconductivity, in proximity to the localized-itinerant transition of Mott insulators. While studies were concentrated on bulk crystals, the recent rapid advance in synthesis has enabled fabrication of high-quality oxide heterostructures, offering a new route to create novel artificial quantum materials.
This dissertation details the investigation on ultrathin films and heterostructures of 3d7(t2g6eg1) systems with …
Soft X-Ray Spectroscopic Investigation Of Oxides For Renewable Energy Applications, 2012 University of Tennessee, Knoxville
Soft X-Ray Spectroscopic Investigation Of Oxides For Renewable Energy Applications, Eric Westbrook Martin
Chancellor’s Honors Program Projects
No abstract provided.
Use Of Ultra High Vacuum Plasma Enhanced Chemical Vapor Deposition For Graphene Fabrication, 2012 University of Arkansas, Fayetteville
Use Of Ultra High Vacuum Plasma Enhanced Chemical Vapor Deposition For Graphene Fabrication, Shannen Adcock
Graduate Theses and Dissertations
Graphene, what some are terming the "new silicon", has the possibility of revolutionizing technology through nanoscale design processes. Fabrication of graphene for device processing is limited largely by the temperatures used in conventional deposition. High temperatures are detrimental to device design where many different materials may be present. For this reason, graphene synthesis at low temperatures using plasma-enhanced chemical vapor deposition is the subject of much research. In this thesis, a tool for ultra-high vacuum plasma-enhanced chemical vapor deposition (UHV-PECVD) and accompanying subsystems, such as control systems and alarms, are designed and implemented to be used in future graphene growths. …
Superconducting Nafe1-Xcoxas: Crystal Growth, Resistivity, And Susceptibility Measurements, 2012 University of Tennessee, Knoxville
Superconducting Nafe1-Xcoxas: Crystal Growth, Resistivity, And Susceptibility Measurements, Tucker Netherton
Chancellor’s Honors Program Projects
No abstract provided.
Highly Charged Ion Interactions With Ultrathin Dielectric Films, 2012 Clemson University
Highly Charged Ion Interactions With Ultrathin Dielectric Films, Russell Lake
All Dissertations
The excitations occurring at a solid surface due to slow highly charged ion (HCI) impacts are interesting from the perspective of fundamental processes in atomic collisions and materials science. This thesis focuses on two questions: 1) How much HCI potential energy deposition is required to form permanent surface modifications?, 2) How does the presence of a thin dielectric surface film change the classical over-the-barrier picture for neutralization above a clean metal?
I describe a measurement of craters in thin dielectric films formed by XeQ+ (26 ≤ Q ≤ 44) projectiles. Tunnel junction devices with ion-irradiated barriers were used to amplify …
Out-Of-Surface Vortices In Spherical Shells, 2012 Bogolyubov Institute for Theoretical Physics Nasu
Out-Of-Surface Vortices In Spherical Shells, Volodymyr P. Kravchuk, Denis D. Sheka, Robert Streubel, Denys Makarov, Oliver G. Schmidt, Yuri Gaididei
Robert Streubel Papers
The interplay of topological defects with curvature is studied for out-of-surface magnetic vortices in thin spherical nanoshells. In the case of an easy-surface Heisenberg magnet it is shown that the curvature of the underlying surface leads to a coupling between the localized out-of-surface component of the vortex with its delocalized in-surface structure, i.e., polarity-chirality coupling. © 2012 American Physical Society.
