WorldWideScience

Sample records for terbium arsenides

  1. Elastic properties of terbium

    DEFF Research Database (Denmark)

    Spichkin, Y.I.; Bohr, Jakob; Tishin, A.M.

    1996-01-01

    The temperature dependence of the Young modulus along the crystallographic axes b and c (E(b) and E(c)), and the internal friction of a terbium single crystal have been measured. At 4.2 K, E(b) and E(c) are equal to 38 and 84.5 GPa, respectively. The lattice part of the Young modulus and the Debye...... temperature has been calculated. The origin of the Young modulus anomalies arising at the transition to the magnetically ordered state is discussed....

  2. A FETISH for gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Barron, A.R. [Rice Univ., Houston, TX (United States)

    1996-12-31

    An overview of the development of a new dielectric material, cubic-GaS, from the synthesis of new organometallic compounds to the fabrication of a new class of gallium arsenide based transistor is presented as a representative example of the possibility that inorganic chemistry can directly effect the development of new semiconductor devices. The gallium sulfido compound [({sup t}Bu)GaS]{sub 4}, readily prepared from tri-tert-butyl gallium, may be used as a precursor for the growth of GaS thin films by metal organic chemical vapor deposition (MOCVD). Photoluminescence and electronic measurements indicate that this material provides a passivation coating for GaAs. Furthermore, the insulating properties of cubic-GaS make it suitable as the insulating gate layer in a new class of GaAs transistor: a field effect transistor with a sulfide heterojunction (FETISH).

  3. Critical scattering of neutrons from terbium

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage; Dietrich, O.W.; Marshall, W.

    1968-01-01

    The inelasticity of the critical scattering of neutrons in terbium has been measured above the Neél temperature at the (0, 0, 2−Q) satellite position. The results show that dynamic slowing down of the fluctuations does occur in a second‐order phase transition in agreement with the general theory...

  4. Semiconductor composition containing iron, dysprosium, and terbium

    Energy Technology Data Exchange (ETDEWEB)

    Pooser, Raphael C.; Lawrie, Benjamin J.; Baddorf, Arthur P.; Malasi, Abhinav; Taz, Humaira; Farah, Annettee E.; Kalyanaraman, Ramakrishnan; Duscher, Gerd Josef Mansfred; Patel, Maulik K.

    2017-09-26

    An amorphous semiconductor composition includes 1 to 70 atomic percent iron, 15 to 65 atomic percent dysprosium, 15 to 35 atomic percent terbium, balance X, wherein X is at least one of an oxidizing element and a reducing element. The composition has an essentially amorphous microstructure, an optical transmittance of at least 50% in at least the visible spectrum and semiconductor electrical properties.

  5. Window structure for passivating solar cells based on gallium arsenide

    Science.gov (United States)

    Barnett, Allen M. (Inventor)

    1985-01-01

    Passivated gallium arsenide solar photovoltaic cells with high resistance to moisture and oxygen are provided by means of a gallium arsenide phosphide window graded through its thickness from arsenic rich to phosphorus rich.

  6. Development of a Multi-layer Anti-reflective Coating for Gallium Arsenide/Aluminum Gallium Arsenide Solar Cells

    Science.gov (United States)

    2015-07-01

    Aluminum Gallium Arsenide Solar Cells by Kimberley A Olver Approved for public release; distribution unlimited...Development of a Multi-layer Anti-reflective Coating for Gallium Arsenide/Aluminum Gallium Arsenide Solar Cells by Kimberley A Olver...Aluminum Gallium Arsenide (AlGaAs) Solar Cells 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Kimberley A Olver

  7. Spin Injection in Indium Arsenide

    Directory of Open Access Journals (Sweden)

    Mark eJohnson

    2015-08-01

    Full Text Available In a two dimensional electron system (2DES, coherent spin precession of a ballistic spin polarized current, controlled by the Rashba spin orbit interaction, is a remarkable phenomenon that’s been observed only recently. Datta and Das predicted this precession would manifest as an oscillation in the source-drain conductance of the channel in a spin-injected field effect transistor (Spin FET. The indium arsenide single quantum well materials system has proven to be ideal for experimental confirmation. The 2DES carriers have high mobility, low sheet resistance, and high spin orbit interaction. Techniques for electrical injection and detection of spin polarized carriers were developed over the last two decades. Adapting the proposed Spin FET to the Johnson-Silsbee nonlocal geometry was a key to the first experimental demonstration of gate voltage controlled coherent spin precession. More recently, a new technique measured the oscillation as a function of channel length. This article gives an overview of the experimental phenomenology of the spin injection technique. We then review details of the application of the technique to InAs single quantum well (SQW devices. The effective magnetic field associated with Rashba spin-orbit coupling is described, and a heuristic model of coherent spin precession is presented. The two successful empirical demonstrations of the Datta Das conductance oscillation are then described and discussed.

  8. Surface magnetism of gallium arsenide nanofilms

    OpenAIRE

    Lu, Huan; Yu, Jin; Guo, Wanlin

    2017-01-01

    Gallium arsenide (GaAs) is the widest used second generation semiconductor with a direct band gap and increasingly used as nanofilms. However, the magnetic properties of GaAs nanofilms have never been studied. Here we find by comprehensive density functional theory calculations that GaAs nanofilms cleaved along the and directions become intrinsically metallic films with strong surface magnetism and magnetoelectric (ME) effect. The surface magnetism and electrical conductivity are realized v...

  9. Superlattice Intermediate Band Solar Cell on Gallium Arsenide

    Science.gov (United States)

    2015-02-09

    AFRL-RV-PS- AFRL-RV-PS- TR-2015-0048 TR-2015-0048 SUPERLATTICE INTERMEDIATE BAND SOLAR CELL ON GALLIUM ARSENIDE Alexandre Freundlich...SUBTITLE 5a. CONTRACT NUMBER FA9453-13-1-0232 Superlattice Intermediate Band Solar Cell on Gallium Arsenide 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER

  10. Heat blocking gallium arsenide solar cells

    Science.gov (United States)

    Rahman, F.; Farmer, C. D.; Schmidt, C.; Pfaff, G.; Stanley, C. R.

    2008-02-01

    The solar cell industry is witnessing an era of unprecedented growth and this trend is set to continue for the foreseeable future. Here we describe a heat reflection pigment-coated single-junction gallium arsenide solar cell that is capable of reflecting heat-inducing near-infrared radiation. The cell maintains its performance better than non-coated cells when exposed to infrared-rich radiant flux. In situations where solar cells get heated mainly from incident infrared radiation, these cells exhibit superior performance. The heat reflecting pigment, cell structure, coating process and cell performance have been described.

  11. Raman spectroscopy study of the doping effect of the encapsulated terbium halogenides on single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Kharlamova, M.V.; Kramberger, C.; Mittelberger, A. [University of Vienna, Faculty of Physics, Vienna (Austria)

    2017-04-15

    In the present work, the doping effect of terbium chloride, terbium bromide, and terbium iodide on single-walled carbon nanotubes (SWCNTs) was compared by Raman spectroscopy. A precise investigation of the doping-induced alterations of the Raman modes of the filled SWCNTs was conducted. The shifts of the components of the Raman modes and modification of their profiles allowed concluding that the inserted terbium halogenides have acceptor doping effect on the SWCNTs, and the doping efficiency increases in the line with terbium iodide, terbium bromide, and terbium chloride. (orig.)

  12. Modelling of the modulation properties of arsenide and nitride VCSELs

    Science.gov (United States)

    Wasiak, Michał; Śpiewak, Patrycja; Moser, Philip; Gebski, Marcin; Schmeckebier, Holger; Sarzała, Robert P.; Lott, James A.

    2017-02-01

    In this paper, using our model of capacitance in vertical-cavity surface-emitting lasers (VCSELs), we analyze certain differences between an oxide-confined arsenide VCSEL emitting in the NIR region, and a nitride VCSEL emitting violet radiation. In the nitride laser its high differential resistance, caused partially by the low conductivity of p-type GaN material and the bottom contact configuration, is one of the main reasons why the nitride VCSEL has much worse modulation properties than the arsenide VCSEL. Using the complicated arsenide structure, we also analyze different possible ways of constructing the laser's equivalent circuit.

  13. Ellipsometric study of silicon nitride on gallium arsenide

    Science.gov (United States)

    Alterovitz, S. A.; Bu-Abbud, G. H.; Woollam, J. A.; Liu, D.; Chung, Y.; Langer, D.

    1982-01-01

    A method for optimizing the sensitivity of ellipsometric measurements for thin dielectric films on semiconductors is described in simple physical terms. The technique is demonstrated for the case of sputtered silicon nitride films on gallium arsenide.

  14. Magnetocaloric effect of thin Terbium films

    Science.gov (United States)

    Mello, V. D.; Anselmo, D. H. A. L.; Vasconcelos, M. S.; Almeida, N. S.

    2017-12-01

    We report a theoretical study of the magnetocaloric effect of Terbium (Tb) thin films due to finite size and surface effects in the helimagnetic phase, corresponding to a temperature range from TC=219 K to TN=231 K, for external fields of the order of kOe. For a Tb thin film of 6 monolayers submitted to an applied field (ΔH =30 kOe, ΔH =50 kOe and ΔH = 70 kOe) we report a significative change in adiabatic temperature, ΔT / ΔH , near the Néel temperature, of the order ten times higher than that observed for Tb bulk. On the other hand, for small values of the magnetic field, large thickness effects are found. For external field strength around few kOe, we have found that the thermal caloric efficiency increases remarkably for ultrathin films. For an ultrathin film with 6 monolayers, we have found ΔT / ΔH = 43 K/T while for thicker films, with 20 monolayers, ΔT / ΔH = 22 K/T. Our results suggest that thin films of Tb are a promising material for magnetocaloric effect devices for applications at intermediate temperatures.

  15. Femtosecond XUV spectroscopy of gadolinium and terbium

    Energy Technology Data Exchange (ETDEWEB)

    Carley, Robert; Frietsch, Bjoern; Doebrich, Kristian; Teichmann, Martin; Gahl, Cornelius; Noack, Frank [Max-Born-Institute, Berlin (Germany); Schwarzkopf, Olaf; Wernet, Philippe [Helmholtz-Zentrum fuer Materialien und Energie (BESSY II), Berlin (Germany); Weinelt, Martin [Max-Born-Institute, Berlin (Germany); Fachbereich Physik, Freie Universitaet, Berlin (Germany)

    2011-07-01

    We present recent results of time-resolved IR-pump-XUV-probe experiments on the ultrafast demagnetization of thin films of Gadolinium(0001) and Terbium(0001) on Tungsten(110). The experiments are the first to be done using a newly developed high-order harmonics (HHG) XUV beamline at the MBI. The beamline delivers monochromated XUV pulses of approximately 150 fs duration with a photon energy resolution of up to 150 meV. Following excitation by intense femtosecond infrared (IR) pulses, photoemission with 35 eV photons allows us to directly probe the 4f electrons and their interaction with the valence band, both in the bulk and at the surface, to follow the ultrafast magnetization dynamics in the Lanthanide metals. As signatures of ultrafast demagnetization of the metal by the IR pulse, we see for the first time, rapid strong reduction of the exchange splitting in the valence band. This is followed by a slower demagnetization due to the spin-lattice interaction.

  16. Gallium Arsenide solar cell radiation damage experiment

    Science.gov (United States)

    Maurer, R. H.; Kinnison, J. D.; Herbert, G. A.; Meulenberg, A.

    1991-01-01

    Gallium arsenide (GaAs) solar cells for space applications from three different manufactures were irradiated with 10 MeV protons or 1 MeV electrons. The electrical performance of the cells was measured at several fluence levels and compared. Silicon cells were included for reference and comparison. All the GaAs cell types performed similarly throughout the testing and showed a 36 to 56 percent power areal density advantage over the silicon cells. Thinner (8-mil versus 12-mil) GaAs cells provide a significant weight reduction. The use of germanium (Ge) substrates to improve mechanical integrity can be implemented with little impact on end of life performance in a radiation environment.

  17. Surface magnetism of gallium arsenide nanofilms

    Science.gov (United States)

    Lu, Huan; Yu, Jin; Guo, Wanlin

    2017-11-01

    Gallium arsenide (GaAs) is the most widely used second-generation semiconductor with a direct band gap, and it is being increasingly used as nanofilms. However, the magnetic properties of GaAs nanofilms have never been studied. Here we find by comprehensive density-functional-theory calculations that GaAs nanofilms cleaved along the 〈111 〉 and 〈100 〉 directions become intrinsically metallic films with strong surface magnetism and the magnetoelectric effect. Surface magnetism and electrical conductivity are realized via a combined effect of charge transfer induced by spontaneous electric polarization through the film thickness and spin-polarized surface states. The surface magnetism of 〈111 〉 nanofilms can be significantly and linearly tuned by a vertically applied electric field, endowing the nanofilms with unexpectedly high magnetoelectric coefficients, which are tens of times higher than those of ferromagnetic metals and transition-metal oxides.

  18. Green fluorescence of terbium ions in lithium fluoroborate glasses ...

    Indian Academy of Sciences (India)

    Glasses; terbium ion; oscillator strengths; fluorescence; lifetimes; fibre lasers. 1. Introduction. Today glasses are most favourable engineering materials for abundant applications due to the wide ability of property altering by compositional modifications. The considerable examination of glass science to achieve required ...

  19. Green fluorescence of terbium ions in lithium fluoroborate glasses ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 3. Green fluorescence of terbium ions in lithium fluoroborate glasses for fibre lasers and display devices. G R DILLIP C MADHUKAR REDDY M RAJESH SHIVANAND CHAURASIA B DEVA PRASAD RAJU S W JOO. Volume 39 Issue 3 June 2016 pp 711-717 ...

  20. Inhalation developmental toxicology studies: Gallium arsenide in mice and rats

    Energy Technology Data Exchange (ETDEWEB)

    Mast, T.J.; Greenspan, B.J.; Dill, J.A.; Stoney, K.H.; Evanoff, J.J.; Rommereim, R.L.

    1990-12-01

    Gallium arsenide is a crystalline compound used extensively in the semiconductor industry. Workers preparing solar cells and gallium arsenide ingots and wafers are potentially at risk from the inhalation of gallium arsenide dust. The potential for gallium arsenide to cause developmental toxicity was assessed in Sprague- Dawley rats and CD-1 (Swiss) mice exposed to 0, 10, 37, or 75 mg/m{sup 3} gallium arsenide, 6 h/day, 7 days/week. Each of the four treatment groups consisted of 10 virgin females (for comparison), and {approx}30 positively mated rats or {approx}24 positively mated mice. Mice were exposed on 4--17 days of gestation (dg), and rats on 4--19 dg. The day of plug or sperm detection was designated as 0 dg. Body weights were obtained throughout the study period, and uterine and fetal body weights were obtained at sacrifice (rats, 20 dg; mice, 18 dg). Implants were enumerated and their status recorded. Live fetuses were sexed and examined for gross, visceral, skeletal, and soft-tissue craniofacial defects. Gallium and arsenic concentrations were determined in the maternal blood and uterine contents of the rats (3/group) at 7, 14, and 20 dg. 37 refs., 11 figs., 30 tabs.

  1. Maskless proton beam writing in gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Mistry, P. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom) and Nano-Electronics Centre, Advanced Technology Institute, University of Surrey, Guildford GU2 7XH (United Kingdom)]. E-mail: p.mistry@surrey.ac.uk; Gomez-Morilla, I. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Smith, R.C. [Nano-Electronics Centre, Advanced Technology Institute, University of Surrey, Guildford GU2 7XH (United Kingdom); Thomson, D. [Advanced Technology Institute, University of Surrey, Guildford GU2 7XH (United Kingdom); Grime, G.W. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Webb, R.P. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Gwilliam, R. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Jeynes, C. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Cansell, A. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Merchant, M. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Kirkby, K.J. [Ion Beam Centre, University of Surrey, Guildford GU2 7XH (United Kingdom)

    2007-07-15

    Proton beam writing (PBW) is a direct write technique that employs a focused MeV proton beam which is scanned in a pre-determined pattern over a target material which is subsequently electrochemically etched or chemically developed. By changing the energy of the protons the range of the protons can be changed. The ultimate depth of the structure is determined by the range of the protons in the material and this allows structures to be formed to different depths. PBW has been successfully employed on etchable glasses, polymers and semiconductor materials such as silicon (Si) and gallium arsenide (GaAs). This study reports on PBW in p-type GaAs and compares experimental results with computer simulations using the Atlas (copy right) semiconductor device package from SILVACO. It has already been proven that hole transport is required for the electrochemical etching of GaAs using Tiron (4,5-dihydroxy-m-benzenedisulfonic acid, di-sodium salt). PBW in GaAs results in carrier removal in the irradiated regions and consequently minimal hole transport (in these regions) during electrochemical etching. As a result the irradiated regions are significantly more etch resistant than the non-irradiated regions. This allows high aspect ratio structures to be formed.

  2. Evaluation of the carcinogenicity of gallium arsenide.

    Science.gov (United States)

    Bomhard, Ernst M; Gelbke, Heinz-Peter; Schenk, Hermann; Williams, Gary M; Cohen, Samuel M

    2013-05-01

    Gallium arsenide (GaAs) is an important semiconductor material. In 2-year inhalation studies, GaAs increased the incidence of lung tumors in female rats, but not in male rats or male and female mice. Alveolar proteinosis followed by chronic active inflammation was the predominant non-neoplastic pulmonary findings. IARC classified GaAs as carcinogenic to humans (group 1) based on the assumption that As and Ga ions are bioavailable. The European Chemical Agency Risk Assessment Committee concluded that GaAs should be classified into Carcinogenicity Category 1B (presumed to have carcinogenic potential for humans; ECHA). We evaluate whether these classifications are justified. Physico-chemical properties of GaAs particles and the degree of mechanical treatment are critical in this evaluation. The available data on mode of action (MOA), genotoxicity and bioavailability do not support the contribution of As or Ga ions to the lung tumors in female rats. Most toxicological studies utilized small particles produced by strong mechanical treatment, destroying the crystalline structure. The resulting amorphous GaAs is not relevant to crystalline GaAs at production and processing sites. The likely tumorigenic MOA is lung toxicity related to particulate-induced inflammation and increased proliferation. It is concluded that there is no evidence for a primary carcinogenic effect of GaAs.

  3. Gallium arsenide processing for gate array logic

    Science.gov (United States)

    Cole, Eric D.

    1989-01-01

    The development of a reliable and reproducible GaAs process was initiated for applications in gate array logic. Gallium Arsenide is an extremely important material for high speed electronic applications in both digital and analog circuits since its electron mobility is 3 to 5 times that of silicon, this allows for faster switching times for devices fabricated with it. Unfortunately GaAs is an extremely difficult material to process with respect to silicon and since it includes the arsenic component GaAs can be quite dangerous (toxic) especially during some heating steps. The first stage of the research was directed at developing a simple process to produce GaAs MESFETs. The MESFET (MEtal Semiconductor Field Effect Transistor) is the most useful, practical and simple active device which can be fabricated in GaAs. It utilizes an ohmic source and drain contact separated by a Schottky gate. The gate width is typically a few microns. Several process steps were required to produce a good working device including ion implantation, photolithography, thermal annealing, and metal deposition. A process was designed to reduce the total number of steps to a minimum so as to reduce possible errors. The first run produced no good devices. The problem occurred during an aluminum etch step while defining the gate contacts. It was found that the chemical etchant attacked the GaAs causing trenching and subsequent severing of the active gate region from the rest of the device. Thus all devices appeared as open circuits. This problem is being corrected and since it was the last step in the process correction should be successful. The second planned stage involves the circuit assembly of the discrete MESFETs into logic gates for test and analysis. Finally the third stage is to incorporate the designed process with the tested circuit in a layout that would produce the gate array as a GaAs integrated circuit.

  4. Terahertz Cherenkov radiation from ultrafast magnetization in terbium gallium garnet

    Science.gov (United States)

    Gorelov, S. D.; Mashkovich, E. A.; Tsarev, M. V.; Bakunov, M. I.

    2013-12-01

    We report an experimental observation of terahertz Cherenkov radiation from a moving magnetic moment produced in terbium gallium garnet by a circularly polarized femtosecond laser pulse via the inverse Faraday effect. Contrary to some existing theoretical predictions, the polarity of the observed radiation unambiguously demonstrates the paramagnetic, rather than diamagnetic, nature of the ultrafast inverse Faraday effect. From measurements of the radiation field, the Verdet constant in the subpicosecond regime is ˜3-10 times smaller than its table quasistatic value.

  5. Electrooptic Waveguide Directional Coupler Modulator in Aluminum Gallium Arsenide-Gallium Arsenide.

    Science.gov (United States)

    Khan, Mujibun Nisa

    A novel optical waveguide intensity modulator in aluminum gallium arsenide and gallium arsenide material system is modeled, designed, and experimentally demonstrated at 0.83 μm wavelength. The modulator utilizes the linear electrooptic effect in a coupled waveguide structure to achieve high extinction ratio at low drive voltage. The device structure consists of a differentially -etched ridge directional coupler, where the ridge height in the gap is smaller that that of the outer sides. The effective index and semivectorial finite difference modeling techniques are developed to analyze the single ridge guides and directional coupler structures. The mode structure results from the two models are compared and the limitations of the effective index method are determined. The differential -etch design is employed to reduce the length as well as the drive voltage of the modulator. A modulation voltage of 2 volts for a 3.5-mm-long device is achieved, which is the lowest reported in literature. These results are compared with those obtained from the simplified analytical expressions for conventional couplers, and higher performance expected from the differential-etch design is verified. The modulator extinction ratio is measured to be 13 dB at 2 volts. The measured optical propagation loss of approximately 3.4 dB/cm for the modulator is speculated to be primarily due to the surface morphology of the epitaxially-grown material, and the light scattering from rough ridge walls produced during the anisotropic dry etching process. The high microwave loss of 15 dB/cm calculated for the modulator electrode design suggests a trade-off between the modulation voltage and the bandwidth, which is expected to be limited to 500 MHz. The measurement of the modulator frequency response up to 100 KHz is presented, because of the test limitations at higher frequencies due to the weak modulated intensity signals.

  6. Trap influence on the performance of gallium arsenide radiation detectors

    Energy Technology Data Exchange (ETDEWEB)

    Castaldini, A.; Cavallini, A.; Polenta, L. [Univ. of Bologna (Italy); Canali, C.; Nava, F. [Univ. of Modena (Italy); Papa, C. del [Univ. of Udine (Italy). Dept. of Physics

    1996-12-31

    Ohmic contacts play an important role in the performance of LEC gallium arsenide particle detectors since they possibly control the injection of charge carriers. Contact characteristics have been compared and related to electrically active defects induced during contact preparation and to the detector efficiency. The electric field distribution has also been analyzed. Spectroscopic investigations have put into evidence that the contact fabrication process significantly influences the trap density whilst it does not change their signatures.

  7. Terbium luminescence in alumina xerogel fabricated in porous anodic alumina matrix under various excitation conditions

    Energy Technology Data Exchange (ETDEWEB)

    Gaponenko, N. V., E-mail: nik@nano.bsuir.edu.by [Belarusian State University of Informatics and Radioelectronics (Belarus); Kortov, V. S. [Yeltsin Ural Federal University (Russian Federation); Orekhovskaya, T. I.; Nikolaenko, I. A. [Belarusian State University of Informatics and Radioelectronics (Belarus); Pustovarov, V. A.; Zvonarev, S. V.; Slesarev, A. I. [Yeltsin Ural Federal University (Russian Federation); Prislopski, S. Ya. [National Academy of Sciences of Belarus, Stepanov Institute of Physics (Belarus)

    2011-07-15

    Terbium-doped alumina xerogel layers are synthesized by the sol-gel method in pores of a porous anodic alumina film 1 {mu}m thick with a pore diameter of 150-180 nm; the film is grown on a silicon substrate. The fabricated structures exhibit terbium photoluminescence with bands typical of trivalent terbium terms. Terbium X-ray luminescence with the most intense band at 542 nm is observed for the first time for such a structure. Morphological analysis of the structure by scanning electron microscopy shows the presence of xerogel clusters in pore channels, while the main pore volume remains unfilled and pore mouths remain open. The data obtained confirm the promising applications of fabricated structures for developing matrix converters of X-rays and other ionizing radiations into visible light. The possibilities of increasing luminescence intensity in the matrix converter are discussed.

  8. Optical Properties of Lithium Terbium Fluoride and Implications for Performance in High Power Lasers (Postprint)

    Science.gov (United States)

    2016-02-01

    AFRL-RX-WP-JA-2016-0323 OPTICAL PROPERTIES OF LITHIUM TERBIUM FLUORIDE AND IMPLICATIONS FOR PERFORMANCE IN HIGH POWER LASERS... AMERICA (STINFO COPY) AIR FORCE RESEARCH LABORATORY MATERIALS AND MANUFACTURING DIRECTORATE WRIGHT-PATTERSON AIR FORCE BASE, OH 45433-7750 AIR...OPTICAL PROPERTIES OF LITHIUM TERBIUM FLUORIDE AND IMPLICATIONS FOR PERFORMANCE IN HIGH POWER LASERS (POSTPRINT) 5a. CONTRACT NUMBER IN-HOUSE 5b

  9. Detection of biothiols in cells by a terbium chelate-Hg (II) system

    Science.gov (United States)

    Tan, Hongliang; Chen, Yang

    2012-01-01

    Great efforts have been devoted to the development of sensitive and specific analysis methods for biothiols because of their important roles in biological systems. We present a new detection system for biothiols that is based on the reversible quenching and restoration of fluorescence of terbium chelate caused by Hg2+ and thiol species. In the presence of biothiols, a restoration of fluorescence of terbium chelate after quenching by Hg2+ was observed due to the interaction of Hg2+ with thiol groups, and the restored fluorescence increased with the concentration of biothiols. This method was sensitive and selective for biothiols. The detection limit was 80 nM for glutathione, 100 nM for Hcy, and 400 nM for Cysteine, respectively. The terbium chelate-Hg (II) system was successfully applied to determine the levels of biothiols in cancer cells and urine samples. Further, it was also shown to be comparable to Ellman's assay. Compared to other fluorescence methods, the terbium chelate probe is advantageous because interference from short-lived nonspecific fluorescence can be efficiently eliminated due to the long fluorescence lifetime of terbium chelate, which allows for detection by time-resolved fluorescence. The terbium chelate probe can serve as a diagnostic tool for the detection of abnormal levels of biothiols in disease.

  10. Cryogenic temperature characteristics of Verdet constant of terbium sesquioxide ceramics

    Science.gov (United States)

    Snetkov, I. L.; Palashov, O. V.

    2016-12-01

    The dependence of the Verdet constant on temperature in the (80-300 K) range for a promising magneto-active material terbium sesquioxide Tb2O3 at the wavelengths of 405-1064 nm is considered. For each of the studied wavelengths, the Verdet constant of the material cooled down to the liquid nitrogen temperature increased by more than a factor of 3.2 as compared to the room temperature value. Similarly to the other paramagnetics, the increase follows the law ∼1/T. Approximations for the temperature dependence of the Verdet constant have been obtained and the value of 1/V·(dV/dT) has been estimated. This information is needed to determine the angle of rotation as well as the variation of the extinction ratio of a Faraday isolator with temperature and extremely important at creation a cryogenic Faraday devices.

  11. Biogenic terbium oxide nanoparticles as the vanguard against osteosarcoma

    Science.gov (United States)

    Iram, Sana; Khan, Salman; Ansary, Abu Ayoobul; Arshad, Mohd; Siddiqui, Sahabjada; Ahmad, Ejaz; Khan, Rizwan H.; Khan, Mohd Sajid

    2016-11-01

    The synthesis of inner transition metal nanoparticles via an ecofriendly route is quite difficult. This study, for the first time, reports synthesis of terbium oxide nanoparticles using fungus, Fusarium oxysporum. The biocompatible terbium oxide nanoparticles (Tb2O3 NPs) were synthesized by incubating Tb4O7 with the biomass of fungus F. oxysporum. Multiple physical characterization techniques, such as UV-visible and photoluminescence spectroscopy, TEM, SAED, and zeta-potential were used to confirm the synthesis, purity, optical and surface characteristics, crystallinity, size, shape, distribution, and stability of the nanoemulsion of Tb2O3 NPs. The Tb2O3 NPs were found to inhibit the propagation of MG-63 and Saos-2 cell-lines (IC50 value of 0.102 μg/mL) and remained non-toxic up to a concentration of 0.373 μg/mL toward primary osteoblasts. Cell viability decreased in a concentration-dependent manner upon exposure to 10 nm Tb2O3 NPs in the concentration range 0.023-0.373 μg/mL. Cell toxicity was evaluated by observing changes in cell morphology, cell viability, oxidative stress parameters, and FACS analysis. Morphological examinations of cells revealed cell shrinkage, nuclear condensation, and formation of apoptotic bodies. The level of ROS within the cells-an indicator of oxidative stress was significantly increased. The induction of apoptosis at concentrations ≤ IC50 was corroborated by 4‧,6-diamidino-2-phenylindole dihydrochloride (DAPI) staining (DNA damage and nuclear fragmentation). Flow-cytometric studies indicated that the response was dose dependent with a threshold effect.

  12. Laser and electron beam processing of silicon and gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Narayan, J.

    1979-10-01

    Laser (photon) and electron beams provide a controlled source of heat by which surface layers of silicon and gallium arsenide can be rapidly melted and cooled with rates exceeding 10/sup 80/C/sec. The melting process has been used to remove displacement damage in ion implanted Si and GaAs, to remove dislocations, loops and precipitates in silicon and to study impurity segregation and solubility limits. The mechanisms associated with various phenomena will be examined. The possible impact of laser and electron beam processing on device technology, particularly with respect to solar cells is discussed.

  13. Anomalous tensoelectric effects in gallium arsenide tunnel diodes

    Energy Technology Data Exchange (ETDEWEB)

    Alekseeva, Z.M.; Vyatkin, A.P.; Krivorotov, N.P.; Shchegol' , A.A.

    1988-02-01

    Anomalous tensoelectric phenomena induced in a tunnel p-n junction by a concentrated load and by hydrostatic compression were studied. The anomalous tensoelectric effects are caused by the action of concentrators of mechanical stresses in the vicinity of the p-n junction, giving rise to local microplastic strain. Under the conditions of hydrostatic compression prolate inclusions approx.100-200 A long play the role of concentrators. Analysis of irreversible changes in the current-voltage characteristics of tunnel p-n junctions made it possible to separate the energy levels of the defects produced with plastic strain of gallium arsenide.

  14. Anomalous tensoelectric effects in gallium arsenide tunnel diodes

    Science.gov (United States)

    Alekseeva, Z. M.; Vyatkin, A. P.; Krivorotov, N. P.; Shchegol', A. A.

    1987-08-01

    Anomalous tensoelectric phenomena induced in a tunnel p-n junction by a concentrated load and by hydrostatic compression were studied. The anomalous tensoelectric effects are caused by the action of concentrators of mechanical stresses in the vicinity of the p-n junction, giving rise to local microplastic strain. Under the conditions of hydrostatic compression prolate inclusions ∿100 200 å long play the role of concentrators. Analysis of irreversible changes in the current-voltage characteristics of tunnel p-n junctions made it possible to separate the energy levels of the defects produced with plastic strain of gallium arsenide.

  15. Testing of gallium arsenide solar cells on the CRRES vehicle

    Science.gov (United States)

    Trumble, T. M.

    A flight experiment was designed to determine the optimum design for gallium arsenide (GaAs) solar cell panels in a radiation environment. Elements of the experiment design include, different coverglass material and thicknesses, welded and soldered interconnects, different solar cell efficiencies, different solar cell types, and measurement of annealing properties. This experiment is scheduled to fly on the Combined Release and Radiation Effects Satellite (CRRES). This satellite will simultaneously measure the radiation environment and provide engineering data on solar cell degradation that can be directly related to radiation damage.

  16. Lattice parameters guide superconductivity in iron-arsenides

    Science.gov (United States)

    Konzen, Lance M. N.; Sefat, Athena S.

    2017-03-01

    The discovery of superconducting materials has led to their use in technological marvels such as magnetic-field sensors in MRI machines, powerful research magnets, short transmission cables, and high-speed trains. Despite such applications, the uses of superconductors are not widespread because they function much below room-temperature, hence the costly cooling. Since the discovery of Cu- and Fe-based high-temperature superconductors (HTS), much intense effort has tried to explain and understand the superconducting phenomenon. While no exact explanations are given, several trends are reported in relation to the materials basis in magnetism and spin excitations. In fact, most HTS have antiferromagnetic undoped ‘parent’ materials that undergo a superconducting transition upon small chemical substitutions in them. As it is currently unclear which ‘dopants’ can favor superconductivity, this manuscript investigates crystal structure changes upon chemical substitutions, to find clues in lattice parameters for the superconducting occurrence. We review the chemical substitution effects on the crystal lattice of iron-arsenide-based crystals (2008 to present). We note that (a) HTS compounds have nearly tetragonal structures with a-lattice parameter close to 4 Å, and (b) superconductivity can depend strongly on the c-lattice parameter changes with chemical substitution. For example, a decrease in c-lattice parameter is required to induce ‘in-plane’ superconductivity. The review of lattice parameter trends in iron-arsenides presented here should guide synthesis of new materials and provoke theoretical input, giving clues for HTS.

  17. Evaluation of the male reproductive toxicity of gallium arsenide.

    Science.gov (United States)

    Bomhard, Ernst M; Cohen, Samuel M; Gelbke, Heinz-Peter; Williams, Gary M

    2012-10-01

    Gallium arsenide is an important semiconductor material marketed in the shape of wafers and thus is not hazardous to the end user. Exposure to GaAs particles may, however, occur during manufacture and processing. Potential hazards require evaluation. In 14-week inhalation studies with small GaAs particles, testicular effects have been reported in rats and mice. These effects occurred only in animals whose lungs showed marked inflammation and also had hematologic changes indicating anemia and hemolysis. The time- and concentration-dependent progressive nature of the lung and blood effects together with bioavailability data on gallium and arsenic lead us to conclude that the testicular/sperm effects are secondary to hypoxemia resulting from lung damage rather than due to a direct chemical effect of gallium or arsenide. Conditions leading to such primary effects are not expected to occur in humans at production and processing sites. This has to be taken into consideration for any classification decision for reproductive toxicity; especially a category 1 according to the EU CLP system is not warranted. Copyright © 2012 Elsevier Inc. All rights reserved.

  18. Macroscopic diffusion models for precipitation in crystalline gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Kimmerle, Sven-Joachim Wolfgang

    2009-09-21

    Based on a thermodynamically consistent model for precipitation in gallium arsenide crystals including surface tension and bulk stresses by Dreyer and Duderstadt, we propose two different mathematical models to describe the size evolution of liquid droplets in a crystalline solid. The first model treats the diffusion-controlled regime of interface motion, while the second model is concerned with the interface-controlled regime of interface motion. Our models take care of conservation of mass and substance. These models generalise the well-known Mullins- Sekerka model for Ostwald ripening. We concentrate on arsenic-rich liquid spherical droplets in a gallium arsenide crystal. Droplets can shrink or grow with time but the centres of droplets remain fixed. The liquid is assumed to be homogeneous in space. Due to different scales for typical distances between droplets and typical radii of liquid droplets we can derive formally so-called mean field models. For a model in the diffusion-controlled regime we prove this limit by homogenisation techniques under plausible assumptions. These mean field models generalise the Lifshitz-Slyozov-Wagner model, which can be derived from the Mullins-Sekerka model rigorously, and is well understood. Mean field models capture the main properties of our system and are well adapted for numerics and further analysis. We determine possible equilibria and discuss their stability. Numerical evidence suggests in which case which one of the two regimes might be appropriate to the experimental situation. (orig.)

  19. First principles predictions of intrinsic defects in aluminum arsenide, AlAs : numerical supplement.

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, Peter Andrew

    2012-04-01

    This Report presents numerical tables summarizing properties of intrinsic defects in aluminum arsenide, AlAs, as computed by density functional theory. This Report serves as a numerical supplement to the results published in: P.A. Schultz, 'First principles predictions of intrinsic defects in Aluminum Arsenide, AlAs', Materials Research Society Symposia Proceedings 1370 (2011; SAND2011-2436C), and intended for use as reference tables for a defect physics package in device models.

  20. Autofluorescence-free Live-cell Imaging Using Terbium Nanoparticles.

    Science.gov (United States)

    Cardoso Dos Santos, Marcelina; Goetz, Joan; Bartenlian, Hortense; Wong, Ka-Leung; Charbonniere, Loïc Joanny; Hildebrandt, Niko

    2018-02-20

    Fluorescent nanoparticles (NPs) have become irreplaceable tools for advanced cellular and sub-cellular imaging. While very bright NPs require excitation with UV or visible light, which can create strong autofluorescence of biological components, NIR-excitable NPs without autofluorescence issues exhibit much lower brightness. Here, we show the application of a new type of surface-photosensitized terbium NPs (Tb-NPs) for autofluorescence-free intracellular imaging in live HeLa cells. Combination of exceptionally high brightness, high photostability, and long photoluminecence (PL) lifetimes for highly efficient suppression of the short-lived autofluorescence, allowed for time-gated PL imaging of intracellular vesicles over 72 h without toxicity and at extremely low Tb-NP concentrations down to 12 pM. Detection of highly resolved long-lifetime (ms) PL decay curves from small (~10 µm2) areas within single cells within a few seconds emphasized the unprecedented photophysical properties of Tb-NPs for live-cell imaging that extend well beyond currently available nanometric imaging agents.

  1. Solar Thermochemical Hydrogen Production via Terbium Oxide Based Redox Reactions

    Directory of Open Access Journals (Sweden)

    Rahul Bhosale

    2016-01-01

    Full Text Available The computational thermodynamic modeling of the terbium oxide based two-step solar thermochemical water splitting (Tb-WS cycle is reported. The 1st step of the Tb-WS cycle involves thermal reduction of TbO2 into Tb and O2, whereas the 2nd step corresponds to the production of H2 through Tb oxidation by water splitting reaction. Equilibrium compositions associated with the thermal reduction and water splitting steps were determined via HSC simulations. Influence of oxygen partial pressure in the inert gas on thermal reduction of TbO2 and effect of water splitting temperature (TL on Gibbs free energy related to the H2 production step were examined in detail. The cycle (ηcycle and solar-to-fuel energy conversion (ηsolar-to-fuel efficiency of the Tb-WS cycle were determined by performing the second-law thermodynamic analysis. Results obtained indicate that ηcycle and ηsolar-to-fuel increase with the decrease in oxygen partial pressure in the inert flushing gas and thermal reduction temperature (TH. It was also realized that the recuperation of the heat released by the water splitting reactor and quench unit further enhances the solar reactor efficiency. At TH=2280 K, by applying 60% heat recuperation, maximum ηcycle of 39.0% and ηsolar-to-fuel of 47.1% for the Tb-WS cycle can be attained.

  2. Folate Receptor Targeted Alpha-Therapy Using Terbium-149

    CERN Document Server

    Müller, Cristina; Haller, Stephanie; Dorrer, Holger; Köster, Ulli; Johnston, Karl; Zhernosekov, Konstantin; Türler, Andreas; Schibli, Roger

    2014-01-01

    Terbium-149 is among the most interesting therapeutic nuclides for medical applications. It decays by emission of short-range α-particles (Eα = 3.967 MeV) with a half-life of 4.12 h. The goal of this study was to investigate the anticancer efficacy of a 149Tb-labeled DOTA-folate conjugate (cm09) using folate receptor (FR)-positive cancer cells in vitro and in tumor-bearing mice. 149Tb was produced at the ISOLDE facility at CERN. Radiolabeling of cm09 with purified 149Tb resulted in a specific activity of ~1.2 MBq/nmol. In vitro assays performed with 149Tb-cm09 revealed a reduced KB cell viability in a FR-specific and activity concentration-dependent manner. Tumor-bearing mice were injected with saline only (group A) or with 149Tb-cm09 (group B: 2.2 MBq; group C: 3.0 MBq). A significant tumor growth delay was found in treated animals resulting in an increased average survival time of mice which received 149Tb-cm09 (B: 30.5 d; C: 43 d) compared to untreated controls (A: 21 d). Analysis of blood parameters rev...

  3. Hardness and dielectric characteristics of flux grown terbium aluminate crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, K.K.; Kotru, P.N. [Jammu Univ. (India). Dept. of Physics; Tandon, R.P. [National Physical Laboratory, New Delhi (India); Wanklyn, B.M. [Clarendon Laboratory, University of Oxford, Oxford (United Kingdom)

    1999-01-29

    Results of indentation induced Vickers hardness testing and dielectric studies conducted on flux-grown terbium aluminate crystals are presented. It is shown that the Vickers hardness value (H{sub v}) is independent of indentation time, but depends on the applied load. Applying the concept of Hays and Kendall, the load independent values are estimated for (110) and (001) planes. Differential behaviour in the crack formation of two different planes (110) and (001) is observed, while (001) plane develops Palmqvist cracks in the whole load range of 10-100 g, (110) plane shows a transition from Palmqvist to median cracks at 70 g. The fracture toughness, brittleness index and yield strength are determined for both the planes. The hardness anisotropy is reported. The dielectric constant, dielectric loss and conductivity are shown to be dependent on temperature and frequency of the applied a.c. field. The dielectric constant versus temperature shows a transition peak at 230 C, which remains independent of the frequency of the applied a.c. field in the range 1 kHz-13 MHz. (orig.) 36 refs.

  4. Thermoluminescence of cerium and terbium -doped calcium pyrophosphate

    Energy Technology Data Exchange (ETDEWEB)

    Roman L, J.; Cruz Z, E. [UNAM, Instituto de Ciencias Nucleares, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Lozano R, I. B.; Diaz G, J. A. I., E-mail: jesus.roman@nucleares.unam.mx [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Av. Legaria No. 694, 11500 Mexico D. F. (Mexico)

    2015-10-15

    The aim of this work is to report the thermoluminescence (Tl) response of Calcium Pyrophosphate phosphor doped with Cerium and Terbium impurities (Ca{sub 2}P{sub 2}O{sub 7}:Ce{sup 3+},Tb{sup 3+}). The phosphors were synthesized using the co-precipitation method and annealed at 900 degrees C by two hours for obtain the β phase. The intentional doping with Ce and Tb ions was 1 at.% and 0.1 at.%, whereas in the EDS results the concentration of impurities was 0.39 at.% and 0.05 at.%, respectively. The superficial morphology of phosphor is mainly composed by thin wafers of different size. All samples were exposed to gamma rays from {sup 60}Co in the Gammacell-200 irradiator. The Tl response of the phosphor was measured from Rt up to 350 degrees C and under nitrogen atmosphere in a Harshaw TLD 3500 reader. The glow curves of the Ca{sub 2}P{sub 2}O{sub 7}:Ce{sup 3+},Tb{sup 3+} powders showed a broad intense Tl peak centered at 165 degrees C and a shoulder at approximate 260 degrees C was observed. A linear Tl response in the range of absorbed dose of 0.2 to 10 Gy was obtained. Tl glow curves were analyzed using the initial rise (IR)and computerized glow curve deconvolution methods to evaluate the kinetics parameters such as activation energy (E), frequency factor (s) and kinetic order (b). (Author)

  5. Solvent polarity and oxygen sensitivity, rather than viscosity, determine lifetimes of biaryl-sensitised terbium luminescence.

    Science.gov (United States)

    Walter, Edward R H; Williams, J A Gareth; Parker, David

    2017-12-14

    In a macrocyclic terbium complex incorporating a biaryl sensitiser, the observed variation of emission lifetime is shown to be determined by the solubility of oxygen in the solvent system and the relative energy of the chromophore excited state, rather than any dependence on solvent viscosity.

  6. Speed gallium arsenide photoconductors; Photoconducteurs rapides en arseniure de gallium

    Energy Technology Data Exchange (ETDEWEB)

    Foulon, F.; Pochet, T. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. d`Electronique et d`Instrumentation Nucleaire; Brullot, B. [CEA Centre d`Etudes de Bruyeres-le-Chatel, 91 (France)

    1993-12-31

    Gallium arsenide detectors are one of the most efficient gamma and X ray detectors at room temperature. Due to the high carrier mobility and short carrier lifetime, GaAs can be used for the detection of ultrafast gamma, X or laser pulses. GaAs photoconductors allow both pulse shape and intensity measurements. In this paper, we review the results of studies carried out jointly by the CEA/LETI/DEIN and CEA/DAM/CEM in France to improve the response of such detectors. The geometry of the photodetectors and their electrical contacts have been optimized for specific radiation measurements: low energy X rays (< 1 KeV), gamma rays or protons. It has been shown that a pre-irradiation treatment with fission neutrons at doses above 10{sup 14} n/cm{sup 2} induces a significant improvement of the response speed. This result from defect generation in the material and the subsequent carrier life time decrease. Detectors with sensitivities of about 10{sup -8} A/R.s for gamma rays and 10{sup -16} coulomb/proton, response times below 100 ps and good linearity over more than five decades are currently fabricated in our laboratory. (authors). 18 refs., 5 figs., 3 tabs.

  7. Magnetoelectric effect in layered structures of amorphous ferromagnetic alloy and gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Bichurin, M.I., E-mail: mirza.bichurin@novsu.ru; Petrov, V.M.; Leontiev, V.S.; Ivanov, S.N.; Sokolov, O.V.

    2017-02-15

    A paper devotes to theoretical and experimental studying the magnetoelectric interaction in layered structures of amorphous ferromagnetic alloy and single- crystal gallium arsenide. The authors investigated the magnetoelectric effect in the (100) plane of gallium arsenide in the electromechanical resonance range of 200–240 kHz and obtained maximal ME voltage coefficient of 120 V/A at bias field equaled 3.6 kA/m for the direction parallel to the [011] axis. Also the magnetoelectric effect in the (110) and (111) planes is discussed. The results can be used for design of new electronic devices based on the magnetostrictive-semiconductor materials. - Highlights: • Theoretical modeling of ME interaction was conducted. • Experimental dependencies in the resonance range were done. • Maximal ME effect of gallium arsenide was observed.

  8. Surface-enhanced gallium arsenide photonic resonator with a quality factor of six million

    CERN Document Server

    Guha, Biswarup; Cadiz, Fabian; Morgenroth, Laurence; Ulin, Vladimir; Berkovitz, Vladimir; Lemaître, Aristide; Gomez, Carmen; Amo, Alberto; Combrié, Sylvian; Gérard, Bruno; Leo, Giuseppe; Favero, Ivan

    2016-01-01

    Gallium Arsenide and related compound semiconductors lie at the heart of optoelectronics and integrated laser technologies. Shaped at the micro and nano-scale, they allow strong interaction with quantum dots and quantum wells, and promise to result in stunning devices. However gallium arsenide optical structures presently exhibit lower performances than their silicon-based counterparts, notably in nanophotonics where the surface plays a chief role. Here we report on advanced surface control of miniature gallium arsenide optical resonators, using two distinct techniques that produce permanent results. One leads to extend the lifetime of free-carriers and enhance luminescence, while the other strongly reduces surface absorption originating from mid-gap states and enables ultra-low optical dissipation devices. With such surface control, the quality factor of wavelength-sized optical disk resonators is observed to rise up to six million at telecom wavelength, greatly surpassing previous realizations and opening n...

  9. The comparison between gallium arsenide and indium gallium arsenide as materials for solar cell performance using Silvaco application

    Energy Technology Data Exchange (ETDEWEB)

    Zahari, Suhaila Mohd; Norizan, Mohd Natashah; Mohamad, Ili Salwani; Osman, Rozana Aina Maulat; Taking, Sanna [School of Microelectronic Engineering, Universiti Malaysia Perlis, Kampus Pauh Putra, 02600 Arau, Perlis (Malaysia)

    2015-05-15

    The work presented in this paper is about the development of single and multilayer solar cells using GaAs and InGaAs in AM1.5 condition. The study includes the modeling structure and simulation of the device using Silvaco applications. The performance in term of efficiency of Indium Gallium Arsenide (InGaAs) and GaAs material was studied by modification of the doping concentration and thickness of material in solar cells. The efficiency of the GaAs solar cell was higher than InGaAs solar cell for single layer solar cell. Single layer GaAs achieved an efficiency about 25% compared to InGaAs which is only 2.65% of efficiency. For multilayer which includes both GaAs and InGaAs, the output power, P{sub max} was 8.91nW/cm² with the efficiency only 8.51%. GaAs is one of the best materials to be used in solar cell as a based compared to InGaAs.

  10. The comparison between gallium arsenide and indium gallium arsenide as materials for solar cell performance using Silvaco application

    Science.gov (United States)

    Zahari, Suhaila Mohd; Norizan, Mohd Natashah; Mohamad, Ili Salwani; Osman, Rozana Aina Maulat; Taking, Sanna

    2015-05-01

    The work presented in this paper is about the development of single and multilayer solar cells using GaAs and InGaAs in AM1.5 condition. The study includes the modeling structure and simulation of the device using Silvaco applications. The performance in term of efficiency of Indium Gallium Arsenide (InGaAs) and GaAs material was studied by modification of the doping concentration and thickness of material in solar cells. The efficiency of the GaAs solar cell was higher than InGaAs solar cell for single layer solar cell. Single layer GaAs achieved an efficiency about 25% compared to InGaAs which is only 2.65% of efficiency. For multilayer which includes both GaAs and InGaAs, the output power, Pmax was 8.91nW/cm² with the efficiency only 8.51%. GaAs is one of the best materials to be used in solar cell as a based compared to InGaAs.

  11. Progress to a Gallium-Arsenide Deep-Center Laser

    Directory of Open Access Journals (Sweden)

    Janet L. Pan

    2009-10-01

    Full Text Available Although photoluminescence from gallium-arsenide (GaAs deep-centers was first observed in the 1960s, semiconductor lasers have always utilized conduction-to-valence-band transitions. Here we review recent materials studies leading to the first GaAs deep-center laser. First, we summarize well-known properties: nature of deep-center complexes, Franck-Condon effect, hotoluminescence. Second, we describe our recent work: insensitivity of photoluminescence with heating, striking differences between electroluminescence and photoluminescence, correlation between transitions to deep-states and absence of bandgap-emission. Room-temperature stimulated-emission from GaAs deep-centers was observed at low electrical injection, and could be tuned from the bandgap to half-the-bandgap (900–1,600 nm by changing the electrical injection. The first GaAs deep-center laser was demonstrated with electrical injection, and exhibited a threshold of less than 27 mA/cm2 in continuous-wave mode at room temperature at the important 1.54 μm fiber-optic wavelength. This small injection for laser action was explained by fast depopulation of the lower state of the optical transition (fast capture of free holes onto deep-centers, which maintains the population inversion. The evidence for laser action included: superlinear L-I curve, quasi-Fermi level separations satisfying Bernard-Duraffourg’s criterion, optical gains larger than known significant losses, clamping of the optical-emission from lossy modes unable to reach laser action, pinning of the population distribution during laser action.

  12. High-field phase-diagram of Fe arsenide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Y.J.; Jaroszynski, J.; Yamamoto, A.; Gurevich, A.; Riggs, S.C.; Boebinger, G.S.; Larbalestier, D. [National High Magnetic Field Laboratory, Florida State University, Tallahassee-FL 32310 (United States); Wen, H.H. [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zhigadlo, N.D.; Katrych, S.; Bukowski, Z.; Karpinski, J. [Laboratory for Solid State Physics, ETH Zuerich, CH-8093 Zuerich (Switzerland); Liu, R.H.; Chen, H.; Chen, X.H. [Hefei National Laboratory for Physical Science a Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Balicas, L., E-mail: balicas@magnet.fsu.ed [National High Magnetic Field Laboratory, Florida State University, Tallahassee-FL 32310 (United States)

    2009-05-01

    Here, we report an overview of the phase-diagram of single-layered and double-layered Fe arsenide superconductors at high magnetic fields. Our systematic magneto-transport measurements of polycrystalline SmFeAsO{sub 1-x}F{sub x} at different doping levels confirm the upward curvature of the upper critical magnetic field H{sub c2}(T) as a function of temperature T defining the phase boundary between the superconducting and metallic states for crystallites with the ab planes oriented nearly perpendicular to the magnetic field. We further show from measurements on single-crystals that this feature, which was interpreted in terms of the existence of two superconducting gaps, is ubiquitous among both series of single- and double-layered compounds. In all compounds explored by us the zero temperature upper critical field H{sub c2}(0), estimated either through the Ginzburg-Landau or the Werthamer-Helfand-Hohenberg single gap theories, strongly surpasses the weak-coupling Pauli paramagnetic limiting field. This clearly indicates the strong-coupling nature of the superconducting state and the importance of magnetic correlations for these materials. Our measurements indicate that the superconducting anisotropy, as estimated through the ratio of the effective masses gamma = (m{sub c}/m{sub ab}){sup 1/2} for carriers moving along the c-axis and the ab-planes, respectively, is relatively modest as compared to the high-T{sub c} cuprates, but it is temperature, field and even doping dependent. Finally, our preliminary estimations of the irreversibility field H{sub m}(T), separating the vortex-solid from the vortex-liquid phase in the single-layered compounds, indicates that it is well described by the melting of a vortex lattice in a moderately anisotropic uniaxial superconductor.

  13. Noble Metal Arsenides and Gold Inclusions in Northwest Africa 8186

    Science.gov (United States)

    Srinivasan, P.; McCubbin, F. M.; Rahman, Z.; Keller, L. P.; Agee, C. B.

    2016-01-01

    CK carbonaceous chondrites are a highly thermally altered group of carbonaceous chondrites, experiencing temperatures ranging between approximately 576-867 degrees Centigrade. Additionally, the mineralogy of the CK chondrites record the highest overall oxygen fugacity of all chondrites, above the fayalite-magnetite-quartz (FMQ) buffer. Me-tallic Fe-Ni is extremely rare in CK chondrites, but magnetite and Fe,Ni sulfides are commonly observed. Noble metal-rich inclusions have previously been found in some magnetite and sulfide grains. These arsenides, tellurides, and sulfides, which contain varying amounts of Pt, Ru, Os, Te, As, Ir, and S, are thought to form either by condensation from a solar gas, or by exsolution during metamorphism on the chondritic parent body. Northwest Africa (NWA) 8186 is a highly metamorphosed CK chondrite. This meteorite is predominately composed of NiO-rich forsteritic olivine (Fo65), with lesser amounts of plagioclase (An52), augite (Fs11Wo49), magnetite (with exsolved titanomagnetite, hercynite, and titanohematite), monosulfide solid solution (with exsolved pentlandite), and the phosphate minerals Cl-apatite and merrillite. This meteorite contains coarse-grained, homogeneous silicates, and has 120-degree triple junctions between mineral phases, which indicates a high degree of thermal metamorphism. The presence of NiO-rich olivine, oxides phases all bearing Fe3 plus, and the absence of metal, are consistent with an oxygen fugacity above the FMQ buffer. We also observed noble metal-rich phases within sulfide grains in NWA 8186, which are the primary focus of the present study.

  14. Indium Phosphide Window Layers for Indium Gallium Arsenide Solar Cells

    Science.gov (United States)

    Jain, Raj K.

    2005-01-01

    Window layers help in reducing the surface recombination at the emitter surface of the solar cells resulting in significant improvement in energy conversion efficiency. Indium gallium arsenide (In(x)Ga(1-x)As) and related materials based solar cells are quite promising for photovoltaic and thermophotovoltaic applications. The flexibility of the change in the bandgap energy and the growth of InGaAs on different substrates make this material very attractive for multi-bandgap energy, multi-junction solar cell approaches. The high efficiency and better radiation performance of the solar cell structures based on InGaAs make them suitable for space power applications. This work investigates the suitability of indium phosphide (InP) window layers for lattice-matched In(0.53)Ga(0.47)As (bandgap energy 0.74 eV) solar cells. We present the first data on the effects of the p-type InP window layer on p-on-n lattice-matched InGaAs solar cells. The modeled quantum efficiency results show a significant improvement in the blue region with the InP window. The bare InGaAs solar cell performance suffers due to high surface recombination velocity (10(exp 7) cm/s). The large band discontinuity at the InP/InGaAs heterojunction offers a great potential barrier to minority carriers. The calculated results demonstrate that the InP window layer effectively passivates the solar cell front surface, hence resulting in reduced surface recombination and therefore, significantly improving the performance of the InGaAs solar cell.

  15. Arginine-responsive terbium luminescent hybrid sensors triggered by two crown ether carboxylic acids

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Lasheng [Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Tang, Ke; Ding, Xiaoping [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Wang, Qianming, E-mail: qmwang@scnu.edu.cn [Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Zhou, Zhan; Xiao, Rui [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China)

    2013-12-01

    Crown ether carboxylic acids constitute main building blocks for the synthesis of terbium containing covalent cross-linked luminescent materials. Both the complexes and the hybrid nanomaterials could exhibit remarkable green emissions in pure water. More importantly, they were found to have a profound effect on the luminescence responses to arginine compared with glutamic acid, histidine, tryptophan, threonine, tyrosine and phenylalanine in aqueous environment. The present study provided the possibility of using a host–guest mechanism as a way of signal transduction based on lanthanide supramolecular hybrid materials. - Highlights: • Crown ether carboxylic acids were found to sensitize terbium ions among a group of ethers. • The complexes and silica hybrid materials were both prepared and characterized. • They could exhibit remarkable green emissions in pure water.

  16. Comparative analysis of conjugated alkynyl chromophore-triazacyclononane ligands for sensitized emission of europium and terbium.

    Science.gov (United States)

    Soulié, Marine; Latzko, Frédéric; Bourrier, Emmanuel; Placide, Virginie; Butler, Stephen J; Pal, Robert; Walton, James W; Baldeck, Patrice L; Le Guennic, Boris; Andraud, Chantal; Zwier, Jurriaan M; Lamarque, Laurent; Parker, David; Maury, Olivier

    2014-07-07

    A series of europium and terbium complexes based on a functionalized triazacyclononane carboxylate or phosphinate macrocyclic ligand is described. The influence of the anionic group, that is, carboxylate, methylphosphinate, or phenylphosphinate, on the photophysical properties was studied and rationalized on the basis of DFT calculated structures. The nature, number, and position of electron-donating or electron-withdrawing aryl substituents were varied systematically within the same phenylethynyl scaffold in order to optimize the brightness of the corresponding europium complexes and investigate their two-photon absorption properties. Finally, the europium complexes were examined in cell-imaging applications, and selected terbium complexes were studied as potential oxygen sensors. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Spectrofluorimetric Determination of Human Serum Albumin Using Terbium-Danofloxacin Probe

    OpenAIRE

    Ramezani, Amir M.; Manzoori, Jamshid L.; Amjadi, Mohammad; Jouyban, Abolghasem

    2012-01-01

    A spectrofluorimetric method is proposed for the determination of human serum albumin (HSA) and bovine serum albumin (BSA) using terbium-danofloxacin (Tb3+-Dano) as a fluorescent probe. These proteins remarkably enhance the fluorescence intensity of the Tb3+-Dano complex at 545 nm, and the enhanced fluorescence intensity of Tb3+-Dano is proportional to the concentration of proteins (HSA and BSA). Optimum conditions for the determination of HSA were investigated and found that the maximum resp...

  18. Gallium arsenide integrated optical devices for high-speed diagnostic systems

    Energy Technology Data Exchange (ETDEWEB)

    McWright, G.; Lowry, M.; Takeuchi, E.; Murphy, G.; Tindall, W.; Koo, J.; Roeske, F.

    1987-01-01

    The design, fabrication, and evaluation of waveguide electro-optic modulators in gallium arsenide for application to high-speed diagnostic systems are discussed specifically. This paper is focused on high bandwidth, single event analog modulation, and radiation susceptibility of these devices.

  19. Genetically Encoded FRET-Sensor Based on Terbium Chelate and Red Fluorescent Protein for Detection of Caspase-3 Activity

    Directory of Open Access Journals (Sweden)

    Alexander S. Goryashchenko

    2015-07-01

    Full Text Available This article describes the genetically encoded caspase-3 FRET-sensor based on the terbium-binding peptide, cleavable linker with caspase-3 recognition site, and red fluorescent protein TagRFP. The engineered construction performs two induction-resonance energy transfer processes: from tryptophan of the terbium-binding peptide to Tb3+ and from sensitized Tb3+ to acceptor—the chromophore of TagRFP. Long-lived terbium-sensitized emission (microseconds, pulse excitation source, and time-resolved detection were utilized to eliminate directly excited TagRFP fluorescence and background cellular autofluorescence, which lasts a fraction of nanosecond, and thus to improve sensitivity of analyses. Furthermore the technique facilitates selective detection of fluorescence, induced by uncleaved acceptor emission. For the first time it was shown that fluorescence resonance energy transfer between sensitized terbium and TagRFP in the engineered construction can be studied via detection of microsecond TagRFP fluorescence intensities. The lifetime and distance distribution between donor and acceptor were calculated using molecular dynamics simulation. Using this data, quantum yield of terbium ions with binding peptide was estimated.

  20. Green light emission in aluminum oxide powders doped with different terbium concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Mariscal B, L; Falcony, C. [IPN, Centro de Investigacion y de Estudios Avanzados, 07360 Ciudad de Mexico (Mexico); Carmona T, S.; Murrieta, H.; Sanchez A, M. A. [UNAM, Instituto de Fisica, 04510 Ciudad de Mexico (Mexico); Vazquez A, R. [IPN, Escuela Superior de Computo, 07738 Ciudad de Mexico (Mexico); Garcia R, C. M., E-mail: mariscal2005@gmail.com [UNAM, Facultad de Ciencias, 04510 Ciudad de Mexico (Mexico)

    2016-11-01

    Different emission intensities presented in aluminum oxide phosphors corresponding to different concentrations of doping performed with terbium are analyzed. The phosphors were synthesized by the evaporation technique and were characterized by photo and cathodoluminescence, X-ray diffraction and EDS techniques for different incorporation percentages of terbium as dopant; they show characteristic transitions in 494, 543, 587 and 622 nm, corresponding to {sup 5}D{sub 4} → {sup 7}F{sub 6}, {sup 5}D{sub 4} → {sup 7}F{sub 5}, {sup 5}D{sub 4} → {sup 7}F{sub 4} and {sup 5}D{sub 4} → {sup 7}F{sub 3}, respectively when they are excited with λ{sub exc} = 380 nm wavelength at room temperature. The results of X-ray diffraction show the presence of α-Al{sub 2}O{sub 3} phases with peaks located at 2θ = 25.78, 35.34, 37.96, 43.56, 45.8, 52.74, 57.7, 61.5, 66.74, 68.44, 77.12 and 80.94, and the δ-Al{sub 2}O-3 phase 2θ = 32.82, 45.8, 61.36 and 66.74. These compounds were heat treated for two hours at 1100 degrees Celsius. EDS analyzes indicate that these compounds have close to 60% oxygen around of 40% aluminum in the presence of terbium as dopant which indicates a stoichiometry close to the expected one for alumina. (Author)

  1. Graphene quantum dots-terbium ions as novel sensitive and selective time-resolved luminescent probes.

    Science.gov (United States)

    Llorent-Martínez, Eulogio J; Durán, Gema M; Ríos, Ángel; Ruiz-Medina, Antonio

    2018-01-01

    We propose an alternative approach for the development of analytical methods based on terbium-sensitized luminescence (TSL). TSL is based on the complexation between Tb(III) ions and fluorescent organic compounds that have appropriate functional groups to complex with Tb(III). We report the use of graphene quantum dot (GQDs) nanoparticles to improve the sensitivity and selectivity of TSL detection. GQDs can react with terbium ions through the carboxylic groups present in their structure. These Tb(III)-GQD complexes, formed in situ in aqueous solution, can be used as time-resolved luminescent probes. Ascorbic acid was selected as a target analyte to demonstrate the suitability of the proposed method. The selectivity of the TSL method was highly improved for most of the interferences tested. Under the optimum conditions [Tb(III) concentration 5 × 10-4 mol L-1, GQD concentration 4 mg L-1], a minimum 100% increase in selectivity was observed for several vitamins and common cations that may be present in the samples to be analyzed. In addition, the analytical signal showed a 30% enhancement with the use of GQDs compared with the use of merely Tb(III) ions, with a detection limit of 0.12 μg mL-1. The repeatability and intermediate precision were lower than 3% and 5%, respectively. From the results obtained, the implementation of GQDs in TSL can lead to the development of novel time-resolved luminescent probes with high analytical potential. Graphical abstract Quenching of Tb(III)-graphene quantum dot (GQD) luminescence by ascorbic acid (AA). TBL terbium-sensitized luminescence.

  2. A Study of Hydrogen Anion Substitution in 1111-type Iron Arsenides

    Science.gov (United States)

    Hosono, Hideo

    2014-03-01

    Hydrogen is the simplest bipolar element and its valence state can be controlled from +1 to -1. We have synthesized the 1111-type iron arsenides CaFeAsH and LnFeAsO1 -xHx (Ln = lanthanide; 0 3d bands (dxy, dyz and dzx), which is caused not only by regularization of the tetrahedral shape of FeAs4 due to chemical pressure effects but also by selective band occupation with doped electrons. Very recently, a new AFM phase was found around x =0.5, suggesting that the double dome Tc structure reflects the presence of two AFM phases at x =0 and 0,5. In this talk, I review the recent progress in superconductivity in 1111-type iron (oxy)arsenides and related compounds induced by hydrogen anion substitution.

  3. Fluorescence study of some terbium-oligopeptide complexes in methanolic solution.

    Science.gov (United States)

    Rabouan, S; Delage, J; Durand, W; Prognon, P; Barthes, D

    2000-04-03

    This study concerned the use of lanthanide chelates to detect glycyl-leucyl-phenylalanine (GLF) and its homologues. Spectroscopic analysis of peptides without or with terbium complexation revealed the formation of (LF)(3)(Tb)(2), (GF)(3)(Tb)(2), (GLF)(3)(Tb)(2) and (FL)(4)Tb, (FG)(4)Tb complexes with high stability constants in methanolic solutions (pK(d)>13). Lanthanide chelate emission displayed a large Stokes shift (>270 nm), which allowed Tb chelates of GLF and its derivatives to be used for detection purposes. However, this preliminary study indicated some important limitations associated with lanthanide chelation, such as high methanolic content.

  4. Electromagnetic properties of terbium gallium garnet at millikelvin temperatures and low photon energy

    Science.gov (United States)

    Kostylev, Nikita; Goryachev, Maxim; Bushev, Pavel; Tobar, Michael E.

    2017-07-01

    Electromagnetic properties of single crystal terbium gallium garnet are characterised from room down to millikelvin temperatures using the whispering gallery mode method. Microwave spectroscopy is performed at low powers equivalent to a few photons in energy and conducted as functions of the magnetic field and temperature. A phase transition is detected close to the temperature of 3.5 K. This is observed for multiple whispering gallery modes causing an abrupt negative frequency shift and a change in transmission due to extra losses in the new phase caused by a change in complex magnetic susceptibility.

