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Sample records for binary gallium-rare-earth chalcogenides

  1. Growth Mechanism of Nanowires: Binary and Ternary Chalcogenides

    NASA Technical Reports Server (NTRS)

    Singh, N. B.; Coriell, S. R.; Su, Ching-Hua; Hopkins, R. H.; Arnold, B.; Choa, Fow-Sen; Cullum, Brian

    2016-01-01

    Semiconductor nanowires exhibit very exciting optical and electrical properties including high transparency and a several order of magnitude better photocurrent than thin film and bulk materials. We present here the mechanism of nanowire growth from the melt-liquid-vapor medium. We describe preliminary results of binary and ternary selenide materials in light of recent theories. Experiments were performed with lead selenide and thallium arsenic selenide systems which are multifunctional material and have been used for detectors, acousto-optical, nonlinear and radiation detection applications. We observed that small units of nanocubes and elongated nanoparticles arrange and rearrange at moderate melt undercooling to form the building block of a nanowire. Since we avoided the catalyst, we observed self-nucleation and uncontrolled growth of wires from different places. Growth of lead selenide nanowires was performed by physical vapor transport method and thallium arsenic selenide nanowire by vapor-liquid-solid (VLS) method. In some cases very long wires (>mm) are formed. To achieve this goal experiments were performed to create situation where nanowires grew on the surface of solid thallium arsenic selenide itself.

  2. Growth mechanism of nanowires: binary and ternary chalcogenides

    NASA Astrophysics Data System (ADS)

    Singh, N. B.; Coriell, S. R.; Su, Ching Hua; Hopkins, R. H.; Arnold, B.; Choa, Fow-Sen; Cullum, Brian

    2016-05-01

    Semiconductor nanowires exhibit very exciting optical and electrical properties including high transparency and a several order of magnitude better photocurrent than thin film and bulk materials. We present here the mechanism of nanowire growth from the melt-liquid-vapor medium. We describe preliminary results of binary and ternary selenide materials in light of recent theories. Experiments were performed with lead selenide and thallium arsenic selenide systems which are multifunctional material and have been used for detectors, acoustooptical, nonlinear and radiation detection applications. We observed that small units of nanocubes and elongated nanoparticles arrange and rearrange at moderate melt undercooling to form the building block of a nanowire. Since we avoided the catalyst, we observed self-nucleation and uncontrolled growth of wires from different places. Growth of lead selenide nanowires was performed by physical vapor transport method and thallium arsenic selenide nanowire by vapor-liquid-solid (VLS) method. In some cases very long wires (>mm) are formed. To achieve this goal experiments were performed to create situation where nanowires grew on the surface of solid thallium arsenic selenide itself.

  3. Compositional trends of γ-induced optical changes observed in chalcogenide glasses of binary As-S system

    SciTech Connect

    Shpotyuk, M.; Shpotyuk, O.; Golovchak, Roman; McCloy, John S.; Riley, Brian J.

    2014-01-23

    Compositional trends of γ-induced optical changes in chalcogenide glasses are studied with the binary As-S system. Effects of γ-irradiation and annealing are compared using the changes measured in the fundamental optical absorption edge region. It is shown that annealing near the glass transition temperature leads to bleaching of As-S glasses, while γ-irradiation leads to darkening; both depend on the glass composition and thermal history of the specimens. These results are explained in terms of competitive destruction–polymerization transformations and physical aging occurring in As-S chalcogenide glasses under the influence of γ-irradiation.

  4. Metal–metal chalcogenide molecular precursors to binary, ternary, and quaternary metal chalcogenide thin films for electronic devices

    DOE PAGES

    Zhang, Ruihong; Cho, Seonghyuk; Lim, Daw Gen; ...

    2016-03-15

    We found that bulk metals and metal chalcogenides dissolve in primary amine–dithiol solvent mixtures at ambient conditions. Thin-films of CuS, SnS, ZnS, Cu2Sn(Sx,Se1-x)3, and Cu2ZnSn(SxSe1-x)4 (0 ≤ x ≤ 1) were deposited using the as-dissolved solutions. Furthermore, Cu2ZnSn(SxSe1-x)4 solar cells with efficiencies of 6.84% and 7.02% under AM1.5 illumination were fabricated from two example solution precursors, respectively.

  5. Metal-metal chalcogenide molecular precursors to binary, ternary, and quaternary metal chalcogenide thin films for electronic devices.

    PubMed

    Zhang, Ruihong; Cho, Seonghyuk; Lim, Daw Gen; Hu, Xianyi; Stach, Eric A; Handwerker, Carol A; Agrawal, Rakesh

    2016-04-11

    Bulk metals and metal chalcogenides are found to dissolve in primary amine-dithiol solvent mixtures at ambient conditions. Thin-films of CuS, SnS, ZnS, Cu2Sn(S(x),Se(1-x))3, and Cu2ZnSn(S(x)Se(1-x))4 (0 ≤ x ≤ 1) were deposited using the as-dissolved solutions. Cu2ZnSn(S(x)Se(1-x))4 solar cells with efficiencies of 6.84% and 7.02% under AM1.5 illumination were fabricated from two example solution precursors, respectively.

  6. Cluster synthesis via ligand-arrested solid growth: triethylphosphine-capped fragments of binary metal chalcogenides.

    PubMed

    Crawford, Nathan R M; Hee, Allan G; Long, Jeffrey R

    2002-12-18

    A new and potentially highly generalizable technique for synthesizing molecular fragments of binary solids is demonstrated through application to selected transition metal chalcogenides. Employing a metal atom reactor, the solids are evaporated with a tungsten heating boat, and the resulting vapor is co-condensed with triethylphosphine. Major cluster products identified from a survey of first-row transition metal sulfides include the known species Cr6S8(PEt3)6, Co6S8(PEt3)6, and Cu12S6(PEt3)8, as well as the unprecedented species Fe4S4(PBun3)4, Ni4S4(PEt3)8, and Cu6S4(PEt3)4. Reactions utilizing Cu2Se resulted in the much larger clusters Cu26Se13(PEt3)14 and Cu70Se35(PEt3)21. The core of the former has a Th-symmetry structure featuring a body-centered icosahedron of Se2- anions, while the latter adopts a triangular structure based on three hexagonal closest packed layers of Se2- anions. In both cases, the Cu+ cations occupy distorted tetrahedral or trigonal planar sites similar to those encountered in Cu2Se; however, emergence of the face-centered cubic anion lattice of the bulk solid is not yet apparent at these cluster sizes.

  7. Metal–metal chalcogenide molecular precursors to binary, ternary, and quaternary metal chalcogenide thin films for electronic devices

    SciTech Connect

    Zhang, Ruihong; Cho, Seonghyuk; Lim, Daw Gen; Hu, Xianyi; Stach, Eric A.; Handwerker, Carol A.; Agrawal, Rakesh

    2016-03-15

    We found that bulk metals and metal chalcogenides dissolve in primary amine–dithiol solvent mixtures at ambient conditions. Thin-films of CuS, SnS, ZnS, Cu2Sn(Sx,Se1-x)3, and Cu2ZnSn(SxSe1-x)4 (0 ≤ x ≤ 1) were deposited using the as-dissolved solutions. Furthermore, Cu2ZnSn(SxSe1-x)4 solar cells with efficiencies of 6.84% and 7.02% under AM1.5 illumination were fabricated from two example solution precursors, respectively.

  8. Controlling the assembly of chalcogenide anions in ionic liquids: from binary Ge/Se through ternary Ge/Sn/Se to binary Sn/Se frameworks.

    PubMed

    Lin, Yumei; Massa, Werner; Dehnen, Stefanie

    2012-10-15

    Seven compounds with binary or ternary Ge/Se, Ge/Sn/Se, or Sn/Se anionic substructures crystallized upon the ionothermal reactions of [K(4)(H(2)O)(3)][Ge(4)Se(10)] with SnCl(4)·5H(2)O or SnCl(2) in [BMMIm][BF(4)] or [BMIm][BF(4)] (BMMIm=1-butyl-2,3-dimethyl-imidazolium, BMIm=1-butyl-3-methyl-imidazolium). The products were obtained by subtly varying the reaction conditions; the nature and amount of an additional amine was the most important parameter in the product selection and in determining the Sn/Ge ratio in the isolated products. The crystal structures of these chalcogenides were based on complex anions with unprecedented topologies that varied from discrete clusters (0D) through 1D chain structures or 2D layers to 3D frameworks. The architecture and composition of the title compounds were well reflected by their optical absorption behavior. Herein, we report a convenient approach for the generation of chalcogenidometallate phases with fine-tunable electronic properties in ionic liquids, which have been inaccessible by traditional methods.

  9. Effects of doping of calcium atom(s) on structural, electronic and optical properties of binary strontium chalcogenides - A theoretical investigation using DFT based FP-LAPW methodology

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Rahul; Chattopadhyaya, Surya

    2017-09-01

    The effects of doping of Ca atom(s) on structural, electronic and optical properties of binary strontium chalcogenide semiconductor compounds have been investigated theoretically using DFT based FP-LAPW approach by modeling the rock-salt (B1) ternary alloys CaxSr1-xS, CaxSr1-xSe and CaxSr1-xTe at some specific concentrations 0 ≤ x ≤ 1 and studying their aforesaid properties. The exchange-correlation potentials for their structural properties have been computed using the Wu-Cohen generalized-gradient approximation (WC-GGA) scheme, while those for the electronic and optical properties have been computed using recently developed Tran-Blaha modified Becke-Johnson (TB-mBJ) scheme. In addition, we have computed the electronic and optical properties with the traditional BLYP and PBE-GGA schemes for comparison. The atomic and orbital origin of different electronic states in the band structure of each of the compounds have been identified from the respective density of states (DOS). Using the approach of Zunger and co-workers, the microscopic origin of band gap bowing has been discussed in term of volume deformation, charge exchange and structural relaxation. Bonding characteristics among the constituent atoms of each of the specimens have been discussed from their charge density contour plots. Optical properties of the binary compounds and ternary alloys have been investigated theoretically in terms of their respective dielectric function, refractive index, normal incidence reflectivity and optical conductivity. Several calculated results have been compared with available experimental and other theoretical data.

  10. Atomic layer deposition of quaternary chalcogenides

    SciTech Connect

    Thimsen, Elijah J; Riha, Shannon C; Martinson, Alex B.F.; Elam, Jeffrey W; Pellin, Michael J

    2014-06-03

    Methods and systems are provided for synthesis and deposition of chalcogenides (including Cu.sub.2ZnSnS.sub.4). Binary compounds, such as metal sulfides, can be deposited by alternating exposures of the substrate to a metal cation precursor and a chalcogen anion precursor with purge steps between.

  11. Single step preparation of quaternary Cu2ZnSnSe4 thin films by RF magnetron sputtering from binary chalcogenide targets

    NASA Astrophysics Data System (ADS)

    Wibowo, Rachmat Adhi; Kim, Woo Seok; Lee, Eun Soo; Munir, Badrul; Kim, Kyoo Ho

    2007-10-01

    Cu2ZnSnSe4 (CZTSe) thin films were grown in a single step procedure by RF magnetron sputtering from a compacted powder consisting of blended chalcogenides. Targets with various chalcogenide mole ratios were designed for the purpose of preparing stoichiometric as-grown films. The material concentrations of the films grown at room temperature were found to depend on the mole ratio of the chalcogenides in the targets. It was found that a significant deviation of material concentration of the films from ideal stoichiometry led to the formation of CuSe, ZnSe and SnSe secondary phases. CZTSe films with a stannite phase could be grown even at room temperature from the sputtering target containing Cu2Se with corresponding growth orientations of (101), (112), (220/204), (312/116) and (332/316). The p-type CZTSe film grown at a substrate temperature of 150C showed a high absorption coefficient of 10cm with an optical band gap of 1.56 eV, resistivity as low as 1.482Ωcm and carrier concentration of 1×10cm. These results suggested that the control of the target compositions was crucial to grow single phase and stoichiometric quaternary CZTSe films.

  12. Chalcogenide optical parametric oscillator.

    PubMed

    Ahmad, Raja; Rochette, Martin

    2012-04-23

    We demonstrate the first optical parametric oscillator (OPO) based on chalcogenide glass. The parametric gain medium is an As(2)Se(3) chalcogenide microwire coated with a layer of polymer. The doubly-resonant OPO oscillates simultaneously at a Stokes and an anti Stokes wavelength shift of >50 nm from the pump wavelength that lies at λ(P) = 1,552 nm. The oscillator has a peak power threshold of 21.6 dBm and a conversion efficiency of >19%. This OPO experiment provides an additional application of the chalcogenide microwire technology; and considering the transparency of As(2)Se(3) glass extending far in the mid-infrared (mid-IR) wavelengths, the device holds promise for realizing mid-IR OPOs utilizing existing optical sources in the telecommunications wavelength region.

  13. Chalcogenide glass microsphere laser.

    PubMed

    Elliott, Gregor R; Murugan, G Senthil; Wilkinson, James S; Zervas, Michalis N; Hewak, Daniel W

    2010-12-06

    Laser action has been demonstrated in chalcogenide glass microsphere. A sub millimeter neodymium-doped gallium lanthanum sulphide glass sphere was pumped at 808 nm with a laser diode and single and multimode laser action demonstrated at wavelengths between 1075 and 1086 nm. The gallium lanthanum sulphide family of glass offer higher thermal stability compared to other chalcogenide glasses, and this, along with an optimized Q-factor for the microcavity allowed laser action to be achieved. When varying the pump power, changes in the output spectrum suggest nonlinear and/or thermal effects have a strong effect on laser action.

  14. Chalcogenide perovskites for photovoltaics.

    PubMed

    Sun, Yi-Yang; Agiorgousis, Michael L; Zhang, Peihong; Zhang, Shengbai

    2015-01-14

    Chalcogenide perovskites are proposed for photovoltaic applications. The predicted band gaps of CaTiS3, BaZrS3, CaZrSe3, and CaHfSe3 with the distorted perovskite structure are within the optimal range for making single-junction solar cells. The predicted optical absorption properties of these materials are superior compared with other high-efficiency solar-cell materials. Possible replacement of the alkaline-earth cations by molecular cations, e.g., (NH3NH3)(2+), as in the organic-inorganic halide perovskites (e.g., CH3NH3PbI3), are also proposed and found to be stable. The chalcogenide perovskites provide promising candidates for addressing the challenging issues regarding halide perovskites such as instability in the presence of moisture and containing the toxic element Pb.

  15. Chalcogenide glass nanostructures

    DOEpatents

    Johnson, Bradley R.; Schweiger, Michael J.; MacIsaac, Brett D.; Sundaram, S. Kamakshi

    2007-05-01

    Chalcogenide nanowires and other micro-and nano scale structures are grown on a preselected portion of on a substrate. They are amorphous and of uniform composition and can be grown by a sublimation-condensation process onto the surface of an amorphous substrate. Among other uses, these structures can be used as coatings on optical fibers, as coatings on implants, as wispering galleries, in electrochemical devices, and in nanolasers.

  16. Process for producing chalcogenide semiconductors

    DOEpatents

    Noufi, R.; Chen, Y.W.

    1985-04-30

    A process for producing chalcogenide semiconductor material is disclosed. The process includes forming a base metal layer and then contacting this layer with a solution having a low pH and containing ions from at least one chalcogen to chalcogenize the layer and form the chalcogenide semiconductor material.

  17. Process for producing chalcogenide semiconductors

    DOEpatents

    Noufi, Rommel; Chen, Yih-Wen

    1987-01-01

    A process for producing chalcogenide semiconductor material is disclosed. The process includes forming a base metal layer and then contacting this layer with a solution having a low pH and containing ions from at least one chalcogen to chalcogenize the layer and form the chalcogenide semiconductor material.

  18. Chalcogenide centred gold complexes.

    PubMed

    Gimeno, M Concepción; Laguna, Antonio

    2008-09-01

    Chalcogenide-centred gold complexes are an important class of compounds in which a central chalcogen is surrounded by several gold atoms or gold and other metals. They have special characteristics such as unusual geometries, electron deficiency and properties such as luminescence or non-linear optical properties. The best known species are the trinuclear [E(AuPR3)3]+, 'oxonium' type species, that have high synthetic applicability, not only in other chalcogen-centred species, but in many other organometallic derivatives. The aurophilic interactions play an important role in the stability, preference for a particular geometry and luminescence properties in this type of derivatives (critical review, 117 references).

  19. Nano-scaled top-down of bismuth chalcogenides based on electrochemical lithium intercalation

    NASA Astrophysics Data System (ADS)

    Chen, Jikun; Zhu, Yingjie; Chen, Nuofu; Liu, Xinling; Sun, Zhengliang; Huang, Zhenghong; Kang, Feiyu; Gao, Qiuming; Jiang, Jun; Chen, Lidong

    2011-12-01

    A two-step method has been used to fabricate nano-particles of layer-structured bismuth chalcogenide compounds, including Bi2Te3, Bi2Se3, and Bi2Se0.3Te2.7, through a nano-scaled top-down route. In the first step, lithium (Li) atoms are intercalated between the van der Waals bonded quintuple layers of bismuth chalcogenide compounds by controllable electrochemical process inside self-designed lithium ion batteries. And in the second step, the Li intercalated bismuth chalcogenides are subsequently exposed to ethanol, in which process the intercalated Li atoms would explode like atom-scaled bombs to exfoliate original microscaled powder into nano-scaled particles with size around 10 nm. The influence of lithium intercalation speed and amount to three types of bismuth chalcogenide compounds are compared and the optimized intercalation conditions are explored. As to maintain the phase purity of the final nano-particle product, the intercalation lithium amount should be well controlled in Se contained bismuth chalcogenide compounds. Besides, compared with binary bismuth chalcogenide compound, lower lithium intercalation speed should be applied in ternary bismuth chalcogenide compound.

  20. Superconducting properties of iron chalcogenide thin films

    PubMed Central

    Mele, Paolo

    2012-01-01

    Iron chalcogenides, binary FeSe, FeTe and ternary FeTexSe1−x, FeTexS1−x and FeTe:Ox, are the simplest compounds amongst the recently discovered iron-based superconductors. Thin films of iron chalcogenides present many attractive features that are covered in this review, such as: (i) easy fabrication and epitaxial growth on common single-crystal substrates; (ii) strong enhancement of superconducting transition temperature with respect to the bulk parent compounds (in FeTe0.5Se0.5, zero-resistance transition temperature Tc0bulk = 13.5 K, but Tc0film = 19 K on LaAlO3 substrate); (iii) high critical current density (Jc ∼ 0.5 ×106 A cm2 at 4.2 K and 0 T for FeTe0.5Se0.5 film deposited on CaF2, and similar values on flexible metallic substrates (Hastelloy tapes buffered by ion-beam assisted deposition) with a weak dependence on magnetic field; (iv) high upper critical field (∼50 T for FeTe0.5Se0.5, Bc2(0), with a low anisotropy, γ ∼ 2). These highlights explain why thin films of iron chalcogenides have been widely studied in recent years and are considered as promising materials for applications requiring high magnetic fields (20–50 T) and low temperatures (2–10 K). PMID:27877514

  1. Space processing of chalcogenide glasses

    NASA Technical Reports Server (NTRS)

    Larsen, D. C.; Ali, M. A.; Crandall, W. B.

    1974-01-01

    Manufacture of chalcogenide glasses in space will eliminate many of the causes of optical non-homogeneity and contamination that are inherent in earth-bound manufacture. A program is outlined to demonstrate the feasibility of various techniques and processes that will be utilized to manufacture chalcogenide glasses in space. Amorphous character, purity, and homogeneity parameters are being investigated at various stages of the glass forming process. These parameters in merit index form will serve to provide guidelines for the design of the actual melting experiment in space, and for the optimization of the exact chalcogenide composition to be included in the space experiments.

  2. Space processing of chalcogenide glass

    NASA Technical Reports Server (NTRS)

    Larsen, D. C.; Ali, M. I.

    1977-01-01

    The manner in which the weightless, containerless nature of in-space processing can be successfully utilized to improve the quality of infrared transmitting chalcogenide glasses is determined. The technique of space processing chalcogenide glass was developed, and the process and equipment necessary to do so was defined. Earthbound processing experiments with As2S3 and G28Sb12Se60 glasses were experimented with. Incorporated into these experiments is the use of an acoustic levitation device.

  3. Amplification With Chalcogenide Glass Fiber

    DTIC Science & Technology

    2001-07-12

    34AMPLIFICATION WITH CHALCOGENIDE GLASS FIBER" request for release for publication. REF: (a) NRL Instruction 5510.40C (b) Chapter 6, ONRINST 5870.1C...Serial Number: Patent Application Navy Case Number: 82,848 AMPLIFICATION WITH CFfALCOGENTDE GLASS FIBER Field of the Invention: This invention...pertains to the use of a low phonon energy chalcogenide glass waveguide in conjunction with stimulated Raman scattering to amplify an optical signal

  4. Compound Copper Chalcogenide Nanocrystals.

    PubMed

    Coughlan, Claudia; Ibáñez, Maria; Dobrozhan, Oleksandr; Singh, Ajay; Cabot, Andreu; Ryan, Kevin M

    2017-05-10

    This review captures the synthesis, assembly, properties, and applications of copper chalcogenide NCs, which have achieved significant research interest in the last decade due to their compositional and structural versatility. The outstanding functional properties of these materials stems from the relationship between their band structure and defect concentration, including charge carrier concentration and electronic conductivity character, which consequently affects their optoelectronic, optical, and plasmonic properties. This, combined with several metastable crystal phases and stoichiometries and the low energy of formation of defects, makes the reproducible synthesis of these materials, with tunable parameters, remarkable. Further to this, the review captures the progress of the hierarchical assembly of these NCs, which bridges the link between their discrete and collective properties. Their ubiquitous application set has cross-cut energy conversion (photovoltaics, photocatalysis, thermoelectrics), energy storage (lithium-ion batteries, hydrogen generation), emissive materials (plasmonics, LEDs, biolabelling), sensors (electrochemical, biochemical), biomedical devices (magnetic resonance imaging, X-ray computer tomography), and medical therapies (photochemothermal therapies, immunotherapy, radiotherapy, and drug delivery). The confluence of advances in the synthesis, assembly, and application of these NCs in the past decade has the potential to significantly impact society, both economically and environmentally.

  5. Space processing of chalcogenide glasses

    NASA Technical Reports Server (NTRS)

    Larsen, D. C.; Ali, M. A.

    1975-01-01

    Chalcogenide glasses are discussed as good infrared transmitters, possessing the strength, corrosion resistance, and scale-up potential necessary for large 10.6-micron windows. The disadvantage of earth-produced chalcogenide glasses is shown to be an infrared absorption coefficient which is unacceptably high relative to alkali halides. This coefficient is traced to optical nonhomogeneities resulting from environmental and container contamination. Space processing is considered as a means of improving the infrared transmission quality of chalcogenides and of eliminating the following problems: optical inhomogeneities caused by thermal currents and density fluctuation in the l-g earth environment; contamination from the earth-melting crucible by oxygen and other elements deleterious to infrared transmission; and, heterogeneous nucleation at the earth-melting crucible-glass interface.

  6. Chalcogenide and germanium hybrid optics

    NASA Astrophysics Data System (ADS)

    Cogburn, Gabriel

    2011-11-01

    When choosing a material to design infrared optics, an optical designer has to decide which material properties are most important to what they are trying to achieve. Factors include; cost, optical performance, index of material, sensor format, manufacturability, mechanical mounting and others. This paper will present an optical design that is made for a 640×480, 17μm sensor and is athermalized by using the material properties of chalcogenide glass and Germanium (Ge). The optical design will be a 3-element, f1.0 optic with an EFL of 20mm at 10μm. It consists of two Ge spherical lenses and a middle chalcogenide aspheric element. By using Ge and chalcogenide, this design utilizes the high index of Ge and combines it with the lower dn/dt of chalcogenide glass to provide an athermalized design without the use of additional electro-optical compensation inside the assembly. This study will start from the optical design process and explain the mechanical and optical properties of the design, then show the manufacturing process of molding an aspheric chalcogenide element. After the three elements are manufactured, they will be assembled and tested throughout the temperature range of -40 to 85°C to compare optical performance to design expectations. Ultimately, this paper will show that a high performance, athermalized optical assembly is possible to manufacture at a lower cost with the use of combining different infrared materials that allow for spherical Ge lenses and only one aspherical chalcogenide element which can be produced in higher volumes at lower costs through glass molding technology.

  7. Focus on superconducting properties of iron chalcogenides

    NASA Astrophysics Data System (ADS)

    Takano, Yoshihiko

    2012-10-01

    Since the discovery of iron-based superconductors, much attention has been given to the exploration of new superconducting compounds. Numerous superconducting iron compounds have been found and categorized into five groups: LnFeAsO (Ln = lanthanide), BaFe2As2, KFeAs, FeSe and FeAs with perovskite blocking layers. Among them, FeSe has the simplest crystal structure. Since the crystal structure is composed of only superconducting Fe layers, the FeSe family must be the best material to investigate the mechanism of iron-based superconductivity. FeSe shows very strong pressure effects. The superconducting transition temperature (Tc) of FeSe is approximately 8 K at ambient pressure. However Tc dramatically increases up to 37 K under applied pressure of 4-6 GPa. This is the third highest Tc value among binary superconductors, surpassed only by CsC60 under pressure (Tc = 38 K) and MgB2 (Tc = 39 K). On the other hand, despite FeTe having a crystal structure analogous to that of FeSe, FeTe shows antiferromagnetic properties without superconductivity. Doping of small ions, either Se or S, however, can induce superconductivity in FeTe1-xSex or FeTe1-xSx . The superconductivity is very weak for small x values, and annealing under certain conditions is required to obtain strong superconductivity, for instance annealing in oxygen or alcoholic beverages such as red wine. The following selection of papers describe many important experimental and theoretical studies on iron chalcogenide superconductors including preparation of single crystals, bulk samples and thin films; NMR measurements; photoemission spectroscopy; high-pressure studies; annealing effects and research on new BiS2-based superconductors. I hope this focus issue will help researchers understand the frontiers of iron chalcogenide superconductors and assist in the discovery of new phenomena related to iron-based superconductivity.

  8. Synthesis, characterization, and structure of reduced tungsten chalcogenide cluster complexes

    SciTech Connect

    Xiaobing, Xie

    1997-10-17

    Over the previous twenty years, ternary molybdenum chalcogenides of the general formula MxMo6Y8 (M = ternary metal cation; Y = chalcogenide), known as Chevrel phases, have been extensively studied. Many of these compounds have been found to have superconductivity, catalytic activity and ionic conductivity. The rich chemistry of the Chevrel phases raises considerable interest in finding the tungsten analogues of these phases. However, no such analogue has ever been synthesized, although the Chevrel phases are usually prepared directly from elements at high temperatures above 1000{degrees}C. The absence of the tungsten analogues may be caused by their thermodynamic instability at such high temperatures. Thus it might be necessary to avoid high-temperature synthetic procedures in order to establish the ternary and binary tungsten chalcogenides. A major focus of the McCarley research group has been on the preparation of M6Y8L6 (M = Mo, W; Y = S, Se, Te) cluster complexes as low temperature pathways to the Chevrel phases.

  9. Space processing of chalcogenide glass

    NASA Technical Reports Server (NTRS)

    Firestone, R. F.; Schramm, S. W.

    1978-01-01

    A program was conducted to develop the technique of space processing for chalcogenide glass, and to define the process and equipment necessary. In the course of this program, successful long term levitation of objects in a 1-g environment was achieved. Glass beads 4 mm diameter were containerless melted and fused together.

  10. Waveguides Based Upon Chalcogenide Glasses

    DTIC Science & Technology

    2001-06-01

    spectroscopic study of extrasolar planets [6]. The second one is environmental metrology. Indeed, the detection of some vibrational modes present in some...chalcogenide glasses in components for two types of applications: spatial interferometry (detection of planets ) and environmental metrology (detection of

  11. Destructive Clustering of Metal Nanoparticles in Chalcogenide and Oxide Glassy Matrices.

    PubMed

    Shpotyuk, M V; Shpotyuk, O I; Cebulski, J; Kozyukhin, S

    2016-12-01

    The energetic χ-criterion is developed to parameterize difference in the origin of high-order optical non-linearity associated with metallic atoms (Cu, Ag, Au) embedded destructively in oxide- and chalcogenide glasses. Within this approach, it is unambiguously proved that covalent-bonded networks of soft semiconductor chalcogenides exemplified by binary As(Ge)-S(Se) glasses differ essentially from those typical for hard dielectric oxides like vitreous silica by impossibility to accommodate pure agglomerates of metallic nanoparticles. In an excellence according to known experimental data, it is suggested that destructive clustering of nanoparticles is possible in Cu-, Ag-, and Au-ion-implanted dielectric oxide glass media, possessing a strongly negative χ-criterion. Some recent speculations trying to ascribe equally this ability to soft chalcogenide glasses despite an obvious difference in the corresponding bond dissociation energies have been disclosed and criticized as inconclusive.

  12. Destructive Clustering of Metal Nanoparticles in Chalcogenide and Oxide Glassy Matrices

    NASA Astrophysics Data System (ADS)

    Shpotyuk, M. V.; Shpotyuk, O. I.; Cebulski, J.; Kozyukhin, S.

    2016-01-01

    The energetic χ-criterion is developed to parameterize difference in the origin of high-order optical non-linearity associated with metallic atoms (Cu, Ag, Au) embedded destructively in oxide- and chalcogenide glasses. Within this approach, it is unambiguously proved that covalent-bonded networks of soft semiconductor chalcogenides exemplified by binary As(Ge)-S(Se) glasses differ essentially from those typical for hard dielectric oxides like vitreous silica by impossibility to accommodate pure agglomerates of metallic nanoparticles. In an excellence according to known experimental data, it is suggested that destructive clustering of nanoparticles is possible in Cu-, Ag-, and Au-ion-implanted dielectric oxide glass media, possessing a strongly negative χ-criterion. Some recent speculations trying to ascribe equally this ability to soft chalcogenide glasses despite an obvious difference in the corresponding bond dissociation energies have been disclosed and criticized as inconclusive.

  13. Phonon dynamics of neptunium chalcogenides

    NASA Astrophysics Data System (ADS)

    Aynyas, Mahendra; Rukmangad, Aditi; Arya, Balwant S.; Sanyal, Sankar P.

    2012-06-01

    We have performed phonon calculations of Neptunium Chalcogenides (NpX) (X= S, Se, Te) based on breathing shell model (BSM) which includes breathing motion of electron of the Np-atoms due to f-d hybridization. The model predicts that the short range breathing phenomenon play a dominant role in the phonon properties. We also report, for the first time specific heat for these compounds.

  14. Chromium-doped chalcogenide lasers

    NASA Astrophysics Data System (ADS)

    Carrig, Timothy J.; Wagner, Gregory J.; Alford, William J.; Zakel, Andrew

    2004-09-01

    Broadly tunable near- and mid-infrared lasers are of interest for a variety of applications including high-resolution spectroscopy, metrology, pumping of nonlinear optical frequency converters such as optical parametric oscillators (OPOs) and standoff chemical sensing. Tunable laser sources in the 2-3 um region include Cr2+ doped chalcogenide lasers; cryogenic systems, such as color center lasers; limited tunability devices, such as Tm and Ho lasers, gas or chemical lasers, and diode lasers; and nonlinear optical devices such as OPOs. Transition-metal-doped chalcogenide lasers are of high interest because of their high versatility, broad room-temperature wavelength tunability, high optical efficiencies, and their potential to be scaled to high powers via direct diode or fiber laser pumping. To date, continuous-wave, gain-switched, Q-switched and mode-locked laser operation has been demonstrated. Material advantages include broad absorption and emission bands, high fluorescence quantum efficiencies at room temperature, high gain cross-sections, and minimal loss mechanisms such as excited-state absorption or upconversion. Additionally, the materials can be produced by a variety of methods, including several direct growth techniques and diffusion doping. The principal material disadvantages include a relatively large change in refractive index with temperature (large dn/dT), which can induce thermal lensing, and a short, microseconds, energy storage time. In this paper we review fundamental material properties, the current state-of-the-art of continuous-wave and pulsed Cr2+ doped chalcogenide lasers, and recent research results.

  15. Physics and chemistry of layered chalcogenide superconductors

    PubMed Central

    Deguchi, Keita; Takano, Yoshihiko; Mizuguchi, Yoshikazu

    2012-01-01

    Structural and physical properties of layered chalcogenide superconductors are summarized. In particular, we review the remarkable properties of the Fe-chalcogenide superconductors, FeSe and FeTe-based materials. Furthermore, we introduce the recently discovered BiS2-based layered superconductors and discuss their prospects. PMID:27877516

  16. Fiber taper coupling to chalcogenide microsphere modes

    SciTech Connect

    Grillet, Christian; Bian Shuning; Magi, Eric C.; Eggleton, Benjamin J.

    2008-04-28

    We report the fabrication and optical characterization of microsphere in chalcogenide (As{sub 2}Se{sub 3}). We show that high Q modes of a 9.2 {mu}m diameter chalcogenide glass can be efficiently excited via evanescent coupling using a silica tapered fiber. Loaded Q factors of more than 20 000 have been measured. Fine analysis of the coupling spectrum around 1619 nm led to an estimation of the microsphere eccentricity of less than 1%. Owing to the unique combination properties of chalcogenide glass and the microspheres geometry, we expect this architecture to offer an ideal environment for versatile applications on both the telecommunication and midinfrared wavelength windows.

  17. Chalcogenide glass photonic crystals: progress and prospects

    NASA Astrophysics Data System (ADS)

    Grillet, Christian; Lee, Michael W.; Gai, Xin; Tomljenovic-Hanic, Snjezana; Monat, Christelle; Mägi, Eric; Moss, David J.; Eggleton, Benjamin J.; Madden, Steve; Choi, Duk-Yong; Bulla, Douglas; Luther-Davies, Barry

    2010-02-01

    In this review, we discuss the progress and prospects offered by chalcogenide glass photonic crystals. We show that by making photonic crystals from a highly-nonlinear chalcogenide glass, we have the potential to integrate a variety of active devices into a photonic chip. We describe the testing of two-dimensional Ge33As12Se55 chalcogenide glass photonic crystal membrane devices (waveguides and microcavities). We then demonstrate the ability to not only post-tune the devices properties but also create high Q cavities by using the material photosensitivity.

  18. Space processing of chalcogenide glass

    NASA Technical Reports Server (NTRS)

    Ali, M. A.; Larsen, D. C.

    1976-01-01

    The manner in which the weightless, containerless nature of in-space processing can be successfully utilized to improve the quality of infrared transmitting chalcogenide glasses was investigated. The following conclusions were reached: (1) Laboratory experiments have established the techniques, processes and equipment necessary for the production of high purity chalcogenide glasses. (2) Processing techniques have been successfully adopted for Ge28Sb12Se60 glass in a 1-g environment. (3) The Ge28Sb12Se60 glasses that have been processed have optical transmission around 63% (5 mm thick). (4) Laboratory experiments have established that the use of precursor materials in powdered form increases the oxygen contamination of the processed glass. This indicates that high purity precursor materials in bar or pellet form should be used. (5) Modifications were made on the MSFC acoustic levitator in an attempt to improve levitation stability during long-time experiments. Room temperature experiments on As2S3 glasses and high temperature experiments on polystyrene were conducted.

  19. Self-assembly of lead chalcogenide nanocrystals.

    PubMed

    Quan, Zewei; Valentin-Bromberg, Loriana; Loc, Welley Siu; Fang, Jiye

    2011-05-02

    This review focuses on recent developments in the self-assembly of lead chalcogenide nanocrystals into two- and three-dimensional superstructures. Self-assembly is categorized by the shapes of building blocks, including nanospheres, nanocubes, nano-octahedra, and nanostars. In the section on nanospheres, rapid assemblies of lead chalcogenide-based multicomponent nanocrystals with additional components, such as semiconductors, noble metals, and magnetic nanocrystals, are further highlighted. In situ self-assembly of lead chalcogenide nanocrystals into one-dimensional nanostructures at elevated temperatures is also covered. Each section of this paper highlights examples extracted from recent publications. Finally, relatively novel properties and applications arising from lead chalcogenide superlattices as typical examples are also discussed.

  20. Method to synthesize metal chalcogenide monolayer nanomaterials

    SciTech Connect

    Hernandez-Sanchez, Bernadette A.; Boyle, Timothy J.

    2016-12-13

    Metal chalcogenide monolayer nanomaterials can be synthesized from metal alkoxide precursors by solution precipitation or solvothermal processing. The synthesis routes are more scalable, less complex and easier to implement than other synthesis routes.

  1. Search for chalcogenide based superconductors: Sulfur based solution growth

    NASA Astrophysics Data System (ADS)

    Kaluarachchi, Udhara; Bud'Ko, Sergey; Canfield, Paul

    2013-03-01

    As part of our effort to develop tools for searching for new chalcogenide based superconductors we are expanding the range of S-based binary melts that we can use for solution growth of single crystals. As a recent example, we have been able to grow single crystals of Rh17S15 and separate them for excess binary melt via high temperature decanting. In addition to refining the details of the Rh-S binary phase diagram, microscopic, thermodynamic and transport measurement on Rh17S15 crystals confirm their Tc ~ 5.5 K as well as their remarkably large Hc2(T) behavior. The possible cause of the enhanced Hc2(T) will be discussed. As time allows we will also review other S-based growths and compounds. This work was supported by AFOSR-MURI grant FA9550-09-1-0603 (UK and PCC) and by US DOE under the Contract No. DE-AC02-07CH11358 (SLB).

  2. Origin of resistivity anomaly in p-type leads chalcogenide multiphase compounds

    SciTech Connect

    Aminorroaya Yamini, Sima E-mail: jsnyder@caltech.edu; Dou, Shi Xue; Mitchell, David R. G.; Wang, Heng; Gibbs, Zachary M.; Pei, Yanzhong; Snyder, G. Jeffrey E-mail: jsnyder@caltech.edu

    2015-05-15

    The electrical resistivity curves for binary phase compounds of p-type lead chalcogenide (PbTe){sub (0.9−x)}(PbSe){sub 0.1}(PbS){sub x,} (x = 0.15, 0.2, 0.25), which contain PbS-rich secondary phases, show different behaviour on heating and cooling between 500-700 K. This is contrast to single phase compounds which exhibit similar behaviour on heating and cooling. We correlate these anomalies in the electrical resistivities of multiphase compounds to the variation in phase composition at high temperatures. The inhomogeneous distribution of dopants between the matrix and secondary phase is found to be crucial in the electronic transport properties of the multiphase compounds. These results can lead to further advances in designing composite Pb-chalcogenides with high thermoelectric performance.

  3. Chalcogenide glasses and structures for quantum sensing

    SciTech Connect

    Sundaram, S K.; Johnson, Bradley R.; Schweiger, Michael J.; Martinez, James E.; Riley, Brian J.; Saraf, Laxmikant V.; Anheier, Norman C.; Allen, Paul J.; Schultz, John F.; Manijeh Razeghi, Gail J. Brown

    2004-08-01

    Chalcogenide glasses are formed by combining chalcogen elements with IV-V elements. Among the family of glasses, As2S3, and As2Se3 are important infrared (IR) transparent materials for a variety of applications such as IR sensors, waveguides, and photonic crystals. With the promise of accessibility to any wavelengths between 3.5 and 16 ?m using tunable quantum cascade lasers (QCL) and chalcogenides with IR properties that can be tuned, ultra-sensitive chemical sensing in mid-wave IR region is within reach now. PNNL has been developing QCLs, chalcogenides, and all other components for an integrated approach to chemical sensing. Significant progress has been made in glass formation and fabrication of different structures at PNNL. Three different glass-forming systems, As-S, As-S-Se, and As-S-Ag have been examined for this application. Purification of constituents from contaminants and thermal history are two major issues in obtaining defect-free glasses. We have shown how the optical properties can be systematically modified by changing the chemistry in As-S-Se system. Different fabrication techniques need to be employed for different geometries and structures. We have successfully fabricated periodic arrays and straight waveguides using laser-writing and characterized the structures. Wet-chemical lithography has been extended to chalcogenides and challenges identified. We have also demonstrated holographic recording or diffraction gratings in chalcogenides.

  4. A highly reactive chalcogenide precursor for the synthesis of metal chalcogenide quantum dots

    NASA Astrophysics Data System (ADS)

    Jiang, Peng; Zhu, Dong-Liang; Zhu, Chun-Nan; Zhang, Zhi-Ling; Zhang, Guo-Jun; Pang, Dai-Wen

    2015-11-01

    Metal chalcogenide semiconductor nanocrystals (NCs) are ideal inorganic materials for solar cells and biomedical labeling. In consideration of the hazard and instability of alkylphosphines, the phosphine-free synthetic route has become one of the most important trends in synthesizing selenide QDs. Here we report a novel phase transfer strategy to prepare phosphine-free chalcogenide precursors. The anions in aqueous solution were transferred to toluene via electrostatic interactions between the anions and didodecyldimethylammonium bromide (DDAB). The obtained chalcogenide precursors show high reactivity with metal ions in the organic phase and could be applied to the low-temperature synthesis of various metal chalcogenide NCs based on a simple reaction between metal ions (e.g. Ag+, Pb2+, Cd2+) and chalcogenide anions (e.g. S2-) in toluene. In addition to chalcogenide anions, other anions such as BH4- ions and AuCl4- ions can also be transferred to the organic phase for synthesizing noble metal NCs (such as Ag and Au NCs).Metal chalcogenide semiconductor nanocrystals (NCs) are ideal inorganic materials for solar cells and biomedical labeling. In consideration of the hazard and instability of alkylphosphines, the phosphine-free synthetic route has become one of the most important trends in synthesizing selenide QDs. Here we report a novel phase transfer strategy to prepare phosphine-free chalcogenide precursors. The anions in aqueous solution were transferred to toluene via electrostatic interactions between the anions and didodecyldimethylammonium bromide (DDAB). The obtained chalcogenide precursors show high reactivity with metal ions in the organic phase and could be applied to the low-temperature synthesis of various metal chalcogenide NCs based on a simple reaction between metal ions (e.g. Ag+, Pb2+, Cd2+) and chalcogenide anions (e.g. S2-) in toluene. In addition to chalcogenide anions, other anions such as BH4- ions and AuCl4- ions can also be transferred to

  5. Chalcogenide Nanoionic-based Radio Frequency Switch

    NASA Technical Reports Server (NTRS)

    Nessel, James (Inventor); Lee, Richard (Inventor)

    2013-01-01

    A nonvolatile nanoionic switch is disclosed. A thin layer of chalcogenide glass engages a substrate and a metal selected from the group of silver and copper photo-dissolved in the chalcogenide glass. A first oxidizable electrode and a second inert electrode engage the chalcogenide glass and are spaced apart from each other forming a gap therebetween. A direct current voltage source is applied with positive polarity applied to the oxidizable electrode and negative polarity applied to the inert electrode which electrodeposits silver or copper across the gap closing the switch. Reversing the polarity of the switch dissolves the electrodeposited metal and returns it to the oxidizable electrode. A capacitor arrangement may be formed with the same structure and process.

  6. Preparation and processing of rare earth chalcogenides

    NASA Astrophysics Data System (ADS)

    Gschneidner, K. A.

    1998-10-01

    Rare earth chalcogenides are initially prepared by a direct combination of the pure rare earth metal and the pure chalogen element with or without a catalyst. The use of iodine (10 to 100 mg) as a fluxing agent (catalyst), especially to prepare heavy lanthanide chalcogenides, greatly speeds up the formation of the rare earth chalcogenide. The resultant powders are consolidated by melting, pressure assisted sintering (PAS), or pressure assisted reaction sintering (PARS) to obtain near theoretical density solids. Mechanical alloying is a useful technique for preparing ternary alloys. In addition, mechanical alloying and mechanical milling can be used to form metastable allotropic forms of the yttrium and heavy lanthanide sulfides. Chemical analysis techniques are also described because it is strongly recommended that samples prepared by melting should have their chemical compositions verified because of chalogen losses in the melting step.

  7. Thermal response of chalcogenide microsphere resonators

    SciTech Connect

    Ahmad, H; Aryanfar, I; Lim, K S; Chong, W Y; Harun, S W

    2012-05-31

    A chalcogenide microsphere resonator (CMR) used for temperature sensing is proposed and demonstrated. The CMR is fabricated using a simple technique of heating chalcogenide glass and allowing the molten glass to form a microsphere on the waist of a tapered silica fibre. The thermal responses of the CMR is investigated and compared to that of a single-mode-fibre (SMF) based microsphere resonator. It is observed that the CMR sensitivity to ambient temperature changes is 8 times higher than that of the SMF-based microsphere resonator. Heating the chalcogenide microsphere with a laser beam periodically turned on and off shows periodic shifts in the transmission spectrum of the resonator. By injecting an intensity-modulated cw signal through the resonator a thermal relaxation time of 55 ms is estimated.

  8. Chalcogenide Nanoionic-Based Radio Frequency Switch

    NASA Technical Reports Server (NTRS)

    Nessel, James (Inventor); Lee, Richard (Inventor)

    2011-01-01

    A nonvolatile nanoionic switch is disclosed. A thin layer of chalcogenide glass engages a substrate and a metal selected from the group of silver and copper photo-dissolved in the chalcogenide glass. A first oxidizable electrode and a second inert electrode engage the chalcogenide glass and are spaced apart from each other forming a gap there between. A direct current voltage source is applied with positive polarity applied to the oxidizable electrode and negative polarity applied to the inert electrode which electrodeposits silver or copper across the gap closing the switch. Reversing the polarity of the switch dissolves the electrodeposited metal and returns it to the oxidizable electrode. A capacitor arrangement may be formed with the same structure and process.

  9. Interfacial properties of semiconducting transition metal chalcogenides

    NASA Astrophysics Data System (ADS)

    Jaegermann, W.; Tributsch, H.

    This review is aimed at the correlation of structural and electronic properies of semiconducting transition metal chalcogenides with molecular surface processes and mechanisms in photoelectrochemistry, (photo)catalysis, geochemistry and hydrometallurgy. Layer-type, pyrite structured and transition metal cluster containing chalcogenides are selected as model systems to explain the principles involved. Special emphasis is given to the discussion of materials which involve transition metal d- states in the interfacial reaction pathways of holes and electrons. Since they initiate and control heterogeneous coordination chemistry at the surfaces they may provide the possibility of tailoring selective and catalytically demanding reactions. Examples of such mechanisms are presented and discussed in relation to surface properties involved.

  10. Metal Chalcogenide Nanocrystalline Solid Thin Films

    NASA Astrophysics Data System (ADS)

    Deo, Soumya R.; Singh, Ajaya K.; Deshmukh, Lata; Abu Bin Hasan Susan, Md.

    2015-11-01

    Over the past decades, chemical bath deposition (CBD) has proven its suitability and has established itself as one of the prominent techniques for depositing different metal chalcogenide semiconductor thin films via ion-by-ion or by adsorption of colloidal particles from the chemical bath on the substrate. It is a simple, cost-effective and convenient method for large-scale deposition and has recently received a surge of interest. This article reviews the research progress in various methods or techniques including CBD for the preparation and study of the properties of metal chalcogenides. Various parameters for efficient preparation and variation in structural, morphological, compositional, optical properties, etc. are also briefly discussed.

  11. Iron chalcogenide superconductors at high magnetic fields

    PubMed Central

    Lei, Hechang; Wang, Kefeng; Hu, Rongwei; Ryu, Hyejin; Abeykoon, Milinda; Bozin, Emil S; Petrovic, Cedomir

    2012-01-01

    Iron chalcogenide superconductors have become one of the most investigated superconducting materials in recent years due to high upper critical fields, competing interactions and complex electronic and magnetic phase diagrams. The structural complexity, defects and atomic site occupancies significantly affect the normal and superconducting states in these compounds. In this work we review the vortex behavior, critical current density and high magnetic field pair-breaking mechanism in iron chalcogenide superconductors. We also point to relevant structural features and normal-state properties. PMID:27877518

  12. Dirac fermions at high-index surfaces of bismuth chalcogenide topological insulator nanostructures

    PubMed Central

    Virk, Naunidh; Yazyev, Oleg V.

    2016-01-01

    Binary bismuth chalcogenides Bi2Se3, Bi2Te3, and related materials are currently being extensively investigated as the reference topological insulators (TIs) due to their simple surface-state band dispersion (single Dirac cone) and relatively large bulk band gaps. Nanostructures of TIs are of particular interest as an increased surface-to-volume ratio enhances the contribution of surfaces states, meaning they are promising candidates for potential device applications. So far, the vast majority of research efforts have focused on the low-energy (0001) surfaces, which correspond to natural cleavage planes in these layered materials. However, the surfaces of low-dimensional nanostructures (nanoplatelets, nanowires, nanoribbons) inevitably involve higher-index facets. We perform a systematic ab initio investigation of the surfaces of bismuth chalcogenide TI nanostructures characterized by different crystallographic orientations, atomic structures and stoichiometric compositions. We find several stable terminations of high-index surfaces, which can be realized at different values of the chemical potential of one of the constituent elements. For the uniquely defined stoichiometric termination, the topological Dirac fermion states are shown to be strongly anisotropic with a clear dependence of Fermi velocities and spin polarization on the surface orientation. Self-doping effects and the presence of topologically trivial mid-gap states are found to characterize the non-stoichiometric surfaces. The results of our study pave the way towards experimental control of topologically protected surface states in bismuth chalcogenide nanostructures. PMID:26847409

  13. Dirac fermions at high-index surfaces of bismuth chalcogenide topological insulator nanostructures.

    PubMed

    Virk, Naunidh; Yazyev, Oleg V

    2016-02-05

    Binary bismuth chalcogenides Bi2Se3, Bi2Te3, and related materials are currently being extensively investigated as the reference topological insulators (TIs) due to their simple surface-state band dispersion (single Dirac cone) and relatively large bulk band gaps. Nanostructures of TIs are of particular interest as an increased surface-to-volume ratio enhances the contribution of surfaces states, meaning they are promising candidates for potential device applications. So far, the vast majority of research efforts have focused on the low-energy (0001) surfaces, which correspond to natural cleavage planes in these layered materials. However, the surfaces of low-dimensional nanostructures (nanoplatelets, nanowires, nanoribbons) inevitably involve higher-index facets. We perform a systematic ab initio investigation of the surfaces of bismuth chalcogenide TI nanostructures characterized by different crystallographic orientations, atomic structures and stoichiometric compositions. We find several stable terminations of high-index surfaces, which can be realized at different values of the chemical potential of one of the constituent elements. For the uniquely defined stoichiometric termination, the topological Dirac fermion states are shown to be strongly anisotropic with a clear dependence of Fermi velocities and spin polarization on the surface orientation. Self-doping effects and the presence of topologically trivial mid-gap states are found to characterize the non-stoichiometric surfaces. The results of our study pave the way towards experimental control of topologically protected surface states in bismuth chalcogenide nanostructures.

  14. Dirac fermions at high-index surfaces of bismuth chalcogenide topological insulator nanostructures

    NASA Astrophysics Data System (ADS)

    Virk, Naunidh; Yazyev, Oleg V.

    2016-02-01

    Binary bismuth chalcogenides Bi2Se3, Bi2Te3, and related materials are currently being extensively investigated as the reference topological insulators (TIs) due to their simple surface-state band dispersion (single Dirac cone) and relatively large bulk band gaps. Nanostructures of TIs are of particular interest as an increased surface-to-volume ratio enhances the contribution of surfaces states, meaning they are promising candidates for potential device applications. So far, the vast majority of research efforts have focused on the low-energy (0001) surfaces, which correspond to natural cleavage planes in these layered materials. However, the surfaces of low-dimensional nanostructures (nanoplatelets, nanowires, nanoribbons) inevitably involve higher-index facets. We perform a systematic ab initio investigation of the surfaces of bismuth chalcogenide TI nanostructures characterized by different crystallographic orientations, atomic structures and stoichiometric compositions. We find several stable terminations of high-index surfaces, which can be realized at different values of the chemical potential of one of the constituent elements. For the uniquely defined stoichiometric termination, the topological Dirac fermion states are shown to be strongly anisotropic with a clear dependence of Fermi velocities and spin polarization on the surface orientation. Self-doping effects and the presence of topologically trivial mid-gap states are found to characterize the non-stoichiometric surfaces. The results of our study pave the way towards experimental control of topologically protected surface states in bismuth chalcogenide nanostructures.

  15. Electroneutral intrinsic point defects in cadmium chalcogenides

    SciTech Connect

    Kharif, Ya.L.; Kudryashov, N.I.; Strunilina, T.A.

    1987-12-01

    Low-mobility electrically neutral intrinsic point defects were observed in cadmium chalcogenides. It was shown that the concentration of these defects is proportional to the cadmium vapor pressure to the 1/3 power at a constant temperature, and a mechanism for the formation of these defects were proposed.

  16. First principles thermodynamical modeling of the binodal and spinodal curves in lead chalcogenides

    NASA Astrophysics Data System (ADS)

    Usanmaz, Demet; Nath, Pinku; Plata, Jose J.; Hart, Gus L. W.; Takeuchi, Ichiro; Nardelli, Marco Buongiorno; Fornari, Marco; Curtarolo, Stefano

    High-throughput ab-initio calculations, cluster expansion techniques and thermodynamic modeling have been synergistically combined to characterize the binodal and the spinodal decompositions features in the pseudo-binary lead chalcogenides PbSe-PbTe, PbS-PbTe, and PbS-PbSe. While our results agree with the available experimental data, our consolute temperatures substantially improve with respect to previous computational modeling. The computed phase diagrams corroborate that the formation of spinodal nanostructures causes low thermal conductivities in these alloys. The presented approach, making a rational use of online quantum repositories, can be extended to study thermodynamical and kinetic properties of materials of technological interest.

  17. Ultra-precision molding of chalcogenide glass aspherical lens

    NASA Astrophysics Data System (ADS)

    Zhang, Feng; Wang, Zhibin; Zhang, Yunlong; Su, Ying; Guo, Rui; Xu, Zengqi; Liu, Xuanmin

    2016-10-01

    With the development of infrared optical systems in military and civil areas, chalcogenide glass aspherical lens possess some advantages, such as large infrared transmission, good thermal stability performance and image quality. Aspherical lens using chalcogenide glass can satisfy the requirements of modern infrared optical systems. Therefore, precision manufacturing of chalcogenide glass aspheric has received more and more attention. The molding technology of chalcogenide glass aspheric has become a research hotspot, because it can achieve mass and low cost manufacturing. The article of molding technology is focusing on a kind of chalcogenide glass aspherical lens. We report on design and fabrication of the mold that through simulation analysis of molding. Finally, through molding test, the fabrication of mold's surface and parameters of molding has been optimized, ensuring the indicators of chalcogenide glass aspherical lens meet the requirements.

  18. Understanding the Effects of Dilute Sulfur Additions, and Metallization, on the Thermoelectric Properties of Pnictogen Chalcogenides and their Interfaces

    NASA Astrophysics Data System (ADS)

    Devender

    Realizing materials with high thermoelectric figure-of-merit ZT is an exacting challenge because it entails simultaneously obtaining a high Seebeck coefficient, a high electrical conductivity, and a low thermal conductivity, while these properties are usually unfavorably coupled. This thesis demonstrates multifold enhancements in the power factor in sulfur-doped binary and ternary pnictogen chalcogenide nanocrystals and assemblies, and describes the property enhancement mechanisms. The correlations between interfacial thermal and electronic transport, and interfacial diffusion and phase formation in metallized n- and p-type pnictogen chalcogenide structures are also revealed. We show that 400 ppm to 2 at.% sulfur doping can increase both Seebeck coefficient and electrical conductivity, while maintaining low thermal conductivity. Our results show that sulfur-induced property enhancements in Bi2Te 2Se are underpinned by increased density of states effective mass, unlike the mechanism of diminished bipolar charge carrier transport prevalent in sulfur-doped Bi2Te3. Exploiting such effects is anticipated to be attractive for realizing higher ZT nanomaterials. We also show that electrical contact conductivity in metallized pnictogen chalcogenide interfaces is sensitive to metal diffusion and telluride formation. In particular, Ni contacts yield the highest electrical contact conductivity and Cu the lowest, correlating with extent of metal diffusion and p-type metal-telluride formation. We finally show that pnictogen chalcogenides metallized with Sn-Ag-Cu/Ni solder-barrier bilayers exhibit ten-fold higher interfacial thermal conductance than that obtained with In/Ni bilayer metallization. Decreased interdiffusion and diminution of interfacial SnTe formation due to Ni layer correlates with the higher interfacial thermal conductance. Our findings should facilitate the design and development of pnictogen chalcogenide-based thermoelectric materials and devices.

  19. Structural properties of rare earth chalcogenides

    SciTech Connect

    Bhardwaj, Ramakant; Bhardwaj, Purvee Singh, Sadhna

    2016-05-06

    The pressure induced NaCl (B1) to CsCl (B2) structural phase transition of rare earth mono-chalcogenide (PuTe) has been investigated in this paper. A modified interaction potential model (MIPM) (including the covalency effect) has been developed. Phase transition pressures are associated with a sudden collapse in volume. The phase transition pressures and associated volume collapses obtained from present potential model show a generally good agreement with available experimental data than others.

  20. Chalcogenide Glass Optical Waveguides for Infrared Biosensing

    PubMed Central

    Anne, Marie-Laure; Keirsse, Julie; Nazabal, Virginie; Hyodo, Koji; Inoue, Satoru; Boussard-Pledel, Catherine; Lhermite, Hervé; Charrier, Joël; Yanakata, Kiyoyuki; Loreal, Olivier; Le Person, Jenny; Colas, Florent; Compère, Chantal; Bureau, Bruno

    2009-01-01

    Due to the remarkable properties of chalcogenide (Chg) glasses, Chg optical waveguides should play a significant role in the development of optical biosensors. This paper describes the fabrication and properties of chalcogenide fibres and planar waveguides. Using optical fibre transparent in the mid-infrared spectral range we have developed a biosensor that can collect information on whole metabolism alterations, rapidly and in situ. Thanks to this sensor it is possible to collect infrared spectra by remote spectroscopy, by simple contact with the sample. In this way, we tried to determine spectral modifications due, on the one hand, to cerebral metabolism alterations caused by a transient focal ischemia in the rat brain and, in the other hand, starvation in the mouse liver. We also applied a microdialysis method, a well known technique for in vivo brain metabolism studies, as reference. In the field of integrated microsensors, reactive ion etching was used to pattern rib waveguides between 2 and 300 μm wide. This technique was used to fabricate Y optical junctions for optical interconnections on chalcogenide amorphous films, which can potentially increase the sensitivity and stability of an optical micro-sensor. The first tests were also carried out to functionalise the Chg planar waveguides with the aim of using them as (bio)sensors. PMID:22423209

  1. Revisiting some chalcogenides for thermoelectricity

    PubMed Central

    Maignan, Antoine; Guilmeau, Emmanuel; Gascoin, Franck; Bréard, Yohann; Hardy, Vincent

    2012-01-01

    Thermoelectric materials that are efficient well above ambient temperature are needed to convert waste-heat into electricity. Many thermoelectric oxides were investigated for this purpose, but their power factor (PF) values were too small (∼10−4 W m−1 K−2) to yield a satisfactory figure of merit zT. Changing the anions from O2− to S2− and then to Se2− is a way to increase the covalency. In this review, some examples of sulfides (binary Cr–S or derived from layered TiS2) and an example of selenides, AgCrSe2, have been selected to illustrate the characteristic features of their physical properties. The comparison of the only two semiconducting binary chromium sulfides and of a layered AgCrSe2 selenide shows that the PF values are also in the same order of magnitude as those of transition metal oxides. In contrast, the PF values of the layered sulfides TiS2 and Cu0.1TiS2 are higher, reaching ∼10−3 W m−1 K−2. Apparently the magnetism related to the Cr–S network is detrimental for the PF when compared to the d0 character of the Ti4+ based sulfides. Finally, the very low PF in AgCrSe2 (PF = 2.25 × 10−4 W m1 K−2 at 700 K) is compensated by a very low thermal conductivity (κ = 0.2 W m−1 K−1 from the measured Cp) leading to the highest zT value among the reviewed compounds (zT700K = 0.8). The existence of a glassy-like state for the Ag+ cations above 475 K is believed to be responsible for this result. This result demonstrates that the phonon engineering in open frameworks is a very interesting way to generate efficient thermoelectric materials. PMID:27877513

  2. Revisiting some chalcogenides for thermoelectricity.

    PubMed

    Maignan, Antoine; Guilmeau, Emmanuel; Gascoin, Franck; Bréard, Yohann; Hardy, Vincent

    2012-10-01

    Thermoelectric materials that are efficient well above ambient temperature are needed to convert waste-heat into electricity. Many thermoelectric oxides were investigated for this purpose, but their power factor (PF) values were too small (∼10(-4) W m(-1) K(-2)) to yield a satisfactory figure of merit zT. Changing the anions from O(2-) to S(2-) and then to Se(2-) is a way to increase the covalency. In this review, some examples of sulfides (binary Cr-S or derived from layered TiS2) and an example of selenides, AgCrSe2, have been selected to illustrate the characteristic features of their physical properties. The comparison of the only two semiconducting binary chromium sulfides and of a layered AgCrSe2 selenide shows that the PF values are also in the same order of magnitude as those of transition metal oxides. In contrast, the PF values of the layered sulfides TiS2 and Cu0.1TiS2 are higher, reaching ∼10(-3) W m(-1) K(-2). Apparently the magnetism related to the Cr-S network is detrimental for the PF when compared to the d(0) character of the Ti(4+) based sulfides. Finally, the very low PF in AgCrSe2 (PF = 2.25 × 10(-4) W m(1) K(-2) at 700 K) is compensated by a very low thermal conductivity (κ = 0.2 W m(-1) K(-1) from the measured Cp) leading to the highest zT value among the reviewed compounds (zT700K = 0.8). The existence of a glassy-like state for the Ag(+) cations above 475 K is believed to be responsible for this result. This result demonstrates that the phonon engineering in open frameworks is a very interesting way to generate efficient thermoelectric materials.

  3. Electronic and optical properties of mixed Be-chalcogenides

    NASA Astrophysics Data System (ADS)

    Khan, Imad; Ahmad, Iftikhar; Zhang, D.; Rahnamaye Aliabad, H. A.; Jalali Asadabadi, S.

    2013-02-01

    The electronic and optical properties of BeSxSe1-x, BeSxTe1-x and BeSexTe1-x, (0≤x≤1) are studied using the highly accurate modified Beck and Johnson (mBJ) potential. The binary Be-chalcogenides are wide and indirect band gap semiconductors and hence they are not efficient materials for optoelectronics. In order to modify them into optically active materials, the anion chalcogen atoms are partially replaced by other chalcogen atoms like BeSxSe1-x, BeSxTe1-x and BeSexTe1-x (0≤x≤1). The modified ternary compounds are of direct band gap nature and hence they are optically active. Some of these direct band gap materials are lattice matched with silicon and can possibly replace Si in semiconductor devices. Keeping in view the importance of these materials in optoelectronics, the optical properties of BeSxSe1-x, BeSxTe1-x and BeSexTe1-x in the full composition range are investigated. It is found that these materials are transparent in the IR, visible and near UV spectral regions. The alloys for the most of the concentrations have band gaps larger than 3 eV, so it is expected that they may be efficient materials for blue, green and UV light emitting diodes.

  4. The Surface Chemistry of Metal Chalcogenide Nanocrystals

    NASA Astrophysics Data System (ADS)

    Anderson, Nicholas Charles

    The surface chemistry of metal chalcogenide nanocrystals is explored through several interrelated analytical investigations. After a brief discussion of the nanocrystal history and applications, molecular orbital theory is used to describe the electronic properties of semiconductors, and how these materials behave on the nanoscale. Quantum confinement plays a major role in dictating the optical properties of metal chalcogenide nanocrystals, however surface states also have an equally significant contribution to the electronic properties of nanocrystals due to the high surface area to volume ratio of nanoscale semiconductors. Controlling surface chemistry is essential to functionalizing these materials for biological imaging and photovoltaic device applications. To better understand the surface chemistry of semiconducting nanocrystals, three competing surface chemistry models are presented: 1.) The TOPO model, 2.) the Non-stoichiometric model, and 3.) the Neutral Fragment model. Both the non-stoichiometric and neutral fragment models accurately describe the behavior of metal chalcogenide nanocrystals. These models rely on the covalent bond classification system, which divides ligands into three classes: 1.) X-type, 1-electron donating ligands that balance charge with excess metal at the nanocrystal surface, 2.) L-type, 2-electron donors that bind metal sites, and 3.) Z-type, 2-electron acceptors that bind chalcogenide sites. Each of these ligand classes is explored in detail to better understand the surface chemistry of metal chalcogenide nanocrystals. First, chloride-terminated, tri-n-butylphosphine (Bu 3P) bound CdSe nanocrystals were prepared by cleaving carboxylate ligands from CdSe nanocrystals with chlorotrimethylsilane in Bu3P solution. 1H and 31P{1H} nuclear magnetic resonance spectra of the isolated nanocrystals allowed assignment of distinct signals from several free and bound species, including surface-bound Bu3P and [Bu3P-H]+[Cl]- ligands as well as a Bu

  5. Solution synthesis of mixed-metal chalcogenide nanoparticles and spray deposition of precursor films

    DOEpatents

    Schulz, Douglas L.; Curtis, Calvin J.; Ginley, David S.

    2000-01-01

    A colloidal suspension comprising metal chalcogenide nanoparticles and a volatile capping agent. The colloidal suspension is made by reacting a metal salt with a chalcogenide salt in an organic solvent to precipitate a metal chalcogenide, recovering the metal chalcogenide, and admixing the metal chalcogenide with a volatile capping agent. The colloidal suspension is spray deposited onto a substrate to produce a semiconductor precursor film which is substantially free of impurities.

  6. Iron-Chalcogenide Based Solar Absorbers

    NASA Astrophysics Data System (ADS)

    Kykyneshi, Robert; Jieratum, Vorranutch; Altschul, Emmeline; Ravichandran, Ram; Pelatt, Brian; Yu, Liping; Zunger, Alex; Wager, John; Keszler, Douglas

    2011-10-01

    Earth abundant, non-toxic solar absorbers are greatly desirable to reduce solar cell production cost. FeS2 pyrite, with a band gap of ˜0.9 eV, is well known for outstanding absorption properties, yet significant photoconversion has never been achieved. Our computational and experimental study recognizes the failure mechanism of iron pyrite as an instability with respect to other FexS (0.5chalcogenide absorbers. Fe2MS4 (M=Si,Ge) are proposed as viable candidates, and merit for solar absorber application discussed.

  7. Chalcogenide Photonic Crystal Filters For Optical Communication

    SciTech Connect

    Suthar, B.; Bhargava, A.

