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Articles 751 - 780 of 801

Full-Text Articles in Materials Science and Engineering

A Photoelectrochemical Investigation Of A.C.Modulated Passive Films On 304 Stainless Steel In Weak-Alkaline And Neutral Solution, Tianbao Du, Chunan Cao, Jiakang Yu, Haichao Lin Nov 1995

A Photoelectrochemical Investigation Of A.C.Modulated Passive Films On 304 Stainless Steel In Weak-Alkaline And Neutral Solution, Tianbao Du, Chunan Cao, Jiakang Yu, Haichao Lin

Journal of Electrochemistry

A photoelectrochemical investigation has been carried out on AISI 304 stainless steeI AV modulated passive film in 0.1mol/L Na2B4O7 and 0.5 mol/L Na2SO4 solution. Photo current curve depends on the potential, passive condition and testing solutions. The results of the measurements indicate that the photoresponse is determined by the defects in the electronic structure of the films whenthe defects lead to localized states in the bandgap region. It is concluded that the passive film on AISI 304 stainless steel is in a highly disordered amorphous state.

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Optical Characterization Of Indium Arsenide Antimonide Semiconductors Grown By Molecular Beam Epitaxy, Michael A. Marciniak Sep 1995

Optical Characterization Of Indium Arsenide Antimonide Semiconductors Grown By Molecular Beam Epitaxy, Michael A. Marciniak

Theses and Dissertations

The material parameters and crystalline quality of undoped, MBE-grown InAs1-xSbx nearly lattice-matched to (100) GaSb (-0.617% ≤ Δ a-a ≤ +0.708%) similar to material used for mid-infrared semiconductor lasers were determined by optical characterization. Absorption measurements at temperatures between 6-295 K determined the energy gap and wavelength-dependent absorption coefficient for each sample. The compositional dependence of the energy gap was anomalous when compared to previously reported data, suggesting phase separation existed in the material. The samples were also studied by temperature- and excitation-dependent photoluminescence (PL), which, for the majority of cases, showed only a single band-edge peak, …

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The Photoelectrochemical Studies Of Passive Films On Rebar Electrodes In Simulated Cement Pore Solution, Wei Chu, Yuanxiang Shi, Baoming Wei, Yong Yang, Xuguang Chen, Zugeng Lin Aug 1995

The Photoelectrochemical Studies Of Passive Films On Rebar Electrodes In Simulated Cement Pore Solution, Wei Chu, Yuanxiang Shi, Baoming Wei, Yong Yang, Xuguang Chen, Zugeng Lin

Journal of Electrochemistry

The electronic properties of the passive film on REBAR electrodes in simulatedcement pore solution (pH=9.0～13.8) have been investigated using in-situ photoelectrochemical methods. The results show that the passive film is composed of mixed oxides of ferrum, and it is an amorphous, n-type semiconductive film. Variations of pH values, ions in the solution and film-formation potentials can affect the composition of the films. There are two main stages in the growthof the film, with two rate functions characterized by linear relation between the film thickness and thelogarithm of time. The addition of inhibitor NaNO2 changes the composition, structure and growth …

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Laser Scanning In-Situ Photoelectrochemical Microscopictechnique And Its Applications, Zugeng Lin, Jinkua You, Xiangdong Zhuo, Chun Zhang, Yong Yang May 1995

Laser Scanning In-Situ Photoelectrochemical Microscopictechnique And Its Applications, Zugeng Lin, Jinkua You, Xiangdong Zhuo, Chun Zhang, Yong Yang

Journal of Electrochemistry

The main factors of the laser scanning in-situ photoelectrochemical microscopic measurement system which is set up in our lab have been discusaed in this paper. Some applications of this technique for in-situ study of modification and processing of semiconductor electrodes, monitoring of electro deposition process of semiconducting material and redox reaction occurring at metal oxide electrodes have also been presented. The results have shown that the technique is very powerful that for studing local photoelectrochemical properties of semiconductors and metal oxide electrodes. These provide important information on the micro structural and electronic properties in the solid/electrolyte interface.

