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Sample records for doped gasb single

  1. Optical and structural characterization of GaSb and Te-doped GaSb single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Tirado-Mejia, L. [Laboratorio de Optoelectronica, Universidad del Quindio, A.A. 460, Armenia, Quindio (Colombia); Villada, J.A. [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Queretaro, Qro (Mexico); Rios, M. de los [Laboratorio de Optoelectronica, Universidad del Quindio, A.A. 460, Armenia, Quindio (Colombia); Penafiel, J.A. [Centro de Fisica Aplicada y Tecnologia Avanzada, Departamento de Nanotecnologia, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro (Mexico); Posgrado en Ciencia e Ingenieria Materiales, Universidad Nacional Autonoma de Mexico, Mexico (Mexico); Fonthal, G. [Laboratorio de Optoelectronica, Universidad del Quindio, A.A. 460, Armenia, Quindio (Colombia); Espinosa-Arbelaez, D.G. [Centro de Fisica Aplicada y Tecnologia Avanzada, Departamento de Nanotecnologia, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro (Mexico); Posgrado en Ciencia e Ingenieria Materiales, Universidad Nacional Autonoma de Mexico, Mexico (Mexico); Ariza-Calderon, H. [Laboratorio de Optoelectronica, Universidad del Quindio, A.A. 460, Armenia, Quindio (Colombia); Rodriguez-Garcia, M.E. [Centro de Fisica Aplicada y Tecnologia Avanzada, Departamento de Nanotecnologia, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro (Mexico)], E-mail: marioga@fata.unam.mx

    2008-11-30

    Optical and structural properties of GaSb and Te-doped GaSb single crystals are reported herein. Utilizing the photoreflectance technique, the band gap energy for doped samples was obtained at 0.814 eV. Photoluminescence (PL) spectra showed a peak at 0.748 eV that according to this research, belongs to electronic states of pure GaSb and not to the longitudinal optical (LO) phonon replica as has been reported by other authors. Analysis of the full width at half maximum (FWHM) values of X-ray diffraction, as well as micro-Raman peaks showed that the inclusion of Te decreases the crystalline quality.

  2. Structural Characterization of Doped GaSb Single Crystals by X-ray Topography

    Energy Technology Data Exchange (ETDEWEB)

    Honnicke, M.G.; Mazzaro, I.; Manica, J.; Benine, E.; M da Costa, E.; Dedavid, B. A.; Cusatis, C.; Huang, X. R.

    2009-09-13

    We characterized GaSb single crystals containing different dopants (Al, Cd and Te), grown by the Czochralski method, by x-ray topography and high angular resolution x-ray diffraction. Lang topography revealed dislocations parallel and perpendicular to the crystal's surface. Double-crystal GaSb 333 x-ray topography shows dislocations and vertical stripes than can be associated with circular growth bands. We compared our high-angular resolution x-ray diffraction measurements (rocking curves) with the findings predicted by the dynamical theory of x-ray diffraction. These measurements show that our GaSb single crystals have a relative variation in the lattice parameter ({Delta}d/d) on the order of 10{sup -5}. This means that they can be used as electronic devices (detectors, for example) and as x-ray monochromators.

  3. Properties of Doped GaSb Whiskers at Low Temperatures

    Science.gov (United States)

    Khytruk, Igor; Druzhinin, Anatoly; Ostrovskii, Igor; Khoverko, Yuriy; Liakh-Kaguy, Natalia; Rogacki, Krzysztof

    2017-02-01

    Temperature dependencies of GaSb whiskers' resistance doped with Te to concentration of 1.7 × 1018 cm-3 were measured in temperature range 1.5-300 K. At 4.2 K temperature, a sharp drop in the whisker resistance was found. The observed effect is likely connected with the contribution of two processes such as the electron localization in the whiskers and transition in superconducting state at temperature below 4.2 K. The whisker magnetoconductance is considered in the framework of weak antilocalization (WAL) model and connected with subsurface layers of the whiskers. The Shubnikov-de Haas (SdH) oscillatory effect is observed in high-quality n-type GaSb whiskers with tellurium doping concentration near the metal-insulator transition (MIT) for both longitudinal and transverse magnetoresistance.

  4. The electronic structures and ferromagnetism of Fe-doped GaSb: The first-principle calculation study

    Science.gov (United States)

    Lin, Xue-ling; Niu, Cao-ping; Pan, Feng-chun; Chen, Huan-ming; Wang, Xu-ming

    2017-09-01

    The electronic structures and the magnetic properties of Fe doped GaSb have been investigated by the first-principles calculation based on the framework of the generalized gradient approximation (GGA) and GGA+U schemes. The calculated results indicated that Fe atoms tend to form the anti-ferromagnetic (AFM) coupling with the nearest-neighbor positions preferentially. Compared with the anti-ferromagnetic coupling, the ferromagnetic interactions occurred at the second nearest-neighbor and third nearest-neighbor sites have a bigger superiority energetically. The effect of strong electron correlation at Fe-d orbit taking on the magnetic properties predicted by GGA+U approach demonstrated that the ferromagnetic (FM) coupling between the Fe ions is even stronger in consideration of the strong electron correlation effect. The ferromagnetism in Fe doped GaSb system predicted by our investigation implied that the doping of Fe into GaSb can be as a vital routine for manufacturing the FM semiconductors with higher Curie temperature.

  5. Quantitative Mobility Spectrum Analysis for Determination of Electron and Magneto Transport Properties of Te-Doped GaSb

    Institute of Scientific and Technical Information of China (English)

    S. Acar; M. Kasap; B. Y. Isik; S.(O)zcelik; N. Tugluoglu; S. Karadeniz

    2005-01-01

    @@ Resistivity, magnetoresistivity and Hall effect measurements in n-type Te-doped GaSb grown by the liquid encapsuled Czochralski technique are carried out as functions of temperature (35-350 K) and magnetic field (0-1.35 T).The power law model is used to explain the temperature-dependent resistivity. The magnetic-field-dependent data are analysed using the quantitative mobility spectrum analysis technique. The effect of individual band parameters (nL, nг, μL, μг, p and μp) on both the electron and magneto transports have been discussed. The EL -- Eг energy separation between the L and conduction band edges is also derived.

  6. Growth of single-crystal metastable semiconducting (GaSb)1-xGex films

    Science.gov (United States)

    Cadien, K. C.; Eltoukhy, A. H.; Greene, J. E.

    1981-05-01

    Epitaxial metastable (GaSb)1-xGex alloys with compostions across the pseudobinary phase diagram have been grown on (100) GaAs substrates by multitarget rf sputtering. An essential feature allowing the growth of these metastable materials was low-energy ion bombardment of the growing film during deposition to enhance surface diffusion, promote mixing, and preferentially sputter incipient second-phase precipitates. Annealing experiments indicated that the metastable films exhibit good high-temperature stability and that they transform through a continuous series of GaSb-rich and Ge-rich phases in which the solute concentrations decrease until the equilibrium two-phase alloy is obtained. While the calculated free-energy difference between the single-phase metastable and equilibrium states is ˜18 meV, the measured activation barrier for the transformation is ˜3 eV. All films were p-type with room-temperature hole concentrations varying from 1016 to 1019 cm-3 and mobilities between 10 and 720 cm2/ V s, depending on film composition.

  7. Electronic structure and magnetism of Mn-doped GaSb for spintronic applications: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Seña, N.; Dussan, A. [Departamento de Física, Grupo de Materiales Nanoestructurados y sus Aplicaciones, Universidad Nacional de Colombia, Bogotá (Colombia); Mesa, F. [Facultad de Ciencias Naturales y Matemáticas, Grupo NanoTech, Universidad del Rosario, Bogotá (Colombia); Castaño, E.; González-Hernández, R., E-mail: rhernandezj@uninorte.edu.co [Grupo de Investigación en Física Aplicada, Departamento de Física, Universidad del Norte, Barranquilla (Colombia)

    2016-08-07

    We have carried out first-principles spin polarized calculations to obtain comprehensive information regarding the structural, magnetic, and electronic properties of the Mn-doped GaSb compound with dopant concentrations: x = 0.062, 0.083, 0.125, 0.25, and 0.50. The plane-wave pseudopotential method was used in order to calculate total energies and electronic structures. It was found that the Mn{sub Ga} substitution is the most stable configuration with a formation energy of ∼1.60 eV/Mn-atom. The calculated density of states shows that the half-metallic ferromagnetism is energetically stable for all dopant concentrations with a total magnetization of about 4.0 μ{sub B}/Mn-atom. The results indicate that the magnetic ground state originates from the strong hybridization between Mn-d and Sb-p states, which agree with previous studies on Mn-doped wide gap semiconductors. This study gives new clues to the fabrication of diluted magnetic semiconductors.

  8. Optical Properties of GaSb Nanofibers

    Directory of Open Access Journals (Sweden)

    Perez-Bergquist Alejandro

    2011-01-01

    Full Text Available Abstract Amorphous GaSb nanofibers were obtained by ion beam irradiation of bulk GaSb single-crystal wafers, resulting in fibers with diameters of ~20 nm. The Raman spectra and photoluminescence (PL of the ion irradiation-induced nanofibers before and after annealing were studied. Results show that the Raman intensity of the GaSb LO phonon mode decreased after ion beam irradiation as a result of the formation of the amorphous nanofibers. A new mode is observed at ~155 cm-1 both from the unannealed and annealed GaSb nanofiber samples related to the A1g mode of Sb–Sb bond vibration. Room temperature PL measurements of the annealed nanofibers present a wide feature band at ~1.4–1.6 eV. The room temperature PL properties of the irradiated samples presents a large blue shift compared to bulk GaSb. Annealed nanofibers and annealed nanofibers with Au nanodots present two different PL peaks (400 and 540 nm, both of which may originate from Ga or O vacancies in GaO. The enhanced PL and new band characteristics in nanostructured GaSb suggest that the nanostructured fibers may have unique applications in optoelectronic devices.

  9. Thermally induced native defect transform in annealed GaSb

    Science.gov (United States)

    Jie, Su; Tong, Liu; Jing-Ming, Liu; Jun, Yang; Yong-Biao, Bai; Gui-Ying, Shen; Zhi-Yuan, Dong; Fang-Fang, Wang; You-Wen, Zhao

    2016-07-01

    Undoped p-type GaSb single crystals were annealed at 550-600 °C for 100 h in ambient antimony. The annealed GaSb samples were investigated by Hall effect measurement, glow discharge mass spectroscopy (GDMS), infrared (IR) optical transmission and photoluminescence (PL) spectroscopy. Compared with the as-grown GaSb single crystal, the annealed GaSb samples have lower hole concentrations and weak native acceptor related PL peaks, indicating the reduction of the concentration of gallium antisite related native acceptor defects. Consequently, the below gap infrared transmission of the GaSb samples is enhanced after the thermal treatment. The mechanism about the reduction of the native defect concentration and its influence on the material property were discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 61474104 and 61504131).

  10. Ultratough single crystal boron-doped diamond

    Science.gov (United States)

    Hemley, Russell J [Carnegie Inst. for Science, Washington, DC ; Mao, Ho-Kwang [Carnegie Inst. for Science, Washington, DC ; Yan, Chih-Shiue [Carnegie Inst. for Science, Washington, DC ; Liang, Qi [Carnegie Inst. for Science, Washington, DC

    2015-05-05

    The invention relates to a single crystal boron doped CVD diamond that has a toughness of at least about 22 MPa m.sup.1/2. The invention further relates to a method of manufacturing single crystal boron doped CVD diamond. The growth rate of the diamond can be from about 20-100 .mu.m/h.

  11. Single Ion Implantation and Deterministic Doping

    Energy Technology Data Exchange (ETDEWEB)

    Schenkel, Thomas

    2010-06-11

    The presence of single atoms, e.g. dopant atoms, in sub-100 nm scale electronic devices can affect the device characteristics, such as the threshold voltage of transistors, or the sub-threshold currents. Fluctuations of the number of dopant atoms thus poses a complication for transistor scaling. In a complementary view, new opportunities emerge when novel functionality can be implemented in devices deterministically doped with single atoms. The grand price of the latter might be a large scale quantum computer, where quantum bits (qubits) are encoded e.g. in the spin states of electrons and nuclei of single dopant atoms in silicon, or in color centers in diamond. Both the possible detrimental effects of dopant fluctuations and single atom device ideas motivate the development of reliable single atom doping techniques which are the subject of this chapter. Single atom doping can be approached with top down and bottom up techniques. Top down refers to the placement of dopant atoms into a more or less structured matrix environment, like a transistor in silicon. Bottom up refers to approaches to introduce single dopant atoms during the growth of the host matrix e.g. by directed self-assembly and scanning probe assisted lithography. Bottom up approaches are discussed in Chapter XYZ. Since the late 1960's, ion implantation has been a widely used technique to introduce dopant atoms into silicon and other materials in order to modify their electronic properties. It works particularly well in silicon since the damage to the crystal lattice that is induced by ion implantation can be repaired by thermal annealing. In addition, the introduced dopant atoms can be incorporated with high efficiency into lattice position in the silicon host crystal which makes them electrically active. This is not the case for e.g. diamond, which makes ion implantation doping to engineer the electrical properties of diamond, especially for n-type doping much harder then for silicon. Ion

  12. Doping monolayer graphene with single atom substitutions

    KAUST Repository

    Wang, Hongtao

    2012-01-11

    Functionalized graphene has been extensively studied with the aim of tailoring properties for gas sensors, superconductors, supercapacitors, nanoelectronics, and spintronics. A bottleneck is the capability to control the carrier type and density by doping. We demonstrate that a two-step process is an efficient way to dope graphene: create vacancies by high-energy atom/ion bombardment and fill these vacancies with desired dopants. Different elements (Pt, Co, and In) have been successfully doped in the single-atom form. The high binding energy of the metal-vacancy complex ensures its stability and is consistent with in situ observation by an aberration-corrected and monochromated transmission electron microscope. © 2011 American Chemical Society.

  13. Raman scattering of polycrystalline GaSb thin films grown by the co-evaporation process

    Institute of Scientific and Technical Information of China (English)

    Qiao Zai-Xiang; Sun Yun; He Wei-Yu; Liu Wei; He Qing; Li Chang-Jian

    2009-01-01

    This paper reports that GaSb thin films have been co-deposited on soda-lime glass substrates. The GaSb thin film structural properties are characterized by Raman spectroscopy. The Sb-A1g/GaSb-TO ratio decreases rapidly with the increase of substrate temperature, which suggests a small amount of crystalline Sb in the GaSb thin film and suggests that Sb atoms in the thin film decrease. In Raman spectra, the transverse optical (TO) mode intensity is stronger than that of the longitudinal optical (LO) mode, which indicates that all the samples arc disordered. The LO/TO intensity ratio increases with increasing substrate temperature which suggests the improved polycrystalline quality of the GaSb thin film. A downshift of the TO and LO frequencies of the polycrystalline GaSb thin film to single crystalline bulk GaSb Raman spectra is also observed. The uniaxial stress in GaSb thin film is calculated and the value is around 1.0 Gpa. The uniaxial stress decreases with increasing substrate temperature. These results suggest that a higher substrate temperature is beneficial in relaxing the stress in GaSb thin film.

  14. Thermal diffusion boron doping of single-crystal natural diamond

    Science.gov (United States)

    Seo, Jung-Hun; Wu, Henry; Mikael, Solomon; Mi, Hongyi; Blanchard, James P.; Venkataramanan, Giri; Zhou, Weidong; Gong, Shaoqin; Morgan, Dane; Ma, Zhenqiang

    2016-05-01

    With the best overall electronic and thermal properties, single crystal diamond (SCD) is the extreme wide bandgap material that is expected to revolutionize power electronics and radio-frequency electronics in the future. However, turning SCD into useful semiconductors requires overcoming doping challenges, as conventional substitutional doping techniques, such as thermal diffusion and ion implantation, are not easily applicable to SCD. Here we report a simple and easily accessible doping strategy demonstrating that electrically activated, substitutional doping in SCD without inducing graphitization transition or lattice damage can be readily realized with thermal diffusion at relatively low temperatures by using heavily doped Si nanomembranes as a unique dopant carrying medium. Atomistic simulations elucidate a vacancy exchange boron doping mechanism that occurs at the bonded interface between Si and diamond. We further demonstrate selectively doped high voltage diodes and half-wave rectifier circuits using such doped SCD. Our new doping strategy has established a reachable path toward using SCDs for future high voltage power conversion systems and for other novel diamond based electronic devices. The novel doping mechanism may find its critical use in other wide bandgap semiconductors.

  15. Assessing Risk with GASB Statement No. 3.

    Science.gov (United States)

    Wood, Venita M.; Scott, Bob

    1987-01-01

    Discusses a Government Accounting Standards Board (GASB) publication designed to provide financial statement users with information to assess a government's actual and future deposit and investment market and credit risk. (MLF)

  16. Nanoscale imaging of freestanding nitrogen doped single layer graphene.

    Science.gov (United States)

    Iyer, Ganjigunte R S; Wang, Jian; Wells, Garth; Bradley, Michael P; Borondics, Ferenc

    2015-02-14

    Graphene can be p-type or n-type doped by introduction of specific species. Doping can modulate the electronic properties of graphene, but opening a sizable-well-tuned bandgap is essential for graphene-based tunable electronic devices. N-doped graphene is widely used for device applications and is mostly achieved by introducing ammonia into the synthesis gas during the chemical vapor deposition (CVD) process. Post synthesis treatment studies to fine-tune the electron hole doping in graphene are limited. In this work realization of N-doping in large area freestanding single layer graphene (LFG) is achieved by post treatment in nitrogen plasma. The changes in the chemical and electronic properties of graphene are followed with Raman microscopy and mapped via synchrotron based scanning transmission X-ray microscopy (STXM) at the nanoscale.

  17. Nanoscale imaging of freestanding nitrogen doped single layer graphene

    Science.gov (United States)

    Iyer, Ganjigunte R. S.; Wang, Jian; Wells, Garth; Bradley, Michael P.; Borondics, Ferenc

    2015-01-01

    Graphene can be p-type or n-type doped by introduction of specific species. Doping can modulate the electronic properties of graphene, but opening a sizable-well-tuned bandgap is essential for graphene-based tunable electronic devices. N-doped graphene is widely used for device applications and is mostly achieved by introducing ammonia into the synthesis gas during the chemical vapor deposition (CVD) process. Post synthesis treatment studies to fine-tune the electron hole doping in graphene are limited. In this work realization of N-doping in large area freestanding single layer graphene (LFG) is achieved by post treatment in nitrogen plasma. The changes in the chemical and electronic properties of graphene are followed with Raman microscopy and mapped via synchrotron based scanning transmission X-ray microscopy (STXM) at the nanoscale.Graphene can be p-type or n-type doped by introduction of specific species. Doping can modulate the electronic properties of graphene, but opening a sizable-well-tuned bandgap is essential for graphene-based tunable electronic devices. N-doped graphene is widely used for device applications and is mostly achieved by introducing ammonia into the synthesis gas during the chemical vapor deposition (CVD) process. Post synthesis treatment studies to fine-tune the electron hole doping in graphene are limited. In this work realization of N-doping in large area freestanding single layer graphene (LFG) is achieved by post treatment in nitrogen plasma. The changes in the chemical and electronic properties of graphene are followed with Raman microscopy and mapped via synchrotron based scanning transmission X-ray microscopy (STXM) at the nanoscale. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05385k

  18. Theoretical Studies of Substitutionally Doped Single-Walled Nanotubes

    Directory of Open Access Journals (Sweden)

    Charles See Yeung

    2010-01-01

    Full Text Available The rich chemistry of single-walled carbon nanotubes (SWCNTs is enhanced by substitutional doping, a process in which a single atom of the nanotube sidewall is replaced by a heteroatom. These so-called heteroatom-substituted SWCNTs (HSWCNTs exhibit unique chemical and physical properties not observed in their corresponding undoped congeners. Herein, we present theoretical studies of both main group element and transition metal-doped HSWCNTs. Within density functional theory (DFT, we discuss mechanistic details of their proposed synthesis from vacancy-defected SWCNTs and describe their geometric and electronic properties. Additionally, we propose applications for these nanomaterials in nanosensing, nanoelectronics, and nanocatalysis.

  19. Growth and properties of benzil doped benzimidazole (BMZ) single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Sukumar, M. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Vasudevan, V. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Shakir, Mohd. [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Ramamurthi, K. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Bhagavannarayana, G. [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India)

    2010-09-15

    In the present work, we have made an attempt to study the effect of benzil doping on the properties of benzimidazole single crystals. For this purpose we have grown pure and benzil doped benzimidazole single crystals by vertical Bridgman technique. The grown crystals were characterized by various characterization techniques. The presence of dopants confirmed by powder X-ray diffraction (XRD). Crystalline perfection of the grown crystals has been analysed by high-resolution X-ray diffraction (HRXRD). The transmittance, electrical property and mechanical strength have been analysed using UV-vis-NIR spectroscopic, dielectric and Vicker's hardness studies. The relative second harmonic generation efficiency of pure and doped benzimidazole crystals measured using Kurtz powder test.

  20. Single mode dye-doped polymer photonic crystal lasers

    DEFF Research Database (Denmark)

    Christiansen, Mads Brøkner; Buss, Thomas; Smith, Cameron

    2010-01-01

    Dye-doped polymer photonic crystal (PhC) lasers fabricated by combined nanoimprint and photolithography are studied for their reproducibility and stability characteristics. We introduce a phase shift in the PhC lattice that substantially improves the yield of single wavelength emission. Single mode...... emission and reproducibility of laser characteristics are important if the lasers are to be mass produced in, e. g., optofluidic sensor chips. The fabrication yield is above 85% with highly reproducible wavelengths (within 0.5%), and the temperature dependence on the wavelength is found to be -0.045 or -0...

  1. Synthesis of nitrogen-doped single-walled carbon nanotubes and monitoring of doping by Raman spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Wu Mu-Hong; Li Xiao; Pan Ding; Liu Lei; Yang Xiao-Xia; Xu Zhi; Wang Wen-Long

    2013-01-01

    Nitrogen-doped single-walled carbon nanotubes (CNx-SWNTs) with tunable dopant concentrations were synthesized by chemical vapor deposition (CVD),and their structure and elemental composition were characterized by using transmission electron microscopy (TEM) in combination with electron energy loss spectroscopy (EELS).By comparing the Raman spectra of pristine and doped nanotubes,we observed the doping-induced Raman G band phonon stiffening and 2D band phonon softening,both of which reflect doping-induced renormalization of the electron and phonon energies in the nanotubes and behave as expected in accord with the n-type doping effect.On the basis of first principles calculations of the distribution of delocalized carrier density in both the pristine and doped nanotubes,we show how the n-type doping occurs when nitrogen heteroatoms are substitutionally incorporated into the honeycomb tube-shell carbon lattice.

  2. GaSb on GaAs solar cells Grown using interfacial misfit arrays (Conference Presentation)

    Science.gov (United States)

    Nelson, George T.; Juang, Bor-Chau; Slocum, Michael A.; Bittner, Zachary S.; Laghumavarapu, Ramesh Babu B.; Huffaker, Diana L.; Hubbard, Seth M.

    2017-04-01

    State of the art InGaP2/GaAs/In0.28Ga0.72As inverted metamorphic (IMM) solar cells have achieved impressive results, however, the thick metamorphic buffer needed between the lattice matched GaAs and lattice mismatched InGaAs requires significant effort and time to grow and retains a fairly high defect density. One approach to this problem is to replace the bottom InGaAs junction with an Sb-based material such as 0.73 eV GaSb or 1.0 eV Al0.2Ga0.8Sb. By using interfacial misfit (IMF) arrays, the high degree of strain (7.8%) between GaAs and GaSb can be relaxed solely by laterally propagating 90° misfit dislocations that are confined to the GaAs-GaSb interface layer. We have used molecular beam epitaxy to grow GaSb single junction solar cells homoepitaxially on GaSb and heteroepitaxially on GaAs using IMF. Under 15-sun AM1.5 illumination, the control cell achieved 5% efficiency with a WOC of 366 mV, while the IMF cell was able to reach 2.1% with WOC of 546 mV. Shunting and high non-radiative dark current were main cause of FF and efficiency loss in the IMF devices. Threading dislocations or point defects were the expected source behind the losses, leading to minority carrier lifetimes less than 1ns. Deep level transient spectroscopy (DLTS) was used to search for defects electrically and two traps were found in IMF material that were not detected in the homoepitaxial GaSb device. One of these traps had a trap density of 7 × 1015 cm-3, about one order of magnitude higher than the control cell defect at 4 × 1016 cm-3.

  3. Effect of indium and antimony doping in SnS single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Chaki, Sunil H., E-mail: sunilchaki@yahoo.co.in; Chaudhary, Mahesh D.; Deshpande, M.P.

    2015-03-15

    Highlights: • Single crystals growth of pure SnS, indium doped SnS and antimony doped SnS by direct vapour transport (DVT) technique. • Doping of In and Sb occurred in SnS single crystals by cation replacement. • The replacement mechanism ascertained by EDAX, XRD and substantiated by Raman spectra analysis. • Dopants concentration affects the optical energy bandgap. • Doping influences electrical transport properties. - Abstract: Single crystals of pure SnS, indium (In) doped SnS and antimony (Sb) doped SnS were grown by direct vapour transport (DVT) technique. Two doping concentrations of 5% and 15% each were employed for both In and Sb dopants. Thus in total five samples were studied viz., pure SnS (S1), 5% In doped SnS (S2), 15% In doped SnS (S3), 5% Sb doped SnS (S4) and 15% Sb doped SnS (S5). The grown single crystal samples were characterized by evaluating their surface microstructure, stoichiometric composition, crystal structure, Raman spectroscopy, optical and electrical transport properties using appropriate techniques. The d.c. electrical resistivity and thermoelectric power variations with temperature showed semiconducting and p-type nature of the as-grown single crystal samples. The room temperature Hall Effect measurements further substantiated the semiconducting and p-type nature of the as-grown single crystal samples. The obtained results are deliberated in detail.

  4. Single-frequency, single-polarization holmium-doped ZBLAN fiber laser

    Science.gov (United States)

    Zhu, X.; Zong, J.; Miller, A.; Wiersma, K.; Norwood, R. A.; Prasad, N. S.; Chavez-Pirson, A.; Peyghambarian, N.

    2013-02-01

    We present the performance of a single frequency, single-polarization holmium (Ho3+)-doped ZBLAN (ZrF4-BaF2-LaF3- AlF3-NaF) fiber laser at 1200 nm. This distributed Bragg reflector (DBR) fiber laser was developed by splicing a 22 mm long highly Ho3+-doped ZBLAN fiber to a pair of silica fiber Bragg gratings (FBG). The successful fusion splicing of silica fiber to ZBLAN fiber, with their very different melting temperatures, was accomplished by using NP Photonics proprietary splicing technique. The 3 mol% Ho3+-doped ZBLAN fiber had a core diameter of 6.5 μm and a cladding diameter of 125 μm. The threshold of this laser was seen to be about 260 mW, and when the pump power was 520 mW, the output power was about 10 mW. The efficiency of the 1200 nm single-frequency fiber laser, i.e. the ratio of the output power to the launched pump power, was about 3.8%. The linewidth of the 1200 nm single-frequency fiber laser was estimated to be about 100 kHz by comparing the measured frequency noise of the 1200 nm single-frequency fiber laser with that of 1 μm NP Photonics single-frequency fiber lasers whose linewidths have been measured to be in the 1- 10 kHz range. The relative intensity noise of this DBR all-fiber laser was measured to be 19 dB. Due to its low phonon energy and long radiative lifetimes, rare-earth-doped ZBLAN allows various transitions that are typically terminated in silica glass, resulting in ultraviolet, visible, and infrared rare-earth doped ZBLAN lasers. Therefore, our results highlight the exciting prospect that the accessible wavelength range of single-frequency DBR fiber lasers can be expanded significantly by using rare-earth-doped ZBLAN fibers.

  5. GaSb quantum rings in GaAs/Al{sub x}Ga{sub 1−x}As quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Hodgson, P. D., E-mail: pdhodgson@hotmail.co.uk; Hayne, M.; Robson, A. J.; Zhuang, Q. D. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom); Danos, L. [Department of Chemistry, Lancaster University, Lancaster LA1 4YB (United Kingdom)

    2016-01-28

    We report the results of continuous and time-resolved photoluminescence measurements on type-II GaSb quantum rings embedded within GaAs/Al{sub x}Ga{sub 1−x}As quantum wells. A range of samples were grown with different well widths, compensation-doping concentrations within the wells, and number of quantum-ring layers. We find that each of these variants have no discernible effect on the radiative recombination, except for the very narrowest (5 nm) quantum well. In contrast, single-particle numerical simulations of the sample predict changes in photoluminescence energy of up to 200 meV. This remarkable difference is explained by the strong Coulomb binding of electrons to rings that are multiply charged with holes. The resilience of the emission to compensation doping indicates that multiple hole occupancy of the quantum rings is required for efficient carrier recombination, regardless of whether these holes come from doping or excitation.

  6. GaSb film growth by liquid phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Cruz, M.L.; Martinez-Juarez, J.; Lopez-Salazar, P. [CIDS-ICUAP, BUAP, Av. 14 Sur y San Claudio, C.U. Edif.103C, Col. Sn Manuel, C.P. 72570, Puebla, Pue. (Mexico); Diaz, G.J. [Centro de Investigacion y Estudios Avanzados, IPN, Av. IPN 2508, Col. Sn. Pedro Zacatenco, C.P. 07360, D.F. (Mexico)

    2010-04-15

    Doped GaSb (Gallium Antimonide) films on p-GaSb substrates have been obtained by means of a low-cost and fast-growth method: the liquid phase epitaxy (LPE) technique. The growth temperature was 400 C, and the growth time was varied between1 and 5 min. Characterization of the films was performed by means of high resolution X-ray Diffraction, low temperature-photoluminescence and current-voltage curve measurements. The X-ray diffraction pattern confirms a zincblende-type crystal structure with a high-thin peak centred at 30.36 . The PL spectra at 27 K allowed to confirm the band-gap energy to be 0.8 eV and the I-V curves presented a PN junction behavior which corresponds to the obtained structured. Metal contacts of Au-Zn and Au-Ge were placed to perform electrical characterization (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Single-frequency, single-polarization ytterbium-doped fiber laser by self-injection locking

    Institute of Scientific and Technical Information of China (English)

    Anting Wang(王安廷); Hai Ming(明海); Feng Li(李锋); Lixin Xu(许立新); Liang Lü(吕亮); Huaqiao Gui(桂华侨); Jing Huang(黄晶); Jianping Xie(谢建平)

    2004-01-01

    We demonstrated a stable single-frequency, single-polarization operation of ytterbium-doped fiber laser. As a novel practical method to realize single-polarization operation of fiber distributed Bragg reflector (DBR)laser, we proposed self-injection locking (SIL) with an active fiber ring feedback cavity. The laser has high output power exceeding 15 mW, wavelength of 1053.20 nm, and side-mode suppression ratio greater than 60 dB. The SIL fiber laser shows the improvements in output power and side-mode suppression compared with the fiber DBR laser. No mode-hopping is observed within 2 hours.

  8. Giant Spin-Orbit Splitting in Inverted InAs /GaSb Double Quantum Wells

    Science.gov (United States)

    Nichele, Fabrizio; Kjaergaard, Morten; Suominen, Henri J.; Skolasinski, Rafal; Wimmer, Michael; Nguyen, Binh-Minh; Kiselev, Andrey A.; Yi, Wei; Sokolich, Marko; Manfra, Michael J.; Qu, Fanming; Beukman, Arjan J. A.; Kouwenhoven, Leo P.; Marcus, Charles M.

    2017-01-01

    Transport measurements in inverted InAs /GaSb quantum wells reveal a giant spin-orbit splitting of the energy bands close to the hybridization gap. The splitting results from the interplay of electron-hole mixing and spin-orbit coupling, and can exceed the hybridization gap. We experimentally investigate the band splitting as a function of top gate voltage for both electronlike and holelike states. Unlike conventional, noninverted two-dimensional electron gases, the Fermi energy in InAs /GaSb can cross a single spin-resolved band, resulting in full spin-orbit polarization. In the fully polarized regime we observe exotic transport phenomena such as quantum Hall plateaus evolving in e2/h steps and a nontrivial Berry phase.

  9. The effect of substrate temperature and growth rate on the doping efficiency of single crystal boron doped diamond

    Energy Technology Data Exchange (ETDEWEB)

    Demlow, SN; Rechenberg, R; Grotjohn, T

    2014-10-01

    The substrate growth temperature dependence of the plasma gas-phase to solid-phase doping efficiency in single crystal, boron doped diamond (BDD) deposition is investigated. Single crystal diamond (SCD) is grown by microwave plasma assisted chemical vapor deposition (MPACVD) on high pressure, high temperature (HPHT) type Ib substrates. Samples are grown at substrate temperatures of 850-950 degrees C for each of five doping concentration levels, to determine the effect of the growth temperature on the doping efficiency and defect morphology. The substrate temperature during growth is shown to have a significant effect on the grown sample defect morphology, and a temperature dependence of the doping efficiency is also shown. The effect of the growth rate on the doping efficiency is discussed, and the ratio of the boron concentration in the gas phase to the flux of carbon incorporated into the solid diamond phase is shown to be a more predictive measure of the resulting boron concentration than the gas phase boron to carbon ratio that is more commonly reported. (C) 2014 Elsevier B.V. All rights reserved.

  10. Electrical properties of n-type GaSb substrates and p-type GaSb buffer layers for InAs/InGaSb superlattice infrared detectors

    Energy Technology Data Exchange (ETDEWEB)

    Mitchel, W. C., E-mail: William.Mitchel.1@us.af.mil; Haugan, H. J.; Mou, Shin; Brown, G. J. [Air Force Research Laboratory, Materials & Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433 (United States); Elhamri, S.; Berney, R. [University of Dayton, Department of Physics, Dayton, Ohio 45469 (United States)

    2015-09-15

    Lightly doped n-type GaSb substrates with p-type GaSb buffer layers are the preferred templates for growth of InAs/InGaSb superlattices used in infrared detector applications because of relatively high infrared transmission and a close lattice match to the superlattices. We report here temperature dependent resistivity and Hall effect measurements of bare substrates and substrate-p-type buffer layer structures grown by molecular beam epitaxy. Multicarrier analysis of the resistivity and Hall coefficient data demonstrate that high temperature transport in the substrates is due to conduction in both the high mobility zone center Γ band and the low mobility off-center L band. High overall mobility values indicate the absence of close compensation and that improved infrared and transport properties were achieved by a reduction in intrinsic acceptor concentration. Standard transport measurements of the undoped buffer layers show p-type conduction up to 300 K indicating electrical isolation of the buffer layer from the lightly n-type GaSb substrate. However, the highest temperature data indicate the early stages of the expected p to n type conversion which leads to apparent anomalously high carrier concentrations and lower than expected mobilities. Data at 77 K indicate very high quality buffer layers.

  11. Electrical properties of n-type GaSb substrates and p-type GaSb buffer layers for InAs/InGaSb superlattice infrared detectors

    Directory of Open Access Journals (Sweden)

    W. C. Mitchel

    2015-09-01

    Full Text Available Lightly doped n-type GaSb substrates with p-type GaSb buffer layers are the preferred templates for growth of InAs/InGaSb superlattices used in infrared detector applications because of relatively high infrared transmission and a close lattice match to the superlattices. We report here temperature dependent resistivity and Hall effect measurements of bare substrates and substrate-p-type buffer layer structures grown by molecular beam epitaxy. Multicarrier analysis of the resistivity and Hall coefficient data demonstrate that high temperature transport in the substrates is due to conduction in both the high mobility zone center Γ band and the low mobility off-center L band. High overall mobility values indicate the absence of close compensation and that improved infrared and transport properties were achieved by a reduction in intrinsic acceptor concentration. Standard transport measurements of the undoped buffer layers show p-type conduction up to 300 K indicating electrical isolation of the buffer layer from the lightly n-type GaSb substrate. However, the highest temperature data indicate the early stages of the expected p to n type conversion which leads to apparent anomalously high carrier concentrations and lower than expected mobilities. Data at 77 K indicate very high quality buffer layers.

  12. Valley polarization in magnetically doped single-layer transition-metal dichalcogenides

    KAUST Repository

    Cheng, Yingchun

    2014-04-28

    We demonstrate that valley polarization can be induced and controlled in semiconducting single-layer transition-metal dichalcogenides by magnetic doping, which is important for spintronics, valleytronics, and photonics devices. As an example, we investigate Mn-doped MoS2 by first-principles calculations. We study how the valley polarization depends on the strength of the spin orbit coupling and the exchange interaction and discuss how it can be controlled by magnetic doping. Valley polarization by magnetic doping is also expected for other honeycomb materials with strong spin orbit coupling and the absence of inversion symmetry.

  13. Doping of single-walled carbon nanotubes controlled via chemical transformation of encapsulated nickelocene

    Science.gov (United States)

    Kharlamova, Marianna V.; Sauer, Markus; Saito, Takeshi; Sato, Yuta; Suenaga, Kazu; Pichler, Thomas; Shiozawa, Hidetsugu

    2015-01-01

    Controlled doping of carbon nanotubes is elemental for their electronic applications. Here we report an approach to tune the polarity and degree of doping of single-walled carbon nanotubes via filling with nickelocene followed by encapsulated reactions. Using Raman, photoemission spectroscopy and transmission electron microscopy, we show that nickelocene molecules transform into nickel carbides, nickel and inner carbon nanotubes with reaction temperatures as low as 250 °C. The doping efficiency is determined for each chemical component. Synchronous charge transfer among the molecular components allows bipolar doping of the carbon nanotubes to be achieved in a broad range of +/-0.0012 e- per carbon.

  14. Thermal instability of GaSb surface oxide

    Science.gov (United States)

    Tsunoda, K.; Matsukura, Y.; Suzuki, R.; Aoki, M.

    2016-05-01

    In the development of InAs/GaSb Type-II superlattice (T2SL) infrared photodetectors, the surface leakage current at the mesa sidewall must be suppressed. To achieve this requirement, both the surface treatment and the passivation layer are key technologies. As a starting point to design these processes, we investigated the GaSb oxide in terms of its growth and thermal stability. We found that the formation of GaSb oxide was very different from those of GaAs. Both Ga and Sb are oxidized at the surface of GaSb. In contrast, only Ga is oxidized and As is barely oxidized in the case of GaAs. Interestingly, the GaSb oxide can be formed even in DI water, which results in a very thick oxide film over 40 nm after 120 minutes. To examine the thermal stability, the GaSb native oxide was annealed in a vacuum and analyzed by XPS and Raman spectroscopy. These analyses suggest that SbOx in the GaSb native oxide will be reduced to metallic Sb above 300°C. To directly evaluate the effect of oxide instability on the device performance, a T2SL p-i-n photodetector was fabricated that has a cutoff wavelength of about 4 μm at 80 K. As a result, the surface leakage component was increased by the post annealing at 325°C. On the basis of these results, it is possible to speculate that a part of GaSb oxide on the sidewall surface will be reduced to metallic Sb, which acts as an origin of additional leakage current path.

  15. Microstructural, optical and electrical properties of Cl-doped CdTe single crystals

    Directory of Open Access Journals (Sweden)

    Choi Hyojeong

    2016-09-01

    Full Text Available Microstructural, optical and electrical properties of Cl-doped CdTe crystals grown by the low pressure Bridgman (LPB method were investigated for four different doping concentrations (unintentionally doped, 4.97 × 1019 cm−3, 9.94 × 1019 cm−3 and 1.99 × 1020 cm−3 and three different locations within the ingots (namely, samples from top, middle and bottom positions in the order of the distance from the tip of the ingot. It was shown that Cl dopant suppressed the unwanted secondary (5 1 1 crystalline orientation. Also, the average size and surface coverage of Te inclusions decreased with an increase in Cl doping concentration. Spectroscopic ellipsometry measurements showed that the optical quality of the Cl-doped CdTe single crystals was enhanced. The resistivity of the CdTe sample doped with Cl at the 1.99 × 1020 cm−3 was above 1010 Ω.cm.

  16. Growth and Characterization of Pure and Doped L-Alanine Tartrate Single Crystals

    Directory of Open Access Journals (Sweden)

    K. Rajesh

    2013-01-01

    Full Text Available Single crystals of pure and Lanthanum doped L-Alanine Tartrate were grown by slow evaporation method. The cell parameters were determined using single crystal X-ray diffraction method. To improve the physical properties of the LAT crystal, Lanthanum dopant was added by 2 mol%. ICP studies confirm the presence of Lanthanum in the grown LAT crystal. Transparency range of the crystal was determined using UV-VIS-NIR spectrophotometer. The functional groups of pure and doped LAT crystals were analyzed by FT-IR spectroscopy. Using Vickers microhardness tester, mechanical strength of the material was found. Dielectric studies of pure and doped LAT single crystals were carried out. The doped LAT crystal is found to have efficiency higher than that of pure LAT crystal.

  17. A compact single-polarization erbium-doped fiber laser by exploiting vernier effect

    Institute of Scientific and Technical Information of China (English)

    Xiangqiao Mao; Fengping Yan; Yongjun Fu; Lin Wang; Jian Peng; Lisong Liu; Shuisheng Jian

    2009-01-01

    @@ A compact single-polarization fiber laser with fiber Bragg gratings inscripted in a polarization-maintaining erbium-doped germanosilicate fiber is demonstrated experimentally.The single-wavelength and single-polarization regime of our studied laser is achieved by applying a radial stress upon one of two gratings and stretching the other one axially to adjust the reflection peak match.Two single-wavelength and single-polarization lasing lines are realized respectively with fine power stability.

  18. Graphene functionalization by single atoms doping - a theoretical study

    Science.gov (United States)

    Natan, Amir; Segev, Elad; Hersam, Mark; Seideman, Tamar

    2014-03-01

    We present first principles results and analysis for the electronic structure of chemically modified graphene. We analyze the cases of fluorine adsorption and nitrogen substitution and show that a simple analytical model can describe the doping level as a function of dopant concentration for both cases. We show the relationship between different physical parameters and the electronic band structure of the modified material and its doping level. Finally, we discuss the possible effects of substrate and of different dopant patterns on the band structure and possible applications. amirnatan@post.tau.ac.il

  19. Effects of phosphorus-doping upon the electronic structures of single wall carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    CHEN AQing; SHAO QingYi; LIN ZhiCheng

    2009-01-01

    The phosphorus-doped single wall carbon nanotube (PSWCNT) is studied by using First-Principle methods based on Density Function Theory (DFT). The formation energy, total energy, band structure, geometry structure and density of states are calculated. It is found that the formation energy of the P-doped single carbon nanotubes increases with diameters; the total energy of carbon nanotubes with the same diameter decreases as the doping rate increases. The effects of impurity position on the im-purity level are discussed. It illustrates that the position of the impurity level may depend on the C-P-C bond angle. According to the above results, it is feasible to substitute a carbon atom with a phosphorus atom in SWCNT. It is also found that P-doped carbon nanotubes are N type semiconductor.

  20. Effects of phosphorus-doping upon the electronic structures of single wall carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The phosphorus-doped single wall carbon nanotube(PSWCNT) is studied by using First-Principle methods based on Density Function Theory(DFT).The formation energy,total energy,band structure,geometry structure and density of states are calculated.It is found that the formation energy of the P-doped single carbon nanotubes increases with diameters;the total energy of carbon nanotubes with the same diameter decreases as the doping rate increases.The effects of impurity position on the impurity level are discussed.It illustrates that the position of the impurity level may depend on the C-P-C bond angle.According to the above results,it is feasible to substitute a carbon atom with a phosphorus atom in SWCNT.It is also found that P-doped carbon nanotubes are N type semiconductor.

  1. Effect of Fe doping on the terahertz conductivity of GaN single crystals

    Science.gov (United States)

    Kadlec, Filip; Kadlec, Christelle; Paskova, Tanya; Evans, Keith

    2010-04-01

    Bulk single crystals of GaN with different degrees of Fe doping were studied using time-domain terahertz spectroscopy at high temperatures. Features due to free carriers were observed in the complex permittivity spectra with a pronounced dependence on both doping and temperature. Fitting the spectra using the Drude model made it possible to deduce a defect ionization energy of 16 meV in the undoped sample while the spectra of doped samples are consistent with an ionization energy of 60 meV. Also, the free carrier concentrations at temperatures from 300 to 900 K were estimated.

  2. Effect of Fe doping on the terahertz conductivity of GaN single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kadlec, Filip; Kadlec, Christelle [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Paskova, Tanya; Evans, Keith [Kyma Technologies, Inc., Raleigh, NC 27617 (United States)

    2010-04-14

    Bulk single crystals of GaN with different degrees of Fe doping were studied using time-domain terahertz spectroscopy at high temperatures. Features due to free carriers were observed in the complex permittivity spectra with a pronounced dependence on both doping and temperature. Fitting the spectra using the Drude model made it possible to deduce a defect ionization energy of 16 meV in the undoped sample while the spectra of doped samples are consistent with an ionization energy of 60 meV. Also, the free carrier concentrations at temperatures from 300 to 900 K were estimated.

  3. Rare Earth Doped Silica Nanoparticles via Thermolysis of a Single Source Metallasilsesquioxane Precursor

    Science.gov (United States)

    Davies, Gemma-Louise; O'Brien, John; Gun'Ko, Yurii K.

    2017-04-01

    Rare earth metal doped silica nanoparticles have significant advantages over traditional organic dyes and quantum dots. Silsesquioxanes are promising precursors in the production of silica nanoparticles by thermolysis, due to their structural similarities with silica materials. This manuscript describes the production of a new Eu3+-based metallasilsesquioxane species and its use as a single source precursor in the thermolytic production of luminescent rare earth metal doped silica nanoparticles with characteristic emission in the visible region of the spectrum.

  4. Lattice Dynamics of Potassium-Doped Single-Walled Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    XIAO Yang; YAN Xiao-Hong; CAO Jue-Xian; MAO Yu-Liang; DENG Yu-Xiang; DING Jian-Wen

    2004-01-01

    @@ We calculate the vibrational properties of potassium-doped single-walled carbon nanotubes within lattice dynamical theory. The results show that the frequency of high-frequency Raman mode E2g for K5C40 downshifts to 1553cm-1, which is in agreement with the value for highly doped samples with effective composition KCs.Moreover, the specific heat curves have a turnover at 22 K, originating from the saturation of K atoms vibrational modes at low energy.

  5. Standardizing large format 5" GaSb and InSb substrate production

    Science.gov (United States)

    Martinez, Becky; Flint, J. Patrick; Dallas, G.; Smith, B.; Tybjerg, M.; Aravazhi, Shanmugam; Furlong, Mark J.

    2017-02-01

    In this paper we report on the maturation of large diameter GaSb and InSb substrate production and the key aspects of product quality and process control that have enabled a level of standardization to be achieved that is on par with mass produced compound semiconductor materials such as GaAs and InP. The evolution of commercial production processes for the crystal growth, wafering and epitaxy-ready polishing of antimonide substrates will be discussed together with specific reference to the process tool sets and production methodologies that have transformed a niche material in to one that has set new standards for wafer level product quality, conformity and control. Results will be presented on the production of single crystal >/=6" ingots grown by a modified version of the Czochralski (LEC) technique. Crystal defect mapping will demonstrate that industry standard InSb (211) growth processes have been refined to consistently deliver ultralow dislocation density substrates. Statistical process control data will be presented for large format 5" epitaxy ready finishing processes and compared alongside in-house data for GaAs and InP. Various surface analytical tools are used to characterize 5" InSb and GaSb substrates and our method of providing a unique characterization `finger print' with each substrate discussed. We conclude that improvements in InSb and GaSb product quality and consistency have been driven by the industry's persistent need to improve device performance and yield. Whilst substrate size requirements in antimonide wafer production may have peaked, we will discuss how to moving to the next step in substrate diameters, 6", is very attainable and within relatively short timescales too.

  6. Staircase and saw-tooth field emission steps from nanopatterned n-type GaSb surfaces

    CERN Document Server

    Kildemo, M.; Le Roy, S.; Søndergård, E.

    2009-01-01

    High resolution field emission experiments from nanopatterned GaSb surfaces consisting of densely packed nanocones prepared by low ion-beam-energy sputtering are presented. Both uncovered and metal-covered nanopatterned surfaces were studied. Surprisingly, the field emission takes place by regular steps in the field emitted current. Depending on the field, the steps are either regular, flat, plateaus, or saw-tooth shaped. To the author’s knowledge, this is the first time that such results have been reported. Each discrete jump in the field emission may be understood in terms of resonant tunneling through an extended surface space charge region in an n-type, high aspect ratio, single GaSb nanocone. The staircase shape may be understood from the spatial distribution of the aspect ratio of the cones.

  7. Tips for School Districts: GASB's New Fund Balance Standards

    Science.gov (United States)

    Mead, Dean Michael

    2010-01-01

    In March 2009, the Governmental Accounting Standards Board (GASB) issued Statement No. 54, "Fund Balance Reporting and Governmental Fund Type Definitions." School districts that prepare financial reports based on generally accepted accounting principles are required to implement this standard no later than the first fiscal year that starts after…

  8. Spectral ellipsometry of GaSb: Experiment and modelling

    Energy Technology Data Exchange (ETDEWEB)

    Charache, G.W.; Mu{tilde n}oz, M.; Wei, K.; Pollak, F.H.; Freeouf, J.L.

    1999-05-01

    The optical constants {epsilon}(E)[{equals}{epsilon}{sub 1}(E) + i{epsilon}{sub 2}(E)] of single crystal GaSb at 300K have been measured using spectral ellipsometry in the range of 0.3--5.3 eV. The {epsilon}(E) spectra displayed distinct structures associated with critical points (CPs) at E{sub 0}(direct gap), spin-orbit split E{sub 0} + {Delta}{sub 0} component, spin-orbit split (E{sub 1}), E{sub 1} + {Delta}{sub 1} and (E{sub 0}{prime}), E{sub 0}{prime} + {Delta}{sub 0}{prime} doublets, as well as E{sub 2}. The experimental data over the entire measured spectral range (after oxide removal) has been fit using the Holden model dielectric function [Phys.Rev.B 56, 4037 (1997)] based on the electronic energy-band structure near these CPs plus excitonic and band-to-band Coulomb enhancement effects at E{sub 0}, E{sub 0} + {Delta}{sub 0}and the E{sub 1}, E{sub 1} + {Delta}{sub 1} doublet. In addition to evaluating the energies of these various band-to-band CPs, information about the binding energy (R{sub 1}) of the two-dimensional exciton related to the E{sub 1}, E{sub 1} + {Delta}{sub 1} CPS was obtained. The value of R{sub 1} was in good agreement with effective mass/{rvec k} {center_dot} {rvec p} theory. The ability to evaluate R{sub 1} has important ramifications for recent first-principles band structure calculations which include exciton effects at E{sub 0}, E{sub 1}, and E{sub 2}.

  9. A computer study and photoelectric property analysis of potassium-doped lithium niobate single crystals.

    Science.gov (United States)

    Wang, Wei; Wang, Rui; Zhang, Wen; Xing, Lili; Xu, Yanling; Wu, Xiaohong

    2013-09-14

    First-principles theory was used to design a potassium-doped lithium niobate single crystal. The structural, electronic, optical and ferroelectric properties of the potassium-doped LiNbO3 single crystal model have been investigated using a generalized gradient approximation within density functional theory. It was found that substitution with potassium drastically changed the optical and electronic nature of the crystal and that the band gap slightly decreases. A series of LiNbO3 single crystals doped with x mol% K (x = 0, 3, 6, 9, 12 mol%) were successfully grown using the Czochralski method. The crystals were characterized using powder X-ray diffraction, UV-vis-infrared absorption spectroscopy and a ferroelectric property test. The experimental test results were consistent with the calculated predictions.

  10. Growth and characterization of pure and doped NLO L-arginine acetate single crystals

    Indian Academy of Sciences (India)

    P Praveen Kumar; V Manivannan; P Sagayaraj; J Madhavan

    2009-08-01

    Single crystals of pure, Cu2+ and Mg2+ doped L-arginine acetate (LAA) were grown successfully by slow evaporation technique. In order to improve the device characteristics of LAA crystals, metal dopants of Cu2+ and Mg2+ were incorporated into the parent crystals. The grown pure and doped crystals were confirmed by X-ray powder diffraction studies. The pure and doped crystals were characterized by Fourier transform Raman (FT–Raman) and thermal studies. Absorptions of these grown crystals were analysed using UV–Vis–NIR studies, and it was found that these crystals possess minimum absorption in the entire visible region. Nonlinear optical studies of pure and doped crystals were carried out and it reveals that the dopants have increased the efficiency of LAA crystals.

  11. Growth and Characterization of Pure and Doped L-Alanine Tartrate Single Crystals

    OpenAIRE

    K. Rajesh; B. Milton Boaz; P. Praveen Kumar

    2013-01-01

    Single crystals of pure and Lanthanum doped L-Alanine Tartrate were grown by slow evaporation method. The cell parameters were determined using single crystal X-ray diffraction method. To improve the physical properties of the LAT crystal, Lanthanum dopant was added by 2 mol%. ICP studies confirm the presence of Lanthanum in the grown LAT crystal. Transparency range of the crystal was determined using UV-VIS-NIR spectrophotometer. The functional groups of pure and doped LAT crystals were a...

  12. Broadband amplified spontaneous emission from Er3+-doped single-mode tellurite fibre

    Institute of Scientific and Technical Information of China (English)

    Chen Dong-Dan; Zhang Qin-Yuan; Liu Yue-Hui; Xu Shan-Hui; Yang Zhong-Min; Deng Zai-De; Jiang Zhong-Hong

    2006-01-01

    This paper reports on the fabrication and characterization of a newly erbium-doped single-mode tellurite glass-fibre applicable for 1.5-μm optical amplifiers. A very broad erbium amplified spontaneous emission in the range 1450-1650 nm from erbium-doped single-mode tclluritc glass-fibre is obtained upon excitation of a 980-nm laser diode. The effects of the length of glass-fibre and the pumping power of laser diode on the amplified spontaneous emission are discussed.The result indicates that the tellurite glass-fibre is a promising candidate for designing fibre-optic amplifiers and lasers.

  13. Growth of metal-catalyst-free nitrogen-doped metallic single-wall carbon nanotubes

    Science.gov (United States)

    Li, Jin-Cheng; Hou, Peng-Xiang; Zhang, Lili; Liu, Chang; Cheng, Hui-Ming

    2014-09-01

    Nitrogen-doped (N-doped) single-wall carbon nanotubes (SWCNTs) were synthesized by chemical vapor deposition using SiOx nanoparticles as a catalyst and ethylenediamine as the source of both carbon and nitrogen. The N-doped SWCNTs have a mean diameter of 1.1 nm and a narrow diameter range, with 92% of them having diameters from 0.7 to 1.4 nm. Multi-wavelength laser Raman spectra and temperature-dependent electrical resistance indicate that the SWCNT sample is enriched with metallic nanotubes. These N-doped SWCNTs showed excellent electrocatalytic activity for the oxygen reduction reaction and highly selective and sensitive sensing ability for dopamine detection.Nitrogen-doped (N-doped) single-wall carbon nanotubes (SWCNTs) were synthesized by chemical vapor deposition using SiOx nanoparticles as a catalyst and ethylenediamine as the source of both carbon and nitrogen. The N-doped SWCNTs have a mean diameter of 1.1 nm and a narrow diameter range, with 92% of them having diameters from 0.7 to 1.4 nm. Multi-wavelength laser Raman spectra and temperature-dependent electrical resistance indicate that the SWCNT sample is enriched with metallic nanotubes. These N-doped SWCNTs showed excellent electrocatalytic activity for the oxygen reduction reaction and highly selective and sensitive sensing ability for dopamine detection. Electronic supplementary information (ESI) available: Additional information including Raman spectra, ORR polarization curves, CV curves, etc. See DOI: 10.1039/c4nr03172e

  14. Design of large-core single-mode Yb3+-doped photonic crystal fiber

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xing-tao; ZHENG Yi; LIU Xiao-xu; ZHOU Gui-yao; LIU Zhao-lun; HOU Lan-tian

    2012-01-01

    The effective index of the cladding fundamental space-filing mode in photonic crystal fiber (PCF) is simulated by the effective index method.The variation of the effective index with the structure parameters of the fiber is achieved.For thefirst thne,the relations of the V parameter ofYb3+-doped PCF with the refractive index of core and the structure parameters of the fiber are provided.The single-mode characteristics of large-core yb3+-doped photonic crystal fibers with 7 and 19 missing air holes in the core are analyzed.The large-core single-mode Yb3+-doped photonic crystal fibers with core diameters of 50 μm,100 μm and 150 μm are designed.The results provide theory instruction for the design and fabrication of fiber.

  15. Unexpected strong magnetism of Cu doped single-layer MoS₂ and its origin.

    Science.gov (United States)

    Yun, Won Seok; Lee, J D

    2014-05-21

    The magnetism of the 3d transition-metal (TM) doped single-layer (1L) MoS2, where the Mo atom is partially replaced by the 3d TM atom, is investigated using the first-principles density functional calculations. In a series of 3d TM doped 1L-MoS2's, the induced spin polarizations are negligible for Sc, Ti, and Cr dopings, while the induced spin polarizations are confirmed for V, Mn, Fe, Co, Ni, Cu, and Zn dopings and the systems become magnetic. Especially, the Cu doped system shows unexpectedly strong magnetism although Cu is nonmagnetic in its bulk state. The driving force is found to be a strong hybridization between Cu 3d states and 3p states of neighboring S, which results in an extreme unbalanced spin-population in the spin-split impurity bands near the Fermi level. Finally, we also discuss further issues of the Cu induced magnetism of 1L-MoS2 such as investigation of additional charge states, the Cu doping at the S site instead of the Mo site, and the Cu adatom on the layer (i.e., 1L-MoS2).

  16. Growth of 4-(dimethylamino) benzaldehyde doped triglycine sulphate single crystals and its characterization

    Energy Technology Data Exchange (ETDEWEB)

    Rai, Chitharanjan, E-mail: raichitharanjan@gmail.co [Department of Physics, Mangalore University, Mangalagangotri 574 199 (India); Kalpataru First Grade Science College, Tiptur 572 202 (India); Sreenivas, K. [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Dharmaprakash, S.M., E-mail: smdharma@yahoo.co [Department of Physics, Mangalore University, Mangalagangotri 574 199 (India)

    2009-11-15

    Single crystals of triglycine sulphate (TGS) doped with 1 mol% of 4-(dimethylamino) benzaldehyde (DB) have been grown from aqueous solution at ambient temperature by slow evaporation technique. The effect of dopant on the crystal growth and dielectric, pyroelectric and mechanical properties of TGS crystal have been investigated. X-ray powder diffraction pattern for pure and doped TGS was collected to determine the lattice parameters. FTIR spectra were employed to confirm the presence of 4-(dimethylamino) benzaldehyde in TGS crystal, qualitatively. The dielectric permittivity has been studied as a function of temperature by cooling the sample at a rate of 1 deg. C/min. An increase in the Curie temperature T{sub c}=51 deg. C (for pure TGS, T{sub c}=48.5 deg. C) and decrease in maximum permittivity has been observed for doped TGS when compared to pure TGS crystal. Pyroelectric studies on doped TGS were carried out to determine pyroelectric coefficient. The Vickers's hardness of the doped TGS crystals along (0 1 0) face is higher than that of pure TGS crystal for the same face. Domain patterns on b-cut plates were observed using scanning electron microscope. The low dielectric constant, higher pyroelectric coefficient and higher value of hardness suggest that doped TGS crystals could be a potential material for IR detectors.

  17. Superconductivity in Sm-doped CaFe2As2 single crystals

    Science.gov (United States)

    Dong-Yun, Chen; Bin-Bin, Ruan; Jia, Yu; Qi, Guo; Xiao-Chuan, Wang; Qing-Ge, Mu; Bo-Jin, Pan; Tong, Liu; Gen-Fu, Chen; Zhi-An, Ren

    2016-06-01

    In this article, the Sm-doping single crystals Ca1 - x Sm x Fe2As2 (x = 0 ˜ 0.2) were prepared by the CaAs flux method, and followed by a rapid quenching treatment after the high temperature growth. The samples were characterized by structural, resistive, and magnetic measurements. The successful Sm-substitution was revealed by the reduction of the lattice parameter c, due to the smaller ionic radius of Sm3+ than Ca2+. Superconductivity was observed in all samples with onset T c varying from 27 K to 44 K upon Sm-doping. The coexistence of a collapsed phase transition and the superconducting transition was found for the lower Sm-doping samples. Zero resistivity and substantial superconducting volume fraction only happen in higher Sm-doping crystals with the nominal x > 0.10. The doping dependences of the c-axis length and onset T c were summarized. The high-T c observed in these quenched crystals may be attributed to simultaneous tuning of electron carriers doping and strain effect caused by lattice reduction of Sm-substitution. Project supported by the National Natural Science Foundation of China (Grant No. 11474339), the National Basic Research Program of China (Grant Nos. 2010CB923000 and 2011CBA00100), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB07020100).

  18. Highly optimized tunable Er3+-doped single longitudinal mode fiber ring laser, experiment and model

    DEFF Research Database (Denmark)

    Poulsen, Christian; Sejka, Milan

    1993-01-01

    A continuous wave (CW) tunable diode-pumped Er3+-doped fiber ring laser, pumped by diode laser at wavelengths around 1480 nm, is discussed. Wavelength tuning range of 42 nm, maximum slope efficiency of 48% and output power of 14.4 mW have been achieved. Single longitudinal mode lasing...

  19. Faraday effect improvement by Dy{sup 3+}-doping of terbium gallium garnet single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhe, E-mail: zhenzhe1201@sina.com; Yang, Lei; Hang, Yin; Wang, Xiangyong

    2016-01-15

    Highly transparent Dy{sup 3+}-doped terbium gallium garnet (TGG) single crystal was grown by Czochralski (Cz) method. Phase composition of the crystal was tested by XRD measurements. The distribution coefficient of Dy{sup 3+} in the crystal was obtained. The optical and magneto-optical properties were analyzed in detail, and magnetic properties of the Dy{sup 3+}-TGG crystal were studied. The paramagnetic behavior is observed down to 10 K. The as-grown crystal exhibited high optical transmittance, particularly in the visible region. The Faraday rotation was investigated over visible and near-infrared regions (VIS–NIR) at room temperature. The Verdet constants increase at measured wavelengths and high thermal stability was found in Dy{sup 3+}-doped TGG, as compared to the properties of pure TGG, indicating that Dy{sup 3+}-doped crystals are preferable for magneto-active materials used in Faraday devices at VIS–NIR wavelengths. - Graphical abstract: Highly transparent Dy{sup 3+}-doped terbium gallium garnet (TGG) and pure TGG single crystals were grown by Czochralski method. The Dy{sup 3+}-doped TGG possesses 20–30% higher Verdet values in reference to TGG independently on wavelength.

  20. Studies on optical properties of pure and Mg2+ doped ZTS single crystal

    Science.gov (United States)

    Sumithra Devi, M.; Arthi, A. P.; Thamizharasan, K.

    2014-09-01

    Single crystal of semiorganic nonlinear optical material of pure and Mg2+ doped ZTS were grown by slow evaporation technique from its aqueous solution. The grown crystal was characterized by single crystal XRD to determine the cell parameters. The Mg2+ doped was characterized by SEM and EDX spectrum. The chemical composition of both the pure ZTS and doped Mg2+ crystals were determined by Fourier transform infrared (FTIR). The optical absorption spectrum recorded in the wavelength was ranged from 200 to 2500 nm and its energy gap (Eg) for both pure ZTS is 4.47 eV and doped Mg2+ is 4.42 eV. The mechanical strength of the grown crystal was found from Vicker's microhardness measurements. It showed that pure and doped ZTS crystals are soft in nature. The dielectric measurement was carried out to study the different polarization mechanism and conductivity of the crystal. Photoconductivity studies revealed that the positive photoconductivity of the both were considered as grown crystals.

  1. Growth and characterization of L-Alanine-doped Zinc Thiourea Chloride single crystal (ZTC)

    Science.gov (United States)

    Dhumane, N. R.; Hussaini, S. S.; Dongre, V. G.; Ghugare, P.; Shirsat, M. D.

    2009-06-01

    Single crystal of L-Alanine-doped Zinc Thiourea Chloride (ZTC) was grown by slow evaporation technique. L-Alanine was added in saturated ZTC solution by molar percent. The second-harmonic generation efficiency was studied by Kurtz and Perry powder SHG test for 1, 2, and 3 mole% L-Alanine-doped ZTC and compared with pure ZTC. We observed enhancement in the SHG efficiency of L-Alanine-doped ZTC. Higher enhancement was observed for 3 mole% L-Alanine-doped ZTC. Incorporation of L-Alanine in the crystal was confirmed by energy dispersive X-ray analysis (EDAX). The Fourier transform infrared spectroscopy (FTIR) qualitatively confirms the presence of all the functional groups. The unit cell parameters and crystal structure were determined by single crystal X-ray diffraction. The UV-visible absorption spectra of L-Alanine-doped ZTC show excellent transmittance from 300 nm to 1100 nm. The thermal stability of the grown crystal was also studied by thermo-gravimetric analysis (TGA).

  2. Flicker noise in degenerately doped Si single crystals near the metal–insulator transition

    Indian Academy of Sciences (India)

    A K Raychaudhuri; Arindam Ghosh; Swastik Kar

    2002-02-01

    In this paper we report some of the important results of experimental investigations of the flicker noise near the metal–insulator (MI) transition in doped silicon single crystals. This is the first comprehensive work to study low-frequency noise in heavily doped Si over an extensive temperature range (2 K < T < 500 K). The measurements of conductance fluctuations (flicker noise) were carried out in the frequency range 10-2 < < 4 × 101 Hz in single crystalline Si across the MI transition by doping with phosphorous and boron. The magnitude of noise in heavily doped Si is much larger than that seen in lightly doped Si over the whole temperature range. The extensive temperature range covered allowed us to detect two distinct noise mechanisms. At low temperatures ( < 100 K) universal conductance fluctuations (UCF) dominate and the spectral dependence of the noise is determined by dephasing the electron from defects with two-levels (TLS). At higher temperatures ( > 200 K) the noise arises from activated defect dynamics. As the MI transition is approached, the 1/ spectral power, typical of the metallic regime, gets modified by the presence of discrete Lorentzians which arise from generation-recombination process which is the characteristic of a semiconductor.

  3. Single-frequency thulium-doped distributed-feedback fiber laser.

    Science.gov (United States)

    Agger, Søren; Povlsen, Jørn Hedegaard; Varming, Poul

    2004-07-01

    We have successfully demonstrated a single-frequency distributed-feedback (DFB) thulium-doped silica fiber laser emitting at a wavelength of 1735 nm. The laser cavity is less than 5 cm long and is formed by intracore UV-written Bragg gratings with a phase shift. The laser is pumped at 790 nm from a Ti:sapphire laser and has a threshold pump power of 59 mW. The laser has a maximum output power of 1 mW in a single-frequency, single-polarization radiation mode and is tunable over a few nanometers. To the best of the authors' knowledge, this is the first report of a single-frequency DFB fiber laser that uses thulium as the amplifying medium. The lasing wavelength is the longest demonstrated with DFB fiber lasers and yet is among the shortest obtained for thulium-doped silica fiber lasers.

  4. Growth of GaSb1-xBix by molecular beam epitaxy

    DEFF Research Database (Denmark)

    Song, Yuxin; Wang, Shumin; Roy, Ivy Saha

    2012-01-01

    Molecular beam epitaxy for GaSb1-xBix is investigated in this article. The growth window for incorporation of Bi in GaSb was found. Strategies of avoiding formation of Bi droplets and enhancing Bi incorporation were studied. The Bi incorporation was confirmed by SIMS and RBS measurements. The Bi...... concentration in the samples was found to increase with increasing growth temperature and Bi flux. The position of GaSb1-xBix layer peak in XRD rocking curves is found to be correlated to Bi composition. Surface and structural properties of the samples were also investigated. Samples grown on GaSb and Ga...

  5. Raman properties of GaSb nanoparticles embedded in SiO2 films

    Institute of Scientific and Technical Information of China (English)

    Liu Fa-Min; Wang Tian-Min; Zhang Li-De

    2004-01-01

    The Raman shifts of nanocrystalline GaSb excited by an Ar+ ion laser at wavelengths 514.5, 496.5, 488.0, 476.5,and 457.9nm are studied by an SPEX-1403 laser Raman spectrometer respectively, and they are explained by phonon confinement, tensile stress, resonant Raman scattering and quantum size effects. The Stokes and anti-Stokes Raman spectra of GaSb nanocrystals strongly support the Raman feature of GaSb nanocrystals. The calculated optical spectra compare well with experimental data on Raman scattering GaSb nanocrystals.

  6. A 980 nm pseudomorphic single quantum well laser for pumping erbium-doped optical fiber amplifiers

    Science.gov (United States)

    Larsson, A.; Forouhar, S.; Cody, J.; Lang, R. J.; Andrekson, P. A.

    1990-01-01

    The authors have fabricated ridge waveguide pseudomorphic InGaAs/GaAs/AlGaAs GRIN-SCH SQW (graded-index separate-confinement-heterostructure single-quantum-well) lasers, emitting at 980 nm, with a maximum output power of 240 mW from one facet and a 22 percent coupling efficiency into a 1.55-micron single-mode optical fiber. These lasers satisfy the requirements on efficient and compact pump sources for Er3+-doped fiber amplifiers.

  7. Continuous Electron Doping of Single-Walled Carbon Nanotube Films Using Inkjet Technique

    Science.gov (United States)

    Matsuzaki, Satoki; Nobusa, Yuki; Shimizu, Ryo; Yanagi, Kazuhiro; Kataura, Hiromichi; Takenobu, Taishi

    2012-06-01

    The fabrication of logic circuits using the inkjet technique has attracted especially strong interest owing to wide range applications such as flexible and printed electronics. Although logic circuits fabricated using the inkjet method have already been accomplished, the precise control of gate threshold voltages has not been realized yet. In this study, we have demonstrated electron doping of single-walled carbon nanotube (SWCNT) films by inkjet printing of dilute poly(ethylene imine) (PEI) ink. We have successfully obtained the continuous threshold voltage shift by varying the number of doping steps, indicating that the carrier concentration in PEI ink is much lower than that of our previous work.

  8. Influence of cysteine doping on photoluminescence intensity from semiconducting single-walled carbon nanotubes

    Science.gov (United States)

    Kurnosov, N. V.; Leontiev, V. S.; Linnik, A. S.; Karachevtsev, V. A.

    2015-03-01

    Photoluminescence (PL) from semiconducting single-walled carbon nanotubes can be applied for detection of cysteine. It is shown that cysteine doping (from 10-8 to 10-3 M) into aqueous suspension of nanotubes with adsorbed DNA leads to increase of PL intensity. The PL intensity was enhanced by 27% at 10-3 M cysteine concentration in suspension. Most likely, the PL intensity increases due to the passivation of p-defects on the nanotube by the cysteine containing reactive thiol group. The effect of doping with other amino acids without this group (methionine, serine, aspartic acid, lysine, proline) on the PL intensity is essentially weaker.

  9. Synthesis and characterization of single-phase Mn-doped ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Chattopadhyay, S.; Dutta, S.; Banerjee, A.; Jana, D. [Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009, West Bengal (India); Bandyopadhyay, S., E-mail: sbaphy@caluniv.ac.i [Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009, West Bengal (India); Chattopadhyay, S. [Department of Physics, Taki Government College, Taki 743 429, West Bengal (India); Sarkar, A. [Department of Physics, Bangabasi Morning College, 19 Rajkumar Chakraborty Sarani, Kolkata 700 009, West Bengal (India)

    2009-05-01

    Different samples of Zn{sub 1-x}Mn{sub x}O series have been prepared using conventional solid-state sintering method. We identified up to what extent doping will enable us to synthesize single-phase polycrystalline Mn-doped ZnO sample, which is one of the prerequisites for dilute magnetic semiconductor, and we have analyzed its some other physical aspects. In synthesizing the samples, proportion of Mn varies from 1 to 5 at%. However, the milling time varied (6, 12, 24, 48 and 96 h) only for 2 at% Mn-doped samples while for other samples (1, 3, 4 and 5 at% Mn doped) the milling time has been fixed to 96 h. Room-temperature X-ray diffraction (XRD) data reveal that all of the prepared samples up to 3 at% of Mn doping exhibit wurtzite-type structure, and no segregation of Mn and/or its oxides has been found. The 4 at% Mn-doped samples show a weak peak of ZnMn{sub 2}O{sub 4} apart from the other usual peaks of ZnO and the intensity of this impurity peak has been further increased for 5 at% of Mn doping. So beyond 3 at% doping, single-phase behavior is destroyed. Band gap for all the 2 at% Mn-doped samples has been estimated to be between 3.21 and 3.19 eV and the reason for this low band gap values has been explained through the grain boundary trapping model. The room-temperature resistivity measurement shows an increase of resistivity up to 48 h of milling and with further milling it saturates. The defect state of these samples has been investigated using the positron annihilation lifetime (PAL) spectroscopy technique. Here all the relevant lifetime parameters of positron i.e. free annihilation (tau{sub 1}) at defect site (tau{sub 2}) and average (tau{sub av}) increases with milling time.

  10. Transfer doping of single isolated nanodiamonds, studied by scanning probe microscopy techniques.

    Science.gov (United States)

    Bolker, Asaf; Saguy, Cecile; Kalish, Rafi

    2014-09-26

    The transfer doping of diamond surfaces has been applied in various novel two-dimensional electronic devices. Its extension to nanodiamonds (ND) is essential for ND-based applications in many fields. In particular, understanding the influence of the crystallite size on transfer doping is desirable. Here, we report the results of a detailed study of the electronic energetic band structure of single, isolated transfer-doped nanodiamonds with nanometric resolution using a combination of scanning tunneling spectroscopy and Kelvin force microscopy measurements. The results show how the band gap, the valence band maximum, the electron affinity and the work function all depend on the ND's size and nanoparticle surface properties. The present analysis, which combines information from both scanning tunneling spectroscopy and Kelvin force microscopy, should be applicable to any nanoparticle or surface that can be measured with scanning probe techniques.

  11. Transfer doping of single isolated nanodiamonds, studied by scanning probe microscopy techniques

    Science.gov (United States)

    Bolker, Asaf; Saguy, Cecile; Kalish, Rafi

    2014-09-01

    The transfer doping of diamond surfaces has been applied in various novel two-dimensional electronic devices. Its extension to nanodiamonds (ND) is essential for ND-based applications in many fields. In particular, understanding the influence of the crystallite size on transfer doping is desirable. Here, we report the results of a detailed study of the electronic energetic band structure of single, isolated transfer-doped nanodiamonds with nanometric resolution using a combination of scanning tunneling spectroscopy and Kelvin force microscopy measurements. The results show how the band gap, the valence band maximum, the electron affinity and the work function all depend on the ND’s size and nanoparticle surface properties. The present analysis, which combines information from both scanning tunneling spectroscopy and Kelvin force microscopy, should be applicable to any nanoparticle or surface that can be measured with scanning probe techniques.

  12. Correlation of doping, structure, and carrier dynamics in a single GaN nanorod

    Science.gov (United States)

    Zhou, Xiang; Lu, Ming-Yen; Lu, Yu-Jung; Gwo, Shangjr; Gradečak, Silvija

    2013-06-01

    We report the nanoscale optical investigation of a single GaN p-n junction nanorod by cathodoluminescence (CL) in a scanning transmission electron microscope. CL emission characteristic of dopant-related transitions was correlated to doping and structural defect in the nanorod, and used to determine p-n junction position and minority carrier diffusion lengths of 650 nm and 165 nm for electrons and holes, respectively. Temperature-dependent CL study reveals an activation energy of 19 meV for non-radiative recombination in Mg-doped GaN nanorods. These results directly correlate doping, structure, carrier dynamics, and optical properties of GaN nanostructure, and provide insights for device design and fabrication.

  13. Scattering mechanisms in Rb-doped single-crystal C{sub 60}

    Energy Technology Data Exchange (ETDEWEB)

    Crespi, V.H.; Cohen, M.L. [Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States)]|[Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States)

    1995-08-01

    The temperature-dependent resistivity of Rb-doped single-crystal C{sub 60} is analyzed within Bloch-Boltzmann transport theory yielding values of the electron-phonon coupling constant consistent with a superconducting {ital T}{sub {ital c}}{approx}30 K and isotope effect exponent {alpha}{approx}0.37 as long as the coupling is not primarily to the on-ball phonons of highest frequency. Disparate sources of information regarding the absolute magnitude of the resistivity are discussed in an attempt to form a more unified picture of the normal state and superconducting properties of both K-doped and Rb-doped C{sub 60}.

