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Sample records for chalcogenides

  1. Applications of chalcogenide fiber

    OpenAIRE

    Hewak, D. W.; Khan, K.; Huang, C. C.

    2011-01-01

    Chalcogenide glass optical fibers have been extensively studied since 1967, when sulphide based fibers and their potential applications were first proposed. While high quality fiber drawn from alloys containing a variety of chalcogen elements have been realized, their delicate nature, complicated fabrication methodology and expense has restricted widespread application and commercial acceptance. In this paper we describe our current work on the fabrication and application of chalcogenide fibe...

  2. Chalcogenide glass microsphere laser

    OpenAIRE

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

    2010-01-01

    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...

  3. Novel Precursors for Chalcogenide Materials

    OpenAIRE

    Oyetunde, Temidayo Timothy

    2011-01-01

    The University of Manchester Temidayo Timothy Oyetunde, PhDNovel Chalcogenide Precursors for Materials2011.Abstract Metal chalcogenides (sulfides, selenides and tellurides) are materials of current interest due to their peculiar properties such as optoelectronic, magnetooptic, thermoelectric and piezoelectric displays. These semiconducting materials have potential applications in solar cell devices, infrared detectors and ambient thermoelectric generators. Previously, these materials...

  4. Superconductivity in Fe-chalcogenides

    International Nuclear Information System (INIS)

    FeSe, which has the simplest crystal structure among the Fe based superconductors, and related chalcogenide superconductors are ideal candidates for investigating the detailed mechanism of the iron-based superconductors. Here, we summarize recent studies on the Fe-chalcogenides, with the goal to address some unresolved questions such as what is the influence of chemical stoichiometry on the phase diagram, what is the exact parent phase of FeSe system, and why can Tcs be so dramatically enhanced in FeSe based superconductors? Recent developments in novel synthesis to prepare chalcogenide crystals, nano-materials and thin films allow the community to begin to address these issues. Then we review physical properties of the Fe chalcogenides, specifically focusing on optical properties, scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy (ARPES) results. These measurements along with recent theories provide a framework for better understanding the origin of superconductivity in FeSe and Fe-chalcogenides

  5. Carbon nanotube-chalcogenide composite

    Czech Academy of Sciences Publication Activity Database

    Stehlík, Š.; Orava, J.; Kohoutek, T.; Wágner, T.; Frumar, M.; Zima, Vítězslav; Hara, T.; Matsui, Y.; Ueda, K.; Pumera, M.

    2010-01-01

    Roč. 183, č. 1 (2010), s. 144-149. ISSN 0022-4596 R&D Projects: GA ČR GA203/08/0208 Institutional research plan: CEZ:AV0Z40500505 Keywords : carbon nanotubes * chalcogenide glasses * composites Subject RIV: CA - Inorganic Chemistry Impact factor: 2.261, year: 2010

  6. Noble-Metal Chalcogenide Nanotubes

    Directory of Open Access Journals (Sweden)

    Nourdine Zibouche

    2014-10-01

    Full Text Available We explore the stability and the electronic properties of hypothetical noble-metal chalcogenide nanotubes PtS2, PtSe2, PdS2 and PdSe2 by means of density functional theory calculations. Our findings show that the strain energy decreases inverse quadratically with the tube diameter, as is typical for other nanotubes. Moreover, the strain energy is independent of the tube chirality and converges towards the same value for large diameters. The band-structure calculations show that all noble-metal chalcogenide nanotubes are indirect band gap semiconductors. The corresponding band gaps increase with the nanotube diameter rapidly approaching the respective pristine 2D monolayer limit.

  7. Nonlinear Integrated Optical Waveguides in Chalcogenide Glasses

    Institute of Scientific and Technical Information of China (English)

    Yinlan; Ruan; Barry; Luther-Davies; Weitang; Li; Andrei; Rode; Marek; Samoc

    2003-01-01

    This paper reports on the study and measurement of the third order optical nonlinearity in bulk sulfide-based chalcogenide glasses; The fabrication process of the ultrafast laser deposited As-S-(Se)-based chalcogenide films and optical waveguides using two techniques: wet chemistry etching and plasma etching.

  8. Chalcogenide-tellurite composite microstructured optical fibre

    Science.gov (United States)

    Kohoutek, T.; Duan, Z.; Kawashima, H.; Yan, X.; Suzuki, T.; Matsumoto, M.; Misumi, Takashi; Ohishi, Y.

    2012-02-01

    We report on fabrication a composite microstructured optical fibre composed of highly nonlinear chalcogenide Ge-Ga- Sb-S glass core and tellurite TeO2-ZnO-Li20-Bi2O3 glass clad. We aimed at obtaining more flattened chromatic dispersion for pumping chalcogenide glass based optical fibre by a pulse laser at current telecommunication wavelengths, i.e. λ = 1.35 - 1.7 μm, which is difficult to achieve by using a single material chalcogenide fibers due to their high refractive index (n > 2.1). A fibre design exploiting a composite of two glasses and one ring of the air holes brings similar options for tuning the fibre dispersion such as use of complex multi rings of air-holes approach. A good choice of glasses, allows for fabricating a composite chalcogenide-tellurite optical fibre benefiting from high nonlinearity of chalcogenide core glass but exploiting a tellurite glass technology and fibre drawing. In the paper, we discuss some aspects of CMOF design concerning current chalcogenide and tellurite glass choice. Also, we show the supercontinuum spectra recorded from current chalcogenide-tellurite CMOF pumped with a custom made femtosecond fibre laser at λ = 1.55 μm with the pulse duration of 400 fs.

  9. Metastable states in amorphous chalcogenide semiconductors

    CERN Document Server

    Mikla, Victor I

    2009-01-01

    This book addresses an interesting and technologically important class of materials, the amorphous chalcogenide semiconductors. Experimental results on the structural and electronic metastable states in Se-rich chalcogenides are presented. Special attention is paid to the states in the mobility gap and their sensitivity to various factors such as irradiation, annealing and composition. Photoinduced changes of structure and physical properties are also considered and structural transformation at photocrystallization is studied in detail. Finally, the authors discuss potential applications of th

  10. Metal chalcogenide nanostructures for renewable energy applications

    CERN Document Server

    Qurashi, Ahsanulhaq

    2014-01-01

    This first ever reference book that focuses on metal chalcogenide semiconductor nanostructures for renewable energy applications encapsulates the state-of-the-art in multidisciplinary research on the metal chalcogenide semiconductor nanostructures (nanocrystals, nanoparticles, nanorods, nanowires,  nanobelts, nanoflowers, nanoribbons and more).  The properties and synthesis of a class of nanomaterials is essential to renewable energy manufacturing and this book focuses on the synthesis of metal chalcogendie nanostructures, their growth mechanism, optical, electrical, and other important prop

  11. Characterization of chalcogenide phase change nanostructures

    OpenAIRE

    Fallica,

    2012-01-01

    This manuscript reports about the characterization of chalcogenide thin films and nanowires for non volatile memory application. In particular, the physical properties of several Te based alloys were analyzed in thin film by Hall effect and resistivity from room temperature to 4 K, and an interpretation on the scatterin mechanisms thereof is given. In addition, the functionality of 1-dimensional nanostructures of single crystal chalcogenide grown by metalorganic vapour deposition was demonstr...

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

    Science.gov (United States)

    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

  13. Photonic crystal fibers based on chalcogenide glasses

    Science.gov (United States)

    Adam, J. L.; Troles, J.; Brilland, L.; Coulombier, Q.; Chartier, T.

    2010-10-01

    Chalcogenide glasses are known for their large transparency in the mid-infrared and their high refractive index (>2). They present also a high non-linear coefficient (n2), 100 to 1000 times larger than for silica, depending on the composition. An original way to obtain single-mode fibers is to design microstructured optical fibers (MOFs). These fibers present unique optical properties thanks to the high degree of freedom in the design of their geometrical structure. A classical method to realize MOFs is the stack-and-draw technique. However, with chalcogenide glasses, that technique induces optical losses at the interfaces in the stack of capillaries. In consequence, we have developed a new casting method to fabricate the chalcogenide preform. This method permits to obtain optical losses around 1 dB/m at 1.55 μm and 0.3 dB/m in the mid-IR region. Various chalcogenide microstructured fibers working in the IR range were prepared in order to take advantage of the non-linear properties of these glasses and of the original MOF properties. For example, fibers with small effective mode area (Aeff supercontinuum sources. On the contrary, for military applications in the 3-5 and 8-12 μm windows, large effective mode area and single mode fibers have been designed to permit the propagation of high-power gaussian laser beams.

  14. Soluble rare-earth chalcogenides

    Science.gov (United States)

    Pernin, Christopher G.

    1999-11-01

    The cluster Eu8(DMF)13(mu4-O)(mu 3-OH)12(Se3)(Se4)2(Se 5)2 was synthesized from the reaction of EuCl3 dissolved in tetrahydrofaran with K2Se4 dissolved in N,N-dimethylformamide (DMF). The Eu8(O)(OH)12 10+ core is the first example such a polyoxometallo-core. The compound is further unusual in that it contains three different polyselenide chain lengths attaching adjacent Eu atoms. A similar reaction between Ln Cl3·6H2O and K2Se4 in DMF was found to produce the cluster compounds Gd8(DMF) 13(mu4-O)(mu3-OH)12(Se3)(Se 4)2(Se5)2, Yb8 (DMF) 11(mu4-O)(mu3-OH)12(Se4) 2(Se5)2Cl2·(DMF), and Y 8(DMF)12(mu4-O)(mu3-OH)12 (Se4)4Cl2·(DMF)6. Each of these clusters has a similar Ln8(mu 4-OH)(mu3-OH)1210+ core coordinated by a variety of polyselenide and chloride ligands. The organometallic rare-earth chalcogenide compounds (C5H 5)2Y [N( Q PPh2)2] ( Q = S, Se) have been prepared in good yield from the protonolysis reaction between CP3Y and HN( Q PPh2)2 in THF. In both compounds, the [N( Q PPh2)2]-- ligand is bound eta 3 to the Y center. The Y atom is also coordinated to two (C5 H5)-- ligands and so is formally 9-coordinate. 1H, 31P, 77Se, and 89Y NMR data indicate that the solid state connectivity is retained in solution. The compounds (C5H5)2Ln[N( Q PPh2)2] (Ln = La, Gd, Er, Yb, for Q = Se; Ln = Yb for Q = S) were synthesized. The series of compounds indicates that the smaller rare-earth elements cannot accommodate eta3-bonding from the imidodiphosphinochalcogenido ligand. The compounds Y[N( Q PPh2)2]3 ( Q = S (1), Se(2)) have been synthesized from the reactions between Y[N(SiMe3)2]3 and HN( Q PPh2)2. In 1, the Y atom is surrounded by three similar [N(SPPh2)2]-- ligands bound eta3 through two S atoms and an N atom. In 2 , the Y atom is surrounded again by three [N(SePPh2) 2]-- ligands, but two are bound eta2 through the two Se atoms and the other ligand is bound eta3 through the two Se atoms and an N atom. Although a fluxional process is detected in the 31P and 77Se NMR spectra

  15. DEFECTS IN AMORPHOUS CHALCOGENIDES AND SILICON

    OpenAIRE

    Adler, D.

    1981-01-01

    Our comprehension of the physical properties of amorphous semiconductors has improved considerably over the past few years, but many puzzles remain. From our present perspective, the major features of chalcogenide glasses appear to be well understood, and some of the fine points which have arisen recently have been explained within the same general model. On the other hand, there are a grear number of unresolved mysteries with regard to amorphous silicon-based alloys. In this paper, the valen...

  16. n-type chalcogenides by ion implantation.

    Science.gov (United States)

    Hughes, Mark A; Fedorenko, Yanina; Gholipour, Behrad; Yao, Jin; Lee, Tae-Hoon; Gwilliam, Russell M; Homewood, Kevin P; Hinder, Steven; Hewak, Daniel W; Elliott, Stephen R; Curry, Richard J

    2014-01-01

    Carrier-type reversal to enable the formation of semiconductor p-n junctions is a prerequisite for many electronic applications. Chalcogenide glasses are p-type semiconductors and their applications have been limited by the extraordinary difficulty in obtaining n-type conductivity. The ability to form chalcogenide glass p-n junctions could improve the performance of phase-change memory and thermoelectric devices and allow the direct electronic control of nonlinear optical devices. Previously, carrier-type reversal has been restricted to the GeCh (Ch=S, Se, Te) family of glasses, with very high Bi or Pb 'doping' concentrations (~5-11 at.%), incorporated during high-temperature glass melting. Here we report the first n-type doping of chalcogenide glasses by ion implantation of Bi into GeTe and GaLaSO amorphous films, demonstrating rectification and photocurrent in a Bi-implanted GaLaSO device. The electrical doping effect of Bi is observed at a 100 times lower concentration than for Bi melt-doped GeCh glasses. PMID:25376988

  17. Chalcogenide Glass Optical Waveguides for Infrared Biosensing

    Directory of Open Access Journals (Sweden)

    Bruno Bureau

    2009-09-01

    Full Text Available 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 (biosensors.

  18. Chalcogenide Glass Optical Waveguides for Infrared Biosensing

    Science.gov (United States)

    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

  19. Chalcogenide materials at the research center of Pardubice University

    Czech Academy of Sciences Publication Activity Database

    Frumar, M.; Wágner, T.; Málek, J.; Němec, P.; Frumarová, Božena; Přikryl, J.; Orava, J.; Kohoutek, T.

    Pardubice : University of Pardubice, 2011. s. 39-40. ISBN 978-80-7395-419-2. [International Days of Materials Science 2011. 16.09.2011-16.09.2011, Pardubice] R&D Projects: GA ČR GA203/09/0827 Institutional research plan: CEZ:AV0Z40500505 Keywords : crystalline chalcogenides * amorphous chalcogenides Subject RIV: CA - Inorganic Chemistry

  20. The Surface Chemistry of Metal Chalcogenide Nanocrystals

    Science.gov (United States)

    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

  1. Chemical Routes to Colloidal Chalcogenide Nanosheets

    Energy Technology Data Exchange (ETDEWEB)

    Schaak, Raymond

    2015-02-19

    This project sought to develop new low-temperature synthetic pathways to intermetallic and chalcogenide nanostructures and powders, with an emphasis on systems that are relevant to advancing the synthesis, processing, and discovery of superconducting materials. The primary synthetic routes involved solution chemistry methods, and several fundamental synthetic challenges that underpinned the formation of these materials were identified and investigated. Methods for incorporating early transition metals and post transition metals into nanoscale and bulk crystals using low-temperature solution chemistry methods were developed and studied, leading to colloidal nanocrystals of elemental indium, manganese, and germanium, as well as nanocrystalline and bulk intermetallic compounds containing germanium, gallium, tin, indium, zinc, bismuth, and lithium. New chemical tools were developed to help target desired phases in complex binary intermetallic and metal chalcogenide systems that contain multiple stable phases, including direct synthesis methods and chemical routes that permit post-synthetic modification. Several phases that are metastable in bulk systems were targeted, synthesized, and characterized as nanocrystalline solids and bulk powders, including the L12-type intermetallic compounds Au3Fe, Au3Ni, and Au3Co, as well as wurtzite-type MnSe. Methods for accessing crystalline metal borides and carbides using direct solution chemistry methods were also developed, with an emphasis on Ni3B and Ni3C, which revealed useful correlations of composition and magnetic properties. Methods for scale-up and nanoparticle purification were explored, providing access to centimeter-scale pressed pellets of polyol-synthesized nanopowders and a bacteriophage-mediated method for separating impure nanoparticle mixtures into their components. Several advances were made in the synthesis of iron selenide and related superconducting materials, including the production of colloidal Fe

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  3. Planar Chalcogenide Quarter Wave Stack Filters for Near - Infrared

    Czech Academy of Sciences Publication Activity Database

    Kohoutek, T.; Orava, J.; Přikryl, J.; Wágner, T.; Vlček, Milan; Knotek, P.; Frumar, M.

    Edmonton : University of Alberta, Edmonton, Canada, 2008, s. 181-181. [Third International Conference on Optical, Optoelectronic and Photonic Materials and Applications. Edmonton (CA), 20.06.2008-25.06.2008] Keywords : chalcogenide thin films Subject RIV: CA - Inorganic Chemistry

  4. Chalcogenide thin film materials for next generation data storage

    OpenAIRE

    Simpson, Robert E.

    2008-01-01

    Data can be stored in the form of amorphous and crystalline marks within a chalcogenide thin film. Commonly Ge. Therefore Ga:La:S:Cu shows potential as a future electrical phase change data storage material.

  5. On the application of chalcogenide glasses in temperature sensors

    OpenAIRE

    Shpotyuk, M.; Chalyy, D.; Shpotyuk, O.; Iovu, M.; Andriesh, A.; Vakiv, M.; Ubizskii, S.

    2012-01-01

    In this paper we report about a possibility of application of chalcogenide glasses as active media in optoelectronic temperature sensors. All investigations were performed on a sample of Ge18As18Se64 chalcogenide glass as typical covalent network glass with rigid structure. Temperature dependence of optical transmission in the fundamental optical absorption edge region was studied through the glass transition interval. A monotone increasing temperature dependence of position of the f...

  6. Radiation-induced defect formation in chalcogenide glasses

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O.I.; Filipecki, J. [Physics Institute of Pedagogical University of Czestochowa, Al. Armii Krajowej 13/15, Czestochowa 42201 (Poland); Kozdras, A. [Physics Laboratory of Opole Technical University, 75 ul. Ozimska, Opole, PL-45370 (Poland); Kavetskyy, T.S. [Lviv Scientific Research Institute of Materials of Scientific Research Company ' Carat' , Stryjska Str. 202, Lviv, UA-79031 (Ukraine)

    2003-10-01

    The modified model of native and radiation-induced microvoid-type positron traps in vitreous chalcogenide semiconductors is developed to explain compositional features of positron annihilation lifetime measurements in stoichiometric As{sub 2}S{sub 3}-GeS{sub 2} and non-stoichiometric As{sub 2}S{sub 3}-Ge{sub 2}S{sub 3} chalcogenide glasses before and after {gamma}-irradiation.

  7. Electrochemical Synthesis and Characterization of Nanostructured Chalcogenide Materials

    OpenAIRE

    Chang, Chong Hyun

    2011-01-01

    Nanostructured materials have attracted extensive attention due to their small dimension and enhanced properties compared to bulk materials, and their large range of potential applications in energy harvesting devices. Among these materials, nanostructured chalcogenides play an important role in thermoelectric and solar cell devices. Electrochemical techniques have drawn attention as an improved method for synthesizing nanostructured chalcogenide materials, since they provide a cost-effective...

  8. Debye temperatures of uranium chalcogenides from their lattice dynamics

    Indian Academy of Sciences (India)

    S Durai; P Babu

    2005-12-01

    Phonon dispersion relations in uranium chalcogenides have been investigated using a modified three-body force shell model. From the phonon frequencies, their Debye temperatures are evaluated. Further, on the basis of the spin fluctuation in the heavy fermion uranium compounds, UPt3 and UBe13, the possible superconducting transition temperatures of chalcogenides are theoretically predicted. The c values are in the same range as of those in UPt3 and UBe13.

  9. Integrated flexible chalcogenide glass photonic devices

    Science.gov (United States)

    Li, Lan; Lin, Hongtao; Qiao, Shutao; Zou, Yi; Danto, Sylvain; Richardson, Kathleen; Musgraves, J. David; Lu, Nanshu; Hu, Juejun

    2014-08-01

    Photonic integration on thin flexible plastic substrates is important for emerging applications ranging from the realization of flexible interconnects to conformal sensors applied to the skin. Such devices are traditionally fabricated using pattern transfer, which is complicated and has limited integration capacity. Here, we report a convenient monolithic approach to realize flexible, integrated high-index-contrast chalcogenide glass photonic devices. By developing local neutral axis designs and suitable fabrication techniques, we realize a suite of photonic devices including waveguides, microdisk resonators, add-drop filters and photonic crystals that have excellent optical performance and mechanical flexibility, enabling repeated bending down to sub-millimetre radii without measurable performance degradation. The approach offers a facile fabrication route for three-dimensional high-index-contrast photonics that are difficult to create using traditional methods.

  10. Chalcogenide photovoltaic solar cells of special interest

    Energy Technology Data Exchange (ETDEWEB)

    Champness, C.H. (McGill Univ., Montreal, Quebec (Canada))

    1988-08-01

    A brief review is given of those semiconducting selenides and tellurides that appear suitable for the absorber layer of a photovoltaic solar cell, with energy gaps in the range 1 to 2 eV. Furthermore, to obtain a lower cost cell, the semiconductor is also required to be used in the form of a thin polycrystalline film, necessitating a high optical absorption coefficient in the material. At the present time the two best chalcogenides meeting these requirements are the compounds CuInSe{sub 2} and CdTe, both of which have been used in polycrystalline thin film structures with CdS, as the window layer, yielding conversion efficiencies of over 10%. They have also demonstrated very good chemical stability.

  11. Multimode supercontinuum generation in chalcogenide glass fibres

    DEFF Research Database (Denmark)

    Kubat, Irnis; Bang, Ole

    2016-01-01

    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 (≤ 10ps) then higher order modes are not important because of temporal...... walk-off. In contrast long pump pulses (≥ 40ps) 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....

  12. Multimode supercontinuum generation in chalcogenide glass fibres.

    Science.gov (United States)

    Kubat, Irnis; Bang, Ole

    2016-02-01

    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. PMID:26906826

  13. Focus on superconducting properties of iron chalcogenides

    Science.gov (United States)

    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.

  14. Calculation of small arsenic and antimony chalcogenide clusters with an application to vitreous chalcogenide structure

    OpenAIRE

    Gurin, V.; Shpotyuk, O.; Boyko, V

    2015-01-01

    Small clusters of the As/Sb-S/Se system that is of importance for simulation of elementary structure units of chalcogenide glasses are calculated using DFT technique. Different structures of As2Xn- and Sb2Xn- (X=S,Se) with proper hydrogen termination are compared by the total electronic energy values. The most stable As-X structures are of corner-sharing (CS) type (i.e. the elementary AsX3-pyramids linked via one X atom, and in the case of Sb-X family a new asymmetrical Sb2Se3 cluster appears...

  15. Hybrid photovoltaic devices based on chalcogenide nanostructures

    Science.gov (United States)

    de Freitas, Jilian N.; Alves, João. Paulo C.; Korala, Lasantha; Brock, Stephanie L.; Nogueira, Ana F.

    2012-09-01

    Solar cells based on the combination of conjugated polymers and fullerenes are among the most promising devices for low-cost solar energy conversion. Significant improvements in the efficiency have been accomplished, but some bottlenecks still persist. The substitution of fullerenes by inorganic semiconductor nanoparticles, especially CdSe and CdS, has been investigated as a promising alternative. In this work, we highlight two aspects to be considered in the pursuit of more efficient devices. By comparing different polymer/CdSe systems, we show how the polymer structure can be used to tune the charge transfer from the polymer to CdSe. Even if this process is efficient, the charges will be trapped in the inorganic phase if the charge carrier transport of the nanoparticles is poor. An elegant way to improve the electron hopping is to form an electrically integrated network of nanoparticles. The use of chalcogenide aerogels is a new alternative which may be interesting for applications requiring maximal transport of charge and is also discussed here.

  16. Hierarchical Architecturing for Layered Thermoelectric Sulfides and Chalcogenides

    Directory of Open Access Journals (Sweden)

    Priyanka Jood

    2015-03-01

    Full Text Available Sulfides are promising candidates for environment-friendly and cost-effective thermoelectric materials. In this article, we review the recent progress in all-length-scale hierarchical architecturing for sulfides and chalcogenides, highlighting the key strategies used to enhance their thermoelectric performance. We primarily focus on TiS2-based layered sulfides, misfit layered sulfides, homologous chalcogenides, accordion-like layered Sn chalcogenides, and thermoelectric minerals. CS2 sulfurization is an appropriate method for preparing sulfide thermoelectric materials. At the atomic scale, the intercalation of guest atoms/layers into host crystal layers, crystal-structural evolution enabled by the homologous series, and low-energy atomic vibration effectively scatter phonons, resulting in a reduced lattice thermal conductivity. At the nanoscale, stacking faults further reduce the lattice thermal conductivity. At the microscale, the highly oriented microtexture allows high carrier mobility in the in-plane direction, leading to a high thermoelectric power factor.

  17. Effect of pressure on the phonon properties of europium chalcogenides

    Indian Academy of Sciences (India)

    U K Sakalle; P K Jha; S P Sanyal

    2000-06-01

    Lattice vibrational properties of europium chalcogenides have been investigated at high pressure by using a simple lattice dynamical model theory viz. the three-body force rigid ion model (TRIM) which includes long range three-body interaction arising due to charge transfer effects. The dispersion curves for the four Eu-chalcogenides agree reasonably well with the available experimental data. Variation of LO, TO, LA and TA phonons with pressure have also been studied at the symmetry points of the brillouin zone (BZ) for Euchalcogenides for the first time by using a lattice dynamical model theory. We have also calculated the one phonon density of states and compared them with the first order Raman scattering results. The calculation of one phonon density of states for Eu-chalcogenides has also been extended up to the phase transition pressure. We observed a pronounced shift in phonon spectrum as pressure is increased.

  18. Optical Nonlinearities in Chalcogenide Glasses and their Applications

    CERN Document Server

    Zakery, A

    2007-01-01

    Photonics, which uses photons for information and image processing, has been labeled the technology of the 21st century, for which non-linear optical processes provide the key functions of frequency conversion and optical switching. Chalcogenide glass fiber is one of the most promising candidates for use as a non-linear optical medium because of its high optical nonlinearity and long interaction length. Since the chalcogenide glass fibers transmit into the IR, there are numerous potential applications in the civil, medical and military areas. One of the most exciting developments in the future is going to be in the area of rare-earth ion doping of chalcogenide fibers for IR fluorescence emission. The IR light sources, lasers and amplifiers developed using this phenomena will be very useful in civil, medical and military applications. Remote IR spectroscopy and imaging using flexible fibers will be realized for applications. Other future research areas which will inevitably be explored includes non-linear opti...

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

    DEFF Research Database (Denmark)

    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...

  20. Nonlinear optical localization in embedded chalcogenide waveguide arrays

    Directory of Open Access Journals (Sweden)

    Mingshan Li

    2014-05-01

    Full Text Available 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/cm2, 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.

  1. High surface area graphene-supported metal chalcogenide assembly

    Science.gov (United States)

    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.

  2. Mid infrared supercontinuum generation from chalcogenide glass waveguides and fibers

    DEFF Research Database (Denmark)

    Luther-Davies, Barry; Yu, Yi; Zhang, Bin;

    2015-01-01

    I report work on mid-infrared super-continuum generation in chalcogenide fibers and waveguides pumped by 320fsec pulses at 21MHz in the 3-4.6µm range. Average powers of ≈20mW were produced with spectral coverage from <2µm to >11µm.......I report work on mid-infrared super-continuum generation in chalcogenide fibers and waveguides pumped by 320fsec pulses at 21MHz in the 3-4.6µm range. Average powers of ≈20mW were produced with spectral coverage from <2µm to >11µm....

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

    Science.gov (United States)

    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. PMID:26821763

  4. High-pressure phases of lead chalcogenides

    International Nuclear Information System (INIS)

    Research highlights: → We show that the intermediate phase transition for these compounds is not the GeS nor the TlI type structures, as previously reported, but the orthorhombic Pnma phase. → All these compounds are predicted to undergo a structural phase transition from the rocksalt to Pnma phase at about 8.13, 7.45 and 5.40 GPa for PbS, PbSe and PbTe respectively. → Further structural phase transitions from this intermediate phase to the CsCl phase have been predicted at about 25.3, 18.76 and 15.43 GPa for PbS, PbSe and PbTe respectively. - Abstract: Ab initio electronic structures have been carried out to find the pressure-induced structural phase transitions of lead chalcogenides (PbS, PbSe and PbTe) compounds. The zinc-blende, wurtzite, rocksalt, CsCl, GeS, TlI and orthorhombic Pnma phases are considered. Results show that the intermediate phase transition for these compounds is not the GeS nor the TlI type structures, as previously reported, but the orthorhombic Pnma phase. All these compounds are predicted to undergo a structural phase transition from the rocksalt to Pnma phase at about 8.13, 7.45 and 5.40 GPa for PbS, PbSe and PbTe respectively. Moreover, further structural phase transitions from this intermediate phase to the CsCl phase have been predicted at about 25.3, 18.76 and 15.43 GPa for PbS, PbSe and PbTe respectively.

  5. Iron based superconductors: Pnictides versus chalcogenides

    International Nuclear Information System (INIS)

    We present a brief review of the present day situation with studies of high-temperature superconductivity in iron pnictides and chalcogenides. Recent discovery of superconductivity with Tc>30K in AxFe2−x/2Se2 (A=K, Cs, Tl, etc) represents the major new step in the development of new concepts in the physics of Fe-based high-temperature superconductors. We compare LDA and ARPES data on the band structure and Fermi surfaces of novel superconductors and those of the previously studied FeAs superconductors, especially isostructural 122-superconductors like BaFe2As2. It appears that electronic structure of new superconductors is rather different from that of FeAs 122-systems. In particular, no nesting properties of electron and hole-like Fermi surfaces is observed, casting doubts on most popular theoretical schemes of Cooper pairing for these systems. Doping of novel materials is extremely important as a number of topological transitions of Fermi surface near the Γ point in the Brillouin zone are observed for different doping levels. The discovery of Fe vacancies ordering and antiferromagnetic (AFM) ordering at pretty high temperatures (TN>500K), much exceeding superconducting Tc makes these systems unique antiferromagnetic superconductors with highest TN observed up to now. This poses very difficult problems for theoretical understanding of superconductivity. We discuss the role of both vacancies and AFM ordering in transformations of band structure and Fermi surfaces, as well as their importance for superconductivity. In particular, we show that system remains metallic with unfolded Fermi surfaces quite similar to that in paramagnetic state. Superconducting transition temperature Tc of new superconductors is discussed within the general picture of superconductivity in multiple band systems. It is demonstrated that both in FeAs-superconductors and in new FeSe-systems the value of Tc correlates with the value of the total density of states (DOSs) at the Fermi level.

  6. Characterization of Ge based chalcogenides doped with Er nd Pr

    Czech Academy of Sciences Publication Activity Database

    Zavadil, Jiří; Kostka, Petr; Žďánský, Karel; Pedlíková, Jitka; Procházková, Olga

    Bucharest : National Institute of Materials Physics, 2007. s. 44--. [ANC-3: International Conference on Amourphous and Nanostructured Chalcogenides /3./. 02.07.20007-06.07.2007, Brasov] R&D Projects: GA ČR GA104/05/0878 Institutional research plan: CEZ:AV0Z20670512; CEZ:AV0Z40320502 Keywords : glasses * transmission * fluorescence Subject RIV: CA - Inorganic Chemistry

  7. Optical properties of chalcogenide multilayer deposited on Au layer

    Czech Academy of Sciences Publication Activity Database

    Kohoutek, T.; Orava, J.; Přikryl, J.; Hrdlička, M.; Wágner, T.; Knotek, P.; Vlček, Milan; Frumar, M.

    2009-01-01

    Roč. 355, 37-42 (2009), s. 1947-1950. ISSN 0022-3093. [XVI.th International Symposium on Non-Oxide and New Optical Glasses. Montpellier, 20.04.2009-25.04.2009] Institutional research plan: CEZ:AV0Z40500505 Keywords : chalcogenides Subject RIV: CA - Inorganic Chemistry Impact factor: 1.252, year: 2009

  8. Recipe for high-Tc transition-metal chalcogenide superconductors

    International Nuclear Information System (INIS)

    The conditions for the occurrence of superconductivity in cuprates are enumerated. There is a minimum of seven, which are discussed in some detail. They may be taken as a recipe in the search for superconductors at elevated temperature with other transition-metal chalcogenide compounds. (orig.)

  9. Laser deposited chalcogenide films with unexpected structure, composition and properties

    Czech Academy of Sciences Publication Activity Database

    Frumar, M.; Frumarová, Božena; Němec, P.; Jedelský, J.; Wágner, T.

    Cape Canaveral : The American Ceramic Society, 2004, s. 38. [International Symposium on Non-Oxide and Novel Optical Glass es/14./. Cape Canaveral (US), 07.11.2004-12.11.2004] Institutional research plan: CEZ:AV0Z4050913 Keywords : pulsed laser deposition * chalcogenide thin films Subject RIV: CA - Inorganic Chemistry

  10. On the instability effects in radiation-sensitive chalcogenide glasses

    Energy Technology Data Exchange (ETDEWEB)

    Balitska, V. [Lviv State University for Vital Activity Safety, 35 Kleparivska str., Lviv, UA-79007 (Ukraine); Lviv Institute of Materials of SRC ' Carat' , 202 Stryjska str., Lviv, UA-79031 (Ukraine); Kovalskiy, A. [Lviv Institute of Materials of SRC ' Carat' , 202 Stryjska str., Lviv, UA-79031 (Ukraine); International Materials Institute for New Functionality in Glass, Lehigh University, 5 East Packer Avenue, Bethlehem, PA 18015-3195 (United States); Shpotyuk, O. [Lviv Institute of Materials of SRC ' Carat' , 202 Stryjska str., Lviv, UA-79031 (Ukraine); International Materials Institute for New Functionality in Glass, Lehigh University, 5 East Packer Avenue, Bethlehem, PA 18015-3195 (United States)], E-mail: shpotyuk@novas.lviv.ua; Vakiv, M. [Lviv Institute of Materials of SRC ' Carat' , 202 Stryjska str., Lviv, UA-79031 (Ukraine)

    2007-04-15

    The features of application of radiation-sensitive media based on chalcogenide glasses of As-Ge-S system for registration of high-energy {gamma}-radiation are analysed. It is shown that compositional features of the observed time-instability effect should be taken into account in order to ensure a higher accuracy of the developed dosimeters.

  11. On the instability effects in radiation-sensitive chalcogenide glasses

    International Nuclear Information System (INIS)

    The features of application of radiation-sensitive media based on chalcogenide glasses of As-Ge-S system for registration of high-energy γ-radiation are analysed. It is shown that compositional features of the observed time-instability effect should be taken into account in order to ensure a higher accuracy of the developed dosimeters

  12. Ag - conducting chalcogenide glasses, their structure, properties and potential applications

    Czech Academy of Sciences Publication Activity Database

    Wágner, T.; Bartoš, M.; Válková, S.; Voleská, I.; Kolář, J.; Zima, Vítězslav; Akola, J.; Jones, R. O.; Jóvári, P.; Kaban, I.; Yannopoulos, S.; Stehlík, Š.; Frumar, M.

    Pardubice: University of Pardubice, 2011. s. 35. ISBN 978-80-7395-419-2. [International Days of Materials Science 2011. 15.09.2011-16.09.2011, Pardubice] Institutional research plan: CEZ:AV0Z40500505 Keywords : chalcogenide glasses * ionic conductivity * impedance spectroscopy Subject RIV: CA - Inorganic Chemistry

  13. Conductivity in Ag-As-S(Se,Te) chalcogenide glasses

    Czech Academy of Sciences Publication Activity Database

    Stehlík, Š.; Kolář, J.; Bartoš, M.; Vlček, Milan; Frumar, M.; Zima, Vítězslav; Wágner, T.

    2010-01-01

    Roč. 181, 37/38 (2010), s. 1625-1630. ISSN 0167-2738 Institutional research plan: CEZ:AV0Z40500505 Keywords : chalcogenide glasses * ionics conductivity * phase separation Subject RIV: CA - Inorganic Chemistry Impact factor: 2.496, year: 2010

  14. Ultrafast Laser Fabrication of Bragg Waveguides in GLS Chalcogenide Glass

    Directory of Open Access Journals (Sweden)

    McMillen Ben

    2013-11-01

    Full Text Available We present work on the fabrication of Bragg waveguides in gallium-lanthanum-sulfide chalcogenide glass using an ultrafast laser. Waveguides were written with a single pass while modulating the writing beam. The spatial and temporal profile of the writing beam was ontrolled during waveguide fabrication in order to control the shape and size of the waveguide cross-section.

  15. Electrical properties of Bi-implanted amorphous chalcogenide films

    International Nuclear Information System (INIS)

    The impact of Bi implantation on the conductivity and the thermopower of GeTe, Ge–Sb–Te, and Ga–La–S films is investigated. The enhanced conductivity appears to be notably sensitive to a dose of an implant. Incorporation of Bi in amorphous chalcogenide films at doses up to 1 × 1015 cm−2 is seen not to change the majority carrier type and activation energy for the conduction process. Higher implantation doses may reverse the majority carrier type in the studied films. Electron conductivity was observed in GeTe films implanted with Bi at a dose of 2 × 1016 cm−2. These studies indicate that native coordination defects present in amorphous chalcogenide semiconductors can be deactivated by means of ion implantation. A substantial density of implantation-induced traps in the studied films and their interfaces with silicon is inferred from analysis of the space-charge-limited current and capacitance-voltage characteristics taken on Au/amorphous chalcogenide/Si structures. - Highlights: • Electron conductivity is observed in Bi-implanted GeTe films. • Higher conductivity in Bi-implanted films stems from increased density of electrically active defects. • Bi implanted in amorphous chalcogenides may promote formation of a more chemically ordered alloy

  16. Electrical properties of Bi-implanted amorphous chalcogenide films

    Energy Technology Data Exchange (ETDEWEB)

    Fedorenko, Yanina G.

    2015-08-31

    The impact of Bi implantation on the conductivity and the thermopower of GeTe, Ge–Sb–Te, and Ga–La–S films is investigated. The enhanced conductivity appears to be notably sensitive to a dose of an implant. Incorporation of Bi in amorphous chalcogenide films at doses up to 1 × 10{sup 15} cm{sup −2} is seen not to change the majority carrier type and activation energy for the conduction process. Higher implantation doses may reverse the majority carrier type in the studied films. Electron conductivity was observed in GeTe films implanted with Bi at a dose of 2 × 10{sup 16} cm{sup −2}. These studies indicate that native coordination defects present in amorphous chalcogenide semiconductors can be deactivated by means of ion implantation. A substantial density of implantation-induced traps in the studied films and their interfaces with silicon is inferred from analysis of the space-charge-limited current and capacitance-voltage characteristics taken on Au/amorphous chalcogenide/Si structures. - Highlights: • Electron conductivity is observed in Bi-implanted GeTe films. • Higher conductivity in Bi-implanted films stems from increased density of electrically active defects. • Bi implanted in amorphous chalcogenides may promote formation of a more chemically ordered alloy.

  17. Tailoring chromatic dispersion in chalcogenide-tellurite microstructured optical fiber

    Science.gov (United States)

    Kohoutek, Tomas; Duan, Zhongchao; Kawashima, Hiroyasu; Cheng, Tonglei; Suzuki, Takenobu; Matsumoto, Morio; Misumi, Takashi; Ohishi, Yasutake

    2014-08-01

    We report fabrication of a highly nonlinear hybrid microstructured optical fiber composed of chalcogenide glass core and tellurite glass cladding. The flattened chromatic dispersion can be achieved in such an optical fiber with near zero dispersion wavelength at telecommunication wavelengths λ = 1.35-1.7 μm, which cannot be achieved in chalcogenide glass optical fibers due to their high refractive index, i.e. n > 2.1. We demonstrate a hybrid 4-air hole chalcogenide-tellurite optical fiber (Δn = 0.25) with flattened chromatic dispersion around λ = 1.55 μm. In optimized 12-air hole optical fiber composed of the same glasses, the chromatic dispersion values were achieved between -20 and 32 ps/nm/km in a broad wavelength range of 1.5-3.8 μm providing the fiber with extremely high nonlinear coefficient 86,000 km-1W-1. Hybrid chalcogenide/tellurite fibers pumped with the near infrared lasers give good promise for broadband optical amplification, wavelength conversion, and supercontinuum generation in the near- to mid-infrared region.

  18. Magnetic excitations in iron chalcogenide superconductors

    Directory of Open Access Journals (Sweden)

    Hisashi Kotegawa

    2012-01-01

    Full Text Available 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.

  19. Iron based superconductors: Pnictides versus chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Sadovskii, M.V., E-mail: sadovski@iep.uran.ru [Institute for Electrophysics, Russian Academy of Sciences, Ural Branch, Amundsen str. 106, Ekaterinburg 620016 (Russian Federation); Institute for Metal Physics, Russian Academy of Sciences, Ural Branch, S. Kovalevskaya str. 18, Ekaterinburg 620990 (Russian Federation); Kuchinskii, E.Z.; Nekrasov, I.A. [Institute for Electrophysics, Russian Academy of Sciences, Ural Branch, Amundsen str. 106, Ekaterinburg 620016 (Russian Federation)

    2012-10-15

    We present a brief review of the present day situation with studies of high-temperature superconductivity in iron pnictides and chalcogenides. Recent discovery of superconductivity with T{sub c}>30K in A{sub x}Fe{sub 2-x/2}Se{sub 2} (A=K, Cs, Tl, etc) represents the major new step in the development of new concepts in the physics of Fe-based high-temperature superconductors. We compare LDA and ARPES data on the band structure and Fermi surfaces of novel superconductors and those of the previously studied FeAs superconductors, especially isostructural 122-superconductors like BaFe{sub 2}As{sub 2}. It appears that electronic structure of new superconductors is rather different from that of FeAs 122-systems. In particular, no nesting properties of electron and hole-like Fermi surfaces is observed, casting doubts on most popular theoretical schemes of Cooper pairing for these systems. Doping of novel materials is extremely important as a number of topological transitions of Fermi surface near the {Gamma} point in the Brillouin zone are observed for different doping levels. The discovery of Fe vacancies ordering and antiferromagnetic (AFM) ordering at pretty high temperatures (T{sub N}>500K), much exceeding superconducting T{sub c} makes these systems unique antiferromagnetic superconductors with highest T{sub N} observed up to now. This poses very difficult problems for theoretical understanding of superconductivity. We discuss the role of both vacancies and AFM ordering in transformations of band structure and Fermi surfaces, as well as their importance for superconductivity. In particular, we show that system remains metallic with unfolded Fermi surfaces quite similar to that in paramagnetic state. Superconducting transition temperature T{sub c} of new superconductors is discussed within the general picture of superconductivity in multiple band systems. It is demonstrated that both in FeAs-superconductors and in new FeSe-systems the value of T{sub c} correlates with

  20. The new materials on base of the pnictides and the chalcogenides of the rare earth elements

    International Nuclear Information System (INIS)

    Full text: Rare earth pnictides, chalcogenides and their solid solutions are prospective materials in which strong magnetooptic, electrooptic and other effects. This presentation will cover the development of new techniques and process investigation for crystal growth of RE pnictides, chalcogenides and their solid solutions. Diagrams of pnictides, chalcogenides and their solid solution have been constructed and the atomic and electronic structure was studied by electron spectroscopy of clean cleaved surfaces

  1. Error-free 640 Gbit/s demultiplexing using a chalcogenide planar waveguide chip

    DEFF Research Database (Denmark)

    Xu, Jing; Galili, Michael; Mulvad, Hans Christian Hansen;

    2008-01-01

    We demonstrate error free, low-penalty demultiplexing of a 640 Gbit/s OTDM signal to 10 Gbit/s using a 5cm long chalcogenide planar waveguide chip. Our approach exploits four-wave mixing by the instantaneous nonlinear response of chalcogenide.......We demonstrate error free, low-penalty demultiplexing of a 640 Gbit/s OTDM signal to 10 Gbit/s using a 5cm long chalcogenide planar waveguide chip. Our approach exploits four-wave mixing by the instantaneous nonlinear response of chalcogenide....