    2011-12-12

    A proper arrangement of photonic crystal waveguide and a point defect cavity gives an important application of photonic filter device in optical communications. We have studied a narrow band filter and a channel drop filter device using 2-D photonic crystal with square lattice structure. A narrow band filter is applied to select a narrow frequency band signal from incoming light, while a channel drop filter is used to drop a particular frequency signal from incoming light. Chalcogenide As{sub 2}S{sub 3} is compared with conventional Si material regarding applications as feasible material for optical devices.

  8. Synthesis and structures of metal chalcogenide precursors

    NASA Technical Reports Server (NTRS)

    Hepp, Aloysius F.; Duraj, Stan A.; Eckles, William E.; Andras, Maria T.

    1990-01-01

    The reactivity of early transition metal sandwich complexes with sulfur-rich molecules such as dithiocarboxylic acids was studied. Researchers recently initiated work on precursors to CuInSe2 and related chalcopyrite semiconductors. Th every high radiation tolerance and the high absorption coefficient of CuInSe2 makes this material extremely attractive for lightweight space solar cells. Their general approach in early transition metal chemistry, the reaction of low-valent metal complexes or metal powders with sulfur and selenium rich compounds, was extended to the synthesis of chalcopyrite precursors. Here, the researchers describe synthesis, structures, and and routes to single molecule precursors to metal chalcogenides.

  9. Laser Desorption Ionization of As2Ch3 (Ch = S, Se, and Te) Chalcogenides Using Quadrupole Ion Trap Time-of-Flight Mass Spectrometry: A Comparative Study

    NASA Astrophysics Data System (ADS)

    Mawale, Ravi Madhukar; Ausekar, Mayuri Vilas; Prokeš, Lubomír; Nazabal, Virginie; Baudet, Emeline; Halenkovič, Tomáš; Bouška, Marek; Alberti, Milan; Němec, Petr; Havel, Josef

    2017-08-01

    Laser desorption ionization using time-of-flight mass spectrometer afforded with quadrupole ion trap was used to study As2Ch3 (Ch = S, Se, and Te) bulk chalcogenide materials. The main goal of the study is the identification of species present in the plasma originating from the interaction of laser pulses with solid state material. The generated clusters in both positive and negative ion mode are identified as 10 unary (S p +/- and As m +/- ) and 34 binary (As m S p +/- ) species for As2S3 glass, 2 unary (Se q +/- ) and 26 binary (As m Se q +/- ) species for As2Se3 glass, 7 unary (Te r +/- ) and 23 binary (As m Te r +/- ) species for As2Te3 material. The fragmentation of chalcogenide materials was diminished using some polymers and in this way 45 new, higher mass clusters have been detected. This novel approach opens a new possibility for laser desorption ionization mass spectrometry analysis of chalcogenides as well as other materials. [Figure not available: see fulltext.

  10. High surface area graphene-supported metal chalcogenide assembly

    DOEpatents

    Worsley, Marcus A.; Kuntz, Joshua D.; Orme, Christine A.

    2017-04-25

    Disclosed here is a method for hydrocarbon conversion, comprising contacting at least one graphene-supported assembly with at least one hydrocarbon feedstock, wherein the graphene-supported assembly comprises (i) a three-dimensional network of graphene sheets crosslinked by covalent carbon bonds and (ii) at least one metal chalcogenide compound disposed on the graphene sheets, wherein the chalcogen of the metal chalcogenide compound is selected from S, Se and Te, and wherein the metal chalcogenide compound accounts for at least 20 wt. % of the graphene-supported assembly.

  11. Vortex pinning properties in Fe-chalcogenides

    NASA Astrophysics Data System (ADS)

    Leo, A.; Grimaldi, G.; Guarino, A.; Avitabile, F.; Nigro, A.; Galluzzi, A.; Mancusi, D.; Polichetti, M.; Pace, S.; Buchkov, K.; Nazarova, E.; Kawale, S.; Bellingeri, E.; Ferdeghini, C.

    2015-12-01

    Among the families of iron-based superconductors, the 11-family is one of the most attractive for high field applications at low temperatures. Optimization of the fabrication processes for bulk, crystalline and/or thin film samples is the first step in producing wires and/or tapes for practical high power conductors. Here we present the results of a comparative study of pinning properties in iron-chalcogenides, investigating the flux pinning mechanisms in optimized Fe(Se{}1-xTe x ) and FeSe samples by current-voltage characterization, magneto-resistance and magnetization measurements. In particular, from Arrhenius plots in magnetic fields up to 9 T, the activation energy is derived as a function of the magnetic field, {U}0(H), whereas the activation energy as a function of temperature, U(T), is derived from relaxation magnetization curves. The high pinning energies, high upper critical field versus temperature slopes near critical temperatures, and highly isotropic pinning properties make iron-chalcogenide superconductors a technological material which could be a real competitor to cuprate high temperature superconductors for high field applications.

  12. Chalcogenide Perovskites for Solar Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Perera, Samanthe

    Methylammonium Lead halide perovskites have recently emerged as a promising candidate for realizing high efficient low cost photovoltaic modules. Charge transport properties of the solution processed halide perovskites are comparable to some of the existing absorbers used in the current PV industry which require sophisticated processing techniques. Due to this simple processing required to achieve high efficiencies, halide perovskites have become an active field of research. As a result, perovskite solar cells are rapidly reaching towards theoretical efficiency limit of close to 30%. It's believed that ionicity inherent to perovskite materials is one of the contributing factors for the excellent charge transport properties of perovskites. Despite the growing interest for solar energy harvesting purposes, these halide perovskites have serious limitations such as toxicity and instability that need to be addressed in order to commercialize the solar cells incorporating them. This dissertation focuses on a new class of ionic semiconductors, chalcogenide perovskites for solar energy harvesting purposes. Coming from the family perovskites they are expected to have same excellent charge transport properties inherent to perovskites due to the ionicity. Inspired by few theoretical studies on chalcogenide perovskites, BaZrS3 and its Ti alloys were synthesized by sulfurizing the oxide counterpart. Structural characterizations have confirmed the predicted distorted perovskite phase. Optical characterizations have verified the direct band gap suitable for thin film single junction solar cells. Anion alloying was demonstrated by synthesizing oxysulfides with widely tunable band gap suitable for applications such as solid state lighting and sensing.

  13. Solution processing of chalcogenide materials using thiol-amine "alkahest" solvent systems.

    PubMed

    McCarthy, Carrie L; Brutchey, Richard L

    2017-05-02

    Macroelectronics is a major focus in electronics research and is driven by large area applications such as flat panel displays and thin film solar cells. Innovations for these technologies, such as flexible substrates and mass production, will require efficient and affordable semiconductor processing. Low-temperature solution processing offers mild deposition methods, inexpensive processing equipment, and the possibility of high-throughput processing. In recent years, the discovery that binary "alkahest" mixtures of ethylenediamine and short chain thiols possess the ability to dissolve bulk inorganic materials to yield molecular inks has lead to the wide study of such systems and the straightforward recovery of phase pure crystalline chalcogenide thin films upon solution processing and mild annealing of the inks. In this review, we recount the work that has been done toward elucidating the scope of this method for the solution processing of inorganic materials for use in applications such as photovoltaic devices, electrocatalysts, photodetectors, thermoelectrics, and nanocrystal ligand exchange. We also take stock of the wide range of bulk materials that can be used as soluble precursors, and discuss the work that has been done to reveal the nature of the dissolved species. This method has provided a vast toolbox of over 65 bulk precursors, which can be utilized to develop new routes to functional chalcogenide materials. Future studies in this area should work toward a better understanding of the mechanisms involved in the dissolution and recovery of bulk materials, as well as broadening the scope of soluble precursors and recoverable functional materials for innovative applications.

  14. Chalcogenide glass fibreoptics for new mid-infrared medical endoscopy

    NASA Astrophysics Data System (ADS)

    Seddon, Angela B.

    2012-01-01

    Chalcogenide glass fiberoptics could underpin new mid-infrared medical endoscopic systems for real-time molecular sensing, imaging and analysis of tissue and for fiber laser surgery at new mid-infrared wavelengths. Moreover, chalcogenide glass fiberoptic and waveguide devices and systems could provide the key to new mid-infrared communications for molecular sensing to inform decision-taking in other sectors as diverse as manufacturing, energy, the environment and security. The development and deployment of chalcogenide glasses for mid-infrared photonics over the next decade or so could mirror the complexity and versatility of silica fiber optics developed in the 20th Century for near-infrared photonics. These ideas are developed in this paper and the current status of chalcogenide glass photonics is briefly surveyed.

  15. Summary of Chalcogenide Glass Processing: Wet-Etching and Photolithography

    SciTech Connect

    Riley, Brian J.; Sundaram, S. K.; Johnson, Bradley R.; Saraf, Laxmikant V.

    2006-12-01

    This report describes a study designed to explore the different properties of two different chalcogenide materials, As2S3 and As24S38Se38, when subjected to photolithographic wet-etching techniques. Chalcogenide glasses are made by combining chalcogen elements S, Se, and Te with Group IV and/or V elements. The etchant was selected from the literature and was composed of sodium hydroxide, isopropyl alcohol, and deionized water and the types of chalcogenide glass for study were As2S3 and As24S38Se38. The main goals here were to obtain a single variable etch rate curve of etch depth per time versus NaOH overall solution concentration in M and to see the difference in etch rate between a given etchant when used on the different chalcogenide stoichiometries. Upon completion of these two goals, future studies will begin to explore creating complex, integrated photonic devices via these methods.

  16. Chalcogenide Glass Fibers for Infrared Sensing and Space Optics

    NASA Astrophysics Data System (ADS)

    Bureau, Bruno; Maurugeon, Sébastien; Charpentier, Frederic; Adam, Jean-Luc; Boussard-Plédel, Catherine; Zhang, Xiang-Hua

    This review deals with chalcogenide glasses and fibers. Chemical compositions and physical properties are given for specific glasses well suited for fiber drawing. Fabrication techniques of glass perform are described. Single-index and step-index single-mode fibers are characterized in terms of optical losses in the infrared. Examples of applications of chalcogenide fibers are given, as well as optical sensors in the fields of environment, microbiology and health, and as mode-filters for infrared interferometry in space.

  17. Shining a light on transition metal chalcogenides for sustainable photovoltaics

    PubMed Central

    Matthews, Peter D.; McNaughter, Paul D.; Lewis, David J.

    2017-01-01

    Transition metal chalcogenides are an important family of materials that have received significant interest in recent years as they have the potential for diverse applications ranging from use in electronics to industrial lubricants. One of their most exciting properties is the ability to generate electricity from incident light. In this perspective we will summarise and highlight the key results and challenges in this area and explain how transition metal chalcogenides are a good choice for future sustainable photovoltaics. PMID:28626562

  18. Shining a light on transition metal chalcogenides for sustainable photovoltaics.

    PubMed

    Matthews, Peter D; McNaughter, Paul D; Lewis, David J; O'Brien, Paul

    2017-06-01

    Transition metal chalcogenides are an important family of materials that have received significant interest in recent years as they have the potential for diverse applications ranging from use in electronics to industrial lubricants. One of their most exciting properties is the ability to generate electricity from incident light. In this perspective we will summarise and highlight the key results and challenges in this area and explain how transition metal chalcogenides are a good choice for future sustainable photovoltaics.

  19. Two-mode interferometric waveguide sensors based on chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Nalivaiko, V. I.; Ponomareva, M. A.

    2017-08-01

    The operation principles of interferometric waveguide sensors have been considered. A comparison of the sensitivity of the two-mode sensors with waveguides of oxide and chalcogenide glass has been performed. The advantages of the two-mode sensors with waveguides made of a material with high refractive index have been shown. It has been shown that the sensors with waveguides made of chalcogenide glass have a sensitivity three orders of magnitude higher.

  20. Thermo-Dynamic Discussions for the Chalcogenide Films of Reversible Optical Disk

    NASA Astrophysics Data System (ADS)

    Okuda, Masahiro; Rhee, Jung Chul; Matsushita, Tatsuhiko

    1987-05-01

    Thermodynamic discussions concerning the melt and solidification of binary and thernary chalcogenide films as well as the temperature distribution in a film during write-erase cycles are presented. For a reversible optical disk, a very high-rate temperature change (108°C/s) and a high-temperature gradient (8.5× 106°C/cm), compared with the usual metal alloy experiments, were experienced. In a Se-Te (isomorphous) system, the Te concentration increases at the circumference due to segregation. Thus, an isomorphous system is not adequate for reversible memory materials. On the other hand, in an eutectic system, segregation has not occured and, thus, many cycle operation is possible.

  1. Thermoelectric properties of rare earth chalcogenides

    NASA Technical Reports Server (NTRS)

    Danielson, L. R.; Raag, V.; Wood, C.

    1985-01-01

    The rare earth chalcogenides are important thermoelectric materials due to their high melting points, self-doping capabilities, and low thermal conductivities. Lanthanum sulfides and lanthanum tellurides have been synthesized in quartz ampules, hot-pressed into samples, and measured. The n-type Seebeck coefficients, electrical resistivities, and power factors generally all increased as the temperature increased from 200 to 1000 C. The figure-of-merit for nonstoichiometric lanthanum telluride was 0.001/deg C at 1000 C, considerably higher than for silicon-germanium. Thermoelectric measurements were made for LaTe(2) and YbS(1.4), and p-type behavior was observed for these compounds from 300 to 1100 C.

  2. Bipolar switching in chalcogenide phase change memory.

    PubMed

    Ciocchini, N; Laudato, M; Boniardi, M; Varesi, E; Fantini, P; Lacaita, A L; Ielmini, D

    2016-07-05

    Phase change materials based on chalcogenides are key enabling technologies for optical storage, such as rewritable CD and DVD, and recently also electrical nonvolatile memory, named phase change memory (PCM). In a PCM, the amorphous or crystalline phase affects the material band structure, hence the device resistance. Although phase transformation is extremely fast and repeatable, the amorphous phase suffers structural relaxation and crystallization at relatively low temperatures, which may affect the temperature stability of PCM state. To improve the time/temperature stability of the PCM, novel operation modes of the device should be identified. Here, we present bipolar switching operation of PCM, which is interpreted by ion migration in the solid state induced by elevated temperature and electric field similar to the bipolar switching in metal oxides. The temperature stability of the high resistance state is demonstrated and explained based on the local depletion of chemical species from the electrode region.

  3. Multimode supercontinuum generation in chalcogenide glass fibres.

    PubMed

    Kubat, Irnis; Bang, Ole

    2016-02-08

    Mid-infrared supercontinuum generation is considered in chalcogenide fibres when taking into account both polarisations and the necessary higher order modes. In particular we focus on high pulse energy supercontinuum generation with long pump pulses. The modeling indicates that when only a single polarisation in the fundamental mode is considered the obtainable supercontinuum bandwidth is substantially exaggerated compared to when both polarisations are taken into account. Our modeling shows that if the pump pulse is short enough (≤ 10 ps) then higher order modes are not important because of temporal walk-off. In contrast long pump pulses (≥ 40 ps) will efficiently excite higher order modes through Raman scattering, which will deplete the fundamental mode of energy and limit the possibility of obtaining a broadband supercontinuum.

  4. Bipolar switching in chalcogenide phase change memory

    NASA Astrophysics Data System (ADS)

    Ciocchini, N.; Laudato, M.; Boniardi, M.; Varesi, E.; Fantini, P.; Lacaita, A. L.; Ielmini, D.

    2016-07-01

    Phase change materials based on chalcogenides are key enabling technologies for optical storage, such as rewritable CD and DVD, and recently also electrical nonvolatile memory, named phase change memory (PCM). In a PCM, the amorphous or crystalline phase affects the material band structure, hence the device resistance. Although phase transformation is extremely fast and repeatable, the amorphous phase suffers structural relaxation and crystallization at relatively low temperatures, which may affect the temperature stability of PCM state. To improve the time/temperature stability of the PCM, novel operation modes of the device should be identified. Here, we present bipolar switching operation of PCM, which is interpreted by ion migration in the solid state induced by elevated temperature and electric field similar to the bipolar switching in metal oxides. The temperature stability of the high resistance state is demonstrated and explained based on the local depletion of chemical species from the electrode region.

  5. Thermoelectric properties of rare earth chalcogenides

    NASA Technical Reports Server (NTRS)

    Danielson, L. R.; Raag, V.; Wood, C.

    1985-01-01

    The rare earth chalcogenides are important thermoelectric materials due to their high melting points, self-doping capabilities, and low thermal conductivities. Lanthanum sulfides and lanthanum tellurides have been synthesized in quartz ampules, hot-pressed into samples, and measured. The n-type Seebeck coefficients, electrical resistivities, and power factors generally all increased as the temperature increased from 200 to 1000 C. The figure-of-merit for nonstoichiometric lanthanum telluride was 0.001/deg C at 1000 C, considerably higher than for silicon-germanium. Thermoelectric measurements were made for LaTe(2) and YbS(1.4), and p-type behavior was observed for these compounds from 300 to 1100 C.

  6. Multiband superconductivity in iron pnictides and chalcogenides

    NASA Astrophysics Data System (ADS)

    Stanev, Valentin G.

    The main subject of this thesis is the recently discovered family of high-temperature superconducting iron pnictides and chalcogenides. One of the unique features of these materials is that they are multiband superconductors, in which interband interactions dominate. This leads to a very rich and interesting phase diagram, and the possibility that they have a distinct physical mechanism behind their superconducting properties. Study of these materials can provide invaluable information in the quest for room-temperature superconductivity. In the beginning of the thesis I outline some of the basic experimental facts and theoretical concepts relevant for these materials. This outline is structured as a short review and is intended to give the reader brief introduction to the physics of pnictides and chalcogenides. After that some important results valid for multiband superconductors are presented (Chapter 3). I start with a two-band system and discuss some basic features of this model. The presence of general repulsive interband pair-scattering term can drive the system superconducting, with an unconventional order parameter---there is a relative minus sign between the gaps on the two (disconnected) parts of the Fermi surface (so-called s' state). After that I apply a modified version of this model to study the isotope effect---such effect was observed in pnictides---in a system with both electron-electron and electron-phonon interactions. I find that strong isotope effect is not restricted to the phonon-dominated regime of superconductivity. More complicated forms of the order parameter, relevant for pnictides and chalcogenides, are introduced and studied in Chapter 4. I start with a three-band model with repulsive pair-scattering interactions only (in Section 1). I construct the phase diagram of this model and discuss its overall features. Generally, I find three possible superconducting order parameters, one of which breaks the time-reversal symmetry in order to

  7. Opal photonic crystals infiltrated with chalcogenide glasses

    SciTech Connect

    Astratov, V. N.; Adawi, A. M.; Skolnick, M. S.; Tikhomirov, V. K.; Lyubin, V.; Lidzey, D. G.; Ariu, M.; Reynolds, A. L.

    2001-06-25

    Composite opal structures for nonlinear applications are obtained by infiltration with chalcogenide glasses As{sub 2}S{sub 3} and AsSe by precipitation from solution. Analysis of spatially resolved optical spectra reveals that the glass aggregates into submillimeter areas inside the opal. These areas exhibit large shifts in the optical stop bands by up to 80 nm, and by comparison with modelling are shown to have uniform glass filling factors of opal pores up to 40%. Characterization of the domain structure of the opals prior to infiltration by large area angle-resolved spectroscopy is an important step in the analysis of the properties of the infiltrated regions. {copyright} 2001 American Institute of Physics.

  8. Bipolar switching in chalcogenide phase change memory

    PubMed Central

    Ciocchini, N.; Laudato, M.; Boniardi, M.; Varesi, E.; Fantini, P.; Lacaita, A. L.; Ielmini, D.

    2016-01-01

    Phase change materials based on chalcogenides are key enabling technologies for optical storage, such as rewritable CD and DVD, and recently also electrical nonvolatile memory, named phase change memory (PCM). In a PCM, the amorphous or crystalline phase affects the material band structure, hence the device resistance. Although phase transformation is extremely fast and repeatable, the amorphous phase suffers structural relaxation and crystallization at relatively low temperatures, which may affect the temperature stability of PCM state. To improve the time/temperature stability of the PCM, novel operation modes of the device should be identified. Here, we present bipolar switching operation of PCM, which is interpreted by ion migration in the solid state induced by elevated temperature and electric field similar to the bipolar switching in metal oxides. The temperature stability of the high resistance state is demonstrated and explained based on the local depletion of chemical species from the electrode region. PMID:27377822

  9. Solution-processing of chalcogenide materials for device applications

    NASA Astrophysics Data System (ADS)

    Zha, Yunlai

    Chalcogenide glasses are well-known for their desirable optical properties, which have enabled many infrared applications in the fields of photonics, medicine, environmental sensing and security. Conventional deposition methods such as thermal evaporation, chemical vapor deposition, sputtering or pulse laser deposition are efficient for fabricating structures on flat surfaces. However, they have limitations in deposition on curved surfaces, deposition of thick layers and component integration. In these cases, solution-based methods, which involve the dissolution of chalcogenide glasses and processing as a liquid, become a better choice for their flexibility. After proper treatment, the associated structures can have similar optical, chemical and physical properties to the bulk. This thesis presents an in-depth study of solution-processing chalcogenide glasses, starting from the "solution state" to the "film state" and the "structure state". Firstly, chalcogenide dissolution is studied to reveal the mechanisms at molecular level and build a foundation for material processing. Dissolution processes for various chalcogenide solvent pairs are reviewed and compared. Secondly, thermal processing, in the context of high temperature annealing, is explained along with the chemical and physical properties of the annealed films. Another focus is on nanopore formation in propylamine-processed arsenic sulfide films. Pore density changes with respect to annealing temperatures and durations are characterized. Base on a proposed vacancy coalescence theory, we have identified new dissolution strategies and achieved the breakthrough of pore-free film deposition. Thirdly, several solution methods developed along with the associated photonic structures are demonstrated. The first example is "spin-coating and lamination", which produces thick (over 10 mum) chalcogenide structures. Both homogeneous thick chalcogenide structures and heterogeneous layers of different chalcogenide glasses

  10. Investigations into the Structure and Dynamics of Chalcogenide Glasses using High-Resolution Nuclear Magnetic Resonance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kaseman, Derrick Charles

    Chalcogenide glasses constitute an important class of materials that are sulfides, selenides or tellurides of group IV and/or V elements, namely Ge, As, P and Si with minor concentrations of other elements such as Ga, Sb, In. Because of their infrared transparency that can be tuned by changing chemistry and can be actively altered by exposure to band gap irradiation, chalcogenide glasses find use in passive and active optical devices for applications in the areas of photonics, remote sensing and memory technology. Therefore, it is important to establish predictive models of structure-property relationships for these materials for optimization of their physical properties for various applications. Structural elucidation of chalcogenide glasses is experimentally challenging and in order to make predictive structural models, structural units at both short and intermediate -range length scales must be identified and quantified. Nuclear Magnetic Resonance (NMR) spectroscopy is an element-specific structural probe that is uniquely suited for this task, but resolution and sensitivity issues have severely limited the applications of such techniques in the past. The recent development of multi-dimensional solid-state NMR techniques, such as Phase Adjusted Spinning Sidebands (PASS) and Magic Angle Turning (MAT) can potentially alleviate such issues. In this study novel two-dimensional, high-resolution 77Se and 125Te MATPASS NMR spectroscopic techniques are utilized to elucidate quantitatively the compositional evolution of the short- and intermediate- range atomic structure in three binary chalcogenide glass-forming systems, namely: GexSe100-x, AsxSe100-x , and AsxTe100-x. The spectroscopic results provide unambiguous site speciation and quantification for short- and intermediate-range structural motifs present in these glasses. In turn, for all systems, robust structural models and the corresponding structure-property relationships are successfully established as a function

  11. Binary Plutinos

    NASA Astrophysics Data System (ADS)

    Noll, Keith S.

    2015-08-01

    The Pluto-Charon binary was the first trans-neptunian binary to be identified in 1978. Pluto-Charon is a true binary with both components orbiting a barycenter located between them. The Pluto system is also the first, and to date only, known binary with a satellite system consisting of four small satellites in near-resonant orbits around the common center of mass. Seven other Plutinos, objects in 3:2 mean motion resonance with Neptune, have orbital companions including 2004 KB19 reported here for the first time. Compared to the Cold Classical population, the Plutinos differ in the frequency of binaries, the relative sizes of the components, and their inclination distribution. These differences point to distinct dynamical histories and binary formation processes encountered by Plutinos.

  12. Epitaxial Growth and Characterization of Iron Chalcogenide/Bismuth Chalcogenide Heterostructures

    NASA Astrophysics Data System (ADS)

    Flanagan, Thomas; Kandala, Abhinav; Lee, Joon Sue; Kempinger, Susan E.; Richardella, Anthony; Samarth, Nitin

    Heterostructures consisting of topological insulators (TIs) interfaced with superconductors and with ferromagnets have been predicted to give rise to phenomena of both fundamental and applied interest. With superconductors, the region of proximity-induced superconductivity should have px + ipy symmetry, and vortices in this region have been predicted to host Majorana modes, which may be useful as quantum bits. With ferromagnets, such phenomena as the topological magnetoelectric effect have been predicted. Iron chalcogenides, such as iron selenide and iron telluride, are ideal candidates for combining with TIs, since, with only minor changes to growth conditions, they can be superconducting, ferromagnetic, or antiferromagnetic. We describe the growth and characterization of heterostructures that combine thin films of the iron and bismuth chalcogenides, focusing on low temperature magnetoresistance measurements. Our measurements reveal a transient hysteretic magnetoresistance with surprisingly long relaxation times (minutes). This phenomenon appears to be a generic characteristic of all heterostructures that interface TIs with magnetic spins, albeit with structure-specific relaxation times. We discuss possible origins of this unusual phenomenon. Funded by ARO/MURI.

  13. Hybrid polymer photonic crystal fiber with integrated chalcogenide glass nanofilms

    PubMed Central

    Markos, Christos; Kubat, Irnis; Bang, Ole

    2014-01-01

    The combination of chalcogenide glasses with polymer photonic crystal fibers (PCFs) is a difficult and challenging task due to their different thermo-mechanical material properties. Here we report the first experimental realization of a hybrid polymer-chalcogenide PCF with integrated As2S3 glass nanofilms at the inner surface of the air-channels of a poly-methyl-methacrylate (PMMA) PCF. The integrated high refractive index glass films introduce distinct antiresonant transmission bands in the 480–900 nm wavelength region. We demonstrate that the ultra-high Kerr nonlinearity of the chalcogenide glass makes the polymer PCF nonlinear and provides a possibility to shift the transmission band edges as much as 17 nm by changing the intensity. The proposed fabrication technique constitutes a new highway towards all-fiber nonlinear tunable devices based on polymer PCFs, which at the moment is not possible with any other fabrication method. PMID:25317501

  14. Pressure and temperature dependent thermodynamical properties of Sm chalcogenides

    NASA Astrophysics Data System (ADS)

    Shriya, S.; Singh, N.; Khenata, R.; Varshney, Dinesh

    2017-05-01

    The pressure and temperature dependent volume collapse, second order Cauchy discrepancy, anisotropy, melting temperature, hardness, heat capacity and thermal expansion coefficient of SmX; (X = O, S, Se, Te) chalcogenides are studied. Pressure dependence of melting temperature (Tm) discerns an increase inferring the hardening or stiffening of the lattice as a consequence of bond compression and bond strengthening. Suppressed TM as functions of temperature infers the weakening of the lattice results in bond weakening in SmX; (X = O, S, Se, Te) chalcogenides. Vickers Hardness (HV), heat capacity and thermal expansion coefficient of SmX; (X = O, S, Se, Te) chalcogenides demonstrates that SmX is mechanically stiffened, thermally softened and brittle on applied pressure and temperature.

  15. Pressure and temperature induced elastic properties of rare earth chalcogenides

    NASA Astrophysics Data System (ADS)

    Shriya, S.; Singh, N.; Sapkale, R.; Varshney, M.; Varshney, Dinesh

    2016-05-01

    The pressure and temperature dependent mechanical properties as Young modulus, Thermal expansion coefficient of rare earth REX (RE = La, Pr, Eu; X = O, S, Se, and Te) chalcogenides are studied. The rare earth chalcogenides showed a structural phase transition (B1-B2). Pressure dependence of Young modulus discerns an increase in pressure inferring the hardening or stiffening of the lattice as a consequence of bond compression and bond strengthening. Suppressed Young modulus as functions of temperature infers the weakening of the lattice results in bond weakening in REX. Thermal expansion coefficient demonstrates that REX (RE = La, Pr, Eu; X = O, S, Se, and Te) chalcogenides is mechanically stiffened, and thermally softened on applied pressure and temperature.

  16. Pressure and temperature induced elastic properties of rare earth chalcogenides

    SciTech Connect

    Shriya, S.; Sapkale, R. Varshney, Dinesh; Singh, N.; Varshney, M.

    2016-05-06

    The pressure and temperature dependent mechanical properties as Young modulus, Thermal expansion coefficient of rare earth REX (RE = La, Pr, Eu; X = O, S, Se, and Te) chalcogenides are studied. The rare earth chalcogenides showed a structural phase transition (B1–B2). Pressure dependence of Young modulus discerns an increase in pressure inferring the hardening or stiffening of the lattice as a consequence of bond compression and bond strengthening. Suppressed Young modulus as functions of temperature infers the weakening of the lattice results in bond weakening in REX. Thermal expansion coefficient demonstrates that REX (RE = La, Pr, Eu; X = O, S, Se, and Te) chalcogenides is mechanically stiffened, and thermally softened on applied pressure and temperature.

  17. Infrared single mode chalcogenide glass fiber for space.

    PubMed

    Houizot, P; Boussard-Plédel, C; Faber, A J; Cheng, L K; Bureau, B; Van Nijnatten, P A; Gielesen, W L M; Pereira do Carmo, J; Lucas, J

    2007-09-17

    An important measuring technique under study for the DARWIN planet finding mission, is nulling interferometry, enabling the detection of the weak infrared emission lines of an orbiting planet. This technique requires a perfect wavefront of the light beams to be combined in the interferometer. By using a single mode waveguide before detection, wavefront errors are filtered and a virtually perfect plane wavefront is obtained. In this paper the results on the development and the optical characterisation of suitable infrared transmitting chalcogenide glasses and mid-IR guiding optical fibers are reported. Two different perform techniques for manufacturing core-cladding chalcogenide fibers are described. Two types of step index fibers, prepared with Te(2)As(3)Se(5) chalcogenide glasses, offer single mode guidance at 10.6 mum.

  18. Nonlinear optical localization in embedded chalcogenide waveguide arrays

    SciTech Connect

    Li, Mingshan; Huang, Sheng; Wang, Qingqing; Chen, Kevin P.; Petek, Hrvoje

    2014-05-15

    We report the nonlinear optical localization in an embedded waveguide array fabricated in chalcogenide glass. The array, which consists of seven waveguides with circularly symmetric cross sections, is realized by ultrafast laser writing. Light propagation in the chalcogenide waveguide array is studied with near infrared laser pulses centered at 1040 nm. The peak intensity required for nonlinear localization for the 1-cm long waveguide array was 35.1 GW/cm{sup 2}, using 10-nJ pulses with 300-fs pulse width, which is 70 times lower than that reported in fused silica waveguide arrays and with over 7 times shorter interaction distance. Results reported in this paper demonstrated that ultrafast laser writing is a viable tool to produce 3D all-optical switching waveguide circuits in chalcogenide glass.

  19. Broadband supercontinuum generation in all-normal dispersion chalcogenide microwires.

    PubMed

    Al-Kadry, Alaa; Li, Lizhu; El Amraoui, Mohammed; North, Thibault; Messaddeq, Younès; Rochette, Martin

    2015-10-15

    We report the first chalcogenide microwire designed with all-normal dispersion to generate supercontinuum by optical wave breaking, a low-noise nonlinear process. The chalcogenide (As2S3) microwire is coated with PMMA and tapered to a diameter of 0.58 μm to achieve the all-normal dispersion regime. The generated supercontinuum spectrum spans over an octave from 960 to >2500  nm using a microwire length of only 3 mm and a low pulse energy of 150 pJ.

  20. High surface area graphene-supported metal chalcogenide assembly

    DOEpatents

    Worsley, Marcus A.; Kuntz, Joshua; Orme, Christine A.

    2016-04-19

    A composition comprising at least one graphene-supported assembly, which comprises a three-dimensional network of graphene sheets crosslinked by covalent carbon bonds, and at least one metal chalcogenide compound disposed on said graphene sheets, wherein the chalcogen of said metal chalcogenide compound is selected from S, Se and Te. Also disclosed are methods for making and using the graphene-supported assembly, including graphene-supported MoS.sub.2. Monoliths with high surface area and conductivity can be achieved. Lower operating temperatures in some applications can be achieved. Pore size and volume can be tuned.

  1. Recent Advances in Layered Metal Chalcogenides as Superconductors and Thermoelectric Materials: Fe-Based and Bi-Based Chalcogenides.

    PubMed

    Mizuguchi, Yoshikazu

    2016-04-01

    Recent advances in layered (Fe-based and Bi-based) chalcogenides as superconductors or functional materials are reviewed. The Fe-chalcogenide (FeCh) family are the simplest Fe-based high-Tc superconductors. The superconductivity in the FeCh family is sensitive to external or chemical pressure, and high Tc is attained when the local structure (anion height) is optimized. The Bi-chalcogenide (BiCh2) family are a new group of layered superconductors with a wide variety of stacking structures. Their physical properties are also sensitive to external or chemical pressure. Recently, we revealed that the emergence of superconductivity and the Tc in this family correlate with the in-plane chemical pressure. Since the flexibility of crystal structure and electronic states are an advantage of the BiCh2 family for designing functionalities, I briefly review recent developments in this family as not only superconductors but also other functional materials.

  2. Hartree Fock and DFT Study of Models for Amorphous Chalcogenide Alloys

    NASA Astrophysics Data System (ADS)

    Edwards, Arthur; Shedd, Walter; Pugh, Robert

    2001-03-01

    Recently, it has been shown that certain chalcogenide alloys can be switched electrically between polycrystalline and amorphous phases for up to 10^14 cycles and that there is an accompanying large change in conductivity. The most prevalent alloy is a pseudo-binary (GeTe)_2(Sb_2Te_3). While there is some X-Ray data and one band structure calculation on the crystalline phase, there is to date neither theory nor spectroscopy on the amorphous phase. We present a series of Hartree-Fock and DFT molecular orbital studies on models for the amorphous state of the constituent materials and of the alloy. The amorphous models are built on the assumption that normal valence is preserved and that the solid should, in principle, be constructed from repeating the chosen bonding unit. For the pseudo-binary we assume single bonds between Ge and Sb. The surfaces of the clusters are terminated with hydrogen atoms to preserve the normal valence. We have calculated equilibrium geometries using a variety of bases and thes

  3. A simple melting theory applied to alkali halide, alkaline-earth chalcogenide, and alkali chalco-genide compounds

    NASA Astrophysics Data System (ADS)

    Liu, Q.; Chen, L. R.

    2005-06-01

    A useful and simple method for studying the melting temperature T-m of ion compounds has been developed by using analyses originally due to diffusional force theory, incorporating Pandey's formulation and Harrison's potential function. The calculated values of T-m for a wide range of compounds of types IA-VII (alkali halide), IIA-VI (alkaline-earth chalcogenide), and IA-VI (alkali chalcogenide) are found to agree fairly well with experimental values for T-m and to be superior to results from previous approaches involving similar methods.

  4. Chalcogenide microstructured optical fibres for mid-IR applications

    NASA Astrophysics Data System (ADS)

    Trolès, Johann; Brilland, Laurent

    2017-01-01

    Compared to oxide-based glasses, vitreous materials composed of chalcogen elements (S, Se, Te) show large transparency windows in the infrared. Indeed, chalcogenide glasses can be transparent from the visible up to 12- 18 μm, depending on their compositions. In addition, chalcogenide glasses contain large polarisable atoms and external lone electron pairs that induce exceptional non-linear properties. Consequently, the non-linear properties can be 100 or 1000 times as high as the non-linearity of silica. An original way to obtain single-mode fibres is to design microstructured optical fibres (MOFs). These fibres present unique optical properties thanks to the high degree of freedom in the design of their geometrical structure. Various chalcogenide MOFs operating in the IR range have been elaborated in order to associate the high non-linear properties of these glasses with the original MOF properties. Indeed, chalcogenide MOFs might lead to new devices with unique optical properties in the mid-infrared domain, like multimode or endlessly single-mode transmission of light, small or large mode area fibres, highly birefringent fibres and non-linear properties for wavelength conversion or generation of supercontinuum sources. xml:lang="fr"

  5. Local tuning of photonic crystal cavities using chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Faraon, Andrei; Englund, Dirk; Bulla, Douglas; Luther-Davies, Barry; Eggleton, Benjamin J.; Stoltz, Nick; Petroff, Pierre; Vučković, Jelena

    2008-01-01

    We demonstrate a method to locally change the refractive index in planar optical devices by photodarkening of a thin chalcogenide glass layer deposited on top of the device. The method is used to tune the resonance of GaAs-based photonic crystal cavities by up to 3nm at 940nm. The method has broad applications for postproduction tuning of photonic devices.

  6. Optical Whispering Gallery Modes in Chalcogenide Arsenic Selenide Microspheres

    NASA Astrophysics Data System (ADS)

    Yue, Hong-Quan

    Anisotropic chalcogenide microsphere is introduced for coupling theoretical analyzing and coupling experiment. Whispering Gallery Modes (WGMs) of isotropic microsphere is introduced and the TE & TM WGMs dispersion relationship is derived from electromagnetic vector equations in the spherical coordinate. The Maxwell equations can be solved in 2D model for the 3D model of axisymmetric or Rotational symmetry isotropic microsphere. First 4 TE&TM WGMs are simulated in 2D model using finite-element weak method. The binding capability, mode volume V and quality factor Q depend on the refractive index and size of the microsphere. Plane wavefront light wave is assumed to propagate inside the microsphere; coupling coefficient is determined by WGMs numbers and the distance between the microsphere and the micro-taper. Coupling related Q factor is analyzed; TE & TM nonlinear microsphere coupling is introduced with Matlab simulation. Chalcogenide coupling experiments for transmission, reflection and drop-port function are conducted. The light waves for coupling are broadband incoherent light source and narrowband tunable laser. Broadband light gave sensitive results while the coherent laser gave easy coupling capability. The chalcogenide microsphere was used as a feedback element of an amplifying medium. Comparing with silica microsphere, chalcogenide microsphere's response is more unstable due to free carriers perturbation and thermal activity

  7. Binary stars.

    PubMed

    Paczynacuteski, B

    1984-07-20

    Most stars in the solar neighborhood are either double or multiple systems. They provide a unique opportunity to measure stellar masses and radii and to study many interesting and important phenomena. The best candidates for black holes are compact massive components of two x-ray binaries: Cygnus X-1 and LMC X-3. The binary radio pulsar PSR 1913 + 16 provides the best available evidence for gravitational radiation. Accretion disks and jets observed in close binaries offer a very good testing ground for models of active galactic nuclei and quasars.

  8. Magnetic excitations in iron chalcogenide superconductors

    PubMed Central

    Kotegawa, Hisashi; Fujita, Masaki

    2012-01-01

    Nuclear magnetic resonance and neutron scattering experiments in iron chalcogenide superconductors are reviewed to make a survey of the magnetic excitations in FeSe, FeSe1−xTex and alkali-metal-doped AxFe2−ySe2 (A = K, Rb, Cs, etc). In FeSe, the intimate relationship between the spin fluctuations and superconductivity can be seen universally for the variations in the off-stoichiometry, the Co-substitution and applied pressure. The isovalent compound FeTe has a magnetic ordering with different wave vector from that of other Fe-based magnetic materials. The transition temperature Tc of FeSe increases with Te substitution in FeSe1−xTex with small x, and decreases in the vicinity of the end member FeTe. The spin fluctuations are drastically modified by the Te substitution. In the vicinity of the end member FeTe, the low-energy part of the spin fluctuation is dominated by the wave vector of the ordered phase of FeTe; however, the reduction of Tc shows that it does not support superconductivity. The presence of same wave vector as that of other Fe-based superconductors in FeSe1−xTex and the observation of the resonance mode demonstrate that FeSe1−xTex belongs to the same group as most of other Fe-based superconductors in the entire range of x, where superconductivity is mediated by the spin fluctuations whose wave vector is the same as the nesting vector between the hole pockets and the electron pockets. On the other hand, the spin fluctuations differ for alkali-metal-doped AxFe2−ySe2 and FeSe or other Fe-based superconductors in their wave vector and strength in the low-energy part, most likely because of the different Fermi surfaces. The resonance mode with different wave vector suggests that AxFe2−ySe2 has an exceptional superconducting symmetry among Fe-based superconductors. PMID:27877515

  9. Magnetic excitations in iron chalcogenide superconductors.

    PubMed

    Kotegawa, Hisashi; Fujita, Masaki

    2012-10-01

    Nuclear magnetic resonance and neutron scattering experiments in iron chalcogenide superconductors are reviewed to make a survey of the magnetic excitations in FeSe, FeSe1-x Te x and alkali-metal-doped Ax Fe2-y Se2 (A = K, Rb, Cs, etc). In FeSe, the intimate relationship between the spin fluctuations and superconductivity can be seen universally for the variations in the off-stoichiometry, the Co-substitution and applied pressure. The isovalent compound FeTe has a magnetic ordering with different wave vector from that of other Fe-based magnetic materials. The transition temperature Tc of FeSe increases with Te substitution in FeSe1-x Te x with small x, and decreases in the vicinity of the end member FeTe. The spin fluctuations are drastically modified by the Te substitution. In the vicinity of the end member FeTe, the low-energy part of the spin fluctuation is dominated by the wave vector of the ordered phase of FeTe; however, the reduction of Tc shows that it does not support superconductivity. The presence of same wave vector as that of other Fe-based superconductors in FeSe1-x Te x and the observation of the resonance mode demonstrate that FeSe1-x Te x belongs to the same group as most of other Fe-based superconductors in the entire range of x, where superconductivity is mediated by the spin fluctuations whose wave vector is the same as the nesting vector between the hole pockets and the electron pockets. On the other hand, the spin fluctuations differ for alkali-metal-doped Ax Fe2-y Se2 and FeSe or other Fe-based superconductors in their wave vector and strength in the low-energy part, most likely because of the different Fermi surfaces. The resonance mode with different wave vector suggests that Ax Fe2-y Se2 has an exceptional superconducting symmetry among Fe-based superconductors.

  10. Maximizing the Bandwidth from Supercontinuum Generation in Photonic Crystal Chalcogenide Fibers

    DTIC Science & Technology

    2010-09-01

    1 Maximizing the Bandwidth from Supercontinuum Generation in Photonic Crystal Chalcogenide Fibers Curtis R. Menyuk based on the PhD dissertation of... Supercontinuum Generation in Photonic Crystal Chalcogenide Fibers 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d...Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 2 Maximizing the Bandwidth from Supercontinuum Generation in Photonic Crystal Chalcogenide

  11. The nanostructuring of surfaces and films using interference lithography and chalcogenide photoresist.

    PubMed

    Dan'ko, Viktor; Indutnyi, Ivan; Myn'ko, Victor; Lukaniuk, Mariia; Shepeliavyi, Petro

    2015-01-01

    The reversible and transient photostimulated structural changes in annealed chalcogenide glass (ChG) layers were used to form interference periodic structures on semiconductor surfaces and metal films. It was shown that negative-action etchants based on amines dissolve illuminated parts of a chalcogenide film, i.e., act as positive etchants. The diffraction gratings and 2-D interference structures on germanium ChGs - more environmentally acceptable compounds than traditionally used arsenic chalcogenides - were recorded, and their characteristics were studied.

  12. Exploratory Solid-State Synthesis of Uranium Chalcogenides and Mixed Anion Uranium Chalcogenides

    NASA Astrophysics Data System (ADS)

    Ward, Matthew David

    Several uranium chalcogenides and mixed anion uranium chalcogenides have been synthesized by solid-state synthetic methods. Structural determinations were carried out via single-crystal X-ray diffraction. Some of these compounds have been further characterized by magnetic measurements, optical properties measurements, Raman spectroscopy, resistivity measurements, XANES and XPS. Eight compounds of the composition MU8Q17 were synthesized and characterized by single-crystal X-ray diffraction. All of these compounds crystallize in the CrU8S17 structure type. XANES measurements indicate that ScU8S17 contains Sc3+ and must be charge balanced with some amount of U 3+. Two compounds of the composition ATiU3Te9 crystallize as black rectangular plates. From single-crystal magnetic measurements, CsTiU 3Te9 is consistent with antiferromagnetic coupling between magnetic U atoms. The uranium chalcogenide compounds NiUS3 and Cr4US 8 were synthesized from reaction of the elements in various fluxes. NiUS3 crystallizes in the GdFeO3 structure type. Cr 4US8 crystallizes in the orthorhombic space group D - Pnma and its structure is related to that of Li4UF 8. The compounds Rh2U6S15, Cs 2Ti2U6Se15, and Cs2Cr 2U6Se15 crystallize as black prisms in the cubic space group O-Im3m. Magnetic measurements on Cs 2Cr2U6Se15 give a value for the Weiss temperature, θWeiss, of 57.59 K, indicative of ferromagnetic coupling. Black plates of CsScU(Se2)Se3 were synthesized from the reaction of the elements in a CsCl flux. CsScU(Se2)Se 3 crystallizes in the orthorhombic space group D- Cmcm . Magnetic susceptibility measurements on CsScU(Se2)Se 3 indicate three regions of magnetic response. The uranium double salt Cs5[U2(μ-S 2)2Cl8]I crystallizes as red plates. Cs 5[U2(μ-S2)2Cl 8]I displays optical anisotropy with band gap energies of 1.99 eV and 2.08 eV along the [001] and [100] polarizations. The uranium oxychalcogenides U7O2Se12 and Na2Ba2(UO2)S4 were synthesized by intentional oxygen contamination

  13. Chalcogenide nanocrystal assembly: Controlling heterogeneity and modulating heterointerfaces

    NASA Astrophysics Data System (ADS)

    Davis, Jessica

    This dissertation work is focused on developing methods to facilitate charge transport in heterostructured materials that comprise a nanoscale component. Multicomponent semiconductor materials were prepared by (1) spin coating of discrete nanomaterials onto porous silicon (pSi) or (2) self-assembly. Spin-coating of colloidal quantum dot (QD) PbS solutions was employed to create prototype PbS QD based radiation detection devices using porous silicon (pSi) as an n-type support and charge transport material. These devices were initially tested as a photodetector to ascertain the possibility of their use in high energy radiation detection. Short chain thiolate ligands (4-fluorothiophenolate) and anion passivation at the particle interface were evaluated to augment interparticle transport. However, the samples showed minimum interaction with the light source possibly due to poor infiltration into the pSi. The second project was also driven by the potential synergistic properties that can be achieved in multicomponent metal chalcogenide nanostructures, potentially useful in optoelectronic devices. Working with well-established methods for single component metal chalcogenide (MQ) particle gels this dissertation research sought to develop practical methods for co-gelation of different component particles with complimentary functionalities. By monitoring the kinetics of aggregation using time resolved dynamic light scattering and NMR spectroscopy the kinetics of aggregation of the two most common crystal structures for CdQ nanocrystals was studied and it was determined that the hexagonal (wurtzite) crystal structure aggregated faster than the cubic (zinc blende) crystal structure. For gel coupling of nanoparticles with differing Q (Q=S, Se and Te), once we accounted for the crystal structure effects, it was determined that the relative redox characteristics of Q govern the reaction rate. The oxidative sol-gel assembly routes were also employed to fabricate metal

  14. Fabrication and evaluation of chalcogenide glass molding lens for car night-vision system

    NASA Astrophysics Data System (ADS)

    Cha, Du Hwan; Hwang, Yeon; Kim, Jeong-Ho; Kim, Hye-Jeong

    2013-05-01

    With the recent development of less costly uncooled detectors technology, expensive optics are among the remaining significant cost drivers. As a potential solution to this problem, the fabrication of IR lenses using chalcogenide glasses has been studied in recent years. We report on fabrication of molded chalcogenide-glass lens for car night-vision and on the evaluation of the lens. The moldability of chalcogenide glass was characterized through transcription properties of the mold's surface. In addition, both IR transmittance and XRD patterns of the molded chalcogenide glass lens were evaluated to verify the compositional and structural stability of the glass material at the corresponding molding condition.

  15. Intermediate-range order in binary and ternary glasses

    SciTech Connect

    Price, D.L.; Susman, S.; Volin, K.J.; Dejus, R.J.

    1988-07-01

    Intermediate-range order in binary and ternary chalcogenide glasses is discussed, with special reference to GeSe/sub 2/ and Ag/sub 4/Ge/sub 3/Se/sub 9/. A signature of this order is provided by the first sharp diffraction peak, which occurs in these glasses at Q /approximately/ 1 /sup /angstrom/A//sup /minus/1/ and shows anomalous behavior in several ways. It is strongly depressed by the addition of Ag to the GeSe/sub 2/ glass. The addition of Ag also leads to a softening of the vibrational spectrum. 11 refs., 4 figs.

  16. Preparation of chalcogenide glass fiber using an improved extrusion method

    NASA Astrophysics Data System (ADS)

    Jiang, Chen; Wang, Xunsi; Zhu, Minming; Xu, Huijuan; Nie, Qiuhua; Dai, Shixun; Tao, Guangming; Shen, Xiang; Cheng, Ci; Zhu, Qingde; Liao, Fangxing; Zhang, Peiquan; Zhang, Peiqing; Liu, Zijun; Zhang, Xianghua

    2016-05-01

    We developed the extrusion method to prepare arsenic-free chalcogenide glass fibers with glass cladding. By using the double nested extrusion molds and the corresponding isolated stacked extrusion method, the utilization rate of glass materials was greatly improved compared with the conventional extrusion method. Fiber preforms with optimal stability of core/cladding ratio throughout the 160 mm length were prepared using the developed extrusion method. Typical fiber structure defects between the core/cladding interface, such as bubbles, cracks, and core diameter variation, were effectively eliminated. Ge-Sb-Se/S chalcogenide glasses were used to form a core/cladding pair and fibers with core/cladding structure were prepared by thermally drawing the extruded preforms. The transmission loss, fiber bending loss, and other optical characters of the fibers were also investigated.

  17. Chalcogenide molded freeform optics for mid-infrared lasers

    NASA Astrophysics Data System (ADS)

    Chenard, Francois; Alvarez, Oseas; Yi, Allen

    2017-05-01

    High-precision chalcogenide molded micro-lenses were produced to collimate mid-infrared Quantum Cascade Lasers (QCLs). Molded cylindrical micro-lens prototypes with aspheric contour (acylindrical), high numerical aperture (NA 0.8) and small focal length (f<2 mm) were fabricated to collimate the QCL fast-axis beam. Another innovative freeform micro-lens has an input acylindrical surface to collimate the fast axis and an orthogonal output acylindrical surface to collimate the slow axis. The thickness of the freeform lens is such that the output fast- and slow-axis beams are circular. This paper presents results on the chalcogenide molded freeform micro-lens designed to collimate and circularize QCL at 4.6 microns.

  18. Mold design with simulation for chalcogenide glass precision molding

    NASA Astrophysics Data System (ADS)

    Zhang, Yunlong; Wang, Zhibin; Li, Junqi; Zhang, Feng; Su, Ying; Wang, Zhongqiang

    2016-10-01

    Compare with the manufacturing of the traditional infrared material, such as signal crystal germanium, zinc sulfide, zinc selenide etc, chalcogenide infrared glass is suitable for precision molding for the low soften temperature to have large mass industry production. So the researches of precision glass molding are necessary, especially for the fast development of infrared product. The mold design is one of the key technologies of precision glass molding. In this paper, the mold processing of a sample chalcogenide glass from the technical drawing, mold design, molding to the lens are introduced. From the result of the precision molding, the technology of finite element simulation is a useful way to guiding the mold design. The molded lens by using mold process fit the design requirement.

  19. Transient photocurrent measurements in alkali chalcogenide ternary compound semiconductors

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Peters, J. A.; Li, H.; Kanatzidis, M. G.; Wessels, B. W.

    2013-01-01

    The charge transport properties of two alkali metal chalcogenide, semiconductor ternary compounds Cs2Cd3Te4 and Cs2Hg6S7, having potential as efficient high-energy radiation detectors, were investigated. A key property that determines the detector performance is the minority carrier lifetime, which was determined by measurement of photocurrent transients using pulsed laser excitation. The alkali metal chalcogenide semiconductor crystals were grown by a modified Bridgman method. The Cs2Cd3Te4 compound has a minority lifetime of 2.45 µs at 295 K, which is comparable to that of cadmium zinc telluride (CZT). The Cs2Hg6S7 showed charge trapping with decay times of 120 µs. The excellent charge transport properties of Cs2Cd3Te4 indicate that this ternary compound semiconductor should be well suited for gamma radiation detector devices that operate at room temperature.

  20. Nonlinear light propagation in chalcogenide photonic crystal slow light waveguides.

    PubMed

    Suzuki, Keijiro; Baba, Toshihiko

    2010-12-06

    Optical nonlinearity can be enhanced by the combination of highly nonlinear chalcogenide glass and photonic crystal waveguides (PCWs) providing strong optical confinement and slow-light effects. In a Ag-As(2)Se(3) chalcogenide PCW, the effective nonlinear parameter γeff reaches 6.3 × 10(4) W(-1)m(-1), which is 200 times larger than that in Si photonic wire waveguides. In this paper, we report the detailed design, fabrication process, and the linear and nonlinear characteristics of this waveguide at silica fiber communication wavelengths. We show that the waveguide exhibits negligible two-photon absorption, and also high-efficiency self-phase modulation and four-wave mixing, which are assisted by low-dispersion slow light.

  1. Electronic structure of ruthenium-doped iron chalcogenides

    SciTech Connect

    Winiarski, M. J. Samsel-Czekała, M.; Ciechan, A.

    2014-12-14

    The structural and electronic properties of hypothetical Ru{sub x}Fe{sub 1−x}Se and Ru{sub x}Fe{sub 1−x}Te systems have been investigated from first principles within the density functional theory (DFT). Reasonable values of lattice parameters and chalcogen atomic positions in the tetragonal unit cell of iron chalcogenides have been obtained with the use of norm-conserving pseudopotentials. The well known discrepancies between experimental data and DFT-calculated results for structural parameters of iron chalcogenides are related to the semicore atomic states which were frozen in the used here approach. Such an approach yields valid results of the electronic structures of the investigated compounds. The Ru-based chalcogenides exhibit the same topology of the Fermi surface (FS) as that of FeSe, differing only in subtle FS nesting features. Our calculations predict that the ground states of RuSe and RuTe are nonmagnetic, whereas those of the solid solutions Ru{sub x}Fe{sub 1−x}Se and Ru{sub x}Fe{sub 1−x}Te become the single- and double-stripe antiferromagnetic, respectively. However, the calculated stabilization energy values are comparable for each system. The phase transitions between these magnetic arrangements may be induced by slight changes of the chalcogen atom positions and the lattice parameters a in the unit cell of iron selenides and tellurides. Since the superconductivity in iron chalcogenides is believed to be mediated by the spin fluctuations in single-stripe magnetic phase, the Ru{sub x}Fe{sub 1−x}Se and Ru{sub x}Fe{sub 1−x}Te systems are good candidates for new superconducting iron-based materials.

  2. Electronic structure of ruthenium-doped iron chalcogenides

    NASA Astrophysics Data System (ADS)

    Winiarski, M. J.; Samsel-Czekała, M.; Ciechan, A.

    2014-12-01

    The structural and electronic properties of hypothetical RuxFe1-xSe and RuxFe1-xTe systems have been investigated from first principles within the density functional theory (DFT). Reasonable values of lattice parameters and chalcogen atomic positions in the tetragonal unit cell of iron chalcogenides have been obtained with the use of norm-conserving pseudopotentials. The well known discrepancies between experimental data and DFT-calculated results for structural parameters of iron chalcogenides are related to the semicore atomic states which were frozen in the used here approach. Such an approach yields valid results of the electronic structures of the investigated compounds. The Ru-based chalcogenides exhibit the same topology of the Fermi surface (FS) as that of FeSe, differing only in subtle FS nesting features. Our calculations predict that the ground states of RuSe and RuTe are nonmagnetic, whereas those of the solid solutions RuxFe1-xSe and RuxFe1-xTe become the single- and double-stripe antiferromagnetic, respectively. However, the calculated stabilization energy values are comparable for each system. The phase transitions between these magnetic arrangements may be induced by slight changes of the chalcogen atom positions and the lattice parameters a in the unit cell of iron selenides and tellurides. Since the superconductivity in iron chalcogenides is believed to be mediated by the spin fluctuations in single-stripe magnetic phase, the RuxFe1-xSe and RuxFe1-xTe systems are good candidates for new superconducting iron-based materials.

  3. Novel Chalcogenide Materials for x ray and Gamma ray Detection

    DTIC Science & Technology

    2016-05-01

    then heated to 800 oC in 8h and kept there for 1 d, and finally cooled to room temperature in 1 d. Orange red crystals can be picked out from the...a new heavy atom chalcogenide family of semiconductors for room temperature gamma radiation detection. Its goal was to accelerate nuclear detector...selection criteria relevant to γ-ray detection at room temperature. These include heavy element composition, extended structures and wide energy

  4. Supercontinuum generation in two kinds of chalcogenide microstructured optical fibers

    NASA Astrophysics Data System (ADS)

    Gao, Weiqing; Hu, Jigang; Li, Yuan; Qiu, Huaili; Yuan, Zijun; Gao, Feng; Duan, Zhongchao; Suzuki, Takenobu; Ohishi, Yasutake

    2014-10-01

    Chalcogenide microstructured fibers (MOFs) have great advantages for supercontinuum (SC) generation in mid-infrared (MIR) region, because they possess the properties of high nonlinearity and wide transmission window, simultaneously. The nonlinear parameters of chalcogenide MOFs can be higher by several tens or hundreds than those of silica, fluoride and tellurite fibers depending on the material components and fiber structures. Chalcogenide MOF can be transparent from visible up to the infrared region of 12 or 15 μm depending on the compositions. In this paper, we demonstrate the SC generation in two kinds of suspended-core chalcogenide MOFs with different material components and fiber structures. One is an As2S3 MOF with three-hole structure (Fiber I). The other is an As2S5 MOF with four-hole structure (Fiber II). For Fiber I, the SC range of 3020 nm (from 1510 to 4530 nm) were obtained in a 2.4 cm fiber, when pumped by the wavelength at 2500 nm. The SC extends to the wavelengths longer than 4 μm. For Fiber II, the SC range of 4280 nm (from 1370 to 5650 nm) is generated in a 4.8 cm fiber when pumped by the wavelength at 2300 nm, which covers more than two octaves. Compared to the SC generated in Fiber I, the SC spectral range in Fiber II has been increased by more than 1200 nm due to the better transmission property of the As2S5 glass; the SC extends to the wavelengths longer than 5 μm.

  5. Influence of ion irradiation on iron-chalcogenide superconducting films

    NASA Astrophysics Data System (ADS)

    Ozaki, Toshinori; Si, Weidong; Zhang, Cheng; Wu, Lijun; Li, Qiang

    2015-03-01

    Iron-chalcogenide superconductors have rather simple crystal structure and no charge reservoir. They also exhibit remarkable properties including small anisotoropy, high upper critical fields, a significant pressure effect on superconductivity. We have grown iron-chalcogenide FeSe0.5Te0.5 (FST) superconducting films on various substrate by pulsed laser deposition. The FST films on CeO2 buffer layer exhibit enhanced Tc (Tconset >20 K, Tczero = 18.0 K), which is about 30% higher than that found in the bulk materials and superior high field performance over the low temperature superconductors.. Recently, we were successful in further enhancement of Jc without Tc degradation by ion irradiation, especially, at high temperature and high magnetic field. The low-energy proton irradiation produces a Jc enhancement of one order of magnitude over the field of 6T//c at 12 K. Extensive TEM studies of the irradiated FST films have been carried out, which revealed an intriguing defect morphology provided by the irradiation. We will discuss the relationship between the superconducting properties and the created defects of the iron-chalcogenide films.

  6. Nonlinear propagation of surface plasmon-polaritons in chalcogenide glass

    NASA Astrophysics Data System (ADS)

    Sagor, Rakibul Hasan

    The field of plasmonics has attracted a lot of research in nano-photonics. Surface Plasmon Polaritons (SPPs) are believed to be strong candidates for nano-scale imaging and computing. SPPs are electromagnetic modes which arise from the coupling effect between photons and the free conduction electrons on the interface between a metal and a dielectric. In integrated optical devices based on SPPs, the light can be confined in sub-wavelength scale, and the resultant EM wave propagates along the metal interface. In this thesis, a time-domain simulation algorithm for the investigation of nonlinear propagation properties of SPPs in chalcogenide glasses is developed. Chalcogenide glasses have become attractive in ultrafast nonlinear devices due to their high material non-linearity. The frequency-dependent dispersion relations as well as third-order non-linearity of chalcogenide glass have been modeled using the general polarization algorithm incorporated in the auxiliary differential equation (ADE). The resulting time domain model has been solved numerically using the Finite Difference Time Domain method. The dynamics of SPP propagation in several plasmonic structures containing third-order nonlinearity have been studied. It was found that non-linear SPP propagation leads to significant changes in the spectrum of the propagated pulse. Such changes can be utilized in novel SPP-based switching and other photonic structur.

  7. Electroactive Nanoporous Metal Oxides and Chalcogenides by Chemical Design

    PubMed Central

    2017-01-01

    The archetypal silica- and aluminosilicate-based zeolite-type materials are renowned for wide-ranging applications in heterogeneous catalysis, gas-separation and ion-exchange. Their compositional space can be expanded to include nanoporous metal chalcogenides, exemplified by germanium and tin sulfides and selenides. By comparison with the properties of bulk metal dichalcogenides and their 2D derivatives, these open-framework analogues may be viewed as three-dimensional semiconductors filled with nanometer voids. Applications exist in a range of molecule size and shape discriminating devices. However, what is the electronic structure of nanoporous metal chalcogenides? Herein, materials modeling is used to describe the properties of a homologous series of nanoporous metal chalcogenides denoted np-MX2, where M = Si, Ge, Sn, Pb, and X = O, S, Se, Te, with Sodalite, LTA and aluminum chromium phosphate-1 structure types. Depending on the choice of metal and anion their properties can be tuned from insulators to semiconductors to metals with additional modification achieved through doping, solid solutions, and inclusion (with fullerene, quantum dots, and hole transport materials). These systems form the basis of a new branch of semiconductor nanochemistry in three dimensions. PMID:28572706

  8. Chalcogenide material strengthening through the lens molding process

    NASA Astrophysics Data System (ADS)

    Nelson, J.; Scordato, M.; Lucas, Pierre; Coleman, Garrett J.

    2016-05-01

    The demand for infrared transmitting materials has grown steadily for several decades as markets realize new applications for longer wavelength sensing and imaging. With this growth has come the demand for new and challenging material requirements that cannot be satisfied with crystalline products alone. Chalcogenide materials, with their unique physical, thermal, and optical properties, have found acceptance by designers and fabricators to meet these demands. No material is perfect in every regard, and chalcogenides are no exception. A cause for concern has been the relatively low fracture toughness and the propensity of the bulk material to fracture. This condition is amplified when traditional subtractive manufacturing processes are employed. This form of processing leaves behind micro fractures and sub surface damage, which act as propagation points for both local and catastrophic failure of the material. Precision lens molding is not a subtractive process, and as a result, micro fractures and sub surface damage are not created. This results in a stronger component than one produced by traditional methods. New processing methods have also been identified that result in an even stronger surface that is more resistant to breakage, without the need for post processing techniques that may compromise surface integrity. This paper will discuss results achieved in the process of lens molding development at Edmund Optics that result in measurably stronger chalcogenide components. Various metrics will be examined and data will be presented that quantifies component strength for different manufacturing processes.

  9. Forced Ion Migration for Chalcogenide Phase Change Memory Device

    NASA Technical Reports Server (NTRS)

    Campbell, Kristy A (Inventor)

    2013-01-01

    Non-volatile memory devices with two stacked layers of chalcogenide materials comprising the active memory device have been investigated for their potential as phase-change memories. The devices tested included GeTe/SnTe, Ge2Se3/SnTe, and Ge2Se3/SnSe stacks. All devices exhibited resistance switching behavior. The polarity of the applied voltage with respect to the SnTe or SnSe layer was critical to the memory switching properties, due to the electric field induced movement of either Sn or Te into the Ge-chalcogenide layer. One embodiment of the invention is a device comprising a stack of chalcogenide-containing layers which exhibit phase-change switching only after a reverse polarity voltage potential is applied across the stack causing ion movement into an adjacent layer and thus "activating" the device to act as a phase-change random access memory device or a reconfigurable electronics device when the applied voltage potential is returned to the normal polarity. Another embodiment of the invention is a device that is capable of exhibiting more than two data states.

  10. Forced ion migration for chalcogenide phase change memory device

    NASA Technical Reports Server (NTRS)

    Campbell, Kristy A. (Inventor)

    2011-01-01

    Non-volatile memory devices with two stacked layers of chalcogenide materials comprising the active memory device have been investigated for their potential as phase change memories. The devices tested included GeTe/SnTe, Ge.sub.2Se.sub.3/SnTe, and Ge.sub.2Se.sub.3/SnSe stacks. All devices exhibited resistance switching behavior. The polarity of the applied voltage with respect to the SnTe or SnSe layer was critical to the memory switching properties, due to the electric field induced movement of either Sn or Te into the Ge-chalcogenide layer. One embodiment of the invention is a device comprising a stack of chalcogenide-containing layers which exhibit phase change switching only after a reverse polarity voltage potential is applied across the stack causing ion movement into an adjacent layer and thus "activating" the device to act as a phase change random access memory device or a reconfigurable electronics device when the applied voltage potential is returned to the normal polarity. Another embodiment of the invention is a device that is capable of exhibiting more that two data states.

  11. Forced ion migration for chalcogenide phase change memory device

    NASA Technical Reports Server (NTRS)

    Campbell, Kristy A. (Inventor)

    2012-01-01

    Non-volatile memory devices with two stacked layers of chalcogenide materials comprising the active memory device have been investigated for their potential as phase-change memories. The devices tested included GeTe/SnTe, Ge.sub.2Se.sub.3/SnTe, and Ge.sub.2Se.sub.3/SnSe stacks. All devices exhibited resistance switching behavior. The polarity of the applied voltage with respect to the SnTe or SnSe layer was critical to the memory switching properties, due to the electric field induced movement of either Sn or Te into the Ge-chalcogenide layer. One embodiment of the invention is a device comprising a stack of chalcogenide-containing layers which exhibit phase-change switching only after a reverse polarity voltage potential is applied across the stack causing ion movement into an adjacent layer and thus "activating" the device to act as a phase-change random access memory device or a reconfigurable electronics device when the applied voltage potential is returned to the normal polarity. Another embodiment of the invention is a device that is capable of exhibiting more than two data states.