  14. Laser-induced down-conversion parameters of singly and doubly doped ZnS phosphors

    Indian Academy of Sciences (India)

    H S Bhatti; Rajesh Sharma; N K Verma

    2005-09-01

    Singly and doubly doped ZnS phosphors have been synthesized using flux method. Laser-induced photoluminescence has been observed in ZnS-doped phosphors when these were excited by the pulsed UV N2 laser radiation. Due to down-conversion phenomenon, fast phosphorescence emission in the visible region is recorded in milliseconds time domain for ZnS:Mn while in the case of ZnS:Mn:killer (Fe, Co and Ni) the lifetime reduces to microseconds time domain. Experimentally observed luminescent emission parameters of excited states such as, lifetimes, trap-depth values and decay constants have been reported here at room temperature. The high efficiency and fast recombination times observed in doped ZnS phosphors make these materials very attractive for optoelectronic applications.

  15. A DFT comparative study of single and double SO{sub 2} adsorption on Pt-doped and Au-doped single-walled carbon nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Yoosefian, Mehdi, E-mail: m.yoosefian@kgut.ac.ir [Department of Chemistry, Graduate University of Advanced Technology, Kerman (Iran, Islamic Republic of); Zahedi, Mansour [Department of Chemistry, Faculty of Sciences, Shahid Beheshti University G.C., P.O. Box 19839-63113, Evin, Tehran 19839 (Iran, Islamic Republic of); Mola, Adeleh [Department of Chemistry, Payame Noor University, Mashhad (Iran, Islamic Republic of); Department of Medical Chemistry, Faculty of Pharmacy, Kerman University of Medical Sciences, Kerman (Iran, Islamic Republic of); Naserian, Samira [Department of Chemistry, Faculty of Sciences, Shahid Beheshti University G.C., P.O. Box 19839-63113, Evin, Tehran 19839 (Iran, Islamic Republic of)

    2015-09-15

    Highlights: • Investigation of the adsorption of SO{sub 2} on Au/SWCNT and Pt/SWCNT. • SO{sub 2} adsorbed on Au/SWCNT and Pt/SWCNT system demonstrate a strong chemisorption. • NBO analysis was done to reach more understanding about intermolecular interactions. - Abstract: Adsorption of single and double SO{sub 2} gas molecule(s) on the surface of Pt-doped and Au-doped (5,5) single-walled carbon nanotubes (Pt/CNT-V and Au/CNT-V) were investigated by using density functional theory (DFT) at B3LYP/LANL2DZ level. The results showed the following: firstly, adsorption on Au/CNT-V is independent of special orientation, secondly, SO{sub 2} adsorption on Pt/CNT-V in single case is stronger than Au/CNT-V, and finally, adsorption of the first molecule influences adsorption of the second one. Upon adsorption of SO{sub 2} molecule(s), the energy gap of Pt/CNT-V were considerably reduced, resulting in enhanced electrical conductivity but in Au/CNT-V, despite of adsorption energy similar to Pt/CNT-V, E{sub g} slightly increased. In order to consider the effect of adsorption on electronic properties, DOS and PDOS calculations were performed. Moreover, NBO analysis was done to reach more understanding about intermolecular interactions. In conclusion, chemical reactivity was investigated in terms of chemical hardness, softness and work function (ϕ)

  16. Single-frequency thulium-doped distributed-feedback fibre laser

    DEFF Research Database (Denmark)

    Agger, Søren; Povlsen, Jørn Hedegaard; Varming, Poul

    2004-01-01

    We have successfully demonstrated a single-frequency distributed-feedback (DFB) thulium-doped silica fiber laser emitting at a wavelength of 1735 nm. The laser cavity is less than 5 cm long and is formed by intracore UV-written Bragg gratings with a phase shift. The laser is pumped at 790 nm from...... that uses thulium as the amplifying medium. The lasing wavelength is the longest demonstrated with DFB fiber lasers and yet is among the shortest obtained for thulium-doped silica fiber lasers....... a Ti:sapphire laser and has a threshold pump power of 59 mW. The laser has a maximum output power of 1 mW in a singlefrequency, single-polarization radiation mode and is tunable over a few nanometers. To the best of the authors’ knowledge, this is the first report of a single-frequency DFB fiber laser...

  17. Single Schottky junction FETs based on Si:P nanowires with axially graded doping

    Science.gov (United States)

    Barreda, Jorge; Keiper, Timothy; Zhang, Mei; Xiong, Peng

    2015-03-01

    Si nanowires (NWs) with a systematic axial increase in phosphorus doping have been synthesized via a vapor-liquid-solid method. Silane and phosphine precursor gases are utilized for the growth and doping, respectively. The phosphorous doping profile is controlled by the flow ratio of the precursor gases. After the as-grown product is ultrasonically agitated into a solution, the Si NWs are dispersed on a SiO2 substrate with a highly doped Si back gate. Individual NWs are identified for the fabrication of field-effect transistors (FETs) with multiple Cr/Ag contacts along the NW. Two-probe and four-probe measurements are taken systematically under vacuum conditions at room temperature and the contribution from each contact and each NW section between adjacent contacts is determined. The graded doping level, produced by a systematic reduction in dopant density along the length of the NWs, is manifested in the regular increases in the channel and contact resistances. Our Si NWs facilitate the fabrication of asymmetric FETs with one ohmic and one Schottky contact. A significant increase in gate modulation is obtained due to the single Schottky-barrier contact. Characterization details and the applicability for sensing purposes will be discussed.

  18. Simulation study on single event burnout in linear doping buffer layer engineered power VDMOSFET

    Science.gov (United States)

    Yunpeng, Jia; Hongyuan, Su; Rui, Jin; Dongqing, Hu; Yu, Wu

    2016-02-01

    The addition of a buffer layer can improve the device's secondary breakdown voltage, thus, improving the single event burnout (SEB) threshold voltage. In this paper, an N type linear doping buffer layer is proposed. According to quasi-stationary avalanche simulation and heavy ion beam simulation, the results show that an optimized linear doping buffer layer is critical. As SEB is induced by heavy ions impacting, the electric field of an optimized linear doping buffer device is much lower than that with an optimized constant doping buffer layer at a given buffer layer thickness and the same biasing voltages. Secondary breakdown voltage and the parasitic bipolar turn-on current are much higher than those with the optimized constant doping buffer layer. So the linear buffer layer is more advantageous to improving the device's SEB performance. Project supported by the National Natural Science Foundation of China (No. 61176071), the Doctoral Fund of Ministry of Education of China (No. 20111103120016), and the Science and Technology Program of State Grid Corporation of China (No. SGRI-WD-71-13-006).

  19. Gain properties of germanate glasses singly doped with Tm3+ and Ho3+ ions

    Institute of Scientific and Technical Information of China (English)

    LIN Qiongfei; XIA Haiping; ZHANG Yuepin; WANG Jinhao; ZHANG Jianli; HE Sailong

    2009-01-01

    Two kinds of germanate glasses singly doped with the ion concentration of 2.0mol.%Tm3+ and 2.0mol.%Ho3+, respectively, were prepared. According to McCumber theory, the absorption and stimulated emission cross-sections corresponding to the 3H6←→3F4 transitions of Tm3+ (at 1.8 μm) and the 5I8←→5I7 transitions of Ho3+ (at 2.0 μm) were obtained, and respective gain cross-section spectra were also computed as a function of population inversion according to absorption and emission cross-sections and the ion concentrations. For Tm3+-doped germanate glasses, the maximum of the absorption, emission, and gain cross-sections reached a value higher than those reported for fluorozirconate, fluoride, and oxyfluoride glasses. For Ho3+-doped germanate glasses, the maximum of absorption, emission, and gain cross-sections reached a value higher than that reported for fluorozircoaluminate glasses. Hence, these Tm3+-doped and Ho3+-doped germanate glasses exhibited an advantage for application in mid-infrared lasers at about 1.8 and 2.0 μm wavelength.

  20. Synthesis and characterization of pure, urea and thiourea doped organic NLO L-arginine trifluoroacetate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Prasanyaa, T. [Department of Physics, Karunya University, Coimbatore 641 114, Tamilnadu (India); Haris, M., E-mail: mharis8@yahoo.com [Department of Physics, Karunya University, Coimbatore 641 114, Tamilnadu (India); Mathivanan, V. [Department of Physics, Karunya University, Coimbatore 641 114, Tamilnadu (India); Department of Physics, United Institute of Technology, Coimbatore (India); Senthilkumar, M. [Department of Physics, Karunya University, Coimbatore 641 114, Tamilnadu (India); Mahalingam, T. [Department of Electrical and Computer Engineering, Ajou University, Suwon 443-749 (Korea, Republic of); Jayaramakrishnan, V. [Department of Physics, P.S.G. College of Arts and Science, Coimbatore 641 014, Tamilnadu (India)

    2014-10-15

    Optically transparent L-arginine trifluoroacetate (LATF) single crystals by doping with organic materials urea and thiourea were grown by slow solvent evaporation technique. Powder X-ray diffraction confirms improvement in the crystalline quality for urea doped crystals. Urea doping in LATF also improves the percentage of transmittance. The vibrational frequencies of the grown crystals were assigned by Fourier Transform infrared spectroscopy. The thermal analysis (TG/DTA) indicated the better thermal stability for urea doped LATF crystals. EDAX analysis was carried out to calculate the percentage of elements present in doped and pure LATF. The hardness has been remarkably improved on urea and thiourea doped LATF crystals. The second harmonic generation (SHG) analysis showed 2.5 times than standard KDP for pure LATF and 2.2, 2.07 times than KDP for urea and thiourea doped LATF. - Highlights: • Urea doped LATF crystals enhances the structural and crystalline quality. • Urea doping enhances optical transparency and thermal stability. • Urea and thiourea doping in LATF improves the hardness. • SHG efficiency of urea, thiourea doped LATF are 2.2 and 2.07 times greater than KDP.

  1. Thermoluminescence characterization of Ag-doped Li2 B4 O7 single crystal materials.

    Science.gov (United States)

    Kuralı, D; Ekdal Karalı, E; Kelemen, A; Holovey, V; Can, N; Karalı, T

    2017-08-01

    In this study, the thermoluminescence (TL) characteristics of Ag-doped and undoped lithium tetraborate (Li2 B4 O7 , LTB) materials, grown using the Czochralski method, were reported. The TL properties of LTB:Ag, such as glow curve structure, dose response, fading and reproducibility, were investigated. The glow curve of the Li2 B4 O7 :Ag single crystal consists of four peaks located at approximately 75, 130, 190 and 275°C; in undoped LTB, the single crystal shows a broad glow curve with peaks at 65, 90, 125, 160 and 190°C using a heating rate of 5°C/s in the 50-350°C temperature region. The high temperature peak of Ag-doped sample at 275°C has a nonlinear dose response within the range from 33 mGy to 9 Gy. There is a linear response in the range of 33-800 mGy; after which, a sublinear region appears up to 9 Gy for Ag-doped LTB single crystal. For undoped single crystal, the dose response is supralinear for low doses and linear for the region between 1 and 9 Gy. The thermal fading ratio of the undoped material is almost 60% for the high temperature peak after 7 days. Ag-doped LTB single crystal exhibits different behaviour over a period of 7 days. Copyright © 2016 John Wiley & Sons, Ltd.

  2. The Insulator to Superconductor Transition in Ga-Doped Semiconductor Ge Single Crystal Induced by the Annealing Temperature

    Directory of Open Access Journals (Sweden)

    Y. B. Sun

    2015-01-01

    Full Text Available We have fabricated the heavily Ga-doped layer in Ge single crystal by the implantation and rapid thermal annealing method. The samples show a crossover from the insulating to the superconducting behavior as the annealing temperature increases. Transport measurements suggest that the superconductivity is from the heavily Ga-doped layer in Ge.

  3. Biocompatibility of GaSb thin films grown by RF magnetron sputtering

    Science.gov (United States)

    Nishimoto, Naoki; Fujihara, Junko; Yoshino, Katsumi

    2017-07-01

    GaSb may be suitable for biological applications, such as cellular sensors and bio-medical instrumentation because of its low toxicity compared with As (III) compounds and its band gap energy. Therefore, the biocompatibility and the film properties under physiological conditions were investigated for GaSb thin films with or without a surface coating. GaSb thin films were grown on quartz substrates by RF magnetron sputtering, and then coated with (3-mercaptopropyl) trimethoxysilane (MPT). The electrical properties, surface morphology, and crystal structure of the GaSb thin film were unaffected by the MPT coating. The cell viability assay suggested that MPT-coated GaSb thin films are biocompatible. Bare GaSb was particularly unstable in pH9 buffer. Ga elution was prevented by the MPT coating, although the Ga concentration in the pH 9 buffer was higher than that in the other solutions. The surface morphology and crystal structure were not changed by exposure to the solutions, except for the pH 9 buffer, and the thin film properties of MPT-coated GaSb exposed to distilled water and H2O2 in saline were maintained. These results indicate that MPT-coated GaSb thin films are biocompatible and could be used for temporary biomedical devices.

  4. Bismuth-induced restructuring of the GaSb(110) surface

    DEFF Research Database (Denmark)

    Gemmeren, T. van; Lottermoser, L.; Falkenberg, G.

    1998-01-01

    The structure of the GaSb(110)(1 x 2)-Bi reconstruction has been solved using surface x-ray diffraction, scanning tunneling microscopy, and photoelectron spectroscopy. The ideal GaSb(110) surface is terminated with zigzag chains of anions and cations running in the [1 (1) over bar 0] direction...

  5. High-Mobility GaSb Nanostructures Cointegrated with InAs on Si.

    Science.gov (United States)

    Borg, Mattias; Schmid, Heinz; Gooth, Johannes; Rossell, Marta D; Cutaia, Davide; Knoedler, Moritz; Bologna, Nicolas; Wirths, Stephan; Moselund, Kirsten E; Riel, Heike

    2017-02-22

    GaSb nanostructures integrated on Si substrates are of high interest for p-type transistors and mid-IR photodetectors. Here, we investigate the MOCVD growth and properties of GaSb nanostructures monolithically integrated onto silicon-on-insulator wafers using template-assisted selective epitaxy. A high degree of morphological control allows for GaSb nanostructures with critical dimensions down to 20 nm. Detailed investigation of growth parameters reveals that the GaSb growth rate is governed by the desorption processes of an Sb surface, and in turn is insensitive to changes in material transport efficiency. The GaSb crystal structure is typically zinc-blende with a low density of rotational twin defects and even occasional twin-free structures are observed. Van der Pauw/Hall measurements are conducted on 20 nm thick GaSb nanostructures, revealing high hole mobility of 760 cm2/Vs, which matches literature values for high-quality bulk GaSb crystals. Finally, we demonstrate a process that enables cointegration of GaSb and InAs nanostructures in close vicinity on Si, a preferred material combination ideally suited for high-performance complementary III-V MOS technology.

  6. Dependence of in-tube doping on the radius and helicity of single-wall carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    刘红; 董锦明; 钱湄杶; 万贤纲

    2003-01-01

    Using the Lennard-Jones interaction potential between the impurity atom and carbon atom, we have studied the dependence of in-tube impurity doping on the radius of a single-wall carbon nanotube (SWNT), as well as its helicity.The obtained results show that the radius of the most stably doped SWNT is different for different kinds of impurity atoms. This is useful for producing the required doped SWNT. In addition, it is found that the helicity of tube has a strong effect on the potential energy of the atoms doped in the SWNT.

  7. 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.)

  8. Verification of electron doping in single-layer graphene due to H{sub 2} exposure with thermoelectric power

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Sung Ju; Kang, Hojin; Soler-Delgado, David; Kim, Kyung Ho; Park, Yung Woo, E-mail: ywpark@phya.snu.ac.kr, E-mail: kbh37@incheon.ac.kr [Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Park, Min [Department of Nano Science and Technology, Seoul National University, Seoul 151-747 (Korea, Republic of); Lee, Minwoo; Jeong, Dae Hong [Department of Chemistry Education, Seoul National University, Seoul 151-742 (Korea, Republic of); Shin, Dong Seok; Kim, Byung Hoon, E-mail: ywpark@phya.snu.ac.kr, E-mail: kbh37@incheon.ac.kr [Department of Physics, Incheon National University, Incheon 406-772 (Korea, Republic of); Kubatkin, Sergey [Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Göteborg (Sweden)

    2015-04-06

    We report the electron doping of single-layer graphene (SLG) grown by chemical vapor deposition (CVD) by means of dissociative hydrogen adsorption. The transfer characteristic showed n-type doping behavior similar to that of mechanically exfoliated graphene. Furthermore, we studied the thermoelectric power (TEP) of CVD-grown SLG before and after exposure to high-pressure H{sub 2} molecules. From the TEP results, which indicate the intrinsic electrical properties, we observed that the CVD-grown SLG is n-type doped without degradation of the quality after hydrogen adsorption. Finally, the electron doping was also verified by Raman spectroscopy.

  9. Lifshitz topological transitions, induced by doping and deformation in single-crystal bismuth wires

    Science.gov (United States)

    Nikolaeva, A. A.; Konopko, L. A.; Huber, T. E.; Kobylianskaya, A. K.; Para, Gh. I.

    2017-02-01

    The features associated with the manifestation of Lifshitz electron topological transitions (ETT) in glass-insulated bismuth wires upon qualitative changes to the topology of the Fermi surface are investigated. The variation of the energy spectrum parameters was implemented by doping Bi with an acceptor impurity Sn and using elastic strain of up to 2%, relative to the elongation in the weakly-doped p-type Bi wires. Pure and doped glass-insulated single-crystal bismuth with different diameters and (1011) orientations along the axis were prepared by the Ulitovsky liquid phase casting method. For the first time, ETT-induced anomalies are observed along the temperature dependences of the thermoemf α(T) as triple-changes of the α sign (given heavy doping of Bi wires with an acceptor impurity Sn). The concentration and energy position of the Σ-band given a high degree of bismuth doping with Sn was assessed using the Shubnikov-de Haas effect oscillations, which were detected both from L-electrons and from T-holes in magnetic fields of up to 14 T. It is shown that the Lifshitz electron-topological transitions with elastic deformation of weakly-doped p-type Bi wires are accompanied by anomalies along the deformation dependences of the thermoemf at low temperatures. The effect is interpreted in terms of the formation of a selective scattering channel of L-carriers into the T-band with a high density of states, which is in good agreement with existing theoretical ETT models.

  10. Stability of short, single-mode erbium-doped fiber lasers

    Energy Technology Data Exchange (ETDEWEB)

    Svalgaard, M.; Gilbert, S.L. [National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80303 (United States)

    1997-07-01

    We conducted a detailed study of the stability of short, erbium-doped fiber lasers fabricated with two UV-induced Bragg gratings written into the doped fiber. We find that the relative intensity noise of single-longitudinal-mode fiber grating lasers is approximately 3 orders of magnitude lower than that of a single-frequency 1.523-{mu}m helium-neon laser. The frequency noise spectrum contains few resonances, none of which exceeds 0.6 kHz/Hz{sup 1/2} rms; the integrated rms frequency noise from 50 Hz to 63 kHz is 36 kHz. We also demonstrate a simple method for monitoring the laser power and number of oscillating modes during laser fabrication. {copyright} 1997 Optical Society of America

  11. Growth and characterization of Arsenic doped CdTe single crystals grown by Cd-solvent traveling-heater method

    Science.gov (United States)

    Nagaoka, Akira; Han, Kyu-Bum; Misra, Sudhajit; Wilenski, Thomas; Sparks, Taylor D.; Scarpulla, Michael A.

    2017-06-01

    We report the growth of p-type As-doped, Cd-rich CdTe single crystals using metallic Cd as the solvent in the traveling-heater method. We investigate the growth process from Cd solution in terms of the solid-liquid interface shape and the effects of As incorporation on p-type doping. The resulting CdTe crystals have Cd-rich composition which enhances p-type doping. The As doping efficacy was measured for As concentrations by the combination of inductively coupled plasma mass spectrometry, capacitance-voltage measurements. The p-type doping concentration varied from 6 × 1015 to 8 × 1016 cm-3 with increasing As concentration, with an apparent doping limit just below 1017 cm-3.

  12. Self-focusing in chromium-doped potassium niobate single ceramic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Castillo T, J.; Gonzalez M, S.; Aguirre L, A.; Hernandez, M.B.; Aguilar M, J.A. [Instituto de Fisica y Matematicas, Universidad Tecnologica de la Mixteca, 69000, Huajuapan de Leon, Oaxaca (Mexico); Hernandez A, J. [lFUNAM, PO Box 20-364, 01000 Mexico, DF (Mexico)]. e-mail: jaimec@mixteco.utm.mx

    2006-07-01

    The self-focusing and nonlinear optical absorption in a chromium-doped potassium niobate single ceramic crystal have been investigated. The third-order electric susceptibility X{sup (3)} at continuous 532 nm radiation is estimated based on a band transport model describing photo refractive properties for this electro-optic material. An anisotropic behavior on its nonlinear optical absorption properties has also been observed due to the presence of chromium ions. (Author)

  13. Growth and characterization of air annealing Mn-doped YAG:Ce single crystal for LED

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Weidong, E-mail: xiangweidong001@126.com [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035 (China); College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Zhong, Jiasong [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035 (China); College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Zhao, Yinsheng [Pan Asia Technical Automotive Center Co. Ltd., Shanghai 201201 (China); Zhao, Binyu [College of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Liang, Xiaojuan [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035 (China); Dong, Yongjun [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800 (China); Zhang, Zhimin; Chen, Zhaoping; Liu, Bingfeng [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035 (China)

    2012-11-25

    Highlights: Black-Right-Pointing-Pointer The YAG:Ce,Mn single crystal was well synthesized by the Czochralski (CZ) method. Black-Right-Pointing-Pointer The emission intensity of the sample has been influenced after annealing. Black-Right-Pointing-Pointer Annealed in the air at 1200 Degree-Sign C was the most optimal annealing condition. Black-Right-Pointing-Pointer The single crystal could be used in the white light LED which emitted by blue light. - Abstract: The growth of Mn-doped YAG:Ce (yttrium aluminum garnet doped cerium) single crystal by the Czochralski (CZ) method and the characterization of its spectroscopy and color-electric parameters are presented. The absorption spectra indicate that the crystal absorbed highly in the 300-500 nm wavelength range. The emission spectrum of the crystal consists of a peak around 538 nm when excited by 460 nm blue light, which prove the YAG:Ce,Mn single crystal could be used in the white light emitting doides (LED). The different charges of Mn ions have different luminescence properties, and the air annealing process for the single crystal would change the concentration of Mn ions with different charges, which could influence the emission intensity of the single crystal.

  14. Single layer graphene band hybridization with silver nanoplates: Interplay between doping and plasmonic enhancement

    Science.gov (United States)

    Syed, Salmaan R.; Lim, Guh-Hwan; Flanders, Stuart J.; Taylor, Adam B.; Lim, Byungkwon; Chon, James W. M.

    2016-09-01

    In this paper, we report single layer graphene (SLG) hybridized with silver nanoplates, in which nanoplates act as either a charge doping or a field enhancement source for the SLG Raman spectrum. Surprisingly, the stiffening of both G and 2D peaks of more than 10 cm-1 was observed with no plasmonic enhancement of peaks, indicating that p-doping from nanoplates on SLG is occurring. Such observation is explained in terms of the contact separation distance between the graphene and the silver nanoplates being enough (˜4 Å) to cause a Fermi level shift in graphene to allow p-doping. When nanoplates were modified in shape with laser irradiation by either photothermal plasmon printing or laser induced ablation, the charge doping was lifted and the strong plasmonic enhancement of Raman signals was observed, indicating that the separation distance is increased. Further, when the nanoplates are oxidized, the two effects on the Raman bands of SLG are turned off, returning the Raman signals back to the original SLG state.

  15. Doping effects of Sb in FeTe1-xSbx single crystals

    Science.gov (United States)

    Wang, X. F.; Zhang, Z. T.; Chen, X. L.; Kan, X. C.; Li, L.; Sun, Y. P.; Zhang, L.; Xi, C. Y.; Pi, L.; Yang, Z. R.; Zhang, Y. H.

    2015-06-01

    We investigated the doping effects of Sb on the magnetic, transport and structural properties in FeTe1-xSbx single crystals. Resistivity, magnetic susceptibility and heat capacity experiments consistently reveal that the magnetic/structural transition temperature TN ∼ 70K in undoped Fe1.05Te is gradually suppressed by Sb doping, but no superconductivity is observed for x up to 10%. It is found that the electronic heat capacity coefficient γ increases with Sb content, implying the increase of the density of states at Fermi level. Referring to previous calculation reports, this means that the Sb substituent plays a role of hole carrier doping, which is consistent with our measurements on Hall coefficient. Structural analysis shows that Sb doping induces an expansion of the lattice along the a axis and a shrinkage along the c axis. Our work suggests that the antiferromagnetism in Fe1+yTe may be different in nature with other parent compounds of FeAs-based systems.

  16. Molecular doping of single-walled carbon nanotube transistors: optoelectronic study

    Science.gov (United States)

    Zhang, Jiangbin; Emelianov, Aleksei V.; Bakulin, Artem A.; Bobrinetskiy, Ivan I.

    2016-09-01

    Single-walled carbon nanotubes (SWCNT) are a promising material for future optoelectronic applications, including flexible electrodes and field-effect transistors. Molecular doping of carbon nanotube surface can be an effective way to control the electronic structure and charge dynamics of these material systems. Herein, two organic semiconductors with different energy level alignment in respect to SWCNT are used to dope the channel of the SWCNT-based transistor. The effects of doping on the device performance are studied with a set of optoelectronic measurements. For the studied system, we observed an opposite change in photo-resistance, depending on the type (electron donor vs electron acceptor) of the dopants. We attribute this effect to interplay between two effects: (i) the change in the carrier concentration and (ii) the formation of trapping states at the SWCNT surface. We also observed a modest 4 pA photocurrent generation in the doped systems, which indicates that the studied system could be used as a platform for multi-pulse optoelectronic experiments with photocurrent detection.

  17. Cobalt-doping effects in single crystalline and polycrystalline EuFe2-xCoxAs2 compounds

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A series of Co-doped EuFe2-xCoxAs2 compounds were prepared in both of single crystalline and polycrystalline forms.The Co-doping effects on the crystal structure,electrical resistivity and magnetic susceptibility were systematically studied.Superconductivity was found in polycrystalline Co-doped samples from zero resistivity effects,with the highest onset superconducting transition temperature at 26 K in the optimum doped EuFe1.84Co0.16As2 compound.While due to the stronger competition between the superconducting order and the Eu2+ magnetic order,the zero resistivity effect is absent in the Co-doped single crystal samples.

  18. All-fiber 194 W single-frequency single-mode Yb-doped master-oscillator power-amplifier

    Science.gov (United States)

    Mermelstein, M. D.; Brar, K.; Andrejco, M. J.; Yablon, A. D.; Fishteyn, M.; Headley, C., III; DiGiovanni, D. J.

    2008-02-01

    A four-stage all-fiber single-frequency single-mode continuous-wave (cw) master-oscillator power-amplifier (MOPA) at 1083 nm is presented. Small mode area (SMA) and large mode area (LMA) amplifier stages are mode matched with a fiber mode converter (MC) and the signal and pumps are combined with tapered fiber bundles (TFBs). The final power stage uses a LMA Yb doped SBS-suppressing fiber. A single-frequency output power of 194 W is demonstrated with optical net and slope efficiencies of 73% and 80%, respectively. Numerical simulations for the signal output power and the SBS-induced Stokes backscattered power in the 4th stage amplifier agree with the experimental results. Pulse amplifier measurements showed a 400 W peak power output that was limited by the forward output ASE. The SBS reflectivity at 400 W output was only 2.75 x 10 -4.

  19. Europium and potassium co-doped strontium metaborate single crystals grown by the Czochralski method

    Science.gov (United States)

    Głowacki, Michał; Solarz, Piotr; Ryba-Romanowski, Witold; Martín, Inocencio R.; Diduszko, Ryszard; Berkowski, Marek

    2017-01-01

    Strontium metaborate (SrB2O4) is a suitable material for use as a matrix for luminescent dopant ions. Similarity of ionic radii of strontium and divalent europium makes it an excellent host for Eu dopant. This paper reports on the Czochralski growth and spectroscopic study of SrB2O4 single crystals doped with europium and co-doped with europium and potassium. Based on recorded luminescence spectra it was found that both Eu3+ and Eu2+ ions occur in this host. Trivalent europium ions give rise to a narrow-band long-lived red luminescence that is not affected by incorporation of potassium ions. Divalent europium ions emit a UV-blue luminescence, consisting of a large spectral band centered at ca 430 nm. In the absence of potassium ions the decay of this luminescence deviates slightly from a single exponential time dependence with a mean lifetime value of 2.0 ns. In potassium-co-doped sample a strong deviation from a single exponential decay was observed for longer stages of decay, beginning at ca 2.5 ns. This phenomenon was attributed to dissimilarity of relaxation rates of a fraction of europium ions distributed in different lattice sites that are distorted by the presence of big potassium ions. By co-doping the host with alkali ions one can influence the oxidation state of europium ions thereby enhancing the emission of trivalent europium ions. It was concluded that the material under study is a promising phosphor for visible light emission applications.

  20. Spectral ellipsometry of GaSb and GaInAsSb: Experiment and modeling

    Energy Technology Data Exchange (ETDEWEB)

    Charache, G.W.; Mu{tilde n}oz, M.; Wei, K.; Pollak, F.H.; Freeouf, J.L.

    1999-06-30

    The optical constants {epsilon}(E)[={epsilon}{sub 1}(E)+i{epsilon}{sub 2}(E)] of single-crystal GaSb at 300K have been measured using spectral ellipsometry in the range of 0.3-5.3 eV. The {epsilon}(E) spectra displayed distinct structures associated with critical points (CPs) at E{sub 0} (direct gap), spin-orbit split E{sub 0}+{Delta}{sub 0} component, spin-orbit split (E{sub 1}, E{sub 1}+{Delta}{sub 1}) and (E{sub 0}{prime}, E{sub 0}{prime}+{Delta}{sub 0}{prime}) doublets, as well as E{sub 2}. The experimental data over the entire measured spectral range (after oxide removal) has been fit using the Holden model dielectric function based on the electronic energy-band structure near these CPs plus excitonic and band-to-band Coulomb enhancement effects at E{sub 0}, E{sub 0}+{Delta}{sub 0} and the E{sub 1}, E{sub 1}+{Delta}{sub 1} doublet. In addition to evaluating the energies of these various band-to-band CPs, information about the binding energy (R{sub 1}) of the two-dimensional exciton related to the E{sub 1}, E{sub 1}+{Delta}{sub 1} CPs was obtained. The value of R{sub 1} was in good agreement with effective mass/k{sup {rightharpoonup}}{center_dot}p{sup {rightharpoonup}} theory. The ability to evaluate R{sub 1} has important ramifications for recent first-principles band structure calculations which include exciton effects at E{sub 0}, E{sub 1}, and E{sub 2}. The experimental results were compared to other evaluations of the optical constants of GaSb.

  1. Single crystal EPR study of VO(II)-doped cadmium potassium phosphate hexahydrate: A substitutional incorporation

    Indian Academy of Sciences (India)

    I Sougandi; T M Rajendiran; R Venkatesan; P Sambasiva Rao

    2002-10-01

    Single crystal EPR studies of VO(II)-doped cadmium potassium phosphate hexahydrate (CPPH) have been carried out at room temperature. The angular variation spectra in the three orthogonal planes indicate that the paramagnetic impurity has entered the lattice only substitutionally in place of Cd(II). Spin Hamiltonian parameters have been obtained from single crystal data. Powder spectra show a set of eight parallel and perpendicular features indicating the presence of only one site. The admixture coefficients have been calculated from the data, which agree well with the literature values.

  2. Growth of optical-quality anthracene crystals doped with dibenzoterrylene for controlled single photon production

    Energy Technology Data Exchange (ETDEWEB)

    Major, Kyle D., E-mail: kyle.major11@imperial.ac.uk; Lien, Yu-Hung; Polisseni, Claudio; Grandi, Samuele; Kho, Kiang Wei; Clark, Alex S.; Hwang, J.; Hinds, E. A., E-mail: ed.hinds@imperial.ac.uk [Centre for Cold Matter, Department of Physics, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom)

    2015-08-15

    Dibenzoterrylene (DBT) molecules within a crystalline anthracene matrix show promise as quantum emitters for controlled, single photon production. We present the design and construction of a chamber in which we reproducibly grow doped anthracene crystals of optical quality that are several mm across and a few μm thick. We demonstrate control of the DBT concentration over the range 6–300 parts per trillion and show that these DBT molecules are stable single-photon emitters. We interpret our data with a simple model that provides some information on the vapour pressure of DBT.

  3. Single frequency 1083nm ytterbium doped fiber master oscillator power amplifier laser.

    Science.gov (United States)

    Huang, Shenghong; Qin, Guanshi; Shirakawa, Akira; Musha, Mitsuru; Ueda, Ken-Ichi

    2005-09-05

    Single frequency 1083nm ytterbium fiber master oscillator power amplifier system was demonstrated. The oscillator was a linear fiber cavity with loop mirror filter and polarization controller. The loop mirror with unpumped ytterbium fiber as a narrow bandwidth filter discriminated and selected laser longitudinal modes efficiently. Spatial hole burning effect was restrained by adjusting polarization controller appropriately in the linear cavity. The amplifier was 5 m ytterbium doped fiber pumped by 976nm pigtail coupled laser diode. The linewidth of the single frequency laser was about 2 KHz. Output power up to 177 mW was produced under the launched pump power of 332 mW.

  4. Antibacterial activity of single crystalline silver-doped anatase TiO{sub 2} nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiangyu, E-mail: zhangxiangyu@tyut.edu.cn; Li, Meng; He, Xiaojing; Hang, Ruiqiang; Huang, Xiaobo; Wang, Yueyue; Yao, Xiaohong; Tang, Bin, E-mail: tangbin@tyut.edu.cn

    2016-05-30

    Graphical abstract: The silver-doped TiO{sub 2} nanowire arrays on titanium foil substrate were synthesized via a two-step process. It includes: deposition of AgTi films on titanium foil by magnetron sputtering; preparation of AgNW arrays on AgTi films via alkali (NaOH) hydrothermal treatment and ion-exchange with HCl, followed by calcinations. - Highlights: • Ag-doped TiO{sub 2} nanowire arrays have been prepared by a duplex-treatment. • The duplex-treatment consisted of magnetron sputtering and hydrothermal growth. • Ag-doped nanowire arrays show excellent antibacterial activity against E. coli. - Abstract: Well-ordered, one-dimensional silver-doped anatase TiO{sub 2} nanowire (AgNW) arrays have been prepared through a hydrothermal growth process on the sputtering-deposited AgTi layers. Electron microscope analyses reveal that the as-synthesized AgNW arrays exhibit a single crystalline phase with highly uniform morphologies, diameters ranging from 85 to 95 nm, and lengths of about 11 μm. Silver is found to be doped into TiO{sub 2} nanowire evenly and mainly exists in the zerovalent state. The AgNW arrays show excellent efficient antibacterial activity against Escherichia coli (E. coli), and all of the bacteria can be killed within 1 h. Additionally, the AgNW arrays can still kill E. coli after immersion for 60 days, suggesting the long-term antibacterial property. The technique reported here is environmental friendly for formation of silver-containing nanostructure without using any toxic organic solvents.

  5. GaSb based ternary and quaternary diffused junction devices for TPV applications

    Energy Technology Data Exchange (ETDEWEB)

    Sundaram, V.S.; Saban, S.B.; Morgan, M.D.; Horne, W.E.; Evans, B.D.; Ketterl, J.R. [EDTEK Inc. 7082 S. 220th Street Kent, Washington 98032 (United States); Morosini, M.B.; Patel, N.B. [Instituto de Fisica, UNICAMP, Campinas, Brasil (Brazil); Field, H. [NREL, Golden, Colorado (United States)

    1997-03-01

    In this work we report the characteristics of ternary, GaInSb (Eg=0.70eV) and quarternary, GaInAsSb (Eg=0.5eV) diffused junction photovoltaic devices. The unique feature of the quarternary device is the extended long-wavelength response to 2.1 microns enabling the efficient use of the blackbody-like thermal sources operating at 1373 K in thermophotovoltaic energy conversion systems. The ternary device was fabricated by diffusing zinc into a n-type (100) oriented GaInSb substrate. For the quarternary, a four micron thick Te doped GaInAsSb layer grown by LPE on a n-type GaSb(100) wafer was used as the starting substrate for zinc diffusion. The ternary device exhibits an open circuit voltage of 0.38 V, Fill Factor of 0.63 and a short circuit current of 0.8A/cm{sup 2}, while the corresponding values for the quarternary device are 0.25 V, 0.58 and 0.8A/cm{sup 2}, respectively. The peak internal quantum efficiency for the ternary is over 90{percent} and that of the quarternary is above 75{percent}. Process optimization should improve the performance charcateristics of the quarternary. {copyright} {ital 1997 American Institute of Physics.}

  6. Synthesis and characterization of p-type boron-doped IIb diamond large single crystals

    Institute of Scientific and Technical Information of China (English)

    Li Shang-Sheng; Ma Hong-An; Li Xiao-Lei; Su Tai-Chao; Huang Guo-Feng; Li Yong; Jia Xiao-Peng

    2011-01-01

    High-quality p-type boron-doped II0b diamond large single crystals are successfully synthesized by the temperature gradient method in a china-type cubic anvil high-pressure apparatus at about 5.5 GPa and 1600 K. The morphologies and surface textures of the synthetic diamond crystals with different boron additive quantities are characterized by using an optical microscope and a scanning electron microscope respectively. The impurities of nitrogen and boron in diamonds are detected by micro Fourier transform infrared technique. The electrical properties including resistivities, Hall coefficients, Hall mobilities and carrier densities of the synthesized samples are measured by a four-point probe and the Hall effect method. The results show that large p-type boron-doped diamond single crystals with few nitrogen impurities have been synthesized. With the increase of quantity of additive boron, some high-index crystal faces such as {113} gradually disappear, and some stripes and triangle pits occur on the crystal surface. This work is helpful for the further research and application of boron-doped semiconductor diamond.

  7. Thiourea-doped ammonium dihydrogen phosphate: A single crystal neutron diffraction investigation

    Indian Academy of Sciences (India)

    A Jayarama; M R Suresh Kumar; S M Dharmaprakash; R Chitra; R R Choudhury

    2008-11-01

    Thiourea-doped ammonium dihydrogen phosphate (TADP) exhibits nonlinear optical property and the second harmonic generation efficiency of these crystals is three times that of pure ammonium dihydrogen phosphate (ADP) crystal. In this context, the study of structural distortion in the thiourea-doped ADP crystal is significant, hence single neutron diffraction investigations were undertaken. The final -factors are: [2 > 2(2)] = 0.11, Goodness of fit () = 1.15. Though the dopant could not be located from the difference Fourier map, the cell parameters ( = = 7.531(3) Å, = 7.544(5) Å) were found to be significantly greater than that of pure ADP at RT ( = = 7.502(1)$ ̊Å, = 7.546(1) Å). This indicates that the dopant concentration in the crystals is small but enough to bring changes in the overall average structure.

  8. Estimation of cut-off wavelength of rare earth doped single-mode fibers

    Science.gov (United States)

    Kaur, Jagneet; Thyagarajan, K.; Pal, B. P.

    1999-11-01

    A new empirical relation is proposed describing spectral variation of mode-field radius (MFR) as inferred from measurements in the far-field of the fiber. It is shown that using this relation, it is possible to estimate the cut-off wavelength ( λc) of the fiber. The proposed technique is successfully tested through measurements made on two standard step index single-mode fibers, as well as on an erbium doped fiber (EDF) having λc falling within its strong absorption band around 980 nm. This empirical formula is more accurate than the widely used Marcuse's formula to describe spectral dependence of MFR determined through measurements made in the fiber's far-field. The proposed technique is especially suited for estimation of λc of doped fibers in which λc falls within an absorption band.

  9. The synthesis and chemical durability of Nd-doped single-phase zirconolite solid solutions

    Science.gov (United States)

    Cai, Xin; Teng, Yuancheng; Wu, Lang; Zhang, Kuibao; Huang, Yi

    2016-10-01

    Nd-doped single-phase zirconolite solid solutions was synthesized by solid-state reaction and following two steps of acid treatment. The phase composition, microstructure, and chemical durability of the zirconolite solid solutions were investigated. About 15 at% Nd was successfully stabilized into the zirconolite. The element mapping images of Ca, Zr, Nd and Ti show that all the elements are almost distributed homogeneously in the zirconolite waste forms. Product Consistency Test (PCT) was conducted under different pH values (pH = 5, 7 and 9) to evaluate the chemical durability of the Nd-doped zirconolite waste forms. The normalized element release rate of Ca (LRCa) in pH = 5 medium is higher than that of pH = 7 and 9, while the LRNd value remains almost unchanged under different pH values. The LRNd value is as low as 10-5 g m-2 d-1 after 42 days.

  10. C-band wavelength-swept single-longitudinalmode erbium-doped fiber ring laser.

    Science.gov (United States)

    Zhang, Kang; Kang, Jin U

    2008-09-01

    A wavelength-swept single-longitudinal-mode erbium-doped fiber ring laser capable of operating at sweeping frequency in the order of a few kHz is designed and demonstrated by using a fiber Fabry-Perot tunable filter and a Sagnac loop incorporated with a 3.5-meter unpumped erbium-doped fiber. The laser operates in continuous-wave (CW) mode and can sweep approximately 45 nm over the entire C-band (1520nm-1570nm) window with linewidth less than 0.7 kHz. The optimum wavelength sweeping frequency in order to achieve the best output power stability was found to be approximately20Hz with sweeping-induced power fluctuation of only 0.1%.

  11. Raman Spectroscopy and Magnetic Properties of Mn-Doped ZnO Bulk Single Crystal

    Institute of Scientific and Technical Information of China (English)

    HE Qing-Bo; XU Jia-Yue; LI Xin-Hua; A.Kamzin; L.Kamzina

    2007-01-01

    Mn doped ZnO bulk single crystals are grown by the modified Bridgman method.The as-grown crystals are red in colour.The additional Raman mode observed at 524 cm-1 is attributed to the Mn ions incorporating into ZnO crystal.The crystal exhibited paramagnetic under lower applied fleld below 2280 Oe.Then diamagnetism is observed in the crystal when the magnetic field rises up and becomes dorainant under applied field above 5270 Oe.The magnetic susceptibility dependence on the temperature follows a Curie law indicating a typical paramagnetic characteristic under an applied field of 2kOe.No ferromagnetic ordering is observed in the as-grown Mn-doped ZnO crystal.

  12. Growth and characterization of pure and doped KHP NLO single crystals

    Science.gov (United States)

    Thilagavathy, S. R.; Rajesh, P.; Ramasamy, P.; Ambujam, K.

    2014-06-01

    Single crystals of Potassium Hydrogen Phthalate doped with amino acid L-lysine were grown successfully by slow evaporation method. The concentration of dopant in the mother solution was 0.5 mol%, 1 mol% and 2 mol%. There is a drastic change in the morphology due to variation in doping rates which is also reflected in the X-ray diffraction data. The Fourier Transform infrared spectroscopy study confirms the incorporation of L-lysine into Potassium Hydrogen Phthalate crystal. The thermal study indicates the dissociating nature of the crystal. The nonlinear optical property of the grown crystal has been confirmed by Kurtz-powder second harmonic generation test. The dopant of 0.5 mol% and 1 mol% shows higher second harmonic generation result than pure Potassium Hydrogen Phthalate. Results are discussed.

  13. Antibacterial activity of single crystalline silver-doped anatase TiO2 nanowire arrays

    Science.gov (United States)

    Zhang, Xiangyu; Li, Meng; He, Xiaojing; Hang, Ruiqiang; Huang, Xiaobo; Wang, Yueyue; Yao, Xiaohong; Tang, Bin

    2016-05-01

    Well-ordered, one-dimensional silver-doped anatase TiO2 nanowire (AgNW) arrays have been prepared through a hydrothermal growth process on the sputtering-deposited AgTi layers. Electron microscope analyses reveal that the as-synthesized AgNW arrays exhibit a single crystalline phase with highly uniform morphologies, diameters ranging from 85 to 95 nm, and lengths of about 11 μm. Silver is found to be doped into TiO2 nanowire evenly and mainly exists in the zerovalent state. The AgNW arrays show excellent efficient antibacterial activity against Escherichia coli (E. coli), and all of the bacteria can be killed within 1 h. Additionally, the AgNW arrays can still kill E. coli after immersion for 60 days, suggesting the long-term antibacterial property. The technique reported here is environmental friendly for formation of silver-containing nanostructure without using any toxic organic solvents.

  14. Retracted-Enhanced X-Ray Absorption Property of Gold-Doped Single Wall Carbon Nanotube

    Directory of Open Access Journals (Sweden)

    Alimin Alimin

    2015-11-01

    Full Text Available Enhanced X-ray absorption property of single wall carbon nanotube (SWCNT through gold (Au doping (Au@SWCNT has been studied. Mass attenuation coefficient of SWCNT increased 5.2-fold after Au doping treatment. The use of ethanol in the liquid phase adsorption could produce Au nanoparticles as confirmed by the X-ray Diffraction (XRD patterns. The possibility of gold nanoparticles encapsulated in the internal tube space of SWCNT was observed by transmission electron microscope technique. A significant decrease of nitrogen uptakes and upshifts of Radial Breathing Mode (RBM of Au@SWCNT specimen suggest that the nanoparticles might be encapsulated in the internal tube spaces of the nanotube. In addition, a decrease intensity of XRD pattern of Au@SWCNT at around 2θ ≈ 2.6° supports the suggestion that Au nanoparticles are really encapsulated into SWCNT.

  15. Thermal, dielectric and photoconductivity studies on pure, Mg{sup 2+} and Zn{sup 2+} doped BTCC single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Selvakumar, S. [Department of Physics, Loyola College, Chennai 600034 (India); Rajasekar, S.A. [Department of Physics, Magna College of Engineering, Chennai 600055 (India); Thamizharasan, K. [Department of Physics, Sir Theagaraya College, Chennai 600021 (India); Sivanesan, S. [Department of Chemical Engineering, Anna University, Chennai 600025 (India); Ramanand, A. [Department of Physics, Loyola College, Chennai 600034 (India); Sagayaraj, P. [Department of Physics, Loyola College, Chennai 600034 (India)]. E-mail: psagayaraj@hotmail.com

    2005-10-15

    Single crystals of pure and doped bis(thiourea) cadmium chloride (BTCC) belonging to semiorganic nonlinear optical materials are grown by slow evaporation technique. The lattice parameters of the grown crystals are determined by single-crystal XRD. Single crystal XRD studies reveal that the incorporation of metallic dopants has not changed the structure of the parent crystal. The TGA traces of doped BTCC crystals indicate a marginal increase in the thermal stability of the samples. The response of dielectric constant in the frequency region of 500 Hz to 500 kHz has been investigated and the influence of metal substitution on the dielectric behaviour has been reported. Photoconductivity studies of pure and doped BTCC crystals revealed the positive photoconducting nature. Optical absorption studies indicate the low percentage of absorption of doped crystals in the visible region, thereby confirming the enhancement of NLO property.

  16. Modified low temperature Czochralski growth of xylenol orange doped benzopheone single crystal for fabricating dual band patch antenna

    Science.gov (United States)

    Yadav, Harsh; Sinha, Nidhi; Kumar, Binay

    2016-09-01

    Organic non-linear optical pure and xylenol orange (XO) doped benzophenone (BP) single crystals have been grown by a modified Czochralski technique. A low cost CZ system was designed and fabricated that is suitable for the growth of single crystals of low melting point organic materials. Structural analysis was performed by powder and single crystal XRD. LC-HRMS spectra reveal that the dye molecules are present in the doped crystal. The linear optical characterization was carried out by UV-vis spectroscopy. In the case of the XO doped BP crystal, two absorption peaks were found at 504 nm and 620 nm. The enhancement of photoluminescence intensity of blue emission was observed in the dye doped crystal. Dielectric studies reveal that the XO doped BP has shown improved a dielectric constant with low dielectric loss. A dual band compact circular patch antenna was simulated and fabricated using the XO doped crystal. Resonant frequencies of the dual bands at 4.80 GHz and 9.22 GHz were achieved by introducing a defect ground state in the circular patch antenna. The piezoelectric coefficient (d33) value was increased from 1 to 4 pC/N by XO dye doping, which opens up the possibilities of simultaneous transducer applications.

  17. Structural, optical, thermal, mechanical and dielectric studies of Sulfamic acid single crystals: An influence of dysprosium (Dy3+) doping

    Science.gov (United States)

    Singh, Budhendra; Shkir, Mohd.; AlFaify, S.; Kaushal, Ajay; Nasani, Narendar; Bdikin, Igor; Shoukry, H.; Yahia, I. S.; Algarni, H.

    2016-09-01

    Sulfamic acid is a potential material that exhibits excellent optical properties. A good quality, pure and dysprosium (Dy3+) doped (2.5 and 5 mol %) Sulfamic acid (SA) single crystals were grown successfully by slow cooling method. Structural study revealed a slight change in its lattice parameters and volume, suggesting the successful incorporation of Dy3+ in crystal system. The existence of dysprosium in the system was also confirmed. Presence of various vibrational modes was confirmed. Optical transparency was found to have a significant effect with variation in the doping concentration. Furthermore, a marked enhancement in its mechanical parameters with doping was also identified by nanoindentation technique. Etching study was also performed on the grown crystals to study the etch-pit formation and growth mechanism. Effect of doping on the thermal stability was analysed. All the results were compared and discussed in detail to get insight of the effect of doping concentration on Sulfamic acid crystal.

  18. Optical Properties of Mg, Fe, Co-Doped Near-Stoichiometric LiTaO3 Single Crystals

    Directory of Open Access Journals (Sweden)

    Chung Wen Lan

    2012-01-01

    Full Text Available Mg, Fe co-doped near-stoichiometric lithium tantalite (SLT single crystals were grown by employing the zone-leveling Czochralski (ZLCz technique. The optical properties, holographic parameters, as well as the composition of the grown crystals were measured. It was found that the Li/Ta ratio decreased with the doping of Mg and Fe ions. A red shift was observed in absorption spectrum for the Mg, Fe co-doped crystals compared to the undoped and Mg-doped ones. The effect of the iron ions (Fe2+ and Fe3+ was further discussed based on the specified absorption bands. Moreover, the occupation mechanism for the defects was discussed by using the IR absorption spectrum, which was attributed to the FeTa3− defects in the highly Fe-doped crystal. In addition, the holographic parameters were also found to be improved with a higher Fe/Ta ratio in the crystals.

  19. Lanthanide-doped CaS and SrS luminescent nanocrystals : A single-source precursor approach for doping

    NARCIS (Netherlands)

    Zhao, Yiming; Rabouw, Freddy T.; Puffelen, Tim Van; van Walree, Kees; Gamelin, Daniel R.; De Mello Donegá, Celso; Meijerink, A

    2014-01-01

    The incorporation of dopants with optical or magnetic functionalities into colloidal nanocrystals (NCs) has been a longstanding challenge for nanomaterial research. A deeper understanding of the doping kinetics will aid a better control of the doping process. In particular, alkaline-earth sulfides a

  20. Comparison of luminescence property of gamma-ray irradiated Tb(3+) -doped and Ce(3)(+) co-doped potassium halide single crystals.

    Science.gov (United States)

    Bangaru, S; Ravi, D; Saradha, K

    2017-05-01

    Single crystals of KCl and KBr singly and doubly doped with Tb(3)(+) and Ce(3)(+) , respectively, were successfully grown using the Bridgeman technique. This work reports the comparative luminescence behavior and optical absorption characterization of non-irradiated and γ-ray-irradiated single crystals of these materials. The existing defect and the defect created by γ-ray irradiation were monitored by optical absorption spectra. The excitation and emission spectra of these materials were measured at room temperature with a spectrofluorometer and the pertaining results were compared. The F-band comparison was made when bleached with F-light for 2 mins. The trap-level changes in KCl and KBr when it is singly and doubly doped enabled us to draw conclusions on the nature of the defect and on the recombination processes involved. Copyright © 2016 John Wiley & Sons, Ltd.

  1. Hopping conductivity in Mn-doped β-FeSi2 single crystals

    Science.gov (United States)

    Arushanov, E.; Lisunov, K. G.; Vinzelberg, H.; Behr, G.; Schumann, J.; Schmidt, O. G.

    2008-09-01

    The article gives a report on resistivity measurements on Mn-doped p-type FeSi2 single crystals and analyzes the data within the framework of different hopping conductivity models. Both the Mott [N. Mott and E. A. Davies, Electron Processes in Non-Crystalline Materials (Clarendon, Oxford, 1979)] and the Shklovskii-Efros [B. I. Shklovskii and A. L. Efros, Electronic Properties o0066 Doped Semiconductors (Springer, Berlin, 1984)] regimes of the variable-range hopping (VRH) conductivity are observed. It is shown that the temperature dependence of the resistivity of Mn-doped β-FeSi2 crystals, which follows a VRH conduction mechanism, can be expressed by a scaling expression of the form ln(ρ /ρ0)=Af(T /Tx). The characteristic and transition temperatures, as well as the complete set of parameters describing the properties of the localized holes (the localization radius, the dielectric permittivity, the width of the Coulomb gap Δ, and the values of the density of states at the Fermi level) are determined. The data above indicate existence of a rigid gap δ in the spectrum of the DOS in addition to Δ and point out to the polaronic nature of the charge carriers in the investigated compound.

  2. Single-step processing of copper-doped titania nanomaterials in a flame aerosol reactor

    Directory of Open Access Journals (Sweden)

    Sahu Manoranjan

    2011-01-01

    Full Text Available Abstract Synthesis and characterization of long wavelength visible-light absorption Cu-doped TiO2 nanomaterials with well-controlled properties such as size, composition, morphology, and crystal phase have been demonstrated in a single-step flame aerosol reactor. This has been feasible by a detailed understanding of the formation and growth of nanoparticles in the high-temperature flame region. The important process parameters controlled were: molar feed ratios of precursors, temperature, and residence time in the high-temperature flame region. The ability to vary the crystal phase of the doped nanomaterials while keeping the primary particle size constant has been demonstrated. Results indicate that increasing the copper dopant concentration promotes an anatase to rutile phase transformation, decreased crystalline nature and primary particle size, and better suspension stability. Annealing the Cu-doped TiO2 nanoparticles increased the crystalline nature and changed the morphology from spherical to hexagonal structure. Measurements indicate a band gap narrowing by 0.8 eV (2.51 eV was achieved at 15-wt.% copper dopant concentration compared to pristine TiO2 (3.31 eV synthesized under the same flame conditions. The change in the crystal phase, size, and band gap is attributed to replacement of titanium atoms by copper atoms in the TiO2 crystal.

  3. Single-step processing of copper-doped titania nanomaterials in a flame aerosol reactor.

    Science.gov (United States)

    Sahu, Manoranjan; Biswas, Pratim

    2011-07-06

    Synthesis and characterization of long wavelength visible-light absorption Cu-doped TiO2 nanomaterials with well-controlled properties such as size, composition, morphology, and crystal phase have been demonstrated in a single-step flame aerosol reactor. This has been feasible by a detailed understanding of the formation and growth of nanoparticles in the high-temperature flame region. The important process parameters controlled were: molar feed ratios of precursors, temperature, and residence time in the high-temperature flame region. The ability to vary the crystal phase of the doped nanomaterials while keeping the primary particle size constant has been demonstrated. Results indicate that increasing the copper dopant concentration promotes an anatase to rutile phase transformation, decreased crystalline nature and primary particle size, and better suspension stability. Annealing the Cu-doped TiO2 nanoparticles increased the crystalline nature and changed the morphology from spherical to hexagonal structure. Measurements indicate a band gap narrowing by 0.8 eV (2.51 eV) was achieved at 15-wt.% copper dopant concentration compared to pristine TiO2 (3.31 eV) synthesized under the same flame conditions. The change in the crystal phase, size, and band gap is attributed to replacement of titanium atoms by copper atoms in the TiO2 crystal.

  4. Single-frequency Yb-doped fiber laser with distributed feedback based on a random FBG

    Science.gov (United States)

    Abdullina, S. R.; Vlasov, A. A.; Lobach, I. A.; Belai, O. V.; Shapiro, D. A.; Babin, S. A.

    2016-07-01

    Single-frequency operation of a 1.03 μm fiber laser with random distributed feedback (RDFB) is demonstrated. The laser cavity is based on a 4 cm long fiber Bragg grating (FBG) consisting of 10 homogeneous subgratings with random phase and amplitude of refractive index modulation inscribed in a polarization maintaining (PM) Yb-doped fiber. Such RDFB laser generates single longitudinal mode with output power up to 25 mW, which is 3.5 times higher than that for a DFB laser based on regular π-shifted FBG of the same length in the same fiber. The single-frequency linewidth is measured to be  <100 kHz in both cases. The observed difference of the DFB and RDFB lasers is confirmed by numerical simulation showing different longitudinal distribution of intra-cavity radiation in these cases, analogous to those in the experiment.

  5. Growth and characterization of Sm3+ doped cerium oxalate single crystals

    Directory of Open Access Journals (Sweden)

    Minu Mary C

    2016-07-01

    Full Text Available Single crystals of Sm3+ doped cerium oxalate decahydrate were synthesized using single diffusion gel technique and the conditions influencing the size, morphology, nucleation density and quality of the crystals were optimized. Highly transparent single crystals of average size 3 mm × 2 mm × 1 mm with well-defined hexagonal morphology were grown during a time period of two weeks. X-ray powder diffraction analysis revealed that the grown crystals crystallize in the monoclinic system with space group P21/c as identical with the pure cerium oxalate. The various functional groups of the oxalate ligand and the water of crystallization were identified by Fourier transform infrared spectroscopy. The photoluminescence spectrum of the Sm3+ doped cerium oxalate indicated that the Sm3+ ions are optically active in the cerium oxalate matrix. The crystal has a strong and efficient orange red emission with a wavelength peak at 595 nm and hence can be effectively used for optical amplification. Microhardness measurements of the crystal revealed that they belong to the soft material category.

  6. Doping dependence of the vortex dynamics in single-crystal superconducting NaFe{}_{1-x}Co x As

    Science.gov (United States)

    Ahmad, D.; Choi, W. J.; Seo, Y. I.; Jung, S.-G.; Kim, Y. C.; Salem-Sugui, S., Jr.; Park, T.; Kwon, Y. S.

    2017-10-01

    We investigate the doping dependence of flux pinning in superconducting NaFe{}1-xCo x As (x = 0.01, 0.03, 0.05 and 0.07) single crystals grown by the Bridgman method. The electronic specific heat displays a pronounced anomaly in a sample series at superconducting transition temperature, which hardly shows any residual part at low temperature. We found that Co doping plays an important role in signifying the secondary peak in the magnetic hysteresis of optimally doped (x = 0.03) and heavily doped (x = 0.05, 0.07) crystals. Furthermore, the dependence of the relaxation rate S = ∣d ln M/d ln t∣ on magnetic field and temperature exhibits a decreasing trend within a certain range corresponding to the secondary peak effect in the optimally and heavily doped samples. The magnetic relaxation rate combined with the Maley analysis of the current-dependent creep energy shows a single-vortex pinning in the lightly doped sample dominant at low applied fields, and plastic pinning at high applied fields, without showing a secondary peak. However, in the optimally and heavily doped samples, the magnetic relaxation rate and U(J) isothermal analysis show that the collective pinning that dominates below H peak crosses over to plastic pinning for fields above H peak.

  7. Growth and superconducting properties of Cd-doped La(O,F)BiS2 single crystals

    Science.gov (United States)

    Nagao, Masanori; Tanaka, Masashi; Watauchi, Satoshi; Takano, Yoshihiko; Tanaka, Isao

    2017-08-01

    Cd-doped La(O,F)BiS2 single crystals were grown using a CsCl/KCl flux. The grown crystals have a plate-like shape with 1-2 mm square size in a well-developed ab-plane. The Cd doping in the crystals was successfully characterized by single crystal X-ray diffraction and electron probe microanalysis techniques. The superconductivity of La(O,F)BiS2 was gradually suppressed with Cd doping. The superconducting transition temperature with zero resistivity of La(O0.54F0.46)(Bi0.92Cd0.08)S2 was 2.3 K. The Cd doping does not change the superconducting anisotropy so much, albeit the considerable suppression of Tc.

  8. Hole subband structure in single and double p-type {delta}-doped diamond quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Vargas, I. [Facultad de Ciencias, Univ. Autonoma del Estado de Morelos, Av. Universidad 1001, C.P. 62209, Cuernavaca (Mexico); Duque, C.A. [Inst. de Fisica, Universidad de Antioquia, AA 1226, Medellin (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Univ. Autonoma del Estado de Morelos, Av. Universidad 1001, C.P. 62209, Cuernavaca (Mexico); Inst. de Ciencia de Materiales de Madrid, CSIC, Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain); Velasco, V.R. [Inst. de Ciencia de Materiales de Madrid, CSIC, Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain)

    2007-07-01

    Heavy, light, and split-off hole states in single and double p-{delta}-doped diamond quantum wells are studied with the use of a 6 x 6 k.p model. The effective mass Hamiltonian is solved using a local density Thomas-Fermi-Dirac approximation for the description of the band bending profile. The features of the valence band spectrum are briefly discussed in both cases. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Raman scattering in heavily boron-doped single-crystal diamond

    Directory of Open Access Journals (Sweden)

    G. Faggio

    2011-09-01

    Full Text Available A series of boron-doped homoepitaxial diamond films grown by Microwave Plasma Enhanced Chemical Vapor Deposition at the University of Rome "Tor Vergata" have been investigated with Raman spectroscopy. As the boron content increases, we observed systematic modifications in the Raman spectra of single-crystal diamonds. A significant change in the lineshape of the first-order Raman peak as well as a wide and structured signal at lower wavenumbers appeared simultaneously in samples grown at higher boron content.

  10. Mechanical and Magnetostrictive Properties of Fe-Doped Ni52Mn24Ga24 Single Crystals

    Institute of Scientific and Technical Information of China (English)

    冯雪; 方岱宁; 黄克智

    2002-01-01

    To improve the magnetic and mechanical properties of a Heusler alloy of Ni52Mn24Ga24, iron was doped withsome contents. Single crystals ot the pseudoquaternary Heusler alloy of Ni52Mn9Fe15 Ga24 have been synthesizedfor mechanicai and magnetostrictive measurements. The magnetostriction loops and stress-strain curves weremeasured under different coupled magnetic-mechanicai loads. The experimental results show that the brittlenessof the sample is clearly improved and Young's modulus of 13. 7 GPa is obtained in the [001] direction due to thepart substitution of Fe for Mn. Furthermore, the toughness and Vickers hardness of the sample are also given byuse of the indentation technique.

  11. Ultralow Self-Doping in 2D Hybrid Perovskite Single Crystals

    KAUST Repository

    Peng, Wei

    2017-06-28

    Unintentional self-doping in semiconductors through shallow defects is detrimental to optoelectronic device performance. It adversely affects junction properties and it introduces electronic noise. This is especially acute for solution-processed semiconductors, including hybrid perovskites, which are usually high in defects due to rapid crystallization. Here, we uncover extremely low self-doping concentrations in single crystals of (C6H5C2H4NH3)2PbI4・(CH3NH3PbI3)n-1 (n=1, 2, and 3)—over three orders of magnitude lower than those of typical three-dimensional hybrid perovskites—by analyzing their conductivity behavior. We propose that crystallization of hybrid perovskites containing large organic cations suppresses defect formation and thus favors a low self-doping level. To exemplify the benefits of this effect, we demonstrate extraordinarily high light-detectivity (1013 Jones) in (C6H5C2H4NH3)2PbI4・(CH3NH3PbI3)n-1 photoconductors due to the reduced electronic noise, which makes them particularly attractive for the detection of weak light signals. Furthermore, the low self-doping concentration reduces the equilibrium charge carrier concentration in (C6H5C2H4NH3)2PbI4・(CH3NH3PbI3)n-1, advantageous in the design of p-i-n heterojunction solar cells by optimizing band alignment and promoting carrier depletion in the intrinsic perovskite layer, thereby enhancing charge extraction.

  12. Fabrication of ZnO Bi-crystals with twist boundaries using Co doped ZnO single crystals

    CERN Document Server

    Ohashi, N; Ohgaki, T; Tsurumi, T; Fukunaga, O; Haneda, H; Tanaka, J

    1999-01-01

    Zn O single crystals doped with Co were grown by using a flux method and their electrical properties were investigated by Hall effect. Then, these crystals were polished with diamond paste and bonded to form bi-crystal by hot pressing under a pressure of 10 MPa at 1000 .deg. C. The bi-crystals showed nonlinear I-V curves, and the curvature of I-V relation agreed with that for Co-doped polycrystalline ZnO.

  13. Simulation and Measurement of Solar Harvesting Enhancement of Silver Plasmonic Nanoparticles on GaSb Nanodots

    Directory of Open Access Journals (Sweden)

    Lorenzo Rosa

    2014-01-01

    Full Text Available The performance of a plasmonic antireflection layer which can be utilized for deep-space radiationresistant GaSb solar cells is investigated numerically and experimentally. The layer consists of nanodots made by plasma etching of a GaSb substrate and subsequent physical vapor deposition of Ag nanoparticles on the nanodot tips, in a partially ordered configuration determined by the plasma energy level. This technique is readily applicable to patterning of silicon. We measure the substrate reflectivity and model the reflection and absorption of the substrates using the 3D finite difference time domain (FDTD method, which are realistically imported as 3D layers from the scanning electron microscopy (SEM images. The variation of the height of the Ag nanoparticles on top of the GaSb pillars shows that the plasmonic effect remarkably enhances the absorption. The presence of GaSb pillars enhances absorption and tunes the maximum absorption wavelength peak.

  14. Polycrystalline GaSb thin films grown by co-evaporation

    Institute of Scientific and Technical Information of China (English)

    Qiao Zaixiang; Sun Yun; He Weiyu; He Qing; Li Changjian

    2009-01-01

    We report optical and electrical properties of polycrystalline GaSb thin films which were successfully grown by co-evaporation on soda-lime glass substrates. The thin films have preferential orientation of the (111)direction. SEM results indicate that the average grain size of GaSb thin film is 500 nm with the substrate temperature of 560 ℃. The average reflectance of GaSb thin film is about 30% and the absorption coefficient is of the order of 104 cm-1. The optical bandgap of GaSb thin film is 0.726 eV. The hole concentration shows a clear increasing trend as the Ga-evaporation-temperature/Sb-evaporation-temperature (TGa/TSb) ratio increases. When the Ga crucible temperature is 810 ℃ and the antinomy crucible temperature is 415 ℃, the hole concentration of polycrystalline GaSb is 2 x 1017 cm-3 and the hole mobility is 130 cm2/(V-s). These results suggest that polycrystalline GaSb thin film is a good candidate for the use as a cheap material in TPV cells.

  15. Interaction of hydrogen molecules on Ni-doped single-walled carbon nanotube

    Institute of Scientific and Technical Information of China (English)

    Ni Mei-Yan; Wang Xian-Long; Zeng Zhi

    2009-01-01

    Adsorption of hydrogen molecules on an Ni-doped (8,0) single-walled carbon nanotube (SWNT) is investigated by using first-principles density functional calculations. The result shows that a single Ni atom adsorbed on the bridge site of the tube could cannot dissociate the H2, however it can chemisorb three H2 at most, with the average binding energy per H2 suitable for the hydrogen storage at the room temperature. More H2 would physisorb around an Ni atom weakly. As for the SWNT with an Ni dimer adsorbed, we find that when the H2approaches the Ni-Ni bond, it dissociates without overcoming any barrier and makes bonds with Ni atom.

  16. Single- and dual-wavelength switchable linear polarized Yb(3+)-doped double-clad fiber laser.

    Science.gov (United States)

    Liu, Guanxiu; Feng, Dejun

    2015-05-10

    A single- and dual-wavelength switchable linear polarized Yb-doped double-clad fiber laser is proposed, in which the resonance cavity was composed of a fiber Bragg grating fabricated in a polarization-maintaining fiber and a dichromatic mirror with high reflectivity. The polarization hole burning is enhanced through selective polarization feedback by the polarization-maintaining fiber Bragg grating. The switchover of single and dual wavelengths is realized by tuning the rotation angle of a cubic polarization beam splitter that is inserted between the dichromatic mirror and the collimator in the cavity. The laser features wavelengths of 1070.08 and 1070.39 nm, output power of 1.0 W, signal to noise ratio of 45 dB, and slope efficiency of 34%, as well as a very narrow linewidth of 0.022 nm. The polarization characteristics are analyzed by measuring the laser power transmitted through a Glan-Thomson polarizer during rotation.

  17. Determination of Ge content in high concentration Ge-doped Czochralski Si single crystals by FTIR

    Institute of Scientific and Technical Information of China (English)

    JIANG Zhongwei; ZHANG Weilian; NIU Xinhuan

    2005-01-01

    SiGe single crystals with different Ge concentrations were measured by Fourier transform infrared (FTIR) spectroscopy at room temperature (RT) and 10 K. A new peak appears at the wave number of 710 cm-1 and the spectroscopy becomes clearer with an increase in Ge content. The absorption strength and wave sharp of the 710 cm-1 peak are independent of temperature. The relation of the absorption coefficient amax, the band width of half maximum (BWHM) W1/2 of the 710 cm-1 peak, and the Ge concentration is determined with the Ge content obtained by SEM-EDX. The conversion factor is k = 1.211 at 10 K. Therefore, the Ge content in high concentration Ge doped CZ-Si single crystals can be determined by FTIR.

  18. Enhancement of single-walled nanotubes luminescence intensity upon dithiothreitol doping

    Science.gov (United States)

    Kurnosov, N. V.; Linnik, A. S.; Leontiev, V. S.; Karachevtsev, V. A.

    2014-09-01

    In the present work the influence of reducing agent dithiothreitol doping on photoluminescence spectra of nanotubes with adsorbed biopolymers (single-stranded DNA and polyC) in aqueous suspensions and films was studied. It is revealed that greater intensity enhancement at 10-3 mol/L dithiothreitol concentration is observed for (7,5) and (6,5) nanotubes in suspension with single-stranded DNA (by more than 150% of initial intensity) comparing to polyC suspension (less than 60%) while for (6,4) and (9,1) nanotubes enhancement is less than 50% for both suspensions. Photoluminescence intensity increasing for nanotube film with DNA is less than 50% without noticeable dependence on nanotube chirality. It is assumed, that different influence of biopolymers on nanotube luminescence intensity enhancement is due to their different coverage of nanotube surface.

  19. Effect of rhenium doping on various physical properties of single crystals of MoSe2

    Institute of Scientific and Technical Information of China (English)

    MihirM. Vora; Aditya M. Vora

    2012-01-01

    Effect of rhenium doping is examined in single crystals of MoSe2 viz.MoRe0.005Se1.995,MoRe0.001Se1.999 and Mo0.995Re0.005Se2,which is grown by using the direct vapor transport (DVT) technique.The grown crystals are structurally characterized by X-ray diffraction,by determining their lattice parameters a and c,and X-ray density.Also,the Hall effect and thermoelectric power (TEP) measurements show that the single crystals exhibit a p-type semiconducting nature.The direct and indirect band gap measurements are also undertaken on these semiconducting materials.

  20. Synthesis and Gas Sensing Properties of Single La-Doped SnO2 Nanobelts

    Directory of Open Access Journals (Sweden)

    Yuemei Wu

    2015-06-01

    Full Text Available Single crystal SnO2 nanobelts (SnO2 NBs and La-SnO2 nanobelts (La-SnO2 NBs were synthesized by thermal evaporation. Both a single SnO2 NB sensor and a single La-SnO2 NB sensor were developed and their sensing properties were investigated. It is found that the single La-SnO2 NB sensor had a high sensitivity of 8.76 to ethanediol at a concentration of 100 ppm at 230 °C, which is the highest sensitivity of a single SnO2 NB to ethanediol among three kinds of volatile organic (VOC liquids studied, including ethanediol, ethanol, and acetone. The La-SnO2 NBs sensor also exhibits a high sensitivity, good selectivity and long-term stability with prompt response time to ethanediol. The mechanism behind the enhanced sensing performance of La-doped SnO2 nanobelts is discussed.

  1. Synthesis and Gas Sensing Properties of Single La-Doped SnO₂ Nanobelts.

    Science.gov (United States)

    Wu, Yuemei; Zhang, Heng; Liu, Yingkai; Chen, Weiwu; Ma, Jiang; Li, Shuanghui; Qin, Zhaojun

    2015-06-16

    Single crystal SnO2 nanobelts (SnO2 NBs) and La-SnO2 nanobelts (La-SnO2 NBs) were synthesized by thermal evaporation. Both a single SnO2 NB sensor and a single La-SnO2 NB sensor were developed and their sensing properties were investigated. It is found that the single La-SnO2 NB sensor had a high sensitivity of 8.76 to ethanediol at a concentration of 100 ppm at 230 °C, which is the highest sensitivity of a single SnO2 NB to ethanediol among three kinds of volatile organic (VOC) liquids studied, including ethanediol, ethanol, and acetone. The La-SnO2 NBs sensor also exhibits a high sensitivity, good selectivity and long-term stability with prompt response time to ethanediol. The mechanism behind the enhanced sensing performance of La-doped SnO2 nanobelts is discussed.

  2. Molecular dynamics of glycine ions in alanine doped TGS single crystal as probed by polarized laser raman spectroscopy

    Science.gov (United States)

    Bajpai, P. K.; Verma, A. L.

    2012-10-01

    Polarized Raman spectra of pure and alanine doped tri-glycine sulfate (TGS) single crystals at 12 K in different scattering geometries are analyzed. Sub species modes due to three crystallographically distinguishable glycine ions G (I), G (II) and G (III) are assigned. It is observed that alanine doping does not change the crystalline field and acts as local perturbation only. The major changes due to doping are observed in the relative intensities of different modes; most of the modes associated with G (I) and SO42- ions show reversal behavior in relative intensity at high doping concentration. The observed spectral changes are analyzed in terms of reorientation of G (I) ions with sub species modes of G (II)/ G (III) following the reorientation due to complex hydrogen bonding network.

  3. Site-selective substitutional doping with atomic precision on stepped Al (111) surface by single-atom manipulation.

    Science.gov (United States)

    Chen, Chang; Zhang, Jinhu; Dong, Guofeng; Shao, Hezhu; Ning, Bo-Yuan; Zhao, Li; Ning, Xi-Jing; Zhuang, Jun

    2014-01-01

    In fabrication of nano- and quantum devices, it is sometimes critical to position individual dopants at certain sites precisely to obtain the specific or enhanced functionalities. With first-principles simulations, we propose a method for substitutional doping of individual atom at a certain position on a stepped metal surface by single-atom manipulation. A selected atom at the step of Al (111) surface could be extracted vertically with an Al trimer-apex tip, and then the dopant atom will be positioned to this site. The details of the entire process including potential energy curves are given, which suggests the reliability of the proposed single-atom doping method.

  4. Optical properties of Sm{sup 3+} doped strontium hexa-aluminate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Gheorghe, C., E-mail: cristina_gheorghe2002@yahoo.com; Gheorghe, L.; Achim, A.; Hau, S.; Avram, R.D.; Stanciu, G.

    2015-02-15

    Highlights: • Investigation of Sm{sup 3+} doped Sr{sub 1-x}Sm{sub y}La{sub x-y}Mg{sub x}Al{sub 12-x}O{sub 19} - Sm: ASL as laser material. • Polarized absorption and emission spectra of Sm: ASL were performed. • The spectroscopic properties of Sm{sup 3+} doped ASL single crystal were evaluated. • Sm: ASL exhibit favorable conditions for laser action in yellow-orange range. - Abstract: Sm{sup 3+} doped disordered strontium hexa-aluminate crystals Sr{sub 1-x}Sm{sub y}La{sub x-y}Mg{sub x}Al{sub 12-x}O{sub 19} (x = 0.2, y = 0.05, 0.1, 0.15) were grown by Czochralski method. Polarized absorption spectra, as well as emission and lifetime measurements were performed. Strong absorption line located at 404 nm, could be utilized for efficient excitation of material by InGaN/GaN laser diodes. The Judd-Ofelt theory, extended to anisotropic system, has been applied to evaluate the Ω{sub t} (t = 2, 4, 6) intensity parameters, radiative transition rates A{sub r}, branching ratios β, and radiative lifetime τ{sub r} of the fluorescent {sup 4}G{sub 5/2} level. The emission cross-section for the {sup 4}G{sub 5/2} → {sup 6}H{sub 7/2} transition at about 593 nm with the highest value of 1.6 × 10{sup -21} cm{sup 2} nm for σ-polarization and an experimental branching ratio β = 49.43%, gives high chance for obtaining laser action in four level operation scheme.