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Photoelectrochemical And Spectroelectrochemical Studies Oniron Oxide Ultrafine Particles, Maizhi Yang, Yongjun Ji, Wen Zhang, Shengmin Cai, Xiaojiang Lu, Zhongqun Tian, Jin Luo May 1995

Photoelectrochemical And Spectroelectrochemical Studies Oniron Oxide Ultrafine Particles, Maizhi Yang, Yongjun Ji, Wen Zhang, Shengmin Cai, Xiaojiang Lu, Zhongqun Tian, Jin Luo

Journal of Electrochemistry

In this paper, Raman spectra, photocurrent and the UV-VIS reflectance aremeasured for studying the α-Fe2O3 ultrafine particles adsorbed on Pt electrode. The blue shifts of Raman peaks demonstrate the size quantization effect for the particles of 50 nm in diameter ascompared with the bulk material. With the changing of the potential, the photocurrent decrcases as the UV-VIS reflectance increases, and vice-versa. Therefore, the potential not only affects the hargetransfer direcdtion in the interface of electrode/redox couple, but also influences the light absortion onthe surface of particles. According to the results of photoelectrochemistry, we suggest that the cathodic …

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A Photoelectrochemical Investigation Of Zirconium Oxide Film, Maizhi Yang, Ping Wei, Di Quarto F., Piazza S., Sunseri C. Feb 1995

A Photoelectrochemical Investigation Of Zirconium Oxide Film, Maizhi Yang, Ping Wei, Di Quarto F., Piazza S., Sunseri C.

Journal of Electrochemistry

A photoelectrochemical investigation has been carried out on zirconium initialoxide film and its oxide film grownanodically at constant rate up to different thickness. Both anodicand cathedic photocurrents on the photocurrent spectrum depended on the potential, but had littlerelation with the forming anedic films or measuring solutions. Photocurrent spectrum and photocurrenttransients suggested that the oxide films on zirconium were duplex layers structure. The internal layerwas ZrO2 and the external layer ZrO2·(H2O)n. The photocurrent included photogenerated carrier ininternal and external oxide films, as well as internal photoinjection process for electrons from thesubstrate metal into the …

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Molten Salt Electrolytes For Electrodeposition Of Cdte Films, Arif Raza, Robert Engelken, Brandon Kemp, Arees Siddiqui, Omer Mustafa Jan 1995

Molten Salt Electrolytes For Electrodeposition Of Cdte Films, Arif Raza, Robert Engelken, Brandon Kemp, Arees Siddiqui, Omer Mustafa

Journal of the Arkansas Academy of Science

We report preliminary investigation of several molten salt electrolytes containing CdCl2 and TeCl4 for the electrodeposition of CdTe films at temperatures well above (>250 °C) those used with aqueous and organic electrolytes. These high temperatures have potential todramatically increase the crystallite size (Poole, Engelken, et al., 1994), as is important for optoelectronic device applications of CdTe, a leading II-VIsemiconductor. This paper willsurvey the results obtained withelectrolytes such as B2O,/HBO2 (m.p. - 230'C), NaCH3COO (m.p. » 324°C), ZnCl2 (m.p. - 283*C), and LiCl/KCl (m.p. * 350 °C), with an emphasis on the latter two. Key material to be presented includes …

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Diagnostics Of Cdte Electrodeposition By Rest Potential Voltammetry, Brandon Kemp, Robert Engelken, Arif Raza, Arees Siddiqui, Omer Mustafa Jan 1995

Diagnostics Of Cdte Electrodeposition By Rest Potential Voltammetry, Brandon Kemp, Robert Engelken, Arif Raza, Arees Siddiqui, Omer Mustafa

Journal of the Arkansas Academy of Science

Due to the extreme sensitivity of the partial elemental currents (i.e.,iCd, iTe) and, hence, stoichiometry to deposition voltage, temperature, mass transport, and ambient light intensity during electrodeposition of semiconductor films, it is important to implement in-situ methods for monitoring the stoichiometry and related semiconductor efficacy of the growing film. We report investigation of open circuit rest potential (Eoc) voltammetry as one such method during electrodeposition of CdTe from aprotic electrolytes such as ethylene glycol. Plots of transient open circuit potential versus sweep voltage exhibit distinct transition and plateau structures corresponding to Te, CdTe, and Cd phases and correlating with the …

