Highly Spin-Polarized Conducting State At The Interface Between Nonmagnetic Band Insulators: Laalo3/Fes2 (001),
2011
University of Nebraska-Lincoln
Highly Spin-Polarized Conducting State At The Interface Between Nonmagnetic Band Insulators: Laalo3/Fes2 (001), John D. Burton, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
First-principles density functional calculations demonstrate that a spin-polarized two-dimensional conducting state can be realized at the interface between two nonmagnetic band insulators. The (001) surface of the diamagnetic insulator FeS2 (pyrite) supports a localized surface state deriving from Fe d orbitals near the conduction band minimum. The deposition of a few unit cells of the polar perovskite oxide LaAlO3 leads to electron transfer into these surface bands, thereby creating a conducting interface. The occupation of these narrow bands leads to an exchange splitting between the spin subbands, yielding a highly spin-polarized conducting state distinct from the rest of …
Tailoring A Two-Dimensional Electron Gas At The Laalo3 ∕ Srtio3 (001) Interface By Epitaxial Strain,
2011
University of Wisconsin - Madison
Tailoring A Two-Dimensional Electron Gas At The Laalo3 ∕ Srtio3 (001) Interface By Epitaxial Strain, C. W. Bark, D. A. Felker, Yong Wang, H. W. Jang, C. M. Folkman, J. W. Park, S. H. Baek, H. Zhou, D. D. Fong, X. Q. Pan, Evgeny Y. Tsymbal, M. S. Rzchowski, Chang-Beom Eom
Evgeny Tsymbal Publications
Recently a metallic state was discovered at the interface between insulating oxides, most notably LaAlO3 and SrTiO3. Properties of this two-dimensional electron gas (2DEG) have attracted significant interest due to its potential applications in nanoelectronics. Control over this carrier density and mobility of the 2DEG is essential for applications of these unique systems, and may be achieved by epitaxial strain. However, despite the rich nature of strain effects on oxide materials properties, such as ferroelectricity, magnetism, and superconductivity, the relationship between the strain and electrical properties of the 2DEG at the LaAlO3∕SrTiO3 heterointerface remains …
A Novel Integrated Platform Combining Atomic Force Microscopy And Fluorescence Correlation Spectroscopy,
2011
Wayne State University
A Novel Integrated Platform Combining Atomic Force Microscopy And Fluorescence Correlation Spectroscopy, Venkatesh Subba Rao
Wayne State University Dissertations
At the nanoscale near an interface, the discrete nature of liquids is expected to influence various properties, such as density, viscosity or diffusion constants. Understanding interfacial properties of liquids is important for the development of nanotechnology, especially for the fields of nano-rheology and nano-tribology, and also for understanding various mechanisms in biological systems at the molecular level, such as protein folding or the self-assembly of lipid vesicles, which invariably involve liquids. Atomic force microscope (AFM) and fluorescence correlation spectroscope (FCS) are two complimentary techniques that are commonly employed investigate mechanics and dynamics of liquids at interfaces. In this thesis, the …
Dynamics Of Nanoparticles In Complex Fluids.,
2011
Wayne State University
Dynamics Of Nanoparticles In Complex Fluids., Rami Ahmad Saleh Omari
Wayne State University Dissertations
Soft matter is a subfield of condensed matter including polymers, colloidal dispersions, surfactants, and liquid crystals. These materials are familiar from our everyday life- glues, paints, soaps, and plastics are examples of soft materials. Many phenomena in these systems have the same underlying physical mechanics. Moreover, it has been recognized that combinations of these systems, like for example polymers and colloids, exhibit new properties which are found in each system separately. These mixed systems have a higher degree of complexity than the separate systems. In order to understand their behavior, knowledge from each subfields of soft matter has to be …
The Study Of Weak Ferromagnetism By Andreev Reflection Spin Spectroscopy And Development Of Bimorph Electro-Thermal Actuators,
2011
Wayne State University
The Study Of Weak Ferromagnetism By Andreev Reflection Spin Spectroscopy And Development Of Bimorph Electro-Thermal Actuators, Pushkal Thapa
Wayne State University Dissertations
It is well accepted that spin polarization of materials has a major role in spintronics to improve the efficiency of spintronic devices. Point contact Andreev reflection (PCAR) spectroscopy, one of the most popular and reliable techniques, was used to obtain the conductance and by analyzing them by modified BTK model, spin polarizations of various materials, generally with low ferromagnetism, were extracted in order to understand the transport properties of spin polarized current and find the relation of spin polarization with other parameters such as saturation magnetization or the Curie temperature so that better spintronic materials can be identified and developed. …
Schottky Barrier Formation At The Au To Rare Earth Doped
Gan Thin Film Interface,
2011
Air Force Institute of Technology
Schottky Barrier Formation At The Au To Rare Earth Doped Gan Thin Film Interface, S. R. Mchale, J. W. Mcclory, J. C. Petrosky, J. Wu, R. Palai, Yaroslav B. Losovyj, Peter A. Dowben
Peter Dowben Publications
The Schottky barriers formed at the interface between gold and various rare earth doped GaN thin films (RE = Yb, Er, Gd) were investigated in situ using synchrotron photoemission spectroscopy. The resultant Schottky barrier heights were measured as 1.68 ± 0.1 eV (Yb:GaN), 1.64 ± 0.1 eV (Er:GaN), and 1.33 ± 0.1 eV (Gd:GaN). We find compelling evidence that thin layers of gold do not wet and uniformly cover the GaN surface, even with rare earth doping of the GaN. Furthermore, the trend of the Schottky barrier heights follows the trend of the rare earth metal work function.