  5. The effect of Fe{sup 3+} doping in Potassium Hydrogen Phthalate single crystals on structural and optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, R. Ashok; Sivakumar, N.; Vizhi, R. Ezhil [Crystal Growth and Crystallography Division, School of Advanced Sciences, VIT University, Vellore, Tamil Nadu (India); Babu, D. Rajan, E-mail: drajanbabu@vit.ac.i [Crystal Growth and Crystallography Division, School of Advanced Sciences, VIT University, Vellore, Tamil Nadu (India)

    2011-02-15

    This work investigates the influence of iron doping on Potassium Hydrogen Phthalate (KHP) single crystals by the slow evaporation solution growth technique. Factors such as evaporation rate, solution pH, solute concentration, super saturation limit, etc. are very important in order to have optically transparent single crystals. As part of the work, the effects of metallic salt FeCl{sub 3} in different concentrations were analyzed with pure KHP. Powder X-ray diffraction suggests that the grown crystals are crystallized in the orthorhombic structure. The functional groups and the effect of moisture on the doped crystals can be analyzed with the help of a FTIR spectrum. The pure and doped KHP single crystal shows good transparency in the entire visible region, which is suitable for optical device applications. The refractive indices along b axis of pure and doped KHP single crystals were analyzed by the prism coupling technique. The emission of green light with the use of a Nd:YAG laser ({lambda}=1064 nm) confirmed the second harmonic generation properties of the grown crystals. -- Research highlights: {yields} Doping of Fe{sup 3+} affects the growth parameters of KHP. {yields} The presence of small amount of impurities such as Ni{sup 2+}, Mg{sup 2+} and Li{sup 2+} plays an important role. {yields} The present work is to grow good quality KHP crystal by doping different concentrations of Fe{sup 3+} ions. {yields} The effects of Fe{sup 3+} ion on the properties of KHP single crystal have been reported.

  6. Properties of Dy 3+-doped PbWO 4 single crystal grown by modified Bridgman method

    Science.gov (United States)

    Huang, Yanlin; Zhu, Wenliang; Feng, Xiqi; Duan, Yong; Man, Zhenyong

    2003-01-01

    Undoped and Dy 3+-doped PbWO 4 single crystals were grown in the same condition by modified Bridgman method. Optical transmittance, X-ray excited luminescence, excitation and emission under UV light, thermoluminescence glow curves and X-ray pulsed excited decays were investigated on Dy 3+:PWO for the first time. Dy 3+-doping has a positive effect similar to that of rare-earth ions La 3+ and Gd 3+, such as improvement of transmittance in the wavelength region of scintillation emission (350-450 nm), compensation of trapping centers that is reflected in the thermoluminescence characteristics and suppression of slow decay component in luminescence kinetics. Analysis of luminescence spectra indicates that energy transfer could take place from the PbWO 4 host to the Dy 3+ ions, followed by characteristic emission line assigned to transition from 4F 9/2 of Dy 3+ ion to lower lying states on basis of the energy level scheme. A tentative concept of energy transfer mechanism is proposed in this paper.

  7. Near-Infrared Luminescence Spectroscopy of Nickelocene Doped into Single Crystals of Ruthenocene.

    Science.gov (United States)

    Davis, Martin J.; Reber, Christian

    1996-05-22

    Single crystals of ruthenocene doped with nickelocene show a near-infrared luminescence band with a maximum at 13 100 cm(-1) and a width of 1100 cm(-1) at 5 K in addition to the ruthenocene luminescence. The band is symmetric and attributed to nickelocene on the basis of a comparison of luminescence and absorption spectra. Energy transfer from the ruthenocene host enhances the nickelocene luminescence intensity at temperatures between 50 and 100 K. An activation barrier of 306(18) cm(-1) is determined from luminescence decay measurements. The Stokes shift of 2200 cm(-1) and the large change of 0.16 Å in nickel-cyclopentadienyl distance in the emitting state confirm the assignment as (3)E(1g), arising from an electron configuration different from that of the ground state. The comparison of experimental and calculated spectra shows that only low-energy vibrational modes contribute to the luminescence band shape, in contrast to the case of cobaltocene doped in the same host lattice, where a distortion along a high-frequency, ligand-centered mode affects the luminescence band shape.

  8. Growth, dispersion, and electronic devices of nitrogen-doped single-wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Oikonomou, Antonios [School of Computer Science, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Susi, Toma; Kauppinen, Esko I. [Nanomaterials Group, Department of Applied Physics, Aalto University School of Science, PO Box 15100, 00076 Aalto (Finland); Vijayaraghavan, Aravind [School of Computer Science, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Centre for Mesoscience and Nanotechnology, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom)

    2012-12-15

    This paper describes the complete processes from growth to electronic devices of nitrogen-doped single-wall carbon nanotubes (N-SWCNTs). The N-SWCNTs were synthesized using a floating catalyst chemical vapor deposition method. The dry-deposited N-SWCNT films were dispersed in N-methylpyrolidone followed by sonication and centrifugation steps to yield a stable dispersion of N-SWCNTs in solution. The length and diameter distribution as well as concentration of N-SWCNTs in solution were measured by atomic force microscopy and optical absorption spectroscopy, respectively. The N-SWCNTs were then assembled into electronic devices using bottom-up dielectrophoresis and characterized as field-effect transistors. Finally, the potential for application of N-SWCNTs in sensors is discussed. The three stages of N-doped SWCNT processing: (a) growth and collection on filter, (b) dispersion in NMP, and (c) dielectrophoretic assembly into transistor device. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Optimum processing conditions for the fabrication of large, single grain Ag-doped YBCO bulk superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Iida, K. [IRC in Superconductivity and Department of Engineering, University of Cambridge, Cavendish Laboratory 19 JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom)], E-mail: k.iida@ifw-dresden.de; Babu, N.H. [IRC in Superconductivity and Department of Engineering, University of Cambridge, Cavendish Laboratory 19 JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom); BCAST, Brunel University, West London UB8 3PH (United Kingdom); Pathak, S.; Shi, Y.; Yeoh, W.K. [IRC in Superconductivity and Department of Engineering, University of Cambridge, Cavendish Laboratory 19 JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Miyazaki, T. [Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548 (Japan); SRL-ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan); Sakai, N. [SRL-ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan); Murakami, M. [Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548 (Japan); Cardwell, D.A. [IRC in Superconductivity and Department of Engineering, University of Cambridge, Cavendish Laboratory 19 JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

    2008-06-15

    A pseudo Time-Temperature-Transformation (TTT) diagram has been constructed for the optimum melt processing conditions for the fabrication of large, single grain Ag-doped Y-Ba-Cu-O (YBCO/Ag) bulk superconductors. The thermal conditions for the formation of homogeneous nuclei have been investigated and the boundary between this region and that for no grain nucleation has been mapped as a function of holding time. YBCO/Ag bulk samples grow typically in the form of single grains when the processing temperature profile lies within the 'no nucleation' region of the pseudo TTT diagram. However, by studying the YBCO/Ag growth process, some samples have been grown in the form of single grains by employing a temperature profile within the homogeneous grain nucleation region of the phase diagram. Such growth may be achieved when the YBCO/Ag phase constitutes the majority of the volume of the pellet before the growth temperature reaches that at the nucleation boundary. A large, single YBCO/Ag grain of diameter 30 mm has been fabricated successfully based on these studies by both cold-seeding and seeded infiltration growth techniques.

  10. Na-doped Cu2ZnSnS4 single crystal grown by traveling-heater method

    Science.gov (United States)

    Nagaoka, Akira; Scarpulla, Michael A.; Yoshino, Kenji

    2016-11-01

    We investigate high-quality Na-doped Cu2ZnSnS4 (CZTS) single crystals grown by using the traveling-heater method and the effect of Na doping on the fundamental properties of these crystals. Na-doped CZTS single crystals were obtained from Sn solution at growth temperatures of 850-900 °C and at speeds of 4 mm/day. The crystals have a kesterite structure, as determined by powder X-ray diffraction and Raman measurements. The Hall effect properties such as hole concentration, conductivity, and hole mobility are enhanced with increasing Na concentration. These results reveal that Na improves the electrical properties of CZTS.

  11. An organic-inorganic broadband photodetector based on a single polyaniline nanowire doped with quantum dots.

    Science.gov (United States)

    Yang, Xianguang; Liu, Yong; Lei, Hongxiang; Li, Baojun

    2016-08-25

    The capability to detect light over a broad waveband is highly important for practical optoelectronic applications and has been achieved with photodetectors of one-dimensional inorganic nanomaterials such as Si, ZnO, and GaN. However, achieving high speed responsivity over an entire waveband within such a photodetector remains a challenge. Here we demonstrate a broadband photodetector using a single polyaniline nanowire doped with quantum dots that is highly responsive over a broadband from 350 to 700 nm. The high responsivity is due to the high density of trapping states at the enormous interfaces between polyaniline and quantum dots. The interface trapping can effectively reduce the recombination rate and enhance the efficiency for light detection. Furthermore, a tunable spectral range can be achieved by size-based spectral tuning of quantum dots. The use of organic-inorganic hybrid polyaniline nanowires in broadband photodetection may offer novel functionalities in optoelectronic devices and circuits.

  12. The new piezoelectric single crystal obtained by the Ge doping in the α-quartz structure

    Science.gov (United States)

    Miclau, M.; Grozescu, A.; Bucur, R.; Poienar, M.; Vlazan, P.; Grozescu, I.; Miclau, N.; Muscutariu, I.

    2009-03-01

    The most interesting properties of the quartz-like crystals are its piezoelectric properties, which are strongly influenced by the intrinsic structural distortions of the material and the crystal growth conditions. Thus, physical properties such as coupling coefficient, the αβ transition can be directly related to structural distortions in terms of the bridging angle. We propose a new way to increase the structural distortion, using Ge to dope the SiO2 structure with respect to α-quartz structure type. Growth of α -SixGe1-xO2 crystal was realized hydrothermally using a temperature gradient method. Single crystals were investigated by electron microprobe analysis, X-ray diffraction and atomic force microscopy. The results open the possibility to tune the piezoelectric properties of these materials by varying the chemical composition.

  13. Mechanism of the initial stages of nitrogen-doped single-walled carbon nanotube growth.

    Science.gov (United States)

    Susi, Toma; Lanzani, Giorgio; Nasibulin, Albert G; Ayala, Paola; Jiang, Tao; Bligaard, Thomas; Laasonen, Kari; Kauppinen, Esko I

    2011-06-21

    We have studied the mechanism of the initial stages of nitrogen-doped single-walled carbon nanotube growth illustrated for the case of a floating catalyst chemical vapor deposition system, which uses carbon monoxide (CO) and ammonia (NH(3)) as precursors and iron as a catalyst. We performed first-principles electronic-structure calculations, fully incorporating the effects of spin polarization and magnetic moments, to investigate the bonding and chemistry of CO, NH(3), and their fragments on a model Fe(55) icosahedral cluster. A possible dissociation path for NH(3) to atomic nitrogen and hydrogen was identified, with a reaction barrier consistent with an experimentally determined value we measured by tandem infrared and mass spectrometry. Both C-C and C-N bond formation reactions were found to be barrierless and exothermic, while a parasitic reaction of HCN formation had a barrier of over 1 eV.

  14. Spatial modulation spectroscopy for imaging and quantitative analysis of single dye-doped organic nanoparticles inside cells

    Science.gov (United States)

    Devadas, Mary Sajini; Devkota, Tuphan; Guha, Samit; Shaw, Scott K.; Smith, Bradley D.; Hartland, Gregory V.

    2015-05-01

    Imaging of non-fluorescent nanoparticles in complex biological environments, such as the cell cytosol, is a challenging problem. For metal nanoparticles, Rayleigh scattering methods can be used, but for organic nanoparticles, such as dye-doped polymer beads or lipid nanoparticles, light scattering does not provide good contrast. In this paper, spatial modulation spectroscopy (SMS) is used to image single organic nanoparticles doped with non-fluorescent, near-IR croconaine dye. SMS is a quantitative imaging technique that yields the absolute extinction cross-section of the nanoparticles, which can be used to determine the number of dye molecules per particle. SMS images were recorded for particles within EMT-6 breast cancer cells. The measurements allowed mapping of the nanoparticle location and the amount of dye in a single cell. The results demonstrate how SMS can facilitate efforts to optimize dye-doped nanoparticles for effective photothermal therapy of cancer.Imaging of non-fluorescent nanoparticles in complex biological environments, such as the cell cytosol, is a challenging problem. For metal nanoparticles, Rayleigh scattering methods can be used, but for organic nanoparticles, such as dye-doped polymer beads or lipid nanoparticles, light scattering does not provide good contrast. In this paper, spatial modulation spectroscopy (SMS) is used to image single organic nanoparticles doped with non-fluorescent, near-IR croconaine dye. SMS is a quantitative imaging technique that yields the absolute extinction cross-section of the nanoparticles, which can be used to determine the number of dye molecules per particle. SMS images were recorded for particles within EMT-6 breast cancer cells. The measurements allowed mapping of the nanoparticle location and the amount of dye in a single cell. The results demonstrate how SMS can facilitate efforts to optimize dye-doped nanoparticles for effective photothermal therapy of cancer. Electronic supplementary information (ESI

  15. Ab initio investigation of Al- and Ga-doped single-walled boron nitride nanotubes as ammonia sensor

    Energy Technology Data Exchange (ETDEWEB)

    Soltani, Alireza, E-mail: Alireza.soltani46@yahoo.com [Young Researchers Club, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Raz, Shima Ghafouri [Department of Chemistry, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Rezaei, Vahid Joveini [Young Researchers Club, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Dehno Khalaji, Aliakbar [Department of Chemistry, Faculty of Science, Golestan University, Gorgan (Iran, Islamic Republic of); Savar, Mohammad [Department of Chemistry, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer The electronic properties of NH{sub 3} on Al- and Ga-doped (8, 0) and (5, 5) BNNT are studied. Black-Right-Pointing-Pointer The adsorption energy for NH{sub 3} on Al-doped (8, 0) BNNT is higher than that of Ga-doped (8, 0) BNNT. Black-Right-Pointing-Pointer The relation between adsorption energy and charge transfer was investigated. - Abstract: We performed first-principles calculations on the ammonia (NH{sub 3}) adsorption properties with zigzag and armchair single-walled BN nanotubes (SWBNNTs) using B3LYP/6-31G* basis set implemented in Gaussian 98 program. We considered the ammonia adsorption on structural and electronic properties of Al- and Ga-doped (8, 0), (5, 5) BNNTs. The adsorption energy for the most stable configuration of NH{sub 3} on Al-doped (8, 0) BNNT is about -0.182 eV, which is typical for the chemisorptions. We determined that both aluminum and gallium doping can significantly enhance the adsorption energy of NH{sub 3}/BNNTs complexes. Our electronic results reveal that there is a significant orbital hybridization between two species in adsorption process being an evidence of covalent interaction.

  16. Catalytic activity of Pd-doped Cu nanoparticles for hydrogenation as a single-atom-alloy catalyst.

    Science.gov (United States)

    Cao, Xinrui; Fu, Qiang; Luo, Yi

    2014-05-14

    The single atom alloy of extended surfaces is known to provide remarkably enhanced catalytic performance toward heterogeneous hydrogenation. Here we demonstrate from first principles calculations that this approach can be extended to nanostructures, such as bimetallic nanoparticles. The catalytic properties of the single-Pd-doped Cu55 nanoparticles have been systemically examined for H2 dissociation as well as H atom adsorption and diffusion, following the concept of single atom alloy. It is found that doping a single Pd atom at the edge site of the Cu55 shell can considerably reduce the activation energy of H2 dissociation, while the single Pd atom doped at the top site or in the inner layers is much less effective. The H atom adsorption on Cu55 is slightly stronger than that on the Cu(111) surface; however, a larger nanoparticle that contains 147 atoms could effectively recover the weak binding of the H atoms. We have also investigated the H atom diffusion on the 55-atom nanoparticle and found that spillover of the produced H atoms could be a feasible process due to the low diffusion barriers. Our results have demonstrated that facile H2 dissociation and weak H atom adsorption could be combined at the nanoscale. Moreover, the effects of doping one more Pd atom on the H2 dissociation and H atom adsorption have also been investigated. We have found that both the doping Pd atoms in the most stable configuration could independently exhibit their catalytic activity, behaving as two single-atom-alloy catalysts.

  17. Single-mode regime in large-mode-area rare-earth-doped rod-type PCFs

    DEFF Research Database (Denmark)

    Poli, F.; Cucinotta, A.; Passaro, D.

    2009-01-01

    In this paper, large-mode-area, double-cladding, rare-earth-doped photonic crystal fibers are investigated in order to understand how the refractive index distribution and the mode competition given by the amplification can assure single-mode propagation. Fibers with different core diameters, i...

  18. An efficient low-noise single-frequency 1033 nm Yb3+-doped MOPA phosphate fiber laser system

    Science.gov (United States)

    Deng, Huaqiu; Chen, Dan; Zhao, Qilai; Yang, Changsheng; Zhang, Yuanfei; Zhang, Yuning; Feng, Zhouming; Yang, Zhongmin; Xu, Shanhui

    2017-06-01

    An efficient low-noise, single-frequency 1033 nm master oscillator power amplifier (MOPA) Yb3+-doped phosphate fiber (YPF) laser system is demonstrated. A maximal output power of 612 mW with a laser linewidth of 65 dB and relative intensity noise (RIN) of laser system has applications in the fields of optical frequency standards and beam combining.

  19. Growth, structural, spectral, mechanical and dielectric characterization of RbCl-doped L-alanine hydrogen chloride monohydrate single crystals

    Science.gov (United States)

    Lucia Rose, A. S. J.; Selvarajan, P.; Perumal, S.

    2011-02-01

    Pure (undoped) and RbCl-doped LAHC single crystals were grown successfully by the solution method with the slow evaporation technique at room temperature. The grown crystals were colourless and transparent. The solubility of the grown samples were found out at various temperatures. The lattice parameters of the grown crystals were determined by the single crystal X-ray diffraction technique and the diffracting planes were indentified by recording the powder X-ray diffraction pattern. UV-visible transmittance studies were carried out for the grown samples. Chemical analysis and atomic absorption studies indicate the presence of rubidium in the doped LAHC crystals. Nonlinear optical studies reveal that the SHG efficiency increases when the LAHC crystal is doped with rubidium chloride (RbCl). From microhardness studies, it is observed that the RbCl-doped LAHC crystal is harder than the pure sample. It is observed that the dielectric properties of the LAHC crystal are altered when it is doped with rubidium chloride.

  20. Antimicrobial activity and second harmonic studies on organic non-centrosymmetric pure and doped ninhydrin single crystals

    Science.gov (United States)

    Prasanyaa, T.; Jayaramakrishnan, V.; Haris, M.

    2013-03-01

    In this paper, we report the successful growth of pure, Cu2+ ions and Cd2+ ions doped on ninhydrin single crystals by slow solvent evaporation technique. The presence of Cu2+ and Cd2+ ions in the specimen of ninhydrin single crystal has been determined by atomic absorption spectroscopy. The powder X-ray diffraction analysis was done to calculate the lattice parameters of the pure and doped crystals. The percentage of transmittance of the crystal was recorded using the UV-Vis Spectrophotometer. Thermal behaviors of the grown crystals have been examined by the thermal gravimetric/differential thermal analysis. The hardness of the grown crystals was assessed and the results show the minor variation in the hardness value for the pure and doped ninhydrin samples. The value of the work hardening coefficient n was found to be 2.0, 1.0 and 1.06 for pure, copper and cadmium doped ninhydrin crystals respectively. The second harmonic generation efficiency of Cd2+ and Cu2+ doped ninhydrin is 8.3 and 6.3 times greater than well known nonlinear crystal of potassium dihydrogen phosphate respectively. The antibacterial and antifungal activities of the title compound were performed by disk diffusion method against the standard bacteria Escherichia coli, Xanthomonas oryzae and against the fungus Aspergillis niger and Aspergillus flavus.

  1. DC current and AC impedance measurements on boron-doped single crystalline diamond films

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Haitao; Gaudin, O.; Jackman, R.B. [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Muret, P.; Gheeraert, E. [Laboratoire d' Etudes des Proprietes Electroniques des Solides, BP166, 38042 Grenoble Cedex 9 (France)

    2003-09-01

    In this paper, we report the first measurement of impedance on boron-doped single crystalline diamond films from 0.1 Hz to 10 MHz with the temperature ranging from -100 C up to 300 C. The Cole-Cole (Z' via Z{sup ''}) plots are well fitted to a RC parallel circuit model and the equivalent Resistance and Capacitance for the diamond films have been estimated using the Zview curve fitting. The results show only one single semicircle response at each temperature measured. It was found that the resistance decreases from 70 G{omega} at -100 C to 5 k{omega} at 300 C. The linear curve fitting from -100 C to 150 C shows the sample has an activation energy of 0.37 eV, which is consistent with the theoretical value published of this kind of material. The equivalent capacitance is maintained at the level of pF up to 300 C suggesting that no grain boundaries are being involved, as expected from a single crystal diamond. The activation energy from the dc current-temperature curves is 0.36 eV, which is consistent with the value from ac impedance. The potential of this under-used technique for diamond film analysis will be discussed. (copyright 2003 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Scintillating screens for micro-imaging based on the Ce-Tb doped LuAP single crystal films

    OpenAIRE

    Douissard, Paul-Antoine; MARTIN, Thierry; Riva, Federica; Mathieu, Eric; Zorenko, Yuriy; Savchyn, Volodymyr; Zorenko, Tetyana; Fedorov, Alexander

    2014-01-01

    Single Crystal Film (SCF) scintillators are key-components of today's high-resolution 2D X-ray detectors used at synchrotrons for applications such as X-ray Radiography, Computed Tomography (CT), laminography, full-field XANES, and topography. Due to its high density and effective atomic number, LuAlO3 (LuAP) perovskite has a great potential to replace or complement the currently used Eu-doped Gd3Ga5O12 (GGG:Eu) and Tb-doped Lu2SiO5 (LSO:Tb) SCFs. In this article we present the growth of LuAP...

  3. Enhanced solar energy conversion in Au-doped, single-wall carbon nanotube-Si heterojunction cells

    Science.gov (United States)

    2013-01-01

    The power conversion efficiency (PCE) of single-wall carbon nanotube (SCNT)/n-type crystalline silicon heterojunction photovoltaic devices is significantly improved by Au doping. It is found that the overall PCE was significantly increased to threefold. The efficiency enhancement of photovoltaic devices is mainly the improved electrical conductivity of SCNT by increasing the carrier concentration and the enhancing the absorbance of active layers by Au nanoparticles. The Au doping can lead to an increase of the open circuit voltage through adjusting the Fermi level of SCNT and then enhancing the built-in potential in the SCNT/n-Si junction. This fabrication is easy, cost-effective, and easily scaled up, which demonstrates that such Au-doped SCNT/Si cells possess promising potential in energy harvesting application. PMID:23663755

  4. Enhancement of the point defect pinning effect in Mo-doped Bi2212 single crystals of reduced anisotropy

    CERN Document Server

    Han, S H; Dai, Y; Zhang, Y; Zhang, H; Zhao, Y

    2002-01-01

    High quality Bi sub 2 Sr sub 2 CaCu sub 2 sub - sub x Mo sub x O sub y (x = 0, 0.01 and 0.02) single crystals have been grown by a self-flux method in a horizontal temperature gradient and their flux pinning and irreversibility behaviour have been investigated. The irreversibility lines of the undoped and Mo-doped Bi2212 crystals have been greatly improved by reducing the anisotropy parameter gamma. However, this improvement is much more pronounced for Mo-doped crystals than for the undoped ones. The peak effect of magnetization loops also changes with both Mo-doping and gamma. The results provide strong evidence that the point defect pinning served by Mo is greatly enhanced when the anisotropy of the system is reduced.

  5. The unusually high Tc in rare-earth-doped single crystalline CaFe2As2

    Science.gov (United States)

    Wei, Fengyan; Lv, Bing; Deng, Liangzi; Meen, James K.; Xue, Yu-Yi; Chu, Ching-Wu

    2014-08-01

    In rare-earth-doped single crystalline CaFe2As2, the mysterious small volume fraction which superconducts up to 49 K, much higher than the bulk Tc ~ 30 s K, has prompted a long search for a hidden variable that could enhance the Tc by more than 30% in iron-based superconductors of the same structure. Here we report a chemical, structural and magnetic study of CaFe2As2 systematically doped with La, Ce, Pr and Nd. Coincident with the high Tc phase, we find extreme magnetic anisotropy, accompanied by an unexpected doping-independent Tc and equally unexpected superparamagnetic clusters associated with As vacancies. These observations lead us to conjecture that the tantalizing Tc enhancement may be associated with naturally occurring chemical interfaces and may thus provide a new paradigm in the search for superconductors with higher Tc.

  6. Property database for single-element doping in ZnO obtained by automated first-principles calculations

    Science.gov (United States)

    Yim, Kanghoon; Lee, Joohee; Lee, Dongheon; Lee, Miso; Cho, Eunae; Lee, Hyo Sug; Nahm, Ho-Hyun; Han, Seungwu

    2017-01-01

    Throughout the past decades, doped-ZnO has been widely used in various optical, electrical, magnetic, and energy devices. While almost every element in the Periodic Table was doped in ZnO, the systematic computational study is still limited to a small number of dopants, which may hinder a firm understanding of experimental observations. In this report, we systematically calculate the single-element doping property of ZnO using first-principles calculations. We develop an automation code that enables efficient and reliable high-throughput calculations on thousands of possible dopant configurations. As a result, we obtain formation-energy diagrams for total 61 dopants, ranging from Li to Bi. Furthermore, we evaluate each dopant in terms of n-type/p-type behaviors by identifying the major dopant configurations and calculating carrier concentrations at a specific dopant density. The existence of localized magnetic moment is also examined for spintronic applications. The property database obtained here for doped ZnO will serve as a useful reference in engineering the material property of ZnO through doping. PMID:28112188

  7. Influence of L-alanine doping on crystalline perfection, SHG efficiency, optical and mechanical properties of KDP single crystals

    Science.gov (United States)

    Shakir, Mohd.; Ganesh, V.; Riscob, B.; Maurya, K. K.; Wahab, M. A.; Bhagavannarayana, G.; Kishan Rao, K.

    2011-09-01

    Pure and L-alanine (LA) doped single crystals of potassium dihydrogen orthophosphate (KDP) were grown by slow evaporation solution technique (SEST) in aqueous solution at ambient temperature. Powder X-ray diffraction study was done to confirm the crystal system and lattice parameters of KDP. No additional phases were observed at all doping concentrations (1-7.5 mol%), which was further confirmed by FT-Raman spectroscopy analysis. The influence of LA doping on the crystalline perfection was assessed by high-resolution X-ray diffractometry (HRXRD) analysis. HRXRD studies revealed that the grown crystals could accommodate LA at the interstitial positions in the crystalline matrix of KDP up to some critical concentration without any deterioration in the crystalline perfection. Above this concentration, very low angle structural grain boundaries were developed and it seems that the excess LA above the critical concentration was segregated along the grain boundaries. The SHG efficiency was measured using the Kurtz powder technique. The relative SHG efficiency of the crystals was found to be increased with doping concentration up to 5 mol% and above this it decreases. Optical transmission study also revealed the same behavior with enhancement up to 5 mol% concentration and later decreased. The hardness values were found to be increased by increasing the doping concentration.

  8. Property database for single-element doping in ZnO obtained by automated first-principles calculations

    Science.gov (United States)

    Yim, Kanghoon; Lee, Joohee; Lee, Dongheon; Lee, Miso; Cho, Eunae; Lee, Hyo Sug; Nahm, Ho-Hyun; Han, Seungwu

    2017-01-01

    Throughout the past decades, doped-ZnO has been widely used in various optical, electrical, magnetic, and energy devices. While almost every element in the Periodic Table was doped in ZnO, the systematic computational study is still limited to a small number of dopants, which may hinder a firm understanding of experimental observations. In this report, we systematically calculate the single-element doping property of ZnO using first-principles calculations. We develop an automation code that enables efficient and reliable high-throughput calculations on thousands of possible dopant configurations. As a result, we obtain formation-energy diagrams for total 61 dopants, ranging from Li to Bi. Furthermore, we evaluate each dopant in terms of n-type/p-type behaviors by identifying the major dopant configurations and calculating carrier concentrations at a specific dopant density. The existence of localized magnetic moment is also examined for spintronic applications. The property database obtained here for doped ZnO will serve as a useful reference in engineering the material property of ZnO through doping.

  9. Excited state dynamics of the Ho3+ ions in holmium singly doped and holmium, praseodymium-codoped fluoride glasses

    Science.gov (United States)

    Librantz, André Felipe Henriques; Jackson, Stuart D.; Jagosich, Fabio Henrique; Gomes, Laércio; Poirier, Gaël; Ribeiro, Sidney José Lima; Messaddeq, Younes

    2007-06-01

    The deactivation of the two lowest excited states of Ho3+ was investigated in Ho3+ singly doped and Ho3+, Pr3+-codoped fluoride (ZBLAN) glasses. We establish that 0.1-0.3mol% Pr3+ can efficiently deactivate the first excited (I75) state of Ho3+ while causing a small reduction of ˜40% of the initial population of the second excited (I65) state. The net effect introduced by the Pr3+ ion deactivation of the Ho3+ ion is the fast recovery of the ground state of Ho3+. The Burshstein model parameters relevant to the Ho3+→Pr3+ energy transfer processes were determined using a least squares fit to the measured luminescence decay. The energy transfer upconversion and cross relaxation parameters for 1948, 1151, and 532nm excitations of singly Ho3+-doped ZBLAN were determined. Using the energy transfer rate parameters we determine from the measured luminescence, a rate equation model for 650nm excitation of Ho3+-doped and Ho3+, Pr3+-doped ZBLAN glasses was developed. The rate equations were solved numerically and the population inversion between the I65 and the I75 excited states of Ho3+ was calculated to examine the beneficial effects on the gain associated with Pr3+ codoping.

  10. The application of highly doped single-layer graphene as the top electrodes of semitransparent organic solar cells.

    Science.gov (United States)

    Liu, Zhike; Li, Jinhua; Sun, Zhen-Hua; Tai, Guoan; Lau, Shu-Ping; Yan, Feng

    2012-01-24

    A single-layer graphene film with high conductance and transparency was realized by effective chemical doping. The conductance of single-layer graphene was increased for more than 400% when it was doped with Au nanoparticles and poly(3,4-ethylenedioxythiophene): poly(styrene sulfonic acid). Then semitransparent organic solar cells based on poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) were fabricated with single-layer graphene and indium tin oxide (ITO) as the top and bottom electrodes, respectively. The performance of the devices was optimized by tuning the active layer thickness and doping the single-layer graphene electrodes. The maximum efficiency of 2.7% was observed in the devices with the area of 20 mm(2) illuminated from graphene electrode under the AM1.5 solar simulator. It is notable that all of the devices showed higher efficiency from the graphene than ITO side, which was attributed to the better transmittance of the graphene electrodes. In addition, the influence of the active area of the organic solar cell on its photovoltaic performance was studied. We found that, when the active areas increased from 6 to 50 mm(2), the power conversion efficiencies decreased from 3% to 2.3% because of the increased series resistances and the decreased edge effect of the devices.

  11. Scintillation properties of the silver doped lithium iodide single crystals at room and low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Sajid [Department of Physics, Kyungpook National University, Daegu 41566 (Korea, Republic of); Department of Physics, Kohat University of Science and Technology, Kohat 26000 (Pakistan); Kim, H.J. [Department of Physics, Kyungpook National University, Daegu 41566 (Korea, Republic of); Lee, M.H., E-mail: mhlee@ibs.re.kr [Center for Underground Physics, Institute for Basic Science (IBS), Daejon 34047 (Korea, Republic of)

    2016-06-11

    This study presents luminescence and scintillation properties of Silver doped LiI crystals. Single crystals of LiI: x% Ag (x=0.02, 0.05, 0.1 and 0.5) were grown by using the Bridgman technique. X-ray induced luminescence spectra show emission bands spanning from 275 nm to 675 nm, dominated by Ag{sup +} band having a peak at 300 nm. Under UV-luminescence, a similar emission band was observed with the peak excitation wavelength of 265 nm. Energy resolution, light yield and decay time profiles of the samples were measured under a {sup 137}Cs γ-ray irradiation. The LiI(0.1%Ag) showed the highest light yield and the best energy resolution among the samples. The light yield of LiI(0.1%Ag) is higher than commercially available LiI(Eu) crystal (15,000±1500 ph/MeV). The LiI(Ag) samples exhibit three exponential decay time components except the LiI(0.02%Ag), where the fitting found two decay time components. Temperature dependences of emission spectra, light yield and decay time were studied from 300 K to 10 K. The LiI(0.1%Ag) crystal showed an increase in the light yield and a shortening of decay time with a decrease in temperature..

  12. Barium iron arsenide, barium cobalt arsenide, barium nickel arsenide single crystals and superconductivity upon cobalt doping

    Energy Technology Data Exchange (ETDEWEB)

    Ronning, Filip [Los Alamos National Laboratory; Sefat, A S [ORNL; Mcguire, M M [ORNL; Sales, B [ORNL; Jin, R [ORNL; Mandrus, D [ORNL

    2009-01-01

    The crystal structure and physical properties of BaFe{sub 2}As{sub 2}, BaCo{sub 2}As{sub 2}, and BaNi{sub 2}As{sub 2} single crystals are surveyed. BaFe{sub 2}As{sub 2} gives a magnetic and structural transition at T{sub N} = 132(1) K, BaCo{sub 2}As{sub 2} is a paramagnetic metal, while BaNi{sub 2}As{sub 2} has a structural phase transition at T{sub 0} = 131 K, followed by superconductivity below {Tc} = 0.69 K. The bulk superconductivity in Co-doped BaFe{sub 2}As{sub 2} below {Tc} = 22 K is demonstrated by resistivity, magnetic susceptibility, and specific heat data. In contrast to the cuprates, the Fe-based system appears to tolerate considerable disorder in the transition metal layers. First principles calculations for BaFe{sub 1.84}Co{sub 0.16}As{sub 2} inter-band scattering due to Co is weak.

  13. EPR and optical study of Mn{sup 2+}-doped lithium hydrogen oxalate monohydrate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kripal, Ram [Department of Physics, University of Allahabad, Allahabad 211002 (India)]. E-mail: ram_kripal2001@rediffmail.com; Govind, Har [Department of Electronics, Ewing Christian College, Allahabad 211003 (India)]. E-mail: chaurasia_har@yahoo.co.in; Maurya, Manju [Department of Physics, University of Allahabad, Allahabad 211002 (India)

    2007-01-15

    EPR study of Mn{sup 2+}-doped lithium hydrogen oxalate monohydrate single crystals are done at room temperature. The Mn{sup 2+} spin-Hamiltonian parameters are evaluated employing a large number of resonant line positions observed for different orientations of the external magnetic field. The values of g, A, B, D, E and a are 1.9942+/-0.0002, 114+/-2x10{sup -4}, 103+/-2x10{sup -4}, 180+/-2x10{sup -4}, 57+/-2x10{sup -4} and 7+/-1x10{sup -4}cm{sup -1}, respectively. The optical absorption study of the crystal is also done. The observed bands are assigned as transitions from the {sup 6}A{sub 1g}(S) ground state to various excited quartet levels of Mn{sup 2+} ion in a cubic crystalline field. These bands are fitted with four parameters, inter-electronic repulsion parameters (B and C), crystal field parameter (D{sub q}) and Tree's correction ({alpha}). The values found for the parameters are B=814cm{sup -1}, C=2255cm{sup -1}, D{sub q}=780cm{sup -1}, and {alpha}=76cm{sup -1}. On the basis of the data obtained, the surrounding crystalline field and the nature of metal-ligand bonding are discussed.

  14. EPR and optical absorption study of Cu{sup 2+}-doped lithium potassium sulphate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kripal, Ram [EPR Laboratory, Department of Physics, University of Allahabad, Allahabad 211002 (India)], E-mail: ram_kripal2001@rediffmail.com; Bajpai, Manisha [EPR Laboratory, Department of Physics, University of Allahabad, Allahabad 211002 (India)], E-mail: bmanisha15@yahoo.co.in; Maurya, Manju [EPR Laboratory, Department of Physics, University of Allahabad, Allahabad 211002 (India); Govind, Har [Department of Electronics, Ewing Christian College, Allahabad (India)

    2008-10-01

    EPR spectra of Cu{sup 2+} ion doped in lithium potassium sulphate single crystal at room temperature are reported. The observed spectra are fitted to a spin Hamiltonian of orthorhombic symmetry with Cu{sup 2+} (site I) g{sub x}=2.0930, g{sub y}=2.1421, g{sub z}=2.2900 ({+-}0.0002) and A{sub x}=85, A{sub y}=89, A{sub z}=184 ({+-}2x10{sup -4} cm{sup -1}); Cu{sup 2+} (site II) g{sub x}=2.0795, g{sub y}=2.1580, g{sub z}=2.2876 ({+-}0.0002) and A{sub x}=93, A{sub y}=95, A{sub z}=189 ({+-}2x10{sup -4} cm{sup -1}); respective errors given in brackets. Copper enters the lattice substitutionally and is trapped at two magnetically inequivalent sites. The ground state wave function of the Cu{sup 2+} ion in this lattice is determined as predominantly |x{sup 2}-y{sup 2}>. The g-factor anisotropy is calculated and compared with the experimental value. The optical absorption of the crystal at room temperature is also recorded. Further, with the help of the optical absorption and EPR data, the nature of bonding in the complex is discussed.

  15. Reversible room-temperature ferromagnetism in Nb-doped SrTiO3 single crystals

    Science.gov (United States)

    Liu, Z. Q.; Lü, W. M.; Lim, S. L.; Qiu, X. P.; Bao, N. N.; Motapothula, M.; Yi, J. B.; Yang, M.; Dhar, S.; Venkatesan, T.; Ariando

    2013-06-01

    The search for oxide-based room-temperature ferromagnetism has been one of the holy grails in condensed matter physics. Room-temperature ferromagnetism observed in Nb-doped SrTiO3 single crystals is reported in this Rapid Communication. The ferromagnetism can be eliminated by air annealing (making the samples predominantly diamagnetic) and can be recovered by subsequent vacuum annealing. The temperature dependence of magnetic moment resembles the temperature dependence of carrier density, indicating that the magnetism is closely related to the free carriers. Our results suggest that the ferromagnetism is induced by oxygen vacancies. In addition, hysteretic magnetoresistance was observed for magnetic field parallel to the current, indicating that the magnetic moments are in the plane of the samples. The x-ray photoemission spectroscopy, the static time-of-flight and the dynamic secondary ion mass spectroscopy and proton induced x-ray emission measurements were performed to examine the magnetic impurities, showing that the observed ferromagnetism is unlikely due to any magnetic contaminant.

  16. EPR and optical absorption studies of Cu 2+ doped bis (glycinato) Mg (II) monohydrate single crystals

    Science.gov (United States)

    Dwivedi, Prashant; kripal, Ram

    2010-02-01

    Electron paramagnetic resonance (EPR) study of Cu 2+ doped bis (glycinato) Mg (II) monohydrate single crystals is carried out at room temperature. Copper enters the lattice substitutionally and is trapped at two magnetically inequivalent sites. The observed spectra are fitted to a spin-Hamiltonian of rhombic symmetry with the following values of the parameters: Cu 2+ (I), gx = 2.1577 ± 0.0002, gy = 2.2018 ± 0.0002, gz = 2.3259 ± 0.0002, Ax = (87 ± 2) × 10 -4 cm -1, Ay = (107 ± 2) × 10 -4 cm -1, Az = (141 ± 2) × 10 -4 cm -1; Cu 2+ (II), gx = 2.1108 ± 0.0002, gy = 2.1622 ± 0.0002, gz = 2.2971 ± 0.0002, Ax = (69 ± 2) × 10 -4 cm -1, Ay = (117 ± 2) × 10 -4 cm -1and Az = (134 ± 2) × 10 -4 cm -1. The ground state wave function of the Cu 2+ ion in this lattice is evaluated to be predominantly | x2 - y2lbond2 . The g-factor anisotropy is also calculated and compared with the experimental value. With the help of the optical absorption study, the nature of bonding in the complex is discussed.

  17. A novel single-step synthesis of N-doped TiO{sub 2} via a sonochemical method

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xi-Kui, E-mail: xk_wang@sdili.edu.cn [College of Chemical Engineering, Shandong Polytechnic University, Jinan 250353 (China); Wang, Chen [College of Chemical Engineering, Shandong Polytechnic University, Jinan 250353 (China); Guo, Wei-Lin; Wang, Jin-Gang [College of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022 (China)

    2011-11-15

    Graphical abstract: The N-doped anatase TiO{sub 2} nanoparticles were synthesized by sonochemical method. The as-prepared sample is characterized by XRD, TEM, XPS and UV-Vis DRS. The photocatalytic activity of the photocatalyst was evaluated by the photodegradation of an azo dye direct sky blue 5B. Highlights: {yields} A novel singal-step sonochemical synthesis method for the preparation of anatase N-doped TiO{sub 2} nanocrystalline at low temperature has been devoleped. {yields} The as-prepared sample is characterized by XRD, TEM, XPS and UV-Vis DRS. {yields} The photodegradation of azo dye direct sky blue 5 showed that the N-doped TiO{sub 2} catalyst is of high visible-light photocatalytic activity. -- Abstract: A novel single-step synthetic method for the preparation of anatase N-doped TiO{sub 2} nanocrystalline at low temperature has been devoleped. The N-doped anatase TiO{sub 2} nanoparticles were synthesized by sonication of the solution of tetraisopropyl titanium and urea in water and isopropyl alcohol at 80 {sup o}C for 150 min. The as-prepared sample was characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis absorption spectrum. The product structure depends on the reaction temperature and reaction time. The photocatalytic activity of the as-prepared photocatalyst was evaluated via the photodegradation of an azo dye direct sky blue 5B. The results show that the N-doped TiO{sub 2} nanocrystalline prepared via sonication exhibit an excellent photocatalytic activity under UV light and simulated sunlight.

  18. Efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser.

    Science.gov (United States)

    Wang, P; Cooper, L J; Sahu, J K; Clarkson, W A

    2006-01-15

    A novel approach to achieving robust single-spatial-mode operation of cladding-pumped fiber lasers with multimode cores is reported. The approach is based on the use of a fiber geometry in which the core has a helical trajectory within the inner cladding to suppress laser oscillation on higher-order modes. In a preliminary proof-of-principle study, efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser with a 30 microm diameter core and a numerical aperture of 0.087 has been demonstrated. The laser yielded 60.4 W of output at 1043 nm in a beam with M2 diode stack at 976 nm. The slope efficiency at pump powers well above threshold was approximately 84%, which compares favorably with the slope efficiencies achievable with conventional straight-core Yb-doped double-clad fiber lasers.

  19. Density functional theory (DFT) study of a new novel bionanosensor hybrid; tryptophan/Pd doped single walled carbon nanotube

    Science.gov (United States)

    Yoosefian, Mehdi; Etminan, Nazanin

    2016-07-01

    In order to explore a new novel L-amino acid/transition metal doped single walled carbon nanotube based biosensor, density functional theory calculations were studied. These hybrid structures of organic-inorganic nanobiosensors are able to detect the smallest amino acid building block of proteins. The configurations of amine and carbonyl group coordination of tryptophan aromatic amino acid adsorbed on Pd/doped single walled carbon nanotube were compared. The frontier molecular orbital theory, quantum theory atom in molecule and natural bond orbital analysis were performed. The molecular electrostatic potential and the electron density surfaces were constructed. The calculations indicated that the Pd/SWCNT was sensitive to tryptophan suggesting the importance of interaction with biological molecule and potential detecting application. The proposed nanobiosensor represents a highly sensitive detection of protein at ultra-low concentration in diagnosis applications.

  20. The synthesis of single-phase yttrium iron garnet doped zinc and some structural and magnetic properties

    Science.gov (United States)

    Peña-Garcia, R.; Delgado, A.; Guerra, Y.; Duarte, G.; Gonçalves, L. A. P.; Padrón-Hernández, E.

    2017-01-01

    This work presents the single phase formation of yttrium iron garnet (YIG) doped with divalent Zn ions in samples fabricated by the sol–gel method and heat treated at 900 °C. We used stoichiometric amounts according to the formula Y3(Fe1‑x Zn x )5O12, (x  =  0, 0.01, 0.03 and 0.05). The x-ray diffraction data show the single phase formation with the lattice parameter increasing with the Zn concentration. The scanning electron microscopy images showed nanoparticles with a rod format, crowding more as the doping increased. Energy dispersive x-ray spectroscopy results confirmed the presence of Zn in the YIG structure. The Raman spectroscopy measurements show characteristic peaks of the YIG structure, and some characteristic peaks increasing with the Zn concentration. This confirms our successful result doping the YIG structure with the divalent Zn ion replacing the Fe positions. Magnetic measurements show coercive field values dominated by the shape and agglomeration of nanoparticles. For low doping we have a value of 88.50 Oe attributed to the particles’ morphology, and for the highest Zn concentrations the effects of agglomeration diminish the coercivity to 50 Oe. The total magnetic moment for low Zn concentrations increases slightly due to the replacement of Fe by Zn. For higher Zn concentrations, we can see a diminution of the magnetic saturation which is due to the growth of the crystal lattice parameter and thus a weakening of the exchange interactions between the magnetic sub-lattices in the Y3(Fe1‑x Zn x )5O12 ferrimagnetic compound. Changes in the magnetic moment do not have large values, showing the possibility of doping without a drastic change in this quantity.

  1. Anode-supported single-chamber SOFCs based on gadolinia doped ceria electrolytes

    Directory of Open Access Journals (Sweden)

    Morales, M.

    2008-12-01

    Full Text Available The utilization of anode supported electrolytes is a useful strategy to increase the electrical properties of the solid oxide fuel cells, because it is possible to decrease considerably the thickness of the electrolytes. We have prepared successfully singlechamber fuel cells of gadolinia doped ceria electrolytes Ce1-xGdxO2-y (CGO supported on an anode formed by a cermet of Ni-CGO. Mixtures of precursor powders of NiO and gadolinium doped ceria with different particle sizes and compositions were analyzed to obtain optimal bulk porous anodes to be used as anode supported fuel cells. Doped ceria electrolytes were prepared by sol-gel related techniques. Then, ceria based electrolytes were deposited by dip coating at different thickness (15-30 µm using an ink prepared with nanometric powders of electrolytes dispersed in a commercial liquid polymer. Cathodes of La1-xSrxCoO3-s (LSCO were also prepared by sol-gel related techniques and were deposited by dip coating on the electrolyte thick films. Finally, electrical properties were determined in a single-chamber reactor where propane as fuel was mixed with synthetic air above the higher explosive limit. Stable density currents were obtained in these experimental conditions, but flow rates of the carrier gas and propane partial pressure were determinants for the optimization of the electrical properties of the fuel cells.

    La utilización de electrolitos soportados en el ánodo es una estrategia muy útil para mejorar las propiedades eléctricas de las pilas de combustible de óxido sólido, debido a que permiten disminuir considerablemente el espesor de los electrolitos. Para este trabajo, se han preparado exitosamente pilas de combustible de óxido sólido con electrolitos de ceria dopada con Gd, Ce1-xGdxO2-y (CGO soportados sobre un ánodo formado por un cermet de Ni/CGO. Dichas pilas se han

  2. Charge transfer of single laser crystallized intrinsic and phosphorus-doped Si-nanocrystals visualized by Kelvin probe force microscopy

    Science.gov (United States)

    Xu, Jie; Xu, Jun; Lu, Peng; Shan, Dan; Li, Wei; Chen, Kunji

    2014-10-01

    Isolated intrinsic and phosphorus doped (P-doped) Si-nanocrystals (Si-NCs) on n- and p-Si substrates are fabricated by excimer laser crystallization techniques. The formation of Si-NCs is confirmed by atomic force microscopy (AFM) and conductive AFM measurements. Kelvin probe force microscopy (KPFM) is then carried out to visualize the trapped charges in a single Si-NC dot which derives from the charge transfer between Si-NCs and Si substrates due to their different Fermi levels. The laser crystallized P-doped Si-NCs have a similar Fermi level around the mid-gap to the intrinsic counterparts, which might be caused by the inactivated impurity atoms or the surface states-related Fermi level pinning. A clear rise of the Fermi level in P-doped Si-NCs is observed after a short time thermal annealing treatment, indicating the activation of dopants in Si-NCs. Moreover, the surface charge quantity can be estimated using a simple parallel plate capacitor model for a quantitative understanding of the KPFM results at the nanoscale.

  3. Charge transfer of single laser crystallized intrinsic and phosphorus-doped Si-nanocrystals visualized by Kelvin probe force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jie; Xu, Jun, E-mail: junxu@nju.edu.cn; Lu, Peng; Shan, Dan; Li, Wei; Chen, Kunji [National Laboratory of Solid State Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China)

    2014-10-07

    Isolated intrinsic and phosphorus doped (P-doped) Si-nanocrystals (Si-NCs) on n- and p-Si substrates are fabricated by excimer laser crystallization techniques. The formation of Si-NCs is confirmed by atomic force microscopy (AFM) and conductive AFM measurements. Kelvin probe force microscopy (KPFM) is then carried out to visualize the trapped charges in a single Si-NC dot which derives from the charge transfer between Si-NCs and Si substrates due to their different Fermi levels. The laser crystallized P-doped Si-NCs have a similar Fermi level around the mid-gap to the intrinsic counterparts, which might be caused by the inactivated impurity atoms or the surface states-related Fermi level pinning. A clear rise of the Fermi level in P-doped Si-NCs is observed after a short time thermal annealing treatment, indicating the activation of dopants in Si-NCs. Moreover, the surface charge quantity can be estimated using a simple parallel plate capacitor model for a quantitative understanding of the KPFM results at the nanoscale.

  4. Thermal conversion of electronic and electrical properties of AuCl3-doped single-walled carbon nanotubes.

    Science.gov (United States)

    Yoon, Seon-Mi; Kim, Un Jeong; Benayad, Anass; Lee, Il Ha; Son, Hyungbin; Shin, Hyeon-Jin; Choi, Won Mook; Lee, Young Hee; Jin, Yong Wan; Lee, Eun-Hong; Lee, Sang Yoon; Choi, Jae-Young; Kim, Jong Min

    2011-02-22

    By using carbon-free inorganic atomic layer involving heat treatment from 150 to 300 °C, environmentally stable and permanent modulation of the electronic and electrical properties of single-walled carbon nanotubes (SWCNTs) from p-type to ambi-polar and possibly to n-type has been demonstrated. At low heat treatment temperature, a strong p-doping effect from Au(3+) ions to CNTs due to a large difference in reduction potential between them is dominant. However at higher temperature, the gold species are thermally reduced, and thermally induced CNT-Cl finally occurs by the decomposition reaction of AuCl(3). Thus, in the AuCl(3)-doped SWCNTs treated at higher temperature, the p-type doping effect is suppressed and an n-type property from CNT-Cl is thermally induced. Thermal conversion of the majority carrier type of AuCl(3)-doped SWNTs is systematically investigated by combining various optical and electrical tools.

  5. 51.5 W monolithic single frequency 1.97 μm Tm-doped fiber amplifier

    Institute of Scientific and Technical Information of China (English)

    Xiong; Wang; Pu; Zhou; Xiaolin; Wang; Hu; Xiao; Lei; Si

    2013-01-01

    We demonstrate a monolithic single frequency Tm-doped fiber amplifier with output power of 51.5 W. A single frequency fiber laser at 1.97 μm is amplified by a cascaded master oscillator power amplifier(MOPA) system with all-fiber configuration. The optical-to-optical conversion efficiency of the main fiber amplifier is 45%. No amplified spontaneous emission(ASE) or stimulated Brillouin scattering(SBS) effect is observed in the fiber amplifier. The output power could be further scaled by launching more pump power.

  6. Pulsed ytterbium-doped fibre laser with a combined modulator based on single-wall carbon nanotubes

    Science.gov (United States)

    Khudyakov, D. V.; Borodkin, A. A.; Lobach, A. S.; Vartapetov, S. K.

    2015-09-01

    This paper describes an all-normal-dispersion pulsed ytterbium-doped fibre ring laser mode-locked by a nonlinear combined modulator based on single-wall carbon nanotubes. We have demonstrated 1.7-ps pulse generation at 1.04 μm with a repetition rate of 35.6 MHz. At the laser output, the pulses were compressed to 180 fs. We have examined an intracavity nonlinear modulator which utilises nonlinear polarisation ellipse rotation in conjunction with a saturable absorber in the form of a polymer-matrix composite film containing single-wall carbon nanotubes.

  7. Pulsed ytterbium-doped fibre laser with a combined modulator based on single-wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Khudyakov, D V; Borodkin, A A; Vartapetov, S K [Physics Instrumentation Center, A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Troitsk, Moscow Region (Russian Federation); Lobach, A S [Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region (Russian Federation)

    2015-09-30

    This paper describes an all-normal-dispersion pulsed ytterbium-doped fibre ring laser mode-locked by a nonlinear combined modulator based on single-wall carbon nanotubes. We have demonstrated 1.7-ps pulse generation at 1.04 μm with a repetition rate of 35.6 MHz. At the laser output, the pulses were compressed to 180 fs. We have examined an intracavity nonlinear modulator which utilises nonlinear polarisation ellipse rotation in conjunction with a saturable absorber in the form of a polymer-matrix composite film containing single-wall carbon nanotubes. (lasers)

  8. Optical and electrical characteristics of pure and doped potassium hydrogen tartrate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Quasim, I; Khosa, S K; Kotru, P N [Crystal Growth and Materials Research Laboratory, Department of Physics and Electronics, University of Jammu, Jammu-180006- India (India); Firdous, A, E-mail: pnkotru@rediffmail.co [Department of Physics, National Institute of Technology, Srinagar - 190006, Jammu and Kashmir (India)

    2009-08-07

    The optical and electrical characteristics of pure, sodium- and lithium-doped potassium hydrogen tartrate crystals grown by the gel technique are reported. An optical absorption study conducted in the UV-Vis range of 200-800 nm reveals the transparency of these crystals in the entire visible range but not in the ultraviolet range. The optical band gap of pure potassium hydrogen tartrate crystals is found to be dependent on doping by Na or Li ions. The non-linear optical behaviour of these crystals is reported and explained. The electrical properties of pure and doped potassium hydrogen tartrate crystals are studied by measuring electrical resistivity from 80 to 300 K. It is shown that while pure potassium hydrogen tartrate crystal is an insulator at room temperature (300 K), doping by Na or Li ions makes it a semiconductor. The results have been explained in terms of the variable range hopping model.

  9. Spectroscopy of Charge Carriers and Traps in Field-Doped Single Crystal Organic Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaoyang [Columbia Univ., New York, NY (United States); Frisbie, Daniel [Univ. of Minnesota, Minneapolis, MN (United States)

    2017-03-31

    The proposed research aims to achieve quantitative, molecular level understanding of charge carriers and traps in field-doped crystalline organic semiconductors via in situ linear and nonlinear optical spectroscopy, in conjunction with transport measurements and molecular/crystal engineering.

  10. Optical Absorption Measurements on Nitrogen-doped 6H-SiC Single Crystals

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    6H-SiC bulk crystals have been prepared by sublimation method in an inductively heated growth reactor. The effect of nitrogen doping on absorption for 6H-SiC was investigated. The absorption measurement based on optical method is a non-destructive and non-contact method. The band-gap narrowing with higher doping concentration was observed.For n-type doping below band-gap absorption band at 623 nm for 6H-SiC was observed. The peak intensity of the absorption band increased with increasing charge carrier concentration obtained from Hall measurements. It is also found that the nitrogen doping level decreased in the radial direction and it was the highest at the beginning of growth.

  11. Powerful greenhouse gas nitrous oxide adsorption onto intrinsic and Pd doped Single walled carbon nanotube

    Science.gov (United States)

    Yoosefian, Mehdi

    2017-01-01

    Density functional studies on the adsorption behavior of nitrous oxide (N2O) onto intrinsic carbon nanotube (CNT) and Pd-doped (5,5) single-walled carbon nanotube (Pd-CNT) have been reported. Introduction of Pd dopant facilitates in adsorption of N2O on the otherwise inert nanotube as observed from the adsorption energies and global reactivity descriptor values. Among three adsorption features of N2O onto CNT, the horizontal adsorption with Eads = -0.16 eV exhibits higher adsorption energy. On the other hand the Pd-CNT exhibit strong affinity toward gas molecule and would cause a huge increase in N2O adsorption energies. Chemical and electronic properties of CNT and Pd-CNT in the absence and presence of N2O were investigated. Adsorption of N2O gas molecule would affect the electronic conductance of Pd-CNT that can serve as a signal of gas sensors and the increased energy gaps demonstrate the formation of more stable systems. The atoms in molecules (AIM) theory and the natural bond orbital (NBO) calculations were performed to get more details about the nature and charge transfers in intermolecular interactions within adsorption process. As a final point, the density of states (DOSs) calculations was achieved to confirm previous results. According to our results, intrinsic CNT cannot act as a suitable adsorbent while Pd-CNT can be introduced as novel detectable complex for designing high sensitive, fast response and high efficient carbon nanotube based gas sensor to detect N2O gas as an air pollutant. Our results could provide helpful information for the design and fabrication of the N2O sensors.

  12. Structural characterization of H plasma-doped ZnO single crystals by Hall measurements and photoluminescence studies

    Energy Technology Data Exchange (ETDEWEB)

    Anwand, Wolfgang; Brauer, Gerhard; Cowan, Thomas E. [Institut fuer Strahlenphysik, Forschungszentrum Dresden-Rossendorf, PO Box 510 119, 01314 Dresden (Germany); Heera, Viton; Schmidt, Heidemarie; Skorupa, Wolfgang [Institut fuer Ionenstrahlphysik und Materialforschung, Forschungszentrum Dresden-Rossendorf, PO Box 510 119, 01314 Dresden (Germany); Wenckstern, Holger von; Brandt, Matthias; Benndorf, Gabriele; Grundmann, Marius [Fakultaet fuer Physik und Geowissenschaften, Institut fuer Experimentelle Physik II, Universitaet Leipzig, Linnestr. 5, 04103 Leipzig (Germany)

    2010-11-15

    Nominally undoped, hydrothermally grown ZnO single crystals have been investigated prior to and after doping in remote H plasma. Characterizations have been made by temperature-dependent Hall effect (TDH) and low temperature photoluminescence measurements. The H content before and after the doping has been determined using nuclear reaction analysis and is compared to the density of shallow donors derived from the TDH measurements. The electrical properties of the as-grown ZnO single crystals are found to differ significantly. This is ascribed to the density ratio of shallow donors and compensating acceptors. PL measurements showed that Al{sub Zn}, Ga{sub Zn}, and interstitial zinc (Zn{sub i}) are prominent shallow donors in the as-grown samples. Remote H plasma treatment produced a metallic conducting near-surface layer thus masking the electrical properties of the bulk. The electrical properties of the investigated samples are very similar after the treatment, independent of the as-grown state, because the density of shallow donors far exceeds that of compensating acceptors in the affected near-surface region. The maximum of the broad near-bandedge emission is found to be located at 3.3595 eV due to the high doping density. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Growth and studies of pure and potassium iodide-doped zinc tris-thiourea sulphate (ZTS) single crystals

    Science.gov (United States)

    Krishnan, C.; Selvarajan, P.; Freeda, T. H.

    2008-12-01

    Single crystals of pure and potassium iodide (KI)-doped Zinc Tris-thiourea Sulphate (ZTS) were grown from aqueous solutions by slow evaporation technique. The grown crystals have been subjected to single crystal X-ray diffraction to determine the unit cell dimensions. The grown crystals were also characterized by recording the powder X-ray diffraction patterns and by identifying the diffracting planes. The Fourier Transform Infrared (FT-IR) spectra have been recorded in the range 400-4500 cm -1. Second harmonic generation (SHG) for the materials of this work was confirmed using Nd:YAG laser. The UV-visible spectra show that the grown crystals have wide optical transparency in the entire visible region. The Thermogravimetric/Differential Thermal Analyses (TG/DTA) thermograms reveal that the materials have good thermal stability. Atomic absorption study reveals the presence of potassium in the doped f crystals. The electrical measurements were made in the temperature range 40-130 °C along c-direction of the grown crystals. The dielectric studies show that there may be a ferroelectric transition at 50 °C for both pure and KI-doped ZTS crystals. DC conductivity for both the samples is found to be increasing with increase in temperature. Activation energy values were also determined for both AC and DC conduction processes in the samples.

  14. Influence of MgSO{sub 4} doping on the properties of zinc tris–thiourea sulphate (ZTS) single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Selvapandiyan, M., E-mail: mselvapandiyan@rediffmail.com [Department of Physics, Sri Vidya Mandir Arts and Science College, Uthangarai 635 207 (India); Arumugam, J. [Department of Physics, Sri Vidya Mandir Arts and Science College, Uthangarai 635 207 (India); Sundaramoorthi, P. [Department of Physics, Thiruvalluvar Government Arts College, Rasipuram 637 401 (India); Sudhakar, S. [CSIR–National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110 012 (India)

    2013-12-15

    Highlights: •The influence of MgSO{sub 4} doping on the properties of ZTS single crystals grown at room temperature. •Thermal stability of the crystals increased with incorporation of Mg atom. •Energy band gap was estimated from UV–vis spectra. •ZTS is a potential material for frequency conversion. •Both pure and doped ZTS crystals are belonging to category of typical insulating materials. -- Abstract: The influence of MgSO{sub 4} doping on the properties of zinc tris–thiourea sulphate single crystals grown at room temperature by slow evaporation solution growth technique was studied. Powder XRD analysis confirmed the orthorhombic crystal structure with noncentrosymmetric space group Pca2{sub 1}. The mechanical properties of the grown crystals were analysed by Vicker’s microhardness method. Functional groups present in the materials were identified by FTIR spectral analysis in the range between 4000 and 400 cm{sup −1}. The UV–Vis spectrum indicates that the UV cut-off wavelength of the crystals has less than 297 nm. The thermal stability of the grown crystals was determined with the aid of thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Second order nonlinear optical behaviour of the grown crystals have been confirmed by Kurtz powder second harmonic generation (SHG) test.

  15. Evidence for interface superconductivity in rare-earth doped CaFe2As2 single crystals

    Science.gov (United States)

    Lv, Bing; Deng, L. Z.; Wei, F. Y.; Xue, Y. Y.; Chu, C. W.

    2014-03-01

    To unravel to the mysterious non-bulk superconductivity up to 49K observed in rare-earth (R =La, Ce, Pr and Nd) doped CaFe2As2 single-crystals whose Tc is higher than that of any known compounds consisting of one or more of its constituent elements of R, Ca, Fe, and As at ambient or under pressures, systematic magnetic, compositional and structural have carried out on different rare-earth-doped (Ca1-xRx) Fe2As2 samples. We have detected extremely large magnetic anisotropy, doping-level independent Tc, unexpected superparamagnetic clusters associated with As vacancies and their close correlation with the superconducting volume fraction, the existence of mesoscopic-2D structures and Josephson-junction arrays in this system. These observations lead us to conjecture that the Tc enhancement may be associated with naturally occurring chemical interfaces and thus provided evidence for the possible interface-enhanced Tc in naturally-grown single crystals of Fe-based superconductors.

  16. Growth and optical properties of ZnWO4 single crystals pure and doped with Ca and Eu

    Science.gov (United States)

    Kowalski, Z.; Kaczmarek, S. M.; Berkowski, M.; Głowacki, M.; Zhydachevskii, Y. A.; Suchocki, A.

    2017-01-01

    In frames of this work a series of ZnWO4 single crystals, pure and doped with either Ca (5 at%) or Ca (4 at%) and Eu (1 at%), has been grown by the Czochralski method. Phase analysis and structural refinement was performed X-ray powder diffraction and the powder diffraction and the patterns were analyzed by the Rietveld refinement method to analyze the lattice parameters of the crystal structure. Additionally, the absorbance, photoluminescence emission (PL) and photoluminescence excitation (PLE) and EPR spectra were measured and compared to investigate influence of Ca and Eu co-doping on optical properties of the obtained crystals. Furthermore the optical band-gap of the crystals has been calculated. The crystal structure of all mentioned ZnWO4 samples has also discussed in the scope of environment symmetry and possible sites of dopant ions.

  17. Stabilized and tunable single-longitudinal-mode erbium fiber laser employing ytterbium-doped fiber based interference filter

    Science.gov (United States)

    Yeh, Chien-Hung; Tsai, Ning; Zhuang, Yuan-Hong; Chow, Chi-Wai; Chen, Jing-Heng

    2017-02-01

    In this demonstration, to achieve stabilized and wavelength-selectable single-longitudinal-mode (SLM) erbium-doped fiber (EDF) laser, a short length of ytterbium-doped fiber (YDF) is utilized to serve as a spatial multi-mode interference (MMI) inside a fiber cavity for suppressing multi-longitudinal-mode (MLM) significantly. In the measurement, the output powers and optical signal to noise ratios (OSNRs) of proposed EDF ring laser are measured between -9.85 and -5.71 dBm; and 38.03 and 47.95 dB, respectively, in the tuning range of 1530.0-1560.0 nm. In addition, the output SLM and stability performance are also analyzed and discussed experimentally.

  18. Spectroscopic Studies of Doping and Charge Transfer in Single Walled Carbon Nanotubes and Lead Sulfide Quantum Dots

    Science.gov (United States)

    Haugen, Neale O.

    The use of single wall carbon nanotubes (SW-CNTs) in solar photovoltaic (PV) devices is a relatively new, but quickly growing field. SW-CNTs have found application as transparent front contacts, and high work function back contacts in thin film solar PV. For the utility of SW-CNTs to be fully realized, however, controllable and stable doping as well as long term protection from doping must be achieved. Spectroscopic techniques facilitate detailed investigations of the intrinsic and variable properties of semiconductor materials without the issues of contact deposition and the possibility of sample contamination. Detailed spectroscopic analysis of the doping induced changes in the optical properties of SW-CNTs has revealed normally hidden excited state transitions in large diameter single walled carbon nanotubes for the first time. Spectroscopic monitoring of the degree of doping in SW-CNTs made possible studies of the dopant complex desorption and readsorption energies and kinetics. The long term protection from doping of SW-CNTs exposed to ambient laboratory conditions was achieved as a result of the more detailed understanding of the doping processes and mechanisms yielded by these spectroscopic studies. The application of SW-CNTs to other roles in solar PV devices was another goal of this research. Efficient collection of photogenerated charge carriers in semiconductor quantum dot (QD) based solar photovoltaic devices has been limited primarily by the poor transport properties and high density of recombination sites in the QD films. Coupling semiconductor QDs to nanomaterials with better transport properties is one potential solution to the poor transport within the QD films. This portion of the work investigated the possibility of charge transfer occurring in nano-heterostructures (NHSs) of PbS QDs and SW-CNTs produced through spontaneous self-assembly in solution. Electronic coupling in the form of charge transfer from the QDs to the SW-CNTs is unambiguously

  19. Photoelectrochemical water splitting on chromium-doped titanium dioxide nanotube photoanodes prepared by single-step anodizing

    Energy Technology Data Exchange (ETDEWEB)

    Momeni, Mohamad Mohsen, E-mail: mm.momeni@cc.iut.ac.ir; Ghayeb, Yousef

    2015-07-15

    Graphical abstract: Current–potential curves with chopped light measured in 1 M NaOH with a scan rate of 5 mV s{sup −1} for the different samples. - Highlights: • Cr-doped TiO{sub 2} nanotube layers (Cr–TiO{sub 2}NTs) were synthesized by anodizing of titanium in a single-step process. • Photoelectrochemical water splitting of Cr–TiO{sub 2}NTs is higher than that of pure TiO{sub 2} nanotubes (TiO{sub 2}NTs). • Quantity effect of chromium in these composite for photoelectrochemical water splitting is investigated. • Maximum hydrogen production of 37 μL/cm{sup 2} after 240 min is obtained. - Abstract: Cr-doped TiO{sub 2} nanotubes (Cr–TiO{sub 2}NTs) with different amounts of chromium were obtained directly by the electrochemical anodic oxidation of titanium foils in a single-step process using potassium chromate as the chromium source. The effects of chromium amount in anodizing solution on the morphologies, structure, photoabsorption and photoelectrochemical water splitting of the TiO{sub 2} nanotube array film were investigated. Diffuse reflectance spectra showed an increase in the visible absorption relative to undoped TiO{sub 2}NTs. The photoelectrochemical performance was examined under visible irradiation in 1 M NaOH electrolyte. Photo-electrochemical characterization shows that chromium doping efficiently enhances the photo-catalytic water splitting performance of Cr-doped TiO{sub 2} nanotube samples. The sample (Cr–TiO{sub 2}NTs-1) exhibited better photo-catalytic activity than the undoped TiO{sub 2}NTs and Cr–TiO{sub 2}NTs fabricated using other chromium concentrations. This can be attributed to the effective separation of photogenerated electron–hole upon the substitutional introduction of appropriate Cr amount in to the TiO{sub 2} nanotube structure.

  20. Preparation and optical properties of GaSb nanoparticles embedded in SiO2 composite films

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The composite films of GaSb nanoparticles embedded in SiO2 matrices were fabricated by radio-frequency magnetron co-sputtering. Transmission electron microscope and X-ray diffraction pattern indicate that the GaSb nanoparticles were uniformly dispersed in SiO2 matrices. Room temperature transmission spectra exhibit a blue shift of about 2.73 eV. The blue shift increases with decreasing size of GaSb nanoparticles, suggesting the existence of quantum size effects. Room temperature Raman spectra show that there is a larger Raman peak red shift and broadening of the composite films than that of bulk GaSb. This phenomenon is explained by photon confinement effect and tensile stress effect.

  1. Monolithic all-fiber repetition-rate tunable gain-switched single-frequency Yb-doped fiber laser.

    Science.gov (United States)

    Hou, Yubin; Zhang, Qian; Qi, Shuxian; Feng, Xian; Wang, Pu

    2016-12-12

    We report a monolithic gain-switched single-frequency Yb-doped fiber laser with widely tunable repetition rate. The single-frequency laser operation is realized by using an Yb-doped distributed Bragg reflection (DBR) fiber cavity, which is pumped by a commercial-available laser diode (LD) at 974 nm. The LD is electronically modulated by the driving current and the diode output contains both continuous wave (CW) and pulsed components. The CW component is set just below the threshold of the single-frequency fiber laser for reducing the requirement of the pump pulse energy. Above the threshold, the gain-switched oscillation is trigged by the pulsed component of the diode. Single-frequency pulsed laser output is achieved at 1.063 μm with a pulse duration of ~150 ns and a linewidth of 14 MHz. The repetition rate of the laser output can be tuned between 10 kHz and 400 kHz by tuning the electronic trigger signal. This kind of lasers shows potential for the applications in the area of coherent LIDAR etc.

  2. Synthesis and investigation of BiSbTeSe single crystal doped with Zr produced using Bridgman method

    Directory of Open Access Journals (Sweden)

    Emina Požega

    2017-09-01

    Full Text Available Single crystal ingot of BiSbTeSe doped with Zr was synthesized using Bridgman method. Energy dispersive spectrometry (EDS analysis was used to determine chemical composition of studied samples as well as to check and confirm samples homogeneity. X-ray diffraction (XRD measurements proved that obtained crystal ingot is a single cristal and confirms Bi2Te3-type compound with orientation (00l of single crystal. Melting point was determined by dilatometrically measured shrinkage during heating. Mobility, concentration, resistivity/conductivity and Hall coefficient of BiSbTeSe doped with Zr samples were determined using a Hall Effect measurement system based on the Van der Pauw method. The Hall Effect was measured at room temperature with an applied magnetic field strength of 0.37 T at different current intensities. The measured ingot samples were cut and cleaved from different regions. Calculated results obtained using a Hall Effect measurement system (Ecopia, HMS-3000 were mutually compared for cleaved and cut samples. Changing of transport and electrical parameters with the increase of the current intensity was also monitored.The results confirmed that electrical and transport properties of single crystal depend on crystal growth direction and mobility was also significantly improved in comparison with theoretical value of Bi2Te3 and available literature data.

  3. Growth and characterization of air annealing Tb-doped YAG:Ce single crystal for white-light-emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Maogao [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China); Xiang, Weidong, E-mail: xiangweidong001@126.com [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China); Liang, Xiaojuan [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China); Zhong, Jiasong; Chen, Daqin [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Huang, Jun; Gu, Guorui; Yang, Cheng; Xiang, Run [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China)

    2015-08-05

    Highlights: • We report preparation of transparent Ce,Tb:YAG single crystal by Czochralski method. • The effect of annealing on Ce,Tb:YAG single crystal had been investigated. • The Ce,Tb:YAG single crystal after annealing exhibited better optical performance. • The Ce,Tb:YAG single crystal could be used as an ideal candidate for WLED. - Abstract: We report the preparation of transparent Ce and Tb co-doped Y{sub 3}Al{sub 5}O{sub 12} single crystal by the Czochralski method. The characterization of the resulting single crystal was accomplished by using X-ray powder diffractometer, scanning electron microscopy and energy dispersive X-ray spectroscopy. Absorption peak of the single crystal at about 460 nm has been obtained from ultraviolet–visible absorption spectrometer and their intensity is changed with different annealing condition. Its optical properties also have been investigated using fluorescence spectrometer. What’s more, its photoelectric parameters were studied by LED fast spectrometer. The constructed single crystal based white-light-emitting diode exhibits a high luminous efficiency of 140.89 lm/W, and a correlated color temperature of 4176 K as well as a color rendering index of 56.7, which reveal the prominent feasibility of the present single crystal material in white-light-emitting diode application.

  4. Transport properties of boron-doped single-walled silicon carbide nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Y.T. [Key laboratory of Ministry of Education for Wide Band Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi' an 710071 (China); Ding, R.X., E-mail: rx_ding@163.co [Key laboratory of Ministry of Education for Wide Band Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi' an 710071 (China); Song, J.X. [Key laboratory of Ministry of Education for Wide Band Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi' an 710071 (China); School of Electronic Engineering, Xi' an Shiyou University, Xi' an 710075 (China)

    2011-01-15

    The doped boron (B) atom in silicon carbide nanotube (SiCNT) can substitute carbon or silicon atom, forming two different structures. The transport properties of both B-doped SiCNT structures are investigated by the method combined non-equilibrium Green's function with density functional theory (DFT). As the bias ranging from 0.8 to 1.0 V, the negative differential resistance (NDR) effect occurs, which is derived from the great difficulty for electrons tunneling from one electrode to another with the increasing of localization of molecular orbital. The high similar transport properties of both B-doped SiCNT indicate that boron is a suitable impurity for fabricating nano-scale SiCNT electronic devices.

  5. A method for adjusting nitrogen doping amount in anatase TiO2 single crystals with well-faceted shape and micron size

    Science.gov (United States)

    Shen, Shaishai; Niu, Jinan; Shen, Shitai; Zhou, Lu; Chen, Hui; Zhang, Shenghui; Ling, Yihan; Liu, Zhangsheng; Feng, Peizhong; Ou, Xuemei; Qiang, Yinghuai

    2017-08-01

    A new approach was developed to adjust N doping amount in anatase single crystals with well-faceted shape and micron size, using a novel liquid dopant from the chemical recycling of the wasted supernatant solution in our previous experiments. The dependence of microstructure and property evolution on N doping amount was investigated systematically. The results show that all prepared N-doped samples are pure anatase with the morphology of truncated octahedral bipyramid including both {001} and {110} reactive facets. With the increase of N doping, the single crystals become angular and the thickness decreases, the aggregation of crystals increases, the photo-absorption capacity in visible region is enhanced and the absorption band edge is gradually red-shifted. The photocatalytic efficiency of the samples for the degradation of methylene blue (MB) or phenol under visible light irradiation gradually increases, but when the volume of dopant increases to 2 ml, the photoactivity of TiO2 decreases. The optimal volume of N dopant is 1 ml and A(6:1) shows the highest photodegradation rate. The effective N doping of wasted supernatant is mainly due to the previously formation of Ti-N linkage, and hence a N doping mechanism is proposed. This work provides a new opportunity for in-situ modification of anatase single crystals with well-faceted shape and micron size, and hence, a basis for development of some advanced materials, for example porous single crystals.

  6. Electro-optic coefficients r13 and r33 of singly Er3+-doped and In3+/Er3+-codoped LiNbO3 crystals

    Science.gov (United States)

    Du, Wan-Ying; Zhang, Pei; Zhang, Zi-Bo; Ren, Shuai; Wong, Wing-Han; Yu, Dao-Yin; Pun, Edwin Yue-Bun; Zhang, De-Long

    2017-01-01

    A series of singly Er3+-doped and doubly In3+/Er3+-doped congruent LiNbO3 crystals were grown by Czochralski method. The Er3+-only doped crystals were grown from the growth melts doped with different concentrations of Er2O3 up to 1 mol%, and the In3+/Er3+-codoped crystals from the melts doped with fixed 0.5 mol% Er2O3 while varied In2O3 contents of 0.0, 0.5, 1.0 and 1.5 mol%. The electro-optic coefficients γ13 and γ33 of these doped crystals were measured by Mach-Zehnder interferometry. Both clamped and unclamped coefficients were measured. The results show that both γ13 and γ33 reveal small Er3+ and In3+ doping effects. In the Er3+-only doping case, γ13 almost does not change within the experimental error of 3%, γ33 reveals a degradation tendency with a rise in Er3+ doping level, but the degradation is no more than 5% in the considered Er3+ concentration range 0-3.0 mol% (in crystal). In the In3+/Er3+-codoping case, both γ13 and γ33 can be regarded as unchanged in the studied In3+ concentration range of 0-2.6 mol% (in crystal) within the error. The small Er3+ or In3+ doping effect is desired in light of electro-optic application of these crystals. It is qualitatively explained on the basis of EO coefficient model and doping effect on defect structure of LiNbO3.

