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Nonlinear Optical Studies Of Bulk And Thin Film Complex Materials, Joel E. Taylor
Nonlinear Optical Studies Of Bulk And Thin Film Complex Materials, Joel E. Taylor
LSU Doctoral Dissertations
Nonlinear optical studies of bulk and thin film materials provide a vast playground for physical and dynamical characterization. In this thesis, we have implemented experimental methods to probe novel phase transitions in single crystals using rotational anisotropic second harmonic generation (RASHG) and carrier dynamics in thin films with time-resolved pump-probe reflectivity. Furthermore, a novel low temperature ultra-high vacuum system coupled to nonlinear optics has been developed to extend lab capabilities. Doping (Bi1-xSbx)2Se3 with antimony, the surface electronic reconstruction near x=80% was identified with RASHG by deviations in the six-fold and three-fold polarization anisotropic …
Photoemission And Photo-Absorption Studies Of Ultrathin Iron Films On Copper(100) Oxidized At Elevated Temperature., Reginaldt Hamilton Madjoe
Photoemission And Photo-Absorption Studies Of Ultrathin Iron Films On Copper(100) Oxidized At Elevated Temperature., Reginaldt Hamilton Madjoe
LSU Historical Dissertations and Theses
In this investigation, I have focused on understanding the structure and morphology of ultrathin iron oxide films and characterizing them by using LEED, photoemission (both angle-resolved and angle-integrated) and photoabsorption measurements. Fe films were deposited on a Cu(100) substrate at room temperature growing in a layer by layer fashion. The sample was then annealed to 810K in oxygen ambient. This oxidation process led to dramatic changes of the sample surface and electronic structure depending on initial Fe coverage. Half-metallic oxides such as CrO2 and Fe3O4 may provide opportunities for new magnetic devices since their single spin orientation at the Fermi …
De Haas-Van Alphen Effect Measurements On Cerium-Lanthanum-M-Indium (M = Cobalt, Rhodium, Iridium) Alloys., Umit Alver
De Haas-Van Alphen Effect Measurements On Cerium-Lanthanum-M-Indium (M = Cobalt, Rhodium, Iridium) Alloys., Umit Alver
LSU Historical Dissertations and Theses
The de Haas van Alphen (dHvA) effect, which measures the oscillatory component of the magnetization, in several CexLa1-x MIn5 (M = Rh, Co, Ir) alloys for 0 ≤ x ≤ 1 has been studied in detail using torque, pulse field and field modulation techniques. The frequencies, associated extremal cross sectional areas of the Fermi surface and effective masses of each sample throughout each of the series are reported. The energy band calculations of CeRhIn5, CeCoIn5 and CeIrIn5 assume that the 4f electrons in Ce are completely delocalized and these electrons make a significant contribution to the topology of the Fermi …
Atomic And Electronic Structure Of Ultra-Thin Metal Epitaxy On Metal And Semiconductor Surfaces., Dustin Alexander Hite
Atomic And Electronic Structure Of Ultra-Thin Metal Epitaxy On Metal And Semiconductor Surfaces., Dustin Alexander Hite
LSU Historical Dissertations and Theses
The fundamental study of heteroepitaxy has proved to have profound influences on technological applications of thin films, particularly due to the reduced dimensionality and quantum mechanical effects found in these unique nanostructured systems. In this study, particular attention is given to the correlations between atomic-scale morphology and the consequential electronic structure of heteroepitaxial systems that exhibit deviations from traditional growth modes in the initial stages of growth. Surface-confined systems are especially interesting because they exhibit properties that are fundamentally different from the bulk and often have no bulk analogs existing in nature. The surface-sensitive techniques of variable-temperature scanning tunneling microscopy …
Magnetic Measurements Of Rare Earth Hexaborides., Alem Abraha Teklu
Magnetic Measurements Of Rare Earth Hexaborides., Alem Abraha Teklu
LSU Historical Dissertations and Theses
The de Haas van Alphen (dHvA) effect is used, using the field modulation method, to study the orientation dependence of the extremal cross-sectional areas of the Fermi surface (FS) and effective masses of CexLa 1--xB6 alloys for x between 0 and 0.05. Previous measurements on these samples, using the pulsed field method, up to x = 1 showed that the FS was spin polarized at very low Ce concentration, at x = 0.05, indicating a spin polarity-dependent scattering mechanism. Moreover, the effective mass was enhanced by the increase of Ce concentration. This was the motivation for the present work which …