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Total Ionizing Dose Effects In Mosfet Devices At 77 K, Kevin J. Daul Dec 1994

Total Ionizing Dose Effects In Mosfet Devices At 77 K, Kevin J. Daul

Theses and Dissertations

Total ionizing dose effects on thermal oxide and reoxidized nitrided oxide (RNO) MOSFET devices at 77 K were studied. The MOSFETs were immersed in liquid nitrogen and irradiated, using a 60Co source, up to 1 Mrad(Si) at a dose rate of 107 rads(Si)-sec. Drain current-gate voltage characteristics were obtained and used to determine threshold voltage and transconductance. At 77 K the subthreshold slopes indicated no observed buildup of interface states in any of the transistors. Furthermore, all transistors experienced very little change in the transconductance. Typical negative shifts in threshold voltage as dose increased were observed in all of …

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Photoluminescence Spectroscopy Of 4h- And 6h-Sic, William A. Davis Dec 1994

Photoluminescence Spectroscopy Of 4h- And 6h-Sic, William A. Davis

Theses and Dissertations

Typical undoped bulk grown SiC shows n- or p-type conductivity due to residual impurities such as nitrogen, boron, or aluminum. In order to produce high resistivity material, vanadium can be used as a compensating dopant. Since vanadium is an amphoteric dopant in SiC, it produces either a donor state, VSi4+(3d1) → VSi5+(3d0), or an acceptor state, VSi4+(3d1) → VSi3+(3d2). Thus, vanadium doping can compensate both n- and p-type conductivity. In this work, vanadium doped and undoped 4H- and 6H-SiC grown …

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Model Of A Single Impurity In A Wide Bandgap Semiconductor Describing Electric Field Screening, Anthony N. Dills Dec 1994

Model Of A Single Impurity In A Wide Bandgap Semiconductor Describing Electric Field Screening, Anthony N. Dills

Theses and Dissertations

A mathematical model of the influence on electric field screening arising from a single impurity in a wide bandgap semiconductor has been numerically investigated and compared with analytically derived solutions. The parameter set chosen to perform the comparison of analytical solution and numerical solution is based upon a bismuth silicate crystal. Both the analytical calculations and the numerical calculations are an attempt to mathematically model the internal electric field within a semiconductor. Two types of impurities were looked at: a single donor level and a single trap impurity level. In general, after an abrupt application of a voltage across the …

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Design, Fabrication, Modeling, And Optical Characterization Of Organic Polymer Nonlinear Directional Couplers, John N. Berry Dec 1994

Design, Fabrication, Modeling, And Optical Characterization Of Organic Polymer Nonlinear Directional Couplers, John N. Berry

Theses and Dissertations

This research was an investigation into the suitability of a recently developed polymer, polyphenylene, as a material for integrated optical circuits (IOCs). Polymers show great promise in the area of IOCs because of material processing advantages, compatibility with most existing integrated circuit technology, and relatively strong nonlinear optical characteristics. This thesis contains an overview of: dielectric waveguides, linear and nonlinear directional coupler theory; various models useful in the design and analysis of optical waveguides; the fabrication of three different waveguide designs; the experimental apparatus and procedure used to optically characterize the waveguides; and the experimental results of the characterization. Waveguiding …

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The Junction Characteristics And Current Conduction Mechanisms Of Gainp2 N+P Diodes And Solar Cells, Kitt C. Reinhardt Dec 1994

The Junction Characteristics And Current Conduction Mechanisms Of Gainp2 N+P Diodes And Solar Cells, Kitt C. Reinhardt