Mesoscale Flux-Closure Domain Formation In Single-Crystal Batio3,
2011
Queen’s University Belfast
Mesoscale Flux-Closure Domain Formation In Single-Crystal Batio3, R. G.P. Mcquaid, L. J. Mcgilly, Pankaj Sharma, Alexei Gruverman, J. M. Gregg
Alexei Gruverman Publications
Over 60 years ago, Charles Kittel predicted that quadrant domains should spontaneously form in small ferromagnetic platelets. He expected that the direction of magnetization within each quadrant should lie parallel to the platelet surface, minimizing demagnetizing fields, and that magnetic moments should be configured into an overall closed loop, or flux-closure arrangement. Although now a ubiquitous observation in ferromagnets, obvious flux-closure patterns have been somewhat elusive in ferroelectric materials. This is despite the analogous behaviour between these two ferroic subgroups and the recent prediction of dipole closure states by atomistic simulations research. Here we show Piezoresponse Force Microscopy images of …
Scanning Capacitance Spectroscopy On N+-P Asymmetrical Junctions In Multicrystalline Si Solar Cells,
2011
National Renewable Energy Laboratory
Scanning Capacitance Spectroscopy On N+-P Asymmetrical Junctions In Multicrystalline Si Solar Cells, Chun-Sheng Jiang, Jennifer T. Heath, Helio R. Moutinho, Mowafak M. Al-Jassim
Faculty Publications
We report on a scanning capacitance spectroscopy (SCS) study on the n+-p junction of multicrystalline silicon solar cells. We found that the spectra taken at space intervals of ∼10 nm exhibit characteristic features that depend strongly on the location relative to the junction. The capacitance-voltage spectra exhibit a local minimum capacitance value at the electrical junction, which allows the junction to be identified with ∼10-nm resolution. The spectra also show complicated transitions from the junction to the n-region with two local capacitance minima on the capacitance-voltage curves; similar spectra to that have not been previously reported in …
Electron-Phonon Interactions And Quantum Confinement Effects On Optical Transitions In Nanoscale Silicon Films,
2011
University at Albany, State University of New York
Electron-Phonon Interactions And Quantum Confinement Effects On Optical Transitions In Nanoscale Silicon Films, Vimal Kumar Kamineni
Legacy Theses & Dissertations (2009 - 2024)
Theoretical studies have attributed the temperature dependence of the linear optical response (dielectric function) of bulk semiconductors to electron-phonon interactions and thermal expansion of the lattice. However, the role of phonons in the optical properties of nanoscale structures is often overlooked. This thesis systematically investigates the impact of both carrier confinement and electron-phonon interactions using nanoscale films of silicon in crystalline silicon quantum wells (c-Si QW). Spectroscopic ellipsometry (SE) is a linear optical technique used to of extract the dielectric function and thickness of very thin films. X-ray reflectivity (XRR) was used as the complementary thickness metrology method. The dielectric …
Band Structures Of Layered Carbon/Boron Nitride Materials With Commensurate Lattices,
2011
University at Albany, State University of New York
Band Structures Of Layered Carbon/Boron Nitride Materials With Commensurate Lattices, Christopher C. Wells
Legacy Theses & Dissertations (2009 - 2024)
The electronic structures of systems consisting of hexagonal boron nitride layers and graphite sheets have been investigated in detail using density functional theory methods with two exchange correlation functions (local density approximation and generalized gradient approximation). The experimental data of graphene, graphite, monolayer hexagonal BN, and hexagonal BN were reproduced well with computational models. The commensurate models used in the investigation were generated by taking the averages of the lattice constants for graphite and h-BN.
