Electromagnetics and Photonics Commons^™

Enhanced Light Extraction Efficiency From Gan Light Emitting Diodes Using Photonic Crystal Grating Structures, Simeon S. Trieu

Master's Theses

Gallium nitride (GaN) light emitting diodes (LED) embody a large field of research that aims to replace inefficient, conventional light sources with LEDs that have lower power, higher luminosity, and longer lifetime. This thesis presents an international collaboration effort between the State Key Laboratory for Mesoscopic Physics in Peking University (PKU) of Beijing, China and the Electrical Engineering Department of California Polytechnic State University, San Luis Obispo. Over the course of 2 years, Cal Poly’s side has simulated GaN LEDs within the pure blue wavelength spectrum (460nm), focusing specifically on the effects of reflection gratings, transmission gratings, top and bottom …

Electroless Deposition Of Superconducting Magnesium Diboride Thin Films On Various Substrates, Khrupa Saagar Vijayaragavan

Wayne State University Theses

ABSTRACT

ELECTROLESS DEPOSITION OF SUPERCONDUCTING MAGNESIUM DIBORIDE THIN FILMS ON VARIOUS SUBSTRATES

by

KHRUPA SAAGAR VIJAYARAGAVAN

MAY 2010

Advisor: Dr. Susil K Putatunda

Dr. Gavin Lawes

Major: Chemical Engineering

Degree: Masters of Science

Superconducting thin films of magnesium diboride were synthesized by a novel electroless plating process. Electroless plating shares many similarities to electroplating with the major difference being the absence of a continuous bias voltage. Significantly, this work represents the first investigation where electroless deposition has been used to prepare compounds, as opposed to the elemental metals considered in all previous studies. Magnesium Diboride is a recently discovered superconducting …

Inductively Coupled Plasma Dry Etching Process On Planar Lightwave Circuit Fabrication., Chuah Khoon Seah

Student Works (2010-2019)

The main objective of this project is to master state-of-the-art techniques and knowledge in silica etching in order to achieve high quality waveguide circuit on Planar Lightwave Circuit devices. Another objective is to optimize the clean room research strength, surface characterization, microscopy techniques and similar semiconductor manufacturing processes.Initially, these processes were conducted with wet etching method that utilized diluted hydrofluoric acid (HF) and buffered oxide etch (BOE). Several problems arising such as mask peel-off, poor sidewall profile and defect waveguide channel during the pattern transfer process due to its’ isotropic nature. Alternatively, dry etching method was conducted via Inductively Coupled …

Focusing Electromagnetic Radiation In Dielectric Media, Mark A. Migliaccio Jr.

Electrical & Computer Engineering Theses & Dissertations

Bioelectrics and microwave imaging requires an ultra-wideband (UWB) antenna to deliver intense, short electromagnetic pulses into biological targets for the purpose of therapy and imaging. Two antennas with different focal distances, predicted by a two­ dimensional model, have been designed for focusing electromagnetic radiation in the near field.

Focusing is achieved through the use of prolate spheroidal reflector antennas with a conical wave launcher submerged in water. For an ultra-wideband feed signal, with a rise time of 200 picoseconds, the maximum electric field was found to be close to the edge of the reflector, a result that differs from the …

Shielding Effectiveness Of Superalloy, Aluminum, And Mumetal Shielding Tapes, Cindy Suit Cheung

Master's Theses

Using MIL-HDBK-419A, MATLAB and Nomographs, Shielding Effectiveness for the Magnetic Field, Electric Field, and Plane Wave were calculated over a frequency range from 10 Hz to 1 GHz. The three shielding tapes used included superalloy, aluminum, and mumetal. Calculations for Shielding Effectiveness involve the computation of Absorption Loss, Reflection Loss, and Re-Reflection Correction Factor. From the outcome of the calculations, it was suitable to conclude that all three metals fulfill the 40 dB Shielding Effectiveness requirements for SGEMP fields for frequencies greater or equal to 1 MHz. Accordingly, all three shielding tapes provide at least 40 dB of shielding to …

Analysis And Application Of The Bi-Directional Scatter Distribution Function Of Photonic Crystals, Robert B. Lamott

Theses and Dissertations

Photonic crystals (PCs) are periodic structures built from materials with different refractive indices repeated at sub-wavelength intervals, which results in unusual optical characteristics, including narrowband laser protection, and zero reflectance and high absorption anomalies. Most of the research into the optical properties of PCs has concentrated only on the small range of wavelengths and angles where these effects occur. To better understand where all light leaving a PC is scattered, a Complete Angle Scatter Instrument was used to analyze the scatter from three Guided Mode Resonance Filters designed for laser protection. In the plane of incidence, measurements of the scatter …

Temperature-Induced Phenomena In Systems Of Magnetic Nanoparticles, Abdul Wazed Bhuiya

Open Access Theses & Dissertations

Magnetic nanoparticle ensembles have received a lot of attention, stemming in part from their current and potential applications in biomedicine and in the development of high-density magnetic storage media. Key to the functionality of these systems are microscopic structures and mechanisms that make them exhibit unique properties and behave differently from their bulk counterparts.