Theses and Dissertations

This work involves an investigation of GaInP2 n+p diode and solar cell dark current mechanisms, the defect centers that affect these mechanisms, and the response of dark current and solar cell photovoltaic parameters to I MeV electron irradiation and thermal annealing. Dark current due to carrier diffusion, recombination, and tunneling were identified, and recombination current was found to dominate at the maximum power-point voltage of the GaInP2 solar cells. Carrier recombination was found to occur via defect centers at the perimeter and within the bulk of the junction. Two deep majority-hole trap centers were found at E …

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The Current Voltage Characteristics Of Electron Beam Controlled Thin Film Diamond Switches, Christopher Anthony Molina Oct 1994

The Current Voltage Characteristics Of Electron Beam Controlled Thin Film Diamond Switches, Christopher Anthony Molina

Electrical & Computer Engineering Theses & Dissertations

The dark current of natural diamond thin films and the induced current due to electron-beam irradiation was measured up to a range of 7000Ncm'. The contact material was aluminum, annealed and unannealed. Switching experiments were performed with electron energies ranging from 70keV to 172keV. The switching results obtained are strongly dependent on the biasing polarity, incident electron energy, and whether the contact is blocking or Ohmic in nature. A simple model which takes traps into consideration allows us to explain the various switching responses. The range of electrons which define, in part, the switch mode was measured for one sample …

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Transient Simulations And Modelling Of Semi-Insulating Gaas Photoconductive Switches, Prasun Kumar Raha Jul 1994

Transient Simulations And Modelling Of Semi-Insulating Gaas Photoconductive Switches, Prasun Kumar Raha

Electrical & Computer Engineering Theses & Dissertations

The primary objective of this thesis is to develop a one-dimensional transient simulator for Photoconductive Semiconductor Switches (PCSS) taking into consideration the material characteristics, the internal physical effects, and the external circuit. Simulations have been performed to study the device behavior at different voltage levels for copper-doped silicon-compensated GaAs material, though other materials could easily be simulated by changing the parameters. The model includes hole transport, and the results demonstrate the effect of hole injection, with and without recombination centers. In addition to developing a one-dimensional transient simulator, the role of various physical effects, such as the field-dependence of trapping …

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The Excitation Mechanism Of Praseodymium-Doped Semiconductors, Paul L. Thee Jun 1994

The Excitation Mechanism Of Praseodymium-Doped Semiconductors, Paul L. Thee

Theses and Dissertations

This study on praseodymium Pr luminescence in AlxGa1-xAs was conducted to enhance the understanding of the excitation mechanism. Pr was implanted at 390 keV with doses from 5 x 1012 to 5 x 1013 cm2 into AlxGa1-xAs x0.0 to 0.50 wafers which were annealed using the rapid thermal annealing RTA method. Low temperature photoluminescence PL was conducted using an Ar-ion laser and Ge detector. PL emissions of Pr from all hosts include peaks near 1.3 and 1.6 µm which are assigned to the intra-4f transitions of 1G4 yielding 3H5 …

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Rapid And Accurate Timing Simulation Of Radiation-Hardened Digital Microelectronics Using Vhdl, Charles P. Brothers Jr. Mar 1994

Rapid And Accurate Timing Simulation Of Radiation-Hardened Digital Microelectronics Using Vhdl, Charles P. Brothers Jr.

Theses and Dissertations

This dissertation presents the development of a fast, accurate, timing simulation capability based on VHSIC Hardware Description Language VHDL without the use of back annotation of timing delay information. This VHDL-based timing simulator is intended for use with radiation-hardened microelectronics in simulating timing of circuit operation in pre-radiation, post-radiation 1 MradSi total dose, and ionizing dose radiation environments. Development of the timing models are presented. The implementation of the timing models are incorporated into a VHDL library composed of basic logic gates and flip-flops. Simulations of complex circuits were run in SPICE and VHDL to assess the timing accuracy and …

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Solid State Nmr Of Hydrogen In Thin Film Synthetic Diamond, G. Burnside, Roger M. Hawk, Richard A. Komoroski, W. D. Brown Jan 1994

Solid State Nmr Of Hydrogen In Thin Film Synthetic Diamond, G. Burnside, Roger M. Hawk, Richard A. Komoroski, W. D. Brown

Journal of the Arkansas Academy of Science

Thin film synthetic diamond promises to be the next semiconductor material, if the manufacturing processes which produce it can be controlled. Solid state nuclear magnetic resonance (NMR) using magic angle spinning (MAS) is used to measure the content of hydrogen in diamond which controls the resistivity of the diamond thin films. Spectral results are presented for proton NMR of thin film synthetic diamond. Experimental calibration techniques using BaF2 as the hydrogen standard will be discussed, as well as acquisition times, pulsing sequences, spinning rates, and rotor composition.