Structure And Magnetism Of Mnau Nanoclusters,
2011
University of Nebraska-Lincoln
Structure And Magnetism Of Mnau Nanoclusters, X. Wei, Damien Le Roy, Ralph Skomski, Xingzhong Li, Zhiguang Sun, Jeffrey E. Shield, M. J. Kramer, David J. Sellmyer
Nebraska Center for Materials and Nanoscience: Faculty Publications
Equiatomic MnAu clusters with average sizes of 4 and 10 nm are produced by inert-gas condensation. As-produced clusters are used to form both dense cluster films and films with clusters embedded in a W matrix with a cluster volume fraction of 25%. Both structure and magnetism are size-dependent. Structural analysis of the 10 nm clusters indicate a distorted tetragonal body-centered cubic structure with lattice parameters a=0.315 and c=0.329 nm. The 4 nm clusters have a partially ordered tetragonal L10 structure with lattice parameters a=0.410 nm and c=0.395 nm. Magnetic properties of the clusters show evidence at …
Metastability Of Free Cobalt And Iron Clusters: A Possible Precursor To Bulk Ferromagnetism,
2011
University of Nebraska-Lincoln
Metastability Of Free Cobalt And Iron Clusters: A Possible Precursor To Bulk Ferromagnetism, Xiaoshan Xu, Shuangye Yin, Ramiro Moro, Anthony Liang, John Bowlan, Walt A. De Heer
Xiaoshan Xu Papers
Homonuclear cobalt and iron clusters CoN and FeN measured in a cryogenic molecular beam exist in two states with distinct magnetic moments (μ), polarizabilities, and ionization potentials, indicating distinct valences. The μ is approximately quantized: μN ~ 2NμB in the ground states and μN* ~ NμB in the excited states for Co; μN ~ 3N μB and μN * ~ NμB for Fe. At a large size, the average μ of the two states converges to the bulk value with diminishing ionization potential differences. …
Hydrodynamic Correlation Functions Of A Driven Granular Fluid In Steady State,
2011
Bucknell University
Hydrodynamic Correlation Functions Of A Driven Granular Fluid In Steady State, Katharina Vollmayr-Lee, Timo Aspelmeier, Annette Zippelius
Faculty Journal Articles
No abstract provided.
Analysis Of Electrodeposited Nickel-Iron Alloy Film Composition Using Particle-Induced X-Ray Emission,
2011
Hope College
Analysis Of Electrodeposited Nickel-Iron Alloy Film Composition Using Particle-Induced X-Ray Emission, Alyssa Frey, Nicholas Wozniak, Timothy Nagi, Matthew Keller, J. Mark Lunderberg, Graham F. Peaslee, Paul Deyoung, Jennifer R. Hampton
Faculty Publications
The elemental composition of electrodeposited NiFe thin films was analyzed with particle-induced X-ray emission (PIXE). The thin films were electrodeposited on polycrystalline Au substrates from a 100mM NiSO4, 10 mM FeSO4, 0.5M H3BO3, and 1M Na2SO4 solution. PIXE spectra of these films were analyzed to obtain relative amounts of Ni and Fe as a function of deposition potential and deposition time. The results show that PIXE can measure the total deposited metal in a sample over at least four orders of magnitude with similar fractional uncertainties. The technique is …
High Temperature And Pressure Resonant Ultrasound Spectroscopy Study Of Metal Hydride Systems,
2011
University of Mississippi
High Temperature And Pressure Resonant Ultrasound Spectroscopy Study Of Metal Hydride Systems, Rasheed Adebisi
Electronic Theses and Dissertations
The goal of this dissertation is to characterize the elastic properties of palladium hydride near the tri-critical point as a classic example of metal hydride systems using the resonant ultrasound spectroscopy. A high temperature and high pressure resonant ultrasound spectroscopy system which include the RUS cell and the direct contact transducer set-up was designed and constructed. The temperature and pressure dependent of elastic moduli of palladium hydride and palladium crystals were obtained at five isotherms near the critical temperature, 293 °C and for pressure range of 250–500 psi. A strong softening of the shear modulus was observed at temperature and …
Metallic And Insulating Oxide Interfaces Controlled By Electronic Correlations,
2011
University of Wisconsin - Madison
Metallic And Insulating Oxide Interfaces Controlled By Electronic Correlations, H. W. Jang, D. A. Felker, C. W. Bark, Y. Wang, Manish K. Niranjan, C. T. Nelson, Y. Zhang, D. Su, C. M. Folkman, S. H. Baek, S. Lee, K. Janicka, Y. Zhu, X. Q. Pan, D. D. Fong, Evgeny Y. Tsymbal, M. S. Rzchowski, Chang-Beom Eom