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

    Science.gov (United States)

    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.

  3. Terahertz-induced Kerr effect in amorphous chalcogenide glasses

    DEFF Research Database (Denmark)

    Zalkovskij, Maksim; Strikwerda, Andrew; Iwaszczuk, Krzysztof; Popescu, A.; Savastru, A.; Malureanu, Radu; Lavrinenko, Andrei; Jepsen, Peter Uhd

    2013-01-01

    We have investigated the terahertz-induced third-order (Kerr) nonlinear optical properties of the amorphous chalcogenide glasses As2S3 and As2Se3. Chalcogenide glasses are known for their high optical Kerr nonlinearities which can be several hundred times greater than those of fused silica. We use...... high-intensity, single-cycle terahertz pulses with a maximum electrical field strength exceeding 400 kV/cm and frequency content from 0.2 to 3.0 THz. By optical Kerr-gate sampling, we measured the terahertz-induced nonlinear refractive indices at 800nm to be n2 = 1.746 x 10-14 cm2/W for As2S3 and n2...

  4. Synthesis of cadmium chalcogenide nanotubes at room temperature

    KAUST Repository

    Pan, Jun

    2012-10-01

    Cadmium chalcogenide (CdE, E=S, Se, Te) polycrystalline nanotubes have been synthesized from precursor of CdS/cadmium thiolate complex at room temperature. The precursor was hydrothermally synthesized at 180 °C using thioglycolic acid (TGA) and cadmium acetate as starting materials. The transformation from the rod-like precursor of CdS/cadmium thiolate complex to CdS, CdSe and CdTe nanotubes were performed under constant stirring at room temperature in aqueous solution containing S 2-, Se 2- and Te 2-, respectively. The nanotube diameter can be controlled from 150 to 400 nm related to the dimension of templates. The XRD patterns show the cadmium chalcogenide nanotubes all corresponding to face-centered cubic structure. © 2012 Elsevier B.V. All rights reserved.

  5. Electronic structure of ruthenium-doped iron chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Winiarski, M. J., E-mail: M.Winiarski@int.pan.wroc.pl; Samsel-Czekała, M. [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, ul. Okólna 2, 50-422 Wrocław (Poland); Ciechan, A. [Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw (Poland)

    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.

  6. Electronic structure of ruthenium-doped iron chalcogenides

    OpenAIRE

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

    2014-01-01

    The structural and electronic properties of hypothetical Ru$_x$Fe$_{1-x}$Se and Ru$_x$Fe$_{1-x}$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 ...

  7. Theoretical prediction of topological insulator in ternary rare earth chalcogenides

    OpenAIRE

    Yan, Binghai; Zhang, Hai-Jun; Liu, Chao-Xing; Qi, Xiao-Liang; Frauenheim, Thomas; Zhang, Shou-Cheng

    2010-01-01

    A new class of three-dimensional topological insulator, ternary rare earth chalcogenides, is theoretically investigated with ab initio calculations. Based on both bulk band structure analysis and the direct calculation of topological surface states, we demonstrate that LaBiTe3 is a topological insulator. La can be substituted by other rare earth elements, which provide candidates for novel topological states such as quantum anomalous Hall insulator, axionic insulator and topological Kondo ins...

  8. New molybdenium chalcogenide cathodes for rechargeable lithium batteries

    International Nuclear Information System (INIS)

    The synthesis, characterization, and electrochemical study of novel molybdenum chalcogenides with application as secondary Li battery cathodes are described. These compounds include oxysulfides having the formula MoOS2 and MoO2S, the selenosulfide MoSe3S, and a rhenium substituted trisulfide Mo.94Re.06S3. The performance of these materials in secondary Li cells is compared to that of MoS3. MoS3 and MoSe3S

  9. Assessment of Lead Chalcogenide Nanostructures as Possible Thermoelectric Materials

    OpenAIRE

    Gabriel, Stefanie

    2013-01-01

    The assembly of nanostructures into “multi”-dimensional materials is one of the main topics occurring in nanoscience today. It is now possible to produce high quality nanostructures reproducibly but for their further application larger structures that are easier to handle are required. Nevertheless during their assembly their nanometer size and accompanying properties must be maintained. This challenge was addressed in this work. Lead chalcogenides have been chosen as an example system becaus...

  10. Glassy and Amorphous Chalcogenides and Chalcohalides with Strong Infrared Luminescence

    Czech Academy of Sciences Publication Activity Database

    Frumarová, Božena; Frumar, M.; Oswald, Jiří; Šourková, P.

    Chandigarh: Department of Physics Panjab University Chandigarh 160014, India , 2011. s. 14. [International Conference on Advances in Condensed and Nano Materials. 23.02.2011-26.02.2011, Chandigarh] R&D Projects: GA ČR GA203/09/0827 Institutional research plan: CEZ:AV0Z40500505; CEZ:AV0Z10100521 Keywords : chalcogenide glasses * luminescence Subject RIV: CA - Inorganic Chemistry

  11. Rare-earth doped chalcogenide glass fibre laser

    OpenAIRE

    Schweizer, T.; Samson, B.N.; Moore, R C; Hewak, D.W.; Payne, D.N.

    1997-01-01

    We report on the first laser action in a rare-earth doped chalcogenide glass fibre. Laser action at 1080nm was obtained in a 22mm long gallium lanthanum sulphide glass fibre with a neodymium doped core, fabricated by the rod-in-tube technique. The laser was pumped continuous wave with a Ti:sapphire laser at 815nm and showed a self-pulsing behaviour.

  12. Forced Ion Migration for Chalcogenide Phase Change Memory Device

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  14. Characterization of pulsed laser deposited chalcogenide thin layers

    International Nuclear Information System (INIS)

    In this work we report on pulsed laser deposition (PLD) of chalcogenide thin films from the systems (AsSe)100-xAgIx and (AsSe)100-xAgx for sensing applications. A KrF* excimer laser (λ = 248 nm; τFWHM = 25 ns) was used to ablate the targets that had been prepared from the synthesised chalcogenide materials. The films were deposited in either vacuum (4 x 10-4 Pa) or argon (5 Pa) on silicon and glass substrates kept at room temperature. The basic properties of the films, including their morphology, topography, structure, and composition were characterised by complementary techniques. Investigations by X-ray diffraction (XRD) confirmed the amorphous nature of the films, as no strong diffraction reflections were found. The film composition was studied by energy dispersive X-ray (EDX) spectroscopy. The morphology of the films investigated by scanning electron microscopy (SEM), revealed a particulate-covered homogeneous surface, typical of PLD. Topographical analyses by atomic force microscopy (AFM) showed that the particulate size was slightly larger in Ar than in vacuum. The uniform surface areas were rather smooth, with root mean square (rms) roughness increasing up to several nanometers with the AgI or Ag doping. Based upon the results from the comprehensive investigation of the basic properties of the chalcogenide films prepared by PLD and their dependence on the process parameters, samples with appropriate sorption properties can be selected for possible applications in cantilever gas sensors

  15. Infrared Emitting and Photoconducting Colloidal Silver Chalcogenide Nanocrystal Quantum Dots from a Silylamide-Promoted Synthesis

    NARCIS (Netherlands)

    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, Guenter; Heiss, Wolfgang; Hesser, Günter

    2011-01-01

    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,

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

    DEFF Research Database (Denmark)

    Markos, Christos

    2014-01-01

    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 n...

  17. Polyol-mediated Synthesis of Chalcogenide Nanoparticles for Thin-film Solar Cells

    OpenAIRE

    Dong, Hailong

    2014-01-01

    The aim of this work was polyol-mediated syntheses of chalcogenide nanoparticles for printable thin-film solar cells. In this thesis, chalcogenide nanoparticles, such as Cu2Se, In2Se3, CZTS, Se@CuSe and Te@Bi2Te3, have been successfully synthesized via a polyol-mediated method.

  18. Effect of Net-Fluence on waveguide formation in ultrafast laser inscribed chalcogenide glass

    OpenAIRE

    Sabapathy, Tamilarasan; Sivakumar, Gayathri; Ayiriveetil, Arunbabu; Ajoy K. Kar; Asokan, Sundarrajan

    2012-01-01

    Waveguides were fabricated on GeGaSEr chalcogenide glass using ultrafast laser inscription method. The thermal diffusion model is discussed for understanding the light matter interaction and shown the effect of net-fluence in waveguide formation on chalcogenide glass. (C) 2012 Optical Society of America

  19. Breakthrough switching speed with an all-optical chalcogenide glass chip: 640 Gbit/s demultiplexing

    DEFF Research Database (Denmark)

    Galili, Michael; Xu, Jing; Mulvad, Hans Christian Hansen;

    2009-01-01

    We report the first demonstration of error-free 640 Gbit/s demultiplexing using the Kerr non-linearity of an only 5 cm long chalcogenide glass waveguide chip. Our approach exploits four-wave mixing by the instantaneous nonlinear response of chalcogenide. Excellent performance is achieved with only...

  20. New electronic phase diagram of iron-chalcogenide superconductor. Suppression of phase separation using film fabrication

    International Nuclear Information System (INIS)

    We have demonstrated a giant enhancement of superconducting critical temperature in iron chalcogenide and new electronic phase diagram of this system. These remarkable results were achieved by fabricating an iron chalcogenide film with a composition that was difficult to obtain in bulk crystals because of spinodal decomposition. (author)

  1. Recent advances in optoelectronic properties and applications of two-dimensional metal chalcogenides

    Science.gov (United States)

    Congxin, Xia; Jingbo, Li

    2016-05-01

    Since two-dimensional (2D) graphene was fabricated successfully, many kinds of graphene-like 2D materials have attracted extensive attention. Among them, the studies of 2D metal chalcogenides have become the focus of intense research due to their unique physical properties and promising applications. Here, we review significant recent advances in optoelectronic properties and applications of 2D metal chalcogenides. This review highlights the recent progress of synthesis, characterization and isolation of single and few layer metal chalcogenides nanosheets. Moreover, we also focus on the recent important progress of electronic, optical properties and optoelectronic devices of 2D metal chalcogenides. Additionally, the theoretical model and understanding on the band structures, optical properties and related physical mechanism are also reviewed. Finally, we give some personal perspectives on potential research problems in the optoelectronic characteristics of 2D metal chalcogenides and related device applications.

  2. Photosensitivity in chalcogenide glass thin films and its applications

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  4. Supercontinuum generation in an ultrafast laser inscribed chalcogenide glass waveguide.

    Science.gov (United States)

    Psaila, Nicholas D; Thomson, Robert R; Bookey, Henry T; Shen, Shaoxiong; Chiodo, Nicola; Osellame, Roberto; Cerullo, Giulio; Jha, Animesh; Kar, Ajoy K

    2007-11-26

    The authors report supercontinuum generation in an ultrafast laser inscribed chalcogenide glass waveguide. The waveguides were fabricated using a Yb:glass cavity-dumped femtosecond oscillator with 600- kHz repetition rate. The waveguides were pumped using an optical parametric amplifier tuned to 1500 nm with a bandwidth of 100 nm. The broadest resulting supercontinuum spanned 600 nm (at -15 dB points) from 1320 to 1920 nm. The supercontinuum was generated in the normal dispersion regime, enhancing stability, and exhibits a smooth spectral shape. PMID:19550862

  5. Reversibility windows in selenide-based chalcogenide glasses

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O. [Lviv Scientific Research Institute of Materials of SRC ' Carat' , 202, Stryjska Street, Lviv, UA 79031 (Ukraine); Institute of Physics of Jan Dlugosz University, 13/15, al. Armii Krajowej, Czestochowa, PL 42200 (Poland); Hyla, M. [Institute of Physics of Jan Dlugosz University, 13/15, al. Armii Krajowej, Czestochowa, PL 42200 (Poland); Boyko, V. [Lviv Scientific Research Institute of Materials of SRC ' Carat' , 202, Stryjska Street, Lviv, UA 79031 (Ukraine); Lviv National Polytechnic University, 12, Bandera Street, Lviv, UA 79013 (Ukraine); Golovchak, R. [Lviv Scientific Research Institute of Materials of SRC ' Carat' , 202, Stryjska Street, Lviv, UA 79031 (Ukraine)], E-mail: golovchak@novas.lviv.ua

    2008-10-01

    A simple route for the estimation of the reversibility windows in the sense of non-ageing ability is developed for chalcogenide glasses obeying '8-N' rule at the example of As-Se, Ge-Se and Ge-As-Se glass systems. The low limit of their reversibility windows is determined at the average coordination number Z=2.4 in full agreement with rigidity percolation theory, while the upper limit is shown to be related to the glass preparation conditions and samples prehistory.

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

    International Nuclear Information System (INIS)

    Using As2S3 and AsS2 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O. [Scientific Research Company “Carat” (Ukraine); Kozyukhin, S. A., E-mail: sergkoz@igic.ras.ru [Russian Academy of Sciences, Kurnakov Institute of General and Inorganic Chemistry (Russian Federation); Shpotyuk, M. [Scientific Research Company “Carat” (Ukraine); Ingram, A. [Opole Technical University (Poland); Szatanik, R. [Opole University (Poland)

    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.

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

    Science.gov (United States)

    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. PMID:26371923

  9. Chalcogenide photovoltaics physics, technologies, and thin film devices

    CERN Document Server

    Scheer, Roland

    2011-01-01

    This first comprehensive description of the most important material properties and device aspects closes the gap between general books on solar cells and journal articles on chalcogenide-based photovoltaics. Written by two very renowned authors with years of practical experience in the field, the book covers II-VI and I-III-VI2 materials as well as energy conversion at heterojunctions. It also discusses the latest semiconductor heterojunction models and presents modern analysis concepts. Thin film technology is explained with an emphasis on current and future techniques for mass production, a

  10. Quasiparticle electronic band structure of the alkali metal chalcogenides

    Directory of Open Access Journals (Sweden)

    S.V. Syrotyuk

    2015-09-01

    Full Text Available The electronic energy band spectra of the alkali metal chalcogenides M2A (M: Li, Na, K, Rb; A: O, S, Se, Te have been evaluated within the projector augmented waves (PAW approach by means of the ABINIT code. The Kohn-Sham single-particle states have been found in the GGA framework. Further, on the basis of these results the quasiparticle energies of electrons as well as the dielectric constants were obtained in the approximation GW. The calculations based on the Green's function have been originally done for all the considered M2A crystals, except Li2O.

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

    Science.gov (United States)

    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. PMID:26981781

  12. Chalcogenide Microsphere Fabricated from Fiber Tapers Using Contact With a High-Temperature Ceramic Surface

    OpenAIRE

    Wang, Pengfei; Murugan, Ganapathy; Bramilla, Gilberto; Ding, Ming; Semenova, Yuliya; Wu, Qiang; Farrell, Gerald

    2012-01-01

    The fabrication 1 and characterization of a 2 chalcogenide glass microsphere resonator has been demonstrated. 3 At wavelengths near 1550 nm, whispering gallery mode 4 resonances can be efficiently excited in a 74-μm-diameter 5 chalcogenide glass microsphere via evanescent coupling using a 6 tapered silica glass fiber with a waist diameter of circa 2 μm. 7 Resonances with Q-factors greater than 105 were observed. 8 Due to the high nonlinearity properties of the chalcogenide 9 material and the ...

  13. Highly nonlinear chalcogenide glass micro/nanofiber devices: Design, theory, and octave-spanning spectral generation

    Science.gov (United States)

    Hudson, Darren D.; Mägi, Eric C.; Judge, Alexander C.; Dekker, Stephen A.; Eggleton, Benjamin J.

    2012-10-01

    In this review we consider the basic elements of tapering chalcogenide optical fibers for the generation of extreme spectral broadening through supercontinuum generation. Creating tapered nanofiber devices in chalcogenide fiber, which has an intrinsic nonlinearity that is two orders of magnitude higher than silica, has resulted in the demonstration of octave-spanning spectra using record low power. We first present a brief theoretical understanding of the tapering process that follows from the basic principle of mass conservation, and a geometric construction tool for the visualization of the shape of tapered fibers. This is followed by a theoretical treatment of dispersion engineering and supercontinuum generation in a chalcogenide nanofiber. In the final section, we cover the experimental implementation of the chalcogenide nanofiber and demonstrate an octave-spanning spectrum created with 150 W of peak power.

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

    International Nuclear Information System (INIS)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Qiao, Li-Na; Wang, H.C.; Shen, Y.; Lin, Yuan-Hua, E-mail: linyh@mail.tsinghua.edu.cn; Nan, Ce-Wen [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    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.

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

    OpenAIRE

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

    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,...

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

    OpenAIRE

    Shpotyuk, M. V.; Shpotyuk, O. I.; J. Cebulski; 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 pu...

  18. New Trends in Amplifiers and Sources via Chalcogenide Photonic Crystal Fibers

    Directory of Open Access Journals (Sweden)

    L. Mescia

    2012-01-01

    Full Text Available Rare-earth-doped chalcogenide glass fiber lasers and amplifiers have great applicative potential in many fields since they are key elements in the near and medium-infrared (mid-IR wavelength range. In this paper, a review, even if not exhaustive, on amplification and lasing obtained by employing rare-earth-doped chalcogenide photonic crystal fibers is reported. Materials, devices, and feasible applications in the mid-IR are briefly mentioned.

  19. Electrical properties of amorphous chalcogenide/silicon heterojunctions modified by ion implantation

    OpenAIRE

    Fedorenko, Yanina G.; Hughes, Mark A.; Colaux, Julien L.; Jeynes, C.; Gwilliam, Russell M.; Homewood, Kevin P.; Yao, Jin; Hewak, Dan W.; Lee, Tae-Hoon; Elliott, Stephen R; Gholipour, B.; Curry, Richard J.

    2014-01-01

    Doping of amorphous chalcogenide films of rather dissimilar bonding type and resistivity, namely, Ga-La-S, GeTe, and Ge-Sb-Te by means of ion implantation of bismuth is considered. To characterize defects induced by ion-beam implantation space-charge-limited conduction and capacitance-voltage characteristics of amorphous chalcogenide/silicon heterojunctions are investigated. It is shown that ion implantation introduces substantial defect densities in the films and their interfaces with silico...

  20. Design of fiber coupled Er3+: Chalcogenide microsphere amplifier via particle swarm optimization algorithm

    OpenAIRE

    Palma, Giuseppe; Bia, Pietro; Mescia, Luciano; Yano, Tetsuji; Nazabal, Virginie; Taguchi, Jun; Moréac, Alain; Prudenzano, Francesco

    2013-01-01

    A mid-IR amplifier consisting of a tapered chalcogenide fiber coupled to an Er3+-doped chalcogenide microsphere has been optimized via a particle swarm optimization (PSO) approach. More precisely, a dedicated three-dimensional numerical model, based on the coupled mode theory and solving the rate equations, has been integrated with the PSO procedure. The rate equations have included the main transitions among the erbium energy levels, the amplified spontaneous emission, and the most important...

  1. Pulsed laser deposition of Ga-La-S chalcogenide glass thin film optical waveguides

    OpenAIRE

    Youden, K.E.; Grevatt, T.; Eason, R. W.; Rutt, H.N.; Deol, R.S.; Wylangowski, G.

    1993-01-01

    Thin film optical waveguides of the chalcogenide glass Ga-La-S have been deposited on substrates of CaF2 and microscope glass by the technique of pulsed laser deposition. The chalcogenide properties of photobleaching, photodoping, and photoinduced refractive index changes have been observed and preliminary experiments carried out. The refractive index and thickness of the layer were verified using a waveguide "dark mode" analysis technique.

  2. High pressure phase transition and elastic properties of Lutetium chalcogenide

    Energy Technology Data Exchange (ETDEWEB)

    Seddik, T., E-mail: sedik_t@yahoo.f [Laboratoire de Physique Quantique et de Modelisation Mathematique (LPQ3M), Departement de Technologie, Universite de Mascara, 29000 Mascara (Algeria); Semari, F. [Physics Department, Faculty of Sciences, University of Sidi-Bel-Abbes, 22000 (Algeria); Khenata, R., E-mail: khenata_rabah@yahoo.f [Laboratoire de Physique Quantique et de Modelisation Mathematique (LPQ3M), Departement de Technologie, Universite de Mascara, 29000 Mascara (Algeria); Bouhemadou, A. [Laboratory for Developing New Materials and their Characterisation, Department of Physics, Faculty of Sciences, University of Setif (Algeria); Amrani, B. [Laboratoire de Physique Quantique et de Modelisation Mathematique (LPQ3M), Departement de Technologie, Universite de Mascara, 29000 Mascara (Algeria)

    2010-01-01

    Using first-principles density functional calculation, the pressure induced structural phase transformation and mechanical properties of NaCl type (B1) structure in Lutetium chalcogenides (LuX: X=S, Se, Te) were studied by means of the full-potential augmented plane wave plus local orbitals (FP-APW+lo) method. The calculations were performed within the generalized gradient approximation (GGA) for the exchange-correlation potential. The calculated ground state properties such us lattice constants agree quit well with the experimental findings. We have determined the full set of first-order elastic constants and their pressure dependence, which have not been calculated and measured yet. The Debye temperature is estimated from the average sound velocity. To our knowledge this is the first quantitative theoretical prediction of the structural phase transition and elastic properties for these compounds and still awaits experimental confirmations.

  3. Copper Antimony Chalcogenide Thin Film PV Device Development

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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

  5. Analysis of switching conditions of chalcogenide alloys during crystallization

    Institute of Scientific and Technical Information of China (English)

    Wanhua Yu; C.D. Wright

    2006-01-01

    To understand the principle and limitation of chalcogenide alloy Ge2Sb2Te5 (GST) in solid-state memory devices during crystallization, it was necessary to develop a physically realistic model that could reflect the electrical and thermal properties of these media. A novel comprehensive numerical model has been developed for simulating these memory devices, which describes the electrical and thermal behavior using the solution of the nonlinear, time-dependent electrical and heat conduction equation. The finite-difference-time-domain technique was adopted to compute the electrical field and heat distribution in the device. Several contributing factors that affect the crystallization switching process such as the geometry of the GST layer, temperature and electric field dependency of the electrical conductivity have been discussed. The results of the simulations were then used to provide critical guidelines for fabrication and optimization of the device performance.

  6. 10 um wavefront spatial filtering first results with chalcogenide fibers

    CERN Document Server

    Bordé, P J; Nguyen, T; Amy-Klein, A; Daussy, C; Raynal, P; Léger, A; Mazé, G; Borde, Pascal; Perrin, Guy; Nguyen, Thanh; Amy-Klein, Anne; Daussy, Christophe; Raynal, Pierre-Ivan; Leger, Alain; Maze, Gwenael

    2003-01-01

    Wavefront cleaning by single-mode fibers has proved to be efficient in optical-infrared interferometry to improve calibration quality. For instance, the FLUOR instrument has demonstrated the capability of fluoride glass single-mode fibers in this respect in the K and L bands. New interferometric instruments developped for the mid-infrared require the same capability for the 8-12 um range. We have initiated a program to develop single-mode fibers in the prospect of the VLTI mid-infrared instrument MIDI and of the ESA/DARWIN and NASA/TPF missions that require excellent wavefront quality. In order to characterize the performances of chalcogenide fibers we are developping, we have set up an experiment to measure the far-field pattern radiated at 10 um. In this paper, we report the first and promising results obtained with this new component.

  7. Meyer–Neldel DC conduction in chalcogenide glasses

    Indian Academy of Sciences (India)

    S PraKash; Kulbir Kaur; Navdeep Goyal; S K Tripathi

    2011-04-01

    Meyer–Neldel (MN) formula for DC conductivity (DC) of chalcogenide glasses is obtained using extended pair model and random free energy barriers. The integral equations for DC hopping conductivity and external conductance are solved by iterative procedure. It is found that MN energy ( MN) originates from temperature-induced configurational and electronic disorders. Single polaron-correlated barrier hopping model is used to calculate DC and the experimental data of Se, As2S3, As2Se3 and As2Te3 are explained. The variation of attempt frequency 0 and MN with parameter (/), where is the intersite separation and is the radius of localized states, is also studied. It is found that 0 and MN decrease with increase of (/), and MN may not be present for low density of defects.

  8. Electrical conduction mechanism in GeSeSb chalcogenide glasses

    Indian Academy of Sciences (India)

    Vandana Kumari; Anusaiya Kaswan; D Patidar; Kananbala Sharma; N S Saxena

    2016-02-01

    Electrical conductivity of chalcogenide glassy system Ge$_{30−x}$Se$_{70}$Sb$_{x}$ ( = 10, 15, 20 and 25) prepared by melt quenching has been determined at different temperatures in bulk through the $I$–$V$ characteristic curves. It is quite evident from results that Poole–Frenkel conduction mechanisms hold good for conduction in these glasses in a given temperature range. The variation in electrical conductivity with composition was attributed to the Se–Sb bond concentration in the Se–Ge–Sb system. Results indicated that Ge$_5$Se$_{70}$Sb$_{25}$ showed the minimum resistance. In view of this the composition Ge$_5$Se$_{70}$Sb$_{25}$ may be coined as ‘critical composition’ in the proposed series. Also the activation energies of conduction of these glassy alloys have been calculated in higher and lower temperature range using the Arrhenius equation.

  9. High pressure phase transition and elastic properties of Lutetium chalcogenide

    International Nuclear Information System (INIS)

    Using first-principles density functional calculation, the pressure induced structural phase transformation and mechanical properties of NaCl type (B1) structure in Lutetium chalcogenides (LuX: X=S, Se, Te) were studied by means of the full-potential augmented plane wave plus local orbitals (FP-APW+lo) method. The calculations were performed within the generalized gradient approximation (GGA) for the exchange-correlation potential. The calculated ground state properties such us lattice constants agree quit well with the experimental findings. We have determined the full set of first-order elastic constants and their pressure dependence, which have not been calculated and measured yet. The Debye temperature is estimated from the average sound velocity. To our knowledge this is the first quantitative theoretical prediction of the structural phase transition and elastic properties for these compounds and still awaits experimental confirmations.

  10. Structural phase transition and elastic properties of mercury chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Varshney, Dinesh, E-mail: vdinesh33@rediffmail.com [School of Physics, Vigyan Bhavan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India); Shriya, S. [School of Physics, Vigyan Bhavan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India); Khenata, R. [Laboratoire de Physique Quantique et de Modelisation Mathematique (LPQ3M), Departement de Technologie, Universite de Mascara, 29000 Mascara (Algeria)

    2012-08-15

    Pressure induced structural transition and elastic properties of ZnS-type (B3) to NaCl-type (B1) structure in mercury chalcogenides (HgX; X = S, Se and Te) are presented. An effective interionic interaction potential (EIOP) with long-range Coulomb, as well charge transfer interactions, Hafemeister and Flygare type short-range overlap repulsion extended up to the second neighbor ions and van der Waals interactions are considered. Emphasis is on the evaluation of the pressure dependent Poisson's ratio {nu}, the ratio R{sub BT/G} of B (bulk modulus) over G (shear modulus), anisotropy parameter, Shear and Young's modulus, Lame constant, Kleinman parameter, elastic wave velocity and thermodynamical property as Debye temperature. The Poisson's ratio behavior infers that Mercury chalcogenides are brittle in nature. To our knowledge this is the first quantitative theoretical prediction of the pressure dependence of elastic and thermodynamical properties explicitly the ductile (brittle) nature of HgX and still awaits experimental confirmations. Highlights: Black-Right-Pointing-Pointer Vast volume discontinuity in phase diagram infers transition from ZnS to NaCl structure. Black-Right-Pointing-Pointer The shear elastic constant C{sub 44} is nonzero confirms the mechanical stability. Black-Right-Pointing-Pointer Pressure dependence of {theta}{sub D} infers the softening of lattice with increasing pressure. Black-Right-Pointing-Pointer Estimated bulk, shear and tetragonal moduli satisfied elastic stability criteria. Black-Right-Pointing-Pointer In both B3 and B1 phases, C{sub 11} and C{sub 12} increase linearly with pressure.

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

    Science.gov (United States)

    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.

  12. Raman and CT scan mapping of chalcogenide glass diffusion generated gradient index profiles

    Science.gov (United States)

    Lindberg, G. P.; Berg, R. H.; Deegan, J.; Benson, R.; Salvaggio, P. S.; Gross, N.; Weinstein, B. A.; Gibson, D.; Bayya, S.; Sanghera, J.; Nguyen, V.; Kotov, M.

    2016-05-01

    Metrology of a gradient index (GRIN) material is non-trivial, especially in the realm of infrared and large refractive index. Traditional methods rely on index matching fluids which are not available for indexes as high as those found in the chalcogenide glasses (2.4-3.2). By diffusing chalcogenide glasses of similar composition one can blend the properties in a continuous way. In an effort to measure this we will present data from both x-ray computed tomography scans (CT scans) and Raman mapping scans of the diffusion profiles. Proof of concept measurements on undiffused bonded sheets of chalcogenide glasses were presented previously. The profiles measured will be of axially stacked sheets of chalcogenide glasses diffused to create a linear GRIN profile and nested tubes of chalcogenide glasses diffused to create a radial parabolic GRIN profile. We will show that the x-ray absorption in the CT scan and the intensity of select Raman peaks spatially measured through the material are indicators of the concentration of the diffusion ions and correlate to the spatial change in refractive index. We will also present finite element modeling (FEM) results and compare them to post precision glass molded (PGM) elements that have undergone CT and Raman mapping.

  13. Thermochemical hydrogen sensor based on chalcogenide nanowire arrays

    International Nuclear Information System (INIS)

    The hydrogen gas-sensing properties have been investigated of two types of thermochemical hydrogen (TCH) sensors composed of thermoelectric layers based on chalcogenide nanowire arrays and anodic aluminum oxide (AAO) templates. The monomorphic-type TCH sensor, which had only Bi2Te3 nanowire arrays, showed an output signal of 23.7 μV in response to 5 vol% hydrogen gas at room temperature, whereas an output signal of 215 μV was obtained from an n–p junction-type TCH sensor made of connected Bi2Te3 and Sb2Te3 nanowire arrays in an AAO template. Despite its small deposition area, the output signal of the n–p sensor was more than nine times that of the monomorphic sensor. This observation can be explained by the difference in electrical connections (parallel and serial conversions) in the TCH sensor between each type of nanowire array. Also, our n–p sensor had a wide detection range for hydrogen gas (from 400 ppm to 45 vol%) and a fast response time of 1.3 s at room temperature without requiring external power. (paper)

  14. Palladium and platinum organochalcogenolates and their transformation into metal chalcogenides

    Indian Academy of Sciences (India)

    S Dey; S Narayan; A Singhal; V K Jain

    2000-06-01

    Platinum group metal chalcogenides find extensive applications in catalysis and in the electronic industry. To develop an efficient low temperature clean preparation of these materials, molecular routes have been explored. Thus the chemistry of mononuclear organochalcogenolates of the type [M(ER 1/4)2(PR3)2], binuclear benzylselenolates, [M2Cl2(∼-SeBz)2(PR3)2], allylpalladium complexes [Pd2(μ-ER)2(3-C4H7)2] and palladium/platinum sulphido/selenido-bridged complexes, [M2(μ-E)2L4] (M = Pd or Pt; E = S, Se or Te; L = tertiary phosphine ligand) has been investigated. All the complexes have been characterized by elemental analysis, NMR (1 H, 31P, 77Se, 195Pt) spectroscopy and in some cases by X-ray diffraction. The thermal behaviour of these complexes has been studied by TGA. The pyrolysis of allylpalladium complexes in refluxing xylene yields Pd4E as established by analysis and XRD patterns.

  15. Chalcogenide coatings of Ge15Sb20S65 and Te20As30Se50.

    Science.gov (United States)

    Nazabal, Virginie; Cathelinaud, Michel; Shen, Weidong; Nemec, Petr; Charpentier, Frédéric; Lhermite, Hervé; Anne, Marie-Laure; Capoulade, Jérémie; Grasset, Fabien; Moreac, Alain; Inoue, Satoru; Frumar, Miloslav; Adam, Jean-Luc; Lequime, Michel; Amra, Claude

    2008-05-01

    Chalcogenide coatings are investigated to obtain either optical components for spectral applications or optochemical sensors in the mid-infrared. The deposition of Ge(15)Sb(20)S(65) and Te(20)As(30)Se(50) chalcogenide glasses is performed by two physical techniques: electron-beam and pulsed-laser deposition. The quality of the film is analyzed by scanning electron microscopy, atomic force microscopy, and energy dispersive spectroscopy to characterize the morphology, topography, and chemical composition. The optical properties and optical constants are also determined. A CF(4) dry etching is performed on these films to obtain a channeled optical waveguide. For a passband filter made by electron-beam deposition, cryolite as a low-refractive-index material and chalcogenide glasses as high-refractive-index materials are used to favor a large refractive-index contrast. A shift of a centered wavelength of a photosensitive passband filter is controlled by illumination time. PMID:18449231

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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. PMID:26787053

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

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

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

    2015-03-01

    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.

  20. Experimental study of the fabrication of chalcogenide glass lenses by using precision glass molding

    International Nuclear Information System (INIS)

    Although the development of small formats (640 x 480 pixel arrays) and amorphous silicon microbolometers has greatly decreased detector cost, another important component of a thermal camera, the optics, still prohibit a breakthrough for high-volume commercial systems. The aspheric lenses used in thermal imaging are typically made using the costly single-point diamond turning (SPDT) process with expensive single-crystal materials (Ge, ZnS, etc.). As a potential solution to reduce cost, the compression molding method using chalcogenide glass has become attractive for fabricating IR optics. The present paper reports the fabrication of a mold and a molded chalcogenide glass lens for a thermal security camera. In addition, the molded chalcogenide glass lens was evaluated using the form error, roughness and decentration for each surface of the molded lens. From the evaluation results, we verified that the molded lens was capable of being used for thermal imaging applications.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chiles, Jeff; Malinowski, Marcin; Rao, Ashutosh [CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816 (United States); Novak, Spencer; Richardson, Kathleen [CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816 (United States); Department of Materials Science and Engineering, COMSET, Clemson University, Clemson, South Carolina 29634 (United States); Fathpour, Sasan, E-mail: fathpour@creol.ucf.edu [CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816 (United States); Department of Electrical Engineering and Computer Science, University of Central Florida, Orlando, Florida 32816 (United States)

    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.

  2. Solubilities of nickel and cobalt chalcogenides in a nuclear waste glass melt

    International Nuclear Information System (INIS)

    The solubilities of NiS, NiSe, NiTe, CoS, and CoSe were determined in the reference glass melt SRL-131 (Savannah River Laboratory frit number-sign 131) as a function of the melt temperature and imposed oxygen fugacity. The solubility of each metal chalcogenide was monitored by the concentration of both the cation and the anion in the glass melt equilibrated with an immiscible metal chalcogenide layer. The solubilities of the chalcogenides decrease with decreasing oxygen fugacity. In general, NIS is the least soluble of these compounds in SRL-131. Thus, processing conditions must be adjusted to avoid the formation of NiS during accidental excursions to reducing conditions; alternatively, NiS could be intentionally precipitated from the waste system to concentrate precious metals

  3. Investigations on the properties of solid solutions of pseudo-binary lead chalcogenides

    International Nuclear Information System (INIS)

    Lead chalcogenides and their solid solutions with detecting and lasing capabilities have great technological importance. High quality polycrystalline thin films of solid solutions of pseudo-binary lead chalcogenides have been deposited onto ultra clean glass substrates by vacuum evaporation technique. Optical, electrical and structural properties of the thin films of the solid solutions of pseudo-binary lead chalcogenides have been investigated. Absorption coefficient and band gap of films were determined by absorbance measurements in wavelength range 2500-5000 nm using FTIR spectrophotometer. dc conductivity and activation energy of films were measured in temperature range 300-380 K using two probe I-V characteristics method. Crystal structure and lattice parameters of films were determined from X-ray diffractogram.

  4. The dynamics of photoinduced defect creation in amorphous chalcogenides: The origin of the stretched exponential function

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, R. J. [Department of Electrical and Electronic Engineering, National University of Timor Lorosa' e, Av. Cidade de Lisboa, Dili, East Timor (Portugal); Shimakawa, K. [Department of General and Inorganic Chemistry, University of Pardubice, Pardubice 53002 (Czech Republic); Department of Electrical and Electronic Engineering, Gifu University, Gifu 501-1193 (Japan); Wagner, T. [Department of General and Inorganic Chemistry, University of Pardubice, Pardubice 53002 (Czech Republic)

    2014-01-07

    The article discusses the dynamics of photoinduced defect creations (PDC) in amorphous chalcogenides, which is described by the stretched exponential function (SEF), while the well known photodarkening (PD) and photoinduced volume expansion (PVE) are governed only by the exponential function. It is shown that the exponential distribution of the thermal activation barrier produces the SEF in PDC, suggesting that thermal energy, as well as photon energy, is incorporated in PDC mechanisms. The differences in dynamics among three major photoinduced effects (PD, PVE, and PDC) in amorphous chalcogenides are now well understood.

  5. Rings, chains and planes: Variation of g with composition in chalcogenide glasses

    Indian Academy of Sciences (India)

    P K Thiruvikraman

    2006-08-01

    We propose a microscopic, phenomenological model for the decrease in the viscosity observed at glass transition. Our model is primarily applicable to chalcogenide glasses. According to this model, the decrease in the viscosity at glass transition is mainly due to the breaking of the Van der Waals bonds in the chalcogenides. Using this model, we derive a relationship between the glass transition temperature, g, and the molar volume m. The validity of this relation is checked using experimental data available in the literature for two binary systems (Ge–Se and As–S) and a pseudo-binary system (As40SeTe60–).

  6. Double optical bistability and its application in nonlinear chalcogenide-fiber Bragg gratings

    International Nuclear Information System (INIS)

    We study the continuous wave (CW) nonlinear transmission characteristics of chalcogenide-fiber Bragg gratings (c-FBGs). The set of Cubic quintic septic nonlinear coupled mode equations (CQSNLCMEs) is derived analytically to govern nonlinear wave propagation in c-FBGs by counting until seventh-order nonlinearity in chalcogenide glass. Double-optical bistability is observed in the CW nonlinear transmission characteristics of π phase-shifted c-FBG. Based on unstable state principle in the hysteresis, all-optical transistor operation is shown as a prominent application of optical bistability in such device

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

    Science.gov (United States)

    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. Charged particle activation analysis of oxygen in fluoride and chalcogenide glasses used for fiber amplifiers

    International Nuclear Information System (INIS)

    The proton activation analysis of oxygen was studied in fluoride and chalcogenide glasses used for fiber amplifiers. First, interfering nuclear reactions from glass matrices were studied to determine the oxygen concentration in these glasses. By using substoichiometric separation for 18F after irradiation, oxygen concentration was found 12 to 204 ppm in InF3-based fluoride glass and 0.04% to 0.7% in chalcogenide glass containing sodium. Relation between oxygen concentration and optical properties such as the infrared absorption spectrum and fluorescence lifetime are also discussed. (author)

  9. High Average Power Mid-infrared Supercontinuum Generation in a Suspended Core Chalcogenide Fiber

    DEFF Research Database (Denmark)

    Møller, Uffe Visbech; Yu, Yi; Petersen, Christian Rosenberg;

    2014-01-01

    Mid-infrared supercontinuum spanning from 2.0 to 6.1 μm is generated in a 9 cm suspended core chalcogenide fiber by pumping close to the fiber zero-dispersion wavelength at 3.5 μm with an OPA system......Mid-infrared supercontinuum spanning from 2.0 to 6.1 μm is generated in a 9 cm suspended core chalcogenide fiber by pumping close to the fiber zero-dispersion wavelength at 3.5 μm with an OPA system...

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

    Science.gov (United States)

    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. PMID:26766722

  11. Generation of correlated photon pairs in a chalcogenide As2S3 waveguide

    NARCIS (Netherlands)

    Xiong, C.; Marshall, G.D.; Peruzzo, A.; Lobino, M.; Clark, A.S.; Choi, D.Y.; Madden, S.J.; Natarajan, C.M.; Tanner, M.G.; Hadfield, R.H.; Dorenbos, S.N.; Zijlstra, T.; Zwiller, V.; Thompson, M.G.; Rarity, J.G.; Steel, M.J.; Luther-Davies, B.; Eggleton, B.J.; O'Brien, J.L.

    2011-01-01

    We demonstrate a 1550 nm correlated photon-pair source in an integrated glass platform—a chalcogenide As2S3 waveguide. A measured pair coincidence rate of 80 s−1 was achieved using 57 mW of continuous-wave pump. The coincidence to accidental ratio was shown to be limited by spontaneous Raman scatter

  12. Diffusion of Ag ions under random potential barriers in silver-containing chalcogenide glasses

    Czech Academy of Sciences Publication Activity Database

    Stehlík, Štěpán; Shimakawa, K.; Wágner, T.; Frumar, M.

    2012-01-01

    Roč. 45, č. 20 (2012), s. 1-5. ISSN 0022-3727 Institutional research plan: CEZ:AV0Z10100521 Keywords : Ag ion diffusion * chalcogenide glass * Nyquist plots Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.528, year: 2012 http://iopscience.iop.org/0022-3727/45/20/205304/

  13. Low-Temperature Growth of Two-Dimensional Layered Chalcogenide Crystals on Liquid.

    Science.gov (United States)

    Zhou, Yubing; Deng, Bing; Zhou, Yu; Ren, Xibiao; Yin, Jianbo; Jin, Chuanhong; Liu, Zhongfan; Peng, Hailin

    2016-03-01

    The growth of high-quality two-dimensional (2D) layered chalcogenide crystals is highly important for practical applications in future electronics, optoelectronics, and photonics. Current route for the synthesis of 2D chalcogenide crystals by vapor deposition method mainly involves an energy intensive high-temperature growth process on solid substrates, often suffering from inhomogeneous nucleation density and grain size distribution. Here, we first demonstrate a facile vapor-phase synthesis of large-area high-quality 2D layered chalcogenide crystals on liquid metal surface with relatively low surface energy at a growth temperature as low as ∼100 °C. Uniform and large-domain-sized 2D crystals of GaSe and GaxIn1-xSe were grown on liquid metal surface even supported on a polyimide film. As-grown 2D GaSe crystals have been fabricated to flexible photodetectors, showing high photoresponse and excellent flexibility. Our strategy of energy-sustainable low-temperature growth on liquid metal surface may open a route to the synthesis of high-quality 2D crystals of Ga-, In-, Bi-, Hg-, Pb-, or Sn-based chalcogenides and halides. PMID:26913671

  14. Native metastability in chalcogenide glasses described within configuration-coordinate model

    International Nuclear Information System (INIS)

    It was created configuration-coordinate model for describing of native metastability in chalcogenide glasses. It was shown that potential should be at least triple-well. System of differential equations for describing transitions between the atomic states was made and solved within present configuration-coordinate model

  15. Native metastability in chalcogenide glasses described within configuration-coordinate model

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, M [Institute of Materials of Scientific Research Company ' Carat' , 202, Stryjska str., Lviv (Ukraine); Vakiv, M [Institute of Materials of Scientific Research Company ' Carat' , 202, Stryjska str., Lviv (Ukraine)

    2007-08-15

    It was created configuration-coordinate model for describing of native metastability in chalcogenide glasses. It was shown that potential should be at least triple-well. System of differential equations for describing transitions between the atomic states was made and solved within present configuration-coordinate model.