  5. Nuclear excitation functions from 40 to 200 MeV proton irradiation of terbium

    Energy Technology Data Exchange (ETDEWEB)

    Engle, Jonathan W., E-mail: jwengle@lanl.gov; Mashnik, Stepan G.; Parker, Lauren A.; Jackman, Kevin R.; Bitteker, Leo J.; Ullmann, John L.; Gulley, Mark S.; Pillai, Chandra; John, Kevin D.; Birnbaum, Eva R.; Nortier, Francois M.

    2016-01-01

    Nuclear formation cross sections are reported for 26 radionuclides, measured with 40–200 MeV proton irradiations of terbium foils. These data provide the basis for the production of medically relevant radionuclides (e.g., {sup 152}Tb, {sup 155}Tb, {sup 155}Eu, and {sup 156}Eu) and {sup 153}Gd, a potential source used in ongoing efforts to characterize stellar nucleosynthesis routes. Computational predictions from the ALICE2011, CEM03.03, Bertini, and INCL + ABLA codes are compared with newly measured data to contribute to the ongoing process of code development, and yields are calculated for selected radionuclides using measured data.

  6. An advanced space photovoltaic concentrator array using Fresnel lenses, gallium arsenide cells, and prismatic cell covers

    Science.gov (United States)

    O'Neill, Mark J.; Piszczor, Michael F.

    1988-01-01

    The current status of a space concentrator array which uses refractive optics, gallium arsenide cells, and prismatic cell covers to achieve excellent performance at a very low array mass is documented. The prismatically covered cells have established records for space cell performance (24.2 percent efficient at 100 AM0 suns and 25 C) and terrestrial single-junction cell performance (29.3 percent efficient at 200 AM1.5 suns and 25 C).

  7. Performance of a Medipix3RX spectroscopic pixel detector with a high resistivity gallium arsenide sensor.

    Science.gov (United States)

    Hamann, Elias; Koenig, Thomas; Zuber, Marcus; Cecilia, Angelica; Tyazhev, Anton; Tolbanov, Oleg; Procz, Simon; Fauler, Alex; Baumbach, Tilo; Fiederle, Michael

    2015-03-01

    High resistivity gallium arsenide is considered a suitable sensor material for spectroscopic X-ray imaging detectors. These sensors typically have thicknesses between a few hundred μm and 1 mm to ensure a high photon detection efficiency. However, for small pixel sizes down to several tens of μm, an effect called charge sharing reduces a detector's spectroscopic performance. The recently developed Medipix3RX readout chip overcomes this limitation by implementing a charge summing circuit, which allows the reconstruction of the full energy information of a photon interaction in a single pixel. In this work, we present the characterization of the first Medipix3RX detector assembly with a 500 μm thick high resistivity, chromium compensated gallium arsenide sensor. We analyze its properties and demonstrate the functionality of the charge summing mode by means of energy response functions recorded at a synchrotron. Furthermore, the imaging properties of the detector, in terms of its modulation transfer functions and signal-to-noise ratios, are investigated. After more than one decade of attempts to establish gallium arsenide as a sensor material for photon counting detectors, our results represent a breakthrough in obtaining detector-grade material. The sensor we introduce is therefore suitable for high resolution X-ray imaging applications.

  8. Two years of on-orbit gallium arsenide performance from the LIPS solar cell panel experiment

    Science.gov (United States)

    Francis, R. W.; Betz, F. E.

    1985-01-01

    The LIPS on-orbit performance of the gallium arsenide panel experiment was analyzed from flight operation telemetry data. Algorithms were developed to calculate the daily maximum power and associated solar array parameters by two independent methods. The first technique utilizes a least mean square polynomial fit to the power curve obtained with intensity and temperature corrected currents and voltages; whereas, the second incorporates an empirical expression for fill factor based on an open circuit voltage and the calculated series resistance. Maximum power, fill factor, open circuit voltage, short circuit current and series resistance of the solar cell array are examined as a function of flight time. Trends are analyzed with respect to possible mechanisms which may affect successive periods of output power during 2 years of flight operation. Degradation factors responsible for the on-orbit performance characteristics of gallium arsenide are discussed in relation to the calculated solar cell parameters. Performance trends and the potential degradation mechanisms are correlated with existing laboratory and flight data on both gallium arsenide and silicon solar cells for similar environments.

  9. Micelle-enhanced and terbium-sensitized spectrofluorimetric determination of gatifloxacin and its interaction mechanism

    Science.gov (United States)

    Guo, Changchuan; Wang, Lei; Hou, Zhun; Jiang, Wei; Sang, Lihong

    2009-05-01

    A terbium-sensitized spectrofluorimetric method using an anionic surfactant, sodium dodecyl benzene sulfonate (SDBS), was developed for the determination of gatifloxacin (GFLX). A coordination complex system of GFLX-Tb 3+-SDBS was studied. It was found that SDBS significantly enhanced the fluorescence intensity of the complex (about 11-fold). Optimal experimental conditions were determined as follows: excitation and emission wavelengths of 331 and 547 nm, pH 7.0, 2.0 × 10 -4 mol l -1 terbium (III), and 2.0 × 10 -4 mol l -1 SDBS. The enhanced fluorescence intensity of the system (Δ If) showed a good linear relationship with the concentration of GFLX over the range of 5.0 × 10 -10 to 5.0 × 10 -8 mol l -1 with a correlation coefficient of 0.9996. The detection limit (3 σ) was determined as 6.0 × 10 -11 mol l -1. This method has been successfully applied to the determination of GFLX in pharmaceuticals and human urine/serum samples. Compared with most of other methods reported, the rapid and simple procedure proposed in the text offers higher sensitivity, wider linear range, and better stability. The interaction mechanism of the system is also studied by the research of ultraviolet absorption spectra, surface tension, solution polarity and fluorescence polarization.

  10. Circularly Polarized Luminescence in Enantiopure Europium and Terbium Complexes with Modular, All-Oxygen Donor Ligands

    Science.gov (United States)

    Seitz, Michael; Do, King; Ingram, Andrew J.; Moore, Evan G.; Muller, Gilles; Raymond, Kenneth N.

    2009-01-01

    Abstract: Circulaly polarized luminescence from terbium(III) complexed and excited by chiral antenna ligands gives strong emission The modular synthesis of three new octadentate, enantiopure ligands are reported - one with the bidentate chelating unit 2-hydroxyisophthalamide (IAM) and two with 1-hydroxy-2-pyridinone (1,2-HOPO) units. A new design principle is introduced for the chiral, non-racemic hexamines which constitute the central backbones for the presented class of ligands. The terbium(III) complex of the IAM ligand, as well as the europium(III) complexes of the 1,2-HOPO ligands are synthesized and characterized by various techniques (NMR, UV, CD, luminescence spectroscopy). All species exhibit excellent stability and moderate to high luminescence efficiency (quantum yields ΦEu = 0.05–0.08 and ΦTb = 0.30–0.57) in aqueous solution at physiological pH. Special focus is put onto the properties of the complexes in regard to circularly polarized luminescence (CPL). The maximum luminescence dissymmetry factors (glum) in aqueous solution are high with |glum|max = 0.08 – 0.40. Together with the very favorable general properties (good stability, high quantum yields, long lifetimes), the presented lanthanide complexes can be considered as good candidates for analytical probes based on CPL in biologically relevant environments. PMID:19639983

  11. Luminescent method of determination of composition of europium and terbium complexes in solution by change of intensity ratio of luminescence bands

    Energy Technology Data Exchange (ETDEWEB)

    Bel' tyukova, S.V.; Nazarenko, N.A.; Poluehktov, N.S.

    1982-03-01

    The complexes of europium and terbium with phenanthroline, ethylenediaminetetraacetate, nitrilotriacetate, some acids-phenol derivatives and ..beta..-diketones series have been used as an example to demonstrate that the value of the ratio of intensities on the two bands of europium(terbium) luminescence spectra - the one corresponding to the hypersensitive'' transition and the other, to the magnetic dipole one - can be used for determination of the complexes composition in solutions.

  12. Effect of gallium-arsenide laser, gallium-aluminum-arsenide laser and healing ointment on cutaneous wound healing in Wistar rats

    Directory of Open Access Journals (Sweden)

    R.V. Gonçalves

    2010-04-01

    Full Text Available This study determined the effects of gallium-aluminum-arsenide laser (GaAlAs, gallium-arsenide laser (GaAs and Dersani® healing ointment on skin wounds in Wistar rats. The parameters analyzed were: type I and III collagen fiber concentrations as well as the rate of wound closure. Five wounds, 12 mm in diameter, were made on the animals’ backs. The depth of the surgical incision was controlled by removing the epithelial tissue until the dorsal muscular fascia was exposed. The animals were anesthetized with ketamine and xylazine via intraperitoneal injection. The rats were randomly divided into five groups of 6 animals each, according to the treatment received. Group 1 (L4: GaAs laser (4 J/cm²; group 2 (L30: GaAlAs laser (30 J/cm²; group 3 (L60: GaAlAs laser (60 J/cm²; group 4 (D: Dersani® ointment; group 5 (control: 0.9% saline. The applications were made daily over a period of 20 days. Tissue fragments were stained with picrosirius to distinguish type I collagen from type III collagen. The collagen fibers were photo-documented and analyzed using the Quantum software based on the primary color spectrum (red, yellow and blue. Significant results for wound closing rate were obtained for group 1 (L4, 7.37 mm/day. The highest concentration of type III collagen fibers was observed in group 2 (L30; 37.80 ± 7.10%, which differed from control (29.86 ± 5.15% on the 20th day of treatment. The type I collagen fibers of group 1 (L4; 2.67 ± 2.23% and group 2 (L30; 2.87 ± 2.40% differed significantly from control (1.77 ± 2.97% on the 20th day of the experiment.

  13. The role of the ohmic contact on the efficiency of gallium arsenide radiation detectors

    Energy Technology Data Exchange (ETDEWEB)

    Castaldini, A. [Bologna Univ. (Italy). Dept. of Phys.; Cavallini, A. [Bologna Univ. (Italy). Dept. of Phys.; Polenta, L. [Bologna Univ. (Italy). Dept. of Phys.; Canali, C. [Department of Engineering Sciences, University of Modena, Via Campi 213/B, Modena (Italy); Del Papa, C. [Department of Physics, University of Udine, Via delle Scienze, Udine (Italy); Nava, F. [Department of Physics, University of Modena, Via Campi 213/A, Modena (Italy)

    1997-04-01

    It has recently been found that in gallium arsenide radiation detectors injecting ohmic contacts impede charge collection efficiency to get 100%, since breakdown occurs as soon as the electric field reaches the contact itself. In the present contribution, this phenomenon is investigated by comparing two sets of ohmic contacts realized by different technological procedures. While the overall defective state results to be nearly the same for both contacts, their performance significantly differs. Deep level junction spectroscopy shows that the defects are the same in both sets whilst there is much difference in density between a few of them. (orig.).

  14. Efficiency Enhancement of Gallium Arsenide Photovoltaics Using Solution-Processed Zinc Oxide Nanoparticle Light Scattering Layers

    Directory of Open Access Journals (Sweden)

    Yangsen Kang

    2015-01-01

    Full Text Available We demonstrate a high-throughput, solution-based process for subwavelength surface texturing of a III-V compound solar cell. A zinc oxide (ZnO nanoparticle ink is spray-coated directly on top of a gallium arsenide (GaAs solar cell. The nanostructured ZnO films have demonstrated antireflection and light scattering properties over the visible/near-infrared (NIR spectrum. The results show a broadband spectral enhancement of the solar cell external quantum efficiency (EQE, a 16% enhancement of short circuit current, and a 10% increase in photovoltaic efficiency.

  15. Development of a Free Carrier Absorption Measurement Instrument for Indium Phosphide and Gallium Arsenide.

    Science.gov (United States)

    1986-10-27

    AD-A174 ř DEVELOPMENT OF R FREE CARRIER ABSORPTION MEASUREMENT 1/2 INSTRUMENT FOR INDTU (U) EAGLE-PICHER RESEARCH LAB MIAMI OK SPECIALTY MATERIALS...SOBI S D Final Report Development of a Free Carrier Absorption Measurement Instrument For Indium Phosphide and Gallium Arsenide EAGLE PICHER R ES EA R CH...i P r OTic S D L C T DEC 0 3 ang Final Report Development of a Free Carrier Absorption Measurement Instrument For Indium Phosphide and Gallium

  16. High Pressure X-ray Diffraction Study on Icosahedral Boron Arsenide (B12As2)

    Energy Technology Data Exchange (ETDEWEB)

    J Wu; H Zhu; D Hou; C Ji; C Whiteley; J Edgar; Y Ma

    2011-12-31

    The high pressure properties of icosahedral boron arsenide (B12As2) were studied by in situ X-ray diffraction measurements at pressures up to 25.5 GPa at room temperature. B12As2 retains its rhombohedral structure; no phase transition was observed in the pressure range. The bulk modulus was determined to be 216 GPa with the pressure derivative 2.2. Anisotropy was observed in the compressibility of B12As2-c-axis was 16.2% more compressible than a-axis. The boron icosahedron plays a dominant role in the compressibility of boron-rich compounds.

  17. Surface plasma-enhanced internal photoemission in gallium arsenide Schottky diodes.

    Science.gov (United States)

    Torosian, K M; Karakashian, A S; Teng, Y Y

    1987-07-01

    An aluminum on n-type gallium arsenide Schottky diode with a prism coupler on the front face was illuminated by a p-polarized Nd:YAG laser to excite the surface plasma resonance in the aluminum barrier contact. The internal photoemission current and reflectance were measured simultaneously as a function of the angle of incidence. The excitation of the surface plasma resonance was observed by a dip in the reflectance which occurred at the same angle as a peak in the photoemission current. These effects disappeared in the case of s-polarization. Enhancement in the photoemission current by as much as a factor of 3 was obtained.

  18. Thermo-transferred thermoluminescence (TTTl) in potassium-yttrium double fluoride doped with terbium

    Energy Technology Data Exchange (ETDEWEB)

    Gallegos, A.; Rivera, T.; Diaz G, J. A. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Legaria 694, Col. Irrigacion, 11500 Mexico D. F. (Mexico); Azorin, J. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco No. 186, Col. Vicentina, 09340 Mexico D. F. (Mexico); Azorin, J. C. [Universidad de Guanajuato, Division de Ciencias e Ingenierias-Campus Leon, Lomas del Bosque No. 103, Col. Lomas del Campestre, 37000 Leon, Guanajuato (Mexico); Licona, R.; Rivas, F.; Hernandez C, G. [Benemerita Universidad Autonoma de Puebla, Facultad de Ciencias Quimicas, 14 Sur y San Claudio, Ciudad Universitaria, Puebla de Zaragoza, Puebla (Mexico); Khaidukov, N. [Institute of General and Inorganic Chemistry, Lenin SK 11 Prospect 31, Moscow 117907 (Russian Federation)

    2011-02-15

    This paper presents results of studying the thermo-transferred thermoluminescence (TTTl) phenomenon in potassium-yttrium double fluoride doped with terbium (K{sub 2}YF{sub 5:}Tb) at different impurity concentrations (0.8%, 0.95% and 0.99%). Previously to study the TTTl phenomenon, structural characterization and chemical composition of the materials were determined. The structural studies were conducted using a scanning electron microscope; meanwhile, chemical composition was analyzed using energy dispersive X-ray spectroscopy. Thermoluminescence kinetics was studied irradiating the samples with {sup 137}Cs gamma rays as well as with {sup 90}Sr/{sup 90}Y beta rays, analyzing the glow curves by the deconvolution method for obtaining the kinetic parameters. (Author)

  19. The influence of pressure on the photoluminescence properties of a terbium-adipate framework

    Science.gov (United States)

    Spencer, Elinor C.; Zhao, Jing; Ross, Nancy L.; Andrews, Michael B.; Surbella, Robert G.; Cahill, Christopher L.

    2013-06-01

    The influence of pressure (over the 0-4.7 GPa range) on the photoluminescence emissions and crystal structure of the known 3D terbium-adipate metal-organic framework material Tb-GWMOF6 has been evaluated by high-pressure single-crystal X-ray diffraction and spectroscopic techniques. The results from this study show that this complex lanthanide framework structure undergoes three phase transitions within the 0-4 GPa pressure range that involve alterations in the number of symmetry independent Tb3+ ion sites within the crystal lattice. These pressure induced modifications to the structure of Tb-GWMOF6 lead to pronounced changes in the profiles of the 5D4→7F5 emission spectra of this complex.

  20. Terbium Radionuclides for Theranostics Applications: A Focus On MEDICIS-PROMED

    Science.gov (United States)

    Cavaier, R. Formento; Haddad, F.; Sounalet, T.; Stora, T.; Zahi, I.

    A new facility, named CERN-MEDICIS, is under construction at CERN to produce radionuclides for medical applications. In parallel, the MEDICIS-PROMED, a Marie Sklodowska-Curie innovative training network of the Horizon 2020 European Commission's program, is being coordinated by CERN to train young scientists on the production and use of innovative radionuclides and develop a network of experts within Europe. One program within MEDICIS-PROMED is to determine the feasibility of producing innovative radioisotopes for theranostics using a commercial middle-sized high-current cyclotron and the mass separation technology developed at CERN-MEDICIS. This will allow the production of high specific activity radioisotopes not achievable with the common post-processing by chemical separation. Radioisotopes of scandium, copper, arsenic and terbium have been identified. Preliminary studies of activation yield and irradiation parameters optimization for the production of Tb-149 will be described.

  1. Dielectric and conducting behavior of gadolinium-terbium fumarate heptahydrate crystals

    Science.gov (United States)

    Shah, M. D.; Want, B.

    2015-07-01

    Gadolinium-terbium fumarate heptahydrate crystals were grown in silica gel by using single gel diffusion technique. The crystals were characterized by different physico-chemical techniques of characterization. Powder X-ray diffraction results showed that the grown material is purely crystalline in nature. Elemental analyses suggested the chemical formula of the compound to be Gd Tb (C4H2O4)3ṡ7H2O. Energy dispersive X-ray analysis confirmed the presence of Gd and Tb in the title compound. The dielectric and conductivity studies of the grown compound were carried as function of frequency of applied field and the temperature. The grown material showed a dielectric anomaly which was correlated with its thermal behavior. The ac conductivity of the material showed Jonscher's power law behavior: σ(ω)=σo+Aωs, with a temperature-dependent power exponent s(<1). The conductivity was found to be a function of temperature and frequency.

  2. Highly sensitive detection of dipicolinic acid with a water-dispersible terbium-metal organic framework.

    Science.gov (United States)

    Bhardwaj, Neha; Bhardwaj, Sanjeev; Mehta, Jyotsana; Kim, Ki-Hyun; Deep, Akash

    2016-12-15

    The sensitive detection of dipicolinic acid (DPA) is strongly associated with the sensing of bacterial organisms in food and many types of environmental samples. To date, the demand for a sensitive detection method for bacterial toxicity has increased remarkably. Herein, we investigated the DPA detection potential of a water-dispersible terbium-metal organic framework (Tb-MOF) based on the fluorescence quenching mechanism. The Tb-MOF showed a highly sensitive ability to detect DPA at a limit of detection of 0.04nM (linear range of detection: 1nM to 5µM) and also offered enhanced selectivity from other commonly associated organic molecules. The present study provides a basis for the application of Tb-MOF for direct, convenient, highly sensitive, and specific detection of DPA in the actual samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. A New Bis(phthalocyaninato) Terbium Single-Ion Magnet with an Overall Excellent Magnetic Performance.

    Science.gov (United States)

    Chen, Yuxiang; Ma, Fang; Chen, Xiaoxiang; Dong, Bowei; Wang, Kang; Jiang, Shangda; Wang, Chiming; Chen, Xin; Qi, Dongdong; Sun, Haoling; Wang, Bingwu; Gao, Song; Jiang, Jianzhuang

    2017-11-20

    Bulky and strong electron-donating dibutylamino groups were incorporated onto the peripheral positions of one of the two phthalocyanine ligands in the bis(phthalocyaninato) terbium complex, resulting in the isolation of heteroleptic double-decker (Pc)Tb{Pc[N(C4H9)2]8} {Pc = phthalocyaninate; Pc[N(C4H9)2]8 = 2,3,9,10,16,17,23,24-octakis(dibutylamino)phthalocyaninate} with the nature of an unsymmetrical molecular structure, a square-antiprismatic coordination geometry, an intensified coordination field strength, and the presence of organic radical-f interaction. As a total result of all these factors, this sandwich-type tetrapyrrole lanthanide single-ion magnet (SIM) exhibits an overall enhanced magnetic performance including a high blocking temperature (TB) of 30 K and large effective spin-reversal energy barrier of Ueff = 939 K, rendering it the best sandwich-type tetrapyrrole lanthanide SIM reported thus far.

  4. Ultralarge magneto-optic rotations and rotary dispersion in terbium gallium garnet single crystal.

    Science.gov (United States)

    Shaheen, Amrozia; Majeed, Hassaan; Anwar, Muhammad Sabieh

    2015-06-10

    We report systematically acquired data on the Verdet constant of terbium gallium garnet for wavelengths ranging from visible to near-infrared (405-830 nm) regime. Our experimental method of Stokes polarimetry is based on the Fourier decomposition of the received light intensity and allows unambiguous determination of both the Faraday rotation and the ellipticity of the emergent light. Temperature-dependent investigations in the range of 8-300 K extend earlier reports and verify the Verdet's constant direct dependence on the magnetization, whose first-order approximation is simply a manifestation of the Curie's law. Further, a least-squares fitting of the experimental data correlates well with theoretical predictions. At a wavelength of 405 nm and temperature of 8 K, the rotation is approximately 500°.

  5. Terbium fluorescence as a sensitive, inexpensive probe for UV-induced damage in nucleic acids

    Energy Technology Data Exchange (ETDEWEB)

    El-Yazbi, Amira F.; Loppnow, Glen R., E-mail: glen.loppnow@ualberta.ca

    2013-07-05

    Graphical abstract: -- Highlights: •Simple, inexpensive, mix-and-read assay for positive detection of DNA damage. •Recognition of undamaged DNA via hybridization to a hairpin probe. •Terbium(III) fluorescence reports the amount of damage by binding to ssDNA. •Tb/hairpin is a highly selective and sensitive fluorescent probe for DNA damage. -- Abstract: Much effort has been focused on developing methods for detecting damaged nucleic acids. However, almost all of the proposed methods consist of multi-step procedures, are limited, require expensive instruments, or suffer from a high level of interferences. In this paper, we present a novel simple, inexpensive, mix-and-read assay that is generally applicable to nucleic acid damage and uses the enhanced luminescence due to energy transfer from nucleic acids to terbium(III) (Tb{sup 3+}). Single-stranded oligonucleotides greatly enhance the Tb{sup 3+} emission, but duplex DNA does not. With the use of a DNA hairpin probe complementary to the oligonucleotide of interest, the Tb{sup 3+}/hairpin probe is applied to detect ultraviolet (UV)-induced DNA damage. The hairpin probe hybridizes only with the undamaged DNA. However, the damaged DNA remains single-stranded and enhances the intrinsic fluorescence of Tb{sup 3+}, producing a detectable signal directly proportional to the amount of DNA damage. This allows the Tb{sup 3+}/hairpin probe to be used for sensitive quantification of UV-induced DNA damage. The Tb{sup 3+}/hairpin probe showed superior selectivity to DNA damage compared to conventional molecular beacons probes (MBs) and its sensitivity is more than 2.5 times higher than MBs with a limit of detection of 4.36 ± 1.2 nM. In addition, this probe is easier to synthesize and more than eight times cheaper than MBs, which makes its use recommended for high-throughput, quantitative analysis of DNA damage.

  6. Fine- and hyperfine structure investigations of even configuration system of atomic terbium

    Science.gov (United States)

    Stefanska, D.; Elantkowska, M.; Ruczkowski, J.; Furmann, B.

    2017-03-01

    In this work a parametric study of the fine structure (fs) and the hyperfine structure (hfs) for the even-parity configurations of atomic terbium (Tb I) is presented, based in considerable part on the new experimental results. Measurements on 134 spectral lines were performed by laser induced fluorescence (LIF) in a hollow cathode discharge lamp; on this basis, the hyperfine structure constants A and B were determined for 52 even-parity levels belonging to the configurations 4f85d6s2, 4f85d26s or 4f96s6p; in all the cases those levels were involved in the transitions investigated as the lower levels. For 40 levels the hfs was examined for the first time, and for the remaining 12 levels the new measurements supplement our earlier results. As a by-product, also preliminary values of the hfs constants for 84 odd-parity levels were determined (the investigations of the odd-parity levels system in the terbium atom are still in progress). This huge amount of new experimental data, supplemented by our earlier published results, were considered for the fine and hyperfine structure analysis. A multi-configuration fit of 7 configurations was performed, taking into account second-order of perturbation theory, including the effects of closed shell-open shell excitations. Predicted values of the level energies, as well as of magnetic dipole and electric quadrupole hyperfine structure constants A and B, are quoted in cases when no experimental values are available. By combining our experimental data with our own semi-empirical procedure it was possible to identify correctly the lower and upper level of the line 544.1440 nm measured by Childs with the use of the atomic-beam laser-rf double-resonance technique (Childs, J Opt Soc Am B 9;1992:191-6).

  7. Structural and optical characterization of terbium doped ZnGa2O4 thin films deposited by RF magnetron sputtering

    Science.gov (United States)

    Somasundaram, K.; Girija, K. G.; Sudarsan, V.; Selvin, P. Christopher; Vatsa, R. K.

    2016-05-01

    Tb3+ doped ZnGa2O4 nanophosphor (21 nm) has been synthesized via low temperature polyol route and subsequently thin films of the same were deposited on glass and ITO substrates by RF magnetron sputtering. The films were characterized by X-ray Diffraction and luminescence measurements. The XRD pattern showed that Tb3+ doped ZnGa2O4 nanophosphor has a cubic spinel phase. Luminescence behavior of the nanophosphor and as deposited sputtered film was investigated. The PL emission spectra of nanophosphor gave a broad ZnGa2O4 host emission band along with a strong terbium emission and the thin films showed only broad host emission band and there was no terbium ion emission.

  8. THE QUANTUM-WELL STRUCTURES OF SELF ELECTROOPTIC-EFFECT DEVICES AND GALLIUM-ARSENIDE

    Directory of Open Access Journals (Sweden)

    Mustafa TEMİZ

    1996-02-01

    Full Text Available Multiple quantum-well (MQW electroabsorptive self electro optic-effect devices (SEEDs are being extensively studied for use in optical switching and computing. The self electro-optic-effect devices which has quantum-well structures is a new optoelectronic technology with capability to obtain both optical inputs and outputs for Gallium-Arsenide/Aluminum Gallium-Arsenide (GaAs/AlGaAs electronic circuits. The optical inputs and outputs are based on quantum-well absorptive properties. These quantum-well structures consist of many thin layers of semiconductors materials of GaAs/AlGaAs which have emerged some important directions recently. The most important advance in the physics of these materials since the early days has been invention of the heterojunction structures which is based at present on GaAs technology. GaAs/AlGaAs structures present some important advantages to relevant band gap and index of refraction which allow to form the quantum-well structures and also to make semiconductor lasers, dedectors and waveguide optical switches.

  9. Liquid immiscibility between arsenide and sulfide melts: evidence from a LA-ICP-MS study in magmatic deposits at Serranía de Ronda (Spain)

    Science.gov (United States)

    Piña, R.; Gervilla, F.; Barnes, S.-J.; Ortega, L.; Lunar, R.

    2015-03-01

    The chromite-Ni arsenide (Cr-Ni-As) and sulfide-graphite (S-G) deposits from the Serranía de Ronda (Málaga, South Spain) contain an arsenide assemblage (nickeline, maucherite and nickeliferous löllingite) that has been interpreted to represent an arsenide melt and a sulfide-graphite assemblage (pyrrhotite, pentlandite, chalcopyrite and graphite) that has been interpreted to represent a sulfide melt, both of which have been interpreted to have segregated as immiscible liquids from an arsenic-rich sulfide melt. We have determined the platinum-group element (PGE), Au, Ag, Se, Sb, Bi and Te contents of the arsenide and sulfide assemblages using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to establish their partitioning behaviour during the immiscibility of an arsenide melt from a sulfide melt. Previous experimental work has shown that PGE partition more strongly into arsenide melts than into sulfide melts and our results fit with this observation. Arsenide minerals are enriched in all PGE, but especially in elements with the strongest affinity for the arsenide melt, including Ir, Rh and Pt. In contrast and also in agreement with previous studies, Se and Ag partition preferentially into the sulfide assemblage. The PGE-depleted nature of sulfides in the S-G deposits along with the discordant morphologies of the bodies suggest that these sulfides are not mantle sulfides, but that they represent the crystallization product of a PGE-depleted sulfide melt due to the sequestering of PGE by an arsenide melt.

  10. Determination of fluoxetine in pharmaceutical and biological samples based on the silver nanoparticle enhanced fluorescence of fluoxetine-terbium complex.

    Science.gov (United States)

    Lotfi, Ali; Manzoori, Jamshid L

    2016-11-01

    In this study, a simple and sensitive spectrofluorimetric method is presented for the determination of fluoxetine based on the enhancing effect of silver nanoparticles (AgNPs) on the terbium-fluoxetine fluorescence emission. The AgNPs were prepared by a simple reduction method and characterized by UV-Vis spectroscopy and transmission electron microscopy. It was indicated that these AgNPs have a remarkable amplifying effect on the terbium-sensitized fluorescence of fluoxetine. The effects of various parameters such as AgNP and Tb(3+) concentration and the pH of the media were investigated. Under obtained optimal conditions, the fluorescence intensity of the terbium-fluoxetine-AgNP system was enhanced linearly by increasing the concentration of fluoxetine in the range of 0.008 to 19 mg/L. The limit of detection (b + 3s) was 8.3 × 10(-4) mg/L. The interference effects of common species found in real samples were also studied. The method had good linearity, recovery, reproducibility and sensitivity, and was satisfactorily applied for the determination of fluoxetine in tablet formulations, human urine and plasma samples. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  11. Neutron Diffraction and Electrical Transport Studies on Magnetic Transition in Terbium at High Pressures and Low Temperatures

    Science.gov (United States)

    Thomas, Sarah; Montgomery, Jeffrey; Tsoi, Georgiy; Vohra, Yogesh; Weir, Samuel; Tulk, Christopher; Moreira Dos Santos, Antonio

    2013-06-01

    Neutron diffraction and electrical transport measurements have been carried out on the heavy rare earth metal terbium at high pressures and low temperatures in order to elucidate its transition from a helical antiferromagnetic to a ferromagnetic ordered phase as a function of pressure. The electrical resistance measurements using designer diamonds show a change in slope as the temperature is lowered through the ferromagnetic Curie temperature. The temperature of the ferromagnetic transition decreases at a rate of -16.7 K/GPa till 3.6 GPa, where terbium undergoes a structural transition from hexagonal close packed (hcp) to an α-Sm phase. Above this pressure, the electrical resistance measurements no longer exhibit a change in slope. In order to confirm the change in magnetic phase suggested by the electrical resistance measurements, neutron diffraction measurements were conducted at the SNAP beamline at the Oak Ridge National Laboratory. Measurements were made at pressures to 5.3 GPa and temperatures as low as 90 K. An abrupt increase in peak intensity in the neutron diffraction spectra signaled the onset of magnetic order below the Curie temperature. A magnetic phase diagram of rare earth metal terbium will be presented to 5.3 GPa and 90 K based on these studies.

  12. A novel three-jet microreactor for localized metal-organic chemical vapour deposition of gallium arsenide : Design and simulation

    NARCIS (Netherlands)

    Konakov, S.A.; Krzhizhanovskaya, V.V.

    2016-01-01

    We present a novel three-jet microreactor design for localized deposition of gallium arsenide (GaAs) by low-pressure Metal-Organic Chemical Vapour Deposition (MOCVD) for semiconductor devices, microelectronics and solar cells. Our approach is advantageous compared to the standard lithography and

  13. Study of Silver Nanoparticles Sensitized Fluorescence and Second-Order Scattering of Terbium(III-Pefloxacin Mesylate Complex and Determination of Pefloxacin Mesylate

    Directory of Open Access Journals (Sweden)

    Aiyun Li

    2014-01-01

    Full Text Available α-Keto acid of pefloxacin mesylate (PFLX can form the complex with Terbium(III. The intramolecular energy from PFLX to Terbium(III ion takes place when excited, and thus Terbium(III excited state is formed and then emits the characteristic fluorescence of Terbium(III, locating at 490, 545, 580, and 620 nm. The second-order scattering (SOS peak at 545 nm also appears for the complex with the exciting wavelength of 273 nm. When the silver nanoparticles are added to the system, the luminescence intensity at 545 nm greatly increased. So, with the adding of nanoparticles to the Terbium(III-PFLX complex, not only is the intramolecular energy promoted but also the SOS intensity is enhanced. The experimental results show that it is the silver nanoparticles with certain size and certain concentration which can greatly enhance the fluorescence-SOS intensity, and the relative intensity at 545 nm is proportional to the amount of PFLX. Based on this phenomenon, a novel method for the determination of PFLX has been developed and applied to the determination of PFLX in capsule and serum samples.

  14. Influence of crystalline structure on the luminescence properties of terbium orthotantalates

    Energy Technology Data Exchange (ETDEWEB)

    Siqueira, Kisla P.F. [Departamento de Química, Universidade Federal de Ouro Preto, Campus Morro do Cruzeiro, ICEB II, Ouro Preto 35400-000, Minas Gerais (Brazil); Carmo, Alexandre P. [Instituto Federal Fluminense, Campus Cabo Frio, RJ 28909-971 (Brazil); Bell, Maria J.V. [Departamento de Física, Universidade Federal de Juiz de Fora, Juiz de Fora 36036-330, MG (Brazil); Dias, Anderson, E-mail: anderson_dias@iceb.ufop.br [Departamento de Química, Universidade Federal de Ouro Preto, Campus Morro do Cruzeiro, ICEB II, Ouro Preto 35400-000, Minas Gerais (Brazil)

    2013-06-15

    Terbium orthotantalate powders were produced with M-fergusonite type (I2/a) and M′-fergusonite type (P2/a) structures. The samples were studied by X-ray diffraction, Raman scattering, and photoluminescence measurements (emission and decay curves). The results showed that crystalline materials were obtained with all the 18 Raman-active modes predicted by group theory calculations. Also, it was observed through photoluminescence decay curves that the Tb{sup 3+} ions occupies only one-symmetry site in both crystallographic arrangements. Photoluminescence emission curves exhibited some variation in spectral shape, peak position, and relative intensity as a consequence of their different crystalline arrangements. The dominated emission of Tb{sup 3+} ({sup 5}D{sub 4}→{sup 7}F{sub 5}) is centered with a maximum intensity at 549.2 nm (M-type) and 543.0 nm (M′-type). Fluorescence lifetimes for M-TbTaO{sub 4} and M′-TbTaO{sub 4} were determined as 33.4 μs and 1.25 ms, respectively. M′-type materials seems to be the most suitable for luminescent devices and could be a potential green luminescent material due to the strongest emission if compared with the M-fergusonite type. -- Highlights: ► Terbium orthotantalates were prepared in two different crystalline structures: I2/a and P2/a. ► XRD and Raman scattering showed that the different space groups obtained were exhibited all the 18 Raman-active modes. ► PL decay curves that the Tb{sup 3+} ions occupies only one-symmetry site in both crystallographic arrangements. ► Dominated emission of Tb{sup 3+} ({sup 5}D{sub 4}→{sup 7}F{sub 5}) is centered with a maximum intensity at 549 nm (M-type) and 543 nm (M′-type). ► Fluorescence lifetimes for M-TbTaO{sub 4} and M′-TbTaO{sub 4} were determined as 33.4 μs and 1.25 ms, respectively.

  15. Electronic structure, magnetic and superconducting properties of co-doped iron-arsenide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Rosner, Helge; Schnelle, Walter; Nicklas, Michael; Leithe-Jasper, Andreas [MPI CPfS Dresden (Germany); Weikert, Franziska [Los Alamos National Laboratory, New Mexico (United States); HLD Dresden Rossendorf (Germany); Wosnitza, Joachim [HLD Dresden Rossendorf (Germany)

    2013-07-01

    We present a joint experimental and theoretical study of co-doped iron-arsenide superconductors of the 122 family A{sub 1-x}K{sub x}Fe{sub 2-y}T{sub y}As{sub 2} (A = Ba,Sr,Eu; T = Co,Ru,Rh). In these systems, the co-doping enables the separation of different parameters - like electron count, disorder or the specific geometry of the FeAs layer - with respect to the position of the respective compounds in the general 122 phase diagram. For a series of compounds, we investigate the relevance of the different parameters for the magnetic, thermodynamic and superconducting properties. Our experimental investigations are supported by density functional electronic structure calculations applying different approximations for doping and disorder.

  16. NMR studies on the new iron arsenide superconductors including the superconducting state

    Energy Technology Data Exchange (ETDEWEB)

    Grafe, Hans-Joachim; Lang, Guillaume; Hammerath, Franziska; Manthey, Katarina; Behr, Guenther; Werner, Jochen; Buechner, Bernd [IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Paar, Dalibor [IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Dept. of Physics, Faculty of Science, Univ. of Zagreb (Croatia); Curro, Nicholas [Dept. of Physics, Univ. of California, Davis, CA 95616 (United States)

    2009-07-01

    We summarize our Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) results on the new iron arsenide superconductor LaO{sub 1-x}F{sub x}FeAs in the normal state, and show new NMR data in the superconducting state. Beyond early evidence of nodes and spin-singlet pairing[2], we find evidence of a deviation of the T{sup 3} behaviour of the spin lattice relaxation rate, 1/T{sub 1}, at temperatures significantly below T{sub c}, which would agree with the suggested extended s-wave symmetry. The deviation of the T{sup 3} behaviour is induced by the pair breaking effect of impurities. Different amounts of impurities would lead to different temperature dependences of 1/T{sub 1}, which would allow to differentiate between d-wave and extended s-wave symmetries.

  17. Systems engineering and technical assistance in support of digital gallium arsenide insertion projects

    Science.gov (United States)

    Butler, Daniel H.

    1992-04-01

    Booz-Allen provided a high level of support, including systems engineering analyses and technical assistance for systems insertion efforts using digital Gallium Arsenide (GaAs). Once insertion candidates were chosen, Booz-Allen supported the insertion efforts by acting as a liaison between the government and GaAs contractors, attending and arranging contractor reviews, providing meeting facilities, and producing presentation materials. A major accomplishment under this contract was the development of a methodology for appraising the likelihood of a successful technology insertion. This methodology is described in detail. Systems analyses and other work performed according to the terms of the statement of work is described as well. The conclusion discusses accomplishments under this project and of the DARPA digital GaAs insertion program generally.

  18. Ultrafast photocurrents and terahertz radiation in gallium arsenide and carbon based nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Prechtel, Hans Leonhard

    2011-08-15

    In this thesis we developed a measurement technique based on a common pump-probe scheme and coplanar stripline circuits that enables time-resolved photocurrent measurements of contacted nanosystems with a micrometer spatial and a picosecond time resolution. The measurement technique was applied to lowtemperature grown gallium arsenide (LT-GaAs), carbon nanotubes (CNTs), graphene, and p-doped gallium arsenide (GaAs) nanowires. The various mechanisms responsible for the generation of current pulses by pulsed laser excitation were reviewed. Furthermore the propagation of the resulting electromagnetic radiation along a coplanar stripline circuit was theoretically and numerically treated. The ultrafast photocurrent response of low-temperature grown GaAs was investigated. We found two photocurrent pulses in the time-resolved response. We showed that the first pulse is consistent with a displacement current pulse. We interpreted the second pulse to result from a transport current process. We further determined the velocity of the photo-generated charge carriers to exceed the drift, thermal and quantum velocities of single charge carriers. Hereby, we interpreted the transport current pulse to stem from an electron-hole plasma excitation. We demonstrated that the photocurrent response of CNTs comprises an ultrafast displacement current and a transport current. The data suggested that the photocurrent is finally terminated by the recombination lifetime of the charge carriers. To the best of our knowledge, we presented in this thesis the first recombination lifetime measurements of contacted, suspended, CVD grown CNT networks. In addition, we studied the ultrafast photocurrent dynamics of freely suspended graphene contacted by metal electrodes. At the graphene-metal interface, we demonstrated that built-in electric fields give rise to a photocurrent with a full-width-half-maximum of a few picoseconds and that a photo-thermoelectric effect generates a current with a decay time

  19. Gallium arsenide quantum well-based far infrared array radiometric imager

    Science.gov (United States)

    Forrest, Kathrine A.; Jhabvala, Murzy D.

    1991-01-01

    We have built an array-based camera (FIRARI) for thermal imaging (lambda = 8 to 12 microns). FIRARI uses a square format 128 by 128 element array of aluminum gallium arsenide quantum well detectors that are indium bump bonded to a high capacity silicon multiplexer. The quantum well detectors offer good responsivity along with high response and noise uniformity, resulting in excellent thermal images without compensation for variation in pixel response. A noise equivalent temperature difference of 0.02 K at a scene temperature of 290 K was achieved with the array operating at 60 K. FIRARI demonstrated that AlGaAS quantum well detector technology can provide large format arrays with performance superior to mercury cadmium telluride at far less cost.

  20. Laser control and temperature switching of luminescence intensity in photostable transparent film based on terbium(III) β-diketonate complex

    Science.gov (United States)

    Lapaev, Dmitry V.; Nikiforov, Victor G.; Safiullin, Georgy M.; Lobkov, Vladimir S.; Salikhov, Kev M.; Knyazev, Andrey A.; Galyametdinov, Yury G.

    2014-11-01

    The study of the terbium(III) and gadolinium(III) β-diketonate complexes by photoluminescence spectroscopy reveals considerable changes of the photophysical properties of the complexes under the UV laser irradiation. The measurements show the enhancement of the luminescence intensities in the vitrified transparent film of the terbium(III) complex as well as the gadolinium(III) complex under the 337 nm laser irradiation at room temperature. The irradiated film of the terbium(III) complex restores the initial photophysical properties after heating close to the melting temperature (∼353 K) and cooling. We observe no change of the luminescent properties of the irradiated film for months. These features can be used for the design of new lanthanide-based photostable systems with laser control of the luminescence intensity.

  1. Development of functionalized terbium fluorescent nanoparticles for antibody labeling and time-resolved fluoroimmunoassay application.

    Science.gov (United States)

    Ye, Zhiqiang; Tan, Mingqian; Wang, Guilan; Yuan, Jingli

    2005-01-15

    Silica-based functionalized terbium fluorescent nanoparticles were prepared, characterized and developed as a fluorescence probe for antibody labeling and time-resolved fluoroimmunoassay. The nanoparticles were prepared in a water-in-oil (W/O) microemulsion containing a strongly fluorescent Tb(3+) chelate, N,N,N(1),N(1)-[2,6-bis(3'-aminomethyl-1'-pyrazolyl)phenylpyridine] tetrakis(acetate)-Tb(3+) (BPTA-Tb(3+)), Triton X-100, octanol, and cyclohexane by controlling copolymerization of tetraethyl orthosilicate (TEOS) and 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (AEPS) with ammonia water. The characterizations by transmission electron microscopy and fluorometric methods show that the nanoparticles are spherical and uniform in size, 45 +/- 3nm in diameter, strongly fluorescent with fluorescence quantum yield of 10% and a long fluorescence lifetime of 2.0ms. The amino groups directly introduced to the nanoparticle's surface by using AEPS in the preparation made the surface modification and bioconjugation of the nanoparticles easier. The nanoparticle-labeled anti-human alpha-fetoprotein antibody was prepared and used for time-resolved fluoroimmunoassay of alpha-fetoprotein (AFP) in human serum samples. The assay response is linear from 0.10ngml(-1) to about 100ngml(-1) with the detection limit of 0.10ngml(-1). The coefficient variations (CVs) of the method are less than 9.0%, and the recoveries are in the range of 84-98% for human serum sample measurements.

  2. Highly efficient precipitation of phosphoproteins using trivalent europium, terbium, and erbium ions

    Energy Technology Data Exchange (ETDEWEB)

    Guezel, Yueksel; Rainer, Matthias; Mirza, Munazza Raza; Bonn, Guenther K. [Leopold-Franzens University, Institute of Analytical Chemistry and Radiochemistry, Innsbruck (Austria)

    2012-05-15

    This study describes a highly efficient method for the selective precipitation of phosphoproteins by trivalent europium, terbium, and erbium metal ions. These metal cations belong to the group of lanthanides and are known to be hard acceptors with an overwhelming preference for oxygen-containing anions such as phosphates to which they form very tight ionic bonds. The method could be successfully applied to specifically precipitate phosphoproteins from complex samples including milk and egg white by forming solid metal-protein complexes. Owing to the low solubility product of the investigated lanthanide salts, the produced metal-protein complexes showed high stability. The protein pellets were extensively washed to remove nonphosphorylated proteins and contaminants. For the analysis of proteins the pellets were first dissolved in 30 % formic acid and subjected to matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) MS. For peptide mass-fingerprint analysis the precipitated phosphoproteins were enzymatically digested using microwave-assisted digestion. The method was found to be highly specific for the isolation and purification of phosphoproteins. Protein quantification was performed by colorimetric detection of total precipitated phosphoproteins and revealed more than 95 % protein recovery for each lanthanide salt. (orig.)

  3. A Terbium Sensitized Luminescence Method for the Assay of Flubiprofen in Pharmaceutical Formulations

    Directory of Open Access Journals (Sweden)

    Salma M.Z. Al-Kindy

    2014-12-01

    Full Text Available A sensitive time-resolved luminescence method for the determination of flubiprofen (FLP in methanol and in aqueous solution is described. The method is based on the luminescence sensitization of terbium (Tb3+ by the formation of a ternary complex with FLP in the presence of 4,7 diphenyl 1,10 phenanthroline (DPP as co-ligand, and Tween-20 as surfactant. The signal for Tb-FLP-DPP was monitored at λex  = 285 nm and λem  = 552 nm. Optimum conditions for the formation of the complex in an aqueous system were TRIS buffer, pH 8.0, DPP (2.5Å~10−7  M, Tween-20 (0.30% and 4Å~10-5  mol L-1  of Tb3+  which allowed the determination of 20–1000 ng mL-1  of FLP with a limit of detection (LOD of 10 ng mL-1 . The relative standard deviations of the method ranged between 0.6 and 1.4% indicating excellent reproducibility of the method. The proposed method was successfully applied for the assays of FLP in pharmaceutical formulations and spiked tap water samples with average recoveries of 87% – 95%.

  4. Sensitization effects of supramolecular assemblies on the luminescence of terbium-ion prulifloxacin complexes

    Energy Technology Data Exchange (ETDEWEB)

    Wang Hong; Yi Chongyue; Li Xue; Fang Fang [School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Yang Yajiang, E-mail: yjyang@mail.hust.edu.c [School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2011-04-15

    Luminescence enhancement of terbium-ion prulifloxacin complexes (Tb(III)-PUFX) in supramolecular hydrogels formed by assembly of 1,3:2,4-di-O-benzylidene-D-sorbitol (DBS) was investigated by steady-state fluorescence, varying temperature fluorescence and time-resolved fluorescence. The luminescence images show that Tb(III)-PUFX were dispersed in the DBS gels. The luminescence intensity of Tb(III)-PUFX in the DBS gels was significantly increased in comparison with that in corresponding aqueous solutions. The varying temperature fluorescent spectra show that the luminescence intensity of Tb(III)-PUFX decreased with an increase in the temperature. This implies that the luminescence enhancement of Tb(III)-PUFX is related to the dissociation and the formation of the DBS assemblies. Time-resolved fluorescence measurements show slower rotational motion in DBS gels in comparison with that in the corresponding aqueous solutions. This may be ascribed to a unique microstructure of three-dimensional network formed by DBC aggregates, resulting in deactivation of the nonradiative relaxation. The images of field emission scanning electron microscopy and polarized optical microscopy indicate that the morphology of the DBS assemblies was not influenced upon addition of Tb(III)-PUFX to the DBS gels.

  5. A Nanoscale Multiresponsive Luminescent Sensor Based on a Terbium(III) Metal-Organic Framework.

    Science.gov (United States)

    Dang, Song; Wang, Ting; Yi, Feiyan; Liu, Qinghui; Yang, Weiting; Sun, Zhong-Ming

    2015-08-01

    A nanoscale terbium-containing metal-organic framework (nTbL), with a layer-like structure and [H2 NMe2 ](+) cations located in the framework channels, was synthesized under hydrothermal conditions. The structure of the as-prepared sample was systematically confirmed by powder XRD and elemental analysis; the morphology was characterized by field-emission SEM and TEM. The photoluminescence studies revealed that rod-like nTbL exhibited bright-green emission, corresponding to (5)D4 →(7)FJ (J=6-3) transitions of the Tb(3+) ion under excitation. Further sensing measurements revealed that as-prepared nTbL could be utilized as a multiresponsive luminescent sensor, which showed significant and exclusive detection ability for Fe(3+) ions and phenylmethanol. These results highlight the practical applications of lanthanide-containing metal-organic frameworks as fluorescent probes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Terbium-Doped VO2 Thin Films: Reduced Phase Transition Temperature and Largely Enhanced Luminous Transmittance.

    Science.gov (United States)

    Wang, Ning; Duchamp, Martial; Dunin-Borkowski, Rafal E; Liu, Shiyu; Zeng, XianTing; Cao, Xun; Long, Yi

    2016-01-26

    Vanadium dioxide (VO2) is a well-known thermochromic material with large IR modulating ability, promising for energy-saving smart windows. The main drawbacks of VO2 are its high phase transition temperature (τ(c) = 68°C), low luminous transmission (T(lum)), and weak solar modulating ability (ΔT(sol)). In this paper, the terbium cation (Tb(3+)) doping was first reported to reduce τ(c) and increase T(lum) of VO2 thin films. Compared with pristine VO2, 2 at. % doping level gives both enhanced T(lum) and ΔT(sol) from 45.8% to 54.0% and 7.7% to 8.3%, respectively. The T(lum) increases with continuous Tb(3+) doping and reaches 79.4% at 6 at. % doping level, representing ∼73.4% relative increment compared with pure VO2. This has surpassed the best reported doped VO2 thin films. The enhanced thermochromic properties is meaningful for smart window applications of VO2 materials.

  7. Luminescent investigations of terbium(III) biosorption as a surrogate for heavy metals and radionuclides.

    Science.gov (United States)

    Achyuthan, Komandoor E; Arango, Dulce C; Carles, Elizabeth L; Cutler, Christopher E; Meyer, Lauren A; Brozik, Susan M

    2009-07-01

    We describe a metal transport system for investigating the interfacial interactions between the anionic surface charge of a gram-negative bacterium (Escherichia coli) and a trivalent cationic metal, Tb3+. We believe this is the first description of the uptake kinetics, sub- and intracellular distribution, and temporal fate of Tb3+ ion in E. coli. We used the luminescence of the terbium-dipicolinic acid chelate to study metal ion transport. The bacteria had a high tolerance for the metal (IC(50) = 4 mM Tb3+). Metal ion transport was passive and metabolism independent. The uptake kinetics rapidly reached a maximum within 15 min, followed by a stasis for 60 min, and declining thereafter between 120 and 240 min, resulting in a biphasic curve. During this period, greater than one-third of the metal ion was sequestered within the cell. Our choice of a safe Biosafety Level I E. coli bacteria and the relatively non-toxic Tb3+ metal represents a model system for luminescent investigations of biosorption, for studying bacterial-water interfacial chemistry and for the bioremediation of heavy metals and radionuclides.

  8. In-Plane Electronic Anisotropy of Underdoped ___122___ Fe-Arsenide Superconductors Revealed by Measurements of Detwinned Single Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, Ian Randal

    2012-05-08

    The parent phases of the Fe-arsenide superconductors harbor an antiferromagnetic ground state. Significantly, the Neel transition is either preceded or accompanied by a structural transition that breaks the four fold symmetry of the high-temperature lattice. Borrowing language from the field of soft condensed matter physics, this broken discrete rotational symmetry is widely referred to as an Ising nematic phase transition. Understanding the origin of this effect is a key component of a complete theoretical description of the occurrence of superconductivity in this family of compounds, motivating both theoretical and experimental investigation of the nematic transition and the associated in-plane anisotropy. Here we review recent experimental progress in determining the intrinsic in-plane electronic anisotropy as revealed by resistivity, reflectivity and ARPES measurements of detwinned single crystals of underdoped Fe arsenide superconductors in the '122' family of compounds.

  9. Construction of the energy matrix for complex atoms. Part VIII: Hyperfine structure HPC calculations for terbium atom

    Science.gov (United States)

    Elantkowska, Magdalena; Ruczkowski, Jarosław; Sikorski, Andrzej; Dembczyński, Jerzy

    2017-11-01

    A parametric analysis of the hyperfine structure (hfs) for the even parity configurations of atomic terbium (Tb I) is presented in this work. We introduce the complete set of 4fN-core states in our high-performance computing (HPC) calculations. For calculations of the huge hyperfine structure matrix, requiring approximately 5000 hours when run on a single CPU, we propose the methods utilizing a personal computer cluster or, alternatively a cluster of Microsoft Azure virtual machines (VM). These methods give a factor 12 performance boost, enabling the calculations to complete in an acceptable time.

  10. Spectrofluorimetric determination of human serum albumin using terbium-danofloxacin probe.

    Science.gov (United States)

    Ramezani, Amir M; Manzoori, Jamshid L; Amjadi, Mohammad; Jouyban, Abolghasem

    2012-01-01

    A spectrofluorimetric method is proposed for the determination of human serum albumin (HSA) and bovine serum albumin (BSA) using terbium-danofloxacin (Tb(3+)-Dano) as a fluorescent probe. These proteins remarkably enhance the fluorescence intensity of the Tb(3+)-Dano complex at 545 nm, and the enhanced fluorescence intensity of Tb(3+)-Dano is proportional to the concentration of proteins (HSA and BSA). Optimum conditions for the determination of HSA were investigated and found that the maximum response was observed at: pH = 7.8, [Tb(3+)] = 8.5 × 10(-5) mol L(-1), [Dano] = 1.5 × 10(-4) mol L(-1). The calibration graphs for standard solutions of BSA, HSA, and plasma samples of HSA were linear in the range of 0.2 × 10(-6) - 1.3 × 10(-6) mol L(-1), 0.2 × 10(-6) - 1.4 × 10(-6) mol L(-1), and 0.2 × 10(-6) - 1 × 10(-6) mol L(-1), respectively. The detection limits (S/N = 3) for BSA, HSA, and plasma sample of HSA were 8.7 × 10(-8) mol L(-1), 6.2 × 10(-8) mol L(-1), and 8.1 × 10(-8) mol L(-1), respectively. The applicability of the method was checked using a number of real biological plasma samples and was compared with the UV spectrometric reference method. The results was showed that the method could be regarded as a simple, practical, and sensitive alternative method for determination of albumin in biological samples.

  11. Spectrofluorimetric Determination of Human Serum Albumin Using Terbium-Danofloxacin Probe

    Directory of Open Access Journals (Sweden)

    Amir M. Ramezani

    2012-01-01

    Full Text Available A spectrofluorimetric method is proposed for the determination of human serum albumin (HSA and bovine serum albumin (BSA using terbium-danofloxacin (Tb3+-Dano as a fluorescent probe. These proteins remarkably enhance the fluorescence intensity of the Tb3+-Dano complex at 545 nm, and the enhanced fluorescence intensity of Tb3+-Dano is proportional to the concentration of proteins (HSA and BSA. Optimum conditions for the determination of HSA were investigated and found that the maximum response was observed at: pH=7.8, [Tb3+] =8.5×10−5 mol L−1, [Dano] =1.5×10−4 mol L−1. The calibration graphs for standard solutions of BSA, HSA, and plasma samples of HSA were linear in the range of 0.2×10−6−1.3×10−6 mol L−1, 0.2×10−6−1.4×10−6 mol L−1, and 0.2×10−6−1×10−6 mol L−1, respectively. The detection limits (S/N = 3 for BSA, HSA, and plasma sample of HSA were 8.7×10−8 mol L−1, 6.2×10−8 mol L−1, and 8.1×10−8 mol L−1, respectively. The applicability of the method was checked using a number of real biological plasma samples and was compared with the UV spectrometric reference method. The results was showed that the method could be regarded as a simple, practical, and sensitive alternative method for determination of albumin in biological samples.

  12. Determination of flavonoids in pharmaceutical preparations using Terbium sensitized fluorescence method

    Directory of Open Access Journals (Sweden)

    M Shaghaghi

    2009-12-01

    Full Text Available "nBackground and the Purpose of the Study: The aim of this study was development and validation of a simple, rapid and sensitive spectrofluorimetric method for determination of total flavonoids in two topical formulations of Calendula officinalis, Ziziphus Spina-christi and an oral drop of Hypiran perforatum L. The proposed method is based on the formation of terbium (Tb3+ "n-flavonoids (quercetin as a reference standard complex at pH 7.0, which has fluorescence intensely with maximum emission at 545 nm when excited at 310 nm. "nMethod "n: For ointments masses of topical formulations were weighed and added to ethanol-aqueous buffer (pH 10.0 and the resulting mixtures were shaken and then two phases were separated by centrifugation. Aqueous phases were filtered and then diluted with water. For Hypiran drops an appropriate portion was diluted with ethanol and then aliquots of sample or standard solutions were determined according to the experimental procedure. "nResults "n: Under the optimum conditions, total concentrations of flavonoids (as quercetin equivalent in three tested formulations were found to be 0.204 mg/g (for Dermatin cream, 0.476 mg/g (for Calendula ointment and 13.50 μg/ml (for Hypiran drops. Analytical recoveries from samples spiked with different amounts of quercetin were 96.1-104.0 % with RSD % of less than 3.5. Conclusion : The proposed method which requires a simple dissolution step without any matrix interferences provided high sensitivity and selectivity and was easily applied to determine total flavonoids in real samples of three investigated formulations with excellent reproducibility.

  13. TOF SIMS analysis and generation of white photoluminescence from strontium silicate codoped with europium and terbium

    Energy Technology Data Exchange (ETDEWEB)

    Tshabalala, Modiehi A.; Swart, Hendrik C.; Ntwaeaborwa, Odireleng M., E-mail: ntwaeab@ufs.ac.za [Department of Physics, University of the Free State, P.O Box 339, Bloemfontein 9300 South Africa (South Africa)

    2014-03-15

    White light emitting terbium (Tb{sup 3+}) and europium (Eu{sup 3+}) codoped strontium silicate (Sr{sub 2}SiO{sub 4}) phosphors were prepared by a solid state reaction process. The structure, particle morphology, chemical composition, ion distribution, photoluminescence (PL), and decay characteristics of the phosphors were analyzed by x-ray diffraction (XRD), scanning electron microscopy (SEM), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and PL spectroscopy, respectively. The XRD data showed that our Sr{sub 2}SiO{sub 4} composed of two phases, namely, β-Sr{sub 2}SiO{sub 4} and α′-Sr{sub 2}SiO{sub 4}, and the α′-Sr{sub 2}SiO{sub 4} phase was more prominent than the β-Sr{sub 2}SiO{sub 4} phase. The SEM micrographs showed that the particles were agglomerated together and they did not have definite shapes. All ions (i.e., negative and positive) present in our materials were identified by TOF-SIMS. In addition, the chemical imaging performed with the TOF-SIMS demonstrated how the individual ions including the dopants (Eu{sup 3+} and Tb{sup 3+}) were distributed in the host lattice. White photoluminescence was observed when the Sr{sub 2}SiO{sub 4}:Tb{sup 3+}, Eu{sup 3+} phosphor was excited at 239 nm using a monochromatized xenon lamp as the excitation source. The phosphor exhibited fast decay lifetimes implying that it is not a good candidate for long afterglow applications.

  14. Synthesis, crystal structure and photophysical properties of europium(III) and terbium(III) complexes with pyridine-2,6-dicarboxamide

    NARCIS (Netherlands)

    Tanase, S.; Gallego, P.M.; Gelder, R. de; Fu, W.T.

    2007-01-01

    The reactions of pyridine-2,6-dicarboxamide with europium(III) and terbium(III) triflates led to the formation of mononuclear complexes of formula [Ln(pcam)(3)](CF3SO3)(3) (Ln = Eu 1, Tb 2; pcam stands for pyridine-2,6-dicarboxamide). From single-crystal X-ray diffraction analysis, the complexes

  15. Zinc sulfide and terbium-doped zinc sulfide films grown by traveling wave reactor atomic layer epitaxy

    CERN Document Server

    Yun, S J; Nam, K S

    1998-01-01

    Zinc sulfide (ZnS) and terbium-doped ZnS (ZnS:Tb) thin films were grown by traveling wave reactor atomic layer epitaxy (ALE). In the present work, ZnCl sub 2 , H sub 2 S, and tris (2,2,6,6-tetramethyl-3,5-heptandionato) terbium (Tb(tmhd) sub 3) were used as the precursors. The dependence of crystallinity and Cl content of ZnS films was investigated on the growth temperature. ZnS and ZnS:Tb films grown at temperatures ranging from 400 to 500 .deg. C showed a hexagonal-2H crystalline structure. The crystallinity of ZnS film was greatly enhanced as the temperature increased. At growth temperatures higher than 450.deg.C, the films showed preferred orientation with mainly (002) diffraction peak. The Cl content decreased from approximately 9 to 1 at.% with the increase in growth temperature from 400 to 500 .deg. C. The segregation of Cl near the surface region and the incorporation of O from Tb(tmhd) sub 3 during ALE process were also observed using Auger electron spectroscopy. The ALE-grown ZnS and ZnS:Tb films re...

  16. Commercializing potassium terbium fluoride, KTF (KTb3F10) faraday crystals for high laser power optical isolator applications

    Science.gov (United States)

    Schlichting, Wolfgang; Stevens, Kevin; Foundos, Greg; Payne, Alexis

    2017-10-01

    Many scientific lasers and increasingly industrial laser systems operate in power regime, require high-performance optical isolators to prevent disruptive light feedback into the laser cavity. The optically active Faraday material is the key optical element inside the isolator. SYNOPTICS has been supplying the laser market with Terbium Gallium Garnet (TGG - Tb3Ga5O12) for many years. It is the most commonly used material for the 650-1100nm range and the key advantages for TGG include its cubic crystal structure for alignment free processing, little to no intrinsic birefringence, and ease of manufacture. However, for high-power laser applications TGG is limited by its absorption at 1064nm and its thermo-optic coefficient, dn/dT. Specifically, thermal lensing and depolarization effects become a limiting factor at high laser powers. While TGG absorption has improved significantly over the past few years, there is an intrinsic limit. Now, SYNOPTICS is commercializing the enhanced new crystal Potassium Terbium Fluoride KTF (KTb3F10) that exhibits much smaller nonlinear refractive index and thermo-optic coefficients, and still exhibits a Verdet constant near that of TGG. This cubic crystal has relatively low absorption and thermo-optic coefficients. It is now fully characterized and available for select production orders. At OPTIFAB in October 2017 we present recent results comparing the performance of KTF to TGG in optical isolators and show SYNOPTICS advances in large volume crystal growth and the production ramp up.

  17. Preparation and photoluminescence enhancement in terbium(III ternary complexes with β-diketone and monodentate auxiliary ligands

    Directory of Open Access Journals (Sweden)

    Devender Singh

    2016-12-01

    Full Text Available A series of new solid ternary complexes of terbium(III ion based on β-diketone ligand acetylacetone (acac and monodentate auxiliary ligands (aqua/urea/triphenylphosphineoxide/pyridine-N-oxide had been prepared. The structural characterizations of synthesized ternary compounds were studied by means of elemental analysis, infrared (IR, and proton nuclear magnetic resonance (NMR spectral techniques. The optical characteristics were investigated with absorption as well as photoluminescence spectroscopy. Thermal behavior of compounds was examined by TGA/DTA analysis and all metal complexes were found to have good thermal stability. The luminescence decay time of complexes were also calculated by monitoring at emission wavelength corresponding to 5D4 → 7F5 transition. A comparative inspection of the luminescent behavior of prepared ternary compounds was performed in order to determine the function of auxiliary ligands in the enhancement of luminescence intensity produced by central terbium(III ion. The color coordinates values suggested that compounds showed bright green emission in visible region in electromagnetic spectrum. Complexes producing green light could play a significant role in the fabrication of efficient light conversion molecular devices for display purposes and lightning systems.

  18. Modelling of the small pixel effect in gallium arsenide X-ray imaging detectors

    CERN Document Server

    Sellin, P J

    1999-01-01

    A Monte Carlo simulation has been carried out to investigate the small pixel effect in highly pixellated X-ray imaging detectors fabricated from semi-insulating gallium arsenide. The presence of highly non-uniform weighting fields in detectors with a small pixel geometry causes the majority of the induced signal to be generated when the moving charges are close to the pixellated contacts. The response of GaAs X-ray imaging detectors is further complicated by the presence of charge trapping, particularly of electrons. In this work detectors are modelled with a pixel pitch of 40 and 150 mu m, and with thicknesses of 300 and 500 mu m. Pulses induced in devices with 40 mu m pixels are due almost totally to the movement of the lightly-trapped holes and can exhibit significantly higher charge collection efficiencies than detectors with large electrodes, in which electron trapping is significant. Details of the charge collection efficiencies as a function of interaction depth in the detector and of the incident phot...

  19. Transport-reaction model for defect and carrier behavior within displacement cascades in gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Wampler, William R.; Myers, Samuel Maxwell,

    2014-02-01

    A model is presented for recombination of charge carriers at displacement damage in gallium arsenide, which includes clustering of the defects in atomic displacement cascades produced by neutron or ion irradiation. The carrier recombination model is based on an atomistic description of capture and emission of carriers by the defects with time evolution resulting from the migration and reaction of the defects. The physics and equations on which the model is based are presented, along with details of the numerical methods used for their solution. The model uses a continuum description of diffusion, field-drift and reaction of carriers and defects within a representative spherically symmetric cluster. The initial radial defect profiles within the cluster were chosen through pair-correlation-function analysis of the spatial distribution of defects obtained from the binary-collision code MARLOWE, using recoil energies for fission neutrons. Charging of the defects can produce high electric fields within the cluster which may influence transport and reaction of carriers and defects, and which may enhance carrier recombination through band-to-trap tunneling. Properties of the defects are discussed and values for their parameters are given, many of which were obtained from density functional theory. The model provides a basis for predicting the transient response of III-V heterojunction bipolar transistors to pulsed neutron irradiation.