Atomic And Electronic Properties Of Neutral And Cationic Metallic Clusters., Andrew Marc Kolchin
Atomic And Electronic Properties Of Neutral And Cationic Metallic Clusters., Andrew Marc Kolchin
LSU Historical Dissertations and Theses
We find optimal atomic and electronic structures for neutral and singly, positively charged clusters of beryllium and beryllium-lithium (of the form BeLik) using density functional theory in the local spin density approximation. Ions are moved with a steepest descent method, and the electronic wave functions optimized using a fictitious dynamics with simulated annealing, as conceived by Car and Parrinello. Shell-like orbitals, filling angular momentum states in the order: 1s 2p 2s 1d, are obtained for the beryllium clusters. The same ordering is found for the BeLik clusters which indicates a departure from the ordering found in pure alkali clusters by …
Electron Paramagnetic Resonance And High Temperature Susceptibility Measurements In Cesium Hexabromide., Cabir Terzioglu
Electron Paramagnetic Resonance And High Temperature Susceptibility Measurements In Cesium Hexabromide., Cabir Terzioglu
LSU Historical Dissertations and Theses
To our knowledge the research reported here represents the first attempt to understand the 4f electronic structure in CeB6 using EPR. We report extensive temperature and angular dependent EPR measurements on a single crystal of CeB6 in the paramagnetic phase from 4 to 300 K at 35, 95, and a few measurements at 220 GHz. The 35 GHz measurements were performed at LSU and the 95 and 220 GHz measurements were performed at the National High Magnetic Field Laboratory, Tallahassee, FL. These experiments were made using a standard microwave frequency-locked spectrometer and magnetic field modulation. The measurements are supplemented by …
Transport And Magnetic Measurements Of Mono -Silicides., Ncholu Ignatius Manyala
Transport And Magnetic Measurements Of Mono -Silicides., Ncholu Ignatius Manyala
LSU Historical Dissertations and Theses
The purpose of this dissertation is to investigate the magnetic and transport properties of the dilution series connecting the mono-silicides FeSi, CoSi, and MnSi. We have focused on these materials since they allow the exploration of carrier doping of an unusual insulator, FeSi, whose properties are dominated by strong Coulomb interactions. These monosilicides all have the same cubic B-20 crystal structure making them ideal for an exploration of Fe1--x MnxSi and Fe1--yCoySi for all x and y between 0 and 1. The carrier sip and densities, as well as the proximity to magnetic phases can be controlled by the level …
Characterization Of Monomer-Containing Monolayer Films On Au Surfaces., Robert J. Willicut
Characterization Of Monomer-Containing Monolayer Films On Au Surfaces., Robert J. Willicut
LSU Historical Dissertations and Theses
Exploration into the nature of ultrathin, surface-confined films capable of electronic conduction has been the primary purpose of this dissertation. Specifically, the confinement of pyrrole monomer to Au surfaces through organosulfur linkages has been investigated. The synthesis of these new $\omega$-(N-pyrrolyl)alkanethiols is described herein. Cyclic voltammetry was utilized in this work to polymerize the monolayers and characterize the resulting films. Voltammetric analysis yielded currents in the correct potential region for poly(N-alkylpyrrole) charging/discharging. Other electrochemical studies revealed the ability of strong nucleophiles and electroinactive diluents to quench surface-confined polymer formation though they did not affect oxidation of the monomer. Exchange experiments …
Magnetic Measurements On Superconductors And Heavy Fermions., Donavan Weslee Hall
Magnetic Measurements On Superconductors And Heavy Fermions., Donavan Weslee Hall
LSU Historical Dissertations and Theses
Magnetization and de Haas - van Alphen (dHvA) measurements have been made on the high temperature superconductor Ba$\sb{0.6}$K$\sb{0.4}$BiO$\sb3$ and the heavy fermion CeB$\sb6$. First ever observations of the dHvA effect in Ba$\sb{0.6}$K$\sb{0.4}$BiO$\sb3$ are reported. Two dHvA spectrometers (pulsed field and field modulation) were used to measure two samples. Four frequencies are found in the field modulation data with the 11.6 kT orbit in good agreement with band structure calculations. The three lowest frequencies were measured with the pulsed field spectrometer. All dHvA measurements were made in the superconducting mixed state. These measurements indicate that Ba$\sb{0.6}$K$\sb{0.4}$BiO$\sb3$ has a Fermi surface. Magnetization …