  16. Positron lifetime study of native vacancy-like defects in chalcogenide glasses

    International Nuclear Information System (INIS)

    Modified model for positron annihilation in vitreous chalcogenide semiconductors is developed to explain a number of previously obtained results on positron lifetime measurements in glassy As-Ge-S of stoichiometric As2S3-GeS2 and non-stoichiometric As2S3-Ge2S3 cut-sections

  17. Ag - conducting chalcogenide glasses, their properties important for potential application as conductive - bridge - memory materials

    Czech Academy of Sciences Publication Activity Database

    Wágner, T.; Stehlík, Š.; Bartoš, M.; Válková, S.; Voleská, I.; Kolář, J.; Zima, Vítězslav; Akola, J.; Jones, R. O.; Frumar, M.

    Nara: Japan Society of the Promotion of Science "Amorphous and Nanocrystalline Materials, 147 Committee", 2011. s. 187. [International Conference on Amorphous and Nanocrystalline Semiconductors /24./ - ICANS 24. 21.08.2011-26.08.2011, Nara] Institutional research plan: CEZ:AV0Z40500505 Keywords : chalcogenide glasses * conductivity * impedance Subject RIV: CA - Inorganic Chemistry

  18. Continuous wave four-wave mixing at 2 micron in Chalcogenide microstructured fiber

    OpenAIRE

    Grassani, Davide; Xing, Sida; Kharitonov, Svyatoslav; Billat, Adrien; Cordette, Steevy Joyce; Vedadi, Armand; Brès, Camille

    2015-01-01

    We present the first demonstration of continuous-wave four-wave mixing at 2μm in short chalcogenide microstructured fiber. Idlers over approximately 15nm on anti-Stokes side of the pump were measured for a coupled pump power of 94mW.

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

    Science.gov (United States)

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

    2016-05-01

    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.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. Electronic supplementary information (ESI) available: The synthetic procedure, facilities information, EDX patterns and UV-Vis data. See DOI: 10.1039/c6nr02525k

  20. THz waveguides, devices and hybrid polymer-chalcogenide photonic crystal fibers

    DEFF Research Database (Denmark)

    Bao, Hualong; Markos, Christos; Nielsen, Kristian; Rasmussen, Henrik K.; Jepsen, Peter Uhd; Bang, Ole

    In this contribution, we review our recent activities in the design, fabrication and characterization of polymer THz waveguides. Besides the THz waveguides, we finally will also briefly show some of our initial results on a novel hybrid polymer photonic crystal fiber with integrated chalcogenide ...

  1. Crystalline, Glassy and Amorphous Chalcogenides, High-Tech Materials with Many Applications

    Czech Academy of Sciences Publication Activity Database

    Frumar, M.; Wágner, T.; Němec, P.; Frumarová, Božena; Přikryl, J.; Kohoutek, T.; Orava, J.; Gutwirth, J.

    Pardubice: University of Pardubice, 2009. s. 8-8. [NIMS - University of Pardubice Workshop on Materials Science. 20.04.2009-20.04.2009, Pardubice] R&D Projects: GA ČR GA203/09/0827 Institutional research plan: CEZ:AV0Z40500505 Keywords : chalcogenides * electronics Subject RIV: CA - Inorganic Chemistry

  2. Modeling of enhancement of nonlinearity in oxide and chalcogenide glasses by introduction of nanometals

    Energy Technology Data Exchange (ETDEWEB)

    Zakery, A. [Department of Physics, College of Science, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of)]. E-mail: zakeri@physics.susc.ac.ir; Shahmirzaee, H. [Department of Physics, College of Science, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of)

    2007-02-12

    In this Letter we extended T-matrix to calculate the nonlinear susceptibilities of a composite nonlinear host and guest medium, and then applied this model to calculate the nonlinear susceptibilities of oxide and chalcogenide glasses by introduction of nanometals. The results of the model is in good agreement with experimental ones.

  3. Modeling of enhancement of nonlinearity in oxide and chalcogenide glasses by introduction of nanometals

    International Nuclear Information System (INIS)

    In this Letter we extended T-matrix to calculate the nonlinear susceptibilities of a composite nonlinear host and guest medium, and then applied this model to calculate the nonlinear susceptibilities of oxide and chalcogenide glasses by introduction of nanometals. The results of the model is in good agreement with experimental ones

  4. Modeling of enhancement of nonlinearity in oxide and chalcogenide glasses by introduction of nanometals

    Science.gov (United States)

    Zakery, A.; Shahmirzaee, H.

    2007-02-01

    In this Letter we extended T-matrix to calculate the nonlinear susceptibilities of a composite nonlinear host and guest medium, and then applied this model to calculate the nonlinear susceptibilities of oxide and chalcogenide glasses by introduction of nanometals. The results of the model is in good agreement with experimental ones.

  5. Iron-catalyzed coupling reactions of vinylic chalcogenides with Grignard reagents

    International Nuclear Information System (INIS)

    A general new method for the cross-coupling reaction between vinylic selenides and tellurides and Grignard reagents catalyzed by Fe(acac)3 at room temperature is described. This reaction proceeded with retention of configuration, providing the respective alkenes in good to excellent yields. This method is also efficient for the coupling reaction of divinyl chalcogenides with Grignard reagents. (author)

  6. Iron-catalyzed coupling reactions of vinylic chalcogenides with Grignard reagents

    Energy Technology Data Exchange (ETDEWEB)

    Silveira, Claudio C.; Mendes, Samuel R.; Wolf, Lucas, E-mail: silveira@quimica.ufsm.b [Universidade Federal de Santa Maria (UFSM), RS (Brazil). Centro de Tecnologia. Dept. de Quimica

    2010-07-01

    A general new method for the cross-coupling reaction between vinylic selenides and tellurides and Grignard reagents catalyzed by Fe(acac){sub 3} at room temperature is described. This reaction proceeded with retention of configuration, providing the respective alkenes in good to excellent yields. This method is also efficient for the coupling reaction of divinyl chalcogenides with Grignard reagents. (author)

  7. Low-temperature photoluminescence in chalcogenide glasses doped with rare-earth ions

    Czech Academy of Sciences Publication Activity Database

    Kostka, Petr; Zavadil, Jiří; Iovu, M.S.; Ivanova, Z. G.; Furniss, D.; Seddon, A.B.

    2015-01-01

    Roč. 648, NOV 5 (2015), s. 237-243. ISSN 0925-8388 R&D Projects: GA ČR GAP106/12/2384 Institutional support: RVO:67985891 ; RVO:67985882 Keywords : chalcogenide glasses * rare earth ions * low-temperature photoluminescence * optical transmission Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 2.999, year: 2014

  8. Laser annealing and defect study of chalcogenide photovoltaic materials

    Science.gov (United States)

    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

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

    Science.gov (United States)

    Liu, Lai; Cheng, Tonglei; Nagasaka, Kenshiro; Tong, Hoang Tuan; Suzuki, Takenobu; Ohishi, Yasutake

    2016-02-01

    We report the coherent mid-infrared supercontinuum generation in an all-solid chalcogenide microstructured fiber with all-normal dispersion. The chalcogenide microstructured fiber is four-hole structure with core material of AsSe2 and air holes are replaced by As2S5 glass rods. Coherent mid-infrared supercontinuum light is generated in a 2-cm-long chalcogenide microstructured fiber pumped by a 2.7 μm laser. The simulated and experimental results have a good match and the coherence property of supercontinuum light in the chalcogenide microstructured fiber has been studied by using the complex degree of coherence theory. Coherent mid-infrared supercontinuum generation is extended to 3.3 μm in this work.

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

    Science.gov (United States)

    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.

  11. Pulsed laser deposited amorphous chalcogenide and alumino-silicate thin films and their multilayered structures for photonic applications

    International Nuclear Information System (INIS)

    Amorphous chalcogenide and alumino-silicate thin films were fabricated by the pulsed laser deposition technique. Prepared films were characterized in terms of their morphology, chemical composition, and optical properties. Multilayered thin film stacks for reflectors and vertical microcavities were designed for telecommunication wavelength and the window of atmosphere transparency (band II) at 1.54 μm and 4.65 μm, respectively. Bearing in mind the benefit coming from the opportunity of an efficient wavelength tuning or, conversely, to stabilize the photoinduced effects in chalcogenide films as well as to improve their mechanical properties and/or their chemical durability, several pairs of materials from pure chalcogenide layers to chalcogenide/oxide layers were investigated. Different layer stacks were fabricated in order to check the compatibility between dissimilar materials which can have a strong influence on the interface roughness, adhesion, density, and homogeneity, for instance. Three different reflector designs were formulated and tested including all-chalcogenide layers (As40Se60/Ge25Sb5S70) and mixed chalcogenide-oxide layers (As40Se60/alumino-silicate and Ga10Ge15Te75/alumino-silicate). Prepared multilayers showed good compatibility between different material pairs deposited by laser ablation despite the diversity of chemical compositions. As40Se60/alumino-silicate reflector showed the best parameters; its stop band (R > 97% at 8° off-normal incidence) has a bandwidth of ∼ 100 nm and it is centered at 1490 nm. The quality of the different mirrors developed was good enough to try to obtain a microcavity structure for the 1.5 μm telecommunication wavelength made of chalcogenide layers. The microcavity structure consists of Ga5Ge20Sb10S65 (doped with 5000 ppm of Er3+) spacer surrounded by two 10-layer As40Se60/Ge25Sb5S70 reflectors. Scanning and transmission electron microscopies showed a good periodicity, great adherence and smooth interfaces

  12. Photonic bandgap amorphous chalcogenide thin films with multilayered structure grown by pulsed laser deposition method

    Science.gov (United States)

    Zhang, Shao-qian; Němec, Petre; Nazabal, Virginie; Jin, Yu-qi

    2016-05-01

    Amorphous chalcogenide thin films were fabricated by the pulsed laser deposition technique. Thereafter, the stacks of multilayered thin films for reflectors and microcavity were designed for telecommunication wavelength. The prepared multilayered thin films for reflectors show good compatibility. The microcavity structure consists of Ge25Ga5Sb10S65 (doped with Er3+) spacer layer surrounded by two 5-layer As40Se60/Ge25Sb5S70 reflectors. Scanning/transmission electron microscopy results show good periodicity, great adherence and smooth interfaces between the alternating dielectric layers, which confirms a suitable compatibility between different materials. The results demonstrate that the chalcogenides can be used for preparing vertical Bragg reflectors and microcavity with high quality.

  13. Recording of polarization holograms in a liquid crystal cell with a photosensitive chalcogenide orientation layer [Invited].

    Science.gov (United States)

    Sheremet, Nina; Kurioz, Yuriy; Slyusarenko, Kostyantyn; Trunov, Michael; Reznikov, Yuriy

    2013-08-01

    Polarization gratings have been recorded in a combined liquid crystal (LC) cell made of a substrate covered with a photosensitive chalcogenide orientation layer and a reference substrate covered with a rubbed polyimide film. The gratings are formed due to the spatially modulated light-induced easy orientation axis on the chalcogenide surface recorded by two beams with opposite circular polarizations. The gratings are permanent, but they can be erased by one of the recording beams and re-recorded. The diffraction intensity of the circularly polarized light is achromatic and does not depend on the birefringence of the LC. The diffraction efficiency of the grating is of the order of a few percents. Application of an ac field causes a strong increase of the diffraction efficiency up to 45%. PMID:23913086

  14. Prediction of free-volume-type correlations in glassy chalcogenides from positron annihilation lifetime measurements

    International Nuclear Information System (INIS)

    Highlights: • Decisive role of specific chemical environment in free-volume correlations in glass. • Realistic free volumes in As–S/Se glass are defined by newly modified τ2-R formula. • Overestimated void sizes in chalcogenide glass as compared with molecular polymers. - Abstract: A newly modified correlation equation between defect-related positron lifetime determined within two-state trapping model and radius of corresponding free-volume-type defects was proposed to describe compositional variations in atomic-deficient structure of covalent-bonded chalcogenides like binary As–S/Se glasses. Specific chemical environment of free-volume voids around neighboring network-forming polyhedrons was shown to play a decisive role in this correlation, leading to systematically enhanced volumes in comparison with typical molecular substrates, such as polymers

  15. Prediction of free-volume-type correlations in glassy chalcogenides from positron annihilation lifetime measurements

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O., E-mail: shpotyuk@novas.lviv.ua [Institute of Materials of SRC “Carat”, 212 Stryjska Str., Lviv 79031 (Ukraine); Institute of Physics of Jan Dlugosz University, 13/15 al. Armii Krajowej, Czestcochowa 42200 (Poland); Ingram, A. [Opole University of Technology, 75 Ozimska Str., Opole 45370 (Poland); Shpotyuk, M. [Institute of Materials of SRC “Carat”, 212 Stryjska Str., Lviv 79031 (Ukraine); Lviv Polytechnic National University, 12 Bandery Str., Lviv 79013 (Ukraine); Filipecki, J. [Institute of Physics of Jan Dlugosz University, 13/15 al. Armii Krajowej, Czestcochowa 42200 (Poland)

    2014-11-01

    Highlights: • Decisive role of specific chemical environment in free-volume correlations in glass. • Realistic free volumes in As–S/Se glass are defined by newly modified τ{sub 2}-R formula. • Overestimated void sizes in chalcogenide glass as compared with molecular polymers. - Abstract: A newly modified correlation equation between defect-related positron lifetime determined within two-state trapping model and radius of corresponding free-volume-type defects was proposed to describe compositional variations in atomic-deficient structure of covalent-bonded chalcogenides like binary As–S/Se glasses. Specific chemical environment of free-volume voids around neighboring network-forming polyhedrons was shown to play a decisive role in this correlation, leading to systematically enhanced volumes in comparison with typical molecular substrates, such as polymers.

  16. Solution processed chalcogenide films and micro-patterns via self-assembly

    Science.gov (United States)

    Singh, Radhakant; Sachan, Priyanka; Dwivedi, Prabhat K.; Sharma, Ashutosh

    2016-05-01

    Chalcogenide (ChG) are the choice materials for IR applications due to their high refractive index, mid IR transparency and high nonlinear optical properties. In this work, we study the characteristics of solution processed Chalcogenide films, As2S3 prepared by various amine solvents, for possible pattern fabrications. Since solution processed ChG films tend to contain solvent related defects, it is important to optimize the process parameters to create defect free films, structurally similar to bulk ChG. We have studied the physical integrity and morphology of solution processed ChG films as a function of annealing conditions and film thickness. Optical and morphological characterizations of these films are carried out in order to fabricate defect free, optically useful micro-structures.

  17. Low-power Mid-IR Supercontinuum and Rogue Wave Generation in Chalcogenide Waveguides

    CERN Document Server

    Hernandez, Santiago M; Bonetti, Juan; Grosz, Diego F

    2016-01-01

    We present numerical results of supercontinuum (SC) generation in the mid-IR spectral region, specifically addressing the molecular fingerprint window ranging from 2.5 to 25 um. By solving the Generalized Nonlinear Schr\\"odinger Equation (GNLSE) in a chalcogenide waveguide, we demonstrate low-power SC generation beyond 10 um from a pump at 5 um. Further, we investigate the short-pulse and CW regimes, and show that a simple linear dispersion profile, applicable to a broad range of chalcogenide media, is sufficient to account for the broad SC generation, and yield rich pulse dynamics leading to the frequent occurrence of rogue wave events. Results are encouraging as they point to the feasibility of producing bright and coherent light, by means of single low-power tabletop laser pumping schemes, in a spectral region that finds applications in such diverse areas as molecular spectroscopy, metrology and tomography, among others, and that is not easily addressable with other light sources

  18. All chalcogenide Raman parametric Laser, Wavelength Converter and Amplifier in a Single Microwire

    CERN Document Server

    Ahmad, Raja

    2013-01-01

    Compact, power efficient and fiber compatible lasers, wavelength converters and amplifiers are vital ingredients for the future fiber optic systems and networks. Nonlinear optical effects, like Raman scattering and parametric four wave mixing, offer a way to realize such devices. Here we use a single chalcogenide microwire to realize a device that provides the functions of a Stokes Raman parametric laser, a four wave mixing anti Stokes wavelength converter, and an ultra broadband Stokes/anti Stokes Raman amplifier or supercontinuum generator. The device operation relies on ultrahigh Raman and Kerr gain (upto five orders of magnitude larger than in silica fibers), precisely engineered chromatic dispersion and high photosensitivity of the chalcogenide microwire. The Raman parametric laser operates at a record low threshold average (peak) pump power of 52 \\muW (207 mW) and a slope efficiency of >2%. A powerful anti Stokes signal is generated via the nonlinear four wave mixing process. As amplifier or the broadba...

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

    International Nuclear Information System (INIS)

    The electrical resistivity curves for binary phase compounds of p-type lead chalcogenide (PbTe)(0.9−x)(PbSe)0.1(PbS)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

  20. Gamma radiation induced effects in floppy and rigid Ge-containing chalcogenide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Ailavajhala, Mahesh S.; Mitkova, Maria [Department of Electrical Engineering, Boise State University, 1910 University Dr. Boise, Idaho 83725-2075 (United States); Gonzalez-Velo, Yago; Barnaby, Hugh; Kozicki, Michael N.; Holbert, Keith [School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287-9309 (United States); Poweleit, Christian [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); Butt, Darryl P. [Department of Material Science and Engineering, Boise State University, 1910 University Dr. Boise, Idaho 83725-2090 (United States)

    2014-01-28

    We explore the radiation induced effects in thin films from the Ge-Se to Ge-Te systems accompanied with silver radiation induced diffusion within these films, emphasizing two distinctive compositional representatives from both systems containing a high concentration of chalcogen or high concentration of Ge. The studies are conducted on blanket chalcogenide films or on device structures containing also a silver source. Data about the electrical conductivity as a function of the radiation dose were collected and discussed based on material characterization analysis. Raman Spectroscopy, X-ray Diffraction Spectroscopy, and Energy Dispersive X-ray Spectroscopy provided us with data about the structure, structural changes occurring as a result of radiation, molecular formations after Ag diffusion into the chalcogenide films, Ag lateral diffusion as a function of radiation and the level of oxidation of the studied films. Analysis of the electrical testing suggests application possibilities of the studied devices for radiation sensing for various conditions.

  1. Magnetic and electronic properties of NiAs-type chromium chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Vadkhiya, L.; Dashora, Alpa [Department of Physics, M. L. Sukhadia University, Udaipur 313002, Rajasthan (India); Bhayani, M.K.; Jani, A.R. [Department of Physics, Sardar Patel University, Vallabh Vidhyanagar 388120, Gujarat (India); Ahuja, B.L., E-mail: blahuja@yahoo.co [Department of Physics, M. L. Sukhadia University, Udaipur 313002, Rajasthan (India)

    2010-10-15

    We have computed spin-dependent energy bands, spin moments and density of states of NiAs-type CrX (X=S, Se and Te) chalcogenides using linear combination of atomic orbitals method within density functional theory as well as full potential augmented plane wave method. In addition, magnetic properties have also been computed using spin polarized relativistic Korringa-Kohn-Rostoker method. We have also obtained the first ever theoretical electron momentum densities of CrX compounds considering linear combination of atomic orbitals and compared the results with the isotropic Compton profiles measured using 20 Ci {sup 137}Cs Compton spectrometer. The Fermi surface topology and magnetic properties are discussed in terms of majority and minority energy bands and density of states. In addition, to highlight the role of Cr (3d) electrons in such type of chalcogenides, we have also reported the magnetic Compton profile of CrTe using the Korringa-Kohn-Rostoker method.

  2. Updated results on prototype chalcogenide fibers for 10-um wavefront spatial filtering

    OpenAIRE

    Borde, P.; Perrin, G.; Amy-Klein, A.; Daussy, C; Maze, G.

    2003-01-01

    The detection of terrestrial planets by Darwin/TPF missions will require extremely high quality wavefronts. Single-mode fibers have proven to be powerful beam cleaning components in the near-infrared, but are currently not available in the mid-infrared where they would be critically needed for Darwin/TPF. In this paper, we present updated measurements on the prototype chalcogenide fibers we are developing for the purpose of mid-infrared spatial filtering. We demonstrate the guiding property o...

  3. Radiation-induced defects in chalcogenide glasses characterized by combined optical spectroscopy, XPS and PALS methods

    International Nuclear Information System (INIS)

    Temperature-dependent optical absorption spectroscopy, high-resolution X-ray photoelectron spectroscopy and positron annihilation lifetimes spectroscopy are utilized to understand radiation-induced changes in Ge-Sb-S chalcogenide glasses. Theoretically predicted topological scheme of γ-induced coordination defect formation in stoichiometric Ge23.5Sb11.8S64.7 glass composition is supported by these measurements. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Positron lifetime study of native vacancy-like defects in chalcogenide glasses

    Energy Technology Data Exchange (ETDEWEB)

    Filipecki, J.; Shpotyuk, O.I. E-mail: shpotyuk@novas.lviv.ua; Kozdras, A.; Kovalskiy, A.P

    2003-11-01

    Modified model for positron annihilation in vitreous chalcogenide semiconductors is developed to explain a number of previously obtained results on positron lifetime measurements in glassy As-Ge-S of stoichiometric As{sub 2}S{sub 3}-GeS{sub 2} and non-stoichiometric As{sub 2}S{sub 3}-Ge{sub 2}S{sub 3} cut-sections.

  5. Radiation-induced effects in chalcogenide glasses: Topological mechanisms and application

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O.I. E-mail: karat@ipm.lviv.ua

    2000-05-02

    Structural transformations in vitreous As{sub 2}S{sub 3}-based chalcogenide semiconducting glasses induced by {gamma}-irradiation have been considered on the basis of IR Fourier spectroscopy results as destruction-polymerization changes of the covalent chemical bonds, associated with specific coordination defects formation. The whole variety of these processes has been taken into account in order to construct the physically real variants of the radiation-induced structural changes.

  6. Radiation-induced effects in chalcogenide glasses: Topological mechanisms and application

    International Nuclear Information System (INIS)

    Structural transformations in vitreous As2S3-based chalcogenide semiconducting glasses induced by γ-irradiation have been considered on the basis of IR Fourier spectroscopy results as destruction-polymerization changes of the covalent chemical bonds, associated with specific coordination defects formation. The whole variety of these processes has been taken into account in order to construct the physically real variants of the radiation-induced structural changes

  7. Amorphous chalcogenide semiconductors for solid state dosimetric systems of high-energetic ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O. [Pedagogical University, Czestochowa (Poland)]|[Institute of Materials, Lvov (Ukraine)

    1997-12-31

    The application possibilities of amorphous chalcogenide semiconductors use as radiation-sensitive elements of high-energetic (E > 1 MeV) dosimetric systems are analysed. It is shown that investigated materials are characterized by more wide region of registered absorbed doses and low temperature threshold of radiation information bleaching in comparison with well-known analogies based on coloring oxide glasses. (author). 16 refs, 1 tab.

  8. Fabrication of tin sulphide and emerging transition metal di-chalcogenides by CVD

    OpenAIRE

    Huang, C.; Alzaidy, Ghadah A.; Aspiotis, Nikolaos; Weatherby, Ed C.; Wang, Shuncai; John C Walker; Jiang, Zheng; Hewak, Daniel

    2015-01-01

    Graphene, one of the most important two dimensional (2D) materials, has been attracting increasing interest and new applications in nano-scale electronic and photonic applications. The zero bandgap of graphene, however, has restricted its use in some optoelectronic applications. Recently, transition metal di-chalcogenides (TMDCs) such as MoS2, MoSe2, WS2 and WSe2 have become a noteworthy complimentary material to graphene sharing many of its properties [1]. They may however offer properties t...

  9. Trends in oxygen reduction and methanol activation on transition metal chalcogenides

    DEFF Research Database (Denmark)

    Tritsaris, Georgios; Nørskov, Jens Kehlet; Rossmeisl, Jan

    2011-01-01

    We use density functional theory calculations to study the oxygen reduction reaction and methanol activation on selenium and sulfur-containing transition metal surfaces. With ruthenium selenium as a starting point, we study the effect of the chalcogen on the activity, selectivity and stability of...... the catalyst. Ruthenium surfaces with moderate content of selenium are calculated active for the oxygen reduction reaction, and insensitive to methanol. A significant upper limit for the activity of transition metal chalcogenides is estimated....

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

    Energy Technology Data Exchange (ETDEWEB)

    Saad, Mahmoud M.; Abdallah, Tamer [Physics Department, Faculty of Science, Ain Shams University, Abbassia, Cairo (Egypt); Easawi, Khalid; Negm, Sohair [Department of Physics and Mathematics, Faculty of Engineering (Shoubra), Benha University (Egypt); Talaat, Hassan, E-mail: hassantalaat@hotmail.com [Physics Department, Faculty of Science, Ain Shams University, Abbassia, Cairo (Egypt)

    2015-05-15

    Graphical abstract: - Highlights: • Comparing band gaps values obtained optically with STS. • Comparing direct imaging with calculated dimensions. • STS determination of the interfacial band bending of metal/chalcogenide. - Abstract: 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.

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

    International Nuclear Information System (INIS)

    Highlights: • Study of thin film chalcogenide glasses under gamma radiation and a proposed radiation sensor design. • Structural changes were observed at various radiation doses. • Formation of Ag2Se in Se depleted glasses with sufficient radiation dose. • In conventional semiconductor chip environment, the proposed sensor has a linear current vs. dose behavior up to 600 J/cm2. - Abstract: 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

  12. Lead Chalcogenide Quantum Dots and Quantum Dot Hybrids for Optoelectronic Devices

    OpenAIRE

    Schornbaum, Julia

    2015-01-01

    Semiconductor quantum dots (QDs) exhibit remarkable properties, which include a size-tunable band gap and narrow emission bands. They are also suitable for large-area and low-cost fabrication, due to their solution-processability. Consequently, QDs are very promising for future applications in printable optoelectronic devices. Near-infrared (NIR) active lead chalcogenide QDs hold an enormous potential, as they exhibit optical properties in a wavelength regime, where efficient photoactive mate...

  13. ZnO and copper indium chalcogenide heterojunctions prepared by inexpensive methods

    Energy Technology Data Exchange (ETDEWEB)

    Berruet, M., E-mail: berruetm@gmail.com [División Electroquímica y Corrosión, Facultad de Ingeniería, INTEMA, CONICET, Universidad Nacional de Mar del Plata, Juan B. Justo 4302, B7608FDQ Mar del Plata (Argentina); Di Iorio, Y. [División Electroquímica y Corrosión, Facultad de Ingeniería, INTEMA, CONICET, Universidad Nacional de Mar del Plata, Juan B. Justo 4302, B7608FDQ Mar del Plata (Argentina); Troviano, M. [Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas (PROBIEN, CONICET-UNCo), Buenos Aires 1400, Q8300IBX Neuquén (Argentina); Vázquez, M. [División Electroquímica y Corrosión, Facultad de Ingeniería, INTEMA, CONICET, Universidad Nacional de Mar del Plata, Juan B. Justo 4302, B7608FDQ Mar del Plata (Argentina)

    2014-12-15

    Solution-based techniques were used to prepare ZnO/CuIn(Se, S){sub 2} heterojunctions that serve as solar cell prototypes. A duplex layer of ZnO (compact + porous) was electrodeposited. Chalcogenide thin films were deposited using successive ionic layer adsorption and reaction method (SILAR). By subsequent thermal treatments in two different atmospheres, CuInSe{sub 2} (CISe) and CuInSe{sub 2−x}S{sub x} (CISeS) were obtained. The composition and morphology of the annealed films were characterized by GXRD, micro-Raman spectroscopy and SEM. Devices prepared with CISe and CISeS show a clear photo-response. The introduction of a buffer layer of TiO{sub 2} into the ZnO/chalcogenide interface was necessary to detect photocurrent. The presence of CISeS improves the response of the cell, with higher values of short circuit current density, open circuit potential and fill factor. These promising results show that it is possible to prepare photovoltaic heterojunctions by depositing chalcogenides onto porous ZnO substrates using low-cost solution-based techniques. - Highlights: • Heterojunctions that serve as solar cell prototypes were prepared using solution-based techniques. • The devices comprised a double layer of ZnO and CuInSe{sub 2} or CuInSe{sub 0.4}S{sub 1.6}. • A TiO{sub 2} buffer layer in the ZnO/chalcogenide interface is necessary to detect photocurrent. • The incorporation of S improved the response of the photovoltaic heterojunction.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Determination of the oxidation state and coordination of a vanadium doped chalcogenide glass

    OpenAIRE

    Hughes, MA; Curry, RJ; Hewak, DW

    2011-01-01

    Vanadium doped chalcogenide glass has potential as an active gain medium, particularly at telecommunications wavelengths. This dopant has three spin allowed absorption transitions at 1100, 737 and 578 nm, and a spin forbidden absorption transition at 1000 nm. X-ray photo electron spectroscopy indicated the presence of vanadium in a range of oxidation states from V+ to V5+. Excitation of each absorption band resulted in the same characteristic emission spectrum and lifetime, indicating that on...

  16. Modeling of Mid-IR Amplifier Based on an Erbium-Doped Chalcogenide Microsphere

    OpenAIRE

    P. Bia; Di Tommaso, A; De Sario, M.

    2012-01-01

    An optical amplifier based on a tapered fiber and an Er3+-doped chalcogenide microsphere is designed and optimized. A dedicated 3D numerical model, which exploits the coupled mode theory and the rate equations, is used. The main transitions among the erbium energy levels, the amplified spontaneous emission, and the most important secondary transitions pertaining to the ion-ion interactions have been considered. Both the pump and signal beams are efficiently injected and obtained by a suitable...

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

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Comparing band gaps values obtained optically with STS. • Comparing direct imaging with calculated dimensions. • STS determination of the interfacial band bending of metal/chalcogenide. - Abstract: 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

  18. Functionalization of Amorphous Chalcogenide and Titanium Oxide Layers by Gold Nanoparticles

    OpenAIRE

    Kökényesi Sándor (1946-) (fizikus); Biri Sándor; Hegedűs Csaba (1953-) (fogszakorvos); Csarnovics István (1986-) (fizikus); Csik Attila

    2014-01-01

    The technology problems of fabricating different, nanometers sized gold particles in the layered composites like light-sensitive chalcogenide glass/gold nanoparticles/transparent substrate or titanium/titanium oxide/gold nanoparticles were investigated in our work. Combination of ion implantation, plasma deposition with annealing processes results physical routes for creation of gold nanoparticles in the mentioned structures, which possess plasmon effects. These functionalized structures are ...

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

    Energy Technology Data Exchange (ETDEWEB)

    Ailavajhala, M.S., E-mail: m.ailavajhala@gmail.com [Department of Electrical and Computer Engineering, Boise State University, Boise, ID 83725 (United States); Gonzalez-Velo, Y. [School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, AZ 85287-5706 (United States); Poweleit, C.D. [Department of Physics, Arizona State University, Tempe, AZ 85287-5706 (United States); Barnaby, H.J.; Kozicki, M.N. [School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, AZ 85287-5706 (United States); Butt, D.P. [Department of Materials Science and Engineering, Boise State University, Boise, ID 83725 (United States); Mitkova, M., E-mail: maheshailavajhala@u.boisestate.edu [Department of Electrical and Computer Engineering, Boise State University, Boise, ID 83725 (United States)

    2014-03-01

    Highlights: • Study of thin film chalcogenide glasses under gamma radiation and a proposed radiation sensor design. • Structural changes were observed at various radiation doses. • Formation of Ag{sub 2}Se in Se depleted glasses with sufficient radiation dose. • In conventional semiconductor chip environment, the proposed sensor has a linear current vs. dose behavior up to 600 J/cm{sup 2}. - Abstract: Data about gamma radiation induced effects in Ge{sub 40}Se{sub 60} 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 Ge{sub 40}Se{sub 60} 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 Ag{sub 2}Se 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.

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

    Science.gov (United States)

    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.

  1. Activity-Dependent Synaptic Plasticity of a Chalcogenide Electronic Synapse for Neuromorphic Systems

    OpenAIRE

    Yi Li; Yingpeng Zhong; Jinjian Zhang; Lei Xu; Qing Wang; Huajun Sun; Hao Tong; Xiaoming Cheng; Xiangshui Miao

    2014-01-01

    Nanoscale inorganic electronic synapses or synaptic devices, which are capable of emulating the functions of biological synapses of brain neuronal systems, are regarded as the basic building blocks for beyond-Von Neumann computing architecture, combining information storage and processing. Here, we demonstrate a Ag/AgInSbTe/Ag structure for chalcogenide memristor-based electronic synapses. The memristive characteristics with reproducible gradual resistance tuning are utilised to mimic the act...

  2. Thermally stable low current consuming gallium and germanium chalcogenides for consumer and automotive memory applications

    OpenAIRE

    Hewak, D. W.; Huang, C. C.; Gholipour, B.; K Knight; Guerin, S.; Hayden, B.; Purdy, G

    2011-01-01

    The phase change technology behind rewritable optical disks and the latest generation of electronic memories has provided clear commercial and technological advances for the field of data storage, by virtue of the many well known attributes, in particular scaling, cycling endurance and speed, that chalcogenide materials offer. While the switching power and current consumption of established germanium antimony telluride based memory cells are a major factor in chip design in real world applica...

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

    Directory of Open Access Journals (Sweden)

    Patrick Houizot

    2014-09-01

    Full Text Available 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.

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

    Science.gov (United States)

    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

  5. Deposition of Ge23Sb7S70 chalcogenide glass films by electrospray

    International Nuclear Information System (INIS)

    Solution-based chalcogenide glass films, traditionally deposited by spin-coating, are attractive for their potential use in chip-based devices operating in the mid-infrared and for ease of nanostructure incorporation. To overcome limitations of spin-coating such as excessive material waste and difficulty for scale-up, this paper introduces electrospray as a film deposition technique for solution-based chalcogenide glasses. Electrospray is shown to produce Ge23Sb7S70 films with similar surface quality and optical properties as films deposited by spin-coating. The advantages of electrospray deposition for nanoparticle dispersion, scalable and continuous manufacturing with little material waste, and comparable film quality to spin-coating make electrospray a promising deposition method for practical applications of chalcogenide glass films. - Highlights: • Electrospray film deposition processing of Ge23Sb7S70 films was developed. • Traditional spin-coated films were also fabricated in parallel. • Optical properties and surface quality found to be similar between two approaches

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

    Science.gov (United States)

    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.

  7. Synthesis and characterization of single-source molecular precursors for the preparation of metal chalcogenides

    Indian Academy of Sciences (India)

    Vimal K Jain

    2006-11-01

    Metal chalcogenides constitute an important family of functional materials. Subtle changes in shape, size and phase of these materials result in variations in physical properties (e.g. electronic and optical), which can be exploited for various technological applications. Several strategies have evolved recently for controlling shape, size and phase of these materials. This work discusses design and synthesis of single-source molecular precursors for the preparation of metal chalcogenides both in bulk and nano-size regime. Precursors for palladium chalcogenides, indium sulphides and II-VI materials are presented. Synthesis of a variety of palladium(II)/platinum(II) complexes with internally functionalised chalcogenolate ligands, selenocarboxylates; gallium and indium dithiolate complexes and zinc/cadmium/mercury complexes with N,N'-dimethylaminoalkylselenolate ligands and their characterization by NMR and X-ray crystallography are also discussed. Data on thermal behaviour of a few representative complexes, [Pd(SeCOAr)2(PR3)2], [PdCl(E∩N)(PR3)], [InMe2(S∩S)], [In(S∩S)3] and [M(E(CH2)NMe2)2] (M = Zn, Cd, Hg; = 2 or 3) are presented.

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

    Science.gov (United States)

    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).

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

    Science.gov (United States)

    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

  10. Limiting of photo induced changes in amorphous chalcogenide/alumino-silicate nanomultilayers

    Energy Technology Data Exchange (ETDEWEB)

    Charnovych, S., E-mail: csari86@gmail.com [Department of Experimental Physics, University of Debrecen, Bem sq. 18/a, 4026 Debrecen (Hungary); Nemec, P. [Department of Graphic Arts and Photophysics, Faculty of Chemical Technology, University of Pardubice, Studentska 573, 53210 Pardubice (Czech Republic); Nazabal, V. [Equipe Verres et Ceramiques, UMR-CNRS 6226, Sciences Chimiques de Rennes (SCR), Universite de Rennes 1, 35042 Rennes Cedex (France); Csik, A. [Institute of Nuclear Research of Hungarian Academy of Sciences (ATOMKI), P.O. Box 51, H-4001 Debrecen (Hungary); Allix, M.; Matzen, G. [CEMHTI-CNRS, Site Haute Temperature, Orleans (France); Kokenyesi, S. [Department of Experimental Physics, University of Debrecen, Bem sq. 18/a, 4026 Debrecen (Hungary)

    2011-11-01

    Highlights: {yields} Amorphous chalcogenides were investigated in this work. {yields} Photo-induced effects were investigated in the created thin films. {yields} Limiting of photo induced changes in amorphous chalcogenide/alumino-silicate nanomultilayers have been studied. - Abstract: Photo induced changes in amorphous As{sub 20}Se{sub 80}/alumino-silicate nanomultilayers (NML) produced by pulsed laser deposition (PLD) method have been studied in this work. The aim was to investigate the photo induced optical and surface relief changes due to the band gap illumination under the size- and hard cover limited conditions. It was observed that the hard cover layer on the surface of the uniform film or alumino-silicate sub-layers in the NML structure influences the photo darkening and restricts surface relief formations in As{sub 20}Se{sub 80} film or in the related NML compared with this effect in a pure chalcogenide layer. The influence of hard layers is supposed to be connected with limiting the free volume formation at the initial stage of the transformation process, which in turn limits the atomic movement and so the surface relief formation.

  11. Limiting of photo induced changes in amorphous chalcogenide/alumino-silicate nanomultilayers

    International Nuclear Information System (INIS)

    Highlights: → Amorphous chalcogenides were investigated in this work. → Photo-induced effects were investigated in the created thin films. → Limiting of photo induced changes in amorphous chalcogenide/alumino-silicate nanomultilayers have been studied. - Abstract: Photo induced changes in amorphous As20Se80/alumino-silicate nanomultilayers (NML) produced by pulsed laser deposition (PLD) method have been studied in this work. The aim was to investigate the photo induced optical and surface relief changes due to the band gap illumination under the size- and hard cover limited conditions. It was observed that the hard cover layer on the surface of the uniform film or alumino-silicate sub-layers in the NML structure influences the photo darkening and restricts surface relief formations in As20Se80 film or in the related NML compared with this effect in a pure chalcogenide layer. The influence of hard layers is supposed to be connected with limiting the free volume formation at the initial stage of the transformation process, which in turn limits the atomic movement and so the surface relief formation.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  13. Non-oxido divanadium(IV) and divanadium(V) thiolate complexes with a new type of chalcogenide bridging motif.

    Science.gov (United States)

    Wu, Hong-Ming; Chang, Ya-Ho; Tsai, Yi-Fang; Hsu, Kuei-Fang; Lee, Gene-Hsiang; Hsu, Hua-Fen

    2015-03-14

    In our effort to study vanadium chalcogenide chemistry, we have synthesized and characterized a class of non-oxido divanadium(IV) and divanadium(V) complexes with chalcogenide and dichalcogenide as bridges. All structures consist of a similar divanadium motif, in which two metal centers are bridged by one μ-chalcogenide and one μ-η(2):η(2)-dichalcogenide, forming a V2(μ-E)(μ-η(2):η(2)-E2) (E = S or Se) core structure. These compounds are [V(IV)2(PS3)2(μ-Se2)(μ-Se)][PPh4]2 (1), [V(V)2(PS3'')2(μ-Se2)(μ-Se)] (2), [V(V)2(PS3'')2(μ-S2)(μ-S)] (3a) and [V(V)2(PS3)2(μ-S2)(μ-S)] (3b) ([PS3](3-) = P(C6H4-2-S)3 and [PS3''](3-) = P(C6H3-3-SiMe3-2-S)3). Compound 1 exhibits diamagnetic behavior, indicating strong antiferromagnetic coupling between two d(1) centers. Compounds 2 and 3a-b have the highest oxidation states for vanadium ions (+5/+5) among those reported divanadium chalcogenide clusters. The work demonstrates that high-valent divanadium chalcogenide clusters can be obtained with the activation of elemental chalcogens by low-valent vanadium ions. PMID:25645817

  14. Robust multimaterial tellurium-based chalcogenide glass fibers for mid-wave and long-wave infrared transmission.

    Science.gov (United States)

    Tao, Guangming; Shabahang, Soroush; Ren, He; Khalilzadeh-Rezaie, Farnood; Peale, Robert E; Yang, Zhiyong; Wang, Xunsi; Abouraddy, Ayman F

    2014-07-01

    We describe an approach for producing robust multimaterial chalcogenide glass fibers for mid-wave and long-wave mid-infrared transmission. By combining the traditional rod-in-tube process with multimaterial coextrusion, we prepare a hybrid glass-polymer preform that is drawn continuously into a robust step-index fiber with a built-in, thermally compatible polymer jacket. Using tellurium-based chalcogenides, the fibers have a transparency window covering the 3-12 μm spectral range, making them particularly attractive for delivering quantum cascade laser light and in space applications. PMID:24978794

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. Femtosecond multi-level phase switching in chalcogenide thin films for all-optical data and image processing

    OpenAIRE

    Wang, Q; Maddock, J; B. Mills; Craig, C; MacDonald, K. F.; Hewak, D.W.; Zheludev, N.I.

    2014-01-01

    We report on the non-volatile switching of amorphous chalcogenide glass thin films to the crystalline phase through a through a number of reproducible, discrete, optically distinguishable intermediate states, and on the re-amorphization of these films using femtosecond laser pulses. Potential applications lie in high-base (>binary) all-optical signal modulation, high-density data storage, image processing and non-Von Neuman computing. Chalcogenide phase-change media such as Ge2Sb2Te5 (GST) ar...

  17. High thermoelectric figure of merit nanostructured pnictogen chalcogenides by bottom-up synthesis and assembly

    Science.gov (United States)

    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 nanocomposites by mixing nanoplates of different materials (e.g., S-doped Sb2Te3 and S-doped Bi2Te3) and forming heterostructures of metals and chalcogenides. The thesis finally demonstrates the extendibility of the novel synthesis and assembly approach to tailor the thermoelectric properties of other non-traditional thermoelectric materials systems.

  18. A feasibility study of unconventional planar ligand spacers in chalcogenide nanocrystals.

    Science.gov (United States)

    Lukose, Binit; Clancy, Paulette

    2016-05-18

    The solar cell efficiency of chalcogenide nanocrystals (quantum dots) has been limited in the past by the insulation between neighboring quantum dots caused by intervening, often long-chain, aliphatic ligands. We have conducted a computationally based feasibility study to investigate the use of ultra-thin, planar, charge-conducting ligands as an alternative to traditional long passive ligands. Not only might these radically unconventional ligands decrease the mean distance between adjacent quantum dots, but, since they are charge-conducting, they have the potential to actively enhance charge migration. Our ab initio studies compare the binding energies, electronic energy gaps, and absorption characteristics for both conventional and unconventional ligands, such as phthalocyanines, porphyrins and coronene. This comparison identified these unconventional ligands with the exception of titanyl phthalocyanine, that bind to themselves more strongly than to the surface of the quantum dot, which is likely to be less desirable for enhancing charge transport. The distribution of finite energy levels of the bound system is sensitive to the ligand's binding site and the levels correspond to delocalized states. We also observed a trap state localized on a single Pb atom when a sulfur-containing phenyldithiocarbamate (PTC) ligand is attached to a slightly off-stoichiometric dot in a manner that the sulfur of the ligand completes stoichiometry of the bound system. Hence, this is indicative of the source of trap state when thio-based ligands are bound to chalcogenide nanocrystals. We also predict that titanyl phthalocyanine in a mix with chalcogenide dots of diameter ∼1.5 Å can form a donor-acceptor system. PMID:26918246

  19. Optical property tuning of bismuth chalcogenides using chemical intercalation (Presentation Recording)

    Science.gov (United States)

    Yao, Jie

    2015-10-01

    Two-dimensional (2D) materials with natural layer structures have been proven to provide extraordinary physical and chemical properties. Bismuth chalcogenides are examples of such two-dimensional materials. They are strongly bonded within layers and weak van der Waals interaction ties those layers together. Such naturally layered structure allows chemical intercalation of foreign atoms into the van der Waals gaps. Here, we show that by adding large number of copper atoms into van der Waals gaps of bismuth chalcogenides, we observed counter-intuitive enhancement of optical transparency together with improved electrical conductivity, which is on the contrary to most bulk materials in which doping reduces the light transmission. This surprising behavior is caused by substantial tuning of material optical property and nanophotonic anti-reflection effect unique to ultra-thin nanoplates. With the intercalation of copper atoms, large number of electrons have been added into the semiconducting material system and effectively lift the Fermi level of the resulting material to its conduction band, as proved by our densityfunctional- theory computations. Occupied lower states in the conduction band do not allow the optical excitation of electrons in the valence band to the bottom of the conduction band, leading to an effective widening of optical band gap. Optical transmission is further enhanced by constructive interference of reflected beams as bismuth chalcogenides have large permittivity than the environment. The synergy of these two effects in two-dimensional nanostructures can be exploited for various optoelectronic applications including transparent electrode. The reversible intercalation process allows potential dynamic tuning capability.