  7. Atomistic description of electron beam damage in nitrogen-doped graphene and single-walled carbon nanotubes.

    Science.gov (United States)

    Susi, Toma; Kotakoski, Jani; Arenal, Raul; Kurasch, Simon; Jiang, Hua; Skakalova, Viera; Stephan, Odile; Krasheninnikov, Arkady V; Kauppinen, Esko I; Kaiser, Ute; Meyer, Jannik C

    2012-10-23

    By combining ab initio simulations with state-of-the-art electron microscopy and electron energy loss spectroscopy, we study the mechanism of electron beam damage in nitrogen-doped graphene and carbon nanotubes. Our results show that the incorporation of nitrogen atoms results in noticeable knock-on damage in these structures already at an acceleration voltage of 80 kV, at which essentially no damage is created in pristine structures at corresponding doses. Contrary to an early estimate predicting rapid destruction via sputtering of the nitrogen atoms, in the case of substitutional doping, damage is initiated by displacement of carbon atoms neighboring the nitrogen dopant, leading to the conversion of substitutional dopant sites into pyridinic ones. Although such events are relatively rare at 80 kV, they become significant at higher voltages typically used in electron energy loss spectroscopy studies. Correspondingly, we measured an energy loss spectrum time series at 100 kV that provides direct evidence for such conversions in nitrogen-doped single-walled carbon nanotubes, in excellent agreement with our theoretical prediction. Besides providing an improved understanding of the irradiation stability of these structures, we show that structural changes cannot be neglected in their characterization employing high-energy electrons.

  8. Doping effects on trimerization and magnetoelectric coupling of single crystal multiferroic (Y,Lu)MnO3

    Science.gov (United States)

    Choi, Seongil; Sim, Hasung; Kang, Soonmin; Choi, Ki-Young; Park, Je-Geun

    2017-03-01

    Hexagonal RMnO3 is a multiferroic compound with a giant spin–lattice coupling at an antiferromagnetic transition temperature, Lee et al (2008 Nature 451 805). Despite extensive studies over the past two decades, the origin and underlying microscopic mechanism of strong spin–lattice coupling remain very much elusive. In this study, we have tried to address this problem by measuring the thermal expansion and dielectric constant of doped single crystals Y1‑x Lu x MnO3 where x  =  0, 0.25, 0.5, 0.75, and 1.0. From these measurements, we confirm that there is a progressive change in the physical properties with doping. At the same time, all our samples exhibit clear anomalies at T N, even in the samples where x  =  0.5 and 0.75. This is opposed to some earlier ideas, which suggests an unusual doping dependence of the anomaly. Our work reveals yet another interesting facet of the spin–lattice coupling issue in hexagonal RMnO3.

  9. Doping-dependent critical current properties in K, Co, and P-doped BaF e2A s2 single crystals

    Science.gov (United States)

    Ishida, Shigeyuki; Song, Dongjoon; Ogino, Hiraku; Iyo, Akira; Eisaki, Hiroshi; Nakajima, Masamichi; Shimoyama, Jun-ichi; Eisterer, Michael

    2017-01-01

    In order to establish the doping dependence of the critical current properties in the iron-based superconductors, the in-plane critical current density Jc of BaF e2A s2 -based superconductors B a1 -xKxF e2A s2 (K-Ba122), Ba (F e1 -xC ox)2A s2 (Co-Ba122), and BaF e2(As1-xPx) 2 (P-Ba122) in a wide range of doping concentration x was investigated by means of magnetization hysteresis loop (MHL) measurements on single-crystal samples. Depending on the dopant elements and their concentration, Jc exhibits a variety of magnetic-field H and temperature T dependences. (1) In the case of K-Ba122, the MHL of the underdoped samples (x ≤0.33 ) exhibits a second magnetization peak (SMP), which sustains high Jc at high H and high T , exceeding 105A /c m2 at T = 25 K and μ0H = 6 T for x = 0.30 . On the other hand, the SMP is missing in the optimally (x ˜ 0.36 -0.40 ) and overdoped (x ˜ 0.50 ) samples and consequently Jc rapidly decreases by more than one order of magnitude, although the change in Tc is within a few K. (2) For Co-Ba122, the SMP is always present over the entire superconducting (SC) dome from the underdoped (x ˜ 0.05 ) to the overdoped (x ˜ 0.12 ) region. However, the magnitude of Jc significantly changes with x , exhibiting a sharp maximum at x ˜ 0.057 , which is a slightly underdoped composition for Co-Ba122. (3) For P-Ba122, the highest Jc is attained at x = 0.30 , corresponding to the highest Tc composition. For the overdoped samples, the MHL is characterized by a SMP located close to the irreversibility field Hirr. Common to the three doping variations, Jc becomes highest at the underdoping side of the SC dome near the phase boundary between the SC phase and the antiferromagnetic-orthorhombic (AFO) phase. Also, the peak appears in a narrow range of doping, distinct from the Tc dome with a broad maximum. These similarities in the three cases indicate that the observed doping dependence of Jc is intrinsic to the BaF e2A s2 -based superconductors. The

  10. Single- and dual-wavelength switchable erbium-doped fiber ring laser based on intracavity polarization selective tilted fiber gratings.

    Science.gov (United States)

    Mou, Chengbo; Saffari, Pouneh; Fu, Hongyan; Zhou, Kaiming; Zhang, Lin; Bennion, Ian

    2009-06-20

    We propose and demonstrate a single- and dual-wavelength switchable erbium-doped fiber laser (EDFL) by utilizing intracavity polarization selective filters based on tilted fiber gratings (TFGs). In the cavity, one 45 degrees TFG functions as an in-fiber polarizer and the other 77 degrees TFG is used as a fiber polarization dependent loss (PDL) filter. The combined polarization effect from these two TFGs enables the laser to switch between the single- and the dual-wavelength operation with a single-polarization state at room temperature. The laser output at each wavelength shows an optical signal-to-noise ratio (OSNR) of >60 dB, a side mode suppression ratio (SMSR) of >50 dB, and a polarization extinction ratio of approximately 35 dB. The proposed EDFL can give stable output under laboratory conditions.

  11. High-resolution temperature sensor through measuring the frequency shift of single-frequency Erbium-doped fiber ring laser

    Science.gov (United States)

    Zhang, Haiwei; Shi, Wei; Duan, Liangcheng; Fu, Shijie; Sheng, Quan; Yao, Jianquan

    2017-02-01

    We propose a principle to achieve a high-resolution temperature sensor through measuring the central frequency shift in the single-frequency Erbium-doped fiber ring laser induced by the thermal drift via the optical heterodyne spectroscopy method. We achieve a temperature sensor with a sensitivity about 9.7 pm/°C and verify the detection accuracy through an experiment. Due to the narrow linewidth of the output singlefrequency signal and the high accuracy of the optical heterodyne spectroscopy method in measuring the frequency shift in the single-frequency ring laser, the temperature sensor can be employed to resolve a temperature drift up to 5.5×10-6 °C theoretically when the single-frequency ring laser has a linewidth of 1 kHz and 10-kHz frequency shift is achieved from the heterodyne spectra.

  12. MoS2 saturable absorber for single frequency oscillation of highly Yb-doped fiber laser

    Institute of Scientific and Technical Information of China (English)

    Baole Lu; Limei Yuan; Xinyuan Qi; Lei Hou; Bo Sun; Pan Fu; Jintao Bai

    2016-01-01

    In this Letter,a single-frequency fiber laser using a molybdenum disulfide (MoS2) thin film as a saturable absorber is demonstrated.We use a short length of highly Yb-doped fiber as the gain medium and a fiber ferrule with MoS2 film adhered to it by index matching gel (IMG) that acts as the saturable absorber.The saturable absorber can be used to discriminate and select the single longitudinal modes.The maximum output power of the single-frequency fiber laser is 15.3 mW at a pump power of 130 mW and the slope efficiency is 15.3%.The optical signal-to-noise ratio and the laser linewidths are ~60 dB and 5.89 kHz,respectively.

  13. Effect of doping different dyes in Alq{sub 3} on electroluminescence and morphology of layers using single furnace method

    Energy Technology Data Exchange (ETDEWEB)

    Janghouri, Mohammad [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran 1983963113 (Iran, Islamic Republic of); Mohajerani, Ezeddin, E-mail: e-mohajerani@sbu.ac.ir [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran 1983963113 (Iran, Islamic Republic of); Khabazi, Amir; Abedi, Zahra; Razavi, Hosein [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran 1983963113 (Iran, Islamic Republic of)

    2013-08-15

    A method for obtaining red emission from organic-light emitting diodes has been developed by dissolving red and green dyes in a common solvent and thermally evaporating the mixture in a single furnace. Devices with fundamental structure of ITO/PEDOT: PSS (55 nm)/PVK (90 nm)/Alq{sub 3}: porphyrin (50 nm)/Al (180 nm) were fabricated. The emission properties and chromaticity coordinates of the devices depend on the energy transfer between the emission of host and the absorption of the dyes. TPP and TPPNO{sub 2} doped in Alq{sub 3} showed more pure red emission compared to 3,4-TPP, and PdTPP doped in Alq{sub 3} based devices. AFM measurement showed that the morphology of the layers depends on the type of dyes and uniform mixing of porphyrin compounds and Alq{sub 3} at constant deposition rate. It is shown that this new method is a promising candidate for fabrication of low cost red OLEDs at more homogeneous layer. -- Highlights: ► We fabricated light emitting layer by dissolving dyes in common solvent followed by thermal evaporation of dyes. ► Achieving red emissions with a single furnace. ► We employed single furnace for the first time to control the emitting color of OLED. ► The morphology of the films depends on the homogeneity and type of dyes. ► Low cost, homogeneity and effective energy transfer are advantages of this method.

  14. Multiple Schottky Barrier-Limited Field-Effect Transistors on a Single Si Nanowire with an Intrinsic Doping Gradient.

    Science.gov (United States)

    Barreda, Jorge L; Keiper, Timothy D; Zhang, Mei; Xiong, Peng

    2017-03-09

    In comparison to conventional (channel-limited) field-effect transistors (FETs), Schottky barrier-limited FETs possess some unique characteristics which make them attractive candidates for some electronic and sensing applications. Consequently, modulation of the nano Schottky barrier at a metal-semiconductor interface promises higher performance for chemical and biomolecular sensor applications when compared to conventional FETs with Ohmic contacts. However, the fabrication and optimization of devices with a combination of ideal Ohmic and Schottky contacts as the source and drain respectively present many challenges. We address this issue by utilizing Si nanowires (NWs) synthesized by a chemical vapor deposition process which yields a pronounced doping gradient along the length of the NWs. Devices with a series of metal contacts on a single Si NW are fabricated in a single lithography and metallization process. The graded doping profile of the NW is manifested in monotonic increases in the channel and junction resistances and variation of the nature of the contacts from Ohmic to Schottky of increasing effective barrier height along the NW. Hence multiple single Schottky junction-limited FETs with extreme asymmetry and high reproducibility are obtained on an individual NW. A definitive correlation between increasing Schottky-barrier height and enhanced gate modulation is revealed. Having access to systematically varying Schottky barrier contacts on the same NW device provides an ideal platform for identifying optimal device characteristics for sensing and electronic applications.

  15. Fabricating large two-dimensional single colloidal crystals by doping with active particles

    NARCIS (Netherlands)

    van der Meer, B; Filion, L; Dijkstra, M

    2016-01-01

    Using simulations we explore the behaviour of two-dimensional colloidal (poly)crystals doped with active particles. We show that these active dopants can provide an elegant new route to removing grain boundaries in polycrystals. Specifically, we show that active dopants both generate and are attract

  16. Single-mode ytterbium-doped large-mode-area photonic bandgap rod fiber amplifier

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Scolari, Lara; Broeng, Jes

    2011-01-01

    bandgap structure. The structure allows resonant coupling of higher-order modes from the core and acts as a spatially Distributed Mode Filter (DMF). With this approach, we demonstrate passive SM performance in an only ~50cm long and straight ytterbium-doped rod fiber. The amplifier has a mode field...

  17. Scintillation characteristics of undoped and Cu+-doped Li2B4O7 single crystals

    CERN Document Server

    Kobayashi, Masaaki; Senguttuvan, Nachimuthu

    2015-01-01

    Scintillation characteristics of undoped and Cu+-doped lithium tetraborate Li2B4O7 (LTB) were studied including optical transmittance, photoluminescence, radioluminescence for X- and gamma-rays, alpha/gamma ratio, and decay kinetics. The total time-integrated LYs in undoped and Cu+-doped LTB for X-rays are ~600 and ~760 ph/MeV (photons/MeV), respectively. The decay kinetics in undoped and Cu+-doped LTB are similar to each other. Typical decay spectra for pulsed X-rays can be fitted with four exponentials: for fast (t1~0.8 ns, t2~25-50 ns), medium (t3~300-400 ns), and slow (t4~20-30 ms) components. The slow component occupies about 60% of the total LY, while the fast ones less than 10%. The 10-90% rise time was 163 ps. The alpha/gamma ratio was 0.18 for external 241Am alpha-rays. The obtained increase in LY due to Cu+ doping remains modest. The Cu+-induced emission contains both fast and slow components, requiring further studies of the emission mechanism to explain the fast component.

  18. Single-mode biological distributed feedback lasers based on vitamin B2 doped gelatin

    DEFF Research Database (Denmark)

    Vannahme, Christoph; Maier-Flaig, F.; Lemmer, U.

    Biological second-order distributed feedback (DFB) lasers are presented. Riboflavin (vitamin B2) doped gelatin as active material is spin-coated onto nanoimprinted polymer with low refractive index. DFB grating periods of 368 nm and 384 nm yield laser emission at 543 nm and 562 nm, respectively....

  19. Nitrogen-doped graphene: beyond single substitution and enhanced molecular sensing

    Science.gov (United States)

    Lv, Ruitao; Li, Qing; Botello-Méndez, Andrés R.; Hayashi, Takuya; Wang, Bei; Berkdemir, Ayse; Hao, Qingzhen; Elías, Ana Laura; Cruz-Silva, Rodolfo; Gutiérrez, Humberto R.; Kim, Yoong Ahm; Muramatsu, Hiroyuki; Zhu, Jun; Endo, Morinobu; Terrones, Humberto; Charlier, Jean-Christophe; Pan, Minghu; Terrones, Mauricio

    2012-01-01

    Graphene is a two-dimensional network in which sp2-hybridized carbon atoms are arranged in two different triangular sub-lattices (A and B). By incorporating nitrogen atoms into graphene, its physico-chemical properties could be significantly altered depending on the doping configuration within the sub-lattices. Here, we describe the synthesis of large-area, highly-crystalline monolayer N-doped graphene (NG) sheets via atmospheric-pressure chemical vapor deposition, yielding a unique N-doping site composed of two quasi-adjacent substitutional nitrogen atoms within the same graphene sub-lattice (N2AA). Scanning tunneling microscopy and spectroscopy (STM and STS) of NG revealed the presence of localized states in the conduction band induced by N2AA-doping, which was confirmed by ab initio calculations. Furthermore, we demonstrated for the first time that NG could be used to efficiently probe organic molecules via a highly improved graphene enhanced Raman scattering. PMID:22905317

  20. Single-mode biological distributed feedback lasers based on vitamin B2 doped gelatin

    DEFF Research Database (Denmark)

    Vannahme, Christoph; Maier-Flaig, F.; Lemmer, U.

    Biological second-order distributed feedback (DFB) lasers are presented. Riboflavin (vitamin B2) doped gelatin as active material is spin-coated onto nanoimprinted polymer with low refractive index. DFB grating periods of 368 nm and 384 nm yield laser emission at 543 nm and 562 nm, respectively....

  1. Dynamics of a Dispersion-Managed Passively Mode-Locked Er-Doped Fiber Laser Using Single Wall Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Norihiko Nishizawa

    2015-07-01

    Full Text Available We investigated the dynamics of a dispersion-managed, passively mode-locked, ultrashort-pulse, Er-doped fiber laser using a single-wall carbon nanotube (SWNT device. A numerical model was constructed for analysis of the SWNT fiber laser. The initial process of passive mode-locking, the characteristics of the output pulse, and the dynamics inside the cavity were investigated numerically for soliton, dissipative-soliton, and stretched-pulse mode-locking conditions. The dependencies on the total dispersion and recovery time of the SWNTs were also examined. Numerical results showed similar behavior to experimental results.

  2. 75 W 40% efficiency single-mode all-fiber erbium-doped laser cladding pumped at 976 nm.

    Science.gov (United States)

    Kotov, L V; Likhachev, M E; Bubnov, M M; Medvedkov, O I; Yashkov, M V; Guryanov, A N; Lhermite, J; Février, S; Cormier, E

    2013-07-01

    Optimization of Yb-free Er-doped fiber for lasers and amplifiers cladding pumped at 976 nm was performed in this Letter. The single-mode fiber design includes an increased core diameter of 34 μm and properly chosen erbium and co-dopant concentrations. We demonstrate an all-fiber high power laser and power amplifier based on this fiber with the record slope efficiency of 40%. To the best of our knowledge, the achieved output power of 75 W is the highest power reported for such lasers.

  3. 177 fs erbium-doped fiber laser mode locked with a cellulose polymer film containing single-wall carbon nanotubes

    Science.gov (United States)

    Tausenev, A. V.; Obraztsova, E. D.; Lobach, A. S.; Chernov, A. I.; Konov, V. I.; Kryukov, P. G.; Konyashchenko, A. V.; Dianov, E. M.

    2008-04-01

    A mode-locked soliton erbium-doped fiber laser generating 177fs pulses is demonstrated. The laser pumped by a 85mW, 980nm laser diode emits 7mW at 1.56μm at a pulse repetition rate of 50MHz. Passive mode locking is achieved with a saturable absorber made of a high-optical quality film based on cellulose derivative with dispersed carbon single-wall nanotubes. The film is prepared with the original technique by using carbon nanotubes synthesized by the arc-discharge method.

  4. EPR and optical absorption study of Cu{sup 2+} doped lithium sulphate monohydrate (LSMH) single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sheela, K. Juliet; Subramanian, P., E-mail: psubramaniangri@gmail.com [Department of Physics, Gandhigram Rural Institute-Deemed University, Gandhigram, Dindigul-624302, Tamilnadu (India); Krishnan, S. Radha; Shanmugam, V. M. [CSIR-Central Electrochemical Research Institute, Karaikudi-63006, Tamilnadu (India)

    2016-05-23

    EPR study of Cu{sup 2+} doped NLO active Lithium Sulphate monohydrate (Li{sub 2}SO{sub 4.}H{sub 2}O) single crystals were grown successfully by slow evaporation method at room temperature. The principal values of g and A tensors indicate existence of orthorhombic symmetry around the Cu{sup 2+} ion. From the direction cosines of g and A tensors, the locations of Cu{sup 2+} in the lattice have been identified as interstitial site. Optical absorption confirms the rhombic symmetry and ground state wave function of the Cu{sup 2+} ion in a lattice as d{sub x2-y2}.

  5. Crystal Growth and Properties of Co2+ doped Y3Sc2Ga3O12 Single Crystal

    Institute of Scientific and Technical Information of China (English)

    Guo Shiyi; Yuan Duorong; Shi Xuzhong; Cheng Xiufeng; Zhang Xiqing; Yu Fapeng

    2007-01-01

    Single crystal of cobalt (Co)-doped Y3Sc2Ga3O12 (YSGG) with the dimensions up to φ20×40mm3 and undoped YSGG crystal with the dimensions up to φ28×60mm3 have been grown using the Czochralski technique. The structure of the crystal was characterized by the X-ray powder diffraction (XRPD) method. The absorbance spectra of the crystal shows that it has strong absorption bands at 606 and 1540nm. The results indicate that the crystal Y3Sc2Ga3O12 may be a kind of good Q-switch material.

  6. Doping - Dependent irreversible magnetic properties of Ba(Fe 1-xCo x) 2As 2 single crystals

    Science.gov (United States)

    Prozorov, R.; Tanatar, M. A.; Blomberg, E. C.; Prommapan, P.; Gordon, R. T.; Ni, N.; Bud'ko, S. L.; Canfield, P. C.

    2009-05-01

    We discuss the irreversible magnetic properties of self-flux grown Ba(Fe 1-xCo x) 2As 2 single crystals for a wide range of concentrations covering the whole phase diagram from the underdoped to the overdoped regime, x = 0.038, 0.047, 0.058, 0.071, 0.074, 0.10, 0.106 and 0.118. Samples were characterized by a magneto-optical method and show excellent spatial uniformity of the superconducting state down to at least the micrometer scale. The in-plane properties are isotropic, as expected for the tetragonal symmetry, and the overall behavior closely follows classical Bean model of the critical state. The field-dependent magnetization exhibits second peak at a temperature and doping - dependent magnetic field, H p( T, x). The evolution of this fishtail feature with doping is discussed. In particular we find that H p, measured at the same reduced temperature for different x, is a unique monotonic function of the superconducting transition temperature, T c( x), across all dopings. Magnetic relaxation is time-logarithmic and unusually fast. Similar to cuprates, there is an apparent crossover from collective elastic to plastic flux creep above H p. At high fields, the field dependence of the relaxation rate becomes doping independent. We discuss our results in the framework of the weak collective pinning and show that vortex physics in iron-based pnictide crystals is much closer to high- T c cuprates than to conventional s-wave (including MgB 2) superconductors.

  7. Dual-wavelength single-longitudinal-mode erbium-doped fiber laser based on inverse-Gaussian apodized fiber Bragg grating and its application in microwave generation

    Science.gov (United States)

    Lin, Bo; Tjin, Swee Chuan; Zhang, Han; Tang, Dingyuan; Liang, Sheng; Hao, Jianzhong; Dong, Bo

    2011-03-01

    We propose a simple erbium-doped fiber ring laser. It consists of an inverse-Gaussian apodized fiber Bragg grating filter which has two ultra-narrow transmission bands, and an unpumped erbium-doped fiber as a saturable absorber. Stable dual-wavelength single-longitudinal-mode lasing with a wavelength separation of approximately 0.082 nm is achieved. A microwave signal at 10.502 GHz is demonstrated by beating the dual wavelengths at a photodetector.

  8. Polarity and growth directions in Sn-seeded GaSb nanowires.

    Science.gov (United States)

    Zamani, Reza R; Gorji Ghalamestani, Sepideh; Niu, Jie; Sköld, Niklas; Dick, Kimberly A

    2017-03-02

    We here investigate the growth mechanism of Sn-seeded GaSb nanowires and demonstrate how the seed particle and its dynamics at the growth interface of the nanowire determine the polarity, as well as the formation of structural defects. We use aberration-corrected scanning transmission electron microscopy imaging methodologies to study the interrelationship between the structural properties, i.e. polarity, growth mechanism, and formation of inclined twin boundaries in pairs. Moreover, the optical properties of the Sn-seeded GaSb nanowires are examined. Their photoluminescence response is compared with one of their Au-seeded counterparts, suggesting the incorporation of Sn atoms from the seed particles into the nanowires.

  9. A tunable yellow emission from three-band emission of singly doped single-phased phosphor BaY2S4:Ho3+

    Institute of Scientific and Technical Information of China (English)

    ZHAO Junfeng; CHEN Xi; RONG Chunying; YU Liping; LIAN Shixun

    2011-01-01

    The establishment of an approach to design tunable yellow emission through singly doped single-phased phosphors to obtain white LED-based InGaN chip was reported. BaY2-xS4:xHo3+ phosphors were prepared by the high temperature solid state reaction and characterized by X-ray diffraction and photoluminescence spectra. Under the excitation of 465 nm, the emission spectra of these phosphors exhibited three sharp emission lines peaked at about 492, 543 and 661 nm of Ho3+ corresponding to 5F3, 5F4 (5S2) and 5F5→5I8 transitions, respectively, with comparable intensities, resulting in a yellow light emission. The luminescence mechanism for Ho3+ in BaY2S4 was explained.

  10. Study of hydrogen implantation-induced blistering in GaSb for potential layer transfer applications

    Science.gov (United States)

    Pathak, Ravi; Dadwal, U.; Singh, R.

    2017-07-01

    GaSb samples were implanted by 100 keV hydrogen ions (H+) at room temperature with fluence values of 1  ×  1017 and 2  ×  1017 ions cm-2. Post-implantation annealing studies revealed that the samples implanted with a fluence of 2  ×  1017 ions cm-2 did not show blistering/exfoliation. For the lower fluence, the samples showed the formation of surface blisters/craters along with the large area exfoliation of the top H-implanted surface. Topographical investigations of the samples were carried out using Nomarski optical microscopy, atomic force microscopy and stylus surface profilometry. The lateral sizes and heights of the blisters varied between 2-5 µm and 5-20 nm respectively. The root mean square roughness of the exfoliated region was about 12 nm while the exfoliation depth was found to be 730 nm. The exfoliation depth in the H-implanted GaSb is close to the damage concentration peak as found from SRIM calculations. The Föppl-von Karman theory of thin plates has been used to understand the effect of internal pressure and stress on the surface blistering. Using the above mentioned implantation and annealing parameters, potential layer transfer of GaSb could be enabled.

  11. Thermally assisted oxidation of GaSb(100) and the effect of initial oxide phases

    Energy Technology Data Exchange (ETDEWEB)

    Mäkelä, J., E-mail: jaakko.m.makela@utu.fi [Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Tuominen, M.; Yasir, M. [Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Kuzmin, M. [Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Ioffe Physical-Technical Institute, Russian Academy of Sciences, St. Petersburg 194021 (Russian Federation); Dahl, J.; Punkkinen, M.P.J. [Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Laukkanen, P., E-mail: pekka.laukkanen@utu.fi [Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Kokko, K. [Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland)

    2016-04-30

    Highlights: • Unforeseen details of GaSb(100) oxidation are revealed with high resolution PES. • Bonding is elucidated with consistent Ga 3d, Sb 3d and O 1s core-level spectral fitting. • Correspondence is found between these and previous microscopic results. • At the first stage, band-gap states arise from the preferential oxidation of Ga. • Oxidation initiates through replacement of Sb with O in the subsurface atomic sites. - Abstract: The oxidation of GaSb(100) surface has been widely studied because it affects the functionality of various devices. However even initial stages of the oxygen incorporation are not completely understood. To clarify this issue, we have investigated the oxidized GaSb(100) surfaces, which have been recently probed by scanning tunneling microscopy and spectroscopy, with high resolution synchrotron radiation photoelectron spectroscopy, in order to interconnect these different measurements. The results give a clear support that the oxidation initiates through saturation of available Ga bonds with; i.e., replacing some of the Sb−Ga bonds with O−Ga in the surface layers. Oxygen atoms have two different bonding environments in consistent with two dominating STM features. Also role of the plasmon features in the spectra have been elucidated.

  12. Growth and characterization of pure and potassium iodide-doped zinc tris-thiourea sulphate (ZTS) single crystals

    Science.gov (United States)

    Krishnan, C.; Selvarajan, P.; Freeda, T. H.; Mahadevan, C. K.

    2009-02-01

    Single crystals of pure and potassium iodide (KI)-doped zinc tris-thiourea sulphate (ZTS) were grown from aqueous solutions by the slow evaporation method. The grown crystals were transparent. The lattice parameters of the grown crystals were determined by the single-crystal X-ray diffraction technique. The grown crystals were also characterized by recording the powder X-ray diffraction pattern and by identifying the diffracting planes. The FT-IR spectrum was recorded in the range 400-4500 cm -1. Second harmonic generation (SHG) was confirmed by the Kurtz powder method. The thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) studies reveal that the materials have good thermal stability. Atomic absorption studies confirm the presence of dopant in ZTS crystals. The electrical measurements were made in the frequency range 10 2-10 6 Hz and in the temperature range 40-130 °C along a-, b- and c-directions of the grown crystals. The present study shows that the electrical parameters viz. dc conductivity, dielectric constant, dielectric loss factor and ac conductivity increase with increase in temperature. Activation energy values were also determined for the ac conduction process in grown crystals. The dc conductivity, dielectric constant, dielectric loss factor and ac conductivity of KI-doped ZTS crystal were found to be more than those of pure ZTS crystals.

  13. A Computational NMR Study for Chemisorption of Oxygen-doped on the Surface of Single-Walled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    A. Ghasemi

    2012-08-01

    Full Text Available In this study computational Nuclear Magnetic Resonance (NMR study and chemisorptions are performed to investigate the electronic structure properties of arm-chair (4, 4 and zig-zag (5, 0 Single-Wall Carbon Nanotubes (SWCNTs. First-principles of Density Function Theory (DFT have applied in calculations on properties of molecular oxygen-doped (O-doped SWCNTs. The results show dramatic differences between two types, (5, 0 zigzag and (4, 4 arm chair, of carbon nano-tubes. Structural models are optimized and chemisorption energies are obtained to investigate the Nuclear Magnetic Resonance (NMR parameters for Odoped (5, 0 zigzag and (4, 4 armchair single-walled carbon nanotubes based on calculations using DFT. The chemical-shielding (σιι tensors were converted to isotropic chemical-shielding (iso and anisotropic chemicalshielding (Δσ and asymmetric (μj parameters of 17O and 13C atom for the optimized structures. We found that introduction oxygen does significantly change the structure of the SWCNT and thus the bonding mode of the structure is remarkably altered. Comparing the results of the zigzag and armchair models and calculated chemical shielding, electric filed gradient tensors at the sites of carbon reveal that O2 chemisorption has a dramatic effect on the electronic structure of SWCNTs.

  14. Single-polarization, switchable dual-wavelength erbium-doped fiber laser with two polarization-maintaining fiber Bragg gratings.

    Science.gov (United States)

    Feng, Suchun; Xu, Ou; Lu, Shaohua; Mao, Xiangqiao; Ning, Tigang; Jian, Shuisheng

    2008-08-04

    An improved erbium-doped fiber laser configuration for achieving single-polarization, switchable dual-wavelength of orthogonal polarizations oscillations at room temperature is proposed. For the first time, two fiber Bragg gratings (FBGs) directly written in a polarization-maintaining (PM) and photosensitive erbium-doped fiber (PMPEDF) as the wavelength-selective component are used in a linear laser cavity. Due to the polarization hole burning (PHB) enhanced by the polarization-maintaining FBG (PMFBG), the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.336 nm at room temperature by adjusting a polarization controller (PC). Each lasing line shows a single polarization with a polarization extinction ratio of >25 dB under different pump levels. The optical signal-to-noise ratio (OSNR) is greater than 50 dB. The amplitude variation with 16 times scans in nearly one and half an hour is less than 0.5 dB at both operating wavelength.

  15. Multi-susceptibile single-phased ceramics with both considerable magnetic and dielectric properties by selectively doping.

    Science.gov (United States)

    Liu, Chuyang; Zhang, Yujing; Jia, Jingguo; Sui, Qiang; Ma, Ning; Du, Piyi

    2015-04-02

    Multiferroic ceramics with extraordinary susceptibilities coexisting are vitally important for the multi-functionality and integration of electronic devices. However, multiferroic composites, as the most potential candidates, will introduce inevitable interface deficiencies and thus dielectric loss from dissimilar phases. In this study, single-phased ferrite ceramics with considerable magnetic and dielectric performances appearing simultaneously were fabricated by doping target ions in higher valence than that of Fe(3+), such as Ti(4+), Nb(5+) and Zr(4+), into BaFe12O19. In terms of charge balance, Fe(3+)/Fe(2+) pair dipoles are produced through the substitution of Fe(3+) by high-valenced ions. The electron hopping between Fe(3+) and Fe(2+) ions results in colossal permittivity. Whilst the single-phased ceramics doped by target ions exhibit low dielectric loss naturally due to the diminishment of interfacial polarization and still maintain typical magnetic properties. This study provides a convenient method to attain practicable materials with both outstanding magnetic and dielectric properties, which may be of interest to integration and multi-functionality of electronic devices.

  16. Stable dual-wavelength single-longitudinal-mode ring erbium-doped fiber laser for optical generation of microwave frequency

    Science.gov (United States)

    Wang, T.; Liang, G.; Miao, X.; Zhou, X.; Li, Q.

    2012-05-01

    We demonstrate a simple dual-wavelength ring erbium-doped fiber laser operating in single-longitudinal-mode (SLM) at room temperature. A pair of reflection type short-period fiber Bragg gratings (FBGs), which have two different center wavelengths of 1545.072 and 1545.284 nm, are used as the wavelength-selective component of the laser. A segment of unpumped polarization maintaining erbium-doped fiber (PM-EDF) is acted as a narrow multiband filter. By turning the polarization controller (PC) to enhance the polarization hole burning (PHB), the single-wavelength and dual-wavelength laser oscillations are observed at 1545.072 and 1545.284 nm. The output power variation is less than 0.6 dB for both wavelengths over a five-minute period and the optical signal to noise ratio (OSNR) is greater than 50 dB. By beating the dual-wavelengths at a photodetector (PD), a microwave signal at 26.44 GHz is demonstrated.

  17. Scintillation detector using an europium-doped calcium fluoride single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Gilar, O.; Pavlicek, Z.; Jursova, L. (Tesla, Premysleni (Czechoslovakia). Vyzkumny Ustav Pristroju Jaderne Techniky)

    1981-06-01

    A europium-doped calcium fluoride monocrystal-based scintillator is suitable for detecting X, alpha, beta and low-energy gamma radiations. It is resistant to thermal and mechanical shocks. Its outstanding physical properties include the index of refraction of 1.443. The results are reported of measuring the spectra of selected radionuclides and the energy resolution dependence on the gamma radiation energy.

  18. Influence of the ytterbium doping technique on the luminescent properties of ZnSe single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Radevici, Ivan, E-mail: ivarad@utu.fi [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., MD-2009 Chisinau, Republic of Moldova (Moldova, Republic of); Sushkevich, Konstantin [Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., MD-2009 Chisinau, Republic of Moldova (Moldova, Republic of); Huhtinen, Hannu [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Nedeoglo, Dmitrii [Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., MD-2009 Chisinau, Republic of Moldova (Moldova, Republic of); Paturi, Petriina [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland)

    2015-02-15

    Luminescent properties of the ytterbium doped zinc selenide crystals with 0.00–8.00 at % concentrations of the Yb impurity within the temperature interval from 6 K to 300 K were studied. Ytterbium doping was performed within three technological processes: during the growth by chemical vapor transport method and by thermal diffusion from the Bi+Yb or Zn+Yb melt. The influence of ytterbium impurity concentration on spectral position and intensity of the various photoluminescent bands in ZnSe emission spectra in visible and infrared range is analyzed. A tendency of ytterbium ions to form associates with background defects was demonstrated. A strong dependence between ytterbium influence on the zinc selenide emission spectra and concentration of selenium vacancies was shown. - Highlights: • Co-doping of ZnSe crystals with Yb and Bi or I impurities was studied. • Influence of Yb concentration on ZnSe emission spectra in visible and infrared range was analyzed. • Tendency of Yb to form associates with background defects was discussed. • Impact of V{sub Se} on formation of Yb-based emission centers was demonstrated.

  19. First-principles calculations on the structure and electronic properties of boron doping zigzag single-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    WEN QingBo; YU ShanSheng; ZHENG WeiTao

    2009-01-01

    Calculations have been made for single-walled zigzag (n, 0) carbon nanotubes containing substitutional boron impurity atoms using ab initio density functional theory. It is found that the formation energies of these nanotubes depend on the tube diameter, as do the electronic properties, and show periodic fea-ture that results from their different π bonding structures compared to those of perfect zigzag carbon nanotubes. When more boron atoms are incorporated into a single-walled zigzag carbon nanotube, the substitutional boron atoms tend to come together to form structure of BC3 nanodomains, and B-doped tubes have striking acceptor states above the top of the valence bands. For the structure of BC3, there are two kinds of configurations with different electronic structures.

  20. Phase-sensitive reflectometer using a single-frequency laser diode and an Er-doped fibre amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Eftimov, T; Stefanov, I; Popov, A; Vodenicharov, S, E-mail: teftimov@uni-plovdiv.b

    2010-11-01

    We report on the observation of phase-sensitive Rayleigh backscattering from a single-mode fiber excited by light pulses obtained from a highly coherent single-frequency laser diode and an Erbium doped fiber amplifier (EDFA). The laser diode stability was tested using a highly imbalanced fiber optic Mach-Zehnder interferometer. The CW laser light was first modulated using fiber-optic EO modulator which formed 100ns to 500 ns pulses that correspond to 20 to 100 m of pulse length in the fiber. The backscattered light power is estimated to be about -51 dB lower than the launched power at the input and about N=500 averages are needed for a sensing length of L{sub s} 40 km to be in the useful dynamic range.

  1. Slope efficiency over 30% single-frequency ytterbium-doped fiber laser based on Sagnac loop mirror filter.

    Science.gov (United States)

    Yin, Mojuan; Huang, Shenghong; Lu, Baole; Chen, Haowei; Ren, Zhaoyu; Bai, Jintao

    2013-09-20

    A high-slope-efficiency single-frequency (SF) ytterbium-doped fiber laser, based on a Sagnac loop mirror filter (LMF), was demonstrated. It combined a simple linear cavity with a Sagnac LMF that acted as a narrow-bandwidth filter to select the longitudinal modes. And we introduced a polarization controller to restrain the spatial hole burning effect in the linear cavity. The system could operate at a stable SF oscillating at 1064 nm with the obtained maximum output power of 32 mW. The slope efficiency was found to be primarily dependent on the reflectivity of the fiber Bragg grating. The slope efficiency of multi-longitudinal modes was higher than 45%, and the highest slope efficiency of the single longitudinal mode we achieved was 33.8%. The power stability and spectrum stability were <2% and <0.1%, respectively, and the signal-to-noise ratio measured was around 60 dB.

  2. Passively mode-locking erbium-doped fiber lasers with 0.3 nm single-walled carbon nanotubes.

    Science.gov (United States)

    Xu, Xintong; Zhai, Jianpang; Li, Ling; Chen, Yanping; Yu, Yongqin; Zhang, Min; Ruan, Shuangchen; Tang, Zikang

    2014-10-24

    We demonstrate a passively mode-locked erbium-doped fiber laser (EDFL) by using the smallest single-walled carbon nanotubes (SWNTs) with a diameter of 0.3 nm as the saturable absorber. These ultrasmall SWNTs are fabricated in the elliptical nanochannels of a ZnAPO₄-11 (AEL) single crystal. By placing an AEL crystal into an EDFL cavity pumped by a 980 nm laser diode, stable passive mode-locking is achieved for a threshold pump power of 280 mW, and 73 ps pulses at 1563.2 nm with a repetition rate of 26.79 MHz.

  3. First-principles calculations on the structure and electronic properties of boron doping zigzag single-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Calculations have been made for single-walled zigzag(n,0) carbon nanotubes containing substitutional boron impurity atoms using ab initio density functional theory.It is found that the formation energies of these nanotubes depend on the tube diameter,as do the electronic properties,and show periodic fea-ture that results from their different π bonding structures compared to those of perfect zigzag carbon nanotubes.When more boron atoms are incorporated into a single-walled zigzag carbon nanotube,the substitutional boron atoms tend to come together to form structure of BC3 nanodomains,and B-doped tubes have striking acceptor states above the top of the valence bands.For the structure of BC3,there are two kinds of configurations with different electronic structures.

  4. Remarkable effect of Ni{sup 2+}doping on structural, second harmonic generation, optical, mechanical and dielectric properties of KDP single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ganesh, V. [Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413 (Saudi Arabia); Shkir, Mohd, E-mail: shkirphysics@gmail.com [Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413 (Saudi Arabia); AlFaify, S.; Algarni, H. [Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413 (Saudi Arabia); Abutalib, M.M. [Faculty of Science-AL Faisaliah, Campus, King Abdulaziz University, P.O. Box 80200, Jeddah 21589 (Saudi Arabia); Yahia, I.S. [Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413 (Saudi Arabia); Nano-Science & Semiconductor Labs., Thin Film Lab., Department of Physics, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt)

    2016-06-15

    The nonlinear optical single crystals of pure and Ni{sup 2+} doped potassium dihydrogen phosphate (KDP) were successfully grown by slow evaporation solution growth technique. The effects of the addition of Ni{sup 2+} with different molar concentration have been studied by powder X-ray diffraction, FT-Raman, second harmonic generation, microscopic and dielectric studies. Its crystallinity was assessed by the FT-Raman technique and its surface, structural imperfections were recorded using high resolution microscope, which clearly reveals that the doping is showing considerable effect on the samples. The SHG measurements also carried out on pure and doped samples, which reveal the relative SHG efficiency has been enhanced due to doping. The optical activities were studied by UV–vis-NIR technique and reveals high optical transparency in doped samples. The remarkable enhancement in mechanical strength was observed due to doping. The enhanced dielectric constant and low dielectric loss confirms that the grown crystals with doping are superior to pure crystals and may be used in optoelectronic devices.

  5. Synthesis, characterization, and transport properties of single-layer pure and molybdenum-doped vanadium oxide thin films on metallic conductive substrates

    Energy Technology Data Exchange (ETDEWEB)

    Karthikeyan, Muthukkumaran; Um, Sukkee, E-mail: sukkeeum@hanyang.ac.kr

    2016-05-01

    Single-layer undoped and 10 mol% molybdenum (Mo)-doped vanadium oxide (V{sub 2}O{sub 3}) thin films with thicknesses of approximately 342 nm are fabricated by an aqueous sol–gel method and then deposited onto 316L stainless steel conductive substrates. The influence of various annealing temperatures (in a nitrogen atmosphere) on the structural and electrical properties of undoped and Mo-doped vanadium oxide thin films is investigated. Through a controlled annealing process, the electrical resistances of the single-layer thin films are optimized to attain the required amount of Joule heating for cold-start fuel cell applications within an ambient temperature range (273.15 to 253.15 K). The films show a negative temperature coefficient (NTC) behavior and a transition from a metal to an insulator at sub-zero temperatures. The highest electrical resistivities are measured to be 0.032 Ω·cm and 0.071 Ω·cm for undoped and Mo-doped vanadium oxide films, respectively, after annealing under 20 sccm N{sub 2} at 673.15 K. Consequently, the equilibrium surface temperature of the single-layer Mo-doped vanadium oxide thin film increases from 253.15 K to 299.46 K upon induced Joule heating at a current density of 0.1 A·cm{sup −2}. Thus, it is concluded that single-layer NTC Mo-doped vanadium oxides can be effectively used for cold-start fuel cell applications. - Highlights: • Single-layer undoped and 10 mol% Mo-doped vanadium oxide films were fabricated. • Mo-doped V{sub 2}O{sub 3} thin films showed am enhanced NTC behavior through annealing. • Mo-doped V{sub 2}O{sub 3} thin films revealed the high resistivity of 0.071 Ω·cm at 253.15 K. • Remarkable temperature rise of a Mo-doped V{sub 2}O{sub 3} film was achieved by Joule heating. • Mo-doped V{sub 2}O{sub 3} films can be effectively used for cold-start fuel cell applications.

  6. Formation, atomic structure, and electronic properties of GaSb quantum dots in GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Timm, R.

    2007-12-14

    In this work, cross-sectional scanning tunneling microscopy and spectroscopy are used for the first time to study the shape, size, strain, chemical composition, and electronic properties of capped GaSb/GaAs QDs at the atomic scale. By evaluating such structural results on a variety of nanostructures built using different epitaxy methods and growth conditions, details on the underlying QD formation processes can be revealed. A cross-over from flat quantum wells (QWs) to optically active QDs can be observed in samples grown by metalorganic chemical vapor deposition (MOCVD) with increasing amount of GaSb, including self-assembled Sb accumulations within a still two-dimensional layer and tiny three-dimensional GaSb islands probably acting as precursor structures. The QWs consist of significantly intermixed material with stoichiometries of maximally 50% GaSb, additionally exhibiting small gaps filled with GaAs. A higher GaSb content up to nearly pure material is found in the QDs, being characterized by small sizes of up to 8 nm baselength and about 2 nm height. In spite of the intermixing, all nanostructures have rather abrupt interfaces, and no significant Sb segregation in growth direction is observed. This changes completely when molecular beam epitaxy (MBE) is used as growth method, in which case individual Sb atoms are found to be distributed over several nm above the nanostructures. Massive group-V atomic exchange processes are causing this strong inter-mixing and Sb segregation during GaAs overgrowth. In combination with the large strain inherent to GaSb/GaAs QDs, this segregation upon overgrowth is assumed to be the reason for a unique structural phenomenon: All MBE-grown QDs, independent of the amount of deposited GaSb, exhibit a ring structure, consisting of a ring body of high GaSb content and a more or less extended central gap filled with GaAs. These rings have formed in a self-assembled way even when the initial GaSb layer was overgrown considerably fast

  7. Effects of Mg-codoping on luminescence and scintillation properties of Ce doped Lu3(Ga,Al)5O12 single crystals

    Science.gov (United States)

    Yamaguchi, Hiroaki; Kamada, Kei; Pejchal, Jan; Kurosawa, Shunsuke; Shoji, Yasuhiro; Yokota, Yuui; Ohashi, Yuji; Yoshikawa, Akira

    2017-03-01

    Effects of Mg co-doping on scintillation properties of Ce:Lu3(Ga,Al)5O12 (LGAG) were investigated. Mg 200 ppm co-doped Ce:LGAG single crystals were prepared by micro pulling down method. Absorption and radioluminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of Mg co-doping. Ce4+ charge transfer absorption was observed below 340 nm in Mg,Ce:LGAG which is in good agreement with previous reports for other garnet-based crystals. The scintillation decay time showed the tendency to be accelerated and the light yield was enhanced by Mg co-doping.

  8. Smart Q-switching for single-pulse generation in an erbium-doped fiber laser.

    Science.gov (United States)

    Escalante-Zarate, Luis; Barmenkov, Yuri O; Kolpakov, Stanislav A; Cruz, José L; Andrés, Miguel V

    2012-02-13

    In this paper, we report an active Q-switching of an erbium-doped fiber laser with special modulation functions and novel laser geometry. We experimentally demonstrate that using such a smart Q-switch approach, Q-switch ripple-free pulses with Gaussian-like shape and 17.3 ns width can be easily obtained. The idea behind the smart Q-switch is to suppress one of two laser waves contra-propagating along the fiber cavity, which arises after Q-cell opening, and to eliminate the minor sub-pulses.

  9. Effects of monovalent cation doping on the structure, microstructure, lattice distortion and magnetic behavior of single crystalline NdMnO3 compounds.

    Science.gov (United States)

    Nandy, Anshuman; Pradhan, S K

    2015-10-21

    Pure and 15 mol% Na, K-doped NdMnO3 compounds with perovskite structures are prepared by sol-gel method. Tiny single crystals are formed after sintering the compounds at 1000 °C. The effect of Na and K doping as well as the effect of sintering temperature on the formation and microstructure of NdMnO3 are studied in detail by the Rietveld refinement technique using X-ray powder diffraction data. Single phase formation and single crystalline growth are also confirmed by high resolution transmission electron microscopy (HRTEM). Bond angles and bond lengths are calculated and shown by 3D diagrams. Monovalent doping induces noticeable changes in the microstructure and yields better structural stability in these compounds. Doping results in the change of Mn-O, Nd-O and Mn-O-Mn bond lengths which in turn reduces the lattice and octahedral distortion in the system along with an increase in the tolerance factor. The magnetic properties of these compounds are also modified as a result of doping. The temperature dependent magnetization results show that the Neel temperature of antiferromagnetic NdMnO3 compound is 67.2 K and the Curie temperatures of ferromagnetic Nd0.85Na0.15MnO3 and Nd0.85K0.15MnO3 compounds are 99.1 K and 98.6 K respectively. Both 15% Na and K doping results in a similar TC in doped NdMnO3 compounds.

  10. Effect of Yb doping on the refractive index and thermo-optic coefficient of YVO4 single crystals.

    Science.gov (United States)

    Soharab, M; Bhaumik, Indranil; Bhatt, R; Saxena, A; Karnal, A K; Gupta, P K

    2017-02-20

    Single crystals of YVO4 with different doping concentrations of Yb (1.5, 3.0, 8.0, and 15.0 at. %) and with good crystalline quality (FWHM ∼43-55 arc sec of rocking curve) were grown by the optical floating zone technique. Refractive index measurements were carried out at four wavelengths as a function of temperature. The measurements show that as the doping concentration of Yb is increased, the refractive index varies marginally for ne whereas there is a significant change in the value of no. The thermo-optic coefficient (dn/dT) was found to be positive with a value ∼10-5/°C, which is 1 order higher than that for the undoped YVO4 crystal. The thermo-optic coefficient is higher for ne compared to that of no. Also, a set of relations describing the wavelength dependence of the thermo-optic coefficient were established that are useful for calculating the thermo-optic coefficient at any temperature in the range 30°C-150°C and at any wavelength in the range 532-1551 nm.

  11. Theoretical Investigation on Single-Wall Carbon Nanotubes Doped with Nitrogen, Pyridine-Like Nitrogen Defects, and Transition Metal Atoms

    Directory of Open Access Journals (Sweden)

    Michael Mananghaya

    2012-01-01

    Full Text Available This study addresses the inherent difficulty in synthesizing single-walled carbon nanotubes (SWCNTs with uniform chirality and well-defined electronic properties through the introduction of dopants, topological defects, and intercalation of metals. Depending on the desired application, one can modify the electronic and magnetic properties of SWCNTs through an appropriate introduction of imperfections. This scheme broadens the application areas of SWCNTs. Under this motivation, we present our ongoing investigations of the following models: (i (10, 0 and (5, 5 SWCNT doped with nitrogen (CNxNT, (ii (10, 0 and (5, 5 SWCNT with pyridine-like defects (3NV-CNxNT, (iii (10, 0 SWCNT with porphyrine-like defects (4ND-CNxNT. Models (ii and (iii were chemically functionalized with 14 transition metals (TMs: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pd, Ag, Pt and Au. Using the spin-unrestricted density functional theory (DFT, stable configurations, deformations, formation and binding energies, the effects of the doping concentration of nitrogen, pyridine-like and porphyrine-like defects on the electronic properties were all examined. Results reveal that the electronic properties of SWCNTs show strong dependence on the concentration and configuration of nitrogen impurities, its defects, and the TMs adsorbed.

  12. A wavelength-switchable single-longitudinal-mode dual-wavelength erbium-doped fiber laser for switchable microwave generation.

    Science.gov (United States)

    Pan, Shilong; Yao, Jianping

    2009-03-30

    A novel wavelength-switchable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber laser (EDFL) implemented based on a sigma architecture that is composed of a ring loop and a linear standing wave arm is experimentally demonstrated. Gain competition that prevents stable dual-wavelength oscillation is effectively suppressed by placing the gain medium in the standing-wave arm and by introducing polarization hole burning (PHB) via polarization multiplexing of the two lasing wavelengths in the ring loop. The SLM operation is guaranteed by an ultranarrow Fabry- Perot filter (FPF) introduced by absorption saturation in an unpumped erbium-doped fiber (EDF) and the gain saturation in the gain medium. In addition, the ring cavity forms a Lyot filter for each wavelength. Thus, wavelength switching is achieved by simply adjusting the polarization state of either wavelength. By beating the two SLM wavelengths at a photodetector (PD), a microwave signal with a frequency tunable from approximately 10 to approximately 50 GHz is experimentally generated.

  13. Micromorphology of pure and PbI{sub 2}-doped CdI{sub 2} dendritic single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Binay [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India); Sinha, Nidhi [Department of Electronics, SGTB Khalsa College, University of Delhi, Delhi-7 (India)

    2005-09-01

    Undoped and PbI{sub 2}-doped dendritic single crystals were grown by vapour growth technique. The basal surfaces of the as grown crystals were examined by optical and electron microscopy to observe wide variety of growth and defect features. Apart from typical features of dendritic growth, features of overgrowth, slip bands, growth steps and their bunching, etc. were observed. The basal surfaces of the crystals were then etched by controlled condensation of water vapour, after optimizing the etching condition, and the microscopic studies were repeated. Etch pits of hexagonal and triangular shape, both symmetric and asymmetric, and of different density, were observed in the case of undoped and doped crystals, respectively. In some cases, crystallographic hillocks were also observed. The crystals were also examined by X-ray diffraction for their polytypism and related behaviour. The results are analyzed to elicit information on the correlation of structure, defects and surface features of the crystals. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Stable single longitudinal mode erbium-doped silica fiber laser based on an asymmetric linear three-cavity structure

    Institute of Scientific and Technical Information of China (English)

    Feng Ting; Yan Feng-Ping; Li Qi; Peng Wan-Jing; Feng Su-Chun; Tan Si-Yu; Wen Xiao-Dong

    2013-01-01

    We present a stable linear-cavity single longitudinal mode (SLM) erbium-doped silica fiber laser.It consists of four fiber Bragg gratings (FBGs) directly written in a section of photosensitive erbium-doped fiber (EDF) to form an asymmetric three-cavity structure.The stable SLM operation at a wavelength of 1545.112 nm with a 3-dB bandwidth of 0.012 nm and an optical signal-to-noise ratio (OSNR) of about 60 dB is verified experimentally.Under laboratory conditions,the performance of a power fluctuation of less than 0.05 dB observed from the power meter for 6 h and a wavelength variation of less than 0.01 nm obtained from the optical spectrum analyzer (OSA) for about 1.5 h are demonstrated.The gain fiber length is no longer limited to only several centimeters for SLM operation because of the excellent mode-selecting ability of the asymmetric three-cavity structure.The proposed scheme provides a simple and cost-effective approach to realizing a stable SLM fiber laser.

  15. p-wave triggered superconductivity in single-layer graphene on an electron-doped oxide superconductor

    Science.gov (United States)

    di Bernardo, A.; Millo, O.; Barbone, M.; Alpern, H.; Kalcheim, Y.; Sassi, U.; Ott, A. K.; de Fazio, D.; Yoon, D.; Amado, M.; Ferrari, A. C.; Linder, J.; Robinson, J. W. A.

    2017-01-01

    Electron pairing in the vast majority of superconductors follows the Bardeen-Cooper-Schrieffer theory of superconductivity, which describes the condensation of electrons into pairs with antiparallel spins in a singlet state with an s-wave symmetry. Unconventional superconductivity was predicted in single-layer graphene (SLG), with the electrons pairing with a p-wave or chiral d-wave symmetry, depending on the position of the Fermi energy with respect to the Dirac point. By placing SLG on an electron-doped (non-chiral) d-wave superconductor and performing local scanning tunnelling microscopy and spectroscopy, here we show evidence for a p-wave triggered superconducting density of states in SLG. The realization of unconventional superconductivity in SLG offers an exciting new route for the development of p-wave superconductivity using two-dimensional materials with transition temperatures above 4.2 K.

  16. p-wave triggered superconductivity in single-layer graphene on an electron-doped oxide superconductor.

    Science.gov (United States)

    Di Bernardo, A; Millo, O; Barbone, M; Alpern, H; Kalcheim, Y; Sassi, U; Ott, A K; De Fazio, D; Yoon, D; Amado, M; Ferrari, A C; Linder, J; Robinson, J W A

    2017-01-19

    Electron pairing in the vast majority of superconductors follows the Bardeen-Cooper-Schrieffer theory of superconductivity, which describes the condensation of electrons into pairs with antiparallel spins in a singlet state with an s-wave symmetry. Unconventional superconductivity was predicted in single-layer graphene (SLG), with the electrons pairing with a p-wave or chiral d-wave symmetry, depending on the position of the Fermi energy with respect to the Dirac point. By placing SLG on an electron-doped (non-chiral) d-wave superconductor and performing local scanning tunnelling microscopy and spectroscopy, here we show evidence for a p-wave triggered superconducting density of states in SLG. The realization of unconventional superconductivity in SLG offers an exciting new route for the development of p-wave superconductivity using two-dimensional materials with transition temperatures above 4.2 K.

  17. Thermal expansion and magnetostriction of pure and doped RAgSb(2) (R = Y, Sm, La) single crystals.

    Science.gov (United States)

    Bud'ko, S L; Law, S A; Canfield, P C; Samolyuk, G D; Torikachvili, M S; Schmiedeshoff, G M

    2008-03-19

    Data on temperature-dependent, anisotropic thermal expansion in pure and doped RAgSb(2) (R = Y, Sm, La) single crystals are presented. Using the Ehrenfest relation and heat capacity measurements, uniaxial pressure derivatives for long range magnetic ordering and charge density wave transition temperatures are evaluated and compared with the results of the direct measurements under hydrostatic pressure. In-plane and c-axis pressure have opposite effects on the phase transitions in these materials, with in-plane effects being significantly weaker. Quantum oscillations in magnetostriction were observed for the three pure compounds, with the possible detection of new frequencies in SmAgSb(2) and LaAgSb(2). The uniaxial (along the c-axis) pressure derivatives of the dominant extreme orbits (β) were evaluated for YAgSb(2) and LaAgSb(2).

  18. Insulating and metallic spin glass in Ni-doped KxFe2-ySe2 single crystals

    Science.gov (United States)

    Ryu, Hyejin; Abeykoon, Milinda; Wang, Kefeng; Lei, Hechang; Lazarevic, N.; Warren, J. B.; Bozin, E. S.; Popovic, Z. V.; Petrovic, C.

    2015-05-01

    We report electron doping effects by Ni in KxFe2-δ -yNiySe2(0.06 ≤y ≤1.44 ) single-crystal alloys. A rich ground-state phase diagram is observed. A small amount of Ni (˜4 %) suppressed superconductivity below 1.8 K, inducing insulating spin-glass magnetic ground state for higher Ni content. With further Ni substitution, metallic resistivity is restored. For high Ni concentration in the lattice the unit cell symmetry is high symmetry I 4 /m m m with no phase separation whereas both I 4 /m +I 4 /m m m space groups were detected in the phase separated crystals when concentration of Ni < Fe. The absence of superconductivity coincides with the absence of crystalline Fe vacancy order.

  19. Ce-doped LuAG single-crystal fibers grown from the melt for high-energy physics

    CERN Document Server

    Xu, X; Moretti, F; Pauwels, K; Lecoq, P; Auffray, E; Dujardin, C

    2014-01-01

    Under a stationary stable regime undoped and Ce-doped LuAG (Lu3Al5O12) single-crystal fibers were grown by a micro-pulling-down technique. The meniscus length corresponding to the equilibrium state was <200 mu m. Fluctuations in the fiber composition and pulling rate were found to have a significant effect on the properties of the fibers grown. A great improvement in the performance was found in samples containing low Ce concentrations (<= 0.1 at.\\%) and produced using pulling rates <0.5 mm min(-1). Under such conditions a good lateral surface fiber quality was obtained and light propagation was significantly improved. Conversely, a high Ce concentration and a high pulling rate resulted in a strong degradation of the fiber surface quality causing defects to appear and a decrease in light output. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  20. Single crystal fiber growth of cerium doped strontium yttrate, SrY2O4:Ce3+

    Science.gov (United States)

    Philippen, J.; Guguschev, C.; Klimm, D.

    2017-02-01

    First single crystal fibers of cerium doped strontium yttrate were fabricated using the laser-heated pedestal growth technique. Through thermodynamic equilibrium calculations and by high-temperature mass spectrometry suitable growth conditions could be determined. The atmosphere played an important role during crystallization. It affected the composition shift, on the one hand, and the valence state of cerium, on the other hand. These dependencies can be explained by combining X-ray diffraction, elemental analysis, and optical spectroscopy. Crystallization in slightly reducing nitrogen atmosphere proved to be a reasonable choice, because evaporation is suppressed and trivalent cerium is stabilized. Strong green emission that depends on the oxygen fugacity during crystallization could be excited using UV light. Optical properties of SrY2O4:Ce3+ were measured for the first time.

  1. Demonstration of a stable and uniform single-wavelength erbium-doped fiber laser based on microfiber knot resonator

    Science.gov (United States)

    Xu, Yiping; Ren, Liyong; Ma, Chengju; Kong, Xudong; Ren, Kaili

    2016-12-01

    We propose and demonstrate an application of microfiber knot resonator (MKR) in the generation of a stable and uniform single-wavelength erbium-doped fiber laser (EDFL). An MKR was fabricated using a microfiber a few micrometers in diameter. By embedding the MKR to the ring cavity of the EDFL, a laser with a wavelength of 1558.818 nm and a 3-dB linewidth of 0.0149 nm is demonstrated. The side mode suppression ratio of the laser is about 30 dB, and the maximum power fluctuation is about 0.85 dB. The results demonstrate that the MKR can be employed as a high-performance comb filter to realize a stable and uniform fiber laser.

  2. An electron spin resonance study of vanadium-doped {alpha} -TeO{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, G.J.; Gilliam, O.R.; Bartram, R.H.; Watterich, A.; Voszka, R.; Niklas, J.R.; Greulich-Weber, S.; Spaeth, J.M. [Dept. of Phys., Connecticut Univ., Storrs, CT (United States)

    1995-04-10

    An ESR study of vanadium-doped paratellurite indicates that vanadium enters the lattice as V{sup 4+}, equally populating the four inequivalent cation sites. The 3d{sup 1} electron exhibits hyperfine interaction with the I=7/2 {sup 51}V nucleus and superhyperfine interaction with two neighbouring I= 1/2 nuclei identified as protons by ENDOR experiments. Spin Hamiltonian parameters computed from ESR measurements show that each V{sup 4+} ion has a single C{sub 2} symmetry axis along one of the (110) directions. The neighbouring hydrogens appear to enhance the symmetry and stability of the defect structure. Group theoretical arguments show that there are two possible linear combinations of d wavefunctions that could represent the ground state of V{sup 4+} in {alpha} -TeO{sub 2}. However, a determination of the lower-lying state was not feasible using only the ESR data. (author)

  3. Strain relief and growth optimization of GaSb on GaP by molecular beam epitaxy.

    Science.gov (United States)

    Wang, Y; Ruterana, P; Chen, J; Desplanque, L; El Kazzi, S; Wallart, X

    2012-08-22

    In this paper, the impact of growth parameters on the strain relaxation of highly lattice mismatched (11.8%) GaSb grown on GaP substrate by molecular beam epitaxy has been investigated. The surface morphology, misfit dislocation and strain relaxation of the GaSb islands are shown to be highly related to the initial surface treatment, growth rate and temperature. More specifically, Sb-rich surface treatment is shown to promote the formation of Lomer misfit dislocations. Analysis of the misfit dislocation and strain relaxation as functions of the growth temperature and rate led to an optimal growth window for a high quality GaSb epitaxial layer on (001) GaP. With this demonstrated optimized growth, a high mobility (25,500 cm(2) V (-1) s(-1) at room temperature) AlSb/InAs heterostructure on a semi-insulating (001) GaP substrate has been achieved.

  4. Field emission properties of N-doped capped single-walled carbon nanotubes: a first-principles density-functional study.

    Science.gov (United States)

    Qiao, L; Zheng, W T; Xu, H; Zhang, L; Jiang, Q

    2007-04-28

    The geometrical structures and field emission properties of pristine and N-doped capped (5,5) single-walled carbon nanotubes have been investigated using first-principles density-functional theory. The structures of N-doped carbon nanotubes are stable under field emission conditions. The calculated work function of N-doped carbon nanotube decreases drastically when compared with pristine carbon nanotube, which means the enhancement of field emission properties. The ionization potentials of N-doped carbon nanotubes are also reduced significantly. The authors analyze the field emission mechanism in terms of energy gap between the lowest unoccupied molecular orbital and the highest occupied molecular orbital, Mulliken charge population, and local density of states. Due to the doping of nitrogen atom, the local density of states at the Fermi level increases dramatically and donor states can be observed above the Fermi level. The authors' results suggest that the field emission properties of carbon nanotubes can be enhanced by the doping of nitrogen atom, which are consistent with the experimental results.

  5. Observation of Fluorescence Emissions from Single-Bubble Sonoluminescence in Water doped with Quinine

    CERN Document Server

    Lu, J Q; Lin, F K; Liu, Y H

    2005-01-01

    Sonoluminescence is a phenomenon involving the transduction of sound into light. The detailed mechanism as well as the energy-focusing potentials are not yet fully explored and understood. So far only optical photons are observed, while emissions in the ultra-violet range are only inferred. By doping the fluorescent dye quinine into water with dilute sulphuric acid, the high energy photons can be converted into the optical photons with slower decay constants. These sonoluminescence and fluorescent emissions were observed in coincidence, and the emitted energy of the two modes can be differentiated by their respective timing profiles. Plans for using this technique as a diagnostic tool to quantitatively study ultra-violet and other high energy emissions in sonoluminescence are discussed.

  6. Ultrahigh power factor and thermoelectric performance in hole-doped single-crystal SnSe.

    Science.gov (United States)

    Zhao, Li-Dong; Tan, Gangjian; Hao, Shiqiang; He, Jiaqing; Pei, Yanling; Chi, Hang; Wang, Heng; Gong, Shengkai; Xu, Huibin; Dravid, Vinayak P; Uher, Ctirad; Snyder, G Jeffrey; Wolverton, Chris; Kanatzidis, Mercouri G

    2016-01-01

    Thermoelectric technology, harvesting electric power directly from heat, is a promising environmentally friendly means of energy savings and power generation. The thermoelectric efficiency is determined by the device dimensionless figure of merit ZT(dev), and optimizing this efficiency requires maximizing ZT values over a broad temperature range. Here, we report a record high ZT(dev) ∼1.34, with ZT ranging from 0.7 to 2.0 at 300 to 773 kelvin, realized in hole-doped tin selenide (SnSe) crystals. The exceptional performance arises from the ultrahigh power factor, which comes from a high electrical conductivity and a strongly enhanced Seebeck coefficient enabled by the contribution of multiple electronic valence bands present in SnSe. SnSe is a robust thermoelectric candidate for energy conversion applications in the low and moderate temperature range.

  7. Thermal and radiative characteristics of oxyfluoride glass singly doped with lanthanide ions

    Institute of Scientific and Technical Information of China (English)

    Barbara; Gra(z)yna; DOMINIAK-DZIK; RYBA-ROMANOWSKI

    2010-01-01

    Rare earths-doped oxyfluoride glasses based on germanium oxide and lead fluoride were prepared from commercial raw materials.The glasses with general composition of 50GeO2-(50-x-y)PbO-yPbF2-xLnF3(Ln=Pr3+-Yb3+),contained different concentrations of optically active dopants(x=0.2 mol.% and 2 mol.%)and PbF2(y≤15 mol.%).The differential thermal analysis(DTA)was used to determine both thermal characteristic and thermal stability properties of the glasses in the function of the kind of dopant,its concentration,and a glass composition.Characteristic glass temperatures such as glass transition temperature(Tg),glass crystallization temperature(Tc)and temperature corresponding to the maximum of the crystallization rate(Tpc)were evaluated.On the basis of obtained results,the thermal stabilities of glasses under study were evaluated using various thermal stability criteria(Dietzel factor △T,Saad-Poulain factors H' and S').It was found that the increase in rare earth fluoride contents influenced thermal characteristics when the characteristic temperatures of the individual glass was shifted towards higher values.The effect of the PbF2 content and the kind of rare earth impurity on the glass stability was observed.Absorption spectra of lanthanide-doped glasses were measured at room temperature and used to determine the phenomenological intensity parameters Ωt and next,to estimate radiative properties of lanthanide ions in this matrix.Radiative transition probabilities of luminescent states of Ln3+,branching ratios and radiative lifetimes were determined.The variation of the Ωt along the lanthanide series was presented and discussed.

  8. Spectroscopic characterization of a single dangling bond on a bare Si(100)- c ( 4 × 2 ) surface for n - and p -type doping

    KAUST Repository

    Mantega, M.

    2012-07-19

    We investigate the charging state of an isolated single dangling bond formed on an unpassivated Si(100) surface with c(4×2) reconstruction, by comparing scanning tunneling microscopy and spectroscopy analysis with density functional theory calculations. The dangling bond is created by placing a single hydrogen atom on the bare surface with the tip of a scanning tunneling microscope. The H atom passivates one of the dimer dangling bonds responsible for the surface one-dimensional electronic structure. This leaves a second dangling at the reacted surface dimer which breaks the surface periodicity. We consider two possible H adsorption configurations for both the neutral and the doped situation (n- and p-type). In the case of n-doping we find that the single dangling bond state is doubly occupied and the most stable configuration is that with H bonded to the bottom Si atom of the surface dimer. In the case of p-doping the dangling bond is instead empty and the configuration with the H attached to the top atom of the dimer is the most stable. Importantly the two configurations have different scattering properties and phase shift fingerprints. This might open up interesting perspectives for fabricating a switching device by tuning the doping level or by locally charging the single dangling bond state. © 2012 American Physical Society.

  9. Elaboration and characterization of a KCl single crystal doped with nanocrystals of a Sb2O3 semiconductor

    Institute of Scientific and Technical Information of China (English)

    L.Bouhdjer; S.Addala; A.Chala; O.Halimi; B.Boudine; M.Sebais

    2013-01-01

    Undoped and doped KCl single crystals have been successfully elaborated via the Czochralski (Cz)method.The effects of dopant Sb2O3 nanocrystals on structural and optical properties were investigated by a number of techniques,including X-ray diffraction (XRD),scanning electron microscopy (SEM),energy dispersive X-ray (EDAX) analysis,UV-visible and photoluminescence (PL) spectrophotometers.An XRD pattern of KCl:Sb2O3 reveals that the Sb2O3 nanocrystals are in the well-crystalline orthorhombic phase.The broadening of diffraction peaks indicated the presence of a Sb2O3 semiconductor in the nanometer size regime.The shift of absorption and PL peaks is observed near 334 nm and 360 nm respectively due to the quantum confinement effect in Sb2O3 nanocrystals.Particle sizes calculated from XRD studies agree fairly well with those estimated from optical studies.An SEM image of the surface KCl:Sb2O3 single crystal shows large quasi-spherical of Sb2O3 crystallites scattered on the surface.The elemental analysis from EDAX demonstrates that the KCl:Sb2O3 single crystal is slightly rich in oxygen and a source of excessive quantities of oxygen is discussed.

  10. Surface passivation of (100 GaSb using self-assembled monolayers of long-chain octadecanethiol

    Directory of Open Access Journals (Sweden)

    E. Papis-Polakowska

    2016-05-01

    Full Text Available The passivation of (100 GaSb surface was investigated by means of the long-chain octadecanethiol (ODT self-assembled monolayer (SAM. The properties of ODT SAM on (100 GaSb were characterized by the atomic force microscopy using Kelvin probe force microscopy mode and X-ray photoelectron spectroscopy. The chemical treatment of 10mM ODT-C2H5OH has been applied to the passivation of a type-II superlattice InAs/GaSb photodetector. The electrical measurements indicate that the current density was reduced by one order of magnitude as compared to an unpassivated photodetector.

  11. GASB proposes new standards for financial reporting of postemployment benefits by state and local governments.

    Science.gov (United States)

    Johnson, Karl D

    2003-03-01

    GASB has proposed new standards that will affect the way in which governments report postemployment health care benefits in audited external financial statements, resulting in more complete and transparent reporting by employers and plans and more relevant and useful information for the users of governmental financial reports. This article provides an overview of current financial reporting standards and practice, the financial reporting objectives of the project, the proposed measurement approach, noteworthy specific proposals, and the projected timetable for completion of the project and implementation of the new standards.

  12. Growth morphology and structure of bismuth thin films on GaSb(110)

    DEFF Research Database (Denmark)

    Gemmeren, T. van; Lottermoser, L.; Falkenberg, G.

    1998-01-01

    Photoelectron spectroscopy, low-energy electron diffraction, scanning tunneling microscopy and surface X-ray diffraction were used to investigate the growth of thin layers of bismuth on GaSb(110). At submonolayer coverages, growth of two-dimensional islands occurs. A uniform (1 x I)-reconstructio...... that the (1 x 1)-phases formed by antimony and bismuth adsorbates on (110) surfaces of other III-V compound semiconductors are also described by the epitaxial continued layer model. (C) 1998 Elsevier Science B.V. All rights reserved....

  13. Antisites and anisotropic diffusion in GaAs and GaSb

    KAUST Repository

    Tahini, H. A.

    2013-10-02

    The significant diffusion of Ga under Ga-rich conditions in GaAs and GaSb is counter intuitive as the concentration of Ga vacancies should be depressed although Ga vacancies are necessary to interpret the experimental evidence for Ga transport. To reconcile the existence of Ga vacancies under Ga-rich conditions, transformation reactions have been proposed. Here, density functional theory is employed to calculate the formation energies of vacancies on both sublattices and the migration energy barriers to overcome the formation of the vacancy-antisite defect. Transformation reactions enhance the vacancy concentration in both materials and migration energy barriers indicate that Ga vacancies will dominate.

  14. GaSb grown from Sn solvent at low temperatures by LPE

    Energy Technology Data Exchange (ETDEWEB)

    Compean, V H; Anda, F de; Mishurnyi, V A; Gorbatchev, A Yu, E-mail: fdeanda@cactus.iico.uaslp.m [Universidad Autonoma de San Luis Potosi, Instituto de Investigacion en Comunicacion Optica, Av. Karakorum 1470, Col. Lomas 4a Sec., San Luis Potosi, SLP, CP 78210 (Mexico)

    2009-05-01

    The LPE growth of GaSb using Sn as a solvent has been studied in the temperature range 250-370 C and using liquid solutions covering a wide range of compositions. In order to find the growth conditions the phase diagram has been determined experimentally around the same temperature region. It is shown the Sn incorporates into the grown layers and that it behaves as an acceptor. The photoluminescence spectra of the grown layers with different Sn contents show characteristic peaks that can be attributed to different recombination processes.

  15. Stable single-polarization single-longitudinal-mode linear cavity erbium-doped fiber laser based on structured chirped fiber Bragg grating.

    Science.gov (United States)

    Yin, Bin; Liu, Zhibo; Feng, Suchun; Bai, Yunlong; Li, Haisu; Jian, Shuisheng

    2015-01-01

    A novel linear cavity erbium-doped fiber (EDF) laser based on a structured chirped fiber Bragg grating (CFBG) filter is proposed for stable single-polarization (SP) single-longitudinal-mode (SLM) operation. For the first time, to the best of our knowledge, a structured CFBG filter with an ultranarrow transmission band which is generated by tapering directly on CFBG is used to select the laser longitudinal mode. The SLM operation is obtained by using the structured CFBG together with an unpumped EDF acting as a saturable absorber. The fluctuations of the laser peak power and center wavelength are less than 0.07 dB and 1 pm in 1 h, respectively. The stable SP operation is achieved by using the inline broadband polarizer. The measured 20 dB laser linewidth is about 27.7 kHz, which indicates the laser linewidth is approximately 1.39 kHz FWHM.

  16. High Power Compact Single-Frequency Volume Bragg Er-Doped Fiber Laser Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The purpose of this NASA SBIR Phase I proposal is to develop the prototype of a compact single-frequency mode one longitudinal and one transverse mode laser...

  17. Tunable Single Frequency 2.05 Micron Fiber Laser Using New Ho-Doped Fiber Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In this proposal, we propose to demonstrate and build a widely tunable, narrow linewidth, single frequency fiber laser near 2.05 micron by developing an innovative...

  18. Tunable Single Frequency 2.054 Micron Fiber Laser Using New Ho-Doped Fiber Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In this proposal, we propose to demonstrate and build a near 2 micron widely tunable, narrow linewidth, single frequency fiber laser by developing an innovative...

  19. Multicolor Photodetector of a Single Er(3+)-Doped CdS Nanoribbon.

    Science.gov (United States)

    Dedong, Hou; Ying-Kai, Liu; Yu, De-Peng

    2015-12-01

    Er(3+)-doped CdS nanoribbons (Er-CdS NRs) are synthesized by thermal evaporation and then characterized by field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and absorption spectra. The Er-CdS NR photodetector is studied systematically, including spectral response, light intensity response, and photoconductance (G) versus temperature (T). It is found that Er-CdS NR has the ability of detecting multicolor light including blue, red, and near-infrared light with higher responsivity (R λ ) and external quantum efficiency (η). The conductance of Er-CdS NR under dark conditions decreases with increasing temperature in the range of 87-237 K, while its conductance increases with increasing temperature in the range of 237-297 K when T is larger than 237 K. These results indicated that ionized impurities and the intrinsic excitation are responsible for the conductance change of Er-CdS NR in the dark. The superior performance of the Er-CdS NR device offers an avenue to develop highly sensitive multicolor photodetector applications.

  20. Recombination luminescence and EPR of Mn doped Li2B4O7 single crystals

    Science.gov (United States)

    Romet, I.; Buryi, M.; Corradi, G.; Feldbach, E.; Laguta, V.; Tichy-Rács, É.; Nagirnyi, V.