An Adiabatic Bond Charge Model For The Phonon Properties Of Ii-Vi Materials And Superlattices., Bhagwan Das Rajput
An Adiabatic Bond Charge Model For The Phonon Properties Of Ii-Vi Materials And Superlattices., Bhagwan Das Rajput
LSU Historical Dissertations and Theses
I present an extension of the adiabatic Bond Charge model to study lattice dynamics of highly polar II-VI semi-conductors and semi-metals and CdTe-HgTe superlattices grown along (001) and (111) directions. This is the first attempt to study phonons in CdTe-HgTe superlattices. My results for phonon dispersion, specific heat and elastic constants for the six bulk materials are in good agreement with experimental observations. The best parameter sets for the six compounds show trends that are consistent with the parameters for group IV elemental semi-conductors and III-V compounds. For CdTe-HgTe superlattices, I find that the long range Coulomb interaction between particles …
Radio-Frequency Impedance Measurements On Thin Films Of Yttrium Barium Copper Oxide., Vibha K. Pant
Radio-Frequency Impedance Measurements On Thin Films Of Yttrium Barium Copper Oxide., Vibha K. Pant
LSU Historical Dissertations and Theses
The Kosterlitz-Thouless phase transition in epitaxial films of YBCO of varying thickness is studied. The phase transition is found to occur in these films in both zero fields and in perpendicular and parallel magnetic fields up to 0.5 T. In addition, the same transition is seen in a lead film of thickness less than the penetration depth in lead. This measurement is used as a calibration to determine the penetration depth in YBCO for both the zero-field case and perpendicular-field case. Once the penetration depth is determined, the effective thickness of the superconducting layer is calculated for all the films. …
Magneto-Optical Properties Of Cubic Ferromagnetic Metals., Neeraj Arvind Mainkar
Magneto-Optical Properties Of Cubic Ferromagnetic Metals., Neeraj Arvind Mainkar
LSU Historical Dissertations and Theses
I present a first principles, all electron, linear combination of Gaussian orbitals calculation of a comprehensive collection of magneto-optical properties of the cubic ferromagnetic metals nickel, iron and cobalt based on density functional theory. Among the many magneto-optical effects, this is the first ab initio study of the equatorial Kerr effect for absorption in the optical as well as the X-ray region, where it is called the X-ray magnetic linear dichroism. I find that in the optical region, this effect is of the order of 2% while in the X-ray region, it is of the order of 1% for the …
Synthesis Of Uv/X-Ray Sensitive Polymers And Their Applications As Resists., Jack Dean Davies
Synthesis Of Uv/X-Ray Sensitive Polymers And Their Applications As Resists., Jack Dean Davies
LSU Historical Dissertations and Theses
Aliphatic polycarbonates were synthesized by condensation of the bischloroformate of 2,2,4,4-tetramethyl-1,3-cyclobutanediol with cyclic aliphatic diols. Polycarbonates that lacked flexible methylene units in the backbone processed T$\sb{\rm g}\ >$ 139$\sp\circ$C. Copolycarbonates acted as resists when combined with cobalt(III)-am(m)ine tetraphenylborate complexes which act as photointiators, with tetraphenylborate serving as counter anion. The photoinitiator liberates either ammonia or ethylene diamine base upon UV exposure and the polycarbonate backbone is subject to nucleophilic attack at the carbonyl linkage by the base. Image tone was dependent on the base used. Amine complexes, Co(NH$\sb3)\sb6\sp{3+}$ effected a positive tone due to ammonia induced main chain degradation at …
Low Temperature Silicon Oxide And Fluorinated Silicon Oxide Films Prepared By Plasma-Enhanced Chemical Vapor Deposition Using Disilane As Silicon Precursor., Juho Song
LSU Historical Dissertations and Theses