  12. Infrared colloidal lead chalcogenide nanocrystals: synthesis, properties, and photovoltaic applications.

    PubMed

    Fu, Huiying; Tsang, Sai-Wing

    2012-04-07

    Simple solution phase, catalyst-free synthetic approaches that offer monodispersed, well passivated, and non-aggregated colloidal semiconductor nanocrystals have presented many research opportunities not only for fundamental science but also for technological applications. The ability to tune the electrical and optical properties of semiconductor nanocrystals by manipulating the size and shape of the crystals during the colloidal synthesis provides potential benefits to a variety of applications including photovoltaic devices, light-emitting diodes, field effect transistors, biological imaging/labeling, and more. Recent advances in the synthesis and characterization of colloidal lead chalcogenide nanocrystals and the achievements in colloidal PbS or PbSe nanocrystals solar cells have demonstrated the promising application of infrared-emitting colloidal lead chalcogenide nanocrystals in photovoltaic devices. Here, we review recent progress in the synthesis and optical properties of colloidal lead chalcogenide nanocrystals. We focus in particular upon the size- and shape-controlled synthesis of PbS, PbSe, and PbTe nanocrystals by using different precursors and various stabilizing surfactants for the growth of the colloidal nanocrystals. We also summarize recent advancements in the field of colloidal nanocrystals solar cells based on colloidal PbS and PbSe nanocrystals. This journal is © The Royal Society of Chemistry 2012

  13. Bond constraint theory studies of chalcogenide phase change memories

    SciTech Connect

    Paesler, M.A.; Baker, D.A.; Lucovsky, G.

    2008-07-08

    Studies of amorphous (a-) semiconductors have been driven by technological advances as well as fundamental theories. Observation of electrical switching, for example, fueled early interest in a-chalcogenides. More recently a-chalcogenide switching has been applied successfully to programmable memory devices as well as DVD technology where the quest for the discovery of better-suited materials continues. Thus, switching grants researchers today with an active arena of technological as well as fundamental study. Bond constraint theory (BCT) and rigidity theory provide a powerful framework for understanding the structure and properties of a-materials. Application of these theories to switching in a-chalcogenides holds the promise of finding the best composition suited for switching applications. Extended X-ray absorption fine structure (EXAFS) spectroscopy is an ideally suited technique to investigate the switching properties of these materials. Films of amorphous Ge{sub 2}Sb{sub 2}Te{sub 4}, Ge{sub 2}Sb{sub 2}Te{sub 5}, and Ge{sub 2}Sb{sub 2}Te{sub 7} exhibit differing bonding structures and bond statistics, which result in different electronic and optical properties. Results of new EXAFS experiments on these three critical compositions in the Ge-Sb-Te system are presented in light of BCT and rigidity theory.

  14. Linear and nonlinear optical properties of chalcogenide microstructured optical fibers

    NASA Astrophysics Data System (ADS)

    Trolès, Johann; Brilland, Laurent; Caillaud, Celine; Renversez, Gilles; Mechin, David; Adam, Jean-Luc

    2015-03-01

    Chalcogenide glasses are known for their large transparency in the mid-infrared and their high linear refractive index (>2). They present also a high non-linear coefficient (n2), 100 to 1000 times larger than for silica, depending on the composition. we have developed a casting method to prepare the microstructured chalcogenide preform. This method allows optical losses as low as 0.4 dB/m at 1.55 µm and less than 0.05 dB/m in the mid IR. Various chalcogenide MOFs operating in the IR range has been fabricated in order to associate the high non-linear properties of these glasses and the original MOF properties. For example, small core fibers have been drawn to enhance the non linearities for telecom applications such as signal regeneration and generation of supercontinuum sources. On another hand, in the 3-12 µm window, single mode fibers and exposed core fibers have been realized for Gaussian beams propagation and sensors applications respectively.

  15. Binary Planets

    NASA Astrophysics Data System (ADS)

    Ryan, Keegan; Nakajima, Miki; Stevenson, David J.

    2014-11-01

    Can a bound pair of similar mass terrestrial planets exist? We are interested here in bodies with a mass ratio of ~ 3:1 or less (so Pluto/Charon or Earth/Moon do not qualify) and we do not regard the absence of any such discoveries in the Kepler data set to be significant since the tidal decay and merger of a close binary is prohibitively fast well inside of 1AU. SPH simulations of equal mass “Earths” were carried out to seek an answer to this question, assuming encounters that were only slightly more energetic than parabolic (zero energy). We were interested in whether the collision or near collision of two similar mass bodies would lead to a binary in which the two bodies remain largely intact, effectively a tidal capture hypothesis though with the tidal distortion being very large. Necessarily, the angular momentum of such an encounter will lead to bodies separated by only a few planetary radii if capture occurs. Consistent with previous work, mostly by Canup, we find that most impacts are disruptive, leading to a dominant mass body surrounded by a disk from which a secondary forms whose mass is small compared to the primary, hence not a binary planet by our adopted definition. However, larger impact parameter “kissing” collisions were found to produce binaries because the dissipation upon first encounter was sufficient to provide a bound orbit that was then rung down by tides to an end state where the planets are only a few planetary radii apart. The long computational times for these simulation make it difficult to fully map the phase space of encounters for which this outcome is likely but the indications are that the probability is not vanishingly small and since planetary encounters are a plausible part of planet formation, we expect binary planets to exist and be a non-negligible fraction of the larger orbital radius exoplanets awaiting discovery.

  16. Materials characterization of silver chalcogenide programmable metallization cells

    NASA Astrophysics Data System (ADS)

    Hilt, Lyndee Lee

    The standardless, quantitative characterization technique of Rutherford Backscattering Spectrometry (RBS) is used to study the photodissolution, thermal diffusion, and materials stability of Ag-chalcogenides ternaries. The photodissolution process of Ag in As2S3 follows the well-known step-like process driven by the chemical potential of Ag with an end solubility of 44.4 at. % Ag. Thermal doping of Ag has a small induction period of 5 minutes before diffusion initiates due to the thermal activation barrier. Both photodissolution and thermal diffusion of Ag in GexSe 1-x show a Gaussian distribution from which the diffusion coefficient is determined by using RBS and solving Fick's diffusion equation. The end Ag solubility for photodissolution and thermal diffusion in GexSe 1-x is 33.3 and 34.8 at. % Ag, respectively. The metastable state that Ag-chalcogenide thin films form upon evaporation contribute to the thermal instability of Ag-As-S and Ag-Ge-Se when annealed at temperatures below the glass transition temperature. Activation energies for As and Ge outdiffusion are obtained from Arrhenius plots of the areal density of material remaining after annealing. The activation energies are less than 0.2 eV for both air and reducing atmosphere ambient, indicating that the thermal barrier is readily overcome. The outdiffusing species are oxides and, at sufficient temperatures, a volatile chalcogenide component. Photodissolution of Ag in chalcogenides create a solid state electrochemical solution. The application of an applied voltage to contacts changes the high impedance state, >100 MO, to a low impedance state, <25 O, by the electrodeposition of Ag creating a programmable metallization cell. The stability of the electrodeposit connection may be further enhanced due to the ability for continued electrodeposition. Ag-Ge-Se device samples show current-voltage characteristic electrochemical curves that are. dependent on the homogeneity of the doping mechanism. In summary

  17. Iron chalcogenide photovoltaic absorbers -- problems and opportunities

    NASA Astrophysics Data System (ADS)

    Kokenyesi, Robert; Jieratum, Vorranutch; Altschul, Emmeline; Keszler, Douglas; Ravichandran, Ram; Pelatt, Brian; Wager, John; Yu, Liping; Lany, Stephan; Zunger, Alex

    2012-02-01

    Realizing new, efficient solar absorbers containing earth-abundant materials represents a critical element for expanding the reach of photovoltaic (PV) technologies, meeting growing energy needs. The use of Fe in PV was proposed more than 25 years ago in the form of FeS2 pyrite. We report a concerted and integrated theoretical and experimental study that provides new insight into the problem of FeS2. Computational results on FeS2 reveal high formation energies for bulk point defects and small formation energies for S vacances near the surface. These findings are consistent with the formation of metallic S-deficient binary Fe-S phases at low temperatures that affect the electrical and optical properties of thin films. We have used this new understanding to propose and implement design rules for identifying new Fe-containing materials---Fe2SiS4 and Fe2GeS4-- that may circumvent the limitations of pyrite. These ternary materials are p-type with direct allowed optical band gaps near 1.5 eV.

  18. Nanoscale structure and atomic disorder in the iron-based chalcogenides.

    PubMed

    Saini, Naurang Lal

    2013-02-01

    The multiband iron-based superconductors have layered structure with a phase diagram characterized by a complex interplay of charge, spin and lattice excitations, with nanoscale atomic structure playing a key role in their fundamental electronic properties. In this paper, we briefly review nanoscale structure and atomic disorder in iron-based chalcogenide superconductors. We focus on the Fe(Se,S)1-x Te x (11-type) and K0.8Fe1.6Se2 (122-type) systems, discussing their local structure obtained by extended x-ray absorption fine structure. Local structure studies on the Fe(Se,S)1-x Te x system reveal clear nanoscale phase separation characterized by coexisting components of different atomic configurations, similar to the case of random alloys. In fact, the Fe-Se/S and Fe-Te distances in the ternary Fe(Se,S)1-x Te x are found to be closer to the respective distances in the binary FeSe/FeS and FeTe systems, showing significant divergence of the local structure from the average one. The observed features are characteristic of ternary random alloys, indicating breaking of the local symmetry in these materials. On the other hand, K0.8Fe1.6Se2 is known for phase separation in an iron-vacancy ordered phase and an in-plane compressed lattice phase. The local structure of these 122-type chalcogenides shows that this system is characterized by a large local disorder. Indeed, the experiments suggest a nanoscale glassy phase in K0.8Fe1.6Se2, with the superconductivity being similar to the granular materials. While the 11-type structure has no spacer layer, the 122-type structure contains intercalated atoms unlike the 1111-type REFeAsO (RE = rare earth) oxypnictides, having well-defined REO spacer layers. It is clear that the interlayer atomic correlations in these iron-based superconducting structures play an important role in structural stability as well as superconductivity and magnetism.

  19. Nanoscale structure and atomic disorder in the iron-based chalcogenides

    PubMed Central

    Saini, Naurang Lal

    2013-01-01

    The multiband iron-based superconductors have layered structure with a phase diagram characterized by a complex interplay of charge, spin and lattice excitations, with nanoscale atomic structure playing a key role in their fundamental electronic properties. In this paper, we briefly review nanoscale structure and atomic disorder in iron-based chalcogenide superconductors. We focus on the Fe(Se,S)1−xTex (11-type) and K0.8Fe1.6Se2 (122-type) systems, discussing their local structure obtained by extended x-ray absorption fine structure. Local structure studies on the Fe(Se,S)1−xTex system reveal clear nanoscale phase separation characterized by coexisting components of different atomic configurations, similar to the case of random alloys. In fact, the Fe–Se/S and Fe–Te distances in the ternary Fe(Se,S)1−xTex are found to be closer to the respective distances in the binary FeSe/FeS and FeTe systems, showing significant divergence of the local structure from the average one. The observed features are characteristic of ternary random alloys, indicating breaking of the local symmetry in these materials. On the other hand, K0.8Fe1.6Se2 is known for phase separation in an iron-vacancy ordered phase and an in-plane compressed lattice phase. The local structure of these 122-type chalcogenides shows that this system is characterized by a large local disorder. Indeed, the experiments suggest a nanoscale glassy phase in K0.8Fe1.6Se2, with the superconductivity being similar to the granular materials. While the 11-type structure has no spacer layer, the 122-type structure contains intercalated atoms unlike the 1111-type REFeAsO (RE = rare earth) oxypnictides, having well-defined REO spacer layers. It is clear that the interlayer atomic correlations in these iron-based superconducting structures play an important role in structural stability as well as superconductivity and magnetism. PMID:27877557

  20. Design, fabrication and characterization of solution-based molded chalcogenide optics for infrared application

    NASA Astrophysics Data System (ADS)

    Dixit, Awakash; Singh, Radhakant; Agarwal, Amit K.; Ghosh, Amitava; Dwivedi, Prabhat K.

    2016-09-01

    We report design, fabrication and characterization of molded chalcogenide microlens array for Infrared sensing applications. A master of desired microlens array with high sag value is prepared using ultraviolet lithography and thermal reflow method on a positive photoresist (ma-P1275HV). The negative replica of the master is created using polydimethylsiloxane which serves as a mold for micro-molding. Further, chalcogenide solution is prepared in ethanolamine solvent and spin coated on a substrate to get a uniform film; these films are characterized and are found to have the same optical properties as the parent bulk chalcogenide glass. Finally, the microlens array is fabricated by the micro-molding of chalcogenide film. Fabricated chalcogenide microlenses are characterized for geometrical parameters, which are used to estimate the optical parameters.

  1. Optical properties of polymer/chalcogenide glass composite materials

    NASA Astrophysics Data System (ADS)

    Bormashenko, Edward; Pogreb, Roman; Sutovski, Semion

    2000-06-01

    The novel composite material based on middle density polyethylene on one hand and thermoplastic chalcogenide glass on other hand has been worked out. Both materials used in the research are highly transparent in the middle and far IR but refraction indexes of components differ dramatically. The basic materials, polymer and glass, have close viscosities at the temperature of polyethylene processing. This fact allowed use of the extrusion technique for homogenization purposes. We proved, that the controlled structure of a composite could be derived through the varying of technological parameters of the mixing process. Single- and twin screw extrusion processes obtained compositions, which contain up to 50% particles of chalcogenide glass, which were dispersed in the polymer matrix. The highly homogeneous compositions that contain perfect spherical glass particles of 1-2 micrometers in diameter dispersed into polymer matrix were obtained as well. Highly oriented structures involving chalcogenide glass fibers immersed in the polymer matrix were prepared under high stretch speeds as well. Such fiberlike structures exhibited pronounced polarization properties. We studied the optical properties of the composite and came to the conclusion that the controlled structure of the composite allows variation in its optical properties. It was established that it is possible to produce a composite that is opaque in the visible and near IR, and highly transparent in the 2-25-micrometers wave length band. Light scattering on oriented and disordered structures was studied by the IR spectro-goniometer. The novel composite which was developed by our group is intended for various IR-optics applications.

  2. Exposed-core chalcogenide microstructured optical fibers for chemical sensing

    NASA Astrophysics Data System (ADS)

    Troles, Johann; Toupin, Perrine; Brilland, Laurent; Boussard-Plédel, Catherine; Bureau, Bruno; Cui, Shuo; Mechin, David; Adam, Jean-Luc

    2013-05-01

    Chemical bonds of most of the molecules vibrate at a frequency corresponding to the near or mid infrared field. It is thus of a great interest to develop sensitive and portable devices for the detection of specific chemicals and biomolecules for various applications in health, the environment, national security and so on. Optical fibers define practical sensing tools. Chalcogenide glasses are known for their transparency in the infrared optical range and their ability to be drawn as fibers. They are consequently good candidates to be used in biological/chemical sensing. For that matter, in the past decade, chalcogenide glass fibers have been successfully implemented in evanescent wave spectroscopy experiments, for the detection of bio-chemical species in various fields of applications including microbiology and medicine, water pollution and CO2 detection. Different types of fiber can be used: single index fibers or microstructured fibers. Besides, in recent years a new configuration of microstructured fibers has been developed: microstructured exposed-core fibers. This design consists of an optical fiber with a suspended micron-scale core that is partially exposed to the external environment. This configuration has been chosen to elaborate, using the molding method, a chalcogenide fiber for chemical species detection. The sensitivity of this fiber to detect molecules such as propan-2-ol and acetone has been compared with those of single index fibers. Although evanescent wave absorption is inversely proportional to the fiber diameter, the result shows that an exposed-core fiber is much more sensitive than a single index fiber having a twice smaller external diameter.

  3. Photosensitivity in chalcogenide glass thin films and its applications

    NASA Astrophysics Data System (ADS)

    Saliminia, Ali

    2002-08-01

    The realization and study of various photoinduced optical elements in As2S3 and As24S38Se38 chalcogenide glass (ChG) thin films constitute the main subject of the present thesis. Various isotropic and anisotropic photosensitive effects occur upon exposure of chalcogenide glass by a near bandgap light. In particular, photodarkening and giant photoexpansion effects have been studied in detail. The holographic fabrication and characterization of the scalar and vectorial volume and surface relief diffraction gratings using an interferometric technique have been presented, where the optimum writing conditions have been obtained so as to realize efficient and stable photoinduced gratings. One of the most important applications of photosensitivity is the fabrication of Bragg gratings in different guiding structures of ChG. The fabrication and characterization of Bragg filters at telecommunication wavelength of 1550 nm in single and multilayer slab/channel waveguides of ChG have been presented in detail. The observed thermal behavior of these Bragg gratings has provided a means for studying the photoinduced changes in optical properties of ChG, where some physical models have also been discussed. The realization of photoinduced Bragg gratings at 1550 nm in planar lightwave circuits (PLC) of chalcogenide glasses could provide many applications such as add-drop filters, and wavelength selective elements in integrated and photonic devices, especially in wavelength division multiplexing (WDM) networks. On the other hand, owing to the giant photoexpansion effect, one and two dimensional holographic microlens networks have been realized in ChG thin films. We also introduce a novel photoinduced anisotropic mass transport phenomenon, leading to extra-ordinary surface deformations and relief gratings in As2S3, with promising applications in grating couplers and photonics bandgap structures.

  4. The intercalation chemistry of layered iron chalcogenide superconductors

    NASA Astrophysics Data System (ADS)

    Vivanco, Hector K.; Rodriguez, Efrain E.

    2016-10-01

    The iron chalcogenides FeSe and FeS are superconductors composed of two-dimensional sheets held together by van der Waals interactions, which makes them prime candidates for the intercalation of various guest species. We review the intercalation chemistry of FeSe and FeS superconductors and discuss their synthesis, structure, and physical properties. Before we review the latest work in this area, we provide a brief background on the intercalation chemistry of other inorganic materials that exhibit enhanced superconducting properties upon intercalation, which include the transition metal dichalcogenides, fullerenes, and layered cobalt oxides. From past studies of these intercalated superconductors, we discuss the role of the intercalates in terms of charge doping, structural distortions, and Fermi surface reconstruction. We also briefly review the physical and chemical properties of the host materials-mackinawite-type FeS and β-FeSe. The three types of intercalates for the iron chalcogenides can be placed in three categories: 1.) alkali and alkaline earth cations intercalated through the liquid ammonia technique; 2.) cations intercalated with organic amines such as ethylenediamine; and 3.) layered hydroxides intercalated during hydrothermal conditions. A recurring theme in these studies is the role of the intercalated guest in electron doping the chalcogenide host and in enhancing the two-dimensionality of the electronic structure by spacing the FeSe layers apart. We end this review discussing possible new avenues in the intercalation chemistry of transition metal monochalcogenides, and the promise of these materials as a unique set of new inorganic two-dimensional systems.

  5. Multimaterial preform coextrusion for robust chalcogenide optical fibers and tapers.

    PubMed

    Tao, Guangming; Shabahang, Soroush; Banaei, Esmaeil-Hooman; Kaufman, Joshua J; Abouraddy, Ayman F

    2012-07-01

    The development of robust infrared fibers is crucial for harnessing the capabilities of new mid-infrared lasers. We present a novel approach to the fabrication of chalcogenide glass fiber preforms: one-step multimaterial extrusion. The preform consists of a glass core and cladding surrounded by a built-in, thermally compatible, polymer jacket for mechanical support. Using this approach we extrude several preform structures and draw them into robust composite fibers. Furthermore, the polymer cladding allows us to produce robust tapers with submicrometer core diameter.

  6. Rare earth chalcogenide stoichiometry determination. [of thermoelectric properties

    NASA Technical Reports Server (NTRS)

    Lockwood, R. A.

    1983-01-01

    Rare earth chalcogenides, and particularly lanthanum sulfide, are currently explored as candidate materials for thermoelectric applications. Since the electrical properties of LaS(x) are largely determined by its stoichiometry, a simple and accurate method has been developed for determining the value of x. The procedure involves dissolving a weighted sample in acid and measuring the amount of hydrogen evolved by the lanthanum that is in excess of the 1.500 ratio of S/La. The analytical error in the determination of x in LaS(x) is about 0.001.

  7. Low-temperature Hall effect in bismuth chalcogenides thin films

    NASA Astrophysics Data System (ADS)

    Kuntsevich, A. Yu.; Gabdullin, A. A.; Prudkogliad, V. A.; Selivanov, Yu. G.; Chizhevskii, E. G.; Pudalov, V. M.

    2016-12-01

    Bismuth chalcogenides are the most studied 3D topological insulators. As a rule, at low temperatures, thin films of these materials demonstrate positive magnetoresistance due to weak antilocalization. Weak antilocalization should lead to resistivity decrease at low temperatures; in experiments, however, resistivity grows as temperature decreases. From transport measurements for several thin films (with various carrier density, thickness, and carrier mobility), and by using a purely phenomenological approach, with no microscopic theory, we show that the low-temperature growth of the resistivity is accompanied by growth of the Hall coefficient, in agreement with the diffusive electron-electron interaction correction mechanism. Our data reasonably explain the low-temperature resistivity upturn.

  8. Validity of the local approximation in iron pnictides and chalcogenides

    NASA Astrophysics Data System (ADS)

    Sémon, Patrick; Haule, Kristjan; Kotliar, Gabriel

    2017-05-01

    We introduce a methodology to treat different degrees of freedom at different levels of approximation. We use cluster DMFT (dynamical mean field theory) for the t2 g electrons and single site DMFT for the eg electrons to study the normal state of the iron pnictides and chalcogenides. In the regime of moderate mass renormalizations, the self-energy is very local, justifying the success of single site DMFT for these materials and for other Hunds metals. We solve the corresponding impurity model with CTQMC (continuous time quantum Monte Carlo) and find that the minus sign problem is not severe in regimes of moderate mass renormalization.

  9. Photoelectric and electric properties of four-component copper chalcogenides

    SciTech Connect

    Saipulaeva, L. A. Gabibov, F. S.; Mel'nikova, N. V.; Alibekov, A. G.; Kheifets, O. L.; Babushkin, A. N.; Kurochka, K. V.

    2012-11-15

    The results of investigation of the electrophysical and photoelectric properties of complex copper chalcogenides are presented, namely, the properties of CuSnAsSe{sub 3}, which exhibits ferroelectric properties, and CuInAsS{sub 3}, which exhibits ionic conductivity. The spectral and temperature regions of photosensitivity of these crystals are determined. The depth of the level of carrier trapping centers, which manifest themselves under thermal activation, are evaluated from the analysis of thermally stimulated conductivity (TSC) curves in CuInAsS{sub 3}.

  10. Narrow linewidth Brillouin laser based on chalcogenide photonic chip.

    PubMed

    Kabakova, Irina V; Pant, Ravi; Choi, Duk-Yong; Debbarma, Sukhanta; Luther-Davies, Barry; Madden, Stephen J; Eggleton, Benjamin J

    2013-09-01

    We present, to the best of our knowledge, the first demonstration of a narrow linewidth, waveguide-based Brillouin laser that is enabled by large Brillouin gain of a chalcogenide chip. The waveguides are equipped with vertical tapers for low-loss coupling. Due to optical feedback for the Stokes wave, the lasing threshold is reduced to 360 mW, which is five times lower than the calculated single-pass Brillouin threshold for the same waveguide. The slope efficiency of the laser is found to be 30%, and the linewidth of 100 kHz is measured using a self-heterodyne method.

  11. Mechanical stiffening and thermal softening of rare earth chalcogenides

    SciTech Connect

    Shriya, S.; Varshney, Dinesh; Singh, Namita; Varshney, M.

    2014-04-24

    The pressure and temperature dependent elastic properties such as melting temperature nature in REX; (RE = La, Pr, Eu; X = O, S, Se, Te) chalcogenides is computed with emphasis on charge transfer interactions and covalent contribution in the effective interionic interaction potential. The pressure dependent elastic constants and melting temperature confirms that REX chalcogens lattice get stiffened as a consequence of bond compression and bond strengthening, however thermal softening arose due to bond expansion and bond weakening is evidenced from temperature dependence of melting temperature (T{sub M})

  12. Mode-locked fiber laser based on chalcogenide microwires.

    PubMed

    Al-Kadry, Alaa; El Amraoui, Mohammed; Messaddeq, Younès; Rochette, Martin

    2015-09-15

    We report the first mode-locked fiber laser using a chalcogenide microwire as the nonlinear medium. The laser is passively mode-locked with nonlinear polarization rotation and can be adjusted for the emission of solitons or noise-like pulses. The use of the microwire leads to a mode-locking threshold at the microwatt level and shortens the cavity length by 4 orders of magnitude with respect to other lasers of its kind. The controlled birefringence of the microwire, combined with a linear polarizer in the cavity, enables multiwavelength laser operation with tunable central wavelength, switchable wavelength separation, and a variable number of laser wavelengths.

  13. Ultrafast laser fabrication of Bragg waveguides in chalcogenide glass.

    PubMed

    McMillen, Ben; Li, Mingshan; Huang, Sheng; Zhang, Botao; Chen, Kevin P

    2014-06-15

    Bragg waveguides are fundamental components in photonic integrated circuits and are particularly interesting for mid-IR applications in high index, highly nonlinear materials. In this work, we present Bragg waveguides fabricated in bulk chalcogenide glass using an ultrafast laser. Waveguides with near circularly symmetric cross sections and low propagation loss are obtained through spatial and temporal beam shaping. Using a single-pass technique, the waveguide and Bragg structure are formed at the same time. First through sixth order gratings with strengths of up to 25 dB are realized, and performance is evaluated based on the modulation duty cycle of the writing beam.

  14. Photochemical Water Splitting by Bismuth Chalcogenide Topological Insulators.

    PubMed

    Rajamathi, Catherine R; Gupta, Uttam; Pal, Koushik; Kumar, Nitesh; Yang, Hao; Sun, Yan; Shekhar, Chandra; Yan, Binghai; Parkin, Stuart; Waghmare, Umesh V; Felser, Claudia; Rao, C N R

    2017-09-06

    As one of the major areas of interest in catalysis revolves around 2D materials based on molybdenum sulfide, we have examined the catalytic properties of bismuth selenides and tellurides, which are among the first chalcogenides to be proven as topological insulators (TIs). We find significant photochemical H2 evolution activity with these TIs as catalysts. H2 evolution increases drastically in nanosheets of Bi2 Te3 compared to single crystals. First-principles calculations show that due to the topology, surface states participate and promote the hydrogen evolution. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Positronics of radiation-induced effects in chalcogenide glassy semiconductors

    SciTech Connect

    Shpotyuk, O.; Kozyukhin, S. A.; Shpotyuk, M.; Ingram, A.; Szatanik, R.

    2015-03-15

    Using As{sub 2}S{sub 3} and AsS{sub 2} glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models.

  16. A new generation of alloyed/multimetal chalcogenide nanowires by chemical transformation

    PubMed Central

    Yang, Yuan; Wang, Kai; Liang, Hai-Wei; Liu, Guo-Qiang; Feng, Mei; Xu, Liang; Liu, Jian-Wei; Wang, Jin-Long; Yu, Shu-Hong

    2015-01-01

    One-dimensional metal chalcogenide nanostructures are important candidates for many technological applications such as photovoltaic and thermoelectric devices. However, the design and synthesis of one-dimensional metal chalcogenide nanostructured materials with controllable components and properties remain a challenge. We report a general chemical transformation process for the synthesis of more than 45 kinds of one-dimensional alloyed/hybrid metal chalcogenide nanostructures inherited from mother template TexSey@Se core-shell nanowires with tunable compositions. As many as nine types of monometal chalcogenide alloy nanowires (including AgSeTe, HgSeTe, CuSeTe, BiSeTe, PbSeTe, CdSeTe, SbSeTe, NiSeTe, and CoSeTe) can be synthesized. Alloyed and hybrid nanowires integrated with two or more alloyed metal chalcogenide phases can also be prepared. The compositions of all of these metal chalcogenide nanowires are tunable within a wide range. This protocol provides a new general route for the controllable synthesis of a new generation of one-dimensional metal chalcogenide nanostructures. PMID:26601137

  17. Fabrication of planar photonic crystals in chalcogenide glass film by maskless projection lithography

    NASA Astrophysics Data System (ADS)

    Zhang, Peiqing; Zhang, Qian; Zeng, Jianghui; Han, Jintao; Zhou, Jie; Zhang, Wei; Jiao, Qing; Wu, Yuehao; Dai, Shixun

    2016-09-01

    Ge20Sb15Se65 chalcogenide glass films were deposited and patterned using maskless projection lithography to create photonic crystal structures. This lithography technology, which is based on a digital micro-mirror device, is demonstrated as a powerful and low-cost tool to produce arbitrary intensity distributions to fabricate photonic devices. Direct photolithography in resist-free chalcogenide films was first studied, and results indicate that the quality of the products is insufficient. High-quality photonic crystals with sub-micrometer size were finally obtained in chalcogenide films with photoresist by maskless projection lithography and inductively coupled plasma technology.

  18. Lead-Chalcogenides Under Pressure: Ab-Initio Study

    NASA Astrophysics Data System (ADS)

    Gupta, Dinesh C.; Hamid, Idris

    ab-initio calculations using fully relativistic pseudo-potential have been performed to investigate the high pressure phase transition, elastic and electronic properties of lead-chalcogenides including the less known lead polonium. The calculated ground state parameters, for the rock-salt structure show good agreement with the experimental data. The enthalpy calculations show that these materials undergo a first-order phase transition from rock-salt to CsCl structure at 19.4, 15.5, 11.5 and 7.3 GPa for PbS, PbSe, PbTe and PbPo, respectively. Present calculations successfully predicted the location of the band gap at L-point of Brillouin zone as well as the value of the band gap in every case at ambient pressure. It is observed that unlike other lead-chalcogenides, PbPo is semi-metal at ambient pressure. The pressure variation of the energy gap indicates that these materials metalized under high pressures. For this purpose, the electronic structure of these materials has also been computed in parent as well as in high pressure phase.

  19. Photosensitive and thermal nonlinear effects in chalcogenide photonic crystal cavities.

    PubMed

    Lee, Michael W; Grillet, Christian; Monat, Christelle; Mägi, Eric; Tomljenovic-Hanic, Snjezana; Gai, Xin; Madden, Steve; Choi, Duk-Yong; Bulla, Douglas; Luther-Davies, Barry; Eggleton, Benjamin J

    2010-12-06

    We investigate the photosensitive and thermo-optic nonlinear properties of chalcogenide glass photonic crystal (PhC) cavities at telecommunications wavelengths. We observe a photosensitive refractive index change in AMTIR-1 (Ge(33)As(12)Se(55)) material in the near-infrared, which is enhanced by light localization in the PhC cavity and manifests in a permanent blue-shift of the nanocavity resonance. Thermo-optic non-linear properties are thoroughly investigated by i) carrying out thermal bistable switching experiments, from which we determined thermal switching times of 63 μs and 93 μs for switch on and switch off respectively and ii) by studying heating of the cavity with a high peak power pulsed laser input, which shows that two-photon absorption is the dominant heating mechanism. Our measurements and analysis highlight the detrimental impact of near-infrared photosensitivity and two-photon absorption on cavity based nonlinear optical switching schemes. We conclude that glass compositions with lower two-photon absorption and more stable properties (reduced photosensitivity) are therefore required for nonlinear applications in chalcogenide photonic crystal cavities.

  20. New promising bulk thermoelectrics: intermetallics, pnictides and chalcogenides

    NASA Astrophysics Data System (ADS)

    Gonçalves, Antonio P.; Godart, Claude

    2014-02-01

    The need of alternative "green" energy sources has recently renewed the interest in thermoelectric (TE) materials, which can directly convert heat to electricity or, conversely, electric current to cooling. The thermoelectric performance of a material can be estimated by the so-called figure of merit, zT = σ α 2 T/ λ ( α the Seebeck coefficient, σ α 2 the power factor, σ and λ the electrical and thermal conductivity, respectively), that depends only on the material. In the middle 1990s the "phonon glass and electron crystal" concept was developed, which, together with a better understanding of the parameters that affect zT and the use of new synthesis methods and characterization techniques, has led to the discovery of improved bulk thermoelectric materials that start being implemented in applications. During last decades, special focus has been made on skutterudites, clathrates, half-Heusler alloys, Si1- x Ge x-, Bi2Te3- and PbTe-based materials. However, many other materials, in particular based on intermetallics, pnictides, chalcogenides, oxides, etc. are now emerging as potential advanced bulk thermoelectrics. Herein we discuss the current understanding in this field, with special emphasis on the strategies to reduce the lattice part of the thermal conductivity and maximize the power factor, and review those new potential thermoelectric bulk materials, in particular based on intermetallics, pnictides and chalcogenides. A final chapter, discussing different shaping techniques leading to bulk materials (eventually from nanostructured TE materials), is also included.

  1. Origin of photo-induced transmitting oscillations in chalcogenide glasses.

    PubMed

    Tao, HaiZheng; Yang, ZhiYong; Lucas, Pierre

    2009-09-28

    Light-induced oscillatory behaviors of transmission in chalcogenide glasses are investigated using a continuous wave tunable Ti-sapphire laser. It is shown that phase change, thermal fluctuation, nonlinear index change and periodic self focusing are not at the origin of light-induced oscillatory transmittance in chalcogenide glasses. Instead, results indicate that the interference of transmitting and reflecting light is at the origin of the oscillatory behaviors of transmitted light. Just like the principle of Fabry-Pérot interferometer, these interferences result in a periodic change in transmission as the related interferential beams get in and out of phase. However, this transmitting oscillatory behavior can be registered by the detector only when the change of optical path length difference initiated by photo-induced effects is slower enough compared with the corresponding response time of the detector. Several photo-structural effects contribute to that phenomenon including photo-expansion, photo-darkening, and permanent self focusing. It appears that fluctuations of the light source intensity induce a wide distribution of the oscillatory periods.

  2. Fabrication of uniformly dispersed nanoparticle-doped chalcogenide glass

    SciTech Connect

    Lu, Chao; Arnold, Craig; Almeida, Juliana M. P.; Yao, Nan

    2014-12-29

    The dispersion of metallic nanoparticles within a chalcogenide glass matrix has the potential for many important applications in active and passive optical materials. However, the challenge of particle agglomeration, which can occur during traditional thin film processing, leads to materials with poor performance. Here, we report on the preparation of a uniformly dispersed Ag-nanoparticle (Ag NP)/chalcogenide glass heterogeneous material prepared through a combined laser- and solution-based process. Laser ablation of bulk silver is performed directly within an arsenic sulfide/propylamine solution resulting in the formation of Ag NPs in solution with an average particle size of less than 15 nm as determined by dynamic light scattering. The prepared solutions are fabricated into thin films using standard coating processes and are then analyzed using energy-dispersive X-ray spectroscopy and transmission electron microscopy to investigate the particle shape and size distribution. By calculating the nearest neighbor index and standard normal deviate of the nanoparticle locations inside the films, we verify that a uniformly dispersed distribution is achieved through this process.

  3. Fabrication and testing of planar chalcogenide waveguide integrated microfluidic sensor.

    PubMed

    Hu, Juejun; Tarasov, Vladimir; Agarwal, Anu; Kimerling, Lionel; Carlie, Nathan; Petit, Laeticia; Richardson, Kathleen

    2007-03-05

    We have fabricated and tested, to the best of our knowledge, the first microfluidic device monolithically integrated with planar chalcogenide glass waveguides on a silicon substrate. High-quality Ge(23)Sb(7)S(70) glass films have been deposited onto oxide coated silicon wafers using thermal evaporation, and high-index-contrast channel waveguides have been defined using SF(6) plasma etching. Microfluidic channel patterning in photocurable resin (SU8) and channel sealing by a polydimethylsiloxane (PDMS) cover completed the device fabrication. The chalcogenide waveguides yield a transmission loss of 2.3 dB/cm at 1550 nm. We show in this letter that using this device, N-methylaniline can be detected using its well-defined absorption fingerprint of the N-H bond near 1496 nm. Our measurements indicate linear response of the sensor to varying N-methylaniline concentrations. From our experiments, a sensitivity of this sensor down to a N-methylaniline concentration 0.7 vol. % is expected. Given the low-cost fabrication process used, and robust device configuration, our integration scheme provides a promising device platform for chemical sensing applications.

  4. Chalcogenide-mold interactions during precision glass molding (PGM) of GeAsSe glasses

    NASA Astrophysics Data System (ADS)

    Gleason, B.; Wachtel, P.; Musgraves, J. D.; Steinkopf, R.; Eberhardt, R.; Richardson, K.

    2013-09-01

    Five chalcogenide glasses in the GeAsSe ternary glass system were melted, fabricated into flats, and molded between planar, uncoated, binderless WC molds using a laboratory-scale precision glass molding machine. The five glasses originate at the binary arsenic triselenide (As40Se60) and are modified by replacing As with Se in 5 mol% increments, or by locking the As:Se ratio and adding Ge, also in 5 mol% increments. The glasses are separated into two groups, one for the Ge-free compositions and the other for the Ge-containing compositions. This effort analyzes the differences between the Ge-containing and the Ge-free glasses on the post-molded glass and mold surface behavior, as well as the mold lifetime. Fabrication features, such as scratch and/or dig marks were present on the glass and mold surfaces prior to the PGM process. White light interferometry analysis of the surfaces shows an overall reduction in the RMS roughness of the glass after molding, and an increase of the roughness of the molds, after 15 molding cycles. After molding, the quantity of observable defects, primarily deposits and dig marks are increased for both the glass and mold surfaces. Deposits found on the WC molds and glasses were analyzed using Electron Dispersive X-ray Spectroscopy (EDS) and showed no evidence of being due to material transfer between the WC molds and the glass constituents. In general the main observable difference in the analysis of the two post molded sets, despite the changes in chemistry, is the quantity of molding induced defects near the edge of the GeAsSe samples.

  5. Multimaterial rod-in-tube coextrusion for robust mid-infrared chalcogenide fibers

    NASA Astrophysics Data System (ADS)

    Tao, Guangming; Shabahang, Soroush; Ren, He; Yang, Zhiyong; Wang, Xunsi; Abouraddy, Ayman F.

    2014-03-01

    The development of quantum cascade lasers that span mid-infrared wavelengths necessitate developing new infrared fibers capable of transmitting light in the 3 ‒ 12 micron range. The main material candidates for producing infrared fibers that cover this spectral region are polycrystalline silver halides and glassy tellurium-based chalcogenide glasses. The latter are more chemically stable, and thus represent a superior choice for infrared fibers. We adapt a fiber fabrication methodology that we recently developed for other chalcogenide glasses to tellurium-based chalcogenides. We introduce a novel infrared optical fiber with tellurium-based chalcogenide core and cladding, which is provided with a built-in polymer jacket. We prepare purified Ge-As-Se-Te glasses that are used in extruding a preform. This preform is then thermally drawn continuously in an ambient environment into extended robust infrared fibers that transmit light in the 3 ‒ 12 micron spectral range.

  6. Method of producing stable metal oxides and chalcogenides and power source

    DOEpatents

    Doddapaneni, N.; Ingersoll, D.

    1996-10-22

    A method is described for making chemically and electrochemically stable oxides or other chalcogenides for use as cathodes for power source applications, and of making batteries comprising such materials. 6 figs.

  7. Superconductivity and magnetism in 11-structure iron chalcogenides in relation to the iron pnictides.

    PubMed

    Singh, David Joseph

    2012-10-01

    This is a review of the magnetism and superconductivity in '11'-type Fe chalcogenides, as compared to the Fe-pnictide materials. The chalcogenides show many differences from the pnictides, as might be anticipated from their very varied chemistries. These differences include stronger renormalizations that might imply stronger correlation effects as well as different magnetic ordering patterns. Nevertheless the superconducting state and mechanism for superconductivity are apparently similar for the two classes of materials. Unanswered questions and challenges to theory are emphasized.

  8. Theoretical study of population inversion in active doped MIR chalcogenide glass fibre lasers (invited).

    PubMed

    Sujecki, S; Oladeji, A; Phillips, A; Seddon, A B; Benson, T M; Sakr, H; Tang, Z; Barney, E; Furniss, D; Sójka, Ł; Bereś-Pawlik, E; Scholle, K; Lamrini, S; Furberg, P

    We study the mechanism of the population inversion in mid-infrared fibre lasers based on a chalcogenide glass host doped with active lanthanide ions. Three lanthanide dopant ions are considered: terbium, dysprosium and praseodymium. We predict the relevant trivalent ion level populations and gain. The simulation parameters were obtained by fabricating and optically characterising a series of trivalent ion doped chalcogenide glass samples. We also provide simple analytical expressions that aid the design of the cascade lasing process.

  9. Chalcogenide glass sensors for bio-molecule detection

    NASA Astrophysics Data System (ADS)

    Lucas, Pierre; Coleman, Garrett J.; Cantoni, Christopher; Jiang, Shibin; Luo, Tao; Bureau, Bruno; Boussard-Pledel, Catherine; Troles, Johann; Yang, Zhiyong

    2017-02-01

    Chalcogenide glasses constitute the only class of materials that remain fully amorphous while exhibiting broad optical transparency over the full infrared region from 2-20 microns. As such, they can be shaped into complex optical elements while retaining a clear optical window that encompass the vibrational signals of virtually any molecules. Chalcogenide glasses are therefore ideal materials for designing biological and chemical sensors based on vibrational spectroscopy. In this paper we review the properties of these glasses and the corresponding design of optical elements for bio-chemical sensing. Amorphous chalcogenides offer a very wide compositional landscape that permit to tune their physical properties to match specific demands for the production of optical devices. This includes tailoring the infrared window over specific ranges of wavelength such as the long-wave infrared region to capture important vibrational signal including the "signature region" of micro-organisms or the bending mode of CO2 molecules. Additionally, compositional engineering enables tuning the viscosity-temperature dependence of the glass melt in order to control the rheological properties that are fundamental to the production of glass elements. Indeed, exquisite control of the viscosity is key to the fabrication process of many optical elements such as fiber drawing, lens molding, surface embossing or reflow of microresonators. Optimal control of these properties then enables the design and fabrication of optimized infrared sensors such as Fiber Evanescent Wave Spectroscopy (FEWS) sensors, Whispering Gallery Modes (WGM) micro-resonator sensors, nanostructured surfaces for integrated optics and surface-enhanced processes, or lens molding for focused collection of infrared signals. Many of these sensor designs can be adapted to collect and monitor the vibrational signal of live microorganisms to study their metabolism in controlled environmental conditions. Further materials

  10. Visible-active photocatalytic behaviors observed in nanostructured lead chalcogenides PbX (X = S, Se, Te)

    NASA Astrophysics Data System (ADS)

    Qiao, Li-Na; Wang, H. C.; Shen, Y.; Lin, Yuan-Hua; Nan, Ce-Wen

    2016-01-01

    Nanostructured lead chalcogenides (PbX, X = Te, Se, S) were prepared via a simple hydrothermal method. The powder samples were characterized by XRD, SEM, SAED and DRS. Phase composition and microstructure analysis indicate that these samples are pure lead chalcogenides phases and have similar morphologies. These lead chalcogenides display efficient absorption in the UV-visible light range. The photocatalytic properties of lead chalcogenides nanoparticles were evaluated by the photodegradation of Congo red under UV-visible light irradiation in air atmosphere. The Congo red solution can be efficiently degraded under visible light in the presence of lead chalcogenides nanoparticles. The photocatalytic activities of lead chalcogenides generally increase with increasing their band gaps and shows no appreciable loss after repeated cycles. Our results may be useful for developing new photocatalyst systems responsive to visible light among narrow band gap semiconductors.

  11. Visible-active photocatalytic behaviors observed in nanostructured lead chalcogenides PbX (X = S, Se, Te)

    SciTech Connect

    Qiao, Li-Na; Wang, H.C.; Shen, Y.; Lin, Yuan-Hua Nan, Ce-Wen

    2016-01-15

    Nanostructured lead chalcogenides (PbX, X = Te, Se, S) were prepared via a simple hydrothermal method. The powder samples were characterized by XRD, SEM, SAED and DRS. Phase composition and microstructure analysis indicate that these samples are pure lead chalcogenides phases and have similar morphologies. These lead chalcogenides display efficient absorption in the UV-visible light range. The photocatalytic properties of lead chalcogenides nanoparticles were evaluated by the photodegradation of Congo red under UV-visible light irradiation in air atmosphere. The Congo red solution can be efficiently degraded under visible light in the presence of lead chalcogenides nanoparticles. The photocatalytic activities of lead chalcogenides generally increase with increasing their band gaps and shows no appreciable loss after repeated cycles. Our results may be useful for developing new photocatalyst systems responsive to visible light among narrow band gap semiconductors.

  12. Chalcogenide phase-change thin films used as grayscale photolithography materials.

    PubMed

    Wang, Rui; Wei, Jingsong; Fan, Yongtao

    2014-03-10

    Chalcogenide phase-change thin films are used in many fields, such as optical information storage and solid-state memory. In this work, we present another application of chalcogenide phase-change thin films, i.e., as grayscale photolithgraphy materials. The grayscale patterns can be directly inscribed on the chalcogenide phase-change thin films by a single process through direct laser writing method. In grayscale photolithography, the laser pulse can induce the formation of bump structure, and the bump height and size can be precisely controlled by changing laser energy. Bumps with different height and size present different optical reflection and transmission spectra, leading to the different gray levels. For example, the continuous-tone grayscale images of lifelike bird and cat are successfully inscribed onto Sb(2)Te(3) chalcogenide phase-change thin films using a home-built laser direct writer, where the expression and appearance of the lifelike bird and cat are fully presented. This work provides a way to fabricate complicated grayscale patterns using laser-induced bump structures onto chalcogenide phase-change thin films, different from current techniques such as photolithography, electron beam lithography, and focused ion beam lithography. The ability to form grayscale patterns of chalcogenide phase-change thin films reveals many potential applications in high-resolution optical images for micro/nano image storage, microartworks, and grayscale photomasks.

  13. Liquid crystal photoalignment on As2S3 chalcogenide thin films

    NASA Astrophysics Data System (ADS)

    Sheremet, N. V.; Sharpnack, L.; Gelbaor-Kirzhner, M.; Agra-Kooijman, D. M.; Chaudhary, A.; Kumar, T. A.; Klebanov, M.; Abdulhalim, I.; Kumar, S.; Reznikov, Yu A.

    2017-02-01

    Recent studies of photoalignment of liquid crystals (LCs) on chalcogenide surfaces have a rich variety of mechanisms responsible for the photoalignment on these materials. Both chalcogenide surface-mediated and LC bulk-mediated photoalignment were observed. We report on investigation toward understanding the origin of the chalcogenide surface-mediated photoalignment. The contributions of light-induced optical and surface morphological anisotropy of the chalcogenide surface were studied. Light-induced optical anisotropy in the film was observed by polarization interferometry and the surface anisotropy was measured by high-resolution x-ray reflectivity. The data reveals the lack of a strong anisotropy in the surfaces’ morphology after irradiation with polarized blue light. At the same time, an evident correlation between the anchoring energy and the quality of the photoalignment was observed. This allows us to conclude that the photoalignment of LCs on chalcogenide surfaces is mainly determined by a light-induced anisotropic distribution of the glass structural elements in the bulk and on the chalcogenide surface.

  14. Inhomogeneous and homogeneous linewidths in Er 3+-doped chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Bigot, L.; Jurdyc, A.-M.; Jacquier, B.; Adam, J.-L.

    2003-10-01

    The erbium 4I 13/2- 4I 15/2 transition around 1.5 μm is of prim interest for telecommunications and depends on the erbium ions surrounding. In glasses, the broadening of a transition comes from two contributions: inhomogeneous (due to the disorder) and homogeneous (due to the electron phonon interaction) broadening. Resonant Fluorescence Line Narrowing (RFLN) is a useful tool to separate this two parameters. We will show in this paper that the 4I 13/2- 4I 15/2 transition in chalcogenide glass (GeGaSSb) presents a strong homogeneous character and a smaller inhomogeneous contribution compared to aluminosilicate and fluoride glasses. Consequences on gain saturation will also be discussed.

  15. Copper Antimony Chalcogenide Thin Film PV Device Development

    SciTech Connect

    Welch, Adam W.; Baranowski, Lauryn L.; de Souza Lucas, Francisco Willian; Toberer, Eric S.; Wolden, Colin A.; Zakutayev, Andriy

    2015-06-14

    Emerging ternary chalcogenide thin film solar cell technologies, such as CuSbS2 and CuSbSe2, have recently attracted attention as simpler alternatives to quaternary Cu2ZnSnS4 (CZTS). Despite suitable photovoltaic properties, the initial energy conversion efficiency of CuSbS2 is rather low (0.3%). Here, we report on our progress towards improving the efficiency of CuSbS2 solar cells using a high throughput approach. The combinatorial methodology quickly results in baseline solar cell prototypes with 0.6% efficiency, and then modification of the back contact architecture leads to 1% PV devices. We then translate the optimal CuSbS2 synthesis parameters to CuSbSe2 devices, which show 3% efficiencies.

  16. Magnetism in Parent Iron Chalcogenides: Quantum Fluctuations Select Plaquette Order

    NASA Astrophysics Data System (ADS)

    Ducatman, Samuel; Perkins, Natalia B.; Chubukov, Andrey

    2012-10-01

    We analyze magnetic order in Fe chalcogenide Fe1+yTe, the parent compound of the high-temperature superconductor Fe1+yTe1-xSex. Experiments show that magnetic order in this material contains components with momentum Q1=(π/2,π/2) and Q2=(π/2,-π/2) in the Fe only Brillouin zone. The actual spin order depends on the interplay between these two components. Previous works assumed that the ordered state has a single Q (either Q1 or Q2). In such a state, spins form double stripes along one of the diagonals breaking the rotational C4 symmetry. We show that quantum fluctuations actually select another order—a double Q plaquette state with equal weight of Q1 and Q2 components, which preserves C4 symmetry. We argue that the order in Fe1+yTe is determined by the competition between quantum fluctuations and magnetoelastic coupling.

  17. Chalcogenide optical fibers for mid-infrared sensing

    NASA Astrophysics Data System (ADS)

    Bureau, Bruno; Boussard, Catherine; Cui, Shuo; Chahal, Radwan; Anne, Marie Laure; Nazabal, Virginie; Sire, Olivier; Loréal, Olivier; Lucas, Pierre; Monbet, Valérie; Doualan, Jean-Louis; Camy, Patrice; Tariel, Hugues; Charpentier, Frédéric; Quetel, Lionel; Adam, Jean-Luc; Lucas, Jacques

    2014-02-01

    Chalcogenide glasses are a matchless material as far as mid-infrared (IR) applications are concerned. They transmit light typically from 2 to 12 μm and even as far as 20 μm depending on their composition, and numerous glass compositions can be designed for optical fibers. One of the most promising applications of these fibers consists in implementing fiber evanescent wave spectroscopy, which enables detection of the mid-IR signature of most biomolecules. The principles of fiber evanescent wave spectroscopy are recalled together with the benefit of using selenide glass to carry out this spectroscopy. Then, two large-scale studies in recent years in medicine and food safety are exposed. To conclude, the future strategy is presented. It focuses on the development of rare earth-doped fibers used as mid-IR sources on one hand and tellurium-based glasses to shift the limit of detection toward longer wavelength on the other hand.

  18. Flexible chalcogenide glass microring resonator for mid-infrared emission

    NASA Astrophysics Data System (ADS)

    Wang, Liangliang; Li, Lijing; Sun, Mingjie

    2016-10-01

    Emerging applications in communication, sensing, medical, and many other fields call for on-chip microring laser, however, the method to make it work at mid-infrared still need to be explored. In this paper, a microring resonator integrated in flexible substrate is designed and evaluated, with high Q-factor ( 105) at pump and signal wavelengths, achieving emission in mid-infrared (3.6μm) using rare earth doped chalcogenide glass. Furthermore, the strain-optical coupling in multilayer flexible materials is numerically verified, and a 0.3 nm/μɛ resonance wavelength shift is achieved by local neutral axis theory, without significant loss of flexible device performance.

  19. Validity of the local approximation in iron pnictides and chalcogenides

    DOE PAGES

    Sémon, Patrick; Haule, Kristjan; Kotliar, Gabriel

    2017-05-08

    We introduce a methodology to treat different degrees of freedom at different levels of approximation. We use cluster DMFT (dynamical mean field theory) for the t 2g electrons and single site DMFT for the e g electrons to study the normal state of the iron pnictides and chalcogenides. Furthermore, in the regime of moderate mass renormalizations, the self-energy is very local, justifying the success of single site DMFT for these materials and for other Hunds metals. Here we solve the corresponding impurity model with CTQMC (continuous time quantum Monte Carlo) and find that the minus sign problem is not severemore » in regimes of moderate mass renormalization.« less

  20. Chalcogenide Glass Radiation Sensor; Materials Development, Design and Device Testing

    SciTech Connect

    Mitkova, Maria; Butt, Darryl; Kozicki, Michael; Barnaby, Hugo

    2013-04-30

    For many decades, various radiation detecting material have been extensively researched, to find a better material or mechanism for radiation sensing. Recently, there is a growing need for a smaller and effective material or device that can perform similar functions of bulkier Geiger counters and other measurement options, which fail the requirement for easy, cheap and accurate radiation dose measurement. Here arises the use of thin film chalcogenide glass, which has unique properties of high thermal stability along with high sensitivity towards short wavelength radiation. The unique properties of chalcogenide glasses are attributed to the lone pair p-shell electrons, which provide some distinctive optical properties when compared to crystalline material. These qualities are derived from the energy band diagram and the presence of localized states in the band gap. Chalcogenide glasses have band tail states and localized states, along with the two band states. These extra states are primarily due to the lone pair electrons as well as the amorphous structure of the glasses. The localized states between the conductance band (CB) and valence band (VB) are primarily due to the presence of the lone pair electrons, while the band tail states are attributed to the Van der Waal's forces between layers of atoms [1]. Localized states are trap locations within the band gap where electrons from the valence band can hop into, in their path towards the conduction band. Tail states on the other hand are locations near the band gap edges and are known as Urbach tail states (Eu). These states are occupied with many electrons that can participate in the various transformations due to interaction with photons. According to Y. Utsugi et. al.[2], the electron-phonon interactions are responsible for the generation of the Urbach tails. These states are responsible for setting the absorption edge for these glasses and photons with energy near the band gap affect these states. We have

  1. Magnetoimpedance and magnetocapacitance of anion-substituted manganese chalcogenides

    NASA Astrophysics Data System (ADS)

    Aplesnin, S. S.; Romanova, O. B.; Korolev, V. V.; Sitnikov, M. N.; Yanushkevich, K. I.

    2017-02-01

    The magnetoresistive effect in MnSe1-XTeX manganese chalcogenides with a substitute concentration of X = 0.1 is studied by impedance spectroscopy. The magnetoimpedance above the Neel temperature is found. The obtained experimental data are explained in the framework of the model of existence of magnetic nanoareas of two types. Two activation energies in the low- and high-frequency regions are determined from the frequency and temperature dependences of the permittivity described in the Debye model. The extrema found in the temperature dependence of the pyroelectric current are consistent with the maxima in the temperature dependence of magnetization. Temperature dependence of the carrier relaxation time is established. The magnetocapacitance of the MnSe1-XTeX solid solutions is found. The change in the carrier type above the Neel temperature and the temperature of the transition to the magnetically ordered state in the MnTe nanoarea is established.

  2. Semiconducting chalcogenide buffer layer for oxide heteroepitaxy on Si(001)

    NASA Astrophysics Data System (ADS)

    Schmidt, D. A.; Ohta, Taisuke; Lu, C.-Y.; Bostwick, Aaron A.; Yu, Q.; Rotenberg, Eli; Ohuchi, F. S.; Olmstead, Marjorie A.

    2006-05-01

    We report controlled laminar growth of a crystalline transition metal oxide on Si(001) without SiOx or silicide formation by utilizing the chalcogenide semiconductor gallium sesquiselenide (Ga2Se3) as a nonreactive buffer layer. Initial nucleation of both pure and Co-doped anatase (TiO2) is along Ga2Se3 nanowire structures, coalescing to a flat, multidomain film within two molecular layers. Arsenic-terminated Si(001) [Si(001):As] is stable against pure O2, but oxidizes when both Ti and O2 are present. The Si -TiO2 valence band offset using either buffer layer is about 2.8eV, producing a staggered band alignment.

  3. Towards integrating chalcogenide based phase change memory with silicon microelectronics

    NASA Astrophysics Data System (ADS)

    Devasia, Archana

    The continued dominance of floating gate technology as the premier non-volatile memory (NVM) technology is expected to hit a roadblock due to issues associated with its inability to catch up with CMOS scaling. The uncertain future of floating gate memory has led to a host of unorthodox NVM technologies to surface as potential heirs. Among the mix is phase change memory (PCM), which is a non-volatile, resistance variable, memory technology wherein the state of the memory bit is defined by the resistance of the memory material. This research study examines novel, bilayer chalcogenide based materials composed of Ge-chalcogenide (GeTe or Ge2Se3) and Sn-chalcogenide (SnTe or SnSe) for phase change memory applications and explores their integration with CMOS technology. By using a layered arrangement, it is possible to induce phase change response in materials, which normally do not exhibit such behavior, and thus form new materials which may have lower threshold voltage and programming current requirements. Also, through the incorporation of a metal containing layer, the phase transition characteristics of the memory layer can be tailored in order to obtain in-situ, a material with optimized phase change properties. Using X-ray diffraction (XRD) and time resolved XRD, it has been demonstrated that stacked phase change memory films exhibit both structural and compositional dependency with annealing temperature. The outcome of the structural transformation of the bottom layer, is an annealing temperature dependent residual stress. By the incorporation of a Sn layer, the phase transition characteristics of Ge-chalcogenide thin films can be tuned. Clear evidence of thermally induced Ge, Sn and chalcogen inter-diffusion, has been discerned via transmission electron microscopy and parallel electron energy loss spectroscopy. The presence of Al2O3 as capping layer has been found to mitigate volatilization and metallic Sn phase separation at high temperatures. Two terminal PCM

  4. Ligand engineering of lead chalcogenide nanoparticle solar cells

    NASA Astrophysics Data System (ADS)

    Voros, Marton; Brawand, Nicholas; Galli, Giulia

    Semiconductor nanoparticles (NP) are promising materials to build cheap and efficient solar cells. One of the key challenges in their utilization for solar energy conversion is the control of ligand-NP interfaces. Recent experiments have shown that by carefully choosing the ligands terminating the NPs, one can tailor electronic and optical absorption properties of NP assemblies, along with their transport properties. By using density functional theory based methods, we investigated how the opto-electronic properties of lead chalcogenide NPs may be tuned by using diverse organic and inorganic ligands. We interpreted experiments, and we showed that an essential prerequisite to avoid detrimental trap states is to ensure charge balance at the ligand-NP interface, possibly with the help of hydrogen treatment. Work supported by the Center for Advanced Solar Photophysics, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.

  5. Role of sodium doping in lead chalcogenide thermoelectrics.

    PubMed

    He, Jiaqing; Zhao, Li-Dong; Zheng, Jin-Cheng; Doak, Jeff W; Wu, Haijun; Wang, Hui-Qiong; Lee, Yeseul; Wolverton, Chris; Kanatzidis, Mercouri G; Dravid, Vinayak P

    2013-03-27

    The solubility of sodium and its effects on phonon scattering in lead chalcogenide PbQ (Q = Te, Se, S) family of thermoelectric materials was investigated by means of transmission electron microscopy and density functional calculations. Among these three systems, Na has the highest solubility limit (~2 mol %) in PbS and the lowest ~0.5 mol %) in PbTe. First-principles electronic structure calculations support the observations, indicating that Na defects have the lowest formation energy in PbS and the highest in PbTe. It was also found that in addition to providing charge carriers (holes) for PbQ, Na introduces point defects (solid solution formation) and nanoscale precipitates; both reduce the lattice thermal conductivity by scattering heat-carrying phonons. These results explain the recent reports of high thermoelectric performance in p-type PbQ materials and may lead to further advances in this class of materials.

  6. Fabrication and characterization of chalcogenide glass photonic crystal waveguides.

    PubMed

    Suzuki, Keijiro; Hamachi, Yohei; Baba, Toshihiko

    2009-12-07

    We report on the fabrication of chalcogenide glass (Ag-As(2)Se(3)) photonic crystal waveguides and the first detailed characterization of the linear and nonlinear optical properties. The waveguides, fabricated by e-beam lithography and ICP etching exhibit typical transmission spectra of photonic crystal waveguides, and exhibit high optical nonlinearity. Nonlinear phase shift of 1.5pi through self-phase modulation is observed at 0.78 W input peak power in a 400 microm long device. The effective nonlinear parameter gamma(eff) estimated from this result reaches 2.6 x 10(4) W(-1)m(-1). Four-wave mixing is also observed in the waveguide, while two-photon absorption at optical communication wavelengths is sufficiently small and the corresponding figure of merit is larger than 11.

  7. Fabrication of chalcogenide glass photonic crystal fibers with mechanical drilling

    NASA Astrophysics Data System (ADS)

    Zhang, Peiqing; Zhang, Jun; Yang, Peilong; Dai, Shixun; Wang, Xunsi; Zhang, Wei

    2015-12-01

    A mechanical drilling method for the preparation of photonic crystal fibers (PCFs) is presented in this paper. Several PCFs were fabricated with Ge20Sb15S65 chalcogenide glasses, which have high transparency in the mid-infrared (IR) range. The mechanical drilling method has been identified as a powerful tool to prepare fibers with a variety of structures and to increase the transmission of the obtained fibers. For a three-ring PCF, the near-field intensity distribution and the transmission loss were measured. It was found that most of the optical energy is contained in the core of the PCF. The profile of the near-field intensity image shows that the prepared PCF can work with a large mode area, which is important in high-power laser propagation and fiber amplifiers.

  8. Microbial synthesis of chalcogenide semiconductor nanoparticles: a review.

    PubMed

    Jacob, Jaya Mary; Lens, Piet N L; Balakrishnan, Raj Mohan

    2016-01-01

    Chalcogenide semiconductor quantum dots are emerging as promising nanomaterials due to their size tunable optoelectronic properties. The commercial synthesis and their subsequent integration for practical uses have, however, been contorted largely due to the toxicity and cost issues associated with the present chemical synthesis protocols. Accordingly, there is an immediate need to develop alternative environment-friendly synthesis procedures. Microbial factories hold immense potential to achieve this objective. Over the past few years, bacteria, fungi and yeasts have been experimented with as eco-friendly and cost-effective tools for the biosynthesis of semiconductor quantum dots. This review provides a detailed overview about the production of chalcogen-based semiconductor quantum particles using the inherent microbial machinery. © 2015 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

  9. Electron-beam recording of patterns in chalcogenide films

    NASA Astrophysics Data System (ADS)

    Sergeev, S. A.; Iovu, M. S.; Iaseniuc, O. V.

    2015-02-01

    Thin films of chalcogenide glasses (ChG) of different composition have been used for e-beam recording of diffraction grating structures. The dependencies of diffraction efficiency of gratings on radiation dose were studied. The influence of ChG film composition on diffraction properties of gratings was shown. It was established that the refractive index gratings formed in As2S3 films exhibit high stability during their dark storage. The diffraction efficiency enhancement caused by uniform light irradiation was observed for gratings recorded in As4S3Se3 thin films, doped with Sn. With use of computer-controlled positioning of electron beam both the raster scan and vector patterns were recorded in As2S3 films. In the former case the images from BMP-files were patterned. In the latter case the mosaic of diffraction gratings, producing the multi-beam light diffraction was recorded.

  10. Magnetism in parent iron chalcogenides: quantum fluctuations select plaquette order.

    PubMed

    Ducatman, Samuel; Perkins, Natalia B; Chubukov, Andrey

    2012-10-12

    We analyze magnetic order in Fe chalcogenide Fe(1+y)Te, the parent compound of the high-temperature superconductor Fe(1+y)Te(1-x)Se(x). Experiments show that magnetic order in this material contains components with momentum Q(1)=(π/2,π/2) and Q(2)=(π/2,-π/2) in the Fe only Brillouin zone. The actual spin order depends on the interplay between these two components. Previous works assumed that the ordered state has a single Q (either Q(1) or Q(2)). In such a state, spins form double stripes along one of the diagonals breaking the rotational C(4) symmetry. We show that quantum fluctuations actually select another order-a double Q plaquette state with equal weight of Q(1) and Q(2) components, which preserves C(4) symmetry. We argue that the order in Fe(1+y)Te is determined by the competition between quantum fluctuations and magnetoelastic coupling.

  11. Frustrated Magnetism and Superconductivity in the Iron Chalcogenides

    NASA Astrophysics Data System (ADS)

    Si, Qimiao

    While studies in the early stage on the iron-based supercondoctors (FeSCs) focused on the iron pnictides, considerable efforts in the more recent past have also been directed towards iron chalcogenides. These studies are giving us renewed hope for even higher transition temperatures in the iron-based materials. In this talk, I will discuss several theoretical issues on the microscopic physics of the iron chalcogenides that teach us much about the overall physics of the FeSCs. One is the proposal we made on the orbital selective Mott phase, for which considerable evidence has come from ARPES and other experiments. The second issue concerns magnetism, in particular the correlation-induced magnetic frustration effect. A major puzzle arises in bulk FeSe, which shows a structural phase transition similar to that seen in the iron pnictides but, unlike the latter, does not exhibit any static antiferromagnetic order. We studied the effect of magnetic frustration associated with the bilinear-biquadratic spin-exchange interactions. Based on the derived phase diagram, we proposed that the structural transition in FeSe originates from an Ising-nematic order of an antiferro-quadrupolar phase. Within this picture, we have predicted that the collective modes of this quadrupolar state show (pi,0) magnetic fluctuations, which have since been verified by inelastic neutron scattering experiments. These results considerably expand on the notion regarding the importance of the bad-metal behavior, and provide a substantially broadened perspective on the magnetic and nematic correlations in the FeSCs. Finally, implications of the frustrated magnetism for superconductivity will also be discussed. Work supported in part by the NSF Grant No. DMR-1309531 and the Robert A. Welch Foundation Grant No. C-1411.

  12. Precision lens molding of asphero diffractive surfaces in chalcogenide materials

    NASA Astrophysics Data System (ADS)

    Nelson, J.; Scordato, M.; Schwertz, K.; Bagwell, J.