    2017-08-01

    Manganese doped Li2B4O7 (LTB) crystals have been studied using luminescence and EPR spectroscopy, extending the investigations for the first time from the X band to the Q band for higher resolution. Mn2+ ions are shown to substitute dominantly at lithium sites charge compensated by a nearby lithium vacancy. Excitation spectra of the Mn2+ ion emission have been studied in the energy range of 2.5-20 eV. Weak excitation bands up to 5.5 eV are ascribed to specific transitions within the same 3d5 electronic configuration according to the Tanabe-Sugano diagram. A doublet of intense excitation bands in the 7-8 eV region is assigned to electronic transitions to the Mn2+6D term split by crystal field into two sub-bands. Thermostimulated luminescence (TSL) curves were studied in the temperature range 5-600 K. Based on the EPR studies and the comparison of TSL spectra of irradiated crystals with spectra of photostimulated luminescence, models of TSL processes are proposed. Emission and TSL processes are shown to be strongly influenced by local lattice relaxation and the mobility of Li vacancies participating in complexes with three different charge states of the Mn dopant.

  1. Dy3+ ions doped single and mixed alkali fluoro tungsten tellurite glasses for LASER and white LED applications

    Science.gov (United States)

    Annapurna Devi, Ch. B.; Mahamuda, Sk.; Venkateswarlu, M.; Swapna, K.; Srinivasa Rao, A.; Vijaya Prakash, G.

    2016-12-01

    A new-fangled series of Dy3+ ions doped Single and Mixed Alkali Fluoro Tungsten Tellurite Glasses have been prepared by using melt quenching technique and their spectroscopic behaviour was investigated by using XRD, optical absorption, photoluminescence and lifetime measurements. The bonding parameter studies reveal the ionic nature of the Dysbnd O bond in the present glasses. From the absorption spectra, the Judd-Ofelt (J-O) intensity parameters have been determined and in turn used to determine various radiative properties for the different emission transitions from the 4F9/2 fluorescent level. The photoluminescence spectra of all the glasses exhibit two intensified peaks in blue and yellow regions corresponding to the transitions 4F9/2 → 6H15/2 (483 nm) and 4F9/2 → 6H13/2 (575 nm) respectively. From the photoluminescence spectra, it is observed that the luminescence intensity is maximum for Dy3+ ion doped potassium combination of tungsten tellurite glass (TeWK:1Dy). The highest emission cross-section and branching ratio values observed for the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions suggest the possible laser action in the visible region from these glasses. By correlating the experimental lifetimes (τexp) measured from the decay spectral features with radiative lifetimes (τR), the quantum efficiencies (η) for all the glasses have been evaluated and found to be maximum for potassium combination tungsten tellurite (TeWK:1Dy) glass. The CIE colour chromaticity coordinates (x, y), (u, v), colour correlated temperature (CCT) and Y/B ratio were also estimated from the photoluminescence spectra for different compositions of glasses. The chromaticity colour coordinates evaluated for all the glasses fall within the white light region and white light emission can be tuned by varying the composition of the glass. From all these studies, it was concluded that 1 mol% of Dy3+ ions doped TeWK glass is more suitable for lasing and white-LED applications.

  2. Effect of Mg co-doping on cathodoluminescence properties of LuGAGG:Ce single crystalline garnet films

    Science.gov (United States)

    Schauer, P.; Lalinský, O.; Kučera, M.; Lučeničová, Z.; Hanuš, M.

    2017-10-01

    Mg2+ co-doped (LuGd)3(GaAl)5O12:Ce (LuGAGG:Ce,Mg) multicomponent single crystalline epitaxial garnet films were prepared and their cathodoluminescence (CL) and thermoluminescence (TSL) properties were studied in this paper. The films were prepared using the liquid phase epitaxy from lead-free BaO-B2O3-BaF2 flux and their scintillation properties were characterized using the 10 keV collimated e-beam. More specifically, temperature dependent CL intensity, CL emission spectra, CL decay characteristics as well as TSL emission characteristics of the mentioned films were measured. At the highest content of Mg (700 ppm), the CL decay time was as low as 28 ns and the CL afterglow was as low as 0.01% at 1 μs after the e-beam excitation cut-off, which are important parameters for electron detectors in e-beam devices. The CL temperature quenching of the studied films began above room temperature. An increase of Mg concentration to or above 280 ppm quenched the characteristic CL emission of LuGAGG:Ce,Mg. The TSL measurements show that the trap population in studied garnet samples is considerably suppressed. The LuGAGG:Ce,Mg multicomponent single crystalline epitaxial films were evaluated as the perspective fast scintillators for the electron detectors in the e-beam devices.

  3. Highly sensitive formaldehyde resistive sensor based on a single Er-doped SnO{sub 2} nanobelt

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shuanghui, E-mail: lishuanghui808@163.com [Key Laboratory of Yunnan Higher Education Institutes for Optoelectric Information & Technology, Kunming 650500 (China); Key Laboratory of Photoelectric Materials & Device, Kunming 650500 (China); Institute of Physics and Electronic Information, Yunnan Normal University, Kunming 650500 (China); Liu, Yingkai, E-mail: liuyingkai99@163.com [Key Laboratory of Yunnan Higher Education Institutes for Optoelectric Information & Technology, Kunming 650500 (China); Key Laboratory of Photoelectric Materials & Device, Kunming 650500 (China); Institute of Physics and Electronic Information, Yunnan Normal University, Kunming 650500 (China); Wu, Yuemei, E-mail: wuyuemei893@163.com [Key Laboratory of Yunnan Higher Education Institutes for Optoelectric Information & Technology, Kunming 650500 (China); Key Laboratory of Photoelectric Materials & Device, Kunming 650500 (China); Institute of Physics and Electronic Information, Yunnan Normal University, Kunming 650500 (China); Chen, Weiwu, E-mail: chenweiwu55@163.com [Key Laboratory of Yunnan Higher Education Institutes for Optoelectric Information & Technology, Kunming 650500 (China); Key Laboratory of Photoelectric Materials & Device, Kunming 650500 (China); Institute of Physics and Electronic Information, Yunnan Normal University, Kunming 650500 (China); Qin, Zhaojun; Gong, Nailiang, E-mail: qinzhaojun031@163.com [Key Laboratory of Yunnan Higher Education Institutes for Optoelectric Information & Technology, Kunming 650500 (China); Key Laboratory of Photoelectric Materials & Device, Kunming 650500 (China); Institute of Physics and Electronic Information, Yunnan Normal University, Kunming 650500 (China); Yu, Dapeng, E-mail: gongnailiang@163.com [Institute of Physics and Electronic Information, Yunnan Normal University, Kunming 650500 (China); State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871 (China)

    2016-05-15

    SnO{sub 2} nanobelts (SnO{sub 2} NBs) and Er{sup 3+}-doped SnO{sub 2} nanobelts (Er–SnO{sub 2} NBs) were synthesized by thermal evaporation. The obtained samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersion spectrometer (EDS), and X-ray photoelectron spectrometer (XPS). It is found that Er–SnO{sub 2} NBs have a good morphology with smooth surface and their thickness are about 30 nm, widths between 200 nm and 600 nm, and lengths 30–80 mm. The nanobelts with good morphology were taken to develop sensors based on a single Er–SnO{sub 2} NB/SnO{sub 2} NB for studying sensitive properties. The results reveal that the response of a single Er–SnO{sub 2} nanobelt device is 9 to the formaldehyde gas with a shorter response (recovery time) of 17 (25) s.

  4. Growth and Physical Property Study of Single Nanowire (Diameter ~45 nm of Half Doped Manganite

    Directory of Open Access Journals (Sweden)

    Subarna Datta

    2013-01-01

    Full Text Available We report here the growth and characterization of functional oxide nanowire of hole doped manganite of La0.5Sr0.5MnO3 (LSMO. We also report four-probe electrical resistance measurement of a single nanowire of LSMO (diameter ~45 nm using focused ion beam (FIB fabricated electrodes. The wires are fabricated by hydrothermal method using autoclave at a temperature of 270 °C. The elemental analysis and physical property like electrical resistivity are studied at an individual nanowire level. The quantitative determination of Mn valency and elemental mapping of constituent elements are done by using Electron Energy Loss Spectroscopy (EELS in the Transmission Electron Microscopy (TEM mode. We address the important issue of whether as a result of size reduction the nanowires can retain the desired composition, structure, and physical properties. The nanowires used are found to have a ferromagnetic transition (TC at around 325 K which is very close to the bulk value of around 330 K found in single crystal of the same composition. It is confirmed that the functional behavior is likely to be retained even after size reduction of the nanowires to a diameter of 45 nm. The electrical resistivity shows insulating behavior within the measured temperature range which is similar to the bulk system.

  5. Self Q-switched characteristic based on single longitudinal DBR erbium-doped fiber laser with narrow linewidth pulse output

    Science.gov (United States)

    Lyu, Chengang; Zhang, Shuai; Zhang, Xugeng; Gao, Jiale; Jie, Jin

    2017-09-01

    The self Q-switched characteristic of the single longitudinal-mode distributed Bragg reflector (DBR) erbium-doped fiber laser (EDFL) with narrow linewidth pulse output is demonstrated without any extra saturable absorber or electro-optic and acoustic-optic modulator, and it is provided with a simpler structure and lower cost. The proposed pulse laser operates at approximately 1550.33 nm with a 20 dB bandwidth of 0.56 nm and signal-to-noise ratio of about 55 dB. By increasing the 980 nm pump power from 80-330 mW, the repetition rate of the output pulse increases from 73.53-147.1 kHz while the pulse width decreases from 1.4-0.2 µs, which shows the feature of the narrow linewidth ideally. The maximum pulse energy of 0.379 nJ and peak power of 1897.2 µW are generated with a repetition rate and pulse width of 147.1 kHz and 0.2 µs, respectively. The result shows that the self Q-switched pulse of the DBR EDFL is obviously dependent on the applied pump power and possesses the characteristic of the single longitudinal mode and the narrow linewidth, offering potential utilization in industrial processing and scientific research.

  6. Investigation of morphological and electrical characteristics of tin doped indium oxide layers produced by a quasi single source precursor system

    Energy Technology Data Exchange (ETDEWEB)

    Veith, M., E-mail: Michael.veith@inm-gmbh.de [INM - Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbruecken (Germany); Saarland University, Inorganic Chemistry, Campus C4 1, 66123 Saarbruecken (Germany); Bubel, C.; Grobelsek, I. [INM - Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbruecken (Germany)

    2012-12-01

    Sol-gel coatings of tin doped indium oxide (ITO) were prepared via spin-coating, using a quasi single source precursor system that enhances homogeneous distribution of the dopant tin inside the oxide lattice. In addition, the implementation of metastable, bivalent tin into the gel layer enables the application of a one-step heat treatment under inert atmosphere, eliminating the need for the usually required critical post reduction treatment after crystallisation. The ITO layers produced were uniformly polycrystalline with a homogeneous thickness of 60 nm. They showed increased electrical conductivity and optical performance in terms of transmission (vis) and IR reflection. The texture was less pronounced and the tensile residual stress determined in the layers was lower than in similar films, manufactured in a conventional two-step annealing process. - Highlights: Black-Right-Pointing-Pointer A quasi single source precursor system enables one-step heat treatment of layers. Black-Right-Pointing-Pointer Thereby less pronounced texture and lower tensile residual stress were obtained. Black-Right-Pointing-Pointer The layers show hardly any fluctuations in the thickness. Black-Right-Pointing-Pointer The electrical conductivity could be increased. Black-Right-Pointing-Pointer Optical performance in terms of transmission (vis) and IR reflection was increased.

  7. Structural and optical properties of nanocrystalline pure and indium doped tin oxide powders synthesized in a single step by flame spray pyrolysis

    Science.gov (United States)

    Silvister Raju, M. J.; Bhattacharya, S. S.

    2017-07-01

    Phase pure tin oxide (SnO2) and indium doped SnO2 nanocrystalline powders were synthesized in a single step by a flame spray pyrolysis method. The as-synthesized powders were characterized by standard techniques of x-ray diffraction, scanning and transmission electron microscopy, x-ray photoelectron spectroscopy and absorption spectroscopy. Using x-ray diffraction, it was established that the powders had the rutile (cassiterite) structure with tetragonal unit cells in the space group P42/mnm. Using the Rietveld refinement method, structural analysis was carried out in order to obtain the lattice parameters, volume and density. X-ray photoelectron spectra confirmed the presence of indium in the doped samples. Absorption spectra revealed that the powders were transparent to the visible spectrum with a sharp absorption below 350 nm. Energy bandgaps, estimated by Tauc plots, established that increasing the doping concentration reduced the bandgap.

  8. Unusual Magnetic Susceptibility Anisotropy in Untwinned La{sub 2{minus}x}Sr{sub x}CuO{sub 4} Single Crystals in the Lightly Doped Region

    Energy Technology Data Exchange (ETDEWEB)

    Lavrov, A. N.; Ando, Yoichi; Komiya, Seiki; Tsukada, I.

    2001-07-02

    We present a study of the magnetic susceptibility {chi} in carefully detwinned La{sub 2{minus}x}Sr {sub x}CuO{sub 4} single crystals in the lightly doped region (x=0{endash}0.03) , which demonstrates a remarkable in-plane anisotropy of the spin system. This anisotropy, {chi}{sub a}/{chi}{sub b} , is found to persist after the long-range antiferromagnetic (AF) order is destroyed by hole doping, suggesting that doped holes break the AF order into domains in which the spin alignment is kept essentially intact. It turns out that the freezing of the spins taking place at low temperatures is also notably anisotropic, implying that the {open_quotes}spin-glass{close_quotes} feature is governed by the domain structure as well.

  9. Unusual Magnetic Susceptibility Anisotropy in Untwinned La{sub 2-x}Sr{sub x}CuO{sub 4} Single Crystals in the Lightly Doped Region

    Energy Technology Data Exchange (ETDEWEB)

    Lavrov, A. N.; Ando, Yoichi; Komiya, Seiki; Tsukada, I.

    2001-07-02

    We present a study of the magnetic susceptibility {chi} in carefully detwinned La{sub 2-x}Sr {sub x}CuO{sub 4} single crystals in the lightly doped region (x=0--0.03) , which demonstrates a remarkable in-plane anisotropy of the spin system. This anisotropy, {chi}{sub a}/{chi}{sub b} , is found to persist after the long-range antiferromagnetic (AF) order is destroyed by hole doping, suggesting that doped holes break the AF order into domains in which the spin alignment is kept essentially intact. It turns out that the freezing of the spins taking place at low temperatures is also notably anisotropic, implying that the ''spin-glass'' feature is governed by the domain structure as well.

  10. Synthesis, characterization and anti-microbial activity of pure, Cu2+ and Cd2+ doped organic NLO l-arginine trifluoroacetate single crystals

    Science.gov (United States)

    Prasanyaa, T.; Haris, M.; Jayaramakrishnan, V.; Amgalan, M.; Mathivanan, V.

    2013-10-01

    Optically transparent Cu2+ and Cd2+ doped l-arginine trifluoroacetate (LATF) single crystals were grown from its aqueous solution using the slow solvent evaporation technique. The grown crystals were characterized by powder x-ray diffraction to confirm the monoclinic crystal structure. The percentage of transmittance measured using the ultraviolet-visible-near infrared spectrophotometer was found to be more than 80% for doped crystals. The functional group analysis of the grown crystals has been made by Fourier transform infrared spectroscopy. Thermogravimetric/differential thermal analysis was performed for the grown crystals. An atomic absorption study was carried out to determine the presence of Cu2+ and Cd2+. The hardness of the grown crystals was assessed and the results show a significant variation in the hardness value between the pure and doped LATF crystals. The second harmonic generation measurements show that Cu2+ doped LATF is 2.8 times greater and Cd2+ doped is 2.6 times greater than KDP. The anti-bacterial and anti-fungal activities of the title compound were performed using the disc diffusion method against standard bacteria Escherichia coli, Xanthomonas oryzae and against the fungus Aspergillus niger and Aspergillus flavus.

  11. MBE growth of Sb-based bulk nBn infrared photodetector structures on 6-inch GaSb substrates

    Science.gov (United States)

    Liu, Amy W. K.; Lubyshev, Dmitri; Qiu, Yueming; Fastenau, Joel M.; Wu, Ying; Furlong, Mark J.; Tybjerg, Marius; Martinez, Rebecca J.; Mowbray, Andrew; Smith, Brian

    2015-06-01

    The GaSb-based 6.1 Å lattice constant family of materials and heterostructures provides rich bandgap engineering possibilities and have received considerable attention for their potential and demonstrated performance in infrared (IR) detection and imaging applications. Mid-wave and long-wave IR photodetectors are progressing toward commercial manufacturing applications. To succeed, they must move from research laboratory settings to general semiconductor production, and high-quality GaSb-based epitaxial wafers with diameter larger than the current standard 3-inch are highly desirable. 4-inch GaSb substrates have been in production for a couple of years and are now commercially available. Recently, epi-ready GaSb substrates with diameter in excess of 6-inch were successfully produced. In this work, we report on the MBE (Molecular Beam Epitaxy) growth of generic MWIR bulk nBn photodetectors on 6-inch diameter GaSb substrates. The surface morphology, optical and structural quality of the epiwafers as evaluated by atomic force microscopy (AFM), Nomarski microscopy, low temperature photoluminescence (PL) spectroscopy, and high-resolution x-ray diffraction (XRD) will be discussed. Current density versus voltage (J-V) and photoresponsivity measurements from large-area mesa diode fabricated will also be reported. Material and device properties of these 6-inch epiwafers will be compared to similar structures grown on commercially available 4-inch diameter GaSb substrates.

  12. Thermoluminescent sensitivity of single clad neodymium doped SiO2 optical fibres measured with 6 MeV photons

    Science.gov (United States)

    Saeed, M. A.; Hossain, I.; Hida, N.; Wagiran, H.

    2013-10-01

    This study investigates the thermoluminescent sensitivity of neodymium doped SiO2 optical fibre with various dose ranges from 0.5 Gy to 4.0 Gy by 6 MeV photon irradiations. The TL responses of the neodymium doped silica fibres are compared with available TLD-100 dosimeter in order to determine the suitability as a TL material. We found that the TLD-100 and neodymium doped silica fibre have a significant linear signal to dose relationship. Neodymium doped fibres sensitivity is approximately 11% of TLD-100.

  13. Synthesis and optical properties of Tb{sup 3+} doped CdF{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Boubekri, H. [Laser Department, Nuclear Technique Division, Nuclear Research Center of Algiers, 02 Bd Frantz Fanon, 16000 Algiers (Algeria); Laboratory of Laser Physics, Optical Spectroscopy and Optoelectronics (LAPLASO), Badji Mokhtar Annaba University, PO Box 12, 23000 Annaba (Algeria); Diaf, M., E-mail: diafma@yahoo.fr [Laboratory of Laser Physics, Optical Spectroscopy and Optoelectronics (LAPLASO), Badji Mokhtar Annaba University, PO Box 12, 23000 Annaba (Algeria); Labbaci, K. [Laboratory of Laser Physics, Optical Spectroscopy and Optoelectronics (LAPLASO), Badji Mokhtar Annaba University, PO Box 12, 23000 Annaba (Algeria); Guerbous, L. [Laser Department, Nuclear Technique Division, Nuclear Research Center of Algiers, 02 Bd Frantz Fanon, 16000 Algiers (Algeria); Duvaut, T.; Jouart, J.P. [ECATHERM/GRESPI, Reims Champagne-Ardenne University (France)

    2013-10-25

    Highlights: •Terbium doped CdF{sub 2} single crystals grown by Bridgman technique. •Absorption, excitation and emission spectra recorded at room temperature. •Spectroscopic properties investigated by use of the Judd–Ofelt theory. •Transition probability, radiative lifetimes, quantum efficiency and branching ratios are calculated. •Emission cross-section is measured by use of Füchtbauer–Ladenburg theory. -- Abstract: This paper reports the optical analysis of Tb{sup 3+} doped CdF{sub 2} single crystals. The pulled crystals were prepared by use of the Bridgman technique from a vacuum furnace in fluoride atmosphere. Absorption, photoluminescence excitation and emission spectra were recorded at room temperature. The Judd–Ofelt (JO) intensity parameters Ω{sub 2}, Ω{sub 4} and Ω{sub 6} for 4f–4f transitions of Tb{sup 3+} ions were computed from the optical absorption spectra using UV, visible and near infrared transitions. These parameters were then used to calculate the radiative transition probabilities (A{sub JJ′}), branching ratios (β{sub JJ′}) and radiative lifetimes of the two main laser emitting levels {sup 5}D{sub 3} and {sup 5}D{sub 4} of Tb{sup 3+} ions. The obtained spectroscopic properties are compared to those of Tb{sup 3+} transitions in other hosts. The excitation spectrum in the UV–Visible spectral range is very close to the absorption spectrum indicating that all observed absorption levels can excite the green emission of Tb{sup 3+} corresponding to {sup 5}D{sub 4} → {sup 7}F{sub 5} transition. The emission spectra exhibit a weak blue emission and a strong green emission in the spectral range 370–460 nm and 478–612 nm which are assigned to {sup 5}D{sub 3} → {sup 7}F{sub J} (J = 6, 5, 4, 3, 2) and {sup 5}D{sub 4} → {sup 7}F{sub J} (J = 6, 5, 4, 3) transitions of Tb{sup 3+}, respectively. The green emission {sup 5}D{sub 4} → {sup 7}F{sub 5} at 532 nm having an emission cross-section equal to 8 × 10{sup −22} cm

  14. Microwave excitation of localized electrons in phosphorus-doped silicon single electron transistors

    Science.gov (United States)

    Creswell, L. A.; Hasko, D. G.; Williams, D. A.

    2009-05-01

    We investigate the effect of microwave irradiation on the source-drain current of a silicon single electron transistor, with fixed source-drain and gate voltages, at a temperature of 4 K. The source-drain current can be increased, decreased, or even reversed by the radiation, depending on the microwave frequency and dc bias conditions. Some of the source-drain current changes take the form of sharp resonances with high quality factor. We investigate the effect of the microwave irradiation coupling method on the form of these resonances. The coupling method does not modify the center frequency of the resonances however it does alter the resonance shape. We discuss the origin of these resonant features and propose that they originate from the microwave induced spatial redistributions of localized electrons in the single electron transistor.

  15. Wavelength tunable single freqeuncy bistability erbium-doped fiber ring laser

    Science.gov (United States)

    Wang, Tianshu; Qian, Sheng; Zhou, Xuefang; Qi, Yongmin; Li, Qiliang

    2008-11-01

    In this paper, a tunable single-frequency fiber laser is designed. For narrow linewidth and single frequency operation, a length of 2.75m unpumped EDF as a saturable absorber is used. The FBG combined with the unpumped EDF provides narrow frequency selection. Counter propagating beams in the unpumped EDF form a standing wave that results in periodic spatial hole burning. This creates a narrower bandwidth absorption grating than the FBG. The output laser wavelength can be changed from 1530nm to 1570nm by the FBG. The 3dB spectrum width of output laser is 0.08nm and the side mode suppression ratio is 55dB. The maximum output power exceeds 12mW, and the stability is less than +/-0.005dB. A nice single-frequency laser is observed. From the relationship of the pump power and output power, it is obvious that the optical bistability switchable phenomena is showed in output characteristics. The bistability switchable phenomena is caused by the saturable absorber in the ring cavity. A 10Gb/s codes rate is used in the fiber laser transmission experiment. The high speed optical signal is transmitted in long distance without regeneration. The eye diagrams of optical transmission are measured, the performance of long haul transmission with high speed modulation is perfect.

  16. EPR and optical study of Yb3+-doped β-PbF2 single crystals and nanocrystals of glass-ceramics

    Science.gov (United States)

    Dantelle, G.; Mortier, M.; Goldner, Ph; Vivien, D.

    2006-08-01

    β-PbF2 single crystals doped with YbF3 (0.2% and 2%) were studied by x-ray diffraction (XRD), electron paramagnetic resonance (EPR) and optical spectroscopy. EPR revealed the presence of only one kind of paramagnetic ion Yb3+, in a cubic symmetry site. The optical absorption, emission and excitation spectra enabled us to identify the transitions attributed to Yb3+ in the cubic site and to determine its energy level diagram. Site-selective laser spectroscopy also evidenced the presence of another type of Yb3+ ions, undetectable by classical EPR. This second type, which dominates in the 2%-doped crystal and exhibits cooperative luminescence, was attributed to Yb3+ ions forming clusters. Transparent oxyfluoride glass-ceramics, containing β-Pb1-yYbyF2+y nanocrystallites, were also synthesized and studied by XRD, EPR and optical spectroscopy. Two types of Yb3+ ions were found, as in β-PbF2 single crystals. The optical properties of the oxyfluoride glass-ceramics turn out to be similar to those of ytterbium activated β-PbF2 single crystals. Moreover, the Yb environments found in PbF2 single crystals seem to already occur in the parent glass. Therefore, these materials are expected to be good laser media, like the rare-earth doped fluorite crystals, either in bulk or fibre form.

  17. EPR and optical absorption study of Cr{sup 3+}-doped tetramethyl ammonium cadmium chloride single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kripal, Ram [Department of Physics, University of Allahabad, Allahabad 211002 (India)]. E-mail: ram_kripal2001@rediffmail.com; Govind, Har [Department of Electronics, Ewing Christian College, Allahabad 211003 (India); Gupta, S.K. [EPR and IR Spectroscopy Section, Material Characterization Division, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012 (India); Arora, Manju [EPR and IR Spectroscopy Section, Material Characterization Division, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012 (India)

    2006-12-15

    EPR study of Cr{sup 3+}-doped tetramethyl cadmium chloride (TMCC) single crystals is carried out at room temperature. The crystal field and spin-Hamiltonian parameters are evaluated from the resonance line positions of different lines observed in the EPR spectra. The g and D parameter values are found to be g=1.9741{+-}0.0002 and D=553{+-}2x10{sup -4} cm{sup -1}, respectively. EPR data indicate that the site symmetry of Cr{sup 3+} ion in the crystal is distorted octahedron. Cr{sup 3+} ions enter the lattice substitutionally replacing Cd{sup 2+} sites and bind to the neighboring extra Cd vacancies necessary for charge compensation. The optical absorption spectra are measured in 195-925 nm wavelength range at room temperature. From optical study the energy values of different orbital levels are estimated. Further, the bonding parameters are obtained by correlating optical and EPR data and the nature of bonding in the crystal is discussed. The values of Racah parameters (B and C), crystal field parameter (Dq) and nephelauxetic parameters (h and k) are obtained to be B=722, C=2845, Dq=2043 cm{sup -1}, h=1.015 and k=0.21.

  18. Control of a White Organic Light Emitting Diode emission parameters using a single doped RGB active layer

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, D. [Departamento de Ciência dos Materiais e i3N – Instituto de Nanoestruturas, Nanomodelação e Nanofabricação, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus da Caparica, 2829-516 Caparica (Portugal); Pinto, A.; Califórnia, A.; Gomes, J. [CeNTI – Centro de Nanotecnologia, Materiais Técnicos, Funcionais e Inteligentes, Rua Fernando Mesquita 2785, 4760-034 Vila Nova de Famalicão (Portugal); Pereira, L., E-mail: luiz@ua.pt [Departmento de Física e i3N – Instituto de Nanoestruturas, Nanomodelação e Nanofabricação, Universidade de Aveiro, 3810-193 Aveiro (Portugal)

    2016-09-15

    Highlights: • A simple WOLED for Solid State Lighting is proposed with high color stability. • Energy transfer and electroluminescence dynamics of a single RGB layer for WOLEDs. • White shade modulation and stability over large emitting areas and applied voltages. - Abstract: Solid State Lighting technologies based on Organic Light Emitting Diodes, became an interesting focus due to their unique properties. The use of a unique RGB active layer for white emission, although simple in theory, shows difficulty to stabilize both CIE coordinates and color modulation. In this work, a WOLED using a simple RGB layer, was developed achieving a high color stability and shade modulation. The RGB matrix comprises a blue host material NPB, doped with two guests, a green (Coumarin 153) and a red (DCM1) in low concentrations. The RGB layer carrier dynamics allows for the white emission in low device complexity and high stability. This was also shown independent of the white shade, obtained through small changes in the red dopant resulting in devices ranging from warm to cool white i.e. an easy color tuning. A detailed analysis of the opto-electrical behavior is made.

  19. EPR and optical studies of VO2+ doped potassium succinate-succinic acid single crystal - Substitutional incorporation

    Science.gov (United States)

    Juliet sheela, K.; Radha Krishnan, S.; Shanmugam, V. M.; Subramanian, P.

    2017-03-01

    EPR and optical absorption studies of VO2+ doped potassium succinate-succinic acid (KSSA) single crystal has been examined at room temperature. EPR spectrum shows that well resolved hyperfine lines. The angular variation of the EPR spectra has shown that two different VO2+ complexes are located in different chemical environments. Among the number of sites, two sites have been followed and reported here. From the EPR analysis, spin Hamiltonian parameters g and A tensors and their directional cosines are evaluated. Both the sites experience rhombic crystal field symmetry around the impurity ion. The VO2+ ion entering the site location of potassium ion has coordination of eight oxygen atoms in a distorted dodecahedral arrangement. The Optical absorption spectrum studied at room temperature shows bands corresponding to C4v symmetry. The crystal field parameter and tetragonal field parameters are calculated. From the Optical and EPR data various molecular orbital coefficients are evaluated and the nature of bonding in the crystal is discussed.

  20. Enhancing the visible light absorption of titania nanoparticles by S and C doping in a single-step process

    Energy Technology Data Exchange (ETDEWEB)

    Scarisoreanu, M. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor, POB MG-36, Magurele, Bucharest 077125 (Romania); Morjan, I., E-mail: ion.morjan@inflpr.ro [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor, POB MG-36, Magurele, Bucharest 077125 (Romania); Alexandrescu, R.; Fleaca, C.T.; Badoi, A.; Dutu, E.; Niculescu, A.-M.; Luculescu, C. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor, POB MG-36, Magurele, Bucharest 077125 (Romania); Vasile, E. [Metav, Research and Development, 31C.A. Rosetti, Bucharest 020011 (Romania); Wang, J.; Bouhadoun, S.; Herlin-Boime, N. [IRAMIS/SPAM/LFP, CEA-CNRS URA 2453, CEA de Saclay, Gif sur Yvettes 91191 (France)

    2014-05-01

    We report the synthesis of carbon coated and sulfur doped titania nanoparticles using a continuous, single-step laser pyrolysis technique. We employed air as oxidant and C{sub 2}H{sub 4} as laser energy transfer agent (sensitizer)/carbon donor, both carrying the TiCl{sub 4} vapors as a titania precursor. The volatile (CH{sub 3}){sub 2}S{sub 2} was used to introduce sulfur as dopant in the nanopowders. The incorporation of C and S atoms in nanopowders with anatase dominant phase and with average particle diameter between 18 and 25 nm was performed through the addition of S{sub 2}(CH{sub 3}){sub 2} and C{sub 2}H{sub 4} to the reactive precursor mixtures. The samples were characterized by: EDX, XRD, TEM, XPS and UV–Vis spectroscopy. By the introduction of the sulfur precursor, the anatase-to-rutile ratio within the resulted TiO{sub 2}-based nanoparticles decreased, as well as their bandgap energy values which are also lower than those of commercial TiO{sub 2} Degussa P25.

  1. Enhancing the visible light absorption of titania nanoparticles by S and C doping in a single-step process

    Science.gov (United States)

    Scarisoreanu, M.; Morjan, I.; Alexandrescu, R.; Fleaca, C. T.; Badoi, A.; Dutu, E.; Niculescu, A.-M.; Luculescu, C.; Vasile, E.; Wang, J.; Bouhadoun, S.; Herlin-Boime, N.

    2014-05-01

    We report the synthesis of carbon coated and sulfur doped titania nanoparticles using a continuous, single-step laser pyrolysis technique. We employed air as oxidant and C2H4 as laser energy transfer agent (sensitizer)/carbon donor, both carrying the TiCl4 vapors as a titania precursor. The volatile (CH3)2S2 was used to introduce sulfur as dopant in the nanopowders. The incorporation of C and S atoms in nanopowders with anatase dominant phase and with average particle diameter between 18 and 25 nm was performed through the addition of S2(CH3)2 and C2H4 to the reactive precursor mixtures. The samples were characterized by: EDX, XRD, TEM, XPS and UV-Vis spectroscopy. By the introduction of the sulfur precursor, the anatase-to-rutile ratio within the resulted TiO2-based nanoparticles decreased, as well as their bandgap energy values which are also lower than those of commercial TiO2 Degussa P25.

  2. Growth and optical properties of Dy doped and undoped n-type InSe single crystal

    Science.gov (United States)

    Gürbulak, B.

    1999-02-01

    Undoped n-InSe and Dy doped n-InSe (n-InSe : Dy) single crystals were grown by a method which is similar to direct freezing method. Ingots had no cracks and voids on the surface. There were no processes to polish and clean treatment at cleavage faces of these samples because of the natural mirror-like cleavage faces. The absorption measurements were carried out in n-InSe and n-InSe : Dy samples in the temperature range 10-320 K. The first exciton energies for n=1 were calculated as 1.331, 1.248 eV in n-InSe and were 1.326, 1.244 eV in n-InSe : Dy at 10 and 300 K, respectively. The second exciton energies for n=2 in n-InSe were calculated as 1.346, 1.336 eV and in n-InSe : Dy were 1.340, 1.332 eV at 10 and 80 K, respectively. Binding energies of n-InSe and n-InSe : Dy were calculated as 19.47 and 18.87 meV, respectively. The direct bands gap for n-InSe are 1.350, 1.267 eV and for n-InSe : Dy are 1.344, 1.263 eV at 10, 300 K, respectively.

  3. Photocatalytic characteristics of single phase Fe-doped anatase TiO{sub 2} nanoparticles sensitized with vitamin B{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Gharagozlou, Mehrnaz, E-mail: gharagozlou@icrc.ac.ir [Department of Nanomaterials and Nanotechnology, Institute for Color Science and Technology, Tehran (Iran, Islamic Republic of); Bayati, R. [Intel Corporation, IMO-SC, SC2, Santa Clara, CA 95054 (United States)

    2015-01-15

    Highlights: • Anatase TiO{sub 2}/B{sub 12} hybrid nanostructured catalyst was successfully synthesized by sol–gel technique. • The nanoparticle catalyst was doped with iron at several concentrations. • Nanoparticles were characterized in detail by XRD, Raman, TEM, EDS, and spectroscopy techniques. • The formation mechanism and role of point defects on photocatalytic properties were discussed. • A structure-property-processing correlation was established. - Abstract: We report a processing-structure-property correlation in B{sub 12}-anatase titania hybrid catalysts doped with several concentrations of iron. Our results clearly show that low-level iron doping alters structure, defect content, and photocatalytic characteristics of TiO{sub 2}. XRD and Raman studies revealed formation of a single-phase anatase TiO{sub 2} where no iron based segregation in particular iron oxide, was detected. FT-IR spectra clearly confirmed sensitization of TiO{sub 2} nanoparticles with vitamin B{sub 12}. TEM micrographs and diffraction patterns confirmed crystallization of anatase nanoparticles with a radius of 15–20 nm. Both XRD and Raman signals showed a peak shift and a peak broadening which are surmised to originate from creation of point defects, namely oxygen vacancy and titanium interstitial. The doped samples revealed a narrower band gap as compared to undoped samples. Photocatalytic activity of the samples was assessed through measuring the decomposition rate of rhodamine B. It was found that sensitization with vitamin B{sub 12} and Fe-doping significantly enhances the photocatalytic efficiency of the anatase nanoparticles. We also showed that there is an optimum Fe-doping level where the maximum photocatalytic activity is achieved. The boost of photocatalytic activity was qualitatively understood to originate from a more effective use of the light photons, formation of point defects, which enhance the charge separation, higher carrier mobility.

  4. Optical investigations on Tb3+ doped L-Histidine hydrochloride mono hydrate single crystals grown by low temperature solution techniques

    Science.gov (United States)

    Rajyalakshmi, S.; Ramachandra Rao, K.; Brahmaji, B.; Samatha, K.; Visweswara Rao, T. K.; Bhagavannarayana, G.

    2016-04-01

    The potential nonlinear optical material of Terbium (Tb3+) ion doped L-Histidine hydrochloride monohydrate (LHHC) single crystals were successfully grown. Tb3+:LHHC crystals of 7 mm × 5 mm × 3 mm and 59 mm length and 15 mm diameter have been grown by the slow solvent evaporation and Sankaranarayanan-Ramasamy (SR) techniques respectively. The grown crystals were characterized by single crystal X-ray diffraction analysis to confirm the crystalline structure and morphology. High resolution X-ray diffraction (HRXRD) studies revealed that the SR grown sample shows relatively good crystalline nature with 9″ full-width at half-maximum (FWHM) for the diffraction curve. Functional groups were identified by Fourier transform infra-red spectroscopy (FTIR). The optical transparency and band gaps of grown crystals were measured by UV-Vis spectroscopy. Thermogravimetric and differential thermal analysis (TG/DTA) studies reveal that the crystal was thermally stable up to 155 °C in SR grown crystal. Surface morphology of the growth plane was observed using scanning electron microscopy (SEM). The incorporation of Tb ion was estimated by EDAX. The frequency-dependent dielectric properties of the crystals were carried out for different temperatures. Vickers hardness study carried out on (1 0 0) face at room temperature shows increased hardness of the SR method grown crystal. Second harmonic generation efficiency of SEST and SR grown crystals are 3.2 and 3.5 times greater than that of pure KDP. The Photoluminescence (PL) studies of Tb3+ ions result from the radiative intra-configurational f-f transitions that occur from the 5D4 excited state to the 7Fj (j = 6, 5, 4, 3) ground states. The decay curve of the 5D4 level of emission was observed with a long life time of 319.2041 μs for the SR grown Tb3+:LHHC crystal.

  5. Luminescence of Single Crystals Cadmium Bromide Doped with Impurities of Argentum

    Directory of Open Access Journals (Sweden)

    N.V. Stetsyk

    2014-06-01

    Full Text Available Temperature behaviors of X-ray luminescence (XL or RL, photoluminescence (PL, and thermoluminescence (TL were studied in CdBr2 : Ag+ single crystals from room temperature to liquid nitrogen temperature. The luminescence is practically absent in the interband (including X-rays excitation crystals CdBr2 : Ag+, but manifested in the excitation light from the region 3.68 eV. In this region of the spectrum selective absorption band of silver impurity centers is observed. It was found that the crystals CdBr2 : Ag+ are sensitive to the action of X-rays and ultraviolet light through the flow of photochemical reactions (FHR in these crystals.

  6. Growth of 2 Inch Eu-doped SrI2 single crystals for scintillator applications

    Science.gov (United States)

    Yoshikawa, Akira; Shoji, Yasuhiro; Yokota, Yuui; Kurosawa, Shunsuke; Hayasaka, Shoki; Chani, Valery I.; Ito, Tomoki; Kamada, Kei; Ohashi, Yuji; Kochurikhin, Vladimir

    2016-10-01

    A vertical Bridgman (VB) crystal growth process was established using modified micro-pulling-down (μ-PD) crystal growth system with a removable chamber that was developed for the growth of deliquescent halide single crystals because conventional μ-PD method does not allow growth of large bulk single crystals. Eu:SrI2 crystals were grown from the melt of (Sr0.98Eu0.02)I2 composition using carbon crucibles. Undoped μ-PD SrI2 crystals were used as seeds that were affixed to the bottom of the crucible. All the preparations preceding the growths and the hot zone assembling were performed in a glove box with Ar gas. Then the removable chamber was taken out of the glove box, attached to the μ-PD system, connected with a Turbo Molecular pump, and evacuated down to 10-4 Pa at 300 °C. After the baking procedure, high purity Ar gas (6N) was injected into the chamber. The crucible was heated by a high frequency induction coil up to the melting point of Eu:SrI2. After melting the starting materials, the crucible was displaced in downward direction for the crystal growth and then cooled down to room temperature. Thus, 2 in. and crack-free Eu:SrI2 bulk crystals were produced. The crystals had high transparency and did not contain any visible inclusions. The crystals were cut and polished in the glove box and then sealed in an aluminum container with an optical window for characterization. The details of the crystal growth are discussed.

  7. Ionization potentials of transparent conductive indium tin oxide films covered with a single layer of fluorine-doped tin oxide nanoparticles grown by spray pyrolysis deposition

    OpenAIRE

    2005-01-01

    Indium tin oxide (ITO) films deposited with single layers of monodispersive fluorine-doped tin oxide (FTO) nanoparticles of several nanometers in size were grown on glass substrates by intermittent spray pyrolysis deposition using conventional atomizers. These films have significantly higher ionization potentials than the bare ITO and FTO films grown using the same technique. The ITO films covered with FTO particles of 7 nm in average size show an ionization potential of 5.01 eV, as compared ...

  8. Ti(3+) Self-Doped Blue TiO2(B) Single-Crystalline Nanorods for Efficient Solar-Driven Photocatalytic Performance.

    Science.gov (United States)

    Zhang, Yan; Xing, Zipeng; Liu, Xuefeng; Li, Zhenzi; Wu, Xiaoyan; Jiang, Jiaojiao; Li, Meng; Zhu, Qi; Zhou, Wei

    2016-10-12

    Ti(3+) self-doped blue TiO2(B) single-crystalline nanorods (b-TR) are fabricated via a simple sol-gelation method, cooperated with hydro-thermal treatment and subsequent in situ treatment method, and afterward annealed at 350 °C in Ar. The structures are characterized by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (UV-vis), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The prepared b-TR with narrow band gap possesses single-crystalline TiO2(B) phase, Ti(3+) self-doping, and one-dimensional (1D) rodlike nanostructure. In addition, the improved photocatalytic performance is studied by decomposition of Rhodamine B (RhB) and hydrogen evolution. The degradation rate of RhB by Ti(3+) self-doped blue TiO2(B) single-crystalline nanorods is ∼6.9- and 2.1-times higher compared with the rates of titanium dioxide nanoparticles and pristine TiO2(B) nanorods under visible light illumination, respectively. The hydrogen evolution rate of b-TR is 26.6 times higher compared with that of titanium dioxide nanoparticles under AM 1.5 irradiation. The enhanced photocatalytic performances arise from the synergetic action of the special TiO2(B) phase, Ti(3+) self-doping, and the 1D rod-shaped single-crystalline nanostructure, favoring the visible light utilization and the separation and transportation of photogenerated charge carriers.

  9. Two-wavelength pump-probe technique using single distributed feedback laser array to probe gain recovery of an erbium-doped fiber amplifier

    Science.gov (United States)

    Kuroda, Keiji; Yoshikuni, Yuzo

    2017-03-01

    We propose a two-wavelength pump-probe technique to probe the gain recovery characteristics of an erbium-doped fiber amplifier. The two-wavelength pulse pairs are generated through the direct modulation of a single distributed feedback laser array. The proposed technique allows us to measure the wavelength dependence of the recovery time after gain saturation is induced by a signal of the same wavelength.

  10. Pressure effect on ionic conductivity in yttrium-oxide-doped single-crystal zirconium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Park, E.T.; Park, J.H.

    1998-06-01

    In this study, the authors investigated the effect of pressure on the ionic conductivity of a 9.5 mol% yttria-stabilized zirconia (YSZ) single crystal. The experiment was conducted in the elastic region, and the oxygen ion transport number was unity (t{sub ion} > 0.99999). A conventional four-probe DC method was used to measure the ionic conductivity of the rectangular-shaped sample under uniaxial pressures up to 600 atm at 750 C in air. Measured ionic conductivity decreased as applied pressure increased. Based on henry Eyring`s absolute reaction rate theory, which states that the calculated activation volume has a positive value ({Delta}V{sup 2} = 2.08 cm{sup 3}/mol of O{sup {minus}2}) for oxygen ion transport in the fluoride cubic lattice, they concluded that the results they obtained could be explained by an oxygen ion transport mechanism. This mechanism can explain the fact that the interionic distance increases during oxygen ion transport from one unit cell to neighboring unit cells.

  11. Radioisotope thermal photovoltaic application of the GaSb solar cell

    Science.gov (United States)

    Morgan, M. D.; Horne, W. E.; Day, A. C.

    1991-01-01

    An examination of a RTVP (radioisotopic thermophotovoltaic) conceptual design has shown a high potential for power densities well above those achievable with radioisotopic thermoelectric generator (RTG) systems. An efficiency of 14.4 percent and system specific power of 9.25 watts/kg were predicted for a system with sixteen GPHS (general purpose heat source) sources operating at 1100 C. The models also showed a 500 watt system power by the strontium-90 isotope at 1200 C at an efficiency of 17.0 percent and a system specific power of 11.8 watts/kg. The key to this level of performance is a high-quality photovoltaic cell with narrow bandgap and a reflective rear contact. Recent work at Boeing on GaSb cells and transparent back GaAs cells indicate that such a cell is well within reach.

  12. N incorporation in GaInNSb alloys and lattice matching to GaSb

    Energy Technology Data Exchange (ETDEWEB)

    Ashwin, M. J.; Jones, T. S. [Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom); Walker, D.; Thomas, P. A. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Veal, T. D. [Stephenson Institute for Renewable Energy, School of Physical Sciences, University of Liverpool, Liverpool L69 4ZF (United Kingdom)

    2013-01-21

    The incorporation of N into MBE grown GaNSb and GaInNSb is investigated. Measurements of the N fraction in GaNSb show the familiar linear dependence on inverse growth rate, followed by a departure from this at low growth rates; a similar behaviour is observed for GaInNSb. Unexpectedly, the point at which there is a departure from this linear behaviour is found to be extended to lower growth rates by the addition of small amounts of In. These results are compared to a kinetic theory-based model from which it is postulated that the change in behaviour can be attributed to an In-induced change in the characteristic surface residence lifetime of the N atoms. In addition, a method is demonstrated for growing GaInNSb lattice-matched to GaSb(001) for compositions with band gaps covering the 2-5 {mu}m region.

  13. Behavior of GaSb (100) and InSb (100) surfaces in the presence of H2O2 in acidic and basic cleaning solutions

    Science.gov (United States)

    Seo, Dongwan; Na, Jihoon; Lee, Seunghyo; Lim, Sangwoo

    2017-03-01

    Gallium antimonide (GaSb) and indium antimonide (InSb) have attracted strong attention as new channel materials for transistors due to their excellent electrical properties and lattice matches with various group III-V compound semiconductors. In this study, the surface behavior of GaSb (100) and InSb (100) was investigated and compared in hydrochloric acid/hydrogen peroxide mixture (HPM) and ammonium hydroxide/hydrogen peroxide mixture (APM) solutions. In the acidic HPM solution, surface oxidation was greater and the etching rates of the GaSb and InSb surfaces increased when the solution is concentrated, which indicates that H2O2 plays a key role in the surface oxidation of GaSb and InSb in acidic HPM solution. However, the GaSb and InSb surfaces were hardly oxidized in basic APM solution in the presence of H2O2 because gallium and indium are in the thermodynamically stable forms of H2GaO3- and InO2-, respectively. When the APM solution was diluted, however, the Ga on the GaSb surface was oxidized by H2O, increasing the etching rate. However, the effect of dilution of the APM solution on the oxidation of the InSb surface was minimal; thus, the InSb surface was less oxidized than the GaSb surface and the change in the etching rate of InSb with dilution of the APM solution was not significant. Additionally, the oxidation behavior of gallium and indium was more sensitive to the composition of the HPM and APM solutions than that of antimony. Therefore, the surface properties and etching characteristics of GaSb and InSb in HPM and APM solutions are mainly dependent on the behavior of the group III elements rather than the group V elements.

  14. Preparation and Optical Absorption Performance of Si Single Quantum Dots and Si/Ge Double Quantum Dots Doped TiO2 Films.

    Science.gov (United States)

    Chen, Lixia; He, Fang; Sun, Zuwen; Zhang, Yan; Li, Fengjiao; Huang, Yuan; Gu, Ruisona

    2015-02-01

    Si single quantum dots (QDs) and Si/Ge double QDs doped TiO2 films were successfully fabricated via layer-by-layer ion beam sputtering assisted by annealing treatment, and their morphology and optical absorption performance were analyzed in this paper. TEM images show that Si QDs and Si/Ge double QDs prepared in the TiO2 matrix are in a uniform size distribution and high density, especially after annealed at 500 °C. XPS results indicate that Si in the TiO2 films mainly exists in the form of elemental Si and SiO2, and Ge is in elemental form. From the optical absorption spectra, the optical response of the TiO2 films is shifted from ultraviolet to visible and near infrared region when they are doped by the QDs, and the Si/Ge double QDs co-doped TiO2 films show better optical response compared with the Si QDs doped TiO2 films, suggesting a hybrid enhanced effect of double QDs.

  15. Growth and optical properties of Cr3+-doped CdWO4 single crystals

    Institute of Scientific and Technical Information of China (English)

    Yuntao Wan; Haoyang Hu; Haiping Xia; Yuepin Zhang; Haochuan Jiang; Hongbing Chen

    2012-01-01

    A high-quality Cra+:CdWO4 single crystal at a size of approximately φ 25×80 mm is grown using the Bridgman method with CdO,WO3,and Cr2O3 as raw materials and their molar ratio of 100∶100∶0.5.The temperature gradient of solid-liquid interface at growth is approximately 50 ℃/cm and the growth rate is 0.05 mm/h.The X-ray diffraction (XRD),absorption,excitation,and emission spectra of different parts of the as-grown and O2-annealed crystals are investigated.Two strong broad optical absorption bands of about 472 and 708 nm are observed,and they are associated with the transitions 4A2 →4T1 and 4A2 →4T2.The weak 4T2 →2E transition (the R-line) at 632 nm is also observed.The crystal-field parameter Dq and the Racah parameters B and C are estimated to be 1412.4,776.8,and 3427.6 cm-1,respectively,according to the absorption spectra and crystal-splitting theory.A broadband fluorescence at about 1000 nm due to 4T2 →4A2 transition is produced by exciting the samples at 675 nm.After being annealed in an O2 atmosphere,the crystals become more transparent,while the effective light absorption of Cr3+ ions is evidently enhanced and the emission intensity is also strengthened due to the reduction of oxygen vacancies in the CdWO4 crystal after annealing.

  16. A Simple Method for the Growth of Very Smooth and Ultra-Thin GaSb Films on GaAs (111) Substrate by MOCVD

    Science.gov (United States)

    Ni, Pei-Nan; Tong, Jin-Chao; Tobing, Landobasa Y. M.; Qiu, Shu-Peng; Xu, Zheng-Ji; Tang, Xiao-Hong; Zhang, Dao-Hua

    2017-02-01

    We present a simple thermal treatment with the antimony source for the metal-organic chemical vapor deposition of thin GaSb films on GaAs (111) substrates for the first time. The properties of the as-grown GaSb films are systematically analyzed by scanning electron microscopy, atomic force microscopy, x-ray diffraction, photo-luminescence (PL) and Hall measurement. It is found that the as-grown GaSb films by the proposed method can be as thin as 35 nm and have a very smooth surface with the root mean square roughness as small as 0.777 nm. Meanwhile, the grown GaSb films also have high crystalline quality, of which the full width at half maximum of the rocking-curve is as small as 218 arcsec. Moreover, the good optical quality of the GaSb films has been demonstrated by the low-temperature PL. This work provides a simple and feasible buffer-free strategy for the growth of high-quality GaSb films directly on GaAs substrates and the strategy may also be applicable to the growth on other substrates and the hetero-growth of other materials.

  17. A Simple Method for the Growth of Very Smooth and Ultra-Thin GaSb Films on GaAs (111) Substrate by MOCVD

    Science.gov (United States)

    Ni, Pei-Nan; Tong, Jin-Chao; Tobing, Landobasa Y. M.; Qiu, Shu-Peng; Xu, Zheng-Ji; Tang, Xiao-Hong; Zhang, Dao-Hua

    2017-07-01

    We present a simple thermal treatment with the antimony source for the metal-organic chemical vapor deposition of thin GaSb films on GaAs (111) substrates for the first time. The properties of the as-grown GaSb films are systematically analyzed by scanning electron microscopy, atomic force microscopy, x-ray diffraction, photo-luminescence (PL) and Hall measurement. It is found that the as-grown GaSb films by the proposed method can be as thin as 35 nm and have a very smooth surface with the root mean square roughness as small as 0.777 nm. Meanwhile, the grown GaSb films also have high crystalline quality, of which the full width at half maximum of the rocking-curve is as small as 218 arcsec. Moreover, the good optical quality of the GaSb films has been demonstrated by the low-temperature PL. This work provides a simple and feasible buffer-free strategy for the growth of high-quality GaSb films directly on GaAs substrates and the strategy may also be applicable to the growth on other substrates and the hetero-growth of other materials.

  18. Characterization of Mn{sup 2+} doped tetramethylammoniumtetrachlorozincate single crystal using EPR and optical absorption

    Energy Technology Data Exchange (ETDEWEB)

    Kripal, Ram [EPR Laboratory, Department of Physics, University of Allahabad, Allahabad 211002, Uttar Pradesh (India)], E-mail: ram_kripal2001@rediffmail.com; Maurya, Manju [EPR Laboratory, Department of Physics, University of Allahabad, Allahabad 211002, Uttar Pradesh (India)], E-mail: mmanju8@yahoo.co.in

    2008-04-15

    Studies of fine and hyperfine structures of paramagnetic resonance spectra in single crystals of Mn{sup 2+}: tetramethylammoniumtetrachlorozincate are reported. As sufficient numbers of lines were not obtained at room temperature, measurements were done at liquid nitrogen temperature (77 K). The Mn{sup 2+} spin Hamiltonian parameters are evaluated employing a large number of resonant line positions observed for various orientations of the external magnetic field. The values of the zero field parameters that give good fit to the observed EPR spectra are obtained. The values of different parameters are: g = 1.9834 {+-} 0.0002, A = (105 {+-} 2) x 10{sup -4} cm{sup -1}, B = (100 {+-} 2) x 10{sup -4} cm{sup -1}, D = (349 {+-} 2) x 10{sup -4} cm{sup -1}, E = (106 {+-} 2) x 10{sup -4} cm{sup -1} and a = (21 {+-} 1) x 10{sup -4} cm{sup -1}. The percentage of covalency of the metal-ligand bond has also been determined. From the optical absorption study, the lattice distortion is suggested. The observed bands are assigned as transitions from the {sup 6}A{sub 1g}(S) ground state to various excited quartet levels of Mn{sup 2+} ion in a cubic crystalline field. The electron repulsion parameters (B and C) and crystal field parameters (D{sub q} and {alpha}) providing a good fit to the observed optical spectra are evaluated and the values are: B = 737 cm{sup -1}, C = 2322 cm{sup -1}, D{sub q} = 670 cm{sup -1} and {alpha} = 76 cm{sup -1}. The considerable decrease in the values of B and C parameters from free ion values (B = 960 cm{sup -1}, C = 3325 cm{sup -1}) has indicated that there exists a fair amount of covalent bonding between the central metal ion and the ligand. On the basis of deviations {delta}g = g - 2.0023 it has been ascertained whether electrons are transferred to or from the central ion by the action of bonding.

  19. High-perfomance Ce-doped multicomponent garnet single crystalline film scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Zorenko, Yu.; Gorbenko, V.; Zorenko, T. [Institute of Physics, Kazimierz Wielki, University in Bydgoszcz, Powstancow, Wielkopolskich str., 2, 85090, Bydgoszcz (Poland); Department of Electronics of Ivan Franko, National University of Lviv, Gen. Tarnavskiy str. 17, 79017, Lviv (Ukraine); Sidletskiy, O. [Institute for Single Crystals, National Academy of Sciences of Ukraine, Lenina str., 60, 61001, Kharkiv (Ukraine); Fedorov, A. [SSI Institute for Single Crystals, National Academy of Sciences of Ukraine, Lenina str., 60, 61178, Kharkiv (Ukraine); Bilski, P.; Twardak, A. [Institute of Nuclear Physic, Polish Academy of Sciences, Radzikowskiego str., 176, 31-342, Krakow (Poland)

    2015-08-15

    We report for the first time the optimized content and excellent scintillation properties of single crystalline film (SCF) scintillators of multicomponent Gd{sub 3-x}Lu{sub x} Al{sub 5-y}Ga{sub y} O{sub 12}:Ce garnet compounds grown by liquid phase epitaxy (LPE) method. The Gd{sub 1.5}Lu{sub 1.5}Al{sub 2.75}Ga{sub 2.25}O{sub 12}:Ce and Gd{sub 3}Al{sub 2.75-2}Ga{sub 2.25-3}O{sub 12}:Ce SCF show the light yield (LY) comparable with that of high-quality bulk crystal analogues of these garnets but faster scintillation decay and very low thermoluminescence in the above room temperature range. To our knowledge, these SCF possess the highest LY values ever obtained in LPE grown garnet SCF scintillators exceeding by at least 1.5-1.6 times the values previously reported for SCF scintillators. Left figure: image of Gd{sub 1.5}Lu{sub 1.5}Al{sub 2.75}Ga{sub 2.25}O{sub 12}:Ce (PbO) (inset, left) and Gd{sub 3}Al{sub 2.35}Ga{sub 2.65}O{sub 12}:Ce (BaO) (inset, right) SCF scintillators, grown by LPE method onto Gd{sub 3}Al{sub 2.5}Ga{sub 2.5}O{sub 12} (GAGG) substrate; in the middle, green-yellow light emitting by Gd{sub 1.5}Lu{sub 1.5}Al{sub 2.75}Ga{sub 2.25}O{sub 12}:Ce (BaO) SCF under 350 nm laser illumination. Right figure: XRD pattern of (1200) planes of the Gd{sub 1.5}Lu{sub 1.5}Al{sub 2.75}Ga{sub 2.25}O{sub 12}:Ce (PbO) (black) and Gd{sub 3}Al{sub 2.75}Ga{sub 2.25}O{sub 12}:Ce (BaO) (red) SCFs, grown onto GAGG substrates. The film/substrate lattice misfit is -0.73% and -0.3%, respectively. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Enhanced upconversion luminescence and single-band red emission of NaErF{sub 4} nanocrystals via Mn{sup 2+} doping

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Haibo [School of Materials Science and Engineering, Key Laboratory of Low-dimensional Materials and Application Technology (Ministry of Education), Xiangtan University, Xiangtan 411105 (China); Lu, Wei [Department of Applied Physics and Materials Research Center, The Hong Kong Polytechnic University (Hong Kong); Yi, Zhigao; Rao, Ling [School of Materials Science and Engineering, Key Laboratory of Low-dimensional Materials and Application Technology (Ministry of Education), Xiangtan University, Xiangtan 411105 (China); Zeng, Songjun, E-mail: songjunz@hunnu.edu.cn [College of Physics and Information Science and Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of the Ministry of Education, Hunan Normal University, Changsha, Hunan (China); Li, Zheng, E-mail: zhengli58@gmail.com [School of Materials Science and Engineering, Key Laboratory of Low-dimensional Materials and Application Technology (Ministry of Education), Xiangtan University, Xiangtan 411105 (China)

    2015-01-05

    Highlights: • The structure and upconversion luminescence can be readily tuned by Mn{sup 2+} doping. • The upconversion luminescence intensity can be remarkably enhanced by doping Mn{sup 2+}. • The single-band red emission can be achieved when the Mn{sup 2+}-doped contents reached 20%. - Abstract: In this paper, the monodispersed NaErF{sub 4}:Yb, Mn nanoparticles (NPs) were successfully synthesized by a simple and mild solvothermal method. The as-prepared NPs were characterized by X-ray diffraction, transmission electron microscopy, and spectrophotometer. The crystal phase, size, morphology, and upconversion (UC) properties of these NPs can be readily tuned by doping Mn{sup 2+}. With increasing Mn{sup 2+} contents, the crystal phase of NaErF{sub 4}:Yb NPs was transferred from hexagonal to cubic, and then a new orthorhombic phase NaMn{sub 3}F{sub 10} appeared. The morphology of NaErF{sub 4}:Yb was tuned from nanodisks to nanocubes and then to large nanoflakes with increasing Mn{sup 2+} dopant contents. Moreover, the UC luminescence (UCL) intensity can be enhanced by increasing Mn{sup 2+} content. Interestingly, single-band red emission can be achieved when the Mn{sup 2+} content reaches 20%. This is mainly ascribed to the efficient energy transfer between Er{sup 3+} and Mn{sup 2+}. The enhanced UCL intensity and single-band red UCL make these NaErF{sub 4}:Yb/Mn NPs ideal probes for optical bioimaging owing to the low tissue absorption and deep tissue penetration of red light.

  1. Single Source Precursor-based Solvothermal Synthesis of Heteroatom-doped Graphene and Its Energy Storage and Conversion Applications

    Science.gov (United States)

    Quan, Bo; Yu, Seung-Ho; Chung, Dong Young; Jin, Aihua; Park, Ji Hyun; Sung, Yung-Eun; Piao, Yuanzhe

    2014-01-01

    Solvothermal processes are considered efficient approaches for the gram-scale production of graphene. Further modification of graphene by chemical doping is an important approach to tailor its properties. In this work, we successfully synthesized sulfur-doped graphene by using a solvothermal method with dimethyl sulfoxide as a precursor, which is a common laboratory reagent. Nitrogen-doped graphene was produced to demonstrate the generality of this process. These heteroatom-doped graphene materials exhibited high surface areas and high contents of heteroatoms. Furthermore, the lithium-ion storage properties and oxygen reduction reaction catalytic activity of these materials were also investigated. The success of this approach might facilitate the development of other advanced graphene-based materials with relative simplicity, scalability, and cost effectiveness for use in various potential applications. PMID:25007833

  2. A systematic analysis of the spectra of the lanthanides doped into single crystal LaF/sub 3/

    Energy Technology Data Exchange (ETDEWEB)

    Carnall, W.T.; Goodman, G.L.; Rajnak, K.; Rana, R.S.

    1988-02-01

    The optical spectra of the lanthanides doped into single crystal LaF/sub 3/ have been interpreted in terms of transitions within 4f/sup N/ configurations. Energy-level calculations were based on a simultaneous diagonalization of the free-ion and crystal-field matrices using an approximate model with C/sub 2v/ site symmetry instead of the actual C/sub 2/ symmetry. Excellent correlations between experimental transition energies and the computed level structures were obtained; predicted levels are given for Pm/sup 3 +/. Previously unpublished experimental results for Nd/sup 3 +/ and Sm/sup 3 +/:LaF/sub 3/ are included in the tabulations. The spectroscopic data for each ion were analyzed independently, then the parameters of the effective-operator model were intercompared and systematic trends were identified. Since many of the 4f/sup N/ configurations extend well into the vacuum ultraviolet region, and thus beyond any presently available experimental observations, some of the free-ion (atomic) parameters were found to be only approximately defined by the accessible levels. However, the crystal-field parameters seem for the most part to be well established by fits to data at low energies. A new chart of the lanthanide ion 4f/sup N/ configuration energy level structures is presented. It was generated by including all of the computed crystal-field levels in the 0-50000 cm/sup -1/ range. In most cases, experimental analyses of individual ions extended to /approximately/40000 cm/sup /minus/1/. 94 refs., 23 figs., 10 tabs.

  3. Multi-layer model vs. single-layer model for N and P doped poly layers in etch bias modeling

    Science.gov (United States)

    Li, Jianliang; Vidal-Russell, Ezequiel; Beale, Daniel; Wang, Chunqing; Melvin, Lawrence S., III

    2010-09-01

    In modern photolithography, ever smaller critical dimension (CD) budgets require tighter control over the entire process, demanding more accurate practice of optical proximity correction (OPC). In last decade, the model based OPC (MBOPC) has outpaced the rule based OPC (RBOPC) and become widely adopted in semiconductor industry. During the MBOPC process, the physical models are called to compute the signal values at the evaluation points and the design patterns are perturbed such that the final model contours are as close to the targets as possible. It has been demonstrated that in addition to simulating the optics and resist effects, the physical models must accommodate the pattern distortion due to etch process as well. While the etch process may be lumped with optics and resist processes into one model for the 65nm and above nodes, it can no longer be treated as small perturbations on photolithographic effects for more advanced nodes and it is highly desired to build a physics-based etch model formulations that differ from the conventional convolution-based process models used to simulate the optical and resist effect. Our previous studies proposed a novel non-linear etch modeling object in combination with conventional convolution kernels, which simulates the non-optics and non-resist proximity effect successfully. This study examines further the non-linear etch modeling method by checking the different behaviors of N and p doped layers which physically have different etching rates and should be represented differently in etch modeling. The experimental results indicate that the fitting accuracy is significantly improved when the data points are split into N and P groups and calibrated separately. The N and P layer etch models are used in staged MBOPCs and the results are compared with single-layer model as well.

  4. A single-source precursor route to anisotropic halogen-doped zinc oxide particles as a promising candidate for new transparent conducting oxide materials

    Directory of Open Access Journals (Sweden)

    Daniela Lehr

    2015-11-01

    Full Text Available Numerous applications in optoelectronics require electrically conducting materials with high optical transparency over the entire visible light range. A solid solution of indium oxide and substantial amounts of tin oxide for electronic doping (ITO is currently the most prominent example for the class of so-called TCOs (transparent conducting oxides. Due to the limited, natural occurrence of indium and its steadily increasing price, it is highly desired to identify materials alternatives containing highly abundant chemical elements. The doping of other metal oxides (e.g., zinc oxide, ZnO is a promising approach, but two problems can be identified. Phase separation might occur at the required high concentration of the doping element, and for successful electronic modification it is mandatory that the introduced heteroelement occupies a defined position in the lattice of the host material. In the case of ZnO, most attention has been attributed so far to n-doping via substitution of Zn2+ by other metals (e.g., Al3+. Here, we present first steps towards n-doped ZnO-based TCO materials via substitution in the anion lattice (O2− versus halogenides. A special approach is presented, using novel single-source precursors containing a potential excerpt of the target lattice 'HalZn·Zn3O3' preorganized on the molecular scale (Hal = I, Br, Cl. We report about the synthesis of the precursors, their transformation into halogene-containing ZnO materials, and finally structural, optical and electronic properties are investigated using a combination of techniques including FT-Raman, low-T photoluminescence, impedance and THz spectroscopies.

  5. Multi-wavelength Erbium-doped fiber laser based on four-wave-mixing effect in single mode fiber and high nonlinear fiber.

    Science.gov (United States)

    Wang, Pinghe; Weng, Danmei; Li, Kun; Liu, Yong; Yu, Xuecai; Zhou, Xiaojun

    2013-05-20

    A multi-wavelength Erbium-doped fiber (EDF) laser based on four-wave-mixing is proposed and experimentally demonstrated. The 5 km single mode fiber in the cavity enhances the four-wave-mixing to suppress the homogenous broadening of the erbium-doped fiber and get the stable multi-wavelength comb. The lasing stability is investigated. When the pump power is 300 mW, the fiber laser has 5-lasing lines and the maximum fluctuation of the output power is about 3.18 dB. At the same time, a laser with 110 m high nonlinear fiber (HNFL) is demonstrated. When the pump power is 300 mW, it has 7-lasing lines (above -30 dBm) and the maximum fluctuation is 0.18dB.

  6. Thermal neutron detection with Ce{sup 3+} doped LiCaAlF{sub 6} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Iwanowska, Joanna, E-mail: j.iwanowska@ipj.gov.pl [Soltan Institute for Nuclear Studies, PL-05-400 Otwock/Swierk (Poland); Swiderski, Lukasz; Moszynski, Marek [Soltan Institute for Nuclear Studies, PL-05-400 Otwock/Swierk (Poland); Yanagida, Takayuki; Yokota, Yuui; Yoshikawa, Akira [IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Fukuda, Kentaro; Kawaguchi, Noriaki; Ishizu, Sumito [Tokuyama Corporation, 6-6-3, Minamiyoshinari, Aoba-ku, Sendai, Miyagi 989-3204 (Japan)

    2011-10-01

    Cerium-doped LiCaAlF{sub 6} (Ce:LiCAF) crystals have been studied as scintillators in application to thermal neutron detection. Three crystals: high-doping Ce:LiCAF, low-doping Ce:LiCAF with 50% enrichment of {sup 6}Li (both 10 mmx10 mmx2 mm, rectangular) and high-doping Ce:LiCAF with 95% enrichment of {sup 6}Li (O50.8 mmx2 mm, discus) coupled to Photonis XP5300B PMT, were tested. The response of these crystals to neutrons emitted from a paraffin moderated {sup 238}PuBe source has been investigated. Thermal neutron peaks have been found at a Gamma Equivalent Energy (GEE) of {approx}2.5 MeV for high-doping Ce:LiCAF (50% {sup 6}Li), {approx}2 MeV for low-doping Ce:LiCAF (50% {sup 6}Li) and {approx}1.9 MeV for high-doping Ce:LiCAF (95% {sup 6}Li). The light output of Ce:LiCAF was also measured (175-250 phe/MeV from sample to sample). Lithium-6 glass GS20 from Saint Gobain was used as a reference scintillator (O50 mmx2 mm, circle). Relative neutron efficiency, normalized to that of GS20 lithium glass, as well as gamma-neutron intrinsic efficiency for all tested samples was calculated. Intrinsic efficiency on thermal neutron detection for small Ce:LiCAF samples was estimated at about 32-35% of that of GS20 and for large Ce:LiCAF sample as about 82% of that of GS20.

  7. Unusually high critical current of clean P-doped BaFe{sub 2}As{sub 2} single crystalline thin film

    Energy Technology Data Exchange (ETDEWEB)

    Kurth, F., E-mail: fritz.kurth@ifw-dresden.de; Engelmann, J.; Schultz, L. [Institute for Metallic Materials, IFW Dresden, 01171 Dresden (Germany); TU Dresden, 01062 Dresden (Germany); Tarantini, C.; Jaroszynski, J. [Applied Superconductivity Center, National High Magnetic Field Laboratory, Florida State University, 2031 East Paul Dirac Drive, Tallahassee, Florida 32310 (United States); Grinenko, V.; Reich, E.; Hühne, R. [Institute for Metallic Materials, IFW Dresden, 01171 Dresden (Germany); Hänisch, J. [Institute for Metallic Materials, IFW Dresden, 01171 Dresden (Germany); Karlsruhe Institute of Technology, Institute for Technical Physics, Hermann von Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Mori, Y.; Sakagami, A.; Kawaguchi, T.; Ikuta, H. [Department of Crystalline Materials Science, Nagoya University, Chikusa, Nagoya 464-8603 (Japan); Holzapfel, B. [Karlsruhe Institute of Technology, Institute for Technical Physics, Hermann von Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Iida, K., E-mail: iida@nuap.nagoya-u.ac.jp [Institute for Metallic Materials, IFW Dresden, 01171 Dresden (Germany); Department of Crystalline Materials Science, Nagoya University, Chikusa, Nagoya 464-8603 (Japan)

    2015-02-16

    Microstructurally clean, isovalently P-doped BaFe{sub 2}As{sub 2} (Ba-122) single crystalline thin films have been prepared on MgO (001) substrates by molecular beam epitaxy. These films show a superconducting transition temperature (T{sub c}) of over 30 K although P content is around 0.22, which is lower than the optimal one for single crystals (i.e., 0.33). The enhanced T{sub c} at this doping level is attributed to the in-plane tensile strain. The strained film shows high transport self-field critical current densities (J{sub c}) of over 6 MA/cm{sup 2} at 4.2 K, which are among the highest for Fe based superconductors (FeSCs). In-field J{sub c} exceeds 0.1 MA/cm{sup 2} at μ{sub 0}H=35 T for H‖ab and μ{sub 0}H=18 T for H‖c at 4.2 K, respectively, in spite of moderate upper critical fields compared to other FeSCs with similar T{sub c}. Structural investigations reveal no defects or misoriented grains pointing to strong pinning centers. We relate this unexpected high J{sub c} to a strong enhancement of the vortex core energy at optimal T{sub c}, driven by in-plane strain and doping. These unusually high J{sub c} make P-doped Ba-122 very favorable for high-field magnet applications.

  8. Isolating GaSb membranes grown metamorphically on GaAs substrates using highly selective substrate removal etch processes

    Energy Technology Data Exchange (ETDEWEB)

    Lavrova, Olga [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Electrical and Computer Engineering. Center for High Technology Materials; Balakrishnan, Ganesh [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Electrical and Computer Engineering. Center for High Technology Materials

    2017-02-24

    The etch rates of NH4OH:H2O2 and C6H8O7:H2O2 for GaAs and GaSb have been investigated to develop a selective etch for GaAs substrates and to isolate GaSb epilayers grown on GaAs. The NH4OH:H2O2 solution has a greater etch rate differential for the GaSb/GaAs material system than C6H8O7:H2O2 solution. The selectivity of NH4OH:H2O2 for GaAs/GaSb under optimized etch conditions has been observed to be as high as 11471 ± 1691 whereas that of C6H8O7:H2O2 has been measured up to 143 ± 2. The etch contrast has been verified by isolating 2 μm thick GaSb epi-layers that were grown on GaAs substrates. GaSb membranes were tested and characterized with high-resolution X-Ray diffraction (HR-XRD) and atomic force microscopy (AFM).

  9. First-principles study of the interaction of H2O with the GaSb (001) surface

    Science.gov (United States)

    Bermudez, V. M.

    2013-05-01

    The adsorption of H2O on the GaSb (001) surface, both clean and with pre-adsorbed H atoms, has been studied computationally using dispersion-corrected density functional theory. The model employed is the α-(4×3) reconstruction consisting of Ga-Sb dimers adsorbed on the Sb-terminated surface, a disordered version of which is believed to constitute the frequently observed Sb-rich (1×3) surface. On the clean surface, molecular adsorption of H2O at a coordinatively unsaturated Ga site is exothermic (ΔE = -0.57 eV), but dissociation of this adsorbed H2O is significantly endothermic (ΔE = +0.45 eV or more). Dissociation can form either a (HO)Ga-Sb(H) site involving a Ga-Sb dimer or a (H)Ga-O(H)-Sb bridge. Other reactions are also energetically feasible, depending on the bond strength of different inequivalent Ga-Sb dimers. The two structures have essentially the same energy, and both can undergo an exothermic reaction with a second H2O. For the (HO)Ga-Sb(H) site, this reaction leads to the breaking of the dimer bond and the adsorption of molecular water, while the (H)Ga-O(H)-Sb bridge transforms to (HO)Ga-O(H)-Sb with the release of H2. On the H-terminated surface, molecular adsorption of H2O can be suppressed and dissociative adsorption enhanced, which means that formation of an OH-terminated surface may be easier when starting with an H-terminated vs. a clean surface. The implications of these results for the growth of oxide/GaSb heterostructures via atomic layer deposition are discussed.

  10. Influence of single and binary doping of strontium and lithium on in vivo biological properties of bioactive glass scaffolds

    Science.gov (United States)

    Khan, Pintu Kumar; Mahato, Arnab; Kundu, Biswanath; Nandi, Samit K.; Mukherjee, Prasenjit; Datta, Someswar; Sarkar, Soumya; Mukherjee, Jayanta; Nath, Shalini; Balla, Vamsi K.; Mandal, Chitra

    2016-09-01

    Effects of strontium and lithium ion doping on the biological properties of bioactive glass (BAG) porous scaffolds have been checked in vitro and in vivo. BAG scaffolds were prepared by conventional glass melting route and subsequently, scaffolds were produced by evaporation of fugitive pore formers. After thorough physico-chemical and in vitro cell characterization, scaffolds were used for pre-clinical study. Soft and hard tissue formation in a rabbit femoral defect model after 2 and 4 months, were assessed using different tools. Histological observations showed excellent osseous tissue formation in Sr and Li + Sr scaffolds and moderate bone regeneration in Li scaffolds. Fluorochrome labeling studies showed wide regions of new bone formation in Sr and Li + Sr doped samples as compared to Li doped samples. SEM revealed abundant collagenous network and minimal or no interfacial gap between bone and implant in Sr and Li + Sr doped samples compared to Li doped samples. Micro CT of Li + Sr samples showed highest degree of peripheral cancellous tissue formation on periphery and cortical tissues inside implanted samples and vascularity among four compositions. Our findings suggest that addition of Sr and/or Li alters physico-chemical properties of BAG and promotes early stage in vivo osseointegration and bone remodeling that may offer new insight in bone tissue engineering.

  11. Synthesis of nanocrystalline thin films of gold on the surface of GaSb by swift heavy ion

    Energy Technology Data Exchange (ETDEWEB)

    Jadhav, Vidya; Dubey, S. K.; Yadav, A. D.; Singh, A. [Department of Physics, University of Mumbai, Santacruz (E), Mumbai-400 098 (India)

    2013-02-05

    Thin films of gold ({approx}100 nm thick) were deposited on p-type GaSb substrates. These samples were irradiated with 100 MeV Fe{sup 7+}ions for the fluence of 1 Multiplication-Sign 10{sup 13} and 1 Multiplication-Sign 10{sup 14} ions cm{sup -2}. After irradiation, samples were characterized using AFM, UV-VIS -NIR, X-Ray Diffraction techniques. AFM studies showed the presence of clusters on the surface of GaSb. R.M.S. roughness of the sample was found to increase w.r.t ion fluence. Absorption coefficient obtained from the Ultra violet - Visible NIR (UV-VIS -NIR) spectra of the samples irradiated with various fluences compared with non irradiated GaSb. The annealing experiment showed a significant improvement in the absorption coefficient after rapid thermal annealing at temperature of 400 Degree-Sign C. X-Ray Diffraction study reveals different orientations of Au film.