  20. Enhancing light emission efficiency without color change in post-transition metal chalcogenides

    Science.gov (United States)

    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

  1. Observation of nonlinear thermal optical dynamics in a chalcogenide nanobeam cavity

    CERN Document Server

    Sun, Yue; Choi, Duk-Yong; Sukhorukov, Andrey A

    2016-01-01

    We present a theoretical and experimental analysis of nonlinear thermo-optic effects in suspended chalcogenide glass nanobeam cavities. We measure the power dependent resonance peaks and characterise the dynamic nonlinear thermo-optic response of the cavity under modulated light input. Several distinct nonlinear characteristics are identified, including a modified spectral response containing periodic fringes, a critical wavelength jump and saturated time delay for modulation frequency faster than the thermal characteristic time. We reveal that the coupling to a parasitic Fabry-Perot cavity enables isolated thermal equilibrium states resulting in the discontinuous thermo-optic critical point.

  2. Theoretical Prediction of Topological Insulators in Thallium-based III-V-VI$_2$ Ternary Chalcogenides

    OpenAIRE

    Yan, Binghai; Liu, Chao-Xing; Zhang, Hai-Jun; Yam, Chi-Yung; Qi, Xiao-Liang; Frauenheim, Thomas; Zhang, Shou-Cheng

    2010-01-01

    We predict a new class of three dimensional topological insulators in thallium-based III-V-VI$_2$ ternary chalcogenides, including TlBiQ$_2$ and TlSbQ$_2$ (Q = Te, Se and S). These topological insulators have robust and simple surface states consisting of a single Dirac cone at the $\\Gamma$ point. The mechanism for topological insulating behavior is elucidated using both first principle calculations and effective field theory models. Remarkably, one topological insulator in this class, TlBiTe...

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

    International Nuclear Information System (INIS)

    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

  4. Chalcogenide glass Photonic Crystal Fiber with flattened dispersion and high nonlinearity at telecommunication wavelength

    OpenAIRE

    Revathi, S.; ABHIJITH CHANDRAN; Amir, A; SRINIVASA RAO INBATHINI

    2013-01-01

    A highly nonlinear photonic crystal fiber with eight ring octagonal structure is proposed. Chalcogenide glass of As2S3 is used as the material for this photonic crystal fiber structure. The finiteelementmethod with perfectly matched boundary layer is employed to analyze the guiding properties. Non linearity of 13,584.5 per W-km is obtained at 1.55 μm with reasonable flattened dispersion of -25ps/nm-km to -28 ps/nm-km. Confinement loss achieved is of the order of 10-6 dB/km. Large negative di...

  5. Photoinduced effects in amorphous semiconductor Ge(S, Se)2 chalcogenide films

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The blue shift of optical transmittance edges were observed in amorphous semiconductor Ge(S, Se)2 chalcogenide films with light illumination. The shift in well-annealed films could be recovered by annealing the films near the glass-transition temperature again. The photocrystallization was also observed in amorphous Ge(S,Se)2 films with light illumination by the transmitting electron microscope measurement. The photoinduced phenomina of the amorphous Ge(S,Se)2 films could be applied to designing some new kinds of optical storage materials.

  6. Charged defects in chalcogenide vitreous semiconductors studied with combined Raman scattering and PALS methods

    International Nuclear Information System (INIS)

    A combination of Raman scattering and positron annihilation lifetime spectroscopy (PALS) techniques to study charged defects in chalcogenide vitreous semiconductors (ChVSs) was applied for the first time in this study. In the case of Ge15.8As21S63.2 glass, it is found that the main radiation-induced switching of heteropolar Ge-S bonds into heteropolar As-S ones, previously detected by IR fast Fourier transform spectroscopy, can also be identified by Raman spectroscopy in the depolarized configuration. Results obtained by Raman scattering are in good agreement with PALS data for the investigated glass composition

  7. Structural modification of covalent-bonded networks: on some methodological resolutions for binary chalcogenide glasses

    International Nuclear Information System (INIS)

    New methodology to estimate efficiency of externally-induced structural modification in chalcogenide glasses is developed. This approach is grounded on the assumption that externally-induced structural modification is fully associated with destruction-polymerization transformations, which reveal themselves as local misbalances in covalent bond distribution, normal atomic coordination and intrinsic electrical fields. The input of each of these components into the total value of structural modification efficiency was probed for quasibinary (As2S3)100-x(Sb2S3)x ChG.

  8. Ageing effects in As10Se90 chalcogenide glasses induced by gamma-irradiation

    International Nuclear Information System (INIS)

    The peculiarities of gamma-induced (Co60source, 1.85 MGy absorbed dose) ageing phenomena in As10Se90 chalcogenide glasses are investigated for the first time. The analogy between the observed radiation-induced ageing and the thermally induced one in vitreous selenium is emphasized. Like to thermal treatment, gamma-irradiation leads to an increase in the glass transition temperature and the relaxation rate towards a thermodynamic equilibrium of supercooled liquid, the value of this increase being greater in the case of radiation influence

  9. Structural modification of covalent-bonded networks: on some methodological resolutions for binary chalcogenide glasses

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, M; Shpotyuk, Ya; Shpotyuk, O, E-mail: shpotyukmy@yahoo.com [Lviv Scientific Research Institute of Materials of SRC ' Carat' , 212, Stryjska str., Lviv, 79031 (Ukraine)

    2011-04-01

    New methodology to estimate efficiency of externally-induced structural modification in chalcogenide glasses is developed. This approach is grounded on the assumption that externally-induced structural modification is fully associated with destruction-polymerization transformations, which reveal themselves as local misbalances in covalent bond distribution, normal atomic coordination and intrinsic electrical fields. The input of each of these components into the total value of structural modification efficiency was probed for quasibinary (As{sub 2}S{sub 3}){sub 100-x}(Sb{sub 2}S{sub 3}){sub x} ChG.

  10. Radiation-induced defects formation in Bi-containing vitreous chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O.; Vakiv, M.; Balitska, V.; Kovalskiy, A. [Institute of Materials, Lvov (Ukraine)

    1997-12-01

    Processes of formation and annihilation of coordination defects in As{sub 2}Se{sub 3}Bi{sub y} and (As{sub 2}Se{sub 3})(Bi{sub 2}Se{sub 3}){sub y} amorphous chalcogenide semiconductors induced by influence of Co{sup 60} gamma-irradiation are investigated by photoelectric spectroscopy method. It is obtained that radiation-induced changes of photoelectrical properties on bioconcentration of As{sub 2}Se{sub 3}Bi{sub y} glasses are characterized by anomalous concentration dependence. The nature of this effect is associated with diamagnetic coordination defects formation. (author). 19 refs, 3 figs.

  11. Radiation-induced defects in chalcogenide glasses characterized by combined optical spectroscopy, XPS and PALS methods

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O. [Institute of Physics of Jan Dlugosz University, 13/15 al. Armii Krajowej, Czestochowa 42201 (Poland); Lehigh University, 5 East Packer Avenue, Bethlehem, PA 18015-3195 (United States); Lviv Institute of Materials of SRC ' ' Carat' ' , 202, Stryjska str., 79031 Lviv (Ukraine); Kovalskiy, A.; Jain, H. [Lehigh University, 5 East Packer Avenue, Bethlehem, PA 18015-3195 (United States); Golovchak, R. [Lehigh University, 5 East Packer Avenue, Bethlehem, PA 18015-3195 (United States); Lviv Institute of Materials of SRC ' ' Carat' ' , 202, Stryjska str., 79031 Lviv (Ukraine); Zurawska, A. [Opole University of Technology, 75, Ozimska str., Opole 45370 (Poland)

    2007-03-15

    Temperature-dependent optical absorption spectroscopy, high-resolution X-ray photoelectron spectroscopy and positron annihilation lifetimes spectroscopy are utilized to understand radiation-induced changes in Ge-Sb-S chalcogenide glasses. Theoretically predicted topological scheme of {gamma}-induced coordination defect formation in stoichiometric Ge{sub 23.5}Sb{sub 11.8}S{sub 64.7} glass composition is supported by these measurements. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Charged defects in chalcogenide vitreous semiconductors studied with combined Raman scattering and PALS methods

    Energy Technology Data Exchange (ETDEWEB)

    Kavetskyy, T.; Vakiv, M. [Lviv Institute of Materials of SRC ' Carat' , 202 Stryjska str., Lviv, UA-79031 (Ukraine); Shpotyuk, O. [Lviv Institute of Materials of SRC ' Carat' , 202 Stryjska str., Lviv, UA-79031 (Ukraine)], E-mail: shpotyuk@novas.lviv.ua

    2007-04-15

    A combination of Raman scattering and positron annihilation lifetime spectroscopy (PALS) techniques to study charged defects in chalcogenide vitreous semiconductors (ChVSs) was applied for the first time in this study. In the case of Ge{sub 15.8}As{sub 21}S{sub 63.2} glass, it is found that the main radiation-induced switching of heteropolar Ge-S bonds into heteropolar As-S ones, previously detected by IR fast Fourier transform spectroscopy, can also be identified by Raman spectroscopy in the depolarized configuration. Results obtained by Raman scattering are in good agreement with PALS data for the investigated glass composition.

  13. Application of positron annihilation lifetime technique for {gamma}-irradiation stresses study in chalcogenide vitreous semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O.; Golovchak, R.; Kovalskiy, A. [Scientific Research Company ' ' Carat' ' , Stryjska str. 20279031 Lviv (Ukraine); Filipecki, J.; Hyla, M. [Physics Institute, Pedagogical University, Al. Armii Krajowej 13/1542201 Czestochowa (Poland)

    2002-08-01

    The influence of {gamma}-irradiation on the positron annihilation lifetime spectra in chalcogenide vitreous semiconductors of As-Ge-S system has been analysed. The correlations between lifetime data, structural features and chemical compositions of glasses have been discussed. The observed lifetime components are connected with bulk positron annihilation and positron annihilation on various native and {gamma}-induced open volume defects. It is concluded that after {gamma}-irradiation of investigated materials the {gamma}-induced microvoids based on S{sub 1}{sup -}, As{sub 2}{sup -}, and Ge{sub 3}{sup -} coordination defects play the major role in positron annihilation processes. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  14. Synthesis, phase stability, structural and physical properties of 11-type iron chalcogenides

    OpenAIRE

    Rößler, Sahana; Koz, Cevriye; Wirth, Steffen; Schwarz, Ulrich

    2016-01-01

    This article reviews recent experimental investigations on two binary Fe-chalcogenides: FeSe and Fe$_{1+y}$Te. The main focus is on synthesis, single crystal growth, chemical composition, as well as on the effect of excess iron on structural, magnetic, and transport properties of these materials. The structurally simplest Fe-based superconductor Fe$_{1+x}$Se with a critical temperature $T_c \\approx$ 8.5 K undergoes a tetragonal to orthorhombic phase transition at a temperature $T_s \\approx$ 8...

  15. Reactive ion etching of tellurite and chalcogenide waveguides using hydrogen, methane, and argon

    International Nuclear Information System (INIS)

    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.

  16. Solution based approach for the fabrication of photonic devices in chalcogenide glasses

    Energy Technology Data Exchange (ETDEWEB)

    Prince,, E-mail: princevish2@gmail.com; Raman, Swati [Dept. Of Physics, Jamia Millia Islamia, New Delhi-110025 (India); Dwivedi, Prabhat K. [Center for Nanoscience, Indian Institute of Technology Kanpur, Kanpur-208016 (India); Zulfequar, M. [Dept. Of Physics, Jamia Millia Islamia, New Delhi-110025 (India); Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia, New Delhi-110025 (India); 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.

  17. Structural and Substructural Properties of the Zinc and Cadmium Chalcogenides Thin Films (a Review

    Directory of Open Access Journals (Sweden)

    C.J. Panchal

    2011-01-01

    Full Text Available In this paper, the structural properties of the zinc and cadmium chalcogenide thin films are considered. The influence of the structural defects such as grain boundaries, dislocations, native point defects, etc., on the optical and electrical properties of the thin films was studied. The methods of the II-VI thin films deposition are described. The influence on the sub-structural properties (phase compositions, texture, grain size, stacking faults concentration, micro deformation levels, and coherent domain size of the thin films grown by the close-spaced vacuum evaporation method was analyzed. The growth conditions of the thin films with optimized parameters have been determined.

  18. Photoinduced GRIN lens formation in chalcogenide Ge-As-S thin films

    Science.gov (United States)

    Palanjyan, K.; Vallée, R.; Galstian, T.

    2014-09-01

    We describe the photo induced formation of gradient index (GRIN) lenses in thin films of chalcogenide glass (ChG) of Ge25As30S45 composition. We examine the changes of thickness of these samples by DekTak profilometry, as well as the optical performance and wave front distortions of the obtained lenses by using a Shack Hartmann sensor. The GRIN formation is related to the photo induced shift of the band gap towards shorter wavelengths (so-called photo-bleaching effect). The corresponding photo-induced birefringence of this material is in the origin of anisotropic GRIN lenses formed [1].

  19. Power-efficient production of photon pairs in a tapered chalcogenide microwire

    CERN Document Server

    Meyer-Scott, Evan; Ahmad, Raja; Li, Lizhu; Rochette, Martin; Jennewein, Thomas

    2015-01-01

    Using tapered fibers of As2Se3 chalcogenide glass, we produce photon pairs at telecommunication wavelengths with pump power as low as 250 nW for a single pump, and 191 nW for the weak pump in a two-pump non-degenerate scheme. 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.

  20. Optical properties of chalcogenide glassy semiconductor Se95Te5 doped by samarium

    International Nuclear Information System (INIS)

    The optical width of forbidden band, refraction index and extinction index are defined by investigation of optical transmission spectrum of chalcogenide glassy semiconductor Se95Te5 doped by samarium Eo is oscillator energy connected with energy gap and Ed is dispersion energy characterizing the interband transition force are defined within the framework of one-oscillator model. The influence of samarium impurity on optical and dispersion parameters can be connected with peculiarity of impurity atom distribution, changes of chemical band and coordination number

  1. Octave-spanning infrared supercontinuum generation in robust chalcogenide nanotapers using picosecond pulses.

    Science.gov (United States)

    Shabahang, Soroush; Marquez, Michael P; Tao, Guangming; Piracha, Mohammad U; Nguyen, Dat; Delfyett, Peter J; Abouraddy, Ayman F

    2012-11-15

    We report on infrared supercontinuum generation extending over more than one octave of bandwidth, from 850 nm to 2.35 μm, produced in a single spatial mode from a robust, compact, composite chalcogenide glass nanotaper. A picosecond laser at 1.55 μm pumps a high-index-contrast, all-solid nanotaper that strongly confines the field to a 480 nm diameter core, while a thermally compatible built-in polymer jacket lends the nanotaper mechanical stability. PMID:23164864

  2. Thickness distribution of thin amorphous chalcogenide films prepared by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Pavlista, Martin; Hrdlicka, Martin; Prikryl, Jan [University of Pardubice, Research Centre Advanced Inorganic Materials, Faculty of Chemical Technology, Pardubice (Czech Republic); Nemec, Petr; Frumar, Miloslav [University of Pardubice, Research Centre Advanced Inorganic Materials, Faculty of Chemical Technology, Pardubice (Czech Republic); University of Pardubice, Department of General and Inorganic Chemistry, Faculty of Chemical Technology, Pardubice (Czech Republic)

    2008-11-15

    Amorphous chalcogenide thin films were prepared from As{sub 2}Se{sub 3}, As{sub 3}Se{sub 2} and InSe bulk glasses by pulsed laser deposition using a KrF excimer laser. Thickness profiles of the films were determined using variable angle spectroscopic ellipsometry. The influence of the laser beam scanning process during the deposition on the thickness distribution of the prepared thin films was evaluated and the corresponding equations suggested. The results were compared with experimental data. (orig.)

  3. Photoluminescence of some chalcogenide glasses doped with rare-earth ions

    Czech Academy of Sciences Publication Activity Database

    Iovu, M.; Lupan, E.; Zavadil, Jiří; Kostka, Petr; Ivanova, Z.; Seddon, A.; Furniss, D.

    Vol. 9258. Bellingham: SPIE-International Society of Optical Engineering, 2015 - (Cristea, I.; Vladescu, M.; Razvan, T.), s. 9258051-9258056 ISBN 978-1-62841-325-0. ISSN 0277-786X. [7th International Conference on Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies (ATOM-N). Constanta (RO), 21.08.2014-24.08.2014] R&D Projects: GA ČR GAP106/12/2384 Institutional support: RVO:67985882 ; RVO:67985891 Keywords : Chalcogenide glasses * Energy transfer mechanism * Photoluminescence Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering; JH - Ceramics, Fire-Resistant Materials and Glass (USMH-B)

  4. Inducing chalcogenide phase change with ultra-narrow carbon nanotube heaters

    Science.gov (United States)

    Xiong, Feng; Liao, Albert; Pop, Eric

    2009-12-01

    Carbon nanotube (CNT) heaters with sub-5 nm diameter induce highly localized phase change in Ge2Sb2Te5 (GST) chalcogenide. A significant reduction in resistance of test structures is measured as the GST near the CNT heater crystallizes. Effective GST heating occurs at currents as low as 25 μA, significantly lower than in conventional phase change memory with metal electrodes (0.1-0.5 mA). Atomic force microscopy reveals nucleation sites associated with phase change in GST around the CNT heater. Finite element simulations confirm electrical characteristics consistent with the experiments, and reveal the current and phase distribution in GST.

  5. Narrow spectral band monolithic lead chalcogenide on Si mid-IR photodetectors

    International Nuclear Information System (INIS)

    Resonant cavity-enhanced detectors (RCEDs) with a narrow linewidth and high peak quantum efficiency have been realized for the first time in the mid-IR range. The detectors are fabricated with epitaxial narrow gap lead chalcogenide layers grown epitaxially on Si-substrates. They consist of an epitaxial bottom distributed Bragg mirror, a spacer layer, and the thin absorber layer followed by a metal top layer which forms the photovoltaic detector and in addition acts as top mirror. Devices with peak wavelengths varying from 4 to 8 μm, spectral widths below 1% and quantum efficiencies above 30% have been realised

  6. Chalcogenide Random Access Memory Cell with Structure of W Sub-Microtube Heater Electrode

    Institute of Scientific and Technical Information of China (English)

    LIU Bo; FENG Gao-Ming; WU Liang-Cai; SONG Zhi-Tang; LIU Qi-Bin; FENG Song-Lin; CHEN Bomy

    2007-01-01

    @@ In order to reduce the reset current of chalcogenide random access memory, a W sub-microtube heater electrode with outer/inner diameter of 260/100nm, which was fabricated with standard 0.18-μm technology, is proposed for the first time to achieve a reset current of about 0.5mA. The reasons may be that sub-microtube increases the number of electrode edge and thermal efficiency is improved greatly because the thermal density on the edge of sub-microtube electrode is generally the highest.

  7. Mid-gap phenomena in chalcogenide glasses and barrier-cluster-heating model

    Science.gov (United States)

    Banik, Ivan; Kubliha, Marián; Lukovičová, Jozefa; Pavlendová, Gabriela

    2015-12-01

    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 As2S3 (or As2Se3) 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.

  8. Ion beam assisted synthesis of nano-crystals in glasses (silver and lead chalcogenides)

    International Nuclear Information System (INIS)

    This work deals with the interest in ion beams for controlling nano-crystals synthesis in glasses. We show two different ways to reach this aim, insisting on importance of redox phenomena induced by the penetration and implantation of ions in glasses. We first show that we can use the great energy density deposited by the ions to tailor reducing conditions, favorable to metallic nano-crystal precipitation. In particular, we show that microscopic mechanism of radiation induced silver precipitation in glasses are analogous to the ones of classical photography. Ion beams can also be used to overcome supersaturation of elements in a given matrix. In this work, we synthesized lead chalcogenide nano-crystals (PbS, PbSe, PbTe) whose optical properties are interesting for telecommunication applications. We demonstrate the influence of complex chalcogenide chemistry in oxide glasses, and its relationship with the observed loss of growth control when nano-crystals are synthesized by sequential implantation of Pb and S in pure silica. As a consequence of this understanding, we demonstrate a novel and controlled synthesis of PbS nano-crystals, consisting in implanting sulfur into a Pb-containing glass, before annealing. Choice of glass composition provides a better control of precipitation physico-chemistry, whereas the use of implantation allows high nano-crystal volume fractions to be reached. Our study of IR emission properties of these nano-crystals shows a very high excitation cross section, and evidence for a 'dark exciton' emitting level. (author)

  9. Hydrazine-hydrothermal method to synthesize three-dimensional chalcogenide framework for photocatalytic hydrogen generation

    International Nuclear Information System (INIS)

    A novel chalcogenide, [Mn2Sb2S5(N2H4)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 SbS3 trigonal-pyramidal geometry, and the Sb2 site adopts a SbS4 trigonal bipyramidal coordination geometry. It has an optical band gap of about ∼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, [Mn2Sb2S5(N2H4)3] (1), synthesized by hydrazine-hydrothermal method, has a band gap of about ∼2.09 eV and displays photocatalytic behaviors under visible light irradiation. Display Omitted

  10. Crystal symmetry breaking and vacancies in colloidal lead chalcogenide quantum dots.

    Science.gov (United States)

    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. PMID:27295101

  11. Functionalized organotin-chalcogenide complexes that exhibit defect heterocubane scaffolds: formation, synthesis, and characterization.

    Science.gov (United States)

    Eußner, Jens P; Barth, Beatrix E K; Leusmann, Eliza; You, Zhiliang; Rinn, Niklas; Dehnen, Stefanie

    2013-10-01

    The synthesis of new functionalized organotin-chalcogenide complexes was achieved by systematic optimization of the reaction conditions. The structures of compounds [(R(1, 2) Sn)3 S4 Cl] (1, 2), [((R(2) Sn)2 SnS4 )2 (μ-S)2 ] (3), [(R(1, 2) Sn)3 Se4 ][SnCl3 ] (4, 5), and [Li(thf)n ][(R(3) Sn)(HR(3) Sn)2 Se4 Cl] (6), in which R(1) =CMe2 CH2 C(O)Me, R(2) =CMe2 CH2 C(NNH2 )Me, and R(3) =CH2 CH2 COO, are based on defect heterocubane scaffolds, as shown by X-ray diffraction, (119) Sn NMR spectroscopy, and ESI mass spectrometry analyses. Compounds 4, 5, and 6 constitute the first examples of defect heterocubane-type metal-chalcogenide complexes that are comprised of selenide ligands. Comprehensive DFT calculations prompted us to search for the formal intermediates [(R(1) SnCl2 )2 (μ-S)] (7) and [(R(1) SnCl)2 (μ-S)2 ] (8), which were isolated and helped to understand the stepwise formation of compounds 1-6. PMID:23963989

  12. Chalcogenide glass fibers: Optical window tailoring and suitability for bio-chemical sensing

    Science.gov (United States)

    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.

  13. The electronic band structures of gadolinium chalcogenides: a first-principles prediction for neutron detecting.

    Science.gov (United States)

    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. PMID:27049355

  14. Crystalline phase responsible for the permanent second-harmonic generation in chalcogenide glass-ceramics

    Science.gov (United States)

    Guignard, Marie; Nazabal, Virginie; Zhang, Xiang-Hua; Smektala, Frédéric; Moréac, Alain; Pechev, Stanislas; Zeghlache, Hassina; Kudlinski, Alexandre; Martinelli, Gilbert; Quiquempois, Yves

    2007-10-01

    Permanent second-harmonic generation (SHG) has been demonstrated in chalcogenide based glass-ceramics containing non-linear micro-crystals with a size of a few micrometers. A glass composition from the Ge-Sb-S system was chosen as the reference glass for its stability against crystallization and atmospheric corrosion. Metallic cadmium was introduced in this matrix to promote crystallite formation resulting in infrared transparent glass-ceramics. A volume crystallization of β-GeS2 phase was obtained within the glass media by heating the glass samples at 370 °C for different durations. The glass-ceramics were then investigated by Raman spectroscopy, X-ray diffraction and NanoSIMS. The second-order non-linear signals were recorded by using Maker fringes experiment and were studied as a function of the crystallized volume fraction. The results indicated a non-linearity in chalcogenide glass-ceramics about one hundred times lower than α-quartz for a 1 mm thick sample heat treated 144 h.

  15. Characterization and modeling of microstructured chalcogenide fibers for efficient mid-infrared wavelength conversion.

    Science.gov (United States)

    Xing, Sida; Grassani, Davide; Kharitonov, Svyatoslav; Billat, Adrien; Brès, Camille-Sophie

    2016-05-01

    We experimentally demonstrate wavelength conversion in the 2 µm region by four-wave mixing in an AsSe and a GeAsSe chalcogenide photonic crystal fibers. A maximum conversion efficiency of -25.4 dB is measured for 112 mW of coupled continuous wave pump in a 27 cm long fiber. We estimate the dispersion parameters and the nonlinear refractive indexes of the chalcogenide PCFs, establishing a good agreement with the values expected from simulations. The different fiber geometries and glass compositions are compared in terms of performance, showing that GeAsSe is a more suited candidate for nonlinear optics at 2 µm. Building from the fitted parameters we then propose a new tapered GeAsSe PCF geometry to tailor the waveguide dispersion and lower the zero dispersion wavelength (ZDW) closer to the 2 µm pump wavelength. Numerical simulations shows that the new design allows both an increased conversion efficiency and bandwidth, and the generation of idler waves further in the mid-IR regions, by tuning the pump wavelength in the vicinity of the fiber ZDW. PMID:27137588

  16. Synthesis and properties of new CdSe-AgI-As2Se3 chalcogenide glasses

    International Nuclear Information System (INIS)

    Research highlights: → Determination of the glass-forming region in the pseudo-ternary CdSe-AgI-As2Se3 system. → Characterization of macroscopic properties of the new CdSe-AgI-As2Se3 glasses. → Far infrared transmission of chalcogenide glasses. → Characterization of the total conductivity of CdSe-AgI-As2Se3 glasses. -- Abstract: The glass-forming region in the pseudo-ternary CdSe-AgI-As2Se3 system was determined. Measurements including differential scanning calorimetry (DSC), density, and X-ray diffraction were performed. The effect resulting from the addition of CdSe or AgI has been highlighted by examining three series of different base glasses. The characteristic temperatures of the glass samples, including glass transition (Tg), crystallisation (Tx), and melting (Tm) temperatures are reported and used to calculate their ΔT = Tx - Tg and their Hruby, Hr = (Tx - Tg)/(Tm - Tx), criteria. Evolution of the total electrical conductivity σ and the room temperature conductivity σ298 was also studied. The terahertz transparency domain in the 50-600 cm-1 region was pointed for different chalcogenide glasses (ChGs) and the potential of the THz spectroscopy was suggested to obtain structural information on ChGs.

  17. Photonic Bandgap Propagation in All-Solid Chalcogenide Microstructured Optical Fibers

    Directory of Open Access Journals (Sweden)

    Celine Caillaud

    2014-08-01

    Full Text Available 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.

  18. Mid-gap phenomena in chalcogenide glasses and barrier-cluster-heating model

    Energy Technology Data Exchange (ETDEWEB)

    Banik, Ivan, E-mail: ivan.banik@stuba.sk; Kubliha, Marián; Lukovičová, Jozefa; Pavlendová, Gabriela [Faculty of Civil Engineering, Slovak University of Technology, 813 68 Bratislava (Slovakia)

    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.

  19. Luminescence at 2.8 μm: Er3+-doped chalcogenide micro-waveguide

    Science.gov (United States)

    Nazabal, V.; Starecki, F.; Doualan, J.-L.; Němec, P.; Camy, P.; Lhermite, H.; Bodiou, L.; Anne, M. L.; Charrier, J.; Adam, J. L.

    2016-08-01

    This paper reports the fabrication of luminescent optical rib/ridge waveguides made of erbium doped Ga-Ge-Sb-S films deposited by RF magnetron sputtering. Several fluorescence emissions of Er3+ ions from the visible to the middle infrared spectral domain were clearly observed within the films. The study of the 4I13/2 level lifetime enabled development of a suitable annealing treatment of the films to reach the value of the bulk counterpart while the variation in surface roughness was limited, thus ensuring reasonable optical losses (0.7-0.9 dB/cm). Amplification experiments were carried out at 1.54 μm leading to complete characterization of the erbium-doped micro-waveguide with ∼3.4 dB/cm on/off gain. A demonstration of mid-IR photoluminescence from Er3+-doped chalcogenide micro-waveguide was recorded at ∼2.76 μm. The multi-luminescence from the visible to mid-IR generated using erbium doped chalcogenide waveguiding micro-structures might find easy-to-use applications concerning telecommunication technologies or on-chip optical sensors for which luminescent sources or amplifiers operating at different wavelengths are required.

  20. Silicon-based thin films as bottom electrodes in chalcogenide nonvolatile memories

    International Nuclear Information System (INIS)

    The effect of the electrical resistivity of a silicon-germanium (SiGe) thin film on the phase transition in a GeSbTe (GST) chalcogenide alloy and the manufacturing aspect of the fabrication process of a chalcogenide memory device employing the SiGe film as bottom electrodes were investigated. While p-type SiGe bottom electrodes were formed using in situ doping techniques, n-type ones could be made in a different manner where phosphorus atoms diffused from highly doped silicon underlayers to undoped SiGe films. The p-n heterojunction did not form between the p-type GST and n-type SiGe layers, and the semiconduction type of the SiGe alloys did not influence the memory device switching. It was confirmed that an optimum resistivity value existed for memory operation in spite of proportionality of Joule heating to electrical resistivity. The very high resistivity of the SiGe film had no effect on the reduction of reset current, which might result from the resistance decrease of the SiGe alloy at high temperatures

  1. The electronic band structures of gadolinium chalcogenides: a first-principles prediction for neutron detecting

    Science.gov (United States)

    Li, Kexue; Liu, Lei; Yu, Peter Y.; Chen, Xiaobo; Shen, D. Z.

    2016-05-01

    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.

  2. The role of the chemical composition on the ablation of the chalcogenide glasses and thin films by pulsed UV laser

    Czech Academy of Sciences Publication Activity Database

    Knotek, P.; Návesník, J.; Vlček, Milan; Kincl, Miloslav; Tichý, Ladislav

    Paris: University Paris Sud, 2014. s. 148-148. ISBN N. [33rd European Conference on Laser Interaction with Matter. 31.08.2014-05.09.2014, Paříž] Institutional support: RVO:61389013 Keywords : chalcogenides * thin films * optical properties Subject RIV: CA - Inorganic Chemistry

  3. Mid-IR supercontinuum generation beyond 7 μm using a silica-fluoride-chalcogenide fiber cascade

    DEFF Research Database (Denmark)

    Petersen, Christian Rosenberg; Moselund, Peter M.; Petersen, Christian;

    2016-01-01

    We report on an experimental demonstration of mid-infrared cascaded supercontinuum generation in commercial silica, fluoride, and chalcogenide fibers as a potentially cheap and practical alternative to direct pumping schemes. A pump continuum up to 4.4 μm was generated in cascaded silica and...

  4. Ionic conductivity study of Lil-Ga2S3-GeS2 chalcogenide glasses using a random – walk approach

    Czech Academy of Sciences Publication Activity Database

    Patil, S. D.; Konale, M. S.; Kolář, J.; Shimakawa, K.; Zima, Vítězslav; Wágner, T.

    2015-01-01

    Roč. 87, č. 3 (2015), s. 249-259. ISSN 0033-4545 Institutional support: RVO:61389013 Keywords : chalcogenide glasses * impedance spectroscopy * ionic conductivity Subject RIV: CA - Inorganic Chemistry Impact factor: 2.492, year: 2014

  5. Photosensitive post tuning of chalcogenide Te 20As 30Se 50 narrow bandpass filters

    Science.gov (United States)

    Shen, Weidong; Cathelinaud, Michel; Lequime, Michel; Nazabal, Virginie; Liu, Xu

    2008-07-01

    We present an experimental study on the photosensitive properties of narrow bandpass filters based on a chalcogenide Te 20As 30Se 50 (TAS) spacer. The transmittance curve of single TAS layer was shifted towards long wavelength direction after 2 h exposure by Xenon arc lamp. The refractive index and extinction coefficient were both increased together with a red shift of optical gap. A maximum 1.7% photo-induced effect was observed. Narrow band filters constituted by TAS and cryolite were manufactured by electron beam deposition. The transmittance spectrum of the filter during the exposure by a wide band source was in situ measured and the resonant wavelength was observed to turn longer gradually till saturation. A spatially localized central wavelength change up to 5.7 nm was finally obtained. The stability of the photo-induced effect was studied and some comments were given at the end of this paper.

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

    International Nuclear Information System (INIS)

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

  7. Updated results on prototype chalcogenide fibers for 10-um wavefront spatial filtering

    CERN Document Server

    Bordé, P J; Amy-Klein, A; Daussy, C; Mazé, G

    2003-01-01

    The detection of terrestrial planets by Darwin/TPF missions will require extremely high quality wavefronts. Single-mode fibers have proven to be powerful beam cleaning components in the near-infrared, but are currently not available in the mid-infrared where they would be critically needed for Darwin/TPF. In this paper, we present updated measurements on the prototype chalcogenide fibers we are developing for the purpose of mid-infrared spatial filtering. We demonstrate the guiding property of our 3rd generation component and we characterize its filtering performances on a 4 mm length: the far-field radiation pattern matches a Gaussian profile at the level of 3% rms and 13% pk-pk.

  8. Bandgaps of the Chalcogenide Glass Hollow-Core Photonic Crystal Fiber

    International Nuclear Information System (INIS)

    Bandgaps of chalcogenide glass hollow-core photonic crystal fibers (GLS HC-PCFs) are analyzed by using the plane-wave expansion method. A mid-infrared laser can propagate in these low confinement loss fibers when the wavelength falls into the bandgaps. For enlarging the bandgap width, an improved GLS HC-PCF is put forward, the normalized frequency kΛ of the improved fiber is from 7.2 to 8.5 in its first bandgap. The improved GLS HC-PCF with pitch of 4.2 μm can transmit the lights with wavelengths ranging from 3.1 μm to 3.7 μm. (fundamental areas of phenomenology(including applications))

  9. Radiation-induced effects in chalcogenide glasses of Ge-As-Se system

    International Nuclear Information System (INIS)

    The radiation-optical properties of the chalcogenide glass-like semiconductors of the Ge-As-S ternary systems by variation of the coordination number from 2.4 up to 2.8 are studied. It is shown, that irradiation of the As2S3-Ge2S3 system samples through gamma-quanta of the 60Co radionuclides leads to increase in the long-wave shift of their fundamental absorption edge. the value and character of the given effect essentially depend on the type of the structure of the studied samples and change by the 2D-3D phase transition. The microstructural mechanism of the observed radiation-optical effects is bound most probably with the processes of coordination defects formation

  10. Valence band structure of binary chalcogenide vitreous semiconductors by high-resolution XPS

    Energy Technology Data Exchange (ETDEWEB)

    Kozyukhin, S., E-mail: sergkoz@igic.ras.ru [Russian Academy of Science, Institute of General and Inorganic Chemistry (Russian Federation); Golovchak, R. [Lviv Scientific Research Institute of Materials of SRC ' Carat' (Ukraine); Kovalskiy, A. [Lehigh University, Department of Materials Science and Engineering (United States); Shpotyuk, O. [Lviv Scientific Research Institute of Materials of SRC ' Carat' (Ukraine); Jain, H. [Lehigh University, Department of Materials Science and Engineering (United States)

    2011-04-15

    High-resolution X-ray photoelectron spectroscopy (XPS) is used to study regularities in the formation of valence band electronic structure in binary As{sub x}Se{sub 100-x}, As{sub x}S{sub 100-x}, Ge{sub x}Se{sub 100-x} and Ge{sub x}S{sub 100-x} chalcogenide vitreous semiconductors. It is shown that the highest occupied energetic states in the valence band of these materials are formed by lone pair electrons of chalcogen atoms, which play dominant role in the formation of valence band electronic structure of chalcogen-rich glasses. A well-expressed contribution from chalcogen bonding p electrons and more deep s orbitals are also recorded in the experimental valence band XPS spectra. Compositional dependences of the observed bands are qualitatively analyzed from structural and compositional points of view.

  11. Ionizing radiation solid detectors on the base of amorphous arsenic chalcogenides

    International Nuclear Information System (INIS)

    The possibility to use radiation-sensitive elements of solid chalcogenide glass-like semiconductors (CGS) - special class of oxygen-free amorphous substances, which are alloys of groups 3, 4 and 5 elements with chalcogens (S, Se, Te), was analyzed. The materials feature lower temperatures of radiation information erasure (440-470 K) than oxide glasses. Radiation-induced electron-defect processes lay at physical basis of operation of CGS-based solid detectors. The processes consist in violation of atom normal coordination at the expense of chemical bond rupture and appearance of other bonds. The main principles of operation are reduced to registration of CGS density at a certain wavelength prior to and after total dose collection. The use of helium-neon laser as a probing radiation source simplifies considerably measurement procedure and permits making measurements without sensor extraction from radiation field

  12. Fabrication of porous nanostructured lead chalcogenide semiconductors for modern thermoelectric and optoelectronic applications

    International Nuclear Information System (INIS)

    Porous structures of lead chalcogenides with porosities of 20-68% and pore dimensions as small as 7-20 nm were fabricated using an anodic electrochemical etching technique applied to epitaxial PbTe and PbSe films on Si. Anodized lead selenide demonstrated two basic types of porous morphology: quasiporous noncontinuous layers and hierarchical porous layers. Lead telluride had a more typical mesoporous morphology, with pores propagating at an angle of 350 to surface, which corresponds to the <100< directions in the epitaxial films and is promising for the fabrication of photonic crystals with Yablonovite-like structure. The sizes of PbTe nanocrystallites in porous layers with high porosity were calculated to be 26 nm, which indicates that quantum confinement conditions are realized in this material. Such low-dimensional morphology of porous lead telluride is prospective for the fabrication of microscale thermoelectric devices with high ZT.

  13. Electron irradiation induced reduction of the permittivity in chalcogenide glass (As2S3) thin film

    KAUST Repository

    San-Román-Alerigi, Damián P.

    2013-01-01

    In this paper, we investigate the effect of electron beam irradiation on the dielectric properties of As 2 S 3 chalcogenide glass. By means of low-loss electron energy loss spectroscopy, we derive the permittivity function, its dispersive relation, and calculate the refractive index and absorption coefficients under the constant permeability approximation. The measured and calculated results show a heretofore unseen phenomenon: a reduction in the permittivity of ? 40 %. Consequently a reduction of the refractive index of 20%, hence, suggests a conspicuous change in the optical properties of the material under irradiation with a 300 keV electron beam. The plausible physical phenomena leading to these observations are discussed in terms of the homopolar and heteropolar bond dynamics under high energy absorption. The reported phenomena, exhibited by As 2 S 3-thin film, can be crucial for the development of photonics integrated circuits using electron beam irradiation method. © 2013 American Institute of Physics.

  14. Power-efficient production of photon pairs in a tapered chalcogenide microwire

    International Nuclear Information System (INIS)

    Using tapered fibers of As2Se3 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

  15. Correlated structural and electronic phase transformations in transition metal chalcogenide under high pressure

    Science.gov (United States)

    Li, Chunyu; Ke, Feng; Hu, Qingyang; Yu, Zhenhai; Zhao, Jinggeng; Chen, Zhiqiang; Yan, Hao

    2016-04-01

    Here, we report comprehensive studies on the high-pressure structural and electrical transport properties of the layered transition metal chalcogenide (Cr2S3) up to 36.3 GPa. A structural phase transition was observed in the rhombohedral Cr2S3 near 16.5 GPa by the synchrotron angle dispersive X-ray diffraction measurement using a diamond anvil cell. Through in situ resistance measurement, the electric resistance value was detected to decrease by an order of three over the pressure range of 7-15 GPa coincided with the structural phase transition. Measurements on the temperature dependence of resistivity indicate that it is a semiconductor-to-metal transition in nature. The results were also confirmed by the electronic energy band calculations. Above results may shed a light on optimizing the performance of Cr2S3 based applications under extreme conditions.

  16. Instantaneous microwave frequency measurement using four-wave mixing in a chalcogenide chip

    Science.gov (United States)

    Pagani, Mattia; Vu, Khu; Choi, Duk-Yong; Madden, Steve J.; Eggleton, Benjamin J.; Marpaung, David

    2016-08-01

    We present the first instantaneous frequency measurement (IFM) system using four-wave mixing (FWM) in a compact photonic chip. We exploit the high nonlinearity of chalcogenide to achieve efficient FWM in a short 23 mm As2S3 waveguide. This reduces the measurement latency by orders of magnitude, compared to fiber-based approaches. We demonstrate the tuning of the system response to maximize measurement bandwidth (40 GHz, limited by the equipment used), or accuracy (740 MHz rms error). Additionally, we modify the previous FWM-based IFM system structure to allow for ultra-fast reconfiguration of the bandwidth and resolution of the measurement. This has the potential to become the first IFM system capable of ultra-fast accurate frequency measurement, with no compromise of bandwidth.

  17. Chalcogenide glass planar MIR couplers for future chip based Bracewell interferometers

    CERN Document Server

    Goldsmith, Harry-Dean Kenchington; Ireland, Michael; Ma, Pan; Tuthill, Peter; Eggleton, Ben; Lawrence, John S; Debbarma, Sukanta; Luther-Davies, Barry; Madden, Stephen J

    2016-01-01

    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.

  18. Origin of the frequency shift of Raman scattering in chalcogenide glasses

    DEFF Research Database (Denmark)

    Han, X.C.; Tao, H.Z.; Gong, L.J.; Wang, X.Y.; Zhao, X.J.; Yue, Yuanzheng

    2014-01-01

    . We keep the number of topological constraints constant in the studied glass series, in order to explore the impact of mediate range structure on the main Raman scattering frequency. The results reveal that the frequency shift is attributed to the alteration of the nearest neighbor connectivity of......Raman scattering is a sensitive method for probing the structural evolution in glasses, especially in covalent ones. Usually the main Raman scattering frequency shifts with composition for Gesingle bondSe chalcogenide glasses. However, it has not been well established whether and how the dependence...... of the shift is associated with the topological connectivity of global network and/or the local environment of structural units, (e.g., tetrahedral GeSe4). Here we show the compositional evolution of the main Raman scattering frequency in Ge(SxSe1−x)2 glasses, and then clarify its structural origin...