  20. Fabrication and applications of orientation-patterned gallium arsenide for mid-infrared generation

    Energy Technology Data Exchange (ETDEWEB)

    Grisard, A.; Gutty, F.; Lallier, E. [Thales Research and Technology France, 1 av. Augustin Fresnel, 91767 Palaiseau Cedex (France); Gerard, B. [III-V Lab, 1 av. Augustin Fresnel, 91767 Palaiseau Cedex (France); Jimenez, J. [GdS Optronlab, Fisica Materia Condensada, Universidad de Valladolid, 47011 Valladolid (Spain)

    2012-07-15

    Nonlinear optical materials play a key role in the development of coherent sources of radiation, by frequency conversion of light from other light sources, e.g. diode, solid-state, and fiber lasers, into spectral ranges where few lasers exist or perform poorly. Based on the principle of the quasi-phase matching, the design and fabrication of orientation-patterned Gallium Arsenide crystals (OP-GaAs) has recently led to demonstrations of second harmonic generation, optical parametric generation, amplification and oscillation from 1 to 12 {mu}m. The most efficient fabrication route for these crystals relies on the use of the near-equilibrium growth process HVPE (Hydride Vapour Phase Epitaxy), by orientation-selective regrowth on OP-GaAs template wafers with a thickness suited to bulk nonlinear optics. This work deals with recent characterizations based on optical experiments and cathodoluminescence measurements, targeting the identification of the main defects, their spatial distribution, and their relation to the optical propagation losses. Latest improvements of the HVPE growth step have enabled to reach an unprecedented level of losses, below 0.016 cm{sup -1}, and a large range of available QPM periods and thickness of structures (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Light transport through disordered layers of dense gallium arsenide submicron particles

    Science.gov (United States)

    van der Beek, T.; Barthelemy, P.; Johnson, P. M.; Wiersma, D. S.; Lagendijk, A.

    2012-03-01

    We present a study of optical transport properties of powder layers with submicrometer, strongly scattering gallium arsenide (GaAs) particles. Uniform, thin samples with well controlled thicknesses were created through the use of varying grinding times, sedimentation fractionation, annealing, and a new sedimentation technique. These fabrication parameters were optimized to produce maximum scattering and minimum absorption. The physical properties were characterized using scanning electron microscopy (SEM) and x-ray diffraction. The optical transport mean-free path, absorption length, and the diffusion constant were determined for each sample using both continuous wave and time-resolved methods. The samples scatter strongly in the near infrared region. Total reflection and transmission measurements show that all of these samples have high absorption. X-ray diffraction results suggest that the source of this absorption is grinding induced strain and/or defects in the crystal structure. For all the different grinded GaAs powder samples that we investigated, the absorption length was less than ten micrometers.

  2. X-Ray diffraction observation of surface damage in chemical-mechanical polished gallium arsenide

    Science.gov (United States)

    Wang, V. S.; Matyi, R. J.

    1992-01-01

    Two novel x-ray diffraction techniques with enhanced surface sensitivity, grazing incidence x-ray diffraction (GIXD) and inclined Bragg plane x-ray diffraction (IBXD), have been used to study surface damage in gallium arsenide (GaAs) due to bromine/methanol (Br2/MeOH) chemical mechanical (CM) polishing. A factorial design was implemented to determine the effects of four polishing variables on the surface structure of GaAs. Precise lattice parameter measurements were made in both the surface regions using GIXD and deeper into subsurface regions using IBXD after the various CM polishing treatments. Bromine concentration was found to primarily affect the surface lattice parameter, while the total polish time influenced both the surface and subsurface lattice parameters in GaAs samples that were heavily damaged prior to CM polishing. The combined effect of polishing pad rotation speed and the force exerted on the sample was found to have a much greater effect on the surface lattice parameter than either variable had alone.

  3. Dynamics and control of gold-encapped gallium arsenide nanowires imaged by 4D electron microscopy.

    Science.gov (United States)

    Chen, Bin; Fu, Xuewen; Tang, Jau; Lysevych, Mykhaylo; Tan, Hark Hoe; Jagadish, Chennupati; Zewail, Ahmed H

    2017-11-20

    Eutectic-related reaction is a special chemical/physical reaction involving multiple phases, solid and liquid. Visualization of a phase reaction of composite nanomaterials with high spatial and temporal resolution provides a key understanding of alloy growth with important industrial applications. However, it has been a rather challenging task. Here, we report the direct imaging and control of the phase reaction dynamics of a single, as-grown free-standing gallium arsenide nanowire encapped with a gold nanoparticle, free from environmental confinement or disturbance, using four-dimensional (4D) electron microscopy. The nondestructive preparation of as-grown free-standing nanowires without supporting films allows us to study their anisotropic properties in their native environment with better statistical character. A laser heating pulse initiates the eutectic-related reaction at a temperature much lower than the melting points of the composite materials, followed by a precisely time-delayed electron pulse to visualize the irreversible transient states of nucleation, growth, and solidification of the complex. Combined with theoretical modeling, useful thermodynamic parameters of the newly formed alloy phases and their crystal structures could be determined. This technique of dynamical control aided by 4D imaging of phase reaction processes on the nanometer-ultrafast time scale opens new venues for engineering various reactions in a wide variety of other systems. Copyright © 2017 the Author(s). Published by PNAS.

  4. Synthesis and luminescent study of Ce{sup 3+}-doped terbium-yttrium aluminum garnet

    Energy Technology Data Exchange (ETDEWEB)

    Dotsenko, V.P., E-mail: ssclab@ukr.net [A.V. Bogatsky Physico-Chemical Institute, National Academy of Sciences of Ukraine, Lustdorfskaya doroga 86, 65080 Odessa (Ukraine); Berezovskaya, I.V.; Zubar, E.V.; Efryushina, N.P. [A.V. Bogatsky Physico-Chemical Institute, National Academy of Sciences of Ukraine, Lustdorfskaya doroga 86, 65080 Odessa (Ukraine); Poletaev, N.I.; Doroshenko, Yu.A. [Institute of Combustion and Advanced Technologies, Mechnikov Odessa National University, Dvoryanskaya 2, 65082 Odessa (Ukraine); Stryganyuk, G.B. [Ivan Franko National University of Lviv, Kirilo i Mefodii 8, 79005 Lviv (Ukraine); HASYLAB at DESY, Notkestrasse 85, 22607 Hamburg (Germany); Voloshinovskii, A.S. [Ivan Franko National University of Lviv, Kirilo i Mefodii 8, 79005 Lviv (Ukraine)

    2013-02-15

    Highlights: Black-Right-Pointing-Pointer Ce{sup 3+}-doped garnets (TYAG) were prepared using nanostructured reagents. Black-Right-Pointing-Pointer The Ce{sup 3+} ions cause a very efficient yellow emission of the samples. Black-Right-Pointing-Pointer The reasons for the long wavelength position of this emission are discussed. Black-Right-Pointing-Pointer Contribution from Al atoms to the conduction band of TYAG is quite essential. - Abstract: Terbium-yttrium aluminum garnets (TYAG) doped with Ce{sup 3+} ions have been prepared by solid state reactions between nanostructured oxides of aluminum and rare earths. The luminescent properties of Ce{sup 3+} ions in (Tb{sub 0.8}Y{sub 0.2}){sub 3(1-x)}Ce{sub 3x}Al{sub 5}O{sub 12} (x = 0.03) have been studied upon excitation in the 2-20 eV region. The substitution of Tb{sup 3+} for Y{sup 3+} in the garnet structure results in broadening the emission band and shifting its maximum towards the longer wavelengths. It was found that in addition to the 4f{sup n} {yields} 4f{sup n-1}5d excitation bands of Ce{sup 3+} and Tb{sup 3+} ions, the excitation spectra for the Ce{sup 3+} emission contain broad bands at 6.73 and {approx}9.5 eV. These bands are attributed to the Ce{sup 3+}-bound exciton formation and O 2p {yields} Al 3s, 3p transitions, respectively. In contrast to the predictions based on the results of electronic structure calculations on Y{sub 3}Al{sub 5}O{sub 12} and Tb{sub 4}Al{sub 2}O{sub 9}, the threshold of interband transitions in TYAG is at high energies ( Greater-Than-Or-Slanted-Equal-To 7.3 eV), and contributions from Al{sub tetr} and Al{sub oct} atoms to the conduction-band density of states are evaluated as quite essential.

  5. Structural variations in terbium(III) complexes with 1,3-adamantanedicarboxylate and diverse co-ligands

    Energy Technology Data Exchange (ETDEWEB)

    Thuéry, Pierre, E-mail: pierre.thuery@cea.fr

    2015-07-15

    Terbium nitrate was reacted with 1,3-adamantanedicarboxylic acid (LH{sub 2}) under solvo-hydrothermal conditions with either N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA) as organic solvents. Hydrolysation of the latter co-solvents resulted in the formation of formate or acetate ions, which are present as co-ligands in the 1D coordination polymer [Tb(L)(HCOO)(H{sub 2}O){sub 2}] (1) and the 2D assembly [Tb(L)(CH{sub 3}COO)(H{sub 2}O)] (2). The increase in dimensionality in the latter arises from the higher connectivity provided by acetate versus formate, the L{sup 2−} ligand being bis-chelating in both cases. The complex [Tb{sub 2}(L){sub 3}(H{sub 2}O){sub 5}][Tb{sub 2}(L){sub 3}(H{sub 2}O){sub 4}]·3H{sub 2}O (3), another 1D species, crystallizes alongside crystals of 2. Further addition of cucurbit[6]uril (CB6), with DMF as co-solvent, gave the two complexes [Tb{sub 2}(L){sub 2}(CB6)(H{sub 2}O){sub 6}](NO{sub 3}){sub 2}·6H{sub 2}O (4) and [H{sub 2}NMe{sub 2}]{sub 2}[Tb(L)(HCOO){sub 2}]{sub 2}·CB6·3H{sub 2}O (5). Complex 4 crystallizes as a 3D framework in which Tb(L){sup +} chains are connected by tetradentate CB6 molecules, while 5 unites a carboxylate-bridged anionic 2D planar assembly and layers of CB6 molecules with counter-cations held at both portals. - Graphical abstract: One- to three-dimensional assemblies are formed in terbium(III) complexes with 1,3-adamantanedicarboxylate obtained under solvo-hydrothermal conditions, these species including formate or acetate co-ligands formed in situ, or additional cucurbit[6]uril molecules. - Highlights: • We report structures of terbium(III) complexes with 1,3-adamantanedicarboxylate. • Solvents able to generate co-ligands or counter-ions in situ have been used. • A 3D species including additional cucurbituril molecules is decribed. • One species displays an alternation of metal–organic and organic sheets.

  6. An Indium Gallium Arsenide Visible/SWIR Focal Plane Array for Low Light Level Imaging

    Science.gov (United States)

    Cohen, Marshall J.; Ettenberg, Martin H.; Lange, Michael J.; Olsen, Gregory H.

    1999-01-01

    PIN photodiodes fabricated from indium gallium arsenide lattice-matched to indium phosphide substrates (In(.53)Ga(.47)As/InP) exhibit low reverse saturation current densities (JD 10(exp 6) omega-sq cm) at T=290K. Backside-illuminated, hybrid-integrated InGaAs FPAs are sensitive from 0.9 micrometers to 1.7 micrometers. 290K detectivities, D(*), greater than 10(exp 14) cm-(square root of Hz/W) are demonstrated. This represents the highest room temperature detectivity of any infrared material. The long wavelength cutoff (1.7 micrometers) makes In(.53)Ga(.47)As an idea match to the available airglow that has major peaks at 1.3 micrometers and 1.6 micrometers. The short wavelength 'cut-on' at 0.9 micrometers is due to absorption in the InP substrate. We will report on new InGaAs FPA epitaxial structures and processing techniques. These have resulted in improved performance in the form of a 10 x increase in detectivity and visible response via removal of the InP substrate. The resulting device features visible and SWIR response with greater than 15% quantum efficiency at 0.5 micrometers while maintaining the long wavelength cutoff. Imaging has been demonstrated under overcast starlight/urban glow conditions with cooling provided by a single stage thermoelectric cooler. Details on the material structure and device fabrication, quantitative characterization of spectral response and detectivity, as well as examples of night vision imagery are presented.

  7. Complete Stokes polarimetry of magneto-optical Faraday effect in a terbium gallium garnet crystal at cryogenic temperatures.

    Science.gov (United States)

    Majeed, Hassaan; Shaheen, Amrozia; Anwar, Muhammad Sabieh

    2013-10-21

    We report the complete determination of the polarization changes caused in linearly polarized incident light due to propagation in a magneto-optically active terbium gallium garnet (TGG) single crystal, at temperatures ranging from 6.3 to 300 K. A 28-fold increase in the Verdet constant of the TGG crystal is seen as its temperature decreases to 6.3 K. In contrast with polarimetry of light emerging from a Faraday material at room temperature, polarimetry at cryogenic temperatures cannot be carried out using the conventional fixed polarizer-analyzer technique because the assumption that ellipticity is negligible becomes increasingly invalid as temperature is lowered. It is shown that complete determination of light polarization in such a case requires the determination of its Stokes parameters, otherwise inaccurate measurements will result with negative implications for practical devices.

  8. Development of Optical Isolators for Visible Light Using Terbium Aluminum Garnet (Tb3Al5O12) Single Crystals

    Science.gov (United States)

    Geho, Mikio; Takagi, Takashi; Chiku, Shinichiro; Fujii, Takashi

    2005-07-01

    We have recently reported the successful growth of incongruently melting terbium aluminum garnet (Tb3Al5O12; TAG) single crystals by the hybrid laser FZ (floating zone) method. Optical property evaluations confirmed a high transmittance and a larger Verdet constant than conventional Tb3Ga5O12 (TGG) crystals and/or Faraday glasses. In this study, we attempted to design, fabricate, and evaluate optical isolators in visible light through near-infrared (NIR) regions using TAG crystals. A finite element method (FEM) simulation of possible models led us to the preferable one based on a radially magnetized magnet. To realize this, we employed a pseudo-radially magnetized magnet. The target wavelengths of the prototype device were 408, 808, and 1064 nm. The typical extinction ratio was more than 30 dB and the insertion loss was less than 0.3 dB for AR-coated devices.

  9. Monte Carlo simulation to calculate the rate of 137Cs gamma rays dispersion in gallium arsenide compound

    Science.gov (United States)

    Haider, F. A.; Chee, F. P.; Abu Hassan, H.; Saafie, S.

    2017-01-01

    Radiation effects on Gallium Arsenide (GaAs) have been tested by exposing samples to Cesium-137 (137Cs) gamma rays. Gallium Arsenide is a basic photonic material for most of the space technology communication, and, therefore, lends itself for applications where this is of concern. Monte Carlo simulations of interaction between direct ionizing radiation and GaAs structure have been performed in TRIM software, being part of SRIM 2011 programming package. An adverse results shows that energy dose does not govern the displacement of atoms and is dependent on the changes of incident angles and thickness of the GaAs target element. At certain thickness of GaAs and incident angle of 137Cs ion, the displacement damage is at its highest value. From the simulation result, it is found that if the thickness of the GaAs semiconductor material is small compared to the projected range at that particular incident energy, the energy loss in the target GaAs will be small. Hence, when the depth of semiconductor material is reduced, the range of damage in the target also decreased. However, the other factors such as quantum size effect, the energy gap between the conduction and valence band must also be taken into consideration when the dimension of the device is diminished.

  10. A hydrometallurgical process for the recovery of terbium from fluorescent lamps: Experimental design, optimization of acid leaching process and process analysis.

    Science.gov (United States)

    Innocenzi, Valentina; Ippolito, Nicolò Maria; De Michelis, Ida; Medici, Franco; Vegliò, Francesco

    2016-12-15

    Terbium and rare earths recovery from fluorescent powders of exhausted lamps by acid leaching with hydrochloric acid was the objective of this study. In order to investigate the factors affecting leaching a series of experiments was performed in according to a full factorial plan with four variables and two levels (4 2 ). The factors studied were temperature, concentration of acid, pulp density and leaching time. Experimental conditions of terbium dissolution were optimized by statistical analysis. The results showed that temperature and pulp density were significant with a positive and negative effect, respectively. The empirical mathematical model deducted by experimental data demonstrated that terbium content was completely dissolved under the following conditions: 90 °C, 2 M hydrochloric acid and 5% of pulp density; while when the pulp density was 15% an extraction of 83% could be obtained at 90 °C and 5 M hydrochloric acid. Finally a flow sheet for the recovery of rare earth elements was proposed. The process was tested and simulated by commercial software for the chemical processes. The mass balance of the process was calculated: from 1 ton of initial powder it was possible to obtain around 160 kg of a concentrate of rare earths having a purity of 99%. The main rare earths elements in the final product was yttrium oxide (86.43%) following by cerium oxide (4.11%), lanthanum oxide (3.18%), europium oxide (3.08%) and terbium oxide (2.20%). The estimated total recovery of the rare earths elements was around 70% for yttrium and europium and 80% for the other rare earths. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Investigation of the luminescent properties of terbium-anthranilate complexes and application to the determination of anthranilic acid derivatives in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Arnaud, N.; Georges, J

    2003-01-10

    The luminescent properties of terbium complexes with furosemide (FR), flufenamic (FF) acid, tolfenamic (TF) acid and mefenamic (MF) acid have been investigated in aqueous solutions. For all four compounds, complexation occurs when the carboxylic acid of the aminobenzoic group is dissociated and is greatly favoured in the presence of trioctylphosphine oxide as co-ligand and Triton X-100 as surfactant. Under optimum conditions, luminescence of the lanthanide ion is efficiently sensitised and the lifetime of the {sup 5}D{sub 4} resonance level of terbium in the complex is ranging between 1 and 1.9 ms, against 0.4 ms for the aqua ion. The sensitivity of the method for the determination of anthranilic acid derivatives is improved by one to two orders of magnitude with respect to that achieved using native fluorescence or terbium-sensitised luminescence in methanol. The limits of detection are 2x10{sup -10}, 5x10{sup -10} and 2x10{sup -9} mol l{sup -1} for flufenamic acid, furosemide and tolfenamic acid, and mefenamic acid, respectively, with within-run RSD values of less than 1%. The method has been applied to the determination of flufenamic acid in spiked calf sera with and without sample pretreatment. Depending on the method and the analyte concentration, the recovery was ranging between 83 and 113% and the lowest concentration attainable in serum samples was close to 1x10{sup -7} mol l{sup -1}.

  12. Recovery of gallium and arsenic from gallium arsenide waste in the electronics industry

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wei-Ting [Doctoral Program, Graduate School of Engineering Science and Technology, National Yunlin University of Science and Technology (NYUST), Douliou, Yunlin (China); Tsai, Lung-Chang; Shu, Chi-Min [Department of Safety, Health, and Environmental Engineering, NYUST, Douliou, Yunlin (China); Tsai, Fang-Chang [Key Laboratory for the Green Preparation and Application of Functional Materials, Ministry of Education, Faculty of Materials Science and Engineering, Hubei University, Wuhan (China)

    2012-05-15

    Gallium arsenide (GaAs) has both high saturated electron velocity and high electron mobility, making it useful as a semiconductor material in a variety of applications, including light-emitting diodes (LEDs), integrated circuits (ICs), and microwave appliances. A side effect of the use of gallium (Ga) is the production of a relatively large amount of hazardous waste. This study aimed at the recovery of Ga and arsenic (As) from GaAs waste using hydrometallurgical methods involving leaching and coagulation and a dry annealing process that involves annealing, vacuum separation, and sublimation by heating. Our research has shown that GaAs can be leached using nitric acid (HNO{sub 3}) to obtain 100% Ga and As with a leaching solution at pH 0.1, with subsequent adjustment of the leaching solution to pH 3 with sodium hydroxide (NaOH). Another method used a leaching solution at pH 2, then adjusting to pH 11 using NaOH. Ferric hydroxide (FeO(OH)) was added at 90 C after NaOH was added to the leaching solution. At pH 2 and 11, 55.5 and 21.9% of the As could be removed from the hazardous waste, respectively. The Ga could also be precipitated. When GaAs powder was heated to 1000 C over 3 h, 100% As removal was achieved, and 92.6% of the Ga was removed by formation of 99.9% gallium trioxide (Ga{sub 2}O{sub 3}). Arsenic was vaporized when the temperature was elevated to 1000 C, allowing arsenic trioxide (As{sub 2}O{sub 3}) to condense with 99.2% purity. The Ga{sub 2}O{sub 3} powder produced was then dissolved and electrolyzed, allowing for 95.9% recovery of Ga with a purity of 99.9%. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Structural and electrooptical characteristics of quantum dots emitting at 1.3 μm on gallium arsenide

    DEFF Research Database (Denmark)

    Fiore, A.; Oesterle, U.; Stanley, R.P.

    2001-01-01

    of approximate to1.8 ns is measured at room temperature, which confirms the excellent structural quality. A fast PL rise (tau (rise) = 10 +/-2 ps) is observed at all temperatures, indicating the potential for high-speed modulation. High-efficiency light-emitting diodes (LEDs) based on these dots are demonstrated......We present a comprehensive study of the structural and emission properties of self-assembled InAs quantum dots emitting at 1.3 mum. The dots are grown by molecular beam epitaxy on gallium arsenide substrates. Room-temperature emission at 1.3 mum is obtained by embedding the dots in an InGaAs layer...

  14. Photodetectors based on carbon nanotubes deposited by using a spray technique on semi-insulating gallium arsenide

    Directory of Open Access Journals (Sweden)

    Domenico Melisi

    2014-11-01

    Full Text Available In this paper, a spray technique is used to perform low temperature deposition of multi-wall carbon nanotubes on semi-insulating gallium arsenide in order to obtain photodectors. A dispersion of nanotube powder in non-polar 1,2-dichloroethane is used as starting material. The morphological properties of the deposited films has been analysed by means of electron microscopy, in scanning and transmission mode. Detectors with different layouts have been prepared and current–voltage characteristics have been recorded in the dark and under irradiation with light in the range from ultraviolet to near infrared. The device spectral efficiency obtained from the electrical characterization is finally reported and an improvement of the photodetector behavior due to the nanotubes is presented and discussed.

  15. Characteristics of trap-filled gallium arsenide photoconductive switches used in high gain pulsed power applications

    Energy Technology Data Exchange (ETDEWEB)

    ISLAM,N.E.; SCHAMILOGLU,E.; MAR,ALAN; LOUBRIEL,GUILLERMO M.; ZUTAVERN,FRED J.; JOSHI,R.P.

    2000-05-30

    The electrical properties of semi-insulating (SI) Gallium Arsenide (GaAs) have been investigated for some time, particularly for its application as a substrate in microelectronics. Of late this material has found a variety of applications other than as an isolation region between devices, or the substrate of an active device. High resistivity SI GaAs is increasingly being used in charged particle detectors and photoconductive semiconductor switches (PCSS). PCSS made from these materials operating in both the linear and non-linear modes have applications such as firing sets, as drivers for lasers, and in high impedance, low current Q-switches or Pockels cells. In the non-linear mode, it has also been used in a system to generate Ultra-Wideband (UWB) High Power Microwaves (HPM). The choice of GaAs over silicon offers the advantage that its material properties allow for fast, repetitive switching action. Furthermore photoconductive switches have advantages over conventional switches such as improved jitter, better impedance matching, compact size, and in some cases, lower laser energy requirement for switching action. The rise time of the PCSS is an important parameter that affects the maximum energy transferred to the load and it depends, in addition to other parameters, on the bias or the average field across the switch. High field operation has been an important goal in PCSS research. Due to surface flashover or premature material breakdown at higher voltages, most PCSS, especially those used in high power operation, need to operate well below the inherent breakdown voltage of the material. The lifetime or the total number of switching operations before breakdown, is another important switch parameter that needs to be considered for operation at high bias conditions. A lifetime of {approximately} 10{sup 4} shots has been reported for PCSS's used in UWB-HPM generation [5], while it has exceeded 10{sup 8} shots for electro-optic drivers. Much effort is currently

  16. Cascaded Orientation-Patterned Gallium Arsenide Optical Parametric Oscillator for Improved Longwave Infrared Conversion Efficiency

    Science.gov (United States)

    Feaver, Ryan K.

    Optical parametric oscillators (OPOs) utilizing quasi-phase matched materials offer an appealing alternative to direct laser sources. Quasi-phase matched materials provide a useful alternative to traditional birefringent nonlinear optical materials and through material engineering, higher nonlinear coefficients can now be accessed. Orientation patterned gallium arsenide (OPGaAs) is an ideal material because of its broad IR transmission and large nonlinear coefficient. In contrast to ferroelectric materials, such as lithium niobate, where the pattern is fabricated through electric poling, zincblende materials, like OPGaAs, are grown epitaxially with the designed pattern. Generating longwave output from a much shorter pump wavelength, however, is relatively inefficiency due to the large quantum defect when compared to similar devices operating in the 3 - 5 mum regime. One method to increase pump to idler conversion efficiency is to recycle the undesired and higher energy signal photons into additional idler photons via a second nonlinear stage. An external amplifier stage can be utilized, where the signal and idler from the OPO are sent to a second nonlinear crystal in which the idler is amplified at the expense of the signal. Alternatively, the second crystal can be placed within the original OPO cavity where the signal from the first-stage acts as the pump for the second crystal and the resonant intensity of the signal is higher. Pumping the second crystal within the OPO should lead to higher conversion efficiency into the longwave idler. The grating period needed for the second crystal to use the signal from the first crystal to produce additional idler has the fortuitous advantage that it will not phase match to the original pump wavelength, avoiding unwanted nonlinear interactions. Therefore, a simple linear cavity can be utilized where the pump from the first-stage will simply propagate through the second crystal without undesired results. Without this feature

  17. Structural investigation and photoluminescent properties of gadolinium(III), europium(III) and terbium(III) 3-mercaptopropionate complexes.

    Science.gov (United States)

    Souza, E R; Mazali, I O; Sigoli, F A

    2014-01-01

    This work reports on the synthesis, crystallographic determination and spectroscopic characterization of gadolinium(III), terbium(III) and europium(III) 3-mercaptopropionate complexes, aqua-tris(3-mercaptopropionate)lanthanide(III)--[Ln(mpa)3(H2O)]. The Judd-Ofelt intensity parameters were experimentally determined from emission spectrum of the [Eu(mpa)3(H2O)]complex and they were also calculated from crystallographic data. The complexes are coordination polymers, where the units of each complex are linked together by carboxylate groups leading to an unidimensional and parallel chains that by chemical interactions form a tridimensional framework. The emission spectrum profile of the [Eu(mpa)3(H2O)] complex is discussed based on point symmetry of the europium(III) ion, that explains the bands splitting observed in its emission spectrum. Photoluminescent analysis of the [Gd(mpa)3(H2O)] complex show no efficient ligand excitation but an intense charge transfer band. The excitation spectra of the [Eu(mpa)3(H2O)] and [Tb(mpa)3(H2O)] complexes do not show evidence of energy transfer from the ligand to the excited levels of these trivalent ions. Therefore the emission bands are originated only by direct f-f intraconfigurational excitation of the lantanide(III) ions.

  18. Fluorometric determination of proteins using the terbium (III)-2-thenoyltrifluoroacetone-sodium dodecyl benzene sulfonate-protein system

    Energy Technology Data Exchange (ETDEWEB)

    Jia Zhen [Key Laboratory of Colloid and Interface Chemistry of Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Department of Chemistry, Dezhou University, Dezhou 253023 (China); Yang Jinghe [Key Laboratory of Colloid and Interface Chemistry of Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China)]. E-mail: yjh@sdu.edu.cn; Wu Xia [Key Laboratory of Colloid and Interface Chemistry of Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Wang Fei [Key Laboratory of Colloid and Interface Chemistry of Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Guo Changying [Key Laboratory of Colloid and Interface Chemistry of Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Liu Shufang [Key Laboratory of Colloid and Interface Chemistry of Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China)

    2006-12-15

    It is found that in hexamethylene tetramine (HMTA)-HCl buffer of pH=8.00, proteins can enhance the fluorescence of terbium (III) (Tb{sup 3+})-2-thenoyltrifluoroacetone (TTA)-sodium dodecyl benzene sulfonate (SDBS) system. Based on this, a sensitive method for the determination of proteins is proposed. The experiments indicate that under the optimum conditions, the enhanced fluorescence intensity is in proportion to the concentration of proteins in the range of 4.0x10{sup -9}-7.5x10{sup -6}g/mL for bovine serum albumin (BSA), 5.0x10{sup -9}-1.5x10{sup -5}g/mL for human serum albumin (HSA), 1.0x10{sup -8}-7.5x10{sup -6}g/mL for egg albumin (EA). Their detection limits (S/N=3) are 0.5, 0.8 and 2.0ng/mL, respectively. The interaction mechanism is also studied.

  19. Terbium to Quantum Dot FRET Bioconjugates for Clinical Diagnostics: Influence of Human Plasma on Optical and Assembly Properties

    Directory of Open Access Journals (Sweden)

    Niko Hildebrandt

    2011-10-01

    Full Text Available Förster resonance energy transfer (FRET from luminescent terbium complexes (LTC as donors to semiconductor quantum dots (QDs as acceptors allows extraordinary large FRET efficiencies due to the long Förster distances afforded. Moreover, time-gated detection permits an efficient suppression of autofluorescent background leading to sub-picomolar detection limits even within multiplexed detection formats. These characteristics make FRET-systems with LTC and QDs excellent candidates for clinical diagnostics. So far, such proofs of principle for highly sensitive multiplexed biosensing have only been performed under optimized buffer conditions and interactions between real-life clinical media such as human serum or plasma and LTC-QD-FRET-systems have not yet been taken into account. Here we present an extensive spectroscopic analysis of absorption, excitation and emission spectra along with the luminescence decay times of both the single components as well as the assembled FRET-systems in TRIS-buffer, TRIS-buffer with 2% bovine serum albumin, and fresh human plasma. Moreover, we evaluated homogeneous LTC-QD FRET assays in QD conjugates assembled with either the well-known, specific biotin-streptavidin biological interaction or, alternatively, the metal-affinity coordination of histidine to zinc. In the case of conjugates assembled with biotin-streptavidin no significant interference with the optical and binding properties occurs whereas the histidine-zinc system appears to be affected by human plasma.

  20. Evidence of mass exchange between inside and outside of sonoluminescing bubble in aqueous solution of terbium chloride

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Jinfu, E-mail: liang.shi2007@163.com [School of Physics and Electronic Science, Guizhou Normal University, Guiyang 550001 (China); Chen, Weizhong, E-mail: wzchen@nju.edu.cn [The Key Laboratory of Modern Acoustics, Ministry of Education, Institution of Acoustics, Nanjing University, Nanjing 210093 (China); Wang, Xun; Yang, Jing; Chen, Zhan [The Key Laboratory of Modern Acoustics, Ministry of Education, Institution of Acoustics, Nanjing University, Nanjing 210093 (China)

    2016-12-16

    Highlights: • Time-resolved spectra of SBSL were obtained for Tb{sup 3+} ions emission lines. • Mass exchange between inside and outside of SL bubble was probed via Tb{sup 3+} ions lines. • The argon rectification hypothesis was tested by time-resolved spectra of SBSL. • The rate of mass exchange inside an SBSL bubble increases with increasing sound pressure. - Abstract: Spectra of single-bubble sonoluminescence (SBSL) were obtained for Tb{sup 3+} ions emission lines from bubbles in an aqueous solution of terbium chloride (TbCl{sub 3}). The spectra provide experimental evidence to prove that an air bubble driven by strong ultrasound will not eventually become a rectified pure argon bubble, which is not as predicted by the argon rectification hypothesis. The time-resolved spectra of SBSL show a mass exchange of material such as Tb{sup 3+} ions between the inside and outside of the bubble. With increasing sound pressure, the rate of mass exchange and the SBSL intensity increases.

  1. Optical properties and electrical transport of thin films of terbium(III bis(phthalocyanine on cobalt

    Directory of Open Access Journals (Sweden)

    Peter Robaschik

    2014-11-01

    Full Text Available The optical and electrical properties of terbium(III bis(phthalocyanine (TbPc2 films on cobalt substrates were studied using variable angle spectroscopic ellipsometry (VASE and current sensing atomic force microscopy (cs-AFM. Thin films of TbPc2 with a thickness between 18 nm and 87 nm were prepared by organic molecular beam deposition onto a cobalt layer grown by electron beam evaporation. The molecular orientation of the molecules on the metallic film was estimated from the analysis of the spectroscopic ellipsometry data. A detailed analysis of the AFM topography shows that the TbPc2 films consist of islands which increase in size with the thickness of the organic film. Furthermore, the cs-AFM technique allows local variations of the organic film topography to be correlated with electrical transport properties. Local current mapping as well as local I–V spectroscopy shows that despite the granular structure of the films, the electrical transport is uniform through the organic films on the microscale. The AFM-based electrical measurements allow the local charge carrier mobility of the TbPc2 thin films to be quantified with nanoscale resolution.

  2. Highly luminescent charge-neutral europium(iii) and terbium(iii) complexes with tridentate nitrogen ligands.

    Science.gov (United States)

    Senthil Kumar, Kuppusamy; Schäfer, Bernhard; Lebedkin, Sergei; Karmazin, Lydia; Kappes, Manfred M; Ruben, Mario

    2015-09-21

    We report on the synthesis of tridentate-nitrogen pyrazole-pyridine-tetrazole (L(1)H) and pyrazole-pyridine-triazole (L(2)H) ligands and their complexation with lanthanides (Ln = Gd(iii), Eu(iii) and Tb(iii)) resulting in stable, charge-neutral complexes Ln(L(1))3 and Ln(L(2))3, respectively. X-ray crystallographic analysis of the complexes with L(1) ligands revealed tricapped trigonal coordination geometry around the lanthanide ions. All complexes show bright photoluminescence (PL) in the solid state, indicating efficient sensitization of the lanthanide emission via the triplet states of the ligands. In particular, the terbium complexes show high PL quantum yields of 65 and 59% for L(1) and L(2), respectively. Lower PL efficiencies of the europium complexes (7.5 and 9%, respectively) are attributed to large energy gaps between the triplet states of the ligands and accepting levels of Eu(iii). The triplet state energy can be reduced by introducing an electron withdrawing (EW) group at the 4 position of the pyridine ring. Such substitution of L(1)H with a carboxylic ester (COOMe) EW group leads to a europium complex with increased PL quantum yield of 31%. A comparatively efficient PL of the complexes dissolved in ethanol indicates that the lanthanide ions are shielded against nonradiative deactivation via solvent molecules.

  3. Micelle enhanced and terbium sensitized spectrofluorimetric determination of danofloxacin in milk using molecularly imprinted solid phase extraction

    Science.gov (United States)

    Kaur, Kuldeep; Saini, Shivender Singh; Malik, Ashok Kumar; Singh, Baldev

    2012-10-01

    An efficient molecularly imprinted solid phase extraction (MISPE)-spectrofluorimetric method was developed to sensitively determine danofloxacin (DAN) in milk samples. Solid phase extraction procedure using MISPE cartridges was first performed on milk samples and then spectrofluorimetric determination was done at 546 nm using an excitation wavelength of 285 nm in presence of terbium and sodium dodecyl benzene sulfonate (SDBS). It was found that SDBS significantly enhanced the fluorescence intensity of the DAN-Tb3+ complex. Various factors affecting the fluorescence intensity of DAN-Tb3+-SDBS system were studied and conditions were optimized. The enhanced fluorescence intensity of the system (ΔF) showed a good linear relationship with the concentration of DAN over the range of 8.4 × 10-9-3.4 × 10-7 mol L-1 with a correlation coefficient of 0.9996. The detection limit was determined as 2.0 × 10-9 mol L-1 and the limit of quantification was determined as 6.5 × 10-9 mol L-1. The MISPE-spectrofluorimetric procedure was successfully applied to the determination of DAN in milk samples. The method is simple, rapid, sensitive and allows interference free determination of DAN in complex fluorescent matrices like milk. The method can be used to determine whether the DAN residues in milk exceed MRLs or not.

  4. Study of quantum dot based on tin/yttrium mixed oxide doped with terbium to be used as biomarker

    Energy Technology Data Exchange (ETDEWEB)

    Paganini, Paula P.; Felinto, Maria Claudia F.C.; Kodaira, Claudia A., E-mail: paulapaganini@usp.b, E-mail: mfelinto@ipen.b, E-mail: claudiakodaira@yahoo.co [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Brito, Hermi F., E-mail: hefbrito@iq.usp.b [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Quimica. Lab. de Elementos do Bloco f; Nunes, Luiz Antonio O., E-mail: luizant@ifsc.usp.b [Universidade de Sao Paulo (USP), Sao Carlos, SP (Brazil). Inst. de Fisica. Dept. de Fisica e Informatica

    2009-07-01

    Quantum dots (semiconductors nanocrystals) have brought a promising field to develop a new generation of luminescent biomarkers. The use of lanthanides ions as luminescent markers has many advantages, for example a security method, low cost, high specificity and also the luminescence can be promptly measured with high sensibility and accuracy. These luminescent dots are functionalized with biomolecules. For the luminophore particle to be connect with biologicals molecules (for example covalent antibody) is necessary a previous chemical treatment to modify luminophore particle surface and this process is called functionalization. A prior chemical treatment with changes on the surface luminophore particle is necessary to couple the luminophore to biological molecules. This process can be used as coating which can protect these particles from being dissolved by acid as well as provide functional groups for biological conjugation. This work presents a photoluminescence study of nanoparticles based on tin/yttrium mixed oxides doped with terbium (SnO{sub 2}/Y{sub 2}O{sub 3}:Tb{sup 3+}), synthesized by coprecipitation method. The nanoparticles were submitted to thermal treatment and characterized by X-Ray Powder Diffraction (XRD) that showed cassiterite phase formation and the influence of thermal treatment on nanoparticles structures. These nanoparticles going to be functionalized with a natural polysaccharide (chitosan) in order to form microspheres. These microspheres going to be irradiated with gamma radiation to sterilization and it can be evaluated if the nanoparticles are resistant to irradiation and they do not lose functionality with this process. (author)

  5. Terbium-doped gadolinium oxysulfide (Gd2O2S:Tb) scintillation-based polymer optical fibre sensor for real time monitoring of radiation dose in oncology

    Science.gov (United States)

    Lewis, E.; O'Keeffe, S.; Grattan, M.; Hounsell, A.; McCarthy, D.; Woulfe, P.; Cronin, J.; Mihai, L.; Sporea, D.; Santhanam, A.; Agazaryan, N.

    2014-05-01

    A PMMA based plastic optical fibre sensor for use in real time radiotherapy dosimetry is presented. The optical fibre tip is coated with a scintillation material, terbium-doped gadolinium oxysulfide (Gd2O2S:Tb), which fluoresces when exposed to ionising radiation (X-Ray). The emitted visible light signal penetrates the sensor optical fibre and propagates along the transmitting fibre at the end of which it is remotely monitored using a fluorescence spectrometer. The results demonstrate good repeatability, with a maximum percentage error of 0.5% and the response is independent of dose rate.

  6. Electron tunneling transport across heterojunctions between europium sulfide and indium arsenide

    Science.gov (United States)

    Kallaher, Raymond L.

    This dissertation presents research done on utilizing the ferromagnetic semiconductor europium sulfide (EuS) to inject spin polarized electrons into the non-magnetic semiconductor indium arsenide (InAs). There is great interest in expanding the functionality of modern day electronic circuits by creating devices that depend not only on the flow of charge in the device, but also on the transport of spin through the device. Within this mindset, there is a concerted effort to establish an efficient means of injecting and detecting spin polarized electrons in a two dimensional electron system (2DES) as the first step in developing a spin based field effect transistor. Thus, the research presented in this thesis has focused on the feasibility of using EuS, in direct electrical contact with InAs, as a spin injecting electrode into an InAs 2DES. Doped EuS is a concentrated ferromagnetic semiconductor, whose conduction band undergoes a giant Zeeman splitting when the material becomes ferromagnetic. The concomitant difference in energy between the spin-up and spin-down energy bands makes the itinerant electrons in EuS highly spin polarized. Thus, in principle, EuS is a good candidate to be used as an injector of spin polarized electrons into non-magnetic materials. In addition, the ability to adjust the conductivity of EuS by varying the doping level in the material makes EuS particularly suited for injecting spins into non-magnetic semiconductors and 2DES. For this research, thin films of EuS have been grown via e-beam evaporation of EuS powder. This growth technique produces EuS films that are sulfur deficient; these sulfur vacancies act as intrinsic electron donors and the resulting EuS films behave like heavily doped ferromagnetic semiconductors. The growth parameters and deposition procedures were varied and optimized in order to fabricate films that have minimal crystalline defects. Various properties and characteristics of these EuS films were measured and compared to

  7. Point defects and electric compensation in gallium arsenide single crystals; Punktdefekte und elektrische Kompensation in Galliumarsenid-Einkristallen

    Energy Technology Data Exchange (ETDEWEB)

    Kretzer, Ulrich

    2007-12-10

    In the present thesis the point-defect budget of gallium arsenide single crystals with different dopings is studied. It is shown, in which way the concentration of the single point defects depende on the concentration of the dopants, the stoichiometry deviation, and the position of the Fermi level. For this serve the results of the measurement-technical characterization of a large number of samples, in the fabrication of which these parameters were directedly varied. The main topic of this thesis lies in the development of models, which allow a quantitative description of the experimentally studied electrical and optical properties of gallium arsenide single crystals starting from the point-defect concentrations. Because from point defects charge carriers can be set free, their concentration determines essentially the charge-carrier concentration in the bands. In the ionized state point defects act as scattering centers for free charge carriers and influence by this the drift mobility of the charge carriers. A thermodynamic modeling of the point-defect formation yields statements on the equilibrium concentrations of the point defects in dependence on dopant concentration and stoichiometry deviation. It is show that the electrical properties of the crystals observed at room temperature result from the kinetic suppression of processes, via which the adjustment of a thermodynamic equilibrium between the point defects is mediated. [German] In der vorliegenden Arbeit wird der Punktdefekthaushalt von Galliumarsenid-Einkristallen mit unterschiedlichen Dotierungen untersucht. Es wird gezeigt, in welcher Weise die Konzentration der einzelnen Punktdefekte von der Konzentration der Dotierstoffe, der Stoechiometrieabweichung und der Lage des Ferminiveaus abhaengen. Dazu dienen die Ergebnisse der messtechnischen Charakterisierung einer grossen Anzahl von Proben, bei deren Herstellung diese Parameter gezielt variiert wurden. Der Schwerpunkt der Arbeit liegt in der Entwicklung

  8. Compact all-fiber optical Faraday components using 65-wt%-terbium-doped fiber with a record Verdet constant of -32 rad/(Tm).

    Science.gov (United States)

    Sun, L; Jiang, S; Marciante, J R

    2010-06-07

    A compact all-fiber Faraday isolator and a Faraday mirror are demonstrated. At the core of each of these components is an all-fiber Faraday rotator made of a 4-cm-long, 65-wt%-terbium-doped silicate fiber. The effective Verdet constant of the terbium-doped fiber is measured to be -32 rad/(Tm), which is 27 x larger than that of silica fiber. This effective Verdet constant is the largest value measured to date in any fiber and is 83% of the Verdet constant of commercially available crystal used in bulk optics-based isolators. Combining the all-fiber Faraday rotator with fiber polarizers results in a fully fusion spliced all-fiber isolator whose isolation is measured to be 19 dB. Combining the all-fiber Faraday rotator with a fiber Bragg grating results in an all-fiber Faraday mirror that rotates the polarization state of the reflected light by 88 +/- 4 degrees .

  9. Picomolar Traces of Americium(III) Introduce Drastic Changes in the Structural Chemistry of Terbium(III): A Break in the "Gadolinium Break".

    Science.gov (United States)

    Welch, Jan M; Müller, Danny; Knoll, Christian; Wilkovitsch, Martin; Giester, Gerald; Ofner, Johannes; Lendl, Bernhard; Weinberger, Peter; Steinhauser, Georg

    2017-10-16

    The crystallization of terbium 5,5'-azobis[1H-tetrazol-1-ide] (ZT) in the presence of trace amounts (ca. 50 Bq, ca. 1.6 pmol) of americium results in 1) the accumulation of the americium tracer in the crystalline solid and 2) a material that adopts a different crystal structure to that formed in the absence of americium. Americium-doped [Tb(Am)(H 2 O) 7 ZT] 2 ZT⋅10 H 2 O is isostructural to light lanthanide (Ce-Gd) 5,5'-azobis[1H-tetrazol-1-ide] compounds, rather than to the heavy lanthanide (Tb-Lu) 5,5'-azobis[1H-tetrazol-1-ide] (e.g., [Tb(H 2 O) 8 ] 2 ZT 3 ⋅6 H 2 O) derivatives. Traces of Am seem to force the Tb compound into a structure normally preferred by the lighter lanthanides, despite a 10 8 -fold Tb excess. The americium-doped material was studied by single-crystal X-ray diffraction, vibrational spectroscopy, radiochemical neutron activation analysis, and scanning electron microcopy. In addition, the inclusion properties of terbium 5,5'-azobis[1H-tetrazol-1-ide] towards americium were quantified, and a model for the crystallization process is proposed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. A novel three-jet microreactor for localized metal-organic chemical vapour deposition of gallium arsenide: design and simulation

    Science.gov (United States)

    Konakov, S. A.; Krzhizhanovskaya, V. V.

    2016-08-01

    We present a novel three-jet microreactor design for localized deposition of gallium arsenide (GaAs) by low-pressure Metal-Organic Chemical Vapour Deposition (MOCVD) for semiconductor devices, microelectronics and solar cells. Our approach is advantageous compared to the standard lithography and etching technology, since it preserves the nanostructure of the deposited material, it is less time-consuming and less expensive. We designed two versions of reactor geometry with a 10-micron central microchannel for precursor supply and with two side jets of a dilutant to control the deposition area. To aid future experiments, we performed computational modeling of a simplified-geometry (twodimensional axisymmetric) microreactor, based on Navier-Stokes equations for a laminar flow of chemically reacting gas mixture of Ga(CH3)3-AsH3-H2. Simulation results show that we can achieve a high-rate deposition (over 0.3 μm/min) on a small area (less than 30 μm diameter). This technology can be used in material production for microelectronics, optoelectronics, photovoltaics, solar cells, etc.

  11. A final report for Gallium arsenide P-I-N detectors for high-sensitivity imaging of thermal neutrons

    CERN Document Server

    Vernon, S M

    1999-01-01

    This SBIR Phase I developed neutron detectors made FR-om gallium arsenide (GaAs) p-type/ intrinsic/n-type (P-I-N) diodes grown by metalorganic chemical vapor deposition (MOCVD) onto semi-insulating (S1) bulk GaAs wafers. A layer of isotonically enriched boron-10 evaporated onto the FR-ont surface serves to convert incoming neutrons into lithium ions and a 1.47 MeV alpha particle which creates electron-hole pairs that are detected by the GaAs diode. Various thicknesses of ''intrinsic'' (I) undoped GaAs were tested, as was use of a back-surface field (BSF) formed FR-om a layer of Al sub x Ga sub 1 sub - sub x As. Schottky-barrier diodes formed FR-om the same structures without the p+ GaAs top layer were tested as a comparison. After mesa etching and application of contacts, devices were tested in visible light before application of the boron coating. Internal quantum efficiency (IQE) of the best diode near the GaAs bandedge is over 90%. The lowest dark current measured is 1 x 10 sup - sup 1 sup 2 amps at -1 V o...

  12. Non-local exchange correlation functionals impact on the structural, electronic and optical properties of III-V arsenides

    KAUST Repository

    Anua, N. Najwa

    2013-08-20

    Exchange correlation (XC) energy functionals play a vital role in the efficiency of density functional theory (DFT) calculations, more soundly in the calculation of fundamental electronic energy bandgap. In the present DFT study of III-arsenides, we investigate the implications of XC-energy functional and corresponding potential on the structural, electronic and optical properties of XAs (X = B, Al, Ga, In). Firstly we report and discuss the optimized structural lattice parameters and the band gap calculations performed within different non-local XC functionals as implemented in the DFT-packages: WIEN2k, CASTEP and SIESTA. These packages are representative of the available code in ab initio studies. We employed the LDA, GGA-PBE, GGA-WC and mBJ-LDA using WIEN2k. In CASTEP, we employed the hybrid functional, sX-LDA. Furthermore LDA, GGA-PBE and meta-GGA were employed using SIESTA code. Our results point to GGA-WC as a more appropriate approximation for the calculations of structural parameters. However our electronic bandstructure calculations at the level of mBJ-LDA potential show considerable improvements over the other XC functionals, even the sX-LDA hybrid functional. We report also the optical properties within mBJ potential, which show a nice agreement with the experimental measurements in addition to other theoretical results. © 2013 IOP Publishing Ltd.

  13. Crystal structures of two mononuclear complexes of terbium(III) nitrate with the tripodal alcohol 1,1,1-tris-(hy-droxy-meth-yl)propane.

    Science.gov (United States)

    Gregório, Thaiane; Giese, Siddhartha O K; Nunes, Giovana G; Soares, Jaísa F; Hughes, David L

    2017-02-01

    Two new mononuclear cationic complexes in which the TbIII ion is bis-chelated by the tripodal alcohol 1,1,1-tris-(hy-droxy-meth-yl)propane (H3LEt, C6H14O3) were prepared from Tb(NO3)3·5H2O and had their crystal and mol-ecular structures solved by single-crystal X-ray diffraction analysis after data collection at 100 K. Both products were isolated in reasonable yields from the same reaction mixture by using different crystallization conditions. The higher-symmetry complex dinitratobis[1,1,1-tris-(hy-droxy-meth-yl)propane]-terbium(III) nitrate di-meth-oxy-ethane hemisolvate, [Tb(NO3)2(H3LEt)2]NO3·0.5C4H10O2, 1, in which the lanthanide ion is 10-coordinate and adopts an s-bicapped square-anti-prismatic coordination geometry, contains two bidentate nitrate ions bound to the metal atom; another nitrate ion functions as a counter-ion and a half-mol-ecule of di-meth-oxy-ethane (completed by a crystallographic twofold rotation axis) is also present. In product aqua-nitratobis[1,1,1-tris-(hy-droxy-meth-yl)propane]-terbium(III) dinitrate, [Tb(NO3)(H3LEt)2(H2O)](NO3)2, 2, one bidentate nitrate ion and one water mol-ecule are bound to the nine-coordinate terbium(III) centre, while two free nitrate ions contribute to charge balance outside the tricapped trigonal-prismatic coordination polyhedron. No free water mol-ecule was found in either of the crystal structures and, only in the case of 1, di-meth-oxy-ethane acts as a crystallizing solvent. In both mol-ecular structures, the two tripodal ligands are bent to one side of the coordination sphere, leaving room for the anionic and water ligands. In complex 2, the methyl group of one of the H3LEt ligands is disordered over two alternative orientations. Strong hydrogen bonds, both intra- and inter-molecular, are found in the crystal structures due to the number of different donor and acceptor groups present.

  14. The response behavior of PPy-DB18C6 electrode to terbium(III in acetonitrile and its thermodynamic application

    Directory of Open Access Journals (Sweden)

    Mohammad Hossein Arbab Zavar

    2016-11-01

    Full Text Available Polypyrrole modified electrode prepared by electropolymerization of pyrrole in the presence of a complexing ligand, dibenzo-18-crown-6(DB18C6, was prepared and investigated as a Tb3+-selective electrode in acetonitrile. The potentiometric response of the electrode was linear within the Tb3+ concentration range 1 × 10−5–1 × 10−2 M with a Nernstian slope of 20.9 mVdecade−1 in AN. The electrode was applied to study the complexation of the terbium(III ion in acetonitrile with such other basic aprotic solvent molecules (D as dimethyl sulfoxide, N,N-dimethyl formamide, propylene carbonate and pyridine. The successive complex formation constant (βi and Gibbs energies of transfer (ΔGtr of Tb3+ in AN in relation to such D were obtained.

  15. Luminescence and Magnetic Properties of Two Three-Dimensional Terbium and Dysprosium MOFs Based on Azobenzene-4,4′-Dicarboxylic Linker

    Directory of Open Access Journals (Sweden)

    Belén Fernández

    2016-02-01

    Full Text Available We report the in situ formation of two novel metal-organic frameworks based on terbium and dysprosium ions using azobenzene-4,4′-dicarboxylic acid (H2abd as ligand, synthesized by soft hydrothermal routes. Both materials show isostructural three-dimensional networks with channels along a axis and display intense photoluminescence properties in the solid state at room temperature. Textural properties of the metal-organic frameworks (MOFs have been fully characterized although no appreciable porosity was obtained. Magnetic properties of these materials were studied, highlighting the dysprosium material displays slightly frequency-dependent out of phase signals when measured under zero external field and under an applied field of 1000 Oe.

  16. Luminescent europium and terbium complexes of dipyridoquinoxaline and dipyridophenazine ligands as photosensitizing antennae: structures and biological perspectives.

    Science.gov (United States)

    Dasari, Srikanth; Patra, Ashis K

    2015-12-14

    The europium(III) and terbium(III) complexes, namely [Eu(dpq)(DMF)2(NO3)3] (1), [Eu(dppz)2(NO3)3] (2), [Tb(dpq)(DMF)2Cl3] (3), and [Tb(dppz)(DMF)2Cl3] (4), where dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 1 and 3), dipyrido[3,2-a:2',3'-c]phenazine (dppz in 2 and 4) and N,N'-dimethylformamide (DMF) have been isolated, characterized from their physicochemical data, luminescence studies and their interaction with DNA, serum albumin protein and photo-induced DNA cleavage activity are studied. The X-ray crystal structures of complexes 1-4 show discrete mononuclear Ln(3+)-based structures. The Eu(3+) in [Eu(dpq)(DMF)2(NO3)3] (1) and [Eu(dppz)2(NO3)3] (2) as [Eu(dppz)2(NO3)3]·dppz (2a) adopts a ten-coordinated bicapped dodecahedron structure with a bidentate N,N-donor dpq ligand, two DMF and three NO3(-) anions in 1 and two bidentate N,N-donor dppz ligands and three NO3(-) anions in 2. Complexes 3 and 4 show a seven-coordinated mono-capped octahedron structure where Tb(3+) contains bidentate dpq/dppz ligands, two DMF and three Cl(-) anions. The complexes are highly luminescent in nature indicating efficient photo-excited energy transfer from the dpq/dppz antenna to Ln(3+) to generate long-lived emissive excited states for characteristic f → f transitions. The time-resolved luminescence spectra of complexes 1-4 show typical narrow emission bands attributed to the (5)D0 → (7)F(J) and (5)D4 → (7)F(J) f-f transitions of Eu(3+) and Tb(3+) ions respectively. The number of inner-sphere water molecules (q) was determined from luminescence lifetime measurements in H2O and D2O confirming ligand-exchange reactions with water in solution. The complexes display significant binding propensity to the CT-DNA giving binding constant values in the range of 1.0 × 10(4)-6.1 × 10(4) M(-1) in the order 2, 4 (dppz) > 1, 3 (dpq). DNA binding data suggest DNA groove binding with the partial intercalation nature of the complexes. All the complexes also show binding propensity (K(BSA)

  17. Spin Waves in Terbium

    DEFF Research Database (Denmark)

    Jensen, J.; Houmann, Jens Christian Gylden

    1975-01-01

    The selection rules for the linear couplings between magnons and phonons propagating in the c direction of a simple basal-plane hcp ferromagnet are determined by general symmetry considerations. The acoustic-optical magnon-phonon interactions observed in the heavy-rare-earth metals have been expl...... by Liu. The coupled magnon—transverse-phonon system for the c direction of Tb is analyzed in detail, and the strengths of the couplings are deduced as a function of wave vector by combining the experimental studies with the theory....

  18. Spin Waves in Terbium

    DEFF Research Database (Denmark)

    Jensen, J.; Houmann, Jens Christian Gylden; Bjerrum Møller, Hans

    1975-01-01

    The energies of spin waves propagating in the c direction of Tb have been studied by inelastic neutron scattering, as a function of a magnetic field applied along the easy and hard directions in the basal plane, and as a function of temperature. From a general spin Hamiltonian, consistent...... with the symmetry, we deduce the dispersion relation for the spin waves in a basal-plane ferromagnet. This phenomenological spin-wave theory accounts for the observed behavior of the magnon energies in Tb. The two q⃗-dependent Bogoliubov components of the magnon energies are derived from the experimental results...

  19. One watt gallium arsenide class-E power amplifier with a thin-film bulk acoustic resonator filter embedded in the output network

    Directory of Open Access Journals (Sweden)

    Kyle Holzer

    2015-05-01

    Full Text Available Integration of a class-E power amplifier (PA and a thin-film bulk acoustic wave resonator (FBAR filter is shown to provide high power added efficiency in addition to superior out-of-band spectrum suppression. A discrete gallium arsenide pseudomorphic high-electron-mobility transistor is implemented to operate as a class-E amplifier from 2496 to 2690 MHz. The ACPF7041 compact bandpass FBAR filter is incorporated to replace the resonant LC tank in a traditional class-E PA. To reduce drain voltage stress, the supply choke is replaced by a finite inductance. The fabricated PA provides up to 1 W of output power with a peak power added efficiency (PAE of 58%. The improved out-of-band spectrum filtering is compared to a traditional class-E with discrete LC resonant filtering. Such PAs can be combined with linearisation techniques to reduce out-of-band emissions.

  20. Two new arsenides, Eu7Cu44As23 and Sr7Cu44As23, with a new filled variety of the BaHg11 structure.

    Science.gov (United States)

    Charkin, Dmitri O; Demchyna, Roman; Prots, Yurii; Borrmann, Horst; Burkhardt, Ulrich; Schwarz, Ulrich; Schnelle, Walter; Plokhikh, Igor V; Kazakov, Sergey M; Abakumov, Artem M; Batuk, Dmitry; Verchenko, Valery Yu; Tsirlin, Alexander A; Curfs, Caroline; Grin, Yuri; Shevelkov, Andrei V

    2014-10-20

    Two new ternary arsenides, namely, Eu7Cu44As23 and Sr7Cu44As23, were synthesized from elements at 800 °C. Their crystal structure represents a new filled version of the BaHg11 motif with cubic voids alternately occupied by Eu(Sr) and As atoms, resulting in a 2 × 2 × 2 superstructure of the aristotype: space group Fm3̅m, a = 16.6707(2) Å and 16.7467(2) Å, respectively. The Eu derivative exhibits ferromagnetic ordering below 17.5 K. In agreement with band structure calculations both compounds are metals, exhibiting relatively low thermopower, but high electrical and low thermal conductivity.

  1. Synthesis and crystal structure of terbium(III) meta-oxoborate Tb(BO{sub 2}){sub 3} ({identical_to} TbB{sub 3}O{sub 6}); Synthese und Kristallstruktur von Terbium(III)-meta-Oxoborat Tb(BO{sub 2}){sub 3} ({identical_to} TbB{sub 3}O{sub 6})

    Energy Technology Data Exchange (ETDEWEB)

    Nikelski, Tanja; Schleid, Thomas [Institut fuer Anorganische Chemie der Universitaet Stuttgart (Germany)

    2003-06-01

    The terbium meta-oxoborate Tb(BO{sub 2}){sub 3} ({identical_to} TbB{sub 3}O{sub 6}) is obtained as single crystals by the reaction of terbium, Tb{sub 4}O{sub 7} and TbCl{sub 3} with an excess of B{sub 2}O{sub 3} in gastight sealed platinum ampoules at 950 C after three weeks. The compound appears to be air- and water-resistant and crystallizes as long, thin, colourless needles which tend to growth-twinning due to their marked fibrous habit. The crystal structure of Tb(BO{sub 2}){sub 3} (orthorhombic, Pnma; a = 1598.97(9), b = 741.39(4), c = 1229.58(7) pm; Z = 16) contains strongly corrugated oxoborate layers {sub {infinity}}{sup 2}{l_brace}(BO{sub 2}){sup -}{r_brace} built of vertex-linked [BO{sub 4}]{sup 5-} tetrahedra (d(B-O) = 143 - 154 pm, and angsph;(O-B-O) = 102-115 ) which spread out parallel (100). The four crystallographically different Tb{sup 3+} cations all exhibit coordination numbers of eight towards the oxygen atoms (d(Tb-O) = 228-287 pm). The corresponding metal cation polyhedra [TbO{sub 8}]{sup 13+} too convene to layers (composition: {sub {infinity}}{sup 2}{l_brace}(Tb{sub 2}O{sub 11}){sup 16-}{r_brace}) which are likewise oriented parallel to the (100) plane. (Abstract Copyright [2003], Wiley Periodicals, Inc.) [German] Das Terbium-meta-Oxoborat Tb(BO{sub 2}){sub 3} ({identical_to} TbB{sub 3}O{sub 6}) entsteht einkristallin bei der Reaktion von Terbium, Tb{sub 4}O{sub 7} und TbCl{sub 3} mit einem Ueberschuss von B{sub 2}O{sub 3} in gasdicht verschlossenen Platinampullen nach drei Wochen bei 950 C. Die Verbindung ist luft- und wasserstabil und faellt in langen, duennen, farblosen Nadeln an, die aufgrund ihres ausgepraegt faserigen Habitus zur Wachstumsverzwillingung neigen. Die Kristallstruktur von Tb(BO{sub 2}){sub 3} (orthorhombisch, Pnma; a = 1598, 97(9), b = 741, 39(4), c = 1229, 58(7) pm; Z = 16) enthaelt parallel (100) verlaufende, stark gewellte Oxoborat-Schichten {sub {infinity}}{sup 2}{l_brace}(BO{sub 2}){sup -}{r_brace} aus

  2. Indium Arsenide Nanowires

    DEFF Research Database (Denmark)

    Madsen, Morten Hannibal

    -ray diffraction. InAs NWs can be used in a broad range of applications, including detectors, high speed electronics and low temperature transport measurements, but in this thesis focus will be put on biological experiments on living cells. Good control of Au-assisted InAs NW growth has been achieved...... by a systematic study to optimize the growth conditions; first the Au deposition, then the growth temperature and finally the beam fluxes. For further control of the growth, Au droplets have been positioned with electron beam lithography and large scale arrays with a > 99 % yield have been made on 2 inch...... and its dependence on growth parameters. By fabricating the NWs on silicon-on-insulator substrates we demonstrate electrically addressable NWs that are still standing vertically on the substrate and can potentially be used for intra-cellular recordings. Devices for biological experiments using vertically...

  3. An integrated logic system for time-resolved fluorescent "turn-on" detection of cysteine and histidine base on terbium (III) coordination polymer-copper (II) ensemble.

    Science.gov (United States)

    Xue, Shi-Fan; Lu, Ling-Fei; Wang, Qi-Xian; Zhang, Shengqiang; Zhang, Min; Shi, Guoyue

    2016-09-01

    Cysteine (Cys) and histidine (His) both play indispensable roles in many important biological activities. An enhanced Cys level can result in Alzheimer's and cardiovascular diseases. Likewise, His plays a significant role in the growth and repair of tissues as well as in controlling the transmission of metal elements in biological bases. Therefore, it is meaningful to detect Cys and His simultaneously. In this work, a novel terbium (III) coordination polymer-Cu (II) ensemble (Tb(3+)/GMP-Cu(2+)) was proposed. Guanosine monophosphate (GMP) can self-assemble with Tb(3+) to form a supramolecular Tb(3+) coordination polymer (Tb(3+)/GMP), which can be suited as a time-resolved probe. The fluorescence of Tb(3+)/GMP would be quenched upon the addition of Cu(2+), and then the fluorescence of the as-prepared Tb(3+)/GMP-Cu(2+) ensemble would be restored again in the presence of Cys or His. By incorporating N-Ethylmaleimide and Ni(2+) as masking agents, Tb(3+)/GMP-Cu(2+) was further exploited as an integrated logic system and a specific time-resolved fluorescent "turn-on" assay for simultaneously sensing His and Cys was designed. Meanwhile it can also be used in plasma samples, showing great potential to meet the need of practical application. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Synthesis and photoluminescence properties of cerium-doped terbium-yttrium aluminum garnet phosphor for white light-emitting diodes applications

    Science.gov (United States)

    Wang, Jun; Han, Tao; Lang, Tianchun; Tu, Mingjing; Peng, Lingling

    2015-11-01

    Cerium-doped terbium-yttrium aluminum garnet phosphors were synthesized using the solid-state reaction method. The crystalline phase, morphology, and photoluminescence properties were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), and fluorescence spectrophotometer, respectively. The XRD results indicate that with an increase of the amount of x (Tb3+), all of the samples have a pure garnet crystal structure without secondary phases. The SEM images reveal that the samples are composed of sphere-like crystallites, which exhibit different degrees of agglomeration. The luminescent properties of Ce ions in )Al5O12∶Ce0.1 have been studied, and it was found that the emission band shifted toward a longer wavelength. The redshift is attributed to the lowering of the 5d energy level centroid of Ce, which can be explained by the nephelauxetic effect and compression effect. These phosphors were coated on blue light-emitting diode (LED) chips to fabricate white light-emitting diodes (WLEDs), and their color-rendering indices, color temperatures, and luminous efficiencies were measured. As a consequence of the addition of Tb, the blue LED pumped )Al5O12∶Ce0.1 phosphors WLEDs showed good optical properties.

  5. Study on the fluorescent enhancement effect in terbium-gadolinium-protein-sodium dodecyl benzene sulfonate system and its application on sensitive detection of protein at nanogram level.

    Science.gov (United States)

    Sun, Changxia; Yang, Jinghe; Wu, Xia; Liu, Shufang; Su, Benyu

    2004-08-01

    The co-luminescence effect in a terbium-gadolinium-protein-sodium dodecyl benzene sulfonate (SDBS) system is reported here. Based on it, the sensitive quantitative analysis of protein at nanogram levels is established. The co-luminescence mechanism is studied using fluorescence, resonance light scattering (RLS), absorption spectroscopy and NMR measurement. It is considered that protein could be unfolded by SDBS, then a efficacious intramolecular fluorescent energy transfer occurs from unfolded protein to rare earth ions through SDBS acting as a "transfer bridge" to enhance the emission fluorescence of Tb3+ in this ternary complex of Tb-SDBS-BSA, where energy transfer from protein to SDBS by aromatic ring stacking is the most important step. Cooperating with the intramolecular energy transfer above is the intermolecular energy transfer between the simultaneous existing complexes of both Tb3+ and Gd3+. The fluorescence quantum yield is increased by an energy-insulating sheath, which is considered to be another reason for the resulting enhancement of the fluorescence. Förster theory is used to calculate the distribution of enhancing factors and has led to a greater understanding of the mechanisms of energy transfer.

  6. [Studies on luminescence properties of seven ternary complexes of terbium with 1,10-phenanthroline and benzoic acid and its derivatives].

    Science.gov (United States)

    Gao, Zhi-hua; Wang, Shu-ping; Liu, Cui-ge; Ma, Rui-xia; Wang, Rui-fen

    2006-04-01

    Seven ternary complexes of Tb(III) were synthesized with benzoic acid (BA), o-, m-, p-methylbenzoic acid (o-MBA, m-MBA, p-MBA), and o-, m-, p-methoxybenzoic acid (o-MOBA, m-MOBA, p-MOBA) as the first ligand, and 1,10-phenanthroline (phen) as the second ligand. The content of C, H and N were measured by using a Flash-EA model 1112 elemental analyzer. Excitation and luminescence spectra of the title solid complexes were recorded by using a Hitachi F-4500 fluorescence spectrophotometer at room temperature. The effects of different varieties and different positions of replacing benzoic acid as the first ligand on fluorescence properties of the ternary complexes of terbium were discussed. The results indicated that the intensity of 5D4-->7F6 (489 nm) and 5D4-->7F5 (545 nm) of substituting benzoic acid complexes was stronger than benzoic acid. Three ternary complexes of Tb(III) with o-, m-, p-methylbenzoic acid showed emission intensity in the consecution: Tb(o-MBA)3 phenMOBA)3phen x H2O>Tb(m-MOBA)3phen x H2O>Tb(p-MOBA)3 phen.