  12. Integration of atomic layer deposited high-k dielectrics on GaSb via hydrogen plasma exposure

    Energy Technology Data Exchange (ETDEWEB)

    Ruppalt, Laura B., E-mail: laura.ruppalt@nrl.navy.mil; Cleveland, Erin R.; Champlain, James G.; Bennett, Brian R.; Prokes, Sharka M. [Electronics Science and Technology Division, Naval Research Laboratory, Washington, DC 20375 (United States)

    2014-12-15

    In this letter we report the efficacy of a hydrogen plasma pretreatment for integrating atomic layer deposited (ALD) high-k dielectric stacks with device-quality p-type GaSb(001) epitaxial layers. Molecular beam eptiaxy-grown GaSb surfaces were subjected to a 30 minute H{sub 2}/Ar plasma treatment and subsequently removed to air. High-k HfO{sub 2} and Al{sub 2}O{sub 3}/HfO{sub 2} bilayer insulating films were then deposited via ALD and samples were processed into standard metal-oxide-semiconductor (MOS) capacitors. The quality of the semiconductor/dielectric interface was probed by current-voltage and variable-frequency admittance measurements. Measurement results indicate that the H{sub 2}-plamsa pretreatment leads to a low density of interface states nearly independent of the deposited dielectric material, suggesting that pre-deposition H{sub 2}-plasma exposure, coupled with ALD of high-k dielectrics, may provide an effective means for achieving high-quality GaSb MOS structures for advanced Sb-based digital and analog electronics.

  13. Integration of atomic layer deposited high-k dielectrics on GaSb via hydrogen plasma exposure

    Directory of Open Access Journals (Sweden)

    Laura B. Ruppalt

    2014-12-01

    Full Text Available In this letter we report the efficacy of a hydrogen plasma pretreatment for integrating atomic layer deposited (ALD high-k dielectric stacks with device-quality p-type GaSb(001 epitaxial layers. Molecular beam eptiaxy-grown GaSb surfaces were subjected to a 30 minute H2/Ar plasma treatment and subsequently removed to air. High-k HfO2 and Al2O3/HfO2 bilayer insulating films were then deposited via ALD and samples were processed into standard metal-oxide-semiconductor (MOS capacitors. The quality of the semiconductor/dielectric interface was probed by current-voltage and variable-frequency admittance measurements. Measurement results indicate that the H2-plamsa pretreatment leads to a low density of interface states nearly independent of the deposited dielectric material, suggesting that pre-deposition H2-plasma exposure, coupled with ALD of high-k dielectrics, may provide an effective means for achieving high-quality GaSb MOS structures for advanced Sb-based digital and analog electronics.

  14. A first-principles study of the adsorption behavior of CO on Al- and Ga-doped single-walled BN nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Peyghan, Ali Ahmadi [Young Researchers Club, Islamshahr Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Soltani, Alireza, E-mail: Alireza.soltani46@yahoo.com [Young Researchers Club, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Pahlevani, Amin Allah [Young Researchers Club, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Kanani, Yaser [Department of Chemistry, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Khajeh, Soheila [Department of Chemistry,Payame Noor University, 19395-3697 Tehran, Islamic Republic of Iran (Iran, Islamic Republic of)

    2013-04-01

    First-principles computations have been applied to scrutinize the adsorption behavior of CO molecule on the external surface of H-capped aluminum- and gallium-doped (6, 0), (8, 0) zigzag and (5, 5) armchair single-walled BN nanotubes (SWBNNTs). Binding energy corresponding to the most stable configuration of CO on the gallium-doped (6, 0) BNNT is found to be −0.83 eV, which is high typical sensitivity to CO molecule. Our results indicate that both Al- and Ga-doping can notably enhance the adsorption energy of CO/BNNTs complexes. Our electronic results reveal that there is a notable orbital hybridization among two species in adsorption process being an evidence of strong interaction. For the CO/BNNTs complexes, the energy gaps, NBO, dipole moments, natural atomic orbital occupancies and global indices are computed. Finally, we reported a novel type of toxic gas sensor that can be used for detecting the presence of CO molecule.

  15. High-performance single-crystalline arsenic-doped indium oxide nanowires for transparent thin-film transistors and active matrix organic light-emitting diode displays.

    Science.gov (United States)

    Chen, Po-Chiang; Shen, Guozhen; Chen, Haitian; Ha, Young-geun; Wu, Chao; Sukcharoenchoke, Saowalak; Fu, Yue; Liu, Jun; Facchetti, Antonio; Marks, Tobin J; Thompson, Mark E; Zhou, Chongwu

    2009-11-24

    We report high-performance arsenic (As)-doped indium oxide (In(2)O(3)) nanowires for transparent electronics, including their implementation in transparent thin-film transistors (TTFTs) and transparent active-matrix organic light-emitting diode (AMOLED) displays. The As-doped In(2)O(3) nanowires were synthesized using a laser ablation process and then fabricated into TTFTs with indium-tin oxide (ITO) as the source, drain, and gate electrodes. The nanowire TTFTs on glass substrates exhibit very high device mobilities (approximately 1490 cm(2) V(-1) s(-1)), current on/off ratios (5.7 x 10(6)), steep subthreshold slopes (88 mV/dec), and a saturation current of 60 microA for a single nanowire. By using a self-assembled nanodielectric (SAND) as the gate dielectric, the device mobilities and saturation current can be further improved up to 2560 cm(2) V(-1) s(-1) and 160 microA, respectively. All devices exhibit good optical transparency (approximately 81% on average) in the visible spectral range. In addition, the nanowire TTFTs were utilized to control green OLEDs with varied intensities. Furthermore, a fully integrated seven-segment AMOLED display was fabricated with a good transparency of 40% and with each pixel controlled by two nanowire transistors. This work demonstrates that the performance enhancement possible by combining nanowire doping and self-assembled nanodielectrics enables silicon-free electronic circuitry for low power consumption, optically transparent, high-frequency devices assembled near room temperature.

  16. Effect of Mg2+ ions co-doping on luminescence and defects formation processes in Gd3(Ga,Al)5O12:Ce single crystals

    Science.gov (United States)

    Babin, V.; Bohacek, P.; Grigorjeva, L.; Kučera, M.; Nikl, M.; Zazubovich, S.; Zolotarjovs, A.

    2017-04-01

    Photo- and radioluminescence and thermally stimulated luminescence characteristics of Ce3+ - doped and Ce3+, Mg2+ co-doped Gd3(Ga,Al)5O12 (GAGG) single crystals of similar composition are investigated in the 9-500 K temperature range. The Ce3+ - related luminescence spectra and the photoluminescence decay kinetics in these crystals are found to be similar. Under photoexcitation in the Ce3+ - and Gd3+ - related absorption bands, no prominent rise of the photoluminescence intensity in time is observed neither in GAGG:Ce,Mg nor in GAGG:Ce crystals. The afterglow is strongly reduced in GAGG:Ce,Mg as compared to GAGG:Ce, and the afterglow decay kinetics is much faster. Co-doping with Mg2+ results in a drastic decrease of the thermally stimulated luminescence (TSL) intensity in the whole investigated temperature range and in the appearance of a new complex Mg2+ - related TSL glow curve peak around 285 K. After irradiation in the Ce3+ - related 3.6 eV absorption band, the TSL intensity in GAGG:Ce,Mg is found to be comparable with that in the GAGG:Ce epitaxial film of similar composition. The Mg2+ - induced changes in the concentration, origin and structure of the crystal lattice defects and their influence on the scintillation characteristics of GAGG:Ce,Mg are discussed.

  17. Effects of post-annealing and cobalt co-doping on superconducting properties of (Ca,Pr)Fe2As2 single crystals

    Science.gov (United States)

    Okada, T.; Ogino, H.; Yakita, H.; Yamamoto, A.; Kishio, K.; Shimoyama, J.

    2014-10-01

    In order to clarify the origin of anomalous superconductivity in (Ca,RE)Fe2As2 system, Pr doped and Pr,Co co-doped CaFe2As2 single crystals were grown by the FeAs flux method. These samples showed two-step superconducting transition with Tc1 = 25-42 K, and Tc2 < 16 K, suggesting that (Ca,RE)Fe2As2 system has two superconducting components. Post-annealing performed for these crystals in evacuated quartz ampoules at various temperatures revealed that post-annealing at ∼400 °C increased the c-axis length for all samples. This indicates that as-grown crystals have a certain level of strain, which is released by post-annealing at ∼400 °C. Superconducting properties also changed dramatically by post-annealing. After annealing at 400 °C, some of the co-doped samples showed large superconducting volume fraction corresponding to the perfect diamagnetism below Tc2 and high Jc values of 104-105 A cm-2 at 2 K in low field, indicating the bulk superconductivity of (Ca,RE)Fe2As2 phase occurred below Tc2. On the contrary, the superconducting volume fraction above Tc2 was always very small, suggesting that 40 K-class superconductivity observed in this system is originating in the local superconductivity in the crystal.

  18. Investigations on the growth, optical, thermal, dielectric, and laser damage threshold properties of crystal violet dye-doped potassium acid phthalate single crystal

    Science.gov (United States)

    Rao, G. Babu; Rajesh, P.; Ramasamy, P.

    2016-03-01

    Influence of crystal violet dye with different concentration on potassium acid phthalate single crystal grown by conventional method has been studied. No change has been observed in the structure, whereas changes have been observed in the external morphology of the crystal when the dyes are incorporated in the crystal lattice. Thermogravimetric and differential thermal analyses show the onset decomposition temperatures to be at 302, 285, 284, and 285 °C for pure, 0.1, 0.3, and 0.5 mol% crystal violet-doped potassium acid phthalate crystals, respectively. The dielectric measurement was carried out on the grown crystals as a function of frequency at various temperatures. In addition, strong luminescent emission bands at 638, 648, and 640 nm were observed in which the relative intensity was found to be reversed as a result of doping concentration. The laser damage threshold value significantly increased for dye-doped crystal in comparison with pure crystal which may make it suitable for the solid-state dye laser applications.

  19. Oxide thickness-dependent effects of source doping profile on the performance of single- and double-gate tunnel field-effect transistors

    Science.gov (United States)

    Chien, Nguyen Dang; Shih, Chun-Hsing

    2017-02-01

    Operated by the band-to-band tunneling at the source-channel junction, the source engineering has been considered as an efficient approach to enhance the performance of tunnel field-effect transistors (TFETs). In this paper, we report a new feature that the effects of source doping profile on the performance of single- and double-gate germanium TFETs depend on equivalent oxide thickness (EOT). Based on the numerical simulations, it is shown that the effect of source concentration on the on-current is stronger with decreasing the EOT, particularly in the double-gate configuration due to the higher gate control capability. Importantly, when the EOT is decreased below a certain value, abrupt source-channel junctions are not only unnecessary, but gradual source doping profiles even improve the performance of TFETs because of the increase in vertical tunneling generation. With the continuous trend of scaling EOT, the oxide thickness-dependent effects of source doping profile should be properly considered in designing TFET devices.

  20. Comparative infrared study of optimally doped and underdoped La{sub 2-x}Sr{sub x}CuO{sub 4} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Pignon, B; Gruener, G; Phuoc, V Ta; Gervais, F; Ammor, L [Laboratoire d' Electrodynamique des Materiaux Avances, UMR 6157 CNRS-CEA, Universite Francois Rabelais, Faculte des Sciences et Techniques, Parc de Grandmont, 37200 Tours (France); Marin, C [Departement de Recherche Fondamentale sur la Matiere Condensee, Service de Physique Statistique, Magnetisme et Supraconductivite, CEA-Grenoble, 17 Rue des Martyrs, 28054 Grenoble Cedex 9 (France)

    2008-02-20

    The temperature dependence of the optical spectra of two La{sub 2-x}Sr{sub x}CuO{sub 4} single crystals was investigated for both in-plane and out-of-plane directions. For the underdoped (x = 0.08) single crystal, the in-plane optical conductivity that was analysed by a generalized Drude formalism shows a suppression of the scattering rate 1/{tau}({omega}) and an increased effective mass m{sup *} as the temperature decreases at low frequencies. Since this behaviour can be explained by the pseudogap effect, it is concluded that the pseudogap is not present at the optimal doping (x = 0.15). This result is confirmed by the c-axis optical conductivity, which decreases only for the underdoped single crystal. The absence of the pseudogap at the optimal composition is in accord with the quantum critical point model and it can explain the phase diagram of high-temperature superconductors.

  1. NMR spin-lattice relaxation study of 7Li and 93Nb nuclei in Ti- or Fe-doped LiNbO3:Mg single crystals

    Directory of Open Access Journals (Sweden)

    Tae Ho Yeom

    2016-04-01

    Full Text Available In this study, to understand the effects of paramagnetic impurities, we investigated the temperature dependent of the spin-lattice relaxation times of pure LiNbO3, LiNbO3:Mg, LiNbO3:Mg/Ti, LiNbO3:Mg/Fe, and LiNbO3:Mg/Fe (thermally treated at 500°C single crystals. The results for the LiNbO3:Mg single crystals doped with Fe3+ or Ti3+ are discussed with respect to the site distribution and atomic mobility of Li and Nb. In addition, the effects of a thermal treatment on LiNbO3:Mg/Fe single crystals were examined based on the T1 analysis of 7Li and 93Nb. It was found that the presence of impurities in the crystals induced systematic changes of activation energies concerning atomic mobility.

  2. Application of Ce3+ single-doped complexes as solar spectral downshifters for enhancing photoelectric conversion efficiencies of a-Si-based solar cells

    Science.gov (United States)

    Song, Pei; Jiang, Chun

    2013-05-01

    The effect on photoelectric conversion efficiency of an a-Si-based solar cell by applying a solar spectral downshifter of rare earth ion Ce3+ single-doped complexes including yttrium aluminum garnet Y3Al5O12 single crystals, nanostructured ceramics, microstructured ceramics and B2O3-SiO2-Gd2O3-BaO glass is studied. The photoluminescence excitation spectra in the region 360-460 nm convert effectively into photoluminescence emission spectra in the region 450-550 nm where a-Si-based solar cells exhibit a higher spectral response. When these Ce3+ single-doped complexes are placed on the top of an a-Si-based solar cell as precursors for solar spectral downshifting, theoretical relative photoelectric conversion efficiencies of nc-Si:H and a-Si:H solar cells approach 1.09-1.13 and 1.04-1.07, respectively, by means of AMPS-1D numerical modeling, potentially benefiting an a-Si-based solar cell with a photoelectric efficiency improvement.

  3. Single-mode amplification in Yb-doped rod-type photonic crystal fibers for high brilliance lasers

    DEFF Research Database (Denmark)

    Poli, F.; Lægsgaard, Jesper; Passaro, D.

    2009-01-01

    This paper presents the effect of a low refractive index ring in the Yb-doped rod-type photonic crystal fibre core on the guided mode propagation and analyzed through a spatial and spectral amplifier model. The ring provides a higher differential overlap between the fundamental mode (FM...

  4. Optical characterization and evaluation of the laser properties of Yb(3+)-doped (La, Sr)(Al, Ta)O(3) single crystals.

    Science.gov (United States)

    Zhao, Chengchun; Hang, Yin; He, Xiaoming; Zhang, Lianhan; Yin, Jigang; Hu, Pengchao; He, Mingzhu; Ma, En

    2011-03-30

    A Yb(3+)-doped mixed-perovskite single crystal (La, Sr)(Al, Ta)O(3) (LSAT) crystal is grown by the Czochralski method. The absorption spectrum, fluorescence spectrum and fluorescence lifetime of Yb(3+) ions have been investigated, and the spectroscopic parameters of Yb:LSAT have also been calculated. This crystal exhibits a remarkably large ground-state splitting (about 1100 cm(-1)), a relatively long fluorescence lifetime (0.85 ms) and broad absorption and emission bandwidths. The results indicate that the Yb(3+):LSAT crystal is a good candidate for diode-pumped ultrashort and tunable solid-state laser applications. © 2011 IOP Publishing Ltd

  5. Achieving high-quality single-atom nitrogen doping of graphene/SiC(0001) by ion implantation and subsequent thermal stabilization.

    Science.gov (United States)

    Telychko, Mykola; Mutombo, Pingo; Ondráček, Martin; Hapala, Prokop; Bocquet, François C; Kolorenč, Jindřich; Vondráček, Martin; Jelínek, Pavel; Švec, Martin

    2014-07-22

    We report a straightforward method to produce high-quality nitrogen-doped graphene on SiC(0001) using direct nitrogen ion implantation and subsequent stabilization at temperatures above 1300 K. We demonstrate that double defects, which comprise two nitrogen defects in a second-nearest-neighbor (meta) configuration, can be formed in a controlled way by adjusting the duration of bombardment. Two types of atomic contrast of single N defects are identified in scanning tunneling microscopy. We attribute the origin of these two contrasts to different tip structures by means of STM simulations. The characteristic dip observed over N defects is explained in terms of the destructive quantum interference.

  6. Optically stimulated luminescence of Tb{sup 3+}/Sm{sup 3+} doubly doped K{sub 2}YF{sub 5} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Camargo, L.; Marcazzo, J.; Santiago, M.; Caselli, E. [Universidad Nacional del Centro de la Provincia de Buenos Aires, Instituto de Fisica Arroyo Seco, Gral. Pinto 399, B7000GHG, Tandil (Argentina); Khaidukov, N. M., E-mail: jmarcass@exa.unicen.edu.ar [Kurnakov Institute of General and Inorganic Chemistry, RAS, Leninskii Prospekt 31, 119991 Moscow (Russian Federation)

    2014-08-15

    In this work optically stimulated luminescence (OSL) properties of K{sub 2}YF{sub 5} crystals doubly doped with Tb{sup 3+} and Sm{sup 3+} ions have been investigated for the first time. OSL responses for different dopant concentration and for optical stimulation with different wavelengths have been analyzed for each compound. Dosimetric properties of the most efficient composition, namely, K{sub 2}YF{sub 5}:1.0 at.% Tb{sup 3+}; 1.0 at.% Sm{sup 3+}, have been studied. Finally, the possible application of this single crystal as OSL dosimeter has been evaluated. (Author)

  7. Doping - Dependent irreversible magnetic properties of Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Prozorov, R., E-mail: prozorov@ameslab.go [Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Tanatar, M.A.; Blomberg, E.C.; Prommapan, P.; Gordon, R.T.; Ni, N.; Bud' ko, S.L.; Canfield, P.C. [Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)

    2009-05-01

    We discuss the irreversible magnetic properties of self-flux grown Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} single crystals for a wide range of concentrations covering the whole phase diagram from the underdoped to the overdoped regime, x = 0.038, 0.047, 0.058, 0.071, 0.074, 0.10, 0.106 and 0.118. Samples were characterized by a magneto-optical method and show excellent spatial uniformity of the superconducting state down to at least the micrometer scale. The in-plane properties are isotropic, as expected for the tetragonal symmetry, and the overall behavior closely follows classical Bean model of the critical state. The field-dependent magnetization exhibits second peak at a temperature and doping - dependent magnetic field, H{sub p}(T, x). The evolution of this fishtail feature with doping is discussed. In particular we find that H{sub p}, measured at the same reduced temperature for different x, is a unique monotonic function of the superconducting transition temperature, T{sub c}(x), across all dopings. Magnetic relaxation is time-logarithmic and unusually fast. Similar to cuprates, there is an apparent crossover from collective elastic to plastic flux creep above H{sub p}. At high fields, the field dependence of the relaxation rate becomes doping independent. We discuss our results in the framework of the weak collective pinning and show that vortex physics in iron-based pnictide crystals is much closer to high-T{sub c} cuprates than to conventional s-wave (including MgB{sub 2}) superconductors.

  8. Fundamental interface studies of GaSb and InAs substrates with atomic layer deposition

    Science.gov (United States)

    Greer, Frank; Baker, L.; Cook, S.; Fisher, A.; Keo, S.; Soibel, A.; Khoshakhlagh, Arezou; Nguyen, J.; Ting, D.; Gunapala, S.

    2012-10-01

    Long Wavelength infrared photodetectors based on Type-II superlattices from the 6.1Å system hold great promise for a wide variety of applications. However, as these materials are fabricated into focal plane arrays for real world applications, the small pixel sizes that are required can result in unacceptably high dark current due to a significant contribution of surface-induced leakage. These surface currents could be substantially reduced or even eliminated by the application of an appropriate passivation material. But, while a considerable amount of effort has gone into developing passivation processes and materials for these detectors (e.g. PECVD SiO2, polyimides, etc.), there is no one widely adopted standard technique in use today. Atomic layer deposition has the possibility of being an excellent method for depositing passivation because of the wide variety of materials that are readily available via ALD and the ability to conformally coat arbitrary topographies that may be found in the patterning of LWIR FPAs. In this work, fundamental materials characterization results and electrical test data will be presented for two wide band gap, high-K dielectrics (Titanium Oxide and Hafnium Oxide) looking at their nucleation and growth behavior on substrates of relevant III-V materials such as GaSb and InAs using ellispometry, XPS, and XRD. These results will be compared to more conventional passivation strategies to highlight the unique features of the ALD technique.

  9. Heavy and light hole transport in nominally undoped GaSb substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kala, Hemendra; Umana-Membreno, Gilberto A.; Jolley, Gregory; Akhavan, Nima Dehdashti; Antoszewski, Jaroslaw; Faraone, Lorenzo [School of Electrical, Electronic and Computer Engineering, The University of Western Australia, Crawley WA 6009 (Australia); Patrashin, Mikhail A.; Akahane, Kouichi [National Institute of Information and Communications Technology, Koganei, Tokyo 1848795 (Japan)

    2015-01-19

    In this work, we report results of a study of electronic transport in nominally undoped p-type GaSb wafers typically employed as substrate material for the epitaxial growth of InAs/GaInSb type-II superlattices. Magnetic field dependent Hall-effect measurements and high-resolution mobility spectrum analysis clearly indicate p-type conductivity due to carriers in both the heavy and light hole bands. The extracted hole concentrations indicate a thermal activation energy of 17.8 meV for the dominant native acceptor-like defects. A temperature-independent effective mass ratio of 9.0 ± 0.8 was determined from the ratio of measured heavy and light hole concentrations. Over the 56 K–300 K temperature range, the light hole mobility was found to be 4.7 ± 0.7 times higher than the heavy hole mobility. The measured room temperature mobilities for the light and heavy holes were 2550 cm{sup 2}/Vs and 520 cm{sup 2}/Vs, respectively.

  10. CONTACT MATERIALS FOR GaSb AND InSb: A PHASE DIAGRAM APPROACH

    Institute of Scientific and Technical Information of China (English)

    K.W. Richter; H. Ipser

    2002-01-01

    The development of well defined and thermally stable ohmic contacts for Ⅲ- Ⅴ semi-conductors like InSb and GaSb is still a challenging problem in semiconductor devicetechnology. As device processing usually includes the exposure to elevated tempera-tures, interface reactions often occur during metallization and further heat treatment.It is thus important to understand the respective phase equilibria of the involved el-ements. From the thermodynamic point of view, binary and ternary compounds inequilibrium with the respective compound semiconductor would be the best choice forcontact materials as these contacts will be stable even after long exposure to elevatedtemperatures. These possible candidates for contact materials may be directly obtainedfrom the phase diagrams.During the last years we investigated several phase diagrams of transition metals withGaSb and InSb. Experimental results in the systems Ga-Ni-Sb, Ga-Pd-Sb, Ga-Pt-Sb,In-Ni-Sb and In-Pd-Sb are summarized and are discussed in the context of contactchemistry.

  11. Sb-based IR photodetector epiwafers on 100 mm GaSb substrates manufactured by MBE

    Science.gov (United States)

    Fastenau, Joel M.; Lubyshev, Dmitri; Qiu, Yueming; Liu, Amy W. K.; Koerperick, Edwin J.; Olesberg, Jon T.; Norton, Dennis

    2013-07-01

    Antimony-based materials continue to provide great interest for infrared photodetector and focal plane array imaging applications. Detector architectures include InAs/Ga(In)Sb strained-layer superlattices, which create a type-II band alignment that can be tailored to cover a wide range of the mid- and long-wavelength bands by varying the thickness and composition of the constituent materials, and bulk InAsSb-based XBn barrier designs. These materials can provide desirable detector features such as wider wavelength range, suppression of tunneling currents, improved quantum efficiency, and higher operating temperatures. In order to bring these advantages to market, a reliable manufacturing process must be established on large diameter substrates. We report our latest work on the molecular beam epitaxy growth of Sb-detector epiwafers on 100 mm diameter GaSb substrates in a multi-wafer production format. The growth process has been established to address the challenges of these demanding structures, including the large numbers of alternating thin layers and mixed group-V elements. Various characterization techniques demonstrate excellent surface morphology, crystalline structure quality, and optical properties of the epiwafers. The measured wafer-to-wafer consistency and cross-wafer uniformity demonstrate the potential for volume manufacturing.

  12. Optical and scintillation properties of ce-doped (Gd2Y1)Ga2.7Al2.3O12 single crystal grown by Czochralski method

    Science.gov (United States)

    Wang, Chao; Wu, Yuntao; Ding, Dongzhou; Li, Huanying; Chen, Xiaofeng; Shi, Jian; Ren, Guohao

    2016-06-01

    Multicomponent garnets, due to their excellent light yield and energy resolution, become one of the most promising scintillators used for homeland security and nuclear non-proliferation applications. This work focuses on the optimization of Ce-doped (Gd,Y)3(Ga,Al)5O12 scintillators using a combination strategy of pre-screening and scale-up. Ce-doped GdxY1-xGayAl5-yO12 (x=1, 2 and y=2, 2.2, 2.5, 2.7, 3) polycrystalline powders were prepared by high-temperature solid state reaction method. The desired garnet phase in all the samples was confirmed using X-ray diffraction measurement. By comparing the radioluminescence intensity, the highest scintillation efficiency was achieved at a component of Gd2Y1Ga2.7Al2.3O12:Ce powders. A (Gd2Y1)Ga2.7Al2.3O12 doped with 1% Ce single crystal with dimensions of Ø35×40 mm was grown by Czochralski method using a oriented seed. Luminescence and scintillation properties were measured. An optical transmittance of 84% was achieved in the concerned wavelength from 500 to 800 nm. Its 5d-4f emission of Ce3+ is at 530 nm. The light yield of a Ce1%: Gd2Y1Ga2.7Al2.3O12 single crystal slab at a size of 5×5×1 mm3 can reach about 65,000±3000 Ph/MeV along with two decay components of 94 and 615 ns under 137Cs source irradiation.

  13. Impacts of thermal stress and doping on intrinsic point defect properties and clustering during single crystal silicon and germanium growth from a melt

    Science.gov (United States)

    Vanhellemont, Jan; Kamiyama, Eiji; Nakamura, Kozo; Śpiewak, Piotr; Sueoka, Koji

    2017-09-01

    This paper reviews recent considerable progress made in the last few years in understanding the behavior and properties of intrinsic point defects close to moving melt/solid Si interfaces during single crystal Si growth from a melt. The so called Voronkov criterion allows to determine whether the grown Si crystal is interstitial I- or vacancy V-rich. This criterion is written as the ratio Γ of the pulling rate v over the thermal gradient G at the interface. Crystals pulled with Γ above a critical value Γcrit are vacancy-rich while below Γcrit, they are interstitial-rich. Various expressions based on the intrinsic point defect thermal equilibrium concentration and diffusivity have been proposed to calculate Γcrit and are briefly discussed in this paper. Recently it was shown that the thermal stress at the interface and heavy doping with neutral and/or electrically active impurities, have a considerable impact on the intrinsic point defect balance and thus also on Γcrit. Furthermore, high energy barriers of formation energies of I and V around three or four atom layers from (001) free surface support a model in which the boundary conditions of the point defect concentrations at the surface in simulations can be set at fixed values. The situation is quite different for Ge single crystal pulling where the vacancy is always the dominant intrinsic point defect so that the Voronkov criterion cannot be applied. Prediction of vacancy cluster concentration/size distributions as a function of the pulling conditions is however still possible. The possibility of reaching Voronkov criterion conditions for Ge by doping with specific impurities is also discussed. Finally, impacts of stress and doping on self-diffusion in Si and Ge are evaluated with comparing the previous experimental results.

  14. Improvement on the Luminescence Property of Y, Sb Co-doped PbWO4 Single Crystal

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The effect of Y and Sb co-doping on the luminescence property of PbWO4 crystals has been investigated. Compared with undoped PbWO4, the transmittance and emission peak intensity of Y∶Sb∶PbWO4 crystals were obviously improved. In addition, its transmittance cutoff wavelength and emission peak shifted to the shorter one. The mechanism of effect of Y and Sb on the transmittance spectra was briefly discussed. The light yield of Y∶Sb∶PbWO4 crystals was 25p.e./MeV, which was two times of that of undoped PbWO4. Our experiments showed that Y and Sb co-doping was a selectable method to improve the luminescence property of PbWO4.

  15. Magnetic, electric and electron magnetic resonance properties of orthorhombic self-doped La sub 1 sub - sub x MnO sub 3 single crystals

    CERN Document Server

    Markovich, V; Shames, A I; Puzniak, R; Rozenberg, E; Yuzhelevski, Y; Mogilyansky, D; Wisniewski, A; Mukovskii, Y M; Gorodetsky, G

    2003-01-01

    The effect of lanthanum deficiency on structural, magnetic, transport, and electron magnetic resonance (EMR) properties has been studied in a series of La sub 1 sub - sub x MnO sub 3 (x = 0.01, 0.05, 0.11, 0.13) single crystals. The x-ray diffraction study results for the crystals were found to be compatible with a single phase of orthorhombic symmetry. The magnetization curves exhibit weak ferromagnetism for all samples below 138 K. It was found that both the spontaneous magnetization and the coercive field increase linearly with x. The pressure coefficient dT sub N /dP decreases linearly with self-doping, from a value of 0.68 K kbar sup - sup 1 for La sub 0 sub . sub 9 sub 9 MnO sub 3 to 0.33 K kbar sup - sup 1 for La sub 0 sub . sub 8 sub 7 MnO sub 3. The resistivity of low-doped La sub 0 sub . sub 9 sub 9 MnO sub 3 crystal is of semiconducting character, while that of La sub 0 sub . sub 8 sub 7 MnO sub 3 depends weakly on temperature between 180 and 210 K. It was found that the magnetic and transport prop...

  16. Unraveling the exciton quenching mechanism of quantum dots on antimony-doped SnO₂ films by transient absorption and single dot fluorescence spectroscopy.

    Science.gov (United States)

    Song, Nianhui; Zhu, Haiming; Liu, Zheng; Huang, Zhuangqun; Wu, David; Lian, Tianquan

    2013-02-26

    Integrating quantum dots (QDs) into modern optoelectronic devices requires an understanding of how a transparent conducting substrate affects the properties of QDs, especially their excited-state dynamics. Here, the exciton quenching dynamics of core/multishell (CdSe/CdS(3ML)ZnCdS(2ML)ZnS(2ML)) quantum dots deposited on glass, tin oxide (SnO₂), and antimony (Sb)-doped tin oxide (ATO) films are studied by transient absorption and single QD fluorescence spectroscopic methods. By comparing ensemble-averaged fluorescence decay and transient absorption kinetics, we show that, for QDs on SnO₂, the exciton is quenched by electron transfer from the QD to SnO₂. At the QD-ATO interface, much faster exciton quenching rates are observed and attributed to fast Auger recombination in charged QDs formed by Fermi level equilibration between the QD and n-doped ATO. Single QDs on SnO₂ and ATO show similar blinking dynamics with correlated fluctuations of emission intensities and lifetimes. Compared to QDs on SnO₂, QDs on ATO films show larger variation of average exciton quenching rates, which is attributed to a broad distribution of the number of charges and nature of charging sites on the QD surface.

  17. Electronic Properties of Boron and Silicon Doped (10, 0 Zigzag Single-Walled Carbon Nanotube upon Gas Molecular Adsorption: A DFT Comparative Study

    Directory of Open Access Journals (Sweden)

    P. A. Gowri sankar

    2013-01-01

    Full Text Available We have performed a comparative study of nine predominant gas molecules (H2, H2O, O2, CO, CO2, NO, NO2, NH3, and CH3OH adsorption property on the top surface of the (10, 0 zigzag single-walled pristine Carbon nanotube (C-CNT, Boron doped carbon nanotube (B-CNT, and Silicon doped carbon nanotube (Si-CNT are investigated by using density functional theory (DFT computations to exploit their potential applications as gas sensors. For the first time, we calculated the optimal equilibrium position, absorption energy (Ead, and density of states (DOS of the considered gas molecules adsorbed on the open end of zigzag single-walled (10, 0 B-CNT and Si-CNT. Our first principle calculations demonstrate that the B-CNT and Si-CNT adsorbent materials are able to adsorb the considered gas molecules with variety of adsorption energy and their electronic structure dramatic changes in the density of states near the Fermi level. The obtained comparative DFT studies results are useful for designing a high-fidelity gas sensor materials and selective adsorbents for a selective gas sensor.

  18. Spontaneous and stimulated emission in Sm{sup 3+}-doped YAl{sub 3}(BO{sub 3}){sub 4} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Ryba-Romanowski, Witold [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-422 Wrocław (Poland); Lisiecki, Radosław, E-mail: R.Lisiecki@int.pan.wroc.pl [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-422 Wrocław (Poland); Beregi, Elena [Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, Budapest (Hungary); Martín, I.R. [Departamento de Física, Instituto de Materiales y Nanotecnología (IMN), Universidad de La Laguna, 38206 S/C de Tenerife, Laguna (Spain)

    2015-11-15

    Single crystals of YAl{sub 3}(BO{sub 3}){sub 4} doped with trivalent samarium were grown by the top-seeded high temperature solution method and their absorption and emission spectra were investigated. Optical pumping into prominent absorption band around 405 nm feeds the {sup 4}G{sub 5/2} metastable level giving rise to intense visible luminescence distributed in several spectral lines with the most intense line around 600 nm characterized by a branching ratio of 0.42 and peak emission cross section of 0.25×10{sup −20} cm{sup 2}. Optical amplification at 600 nm with a gain coefficient of 2.9 cm{sup −1} was achieved during a pump-and-probe experiment. - Highlights: • YAB:Sm crystal grown by the top-seeded high temperature solution method. • Spectroscopic qualities relevant for visible laser operation. • YAB:Sm single crystal used in a pump-and-probe experiment. • Optical amplification properties of samarium doped YAl{sub 3}(BO{sub 3}){sub 4}.

  19. Eu-concentration dependence of optical and scintillation properties for Eu-doped SrF{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kurosawa, Shunsuke; Yokota, Yuui [Institute for Materials Research, Tohoku University, Katahira 2-1-1, 980-8577 Sendai (Japan); Yanagida, Takayuki [New Industry Creation Hatchery Center (NICHe), Aoba 6-6-10, Aramaki, 980-8579 Aoba-ku, Sendai (Japan); Yoshikawa, Akira [Institute for Materials Research, Tohoku University, Katahira 2-1-1, 980-8577 Sendai (Japan); New Industry Creation Hatchery Center (NICHe), Aoba 6-6-10, Aramaki, 980-8579 Aoba-ku, Sendai (Japan)

    2012-12-15

    Some Eu-doped scintillators, such as Eu:SrI{sub 2}, emit around 400-nm wavelength that originates from 5d-4f transition of Eu{sup 2+}, while some Eu-doped crystals have emissions from Eu{sup 3+} (f-f emission). In this report, effect of Eu-doping on optical and scintillation properties of SrF{sub 2} crystals with Core-valence luminescence is discussed. The samples had 0.1, 0.2, 0.5, 1.0, and 2.0 mol% of Eu and were grown by an annealing method. As a result, {sup 5}D{sub 0}-{sup 7}F{sub i} (i =1, 2) transition (Eu{sup 3+}) was detected in the SrF{sub 2}, containing over 0.5 mol% of Eu, while emission from 0.1 and 0.2-mol% Eu:SrF{sub 2} originated from 5d-4f transition of Eu{sup 2+} and Core-valence luminescence. The light output of SrF{sub 2} doped with 0.1, 0.2, 0.5, 1.0 and 2.0 mol% Eu was estimated to be 13,000 {+-} 1,000, 12,000 {+-} 1,000, 13,000 {+-} 2,000, 8,000 {+-} 1,000 and 7,000 {+-} 1,000 photons/MeV, respectively. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Material and Doping Dependence of the Nodal and Anti-Nodal Dispersion Renormalizations in Single- and Multi-Layer Cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, S.; /Waterloo U. /SLAC; Lee, W.S.; /Stanford U., Geballe Lab. /SLAC; Nowadnick, E.A.; /SLAC /Stanford U., Phys. Dept.; Moritz, B.; /SLAC /North Dakota U.; Shen, Z.-X.; /Stanford U., Geballe Lab. /SLAC /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept.; Devereaux, T.P.; /Stanford U., Geballe Lab. /SLAC

    2010-02-15

    In this paper we present a review of bosonic renormalization effects on electronic carriers observed from angle-resolved photoemission spectra in the cuprates. Specifically, we discuss the viewpoint that these renormalizations represent coupling of the electrons to the lattice and review how materials dependence, such as the number of CuO{sub 2} layers, and doping dependence can be understood straightforwardly in terms of several aspects of electron-phonon coupling in layered correlated materials.

  1. Intense intrashell luminescence of Eu-doped single ZnO nanowires at room temperature by implantation created Eu-Oi complexes.

    Science.gov (United States)

    Geburt, Sebastian; Lorke, Michael; da Rosa, Andreia L; Frauenheim, Thomas; Röder, Robert; Voss, Tobias; Kaiser, Uwe; Heimbrodt, Wolfram; Ronning, Carsten

    2014-08-13

    Successful doping and excellent optical activation of Eu(3+) ions in ZnO nanowires were achieved by ion implantation. We identified and assigned the origin of the intra-4f luminescence of Eu(3+) ions in ZnO by first-principles calculations to Eu-Oi complexes, which are formed during the nonequilibrium ion implantation process and subsequent annealing at 700 °C in air. Our targeted defect engineering resulted in intense intrashell luminescence of single ZnO:Eu nanowires dominating the photoluminescence spectrum even at room temperature. The high intensity enabled us to study the luminescence of single ZnO nanowires in detail, their behavior as a function of excitation power, waveguiding properties, and the decay time of the transition.

  2. Improvement of refrigerant capacity of La0.67Ca0.33MnO3 single crystal with a few percent Fe doping

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Large low-field-induced magnetic entropy changes, ΔSM, are observed in La0.67Ca0.33MnO3 and La0.67-Ca0.33Mn0.96Fe0.04O3 single crystals. The peaks of ΔSM broadened asymmetrically to high temperatures under higher magnetic fields for two materials should be attributed to the first-order magnetic phase transition at Tc. A small amount of iron doping results in an increase in the refrigerant capacity of the material though the magnetic entropy change decreases. The discovery of excellent magnetocaloric features of these single crystals in the low magnetic field can provide some ideas for exploring novel magnetic refrigerants operating under permanent magnet rather than superconducting one as magnetic field source.

  3. Crystal growth and scintillation properties of Er-doped Lu{sub 3}Al{sub 5}O{sub 12} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, Makoto, E-mail: makoto.sugiyama@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Fujimoto, Yutaka [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Yanagida, Takayuki [New Industry Creation Hatchery Center (NICHe), Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Totsuka, Daisuke [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Nihon Kessho Kogaku Co. Ltd., 810-5 Nobe-cho Tatebayashi Gunma (Japan); Kurosawa, Shunsuke; Futami, Yoshisuke; Yokota, Yuui; Chani, Valery [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Yoshikawa, Akira [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan)

    2012-02-01

    Er-doped Lu{sub 3}Al{sub 5}O{sub 12} (Er:LuAG) single crystalline scintillators with different Er concentrations of 0.1, 0.5, 1, and 3% were grown by the micro-pulling-down ({mu}-PD) method. The grown crystals were composed of single-phase material, as demonstrated by powder X-ray diffraction (XRD). The radioluminescence spectra measured under {sup 241}Am {alpha}-ray excitation indicated host emission at approximately 350 nm and Er{sup 3+} 4f-4f emissions. According to the pulse height spectra recorded under {gamma}-ray irradiation, the 0.5% Er:LuAG exhibited the highest peak channel among the samples. The {gamma}-ray excited decay time profiles were well fitted by the two-component exponential approximation (0.8 {mu}s and 6-10 {mu}s).

  4. Passively mode-locking erbium-doped fiber lasers with 0.3 nm Single-Walled Carbon Nanotubes

    Science.gov (United States)

    Xu, Xintong; Zhai, Jianpang; Li, Ling; Chen, Yanping; Yu, Yongqin; Zhang, Min; Ruan, Shuangchen; Tang, Zikang

    2014-01-01

    We demonstrate a passively mode-locked erbium-doped fiber laser (EDFL) by using the smallest single-walled carbon nanotubes (SWNTs) with a diameter of 0.3 nm as the saturable absorber. These ultrasmall SWNTs are fabricated in the elliptical nanochannels of a ZnAPO4-11 (AEL) single crystal. By placing an AEL crystal into an EDFL cavity pumped by a 980 nm laser diode, stable passive mode-locking is achieved for a threshold pump power of 280 mW, and 73 ps pulses at 1563.2 nm with a repetition rate of 26.79 MHz. PMID:25342292

  5. Structure of and phase transformations in bulk amorphous (GaSb) sub 1 sub - sub x (Ge sub 2) sub x

    CERN Document Server

    Sapelkin, A V

    1997-01-01

    temperatures, under high pressures and at ambient conditions. Combined EXAFS and powder diffraction methods have been used to study the high pressure behavior of materials. The results revealed a complex picture of structural transformations in (GaSb) sub 1 sub - sub x (Ge sub 2) sub x owing to the meta-stable nature of samples. The semiconductor-to-metal transition observed previously is found to be due to percolation through the high pressure metallic phase GaSb II. It is showed that the combination of two structural techniques, powder diffraction and EXAFS, can provide quite detailed information on the structural behavior of amorphous materials under high pressures. The temperature-dependent EXAFS studies showed that semiconducting amorphous GaSb is likely to be chemically ordered. Issues concerning determination of the structure of amorphous materials and information theory are widely discussed. Amorphous materials are not new to scientists and mankind -- man has been using glass and glassy materials for ...

  6. Optical properties of GaSb(001)-c(2 x 6): The role of surface antisite defects

    Energy Technology Data Exchange (ETDEWEB)

    Hogan, Conor; Del Sole, Rodolfo [Department of Physics, CNR-INFM-SMC, Roma (Italy); European Theoretical Spectroscopy Facility (ETSF), University of Rome ' ' Tor Vergata' ' , Roma (Italy); Magri, Rita [Centro S3-CNR-Istituto di Nanoscienze, Modena (Italy); Department of Physics, University of Modena and Reggio Emilia, Modena (Italy)

    2010-08-15

    We consider the formation of surface antisite defects on a previously proposed model for the GaSb(001)-c(2 x 6) surface. Based on ab initio total energy calculations, we show how these defects stabilize the otherwise metallic surface and how their formation is driven by the excess charge associated with the Sb-rich surface conditions. The surface-sensitive optical technique of reflectance anisotropy spectroscopy is shown to be crucial for detecting the defects, and computation of spectra yields a good agreement with experiment when defects are included in the surface reconstruction. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  7. Creation of domains by direct electron beam writing in magnesium-doped LiNbO{sub 3} and LiNbO{sub 3}:Fe single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Palatnikov, M.N. [Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, 26a Akademgorodok, Apatity, Murmansk 184209 (Russian Federation); Kokhanchik, L.S.; Emelin, E.V. [Institute of Microelectronics Technology and High Purity Materials of Russian Academy of Sciences, 6 Academician Ossipyan st, Chernogolovka, Moscow 142432 (Russian Federation); Sidorov, N.V. [Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, 26a Akademgorodok, Apatity, Murmansk 184209 (Russian Federation); Manukovskaya, D.V., E-mail: deenka@yandex.ru [Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, 26a Akademgorodok, Apatity, Murmansk 184209 (Russian Federation)

    2016-03-01

    Highlights: • The periodic domains are created in crystal LiNbO{sub 3}:Mg by direct electron beam writing. • Periodic domains appear only at equilibrium between switching and screening times. • Equilibrium exists in crystal co-doped by Fe. • Shape and appearance of domains depend on the conductivity type. - Abstract: Domain structures in the Z-cut of highly doped LiNbO{sub 3}:Mg and LiNbO{sub 3}:Mg,Fe single crystals were created by direct electron beam writing (DEBW). It was found that the value and type of electron conductivity influence the shape and number of domains thus created. Controlled electron beam regular domains were created only in samples of the crystal LiNbO{sub 3}:Mg,Fe [MgO] = 5.16 mol.%, [Fe] = 0.007 mol.%. In highly doped LiNbO{sub 3}:Mg ([MgO] = 5.19 mol.%) crystal, the domains were formed chaotically and controlled creation of domains did not occur. The domain shapes were analyzed in the framework of the theory of screening of domain nuclei depolarizing electric fields and the influence of screening on the final shape of domains. It was found that screening of intrinsic electric fields is faster in the LiNbO{sub 3}:Mg,Fe crystal. This crystal has a high electronic conductivity of hopping type with a high mobility of charge carriers. Thus, a small amount of Fe provides equilibrium between the ferroelectric switching velocity and screening of the depolarizing electric field velocity. The results are discussed considering differences in the electron conductivity mechanisms, which control the screening of depolarizing electric field velocity and spatial charge area formed under an electron beam.

  8. Preclinical and first clinical experience with the gastrin-releasing peptide receptor-antagonist [{sup 68}Ga]SB3 and PET/CT

    Energy Technology Data Exchange (ETDEWEB)

    Maina, Theodosia; Charalambidis, David; Nock, Berthold A. [INRASTES, NCSR ' ' Demokritos' ' , Molecular Radiopharmacy, Athens (Greece); Bergsma, Hendrik; Krenning, Eric P. [Erasmus MC, Department of Nuclear Medicine, Rotterdam (Netherlands); Kulkarni, Harshad R.; Mueller, Dirk; Baum, Richard P. [Zentralklinik, Molecular Radiotherapy and Molecular Imaging, Bad Berka (Germany); Jong, Marion de [Erasmus MC, Department of Nuclear Medicine, Rotterdam (Netherlands); Erasmus MC, Department of Radiology, Rotterdam (Netherlands)

    2016-05-15

    Gastrin-releasing peptide receptors (GRPR) represent attractive targets for tumor diagnosis and therapy because of their overexpression in major human cancers. Internalizing GRPR agonists were initially proposed for prolonged lesion retention, but a shift of paradigm to GRPR antagonists has recently been made. Surprisingly, radioantagonists, such as [{sup 99m}Tc]DB1 ({sup 99m}Tc-N{sub 4}'-DPhe{sup 6},Leu-NHEt{sup 13}BBN(6-13)), displayed better pharmacokinetics than radioagonists, in addition to their higher inherent biosafety. We introduce here [{sup 68}Ga]SB3, a [{sup 99m}Tc]DB1 mimic-carrying, instead of the {sup 99m}Tc-binding tetraamine, the chelator DOTA for labeling with the PET radiometal {sup 68}Ga. Competition binding assays of SB3 and [{sup nat}Ga]SB3 were conducted against [{sup 125}I-Tyr{sup 4}]BBN in PC-3 cell membranes. Blood samples collected 5 min postinjection (pi) of the [{sup 67}Ga]SB3 surrogate in mice were analyzed using high-performance liquid chromatography (HPLC) for degradation products. Likewise, biodistribution was performed after injection of [{sup 67}Ga]SB3 (37 kBq, 100 μL, 10 pmol peptide) in severe combined immunodeficiency (SCID) mice bearing PC-3 xenografts. Eventually, [{sup 68}Ga]SB3 (283 ± 91 MBq, 23 ± 7 nmol) was injected into 17 patients with breast (8) and prostate (9) cancer. All patients had disseminated disease and had received previous therapies. PET/CT fusion images were acquired 60-115 min pi. SB3 and [{sup nat}Ga]SB3 bound to the human GRPR with high affinity (IC{sub 50}: 4.6 ± 0.5 nM and 1.5 ± 0.3 nM, respectively). [{sup 67}Ga]SB3 displayed good in vivo stability (>85 % intact at 5 min pi). [{sup 67}Ga]SB3 showed high, GRPR-specific and prolonged retention in PC-3 xenografts (33.1 ± 3.9%ID/g at 1 h pi - 27.0 ± 0.9%ID/g at 24 h pi), but much faster clearance from the GRPR-rich pancreas (∼160%ID/g at 1 h pi to <17%ID/g at 24 h pi) in mice. In patients, [{sup 68}Ga]SB3 elicited no adverse effects and

  9. Significant increase of salivary testosterone levels after single therapeutic transdermal administration of testosterone: suitability as a potential screening parameter in doping control.

    Science.gov (United States)

    Thieme, Detlef; Rautenberg, Claudia; Grosse, Joachim; Schoenfelder, Martin

    2013-01-01

    The legally defensible proof of the abuse of endogenous steroids in sports is currently based on carbon isotope ratio mass spectrometry (IRMS), i.e. a comparison between (13)C/(12)C ratios of diagnostic precursors and metabolites of testosterone. The application of this technique requires a chromatographic baseline separation of respective steroids prior to IRMS detection and hence laborious sample pre-processing of the urinary steroid extracts including clean up by solid-phase extraction and/or liquid chromatography. Consequently, an efficient pre-selection of suspicious control urine samples is essential for appropriate follow up confirmation by IRMS and effective doping control. Two single transdermal administration studies of testosterone (50 mg Testogel® and Testopatch® at 3.8 mg in 16 h, respectively) were conducted and resulting profiles of salivary testosterone and urinary steroid profiles and corresponding carbon isotope ratios were determined. Conventional doping control markers (testosterone/epitestosterone ratio, threshold concentrations of androsterone, etiocholanolone, or androstanediols) did not approach or exceed critical thresholds. In contrast to these moderate variations, the testosterone concentration in oral fluid increased from basal values (30-142 pg/mg) to peak concentrations above 1000 pg/mg. It is likely that this significant increase in oral fluid is due to a pulsatile elevation of free (protein unbound) circulating testosterone after transdermal administration and may be assumed to represent a more diagnostic marker for transdermal testosterone administration.

  10. Eu{sup 3+} ions co-doped CLPO: Dy{sup 3+} single phase white-light emitting phosphors for near UV-based white LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Yong Il; Bharat, L. Krishna; Yu, Jae Su, E-mail: jsyu@khu.ac.kr

    2015-11-15

    CaLaP{sub 3}O{sub 10}: Dy{sup 3+}/Eu{sup 3+} phosphor powders were prepared by a facile sol–gel method. These samples were thermally treated at 900 °C for 6 h to get monazite type structure with monoclinic unit cell. The phase, morphology and optical properties of phosphor samples were characterized by X-ray diffraction patterns, Fourier transform infrared spectra, scanning/transmission electron microscope images, and photoluminescence excitation and emission spectra. The Dy{sup 3+}/Eu{sup 3+} ions co-doped samples showed warm white-light emissions with lower correlated color temperature values at higher Eu{sup 3+} ion concentrations. The near-ultraviolet (NUV) excitation and the effective energy transfer form Dy{sup 3+} to Eu{sup 3+} ions can make these phosphors as potential candidates for NUV excitation based white light-emitting diodes. - Highlights: • Single crystalline CLPO phosphors were successfully prepared by a sol–gel process. • CLPO has monazite type structure with monoclinic unit cells. • Eu{sup 3+} co-doped CLPO: Dy{sup 3+} samples give warm white-light emission with low CCT values. • The NUV excitation (392 nm) allows the use of this material for WLED applications.

  11. Effect of Ar ion irradiation on the room temperature ferromagnetism of undoped and Cu-doped rutile TiO2 single crystals

    Science.gov (United States)

    Xu, Nan-Nan; Li, Gong-Ping; Lin, Qiao-Lu; Liu, Huan; Bao, Liang-Man

    2016-11-01

    Remarkable room-temperature ferromagnetism was observed both in undoped and Cu-doped rutile TiO2 single crystals (SCs). To tune their magnetism, Ar ion irradiation was quantitatively performed on the two crystals in which the saturation magnetizations for the samples were enhanced distinctively. The post-irradiation led to a spongelike layer in the near surface of the Cu-doped TiO2. Meanwhile, a new CuO-like species present in the sample was found to be dissolved after the post-irradiation. Analyzing the magnetization data unambiguously reveals that the experimentally observed ferromagnetism is related to the intrinsic defects rather than the exotic Cu ions, while these ions are directly involved in boosting the absorption in the visible region. Project supported by the National Natural Science Foundation of China (Grant No. 11575074), the Open Project of State Key laboratory of Crystal Material, Shandong University, China (Grant No. KF1311), the Open Project of Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, China (Grant No. LZUMMM2012003), the Open Project of Key Laboratory of Beam Technology and Material Modification of Ministry of Education, Beijing Normal University, China (Grant No. 201204), and the Fundamental Research Funds for the Central Universities, China (Grant No. lzujbky-2015-240).

  12. High electron density and mobility in single and double planar doped InGaAs/InAlAs heterojunctions in InP

    Energy Technology Data Exchange (ETDEWEB)

    Gueissaz, F.; Houdre, R.; Ilegems, M. (Inst. de Micro- et Optoelectronique, Ecole Polytechnique Federale de Lausanne (Switzerland))

    1991-05-01

    We present results of a growth study concerning the electrical properties of lattice matched InAlGa/InGaAs single planar doped (SPD) and double planar doped (DPD) heterostructures grwon on InP by molecular beam epitaxy (MBE). It is shown that room temperature electron mobilities ({mu}{sub H}) as high as 11000 cm{sup 2}/V.s at high sheet densities of 2.8x10{sup 12} cm{sup -2} can be obtained by optimizing the growth temperatures of each material in the SPD structure. High performance two-dimensional electron gas field effect transistors (TEGFET's) are demonstrated, with transconductances as high as 420 mS/mm at 1 {mu}m gatelength and f{sub T}'s of 46 GHz at 0.7 {mu}m gatelength. The DPD heterostructures further boost the n{sub s} values up to 6.2x10{sup 12} cm{sup -2} at {mu}{sub H} (300 K)=6000 cm{sup 2}/V.s. (orig.).

  13. Study of flux pinning mechanism under hydrostatic pressure in optimally doped (Ba,K)Fe2As2 single crystals.

    Science.gov (United States)

    Shabbir, Babar; Wang, Xiaolin; Ma, Y; Dou, S X; Yan, S S; Mei, L M

    2016-03-17

    Strong pinning depends on the pinning force strength and number density of effective defects. Using the hydrostatic pressure method, we demonstrate here that hydrostatic pressure of 1.2 GPa can significantly enhance flux pinning or the critical current density (Jc) of optimally doped Ba0.6K0.4Fe2As2 crystals by a factor of up to 5 in both low and high fields, which is generally rare with other Jc enhancement techniques. At 4.1 K, high pressure can significantly enhance Jc from 5 × 10(5 )A/cm(2) to nearly 10(6 )A/cm(2) at 2 T, and from 2 × 10(5 )A/cm(2) to nearly 5.5 × 10(5 )A/cm(2) at 12 T. Our systematic analysis of the flux pinning mechanism indicates that both the pinning centre number density and the pinning force are greatly increased by the pressure and enhance the pinning. This study also shows that superconducting performance in terms of flux pinning or Jc for optimally doped superconducting materials can be further improved by using pressure.

  14. The divalent ion codoping effect on Ce-doped (Gd, La)2Si2O7 single crystals

    Science.gov (United States)

    Horiai, Takahiko; Murakami, Rikito; Kurosawa, Shunsuke; Shoji, Yasuhiro; Yamaji, Akihiro; Pejchal, Jan; Ohashi, Yuji; Arakawa, Mototaka; Kamada, Kei; Yokota, Yuui; Yoshikawa, Akira

    2017-06-01

    Ce-doped (Gd, La)2Si2O7 scintillators have fast decay time and keep high light output even at high temperature (∼150°C). To improve the scintillation properties such as light output and decay time, Ce-doped (Gd, La)2Si2O7 scintillators codoped with the divalent ions (e.g. Mg2+, Ca2+) have been studied. In this study, we focused on the other divalent ions (Sr2+ and Ba2+), and investigated their effect on the scintillation properties and temperature dependence of light output. The absorption due to Ce4+ was not observed for Sr or Ba codoping. The light outputs were degraded by Sr2+ or Ba2+ codoping, while the decay times at room temperature were not changed for the samples codoped with divalent ions. On the other hand, the temperature dependence of light output for Ba-codoped sample was improved, and the light output value at 175°C was 36,000 photons/MeV, which was 93% of that at 25°C.

  15. Effects of post-annealing and cobalt co-doping on superconducting properties of (Ca,Pr)Fe{sub 2}As{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Okada, T., E-mail: 8781303601@mail.ecc.u-tokyo.ac.jp; Ogino, H.; Yakita, H.; Yamamoto, A.; Kishio, K.; Shimoyama, J.

    2014-10-15

    Highlights: • Post-annealing at 400 °C killed superconductivity for Co-free sample. • Pr,Co co-doped samples maintained superconductivity even after annealing. • Two-step superconducting transition was observed via magnetization measurement. • Bulk superconductivity of low-T{sub c} component was confirmed. • Superconducting volume fraction of high-T{sub c} component was always small. - Abstract: In order to clarify the origin of anomalous superconductivity in (Ca,RE)Fe{sub 2}As{sub 2} system, Pr doped and Pr,Co co-doped CaFe{sub 2}As{sub 2} single crystals were grown by the FeAs flux method. These samples showed two-step superconducting transition with T{sub c1} = 25–42 K, and T{sub c2} < 16 K, suggesting that (Ca,RE)Fe{sub 2}As{sub 2} system has two superconducting components. Post-annealing performed for these crystals in evacuated quartz ampoules at various temperatures revealed that post-annealing at ∼400 °C increased the c-axis length for all samples. This indicates that as-grown crystals have a certain level of strain, which is released by post-annealing at ∼400 °C. Superconducting properties also changed dramatically by post-annealing. After annealing at 400 °C, some of the co-doped samples showed large superconducting volume fraction corresponding to the perfect diamagnetism below T{sub c2} and high J{sub c} values of 10{sup 4}–10{sup 5} A cm{sup −2} at 2 K in low field, indicating the bulk superconductivity of (Ca,RE)Fe{sub 2}As{sub 2} phase occurred below T{sub c2}. On the contrary, the superconducting volume fraction above T{sub c2} was always very small, suggesting that 40 K-class superconductivity observed in this system is originating in the local superconductivity in the crystal.

  16. Determination of designer doping agent--2-ethylamino-1-phenylbutane--in dietary supplements and excretion study following single oral supplement dose.

    Science.gov (United States)

    Wójtowicz, Marzena; Jarek, Anna; Chajewska, Katarzyna; Turek-Lepa, Ewa; Kwiatkowska, Dorota

    2015-11-10

    The quantitative analysis of a new designer doping agent, 2-ethylamino-1-phenylbutane (EAPB) and its metabolite, 2-amino-1-phenylbutane (APB) in urine samples, and the determination of EAPB in dietary supplement samples, have been presented. The main purpose of the present study was to develop simple and reliable gas chromatography-mass spectrometry method (GC-MS) for excretion study following a single oral administration of dietary supplements containing EAPB. Three analytical methods for the determination of EAPB in urine and supplement samples, and APB in urine samples using the GC-MS system, have been validated. The method of the determination of EAPB in supplement samples was applied to analyze seventeen dietary supplements, CRAZE and DETONATE. Two other methods were used to determine the urinary excretion profile of EAPB and APB in the case of three healthy volunteers and, on further investigation, it was applied to the anti-doping control in sport. Quantification was obtained on the basis of the ions at m/z 86, 58 and 169, monitored for EAPB, APB and diphenylamine (used as an internal standard), respectively. The limits of detection and quantification were 2.4 and 7.3μg/g for EAPB in the case of supplement analysis, 2.9 and 8.8ng/mL for EAPB in the case of urine analysis, and 3.2 and 9.7ng/mL for APB. The other validation parameters as linearity, precision and trueness have been also investigated with the acceptable results. The extraction yield of all presented methods was above 69%. EAPB was detected in fourteen analyzed supplements (not included EAPB in their labels) and its content varied between 1.8 and 16.1mg/g. Following oral administration of three supplements with EAPB to one male and two female volunteers, the parent compound of EAPB and its metabolite were monitored and the excretion parameters as the maximum concentration of the analyte in urine (2.2-4.2μg/mL for EAPB; 1.1-5.1μg/mL for APB) and the time for the maximum height of the excretion

  17. Utilizing Neon Ion Microscope for GaSb nanopatterning studies: Nanostructure formation and comparison with low energy nanopatterning

    Science.gov (United States)

    El-Atwani, Osman; Huynh, Chuong; Norris, Scott

    2016-05-01

    Low energy irradiation of GaSb surfaces has been shown to lead to nanopillar formation. Being performed ex-situ, controlling the parameters of the ion beam for controlled nanopattern formation is challenging. While mainly utilized for imaging and cutting purposes, the development of multibeam (helium/neon) ion microscopes has opened the path towards the use of these microscopes for in-situ ion irradiation and nanopatterning studies. In this study, in-situ irradiation (neon ions)/imaging (helium ions) of GaSb surfaces is performed using Carl Zeiss-neon ion microscope at low energies (5 and 10 keV). Imaging with helium ions, nanodots were shown to form at particular fluences after which are smoothed. Ex-situ imaging with SEM showed nanopore formation of size controlled by the ion energy and fluence. Compared to lower energy ex-situ neon ion irradiation at similar fluxes, where nanopillars are formed, the results demonstrated a transition in the nanostructure type and formation mechanism as the energy is changed from 2 to 5 keV. Simulations show an increase in the ballistic diffusion and a decrease in the strength of phase separation as a function of ion energy in agreement with the suppression of nanopillar formation at higher energies. Collision cascade simulations suggest a transition toward bulk-driven mechanisms.

  18. A noble and single source precursor for the synthesis of metal-rich sulphides embedded in an N-doped carbon framework for highly active OER electrocatalysts.

    Science.gov (United States)

    Barman, Barun Kumar; Nanda, Karuna Kar

    2016-04-21

    Here, we demonstrate a green and environment-friendly pyrolysis route for the synthesis of metal-rich sulphide embedded in an N-doped carbon (NC) framework in the absence of sulphide ions (S(2-)). The metal-chelate complex (tris(ethylenediamine) metal(ii) sulfate) serves as a new and single source precursor for the synthesis of earth abundant and non-precious hybrid structures such as metal-rich sulphides Co9S8@NC and Ni3S2@NC when M(II) = Co(2+) and Ni(2+) and counter sulphate (SO4(2-)) ions are the source of S. Both the hybrids show superior OER activity as compared to commercial RuO2.

  19. Photoluminescence of anti-modulation doped near-surface GaAs/AlGaAs single quantum well structures exposed to hydrogen plasma

    CERN Document Server

    Bumaj, Y A; Goldkhan, R; Shtajn, N; Golombek, A; Nakov, V; Cheng, T S

    2002-01-01

    The anti-modulation Si-doped GaAs/AlGaAs structures with near-surface single quantum wells grown by molecular-beam epitaxy were exposed to hydrogen plasma at 260 deg C and investigated by low-temperature photoluminescence, photoluminescence excitation and photoreflectance spectroscopy. After hydrogenation, the quenching of the exciton luminescence for the below AlGaAs band gap excitation due to the increase of electric field in the structure has been observed. The effect is consistent with unpinning of Fermi level from mid gap of nominally undoped (p-type) GaAs cap layer due to passivation of surface states by hydrogen without neutralization of shallow impurities in the epilayers

  20. Broadband near-infrared luminescence in gamma-irradiated Bi-doped alpha-BaB(2)O(4) single crystals.

    Science.gov (United States)

    Su, Liangbi; Yu, Jun; Zhou, Peng; Li, Hongjun; Zheng, Lihe; Yang, Yan; Wu, Feng; Xia, Haiping; Xu, Jun

    2009-08-15

    Spectroscopic properties of as-grown and gamma-irradiated undoped and Bi-doped alpha-BBO (BaB(2)O(4)) single crystals were investigated. Bi(2+) and color centers in Bi:alpha-BBO crystals were investigated to be nonluminescent in the near-infrared (NIR) region. Broadband NIR luminescence at 1139 nm with a FWHM of 108 nm and a decay time of 526 mus was realized in Bi:alpha-BBO crystal through gamma irradiation. Bi(+) was attributed to be responsible for the NIR emission, which can be bleached by thermal annealing. The involved physical processes in Bi:alpha-BBO crystal during the courses of irradiation and heat annealing were tentatively established.

  1. Direct and Dry Deposited Single-Walled Carbon Nanotube Films Doped with MoO(x) as Electron-Blocking Transparent Electrodes for Flexible Organic Solar Cells.

    Science.gov (United States)

    Jeon, Il; Cui, Kehang; Chiba, Takaaki; Anisimov, Anton; Nasibulin, Albert G; Kauppinen, Esko I; Maruyama, Shigeo; Matsuo, Yutaka

    2015-07-01

    Organic solar cells have been regarded as a promising electrical energy source. Transparent and conductive carbon nanotube film offers an alternative to commonly used ITO in photovoltaics with superior flexibility. This communication reports carbon nanotube-based indium-free organic solar cells and their flexible application. Direct and dry deposited carbon nanotube film doped with MoO(x) functions as an electron-blocking transparent electrode, and its performance is enhanced further by overcoating with PSS. The single-walled carbon nanotube organic solar cell in this work shows a power conversion efficiency of 6.04%. This value is 83% of the leading ITO-based device performance (7.48%). Flexible application shows 3.91% efficiency and is capable of withstanding a severe cyclic flex test.

  2. Electron-beam induced disorder effects in optimally doped Bi2Sr2CaCu2O8+x single crystal samples

    Science.gov (United States)

    Vobornik, I.; Berger, H.; Pavuna, D.; Margaritondo, G.; Forro, L.; Grioni, M.; Rullier-Albenque, F.; Onellion, M.; EPFL Collaboration; Laboratoire Des Solides Irradiés Collaboration

    2000-03-01

    We report on the effects of electron-beam induced disorder in optimally doped Bi2Sr2CaCu2O8+x single crystal samples, measured with angle-resolved photoemission. In the superconducting state, the disorder fills in the gap, without changing the binding energy or the width of the narrow coherent feature.[1] In the normal state, disorder leads to an anisotropic pseudogap in angle-resolved photoemission, with the largest pseudogap near the (0,p) point and no pseudogap in the direction.[2,3] We discuss implications of these data. 1. I. Vobornik et.al., Phys. Rev. Lett. 82 , 3128 (1999). 2. I. Vobornik, Ph.D. thesis, EPFL, Lausanne, Switzerland, October, 1999. 3. I. Vobornik et.al., unpublished.

  3. First-principle study on the X (X=N, P, As, Sb) doped (9.0) single-walled SiC nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Jianfeng, E-mail: jfdai1963@sohu.com [State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou 730050 (China); School of Science, Lanzhou University of Technology, Lanzhou 730050 (China); Chen, Dacheng [School of Science, Lanzhou University of Technology, Lanzhou 730050 (China); Li, Qiang [Computational Physics Key Laboratory of Sichuan Province Yibin University, Yibin 644007 (China)

    2014-08-15

    The structural and electronic properties of N, P, As and Sb doped (9.0) single-walled SiC nanotubes (SWSiCNTs) are investigated by the first-principle theory. The calculated results indicated that one P, As or Sb atom substituted for one C atom, which could be considered as n-type semiconductors. When one N, P, As or Sb replace one Si atom, the model shows the character of semi-metallic, n-type semiconductor, p-type semiconductor respectively. These results indicated that with the addition of atomic radius and reduction of electronegativity, dopant of VA elements will bring bizarre change of electronic properties. These results are expected to give valuable information in building nanoscale electronic devices.

  4. Highly efficient metal-free growth of nitrogen-doped single-walled carbon nanotubes on plasma-etched substrates for oxygen reduction.

    Science.gov (United States)

    Yu, Dingshan; Zhang, Qiang; Dai, Liming

    2010-11-03

    We have for the first time developed a simple plasma-etching technology to effectively generate metal-free particle catalysts for efficient metal-free growth of undoped and/or nitrogen-doped single-walled carbon nanotubes (CNTs). Compared with undoped CNTs, the newly produced metal-free nitrogen-containing CNTs were demonstrated to show relatively good electrocatalytic activity and long-term stability toward oxygen reduction reaction (ORR) in an acidic medium. Owing to the highly generic nature of the plasma etching technique, the methodology developed in this study can be applied to many other substrates for efficient growth of metal-free CNTs for various applications, ranging from energy related to electronic and to biomedical systems.

  5. Degradation of optical properties of a film-type single-wall carbon nanotubes saturable absorber (SWNT-SA) with an Er-doped all-fiber laser.

    Science.gov (United States)

    Ryu, Sung Yoon; Kim, Kyung-Soo; Kim, Jungwon; Kim, Soohyun

    2012-06-04

    Single-wall carbon nanotubes (SWNTs) are promising materials for saturable absorbers (SAs) in mode-locked lasers. However it has been widely recognized that the degradation of optical properties of film-type SWNTs used in femtosecond mode-locked lasers limits the achievable long-term stability of such lasers. In this paper, we study the degradation of optical properties of SWNT-SA fabricated as sandwich type using HiPCO SWNTs with an Er-doped all-fiber laser. The thresholds of laser pump power are examined to avoid the damage of the SWNT-SA. Based on the proposed analysis, it is shown that all-fiber laser pulses of 300 fs pulse width, 3.85 mW average output power, 211.7 MW/cm² peak intensity and 69.9 MHz repetition rate can be reliably generated without any significant damage to the SWNT-SA film.

  6. Nanosecond soliton pulse generation by mode-locked erbium-doped fiber laser using single-walled carbon-nanotube-based saturable absorber.

    Science.gov (United States)

    Ismail, Mohd Afiq; Harun, Sulaiman Wadi; Zulkepely, Nurul Rozullyah; Nor, Roslan Md; Ahmad, Fauzan; Ahmad, Harith

    2012-12-20

    We demonstrate a simple and low cost mode-locked erbium-doped fiber laser (EDFL) operating in the nanosecond region using a single-walled carbon nanotube (SWCNT)-based saturable absorber (SA). A droplet of SWCNT solution is applied on the end of a fiber ferrule, which is then mated to another clean connector ferrule to construct an SA. Then the SA is integrated into a ring EDFL cavity for nanosecond pulse generation. The EDFL operates at around 1570.4 nm, with a soliton-like spectrum with small Kelly sidebands, which confirms the attainment of the anomalous dispersion. It produces a soliton pulse train with a 332 ns width, repetition rate of 909.1 kHz, an average output power of 0.31 mW, and energy of 0.34 nJ at the maximum pump power of 130.8 mW.

  7. ZnO nanowires array grown on Ga-doped ZnO single crystal for dye-sensitized solar cells.

    Science.gov (United States)

    Hu, Qichang; Li, Yafeng; Huang, Feng; Zhang, Zhaojun; Ding, Kai; Wei, Mingdeng; Lin, Zhang

    2015-06-23

    High quality ZnO nanowires arrays were homoepitaxial grown on Ga-doped ZnO single crystal (GZOSC), which have the advantages of high conductivity, high carrier mobility and high thermal stability. When it was employed as a photoanode in the DSSCs, the cell exhibited a 1.44% power-conversion efficiency under the illumination of one sun (AM 1.5G). The performance is superior to our ZnO nanowires/FTO based DSSCs under the same condition. This enhanced performance is mainly attributed to the perfect interface between the ZnO nanowires and the GZOSC substrate that contributes to lower carrier scattering and recombination rates compared with that grown on traditional FTO substrate.

  8. Spectroscopic and Neutron Detection Properties of Rare Earth and Titanium Doped LiAlO2 Single Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dickens, Peter T.; Marcial, Jose; McCloy, John S.; McDonald, Benjamin S.; Lynn, Kelvin G.

    2017-10-02

    In this study, LiAlO2 crystals doped with rare-earth elements and Ti were produced by the CZ method and spectroscopic and neutron detection properties were investigated. Photoluminescence revealed no clear luminescent activation of LiAlO2 by the rare-earth dopants though some interesting luminescence was observed from secondary phases within the crystal. Gamma-ray pulse height spectra collected using a 137Cs source exhibited only a Compton edge for the crystals. Neutron modeling using Monte Carlo N-Particle Transport Code revealed most neutrons used in the detection setup are thermalized, and while using natural lithium in the crystal growth, which contains 7.6 % 6Li, a 10 mm Ø by 10 mm sample of LiAlO2 has a 70.7 % intrinsic thermal neutron capture efficiency. Furthermore, the pulse height spectra collected using a 241Am-Be neutron source demonstrated a distinct neutron peak.

  9. Homogeneity and variation of donor doping in Verneuil-grown SrTiO3:Nb single crystals

    Science.gov (United States)

    Rodenbücher, C.; Luysberg, M.; Schwedt, A.; Havel, V.; Gunkel, F.; Mayer, J.; Waser, R.

    2016-08-01

    The homogeneity of Verneuil-grown SrTiO3:Nb crystals was investigated. Due to the fast crystal growth process, inhomogeneities in the donor dopant distribution and variation in the dislocation density are expected to occur. In fact, for some crystals optical studies show variations in the density of Ti3+ states on the microscale and a cluster-like surface conductivity was reported in tip-induced resistive switching studies. However, our investigations by TEM, EDX mapping, and 3D atom probe reveal that the Nb donors are distributed in a statistically random manner, indicating that there is clearly no inhomogeneity on the macro-, micro-, and nanoscale in high quality Verneuil-grown crystals. In consequence, the electronic transport in the bulk of donor-doped crystals is homogeneous and it is not significantly channelled by extended defects such as dislocations which justifies using this material, for example, as electronically conducting substrate for epitaxial oxide film growth.

  10. Tunable and switchable dual-wavelength single polarization narrow linewidth SLM erbium-doped fiber laser based on a PM-CMFBG filter.

    Science.gov (United States)

    Yin, Bin; Feng, Suchun; Liu, Zhibo; Bai, Yunlong; Jian, Shuisheng

    2014-09-22

    A tunable and switchable dual-wavelength single polarization narrow linewidth single-longitudinal-mode (SLM) erbium-doped fiber (EDF) ring laser based on polarization-maintaining chirped moiré fiber Bragg grating (PM-CMFBG) filter is proposed and demonstrated. For the first time as we know, the CMFBG inscribed on the PM fiber is applied for the wavelength-tunable and-switchable dual-wavelength laser. The PM-CMFBG filter with ultra-narrow transmission band (0.1 pm) and a uniform polarization-maintaining fiber Bragg grating (PM-FBG) are used to select the laser longitudinal mode. The stable single polarization SLM operation is guaranteed by the PM-CMFBG filter and polarization controller. A tuning range of about 0.25 nm with about 0.075 nm step is achieved by stretching the uniform PM-FBG. Meanwhile, the linewidth of the fiber laser for each wavelength is approximate 6.5 and 7.1 kHz with a 20 dB linewidth, which indicates the laser linewidth is approximate 325 Hz and 355 Hz FWHM.

  11. Effects of Ga-induced reconstructed surfaces and atomic steps on the morphology of GaSb islands on Si(1 0 0)

    Energy Technology Data Exchange (ETDEWEB)

    Machida, Ryuto, E-mail: 8113703@ed.tus.ac.jp [Department of Applied Electronics, Graduate School of Industrial Science and Technology, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585 (Japan); Toda, Ryusuke; Fujikawa, Sachie [Department of Applied Electronics, Graduate School of Industrial Science and Technology, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585 (Japan); Hara, Shinsuke; Watanabe, Issei [National Institute of Information and Communications Technology (NICT), 4-2-1 Nukui-Kitamachi, Koganei, Tokyo 184-8795 (Japan); Fujishiro, Hiroki I., E-mail: fujisiro@te.noda.tus.ac.jp [Department of Applied Electronics, Graduate School of Industrial Science and Technology, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585 (Japan)

    2015-10-01

    Highlights: • The shape and morphology of GaSb islands were studied under various conditions. • The atomic step type affected the shape and morphology of the GaSb islands. • The reconstructed surface type affects the density and size of the islands. - Abstract: The effects of the Ga-induced reconstructed surface and atomic step type on the shape and morphology of GaSb islands on a Si(1 0 0) surface were studied using ultrahigh-vacuum scanning tunneling microscopy and atomic force microscopy. Though both anisotropic elongated islands and isotropic islands were formed on clean Si and Ga/Si(1 0 0)-2 × 3 substrates, isotropic islands were dominantly formed on Ga/Si(1 0 0)-2 × 2 substrates at 300 °C. The density and size of GaSb islands on 2 × 2-Ga at 300 °C were estimated to be 4.9 × 10{sup 10} cm{sup −2} and 29.1 nm, respectively. The difference in the GaSb island shapes could be caused by the terrace and step of the substrate surface being changed by step rearrangement due to the deposition of Ga atoms at high temperatures. Above 350 °C, the density and size of islands decreased to 2.7 × 10{sup 9} cm{sup −2} and increased to 62.0 nm, respectively. In the initial growth stage, scanning tunneling microscopy results revealed that a Sb/Si(1 0 0)-2 × 1 reconstructed surface was formed above 350 °C. The large islands were assumed to aggregate from the surface diffusion of each atom because the Sb-terminated Si surface is inactive against Ga and Sb atoms. The type of the reconstructed surface is also suggested to affect the density and size of the islands.