We studied microscopic structures and processes that dictate macroscopic properties, behavior and functionality of magnetic nanoparticle ensembles. As the temperature T strongly influences the magnetic behavior of these systems, we studied temperature dependent magnetic properties using AC-susceptibility and DC-magnetization measurements carried out over a broad range …

Model For Alumina Nanopore-Based Optical Filter, Nathan Lehman, Rama Venkat, Robert A. Schill

Electrical & Computer Engineering Faculty Research

Alumina nanopore structures find applications in magnetic sensors, optical filters, and various biological devices. In this work, we present a ray-optics model for the optical filter. We present a detailed simulation and a simplified analytical expression for the reflectance as a function of the alumina parameters such as pore diameter, pore density, alumina thickness, and a function of the wavelength and angle of incidence of the illuminating plane electromagnetic wave. The reflectance vs wavelength in the range of 400–800nm obtained from the simulation and the analytical expression are compared with that of the experiments for thin and thick alumina. All …

The Effect Of Radiation On The Electrical Properties Of Aluminum Gallium Nitride/Gallium Nitride Heterostructures, John W. Mcclory

Theses and Dissertations

AlGaN/GaN Heterojunction Field Effect Transistors (HFETs) were irradiated at low temperature and the temperature dependent changes to drain current, gate current, capacitance, and transconductance were measured. The results were compared to the charge control model of the drain current and trap-assisted tunneling model of the gate current to determine the source of the radiation-induced changes. AlGaN/GaN HFETs demonstrated threshold voltage shifts and drain current changes after irradiation. After electron and neutron irradiation applied at ~80 K, measurement of the drain current at this temperature showed an increase that saturated after 10¹³ electrons/cm² or 10¹⁰ neutrons/cm² due …

Heating Methods And Detection Limits For Infrared Thermography Inspection Of Fiber-Reinforced Polymer Composites, Jeff R. Brown, H. R. Hamilton

Publications

The use of fiber-reinforced polymer (FRP) composites to strengthen existing civil infrastructure is expanding rapidly. Many FRP systems used to strengthen reinforced concrete are applied using a wet lay-up method in which dry fibers are saturated on site and then applied to the surface. This research investigated using infrared thermography (IRT) as a nondestructive evaluation (NDE) tool for detecting air voids and epoxy-filled holes in FRP systems bonded to a concrete substrate. Four small-scale specimens with FRP thicknesses ranging from 1 to 4 mm (0.04 to 0.16 in.) containing fabricated defects were constructed and inspected in a laboratory setting. Three …

Combinatorial Study Of Ni-Ti-Pt Ternary Metal Gate Electrodes On Hfo2 For The Advanced Gate Stack, K.-S. Chang, M. L. Green, J. Suehle, E. M. Vogel, H. Xiong, Jason R. Hattrick-Simpers, I. Takeuchi, O. Famodu, K. Ohmori, P. Ahmet, T. Chikyow, P. Majhi, B.-H. Lee, M. Gardner

Faculty Publications

The authors have fabricated combinatorial Ni–Ti–Pt ternary metal gate thin film libraries on HfO₂ using magnetron co-sputtering to investigate flatband voltage shift (ΔV_fb) , work function (Φ_m) , and leakage current density (J_L) variations. A more negative ΔV_fb is observed close to the Ti-rich corner than at the Ni- and Pt-rich corners, implying smaller Φ_m near the Ti-rich corners and higher Φ_m near the Ni- and Pt-rich corners. In addition, measured J_L values can be explained consistently with the observed Φ_m variations. Combinatorial methodologies prove to be useful …

Tunable Multiferroic Properties In Nanocomposite Pbtio3-Cofe2O4 Epitaxial Thin Films, M. Murakami, K.-S. Chang, M. A. Aronova, C.-L. Lin, Ming H. Yu, Jason R. Hattrick-Simpers, M. Wuttig, I. Takeuchi, C. Gao, B. Hu, S. E. Lofland, L. A. Knauss, L. A. Bendersky