    2015-10-01

    Finished lens molding, and the similar process of precision lens molding, have long been practiced for high volume, accurate replication of optical surfaces on oxide glass. The physics surrounding these processes are well understood, and the processes are capable of producing high quality optics with great fidelity. However, several limitations exist due to properties inherent with oxide glasses. Tooling materials that can withstand the severe environmental conditions of oxide glass molding cannot easily be machined to produce complex geometries such as diffractive surfaces, lens arrays, and off axis features. Current machining technologies coupled with a limited selection of tool materials greatly limits the type of structures that can be molded into the finished optic. Tooling for chalcogenide glasses are not bound by these restrictions since the molding temperatures required are much lower than for oxide glasses. Innovations in tooling materials and manufacturing techniques have enabled the production of complex geometries to optical quality specifications and have demonstrated the viability of creating tools for molding diffractive surfaces, off axis features, datums, and arrays. Applications for optics having these features are found in automotive, defense, security, medical, and industrial domains. This paper will discuss results achieved in the study of various molding techniques for the formation of positive diffractive features on a concave spherical surface molded from As2Se3 chalcogenide glass. Examples and results of molding with tools having CTE match with the glass and non CTE match will be reviewed. The formation of stress within the glass during molding will be discussed, and methods of stress management will also be demonstrated and discussed. Results of process development methods and production of good diffractive surfaces will be shown.

  13. Surface effects on electronic transport of 2D chalcogenide thin films and nanostructures.

    PubMed

    Jung, Yeonwoong; Shen, Jie; Cha, Judy J

    2014-01-01

    The renewed interest in two-dimensional materials, particularly transition metal dichalcogenides, has been explosive, evident in a number of review and perspective articles on the topic. Our ability to synthesize and study these 2D materials down to a single layer and to stack them to form van der Waals heterostructures opens up a wide range of possibilities from fundamental studies of nanoscale effects to future electronic and optoelectronic applications. Bottom-up and top-down synthesis and basic electronic properties of 2D chalcogenide materials have been covered in great detail elsewhere. Here, we bring attention to more subtle effects: how the environmental, surface, and crystal defects modify the electronic band structure and transport properties of 2D chalcogenide nanomaterials. Surface effects such as surface oxidation and substrate influence may dominate the overall transport properties, particularly in single layer chalcogenide devices. Thus, understanding such effects is critical for successful applications based on these materials. In this review, we discuss two classes of chalcogenides - Bi-based and Mo-based chalcogenides. The first are topological insulators with unique surface electronic properties and the second are promising for flexible optoelectronic applications as well as hydrogen evolution catalytic reactions.

  14. A Strong Donor-Acceptor System Based on a Metal Chalcogenide Cluster and Porphyrin.

    PubMed

    Xu, Jing; Xue, Li-Jun; Hou, Jin-Le; Yin, Zhong-Nan; Zhang, Xuan; Zhu, Qin-Yu; Dai, Jie

    2017-07-17

    Although great progress has been made for charge transfer (CT) compounds of various organic donor-acceptor systems, no CT compounds containing both inorganic chalcogenide cluster anions and organic porphyrin cations have been reported. Herein, a germanium chalcogenide cluster (Ge4S10(4-)) is chosen as an electron donor and a methylated tetrakis(4-pyridyl)porphyrin (5,10,15,20-tetrakis(N-methyl-4-pyridyl)porphyrin, TMPyP) is selected as an electron acceptor to create chalcogenide cluster-porphyrin CT compounds (TMPyP-Ge4S10)·5H2O (1) and (MnTMPyP-Ge4S10)·13H2O (2). Their crystal structures have been characterized by single-crystal X-ray diffraction. Compound 1 is an ionic CT salt assembled through interion interactions, and compound 2 is a neutral CT dyad formed by metal-ligand axial coordination of the chalcogenide cluster with manganese porphyrin. The strong charge transfer properties are revealed by electronic spectra, theoretical calculations, (1)H NMR, and ESR. The CT intensity of the chalcogenide cluster-porphyrin system can be modulated by metalation. The fluorescence and photocurrent response properties of 1 and 2 are related to the CT intensity.

  15. Infrared emitting and photoconducting colloidal silver chalcogenide nanocrystal quantum dots from a silylamide-promoted synthesis.

    PubMed

    Yarema, Maksym; Pichler, Stefan; Sytnyk, Mykhailo; Seyrkammer, Robert; Lechner, Rainer T; Fritz-Popovski, Gerhard; Jarzab, Dorota; Szendrei, Krisztina; Resel, Roland; Korovyanko, Oleksandra; Loi, Maria Antonietta; Paris, Oskar; Hesser, Günter; Heiss, Wolfgang

    2011-05-24

    Here, we present a hot injection synthesis of colloidal Ag chalcogenide nanocrystals (Ag(2)Se, Ag(2)Te, and Ag(2)S) that resulted in exceptionally small nanocrystal sizes in the range between 2 and 4 nm. Ag chalcogenide nanocrystals exhibit band gap energies within the near-infrared spectral region, making these materials promising as environmentally benign alternatives to established infrared active nanocrystals containing toxic metals such as Hg, Cd, and Pb. We present Ag(2)Se nanocrystals in detail, giving size-tunable luminescence with quantum yields above 1.7%. The luminescence, with a decay time on the order of 130 ns, was shown to improve due to the growth of a monolayer thick ZnSe shell. Photoconductivity with a quantum efficiency of 27% was achieved by blending the Ag(2)Se nanocrystals with a soluble fullerene derivative. The co-injection of lithium silylamide was found to be crucial to the synthesis of Ag chalcogenide nanocrystals, which drastically increased their nucleation rate even at relatively low growth temperatures. Because the same observation was made for the nucleation of Cd chalcogenide nanocrystals, we conclude that the addition of lithium silylamide might generally promote wet-chemical synthesis of metal chalcogenide nanocrystals, including in as-yet unexplored materials.

  16. An investigation of dynamic processes in selenium based chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Gulbiten, Ozgur

    Owing to their excellent infrared transmittance and good rheological properties, selenium based chalcogenide glasses have been materials of choice for a number of technological applications. However, chalcogenide glasses can undergo substantial structural relaxation even at room temperature due to their low glass transition temperatures. The origins of these dynamic processes and their correlation to the glass structure is therefore of fundamental and practical interest. In particular, a deep understanding of the dynamic response near the glass transition region could help elucidate the mechanism of these structural relaxation processes. The correlation between structure and dynamic properties of selenium based glass systems were therefore investigated. NMR and Raman spectroscopy measurements reveal that the structure of Asx Se1-x glass follow the chain crossing model in selenium-rich glasses but contain increasing amounts of cage molecules in arsenic-rich compositions. This structural pattern leads to systematic extrema in physical properties at the stoichiometric composition As40Se60. The dynamic response of AsxSe1-x glasses investigated by heat capacity spectroscopy shows two minima in melt fragility as a function of composition which correlate well with the dimensionality of the glassy network. The structure evolves from 2D to 3D during crosslinking of selenium chains by arsenic but reduces into a 2D layer-like structure at the stoichiometric composition. Upon precipitation of arsenic-rich cages the network first reverts back to 3D and eventually becomes a mix of 2D and 0D structural units. The presence of molecular clusters in the network is evidenced by a strong bimodal dynamic response at high arsenic contents. NMR and Raman spectroscopy measurements of GexSe1-x glasses suggest a structure composed of aggregated tetrahedral units and long selenium chains with little or no connectivity. Distinct dynamic responses of these two separated structural motifs are

  17. NMR and transport measurements of copper chalcogenide and clathrate compounds

    NASA Astrophysics Data System (ADS)

    Sirusi Arvij, Ali

    Due to limited sources of fossil fuels worldwide and a large percentage wasted as heat energy, searching for efficient thermoelectric materials to convert heat to electricity has gained a great deal of attention. Most of the attempts are focused on materials with substantially lower lattice thermal conductivity and narrow band gaps. Among them, inorganic clathrates and copper-based chalcogenides possess intrinsic low thermal conductivity which makes them promising thermoelectrics. In this work, nuclear magnetic resonance (NMR), transport, and magnetic measurements were performed on clathrates and copper-based chalcogenides to investigate their vibrational and electronic charge carrier properties, as well as the unknown structures of Cu2Se and Cu 2Te at low temperatures, and the effect of rattling of guest atoms in the clathrates. The NMR results in Ba8Ga16Ge30 indicate a pseudogap in the Ga electronic density of states, superposed upon a surprisingly large Ba contribution to the conduction band. Meanwhile, the phonon contributions to the Ga relaxation rates are large and increase more rapidly with temperature than typical semiconductors due to enhanced anharmonicity of the propagative phonon modes over a wide range. Moreover, the observed NMR shifts in the Ba8Cu5Si xGe41-x clathrates change in a nonlinear way with increasing Si substitution: from x = 0 to about 20 the shifts are essentially constant, while approaching x = 41 they increase rapidly, demonstrating a significant change in hybridizations vs Si substitution. NMR studies of Cu2Se show an initial appearance of ionic hopping in a narrow temperature range above 100 K, coinciding with the recently observed low-temperature phase transition. At room temperature and above, this goes over to rapid Cu-ion hopping and a single motionally narrowed line both above and below the alpha-beta structural transition. Furthermore, the NMR results on Cu2Te and Cu 1.98Ag0.2Te demonstrate unusually large negative chemical

  18. General synthetic approach to heterostructured nanocrystals based on noble metals and I-VI, II-VI, and I-III-VI metal chalcogenides.

    PubMed

    Liu, Minghui; Zeng, Hua Chun

    2014-08-19

    Solid metal precursors (alloys or monometals) can serve both as a starting template and as a source material for chemical transformation to metal chalcogenides. Herein, we develop a simple solution-based strategy to obtain highly monodisperse noble-metal-based heterostructured nanocrystals from such precursor seeds. By utilizing chemical and structural inhomogeneity of these metal seeds, in this work, we have synthesized a total of five I-VI (Ag2S, Ag2Se, Ag3AuS2, Ag3AuSe2, and Cu9S5), three II-VI (CdS, CdSe, and CuSe), and four I-III-VI (AgInS2, AgInSe2, CuInS2, and CuInSe2) chalcogenides, together with their fifteen associated heterodimers (Au-Ag2S, Au-Ag2Se, Au-Ag3AuS2, Au-Ag3AuSe2, Au-AgInS2, Au-AgInSe2, Au-CdS, Au-CdSe, Ag-Ag2S, Ag-AgInS2, Au-Cu9S5, Au-CuInS2, Au-CuSe, Au-CuInSe2, and Pt-AgInS2) to affirm the process generality. Briefly, by adding elemental sulfur or selenium to AuAg alloy seeds and tuning the reaction conditions, we can readily obtain phase-pure Au-Ag2S, Au-Ag2Se, Au-Ag3AuS2, and Au-Ag3AuSe2 heterostructures. Similarly, we can also fabricate Au-AgInS2 and Au-AgInSe2 heterostructures from the AuAg seeds by adding sulfur/selenium and indium precursors. Furthermore, by partial or full conversion of Ag seeds, we can prepare both single-phase Ag chalcogenide nanocrystals and Ag-based heterostructures. To demonstrate wide applicability of this strategy, we have also synthesized Au-based binary and ternary Cu chalcogenide (Au-Cu9S5, Au-CuSe, Au-CuInS2, and Au-CuInSe2) heterostructures from alloy seeds of AuCu and Pt chalcogenides (e.g., Pt-AgInS2) from alloy seeds of PtAg. The structure and composition of the above products have been confirmed with X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy methods. A kinetic investigation of the formation mechanism of these heterostructures is brought forward using Au-AgInS2 and Ag-CuInS2 as model examples.

  19. Nanoscale Andreev Reflection Spectroscopy on Bismuth-Chalcogenide Topological Insulators

    NASA Astrophysics Data System (ADS)

    Granstrom, C. R.; Fridman, I.; Liang, R. X.; Lei, H.; Petrovic, C.; Yang, Shuo; Wu, K. H.; Wei, J. Y. T.

    Andreev reflection (AR) is the basic mechanism underlying the superconducting proximity effect which, at the interface between a topological insulator (TI) and a spin-singlet superconductor, can induce chiral p-wave pairing in the TI. Despite this novel importance, it is not well understood how AR is affected by the unique attributes of a three-dimensional TI, namely the Dirac dispersion and helical spin-polarization of its surface states. In this work, we use both s-wave and d-wave superconducting tips to perform AR spectroscopy at 4.2 K on flux-grown Bi2Se3 and Bi2Te3 single crystals, as well as epitaxial Bi2Se3 thin films grown on SrTiO3 substrates by molecular beam epitaxy. These AR measurements are complemented by scanning tunneling spectroscopy, in order to characterize the superconducting tip as well as the doping level and surface condition of the TI sample. Our data are analyzed using BTK theory, in light of the characteristic band structure of bismuth chalcogenides, to elucidate how the band structure affects the AR process. Work supported by: NSERC, CFI-OIT, the Canadian Institute for Advanced Research, and the Department of Energy.

  20. Andreev Reflection Spectroscopy on Bismuth- Chalcogenide Topological Insulators

    NASA Astrophysics Data System (ADS)

    Granstrom, C. R.; Fridman, I.; Wei, J. Y. T.; Lei, H.; Petrovic, C.; Liang, R. X.

    2015-03-01

    Andreev reflection (AR) is the basic mechanism underlying the superconducting proximity effect which, at the interface between a topological insulator (TI) and a spin-singlet superconductor, can give rise to Majorana-like states. Despite this basic importance, little is known about how AR is affected by the unique attributes of a three-dimensional TI, namely the linear dispersion and spin-momentum locking of its surface states. In this study, we use both s-wave and d-wave superconducting tips to perform AR spectroscopy on variously flux-grown Bi2Se3andBi2Te3 single crystals. The AR measurements are complemented by in-situ scanning tunneling spectroscopy, down to 300 mK and up to 9 T, in order to determine the doping level and characterize both the sample surface and tip condition. Our data are analyzed in terms of the characteristic band structure of Bi-chalcogenides, to elucidate how it affects the AR process. Work supported by NSERC, CFI-OIT, CIFAR, and the Center for Emergent Superconductivity, an Energy Frontier Research Center funded by the U.S. DOE, Office for Basic Energy Science.

  1. Band gap anomaly and topological properties in lead chalcogenides

    NASA Astrophysics Data System (ADS)

    Simin, Nie; Xiao, Yan Xu; Gang, Xu; Zhong, Fang

    2016-03-01

    Band gap anomaly is a well-known issue in lead chalcogenides PbX (X = S, Se, Te, Po). Combining ab initio calculations and tight-binding (TB) method, we have studied the band evolution in PbX, and found that the band gap anomaly in PbTe is mainly related to the high on-site energy of Te 5s orbital and the large s-p hopping originated from the irregular extended distribution of Te 5s electrons. Furthermore, our calculations show that PbPo is an indirect band gap (6.5 meV) semiconductor with band inversion at L point, which clearly indicates that PbPo is a topological crystalline insulator (TCI). The calculated mirror Chern number and surface states double confirm this conclusion. Project supported by the National Natural Science Foundation of China (Grant No. 11204359), the National Basic Research Program of China (Grant No. 2013CB921700), and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB07020100).

  2. Alloyed copper chalcogenide nanoplatelets via partial cation exchange reactions.

    PubMed

    Lesnyak, Vladimir; George, Chandramohan; Genovese, Alessandro; Prato, Mirko; Casu, Alberto; Ayyappan, S; Scarpellini, Alice; Manna, Liberato

    2014-08-26

    We report the synthesis of alloyed quaternary and quinary nanocrystals based on copper chalcogenides, namely, copper zinc selenide-sulfide (CZSeS), copper tin selenide-sulfide (CTSeS), and copper zinc tin selenide-sulfide (CZTSeS) nanoplatelets (NPLs) (∼20 nm wide) with tunable chemical composition. Our synthesis scheme consisted of two facile steps: i.e., the preparation of copper selenide-sulfide (Cu2-xSeyS1-y) platelet shaped nanocrystals via the colloidal route, followed by an in situ cation exchange reaction. During the latter step, the cation exchange proceeded through a partial replacement of copper ions by zinc or/and tin cations, yielding homogeneously alloyed nanocrystals with platelet shape. Overall, the chemical composition of the alloyed nanocrystals can easily be controlled by the amount of precursors that contain cations of interest (e.g., Zn, Sn) to be incorporated/alloyed. We have also optimized the reaction conditions that allow a complete preservation of the size, morphology, and crystal structure as that of the starting Cu2-xSeyS1-y NPLs. The alloyed NPLs were characterized by optical spectroscopy (UV-vis-NIR) and cyclic voltammetry (CV), which demonstrated tunability of their light absorption characteristics as well as their electrochemical band gaps.

  3. Polaronic transport in Ag-based quaternary chalcogenides

    NASA Astrophysics Data System (ADS)

    Wei, Kaya; Khabibullin, Artem R.; Stedman, Troy; Woods, Lilia M.; Nolas, George S.

    2017-09-01

    Low temperature resistivity measurements on dense polycrystalline quaternary chalcogenides Ag2+xZn1-xSnSe4, with x = 0, 0.1, and 0.3, indicate polaronic type transport which we analyze employing a two-component Holstein model based on itinerant and localized polaron contributions. Electronic structure property calculations via density functional theory simulations on Ag2ZnSnSe4 for both energetically similar kesterite and stannite structure types were also performed in order to compare our results to those of the compositionally similar but well known Cu2ZnSnSe4. This theoretical comparison is crucial in understanding the bonding that results in polaronic type transport for Ag2ZnSnSe4, as well as the structural and electronic properties of both crystal structure types. In addition to possessing this unique electronic transport, the thermal conductivity of Ag2ZnSnSe4 is low and decreases with increasing silver content. This work reveals unique structure-property relationships in materials that continue to be of interest for thermoelectric and photovoltaic applications.

  4. Nonlinear characterization of GeSbS chalcogenide glass waveguides.

    PubMed

    Choi, Ju Won; Han, Zhaohong; Sohn, Byoung-Uk; Chen, George F R; Smith, Charmayne; Kimerling, Lionel C; Richardson, Kathleen A; Agarwal, Anuradha M; Tan, Dawn T H

    2016-12-21

    GeSbS ridge waveguides have recently been demonstrated as a promising mid - infrared platform for integrated waveguide - based chemical sensing and photodetection. To date, their nonlinear optical properties remain relatively unexplored. In this paper, we characterize the nonlinear optical properties of GeSbS glasses, and show negligible nonlinear losses at 1.55 μm. Using self - phase modulation experiments, we characterize a waveguide nonlinear parameter of 7 W(-1)/m and nonlinear refractive index of 3.71 × 10(-18) m(2)/W. GeSbS waveguides are used to generate supercontinuum from 1280 nm to 2120 nm at the -30 dB level. The spectrum expands along the red shifted side of the spectrum faster than on the blue shifted side, facilitated by cascaded stimulated Raman scattering arising from the large Raman gain of chalcogenides. Fourier transform infrared spectroscopic measurements show that these glasses are optically transparent up to 25 μm, making them useful for short - wave to long - wave infrared applications in both linear and nonlinear optics.

  5. Alloyed Copper Chalcogenide Nanoplatelets via Partial Cation Exchange Reactions

    PubMed Central

    2014-01-01

    We report the synthesis of alloyed quaternary and quinary nanocrystals based on copper chalcogenides, namely, copper zinc selenide–sulfide (CZSeS), copper tin selenide–sulfide (CTSeS), and copper zinc tin selenide–sulfide (CZTSeS) nanoplatelets (NPLs) (∼20 nm wide) with tunable chemical composition. Our synthesis scheme consisted of two facile steps: i.e., the preparation of copper selenide–sulfide (Cu2–xSeyS1–y) platelet shaped nanocrystals via the colloidal route, followed by an in situ cation exchange reaction. During the latter step, the cation exchange proceeded through a partial replacement of copper ions by zinc or/and tin cations, yielding homogeneously alloyed nanocrystals with platelet shape. Overall, the chemical composition of the alloyed nanocrystals can easily be controlled by the amount of precursors that contain cations of interest (e.g., Zn, Sn) to be incorporated/alloyed. We have also optimized the reaction conditions that allow a complete preservation of the size, morphology, and crystal structure as that of the starting Cu2–xSeyS1–y NPLs. The alloyed NPLs were characterized by optical spectroscopy (UV–vis–NIR) and cyclic voltammetry (CV), which demonstrated tunability of their light absorption characteristics as well as their electrochemical band gaps. PMID:25050455

  6. Ultrafast exciton fine structure relaxation dynamics in lead chalcogenide nanocrystals.

    PubMed

    Johnson, Justin C; Gerth, Kathrine A; Song, Qing; Murphy, James E; Nozik, Arthur J; Scholes, Gregory D

    2008-05-01

    The rates of fine structure relaxation in PbS, PbSe, and PbTe nanocrystals were measured on a femtosecond time scale as a function of temperature with no applied magnetic field by cross-polarized transient grating spectroscopy (CPTG) and circularly polarized pump-probe spectroscopy. The relaxation rates among exciton fine structure states follow trends with nanocrystal composition and size that are consistent with the expected influence of material dependent spin-orbit coupling, confinement enhanced electron-hole exchange interaction, and splitting between L valleys that are degenerate in the bulk. The size dependence of the fine structure relaxation rate is considerably different from what is observed for small CdSe nanocrystals, which appears to result from the unique material properties of the highly confined lead chalcogenide quantum dots. Modeling and qualitative considerations lead to conclusions about the fine structure of the lowest exciton absorption band, which has a potentially significant bearing on photophysical processes that make these materials attractive for practical purposes.

  7. Multi-layered chalcogenides with potential for magnetism and superconductivity

    SciTech Connect

    Li, Li; Parker, David S.; dela Cruz, Clarina R.; Sefat, Athena Safa

    2016-10-24

    Layered thallium copper chalcogenides can form single, double, or triple layers of Cu–Ch separated by Tl sheets. Here we report on the preparation and properties of Tl-based materials of TlCu2Se2, TlCu4S3, TlCu4Se3 and TlCu6S4. Having no long-range magnetism for these materials is quite surprising considering the possibilities of inter- and intra-layer exchange interactions through Cu 3d, and we measure by magnetic susceptibility and confirm by neutron diffraction. First principles density-functional theory calculations for both the single-layer TlCu2Se2 (isostructural to the ‘122’ iron-based superconductors) and the double-layer TlCu4Se3 suggest a lack of Fermi-level spectral weight that is needed to drive a magnetic or superconducting instability. Furthermore, for multiple structural layers with Fe, there is much greater likelihood for magnetism and superconductivity.

  8. Multi-layered chalcogenides with potential for magnetism and superconductivity

    DOE PAGES

    Li, Li; Parker, David S.; dela Cruz, Clarina R.; ...

    2016-10-24

    Layered thallium copper chalcogenides can form single, double, or triple layers of Cu–Ch separated by Tl sheets. Here we report on the preparation and properties of Tl-based materials of TlCu2Se2, TlCu4S3, TlCu4Se3 and TlCu6S4. Having no long-range magnetism for these materials is quite surprising considering the possibilities of inter- and intra-layer exchange interactions through Cu 3d, and we measure by magnetic susceptibility and confirm by neutron diffraction. First principles density-functional theory calculations for both the single-layer TlCu2Se2 (isostructural to the ‘122’ iron-based superconductors) and the double-layer TlCu4Se3 suggest a lack of Fermi-level spectral weight that is needed to drive amore » magnetic or superconducting instability. Furthermore, for multiple structural layers with Fe, there is much greater likelihood for magnetism and superconductivity.« less

  9. Multi-layered Chalcogenides with potential for magnetism and superconductivity

    NASA Astrophysics Data System (ADS)

    Li, Li; Parker, David S.; dela Cruz, Clarina R.; Sefat, Athena S.

    2016-12-01

    Layered thallium copper chalcogenides can form single, double, or triple layers of Cu-Ch separated by Tl sheets. Here we report on the preparation and properties of Tl-based materials of TlCu2Se2, TlCu4S3, TlCu4Se3 and TlCu6S4. Having no long-range magnetism for these materials is quite surprising considering the possibilities of inter- and intra-layer exchange interactions through Cu 3d, and we measure by magnetic susceptibility and confirm by neutron diffraction. First principles density-functional theory calculations for both the single-layer TlCu2Se2 (isostructural to the '122' iron-based superconductors) and the double-layer TlCu4Se3 suggest a lack of Fermi-level spectral weight that is needed to drive a magnetic or superconducting instability. However, for multiple structural layers with Fe, there is much greater likelihood for magnetism and superconductivity.

  10. Preparation and magnetoresistance of silver and copper chalcogenide thin films

    NASA Astrophysics Data System (ADS)

    Chuprakov, Ilya; Watts, Steven; Wirth, Steffen; von Molnár, Stephan; Dahmen, Klaus-Hermann

    1998-03-01

    An unexpected giant positive magnetoresitance was recently discovered in non-stoichiometric crystals of Ag_2Te and Ag_2Se [1]. There, a linear magnetoresistance effect as high as 120% was observed in fields of 4 T at room temperature. Here we report on thin films of copper and silver chalcogenides prepared by a vapor phase transport method. A prefered grain orientation is found in the films after annealing. Resistance, magnetoresistance and Hall effect were measured. Typically, the resistivity is temperature independent below 70 K with a value of 1 mΩ cm. As in the crystals, there is a large positive magnetoresistance, but the field dependence is non-linear with a typical value of 50% at room temperature and 200% at temperatures below 100 K for applied fields of 6 T. Variations of the deposition techniques are explored in order to establish the relationship between the deposition conditions and transport properties. [0.25cm] [1] R. Xu, A. Husmann, T.F. Rosenbaum, M.-L. Saboungi, E.J. Enderby and P.B. Littlewood, Nature 390, 57 (1997).

  11. Nonlinear characterization of GeSbS chalcogenide glass waveguides

    PubMed Central

    Choi, Ju Won; Han, Zhaohong; Sohn, Byoung-Uk; Chen, George F. R.; Smith, Charmayne; Kimerling, Lionel C.; Richardson, Kathleen A.; Agarwal, Anuradha M.; Tan, Dawn T. H.

    2016-01-01

    GeSbS ridge waveguides have recently been demonstrated as a promising mid – infrared platform for integrated waveguide – based chemical sensing and photodetection. To date, their nonlinear optical properties remain relatively unexplored. In this paper, we characterize the nonlinear optical properties of GeSbS glasses, and show negligible nonlinear losses at 1.55 μm. Using self – phase modulation experiments, we characterize a waveguide nonlinear parameter of 7 W−1/m and nonlinear refractive index of 3.71 × 10−18 m2/W. GeSbS waveguides are used to generate supercontinuum from 1280 nm to 2120 nm at the −30 dB level. The spectrum expands along the red shifted side of the spectrum faster than on the blue shifted side, facilitated by cascaded stimulated Raman scattering arising from the large Raman gain of chalcogenides. Fourier transform infrared spectroscopic measurements show that these glasses are optically transparent up to 25 μm, making them useful for short – wave to long – wave infrared applications in both linear and nonlinear optics. PMID:28000725

  12. Surface analysis of chalcogenide semiconductors used in photovoltaics (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Rockett, Angus A.

    2017-04-01

    Both CdTe and Cu(In,Ga)Se2 have produced highly efficient thin film solar cells, exceeding 22% in champion devices. Both are also manufactured in large scales and show promise as future energy technologies. However, understanding the current collection mechanisms and mechanisms of instability in the devices remain a concern. To address these questions, we have used scanning probe and photoemission spectroscopies to study the response of chalcogenide materials to light and how charge is collected. Results of scanning microwave impedance microscopy and conductive atomic force microscopy show dramatic differences in the behavior of CdTe and Cu(In,Ga)Se2 (CIGS). The results include characterization of the effect of CdCl2 treatment on the properties CdTe grains and grain boundaries. This treatment dramatically increases the current collection in the grain boundaries. Thus we show that CdTe solar cells operate apparently by generation of electron hole pairs in the CdTe grains and collection of electrons to the grain boundaries. By contrast, CIGS grains show little or no contrast between the grains and grain boundaries and no obvious conduction pathway through the grain boundaries appears to exist. Our surface analysis results are supplemented with other measurements of both surface and bulk microchemistry and microstructure.

  13. Effect of pressure on band structure properties of Zinc Chalcogenides

    NASA Astrophysics Data System (ADS)

    Singh, Dharmbir

    2013-06-01

    The first principal calculations have been carried out to study the effect of pressure on band structure of Zinc Chalcogenides. The tight-binding linear muffin-tin orbital method (TB-LMTO) within local density approximation (LDA) has been used to study the band structure properties at abmbient and high pressure. The phase stability is determined from the total energy calculations within the atomic-sphere approximation (ASA). The purely theoretical calculations show that in these materials (i) at ambient pressure, zinc blende type (B3) phase is more stable than rock salt type (B1) phase; and (ii) it exhibits a phase transition from zinc blende (B3) type to NaCl type (B1) type structure at high pressure. At further ultrahigh pressure there is phase transition from NaCl type (B1) phase to CsCl type (B2) phase. Although the calculated lattice parameter, transition pressure, volume of collapse is found to be little less than the experimentally observed value, but this has been explained from the fact that the calculation has been carried out at 0 K while the experiments have been performed at room temperature. Ambient & high pressure band structural results are compared with earlier obtained similar results and explained in details. The Author would like to thank to Director, PIET for all the motivation and support.

  14. Generation of λ/12 nanowires in chalcogenide glasses.

    PubMed

    Nicoletti, Elisa; Bulla, Douglas; Luther-Davies, Barry; Gu, Min

    2011-10-12

    Nanowires have been widely studied and have gained a lot of interest in the past decade. Because of their high refractive index and high nonlinearity, chalcogenide glasses (ChGs) are a good candidate for the fabrication of photonic nanowires as such nanowaveguides provide the maximal confinement of light, enabling large enhancement of nonlinear interactions and group-velocity dispersion engineering. Here we report on the generation of λ/12 (∼68 nm) nanowires based on the theoretical and experimental study of the influence of the laser repetition rate on the direct laser fabrication in ChGs (λ = 800 nm). Through a numerical model of cumulative heating, the optimum conditions for high-resolution fabrication in As(2)S(3) are found. Nanowires with dimensions down to ∼λ/12 are for the first time successfully fabricated in ChGs. We show that the generated nanowires can be stacked to form a three-dimensional woodpile photonic crystal with a pronounced stop gap.

  15. Structural analysis of chalcogenide waveguides using Rutherford backscattering spectroscopy (RBS)

    NASA Astrophysics Data System (ADS)

    Rivero, Clara; Sharek, Patricia S.; Nootz, Gero; Lopez, Cedric; Richardson, Kathleen A.; Schulte, Alfons; Irwin, Richard; Galstian, Tigran V.; Hamel, Vincent; Turcotte, Karine; Villeneuve, Alain; Valee, Real

    2001-12-01

    In an effort to develop an improved medium for optical communication, chalcogenide glasses are being investigated for waveguide and integrated optical components. These glasses are attractive for integrated optics applications due to their good infrared transmission and high nonlinear Kerr effects. The fact that these glasses can be fabricated in thin films and optical fiber forms constitute a major advantage for future high-speed optical devices applications. However, to advance these novel characteristics, it is crucial to identify the structure/property relationship in the glass, in both bulk and film materials. Rutherford Backscattering Spectroscopy (RBS) is an analytical tool that gives very useful information regarding compositional and structural analysis of the films, as well as a precise measurement of the film's layer thickness. Results obtained showed no apparent variation in composition and small (less than 10%) density variation in single layer As2S3 films. Multilayer films, which thickness were measured using SEM images, displayed compositional and density modifications associated with the annealing process. The same calculations were conducted after almost a year from the previous measurements to study changes induced due to film aging. Stoichiometric and thickness modifications, caused by aging, were observed in unannealed structures. No apparent changes were detected in annealed films. Waveguide Raman Spectroscopy was used as a complementary tool to identify the molecular features responsible for the changes.

  16. Photo-induced changes in a hybrid amorphous chalcogenide/silica photonic crystal fiber

    SciTech Connect

    Markos, Christos

    2014-01-06

    Photostructural changes in a hybrid photonic crystal fiber with chalcogenide nanofilms inside the inner surface of the cladding holes are experimentally demonstrated. The deposition of the amorphous chalcogenide glass films inside the silica capillaries of the fiber was made by infiltrating the nanocolloidal solution-based As{sub 25}S{sub 75}, while the photoinduced changes were performed by side illuminating the fiber near the bandgap edge of the formed glass nanofilms. The photoinduced effect of the chalcogenide glass directly red-shifts the transmission bandgap position of the fiber as high as ∼20.6 nm at around 1600 nm wavelength, while the maximum bandgap intensity change at ∼1270 nm was −3 dB.

  17. Low-loss, submicron chalcogenide integrated photonics with chlorine plasma etching

    SciTech Connect

    Chiles, Jeff; Malinowski, Marcin; Rao, Ashutosh; Novak, Spencer; Richardson, Kathleen; Fathpour, Sasan

    2015-03-16

    A chlorine plasma etching-based method for the fabrication of high-performance chalcogenide-based integrated photonics on silicon substrates is presented. By optimizing the etching conditions, chlorine plasma is employed to produce extremely low-roughness etched sidewalls on waveguides with minimal penalty to propagation loss. Using this fabrication method, microring resonators with record-high intrinsic Q-factors as high as 450 000 and a corresponding propagation loss as low as 0.42 dB/cm are demonstrated in submicron chalcogenide waveguides. Furthermore, the developed chlorine plasma etching process is utilized to demonstrate fiber-to-waveguide grating couplers in chalcogenide photonics with high power coupling efficiency of 37% for transverse-electric polarized modes.

  18. Stoichiometric control of lead chalcogenide nanocrystal solids to enhance their electronic and optoelectronic device performance.

    PubMed

    Oh, Soong Ju; Berry, Nathaniel E; Choi, Ji-Hyuk; Gaulding, E Ashley; Paik, Taejong; Hong, Sung-Hoon; Murray, Christopher B; Kagan, Cherie R

    2013-03-26

    We investigate the effects of stoichiometric imbalance on the electronic properties of lead chalcogenide nanocrystal films by introducing excess lead (Pb) or selenium (Se) through thermal evaporation. Hall-effect and capacitance-voltage measurements show that the carrier type, concentration, and Fermi level in nanocrystal solids may be precisely controlled through their stoichiometry. By manipulating only the stoichiometry of the nanocrystal solids, we engineer the characteristics of electronic and optoelectronic devices. Lead chalcogenide nanocrystal field-effect transistors (FETs) are fabricated at room temperature to form ambipolar, unipolar n-type, and unipolar p-type semiconducting channels as-prepared and with excess Pb and Se, respectively. Introducing excess Pb forms nanocrystal FETs with electron mobilities of 10 cm(2)/(V s), which is an order of magnitude higher than previously reported in lead chalcogenide nanocrystal devices. Adding excess Se to semiconductor nanocrystal solids in PbSe Schottky solar cells enhances the power conversion efficiency.

  19. Ultrafast optical manipulation of atomic arrangements in chalcogenide alloy memory materials.

    PubMed

    Makino, Kotaro; Tominaga, Junji; Hase, Muneaki

    2011-01-17

    A class of chalcogenide alloy materials that shows significant changes in optical properties upon an amorphous-to-crystalline phase transition has lead to development of large data capacities in modern optical data storage. Among chalcogenide phase-change materials, Ge2Sb2Te5 (GST) is most widely used because of its reliability. We use a pair of femtosecond light pulses to demonstrate the ultrafast optical manipulation of atomic arrangements from tetrahedral (amorphous) to octahedral (crystalline) Ge-coordination in GST superlattices. Depending on the parameters of the second pump-pulse, ultrafast nonthermal phase-change occurred within only few-cycles (≈1 picosecond) of the coherent motion corresponding to a GeTe4 local vibration. Using the ultrafast switch in chalcogenide alloy memory could lead to a major paradigm shift in memory devices beyond the current generation of silicon-based flash-memory.

  20. Growth Mechanisms and Structural Properties of Lead Chalcogenide Films Grown by Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Virt, I. S.; Rudyi, I. O.; Lopatynskyi, I. Ye.; Dubov, Yu.; Tur, Y.; Lusakowska, E.; Luka, G.

    2017-01-01

    Three lead chalcogenide films, PbTe, PbSe, and PbS, with a high structural quality were grown by pulsed lased deposition (PLD). The films were grown on single crystal substrates (Si, KCl, Al2O3) and on Si covered with a Si3N4 buffer layer. The Si3N4 layer latter facilitated the lead chalcogenide layer nucleation during the first growth stages and resulted in a more homogeneous surface morphology and a lower surface roughness. The surface geometry (roughness) of the films grown on Si3N4 was studied by means of the power spectral density analysis. Different growth modes, ranging from plasma plume condensation to bulk diffusion, resulting in observed film morphologies were identified. The investigations were complemented by electrical characterization of the chalcogenide films.

  1. Search for Binary Trojans

    NASA Astrophysics Data System (ADS)

    Noll, Keith S.; Grundy, W. M.; Ryan, E. L.; Benecchi, S. D.

    2015-11-01

    We have reexamined 41 Trojan asteroids observed with the Hubble Space Telescope (HST) to search for unresolved binaries. We have identified one candidate binary with a separation of 53 milliarcsec, about the width of the diffraction limited point-spread function (PSF). Sub-resolution-element detection of binaries is possible with HST because of the high signal-to-noise ratio of the observations and the stability of the PSF. Identification and confirmation of binary Trojans is important because a Trojan Tour is one of five possible New Frontiers missions. A binary could constitute a potentially high value target because of the opportunity to study two objects and to test models of the primordial nature of binaries. The potential to derive mass-based physical information from the binary orbit could yield more clues to the origin of Trojans.

  2. Precision glass molding of complex shaped chalcogenide glass lenses for IR applications

    NASA Astrophysics Data System (ADS)

    Staasmeyer, Jan-Helge; Wang, Yang; Liu, Gang; Dambon, Olaf; Klocke, Fritz

    2016-09-01

    The use of chalcogenide glass in the thermal infrared domain is an emerging alternative to commonly used crystalline materials such as germanium. The main advantage of chalcogenide glass is the possibility of mass production of complex shaped geometries with replicative processes such as precision glass molding. Thus costly single point diamond turning processes are shifted to mold manufacturing and do not have to be applied to every single lens produced. The usage of FEM-Simulation is mandatory for developing a molding process for complex e.g. non rotational symmetric chalcogenide glass lenses in order to predict the flow of glass. This talk will present state of the art modelling of the precision glass molding process for chalcogenide glass lenses, based on thermal- and mechanical models. Input data for modelling are a set of material properties of the specific chalcogenide glass in conjunction with properties of mold material and wear protective coatings. Specific properties for the mold-glass interaction such as stress relaxation or friction at the glassmold interface cannot be obtained from datasheets and must be determined experimentally. A qualified model is a powerful tool to optimize mold and preform designs in advance in order to achieve sufficient mold filling and compensate for glass shrinkage. Application of these models in an FEM-Simulation "case study" for molding a complex shaped non-rotational symmetric lens is shown. The outlook will examine relevant issues for modelling the precision glass molding process of chalcogenide glasses in order to realize scaled up production in terms of multi cavity- and wafer level molding.

  3. Open framework metal chalcogenides as efficient photocatalysts for reduction of CO2 into renewable hydrocarbon fuel.

    PubMed

    Sasan, Koroush; Lin, Qipu; Mao, Chengyu; Feng, Pingyun

    2016-06-07

    Open framework metal chalcogenides are a family of porous semiconducting materials with diverse chemical compositions. Here we show that these materials containing covalent three-dimensional superlattices of nanosized supertetrahedral clusters can function as efficient photocatalysts for the reduction of CO2 to CH4. Unlike dense semiconductors, metal cations are successfully incorporated into the channels of the porous semiconducting materials to further tune the physical properties of the materials such as electrical conductivity and band gaps. In terms of the photocatalytic properties, the metal-incorporated porous chalcogenides demonstrated enhanced solar energy absorption and higher electrical conductivity and improved photocatalytic activity.

  4. Homogeneity and internal defects detect of infrared Se-based chalcogenide glass

    NASA Astrophysics Data System (ADS)

    Li, Zupana; Wu, Ligang; Lin, Changgui; Song, Bao'an; Wang, Xunsi; Shen, Xiang; Dai, Shixunb

    2011-10-01

    Ge-Sb-Se chalcogenide glasses is a kind of excellent infrared optical material, which has been enviromental friendly and widely used in infrared thermal imaging systems. However, due to the opaque feature of Se-based glasses in visible spectral region, it's difficult to measure their homogeneity and internal defect as the common oxide ones. In this study, a measurement was proposed to observe the homogeneity and internal defect of these glasses based on near-IR imaging technique and an effective measurement system was also constructed. The testing result indicated the method can gives the information of homogeneity and internal defect of infrared Se-based chalcogenide glass clearly and intuitionally.

  5. Compositional trends of radiation-induced effects in ternary systems of chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Kovalskiy, A.

    2003-01-01

    The effect of gamma-irradiation on the optical transmittance spectra of pseudobinary stoichiometric and non-stoichiometric cuts of ternary systems of chalcogenide glasses was studied. The application of chemical-bond approach is proposed to explain the features of compositional dependencies of radiation-induced effects in these materials. It is shown that free volume concept must be taken into consideration at the presence of different radiation-sensitive structural units. The creation processes of coordination defects connected with the formation of free volume and coupled with the capability of the constituent atoms to passivation are the main factors determining the magnitude of the radiation-induced effects in chalcogenide glasses.

  6. A phonon scattering bottleneck for carrier cooling in lead chalcogenide nanocrystals.

    PubMed

    Geiregat, Pieter; Delerue, Christophe; Justo, Yolanda; Aerts, Michiel; Spoor, Frank; Van Thourhout, Dries; Siebbeles, Laurens D A; Allan, Guy; Houtepen, Arjan J; Hens, Zeger

    2015-01-27

    The cooling dynamics of hot charge carriers in colloidal lead chalcogenide nanocrystals is studied by hyperspectral transient absorption spectroscopy. We demonstrate a transient accumulation of charge carriers at a high energy critical point in the Brillouin zone. Using a theoretical study of the cooling rate in lead chalcogenides, we attribute this slowing down of charge carrier cooling to a phonon scattering bottleneck around this critical point. The relevance of this observation for the possible harvesting of the excess energy of hot carriers by schemes such as multiexciton generation is discussed.

  7. Engineering excitonic dynamics and environmental stability of post-transition metal chalcogenides by pyridine functionalization technique

    NASA Astrophysics Data System (ADS)

    Meng, Xiuqing; Pant, Anupum; Cai, Hui; Kang, Jun; Sahin, Hasan; Chen, Bin; Wu, Kedi; Yang, Sijie; Suslu, Aslihan; Peeters, F. M.; Tongay, Sefaattin

    2015-10-01

    Owing to their strong photon emission, low excitonic binding energies, and nearly-ideal band offset values for water splitting reactions, direct gap quasi-2D gallium chalcogenides are potential candidates for applications in energy harvesting, optoelectronics, and photonics. Unlike other 2D materials systems, chemical functionalization of gallium chalcogenides is still at its seminal stages. Here, we propose vapor phase pyridine intercalation technique to manipulate optical properties of gallium chalcogenides. After functionalization, the excitonic dynamics of quasi-2D GaSe change significantly as evidenced by an increase in integrated PL intensity and emergence of a new emission feature that is below the band edge. Based on our DFT calculations, we attribute these to formation of bound exciton complexes at the trap sites introduced by chemical reaction between pyridine and GaSe. On the contrary, pyridine functionalization does not impact the optical properties of GaTe, instead treats GaTe surface to prevent oxidization of tellurium atoms. Overall, results suggest novel ways to control properties of gallium chalcogenides on demand and unleash their full potential for a range of applications in photonics and optoelectronics.Owing to their strong photon emission, low excitonic binding energies, and nearly-ideal band offset values for water splitting reactions, direct gap quasi-2D gallium chalcogenides are potential candidates for applications in energy harvesting, optoelectronics, and photonics. Unlike other 2D materials systems, chemical functionalization of gallium chalcogenides is still at its seminal stages. Here, we propose vapor phase pyridine intercalation technique to manipulate optical properties of gallium chalcogenides. After functionalization, the excitonic dynamics of quasi-2D GaSe change significantly as evidenced by an increase in integrated PL intensity and emergence of a new emission feature that is below the band edge. Based on our DFT calculations

  8. Permanent photoalignment of liquid crystals on nanostructured chalcogenide glassy thin films

    SciTech Connect

    Gelbaor, Miri; Abdulhalim, I.; Klebanov, Matvey; Lyubin, Victor

    2011-02-14

    Photoalignment of nematic liquid crystals is obtained on the chalcogenide glassy thin film of As{sub 2}S{sub 3} using irradiation with polarized blue light. A uniform homogeneously aligned device is obtained with high contrast and strong anchoring. The device alignment quality is permanent as checked by following its functionality over a period of few months. The origin of the observed photoalignment is attributed to the photoinduced anisotropy in chalcogenide glasses. No differences between the different As{sub 2}S{sub 3} film thicknesses observed, thus supporting the proposition that some orientational order is photoinduced on the surface of the glass and responsible for the photoalignment.

  9. Superconductivity and magnetism in 11-structure iron chalcogenides in relation to the iron pnictides

    PubMed Central

    Singh, David Joseph

    2012-01-01

    This is a review of the magnetism and superconductivity in ‘11’-type Fe chalcogenides, as compared to the Fe-pnictide materials. The chalcogenides show many differences from the pnictides, as might be anticipated from their very varied chemistries. These differences include stronger renormalizations that might imply stronger correlation effects as well as different magnetic ordering patterns. Nevertheless the superconducting state and mechanism for superconductivity are apparently similar for the two classes of materials. Unanswered questions and challenges to theory are emphasized. PMID:27877517

  10. PHOEBE: PHysics Of Eclipsing BinariEs

    NASA Astrophysics Data System (ADS)

    Prsa, Andrej; Matijevic, Gal; Latkovic, Olivera; Vilardell, Francesc; Wils, Patrick

    2011-06-01

    PHOEBE (PHysics Of Eclipsing BinariEs) is a modeling package for eclipsing binary stars, built on top of the widely used WD program (Wilson & Devinney 1971). This introductory paper overviews most important scientific extensions (incorporating observational spectra of eclipsing binaries into the solution-seeking process, extracting individual temperatures from observed color indices, main-sequence constraining and proper treatment of the reddening), numerical innovations (suggested improvements to WD's Differential Corrections method, the new Nelder & Mead's downhill Simplex method) and technical aspects (back-end scripter structure, graphical user interface). While PHOEBE retains 100% WD compatibility, its add-ons are a powerful way to enhance WD by encompassing even more physics and solution reliability.

  11. X-ray Binaries

    NASA Astrophysics Data System (ADS)

    Lewin, Walter H. G.; van Paradijs, Jan; van den Heuvel, Edward Peter Jacobus

    1997-01-01

    Preface; 1. The properties of X-ray binaries, N. E. White, F. Nagase and A. N. Parmar; 2. Optical and ultraviolet observations of X-ray binaries J. van Paradijs and J. E. McClintock; 3. Black-hole binaries Y. Tanaka and W. H. G. Lewin; 4. X-ray bursts Walter H. G. Lewin, Jan Van Paradijs and Ronald E. Taam; 5. Millisecond pulsars D. Bhattacharya; 6. Rapid aperiodic variability in binaries M. van der Klis; 7. Radio properties of X-ray binaries R. M. Hjellming and X. Han; 8. Cataclysmic variable stars France Anne-Dominic Córdova; 9. Normal galaxies and their X-ray binary populations G. Fabbiano; 10. Accretion in close binaries Andrew King; 11. Formation and evolution of neutron stars and black holes in binaries F. Verbunt and E. P. J. van den Heuvel; 12. The magnetic fields of neutron stars and their evolution D. Bhattacharya and G. Srinivasan; 13. Cosmic gamma-ray bursts K. Hurley; 14. A catalogue of X-ray binaries Jan van Paradijs; 15. A compilation of cataclysmic binaries with known or suspected orbital periods Hans Ritter and Ulrich Kolb; References; Index.

  12. Localized rapid heating process for precision chalcogenide glass molding

    NASA Astrophysics Data System (ADS)

    Li, Hui; He, Peng; Yu, Jianfeng; Lee, L. James; Yi, Allen Y.

    2015-10-01

    Precision glass molding is an important process for high volume optical fabrication. However, conventional glass molding is a bulk heating process that usually requires a long thermal cycle, where molding assembly and other mechanical parts are heated and cooled together. This often causes low efficiency and other heating and cooling related problems, such as large thermal expansion in both the molds and molded optics. To cope with this issue, we developed a localized rapid heating process to effectively heat only very small part of the glass. This localized rapid heating study utilized a fused silica wafer coated with a thin graphene layer to heat only the surface of the glass. The graphene coating functions as an electrical resistant heater when a power source was applied across the thin film coating, generating heat on and near the coating. The feasibility of this process was validated by both experiments and numerical simulation. To demonstrate the advantages of the localized rapid heating, both localized rapid heating process and bulk heating process were performed and carefully compared. The uniformity and quality of the molded sample by localized rapid heating process was also demonstrated. In summary, localized rapid heating process by using graphene coated fused silica wafer was characterized and can be readily implemented in replication of micro scale chalcogenide glasses. A fused silica wafer coated with a thin graphene layer was utilized for localized rapid heating only the surface of the glass. The graphene coating functions as an electrical resistant heater when a power source was applied across the thin film coating, generating high temperature on and near the coating. This process is fast and efficient since only interested areas are heated without affecting the entire glass substrate or the mold assembly. The uniformity and quality of the molded sample by localized rapid heating process was demonstrated by comparing both localized rapid heating

  13. An overview of the Fe-chalcogenide superconductors

    NASA Astrophysics Data System (ADS)

    Wu, M. K.; Wu, P. M.; Wen, Y. C.; Wang, M. J.; Lin, P. H.; Lee, W. C.; Chen, T. K.; Chang, C. C.

    2015-08-01

    This review intends to summarize recent advancements in FeSe and related systems. The FeSe and related superconductors are currently receiving considerable attention for the high critical temperature (T C) observed and for many similar features to the high T C cuprate superconductors. These similarities suggest that understanding the FeSe-based compounds could potentially help our understanding of the cuprates. We begin the review by presenting common features observed in the FeSe- and FeAs-based systems. Then we discuss the importance of careful control of the material preparation allowing for a systematic structure characterization. With this control, numerous rich phases have been observed. Importantly, we suggest that the Fe-vacancy ordered phases found in the FeSe-based compounds, which are non-superconducting magnetic Mott insulators, are the parent compounds of the superconductors. Superconductivity can emerge from the parent phases by disordering the Fe vacancy order, often by a simple annealing treatment. Then we review physical properties of the Fe chalcogenides, specifically the optical properties and angle-resolved photoemission spectroscopy (ARPES) results. From the literature, strong evidence points to the existence of orbital modification accompanied by a gap-opening, prior to the structural phase transition, which is closely related to the occurrence of superconductivity. Furthermore, strong lattice to spin coupling are important for the occurrence of superconductivity in FeSe. Therefore, it is believed that the iron selenides and related compounds will provide essential information to understand the origin of superconductivity in the iron-based superconductors, and possibly the superconducting cuprates.

  14. Static Behavior of Chalcogenide Based Programmable Metallization Cells

    NASA Astrophysics Data System (ADS)

    Rajabi, Saba

    Nonvolatile memory (NVM) technologies have been an integral part of electronic systems for the past 30 years. The ideal non-volatile memory have minimal physical size, energy usage, and cost while having maximal speed, capacity, retention time, and radiation hardness. A promising candidate for next-generation memory is ion-conducting bridging RAM which is referred to as programmable metallization cell (PMC), conductive bridge RAM (CBRAM), or electrochemical metallization memory (ECM), which is likely to surpass flash memory in all the ideal memory characteristics. A comprehensive physics-based model is needed to completely understand PMC operation and assist in design optimization. To advance the PMC modeling effort, this thesis presents a precise physical model parameterizing materials associated with both ion-rich and ion-poor layers of the PMC's solid electrolyte, so that captures the static electrical behavior of the PMC in both its low-resistance on-state (LRS) and high resistance off-state (HRS). The experimental data is measured from a chalcogenide glass PMC designed and manufactured at ASU. The static on- and off-state resistance of a PMC device composed of a layered (Ag-rich/Ag-poor) Ge30Se70 ChG film is characterized and modeled using three dimensional simulation code written in Silvaco Atlas finite element analysis software. Calibrating the model to experimental data enables the extraction of device parameters such as material bandgaps, workfunctions, density of states, carrier mobilities, dielectric constants, and affinities. The sensitivity of our modeled PMC to the variation of its prominent achieved material parameters is examined on the HRS and LRS impedance behavior. The obtained accurate set of material parameters for both Ag-rich and Ag-poor ChG systems and process variation verification on electrical characteristics enables greater fidelity in PMC device simulation, which significantly enhances our ability to understand the underlying physics of

  15. Coherent mid-infrared supercontinuum generation in all-solid chalcogenide microstructured fibers with all-normal dispersion.

    PubMed

    Liu, Lai; Cheng, Tonglei; Nagasaka, Kenshiro; Tong, Hoangtuan; Qin, Guanshi; Suzuki, Takenobu; Ohishi, Yasutake

    2016-01-15

    We report the coherent mid-infrared supercontinuum generation in an all-solid chalcogenide microstructured fiber with all-normal dispersion. The chalcogenide microstructured fiber is a four-hole structure with core material of AsSe2 and air holes that are replaced by As2S5 glass rods. Coherent mid-infrared supercontinuum light extended to 3.3 μm is generated in a 2 cm long chalcogenide microstructured fiber pumped by a 2.7 μm laser.

  16. Study of kinetics of crystallization of Ge7Se75Sb18 chalcogenide glass

    NASA Astrophysics Data System (ADS)

    Tanwar, Naveen; Saraswat, Vibhav K.

    2014-04-01

    Present paper is an attempt to study kinetics of crystallization of Ge7Se75Sb18 chalcogenide glass by Differential Scanning Calorimetery (DSC) under non-isothermal condition. The sample was prepared by melt quenched technique and amorphous nature has been confirmed by XRD. Activation energy of crystallization has been evaluated using Kissinger, Augis-Bennett and Ozawa models.

  17. Bandgap Control via Structural and Chemical Tuning of Transition Metal Perovskite Chalcogenides.

    PubMed

    Niu, Shanyuan; Huyan, Huaixun; Liu, Yang; Yeung, Matthew; Ye, Kevin; Blankemeier, Louis; Orvis, Thomas; Sarkar, Debarghya; Singh, David J; Kapadia, Rehan; Ravichandran, Jayakanth

    2017-03-01

    Transition metal perovskite chalcogenides are a new class of versatile semiconductors with high absorption coefficient and luminescence efficiency. Polycrystalline materials synthesized by an iodine-catalyzed solid-state reaction show distinctive optical colors and tunable bandgaps across the visible range in photoluminescence, with one of the materials' external efficiency approaching the level of single-crystal InP and CdSe.

  18. Measurement of chalcogenide glass optical dispersion using a mid-infrared prism coupler

    SciTech Connect

    Qiao, Hong; Anheier, Norman C.; Musgraves, Jonathan D.; Richardson, Kathleen; Hewak, Daniel W.

    2011-05-01

    Physical properties of chalcogenide glass, including broadband infrared transparency, high refractive index, low glass transition temperature, and nonlinear properties, make them attractive candidates for advanced mid-infrared (3 to 12 {micro}m) optical designs. Efforts focused at developing new chalcogenide glass formulations and processing methods require rapid quantitative evaluation of their optical contents to guide the materials research. However, characterization of important optical parameters such as optical dispersion remains a slow and costly process, generally with limited accuracy. The recent development of a prism coupler at the Pacific Northwest National Laboratory (PNNL) now enables rapid, high precision measurement of refractive indices at discrete wavelengths from the visible to the mid-infrared. Optical dispersion data of several chalcogenide glass families were collected using this method. Variations in the optical dispersion were correlated to glass composition and compared against measurements using other methods. While this work has been focused on facilitating chalcogenide glass synthesis, mid-infrared prism coupler analysis has broader applications to other mid-infrared optical material development efforts, including oxide glasses and crystalline materials.

  19. Internal gain in Er-doped As₂S₃ chalcogenide planar waveguides.

    PubMed

    Yan, Kunlun; Vu, Khu; Madden, Steve

    2015-03-01

    Low-loss erbium-doped As₂S₃ planar waveguides are fabricated by cothermal evaporation and plasma etching. Internal gain in the telecommunications band is demonstrated for the first time in any chalcogenide glass and additionally in a thin film planar waveguide amplifier configuration.

  20. On-chip chalcogenide glass waveguide-integrated mid-infrared PbTe detectors

    NASA Astrophysics Data System (ADS)

    Han, Z.; Singh, V.; Kita, D.; Monmeyran, C.; Becla, P.; Su, P.; Li, J.; Huang, X.; Kimerling, L. C.; Hu, J.; Richardson, K.; Tan, D. T. H.; Agarwal, A.

    2016-08-01

    We experimentally demonstrate an on-chip polycrystalline PbTe photoconductive detector integrated with a chalcogenide glass waveguide. The device is monolithically fabricated on silicon, operates at room-temperature, and exhibits a responsivity of 1.0 A/W at wavelengths between 2.1 and 2.5 μm.

  1. Driving Oxygen Coordinated Ligand Exchange at Nanocrystal Surfaces using Trialkylsilylated Chalcogenides

    SciTech Connect

    Caldwell, Marissa A.; Albers, Aaron E.; Levy, Seth C.; Pick, Teresa E.; Cohen, Bruce E.; Helms, Brett A.; Milliron, Delia J.

    2010-11-11

    A general, efficient method is demonstrated for exchanging native oxyanionic ligands on inorganic nanocrystals with functional trimethylsilylated (TMS) chalcogenido ligands. In addition, newly synthesized TMS mixed chalcogenides leverage preferential reactivity of TMS-S bonds over TMS-O bonds, enabling efficient transfer of luminescent nanocrystals into aqueous media with retention of their optical properties.

  2. Electronic origins of the magnetic phase transitions in zinc-blende Mn chalcogenides

    SciTech Connect

    Wei, S.; Zunger, A. )

    1993-09-01

    Precise first-principles spin-polarized total-energy and band-structure calculations have been performed for the zinc-blende Mn chalcogenides with the use of the local-spin-density (LSD) approach. We find that the LSD is capable of identifying the correct magnetic-ground-state structure, but it overestimates the ordering temperature [ital T][sub [ital N

  3. Case A Binary Evolution

    SciTech Connect

    Nelson, C A; Eggleton, P P

    2001-03-28

    We undertake a comparison of observed Algol-type binaries with a library of computed Case A binary evolution tracks. The library consists of 5500 binary tracks with various values of initial primary mass M{sub 10}, mass ratio q{sub 0}, and period P{sub 0}, designed to sample the phase-space of Case A binaries in the range -0.10 {le} log M{sub 10} {le} 1.7. Each binary is evolved using a standard code with the assumption that both total mass and orbital angular momentum are conserved. This code follows the evolution of both stars until the point where contact or reverse mass transfer occurs. The resulting binary tracks show a rich variety of behavior which we sort into several subclasses of Case A and Case B. We present the results of this classification, the final mass ratio and the fraction of time spent in Roche Lobe overflow for each binary system. The conservative assumption under which we created this library is expected to hold for a broad range of binaries, where both components have spectra in the range G0 to B1 and luminosity class III - V. We gather a list of relatively well-determined observed hot Algol-type binaries meeting this criterion, as well as a list of cooler Algol-type binaries where we expect significant dynamo-driven mass loss and angular momentum loss. We fit each observed binary to our library of tracks using a {chi}{sup 2}-minimizing procedure. We find that the hot Algols display overall acceptable {chi}{sup 2}, confirming the conservative assumption, while the cool Algols show much less acceptable {chi}{sup 2} suggesting the need for more free parameters, such as mass and angular momentum loss.

  4. The third-order optical nonlinearities of Ge-Ga-Sb(In)-S chalcogenide glasses

    SciTech Connect

    Guo, Haitao; Chen, Hongyan; Hou, Chaoqi; Lin, Aoxiang; Zhu, Yonggang; Lu, Shoudi; Gu, Shaoxuan; Lu, Min; Peng, Bo

    2011-05-15

    Research highlights: {yields} It is firstly demonstrated that the nonlinear refractive index n{sub 2} is dependent on the covalency of bonds in chalcogenide glass. {yields} Homopolar metallic bonds in chalcogenide glass have positive contribution to large nonlinear refractive index n{sub 2} also. {yields} The 80GeS{sub 2}.20Sb{sub 2}S{sub 3} glass would be expected to be used in the all-optical switches working at 1330 nm and 1550 nm telecommunication wavelengths. -- Abstract: The third-order optical nonlinearities of 80GeS{sub 2}.(20 - x)Ga{sub 2}S{sub 3}.xY{sub 2}S{sub 3} (x = 0, 5, 10, 15, 20 and Y = Sb or In) chalcogenide glasses were investigated utilizing the Z-scan method at the wavelength of 800 nm and their linear optical properties and structure were also studied. By analyzing the compositional dependences and possible influencing factors including the linear refractive index, the concentration of lone electron pairs, the optical bandgap and the amount of weak covalent/homopolar bonds, it indicates that the electronic contribution in weak heteropolar covalent and homopolar metallic bonds is responsible for large nonlinear refractive index n{sub 2} in the chalcogenide glasses. These chalcogenide glasses have characteristics of environmentally friendship, wide transparency in the visible region, high nonlinear refractive index n{sub 2} and low nonlinear absorption coefficient {beta}, and would be expected to be used in the all-optical switches working at 1330 nm and 1550 nm telecommunication wavelengths.

  5. Wireless Chalcogenide Nanoionic-Based Radio-Frequency Switch

    NASA Technical Reports Server (NTRS)

    Nessel, James; Miranda, Felix

    2013-01-01

    A new nonvolatile nanoionic switch is powered and controlled through wireless radio-frequency (RF) transmission. A thin layer of chalcogenide glass doped with a metal ion, such as silver, comprises the operational portion of the switch. For the switch to function, an oxidizable electrode is made positive (anode) with respect to an opposing electrode (cathode) when sufficient bias, typically on the order of a few tenths of a volt or more, is applied. This action causes the metal ions to flow toward the cathode through a coordinated hopping mechanism. At the cathode, a reduction reaction occurs to form a metal deposit. This metal deposit creates a conductive path that bridges the gap between electrodes to turn the switch on. Once this conductive path is formed, no further power is required to maintain it. To reverse this process, the metal deposit is made positive with respect to the original oxidizable electrode, causing the dissolution of the metal bridge thereby turning the switch off. Once the metal deposit has been completely dissolved, the process self-terminates. This switching process features the following attributes. It requires very little to change states (i.e., on and off). Furthermore, no power is required to maintain the states; hence, the state of the switch is nonvolatile. Because of these attributes the integration of a rectenna to provide the necessary power and control is unique to this embodiment. A rectenna, or rectifying antenna, generates DC power from an incident RF signal. The low voltages and power required for the nanoionic switch control are easily generated from this system and provide the switch with a novel capability to be operated and powered from an external wireless device. In one realization, an RF signal of a specific frequency can be used to set the switch into an off state, while another frequency can be used to set the switch to an on state. The wireless, miniaturized, and nomoving- part features of this switch make it

  6. Engineered Transition Metal Chalcogenides for Photovoltaic, Thermoelectric, and Magnetic Applications

    NASA Astrophysics Data System (ADS)

    Moroz, Nicholas Anton

    This work focuses on the development of ternary and quaternary chalcogenide compounds featuring transition metal cations through careful engineering of the electronic and thermal transport as well as magnetic properties by traditional solid-state doping techniques and novel template structure synthesis methods for improvements in thermoelectric performance, diluted magnetic semiconductors, and photovoltaic conversion. Presented here is an innovative low-temperature batch synthesis that was developed to create hexagonal nanoplatelets of thermoelectrically interesting CuAgSe. This process utilized room temperature ion exchange reactions to convert cubic Cu2-xSe nanoplatelets into CuAgSe by replacing a portion of the Cu+ ions with Ag+ while maintaining the morphology of the nanoplatelet. This simple reaction process offers an energy efficient and versatile strategy to create interesting materials with superior thermoelectric performance. An investigation of the thermal and electronic transport of CuAl(S xSe1-x)2 solid solutions was also conducted. While these compounds yielded low thermal conductivity, they also exhibited low electronic conductivity. Doping with transition metals Ag, Hf, and Ti further reduced the thermal conductivity below 1 W/mK; however, most exciting was the determination that the thermal transport of the system could be modified by doping at the Al3+ site without affecting the electronic structure of the system, potentially leading to the use of CuAl(SxSe 1-x)2 as a heavily doped thermoelectric material. The effect of local carrier concentration in the diluted magnetic semiconductor FeSb2Se4 was studied by substitution of In3+ for Sb3+. Using systematic Rietveld refinement, it was determined that In3+ resides in the semiconducting layer of the structure for concentrations of x ≤ 0.1, and the magnetic layer for x > 0.1. The increase in local carrier concentration has an appreciable effect on the electronic and magnetic properties of the material

  7. Tolerant chalcogenide cathodes of membraneless micro fuel cells.

    PubMed

    Gago, Aldo Saul; Gochi-Ponce, Yadira; Feng, Yong-Jun; Esquivel, Juan Pablo; Sabaté, Neus; Santander, Joaquin; Alonso-Vante, Nicolas

    2012-08-01

    The most critical issues to overcome in micro direct methanol fuel cells (μDMFCs) are the lack of tolerance of the platinum cathode and fuel crossover through the polymer membrane. Thus, two novel tolerant cathodes of a membraneless microlaminar-flow fuel cell (μLFFC), Pt(x)S(y) and CoSe(2), were developed. The multichannel structure of the system was microfabricated in SU-8 polymer. A commercial platinum cathode served for comparison. When using 5 M CH(3)OH as the fuel, maximum power densities of 6.5, 4, and 0.23 mW cm(-2) were achieved for the μLFFC with Pt, Pt(x)S(y), and CoSe(2) cathodes, respectively. The Pt(x)S(y) cathode outperformed Pt in the same fuel cell when using CH(3)OH at concentrations above 10 M. In a situation where fuel crossover is 100 %, that is, mixing the fuel with the reactant, the maximum power density of the micro fuel cell with Pt decreased by 80 %. However, for Pt(x)S(y) this decrease corresponded to 35 % and for CoSe(2) there was no change in performance. This result is the consequence of the high tolerance of the chalcogenide-based cathodes. When using 10 M HCOOH and a palladium-based anode, the μLFFC with a CoSe(2) cathode achieved a maxiumum power density of 1.04 mW cm(-2). This micro fuel cell does not contain either Nafion membrane or platinum. We report, for the first time, the evaluation of Pt(x)S(y)- and CoSe(2)-based cathodes in membraneless micro fuel cells. The results suggest the development of a novel system that is not size restricted and its operation is mainly based on the selectivity of its electrodes. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Syntheses, structures, magnetism, and optical properties of gadolinium scandium chalcogenides

    SciTech Connect

    Jin Gengbang; Choi, Eun Sang; Albrecht-Schmitt, Thomas E.