  12. Magnetic and magnetostrictive behavior of Dy 3+ doped CoFe 2O 4 single crystals grown by flux method

    Science.gov (United States)

    Kambale, Rahul C.; Song, K. M.; Won, C. J.; Lee, K. D.; Hur, N.

    2012-02-01

    We studied the effect of Dy 3+ content on the magnetic properties of cobalt ferrite single crystal. The single crystals of CoFe 1.9Dy 0.1O 4 were grown by the flux method using Na 2B 4O 7.10 H 2O (Borax) as a solvent (flux). The black and shiny single crystals were obtained as a product. The X-ray diffraction analysis at room temperature confirmed the spinel cubic structure with lattice constant a=8.42 Å of the single crystals. The compositional analysis endorses the presence of constituents Co, Fe and Dy elements after sintering at 1300 °C within the final structure. The magnetic hysteresis measurements at various temperatures viz. 10 K, 100 K, 200 K and 300 K reveal the soft ferrimagnetic nature of the single crystal than that of for pure CoFe 2O 4. The observed saturation magnetization ( Ms) and coercivity ( Hc) are found to be lower than that of pure CoFe 2O 4 single crystal. The magnetostriction ( λ) measurement was carried out along the [001] direction. The magnetic measurements lead to conclude that the present single crystals can be used for magneto-optic recording media.

  13. Growth and annealing study of hydrogen-doped single diamond crystals under high pressure and high temperature

    Institute of Scientific and Technical Information of China (English)

    Li Yong; Jia Xiao-Peng; Hu Mei-Hua; Liu Xiao-Bing; Yan Bing-Min; Zhou Zhen-Xiang; Zhang Zhuang-Fei; Ma Hong-An

    2012-01-01

    A series of diamond crystals doped with hydrogen is successfully synthesized using LiH as the hydrogen source in a catalyst-carbon system at a pressure of 6.0 GPa and temperature ranging from 1255 ℃ to 1350 ℃.It is shown that the high temperature plays a key role in the incorporation of hydrogen atoms during diamond crystallization.Fourier transform infrared micro-spectroscopy reveals that most of the hydrogen atoms in the synthesized diamond are incorporated into the crystal structure as sp3-CH2-symmetric(2850 cm-1)and sp3 CH2-antisymmetric vibrations(2920 cm-1).The intensities of these peaks increase gradually with an increase in the content of the hydrogen source in the catalyst.The incorporation of hydrogen impurity leads to a significant shift towards higher frequencies of the Raman peak from 1332.06 cm-1 to 1333.05 cm-1 and gives rise to some compressive stress in the diamond crystal lattice.Furthermore,hydrogen to carbon bonds are evident in the annealed diamond,indicating that the bonds that remain throughout the annealing process and the vibration frequencies centred at 2850 and 2920 cm-1 have no observable shift.Therefore,we suggest that the spa C-H bond is rather stable in diamond crystals.

  14. Study of Blue Photoluminescence in Titanium Doped Al{sub 2}O{sub 3} Single-Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Daimon, T; Naruse, H; Watanabe, H; Oda, H; Yamanaka, A, E-mail: a-yamana@photon.chitose.ac.jp [Chitose Institute of Science and Technology, Bibi 758-65, Chitose, Hokkaido 066-8655 (Japan)

    2011-05-15

    Optical properties have been investigated in titanium doped sapphire, prepared under oxidized condition. Charge-transfer transitions to 3d states of tetravalent Ti{sup 4+} from 2p ones of O{sup 2-} are found to be located below the fundamental absorption edge of Al{sub 2}O{sub 3}. The photo-excitation for this band leads to the intense blue emission, the spectrum of which is quite different from the luminescence of the d-d transitions in trivalent Ti{sup 3+}. The UV-irradiation also leads to an absorption peak below the charge-transfer band, resulted from that the photo-excited electrons in part form color centers. The post-annealing at higher temperatures above 300 deg. C completely destroys the color centers. The blue photoluminescence is found to be greatly suppressed by the UV-irradiation and is recovered by the post-annealing. This fact indicates that the color centers prevent the blue emission.

  15. Estimation of low-temperature spectra behavior in Nd-doped Sc2SiO5 single crystal.

    Science.gov (United States)

    Zheng, Lihe; Xu, Jun; Su, Liangbi; Li, Hongjun; Wang, Qingguo; Ryba-Romanowski, Witold; Lisiecki, Radosław; Wu, Feng

    2009-11-15

    High optical quality Nd-doped Sc(2)SiO(5) crystal with size of diameter 27 mm x 60 mm was obtained by Czochralski method. An x-ray diffraction pattern of Nd:SSO crystal confirmed that the as-grown crystal was isostructual with the SSO crystal. Absorption and emission spectra were recorded at 10 K. The Judd-Ofelt theory was applied to obtain standard parameters Omega t(t=2,4,6) and the fitting result of experimental absorption line strengths, which provided the F3/24 radiative lifetime (tau(rad)) of 219 micros and the luminescence branching ratio beta of 0.57 for the (4)F(3/2)-(4)I(9/2) laser transition. The stimulated emission cross section of 1.04 x 10(-19) cm(2) at 1074 nm was calculated using the Füchtbauer-Ladenburg equation. The (4)F(3/2) luminescence lifetimes with 215 micros at 10 K and 198 micros at 300 K were determined from luminescence decay curves, indicating high quantum efficiency in the Nd:SSO crystal. All these results showed that Nd:SSO would be a promising gain media in solid-state lasers.

  16. Low temperature EPR investigation of Co2+ ion doped into rutile TiO2 single crystal: Experiments and simulations

    Science.gov (United States)

    Zerentürk, A.; Açıkgöz, M.; Kazan, S.; Yıldız, F.; Aktaş, B.

    2017-02-01

    In this paper, we present the results of X-band EPR spectra of Co2+ ion doped rutile (TiO2) which is one of the most promising memristor material. We obtained the angular variation of spectra in three mutually perpendicular planes at liquid helium (7-13 K) temperatures. Since the impurity ions have ½ effective spin and 7/2 nuclear spin, a relatively simple spin Hamiltonian containing only electronic Zeeman and hyperfine terms was utilized. Two different methods were used in theoretical analysis. Firstly, a linear regression analysis of spectra based on perturbation theory was studied. However, this approach is not sufficient for analyzing Co+2 spectra and leads to complex eigenvectors for G and A tensors due to large anisotropy of eigenvalues. Therefore, all spectra were analyzed again with exact diagonalization of spin Hamiltonian and the high accuracy eigenvalues and eigenvectors of G and A tensors were obtained by taking into account the effect of small sample misalignment from the exact crystallographic planes due to experimental conditions. Our results show that eigen-axes of g and A tensors are parallel to crystallographic directions. Hence, our EPR experiments proves that Co2+ ions substitute for Ti4+ ions in lattice. The obtained principal values of g tensor are gx=2.110(6), gy=5.890(2), gz=3.725(7) and principal values of hyperfine tensor are Ax=42.4, Ay=152.7, Az=26 (in 10-4/cm).

  17. The role of matching thickness on the wideband electromagnetic wave suppresser using single layer doped barium ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Shams Alam, Reza, E-mail: r.shamsalam@gmail.co [Department of Physics, University of Shiraz, Shiraz (Iran, Islamic Republic of); Kavosh Tehrani, Masoud [Department of Physics, Malek Ashtar University of Technology, Shahin Shar (Iran, Islamic Republic of); Moradi, Mahmood [Department of Physics, University of Shiraz, Shiraz (Iran, Islamic Republic of); Hosseinpour, Ehsaneh [Science and Research Branch of Islamic Azad University, Tehran (Iran, Islamic Republic of); Sharbati, Ali [Department of Physics, University of Semnan, Semnan (Iran, Islamic Republic of)

    2011-04-15

    The effect of Mg{sup 2+}, Co{sup 2+}and Ti{sup 4+} substitution on microwave absorption has been studied for BaMg{sub 0.5}Co{sub 0.5}Ti{sub 1.0}Fe{sub 10}O{sub 19} ferrite-acrylic resin composite in frequency range from 13 to 20 GHz. X-ray diffraction (XRD), scanning electron microscopy (SEM), vector network analysis and vibrating sample magnetometry (VSM) were employed to analyze structure, electromagnetic and microwave absorption properties of prepared ferrite. The obtained results of reflectivity demonstrate that by varying matching thickness along with weight percentage of ferrite to acrylic resin, the bandwidth coupled with reflection loss values of prepared composites can be easily tuned. Based on microwave measurement on reflectivity, it is found that BaMg{sub 0.5}Co{sub 0.5}Ti{sub 1.0}Fe{sub 10}O{sub 19} is a good candidate for wideband electromagnetic compatibility and other practical applications at high frequency. - Research highlights: > In our previous paper, the microwave attenuation properties of doped ferrites were evaluated. > Here we deal with the new substitution in barium ferrite which can easily tune the bandwidth of the reflection loss properties. > To the best of knowledge, this is a so simple composition which can offer practical applications in the field.

  18. Transverse UV-laser irradiation-induced defects and absorption in a single-mode erbium-doped optical fiber

    Energy Technology Data Exchange (ETDEWEB)

    Tortech, B.; Ouerdane, Y.; Boukenter, A.; Meunier, J. P. [Univ St Etienne, Lab Hubert Curien, CNRS, UMR 5516, F-42000 St Etienne (France); Girard, S. [CEA Bruyeres le Chatel, DIF, 91 (France); Van Uffelen, M.; Berghmans, F. [CEN SCK, B-2400 Mol (Belgium); Regnier, E. [Draka Comteq France, Data Ctr 4, F-91460 Marcoussis (France); Berghmans, F.; Thienpont, H. [Vrije Univ Brussels, B-1050 Brussels, (Belgium)

    2009-07-15

    Near UV-visible absorption coefficients of an erbium-doped optical fiber were investigated through an original technique based on a transverse cw UV-laser irradiation operating at 244 nm. Such irradiation leads to the generation of a quite intense guided luminescence signal in near UV spectral range. This photoluminescence probe source combined with a longitudinal translation of the fiber sample (at a constant velocity) along the UV-laser irradiation, presents several major advantages: (i) we bypass and avoid the procedures classically used to study the radiation induced attenuation which are not adapted to our case mainly because the samples present a very strong absorption with significant difficulties due to the injection of adequate UV-light levels in a small fiber diameter: (ii) the influence of the laser irradiation on the host matrix of the optical fiber is directly correlated to the evolution of the generated photoluminescence signal and (iii) in our experimental conditions, short fiber sample lengths (typically 20-30 cm) suffice to determine the associated absorption coefficients over the entire studied spectral domain. The generated photoluminescence signal is also used to characterize the absorption of the erbium ions in the same wavelength range with no cut-back method needed. (authors)

  19. Study on electrical conductivity and phase transition in singly doped BIPBVOX (Bi2V1-xPbxO5.5-x/2) solid electrolyte

    Science.gov (United States)

    Beg, Saba; Naqvi, Faria K.; Al-Areqi, Niyazi A. S.

    2014-12-01

    Samples of bismuth lead vanadium oxide (BIPBVOX) (Bi2V1-xPbxO5.5-x/2) singly substituted system in the composition range 0.05 ≤ x ≤ 0.20 were prepared by sol-gel synthesis route. Structural investigations were carried out by using a combination of differential thermal analysis (DTA) and powder X-ray diffraction (PXRD) technique. Energy dispersive X-ray spectroscopy analysis (EDXA) of doped samples was carried out to predict the sample purity and doping concentration. Transitions, α↔β, β↔γ and γ‧↔γ were detected by XRD, DTA and variation in the Arrhenius plots of conductivity. The ionic conductivity was measured by AC impedance spectroscopy. The solid solutions with composition x ≤ 0.07 undergo α↔β phase transition, at 329 °C and β↔γ phase transition at 419 °C. The highly conducting γ‧-phase was effectively stabilized at room temperature for compositions with x ≥ 0.17 whose thermal stability increases with Pb content. At 300 °C, the highest value of conductivity 6.234 × 10-5 S cm-1 was obtained for composition x = 0.15 and at 600 °C the highest value of conductivity 0.65 S cm-1 is observed for x = 0.17. AC impedance plots reveal that the conductivity is mainly due to the grain contribution to oxide ion conductivity.

  20. Identification of doped paramagnetic vanadyl impurity in dipotassium diaquabis(malonato-kappa O-2,O ') zincate dihydrate single crystal using EPR and optical techniques

    Science.gov (United States)

    Natarajan, B.; Mithira, S.; Deepa, S.; Ravikumar, Rvs. S. N.; Rao, P. S.

    2006-03-01

    Single crystal electron paramagnetic resonance (EPR) spectroscopic investigation of VO(II) doped dipotassium diaquabis(malonato-kappa O-2,O') zincate dihydrate has been carried out at X-band frequencies at 300 K. Single crystal, rotated along the three orthogonal crystallographic axes, has yielded spin Hamiltonian parameters g and A as g(xx) =1.978, g(yy) =1.972, g(zz) =1.936 and A(xx) =7.12, A(yy) =6.73, A(zz) =18.24 mT, respectively. These spin Hamiltonian parameters reflect a slight deviation from axial symmetry to rhombic, which is explained by the interstitial occupation of vanadyl ions. The isofrequency plots and powder EPR spectrum have been simulated using the calculated spin Hamiltonian parameters. The percentage of metal-oxygen bond has been estimated to be 20%. The admixture coefficients and bonding parameters have also been calculated by combining the EPR data with optical data.

  1. Dielectric and conductivity behavior of Mn-doped K0.5Na0.5NbO3 single crystal

    Science.gov (United States)

    Yan, Tianxiang; Sun, Xiaojun; Deng, Jianming; Liu, Saisai; Han, Feifei; Liu, Xiaoqi; Fang, Liang; Lin, Dabing; Peng, Biaolin; Liu, Laijun

    2017-09-01

    Dielectric and conduction behaviors of [001]-oriented K0.5Na0.5Nb0.5O3 single crystal (KNN) and 0.5 at% Mn-doped KNN single crystal (KNN-Mn) have been investigated in a broad temperature range. At low temperatures (330-400 K), an observed slight decrease of conductivity could be connected with the decreases of hole carrier concentration and mobility for the KNN-Mn. At high temperatures (723-773 K) above Cure temperature, the dielectric relaxation and conduction behavior of the samples were analyzed by measurements of impedance spectroscopy and universal dielectric response law. The activation energy values for relaxation frequency and conduction were 0.97 eV and 0.60 eV for the KNN-Mn, respectively. They could be attributed to the thermal motion of double ionized oxygen vacancies and the formation of defect dipoles. The defect compensation mechanism was proposed based on Mn4+ ion substitution. The KNN-Mn promoted a higher concentration of oxygen vacancies compared with KNN crystal, which gave rise to smaller domain size and higher piezoelectric properties.

  2. LASERS: Ultrashort-pulse erbium-doped fibre laser using a saturable absorber based on single-wall carbon nanotubes synthesised by the arc-discharge method

    Science.gov (United States)

    Tausenev, A. V.; Obraztsova, E. D.; Lobach, A. S.; Konov, V. I.; Konyashchenko, A. V.; Kryukov, P. G.; Dianov, E. M.

    2007-09-01

    An erbium-doped fibre laser operating in self-mode-locked regime achieved with the help of a saturable absorber based on single-wall carbon nanotubes synthesised by the arc-discharge method is fabricated and studied. Due to the development of an original method for preparing samples, films of the optical quality containing individual single-wall carbon nanotubes were synthesised. The study of the dependence of resonance absorption at a wavelength of 1.5 μm on the laser radiation intensity transmitted through a film showed that these films have nonlinear transmission and can be used in fibre lasers as saturable absorbers to provide self-mode locking. Stable transform-limited pulses having the shape of optical solitons were generated at a wavelength of 1557.5 nm in the laser with a ring resonator. The pulse duration was 1.13 ps at a pulse repetition rate of 20.5 MHz. The continuous output power achieved 1.1 mW upon pumping by a 25-mW laser diode at 980 nm.

  3. A switchable and stable single-longitudinal-mode, dual-wavelength erbium-doped fiber laser assisted by Rayleigh backscattering in tapered fiber

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Jian; Yang, Yanfu, E-mail: yangyanfu@hotmail.com; Zhang, Jianyu; Wang, Xiaorui; Yuan, Yijun; Yao, Yong [College of Electronic and Information Engineering, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen, Guangdong Province 518055 (China); Liu, Meng [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798 Singapore (Singapore)

    2015-09-14

    We have proposed and demonstrated a novel switchable single-longitudinal-mode (SLM), dual-wavelength erbium-doped fiber laser (DWEDFL) assisted by Rayleigh backscattering (RBS) in a tapered fiber in a ring laser configuration. The RBS feedback in a tapered fiber is a key mechanism as linewidth narrowing for laser output. A compound laser cavity ensured that the EDFL operated in the SLM state and a saturable absorber (SA) is employed to form a gain grating for both filtering and improving wavelength stability. The fiber laser can output dual wavelengths simultaneously or operate at single wavelength in a switchable manner. Experiment results show that with the proper SA, the peak power drift was improved from 1–2 dB to 0.31 dB and the optical signal to noise ratio was higher than 60 dB. Under the assistance of RBS feedback, the laser linewidths are compressed by around three times and the Lorentzian 3 dB linewidths of 445 Hz and 425 Hz are obtained at 1550 nm and 1554 nm, respectively.

  4. Minimizing Unintentional Strain and Doping of Single-Layer Graphene on SiO2 in Aqueous Environments by Acid Treatments.

    Science.gov (United States)

    Masuda, Katsuya; Sano, Masahito

    2015-05-05

    The effects of treating SiO2/Si with either acidic or alkaline solutions on single-layer graphene were investigated using Raman microscopy. It is well-known that in air graphene on SiO2 is unintentionally strained and hole-doped to different degrees, varying widely by sample. It is also known that various amine compounds act as electron donors to graphitic materials. In this study, a SiO2/Si substrate was simply dipped in either a concentrated HCl solution or pH 9.0 NaOH solution and then rinsed, prior to transferring graphene on it. The G and 2D peaks were followed at a fixed position on a single-layer graphene flake in water and various concentrations of pH 7.4 tris(hydroxymethyl)aminomethane (Tris) buffer. The results demonstrate that these treatments reduce the sample variation, improve the stability against Tris, and even bring some graphene samples close to a freestanding state. The Raman analysis reveals that the main effect of dipping is to relieve strain. The undoping effect on some samples is explained by the HCl solution becoming trapped between the graphene and SiO2 surface.

  5. EPR and optical absorption study of Mn{sup 2+}-doped zinc ammonium phosphate hexahydrate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kripal, Ram [Department of Physics, University of Allahabad, Allahabad 211002 (India)]. E-mail: ram_kripal2001@rediffmail.com; Govind, Har [Department of Electronics, Ewing Christian College, Allahabad 211003 (India)]. E-mail: chaurasia_har@yahoo.co.in; Gupta, S.K. [EPR and IR Spectroscopy Section, Material Characterization Division, National Physical Laboratory, New Delhi 110012 (India); Arora, Manju [EPR and IR Spectroscopy Section, Material Characterization Division, National Physical Laboratory, New Delhi 110012 (India)

    2007-04-15

    EPR study of Mn{sup 2+}-doped zinc ammonium phosphate hexahydrate (ZAPH) is done at room temperature. The Mn{sup 2+} spin Hamiltonian parameters are evaluated employing a large number of resonant line positions observed for different orientations of the external magnetic field. The evaluated value of g-factor is 1.9527+/-0.0002 and the values of other parameters D, E, a, A and B (in 10{sup -4}cm{sup -1}) are, 175+/-2, 58+/-2, 10+/-1, 92+/-2 and 86+/-2, respectively. The optical absorption study of the crystal is also done. The observed bands are assigned as transitions from the {sup 6}A{sub 1g}(S) ground state to various excited quartet levels of Mn{sup 2+} ion in a cubic crystal field. These bands are fitted with four parameters: inter-electronic repulsion parameters (B and C), cubic crystal field splitting parameter (Dq), and Tree's correction ({alpha}). The values obtained for the parameters are B=917, C=2254, Dq=756 and {alpha}=76cm{sup -1}. From the data obtained the surrounding crystal field and the nature of metal-ligand bonding are discussed. The considerable decrease in the values of B and C from their free ion values indicates the existence of a fair amount of covalent bonding between the central metal ion and the ligand. On the basis of the deviations {delta}g=g-2.0023, the transfer of electrons to or from the central metal ion for bond formation is ascertained.

  6. Dispersion relations in heavily-doped nanostructures

    CERN Document Server

    Ghatak, Kamakhya Prasad

    2016-01-01

    This book presents the dispersion relation in heavily doped nano-structures. The materials considered are III-V, II-VI, IV-VI, GaP, Ge, Platinum Antimonide, stressed, GaSb, Te, II-V, HgTe/CdTe superlattices and Bismuth Telluride semiconductors. The dispersion relation is discussed under magnetic quantization and on the basis of carrier energy spectra. The influences of magnetic field, magneto inversion, and magneto nipi structures on nano-structures is analyzed. The band structure of optoelectronic materials changes with photo-excitation in a fundamental way according to newly formulated electron dispersion laws. They control the quantum effect in optoelectronic devices in the presence of light. The measurement of band gaps in optoelectronic materials in the presence of external photo-excitation is displayed. The influences of magnetic quantization, crossed electric and quantizing fields, intense electric fields on the on the dispersion relation in heavily doped semiconductors and super-lattices are also disc...

  7. Comparison of high power large mode area and single mode 1908nm Tm-doped fiber lasers

    Science.gov (United States)

    Johnson, Benjamin R.; Creeden, Daniel; Limongelli, Julia; Pretorius, Herman; Blanchard, Jon; Setzler, Scott D.

    2016-03-01

    We compare large mode area (LMA) and single-mode (SM) double-clad fiber geometries for use in high power 1908nm fiber lasers. With a simple end-pumped architecture, we have generated 100W of 1908nm power with LMA fiber at 40% optical efficiency and 117W at 52.2% optical efficiency with single-mode fiber. We show the LMA fiber is capable of generating >200W and the SM fiber is capable of >300W at 1908nm. In all cases, the fiber lasers are monolithic power-oscillators with no free-space coupling.

  8. Doping effect of L-cystine on structural, UV-visible, SHG efficiency, third order nonlinear optical, laser damage threshold and surface properties of cadmium thiourea acetate single crystal

    Science.gov (United States)

    Azhar, S. M.; Anis, Mohd; Hussaini, S. S.; Kalainathan, S.; Shirsat, M. D.; Rabbani, G.

    2017-01-01

    The present article is focused to investigate the influence of L-cystine (LC) on linear-non-linear optical and laser damage threshold of cadmium thiourea acetate (CTA) crystal. The structural parameters of pure and LC doped CTA crystals have been determined using the single crystal X-ray diffraction technique. The functional groups of grown crystals have been identified by means of fourier transform infrared (FT-IR) analysis. The UV-visible spectral analysis has been done in the range of 200-900 nm to ascertain the uplifting influence of LC on optical properties of CTA crystal. The second harmonic generation (SHG) efficiency of LC doped CTA crystal is found to be higher than CTA and KDP crystal. The Z-scan technique has been employed to determine the third order nonlinear optical (TONLO) nature of LC doped CTA crystal at 632.8 nm. The self focusing tendency confirmed the strong kerr lensing ability of LC doped CTA crystal. The TONLO susceptibility (χ3), refraction (n2) and absorption coefficient (β) has been calculated using the Z-scan data. The laser damage threshold of pure and LC doped CTA crystals has been measured using the Q-switched Nd:YAG laser and its is found to be in range of GW/cm2. The surface analysis has been done by means of etching studies.

  9. Short-wave infrared barriode detectors using InGaAsSb absorption material lattice matched to GaSb

    Energy Technology Data Exchange (ETDEWEB)

    Craig, A. P.; Percy, B.; Marshall, A. R. J. [Physics Department, Lancaster University, Lancaster LA1 4YB (United Kingdom); Jain, M. [Amethyst Research Ltd., Kelvin Campus, West of Scotland Science Park, Glasgow G20 0SP (United Kingdom); Wicks, G.; Hossain, K. [Amethyst Research, Inc., 123 Case Circle, Ardmore, Oklahoma 73401 (United States); Golding, T. [Amethyst Research Ltd., Kelvin Campus, West of Scotland Science Park, Glasgow G20 0SP (United Kingdom); Amethyst Research, Inc., 123 Case Circle, Ardmore, Oklahoma 73401 (United States); McEwan, K.; Howle, C. [Defence Science and Technology Laboratory, Porton Down, Salisbury, Wiltshire SP4 0JQ (United Kingdom)

    2015-05-18

    Short-wave infrared barriode detectors were grown by molecular beam epitaxy. An absorption layer composition of In{sub 0.28}Ga{sub 0.72}As{sub 0.25}Sb{sub 0.75} allowed for lattice matching to GaSb and cut-off wavelengths of 2.9 μm at 250 K and 3.0 μm at room temperature. Arrhenius plots of the dark current density showed diffusion limited dark currents approaching those expected for optimized HgCdTe-based detectors. Specific detectivity figures of around 7×10{sup 10} Jones and 1×10{sup 10} Jones were calculated, for 240 K and room temperature, respectively. Significantly, these devices could support focal plane arrays working at higher operating temperatures.

  10. Surface Characterisation and Cathodoluminescent Response of Nanodot-Patterned GaSb Surfaces by Low Energy Ion Sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Plaza, J L [Laboratorio de Crecimiento de Cristales, Departamento de Fisica de Materiales, Facultad de Ciencias, Universidad Autonoma de Madrid, 28049, Cantoblanco, Madrid (Spain); Hidalgo, P [Departamento de Fisica de Materiales, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, 28045, Madrid (Spain); Dieguez, E [Laboratorio de Crecimiento de Cristales, Departamento de Fisica de Materiales, Facultad de Ciencias, Universidad Autonoma de Madrid, 28049, Cantoblanco, Madrid (Spain)

    2007-04-15

    The scope of this paper is to analyse the effect of Au and Cr impurities, diffused onto GaSb substrates on the formation of nanodots created by LEIS using Ar+ ions It is concluded that oblique incidence in rotating configuration delays the formation of the nanodots compared to previously reported normal incidence experiments. The presence of cracks induced by the sputtering process has been observed both in the Au and Cr diffused samples. Cathodoluminescence (CL) spectra obtained in irradiated samples both pure and Crdiffused have revealed no difference between them, showing the usual three band encountered in this material (Band Gap at 798 meV, A Band at 777 meV and tail-states at 815 meV). However, a fourth band has been detected in the Au sample centered at 769 meV.

  11. Structural differences between capped GaSb nanostructures grown by Stranski-Krastanov and droplet epitaxy growth modes

    Science.gov (United States)

    DeJarld, Matt; Yan, Lifan; Luengo-Kovac, Marta; Sih, Vanessa; Millunchick, Joanna

    2017-01-01

    Droplet epitaxy (DE) has emerged as an alternative to Stranski-Krastanov (SK) as a method for epitaxial nanostructure formation. We find significant structural differences of similar sized nanostructures embedded in GaAs between the two methods. Atomic force microscopy and atom probe tomography measurements reveal that uncapped and capped SK structures resemble each other. However, the DE nanostructures appear as rings topographically but are quantum dots compositionally. A GaSb wetting layer is present regardless of the growth method and shares a nearly identical Sb concentration profile. DE nanostructures are shown to have a lower Sb concentration, and transmission electron microscopy measurements reveal that they produce less strain on the capping layer. Despite significant structural differences, SK and DE nanostructures exhibit the same photoluminescence response, suggesting that the emission is from a shared feature such as the wetting layer, rather than the nanostructures.

  12. Confining H{sub 2} by adsorption in microporous carbons (single-wall carbon nano-tubes and activated carbons) doped by K or Li; Confinement de l'hydrogene et du deuterium par adsorption dans des carbones microporeux (nanotubes monoparois et carbones actives) dopes par des metaux alcalins

    Energy Technology Data Exchange (ETDEWEB)

    Los, S.; Azais, Ph.; Duclaux, L.; Breton, Y. [Orleans Univ. et CNRS, Centre de Recherches sur la Matiere Divisees, 45 (France); Pellenq, R. [Centre de Recherches en Matiere Condensee et Nanosciences, CNRS, 13 - Marseille (France); Isnard, O. [Centre National de la Recherche Scientifique (CNRS), Lab. Cristallographie, 38 - Grenoble (France)

    2005-08-01

    Doping of microporous carbon by Li or K leads to an increase in the energy of adsorption of H{sub 2} or D{sub 2} molecules. Thus, the room temperature sorption capacities (at P<3 MPa) can be higher than that of the raw materials after slight doping. However, the maximum H{sub 2} (or D{sub 2}) storage measured at T< 77 K is lower than the one of pristine materials as the sites of adsorption are occupied by alkali ions inserted in the micropores. The microporous adsorption sites of doped single-walled carbon nano-tubes, identified by neutron diffraction, are both the interstitial voids (in electric-arc or HiPCO tubes) in between the tubes and the central canals of the tubes (only in HiPCO tubes). (authors)

  13. Synthesis of alpha-aluminum oxide and hafnium-doped beta-nickel aluminide coatings on single crystal nickel-based superalloy by chemical vapor deposition

    Science.gov (United States)

    He, Limin

    Thermal barrier coatings (TBCs) are widely used for air-cooled turbine components in advanced aircraft engines and power generation systems. The dominant failure mode observed in TBCs is progressive fracture of the metal-oxide interface upon oxidation and thermal cycling. Two potential coating methods for improving TBC performance were studied: (1) preparing a high-quality alpha-Al 2O3 coating layer on the surface of a single crystal Ni-based superalloy (Rene N5) to extend the oxidative stability of the interface and (2) doping beta-NiAl bond coating with a small amount of Hf to improve the adhesion of thermally grown oxide (TGO) at the interface. In the first coating method, a novel chemical vapor deposition (CVD) procedure was developed using AlCl3, CO2 and H 2 as precursors. A critical part of this procedure was a short-time pre-oxidation step (1 min) with CO2 and H2 in the CVD chamber, prior to introducing the AlCl3, vapor. Without this pre-oxidation step, extensive whisker formation was observed on the alloy surface. Characterization results showed that the pre-oxidation step resulted in the formation of a continuous oxide layer (˜50 nm) on the alloy surface. The outer part of this layer (˜20 nm) appeared to contain mixed oxides whereas the inner part (˜30 nm) consisted of alpha-Al2O3 as a dominant major phase and theta-Al2O3 as a minor phase. It appeared that the preferential nucleation of beta-Al2O3 in the pre-oxidized layer was promoted by: (1) rapid heating (˜10 sec) of the alloy surface to the temperature region, where alpha-Al 2O3 was expected to nucleate instead of metastable Al 2O3 phases, (2) the low oxygen pressure environment of the pre-oxidation step which kept the rate of oxidation low, and (3) contamination of the CVD chamber with HfCl4. It appeared that the role of HfCl 4 was to enhance the preferential nucleation of alpha-Al2O 3 in the pre-oxidized layer. In our second coating method, we utilized the dynamic versatility of CVD as an avenue

  14. Neutron transmutation doped Ge bolometers

    Science.gov (United States)

    Haller, E. E.; Kreysa, E.; Palaio, N. P.; Richards, P. L.; Rodder, M.

    1983-01-01

    Some conclusions reached are as follow. Neutron Transmutation Doping (NTD) of high quality Ge single crystals provides perfect control of doping concentration and uniformity. The resistivity can be tailored to any given bolometer operating temperature down to 0.1 K and probably lower. The excellent uniformity is advantaged for detector array development.

  15. Pulsed and CW adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser system for surgical laser soft tissue ablation applications.

    Science.gov (United States)

    Huang, Yize; Jivraj, Jamil; Zhou, Jiaqi; Ramjist, Joel; Wong, Ronnie; Gu, Xijia; Yang, Victor X D

    2016-07-25

    A surgical laser soft tissue ablation system based on an adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser operating in pulsed or CW mode with nitrogen assistance is demonstrated. Ex vivo ablation on soft tissue targets such as muscle (chicken breast) and spinal cord (porcine) with intact dura are performed at different ablation conditions to examine the relationship between the system parameters and ablation outcomes. The maximum laser average power is 14.4 W, and its maximum peak power is 133.1 W with 21.3 μJ pulse energy. The maximum CW power density is 2.33 × 106 W/cm2 and the maximum pulsed peak power density is 2.16 × 107 W/cm2. The system parameters examined include the average laser power in CW or pulsed operation mode, gain-switching frequency, total ablation exposure time, and the input gas flow rate. The ablation effects were measured by microscopy and optical coherence tomography (OCT) to evaluate the ablation depth, superficial heat-affected zone diameter (HAZD) and charring diameter (CD). Our results conclude that the system parameters can be tailored to meet different clinical requirements such as ablation for soft tissue cutting or thermal coagulation for future applications of hemostasis.

  16. Fe2+-doped CdSe single crystal: growth, spectroscopic and laser properties, potential use as a 6 µm broadband amplifier

    Science.gov (United States)

    Frolov, M. P.; Gordienko, V. M.; Korostelin, Yu V.; Kozlovsky, V. I.; Podmar'kov, Yu P.; Potemkin, F. V.; Skasyrsky, Ya K.

    2017-02-01

    We report on the successful growth of single crystals of Fe2+:CdSe by seeded physical vapor transport (SPVT) technique with doping within the growing process and subsequent annealing in Se vapor. Luminescence lifetime measurements, spectroscopic studies of 5E-5T2 transition of Fe2+ in CdSe, and laser experiments were performed. The lifetime of the 5T2 energy level was measured to be 20  ±  5 ns at a room temperature (RT) of 290 K. At liquid nitrogen (LN) temperature, luminescence kinetics displayed a non-exponential decay, which can be fitted to a bi-exponential function with time constants τ 1  =  6 µs and τ 2  =  29 µs. As much as 3.2 mJ of output energy at 5.2 µm with 27% absorbed pump energy slope efficiency of an Fe2+:CdSe laser was achieved at RT under 2.94 µm nanosecond Er:YAG laser pumping. The Fe2+:CdSe laser was tuned from 4.63 to 6.10 µm. Obtained characteristics of Fe2+:CdSe indicate that the crystal can be considered a promising medium for amplification of femtosecond pulses in the middle infrared range up to 6 µm.

  17. Conductance Modulation across the Metal-Insulator Transition in Single Nanowire Devices of doped-VO2 Gated with Ionic Liquid

    Science.gov (United States)

    Stabile, Adam; Whittaker, Luisa; Banerjee, Sarbajit; Sambandamurthy, G.

    2013-03-01

    Studies of the effects of charge modulation in VO2 systems may provide useful insights into the microscopic mechanisms behind its metal-insulator transition (MIT). Recently, ionic liquid (IL) has become a popular material for gating nanodevices due to its superior charge accumulation capabilities. Thus, using IL to gate single nanowires of W-doped-VO2, we systematically study the modulation of electrical transport across the temperature-driven and voltage-driven MIT as a function of gate voltage. We report the manifestation of hysteresis loops, which show an unprecedented modulation of resistance and current by as large as 20%. Moreover, we show that the largest modulation loop coincides with the largest changes in resistance across the temperature-driven MIT suggesting that the memory behavior in VO2 and its MIT are closely linked. Similar behavior is also observed across the voltage-driven MIT. These studies lay the ground work for an alternative approach to understanding the mechanisms behind the MIT in VO2 systems when driven by different external parameters.

  18. Measurement of the topological surface state optical conductance in bulk-insulating Sn-doped Bi1.1Sb0.9Te2S single crystals

    Science.gov (United States)

    Cheng, Bing; Wu, Liang; Kushwaha, S. K.; Cava, R. J.; Armitage, N. P.

    2016-11-01

    Topological surface states have been extensively observed via optics in thin films of topological insulators. However, in typical thick single crystals of these materials, bulk states are dominant and it is difficult for optics to verify the existence of topological surface states definitively. In this Rapid Communication, we study the charge dynamics of the newly formulated bulk-insulating Sn-doped Bi1.1Sb0.9Te2S crystal by using time-domain terahertz spectroscopy. This compound shows much better insulating behavior than any other bulk-insulating topological insulators reported previously. The transmission can be enhanced an amount which is 5 % of the zero-field transmission by applying magnetic field to 7 T, an effect which we believe is due to the suppression of topological surface states. This suppression is essentially independent of the thicknesses of the samples, showing the two-dimensional nature of the transport. The suppression of surface states in field allows us to use the crystal slab itself as a reference sample to extract the surface conductance, mobility, charge density, and scattering rate. Our measurements set the stage for the investigation of phenomena out of the semiclassical regime, such as the topological magnetoelectric effect.

  19. Self-mode-locking in erbium-doped fibre lasers with saturable polymer film absorbers containing single-wall carbon nanotubes synthesised by the arc discharge method

    Science.gov (United States)

    Tausenev, Anton V.; Obraztsova, Elena D.; Lobach, A. S.; Chernov, A. I.; Konov, Vitalii I.; Konyashchenko, Aleksandr V.; Kryukov, P. G.; Dianov, Evgenii M.

    2007-03-01

    We studied the ring and linear schemes of erbium-doped fibre lasers in which passive mode locking was achieved with the help of saturable absorbers made of high-optical quality films based on cellulose derivatives with dispersed single-wall carbon nanotubes. The films were prepared by the original method with the use of nanotubes synthesised by the arc discharge method. The films exhibit nonlinear absorption at a wavelength of 1.5 μm. Pulses in the form of optical solitons of duration 1.17 ps at a avelength of 1.56 μm were generated in the ring scheme of the erbium laser. The average output power was 1.1 mW at a pulse repetition rate of 20.5 MHz upon pumping by the 980-nm, 25-mW radiation from a laser diode. The pulse duration in the linear scheme was reduced to 466 fs for the output power up to 4 mW and a pulse repetition rate of 28.5 MHz. The specific feature of these lasers is a low pump threshold in the regime of generation of ultrashort pulses.

  20. A comparative study of field emission from NanoBuds, nanographite and pure or N-doped single-wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Kleshch, V.I. [Department of Physics, M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); A.M. Prokhorov General Physics Institute, RAS, 119991 Moscow (Russian Federation); Susi, T.; Nasibulin, A.G.; Kauppinen, E.I. [NanoMaterials Group, Department of Applied Physics, Aalto University, P.O. Box 15100, 00076 Aalto, Espoo (Finland); Obraztsova, E.D. [A.M. Prokhorov General Physics Institute, RAS, 119991 Moscow (Russian Federation); Obraztsov, A.N. [Department of Physics, M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Department of Physics and Mathematics, University of Eastern Finland, 80101 Joensuu (Finland)

    2010-12-15

    Field emission characteristics of multi-emitter flat cathodes prepared from NanoBuds, few-layer graphite flakes (nanographite, NG) and pure or N-doped single-wall carbon nanotubes (SWNTs) have been examined. The cathodes demonstrated a low-voltage electron emission with the threshold field values of few Volts per micron, which were ascribed to the high-aspect ratio of nanocarbons. The films of NanoBuds and NG possess excellent emission pattern homogeneity with an emission site density of more than 10{sup 5} cm{sup -2}. This is much higher than for cathodes made of conventional SWNT films. It was found that the achievable maximal current density depends on the type of carbon material and reaches 10 A/cm{sup 2} for NanoBuds film, while for the NG film cathodes, it is about one order of magnitude less. Possible mechanisms responsible for the experimentally observed differences are discussed. The materials examined are of great interest due to their high-emission characteristics and are promising for the development of new types of vacuum electronic devices. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Utilizing dual-pass composite-ring architecture for a stabilized and wavelength-selectable single-longitudinal-mode erbium-doped fiber laser

    Science.gov (United States)

    Yeh, Chien-Hung; Zhuang, Yuan-Hong; Tsai, Ning; Chen, Jing-Heng; Chow, Chi-Wai

    2016-10-01

    In this paper, we propose using a dual-pass composite-ring construction for a stable and wavelength-tunable erbium-doped fiber (EDF) laser with a single-longitudinal-mode (SLM) output. According to the proposed laser architecture, a flattened output power spectrum within a 0.57 dB power variation can be obtained in the tuning range of 1530 to 1560 nm. In addition, the measured optical signal-to-noise ratio (OSNR) of each output wavelength can be larger than 62.1 dB. Furthermore, a stable and tunable dual-wavelength output of the proposed EDF laser scheme can also be achieved in the same operation range by using two optical filters inside a ring cavity. Here, the maximum and minimum mode spacing of dual-wavelength lasing in the proposed EDF laser are 28.01 and 1.04 nm, respectively. In this measurement, the SLM performance and output stability of the proposed EDF laser are analyzed and discussed experimentally.

  2. Optical and magnetic spectroscopy of rare-earth-doped yttrium aluminium borate (YAl3(BO3)4) single crystals

    Science.gov (United States)

    Watterich, A.; Aleshkevych, P.; Borowiec, M. T.; Zayarnyuk, T.; Szymczak, H.; Beregi, E.; Kovács, L.

    2003-05-01

    For Ce3+, Er3+ and Yb3+ ions, electron paramagnetic resonance (EPR) spectra typical for S' = 1/2 ions are measured for YAl3(BO3)4 (YAB) single crystal. The spectra show axial symmetry indicating that all three dopants replace Y3+ at the given dopant concentration. Corresponding tilde g- and hyperfine tilde A-tensors are determined. The EPR linewidth of Ce broadens with increasing temperature due to an Orbach relaxation process. Fitting the curve with an exponential, the energy difference is found to be equal to 270 +/- 16 cm-1. The optical absorption and excitation spectra of Ce in YAB single crystal measured at 300 K are similar to those found for polycrystalline materials. High-resolution polarized emission from the lowest excited to the 2 F 5/2 ground state, measured at 4.2 K, indicates a splitting of the ground state into three levels. The second level is located 277 +/- 18 cm-1 above the first one, in excellent agreement with the EPR result, and the third level is located 140 +/- 10 cm-1 above the second one.

  3. Heisenberg like critical properties, magnetocaloric effect and scaling in lead doped NdMnO{sub 3} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Nilotpal [School of Advanced Sciences, VIT University, Vellore-632014, Tamilnadu (India)

    2013-07-01

    Magnetic isotherms for single crystals of Nd{sub 0.7}Pb{sub 0.3}MnO{sub 3} have been measured around the ferromagnetic(FM) to paramagnetic(PM) transition temperature T{sub C}. Critical exponents have been obtained by modified Arrott plots and the Kouvel Fisher method. The values of exponents are consistent with those expected for 3D Heisenberg universality class. Magnetocaloric effect (MCE) has been also studied from the magnetic isotherms. Relative cooling power (RCP) is estimated as 56.725, 66.252 and 77.163 J/Kg for 1.2, 2.2 and 4.8 T fields respectively. Universal scaling behaviour in the relative change of magnetic entropy ΔS{sub M} has been observed. The rescaled magnetic entropy change curves for different applied fields are noticed to collapse onto a single curve. It has been found that the peak entropy change, ΔS{sub M} peak at T{sub C} and RCP follow a scaling power law in magnetic field H with the exponents which are reduced in comparison to their theoretically estimated value.

  4. Research Update: Stable single-phase Zn-rich Cu2ZnSnSe4 through In doping

    Science.gov (United States)

    Hartnauer, Stefan; Körbel, Sabine; Marques, Miguel A. L.; Botti, Silvana; Pistor, Paul; Scheer, Roland

    2016-07-01

    Alloying in the system Cu2ZnSnSe4-CuInSe2-ZnSe (CZTISe) is investigated experimentally and theoretically. The goal is to distinguish single-phase and multi-phase regions within the Cu2ZnSnSe4-2CuInSe2-4ZnSe pseudo-ternary phase diagram. CZTISe thin films are prepared by co-evaporation of the chemical elements and are investigated in real-time during growth using in situ angle dispersive X-ray diffraction. The focus is mainly on thin films along the Cu2ZnSnSe4-2CuInSe2 isopleth with small ZnSe addition as well as on films along the Cu2ZnSnSe4-4ZnSe isopleth with small CuInSe2 addition. For both cases, ab initio calculations with density-functional theory are performed to estimate the stability of the alloy with respect to the formation of secondary phases. Both in experiment and calculation, we find a surprisingly large single-phase region in the Cu2ZnSnSe4 corner of the pseudo-ternary phase diagram slightly off the Cu2ZnSnSe4-4ZnSe isopleth. This may help avoiding secondary phase formation under Zn-rich conditions and open up new possibilities for the application of CZTISe thin films in solar cells.

  5. Growth and scintillation characterization of Ce{sup 3+}-doped Rb{sub 2}LiGdBr{sub 6} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Rooh, Gul [Department of Physics, Abdul Wali Khan University, Mardan 23200 (Pakistan); Kim, H.J., E-mail: hongjoo@knu.ac.kr [Department of Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Sunghwan [Department of Radiological Science, Cheongju University, Cheongju 360-764 (Korea, Republic of); Khan, Sajid [Department of Physics, Kohat University of Science & Technology, 26000 (Pakistan)

    2016-10-01

    Growth and scintillation characterizations of the newly developed cerium doped Rb{sub 2}LiGdBr{sub 6} (RLGB) single crystals were investigated. RLGB, which belongs to bromo-elpasolite crystal family, was grown by the vertical Bridgman technique with nominally 1%, 5%, and 10% Ce{sup 3+}-concentration (mole%). X-ray excited luminescence spectra show typical Ce{sup 3+} bands between 350 to 460 nm wavelength regions. A good energy resolution of 5.5% (FWHM) and light yield of 25,500±2600 ph/MeV for 662 keV γ-rays were observed at 5% Ce{sup 3+}-concentration. Under γ-ray excitation, RLGB:Ce{sup 3+} crystals display multi-exponential decays with Ce{sup 3+} like decay components at 23 ns and 29 ns for 1% and 5% Ce-concentrations, respectively. From the results, it is expected that this scintillator could be used as a thermal neutron detector because of Li and Gd ions in the host lattice. Also, like other inorganic halide scintillators, it is very hygroscopic. - Highlights: • Scintillation properties of new Rb{sub 2}LiGdBr{sub 6}:Ce{sup 3+} were presented. • Single crystals of Rb{sub 2}LiGdBr{sub 6} were grown by two zone vertical Bridgman technique. • The grown material was highly hygroscopic and belongs to elpasolite crystal family. • Good energy resolution of 5.5% (FWHM) and light yield of 25,500±2600 ph/MeV were obtained under γ-ray excitation. • This material displayed multiexponential decays with Ce{sup 3+} like decay components.

  6. Spectroscopic features of erbium-doped CaM{sub 2}O{sub 6} (M=Nb, Ta) single crystal fibers grown by the laser-heated pedestal growth technique

    Energy Technology Data Exchange (ETDEWEB)

    Camargo, A.S.S. de [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo (USP), C.P. 369, CEP 13560-970, Sao Carlos, SP (Brazil)], E-mail: andreasc@if.sc.usp.br; Ferrari, C.R.; Silva, R.A.; Nunes, L.A.O.; Hernandes, A.C.; Andreeta, J.P. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo (USP), C.P. 369, CEP 13560-970, Sao Carlos, SP (Brazil)

    2008-02-15

    Erbium-doped single crystal fibers, with low phonon energy and fairly high absorption and emission cross sections are interesting laser active media, for compact, near-infrared and/or upconversion lasers. In this work, high optical quality Er{sup 3+}-doped CaNb{sub 2}O{sub 6} and CaTa{sub 2}O{sub 6} single crystal fibers were successfully grown by the versatile laser-heated pedestal growth technique, and characterized from the structural and spectroscopic points of view. The results indicate that these crystal fiber compositions, which had not been explored so far, offer potential applications, not only as laser active media, but also in other optical devices.

  7. GaAs and AlGaAs APDs with GaSb absorption regions in a separate absorption and multiplication structure using a hetero-lattice interface

    Science.gov (United States)

    Marshall, A. R. J.; Craig, A. P.; Reyner, C. J.; Huffaker, D. L.

    2015-05-01

    Interfacial misfit (IMF) arrays were used to create two APD structures, allowing GaSb absorption layers to be combined with wide-gap multiplication regions, grown using GaAs and Al0.8Ga0.2As, respectively. The GaAs APD represents a proof-of-principle, which is developed in the Al0.8Ga0.2As APD to achieve reduced dark currents, of 5.07 μA cm-2 at 90% of the breakdown voltage, and values for effective k = β/α below 0.2. A random-path-length (RPL) simulation was used to model the excess noise in both structures, taking into account the effects of dead space. It is envisaged that the GaSb absorption regions could be replaced with other materials from the 6.1 Å family, allowing for long-wavelength APDs with reduced dark currents and excess noise.

  8. Doping evolution of the magnetic susceptibility and transport properties of Fe{sub 1+{delta}T}e{sub 1-x}Se{sub x} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y; Kremer, R K; Lin, C T [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart (Germany)

    2011-03-15

    A study of the doping evolution of the magnetic susceptibility and transport properties was performed on Fe{sub 1+{delta}T}e{sub 1-x}Se{sub x} (x = 0, 0.22, 0.32, 0.37 and 0.40) single crystals grown by the self-flux method. For x = 0, 0.22 and 0.32 the paramagnetic susceptibility {chi}(T) in the high-temperature regime can be well fitted with a modified Curie-Weiss law. The Curie-Weiss temperature {theta}{sub p} systematically decreases with increasing Se content, indicating the breakdown of the predominant antiferromagnetic (AFM) interactions originating from FeTe (x = 0). Bulk superconductivity is established for x = 0.37 and 0.40, while {chi}(T) monotonically increases with increasing temperature in the high-temperature regime, as widely observed in iron arsenides. The resistivity {rho}{sub ab} simultaneously changes from a semiconducting behavior for x = 0, 0.22, and 0.32 to metallic transport below 200 K for x = 0.37 and 0.40. A sudden drop of the Hall coefficient R{sub H} from positive to negative values signifies the AFM transition of the sample for x = 0 at T{sub N} = 68 K, as evidenced by the magnetic susceptibility measurements. For x = 0.22 and 0.32, R{sub H} is positive and monotonically increases with decreasing temperature. A dramatic change in R{sub H} is observed for x = 0.37 and 0.40, where the positive R{sub H} starts to decrease below T{sub N} = 68 K. A change of sign further occurs at 40 K for x = 0.40. The anomalous doping-dependent behavior for both magnetic susceptibility {chi}(T) and Hall coefficient R{sub H} can be interpreted with the scenario that the Fe{sub 1+{delta}T}e{sub 1-x}Se{sub x} system undergoes a critical transition from the ({pi}, 0) magnetic order of FeTe to the dominant ({pi}, {pi}) spin fluctuations of FeSe with the establishment of bulk superconductivity.

  9. NIR-to-NIR Two-Photon Scanning Laser Microscopy Imaging of Single Nanoparticles Doped by Yb(III) Complexes.

    Science.gov (United States)

    Bourdolle, Adrien; D'Aléo, Anthony; Philippot, Cécile; Baldeck, Patrice L; Guyot, Yannick; Dubois, Fabien; Ibanez, Alain; Andraud, Chantal; Brasselet, Sophie; Maury, Olivier

    2016-01-04

    The photophysical and nonlinear optical properties of water-soluble chromophore-functionalised tris-dipicolinate complexes [LnL3](3-) (Ln=Yb and Nd) are thoroughly studied, revealing that only the Yb(III) luminescence can be sensitized by a two-photon excitation process. The stability of the complex in water is strongly enhanced by embedding in dispersible organosilicate nanoparticles (NPs). Finally, the spectroscopic properties of [NBu4]3 [YbL3] are studied in solution and in the solid state. The high brightness of the NPs allows imaging them as single objects using a modified two-photon microscopy setup in a NIR-to-NIR configuration.

  10. Direct measurement of the effective infrared dielectric response of a highly doped semiconductor metamaterial

    Science.gov (United States)

    Mohtar, Abeer Al; Kazan, Michel; Taliercio, Thierry; Cerutti, Laurent; Blaize, Sylvain; Bruyant, Aurélien

    2017-03-01

    We have investigated the effective dielectric response of a subwavelength grating made of highly doped semiconductors (HDS) excited in reflection, using numerical simulations and spectroscopic measurement. The studied system can exhibit strong localized surface resonances and has, therefore, a great potential for surface-enhanced infrared absorption (SEIRA) spectroscopy application. It consists of a highly doped InAsSb grating deposited on lattice-matched GaSb. The numerical analysis demonstrated that the resonance frequencies can be inferred from the dielectric function of an equivalent homogeneous slab by accounting for the complex reflectivity of the composite layer. Fourier transform infrared reflectivity (FTIR) measurements, analyzed with the Kramers–Kronig conversion technique, were used to deduce the effective response in reflection of the investigated system. From the knowledge of this phenomenological dielectric function, transversal and longitudinal energy-loss functions were extracted and attributed to transverse and longitudinal resonance modes frequencies.

  11. HREELS and photoemission study of GaSb( 1 0 0 )-(1×3) surfaces prepared by optimal atomic hydrogen cleaning

    Science.gov (United States)

    Veal, T. D.; Lowe, M. J.; McConville, C. F.

    2002-03-01

    High-resolution electron-energy-loss spectroscopy (HREELS) and synchrotron-radiation photoemission spectroscopy (SRPES) have been used to study the Sb-stabilised GaSb(1 0 0)-(1×3) surface prepared by a two-stage low-temperature atomic hydrogen cleaning (AHC) procedure. The use of a maximum annealing temperature of 300 °C avoids the degradation of surface stoichiometry associated with higher annealing temperatures. After AHC at a sample temperature of 100 °C, SRPES results show that all Sb oxides have been removed and only a small amount of Ga oxide remains. Further AHC treatment at 300 °C results in a clean surface with a sharp (1×3) low energy electron diffraction pattern. SRPES results indicate that the surface stoichiometry is identical to that previously found for GaSb(1 0 0)-(1×3) prepared by in situ molecular beam epitaxy. Electron energy-dependent HREEL spectra exhibit a coupled plasmon-phonon mode which has been used to study the electronic structure of the near-surface region. Semi-classical dielectric theory simulations of the HREEL spectra of the clean GaSb(1 0 0)-(1×3) surface indicate no detectable electronic damage or dopant passivation results from the AHC treatment. Valence band SRPES indicates that the surface Fermi level is close to the valence band maximum, suggesting the presence of an inversion layer at the surface.

  12. Molecular Doping of the Hole-Transporting Layer for Efficient, Single-Step Deposited Colloidal Quantum Dot Photovoltaics

    KAUST Repository

    Kirmani, Ahmad R.

    2017-07-31

    Employment of thin perovskite shells and metal halides as surface-passivants for colloidal quantum dots (CQDs) have been important, recent developments in CQD optoelectronics. These have opened the route to single-step deposited high-performing CQD solar cells. These promising architectures employ a QD hole-transporting layer (HTL) whose intrinsically shallow Fermi level (EF) restricts band-bending at maximum power-point during solar cell operation limiting charge collection. Here, we demonstrate a generalized approach to effectively balance band-edge energy levels of the main CQD absorber and charge-transport layer for these high-performance solar cells. Briefly soaking the QD HTL in a solution of the metal-organic p-dopant, molybdenum tris(1-(trifluoroacetyl)-2-(trifluoromethyl)ethane-1,2-dithiolene), effectively deepens its Fermi level, resulting in enhanced band bending at the HTL:absorber junction. This blocks the back-flow of photo-generated electrons, leading to enhanced photocurrent and fill factor compared to undoped devices. We demonstrate 9.0% perovskite-shelled and 9.5% metal-halide-passivated CQD solar cells, both achieving ca. 10% relative enhancements over undoped baselines.

  13. Study of Nuclear Quadrupole Resonance on CO-Doped Single-Walled Carbon Nanotubes: A DFT Computation

    Directory of Open Access Journals (Sweden)

    A. Ghasemi

    2012-08-01

    Full Text Available Carbon Monoxide (CO gas adsorption on external surface of zig-zag (5, 0 and armchair (4, 4 semiconducting Single-Walled Carbon Nanotube (SWCNTs were studied using Density Functional Theory (DFT calculations. Geometry optimizations were carried out by B3LYP/ DFT method at 6-311G* level of theory using the Gaussian98. SWCNTs have been proposed as ideal candidates for various applications of gas sensors due to their amazing physical adsorption properties. We studied the Nuclear Quadrupole Resonance (NQR of the zigzag (5, 0 and armchair (4, 4 SWCNTs with the optimal length of 7.13 and 9.8 Å, respectively. For the first time, DFT calculations were performed to calculate the interaction of 13-Carbon quadrupole moment with EFG in the considered model of CO-SWCNTs. The evaluated NQR parameters reveal that the EFG tensors of 13-Carbon are influenced and show particular trends from gas molecules in the SWCNTs due to contribution of C-O gas molecule of SWCNTs.

  14. Investigations on structural and photoluminescence mechanism of cerium doped L-Histidine hydrochloride mono hydrate single crystals for optical applications

    Science.gov (United States)

    Rajyalakshmi, S.; Ramachandra Rao, K.; Brahmaji, B.; Samatha, K.; Visweswara Rao, T. K.; Ramakrishna, Y.

    2017-02-01

    Semi organic nonlinear optical material of Ce3+ ion added L-Histidine hydrochloride monohydrate (LHHC) crystals have been grown successfully by the slow evaporation solution technique (SEST) as well as Sankaranarayanan-Ramasamy (SR) technique. Unit cell data have been measured from the single crystal X-ray diffraction analysis and High resolution X-ray diffraction analysis (HRXRD) study shows relatively a good crystalline perfection. Fourier transform infra-red spectroscopy (FTIR) spectra indicates that the Ce3+ ion is coordinated with carboxylate group of grown crystal. The lower UV-cutoff wavelength of the incorporation of Ce3+ ion in LHHC is 240 nm. The incorporation of Ce3+ ion in the crystal lattice was observed by energy dispersive X-ray analysis (EDAX). The nonlinear optical (NLO) efficiency of SR-grown crystal is 3.7 times greater with respect to potassium dihydrogen phosphate (KDP). We report first-time the photoluminescence (PL) mechanism of emission spectrum, which shows broad band located at 350 nm corresponding to 5d → 4f transition of Ce3+ ion and excited by 250 nm wavelength. The excitation spectrum shows a band at 258 nm due to the 4f → 5d transition of Ce3+ ion. The nature of decay curve of the grown crystal is bi-exponential with a long life time of τ2 is 8.8270 μs.

  15. Co-co-doping Effect on Superconducting Properties of 112-Type Ca0.8La0.2FeAs2 Single Crystals

    Science.gov (United States)

    Xing, Xiangzhuo; Zhou, Wei; Xu, Baozhang; Li, Na; Sun, Yiran; Zhang, Yufeng; Shi, Zhixiang

    2015-07-01

    We systematically investigated the Co-co-doping effects in Ca0.8La0.2FeAs2 superconductors. The superconducting transition temperature (Tc) decreases almost linearly with increasing Co content. Simultaneously, it is found that the (Ca,La)112 phase is so sensitive to the Co doping level that chemical phase separation becomes more and more apparent as a result of formation of the (Ca,La)122 phase. The maximum Co doping level for 112 phase seems very low, indicating a quite cruel growth condition for 112 compared with other IBSs.

  16. Influence of cerium doping on the dielectric relaxation of Sr{sub 0.75}Ba{sub 0.25}Nb{sub 2}O{sub 6} single crystal grown by the double crucible Stepanov technique

    Energy Technology Data Exchange (ETDEWEB)

    Bhaumik, Indranil, E-mail: neel@rrcat.gov.in [Crystal Growth Laboratory, LMDDD, Raja Ramanna Centre for Advanced Technology, Indore (India); Ganesamoorthy, S. [XS and CGS, CMPD, MSG, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Bhatt, R. [Crystal Growth Laboratory, LMDDD, Raja Ramanna Centre for Advanced Technology, Indore (India); Subramanian, N. [XS and CGS, CMPD, MSG, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Karnal, A.K.; Gupta, P.K. [Crystal Growth Laboratory, LMDDD, Raja Ramanna Centre for Advanced Technology, Indore (India); Takekawa, S.; Kitamura, K. [Polar Domain Engineering Group, NIMS, Namiki, Tsukuba (Japan)

    2015-02-05

    Highlights: • Incorporation of Ce in the lattice reduces dielectric maxima in Sr{sub 0.75}Ba{sub 0.25}Nb{sub 2}O{sub 6}. • It increases degree of diffusiveness and lowers the temperature of dielectric maxima. • These are due to introduction of addition random field via created point defects. • Both of the crystals undergo non-debye type relaxation. • VF fitting revealed that attempt frequency reduced by one order on Ce doping. - Abstract: The effect of Ce doping on the dielectric relaxation in Sr{sub 0.75}Ba{sub 0.25}Nb{sub 2}O{sub 6} single crystal grown by double crucible Stepanov technique has been investigated. It has been observed that the incorporation of Ce ion in the lattice reduces the dielectric maxima. It further increases the degree of diffusiveness and lowers the temperature of dielectric maxima as a result of the introduction of additional random field via created point defects. Both the undoped and Ce doped crystals undergo a non-debye type relaxation. Vogel–Fulcher fitting reveals that the attempt frequency reduced by one order of magnitude on Ce doping.

  17. Super-fast switching of twisted nematic liquid crystals with a single-wall-carbon-nanotube-doped alignment layer

    Science.gov (United States)

    Liu, Yang; Lim, Young Jin; Kundu, Sudarshan; Lee, Seung Hee; Lee, Gi-Dong

    2015-03-01

    The application of a single-wall carbon-nanotube (SWCNT) and polyimide (PI) composite thin film on an indium tin-oxide (ITO) glass substrate, working as the command surface in a twisted nematic liquid crystal display (LCD), is described. SWCNTs were chopped and oxidized in a strong acid medium to make them more miscible in a polyimide solution. A film of this newly-developed PISWCNT composite was rubbed to determine the director direction for the LC molecules. The newlyfabricated command surface was examined using a laser beam profiler and atomic force microscopy. Sizes of shortened SWCNTs were characterized by using field-emission scanning electron microscopy (FE-SEM). Finally, small-sized test panels were fabricated from this composite-coated ITO glass, and their electro-optic performances were measured. Although the operating voltage to switch a cell was increased by around 41%, the switching speed was improved remarkably. The rise time of the test cells was found to be improved by around 10.12% and the decay time by around 29.77%. Thus, an overall improvement of around 16.12% in the total switching time was achieved. The change in the surface morphology of the newly-developed composite materials was found to be one of the factors responsible for the faster switching of the device. Detailed discussions are given in this report to explain the faster switching of the newly-developed twisted nematic liquid crystal display (TN-LCD). The device can be useful for practical applications.

  18. Anisotropy of the upper critical field in a Co-doped BaFe2As2 single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Kano, M. [Florida State University; Kohama, Y. [National High Magnetic Field Laboratory, Los Alamos National Lab, Los Alamos; Graf, D. [Florida State University; Balakirev, F F [National High Magnetic Field Laboratory, Los Alamos National Lab, Los Alamos; Sefat, A. S. [Oak Ridge National Laboratory (ORNL); McGuire, Michael A [ORNL; Sales, Brian C [ORNL; Mandrus, David [ORNL; Tozer, Stan [Florida State University

    2009-01-01

    The temperature dependence of the upper critical magnetic field (H{sub c2}) in a BaFe{sub 1.84}Co{sub 0.16}As{sub 2} single crystal was determined via resistivity, for the inter-plane (H {perpendicular} ab) and in-plane (H {parallel} ab) directions in pulsed and static magnetic fields of up to 60 T. Suppressing superconductivity in a pulsed magnetic field at {sup 3}He temperatures permits us to construct an H{sub c2}-T phase diagram from quantitative H{sub c2}(0) values and determine its behavior in low temperatures. H{sub c2}(0) with H {parallel} ab [H{sub c2{parallel}} (0)] and H {perpendicular} ab [H{sub c2{perpendicular}} (0)] are -55 and -50 T respectively. These values are -1.2-1.4 times larger than the weak-coupling Pauli paramagnetic limit (H{sub p} = 1.84 T{sub c}), indicating that enhanced paramagnetic limiting is essential and this superconductor is unconventional. While H{sub c2} {parallel} ab is saturated at low temperature, H{sub c2} with H {perpendicular} ab (H{sub c2{perpendicular}}) exhibits almost linear temperature dependence towards T = 0 K which results in reduced anisotropy of H{sub c2} in low temperature. The anisotropy of H{sub c2} was -3.4 near T{sub c}, and decreases rapidly with lower temperatures reaching -1.1 at T=0.7 K.

  19. Molecular doping of graphene.

    Science.gov (United States)

    Wehling, T O; Novoselov, K S; Morozov, S V; Vdovin, E E; Katsnelson, M I; Geim, A K; Lichtenstein, A I

    2008-01-01

    Graphene is considered as one of the most promising materials for post silicon electronics, as it combines high electron mobility with atomic thickness [Novoselov et al. Science 2004, 306, 666-669. Novoselov et al. Proc. Natl. Acad. Sci. U.S.A. 2005, 102, 10451-10453]. The possibility of chemical doping and related excellent chemical sensor properties of graphene have been demonstrated experimentally [Schedin et al. Nat. Mater. 2007, 6, 652-655], but a microscopic understanding of these effects has been lacking, so far. In this letter, we present the first joint experimental and theoretical investigation of adsorbate-induced doping of graphene. A general relation between the doping strength and whether adsorbates are open- or closed-shell systems is demonstrated with the NO2 system: The single, open shell NO2 molecule is found to be a strong acceptor, whereas its closed shell dimer N2O4 causes only weak doping. This effect is pronounced by graphene's peculiar density of states (DOS), which provides an ideal situation for model studies of doping effects in semiconductors. We show that this DOS is ideal for "chemical sensor" applications and explain the recently observed [Schedin et al. Nat. Mater. 2007, 6, 652-655] NO2 single molecule detection.

  20. NMR and NQR parameters of the SiC-doped on the (4,4) armchair single-walled BPNT: a computational study.

    Science.gov (United States)

    Baei, Mohammad T; Sayyad-Alangi, S Zahra; Moradi, Ali Varasteh; Torabi, Parviz

    2012-03-01

    The structural properties, NMR and NQR parameters in the pristine and silicon carbide (SiC) doped boron phosphide nanotubes (BPNTs) were calculated using DFT methods (BLYP, B3LYP/6-31G) in order to evaluate the influence of SiC-doped on the (4,4) armchair BPNTs. Nuclear magnetic resonance (NMR) parameters including isotropic (CS(I)) and anisotropic (CS(A)) chemical shielding parameters for the sites of various (13)C, (29)Si, (11)B, and (31)P atoms and quadrupole coupling constant (C ( Q )), and asymmetry parameter (η ( Q )) at the sites of various (11)B nuclei were calculated in pristine and SiC- doped (4,4) armchair boron phosphide nanotubes models. The calculations indicated that doping of (11)B and (31)P atoms by C and Si atoms had a more significant influence on the calculated NMR and NQR parameters than did doping of the B and P atoms by Si and C atoms. In comparison with the pristine model, the SiC- doping in Si(P)C(B) model of the (4,4) armchair BPNTs reduces the energy gaps of the nanotubes and increases their electrical conductance. The NMR results showed that the B and P atoms which are directly bonded to the C atoms in the SiC-doped BPNTs have significant changes in the NMR parameters with respect to the B and P atoms which are directly bonded to the Si atoms in the SiC-doped BPNTs. The NQR results showed that in BPNTs, the B atoms at the edges of nanotubes play dominant roles in determining the electronic behaviors of BPNTs. Also, the NMR and NQR results detect that the Fig. 1b (Si(P)C(B)) model is a more reactive material than the pristine and the Fig. 1a (Si(B)C(p)) models of the (4,4) armchair BPNTs.

  1. Optical properties of silica sol-gel materials singly-and doubly-doped with Eu3+and Gd3+ions

    Institute of Scientific and Technical Information of China (English)

    Natalia Pawlik; Barbara Szpikowska-Sroka; Marta Sołtys; Wojciech A.Pisarski

    2016-01-01

    In present work, the optical and structural properties of silica sol-gel glasses and glass-ceramic materials singly-and dou-bly-doped with Eu3+and Gd3+ions were investigated. The optical properties of studied systems were determined based on absorption, excitation and emission spectra as well as luminescence decay analysis. Conducted studies clearly indicated a significant enhance-ment of visible emission originated from Eu3+ions as a result of changing the excitation mechanism, via Gd3+→Eu3+energy transfer. The luminescence intensity R-ratio was analyzed before and after heat-treatment process upon excitation atλex=393 nm andλex=273 nm. Moreover, the influence of excitation wavelength on luminescence decay time of the 5D0 excited state was also analyzed. The Gd3+→Eu3+energy transfer efficiencies for precursor and annealed samples were calculated based on luminescence lifetime of the 6P7/2 level of Gd3+ions. The X-ray diffraction measurements were conducted to verify the nature of obtained sol-gel materials. In re-sult, the formation of orthorhombic GdF3 nanocrystal phase dispersed in amorphous silica glass host was identified after annealing. Obtained results clearly indicated an incorporation of Eu3+ activators into formed GdF3 nanocrystals. Thus, conducted heat-treatment process led to considerable changes in surrounding environment around Eu3+ions. Actually, it was found that en-ergy transfer phenomenon and heat-treatment process were responsible for significant improvement of Eu3+luminescence in stud-ied sol-gel samples.

  2. Effect of Ce doping on the electrocaloric effect of SrxBa1-xNb2O6 single crystals

    Science.gov (United States)

    Le Goupil, Florian; Axelsson, Anna-Karin; Valant, Matjaz; Lukasiewicz, Tadeusz; Dec, Jan; Berenov, Andrey; Alford, Neil McN.

    2014-06-01

    The electrocaloric effect (ECE) of SrxBa(1-x)Nb2O6 (SBN100x) single crystals, with a tetragonal tungsten bronze structure and a high ECE near room temperature, is studied by direct measurements. It is shown that although the onset of the ECE peak is closer to room temperature in SBN80 than in SBN75, the effect of the increase of the strontium content is very detrimental to the ECE performances with a decrease to ΔTEC = 0.23 K for SBN80 from the reported value of ΔTEC = 0.42 K under 10 kV/cm for SBN75 [F. Le Goupil et al., "Anisotropy of the electrocaloric effect in lead-free relaxor ferroelectrics," Adv. Energy Mater. (published online)]. However, when 1.40% of cerium is introduced in SBN61, the temperature of depolarisation is shifted below 30 °C, while an ECE above 0.6 K is maintained over more than 70 K for a low electric field of 28 kV/cm. The maximum ECE ΔTEC = 0.85 K is measured at 61 °C. In addition to having an ECE peak close to room temperature, the ECE measured in Ce-doped SBN61 is comparable with the best reported values for lead-free materials [Y. Bai et al., J. Appl. Phys. 110, 094103 (2011); X.-S. Qian et al., Adv. Funct. Mater. 24, 1300 (2014)], when linearly extrapolated to higher electric fields.

  3. On-Demand Guided Bone Regeneration with Microbial Protection of Ornamented SPU Scaffold with Bismuth-Doped Single Crystalline Hydroxyapatite: Augmentation and Cartilage Formation.

    Science.gov (United States)

    Selvakumar, M; Srivastava, Priyanka; Pawar, Harpreet Singh; Francis, Nimmy K; Das, Bodhisatwa; Sathishkumar, G; Subramanian, Bhuvaneshwaran; Jaganathan, Saravana Kumar; George, Gibin; Anandhan, S; Dhara, Santanu; Nando, Golok B; Chattopadhyay, Santanu

    2016-02-17

    Guided bone regeneration (GBR) scaffolds are futile in many clinical applications due to infection problems. In this work, we fabricated GBR with an anti-infective scaffold by ornamenting 2D single crystalline bismuth-doped nanohydroxyapatite (Bi-nHA) rods onto segmented polyurethane (SPU). Bi-nHA with high aspect ratio was prepared without any templates. Subsequently, it was introduced into an unprecedented synthesized SPU matrix based on dual soft segments (PCL-b-PDMS) of poly(ε-caprolactone) (PCL) and poly(dimethylsiloxane) (PDMS), by an in situ technique followed by electrospinning to fabricate scaffolds. For comparison, undoped pristine nHA rods were also ornamented into it. The enzymatic ring-opening polymerization technique was adapted to synthesize soft segments of PCL-b-PDMS copolymers of SPU. Structure elucidation of the synthesized polymers is done by nuclear magnetic resonance spectroscopy. Sparingly, Bi-nHA ornamented scaffolds exhibit tremendous improvement (155%) in the mechanical properties with excellent antimicrobial activity against various human pathogens. After confirmation of high osteoconductivity, improved biodegradation, and excellent biocompatibility against osteoblast cells (in vitro), the scaffolds were implanted in rabbits by subcutaneous and intraosseous (tibial) sites. Various histological sections reveal the signatures of early cartilage formation, endochondral ossification, and rapid bone healing at 4 weeks of the critical defects filled with ornamented scaffold compared to SPU scaffold. This implies osteogenic potential and ability to provide an adequate biomimetic microenvironment for mineralization for GBR of the scaffolds. Organ toxicity studies further confirm that no tissue architecture abnormalities were observed in hepatic, cardiac, and renal tissue sections. This finding manifests the feasibility of fabricating a mechanically adequate nanofibrous SPU scaffold by a biomimetic strategy and the advantages of Bi

  4. The effect of Nd and Mg doping on the micro-Raman spectra of LiNbO{sub 3} single-crystals

    Energy Technology Data Exchange (ETDEWEB)

    Quispe-Siccha, R; Villagran-Muniz, M [Laboratorio de FotofIsica, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, AP 70-186, DF (Mexico); MejIa-Uriarte, E V [Laboratorio de Fotonica de Microondas, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, AP 70-186, DF (Mexico); Jaque, D; GarcIa Sole, J; Jaque, F [Laboratorio de Espectroscopia Laser, Departamentode Fisica de Materiales, Universidad Autonoma de Madrid, Madrid 28049 (Spain); Sato-Berru, R Y [Laboratorio de Materiales y NanotecnologIa, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, AP 70-186, DF (Mexico); Camarillo, E; Hernandez A, J; Murrieta S, H [Laboratorio Propiedades Opticas, Instituto de Fisica, Universidad Nacional Autonoma de Mexico, AP 20-364 (Mexico)], E-mail: rosa.quispe@gmail.com, E-mail: elsi.mejia@ccadet.unam.mx, E-mail: mayo.villagran@ccadet.unam.mx, E-mail: dani.jaque@uam.es, E-mail: jose.garcia_sole@uam.es, E-mail: francisco.jaque@uam.es, E-mail: roberto.sato@ccadet.unam.mx, E-mail: cgarcia@fisica.unam.mx, E-mail: josemh@fisica.unam.mx, E-mail: murrieta@fisica.unam.mx

    2009-04-08

    The LiNbO{sub 3} congruent crystals doped with small Nd concentrations, <1 mol% Nd, and co-doped with Mg ions, 0-9 mol% Mg, were systematically investigated by means of micro-Raman spectroscopy in the Y and Z crystal directions. Results obtained from an undoped congruent crystal, an Nd-doped crystal, a Mg-doped crystal and Nd, Mg-co-doped crystals are compared. From the analyses of the results obtained in the Y direction, the Nd and Mg content dependence of the two lowest-Raman A{sub 1}(TO{sub 1}) and A{sub 1}(TO{sub 2}) modes, the half-width composition and the area ratio of the A{sub 1}(TO{sub 4}) and E(TO{sub 8}) bands, we reached several conclusions about the incorporation mechanism of the Nd and Mg ions into the LiNbO{sub 3} lattice. Likewise the Raman shift and half-width of the E(TO{sub 1}) and E(TO{sub 7}) modes were investigated in the Z direction. Results indicate that Mg and Nd ions are located in the Li site for low doping concentrations and for larger concentrations there is a replacement in both Li and Nb ion sites.