  7. Self-diffusion coefficients of the trivalent f-element ion series in dilute and moderately dilute aqueous solutions: A comparative study between europium, gadolinium, terbium and berkelium

    Science.gov (United States)

    Rafik, Besbes; Noureddine, Ouerfelli; Abderabbou, Abdelmanef; Habib, Latrous

    2010-03-01

    We have continued the studies on the trivalent ions of the 4f and 5f elements. In this paper, we compare the transport properties (self-diffusion coefficient) of the trivalent aquo ions over two ranges of concentrations (0 — 2×10-3M) and (2×10-3 — 1.5M). Self-diffusion coefficients, D, of the trivalent f-element aquo ion series have been determined in aqueous background electrolytes of Gd(NO3)3 and Nd(ClO4)3, at pH=2.5 (HNO3, HClO4) and at 25°C using the open-end capillary method (O.E.C.M.). This method measures the transportation time of ions across a fixed distance. In this paper, we complete a measurement of self-diffusion coefficient for terbium. We optimized the pH to avoid hydrolysis, ion-pairing and complexation of the trivalent 4f and 5f ions. The variation of D versus √C is not linear for dilute solutions (0 — 2×10-3M) and quasi-linear in moderate concentrations (C<=1.5 M). Similar behavior was observed for Tb, as compared with those for Bk, Eu and Gd. We complete the comparison variation of D/D° versus √C for all studied 4f and 5f elements from concentration 0 to 1.5M and we obtained the same variation with √C for all studied elements. All 4f and 5f elements studied follow the Nernst-Hartley expression.

  8. Terbium-based time-gated Förster resonance energy transfer imaging for evaluating protein-protein interactions on cell membranes.

    Science.gov (United States)

    Lindén, Stina; Singh, Manish Kumar; Wegner, K David; Regairaz, Marie; Dautry, François; Treussart, François; Hildebrandt, Niko

    2015-03-21

    Fluorescence imaging of cells and subcellular compartments is an essential tool to investigate biological processes and to evaluate the development and progression of diseases. In particular, protein-protein interactions can be monitored by Förster resonance energy transfer (FRET) between two proximal fluorophores that are attached to specific recognition biomolecules such as antibodies. We investigated the membrane expression of E- and N-cadherins in three different cell lines used as model systems to study epithelial to mesenchymal transition (EMT) and a possible detection of circulating tumour cells (CTCs). EMT is a key process in cancer metastasis, during which epithelial markers (such as E-cadherin) are down-regulated in the primary tumour whereas mesenchymal markers (such as N-cadherin) are up-regulated, leading to enhanced cell motility, intravasation, and appearance of CTCs. Various FRET donor-acceptor pairs and protein recognition strategies were utilized, in which Lumi4-Tb terbium complexes (Tb) and different organic dyes were conjugated to several distinct E- and N-cadherin-specific antibodies. Pulsed excitation of Tb at low repetition rates (100 Hz) and time-gated (TG) imaging of both the Tb-donor and the dye-acceptor photoluminescence (PL) allowed efficient detection of the EMT markers as well as FRET in the case of sufficient donor-acceptor proximity. Efficient FRET was observed only between two E-cadherin-specific antibodies and further experiments indicated that these antibodies recognized the same E-cadherin molecule, suggesting a limited accessibility of cadherins when they are clustered at adherens junctions. The investigated Tb-to-dye FRET systems provided reduced photobleaching compared to the AlexaFluor 488-568 donor-acceptor pair. Our results demonstrate the applicability and advantages of Tb-based TG FRET for efficient and stable imaging of antibody-antibody interactions on different cell lines. They also reveal the limitations of

  9. A broad G protein-coupled receptor internalization assay that combines SNAP-tag labeling, diffusion-enhanced resonance energy transfer, and a highly emissive terbium cryptate acceptor

    Directory of Open Access Journals (Sweden)

    Angélique eLEVOYE

    2015-11-01

    Full Text Available Although G protein-coupled receptor (GPCR internalization has long been considered a major aspect of the desensitization process that tunes ligand responsiveness, internalization is also involved in receptor resensitization and signaling, as well as the ligand scavenging function of some atypical receptors. Internalization thus contributes to the diversity of GPCR-dependent signaling, and its dynamics and quantification in living cells has generated considerable interest. We developed a robust and sensitive assay to follow and quantify ligand-induced and constitutive GPCR internalization but also receptor recycling in living cells. This assay is based on diffusion-enhanced resonance energy transfer (DERET between cell surface GPCRs labeled with a luminescent terbium cryptate donor and a fluorescein acceptor present in the culture medium. GPCR internalization results in a quantifiable reduction of energy transfer. This method yields a high signal-to-noise ratio due to time-resolved measurements. For various GPCRs belonging to different classes, we demonstrated that constitutive and ligand-induced internalization could be monitored as a function of time and ligand concentration, thus allowing accurate quantitative determination of kinetics of receptor internalization but also half-maximal effective or inhibitory concentrations of compounds. In addition to its selectivity and sensitivity, we provided evidence that DERET-based internalization assay is particularly suitable for characterizing biased ligands. Furthermore, the determination of a Z’-factor value of 0.45 indicates the quality and suitability of DERET-based internalization assay for high-throughput screening (HTS of compounds that may modulate GPCRs internalization.

  10. Crystal structure of an eight-coordinate terbium(III ion chelated by N,N′-bis(2-hydroxybenzyl-N,N′-bis(pyridin-2-ylmethylethylenediamine (bbpen2− and nitrate

    Directory of Open Access Journals (Sweden)

    Thaiane Gregório

    2015-01-01

    Full Text Available The reaction of terbium(III nitrate pentahydrate in acetonitrile with N,N′-bis(2-hydroxybenzyl-N,N′-bis(pyridin-2-ylmethylethylenediamine (H2bbpen, previously deprotonated with triethylamine, produced the mononuclear compound [N,N′-bis(2-oxidobenzyl-κO-N,N′-bis(pyridin-2-ylmethyl-κNethylenediamine-κ2N,N′](nitrato-κ2O,O′terbium(III, [Tb(C28H28N4O2(NO3]. The molecule lies on a twofold rotation axis and the TbIII ion is eight-coordinate with a slightly distorted dodecahedral coordination geometry. In the symmetry-unique part of the molecule, the pyridine and benzene rings are both essentially planar and form a dihedral angle of 61.42 (7°. In the molecular structure, the N4O4 coordination environment is defined by the hexadentate bbpen ligand and the bidentate nitrate anion. In the crystal, a weak C—H...O hydrogen bond links molecules into a two-dimensional network parallel to (001.

  11. The effect of gallium arsenide aluminum laser therapy in the management of cervical myofascial pain syndrome: a double blind, placebo-controlled study.

    Science.gov (United States)

    Dundar, U; Evcik, D; Samli, F; Pusak, H; Kavuncu, V

    2007-06-01

    The efficacy of low-level laser therapy (LLLT) in myofascial pain syndrome (MPS) seems controversial. A prospective, double-blind, randomized controlled trial was conducted in patients with chronic MPS in the neck to evaluate the effects of low-level 830-nm gallium arsenide aluminum (Ga-As-Al) laser therapy. The study group consisted of 64 MPS patients. The patients were randomly assigned into two groups. In group 1 (n = 32), Ga-As-Al laser treatment was applied over three trigger points bilaterally for 2 min over each point once a day for 15 days during a period of 3 weeks. In group 2 (n = 32), the same treatment protocol was given, but the laser instrument was switched off during applications. All patients in both groups performed daily isometric exercise and stretching exercises for cervical region. Parameters were measured at baseline and after 4 weeks. All patients were evaluated with respect to pain (at rest, movement, and night) and assessed by visual analog scale, measurement of active range of motion using an inclinometer and a goniometer, and the neck disability index. In both groups, statistically significant improvements were detected in all outcome measures compared with baseline (p 0.05). In conclusion, although the laser therapy has no superiority over placebo groups in this study, we cannot exclude the possibility of effectivity with another treatment regimen including different laser wavelengths and dosages (different intensity and density and/or treatment interval).

  12. A novel wide range, real-time neutron fluence monitor based on commercial off the shelf gallium arsenide light emitting diodes

    Science.gov (United States)

    Mukherjee, B.; Hentschel, R.; Lambert, J.; Deya, W.; Farr, J.

    2011-10-01

    Displacement damage produced by high-energy neutrons in gallium arsenide (GaAs) light emitting diodes (LED) results in the reduction of light output. Based on this principle we have developed a simple, cost effective, neutron detector using commercial off the shelf (COTS) GaAs-LED for the assessment of neutron fluence and KERMA at critical locations in the vicinity of the 230 MeV proton therapy cyclotron operated by Westdeutsches Protonentherapiezentrum Essen (WPE). The LED detector response (mV) was found to be linear within the neutron fluence range of 3.0×10 8-1.0×10 11 neutron cm -2. The response of the LED detector was proportional to neutron induced displacement damage in LED; hence, by using the differential KERMA coefficient of neutrons in GaAs, we have rescaled the calibration curve for two mono-energetic sources, i.e. 1 MeV neutrons and 14 MeV neutrons generated by D+T fusion reaction. In this paper we present the principle of the real-time GaAs-LED based neutron fluence monitor as mentioned above. The device was calibrated using fast neutrons produced by bombarding a thick beryllium target with 14 MeV deuterons from a TCC CV 28 medical cyclotron of the Strahlenklinik University Hospital Essen.

  13. Correlation between non-Fermi-liquid behavior and superconductivity in (Ca, La)(Fe,Co)As2 iron arsenides: A high-pressure study

    Science.gov (United States)

    Zhou, W.; Ke, F.; Xu, Xiaofeng; Sankar, R.; Xing, X.; Xu, C. Q.; Jiang, X. F.; Qian, B.; Zhou, N.; Zhang, Y.; Xu, M.; Li, B.; Chen, B.; Shi, Z. X.

    2017-11-01

    Non-Fermi-liquid (NFL) phenomena associated with correlation effects have been widely observed in the phase diagrams of unconventional superconducting families. Exploration of the correlation between the normal state NFL, regardless of its microscopic origins, and the superconductivity has been argued as a key to unveiling the mystery of the high-Tc pairing mechanism. Here we systematically investigate the pressure-dependent in-plane resistivity (ρ ) and Hall coefficient (RH) of a high-quality 112-type Fe-based superconductor Ca1 -xLaxFe1 -yCoyAs2 (x =0.2 ,y =0.02 ). With increasing pressure, the normal-state resistivity of the studied sample exhibits a pronounced crossover from non-Fermi-liquid to Fermi-liquid behaviors. Accompanied with this crossover, Tc is gradually suppressed. In parallel, the extremum in the Hall coefficient RH(T ) curve, possibly due to anisotropic scattering induced by spin fluctuations, is also gradually suppressed. The symbiosis of NFL and superconductivity implies that these two phenomena are intimately related. Further study on the pressure-dependent upper critical field reveals that the two-band effects are also gradually weakened with increasing pressure and reduced to the one-band Werthamer-Helfand-Hohenberg limit in the low-Tc regime. Overall, our paper supports the picture that NFL, multigap, and extreme RH(T ) are all of the same magnetic origin, i.e., the spin fluctuations in the 112 iron arsenide superconductors.

  14. Platinum-group elements fractionation by selective complexing, the Os, Ir, Ru, Rh-arsenide-sulfide systems above 1020 °C

    Science.gov (United States)

    Helmy, Hassan M.; Bragagni, Alessandro

    2017-11-01

    The platinum-group element (PGE) contents in magmatic ores and rocks are normally in the low μg/g (even in the ng/g) level, yet they form discrete platinum-group mineral (PGM) phases. IPGE (Os, Ir, Ru) + Rh form alloys, sulfides, and sulfarsenides while Pt and Pd form arsenides, tellurides, bismuthoids and antimonides. We experimentally investigate the behavior of Os, Ru, Ir and Rh in As-bearing sulfide system between 1300 and 1020 °C and show that the prominent mineralogical difference between IPGE (+Rh) and Pt and Pd reflects different chemical preference in the sulfide melt. At temperatures above 1200 °C, Os shows a tendency to form alloys. Ruthenium forms a sulfide (laurite RuS2) while Ir and Rh form sulfarsenides (irarsite IrAsS and hollingworthite RhAsS, respectively). The chemical preference of PGE is selective: IPGE + Rh form metal-metal, metal-S and metal-AsS complexes while Pt and Pd form semimetal complexes. Selective complexing followed by mechanical separation of IPGE (and Rh)-ligand from Pt- and Pd-ligand associations lead to PGE fractionation.

  15. Solubility of platinum-arsenide melt and sperrylite in synthetic basalt at 0.1 MPa and 1200 °C with implications for arsenic speciation and platinum sequestration in mafic igneous systems

    Science.gov (United States)

    Canali, A. C.; Brenan, J. M.; Sullivan, N. A.

    2017-11-01

    To better understand the Pt-As association in natural magmas, experiments were done at 1200 °C and 0.1 MPa to measure the solubility of Pt and Pt-arsenide phases (melt and sperrylite, PtAs2), as well as to determine the oxidation state, and identify evidence for Pt-As complexing, in molten silicate. Samples consisting of synthetic basalt contained in chromite crucibles were subject to three experimental procedures. In the first, platinum solubility in the synthetic basalt was determined without added arsenic by equilibrating the sample with a platinum source (embedded wire or bead) in a gas-mixing furnace. In the second, the sample plus a Pt-arsenide source was equilibrated in a vacuum-sealed fused quartz tube containing a solid-oxide oxygen buffer. The third approach involved two steps: first equilibrating the sample in a gas-mixing furnace, then with added arsenide melt in a sealed quartz tube. Oxygen fugacity was estimated in the latter step using chromite/melt partitioning of vanadium. Method two experiments done at high initial arsenic activity (PtAs melt + PtAs2), showed significant loss of arsenic from the sample, the result of vapour transfer to newly-formed arsenide phases in the buffer. Method three experiments showed no loss of arsenic, yielding a uniform final distribution in the sample. Analyses of run-product glasses from experiments which did not show arsenic loss reveal significant increase in arsenic concentrations with fO2, varying from ∼10 ppm (FMQ-3.25) to >10,000 ppm (FMQ + 5.5). Despite very high arsenic loadings (>1000 ppm), the solubility of Pt is similar in arsenic-bearing and arsenic-free glasses. The variation in arsenic solubility with fO2 shows a linear relationship, that when corrected for the change in the activity of dissolved arsenic with the melt ferric/ferrous ratio, yields a solubility-fO2 relationship consistent with As3+ as the dissolved species. This result is confirmed by X-ray absorption near edge structure (XANES

  16. High Final Energy of Low-Level Gallium Arsenide Laser Therapy Enhances Skeletal Muscle Recovery without a Positive Effect on Collagen Remodeling.

    Science.gov (United States)

    de Freitas, Carlos Eduardo Assumpção; Bertaglia, Raquel Santilone; Vechetti Júnior, Ivan José; Mareco, Edson Assunção; Salomão, Rondinelle Artur Simões; de Paula, Tassiana Gutierrez; Nai, Gisele Alborghetti; Carvalho, Robson Francisco; Pacagnelli, Francis Lopes; Dal-Pai-Silva, Maeli

    2015-01-01

    The aim of this study was to evaluate the effects of a Gallium Arsenide (GaAs) laser, using a high final energy of 4.8 J, during muscle regeneration after cryoinjury. Thirty Wistar rats were divided into three groups: Control (C, n = 10); Injured (I, n = 10) and Injured and laser treated (Injured/LLLT, n = 10). The cryoinjury was induced in the central region of the tibialis anterior muscle (TA). The applications of the laser (904 nm, 50 mW average power) were initiated 24 h after injury, at energy density of 69 J cm(-1) for 48 s, for 5 days, to two points of the lesion. Twenty-four hours after the final application, the TA muscle was removed and frozen in liquid nitrogen to assess the general muscle morphology and the gene expression of TNF-α, TGF-β, MyoD, and Myogenin. The Injured/LLLT group presented a higher number of regenerating fibers and fewer degenerating fibers (P < 0.05) without changes in the collagen remodeling. In addition, the Injured/LLLT group presented a significant decrease in the expression of TNF-α and myogenin compared to the injured group (P < 0.05). The results suggest that the GaAs laser, using a high final energy after cryoinjury, promotes muscle recovery without changing the collagen remodeling in the muscle extracellular matrix. © 2015 The American Society of Photobiology.

  17. Selective Sensing of Fe(3+) and Al(3+) Ions and Detection of 2,4,6-Trinitrophenol by a Water-Stable Terbium-Based Metal-Organic Framework.

    Science.gov (United States)

    Cao, Li-Hui; Shi, Fang; Zhang, Wen-Min; Zang, Shuang-Quan; Mak, Thomas C W

    2015-10-26

    A water-stable luminescent terbium-based metal-organic framework (MOF), {[Tb(L1 )1.5 (H2 O)]⋅3 H2 O}n (Tb-MOF), with rod-shaped secondary building units (SBUs) and honeycomb-type tubular channels has been synthesized and structurally characterized by single-crystal X-ray diffraction. The high green emission intensity and the microporous nature of the Tb-MOF indicate that it can potentially be used as a luminescent sensor. In this work, we show that Tb-MOF can selectively sense Fe(3+) and Al(3+) ions from mixed metal ions in water through different detection mechanisms. In addition, it also exhibits high sensitivity for 2,4,6-trinitrophenol (TNP) in the presence of other nitro aromatic compounds in aqueous solution by luminescence quenching experiments. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Picomolar traces of americium(III) introduce drastic changes in the structural chemistry of terbium(III). A break in the ''gadolinium break''

    Energy Technology Data Exchange (ETDEWEB)

    Welch, Jan M. [TU Wien, Atominstitut, Vienna (Austria); Mueller, Danny; Knoll, Christian; Wilkovitsch, Martin; Weinberger, Peter [TU Wien, Institute of Applied Synthetic Chemistry, Vienna (Austria); Giester, Gerald [University of Vienna, Institute of Mineralogy and Crystallography, Vienna (Austria); Ofner, Johannes; Lendl, Bernhard [TU Wien, Institute of Chemical Technologies and Analytics, Vienna (Austria); Steinhauser, Georg [Leibniz Universitaet Hannover, Institute of Radioecology and Radiation Protection (Germany)

    2017-10-16

    The crystallization of terbium 5,5{sup '}-azobis[1H-tetrazol-1-ide] (ZT) in the presence of trace amounts (ca. 50 Bq, ca. 1.6 pmol) of americium results in 1) the accumulation of the americium tracer in the crystalline solid and 2) a material that adopts a different crystal structure to that formed in the absence of americium. Americium-doped [Tb(Am)(H{sub 2}O){sub 7}ZT]{sub 2} ZT.10 H{sub 2}O is isostructural to light lanthanide (Ce-Gd) 5,5{sup '}-azobis[1H-tetrazol-1-ide] compounds, rather than to the heavy lanthanide (Tb-Lu) 5,5{sup '}-azobis[1H-tetrazol-1-ide] (e.g., [Tb(H{sub 2}O){sub 8}]{sub 2}ZT{sub 3}.6 H{sub 2}O) derivatives. Traces of Am seem to force the Tb compound into a structure normally preferred by the lighter lanthanides, despite a 10{sup 8}-fold Tb excess. The americium-doped material was studied by single-crystal X-ray diffraction, vibrational spectroscopy, radiochemical neutron activation analysis, and scanning electron microscopy. In addition, the inclusion properties of terbium 5,5{sup '}-azobis[1H-tetrazol-1-ide] towards americium were quantified, and a model for the crystallization process is proposed. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Sodium terbium(III polyphosphate

    Directory of Open Access Journals (Sweden)

    Abdelghani Oudahmane

    2010-04-01

    Full Text Available Single crystals of the title compound, NaTb(PO34, were obtained by solid-state reaction. This compound belongs to type II of long-chain polyphosphates with the general formula AIBIII(PO34. It is isotypic with the NaNd(PO34 and NaEr(PO34 homologues. The crystal structure is built up of infinite crenelated chains of corner-sharing PO4 tetrahedra with a repeating unit of four tetrahedra. These chains, extending parallel to [100], are linked by isolated TbO8 square antiprisms, forming a three-dimensional framework. The Na+ ions are located in channels running along [010] and are surrounded by six oxygen atoms in a distorted octahedral environment within a cut-off distance <2.9 Å.

  20. Quantificaion of ion diffusion in gallium arsenide-based spintronic Light-Emitting Diode devices using time-of-flight secondary ion mass spectrometry

    Science.gov (United States)

    Cogswell, Jeffrey Ryan

    Depth profiling using Secondary Ion Mass Spectrometry (SIMS) is a direct method to measure diffusion of atomic or molecular species that have migrated distances of nanometers/micrometers in a specific material. For this research, the diffusion of Mn, sequentially Ga ions, in Gallium Arsenide (GaAs)-based spin Light Emitting Diode (LED) devices is studied by quantitative Time-of-Flight (ToF) SIMS. The goal is to prove conclusively the driving force and mechanism behind Mn diffusion in GaAs by quantifying the diffusion of these ions in each device. Previous work has identified two competing processes for the movement of Mn in GaAs: diffusion and phase separation. The process is dependent on the temperature the sample is exposed to, either by post-annealing, or during the molecular beam epitaxy (MBE) growth process. The hypothesis is that Manganese Arsenide (MnAs) is thermodynamically more stable than randomly distributed Mn ions in GaAs, and that by annealing at a certain temperature, a pure MnAs layer can be produced from a GaMnAs layer in a working spin LED device. Secondly, the spin efficiencies will be measured and the difference will be related to the formation of a pure MnAs layer. The first chapter of this dissertation discusses the history of spintronic devices, including details on the established methods for characterization, the importance for potential application to the semiconductor industry, and the requirements for the full implementation of spintronic devices in modern-day computers. MnAs and GaMnAs devices are studied, their preparation and properties are described, and the study's experimental design is covered in the latter part of Chapter 1. Chapter 2 includes a review of diffusion in semiconductors, including the types of diffusion, mechanisms they follow, and the different established experimental methods for studying diffusion. The later sections include summaries of Mn diffusion and previous studies investigating Mn diffusion in different

  1. Wet chemical functionalization of III-V semiconductor surfaces: alkylation of gallium arsenide and gallium nitride by a Grignard reaction sequence.

    Science.gov (United States)

    Peczonczyk, Sabrina L; Mukherjee, Jhindan; Carim, Azhar I; Maldonado, Stephen

    2012-03-13

    Crystalline gallium arsenide (GaAs) (111)A and gallium nitride (GaN) (0001) surfaces have been functionalized with alkyl groups via a sequential wet chemical chlorine activation, Grignard reaction process. For GaAs(111)A, etching in HCl in diethyl ether effected both oxide removal and surface-bound Cl. X-ray photoelectron (XP) spectra demonstrated selective surface chlorination after exposure to 2 M HCl in diethyl ether for freshly etched GaAs(111)A but not GaAs(111)B surfaces. GaN(0001) surfaces exposed to PCl(5) in chlorobenzene showed reproducible XP spectroscopic evidence for Cl-termination. The Cl-activated GaAs(111)A and GaN(0001) surfaces were both reactive toward alkyl Grignard reagents, with pronounced decreases in detectable Cl signal as measured by XP spectroscopy. Sessile contact angle measurements between water and GaAs(111)A interfaces after various levels of treatment showed that GaAs(111)A surfaces became significantly more hydrophobic following reaction with C(n)H(2n-1)MgCl (n = 1, 2, 4, 8, 14, 18). High-resolution As 3d XP spectra taken at various times during prolonged direct exposure to ambient lab air indicated that the resistance of GaAs(111)A to surface oxidation was greatly enhanced after reaction with Grignard reagents. GaAs(111)A surfaces terminated with C(18)H(37) groups were also used in Schottky heterojunctions with Hg. These heterojunctions exhibited better stability over repeated cycling than heterojunctions based on GaAs(111)A modified with C(18)H(37)S groups. Raman spectra were separately collected that suggested electronic passivation by surficial Ga-C bonds at GaAs(111)A. Specifically, GaAs(111)A surfaces reacted with alkyl Grignard reagents exhibited Raman signatures comparable to those of samples treated with 10% Na(2)S in tert-butanol. For GaN(0001), high-resolution C 1s spectra exhibited the characteristic low binding energy shoulder demonstrative of surface Ga-C bonds following reaction with CH(3)MgCl. In addition, 4

  2. Quaternary rare-earth arsenides REAg{sub 1−x}Zn{sub y}As{sub 2} (RE=La–Nd, Sm, Gd–Dy) with tetragonal SrZnBi{sub 2}- and HfCuSi{sub 2}-type structures

    Energy Technology Data Exchange (ETDEWEB)

    Ramachandran, Krishna K.; Genet, Clément; Mar, Arthur, E-mail: arthur.mar@ualberta.ca

    2015-11-15

    Reactions of the elements at 800 °C with the nominal compositions REAg{sub 1−x}Zn{sub x}As{sub 2} resulted in quaternary arsenides REAg{sub 1−x}Zn{sub y}As{sub 2} in which the combined Ag and Zn content deviates increasingly from unity in the Zn-richer phases, reflecting the transition from the fully stoichiometric ternary silver-containing arsenides REAgAs{sub 2} to the substoichiometric zinc-containing ones REZn{sub 0.67}As{sub 2}. Powder X-ray diffraction analysis indicated SrZnBi{sub 2}-type (space group I4/mmm, Z=4; RE=La, Ce) and HfCuSi{sub 2}-type structures (space group P4/nmm, Z=2; RE=Pr, Nd, Sm, Gd, Tb, Dy). Single-crystal X-ray diffraction analysis performed on LaAg{sub 0.5}Zn{sub 0.5}As{sub 2}, PrAg{sub 0.5}Zn{sub 0.5}As{sub 2}, and NdAg{sub 0.5}Zn{sub 0.5}As{sub 2} indicated that the Ag and Zn atoms are disordered within metal-centred tetrahedra and provided no evidence for distortion of the square As nets. The small electron excess tolerated in these quaternary arsenides and the absence of distortion in the square nets can be traced to the occurrence of As–As states that are only weakly antibonding near the Fermi level. PrAg{sub 0.5}Zn{sub 0.5}As{sub 2} and NdAg{sub 0.5}Zn{sub 0.5}As{sub 2} are paramagnetic with effective magnetic moments consistent with trivalent RE species. - Graphical abstract: On proceeding from fully stoichiometric REAgAs{sub 2} to substoichiometric REZn{sub 0.67}As{sub 2}, deficiencies in Zn content become increasingly prominent in quaternary arsenides REAg{sub 1−x}Zn{sub y}As{sub 2}. - Highlights: • Ag and Zn atoms are disordered within quaternary arsenides REAg{sub 1−x}Zn{sub y}As{sub 2}. • In Zn-richer phases, Zn deficiencies develop to counteract electron excess. • Distortions of square As net appear to be suppressed.

  3. A europium- and terbium-coated magnetic nanocomposite as sorbent in dispersive solid phase extraction coupled with ultra-high performance liquid chromatography for antibiotic determination in meat samples.

    Science.gov (United States)

    Castillo-García, M L; Aguilar-Caballos, M P; Gómez-Hens, A

    2015-12-18

    A new magnetic dispersive solid-phase extraction approach based on Eu- and Tb-coated magnetic nanocomposites, combined with ultra-high performance liquid chromatography with fluorometric detection, is reported for the extraction and simultaneous determination of veterinary antibiotics. The method is aimed at monitoring of potential residues of three tetracyclines, namely oxytetracycline, tetracycline, chlortetracycline and three acidic quinolones, such as oxolinic acid, nalidixic acid and flumequine, chosen as model analytes, in animal muscle samples. The nanocomposites were obtained by synthesizing magnetic nanoparticles by a co-precipitation method and their coating with terbium and europium ions. The limits of detection obtained using standard solutions were: 1.0, 1.5, 3.8, 0.25, 0.7 and 1.2ngmL(-1), which corresponds to 3.3, 5.0, 12.7, 0.8, 2.3 and 4.0μgkg(-1) for oxytetracycline, tetracycline, chlortetracycline, oxolinic acid, nalidixic acid and flumequine, respectively, in meat samples. The precision values, obtained in the presence of the sample matrix, were in the ranges 0.12-2.0% and 2.6-15.4% for retention times and areas, respectively. The selectivity of the method was checked by assaying different veterinary drugs, finding that most of them did not interfere at the same concentration levels as that of analytes. A recovery study was performed in the presence of chicken and pork muscle samples, which provided values in the range of 61.5-102.6%. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Spectroscopic analysis of lithium terbium tetrafluoride

    DEFF Research Database (Denmark)

    Christensen, H.P.

    1978-01-01

    . The rare-earth site in LiTbF4 possesses S4 symmetry, which allows six crystal-field parameters. ζ and the six Bim were varied to obtain the best agreement with the experimentally observed levels. Keeping F2=434 cm-1 fixed, a fit with a standard deviation of 12 cm-1 was obtained at 10 K with the following...... were calculated by diagonalizing an effective spin-orbit and crystal-field Hamiltonian in an LS basis. H=Σλi(L→·S→)i+ΣαiΣBimOim, where the parameters λi are functions of the spin-orbit parameter ζ and the Slater parameter F2. The Oim and αi are Racah operators and reduced matrix elements, respectively...

  5. Inelastic critical scattering of neutrons from terbium

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage; Dietrich, O.W.; Marshall, W.

    1967-01-01

    We have measured the inelasticity of the critical neutron scattering in Tb above the Néel temperature. The results show that dynamical slowing down of fluctuations does occur at a second order phase transition.......We have measured the inelasticity of the critical neutron scattering in Tb above the Néel temperature. The results show that dynamical slowing down of fluctuations does occur at a second order phase transition....

  6. Efficient injection of spin-polarized electrons from manganese arsenide contacts into aluminum gallium arsenide/gallium arsenide spin LEDs

    Science.gov (United States)

    Schweidenback, Lars

    In this thesis we describe two spectroscopic projects project on semiconductor heterostructures, as well as putting together and testing a micro-photoluminescence/7 tesla magnet system for the study of micron size two-dimensional crystals. Below we discuss the three parts in more detail. i) MnAs-based spin light emitting diodes. We have studied the injection of spin-polarized electrons from a ferromagnetic MnAs contact into an AlGaAs(n)/GaAs(i)/AlGaAs(p) n-i-p light emitting diode. We have recorder the emitted electroluminescence as function of magnetic field applied at right angles to the device plane in the 7-300 K temperature range. It was found that at 7 Kelvin the emitted light is circularly polarized with a polarization that is proportional to the MnAs contact magnetization with a saturation value of 26% for B > 1.25 tesla. The polarization persists up to room temperature with a saturation value of 6%. ii) Optical Aharonov-Bohm effect in InGaAs quantum wells. The excitonic photoluminescence intensity from InGaAs quantum wells as function of magnetic field exhibits two local maxima superimposed on a decreasing background. The maxima are attributed to the optical Aharonov-Bohm effect of electrons orbiting around a hole localized at the center of an Indium rich InGaAs islands detected by cross sectional scanning tunneling microscopy. Analysis of the position of the maxima yields a value of the electron orbit radius. iii) Micro-Photoluminescence. We have put together a micro-photoluminescence /7 tesla system for the study of two dimensional crystals. The samples are placed inside a continuous flow cryostat whose tail is positioned in the bore of the 7 tesla magnet. A microscope objective is used to focus the exciting laser light and collect the emitted photoluminescence. The system was tested by recording the photoluminescence spectra of WS2 and WSe 2 monolayers at T = 77 K.

  7. Phonon heat transport in gallium arsenide

    Indian Academy of Sciences (India)

    [7] P Erdos and S B Haley, Phys. Rev. 184, 951 (1969). [8] M G Holland, Phys. Rev. 132, 2461 (1963). [9] M G Holland, Phys. Rev. 134, A471 (1963). [10] P G Klemens, Proc. R. Soc. London A68, 1113 (1965). [11] P C Sharma, K S Dubey and G S Verma, Phys. Rev. B3, 1985 (1971). [12] M D Tiwari and Bal K Agrawal, Phys.

  8. Gallium Arsenide and Related Compounds, 1986.

    Science.gov (United States)

    1986-01-01

    Neida, S JPearton, MStavola and R Caruso 63-68 The use of selective pair luminescence to characterize semi-insulating GaAs E S Koteles, J Kafalas, S...changing the charge state iy t he neutron irradiation. 4. Summary The main acceptor in urdoped LEC SI-GaAs has been considered to be carbon. However, the...1986 Correlation between melt stoichiometry and activation efficiency in Si-implanted GaAs A. R. Von Neida, S. J. Pearton, M. Stavola, and R. Caruso AT&T

  9. Thin Crystalline Gallium Arsenide Optoelectronic Devices

    Science.gov (United States)

    Patkar, Mahesh Pandharinath

    1995-01-01

    The numerous existing and developing applications for two closely related devices, III-V light emitting diode (LEDs) and solar cells, demand improved device efficiencies. Removing the substrate should increase the efficiency of both LEDs and solar cells by eliminating the absorption losses in the substrate. We have used the phenomenon of photon recycling in thin-crystalline device geometries to enhance efficiencies of LEDs and solar cells. GaAs LEDs were fabricated and removed from the substrate by the epitaxial lift-off process. Devices with and without an underlying GaAs substrate were then characterized by optical and electrical measurements. Efficiency enhancements of up to a factor of six were achieved. By carefully analyzing the electrical and optical measurements, we demonstrate that the device operation can be explained in terms of accepted theories for radiative recombination and photon recycling which supports our hypothesis that the efficiency enhancement is due to photon recycling in the thin-crystalline device structure. Electrical and optical characterization of ELO LEDs is also shown to be a convenient diagnostic tool for examining recombination losses in thin-crystalline solar cells. Thin crystalline solar cells were fabricated and characterized by I-V and QE measurements. Alloyed ohmic contacts are used extensively for GaAs devices. However, alloyed contacts produce rough interfaces that do not make good reflectors needed for many optoelectronic devices. Non-alloyed ohmic contacts to optoelectronic devices could make good reflectors, if one uses highly reflective metal like Au to make an ohmic contact. Ex-situ non-alloyed contacts to n-GaAs were made by using low temperature molecular beam epitaxy. Ag and Ti/Au contacts to this structure exhibited specific contact resistivities of mid 10^{-7} Omega-cm^2. Low temperature molecular beam epitaxy of GaAs with high concentrations of Be followed by an anneal under As over pressure was used to minimize the fast diffusing interstitial Be concentration in p^{++}-GaAs. Non-alloyed Ti/Au ohmic contacts to such p-type GaAs exhibited specific contact resistivities of about 10^{ -7} Omega-cm^2. A new amalgamation technique was developed for mounting thin crystalline devices on a substrate different from a host substrate.

  10. Deep Impurity States in Gallium Arsenide.

    Science.gov (United States)

    1981-10-01

    the conduccion band of the host i o o t) do ,;e 𔃼 i ,’ to , V. "owtilj M-terid 1) , as a :uwhti(’ of disepQa"I C in ’~~’ ,t,’ied i nont’. ’n.1 ea:" d

  11. Effect of dislocations on gallium arsenide FETs

    Science.gov (United States)

    Barrett, D. L.; McGuigan, S.; Eldridge, G. W.; Swanson, B. W.; Thomas, R. N.

    1985-02-01

    Indium doping at 5 x 10 to the 19th power/cc was found to be optimum for the growth of low-dislocation GaAs crystals, and to avoid constitutional supercooling effects. Dislocation etch pit densities of near 200/cc were measured in the central region of In-doped crystals, increasing to above 1000/sq cm in the peripheral regions. Based on the concept that dislocations are generated to relieve excess thermoelastic stress, a preliminary thermal model was used to design a hot zone shield to reduce thermal gradients during growth. An optimum combination of indium-doping, reduced thermal gradient growth, and appropriate growth parameters are expected to yield completely dislocation-free GaAs crystals. A FET metrology mask has been fabricated and preliminary FET device Fabrication begun, for evaluation of the effects of dislocations on FET device parameters. Twenty state-of-the-art, low dislocation, indium-doped GaAs wafers were delivered to the contractor for DARPA-related program evaluation.

  12. Uso do laser arseneto de gálio (904nm após excisão artroplástica da cabeça do fêmur em cães Use of low-power gallium arsenide laser (904nm after arthroplasty excision of the femoral head in dogs

    Directory of Open Access Journals (Sweden)

    Julia Maria Matera

    2003-03-01

    Full Text Available OBJETIVO: Avaliar a ação do laser diodo Arseneto de Gálio na evolução pós-operatória de cães submetidos à excisão artroplástica da cabeça e colo do fêmur. MÉTODOS: Treze cães portadores de Legg-Calvé-Perthes Disease ou Necrose Asséptica da Cabeça do Fêmur (NACF foram divididos em dois grupos: (I sete cães que não foram irradiados - grupo controle; (II seis cães irradiados uma vez ao dia durante cinco dias consecutivos com o laser Arseneto de Gálio (904nm, densidade de energia 4J/cm2 e tempo de exposição automaticamente ajustado pelo aparelho. Para a avaliação da evolução pós-operatória preencheu-se protocolo com graduação da dor de apoio do membro operado. Utilizou-se teste estatístico não paramétrico U de Mann-Whitney para análise dos resultados. RESULTADOS: O grupo I iniciou o apoio do membro com uma média de 12 dias de pós-operatório e o grupo II com uma média de quatro dias de pós-operatório, sendo estatisticamente significante (p=0.0012. CONCLUSÃO: A irradiação com o laser de baixa potência Arseneto de Gálio (904nm na dose 4J/cm2, periarticular, promoveu rápido retorno da função do membro em cães após a excisão artroplástica da cabeça do fêmur, otimizando a recuperação pós-operatória.PURPOSE: Evaluate the action of the Gallium Arsenide semiconductor laser in the post-operative evolution in dogs after the femoral head and neck artroplastic excision. METHODS: Thirteen dogs bearing Legg-Calvé-Perthes Disease were divided into two groups: (I 7 non-radiated dogs - control group; (II 6 dogs irradiated once a day for 5 consecutive days with the Galium Arsenide laser (904nm, energy density 4J/cm² and exposition time automatically adjusted by the device. In order to evaluate the post-operative evolution it was needed to fill a report stating the degree of the pain as well as the weight bearing of the affected limb. A U non-parametric statistics test of Mann-Whitney was used to perform

  13. Studies of electron traps in gallium arsenide and gallium arsenide phosphide by deep level transient spectroscopy

    Science.gov (United States)

    Day, D. Y. S.

    1980-03-01

    System effects and data analysis for deep level transient spectroscopy (DLTS) have been examined and applied to study the deel levels in the GaAs-GaP system. Studies of typical DLTS systems using either the lock-in amplifier or the dual-channel boxcar averager are presented. The effects of non-zero gate width for the boxcar averager, phase angle adjustment for the lock-in amplifier, and response time of a typical commercial capacitance meter are investigated. Errors introduced in the measurements by these effects are calculated for typical cases. Measurements of gold level in silicon are presented, along with calculated corrections. We find the correction to be minimal in the boxcar-averager method, but significant in the lock-in amplifier approach. A DLTS system is described for measuring deep levels in diodes exhibiting large leakage currents. A capacitance bridge is used employing the diode to be tested along with a dummy diode of similar characteristics. The DLTS spectrum of a leaky GaAs planar diode is measured and compared to experimental results obtained with two standard DLTS systems . It is shown that measurements with the standard systems are impossible in certain temperature ranges because of overloading problems. The approach described here, however, gives the DLTS spectrum between 77 K and 300 K.

  14. Characterizing and engineering tunable spin functionality inside indium arsenide/gallium arsenide quantum dot molecules

    Science.gov (United States)

    Liu, Weiwen

    The continual downsizing of the basic functional units used in the electronics industry has motivated the study of the quantum computation and related topics. To overcome the limitations of classical physics and engineering, some unique quantum mechanical features, especially entanglement and superpositions have begun to be considered as important properties for future bits. Including these quantum mechanical features is attractive because the ability to utilize quantum mechanics can dramatically enhance computational power. Among the various ways of constructing the basic building blocks for quantum computation, we are particularly interested in using spins inside epitaxially grown InAs/GaAs quantum dot molecules as quantum bits (qubits). The ability to design and engineer nanostructures with tailored quantum properties is critical to engineering quantum computers and other novel electro-optical devices and is one of the key challenges for scaling up new ideas for device application. In this thesis, we will focus on how the structure and composition of quantum dot molecules can be used to control spin properties and charge interactions. Tunable spin and charge properties can enable new, more scalable, methods of initializing and manipulating quantum information. In this thesis, we demonstrate one method to enable electric-field tunability of Zeeman splitting for a single electron spin inside a quantum dot molecules by using heterostructure engineering techniques to modify the barrier that separates quantum dots. We describe how these structural changes to the quantum dot molecules also change charge interactions and propose ways to use this effect to enable accurate measurement of coulomb interactions and possibly charge occupancy inside these complicated quantum dot molecules.

  15. Experimental Studies of Lateral Electron Transport in Gallium Arsenide-Aluminum Gallium Arsenide Heterostructures.

    Science.gov (United States)

    1982-12-01

    34A new field-effect transistor with selectively doped GaAs/n-Al xGa As teoucin. u. L. A2I. EhM ., vol. 19, pp. L225-L227, 190 h 12. D. Delagebeaudeuf, P...photoconductivity in thin epitaxial GaAs," 1. Anl. EhMs ., vol. 52, pp. 5718-5721, 1981. 129. K. Hess and N. Holonyak, Jr., "Hot electrons in layered

  16. Electroluminescence Studies on Longwavelength Indium Arsenide Quantum Dot Microcavities Grown on Gallium Arsenide

    Science.gov (United States)

    2011-12-01

    committee members, Dr. Bill Siskaninetz, Dr. Ronald Coutu, and Dr. Michael Marciniak for their assistance and the extraordinary amount of patience...6 2.2. (a) Structure of a through DBR contacted VCSEL and ( b ) an...DBR mirror and a ( b ) bottom DBR mirror ......8 2.4. Calculated power reflectance, transmittance, and absorptance of a DBR

  17. Clinical evaluation of dentin hypersensitivity treatment with the low intensity Gallium-Aluminum-Arsenide laser - AsGaAl Avaliação clínica do tratamento da hiperestesia dentinária com laser de baixa potência de Arseniato de Gálio-Alumínio - AsGaAl

    Directory of Open Access Journals (Sweden)

    Luciana Chucre Gentile

    2004-12-01

    Full Text Available The dentin hypersensitivity is a painful condition rather prevalent in the general population. There are several ways of treatment for such condition, including the low intensity lasers. The proposal of this study was to verify the effectiveness of the Gallium-Aluminum-Arsenide diode laser in the treatment of this painful condition, using a placebo as control. MATERIALS AND METHODS: Thirty-two patients were selected, 22 females and 10 males, with ages ranging from 20 to 52 years old. The 32 patients were randomly distributed into two groups, treated and control; the sample consisted of 68 teeth, 35 in the treated group and 33 in the control group. The treated group was exposed to six laser applications with intervals from 48 to 72 hours, and the control group received, as placebo, applications of a curing light. RESULTS: A significant reduction was observed in the pain condition between the initial phase and after six laser applications; however, such reduction could also be observed for the control group exposed to the placebo. CONCLUSION: Therapy with the low intensity Gallium-Aluminum-Arsenide laser - AsGaAl induces a statistically significant reduction in the painful condition after each application and between the beginning and end of treatment, although there was no statistically significant difference between the treated group (laser and the control group (placebo at the end of treatment and after the mediate evaluation results (after 6 weeks, this way impairing the real measurement of laser effectiveness and placebo effect.A hiperestesia dentinária trata-se de uma condição dolorosa bastante prevalente nas populações mundiais. Várias são as modalidades de tratamento para tal condição, entre elas, os lasers de baixa potência. A proposta deste estudo foi a de verificar a efetividade do laser de diodo de Arseniato de Gálio-Alumínio no tratamento desta condição dolorosa, utilizando-se um placebo como controle. MATERIAIS E M

  18. Inelastic scattering of neutrons by spin waves in terbium

    DEFF Research Database (Denmark)

    Bjerrum Møller, Hans; Houmann, Jens Christian Gylden

    1966-01-01

    Measurements of spin-wave dispersion relations for magnons propagating in symmetry directions in ferromagnetic Tb; it is first experiment to give detailed information on magnetic excitations in heavy rare earths; Tb was chosen for these measurements because it is one of few rare-earth metals whic...... does not have very high thermal-neutron capture cross section, so that inelastic neutron scattering experiments can give satisfactory information on magnon dispersion relations....

  19. Coherent magnetic structures in terbium/holmium superlattices

    DEFF Research Database (Denmark)

    Bryn-Jacobsen, C.; Cowley, R.A.; McMorrow, D.F.

    1997-01-01

    Neutron-scattering techniques have been used to investigate the magnetic properties of three Tb/Ho superlattices grown by molecular-beam epitaxy. It is revealed that for temperatures in the range T = 10 to T-N(Ho)approximate to 130 K, there is a basal-plane ferromagnetic alignment of Tb moments w...

  20. Photoluminescence Study of Ion Implantation Damage in Gallium Arsenide.

    Science.gov (United States)

    1981-12-01

    The completion of this thesis was a very gratifying and educational experience. It provided valuable exposure to topics which were heretofore...Engjineering, Air Force, Institute of Technology, December 1978. 21. Yu , P. W . and Y’. S. Park. "PhoLel uminlescence in M11- implmnted GaiAs --anm...1946 in Caracas, Venezuela, the son of Edward and Margaret Key. Ile received his high school education at Riverside Military Academy in Gainesville

  1. Noise-margin limitations on gallium-arsenide VLSI

    Science.gov (United States)

    Long, Stephen I.; Sundaram, Mani

    1988-01-01

    Two factors which limit the complexity of GaAs MESFET VLSI circuits are considered. Power dissipation sets an upper complexity limit for a given logic circuit implementation and thermal design. Uniformity of device characteristics and the circuit configuration determines the electrical functional yield. Projection of VLSI complexity based on these factors indicates that logic chips of 15,000 gates are feasible with the most promising static circuits if a maximum power dissipation of 5 W per chip is assumed. While lower power per gate and therefore more gates per chip can be obtained by using a popular E/D FET circuit, yields are shown to be small when practical device parameter tolerances are applied. Further improvements in materials, devices, and circuits wil be needed to extend circuit complexity to the range currently dominated by silicon.

  2. Measurement of the thermopower anisotropy in iron arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, T., E-mail: fujii@crc.u-tokyo.ac.jp [Cryogenic Research Center, the University of Tokyo, 2-11-16 Yayoi, Bunkyo, Tokyo 113-0032 (Japan); Shirachi, T. [Department of Applied Physics, the University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Asamitsu, A. [Cryogenic Research Center, the University of Tokyo, 2-11-16 Yayoi, Bunkyo, Tokyo 113-0032 (Japan); Department of Applied Physics, the University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Ashikaga Institute of Technology, 268-1 Omae, Ashikaga, Tochigi 326-8558 (Japan)

    2016-11-15

    Highlights: • In this study, in order to investigate the origin of the in-plane anisotropy, the in-plane anisotropy of the thermopower was measured for the detwined single crystals of BFe{sub 2}As{sub 2}. And, we found no anisotropy in the thermopower above T{sub AFO}, although there is a large anisotropy in the resistivity. This result gives evidence that the anisotropy in the resistivity arise from the anisotropy of the scattering time, and the energy dependence of the scattering time can be considered negligible. In the case of iron pnictides, the proposed orbital ordering more likely results in an anisotropy of electronic structure below T{sub AFO}, whereas the spin-nematic ordering leads to an anisotropy of electron scattering above T{sub AFO}. Therefore, our results suggest that nematicity above T{sub AFO} results from anisotropic magnetic scattering. - Abstract: We investigated the in-plane anisotropy of the thermopower and electrical resistivity on detwinned single crystals of BaFe{sub 2}As{sub 2}. The in-plane anisotropy of the resistivity was clearly observed far above the magnetostructural transition temperature T{sub AFO}. While, the thermopower showed the in-plane anisotropy only below T{sub AFO}. These results are associated with the different origin of the anisotropy above and below T{sub AFO}. Since the thermopower does not depend on the scattering time, the anisotropy of the resistivity above T{sub AFO} is considered to be due to the anisotropic scattering. On the other hand, the anisotropy in the thermopower below T{sub AFO} is ascribed to the reconstructed Fermi surface.

  3. Radiation annealing of gallium arsenide implanted with sulphur

    CERN Document Server

    Ardyshev, V M

    2002-01-01

    Sulfur ions were implanted in a semi-insulating GaAs. Photon annealing (805 deg C/(10-12) s) and the thermal one (800 deg C/30 min) were conducted under SiO sub 2 -films coating obtained by different ways. Contents of GaAs components in films were determined from Rutherford backscattering spectra; concentration profiles of electrons were measured by the voltage-capacitance method. Diffusion of sulfur was shown to go in two directions - to the surface and into bulk of GaAs. The first process was induced by vacancies that had been formed near the surface of semiconductors during the dielectric coating. The coefficient of the bulk-diffusion and diffusion-to-surface of sulfur ions under photon annealing was twice as much as that under thermal one. The doping efficiency was also larger

  4. Epitaxial metal-gallium arsenide contacts via electrodeposition

    Science.gov (United States)

    Bao, Zhi Liang

    The fabrication of epitaxial metal-GaAs contacts via electrodeposition and the electrical properties of the Schottky diodes are reported in this dissertation. Epitaxial electrodeposition of copper, iron, cobalt, iron-nickel, and bismuth on GaAs was discovered to rely on three major factors: the preparation of the GaAs surface by (NH4)OH etching, the addition of (NH 4)2SO4 to the electrolytes, and the control of deposition current density. The surface preparation by (NH4)OH provides a hydrophilic surface likely due to passivation via a layer of hydroxide bonds. Ammonium sulphate inhibits oxidation of the metal cations and likely acts as a surfactant both on the metal and GaAs surfaces. Control of adatom flux, similar to vacuum deposition techniques such as molecular beam epitaxy, determined the crystallinity, varying from polycrystalline to epitaxial to dendritic for current densities from 0.01 to 1 mA/mm2. The effects of other electrodeposition conditions including pH and electrolyte temperature were also investigated. Neutral electrolytes are needed for copper, iron, nickel-iron alloy, and cobalt epitaxial deposition, while acidic solution works for bismuth deposition indicating that the control of hydrogen evolution may be important. Cobalt nanodisc formation was obtained for lower temperatures (2 - 22°C) while optimal copper, iron, and bismuth epitaxy required higher deposition temperatures, 53, 56, and 70°C, respectively. The growth is via island nucleation and coalescence. The iron films develop a small decrease in lattice constant with residual compressive stress, which is a function of temperature. This is likely due to an impurity such as oxygen. Copper and cobalt formed nanometer scale reacted interfaces with GaAs, while iron and bismuth/GaAs formed abrupt interfaces. The electrical properties of these Schottky diodes were, nevertheless, found to be close to ideal and comparable to vacuum deposited diodes. Fe and Co/GaAs diodes showed identical electrical properties for GaAs (100), (110) and (111)B substrate orientations, consistent with uniform and defect-free interfaces. Cu and Bi/GaAs showed a much greater orientational dependence perhaps due to the larger lattice mismatch. Iron and nickel-iron alloy films showed anisotropic magnetic properties consistent with single crystalline material. These metal/GaAs contacts are potentially interesting for spintronics applications. Keywords. electrodeposition; epitaxy; metal-GaAs; Spintronics; (NH4)2SO4

  5. The effects of radiation on gallium arsenide radiation detectors

    CERN Document Server

    Bates, R L; D'Auria, S D; O'Shea, V; Raine, C; Smith, K M

    1997-01-01

    Semi-insulating, undoped, Liquid Encapsulated Czochralski (SI-U LEC) GaAs detectors have been irradiated with 1MeV neutrons, 24GeV/c protons, and 300MeV/c pions. The maximum fluences used were 6, 3, and 1.8~10$^{14}$ particles/cm$^{2}$ respectively. For all three types of irradiation the charge collection efficiencies (cce) of the detector are reduced due to the reduction in the electron and hole mean free paths. Pion and proton irradiations produce a greater reduction in cce than neutron irradiation with the pions having the greatest effect. The effect of annealing the detectors at room temperature, at 200$^{o}$C and at 450$^{o}$C with a flash lamp have been shown to reduce the leakage current and increase the cce of the irradiated detectors. The flash-lamp anneal produced the greatest increase in the cce from 26% to 70% by increasing the mean free path of the electrons. Two indium-doped samples were irradiated with 24GeV/c protons and demonstrated no improvement over SI U GaAs with respect to post-irradiati...

  6. Gallium Arsenide Pilot Line for High Performance Components

    Science.gov (United States)

    1992-05-28

    generally accepted values and/or the values in the center of the reported ranges.) Table 6 gives expected lifetimes for aluminum at 2.0 x 05 Acn - 2 (the...iew This sijxe g"v& an~~I ehbrodance W-lo (e* aw powd Oft" ad 41111ago She dwo bwmodswo u64nd Gmma s Linds U SP~aRAPTow 1~bm30 𔃻 BYA PI ol

  7. Gallium arsenide based surface plasmon resonance for glucose monitoring

    Science.gov (United States)

    Patil, Harshada; Sane, Vani; Sriram, G.; Indumathi, T. S; Sharan, Preeta

    2015-07-01

    The recent trends in the semiconductor and microwave industries has enabled the development of scalable microfabrication technology which produces a superior set of performance as against its counterparts. Surface Plasmon Resonance (SPR) based biosensors are a special class of optical sensors that become affected by electromagnetic waves. It is found that bio-molecular recognition element immobilized on the SPR sensor surface layer reveals a characteristic interaction with various sample solutions during the passage of light. The present work revolves around developing painless glucose monitoring systems using fluids containing glucose like saliva, urine, sweat or tears instead of blood samples. Non-invasive glucose monitoring has long been simulated using label free detection mechanisms and the same concept is adapted. In label-free detection, target molecules are not labeled or altered, and are detected in their natural forms. Label-free detection mechanisms involves the measurement of refractive index (RI) change induced by molecular interactions. These interactions relates the sample concentration or surface density, instead of total sample mass. After simulation it has been observed that the result obtained is highly accurate and sensitive. The structure used here is SPR sensor based on channel waveguide. The tools used for simulation are RSOFT FULLWAVE, MEEP and MATLAB etc.

  8. Subthreshold Laser Radiation of Rhesus Monkey Retina. Gallium Arsenide Bioeffects.

    Science.gov (United States)

    1982-08-01

    hrs but they could find no histologic or fluorescein leakage correlate. If comparable at all to this study, then t" the appearance of the pale PE cells... ANATOMY 9 BORWdEIN AUG 82 UNCLASSIFIEDi DAMDi7-81-6-9489 F/6 6/18 N U EUEEECEE .. . .... -.!-4 . -- - - 111 L4.0 L2 .m1208 JfJ .11111 .45 111.6...Development Command Fort Detrick, Frederick, Maryland 21701-5012 .Grant No. DAD17-81-G-9489D, o.°,,o.DTIC .’ Department of Anatomy IELECTEr’ The University

  9. Structural and optical properties of porous gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Belogorokhov, A.I. [Institute of Rare Metals, 119017 Moscow (Russian Federation); Gavrilov, S.A. [Moscow Institute of Electronic Technology (Technical University), 103498 Moscow (Russian Federation); Belogorokhov, I.A. [Physics Department, M.V. Lomonosov Moscow State University, 119899 Moscow (Russian Federation)

    2005-06-01

    The optical and structural properties of a porous GaAs have been studied. The samples a of porous GaAs were fabricated by an electrochemical method on n- and p-type GaAs(100). The GaAs wafer doping type considerably affects nanocrystal shape, nanocrystal average diameter and chemical surface states. Low-frequency Raman shift of the peaks, conditioned by the main optical phonons, in the Raman spectra of the porous GaAs was observed. The values of the frequencies of surface phonons obtained from the Raman spectra and Infrared reflectivity spectra well coincide. Comparing the reflectivity spectra of porous GaAs with the ones of the single crystal GaAs, the changes in the spectral dependencies of the reflectance within the phonon resonance region may be seen which coincide with appearance of additional oscillators caused by sized confinement of the lattice vibrations of GaAs nanocrystals. The surface morphology of porous GaAs prepared on the substrate of n-type GaAs has been studied using atomic-force microscopy. Nanosized contour of the porous GaAs surface was watched. Estimations of the size of nanocrystals in a porous GaAs by the Raman and Infrared spectroscopy, photoluminescence (PL) and atomic-force microscopy well agree with each other. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. High Efficiency Solar Panel. Phase II. Gallium Arsenide.

    Science.gov (United States)

    1981-03-01

    distance apartare lowered onto an interconnect/cell assembly with a calibrated force. Activation of an electrical switch introduces a voltage and current...the working area of the parallel gap Aelder is shown in Figure 8. Here two electrodes, a set distance apartare lowered onto an interconnect/cell

  11. Gallium Arsenide Pilot Line for High Performance Components

    Science.gov (United States)

    1988-06-02

    a self - consistent solution of the coupled, nonlinear Poisson - Schrodinger equations for the SARGIC HFET heterostructures.) These models were used in...will be functional at 200 MHz. This expectation is based on the consistency of the measured and simulated results obtained at AT&T-Reading, AT&T...CAD tools. The layout floorplan consists of 33 blocks. These blocks were carefully arranged to butt next to each other without using routing channels

  12. a 9-BIT, Pipelined Gallium Arsenide Analog-Digital Converter

    Science.gov (United States)

    Breevoort, Cornelius Marius

    1992-01-01

    Excellent Short Take-Off and Landing (STOL) performance is achieved by Upper Surface Blowing (USB) aircraft as a result of mounting high by-pass turbofan engines over the forward part of the wing. High lift levels are generated by directing the engine exhaust over the wing upper surface to entrain additional airflow and by using the Coanda effect to turn the exhaust flow downward over a large radius "Coanda" flap. Commercial application of USB technology could reduce airport congestion and community noise if future configurations can be designed with economically acceptable cruise drag levels. An experimental investigation of the high speed aerodynamics of USB aircraft configurations has been conducted to accurately define the magnitude and causes of the powered configuration cruise drag. A highly instrumented wind tunnel model of a realistic USB configuration has been used which permitted parametric variations in the number and spanwise location of the nacelles and accurately modeled the engine power effects with turbofan propulsion simulators. The measured force data provides an accurate definition of the cruise drag penalty associated with each configuration and the constructed pressure contour plots provide detailed insight into their causes. It was found that the high speed aerodynamics of USB configurations is a complex interaction of jet induced and wing transonic flowfields. The presence of the nacelles on the wing upper surface created a severe drag penalty which increased with freestream Mach number, power setting and angle of attack. The more widely spaced two nacelle configurations exhibited improved flowfields at moderate Mach numbers but suffered from drag levels comparable to the baseline configuration for high speed cruise conditions. At high Mach numbers and power settings, all of the tested configurations displayed strong shocks and separated zones in the wing/nacelle junction regions. Detailed discussions of the causes of the cruise drag penalty and recommended future design improvements are presented.

  13. Gallium Arsenide Field Effect Transistors with Semi-Insulated Gates.

    Science.gov (United States)

    1977-09-01

    insulating substrate. Ohmic source and drain contacts of width Z are placed as shown. Between them is a Schottky barrier “gate” of l ength ~,. In norma ...in this manner is given in Figure 22. FETs were fabricated from this material using two different procedures. Both are essential l y the norma l...Forward, and H. L. Hartnagel , App l . Phys. Lett. 26, 569 (1975). 3. a. R. Pr un iaux , J. C. North , and A. V. Payer, IEEE Trans. Electron Devices ED

  14. Spin dynamics of equilibrium electrons in gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Georg Martin

    2010-12-08

    In this dissertation, spin noise spectroscopy is applied to study spin dynamics in GaAs based semiconductor structures close to thermal equilibrium. Semiconductor spin noise spectroscopy measures the stochastic spin polarization of the electron ensemble via off-resonant Faraday rotation. Correspondingly, no energy has to be deposited in the sample system contrary to other experimental techniques, in which the dephasing or the depolarization of an artificially injected spin polarization is measured. Since the spin fluctuations are measured in real-time, spin noise spectroscopy had been hitherto limited to frequencies below 1 GHz. This thesis introduces the experimental advancement of ultrafast spin noise spectroscopy, in which the fluctuations are probed by pulsed light, and detection of spin noise at frequencies up to 16 GHz is demonstrated. These frequencies exceed the bandwidth of the photoreceiver by a factor of around 200. To further explore the limitations of the finite bandwidth of the detection system, electrical frequency mixing is applied for down-conversion of the electrical spin noise signal. Furthermore, spin noise measurements are simulated revealing that also ultrafast digitizers with low resolution can be utilized for spectral analysis in spin noise spectroscopy without any significant loss of sensitivity. The spin dynamics in a symmetrically grown, modulation-doped, (110)-oriented GaAs/AlGaAs multiple quantum well structure are investigated in this work. This experiment represents the first spin noise measurements on a semiconductor system of reduced effective dimensionality. The Dyakonov-Perel mechanism that usually dominates spin dephasing of free electrons in GaAs is ineffective in (110)-oriented structures for spins along the growth direction. Nevertheless, the correspondingly anticipated long spin dephasing times in (110) GaAs/AlGaAs quantum wells at low temperatures are not accessible with conventional experiments that rely on optical spin orientation since the photocreation of holes obviates the observed spin dephasing times due to the Bir-Aronov-Pikus mechanism. Spin noise spectroscopy however enables measurements in the absence of optically created holes and the measured spin dephasing times in this work represent the longest reported spin dephasing times for delocalized electrons in GaAs quantum wells. Additionally, the anisotropic spin dynamics, which result from the Dyakonov-Perel mechanism that is still effective for the spins in the quantum well plane, as well as the time-of-flight broadening of the spin noise spectra, which originates from the finite transit time of the electrons through the probe volume, are experimentally investigated. The experimental technique of ultrafast spin noise spectroscopy enables investigation of spin dynamics in n-type bulk GaAs at high magnetic fields. The examined samples have a doping concentration slightly below and above the metal-to-insulator transition. The temperature, doping and magnetic field dependence of the effective electron Lande factor is studied as well as the spin dephasing in a transverse magnetic field. Finally, semiconductor spin noise spectroscopy is carried out with a magnetic field oriented with an arbitrary angle to the direction of light propagation while usually the magnetic field is applied transverse to the light wavevector. This novel geometry for spin noise spectroscopy allows the investigation of spin dephasing and spin relaxation in a single measurement. (orig.)

  15. Threshold extension of gallium arsenide/aluminum(x) gallium(1-x) arsenide terahertz detectors and switching in heterostructures

    Science.gov (United States)

    Rinzan, Mohamed B.

    In this work, homojunction interfacial workfunction internal photoemission (HIWIP) detectors based on GaAs, and heterojunction interfacial workfunction internal photoemission (HEIWIP) detectors based mainly on the GaAs/Al xGa1-xAs material system are presented. Design principles of HIWIP and HEIWIP detectors, such as free carrier absorption, photocarrier generation, photoemission, and responsivity, are discussed in detail. Results of p-type HIWIPs based on GaAs material are presented. Homojunction detectors based on p-type GaAs were found to limit their operating wavelength range. This is mainly due to band depletion arising through carrier transitions from the heavy/light hole bands to the split off band. Designing n-type GaAs HIWIP detectors is difficult as it is strenuous to control their workfunction. Heterojunction detectors based on GaAs/AlxGa 1-xAs material system will allow tuning their threshold wavelength by adjusting the alloy composition of the Al xGa1-xAs barrier, while keeping a fixed doping density in the emitter. The detectors covered in this work operate from 1 to 128 microm (300 to 2.3 THz). Enhancement of detector response using resonance cavity architecture is demonstrated. Threshold wavelength extension of HEIWIPs by varying the Al composition of the barrier was investigated. The threshold limit of ˜ 3.3 THz (92 microm), due to a practical Al fraction limit of ˜ 0.005, can be overcome by replacing GaAs emitters in GaAs/AlxGa1-xAs HEIWIPs with AlxGa1-xAs emitters. As the initial step, terahertz absorption for 1 microm-thick Be-doped AlxGa1-xAs epilayers (with different Al fraction and doping density) grown on GaAs substrates was measured. The absorption probability of the epilayers was derived from these absorption measurements. Based on the terahertz absorption results, an AlxGa1-xAs/GaAs HEIWIP detector was designed and the extension of threshold frequency ( f0) to 2.3 THz was successfully demonstrated. In a different study, switching in GaAs/AlxGa1- xAs heterostructures from a tunneling dominated low conductance branch to a thermal emission dominated high conductance branch was investigated. This bistability leads to neuron-like voltage pulses observed in some heterostructure devices. The bias field that initiates the switching was determined from an iterative method that uses feedback information, such as carrier drift velocity and electron temperature, from hot carrier transport. The bias voltage needed to switch the device was found to decrease with the increasing device temperature.