Bulk Fermi Surface And Momentum Density In Heavily Doped La₂₋ₓsrₓcuo₄ Using High-Resolution Compton Scattering And Positron Annihilation Spectroscopies, 2012 Northeastern University
Bulk Fermi Surface And Momentum Density In Heavily Doped La₂₋ₓsrₓcuo₄ Using High-Resolution Compton Scattering And Positron Annihilation Spectroscopies, W. Al-Sawai, B. Barbiellini, Y. Sakurai, M. Itou, P. E. Mijnarends, R. S. Markiewicz, S. Kaprzyk, S. Wakimoto, M. Fujita, S. Basak, H. Lin, Yung Jui Wang, S. W. H. Eijt, H. Schut, K. Yamada, A. Bansil
Arun Bansil
We have observed the bulk Fermi surface (FS) in an overdoped (x=0.3) single crystal of La₂₋ₓSrₓCuO₄ by using Compton scattering. A two-dimensional (2D) momentum density reconstruction from measured Compton profiles yields a clear FS signature in the third Brillouin zone along [100]. The quantitative agreement between density functional theory (DFT) calculations and momentum density experiment suggests that Fermi-liquid physics is restored in the overdoped regime. In particular the predicted FS topology is found to be in good accord with the corresponding experimental data. We find similar quantitative agreement between the measured 2D angular correlation of positron annihilation radiation (2D-ACAR) spectra …
Fermi-Surface Topology And Low-Lying Electronic Structure Of The Iron-Based Superconductor Ca₁₀(Pt₃As₈)(Fe₂As₂)₅, 2012 Princeton University
Fermi-Surface Topology And Low-Lying Electronic Structure Of The Iron-Based Superconductor Ca₁₀(Pt₃As₈)(Fe₂As₂)₅, Madhab Neupane, Chang Liu, Su-Yang Xu, Yung-Jui Wang, Ni Ni, J. M. Allred, N. Alidoust, Hsin Lin, R. S. Markiewicz, A. Bansil, R. J. Cava, M. Z. Hasan
Arun Bansil
We report a study of low-energy electronic structure and Fermi surface topology for the recently discovered iron-based superconductor Ca₁₀(Pt₃As₈)(Fe₂As₂)₅(the 10-3-8 phase, with Tc∼8 K), via angle-resolved photoemission spectroscopy (ARPES). Despite its triclinic crystal structure, ARPES results reveal a fourfold symmetric band structure with the absence of Dirac-cone-like Fermi dots (related to magnetism) found around the Brillouin zone corners in other iron-based superconductors. Considering that the triclinic lattice and structural supercell arise from the Pt₃As₈ intermediary layers, these results indicate that those layers couple only weakly to the FeAs layers in this new superconductor at least near the surface, which has …
New View Of The Occupied Band Structure Of Mo(112), 2012 University of Nebraska-Lincoln
New View Of The Occupied Band Structure Of Mo(112), Keisuke Fukutani, Hirokazu Hayashi, I. N. Yakovkin, Tula R. Paudel, Takafumi Habuchi, Daisuke Hirayama, Jian Jiang, Hideaki Iwasawa, Kenya Shimada, Ning Wu, Evgeny Y. Tsymbal, Yaroslav B. Losovyj, Peter A. Dowben
Evgeny Tsymbal Publications
We present a comprehensive examination of the occupied surface-weighted band structure of Mo(112) along the two high-symmetry directions of the surface Brillouin zone, both from theoretical and experimental perspectives. The band structures are found to be significantly different for the states along the two high-symmetry directions and for the states with even and odd reflection parities with respect to the mirror planes. The present study suggests the existence of a number of surface-weighted bands along both high-symmetry directions. The complexity of the band structure near the Fermi level may impose potential difficulties in experimental determination of the electronphonon coupling parameters …
Bulk Fermi Surface And Momentum Density In Heavily Doped La₂₋ₓsrₓcuo₄ Using High-Resolution Compton Scattering And Positron Annihilation Spectroscopies, 2012 Northeastern University
Bulk Fermi Surface And Momentum Density In Heavily Doped La₂₋ₓsrₓcuo₄ Using High-Resolution Compton Scattering And Positron Annihilation Spectroscopies, W. Al-Sawai, B. Barbiellini, Y. Sakurai, M. Itou, P. E. Mijnarends, R. S. Markiewicz, S. Kaprzyk, S. Wakimoto, M. Fujita, S. Basak, H. Lin, Yung Jui Wang, S. W. H. Eijt, H. Schut, K. Yamada, A. Bansil