    2009-05-15

    Three gadolinium scandium chalcogenides have been synthesized using Sb{sub 2}Q{sub 3} (Q=S, Se) fluxes at 975 deg. C. Gd{sub 3.04}Sc{sub 0.96}S{sub 6}, GdScS{sub 3}, and Gd{sub 1.05}Sc{sub 0.95}Se{sub 3} are crystallized in U{sub 3}ScS{sub 6} type, GdFeO{sub 3} type, and UFeS{sub 3} type structures, respectively. The magnetic susceptibilities for these compounds follow the Curie-Weiss law above their transition temperatures. The effective magnetic moments are close to calculated values for free Gd{sup 3+} ions. The Weiss constants for Gd{sub 3.04}Sc{sub 0.96}S{sub 6}, GdScS{sub 3}, and Gd{sub 1.05}Sc{sub 0.95}Se{sub 3} are determined to be -3.3(1), -4.5(4), and 1.5(1) K, respectively. Gd{sub 3.04}Sc{sub 0.96}S{sub 6} orders antiferromagnetically below 9 K. GdScS{sub 3} exhibits an antiferromagnetic ordering below 3 K with a weak ferromagnetism. Gd{sub 1.05}Sc{sub 0.95}Se{sub 3} undergoes a ferromagnetic transition around 5 K. The optical band gaps for Gd{sub 3.04}Sc{sub 0.96}S{sub 6}, GdScS{sub 3}, and Gd{sub 1.05}Sc{sub 0.95}Se{sub 3} are 1.5, 2.1, and 1.2 eV, respectively. - Graphical abstract: A view of the three-dimensional structure of Gd{sub 3.04}Sc{sub 0.96}S{sub 6} along the c axis.

  9. Laser annealing and defect study of chalcogenide photovoltaic materials

    NASA Astrophysics Data System (ADS)

    Bhatia, Ashish

    Cu(In,Ga)Se2 (CIGSe), CuZnSn(S,Se)4(CZTSSe), etc., are the potential chalcogenide semiconductors being investigated for next-generation thin film photovoltaics (TFPV). While the champion cell efficiency of CIGSe has exceeded 20%, CZTSSe has crossed the 10% mark. This work investigates the effect of laser annealing on CISe films, and compares the electrical characteristics of CIGSe (chalcopyrite) and CZTSe (kesterite) solar cells. Chapter 1 through 3 provide a background on semiconductors and TFPV, properties of chalcopyrite and kesterite materials, and their characterization using deep level transient spectroscopy (DLTS) and thermal admittance spectroscopy (TAS). Chapter 4 investigates electrochemical deposition (nonvacuum synthesis) of CISe followed by continuous wave laser annealing (CWLA) using a 1064 nm laser. It is found that CWLA at ≈ 50 W/cm2 results in structural changes without melting and dewetting of the films. While Cu-poor samples show about 40% reduction in the full width at half maximum of the respective x-ray diffraction peaks, identically treated Cu-rich samples register more than 80% reduction. This study demonstrates that an entirely solid-phase laser annealing path exists for chalcopyrite phase formation and crystallization. Chapter 5 investigates the changes in defect populations after pulse laser annealing in submelting regime of electrochemically deposited and furnace annealed CISe films. DLTS on Schottky diodes reveal that the ionization energy of the dominant majority carrier defect state changes nonmonotonically from 215+/-10 meV for the reference sample, to 330+/-10 meV for samples irradiated at 20 and 30 mJ/cm2, and then back to 215+/-10 meV for samples irradiated at 40 mJ/cm2. A hypothesis involving competing processes of diffusion of Cu and laser-induced generation of In vacancies may explain this behavior. Chapter 6 compares the electrical characteristics of chalcopyrite and kesterite materials. Experiments reveal CZTSe cell has an

  10. Binary Galaxies in Clusters

    NASA Astrophysics Data System (ADS)

    Ip, Peter Shun Sang

    1994-01-01

    CCD images of the binary-rich clusters of galaxies A373, A408, A667, A890, and A1250 taken at the Canada-France-Hawaii telescope show that about half the binary galaxies' are actually star-galaxy or star-star pairs. These clusters are not binary-rich. N-body simulations are used to study the effect of static cluster potentials on binary and single galaxies. The softening procedure is discussed in detail. Since Plummer softening is not self-consistent, and since the force laws for various other density models are similar to each other, uniform-density softening is used. The choice of the theoretical galaxy model in terms of the potential at various locations. A fixed cluster potential cannot stabilize binary galaxies against merger, but can disrupt even quite tightly bound binaries. A moderately good predictor of whether a binary merges or disrupts is the mean torque over a quarter of the initial binary period. But the dynamics of the situation is quite complicated, and depends on an interplay between the motion of the binary through the cluster and the absorption of orbital energy by the galaxies. There is also a substantial amount of mass loss. Simulations of single galaxies in cluster show that this mass loss is due mainly to the cluster potential, and not to an interplay between the merging binary and the cluster. This mass loss is driven partially by virial equilibrium responding to the initial tidal truncation by the cluster. Besides verifying some general results of mass loss from satellite systems in the tidal field of larger bodies, it was found that the galaxy loses mass at an exponential rate.

  11. Copper-Catalyzed Synthesis of Unsymmetrical Diorganyl Chalcogenides (Te/Se/S) from Boronic Acids under Solvent-Free Conditions.

    PubMed

    Saba, Sumbal; Botteselle, Giancarlo Vaccari; Godoi, Marcelo; Frizon, Tiago Elias Allievi; Galetto, Fábio Zazyki; Rafique, Jamal; Braga, Antonio L

    2017-08-18

    The efficient and mild copper-catalyzed synthesis of unsymmetrical diorganyl chalcogenides under ligand- and solvent-free conditions is described. The cross-coupling reaction was performed using aryl boric acids and 0.5 equiv. of diorganyl dichalcogenides (Te/Se/S) in the presence of 3 mol % of CuI and 3 equiv. of DMSO, under microwave irradiation. This new protocol allowed the preparation of several unsymmetrical diorganyl chalcogenides in good to excellent yields.

  12. Nanoscale Device Properties of Tellurium-based Chalcogenide Compounds

    NASA Astrophysics Data System (ADS)

    Dahal, Bishnu R.

    The great progress achieved in miniaturization of microelectronic devices has now reached a distinct bottleneck, as devices are starting to approach the fundamental fabrication and performance limit. Even if a major breakthrough is made in the fabrication process, these scaled down electronic devices will not function properly since the quantum effects can no longer be neglected in the nanoscale regime. Advances in nanotechnology and new materials are driving novel technologies for future device applications. Current microelectronic devices have the smallest feature size, around 10 nm, and the industry is planning to switch away from silicon technology in the near future. The new technology will be fundamentally different. There are several leading technologies based on spintronics, tunneling transistors, and the newly discovered 2-dimensional material systems. All of these technologies are at the research level, and are far from ready for use in making devices in large volumes. This dissertation will focus on a very promising material system, Te-based chalcogenides, which have potential applications in spintronics, thermoelectricity and topological insulators that can lead to low-power-consumption electronics. Very recently it was predicted and experimentally observed that the spin-orbit interaction in certain materials can lead to a new electronic state called topological insulating phase. The topological insulator, like an ordinary insulator, has a bulk energy gap separating the highest occupied electronic band from the lowest empty band. However, the surface states in the case of a three-dimensional or edge states in a two-dimensional topological insulator allow electrons to conduct at the surface, due to the topological character of the bulk wavefunctions. These conducting states are protected by time-reversal symmetry, and cannot be eliminated by defects or chemical passivation. The edge/surface states satisfy Dirac dispersion relations, and hence the physics

  13. Effect of the Chalcogenide Element Doping on the Electronic Properties of Co2FeAl Heusler Alloys

    NASA Astrophysics Data System (ADS)

    Huang, Ting; Cheng, Xiao-min; Guan, Xia-wei; Miao, Xiang-shui

    2016-02-01

    The electronic properties of the typical Heusler compound Co2FeAl with chalcogenide element doping were investigated by means of first principles calculations within the local spin-density approximation (LSDA) + Hubbard U parameter (U). The calculations indicate that, only when 25% of the number of Al atoms is substituted by the chalcogenide element, the chalcogenide element-doped Co2FeAl shows the half metallic properties. The Fermi energy ( E F) of the 25% chalcogenide element-doped Co2FeAl is located in the middle of the gap of the minority states instead of around the top of the valence band as in Co2FeAl. Moreover, the band gap of 25% Te-doped Co2FeAl (0.80 eV) is wider than that of Co2FeAl (0.74 eV). These improved electronic structures will make 25% chalcogenide element-doped Co2FeAl more stable against temperature variation. Therefore, the expected excellent stability of the 25% chalcogenide element-doped Co2FeAl make it more suitable for spintronic applications than Co2FeAl.

  14. Taming the binaries

    NASA Astrophysics Data System (ADS)

    Pourbaix, D.

    2008-07-01

    Astrometric binaries are both a gold mine and a nightmare. They are a gold mine because they are sometimes the unique source of orbital inclination for spectroscopic binaries, thus making it possible for astrophysicists to get some clues about the mass of the often invisible secondary. However, this is an ideal situation in the sense that one benefits from the additional knowledge that it is a binary for which some orbital parameters are somehow secured (e.g. the orbital period). On the other hand, binaries are a nightmare, especially when their binary nature is not established yet. Indeed, in such cases, depending on the time interval covered by the observations compared to the orbital period, either the parallax or the proper motion can be severely biased if the successive positions of the binary are modelled assuming it is a single star. With large survey campaigns sometimes monitoring some stars for the first time ever, it is therefore crucial to design robust reduction pipelines in which such troublesome objects are quickly identified and either removed or processed accordingly. Finally, even if an object is known not to be a single star, the binary model might turn out not to be the most appropriate for describing the observations. These different situations will be covered.

  15. Transition metal chalcogenides: ultrathin inorganic materials with tunable electronic properties.

    PubMed

    Heine, Thomas

    2015-01-20

    CONSPECTUS: After the discovery of graphene and the development of powerful exfoliation techniques, experimental preparation of two-dimensional (2D) crystals can be expected for any layered material that is known to chemistry. Besides graphene and hexagonal boron nitride (h-BN), transition metal chalcogenides (TMC) are among the most studied ultrathin materials. In particular, single-layer MoS2, a direct band gap semiconductor with ∼1.9 eV energy gap, is popular in physics and nanoelectronics, because it nicely complements semimetallic graphene and insulating h-BN monolayer as a construction component for flexible 2D electronics and because it was already successfully applied in the laboratory as basis material for transistors and other electronic and optoelectronic devices. Two-dimensional crystals are subject to significant quantum confinement: compared with their parent layered 3D material, they show different structural, electronic, and optical properties, such as spontaneous rippling as free-standing monolayer, significant changes of the electronic band structure, giant spin-orbit splitting, and enhanced photoluminescence. Most of those properties are intrinsic for the monolayer and already absent for two-layer stacks of the same 2D crystal. For example, single-layer MoS2 is a direct band gap semiconductor with spin-orbit splitting of 150 meV in the valence band, while the bilayer of the same material is an indirect band gap semiconductor without observable spin-orbit splitting. All these properties have been observed experimentally and are in excellent agreement with calculations based on density-functional theory. This Account reports theoretical studies of a subgroup of transition metal dichalcogenides with the composition MX2, with M = Mo, or W and X = Se or S, also referred to as "MoWSeS materials". Results on the electronic structure, quantum confinement, spin-orbit coupling, spontaneous monolayer rippling, and change of electronic properties in the

  16. Binary Minor Planets

    NASA Astrophysics Data System (ADS)

    Richardson, Derek C.; Walsh, Kevin J.

    2006-05-01

    A review of observations and theories regarding binary asteroids and binary trans-Neptunian objects [collectively, binary minor planets (BMPs)] is presented. To date, these objects have been discovered using a combination of direct imaging, lightcurve analysis, and radar. They are found throughout the Solar System, and present a challenge for theorists modeling their formation in the context of Solar System evolution. The most promising models invoke rotational disruption for the smallest, shortest-lived objects (the asteroids nearest to Earth), consistent with the observed fast rotation of these bodies; impacts for the larger, longer-lived asteroids in the main belt, consistent with the range of size ratios of their components and slower rotation rates; and mutual capture for the distant, icy, trans-Neptunian objects, consistent with their large component separations and near-equal sizes. Numerical simulations have successfully reproduced key features of the binaries in the first two categories; the third remains to be investigated in detail.

  17. Binaries in globular clusters

    NASA Technical Reports Server (NTRS)

    Hut, Piet; Mcmillan, Steve; Goodman, Jeremy; Mateo, Mario; Phinney, E. S.; Pryor, Carlton; Richer, Harvey B.; Verbunt, Frank; Weinberg, Martin

    1992-01-01

    Recent observations have shown that globular clusters contain a substantial number of binaries most of which are believed to be primordial. We discuss different successful optical search techniques, based on radial-velocity variables, photometric variables, and the positions of stars in the color-magnitude diagram. In addition, we review searches in other wavelengths, which have turned up low-mass X-ray binaries and more recently a variety of radio pulsars. On the theoretical side, we give an overview of the different physical mechanisms through which individual binaries evolve. We discuss the various simulation techniques which recently have been employed to study the effects of a primordial binary population, and the fascinating interplay between stellar evolution and stellar dynamics which drives globular-cluster evolution.

  18. Double Degenerate Binary Systems

    SciTech Connect

    Yakut, K.

    2011-09-21

    In this study, angular momentum loss via gravitational radiation in double degenerate binary (DDB)systems (NS + NS, NS + WD, WD + WD, and AM CVn) is studied. Energy loss by gravitational waves has been estimated for each type of systems.

  19. From Binaries to Triples

    NASA Astrophysics Data System (ADS)

    Freismuth, T.; Tokovinin, A.

    2002-12-01

    About 10% of all binary systems are close binaries (P<1000 days). Among those with P<10d, over 40% are known to belong to higher-multiplicity systems (triples, quadruples, etc.). Do ALL close systems have tertiary companions? For a selection of 12 nearby, and apparently "single" close binaries with solar-mass dwarf primary components from the 8-th catalogue of spectroscopic binary orbits, images in the B and R filters were taken at the CTIO 0.9m telescope and suitable tertiary candidates were be identified on color-magnitude diagrams (CMDs). Of the 12 SBs, four were found to have tertiary candidates: HD 67084, HD 120734, HD 93486, and VV Mon. However, none of these candidates were found to be common proper motion companions. Follow up observations using adaptive optics reveal a companion to HD 148704. Future observations are planned.

  20. Binary technetium halides

    NASA Astrophysics Data System (ADS)

    Johnstone, Erik Vaughan

    In this work, the synthetic and coordination chemistry as well as the physico-chemical properties of binary technetium (Tc) chlorides, bromides, and iodides were investigated. Resulting from these studies was the discovery of five new binary Tc halide phases: alpha/beta-TcCl3, alpha/beta-TcCl 2, and TcI3, and the reinvestigation of the chemistries of TcBr3 and TcX4 (X = Cl, Br). Prior to 2009, the chemistry of binary Tc halides was poorly studied and defined by only three compounds, i.e., TcF6, TcF5, and TcCl4. Today, ten phases are known (i.e., TcF6, TcF5, TcCl4, TcBr 4, TcBr3, TcI3, alpha/beta-TcCl3 and alpha/beta-TcCl2) making the binary halide system of Tc comparable to those of its neighboring elements. Technetium binary halides were synthesized using three methods: reactions of the elements in sealed tubes, reactions of flowing HX(g) (X = Cl, Br, and I) with Tc2(O2CCH3)4Cl2, and thermal decompositions of TcX4 (X = Cl, Br) and alpha-TcCl 3 in sealed tubes under vacuum. Binary Tc halides can be found in various dimensionalities such as molecular solids (TcF6), extended chains (TcF5, TcCl4, alpha/beta-TcCl2, TcBr 3, TcI3), infinite layers (beta-TcCl3), and bidimensional networks of clusters (alpha-TcCl3); eight structure-types with varying degrees of metal-metal interactions are now known. The coordination chemistry of Tc binary halides can resemble that of the adjacent elements: molybdenum and ruthenium (beta-TcCl3, TcBr3, TcI 3), rhenium (TcF5, alpha-TcCl3), platinum (TcCl 4, TcBr4), or can be unique (alpha-TcCl2 and beta-TcCl 2) in respect to other known transition metal binary halides. Technetium binary halides display a range of interesting physical properties that are manifested from their electronic and structural configurations. The thermochemistry of binary Tc halides is extensive. These compounds can selectively volatilize, decompose, disproportionate, or convert to other phases. Ultimately, binary Tc halides may find application in the nuclear fuel

  1. X-ray binaries

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Satellite X-ray experiments and ground-based programs aimed at observation of X-ray binaries are discussed. Experiments aboard OAO-3, OSO-8, Ariel 5, Uhuru, and Skylab are included along with rocket and ground-based observations. Major topics covered are: Her X-1, Cyg X-3, Cen X-3, Cyg X-1, the transient source A0620-00, other possible X-ray binaries, and plans and prospects for future observational programs.

  2. Learning binary matroid ports

    SciTech Connect

    Coullard, C.; Hellerstein, L.

    1994-12-31

    Given a binary matroid M specified by a port oracle, we can in polynomial number of calls to the oracle construct a binary representation for M. For general matroids, we can in polynomial number of calls to a port oracle determine whether a given subset is independent (that is, we can simulate an independence oracle with a port oracle). The work is related to a theorem of Lehman on matroid ports, and is motivated by issues in computational learning theory.

  3. Binary-Symmetry Detection

    NASA Technical Reports Server (NTRS)

    Lopez, Hiram

    1987-01-01

    Transmission errors for zeros and ones tabulated separately. Binary-symmetry detector employs psuedo-random data pattern used as test message coming through channel. Message then modulo-2 added to locally generated and synchronized version of test data pattern in same manner found in manufactured test sets of today. Binary symmetrical channel shows nearly 50-percent ones to 50-percent zeroes correspondence. Degree of asymmetry represents imbalances due to either modulation, transmission, or demodulation processes of system when perturbed by noise.

  4. Spectroscopic Binary Stars

    NASA Astrophysics Data System (ADS)

    Batten, A.; Murdin, P.

    2000-11-01

    Historically, spectroscopic binary stars were binary systems whose nature was discovered by the changing DOPPLER EFFECT or shift of the spectral lines of one or both of the component stars. The observed Doppler shift is a combination of that produced by the constant RADIAL VELOCITY (i.e. line-of-sight velocity) of the center of mass of the whole system, and the variable shift resulting from the o...

  5. Scattering from binary optics

    NASA Technical Reports Server (NTRS)

    Ricks, Douglas W.

    1993-01-01

    There are a number of sources of scattering in binary optics: etch depth errors, line edge errors, quantization errors, roughness, and the binary approximation to the ideal surface. These sources of scattering can be systematic (deterministic) or random. In this paper, scattering formulas for both systematic and random errors are derived using Fourier optics. These formulas can be used to explain the results of scattering measurements and computer simulations.

  6. Progress on a New Non-Volatile Memory for Space Based on Chalcogenide Glass

    SciTech Connect

    Maimon, J.; Hunt, K.; Rodgers, J.; Burcin, L.; Knowles, K.

    2004-02-04

    We report on the progress of a recent addition to non-volatile solid state memory technologies suited for space and other ionizing radiation environments. We summarize the material and processing science behind the current generation of chalcogenide phase-change memories fabricated on CMOS structures. The chalcogenide material used for phase-change applications in rewritable optical storage (Ge2Sb2Te5) has been integrated with a radiation hardened CMOS process to produce 64kbit memory arrays. On selected arrays electrical testing demonstrated up to 100% memory cell yield, 100ns programming and read speeds, and write currents as low as 1mA/bit. Devices functioned normally from - 55 deg. C to 125 deg. C. Write/read endurance has been demonstrated to 1 x 108 before first bit failure. Radiation results show no degradation to the hardened CMOS or effects that can be attributed to the phase-change material. Future applications of the technology are discussed.

  7. The mechanism of alcoholic beverage induced superconductivity in Fe-chalcogenide compounds

    NASA Astrophysics Data System (ADS)

    Deguchi, Keita; Demura, Satoshi; Okazaki, Hiroyuki; Denholme, Saleem; Fujioka, Masaya; Ozaki, Toshinori; Yamaguchi, Takahide; Takeya, Hiroyuki; Takano, Yoshihiko

    2013-03-01

    We have clarified the mechanism of alcoholic beverage induced superconductivity in Fe-chalcogenide compounds. Previously we reported that the bulk superconductivity in Fe-based compounds Fe(Te, Se) and Fe(Te, S) is achieved by heating in alcoholic beverages. However, the exact mechanism of how they act to enhance the superconductivity in the compounds remains unsolved. To understand the effect of alcoholic beverage treatment, we investigated the mechanism using a technology of metabolomic analysis. We found that weak acid in alcoholic beverages has the ability to deintercalate the excess Fe, which is not in favor of superconductivity. In this presentation, we will discuss the systematic mechanism to induce superconductivity in Fe-chalcogenide compounds.

  8. Structural investigation of Bi doped InSe chalcogenide thin films using Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Sharma, Shaveta; Sharma, Rita; Kumar, Praveen; Chander, Ravi; Thangaraj, R.; Mian, M.

    2015-05-01

    The infrared transparency of the chalcogenide glasses have been investigated presently for the CO/CO2 laser power in various medical diagnostic applications. The addition of Bi improves the chemical durability and broadens the IR transparency region of various chalcogenide glassy systems. In the present work, we have studied the effect of Bi addition on the structural properties of In-Se thin films by using the RAMAN spectroscopy. The melt quenched bulk ingot of BixIn25-xSe75 (1≤ x≤ 7) alloys were used for the vacuum thermal evaporation of films in a vacuum better than 10-5 mbar. RAMAN bands at 1575, 1354 and 525 cm-1 has been observed, while with the increase in the Bi concentration vibrational band disappear at 525 cm-1 in sample x=7.

  9. Revisiting the Local Structure in Ge-Sb-Te based Chalcogenide Superlattices

    PubMed Central

    Casarin, Barbara; Caretta, Antonio; Momand, Jamo; Kooi, Bart J.; Verheijen, Marcel A.; Bragaglia, Valeria; Calarco, Raffaella; Chukalina, Marina; Yu, Xiaoming; Robertson, John; Lange, Felix R. L.; Wuttig, Matthias; Redaelli, Andrea; Varesi, Enrico; Parmigiani, Fulvio; Malvestuto, Marco

    2016-01-01

    The technological success of phase-change materials in the field of data storage and functional systems stems from their distinctive electronic and structural peculiarities on the nanoscale. Recently, superlattice structures have been demonstrated to dramatically improve the optical and electrical performances of these chalcogenide based phase-change materials. In this perspective, unravelling the atomistic structure that originates the improvements in switching time and switching energy is paramount in order to design nanoscale structures with even enhanced functional properties. This study reveals a high- resolution atomistic insight of the [GeTe/Sb2Te3] interfacial structure by means of Extended X-Ray Absorption Fine Structure spectroscopy and Transmission Electron Microscopy. Based on our results we propose a consistent novel structure for this kind of chalcogenide superlattices. PMID:26926116

  10. Numerical investigation of highly coherent mid-infrared supercontinuum generation in chalcogenide double-clad fiber

    NASA Astrophysics Data System (ADS)

    Nagasaka, Kenshiro; Liu, Lai; Tuan, Tong Hoang; Cheng, Tonglei; Matsumoto, Morio; Tezuka, Hiroshige; Suzuki, Takenobu; Ohishi, Yasutake

    2017-07-01

    It is shown that chalcogenide double-clad fibers (Ch-DCFs) have large potential to realize the highly coherent mid-infrared (MIR) supercontinuum generation. We design the Ch-DCFs with flatter chromatic dispersion and smaller effective mode diameter than chalcogenide step index fibers in the MIR region. We numerically investigate MIR supercontinuum generation in designed Ch-DCFs. It is numerically demonstrated that highly coherent MIR supercontinuum extending from 3.3 to 10.4 μm in the Ch-DCFs can be generated by pumping with hyperbolic secant pulse at 6 μm, the peak power of 2 kW, and the full width at half maximum of 300 fs.

  11. Design of rare-earth-ion doped chalcogenide photonic crystals for enhancing the fluorescence emission

    NASA Astrophysics Data System (ADS)

    Zhang, Peiqing; Dai, Shixun; Niu, Xueke; Xu, Yinsheng; Zhang, Wei; Wu, Yuehao; Xu, Tiefeng; Nie, Qiuhua

    2014-07-01

    Rare-earth-ion doped chalcogenide glass is a promising material for developing mid-infrared light sources. In this work, Tm3+-doped chalcogenide glass was prepared and photonic crystal structures were designed to enhance its fluorescence emission at approximately 3.8 μm. By employing the finite-difference time-domain (FDTD) simulation, the emission characteristics of the luminescent centers in the bulk material and in the photonic crystals were worked out. Utilizing analysis of the photon excitation inside the sample and the photon extraction on the sample surface, it was found that fluorescence emission can be significantly enhanced 260-fold with the designed photonic crystal structure. The results of this work can be used to realize high-efficiency mid-infrared light sources.

  12. Theoretical investigation of the 67Zn Mössbauer isomer shifts in the zinc chalcogenides

    NASA Astrophysics Data System (ADS)

    Svane, A.; Antoncik, E.

    1986-06-01

    The band structures of the zinc chalcogenides ZnO, ZnS, ZnSe, and ZnTe having the sphalerite crystal structure are calculated. The first-principles linear muffin-tin-orbital-atomic sphere approximation method is employed, in which all solid-state and scalar relativistic effects are taken into account, including the self-consistency of the crystal potential and the charge density. The corresponding electronic configurations are discussed, and the electron contact densities at the zinc nucleus are obtained and compared to experimental isomer-shift data with good agreement. The estimated static charge transfers of the zinc chalcogenides are demonstrated to correlate neatly with the isomer shift. For the first time an accurate value of the calibration constant for the 67Zn isomer transition is derived: ΔR/R=(7.0+/-1.0)×10-4.

  13. Optical characterization of CdSe quantum dots with metal chalcogenide ligands in solutions and solids

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Q.; Cao, X. A.

    2011-07-01

    The exchange of the original organic ligands of colloidal CdSe core and CdSe/CdS/ZnS core/multishell quantum dots (QDs) with inorganic metal chalcogenide ligands (SnS44-) resulted in carrier delocalization in solutions and enhanced inter-QD electronic coupling in solids, as inferred from peak redshift and broadening of the absorption and photoluminescence (PL) spectra. The SnS4-capped QDs retained strong excitonic absorption but suffered significant PL quenching. Mild thermal treatment below 350 °C transformed the SnS4 ligands into a more conductive phase, leading to stronger coupling yet complete PL quenching. These findings suggest that QD solids with metal chalcogenide ligands may have high quantum yields of photocurrent generation and can be used as functional blocks in thin-film solar cells for efficient solar energy conversion.

  14. Chalcogenide-based optical parametric oscillator at 2  μm.

    PubMed

    Abdukerim, Nurmemet; Li, Lizhu; Rochette, Martin

    2016-09-15

    We report the first chalcogenide-based optical parametric oscillator (OPO) relying on pure parametric gain. The all-fiber OPO operates in the wavelength range of 2 μm and is tunable over 290 nm from the combined Stokes and anti-Stokes contributions. The gain medium is a 10 cm long chalcogenide microwire made from a high modal confinement As2Se3 core with cyclo olefin polymer cladding, leading to optimized chromatic dispersion, high nonlinearity, and broadband transparency. With a power threshold of only a fraction of a milliwatt, this design is promising for the fabrication of tunable, compact, and low-power consumption mid-infrared sources.

  15. Chalcogenide microresonators tailored to distinct morphologies by the shaping of glasses on silica tapers.

    PubMed

    Aktaş, Ozan

    2017-03-01

    Production of chalcogenide (As2Se3) microresonators in sphere, loop, and bottle morphologies by the shaping of glasses at appropriate temperatures between cleaved silica tapers is reported. The quality factors exceed QS=6.2×105, QB=6.7×105, and QL=1.6×104 for the sphere, bottle, and loop microresonators, respectively. All-optical thermally assisted tuning with a rate of 0.61 nm/mW is demonstrated for a bottle microcavity pumped via a silica taper at a wavelength of 670 nm. This technique enables practical and robust in situ production of chalcogenide microresonators thermally spliced to silica fibers in several morphologies with a wide tuning range of size.

  16. Enhanced surface patterning of chalcogenide glass via imprinting process using a buffer layer

    NASA Astrophysics Data System (ADS)

    Jin, Byeong Kyou; Choi, Duk-Yong; Chung, Woon Jin; Choi, Yong Gyu

    2017-09-01

    In an effort to enhance transcriptability of quasi-three-dimensional patterns present in silicon stamp onto the surface of 'bulk' chalcogenide glass, a buffer layer was introduced during the replication process via imprinting. Dissimilar patterns with diverse depths along the surface normal direction were imprinted with or without the buffer layer, and the resulting patterns on the glass surface were compared with regard to the transcription quality in both the lateral and vertical directions. After assessing the processing conditions appropriate for imprinting bulk As2S3 glass especially in terms of temperature and duration, candidate materials suitable for the buffer layer were screened: Commercially available polydimethylsiloxane was then chosen, and impact of this buffer layer was elucidated. The imprinted patterns turned out to become more uniform over large surface areas when the buffer layer was inserted. This finding confirmed that the use of buffer layer conspicuously enhanced the transcriptability of imprinting process for bulk chalcogenide glass.

  17. Many-Body Effects in Iron Pnictides and Chalcogenides: Nonlocal Versus Dynamic Origin of Effective Masses

    NASA Astrophysics Data System (ADS)

    Tomczak, Jan M.; van Schilfgaarde, M.; Kotliar, G.

    2012-12-01

    We apply the quasiparticle self-consistent GW approximation (QSGW) to some of the iron pnictide and chalcogenide superconductors. We compute Fermi surfaces and density of states, and find excellent agreement with experiment, substantially improving over standard band-structure methods. Analyzing the QSGW self-energy we discuss nonlocal and dynamic contributions to effective masses. We present evidence that the two contributions are mostly separable, since the quasiparticle weight is found to be essentially independent of momentum. The main effect of nonlocality is captured by the static but nonlocal QSGW effective potential. Moreover, these nonlocal self-energy corrections, absent in, e.g., dynamical mean field theory, can be relatively large. We show, on the other hand, that QSGW only partially accounts for dynamic renormalizations at low energies. These findings suggest that QSGW combined with dynamical mean field theory will capture most of the many-body physics in the iron pnictides and chalcogenides.

  18. Hydrogen treatment as a detergent of electronic trap states in lead chalcogenide nanoparticles

    DOE PAGES

    Vörös, Márton; Brawand, Nicholas P.; Galli, Giulia

    2016-11-15

    Lead chalcogenide (PbX) nanoparticles are promising materials for solar energy conversion. However, the presence of trap states in their electronic gap limits their usability, and developing a universal strategy to remove trap states is a persistent challenge. Using calculations based on density functional theory, we show that hydrogen acts as an amphoteric impurity on PbX nanoparticle surfaces; hydrogen atoms may passivate defects arising from ligand imbalance or off-stoichiometric surface terminations irrespective of whether they originate from cation or anion excess. In addition, we show, using constrained density functional theory calculations, that hydrogen treatment of defective nanoparticles is also beneficial formore » charge transport in films. We also find that hydrogen adsorption on stoichiometric nanoparticles leads to electronic doping, preferentially n-type. Lastly, our findings suggest that postsynthesis hydrogen treatment of lead chalcogenide nanoparticle films is a viable approach to reduce electronic trap states or to dope well-passivated films.« less

  19. Hydrogen treatment as a detergent of electronic trap states in lead chalcogenide nanoparticles

    SciTech Connect

    Vörös, Márton; Brawand, Nicholas P.; Galli, Giulia

    2016-11-15

    Lead chalcogenide (PbX) nanoparticles are promising materials for solar energy conversion. However, the presence of trap states in their electronic gap limits their usability, and developing a universal strategy to remove trap states is a persistent challenge. Using calculations based on density functional theory, we show that hydrogen acts as an amphoteric impurity on PbX nanoparticle surfaces; hydrogen atoms may passivate defects arising from ligand imbalance or off-stoichiometric surface terminations irrespective of whether they originate from cation or anion excess. In addition, we show, using constrained density functional theory calculations, that hydrogen treatment of defective nanoparticles is also beneficial for charge transport in films. We also find that hydrogen adsorption on stoichiometric nanoparticles leads to electronic doping, preferentially n-type. Lastly, our findings suggest that postsynthesis hydrogen treatment of lead chalcogenide nanoparticle films is a viable approach to reduce electronic trap states or to dope well-passivated films.

  20. Optical transmission enhancement through chemically tuned two-dimensional bismuth chalcogenide nanoplates.

    PubMed

    Yao, Jie; Koski, Kristie J; Luo, Weidong; Cha, Judy J; Hu, Liangbing; Kong, Desheng; Narasimhan, Vijay Kris; Huo, Kaifu; Cui, Yi

    2014-11-28

    Layer-structured two-dimensional nanomaterials are a family of materials with strong covalent bonding within layers and weak van der Waals interaction between layers, whose vertical thickness can be thinned down to few nanometer and even single atomic layer. Bismuth chalcogenides are examples of such two-dimensional materials. Here, we present our discovery of significant enhancement of light transmission through thin nanoplates of layered bismuth chalcogenides by intercalation of copper atoms, which is on the contrary to most bulk materials in which doping reduces the light transmission. This surprising behaviour results from two mechanisms: chemical tuning effect of substantial reduction of material absorption after intercalation and nanophotonic effect of zero-wave anti-reflection unique to ultra-small thickness of nanoplates. We demonstrate that the synergy of these two effects in two-dimensional nanostructures can be exploited for various optoelectronic applications including transparent electrode. The intercalation mechanism allows potential dynamic tuning capability.

  1. Direct imprinting on chalcogenide glass and fabrication of infrared wire-grid polarizer

    NASA Astrophysics Data System (ADS)

    Yamada, Itsunari; Yamashita, Naoto; Einishi, Toshihiko; Saito, Mitsunori; Fukumi, Kouhei; Nishii, Junji

    2013-05-01

    Infrared wire-grid polarizers were fabricated consisting of a 500-nm pitch Al grating on a low toxic chalcogenide glass (Sb-Ge-Sn-S system) using the direct imprinting of subwavelength grating followed by a deposition of Al metal by thermal evaporation. To fabricate the subwavelength grating on a chalcogenide glass more easily, the sharp grating was formed on the mold surface. The fabricated polarizer with Al thickness of 130 nm exhibited a polarization function with a transverse magnetic transmittance greater than 60% in the 5-9-μm wavelength range, and an extinction ratio greater than 20 dB in the 4-11-μm wavelength range. The polarizer can be fabricated at lower costs and simpler fabrication processes compared to conventional infrared polarizers.

  2. Fabrication of Achromatic Infrared Wave Plate by Direct Imprinting Process on Chalcogenide Glass

    NASA Astrophysics Data System (ADS)

    Yamada, Itsunari; Yamashita, Naoto; Tani, Kunihiko; Einishi, Toshihiko; Saito, Mitsunori; Fukumi, Kouhei; Nishii, Junji

    2012-07-01

    An achromatic infrared wave plate was fabricated by forming a subwavelength grating on the chalcogenide glass using direct imprint lithography. A low toxic chalcogenide glass (Sb-Ge-Sn-S system) substrate was imprinted with a grating of 1.63-µm depth, a fill factor of 0.7, and 3-µm period using glassy carbon as a mold at 253 °C and 3.8 MPa. Phase retardation of the element reached around 30° at 8.5-10.5 µm wavelengths, and the transmittance exceeded that of a flat substrate over 8 µm wavelength. Fabrication of the mid-infrared wave plate is thereby less expensive than that of conventional crystalline wave plates.

  3. Infrared Polarizer Fabrication by Imprinting on Sb-Ge-Sn-S Chalcogenide Glass

    NASA Astrophysics Data System (ADS)

    Yamada, Itsunari; Yamashita, Naoto; Tani, Kunihiko; Einishi, Toshihiko; Saito, Mitsunori; Fukumi, Kouhei; Nishii, Junji

    2012-01-01

    We fabricated infrared wire-grid polarizers consisting of a 500-nm pitch Al grating on a low toxic chalcogenide glass (Sb-Ge-Sn-S system) using the direct imprinting of subwavelength grating followed by a deposition of Al metal by thermal evaporation. To fabricate the subwavelength grating on a chalcogenide glass more easily, the sharp grating was formed on the mold surface. The fabricated polarizer with Al thickness of 130 nm exhibited a polarization function with a transverse magnetic transmittance greater than 60% in the 5-9 µm wavelength range, and an extinction ratio greater than 20 dB in 3.5-11 µm wavelength range. The extinction ratio of the element with Al wires of 180-nm thickness reached 27 dB at 5.4-µm wavelength. The polarizer can be fabricated at lower costs and simpler fabrication processes compared to conventional infrared polarizers.

  4. Pressure-induced structural phase transition and elastic properties of rare earth Pr chalcogenides and pnictides

    NASA Astrophysics Data System (ADS)

    Varshney, Dinesh; Shriya, Swarna; Varshney, Meenu; Khenata, R.

    2015-01-01

    Pressure-induced structural aspects and elastic properties of NaCl-type (B1) to CsCl-type (B2) structure in praseodymium chalcogenides and pnictides are presented. Ground-state properties are numerically computed by considering long-range Coulomb interactions, Hafemeister and Flygare type short-range overlap repulsion, and van der Waals interaction in the interionic potential. From the elastic constants, Poisson's ratio ν, the ratio RG/B of G (shear modulus) over B (bulk modulus), anisotropy parameter, shear and Young's moduli, Lamé's constant, Kleinman parameter, elastic wave velocity and thermodynamical property such as Debye temperature are calculated. Poisson's ratio ν and the ratio RG/B indicate that PrX and PrY are brittle in B1 phase and ductile in B2 phase. To our knowledge, this is the first quantitative theoretical prediction of the ductile (brittle) nature of praseodymium chalcogenides and pnictides and still awaits experimental confirmation.

  5. A comprehensive review of the application of chalcogenide nanoparticles in polymer solar cells.

    PubMed

    Freitas, Jilian N; Gonçalves, Agnaldo S; Nogueira, Ana F

    2014-06-21

    In this review the use of solution-processed chalcogenide quantum dots (CdS, CdSe, PbS, etc.) in hybrid organic-inorganic solar cells is explored. Such devices are known as potential candidates for low-cost and efficient solar energy conversion, and compose the so-called third generation solar cells. The incorporation of oxides and metal nanoparticles has also been successfully achieved in this new class of photovoltaic devices; however, we choose to explore here chalcogenide quantum dots in light of their particularly attractive optical and electronic properties. We address herein a comprehensive review of the historical background and state-of-the-art comprising the incorporation of such nanoparticles in polymer matrices. Later strategies for surface chemistry manipulation, in situ synthesis of nanoparticles, use of continuous 3D nanoparticles network (aerogels) and ternary systems are also reviewed.

  6. A comprehensive review of the application of chalcogenide nanoparticles in polymer solar cells

    NASA Astrophysics Data System (ADS)

    Freitas, Jilian N.; Gonçalves, Agnaldo S.; Nogueira, Ana F.

    2014-05-01

    In this review the use of solution-processed chalcogenide quantum dots (CdS, CdSe, PbS, etc.) in hybrid organic-inorganic solar cells is explored. Such devices are known as potential candidates for low-cost and efficient solar energy conversion, and compose the so-called third generation solar cells. The incorporation of oxides and metal nanoparticles has also been successfully achieved in this new class of photovoltaic devices; however, we choose to explore here chalcogenide quantum dots in light of their particularly attractive optical and electronic properties. We address herein a comprehensive review of the historical background and state-of-the-art comprising the incorporation of such nanoparticles in polymer matrices. Later strategies for surface chemistry manipulation, in situ synthesis of nanoparticles, use of continuous 3D nanoparticles network (aerogels) and ternary systems are also reviewed.

  7. Fabrication of submicron chalcogenide glass photonic crystal by resist-free nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Zeng, Jianghui; Zhang, Qian; Zhang, Peiqing; Tang, Junzhou; Xu, Yinsheng; Chen, Feifei; Shen, Xiang; Dai, Shixun

    2017-09-01

    We reported the fabrication of submicron photonic crystal with As40Se40Te20 chalcogenide glass by resist-free thermal nanoimprint using a soft stamp. The As40Se40Te20 glass was prepared with melt-quenching method, and measured to have broad transmission range, high linear and nonlinear refractive index, and good thermal stability. Due to the very low glass transition temperature, the thermal nanoimprint was accomplished directly on the resist-free bulk glass with the soft stamp. By choosing suitable imprint condition, submicron chalcogenide glass photonic crystal with the band gap covering telecom wavelength was obtained. Taking advantage of the high nonlinearity of As40Se40Te20 glass, the imprinted PC structure may have potential applications for all-optical switch in optical communications.

  8. Magnetic Properties Controlled by Interstitial or Interlayer Cations in Iron Chalcogenides

    PubMed Central

    Tang, Shan-Chang; Ding, Ming-Cui; Zhang, Yu-Zhong

    2016-01-01

    By applying density functional theory calculations to iron chalcogenides, we find that magnetic order in Fe1+yTe and magnetic instability at (π, π) in KyFe2Se2 are controlled by interstitial and interlayer cations, respectively. While in Fe1+yTe, magnetic phase transitions occur among collinear, exotic bicollinear and plaquette-ordered antiferronmagnetic states when the height of interstitial irons measured from iron plane or the concentration of interstitial irons is varied, the magnetic instability at (π, π) which is believed to be responsible for the Cooper pairing in iron pnictides is significantly enhanced when y is much smaller than 1 in KyFe2Se2. Our results indicate that, similar to iron pnictides, itinerant electrons play important roles in iron chalcogenides, even though the fluctuating local moments become larger. PMID:26742455

  9. Bending-induced mode non-degeneracy and coupling in chalcogenide negative curvature fibers.

    PubMed

    Wei, Chengli; Menyuk, Curtis R; Hu, Jonathan

    2016-05-30

    We study bend loss in chalcogenide negative curvature fibers with different polarizations, different tube wall thicknesses, and different bend directions relative to the mode polarization. The coupling between the core mode and tube modes induces bend loss peaks in the two non-degenerate modes at the same bend radius. There is as much as a factor of 28 difference between the losses of the two polarization modes. The fiber with a larger tube wall thickness, corresponding to a smaller inner tube diameter, can sustain a smaller bend radius. The bend loss is sensitive to the bend direction when coupling occurs between the core mode and tube modes. A bend loss of 0.2 dB/m at a bend radius of 16 cm, corresponding to 0.2 dB/turn, can be achieved in a chalcogenide negative curvature fiber.

  10. Tuning the Synthesis of Ternary Lead Chalcogenide Quantum Dots by Balancing Precursor Reactivity

    SciTech Connect

    Smith, Danielle K.; Luther, Joseph M; Semonin, Octavi Escala; Nozik, Arthur J; Beard, Matthew C

    2011-01-25

    We report the synthesis and characterization of composition-tunable ternary lead chalcogenide alloys PbSe{sub x}Te{sub 1-x}, PbS{sub x}Te{sub 1-x}, and PbS{sub x}Se{sub 1-x}. This work explores the relative reaction rates of chalcogenide precursors to produce alloyed quantum dots (QDs), and we find the highly reactive bis(trimethylsilyl) (TMS{sub 2})-based precursors allow for the homogeneous incorporation of anions. By varying the Pb to oleic acid ratio, we demonstrate size control of similar composition alloys. We find the resulting QDs are Pb-rich but the Pb/anion ratio is size- and composition-dependent in all alloyed QD as well as in PbSe, PbTe, and PbS QDs and is consistent with the reaction rates of the anion precursors. A more reactive anion precursor results in a lower Pb/anion ratio.

  11. Enhancing extraction efficiency of mid-infrared fluorescence in chalcogenide glass via photonic crystal

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Zhang, Peiqing; Ma, Beijiao; Dai, Shixun; Zhang, Wei; Nie, Qiuhua

    2016-04-01

    The use of rare earth-doped chalcogenide glass is an attractive method to develop mid-infrared sources. In this work, Er3+-doped chalcogenide glass is prepared, and photonic crystal (PC) pattern is designed to improve the extraction efficiency of light emission from the sample surface. The finite difference time domain simulation shows that the light extraction efficiency from the sample surface can be 1.62 times stronger than that from the sample without PC structure by introducing a simple two-dimensional (2D) PC structure into glass samples. This improvement was the result of the efficient light diffraction on the surface because of the integrated 2D PC. Results in this work offer a potential in developing midinfrared light sources.

  12. Analysis of spectral response of optical switching devices based on chalcogenide bistable fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Scholtz, Łubomír.; Solanská, Michaela; Ladányi, Libor; Müllerová, Jarmila

    2016-12-01

    Although nonlinear fiber Bragg gratings (FBGs) are well known devices more than three decades their using as all-optical switching elements is still investigated. Current research is focused on optimization their properties for their using in future all-optical networks. The main problem is minimizing of switching intensities needed for achieving the changes of transmission state. Switching intensities were over several years reduced from hundreds of GW/cm2 to tens of MW/cm2. Reduction of switching intensities can be achieved by selecting appropriate gratings and signal parameters or using suitable materials. This contribution is focused on nonlinear FBGs based on chalcogenide glasses which are very often used in various applications. Chalcogenide glasses thanks to their high nonlinear parameters are suitable candidates for reducing switching intensities of nonlinear FBGs.

  13. Dynamics of silver photo-diffusion into Ge-chalcogenide films: time-resolved neutron reflectometry

    NASA Astrophysics Data System (ADS)

    Sakaguchi, Y.; Asaoka, H.; Uozumi, Y.; Kawakita, Y.; Ito, T.; Kubota, M.; Yamazaki, D.; Soyama, K.; Ailavajhala, M.; Latif, M. R.; Wolf, K.; Mitkova, M.; Skoda, M. W. A.

    2015-06-01

    Silver diffuses into an amorphous (a-) chalcogenide layer while visible light illuminates Ag/a-chalcogenide films and neutron reflectometry is a suitable technique probing time evolution of the depth profiles without damaging the sample by the probe beam itself. In this paper, we report the results of time-resolved neutron reflectivity measurements of a-Ge40Se60/Ag/ Si films taken while the films are exposed to visible light. From the measurements, we found enormous changes in the neutron reflectivity profile, including a loss of total reflection region, with continuous illumination even after forming one homogeneous layer, which occurred about 50 min after starting illumination. At this stage, a clear off-specular scattering was observed by a linear detector and a surface roughness was observed with naked eyes.

  14. Large magnetoresistance in non-magnetic silver chalcogenides and new class of magnetoresistive compounds

    DOEpatents

    Saboungi, Marie-Louis; Price, David C. L.; Rosenbaum, Thomas F.; Xu, Rong; Husmann, Anke

    2001-01-01

    The heavily-doped silver chalcogenides, Ag.sub.2+.delta. Se and Ag.sub.2+.delta. Te, show magnetoresistance effects on a scale comparable to the "colossal" magnetoresistance (CMR) compounds. Hall coefficient, magnetoconductivity, and hydrostatic pressure experiments establish that elements of narrow-gap semiconductor physics apply, but both the size of the effects at room temperature and the linear field dependence down to fields of a few Oersteds are surprising new features.

  15. High Cost/High Risk Components to Chalcogenide Molded Lens Model: Molding Preforms and Mold Technology

    SciTech Connect

    Bernacki, Bruce E.

    2012-10-05

    This brief report contains a critique of two key components of FiveFocal's cost model for glass compression molding of chalcogenide lenses for infrared applications. Molding preforms and mold technology have the greatest influence on the ultimate cost of the product and help determine the volumes needed to select glass molding over conventional single-point diamond turning or grinding and polishing. This brief report highlights key areas of both technologies with recommendations for further study.

  16. Low loss Chalcogenide glass waveguides by thermal nano-imprint lithography.

    PubMed

    Han, Ting; Madden, Steve; Bulla, Douglas; Luther-Davies, Barry

    2010-08-30

    We report the fabrication of low loss rib waveguides from chalcogenide glass films by thermal nano-imprint using a soft stamp. Waveguides 2-4 µm wide and 1 µm high were fabricated with extremely smooth sidewalls and optical losses limited by Rayleigh scattering to values of 0.26 dB/cm for the TM and 0.27 dB/cm for TE polarizations at 1550 nm.

  17. Dielectric and structural characterisation of chalcogenide glasses via terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Ravagli, A.; Naftaly, M.; Craig, C.; Weatherby, E.; Hewak, D. W.

    2017-07-01

    Terahertz time-domain spectroscopy (THz TDS) was used to investigate a series of chalcogenide glasses. In particular, the dielectric properties at terahertz frequencies were determined and correlated with the glass composition. The experimental results showed a strong relationship between the dielectric properties and the polarizability of the glasses studied. A new explanation based on the coordination number of the metallic cations was proposed to understand these observations.

  18. Minority carrier device comprising a passivating layer including a Group 13 element and a chalcogenide component

    NASA Technical Reports Server (NTRS)

    Barron, Andrew R. (Inventor); Hepp, Aloysius F. (Inventor); Jenkins, Phillip P. (Inventor); MacInnes, Andrew N. (Inventor)

    1999-01-01

    A minority carrier device includes at least one junction of at least two dissimilar materials, at least one of which is a semiconductor, and a passivating layer on at least one surface of the device. The passivating layer includes a Group 13 element and a chalcogenide component. Embodiments of the minority carrier device include, for example, laser diodes, light emitting diodes, heterojunction bipolar transistors, and solar cells.

  19. Energy band alignment in chalcogenide thin film solar cells from photoelectron spectroscopy.

    PubMed

    Klein, Andreas

    2015-04-10

    Energy band alignment plays an important role in thin film solar cells. This article presents an overview of the energy band alignment in chalcogenide thin film solar cells with a particular focus on the commercially available material systems CdTe and Cu(In,Ga)Se2. Experimental results from two decades of photoelectron spectroscopy experiments are compared with density functional theory calculations taken from literature. It is found that the experimentally determined energy band alignment is in good agreement with theoretical predictions for many interfaces. These alignments, in particular the theoretically predicted alignments, can therefore be considered as the intrinsic or natural alignments for a given material combination. The good agreement between experiment and theory enables a detailed discussion of the interfacial composition of Cu(In,Ga)Se2/CdS interfaces in terms of the contribution of ordered vacancy compounds to the alignment of the energy bands. It is furthermore shown that the most important interfaces in chalcogenide thin film solar cells, those between Cu(In,Ga)Se2 and CdS and between CdS and CdTe are quite insensitive to the processing of the layers. There are plenty of examples where a significant deviation between experimentally-determined band alignment and theoretical predictions are evident. In such cases a variation of band alignment of sometimes more than 1 eV depending on interface preparation can be obtained. This variation can lead to a significant deterioration of device properties. It is suggested that these modifications are related to the presence of high defect concentrations in the materials forming the contact. The particular defect chemistry of chalcogenide semiconductors, which is related to the ionicity of the chemical bond in these materials and which can be beneficial for material and device properties, can therefore cause significant device limitations, as e.g. in the case of the CuInS2 thin film solar cells or for new

  20. A motion- and sound-activated, 3D-printed, chalcogenide-based triboelectric nanogenerator.

    PubMed

    Kanik, Mehmet; Say, Mehmet Girayhan; Daglar, Bihter; Yavuz, Ahmet Faruk; Dolas, Muhammet Halit; El-Ashry, Mostafa M; Bayindir, Mehmet

    2015-04-08

    A multilayered triboelectric nanogenerator (MULTENG) that can be actuated by acoustic waves, vibration of a moving car, and tapping motion is built using a 3D-printing technique. The MULTENG can generate an open-circuit voltage of up to 396 V and a short-circuit current of up to 1.62 mA, and can power 38 LEDs. The layers of the triboelectric generator are made of polyetherimide nanopillars and chalcogenide core-shell nanofibers.

  1. Fast solid state synthesis of metal vanadates and chalcogenides using microwave irradiation

    SciTech Connect

    Vaidhyanathan, B.; Ganguli, M.; Rao, K.J.

    1995-09-01

    Metal vanadates and chalcogenides have been prepared in rapid time scales using a domestic microwave oven. The products exhibit high phase purity and homogeneity. The thermal and spectroscopic properties of the microwave prepared metal vanadates match well with those prepared by conventional methods. The most important advantages in microwave assisted synthesis appear to be the very short time scales required for the preparation and the selectivity in energy transfer from microwave field.

  2. On-chip mid-infrared gas detection using chalcogenide glass waveguide

    NASA Astrophysics Data System (ADS)

    Han, Z.; Lin, P.; Singh, V.; Kimerling, L.; Hu, J.; Richardson, K.; Agarwal, A.; Tan, D. T. H.

    2016-04-01

    We demonstrate an on-chip sensor for room-temperature detection of methane gas using a broadband spiral chalcogenide glass waveguide coupled with off-chip laser and detector. The waveguide is fabricated using UV lithography patterning and lift-off after thermal evaporation. We measure the intensity change due to the presence and concentration of methane gas in the mid-infrared (MIR) range. This work provides an approach for broadband planar MIR gas sensing.

  3. GeAsSe chalcogenide slot optical waveguide ring resonator for refractive index sensing

    NASA Astrophysics Data System (ADS)

    Ashok, N.; Lee, Yeung Lak; Shin, WooJin

    2017-04-01

    We present a slot optical waveguide ring resonator that can be used as a refractive index sensor. The proposed ring resonator works on the principle of coupling of the mode from the bus waveguide to the ring waveguide. The ring resonator was analyzed using the finite-difference time-domain method. Our proposed waveguide structure showed a sensitivity of 42 nm/RIU. Our aim is to design a chalcogenide ring resonator for refractive index sensing in midinfrared wavelengths.

  4. Strong relief grating fabrication in amorphous chalcogenide glasses by light polarization modulation

    NASA Astrophysics Data System (ADS)

    Asatryan, Karen E.; Galstian, Tigran; Vallee, Real

    2004-12-01

    We report on the possibility of strong relief grating fabrication in amorphous chalcogenide As2S3 glass using polarization modulated near bandgap light illumination. Such gratings are created using low intensity and spatially uniform light illumination. The obtained relief structures are strong, very smooth and do not require post-exposure development procedures. They are stable to the heat treatment and the uniform photo-exposure. The possible mechanism of such relief structure formation is also briefly discussed.

  5. Fabrication of an IR hollow-core Bragg fiber based on chalcogenide glass extrusion

    NASA Astrophysics Data System (ADS)

    Zhu, Minming; Wang, Xunsi; Pan, Zhanghao; Cheng, Ci; Zhu, Qingde; Jiang, Chen; Nie, Qiuhua; Zhang, Peiqing; Wu, Yuehao; Dai, Shixun; Xu, Tiefeng; Tao, Guangming; Zhang, Xianghua

    2015-05-01

    The theoretical analysis and experimental preparation of a hollow-core Bragg fiber based on chalcogenide glasses are demonstrated. The fiber has potential applications in bio-sensing and IR energy transmission. Two chalcogenide glasses with, respectively, high and low refractive indexes are investigated in detail for the fabrication of hollow-core Bragg fibers. The most appropriate structure is selected; this structure is composed of four concentric rings and a center air hole . Its band gap for the Bragg fiber is analyzed by the plane wave method. The chalcogenide glasses Ge15Sb20S58.5I13 and Ge15Sb10Se75 are chosen to extrude the robust multi-material glass preform with a specialized punch and glass container. The glass preform is simultaneously protected with a polyetherimide polymer. The hollow-core Bragg fibers are finally obtained after glass preform extrusion, fiber preform fabrication, and fiber drawing. Results showed that the fiber has a transparency window from 2.5 to 14 μm, including a low-loss transmission window from 10.5 to 12 μm. The location of this low-loss transmission window matches the predicted photonic band gap in the simulation.

  6. High-energy exciton transitions in quasi-two-dimensional cadmium chalcogenide nanoplatelets

    NASA Astrophysics Data System (ADS)

    Vasiliev, Roman B.; Lebedev, Alexander I.; Lazareva, Elizabeth P.; Shlenskaya, Natalia N.; Zaytsev, Vladimir B.; Vitukhnovsky, Alexei G.; Yao, Yuanzhao; Sakoda, Kazuaki

    2017-04-01

    Semiconductor nanoparticles of cadmium chalcogenides are known to exhibit pronounced thickness-dependent E0 series of exciton transitions at the Γ point of the Brillouin zone (BZ). In this work we report an experimental evidence for high-energy series of exciton transitions, which originates from BZ points different from the Γ point, in the family of cadmium chalcogenide quasi-two-dimensional (2D) nanoplatelets (NPLs). Intensive UV absorption bands demonstrating a pronounced size effect are observed for CdTe, CdSe, and CdS NPLs in addition to the E0 exciton bands in the visible region. These additional bands are attributed to transitions analogous to the E1,E1+Δ1 , and E2 series observed in bulk crystals. First-principles DFT calculations of the electronic structure and absorption spectra support this explanation and show that the main contribution to these optical transitions comes from X and M points of the 2D BZ, which originate from L and X points of the 3D BZ. At the same time, the E0 series of transitions at the Γ point is well described by the multiband effective-mass model. The observation of the UV exciton bands reveals tunable optical properties of cadmium chalcogenide NPLs in UV spectral region, which may be interesting for practical applications.

  7. Chemically Engineered Substrates for Patternable Growth of Two-Dimensional Chalcogenide Crystals.

    PubMed

    Wang, Mingzhan; Wu, Jinxiong; Lin, Li; Liu, Yujing; Deng, Bing; Guo, Yunfan; Lin, Yuanwei; Xie, Tian; Dang, Wenhui; Zhou, Yubing; Peng, Hailin

    2016-11-22

    The key challenge of direct integration of two-dimensional (2D) chalcogenide crystals into functional modules is precise control of the nucleation sites of the building blocks. Herein, we exploit the chemical activities and surface engineering of the substrates to manipulate the nucleation energy barrier of 2D crystals and thereby realize the patternable growth of 2D crystals. The selective-region chemical modifications of the substrates are achieved via microcontact printing combined with the elegant self-assembly of octadecyltrichlorosilane molecules on the substrates. The patternable growth method is versatile and can be used as a general strategy for growing a broad class of high-quality 2D chalcogenide crystals with tailorable configurations on a variety of chemically engineered substrates. Moreover, we demonstrate flexible transparent electrodes based on large-scale patterned nanogrids of topological insulator Bi2Se3, which possess tailored trade-off between electric conductivity and optical transmittance across the visible to near-infrared regime. We hope this method may open an avenue to the efficient integration and batch production of 2D chalcogenide crystals and could inspire ongoing efforts of the fabrication of van der Waals heterostructures.

  8. Digital Transfer Growth of Patterned 2D Metal Chalcogenides by Confined Nanoparticle Evaporation

    SciTech Connect

    Mahjouri-Samani, Masoud; Tian, Mengkun; Wang, Kai; Boulesbaa, Abdelaziz; Rouleau, Christopher M.; Puretzky, Alexander A.; McGuire, Michael A.; Srijanto, Bernadeta R.; Xiao, Kai; Eres, Gyula; Duscher, Gerd; Geohegan, David B.

    2014-10-19

    Developing methods for the facile synthesis of two-dimensional (2D) metal chalcogenides and other layered materials is crucial for emerging applications in functional devices. Controlling the stoichiometry, number of the layers, crystallite size, growth location, and areal uniformity is challenging in conventional vapor phase synthesis. Here, we demonstrate a new route to control these parameters in the growth of metal chalcogenide (GaSe) and dichalcogenide (MoSe2) 2D crystals by precisely defining the mass and location of the source materials in a confined transfer growth system. A uniform and precise amount of stoichiometric nanoparticles are first synthesized and deposited onto a substrate by pulsed laser deposition (PLD) at room temperature. This source substrate is then covered with a receiver substrate to form a confined vapor transport growth (VTG) system. By simply heating the source substrate in an inert background gas, a natural temperature gradient is formed that evaporates the confined nanoparticles to grow large, crystalline 2D nanosheets on the cooler receiver substrate, the temperature of which is controlled by the background gas pressure. Large monolayer crystalline domains (~ 100 m lateral sizes) of GaSe and MoSe2 are demonstrated, as well as continuous monolayer films through the deposition of additional precursor materials. This novel PLD-VTG synthesis and processing method offers a unique approach for the controlled growth of large-area, metal chalcogenides with a controlled number of layers in patterned growth locations for optoelectronics and energy related applications.

  9. Solution-processed chalcogenide glass for integrated single-mode mid-infrared waveguides.

    PubMed

    Tsay, Candice; Zha, Yunlai; Arnold, Craig B

    2010-12-06

    Chalcogenide glass materials exhibit a variety of optical properties that make them desirable for near- and mid-infrared communications and sensing applications. However, processing limitations for these photorefractive materials have made the direct integration of waveguides with sources or detectors challenging. Here we demonstrate the viability of two complementary soft lithography methods for patterning and integrating chalcogenide glass waveguides from solution. One method, micro-molding in capillaries (MIMIC), is shown to fabricate multi-mode As(2)S(3) waveguides which are directly integrated with quantum cascade lasers (QCLs). In a second method, we demonstrate the ability of micro-transfer molding (µTM), to produce arrays of single mode rib waveguides (2.5 µm wide and 4.5 µm high) over areas larger than 6 cm(2) while maintaining edge roughness below 5.1 nm. These methods form a suite of processes that can be applied to chalcogenide solutions to create a diverse array of mid-IR optical and photonic structures ranging from <5 to 10's of µm in dimension.

  10. Observation of universal strong orbital-dependent correlation effects in iron chalcogenides

    SciTech Connect

    Yi, M.; Liu, Z. -K.; Zhang, Y.; Yu, R.; Zhu, J. -X.; Lee, J. J.; Moore, R. G.; Schmitt, F. T.; Li, W.; Riggs, S. C.; Chu, J. -H.; Lv, B.; Hu, J.; Hashimoto, M.; Mo, S. -K.; Hussain, Z.; Mao, Z. Q.; Chu, C. W.; Fisher, I. R.; Si, Q.; Shen, Z. -X.; Lu, D. H.

    2015-07-23

    Establishing the appropriate theoretical framework for unconventional superconductivity in the iron-based materials requires correct understanding of both the electron correlation strength and the role of Fermi surfaces. This fundamental issue becomes especially relevant with the discovery of the iron chalcogenide superconductors. Here, we use angle-resolved photoemission spectroscopy to measure three representative iron chalcogenides, FeTe0.56Se0.44, monolayer FeSe grown on SrTiO3 and K0.76Fe1.72Se2. We show that these superconductors are all strongly correlated, with an orbital-selective strong renormalization in the dxy bands despite having drastically different Fermi surface topologies. Furthermore, raising temperature brings all three compounds from a metallic state to a phase where the dxy orbital loses all spectral weight while other orbitals remain itinerant. As a result, these observations establish that iron chalcogenides display universal orbital-selective strong correlations that are insensitive to the Fermi surface topology, and are close to an orbital-selective Mott phase, hence placing strong constraints for theoretical understanding of iron-based superconductors.

  11. Shaping of Looped Miniaturized Chalcogenide Fiber Sensing Heads for Mid-Infrared Sensing

    PubMed Central

    Houizot, Patrick; Anne, Marie-Laure; Boussard-Plédel, Catherine; Loréal, Olivier; Tariel, Hugues; Lucas, Jacques; Bureau, Bruno

    2014-01-01

    Chalcogenide glass fibers are promising photonic tools to develop Fiber Evanescent Wave Spectroscopy (FEWS) optical sensors working in the mid-infrared region. Numerous pioneering works have already been carried out showing their efficiency, especially for bio-medical applications. Nevertheless, this technology remains confined to academic studies at the laboratory scale because chalcogenide glass fibers are difficult to shape to produce reliable, sensitive and compact sensors. In this paper, a new method for designing and fabricating a compact and robust sensing head with a selenide glass fiber is described. Compact looped sensing heads with diameter equal to 2 mm were thus shaped. This represents an outstanding achievement considering the brittleness of such uncoated fibers. FEWS experiments were implemented using alcoholic solutions as target samples showing that the sensitivity is higher than with the routinely used classical fiber. It is also shown that the best compromise in term of sensitivity is to fabricate a sensing head including two full loops. From a mechanical point of view, the breaking loads of the loop shaped head are also much higher than with classical fiber. Finally, this achievement paves the way for the use of mid-infrared technology during in situ and even in vivo medical operations. Indeed, is is now possible to slide a chalcogenide glass fiber in the operating channel of a standard 2.8 mm diameter catheter. PMID:25264953

  12. Observation of universal strong orbital-dependent correlation effects in iron chalcogenides

    DOE PAGES

    Yi, M.; Liu, Z. -K.; Zhang, Y.; ...

    2015-07-23

    Establishing the appropriate theoretical framework for unconventional superconductivity in the iron-based materials requires correct understanding of both the electron correlation strength and the role of Fermi surfaces. This fundamental issue becomes especially relevant with the discovery of the iron chalcogenide superconductors. Here, we use angle-resolved photoemission spectroscopy to measure three representative iron chalcogenides, FeTe0.56Se0.44, monolayer FeSe grown on SrTiO3 and K0.76Fe1.72Se2. We show that these superconductors are all strongly correlated, with an orbital-selective strong renormalization in the dxy bands despite having drastically different Fermi surface topologies. Furthermore, raising temperature brings all three compounds from a metallic state to a phasemore » where the dxy orbital loses all spectral weight while other orbitals remain itinerant. As a result, these observations establish that iron chalcogenides display universal orbital-selective strong correlations that are insensitive to the Fermi surface topology, and are close to an orbital-selective Mott phase, hence placing strong constraints for theoretical understanding of iron-based superconductors.« less

  13. New functionality of chalcogenide glasses for radiation sensing of nuclear wastes.

    PubMed

    Ailavajhala, M S; Gonzalez-Velo, Y; Poweleit, C D; Barnaby, H J; Kozicki, M N; Butt, D P; Mitkova, M

    2014-03-30

    Data about gamma radiation induced effects in Ge40Se60 chalcogenide thin films and radiation induced silver diffusion within these are presented. Blanket films and devices were created to study the structural changes, diffusion products, and device performance. Raman spectroscopy, X-ray diffraction, current vs. voltage (I-V) and impedance measurements expound the behavior of Ge40Se60 glass and silver diffusion within this glass under radiation. Raman study shows that there is a decrease in the area ratio between edge shared and corner shared structural units revealing structural reorganization occurring in the glasses as a result of gamma radiation. X-ray diffraction studies revealed that with sufficiently radiation dose it is also possible to create Ag2Se in selenium-depleted systems. Oxidation of the Ge enriched chalcogenide backbone is confirmed through the electrical performance of the sensing elements based on these films. Combination of these structural and diffusion products influences the device performance. The I-V behavior is characterized by increase in current and then stabilization as a function of radiation dose. Additionally, device modeling is also presented using Silvaco software and analytical methods to shed light on the device behavior. This type of sensor design and material characterizations facilitate in improving the radiation sensing capabilities of silver containing chalcogenide glass thin films.