Faculty Publications

We report on the synthesis of PbTiO₃–CoFe₂O₄ multiferroic nanocomposites and continuous tuning of their ferroelectric and magnetic properties as a function of the average composition on thin-film composition spreads. The highest dielectric constant and nonlinear dielectric signal was observed at (PbTiO₃)₈₅–(CoFe₂O₄)₁₅, where robust magnetism was also observed. Transmission electron microscopy revealed a pancake-shaped epitaxial nanostructure of PbTiO₃ on the order of 30 nm embedded in the matrix of CoFe₂O₄ at this composition. Composition dependent ferroics properties observed here indicate that there …

Exploration Of Artificial Multiferroic Thin-Film Heterostructures Using Composition Spreads, K.-S. Chang, M. A. Aronova, C.-L. Lin, M. Murakami, M.-H. Yu, Jason R. Hattrick-Simpers, O. O. Famodu, S. Y. Lee, R. Ramesh, M. Wuttig, I. Takeuchi, C. Gao, L. A. Bendersky

Faculty Publications

We have fabricated a series of composition spreads consisting of ferroelectric BaTiO₃ and piezomagnetic CoFe₂O₄ layers of varying thicknesses modulated at nanometer level in order to explore artificial magnetoelectricthin-film heterostructures. Scanning microwavemicroscopy and scanning superconducting quantum interference device microscopy were used to map the dielectric and magnetic properties as a function of continuously changing average composition across the spreads, respectively. Compositions in the middle of the spreads were found to exhibit ferromagnetism while displaying a dielectric constant as high as ≈120.

Effect Of Ga Content On Defect States In Cuin1-XGaXSe2 Photovoltaic Devices, Jennifer T. Heath, J. David Cohen, William N. Shafarman, Dongxiang Liao, Angus Rockett

Faculty Publications

Defects in the band gap of CuIn_1-xGa_xSe₂ have been characterized using transient photocapacitance spectroscopy. The measured spectra clearly show response from a band of defects centered around 0.8 eV from the valence band edge as well as an exponential distribution of band tail states. Despite Ga contents ranging from Ga/(In+Ga)=0.0 to 0.8, the defect bandwidth and its position relative to the valence band remain constant. This defect band may act as an important recombination center, contributing to the decrease in device efficiency with increasing Ga content.

The Effect Of Weak Acids Hydrolysis On The Sol-Gel Fabrication Of Silica Thin Film, Abdul Hamid

Student Works (2000-2009)

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Nitriding Of Titanium By Inductively Coupled Plasma, Abdul Hakim Hashim

Student Works (2000-2009)

A RF planar coil inductively coupled plasma syslem (ICP) is used in this project to nitride a commercially pure titanium substrate. The system is powered by a 600 W, 13.56 MHz, 50 Ω RF generator. The impedance matching is achieved by using an air­-core step-down transformer and a tunable vacuum capacitor. The electrical discharge characteristics of argon and argon-nitrogen admixture plasmas are investigated. Coil current, ion density and RF power transferred in the plasma at different pressure are studied. Nitriding of titanium using the system is found to be able to produce θ-TiN, ε-Ti2N and α-Ti(N) layers, as confirmed by …

Optical And Etching Studies Of Native Aluminum Oxide Layers For Use In Microcavity Photonic Devices, William L. Bernhard

Theses and Dissertations

Optical communication and computing systems are required to meet future information transfer and processing needs. Microcavity devices serve as an enabling technology to implement and integrate optoelectronic systems. It is important to understand the optical and mechanical properties of materials utilize within microcavity devices. Only then is it possible to accurately model and analyze structures. Microcavity structures incorporating a high aluminum content AlGaAs layers are designed, grown, processed, and measured. The processing of these devices includes the conversion of high aluminum-content AlGaAs layers to native aluminum oxide (AlO) layers through the process of thermal oxidation. This selective conversion of microcavity …

Multimode Quantitative Scanning Microwave Microscopy Of In Situ Grown Epitaxial Ba1-XSrXTio3 Composition Spreads, K. S. Chang, M. Aronova, O. Famodu, I. Takeuchi, S. E. Lofland, Jason R. Hattrick-Simpers, H. Chang

Faculty Publications

We have performed variable-temperature multimode quantitative microwavemicroscopy of in situepitaxial Ba_1−xSr_xTiO₃ thin-film composition spreads fabricated on (100) LaA₁O₃ substrates. Dielectric properties were mapped as a function of continuously varying composition from BaTiO₃ to SrTiO₃. We have demonstrated nondestructive temperature-dependent dielectric characterization of local thin-film regions. Measurements are simultaneously taken at multiple resonant frequencies of the microscope cavity. The multimode measurements allow frequency dispersion studies. We observe strong composition-dependent dielectric relaxation in Ba_1−xSr_xTiO₃ at microwave frequencies.