The deposition and characterization of the silicon oxide and fluorinated silicon oxide films, as interlevel dielectrics in microelectronics devices, prepared by plasma enhanced chemical vapor deposition at low substrate temperature using $\rm Si\sb2H\sb6$ as silicon precursor are studied. The film deposition is limited by the mass transport regime, resulting in nearly temperature independent deposition rate. The characteristics for the silicon oxide films deposited at 120$\sp\circ$C show that the film etch rate is comparable to that obtained by TEOS-based PECVD at 400$\sp\circ$C and the leakage current is comparable to that of the films deposited at 350$\sp\circ$C with conventional SiH$\sb4$ precursor. It …
The Study Of Oxidation Of Magnesium(0001)., Anura Upul Goonewardene
The Study Of Oxidation Of Magnesium(0001)., Anura Upul Goonewardene
LSU Historical Dissertations and Theses
The oxidation of Mg(0001) was studied using ESDIAD (Electron Stimulated Desorption Ion Angular Distributions), LEED (Low Energy Electron Diffraction) and STM (Scanning Tunneling Microscopy). Disassociated oxygen and two species of oxygen were observed morphologically by STM and were identified as incorporated oxygen (mixed layer) and ionic oxide MgO(111). We observed that the step terraces and the dissociated oxygen are highly mobile and interact easily with the STM tip at room temperature. The true oxide was first observed on a double step pinning site as a protrusion elongated along the step edge. These sites pin the top terrace to the one …
Photoemission Studies Of Electronic Dispersion In Metals And Thin Film Systems., Zhe Qu
Photoemission Studies Of Electronic Dispersion In Metals And Thin Film Systems., Zhe Qu
LSU Historical Dissertations and Theses
We have studied the electronic dispersion of Cu and the Cu/Ru(0001) bimetallic system using photoelectron spectroscopy. Images of electron emission from Cu(100), Cu(111), and Cu/Ru(0001) have been obtained using an ellipsoidal-mirror analyzer (EMA). This energy analyzer collects photoemitted electrons over a large solid angle, preserving their angular information and providing an image of intensity versus emission angle. The images provide direct information on band dispersion. The surface state of Cu(111) was measured using the EMA at different binding energies. By combining these images, we have obtained the surface state dispersion in three dimensional E vs k space. Our results are …
Self-Consistent Cluster Embedding Calculation Method And The Electronic Structure Of Nickel Oxide And Cobalt Oxide., Haoping Zheng
Self-Consistent Cluster Embedding Calculation Method And The Electronic Structure Of Nickel Oxide And Cobalt Oxide., Haoping Zheng
LSU Historical Dissertations and Theses
We present a self-consistent cluster embedding method to study the electronic structure of solids by ab initio, local spin density functional calculations. A theoretical discussion from the viewpoint of total energy is given, and a definition of the total energy for an embedded cluster is introduced. We have constructed a general LCGO cluster-embedding program package, and developed a procedure to simulate the spin disordered states with local antiferromagnetic (AF) order. The electronic structures of NiO and CoO are studied by this method with a high quality basis set. The two materials show similar antiferromagnetic insulating ground states with both localized …
Magnetic Field Dependence Of The Specific Heat Of A Heavy Fermion System., Jai Won Kim
Magnetic Field Dependence Of The Specific Heat Of A Heavy Fermion System., Jai Won Kim
LSU Historical Dissertations and Theses
One of the distinguishing characteristics of heavy Fermion materials is the extraordinarily large size of the electronic specific heat at low temperatures. It is also observed that in some cases, the specific heat is reduced drastically by an external magnetic field. We show that this behavior can be simulated by using the non-degenerate lattice Anderson model on a 4-site tetrahedral cluster. Interactions included in the model are the on-site Couloumb repulsion between electrons in the f-orbital and the off-site spin conserving hybridization between electrons in the conduction and the f-orbitals. Our calculation is done by using the exact diagonalization method. …
Dynamic Properties Of Interacting Electrons., Lun Tan
Dynamic Properties Of Interacting Electrons., Lun Tan
LSU Historical Dissertations and Theses