  14. Shaping of looped miniaturized chalcogenide fiber sensing heads for mid-infrared sensing.

    PubMed

    Houizot, Patrick; Anne, Marie-Laure; Boussard-Plédel, Catherine; Loréal, Olivier; Tariel, Hugues; Lucas, Jacques; Bureau, Bruno

    2014-09-26

    Chalcogenide glass fibers are promising photonic tools to develop Fiber Evanescent Wave Spectroscopy (FEWS) optical sensors working in the mid-infrared region. Numerous pioneering works have already been carried out showing their efficiency, especially for bio-medical applications. Nevertheless, this technology remains confined to academic studies at the laboratory scale because chalcogenide glass fibers are difficult to shape to produce reliable, sensitive and compact sensors. In this paper, a new method for designing and fabricating a compact and robust sensing head with a selenide glass fiber is described. Compact looped sensing heads with diameter equal to 2 mm were thus shaped. This represents an outstanding achievement considering the brittleness of such uncoated fibers. FEWS experiments were implemented using alcoholic solutions as target samples showing that the sensitivity is higher than with the routinely used classical fiber. It is also shown that the best compromise in term of sensitivity is to fabricate a sensing head including two full loops. From a mechanical point of view, the breaking loads of the loop shaped head are also much higher than with classical fiber. Finally, this achievement paves the way for the use of mid-infrared technology during in situ and even in vivo medical operations. Indeed, is is now possible to slide a chalcogenide glass fiber in the operating channel of a standard 2.8 mm diameter catheter.

  15. Low threshold fiber taper coupled rare earth ion-doped chalcogenide microsphere laser

    NASA Astrophysics Data System (ADS)

    Li, Chao-Ran; Dai, Shi-Xun; Zhang, Qing-Yuan; Shen, Xiang; Wang, Xun-Si; Zhang, Pei-Qing; Lu, Lai-Wei; Wu, Yue-Hao; Lv, She-Qin

    2015-04-01

    We report the applications of a low-cost and environmentally friendly chalcogenide glass, 75GeS2-15Ga2S3-10CsI, in building active microsphere laser oscillators. A silica fiber taper is used as the coupling mechanism. With an 808-nm laser diode as a pump source, we show that a high-Q (˜ 6×104) laser mode could be obtained from a 75-μm diameter microsphere that is coupled with a 1.77-μm waist-diameter fiber taper. The threshold of the incident pump power is 1.39 mW, which is considerably lower than those of previously reported free-space coupled chalcogenide microsphere lasers. We also note an apparent enhancement in laser power generated from this chalcogenide microsphere laser. Project supported by the National Natural Science Foundation of China (Grant Nos. 61177087 and 61435009), the National Key Basic Research Program of China (Grant No. 2012CB722703), the Program for Innovative Research Team of Ningbo City, China (Grant No. 2009B21007) , the K. C. Wong Magna Fund in Ningbo University, the Open Fund of the State Key Laboratory of Luminescent Materials and Devices (South China University of Technology), China (Grant No. 2014-skllmd-01), and the Natural Science Foundation of Ningbo City, China (Grant No. 2014A610125).

  16. Ultrafast Microwave Nano-manufacturing of Fullerene-Like Metal Chalcogenides

    NASA Astrophysics Data System (ADS)

    Liu, Zhen; Zhang, Lin; Wang, Ruigang; Poyraz, Selcuk; Cook, Jonathan; Bozack, Michael J.; Das, Siddhartha; Zhang, Xinyu; Hu, Liangbing

    2016-03-01

    Metal Chalcogenides (MCs) have emerged as an extremely important class of nanomaterials with applications ranging from lubrication to energy storage devices. Here we report our discovery of a universal, ultrafast (60 seconds), energy-efficient, and facile technique of synthesizing MC nanoparticles and nanostructures, using microwave-assisted heating. A suitable combination of chemicals was selected for reactions on Polypyrrole nanofibers (PPy-NF) in presence of microwave irradiation. The PPy-NF serves as the conducting medium to absorb microwave energy to heat the chemicals that provide the metal and the chalcogenide constituents separately. The MCs are formed as nanoparticles that eventually undergo a size-dependent, multi-stage aggregation process to yield different kinds of MC nanostructures. Most importantly, this is a single-step metal chalcogenide formation process that is much faster and much more energy-efficient than all the other existing methods and can be universally employed to produce different kinds of MCs (e.g., MoS2, and WS2).

  17. Development of chalcogenide glass with thermal stability for molded infrared lens

    NASA Astrophysics Data System (ADS)

    Choi, Ju H.; Cha, Du Hwan; Kang, Hee Young; Kim, Jeong-Ho; Kim, Hye-Jeong

    2014-03-01

    Chalcogenide glasses have been attracted because of their use in moldable lenses for the application in range of 3-12 μm. In this study, amorphous Ge-Sb-Se chalcogenide was prepared by a standard melt-quenching technique for moldable lens. Moldable lens should have unique thermal mechanic properties in order to be applied to molding process. Thus, the optical and thermal properties to find out right composition were characterized by IR transmission spectroscopy and DSC, respectively. Specifically, the Ge:Sb ratio were controlled in order to find out the most stable glass forming area. The relations between thermal properties and the moldability were studied by using an optical microscopy in term of thermal properties such as Tg and Tx. Transcription properties of the surface of lens or molds were explained in terms of thermal properties in their composition The preferential Ge:Sb ratio in Ge-Sb-Se based chalcogenide glasses was selected for producing moldable lens.

  18. Interfacial scanning tunneling spectroscopy (STS) of chalcogenide/metal hybrid nanostructure

    NASA Astrophysics Data System (ADS)

    Saad, Mahmoud M.; Abdallah, Tamer; Easawi, Khalid; Negm, Sohair; Talaat, Hassan

    2015-05-01

    The electronic structure at the interface of chalcogenide/metal hybrid nanostructure (CdSe-Au tipped) had been studied by UHV scanning tunneling spectroscopy (STS) technique at room temperature. This nanostructure was synthesized by a phase transfer chemical method. The optical absorption of this hybrid nanostructure was recorded, and the application of the effective mass approximation (EMA) model gave dimensions that were confirmed by the direct measurements using the scanning tunneling microscopy (STM) as well as the high-resolution transmission electron microscope (HRTEM). The energy band gap obtained by STS agrees with the values obtained from the optical absorption. Moreover, the STS at the interface of CdSe-Au tipped hybrid nanostructure between CdSe of size about 4.1 ± 0.19 nm and Au tip of size about 3.5 ± 0.29 nm shows a band bending about 0.18 ± 0.03 eV in CdSe down in the direction of the interface. Such a result gives a direct observation of the electron accumulation at the interface of CdSe-Au tipped hybrid nanostructure, consistent with its energy band diagram. The presence of the electron accumulation at the interface of chalcogenides with metals has an important implication for hybrid nanoelectronic devices and the newly developed plasmon/chalcogenide photovoltaic solar energy conversion.

  19. III-V nanocrystals capped with molecular metal chalcogenide ligands: high electron mobility and ambipolar photoresponse.

    PubMed

    Liu, Wenyong; Lee, Jong-Soo; Talapin, Dmitri V

    2013-01-30

    In this work, we synthesized InP and InAs nanocrystals (NCs) capped with different inorganic ligands, including various molecular metal chalcogenide complexes (MCCs) and chalcogenide ions. We found that MCCs and chalcogenide ions can quantitatively displace organic ligands from the surface of III-V NCs and serve as the inorganic capping groups for III-V NC surfaces. These inorganic ligands stabilize colloidal solutions of InP and InAs NCs in polar solvents and greatly facilitate charge transport between individual NCs. Charge transport studies revealed high electron mobility in the films of MCC-capped InP and InAs NCs. For example, we found that bridging InAs NCs with Cu(7)S(4)(-) MCC ligands can lead to very high electron mobility exceeding 15 cm(2)/(V s). In addition, we observed unprecedented ambipolar (positive/negative) photoresponse of MCC-capped InAs NC solids that changed sign depending on the ligand chemistry, illumination wavelength, and doping of the NC solid. For example, the sign of photoconductance of InAs NCs capped with Cu(7)S(4)(-) or Sn(2)S(6)(4-) ions converted from positive at 0.80 and 0.95 eV to negative at 1.27 and 1.91 eV. We propose an explanation of this unusually complex photoconductivity of InAs NC solids.

  20. Mixed-metal chalcogenide tetrahedral clusters with an exo-polyhedral metal fragment.

    PubMed

    Yuvaraj, K; Roy, Dipak Kumar; Anju, V P; Mondal, Bijnaneswar; Varghese, Babu; Ghosh, Sundargopal

    2014-12-07

    The reaction of metal carbonyl compounds with group 6 and 8 metallaboranes led us to report the synthesis and structural characterization of several novel mixed-metal chalcogenide tetrahedral clusters. Thermolysis of arachno-[(Cp*RuCO)2B2H6], 1, and [Os3(CO)12] in the presence of 2-methylthiophene yielded [Cp*Ru(CO)2(μ-H){Os3(CO)9}S], 3, and [Cp*Ru(μ-H){Os3(CO)11}], 4. In a similar fashion, the reaction of [(Cp*Mo)2B5H9], 2, with [Ru3(CO)12] and 2-methylthiophene yielded [Cp*Ru(CO)2(μ-H){Ru3(CO)9}S], 5, and conjuncto-[(Cp*Mo)2B5H8(μ-H){Ru3(CO)9}S], 6. Both compounds 3 and 5 can be described as 50-cve (cluster valence electron) mixed-metal chalcogenide clusters, in which a sulfur atom replaces one of the vertices of the tetrahedral core. Compounds 3 and 5 possess a [M3S] tetrahedral core, in which the sulfur is attached to an exo-metal fragment, unique in the [M3S] metal chalcogenide tetrahedral arrangements. All the compounds have been characterized by mass spectrometry, IR, and (1)H, (11)B and (13)C NMR spectroscopy in solution, and the solid state structures were unequivocally established by crystallographic analysis of compounds 3, 5 and 6.

  1. Ultrafast Microwave Nano-manufacturing of Fullerene-Like Metal Chalcogenides

    PubMed Central

    Liu, Zhen; Zhang, Lin; Wang, Ruigang; Poyraz, Selcuk; Cook, Jonathan; Bozack, Michael J.; Das, Siddhartha; Zhang, Xinyu; Hu, Liangbing

    2016-01-01

    Metal Chalcogenides (MCs) have emerged as an extremely important class of nanomaterials with applications ranging from lubrication to energy storage devices. Here we report our discovery of a universal, ultrafast (60 seconds), energy-efficient, and facile technique of synthesizing MC nanoparticles and nanostructures, using microwave-assisted heating. A suitable combination of chemicals was selected for reactions on Polypyrrole nanofibers (PPy-NF) in presence of microwave irradiation. The PPy-NF serves as the conducting medium to absorb microwave energy to heat the chemicals that provide the metal and the chalcogenide constituents separately. The MCs are formed as nanoparticles that eventually undergo a size-dependent, multi-stage aggregation process to yield different kinds of MC nanostructures. Most importantly, this is a single-step metal chalcogenide formation process that is much faster and much more energy-efficient than all the other existing methods and can be universally employed to produce different kinds of MCs (e.g., MoS2, and WS2). PMID:26931353

  2. Semiconducting quaternary chalcogenide glasses as new potential thermoelectric materials: an As-Ge-Se-Sb case.

    PubMed

    Dahshan, A; Sharma, Pankaj; Aly, K A

    2015-09-07

    The performance of thermoelectric materials may be improved via complex structures, impurities, disorder etc. Chalcogenide glasses possess such properties. In the present paper, we report the electrical and thermoelectric properties of As14Ge14Se72-xSbx (where x = 3, 6, 9, 12, 15 at%) chalcogenide glasses in the temperature range of 300 K-450 K. The electrical conductivity has been observed to increase from 1.46 × 10(-9) Ω(-1) cm(-1) to 1.80 × 10(-6) Ω(-1) cm(-1) for x = 3 at% to x = 15 at%. The addition of Sb increases the Seebeck coefficient to a large value of 1124 μV K(-1) for x = 15 at% at 333 K. As a result of increased electrical conductivity and Seebeck coefficient for enhanced values of Sb, the power factor (a measure of the performance of the thermoelectric energy converters) has been observed to increase strongly. Results indicate that the investigated chalcogenide glassy compositions may be potential candidates for incurring high action thermoelectric materials.

  3. Nuclear quadrupole resonance in the chalcogenide and pnictide amorphous semiconductors. Interim report

    SciTech Connect

    Taylor, P.C.

    1983-01-01

    The absence of long range periodic order in amorphous semiconductors makes the interpretation of the usual scattering experiments, such as x-ray, neutron, or electron scattering, both difficult and model dependent. For this reason information concerning the static and dynamic properties of these solids must be gathered using many different experimental techniques. In the chalcogenide (group VI) and pnictide (group V) amorphous semiconductors nuclear quadrupole resonance (NQR) spectroscopy has proved to be one of the important techniques. The NQR technique provides information on a scale of the interatomic spacings and is thus a sensitive probe of the local environments of the major constituent atoms in an amorphous semiconductor. In the specific case of 75As, analyses of the NQR lineshapes and of nuclear spin-spin phenomena yield detailed structural information concerning not only the local bonding at an arsenic site but also the presence of intermediate range order in some chalcogenide glasses. The lineshapes also provide a very sensitive probe of photo-induced polymerization in films of amorphous chalcogenides.

  4. Multitopic ligand directed assembly of low-dimensional metal-chalcogenide organic frameworks.

    PubMed

    Liu, Yi; Ye, Kaiqi; Wang, Yue; Zhang, Qichun; Bu, Xianhui; Feng, Pingyun

    2017-01-31

    Despite tremendous progress in metal-organic frameworks, only limited success has been achieved with metal-chalcogenide organic frameworks. Metal-chalcogenide organic frameworks are desirable because they offer a promising route towards tunable semiconducting porous frameworks. Here, four novel semiconducting chalcogenide-organic hybrid compounds have been synthesized through a solvothermal method. Multitopic organic molecules, i.e., 1,2-di-(4-pyridyl)ethylene (L(1)), 1,3,5-tris(4-pyridyl-trans-ethenyl)benzene (L(2)) and tetrakis(4-pyridyloxymethylene)methane (L(3)), have been used as linkers to assemble Zn(SAr)2 or Zn2(SAr)4 units to generate different patterns of spatial organizations. Single-crystal structural analyses indicate that compounds NTU-2, NTU-3 and NTU-4 possess two-dimensional layer structures, while compound NTU-1 adopts a one-dimensional coordination framework (NTU-n, where n is the number related to a specific structure). The diffuse-reflectance spectra demonstrate that these four compounds possess indirect bandgaps and their tunable bandgaps are correlated with their compositions and crystal structures.

  5. Case studies on the formation of chalcogenide self-assembled monolayers on surfaces and dissociative processes

    PubMed Central

    Bendounan, Azzedine; Harish, Makri Nimbegondi Kotresh; Giglia, Angelo; Kubsky, Stefan; Sirotti, Fausto; Pasquali, Luca; Sampath, Srinivasan

    2016-01-01

    Summary This report examines the assembly of chalcogenide organic molecules on various surfaces, focusing on cases when chemisorption is accompanied by carbon–chalcogen atom-bond scission. In the case of alkane and benzyl chalcogenides, this induces formation of a chalcogenized interface layer. This process can occur during the initial stages of adsorption and then, after passivation of the surface, molecular adsorption can proceed. The characteristics of the chalcogenized interface layer can be significantly different from the metal layer and can affect various properties such as electron conduction. For chalcogenophenes, the carbon–chalcogen atom-bond breaking can lead to opening of the ring and adsorption of an alkene chalcogenide. Such a disruption of the π-electron system affects charge transport along the chains. Awareness about these effects is of importance from the point of view of molecular electronics. We discuss some recent studies based on X-ray photoelectron spectroscopy that shed light on these aspects for a series of such organic molecules. PMID:26977383

  6. Chemical Control of Plasmons in Metal Chalcogenide and Metal Oxide Nanostructures.

    PubMed

    Mattox, Tracy M; Ye, Xingchen; Manthiram, Karthish; Schuck, P James; Alivisatos, A Paul; Urban, Jeffrey J

    2015-10-14

    The field of plasmonics has grown to impact a diverse set of scientific disciplines ranging from quantum optics and photovoltaics to metamaterials and medicine. Plasmonics research has traditionally focused on noble metals; however, any material with a sufficiently high carrier density can support surface plasmon modes. Recently, researchers have made great gains in the synthetic (both intrinsic and extrinsic) control over the morphology and doping of nanoscale oxides, pnictides, sulfides, and selenides. These synthetic advances have, collectively, blossomed into a new, emerging class of plasmonic metal chalcogenides that complement traditional metallic materials. Chalcogenide and oxide nanostructures expand plasmonic properties into new spectral domains and also provide a rich suite of chemical controls available to manipulate plasmons, such as particle doping, shape, and composition. New opportunities in plasmonic chalcogenide nanomaterials are highlighted in this article, showing how they may be used to fundamentally tune the interaction and localization of electromagnetic fields on semiconductor surfaces in a way that enables new horizons in basic research and energy-relevant applications.

  7. Observation of universal strong orbital-dependent correlation effects in iron chalcogenides

    PubMed Central

    Yi, M.; Liu, Z-K; Zhang, Y.; Yu, R.; Zhu, J.-X.; Lee, J.J.; Moore, R.G.; Schmitt, F.T.; Li, W.; Riggs, S.C.; Chu, J.-H.; Lv, B.; Hu, J.; Hashimoto, M.; Mo, S.-K.; Hussain, Z.; Mao, Z.Q.; Chu, C.W.; Fisher, I.R.; Si, Q.; Shen, Z.-X.; Lu, D.H.

    2015-01-01

    Establishing the appropriate theoretical framework for unconventional superconductivity in the iron-based materials requires correct understanding of both the electron correlation strength and the role of Fermi surfaces. This fundamental issue becomes especially relevant with the discovery of the iron chalcogenide superconductors. Here, we use angle-resolved photoemission spectroscopy to measure three representative iron chalcogenides, FeTe0.56Se0.44, monolayer FeSe grown on SrTiO3 and K0.76Fe1.72Se2. We show that these superconductors are all strongly correlated, with an orbital-selective strong renormalization in the dxy bands despite having drastically different Fermi surface topologies. Furthermore, raising temperature brings all three compounds from a metallic state to a phase where the dxy orbital loses all spectral weight while other orbitals remain itinerant. These observations establish that iron chalcogenides display universal orbital-selective strong correlations that are insensitive to the Fermi surface topology, and are close to an orbital-selective Mott phase, hence placing strong constraints for theoretical understanding of iron-based superconductors. PMID:26204461

  8. Template-directed assembly of metal-chalcogenide nanocrystals into ordered mesoporous networks.

    SciTech Connect

    Vamvasakis, Ioannis; Subrahmanyam, Kota S.; Kanatzidis, Mercouri G.; Armatas, Gerasimos S.

    2015-04-01

    Although great progress in the synthesis of porous networks of metal and metal oxide nanoparticles with highly accessible pore surface and ordered mesoscale pores has been achieved, synthesis of assembled 3D mesostructures of metal-chalcogenide nanocrystals is still challenging. In this work we demonstrate that ordered mesoporous networks, which comprise well-defined interconnected metal sulfide nanocrystals, can be prepared through a polymer-templated oxidative polymerization process. The resulting self-assembled mesostructures that were obtained after solvent extraction of the polymer template impart the unique combination of light-emitting metal chalcogenide nanocrystals, three-dimensional open-pore structure, high surface area, and uniform pores. We show that the pore surface of these materials is active and accessible to incoming molecules, exhibiting high photocatalytic activity and stability, for instance, in oxidation of 1-phenylethanol into acetophenone. We demonstrate through appropriate selection of the synthetic components that this method is general to prepare ordered mesoporous materials from metal chalcogenide nanocrystals with various sizes and compositions.

  9. Solar System binaries

    NASA Astrophysics Data System (ADS)

    Noll, Keith S.

    The discovery of binaries in each of the major populations of minor bodies in the solar system is propelling a rapid growth of heretofore unattainable physical information. The availability of mass and density constraints for minor bodies opens the door to studies of internal structure, comparisons with meteorite samples, and correlations between bulk-physical and surface-spectral properties. The number of known binaries is now more than 70 and is growing rapidly. A smaller number have had the extensive followup observations needed to derive mass and albedo information, but this list is growing as well. It will soon be the case that we will know more about the physical parameters of objects in the Kuiper Belt than has been known about asteroids in the Main Belt for the last 200 years. Another important aspect of binaries is understanding the mechanisms that lead to their formation and survival. The relative sizes and separations of binaries in the different minor body populations point to more than one mechanism for forming bound pairs. Collisions appear to play a major role in the Main Belt. Rotational and/or tidal fission may be important in the Near Earth population. For the Kuiper Belt, capture in multi-body interactions may be the preferred formation mechanism. However, all of these conclusions remain tentative and limited by observational and theoretical incompleteness. Observational techniques for identifying binaries are equally varied. High angular resolution observations from space and from the ground are critical for detection of the relatively distant binaries in the Main Belt and the Kuiper Belt. Radar has been the most productive method for detection of Near Earth binaries. Lightcurve analysis is an independent technique that is capable of exploring phase space inaccessible to direct observations. Finally, spacecraft flybys have played a crucial paradigm-changing role with discoveries that unlocked this now-burgeoning field.

  10. Fundamental studies of chalcogenide nanocrystals, carbonaceous nanoparticles, and chromatographic materials

    NASA Astrophysics Data System (ADS)

    Baker, Jared Scott

    2011-12-01

    The development of novel nanomaterials and the understanding of their fundamental physical and chemical properties represent an exciting area of research. These materials are continuously being sought for ever-increasing applications; finding their way into uses that influence mankind on a daily basis. Combining elements from traditional nanoparticle characterization with electrophoretic-based techniques, this dissertation presents the analysis of carbon nanoparticles (CNPs) generated from a novel source (candle soot) as well as a unique perspective on the reactivity and degradation process of magic-sized cadmium chalcogenide nanocrystals. One potential application of CNPs is their use as an alternative fluorophore in a separation-based sensor system. Laser-induced-fluorescence (LIF) is a commonly used manner of detection in this type of platform, but is limited in many cases by problems associated with the fluorophore. Carbon-based nanoparticles have the potential to improve upon traditional fluorophores in applications that make use of LIF as the detection scheme. CNPs were extracted from the carbonaceous material produced by the incomplete combustion of a candle. The soot was submitted to an oxidizing treatment and extraction/filtration procedures rendering watersoluble luminescent species. Electron microscopy was used to identify globular, amorphous structures in the nanometer size-range. An aqueous suspension of CNPs demonstrated excellent stability in terms of its electronic properties, showing little change in absorption and emission spectra upon storage under ambient conditions over a two-year period. Capitalizing on the strengths of capillary electrophoresis (CE) as a characterization technique, we have analyzed the negatively-charged CNPs in terms of charge and size by studying the influence of variable CE conditions on the resulting separation. Separations at different pH revealed a highly complex mixture of CNPs, containing species with large

  11. Binary ferrihydrite catalysts

    DOEpatents

    Huffman, G.P.; Zhao, J.; Feng, Z.

    1996-12-03

    A method of preparing a catalyst precursor comprises dissolving an iron salt and a salt of an oxoanion forming agent, in water so that a solution of the iron salt and oxoanion forming agent salt has a ratio of oxoanion/Fe of between 0.0001:1 to 0.5:1. Next is increasing the pH of the solution to 10 by adding a strong base followed by collecting of precipitate having a binary ferrihydrite structure. A binary ferrihydrite catalyst precursor is also prepared by dissolving an iron salt in water. The solution is brought to a pH of substantially 10 to obtain ferrihydrite precipitate. The precipitate is then filtered and washed with distilled water and subsequently admixed with a hydroxy carboxylic acid solution. The admixture is mixed/agitated and the binary ferrihydrite precipitate is then filtered and recovered. 3 figs.

  12. Binary and Millisecond Pulsars.

    PubMed

    Lorimer, Duncan R

    2008-01-01

    We review the main properties, demographics and applications of binary and millisecond radio pulsars. Our knowledge of these exciting objects has greatly increased in recent years, mainly due to successful surveys which have brought the known pulsar population to over 1800. There are now 83 binary and millisecond pulsars associated with the disk of our Galaxy, and a further 140 pulsars in 26 of the Galactic globular clusters. Recent highlights include the discovery of the young relativistic binary system PSR J1906+0746, a rejuvination in globular cluster pulsar research including growing numbers of pulsars with masses in excess of 1.5 M⊙, a precise measurement of relativistic spin precession in the double pulsar system and a Galactic millisecond pulsar in an eccentric (e = 0.44) orbit around an unevolved companion.

  13. Binary ferrihydrite catalysts

    DOEpatents

    Huffman, Gerald P.; Zhao, Jianmin; Feng, Zhen

    1996-01-01

    A method of preparing a catalyst precursor comprises dissolving an iron salt and a salt of an oxoanion forming agent, in water so that a solution of the iron salt and oxoanion forming agent salt has a ratio of oxoanion/Fe of between 0.0001:1 to 0.5:1. Next is increasing the pH of the solution to 10 by adding a strong base followed by collecting of precipitate having a binary ferrihydrite structure. A binary ferrihydrite catalyst precursor is also prepared by dissolving an iron salt in water. The solution is brought to a pH of substantially 10 to obtain ferrihydrite precipitate. The precipitate is then filtered and washed with distilled water and subsequently admixed with a hydroxy carboxylic acid solution. The admixture is mixed/agitated and the binary ferrihydrite precipitate is then filtered and recovered.

  14. Binary catalogue of exoplanets

    NASA Astrophysics Data System (ADS)

    Schwarz, Richard; Bazso, Akos; Zechner, Renate; Funk, Barbara

    2016-02-01

    Since 1995 there is a database which list most of the known exoplanets (The Extrasolar Planets Encyclopaedia at http://exoplanet.eu/). With the growing number of detected exoplanets in binary and multiple star systems it became more important to mark and to separate them into a new database, which is not available in the Extrasolar Planets Encyclopaedia. Therefore we established an online database (which can be found at: http://www.univie.ac.at/adg/schwarz/multiple.html) for all known exoplanets in binary star systems and in addition for multiple star systems, which will be updated regularly and linked to the Extrasolar Planets Encyclopaedia. The binary catalogue of exoplanets is available online as data file and can be used for statistical purposes. Our database is divided into two parts: the data of the stars and the planets, given in a separate list. We describe also the different parameters of the exoplanetary systems and present some applications.

  15. Binary and Millisecond Pulsars.

    PubMed

    Lorimer, Duncan R

    2005-01-01

    We review the main properties, demographics and applications of binary and millisecond radio pulsars. Our knowledge of these exciting objects has greatly increased in recent years, mainly due to successful surveys which have brought the known pulsar population to over 1700. There are now 80 binary and millisecond pulsars associated with the disk of our Galaxy, and a further 103 pulsars in 24 of the Galactic globular clusters. Recent highlights have been the discovery of the first ever double pulsar system and a recent flurry of discoveries in globular clusters, in particular Terzan 5.

  16. Binary Oscillatory Crossflow Electrophoresis

    NASA Technical Reports Server (NTRS)

    Molloy, Richard F.; Gallagher, Christopher T.; Leighton, David T., Jr.

    1996-01-01

    We present preliminary results of our implementation of a novel electrophoresis separation technique: Binary Oscillatory Cross flow Electrophoresis (BOCE). The technique utilizes the interaction of two driving forces, an oscillatory electric field and an oscillatory shear flow, to create an active binary filter for the separation of charged species. Analytical and numerical studies have indicated that this technique is capable of separating proteins with electrophoretic mobilities differing by less than 10%. With an experimental device containing a separation chamber 20 cm long, 5 cm wide, and 1 mm thick, an order of magnitude increase in throughput over commercially available electrophoresis devices is theoretically possible.

  17. Identification list of binaries

    NASA Astrophysics Data System (ADS)

    Malkov,, O.; Karchevsky,, A.; Kaygorodov, P.; Kovaleva, D.

    The Identification List of Binaries (ILB) is a star catalogue constructed to facilitate cross-referencing between different catalogues of binary stars. As of 2015, it comprises designations for approximately 120,000 double/multiple systems. ILB contains star coordinates and cross-references to the Bayer/Flemsteed, DM (BD/CD/CPD), HD, HIP, ADS, WDS, CCDM, TDSC, GCVS, SBC9, IGR (and some other X-ray catalogues), PSR designations, as well as identifications in the recently developed BSDB system. ILB eventually became a part of the BDB stellar database.

  18. Beam scanning binary logic

    NASA Astrophysics Data System (ADS)

    Itoh, Hideo; Mukai, Seiji; Watanabe, Masanobu; Mori, Masahiko; Yajima, Hiroyoshi

    1990-07-01

    A beam-scanning laser diode (BSLD) is presently applied to a novel optoelectronic logic operation, designated 'beam-scanning binary logic' (BSBL), that covers the implementation of both the basic logic gates and a spatial code encoder for photodetection, while allowing a greater reduction of the number of active devices than ordinary binary logic operations. BSBL executes multifunctional logic operations simultaneously. The data connections between logic gates in BSLD are flexible, due to the ability to electrically control both output power and laser-beam direction.

  19. T Tauri Spectroscopic Binaries

    NASA Astrophysics Data System (ADS)

    Dudorov, A. E.; Eretnova, O. V.

    2017-06-01

    The Hertzsprung-Russell diagram, the excess radius-age, and the eccentricity-period relations are constructed for double-lined spectroscopic T Tauri binaries. The masses and the ages of the classical T Tauri and the weak-line T Tauri stars are compared. All components of T Tauri stars have the excess radius in comparison with initial Main Sequence stars of corresponding mass. The younger the star the more excess radius it has. The overwhelming majority of close binaries (P<10d) have eccentricity near to zero. The fraction of quadruple systems in our sample are higher than for Main Sequence stars.

  20. Binary coding for hyperspectral imagery

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Chang, Chein-I.; Chang, Chein-Chi; Lin, Chinsu

    2004-10-01

    Binary coding is one of simplest ways to characterize spectral features. One commonly used method is a binary coding-based image software system, called Spectral Analysis Manager (SPAM) for remotely sensed imagery developed by Mazer et al. For a given spectral signature, the SPAM calculates its spectral mean and inter-band spectral difference and uses them as thresholds to generate a binary code word for this particular spectral signature. Such coding scheme is generally effective and also very simple to implement. This paper revisits the SPAM and further develops three new SPAM-based binary coding methods, called equal probability partition (EPP) binary coding, halfway partition (HP) binary coding and median partition (MP) binary coding. These three binary coding methods along with the SPAM well be evaluated for spectral discrimination and identification. In doing so, a new criterion, called a posteriori discrimination probability (APDP) is also introduced for performance measure.

  1. Eclipsing Binary Update, No. 2.

    NASA Astrophysics Data System (ADS)

    Williams, D. B.

    1996-01-01

    Contents: 1. Wrong again! The elusive period of DHK 41. 2. Stars observed and not observed. 3. Eclipsing binary chart information. 4. Eclipsing binary news and notes. 5. A note on SS Arietis. 6. Featured star: TX Ursae Majoris.

  2. Wide-angle stop-gap chalcogenide photonic crystals generated by direct multiple-line laser writing

    NASA Astrophysics Data System (ADS)

    Nicoletti, E.; Bulla, D.; Luther-Davies, B.; Gu, M.

    2011-12-01

    We present the fabrication and the angle-resolved optical characterizations of three-dimensional chalcogenide photonic crystals with a wide-angle stop gap. Multiple-line scanning provides an effective remedy to the elongation of the focal spot in the z direction during direct laser writing fabrication in high refractive index and highly nonlinear chalcogenide glasses. The aspect ratio of the rods is reduced from 4.46 to 1.53, thus allowing the successful fabrication of three-dimensional chalcogenide photonic crystals with a face-centered cubic symmetry and quasi-circular rods. Suppression of the angle-resolved transmission spectra is observed at a wide range of incident angles.

  3. Investigation of As40Se60 chalcogenide glass in precision glass molding for high-volume thermal imaging lenses

    NASA Astrophysics Data System (ADS)

    Huddleston, Jeremy; Novak, Jacklyn; Moreshead, William V.; Symmons, Alan; Foote, Edward

    2015-05-01

    The growing demand for thermal imaging sensors and cameras has focused attention on the need for larger volumes of lower cost optics in this infrared region. A major component of the cost of thermal imaging lenses is the germanium content. As40Se60 was developed as a moldable, germanium-free chalcogenide glass that can serve as a low cost alternative to germanium and other infrared materials. This material also has promising characteristics for improved optical performance, especially with regard to reduced thermal sensitivity. As40Se60 has found acceptance as a material to be diamond turned or polished, but it is only now emerging as a legitimate candidate for precision glass molding. This paper will review chalcogenide molding and characterize As40Se60 for widespread use in highvolume thermal imaging optics. The relative advantages and disadvantages of As40Se60 as compared to other chalcogenide glasses will also be discussed.

  4. Separation in Binary Alloys

    NASA Technical Reports Server (NTRS)

    Frazier, D. O.; Facemire, B. R.; Kaukler, W. F.; Witherow, W. K.; Fanning, U.

    1986-01-01

    Studies of monotectic alloys and alloy analogs reviewed. Report surveys research on liquid/liquid and solid/liquid separation in binary monotectic alloys. Emphasizes separation processes in low gravity, such as in outer space or in free fall in drop towers. Advances in methods of controlling separation in experiments highlighted.

  5. Orbits For Sixteen Binaries

    NASA Astrophysics Data System (ADS)

    Cvetkovic, Z.; Novakovic, B.

    2006-12-01

    In this paper orbits for 13 binaries are recalculated and presented. The reason is that recent observations show higher residuals than the corresponding ephemerides calculated by using the orbital elements given in the Sixth Catalog of Orbits of Visual Binary Stars. The binaries studied were: WDS 00182+7257 = A 803, WDS 00335+4006 = HO 3, WDS 00583+2124 = BU 302, WDS 01011+6022 = A 926, WDS 01014+1155 = BU 867, WDS 01112+4113 = A 655, WDS 01361-2954 + HJ 3447, WDS 02333+5219 = STT 42 AB, WDS 04362+0814 = A 1840 AB, WDS 08017-0836 = A 1580, WDS 08277-0425 = A 550, WDS 17471+1742 = STF 2215 and WDS 18025+4414 = BU 1127 Aa-B. In addition, for three binaries - WDS 01532+1526 = BU 260, WDS 02563+7253 =STF 312 AB and WDS 05003+3924 = STT 92 AB - the orbital elements are calculated for the first time. In this paper the authors present not only the orbital elements, but the masses, dynamical parallaxes, absolute magnitudes and ephemerides for the next five years, as well.

  6. Structure and Properties of Modified and Charge-Compensated Chalcogenide Glasses in the Na/Ba-Ga-Ge Selenide System

    NASA Astrophysics Data System (ADS)

    Mao, Alvin W.

    Se, and consequently the removal of Ge-Ge bonds. This observation was ascribed instead to the formation of Ba-Se bonds, which are associated with a lower bandgap compared to the (Ga/Ge)-Se bonds that they replace. Finally, there is no straightforward structural explanation for trends in fragility, because it is related to the number of structural configurations dynamically available to the supercooled liquid. In the binary Ga2Se3--GeSe2 glasses, the fragility tends to increase with the formation of homopolar Ge-Ge bonds, which is consistent with other chalcogenide systems in which fragility increases with the removal of heteropolar bonds within corner-sharing tetrahedra and pyramids. In the stoichiometric BaSe--Ga2Se3--GeSe2 glasses on the other hand, a shift in trend near the compositions where BaSe:Ga 2Se3 = 1 coincides with a structural shift between the formation of Ge-Ge bonds and Se-Se/non-bridging Se.

  7. Planetary systems in binaries

    NASA Astrophysics Data System (ADS)

    Takeda, Genya

    In this thesis we investigate the orbital evolution of planets in binaries. Unlike our own Solar System, at least one out of five planetary systems known to date is associated with additional stellar companions. Despite their large distances from the planetary systems, these stellar companions play an important role in significantly altering the planetary architecture over very long timescales. Most of the planets in binaries are found in hierarchical configurations in which a planet orbits around a component of a wide stellar binary. The evolution of such hierarchical triples has been analytically understood through the framework of the Kozai mechanism, in which the orbital eccentricity of a planet secularly grows through angular momentum exchange with the stellar companion. The aim of our first study is to investigate the global effect of stellar companions in exciting planetary eccentricities through the Kozai mechanism, using synthetic eccentricity distributions computed numerically from various initial assumptions motivated by observational studies. As inferred from observations and theoretical planet formation simulations, newly formed planetary systems are more likely to be oligarchic, containing multiple giant planets. However, the long-term evolution of gravitationally coupled planets perturbed by a stellar companion has been little understood in the previous studies. From a large ensemble of numerical integrations of double-planet systems in binaries, we have found that there are various evolutionary classes of multiple planets in binaries compared to simple hierarchical triple systems containing only one planet. Using the Kozai mechanism and the Laplace-Lagrange secular theory, we also provide analytic criteria that can readily predict the secular evolutionary behavior of a pair of planetary orbits in binaries. In the last part of this thesis we discuss an alternative channel of planetary migration induced by a combined effect of dissipative tidal forces

  8. Correlated binary regression with covariates specific to each binary observation.

    PubMed

    Prentice, R L

    1988-12-01

    Regression methods are considered for the analysis of correlated binary data when each binary observation may have its own covariates. It is argued that binary response models that condition on some or all binary responses in a given "block" are useful for studying certain types of dependencies, but not for the estimation of marginal response probabilities or pairwise correlations. Fully parametric approaches to these latter problems appear to be unduly complicated except in such special cases as the analysis of paired binary data. Hence, a generalized estimating equation approach is advocated for inference on response probabilities and correlations. Illustrations involving both small and large block sizes are provided.

  9. Astrometric Binaries: White Dwarfs?

    NASA Astrophysics Data System (ADS)

    Oliversen, Nancy A.

    We propose to observe a selection of astrometric or spectroscopicastrometric binaries nearer than about 20 pc with unseen low mass companions. Systems of this type are important for determining the luminosity function of low mass stars (white dwarfs and very late main sequence M stars), and their contribution to the total mass of the galaxy. Systems of this type are also important because the low mass, invisible companions are potential candidates in the search for planets. Our target list is selected primarily from the list of 31 astrometric binaries near the sun by Lippincott (1978, Space Sci. Rev., 22, 153), with additional candidates from recent observations by Kamper. The elimination of stars with previous IUE observations, red companions resolved by infrared speckle interferometry, or primaries later than M1 (because if white dwarf companions are present they should have been detected in the visible region) reduces the list to 5 targets which need further information. IUE SWP low dispersion observations of these targets will show clearly whether the remaining unseen companions are white dwarfs, thus eliminating very cool main sequence stars or planets. This is also important in providing complete statistical information about the nearest stars. The discovery of a white dwarf in such a nearby system would provide important additional information about the masses of white dwarfs. Recent results by Greenstein (1986, A. J., 92, 859) from binary systems containing white dwarfs imply that 80% of such systems are as yet undetected. The preference of binaries for companions of approximately equal mass makes the Lippincott-Kamper list of A through K primaries with unseen companions a good one to use to search for white dwarfs. The mass and light dominance of the current primary over the white dwarf in the visible makes ultraviolet observations essential to obtain an accurate census of white dwarf binaries.

  10. Learning to assign binary weights to binary descriptor

    NASA Astrophysics Data System (ADS)

    Huang, Zhoudi; Wei, Zhenzhong; Zhang, Guangjun

    2016-10-01

    Constructing robust binary local feature descriptors are receiving increasing interest due to their binary nature, which can enable fast processing while requiring significantly less memory than their floating-point competitors. To bridge the performance gap between the binary and floating-point descriptors without increasing the computational cost of computing and matching, optimal binary weights are learning to assign to binary descriptor for considering each bit might contribute differently to the distinctiveness and robustness. Technically, a large-scale regularized optimization method is applied to learn float weights for each bit of the binary descriptor. Furthermore, binary approximation for the float weights is performed by utilizing an efficient alternatively greedy strategy, which can significantly improve the discriminative power while preserve fast matching advantage. Extensive experimental results on two challenging datasets (Brown dataset and Oxford dataset) demonstrate the effectiveness and efficiency of the proposed method.

  11. Digital Transfer Growth of Patterned 2D Metal Chalcogenides by Confined Nanoparticle Evaporation

    DOE PAGES

    Mahjouri-Samani, Masoud; Tian, Mengkun; Wang, Kai; ...

    2014-10-19

    Developing methods for the facile synthesis of two-dimensional (2D) metal chalcogenides and other layered materials is crucial for emerging applications in functional devices. Controlling the stoichiometry, number of the layers, crystallite size, growth location, and areal uniformity is challenging in conventional vapor phase synthesis. Here, we demonstrate a new route to control these parameters in the growth of metal chalcogenide (GaSe) and dichalcogenide (MoSe2) 2D crystals by precisely defining the mass and location of the source materials in a confined transfer growth system. A uniform and precise amount of stoichiometric nanoparticles are first synthesized and deposited onto a substrate bymore » pulsed laser deposition (PLD) at room temperature. This source substrate is then covered with a receiver substrate to form a confined vapor transport growth (VTG) system. By simply heating the source substrate in an inert background gas, a natural temperature gradient is formed that evaporates the confined nanoparticles to grow large, crystalline 2D nanosheets on the cooler receiver substrate, the temperature of which is controlled by the background gas pressure. Large monolayer crystalline domains (~ 100 m lateral sizes) of GaSe and MoSe2 are demonstrated, as well as continuous monolayer films through the deposition of additional precursor materials. This novel PLD-VTG synthesis and processing method offers a unique approach for the controlled growth of large-area, metal chalcogenides with a controlled number of layers in patterned growth locations for optoelectronics and energy related applications.« less

  12. Optical sampling of ultrahigh bitrate signals using highly nonlinear chalcogenide planar waveguides or tapered fibers

    NASA Astrophysics Data System (ADS)

    Van Erps, Jürgen; Luan, Feng; Pelusi, Mark D.; Mägi, Eric; Iredale, Tim; Madden, Steve; Choi, Duk Yong; Bulla, Douglas A.; Luther-Davies, Barry; Thienpont, Hugo; Eggleton, Benjamin J.

    2010-06-01

    As the bit rates of optical networks increase, the ability of accurate monitoring of optical waveforms has become increasingly important. In recent years, optical sampling has emerged as a technique to perform time-resolved measurements of optical data signals at high data rates with a bandwidth that cannot be reached by conventional photodetectors and oscilloscopes. In an optical sampling system, the optical signal is sampled in the optical domain by a nonlinear optical sampling gate before the resulting samples are converted to an electrical signal. This avoids the need for high bandwidth electronics if the optical sampling gate is operated with a modest repetition frequency. In this paper, we present an optical sampling system using the optical Kerr effect in a highly nonlinear chalcogenide device, enabling combined capability for femtosecond resolution and broadband signal wavelength tunability. A temporal resolution 450-fs is achieved using four-wave mixing (FWM) in dispersion-engineered chalcogenide waveguides: on one hand a 7-cm long planar waveguide (integrated on a photonic chip) and on the other hand a 5-cm long tapered fiber. The use of a short length, dispersion-shifted waveguide with ultrahigh nonlinearity (10000/W/km) enables high-resolution optical sampling without the detrimental effect of chromatic dispersion on the temporal distortion of the signal and sampling pulses, as well as their phase mismatch (which in turn would degrade the FWM efficiency and the sensitivity of the measurement). Using these chalcogenide devices, we successfully monitor a 640-Gb/s optical time-division multiplexing (OTDM) datastream, showcasing its potential for monitoring of signals at bitrates approaching and beyond Tb/s. We compare the advantages and disadvantages of both approaches and discuss fundamental limitations as well as potential improvements.

  13. Frequency dependent electrical measurements of amorphous GeSbSe chalcogenide thin films

    SciTech Connect

    Mirsaneh, M.; Furman, E.; Ryan, Joseph V.; Lanagan, M. T.; Pantano, C. G.

    2010-03-22

    A commercial bulk chalcogenide glass (Ge28Sb12Se60) was used as a source to fabricate amorphous thin films via thermal evaporation technique. At low frequencies (1 MHz) impedance spectroscopy was performed to measure electrical properties. To measure ac conductivity at microwave frequencies, a split resonance cavity technique was applied for which a model based on parallel arrangement of substrate and film capacitors was developed. This model was used to extract tan8 and ac conductivity of the films. Microwave ac conductivity was correlated with the extrapolated low frequency conductivity data confirming applicability of the universal law commonly observed in amorphous semiconductors.

  14. Single-mode low-loss chalcogenide glass waveguides for the mid-infrared.

    PubMed

    Hô, Nicolas; Phillips, Mark C; Qiao, Hong; Allen, Paul J; Krishnaswami, Kannan; Riley, Brian J; Myers, Tanya L; Anheier, Norman C

    2006-06-15

    We demonstrate the design, fabrication, and characterization of single-mode low-loss waveguides for mid-infrared (MIR) wavelengths. Planar waveguide structures were fabricated from multilayer thin films of arsenic-based chalcogenide glasses followed by the creation of channel waveguides by using the photodarkening effect. Propagation losses as low as 0.5 dB/cm were measured for a quantum cascade laser end-fire coupled into the waveguides. This is a first step toward the design and fabrication of integrated optical components for MIR applications.

  15. Supercontinuum generation in the normal dispersion regime using chalcogenide double-clad fiber

    NASA Astrophysics Data System (ADS)

    Nagasaka, Kenshiro; Hoang Tuan, Tong; Cheng, Tonglei; Matsumoto, Morio; Tezuka, Hiroshige; Suzuki, Takenobu; Ohishi, Yasutake

    2017-03-01

    We experimentally demonstrate mid-infrared (MIR) supercontinuum (SC) generation in a 2.8-cm-long chalcogenide double-clad fiber (Ch-DCF). The Ch-DCF made of As2Se3, AsSe2, and As2S5 glasses has near-zero chromatic dispersion in the normal dispersion regime. We pump the Ch-DCF using a 200 fs pulse laser at 10 µm, and obtain MIR SC extending from 2 to 14 µm. Numerical results show that the Ch-DCF has the potential of generating a highly coherent MIR SC light source.

  16. Relaxation dynamics in the strong chalcogenide glass-former of Ge22Se78

    NASA Astrophysics Data System (ADS)

    Li, Pengfei; Zhang, Yaqi; Chen, Zeming; Gao, Peng; Wu, Tao; Wang, Li-Min

    2017-01-01

    The enthalpy relaxation is performed in the glassy Ge22Se78 to understand the dynamic behaviors. The structure of the glass is examined by X-ray diffraction and Raman spectra. The dynamic parameters such as the fragility, stretching exponent and non-linear factor are determined. A low fragility of m = 27 is exhibited for the chalcogenide, however, the stretching exponent is found not to have a larger value. The enthalpy relaxation spectra are constructed for various glass formers, and a relationship between the fragility and the symmetry of the spectra is demonstrated. The dynamic results are used to evaluate the structure of the Ge22Se78 glass.

  17. Stability analysis of IV-V-VI chalcogenide glasses using glass transition and crystallization temperature

    NASA Astrophysics Data System (ADS)

    Sharma, Neha; Sharda, Sunanda; Sharma, Vineet; Sharma, Pankaj

    2013-06-01

    Selenium based chalcogenide glasses are attractive candidates for IR devices due to their low transmission loss. Thermal studies for Ge19Se81-xSbx (x = 0, 4, 8, 12, 16, 17.2, 20) have been carried out using differential thermal analysis. Glass transition temperature has been calculated using Tanaka's relation. Marseglia's and Ozawa's methods have been used for the calculation of activation energy for crystallization. Effect of Sb addition on GeSe base system shows that resistance to devitrification increases up to x = 17.2.

  18. Specific features of utilizing bismuth antimony chalcogenide single crystals in miniature coolers

    SciTech Connect

    Semenyuk, V.A.; Ivanova, L.D.; Svechnikova, T.E.

    1995-01-01

    A procedure for growing perfect single crystals of bismuth antimony chalcogenide solid solutions by the Czochralski technique with melt feeding from a floating crucible was developed at the Baikov Institute of Metallurgy. Given that the single crystals in question readily split along the cleavage planes, the problem of acceptable yield of suitable products in the manufacture of thermoelements and cooling modules arises. To solve this problem, investigations were undertaken along two lines: (1) development of nondestructive, damage-free technologies; and (2) development of methods for making low-resistance antidiffusion contacts on the end faces of the thermoelements.

  19. Chalcogenide double index fibers: fabrication, design, and application as a chemical sensor

    SciTech Connect

    Le Coq, D.; Boussard-Pledel, C.; Fonteneau, G.; Pain, T.; Bureau, B.; Adam, J.L

    2003-10-30

    Double index chalcogenide fibers, based on tellurium, arsenic, and selenium, have been made by an original technique. This technique, based on the build-in-casting method, is achieved in a sealed silica ampoule. In view of the low attenuation obtained in the mid-infrared (IR), these fibers are used to implement Fiber Evanescent Wave Spectroscopy (FEWS). As the IR light is only propagated through the core of the waveguide, a chemical etching is applied in order to remove the glassy cladding of the sensing zone. IR spectra of ethanol and chloroform, recorded with such sensor, are presented showing the high sensitivity of the method.

  20. Demonstration of high-Q mid-infrared chalcogenide glass-on-silicon resonators.

    PubMed

    Lin, Hongtao; Li, Lan; Zou, Yi; Danto, Sylvain; Musgraves, J David; Richardson, Kathleen; Kozacik, Stephen; Murakowski, Maciej; Prather, Dennis; Lin, Pao T; Singh, Vivek; Agarwal, Anu; Kimerling, Lionel C; Hu, Juejun

    2013-05-01

    We demonstrated high-index-contrast, waveguide-coupled As2Se3 chalcogenide glass resonators monolithically integrated on silicon fabricated using optical lithography and a lift-off process. The resonators exhibited a high intrinsic quality factor of 2×10(5) at 5.2 μm wavelength, which is among the highest values reported in on-chip mid-infrared (mid-IR) photonic devices. The resonator can serve as a key building block for mid-IR planar photonic circuits.

  1. Adaptive optics enhanced direct laser writing of high refractive index gyroid photonic crystals in chalcogenide glass.

    PubMed

    Cumming, Benjamin P; Turner, Mark D; Schröder-Turk, Gerd E; Debbarma, Sukanta; Luther-Davies, Barry; Gu, Min

    2014-01-13

    Chiral gyroid photonic crystals are fabricated in the high refractive index chalcogenide glass arsenic trisulfide with an adaptive optics enhanced direct laser writing system. The severe spherical aberration imparted when focusing into the arsenic trisulfide is mitigated with a defocus decoupled aberration compensation technique that reduces the level of aberration that must be compensated by over an order of magnitude. The fabricated gyroids are shown to have excellent uniformity after our adaptive optics method is employed, and the transmission spectra of the gyroids are shown to have good agreement with numerical simulations that are based on a uniform and diffraction limited fabrication resolution.

  2. An ab initio study of the electronic structure of indium and gallium chalcogenide bilayers.

    PubMed

    Ayadi, T; Debbichi, L; Said, M; Lebègue, S

    2017-09-21

    Using first principle calculations, we have studied the structural and electronic properties of two dimensional bilayers of indium and gallium chalcogenides. With density functional theory corrected for van der Waals interactions, the different modes of stacking were investigated in a systematic way, and several of them were found to compete in energy. Then, their band structures were obtained with the GW approximation and found to correspond to indirect bandgap semiconductors with a small dependency on the mode of stacking. Finally, by analysing the electron density, it appeared that GaSe-InS is a promising system for electron-hole separation.

  3. Analysis of spectral response of optical switching devices based on chalcogenide bistable fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Scholtz, Lubomír.; Müllerová, Jarmila

    2015-01-01

    Fiber Bragg gratings (FBGs) are novel and promising devices for all-optical switching, ADD/DROP multiplexers, AND gates, switches, all-optical memory elements. Optical switching based on optical Kerr effects induced with high pump laser light incident on the FBGs cause the change of spectral characteristics of grating depending on the incident power. In this paper numerical studies of the nonlinear FBGs are presented. Optical switching based on the optical bistability in nonlinear chalcogenide FBGs is investigated. The spectral response of nonlinear FBGs is discussed from theoretical viewpoint. The simulations are based on the nonlinear coupled mode theory.

  4. The electronic structure of the antimony chalcogenide series: Prospects for optoelectronic applications

    SciTech Connect

    Carey, John J.; Allen, Jeremy P.; Scanlon, David O.; Watson, Graeme W.

    2014-05-01

    In this study, density functional theory is used to evaluate the electronic structure of the antimony chalcogenide series. Analysis of the electronic density of states and charge density shows that asymmetric density, or ‘lone pairs’, forms on the Sb{sup III} cations in the distorted oxide, sulphide and selenide materials. The asymmetric density progressively weakens down the series, due to the increase in energy of valence p states from O to Te, and is absent for Sb{sub 2}Te{sub 3}. The fundamental and optical band gaps were calculated and Sb{sub 2}O{sub 3}, Sb{sub 2}S{sub 3} and Sb{sub 2}Se{sub 3} have indirect band gaps, while Sb{sub 2}Te{sub 3} was calculated to have a direct band gap at Γ. The band gaps are also seen to reduce from Sb{sub 2}O{sub 3} to Sb{sub 2}Te{sub 3}. The optical band gap for Sb{sub 2}O{sub 3} makes it a candidate as a transparent conducting oxide, while Sb{sub 2}S{sub 3} and Sb{sub 2}Se{sub 3} have suitable band gaps for thin film solar cell absorbers. - Graphical abstract: A schematic illustrating the interaction between the Sb{sup III} cations and the chalcogenide anions and the change in their respective energy levels down the series. - Highlights: • The electronic structure of the antimony chalcogenide series is modelled using DFT. • Asymmetric density is present on distorted systems and absent on the symmetric telluride system. • Asymmetric density is formed from the mixing of Sb 5s and anion p states, where the anti-bonding combination is stabilised by the Sb 5p states. • The asymmetric density weakens down the series due to the increase in energy of chalcogenide p states. • The increase in energy of the anion p states reduces the fundamental and optical band gaps.

  5. Structural and optical investigation of Te-based chalcogenide thin films

    NASA Astrophysics Data System (ADS)

    Sharma, Rita; Sharma, Shaveta; Chander, Ravi; Kumar, Praveen; Thangaraj, R.; Mian, M.

    2015-05-01

    We report the structural and optical properties of thermally evaporated Bi2Te3, In2Te3 and InBiTe3 films by using X-ray diffraction, optical and Raman Spectroscopy techniques. The as-prepared thin films were found to be Semi-crystalline by X-ray diffraction. Particle Size and Strain has been calculated from XRD data. The optical constants, film thickness, refractive index and optical band gap (Eg) has been reported for In2Te3, InBiTe3 films. Raman Spectroscopy was performed to investigate the effect of Bi, In, on lattice vibration and chemical bonding in Te based chalcogenide glassy alloys.

  6. Two-Dimensional Metal–Chalcogenide Films in Tunable Optical Microcavities

    PubMed Central

    2014-01-01

    Integration of quasi-two-dimensional (2D) films of metal–chalcogenides in optical microcavities permits new photonic applications of these materials. Here we present tunable microcavities with monolayer MoS2 or few monolayer GaSe films. We observe significant modification of spectral and temporal properties of photoluminescence (PL): PL is emitted in spectrally narrow and wavelength-tunable cavity modes with quality factors up to 7400; a 10-fold PL lifetime shortening is achieved, a consequence of Purcell enhancement of the spontaneous emission rate. PMID:25375802

  7. Second-order Bragg gratings in single-mode chalcogenide fibres

    SciTech Connect

    Bernier, M; Asatryan, K E; Vallee, R; Galstian, T M; Vasil'ev, Sergei A; Medvedkov, O I; Plotnichenko, V G; Gnusin, P I; Dianov, Evgenii M

    2011-05-31

    Bragg gratings with a second-order resonance wavelength in the near-IR spectral region have been inscribed into single-mode chalcogenide (As{sub 2}S{sub 3}) glass fibre by a He - Ne laser beam using a configuration typical of Bragg grating fabrication in germanosilicate fibre, with the use of a phase mask that ensures effective diffraction of the writing light into the +1 and -1 orders. The spectra of the inscribed gratings show no resonances due to cladding mode excitation because the cladding material is photosensitive. (fibre optics)

  8. An ab initio study of the electronic structure of indium and gallium chalcogenide bilayers

    NASA Astrophysics Data System (ADS)

    Ayadi, T.; Debbichi, L.; Said, M.; Lebègue, S.

    2017-09-01

    Using first principle calculations, we have studied the structural and electronic properties of two dimensional bilayers of indium and gallium chalcogenides. With density functional theory corrected for van der Waals interactions, the different modes of stacking were investigated in a systematic way, and several of them were found to compete in energy. Then, their band structures were obtained with the GW approximation and found to correspond to indirect bandgap semiconductors with a small dependency on the mode of stacking. Finally, by analysing the electron density, it appeared that GaSe-InS is a promising system for electron-hole separation.

  9. Chalcogenide glasses for infrared applications: New synthesis routes and rare earth doping

    NASA Astrophysics Data System (ADS)

    Hubert, Mathieu

    Chalcogenide glasses and glass-ceramics present a high interest for the production of thermal imaging lenses transparent in the 3--5 microm and 8--12 microm windows. However, chalcogenide glasses are conventionally synthesized utilizing expensive and single use silica ampoules sealed under vacuum. The present work addresses the development of innovative synthesis methods for chalcogenide glasses that can present an alternative to the silica tube route. The first approach assessed by melting the raw starting elements in reusable silica containers appears inadequate for synthesis of glasses from the system Ge-Ga-Se. The second synthesis approach consists of the preparation of amorphous chalcogenide powders by ball milling of raw elements (mechanosynthesis) followed by consolidation of the as-prepared powders. Hot Uniaxial Pressing is suitable for sintering of powders with compositions stable against crystallization but uncontrolled crystallization occurs for the unstable compositions. In contrast, consolidation through Spark Plasma Sintering (SPS) allows production of bulk glasses with large dimensions in a short duration and at relatively low temperatures. Moreover, increased SPS treatment duration yields infrared transparent glass-ceramics with enhanced mechanical properties. This innovative synthesis method combining mechanosynthesis and SPS has been patented in the framework if this study. The controlled etching of 80GeSe2-20Ga2Se 3 glass-ceramics in acid solution yields nanoporous materials with enhanced surface area. The porous layer created on the surface of the glass-ceramic plays the role of anti-reflection coating and increases the optical transmission in the infrared range by 10%. These materials present potential for the production of sensors with increased sensitivity. The influence of indium and lead addition on the thermal and optical properties of the 80GeSe2-20Ga2Se3 glass is also assessed. Increased In or Pb contents tend to decrease the Tg and

  10. Chemical bonding topology of superconductors. 1. Ternary molybdenum chalcogenides (Chevrel phases)

    NASA Astrophysics Data System (ADS)

    King, R. B.

    1987-03-01

    Models for the chemical bonding topologies of ternary molybdenum chalcogenides (Chevrel phases) are derived using methods based on graph theory. The molybdenum sulfite Chevrel phases as well as their selenium analogs are viewed as three-dimensional lattices of edge-localized discrete molybdenum octahedra through face-sharing leads successively to the Mo9S11 napthalene analog and the Mo12S14 anathracene analog with increasing fusion leading to increasing delocalization of the chemical bonding topology within individual molybdenum cluster units. The infinite limit of such fusion of molybdenum octahedra corresponds to the infinite chain pseudo-one-dimensional metals which are formulated with globally delocalized octahedral cavities.

  11. Applications of highly nonlinear chalcogenide glass fibers in ultrafast all-optical switches

    SciTech Connect

    Asobe, Masaki ); Kanamori, Terutoshi ); Kubodera, Ken'ichi )

    1993-08-01

    The authors report applications of chalcogenide glass fibers in ultrafast all-optical switches. The switching performance is studied with optical Kerr shutter experiments and through calculation analysis taking the effect of group velocity dispersion and two-photon absorption into account. The nonlinear refractive index of the As[sub 2]S[sub 3]-based glass is estimated to be n[sub 2] = 4.0 [times] 10[sup [minus]14](sm[sup 2]/W), which is higher by two orders of magnitude than silica glass fiber. They also discuss the capabilities of low power switching.

  12. Reactive ion etching of tellurite and chalcogenide waveguides using hydrogen, methane, and argon

    SciTech Connect

    Vu, K. T.; Madden, S. J.

    2011-01-15

    The authors report in detail on the reactive plasma etching properties of tellurium and demonstrate a high quality etching process using hydrogen, methane, and argon. Very low loss planar ridge waveguides are demonstrated. Optical losses in tellurium dioxide waveguides below 0.1 dB/cm in most of the near infrared region of the electromagnetic spectrum and at 1550 nm have been achieved--the lowest ever reported by more than an order of magnitude and clearly suitable for planar integrated devices. The etch process is also shown to be suitable for chalcogenide glasses which may be of importance in applications such as phase change memory devices and nonlinear integrated optics.

  13. Electron transport in some transition metal di-chalcogenides: MoS2 and WS2

    NASA Astrophysics Data System (ADS)

    Ferry, D. K.

    2017-08-01

    The transition metal di-chalcogenides are promising single monolayer materials that hold promise for applications in several fields, including nanoelectronics. Here, I study the transport of electrons in two of these materials, MoS2 and WS2. While the low-field behavior shows very low mobility, due mostly to impurity scattering, the high-field behavior shows a relatively high saturated velocity and a high breakdown field. Complications arise due to the relative narrowness of the conduction band, and the effect of this on the transport is discussed.

  14. Solution based approach for the fabrication of photonic devices in chalcogenide glasses

    SciTech Connect

    Prince, Raman, Swati; Dwivedi, Prabhat K.; Zulfequar, M.; Husain, M.

    2015-06-24

    In this report, we describe the solution preparation conditions of various chalcogenide glasses. The dissolution mechanism of (As{sub 2}S{sub 3}){sub 60}Ge{sub 40}, (As{sub 2}S{sub 3}){sub 60}Se{sub 40} in ethanolamine is studied. Dynamic light scattering (DLS)measurements confirms that the particles in suspension are <10 nm in all the solutions.Prepared solutions are shown to possess similar molecular structure to the parent bulk glasses. Optical properties of the prepared solution are also discussed.

  15. Theory of Two-Magnon Raman Scattering in Iron Pnictides and Chalcogenides

    SciTech Connect

    Chen, C. C.

    2011-08-15

    Although the parent iron-based pnictides and chalcogenides are itinerant antiferromagnets, the use of local moment picture to understand their magnetic properties is still widespread. We study magnetic Raman scattering from a local moment perspective for various quantum spin models proposed for this new class of superconductors. These models vary greatly in the level of magnetic frustration and show a vastly different two-magnon Raman response. Light scattering by two-magnon excitations thus provides a robust and independent measure of the underlying spin interactions. In accord with other recent experiments, our results indicate that the amount of magnetic frustration in these systems may be small.

  16. Enhancing light emission efficiency without color change in post-transition metal chalcogenides

    NASA Astrophysics Data System (ADS)

    Wang, Cong; Yang, Shengxue; Cai, Hui; Ataca, Can; Chen, Hui; Zhang, Xinzheng; Xu, Jingjun; Chen, Bin; Wu, Kedi; Zhang, Haoran; Liu, Luqi; Li, Jingbo; Grossman, Jeffrey C.; Tongay, Sefaattin; Liu, Qian

    2016-03-01

    Two-dimensional (2D) materials can take a large amount of mechanical deformation before reaching the fracture limit due to their high Young's modulus, and this in return, provides a way to tune the properties of 2D materials by strain engineering. Previous works have shown that the optical band gap of transition metal chalcogenides (TMDs) can be modulated by strain, resulting in a drift of the photoluminescence (PL) peak position and a decrease (or little change) in PL intensity. Here, we report a member of the post-transition metal chalcogenides (PTMCs), 2D-GaSe sheets, displaying vastly different phenomena under strain. Strained 2D-GaSe emits photons at almost the same wavelength as unstrained material but appears an order of magnitude brighter. In contrast to TMDs, optical spectroscopy measurements reveal that changes in the optical properties are mostly related to the colossal optical absorption anisotropy of GaSe, instead of commonly accepted strain-induced band renormalization. Results suggest that the light-matter interaction and the optical properties of 2D-GaSe can be controlled at will by manipulating the optical absorption.Two-dimensional (2D) materials can take a large amount of mechanical deformation before reaching the fracture limit due to their high Young's modulus, and this in return, provides a way to tune the properties of 2D materials by strain engineering. Previous works have shown that the optical band gap of transition metal chalcogenides (TMDs) can be modulated by strain, resulting in a drift of the photoluminescence (PL) peak position and a decrease (or little change) in PL intensity. Here, we report a member of the post-transition metal chalcogenides (PTMCs), 2D-GaSe sheets, displaying vastly different phenomena under strain. Strained 2D-GaSe emits photons at almost the same wavelength as unstrained material but appears an order of magnitude brighter. In contrast to TMDs, optical spectroscopy measurements reveal that changes in the optical

  17. NEA rotations and binaries

    NASA Astrophysics Data System (ADS)

    Pravec, Petr; Harris, A. W.; Warner, B. D.