Mössbauer Effect Determination Of Relative Recoilless Fractions For Iron Oxides, Sei J. Oh, Desmond C. Cook

Physics Faculty Publications

The relative recoilless fraction (F-value) of each of six iron oxides, defined as the ratio of the recoil-free fractions of two different materials, was experimentally determined relative to hematite at 300 K and 77 K by Mössbauer spectroscopy. Using the relative recoil-free fractions compared to that of hematite, the relative recoilless fractions between all pairs of the seven iron oxides were determined. The F-values can allow conversion of Mössbauer subspectral areas to the relative atomic, molecular, or weight fractions of each iron oxide present in a mixed oxide phase sample.

Comparison Of Time-Domain Reflectometry Performance Factors For Several Dielectric Geometries: Theory And Experiments, S. V. Maheshwarla, R. Venkatasubramanian, Robert F. Boehm

Electrical & Computer Engineering Faculty Research

We propose three nontraditional dielectric geometries and present an experimental and theoretical analysis and comparison of time domain reflectometry (TDR) performances for them. The traditional geometry (the probes inserted in material of essentially infinite extent) is compared to three nontraditional geometries where the probes are affixed outside of a core sample, inside of a bore, or flat on the surface of a semi-infinite solid. Our derivation relates the velocity of electromagnetic wave propagation to the complex permittivities and permeabilities of the media and the geometry for the three nontraditional configurations. Experimental results for air, styrofoam, dry sand, wet sand of …

Electrical Properties Of P-Type Gainp2, Roy S. Calfas

Theses and Dissertations

The GaInP₂ n⁺—p junction diode has recently become important to the development of high efficiency GaInP₂GaAs dual junction solar cells, which have a demonstrated air mass 1.5 conversion efficiencies in excess of 27. In order to study the effects of long term exposure to the space environment, the GaInP₂ n+—p junction diodes were irradiated with a 1 MeV electron beam with a fluence of 10¹⁶ electrons/cm². Since little is known about deep level defects traps in GaInP₂, a deep level transient spectroscopy DLTS study was made to characterize the …

Cathodoluminescence Of Gaas, Tyler Smith

Electrical & Computer Engineering Theses & Dissertations

Cathodoluminescence of band-gap radiation across the bulk of a proposed semiconductor switch has been studied. Such a device relies on the efficient use of cathodoluminescence to modulate the conductivity of the switch. Diagnostics were configured to measure the intensity of band-gap radiation across the bulk of several switch samples. The measured results were compared to calculations based on a four energy level band-gap model which included two deep levels EL2 and HL10.

Magnetic-Field Distributions In Zinc-Nickel Ferrite, T. A. Dooling, Desmond C. Cook

Physics Faculty Publications

The Mössbauer effect has been used to study the microscopic magnetic properties of the cubic microwave ferrite (Zn_0.41Ni_0.59)Fe₂O₄ at 300 K. The magnetically split spectrum is broad and unresolved due to the overlap of the hyperfine magnetic fields at the tetrahedral and octahedral sites. This is caused by a distribution of magnetic fields at each site. The distribution is especially large and asymmetric at the octahedral site and is due to the fact that the iron atoms at this site are influenced by the presence of both iron and zinc at the tetrahedral …

Phase Changes In Plasma‐Sprayed Zinc‐Nickel Ferrite, T. A. Dooling, Desmond C. Cook

Physics Faculty Publications

The magnetic and crystalline properties of a plasma‐sprayed coating of the microwave absorbing zinc‐nickel ferrite, (Zn_0.41Ni_0.59 )Fe₂O₄ have been studied at 300 K using the Mössbauer effect and x‐ray diffraction (XRD). Both techniques indicate that the plasma‐sprayed material separated into two phases. The first is a nickel‐rich phase with magnetic fields of 47.5 and 44.5 T at the tetrahedral and octahedral sites, respectively. The second is a zinc‐rich phase, zinc meta‐ferrite, having a small magnetic field of 4.2 T. The quadrupole splitting of this second phase is ΔE=0.34 mm s⁻¹, …