Bernardo Barbiellini
We have observed the bulk Fermi surface (FS) in an overdoped (x=0.3) single crystal of La₂₋ₓSrₓCuO₄ by using Compton scattering. A two-dimensional (2D) momentum density reconstruction from measured Compton profiles yields a clear FS signature in the third Brillouin zone along [100]. The quantitative agreement between density functional theory (DFT) calculations and momentum density experiment suggests that Fermi-liquid physics is restored in the overdoped regime. In particular the predicted FS topology is found to be in good accord with the corresponding experimental data. We find similar quantitative agreement between the measured 2D angular correlation of positron annihilation radiation (2D-ACAR) spectra …
Surface Roughness And Dry Friction, 2012 Northeastern University
Surface Roughness And Dry Friction, J. Sokoloff
Jeffrey Sokoloff
Persson's multiscale contact mechanics theory combined with a multiscale Brillouin-Prandtl-Tomlinson model is used to show that on the basis of these models “dry friction” [i.e., kinetic friction that remains at exceedingly small velocities (but still above the creep range) close to its value at higher velocities] should almost always occur for self-affine surfaces when the dominant interaction between two surfaces in contact is due to interatomic hard core repulsion, except for extremely smooth surfaces (i.e., surfaces with a Hurst index very close to 1).
Comparison Of The Kinetic Friction Of Planar Neutral And Polyelectrolyte Polymer Brushes Using Molecular Dynamics Simulations, 2012 Northeastern Univeristy
Comparison Of The Kinetic Friction Of Planar Neutral And Polyelectrolyte Polymer Brushes Using Molecular Dynamics Simulations, Yangpeng Ou, Jeffrey B. Sokoloff, Mark J. Stevens
Jeffrey Sokoloff
We have simulated the relative shear motion of both neutral and polyelectrolyte end-grafted polymer brushes using molecular dynamics. The flexible neutral polymer brush is treated as a bead-spring model, and the polyelectrolyte brush is treated the same way except that each bead is charged and there are counterions present to neutralize the charge. We investigated the friction coefficient, monomer density, and brush penetration for both polyelectrolyte and neutral brushes with both equal grafting density and equal normal force under good solvent conditions. We found that polyelectrolyte brushes had a smaller friction coefficient and monomer penetration than neutral polymer brushes with …
Bulk Fermi Surface And Momentum Density In Heavily Doped La₂₋ₓsrₓcuo₄ Using High-Resolution Compton Scattering And Positron Annihilation Spectroscopies, 2012 Northeastern University
Bulk Fermi Surface And Momentum Density In Heavily Doped La₂₋ₓsrₓcuo₄ Using High-Resolution Compton Scattering And Positron Annihilation Spectroscopies, W. Al-Sawai, B. Barbiellini, Y. Sakurai, M. Itou, P. Mijnarends, R. Markiewicz, S. Kaprzyk, S. Wakimoto, M. Fujita, S. Basak, H. Lin, Yung Jui Wang, S. Eijt, H. Schut, K. Yamada, A. Bansil
Robert Markiewicz
We have observed the bulk Fermi surface (FS) in an overdoped (x=0.3) single crystal of La₂₋ₓSrₓCuO₄ by using Compton scattering. A two-dimensional (2D) momentum density reconstruction from measured Compton profiles yields a clear FS signature in the third Brillouin zone along [100]. The quantitative agreement between density functional theory (DFT) calculations and momentum density experiment suggests that Fermi-liquid physics is restored in the overdoped regime. In particular the predicted FS topology is found to be in good accord with the corresponding experimental data. We find similar quantitative agreement between the measured 2D angular correlation of positron annihilation radiation (2D-ACAR) spectra …
Fermi-Surface Topology And Low-Lying Electronic Structure Of The Iron-Based Superconductor Ca₁₀(Pt₃As₈)(Fe₂As₂)₅, 2012 Princeton University
Fermi-Surface Topology And Low-Lying Electronic Structure Of The Iron-Based Superconductor Ca₁₀(Pt₃As₈)(Fe₂As₂)₅, Madhab Neupane, Chang Liu, Su-Yang Xu, Yung-Jui Wang, Ni Ni, J. M. Allred, N. Alidoust, Hsin Lin, R. S. Markiewicz, A. Bansil, R. J. Cava, M. Z. Hasan