  5. LPE Growth of Single Crystalline Film Scintillators Based on Ce3+ Doped Tb3−xGdxAl5−yGayO12 Mixed Garnets

    Directory of Open Access Journals (Sweden)

    Vitalii Gorbenko

    2017-08-01

    Full Text Available The growth of single crystalline films (SCFs with excellent scintillation properties based on the Tb1.5Gd1.5Al5−yGayO12:Ce mixed garnet at y = 2–3.85 by Liquid Phase Epitaxy (LPE method onto Gd3Al2.5Ga2.5O12 (GAGG substrates from BaO based flux is reported in this work. We have found that the best scintillation properties are shown by Tb1.5Gd1.5Al3Ga2O12:Ce SCFs. These SCFs possess the highest light yield (LY ever obtained in our group for LPE grown garnet SCF scintillators exceeding by at least 10% the LY of previously reported Lu1.5Gd1.5Al2.75Ga2.25O12:Ce and Gd3Al2–2.75 Ga3–2.25O12:Ce SCF scintillators, grown from BaO based flux. Under α-particles excitation, the Tb1.5Gd1.5 Al3Ga2O12:Ce SCF show LY comparable with that of high-quality Gd3Al2.5Ga2.5O12:Ce single crystal (SC scintillator with the LY above 10,000 photons/MeV but faster (at least by 2 times scintillation decay times t1/e and t1/20 of 230 and 730 ns, respectively. The LY of Tb1.5Gd1.5Al2.5Ga2.5O12:Ce SCFs, grown from PbO flux, is comparable with the LY of their counterparts grown from BaO flux, but these SCFs possess slightly slower scintillation response with decay times t1/e and t1/20 of 330 and 990 ns, respectively. Taking into account that the SCFs of the Tb1.5Gd1.5Al3–2.25Ga2–2.75O12:Ce garnet can also be grown onto Ce3+ doped GAGG substrates, the LPE method can also be used for the creation of the hybrid film-substrate scintillators for simultaneous registration of the different components of ionization fluxes.

  6. X-ray photoelectron spectroscopy, high-resolution X-ray diffraction and refractive index analyses of Ti-doped lithium niobate (Ti:LiNbO3) nonlinear optical single crystal

    Indian Academy of Sciences (India)

    P Kumar; S Moorthy Babu; S Perero; Rajamaniccam L Sai; I Bhaumik; S Ganesamoorthy; A K Karnal

    2010-11-01

    Congruent LiNbO3 single crystals with Ti ion dopants (2 and 5 mol%) were successfully grown by Czochralski technique in the automatic diameter control facility. As-grown crystal boules were oriented into (0 0 1) direction cut and optically polished for all measurements. Influence of Ti-ion incorporation into LiNbO3 was studied by core level XPS analysis. Powder X-ray diffraction studies were carried out on doped lithium niobate for phase identification. High-resolution X-ray diffraction technique was used to study the crystalline quality through full-width at half-maximum values. The refractive index values are more for doped samples than for pure sample as determined by prism coupling technique with different laser sources.

  7. Transmission electron microscopy analysis of phase separation in GaInAsSb films grown on GaSb substrate.

    Science.gov (United States)

    Szczeszek, P; Amariei, A; Schöne, J; Zoulis, G; Vouroutzis, N; Polychroniadis, E K; Stróz, D

    2006-10-01

    The GaSb-based quaternary alloys are a good choice for thermophotovoltaic applications. The thermophotovoltaic cell converts infrared radiation to electricity, using the same principles as photovoltaic devices. The aim of the present work was the microstructural study of such an alloy, namely Ga(0.84)In(0.16)As(0.12)Sb(0.88). A thin film of the material was grown by metal organic vapour phase epitaxy on a (100)alpha-->[111]B (alpha = 2 degrees, 4 degrees, 6 degrees) GaSb substrate. The GaInAsSb alloy has an appropriate band gap, but suffers from a phase separation consisting of GaAs-rich and InSb-rich regions that is disadvantageous for cell efficiency. In this work, we employed a morphological approach to phase separation, with the use of conventional transmission electron microscopy and atomic force microscopy. The phase separation occurs in two different orientations: parallel to the growth direction (vertical) and inclined (lateral). After application of fast Fourier transformation filtering, the vertical periodicity was found to be lambda = 5 nm for the pair (black and white) of layers independently of the cut-off angle, whereas the lateral periodicity was related to it.

  8. Nitrogen doping in carbon nanotubes.

    Science.gov (United States)

    Ewels, C P; Glerup, M

    2005-09-01

    Nitrogen doping of single and multi-walled carbon nanotubes is of great interest both fundamentally, to explore the effect of dopants on quasi-1D electrical conductors, and for applications such as field emission tips, lithium storage, composites and nanoelectronic devices. We present an extensive review of the current state of the art in nitrogen doping of carbon nanotubes, including synthesis techniques, and comparison with nitrogen doped carbon thin films and azofullerenes. Nitrogen doping significantly alters nanotube morphology, leading to compartmentalised 'bamboo' nanotube structures. We review spectroscopic studies of nitrogen dopants using techniques such as X-ray photoemission spectroscopy, electron energy loss spectroscopy and Raman studies, and associated theoretical models. We discuss the role of nanotube curvature and chirality (notably whether the nanotubes are metallic or semiconducting), and the effect of doping on nanotube surface chemistry. Finally we review the effect of nitrogen on the transport properties of carbon nanotubes, notably its ability to induce negative differential resistance in semiconducting tubes.

  9. Effect of Mg co-doping on scintillation properties of Ce:Gd3(Ga, Al)5O12 single crystals with various Ga/Al ratios

    Science.gov (United States)

    Yoshino, Masao; Kamada, Kei; Shoji, Yasuhiro; Yamaji, Akihiro; Kurosawa, Shunsuke; Yokota, Yuui; Ohashi, Yuji; Yoshikawa, Akira; Chani, Valery I.

    2017-06-01

    Mg co-doped Ce1%:Gd3GaxAl5-xO12 (Ce:GAGG) crystals (x=2.4, 2.7, 3.0) were successfully grown by the Czochralski (Cz) method. Effect of Mg co-doping on the scintillation properties of Ce:GAGG was examined. This study covers measurements of solidification fraction and scintillation properties such as light yield, energy resolution and non-proportionality for each crystal. Pulse-height spectra of various gamma and X-ray sources with energies ranged from 30 keV to 662 keV were measured. Regardless of the presence/absence of Mg dopant, the non-proportionality curves with lower content of gallium in the crystal structure tend to improve. Mg co-doped Ce:GAGG samples did not show a significant difference as compared with non co-doped Ce:GAGG. Mg co-doped crystals with x=2.4 and 2.7 showed the promising scintillation properties of faster decay time and higher energy resolution than those with x=3.0.

  10. Single Junction Inverted Polymer Solar Cell Reaching Power Conversion Efficiency 10.31% by Employing Dual-Doped Zinc Oxide Nano-Film as Cathode Interlayer

    OpenAIRE

    2014-01-01

    We present high efficiency and stable inverted PSCs (i-PSC) by employing sol-gel processed simultaneously doped ZnO by Indium and fullerene derivative (BisNPC60-OH) (denoted as InZnO-BisC60) film as cathode interlayer and PTB7-Th:PC71BM as the active layer (where PTB7-Th is a low bandgap polymer we proposed previously). This dual-doped ZnO, InZnO-BisC60, film shows dual and opposite gradient dopant concentration profiles, being rich in fullerene derivative at the cathode surface in contact wi...

  11. Measurements of a low temperature mechanical dissipation peak in a single layer of Ta2O5 doped with TiO2

    CERN Document Server

    Martin, I; Comtet, C; Fejer, M M; Gretarsson, A; Harry, G; Hough, J; Mackowski, J-M M; MacLaren, I; Michel, C; Montorio, J-L; Morgado, N; Nawrodt, R; Penn, S; Reid, S; Remillieux, A; Route, R; Rowan, S; Schwarz, C; Seidel, P; Vodel, W; Zimmer, A

    2008-01-01

    Thermal noise arising from mechanical dissipation in oxide coatings is a major limitation to many precision measurement systems, including optical frequency standards, high resolution optical spectroscopy and interferometric gravity wave detectors. Presented here are measurements of dissipation as a function of temperature between 7 K and 290 K in ion-beam sputtered Ta2O5 doped with TiO2, showing a loss peak at 20 K. Analysis of the peak provides the first evidence of the source of dissipation in doped Ta2O5 coatings, leading to possibilities for the reduction of thermal noise effects.

  12. Aging Effect on Electrical Conductivity of Pure and Al-Doped YBa2Cu3O7−δ Single Crystals with a Given Topology of Planar Defects

    Directory of Open Access Journals (Sweden)

    Ruslan V. Vovk

    2013-01-01

    Full Text Available The conducting properties in the basal ab plane of pure and Al-doped YBa2Cu3O7-δ single crystals before and after long-time exposure in air atmosphere are investigated. It is shown that prolonged aging leads to an increase of the density of effective scattering centers for the normal carriers. The aluminum doping has been revealed to partially slowdown the degradation of the conducting properties in process of aging. The excess conductivity, Δσ(T, has been found to obey exponential dependence in the broad temperature range Tcdoping and prolonged aging have been found to essentially expand the temperature interval of implementation of the pseudogap state, thus narrowing the linear section in the dependence ρab(T.

  13. Spectroscopic properties of KGd(WO{sub 4}){sub 2} single crystals doped with Er{sup 3+}, Ho{sup 3+}, Tm{sup 3+} and Yb{sup 3+} ions: Luminescence and micro-Raman investigations

    Energy Technology Data Exchange (ETDEWEB)

    Kasprowicz, D., E-mail: Dobroslawa.Kasprowicz@put.poznan.pl [Faculty of Technical Physics, Poznan University of Technology, Nieszawska 13 A, 60-965 Poznan (Poland); Brik, M.G. [Institute of Physics, University of Tartu, Riia 142, Tartu 51014 (Estonia); Majchrowski, A. [Institute of Applied Physics, Military University of Technology, Kaliskiego 2, 00-908 Warszawa (Poland); Michalski, E. [Institute of Optoelectronics, Military University of Technology, Kaliskiego 2, 00-908 Warszawa (Poland); Głuchowski, P. [Institute of Low Temperature and Structure Research of Polish Academy of Sciences, Okólna 2, 50-422 Wroclaw (Poland)

    2013-11-15

    Highlights: •Investigations of KGd(WO{sub 4}){sub 2} crystals doped with Ho/Yb/Er and Ho/Tm/Yb/Er ions. •The vibrational properties were studied using micro-Raman spectroscopy. •The multicolor up-converted luminescence was investigated. -- Abstract: KGd(WO{sub 4}){sub 2} single crystals doped with Ho{sup 3+}/Yb{sup 3+}/Er{sup 3+} and Ho{sup 3+}/Tm{sup 3+}/Yb{sup 3+}/Er{sup 3+} ions were grown by means of the Top Seeded Solution Growth (TSSG) method. It was shown that these systems exhibit multicolor up-conversion luminescence in the visible and near-infrared spectral ranges under 980 nm laser excitation. In the investigated crystals the Yb{sup 3+} ions were used as the energy sensitizer ion and the up-converted luminescence originates from transitions between the energy levels of other co-doped rare earth ions such as Er{sup 3+}, Ho{sup 3+} or Tm{sup 3+}, which play the role of the energy activator ions. The vibrational properties of the crystals were investigated using micro-Raman spectroscopy and the role of vibrational energy in the effective energy transfer process between the rare earth ions was discussed. The proposed combinations of activator ions may be suitable for gaining novel materials with effective green, red and near-infrared emission.

  14. Impact of charge stripes on the c-axis transport properties of lightly doped La{sub 2-x}Sr{sub x}CuO{sub 4} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Komiya, S.; Sun, X.F.; Lavrov, A.N.; Ando, Y

    2003-10-15

    The in-plane and out-of-plane resistivities ({rho}{sub ab} and {rho}{sub c}) of La{sub 2-x}Sr{sub x}CuO{sub 4} single crystals (x=0.005-0.10) are measured and the evolution of the anisotropy ratio ({rho}{sub c}/{rho}{sub ab}) is analyzed. The most striking feature is that {rho}{sub c}/{rho}{sub ab} at moderate temperatures (100-300 K) is almost completely independent of doping for x=0.01-0.05. This doping-independence of {rho}{sub c}/{rho}{sub ab} is consistent with the idea that charges form a self-organized network of hole-rich paths, because in such a situation the antiferromagnetic correlation along the c-axis would align hole-rich domain boundaries (stripes) along the c-axis, thereby causing the anisotropy ratio {rho}{sub c}/{rho}{sub ab} to be determined by the local electronic structure that is insensitive to doping.

  15. VUV spectroscopy of nominally pure and rare-earth ions doped LiCaAIF6 single crystals as promising materials for 157 nm photolithography

    Science.gov (United States)

    Cefalas, Alkiviadis C.; Sarantopoulou, Evangelia; Kollia, Z.; Abdulsabirov, R. Y.; Korableva, S. L.; Naumov, A. K.; Semashko, V. V.; Kobe, S.; McGuiness, P. J.

    2002-07-01

    Recently it was found that birefringence is induced in CaF2 crystals when they are illuminated with laser light at 157 nm. Taking into consideration that CaF2 is the only optical material used in 157 nm photolithography today, the possibility to use new wide band gap fluoride crystals as optical elements for 157 nm photolithography, even those of non-cubic symmetry, should be considered. Additionally fluoride dielectric crystals with wide band gaps doped with trivalent rare-earth (RE) ions can be used as passive or active optical elements int eh VUV. For doped crystals, applications depend on the structure of the energy level pattern of the 4fn-15d electronic configuration and RE ion concentration. In this work we are exploiting the use of wide band gap fluoride dielectric crystals doped with RE ions. The laser induced fluorescence spectrum at 157 nm, and the absorption spectra of the LiCaAlF6 crystals, pure and doped with RE ions, were investigated in the VUV region of the spectrum. A new m4tehod for monitoring RE concentration in wide band gap fluoride crystals, that is based on vibrating sample magnetometer measurement is presented as well.

  16. NMR and NQR study of Si-doped (6,0) zigzag single-walled aluminum nitride nanotube as n or P-semiconductors.

    Science.gov (United States)

    Baei, Mohammad T; Peyghan, Ali Ahmadi; Tavakoli, Khadijeh; Babaheydari, Ali Kazemi; Moghimi, Masoumeh

    2012-09-01

    Density functional theory (DFT) calculations were performed to investigate the electronic structure properties of pristine and Si-doped aluminum nitride nanotubes as n or P-semiconductors at the B3LYP/6-31G* level of theory in order to evaluate the influence of Si-doped in the (6,0) zigzag AlNNTs. We extended the DFT calculation to predict the electronic structure properties of Si-doped aluminum nitride nanotubes, which are very important for production of solid-state devices and other applications. To this aim, pristine and Si-doped AlNNT structures in two models (Si(N) and Si(Al)) were optimized, and then the electronic properties, the isotropic (CS(I)) and anisotropic (CS(A)) chemical shielding parameters for the sites of various (27)Al and (14)N atoms, NQR parameters for the sites of various of (27)Al and (14)N atoms, and quantum molecular descriptors were calculated in the optimized structures. The optimized structures, the electronic properties, NMR and NQR parameters, and quantum molecular descriptors for the Si(N) and Si(Al) models show that the Si(N) model is a more reactive material than the pristine or Si(Al) model.

  17. Inelastic x-ray scattering study of superconducting SmFeAsO1-xFy single crystals: Evidence for strong momentum-dependent doping-induced renormalizations of optical phonons

    Science.gov (United States)

    Le Tacon, M.; Forrest, T. R.; Rüegg, Ch.; Bosak, A.; Walters, A. C.; Mittal, R.; Rønnow, H. M.; Zhigadlo, N. D.; Katrych, S.; Karpinski, J.; Hill, J. P.; Krisch, M.; McMorrow, D. F.

    2009-12-01

    We report inelastic x-ray scattering experiments on the lattice dynamics in SmFeAsO and superconducting SmFeAsO0.60F0.35 single crystals. Particular attention was paid to the dispersions along the [100] direction of three optical modes close to 23 meV, polarized out of the FeAs planes. Remarkably, two of these modes are strongly renormalized upon fluorine doping. These results provide significant insight into the energy and momentum dependence of the coupling of the lattice to the electron system and underline the importance of spin-phonon coupling in the superconducting iron pnictides.

  18. Inelastic X-ray Scattering Study of SmFeAs(O1−xFy) Single Crystals: Evidence for Strong Momentum-Dependent Doping-Induced Renormalizations of Optical Phonons

    Energy Technology Data Exchange (ETDEWEB)

    Hill, J.P.; Le Tacon, M.; Forrest, T.R.; Ruegg, Ch.; Bosak, A.; Walters, A.C.; Mittal, R.; Rønnow, H.M.; Zhigadlo, N.D.; Katrych, S.; Karpinski, J.; Krisch, M.; McMorrow, D.F.

    2009-12-01

    We report inelastic x-ray scattering experiments on the lattice dynamics in SmFeAsO and superconducting SmFeAsO{sub 0.60}F{sub 0.35} single crystals. Particular attention was paid to the dispersions along the [100] direction of three optical modes close to 23 meV, polarized out of the FeAs planes. Remarkably, two of these modes are strongly renormalized upon fluorine doping. These results provide significant insight into the energy and momentum dependence of the coupling of the lattice to the electron system and underline the importance of spin-phonon coupling in the superconducting iron pnictides.

  19. Switchable dual-wavelength single-longitudinal-mode erbium-doped fiber laser using an inverse-Gaussian apodized fiber Bragg grating filter and a low-gain semiconductor optical amplifier.

    Science.gov (United States)

    Lin, Bo; Tjin, Swee Chuan; Zhang, Han; Tang, Dingyuan; Hao, Jianzhong; Dong, Bo; Liang, Sheng

    2010-12-20

    We present a stable and switchable dual-wavelength erbium-doped fiber laser. In the ring cavity, an inverse-Gaussian apodized fiber Bragg grating serves as an ultranarrow dual-wavelength passband filter, a semiconductor optical amplifier biased in the low-gain regime reduces the gain competition of the two wavelengths, and a feedback fiber loop acts as a mode filter to guarantee a stable single-longitudinal-mode operation. Two lasing lines with a wavelength separation of approximately 0.1 nm are obtained experimentally. A microwave signal at 12.51 GHz is demonstrated by beating the dual wavelengths at a photodetector.

  20. SEMICONDUCTOR MATERIALS: Chemical etching of a GaSb crystal incorporated with Mn grown by the Bridgman method under microgravity conditions

    Science.gov (United States)

    Xiaofeng, Chen; Nuofu, Chen; Jinliang, Wu; Xiulan, Zhang; Chunlin, Chai; Yude, Yu

    2009-08-01

    A GaSb crystal incorporated with Mn has been grown by the Bridgman method on the Polizon facility onboard the FOTON-M3 spacecraft. Structural defects and growth striations have been successfully revealed by the chemical etching method. By calculating various parameters of the convection, the striation patterns can be explained, and the critical value of the Taylor number, which characterizes the convective condition of the rotating magnetic field induced azimuthal flow, was shown. The stresses generated during crystal growth can be reflected by the observations of etch pit distribution and other structural defects. Suggestions for improving the space experiment to improve the quality of the crystal are given.

  1. White light emission in host-sensitized Dy{sup 3+}-single-doped NaIn(WO{sub 4}){sub 2} phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, F.B., E-mail: fbxiong@xmut.edu.cn; Lin, H.F.; Wang, L.J.; Meng, X.G.; Zhu, W.Z., E-mail: wzzhu@xmut.edu.cn

    2015-02-15

    A novel white NaIn{sub 1−x}(WO{sub 4}){sub 2}: xDy{sup 3+} (x=0, 0.02, 0.04, 0.06 and 0.08) phosphors in pure phase were prepared via high temperature solid-state reaction, and luminescent properties of the phosphors were investigated. The crystal structure of the phosphor was characterized by powder X-ray diffraction, and the spectroscopic properties of Dy{sup 3+}-doped NaIn(WO{sub 4}){sub 2} were investigated by diffuse reflectance spectra, photoluminescence emission and photoluminescence excitation spectroscopy. Those spectra illustrated that the Dy{sup 3+}-doped NaIn(WO{sub 4}){sub 2} phosphors could be efficiently excited by the host-sensitized excitation in the spectral range of 280–350 nm, and the host-sensitized excitation is more efficient than the Dy{sup 3+} excitation. The 6 mol% Dy{sup 3+} doping concentration in NaIn(WO{sub 4}){sub 2} is optimum, and the luminescence concentration quenching occurs beyond the 6 mol% concentration. The concentration quenching mechanism could be attributed to the dipole–dipole interaction between the Dy{sup 3+} ions. The CIE color coordinate of the 6 mol% Dy{sup 3+}-doped NaIn(WO{sub 4}){sub 2} is (0.319, 0.325). The present work suggests that Dy{sup 3+}-doped NaIn(WO{sub 4}){sub 2} could be a promising host-sensitized phosphor applied in white LEDs, and white emission can be obtained by combining the blue host emission with the yellow Dy{sup 3+} emission.

  2. Intermediate temperature single-chamber methane fed SOFC based on Gd doped ceria electrolyte and La 0.5Sr 0.5CoO 3- δ as cathode

    Science.gov (United States)

    Morales, M.; Piñol, S.; Segarra, M.

    Single-chamber fuel cells with electrodes supported on an electrolyte of gadolinium doped ceria Ce 1- xGd xO 2- y with x = 0.2 (CGO) 200 μm thickness has been successfully prepared and characterized. The cells were fed directly with a mixture of methane and air. Doped ceria electrolyte supports were prepared from powders obtained by the acetyl-acetonate sol-gel related method. Inks prepared from mixtures of precursor powders of NiO and CGO with different particle sizes and compositions were prepared, analysed and used to obtain optimal porous anodes thick films. Cathodes based on La 0.5Sr 0.5CoO 3 perovskites (LSCO) were also prepared and deposited on the other side of the electrolyte by inks prepared with a mixture of powders of LSCO, CGO and AgO obtained also by sol-gel related techniques. Both electrodes were deposited by dip coating at different thicknesses (20-30 μm) using a commercial resin where the electrode powders were dispersed. Finally, electrical properties were determined in a single-chamber reactor where methane, as fuel, was mixed with synthetic air below the direct combustion limit. Stable density currents were obtained in these experimental conditions. Temperature, composition and flux rate values of the carrier gas were determinants for the optimization of the electrical properties of the fuel cells.

  3. Formation of static stripes in lightly-doped La_2-xSr_xCuO4 as manifested in magnetic and transport properties of untwinned single crystals.

    Science.gov (United States)

    Lavrov, A. N.; Komiya, S.; Ando, Y.

    2002-03-01

    There is growing evidence from neutron and ARPES studies that the doped holes in cuprates may self-organize in a stripe manner; however, little is known about the influence of the stripes on macroscopic properties. We report on the novel anisotropy in the magnetic susceptibility \\chi and magnetoresistance of untwinned La_2-xSr_xCuO4 crystals in the lightly-doped region, which is likely to be a manifestation of the stripes. The in-plane anisotropy of \\chi, found in the ``paramagnetic’’ and ``spin-glass’’ regions of the phase diagram, implies that antiferromagnetically ordered domains, separated by antiphase boundaries (stripes), persist after the Néel order is destroyed by hole doping. Interestingly, the anisotropy in \\chi is found to be large enough so that the magnetic field can rearrange the stripes. Such rearrangement changes the in-plane resistivity by as large as a factor of two, indicating that stripes can significantly affect the hole motion. Furthermore, the hysteretic behavior is observed in both resistivity and magnetic susceptibility at low temperatures, which signals the freezing of stripes upon cooling.

  4. Phase diagram and transport properties of Sb-doped Ca0.88La0.12Fe2As2 single crystals

    Science.gov (United States)

    Xing, Xiang-Zhuo; Zhou, Wei; Xu, Chun-Qiang; Zhou, Nan; Yuan, Fei-Fei; Zhang, Yu-Feng; Xu, Xiao-Feng; Shi, Zhi-Xiang

    2017-08-01

    The effects of isovalent Sb substitution on the superconducting properties of the Ca0.88La0.12Fe2(As1- y Sb y )2 system have been studied through electrical resistivity measurements. It is seen that the antiferromagnetic or structural transition is suppressed with Sb content, and a high- T c superconducting phase, accompanied by a low- T c phase, emerges at 0.02 ≤ y ≤ 0.06. In this intermediate-doping regime, normal-state transport shows non-Fermi-liquid-like behaviors with nearly T-linear resistivity above the high- T c phase. With further Sb doping, this high- T c phase abruptly vanishes for y > 0.06 and the conventional Fermi liquid is restored, while the low- T c phase remains robust against Sb impurities. The coincidence of the high- T c phase and non-Fermi liquid transport behaviors in the intermediate Sb-doping regime suggests that AFM fluctuations play an important role in the observed non-Fermi liquid behaviors, which may be intimately related to the unusual nonbulk high- T c phase in this system.

  5. Precise control of photoluminescence of silicon-vacancy color centers in homoepitaxial single-crystal diamond: evaluation of efficiency of Si doping from gas phase

    Science.gov (United States)

    Ralchenko, Victor; Sedov, Vadim; Saraykin, Vladimir; Bolshakov, Andrey; Zavedeev, Evgeny; Ashkinazi, Evgeny; Khomich, Andrew

    2016-09-01

    Ability to precisely control the Si-related color center abundance in diamond is important for the use of silicon-vacancy (SiV) defects with bright photoluminescence (PL) in quantum information technologies and optical biomarkers. Here, we evaluated the efficiency of Si incorporation in (100) plane of homoepitaxial diamond layers upon in situ doping by adding silane SiH4 in the course of diamond chemical vapor deposition in microwave plasma using CH4-H2 mixtures. Both the Si concentration in the doped samples, as determined by secondary ion mass spectrometry, and PL intensity of SiV centers at 738 nm wavelength, measured at excitation wavelength of 473 nm, demonstrate a linear increase with silane content in feed gas in the range. The incorporation efficiency f, defined as the ratio of Si concentration in diamond to that in gas, f = [Si/C]dia/[Si/C]gas is found to be (1.1 ± 0.5) × 10-3 for the silane concentrations explored, [SiH4/CH4] < 0.7 %; thus, the Si atoms are accommodated in (100) diamond face easier than nitrogen and phosphorus, but more difficult than boron. This finding allows a tailoring of the Si content and photoluminescence intensity of SiV centers in in situ doped CVD diamond.

  6. Study of Te diffused into GaSb by photoluminescence and HRXRD

    Energy Technology Data Exchange (ETDEWEB)

    Vargas-Sanabria, R.; Rosendo, E.; Rosendo-Francisco, P. [FC, UAEMex, Instituto Literario 100 Col. Centro, Toluca (Mexico); Martinez, J.; Diaz, T.; Juarez, H.; Garcia, G. [CIDS-ICUAP, 14 Sur y San Claudio, Col San Manuel, Puebla (Mexico); Rubin, M. [FCC-BUAP, 14 Sur y San Claudio, Col San Manuel, Puebla (Mexico); de Anda, F. [IICO-UASLP Ave. Karakorum 1470, Lomas Cuarta (Mexico)

    2007-04-15

    Photoluminescence (PL) and High Resolution X-Ray Diffraction (HRXRD) measurements were used to study the diffusion of Te on GaSb-p thin films deposited on GaSb-n substrates by Liquid Phase Epitaxy (LPE). The studied samples consist of an n-type layer on a p-type layer to carry out the diffusion. The diffusion process was done through thermic treatment at 450 C and 2, 4 and 6 hours in to the hydrogen atmosphere. After carrying out the heat treatment, the n-type layer was removed with the purpose of studying the diffusion behavior of Te. The PL spectra show that when the time of diffusion increases, the signal produced by the excitonic transitions increases its intensity, this can be attributed to the increase of the concentration of Te in the GaSb-p film. The X-ray spectra show that in agreement it increases the time of diffusion, the amount of Te increases until having a single peak to 6 hrs of diffusion. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Exciton generation/dissociation/charge-transfer enhancement in inorganic/organic hybrid solar cells by robust single nanocrystalline LnPxOy (Ln = Eu, Y) doping.

    Science.gov (United States)

    Jin, Xiao; Sun, Weifu; Chen, Zihan; Wei, Taihuei; Chen, Chuyang; He, Xingdao; Yuan, Yongbiao; Li, Yue; Li, Qinghua

    2014-06-11

    Low-temperature solution-processed photovoltaics suffer from low efficiencies because of poor exciton or electron-hole transfer. Inorganic/organic hybrid solar cell, although still in its infancy, has attracted great interest thus far. One of the promising ways to enhance exciton dissociation or electron-hole transport is the doping of lanthanide phosphate ions. However, the underlying photophysical mechanism remains poorly understood. Herein, by applying femtosecond transient absorption spectroscopy, we successfully distinguished hot electron, less energetic electron, hole transport from electron-hole recombination. Concrete evidence has been provided that lanthanide phosphate doping improves the efficiency of both hot electron and "less energetic" electron transfers from donor to acceptor, but the hole transport almost remains unchanged. In particular, the hot electron transfer lifetime was shortened from 30.2 to 12.7 ps, that is, more than 60% faster than pure TiO2 acceptor. Such improvement was ascribed to the facts that the conduction band (CB) edge energy level of TiO2 has been elevated by 0.2 eV, while the valence band level almost remains unchanged, thus not only narrowing the energy offset between CB levels of TiO2 and P3HT, but also meanwhile enlarging the band gap of TiO2 itself that permits one to inhibit electron-hole recombination within TiO2. Consequently, lanthanide phosphate doped TiO2/P3HT bulk-heterojunction solar cell has been demonstrated to be a promising hybrid solar cell, and a notable power conversion efficiency of 2.91% is therefore attained. This work indicates that lanthanide compound ions can efficiently facilitate exciton generation, dissociation, and charge transport, thus enhancing photovoltaic performance.

  8. DFT study of Al doped armchair SWCNTs

    Energy Technology Data Exchange (ETDEWEB)

    Dhiman, Shobhna, E-mail: s-dhiman@hotmail.com [Department of Applied Science, PEC, University of Technology, Chandigarh -160012 (India); Rani, Anita [Guru Nanak College for Girls, Sri Muktsar Sahib, Punjab-152026 (India); Kumar, Ranjan; Dharamvir, Keya [Department of Physics, Panjab University, Chandigarh-160014 (India)

    2016-05-23

    Electronic properties of endohedrally doped armchair single-walled carbon nanotubes (SWCNTs) with a chain of six Al atoms have been studied using ab-initio density functional theory. We investigate the binding energy/atom, ionization potential, electron Affinity and Homo-Lumo gap of doped armchair SWNTs from (4,4) to (6,6) with two ends open. BE/dopant atom and ionization potential is maximum for (6, 6) doped armchair carbon nanotube; suggest that it is more stable than (4, 4) and (5, 5) doped tubes. HOMO - LUMO gap of Al doped arm chair carbon nanotubes decreases linearly with the increase in diameter of the tube. This shows that confinement induce a strong effect on electronic properties of doped tubes. These combined systems can be used for future nano electronics. The ab–initio calculations were performed with SIESTA code using generalized gradient approximation (GGA).

  9. Structural and optical characterization of InAs/GaSb type-II superlattices: Influence of the change in InAs and GaSb layer thicknesses for fixed InSb-like interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Arikan, Bulent, E-mail: bulentarikanx@gmail.com; Korkmaz, Melih; Aslan, Bulent; Serincan, Uğur

    2015-08-31

    In this article, we report on the molecular beam epitaxy growth and characterization of a 140 period InAs/GaSb type-II superlattice structure designed for mid infrared detection. Thickness of a period was systematically altered in each sample by changing the thickness of InAs (GaSb) layers from 9 to 7 monolayers (ML) for a fixed GaSb (InAs) layer at 9 ML (7 ML). The same InSb-like strain compensation interface was used for all samples. High resolution X-ray diffraction analysis, spectral responsivity and external quantum efficiency (QE) measurements were performed to express the effects of layer thickness variations on both structural and photodetector features. The decrease in the InAs thickness resulted in the increased mismatch from 0 to + 1626 ppm and the blue shift in the 50% cut-off wavelength (λ{sub c}) from 5.41 to 4.36 μm at 77 K. The additional decrease in GaSb thickness caused further increase in the mismatch up to + 1791 ppm. The steepness of the photoresponse at the absorption band edge was quantified and presented comparatively with different photodetector parameters and material properties for a complete picture. The highest optical response was obtained from sample having 8 ML InAs and 9 ML GaSb with λ{sub c} = 4.76 μm and QE = 23.7% at 4 μm. - Highlights: • Detailed growth conditions for InAs/GaSb SLs designed for infrared detection • Precisely engineering the λ{sub c} and the ∆a{sub ⊥}/a by controlling the SL layer thicknesses • InAs layer thickness changes are more effective than the GaSb on the λ{sub c} and ∆a{sub ⊥}/a.

  10. The psychology of doping.

    Science.gov (United States)

    Elbe, Anne-Marie; Barkoukis, Vassilis

    2017-08-01

    Doping is increasingly becoming a problem in both elite and recreational sports. It is therefore important to understand the psychological factors which can explain doping behavior in order to prevent it. The present paper briefly presents evidence on the prevalence of doping use in competitive sports and the measurement approaches to assess doping behavior and doping-related variables. Furthermore, the integrative theoretical approaches used to describe the psychological processes underlying doping use are discussed. Finally, the paper provides suggestions for appropriate measurement of doping behavior and doping-related variables, key preventive efforts against doping as well as avenues for future research. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Interconnection between zero resistance and magnetic irreversibility temperatures in the hole doped Y0.9Ca0.1Ba2Cu3O7-δ single crystal

    Science.gov (United States)

    Macedo, D. G.; Vieira, V. N.; Dias, F. T.; da Silva, D. L.; Jaeckel, S.; Pureur, P.; Schaf, J.

    2014-12-01

    We report on ac magnetoresistance, R(T,H) and ZFC [MZFC(T)] and FCC [MFCC(T)] dc magnetizations measurements of the a hole doped Y0.9Ca0.1Ba2Cu3O7-δ single crystal with the propose of to disclose the correlation between the zero resistance, TR0(H) and the magnetic irreversibility, Tirr(H) temperatures. The R(T,H) measurements were performed with a PPMS with the measurement current density applied parallel to the sample ab plane. The MZFC(T) and MFCC(T) measurements were performed with a commercial SQUID magnetometer. For the both measurements H 5kOe the TR0(H) data matches to the Tirr(H) data. We attributed to the establishment of a superconducting granular scenario provided for Ca doping as responsible for the observation of these features. At this scenario, Tirr(H) and TR0(H) do not depend of the same parts of the sample. While the Tirr(H) depends on well coupled grain clusters the TR0(H) depends on grain arrays traversing the whole sample. The granular aspect of this result is discussed at the light of the superconducting glass theories.

  12. Synthesis of Antibodies-Conjugated Fluorescent Dye-Doped Silica Nanoparticles for a Rapid Single Step Detection of Campylobacter jejuni in Live Poultry

    Directory of Open Access Journals (Sweden)

    Wachira Tansub

    2012-01-01

    Full Text Available The preparation of antibodies-conjugated fluorescent dye-doped silica nanoparticles (FDS-NPs was developed to detect Campylobacter jejuni cells under a fluorescence microscope. The particles prepared by sol-gel microemulsion techniques have a round shape with an average size of 43 ± 4 nm. They were highly photo stable and could emit strong orange fluorescent for 60 min. Both amine- and carboxyl-functionalized properties were evident from FTIR and FT Raman spectra. The FDS-NPs conjugated with antibodies against C. jejuni were well dispersed in PBS solution at 20 mM of NaCl. The conjugation with monoclonal antibodies against C. jejuni was successful. The direct observation of the antibodies-conjugated FDS-NPs- that bounds C. jejuni with Petroff Hausser counting chamber at 40x was clear. The different focus lengths clearly separated bound and unbound FDS-NPs under the microscope. We successfully synthesis the bio-conjugated dye doped silica nanoparticles for C. jejuni that are easy to use and giving clear detection in due time.

  13. Self-Assembled Fe-N-Doped Carbon Nanotube Aerogels with Single-Atom Catalyst Feature as High-Efficiency Oxygen Reduction Electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Chengzhou [School of Mechanical and Materials Engineering, Washington State University, Pullman WA 99164 USA; Fu, Shaofang [School of Mechanical and Materials Engineering, Washington State University, Pullman WA 99164 USA; Song, Junhua [School of Mechanical and Materials Engineering, Washington State University, Pullman WA 99164 USA; Shi, Qiurong [School of Mechanical and Materials Engineering, Washington State University, Pullman WA 99164 USA; Su, Dong [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton NY 11973 USA; Engelhard, Mark H. [Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland WA 99354 USA; Li, Xiaolin [Energy and Environmental Directory, Pacific Northwest National Laboratory, Richland WA 99354 USA; Xiao, Dongdong [Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland WA 99354 USA; Li, Dongsheng [Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland WA 99354 USA; Estevez, Luis [Energy and Environmental Directory, Pacific Northwest National Laboratory, Richland WA 99354 USA; Du, Dan [School of Mechanical and Materials Engineering, Washington State University, Pullman WA 99164 USA; Lin, Yuehe [School of Mechanical and Materials Engineering, Washington State University, Pullman WA 99164 USA; Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland WA 99354 USA

    2017-02-06

    Finely controlled synthesis of high active and robust non-precious metal catalysts with excellent electrocatalytic efficiency towards oxygen reduction reaction is extremely vital for successful implementation of fuel cells and metal batteries. Unprecedented oxygen reduction reaction electrocatalytic performances and the diversified synthetic procedure in term of favorable structure/morphology characteristics make transition metals-derived M–N–C (M=Fe, Co) structures the most promising nanocatalysts. Herein, using the nitrogen-containing small molecular and inorganic salt as precursors and ultrathin tellurium nanowires as templates, we successfully synthesized a series of well-defined M-N-doped hollow carbon nanowire aerogels through one step hydrothermal route and subsequent facile annealing treatment. Taking advantage of the porous nanostructures, one-dimensional building block as well as homogeneity of active sites, the resultant Fe-N-doped carbon hollow nanowire aerogels exhibited excellent ORR electrocatalytic performance even better than commercial Pt/C in alkaline solution, holding great potential in fuel cell applications.

  14. The influence of exercise and dehydration on the urine concentrations of salbutamol after inhaled administration of 1600 µg salbutamol as a single dose in relation to doping analysis.

    Science.gov (United States)

    Haase, Christoffer Bjerre; Backer, Vibeke; Kalsen, Anders; Rzeppa, Sebastian; Hemmersbach, Peter; Hostrup, Morten

    2016-07-01

    The present study investigated the influence of exercise and dehydration on the urine concentrations of salbutamol after inhalation of that maximal permitted (1600 µg) on the 2015 World Anti-Doping Agency (WADA) prohibited list. Thirteen healthy males participated in the study. Urine concentrations of salbutamol were measured during three conditions: exercise (EX), exercise+dehydration (EXD), and rest (R). Exercise consisted of 75 min cycling at 60% of VO2max and a 20-km time-trial. Fluid intake was 2300, 270, and 1100 mL during EX, EXD, and R, respectively. Urine samples of salbutamol were collected 0-24 h after drug administration. Adjustment of urine concentrations of salbutamol to a specific gravity (USG) of 1.020 g/mL was compared with no adjustment. The 2015 WADA decision limit (1200 ng/mL) for salbutamol was exceeded in 23, 31, and 10% of the urine samples during EX, EXD, and R, respectively, when unadjusted for USG. When adjusted for USG, the corresponding percentages fell to 21, 15, and 8%. During EXD, mean urine concentrations of salbutamol exceeded (1325±599 ng/mL) the decision limit 4 h after administration when unadjusted for USG. Serum salbutamol Cmax was lower (Psalbutamol and increase the risk of Adverse Analytical Findings in samples collected after inhalation of that maximal permitted (1600 µg) for salbutamol. This should be taken into account when evaluating doping cases of salbutamol. Copyright © 2015 John Wiley & Sons, Ltd.

  15. A variable temperature EPR study of Mn(2+)-doped NH(4)Cl(0.9)I(0.1) single crystal at 170 GHz: zero-field splitting parameter and its absolute sign.

    Science.gov (United States)

    Misra, Sushil K; Andronenko, Serguei I; Chand, Prem; Earle, Keith A; Paschenko, Sergei V; Freed, Jack H

    2005-06-01

    EPR measurements have been carried out on a single crystal of Mn(2+)-doped NH(4)Cl(0.9)I(0.1) at 170-GHz in the temperature range of 312-4.2K. The spectra have been analyzed (i) to estimate the spin-Hamiltonian parameters; (ii) to study the temperature variation of the zero-field splitting (ZFS) parameter; (iii) to confirm the negative absolute sign of the ZFS parameter unequivocally from the temperature-dependent relative intensities of hyperfine sextets at temperatures below 10K; and (iv) to detect the occurrence of a structural phase transition at 4.35K from the change in the structure of the EPR lines with temperature below 10K.

  16. High frequency cut-off in 1/f conductivity noise of hole-doped La1-x Ca x MnO3 manganite single crystals

    Science.gov (United States)

    Przybytek, Jacek; Fink-Finowicki, Jan; Puźniak, Roman; Jung, Grzegorz

    2016-05-01

    High frequency bias and temperature-dependent Lorentzian cut-off has been observed in the 1/f spectra of the conductivity fluctuations in low hole-doped ferromagnetic insulating La1-x Ca x MnO3 manganite at low temperatures. The cut-off frequency depends on dc current bias and temperature. The high frequency cut-off has been tentatively associated with intrinsic limits of the appearance of 1/f noise in the hopping regime of the Coulomb glass state. The assumption is validated by the fact that the Efros-Shklovskii temperature {{T}\\text{ES}} , estimated from the fit of the model to the experimentally measured temperature dependence of the cut-off frequency, has the same value as the temperature {{T}\\text{ES}} evaluated independently from the temperature dependence of the resistivity in the corresponding temperature range.

  17. The influence of exercise and dehydration on the urine concentrations of salbutamol after inhaled administration of 1600 µg salbutamol as a single dose in relation to doping analysis

    DEFF Research Database (Denmark)

    Haase, Christoffer Bjerre; Backer, Vibeke; Kalsen, Anders

    2016-01-01

    The present study investigated the influence of exercise and dehydration on the urine concentrations of salbutamol after inhalation of that maximal permitted (1600 µg) on the 2015 World Anti-Doping Agency (WADA) prohibited list. Thirteen healthy males participated in the study. Urine concentrations......-24 h after drug administration. Adjustment of urine concentrations of salbutamol to a specific gravity (USG) of 1.020 g/mL was compared with no adjustment. The 2015 WADA decision limit (1200 ng/mL) for salbutamol was exceeded in 23, 31, and 10% of the urine samples during EX, EXD, and R, respectively......, when unadjusted for USG. When adjusted for USG, the corresponding percentages fell to 21, 15, and 8%. During EXD, mean urine concentrations of salbutamol exceeded (1325±599 ng/mL) the decision limit 4 h after administration when unadjusted for USG. Serum salbutamol Cmax was lower (P

  18. Optical and scintillation properties of Ce-doped (Gd{sub 2}Y{sub 1})Ga{sub 2.7}Al{sub 2.3}O{sub 12} single crystal grown by Czochralski method

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chao; Wu, Yuntao; Ding, Dongzhou; Li, Huanying; Chen, Xiaofeng; Shi, Jian; Ren, Guohao, E-mail: rgh@mail.sic.ac.cn

    2016-06-01

    Multicomponent garnets, due to their excellent light yield and energy resolution, become one of the most promising scintillators used for homeland security and nuclear non-proliferation applications. This work focuses on the optimization of Ce-doped (Gd,Y){sub 3}(Ga,Al){sub 5}O{sub 12} scintillators using a combination strategy of pre-screening and scale-up. Ce-doped Gd{sub x}Y{sub 1−x}Ga{sub y}Al{sub 5−y}O{sub 12} (x=1, 2 and y=2, 2.2, 2.5, 2.7, 3) polycrystalline powders were prepared by high-temperature solid state reaction method. The desired garnet phase in all the samples was confirmed using X-ray diffraction measurement. By comparing the radioluminescence intensity, the highest scintillation efficiency was achieved at a component of Gd{sub 2}Y{sub 1}Ga{sub 2.7}Al{sub 2.3}O{sub 12}:Ce powders. A (Gd{sub 2}Y{sub 1})Ga{sub 2.7}Al{sub 2.3}O{sub 12} doped with 1% Ce single crystal with dimensions of Ø35×40 mm was grown by Czochralski method using a <111> oriented seed. Luminescence and scintillation properties were measured. An optical transmittance of 84% was achieved in the concerned wavelength from 500 to 800 nm. Its 5d–4f emission of Ce{sup 3+} is at 530 nm. The light yield of a Ce1%: Gd{sub 2}Y{sub 1}Ga{sub 2.7}Al{sub 2.3}O{sub 12} single crystal slab at a size of 5×5×1 mm{sup 3} can reach about 65,000±3000 Ph/MeV along with two decay components of 94 and 615 ns under {sup 137}Cs source irradiation.

  19. 1.8 μm luminescent properties and energy transfer of Yb{sup 3+}/Tm{sup 3+} co-doped α-NaYF{sub 4} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Zhigang [Key Laboratory of Photo-electronic Materials, Ningbo University, Ningbo, Zhejiang, 315211 (China); Xia, Haiping, E-mail: hpxcm@nbu.edu.cn [Key Laboratory of Photo-electronic Materials, Ningbo University, Ningbo, Zhejiang, 315211 (China); Wang, Cheng; Zhang, Zhixiong; Jiang, Dongsheng; Zhang, Jian; He, Shinan; Tang, Qingyang; Sheng, Qiguo; Gu, Xuemei; Zhang, Yuepin [Key Laboratory of Photo-electronic Materials, Ningbo University, Ningbo, Zhejiang, 315211 (China); Chen, Baojiu [Department of Physics, Dalian Maritime University, Dalian, Liaoning Province, 116026 (China); Jiang, Haochuan, E-mail: jianghaochuan@nimte.ac.cn [Ningbo Institute of Materials Technology and Engineering, The Chinese Academy of Sciences, Ningbo, Zhejiang, 315211 (China)

    2016-09-25

    This paper reports on successful preparation of α-NaYF{sub 4} single crystals co-doped with ∼1.9 mol% Tm{sup 3+} and various concentrations (3.85 mol%, 7.69 mol%, 11.54 mol%, 15.38 mol%) of Yb{sup 3+} by using a flux-Bridgman method. The fluorescence decay curve was measured to investigate the luminescent properties of the Yb{sup 3+}/Tm{sup 3+} co-doped α-NaYF{sub 4}, and the energy transfer process from Yb{sup 3+} to Tm{sup 3+}; the J-O intensity parameters of Tm{sup 3+} were further calculated and analyzed according to the absorption spectra. Results show that, an intense 1.8 μm emission was achieved with Yb{sup 3+} as sensitizer for Tm{sup 3+} in the α-NaYF{sub 4} single crystal under the excitation of 980 nm LD (Laser Diode) because of the strong energy transfer from Yb{sup 3+} to Tm{sup 3+}. The maximum emission intensity at 1.8 μm is obtained at about 15.38 mol% doping concentration of Yb{sup 3+} when the concentration of Tm{sup 3+} ions is fixed at ∼1.90 mol% in the current research. Moreover, the calculated maximum value of emission cross section at 1.8 μm is 1.63 × 10{sup −20} cm{sup 2} for 3.85 mol% Yb{sup 3+}/1.9 mol% Tm{sup 3+} sample, and the obtained energy transfer rate (W{sub ET}) and energy transfer efficiency (η) are 1543 s{sup −1} and 83.8%, respectively. Our analysis of the fluorescence dynamics indicates that electric dipole-dipole interaction is dominant for the energy transfer from Yb{sup 3+} ions to Tm{sup 3+} ions by using Inokuti-Hirayama’s model. - Highlights: • The Tm{sup 3+}/Yb{sup 3+} co-doped α-NaYF{sub 4} single crystals were grown by Bridgman method. • The 1.8 μm emission intensity is obtained at 15.38 mol% Yb{sup 3+}/1.90 mol% Tm{sup 3+} sample. • The maximum value of emission cross section at 1.8 μm is 1.63 × 10{sup −20} cm{sup 2}. • The energy transfer rate is 1543 s{sup −1} and energy transfer efficiency is 83.8%. • The physical mechanism for energy transfer from Yb{sup 3+} to Tm{sup 3+} ions

  20. The effect of exceptionally high fluorine doping on the anisotropy of single crystalline SmFeAsO1-xFx

    Science.gov (United States)

    Fujioka, Masaya; Denholme, Saleem J.; Tanaka, Masashi; Takeya, Hiroyuki; Yamaguchi, Takahide; Takano, Yoshihiko

    2014-09-01

    We prepared single crystalline SmFeAsO1-xFx with an exceptionally high fluorine concentration by using a CsCl flux method. Comparing to conventional flux methods, this method can introduce about double the amount of fluorine into the oxygen site. The obtained single crystal shows the highest superconducting transition temperature (Tc = 57.5 K) in single crystalline iron pnictides. In addition, the residual resistivity ratio is almost three times as large as that of previously reported single crystals. This suggests that our single crystals are suitable for investigation of the intrinsic superconducting properties, since they have few defects and impurities. Using both the Werthamer-Helfand-Hohenberg model and the effective mass model, we demonstrated that a higher fluorine concentration suppresses the anisotropic superconductivity of SmFeAsO1-xFx.

  1. Influence of manganese doping to the full tensor properties of 0.24Pb(In1/2Nb1/2)O3-0.47Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 single crystals.

    Science.gov (United States)

    Sun, Enwei; Zhang, Rui; Wu, Fengmin; Yang, Bin; Cao, Wenwu

    2013-02-21

    Complete sets of elastic, piezoelectric, dielectric, and electromechanical properties of [001]c and [011]c poled pure and 0.5 wt. % manganese-doped 0.24Pb(In1/2Nb1/2)O3-0.47Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 single crystals have been characterized at room temperature. The results indicate that manganese ion substitution in the B-site of perovskite 0.24PIN-0.47PMN-0.29PT single crystals makes the material harder with much higher mechanical quality factor Qm and slight decrease in piezoelectric and dielectric constants. The much improved Qm value (200-900) makes Mn-doped single crystals more suitable for high-power transducer applications than pure single crystals.

  2. Analysis of single and binary phases in cerium doped sodium bismuth titanate -inorganic materials Na{sub 0}.5Bi{sub (}0.5-x)Ce{sub x}TiO{sub 3}; Estudio de fases simples y binarias en BNT puro y dopado con cerio Na{sub 0},5Bi{sub (}0,5-x)Ce{sub x}TiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Supriya, S.; Dos Santos-Garcia, A. J.; Frutos, J. de; Fernandez-Martinez, F.

    2015-07-01

    The pure and cerium doped sodium bismuth titanate (NBT) inorganic powders were synthesized by solid-state reaction method. The presence of rhombohedral phase was observed in cerium doped NBT compounds. When x= 0.05 of cerium doped NBT is heat treated at 1200 degree centigrade, the compound forms single perovskite phase. The samples of x = 0.10 and 0.15 were heat treated up to 1350 degree centigrade, the binary phases with cerium and bismuth oxides were observed. The X-ray diffraction, Fourier transform infrared spectroscopy, reflectance spectra, differential thermal analysis and thermogravimetric analysis were used to analyze the various properties of samples. Moreover, the effects of cerium doping and calcining temperature on NBT samples were investigated. In this work, we present our recent results on the synthesis and characterization of cerium doped sodium bismuth titanate materials. (Author)

  3. Synthesis of undoped and manganese-doped hgte nanoparticles using [Hg(TeCH2CH2NMe2)2] as a single source precursor.

    Science.gov (United States)

    Kedarnath, Gotluru; Dey, Sandip; Jain, Vimal K; Dey, Gautam K; Kadam, Ramakant M

    2008-09-01

    The Reaction of [HgCl2(tmeda)] with NaTeCH2CH2NMe2 gave a mercury tellurolate, [Hg(TeCH2CH2. NMe2)2] (1) as a yellow crystalline solid, which was characterized by elemental analysis, UV-vis, mass and NMR (1H, 13C, 125Te, 199Hg) spectroscopy. Thermolysis of 1 in hexadecylamine (HDA) at 90 degrees C in the absence and presence of Mn(OAc)2.4H2O gave undoped and Mn-doped HgTe nanoparticles which were characterized by XRD, EDAX, TEM, EPR and magnetic measurements. These particles could be synthesized with mean particle size of 6-7 nm (from TEM). Manganese substitution at Hg site in HgTe lead to a linear decrease in lattice parameter with increasing concentration of Mn. Magnetization measurements showed ferromagnetic ordering at room temperature with very small coercive field (Hc, 50 Oe) for Hg0.973 Mn0.027 Te sample. This sample also exhibited distinct ferromagnetic resonance (FMR) in the EPR spectrum.

  4. Spectroscopic and laser properties of BeLaAl11O19 single crystals doped with Cr3+, Ti3+, and Nd3+ ions

    Science.gov (United States)

    Pestryakov, Efim V.; Petrov, V. V.; Trunov, V. I.; Kirpichnikov, A. V.; Alimpiev, A. I.

    2001-03-01

    The new laser crystals BeLaAl11O19 doped with Cr3+, Ti3+ and Nd3+ ions were grown by the Czochralski technique. The absorption and fluorescence spectra of impurity ions are reported and the temperature dependence of the fluorescence lifetime are described. The laser properties of these ions were investigated. The laser action has been achieved on 4F3/2-4I11/2 (1052 nm) transition of Nd3+ -ions under selective laser pumping. The physical properties of BeLaAl11O19 crystal were studied: the values of all independent component of elastic constant tensor were determined. On the base of a number of dynamic parameters of crystals, such as Young's modulus, the shear modulus, the volume elasticity modulus and Poisson's factor, Debye temperature and specific heat capacity were calculated. The investigation show that the BeLaAl11O19 is a promising host for a creature the new solid state laser media.

  5. Aptameric Recognition-Modulated Electroactivity of Poly(4-Styrenesolfonic Acid)-Doped Polyaniline Films for Single-Shot Detection of Tetrodotoxin

    Science.gov (United States)

    Fomo, Gertrude; Waryo, Tesfaye T.; Sunday, Christopher E.; Baleg, Abd A.; Baker, Priscilla G.; Iwuoha, Emmanuel I.

    2015-01-01

    The work being reported is the first electrochemical sensor for tetrodotoxin (TTX). It was developed on a glassy carbon electrodes (C) that was modified with poly(4-styrenesolfonic acid)-doped polyaniline film (PANI/PSSA). An amine-end functionalized TTX-binding aptamer, 5′-NH2-AAAAATTTCACACGGGTGCCTCGGCTGTCC-3′ (NH2-Apt), was grafted via covalent glutaraldehyde (glu) cross-linking. The resulting aptasensor (C//PANI+/PSSA-glu-NH2-Apt) was interrogated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in sodium acetate buffer (NaOAc, pH 4.8) before and after 30 min incubation in standard TTX solutions. Both CV and EIS results confirmed that the binding of the analyte to the immobilized aptamer modulated the electrochemical properties of the sensor: particularly the charge transfer resistance (Rct) of the PANI+/PSSA film, which served as a signal reporter. Based on the Rct calibration curve of the TTX aptasensor, the values of the dynamic linear range (DLR), sensitivity and limit of detection (LOD) of the sensor were determined to be 0.23–1.07 ng·mL−1 TTX, 134.88 ± 11.42 Ω·ng·mL−1 and 0.199 ng·mL−1, respectively. Further studies are being planned to improve the DLR as well as to evaluate selectivity and matrix effects in real samples. PMID:26370994

  6. Multi-minimum adiabatic potential in the single crystal normal spinel ZnAl{sub 2}O{sub 4}, doped by Cu{sup 2+} ions

    Energy Technology Data Exchange (ETDEWEB)

    Shapovalov, V A; Zhitlukhina, E S; Lamonova, K V; Orel, S M; Pashkevich, Yu G [A A Galkin Donetsk Institute for Physics and Engineering of NASU, 83114, Donetsk (Ukraine); Shapovalov, V V; Rafailovich, M [Garcia Center for Polymers at Engineered Interfaces, Department of Materials Science and Engineering, SUNY Stony Brook, NY 11794 (United States); Schwarz, S A [Department of Physics, Queens College of the City University of New York, NY 11367 (United States); Jahoda, R; Reidy, V J, E-mail: lamonova@fti.dn.u [Bronx High School of Science, NY 10468 (United States)

    2010-06-23

    Spectroscopic investigations of a ZnAl{sub 2}O{sub 4} spinel doped with bivalent copper ions of 0.05% concentration have been carried out in the temperature range 4.2-290 K using a 3 cm{sup -1} range electron paramagnetic resonance (EPR) spectrometer having an operational frequency f = (9.241 {+-} 0.001) GHz. The spectrum can be represented as a superposition of two components: a low-temperature (LT) and a high-temperature (HT) one. Redistribution of integrated intensity between HT and LT components of the spectra occurs with temperature change that is typical of systems with multi-minimum adiabatic potential. Spectra observed are explained within the modified theory of crystalline field (MTCF). The electron levels of a Cu{sup 2+} ion placed in an octahedral coordination center with trigonal distortion [CuO{sub 6}]{sup 10-} have been calculated. The influence of possible types of oxygen octahedron distortions and possible displacement of copper ions from the symmetry center on the electron spectrum, as well as the shape of the adiabatic potential, has been analyzed. It is shown that in the low-temperature phase the multiple minima of the adiabatic potential occur due to tetragonal distortions while the depth of a minimum is determined by the degree of trigonal octahedron distortions. Tetragonal distortion values and multi-minimum potential barrier heights have been determined.

  7. Effects of single O vacancy on the magnetism and electronic structure of Ti doped CoO: A first principle study

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, J. [Tianjin Key Laboratory of Film Electronic & Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300191 (China); Wang, X.C., E-mail: wangxccn@126.com [Tianjin Key Laboratory of Film Electronic & Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300191 (China); Chen, G.F. [School of Material Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Yang, B.H. [Tianjin Key Laboratory of Film Electronic & Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300191 (China)

    2015-12-15

    The electronic structure and magnetism of Co{sub 14}Ti{sub 2}O{sub 15} systems are investigated by first-principles calculations. CoO is an antiferromagnetic insulator. The Ti doped CoO at positions 9 and 11 shows a half-metallic character. The O vacancy near Ti has a great effect on Ti magnetic moment due to the electron transfer. When the O vacancy at position 6 or 9, the Ti magnetic moment is very small and the systems are magnetic insulator. As the O vacancy locates at position 1, the Ti magnetic moment is smaller than that in Co{sub 14}Ti{sub 2}O{sub 16} system, showing a metallic character that makes its conductivity enhanced. The system with O vacancy at position 2 shows a half-metallic character due to the strong hybridization between Ti and Co atoms. The system with O vacancy at position 5 shows a metallic character; the system with O vacancy at position 13 or 14 shows a half-metallic character. - Highlights: • When the O vacancies at 6 position and 9, the systems are magnetic insulator. • The system with O vacancy at position 5 shows the metallic characteristic. • The system with O vacancy at position 2, 13 or 14 shows a half-metallic character.

  8. Growth and luminescent properties of single crystalline films of Ce3+ doped Pr1-xLuxAlO3 and Gd1-xLuxAlO3 perovskites

    Science.gov (United States)

    Zorenko, Yu; Gorbenko, V.; Zorenko, T.; Voznyak, T.; Riva, F.; Douissard, P. A.; Martin, T.; Fedorov, A.; Suchocki, A.; Zhydachevskii, Ya.

    2017-01-01

    The paper is dedicated to development of UV emitting scintillating screens for microimaging applications based on the single crystalline films (SCFs) of Ce doped Gd1-xLuxAlO3 and Pr1-xLuxAlO3 (x=0-1) multicomponent perovskites grown onto YAlO3 (YAP) substrates using the liquid phase epitaxy (LPE) method with the objective to improve the X-ray stopping power. Recently Riva et al. [1] have reported that the full set of GdxLu1-xAlO3 SCFs with x values in x=0-1.0 range can be crystallized on YAP substrates using this technique. We report here that PrxLu1-xAlO3 SCFs with x values in x=0-0.5 range can be grown also by the LPE method from PbO-B2O3 flux onto the same YAP substrates. The structural quality of the films was studied using X-ray diffraction. The optical properties of Ce3+ doped of Gd1-xLuxAlO3 and Pr1-xLuxAlO3 (x=0-1) multicomponent perovskite films, studied by traditional spectroscopic methods, such as absorption, cathodoluminescence, photoluminescence and light yield measurements under α-particles excitation, are also reported in this work. We have shown that Pb2+ flux related impurity has significantly larger influence on the light yield of Pr0.5Lu0.5AlO3:Ce, GdAlO3:Ce and Gd0.5Lu0.5AlO3:Ce SCFs in comparison with the YAP:Ce and LuAlO3:Ce counterparts grown onto YAP substrates.

  9. Internal static electric and magnetic field at the copper cite in a single crystal of the electron-doped high-Tc superconductor Pr1.85Ce0.15CuO4 -y

    Science.gov (United States)

    Wu, Guoqing; Zamborszky, F.; Reyes, A. P.; Kuhns, P. L.; Greene, R. L.; Clark, W. G.

    2014-12-01

    We report 63 ,65Cu -NMR spectroscopy and Knight shift measurements on a single crystal of the electron-doped high-Tc superconductor Pr1.85Ce0.15CuO4 -y with an applied magnetic field (H ) up to 26.42 T. A very small NQR frequency is obtained with the observation of the spectrum, which shows an extremely wide continuous distribution of it that becomes significantly narrower below 20 K at H ∥c where the superconductivity is completely suppressed, indicating a significant change in the charge distribution at the Cu site, while the corresponding change at H ⊥c is negligible when the superconductivity is present or not fully suppressed. The Knight shift and central linewidth are proportional to the applied magnetic field with a high anisotropy. We find that the magnitude of the internal static magnetic field at the copper is dominated by the anisotropic Cu2 + 3 d orbital contributions, while its weak temperature dependence is mainly determined by the isotropic contact hyperfine coupling to the paramagnetic Pr3 + spins, which also gives rise to the full distribution of the internal static magnetic field at the copper for H ⊥c . This internal static electric and magnetic field environment at the copper is very different from that in the hole-doped cuprates, and may provide new insight into the understanding of high-Tc superconductivity. Other experimental techniques are needed to verify whether the observed significant narrowing of the charge distribution at the Cu site with H ∥c is caused by the charge ordering [E. H. da Silva Neto et al., Science (to be published, 2014)] or a new type of charge modulation.

  10. Single mode solid state distributed feedback dye laser fabricated by grey scale electron beam lithography on dye doped SU-8 resist

    DEFF Research Database (Denmark)

    Balslev, Søren; Rasmussen, Torben; Shi, Peixiong

    2005-01-01

    are optically pumped at 532 nm, and exhibit low lasing threshold from 530 nJ/mm2 and single mode output at selectable wavelengths from 580 to 630 nm, determined by the grating pitch. The lasers are well suited for integration into polymer based lab-on-chip circuits for interference based sensing....

  11. Crystal growth and evaluation of scintillation properties of Eu and alkali-metal co-doped LiSrAlF{sub 6} single crystals for thermal neutron detector

    Energy Technology Data Exchange (ETDEWEB)

    Wakahara, Shingo; Yokota, Yuui; Yamaji, Akihiro; Fujimoto, Yutaka; Sugiyama, Makoto; Kurosawa, Shunsuke [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Yanagida, Takayuki [New Industry Creation Hatchery Center (NICHe), 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Pejchal, Jan [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Institute of Physics AS CR, Cukrovarnicka 10, Prague 16253 (Czech Republic); Kawaguchi, Noriaki [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Tokuyama, Co. Ltd., Shibuya 3-chome, Shibuya-ku, Tokyo 150-8383 (Japan); Fukuda, Kentaro [Tokuyama, Co. Ltd., Shibuya 3-chome, Shibuya-ku, Tokyo 150-8383 (Japan); Yoshikawa, Akira [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan)

    2012-12-15

    In recent work, Na co-doping have found to improve the light output of Eu doped LiCaAlF{sub 6} (Eu:LiCAF) for thermal neutron scintillator. We grew Eu 2% and alkali metal 1% co-doped LiSAF crystals by Micro-Pulling down method to understand the effect of alkali metal co-doping on scintillation properties and mechanism compared with LiCAF. In photo- and {alpha}-ray induced radio-luminescence spectra of the all grown crystals, the emissions from d-f transition of Eu{sup 2+} were observed. Without relation to excitation source, decay times of co-doped LiSAF were longer than Eu only doped one. The light yield of Na, K and Cs co-doped LiSAF under {sup 252}Cf neutron excitation were improved. Especially, K co-doped Eu:LiSAF reached 33200 ph/n, which outperformed Eu only doped one by approximately 20% (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Structure-property relations in new fluorophosphate glasses singly- and co-doped with Er{sup 3+} and Yb{sup 3+}

    Energy Technology Data Exchange (ETDEWEB)

    Gonçalves, Tássia S.; Moreira Silva, Raphaell J.; Oliveira Junior, Marcos de; Ferrari, Cynthia R. [Physics Institute of São Carlos, University of São Paulo, São Carlos, SP 13566-590 (Brazil); Poirier, Gäel Y. [Science and Technology Institute, Federal University of Alfenas, Poços de Caldas, MG 37715-400 (Brazil); Eckert, Hellmut, E-mail: eckert@ifsc.usp.br [Physics Institute of São Carlos, University of São Paulo, São Carlos, SP 13566-590 (Brazil); Physical Chemistry Institute, Westfälische Wilhelms Universität Münster, Münster D-48149 (Germany); Camargo, Andrea S.S. de, E-mail: andreasc@ifsc.usp.br [Physics Institute of São Carlos, University of São Paulo, São Carlos, SP 13566-590 (Brazil)

    2015-05-01

    Rare earth (RE{sup 3+})-doped fluorophosphate glasses are among the most promising candidates for high-efficiency laser generation in the near-infrared spectral region. By proper choice of composition, these materials can combine the advantages of fluorides (low phonon energies, low refractive indices, extensive optical window, low hygroscopicity) and of oxides (high chemical and mechanical stability and high dopant solubility), resulting in enhancement of the RE{sup 3+} emissive properties. In this work, we present the synthesis and structural/spectroscopic investigation of new glasses with composition 25BaF{sub 2}25SrF{sub 2}(30-x)Al(PO{sub 3}){sub 3}xAlF{sub 3}(20-z)YF{sub 3}:zREF{sub 3}, where x = 20 or 15, RE = Er{sup 3+} and/or Yb{sup 3+}, z = 0.25–5.0 mol%. Results indicate considerable improvement of the emissive properties of both ions when compared to phosphate or even other fluorophosphate host compositions. Long excited state lifetimes (τ = 10 ms for the Er{sup 3+} level {sup 4}I{sub 13/2}, and τ = 1.3 ms for the Yb{sup 3+} level {sup 2}F{sub 5/2}) imply high fluorescence quantum efficiencies η (up to 85% for both ions). Structural characterization by Raman and multinuclear solid state NMR spectroscopies indicate that the metaphosphate-type chain structure of the Al(PO{sub 3}){sub 3} vitreous framework is partially depolymerized and dominated by Q{sup (0)} and Q{sup (1)} units crosslinked by six-coordinate Al species. As revealed by {sup 27}Al{"3"1P} rotational echo double resonance (REDOR) NMR results the average local aluminum environment of the x = 20 sample comprises 1.6 phosphate and 4.4 fluoride species. These results indicate a clear bonding preference between aluminum and phosphorus, which is consistent with the desired dominance of fluoride species in the local environment of the rare earth and alkaline earth atoms in these glasses. - Highlights: • New fluorophosphate glass composition with excellent photophysical properties.

  13. Improvement of refrigerant capacity of La0.67Ca0.33MnO3single crystal with a few percent Fe doping

    Institute of Scientific and Technical Information of China (English)

    LI GuoKe; ZHANG XiangQun; KOU ZhiQi; LI QingAn; SUN Young; CHENG ZhaoHua

    2009-01-01

    Large low-field-induced magnetic entropy changes, ASM, are observed in La0.67Ca0.33MnO3 and La0.67∞ Ca0.33Mn0.96Fe0.04O3 single crystals. The peaks of △SM broadened asymmetrically to high temperatures under higher magnetic fields for two materials should be attributed to the first-order magnetic phase material though the magnetic entropy change decreases. The discovery of excellent magnetocaloric features of these single crystals in the low magnetic field can provide some ideas for exploring novel magnetic refrigerants operating under permanent magnet rather than superconducting one as magnetic field source.

  14. Generation of 130 W narrow-linewidth high-peak-power picosecond pulses directly from a compact Yb-doped single-stage fiber amplifier

    Science.gov (United States)

    Qi, Yaoyao; Yu, Haijuan; Zhang, Jingyuan; Wang, Lei; Zhang, Ling; Lin, Xuechun

    2015-09-01

    We report a compact, 130-W single-stage master oscillator power amplifier with a high peak power of 51.3 kW and a narrow spectral linewidth of 0.1 nm. The seed source is a single-mode, passively mode-locked solid-state laser at 1064 nm with an average power of 2 W. At a repetition rate of 73.5 MHz, the pulse duration is 30 ps. After amplification, it stretches to 34.5 ps. The experiment enables the optical-to-optical conversion efficiency to reach 75%. To the best of our knowledge, this is the first report of such a high-power, narrow spectral linewidth, high peak power picosecond-pulse fiber amplifier based on a continuous-wave, mode-locked solid-state seeding laser. No amplified spontaneous emission and stimulated Raman scattering were observed when the pump was increased.

  15. Growth and scintillation properties of 3 in. diameter Ce doped Gd3Ga3Al2O12 scintillation single crystal

    Science.gov (United States)

    Kamada, Kei; Shoji, Yasuhiro; Kochurikhin, Vladimir V.; Okumura, Satoshi; Yamamoto, Seiichi; Nagura, Aya; Yeom, Jung Yeol; Kurosawa, Shunsuke; Yokota, Yuui; Ohashi, Yuji; Nikl, Martin; Yoshikawa, Akira

    2016-10-01

    The 3 in. size Ce1%:Gd3Al2Ga3O12 single crystals were prepared by the Czochralski (Cz) method. Optical constants were measured. Chemical composition analysis and uniformity of scintillation decay and light yield along growth direction were evaluated. The timing resolution measurement for a pair of 3 mm×3 mm×3 mm size Ce:GAGG scintillator crystals was performed using Si-PMs.

  16. The single cell of low temperature solid oxide fuel cell with sodium carbonate-SDC (samarium-doped ceria) as electrolyte and biodiesel as fuel

    Science.gov (United States)

    Rahmawati, F.; Nuryanto, A.; Nugrahaningtyas, K. D.

    2016-02-01

    In this research NSDC (composite of Na2CO3-SDC) was prepared by the sol-gel method to produce NSDC1 and also by the ceramic method to produce NSDC2. The prepared NSDC then were analyzed by XRD embedded with Le Bail refinement to study the change of characteristic peaks, their crystal structure, and their cell parameters. Meanwhile, the measurement of impedance was conducted to study the electrical conductivity of the prepared materials. A single cell was prepared by coating NSDC-L (a composite of NSDC with Li0.2Ni0.7Cu0.1O2) on both surfaces of NSDC. The NSDC-L was used as anode and cathode. The ionic conductivity of NSDC1 and NSDC2 at 400 oC are 4.1109 x 10-2 S.cm-1 and 1.6231 x 10-2 S.cm-1, respectively. Both electrolytes have ionic conductivity higher than 1 x 10-4 S.cm-1, therefore, can be categorized as good electrolyte [1]. However, the NSDC1 shows electrodeelectrolyte conduction. It indicates the existence of electronic migration from electrolyte- electrode or vice versa. Those may cause a short circuit during fuel cell operation and will reduce the fuel cell performance fastly. The single cell tests were conducted at 300, 400, 500 and 600 °C. The single fuel cell with NSDC1 and NSDC2 as electrolyte show maximum power density at 400 °C with the power density of 3.736 x 10-2 mW.cm-2 and 2.245 x 10-2 mW.cm-2, respectively.

  17. Controllable optical modulation of blue/green up-conversion fluorescence from Tm3+ (Er3+) single-doped glass ceramics upon two-step excitation of two-wavelengths

    Science.gov (United States)

    Chen, Zhi; Kang, Shiliang; Zhang, Hang; Wang, Ting; Lv, Shichao; Chen, Qiuqun; Dong, Guoping; Qiu, Jianrong

    2017-04-01

    Optical modulation is a crucial operation in photonics for network data processing with the aim to overcome information bottleneck in terms of speed, energy consumption, dispersion and cross-talking from conventional electronic interconnection approach. However, due to the weak interactions between photons, a facile physical approach is required to efficiently manipulate photon-photon interactions. Herein, we demonstrate that transparent glass ceramics containing LaF3: Tm3+ (Er3+) nanocrystals can enable fast-slow optical modulation of blue/green up-conversion fluorescence upon two-step excitation of two-wavelengths at telecom windows (0.8-1.8 μm). We show an optical modulation of more than 1500% (800%) of the green (blue) up-conversion fluorescence intensity, and fast response of 280 μs (367 μs) as well as slow response of 5.82 ms (618 μs) in the green (blue) up-conversion fluorescence signal, respectively. The success of manipulating laser at telecom windows for fast-slow optical modulation from rear-earth single-doped glass ceramics may find application in all-optical fiber telecommunication areas.

  18. Optical and magnetic spectroscopy of rare-earth-doped yttrium aluminium borate (YAl sub 3 (BO sub 3) sub 4) single crystals

    CERN Document Server

    Watterich, A; Borowiec, M T; Zayarnyuk, T; Szymczak, H; Beregi, E; Kovács, L G

    2003-01-01

    For Ce sup 3 sup + , Er sup 3 sup + and Yb sup 3 sup + ions, electron paramagnetic resonance (EPR) spectra typical for S' = 1/2 ions are measured for YAl sub 3 (BO sub 3) sub 4 (YAB) single crystal. The spectra show axial symmetry indicating that all three dopants replace Y sup 3 sup + at the given dopant concentration. Corresponding g-tilde - and hyperfine A-tilde -tensors are determined. The EPR linewidth of Ce broadens with increasing temperature due to an Orbach relaxation process. Fitting the curve with an exponential, the energy difference is found to be equal to 270 +- 16 cm sup - sup 1. The optical absorption and excitation spectra of Ce in YAB single crystal measured at 300 K are similar to those found for polycrystalline materials. High-resolution polarized emission from the lowest excited to the sup 2 F sub 5 sub / sub 2 ground state, measured at 4.2 K, indicates a splitting of the ground state into three levels. The second level is located 277 +- 18 cm sup - sup 1 above the first one, in excellent...

  19. Doped semiconductor nanocrystal junctions

    Energy Technology Data Exchange (ETDEWEB)

    Borowik, Ł.; Mélin, T., E-mail: thierry.melin@isen.iemn.univ-lille1.fr [Institut d’Electronique, de Microélectronique et de Nanotechnologie, CNRS-UMR8520, Avenue Poincaré, F-59652 Villeneuve d’Ascq (France); Nguyen-Tran, T.; Roca i Cabarrocas, P. [Laboratoire de Physique des Interfaces et des Couches Minces, CNRS-UMR7647, Ecole Polytechnique, F-91128 Palaiseau (France)

    2013-11-28

    Semiconductor junctions are the basis of electronic and photovoltaic devices. Here, we investigate junctions formed from highly doped (N{sub D}≈10{sup 20}−10{sup 21}cm{sup −3}) silicon nanocrystals (NCs) in the 2–50 nm size range, using Kelvin probe force microscopy experiments with single charge sensitivity. We show that the charge transfer from doped NCs towards a two-dimensional layer experimentally follows a simple phenomenological law, corresponding to formation of an interface dipole linearly increasing with the NC diameter. This feature leads to analytically predictable junction properties down to quantum size regimes: NC depletion width independent of the NC size and varying as N{sub D}{sup −1/3}, and depleted charge linearly increasing with the NC diameter and varying as N{sub D}{sup 1/3}. We thus establish a “nanocrystal counterpart” of conventional semiconductor planar junctions, here however valid in regimes of strong electrostatic and quantum confinements.

  20. Luminescence properties of Er3+/Nd3+ co-doped Na5Lu9F32 single crystals for 2.7 μm mid-infrared laser

    Science.gov (United States)

    Tang, Qingyang; Xia, Haiping; Sheng, Qiguo; He, Shinan; Zhang, Jianli; Chen, Baojiu

    2017-10-01

    The enhanced 2.7 μm mid-infrared emission from the Er3+:4I11/2 → 4I13/2 transition with Nd3+ ions as the sensitizer was achieved in the Na5Lu9F32 single crystal which was successfully grown by a Bridgman method. The transmission spectrum was tested and almost no absorption of 2.7 μm band was observed. It was indicated that the content of OH- ion was very low in the crystal and it was beneficial to the 2.7 μm mid-infrared laser output. Intense 2.7 μm emissions were achieved with Nd3+ ions sensitizing Er3+ ions under the 800 nm LD pumping and the energy transfer processes between Er3+ and Nd3+ ions were analyzed. Meanwhile, the greatly decreased near infrared emission at 1.5 μm and green up-conversion emission were obtained. Additionally, the optimized concentration ratio of Er3+ to Nd3+ for efficient 2.7 μm emission was investigated in this work and the maximum emission cross section at 2.7 μm was calculated. The decay curve of 1.5 μm emission could be well fitted by Inokuti-Hirayama expression, which was strongly indicated the dipole-dipole energy transfer from Er3+ to Nd3+ ions. The results showed that Er3+/Nd3+ co-doped Na5Lu9F32 single crystal had potential applications in 2.7 μm mid-infrared laser.