  16. Doped Aluminum Gallium Arsenide (AlGaAs)/Gallium Arsenide (GaAs) Photoconductive Semiconductor Switch (PCSS) Fabrication

    Science.gov (United States)

    2016-09-27

    test devices without anti- reflection (AR) protection caps but now serve as duplicate devices to combat fabrication yield issues. The columns of...step. 2. Methods, Assumptions, and Procedures 2.1 Alignment Marks Due to the negligible effect the n-type dopant annealing has on the surface of the...A-1 of the Appendix, photoresist makes an adequate mask for this short plasma etch. The etch is a simple boron trichloride (BCl3) and argon (Ar

  17. Efeito da terapia com laser de arsenieto de gálio e alumínio (660Nm sobre a recuperação do nervo ciático de ratos após lesão por neurotmese seguida de anastomose epineural: análise funcional Effect of gallium-aluminum-arsenide laser therapy (660Nm on recovery of the sciatic nerve in rats following neurotmesis lesion and epineural anastomosis: functional analysis

    Directory of Open Access Journals (Sweden)

    FA Reis

    2008-06-01

    Full Text Available CONTEXTUALIZAÇÃO: As lesões nervosas periféricas podem comprometer atividades diárias de um indivíduo e resultam em perda da sensibilidade e motricidade do território inervado. OBJETIVO: Com o intuito de acelerar os processos regenerativos, objetivou-se analisar a influência da aplicação do laser de arsenieto de gálio e alumínio (AsGaAl, 660Nm sobre a recuperação funcional do nervo ciático de ratos. MATERIAIS E MÉTODOS: O nervo ciático de 12 ratos Wistar foi submetido à lesão por neurotmese e anastomose epineural e divididos em dois grupos: controle e laserterapia. Após a lesão, utilizou-se o laser de GaAlAs, 660Nm, 4J/cm², 26,3mW, feixe de 0,63cm², em três pontos eqüidistantes sobre a lesão, por 20 dias. As impressões das pegadas dos animais foram obtidas antes e após (sete, 14 e 21 dias pós-operatórios o procedimento cirúrgico e calculou-se o índice funcional do ciático (IFC. RESULTADOS: A comparação do IFC não resultou em diferença significante (p>0,05 entre os grupos. CONCLUSÕES: Conclui-se que os parâmetros e métodos empregados na laserterapia demonstram resultados nulos sobre o IFC no período avaliado.CONTEXT: Peripheral nerve injuries result in sensory and motor losses in the innervated area and can hinder individuals’ daily activities. Objective: The objective was to analyze the influence of applying gallium-aluminum-arsenide (GaAlAs laser (660Nm on the functional recovery of the sciatic nerve in rats. METHODS: The sciatic nerve of 12 Wistar rats was subjected to injury consisting of neurotmesis and epineural anastomosis. The rats were divided into two groups: control and laser therapy. After the injury, a GaAlAs laser was used (660Nm, 4J/cm², 26.3mW and 0.63cm² beam at three equidistant points on the injury, for 20 days. Footprint impressions were obtained from the animals before and seven, 14 and 21 days after the surgical procedure and the sciatic functional index (SFI was calculated

  18. Multiband Gutzwiller theory of the band magnetism of LaO iron arsenide; Multiband Gutzwiller-Theorie des Bandmagnetismus von LaO-Eisen-Arsenid

    Energy Technology Data Exchange (ETDEWEB)

    Schickling, Tobias

    2012-02-23

    In this work we apply the Gutzwiller theory for various models for LaOFeAs. It was discovered in 2008 that doped LaOFeAs is superconducting below a temperature of T{sub c} = 28 K. Soon after that discovery, more iron based materials were found which have an atomic structure that is similar to the one of LaOFeAs and which are also superconducting. These materials form the class of iron-based superconductors. Many properties of this material class are in astonishing agreement with the properties of the cuprates. Therefore, studying this new material may promote our understanding of high-T{sub c} superconductivity. Despite great efforts, however, Density Functional Theory calculations cannot reproduce the small magnetic moment in the ground state of undoped LaOFeAs. Such calculations overestimate the magnetic moment by a factor 2-3. Within our Gutzwiller approach, we take additional local Coulomb correlations into account. We show that it is necessary to work with the iron 3d-orbitals and the arsenic 4p-orbitals to obtain a realistic description of LaOFeAs. For a broad parameter regime of the electronic interactions, we find a magnetic moment that is in the region of the experimentally observed values. We claim that the magnetic phase in LaOFeAs can be described as a spin-density wave of Landau-Gutzwiller quasi-particles.

  19. Bragg Reflector-Induced Increased Nonradiative Lifetime in Gallium Arsenide (GaAs)/Aluminum Gallium Arsenide (AlGaAs) Double Heterostructures

    Science.gov (United States)

    2015-09-01

    ORGANIZATION NAME(S) AND ADDRESS(ES) US Army Research Laboratory ATTN: RDRL-SED-E 2800 Powder Mill Road Adelphi, MD 20783-1138 8. PERFORMING...solar cell uses a GaAs/AlGaAs DH with a roughly 1–2 µm GaAs active region on top of an internal distributed Bragg reflector (BR) to take advantage of...to minimize the laser scattering signal, with a fast 300-µm diameter silicon (Si) photodiode. Data were acquired on a PCI averager card. The system

  20. Design of Indium Arsenide nanowire sensors for pH and biological sensing and low temperature transport through p-doped Indium Arsenide nanowires

    DEFF Research Database (Denmark)

    Upadhyay, Shivendra

    the fabrication of nanowire transistors using UV and electron beam lithography as well as the steps to encapsulate the nanowire transistors into a sensor. Several iterations of experiments demonstrating pH sensitivity of the NW sensor are presented. Having established and tested a stable sensing platform via p......H sensing, we apply the same to a more complex system - proteins. The sensing protocol involves the functionalization of the sensor surface with a receptor protein followed by the addition of the protein of interest. Sensor response to oppositely charged proteins is used to confirm the sensitivity...... of the sensor to the protein charge....

  1. Photoluminescence studies of a Terbium(III) complex as a fluorescent probe for DNA detection

    Energy Technology Data Exchange (ETDEWEB)

    Khorasani-Motlagh, Mozhgan, E-mail: mkhorasani@chem.usb.ac.ir; Noroozifar, Meissam; Niroomand, Sona; Moodi, Asieh

    2013-11-15

    The photoluminescence properties of a Tb(III) complex of the form [Tb(phen){sub 2}Cl{sub 3}·OH{sub 2}] (phen=1,10-phenanthroline) in different solvents are presented. It shows the characteristic luminescence of the corresponding Ln{sup 3+} ion in the visible region. The emission intensity of this complex in coordinating solvent is higher than non-coordinating one. The suggested mechanism for the energy transfer between the ligand and Tb{sup 3+} ion is the intramolecular energy transfer mechanism. The interactions of the Tb(III) complex with fish salmon DNA are studied by fluorescence spectroscopy, circular dichroism study and viscosity measurements. The results of fluorescence titration reveal that DNA strongly quenches the intrinsic fluorescence of the complex through a static quenching procedure. The binding constant (K{sub b}) of the above metal complex at 25 °C is determined by the fluorescence titration method and it is found to be (8.06±0.01)×10{sup 3} M{sup −1}. The thermodynamic parameters (ΔH{sup 0}>0, ΔS{sup 0}>0 and ΔG{sup 0}<0) indicate that the hydrophobic interactions play a major role in DNA–Tb complex association. The results support the claim that the title complex bonds to FS-DNA by a groove mode. -- Highlights: • Photoluminescence of [Tb(phen){sub 2}Cl{sub 3}·OH{sub 2}] in different solvents are studied. • Tb(III) complex shows good binding affinity to FS DNA with K{sub b}=(8.06±0.01)×10{sup 3} M{sup −1}. • Viscosity of DNA almost unchanged by increasing amount of Tb complex. • CD spectrum of DNA has a little change with increasing amount of Tb complex. • Thermodynamic parameters indicate that the binding reaction is entropically driven.

  2. Lanthanides in Nuclear Medicine. The Production of Terbium-149 by Heavy Ion Beams

    CERN Document Server

    Dmitriev, S N; Zaitseva, N G; Maslov, O D; Molokanova, L G; Starodub, G Ya; Shishkin, S V; Shishkina, T V

    2001-01-01

    Among radioactive isotopes of lanthanide series elements, finding the increasing using in nuclear medicine, alpha-emitter {149}Tb (T_{1/2} = 4.118 h; EC 76.2 %; beta^+ 7.1 %; alpha 16.7 %) is considered as a perspective radionuclide for radioimmunotherapy. The aim of the present work is to study experimental conditions of the {149}Tb production in reactions Nd({12}C, xn){149}Dy (4.23 min; beta^+, EC)\\to {149}Tb when the Nd targets have been irradiated by heavy ions of carbon. On the basis of results of formation and decay of {149}Dy\\to{149}Tb evaluation of the {149}Tb activity, is made which can be received under optimum conditions (enriched {142}Nd target, {12}C ions with the energy 120 MeV and up to current 100 mu A, time of irradiating 8-10 hours). Under these conditions {149}Tb can be obtained up to 30 GBq (up to 0.8 Ci).

  3. Poly[[aqua-?3-picolinato-?2-picolinato-dipicolinatopotassium(I)terbium(III)] 2.5-hydrate

    OpenAIRE

    Filipe A. Almeida Paz; João Rocha; Jacek Klinowski; Tito Trindade; Nogueira,Helena I. S.; Soares-Santos, Paula C. R.; Cunha-Silva, Lu?s

    2008-01-01

    In the title compound, [KTb(C6H4NO2)4(H2O)]·2.5H2O, each Tb3+ centre is coordinated by four N and five O atoms from five distinct picolinate ligands in a geometry resembling a highly distorted tricapped trigonal prism. One of the ligands establishes a skew bridge between neighbouring Tb3+ centres, leading to the formation of one-dimensional anionic polymeric chains, {[(C6H4NO2)4Tb]−}n, running along the direction [010]. Each K+ cation is seven-coordinated by six O atoms from one an...

  4. Spin waves in terbium. III. Magnetic anisotropy at zero wave vector

    DEFF Research Database (Denmark)

    Houmann, Jens Christian Gylden; Jensen, J.; Touborg, P.

    1975-01-01

    The energy gap at zero wave vector in the spin-wave dispersion relation of ferromagnetic. Tb has been studied by inelastic neutron scattering. The energy was measured as a function of temperature and applied magnetic field, and the dynamic anisotropy parameters were deduced from the results....... The axial anisotropy is found to depend sensitively on the orientation of the magnetic moments in the basal plane. This behavior is shown to be a convincing indication of considerable two-ion contributions to the magnetic anisotropy at zero wave vector. With the exception of the sixfold basal...... the effects of zero-point deviations from the fully aligned ground state, and we tentatively propose polarization-dependent two-ion couplings as their origin....

  5. Structural and Magnetic Anisotropy in Amorphous Terbium-Iron Thin Films

    Science.gov (United States)

    Hufnagel, Todd Clayton

    1995-01-01

    High density, removable media magnetooptic disk drives have recently begun to make significant gains in the information mass storage market. The media in these disks are amorphous rare-earth/transition-metal (RE-TM) alloys. One vital property of these materials is a large perpendicular magnetic anisotropy; that is, an easy axis of magnetization which is perpendicular to the plane of the film. A variety of theories, sometimes contradictory, have been proposed to account for this surprising presence of an anisotropic property in an amorphous material. Recent research indicates that there is an underlying atomic-scale structural anisotropy which is responsible for the observed magnetic anisotropy. Several different types of structural anisotropy have been proposed to account for the observed magnetic anisotropy, including pair-ordering anisotropy (anisotropic chemical short-range order) and bond orientation anisotropy (an anisotropy in coordination number or distances independent of chemical ordering). We have studied the structural origins of perpendicular magnetic anisotropy in amorphous Tb-Fe thin films by employing high-energy and anomalous dispersion x-ray scattering. The as-deposited films show a clear structural anisotropy, with a preference for Tb-Fe near neighbors to align in the out-of-plane direction. These films also have a large perpendicular magnetic anisotropy. Upon annealing, the magnetic anisotropy energy drops significantly, and we see a corresponding reduction in the structural anisotropy. The radial distribution functions indicate that the number of Tb-Fe near-neighbors increases in the in-plane direction, but does not change in the out-of-plane direction. Therefore, the distribution of Tb-Fe near-neighbors becomes more uniform upon annealing. We propose that the observed reduction in perpendicular magnetic anisotropy energy is a result of this change in structure. Our results support the pair -ordering anisotropy model of the structural anisotropy in amorphous Tb-Fe thin films. We see no evidence to support the bond orientation anisotropy model.

  6. Luminescence properties of terbium-doped Li3PO4 phosphor for ...

    Indian Academy of Sciences (India)

    Antonov-Romanovskii et al [2] firstly suggested applications of OSL for personal dosime- try. This technique got momentum for personnel dosime- try after the development of α-Al2O3:C. OSL properties of α-Al2O3:C have been investigated for personnel dosimetry, environmental dosimetry, medical dosimetry and space.

  7. Luminescence properties of terbium-doped Li3PO4 phosphor for ...

    Indian Academy of Sciences (India)

    The powder X-ray diffraction (PXRD), photoluminescence (PL) emission and excitation spectra, thermoluminescence (TL) and optically stimulated luminescence (OSL) were measured. The particle size was calculated using the Debye Scherrer formula and found to be 79.42 nm. PL emission spectra of Li 3 PO 4 :Tb 3 + ...

  8. Charge-transfer-based terbium MOF nanoparticles as fluorescent pH sensor for extreme acidity.

    Science.gov (United States)

    Qi, Zewan; Chen, Yang

    2017-01-15

    Newly emerged metal organic frameworks (MOFs) have aroused the great interest in designing functional materials by means of its flexible structure and component. In this study, we used lanthanide Tb 3+ ions and small molecular ligands to design and assemble a kind of pH-sensitive MOF nanoparticle based on intramolecular-charge-transfer effect. This kind of made-to-order MOF nanoparticle for H + is highly specific and sensitive and could be used to fluorescently indicate pH value of strong acidic solution via preset mechanism through luminescence of Tb 3+ . The long luminescence lifetime of Tb 3+ allows eliminating concomitant non-specific fluorescence by time-revised fluorescence techniques, processing an advantage in sensing H + in biological media with strong autofluorescence. Our method showed a great potential of MOF structures in designing and constructing sensitive sensing materials for specific analytes directly via the assembly of functional ions/ligands. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Assessment of terbium (III) as a luminescent probe for the detection of tuberculosis biomarkers

    Energy Technology Data Exchange (ETDEWEB)

    Bamogo, W. [CNRS, IRAMIS, UMR 3685 NIMBE/LEDNA, F-91191 Gif-sur-Yvette (France); Mugherli, L. [CEA, IRAMIS, UMR 3685 NIMBE/LEDNA, F-91191 Gif-sur-Yvette (France); Banyasz, A. [CNRS, IRAMIS, LIDyL/Laboratoire Francis Perrin, URA 2453, F-91191 Gif-sur-Yvette (France); Novelli-Rousseau, A.; Mallard, F. [BioMérieux SA, F-38000 Grenoble (France); Tran-Thi, T.-H., E-mail: thu-hoa.tran-thi@cea.fr [CNRS, IRAMIS, UMR 3685 NIMBE/LEDNA, F-91191 Gif-sur-Yvette (France)

    2015-10-08

    A detection method for nicotinic acid, a specific metabolite marker of Mycobacterium tuberculosis present in cultures and patients' breath, is studied in complex solutions containing other metabolites and in biological media such as urine, saliva and breath condensate. The method is based on the analysis of the luminescence increase of Tb{sup 3+} complexes in the presence of nicotinic acid due to the energy transfer from the excited ligand to the lanthanide ion. It is shown that other potential markers found in M. tuberculosis culture supernatant, such as methyl phenylacetate, p-methyl anisate, methyl nicotinate and 2-methoxy biphenyl, can interfere with nicotinic acid via a competitive absorption of the excitation photons. A new strategy to circumvent these interferences is proposed with an upstream trapping of volatile markers preceding the detection of nicotinic acid in the liquid phase via the luminescence of Tb{sup 3+} complexes. The cost of the method is evaluated and compared with the Xpert MTB/RIF test endorsed by the World Health Organization. - Highlights: • Nicotinic acid, a specific marker of M. tuberculosis, can be detected via luminescence. • The detection limit with a commercial phosphorimeter is 0.4 µmol·L{sup -1}. • Other metabolites of M. tuberculosis can interfere via absorbed excitation light. • The interference can be removed via trapping of the most volatile metabolites. • A breath analysis procedure's cost is compared with the Xpert TBM/RIF test.

  10. A highly porous luminescent terbium-organic framework for reversible anion sensing

    Energy Technology Data Exchange (ETDEWEB)

    Wong, K.L.; Law, G.L.; Wong, W.T. [Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong (China); Yang, Y.Y. [School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

    2006-04-18

    Unique tailored porous frameworks incorporating a lanthanide metal center have been designed to function as chemical detectors. A flexible multidentate ligand, mucic acid, is used to differentiate between several anions, thus creating an organic framework that is ideally suited for applications in gas separation, sensors, and chemical switches. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  11. Synthesis and characterization of wide bandgap semiconductors doped with terbium for electroluminescent devices

    OpenAIRE

    Montañez Huamán, Liz Margarita

    2016-01-01

    En el presente trabajo de investigación se ha estudiado propiedades estequiometrias, estructurales y de emisión de luz de semiconductor de amplio ancho de banda dopados con terbio. La difracción de rayos-X en ángulo rasante confirma el estado amorfo de las películas. Los espectros de absorción infrarroja muestran la formación de óxidos en las películas y la espectroscopia de foto-electrones de rayos-X revela la formación de oxinitruro de aluminio y oxicarburo de silicio. Las pe...

  12. Synthesis and characterization of terbium-doped SrSnO3 pigments

    Czech Academy of Sciences Publication Activity Database

    Dohnalová, Ž.; Gorodylova, N.; Šulcová, P.; Vlček, Milan

    2014-01-01

    Roč. 40, č. 8 (2014), s. 12637-12645 ISSN 0272-8842 Institutional support: RVO:61389013 Keywords : pigments * solid state reaction * perovskites Subject RIV: CA - Inorganic Chemistry Impact factor: 2.605, year: 2014

  13. An optical material for the detection of β-hydroxybutyrate based on a terbium complex

    Science.gov (United States)

    Wang, Xiaomiao; Chen, Huili; Li, Hua

    2014-02-01

    A novel Tb3+ complex (Tb(C14H10O4)ṡCl, TbL2) based on benzoic acid (L+H) was successfully synthesized, and gave a weak green emission in methanol-water (V:V, 4:1, pH 4.49). With the addition of β-hydroxybutyrate (β-HB) to a semi-aqueous solution of TbL2, an increment of the luminescent intensity at 545 nm assigned to 5D4 → 7F5 transition of Tb3+ was measured, which was evident to the naked eye. The response showed high selectivity for β-HB compared with other common anions including Cl-, NO3-, CO32-, PO43-, HPO42-, HPO4-, CO42-, PO74-, SO42-, lactate, AcO-, citrate, malate therefore it has the potential to be applied as a luminescent sensor for β-HB.

  14. The Photoresponse of the Gallium Arsenide Metal Semiconductor Field Effect Transistor

    Science.gov (United States)

    Paolella, Arthur

    The combining of optical and microwave technology is imminent, especially the integration of optical and microwave circuit functions on the same circuit or chip. Exploring the properties of the metal semiconductor field effect transistor (MESFET) as an optical detector for the detection of microwave and control signals in fiber optic links make sense because the MESFET is the main active component of GaAs MMICs. In this thesis, photocurrents and photovoltages of three MESFETs were measured as a function of the optical input (wavelength, intensity and modulation frequency), electrical input (gate voltage and gate resistance), and device characteristics. A model of the photoresponse, based on the drift and diffusion equations for the current density was developed, which established the internal photovoltaic effect at the channel-substrate interface as the dominant mechanism for the generation of photocurrent in the MESFET. The gain, bandwidth and gain-bandwidth products for each of the major photoeffects were determined mathematically. A maximum photocurrent of 16 mA, and an internal photovoltage of -0.5 volts was measured at 3.5 mW of optical power. The addition of a resistance in the gate circuit enhanced the photoresponse. With a resistor of 1 MOmega, the maximum photocurrent produced was 84.0 mA, resulting from an external photovoltage of 3.07 volts. The dynamic photoresponse of the MESFET as measured, showed a strong dependence with the intensity of the optical signal as well as with bias. The low frequency response varied from -15 dB to -41 dB, and the bandwidth changed from 50 MHz to 5 MHz as the optical signal decreased 18 dB. The low frequency response and bandwidth also showed strong dependence of bias. The low frequency response varied over a 7 dB range and the bandwidth changed from 45 MHz to 100 MHz as the gate was reversed biased (0 to -3.0 volts). Used as an optical detector, the MESFET function successfully in controlling the gain (15 dB) and phase (360^circ) of a T/R module as well as in switching functions of microwave MMICs. The techniques used were compatible with present MMIC processing technology.

  15. Gallium arsenide single crystal solar cell structure and method of making

    Science.gov (United States)

    Stirn, Richard J. (Inventor)

    1983-01-01

    A production method and structure for a thin-film GaAs crystal for a solar cell on a single-crystal silicon substrate (10) comprising the steps of growing a single-crystal interlayer (12) of material having a closer match in lattice and thermal expansion with single-crystal GaAs than the single-crystal silicon of the substrate, and epitaxially growing a single-crystal film (14) on the interlayer. The material of the interlayer may be germanium or graded germanium-silicon alloy, with low germanium content at the silicon substrate interface, and high germanium content at the upper surface. The surface of the interface layer (12) is annealed for recrystallization by a pulsed beam of energy (laser or electron) prior to growing the interlayer. The solar cell structure may be grown as a single-crystal n.sup.+ /p shallow homojunction film or as a p/n or n/p junction film. A Ga(Al)AS heteroface film may be grown over the GaAs film.

  16. Synthesis and characterization of rare-earth oxide transition-metal arsenides and selenides

    Energy Technology Data Exchange (ETDEWEB)

    Peschke, Simon Friedrich

    2017-04-06

    The present thesis includes two different quaternary systems that have been studied extensively. On the one hand, several samples of the REFeAsO{sub 1-x}F{sub x} family of iron-based superconductors were prepared using a novel solid state metathesis reaction, which also provided a possibility to prepare late rare-earth compounds of this family at ambient pressure. Comparison of structural and physical properties of those samples with samples from conventional solid state and high pressure syntheses revealed both, commonalities as well as striking differences. The observations gave reason to the conclusion that superconducting properties strongly depend, beside electronic infl uence, on the structural parameters. On the other hand, the quaternary system RE-T-Se-O with T = Ti-Mn was investigated using a NaI/KI flux mediated synthesis route. It has been shown that oC -La{sub 2}O{sub 2}MnSe{sub 2} is exclusively accessible in su fficient purity by the use of a fl ux material. Therefore, further syntheses in this quaternary system were performed by a flux mediated synthesis route leading to a large amount of new materials. Among them, a new polymorph mC-La{sub 2}O{sub 2}MnSe{sub 2} which forms, together with La{sub 4}MnSe{sub 3}O{sub 4} and La{sub 6}MnSe{sub 4}O{sub 6}, the series La{sub 2n+2}MnSe{sub n+2}O{sub 2n+2}. In addition, the alternative preparation method also enabled a large scale synthesis of the first examples of rare-earth chromium oxyselenides with chromium in the oxidation state +II, namely RE{sub 2}CrSe{sub 2}O{sub 2} (RE = La-Nd), which opened the door to study their magnetism in detail by powder neutron diffraction and muon spin rotation techniques. Research into the La-V-Se-O system revealed the first fi ve quaternary compounds of this family with interesting magnetic properties including ferromagnetism, antiferromagnetism, metamagnetism and more complex behaviour. In addition, the crystal structure of two new quaternary titanium containing oxyselenides were identifi ed and revealed unique structural building blocks that have not been observed in these systems before. The results of this thesis demonstrate not only the power of alternative preparation methods, but also the still increasing structural variety in the discussed quaternary systems. Strategic research in the field of transition-metal oxypnictides and oxychalcogenides, which still include a multiplicity of unknown materials, revealed numerous compounds with interesting physical properties and further investigations will probably uncover also new superconducting materials.

  17. Morphology- and orientation-controlled gallium arsenide nanowires on silicon substrates.

    Science.gov (United States)

    Ihn, Soo-Ghang; Song, Jong-In; Kim, Tae-Wook; Leem, Dong-Seok; Lee, Takhee; Lee, Sang-Geul; Koh, Eui Kwan; Song, Kyung

    2007-01-01

    GaAs nanowires were epitaxially grown on Si(001) and Si(111) substrates by using Au-catalyzed vapor-liquid-solid (VLS) growth in a solid source molecular beam epitaxy system. Scanning electron microscopy analysis revealed that almost all the GaAs nanowires were grown along directions on both Si substrates for growth conditions investigated. The GaAs nanowires had a very uniform diameter along the growth direction. X-ray diffraction data and transmission electron microscopy analysis revealed that the GaAs nanowires had a mixed crystal structure of the hexagonal wurtzite and the cubic zinc-blende. Current-voltage characteristics of junctions formed by the epitaxially grown GaAs nanowires and the Si substrate were investigated by using a current-sensing atomic force microscopy.

  18. Direct Electrical Probing of Periodic Modulation of Zinc-Dopant Distributions in Planar Gallium Arsenide Nanowires.

    Science.gov (United States)

    Choi, Wonsik; Seabron, Eric; Mohseni, Parsian K; Kim, Jeong Dong; Gokus, Tobias; Cernescu, Adrian; Pochet, Pascal; Johnson, Harley T; Wilson, William L; Li, Xiuling

    2017-02-28

    Selective lateral epitaxial (SLE) semiconductor nanowires (NWs), with their perfect in-plane epitaxial alignment, ability to form lateral complex p-n junctions in situ, and compatibility with planar processing, are a distinctive platform for next-generation device development. However, the incorporation and distribution of impurity dopants in these planar NWs via the vapor-liquid-solid growth mechanism remain relatively unexplored. Here, we present a detailed study of SLE planar GaAs NWs containing multiple alternating axial segments doped with Si and Zn impurities by metalorganic chemical vapor deposition. The dopant profile of the lateral multi-p-n junction GaAs NWs was imaged simultaneously with nanowire topography using scanning microwave impedance microscopy and correlated with infrared scattering-type near-field optical microscopy. Our results provide unambiguous evidence that Zn dopants in the periodically twinned and topologically corrugated p-type segments are preferentially segregated at twin plane boundaries, while Si impurity atoms are uniformly distributed within the n-type segments of the NWs. These results are further supported by microwave impedance modulation microscopy. The density functional theory based modeling shows that the presence of Zn dopant atoms reduces the formation energy of these twin planes, and the effect becomes significantly stronger with a slight increase of Zn concentration. This implies that the twin formation is expected to appear when a threshold planar concentration of Zn is achieved, making the onset and twin periodicity dependent on both Zn concentration and nanowire diameter, in perfect agreement with our experimental observations.

  19. System architecture of a gallium arsenide one-gigahertz digital IC tester

    Science.gov (United States)

    Fouts, Douglas J.; Johnson, John M.; Butner, Steven E.; Long, Stephen I.

    1987-01-01

    The design for a 1-GHz digital integrated circuit tester for the evaluation of custom GaAs chips and subsystems is discussed. Technology-related problems affecting the design of a GaAs computer are discussed, with emphasis on the problems introduced by long printed-circuit-board interconnect. High-speed interface modules provide a link between the low-speed microprocessor and the chip under test. Memory-multiplexer and memory-shift register architectures for the storage of test vectors are described in addition to an architecture for local data storage consisting of a long chain of GaAs shift registers. The tester is constructed around a VME system card cage and backplane, and very little high-speed interconnect exists between boards. The tester has a three part self-test consisting of a CPU board confidence test, a main memory confidence test, and a high-speed interface module functional test.

  20. Improved defect analysis of Gallium Arsenide solar cells using image enhancement

    Science.gov (United States)

    Kilmer, Louis C.; Honsberg, Christiana; Barnett, Allen M.; Phillips, James E.

    1989-01-01

    A new technique has been developed to capture, digitize, and enhance the image of light emission from a forward biased direct bandgap solar cell. Since the forward biased light emission from a direct bandgap solar cell has been shown to display both qualitative and quantitative information about the solar cell's performance and its defects, signal processing techniques can be applied to the light emission images to identify and analyze shunt diodes. Shunt diodes are of particular importance because they have been found to be the type of defect which is likely to cause failure in a GaAs solar cell. The presence of a shunt diode can be detected from the light emission by using a photodetector to measure the quantity of light emitted at various current densities. However, to analyze how the shunt diodes affect the quality of the solar cell the pattern of the light emission must be studied. With the use of image enhancement routines, the light emission can be studied at low light emission levels where shunt diode effects are dominant.

  1. Noise suppression and long-range exchange coupling for gallium arsenide spin qubits

    DEFF Research Database (Denmark)

    Malinowski, Filip

    of the qubit splitting with respect to gate voltages. We show that for singlet-triplet and resonant exchange qubit this can be achieved by operating a quantum dot array in a highly symmetric configuration. The symmetrization approach results in a factor-of-six improvement of the double dot singlet......-triplet exchange oscillations quality factor while the dephasing times for the threeelectron resonant exchange qubit are marginally longer. Second, we present the study of the Overhauser field noise arising due to interaction with the nuclear spin bath. We show that the Overhauser field noise conforms to classical...... dot in nine different charge occupancies and identify ground state spin in all cases. For even-occupied spin-1/2 multielectron quantum dot a variation of the gate voltage by a few milivolts in the vicinity of the charge transition leads to sign change of the exchange interaction with a single...

  2. Development of Ultra-Low Resistance Ohmic Contacts for indium gallium arsenide/indium phosphide HBTs

    Science.gov (United States)

    Baraskar, Ashish

    With the continued scaling of transistors to obtain increased transistor bandwidth and packing density, achieving very low resistance metal-semiconductor contacts becomes crucial. The base and emitter contact resistivities in heterojunction bipolar transistors (HBTs) must decrease in proportion to the inverse square of the transistor cutoff frequency. Similarly for field-effect transistors (FETs), progressive reduction in contact resistivity is required for both increased speed of operation and increased device packing density. Contact resistivities less than 10-8 O-cm2 are required for III-V HBTs and FETs for having simultaneous 1.5 THz current-gain (ft) and power-gain (fmax) cut-off frequencies. Owing to higher electron velocity, higher transistor bandwidths are more readily obtained in InGaAs than in Si, hence there is strong motivation to develop low resistance ohmic contacts to InGaAs. This dissertation focuses on development of ultra-low resistance ohmic contacts to n-In0.53Ga0.47As, n-InAs and p-In0.53 Ga0.47As for their application in InP based HBTs. There were four main challenges in obtaining ultra-low contact resistivities: 1. High doping: Attainment of high active carrier concentration which is required for reducing the depletion region in the semiconductor. Reduced depletion region results in enhanced tunneling of carriers across the metal semiconductor junction. 2. Surface preparation: Contact resistivity strongly depends on surface preparation and obtaining resistivities less than 10-8 O-cm 2 requires a significant attention to removal of semiconductor surface oxides before the contacts are made. 3. Refractory metal contact: Owing to high current densities (≈ 50 mA/mum2) and high temperatures involved during fabrication of scaled HBTs and FETs, it becomes important to keep the metal semiconductor junctions thermally stable for their continued operation as desired. To achieve thermal stability, it is required to use refractory metals for making the contact. 4. Accurate extraction of contact resistivities. In this work, molecular beam epitaxy thin-film growth technique was used to grow the semiconductor thin films. After careful growth optimization and calibrations, the highest active carrier concentration obtained was 6 x 1019 cm-3, 1 x 1020 cm -3 (record highest) and 2.2 x 1020 cm -3 for n-In0.53Ga0.47As, n-InAs and p-In 0.53Ga0.47As, respectively. W, Mo and Ir refractory metals were chosen to form contacts to these semiconductors to achieve thermal stability. Transmission line model structures were designed to accurately determine the contact resistivities. The lowest contact resistivities obtained were (0.9 +/- 0.5) x 10-8 O-cm2, (0.6 +/- 0.4) x 10-8 O-cm2 and (0.6 +/- 0.5) x 10-8 O-cm2 for contacts to n- In0.53Ga0.47As, n-InAs and p-In0.53Ga 0.47As, respectively, which are the lowest contact resistivities reported to date for these semiconductors. Contacts to n-In0.53Ga0.47 As and n-InAs were found to remain thermally stable. However, slight degradation on annealing was observed for contacts made to p-In0.53Ga 0.47As. We have also developed theoretical models to validate our experimental data. The models are extended to calculate the lowest possible contact resistivities for GaAs, InP, InSb and GaSb. In summary, the ultra-low resistance, refractory metal contacts developed in this work make them a potential candidate to be applied in highly scaled HBTs and other devices of near-terahertz bandwidths.

  3. Radiation and temperature effects in gallium arsenide, indium phosphide, and silicon solar cells

    Science.gov (United States)

    Weinberg, I.; Swartz, C. K.; Hart, R. E., Jr.; Statler, R. L.

    1987-01-01

    The effects of radiation on performance are determined for both n+p and p+n GaAs and InP cells and for silicon n+p cells. It is found that the radiation resistance of InP is greater than that of both GaAs and Si under 1-MeV electron irradiation. For silicon, the observed decreased radiation resistance with decreased resistivity is attributed to the presence of a radiation-induced boron-oxygen defect. Comparison of radiation damage in both p+n and n+p GaAs cells yields a decreased radiation resistance for the n+p cell attributable to increased series resistance, decreased shunt resistance, and relatively greater losses in the cell's p-region. For InP, the n+p configuration is found to have greater radiation resistance than the p+n cell. The increased loss in this latter cell is attributed to losses in the cell's emitter region. Temperature dependency results are interpreted using a theoretical relation for dVoc/dT, which predicts that increased Voc should result in decreased numerical values for dPm/dT. The predicted correlation is observed for GaAs but not for InP, a result which is attributed to variations in cell processing.

  4. Dose rate effects on damage formation in ion-implanted gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Haynes, T.E.; Holland, O.W.

    1990-09-01

    The residual damage in GaAs was measured by ion channeling following implantation of either 100 keV {sup 30}Si{sup +} at temperatures of 300K or 77K, or 360 keV {sup 120}Sn{sup +} at 300K. For room-temperature Si implants and fluences between 1 and 10 {times} 10{sup 14} Si/cm{sup 2}, the amount of damage created was strongly dependent upon the ion current density, which was varied between 0.05 and 12 {mu}A/cm{sup 2}. Two different stages of damage growth were identified by an abrupt increase in the damage growth rate as a function of fluence, and the threshold fluence for the onset of the second stage was found to be dependent on the dose rate. The dose rate effect on damage was substantially weaker for {sup 120}Sn{sup +} implants and was negligible for Si implants at 77K. The damage was found to be most sensitive to the average current density, demonstrating that the defects which are the precursors to the residual dose-rate dependent damage have active lifetimes of at least 3 {times} 10{sup {minus}4} s. The dose rate effect and its variation with ion mass and temperature are discussed in the context of homogeneous nucleation and growth of damage during ion irradiation.

  5. Microwave Semiconductor Research - Materials, Devices and Circuits and Gallium Arsenide Ballistic Electron Transistors.

    Science.gov (United States)

    1985-04-01

    Semiconductors", L.F. Eastman, Third Inter. Conf. on Hot Carriers in Semiconductors, Montpellier , France (July 1981); J. de Physique, Col. C7, Sup. 010, Tome...ballistic electrons, the verage electron velocity is as high as 8 x 107cm/s across a short drift pace (< .5-.75 micron for ion density at or below

  6. Femtosecond Laser Machining of Gallium Arsenide Wafers for the Creation of Quasi-Phasematched Devices

    Science.gov (United States)

    2006-02-21

    visible structural damage, creating a tightly fitting sample as shown in the optical micrographs in Figure 5.5 below. Figure 5.5 Interlaced ...power photonics group at Heriot Watt University. The CO2 laser, operating at a wavelength of 10.6µm was a pulsed laser with variable repetition rate...above that of GaAs. Their Tg would be ~160°C”. In this case we could heat up a “blob” of glass on top of the interlaced comb structure, and let it flow

  7. Advanced Composite High-k Gate Stack for Mixed Anion Arsenide-Antimonide Quantum Well Transistors

    Science.gov (United States)

    2010-12-01

    and interface defect scattering5 dominate. Shubnikov-de Haas ( SdH ) oscillations (Fig. 8a) are observed at low temperature (2- 15K) and high magnetic...the amplitude of SdH oscillations, which is lower than 0.05m0 reported for InAs QW due to quantization and band non-parabolicity6. FFT of SdH ...ρ 0 1/B [T-1] 2K 4K 6K 10K 15K Δ(1/B) = 0.024 T -1 m*=.043m0 (b) Fig. 8 (a) Shubnikov-de Haas ( SdH ) oscillations in the sheet resistance

  8. Structural features of indium antimonide quantum dots on the indium arsenide substrate

    Directory of Open Access Journals (Sweden)

    Liliya A. Sokura

    2015-06-01

    Full Text Available The properties of InSb/InAs quantum dots (QDs have been investigated by transmission electron microscopy (TEM. Specific features of diffraction contrast were discovered in plan-view TEM images of big (9–10 nm in height and 38–50 nm in diameter InSb QDs. To understand the origin of such distortions, a model of an InSb QD on InAs substrate containing a partial Frank dislocation (FD was developed and used for calculations of the displacement field and the subsequent diffraction image simulation of an InSb QD for the first time. The shape of the QD was established to have an insignificant influence on the magnitude of radial displacements. The insertion of a misfit defect (a partial Frank dislocation into the QD reduces the strain at the edges of the QD almost by 30%. The comparison of experimental and simulated data allowed us to explain the observed features of the moiré pattern in the image of a big InSb QD by the presence of a misfit defect at the QD-substrate interface.

  9. Covalent Surface Modification of Gallium Arsenide Photocathodes for Water Splitting in Highly Acidic Electrolyte.

    Science.gov (United States)

    Garner, Logan E; Steirer, K Xerxes; Young, James L; Anderson, Nicholas C; Miller, Elisa M; Tinkham, Jonathan S; Deutsch, Todd G; Sellinger, Alan; Turner, John A; Neale, Nathan R

    2017-02-22

    Efficient water splitting using light as the only energy input requires stable semiconductor electrodes with favorable energetics for the water-oxidation and proton-reduction reactions. Strategies to tune electrode potentials using molecular dipoles adsorbed to the semiconductor surface have been pursued for decades but are often based on weak interactions and quickly react to desorb the molecule under conditions relevant to sustained photoelectrolysis. Here, we show that covalent attachment of fluorinated, aromatic molecules to p-GaAs(1 0 0) surfaces can be employed to tune the photocurrent onset potentials of p-GaAs(1 0 0) photocathodes and reduce the external energy required for water splitting. Results indicate that initial photocurrent onset potentials can be shifted by nearly 150 mV in pH -0.5 electrolyte under 1 Sun (1000 W m-2 ) illumination resulting from the covalently bound surface dipole. Though X-ray photoelectron spectroscopy analysis reveals that the covalent molecular dipole attachment is not robust under extended 50 h photoelectrolysis, the modified surface delays arsenic oxide formation that results in a p-GaAs(1 0 0) photoelectrode operating at a sustained photocurrent density of -20.5 mA cm-2 within -0.5 V of the reversible hydrogen electrode. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Superconductor-semiconductor-superconductor planar junctions of aluminium on DELTA-doped gallium arsenide

    DEFF Research Database (Denmark)

    Taboryski, Rafael Jozef; Clausen, Thomas; Kutchinsky, jonatan

    1997-01-01

    We have fabricated and characterized planar superconductor-semiconductor-superconductor (S-Sm-S) junctions with a high quality (i.e. low barrier) interface between an n++ modulation doped conduction layer in MBE grown GaAs and in situ deposited Al electrodes. The Schottky barrier at the S...

  11. Investigations into molecular beam epitaxial growth of Indium Arsenide/Gallium antimonide superlattices

    Science.gov (United States)

    Murray, Lee Michael

    InAs/GaSb superlattices are a material system well suited to growth via molecular beam epitaxy. The ability to tune the band gap over the entire mid and long wave infrared spectrum gives a large number of applications for devices made from InAs/GaSb superlattice material. The growth of high quality InAs/GaSb superlattice material requires a careful study of the parameters used during epitaxial growth. This work investigates the growth of tunnel junctions for InAs/GaSb based superlattice light emitting diodes, the presence of defects in GaSb homoepitaxial layers, and variations in the growth rate of InAs/GaSb superlattice samples. Tunnel junctions in cascaded structures must provide adequate barriers to prevent carriers from leaking from one emission region to the next without first recombining radiatively, while at the same time remain low in tunneling resistance for current recycling. A variety of tunnel junction designs are compared in otherwise identical four stage InAs/GaSb superlattice light emitting diodes, which past studies have found hole confinement to be problematic. GaSb was used on the p-side of the junction, while various materials were used on the n-side. Al0.20In0.80As0.73Sb0.27 tunnel junctions function best due to the combination of favorable band alignment and ease of growth. Pyramidal defects have been observed in layers of GaSb grown by molecular beam epitaxy on GaSb substrates. These defects are typically 3-8 nanometers high, 1-3 microns in diameter, and shaped like pyramids. Their occurrence in the growth of GaSb buffer layers can propagate into subsequent layers. Defects are nucleated during the early stages of growth after the thermal desorption of native oxide from the GaSb substrate. These defects grow into pyramids due to a repulsive Ehrlich-Schwoebel potential on atomic step edges leading to an upward adatom current. The defects reduce in density with growth of GaSb. The insertion of a thin AlAsSb layer into the early stages of the GaSb buffer increases the rate of elimination of the defects, resulting in a smooth surface within 500nm. The acceleration of defect reduction is due to the temporary interruption of step-flow growth induced by the AlAsSb layer. This leads to a reduced isolation of the pyramids from the GaSb epitaxial layer, and allows the pyramidal defects to smooth out. Investigations into varying the superlattice growth rate have not been reported widely in the literature. Due to the frequent use of soaks, growth interrupts, and other interface structuring steps the superlattice growth rate and the interface layer sequence are linked. In order to properly study the effects of growth rate variations and interface design changes it is necessary to account for the effect on growth rate due to the interfaces. To this end it is useful to think of the effective growth rate of the superlattice, which is the total layer thickness divided by the total time, per superlattice period. Varying the effective growth rate of superlattice photoluminescence samples shows a peak in output at ~0.5 monolayers per second. Investigations into the structural properties of the superlattices show no decrease in structural uniformity for effective growth rates up to ~1.4 monolayers per second.

  12. Gallium arsenide p+–n–p+-structures with impoverished base area

    Directory of Open Access Journals (Sweden)

    Karimov A. V.

    2009-06-01

    Full Text Available It is displayed experimentally, that the current transport’s mechanism through p+GaAs–nGaAs–p+GaAs-structure is formed by injection-tunnel and generation-recombination mechanisms. Injection-tunnel current prevails at modulation of base’s part which contains defects, and generation-recombination currents are determinative at modulation of base’s part with lesser defectiveness. p+GaAs–nGaAs–p+GaAs-structures are of interest for creating voltage suppressors and electronic switches on their base.

  13. Pilot Line 3: Gallium Arsenide Pilot Line for High Performance Components

    Science.gov (United States)

    1988-10-20

    C&onVoJud Im"pedanco DESCRIPTON 4 t taw OpO ~’* On-Package The MLC44 package is 8 highspeed muiUa’,w ceamc package developed at c~m TrQuint...will be a cluster of early failures ( infant mortality), usually followed by failure mechanisms that take longer to occur. For integrated circuit...production, the infant mortality failures are removed before shipment by a bum-in procedure. For this program, a bum-in operation will not be performed on

  14. Indium arsenide as a material for biological applications: Assessment of surface modifications, toxicity, and biocompatibility

    Science.gov (United States)

    Jewett, Scott A.

    III-V semiconductors such as InAs have recently been employed in a variety of applications where the electronic and optical characteristics of traditional, silicon-based materials are inadequate. InAs has a narrow band gap and very high electron mobility in the near-surface region, which makes it very attractive for high performance transistors, optical applications, and chemical sensing. However, InAs forms an unstable surface oxide layer in ambient conditions, which can corrode over time and leach toxic indium and arsenic components. Current research has gone into making InAs more attractive for biological applications through passivation of the surface by adlayer adsorption. In particular, wet-chemical methods are current routes of exploration due to their simplicity, low cost, and flexibility in the type of passivating molecule. This dissertation focuses on surface modifications of InAs using wet-chemical methods in order to further its use in biological applications. First, the adsorption of collagen binding peptides and mixed peptide/thiol adlayers onto InAs was assessed. X-ray photoelectron spectroscopy (XPS) along with atomic force microscopy (AFM) data suggested that the peptides successfully adsorbed onto InAs, but were only able to block oxide regrowth to a relatively low extent. This low passivation ability is due to the lack of covalent bonds of the peptide to InAs, which are necessary to effectively block oxide regrowth. The addition of a thiol, in the form of mixed peptide/thiol adlayers greatly enhanced passivation of InAs while maintaining peptide presence on the surface. Thiols form tight, covalent bonds with InAs, which prevents oxide regrowth. The presence of the collagen-binding peptide on the surface opens the door to subsequent modification with collagen or polyelectrolyte-based adlayers. Next, the stability and toxicity of modified InAs substrates were determined using inductively coupled plasma mass spectrometry (ICP-MS) and zebrafish studies. InAs substrates modified with a poly(ethylene glycol) (PEG) based adlayer showed the highest stability in physiological conditions by leaching the lowest amounts of indium and arsenic. Modified substrates also showed no toxicity to zebrafish after incubation for 120 hours. Overall, these findings suggest that a variety of adlayers can be functionalized onto InAs surfaces and successfully passivate the surface, along with decreasing InAs toxicity. Finally, we demonstrate how surface modifications can be applied to a different III-V semiconductor, GaN, in order to modulate cellular adhesion. Modification of GaN with a laminin-derived peptide increases the adhesion of PC12 neuronal cells and alters the physical morphology of the adhered cells. Additionally, no toxicity to cells is observed, further demonstrating the potential for employing III-V semiconductors in biological applications.

  15. Gallium Arsenide detectors for X-ray and electron (beta particle) spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lioliou, G.; Barnett, A.M.

    2016-11-11

    Results characterizing GaAs p{sup +}-i-n{sup +} mesa photodiodes with a 10 µm i layer for their spectral response under illumination of X-rays and beta particles are presented. A total of 22 devices, having diameters of 200 µm and 400 µm, were electrically characterized at room temperature. All devices showed comparable characteristics with a measured leakage current ranging from 4 nA/cm{sup 2} to 67 nA/cm{sup 2} at an internal electric field of 50 kV/cm. Their unintentionally doped i layers were found to be almost fully depleted at 0 V due to their low doping density. {sup 55}Fe X-ray spectra were obtained using one 200 µm diameter device and one 400 µm diameter device. The best energy resolution (FWHM at 5.9 keV) achieved was 625 eV using the 200 µm and 740 eV using the 400 µm diameter device, respectively. Noise analysis showed that the limiting factor for the energy resolution of the system was the dielectric noise; if this noise was eliminated by better design of the front end of the readout electronics, the achievable resolution would be 250 eV. {sup 63}Ni beta particle spectra obtained using the 200 µm diameter device showed the potential utility of these detectors for electron and beta particle detection. The development of semiconductor electron spectrometers is important particularly for space plasma physics; such devices may find use in future space missions to study the plasma environment of Jupiter and Europa and the predicted electron impact excitation of water vapor plumes from Europa hypothesized as a result of recent Hubble Space Telescope (HST) UV observations.

  16. Cathodoluminescence on the Effects of Te Implantation and Laser Annealing in Gallium Arsenide.

    Science.gov (United States)

    1978-12-01

    to me by Jim Miskimen , George Gergal , and Ron Gabriel of the AFIT Physics Laboratory staff . Finally , I would like to thank my wife for her...wavelength counter) . The spectrometer could also be driven externally by signals from a step motor driver designed and constructed by G . Gergal (Ref 13

  17. FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): Mechanism of Current Oscillations in Gallium Arsenide Photoconductive Semiconductor Switches

    Science.gov (United States)

    Tian, Li-Qiang; Shi, Wei

    2008-07-01

    Semi-insulating photoconductive semiconductor switch with an electrode gap of 4 mm, triggered by a laser pulse with energy of 0.5mJ, and applied bias of 2.5kV, the periodicity current oscillation with a cycle of 12ns is obtained. It is indicated that the current oscillation is one mode of transferred electron effect, namely quenched domain mode. This mode of trans-electron oscillator is obtained when the instantaneous bias electric field drops below the sustaining field (the minimum electric field required to support the domain) before the domain reaches the anode, which leads to the domain disappears somewhere in the bulk of the switch and away from the ohmic contacts. We mainly analyse the time-dependent characteristic of the mode, the theoretical analysis results are in excellent agreement with the experiment.

  18. Density functional study of optical properties of beryllium chalcogenides compounds in nickel arsenide B8 structure

    Energy Technology Data Exchange (ETDEWEB)

    Al-Douri, Y., E-mail: yaldouri@yahoo.com [Institute of Nano Electronic Engineering, University Malaysia Perlis, 01000 Kangar, Perlis (Malaysia); Baaziz, H., E-mail: baaziz_hakim@yahoo.fr [Physics Department, Faculty of Science University of M' sila, 28000 M' sila (Algeria); Charifi, Z. [Physics Department, Faculty of Science University of M' sila, 28000 M' sila (Algeria); Reshak, Ali H. [School of complex systems, FFWP-South Bohemia University, Nove Hrady 37333 (Czech Republic); School of Material Engineering, Malaysia University of Perlis, P.O. Box 77, d/a Pejabat Pos Besar, 01007 Kangar, Perlis (Malaysia)

    2012-02-01

    The structural, electronic and optical properties of beryllium chalcogenides BeS, BeSe and BeTe using the full-potential linear augmented plane wave (FP-LAPW) method are investigated. The exchange-correlation energy within the local density approximation (LDA) and the generalized gradient approximation (GGA) are described. The Engel-Vosko (EVGGA) formalism is applied for electronic and optical properties. The structural parameters of our model and the transition pressure from zinc-blende (B3) to the NiAs (B8) phase are confirmed. It is found that these compounds have indirect band gaps except for BeTe in NiAs (B8) phase. The results of reflectivity, refractive index and optical dielectric functions of Be compounds are investigated. An agreement is found between our results and those of other theoretical calculations and the experimental data.

  19. Triple crystal x-ray diffraction analysis of chemical-mechanical polished gallium arsenide

    Science.gov (United States)

    Wang, V. S.; Matyi, R. J.

    1992-12-01

    High-resolution triple crystal x-ray diffraction has been used to monitor the magnitude of diffuse scattering from chemical-mechanical (CM) polished GaAs. The diffuse scattering, which is attributed to kinematic scattering arising from polish-induced crystallographic defects, was found to be only slightly affected when each of four CM polish parameters (bromine concentration in Br2/methanol, total polish time, polish pad rotation speed, and force on sample) was varied individually. The combined effect of increases in both the pad rotation speed and the force on the sample increased the magnitude of the diffuse scattering, suggesting the generation of mechanical damage. When all four variables were increased to their maximum values, the diffuse scattering increased dramatically and became anisotropic. We have expressed the magnitude of the diffuse scattering in terms of an ``excess intensity'' in reciprocal space to provide a semi-quantitative relation between CM polish parameters and the generation of polish-induced damage.

  20. The attachment and characterization of DNA probes on gallium arsenide-based semiconductor surfaces

    Science.gov (United States)

    Yang, Joonhyuk

    2007-12-01

    Immobilization of nucleic acid molecules on solid surfaces is the core of numerous important technologies in the genomics, disease diagnostics and biosensors applications. The architecture and density of immobilized probe molecules depend on the type of the solid surface on which they are anchored. Even though many different types of surfaces have been studied as substrates for deoxyribonucleic acid (DNA) attachment, the development of a new type of substrate, which is reproducible, stable, highly controlled and easily transferred to practical applications, is still needed. Recent studies have shown that As terminated GaAs-based semiconductors can be used as substrates for immobilized DNA layers. In this study, I aim to understand the attachment of nucleic acid onto the surfaces of As-terminated GaAs-based semiconductors and focus on improving the "brush-structure", which is essential for high quality of biochip based on a DNA layer. Attachment of 8-base and 100-base thiolated ssDNA layers on arsenic terminated GaAs(001) was achieved and characterized. The covalent bonds between the thiolated oligonucleotides with As atoms on the GaAs surface were investigated using x-ray photoelectron spectroscopy (XPS), and the surface morphology was obtained using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). In addition, I studied the effect of DNA length and the presence of a good solvent, such as water, on the oligonucleotides on a GaAs surface. I also investigated the effects of the thiol-based spacer and electrolyte concentration to improve the brush-like structure of the DNA layer. Finally, irradiation effects and AlGaAs resonators have been studied for the applications of DNA brush layer on GaAs as biosensor during the change of attachment probe DNA and hybridization to target DNA. For the 8-base thiolated ssDNA case, AFM results showed that the layer thickness was about ˜2.2 nm in dry mode and increased in wet mode. Replacement reaction from N-, O-As bonds to S-As bonds was observed with addition of MCH as indicated by analysis of XPS spectra. The concentration of electrolyte affected the brush like layer structure. In the case of the longer, more flexible DNA with 100 bases, the DNA molecules strongly interacted with each other and formed big cluster, of 330˜440nm in diameter on the surface. Finally, for the applications, a high level of radiation destroyed the brush layer. An AlGaAs resonator used as proof of concept a change in mass by a change in resonance frequency under hybridization reaction with complementary target DNA. This result shows that the design is viable and has a defection of ˜25pg.

  1. Lower critical field and SNS-Andreev spectroscopy of 122-arsenides: Evidence of nodeless superconducting gap

    Science.gov (United States)

    Abdel-Hafiez, M.; Pereira, P. J.; Kuzmichev, S. A.; Kuzmicheva, T. E.; Pudalov, V. M.; Harnagea, L.; Kordyuk, A. A.; Silhanek, A. V.; Moshchalkov, V. V.; Shen, B.; Wen, Hai-Hu; Vasiliev, A. N.; Chen, Xiao-Jia

    2014-08-01

    Using two experimental techniques, we studied single crystals of the 122-FeAs family with almost the same critical temperature, Tc. We investigated the temperature dependence of the lower critical field Hc1(T ) of a Ca0.32Na0.68Fe2As2 (Tc≈34K) single crystal under static magnetic fields H parallel to the c axis. The temperature dependence of the London penetration depth can be described equally well either by a single anisotropic s-wave-like gap or by a two-gap model, while a d-wave approach cannot be used to fit the London penetration depth data. Intrinsic multiple Andreev reflection effect spectroscopy was used to detect bulk gap values in single crystals of the intimate compound Ba0.65K0.35Fe2As2, with the same Tc. We estimated the range of the large gap value ΔL=6-8 meV (depending on small variation of Tc) and its a k space anisotropy of about 30%, and the small gap ΔS≈1.7±0.3 meV. This clearly indicates that the gap structure of our investigated systems more likely corresponds to a nodeless s-wave two gaps.

  2. Formation of defects at high temperature plastic deformation of gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Mikhnovich, V.V.

    2006-03-14

    The purpose of the present thesis consists in acquiring more concrete information concerning the mechanism of the movement of dislocations and types of defects that appear during the process of dislocation motion on the basis of systematic experimental studies of the GaAs deformation. Experimental studies concerning the dependence of the stress of the samples from their deformation at different values of the deformation parameters (like temperature and deformation speed) were conducted in this paper. To determine the concentration of defects introduced in samples during the deformation process the positron annihilation spectroscopy (PAS) method was used. The second chapter of this paper deals with models of movement of dislocations and origination of defects during deformation of the samples. In the third chapter channels and models of positron annihilation in the GaAs samples are investigated. In the forth chapter the used experimental methods, preparation procedure of test samples and technical data of conducted experiments are described. The fifth chapter shows the results of deformation experiments. The sixth chapter shows the results of positron lifetime measurements by the PAS method. In the seventh chapter one can find analyses of the values of defects concentration that were introduced in samples during deformation. (orig.)

  3. The scaling of the effective band gaps in indium-arsenide quantum dots and wires.

    Science.gov (United States)

    Wang, Fudong; Yu, Heng; Jeong, Sohee; Pietryga, Jeffrey M; Hollingsworth, Jennifer A; Gibbons, Patrick C; Buhro, William E

    2008-09-23

    Colloidal InAs quantum wires having diameters in the range of 5-57 nm and narrow diameter distributions are grown from Bi nanoparticles by the solution-liquid-solid (SLS) mechanism. The diameter dependence of the effective band gaps (DeltaE(g)s) in the wires is determined from photoluminescence spectra and compared to the experimental results for InAs quantum dots and rods and to the predictions of various theoretical models. The DeltaE(g) values for InAs quantum dots and wires are found to scale linearly with inverse diameter (d(-1)), whereas the simplest confinement models predict that DeltaE(g) should scale with inverse-square diameter (d(-2)). The difference in the observed and predicted scaling dimension is attributed to conduction-band nonparabolicity induced by strong valence-band-conduction-band coupling in the narrow-gap InAs semiconductor.

  4. Computer modeling characterization, and applications of Gallium Arsenide Gunn diodes in radiation environments

    Energy Technology Data Exchange (ETDEWEB)

    El- Basit, Wafaa Abd; El-Ghanam, Safaa Mohamed; Kamh, Sanaa Abd El-Tawab [Electronics Research Laboratory, Physics Department, Faculty of Women for Arts, Science and Education, Ain-Shams University, Cairo (Egypt); Abdel-Maksood, Ashraf Mosleh; Soliman, Fouad Abd El-Moniem Saad [Nuclear Materials Authority, Cairo (Egypt)

    2016-10-15

    The present paper reports on a trial to shed further light on the characterization, applications, and operation of radar speed guns or Gunn diodes on different radiation environments of neutron or γ fields. To this end, theoretical and experimental investigations of microwave oscillating system for outer-space applications were carried out. Radiation effects on the transient parameters and electrical properties of the proposed devices have been studied in detail with the application of computer programming. Also, the oscillation parameters, power characteristics, and bias current were plotted under the influence of different γ and neutron irradiation levels. Finally, shelf or oven annealing processes were shown to be satisfactory techniques to recover the initial characteristics of the irradiated devices.

  5. Origin of optical losses in gallium arsenide disk whispering gallery resonators

    CERN Document Server

    Parrain, David; Wang, Guillaume; Guha, Biswarup; Santos, Eduardo Gil; Lemaitre, Aristide; Senellart, Pascale; Leo, Giuseppe; Ducci, Sara; Favero, Ivan

    2015-01-01

    Whispering gallery modes in GaAs disk resonators reach half a million of optical quality factor. These high Qs remain still well below the ultimate design limit set by bending losses. Here we investigate the origin of residual optical dissipation in these devices. A Transmission Electron Microscope analysis is combined with an improved Volume Current Method to precisely quantify optical scattering losses by roughness and waviness of the structures, and gauge their importance relative to intrinsic material and radiation losses. The analysis also provides a qualitative description of the surface reconstruction layer, whose optical absorption is then revealed by comparing spectroscopy experiments in air and in different liquids. Other linear and nonlinear optical loss channels in the disks are evaluated likewise. Routes are given to further improve the performances of these miniature GaAs cavities.

  6. Size-effects in indium gallium arsenide nanowire field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Zota, Cezar B., E-mail: cezar.zota@eit.lth.se; Lind, E. [Department of Electrical and Information Technology, Lund University, Lund 22101 (Sweden)

    2016-08-08

    We fabricate and analyze InGaAs nanowire MOSFETs with channel widths down to 18 nm. Low-temperature measurements reveal quantized conductance due to subband splitting, a characteristic of 1D systems. We relate these features to device performance at room-temperature. In particular, the threshold voltage versus nanowire width is explained by direct observation of quantization of the first sub-band, i.e., band gap widening. An analytical effective mass quantum well model is able to describe the observed band structure. The results reveal a compromise between reliability, i.e., V{sub T} variability, and on-current, through the mean free path, in the choice of the channel material.

  7. Gate Last Indium-Gallium-Arsenide MOSFETs with Regrown Source-Drain Regions and ALD Dielectrics

    Science.gov (United States)

    Carter, Andrew Daniel

    III-V-based MOSFETs have the potential to exceed the performance of silicon-based MOSFETs due to the semiconductor's small electron effective mass. Modern silicon-based MOSFETs with 22 nm gate lengths utilize high-k gate insulators and non-planar device geometries to optimize device performance. III-V HEMT technology has achieved similar gate lengths, but large source-drain access resistances and the lack of high-quality gate insulators prevent further device performance scaling. Sub-22 nm gate length III-V MOSFETs require metal-semiconductor contact resistivity to be less than 1 ohm-micron squared, gate insulators with less than 1 nm effective oxide thickness, and semiconductor-insulator interface trap densities less than 2E12 per square centimeter per electron volt. This dissertation presents InGaAs-based III-V MOSFET process flows and device results to assess their use in VLSI circuits. Previous III-V MOSFET results focused on long (>100 nm) gate lengths and ion implantation for source-drain region formation. Scaling III-V MOSFETs to shorter gate lengths requires source-drain regions that have low sheet resistance, high mobile charge densities, and low metal-semiconductor contact resistance. MBE- and MOCVD-based raised epitaxial source-drain regrowth meet these requirements. MBE InAs source-drain regrowth samples have shown 0.5 to 2 ohm-micron squared metal semiconductor contact resistivities. MOCVD InGaAs source-drain regrowth samples have shown resistance to InGaAs MOSFETs. Gate insulators on III-V materials require large conduction band offsets to the channel, high dielectric permittivities, and low semiconductor-insulator interface trap densities. An in-situ hydrogen plasma / trimethylaluminum treatment has been developed to lower the gate semiconductor-insulator interface trap density. This treatment, done immediately before gate insulator deposition, has been shown to lower MOS capacitor interface trap densities by more than a factor of two. Devices using gate-first MBE regrowth, gate-last MBE regrowth, and gate-last MOCVD regrowth were fabricated and resulting devices characterized. 65 nm gate length gate-first MBE regrowth devices employing a 2.2 nm EOT Al 2O3 gate insulator show peak transconductances of 0.3 mS/micron at 1 V Vds. Gate-first FET performance scaling is limited by processed-induced damage and ungated access regions. 64 nm gate length gate-last MBE regrowth devices employing a 1.21 nm EOT Al2O 3 / HfO2 bi-layer gate insulator show peak transconductances of 1.4 mS/micron at 0.5 V Vds. Other gate-last MBE samples had long channel subthreshold swings as low as 117 mV/dec. 48 nm gate length gate-last MOCVD MOSFETs employing a 0.8 nm EOT HfO2 gate insulator and digital channel etching show peak transconductances of 2 mS/micron at 0.5 V Vds, with long channel devices having 97 mV/dec subthreshold swing.

  8. Atomistic simulation studies of iron sulphide, platinum antimonide and platinum arsenide

    CSIR Research Space (South Africa)

    Ngoepe, PE

    2005-09-01

    Full Text Available The authors present the results of atomistic simulations using derived interatomic potentials for the pyrite-structured metal chalcogenides FeS2, PtSb2 and PtAs2. Structural and elastic constants were calculated and compared with experimental...

  9. Quasilinear quantum magnetoresistance in pressure-induced nonsymmorphic superconductor chromium arsenide.

    Science.gov (United States)

    Niu, Q; Yu, W C; Yip, K Y; Lim, Z L; Kotegawa, H; Matsuoka, E; Sugawara, H; Tou, H; Yanase, Y; Goh, Swee K

    2017-06-05

    In conventional metals, modification of electron trajectories under magnetic field gives rise to a magnetoresistance that varies quadratically at low field, followed by a saturation at high field for closed orbits on the Fermi surface. Deviations from the conventional behaviour, for example, the observation of a linear magnetoresistance, or a non-saturating magnetoresistance, have been attributed to exotic electron scattering mechanisms. Recently, linear magnetoresistance has been observed in many Dirac materials, in which the electron-electron correlation is relatively weak. The strongly correlated helimagnet CrAs undergoes a quantum phase transition to a nonmagnetic superconductor under pressure. Here we observe, near the magnetic instability, a large and non-saturating quasilinear magnetoresistance from the upper critical field to 14 T at low temperatures. We show that the quasilinear magnetoresistance may arise from an intricate interplay between a nontrivial band crossing protected by nonsymmorphic crystal symmetry and strong magnetic fluctuations.

  10. Digital Logic and Reconfigurable Interconnects Using Aluminum Gallium Arsenide Electro-Optic Fredkin Gates

    Science.gov (United States)

    1994-06-01

    growth and characte . Anthony Ticknor, of Lockheed, was responsbe for the beam propagation method computer program. I have also enjoyed valuable...134. R. J. Pressley , ed., Handbook of Lasers With Selected Data on Optical Technolgav, CRC Press, Cleveland, OH, 1971. 135. A. Kurnar and T. P

  11. pH dependent photophysical studies of new europium and terbium complexes of tripodal ligand: Experimental and semiempirical approach

    Energy Technology Data Exchange (ETDEWEB)

    Akbar, Rifat [Department of Chemistry, Sant Longowal Institute of Engineering & Technology, Longowal, Punjab 148106 (India); Baral, Minati [Department of Chemistry, National Institute of Technology Kurukshetra, Haryana 136119 (India); Kanungo, B K, E-mail: b.kanungo@gmail.com [Department of Chemistry, Sant Longowal Institute of Engineering & Technology, Longowal, Punjab 148106 (India)

    2015-11-15

    The photophysical properties of adduct of a novel nonadentate tripodal ligand, 5,5′-(2-(((8-hydroxyquinolin-5-yl)methylamino)methyl)-2-methylpropane-1, 3-diyl)bis(azanediyl)bis(methylene diquinolin-8-ol, (TAME5OX), with Eu{sup 3+} and Tb{sup 3+} metal ions have been probed for photonics applications. The absorption spectroscopy of these complexes show remarkable spectral changes due to characteristic lanthanide transitions, which support the use of TAME5OX as a sensitive optical pH based sensor to detect Ln{sup 3+} metal ions in biological systems. In addition, these complexes have also been shown to exhibit strong green fluorescence allowing simultaneous sensing within the visible region under physiological pH in competitive medium for both Eu{sup 3+} and Tb{sup 3+} ions. The intense fluorescence from these compounds were revealed to intermittently get quenched under acidic as well as basic conditions due to the photoinduced intramolecular electron transfer from excited 8-hydroxyquinoline (8-HQ) moiety to metal ion, just an opposite process. This renders these compounds the OFF–ON–OFF type of pH-dependent fluorescent sensor. The thermodynamic stability and aqueous coordination chemistry of the chelator with the said lanthanide ions have also been probed by potentiometric, UV–visible and fluorescence spectrophotometric method. TAME5OX has been found to form two protonated complexes [Ln(H{sub 5}L)]{sup 5+} and [Ln(H{sub 4}L)]{sup 4+} below pH 2.5 with both metal ions, which consecutively deprotonates through one proton process with rise of pH. The formation constants (log β{sub 11n}) of neutral complexes have been determined to be 33.51 and 32.16 with pLn (pLn=−log[Ln{sup 3+}]) values of 16.14 and 19.48 for Eu{sup 3+} and Tb{sup 3+} ions, respectively, calculated at pH 7.4, indicating TAME5OX is a good lanthanide synthetic chelator. The emission lifetimes of the Eu{sup 3+} and Tb{sup 3+} complexes recorded in D{sub 2}O and H{sub 2}O suggest the presence of water molecules in the first coordination sphere of the metal ions. NMR titrations were carried out to determine the stoichiometry of chelates. The complexe's coordination geometries were optimized by using PM7 as sparkle/PM7 model. The theoretical electronic behavior was evaluated to support the experimental findings, based on ZINDO/S methodology at configuration interaction with single excitations (CIS) level. These results emphasize the capability of the use of the theoretical models in prediction of geometries and all other calculations of compounds containing lanthanide ions and create new interesting possibilities for the design in-silico of novel and highly efficient lanthanide–organic edifice. - Highlights: • Photophysical behavior of Eu{sup 3+} and Tb{sup 3+} complexes of TAME5OX has been investigated. • This tripodal ligand forms thermodynamically stable Ln{sup 3+} complexes. • These compounds exhibit strong green fluorescence under physiological pH. • Green fluorescence gets quenched under acidic and basic conditions, due to PET process. • This renders these compounds the OFF–ON–OFF type of pH-dependent fluorescent sensors.

  12. Visible photoluminescence in polycrystalline terbium doped aluminum nitride (Tb:AlN) ceramics with high thermal conductivity

    Science.gov (United States)

    Wieg, A. T.; Kodera, Y.; Wang, Z.; Imai, T.; Dames, C.; Garay, J. E.