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Reaction Of Titanocene Dichloride With Acetylenedicarboxylate, Tanya L. Hagler, Mark Draganjac, Paul M. Nave, J. Ed Bennett, Farooq Kahn, Robert Engelken, Gerard Williams, Chris Poole, Kwok Fai Yu Jan 1994

Reaction Of Titanocene Dichloride With Acetylenedicarboxylate, Tanya L. Hagler, Mark Draganjac, Paul M. Nave, J. Ed Bennett, Farooq Kahn, Robert Engelken, Gerard Williams, Chris Poole, Kwok Fai Yu

Journal of the Arkansas Academy of Science

The reaction of Cp2TiCl2 with either the mono- or dipotassium salt of acetylenedicarboxylic acid (ADC) gives high yields of an insoluble orange product. The insoluble compound shows potential semiconductor behavior, as evidenced by an apparent bandgap in the orange region of the visible spectrum. Under N2 ,the compound decomposes at 238° C, eventually losing approximately 46% total mass up to 1350° C. The exothermic decomposition in air, beginning at 235° C, results in the formation of titanium oxides.

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Tetraethylene Gycol-Based Electrolytes For High Temperature Electrodeposition Of Compound Semiconductors, Chris Poole, Robert Engelken, Brandon Kemp, Jason Brannen Jan 1994

Tetraethylene Gycol-Based Electrolytes For High Temperature Electrodeposition Of Compound Semiconductors, Chris Poole, Robert Engelken, Brandon Kemp, Jason Brannen

Journal of the Arkansas Academy of Science

We report an investigation of tetraethylene glycol (TEG) solutions of chloride salts (CdCl2 ,TeCl4 ,and HgCl2 ) for electrodeposition of films of CdTe and Hg1.xCdxTe, leading II-VI semiconductors. The high boiling point (314°C), below-room temperature (T) (-6°C) melting point, adequate metal chloride solubilities, and low toxicity of TEG make it a good candidate for electrodeposition at T > 200°C. Such temperatures tend to activate growth of larger crystallites than with aqueous electrolytes at T< 100 °C, as are advantageous in optoelectronic applications. Initial results do, indeed, indicate a dramatic increase in crystallinity with deposition temperature, especially for the CdTe films which are nearly amorphous when grown at room temperature. Hg1.xCdxTe films (x< 0.5) are marginally polycrystalline when grown at room temperature but also improve in crystallinity at higher growth temperatures. There appears to be a strong decrease in film adherence and uniformity as growth temperature increases for both materials probably because the greatly increased carrier concentrations at higher temperatures increase film conductivity which, in turn, supports easy electroplating of protruding loose dendritic and/or columnar crystallites, instead of the monolayer-by monolayer growth of lower conductivity material as occurs at lower temperatures, especially in the higher bandgap/lower conductivity CdTe. The same increase in film conductivity with temperature is responsible for the decrease in the relative photosensitivity of both the CdTe and Hg1.x CdxTe with temperature. At all temperatures, the inferior adherence, uniformity, and photosensitivity as well as the superior crystallinity of Hg1.xCd xTe over that of the CdTe are also explained by its lower bandgap and higher conductivity. On balance, however, the initial results prove the utility of high temperature TEG electrolytes for electrodepositing CdTe and Hg1.xCdxTe films with much better crystallinity than for those grown at lower temperatures, notably in aqueous baths.