The spectral weight functions and the optical conductivity of a highly correlated electronic system described by a simple Hubbard model are studied. The calculations are carried out for a small system, a cubic cluster of eight sites, by means of exact diagonalization using symmetrized basis functions. The spectral weight functions of a single hole (or electron) placed in an otherwise half-filled band are obtained. The density of states at different interaction strengths, ranging from weak to strong couplings, is studied. We observe the spreading of the spectral weight associated with some single-particle eigenstates over a large range of energies, and …
Neutral Impurity Scattering In Semiconductors., Kwok Chuen Kwong
Neutral Impurity Scattering In Semiconductors., Kwok Chuen Kwong
LSU Historical Dissertations and Theses
Neutral impurity scattering is a relatively untouched subject because it is only significant at very low temperatures. With the development of a new class of impurity band conduction devices that operate at cryogenic temperatures, it becomes necessary to describe the scattering in a more realistic fashion. We have calculated both elastic and inelastic scattering of electrons by substitional As in n-type Si, taking into account the anisotropy of the host band structure. Specifically, in regard to inelastic scattering, we calculated the differential and integrated cross sections for transitions from the ground state to the valley-orbit split states $\Gamma\sb{15}$ and $\Gamma\sb{12}$. …
Quantum Monte Carlo Simulations Of Hubbard And Anderson Models., Yi Zhang
Quantum Monte Carlo Simulations Of Hubbard And Anderson Models., Yi Zhang
LSU Historical Dissertations and Theses
We present, in this dissertation, a numerical simulation method to study interacting fermion systems. The general simulation procedures are discussed in connection with a description of a Quantum Monte Carlo simulation algorithm for interacting electrons on lattices. The algorithm presented here has been used to simulate interacting electrons on lattices, and it makes possible the study of substantially larger systems than can be studied by other numerical methods. As long as certain limits of applicability are respected, model Hamiltonians of interacting electrons can be studied without resort to uncontrolled approximations. The method then provides nearly exact solutions to model Hamiltonians …
Small Sample Calorimetry, And Specific Heat Of Gadolinium(1)Barium(2-X)Strontium(X)Copper(3)Oxygen(7)., Carter Harrison Watson
Small Sample Calorimetry, And Specific Heat Of Gadolinium(1)Barium(2-X)Strontium(X)Copper(3)Oxygen(7)., Carter Harrison Watson
LSU Historical Dissertations and Theses
The development of an automated small sample (0.5 to 50mg) calorimeter is discussed and evaluated. With this calorimeter, measurements of the specific heat of Gd$\sb1$Ba$\sb{\rm 2-x}$Sr$\sb{\rm x}$Cu$\sb3$O$\sb7$ for x = 0, 0.25, and 0.5 in the temperature range 0.6 to 3 K are reported. Measurements on the x = 0 sample agree with data collected by other groups. In addition, measurements in magnetic fields from 0 to 3 T for the x = 0 sample are reported. In each case a peak in the specific heat at the antiferromagnetic ordering temperature (the Neel temperature) is recorded and analyzed. Strontium doping …
The Study Of Model Hamiltonians On Finite Clusters., Duan Pin Chen
The Study Of Model Hamiltonians On Finite Clusters., Duan Pin Chen
LSU Historical Dissertations and Theses
We present two methods to study model Hamiltonians defined on clusters. One is the symmetrization of the Hilbert space basis according to irreducible representations of the symmetry group of the Hamiltonian. The other one adapts the Lanczos diagonalization method directly to the second quantized form of the Hamiltonian studied. By the symmetrization of the basis, one takes advantage of the symmetries of the Hamiltonian, and uses the group theory to find the invariant subspaces of the Hamiltonian in the complete Hilbert space. Then one needs only to work within the invariant subspaces. This method cuts down substantially the size of …
Magnetism In Bcc And Fcc Manganese., Gonzalo Fuster
Magnetism In Bcc And Fcc Manganese., Gonzalo Fuster
LSU Historical Dissertations and Theses
The electronic band structure, magnetic moment, and density of states of bcc and fcc manganese are calculated as a function of the lattice constant, using the LCGO method, on the local density approximation. For bcc manganese, two magnetic phases were found: a low moment state (m $\simeq$ 1 $\mu\sb{\rm B}$) and a high moment state (m $\ge$ 2.4 $\mu\sb{\rm B}$). For a small range of lattice constants (a = 5.9 to 6.025 a.u.), two local minima of the energy can coexist, yielding two different values of the moment for the same lattice constant. For fcc manganese, two phases were found: …