    2012-09-01

    Thermal management continues to be one of the major challenges in the development of high powered light sources such as solid state lasers. In particular, the relatively low thermal conductivity of standard photoluminescent (PL) materials limits the overall power output and/or duty cycle. We present a method based on current activated pressure assisted densification for the fabrication of high thermal conductivity PL materials: rare earth doped polycrystalline bulk aluminum nitride. Specifically, the ceramics are translucent and are doped with Tb3+, allowing for emission in the visible. Remarkably, the ceramics have a room temperature thermal conductivity of 94 W/(m K) which is almost seven times higher than that of the state of the art host material, Nd-doped yttrium aluminum garnet. These light emitting properties coupled with very high thermal conductivity should enable the development of a wide variety of more powerful light sources.

  13. Preparation of extractive resins for producing terbium-161; Preparacion de resinas extractivas para produccion de terbio-161

    Energy Technology Data Exchange (ETDEWEB)

    De la Cruz B, C. C.; Monroy G, F. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)], e-mail: fabiola.monroy@inin.gob.mx

    2009-10-15

    This paper presents the development of a methodology for extractive resins preparation to base of HDEHP, which allows to separation of Tb from Gd generating an own technology of preparation of these resins. The study included the extractive resins preparation from 6 different supports: kieselguhr Dg, alumina, red volcanic rock, chiluca, quarry and fluorite; two treatment types of of supports and varied concentrations of HDEHP extractant (di(2-etil hexyl) orthophosphoric acid), in order to determine which resin has improved efficiency of Gd and Tb separation, and radionuclide purity of {sup 161}Tb. Resins were prepared to base of kieselguhr to determine the most appropriate silicon deposition process. Two silicon deposition treatments were realized: treatment I , by contact with silicon deposition solution (dimethyldichlorosilane / heptane 1:30) and treatment II by contact with vapors of dimethyldichlorosilane in vacuum. The extractant retention was carried out to different concentrations of HDEHP / acetone: 1:4, 1:8, 1:15, 1:20, 1:30 and 1:40. According to the results, there is not direct relation of HDEHP concentration used in extractive resins preparation to base of kieselguhr over the efficiency of Gd and Tb separation and of radionuclide purity of {sup 161}Tb. The effect of support in the efficiency of Gd and Tb separation was studied to prepare resins with the supports kieselguhr, alumina, quarry, chiluca, volcanic rock and fluorite, using the silicon deposition treatment II for the supports and a concentration of HDEHP / acetone 1:20, for extractant retention. Only resins based on kieselguhr could separate to Gd from Tb quantitatively, the resin at a concentration of HDEHP / Acetone 1:20 was the best results obtained in Gd and Tb separation, achieving a separation efficiency greater than 90% and a radionuclide purity higher than 99%. (Author)

  14. Synthesis and Characterization of Europium(III) and Terbium(III) Complexes: An Advanced Undergraduate Inorganic Chemistry Experiment

    Science.gov (United States)

    Swavey, Shawn

    2010-01-01

    Undergraduate laboratories rarely involve lanthanide coordination chemistry. This is unfortunate in light of the ease with which many of these complexes are made and the interesting and instructive photophysical properties they entail. The forbidden nature of the 4f transitions associated with the lanthanides is overcome by incorporation of…

  15. Sensitized green emission of terbium with dibenzoylmethane and 1, 10 phenanthroline in polyvinyl alcohol and polyvinyl pyrrolidone blends

    Science.gov (United States)

    Kumar, Brijesh; Kaur, Gagandeep; Rai, S. B.

    2017-12-01

    Tb doped polyvinyl alcohol: polyvinyl pyrrolidone blends with dibenzoylmethane (DBM) and 1, 10 Phenanthroline (Phen) have been prepared by solution cast technique. Bond formation amongst the ligands and Tb3 + ions in the doped polymer has been confirmed employing Fourier Transform Infrared (FTIR) techniques. Optical properties of the Tb3 + ions have been investigated using UV-Vis absorption, excitation and fluorescence studies excited by different radiations. Addition of dimethylbenzoate and 1, 10 Phenanthroline to the polymer blend increases the luminescence from Tb3 + ions along with energy transfer from the polymer blend itself. Luminescence decay curve analysis affirms the non-radiative energy transfer from DBM and Phen to Tb3 + ions, which is identified as the reason behind this enhancement. The fluorescence decay time of PVA-PVP host decreases from 6.02 ns to 2.31 ns showing an evidence of energy transfer from the host blend to the complexed Tb ions. Similarly the lifetime of DBM and Phen and both in the blend reduces in the complexed system showing the feasibility of energy transfer from these excited DBM and Phen to Tb3 + and is proposed as the cause of the above observations. These entire phenomena have been explained by the energy level diagram.

  16. A Terbium Metal-Organic Framework for Highly Selective and Sensitive Luminescence Sensing of Hg2+Ions in Aqueous Solution.

    Science.gov (United States)

    Xia, Tifeng; Song, Tao; Zhang, Gege; Cui, Yuanjing; Yang, Yu; Wang, Zhiyu; Qian, Guodong

    2016-12-19

    A series of isomorphic lanthanide metal-organic frameworks (MOFs) Ln(TATAB)⋅(DMF) 4 (H 2 O)(MeOH) 0.5 (LnTATAB, Ln=Eu, Tb, Sm, Dy, Gd; H 3 TATAB=4,4',4''-s-triazine-1,3,5-triyltri-p-aminobenzoic acid) have been solvothermally synthesized and structurally characterized. Among these MOFs, TbTATAB exhibits good water stability and a high fluorescence quantum yield. Because mercury ions (Hg 2+ ) have a high affinity to nitrogen atoms, and the space between multiple nitrogen atoms from triazine and imino groups is suitable for interacting with Hg 2+ ions, TbTATAB shows highly selective and sensitive detection of Hg 2+ in aqueous solution with a detection limit of 4.4 nm. Furthermore, it was successfully applied to detect Hg 2+ ions in natural water samples. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Optimization and Characterization of Indium Arsenide Quantum Dots for Application in III-V Material Solar Cells

    Science.gov (United States)

    Podell, Adam P.

    In this work, InAs quantum dots grown by organometallic vapor-phase epitaxy (OMVPE) are investigated for application in III - V material solar cells. The first focus is on the opti- mization of growth parameters to produce high densities of uniform defect-free quantum dots via growth on 2" vicinal GaAs substrates. Parameters studied are InAs coverage, V/III ratio and growth rate. QDs are grown by the Stranski-Krastanov (SK) growth mode on (100) GaAs substrates misoriented toward (110) or (111) planes with various degrees of misorientation from 0° to 6°. Atomic force microscopy results indicated that as misorientation angle increased toward(110),critical thickness for quantum dot formation increased with theta c =1.8ML,1.9ML and 2.0 ML corresponding to 0°, 2° and 6°, respectively. Results for quantum dots grown on (111) misoriented substrates indicated, on average, that higher densities of quantum dots were achieved, compared with similar growths on substrates misoriented toward (110). Most notably, a stable average number density of 8 x 1010cm -2 was observed over a range of growth rates of 0.1ML/s - 0.4ML/s on (111) misoriented substrates compared with a decreasing number density as low as 2.85 x 1010cm -2 corresponding to a growth rate of 0.4ML/s grown on (110) misoriented substrates. p-i-n solar cell devices with a 10-layer quantum dot super- lattice imbedded in the i-region were also grown on (100) GaAs substrates misoriented 0°, 2° and 6° toward (110) as well as a set of devices grown on substrates misoriented toward (111). Device results showed a 1.0mA/cm2 enhancement to the short-circuit current for a v 2° misoriented device with 2.2 ML InAs coverage per quantum dot layer. Spectral response measurements were performed and integrated spectral response showed sub-GaAs bandgap short-circuit contribution which increased with increasing InAs coverage in the quantum dot layers from 0.04mA/cm2/ML, 0.28mA/cm2/ ML and 0.19mA/cm2/ML corresponding to 0°, 2° and 6° misorientation, respectively. The second focus of this study was on the OMVPE growth of InAs quantum dots in a large-area commercial reactor. Quantum dot growth parameters require careful balancing in the large-scale reactor due to different thermodynamic and flow profiles compared with smaller- area reactors. The goal of the work was to control the growth process in order to produce high densities of uniform quantum dots for inclusion in double and triple junction III - V material solar cells. Initial growth proved unsuccessful due to lack of familiarity with the process but through balancing of injector flows of alkyl gasses, coherent and optically active quantum dots were able to first be formed at low densities (0.5 - 0.7 x 1010 cm-2). Further optimization included increased quantum dot growth times leading to number densities in the (2.1-2.7x10 10cm-2 with improved optical performance as measured by photoluminescence (PL) spectroscopy. Finally, an investigation of GaAs spacer layer thickness for improved optical coupling was performed, indicating that a combined low temperature and high temperature GaAs thickness of 9.3nm led to strong PL intensity indicating good optical coupling of QD layers. Ge/(In)GaAs double junction solar cells were grown and fabricated with and without quantum dots in the (In)GaAs cell to investigate the effect of quantum dot inclusion on device performance. AM 0 measurements showed an average increase of 1.0mA/cm 2 in short-circuit current for these devices. Integrated spectral response measurements revealed a contribution to short-circuit current of 0.02mA/cm2/QDlayer which is consistent with reports seen in literature. The current improvement for the double junction solar cells motivated the investigation of quantum dot inclusion in the (In)GaAs junction of a Ge/(In)GaAs/InGaP triple junction solar cell. AM0 measurements on these cells did not reveal any increase in current for quantum dot enhanced devices over a baseline device. Integrated spectral response for each junction revealed an increase of 0.3mA/cm 2 in current for the middle junction and the top junction, respectively, compared with baseline results for these junctions, but also that the InGaP top junction was current limiting. This potentially is due to poor material quality in the InGaP junction as a result of quantum dot inclusion in the junction beneath it or to strain effects re- sulting from quantum dot inclusion. This current limiting nature of the top junction may have led to a reduced efficiency for quantum dot devices compared with a baseline and further opti- mization is required in order increase the efficiency of the quantum dot device compared with a baseline device.

  18. Thin films of gallium arsenide on low-cost substrates. Final report, July 5, 1976--July 2, 1977

    Energy Technology Data Exchange (ETDEWEB)

    Ruth, R.P.; Dapkus, P.D.; Dupuis, R.D.; Campbell, A.G.; Johnson, R.E.; Manasevit, H.M.; Moudy, L.A.; Yang, J.J.; Yingling, R.D.

    1977-08-01

    The metalorganic chemical vapor deposition (MO-CVD) technique has been applied to the growth of thin films of GaAs and GaAlAs on inexpensive polycrystalline or amorphous substrate materials (glasses, glass-ceramics, alumina ceramics, and metals) for use in fabrication of large-area low-cost photovoltaic device structures. Trimethylgallium (TMG), arsine (AsH/sub 3/), and trimethylaluminum (TMAl) are mixed in appropriate concentrations at room temperature in the gaseous state and pyrolyzed at the substrate, which is heated in a vertical reactor chamber to temperature in the range 600 to 800/sup 0/C, to produce the desired film composition and properties. Of ten candidate low-cost substrates initially identified for investigation, Corning Code 0317 glass and composites of CVD Ge/glass and sputtered Mo/glass were found to be the most satisfactory, the latter eventually serving as a reference substrate against which to compare the performance of other substrates. Single-crystal window-type solar cells, polycrystalline Schottky-barrier cells, and deposited-junction polycrystalline cells have been grown, fabricated, and characterized. Epitaxial GaAlAs/GaAs p-n junction cells with thin (approx. 500A) Ga/sub 0/ /sub 2/Al/sub 0/ /sub 8/As windows and GaAs:Zn - GaAs:Se junctions were made with AMO efficiencies as high as 12.8 percent with no AR coating. Schottky barrier cells with efficiencies of 2.25 percent AMO (no AR coating) have been made on n/n polycrystalline GaAs structures on Mo/glass composite substrates, with short-circuit current densities up to 12.5 mA/cm/sup 2/. Also, results of analyses of material and processing costs associated with fabrication of thin-film GaAlAs/GaAs solar cells by the MO-CVD process are discussed.

  19. Gallium arsenide-based apertured vertical-cavity surface-emitting lasers and microcavity light emitting diodes

    Science.gov (United States)

    Chen, Hao

    A new design approach for all all-epitaxial index-guiding VCSEL fabrication with self-aligned current and optical confinement is proposed and demonstrated using MBE regrowth. The epitaxial regrowth approach has significant advantages over oxide confinement due to elimination of strain, aperture size controllability across wafer, and the aperture size controllability from wafer to wafer. A simple microcavity model is used to demonstrate the lateral mode confinement effect obtained by blue-shifting resonance frequency in the lateral regions of cavity, which leads to the new design concept for engineering waveguided VCSELs by modulation of the optical cavity length through MBE regrowth over selectively etched surface structures. The lithographically-defined aperture can be scaled to submicron level---simplifying its post-growth processing and thus making it easier to incorporate additional structural modifications (such as air-gap DBR VCSELs) for improved device performance. Enabling techniques, which include various surface protection and current blocking methods, have been developed in this work for the epitaxial regrowth approach. In-situ low-temperature-grown InAs capping is used to protect the first-step-grown wafer from standard chemical process, and is gently evaporated inside growth chamber before regrowth. Various current blocking structures have been investigated including reversed p-n junction assisted with resistive LT material, buried tunnel junction, and implanted current aperture. Excellent current confinement is achieved, which consequently leads to the first demonstration of GaAs-based air-gap DBR VCSELs and buried tunnel junction (BTJ) VCSELs. A novel fabrication process of air-gap/GaAs DBR mirrors has been realized by selectively removing AlGaAs sacrificial layers. Air-gap/GaAs DBR mirrors have the highest achievable refractive index contrast. This allows Air-gap/GaAs DBR mirrors to achieve desirable features, including a higher reflectivity, wider reflection stopband, lower diffraction loss, and smaller penetration depth than conventional DBR mirrors. An electrically-pumped MBE-regrown 980 nm VCSELs using p-type air-gap DBRs is demonstrated with a low threshold current density of 764 A/cm2 at room temperature under continuous-wave operation. (Abstract shortened by UMI.)

  20. Formation of indium arsenide atomic wires on the In/Si(111)-4 × 1 surface

    Science.gov (United States)

    Guerrero-Sánchez, J.

    2017-03-01

    Density functional theory calculations have been applied to describe the formation of InAs atomic-size wires on the In/Si(111)-4 × 1 surface. Two different coverages, ¼ ML and ½ ML, were considered. We have taken in to consideration different high symmetry sites for As adsorption. At ¼ ML coverage, in the energetically stable configuration, As and In atoms form atomic wires. Upon increasing the coverage up to ½ ML of As, a pair of InAs atomic wires are formed. Surface formation energy calculations help to clarify the stability ranges of these structures: for arsenic poor conditions the stable configuration corresponds to the In/Si(111)-4 × 1 surface (with no As atoms). Increasing the arsenic content, for intermediate to rich As conditions, results in the formation of an InAs wire. At the arsenic rich limit, the formation of two InAs wires is favorable. The InAs wires are highly symmetric, and charge density distributions and projected density of states show the covalent character of the Insbnd As bonds of the wire. These results demonstrate that the In/Si(111)-4 × 1 surface may be used as a substrate to growth quasi-unidimensional InAs wires.

  1. Boron, bismuth co-doping of gallium arsenide and other compounds for photonic and heterojunction bipolar transistor devices

    Science.gov (United States)

    Mascarenhas, Angelo

    2015-07-07

    Isoelectronic co-doping of semiconductor compounds and alloys with acceptors and deep donors is sued to decrease bandgap, to increase concentration of the dopant constituents in the resulting alloys, and to increase carrier mobilities lifetimes. For example, Group III-V compounds and alloys, such as GaAs and GaP, are isoelectronically co-doped with, for example, B and Bi, to customize solar cells, and other semiconductor devices. Isoelectronically co-doped Group II-VI compounds and alloys are also included.

  2. Boron, bismuth co-doping of gallium arsenide and other compounds for photonic and heterojunction bipolar transistor devices

    Energy Technology Data Exchange (ETDEWEB)

    Mascarenhas, Angelo

    2017-08-01

    Isoelectronic co-doping of semiconductor compounds and alloys with acceptors and deep donors is used to decrease bandgap, to increase concentration of the dopant constituents in the resulting alloys, and to increase carrier mobilities lifetimes. For example, Group III-V compounds and alloys, such as GaAs and GaP, are isoelectronically co-doped with, for example, B and Bi, to customize solar cells, and other semiconductor devices. Isoelectronically co-doped Group II-VI compounds and alloys are also included.

  3. Optical and Electrical Characterization of Melt-Grown Bulk Indium Gallium Arsenide and Indium Arsenic Phosphide Alloys

    Science.gov (United States)

    2011-03-01

    Russia semiconductor web: http://www.ioffe.ru/ SVA /NSM/Semicond/ 119 6.4 Refractive Index Measurements Refractive index measurements on wafer shaped...coefficient”, Appl. Phys. Lett. 66 (16) p2101-2103, (1995). 76. http://www.ioffe.ru/ SVA /NSM/Semicond 77. Sadao Adachi, “Band gaps and refractive indices

  4. Ohmic contact formation process on low n-type gallium arsenide (GaAs) using indium gallium zinc oxide (IGZO)

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Seong-Uk [Samsung-SKKU Graphene Center and School of Electronics and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Product and Test Engineering Team, System LSI Division, Samsung Electronics Co., Ltd, Yongin 446-711 (Korea, Republic of); Jung, Woo-Shik [Department of Electrical Engineering, Stanford University, Stanford, CA 94305 (United States); Lee, In-Yeal; Jung, Hyun-Wook; Kim, Gil-Ho [Samsung-SKKU Graphene Center and School of Electronics and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Park, Jin-Hong, E-mail: jhpark9@skku.edu [Samsung-SKKU Graphene Center and School of Electronics and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2014-02-01

    Highlights: • We propose a method to fabricate non-gold Ohmic contact on low n-type GaAs with IGZO. • 0.15 A/cm{sup 2} on-current and 1.5 on/off-current ratio are achieved in the junction. • InAs and InGaAs formed by this process decrease an electron barrier height. • Traps generated by diffused O atoms also induce a trap-assisted tunneling phenomenon. - Abstract: Here, an excellent non-gold Ohmic contact on low n-type GaAs is demonstrated by using indium gallium zinc oxide and investigating through time of flight-secondary ion mass spectrometry, X-ray photoelectron spectroscopy, transmission electron microscopy, J–V measurement, and H [enthalpy], S [entropy], Cp [heat capacity] chemistry simulation. In is diffused through GaAs during annealing and reacts with As, forming InAs and InGaAs phases with lower energy bandgap. As a result, it decreases the electron barrier height, eventually increasing the reverse current. In addition, traps generated by diffused O atoms induce a trap-assisted tunneling phenomenon, increasing generation current and subsequently the reverse current. Therefore, an excellent Ohmic contact with 0.15 A/cm{sup 2} on-current density and 1.5 on/off-current ratio is achieved on n-type GaAs.

  5. Infrared focal plane array based on gallium indium arsenideGaInAs/InP quantum well infrared photodetectors

    Science.gov (United States)

    Jiang, Jutao

    There are many military and commercial applications for Infrared (IR) focal plane arrays (FPAs). Today, most IR FPAs are made with intrinsic HgCdTe (MCT) photodetectors. IR photodetectors based on intersubband-transition mechanism, such as quantum well infrared photodetectors (QWIPs), possess many advantages by comparing with MCTs. The goal of this research is to develop IR FPAs based on these novel QWIPS. First, the relevant theoretical basis for intersubband n-type QWIP and infrared imaging array will be presented. Next, the material growth and characterization using low-pressure metalorganic chemical vapor deposition technique will be discussed in detail. Developing a FPA fabrication process is the most important part of this work and it will be given in detail. The important technologies and equipment involved in the fabrication process will also be described. The FPA sample is bonded to a 256 x 256 Litton readout integrated circuit chip for testing. Important aspects related to the Litton chip will also be discussed. Finally, the infrared FPA testing and results will be described in detail. Additionally, to prepare for our long-term goal---monolithic integration of focal plane array with Silicon based readout circuit, the growth technique of QWIP on Si substrate is also studied in this work. The culmination of this work includes many "best" and "first" reported results: a record high detectivity of QWIP grown on Si substrate and the first reported long-wavelength IR FPA based on Al-free corrugated InGaAs/InP QWIPs.

  6. A Novel Approach to Modeling the Effects of Radiation in Gallium-Arsenide Solar Cells Using Silvaco's ATLAS Software

    National Research Council Canada - National Science Library

    Crespin, Aaron

    2004-01-01

    The effects of radiation in GaAs solar cells has been extensively researched and the results of numerous investigation have yielded a considerable amount of information about the degradation in irradiated solar cells...

  7. Physicochemical conditions for the stability of manganese-doped nanolayers of gallium arsenide and its iso-electronic analogues

    Directory of Open Access Journals (Sweden)

    Yu. V. Terenteva

    2015-03-01

    Full Text Available In this paper research of stability of nanolayers of manganese doped materials of AIIIBV and AIIBIVСV2 types holding much promise as spintronic semiconductor compounds is described. The method of non-local density functional has been applied to calculate bonding energies {εij (r} in atomic pairs for structures of AIIIBV and AIIBIVСV2 types and for MnAs. According to the calculations of internal energy, entropy and free energy of Helmholtz (Т = 298К, in the context of used models, addition of manganese to the arsenide’s AIIIBV and AIIBIVСV2 nanolayers affects its stability in different ways depending on its morphology and substitution mode. However, a critical instability in nanofilm leading to the tendency of growing of a new phase germ may be formed under any manganese concentrations. This leads to deterioration of electrophysical parameters of magnetic semiconductor compounds that is agreed with experimental data.

  8. The galium arsenide (GaAs laser radiation in the radial nerve regeneration submitted to secundary surgical repair

    Directory of Open Access Journals (Sweden)

    Daniel Roulim Stainki

    1998-01-01

    Full Text Available Vinte e quatro cães adultos, sem raça definida, foram separados em quatro grupos e submetidos a neurotomia bilateral do nervo radial, em nível do terço distal do úmero e, 21 dias após, sofreram anastomose epineural secundária, término-terminal. Nos 10 dias subseqüentes à neuroanastomose, o membro esquerdo de todos os cães foi irradiado com laser arseneto de gálio no intuito de investigar sua influência na regeneração do nervo. O membro contralateral serviu como testemunha. A recuperação funcional foi verificada através da característica da deambulação, testes de sensibilidade e avaliação motora. Foram efetuadas biópsias bilaterais, na região de anastomose, aos 10 dias (grupo A, 30 dias (grupo B, 60 dias (grupo C e 90 dias (grupo D após a reconstituição cirúrgica, para estudo morfológico em microscopia óptica. A proliferação de tecido conjuntivo na linha de anastomose é a complicação mais séria no processo de regeneração nervosa. A radiação laser diminui a intensidade da resposta inflamatória ao fio de sutura, mas pode contribuir para a formação de neuroma mais exuberante.

  9. Terahertz sources based on intracavity parametric frequency down-conversion using quasi-phase-matched gallium arsenide

    Science.gov (United States)

    Schaar, Joseph Eden

    Three types of micro-structured GaAs have been used to generate THz radiation by parametric frequency down-conversion: (i) orientation-patterned GaAs, OP-GaAs, (ii) optically contacted GaAs wafers, OC-GaAs, and (iii) diffusion-bonded GaAs plates, DB-GaAs. THz frequencies between 0.5--3.5 THz were generated using the various GaAs samples. THz average powers as large as 1 mW generated from a pump power of 8.5 W, corresponding to an optical-to-THz power conversion efficiency of 1.2 x 10-4, were observed by placing the GaAs inside a doubly resonant synchronously pumped optical parametric oscillator. The quantum conversion efficiencies were as large as 1.2%. The parametric conversion efficiency for THz generation is inherently small since the ratio of the THz and optical frequencies is small. Difference-frequency generation (DFG) between the intracavity signal and idler waves generated the THz radiation. The doubly resonant optical parametric oscillator (DRO) resonated the signal and idler pulses, with picosecond-scale pulse widths and greater than 50 W of average power in each wave at lambda ≈ 2 microm. The frequency splitting between the signal and idler waves was tuned by adjusting the temperature of the DRO gain material, periodically poled LiNbO3 (PPLN). The bandwidths of the resonant signal and idler waves were between 100--200 GHz since the OPO process used Type-II QPM where the signal and idler fields were orthogonally polarized. Designs for maximizing the THz power for both the singly and doubly resonant OPOs were described yielding expressions for the THz, signal, idler, and pump powers in terms of crystal length, optical beam size, and optical absorption coefficient. A THz-cascading process was observed during which the THz wave was amplified in the GaAs crystal by multiple pairs of infrared waves. Quantum-mechanically, THz cascading corresponds to the generation of multiple THz photons from a single infrared photon. For proper designs of the OPO-cavity losses and compensation of the dispersion of the intracavity PPLN and GaAs crystals, quantum conversion efficiencies far greater than 100% can be achieved. An electronic feedback system was developed to stabilize the intracavity power of the DRO as well as the generated THz power. Locked operation lasted as long as 30 minutes limited only by the thermal expansion of the optical table and the finite expansion of the PZT element. A passive thermo-optic feedback effect also stabilized the DRO power, where absorbed optical power in the GaAs deposited heat leading to a rise in the refractive index of the GaAs. A characterization of this thermo-optic effect in terms of a negative feedback system has been described. Independently varying the signal and idler cavity lengths in the DRO led to the discovery of certain cavity-length regimes where oscillation may not occur as well as cavity-length regimes where the temporal overlap of the signal and idler pulses is maximized. A numerical simulation was developed modeling the temporal features of the DRO. The results of the numerical simulations agreed well with experimental measurements. The temporal overlap of the pulses was calculated for several values of parametric gain and DRO round-trip loss, and operating regimes where the pulses were symmetric and the temporal overlap was nearly maximized were identified. An approach to re-time the pulses using a pair of intracavity birefringent crystals, such that the temporal overlap is maximized, is described. Fluctuations of the intracavity power of the synchronously pumped optical parametric oscillator were measured. Over certain cavity-length detunings, the fluctuations were aperiodic with microsecond-scale transients. At longer cavity-length detunings, the fluctuations were periodic (and nearly sinusoidal) with fundamental frequencies between 200--700 kHz. The numerical simulations reproduced the fluctuations and showed that the minimum set of physical effects necessary to produce the fluctuations are three-wave mixing, group-velocity mismatch, and self-phase-modulation of the resonant wave in the case of a singly resonant oscillator. The fluctuations were also observed in the doubly resonant OPO both experimentally and in the results of the numerical simulations. Operating regimes that evade the appearance of these oscillations were identified. (Abstract shortened by UMI.)

  10. Experimental Determination of Quantum and Centroid Capacitance in Arsenide-Antimonide Quantum-Well MOSFETs Incorporating Nonparabolicity Effect

    Science.gov (United States)

    2011-05-01

    14]. While extracting the effective mass from SdH oscillations, the background magnetoresistance was corrected as follows. The envelope of maxima... magnetoresistance that was subtracted from the measured ρXX. Fig. 10 shows the periodic SdH oscillations in ΔρXX/ρ0 (after removing the background...demonstration of metal gate plasmon screening and channel strain engineering in high-κ/metal-gate CMOS transistors, and the investigation of the

  11. Growth of thick lattice mismatched layers of gallium indium arsenic antimonide on gallium arsenide substrates from quaternary melts

    Science.gov (United States)

    Kumar, Anika

    Compound semiconductors (III-V, II-VI, IV-IV) with variable band gaps are desirable to obtain high performance electronic and optoelectronic devices. Currently, lattice mismatched epilayers of variable bandgap semiconductors are grown on commercially available binary substrates by non-equilibrium growth techniques (such as MOCVD and MBE) using a variety of buffer layer schemes. Although thick epilayers are observed to result in lower dislocation densities even for large lattice mismatches, achieving thick epitaxial layers remains a challenge due to the slow growth rates of MBE and MOCVD techniques that are commonly used in the industry. Hence, there is a necessity for devising a technique that will grow thick layers of lattice mismatched compounds at high growth rates. In this research, we have demonstrated a new quaternary melt thermochemistry to grow thick layers of uniform composition of desired ternaries and quaternaries on commercially available binary substrates (such as GaAs). Using this approach, we have achieved the growth of thick (˜ 100 mum) uniform composition GaxIn1-xAs, InxGa1-xSb yAs1-y and InAs ySb1-y layers on GaAs substrate. The growth rates achieved in our growth experiments are significantly higher than any other traditional epitaxial growth process. One of the interesting features observed in our growth experiments is the occurance of a compositionally graded quaternary buffer layer between the substrate and the final layer (of uniform composition). This is found to efficiently relieve misfit strain and lead to lower dislocation densities in the epilayers. It is important to point out that no specific efforts were made to change growth conditions (during epi-growth) to compositionally grade the buffer layers, making this growth scheme extremely simple to implement for large scale applications. One of the key achievements of this work is the growth of thick In xGa1-xAs ySb1-y layers of constant composition with cut off wavelength of 10 mum on GaAs substrates. The dislocation densities were found to be as low as 7 x 105 cm -2 for a lattice mismatch of 13.08% which is considerable less than any reported value for similar mismatches. The layers had a room temperature electron mobility as high as 1.4 x 104 cm2/Vs and carrier concentration of 4.2 x 1016 cm-3 has been achieved indicating the high quality of the grown epilayers and potential applications for infra-red detectors. Transmission electron microscopy studies have been used to investigate the interfacial and crystalline quality of the epilayers. It is observed that the dissolution of GaAs by the InSb melt leads to the delineation of the (111) family of planes. Twin ning is also observed within the epilayer. These observations have helped us arrive at a model for the growth mechanism and the explanation of the polycrystallinity of the epilayer.

  12. Transient Velocity Assessment in Gallium Arsenide, and of Other GaAs Characteristics Related to Device Functions.

    Science.gov (United States)

    1985-10-22

    it is vital that it be amenable to comp- lete control, since the existence of SI GaAs grown by the "undoped LEC" method in a boron nitride crucible is...cation Crystals used or Journal Date (a) Based on Etch Pit Counting Grant at a1. Evian Conf. 1982 50 n LEC (lIP) Mosaic sap display of EPD bonnet at al...34 " 1982 50 n LEC (RP) Mosaic map of EPD Holnes at al. A.P.L. 1983 75 a LEC (HP) Radial line trace of EPD Nmtsusura et al. J.J.A.P. 1983 50 - LEC (HP

  13. Anti-L1CAM radioimmunotherapy is more effective with the radiolanthanide terbium-161 compared to lutetium-177 in an ovarian cancer model

    Energy Technology Data Exchange (ETDEWEB)

    Gruenberg, Juergen; Lindenblatt, Dennis; Cohrs, Susan; Fischer, Eliane [Paul Scherrer Institute, Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Villigen (Switzerland); Dorrer, Holger [Paul Scherrer Institute, Laboratory of Radiochemistry and Environmental Chemistry, Villigen (Switzerland); Zhernosekov, Konstantin [ITG Isotope Technologies Garching GmbH, Garching (Germany); Koester, Ulli [Institut Laue-Langevin, Grenoble (France); Tuerler, Andreas [Paul Scherrer Institute, Laboratory of Radiochemistry and Environmental Chemistry, Villigen (Switzerland); University of Bern, Department of Chemistry and Biochemistry, Berne (Switzerland); Schibli, Roger [Paul Scherrer Institute, Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Villigen (Switzerland); ETH Zurich, Department of Chemistry and Applied Biosciences, Zurich (Switzerland)

    2014-10-15

    The L1 cell adhesion molecule (L1CAM) is considered a valuable target for therapeutic intervention in different types of cancer. Recent studies have shown that anti-L1CAM radioimmunotherapy (RIT) with {sup 67}Cu- and {sup 177}Lu-labelled internalising monoclonal antibody (mAb) chCE7 was effective in the treatment of human ovarian cancer xenografts. In this study, we directly compared the therapeutic efficacy of anti-L1CAM RIT against human ovarian cancer under equitoxic conditions with the radiolanthanide {sup 177}Lu and the potential alternative {sup 161}Tb in an ovarian cancer therapy model. Tb was produced by neutron bombardment of enriched {sup 160}Gd targets. {sup 161}Tb and {sup 177}Lu were used for radiolabelling of DOTA-conjugated antibodies. The in vivo behaviour of the radioimmunoconjugates (RICs) was assessed in IGROV1 tumour-bearing nude mice using biodistribution experiments and SPECT/CT imaging. After ascertaining the maximal tolerated doses (MTD) the therapeutic impact of 50 % MTD of {sup 177}Lu- and {sup 161}Tb-DOTA-chCE7 was evaluated in groups of ten mice by monitoring the tumour size of subcutaneous IGROV1 tumours. The average number of DOTA ligands per antibody was 2.5 and maximum specific activities of 600 MBq/mg were achieved under identical radiolabelling conditions. RICs were stable in human plasma for at least 48 h. {sup 177}Lu- and {sup 161}Tb-DOTA-chCE7 showed high tumour uptake (37.8-39.0 %IA/g, 144 h p.i.) with low levels in off-target organs. SPECT/CT images confirmed the biodistribution data. {sup 161}Tb-labelled chCE7 revealed a higher radiotoxicity in nude mice (MTD: 10 MBq) than the {sup 177}Lu-labelled counterpart (MTD: 12 MBq). In a comparative therapy study with equitoxic doses, tumour growth inhibition was better by 82.6 % for the {sup 161}Tb-DOTA-chCE7 than the {sup 177}Lu-DOTA-chCE7 RIT. Our study is the first to show that anti-L1CAM {sup 161}Tb RIT is more effective compared to {sup 177}Lu RIT in ovarian cancer xenografts. These results suggest that {sup 161}Tb is a promising candidate for future clinical applications in combination with internalising antibodies. (orig.)

  14. CCDC 954774: Experimental Crystal Structure Determination : Dimethylammonium tri-terbium tris(4'-(tetrazol-2-id-5-yl)biphenyl-4-carboxylate) tetrahydroxide trihydrate unknown solvate

    KAUST Repository

    Xue, Dongxu

    2013-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  15. CCDC 959634: Experimental Crystal Structure Determination : octakis(mu~3~-Hydroxo)-undecakis(mu~2~-2-fluorobenzoato)-(N,N-dimethylformamide)-nitrato-hexa-aqua-hexa-terbium

    KAUST Repository

    Guillerm, Vincent

    2014-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  16. CCDC 954773: Experimental Crystal Structure Determination : Dimethylammonium tri-terbium tris(4-(tetrazol-2-id-5-yl)benzoate) tetrahydroxide trihydrate unknown solvate

    KAUST Repository

    Xue, Dongxu

    2013-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  17. CCDC 954775: Experimental Crystal Structure Determination : Dimethylammonium tri-terbium tris(2-fluoro-4-(1H-tetrazol-5-yl)benzoate) tetrahydroxide tetradecahydrate

    KAUST Repository

    Xue, Dongxu

    2013-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  18. CCDC 1411423: Experimental Crystal Structure Determination : catena-[dimethylammonium hexakis(mu-fumarato)-octakis(mu-hydroxo)-hexa-terbium N,N-dimethylformamide solvate hexahydrate

    KAUST Repository

    Assen, Ayalew H.

    2016-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  19. CCDC 1410946: Experimental Crystal Structure Determination : catena-[dimethylammonium tris(mu-naphthalene-1,4-dicarboxylato)-tetrakis(mu-hydroxo)-triaqua-tri-terbium(iii) unknown solvate

    KAUST Repository

    Xue, Dongxu

    2015-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  20. Phthalimides: Supramolecular Interactions in Crystals, Hypersensitive Solution 1H-NMR Dynamics and Energy Transfer to Europium(III and Terbium(III States

    Directory of Open Access Journals (Sweden)

    David J. Williams

    2003-07-01

    Full Text Available Detailed crystal structures and 1H-NMR characteristics of some alkylaminephthalimides, including dendritic polyphthalimides, are reported. These investigations were undertaken in order to obtain a better understanding of the relationship between solid-state supramolecular interactions, their persistence in solution and associated dynamics of magnetically hypersensitive phthalimide aromatic AA'BB'-AA'XX' proton NMR resonances. Some alkylamine phthalimides feature folded molecular geometries, which we attribute to n-π interactions among proximal amine-phthalimide sites; those alkylamine-phthalimides that have no possibility for such interactions feature fully extended phthalimide functionalities. Accordingly, alkylamine phthalimide compounds with folded solid-state geometries feature solvent and temperature dependent hypersensitive AA'BB'-AA'XX' 1H-NMR line profiles, which we attribute to the n-π interactions. Luminescence of Eu3+(5D0 and Tb3+(5D4 states show well defined metal ion environments in their complexes with dendritic phthalimides, as well as relatively weak phthalimide-lanthanide(III interactions.

  1. Analysis of tryptophan at nmoll(-1) level based on the fluorescence enhancement of terbium-gadolinium-tryptophan-sodium dodecyl benzene sulfonate system.

    Science.gov (United States)

    Liu, Shufang; Yang, Jinghe; Wu, Xia; Su, Benyu; Sun, Changxia; Wang, Feng

    2004-10-08

    It is found that Tb(3+) can react with tryptophan (Trp) and sodium dodecyl benzene sulfonate (SDBS), and emits the intrinsic fluoresence of Tb(3+). The fluorescence intensity can be enhanced by La(3+), Gd(3+), Lu(3+), Sc(3+) and Y(3+), among which Gd(3+) has the greatest enhancement. This is a new co-luminescence system. The studies indicate that in the Tb-Gd-Trp-SDBS system, there is both Tb-Trp-SDBS and Gd-Trp-SDBS complexes, and they aggregate together and form a large congeries. The fluorescence enhancement of the Tb-Gd-Trp-SDBS system is considered to originate from intramolecular and intermolecular energy transfers, and the energy-insulating sheath effect of Gd-Trp-SDBS complex. Under the optimum conditions, the enhanced intensity of fluorescence is in proportion to the concentration of Trp in the range from 4x10(-8) to 4x10(-5)moll(-1). The detection limit is 10(-9)moll(-1). The proposed method is one of the most sensitive fluoremetries of Trp.

  2. Preparation, characterization, and properties of PMMA-doped polymer film materials: a study on the effect of terbium ions on luminescence and lifetime enhancement.

    Science.gov (United States)

    Zhang, Hui-Jie; Fan, Rui-Qing; Wang, Xin-Ming; Wang, Ping; Wang, Yu-Lei; Yang, Yu-Lin

    2015-02-14

    Poly(methylmethacrylate) (PMMA) doped with Tb-based imidazole derivative coordination polymer {[Tb(3)(L)(μ(3)-OH)(7)]·H(2)O}(n) (1) (L = N,N'-bis(acetoxy)biimidazole) was synthesized and its photophysical properties were studied. The L'(L' = N,N'-bis(ethylacetate)biimidazole) ligand was synthesized by an N-alkylation reaction process followed by ester hydrolysis to produce ligand L. Polymer 1 and ligand L' have been characterized by (1)H NMR and IR spectroscopy, elemental analysis, PXRD and X-ray single-crystal diffraction. Coordination polymer 1 is the first observation of a CdCl(2) structure constructed with hydroxy groups and decorated by ligand L in lanthanide N-heterocyclic coordination polymers. In the 2D layered structure of 1, each Tb3 metal center is connected with three Tb1 and three Tb2 metal centers by seven hydroxyl groups in different directions, resulting in a six-membered ring. After doping, not only the luminescence intensity and lifetime enhanced, but also their thermal stability was increased in comparison with 1. When 1 was doped into poly(methylmethacrylate) (1@PMMA), polymer film materials were formed with the PMMA polymer matrix (w/w = 2.5%-12.5%) acting as a co-sensitizer for Tb(3+) ions. The luminescence intensity of the Tb(3+) emission at 544 nm increases when the content of Tb(3+) was 10%. The lifetime of 1@PMMA (914.88 μs) is more than four times longer than that of 1 (196.24 μs). All τ values for the doped polymer systems are higher than coordination polymer 1, indicating that radiative processes are operative in all the doped polymer films. This is because PMMA coupling with the O-H oscillators from {[Tb(3)(L)(μ(3)-OH)(7)]·H(2)O}(n) can suppress multiphonon relaxation. According to the variable-temperature luminescence (VT-luminescence) investigation, 1@PMMA was confirmed to be a stable green luminescent polymer film material.

  3. Changing Single-Molecule Magnet Properties of a Windmill-Like Distorted Terbium(III) α-Butoxy-Substituted Phthalocyaninato Double-Decker Complex by Protonation/Deprotonation.

    Science.gov (United States)

    Horii, Yoji; Horie, Yusuke; Katoh, Keiichi; Breedlove, Brian K; Yamashita, Masahiro

    2018-01-16

    Synthesis, structures, and magnetic properties of α-butoxy-substituted phthalocyaninato double-decker complexes Tb(α-obPc)2 (1-) (α-obPc: dianion of 1,4,8,11,15,18,22,25-octa(n-butoxy)phthalocyaninato) with protonated (1H), deprotonated (1[HDBU]), and diprotonated forms (1H2+) are discussed. X-ray analysis was used to confirm the position of the proton in 1H, and it was revealed that the protonation induced asymmetric distortion in 1H. In contrast, 1[HDBU] was distorted in a highly symmetric windmill-like fashion. 1H is arranged in a slipped column array in the crystal packing, whereas 1[HDBU] is arranged in a one-dimensional fashion, in which the magnetic easy axes of 1[HDBU] lie along the same line. From direct-current (dc) magnetic measurements, ferromagnetic Tb-Tb interactions occur in both 1H and 1[HDBU], and magnetic hysteresis was observed. However, the area of the magnetic hysteresis in 1[HDBU] is larger than that in 1H, meaning that magnetic relaxation time (τ) is longer in 1[HDBU]. In addition, the results of alternating-current magnetic measurements in a zero dc magnetic field indicate that τ of 1[HDBU] is longer as compared to 1H. In other words, protonation/deprotonation affects not only the molecular structures and crystal packing but also the single-molecule magnet properties.

  4. A Water-Stable Dual-Channel Luminescence Sensor for UO22+Ions Based on an Anionic Terbium(III) Metal-Organic Framework.

    Science.gov (United States)

    Ye, Junwei; Bogale, Raji F; Shi, Yangwei; Chen, Yanzhen; Liu, Xigang; Zhang, Siqi; Yang, Yaoyao; Zhao, Jianzhang; Ning, Guiling

    2017-06-07

    A stable 3D Tb III -based metal-organic framework [Tb(BPDC) 2 ]⋅(CH 3 ) 2 NH 2 (DUT-101) was synthesized, and it is the first efficient dual-channel luminescence sensor for aqueous UO 2 2+ ions. DUT-101 contains an anionic three-dimensional framework and protonated dimethylamine molecules embedded within the channels. The intense green emission of DUT-101 could be highly selectively and sensitively quenched by UO 2 2+ ions even in the presence of other competing metal ions. A possible sensing mechanism was proposed based on both suppression of luminescence resonance energy transfer and enhancement of intermolecular electron transfer. Furthermore, visual green fluorescent test papers based on DUT-101 were fabricated and could be used to discriminate UO 2 2+ ions among various metal ions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. [?-N,N?-Bis(3-meth?oxy-2-oxidobenzyl?idene)propane-1,3-diamine]trinitratocopper(II)terbium(III) acetone solvate

    OpenAIRE

    Zhang Fang; Liu Fei

    2008-01-01

    In the title complex, [CuTb(C19H20N2O4)(NO3)3]·CH3COCH3, the CuII atom is four-coordinated by two O atoms and two N atoms from the deprotonated Schiff base in a square-planar geometry, while the TbIII atom is ten-coordinated by four O atoms from the deprotonated Schiff base and six O atoms from three bidentate nitrate anions. The compound is isostructural with the previously reported GdIII analogue [Elmali & Elerman (2004). Z. Naturforsch. Teil B, 59, 535–540], which was described ...

  6. Crystal structure of a mixed-ligand terbium(III coordination polymer containing oxalate and formate ligands, having a three-dimensional fcu topology

    Directory of Open Access Journals (Sweden)

    Chainok Kittipong

    2016-01-01

    Full Text Available The title compound, poly[(μ3-formato(μ4-oxalatoterbium(III], [Tb(CHO2(C2O4]n, is a three-dimensional coordination polymer, and is isotypic with the LaIII, CeIII and SmIII analogues. The asymmetric unit contains one TbIII ion, one formate anion (CHO2− and half of an oxalate anion (C2O42−, the latter being completed by application of inversion symmetry. The TbIII ion is nine-coordinated in a distorted tricapped trigonal–prismatic manner by two chelating carboxylate groups from two C2O42− ligands, two carboxylate oxygen atoms from another two C2O42− ligands and three oxygen atoms from three CHO2− ligands, with the Tb—O bond lengths and the O—Tb—O bond angles ranging from 2.4165 (19 to 2.478 (3 Å and 64.53 (6 to 144.49 (4°, respectively. The CHO2− and C2O42− anions adopt μ3-bridging and μ4-chelating-bridging coordination modes, respectively, linking adjacent TbIII ions into a three-dimensional 12-connected fcu topology with point symbol (324.436.56. The title compound exhibits thermal stability up to 623 K, and also displays strong green photoluminescence in the solid state at room temperature.

  7. RF-to-DC Characteristics of Direct Irradiated On-Chip Gallium Arsenide Schottky Diode and Antenna for Application in Proximity Communication System

    Directory of Open Access Journals (Sweden)

    Farahiyah Mustafa

    2014-02-01

    Full Text Available We report the RF-to-DC characteristics of the integrated AlGaAs/GaAs Schottky diode and antenna under the direct injection and irradiation condition. The conversion efficiency up to 80% under direct injection of 1 GHz signal to the diode was achieved. It was found that the reduction of series resistance and parallel connection of diode and load tend to lead to the improvement of RF-to-DC conversion efficiency. Under direct irradiation from antenna-to-antenna method, the output voltage of 35 mV was still obtainable for the distance of 8 cm between both antennas in spite of large mismatch in the resonant frequency between the diode and the connected antenna. Higher output voltage in volt range is expected to be achievable for the well-matching condition. The proposed on-chip AlGaAs/GaAs HEMT Schottky diode and antenna seems to be a promising candidate to be used for application in proximity communication system as a wireless low power source as well as a highly sensitive RF detector.

  8. Lifetime Measurements of High Polarization Strained-Superlattice Gallium Arsenide at Beam Current > 1 Milliamp using a New 100kV Load Lock Photogun

    Energy Technology Data Exchange (ETDEWEB)

    J. M. Grames; P. A. Adderley; J. Brittian; J. Clark; J. Hansknecht; D. Machie; M. Poelker; M. L. Stutzman; R. Suleiman; K. E. L. Surles-Law

    2007-08-01

    A new 100 kV GaAs DC Load Lock Photogun has been constructed at Jefferson Laboratory, with improvements for photocathode preparation and for operation in a high voltage, ultra-high vacuum environment. Although difficult to gauge directly, we believe that the new gun design has better vacuum conditions compared to the previous gun design, as evidenced by longer photocathode lifetime, that is, the amount of charge extracted before the quantum efficiency of the photocathode drops by 1/e of the initial value via the ion back-bombardment mechanism. Photocathode lifetime measurements at DC beam intensity of up to 10 mA have been performed to benchmark operation of the new gun and for fundamental studies of the use of GaAs photocathodes at high average current*. These measurements demonstrate photocathode lifetime longer than one million Coulombs per square centimeter at a beam intensity higher than 1 mA. The photogun has been reconfigured with a high polarization strained superlattice photocathode (GaAs/GaAsP) and a mode-locked Ti:Sapphire laser operating near band-gap. Photocathode lifetime measurements at beam intensity greater than 1 mA are measured and presented for comparison.

  9. A Novel Approach to Modeling the Effects of Radiation in Gallium-Arsenide Solar Cells Using Silvaco’s ATLAS Software

    Science.gov (United States)

    2004-09-01

    software version 5.6.0.R, Silvaco International, Sunnyvale, CA, 2003. 7. Kasap , S.O., Principles of Electronic Materials and Devices , McGraw Hill, New... electron , displacement damage, trap, ATLAS, Silvaco, GaAs, AlGaAs, physically based device simulation, simulation, model 16. PRICE CODE 17. SECURITY...obtained from an article published in IEEE Trans- actions on Electronic Devices , written by Robert Y. Loo, Sanj iv Kamath, and Sheng S. Li in 1990

  10. Synergic phototoxic effect of visible light or Gallium-Arsenide laser in the presence of different photo-sensitizers on Porphyromonas gingivalis and Fusobacterium nucleatum

    Directory of Open Access Journals (Sweden)

    Habibollah Ghanbari

    2015-01-01

    Conclusion: Within the limitations of this study, the synergic phototoxic effect of visible light in combination with each of the photosensitizers on P. gingivalis and F. nucleatum. However, the synergic phototoxic effect of laser exposure and hydrogen peroxide and curcumin as photosensitizers on F. nucleatum was not shown.

  11. Pre-Irradiation of blood by gallium aluminum arsenide (830 nm) low-level laser enhances peripheral endogenous opioid analgesia in rats.

    Science.gov (United States)

    Hagiwara, Satoshi; Iwasaka, Hideo; Hasegawa, Akira; Noguchi, Takayuki

    2008-09-01

    Low-level laser therapy (LLLT) has been reported to relieve pain, free of side effects. However, the mechanisms underlying LLLT are not well understood. Recent studies have also demonstrated that opioid-containing immune cells migrate to inflamed sites and release beta-endorphins to inhibit pain as a mode of peripheral endogenous opioid analgesia. We investigated whether pre-irradiation of blood by LLLT enhances peripheral endogenous opioid analgesia. The effect of LLLT pretreatment of blood on peripheral endogenous opioid analgesia was evaluated in a rat model of inflammation. Additionally, the effect of LLLT on opioid production was also investigated in vitro in rat blood cells. The expression of the beta-endorphin precursors, proopiomelanocortin and corticotrophin releasing factor, were investigated by reverse transcription polymerase chain reaction. LLLT pretreatment produced an analgesic effect in inflamed peripheral tissue, which was transiently antagonized by naloxone. Correspondingly, beta-endorphin precursor mRNA expression increased with LLLT, both in vivo and in vitro. These findings suggest that that LLLT pretreatment of blood induces analgesia in rats by enhancing peripheral endogenous opioid production, in addition to previously reported mechanisms.

  12. Surface passivation and performance characteristics of type-II indium arsenide/gallium antimonide superlattice infrared photodetectors for focal plane arrays

    Science.gov (United States)

    Hood, Andrew D.

    Leakage currents limit the operation of high performance type II InAs/GaSb superlattice photodiode technology. Surface leakage current becomes a dominant, limiting factor to the ideal performance of a photodiode, especially at the scale of a focal plane array pixel (cleaning, prior to passivation, is demonstrated as well. Some sample preparation suggestions are given to reduce the formation of oxides and adsorption of deleterious process contaminants on the semiconductor surface. In addition to work centered on surface passivation, type II photodetector performance characteristics will be analyzed and discussed. These will include capacitance voltage measurements done on type II superlattice photodiodes to identify record low residual impurity background concentration values, indicating very high quality material growth. Additionally, enhancement of the device quantum efficiency for LWIR photodetectors is shown through modeling and growth optimization. Two custom designed systems are also presented, which include a portable, reconfigurable infrared and UV camera system as well as a mid infrared free-space communications system operating at room temperature with a quantum cascade laser as the source and a mid infrared type II InAs/GaSb superlattice photodiode as the receiver.

  13. Time-resolved characterization of InAs/InGaAs quantum dot gain material for 1.3 µm lasers on gallium arsenide

    DEFF Research Database (Denmark)

    Fiore, Andrea; Borri, Paola; Langbein, Wolfgang

    2000-01-01

    The time-resolved optical characterization of InAs/InGaAs quantum dots emitting at 1.3 ìm is presented. A photoluminescence decay time of 1.8 ns and a fast rise time of 10ps are measured close to room temperature.......The time-resolved optical characterization of InAs/InGaAs quantum dots emitting at 1.3 ìm is presented. A photoluminescence decay time of 1.8 ns and a fast rise time of 10ps are measured close to room temperature....

  14. An experimental investigation of the feasibility of using silicone and gallium arsenide solar batteries on space vehicles for receiving energy of laser infrared emission

    Science.gov (United States)

    Bogushevskaya, V. A.; Zhalnin, B. V.; Zayats, O. V.; Maslyakov, Ya. N.; Matsak, I. S.; Nikonov, A. A.; Obrucheva, Ye. V.; Tugaenko, V. Yu.

    2012-12-01

    The feasibility of transmitting electric power in space to solar batteries of space vehicles via the channel of laser infrared emission is shown. Evaluation of the efficiency of solar batteries for the given type of power transmission has been made. Possible methods of optimizing the design of space solar batteries in regard to conditions of detection of energy of laser infrared emission have been discussed.

  15. Initial hafnium oxide growth on silicon(100) and gallium arsenide(100) substrates using TEMAH+water and TDMAH+water ALD processes

    Science.gov (United States)

    Hackley, Justin Cain

    Atomic layer deposition (ALD) is a cyclic growth process that is distinguished by a self-limiting, two-step surface reaction that results in precise growth control and high quality, conformal thin films. Due to the continuous downscaling of MOSFET devices, a large interest has recently developed in the ALD of high-kappa dielectric materials as gate oxide layers on Si and III-V substrates. The ALD of HfO2 is an established process; however, there is still controversy over the initial growth mechanisms on differently prepared Si surfaces. This motivated a comparison of the nucleation stage of HfO 2 films grown on OH-(Si-OH) and H-terminated (Si-H) Si(100) surfaces. Two different ALD chemistries are investigated, including tetrakis[ethylmethylamino]hafnium (Hf[N(CH3)(C2H5)]4), abbreviated as TEMAH, and tetrakis[dimethylamino]hafnium (Hf[N(CH3)2] 4, abbreviated as TDMAH. H2O is used as the oxidizing precursor. Deposition temperatures of 250-275°C result in a linear growth per cycle of 1 A/cycle. Techniques including Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), and transmission electron microscopy are used to examine the film interface and initial film growth. HfO2 films are also subjected to post-deposition anneals, and the film morphology is examined with X-ray diffraction, Fourier transform infrared spectroscopy and atomic force microscopy. GaAs MOSFET devices have long proven elusive due to the lack of a stable native oxide. Recent research into high-kappa dielectric materials for use in Si-based devices has presented many new options for insulating layers on GaAs. HfO2 growth on GaAs(100) from a TDMAH+H2O ALD process is studied here. Three different GaAs surface treatments are examined, including buffered oxide etch (BOE), NH4OH, and a simple acetone/methanol wash (to retain the native oxide surface). Initial HfO2 growth on these surfaces is characterized with RBS and SE. The interfacial composition is examined with XPS both before and after HfO2 deposition. Also, an interesting native oxide 'consumption' mechanism is investigated, which involves the dissolution of the GaAs native oxide during the ALD process. This project presents the first detailed study of HfO2 growth on GaAs with the TDMAH/H2O ALD chemistry, providing XPS, RBS and SE characterization of early film growth.

  16. Local Orthorhombicity in the Magnetic C4 Phase of the Hole-Doped Iron-Arsenide Superconductor Sr1 -xNax Fe2 As2

    Science.gov (United States)

    Frandsen, Benjamin A.; Taddei, Keith M.; Yi, Ming; Frano, Alex; Guguchia, Zurab; Yu, Rong; Si, Qimiao; Bugaris, Daniel E.; Stadel, Ryan; Osborn, Raymond; Rosenkranz, Stephan; Chmaissem, Omar; Birgeneau, Robert J.

    2017-11-01

    We report on temperature-dependent pair distribution function measurements of Sr1 -xNax Fe2 As2 , an iron-based superconductor system that contains a magnetic phase with reentrant tetragonal symmetry, known as the magnetic C4 phase. Quantitative refinements indicate that the instantaneous local structure in the C4 phase comprises fluctuating orthorhombic regions with a length scale of ˜2 nm , despite the tetragonal symmetry of the average static structure. Additionally, local orthorhombic fluctuations exist on a similar length scale at temperatures well into the paramagnetic tetragonal phase. These results highlight the exceptionally large nematic susceptibility of iron-based superconductors and have significant implications for the magnetic C4 phase and the neighboring C2 and superconducting phases.

  17. Local Orthorhombicity in the Magnetic C_{4} Phase of the Hole-Doped Iron-Arsenide Superconductor Sr_{1-x}Na_{x}Fe_{2}As_{2}.

    Science.gov (United States)

    Frandsen, Benjamin A; Taddei, Keith M; Yi, Ming; Frano, Alex; Guguchia, Zurab; Yu, Rong; Si, Qimiao; Bugaris, Daniel E; Stadel, Ryan; Osborn, Raymond; Rosenkranz, Stephan; Chmaissem, Omar; Birgeneau, Robert J

    2017-11-03

    We report on temperature-dependent pair distribution function measurements of Sr_{1-x}Na_{x}Fe_{2}As_{2}, an iron-based superconductor system that contains a magnetic phase with reentrant tetragonal symmetry, known as the magnetic C_{4} phase. Quantitative refinements indicate that the instantaneous local structure in the C_{4} phase comprises fluctuating orthorhombic regions with a length scale of ∼2  nm, despite the tetragonal symmetry of the average static structure. Additionally, local orthorhombic fluctuations exist on a similar length scale at temperatures well into the paramagnetic tetragonal phase. These results highlight the exceptionally large nematic susceptibility of iron-based superconductors and have significant implications for the magnetic C_{4} phase and the neighboring C_{2} and superconducting phases.

  18. CCDC 1410822: Experimental Crystal Structure Determination : heptakis(dimethylammonium) dodecakis(mu-hydroxo)-bis(mu-oxo)-nonaaqua-nona-terbium tris(octakis(mu-hydroxo)-triaqua-bis(2-fluorobenzoato)-bis(formato)-hexa-terbium) dodecakis(5-[(4-carboxylatophenyl)methoxy]benzene-1,3-dicarboxylate) unknown solvate

    KAUST Repository

    Alezi, Dalal

    2015-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  19. BASIC RESEARCH ON THE SEPARATION OF SCANDIUM YTTRIUM, AND THE RARE EARTHS BY SOLVENT EXTRACTION.

    Science.gov (United States)

    RARE EARTH ELEMENTS, * SOLVENT EXTRACTION ), (*CHELATE COMPOUNDS, RARE EARTH ELEMENTS), PURIFICATION, ATOMIC SPECTROSCOPY, SCANDIUM, YTTRIUM, PRASEODYMIUM, SAMARIUM, EUROPIUM, GADOLINIUM, TERBIUM, FLUORINE COMPOUNDS, KETONES

  20. A validated spectrofluorimetric method for the determination of citalopram in bulk and pharmaceutical preparations based on the measurement of the silver nanoparticles-enhanced fluorescence of citalopram/terbium complexes.

    Science.gov (United States)

    Khan, Muhammad Naeem; Shah, Jasmin; Jan, Muhammad Rasul; Lee, Sang Hak

    2013-01-01

    A simple, sensitive, and accurate spectrofluorimetric method was developed for the determination of citalopram in bulk and pharmaceutical preparations. The method is based on the enhancement of the weak fluorescence signal (FL) of the Tb (III)-citalopram system in the presence of silver nanoparticles. Fluorescence intensities were measured at 555 nm after excitation at 281 nm. Prepared silver nanoparticles (AgNPs) were characterized by UV-Visible spectra and transmission electron microscopy (TEM). Various factors affecting the formation of citalopram-Tb (III)-AgNPs complexes were studied and optimized. The fluorescence intensity versus concentration plot was linear over the range 0.02-14 μg mL(-1), with an excellent correlation coefficient of 0.9978. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 7.15 × 10(-6) μg mL(-1) and 2.38 × 10(-5) μg mL(-1) respectively. The proposed method was found to have good reproducibility with a relative standard deviation of 3.66% (n = 6). The interference effects of common excipients found in pharmaceutical preparations were studied. The developed method was validated statistically by performing recoveries studies and successfully applied for the assay of citalopram in bulk powder and pharmaceutical preparations. Percent recoveries were found to range from 98.98% to 100.97% for bulk powder and from 96.57% to 101.77% for pharmaceutical preparations.

  1. A "plug-and-play" approach to the preparation of transparent luminescent hybrid materials based on poly(methyl methacrylate), a calix[4]arene cross-linking agent, and terbium ions.

    Science.gov (United States)

    Driscoll, Christopher R; Reid, Brodie L; McIldowie, Matthew J; Muzzioli, Sara; Nealon, Gareth L; Skelton, Brian W; Stagni, Stefano; Brown, David H; Massi, Massimiliano; Ogden, Mark I

    2011-04-07

    A novel methodology to prepare transparent luminescent hybrid materials is reported. Using a calixarene ionophore as a PMMA cross-linker avoids problems, such as phase segregation, and produces a polymer monolith that can be loaded with the metal ion required for luminescence post-synthesis. This approach is versatile and will simplify the production of such materials.

  2. CCDC 954772: Experimental Crystal Structure Determination : catena-(Dimethylammonium tris(mu~4~-3-fluorobiphenyl-4,4'-dicarboxylato)-tetrakis(mu~3~-hydroxo)-triaqua-tri-terbium unknown solvate)

    KAUST Repository

    Xue, Dongxu

    2013-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  3. CCDC 1410820: Experimental Crystal Structure Determination : heptakis(dimethylammonium) heptacosa-terbium dodecakis((1,1'-biphenyl)-3,4',5-tricarboxylate) hexakis(2-fluorobenzoate) hexakis(formate) hexatriacontakis(hydroxide) bis(oxide) unknown solvate hydrate

    KAUST Repository

    Alezi, Dalal

    2015-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  4. Terbium doped SnO2 nanoparticles as white emitters and SnO2:5Tb/Fe3O4 magnetic luminescent nanohybrids for hyperthermia application and biocompatibility with HeLa cancer cells.

    Science.gov (United States)

    Singh, Laishram Priyobarta; Singh, Ningthoujam Premananda; Srivastava, Sri Krishna

    2015-04-14

    SnO2:5Tb (SnO2 doped with 5 at% Tb(3+)) nanoparticles were synthesised by a polyol method and their luminescence properties at different annealing temperatures were studied. Characterization of nanomaterials was done by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). XRD studies indicate that the prepared nanoparticles were of tetragonal structures. Upon Tb(3+) ion incorporation into SnO2, Sn(4+) changes to Sn(2+) and, on annealing again at higher temperature, Sn(2+) changes to Sn(4+). The prepared nanoparticles were spherical in shape. Sn-O vibrations were found from the FTIR studies. In photoluminescence studies, the intensity of the emission peaks of Tb(3+) ions increases with the increase of annealing temperature, and emission spectra lie in the region of white emission in the CIE diagram. CCT calculations show that the SnO2:5Tb emission lies in cold white emission. Quantum yields up to 38% can be obtained for 900 °C annealed samples. SnO2:5Tb nanoparticles were well incorporated into the PVA polymer and such a material incorporated into the polymer can be used for display devices. The SnO2:5Tb/Fe3O4 nanohybrid was prepared and investigated for hyperthermia applications at different concentrations of the nanohybrid. This achieves a hyperthermia temperature (42 °C) under an AC magnetic field. The hybrid nanomaterial SnO2:5Tb/Fe3O4 was found to exhibit biocompatibility with HeLa cells (human cervical cancer cells) at concentrations up to 74% for 100 μg L(-1). Also, this nanohybrid shows green emission and thus it will be helpful in tracing magnetic nanoparticles through optical imaging in vivo and in vitro application.

  5. Filmes delgados luminescentes obtidos a partir de hidroxicarbonatos de ítrio ativados por európio ou térbio Luminescent thin films obtained from ytrium hydroxycarbonates activated by terbium or europium

    Directory of Open Access Journals (Sweden)

    Emy Niyama

    2004-04-01

    Full Text Available These films were obtained by dip coating. Parameters like dislocation velocity; number of deposits, suspension concentration, and number of deposits followed or not by heat treatment between each deposit and calcination temperature were evaluated for establishing the best homogeneity. The obtained films were characterized in terms of their morphology, optical quality and photoluminescence by scanning electron microscopy (SEM, UV-vis absorption spectrophotometry and luminescence spectroscopy, respectively. The morphologic and luminescent characteristics showed dip coating as good laboratory technique for development of thin films for optical applications.

  6. Onboard high data rate signal processing and storage

    Science.gov (United States)

    Miller, Warner H.

    1985-01-01

    The objective is to advance the state of the art in onboard image data processing and storage through the use of advanced gallium arsenide integrated circuit technology. Viewgraphs are given on research and development efforts, an adaptive programmable processor chip set, design characteristics of an eight bit general processor, and a density comparison of silicon and gallium arsenide integrated circuits.

  7. Compression and Associated Properties of Boron Carbide

    Science.gov (United States)

    2008-12-01

    arsenide have been associated with icosahedron - chain modes (Tallent et al., 1989). Therefore, we tentatively assign these features in B4C to... icosahedron - chain modes. In boron arsenide, the intensity of these modes was found to be immensely sensitive to the crystalline orientation and a

  8. Synthesis and characterization of spherical Tb-MCM-41

    Energy Technology Data Exchange (ETDEWEB)

    Pires, Luiza H.O., E-mail: lulenapires@hotmail.co [Universidade Federal do Para, Instituto de Ciencias Exatas e Naturais, Laboratorio de Catalise e Oleoquimica, CP 479, CEP 66075-110, Belem, PA (Brazil); Queiroz, Renan M.; Souza, Ruth P.; Costa, Carlos E.F. da; Zamian, Jose R. [Universidade Federal do Para, Instituto de Ciencias Exatas e Naturais, Laboratorio de Catalise e Oleoquimica, CP 479, CEP 66075-110, Belem, PA (Brazil); Weber, Ingrid T. [Universidade Federal de Pernambuco, Centro de Ciencias Exatas e da Natureza, Av. Prof. Luis Barros Freire, s/n, Cidade Universitaria, 50670-901 Recife, PE (Brazil); Filho, Geraldo N. da Rocha [Universidade Federal do Para, Instituto de Ciencias Exatas e Naturais, Laboratorio de Catalise e Oleoquimica, CP 479, CEP 66075-110, Belem, PA (Brazil)

    2010-02-04

    Spherical MCM-41 was synthesized at room temperature and functionalized by means of direct synthesis method. Evidence for the terbium presence in the silica matrix was obtained by means of EDX. Scanning electron microscopy (SEM) micrographs showed that terbium incorporation did not change significantly MCM-41 morphology. The maintenance of the hexagonal structure was confirmed by X-ray diffraction (XRD) pattern analysis. The cell parameter increase and the surface area decrease, observed by N{sub 2} adsorption-desorption technique, were taken as evidence of terbium introduction inside the MCM-41 framework. By FT-IR spectra it was found that the main features of the silica framework were maintained. The presence of a strong absorption band centered at ca. 220 nm in the diffuse reflectance UV-vis spectra could indicate the presence of tetra-coordinated terbium in the silica network of Tb-MCM-41 samples.