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Evaluation Of Photodiode Arrays For Use In Rocket Plume Monitoring And Diagnostics, Dallas Snider, M. Keith Hudson, Robert B. Shanks, Reagan Cole Jan 1994

Evaluation Of Photodiode Arrays For Use In Rocket Plume Monitoring And Diagnostics, Dallas Snider, M. Keith Hudson, Robert B. Shanks, Reagan Cole

Journal of the Arkansas Academy of Science

The spectroscopic analysis of plume emissions is a non-intrusive method which has been used to check for fatigue and possible damage throughout the pumps and other mechanisms in a rocket motor or engine. These components are made of various alloys. Knowing the composition of the alloys and for which parts they are used, one can potentially determine from the emissions in the plume which component is failing. Currently, Optical Multichannel Analyzer systems are being used which utilize charge coupled devices, cost tens of thousands of dollars, are somewhat delicate, and usually require cooling. We have developed two rugged instruments using …

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Influence Of Embedded Optical Fibers On Compressive Strength Of Advanced Composites, Stefan B. Dosedel Dec 1993

Influence Of Embedded Optical Fibers On Compressive Strength Of Advanced Composites, Stefan B. Dosedel

Theses and Dissertations

This study investigated the effects of embedding optical fibers into advanced composite materials. This combination was meant to simulate 'smart structures' that have been shown to sense several different variables in the composite including strain, temperature, and damage. A laminate orientation taken from an existing aircraft structure was used to fabricate sixteen groups of specimens which were subjected to compression testing in an IITRI fixture to determine the ultimate compressive strength and modulus of elasticity. Ten of these groups were fabricated with optical fibers while the other six were control groups and contained no optical fibers. This study showed that …

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The Effects Of Optical Feedback On Polarization Of Vertical Cavity Surface Emitting Lasers, Gregory J. Vansuch Dec 1993

The Effects Of Optical Feedback On Polarization Of Vertical Cavity Surface Emitting Lasers, Gregory J. Vansuch

Theses and Dissertations

Vertical Cavity Surface Emitting Lasers VCSELs are a type of semiconductor laser with a cavity oriented orthogonally to the planes of material growth. These lasers differ from conventional edge emitting lasers in several important ways. They have symmetric output beams and they are easily built into two dimensional arrays, making them very attractive as photonic components. The characteristic of interest in this thesis is polarization. While the asymmetric cavities of edge emitters exhibit a clear preference for light polarized in a particular direction, the cylindrically symmetric cavity of a VCSEL has no clear preference. Therefore, it should be relatively easy …

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Light Injection From An Active Cladding To The Core Of A Fiber Optic Fluorosensor, Alvin Leon Bryant Jul 1993

Light Injection From An Active Cladding To The Core Of A Fiber Optic Fluorosensor, Alvin Leon Bryant

Electrical & Computer Engineering Theses & Dissertations

A fluorosensor works on the basis of light injection from the clad into the core of an optical fiber. The sensitivity of such a sensor depends on the efficiency of light injection. Conditions necessary for a high injection efficiency are experimentally determined. The refractive index difference between the core and the clad,ncore -nclad, must be maximized to achieve a high injection efficiency. Since an air clad has the least refractive index, a bare core fiber will have a maximum efficiency. Standard optical fibers used for communication employ a minimum value for ncore -nclad, in order …

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Study Of Single-Fiber Fiber Optic Lever Microphone, Trung Duc Nguyen Jul 1993

Study Of Single-Fiber Fiber Optic Lever Microphone, Trung Duc Nguyen

Electrical & Computer Engineering Theses & Dissertations

Fiber optic sensors are widely used in today's technological applications, providing many advantages that conventional sensors lack. In particular, there is a demand in hypersonic applications to develop microphones to measure acoustic pressure that performs in high temperature and noisy surroundings. This thesis analyzes fiber optic lever microphones (FOLM), since they perform at high temperatures. An FOLM system is an intensity modulated sensor, which is simple to implement and is small in size. Two models of the FOLM have been fabricated and calibrated. The first model uses a seven-element fiber array while the second uses a single-fiber to transmit and …

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Design And Performance Evaluation Of A Gas Chromatograph Micromachined In A Single Crystal Silicon Substrate, Rocky R. Reston Mar 1993