Robert Markiewicz
We report a study of low-energy electronic structure and Fermi surface topology for the recently discovered iron-based superconductor Ca₁₀(Pt₃As₈)(Fe₂As₂)₅(the 10-3-8 phase, with Tc∼8 K), via angle-resolved photoemission spectroscopy (ARPES). Despite its triclinic crystal structure, ARPES results reveal a fourfold symmetric band structure with the absence of Dirac-cone-like Fermi dots (related to magnetism) found around the Brillouin zone corners in other iron-based superconductors. Considering that the triclinic lattice and structural supercell arise from the Pt₃As₈ intermediary layers, these results indicate that those layers couple only weakly to the FeAs layers in this new superconductor at least near the surface, which has …
Nanotopography Influences Adhesion, Spreading, And Self-Renewal Of Human Embryonic Stem Cells, 2012 University of Michigan - Ann Arbor
Nanotopography Influences Adhesion, Spreading, And Self-Renewal Of Human Embryonic Stem Cells, Weiqiang Chen, Luis G. Villa-Diaz, Yubing Sun, Shinuo Weng, Jin Koo Kim, Raymond H. W. Lam, Lin Han, Rong Fan, Paul H. Krebsbach, Jianping Fu
Weiqiang Chen
Human embryonic stem cells (hESCs) have great potentials for future cell-based therapeutics. However, their mechanosensitivity to biophysical signals from the cellular microenvironment is not well characterized. Here we introduced an effective microfabrication strategy for accurate control and patterning of nanoroughness on glass surfaces. Our results demonstrated that nanotopography could provide a potent regulatory signal over different hESC behaviors, including cell morphology, adhesion, proliferation, clonal expansion, and self-renewal. Our results indicated that topological sensing of hESCs might include feedback regulation involving mechanosensory integrin-mediated cell matrix adhesion, myosin II, and E-cadherin. Our results also demonstrated that cellular responses to nanotopography were cell-type …
Magnetic Properties And Defects In Iron Implanted Strontium Titanate Single Crystals And Thin Films, 2012 The University of Western Ontario
Magnetic Properties And Defects In Iron Implanted Strontium Titanate Single Crystals And Thin Films, Misha Chavarha
Electronic Thesis and Dissertation Repository
Physical vapor deposition was used to grow good quality crystalline stoichiometric SrTiO3 thin films on Si(001) substrate using a systematic approach starting from understanding of kinetics and thermodynamics of the system and finishing with the development of procedure for high quality SrTiO3/Si interface. Growth of optimized SrTiO3 perovskite structure on Si requires careful transformation of a thin interfacial SrSix layer into the initial SrTiO3 lattice cells. The critical aspects of the growth, such as low temperature and low oxidant partial pressure, are explained in details. Crystallinity and stoichiometry of SrTiO3 were verified using powder …
Temperature-Sensitive Chemical Cell Based On Nickel (Ii) Phthalocyanine-Tetrasulfonic Acid Tetrasodium Salt, 2012 Low Dimensional Material Research Centre, Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia
Temperature-Sensitive Chemical Cell Based On Nickel (Ii) Phthalocyanine-Tetrasulfonic Acid Tetrasodium Salt, Shahino Mah Abdullah
Shahino Mah Abdullah
An organic compound Nickel (II) phthalocyanine-tetrasulfonic acid tetrasodium salt (NiTSPc) has been studied as a potential material for a solution based temperature sensor. Using NiTSPc, an ITO/NiTSPc solution/ITO chemical cell has been made and characterized in the temperature range of 20–85 ◦C. This sensor works on the principle of change in the resistance and capacitance of the chemical cell caused by the temperature variation. Good response/recovery and small hysteresis have been attained. The proposed sensor is aimed to evolve towards highly sensitive organic temperature sensor in a specific temperature range.