  9. Therapeutic use of radioactive isotopes

    CERN Multimedia

    Caroline Duc

    2013-01-01

    In December, researchers from ISOLDE-CERN, the Paul Scherrer Institute (PSI) and the Institut Laue-Langevin (ILL) published the results of an in vivo study which successfully proved the effectiveness of four terbium isotopes for diagnosing and treating cancerous tumours.   Four terbium isotopes suitable for clinical purposes. “ISOLDE is the only installation capable of supplying terbium isotopes of such purity and intensity in the case of three out of the four types used in this study,” explains Karl Johnson, a physicist at ISOLDE.  “Producing over a thousand different isotopes, our equipment offers the widest choice of isotopes in the world!” Initially intended for fundamental physics research, ISOLDE has diversified its activities over time to invest in various projects in the materials science, biochemistry and nuclear medicine fields. The proof-of-concept study has confirmed that the four terbium isotopes 149Tb, 152Tb, 155Tb produ...

  10. Thermal History Using Microparticle Trap Luminescence

    Science.gov (United States)

    2012-06-01

    and thermoluminescence of terbium-activated silicates and aluminates " . Radiat. Meas. 43, 323-326 (2008). HDTRA1-07-1-0016 University of...of terbium-activated silicates and aluminates " . 15th Solid State Dosimetry Conference, Delft, The Netherlands, July 8-13 (2007). 2 INTRODUCTION...increased to 500°C until combustion occurred (- 7 min). The remaining powder was collected, crushed in a agate mortar, and annealed (typically at 900

  11. Polarized electron sources

    Energy Technology Data Exchange (ETDEWEB)

    Prepost, R. [Univ. of Wisconsin, Madison, WI (United States)

    1994-12-01

    The fundamentals of polarized electron sources are described with particular application to the Stanford Linear Accelerator Center. The SLAC polarized electron source is based on the principle of polarized photoemission from Gallium Arsenide. Recent developments using epitaxially grown, strained Gallium Arsenide cathodes have made it possible to obtain electron polarization significantly in excess of the conventional 50% polarization limit. The basic principles for Gallium and Arsenide polarized photoemitters are reviewed, and the extension of the basic technique to strained cathode structures is described. Results from laboratory measurements of strained photocathodes as well as operational results from the SLAC polarized source are presented.

  12. NREL preprints for the 23rd IEEE Photovoltaic Specialists Conference

    Energy Technology Data Exchange (ETDEWEB)

    Fitzgerald, M. [ed.

    1993-05-01

    Topics covered include various aspects of solar cell fabrication and performance. Aluminium-gallium arsenides, cadmium telluride, amorphous silicon, and copper-indium-gallium selenides are all characterized in their applicability in solar cells.

  13. High-power X- and Ka-band Gallium Nitride Amplifiers with Exceptional Efficiency Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Achieving very high-power amplification with maximum efficiency at X- and Ka-band is challenging using solid-state technology. Gallium Arsenide (GaAs) has been the...

  14. POLLUTION PREVENTION IN THE SEMICONDUCTOR INDUSTRY THROUGH RECOVERY AND RECYCLING OF GALLIUM AND ARSENIC FROM GAAS POLISHING WASTES

    Science.gov (United States)

    A process was developed for the recovery of both arsenic and gallium from gallium arsenide polishing wastes. The economics associated with the current disposal techniques utilizing ferric hydroxide precipitation dictate that sequential recovery of toxic arsenic and valuble galliu...

  15. Suitability of integrated protection diodes from diverse semiconductor technologies

    NARCIS (Netherlands)

    van Wanum, Maurice; Lebouille, Tom; Visser, Guido; van Vliet, Frank Edward

    2009-01-01

    Abstract In this article diodes from three different semiconductor technologies are compared based on their suitability to protect a receiver. The semiconductor materials involved are silicon, gallium arsenide and gallium nitride. The diodes in the diverse semiconductor technologies themselves are

  16. Point Source X-Ray Lithography System for Sub-0.15 Micron Design Rules

    National Research Council Canada - National Science Library

    Henson, Richard

    1998-01-01

    .... Sanders is leading development of gallium arsenide wafer processing technology for the MMIC "T" gate process, and is carrying out a prototype fabrication run of 35 GHz MMIC low noise amplifiers...

  17. On the quenching of trivalent terbium luminescence by ligand low lying triplet state energy and the role of the {sup 7}F{sub 5} level: The [Tb(tta){sub 3} (H{sub 2}O){sub 2}] case

    Energy Technology Data Exchange (ETDEWEB)

    Souza, A.S., E-mail: adelmosaturnino@hotmail.com [Departamento de Química Fundamental, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Nunes, L.A. [Instituto de Física de São Carlos, Universidade de São Paulo, 13560-970 São Carlos, SP (Brazil); Felinto, M.C.F.C. [Instituto de Pesquisas Energéticas e Nucleares-IPEN, 05505-800 São Paulo, SP (Brazil); Brito, H.F. [Instituto de Química, Universidade de São Paulo, 05508-900 São Paulo, SP (Brazil); Malta, O.L. [Departamento de Química Fundamental, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil)

    2015-11-15

    In this work we discuss the observed Tb{sup 3+} ion luminescence quenching, due to the relative ligand low lying triplet state energy, in the [Tb(tta){sub 3} (H{sub 2}O){sub 2}] compound at low and room temperature (tta=thenoyltrifluoroacetonate). Theoretical energy transfer rates, for both multipolar and exchange mechanisms, were calculated and discussed on the basis of selection rules and energy mismatch conditions from the [Tb(tta){sub 3} (H{sub 2}O){sub 2}] emission spectra. We have concluded that the exchange mechanism by far dominates, in the present case, and that the long first excited state {sup 7}F{sub 5} lifetime (in the millisecond scale) plays a crucial role in the Tb{sup 3+} luminescence quenching. - Highlights: • The energy exchange between the ligand T{sub 1} and Tb{sup 3+5}D{sub 4} levels occur by the exchange interaction. • The Tb{sup 3+} first excited {sup 7}F{sub 5} level plays a crucial role in this process due to its long lifetime. • At room temperature the energy exchanged between the {sup 5}D{sub 4} level of the Tb{sup 3+} ion and the T{sub 1} of the ligand is lost via the intersystem crossing T{sub 1} → S{sub 0} channel.

  18. Synthesis, structure, and magnetic properties of a new family of tetra-nuclear {Mn2(III)Ln2}(Ln = Dy, Gd, Tb, Ho) clusters with an arch-type topology: single-molecule magnetism behavior in the dysprosium and terbium analogues.

    Science.gov (United States)

    Chandrasekhar, Vadapalli; Bag, Prasenjit; Speldrich, Manfred; van Leusen, Jan; Kögerler, Paul

    2013-05-06

    Sequential reaction of Mn(II) and lanthanide(III) salts with a new multidentate ligand, 2,2'-(2-hydroxy-3-methoxy-5-methylbenzylazanediyl)diethanol (LH3), containing two flexible ethanolic arms, one phenolic oxygen, and a methoxy group afforded heterometallic tetranuclear complexes [Mn2Dy2(LH)4(μ-OAc)2](NO3)2·2CH3OH·3H2O (1), [Mn2Gd2(LH)4(μ-OAc)2](NO3)2·2CH3OH·3H2O (2), [Mn2Tb2(LH)4(μ-OAc)2](NO3)2·2H2O·2CH3OH·Et2O (3), and [Mn2Ho2(LH)4(μ-OAc)2]Cl2·5CH3OH (4). All of these dicationic complexes possess an arch-like structural topology containing a central Mn(III)-Ln-Ln-Mn(III) core. The two central lanthanide ions are connected via two phenolate oxygen atoms. The remaining ligand manifold assists in linking the central lanthanide ions with the peripheral Mn(III) ions. Four doubly deprotonated LH(2-) chelating ligands are involved in stabilizing the tetranuclear assembly. A magnetochemical analysis reveals that single-ion effects dominate the observed susceptibility data for all compounds, with comparably weak Ln···Ln and very weak Ln···Mn(III) couplings. The axial, approximately square-antiprismatic coordination environment of the Ln(3+) ions in 1-4 causes pronounced zero-field splitting for Tb(3+), Dy(3+), and Ho(3+). For 1 and 3, the onset of a slowing down of the magnetic relaxation was observed at temperatures below approximately 5 K (1) and 13 K (3) in frequency-dependent alternating current (AC) susceptibility measurements, yielding effective relaxation energy barriers of ΔE = 16.8 cm(-1) (1) and 33.8 cm(-1) (3).

  19. Ultra-broadband optical signal processing using AlGaAs-OI devices

    DEFF Research Database (Denmark)

    Galili, Michael; Da Ros, Francesco; Hu, Hao

    2017-01-01

    Aluminum Gallium Arsenide on insulator (AlGaAs-OI) has recently been developed into a very attractive platform for optical signal processing. This paper reviews key results of broadband optical signal processing using this platform.......Aluminum Gallium Arsenide on insulator (AlGaAs-OI) has recently been developed into a very attractive platform for optical signal processing. This paper reviews key results of broadband optical signal processing using this platform....

  20. Inflammatory process decrease by gallium-aluminium-arsenide (GaAlAs) low intensity laser irradiation on postoperative extraction of impacted lower third molar; Reducao de processo inflamatorio com aplicacao de laser de arseneto de galio aluminio ({lambda}=830 nm) em pos-operatorio de exodontia de terceiros molares inferiores inclusos ou semi-inclusos

    Energy Technology Data Exchange (ETDEWEB)

    Atihe, Mauricio Martins

    2002-07-01

    This study aimed the observation of inflammatory process decrease by the use of GaAlAs Low Intensity Laser ({lambda}=830 nm; 40 mW) irradiation. Five patients were selected and submitted to surgery of impacted lower third molars, both right and left sides at different occasions. On a first stage, a tooth of a random chosen side - right or left - was extracted by conventional surgery, without LILT. The inflammatory process was measured at postoperative on the first, third and seventh days. This side was then called 'control side'. After 21 days, period in which the inflammatory process of the first surgery was terminated, the other side surgery took place, this time using LILT (4 J at four spots) at postoperative, first and third days. As the previous surgery, the inflammatory process was also measured at postoperative on the first, third and seventh days. This side was called 'experimental or lased side'. The inflammatory process was evaluated by measuring its four characteristic signs: swelling, pain, color and temperature. It was clearly observed a decrease for swelling, pain and color on the lased side which presented significant inference and descriptive statistics. It can be concluded that GaAlAs Low Intensity Laser ({lambda}=830 nm) can surely be used as an additional and important anti-inflammatory source on impacted lower third molar surgeries. (author)

  1. Reactive Chemical Vapor Deposition Method as New Approach for Obtaining Electroluminescent Thin Film Materials

    Directory of Open Access Journals (Sweden)

    Valentina V. Utochnikova

    2012-01-01

    Full Text Available The new reactive chemical vapor deposition (RCVD method has been proposed for thin film deposition of luminescent nonvolatile lanthanide aromatic carboxylates. This method is based on metathesis reaction between the vapors of volatile lanthanide dipivaloylmethanate (Ln(dpm3 and carboxylic acid (HCarb orH2Carb′ and was successfully used in case of HCarb. Advantages of the method were demonstrated on example of terbium benzoate (Tb(bz3 and o-phenoxybenzoate thin films, and Tb(bz3 thin films were successfully examined in the OLED with the following structure glass/ITO/PEDOT:PSS/TPD/Tb(bz3/Ca/Al. Electroluminescence spectra of Tb(bz3 showed only typical luminescent bands, originated from transitions of the terbium ion. Method peculiarities for deposition of compounds of dibasic acids H2Carb′ are established on example of terbium and europium terephtalates and europium 2,6-naphtalenedicarboxylate.

  2. Spatial resolution in X-ray imaging with scintillating glass optical fiber plates

    Science.gov (United States)

    Pavan, P.; Zanella, G.; Zannoni, R.; Marigo, A.

    1993-04-01

    Some scintillating optical fiber plates, fabricated with terbium glasses are tested for their intrinsic spatial resolution under X-ray irradiation and the result is compared with a typical phosphor screen. The spatial resolution (CTF and MTF) is measured as a function of spatial frequency and the standard deviation of the corresponding Gaussian PSF is derived.

  3. PROCESS FOR THE PREPARATION OF ALLOY NANOPARTICLES COMPRISING A NOBLE AND A NON-NOBLE METAL

    DEFF Research Database (Denmark)

    2017-01-01

    The present invention concerns a chemical process for preparing nanoparticles of an alloy comprising both a noble metal, such as platinum, and a non-noble transition or lanthanide metal, such as yttrium, gadolinium or terbium. The process is carried out by reduction with hydrogen and removal...

  4. Multiplet effects in the electronic structure of heavy rare-earth metals

    NARCIS (Netherlands)

    Lebegue, S.; Svane, A.; Katsnelson, M.I.; Lichtenstein, A.I.; Eriksson, O.

    2006-01-01

    The spectroscopic properties of elemental terbium, dysprosium, holmium, and erbium are investigated using first-principles calculations taking into account intra-atomic correlation effects. In order to describe the strongly localized f electrons together with the conduction bands, we have used the

  5. Performance of 20 Ci 137Cs γ-ray Compton spectrometer for the ...

    Indian Academy of Sciences (India)

    The in-house 137Cs spectrometer is very useful for the measurement of momentum densities of heavy materials. The performance of the machine is assessed using aluminum, terbium and mercury samples and the exper- imental data from comparable apparatus. Keywords. Compton scattering; electron momentum density; ...

  6. Author Details

    African Journals Online (AJOL)

    Pengkiliya, P. Vol 67 (2014) - Articles Interaction of 3-Hydroxypicolinamide with TbIII and its Sensitizing Effect on Terbium Luminescence as a Function of pH and Medium Abstract PDF. ISSN: 0379-4350. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about ...

  7. Author Details

    African Journals Online (AJOL)

    Devi, TP. Vol 67 (2014) - Articles Interaction of 3-Hydroxypicolinamide with TbIII and its Sensitizing Effect on Terbium Luminescence as a Function of pH and Medium Abstract PDF. ISSN: 0379-4350. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about AJOL ...

  8. THz near-field Faraday imaging in hybrid metamaterials

    NARCIS (Netherlands)

    Kumar, N.; Strikwerda, A.C.; Fan, K.; Zhang, X.; Averitt, R.D.; Planken, P.C.M.; Adam, A.J.L.

    2012-01-01

    We report on direct measurements of the magnetic near-field of metamaterial split ring resonators at terahertz frequencies using a magnetic field sensitive material. Specifically, planar split ring resonators are fabricated on a single magneto-optically active terbium gallium garnet crystal.

  9. Synthesis and photoluminescence properties of CaSixOy:Tb3+ phosphors prepared using solution-combustion method

    CSIR Research Space (South Africa)

    Dejene, FB

    2011-07-01

    Full Text Available to Ca3Si2O7 as the terbium concentration increase. Broad band excitations peaking between 280 - 360 nm derived from excited states of Tb3+ ions were observed for all powders grown from various Tb compositions. The green emission peak at 545 nm due...

  10. Scanning Electron Microscope-Cathodoluminescence Analysis of Rare-Earth Elements in Magnets.

    Science.gov (United States)

    Imashuku, Susumu; Wagatsuma, Kazuaki; Kawai, Jun

    2016-02-01

    Scanning electron microscope-cathodoluminescence (SEM-CL) analysis was performed for neodymium-iron-boron (NdFeB) and samarium-cobalt (Sm-Co) magnets to analyze the rare-earth elements present in the magnets. We examined the advantages of SEM-CL analysis over conventional analytical methods such as SEM-energy-dispersive X-ray (EDX) spectroscopy and SEM-wavelength-dispersive X-ray (WDX) spectroscopy for elemental analysis of rare-earth elements in NdFeB magnets. Luminescence spectra of chloride compounds of elements in the magnets were measured by the SEM-CL method. Chloride compounds were obtained by the dropwise addition of hydrochloric acid on the magnets followed by drying in vacuum. Neodymium, praseodymium, terbium, and dysprosium were separately detected in the NdFeB magnets, and samarium was detected in the Sm-Co magnet by the SEM-CL method. In contrast, it was difficult to distinguish terbium and dysprosium in the NdFeB magnet with a dysprosium concentration of 1.05 wt% by conventional SEM-EDX analysis. Terbium with a concentration of 0.02 wt% in an NdFeB magnet was detected by SEM-CL analysis, but not by conventional SEM-WDX analysis. SEM-CL analysis is advantageous over conventional SEM-EDX and SEM-WDX analyses for detecting trace rare-earth elements in NdFeB magnets, particularly dysprosium and terbium.

  11. Performance of 20 Ci 137Cs γ-ray Compton spectrometer for the ...

    Indian Academy of Sciences (India)

    ... than the conventional 241Am Compton spectrometers. The in-house 137Cs spectrometer is very useful for the measurement of momentum densities of heavy materials. The performance of the machine is assessed using aluminum, terbium and mercury samples and the experimental data from comparable apparatus.

  12. Faraday isolator based on TSAG crystal for high power lasers.

    Science.gov (United States)

    Mironov, E A; Palashov, O V

    2014-09-22

    A Faraday isolator based on a new magneto-optical medium, TSAG (terbium scandium aluminum garnet) crystal, has been constructed and investigated experimentally. The device provides an isolation ratio of more than 30 dB at 500 W laser power. It is shown that this medium can be used in Faraday isolators for kilowatt-level laser powers.

  13. 1. Novel Dopants in Silica Based Fibers. 2. Applications of Embedded Optical Fiber Sensors in Reinforced Concrete Buildings and Structures

    Science.gov (United States)

    1990-05-20

    effects in fibers, and nonlinear phenomena in fibers. We also use NMR, ESR and Raman techniques to study incorporation of novel as well as...neodymium, erbium, holmium or terbium. These products can be vacuum dried at elevated temperature. The acac-compound is less expensive since the hfa

  14. Time-gated FRET nanoassemblies for rapid and sensitive intra- and extracellular fluorescence imaging

    NARCIS (Netherlands)

    Afsari, Hamid Samareh; Cardoso Dos Santos, Marcelina; Lindén, Stina; Chen, Ting; Qiu, Xue; van Bergen En Henegouwen, Paul M P|info:eu-repo/dai/nl/071919481; Jennings, Travis L; Susumu, Kimihiro; Medintz, Igor L; Hildebrandt, Niko; Miller, Lawrence W

    Time-gated Förster resonance energy transfer (FRET) using the unique material combination of long-lifetime terbium complexes (Tb) and semiconductor quantum dots (QDs) provides many advantages for highly sensitive and multiplexed biosensing. Although time-gated detection can efficiently suppress

  15. Bulletin of Materials Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 7. Issue front cover thumbnail. Volume 39, Issue 7. December 2016, pages 1619-1889. pp 1619-1623. Luminescence properties of terbium-doped Li 3 PO 4 phosphor for radiation dosimetry · C B PALAN N S BAJAJ S K OMANWAR · More Details Abstract ...

  16. Interaction of 3-Hydroxypicolinamide with Tb III and its Sensitizing ...

    African Journals Online (AJOL)

    Interaction of 3-Hydroxypicolinamide with Tb III and its Sensitizing Effect on Terbium Luminescence as a Function of pH and Medium. ... The complex formed exists asML2 species in which HPA behaves as anO,O,N,N-chelating ligand. The solid complex is isolated from aqueous medium and characterized employing ...

  17. Lanthanide Enhanced Luminescence (LEL) with One and Two Photon Excitation of Quantum Dyes(copyright) Lanthanide(III)-Macrocycles

    National Research Council Canada - National Science Library

    Leif, Robert C; Becker, Margie C; Bromm Jr., Al; Chen, Nanguang; Cowan, Ann E; Vallarino, Lidia M; Yang, Sean; Zucker, Robert M

    2004-01-01

    .... Preliminary studies indicate that cells stained with the europium Quantum Dye can be observed both by conventional UV laser excitation and by infrared two-photon confocal microscopy. An enhancer has been found that enables the observation of simultaneous emissions from both the europium and terbium Quantum Dyes.

  18. Kinetically inert lanthanide complexes as reporter groups for binding of potassium by 18-crown-6

    DEFF Research Database (Denmark)

    Junker, Anne Kathrine Ravnsborg; Tropiano, Manuel; Faulkner, Stephen

    2016-01-01

    in a copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) “click” reaction with azide-functionalized crown ethers. The resulting complexes were investigated using NMR and optical methods. Titrations with potassium chloride in methanol observing the sensititzed europium- and terbium-centered emissions were...

  19. Space-based solar power conversion and delivery systems study. Volume 4: Energy conversion systems studies

    Science.gov (United States)

    1977-01-01

    Solar cells and optical configurations for the SSPS were examined. In this task, three specific solar cell materials were examined: single crystal silicon, single crystal gallium arsenide, and polycrystalline cadmium sulfide. The comparison of the three different cells on the basis of a subsystem parametric cost per kW of SSPS-generated power at the terrestrial utility interface showed that gallium arsenide was the most promising solar cell material at high concentration ratios. The most promising solar cell material with no concentration, was dependent upon the particular combination of parameters representing cost, mass and performance that were chosen to represent each cell in this deterministic comparative analysis. The potential for mass production, based on the projections of the present state-of-the-art would tend to favor cadmium sulfide in lieu of single crystal silicon or gallium arsenide solar cells.

  20. Space station automation study: Automation requriements derived from space manufacturing concepts,volume 2

    Science.gov (United States)

    1984-01-01

    Automation reuirements were developed for two manufacturing concepts: (1) Gallium Arsenide Electroepitaxial Crystal Production and Wafer Manufacturing Facility, and (2) Gallium Arsenide VLSI Microelectronics Chip Processing Facility. A functional overview of the ultimate design concept incoporating the two manufacturing facilities on the space station are provided. The concepts were selected to facilitate an in-depth analysis of manufacturing automation requirements in the form of process mechanization, teleoperation and robotics, sensors, and artificial intelligence. While the cost-effectiveness of these facilities was not analyzed, both appear entirely feasible for the year 2000 timeframe.

  1. Electrochemical capacitance-voltage measurements and modeling of GaAs nanostructures with delta-doped layers

    Science.gov (United States)

    Shestakova, L.; Yakovlev, G.; Zubkov, V.

    2017-03-01

    The paper presents the results of electrochemical capacitance-voltage profiling and simulation of quantum-sized semiconductor structures with quantum wells and delta-doped layers based on gallium arsenide. The experimental ECV data were obtained by superposition of measured capacitance-voltage characteristics during the gradual etching of the nanostructure. As a result of simulation, the concentration distribution and energy lineups for structures with delta-layers and quantum wells in gallium arsenide were calculated. The results of simulation are in qualitative agreement with the experimental results and data found in literature.

  2. Current switching in superconductor semiconductor bilayers

    Science.gov (United States)

    Rahman, F.; Thornton, T. J.; Huber, R.

    2006-09-01

    We describe results of electrical transport experiments on niobium-on-indium arsenide and aluminium-on-indium arsenide bilayers. The temperature-dependent properties of electrical conduction in these bilayers is examined first in order to characterize the quality of super-semi interfaces. Next, we look at the differential resistance of the bilayers as a function of bias current. The switching of current between the metal and semiconductor components of the bilayer gives rise to a quasi-inductive effect as it causes voltage spikes in the composite system. Also described is the variation of critical current for these bilayers with temperature and magnetic field.

  3. Feasibility of producing photodiode bases on a single crystal strip of germanium obtained by Stephanov's method

    CERN Document Server

    Menshikova, V A; Zatalovskii, L M; Chaikin, P M; Frimer, A I

    1972-01-01

    The single-crystal strip was obtained by Stepanov's method. involving the use of a fusing shaper and a flexible priming wire holder. The epitaxial growth of a gallium arsenide layer on this strip was then studied, and photodiodes were prepared from it. The surface properties of the strip were investigated microstructurally and deposition rates for gallium arsenide recorded at different temperatures. At each stage the figures were compared with results obtained with common germanium. The characteristics of photodiodes prepared from the single-crystal strip and common germanium were compared, and the former gave greater integral sensitivity. (3 refs).

  4. Semiconducting III-V compounds

    CERN Document Server

    Hilsum, C; Henisch, Heinz R

    1961-01-01

    Semiconducting III-V Compounds deals with the properties of III-V compounds as a family of semiconducting crystals and relates these compounds to the monatomic semiconductors silicon and germanium. Emphasis is placed on physical processes that are peculiar to III-V compounds, particularly those that combine boron, aluminum, gallium, and indium with phosphorus, arsenic, and antimony (for example, indium antimonide, indium arsenide, gallium antimonide, and gallium arsenide).Comprised of eight chapters, this book begins with an assessment of the crystal structure and binding of III-V compounds, f

  5. LPEE Growth and Characterization of InxGa(1-x)ASySb(1-y) Lattice Matched to GaSb and InAs for Photodetectors

    Science.gov (United States)

    1994-06-01

    S. Nishiyama, S. Isozumi and K.Nakajima, Appl.Phys.Lett. 56, 239 (1990). 25. S.J.Eglash and H.K. Choi , Gallium Arsenide and Related Compounds. 1991...51 (1986). 3*S. J, Eglash and H. K. Choi , in Gallium Arsenide and Related Compounds, 1991, edited by G. B. Stringfellow (IOP, London, 1992), p...GalnAsSb layers on a (100) GaSb substrate. Considering the fact that this is a quater- nary alloy system and hence even a small statistical inho

  6. Simple intrinsic defects in GaAs : numerical supplement.

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, Peter Andrew

    2012-04-01

    This Report presents numerical tables summarizing properties of intrinsic defects in gallium arsenide, GaAs, as computed by density functional theory. This Report serves as a numerical supplement to the results published in: P.A. Schultz and O.A. von Lilienfeld, 'Simple intrinsic defects in GaAs', Modelling Simul. Mater. Sci Eng., Vol. 17, 084007 (2009), and intended for use as reference tables for a defect physics package in device models. The numerical results for density functional theory calculations of properties of simple intrinsic defects in gallium arsenide are presented.

  7. Temperature Insensitive and Radiation Hard Photonics

    Science.gov (United States)

    2014-03-19

    stacks of InAs quantum dots in an InGaAs quantum well , the so-called DWELL structure. These layers are separated by GaAs barriers grown by elemental...layers buffering the gain region act as the optical waveguide boundaries as well as strain mitigation. A low step index, 30% AlGaAs cladding...HR High-Reflection InAs Indium Arsenide InGaAs Indium Gallium Arsenide LEO Low Earth Orbit MBE Molecular Beam Epitaxy QD Quantum Dot QDMLL Quantum

  8. Modeling the cutoff frequency of single-heterojunction bipolar transistors subjected to high collector-layer current

    Science.gov (United States)

    Liou, J. J.; Lindholm, F. A.; Wu, B. S.

    1990-06-01

    High current densities in the collector layer reduce the cutoff frequency of heterojunction bipolar transistors. A model is developed based on analytical expressions that describe this reduction. These expressions represent the contributions from each of six regions defined in the output current-voltage characteristic. The model has parameters determined entirely by device physical makeup. It has no fitting parameters. Its predictions agree well with experimental data taken on two N/p+/n aluminum-gallium-arsenide/gallium-arsenide transistors having abrupt junctions grown by molecular-beam epitaxy. The development of the model considers the effects that compound-semiconductor properties, such as velocity overshoot, have on the cutoff frequency.

  9. None

    Energy Technology Data Exchange (ETDEWEB)

    Cason, D.L. [ed.; Kane, L.S.; Henline, D.M.

    1995-02-01

    Photovoltaic Energy: Electricity from Sunlight (PHV) announces on a bimonthly basis the current worldwide information available on all aspects of photovoltaic amorphous technology, polycrystalline thin films, gallium arsenide, crystalline silicon, concentrator technology, and systems research. This publication contains the abstracts of DOE reports, journal articles, conference papers, patents, theses, and monographs added to the Energy Science and Technology Database during the past two months.

  10. None

    Energy Technology Data Exchange (ETDEWEB)

    Cason, D.L.; Hicks, S.C. [eds.

    1993-02-01

    This publication announces on a bimonthly basis the current worldwide information available on all aspects of photovoltaic amporphous technology, polycrystalline thin films, gallium arsenide, crystalline silicon, concentrator technology, and systems research. The abstracts are arranged under the headings Solar Cells, and Photovoltaic Power Supplies.

  11. Modulation of fluorescence signals from biomolecules along nanowires due to interaction of light with oriented nanostructures

    DEFF Research Database (Denmark)

    Frederiksen, Rune Schøneberg; Alarcon-Llado, Esther; Madsen, Morten H.

    2015-01-01

    High aspect ratio nanostructures have gained increasing interest as highly sensitive platforms for biosensing. Here, well-defined biofunctionalized vertical indium arsenide nanowires are used to map the interaction of light with nanowires depending on their orientation and the excitation waveleng...

  12. Notch filtering the nuclear environment of a spin qubit

    DEFF Research Database (Denmark)

    Malinowski, F. K.; Martins, F.; Nissen, P. D.

    2016-01-01

    Electron spins in gate-defined quantum dots provide a promising platform for quantum computation. In particular, spin-based quantum computing in gallium arsenide takes advantage of the high quality of semiconducting materials, reliability in fabricating arrays of quantum dots, and accurate qubit ...

  13. Endangered Elements of the Periodic Table

    Indian Academy of Sciences (India)

    (Z = 47), tin (Z = 50), and lead (Z = 82), 70% of gold (Z = 79) and zinc (Z = 30), and 50% of copper (Z = 29) and ... indium is obtained as a byproduct during the extraction. Since 1960's gallium arsenide-based ... recovery of indium from unwanted devices is not very cost effec- tive. So scientists are thinking of alternatives to ...

  14. Resonance-like tunneling across a barrier with adjacent wells

    Indian Academy of Sciences (India)

    Furthermore, with the advent of nanotechnology it is envisaged .... we describe the potential application of the concept of resonant tunneling in the design of novel electronic devices using the electrical properties of gallium arsenide and SiO2. In the emerging era of nanoscience these concepts will have wider appli- cations.

  15. Nonlinear optical study of ultrafast carrier dynamics in GaAs

    NARCIS (Netherlands)

    Jong, W. de

    1999-01-01

    This thesis reports on optical second harmonic generation (SHG) and electric field induced SHG (EFISHG) studies performed on gold-gallium arsenide (Au-GaAs) Schottky barrier (SB) systems. The most interesting are the dynamics of excited carriers behind the Schottky barrier interface which are

  16. Fiber grating sensing interrogation based on an InGaAs photodiode linear array.

    Science.gov (United States)

    Li, Guoyu; Guo, Tuan; Zhang, Hao; Gao, Hongwei; Zhang, Jian; Liu, Bo; Yuan, Shuzhong; Kai, Guiyun; Dong, Xiaoyi

    2007-01-20

    We present a new method of the fiber grating sensing interrogation technique by utilizing an indium gallium arsenide photodiode linear array and blazed fiber Bragg gratings. An interrogation system based on an InGaAs photodiode linear array is designed, and the system performance is analyzed. The interrogation system shows a good prospect for smart sensing.

  17. Suitability of integrated protection diodes from diverse semiconductor technologies

    NARCIS (Netherlands)

    Wanum, M. van; Lebouille, T.T.N.; Visser, G.C.; Vliet, F.E. van

    2009-01-01

    In this article diodes from three different semiconductor technologies are compared based on their suitability to protect a receiver. The semiconductor materials involved are Silicon, Gallium Arsenide and Gallium Nitride. The diodes in the diverse semiconductor technologies themselves are close in

  18. Hybrid Spintronic Structures With Magnetic Oxides and Heusler Alloys

    DEFF Research Database (Denmark)

    Xu, Y. B.; Hassan, S. S. A.; Wong, P. K. J.

    2008-01-01

    As(100) and the unit cell of the Fe3O4 was found to be rotated by 45 degrees to match the gallium arsenide GaAs. The films were found to have a bulk-like moment down to 3-4 nm and a low coercivity indicating a high-quality magnetic interface. The magnetization hysteresis loops of the ultrathin films...

  19. Alkali Metal Thermal to Electric Conversion Research.

    Science.gov (United States)

    1995-03-01

    Acquisition System GaAs Gallium Arsenide HCI Hydrochloric Acid Mo Molybdenum Na Sodium NaS Sodium Sulfur PL Phillips Laboratory Si Silicon TC Thermocouple...back to the heat source and the hot liquid reservoir to complete the thermodynamic cycle. The Sodium - Sulfur (NaS) battery differs from AMTEC only in

  20. The Physics and Operations of Ultra-Submicron Length Semiconductor Devices

    Science.gov (United States)

    1974-05-01

    Shaw, P. R. Solomon , and H. L. Grubin, IBM J. Res. Dev: 13, 587 (1%9). 26 INTRODUCTION TO THE PHYSICS OF GALLIUM ARSENIDE DEVICES 17. E. M. Azoff...and P. Kocevar, Phys. Rev. B 28, 7040 (1980). 9. M. Asche and 0. G. Sarbei, Phys. Stat. Sol. (b) 126, 607 (1984). 10. M. A. Osman, U. Ravaioli, R

  1. Quaterly Assessment of Irradiance Variation on Power Output and Storable Excess Power of Solar Panels

    National Research Council Canada - National Science Library

    T O Familusi; Y K Sanusi; H O Efunwole; A M Raimi

    2014-01-01

      This paper verified the input solar irradiance and average power output per day of a 10W polycrystalline silicon solar panel and a 10W gallium arsenide solar panel, both of dimension 350x290x25mm^sup 3^, fill-factor...

  2. Modeling the Growth of Aluminum Gallium Nitride ((Al)GaN) Films Grown on Aluminum Nitride (AlN) Substrates

    Science.gov (United States)

    2011-03-01

    cadmium zinc telluride ( CdZnTe or CZT) on Si using a superlattice (SL) in which the SL layers had different compositions (10). We found that the...Abbreviations, and Acronyms (Al)GaN aluminum gallium arsenide AlN aluminum nitride ARL U.S. Army Research Laboratory CdZnTe or CZT cadmium zinc

  3. Surround-gated vertical nanowire quantum dots

    NARCIS (Netherlands)

    Van Weert, M.H.M.; Den Heijer, M.; Van Kouwen, M.P.; Algra, R.E.; Bakkers, E.P.A.M.; Kouwenhoven, L.P.; Zwiller, V.

    2010-01-01

    We report voltage dependent photoluminescence experiments on single indium arsenide phosphide (InAsP) quantum dots embedded in vertical surround-gated indium phosphide (InP) nanowires. We show that by tuning the gate voltage, we can access different quantum dot charge states. We study the

  4. Low temperature transport in p-doped InAs nanowires

    DEFF Research Database (Denmark)

    Upadhyay, Shivendra; Jespersen, Thomas Sand; Madsen, Morten Hannibal

    2013-01-01

    We present low temperature electrical measurements of p-type Indium Arsenide nanowires grown via molecular beam epitaxy using Beryllium as a dopant. Growth of p-type wires without stacking faults is demonstrated. Devices in field-effect geometries exhibit ambipolar behavior, and the temperature d...

  5. The Effects of Strain on the Electrical Properties of Thin Evaporated Films of Semiconductor Compounds

    Science.gov (United States)

    Steel, G. G.

    1970-01-01

    Reports on project intended to establish how electrical resistance, Hall voltage, and magnetoresistance change when a thin film specimen is subjected to mechanical strain. Found resistance of semiconducting film of indium arsenide and indium antimonide decreases with tension and increases with compression. (LS)

  6. Simple intrinsic defects in InAs :

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, Peter Andrew

    2013-03-01

    This Report presents numerical tables summarizing properties of intrinsic defects in indium arsenide, InAs, as computed by density functional theory using semi-local density functionals, intended for use as reference tables for a defect physics package in device models.

  7. 500 MHz transient digitizers based on GaAs CCds (charged coupled devices)

    Energy Technology Data Exchange (ETDEWEB)

    Bryman, D.; Cresswell, J.V.; LeNoble, M.; Poutissou, R.

    1990-06-01

    A wide bandwidth transient digitizer based on a recently produced gallium arsenide charge coupled device (CCD) is under development. The CCD's have 128 pixels and operate at 500 MHz. Initial testing of prototype modules in Experiment 787 at Brookhaven National Laboratory is reported. 8 refs., 6 figs.

  8. 500 MHz transient digitizers based on GaAs CCDs

    Science.gov (United States)

    Bryman, D.; Cresswell, J. V.; LeNoble, M.; Poutissou, R.

    1991-04-01

    A wide-bandwidth transient digitizer based on a gallium arsenide charged-coupled device (CCD) is under development. The CCDs have 128 pixels and operate at 500 MHz. Prototype CCD digitizers which sample at 2-ns intervals for a period of 256 ns have been constructed and tested in Experiment 787 at Brookhaven National Laboratory.

  9. 500 MHz transient digitizers based on GaAs CCDs

    Science.gov (United States)

    Bryman, D. A.; Constable, M.; Cresswell, J. V.; Daviel, A.; LeNoble, M.; Mildenberger, J.; Poutissou, R.

    1997-02-01

    A system of 500 MHz transient digitizers based on gallium arsenide resistive gate charged coupled devices has been developed for an experiment to study rare K decays. CCDs with dynamic range of 8-bits and 128 or 320 pixels are used as analog pipelines. The CCDs are driven by a single phase transport system. Data readout and manipulation occurs at 15.6 MHz.

  10. Extreme sensitivity of superconductivity to stoichiometry in Fe1+?Se

    NARCIS (Netherlands)

    McQueen, T.M.; Huang, Q.; Ksenofontov, V.; Felser, C.; Xu, Q.; Zandbergen, H.; Hor, Y.S.; Allred, J.; Williams, A.J.; Qu, D.; Checkelsky, J.; Ong, N.P.; Cava, R.J.

    2009-01-01

    The recently discovered iron arsenide superconductors appear to display a universal set of characteristic features, including proximity to a magnetically ordered state and robustness of the superconductivity in the presence of disorder. Here we show that superconductivity in Fe1+?Se, which can be

  11. Modeling of High Efficiency Solar Cells Under Laser Pulse for Power Beaming Applications

    Science.gov (United States)

    Jain, Raj K.; Landis, Geoffrey A.

    1994-01-01

    Solar cells may be used as receivers for laser power beaming. To understand the behavior of solar cells when illuminated by a pulsed laser, the time response of gallium arsenide and silicon solar cells to pulsed monochromatic input has been modeled using a finite element solar cell model.

  12. High-performance green flexible electronics based on biodegradable cellulose nanofibril paper

    Science.gov (United States)

    Yei Hwan Jung; Tzu-Hsuan Chang; Huilong Zhang; Chunhua Yao; Qifeng Zheng; Vina W. Yang; Hongyi Mi; Munho Kim; Sang June Cho; Dong-Wook Park; Hao Jiang; Juhwan Lee; Yijie Qiu; Weidong Zhou; Zhiyong Cai; Shaoqin Gong; Zhenqiang Ma

    2015-01-01

    Today’s consumer electronics, such as cell phones, tablets and other portable electronic devices, are typically made of non-renewable, non-biodegradable, and sometimes potentially toxic (for example, gallium arsenide) materials. These consumer electronics are frequently upgraded or discarded, leading to serious environmental contamination. Thus, electronic systems...

  13. High-temperature optically activated GaAs power switching for aircraft digital electronic control

    Science.gov (United States)

    Berak, J. M.; Grantham, D. H.; Swindal, J. L.; Black, J. F.; Allen, L. B.

    1983-01-01

    Gallium arsenide high-temperature devices were fabricated and assembled into an optically activated pulse-width-modulated power control for a torque motor typical of the kinds used in jet engine actuators. A bipolar heterojunction phototransistor with gallium aluminum arsenide emitter/window, a gallium arsenide junction field-effect power transistor and a gallium arsenide transient protection diode were designed and fabricated. A high-temperature fiber optic/phototransistor coupling scheme was implemented. The devices assembled into the demonstrator were successfully tested at 250 C, proving the feasibility of actuator-located switching of control power using optical signals transmitted by fibers. Assessments of the efficiency and technical merits were made for extension of this high-temperature technology to local conversion of optical power to electrical power and its control at levels useful for driving actuators. Optical power sources included in the comparisons were an infrared light-emitting diode, an injection laser diode, tungsten-halogen lamps and arc lamps. Optical-to-electrical power conversion was limited to photovoltaics located at the actuator. Impedance matching of the photovoltaic array to the load was considered over the full temperature range, -55 C to 260 C. Loss of photovoltaic efficiency at higher temperatures was taken into account. Serious losses in efficiency are: (1) in the optical source and the cooling which they may require in the assumed 125 C ambient, (2) in the decreased conversion efficiency of the gallium arsenide photovoltaic at 260 C, and (3) in impedance matching. Practical systems require improvements in these areas.

  14. Luminescent properties of Al{sub 2}O{sub 3}: Tb powders; Propiedades luminiscentes de polvos de Al{sub 2}O{sub 3}: Tb

    Energy Technology Data Exchange (ETDEWEB)

    Esparza G, A.E.; Garcia, M.; Falcony, C.; Azorin N, J. [CICATA-IPN, Legaria 694, Col. Irrigacion, 11500 Mexico D.F. (Mexico)

    2000-07-01

    In this work the photo luminescent and cathode luminescent characteristics of aluminium oxide (Al{sub 2}O{sub 3}) powders impurified with terbium (Tb) were studied for their use in dosimetry. The optical, structural, morphological characteristics of the powders as function of variation in the impurity concentration and the annealing temperature will be presented. As regards the optical properties of powders (photoluminescence and cathode luminescence) it was observed a characteristic emission associated with radiative transitions between electron energy levels of terbium, the spectra associated with this emission consists of several peaks associated with such transitions. In the structural and morphological characterization (X-ray diffraction and scanning electron microscopy) it was appreciated that in accordance the annealing temperature of powders is augmented it is evident the apparition of certain crystalline phases. The results show that this is a promissory material for radiation dosimetry. (Author)

  15. Plastic optical fibre sensor for in-vivo radiation monitoring during brachytherapy

    Science.gov (United States)

    Woulfe, P.; Sullivan, F. J.; Lewis, E.; O'Keeffe, S.

    2015-09-01

    An optical fibre sensor is presented for applications in real-time in-vivo monitoring of the radiation dose a cancer patient receives during seed implantation in Brachytherapy. The sensor is based on radioluminescence whereby radiation sensitive scintillation material is embedded in the core of a 1mm plastic optical fibre. Three scintillation materials are investigated: thallium-doped caesium iodide (CsI:Tl), terbium-doped gadolinium oxysulphide (Gd2O2S:Tb) and europium-doped lanthanum oxysulphide (La2O2S:Eu). Terbium-doped gadolinium oxysulphide was identified as being the most suitable scintillator and further testing demonstrates its measureable response to different activities of Iodine-125, the radio-active source commonly used in Brachytherapy for treating prostate cancer.

  16. [Luminescent cytochemical methods of detecting microorganisms].

    Science.gov (United States)

    Ivanovskaia, N P; Osin, N S; Khramov, E N; Zlobin, V N

    1999-01-01

    The paper shows that the luminescence cytochemical technique can be used for identification of microorganisms and microbiological synthesis products. The method is based on the interaction of specific fluorescence probes (ANS, terbium ions, and beta-diketonate complexes of europium, as well as metal-containing porphyrines) with major microbial intracellular components and toxins. Unlike classical microbiological, immunochemical or biochemical methods of detection, the proposed method has a reasonable versatility, specificity, sensitivity, rapid action, and possible automation.

  17. Radiotherapy dosimetry based on plastic optical fibre sensors

    Science.gov (United States)

    O'Keeffe, S.; Grattan, M.; Hounsell, A.; McCarthy, D.; Woulfe, P.; Cronin, J.; Lewis, E.

    2013-05-01

    The use of a PMMA based plastic optical fibre in radiotherapy dosimetry is presented. The optical fibre tip is coated with a scintillation material, terbium-doped gadolinium oxysulfide (Gd2O2S:Tb), which fluoresces under ionising radiation. The emitted signal penetrates the fibre and propagates along the fibre where it is remotely monitored using a fluorescence spectrometer. The results demonstrate good repeatability, with a maximum percentage error of 0.59% and the response is independent of dose rate.

  18. Luminescent Lanthanide Metal Organic Frameworks for cis-Selective Isoprene Polymerization Catalysis

    OpenAIRE

    Samantha Russell; Thierry Loiseau; Christophe Volkringer; Marc Visseaux

    2015-01-01

    In this study, we are combining two areas of chemistry; solid-state coordination polymers (or Metal-Organic Framework—MOF) and polymerization catalysis. MOF compounds combining two sets of different lanthanide elements (Nd3+, Eu3+/Tb3+) were used for that purpose: the use of neodymium was required due to its well-known catalytic properties in dienes polymerization. A second lanthanide, europium or terbium, was included in the MOF structure with the aim to provide luminescent properties. Sev...

  19. Modeled Neutron Induced Nuclear Reaction Cross Sections for Radiochemsitry in the region of Thulium, Lutetium, and Tantalum I. Results of Built in Spherical Symmetry in a Deformed Region

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, R. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2013-09-06

    We have developed a set of modeled nuclear reaction cross sections for use in radiochemical diagnostics. Systematics for the input parameters required by the Hauser-Feshbach statistical model were developed and used to calculate neutron induced nuclear reaction cross sections for targets ranging from Terbium (Z = 65) to Rhenium (Z = 75). Of particular interest are the cross sections on Tm, Lu, and Ta including reactions on isomeric targets.

  20. Factors Affecting the Efficiency of Excited-States Interactions of Complexes between Some Visible Light-Emitting Lanthanide Ions and Cyclophanes Containing Spirobiindanol Phosphonates

    Directory of Open Access Journals (Sweden)

    M. S. Attia

    2007-01-01

    Full Text Available The efficiency of excited-states interactions between lanthanide ions Tb3+ and Eu3+ and some new cyclophanes (I, II, and III has been studied in different media. High luminescence quantum yield values for terbium and europium complexes in DMSO and PMMA were obtained. The photophysical properties of the green and red emissive Tb3+ and Eu3+ complexes have been elucidated, respectively.

  1. The effect of core and lanthanide ion dopants in sodium fluoride-based nanocrystals on phagocytic activity of human blood leukocytes

    Science.gov (United States)

    Sojka, Bartlomiej; Liskova, Aurelia; Kuricova, Miroslava; Banski, Mateusz; Misiewicz, Jan; Dusinska, Maria; Horvathova, Mira; Ilavska, Silvia; Szabova, Michaela; Rollerova, Eva; Podhorodecki, Artur; Tulinska, Jana

    2017-02-01

    Sodium fluoride-based β-NaLnF4 nanoparticles (NPs) doped with lanthanide ions are promising materials for application as luminescent markers in bio-imaging. In this work, the effect of NPs doped with yttrium (Y), gadolinium (Gd), europium (Eu), thulium (Tm), ytterbium (Yb) and terbium (Tb) ions on phagocytic activity of monocytes and granulocytes and the respiratory burst was examined. The surface functionalization of leukocytes and respiratory burst of cells was observed for limited number of samples.

  2. The effect of metal distribution on the luminescence properties of mixed-lanthanide metal-organic frameworks.

    Science.gov (United States)

    Cadman, Laura K; Mahon, Mary F; Burrows, Andrew D

    2018-02-13

    A series of lanthanide metal-organic frameworks (MOFs) of the general formula [Ln(Hodip)(H 2 O)]·nH 2 O (Sm, 1; Eu, 2; Gd, 3; Tb, 4; Dy, 5; Er, 6; H 4 odip = 5,5'-oxydiisophthalic acid) have been prepared and shown crystallographically to have isostructural three-dimensional frameworks. The fluorescence emission spectra of the europium compound 2, which is red, and the terbium compound 4, which is green, show characteristic peaks for transitions involving the metal centres, whereas that for the gadolinium compound 3 is dominated by transitions involving Hodip. Using a 1 : 1 : 1 mixture of europium, gadolinium and terbium nitrates in the synthesis resulted in the mixed-metal MOF [Gd 0.17 Tb 0.19 Eu 0.64 (Hodip)(H 2 O)]·nH 2 O 7, for which the ratio of the metal ions was determined using EDX spectroscopy. The fluorescence emission spectrum of 7 is dominated by europium emission bands reflecting the higher proportion of Eu 3+ centres and quenching of the terbium fluorescence by metal-to-metal energy transfer. A series of core-shell MOF materials based on the Ln(Hodip)(H 2 O) framework have been prepared in order to isolate the lanthanides in different domains within the crystals. The emission spectra for materials with Gd@Tb@Eu (8) and Tb@Eu@Gd (9) are dominated by terbium emissions, suggesting that physical separation from europium suppresses quenching. In contrast, the material with Eu@Gd@Tb (10) shows only broad ligand bands and europium emissions. This confirms that core-shell MOFs have different fluorescence properties to simple mixed-metal MOFs, demonstrating that the spatial distribution of the metals within a mixed-lanthanide MOF affects the fluorescence behaviour.

  3. Synthesis and stimulated luminescence property of Zn(BO2)2:Tb(3).

    Science.gov (United States)

    Del Rosario, G Cedillo; Cruz-Zaragoza, E; Hipólito, M García; Marcazzó, J; Hernández A, J M; Murrieta S, H

    2017-09-01

    Zinc borate, Zn(BO2)2, doped with different concentrations of terbium (0.5-8mol%) was synthesized and polycrystalline samples were characterized by Scanning Electron Microscopy and X-Ray Diffraction. The Zn(BO2)2 was formed in the pure samples sintered at 750 and 800°C which has the body centered cubic structure, and a ZnB4O7 primitive orthorhombic phase was present. The thermoluminescent intensity was dependents on the thermal treatment (250-500°C) and also on the impurity concentration. The linear dose-response was obtained between 0.022-27.7Gy and 0.5-50Gy when the samples were exposed to beta and gamma radiation, respectively. The complex structure of the glow curves was analyzed by the Computerized Glow Curve Deconvolution method. The kinetics parameters were calculated assuming the general order kinetics model describing accurately the TL process. The glow curves of Tb(3+)-doped zinc borate phosphor were well deconvolved by six glow peaks. Zinc borate with 8mol% of impurity concentration exhibited an intense radioluminescent emission. The radioluminescent spectra show their maximum bands at 370, 490, 545 and 700nm related to the terbium ion in the zinc borate. These obtained results suggest that the terbium doped zinc borate is a promising phosphor for use in radiation dosimetry because of its high TL sensitivity to the ionizing radiation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Effect of Ising-type Tb3+ ions on the low-temperature magnetism of La, Ca cobaltite.

    Science.gov (United States)

    Knížek, K; Jirák, Z; Hejtmánek, J; Veverka, M; Kaman, O; Maryško, M; Santavá, E; André, G

    2014-03-19

    Crystal and magnetic structures of the x = 0.2 member of the La0.8-xTbxCa0.2CoO3 perovskite series have been determined from powder neutron diffraction. Enhancement of the diffraction peaks due to ferromagnetic or cluster glass ordering is observed below TC = 55 K. The moments first evolve on Co sites, and ordering of Ising-type Tb(3+) moments is induced at lower temperatures by a molecular field due to Co ions. The final magnetic configuration is collinear Fx for the cobalt subsystem, while it is canted FxCy for terbium ions. The rare-earth moments align along local Ising axes within the ab-plane of the orthorhombic Pbnm structure. The behavior in external fields up to 70-90 kOe has been probed by magnetization and heat capacity measurements. The dilute terbium ions contribute to significant coercivity and remanence that both steeply increase with decreasing temperature. A remarkable manifestation of the Tb(3+) Ising character is the observation of a low-temperature region with an anomalously large linear term of heat capacity and its field dependence. Similar behaviors are detected also for other terbium dopings x = 0.1 and 0.3.

  5. Luminescence enhancement by energy transfer in melamine-Y{sub 2}O{sub 3}:Tb{sup 3+} nanohybrids

    Energy Technology Data Exchange (ETDEWEB)

    Stagi, Luigi, E-mail: luigi.stagi@dsf.unica.it; Chiriu, Daniele; Carbonaro, Carlo M.; Ricci, Pier Carlo [Dipartimento di Fisica, Università degli Studi di Cagliari, S.P. Monserrato-Sestu Km 0,700, 09042 Monserrato (Italy); Ardu, Andrea; Cannas, Carla [Departimento di Scienze Chimiche e Geologiche and INSTM, Università d Cagliari, SS 554 bivio Sestu, I-09042 Monserrato (Italy)

    2015-09-28

    The phenomenon of luminescence enhancement was studied in melamine-Y{sub 2}O{sub 3}:Tb hybrids. Terbium doped Y{sub 2}O{sub 3} mesoporous nanowires were synthesized by hydrothermal method. X-ray diffraction patterns and Raman scattering spectra testified the realization of a cubic crystal phase. Organic-inorganic melamine-Y{sub 2}O{sub 3}:Tb{sup 3+} hybrid system was successfully obtained by vapour deposition method. Vibration Raman active modes of the organic counterpart were investigated in order to verify the achievement of hybrid system. Photoluminescence excitation and photoluminescence spectra, preformed in the region between 250 and 350 nm, suggest a strong interaction among melamine and Terbium ions. In particular, a remarkable improvement of {sup 5}D{sub 4}→ F{sub J} Rare Earth emission (at about 542 nm) of about 10{sup 2} fold was observed and attributed to an efficient organic-Tb energy transfer. The energy transfer mechanism was studied by the use of time resolved photoluminescence measurements. The melamine lifetime undergoes to a significant decrease when adsorbed to oxide surfaces and it was connected to a sensitization mechanism. The detailed analysis of time decay profile of Terbium radiative recombination shows a variation of double exponential law toward a single exponential one. Its correlation with surface defects and non-radiative recombination was thus discussed.

  6. Annealing furnace for III-V semiconductor devices

    Science.gov (United States)

    O'Connor, J. M.; Hier, H. S.; Ketchum, R. M.

    1986-02-01

    A furnace for annealing ion implantation damage in III-V semiconductors has been built and tested. Designed for research applications, the furnace can accommodate odd shapes of material up to 2 in. in diameter. Samples are loaded onto a novel cantilevered support and are not moved during the annealing operation, facilitating proximity annealing techniques. Both chambers of this dual chambered system are O-ring sealed for added safety during annealing in an arsine gas ambient. Electron mobilities between 4400 and 4600 cm2/V s at 300 K are routinely measured for 2×1017 cm-3 gallium arsenide material annealed in this sytem. The system has been used to anneal indium phosphide as well as gallium arsenide wafers.

  7. High-performance green flexible electronics based on biodegradable cellulose nanofibril paper

    Science.gov (United States)

    Jung, Yei Hwan; Chang, Tzu-Hsuan; Zhang, Huilong; Yao, Chunhua; Zheng, Qifeng; Yang, Vina W.; Mi, Hongyi; Kim, Munho; Cho, Sang June; Park, Dong-Wook; Jiang, Hao; Lee, Juhwan; Qiu, Yijie; Zhou, Weidong; Cai, Zhiyong; Gong, Shaoqin; Ma, Zhenqiang

    2015-01-01

    Today's consumer electronics, such as cell phones, tablets and other portable electronic devices, are typically made of non-renewable, non-biodegradable, and sometimes potentially toxic (for example, gallium arsenide) materials. These consumer electronics are frequently upgraded or discarded, leading to serious environmental contamination. Thus, electronic systems consisting of renewable and biodegradable materials and minimal amount of potentially toxic materials are desirable. Here we report high-performance flexible microwave and digital electronics that consume the smallest amount of potentially toxic materials on biobased, biodegradable and flexible cellulose nanofibril papers. Furthermore, we demonstrate gallium arsenide microwave devices, the consumer wireless workhorse, in a transferrable thin-film form. Successful fabrication of key electrical components on the flexible cellulose nanofibril paper with comparable performance to their rigid counterparts and clear demonstration of fungal biodegradation of the cellulose-nanofibril-based electronics suggest that it is feasible to fabricate high-performance flexible electronics using ecofriendly materials. PMID:26006731

  8. Solar-electrochemical power system for a Mars mission

    Science.gov (United States)

    Withrow, Colleen A.; Morales, Nelson

    1994-12-01

    This report documents a sizing study of a variety of solar electrochemical power systems for the intercenter NASA study known as 'Mars Exploration Reference Mission'. Power systems are characterized for a variety of rovers, habitation modules, and space transport vehicles based on requirements derived from the reference mission. The mission features a six-person crew living on Mars for 500 days. Mission power requirements range from 4 kWe to 120 kWe. Primary hydrogen and oxygen fuel cells, regenerative hydrogen and oxygen fuel cells, sodium sulfur batteries advanced photovoltaic solar arrays of gallium arsenide on germanium with tracking and nontracking mechanisms, and tent solar arrays of gallium arsenide on germanium are evaluated and compared.

  9. 31% European InGaP/GaAs/InGaAs Solar Cells for Space Application

    Directory of Open Access Journals (Sweden)

    Campesato Roberta

    2017-01-01

    Full Text Available We report a triple junction InGaP/GaAs/InGaNAs solar cell with efficiency of ~31% at AM0, 25 °C fabricated using a combined molecular beam epitaxy (MBE and metal-organic chemical vapour deposition (MOCVD processes. The prototype cells comprise of InGaNAs (Indium Gallium Nitride Arsenide bottom junction grown on a GaAs (Gallium Arsenide substrate by MBE and middle and top junctions deposited by MOCVD. Repeatable cell characteristics and uniform efficiency pattern over 4-inch wafers were obtained. Combining the advantages offered by MBE and MOCVD opens a new perspective for fabrication of high-efficiency space tandem solar cells with three or more junctions. Results of radiation resistance of the sub-cells are also presented and critically evaluated to achieve high efficiency in EOL conditions.

  10. Terminal tungsten pnictide complex formation through pnictaethynolate decarbonylation.

    Science.gov (United States)

    Joost, Maximilian; Transue, Wesley J; Cummins, Christopher C

    2017-09-26

    Tungsten(iv) tetrakis(2,6-diisopropylphenoxide) (1) has been demonstrated to be a competent platform for decarbonylative formation of anionic terminal pnictide complexes upon treatment with pnictaethynolate anions: cyanate, 2-phosphaethynolate, and 2-arsaethynolate. These transformations constitute the first examples of terminal phosphide and arsenide complex formation at a transition metal center from OCP- and OCAs-, respectively. The phosphide and arsenide complexes are also the first to be isolated in a tetragonal, all-oxygen ligand environment. The scalar NMR coupling constants between tungsten-183 and nitrogen-15 or phosphorus-31 have been measured and contextualized using natural bond orbital (NBO) methods in terms of s orbital character in the σ bonding orbital and pnictide lone pair.

  11. Coherent Cancellation of Photothermal Noise in GaAs/Al$_{0.92}$Ga$_{0.08}$As Bragg Mirrors

    CERN Document Server

    Chalermsongsak, Tara; Cole, Garrett D; Follman, David; Seifert, Frank; Arai, Koji; Gustafson, Eric K; Smith, Joshua R; Aspelmeyer, Markus; Adhikari, Rana X

    2015-01-01

    Thermal noise is a limiting factor in many high-precision optical experiments. A search is underway for novel optical materials with reduced thermal noise. One such pair of materials, gallium arsenide and aluminum-alloyed gallium arsenide (collectively referred to as AlGaAs), shows promise for its low Brownian noise when compared to conventional materials such as silica and tantala. However, AlGaAs has the potential to produce a high level of thermo-optic noise. We have fabricated a set of AlGaAs crystalline coatings, transferred to fused silica substrates, whose layer structure has been optimized to reduce thermo-optic noise by inducing coherent cancellation of the thermoelastic and thermorefractive effects. By measuring the photothermal transfer function of these mirrors, we find evidence that this optimization has been successful.

  12. Space station automation study. Automation requirements derived from space manufacturing concepts. Volume 1: Executive summary

    Science.gov (United States)

    1984-01-01

    The two manufacturing concepts developed represent innovative, technologically advanced manufacturing schemes. The concepts were selected to facilitate an in depth analysis of manufacturing automation requirements in the form of process mechanization, teleoperation and robotics, and artificial intelligence. While the cost effectiveness of these facilities has not been analyzed as part of this study, both appear entirely feasible for the year 2000 timeframe. The growing demand for high quality gallium arsenide microelectronics may warrant the ventures.

  13. Textural, mineralogical and stable isotope studies of hydrothermal alteration in the main sulfide zone of the Great Dyke, Zimbabwe and the precious metals zone of the Sonju Lake Intrusion, Minnesota, USA

    Science.gov (United States)

    Li, C.; Ripley, E.M.; Oberthur, T.; Miller, J.D.; Joslin, G.D.

    2008-01-01

    Stratigraphic offsets in the peak concentrations of platinum-group elements (PGE) and base-metal sulfides in the main sulfide zone of the Great Dyke and the precious metals zone of the Sonju Lake Intrusion have, in part, been attributed to the interaction between magmatic PGE-bearing base-metal sulfide assemblages and hydrothermal fluids. In this paper, we provide mineralogical and textural evidence that indicates alteration of base-metal sulfides and mobilization of metals and S during hydrothermal alteration in both mineralized intrusions. Stable isotopic data suggest that the fluids involved in the alteration were of magmatic origin in the Great Dyke but that a meteoric water component was involved in the alteration of the Sonju Lake Intrusion. The strong spatial association of platinum-group minerals, principally Pt and Pd sulfides, arsenides, and tellurides, with base-metal sulfide assemblages in the main sulfide zone of the Great Dyke is consistent with residual enrichment of Pt and Pd during hydrothermal alteration. However, such an interpretation is more tenuous for the precious metals zone of the Sonju Lake Intrusion where important Pt and Pd arsenides and antimonides occur as inclusions within individual plagioclase crystals and within alteration assemblages that are free of base-metal sulfides. Our observations suggest that Pt and Pd tellurides, antimonides, and arsenides may form during both magmatic crystallization and subsolidus hydrothermal alteration. Experimental studies of magmatic crystallization and hydrothermal transport/deposition in systems involving arsenides, tellurides, antimonides, and base metal sulfides are needed to better understand the relative importance of magmatic and hydrothermal processes in controlling the distribution of PGE in mineralized layered intrusions of this type. ?? Springer-Verlag 2007.

  14. Use of accelerated helium-3 ions for determining oxygen and carbon impurities in some pure materials

    Science.gov (United States)

    Aleksandrova, G. I.; Borisov, G. I.; Demidov, A. M.; Zakharov, Y. A.; Sukhov, G. V.; Shmanenkova, G. I.; Shchelkova, V. P.

    1978-01-01

    Methods are developed for the determination of O impurity in Be and Si carbide and concurrent determination of C and O impurities in Si and W by irradiation with accelerated He-3 ions and subsequent activity measurements of C-11 and F-18 formed from C and O with the aid of a gamma-gamma coincidence spectrometer. Techniques for determining O in Ge and Ga arsenide with radiochemical separation of F-18 are also described.

  15. Use of a semiconductor-diode laser in urology

    Science.gov (United States)

    Watson, Graham M.

    1994-05-01

    The gallium arsenide semiconductor laser can emit in the near infrared where the depth of penetration into tissue is great although scattering is less than with the Nd:YAG laser. The laser is highly compact. It runs off a normal electrical outlet with no cooling requirement. It is therefore quiet and convenient. The laser has been assessed in a wide variety of applications in our urological department.

  16. Optical beam induced current investigations of particle detectors

    Energy Technology Data Exchange (ETDEWEB)

    Castaldini, A.; Cavallini, A.; Polenta, L. [INFM, Bologna (Italy)

    2000-11-01

    OBIC analyses of particle detectors are presented. The depletion layer width W of semi-insulating gallium arsenide Schottky detectors versus biasing has been studied and it is concluded that at high voltages W linearly increases with the applied bias. Furthermore, the electric field distribution in silicon p-i-n detectors has been investigated before and after heavy irradiation and a V-shaped distribution has been assessed. (orig.)

  17. None

    Energy Technology Data Exchange (ETDEWEB)

    Cason, D.L.; Hicks, S.C. [eds.

    1994-03-01

    This publication announces, bimonthly, current worldwide information available on all aspects of photovoltaic amorphous technology, polycrystalline thin films, gallium arsenide, crystalline silicon, concentrator technology, and systems research. It contains abstracts of DOE reports, journal articles, conference papers, patents, theses, and monographs added to the Energy Science and Technology Database during the past two months. Also included are U.S. information obtained through acquisition programs or interagency agreements and international information.

  18. The AMOS cell - An improved metal-semiconductor solar cell. [Antireflection coated Metal Oxide Semiconductor

    Science.gov (United States)

    Stirn, R. J.; Yeh, Y.-C. M.

    1975-01-01

    A new fabrication process is being developed which significantly improves the efficiency of metal-semiconductor solar cells. The resultant effect, a marked increase in the open-circuit voltage, is produced by the addition of an interfacial layer oxide on the semiconductor. Cells using gold on n-type gallium arsenide have been made in small areas (0.17 sq cm) with conversion efficiencies of 15% in terrestrial sunlight.

  19. JPRS Report, Science & Technology, Europe

    Science.gov (United States)

    1991-12-30

    Microprocessor Program Launched [R. Loukil; Paris INDUSTRIES ET TECHNIQUES, 20 Sep 91] 43 Eastern German Firm Becomes Sole European Gallium Arsenide Producer...that the reaction of tissues in contact with a nickel-titanium prosthesis stabilizes, as with stainless steel, within the first 3 months after...many others, has been brought to its knees by Japan, could adopt SLMI, since it is a highly innovative product that can be used to develop an

  20. Embedment of metal nanoparticles in GaAs and Si for plasmonic absorption enhancement in intermediate band solar cells

    OpenAIRE

    Moura Dias Mendes, Manuel Joao de; Hernández Martín, Estela; Tobías Galicia, Ignacio; Martí Vega, Antonio; Luque López, Antonio

    2010-01-01

    The high near-field enhancement occurring in the vicinity of metallic nanoparticles (MNPs) sustaining surface plasmons can only be fully exploited in photovoltaic devices if the MNPs are placed inside their semiconducting material, in the photoactive region. In this work an experimental procedure is studied to embed MNPs in gallium arsenide (GaAs) and silicon (Si), which can be applied to other semiconductor host materials. The approach consists in spin-coating colloidal MNPs dispersed i...

  1. Spatial light modulation in compound semiconductor materials

    Science.gov (United States)

    Cheng, Li-Jen (Inventor); Gheen, Gregory O. (Inventor); Partovi, Afshin (Inventor)

    1990-01-01

    Spatial light modulation (22) in a III-V single crystal (12), e.g., gallium arsenide, is achieved using the photorefractive effect. Polarization rotation created by beam coupling is utilized in one embodiment. In particular, information (16)on a control beam (14) incident on the crystal is transferred to an input beam (10), also incident on the crystal. An output beam (18) modulated in intensity is obtained by passing the polarization-modulated input beam through a polarizer (20).

  2. Base-Level Management of Laser Radiation Protection Program

    Science.gov (United States)

    1992-02-01

    gallium-aluminum-arsenide (GaAlAs), or alexandrite. Liquid materials that are used as active mediums include: rhodamine dye and coumarin . Section D...a source of radiation and the dye emits radiation at a longer wavelength. Coumarin dyes are useful as active media for emissions inthe blue to green...plastic, or quartz. Optical fibers have found uses in many areas including: industrial laser welding; medical surgery; dental work; product-code

  3. Failure Mechanisms of GaAs Transistors - A Literature Survey

    Science.gov (United States)

    1990-03-01

    Orito et al, Large Size Dislocation-Free Gallium Arsenide Single Crystals for LSI Applications, GaAs IC Symposium, October 1986, Technical Digest 1986...the channel resistance is modulated by the channel dimensions and the transconductance is degraded by the parasitic resistance. gn = gmo /(l+Rs gmo ...gm is the terminal transconductance, gmo is the internal (Rs=0 ) transconductance and Rs is the parasitic source resistance. It’s obvious that it’s

  4. Diffusion theory and optimization of ohmic contacts to n-layer of bipolar nanoheterostructures

    Science.gov (United States)

    Nezhentsev, A. V.; Zemlyakov, V. E.; Egorkin, V. I.; Garmash, V. I.