Electronic Structure Of Diatomic Molecules In The Local Density Approximation., Sitangshu Dhar
Electronic Structure Of Diatomic Molecules In The Local Density Approximation., Sitangshu Dhar
LSU Historical Dissertations and Theses
Ab initio self consistent spin polarized calculations have been performed for the electronic structure of diatomic molecules LiH, CO, NO, B(,2), O(,2), and F(,2), and for the transition metal atoms Fe, Co, and Ni. The local spin density functional theory was used. The single particle Kohn Sham equations are solved with the use of a Gaussian orbital approach. All the one and two electron integrals are calculated exactly. The matrix elements of the exchange correlation potential are computed numerically, using a two dimensional doubling grid for the molecules, and a one dimensional grid for the atoms. The total energy and …
Surface Landau-Level Resonance In Silver., John William Mitchell
Surface Landau-Level Resonance In Silver., John William Mitchell
LSU Historical Dissertations and Theses
Local values of the Fermi velocity of Ag are determined along the central zones of the (100) and (110) sample planes and at the neck in the (111) plane. Resonance spectra of magentic field induced quantum surface states, known as surface Landau-level resonances (SLLR), are used along with geometric factors calculated from analytical expressions for the Fermi surface to determine the location and Fermi velocity of the resonant electrons by an iterative process. These velocities are compared to those previously derived from inversions of cyclotron mass data and to point measurements made in the time of flight effect. In addition, …
Magneto-Optical Investigations Of Surface Space-Charge Layers In Metal-Oxide - Semiconductor (Mos) Systems., Asif Khandker
Magneto-Optical Investigations Of Surface Space-Charge Layers In Metal-Oxide - Semiconductor (Mos) Systems., Asif Khandker
LSU Historical Dissertations and Theses
The effect of finite boundaries on the Faraday rotation and ellipticity due to the two dimensional electron gas (2DEG) formed in the inversion layer of a metal-oxide-semiconductor (MOS) system is considered. Although the 2D Drude model is mainly used, many body effects are also considered using the memory-function approach. The validity of using a 2D model for the inversion layer is justified by showing its equivalence to a three dimensional model which includes multiple reflections within the inversion layer. The free carriers in the metal gate are investigated by calculating the surface admittance of the gate. It is found that …
Electronic Structure Of Small Iron Clusters., Keeyung Lee
Electronic Structure Of Small Iron Clusters., Keeyung Lee
LSU Historical Dissertations and Theses
The linear combination of Gaussian orbitals (LCGO) method has been adopted in developing a spin-polarized molecular orbital calculation code. The calculations are based on density functional theory using local density approximation for the exchange-correlation potential. A variational fitting method is used to obtain a charge density fit to avoid the need for using four-center integrals in evaluating the Coulomb potential. The matrix elements of the exchange potential are evaluated by direct numerical integration using a doubling grid developed for this purpose. Self-consistent solutions have been obtained using this method for Fe(,9) and Fe(,15) clusters with open boundaries and with body-centered …
Magnetic Susceptibility Of Nickel., Arun Kumar Chatterjee
Magnetic Susceptibility Of Nickel., Arun Kumar Chatterjee
LSU Historical Dissertations and Theses
Using density and functional theory, expressions for the longitudinal and transverse spin susceptibility of ferromagnetic metals have been derived in the local density approximation. The self consistent calculation of these susceptibilities necessitates the inversion of some infinite dimensional matrices, which have been done analytically using tight binding wave function for the 3d electrons. This amounted to a transformation from a Fourier representation to an orbital representation. This method is then applied for nickel using a semi-empirical band structure. In the light of these approximations it proved worthwhile to introduce some adjustable parameters to describe the electron interactions. In the transverse …