  19. Synthesis of chalcogenide and pnictide crystals in salt melts using a steady-state temperature gradient

    Science.gov (United States)

    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.

  20. NMR study of the zinc chalcogenides (ZnX, X = O, S, Se, Te)

    International Nuclear Information System (INIS)

    A nuclear magnetic resonance investigation of the solid zinc chalcogenides ZnX (X = O, S, Se, Te) is carried out, using the following nuclei as probes, 67Zn, 17O, 33S, 77Se, and 125Te. The spectra yield nuclear quadrupole coupling constants and chemical-shift parameters for polycrystalline ZnO and ZnS in the wurtzite (hexagonal) form, and chemical shifts and linewidths for polycrystalline ZnS, ZnSe, and ZnTe in the sphalerite (cubic) form. A single crystal of ZnO is used to obtain an accurate measurement of the quadrupole coupling constant for 67Zn, |e2qQ/h| = 2.4065(15) MHz at 296 K, in agreement with a recent Moessbauer-effect measurement. The electric field gradient of the wurtzite structures is analysed with a simple ionic model, and the results are found to be in semiquantitative agreement with experiment. (author)

  1. Determination of the oxidation state and coordination of a vanadium doped chalcogenide glass

    Science.gov (United States)

    Hughes, Mark A.; Curry, Richard J.; Hewak, Daniel W.

    2011-01-01

    Vanadium doped chalcogenide glass has potential as an active gain medium, particularly at telecommunications wavelengths. This dopant has three spin allowed absorption transitions at 1100, 737 and 578 nm, and a spin forbidden absorption transition at 1000 nm. X-ray photoelectron spectroscopy indicated the presence of vanadium in a range of oxidation states from V+ to V5+. Excitation of each absorption band resulted in the same characteristic emission spectrum and lifetime, indicating that only one oxidation state is optically active. Arguments based on Tanabe-Sugano analysis indicated that the configuration of the optically active vanadium ion was octahedral V2+. The calculated crystal field parameters (Dq/B, B and C/B) were 1.85, 485.1 and 4.55, respectively.

  2. Ultrabroadband, Midinfrared Supercontinuum Generation in Dispersion Engineered As2Se3-Based Chalcogenide Photonic Crystal Fibers

    Directory of Open Access Journals (Sweden)

    Rim Cherif

    2013-01-01

    Full Text Available Small core As2Se3-based photonic crystal fibers (PCFs are accurately characterized for compact, high power, ultrabroadband, and coherent supercontinuum generation within few millimeters fiber length. Bandwidths of ~5.3 μm, 5 μm, and 3.2 μm were calculated for hole-to-hole spacings Λ= 3.5 μm, 4.5 μm, and 5.5 μm, respectively. The spectral broadening in the chalcogenide PCF is mainly caused by self-phase modulation and Raman-induced soliton self-frequency shift. The results show that small core As2Se3 PCFs are a promising candidate for mid-IR SCG up to ~8 μm.

  3. Chalcogenide glass Photonic Crystal Fiber with flattened dispersion and high nonlinearity at telecommunication wavelength

    Directory of Open Access Journals (Sweden)

    S.REVATHI

    2013-04-01

    Full Text Available A highly nonlinear photonic crystal fiber with eight ring octagonal structure is proposed. Chalcogenide glass of As2S3 is used as the material for this photonic crystal fiber structure. The finiteelementmethod with perfectly matched boundary layer is employed to analyze the guiding properties. Non linearity of 13,584.5 per W-km is obtained at 1.55 μm with reasonable flattened dispersion of -25ps/nm-km to -28 ps/nm-km. Confinement loss achieved is of the order of 10-6 dB/km. Large negative dispersion is also obtained ranging from wavelength of 0.85 μm to 1.95 μm, which can be used for dispersion compensation in fiber optic communication. This Photonic Crystal Fiber structure can also be used for nonlinear applications like ultra short soliton pulse transmission, optical parametricamplification, supercontinuum generation.

  4. Recent advances in very highly nonlinear chalcogenide photonic crystal fibers and their applications

    Science.gov (United States)

    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.

  5. High-quality chalcogenide glass waveguide fabrication by hot melt smoothing and micro-trench filling

    Science.gov (United States)

    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.

  6. Plasma diagnostics in pulsed laser deposition of GaLaS chalcogenides

    International Nuclear Information System (INIS)

    The aim of this work is to characterize the ejection plume obtained by laser ablation of GaLaS (GLS) samples in order to better understand the ablation phenomena for optimizing the pulsed laser deposition of chalcogenide thin films. The dynamics of the plasma between target and substrate was investigated through time- and space-resolved optical emission spectroscopy. High-resolution optical spectra have been recorded in the UV–VIS range using a 500-mm focal length monochromator and a fast gate ICCD camera. From the space–time evolution of the optical signals, the velocities of various species (including neutrals and ions) have been derived. Using the relative intensity method, the space- and time-evolution of the excitation temperature and electronic density have been determined. A complex behavior of the laser ablation plasma has been revealed.

  7. Plasma diagnostics in pulsed laser deposition of GaLaS chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Pompilian, O.G. [Laboratoire de Physique des Lasers, Atomes et Molécules (UMR 8523), Université Lille 1, 59655 Villeneuve d’Ascq cedex (France); Gurlui, S., E-mail: sgurlui@uaic.ro [Physics Department, Alexandru Ioan Cuza University of Iasi, 700506 Iasi (Romania); Nemec, P. [Faculty of Chemical Technology, University of Pardubice, Studentska 573, 53210 Pardubice (Czech Republic); Nazabal, V. [Laboratoire des Verres et Céramiques, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex (France); Ziskind, M.; Focsa, C. [Laboratoire de Physique des Lasers, Atomes et Molécules (UMR 8523), Université Lille 1, 59655 Villeneuve d’Ascq cedex (France)

    2013-08-01

    The aim of this work is to characterize the ejection plume obtained by laser ablation of GaLaS (GLS) samples in order to better understand the ablation phenomena for optimizing the pulsed laser deposition of chalcogenide thin films. The dynamics of the plasma between target and substrate was investigated through time- and space-resolved optical emission spectroscopy. High-resolution optical spectra have been recorded in the UV–VIS range using a 500-mm focal length monochromator and a fast gate ICCD camera. From the space–time evolution of the optical signals, the velocities of various species (including neutrals and ions) have been derived. Using the relative intensity method, the space- and time-evolution of the excitation temperature and electronic density have been determined. A complex behavior of the laser ablation plasma has been revealed.

  8. Si1Sb2Te3 phase change material for chalcogenide random access memory

    Institute of Scientific and Technical Information of China (English)

    Zhang Ting; Song Zhi-Tang; Liu Bo; Liu Wei-Li; Feng Song-Lin; Chen Bomy

    2007-01-01

    This paper investigated phase change Si1Sb2Te3 material for application of chalcogenide random access memory.Current-voltage performance was conducted to determine threshold current of phase change from amorphous phase to polycrystalline phase.The film holds a threshold current about 0.155 mA,which is smaller than the value 0.31 mA of Ge2Sb2Te5 film.Amorphous Si1Sb2Te3 changes to face-centred-cubic structure at~180°C and changes to hexagonal structure at~270°C.Annealing temperature dependent electric resistivity of Si1Sb2Te3 film was studied by four-point probe method.Data retention of the films was characterized as well.

  9. Power-efficient production of photon pairs in a tapered chalcogenide microwire

    Energy Technology Data Exchange (ETDEWEB)

    Meyer-Scott, Evan, E-mail: emeyersc@uwaterloo.ca; Dot, Audrey [Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1 (Canada); Ahmad, Raja; Li, Lizhu; Rochette, Martin [Department of Electrical and Computer Engineering, McGill University, 3480 University Street, Montréal, Québec H3A 2A7 (Canada); Jennewein, Thomas [Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1 (Canada); Quantum Information Science Program, Canadian Institute for Advanced Research, 180 Dundas Street West, Suite 1400, Toronto, Ontario M5G 1Z8 (Canada)

    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.

  10. Modeling of Mid-IR Amplifier Based on an Erbium-Doped Chalcogenide Microsphere

    Directory of Open Access Journals (Sweden)

    P. Bia

    2012-01-01

    Full Text Available An optical amplifier based on a tapered fiber and an Er3+-doped chalcogenide microsphere is designed and optimized. A dedicated 3D numerical model, which exploits the coupled mode theory and the rate equations, is used. The main transitions among the erbium energy levels, the amplified spontaneous emission, and the most important secondary transitions pertaining to the ion-ion interactions have been considered. Both the pump and signal beams are efficiently injected and obtained by a suitable design of the taper angle and the fiber-microsphere gap. Moreover, a good overlapping between the optical signals and the rare-earth-doped region is also obtained. In order to evaluate the amplifier performance in reduced computational time, the doped area is partitioned in sectors. The obtained simulation results highlight that a high-efficiency midinfrared amplification can be obtained by using a quite small microsphere.

  11. Effect of band filling in the paramagnetic tetragonal phase of iron chalcogenides

    International Nuclear Information System (INIS)

    The normal state of layered Fe-chalcogenide superconductors shows a range of anomalous, non-Fermi liquid responses. Unconventional metallic resistivity, characteristic pseudogap and saturating features and proximity to insulating states mark these systems as correlated metals. Motivated thereby, we use a combination of first-principles and many-particle calculations to show that multiband electronic correlations generate a low-energy pseudogap in the normal state of Fe(Te,Se) end-members, which, depending on the band filling, promotes incoherent metallic or orbital-selective insulating states. Upon comparison, good qualitative agreement with experimental (photoemission and electrical resistivity) data of FeTe1−xSe x systems is found. Based on observed charge transport we propose that the parent bulk compounds are best described as partially filled multiband systems. (paper)

  12. Photoconductivity of amorphous As2S8 chalcogenide film under bandgap light irradiation

    Directory of Open Access Journals (Sweden)

    L. E. Zou

    2013-06-01

    Full Text Available The photoconductivity of amorphous As2S8 chalcogenide film under the irradiation of bandgap light is investigated. In the temperature range 300–350 K, the dark conductivity and photoconductivity of the annealed As2S8 film increase with the temperature, and the dependence of the both on temperature shows that the conduction in As2S8 film is an activated process having single activation energy. Under the irradiation of bandgap light, the photocurrents of the annealed and illuminated As2S8 film increase with the irradiation intensity, and their difference indicates the existence of the light-soaked effect. Meanwhile, the photoconductivity degradation during the irradiation and the photocurrent decay after stopping the irradiation are observed. By adding the irradiation of the sub-bandgap light, the enhancement of photoinduced voltage occurs.

  13. Dy3+-doped Ga–Sb–S chalcogenide glasses for mid-infrared lasers

    International Nuclear Information System (INIS)

    Highlights: • Novel Ga–Sb–S chalcogenide glasses doped with Dy3+ 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 Dy3+ 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−1), and intense emissions centered at 2.95, 3.59, 4.17 and 4.40 μm. Three Judd–Ofelt intensity parameters (Ω2 = 8.51 × 10−20 cm2, Ω4 = 2.09 × 10−20 cm2, and Ω6 = 1.60 × 10−20 cm2) 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 × 10−20 cm2 for 2.95 μm emission, 75.90% and 0.38 × 10−20 cm2 for 4.40 μm emission, respectively) in the Dy3+-doped Ga–Sb–S glasses make them promising gain materials for the MIR lasers

  14. Effects of Metal Particles Decoration on n-Type Chalcogenides Processed by Open Die Pressing

    Science.gov (United States)

    Fanciulli, C.; Codecasa, M.; Passaretti, F.; Vasilevskiy, D.

    2014-06-01

    The effects of copper particles dispersed into Bi1.9Sb0.1Te2.85Se0.15 nanopowders and sintered by open die pressing (ODP) have been investigated. Submicrometric copper particles were obtained by decomposing copper acetate molecules dispersed into chalcogenides nanopowders. The acetate powders were decomposed during the sintering process at 390 °C obtaining a fine dispersion of copper particles with dimensions in the order of 500 nm. Contents up to 0.2 wt.% of copper were investigated. ODP, previously introduced as a forming process for sintering and texturing p-type (Bi0.2Sb0.8)2Te3 nanopowders, has been applied to n-type chalcogenide: the mixed alloy nanopowders and copper acetate were compacted inside a metallic protective shell and fast pressed between two heated plates, keeping the composite under load for sintering. ODP processing ensures complete consolidation of nanopowders and material texturing with the basal (00 l) planes of the hexagonal crystal cell oriented parallel to the plates. The X-ray diffraction pattern shows an orientation factor, f, obtained by the Lotgering method, up to 64 %. Thermoelectric performance of the samples was measured by the Harman method in the range of 20-170 °C. Figure of merit ( ZT) behavior with temperature was improved in copper-dispersed samples showing a shift of the maximum value at higher temperatures. This effect can be mainly associated with an improvement of electrical conductivity, due to the presence of the copper particles.

  15. Dy{sup 3+}-doped Ga–Sb–S chalcogenide glasses for mid-infrared lasers

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Mingjie [Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, Jiangsu 221116 (China); Yang, Anping, E-mail: apyang@jsnu.edu.cn [Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, Jiangsu 221116 (China); Peng, Yuefeng [Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Zhang, Bin; Ren, He; Guo, Wei; Yang, Yan; Zhai, Chengcheng; Wang, Yuwei; Yang, Zhiyong; Tang, Dingyuan [Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, Jiangsu 221116 (China)

    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.

  16. Thermoelectric performance of tellurium-reduced quaternary p-type lead–chalcogenide composites

    International Nuclear Information System (INIS)

    Graphical abstract: - Abstract: A long-standing technological challenge to the widespread application of thermoelectric generators is obtaining high-performance thermoelectric materials from abundant elements. Intensive study on PbTe alloys has resulted in a high figure of merit for the single-phase ternary PbTe–PbSe system through band structure engineering, and the low thermal conductivity achieved due to nanostructuring leads to high thermoelectric performance for ternary PbTe–PbS compounds. Recently, the single-phase p-type quaternary PbTe–PbSe–PbS alloys have been shown to provide thermoelectric performance superior to the binary and ternary lead chalcogenides. This occurs via tuning of the band structure and from an extraordinary low thermal conductivity resulting from high-contrast atomic mass solute atoms. Here, we present the thermoelectric efficiency of nanostructured p-type quaternary PbTe–PbSe–PbS composites and compare the results with corresponding single-phase quaternary lead chalcogenide alloys. We demonstrate that the very low lattice thermal conductivity achieved is attributed to phonon scattering at high-contrast atomic mass solute atoms rather than from the contribution of secondary phases. This results in a thermoelectric efficiency of ∼1.4 over a wide temperature range (650–850 K) in a p-type quaternary (PbTe)0.65(PbSe)0.1(PbS)0.25 composite that is lower than that of single-phase (PbTe)0.85(PbSe)0.1(PbS)0.05 alloy without secondary phases

  17. Surface corrugating direct laser writing of microstructures in ternary chalcogenide films using a continuous-wave super-bandgap laser

    International Nuclear Information System (INIS)

    Direct laser writing using a tightly focused 442 nm continuous-wave laser was applied to corrugate the surface of ternary As–S–Se chalcogenide thin films with high spatial resolution. The topography of the emerging surface relief structures and analyses of the underlying photo-thermal processes indicate that depending on the beam intensity and writing speed the formation mechanisms of the surface patterns are mainly based on photoexpansion caused by thermoelastic deformation, mass flow out of the region of the highest local intensity in the centre of the exposing laser beam resulting from an induced surface tension gradient, and decomposition/vaporization processes generated by the local heating due to absorption of the laser light. Examples of written periodic pattern arrays demonstrate that direct laser writing is a very promising method for the fabrication of surface relief structures into ternary chalcogenide thin films. (paper)

  18. Pinning down high-performance Cu-chalcogenides as thin-film solar cell absorbers: A successive screening approach.

    Science.gov (United States)

    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. PMID:27208964

  19. Pinning down high-performance Cu-chalcogenides as thin-film solar cell absorbers: A successive screening approach

    Science.gov (United States)

    Zhang, Yubo; Wang, Youwei; Zhang, Jiawei; Xi, Lili; Zhang, Peihong; Zhang, Wenqing

    2016-05-01

    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.

  20. Mid-infrared supercontinuum generation spanning more than 11 μm in a chalcogenide step-index fiber

    DEFF Research Database (Denmark)

    Petersen, Christian Rosenberg; Møller, Uffe Visbech; Kubat, Irnis;

    2015-01-01

    Supercontinuum generation covering an ultra-broad spectrum from 1.5-11.7μm and 1.4-13.3μm is experimentally demonstrated by pumping an 85mm chalcogenide step-index fiber with 100fs pulses at a wavelength of 4.5μm and 6.3μm, respectively.......Supercontinuum generation covering an ultra-broad spectrum from 1.5-11.7μm and 1.4-13.3μm is experimentally demonstrated by pumping an 85mm chalcogenide step-index fiber with 100fs pulses at a wavelength of 4.5μm and 6.3μm, respectively....

  1. A Tapered Chalcogenide Microstructured Optical Fiber for Mid-IR Parabolic Pulse Generation: Design and Performance Study

    OpenAIRE

    Barh, Ajanta; Ghosh, S.; Varshney, Ravi K.; Pal, Bishnu P.

    2013-01-01

    This paper presents a theoretical design of chalcogenide glass based tapered microstructured optical fiber (MOF) to generate high power parabolic pulses (PPs) at the mid-IR wavelength (~ 2 {\\mu}m). We optimize fiber cross-section by the multipole method and studied pulse evolution by well known Symmetrized Split-Step Fourier Method. Our numerical investigation reveals the possibility of highly efficient PP generation within a very short length (~ 18 cm) of this MOF for a Gaussian input pulse ...

  2. A Self-Templating Scheme for the Synthesis of Nanostructured Transition Metal Chalcogenide Electrodes for Capacitive Energy Storage

    KAUST Repository

    Xia, Chuan

    2015-06-11

    Due to their unique structural features including well-defined interior voids, low density, low coefficients of thermal expansion, large surface area and surface permeability, hollow micro/nanostructured transition metal sulfides with high conductivity have been investigated as new class of electrode materials for pseudocapacitor applications. Herein, we report a novel self-templating strategy to fabricate well-defined single and double-shell NiCo2S4 hollow spheres, as a promising electrode material for pseudocapacitors. The surfaces of the NiCo2S4 hollow spheres consist of self-assembled 2D mesoporous nanosheets. This unique morphology results in a high specific capacitance (1257 F g-1 at 2 A g-1), remarkable rate performance (76.4% retention of initial capacitance from 2 A g-1 to 60 A g-1) and exceptional reversibility with a cycling efficiency of 93.8% and 87% after 10,000 and 20,000 cycles, respectively, at a high current density of 10 A g-1. The cycling stability of our ternary chalcogenides is comparable to carbonaceous electrode materials, but with much higher specific capacitance (higher than any previously reported ternary chalcogenide), suggesting that these unique chalcogenide structures have potential application in next-generation commercial pseudocapacitors.

  3. Designing mid-wave infrared (MWIR) thermo-optic coefficient (dn/dT) in chalcogenide glasses

    Science.gov (United States)

    Gleason, Benn; Sisken, Laura; Smith, Charmayne; Richardson, Kathleen

    2016-05-01

    Seventeen infrared-transmitting GeAsSe chalcogenide glasses were fabricated to determine the role of chemistry and structure on mid-wave infrared (MWIR) optical properties. The refractive index and thermoptic coefficients of samples were measured at λ = 4.515 μm using an IR-modified Metricon prism coupler, located at University of Central Florida. Thermo-optic coefficient (dn/dT) values were shown to range from approximately -40 ppm/°C to +65 ppm/°C, and refractive index was shown to vary between approximately 2.5000 and 2.8000. Trends in refractive index and dn/dT were found to be related to the atomic structures present within the glassy network, as opposed to the atomic percentage of any individual constituent. A linear correlation was found between the quantity (n-3•dn/dT) and the coefficient of thermal expansion (CTE) of the glass, suggesting the ability to compositionally design chalcogenide glass compositions with zero dn/dT, regardless of refractive index or dispersion performance. The tunability of these novel glasses offer increased thermal and mechanical stability as compared to the current commercial zero dn/dT options such as AMTIR-5 from Amorphous Materials Inc. For IR imaging systems designed to achieve passive athermalization, utilizing chalcogenide glasses with their tunable ranges of dn/dT (including zero) can be key to addressing system size, weight, and power (SWaP) limitations.

  4. Synthesis of metals chalcogenides nano-particles from H2X (X=S, Se, Te) produced electrochemically

    International Nuclear Information System (INIS)

    In this work, an electrochemical method to produce H2X (X=S, Se, Te) hydrides in a controlled way (without being able to store them) and to transfer them directly in the synthesis reactor has been perfected. By this method, the use of H2Te has been possible. The method uses the reduction of the elementary chalcogenide in acid medium. The Te being conductor, it can be directly used as electrode, on the other hand S and Se are insulators. Nevertheless, graphite-S or Se conducing composite electrodes can also be used. When the electrolyte composition (pH, salts presence) is well adjusted, the essential of the cathodic current is consumed by the chalcogenide reduction (low evolution of H2) with faradic yields of about 100% for H2S and H2Se and 40% for HeTe. The use of H2X allows the synthesis of nano-particles of metals chalcogenides directly by reaction with dissolved metallic salts in aqueous or organic medium and precipitation. Thus it has been possible to prepare all the CdX compounds under the form of nano-particles of diameter between 3 and 5 nm by bubbling of the gaseous hydrides in aqueous acetate solutions of Cd. In producing concomitantly H2S and H2Se, nano-particles of solid solutions CdSxSe1-x have been synthesized too. (O.M.)

  5. High power broadband mid-infrared supercontinuum fiber laser using a novel chalcogenide AsSe2 photonic crystal fiber

    Science.gov (United States)

    Diouf, Mbaye; Ben Salem, Amine; Cherif, Rim; Wague, Ahmadou; Zghal, Mourad

    2016-05-01

    A high power supercontinuum (SC) based on a new type of chalcogenide AsSe2 material for broadband mid-infrared light source is numerically reported. Ultra-broadband coherent mid-IR SC generation with more than 3 octave-spanning from 1.7 to 14 μm in a novel design of chalcogenide AsSe2 photonic crystal fiber (PCF) is demonstrated. To the best of our knowledge and aiming to properly model the nonlinear propagation, an accurate fit of the Raman response function and the corresponding Raman gain of the novel AsSe2 chalcogenide glass are proposed numerically for the first time. The obtained SC is generated by pumping at 3.9 μm in the anomalous dispersion regime in only 8 mm long fiber. Our study shows that the initially generated SC from 150 fs pulse duration with 8.8 kW peak power exhibits high power proportion of more than 80% for wavelengths beyond 3 μm which is very promising for designing high power SC fiber laser sources in the mid-IR atmospheric windows and the molecular fingerprint region.

  6. Interfacial band bending in Au-tipped Cd-chalcogenides hybrid nanostructures

    Science.gov (United States)

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

    2015-12-01

    The interfacial electronic structure of Au-tipped CdX (X = S, Se and Te) hybrid nanostructures (HNSs) have been studied by UHV scanning tunneling spectroscopy (STS) at room temperature. Au-tipped CdX (X = S, Se and Te) HNSs were synthesized by phase transfer chemical methods. The dimensions were determined by the scanning tunneling microscope (STM), the high resolution transmission electron microscope (HRTEM) and the optical absorption. The measured dimensions using these techniques are consistent, giving Au tip average size within the range of [2.5, 3.5] nm and Cd-chalcogenides quantum dots (QDs) nanoparticles (NPs) average size within the range of [3.5, 4] nm. The STS at the interface of Au-tipped CdS and CdSe HNSs detects a downward band bending towards the interface ∼0.25 ± 0.01 eV and 0.18 ± 0.03 eV respectively, indicating an electron accumulation at these interfaces. However, an upward band bending towards the interface of ∼0.78 ± 0.01 eV is measured by the STS at the interface of Au-tipped CdTe HNS, indicating electron depletion at the interface. The band bending values were also confirmed using the corresponding calculated models of the energy band diagrams. These different behaviors were also observed in the UV-vis absorption of Au-tipped CdS and CdSe HNSs, which shows exciton bleaching features, but an exciton increasing feature is observed in the case of Au-tipped CdTe HNS. These later results are explained as a result of the presence of electron accumulation at the interface of Au-tipped CdS and CdSe HNSs, and also an electron depletion at the interface of Au-tipped CdTe HNS. Such determinations of the interfacial band bending in Au-tipped Cd-chalcogenides HNSs have significant consequences on the charge separation efficiency and the photo-response behavior. Furthermore, the presence of these bands has a direct impact in the field of applying plasmonics for improved photovoltaic solarcells.

  7. Molecular structure and intermediate phases in group-V binary chalcogenide glasses

    Science.gov (United States)

    Georgiev, Daniel Georgiev

    Chalcogenide glasses offer unique opportunities for basic science and technological applications. The physical properties of such network-forming glasses, including the glass-forming tendency, are intimately connected to global connectivity of their backbones. In particular, the elastic behavior of glasses leads to the existence of three distinct phases that appears to be generic in network forming systems. Weakly cross-linked networks are mechanically soft and form floppy phases. Optimally cross-linked networks lead to stress-free or self-organized networks, and are identified with intermediate phases. Strongly cross-linked networks are mechanically stiff and usually form part of stressed-rigid phases. The floppy-intermediate and stressed-rigid classification of the group V chalcogenides is recognized in this work for the first time. The glass systems examined include P-Se, As-Se, and As-S. Thermally reversing windows (glass compositions wherein Tg become almost completely reversing) are observed in the three binary glass systems using temperature-Modulated Differential Scanning Calorimetry (MDSC), and are identified with the opening of (non-mean-field) intermediate phases . The molecular structure of these glasses is studied by Raman scattering, MDSC and 31P NMR, and the local structures responsible for intermediate phases are identified with assistance from constraint counting procedures. Raman scattering and Nuclear Magnetic Resonance (NMR) results on P-Se glasses provide compelling evidence for existence of four-fold coordinated phosphorous species that are bonded to three bridging and one terminal selenium, Se = P(Se1/2)3. The structure results provide a basis to quantitatively understand compositional trends in Tg in the stochastic agglomeration limit. The existence of analog four-fold coordinated As species is suggested by MDSC experiments on As-Se glasses. Our experimental results also show that stressed-rigid phases in the examined glasses are usually

  8. Surface functionalization of two-dimensional metal chalcogenides by Lewis acid–base chemistry

    Science.gov (United States)

    Lei, Sidong; Wang, Xifan; Li, Bo; Kang, Jiahao; He, Yongmin; George, Antony; Ge, Liehui; Gong, Yongji; Dong, Pei; Jin, Zehua; Brunetto, Gustavo; Chen, Weibing; Lin, Zuan-Tao; Baines, Robert; Galvão, Douglas S.; Lou, Jun; Barrera, Enrique; Banerjee, Kaustav; Vajtai, Robert; Ajayan, Pulickel

    2016-05-01

    Precise control of the electronic surface states of two-dimensional (2D) materials could improve their versatility and widen their applicability in electronics and sensing. To this end, chemical surface functionalization has been used to adjust the electronic properties of 2D materials. So far, however, chemical functionalization has relied on lattice defects and physisorption methods that inevitably modify the topological characteristics of the atomic layers. Here we make use of the lone pair electrons found in most of 2D metal chalcogenides and report a functionalization method via a Lewis acid–base reaction that does not alter the host structure. Atomic layers of n-type InSe react with Ti4+ to form planar p-type [Ti4+n(InSe)] coordination complexes. Using this strategy, we fabricate planar p–n junctions on 2D InSe with improved rectification and photovoltaic properties, without requiring heterostructure growth procedures or device fabrication processes. We also show that this functionalization approach works with other Lewis acids (such as B3+, Al3+ and Sn4+) and can be applied to other 2D materials (for example MoS2, MoSe2). Finally, we show that it is possible to use Lewis acid–base chemistry as a bridge to connect molecules to 2D atomic layers and fabricate a proof-of-principle dye-sensitized photosensing device.

  9. Surface functionalization of two-dimensional metal chalcogenides by Lewis acid-base chemistry.

    Science.gov (United States)

    Lei, Sidong; Wang, Xifan; Li, Bo; Kang, Jiahao; He, Yongmin; George, Antony; Ge, Liehui; Gong, Yongji; Dong, Pei; Jin, Zehua; Brunetto, Gustavo; Chen, Weibing; Lin, Zuan-Tao; Baines, Robert; Galvão, Douglas S; Lou, Jun; Barrera, Enrique; Banerjee, Kaustav; Vajtai, Robert; Ajayan, Pulickel

    2016-05-01

    Precise control of the electronic surface states of two-dimensional (2D) materials could improve their versatility and widen their applicability in electronics and sensing. To this end, chemical surface functionalization has been used to adjust the electronic properties of 2D materials. So far, however, chemical functionalization has relied on lattice defects and physisorption methods that inevitably modify the topological characteristics of the atomic layers. Here we make use of the lone pair electrons found in most of 2D metal chalcogenides and report a functionalization method via a Lewis acid-base reaction that does not alter the host structure. Atomic layers of n-type InSe react with Ti(4+) to form planar p-type [Ti(4+)n(InSe)] coordination complexes. Using this strategy, we fabricate planar p-n junctions on 2D InSe with improved rectification and photovoltaic properties, without requiring heterostructure growth procedures or device fabrication processes. We also show that this functionalization approach works with other Lewis acids (such as B(3+), Al(3+) and Sn(4+)) and can be applied to other 2D materials (for example MoS2, MoSe2). Finally, we show that it is possible to use Lewis acid-base chemistry as a bridge to connect molecules to 2D atomic layers and fabricate a proof-of-principle dye-sensitized photosensing device. PMID:26828848

  10. High pressure study of structural and electronic properties of calcium chalcogenides

    International Nuclear Information System (INIS)

    The structural and electronic properties of calcium chalcogenides CaX (X = S,Se,Te) under high pressure have been investigated using the full potential linearized augmented plane wave method within density functional theory. We used both the local density approximation and the generalized gradient approximation (GGA) that is based on exchange-correlation energy optimization for calculating the total energy. Moreover, the Engel-Vosko GGA formalism is applied so as to optimize the corresponding potential for band structure calculations. The equilibrium lattice constant for CaX compounds agrees well with the experimental results. The pressures at which these compounds undergo a structural phase transition from NaCl-type to CsCl-type were calculated. A numerical first-principles calculation of the elastic constants was used to calculate C11, C12 and C44. The energy band gaps at ambient conditions in the NaCl-type structure and the volume dependence of band gaps in the CsCl-type structure up to the band overlap metallization were investigated. Besides this, the nature of the chemical bond in these compounds was analysed in terms of electronic charge density

  11. High-pressure and temperature-induced structural, elastic, and thermodynamical properties of strontium chalcogenides

    Science.gov (United States)

    Varshney, Dinesh; Jain, S.; Shriya, S.; Khenata, R.

    2016-09-01

    Pressure- and temperature-dependent mechanical, elastic, and thermodynamical properties of rock salt to CsCl structures in semiconducting Sr X ( X = O, S, Se, and Te) chalcogenides are presented based on model interatomic interaction potential with emphasis on charge transfer interactions, covalency effect, and zero point energy effects apart from long-range Coulomb, short-range overlap repulsion extended and van der Waals interactions. The developed potential with non-central forces validates the Cauchy discrepancy among elastic constants. The volume collapse ( V P/ V 0) in terms of compressions in Sr X at higher pressure indicates the mechanical stiffening of lattice. The expansion of Sr X lattice is inferred from steep increase in V T/ V 0 and is attributed to thermal softening of Sr X lattice. We also present the results for the temperature-dependent behaviors of hardness, heat capacity, and thermal expansion coefficient. From the Pugh's ratio (ϕ = B T /G H), the Poisson's ratio ( ν) and the Cauchy's pressure ( C 12- C 44), we classify SrO as ductile but SrS, SrSe, and SrTe are brittle material. To our knowledge these are the first quantitative theoretical prediction of the pressure and temperature dependence of mechanical stiffening, thermally softening, and brittle nature of Sr X ( X = O, S, Se, and Te) and still await experimental confirmations.

  12. Infrared waveguide fabrications with an E-beam evaporated chalcogenide glass film

    KAUST Repository

    Yang, Xiaoming

    2014-12-12

    Chalcogenide glasses have a variety of unique optical properties due to the intrinsic structural flexibility and bonds metastability. They are desirable materials for many applications, such as infrared communication sensors, holographic grating, optical imaging, and ultrafast nonlinear optic devices. Here, we introduce a novel electron-beam evaporation process to deposit the good quality arsenic trisulfide (As2S3) films and then the As2S3 films were used to fabricate the As2S3 waveguides with three approaches. The first method is photoresist lift-off. Because of the restriction of thermal budget of photoresist, the As2S3 film must be deposited at the room temperature. The second one is the silicon dioxide lift-off process on sapphire substrates, in which the As2S3 film could be evaporated at a high temperature (>180 °C) for better film quality. The third one is the plasma etching process with a metal protective thin layer in the pattern development process.

  13. Optical properties and local structure of Dy3+-doped chalcogenide and chalcohalide glasses

    Institute of Scientific and Technical Information of China (English)

    TANG Gao; YANG Zhiyong; LUO Lan; CHEN Wei

    2008-01-01

    Dy3+-doped Ge-Ga-Se chalcogenide glasses and GeSe2-Ga2Se3-CsI chalcohalide glasses were prepared. The absorption, emission properties, and local structure of the glasses were investigated. When excited at 808 nm diode laser, intense 1.32 and 1.55 μm near-infrared luminescence were observed with full width at half maximum (FWHM) of about 90 and 50 rim, respectively. The lifetime of the 1.32 μm emission varied due to changes in the local structure surrounding Dy3+ ions. The longest lifetime was over 2.5 ms, and the value was signifi-cantly higher than that in other Dy3+-doped glasses. Some other spectroscopic parameters were calculated by using Judd-Ofelt theory. Meanwhile, Ge-Ga-Se and GeSe2-Ga2Se3-CsI glasses showed good infrared transmittance. As a result, Dy3+-doped Ge-Ga-Se and GeSe2-Ga2Se3-CsI glasses were believed to be useful hosts for 1.3 μm optical fiber amplifier.

  14. Non-Newtonian flow of an ultralow-melting chalcogenide liquid in strongly confined geometry

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Siyuan; Jain, Chhavi; Wondraczek, Katrin; Kobelke, Jens [Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena (Germany); Wondraczek, Lothar [Otto Schott Institute of Material Research (OSIM), Friedrich Schiller University Jena, Fraunhoferstr. 6, 07743 Jena (Germany); Troles, Johann; Caillaud, Celine [Université de Rennes I, Equipe Verres et Céramiques, UMR 6226 Sciences Chimiques de Rennes, Campus de Beaulieu, 35042 Rennes (France); Schmidt, Markus A., E-mail: markus.schmidt@ipht-jena.de [Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena (Germany); Otto Schott Institute of Material Research (OSIM), Friedrich Schiller University Jena, Fraunhoferstr. 6, 07743 Jena (Germany)

    2015-05-18

    The flow of high-viscosity liquids inside micrometer-size holes can be substantially different from the flow in the bulk, non-confined state of the same liquid. Such non-Newtonian behavior can be employed to generate structural anisotropy in the frozen-in liquid, i.e., in the glassy state. Here, we report on the observation of non-Newtonian flow of an ultralow melting chalcogenide glass inside a silica microcapillary, leading to a strong deviation of the shear viscosity from its value in the bulk material. In particular, we experimentally show that the viscosity is radius-dependent, which is a clear indication that the microscopic rearrangement of the glass network needs to be considered if the lateral confinement falls below a certain limit. The experiments have been conducted using pressure-assisted melt filling, which provides access to the rheological properties of high-viscosity melt flow under previously inaccessible experimental conditions. The resulting flow-induced structural anisotropy can pave the way towards integration of anisotropic glasses inside hybrid photonic waveguides.

  15. Thermal behavior in Se-Te chalcogenide system: Interplay of thermodynamics and kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Svoboda, Roman, E-mail: roman.svoboda@upce.cz; Málek, Jiří [Faculty of Chemical Technology, Department of Physical Chemistry, University of Pardubice, Studentska 573, 532 10 Pardubice (Czech Republic)

    2014-12-14

    Heat capacity measurements were performed for Se, Se{sub 90}Te{sub 10}, Se{sub 80}Te{sub 20}, and Se{sub 70}Te{sub 30} materials in the 230–630 K temperature range. Both glassy and crystalline C{sub p} dependences were found to be identical within the experimental error. The compositional dependence of the N-type undercooled liquid C{sub p} evolution was explained on the basis of free-volume theory; vibrational and chemical contributions to heat capacity were found to be roughly similar for all Se-Te compositions. The thermal behavior in the Se-Te chalcogenide system was thoroughly studied: glass transition, cold crystallization, and melting were investigated in dependence on composition and various experimental conditions (heating rate, particle size, and pre-nucleation period). The kinetics of the structural relaxation and crystallization processes are described in terms of the Tool-Narayanaswamy-Moynihan and Johnson-Mehl-Avrami models. The complexity of these processes is thoroughly discussed with regard to the compositionally determined changes of molecular structures. The discussion is conducted in terms of the mutual interplay between the thermodynamics and kinetics in this system.

  16. Thermal behavior in Se-Te chalcogenide system: interplay of thermodynamics and kinetics.

    Science.gov (United States)

    Svoboda, Roman; Málek, Jiří

    2014-12-14

    Heat capacity measurements were performed for Se, Se90Te10, Se80Te20, and Se70Te30 materials in the 230-630 K temperature range. Both glassy and crystalline Cp dependences were found to be identical within the experimental error. The compositional dependence of the N-type undercooled liquid Cp evolution was explained on the basis of free-volume theory; vibrational and chemical contributions to heat capacity were found to be roughly similar for all Se-Te compositions. The thermal behavior in the Se-Te chalcogenide system was thoroughly studied: glass transition, cold crystallization, and melting were investigated in dependence on composition and various experimental conditions (heating rate, particle size, and pre-nucleation period). The kinetics of the structural relaxation and crystallization processes are described in terms of the Tool-Narayanaswamy-Moynihan and Johnson-Mehl-Avrami models. The complexity of these processes is thoroughly discussed with regard to the compositionally determined changes of molecular structures. The discussion is conducted in terms of the mutual interplay between the thermodynamics and kinetics in this system. PMID:25494760

  17. Charge transport and mobility engineering in two-dimensional transition metal chalcogenide semiconductors.

    Science.gov (United States)

    Li, Song-Lin; Tsukagoshi, Kazuhito; Orgiu, Emanuele; Samorì, Paolo

    2016-01-01

    Two-dimensional (2D) van der Waals semiconductors represent the thinnest, air stable semiconducting materials known. Their unique optical, electronic and mechanical properties hold great potential for harnessing them as key components in novel applications for electronics and optoelectronics. However, the charge transport behavior in 2D semiconductors is more susceptible to external surroundings (e.g. gaseous adsorbates from air and trapped charges in substrates) and their electronic performance is generally lower than corresponding bulk materials due to the fact that the surface and bulk coincide. In this article, we review recent progress on the charge transport properties and carrier mobility engineering of 2D transition metal chalcogenides, with a particular focus on the markedly high dependence of carrier mobility on thickness. We unveil the origin of this unique thickness dependence and elaborate the devised strategies to master it for carrier mobility optimization. Specifically, physical and chemical methods towards the optimization of the major factors influencing the extrinsic transport such as electrode/semiconductor contacts, interfacial Coulomb impurities and atomic defects are discussed. In particular, the use of ad hoc molecules makes it possible to engineer the interface with the dielectric and heal the vacancies in such materials. By casting fresh light on the theoretical and experimental studies, we provide a guide for improving the electronic performance of 2D semiconductors, with the ultimate goal of achieving technologically viable atomically thin (opto)electronics. PMID:26593874

  18. Evidence for segregation of Te in ``phase-change" thin chalcogenide Ge-Sb-Te films

    Science.gov (United States)

    Cabral, C., Jr.; Krusin-Elbaum, L..; Chen, K. N.; Copel, M.; Bruley, J.; Deline, V. R.

    2007-03-01

    The novel chalcogenide phase-change materials are promising candidates for new technologies such as nonvolatile memories and programmable switches in 3D integration and planar logic. They are typically thin Ge-Sb-Te (GST) films, where a thermally induced amorphous-to-crystalline phase transformation can be fast and reversible, with the corresponding large swing in resistance values between the two stable structural states. Here we report on the structural evolution of GST films during thermal cycling and demonstrate using high-resolution (0.5 nm focused probe STEM) scans that Te segregates to the grain boundaries at fairly low temperatures. We show that diffusion of Te along grain boundaries results in its pileup at the free surface and interaction with Ti in adhesion layers in device- compatible stacks. This is consistent with impeded grain growth and with post-crystallization stress release. This motion may impact the ultimate life-cycle of phase-change based devices and should guide the optimal GST material design.

  19. Two-dimensional topological insulators in group-11 chalcogenide compounds: M2Te (M =Cu ,Ag )

    Science.gov (United States)

    Ma, Yandong; Kou, Liangzhi; Dai, Ying; Heine, Thomas

    2016-06-01

    Two-dimensional (2D) topological insulators (TIs) are recently recognized states of quantum matter that are highly interesting for lower-power-consuming electronic devices owing to their nondissipative transport properties protected from backscattering. So far, only few 2D TIs, suffering from small bulk band gap (family of 2D TIs in group-11 chalcogenide 2D crystals, M2Te (M =Cu ,Ag ) . The nontrivial topological states in C u2Te and A g2Te 2D crystals, identified by topological invariant and edge state calculations, exhibit sizeable bulk gaps of 78 and 150 meV, respectively, suggesting that they are candidates for room-temperature applications. Moreover, strain engineering leads to effective control of the nontrivial gaps of C u2Te and A g2Te , and a topological phase transition can be realized in C u2Te , while the nontrivial phase in A g2Te is stable against strain. Their dynamic and thermal stabilities are further confirmed by employing phonon calculations and ab initio molecular dynamic simulations.

  20. Elucidating the magnetic and superconducting phases in the alkali metal intercalated iron chalcogenides

    Science.gov (United States)

    Wang, Meng; Yi, Ming; Tian, Wei; Bourret-Courchesne, Edith; Birgeneau, Robert J.

    2016-02-01

    The complex interdigitated phases have greatly frustrated attempts to document the basic features of the superconductivity in the alkali metal intercalated iron chalcogenides. Here, using elastic neutron scattering, energy-dispersive x-ray spectroscopy, and resistivity measurements, we elucidate the relations of these phases in RbxFeySe2 -zSz . We find (i) the iron content is crucial in stabilizing the stripe antiferromagnetic (AF) phase with rhombic iron vacancy order (y ≈1.5 ) , the block AF phase with √{5 }×√{5 } iron vacancy order (y ≈1.6 ) , and the iron vacancy-free phase (y ≈2 ) ; and (ii) the iron vacancy-free superconducting phase (z =0 ) evolves into an iron vacancy-free metallic phase with sulfur substitution (z >1.5 ) due to the progressive decrease of the electronic correlation strength. Both the stripe AF phase and the block AF phase are Mott insulators. The iron-rich compounds (y >1.6 ) undergo a first order transition from an iron vacancy disordered phase at high temperatures into the √{5 }×√{5 } iron vacancy ordered phase and the iron vacancy-free phase below Ts. Our data demonstrate that there are miscibility gaps between these three phases. The existence of the miscibility gaps in the iron content is a key to understanding the relationship between these complicated phases.