    2017-11-01

    Ohmic contacts to n-layers of gallium arsenide-based heterobipolar nanoheterostructures obtained by layer electron-beam evaporation Ge/Au/Ni/Au are studied. Time and temperature dependencies of diffusion profiles of doping Ge distribution are calculated. The interface of metal-semiconductor is analyzed with SEM, then an RTA installation design and methodology of RTA are suggested based on the results of this study. This allows to obtain ohmic contacts with low resistance and minimum transition layer.

  5. Lunar Laser Communication System

    Science.gov (United States)

    2014-10-01

    gallium arsenide ( InGaAs ) quad- rant detector enables fast spatial acqui- sition and coarse tracking of the optical uplink. Transmit and receive...October–November 2013 month-long demonstration of the high-data-rate transmission from a lunar-orbiting satellite. The array of transmit apertures is...located above the array of receive apertures. This work is sponsored by the National Aeronautics and Space Administration under U.S. Air Force

  6. [Use of laser therapy in inflammatory diseases of the paranasal sinuses].

    Science.gov (United States)

    Elistratov, V V; Naumov, G P; Naumov, O G; Fishkin, V A

    1996-01-01

    105 patients with acute and chronic inflammation of the paranasal sinuses were exposed to the radiation of the semiconductor laser Uzor using gallium arsenide. The treatment combined antiinflammatory drugs with vasoconstrictive nasal drops, maxillary puncture and laser radiation. Intolerance to laser effects was registered in 3 patients. The course of treatment included 5-6 sessions in acute sinusitis and 10 sessions in chronic sinusitis. Laser therapy was found effective as it reduced the time of treatment by 1-2 days.

  7. Small Business Innovations (Photodetector)

    Science.gov (United States)

    1991-01-01

    Epitaxx, Inc. of Princeton, NJ, developed the Epitaxx Near Infrared Room Temperature Indium-Gallium-Arsenide (InGaAs) Photodetector based on their Goddard Space Flight Center Small Business Innovation Research (SBIR) contract work to develop a linear detector array for satellite imaging applications using InGaAs alloys that didn't need to be cooled to (difficult and expensive) cryogenic temperatures. The photodetectors can be used for remote sensing, fiber optic and laser position-sensing applications.

  8. Design and characterization of a novel diamond resonator

    OpenAIRE

    Maricar, Mohamed Ismaeel; Glover, James; Evans, Gwynne; Khalid, Ata-ul-Habib; Cumming, David; Oxley, Chris

    2014-01-01

    In this article, the resonant frequency and quality factor of a novel coplanar waveguide (cpw) diamond-shaped resonator were analyzed using advanced design system-2009 momentum model software. The diamond resonator was compared with the cpw radial stub resonator on gallium arsenide (GaAs); the work indicated that the diamond resonator had a smaller physical size and higher quality factor (Q) at millimetric wave frequencies. Experimentally measured diamond cpw resonators fabricated on GaAs wer...

  9. Kondo physics in tunable semiconductor nanowire quantum dots

    OpenAIRE

    Jespersen, T. S.; Aagesen, M.; Soerensen, C.; Lindelof, P. E.; Nygaard, J.

    2006-01-01

    We have observed the Kondo effect in strongly coupled semiconducting nanowire quantum dots. The devices are made from indium arsenide nanowires, grown by molecular beam epitaxy, and contacted by titanium leads. The device transparency can be tuned by changing the potential on a gate electrode, and for increasing transparencies the effects dominating the transport changes from Coulomb Blockade to Universal Conductance Fluctuations with Kondo physics appearing in the intermediate region.

  10. TEM EDS analysis of epitaxially-grown self-assembled indium islands

    Directory of Open Access Journals (Sweden)

    Jasmine Sears

    2017-05-01

    Full Text Available Epitaxially-grown self-assembled indium nanostructures, or islands, show promise as nanoantennas. The elemental composition and internal structure of indium islands grown on gallium arsenide are explored using Transmission Electron Microscopy (TEM Energy Dispersive Spectroscopy (EDS. Several sizes of islands are examined, with larger islands exhibiting high (>94% average indium purity and smaller islands containing inhomogeneous gallium and arsenic contamination. These results enable more accurate predictions of indium nanoantenna behavior as a function of growth parameters.

  11. Low-level laser therapy: Case-control study in dogs with sterile pyogranulomatous pododermatitis

    OpenAIRE

    Roberta Perego; Proverbio, D.; Zuccaro, A.; Spada, E.

    2016-01-01

    Aim: Low-level laser therapy (LLLT) is a therapeutic photobiostimulation with properties in reducing swelling, inflammation, and promoting tissue healing. The objective of this pilot study was to evaluate LLLT in sterile pyogranulomatous pododermatitis in five dogs. Materials and Methods: In each dog, one lesion was designated as the control (treated with a 0.0584% hydrocortisone aceponate spray), and one or more other lesions were treated with a gallium aluminum arsenide-laser, daily for ...

  12. Air Force Manufacturing Technology Electronics Program, FY72-FY85.

    Science.gov (United States)

    1985-04-01

    magnetic films of the composition Yl.52 EuO.30 TmO.30 CaO.88 Fe4.12 012 on 1.5 inch and 2.0 inch gadolinium gallium garnet substrates. Ten film were...economical and reliable manufacture of complex thin walled extruded aluminum alloy precision parts for antenna systems. Process 42 quantities of gallium ... gallium arsenide materials, mini traveling wave tubes, polyimide printed wiring boards, hermetic chip carriers, and the laser pattern generator to

  13. Low power laser irradiation does not affect the generation of signals in a sensory receptor

    Energy Technology Data Exchange (ETDEWEB)

    Lundeberg, T.; Zhou, J.

    1989-01-01

    The effect of low power Helium-Neon (He-Ne) and Gallium-Arsenide (Ga-As) laser on the slowly adapting crustacean stretch receptor was studied. The results showed that low power laser irradiation did not affect the membrane potential of the stretch receptor. These results are discussed in relation to the use of low power laser irradiation on the skin overlaying acupuncture points in treatment of pain syndrome.

  14. ONR Far East Scientific Bulletin. Volume 7. Number 1, January-March 1982.

    Science.gov (United States)

    1982-03-01

    of deep levels and Shanghai Institute of Metallurgy space charge in Gallium Arsenide Chinese Academy of Sciences 865 Change Ning Road Shanghai 200050...plant for Kuwait, equipment for a power plant in Shanghai for steel manufacture, and an impressive control system for subways in Hong Kong. A great deal...are primarily towards small refrigerators of LOW capacity at 4.2 K for use as onboard refrigerators on MAGLEV vehicles and foi cryopumps. When

  15. SPS Energy Conversion Power Management Workshop

    Science.gov (United States)

    1980-01-01

    Energy technology concerning photovoltaic conversion, solar thermal conversion systems, and electrical power distribution processing is discussed. The manufacturing processes involving solar cells and solar array production are summarized. Resource issues concerning gallium arsenides and silicon alternatives are reported. Collector structures for solar construction are described and estimates in their service life, failure rates, and capabilities are presented. Theories of advanced thermal power cycles are summarized. Power distribution system configurations and processing components are presented.

  16. Manhattan Project Technical Series The Chemistry of Uranium (I) Chapters 1-10

    Energy Technology Data Exchange (ETDEWEB)

    Rabinowitch, E. I. [Argonne National Laboratory (ANL), Argonne, IL (United States); Katz, J. J. [Argonne National Laboratory (ANL), Argonne, IL (United States)

    1946-09-30

    This constitutes Chapters 1 through 10. inclusive, of The Survey Volume on Uranium Chemistry prepared for the Manhattan Project Technical Series. Chapters are titled: Nuclear Properties of Uranium; Properties of the Uranium Atom; Uranium in Nature; Extraction of Uranium from Ores and Preparation of Uranium Metal; Physical Properties of Uranium Metal; Chemical Properties of Uranium Metal; Intermetallic Compounds and Alloy systems of Uranium; the Uranium-Hydrogen System; Uranium Borides, Carbides, and Silicides; Uranium Nitrides, Phosphides, Arsenides, and Antimonides.

  17. Monolithic AlGaAs second-harmonic nanoantennas

    CERN Document Server

    Gili, V F; Locatelli, A; Rocco, D; Finazzi, M; Ghirardini, L; Favero, I; Gomez, C; Lemaître, A; Celebrano, M; De Angelis, C; Leo, G

    2016-01-01

    We demonstrate monolithic aluminum gallium arsenide (AlGaAs) optical anoantennas. Using a selective oxidation technique, we fabricate such epitaxial semiconductor nanoparticles on an aluminum oxide substrate. Second harmonic generation from an AlGaAs nanocylinder of height h=400 nm and varying radius pumped with femtosecond pulses delivered at 1554-nm wavelength has been measured, revealing a peak conversion efficiency exceeding 10-5 for nanocylinders with an otpimized geometry.

  18. Influence of Substrate Material on Radiation Characteristics of THz Photoconductive Emitters

    Directory of Open Access Journals (Sweden)

    Jens Klier

    2015-01-01

    Full Text Available We present in this paper spectral and spatial characteristics of terahertz emission from standard dipole antenna structures used as emitters depending on the substrate material. All antenna structures were lithographically fabricated on low-temperature (LT grown, few-micrometers-thick gallium arsenide (GaAs layers. To investigate the effect of the substrate material on the radiation pattern of terahertz beams, either semi-insulating gallium arsenide or high-resistivity silicon substrate wafers have been used. As detector a standard 40 µm long dipole antenna on a semi-insulating GaAs substrate with a low-temperature grown gallium arsenide layer on it has been employed; this configuration allows for broadband detection and is still efficient enough for the characterization purpose. Strong dependence of the radiation pattern on the substrate used for the terahertz source is demonstrated. The measured patterns and differences between the two cases of substrates are well explained by means of classical diffraction.

  19. LLE Review 120 (July-September 2009)

    Energy Technology Data Exchange (ETDEWEB)

    Edgell, D.H., editor

    2001-02-19

    This issue has the following articles: (1) The Omega Laser Facility Users Group Workshop; (2) The Effect of Condensates and Inner Coatings on the Performance of Vacuum Hohlraum Targets; (3) Zirconia-Coated-Carbonyl-Iron-Particle-Based Magnetorheological Fluid for Polishing Optical Glasses and Ceramics; (4) All-Fiber Optical Magnetic Field Sensor Based on Faraday Rotation in Highly Terbium Doped Fiber; (5) Femtosecond Optical Pump-Probe Characterization of High-Pressure-Grown Al{sub 0.86}Ga{sub 0.14}N Single Crystals; (6) LLE's Summer High School Research Program; (7) Laser Facility Report; and (8) National Laser Users Facility and External Users Programs.

  20. Luminescent trimethoprim-polyaminocarboxylate lanthanide complex conjugates for selective protein labeling and time-resolved bioassays

    Science.gov (United States)

    Reddy, D. Rajasekhar; Pedró Rosa, Laura E.; Miller, Lawrence W.

    2011-01-01

    Labeling proteins with long-lifetime emitting lanthanide (III) chelate reporters enables sensitive, time-resolved luminescence bioaffinity assays. Heterodimers of trimethoprim (TMP) covalently linked to various cs124-sensitized, polyaminocarboxylate chelates stably retain lanthanide ions and exhibit quantum yields of europium emission up to 20% in water. A time-resolved, luminescence resonance energy transfer (LRET) assay showed that TMP-polyaminocarboxylates bind to Escherichia coli dihydrofolate reductase (eDHFR) fusion proteins with nanomolar affinity in purified solutions and in bacterial lysates. The ability to selectively impart terbium or europium luminescence to fusion proteins in complex physiological mixtures bypasses the need for specific antibodies and simplifies sample preparation. PMID:21619068

  1. Micro-meter size organogelator with tri-color luminescence (blue, green and red) activated by Dy3+, Tb3+ and Eu3+ ions.

    Science.gov (United States)

    Wang, QianMing

    2009-09-01

    The preparation of a novel type of low-molecular-weight amphiphilic organogelator bearing three long 14-alkyl chains and hydrophilic oligo(oxyethylene) groups was described. Ultra-violet absorption and fluorescence spectra give evidence of the energy transfer between organic ligands to lanthanide ions. Characteristic green, blue and red luminescence of the organogels were obtained and interesting emission properties of terbium, dysprosium and europium ions were unexpectedly observed at the first time during the order-disorder phase transition point (29 degrees C).

  2. Giant onsite electronic entropy enhances the performance of ceria for water splitting

    DEFF Research Database (Denmark)

    Naghavi, S. Shahab; Emery, Antoine A.; Hansen, Heine Anton

    2017-01-01

    lanthanides, and reaches a maximum value of ≈4.7 kB per oxygen vacancy for Ce4+/Ce3+ reduction. This unique and large positive entropy source in ceria explains its excellent performance for high-temperature catalytic redox reactions such as water splitting. Our calculations also show that terbium dioxide has......Previous studies have shown that a large solid-state entropy of reduction increases the thermodynamic efficiency of metal oxides, such as ceria, for two-step thermochemical water splitting cycles. In this context, the configurational entropy arising from oxygen off-stoichiometry in the oxide, has...

  3. Surface-Modified Gold Nanoparticles Possessing Two-Channel Responsive Eu(III) /Tb(III) Cyclen Complexes as Luminescent Logic Gate Mimics.

    Science.gov (United States)

    Truman, Laura K; Bradberry, Samuel J; Comby, Steve; Kotova, Oxana; Gunnlaugsson, Thorfinnur

    2017-07-05

    The development of material-supported molecular logic gate mimics (MGLMs) for contained application and device fabrication has become of increasing interest. Herein, we present the formation of ≈5 nm gold nanoparticles (AuNPs) that have been surface-modified (via a thiol linkage) with heptadentate cyclen-based complexes of europium and terbium for sensing applications using delayed lanthanide luminescence and as integrated logic gate mimics within competitive media. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Synthesis and characterization of multifunctional silica core-shell nanocomposites with magnetic and fluorescent functionalities

    Energy Technology Data Exchange (ETDEWEB)

    Ma Zhiya; Dosev, Dosi [Department of Mechanical and Aeronautical Engineering, University of California-Davis, One Shields Avenue, Davis CA 95616 (United States); Nichkova, Mikaela [Department of Entomology, University of California-Davis, One Shields Avenue, Davis CA 95616 (United States); Dumas, Randy K. [Department of Physics, University of California-Davis, One Shields Avenue, Davis CA 95616 (United States); Gee, Shirley J.; Hammock, Bruce D. [Department of Entomology, University of California-Davis, One Shields Avenue, Davis CA 95616 (United States); Liu Kai [Department of Physics, University of California-Davis, One Shields Avenue, Davis CA 95616 (United States); Kennedy, Ian M. [Department of Mechanical and Aeronautical Engineering, University of California-Davis, One Shields Avenue, Davis CA 95616 (United States)], E-mail: imkennedy@ucdavis.edu

    2009-05-15

    Multifunctional core-shell nanocomposites with a magnetic core and a silica shell doped with lanthanide chelate have been prepared by a simple method. First, citric acid-modified magnetite nanoparticles were synthesized by a chemical coprecipitation method. Then the magnetite nanoparticles were coated with silica shells doped with terbium (Tb{sup 3+}) complex by a modified Stoeber method based on hydrolyzing and condensation of tetraethyl orthosilicate (TEOS) and a silane precursor. These multifunctional nanocomposites are potentially useful in a variety of biological areas such as bio-imaging, bio-labeling and bioassays because they can be simultaneously manipulated with an external magnetic field and exhibit unique phosphorescence properties.

  5. Luminescent probing of the simplest chiral α-amino acid-alanine in an enantiopure and racemic state.

    Science.gov (United States)

    Tarasevych, Arkadii V; Kostyukov, Anton I; Baronskiy, Mark G; Rastorguev, Alexander A; Guillemin, Jean-Claude; Snytnikov, Valeriy N

    2017-07-01

    Luminescent spectroscopy combined with the technique of luminescent probing with rare earth ions (europium, gadolinium, terbium) and an actinide ion (uranyl) was used to differentiate enantiopure and racemic alanine, the simplest chiral proteinogenic amino acid. Using the achiral luminescent probes, small differences between pure L and DL alanine in the solid state were strongly amplified. Based on the observed electronic transitions of the probes, the position of the triplet level of the coordinated alanine was estimated. Formation of homo- and heterochiral complexes between enantiomers of alanine and the metal ions is discussed as a possible mechanism of chiral self-discrimination. © 2017 Wiley Periodicals, Inc.

  6. Investigation of magnon dispersion relations and neutron scattering cross sections with special attention to anisotropy effects

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker; Kowalska, A.; Laut, Peter

    1967-01-01

    -helical structure. A numerical calculation is performed for terbium on the basis of the Kaplan-Lyons Hamiltonian with added crystalline anisotropy. The non-istropic exchange part is shown to have a small effect on the dispersion curves, and it turns out that radical changes of the Ruderman-Kittel-type functions...... for the exchange interaction seem to be necessary for agreement with experimental dispersion curves be obtained. The effect of the anisotropy in the cross section is estimated and shown to be important for small magnon energies....

  7. Rare (Earth Elements [score

    Directory of Open Access Journals (Sweden)

    Camilo Méndez

    2014-12-01

    Full Text Available Rare (Earth Elements is a cycle of works for solo piano. The cycle was inspired by James Dillon’s Book of Elements (Vol. I-V. The complete cycle will consist of 14 pieces; one for each selected rare (earth element. The chosen elements are Neodymium, Erbium, Tellurium, Hafnium, Tantalum, Technetium, Indium, Dysprosium, Lanthanium, Cerium, Europium, Terbium, Yttrium and Darmstadtium. These elements were selected due to their special atomic properties that in many cases make them extremely valuable for the development of new technologies, and also because of their scarcity. To date, only 4 works have been completed Yttrium, Technetium, Indium and Tellurium.

  8. Alaska's rare earth deposits and resource potential

    Science.gov (United States)

    Barker, James C.; Van Gosen, Bradley S.

    2012-01-01

    Alaska’s known mineral endowment includes some of the largest and highest grade deposits of various metals, including gold, copper and zinc. Recently, Alaska has also been active in the worldwide search for sources of rare earth elements (REE) to replace exports now being limitedby China. Driven by limited supply of the rare earths, combined with their increasing use in new ‘green’ energy, lighting, transportation, and many other technological applications, the rare earth metals neodymium, europium and, in particular, the heavy rare earth elements terbium, dysprosium and yttrium are forecast to soon be in critical short supply (U.S. Department of Energy, 2010).

  9. Sol-Gel Electrolytes Incorporated by Lanthanide Luminescent Materials and Their Photophysical Properties

    Science.gov (United States)

    Yu, Chufang; Zhang, Zhengyang; Fu, Meizhen; Gao, Jinwei; Zheng, Yuhui

    2017-10-01

    A group of silica gel electrolytes with lanthanide luminescent hybrid materials were assembled and investigated. Photophysical studies showed that terbium and europium hybrids displayed characteristic green and red emissions within the electrolytes. The influence of different concentration of the lanthanide hybrids on the electrochemical behavior of a gelled electrolyte valve-regulated lead-acid battery were studied through cyclic voltammograms, electrochemical impedance spectroscopy, water holding experiments and mobility tests. The morphology and particle size were analyzed by scanning electron microscopy. The results proved that lanthanide (Tb3+/Eu3+) luminescent materials are effective additives which will significantly improve the electrochemical properties of lead-acid batteries.

  10. SPECTROSCOPIC PROPERTIES OF THE Ln-Ge COMPLEXES WITH DIETHYLENETRIAMINEPENTAACETIC ACID

    Directory of Open Access Journals (Sweden)

    Sergiy Smola

    2007-06-01

    Full Text Available Four new heteronuclear lanthanide complexes with general formula [Ge(OH(μ-HDTPALnGe(OH (μ-DTPA] (Ln = Sm – Dy were synthesized and subsequently characterized by different physico- chemical methods. The structures of new compounds have been proposed. In considered complexes the 4f-luminescence of three-charged ions of samarium, europium, terbium and dysprosium is realized at UV-excitation. It is noteworthy that it is the first observation of 4f-luminescence in water solutions of heteronuclear f-p-complexes. The comparison of luminescent characteristics of hetero- and homonuclear landthanide complexes is described and discussed as well.

  11. Tetrakis(μ-2-phenoxypropionato-κ3O,O′:O′;κ3O:O,O′,κ4O:O′-bis[(1,10-phenanthroline-κ2N,N′(2-phenoxypropionato-κ2O,O′praseodymium(III

    Directory of Open Access Journals (Sweden)

    Jin-Bei Shen

    2011-09-01

    Full Text Available In the centrosymmetric binuclear title complex, [Pr2(C9H9O36(C12H8N22], the two PrIII ions are linked by four 2-phenoxypropionate (L groups through their bi- and tridentate bridging modes. Each PrIII ion is nine-coordinated by one 1,10-phenanthroline molecule, one bidentate carboxylate group and four bridging carboxylate groups in a distorted PrN2O7 monocapped square-antiprismatic geometry. The title compound is isotypic with its terbium- and dysprosium-containing analogues.

  12. Detection of rare earth elements in Powder River Basin sub-bituminous coal ash using laser-induced breakdown spectroscopy (LIBS)

    Energy Technology Data Exchange (ETDEWEB)

    Tran, Phuoc [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United State; Mcintyre, Dustin [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United State

    2015-10-01

    We reported our preliminary results on the use of laser-induced breakdown spectroscopy to analyze the rare earth elements contained in ash samples from Powder River Basin sub-bituminous coal (PRB-coal). We have identified many elements in the lanthanide series (cerium, europium, holmium, lanthanum, lutetium, praseodymium, promethium, samarium, terbium, ytterbium) and some elements in the actinide series (actinium, thorium, uranium, plutonium, berkelium, californium) in the ash samples. In addition, various metals were also seen to present in the ash samples

  13. Faraday rotator based on TSAG crystal with orientation.

    Science.gov (United States)

    Yasuhara, Ryo; Snetkov, Ilya; Starobor, Aleksey; Mironov, Evgeniy; Palashov, Oleg

    2016-07-11

    A Faraday isolator (FI) for high-power lasers with kilowatt-level average power and 1-µm wavelength was demonstrated using a terbium scandium aluminum garnet (TSAG) with its crystal axis aligned in the direction. Furthermore, no compensation scheme for thermally induced depolarization in a magnetic field was used. An isolation ratio of 35.4 dB (depolarization ratio γ of 2.9 × 10-4) was experimentally observed at a maximum laser power of 1470 W. This result for room-temperature FIs is the best reported, and provides a simple, practical solution for achieving optical isolation in high-power laser systems.

  14. Detection of bacterial spores with lanthanide-macrocycle binary complexes.

    Science.gov (United States)

    Cable, Morgan L; Kirby, James P; Levine, Dana J; Manary, Micah J; Gray, Harry B; Ponce, Adrian

    2009-07-15

    The detection of bacterial spores via dipicolinate-triggered lanthanide luminescence has been improved in terms of detection limit, stability, and susceptibility to interferents by use of lanthanide-macrocycle binary complexes. Specifically, we compared the effectiveness of Sm, Eu, Tb, and Dy complexes with the macrocycle 1,4,7,10-tetraazacyclododecane-1,7-diacetate (DO2A) to the corresponding lanthanide aquo ions. The Ln(DO2A)(+) binary complexes bind dipicolinic acid (DPA), a major constituent of bacterial spores, with greater affinity and demonstrate significant improvement in bacterial spore detection. Of the four luminescent lanthanides studied, the terbium complex exhibits the greatest dipicolinate binding affinity (100-fold greater than Tb(3+) alone, and 10-fold greater than other Ln(DO2A)(+) complexes) and highest quantum yield. Moreover, the inclusion of DO2A extends the pH range over which Tb-DPA coordination is stable, reduces the interference of calcium ions nearly 5-fold, and mitigates phosphate interference 1000-fold compared to free terbium alone. In addition, detection of Bacillus atrophaeus bacterial spores was improved by the use of Tb(DO2A)(+), yielding a 3-fold increase in the signal-to-noise ratio over Tb(3+). Out of the eight cases investigated, the Tb(DO2A)(+) binary complex is best for the detection of bacterial spores.

  15. Structural Characterization and Absolute Luminescence Efficiency Evaluation of Gd2O2S High Packing Density Ceramic Screens Doped with Tb3+ and Eu3+ for further Applications in Radiology

    Science.gov (United States)

    Dezi, Anna; Monachesi, Elenasophie; D’Ignazio, Michela; Scalise, Lorenzo; Montalto, Luigi; Paone, Nicola; Rinaldi, Daniele; Mengucci, Paolo; Loudos, George; Bakas, Athanasios; Michail, Christos; Valais, Ioannis; Fountzoula, Christine; Fountos, George; David, Stratos

    2017-11-01

    Rare earth activators are impurities added in the phosphor material to enhance probability of visible photon emission during the luminescence process. The main activators employed are rare earth trivalent ions such as Ce+3, Tb+3, Pr3+ and Eu+3. In this work, four terbium-activated Gd2O2S (GOS) powder screens with different thicknesses (1049 mg/cm2, 425.41 mg/cm2, 313 mg/cm2 and 187.36 mg/cm2) and one europium-activated GOS powder screen (232.18 mg/cm2) were studied to investigate possible applications for general radiology detectors. Results presented relevant differences in crystallinity between the GOS:Tb doped screens and GOS:Eu screens in respect to the dopant agent present. The AE (Absolute efficiency) was found to rise (i) with the increase of the X-ray tube voltage with the highest peaking at 110kVp and (ii) with the decrease of the thickness among the four GOS:Tb. Comparing similar thickness values, the europium-activated powder screen showed lower AE than the corresponding terbium-activated.

  16. Synthesis and characterization of magnetic nanoparticles of oxides for dual MnFe{sub 2}O{sub 4} bioseparation, stabilized in fatty acid and the system chitosan - Eu(TTA){sub 3}(TPPO){sub 2}. Studies on the influence of doping with Gd{sup 3+}, Tb{sup 3+}, Ho{sup 3+} e Eu{sup 3+} in structural and magnetic properties; Sintese e caracterizacao de nanoparticulas magneticas de oxidos duplos de MnFe{sub 2}O{sub 4} para biosseparacao, estabilizadas em acido graxo e recobertas pelo sistema quitosana - Eu(TTA){sub 3}(TPPO){sub 2}. Estudo da influencia da dopagem com Gd{sup 3+}, Tb{sup 3+}, Ho{sup 3+} e Eu{sup 3+} nas propriedades estruturais e magneticas

    Energy Technology Data Exchange (ETDEWEB)

    Kovacs, Thelma Antunes Rodrigues

    2014-07-01

    This work was synthesized and characterized ferrite magnetic nanoparticles manganese, using the chemical coprecipitation method. By varying the heating time under 98°C (0, 10,20,40,60 3 80 minutes), the molar percentage of doping (1, 3, 5, 7, and 10%), gadolinium, europium, terbium and holmium. Magnetic ferrite nanoparticles and manganese ferrite doped with manganese were synthesized by coprecipitation method starting with chloride solutions of metals (iron (III), manganese (II), europium (III), gadolinium (III), terbium (III) and holmium (III)) and NaOH 5mol.L{sup -1} as precipitating agent. The magnetic nanoparticles were characterized by scanning electron microscopy, infrared spectroscopy, X-ray diffraction, magnetization curves, and thermal analysis. Most of manganese ferrite particles showed superparamagnetic behavior. After the characterization it was found that the samples synthesized manganese ferrite with more than 40 minutes heating time, crystal structure showed the characteristic pattern of the inverted manganese ferrite spinel type. The stabilization of the samples in oleic acid nanoparticles produced with a hydrophobic outer layer and facilitated by coating chitosan biopolymer, since this has a positive charge. Among the doped samples there was no significant change in the magnetic behavior. Several techniques for characterizing these materials have been used such as X-ray diffraction spectrum in the infrared region, magnetization curves and thermal analysis. The resins were tested as magnetic material for the separation of biological materials. In this paper, are used as biological targets separation of bovine serum albumin. (author)

  17. Cerium fluoride nanoparticles protect cells against oxidative stress

    Energy Technology Data Exchange (ETDEWEB)

    Shcherbakov, Alexander B.; Zholobak, Nadezhda M. [Zabolotny Institute of Microbiology and Virology, National Academy of Sciences of Ukraine, Kyiv D0368 (Ukraine); Baranchikov, Alexander E. [Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Moscow 119991 (Russian Federation); Ryabova, Anastasia V. [Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow 119991 (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow 115409 (Russian Federation); Ivanov, Vladimir K., E-mail: van@igic.ras.ru [Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Moscow 119991 (Russian Federation); National Research Tomsk State University, Tomsk 634050 (Russian Federation)

    2015-05-01

    A novel facile method of non-doped and fluorescent terbium-doped cerium fluoride stable aqueous sols synthesis is proposed. Intense green luminescence of CeF{sub 3}:Tb nanoparticles can be used to visualize these nanoparticles' accumulation in cells using confocal laser scanning microscopy. Cerium fluoride nanoparticles are shown for the first time to protect both organic molecules and living cells from the oxidative action of hydrogen peroxide. Both non-doped and terbium-doped CeF{sub 3} nanoparticles are shown to provide noteworthy protection to cells against the vesicular stomatitis virus. - Highlights: • Facile method of CeF{sub 3} and CeF{sub 3}:Tb stable aqueous sols synthesis is proposed. • Naked CeF{sub 3} nanoparticles are shown to be non-toxic and to protect cells from the action of H{sub 2}O{sub 2}. • CeF{sub 3} and CeF{sub 3}:Tb nanoparticles are shown to protect living cells against the vesicular stomatitis virus.

  18. Synthesis and characterization of Tin / Titanium mixed oxide nanoparticles doped with lanthanide for biomarking; Sintese e caracterizacao de nanoparticulas de oxido misto de estanho/titanio dopadas com lantanideos para marcacao biologica

    Energy Technology Data Exchange (ETDEWEB)

    Paganini, Paula Pinheiro

    2012-07-01

    This work presents the synthesis, characterization and photo luminescent study of tin and titanium mixed oxide nanoparticles doped with europium, terbium and neodymium to be used with luminescent markers on biological systems. The syntheses were done by co-precipitation, protein sol-gel and Pechini methods and the nanoparticles were characterized by infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, X-ray diffraction and X-ray absorption spectroscopy. The photo luminescent properties studies were conducted for luminophores doped with europium, terbium and neodymium synthesized by coprecipitation method. For luminophore doped with europium it was possible to calculate the intensity parameters and quantum yield and it showed satisfactory results. In the case of biological system marking it was necessary the functionalization of these particles to allow them to bind to the biological part to be studied. So the nanoparticles were functionalized by microwave and Stoeber methods and characterized by infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction obtaining qualitative response of functionalization efficacy. The ninhydrin spectroscopic method was used for quantification of luminophores functionalization. The photo luminescent studies of functionalized particles demonstrate the potential applying of these luminophores as luminescent markers. (author)

  19. Fabrication of Tb3Al5O12 transparent ceramics using co-precipitated nanopowders

    Science.gov (United States)

    Dai, Jiawei; Pan, Yubai; Wang, Wei; Luo, Wei; Xie, Tengfei; Kou, Huamin; Li, Jiang

    2017-11-01

    Terbium aluminum garnet (TAG) precursor was synthesized by a co-precipitation method from a mixed solution of terbium and aluminum nitrates using ammonium hydrogen carbonate (AHC) as the precipitant. The powders calcined at different temperatures were investigated by XRD, FTIR and FESEM in order to choose the optimal calcination temperature. Fine and low-agglomerated TAG powders with average particle size of 88 nm were obtained by calcining the precursor at 1100 °C for 4 h. Using this powder as starting material, TAG transparent ceramics were fabricated by vacuum sintering combined with hot isostatic pressing (HIP) sintering. For the sample pre-sintered at 1700 °C for 20 h with HIP post-treated at 1700 °C for 3 h, the average grain size is about 3.9 μm and the in-line transmittance is beyond 55% in the region of 500-1600 nm, reaching a maximum transmittance of 64.2% at the wavelength of 1450 nm. The Verdet constant at 633 nm is measured to be -178.9 rad T-1 m-1, which is 33% larger than that of the commercial TGG single crystal (-134 rad T-1 m-1).

  20. Incorporation of Ln-Doped LaPO4 Nanocrystals as Luminescent Markers in Silica Nanoparticles.

    Science.gov (United States)

    van Hest, Jacobine J H A; Blab, Gerhard A; Gerritsen, Hans C; Donega, Celso de Mello; Meijerink, Andries

    2016-12-01

    Lanthanide ions are promising for the labeling of silica nanoparticles with a specific luminescent fingerprint due to their sharp line emission at characteristic wavelengths. With the increasing use of silica nanoparticles in consumer products, it is important to label silica nanoparticles in order to trace the biodistribution, both in the environment and living organisms.In this work, we synthesized LaPO4 nanocrystals (NCs) with sizes ranging from 4 to 8 nm doped with europium or cerium and terbium. After silica growth using an inverse micelle method, monodisperse silica spheres were obtained with a single LaPO4 NC in the center. We demonstrate that the size of the silica spheres can be tuned in the 25-55 nm range by addition of small volumes of methanol during the silica growth reaction. Both the LaPO4 core and silica nanocrystal showed sharp line emission characteristic for europium and terbium providing unique optical labels in silica nanoparticles of variable sizes.

  1. Magnetic phase transitions in TbFe sub 2 Al sub 1 sub 0 , HoFe sub 2 Al sub 1 sub 0 and ErFe sub 2 Al sub 1 sub 0

    CERN Document Server

    Reehuis, M; Krimmel, A; Scheidt, E W; Stüsser, N; Loidl, A; Jeitschko, W

    2003-01-01

    The magnetic order of the orthorhombic aluminides TbFe sub 2 Al sub 1 sub 0 , HoFe sub 2 Al sub 1 sub 0 and ErFe sub 2 Al sub 1 sub 0 (space group Cmcm) has been studied by specific heat and magnetic measurements, as well as by neutron powder diffraction down to 100 mK and in external fields up to 5 T. Only the rare-earth ions carry a magnetic moment. At T = 1.5 K the terbium moments in TbFe sub 2 Al sub 1 sub 0 show a square-wave modulated magnetic order with wavevector k = (0, 0.7977, 0) and a moment direction parallel to the a-axis. At a critical field of H sub c sub 1 = 0.9 T one of ten spins is forced to flip, going into an intermediate ferrimagnetic phase that is stable up to the critical field H sub c sub 2 = 1.8 T. Above this field finally all the rest of the spins flip, resulting in a ferromagnetic order of the terbium moments. ErFe sub 2 Al sub 1 sub 0 orders antiferromagnetically below T sub N 1.77(7) K with a similar magnetic structure characterized by a wavevector k (0, approx 0.8, 0). In contras...

  2. Deuteron induced Tb-155 production, a theranostic isotope for SPECT imaging and auger therapy.

    Science.gov (United States)

    Duchemin, C; Guertin, A; Haddad, F; Michel, N; Métivier, V

    2016-12-01

    Several terbium isotopes are suited for diagnosis or therapy in nuclear medicine. Tb-155 is of interest for SPECT imaging and/or Auger therapy. High radionuclide purity is mandatory for many applications in medicine. The quantification of the activity of the produced contaminants is therefore as important as that of the radionuclide of interest. The experiments performed at the ARRONAX cyclotron (Nantes, France), using the deuteron beam delivered up to 34MeV, provide an additional measurement of the excitation function of the Gd-nat(d,x)Tb-155 reaction and of the produced terbium and gadolinium contaminants. In this study, we investigate the achievable yield for each radionuclide produced in natural gadolinium as a function of the deuteron energy. Other reactions are discussed in order to define the production route that could provide Tb-155 with a high yield and a high radionuclide purity. This article aims to improve data for the Gd-nat(d,x) reaction and to optimize the irradiation conditions required to produce Tb-155. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Nonlinear THz spectroscopy on n-type GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Gaal, Peter

    2008-06-23

    In this thesis, the ultrafast dynamics of conduction band electrons in semiconductors are investigated by nonlinear terahertz (THz) spectroscopy. In particular, n-doped gallium arsenide samples with doping concentrations in the range of 10{sup 16} cm{sup -3} to 10{sup 17} cm{sup -3} are studied. A novel source for the generation of intense THz radiation is developed which yields single-cycle THz transients with field amplitudes of more then 400 kV/cm. The THz source uses ultrashort optical laser pulses provided by a Ti:sapphire oscillator. In addition, a two-color THz-pump mid-infrared-probe setup is implemented, which allows for two-dimensional time-resolved experiments in the far-infrared wavelength range. Field ionization of neutral shallow donors in gallium arsenide with intense, ultrashort THz pulses and subsequent coherent radiative recombination of electrons to impurity ground states is observed at room temperature. The superradiant decay of the nonlinear polarization results in the emission of a coherent signal with picosecond lifetimes. Such nonlinear signals, which exhibit a lifetime ten times longer than in the linear regime are observed for the first time. At low temperatures and THz field strengths below 5 kV/cm, Rabi flopping on shallow donor transitions is demonstrated. For the first time, the polar electron-LO phonon interaction is directly measured in the quantum kinetic transport regime. Quasi-instantaneous acceleration of conduction band electrons in the polar gallium arsenide lattice by the electric field of intense THz pulses and subsequent probing of the mid-infrared transmission reveals a modulation of the transmission along the THz-mid-infrared delay coordinate with the frequency of the LO phonon. These modulations directly display the relative phase between the electron motion and its surrounding virtual phonon cloud. Quantum kinetic model calculations fully account for the observed phenomena. (orig.)

  4. Medical Applications and Toxicities of Gallium Compounds

    Science.gov (United States)

    Chitambar, Christopher R.

    2010-01-01

    Over the past two to three decades, gallium compounds have gained importance in the fields of medicine and electronics. In clinical medicine, radioactive gallium and stable gallium nitrate are used as diagnostic and therapeutic agents in cancer and disorders of calcium and bone metabolism. In addition, gallium compounds have displayed anti-inflammatory and immunosuppressive activity in animal models of human disease while more recent studies have shown that gallium compounds may function as antimicrobial agents against certain pathogens. In a totally different realm, the chemical properties of gallium arsenide have led to its use in the semiconductor industry. Gallium compounds, whether used medically or in the electronics field, have toxicities. Patients receiving gallium nitrate for the treatment of various diseases may benefit from such therapy, but knowledge of the therapeutic index of this drug is necessary to avoid clinical toxicities. Animals exposed to gallium arsenide display toxicities in certain organ systems suggesting that environmental risks may exist for individuals exposed to this compound in the workplace. Although the arsenic moiety of gallium arsenide appears to be mainly responsible for its pulmonary toxicity, gallium may contribute to some of the detrimental effects in other organs. The use of older and newer gallium compounds in clinical medicine may be advanced by a better understanding of their mechanisms of action, drug resistance, pharmacology, and side-effects. This review will discuss the medical applications of gallium and its mechanisms of action, the newer gallium compounds and future directions for development, and the toxicities of gallium compounds in current use. PMID:20623028

  5. Medical Applications and Toxicities of Gallium Compounds

    Directory of Open Access Journals (Sweden)

    Christopher R. Chitambar

    2010-05-01

    Full Text Available Over the past two to three decades, gallium compounds have gained importance in the fields of medicine and electronics. In clinical medicine, radioactive gallium and stable gallium nitrate are used as diagnostic and therapeutic agents in cancer and disorders of calcium and bone metabolism. In addition, gallium compounds have displayed anti-inflammatory and immunosuppressive activity in animal models of human disease while more recent studies have shown that gallium compounds may function as antimicrobial agents against certain pathogens. In a totally different realm, the chemical properties of gallium arsenide have led to its use in the semiconductor industry. Gallium compounds, whether used medically or in the electronics field, have toxicities. Patients receiving gallium nitrate for the treatment of various diseases may benefit from such therapy, but knowledge of the therapeutic index of this drug is necessary to avoid clinical toxicities. Animals exposed to gallium arsenide display toxicities in certain organ systems suggesting that environmental risks may exist for individuals exposed to this compound in the workplace. Although the arsenic moiety of gallium arsenide appears to be mainly responsible for its pulmonary toxicity, gallium may contribute to some of the detrimental effects in other organs. The use of older and newer gallium compounds in clinical medicine may be advanced by a better understanding of their mechanisms of action, drug resistance, pharmacology, and side-effects. This review will discuss the medical applications of gallium and its mechanisms of action, the newer gallium compounds and future directions for development, and the toxicities of gallium compounds in current use.

  6. Ultrafast properties of femtosecond-laser-ablated GaAs and its application to terahertz optoelectronics.

    Science.gov (United States)

    Madéo, Julien; Margiolakis, Athanasios; Zhao, Zhen-Yu; Hale, Peter J; Man, Michael K L; Zhao, Quan-Zhong; Peng, Wei; Shi, Wang-Zhou; Dani, Keshav M

    2015-07-15

    We report on the first terahertz (THz) emitter based on femtosecond-laser-ablated gallium arsenide (GaAs), demonstrating a 65% enhancement in THz emission at high optical power compared to the nonablated device. Counter-intuitively, the ablated device shows significantly lower photocurrent and carrier mobility. We understand this behavior in terms of n-doping, shorter carrier lifetime, and enhanced photoabsorption arising from the ablation process. Our results show that laser ablation allows for efficient and cost-effective optoelectronic THz devices via the manipulation of fundamental properties of materials.

  7. Detection and study of photo-generated spin currents in nonmagnetic semiconductor materials

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. Idrish [Nanoscale Science and Technology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)], E-mail: m.miah@griffith.edu.au; Kityk, I.V. [Institute of Physics, J. Dlugosz University Czestochowa, PL-42201 Czestochowa (Poland); Gray, E. MacA. [Nanoscale Science and Technology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)

    2007-10-15

    The longitudinal current in Si-doped gallium arsenide was spin-polarized using circularly polarized light. The spin current was detected by the extraordinary Hall effect. An enhancement of Hall conductivity with increasing moderately Si-doping was found, indicating that the introduction of dopants increases the electronic spin polarization. This finding may provide an opportunity for controlling and manipulating nonmagnetic semiconductors via electron spin for operating device applications. Band energy calculations using pseudopotentials confirm the influence of Si content and electron-phonon interaction on the behaviour of the spin current and hence on the spin-dependent Hall voltage.

  8. Electric field and space-charge distribution in SI GaAs: effect of high-energy proton irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Castaldini, A.; Cavallini, A. E-mail: anna.cavallini@bo.infn.it; Polenta, L.; Canali, C.; Nava, F

    1999-04-21

    The effect of irradiation on semi-insulating gallium arsenide Schottky diodes has been investigated by means of surface potential measurements and spectroscopic techniques. Before and after irradiation the electric field exhibits a Mott barrier-like distribution, and the box-shaped space charge modifies its distribution with irradiation. The increase in density or the generation of some traps changes the compensation ratio producing a deeper active region and a more homogeneous distribution of the electric field. The latter phenomenon is also observed by EBIC images of edge-mounted diodes.

  9. Photovoltaic Energy: Electricity from Sunlight

    Energy Technology Data Exchange (ETDEWEB)

    Cason, D.L.; Pitsenbarger, J. [eds.

    1996-03-01

    Photovoltaic Energy: Electricity from Sunlight (PHV) announces on a bimonthly basis the current worldwide information available on all aspects of photovoltaic amorphous technology, polycrystalline thin films, gallium arsenide, crystalline silicon, concentrator technology, and systems research. This publication contains the abstracts of DOE reports, journal articles, conference papers, patents, theses, and monographs added to the Energy Science and Technology Database during the past two months. Also included are US information obtained through acquisition programs or interagency agreements and international information obtained through the International Energy Agency`s Energy Technology Data Exchange or government-to-government agreements.

  10. A 15% efficient antireflection-coated metal-oxide-semiconductor solar cell

    Science.gov (United States)

    Stirn, R. J.; Yeh, Y. C. M.

    1975-01-01

    A new effect is being developed which significantly improves the conversion efficiency of antireflection-coated metal-oxide-semiconductor (AMOS) solar cells. The effect, a marked increase in the open-circuit voltage, is produced by the addition of an oxide layer to the semiconductor. Cells using gold on n-type gallium arsenide have been made with efficiencies up to 15% in terrestrial sunlight. All processing steps are amenable to the use of low-cost polycrystalline films of GaAs in place of the single crystals now used.

  11. Site control technique for quantum dots using electron beam induced deposition

    Energy Technology Data Exchange (ETDEWEB)

    Iizuka, Kanji; Jung, JaeHun; Yokota, Hiroshi [Nippon Institute of Technology, 4-1 Gakuendai, Miyashiro, Minami-saitama, Saitama 3458501 (Japan)

    2014-05-15

    To develop simple and high throughput sit definition technique for quantum dots (QDs), the electron beam induced deposition (EBID) method was used as desorption guide of phosphorus atoms form InP substrate. As the results one or a few indium (In) droplets (DLs) were created in the carbon grid pattern by thermal annealing at a temperature of 450°C for 10 min in the ultra high vacuum condition. The size of In DLs was larger than QDs, but arsenide DLs by molecular beam in growth chamber emitted wavelength of 1.028μm at 50K by photoluminescence measurement.

  12. Electric field and space-charge distribution in SI GaAs: effect of high-energy proton irradiation

    CERN Document Server

    Castaldini, A; Polenta, L; Canali, C; Nava, F

    1999-01-01

    The effect of irradiation on semi-insulating gallium arsenide Schottky diodes has been investigated by means of surface potential measurements and spectroscopic techniques. Before and after irradiation the electric field exhibits a Mott barrier-like distribution, and the box-shaped space charge modifies its distribution with irradiation. The increase in density or the generation of some traps changes the compensation ratio producing a deeper active region and a more homogeneous distribution of the electric field. The latter phenomenon is also observed by EBIC images of edge-mounted diodes.

  13. Ab-initio study of the electronic structure of sup 1 sup 9 F implanted in GaAs and GaN crystals

    CERN Document Server

    Park, J H; Cho, H S; Shin, Y N

    1998-01-01

    We have studied the nuclear quadrupole interaction of a fluorine atom implanted in gallium arsenide and gallium nitride cluster models using the ab-initio Hartree-Fock theory. For the three possible fluorine sites in GaAs and GaN, we have determined the location of the implanted fluorine atom by using a self-consistent calculation, the electric field gradient at the implanted atom, and the electronic structure. Good agreement is found with experimental data wherever they are available. Predictions are made for the implanted fluorine site associated with the total energy and the electric field gradient which are expected to be measurable by a variety of experimental techniques.

  14. Comparative High Field Magneto-transport Of Rare Earth Oxypnictides With Maximum Transition Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Balakirev, Fedor F [Los Alamos National Laboratory; Migliori, A [MPA-NHMFL; Riggs, S [NHMFL-FSU; Hunte, F [NHMFL-FSU; Gurevich, A [NHMFL-FSU; Larbalestier, D [NHMFL-FSU; Boebinger, G [NHMFL-FSU; Jaroszynski, J [NHMFL-FSU; Ren, Z [CHINA; Lu, W [CHINA; Yang, J [CHINA; Shen, X [CHINA; Dong, X [CHINA; Zhao, Z [CHINA; Jin, R [ORNL; Sefat, A [ORNL; Mcguire, M [ORNL; Sales, B [ORNL; Christen, D [ORNL; Mandrus, D [ORNL

    2008-01-01

    We compare magnetotransport of the three iron-arsenide-based compounds ReFeAsO (Re=La, Sm, Nd) in very high DC and pulsed magnetic fields up to 45 and 54 T, respectively. Each sample studied exhibits a superconducting transition temperature near the maximum reported to date for that particular compound. While high magnetic fields do not suppress the superconducting state appreciably, the resistivity, Hall coefficient, and critical magnetic fields, taken together, suggest that the phenomenology and superconducting parameters of the oxypnictide superconductors bridges the gap between MgB{sub 2} and YBCO.

  15. Raman spectroscopy and electrical properties of InAs nanowires with local oxidation enabled by substrate micro-trenches and laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Tanta, R.; Krogstrup, P.; Nygård, J.; Jespersen, T. S., E-mail: tsand@fys.ku.dk [Center for Quantum Devices and Nano Science Center, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100 (Denmark); Madsen, M. H. [Danish Fundamental Metrology, Matematiktorvet 307, Kgs. Lyngby 2800 (Denmark); Liao, Z.; Vosch, T. [Nano-Science Center, Department of Chemistry, University of Copenhagen, Copenhagen 2100 (Denmark)

    2015-12-14

    The thermal gradients along indium arsenide nanowires were engineered by a combination of fabricated micro-trenches in the supporting substrate and focused laser irradiation. This allowed local spatial control of thermally activated oxidation reactions of the nanowire on the scale of the diffraction limit. The locality of the oxidation was detected by micro-Raman mapping, and the results were found to be consistent with numerical simulations of the temperature profile. Applying the technique to nanowires in electrical devices the locally oxidized nanowires remained conducting with a lower conductance as expected for an effectively thinner conducting core.

  16. X-ray detection with GaAs RGCCDs

    CERN Document Server

    Passmore, S; Rogalla, M; Runge, K; Bryman, D; Cresswell, J

    1999-01-01

    Gallium-Arsenide Resistive-Gate CCDs with an active depth of up to 30 mu m were used to detect X-rays with energies between 14 and 60 keV. Five different X-ray sources were used to investigate the signal-to-noise ratio, energy resolution and linearity of the device. An energy resolution better than 11% at 60 keV was observed. The charge transport efficiency (CTE) of these 128 pixel CCDs was determined using two independent methods to be CTE>0.9992. (author)

  17. A comparative evaluation to assess the efficacy of 5% sodium fluoride varnish and diode laser and their combined application in the treatment of dentin hypersensitivity

    OpenAIRE

    Suri, Isha; Singh, Poonam; Shakir, Quaid Johar; Shetty, Arvind; Bapat, Ranjeet; Thakur, Roshani

    2016-01-01

    Background: Dentin hypersensitivity (DH) is an age old complaint with a great number of treatment modalities, but none of these are totally effective till date. Lasers being one of the latest treatment options in periodontics, a study was conducted to test the efficacy of diode laser (DL) in DH alone and in comparison with 5% sodium fluoride (NaF) varnish. Aim: The aim of the present study was to compare the effectiveness of 5% topical NaF varnish and 980 nm gallium aluminum arsenide (GaAlAs)...

  18. Resonant metamaterial detectors based on THz quantum-cascade structures

    Science.gov (United States)

    Benz, A.; Krall, M.; Schwarz, S.; Dietze, D.; Detz, H.; Andrews, A. M.; Schrenk, W.; Strasser, G.; Unterrainer, K.

    2014-01-01

    We present the design, fabrication and characterisation of an intersubband detector employing a resonant metamaterial coupling structure. The semiconductor heterostructure relies on a conventional THz quantum-cascade laser design and is operated at zero bias for the detector operation. The same active region can be used to generate or detect light depending on the bias conditions and the vertical confinement. The metamaterial is processed directly into the top metal contact and is used to couple normal incidence radiation resonantly to the intersubband transitions. The device is capable of detecting light below and above the reststrahlenband of gallium-arsenide corresponding to the mid-infrared and THz spectral region. PMID:24608677

  19. Efficient frequency comb generation in AlGaAs-on-insulator

    DEFF Research Database (Denmark)

    Pu, Minhao; Ottaviano, Luisa; Semenova, Elizaveta

    2016-01-01

    The combination of nonlinear and integrated photonics enables Kerr frequency comb generation in stable chip-based microresonators. Such a comb system will revolutionize applications, including multi-wavelength lasers, metrology, and spectroscopy. Aluminum gallium arsenide (AlGaAs) exhibits very...... high material nonlinearity and low nonlinear loss. However, difficulties in device processing and low device effective nonlinearity made Kerr frequency comb generation elusive. Here, we demonstrate AlGaAs-on-insulator as a nonlinear platform at telecom wavelengths with an ultra-high device nonlinearity...

  20. Molecular beam epitaxy

    CERN Document Server

    Pamplin, Brian R

    1980-01-01

    Molecular Beam Epitaxy introduces the reader to the use of molecular beam epitaxy (MBE) in the generation of III-V and IV-VI compounds and alloys and describes the semiconductor and integrated optics reasons for using the technique. Topics covered include semiconductor superlattices by MBE; design considerations for MBE systems; periodic doping structure in gallium arsenide (GaAs); nonstoichiometry and carrier concentration control in MBE of compound semiconductors; and MBE techniques for IV-VI optoelectronic devices. The use of MBE to fabricate integrated optical devices and to study semicond

  1. Study of terahertz intensity dependence on time resolved dynamic fringes in the interferometric autocorrelation setup

    Science.gov (United States)

    Venkatesh, M.; Chaudhary, A. K.

    2014-10-01

    Terahertz signal is generated from Low temperature gallium arsenide photoconductive dipole antennas (gap = 5μm, length = 20μm) by focusing 15 fs laser pulses and applying 12V DC across it. Terahertz intensity is detected by Pyroelectric detector (THZ1.5MB-USB). The collinear autocorrelation arrangement provides dynamic fringes which are allowed to be incident on photoconductive antennas to study the variation in terahertz intensity with respect to delay between laser pulses. Interestingly, the profile of THz intensity variation was similar to interferometric autocorrelation signal of laser pulses. The THz power attenuation with its propagation distance in atmosphere was measured.

  2. Role of substrate quality on IC performance and yields

    Science.gov (United States)

    Thomas, R. N.

    1981-01-01

    The development of silicon and gallium arsenide crystal growth for the production of large diameter substrates are discussed. Large area substrates of significantly improved compositional purity, dopant distribution and structural perfection on a microscopic as well as macroscopic scale are important requirements. The exploratory use of magnetic fields to suppress convection effects in Czochralski crystal growth is addressed. The growth of large crystals in space appears impractical at present however the efforts to improve substrate quality could benefit from the experiences gained in smaller scale growth experiments conducted in the zero gravity environment of space.

  3. Infrared and millimeter waves v.14 millimeter components and techniques, pt.V

    CERN Document Server

    Button, Kenneth J

    1985-01-01

    Infrared and Millimeter Waves, Volume 14: Millimeter Components and Techniques, Part V is concerned with millimeter-wave guided propagation and integrated circuits. In addition to millimeter-wave planar integrated circuits and subsystems, this book covers transducer configurations and integrated-circuit techniques, antenna arrays, optoelectronic devices, and tunable gyrotrons. Millimeter-wave gallium arsenide (GaAs) IMPATT diodes are also discussed. This monograph is comprised of six chapters and begins with a description of millimeter-wave integrated-circuit transducers, focusing on vario

  4. Functional and electrophysiological evaluation of the effect of laser therapy in the treatment of peripheral facial paralysis

    Science.gov (United States)

    Ladalardo, Thereza C.; Brugnera, Aldo, Jr.; Takamoto, Marcia; Pinheiro, Antonio L. B.; Campos, Roberto A. d. C.; Castanho Garrini, Ana E.; Bologna, Elisangela D.; Settanni, Flavio

    2001-04-01

    This clinical case report relates to a total of 4 patients, carriers of idiopathic facial paralysis, treated with Low Level Laser Therapy using a Gallium-Aluminum-Arsenide diode laser of 780 nm, 50 mW, continuous wave emission, spot size 3 mm2 and total dosage of 20 joules per session distributed to the peripheral trajectory of the injured nerve in a point by point contact mode. Altogether 24 treatment sessions were performed in a period of 12 consecutive weeks twice a week All treated patients presented recovery signs from the initial degree of paralysis.

  5. Absence of phase-dependent noise in time-domain reflectivity studies of impulsively excited phonons

    KAUST Repository

    Hussain, A.

    2010-06-17

    There have been several reports of phase-dependent noise in time-domain reflectivity studies of optical phonons excited by femtosecond laser pulses in semiconductors, semimetals, and superconductors. It was suggested that such behavior is associated with the creation of squeezed phonon states although there is no theoretical model that directly supports such a proposal. We have experimentally re-examined the studies of phonons in bismuth and gallium arsenide, and find no evidence of any phase-dependent noise signature associated with the phonons. We place an upper limit on any such noise at least 40–50 dB lower than previously reported.

  6. Modeling distributed feedback GaAs-based lasers in dentistry

    Science.gov (United States)

    Shih, Meng-Mu

    2012-01-01

    Distributed-feedback gallium-arsenide-based lasers with metal-gratings can generate stable wavelength at 980nm for applications in dentistry. This model uses the periodic optical waveguide method to calculate the coupling coefficient, which is a key parameter of laser performance. This model shows how the optical, geometrical, and material parameters depending on each other and how they affect the coupling coefficients in the laser waveguides. Numerical results compare the coupling coefficients of 980 nm lasers with those of 810 nm lasers. The modeling processes, including results, discussions, and physical interpretations, help to design and analyze lasers for more clinical and research applications in dentistry.

  7. Polarization-dependent optical 2D Fourier transform spectroscopy of semiconductors.

    Science.gov (United States)

    Zhang, Tianhao; Kuznetsova, Irina; Meier, Torsten; Li, Xiaoqin; Mirin, Richard P; Thomas, Peter; Cundiff, Steven T

    2007-09-04

    Optical 2D Fourier transform spectroscopy (2DFTS) provides insight into the many-body interactions in direct gap semiconductors by separating the contributions to the coherent nonlinear optical response. We demonstrate these features of optical 2DFTS by studying the heavy-hole and light-hole excitonic resonances in a gallium arsenide quantum well at low temperature. Varying the polarization of the incident beams exploits selection rules to achieve further separation. Calculations using a full many-body theory agree well with experimental results and unambiguously demonstrate the dominance of many-body physics.

  8. NLO 󈨞. Nonlinear Optics: Materials, Phenomena and Devices Digest. Internation Meeting on Nonlinear Optics (1st) Held in Kauai, Hawaii on 16-20 July 1990

    Science.gov (United States)

    1991-03-13

    hear all oral presentations and discussions. We hope you will take full advantage of the free time in the afternoons to enjoy Hawaii and to discuss...Hagan, M. Sheik- Bahae , and M.J. Soileau 311 FI 1 Nonlinearities of Gallium Arsenide Doping Superlattices, M.S. Tobin, G.J. Simonis, and J.D. Bruno 313 Fl...An averaging of the atom-field interaction is required simultaneously over the temporal aid sp.-tial variations of the fieids. A solution has been

  9. Cameras Reveal Elements in the Short Wave Infrared

    Science.gov (United States)

    2010-01-01

    Goodrich ISR Systems Inc. (formerly Sensors Unlimited Inc.), based out of Princeton, New Jersey, received Small Business Innovation Research (SBIR) contracts from the Jet Propulsion Laboratory, Marshall Space Flight Center, Kennedy Space Center, Goddard Space Flight Center, Ames Research Center, Stennis Space Center, and Langley Research Center to assist in advancing and refining indium gallium arsenide imaging technology. Used on the Lunar Crater Observation and Sensing Satellite (LCROSS) mission in 2009 for imaging the short wave infrared wavelengths, the technology has dozens of applications in military, security and surveillance, machine vision, medical, spectroscopy, semiconductor inspection, instrumentation, thermography, and telecommunications.

  10. NIEL calculations for estimating the displacement damage introduced in GaAs irradiated with charged particles

    Science.gov (United States)

    El Allam, E.; Inguimbert, C.; Addarkaoui, S.; Meulenberg, A.; Jorio, A.; Zorkani, I.

    2017-03-01

    The application of Non-Ionizing Energy Loss (NIEL) in estimating the impact of electron, proton, and heavy ion irradiations on Gallium Arsenide is presented in this paper. The NIEL for deuteron, alpha particle, lithium ion and oxygen ion is computed using the SR-NIEL and NEMO codes. The NIEL calculations are compared with the introduction rate of displacement damage measured in n-type GaAs. Very good agreement is found between the NIEL and experimental results for protons (ions. However, a discrepancy can be observed for high-energy protons.

  11. Overview of SWIR detectors, cameras, and applications

    Science.gov (United States)

    Hansen, Marc P.; Malchow, Douglas S.

    2008-03-01

    Imaging in the short wave infrared (SWIR) can bring useful contrast to situations and applications where visible or thermal imaging cameras are ineffective. This paper will define the short wave infrared technology and discuss developing imaging applications; then describe newly available 2-D (area) and 1-D (linear) arrays made with indium-gallium-arsenide (InGaAs), while presenting the wide range of applications with images and videos. Applications mentioned will be web inspection of continuous processes such as high temperature manufacturing processes, agricultural raw material cleaning and sorting, plastics recycling of automotive and consumer products, and a growing biological imaging technique, Spectral-Domain Optical Coherence Tomography.

  12. Integrated semiconductor optical sensors for chronic, minimally-invasive imaging of brain function.

    Science.gov (United States)

    Lee, Thomas T; Levi, Ofer; Cang, Jianhua; Kaneko, Megumi; Stryker, Michael P; Smith, Stephen J; Shenoy, Krishna V; Harris, James S

    2006-01-01

    Intrinsic optical signal (IOS) imaging is a widely accepted technique for imaging brain activity. We propose an integrated device consisting of interleaved arrays of gallium arsenide (GaAs) based semiconductor light sources and detectors operating at telecommunications wavelengths in the near-infrared. Such a device will allow for long-term, minimally invasive monitoring of neural activity in freely behaving subjects, and will enable the use of structured illumination patterns to improve system performance. In this work we describe the proposed system and show that near-infrared IOS imaging at wavelengths compatible with semiconductor devices can produce physiologically significant images in mice, even through skull.

  13. Development of Non-Toxic Quantum Dots for Flexible Display Applications

    Science.gov (United States)

    2013-11-14

    and VI (Fig. 2) have significant impact on our day to day life. Materials such as CdSe, ZnS, CdS, CdTe , GaAs, aluminum gallium arsenide (AlGaAs...gallium nitride (GaN), indium phosphide (InP), zincselenide (ZnSe), cadmiumtelluride ( CdTe ), and copper indium gallium selenide Cu(In1-xGax)Se2 (CIGS...regards specifically to InGaN, full compositional tunability has been claimed in nanowires, though mild compositional modulation was observed for 70

  14. Small-scale and large-scale testing of photo-electrochemically activated leaching technology in Aprelkovo and Delmachik Mines

    Science.gov (United States)

    Sekisov, AG; Lavrov, AYu; Rubtsov, YuI

    2017-02-01

    The paper gives a description of tests and trials of the technology of heap gold leaching from rebellious ore in Aprelkovo and Delmachik Mines. Efficiency of leaching flowsheets with the stage-wise use of activated solutions of different reagents, including active forms of oxygen, is evaluated. Carbonate-peroxide solutions are used at the first stage of leaching to oxidize sulfide and sulfide-arsenide ore minerals to recover iron and copper from them. The second stage leaching uses active cyanide solutions to leach encapsulated and disperse gold and silver.

  15. The role of cobalt in the ecosystem – likelihood of adverse effects

    Directory of Open Access Journals (Sweden)

    Henryka Langauer-Lewowicka

    2012-12-01

    Full Text Available Cobalt occurs in nature primarily as arsenides, oxides and sulphides. It is an essential element necessary for the formation of vitamin B12. It is also indispensable for regular growth of animals, plankton, and plants life. For the general population the diet is the main source of exposure to cobalt. The toxic effect due to environmental exposure has not been detected so far with the exception of cardiomyopathy in beer drinkers. Contaminated soils in the vicinity of industrial emittors pose a particular threat to children

  16. Summary of Research 1993

    Science.gov (United States)

    1993-12-31

    DIUNEs Wolfe , Kurtio A., about the same sensitivity to SEUs, LT, USK, S8ingle Event Upsets in or is perhaps a little les Gallium Arsenide Two-Phase...CUITIY:L"X To analyze the present Bruneau, T. C., "The Role of the and likely relationships between the Provisional Governments in the Iberian ...and the two Iberian countries of Portugal and Spain have 0U3 PRUBJE7I3=00: Bruneau, changed very substantially during the T. C., OPortuguese Defense

  17. Laser Atmospheric Absorption Studies.

    Science.gov (United States)

    1977-05-01

    uuuuuyyuuuyuiyuJijUJUJuiUiUJuuuuyuJUJuJUJULj "U*-ON C\\l*4KO»0©[Ve\\.*l{C»«O«-l*-*Ha>»0* 0>0»^OMOVŘN • QlJUr**<M»N« HDn »flRljr»ClflOK>WC«)OlflW^D*0*ONmfy«-t*r- f-»-i ►- •■ H»il...An interesting aspect of this laser is introduced by the presence of the gallium arsenide flat, which serves as the output mirror, i.e., it is

  18. X-ray detection with GaAs RGCCDs

    Science.gov (United States)

    Passmore, S.; Ludwig, J.; Rogalla, M.; Runge, K.; Bryman, D.; Cresswell, J.

    1999-09-01

    Gallium-Arsenide Resistive-Gate CCDs with an active depth of up to 30 μm were used to detect X-rays with energies between 14 and 60 keV. Five different X-ray sources were used to investigate the signal-to-noise ratio, energy resolution and linearity of the device. An energy resolution better than 11% at 60 keV was observed. The charge transport efficiency (CTE) of these 128 pixel CCDs was determined using two independent methods to be CTE>0.9992.

  19. X-ray detection with GaAs RGCCDs

    Energy Technology Data Exchange (ETDEWEB)

    Passmore, S. E-mail: s.passmore@physics.gla.ac.uk; Ludwig, J.; Rogalla, M.; Runge, K.; Bryman, D.; Cresswell, J

    1999-09-11

    Gallium-Arsenide Resistive-Gate CCDs with an active depth of up to 30 {mu}m were used to detect X-rays with energies between 14 and 60 keV. Five different X-ray sources were used to investigate the signal-to-noise ratio, energy resolution and linearity of the device. An energy resolution better than 11% at 60 keV was observed. The charge transport efficiency (CTE) of these 128 pixel CCDs was determined using two independent methods to be CTE>0.9992. (author)

  20. Organic compounds used in animal husbandry: Chapter 13

    Science.gov (United States)

    Wershaw, Robert L.; Shore, Laurence S.; Pruden, Amy; Shore, Laurence S.

    2009-01-01

    Although in general, the same drugs are used by humans as for animal husbandry, some compounds are unique to CAFOs. In raising and fattening steers, anabolic steroids are widely used in the US. In the cattle industry, large use is made of the acaricides, avermectins, and the cypermethrins as well as juvenile growth hormone inhibitor for fly and tick control that could affect soil fauna in very small quantities as they reach the environment without any modification. In poultry, the organic arsenides have been widely used for decades to control coccidiosis and increase growth. The environmental fate of the arsenic excreted in the poultry feces is therefore been an area of concern.