    2007-05-01

    Of nearly 3900 near-Earth asteroids known in June 2006, 325 have got estimated rotation periods. NEAs with sizes down to 10 meters have been sampled. Observed spin distribution shows a major changing point around D=200 m. Larger NEAs show a barrier against spin rates >11 d-1 (period P~2.2 h) that shifts to slower rates with increasing equatorial elongation. The spin barrier is interpreted as a critical spin rate for bodies held together by self-gravitation only, suggesting that NEAs larger than 200 m are mostly strenghtless bodies (i.e., with zero tensile strength), so called `rubble piles'. The barrier disappears at D<200 m where most objects rotate too fast to be held together by self-gravitation only, so a non-zero cohesion is implied in the smaller NEAs. The distribution of NEA spin rates in the `rubble pile' range (D>0.2 km) is non-Maxwellian, suggesting that other mechanisms than just collisions worked there. There is a pile up in front of the barrier (P of 2-3 h). It may be related to a spin up mechanism crowding asteroids to the barrier. An excess of slow rotators is seen at P>30 h. The spin-down mechanism has no clear lower limit on spin rate; periods as long as tens of days occur. Most NEAs appear to be in basic spin states with rotation around the principal axis. Excited rotations are present among and actually dominate in slow rotators with damping timescales >4.5 byr. A few tumblers observed among fast rotating coherent objects consistently appear to be more rigid or younger than the larger, rubble-pile tumblers. An abundant population of binary systems among NEAs has been found. The fraction of binaries among NEAs larger than 0.3 km has been estimated to be 15 +/-4%. Primaries of the binary systems concentrate at fast spin rates (periods 2-3 h) and low amplitudes, i.e., they lie just below the spin barrier. The total angular momentum content in the binary systems suggests that they formed at the critical spin rate, and that little or no angular

  18. Microfluidic binary phase flow

    NASA Astrophysics Data System (ADS)

    Angelescu, Dan; Menetrier, Laure; Wong, Joyce; Tabeling, Patrick; Salamitou, Philippe

    2004-03-01

    We present a novel binary phase flow regime where the two phases differ substantially in both their wetting and viscous properties. Optical tracking particles are used in order to investigate the details of such multiphase flow inside capillary channels. We also describe microfluidic filters we have developed, capable of separating the two phases based on capillary pressure. The performance of the filters in separating oil-water emulsions is discussed. Binary phase flow has been previously used in microchannels in applications such as emulsion generation, enhancement of mixing and assembly of custom colloidal paticles. Such microfluidic systems are increasingly used in a number of applications spanning a diverse range of industries, such as biotech, pharmaceuticals and more recently the oil industry.

  19. Binary Love relations

    NASA Astrophysics Data System (ADS)

    Yagi, Kent; Yunes, Nicolás

    2016-07-01

    When in a tight binary, the mutual tidal deformations of neutron stars get imprinted onto observables, encoding information about their internal structure at supranuclear densities and gravity in the extreme-gravity regime. Gravitational wave (GW) observations of their late binary inspiral may serve as a tool to extract the individual tidal deformabilities, but this is made difficult by degeneracies between them in the GW model. We here resolve this problem by discovering approximately equation-of-state (EoS)-insensitive relations between dimensionless combinations of the individual tidal deformabilities. We show that these relations break degeneracies in the GW model, allowing for the accurate extraction of both deformabilities. Such measurements can be used to better differentiate between EoS models, and improve tests of general relativity and cosmology.

  20. Parametric binary dissection

    NASA Technical Reports Server (NTRS)

    Bokhari, Shahid H.; Crockett, Thomas W.; Nicol, David M.

    1993-01-01

    Binary dissection is widely used to partition non-uniform domains over parallel computers. This algorithm does not consider the perimeter, surface area, or aspect ratio of the regions being generated and can yield decompositions that have poor communication to computation ratio. Parametric Binary Dissection (PBD) is a new algorithm in which each cut is chosen to minimize load + lambda x(shape). In a 2 (or 3) dimensional problem, load is the amount of computation to be performed in a subregion and shape could refer to the perimeter (respectively surface) of that subregion. Shape is a measure of communication overhead and the parameter permits us to trade off load imbalance against communication overhead. When A is zero, the algorithm reduces to plain binary dissection. This algorithm can be used to partition graphs embedded in 2 or 3-d. Load is the number of nodes in a subregion, shape the number of edges that leave that subregion, and lambda the ratio of time to communicate over an edge to the time to compute at a node. An algorithm is presented that finds the depth d parametric dissection of an embedded graph with n vertices and e edges in O(max(n log n, de)) time, which is an improvement over the O(dn log n) time of plain binary dissection. Parallel versions of this algorithm are also presented; the best of these requires O((n/p) log(sup 3)p) time on a p processor hypercube, assuming graphs of bounded degree. How PBD is applied to 3-d unstructured meshes and yields partitions that are better than those obtained by plain dissection is described. Its application to the color image quantization problem is also discussed, in which samples in a high-resolution color space are mapped onto a lower resolution space in a way that minimizes the color error.

  1. Binary Optics Toolkit

    SciTech Connect

    Neal, Daniel

    1996-04-02

    This software is a set of tools for the design and analysis of binary optics. It consists of a series of stand-alone programs written in C and some scripts written in an application-specific language interpreted by a CAD program called DW2000. This software can be used to optimize the design and placement of a complex lens array from input to output and produce contours, mask designs, and data exported for diffractive optic analysis.

  2. Processing Of Binary Images

    NASA Astrophysics Data System (ADS)

    Hou, H. S.

    1985-07-01

    An overview of the recent progress in the area of digital processing of binary images in the context of document processing is presented here. The topics covered include input scan, adaptive thresholding, halftoning, scaling and resolution conversion, data compression, character recognition, electronic mail, digital typography, and output scan. Emphasis has been placed on illustrating the basic principles rather than descriptions of a particular system. Recent technology advances and research in this field are also mentioned.

  3. Double Eclipsing Binary Fitting

    NASA Astrophysics Data System (ADS)

    Cagas, P.; Pejcha, O.

    2012-06-01

    The parameters of the mutual orbit of eclipsing binaries that are physically connected can be obtained by precision timing of minima over time through light travel time effect, apsidal motion or orbital precession. This, however, requires joint analysis of data from different sources obtained through various techniques and with insufficiently quantified uncertainties. In particular, photometric uncertainties are often underestimated, which yields too small uncertainties in minima timings if determined through analysis of a χ2 surface. The task is even more difficult for double eclipsing binaries, especially those with periods close to a resonance such as CzeV344, where minima get often blended with each other. This code solves the double binary parameters simultaneously and then uses these parameters to determine minima timings (or more specifically O-C values) for individual datasets. In both cases, the uncertainties (or more precisely confidence intervals) are determined through bootstrap resampling of the original data. This procedure to a large extent alleviates the common problem with underestimated photometric uncertainties and provides a check on possible degeneracies in the parameters and the stability of the results. While there are shortcomings to this method as well when compared to Markov Chain Monte Carlo methods, the ease of the implementation of bootstrapping is a significant advantage.

  4. Mid-gap phenomena in chalcogenide glasses and barrier-cluster-heating model

    SciTech Connect

    Banik, Ivan Kubliha, Marián; Lukovičová, Jozefa; Pavlendová, Gabriela

    2015-12-07

    The physical mechanism of photoluminescence spectrum formation of chalcogenide glasses (CHG) belongs to the important unsolved problems in physics of non-crystalline materials. Photoluminescence is an important means of the electron spectrum investigation. PL spectrum in CHG is produced mostly in the middle of the band gap, and its profile is normal - Gaussian. Several features of PL spectra in CHG is still a great mystery. The aim of the paper is to make reader acquainted with the new insight into the problem. In this article we also deal with the issue of clarifying the nature of mid-gap absorption. From the experiments it is known that after excitation of the glass As{sub 2}S{sub 3} (or As{sub 2}Se{sub 3}) with primary radiation from Urbach-tail region the glass will be able to absorb the photons of low energy (IR) radiation from mid-gap region of spectra. This low photon absorption without action of the primary excitation radiation of the higher photon energy is impossible. Mid-gap absorption yields boost in the photoluminescence. The paper gives the reader the new insights into some, until now, unexplained effects and contexts in chalcogenide glasses from the position of barrier-cluster-heating model.

  5. The electronic band structures of gadolinium chalcogenides: a first-principles prediction for neutron detecting.

    PubMed

    Li, Kexue; Liu, Lei; Yu, Peter Y; Chen, Xiaobo; Shen, D Z

    2016-05-11

    By converting the energy of nuclear radiation to excited electrons and holes, semiconductor detectors have provided a highly efficient way for detecting them, such as photons or charged particles. However, for detecting the radiated neutrons, those conventional semiconductors hardly behave well, as few of them possess enough capability for capturing these neutral particles. While the element Gd has the highest nuclear cross section, here for searching proper neutron-detecting semiconductors, we investigate theoretically the Gd chalcogenides whose electronic band structures have never been characterized clearly. Among them, we identify that γ-phase Gd2Se3 should be the best candidate for neutron detecting since it possesses not only the right bandgap of 1.76 eV for devices working under room temperature but also the desired indirect gap nature for charge carriers surviving longer. We propose further that semiconductor neutron detectors with single-neutron sensitivity can be realized with such a Gd-chalcogenide on the condition that their crystals can be grown with good quality.

  6. Mid-infrared supercontinuum generation in chalcogenide multi-step index fibers with normal chromatic dispersion

    NASA Astrophysics Data System (ADS)

    Nagasaka, K.; Tong, Hoang Tuan; Liu, Lai; Matsumoto, Morio; Tezuka, Hiroshige; Suzuki, Takenobu; Ohishi, Yasutake

    2017-02-01

    We experimentally demonstrate mid-infrared supercontinuum (SC) generation in chalcogenide multi-step index fibers (MSIF) pumped by a femtosecond laser. The fabricated chalcogenide MSIF is composed of a high refractive index core (C1) in the center, which is enclosed by a lower refractive index core layer (C2) and an outer cladding. This fiber structure is advantageous to tailor the chromatic dispersion with higher freedom and to keep the effective mode area small at long wavelengths. The high refractive index core, low refractive index core, and the outer cladding materials are As2Se3, AsSe2 and As2S5, respectively. When the diameter of C1 and C2 are 7.8 and 30 μm, respectively, the zerodispersion wavelength (ZDW) of the fiber is 12.5 μm. The chromatic dispersion profile is near-zero and flattened within the range of +/-20 ps/km/nm in the wavelength range from 4 to 17 μm and a broad normal dispersion region is obtained in the wavelength range shorter than the ZDW. In practice, a 2.8 cm long fiber is pumped at 10 μm by using a femtosecond laser whose pulse width is 200 fs. The SC generation extending from 2 to 14 μm is obtained. Most of its spectrum is in the normal dispersion region of the fiber. These results are promising for the highly coherent mid-infrared SC generation.

  7. Magnetic and electronic properties of Neptunium chalcogenides from GGA + U + SOC and DFT investigations

    NASA Astrophysics Data System (ADS)

    Khan, Wilayat; Goumri-Said, Souraya

    2017-06-01

    First-principles calculations techniques were employed to explore the structural, electronic and magnetic properties of Neptunium chalcogenides (Np2X5, X = S, Se and Te). No experimental or theoretical studies of their physical properties have been previously reported in the literature. The presence of highly localized f states has requested the employment of the spin orbit coupling and GGA + U approach in order to describe correctly the f-f coupling. Np2X5 was found metallic with high magnetic character due to the Neptunium presence. Fermi surfaces of Np2Te5 have shown a greater electrical conductivity compared to Np2Se5 and Np2S5. The magnetic moment was found to be between 13.24 and 13.92μB, principally induced by Np f and d-orbitals as well as the spin-polarization of the chalcogenes (Te, Se, S) induced by Np. Neptunium chalcogenides have shown interesting magnetic properties and should be manipulated with precaution due to their radioactive properties.

  8. Chalcogenide glass fibers: Optical window tailoring and suitability for bio-chemical sensing

    NASA Astrophysics Data System (ADS)

    Lucas, Pierre; Coleman, Garrett J.; Jiang, Shibin; Luo, Tao; Yang, Zhiyong

    2015-09-01

    Glassy materials based on chalcogen elements are becoming increasingly prominent in the development of advanced infrared sensors. In particular, infrared fibers constitute a desirable sensing platform due to their high sensitivity and versatile remote collection capabilities for in-situ detection. Tailoring the transparency window of an optical material to the vibrational signature of a target molecule is important for the design of infrared sensor, and particularly for fiber evanescent wave spectroscopy. Here we review the basic principles and recent developments in the fabrication of chalcogenide glass infrared fibers for application as bio-chemical sensors. We emphasize the challenges in designing materials that combine good rheological properties with chemical stability and sufficiently wide optical windows for bio-chemical sensing. The limitation in optical transparency due to higher order overtones of the amorphous network vibrations is established for this family of glasses. It is shown that glasses with wide optical window suffer from higher order overtone absorptions. Compositional engineering with heavy elements such as iodine is shown to widen the optical window but at the cost of lower chemical stability. The optical attenuations of various families of chalcogenide glass fibers are presented and weighed for their applications as chemical sensors. It is then shown that long-wave infrared fibers can be designed to optimize the collection of selective signal from bio-molecules such as cells and tissues. Issues of toxicity and mechanical resistance in the context of bio-sensing are also discussed.

  9. Mid-infrared transmission gratings in chalcogenide glass manufactured using ultrafast laser inscription

    NASA Astrophysics Data System (ADS)

    Lee, David; MacLachlan, David G.; Butcher, Helen L.; Brownsword, Richard A.; Weidmann, Damien; Cunningham, Colin R.; Schnetler, H.; Thomson, Robert R.

    2016-07-01

    Ultrafast laser inscription is a versatile manufacturing technique which can be used to modify the refractive index of various glasses on a microscopic scale. This enables the production of a number of photonic devices such as waveguides, beam-splitters, photonic lanterns, and diffraction gratings. In this paper, we report on the use of ultrafast laser inscription to fabricate volume phase transmission gratings in mid-infrared transmitting chalcogenide glass. We describe the optimisation of the laser inscription process parameters enhancing grating performances via the combination of spectrally resolved grating transmission measurements and theoretical analysis models. The first order diffraction efficiency of the gratings was measured at mid-infrared wavelengths (3-5 μm), and found to exceed 60% at the Littrow blaze wavelength, compared to a substrate external transmittance of 67%. This impressive result implies the diffraction efficiency should exceed 90% for a grating substrate treated with an anti-reflection coating. There is excellent agreement between the modelled grating efficiency and the measured data, and from a least squares fit to the measured data the refractive index modulation achieved during the inscription process is inferred. These encouraging initial results demonstrate that ultrafast laser inscription of chalcogenide glass may provide a potential new and alternative technology for the manufacture of astronomical diffraction gratings for use at near-infrared and mid-infrared wavelengths.

  10. Crystal symmetry breaking and vacancies in colloidal lead chalcogenide quantum dots

    NASA Astrophysics Data System (ADS)

    Bertolotti, Federica; Dirin, Dmitry N.; Ibáñez, Maria; Krumeich, Frank; Cervellino, Antonio; Frison, Ruggero; Voznyy, Oleksandr; Sargent, Edward H.; Kovalenko, Maksym V.; Guagliardi, Antonietta; Masciocchi, Norberto

    2016-09-01

    Size and shape tunability and low-cost solution processability make colloidal lead chalcogenide quantum dots (QDs) an emerging class of building blocks for innovative photovoltaic, thermoelectric and optoelectronic devices. Lead chalcogenide QDs are known to crystallize in the rock-salt structure, although with very different atomic order and stoichiometry in the core and surface regions; however, there exists no convincing prior identification of how extreme downsizing and surface-induced ligand effects influence structural distortion. Using forefront X-ray scattering techniques and density functional theory calculations, here we have identified that, at sizes below 8 nm, PbS and PbSe QDs undergo a lattice distortion with displacement of the Pb sublattice, driven by ligand-induced tensile strain. The resulting permanent electric dipoles may have implications on the oriented attachment of these QDs. Evidence is found for a Pb-deficient core and, in the as-synthesized QDs, for a rhombic dodecahedral shape with nonpolar {110} facets. On varying the nature of the surface ligands, differences in lattice strains are found.

  11. Thermal and Electrical Conductivity of Ge1Sb4Te7 Chalcogenide Alloy

    NASA Astrophysics Data System (ADS)

    Lan, Rui; Endo, Rie; Kuwahara, Masashi; Kobayashi, Yoshinao; Susa, Masahiro

    2017-02-01

    The unique properties of the Ge1Sb4Te7 alloy as a chalcogenide make it a good candidate for application in phase-change random access memory as well as thermoelectric materials. The thermal and electrical conductivity of the Ge1Sb4Te7 alloy play an important role in both applications. This work aims to determine the thermal conductivity and electrical resistivity of the Ge1Sb4Te7 alloy as a function of temperature and to discuss the thermal conduction mechanism. Thermal conductivity and electrical resistivity were measured from room temperature to 778 K using the hot strip method and the four-terminal method, respectively. The thermal conductivity of the Ge1Sb4Te7 alloy shows an interesting temperature dependence: it decreases up to about 600 K, and then increases with increasing temperature. The electrical resistivity shows a monotonic increase with increasing temperature. Through a discussion of the thermal conductivity results together with electrical resistivity results, it is proposed that electronic thermal conductivity dominates the thermal conductivity, while the bipolar diffusion contributes to the increase in the thermal conductivity at higher temperatures. The resonance bonding existing in this chalcogenide alloy accounts for the low lattice thermal conductivity.

  12. Nanostructured metal chalcogenides: synthesis, modification, and applications in energy conversion and storage devices.

    PubMed

    Gao, Min-Rui; Xu, Yun-Fei; Jiang, Jun; Yu, Shu-Hong

    2013-04-07

    Advanced energy conversion and storage (ECS) devices (including fuel cells, photoelectrochemical water splitting cells, solar cells, Li-ion batteries and supercapacitors) are expected to play a major role in the development of sustainable technologies that alleviate the energy and environmental challenges we are currently facing. The successful utilization of ECS devices depends critically on synthesizing new nanomaterials with merits of low cost, high efficiency, and outstanding properties. Recent progress has demonstrated that nanostructured metal chalcogenides (MCs) are very promising candidates for efficient ECS systems based on their unique physical and chemical properties, such as conductivity, mechanical and thermal stability and cyclability. In this review, we aim to provide a summary on the liquid-phase synthesis, modifications, and energy-related applications of nanostructured metal chalcogenide (MC) materials. The liquid-phase syntheses of various MC nanomaterials are primarily categorized with the preparation method (mainly 15 kinds of methods). To obtain optimized, enhanced or even new properties, the nanostructured MC materials can be modified by other functional nanomaterials such as carbon-based materials, noble metals, metal oxides, or MCs themselves. Thus, this review will then be focused on the recent strategies used to realize the modifications of MC nanomaterials. After that, the ECS applications of the MC/modified-MC nanomaterials have been systematically summarized based on a great number of successful cases. Moreover, remarks on the challenges and perspectives for future MC research are proposed (403 references).

  13. Chalcogenide-based van der Waals epitaxy: Interface conductivity of tellurium on Si(111)

    NASA Astrophysics Data System (ADS)

    Lüpke, Felix; Just, Sven; Bihlmayer, Gustav; Lanius, Martin; Luysberg, Martina; Doležal, Jiří; Neumann, Elmar; Cherepanov, Vasily; Ošt'ádal, Ivan; Mussler, Gregor; Grützmacher, Detlev; Voigtländer, Bert

    2017-07-01

    We present a combined experimental and theoretical analysis of a Te rich interface layer which represents a template for chalcogenide-based van der Waals epitaxy on Si(111). On a clean Si(111)-(1 ×1 ) surface, we find Te to form a Te/Si(111)-(1 ×1 ) reconstruction to saturate the substrate bonds. A problem arising is that such an interface layer can potentially be highly conductive, undermining the applicability of the on-top grown films in electric devices. We perform here a detailed structural analysis of the pristine Te termination and present direct measurements of its electrical conductivity by in situ distance-dependent four-probe measurements. The experimental results are analyzed with respect to density functional theory calculations and the implications of the interface termination with respect to the electrical conductivity of chalcogenide-based topological insulator thin films are discussed. In detail, we find a Te/Si(111)-(1 ×1 ) interface conductivity of σ2D Te=2.6 (5 ) ×10-7S /□ , which is small compared to the typical conductivity of topological surface states.

  14. Dysprosium-doped chalcogenide films prepared by pulsed-laser deposition

    NASA Astrophysics Data System (ADS)

    Nazabal, Virginie; Nemec, Petr; Jedelský, Jaroslav; Duverger, Claire; Le Person, Jenny; Adam, Jean-Luc; Frumar, Miloslav

    2004-08-01

    The chalcogenide glasses possess interesting optical properties such as a good transmission in the nIR-mIR wavelength region, high linear and non-linear refractive index and photosensitivity, which allows holographic patterns writing. Moreover, their low-phonon energy makes them good candidates for optical amplification. In order to design an integrated circuit on chalcogenide glasses, the pulsed laser deposition (PLD) technique is a suitable method for deposition of glass with complex composition. Amorphous Ge-Ga-Sb-S films (pure and dysprosium doped) were prepared by PLD using different energy of the laser beam pulses. Compositional, morphological and structural characteristics of the films were studied by MEB-EDS, atomic force, scanning electron microscopy, X-ray diffraction and Raman spectroscopy analyses. The photo-luminescence of Dy doped Ge-Ga-Sb-S films was investigated. The emission band centered at 1340 nm corresponding to 6F11/2, 6H9/2-6H15/2 electron transitions of Dy3+ ions was identified in luminescence spectra of dysprosium doped thin films. A study of the optical properties and the effects of exposure and thermal annealing below the glass transition temperature on the optical parameters of thin films from the Ge-Ga-Sb-S system will be presented.

  15. Identification of Abnormal Phase and its Formation Mechanism in Synthesizing Chalcogenide Films

    NASA Astrophysics Data System (ADS)

    Liu, Kegao; Ji, Nianjing; Xu, Yong; Liu, Hong

    2016-09-01

    Chalcogenide films can be used in thin-film solar cells due to their high photoelectric conversion efficiencies. It was difficult to identify one abnormal phase with high X-ray diffraction (XRD) intensity and preferred orientation in the samples for preparing chalcogenide films by spin-coating and co-reduction on soda-lime glass (Na2OṡCaOṡ6SiO2) substrates. The raw materials and reductant are metal chlorides and hydrazine hydrate respectively. In order to identify this phase, a series of experiments were done under different conditions. The phases of obtained products were analyzed by XRD and the size and morphology were characterized by scanning electron microscope (SEM) and atomic force microscopy (AFM). From the experimental results, first it was proved that the abnormal phase was water-soluble by water immersion experiment, then it was identified as NaCl crystal through XRD, energy dispersive spectrometer (EDS) and SEM. The cubic NaCl crystals have high crystallinity with size lengths of about 0.5-2μm and show a <100> preferred orientation. The reaction mechanism of NaCl crystal was proposed as follows: The NaCl crystal was formed by reaction of Na2O and HCl in a certain experimental conditions.

  16. Ultrahigh refractive index chalcogenide based copolymers for infrared optics (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Anderson, Laura E.; Namnabat, Soha; Char, Kookheon; Glass, Richard; Norwood, Robert A.; Pyun, Jeffrey

    2016-09-01

    Current trends in technology development demand increased miniaturization and higher level integration of electronic and photonic components. Such needs arise in emerging imaging systems, optoelectronic devices, optical interconnects and photonic integrated circuits. Compact, integrated photonics requires high refractive index materials, which primarily comprise crystalline and amorphous semiconductors, as well as chalcogenide glasses, which can possess refractive indices higher than 4 and good infrared transparency. There is currently no high refractive index (n 2 or above) that has the low cost production and ease of processing available in optical polymers. Such polymers would potentially cover applications that are not convenient or possible with crystalline and vitreous semiconductors. Examples of such applications include micro lens arrays for image sensors, optical adhesives for bonding and antireflection coatings, and high contrast optical waveguides. While much of the focus has been in the telecommunications transparency regions, significant new opportunities exist for a polymer which is capable of transmitting efficiently in the MWIR region. While there are polymers that have been synthesized with refractive indices as high as 1.75, these polymers are generally conjugated and incorporate heteroatoms such as sulfur or metals, and generally have complex and expensive syntheses. Here we report on new chalcogenide based copolymers with very high refractive index (n 2) that also have good optical transmission properties in the near-, short- and mid-wave infrared up to 5µm. These polymers are rich in sulfur, have low hydrogen content and were made using inverse vulcanization.

  17. Preparation of Cd/Pb Chalcogenide Heterostructured Janus Particles via Controllable Cation Exchange

    SciTech Connect

    Zhang, Jianbing; Chernomordik, Boris D.; Crisp, Ryan W.; Kroupa, Daniel M.; Luther, Joseph M.; Miller, Elisa M.; Gao, Jianbo; Beard, Matthew C.

    2015-07-28

    We developed a strategy for producing quasi-spherical nanocrystals of anisotropic heterostructures of Cd/Pb chalcogenides. The nanostructures are fabricated via a controlled cation exchange reaction where the Cd2+ cation is exchanged for the Pb2+ cation. The cation exchange reaction is thermally activated and can be controlled by adjusting the reaction temperature or time. We characterized the particles using TEM, XPS, PL, and absorption spectroscopy. With complete exchange, high quality Pb-chalcogenide quantum dots are produced. In addition to Cd2+, we also find suitable conditions for the exchange of Zn2+ cations for Pb2+ cations. The cation exchange is anisotropic starting at one edge of the nanocrystals and proceeds along the <111> direction producing a sharp interface at a (111) crystallographic plane. Instead of spherical core/shell structures, we produced and studied quasi-spherical CdS/PbS and CdSe/PbSe Janus-type heterostructures. Nontrivial PL behavior was observed from the CdS(e)/PbS(e) heterostructures as the Pb:Cd ratio is increased.

  18. Photonic Bandgap Propagation in All-Solid Chalcogenide Microstructured Optical Fibers

    PubMed Central

    Caillaud, Celine; Renversez, Gilles; Brilland, Laurent; Mechin, David; Calvez, Laurent; Adam, Jean-Luc; Troles, Johann

    2014-01-01

    An original way to obtain fibers with special chromatic dispersion and single-mode behavior is to consider microstructured optical fibers (MOFs). These fibers present unique optical properties thanks to the high degree of freedom in the design of their geometrical structure. In this study, the first all-solid all-chalcogenide MOFs exhibiting photonic bandgap transmission have been achieved and optically characterized. The fibers are made of an As38Se62 matrix, with inclusions of Te20As30Se50 glass that shows a higher refractive index (n = 2.9). In those fibers, several transmission bands have been observed in mid infrared depending on the geometry. In addition, for the first time, propagation by photonic bandgap effect in an all-chalcogenide MOF has been observed at 3.39 µm, 9.3 µm, and 10.6 µm. The numerical simulations based on the optogeometric properties of the fibers agree well with the experimental characterizations. PMID:28788180

  19. Two-dimensional chalcogenide nanoplates as tunable metamaterials via chemical intercalation.

    PubMed

    Cha, Judy J; Koski, Kristie J; Huang, Kevin C Y; Wang, Ken Xingze; Luo, Weidong; Kong, Desheng; Yu, Zongfu; Fan, Shanhui; Brongersma, Mark L; Cui, Yi

    2013-01-01

    New plasmonic materials with tunable properties are in great need for nanophotonics and metamaterials applications. Here we present two-dimensional layered, metal chalcogenides as tunable metamaterials that feature both dielectric photonic and plasmonic modes across a wide spectral range from the infrared to ultraviolet. The anisotropic layered structure allows intercalation of organic molecules and metal atoms at the van der Waals gap of the host chalcogenide, presenting a chemical route to create heterostructures with molecular and atomic precision for photonic and plasmonic applications. This marks a departure from a lithographic method to create metamaterials. Monochromated electron energy-loss spectroscopy in a scanning transmission electron microscope was used to first establish the presence of the dielectric photonic and plasmonic modes in M2E3 (M = Bi, Sb; E = Se, Te) nanoplates and to observe marked changes in these modes after chemical intercalation. We show that these modal properties can also be tuned effectively by more conventional methods such as thickness control and alloy composition of the nanoplates.

  20. Crystal symmetry breaking and vacancies in colloidal lead chalcogenide quantum dots.

    PubMed

    Bertolotti, Federica; Dirin, Dmitry N; Ibáñez, Maria; Krumeich, Frank; Cervellino, Antonio; Frison, Ruggero; Voznyy, Oleksandr; Sargent, Edward H; Kovalenko, Maksym V; Guagliardi, Antonietta; Masciocchi, Norberto

    2016-09-01

    Size and shape tunability and low-cost solution processability make colloidal lead chalcogenide quantum dots (QDs) an emerging class of building blocks for innovative photovoltaic, thermoelectric and optoelectronic devices. Lead chalcogenide QDs are known to crystallize in the rock-salt structure, although with very different atomic order and stoichiometry in the core and surface regions; however, there exists no convincing prior identification of how extreme downsizing and surface-induced ligand effects influence structural distortion. Using forefront X-ray scattering techniques and density functional theory calculations, here we have identified that, at sizes below 8 nm, PbS and PbSe QDs undergo a lattice distortion with displacement of the Pb sublattice, driven by ligand-induced tensile strain. The resulting permanent electric dipoles may have implications on the oriented attachment of these QDs. Evidence is found for a Pb-deficient core and, in the as-synthesized QDs, for a rhombic dodecahedral shape with nonpolar {110} facets. On varying the nature of the surface ligands, differences in lattice strains are found.

  1. Laser processing for thin film chalcogenide photovoltaics: a review and prospectus

    NASA Astrophysics Data System (ADS)

    Simonds, Brian J.; Meadows, Helene J.; Misra, Sudhajit; Ferekides, Christos; Dale, Phillip J.; Scarpulla, Michael A.

    2015-01-01

    We review prior and on-going works in using laser annealing (LA) techniques in the development of chalcogenide-based [CdTe and Cu(In,Ga)S] solar cells. LA can achieve unique processing regimes as the wavelength and pulse duration can be chosen to selectively heat particular layers of a thin film solar cell or even particular regions within a single layer. Pulsed LA, in particular, can achieve non-steady-state conditions that allow for stoichiometry control by preferential evaporation, which has been utilized in CdTe solar cells to create Ohmic back contacts. Pulsed lasers have also been used with Cu(In,Ga)S to improve device performance by surface-defect annealing as well as bulk deep-defect annealing. Continuous-wave LA shows promise for use as a replacement for furnace annealing as it almost instantaneously supplies heat to the absorbing film without wasting time or energy to bring the much thicker substrate to temperature. Optimizing and utilizing such a technology would allow production lines to increase throughput and thus manufacturing capacity. Lasers have also been used to create potentially low-cost chalcogenide thin films from precursors, which is also reviewed.

  2. Investigation of Optical Nonlinearities in Bi-Doped Se-Te Chalcogenide Thin Films

    NASA Astrophysics Data System (ADS)

    Yadav, Preeti; Sharma, Ambika

    2015-03-01

    The present paper reports the nonlinear optical properties of chalcogenide Se85- x Te15Bi x (0 ≤ x ≤ 5) thin films. The formulation proposed by Boling, Fournier, and Snitzer and Tichy and Ticha has been used to compute the nonlinear refractive index n 2. The two-photon absorption coefficient β 2, and first- and third-order susceptibilities [ χ (1) and χ (3)] are also reported. The nonlinear refractive index n 2 is well correlated with the linear refractive index n and Wemple-DiDomenico (WDD) parameters, in turn depending on the density ρ and molar volume V m of the system. The density of the system is calculated experimentally by using Archimedes' principle. The linear optical parameters, viz. n, WDD parameters, and optical bandgap E g, are measured experimentally using ellipsometric curves obtained by spectrophotometry. The composition-dependent behavior of n 2 is analyzed on the basis of various parameters, viz. density, bond distribution, cohesive energy (CE), and optical bandgap E g, of the system. The variation of n 2 and β 2 with changing bandgap E g is also reported. The values of n 2 and χ (3) of the investigated chalcogenides are compared with those of pure silica, oxide, and other Se-based glasses.

  3. Binary-Signal Recovery

    NASA Technical Reports Server (NTRS)

    Griebeler, Elmer L.

    2011-01-01

    Binary communication through long cables, opto-isolators, isolating transformers, or repeaters can become distorted in characteristic ways. The usual solution is to slow the communication rate, change to a different method, or improve the communication media. It would help if the characteristic distortions could be accommodated at the receiving end to ease the communication problem. The distortions come from loss of the high-frequency content, which adds slopes to the transitions from ones to zeroes and zeroes to ones. This weakens the definition of the ones and zeroes in the time domain. The other major distortion is the reduction of low frequency, which causes the voltage that defines the ones or zeroes to drift out of recognizable range. This development describes a method for recovering a binary data stream from a signal that has been subjected to a loss of both higher-frequency content and low-frequency content that is essential to define the difference between ones and zeroes. The method makes use of the frequency structure of the waveform created by the data stream, and then enhances the characteristics related to the data to reconstruct the binary switching pattern. A major issue is simplicity. The approach taken here is to take the first derivative of the signal and then feed it to a hysteresis switch. This is equivalent in practice to using a non-resonant band pass filter feeding a Schmitt trigger. Obviously, the derivative signal needs to be offset to halfway between the thresholds of the hysteresis switch, and amplified so that the derivatives reliably exceed the thresholds. A transition from a zero to a one is the most substantial, fastest plus movement of voltage, and therefore will create the largest plus first derivative pulse. Since the quiet state of the derivative is sitting between the hysteresis thresholds, the plus pulse exceeds the plus threshold, switching the hysteresis switch plus, which re-establishes the data zero to one transition

  4. A unifying phase diagram with correlation-driven superconductor-to-insulator transition for the 122 series of iron chalcogenides

    NASA Astrophysics Data System (ADS)

    Niu, X. H.; Chen, S. D.; Jiang, J.; Ye, Z. R.; Yu, T. L.; Xu, D. F.; Xu, M.; Feng, Y.; Yan, Y. J.; Xie, B. P.; Zhao, J.; Gu, D. C.; Sun, L. L.; Mao, Qianhui; Wang, Hangdong; Fang, Minghu; Zhang, C. J.; Hu, J. P.; Sun, Z.; Feng, D. L.

    2016-02-01

    The 122 series of iron chalcogenide superconductors, for example KxFe2 -ySe2 , only possesses electron Fermi pockets. Their distinctive electronic structure challenges the picture built upon iron pnictide superconductors, where both electron and hole Fermi pockets coexist. However, partly due to the intrinsic phase separation in this family of compounds, many aspects of their behavior remain elusive. In particular, the evolution of the 122 series of iron chalcogenides with chemical substitution still lacks a microscopic and unified interpretation. Using angle-resolved photoemission spectroscopy, we studied a major fraction of 122 iron chalcogenides, including the isovalently "doped" KxFe2 -ySe2 -zSz,RbxFe2 -ySe2 -zTez , and (Tl,K) xFe2 -ySe2 -zSz . We found that the bandwidths of the low energy Fe 3 d bands in these materials depend on doping; and more crucially, as the bandwidth decreases, the ground state evolves from a metal to a superconductor, and eventually to an insulator, yet the Fermi surface in the metallic phases is unaffected by the isovalent dopants. Moreover, the correlation-driven insulator found here with small band filling may be a novel insulating phase. Our study shows that almost all the known 122-series iron chalcogenides can be understood via one unifying phase diagram which implies that moderate correlation strength is beneficial for the superconductivity.

  5. Highly nonlinear chalcogenide hybrid microstructured optical fibers with buffer layer and their potential performance of supercontinuum generation

    NASA Astrophysics Data System (ADS)

    Tong, Hoang Tuan; Nagasaka, Kenshiro; Nguyen Phuoc, Trung Hoa; Suzuki, Takenobu; Ohishi, Yasutake

    2017-02-01

    We report here the design of a new chalcogenide hybrid microstructured optical fiber (HMOF) with a buffer layer around the core and its potential performance of tailoring chromatic dispersion and supercontinuum (SC) generation. The new chalcogenide HMOF has an AsSe2 core. The refractive index difference Δn between the AsSe2 core and cladding material is supposed to be 0.3. The fiber microstructure and the Δn between the core and buffer materials are designed in order to obtain broad anomalous dispersion regimes with near-zero and flattened chromatic dispersion profiles for broadband SC generation. Moreover, the suppression of chromatic dispersion fluctuation caused by fiber transverse geometry variation is investigated. By using the proposed chalcogenide buffer-embed HMOFs, the calculation shows that near-zero and flattened anomalous chromatic dispersion regimes from 4.5 μm can be obtained. When the variation of fiber structure occurs for +/-1, +/-5 and +/-10 %, the chromatic dispersion fluctuation can be greatly suppressed. In addition, the calculation shows that a broad SC spectrum from 2.5 to more than 16.0 μm can be obtained when a 0.9-cmlong section of the new chalcogenide buffer-embed HMOF is pumped at 5.0 μm by a femtosecond laser with 1-kW peak power.

  6. Application of photo-doping phenomenon in amorphous chalcogenide GeS2 film to optical device

    NASA Astrophysics Data System (ADS)

    Murakami, Yoshihisa; Arai, Katsuya; Wakaki, Moriaki; Shibuya, Takehisa; Shintaku, Toshihiro

    2015-03-01

    Photodoping phenomenon is observed when a double-layer consisting of an amorphous chalcogenide film (As2S3, GeS2, GeSe2 etc.) and a metal (Ag, Cu etc.) film is illuminated by light. The metal diffuses abnormally into the amorphous chalcogenide layer. Amorphous chalcogenide films of GeS2 with an Ag over layer exhibited large increase of refractive index through the abnormal doping of Ag by irradiating the light around the absorption edge of the GeS2 chalcogenide. In this study, we aimed the application of this effect for the fabrication of optical devices and fabricated various micro doped patterns by using a laser beam. Mask less pattering with refractive index modified films are possible by manipulating the scanning of the laser beam. Micro gratings were fabricated using a confocal laser microscope to work as both fabrication and observation system. Waveguides were also fabricated by scanning the laser beam for photodoping. Holographic gratings were fabricated by utilizing the photodoping of the two beam interference pattern, which showed the possibility to produce large scale optical devices or mass production.

  7. Towards efficient solar-to-hydrogen conversion: Fundamentals and recent progress in copper-based chalcogenide photocathodes

    NASA Astrophysics Data System (ADS)

    Chen, Yubin; Feng, Xiaoyang; Liu, Maochang; Su, Jinzhan; Shen, Shaohua

    2016-09-01

    Photoelectrochemical (PEC) water splitting for hydrogen generation has been considered as a promising route to convert and store solar energy into chemical fuels. In terms of its large-scale application, seeking semiconductor photoelectrodes with high efficiency and good stability should be essential. Although an enormous number of materials have been explored for solar water splitting in the last several decades, challenges still remain for the practical application. P-type copper-based chalcogenides, such as Cu(In, Ga)Se2 and Cu2ZnSnS4, have shown impressive performance in photovoltaics due to narrow bandgaps, high absorption coefficients, and good carrier transport properties. The obtained high efficiencies in photovoltaics have promoted the utilization of these materials into the field of PEC water splitting. A comprehensive review on copper-based chalcogenides for solar-to-hydrogen conversion would help advance the research in this expanding area. This review will cover the physicochemical properties of copper-based chalco-genides, developments of various photocathodes, strategies to enhance the PEC activity and stability, introductions of tandem PEC cells, and finally, prospects on their potential for the practical solar-to-hydrogen conversion. We believe this review article can provide some insights of fundamentals and applications of copper-based chalco-genide thin films for PEC water splitting.

  8. Solid-state chemistry on a surface and in a beaker: Unconventional routes to transition metal chalcogenide nanomaterials

    SciTech Connect

    Stender, Christopher L.; Sekar, Perumal; Odom, Teri W.

    2008-07-15

    This article focuses on two different approaches to create nanoscale transition metal chalcogenide materials. First, we used chemical nanofabrication, a combination of top-down patterning and bottom-up solid-state synthesis, to achieve control over the shape, size, and ordering of the patterned nanomaterials. We demonstrated orientational control over nanocrystals within sub-300 nm patterns of MoS{sub 2} and formed free-standing nanostructures of crystalline NiS{sub 2}. In addition, crossed line arrays of mixed metal chalcogenide nanostructures were achieved, and TaS{sub 2} nanopatterns were made by the chemical transformation of tantalum oxide templates. Second, we developed a one-pot procedure using molecular precursors to synthesize two-dimensional NbSe{sub 2}, TaS{sub 2} and TaSe{sub 2} nanoplates and one-dimensional NbSe{sub 2} wires depending on the relative amount of surfactants in the reaction mixture. Prospects for these transition metal chalcogenide nanomaterials with controlled shapes and morphologies will be discussed. - Graphical abstract: This paper describes how transition metal chalcogenide nanomaterials can be produced by two approaches. First, chemical nanofabrication-a combination of top-down patterning and bottom-up solid-state synthesis-was used to achieve control over the shape, size, and ordering of patterned nanomaterials. Second, a one-pot procedure using molecular precursors was developed to synthesize two-dimensional nanoplates and one-dimensional nanowires of conducting transition metal dichalcogenides.

  9. Visual binary stars: data to investigate formation of binaries

    NASA Astrophysics Data System (ADS)

    Kovaleva,, D.; Malkov,, O.; Yungelson, L.; Chulkov, D.

    Statistics of orbital parameters of binary stars as well as statistics of their physical characteristics bear traces of star formation history. However, statistical investigations of binaries are complicated by incomplete or missing observational data and by a number of observational selection effects. Visual binaries are the most common type of observed binary stars, with the number of pairs exceeding 130 000. The most complete list of presently known visual binary stars was compiled by cross-matching objects and combining data of the three largest catalogues of visual binaries. This list was supplemented by the data on parallaxes, multicolor photometry, and spectral characteristics taken from other catalogues. This allowed us to compensate partly for the lack of observational data for these objects. The combined data allowed us to check the validity of observational values and to investigate statistics of the orbital and physical parameters of visual binaries. Corrections for incompleteness of observational data are discussed. The datasets obtained, together with modern distributions of binary parameters, will be used to reconstruct the initial distributions and parameters of the function of star formation for binary systems.

  10. Binary optics: Trends and limitations

    NASA Astrophysics Data System (ADS)

    Farn, Michael W.; Veldkamp, Wilfrid B.

    1993-08-01

    We describe the current state of binary optics, addressing both the technology and the industry (i.e., marketplace). With respect to the technology, the two dominant aspects are optical design methods and fabrication capabilities, with the optical design problem being limited by human innovation in the search for new applications and the fabrication issue being limited by the availability of resources required to improve fabrication capabilities. With respect to the industry, the current marketplace does not favor binary optics as a separate product line and so we expect that companies whose primary purpose is the production of binary optics will not represent the bulk of binary optics production. Rather, binary optics' more natural role is as an enabling technology - a technology which will directly result in a competitive advantage in a company's other business areas - and so we expect that the majority of binary optics will be produced for internal use.

  11. Binary optics: Trends and limitations

    NASA Technical Reports Server (NTRS)

    Farn, Michael W.; Veldkamp, Wilfrid B.

    1993-01-01

    We describe the current state of binary optics, addressing both the technology and the industry (i.e., marketplace). With respect to the technology, the two dominant aspects are optical design methods and fabrication capabilities, with the optical design problem being limited by human innovation in the search for new applications and the fabrication issue being limited by the availability of resources required to improve fabrication capabilities. With respect to the industry, the current marketplace does not favor binary optics as a separate product line and so we expect that companies whose primary purpose is the production of binary optics will not represent the bulk of binary optics production. Rather, binary optics' more natural role is as an enabling technology - a technology which will directly result in a competitive advantage in a company's other business areas - and so we expect that the majority of binary optics will be produced for internal use.

  12. New superconducting ternary molybdenum chalcogenides InMo6Se8,T1Mo6S8, and T1Mo6Se8

    NASA Astrophysics Data System (ADS)

    Tarascon, J. M.; Disalvo, F. J.; Murphy, D. W.; Hull, G.; Waszczak, J. V.

    1984-01-01

    We present the synthesis and the physical properties of new ternary molybdenum chalcogenides MMo6X8 (M=In, T1;X=S, Se) that cannot be made by the usual high-temperature techniques (except for InMo6S8). These materials were obtained by diffusion of the ternary element into the binary phase Mo6X8 at a relatively low temperature (430°C and 520°C for the sulfides and selenides, respectively). They crystallize in the rhombohedral space group R3 (C43) with (ar=6.78 Å, αr=89.86°) when M=In and X=Se and with (ar=6.57 Å, αr=88.45°) and (ar=6.836 Å, αr=88.35°) when M=T1 and X=S and Se, respectively. T1Mo6Se8 presents a large temperature-dependent paramagnetism and begins superconducting at 12.2 K, the highest value ever observed in the selenide Chevrel phases, while that of T1Mo6S8 is lower, 8.7 K. The susceptibility of InMo6Se8 reveals the existence of two first-order transitions that have considerable hysteresis, while only one transition without hysteresis is observed for InMo6S8. The absence of superconductivity down to 1.5 K has been confirmed for this last compound, while the homolog selenide begins superconducting at 8.2 K.

  13. Effect of chemical ordering on the crystallization behavior of Se90Te10-xSnx (x=2, 4, 6, and 8) chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Lafi, Omar A.; Imran, Mousa M. A.; Abu-Shaweesh, Nazem I.; Al-Kurdi, Fares M.; Khatatbeh, Ibtehaj K.

    2014-06-01

    Ternary Se90Te10-xSnx (x=2, 4, 6, and 8) chalcogenide glassy alloys have been prepared by melt quenching technique. Various crystallization parameters, such as onset (Tc) and peak (Tp) crystallization temperatures, activation energy of crystallization (Ec) and Avrami exponent (n) have been determined for these alloys. Tc and Tp have been determined directly from the non-isothermal differential scanning calorimeter (DSC) thermograms. The value of Ec has been calculated from the variation of both Tc and Tp with the heating rate (β) according to Kissinger, Takhor, Augis-Bennett and Ozawa models while Augis-Bennett method has been used to deduce the value of n for the studied samples. The obtained values of the crystallization parameters have been correlated with the character and the energy of the chemical bonds through the calculation of the heteronuclear bond energies of the constituent atoms using Pauling principle. In addition to that, Tichy-Ticha model was used to estimate the mean bond energy of the average cross-linking per atom , the average bond energy per atom of the remaining matrix , and the overall mean bond energy of the studied glasses. Results reveal that both of Tc and Tp decreases with increases Sn content. This is may be attributed to the decreasing in the overall mean bond energy . Besides, the plot of Ec (and also Tg) against was found to be non linear, which contradicts the well known linear correlation between Ec and Tg with as suggested by Tichy-Ticha model. This discrepancy may be due to the fact that the Tichy-Ticha linear correlation model was based on the assumption of covalent glassy network, while in the present glassy alloys, Se-Te binary doped with heavy elements such as Sn exhibit iono-covalent bonding. The calculated values of the ionicity are in support of this argument.

  14. The Search for Trojan Binaries

    NASA Astrophysics Data System (ADS)

    Merline, William J.; Tamblyn, P. M.; Dumas, C.; Close, L. M.; Chapman, C. R.; Durda, D. D.; Levison, H. F.; Hamilton, D. P.; Nesvorny, D.; Storrs, A.; Enke, B.; Menard, F.

    2007-10-01

    We report on observations of Jupiter Trojan asteroids in search of binaries. We made observations using HST/ACS of 35 small (V = 17.5-19.5) objects in Cycle 14, without detecting any binaires. We have also observed a few dozen Trojans in our ground-based study of larger Trojans, discovering only one binary. The result is that the frequency of moderately-separated binaries among the Trojans seem rather low, likely less than 5%. Although we have only statistics of small numbers, it appears that the binary frequencies are more akin to the larger Main-Belt asteroids, than to the frequency in the TNO region, which probably exceeds 10%. The low frequency is inconsistent with the projections based on Trojan contact binaries by Mann et al. (2006, BAAS 38, 6509), although our work cannot detect very close or contact binaries. We discovered and characterized the orbit and density of the first Trojan binary, (617) Patroclus using the Gemini AO system (Merline et al. 2001 IAUC 7741). A second binary, (624) Hecktor, has now been reported by Marchis et al. (2006, IAUC 8732). In a broad survey of Main Belt asteroids, we found that, among the larger objects, the binary fraction is about 2%, while we are finding that the fraction is significantly higher among smaller asteroids (and this is even more apparent from lightcurve discoveries). Further, characteristics of these smaller systems indicate a distinctly different formation mechanism the the larger MB binaries. Because the Trojans have compositions that are more like the KBOs, while they live in a collisional environment much more like the Main Belt than the KBOs, these objects should hold vital clues to binary formation mechanics. And because there seems to be a distinct difference in larger and smaller main-belt binaries, we sought to detect such differences among the Trojans as well.

  15. Radio emission from binary stars

    NASA Technical Reports Server (NTRS)

    Dulk, G. A.

    1986-01-01

    This paper reviews the radio emission from binary star systems - the emission processes that occur, the characteristics of the binary systems inferred from the radio observations, and the reasons for the activity. Several classes of binary stars are described including those with two main sequence stars, those with one normal star and a white dwarf, and those containing a neutron star or a black hole.

  16. Particle acceleration in binaries

    NASA Astrophysics Data System (ADS)

    Sinitsyna, V. G.; Sinitsyna, V. Y.

    2017-06-01

    Cygnus X-3 massive binary system is one of the powerful sources of radio and X-ray emission consisting of an accreting compact object, probably a black hole, with a Wolf-Rayet star companion. Based on the detections of ultra high energy gamma-rays by Kiel and Havera Park, Cygnus X-3 has been proposed to be one of the most powerful sources of charged cosmic ray particles in the Galaxy. The results of long-term observations of the Cyg X-3 binary at energies 800 GeV-85 TeV detected by SHALON in 1995 are presented with images, integral spectra and spectral energy distribution. The identification of source with Cygnus X-3 detected by SHALON was secured by the detection of its 4.8 hour orbital period in TeV gamma-rays. During the whole observation period of Cyg X-3 with SHALON significant flux increases were detected at energies above 0.8 TeV. These TeV flux increases are correlated with flaring activity at a lower energy range of X-ray and/or at observations of Fermi LAT as well as with radio emission from the relativistic jets of Cygnus X-3. The variability of very high-energy gamma-radiation and correlation of radiation activity in the wide energy range can provide essential information on particle mechanism production up to very high energies. Whereas, modulation of very high energy emission connected to the orbital motion of the binary system, provides an understanding of the emission processes, nature and location of particle acceleration.

  17. Very Wide Binaries

    NASA Astrophysics Data System (ADS)

    Olling, Robert; Shaya, E.

    2011-01-01

    We develop Bayesian statistical methods for discovering and assigning probabilities to physical stellar companions. The probabilities depend on similarities in "corrected" proper motion, parallax, and the phase-space density of field stars. Very wide binaries with separations over 10,000 AU have recently been predicted to form during the dissolution process of low-mass star clusters. In this case, these wide systems would still carry information about the density and size of the star cluster in which they formed. Alternatively, Galactic tides and weak interactions with passing stars peel off stars from such very wide binaries in less than 1/2 of a Hubble time. In the past, these systems have been used to rule in/out MACHOs or less compact dark (matter) objects. Ours is the first all-sky survey to locate escaped companions that are still drifting along with each other, long after their binary bond has been broken. We test stars for companionship up to an apparent separation of 8 parsec: 10 to 100 times wider than previous searches. Among Hipparcos stars within 100 pc, we find about 260 systems with separations between 0.01 and 1 pc, and another 190 with separation from 1 to 8 parsec. We find a number of previously unnoticed naked-eye companions, among which: Capella & 50 Per; Alioth, Megrez & Alcor; gamma & tau Cen; phi Eri & eta Hor; 62 & 63 Cnc; gamma & tau Per; zeta & delta Hya; beta01, beta02 & beta03 Tuc; 44 & 58 Oph and pi & rho Cep. At least 15 of our candidates are exoplanet host stars.

  18. Evolution of Close Binary Systems

    SciTech Connect

    Yakut, K; Eggleton, P

    2005-01-24

    We collected data on the masses, radii, etc. of three classes of close binary stars: low-temperature contact binaries (LTCBs), near-contact binaries (NCBs), and detached close binaries (DCBs). They restrict themselves to systems where (1) both components are, at least arguably, near the Main Sequence, (2) the periods are less than a day, and (3) there is both spectroscopic and photometric analysis leading to reasonably reliable data. They discuss the possible evolutionary connections between these three classes, emphasizing the roles played by mass loss and angular momentum loss in rapidly-rotating cool stars.

  19. Ecospheres around binary stars

    NASA Astrophysics Data System (ADS)

    Deka, B.

    2011-01-01

    Scientific investigations concerning ecospheres of other stars are very important for understanding the posibilities of existence and evolution of extraterrestrial life. In several last years astronomers discovered hundreds of extrasolar planets. Identification of stars with ecospheres is the first step in selecting those planets which could be inhabited. Usually an ecosphere of a single star is considered but it may also exist in planetary systems with two suns. This possibility is very promising in search for life on other planets as more that 60 % of stars reside in binary or multiple systems.

  20. Low autocorrelation binary sequences

    NASA Astrophysics Data System (ADS)

    Packebusch, Tom; Mertens, Stephan

    2016-04-01

    Binary sequences with minimal autocorrelations have applications in communication engineering, mathematics and computer science. In statistical physics they appear as groundstates of the Bernasconi model. Finding these sequences is a notoriously hard problem, that so far can be solved only by exhaustive search. We review recent algorithms and present a new algorithm that finds optimal sequences of length N in time O(N {1.73}N). We computed all optimal sequences for N≤slant 66 and all optimal skewsymmetric sequences for N≤slant 119.

  1. BINARY STORAGE ELEMENT

    DOEpatents

    Chu, J.C.

    1958-06-10

    A binary storage device is described comprising a toggle provided with associsted improved driver circuits adapted to produce reliable action of the toggle during clearing of the toggle to one of its two states. or transferring information into and out of the toggle. The invention resides in the development of a self-regulating driver circuit to minimize the fluctuation of the driving voltages for the toggle. The disclosed driver circuit produces two pulses in response to an input pulse: a first or ''clear'' pulse beginning nt substantially the same time but endlrg slightly sooner than the second or ''transfer'' output pulse.

  2. Synthesis, crystal structure and electrical properties of the tetrahedral quaternary chalcogenides CuM2InTe4 (M=Zn, Cd)

    NASA Astrophysics Data System (ADS)

    Nolas, George S.; Hassan, M. Shafiq; Dong, Yongkwan; Martin, Joshua

    2016-10-01

    Quaternary chalcogenides form a large class of materials that continue to be of interest for energy-related applications. Certain compositions have recently been identified as possessing good thermoelectric properties however these materials typically have the kesterite structure type with limited variation in composition. In this study we report on the structural, optical and electrical properties of the quaternary chalcogenides CuZn2InTe4 and CuCd2InTe4 which crystallize in the modified zinc-blende crystal structure, and compare their properties with that of CuZn2InSe4. These p-type semiconductors have direct band gaps of about 1 eV resulting in relatively high Seebeck coefficient and resistivity values. This work expands on the research into quaternary chalcogenides with new compositions and structure types in order to further the fundamental investigation of multinary chalcogenides for potential thermoelectrics applications.

  3. A general solution-phase approach to oriented nanostructured films of metal chalcogenides on metal foils: the case of nickel sulfide.

    PubMed

    Zhang, Lizhi; Yu, Jimmy C; Mo, Maosong; Wu, Ling; Li, Quan; Kwong, Kwan Wai

    2004-07-07

    Oriented films of nickel sulfide nanostructures, ranging from hierarchical dendrites to nanobelts and nanorods, were hydrothermally grown on Ni foils. This approach has proven to be a general method for preparing nanostructured metal chalcogenides films on corresponding metal foils.

  4. Observational Types of Binaries in the Binary Star Database

    NASA Astrophysics Data System (ADS)

    Malkov, O.; Kovaleva, D.; Kaygorodov, P.

    2017-06-01

    In the present paper we describe observational types of binaries, included in BDB, the Binary star database, which presently contains data on physical and positional parameters for about 260 000 components of 120 000 stellar systems of multiplicity 2 to more than 20, taken from a large variety of published catalogues and databases.

  5. High thermoelectric figure of merit nanostructured pnictogen chalcogenides by bottom-up synthesis and assembly

    NASA Astrophysics Data System (ADS)

    Mehta, Rutvik J.

    Thermoelectric materials offer promise for realizing transformative environmentallyfriendly solid-state refrigeration technologies that could replace current technologies based on ozone-depleting liquid coolants. The fruition of this vision requires factorial enhancements in the figure of merit (ZT) of thermoelectric materials, necessitating high Seebeck coefficient (alpha), high electrical conductivity (sigma) and low thermal conductivity (kappa). This thesis reports a novel bottom-up approach to scalably sculpt large quantities (>10g/minute) of V 2VI3 nanocrystals with controllable shapes and sizes, and assemble them into bulk samples to obtain both high power factors alpha 2sigma as well as unprecedentedly low kappa through tunable doping and nanostructuring. The thesis demonstrates a surfactant-mediated microwave-solvothermal synthesis technique that selectively yields both n- and p-typed pnictogen chalcogenide (Bi2Te3, Sb2Te3, Bi2Se3) nanoplates and, nanowires and nanotubes (Sb 2Se3) that can be sintered to obtain 25-250 % increases in ZT>1 compared to their non-nanostructured and un-doped counterparts. A key result is that nanostructuring diminishes the lattice thermal conductivity kappa L to ultra-low values of 0.2-0.5 Wm-1K-1. Sub-atomic-percent sulfur doping and sulfurization of the pnictogen chalcogenides induced through mercaptan-terminated organic surfactants used in the synthesis result in large Seebeck coefficients between -240 < alpha < 298 muV/K and high sigma between 0.2-2.5 x 105 O -1m-1 as a consequence of high carrier mobilities 250-60 cm2/Vs, comparable to single-crystal values. The unique combination of properties results in the realization of a phonon-glass electron-crystal material, ideal for thermoelectric conversion and hence high ZT. The high power factors are shown to arise due to sulfur doping induced changes in the electronic structure and defect chemistries. These correlations are verified by detailed materials characterization, Hall

  6. Cepheid Binary Companions

    NASA Astrophysics Data System (ADS)

    Remage Evans, Nancy

    Blue main sequence companions of binary Cepheids can be used to determine Clio luminosity of the Cepheids. By matching the composite spectrum of the companion and the Cepheid with those of standard stars, the spectral type of the companion and the magnitude difference between the two stars can be determined. The main sequence absolute magnitude calibration of the companion then leads to the absolute magnitude of the Cepheid. The aim of this project is to obtain low dispersion SWP spectra of three Cepheids (T Vul, Y Lac, and RS Ori) for which the LWP spectra show excess flux at 2500 from the companion. In addition, we request LWP low dispersion spectra of five Cepheids to complete the survey of all Cepheids brighter than 8" magnitude to look for companions. Archival IUE spectra are non-existant or inadequate (no LWP or overexposed). The purpose of this survey is to accurately determine the percentage of Cepheids which are binaries, to compare with evolutionary predictions. This IUE survey will identify definitively Cepheids with blue companions, about which there is come confusion from groundbased photometric techniques, and hence prevent distortions to such parameters as luminosity, color and reddening. In addition, the distribution of mass ratios (from the spectral type of the main sequence mass and the evolutionary mass of the Cepheid (Evans and Bolton, 1989)), is basic information about star formation.

  7. Relativistic Binaries in Globular Clusters.

    PubMed

    Benacquista, Matthew J; Downing, Jonathan M B

    2013-01-01

    Galactic globular clusters are old, dense star systems typically containing 10(4)-10(6) stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or two compact objects. In this review, we discuss theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution that leads to relativistic binaries, and current and possible future observational evidence for this population. Our discussion of globular cluster evolution will focus on the processes that boost the production of tight binary systems and the subsequent interaction of these binaries that can alter the properties of both bodies and can lead to exotic objects. Direct N-body integrations and Fokker-Planck simulations of the evolution of globular clusters that incorporate tidal interactions and lead to predictions of relativistic binary populations are also discussed. We discuss the current observational evidence for cataclysmic variables, millisecond pulsars, and low-mass X-ray binaries as well as possible future detection of relativistic binaries with gravitational radiation.

  8. Multilevel Models for Binary Data

    ERIC Educational Resources Information Center

    Powers, Daniel A.

    2012-01-01

    The methods and models for categorical data analysis cover considerable ground, ranging from regression-type models for binary and binomial data, count data, to ordered and unordered polytomous variables, as well as regression models that mix qualitative and continuous data. This article focuses on methods for binary or binomial data, which are…

  9. Multilevel Models for Binary Data

    ERIC Educational Resources Information Center

    Powers, Daniel A.

    2012-01-01

    The methods and models for categorical data analysis cover considerable ground, ranging from regression-type models for binary and binomial data, count data, to ordered and unordered polytomous variables, as well as regression models that mix qualitative and continuous data. This article focuses on methods for binary or binomial data, which are…

  10. Andreev Reflection Spectroscopy on Single Crystals of Bismuth-Chalcogenide Topological Insulators

    NASA Astrophysics Data System (ADS)

    Granstrom, Chris; Fridman, Igor; Wei, J. Y. T.; Lei, Hechang; Petrovic, Cedomir

    2014-03-01

    Topological insulators have received great research interest in recent years. One salient feature of these materials is the helical spin polarization of their electronic surface states. Andreev reflection, a fundamental process that occurs between a superconductor and conducting material, has often been used to probe the spin polarization of various magnetic materials. In this work, we use superconducting Nb tips to make cryomagnetic Andreev reflection spectroscopy measurements on bismuth-chalcogenide single crystals. We analyze our spectral data, which show Andreev-like features, in the context of both calculated and measured spin-dependent band structures of these topological insulators. Work supported by NSERC, CFI-OIT and the Canadian Institute for Advanced Research. Work at Brookhaven is supported by the U.S. DOE under contract No. DE-AC02-98CH10886.

  11. Engineering of chalcogenide materials for embedded applications of Phase Change Memory

    NASA Astrophysics Data System (ADS)

    Zuliani, Paola; Palumbo, Elisabetta; Borghi, Massimo; Dalla Libera, Giovanna; Annunziata, Roberto

    2015-09-01

    Phase Change Memory technology can be a real breakthrough for process cost saving and performances for embedded applications. The feasibility at 90 nm technology node has been solidly proven in an industrial environment and the added value of this solution demonstrated. Nevertheless, for specific applications some improvement in High Temperature Data Retention (HTDR) characteristics is needed. In this work we present the engineering of chalcogenide materials in order to increase the stability of RESET state as a function of temperature. This goal has been achieved by exploring Ge-rich compounds in the Ge-Sb-Te ternary diagram. In particular, an optimized GexSbyTez Phase Change material, able to guarantee code integrity of the memory content after soldering thermal profile and data retention in extended temperature range has been obtained. Extrapolation of data retention at 10 years for temperatures higher than 150 °C cell-level has been demonstrated, thus enabling automotive applications.

  12. Evaluation of chalcogenide glasses for multispectral imaging in the visible, SWIR and LWIR spectral regions

    NASA Astrophysics Data System (ADS)

    Bréhault, A.; Calvez, L.; Pain, T.; Ma, H. L.; Bigou, D.; Duchêne, M.; Adam, P.; Rollin, J.; Zhang, X. H.

    2016-05-01

    In this paper, a first part will present the mechanical properties of the chalcohalide glass system GeS2-Ga2S3-CsCl. The hardness, Young's modulus, shear modulus and toughness of a series of glasses (0.8 GeS2 - 0.2 Ga2S3)100-x CsClx with x = 0, 5, 10, 15 have been investigated and compared with other glasses. Two particular compositions 75 GeS2 - 15 Ga2S3 - 10 CsCl and 65 GeS2 - 20 Ga2S3 - 15 CsCl are compared with existing industrial chalcogenide glasses. In a second part, two multispectral antireflective coatings are presented. These coatings, developed for a multispectral application, enhanced the transmissions in specific bands.

  13. Electronic correlations in vanadium chalcogenides: BaV Se(3) versus BaV S(3).

    PubMed

    Grieger, Daniel; Boehnke, Lewin; Lechermann, Frank

    2010-07-14

    Albeit structurally and electronically very similar, at low temperature the quasi-one-dimensional vanadium sulfide BaV S(3) shows a metal-to-insulator transition via the appearance of a charge-density-wave state, while BaV Se(3) apparently remains metallic down to zero temperature. This different behavior upon cooling is studied by means of density functional theory and its combination with the dynamical mean-field theory and the rotationally invariant slave-boson method. We reveal several subtle differences between these chalcogenides that provide indications for the deviant behavior of BaV Se(3) at low temperature. In this regard, a smaller Hubbard U in line with an increased relevance of the Hund's exchange J plays a vital role.

  14. Electronic correlations in vanadium chalcogenides: BaV Se3 versus BaV S3

    NASA Astrophysics Data System (ADS)

    Grieger, Daniel; Boehnke, Lewin; Lechermann, Frank

    2010-07-01

    Albeit structurally and electronically very similar, at low temperature the quasi-one-dimensional vanadium sulfide BaV S3 shows a metal-to-insulator transition via the appearance of a charge-density-wave state, while BaV Se3 apparently remains metallic down to zero temperature. This different behavior upon cooling is studied by means of density functional theory and its combination with the dynamical mean-field theory and the rotationally invariant slave-boson method. We reveal several subtle differences between these chalcogenides that provide indications for the deviant behavior of BaV Se3 at low temperature. In this regard, a smaller Hubbard U in line with an increased relevance of the Hund's exchange J plays a vital role.

  15. Structural Flexibility and Alloying in Ultrathin Transition-Metal Chalcogenide Nanowires

    DOE PAGES

    Lin, Junhao; Zhang, Yuyang; Zhou, Wu; ...

    2016-01-18

    Metallic transition-metal chalcogenide (TMC) nanowires are an important building block for 2D electronics that may be fabricated within semiconducting transition-metal dichalcogenide (TMDC) monolayers. Tuning the geometric structure and electronic properties of such nanowires is a promising way to pattern diverse functional channels for wiring multiple units inside a 2D electronic circuit. Nevertheless, few experimental investigations have been reported exploring the structural and compositional tunability of these nanowires, due to difficulties in manipulating the structure and chemical composition of an individual nanowire. Here, using a combination of scanning transmission electron microscopy (STEM) and density functional theory (DFT), we report that TMCmore » nanowires have substantial intrinsic structural flexibility and their chemical composition can be manipulated.« less

  16. Cadmium Chalcogenide Nano-Heteroplatelets: Creating Advanced Nanostructured Materials by Shell Growth, Substitution, and Attachment.