Evgeny Tsymbal Publications
The formation of two-dimensional electron gases (2DEGs) at complex oxide interfaces is directly influenced by the oxide electronic properties. We investigated how local electron correlations control the 2DEG by inserting a single atomic layer of a rare-earth oxide (RO) [(R is lanthanum (La), praseodymium (Pr), neodymium (Nd), samarium (Sm), or yttrium (Y)] into an epitaxial strontium titanate oxide (SrTiO3) matrix using pulsed-laser deposition with atomic layer control. We find that structures with La, Pr, and Nd ions result in conducting 2DEGs at the inserted layer, whereas the structures with Sm or Y ions are insulating. Our local …
Transport Spin Polarization Of High-Curie Temperature Mnbi Films,
2011
University of Nebraska-Lincoln
Transport Spin Polarization Of High-Curie Temperature Mnbi Films, Parashu Kharel, P. Thapa, Pavel V. Lukashev, Renat F. Sabirianov, Evgeny Y. Tsymbal, D. J. Sellmyer, Boris Nadgorny
Evgeny Tsymbal Publications
We report on the study of the structural, magnetic, and transport properties of highly textured MnBi films with the Curie temperature of 628 K. In addition to detailed measurements of resistivity and magnetization, we measure transport spin polarization of MnBi by Andreev reflection spectroscopy and perform fully relativistic band-structure calculations of MnBi. A spin polarization from 51% ± 1% to 63% ± 1% is observed, consistent with the calculations and with an observation of a large magnetoresistance in MnBi contacts. The band-structure calculations indicate that in spite of almost identical densities of states at the Fermi energy, the large disparity …
A Giant Tunneling Electroresistance Effect Driven By Electrically Controlled Spin Valve At A Complex Oxide Interface,
2011
University of Nebraska-Lincoln
A Giant Tunneling Electroresistance Effect Driven By Electrically Controlled Spin Valve At A Complex Oxide Interface, John D. Burton, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
A giant tunneling electroresistance effect may be achieved in a ferroelectric tunnel junction by exploiting the magnetoelectric effect at the interface between the ferroelectric barrier and a magnetic La1-xSrxMnO3 electrode. Using first-principles density-functional theory we demonstrate that a few magnetic monolayers of La1-xSrxMnO3 near the interface act, in response to ferroelectric polarization reversal, as an atomic-scale spin valve by filtering spin-dependent current. This produces more than an order of magnitude change in conductance, and thus constitutes a giant resistive switching effect.
Resonant Photoemission Of Rare Earth Doped Gan Thin Films,
2011
Air Force Institute of Technology
Resonant Photoemission Of Rare Earth Doped Gan Thin Films, S. R. Mchale, J. W. Mcclory, J. C. Petrosky, J. Wu, R. Palai, Yaroslav B. Losovyj, Peter A. Dowben
Peter Dowben Publications
The 4d → 4f Fano resonances for various rare earth doped GaN thin films (RE = Gd, Er, Yb) were investigated using synchrotron photoemission spectroscopy. The resonant photoemission Fano profiles show that the major Gd and Er rare earth 4f weight is at about 5–6 eV below the valence band maximum, similar to the 4f weights in the valence band of many other rare earth doped semiconductors. For Yb, there is very little resonant enhancement of the valence band of Yb doped GaN, consistent with a largely 4f14 occupancy.
Magnetism Of Cluster-Deposited Y–Co Nanoparticles,
2011
University of Nebraska-Lincoln
Magnetism Of Cluster-Deposited Y–Co Nanoparticles, Balamuruga Balamurugan, Ralph Skomski, Xingzhong Li, V. R. Shah, George C. Hadjipanayis, Jeffrey E. Shield, David J. Sellmyer
Nebraska Center for Materials and Nanoscience: Faculty Publications
Nanoparticles of YCo2, YCo3, and YCo5 are produced by cluster-deposition and investigated both structurally and magnetically. The nanoparticles have sizes of less than 10 nm and are superparamagnetic at 300 K, irrespective of stoichiometry. As-produced nanoparticles exhibit disordered structures with magnetic properties differing from those of the bulk particles. The temperature-dependent magnetization curves of the nanoparticles reveal blocking temperatures from 110 to 250 K, depending on stoichiometry. The magnetic anisotropy constant K1 of disordered YCo5 nanoparticles of 7.8 nm in size is 3.5×106ergs/cm3, higher than those of the disordered YCo …