Design And Performance Evaluation Of A Gas Chromatograph Micromachined In A Single Crystal Silicon Substrate, Rocky R. Reston

Theses and Dissertations

This investigation designed and developed a miniature gas chromatograph (GC) using silicon micromachining techniques. The GC is composed of a miniature sample injector (10 µl sample loop); a 0.9 m long, rectangular-shaped (300 µm width and 10 micrometers height) capillary column coated with a 0.2 µm thick copper phthalocyanine (CuPc) stationary phase; and a dual-detector scheme incorporating a CuPc-coated chemiresistor and a 125 µm diameter thermal conductivity detector bead. Micromachining was employed to fabricate the sample injector interface, the GC column, and the dual-detector cavity. A novel processing technique was developed to sublime the CuPc stationary phase coating on the …

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Luminescence Study Of Ion-Implanted And Mbe-Grown Er-Doped Gaas And AlXGa1-XAs, Jose E. Colon Mar 1993

Luminescence Study Of Ion-Implanted And Mbe-Grown Er-Doped Gaas And AlXGa1-XAs, Jose E. Colon

Theses and Dissertations

The excitation and de-excitation mechanisms of the 1.54 microns emissions, from ion implanted and MBE grown GaAs:Er and AlxGa1-xAs:Er, were studied through luminescence experiments. Experimental techniques included photoluminescence, time resolved photoluminescence, and selective excitation photoluminescence. The Er3+ emissions were studied as a function of Er concentration, aluminum mole friction, n- and p-type doping level, and annealing temperature. In addition oxygen co-doping studies were done in order to determine the role played by oxygen in the Er3+ luminescence.

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Excitation And De-Excitation Mechanisms Of Er-Doped Gaas And Algaas, David W. Elsaesser Dec 1992

Excitation And De-Excitation Mechanisms Of Er-Doped Gaas And Algaas, David W. Elsaesser

Theses and Dissertations

Electrical and optical characterization have been performed on GaAs and AlxGa1-xAs samples doped with Er either by ion implantation or during Molecular Beam Epitaxial (MBE) growth. Deep Level Transient Spectroscopy (DLTS) and Temperature-Dependent Hall Effect (TDH) measurements indicated the presence of two hole traps in Er-doped GaAs, at 35 and 360 meV above the valence band maximum. The former (shallower) center was thought to be due to Er substituting for a Ga atom (ErGa) and giving rise to an isoelectronic impurity potential. The second center was attributed to an Er atom occupying an interstitial …

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Phase Conjugation In Optical Fiber Via Stimulated Brillouin Scattering With Feedback From A Barium Titanate Crystal, Patrick R. Emmert Dec 1992

Phase Conjugation In Optical Fiber Via Stimulated Brillouin Scattering With Feedback From A Barium Titanate Crystal, Patrick R. Emmert

Theses and Dissertations

The goal of this thesis was to obtain phase conjugation in multi-mode optical fiber via stimulated Brillouin scattering (SBS) with the aid of a barium titanate crystal which formed a phase conjugate cavity for the Stokes beam. SBS was demonstrated but the SBS threshold was unaffected by the presence of the barium titanate crystal and no evidence for the presence of phase conjugation in the optical fiber was obtained.

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Processability Of Polythiophene Thin Films By Ultraviolet Photo Bleaching, Derek D. Fletcher Dec 1992

Processability Of Polythiophene Thin Films By Ultraviolet Photo Bleaching, Derek D. Fletcher

Theses and Dissertations

Materials possessing strong ��(3) optical properties such as Polythiophene are sought for the production of optical switches. Polythiophene thin films produced by plasma enhanced CVD show a surface rms roughness of 10-15 angstroms over single square micron areas which is acceptable for wave guiding in the near IR. This research investigates permanently changing the optical properties of such a thin film by exposure to UV radiation (254 nm, 35 mW/cm2), known as photo bleaching, in hope of creating a refractive index boundary for use in total internal reflection. After 60 minutes exposure the refractive index shows …

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