    PubMed

    Kormilina, Tatiana K; Cherevkov, Sergei A; Fedorov, Anatoly V; Baranov, Alexander V

    2017-09-12

    The current direction in the evolution of 2D semiconductor nanocrystals involves the combination of metal and semiconductor components to form new nanoengineered materials called nano-heteroplatelets. This Review covers different heterostructure architectures that can be applied to cadmium chalcogenide nanoplatelets, including variously shaped shell, metal nanoparticle decoration, and doped and alloy systems. Here, for the first time a complete classification of nano-heteroplatelet types is provided with recommended notations and a systematization of the existing knowledge and experience concerning heterostructure formation techniques, addressing the morphology, optoelectronic and magnetic properties, and novel features of different heterostructures. This Review is also devoted to possible applications of these heterostructures and of one-component nanoplatelets in multiple fields, including light-emitting devices and biological imaging. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Supercontinuum generation in chalcogenide double-clad fiber with near zero-flattened normal dispersion profile

    NASA Astrophysics Data System (ADS)

    Nagasaka, Kenshiro; Liu, Lai; Hoang Tuan, Tong; Cheng, Tonglei; Matsumoto, Morio; Tezuka, Hiroshige; Suzuki, Takenobu; Ohishi, Yasutake

    2017-09-01

    We demonstrate supercontinuum (SC) generation in a 2.8-cm-long chalcogenide double-clad fiber (Ch-DCF). The calculated chromatic dispersion of the fundamental mode shows that the Ch-DCF has flattened chromatic dispersion, which is within -10 ± 10 ps/nm/km from 3.8 to 12.6 μ {{m}} in the normal dispersion regime. The variation of SC spectra is investigated by changing the pump wavelength and pump peak power. The broadband SC spectra extending from 2 to 14 μm at the -40 dB level is observed when the pump wavelength of 10 μm and pump peak power of 1.3 MW. The SC generation is simulated by the scalar generalized nonlinear Schrödinger equation. The simulation results are mostly the same as the experimental results and show that the supercontinua generated in the Ch-DCF are highly coherent.

  18. Modeling of switching mechanism in GeSbTe chalcogenide superlattices

    NASA Astrophysics Data System (ADS)

    Yu, Xiaoming; Robertson, John

    2015-07-01

    We study the switching process in chalcogenide superlattice (CSL) phase-change memory materials by describing the motion of an atomic layer between the low and high resistance states. Two models have been proposed by different groups based on high-resolution electron microscope images. Model 1 proposes a transition from Ferro to Inverted Petrov state. Model 2 proposes a switch between Petrov and Inverted Petrov states. For each case, we note that the main transition is actually a vertical displacement of a Ge layer through a Te layer, followed by a lateral motion of GeTe sublayer to the final, low energy structure. Through calculating energy barriers, the rate-determining step is the displacive transition.

  19. Atomic Layering, Intermixing and Switching Mechanism in Ge-Sb-Te based Chalcogenide Superlattices

    NASA Astrophysics Data System (ADS)

    Yu, Xiaoming; Robertson, John

    2016-11-01

    GeSbTe-based chalcogenide superlattice (CSLs) phase-change memories consist of GeSbTe layer blocks separated by van der Waals bonding gaps. Recent high resolution electron microscopy found two types of disorder in CSLs, a chemical disorder within individual layers, and SbTe bilayer stacking faults connecting one block to an adjacent block which allows individual block heights to vary. The disorder requires a generalization of the previous switching models developed for CSL systems. Density functional calculations are used to describe the stability of various types of intra-layer disorder, how the block heights can vary by means of SbTe-based stacking faults and using a vacancy-mediated kink motion, and also to understand the nature of the switching process in more chemically disordered CSLs.

  20. Atomic Layering, Intermixing and Switching Mechanism in Ge-Sb-Te based Chalcogenide Superlattices

    PubMed Central

    Yu, Xiaoming; Robertson, John

    2016-01-01

    GeSbTe-based chalcogenide superlattice (CSLs) phase-change memories consist of GeSbTe layer blocks separated by van der Waals bonding gaps. Recent high resolution electron microscopy found two types of disorder in CSLs, a chemical disorder within individual layers, and SbTe bilayer stacking faults connecting one block to an adjacent block which allows individual block heights to vary. The disorder requires a generalization of the previous switching models developed for CSL systems. Density functional calculations are used to describe the stability of various types of intra-layer disorder, how the block heights can vary by means of SbTe-based stacking faults and using a vacancy-mediated kink motion, and also to understand the nature of the switching process in more chemically disordered CSLs. PMID:27853289

  1. EFFECTS OF LASER RADIATION ON MATTER: Photoinduced absorption in chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Ponomar', V. V.

    1990-08-01

    A dependence of the absorption coefficient on the optical radiation intensity in the range 10 - 5 - 1 W/cm2 was observed for chalcogenide glasses at a photon energy less than the band gap of the material. The absorption coefficient depended on the irradiation time. In the case of arsenic sulfide in the range 1.6-1.7 eV an absorption peak was observed at intensities of the order of 10 - 3 W/cm2. In this part of the spectrum the absorption probably involved metastable As-As, S-Se, and Se-Se "defect" bonds and was similar to the photoinduced degradation of hydrogenated amorphous silicon.

  2. Magnetoelectric and multiferroic properties of ternary copper chalcogenides Cu2MIIMIVS4

    NASA Astrophysics Data System (ADS)

    Nénert, G.; Palstra, T. T. M.

    2009-04-01

    We investigate theoretically the ternary copper chalcogenides with the general formula Cu2MIIMIVS4. This family of compounds can crystallize in two different non-centrosymmetric structures, I\\bar {4}2m or Pnm 21. We show that all the reported members of Cu2MIIMIVS4 having the Pnm 21 symmetry exhibit a large spontaneous polarization. This result suggests that several of these materials are likely to be multiferroics since they order magnetically at low temperature. We discuss in detail in the framework of Landau theory the members Cu2MnSnS4 and Cu2MnGeS4 which should present both a linear magnetoelectric effect and multiferroic behavior.

  3. Atomistic origin of an ordered superstructure induced superconductivity in layered chalcogenides.

    PubMed

    Ang, R; Wang, Z C; Chen, C L; Tang, J; Liu, N; Liu, Y; Lu, W J; Sun, Y P; Mori, T; Ikuhara, Y

    2015-01-27

    Interplay among various collective electronic states such as charge density wave and superconductivity is of tremendous significance in low-dimensional electron systems. However, the atomistic and physical nature of the electronic structures underlying the interplay of exotic states, which is critical to clarifying its effect on remarkable properties of the electron systems, remains elusive, limiting our understanding of the superconducting mechanism. Here, we show evidence that an ordering of selenium and sulphur atoms surrounding tantalum within star-of-David clusters can boost superconductivity in a layered chalcogenide 1T-TaS2-xSex, which undergoes a superconducting transition in the nearly commensurate charge density wave phase. Advanced electron microscopy investigations reveal that such an ordered superstructure forms only in the x area, where the superconductivity manifests, and is destructible to the occurrence of the Mott metal-insulator transition. The present findings provide a novel dimension in understanding the relationship between lattice and electronic degrees of freedom.

  4. Organic phase synthesis of noble metal-zinc chalcogenide core-shell nanostructures.

    PubMed

    Kumar, Prashant; Diab, Mahmud; Flomin, Kobi; Rukenstein, Pazit; Mokari, Taleb

    2016-10-15

    Multi-component nanostructures have been attracting tremendous attention due to their ability to form novel materials with unique chemical, optical and physical properties. Development of hybrid nanostructures that are composed of metal-semiconductor components using a simple approach is of interest. Herein, we report a robust and general organic phase synthesis of metal (Au or Ag)-Zinc chalcogenide (ZnS or ZnSe) core-shell nanostructures. This synthetic protocol also enabled the growth of more compositionally complex nanostructures of Au-ZnSxSe1-x alloys and Au-ZnS-ZnSe core-shell-shell. The optical and structural properties of these hybrid nanostructures are also presented.

  5. An SMS structure based temperature sensor using a chalcogenide multimode fibre

    NASA Astrophysics Data System (ADS)

    Wang, Pengfei; Yuan, Libo; Brambilla, Gilberto; Farrell, Gerald

    2016-11-01

    In this work we investigated the fabrication of a singlemode-multimode-singlemode (SMS) fibre structure based on a chalcogenide (As2S3 and AsxS1-x) multimode fibre (MMF) sandwiched between two standard silica singlemode fibres (SMFs) using a commercial fibre fusion splicer. The temperature dependence of this hybrid fibre structure was also investigated. A first proof of concept showed that the hybrid SMS fibre structure has an average experimental temperature sensitivity of 50.63 pm/°C over a temperature range of 20 °C 100°C at wavelengths around 1.55 μm. The measured results show a general agreement with numerical simulations based on a guided-mode propagation analysis method. Our result provides a potential platform for the development of compact, high-optical-quality and robust sensing devices operating at the mid-infrared wavelength range.

  6. Structural Flexibility and Alloying in Ultrathin Transition-Metal Chalcogenide Nanowires

    SciTech Connect

    Lin, Junhao; Zhang, Yuyang; Zhou, Wu; Pantelides, Sokrates T.

    2016-01-18

    Metallic transition-metal chalcogenide (TMC) nanowires are an important building block for 2D electronics that may be fabricated within semiconducting transition-metal dichalcogenide (TMDC) monolayers. Tuning the geometric structure and electronic properties of such nanowires is a promising way to pattern diverse functional channels for wiring multiple units inside a 2D electronic circuit. Nevertheless, few experimental investigations have been reported exploring the structural and compositional tunability of these nanowires, due to difficulties in manipulating the structure and chemical composition of an individual nanowire. Here, using a combination of scanning transmission electron microscopy (STEM) and density functional theory (DFT), we report that TMC nanowires have substantial intrinsic structural flexibility and their chemical composition can be manipulated.

  7. Superconductivity and oscillatory magnetoresistance at a topological-insulator/chalcogenide interface

    NASA Astrophysics Data System (ADS)

    Dean, C. L.; Kunchur, M. N.; Shahesteh-Mogaddam, N.; Varner, S. D.; Knight, J. M.; Ivlev, B. I.; He, Q. L.; Liu, H.; Wang, J.; Lortz, R.; Sou, I. K.

    2017-05-01

    The Bi2Te3/FeTe heterostructure intersects several phenomena and key classes of materials in condensed matter physics: topological insulators, superconductivity, magnetism, and the physics of interfaces. While neither the topological insulator (Bi2Te3) nor the iron chalcogenide (FeTe) are themselves superconductors, superconductivity forms in a thin 7nm interfacial layer between the two. The restricted dimensionality and the extraordinarily conductive normal state, possibly sourced by the topologically protected surface states, have led to the observation of novel phenomena such as the Likharev vortex explosion and transitions in behavior resulting from the interplay between current induced depairing and the Berezinski-Kosterlitz-Thouless regime. Bi2Te3/FeTe also displays the anomalous oscillatory magnetoresistance phenomenon, which we had previously observed in cuprates.

  8. Synthesis of chalcogenide and pnictide crystals in salt melts using a steady-state temperature gradient

    NASA Astrophysics Data System (ADS)

    Chareev, D. A.; Volkova, O. S.; Geringer, N. V.; Koshelev, A. V.; Nekrasov, A. N.; Osadchii, V. O.; Osadchii, E. G.; Filimonova, O. N.

    2016-07-01

    Some examples of growing crystals of metals, alloys, chalcogenides, and pnictides in melts of halides of alkali metals and aluminum at a steady-state temperature gradient are described. Transport media are chosen to be salt melts of eutectic composition with the participation of LiCl, NaCl, KCl, RbCl, CsCl, AlCl3, AlBr3, KBr, and KI in a temperature range of 850-150°C. Some crystals have been synthesized only using a conducting contour. This technique of crystal growth is similar to the electrochemical method. In some cases, to exclude mutual influence, some elements have been isolated and forced to migrate to the crystal growth region through independent channels. As a result, crystals of desired quality have been obtained using no special equipment and with sizes sufficient for study under laboratory conditions.

  9. Low-phonon-frequency chalcogenide crystalline hosts for rare earth lasers operating beyond three microns

    DOEpatents

    Payne, Stephen A.; Page, Ralph H.; Schaffers, Kathleen I.; Nostrand, Michael C.; Krupke, William F.; Schunemann, Peter G.

    2000-01-01

    The invention comprises a RE-doped MA.sub.2 X.sub.4 crystalline gain medium, where M includes a divalent ion such as Mg, Ca, Sr, Ba, Pb, Eu, or Yb; A is selected from trivalent ions including Al, Ga, and In; X is one of the chalcogenide ions S, Se, and Te; and RE represents the trivalent rare earth ions. The MA.sub.2 X.sub.4 gain medium can be employed in a laser oscillator or a laser amplifier. Possible pump sources include diode lasers, as well as other laser pump sources. The laser wavelengths generated are greater than 3 microns, as becomes possible because of the low phonon frequency of this host medium. The invention may be used to seed optical devices such as optical parametric oscillators and other lasers.

  10. Second harmonic generation in nanoscale films of transition metal chalcogenides: Taking into account multibeam interference

    NASA Astrophysics Data System (ADS)

    Lavrov, S. D.; Kudryavtsev, A. V.; Shestakova, A. P.; Kulyuk, L.; Mishina, E. D.

    2016-05-01

    Second harmonic generation is studied in structures containing nanoscale layers of transition metal chalcogenides that are two-dimensional semiconductors and deposited on a SiO2/Si substrate. The second harmonic generation intensity is calculated with allowance for multibeam interference in layers of dichalcogenide and silicon oxide. The coefficient of reflection from the SiO2-layer-based Fabry-Perot cavity is subsequently calculated for pump wave fields initiating nonlinear polarization at every point of dichalcogenide, which is followed by integration of all second harmonic waves generated by this polarization. Calculated second harmonic intensities are presented as functions of dichalcogenide and silicon oxide layer thicknesses. The dependence of the second harmonic intensity on the MoS2 layer thickness is studied experimentally in the layer of 2-140 nm. A good coincidence of the experimental data and numerical simulation results has been obtained.

  11. Chalcogenide glass planar MIR couplers for future chip based Bracewell interferometers

    NASA Astrophysics Data System (ADS)

    Kenchington Goldsmith, H.-D.; Cvetojevic, N.; Ireland, M.; Ma, P.; Tuthill, P.; Eggleton, B.; Lawrence, J. S.; Debbarma, S.; Luther-Davies, B.; Madden, S. J.

    2016-08-01

    Photonic integrated circuits are established as the technique of choice for a number of astronomical processing functions due to their compactness, high level of integration, low losses, and stability. Temperature control, mechanical vibration and acoustic noise become controllable for such a device enabling much more complex processing than can realistically be considered with bulk optics. To date the benefits have mainly been at wavelengths around 1550 nm but in the important Mid-Infrared region, standard photonic chips absorb light strongly. Chalcogenide glasses are well known for their transparency to beyond 10000 nm, and the first results from coupler devices intended for use in an interferometric nuller for exoplanetary observation in the Mid-Infrared L' band (3800-4200 nm) are presented here showing that suitable performance can be obtained both theoretically and experimentally for the first fabricated devices operating at 4000 nm.

  12. Tunability in electron transport of molybdenum chalcogenide nanowires by theoretical prediction

    NASA Astrophysics Data System (ADS)

    Akdim, Brahim; Pachter, Ruth; Vaia, Richard A.

    2014-11-01

    Transition metal chalcogenide nanowires could comprise an alternative for nanoelectronics application, yet this class of materials is not well-characterized. Here we predict tunability in I-V characteristics of MoX (X = S, Se) nanowires, dependent on chalcogen atom, Li doping, type of electrode, and morphology. We show an intrinsic negative differential resistance (NDR)-like behavior for Mo6S6 nanowires, explained by bands mismatch in the electronic structure calculated by density functional theory (DFT) within the non-equilibrium Green's function formalism. The NDR-like behavior is suppressed upon Li intercalation or for gold leads. The electron transport results are based on optimized configurations using a non-empirical London dispersion-corrected DFT functional.

  13. Chalcogenide glass fibers used for in situ infrared spectroscopy in biology and medicine

    NASA Astrophysics Data System (ADS)

    Keirsse, Julie; Bureau, Bruno; Boussard-Pledel, Catherine; Leroyer, P.; Ropert, M.; Dupont, Virginie; Anne, Marie L.; Ribault, C.; Sire, Olivier; Loreal, Olivier; Adam, Jean Luc

    2004-09-01

    Chalcogenide glass optical fibers possess very low optical losses in the middle infrared range from 2 to 12 mm. They were used to implement remote infrared spectroscopy, known as Fiber Evanescent Wave Spectroscopy (FEWS). Due to their hydrophobic behavior, such sensor is especially suitable for application in biology and medicine where water is a nuisance to detect relevant information. Moreover, the design of the sensor using tapered fibers enables to improve the signal to noise ratio. Then, once coupled with unsupervised analysis technique such as Principle Component Analysis (PCA), it has been shown that this tool is efficient to differentiate between obese and control mice by recording their serum FEWS spectra. The same method has been carried out to detect in situ the both phenotypes of a bacterial culture.

  14. Simulation of an erbium-doped chalcogenide micro-disk mid-infrared laser source.

    PubMed

    Al Tal, Faleh; Dimas, Clara; Hu, Juejun; Agarwal, Anu; Kimerling, Lionel C

    2011-06-20

    The feasibility of mid-infrared (MIR) lasing in erbium-doped gallium lanthanum sulfide (GLS) micro-disks was examined. Lasing condition at 4.5 µm signal using 800 nm pump source was simulated using rate equations, mode propagation and transfer matrix formulation. Cavity quality (Q) factors of 1.48 × 10(4) and 1.53 × 10(6) were assumed at the pump and signal wavelengths, respectively, based on state-of-the-art chalcogenide micro-disk resonator parameters. With an 80 µm disk diameter and an active erbium concentration of 2.8 × 10(20) cm(-3), lasing was shown to be possible with a maximum slope efficiency of 1.26 × 10(-4) and associated pump threshold of 0.5 mW.

  15. Mechanical model of giant photoexpansion in a chalcogenide glass and the role of photofluidity

    NASA Astrophysics Data System (ADS)

    Buisson, Manuel; Gueguen, Yann; Laniel, Romain; Cantoni, Christopher; Houizot, Patrick; Bureau, Bruno; Sangleboeuf, Jean-Christophe; Lucas, Pierre

    2017-07-01

    An analytical model is developed to describe the phenomenon of giant photoexpansion in chalcogenide glasses. The proposed micro-mechanical model is based on the description of photoexpansion as a new type of eigenstrain, i.e. a deformation analogous to thermal expansion induced without external forces. In this framework, it is the viscoelastic flow induced by photofluidity which enable the conversion of the self-equilibrated stress into giant photoexpansion. This simple approach yields good fits to experimental data and demonstrates, for the first time, that the photoinduced viscous flow actually enhances the giant photoexpansion or the giant photocontraction as it has been suggested in the literature. Moreover, it highlights that the shear relaxation time due to photofluidity controls the expansion kinetic. This model is the first step towards describing giant photoexpansion from the point of view of mechanics and it provides the framework for investigating this phenomenon via numerical simulations.

  16. Transport and thermoelectric properties in Copper intercalated TiS{sub 2} chalcogenide

    SciTech Connect

    Guilmeau, E.; Breard, Y.; Maignan, A.

    2011-08-01

    We report on the thermoelectric properties of Cu{sub x}TiS{sub 2} bulk compounds. Copper cations have been intercalated into the layered chalcogenide TiS{sub 2} by spark plasma sintering. X-ray diffraction analysis coupled to transmission electron microscopy shows that the lattice constant c expands linearly as the Cu content x increases. The Cu-intercalation into TiS{sub 2} leads to substantial decrease in both electrical resistivity and lattice thermal conductivity as compared to those of pristine TiS{sub 2}. The figure of merit, ZT, is increased up to 0.45 at 800 K for x = 0.02. The power factor, PF, reaches 1.7 mW/mK{sup 2} in TiS{sub 2} at 325 K.

  17. Investigations of Ge-Te-AgI chalcogenide glass for far-infrared application.

    PubMed

    Wang, Xunsi; Nie, Qiuhua; Wang, Guoxiang; Sun, Jie; Song, Baoan; Dai, Shixun; Zhang, Xianghua; Bureau, Bruno; Boussard, Catherine; Conseil, Clément; Ma, Hongli

    2012-02-01

    A serious of tellurium based chalcogenide glass were prepared and investigated. As it being transparent nearly up to 25 μm and strong anti-hydrability, it becomes an optimized material for far-infrared application. Here, AgI was incorporated into the glasses acting as a glass modifier. With the help of AgI, a highest glass transition temperature, T(g) (151 °C) can be obtained. Detailed physics and chemic properties of the glasses were analyzed with DTA and XRD. The infrared optical transmission spectra were studied with the help of FTIR and Raman test. A purifying process was adopted to eliminate the affections of impurities in the tellurium glass. These serious of glasses are all high transparent in the 8-20 μm region, which fits for the applications of far-infrared optic imaging and sensing. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. High-quality chalcogenide glass waveguide fabrication by hot melt smoothing and micro-trench filling

    NASA Astrophysics Data System (ADS)

    Zhai, Yanfen; Qi, Renduo; Yuan, Chenzhi; Zhang, Wei; Huang, Yidong

    2016-05-01

    We propose a fabrication method for chalcogenide glass (ChG) waveguides based on hot melt smoothing and micro-trench filling. ChGs has low melting points and good flowability. Experiments show that this method can realize high quality As2S7 glass waveguides with reverse ridge structures. The attenuations of the fundamental quasi-TE mode and quasi-TM mode are 0.1 and 0.9 dB/cm, respectively. This method avoids fabrication processes, such as photolithography, lift-off, and dry or wet etching that are directly applied to the ChG films. It provides a simple way to fabricate high quality ChG waveguides, which have great potential for applications in integrated nonlinear optical devices.

  19. Light trimming of a narrow bandpass filter based on a photosensitive chalcogenide spacer.

    PubMed

    Shen, W D; Cathelinaud, M; Lequime, M D; Charpentier, F; Nazabal, V

    2008-01-07

    We present an experimental study of the photosensitive properties of a narrow bandpass filter based on a Ge(15)Sb(20)S(65) spacer fabricated by electron beam deposition. For a single layer, near the optical bandgap of this chalcogenide material, the efficiency of the photo-bleaching increases as the central wavelength of the light source for exposure decreases. The maximum relative photo-induced change of the optical thickness reaches about 1%. By using controlled light exposure around 480 nm of a photosensitive narrow bandpass filter centered at 1550 nm, we obtained a spatially localized shift of its peak wavelength up to 5.4 nm. This property is used to perform, for the first time at our knowledge, the post trimming of a narrow bandpass filter with a light beam. A 5 x 5 mm(2) ultra uniform area in which the relative spatial variation of its peak wavelength remains below 0.004% is demonstrated.

  20. Tuning the LSPR in copper chalcogenide nanoparticles by cation intercalation, cation exchange and metal growth.

    PubMed

    Wolf, Andreas; Kodanek, Torben; Dorfs, Dirk

    2015-12-14

    Localized surface plasmon resonances (LSPRs) of degenerately doped copper chalcogenide nanoparticles (NPs) (Cu2-xSe berzelianite and Cu1.1S covellite) have been modified applying different methods. The comparison of the cation exchange (Cu2-xSe) and intercalation (Cu1.1S) of Ag(I) and Cu(I) has shown that Ag(I) causes a non reversible, air stable shift of the LSPR. This was compared to the influence of Au(I) cation exchange into Cu1.1S platelets under the formation of Cu1.1S-Au2S mixed nanoplatelets. Furthermore, we show the growth of Au domains on Cu2-xSe, and discuss the interaction of the two plasmonic parts of the obtained dual plasmonic Cu2-xSe-Au hybrid particles.

  1. Power-efficient production of photon pairs in a tapered chalcogenide microwire

    SciTech Connect

    Meyer-Scott, Evan Dot, Audrey; Ahmad, Raja; Li, Lizhu; Rochette, Martin; Jennewein, Thomas

    2015-02-23

    Using tapered fibers of As{sub 2}Se{sub 3} chalcogenide glass, we produce photon pairs at telecommunication wavelengths with low pump powers. We found maximum coincidences-to-accidentals ratios of 2.13 ± 0.07 for degenerate pumping with 3.2 μW average power, and 1.33 ± 0.03 for non-degenerate pumping with 1.0 μW and 1.5 μW average power of the two pumps. Our results show that the ultrahigh nonlinearity in these microwires could allow single-photon pumping to produce photon pairs, enabling the production of large entangled states, heralding of single photons after lossy transmission, and photonic quantum information processing with nonlinear optics.

  2. General sacrificial template method for the synthesis of cadmium chalcogenide hollow structures.

    PubMed

    Miao, Jian-Jun; Jiang, Li-Ping; Liu, Chang; Zhu, Jian-Min; Zhu, Jun-Jie

    2007-07-09

    Semiconductor CdX (X=Te, Se, S) hollow structures have been successfully prepared by using Cd(OH)Cl precursors as a sacrificial template. The hollow structures can be hollow spheres or tubes by controlling the shape of the sacrificial template. The products were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy-dispersive spectrometry. The obtained results showed that the hollow structures had complementary shapes and sizes of the original sacrificial templates. This is a general method for the synthesis of cadmium chalcogenide hollow structures, and the method is simpler and more practical than direct synthesis of certain hollow structures, which further widens the avenue to using those materials that have been synthesized with various shapes to fabricate specific hollow structures.

  3. Third-harmonic generation in slow-light chalcogenide glass photonic crystal waveguides

    NASA Astrophysics Data System (ADS)

    Monat, Christelle; Spurny, Marcel; Grillet, Christian; O'Faolain, Liam; Krauss, Thomas F.; Eggleton, Benjamin J.; Bulla, Douglas; Madden, Steve; Luther-Davies, Barry

    2011-08-01

    We demonstrate third-harmonic generation (THG) in a dispersion-engineered slow-light photonic crystal waveguide fabricated in AMTIR-1 chalcogenide glass. Owing to the relatively low loss and low dispersion in the slow-light (c/30) regime, combined with the high nonlinear figure of merit of the material (˜2), we obtain a relatively large conversion efficiency (1.4×10-8/W2), which is 30× higher than in comparable silicon waveguides, and observe a uniform visible light pattern along the waveguide. These results widen the number of applications underpinned by THG in slow-light platforms, such as the direct observation of the spatial evolution of the propagating mode.

  4. 2 μm Raman fiber laser based on a multimaterial chalcogenide microwire

    NASA Astrophysics Data System (ADS)

    Abdukerim, Nurmemet; Li, Lizhu; El Amraoui, Mohammed; Messaddeq, Younès; Rochette, Martin

    2017-04-01

    We report a Raman fiber laser based on a multimaterial chalcogenide microwire. The microwire structure comprises a core of As38Se62, a cladding of As38S62, and a coating of poly-methyl methacrylate. The microwire is a robust, high confinement waveguide compatible with the mid-infrared. With the microwire inserted in a ring cavity, Raman laser oscillation at a wavelength of 2.025 μm occurs from synchronous pumping at a wavelength of 1.938 μm. The input peak power required to reach threshold is 4.6 W and the power slope efficiency is 4.5%. Numerical simulations are in good agreement with experimental results and predict chirp-free femtosecond pulses.

  5. Low-loss chalcogenide waveguides for chemical sensing in the mid-infrared.

    PubMed

    Ma, Pan; Choi, Duk-Yong; Yu, Yi; Gai, Xin; Yang, Zhiyong; Debbarma, Sukanta; Madden, Steve; Luther-Davies, Barry

    2013-12-02

    We report the characteristics of low-loss chalcogenide waveguides for sensing in the mid-infrared (MIR). The waveguides consisted of a Ge₁₁.₅As₂₄Se₆₄.₅ rib waveguide core with a 10nm fluoropolymer coating on a Ge₁₁.₅As₂₄S₆₄.₅ bottom cladding and were fabricated by thermal evaporation, photolithography and ICP plasma etching. Over most of the functional group band from 1500 to 4000 cm⁻¹ the losses were < 1 dB/cm with a minimum of 0.3 dB/cm at 2000 cm⁻¹. The basic capabilities of these waveguides for spectroscopy were demonstrated by measuring the absorption spectrum of soluble Prussian blue in Dimethyl Sulphoxide.

  6. The development of two dimensional group IV chalcogenides, blocks for van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Sa, Baisheng; Sun, Zhimei; Wu, Bo

    2015-12-01

    In this work, we introduce a series of two dimensional (2D) group IV chalcogenides (AX)2 with the building block X-A-A-X (A = Si, Ge, Sn, and Pb, and X = Se and Te) on the basis of ab initio calculations. The analysis of energy evaluation, lattice vibration as well as the chemical bonding demonstrate the good stability of these 2D materials. Furthermore, the pictures for the chemical bonding and electronic features of the 2D (AX)2 are drawn. Their narrow gapped semiconducting nature is unraveled. Especially, strong interactions between the electrons and phonons as well as the topological insulating nature in (SiTe)2 are observed. The present results indicate that such remarkable artificial 2D (AX)2 are building blocks for van der Waals heterostructure engineering, which shows potential applications in nanoscaled electronics and optoelectronics.

  7. Light-induced switching of a chalcogenide-coated side-polished fiber device

    NASA Astrophysics Data System (ADS)

    Wen, Shu-Chen; Chang, Chih-Wei; Lin, Chia-Ming; Liu, Hua-an; Hsiao, Vincent K. S.; Yu, Jianhui; Chen, Zhe

    2015-01-01

    In this report, we describe light-induced switching of the state of polarization of a side-polished fiber (SPF) coated with a chalcogenide (ChG) film, amorphous As2Se3 (a-As2Se3). The transient photodarkening effect produced by a-As2Se3 under 532-nm laser illumination modulated the refractive index of the coated ChG, changed the refractive index of the a-As2Se3-coated SPF device, and controlled and switched the phase retardation. When this design was used, a 70° phase change coupled with an optical loss of <0.2 dB was achieved at a probe-beam wavelength of 1550 nm; moreover, the extinction ratio achieved using an inline fiber polarizer was 22.8 dB.

  8. First-principles study of thermoelectric transport properties of monolayer gallium chalcogenides

    NASA Astrophysics Data System (ADS)

    Ge, Xu-Jin; Qin, Dan; Yao, Kai-Lun; Lü, Jing-Tao

    2017-10-01

    Through first-principles calculations, we study the thermoelectric transport properties of monolayer gallium chalcogenides GaX with X being S, Se or Te. We show that, the Mexican-hat-shaped dispersion near the valence band maximum, absent in the bulk, effectively enhances their thermoelectric performance. We analyze these results using a simple model Hamiltonian, and show that it can be understood as an effective one-dimensional band structure emerging from these two-dimensional materials. These results support recent proposals of using low-dimensional electronic band in high-dimensional materials in the search of new high-performance thermoelectric materials. Moreover, for n-doping, we find that strain engineering could be an efficient way of tuning the position of conduction band minimum and the corresponding thermoelectric performance.

  9. Anisotropic crystallization in solution processed chalcogenide thin film by linearly polarized laser

    NASA Astrophysics Data System (ADS)

    Gu, Tingyi; Jeong, Hyuncheol; Yang, Kengran; Wu, Fan; Yao, Nan; Priestley, Rodney D.; White, Claire E.; Arnold, Craig B.

    2017-01-01

    The low activation energy associated with amorphous chalcogenide structures offers broad tunability of material properties with laser-based or thermal processing. In this paper, we study near-bandgap laser induced anisotropic crystallization in solution processed arsenic sulfide. The modified electronic bandtail states associated with laser irradiation lead to a distinctive photoluminescence spectrum, compared to thermally annealed amorphous glass. Laser crystalized materials exhibit a periodic subwavelength ripple structure in transmission electron microscopy experiments and show polarization dependent photoluminescence. Analysis of the local atomic structure of these materials using laboratory-based X-ray pair distribution function analysis indicates that laser irradiation causes a slight rearrangement at the atomic length scale, with a small percentage of S-S homopolar bonds converting to As-S heteropolar bonds. These results highlight fundamental differences between laser and thermal processing in this important class of materials.

  10. Review on Chalcogenide 3D Nano-structured Crystals: Synthesis and Growth Mechanism.

    PubMed

    Qiu, Qi

    2015-01-01

    Three dimensional (3D) nano-structured crystals have received extensive attention for their superior properties over zero dimensional (0D), one dimensional (1D), or two dimensional (2D) nanomaterials in many areas. This review is generalized for the group of chalcogenide nanoflowers (NFs) by the synthetic techniques, such as solvothermal, wet chemical, sol-gel, surface oxidation, microwave, coating, electrochemical, and several other methods. The formation mechanism was also described for the purpose of opening up new food for thoughts to bring up new functionality of materials by tuning the morphology of crystals. The pH value or the template plays fundamental role in forming the nano-flowered structure. Moreover, the correlations between the surface area (SA), contact angle (CA), and the NFs are also discussed within the context. Here, we also discussed some patents relevant to the topic.

  11. Fabrication of a mid-IR wire-grid polarizer by direct imprinting on chalcogenide glass.

    PubMed

    Yamada, Itsunari; Yamashita, Naoto; Tani, Kunihiko; Einishi, Toshihiko; Saito, Mitsunori; Fukumi, Kouhei; Nishii, Junji

    2011-10-01

    A mid-IR wire-grid polarizer with a 500 nm pitch was fabricated on a low toxic chalcogenide glass (Sb-Ge-Sn-S system) by the thermal imprinting of periodic grating followed by the thermal evaporation of Al metal. After imprinting, deposition of Al on the grating at an oblique angle produced a wire-grid polarizer. The fabricated polarizer showed polarization with TM transmittance greater than 60% at 5-9 μm wavelengths and an extinction ratio greater than 20 dB at 3.5-11 μm wavelengths. This polarizer with a high extinction ratio can be fabricated more simply and less expensively than conventional IR polarizers.

  12. Atomistic origin of an ordered superstructure induced superconductivity in layered chalcogenides

    NASA Astrophysics Data System (ADS)

    Ang, R.; Wang, Z. C.; Chen, C. L.; Tang, J.; Liu, N.; Liu, Y.; Lu, W. J.; Sun, Y. P.; Mori, T.; Ikuhara, Y.

    2015-01-01

    Interplay among various collective electronic states such as charge density wave and superconductivity is of tremendous significance in low-dimensional electron systems. However, the atomistic and physical nature of the electronic structures underlying the interplay of exotic states, which is critical to clarifying its effect on remarkable properties of the electron systems, remains elusive, limiting our understanding of the superconducting mechanism. Here, we show evidence that an ordering of selenium and sulphur atoms surrounding tantalum within star-of-David clusters can boost superconductivity in a layered chalcogenide 1T-TaS2-xSex, which undergoes a superconducting transition in the nearly commensurate charge density wave phase. Advanced electron microscopy investigations reveal that such an ordered superstructure forms only in the x area, where the superconductivity manifests, and is destructible to the occurrence of the Mott metal-insulator transition. The present findings provide a novel dimension in understanding the relationship between lattice and electronic degrees of freedom.

  13. Dynamics of the current filament formation and its steady-state characteristics in chalcogenide based PCM

    NASA Astrophysics Data System (ADS)

    Bogoslovskiy, Nikita; Tsendin, Konstantin

    2017-03-01

    In the phase-change memory (PCM) crystallization occurs in the high-current filament which forms during switching to the conductive state. In the present paper we conduct a numerical modeling of the current filament formation dynamics in thin chalcogenide films using an electronic-thermal model based on negative-U centers tunnel ionization and Joule heating. The key role of inhomogeneities in the filament formation process is shown. Steady-state filament parameters were obtained from the analysis of the stationary heat conduction equation. The filament formation dynamics and the steady-state filament radius and temperature could be controlled by material parameters and contact resistance. Consequently it is possible to control the size of the region wherein crystallization occurs. A good agreement with numerous experimental data leads to the conclusion that thermal effects play a significant role in CGS conduction and high-current filament formation while switching.

  14. Relaxation dynamics in the strong chalcogenide glass-former of Ge22Se78

    PubMed Central

    Li, Pengfei; Zhang, Yaqi; Chen, Zeming; Gao, Peng; Wu, Tao; Wang, Li-Min

    2017-01-01

    The enthalpy relaxation is performed in the glassy Ge22Se78 to understand the dynamic behaviors. The structure of the glass is examined by X-ray diffraction and Raman spectra. The dynamic parameters such as the fragility, stretching exponent and non-linear factor are determined. A low fragility of m = 27 is exhibited for the chalcogenide, however, the stretching exponent is found not to have a larger value. The enthalpy relaxation spectra are constructed for various glass formers, and a relationship between the fragility and the symmetry of the spectra is demonstrated. The dynamic results are used to evaluate the structure of the Ge22Se78 glass. PMID:28094287

  15. Recent advances in very highly nonlinear chalcogenide photonic crystal fibers and their applications

    NASA Astrophysics Data System (ADS)

    Méchin, David; Brilland, Laurent; Troles, Johann; Chartier, Thierry; Besnard, Pascal; Canat, Guillaume; Renversez, Gilles

    2012-02-01

    Perfos and the laboratory Glasses and Ceramics Group of University of Rennes 1 have worked together to develop a new fabrication technique for chalcogenide preforms based on the glass-casting process. Various fiber profiles have been designed by the Fresnel Institute and fiber losses have been significantly improved, approaching those of the material losses. Using this technology, we have manufactured an AsSe CPCF exhibiting a nonlinear coefficient γ of 46 000 W-1km-1. Self-phase modulation, Raman effect, Brillouin effect, Four-Wave Mixing have been observed leading to the demonstration of various optical functions such four-wave mixing based wavelength conversion at 1.55 μm by FOTON, the demonstration of Raman Shifts and the generation of a mid-IR supercontinuum source by ONERA and the demonstration of a Brillouin fiber laser by FOTON.

  16. Structural and optical investigation of Te-based chalcogenide thin films

    SciTech Connect

    Sharma, Rita Sharma, Shaveta; Thangaraj, R.; Mian, M.; Chander, Ravi; Kumar, Praveen

    2015-05-15

    We report the structural and optical properties of thermally evaporated Bi{sub 2}Te{sub 3}, In{sub 2}Te{sub 3} and InBiTe{sub 3} films by using X-ray diffraction, optical and Raman Spectroscopy techniques. The as-prepared thin films were found to be Semi-crystalline by X-ray diffraction. Particle Size and Strain has been calculated from XRD data. The optical constants, film thickness, refractive index and optical band gap (E{sub g}) has been reported for In{sub 2}Te{sub 3}, InBiTe{sub 3} films. Raman Spectroscopy was performed to investigate the effect of Bi, In, on lattice vibration and chemical bonding in Te based chalcogenide glassy alloys.

  17. Enhanced Kerr nonlinearity in As IISe 3 chalcogenide fibre tapers with sub-wavelength diameter

    NASA Astrophysics Data System (ADS)

    Nguyen, Hong C.; Mägi, Eric C.; Yeom, Dong-Il; Fu, Libin; Eggleton, Benjamin J.

    2007-05-01

    The nonlinearity in optical fibres can be enhanced significantly by reducing the effective mode area or by using materials with higher nonlinear-index coefficient (n II). In this paper we combine these two concepts and experimentally demonstrate enhanced Kerr nonlinear effects in tapered highly nonlinear As IISe 3 chalcogenide fibre. We taper the fibre to sub-wavelength waist diameter of 1.2 μm and observe enhanced nonlinearity of 63,600 W -1km -1. This is 40,000 times larger than in silica single-mode fibre, owing to the 400 times larger n II and almost 100 times smaller effective mode area. We also discuss the role of group velocity dispersion in these highly nonlinear fibre tapers.

  18. Signature Visualization of Software Binaries

    SciTech Connect

    Panas, T

    2008-07-01

    In this paper we present work on the visualization of software binaries. In particular, we utilize ROSE, an open source compiler infrastructure, to pre-process software binaries, and we apply a landscape metaphor to visualize the signature of each binary (malware). We define the signature of a binary as a metric-based layout of the functions contained in the binary. In our initial experiment, we visualize the signatures of a series of computer worms that all originate from the same line. These visualizations are useful for a number of reasons. First, the images reveal how the archetype has evolved over a series of versions of one worm. Second, one can see the distinct changes between version. This allows the viewer to form conclusions about the development cycle of a particular worm.

  19. Magnetic activity of interacting binaries

    NASA Astrophysics Data System (ADS)

    Hill, Colin A.

    2017-10-01

    Interacting binaries provide unique parameter regimes, both rapid rotation and tidal distortion, in which to test stellar dynamo theories and study the resulting magnetic activity. Close binaries such as cataclysmic variables (CVs) have been found to differentially rotate, and so can provide testbeds for tidal dissipation efficiency in stellar convective envelopes, with implications for both CV and planet-star evolution. Furthermore, CVs show evidence of preferential emergence of magnetic flux tubes towards the companion star, as well as large, long-lived prominences that form preferentially within the binary geometry. Moreover, RS CVn binaries also show clear magnetic interactions between the two components in the form of coronal X-ray emission. Here, we review several examples of magnetic interactions in different types of close binaries.

  20. How do binary clusters form?

    NASA Astrophysics Data System (ADS)

    Arnold, Becky; Goodwin, Simon P.; Griffiths, D. W.; Parker, Richard. J.

    2017-10-01

    Approximately 10 per cent of star clusters are found in pairs, known as binary clusters. We propose a mechanism for binary cluster formation; we use N-body simulations to show that velocity substructure in a single (even fairly smooth) region can cause binary clusters to form. This process is highly stochastic and it is not obvious from a region's initial conditions whether a binary will form and, if it does, which stars will end up in which cluster. We find the probability that a region will divide is mainly determined by its virial ratio, and a virial ratio above 'equilibrium' is generally necessary for binary formation. We also find that the mass ratio of the two clusters is strongly influenced by the initial degree of spatial substructure in the region.

  1. Characterization of Single-mode Chalcogenide Optical Fiber for Mid-Infrared Applications

    SciTech Connect

    Krishnaswami, Kannan; Qiao, Hong; Bernacki, Bruce E.; Anheier, Norman C.

    2009-04-01

    Chalcogenide fibers display a wide transmission window ranging from 2-10.6 μm, ideally suited to the development of passive and active mid-infrared (MIR) sensors. They are essential building blocks for the integration and miniaturization of laser-based MIR optical systems for terrestrial, airborne and space-based sensing platforms. Single-mode chalcogenide fibers have only recently become commercially available and therefore performance data and standard reproducible processing techniques have not been widely reported. In this paper we present a method for producing high quality facets on commercial single-mode As-Se fibers with core and cladding diameters of 28.1 and 169.9μm respectively. The emitted beam profile from these fibers, using the 9.4μm line of a tunable CO2 laser, showed the presence of leaky cladding modes due to waveguiding conditions created by the protective acrylate jacket. These undesirable cladding modes were easily suppressed by applying a gallium coating on the cladding near both input and output facets. We provide experimental data of efficient mode suppression and the emission of a circular near-perfect Gaussian beam profile from the fiber. A model to determine appropriate placement of gallium coatings to minimize processing while maximizing cladding mode suppression is currently underway. Furthermore, analyses of the beam, acquired by scanning an HgCdTe detector, yielded a 1/e2 numerical aperture of 0.11 with a full width half maximum divergence of 11° for these fibers. The availability of single-mode MIR fibers, in conjunction with recent advances in room temperature quantum cascade lasers (QCL), could provide compact and light-weight transmitter solutions for several critical defense and nuclear non-proliferation needs.

  2. Dy{sup 3+}-doped Ga–Sb–S chalcogenide glasses for mid-infrared lasers

    SciTech Connect

    Zhang, Mingjie; Yang, Anping; Peng, Yuefeng; Zhang, Bin; Ren, He; Guo, Wei; Yang, Yan; Zhai, Chengcheng; Wang, Yuwei; Yang, Zhiyong; Tang, Dingyuan

    2015-10-15

    Highlights: • Novel Ga–Sb–S chalcogenide glasses doped with Dy{sup 3+} ions were synthesized. • The glasses show good thermal stability and excellent infrared transparency. • The glasses show low phonon energy and intense mid-infrared emissions. • The mid-infrared emissions have high quantum efficiency. • The mid-infrared emissions have large stimulated emission cross sections. - Abstract: Novel Ga–Sb–S chalcogenide glasses doped with different amount of Dy{sup 3+} ions were prepared. Their thermal stability, optical properties, and mid-infrared (MIR) emission properties were investigated. The glasses show good thermal stability, excellent infrared transparency, very low phonon energy (∼306 cm{sup −1}), and intense emissions centered at 2.95, 3.59, 4.17 and 4.40 μm. Three Judd–Ofelt intensity parameters (Ω{sub 2} = 8.51 × 10{sup −20} cm{sup 2}, Ω{sub 4} = 2.09 × 10{sup −20} cm{sup 2}, and Ω{sub 6} = 1.60 × 10{sup −20} cm{sup 2}) are obtained, and the related radiative transition properties are evaluated. The high quantum efficiencies and large stimulated emission cross sections of the MIR emissions (88.10% and 1.11 × 10{sup −20} cm{sup 2} for 2.95 μm emission, 75.90% and 0.38 × 10{sup −20} cm{sup 2} for 4.40 μm emission, respectively) in the Dy{sup 3+}-doped Ga–Sb–S glasses make them promising gain materials for the MIR lasers.

  3. Hubbard interactions in iron-based pnictides and chalcogenides: Slater parametrization, screening channels, and frequency dependence

    NASA Astrophysics Data System (ADS)

    van Roekeghem, Ambroise; Vaugier, Loïg; Jiang, Hong; Biermann, Silke

    2016-09-01

    We calculate the strength of the frequency-dependent on-site electronic interactions in the iron pnictides LaFeAsO, BaFe2As2 , BaRu2As2 , and LiFeAs and the chalcogenide FeSe from first principles within the constrained random phase approximation. We discuss the accuracy of an atomiclike parametrization of the two-index density-density interaction matrices based on the calculation of an optimal set of three independent Slater integrals, assuming that the angular part of the Fe d localized orbitals can be described within spherical harmonics as for isolated Fe atoms. We show that its quality depends on the ligand-metal bonding character rather than on the dimensionality of the lattice: it is excellent for ionic-like Fe-Se (FeSe) chalcogenides and a more severe approximation for more covalent Fe-As (LaFeAsO, BaFe2As2 ) pnictides. We furthermore analyze the relative importance of different screening channels, with similar conclusions for the different pnictides but a somewhat different picture for the benchmark oxide SrVO3: the ligand channel does not appear to be dominant in the pnictides, while oxygen screening is the most important process in the oxide. Finally, we analyze the frequency dependence of the interaction. In contrast to simple oxides, in iron pnictides its functional form cannot be simply modeled by a single plasmon, and the actual density of modes enters the construction of an effective Hamiltonian determining the low-energy properties.

  4. Surface oxidation of tin chalcogenide nanocrystals revealed by 119Sn-Mössbauer spectroscopy.

    PubMed

    de Kergommeaux, Antoine; Faure-Vincent, Jérôme; Pron, Adam; de Bettignies, Rémi; Malaman, Bernard; Reiss, Peter

    2012-07-18

    Narrow band gap tin(II) chalcogenide (SnS, SnSe, SnTe) nanocrystals are of high interest for optoelectronic applications such as thin film solar cells or photodetectors. However, charge transfer and charge transport processes strongly depend on nanocrystals' surface quality. Using (119)Sn-Mössbauer spectroscopy, which is the most sensitive tool for probing the Sn oxidation state, we show that SnS nanocrystals exhibit a Sn((IV))/Sn((II)) ratio of around 20:80 before and 40:60 after five minutes exposure to air. Regardless of the tin or sulfur precursors used, similar results are obtained using six different synthesis protocols. The Sn((IV)) content before air exposure arises from surface related SnS(2) and Sn(2)S(3) species as well as from surface Sn atoms bound to oleic acid ligands. The increase of the Sn((IV)) content upon air exposure results from surface oxidation. Full oxidation of the SnS nanocrystals without size change is achieved by annealing at 500 °C in air. With the goal to prevent surface oxidation, SnS nanocrystals are capped with a cadmium-phosphonate complex. A broad photoluminescence signal centered at 600 nm indicates successful capping, which however does not reduce the air sensitivity. Finally we demonstrate that SnSe nanocrystals exhibit a very similar behavior with a Sn((IV))/Sn((II)) ratio of 43:57 after air exposure. In the case of SnTe nanocrystals, the ratio of 55:45 is evidence of a more pronounced tendency for oxidation. These results demonstrate that prior to their use in optoelectronics further surface engineering of tin chalcogenide nanocrystals is required, which otherwise have to be stored and processed under inert atmosphere.

  5. Local structural order and relaxation effects in metal-chalcogenide glasses

    SciTech Connect

    Saleh, Z.M.

    1990-01-01

    Nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) have been employed to study the local structural order and the relaxation mechanisms in metal-arsenic-chalcogenide glasses for metal concentrations within the glass forming region. The glass forming region in the Cu-As-S and Cu-As-se glassy systems extends approximately to 6 and 25 at. % copper, respectively. In the composition Cu[sub x](As[sub 2/5]Ch[sub 3/5])[sub 1[minus]x], where Ch = S or Se, there is evidence of dramatic changes in the local structure as copper is added to the system. One important change is the formation of As-As bonds which are absent in As[sub 2]Ch[sub 3]. The [sup 75]As NQR measurements indicate that the density of these bonds increases with copper concentration x. These results are consistent with the predictions of a model proposed recently to explain the local structural order in glassy metal chalcogenides. While NQR data show that arsenic atoms are threefold coordinated, EXAFs measurements have shown that copper is fourfold coordinated within the glass forming ranges in both systems. The NMR measurements confirm this result and quantitatively determine the local environment around the copper nuclei. For the naturally occurring mineral luzonite (Cu[sub 3]AsS[sub 4]) copper is fourfold coordinated. The known structure of this mineral has been used as a guide to understanding the local structure in the glasses. Copper and arsenic nuclear relaxation measurements were used to study the dynamics of these systems. The temperature and frequency dependence of the spin-lattice and spin-spin relaxation times have been carefully measured to determine the relaxation mechanisms.

  6. Hydrazine-hydrothermal method to synthesize three-dimensional chalcogenide framework for photocatalytic hydrogen generation

    SciTech Connect

    Liu Yi; Kanhere, Pushkar D.; Wong, Chui Ling; Tian Yuefeng; Feng Yuhua; Boey, Freddy; Wu, Tom; Chen Hongyu; White, Tim J.; Chen Zhong; Zhang Qichun

    2010-11-15

    A novel chalcogenide, [Mn{sub 2}Sb{sub 2}S{sub 5}(N{sub 2}H{sub 4}){sub 3}] (1), has been synthesized by the hydrazine-hydrothermal method. X-ray crystallography study reveals that the new compound 1 crystallizes in space group P1-bar (no. 2) of the triclinic system. The structure features an open neutral three-dimensional framework, where two-dimensional mesh-like inorganic layers are bridged by intra- and inter-layer hydrazine ligands. Both two Mn1 and Mn2 sites adopt distorted octahedral coordination. While two Sb1 and Sb2 sites exhibit two different coordination geometries, the Sb1 site is coordinated with three S atoms to generate a SbS{sub 3} trigonal-pyramidal geometry, and the Sb2 site adopts a SbS{sub 4} trigonal bipyramidal coordination geometry. It has an optical band gap of about {approx}2.09 eV, which was deduced from the diffuse reflectance spectrum, and displays photocatalytic behaviors under visible light irradiation. Magnetic susceptibility measurements show compound 1 obeys the Curie-Weiss law in the range of 50-300 K. -- Graphical abstract: A novel chalcogenide, [Mn{sub 2}Sb{sub 2}S{sub 5}(N{sub 2}H{sub 4}){sub 3}] (1), synthesized by hydrazine-hydrothermal method, has a band gap of about {approx}2.09 eV and displays photocatalytic behaviors under visible light irradiation. Display Omitted

  7. BINARY ASTROMETRIC MICROLENSING WITH GAIA

    SciTech Connect

    Sajadian, Sedighe

    2015-04-15

    We investigate whether or not Gaia can specify the binary fractions of massive stellar populations in the Galactic disk through astrometric microlensing. Furthermore, we study whether or not some information about their mass distributions can be inferred via this method. In this regard, we simulate the binary astrometric microlensing events due to massive stellar populations according to the Gaia observing strategy by considering (i) stellar-mass black holes, (ii) neutron stars, (iii) white dwarfs, and (iv) main-sequence stars as microlenses. The Gaia efficiency for detecting the binary signatures in binary astrometric microlensing events is ∼10%–20%. By calculating the optical depth due to the mentioned stellar populations, the numbers of the binary astrometric microlensing events being observed with Gaia with detectable binary signatures, for the binary fraction of about 0.1, are estimated to be 6, 11, 77, and 1316, respectively. Consequently, Gaia can potentially specify the binary fractions of these massive stellar populations. However, the binary fraction of black holes measured with this method has a large uncertainty owing to a low number of the estimated events. Knowing the binary fractions in massive stellar populations helps with studying the gravitational waves. Moreover, we investigate the number of massive microlenses for which Gaia specifies masses through astrometric microlensing of single lenses toward the Galactic bulge. The resulting efficiencies of measuring the mass of mentioned populations are 9.8%, 2.9%, 1.2%, and 0.8%, respectively. The numbers of their astrometric microlensing events being observed in the Gaia era in which the lens mass can be inferred with the relative error less than 0.5 toward the Galactic bulge are estimated as 45, 34, 76, and 786, respectively. Hence, Gaia potentially gives us some information about the mass distribution of these massive stellar populations.

  8. VLSI binary updown counter

    NASA Technical Reports Server (NTRS)

    Truong, Trieu-Kie (Inventor); Hsu, In-Shek (Inventor); Reed, Irving S. (Inventor)

    1989-01-01

    A pipeline binary updown counter is comprised of simple stages that may be readily replicated. Each stage is defined by the Boolean logic equation: A(sub n)(t) = A(sub n)(t - 1) exclusive OR (U AND P(sub n)) inclusive OR (D AND Q(sub n)), where A(sub n)(t) denotes the value of the nth bit at time t. The input to the counter has three values represented by two binary signals U and D such that if both are zero, the input is zero, if U = 0 and D = 1, the input is -1 and if U = 1 and D = 0, the input is +1. P(sub n) represents a product of A(sub k)'s for 1 is less than or equal to k is less than or equal to -1, while Q(sub n) represents the product of bar A's for 1 is less than or equal to K is less than or equal to n - 1, where bar A(sub k) is the complement of A(sub k) and P(sub n) and Q(sub n) are expressed as the following two equations: P(sub n) = A(sub n - 1) A(sub n - 2)...A(sub 1) and Q(sub n) = bar A(sub n - 1) bar A(sub n - 2)...bar A(sub 1), which can be written in recursive form as P(sub n) = P(sub n - 1) AND bar A(sub n - 1) and Q(sub n) = Q(sub n - 1) AND bar A(sub n - 1) with the initial values P(sub 1) = 1 and Q(sub 1) = 1.

  9. Infrared imaging spectrometry by the use of bundled chalcogenide glass fibers and a PtSi CCD camera

    NASA Astrophysics Data System (ADS)

    Saito, Mitsunori; Kikuchi, Katsuhiro; Tanaka, Chinari; Sone, Hiroshi; Morimoto, Shozo; Yamashita, Toshiharu T.; Nishii, Junji

    1999-10-01

    A coherent fiber bundle for infrared image transmission was prepared by arranging 8400 chalcogenide (AsS) glass fibers. The fiber bundle, 1 m in length, is transmissive in the infrared spectral region of 1 - 6 micrometer. A remote spectroscopic imaging system was constructed with the fiber bundle and an infrared PtSi CCD camera. The system was used for the real-time observation (frame time: 1/60 s) of gas distribution. Infrared light from a SiC heater was delivered to a gas cell through a chalcogenide fiber, and transmitted light was observed through the fiber bundle. A band-pass filter was used for the selection of gas species. A He-Ne laser of 3.4 micrometer wavelength was also used for the observation of hydrocarbon gases. Gases bursting from a nozzle were observed successfully by a remote imaging system.

  10. Iron-chalcogenide FeSe(0.5)Te(0.5) Coated Superconducting Tapes for High Field Applications

    SciTech Connect

    Si, W.; Johnson, P.; Zhou, J.; Jie, Q.; Dimitrov, I.; Solovyov, V.; Jaroszynski, J.; Matias, V.; Sheehan, C.; Li, Q.

    2011-07-01

    The high upper critical field characteristic of the recently discovered iron-based superconducting chalcogenides opens the possibility of developing a new type of non-oxide high-field superconducting wires. In this work, we utilize a buffered metal template on which we grow a textured FeSe{sub 0.5}Te{sub 0.5} layer, an approach developed originally for high temperature superconducting coated conductors. These tapes carry high critical current densities (> 1 x 10{sup 4} A/cm{sup 2}) at about 4.2 K under magnetic field as high as 25 T, which are nearly isotropic to the field direction. This demonstrates a very promising future for iron chalcogenides for high field applications at liquid helium temperatures. Flux pinning force analysis indicates a point defect pinning mechanism, creating prospects for a straightforward approach to conductor optimization.

  11. General behavior of chalcogenides of rare-earth metals in transition to the intermediate valence state under high pressures

    NASA Astrophysics Data System (ADS)

    Tsiok, O. B.; Khvostantsev, L. G.; Golubkov, A. V.; Smirnov, I. A.; Brazhkin, V. V.

    2014-10-01

    High-precision measurements of the electric resistance, thermopower, and volume of TmS, TmSe, and TmTe under hydrostatic pressures up to 8.5 GPa were conducted. Comparison of the behavior of the electron-transport characteristics and volume of TmTe and SmTe in the electron transition region demonstrates a complete analogy up to the quantitative coincidence. We found that the thermopower of all samarium and thulium chalcogenides in the lattice-collapse region and during the subsequent reconstruction of the electronic spectrum obeys the universal dependence, which corresponds to the intersection of the Fermi level with the peak of the electron density of states. The results obtained testify in favor of the exciton nature of the intermediate valence state in chalcogenides of the rare-earth metals.

  12. Design for broadband on-chip isolator using Stimulated Brillouin Scattering in dispersion-engineered chalcogenide waveguides.

    PubMed

    Poulton, Christopher G; Pant, Ravi; Byrnes, Adam; Fan, Shanhui; Steel, M J; Eggleton, Benjamin J

    2012-09-10

    We propose a scheme for on-chip isolation in chalcogenide (As₂S₃) rib waveguides, in which Stimulated Brillouin Scattering is used to induce non-reciprocal mode conversion within a multi-moded waveguide. The design exploits the idea that a chalcogenide rib buried in a silica matrix acts as waveguide for both light and sound, and can also be designed to be multi-moded for both optical and acoustic waves. The enhanced opto-acoustic coupling allows significant isolation (> 20 dB) within a chip-scale (cm-long) device (< 10 cm). We also show that the bandwidth of this device can be dramatically increased by tuning the dispersion of the waveguide to match the group velocity between optical modes: we find that 20 dB isolation can be extended over a bandwidth of 25 nm.

  13. Pinning down high-performance Cu-chalcogenides as thin-film solar cell absorbers: A successive screening approach.

    PubMed

    Zhang, Yubo; Wang, Youwei; Zhang, Jiawei; Xi, Lili; Zhang, Peihong; Zhang, Wenqing

    2016-05-21

    Photovoltaic performances of Cu-chalcogenides solar cells are strongly correlated with the absorber fundamental properties such as optimal bandgap, desired band alignment with window material, and high photon absorption ability. According to these criteria, we carry out a successive screening for 90 Cu-chalcogenides using efficient theoretical approaches. Besides the well-recognized CuInSe2 and Cu2ZnSnSe4 materials, several novel candidates are identified to have optimal bandgaps of around 1.0-1.5 eV, spike-like band alignments with CdS window layer, sharp photon absorption edges, and high absorption coefficients. These new systems have great potential to be superior absorbers for photovolatic applications if their carrrier transport and defect properties are properly optimized.

  14. Optical properties of polysiloxane hybrid thin films containing nano-sized Ag-As-Se chalcogenide clusters

    NASA Astrophysics Data System (ADS)

    Zha, Congji; Osvath, Peter; Wilson, Gerry; Launikonis, Anton

    2009-02-01

    Chalcogenide glasses are attractive for all-optical signal processing due to their outstanding optical properties, including large optical nonlinearity, a high refractive index and high photosensitivity. In device fabrication, a challenge lies in the difficulty of obtaining thin films with a high stability and good uniformity. In this paper, optical thin films containing nano-sized chalcogenide clusters in polysiloxane matrices are fabricated by a modified plasma deposition process. The optical absorption and luminescence emission properties of the hybrid thin films were characterized by UV-Vis-NIR and fluorescence spectroscopy. Luminescent emission from Ag-As-Se nano-sized clusters was observed for the first time in these nano-hybrid thin films, and the mechanism was discussed.

  15. BINARIES AMONG DEBRIS DISK STARS

    SciTech Connect

    Rodriguez, David R.; Zuckerman, B.

    2012-02-01

    We have gathered a sample of 112 main-sequence stars with known debris disks. We collected published information and performed adaptive optics observations at Lick Observatory to determine if these debris disks are associated with binary or multiple stars. We discovered a previously unknown M-star companion to HD 1051 at a projected separation of 628 AU. We found that 25% {+-} 4% of our debris disk systems are binary or triple star systems, substantially less than the expected {approx}50%. The period distribution for these suggests a relative lack of systems with 1-100 AU separations. Only a few systems have blackbody disk radii comparable to the binary/triple separation. Together, these two characteristics suggest that binaries with intermediate separations of 1-100 AU readily clear out their disks. We find that the fractional disk luminosity, as a proxy for disk mass, is generally lower for multiple systems than for single stars at any given age. Hence, for a binary to possess a disk (or form planets) it must either be a very widely separated binary with disk particles orbiting a single star or it must be a small separation binary with a circumbinary disk.

  16. Binaries and Multiple Stellar Systems

    NASA Astrophysics Data System (ADS)

    Horch, Elliott

    Binary and multiple stellar systems have importance in three main areas of astronomy and astrophysics. First, because of the relatively simple gravitational interaction at work in the case of binary stars, these systems provide a basic check on stellar structure and evolution theory since the masses may be determined through observation. When these masses can be linked to other properties of the two stars, such as luminosity, color, and radius, they can provide very stringent constraints on stellar models. Second, the statistics of binary and multiple star systems provide clues to star formation mechanisms and environmental effects in the galactic gravitational potential and in clusters. Although a number of good results have been obtained in nearby star clusters and associations, knowledge of the field population has been somewhat limited until recently by a lack of large, complete samples of binaries. However, there appears to be a great deal of promise in this area for the coming decade in part due to astrometric satellites such as Hipparcos and Gaia. Third, the binary scenario is invoked to explain several important types of astrophysical phenomena such as Type Ia supernovae, cataclysmic variables, and stellar x-ray sources. Since the first of these mentioned is a standard candle for the extragalactic distance scale, it may even be said binary stars play a minor role in field of cosmology. However, in this chapter, the focus will mainly be on normal stars in binary and multiple-stellar systems. The basic physics of binaries will be reviewed, and the observational methods in use today will be discussed together with their limitations and prospects for the future. Finally, an overview of the current science in the three main areas mentioned where binaries have a significant impact will be given.

  17. Phase-sensitive amplification of light in a χ(3) photonic chip using a dispersion engineered chalcogenide ridge waveguide.

    PubMed

    Neo, Richard; Schröder, Jochen; Paquot, Yvan; Choi, Duk-Yong; Madden, Steve; Luther-Davies, Barry; Eggleton, Benjamin J

    2013-04-08

    We report phase-sensitive amplification of light using χ((3)) parametric processes in a chalcogenide ridge waveguide. By spectrally slicing pump, signal and idler waves from a single pulsed source, we are able to observe 9.9 dB of on-chip phase-sensitive extinction with a signal-degenerate dual pump four-wave mixing architecture in good agreement with numerical simulations.

  18. Stimulated Brillouin scattering in single-mode As(2)S(3) and As(2)Se(3) chalcogenide fibers.

    PubMed

    Florea, Catalin; Bashkansky, Mark; Dutton, Zachary; Sanghera, Jasbinder; Pureza, Paul; Aggarwal, Ishwar

    2006-12-11

    Stimulated Brillouin scattering was investigated for the first time in As(2)S(3) single-mode fibers, and also in As(2)Se(3). The propagation loss and numerical aperture of the fibers at 1.56 mum, along with the threshold intensity for the stimulated Brillouin scattering process were measured. From the threshold values we estimate the Brillouin gain coefficient and demonstrate record figure of merit for slow-light based applications in chalcogenide fibers.

  19. Modified evolution of stellar binaries from supermassive black hole binaries

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Wang, Yi-Han; Yuan, Ye-Fei

    2017-04-01

    The evolution of main-sequence binaries resided in the galactic centre is influenced a lot by the central supermassive black hole (SMBH). Due to this perturbation, the stars in a dense environment are likely to experience mergers or collisions through secular or non-secular interactions. In this work, we study the dynamics of the stellar binaries at galactic centre, perturbed by another distant SMBH. Geometrically, such a four-body system is supposed to be decomposed into the inner triple (SMBH-star-star) and the outer triple (SMBH-stellar binary-SMBH). We survey the parameter space and determine the criteria analytically for the stellar mergers and the tidal disruption events (TDEs). For a relative distant and equal masses SMBH binary, the stars have more opportunities to merge as a result from the Lidov-Kozai (LK) oscillations in the inner triple. With a sample of tight stellar binaries, our numerical experiments reveal that a significant fraction of the binaries, ˜70 per cent, experience merger eventually. Whereas the majority of the stellar TDEs are likely to occur at a close periapses to the SMBH, induced by the outer Kozai effect. The tidal disruptions are found numerically as many as ˜10 per cent for a close SMBH binary that is enhanced significantly than the one without the external SMBH. These effects require the outer perturber to have an inclined orbit (≥40°) relatively to the inner orbital plane and may lead to a burst of the extremely astronomical events associated with the detection of the SMBH binary.

  20. Binary Oscillatory Crossflow Electrophoresis

    NASA Technical Reports Server (NTRS)

    Molloy, Richard F.; Gallagher, Christopher T.; Leighton, David T., Jr.

    1997-01-01

    Electrophoresis has long been recognized as an effective analytic technique for the separation of proteins and other charged species, however attempts at scaling up to accommodate commercial volumes have met with limited success. In this report we describe a novel electrophoretic separation technique - Binary Oscillatory Crossflow Electrophoresis (BOCE). Numerical simulations indicate that the technique has the potential for preparative scale throughputs with high resolution, while simultaneously avoiding many problems common to conventional electrophoresis. The technique utilizes the interaction of an oscillatory electric field and a transverse oscillatory shear flow to create an active binary filter for the separation of charged protein species. An oscillatory electric field is applied across the narrow gap of a rectangular channel inducing a periodic motion of charged protein species. The amplitude of this motion depends on the dimensionless electrophoretic mobility, alpha = E(sub o)mu/(omega)d, where E(sub o) is the amplitude of the electric field oscillations, mu is the dimensional mobility, omega is the angular frequency of oscillation and d is the channel gap width. An oscillatory shear flow is induced along the length of the channel resulting in the separation of species with different mobilities. We present a model that predicts the oscillatory behavior of charged species and allows estimation of both the magnitude of the induced convective velocity and the effective diffusivity as a function of a in infinitely long channels. Numerical results indicate that in addition to the mobility dependence, the steady state behavior of solute species may be strongly affected by oscillating fluid into and out of the active electric field region at the ends of the cell. The effect is most pronounced using time dependent shear flows of the same frequency (cos((omega)t)) flow mode) as the electric field oscillations. Under such conditions, experiments indicate that