  1. Molybdenum-Bismuth Bimetallic Chalcogenide Nanosheets for Highly Efficient Electrocatalytic Reduction of Carbon Dioxide to Methanol.

    Science.gov (United States)

    Sun, Xiaofu; Zhu, Qinggong; Kang, Xinchen; Liu, Huizhen; Qian, Qingli; Zhang, Zhaofu; Han, Buxing

    2016-06-01

    Methanol is a very useful platform molecule and liquid fuel. Electrocatalytic reduction of CO2 to methanol is a promising route, which currently suffers from low efficiency and poor selectivity. Herein we report the first work to use a Mo-Bi bimetallic chalcogenide (BMC) as an electrocatalyst for CO2 reduction. By using the Mo-Bi BMC on carbon paper as the electrode and 1-butyl-3-methylimidazolium tetrafluoroborate in MeCN as the electrolyte, the Faradaic efficiency of methanol could reach 71.2 % with a current density of 12.1 mA cm(-2) , which is much higher than the best result reported to date. The superior performance of the electrode resulted from the excellent synergistic effect of Mo and Bi for producing methanol. The reaction mechanism was proposed and the reason for the synergistic effect of Mo and Bi was discussed on the basis of some control experiments. This work opens a way to produce methanol efficiently by electrochemical reduction of CO2 . PMID:27098284

  2. Spin-liquid polymorphism in an underdoped iron-chalcogenide superconductor

    Science.gov (United States)

    Zaliznyak, Igor; Savici, Andrei; Lumsden, Mark; Tsvelik, Alexei; Hu, Rongwei; Petrovic, Cedomir

    We report neutron scattering measurements which reveal spin-liquid polymorphism in an ``11'' iron chalcogenide superconductor. It occurs when a poorly metallic magnetic state of FeTe is driven toward superconductivity by substitution of a small amount of tellurium with isoelectronic sulfur. We observe a liquid-like magnetic response, which is described by the coexistence of two disordered magnetic phases with different local structures whose relative abundance depends on temperature. One is the ferromagnetic (FM) plaquette phase observed in undoped, nonsuperconducting FeTe, which preserves the C4 symmetry of the underlying square lattice and is favored at high temperatures, whereas the other is the antiferromagnetic plaquette phase with broken C4 symmetry, which emerges with doping and is predominant at low temperatures. These findings suggest the coexistence of and competition between two distinct liquid states, and a liquid-liquid phase transformation between these states, in the electronic spin system of FeTe1-x(S,Se)x. Our results shed light on many recent experimental data in unconventional superconductors. The phase with lower, C2 local symmetry, whose emergence precedes superconductivity, naturally accounts for a propensity to electronic nematic states. Work at BNL is supported by the Office of Basic Energy Sciences, US DOE, under Contract DE-SC00112704.

  3. Large and Ultrafast Third-Order Nonlinear Optical Properties of Ge-S Based Chalcogenide Glasses

    Institute of Scientific and Technical Information of China (English)

    CHU Sai-Sai; WANG Shu-Feng; TAO Hai-Zheng; WANG Zhen-Wei; YANG Hong; LIN Chang-Gui; GONG Qi-Huang; ZHAO Xiu-Jian

    2007-01-01

    We report ultrafast third-order nonlinear optical (NLO) properties of several chalcogenide glasses GeSx (x = 1.8,2.0, 2.5) measured by femtosecond time-resolved optical Kerr gate technique at 820nm. The third-order nonlinear susceptibility of GeS1.8 glass is determined to be as large as 1.41 × 10-12 esu, which is the maximum value of the third order nonlinear susceptibility X(3) for the three compositions investigated. The symmetric Gauss profiles of optical Kerr signals reveal the nature of ultrafast nonlinear response of these samples, which are originated from the ultrafast polarization of the electron clouds. By detailed microstructural analysis of these glasses based on the chain-crossing model (CCM) and the random-covalent-network model (RCNM), it can be concluded that X(3) value of GeSx glasses can be enhanced greatly by S-S covalent bonds or S3Ge-GeS3 ethane-like units.

  4. Integral-equation approach to medium-range order in molten and glassy chalcogenides

    International Nuclear Information System (INIS)

    The first sharp diffraction peak (FSDP), a signature of medium-range order in molten and vitreous chalcogenides, is investigated using the integral-equation method. A variety of interatomic potentials, including uncharged and charged hard spheres, and realistic two-body interactions, are used in this study. The two-body potential consists of steric repulsions, Coulomb interactions due to charge-transfer effects, and the effects of electronic polarizability of ions. GeSe2 is treated as a specific example. The FSDP is observed in both the charged-hard-sphere and the realistic two-body interaction models. In both models steric and charge-transfer effects are found to give rise to Ge(Se1/2)4 tetrahedra whose packing determines the medium-range order and the attendant FSDP. From the charge-charge structure factor it is found that the FSDP arises from spatial correlations where charge neutrality prevails. The nature of the medium-range correlation is elucidated through the temperature and density dependence of the FSDP and the thermal expansion determined from the shifts of the peaks in the static structure factor. We have also studied the effects of the potential parameters on the position of the FSDP. The results of the hypernetted-chain theory are compared with the molecular-dynamics results

  5. Deposition of metal chalcogenide thin films by successive ionic layer adsorption and reaction (SILAR) method

    Indian Academy of Sciences (India)

    H M Pathan; C D Lokhande

    2004-04-01

    During last three decades, successive ionic layer adsorption and reaction (SILAR) method, has emerged as one of the solution methods to deposit a variety of compound materials in thin film form. The SILAR method is inexpensive, simple and convenient for large area deposition. A variety of substrates such as insulators, semiconductors, metals and temperature sensitive substrates (like polyester) can be used since the deposition is carried out at or near to room temperature. As a low temperature process, it also avoids oxidation and corrosion of the substrate. The prime requisite for obtaining good quality thin film is the optimization of preparative provisos viz. concentration of the precursors, nature of complexing agent, pH of the precursor solutions and adsorption, reaction and rinsing time durations etc. In the present review article, we have described in detail, successive ionic layer adsorption and reaction (SILAR) method of metal chalcogenide thin films. An extensive survey of thin film materials prepared during past years is made to demonstrate the versatility of SILAR method. Their preparative parameters and structural, optical, electrical properties etc are described. Theoretical background necessary for the SILAR method is also discussed.

  6. Superior Electrical Conductivity in Hydrogenated Layered Ternary Chalcogenide Nanosheets for Flexible All-Solid-State Supercapacitors.

    Science.gov (United States)

    Hu, Xin; Shao, Wei; Hang, Xudong; Zhang, Xiaodong; Zhu, Wenguang; Xie, Yi

    2016-05-01

    As the properties of ultrathin two-dimensional (2D) crystals are strongly related to their electronic structures, more and more attempts were carried out to tune their electronic structures to meet the high standards for the construction of next-generation smart electronics. Herein, for the first time, we show that the conductive nature of layered ternary chalcogenide with formula of Cu2 WS4 can be switched from semiconducting to metallic by hydrogen incorporation, accompanied by a high increase in electrical conductivity. In detail, the room-temperature electrical conductivity of hydrogenated-Cu2 WS4 nanosheet film was almost 10(10) times higher than that of pristine bulk sample with a value of about 2.9×10(4)  S m(-1) , which is among the best values for conductive 2D nanosheets. In addition, the metallicity in the hydrogenated-Cu2 WS4 is robust and can be retained under high-temperature treatment. The fabricated all-solid-state flexible supercapacitor based on the hydrogenated-Cu2 WS4 nanosheet film shows promising electrochemical performances with capacitance of 583.3 F cm(-3) at a current density of 0.31 A cm(-3) . This work not only offers a prototype material for the study of electronic structure regulation in 2D crystals, but also paves the way in searching for highly conductive electrodes. PMID:27060363

  7. Microorganism mediated biosynthesis of metal chalcogenides; a powerful tool to transform toxic effluents into functional nanomaterials.

    Science.gov (United States)

    Vena, M Paula; Jobbágy, Matías; Bilmes, Sara A

    2016-09-15

    Cadmium contained in soil and water can be taken up by certain crops and aquatic organisms and accumulate in the food-chain, thus removal of Cd from mining or industrial effluents - i.e. Ni-Cd batteries, electroplating, pigments, fertilizers - becomes mandatory for human health. In parallel, there is an increased interest in the production of luminescent Q-dots for applications in bioimaging, sensors and electronic devices, even the present synthesis methods are economic and environmentally costly. An alternative green pathway for producing Metal chalcogenides (MC: CdS, CdSe, CdTe) nanocrystals is based on the metabolic activity of living organisms. Intracellular and extracellular biosynthesis of can be achieved within a biomimetic approach feeding living organisms with Cd precursors providing new routes for combining bioremediation with green routes for producing MC nanoparticles. In this mini-review we present the state-of-the-art of biosynthesis of MC nanoparticles with a critical discussion of parameters involved and protocols. Few existing examples of scaling-up are also discussed. A modular reactor based on microorganisms entrapped in biocompatible mineral matrices - already proven for bioremediation of dissolved dyes - is proposed for combining both Cd-depletion and MC nanoparticle's production. PMID:27157896

  8. Photoelectric properties of defect chalcogenide HgGa2X4 (x=S, Se, Te)

    Science.gov (United States)

    Sharma, Ramesh; Dwivedi, Shalini; Sharma, Yamini

    2016-05-01

    We present results of ab initio study of ordered vacancy compounds of mercury. The electronic structure, charge density, optical and transport properties of the semiconductor family HgGa2X4 (X=S, Se, Te) are calculated using the full potential linearized augmented plane wave method which is based on the density functional theory. A direct bandgap is observed in these compounds, which reduces in the order S>Se>Te. From the density of states it is observed that there is strong hybridization of Hg-d, Ga-d and X-p states. The optical properties show a red shift with increasing size and atomic no. of the chalcogenide atoms. We have also reported the transport properties of mercury thiogallates for the first time. The selenide compound exhibits n-type nature whereas HgGa2S4 and HgGa2Te4 show p-type behavior. The power factor and ZT for the HGS increases at low temperatures, the figure of merit is highest for HgGa2Se4 (1.17) at 19 K.

  9. Mid-infrared supercontinuum generation in a suspended core chalcogenide fiber

    DEFF Research Database (Denmark)

    Møller, Uffe Visbech; Yu, Yi; Gai, Xin;

    control [2], gas sensing [3] and medical diagnostics [4] . We have used a low-loss suspended core As 38 Se 62 fiber with core diameter of 4.5 μ m and a zero - dispersion wavelength of 3.5 μ m to generate mid-infrared supercontinuum by pumping with an optical parametric amplifier delivering 320 fs pulses...... with a peak power of ~5.5 kW at a repetition rate of 21 MHz at different wavelengths from 3.3 to 4.7 μ m . By pumping at 4.4 μ m with a peak power of 5.2 kW coupled to the fiber a supercontinuum spanning from 1.7 to 7.5 μ m with an average output power of 15.6 mW was obtained. Figure 1 shows the...... results obtained when pumping at to 3.5 μ m . We have recently demonstrated a record-breaking supercontinuum spanning from 1. 4-13.3 μ m in a step - index chalcogenide fiber [5]. The results in this presentation are however to our knowledge the first reported supercontinuum generated beyond 6 μm in a...

  10. Fabrication and characterization of a chalcogenide-tellurite composite microstructure fiber with high nonlinearity.

    Science.gov (United States)

    Liao, Meisong; Chaudhari, Chitrarekha; Qin, Guanshi; Yan, Xin; Kito, Chihiro; Suzuki, Takenobu; Ohishi, Yasutake; Matsumoto, Morio; Misumi, Takashi

    2009-11-23

    A highly nonlinear composite fiber, which has a 1.5 microm chalcogenide glass core surrounded by a tellurite glass microstructure cladding, has been fabricated by the method of stack and draw. A tellurite glass capillary containing a As(2)S(3) rod was sealed with negative pressure inside. Then this capillary and other empty capillaries were stacked into a tellurite glass tube, and elongated into a cane. This cane was then inserted into another tellurite glass jacket tube and drawn into the composite microstructure fiber. The fiber has a flattened chromatic dispersion together with a zero dispersion wavelength located in the near infrared range. The propagation losses at 1.55 microm were 18.3 dB/m. The nonlinear coefficient at 1.55 microm was 9.3 m(-1)W(-1). Such a high nonlinear coefficient counteracts the high propagation losses to a large extent. A supercontinuum spectrum of 20-dB bandwidth covering 800-2400 nm was generated by this composite microstructure fiber. PMID:19997402

  11. High-pressure and temperature-induced structural, elastic, and thermodynamical properties of strontium chalcogenides

    Science.gov (United States)

    Varshney, Dinesh; Jain, S.; Shriya, S.; Khenata, R.

    2016-04-01

    Pressure- and temperature-dependent mechanical, elastic, and thermodynamical properties of rock salt to CsCl structures in semiconducting SrX (X = O, S, Se, and Te) chalcogenides are presented based on model interatomic interaction potential with emphasis on charge transfer interactions, covalency effect, and zero point energy effects apart from long-range Coulomb, short-range overlap repulsion extended and van der Waals interactions. The developed potential with non-central forces validates the Cauchy discrepancy among elastic constants. The volume collapse (V P/V 0) in terms of compressions in SrX at higher pressure indicates the mechanical stiffening of lattice. The expansion of SrX lattice is inferred from steep increase in V T/V 0 and is attributed to thermal softening of SrX lattice. We also present the results for the temperature-dependent behaviors of hardness, heat capacity, and thermal expansion coefficient. From the Pugh's ratio (ϕ = B T /G H), the Poisson's ratio (ν) and the Cauchy's pressure (C 12-C 44), we classify SrO as ductile but SrS, SrSe, and SrTe are brittle material. To our knowledge these are the first quantitative theoretical prediction of the pressure and temperature dependence of mechanical stiffening, thermally softening, and brittle nature of SrX (X = O, S, Se, and Te) and still await experimental confirmations.

  12. Ab initio studies of magnetism in the iron chalcogenides FeTe and FeSe

    International Nuclear Information System (INIS)

    The iron chalcogenides FeTe and FeSe belong to the family of iron-based superconductors. We study the magnetism in these compounds in the normal state using the ab initio downfolding scheme developed for strongly correlated electron systems. In deriving ab initio low-energy effective models, we employ the constrained GW method to eliminate the double counting of electron correlations originating from the exchange correlations already taken into account in the density functional theory. By solving the derived ab initio effective models, we reveal that the elimination of the double counting is important in reproducing the bicollinear antiferromagnetic order in FeTe, as is observed in experiments. We also show that the elimination of the double counting induces a unique degeneracy of several magnetic orders in FeSe, which may explain the absence of the magnetic ordering. We discuss the relationship between the degeneracy and the recently found puzzling phenomena in FeSe as well as the magnetic ordering found under pressure. (author)

  13. Polytypic Nanocrystals of Cu-Based Ternary Chalcogenides: Colloidal Synthesis and Photoelectrochemical Properties.

    Science.gov (United States)

    Wu, Liang; Chen, Shi-You; Fan, Feng-Jia; Zhuang, Tao-Tao; Dai, Chen-Min; Yu, Shu-Hong

    2016-05-01

    Heterocrystalline polytype nanostructured semiconductors have been attracting more and more attention in recent years due to their novel structures and special interfaces. Up to now, controlled polytypic nanostructures are mostly realized in II-VI and III-V semiconductors. Herein, we report the synthesis and photoelectrochemical properties of Cu-based ternary I-III-VI2 chalcogenide polytypic nanocrystals, with a focus on polytypic CuInS2 (CIS), CuInSe2 (CISe), and CuIn(S0.5Se0.5)2 alloy nanocrystals. Each obtained polytypic nanocrystal is constructed with a wurtzite hexagonal column and a zinc blende/chalcopyrite cusp, regardless of the S/Se ratio. The growth mechanisms of polytypic CIS and CISe nanocrystals have been studied by time-dependent experiments. The polytypic nanocrystals are solution-deposited on indium-tin oxide glass substrate and used as a photoelectrode, thus showing stable photoelectrochemical activity in aqueous solution. Density functional theory calculation was used to study the electronic structure and the band gap alignment. This versatile synthetic method provides a new route for synthesis of novel polytypic nanostructured semiconductors with unique properties. PMID:27063512

  14. Activity-dependent synaptic plasticity of a chalcogenide electronic synapse for neuromorphic systems.

    Science.gov (United States)

    Li, Yi; Zhong, Yingpeng; Zhang, Jinjian; Xu, Lei; Wang, Qing; Sun, Huajun; Tong, Hao; Cheng, Xiaoming; Miao, Xiangshui

    2014-01-01

    Nanoscale inorganic electronic synapses or synaptic devices, which are capable of emulating the functions of biological synapses of brain neuronal systems, are regarded as the basic building blocks for beyond-Von Neumann computing architecture, combining information storage and processing. Here, we demonstrate a Ag/AgInSbTe/Ag structure for chalcogenide memristor-based electronic synapses. The memristive characteristics with reproducible gradual resistance tuning are utilised to mimic the activity-dependent synaptic plasticity that serves as the basis of memory and learning. Bidirectional long-term Hebbian plasticity modulation is implemented by the coactivity of pre- and postsynaptic spikes, and the sign and degree are affected by assorted factors including the temporal difference, spike rate and voltage. Moreover, synaptic saturation is observed to be an adjustment of Hebbian rules to stabilise the growth of synaptic weights. Our results may contribute to the development of highly functional plastic electronic synapses and the further construction of next-generation parallel neuromorphic computing architecture. PMID:24809396

  15. Ultra-broadband modulation instability gain characteristics in As2S3 and As2Se3 chalcogenide glass photonic crystal fiber

    Science.gov (United States)

    He-Lin, Wang; Bin, Wu; Xiao-Long, Wang

    2016-06-01

    Based on the designed As2Se3 and As2S3 chalcogenide glass photonic crystal fiber (PCF) and the scalar nonlinear Schrödinger equation, the effects of pump power and wavelength on modulation instability (MI) gain are comprehensively studied in the abnormal dispersion regime of chalcogenide glass PCF. Owing to high Raman effect and high nonlinearity, ultra-broadband MI gain is obtained in chalcogenide glass PCF. By choosing the appropriate pump parameter, the MI gain bandwidth reaches 2738 nm for the As2Se3 glass PCF in the abnormal-dispersion region, while it is 1961 nm for the As2S3 glass PCF. Project supported by the National Natural Science Fundation of China (Grant No. 11404286), the Natural Science Fundation of Zhejiang Province, China (Grant No. LY15F050010), and the Scientific Research Foundation of Zhejiang University of Technology, China (Grant No. 1401109012408).

  16. Mid-infrared supercontinuum generation to 12.5μm in large NA chalcogenide step-index fibres pumped at 4.5μm

    DEFF Research Database (Denmark)

    Kubat, Irnis; Agger, Christian; Møller, Uffe Visbech; Seddon, Angela B.; Tang, Zhuoqi; Sujecki, Slawomir; Benson, Trevor M.; Furniss, David; Lamrini, Samir; Scholle, Karsten; Fuhrberg, Peter; Napier, Bruce; Farries, Mark; Ward, Jon; Moselund, Peter M.; Bang, Ole

    2014-01-01

    We present numerical modeling of mid-infrared (MIR) supercontinuum generation (SCG) in dispersion-optimized chalcogenide (CHALC) step-index fibres (SIFs) with exceptionally high numerical aperture (NA) around one, pumped with mode-locked praseodymium-doped (Pr3+) chalcogenide fibre lasers. The 4.......5um laser is assumed to have a repetition rate of 4MHz with 50ps long pulses having a peak power of 4.7kW. A thorough fibre design optimisation was conducted using measured material dispersion (As-Se/Ge-As-Se) and measured fibre loss obtained in fabricated fibre of the same materials. The loss was...

  17. Photoelectrochemical Infiltration of a Conducting Polymer (PEDOT) into Metal-Chalcogenide Decorated TiO2 Nanotube Arrays

    International Nuclear Information System (INIS)

    Graphical abstract: In situ photoelectrosynthesis of nanostructured TiO2/CdX/PEDOT ternary hybrid assemblies was achieved exploiting the semiconductor behavior of both inorganic components. - Highlights: • Concept of light induced electrodeposition of conducting polymers has been extended to TiO2/ metal chalcogenide (CdX) scaffolds. • Interfacial energetics affected the concurrent nucleation and growth of the PEDOT oligomers. • Both collective and selective excitation of the SC components was exploited for the photoelectrochemical polymerization of EDOT and bis-EDOT. • Sensitizer QDs act as seeds for the initial growth of PEDOT. • Parallel optimization of the monomer, irradiation wavelength, and the electrochemical method is indeed necessary. - ABSTRACT: Photoelectrochemical synthesis of TiO2/CdX/PEDOT [X: S, Se; PEDOT = poly(3,4-ethylenedioxythiophene)] ternary hybrids was carried out by exploiting the semiconductor (SC) nature of both the oxide and the chalcogenide component. To this end, TiO2 nanotube arrays were initially electrosynthesized on titanium foils by anodization in fluoride-containing aqueous media. CdS and CdSe quantum dots were subsequently deposited on the nanotubes using successive ionic layer adsorption and reaction (SILAR). The conjugated polymer, PEDOT, was then grafted using photoelectrochemical excitation of the SC matrix and potentiodynamic deposition, to ultimately afford the ternary hybrid architecture. The morphology, structural properties, and chemical composition of these assemblies were evaluated by scanning electron microscopy, diffuse reflectance UV-Vis spectrophotometry, and Raman spectroscopy, while their electroactivity was evaluated by cyclic voltammetry. Photoelectrochemical deposition of the conducting polymer was carried out both through selective excitation of the chalcogenide sensitizer and the collective photoexcitation of the two SC components. Two precursor molecules, namely, EDOT or bis-EDOT were compared and

  18. Evidence of network demixing in GeS2-Ga2S3 chalcogenide glasses: A phase transformation study

    International Nuclear Information System (INIS)

    The information of phase transformation is attained by in situ XRD experiments leading to the knowledge of topological threshold in GeS2-Ga2S3 glasses. The turning point of phase transformation behavior is demonstrated to be glasses containing 14-15 mol% Ga2S3. To interpret it a network demixing model is further improved and proposed for the structure of these ternary or quasi-binary chalcogenide glasses. For the nearest-neighbor coordination environment of glass with a transitional composition of 85.7 mol% (6/7) GeS2.14.3 mol% (1/7) Ga2S3, six-coordinated [S3Ga-X-GaS3] units (X=S or None) are well isolated by the [GeS4] structures, which contributes to the decreasing of precipitation of Ga2S3 crystals in (100-x)GeS2-xGa2S3 (x≤14.3) glasses corresponding to the experimental evidence of the phase transformation behavior. This scenario of intermediate-range structural order, firstly, includes the arrangement of structural units which is consistent with and provides an atomistic explanation of the compositional evolution of phase transformation behavior in these glasses. -- Graphical abstract: Synopsis: network demixing in GeS2-Ga2S3 chalcogenide glasses. Display Omitted Highlights: → Phase transformation in GeS2-Ga2S3 glasses. → Turning point of the phase transformation behavior. → Medium-range order structure of chalcogenide glasses. → Network demixing model for GeS2-Ga2S3 glasses.

  19. Dispersion of the refractive index of a samarium-doped Se95Te5 chalcogenide glassy semiconductor

    International Nuclear Information System (INIS)

    The transmission spectrum of a Se95Te5 chalcogenide glassy semiconductor doped with samarium (0.05, 0.1, 0.25, 0.5, and 1 at %) is studied; the Swanepoel method and the single-oscillator model are used to determine the oscillator energy E0, dispersion energy Ed, optical width of the band gap Eg, and linear (n) and nonlinear (n2) refractive indices. The changes in the values of these parameters as a result of doping are attributed to modification of the local structure and to a change in the concentration of defect states

  20. Experimental demonstration of linearly polarized 2-10  μm supercontinuum generation in a chalcogenide rib waveguide.

    Science.gov (United States)

    Yu, Yi; Gai, Xin; Ma, Pan; Vu, Khu; Yang, Zhiyong; Wang, Rongping; Choi, Duk-Yong; Madden, Steve; Luther-Davies, Barry

    2016-03-01

    This Letter reports the production of a supercontinuum extending from ≈2  μm to >10  μm generated using a chalcogenide buried rib waveguide pumped with 330 femtosecond pulses at 4.184 μm. This is, to the best of our knowledge, the broadest mid-infrared supercontinuum generated in any planar waveguide platform. Because the waveguide is birefringent, quasi-single-mode, and uses an optimized dispersion design, the supercontinuum is linearly polarized with an extinction ratio >100. Dual beam spectrophotometry is performed easily using this source. PMID:26974090

  1. Dimensional Reduction of a Layered Metal Chalcogenide into a 1D Near-IR Direct Band Gap Semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yi-Hsin; Porter, Spencer H.; Goldberger, Joshua E. (OSU)

    2012-07-24

    Reducing the dimensionality of inorganic lattices allows for the creation of new materials that have unique optoelectronic properties. We demonstrate that a layered metal chalcogenide lattice, TiS{sub 2}, can form a dimensionally reduced crystalline one-dimensional hybrid organic/inorganic TiS{sub 2}(ethylenediamine) framework when synthesized from molecular precursors in solution. This solid has strong absorption above 1.70 eV and pronounced emission in the near-IR regime. The energy dependence of the absorption, the near-IR photoluminescence, and electronic band structure calculations confirm that TiS{sub 2}(ethylenediamine) has a direct band gap.

  2. Nano-scale engineering using lead chalcogenide nanocrystals for opto-electronic applications

    Science.gov (United States)

    Xu, Fan

    Colloidal quantum dots (QDs) or nanocrystals of inorganic semiconductors exhibit exceptional optoelectronic properties such as tunable band-gap, high absorption cross-section and narrow emission spectra. This thesis discusses the characterizations and physical properties of lead-chalcogenide nanocrystals, their assembly into more complex nanostructures and applications in solar cells and near-infrared light-emitting devices. In the first part of this work, we demonstrate that the band edge emission of PbS quantum dots can be tuned from the visible to the mid-infrared region through size control, while the self-attachment of PbS nanocrystals can lead to the formation of 1-D nanowires, 2-D quantum dot monolayers and 3-D quantum dot solids. In particular, the assembly of closely-packed quantum dot solids has attracted enormous attention. A series of distinctive optoelectronic properties has been observed, such as superb multiple exciton generation efficiencies, efficient hot-electron transfer and cold-exciton recycling. Since the surfactant determines the quantum dot surface passivation and inter dot electronic coupling, we examine the influence of different cross-linking surfactants on the optoelectronic properties of the quantum dot solids. Then, we discuss the ability to tune the quantum dot band-gap combined with the controllable assembly of lead-chalcogenide quantum dots, which opens new possibilities to engineer the properties of quantum dot solids. The PbS and PbSe quantum dot cascade structures and PbS/PbSe quantum dot heterojunctions are assembled using the layer-by-layer deposition method. We show that exciton funnelling and trap state-bound exciton recycling in the quantum dot cascade structure dramatically enhances the quantum dots photoluminescence. Moreover, we show that both type-I and type-II PbS/PbSe quantum dot heterojunctions can be assembled by carefully choosing the quantum dot sizes. In type-I heterojunctions, the excited electron-hole pairs tend

  3. Electrospray deposition of chalcogenide glass films for gradient refractive index and quantum dot incorporation

    Science.gov (United States)

    Novak, Spencer

    Chalcogenide glasses (ChGs) are well-known for their optical properties, making them ideal candidates for emerging applications of mid-infrared microphotonic devices, such as lab-on-a-chip chemical sensing devices, which currently demand additional flexibility in processing and materials available to realize new device designs. Solution-derived processing of ChG films, initially developed in the 1980s by Chern and Lauks, has consisted mainly of spin-coating and offers unique advantages over the more traditional physical vapor deposition techniques. In the present effort, the nanoparticles of interest are luminescent quantum dots (QDs), which can be used as an on-chip source of light for a planar chemical sensing device. Prior efforts of QD incorporation have exposed limitations of spin-coating of ChG solutions, namely QD aggregation and material waste, along with incompatibility with larger scale manufacturing methods such roll-to-roll processing. This dissertation has evaluated electrospray (ES) as an alternative method of solution-derived chalcogenide glass film deposition. While employed in other materials systems, deposition of optical quality ChG films via electrospray has not been previously attempted, nor have parameters until now, been defined. This study has defined pre-cursor solution chemistry, electrospray jet process parameters required for formation of stable films, annealing protocols and resulting film attributes, yielding important correlations needed to realize high optical quality films. Electrosprayed films attributes were compared to those seen for spin coating and trade-offs in processing route and resulting quality, were identified. Optical properties of importance to device applications were defined, including surface roughness, refractive index, and infrared transmission. The use of a serpentine path of the spray over the substrate was demonstrated to obtain uniform thickness, blanket films, and demonstrates process compatibility with roll

  4. From Exploratory Synthesis to Hard Radiation Detection: Crystal Growth and Characterization of Chalcogenide and Chalcohalide Materials

    Science.gov (United States)

    Nguyen, Sandy Linhsa

    In the first half of this thesis work, exploratory synthesis of materials using mixed polychalcogenide fluxes yielded four quaternary mixed Te/S compounds, with the respective chalcogen atoms residing in different crystallographic sites. Two-dimensional thiotellurite compounds (Ag2TeS3) 2·A2S6 (A = Rb, Cs), containing the trigonal pyramidal [TeS 3]2- unit, were synthesized and characterized. These structures are composed of layers of neutral [Ag2TeS3] alternating with charge-balanced salt layers containing the polysulfide chain [S6]2- and alkali metal ions. Using mixed Te/S polychalcogenide fluxes for compound discovery, we then investigated a new set of layered metal dichalcogenides, Ag2Te(MS2)3 (M = V, Nb) crystallizing in the P-62m space group. Ag2Te(MS2)3 contains layers of [Ag2Te] sandwiched between layers of [MS2] (M = V, Nb). The Ag and, more interestingly, Te atoms are linearly coordinated by S atoms in the [MS2] layers. This linear coordination of the Te atom by S atoms is unprecedented in the literature and stabilized by charge transfer within the [Ag2Te] layers. In the latter half, we report the bulk crystal growth and characterization of Tl-based chalcogenide and chalcohalide materials for hard radiation (X- and gamma-ray) detection, which requires high density, wide band gaps, and high resistivity. Lattice hybridization was applied to identify materials with optimal properties for hard radiation detection, resulting in the chalcohalide compound Tl6SI4. Tl6SI4 exhibits low effective mass of carriers, high resistivity, optimal band gap, and large hardness values. The figure of merit mutau products, (mutau) e = 2.1 x 10-3 cm2V-1 and (mutau)h = 2.3 x 10-5 cm2V -1, are comparable to state-of-the-art commercially used materials. Furthermore, high resolution detection of Ag X-rays by Tl6SI 4 was seen at 22 keV (2.6%). Dimensional reduction was used to identify Tl-based chalcogenide materials Tl2MS3 (M = Ge, Sn). Tl2MS3 show great potential for use as hard

  5. Penternary chalcogenides nanocrystals as catalytic materials for efficient counter electrodes in dye-synthesized solar cells

    Science.gov (United States)

    Özel, Faruk; Sarılmaz, Adem; İstanbullu, Bilal; Aljabour, Abdalaziz; Kuş, Mahmut; Sönmezoğlu, Savaş

    2016-01-01

    The penternary chalcogenides Cu2CoSn(SeS)4 and Cu2ZnSn(SeS)4 were successfully synthesized by hot-injection method, and employed as a catalytic materials for efficient counter electrodes in dye-synthesized solar cells (DSSCs). The structural, compositional, morphological and optical properties of these pentenary semiconductors were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), energy-dispersive spectrometer (EDS) and ultraviolet-visible (UV–Vis) spectroscopy. The Cu2CoSn(SeS)4 and Cu2ZnSn(SeS)4 nanocrystals had a single crystalline, kesterite phase, adequate stoichiometric ratio, 18–25 nm particle sizes which are forming nanospheres, and band gap energy of 1.18 and 1.45 eV, respectively. Furthermore, the electrochemical impedance spectroscopy and cyclic voltammograms indicated that Cu2CoSn(SeS)4 nanocrystals as counter electrodes exhibited better electrocatalytic activity for the reduction of iodine/iodide electrolyte than that of Cu2ZnSn(SeS)4 nanocrystals and conventional platinum (Pt). The photovoltaic results demonstrated that DSSC with a Cu2CoSn(SeS)4 nanocrystals-based counter electrode achieved the best efficiency of 6.47%, which is higher than the same photoanode employing a Cu2ZnSn(SeS)4 nanocrystals (3.18%) and Pt (5.41%) counter electrodes. These promising results highlight the potential application of penternary chalcogen Cu2CoSn(SeS)4 nanocrystals in low-cost, high-efficiency, Pt-free DSSCs. PMID:27380957

  6. Penternary chalcogenides nanocrystals as catalytic materials for efficient counter electrodes in dye-synthesized solar cells

    Science.gov (United States)

    Özel, Faruk; Sarılmaz, Adem; Istanbullu, Bilal; Aljabour, Abdalaziz; Kuş, Mahmut; Sönmezoğlu, Savaş

    2016-07-01

    The penternary chalcogenides Cu2CoSn(SeS)4 and Cu2ZnSn(SeS)4 were successfully synthesized by hot-injection method, and employed as a catalytic materials for efficient counter electrodes in dye-synthesized solar cells (DSSCs). The structural, compositional, morphological and optical properties of these pentenary semiconductors were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), energy-dispersive spectrometer (EDS) and ultraviolet-visible (UV–Vis) spectroscopy. The Cu2CoSn(SeS)4 and Cu2ZnSn(SeS)4 nanocrystals had a single crystalline, kesterite phase, adequate stoichiometric ratio, 18–25 nm particle sizes which are forming nanospheres, and band gap energy of 1.18 and 1.45 eV, respectively. Furthermore, the electrochemical impedance spectroscopy and cyclic voltammograms indicated that Cu2CoSn(SeS)4 nanocrystals as counter electrodes exhibited better electrocatalytic activity for the reduction of iodine/iodide electrolyte than that of Cu2ZnSn(SeS)4 nanocrystals and conventional platinum (Pt). The photovoltaic results demonstrated that DSSC with a Cu2CoSn(SeS)4 nanocrystals-based counter electrode achieved the best efficiency of 6.47%, which is higher than the same photoanode employing a Cu2ZnSn(SeS)4 nanocrystals (3.18%) and Pt (5.41%) counter electrodes. These promising results highlight the potential application of penternary chalcogen Cu2CoSn(SeS)4 nanocrystals in low-cost, high-efficiency, Pt-free DSSCs.

  7. Penternary chalcogenides nanocrystals as catalytic materials for efficient counter electrodes in dye-synthesized solar cells.

    Science.gov (United States)

    Özel, Faruk; Sarılmaz, Adem; İstanbullu, Bilal; Aljabour, Abdalaziz; Kuş, Mahmut; Sönmezoğlu, Savaş

    2016-01-01

    The penternary chalcogenides Cu2CoSn(SeS)4 and Cu2ZnSn(SeS)4 were successfully synthesized by hot-injection method, and employed as a catalytic materials for efficient counter electrodes in dye-synthesized solar cells (DSSCs). The structural, compositional, morphological and optical properties of these pentenary semiconductors were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), energy-dispersive spectrometer (EDS) and ultraviolet-visible (UV-Vis) spectroscopy. The Cu2CoSn(SeS)4 and Cu2ZnSn(SeS)4 nanocrystals had a single crystalline, kesterite phase, adequate stoichiometric ratio, 18-25 nm particle sizes which are forming nanospheres, and band gap energy of 1.18 and 1.45 eV, respectively. Furthermore, the electrochemical impedance spectroscopy and cyclic voltammograms indicated that Cu2CoSn(SeS)4 nanocrystals as counter electrodes exhibited better electrocatalytic activity for the reduction of iodine/iodide electrolyte than that of Cu2ZnSn(SeS)4 nanocrystals and conventional platinum (Pt). The photovoltaic results demonstrated that DSSC with a Cu2CoSn(SeS)4 nanocrystals-based counter electrode achieved the best efficiency of 6.47%, which is higher than the same photoanode employing a Cu2ZnSn(SeS)4 nanocrystals (3.18%) and Pt (5.41%) counter electrodes. These promising results highlight the potential application of penternary chalcogen Cu2CoSn(SeS)4 nanocrystals in low-cost, high-efficiency, Pt-free DSSCs. PMID:27380957

  8. Design and Growth of Novel Compounds for Radiation Sensors: Multinary Chalcogenides

    Science.gov (United States)

    Singh, N. B.; Su, Ching-Hua; Nagaradona, Teja; Arnold, Brad; Choa, Fow-Sen

    2016-01-01

    Increasing threats of radiological weapons have revitalized the researches for low cost large volume ?-ray and neutron ray sensors In the past few years we have designed and grown ternary and quaternary lead and thallium chalcogenides and lead selenoiodides for detectors to meet these challenges. These materials are congruent, can be tailored to enhance the parameters required for radiation sensors. In addition, this class of compounds can be grown by Bridgman method which promises for large volume productions. We have single crystals of several compounds from the melt including Tl3AsSe3, Tl3AsSe3-xSx, TlGaSe2, AgGaGe3Se8, AgxLi1-xAgGaGe3Se8 and PbTlI5-x Sex compounds. Experimental studies indicate that these have very low absorption coefficient, low defect density and can be fabricated in any shape and sizes. These crystals do not require post growth annealing and do not show any second phase precipitates when processed for electrode bonding and other fabrication steps. In this paper we report purification, growth and fabrication of large Tl3AsSe3 (TAS) crystals. We observed that TAS crystals grown by using further purification of as supplied high purity source materials followed by directionally solidified charge showed higher resistivity than previously reported values. TAS also showed constant value as the function of voltage. A low thermal gradient and high purity source material were used to reduce thermal stresses in large crystals. By improving the purification of the as supplied source materials very high quality thallium, selenium and arsenic was achieved for preparing stoichiometric Tl3AsSe3 compound. Low gradient (5cm/day) showed very different morphologies on the surface of the crystals. Electrical resistivity was one order of magnitude higher than previously reported value and it was observed to be constant as the function of frequency.

  9. New chalcogenide glasses in the CdTe–AgI–As2Te3 system

    International Nuclear Information System (INIS)

    Highlights: ► Determination of the glass-forming region in the pseudo-ternary CdTe–AgI–As2Te3 system. ► Characterization of macroscopic properties of the new CdTe–AgI–As2Te3 glasses. ► Characterization of the total conductivity of CdTe–AgI–As2Te3 glasses. ► Comparison between the selenide and telluride equivalent systems. -- Abstract: Chalcogenide glasses in the pseudo-ternary CdTe–AgI–As2Te3 system were synthesized and the glass-forming range was determined. The maximum content of CdTe in this glass system was found to be equal to 15 mol.%. The macroscopic characterizations of samples have consisted in Differential Scanning Calorimetry, density, and X-ray diffraction measurements. The cadmium telluride addition does not generate any significant change in the glass transition temperature but the resistance of binary AgI–As2Te3 glasses towards crystallisation is estimated to be decreasing on the base of ΔT = Tx − Tg parameter. The total electrical conductivity σ was measured by complex impedance spectroscopy. First, the CdTe additions in the (AgI)0.5(As2Te3)0.5 host glass, (CdTe)x(AgI)0.5−x/2(As2Te3)0.5−x/2 lead to a conductivity decrease at x ≤ 0.05. Then, the behaviour is reversed at 0.05 ≤ x ≤ 0.15. The obtained results are discussed by comparison with the equivalent selenide system.

  10. Single-Crystal Electrical Resistivities of Some Ta-Rich Chalcogenides

    Science.gov (United States)

    Ahn, Kyungsoo; Hughbanks, Timothy

    1993-02-01

    Vapor phase transport synthesis of several Ta-rich chalcogenides affords us good single crystals for four-probe measurements of their electrical resistivities. A comparison of the temperature dependent resistivities of Ta2S and Ta3S2 show that the latter compound is a considerably poorer conductor for all temperatures from 15 to 270 K, as predicted in our earlier band structure study of these materials and consistent with the recent work of Nozaki and coworkers. In both cases, resistivities were measured along the direction parallel to the 1x [Ta5Ta] chains that serve as these materials' basic structural building blocks. The compounds Ta9M2S6 (M = Fe, Co, Ni) show normal metallic behavior over the same range of temperatures. A distortion that leads to a doubling of the c-axis length for the Fe and Co containing compounds seems to have no significant effect on the electronic density of states at the Fermi level in either material. In contrast, the compounds Ta11M2Se8 (M = Fe, Co, Ni) exhibit markedly different resistivities as a function of temperature. While Ta11Fe2Se8 and Ta11Ni2Se8 behave much like the structurally similar Ta9M2S6 compounds, the resistivity of Ta11Co2Se8 shows a curiously weak temperature dependence and a high residual value at the lowest temperatures of measurement (15 K). Powder diffraction data for this compound suggests that crystals prepared at low temperature have lower symmetry than the Pnnm space group originally reported.

  11. Compositional-tailoring of optical properties in IR transparent chalcogenide glasses for precision glass molding

    Science.gov (United States)

    Gleason, B.; Wachtel, P.; Musgraves, J. D.; Qiao, A.; Anheier, N.; Richardson, K.

    2013-09-01

    The structural and optical properties of AsSe chalcogenide glass, starting with As40Se60, were studied as a function of Ge or Se additions. These elements provide broad glass forming options when combined with the host matrix to allow for compositional tuning of properties. Optimization of glass composition has been shown to produce bulk glasses with a thermoptic coefficient (dn/dT) equal to zero, as well as a composition which could demonstrate a net zero change in index after precision glass molding (PGM). The bulk glass density, coefficient of thermal expansion (CTE), refractive index, and dn/dT were measured for all bulk compositions, as was the refractive index after PGM. For the bulk glasses examined, both the refractive index (measured at discrete laser wavelengths from 3.4 to10.6 μm) and dn/dT were observed to decrease as the molecular percentage of either Ge or Se is increased. Compared to the starting glass' network, additions of either Ge or Se lead to a deviation from the "optimally constrained" binary glass' average coordination number = 2.4. Additions of Se or Ge serve to decrease or increase the average coordination number (CN) of the glass, respectively, while also changing the network's polarizability. After a representative PGM process, glasses exhibited an "index drop" consistent with that seen for oxide glasses.1 Based on our evaluation, both the Gecontaining and Ge-free tielines show potential for developing unique compositions with either a zero dn/dT for the unmolded, bulk glass, as well as the potential for a glass that demonstrates a net zero "index drop" after molding. Such correlation of glass chemistry, network, physical and optical properties will enable the tailoring of novel compositions suitable for prototyping towards targeted molding behavior and final properties.

  12. Layered Chalcogenides beyond Graphene: from Electronic Structure Evolution to the Spin Transport

    Science.gov (United States)

    Yuan, Hongtao

    2014-03-01

    Recent efforts on graphene-like atomic layer materials, aiming at novel electronic properties and quantum phenomena beyond graphene, have attracted much attention for potential electronics/spintronics applications. Compared to the weak spin-orbit-interaction (SOI) in graphene, metal chalcogenides MX2 have heavy 4d/5d elements with strong atomic SOI, providing a unique way for generating spin polarization based on valleytronics physics. Indeed, such a spin-polarized band structure has been demonstrated theoretically and supported by optical investigations. However, despite these exciting progresses, following two important issues in MX2 community remain elusive: 1. the quantitative band structure of MX2 compounds (where are the valleys -band maxima/minima- locating in the BZ) have not been experimentally confirmed. Especially for those cleaved ultrathin mono- and bi-layer flakes hosting most of recently-reported exotic phenomena at the 2D limit, the direct detection for band dispersion becomes of great importance for valleytronics. 2. Spin transports have seldom been reported even though such a strong SOI system can serve as an ideal platform for the spin polarization and spin transport. In this work, we started from the basic electronic structures of representative MX2, obtained by ARPES, and investigated both the band variation between these compounds and their band evolution from bulk to the monolayer limit. After having a systematic understanding on band structures, we reported a giant Zeeman-type spin-polarization generated and modulated by an external electric field in WSe2 electric-double-layer transistors. The non-magnetic approach for realizing such an intriguing spin splitting not only keeps the system time-reversally invariant but also suggests a new paradigm for manipulating the spin-degrees of freedom of electrons. Acknowledge the support from DoE, BES, Division of MSE under contract DE-AC02-76SF00515.

  13. Microbial manufacture of chalcogenide-based nanoparticles via the reduction of selenite using Veillonella atypica: an in situ EXAFS study

    Science.gov (United States)

    Pearce, Carolyn I.; Coker, Victoria S.; Charnock, John M.; Pattrick, Richard A. D.; Mosselmans, J. Frederick W.; Law, Nicholas; Beveridge, Terry J.; Lloyd, Jonathan R.

    2008-04-01

    The ability of metal-reducing bacteria to produce nanoparticles, and their precursors, can be harnessed for the biological manufacture of fluorescent, semiconducting nanomaterials. The anaerobic bacterium Veillonella atypica can reduce selenium oxyanions to form nanospheres of elemental selenium. These selenium nanospheres are then further reduced by the bacterium to form reactive selenide which could be precipitated with a suitable metal cation to produce nanoscale chalcogenide precipitates, such as zinc selenide, with optical and semiconducting properties. The whole cells used hydrogen as the electron donor for selenite reduction and an enhancement of the reduction rate was observed with the addition of a redox mediator (anthraquinone disulfonic acid). A novel synchrotron-based in situ time-resolved x-ray absorption spectroscopy technique was used, in conjunction with ion chromatography and inductively coupled plasma-atomic emission spectroscopy, to study the mechanisms and kinetics of the microbial reduction of selenite to selenide. The products of this biotransformation were also assessed using electron microscopy, energy-dispersive spectroscopy, x-ray diffraction and fluorescence spectroscopy. This process offers the potential to prepare chalcogenide-based nanocrystals, for application in optoelectronic devices and biological labelling, from more environmentally benign precursors than those used in conventional organometallic synthesis.

  14. Microbial manufacture of chalcogenide-based nanoparticles via the reduction of selenite using Veillonella atypica: an in situ EXAFS study

    International Nuclear Information System (INIS)

    The ability of metal-reducing bacteria to produce nanoparticles, and their precursors, can be harnessed for the biological manufacture of fluorescent, semiconducting nanomaterials. The anaerobic bacterium Veillonella atypica can reduce selenium oxyanions to form nanospheres of elemental selenium. These selenium nanospheres are then further reduced by the bacterium to form reactive selenide which could be precipitated with a suitable metal cation to produce nanoscale chalcogenide precipitates, such as zinc selenide, with optical and semiconducting properties. The whole cells used hydrogen as the electron donor for selenite reduction and an enhancement of the reduction rate was observed with the addition of a redox mediator (anthraquinone disulfonic acid). A novel synchrotron-based in situ time-resolved x-ray absorption spectroscopy technique was used, in conjunction with ion chromatography and inductively coupled plasma-atomic emission spectroscopy, to study the mechanisms and kinetics of the microbial reduction of selenite to selenide. The products of this biotransformation were also assessed using electron microscopy, energy-dispersive spectroscopy, x-ray diffraction and fluorescence spectroscopy. This process offers the potential to prepare chalcogenide-based nanocrystals, for application in optoelectronic devices and biological labelling, from more environmentally benign precursors than those used in conventional organometallic synthesis

  15. Destruction-polymerization transformations as a source of radiation-induced extended defects in chalcogenide glassy semiconductors

    International Nuclear Information System (INIS)

    Long-wave shift of the optical transmission spectrum in the region of fundamental optical absorption edge is registered for As2S3 chalcogenide glassy semiconductors after γ-irradiation. This effect is explained in the frameworks of the destruction-polymerization transformations concept by accepting the switching of the heteropolar As-S covalent bonds into homopolar As-As ones. It is assumed that (As4+; S1-) defect pairs are created under such switching. Formula to calculate content of the induced defects in chalcogenide glassy semiconductors is proposed. It is assumed that defects concentration depends on energy of broken covalent bond, bond-switching energy balance, correlation energy, optical band-gap and energy of excitation light. It is shown that theoretically calculated maximally possible content of radiation-induced defects in As2S3 is about 1.6% while concentration of native defects is negligible. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Destruction-polymerization transformations as a source of radiation-induced extended defects in chalcogenide glassy semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, Oleh [Institute of Physics, Jan Dlugosz University, Al. Armii Krajowej 13/15, 42200, Czestochowa (Poland); Lviv Scientific Research Institute of Materials, SRC ' ' Carat' ' , Stryjska str. 202, 79031 Lviv (Ukraine); Filipecki, Jacek [Lviv Scientific Research Institute of Materials, SRC ' ' Carat' ' , Stryjska str. 202, 79031 Lviv (Ukraine); Shpotyuk, Mykhaylo [Lviv Scientific Research Institute of Materials, SRC ' ' Carat' ' , Stryjska str. 202, 79031 Lviv (Ukraine); Department of Semiconductor Electronics, Lviv Polytechnic National University, Bandery str. 12, 79013 Lviv (Ukraine)

    2013-01-15

    Long-wave shift of the optical transmission spectrum in the region of fundamental optical absorption edge is registered for As{sub 2}S{sub 3} chalcogenide glassy semiconductors after {gamma}-irradiation. This effect is explained in the frameworks of the destruction-polymerization transformations concept by accepting the switching of the heteropolar As-S covalent bonds into homopolar As-As ones. It is assumed that (As{sub 4}{sup +}; S{sub 1}{sup -}) defect pairs are created under such switching. Formula to calculate content of the induced defects in chalcogenide glassy semiconductors is proposed. It is assumed that defects concentration depends on energy of broken covalent bond, bond-switching energy balance, correlation energy, optical band-gap and energy of excitation light. It is shown that theoretically calculated maximally possible content of radiation-induced defects in As{sub 2}S{sub 3} is about 1.6% while concentration of native defects is negligible. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Effect of Sn doping on nonlinear optical properties of quaternary Se-Sn-(Bi,Te) chalcogenide thin films

    International Nuclear Information System (INIS)

    The aim of this work is to report the effect of Sn doping on the third order nonlinear optical properties of chalcogenide Se84-xTe15Bi1.0Snx thin films. Melt quenching technique has been used for the preparation of bulk chalcogenide glasses. Thin films of the studied composition are deposited on cleaned glass substrate by thermal evaporation technique. Optical band gap (Eg) is calculated by using Tauc extrapolation method and is found to increase from 1.27 eV to 1.64 eV with the incorporation of Sn content. Stryland approach is utilized for the calculation of two photon absorption coefficient (β2). The nonlinear refractive index (n2) and third order susceptibility (χ(3) are calculated using Tichy and Ticha approach. The result shows that nonlinear refractive index (n2) follows the same trend as that of linear refractive index (n). The values of n2 of studied composition as compared to pure silica are 1000-5000 times higher

  18. Hierarchical active factors to band gap and nonlinear optical response in Ag-containing quaternary-chalcogenide compounds

    Science.gov (United States)

    Huang, Jun-ben; Mamat, Mamatrishat; Pan, Shilie; Yang, Zhihua

    2016-07-01

    In this research work, Ag-containing quaternary-chalcogenide compounds KAg2TS4 (T=P, Sb) (I-II) and RbAg2SbS4 (III) have been studied by means of Density Functional Theory as potential IR nonlinear optical materials. The origin of wide band gap, different optical anisotropy and large SHG response is explained via a combination of density of states, electronic density difference and bond population analysis. It is indicated that the different covalent interaction behavior of P-S and Sb-S bonds dominates the band gap and birefringence. Specifically, the Ag-containing chalcogenide compound KAg2PS4 possesses wide band gap and SHG response comparable with that of AgGaS2. By exploring the origin of the band gap and NLO response for compounds KAg2TS4 (T=P, Sb), we found the determination factor to the properties is different, especially the roles of Ag-d orbitals and bonding behavior of P-S or Sb-S. Thus, the compounds KAg2TS4 (T=P, Sb) and RbAg2SbS4 can be used in infrared (IR) region.

  19. All-optical demultiplexing of 1.28~Tb/s to 10~Gb/s using a chalcogenide photonic chip

    DEFF Research Database (Denmark)

    Vo, T.D.; Hu, Hao; Galili, Michael;

    2010-01-01

    We report the first demonstration of all-optical Tbaud switching on a compact photonic chip. A 1.28 Tbaud return-to-zero signal was demultiplexed via four-wave mixing in a highly nonlinear, dispersion-engineered 7-cm Chalcogenide planar waveguide....

  20. The Agx(As0.33S0.64)1-x Amorphous Chalcogenide Bulk Glasses and Films Prepared by Pulsed Laser Deposition

    Czech Academy of Sciences Publication Activity Database

    Wágner, T.; Krbal, M.; Němec, P.; Frumarová, Božena; Vlček, Milan; Frumar, M.; Kasap, S. O.

    Cape Canaveral : The American Ceramic Society, 2004, s. 65. [International Symposium on Non-Oxide and Novel Optical Glass es/14./. Cape Canaveral (US), 07.11.2004-12.11.2004] Keywords : chalcogenide thin film * pulsed laser deposition Subject RIV: CA - Inorganic Chemistry

  1. Mid-infrared supercontinuum generation in chalcogenide step-index fibers pumped at 2.9 and 4.5µm

    DEFF Research Database (Denmark)

    Kubat, Irnis; Agger, Christian; Møller, Uffe Visbech; Seddon, Angela; Tang, Zhuoqi; Sujecki, Slawomir; Benson, Trevor M.; Furniss, David; Lamrini, Samir; Scholle, Karsten; Fuhrberg, Peter; Napier, Bruce; Farries, Mark; Ward, Jon; Moselund, Peter M.; Bang, Ole

    optical properties of fibers (dispersion, nonlinearity and confinement loss) are modeled using the finite element tools based on measured refractive indices of the core and the cladding chalcogenide compositions. Generation of MIR SC is investigated using the Generalized Nonlinear Schrödinger Equation...

  2. Up-conversion in Er3+ - doped Ge25Ga5Sb5S65 chalcogenide glass for enhancement of silicon solar cell efficiency

    Czech Academy of Sciences Publication Activity Database

    Wágner, T.; Střižík, L.; Košťál, P.; Frumar, M.; Frumarová, Božena; Vlček, Milan; Beneš, L.

    Shanghai: IEEE Photonics SocietyIEEE Photonics Society, 2012, s. 566-569. ISBN 978-1-4577-0911-1. [The International Symposium on Photonics and Optoelectronics. Shanghai (CN), 21.05.2012-23.05.2012] Institutional support: RVO:61389013 Keywords : luminescence * chalcogenide glass * rare earth Subject RIV: CA - Inorganic Chemistry

  3. Extraction and recovery of mercury and lead from aqueous waste streams using redox-active layered metal chalcogenides. Annual progress report, September 15, 1996 - September 14, 1997

    International Nuclear Information System (INIS)

    'The authors have begun to examine the extraction and recovery of heavy elements from aqueous waste streams using redox-active metal chalcogenides. They have been able to prepare extractants from known chalcogenide starting materials, studied the efficacy of the extractants for selective removal of soft metal ions from aqueous phases, studied the deactivation of extractants and the concomitant recovery of soft metal ions from the extractants, and characterized all of the solids and solutions thus far in the study. The study was proposed as two parallel tasks: Part 1 and Part 2 emphasize the study and development of known metal chalcogenide extractants and the synthesis and development of new metal chalcogenide extractants, respectively. The two tasks were divided into sub-sections that study the extractants and their chemistry as detailed below: Preparation and reactivity of metal chalcogenide host solids Extraction of target waste (guest) ions from simulated waste streams Examination of the guest-host solids recovery of the guest metal and reuse of extractant Each section of the two tasks was divided into focused subsections that detail the specific problems and solutions to those problems that were proposed. The extent to which those tasks have been accomplished and the continued efforts of the team are described in detail below. (b) Progress and Results. The DOE-supported research has proceeded largely as proposed and has been productive in its first 12 months. Two full-paper manuscripts were submitted and are currently under peer review. A third paper is in preparation and will be submitted shortly. In addition, 5 submitted or invited presentations have been made.'

  4. Spin dynamics of complex oxides, bismuth-antimony alloys, and bismuth chalcogenides

    Science.gov (United States)

    Sahin, Cuneyt

    V, suggesting the potential for doping or voltage tuned spin Hall current. We have also calculated intrinsic spin Hall conductivities of bismuth selenide and bismuth telluride topological insulators from an effective tight-binding Hamiltonian including two nearest-neighbor interactions. We showed that both materials exhibit giant spin Hall conductivities calculated from the Kubo formula in linear response theory and the clean static limit. We conclude that bismuth-antimony alloys and bismuth chalcogenides are primary candidates for efficiently generating spin currents through the spin Hall effect.

  5. Colloidal chemical synthesis and formation kinetics of uniformly sized nanocrystals of metals, oxides, and chalcogenides.

    Science.gov (United States)

    Kwon, Soon Gu; Hyeon, Taeghwan

    2008-12-01

    nanoparticles of copper and nickel using metal(II) acetylacetonates. Ni/Pd core/shell nanoparticles were synthesized by simply heating the reaction mixture composed of acetylacetonates of nickel and palladium. Using alternative chalcogen reagents, we synthesized uniform nanocrystals of various metal chalcogenides. Uniform nanocrystals of PbS, ZnS, CdS, and MnS were obtained by heating reaction mixtures composed of metal chlorides and sulfur dissolved in oleylamine. In the future, a detailed understanding of nanocrystal formation kinetics and synthetic chemistry will lead to the synthesis of uniform nanocrystals with controlled size, shape, and composition. In particular, the synthesis of uniform nanocrystals of doped materials, core/shell materials, and multicomponent materials is still a challenge. We expect that these uniformly sized nanocrystals will find important applications in areas including information technology, biomedicine, and energy/environmental technology. PMID:18681462

  6. Structure, ionic Conductivity and mobile Carrier Density in Fast Ionic Conducting Chalcogenide Glasses

    International Nuclear Information System (INIS)

    This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M2S + (0.1 Ga2S3 + 0.9 GeS2) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays an important role in determining the ionic conductivity in glasses, the glass forming range for the addition of different alkalis into the basic glass forming system 0.1 Ga2S3 + 0.9 GeS2 was studied. The study found that the change of the alkali radius for the same nominal composition causes significant structure change to the glasses. The third section is a paper that investigates the ionic conductivity of MI + M2S + (0.1Ga2S3 + 0.9 GeS2) (M = Li, Na, K and Cs) glasses system. Corresponding to the compositional changes in these fast ionic conducting glasses, the ionic conductivity shows changes due to the induced structural changes. The ionic radius effect on the ionic conductivity in these glasses was investigated. The fourth section is a paper that examines the mobile carrier density based upon the measurements of space charge polarization. For the first time, the charge carrier number density in fast ionic conducting chalcogenide glasses was determined. The experimental impedance data were fitted using equivalent circuits and the obtained parameters were used to determine the mobile carrier density. The influence of mobile carrier density and mobility on the ionic conductivity was separated. The fifth section is a paper that studies the structures of low-alkali-content Na2S + B2S3 (x (le) 0.2) glasses by neutron and synchrotron x-ray diffraction. Similar results were obtained both in neutron and synchrotron x-ray diffraction experiments. The results provide direct structural evidence that doping

  7. Thermo-chemical properties and electrical resistivity of Zr-based arsenide chalcogenides

    Directory of Open Access Journals (Sweden)

    A. Schlechte, R. Niewa, M. Schmidt, G. Auffermann, Yu. Prots, W. Schnelle, D. Gnida, T. Cichorek, F. Steglich and R. Kniep

    2007-01-01

    Full Text Available Ternary phases in the systems Zr–As–Se and Zr–As–Te were studied using single crystals of ZrAs1.40(1Se0.50(1 and ZrAs1.60(2Te0.40(1 (PbFCl-type of structure, space group P4/nmm as well as ZrAs0.70(1Se1.30(1 and ZrAs0.75(1Te1.25(1 (NbPS-type of structure, space group Immm. The characterization covers chemical compositions, crystal structures, homogeneity ranges and electrical resistivities. At 1223 K, the Te-containing phases can be described with the general formula ZrAsxTe2−x, with 1.53(1≤x≤1.65(1 (As-rich and 0.58(1≤x≤0.75(1 (Te-rich. Both phases are located directly on the tie-line between ZrAs2 and ZrTe2, with no indication for any deviation. Similar is true for the Se-rich phase ZrAsxSe2−x with 0.70(1≤x≤0.75(1. However, the compositional range of the respective As-rich phase ZrAsx−ySe2−x (0.03(1≤y≤0.10(1; 1.42(1≤x≤1.70(1 is not located on the tie-line ZrAs2–ZrSe2, and exhibits a triangular region of existence with intrinsic deviation of the composition towards lower non-metal contents. Except for ZrAs0.75Se1.25, from the homogeneity range of the Se-rich phase, all compounds under investigation show metallic characteristics of electrical resistivity at temperatures >20 K. Related uranium and thorium arsenide selenides display a typical magnetic field-independent rise of the resistivity towards lower temperatures, which has been explained by a non-magnetic Kondo effect. However, a similar observation has been made for ZrAs1.40Se0.50, which, among the Zr-based arsenide chalcogenides, is the only system with a large concentration of intrinsic defects in the anionic substructure.

  8. Structure, ionic Conductivity and mobile Carrier Density in Fast Ionic Conducting Chalcogenide Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Wenlong Yao

    2006-12-12

    This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M{sub 2}S + (0.1 Ga{sub 2}S{sub 3} + 0.9 GeS{sub 2}) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays an important role in determining the ionic conductivity in glasses, the glass forming range for the addition of different alkalis into the basic glass forming system 0.1 Ga{sub 2}S{sub 3} + 0.9 GeS{sub 2} was studied. The study found that the change of the alkali radius for the same nominal composition causes significant structure change to the glasses. The third section is a paper that investigates the ionic conductivity of MI + M{sub 2}S + (0.1Ga{sub 2}S{sub 3} + 0.9 GeS{sub 2}) (M = Li, Na, K and Cs) glasses system. Corresponding to the compositional changes in these fast ionic conducting glasses, the ionic conductivity shows changes due to the induced structural changes. The ionic radius effect on the ionic conductivity in these glasses was investigated. The fourth section is a paper that examines the mobile carrier density based upon the measurements of space charge polarization. For the first time, the charge carrier number density in fast ionic conducting chalcogenide glasses was determined. The experimental impedance data were fitted using equivalent circuits and the obtained parameters were used to determine the mobile carrier density. The influence of mobile carrier density and mobility on the ionic conductivity was separated. The fifth section is a paper that studies the structures of low-alkali-content Na{sub 2}S + B{sub 2}S{sub 3} (x {le} 0.2) glasses by neutron and synchrotron x-ray diffraction. Similar results were obtained both in neutron and synchrotron x

  9. Inelastic Scattering in STEM for Studying Structural and Electronic Properties of Chalcogenide-Based Semiconductor Nanocrystals

    Science.gov (United States)

    Gunawan, Aloysius Andhika

    Transmission electron microscopy (TEM) relies upon elastic and inelastic scattering signals to perform imaging and analysis of materials. TEM images typically contain contributions from both types of scattering. The ability to separate the contributions from elastic and inelastic processes individually through energy filter or electron energy loss spectroscopy (EELS) allows unique analysis that is otherwise unachievable. Two prominent types of inelastic scattering probed by EELS, namely plasmon and core-loss excitations, are useful for elucidating structural and electronic properties of chalcogenide-based semiconductor nanocrystals. The elastic scattering, however, is still a critical part of the analysis and used in conjunction with the separated inelastic scattering signals. The capability of TEM operated in scanning mode (STEM) to perform localized atomic length scale analysis also permits the understanding of the nanocrystals unattainable by other techniques. Despite the pivotal role of inelastic scatterings, their contributions for STEM imaging, particularly high-angle annular dark field STEM (HAADF-STEM), are not completely understood. This is not surprising since it is currently impossible to experimentally separate the inelastic signals contributing to HAADF-STEM images although images obtained under bright-field TEM mode can be analyzed separately from their scattering contributions using energy-filtering devices. In order to circumvent such problem, analysis based on simulation was done. The existing TEM image simulation algorithm called Multislice method, however, only accounts for elastic scattering. The existing Multislice algorithm was modified to incorporate (bulk or volume) plasmon inelastic scattering. The results were verified based on data from convergent-beam electron diffraction (CBED), electron energy loss spectroscopy (EELS), and HAADF-STEM imaging as well as comparison to experimental data. Dopant atoms are crucial factors which control

  10. KFeSbTe3: A quaternary chalcogenide aerogel for preferential adsorption of polarizable hydrocarbons and gases

    KAUST Repository

    Ahmed, Ejaz

    2015-01-01

    The first telluride-based quaternary aerogel KFeSbTe3 is synthesized by a sol-gel metathesis reaction between Fe(OAc)2 and K3SbTe3 in dimethyl formamide. The aerogel has an exceptionally large surface area 652 m2 g-1 which is amongst the highest reported for chalcogenide-based aerogels. This predominantly mesoporous material shows preferential adsorption for toluene vapors over cyclohexane or cyclopentane and CO2 over CH4 or H2. The remarkably high adsorption capacity for toluene (9.31 mmol g-1) and high selectivity for gases (CO2/H2: 121 and CO2/CH4: 75) suggest a potential use of such materials in adsorption-based separation processes for the effective purification of hydrocarbons and gases. © The Royal Society of Chemistry 2015.

  11. Radiation stimulated changes in the transmission of chalcogenide glasses As2S3-Ge2S3

    International Nuclear Information System (INIS)

    The radiation - optical properties of chalcogenide glass-like semiconductors systems As2S3-Ge2S3 in the field of topological 2D-3D of phase transition are investigated. It is shown, that a gamma irradiation by an absorbed doze 4.4·106 Gy results in long-wave shift of a spectral position of their edge of optical passing. The observable effect depends on a structural type of researched glasses and essentially varies near to 2D-3D of phase transition. Two making shifts of an edge of passing are detected: static, remaining a constant long time after irradiation and dynamic, gradually damping during 2-3 months. It is supposed, that the microstructural mechanism of the data changes is stipulated by processes coordination defect creation in a structural framework of samples

  12. Extended free-volume defects in chalcogenide glassy semiconductors induced by high-energy {gamma}-irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Balitska, Valentina [Lviv Institute of Materials of SRC (Ukraine); State University of Vital Activity Safety, Lviv 79007 (Ukraine); Filipecki, Jacek; Shpotyuk, Oleh [Institute of Physics, Jan Dlugosz University, Czestochowa (Poland)

    2009-08-15

    It was shown that under-coordinated topological defects induced by high-energy {gamma}-irradiation can be a reason for significant changes in positron annihilation lifetime spectra of multicomponent chalcogenide glassy semiconductors within ternary Ge-As(Sb)-S systems. In the case of negatively-charged sulphur and arsenic atoms, the excess of free volume is quite enough to produce additional input in the second defect-related channel of positron trapping, while under-coordinated germanium atoms are practically non-detectable with this technique because of low associated free volume. Despite radiation-induced densification, the average positron lifetime demonstrate both growing and decaying tendencies after {gamma}-irradiation depending on glass composition. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Extended free-volume defects in chalcogenide glassy semiconductors induced by high-energy γ-irradiation

    International Nuclear Information System (INIS)

    It was shown that under-coordinated topological defects induced by high-energy γ-irradiation can be a reason for significant changes in positron annihilation lifetime spectra of multicomponent chalcogenide glassy semiconductors within ternary Ge-As(Sb)-S systems. In the case of negatively-charged sulphur and arsenic atoms, the excess of free volume is quite enough to produce additional input in the second defect-related channel of positron trapping, while under-coordinated germanium atoms are practically non-detectable with this technique because of low associated free volume. Despite radiation-induced densification, the average positron lifetime demonstrate both growing and decaying tendencies after γ-irradiation depending on glass composition. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Magnetic structure of TlFeS{sup 2} and TlFeSe{sup 2} chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Asgerov, E. B., E-mail: elmar@jinr.ru [Joint Institute for Nuclear Research (Russian Federation); Dang, N. T. [Duy Tan University, Institute of Research and Development (Viet Nam); Beskrovnyy, A. I.; Madadzada, A. I. [Joint Institute for Nuclear Research (Russian Federation); Ismayilov, D. I. [National Academy of Sciences of Azerbaijan, Abdullaev Institute of Physics (Azerbaijan); Mehdiyeva, R. N. [National Academy of Sciences of Azerbaijan, Institute of Radiation Problems (Azerbaijan); Jabarov, S. H. [National Academy of Sciences of Azerbaijan, Abdullaev Institute of Physics (Azerbaijan); Karimova, E. M. [Universitet Bayreuth, Bayerisces Geoinstitut (Germany)

    2015-07-15

    The crystal and magnetic structures of TlFeS{sup 2} and TlFeSe{sup 2} chalcogenides are studied by neutron diffraction in the temperature range 10–300 K. The investigated compounds feature monoclinic crystal symmetry with the C2/m space group. Antiferromagnetic ordering occurs in TlFeS{sup 2} and TlFeSe{sup 2} at the Néel temperature T{sup N} = 210(5) and 295(5) K, respectively. The temperature dependences of magnetic moments, Fe–Fe bond lengths, and unit-cell volume are established. The coefficients of thermal expansion for the paramagnetic and antiferromagnetic phases are calculated.

  15. A projection operator approach for computing the dynamics of AS2S3 chalcogenide birefringent photonic crystal fiber coupler

    Science.gov (United States)

    Uthayakumar, T.; Vasantha Jayakantha Raja, R.; Porsezian, K.

    2015-02-01

    A variety of AS2S3 chalcogenide photonic crystal fiber coupler of special properties are proposed to study the role of birefringence in all optical coupling characteristics based on the projection operator method (POM). The equations of motion describing the dynamics of the individual pulse parameters through x- and y-polarized modes are arrived at by employing POM from the coupled nonlinear Schrödinger equations. From the pulse parameter dynamics, it is observed that the amplitudes of the polarization components are significantly influenced by the pulse being introduced with different polarizing angle even at low input power level. Such a selective polarizing angles of the input pulse will provide efficient control over the desired splitting ratio as well as the ability to decide the desired polarization component.

  16. Post-radiation degradation-relaxation transformation in chalcogenide glass semiconductors: phenomenology of kinetics and possible microstructures mechanisms

    International Nuclear Information System (INIS)

    The results on the time degradation of radiation-induced changes of optical properties in chalcogenide vitreous semiconductors of (As2S3)x(Ge2S3)1-x and (Sb2S3)1-x nonstoichiometric systems at the average coordination number Z variation were discussed. It was established that an adequate mathematical model for the description of these processes could be developed on the basis of the bimolecular relaxation function corresponding to the annihilation of structural defects in the form of oppositely charged atoms with anomaly coordination. The extreme character of glass properties in the point of Z = 2.67 proves to follow from owing to the performed calculations.

  17. Temperature and frequency dependence of AC conductivity of new quaternary Se-Te-Bi-Pb chalcogenide glasses

    Science.gov (United States)

    Yadav, Preeti; Sharma, Ambika

    2016-05-01

    The aim of the present work is to study the temperature and frequency dependence of ac conductivity of new quaternary Se84-xTe15Bi1.0Pbx chalcogenide glasses. The Se84-xTe15Bi1.0Pbx (x = 2, 6) glassy alloys are prepared by using melt quenching technique. The temperature and frequency dependent behavior of ac conductivity σac(ω) has been carried out in the frequency range 42 Hz to 5 MHz and in the temperature range of 298-323 K below glass transition temperature. The behavior of ac conductivity is described in terms of the power law ωs. The obtained temperature dependence behavior of ac conductivity and frequency component (s) are explained by means of correlated barrier hopping model recommended by Elliot.

  18. General principles of the synthesis of chalcogenides and pnictides in salt melts using a steady-state temperature gradient

    Science.gov (United States)

    Chareev, D. A.

    2016-05-01

    The possibilities of growing crystals of metals, alloys, chalcogenides, and pnictides in halide melts using a steady-state temperature gradient are analyzed. Halides of alkali metals and aluminum can be used as transport media. The choice is determined by the melting temperature of salt mixtures. A conducting contour can also be applied to increase transport efficiency. This technique of crystal growth is similar to the electrochemical method. To eliminate interference during migration, some elements can be isolated and forced to migrate through independent channels to the crystal formation region. The technique considered here makes it possible to grow crystals of necessary quality without special equipment; the small crystal sizes are sufficient for laboratory study.

  19. Wild Band Edges: The Role of Bandgap Grading and Band-Edge Fluctuations in High-Efficiency Chalcogenide Devices: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Repins, Ingrid; Mansfield, Lorelle; Kanevce, Ana; Jensen, Soren A.; Kuciauskas, Darius; Glynn, Stephen; Barnes, Teresa; Metzger, Wyatt; Burst, James; Jiang, Chun-Sheng; Dippo, Patricia; Harvey, Steve; Teeter, Glenn; Perkins, Craig; Egaas, Brian; Zakutayev, Andriy; Alsmeier, J.-H.; Lussky, T.; Korte, L.; Wilks, R. G.; Bar, M.; Yan, Y.; Lany, Stephan; Zawadzki, Pawel; Park, Ji-Sang; Wei, Suhuai

    2016-06-16

    Band-edge effects -- including grading, electrostatic fluctuations, bandgap fluctuations, and band tails -- affect chalcogenide device efficiency. These effects now require more careful consideration as efficiencies increase beyond 20%. Several aspects of the relationships between band-edge phenomena and device performance for NREL absorbers are examined. For Cu(In,Ga)Se2 devices, recent increases in diffusion length imply changes to optimum bandgap profile. The origin, impact, and modification of electrostatic and bandgap fluctuations are also discussed. The application of the same principles to devices based on CdTe, kesterites, and emerging absorbers (Cu2SnS3, CuSbS2), considering differences in materials properties and defect formation energies, is examined.

  20. A Tapered Chalcogenide Microstructured Optical Fiber for Mid-IR Parabolic Pulse Generation: Design and Performance Study

    CERN Document Server

    Barh, Ajanta; Varshney, Ravi K; Pal, Bishnu P

    2013-01-01

    This paper presents a theoretical design of chalcogenide glass based tapered microstructured optical fiber (MOF) to generate high power parabolic pulses (PPs) at the mid-IR wavelength (~ 2 {\\mu}m). We optimize fiber cross-section by the multipole method and studied pulse evolution by well known Symmetrized Split-Step Fourier Method. Our numerical investigation reveals the possibility of highly efficient PP generation within a very short length (~ 18 cm) of this MOF for a Gaussian input pulse of 60 W peak power and FWHM of 3.5 ps. We examined quality of the generated PP by calculating the misfit parameter including the third order dispersion and fiber loss. Further, the effects of variations in input pulse power, pulse width and pulse energy on generated PP were also studied.

  1. Refractive index dispersion of chalcogenide glasses for ultra-high numerical-aperture fiber for mid-infrared supercontinuum generation

    DEFF Research Database (Denmark)

    Dantanarayana, Harshana G.; Abdel-Moneim, Nabil; Tang, Zhuoqi; Sojka, Lukasz; Sujecki, Slawomir; Furniss, David; Seddon, Angela B.; Kubat, Irnis; Bang, Ole; Benson, Trevor M.

    2014-01-01

    We select a chalcogenide core glass, AsSe, and cladding glass, GeAsSe, for their disparate refractive indices yet sufficient thermal-compatibility for fabricating step index fiber (SIF) for mid-infrared supercontinuum generation (MIR-SCG). The refractive index dispersion of both bulk glasses is...... measured over the 0.4 μm–33 μm wavelength-range, probing the electronic and vibrational behavior of these glasses. We verify that a two-term Sellmeier model is unique and sufficient to describe the refractive index dispersion over the wavelength range for which the experimentally determined extinction...... coefficient is insignificant. A SIF composed of the glasses is fabricated and calculated to exhibit an ultra-high numerical aperture >0.97 over the entire wavelength range 0.4-33 μm suggesting that the SIF glass pair is a promising candidate for MIR-SCG. Material dispersion characteristics and the zero...

  2. Kinetics of crystallization of Ge30-xSe70Sbx (x = 15, 20, 25 chalcogenide glasses

    Directory of Open Access Journals (Sweden)

    Anusaiya Kaswan

    2014-03-01

    Full Text Available The kinetics of crystallization of Ge30-xSe70Sbx (x = 15, 20, 25 chalcogenide glasses has been investigated using differential scanning calorimetery at different heating rates under non-isothermal conditions. The kinetic analysis of crystallization has been discussed using different theoretical approaches such as Ozawa model, Augis and Bennet model, Matusita model and Gao-Wang model. It is evident from this study that the activation energy of crystallization Ec is composition dependent. The activation energy decreases with increasing Sb content due to the increasing of rate of crystallization. The minimum value of the frequency factor Ko, which is defined as the number of attempts made by the nuclei per second to overcome the energy barrier, confirms the fact that glass is more stable. It has been found that Ge15Se70Sb15 glass is more stable compared to the other compositions.

  3. Mid-IR supercontinuum generation beyond 7 μm using a silica-fluoride-chalcogenide fiber cascade

    Science.gov (United States)

    Petersen, Christian R.; Moselund, Peter M.; Petersen, Christian; Møller, Uffe; Bang, Ole

    2016-03-01

    We report on an experimental demonstration of mid-infrared cascaded supercontinuum generation in commercial silica, fluoride, and chalcogenide fibers as a potentially cheap and practical alternative to direct pumping schemes. A pump continuum up to 4.4 μm was generated in cascaded silica and fluoride fibers by an amplified 1.55 μm nanosecond diode laser. By pumping a commercial Ge10As22Se68 single-material photonic crystal fiber with 135.7 mW of the pump continuum from 3.5- 4.4 μm, we obtained a continuum up to 7.2 μm with a total output power after the collimating lens of 54.5 mW, and 3.7 mW above 4.5 μm.

  4. Synthesis and solid state structures of Chalcogenide compounds of Imidazolin-2-ylidene-1,1-Diphenyl-phosphinamine

    Indian Academy of Sciences (India)

    Naktode Kishor; Suman Das; Abhinanda Kundu; Hari Pada Nayek; Tarun K Panda

    2016-03-01

    We report the synthesis and solid state structures of 1,3-di-aryl-imidazolin-2-ylidine-1,1-diphenylphosphinamine [(aryl=mesityl (1a) and aryl=2,6-diisopripyl (1b)] and their chalcogenide compounds 3-di-aryl-imidazolin-2-ylidine-P, P-diphenylphosphinicamide (2a,b), 1,3-di-aryl-imidazolin-2-ylidine-P,P diphenyl-phosphinothioicamide (3a,b) and 1,3-diaryl-imidazolin-2-ylidine-P,P -diphenyl-phosphinoselenoicamide (4a,b).The compounds 1a,b were prepared in good yield by the reaction of 1,3-di-aryl-imidazolin-2-imine and chlorodiphenylphosphine in the presence of triethylamine in toluene. The reactions of 1a,b with elemental sulphur and selenium afforded the corresponding chalcogenide compounds 3a,b and 4a,b respectively.The corresponding oxo- derivative (2a,b) was obtained by reacting compound 1a,b with 30% aqueous hydrogen peroxide in THF. The molecular structures of 1a, 2a, 3a and 4a,b have been established by single crystal X-ray diffraction analyses. The molecular structures reveal that even C1–N1–P1 angle (124.62o) in compound 1a is less obtuse compared to the corresponding C1–N1–Si1 angles (157.8o) observed in related N-silylated 2-iminoimidazolines and trimethylsilyl iminophosphoranes. C1–N1–P1 angles are further widened in compounds 2a, 3a, and 4a,b due to the attachment of chalcogen atoms onto phosphorus atom.

  5. Thermal analysis of chalcogenide glasses of the system (As2Se3)sub(1-x): (Tl2Se)sub(x)

    International Nuclear Information System (INIS)

    In this paper differential thermal analysis (DTA) measurements of chalcogenide glasses of the system (As2Se3)sub(1-x): (Tl2Se)sub(x), with x=0, 0.125, 0.25, and 0.50 are reported. The glass-forming tendencies of these materials have been calculated. The glass-forming tendency of As2Se3 has been found to be the highest among the member glasses of this family of chalcogenides. Also it was found that the glass-forming tendency of As2Se3 decreases gradually as the Tl2Se concentration increases. Tl2Se additions also lower the glass transition temperature Tsub(g) and the area under the endothermic peak for glass transition temperature, suggesting a tendency for relatively weaker bonding and hence less stability of Tl-rich glass compositions. These studies also show that Tl2Se concentrations result in glasses with progressively higher crystallization tendencies. (author)

  6. Numerical demonstration of 3-12μm supercontinuum generation in large-core step-index chalcogenide fibers pumped at 4.5μm

    DEFF Research Database (Denmark)

    Agger, Christian; Kubat, Irnis; Møller, Uffe Visbech;

    2013-01-01

    We numerically demonstrate the generation of a 3-12μm mid-infrared supercontinuum in a large-core (20μm diameter) step-index fiber made from highly nonlinear chalcogenide (As2Se3) pumped at 4.5μm with 40ps, 1kW peak power pulses. © OSA 2013.......We numerically demonstrate the generation of a 3-12μm mid-infrared supercontinuum in a large-core (20μm diameter) step-index fiber made from highly nonlinear chalcogenide (As2Se3) pumped at 4.5μm with 40ps, 1kW peak power pulses. © OSA 2013....

  7. Universal behavior of chalcogenides of rare-earth metals in the transition to a state with intermediate valence at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Tsiok, O. B.; Khvostantsev, L. G.; Brazhkin, V. V., E-mail: brazhkin@hppi.troitsk.ru [Russian Academy of Sciences, Vereshchagin Institute of High-Pressure Physics (Russian Federation)

    2015-06-15

    Precision measurements of resistivity, thermopower, and volume are performed for TmS, TmSe, and TmTe under a hydrostatic pressure up to 8 GPa. Comparison of the transport properties and volume of TmTe and SmTe in the valence transition region demonstrates a complete analogy up to quantitative coincidence. It is shown that the thermopower of all thulium and samarium chalcogenides in the lattice collapse region and in subsequent rearrangement of the electron spectrum in a wide range of pressures follow a universal dependence corresponding the passage of the Fermi level through the peak of the density of states (DOS). The results are considered in the context of ideas about the exciton nature of the intermediate valence in chalcogenides of rare-earth metals.

  8. Universal behavior of chalcogenides of rare-earth metals in the transition to a state with intermediate valence at high pressures

    Science.gov (United States)

    Tsiok, O. B.; Khvostantsev, L. G.; Brazhkin, V. V.

    2015-06-01

    Precision measurements of resistivity, thermopower, and volume are performed for TmS, TmSe, and TmTe under a hydrostatic pressure up to 8 GPa. Comparison of the transport properties and volume of TmTe and SmTe in the valence transition region demonstrates a complete analogy up to quantitative coincidence. It is shown that the thermopower of all thulium and samarium chalcogenides in the lattice collapse region and in subsequent rearrangement of the electron spectrum in a wide range of pressures follow a universal dependence corresponding the passage of the Fermi level through the peak of the density of states (DOS). The results are considered in the context of ideas about the exciton nature of the intermediate valence in chalcogenides of rare-earth metals.

  9. In situ photo-assisted deposition and photocatalysis of ZnIn2S4/transition metal chalcogenides for enhanced degradation and hydrogen evolution under visible light.

    Science.gov (United States)

    Lim, Wei Yang; Hong, Minghui; Ho, Ghim Wei

    2016-01-14

    The effective immobilization of a transition chalcogenide co-catalyst via an in situ aqueous photo-assisted deposition technique has shown great accessibility to complex ZnIn2S4 host hierarchical nanostructured materials with homogeneous distribution. The complementary photo-assisted deposition readily deposits finely-dispersed co-catalyst particles and simultaneously generates photocatalytic hydrogen. Another added advantage is that the photo-assisted deposition of the co-catalyst does not compromise the crystal structure or the integrity of the host photocatalyst, hence offering a better alternative to the doping technique. A systematic study of various transition metal chalcogenide co-catalysts and optimization of wt% MoS2, CuS and Ag2S loadings were demonstrated. Among them, the ZnIn2S4/MoS2 composite exhibits exceptional photocatalytic hydrogen production and stability as well as superior MO degradation under visible light irradiation. The present methodology is expected to be extendable to various transition metal oxides/chalcogenides since ionic derivatives exhibit high affinity to a variety of materials under photoirradiation. PMID:26605503

  10. Thulium pumped mid-infrared 0.9–9μm supercontinuum generation in concatenated fluoride and chalcogenide glass fibers

    DEFF Research Database (Denmark)

    Kubat, Irnis; Petersen, Christian Rosenberg; Møller, Uffe Visbech; Seddon, Angela; Benson, Trevor; Brilland, Laurent; Méchin, David; Moselund, Peter M.; Bang, Ole

    2014-01-01

    We theoretically demonstrate a novel approach for generating Mid-InfraRed SuperContinuum (MIR SC) by using concatenated fluoride and chalcogenide glass fibers pumped with a standard pulsed Thulium (Tm) laser (TFWHM=3.5ps, P0=20kW, νR=30MHz, and Pavg=2W). The fluoride fiber SC is generated in 10m of...... ZBLAN spanning the 0.9–4.1μm SC at the −30dB level. The ZBLAN fiber SC is then coupled into 10cm of As2Se3 chalcogenide Microstructured Optical Fiber (MOF) designed to have a zero-dispersion wavelength (λZDW) significantly below the 4.1μm InfraRed (IR) edge of the ZBLAN fiber SC, here 3.55μm. This...... allows the MIR solitons in the ZBLAN fiber SC to couple into anomalous dispersion in the chalcogenide fiber and further redshift out to the fiber loss edge at around 9μm. The final 0.9–9μm SC covers over 3 octaves in the MIR with around 15mW of power converted into the 6–9μm range....

  11. How metallic is the binding state of indium hosted by excess-metal chalcogenides in ore deposits?

    Science.gov (United States)

    Ondina Figueiredo, Maria; Pena Silva, Teresa; Oliveira, Daniel; Rosa, Diogo

    2010-05-01

    Discovered in 1863, indium is nowadays a strategic scarce metal used both in classical technologic fields (like low melting-temperature alloys and solders) and in innovative nano-technologies to produce "high-tech devices" by means of new materials, namely liquid crystal displays (LCDs), organic light emitting diodes (OLEDs) and the recently introduced transparent flexible thin-films manufactured with ionic amorphous oxide semiconductors (IAOS). Indium is a typical chalcophile element, seldom forming specific minerals and occurring mainly dispersed within polymetallic sulphides, particularly with excess metal ions [1]. The average content of indium in the Earth's crust is very low but a further increase in its demand is still expected in the next years, thus focusing a special interest in uncovering new exploitation sites through promising polymetallic sulphide ores - e.g., the Iberian Pyrite Belt (IPB) [2] - and in improving recycling technologies. Indium recovery stands mostly on zinc extraction from sphalerite, the natural cubic sulphide which is the prototype of so-called "tetrahedral sulphides" where metal ions fill half of the available tetrahedral sites within the cubic closest packing of sulphur anions where the double of unfilled interstices are available for further in-filling. It is worth remarking that such packing array is particularly suitable for accommodating polymetallic cations by filling closely located interstitial sites [3] as happens in excess-metal tetrahedral sulphides - e.g. bornite, ideally Cu5FeS4, recognized as an In-carrying mineral [4]. Studying the tendency towards In-In interactions able of leading to the formation of polycations would efficiently contribute to understand indium crystal chemistry and the metal binding state in natural chalcogenides. Accordingly, an X-ray absorption near-edge spectroscopy (XANES) study at In L3-edge was undertaken using the instrumental set-up of ID21 beamline at the ESRF (European Synchrotron

  12. Preparation of Low-loss Ge15Ga10Te75 chalcogenide glass for far-IR optics applications

    Science.gov (United States)

    Xu, Huijuan; He, Yuju; Wang, Xunsi; Nie, Qiuhua; Zhang, Peiquan; Xu, Tiefeng; Dai, Shixun; Zhang, Xianghua; Tao, Guangming

    2014-07-01

    Ge15Ga10Te75 (GGT) glass shows good transparency between 2 and 25 μm wavelengths, good chemical and thermal stability to be drawn into fiber, which appears to be a good candidate for developing far-IR fiber-optics devices, although there are strong absorption peaks caused by impurities in the glass. With the aim of decreasing the content of impurities and micro-crystal particles in prepared GGT glass samples, a rapid heating furnace and the fast distillation method based on vapor evaporation plus deposition under vacuum condition was adopted. Properties measurements including Differential Scanning Calorimeter (DSC), Vis-NIR and IR transmitting spectra were performed on the prepared glass samples. Dependence of optical loss on the types of oxygenic getters and their contents and glass quenching temperature was also studied. All these results show that the average optical losses of distilled glass samples were greatly improved by the designated purification processes. Besides, the quality of the glass samples can be improved with the optimized quenching temperature. In all, the optical loss of the glass can be reduced effectively. Minimum optical losses of 0.042 dB/mm at 9 μm and 0.037 dB/mm at 12 μm are obtained after a right purification process, which are the lowest loss of the GGT chalcogenide glass nowadays.

  13. Low-loss, robust fusion splicing of silica to chalcogenide fiber for integrated mid-infrared laser technology development.

    Science.gov (United States)

    Thapa, Rajesh; Gattass, Rafael R; Nguyen, Vinh; Chin, Geoff; Gibson, Dan; Kim, Woohong; Shaw, L Brandon; Sanghera, Jasbinder S

    2015-11-01

    We demonstrate a low-loss, repeatable, and robust splice between single-mode silica fiber and single-mode chalcogenide (CHG) fiber. These splices are particularly difficult to create because of the significant difference in the two fibers' glass transition temperatures (∼1000°C) as well as the large difference in the coefficients of thermal expansion between the fibers (∼20×10(-6)/°C). With 90% light coupled through the silica-CHG fiber splice, predominantly in the fundamental circular-symmetric mode, into the core of the CHG fiber and with 0.5 dB of splice loss measured around the wavelength of 2.5 μm, after correcting only for the Fresnel loss, the silica-CHG splice offers excellent beam quality and coupling efficiency. The tensile strength of the splice is greater than 12 kpsi, and the laser damage threshold is greater than 2 W (CW) and was limited by the available laser pump power. We also utilized this splicing technique to demonstrate 2 to 4.5 μm ultrabroadband supercontinuum generation in a monolithic all-fiber system comprising a CHG fiber and a high peak power 2 μm pulsed Raman-shifted thulium fiber laser. This is a major development toward compact form factor commercial applications of soft-glass mid-IR fibers. PMID:26512522

  14. Size-controlled Intercalation to Conversion Transition in Lithiation of Transition-Metal Chalcogenides – NbSe3

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Langli; Zhao, Benliang; Xiang, Bin; Wang, Chong M.

    2016-01-23

    Transition metal chalcogenides (TMCs) can either be used as intercalation cathodes or as conversion type anodes for lithium ion batteries, for which two distinctively different lithiation reaction mechanisms govern the electrochemical performance of TMCs. However, it remains elusive that what controls the transition of lithiation mechanisms. Herein, we investigated the lithiation process of NbSe3 ribbons using in situ transmission electron microscopy (TEM) and observed a size dependent transition from intercalation to conversion reaction. The large NbSe3 ribbons can accommodate high concentration of Li+ through intercalation by relaxing its internal spacing, while lithiation of small NbSe3 ribbons proceeds readily to full conversion reaction. We find that the size dependent variation of lithiation mechanism is attributed to the Li+ diffusion in NbSe3 and the accommodation of newly formed phases, i.e., insufficient Li+ diffusion and limited space for accommodating the volume expansion induced by forming new phases in large size ribbons both impede the intercalation-to-conversion transition. These results demonstrate the inherent structural instability of NbSe3 as an intercalation cathode and fast lithiation rate as a promising conversion type anode.

  15. Fabrication and characterization of Ge20Sb15Se65 chalcogenide glass rib waveguides for telecommunication wavelengths

    International Nuclear Information System (INIS)

    We report on the fabrication and optical properties of Ge20Sb15Se65 chalcogenide glass rib waveguides on a single photonic chip. Radio-frequency magnetron sputtering method is employed to deposit 1.36-μm-thick films and reactive ion etching with CHF3 is used to pattern 0.76-μm-deep rib waveguides of 1–4 μm wide with low surface roughness and vertical sidewalls. Using lensed fibers, the insertion losses for rib waveguides of different widths are measured and propagation losses are estimated to be lower than 1 dB/cm. Finite difference method simulations and refractive index/curve fitting are used to observe a moderate normal dispersion of the waveguides at 1550 nm. - Highlights: • RF magnetron sputtering was used to deposit uniform Ge20Sb15Se65 thin films. • CHF3 reactive ion etching of rib waveguides vertical profile and smooth sidewall. • Insertion losses at 1550 nm measured and low propagation losses estimated. • Dispersion engineered by finite difference methods and refractive curve fitting

  16. Electronic structures and thermoelectric properties of layered chalcogenide PbBi4Te7 from first principles

    Science.gov (United States)

    Quang, Tran Van; Kim, Miyoung

    2016-02-01

    The electronic structures and the thermoelectric (TE) properties of the ternary chalcogenide PbBi4Te7 are investigated by using first-principles calculations within the density functional theory and the solutions of semi-classical Boltzmann equation. Employing the screened-exchange local density approximation, we found that PbBi4Te7 to be a narrow-gap semiconductor with an indirect band gap of 0.11 eV. The combination of light and heavy valence bands near the band edge gives rise to large Seebeck coefficients, S, for p-type doping, which is found to be improved by 11% from that of Bi2Te3 at room temperature (RT). Moreover, in contrast to conventional Bi2Te3 where the value of S decreases rapidly with temperatures higher than RT, the values of S increases with temperature reaching up to 350 μVK-1 at 500 K indicating that PbBi4Te7 is a promising TE material with operating temperatures above RT. Our result also reveals that the intrinsic layered structure results in a prominent anisotropy in the TE coefficients, implying that the TE performance can be optimized by using the transport direction, as well as the type and the level of doping.

  17. A Versatile Strategy for Shish-Kebab-like Multi-heterostructured Chalcogenides and Enhanced Photocatalytic Hydrogen Evolution.

    Science.gov (United States)

    Hu, Jianqiang; Liu, Aili; Jin, Huile; Ma, Dekun; Yin, Dewu; Ling, Pengsheng; Wang, Shun; Lin, Zhiqun; Wang, Jichang

    2015-09-01

    A series of multi-heterostructured metal chalcogenides (CdS-Te, NiS/CdS-Te, and MoS2/CdS-Te) with a surprising shish-kebab-like structure have been synthesized via a one-step microwave-assisted pyrolysis of dithiocarbamate precursors in ethylene glycol. Subsequently, CdS-Te composites were exploited as a self-sacrificial template to craft various CdS-Te@(Pt, Pd) multi-heterostructures. Highly uniform dispersion and intimate interactions between CdS and multicomponent cocatalysts, together with improved separation of photogenerated carriers due to the presence of Te nanotubes (NTs) and trace CdTe, enable CdS-based heterostructured photocatalysts to exhibit greatly enhanced efficiency and stability in the photocatalytic production of H2. Thorough morphological characterizations revealed that the growth of metal sulfide/Te heterostructures originates from the growth of Te tubes, which is likely governed by diffusion-limited depletion of the Te precursor and the dissolution-crystallization process of Te seeds followed by the formation of metal sulfide kebabs. PMID:26270392

  18. Phase change and optical band gap behavior of Se0.8S0.2 chalcogenide glass films

    International Nuclear Information System (INIS)

    Se0.8S0.2 chalcogenide glass films have been prepared by thermal vacuum evaporation technique with thickness 583 nm. Annealing process at T ≥ 333 K crystallizes the films and nanostructured films are formed. The crystallite size was increased to 24 nm as the annealing temperature increased to 373 K. Orthorhombic crystalline system was identified for the annealed films. SEM micrographs show that films consist of two parallel surfaces and the thickness was determined by cross section imaging. The optical transmittance is characterized by interference patterns as a result of these two parallel surfaces, besides their average value at longer wavelength decreases as a result of annealing process. The band gap, Eg is red shifted due to crystallization by annealing. As the phase of the films changes from amorphous to crystalline in the annealing temperature range 333-363 K, a non sharp change of the band gap (Eg) is observed. This change was explained by Brus's model of the energy gap confinement behavior of the nanostructured films. The optical refractive index increases suddenly when the system starts to be crystallized by annealing

  19. Structural characterizations and thermal analyses of Se{sub 70}Te{sub 30} chalcogenide glassy alloy

    Energy Technology Data Exchange (ETDEWEB)

    Abd-Elrahman, M.I., E-mail: mostafaia11@yahoo.com [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt); Khafagy, Rasha M. [Materials Science Laboratory, Physics Department, Girls College for Arts, Science, and Education, Ain Shams University, Cairo (Egypt); Zaki, Shiamaa A.; Hafiz, M.M. [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt)

    2014-01-10

    Highlights: • Thermal annealing results in amorphous-crystalline change in Se{sub 70}Te{sub 30}. • The average crystallite size increases when the temperature annealing increases. • The kinetics study includes the estimation of the crystallization parameters. - Abstract: The structural characterizations of Se{sub 70}Te{sub 30} chalcogenide glass for the as-prepared and thermal annealed samples are identified using the X-ray diffraction (XRD) and scanning electron microscopy (SEM). The isothermal thermal annealing process results in a transformation from the amorphous to the crystalline state. The average crystallite size increases from 8.67 to 11.24 nm when the temperature annealing increases from 95 to 118 °C. The thermal analyses of Se{sub 70}Te{sub 30} glass are investigated using a differential thermal analyzer (DTA) at five different heating rates under non-isothermal conditions. The activation energy of the glass forming (E{sub g}) as a parameter for the glass transition is estimated by employing different approaches proposed for thermal analyses. The study of crystallization kinetics includes the estimation of the activation energy of crystallization (E{sub c}), frequency factor (K{sub o}) and Avrami exponent (n)

  20. Fermi resonance in the phonon spectra of quaternary chalcogenides of the type Cu2ZnGeS4.

    Science.gov (United States)

    Valakh, M Ya; Litvinchuk, A P; Dzhagan, V M; Yukhymchuk, V O; Yaremko, A M; Romanyuk, Yu A; Guc, M; Bodnar, I V; Pérez-Rodríguez, A; Zahn, D R T

    2016-02-17

    The experimental resonant and non-resonant Raman scattering spectra of the kesterite structural modification of Cu2ZnGeS4 single crystals are reported. The results are compared with those calculated theoretically within the density functional perturbation theory. For the majority of lines a good agreement (within 2-5 cm(-1)) is established between experimental and calculated mode frequencies. However, several dominant spectral lines, in particular the two intense fully symmetric modes, are found to deviate from the calculated values by as much as 20 cm(-1). A possible reason for this discrepancy is found to be associated with the Fermi resonant interaction between one and two-phonon vibrational excitations. The modelling of spectra, which takes into account the symmetry of interacting states, allows a qualitative description of the observed experimental findings. Due to the similarity of the vibrational spectra of Cu2A (II) B (IV) S4 (A  =  Zn, Mn, Cd; B  =  Sn, Ge, Si) chalcogenides, Fermi resonance is argued to be a general phenomenon for this class of compounds. PMID:26795711

  1. Correlation between structure and physical properties of chalcogenide glasses in the AsxSe1-x system

    Science.gov (United States)

    Yang, Guang; Bureau, Bruno; Rouxel, Tanguy; Gueguen, Yann; Gulbiten, Ozgur; Roiland, Claire; Soignard, Emmanuel; Yarger, Jeffery L.; Troles, Johann; Sangleboeuf, Jean-Christophe; Lucas, Pierre

    2010-11-01

    Physical properties of chalcogenide glasses in the AsxSe1-x system have been measured as a function of composition including the Young’s modulus E , shear modulus G , bulk modulus K , Poisson’s ratio ν , the density ρ , and the glass transition Tg . All these properties exhibit a relatively sharp extremum at the average coordination number ⟨r⟩=2.4 . The structural origin of this trend is investigated by Raman spectroscopy and nuclear magnetic resonance. It is shown that the reticulation of the glass structure increases continuously until x=0.4 following the “chain crossing model” and then undergoes a transition toward a lower dimension pyramidal network containing an increasing number of molecular inclusions at x>0.4 . Simple theoretical estimates of the network bonding energy confirm a mismatch between the values of mechanical properties measured experimentally and the values predicted from a continuously reticulated structure, therefore corroborating the formation of a lower dimension network at high As content. The evolution of a wide range of physical properties is consistent with this sharp structural transition and suggests that there is no intermediate phase in these glasses at room temperature.

  2. Physical properties of disordered Chalcogenide solar cell from Pb20GexSe80-x thin films

    International Nuclear Information System (INIS)

    The preparation and study of homogeneous p-n junctions from amorphous chalcogenide Pb20GexSe80-x by thermal evaporation are presented. Such p-n junction is a novel module since no one had fabricated such homogeneous cell from these amorphous compounds yet. The p-type layer is Pb20Ge20Se60 and the n-type is Pb20Ge25Se55 elemental analysis of n- and p-types of Pb20GexSe80-x is confirmed by energy dispersive X-ray analysis. Optical energy gaps were determined from transmission spectra in the range of 300 to 2500 nm; these values was 1.9 eV for p-Pb20Ge20Se60 and 2.0 eV for n-Pb20Ge25Se55 thin films. The J-V characteristics in the dark are exhibited rectification in the reverse voltage resulting from junction. The reverse current under illumination shows no saturation with voltage. From I-V characteristics under illumination and the spectral response the open circuit voltage Voc and Isc were measured. Capacitance measurements are the main method to evaluate doping concentration through the solar cell. The distribution of charged carriers across the depletion region was calculated and interpreted. (authors)

  3. Systematics in the optical and electronic properties of the binary lanthanide halide, chalcogenide and pnictide compounds: an overview

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, E; Dorenbos, P; Van der Kolk, E, E-mail: e.g.rogers@tudelft.nl [Luminescent Material Research Group, Faculty of Applied Sciences, Delft University of Technology, Faculty of Applied Sciences Mekelweg 15, NL-2629 JB Delft (Netherlands)

    2011-09-15

    The basic optical, electrical and chemical properties of the binary divalent, trivalent and tetravalent lanthanide (Ln = La, ..., Lu) halides (F, Cl, Br and I), chalcogenides (O, S, Se and Te) and pnictides (N, P, As and Sb) were studied using an empirical model that utilizes the systematic behaviour in the energy difference between the localized 4f{sup n}-states, the 5d-derived conduction band and the mp-derived valence band (m = 2,...,5) over the Lanthanide series. As the wide variety in the electrical and optical properties of Ln materials is to a large extent controlled by the energy of these states relative to each other, it is possible to simultaneously predict insulating, semiconducting or metallic behaviour, the nature and magnitude of bandgap energies and the chemical stability of Ln materials as well as valence and valence changes of Ln ions. It can thus be used to predict the basic electronic structure of materials for which no experimental data can be found, and may be a guideline for theoretical modelling.

  4. Glass forming tendencies of chalcogenides of the system (As2Se3)sub(1-x):(T12Se)sub(x)

    International Nuclear Information System (INIS)

    In this paper glass forming capabilities of chalcogenide glasses based on As2Se3 with T12Se concentrations are discussed. The studies were made using the differential thermal analysis (DTA) technique. These studies show that the glass forming tendency of As2Se3 decreases as the concentrations of T12Se molecules are increased. Also these studies show that with addition of T12Se, the glass transition temperature Tsub(g) of As2Se3 decreases, suggesting a tendency for weaker bonding and hence less stability of T1-rich compositions. (author)

  5. Noncentrosymmetric rare-earth copper gallium chalcogenides RE{sub 3}CuGaCh{sub 7} (RE=La–Nd; Ch=S, Se): An unexpected combination

    Energy Technology Data Exchange (ETDEWEB)

    Iyer, Abishek K.; Rudyk, Brent W.; Lin, Xinsong; Singh, Harpreet [Department of Chemistry, University of Alberta, Edmonton, AB Canada T6G 2G2 (Canada); Sharma, Arzoo Z. [Department of Chemistry, University of Manitoba, Winnipeg, MB Canada R3T 2N2 (Canada); Wiebe, Christopher R. [Department of Chemistry, University of Manitoba, Winnipeg, MB Canada R3T 2N2 (Canada); Department of Chemistry, The University of Winnipeg, Winnipeg, MB Canada R3B 2G3 (Canada); Canadian Institute for Advanced Research, Toronto, ON, Canada M5G 1Z8 (Canada); Mar, Arthur, E-mail: arthur.mar@ualberta.ca [Department of Chemistry, University of Alberta, Edmonton, AB Canada T6G 2G2 (Canada)

    2015-09-15

    The quaternary rare-earth chalcogenides RE{sub 3}CuGaS{sub 7} and RE{sub 3}CuGaSe{sub 7} (RE=La–Nd) have been prepared by reactions of the elements at 1050 °C and 900 °C, respectively. They crystallize in the noncentrosymmetric La{sub 3}CuSiS{sub 7}-type structure (hexagonal, space group P6{sub 3}, Z=2) in which the a-parameter is largely controlled by the RE component (a=10.0–10.3 Å for the sulfides and 10.3–10.6 Å for the selenides) whereas the c-parameter is essentially fixed by the choice of Ga and chalcogen atoms within tetrahedral units (c=6.1 Å for the sulfides and 6.4 Å for the selenides). They extend the series RE{sub 3}MGaCh{sub 7}, previously known for divalent metal atoms (M=Mn–Ni), differing in that the Cu atoms in RE{sub 3}CuGaCh{sub 7} occupy trigonal planar sites instead of octahedral sites. Among quaternary chalcogenides RE{sub 3}MM′Ch{sub 7}, the combination of monovalent (M=Cu) and trivalent (M′=Ga) metals is unusual because it appears to violate the condition of charge balance satisfied by most La{sub 3}CuSiS{sub 7}-type compounds. The possibility of divalent Cu atoms was ruled out by bond valence sum analysis, magnetic measurements, and X-ray photoelectron spectroscopy. The electron deficiency in RE{sub 3}CuGaCh{sub 7} is accommodated through S-based holes at the top of the valence band, as shown by band structure calculations on La{sub 3}CuGaS{sub 7}. An optical band gap of about 2.0 eV was found for La{sub 3}CuGaSe{sub 7}. - Graphical abstract: The chalcogenides RE{sub 3}CuGaCh{sub 7} contain monovalent Cu in trigonal planes and trivalent Ga in tetrahedra; they are electron-deficient representatives of La{sub 3}CuSiS{sub 7}-type compounds, which normally satisfy charge balance. - Highlights: • Quaternary chalcogenides RE{sub 3}CuGaCh{sub 7} (RE=La–Nd; Ch=S, Se) were prepared. • Bond valence sums, magnetism, and XPS data give evidence for monovalent Cu. • Crystal structures reveal high anisotropy of Cu displacement.

  6. Noncentrosymmetric rare-earth copper gallium chalcogenides RE3CuGaCh7 (RE=La–Nd; Ch=S, Se): An unexpected combination

    International Nuclear Information System (INIS)

    The quaternary rare-earth chalcogenides RE3CuGaS7 and RE3CuGaSe7 (RE=La–Nd) have been prepared by reactions of the elements at 1050 °C and 900 °C, respectively. They crystallize in the noncentrosymmetric La3CuSiS7-type structure (hexagonal, space group P63, Z=2) in which the a-parameter is largely controlled by the RE component (a=10.0–10.3 Å for the sulfides and 10.3–10.6 Å for the selenides) whereas the c-parameter is essentially fixed by the choice of Ga and chalcogen atoms within tetrahedral units (c=6.1 Å for the sulfides and 6.4 Å for the selenides). They extend the series RE3MGaCh7, previously known for divalent metal atoms (M=Mn–Ni), differing in that the Cu atoms in RE3CuGaCh7 occupy trigonal planar sites instead of octahedral sites. Among quaternary chalcogenides RE3MM′Ch7, the combination of monovalent (M=Cu) and trivalent (M′=Ga) metals is unusual because it appears to violate the condition of charge balance satisfied by most La3CuSiS7-type compounds. The possibility of divalent Cu atoms was ruled out by bond valence sum analysis, magnetic measurements, and X-ray photoelectron spectroscopy. The electron deficiency in RE3CuGaCh7 is accommodated through S-based holes at the top of the valence band, as shown by band structure calculations on La3CuGaS7. An optical band gap of about 2.0 eV was found for La3CuGaSe7. - Graphical abstract: The chalcogenides RE3CuGaCh7 contain monovalent Cu in trigonal planes and trivalent Ga in tetrahedra; they are electron-deficient representatives of La3CuSiS7-type compounds, which normally satisfy charge balance. - Highlights: • Quaternary chalcogenides RE3CuGaCh7 (RE=La–Nd; Ch=S, Se) were prepared. • Bond valence sums, magnetism, and XPS data give evidence for monovalent Cu. • Crystal structures reveal high anisotropy of Cu displacement. • Electron deficiency is accommodated by S-based holes in valence band

  7. Extraction and recovery of mercury and lead from aqueous waste streams using redox-active layered metal chalcogenides. 1998 annual progress report

    International Nuclear Information System (INIS)

    'Mercury and other highly-toxic heavy metals such as cadmium and lead are present in many aquatic environments, and the remediation of such environments or the avoidance of heavy-metal contamination in the first place is an area of active interest. In recent years tougher environmental regulations and the high initial cost of new, more effective, and more selective extractants has made the reuse of extractant materials and the minimization of secondary waste volume a focus of their scientific effort. The authors research has involved the investigation of redox-active layered metal chalcogenides as selective, effective, and redox-recyclable extractants for heavy metals from aqueous solution.'

  8. Mid-infrared supercontinuum generation spanning 2.0 to 15.1  μm in a chalcogenide step-index fiber.

    Science.gov (United States)

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

    2016-05-01

    We experimentally demonstrate mid-infrared (MIR) supercontinuum (SC) generation spanning ∼2.0 to 15.1 μm in a 3 cm-long chalcogenide step-index fiber. The pump source is generated by the difference frequency generation with a pulse width of ∼170  fs, a repetition rate of ∼1000  Hz, and a wavelength range tunable from 2.4 to 11 μm. To the best of our knowledge, this is the broadest MIR SC generation observed so far in optical fibers. It facilitates fiber-based applications in sensing, medical, and biological imaging areas. PMID:27128088

  9. A New Design of As2Se3‎ Chalcogenide Glass Photonic Crystal Fiber with Ultra-Flattened Dispersion in Mid-Infrared Wavelength Range

    OpenAIRE

    Mahmood Seifouri; Saeed Olyaee; Moslem Dekamin

    2014-01-01

    In this paper, we report a new design of As2Se3‎ chalcogenide glass photonic crystal fiber (PCF) with ultra-flattened dispersion at mid-infrared wavelength range. We have used the plane wave expansion method (PWE) for designing the structure of As2Se3‎ glass PCF at different wavelength windows. In the proposed structure with hole to hole spacing and , the negative dispersion is -1025 ps/nm/km at the wavelength of 1.55µm, and also an ultra-flattened dispersion is achieved at the wavelength ra...

  10. In situ dynamic HR-TEM and EELS study on phase transitions of Ge2Sb2Te5 chalcogenides

    International Nuclear Information System (INIS)

    The phase transition phenomena of Ge2Sb2Te5 chalcogenides were investigated by in situ dynamic high-resolution transmission electron microscopy (HR-TEM) and electron energy loss spectroscopy (EELS). A 300 kV field emission TEM and a 1250 kV high voltage TEM were employed for the in situ heating experiments from 20 to 500 deg. C for undoped and 3 wt% nitrogen-doped Ge2Sb2Te5 thin films deposited by DC sputtering. Crystallization of amorphous Ge2Sb2Te5 to its cubic structure phase started at 130 deg. C and then rapid crystal growth developed from cubic to hexagonal phase in the range of 130-350 deg. C; finally, the hexagonal crystals started to melt at 500 deg. C. For nitrogen-doped Ge2Sb2Te5, its crystallization from amorphous film occurred at higher temperature of ca. 200 deg. C, and the cubic and hexagonal phases were usually formed simultaneously without significant growth of crystals at further heating to 400 deg. C. EELS measurements showed that the electronic structures of Ge, Sb and Te stayed almost the same regardless of the amorphous, FCC and hexagonal phases. The nitrogen doped in Ge2Sb2Te5 was confirmed to exist as a nitride. Also, the doped nitrogen distributed homogeneously in both amorphous and crystalline phases. Localization of doped nitrogen was not found in the grain boundary of crystallized phases. The dynamic process of phase transition was enhanced by high-energy electron irradiation. Peeling of atomic layers in nitrogen-doped Ge2Sb2Te5 film was detected during heating assisted with electron beam irradiation

  11. Thermal analysis of chalcogenide glasses of the system (As/sub/2Se/sub/3)/sub/(1-x):(Tl/sub/2Se)/sub/x

    International Nuclear Information System (INIS)

    In this paper differential thermal analysis (DTA) measurements of chalcogenide glasses of the system (As/sub/2Se/sub/3)/sub/(1-x): (Tl/sub/2Se)/sub/x, with x=0, 0.125, 0.25 and 0.50 are reported. The glass-forming tendencies of these materials have been calculated. The glass-forming tendency of As/sub/2Se/sub/3 has been found to be the highest among the member glasses of this family of chalcogenides. It was found that the glass-forming tendency of As/sub/2Se/sub/3 decreasing gradually at the Tl/sub/2/Se concentration increases. Tl/sub/2Se additions lower the glass transition temperature T/sub/q and the area under the endothermic peak for glass transition temperature, suggesting a tendency for relatively weaker bonding and hence less stability of Tl-rich glass compositions. These studies show that Tl/sub/2Se concentrations result in glasses with progressively higher crystallization tendencies. (author)

  12. A New Design of As2Se3‎ Chalcogenide Glass Photonic Crystal Fiber with Ultra-Flattened Dispersion in Mid-Infrared Wavelength Range

    Directory of Open Access Journals (Sweden)

    Mahmood Seifouri

    2014-12-01

    Full Text Available In this paper, we report a new design of As2Se3‎ chalcogenide glass photonic crystal fiber (PCF with ultra-flattened dispersion at mid-infrared wavelength range. We have used the plane wave expansion method (PWE for designing the structure of As2Se3‎ glass PCF at different wavelength windows. In the proposed structure with hole to hole spacing and , the negative dispersion is -1025 ps/nm/km at the wavelength of 1.55µm, and also an ultra-flattened dispersion is achieved at the wavelength range of 3.5-18μm. Hence such PCFs have a high potential to be used as dispersion compensating fibers at 1.55µm wavelength in optical communication systems. The ultra-flattened dispersion at the wavelength range of 3.5-18μm can be employed to achieve high power super-continuum generation. The nonlinear coefficient of the proposed PCF is 1.5 W-1m-1 at the wavelength of 1.55µm. Chalcogenide glasses are known to have both high transparency and nonlinearity in a wide range of infrared wavelengths compared to silica glasses.

  13. Engel-Vosko GGA Approach Within DFT Investigations of the Optoelectronic Structure of the Metal Chalcogenide Semiconductor CsAgGa2Se4

    Science.gov (United States)

    Azam, Sikander; Khan, Saleem Ayaz; Goumri-Said, Souraya

    2016-01-01

    Metal chalcogenide semiconductors have a significant role in the development of materials for energy and nanotechnology applications. First principle calculations were applied on CsAgGa2Se4 to investigate its optoelectronic structure and bonding characteristics, using the full-potential linear augmented plane wave method within the framework of generalized gradient approximations (GGA) and Engel-Vosko GGA functionals (EV-GGA). The band structure from EV-GGA shows that the valence band maximum and conduction band minimum are situated at Γ with a band gap value of 2.15 eV. A mixture of orbitals from Ag 4 p 6/4 d 10, Se 3 d 10, Ga 4 p 1, Se 4 p 4 , and Ga 4 s 2 states have a primary role to lead to a semiconducting character of the present chalcogenide. The charge density iso-surface shows a strong covalent bonding between Ag-Se and Ga-Se atoms. The imaginary part of dielectric constant reveals that the threshold (first optical critical point) energy of dielectric function occurs 2.15 eV. It is obvious that with a direct large band gap and large absorption coefficient, CsAgGa2Se4 might be considered a potential material for photovoltaic applications.

  14. Ge and As x-ray absorption fine structure spectroscopic study of homopolar bonding, chemical order, and topology in Ge-As-S chalcogenide glasses

    International Nuclear Information System (INIS)

    The coordination environments of Ge and As atoms in GexAsyS1-x-y glasses with x:y=1:2, 1:1, and 2.5:1 and with wide-ranging S contents have been studied with Ge and As K-edge x-ray absorption fine structure spectroscopy. The coordination numbers of Ge and As atoms are found to be 4 and 3, respectively, in all glasses. The first coordination shells of Ge and As atoms in the stoichiometric and S-excess glasses consist of S atoms only, implying the preservation of chemical order at least over the length scale of the first coordination shell. As-As homopolar bonds are found to appear at low and intermediate levels of S deficiency, whereas Ge-Ge bonds are formed only in strongly S-deficient glasses indicating clustering of metal atoms and violation of chemical order in S-deficient glasses. The composition-dependent variation in chemical order in chalcogenide glasses has been hypothesized to result in topological changes in the intermediate-range structural units. The role of such topological transitions in controlling the structure-property relationships in chalcogenide glasses is discussed

  15. Impedance analysis of [(GeS2)]100 2x(Ga2S3)x(AgI)x]100y Agy chalcogenide system and study of power dependency correlation

    Czech Academy of Sciences Publication Activity Database

    Patil, D.; Konale, M. S.; Ren, J.; Yan, Q.; Zima, Vítězslav; Shimakawa, K.; Wágner, T.

    Bratislava: Slovak Academy of Science, 2014. [11th Conference on Solid State Chemistry. 06.07.2014-11.07.2014, Trenčianské Teplice] Institutional support: RVO:61389013 Keywords : chalcogenide glasses * impedance study * power dependence Subject RIV: CA - Inorganic Chemistry

  16. Green, red and near-infrared photon up-conversion in Ga–Ge–Sb–S:Er3+ amorphous chalcogenides

    International Nuclear Information System (INIS)

    We report on compositional tuning in Er3+ ions doped Ga–Ge–Sb–S glassy system allowing for effective 2H11/2→4I15/2 (530 nm), 4S3/2→4I15/2 (550 nm), 4F9/2→4I15/2 (660 nm), 4I9/2→4I15/2 (810 nm), 4I11/2→4I15/2 (990 nm) intra-4f electronic transition emissions of Er3+ ions under 808 nm, 980 nm or 1550 nm laser pumping. We changed the composition of well-known Ge20Ga5Sb10S65 glass to Ge25Ga10−xSbxS65, where x=0.5 at%, 2.5 at% or 5.0 at% and doped it with 0.5 at% of Er3+ ions. The short-wavelength absorption edge of the studied glassy hosts is blue-shifted by substitution of Sb with Ga to ∼500 nm making the green emission at 530 nm and 550 nm and even 495 nm (4F7/2→4I15/2) observable, while the glass stability was kept high characterized with the difference of Tc−Tg>100 K and mean coordination numbers 2.67–2.71. Up-conversion emission decay times of all anti-Stokes emissions were in the range of 0.2–2.1 ms. The influence of Ga substitution with Sb on the structure and the optical properties was investigated. The spectroscopic parameters for Er3+ ions with local environment change were analyzed based on Judd–Ofelt theory. -- Highlights: • Compositional tuning of Ga–Ge–Sb–S:Er3+ phosphor leads to efficient photon up-conversion under 808 nm, 980 nm and 1550 nm laser pumping. • The 530 nm, 550 nm, 660 nm, 810 nm and 990 nm up-conversion emission bands were detected and their lifetimes determined. • Judd–Ofelt theory was used to study the Er3+ local environment in Ga–Ge–Sb–S glassy host matrix. • Thermally stable chalcogenide Ga–Ge–Sb–S:Er3+ phosphors are proposed as candidates for up-converting layers enhancing the silicon solar cell efficiency

  17. Characterization of phase change Ga{sub 15}Se{sub 77}Ag{sub 8} chalcogenide thin films by laser-irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Alvi, M.A., E-mail: alveema@hotmail.com [Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Zulfequar, M. [Department of Physics, Jamia Millia Islamia, New Delhi 110025 (India); Al-Ghamdi, A.A. [Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

    2013-02-15

    Highlights: Black-Right-Pointing-Pointer Effect of laser-irradiation on structure and optical band gap has been investigated. Black-Right-Pointing-Pointer The amorphous nature has been verified by X-ray diffraction and DSC measurements. Black-Right-Pointing-Pointer Laser-irradiation causes a decrease in optical band gap in Ga{sub 15}Se{sub 77}Ag{sub 8} thin films. Black-Right-Pointing-Pointer The decrease in optical band gap can be interpreted on the basis of amorphous-crystalline phase transformation. Black-Right-Pointing-Pointer Optical absorption data showed that the rules of the non-direct transitions predominate. - Abstract: Phase change Ga{sub 15}Se{sub 77}Ag{sub 8} chalcogenide thin films were prepared by thermal evaporation technique. Thin films were then irradiated by Transverse Electrical Excitation at Atmospheric Pressure (TEA) nitrogen laser for different time intervals. The X-ray structural characterization revealed the amorphous nature of as-prepared films while the laser irradiated films show the polycrystalline nature. Field Emission Scanning Electron Microscope (FESEM) has been used to study the structural changes. The results are discussed in terms of the structural aspects and amorphous to crystalline phase change in Ga{sub 15}Se{sub 77}Ag{sub 8} chalcogenide thin films. The observed changes are associated with the interaction of the incident photon and the lone-pairs electrons which affects the band gap of the Ga{sub 15}Se{sub 77}Ag{sub 8} chalcogenide thin films. The optical constants of these thin films are measured by using the absorption spectra measurements as a function of photon energy in the wavelength region 400-1100 nm. It is found that the optical band gap decreases while the absorption coefficient and extinction coefficient increases with increasing the laser-irradiation time. The decrease in the optical band gap has been explained on the basis of change in nature of films, from amorphous to polycrystalline state. The dc

  18. Photo-Darkening Kinetics and Structural Anisotropic Modifications in the Chalcogenide Glass Arsenic Trisulfide: a Study of Kinetic X-Ray Absorption Spectroscopy

    Science.gov (United States)

    Lee, Jay Min

    1990-08-01

    The purpose of the study is to investigate the mechanisms involved with photo-induced atomic structural modifications in the chalcogenide glass As_2 S_3. This glass exhibits the reversible effects of photo-darkening followed by thermal bleaching. We observed the time behavior of photo-induced properties under the influence of linearly polarized band -gap light. In a macroscopic optical investigation, we monitor optical changes in the photo-darkening process, and in a local structural probe we study kinetic (or time -resolved dispersive) x-ray absorption spectroscopy. Our observations center on kinetic phenomena and structural modifications induced by polarized excitation of lone-pair orbitals in the chalcogenide glass. Experimental results include the following observations: (i) The polarity of the optically induced anisotropy is critically dependent on the intensity and the polarization of the band-gap irradiation beam. (ii) The near edge peak height in x-ray absorption spectra shows subtle but sensitive change during the photo-darkening process. (iii) Photon intensity dependent dichroic kinetics reflect a connection between the optically probed macroscopic property and the x-ray probed local anisotropic structure. Analysis of the x-ray absorption results includes a computer simulation of the polarized absorption spectra. These results suggest that specific structural units tend to orient themselves with respect to the photon polarization. A substantial part of the analysis involves a major effort in dealing with the x-ray kinetic data manipulation and the experimental difficulties caused by a synchrotron instability problem. Based on our observations, we propose a possible mechanism for the observed photo-structural modifications. Through a model of computer relaxed photo-darkening kinetics, we support the notion that a twisting of a specific intermediate range order structure is responsible for local directional variations and global network distortions. In the

  19. Spectroscopic investigation of the chemical and electronic properties of chalcogenide materials for thin-film optoelectronic devices

    Science.gov (United States)

    Horsley, Kimberly Anne

    Chalcogen-based materials are at the forefront of technologies for sustainable energy production. This progress has come only from decades of research, and further investigation is needed to continue improvement of these materials. For this dissertation, a number of chalcogenide systems were studied, which have applications in optoelectronic devices, such as LEDs and Photovoltaics. The systems studied include Cu(In,Ga)Se2 (CIGSe) and CuInSe 2 (CISe) thin-film absorbers, CdTe-based photovoltaic structures, and CdTe-ZnO nanocomposite materials. For each project, a sample set was prepared through collaboration with outside institutions, and a suite of spectroscopy techniques was employed to answer specific questions about the system. These techniques enabled the investigation of the chemical and electronic structure of the materials, both at the surface and towards the bulk. CdS/Cu(In,Ga)Se2 thin-films produced from the roll-to-roll, ambient pressure, Nanosolar industrial line were studied. While record-breaking efficiency cells are usually prepared in high-vacuum (HV) or ultra-high vacuum (UHV) environments, these samples demonstrate competitive mass-production efficiency without the high-cost deposition environment. We found relatively low levels of C contaminants, limited Na and Se oxidation, and a S-Se intermixing at the CdS/CIGSe interface. The surface band gap compared closely to previously investigated CIGSe thin-films deposited under vacuum, illustrating that roll-to-roll processing is a promising and less-expensive alternative for solar cell production. An alternative deposition process for CuInSe2 was also studied, in collaboration with the University of Luxembourg. CuInSe2 absorbers were prepared with varying Cu content and surface treatments to investigate the potential to produce an absorber with a Cu-rich bulk and Cu-poor surface. This is desired to combine the bulk characteristics of reduced defects and larger grains in Cu-rich films, while maintaining

  20. First principles calculations of structural, electronic and thermal properties of lead chalcogenides PbS, PbSe and PbTe compounds

    Indian Academy of Sciences (India)

    N Boukhris; H Meradji; S Amara Korba; S Drablia; S Ghemid; F El Haj Hassan

    2014-08-01

    The structural, electronic and thermal properties of lead chalcogenides PbS, PbSe and BeTe using full-potential linear augmented plane wave (FP-LAPW) method are investigated. The exchange–correlation energy within the local density approximation (LDA) and the generalized gradient approximation (GGA) are described. The calculated structural parameters are in reasonable agreement with the available experimental and theoretical data. The electronic band structure shows that the fundamental energy gap is direct (L–L) for all the compounds. Thermal effects on some macroscopic properties of these compounds are predicted using the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variations of the lattice constant, bulk modulus, heat capacity, volume expansion coefficient and Debye temperature with temperature and pressure are obtained successfully. The effect of spin–orbit interaction is found to be negligible in determining the thermal properties and leads to a richer electronic structure.

  1. Dispersion of the refractive index of a samarium-doped Se{sup 95}Te{sup 5} chalcogenide glassy semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Atayeva, S. U., E-mail: seva-atayeva@mail.ru; Mekhtiyeva, S. I.; Isayev, A. I. [National Academy of Sciences of Azerbaijan, Abdullaev Institute of Physics (Azerbaijan)

    2015-07-15

    The transmission spectrum of a Se{sup 95}Te{sup 5} chalcogenide glassy semiconductor doped with samarium (0.05, 0.1, 0.25, 0.5, and 1 at %) is studied; the Swanepoel method and the single-oscillator model are used to determine the oscillator energy E{sup 0}, dispersion energy E{sup d}, optical width of the band gap E{sup g}, and linear (n) and nonlinear (n{sup 2}) refractive indices. The changes in the values of these parameters as a result of doping are attributed to modification of the local structure and to a change in the concentration of defect states.

  2. Ab-initio study of the electronic and elastic properties of beryllium chalcogenides BeX (X=S, Se and Te)

    Energy Technology Data Exchange (ETDEWEB)

    Munjal, N; Sharma, G; Vyas, V [Department of Physics, Banasthali University, Banasthali-304022 (India); Sharma, V; Lowther, J E [School of Physics and DST/NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, Johannesburg-2050 (South Africa); Sharma, B K, E-mail: gsphysics@gmail.com [Department of Physics, University of Rajasthan, Jaipur-302004 (India)

    2011-09-15

    Ab-initio methods have been employed to investigate the electronic and elastic properties of beryllium chalcogenides (namely BeS, BeSe and BeTe). The electron momentum density, autocorrelation function and energy band gap have been computed using the linear combination of atomic orbitals method. Using the full potential linearized augmented plane-wave and projector-augmented wave methods, the energy bands and density of states (DOS) along with elastic properties are also calculated. The electronic band structure, total and partial DOS and elastic moduli obtained from the present calculations are found to be in good agreement with available earlier data. The calculated valence band width, equal valence electron density curve and bulk modulus confirm the trend of ionicity BeS>BeSe>BeTe.

  3. Ge1Sb2Te4 Based Chalcogenide Random Access Memory Array Fabricated by 0.18-μm CMOS Technology

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ting; SONG Zhi-Tang; FENG Gao-Ming; LIU Bo; WU Liang-Cai; FENG Song-Lin; CHEN Bomy

    2007-01-01

    Ge1Sb2Te4-based chalcogenide random access memory array, with a tungsten heating electrode of 260nm in diameter, is fabricated by 0.18-μm CMOS technology. Electrical performance of the device, as well as physical and electrical properties of Ge1Sb2Te4 thin film, is characterized. SET and RESET programming currents are 1.6 and 4.1 mA, respectively, when pulse width is 100ns. Both the values are larger than those of the Ge2Sb2 Te5-based ones with the same structure and contact size. Endurance up to 106 cycles with a resistance ratio of about 100 has been achieved.

  4. Noncentrosymmetric rare-earth copper gallium chalcogenides RE3CuGaCh7 (RE=La-Nd; Ch=S, Se): An unexpected combination

    Science.gov (United States)

    Iyer, Abishek K.; Rudyk, Brent W.; Lin, Xinsong; Singh, Harpreet; Sharma, Arzoo Z.; Wiebe, Christopher R.; Mar, Arthur

    2015-09-01

    The quaternary rare-earth chalcogenides RE3CuGaS7 and RE3CuGaSe7 (RE=La-Nd) have been prepared by reactions of the elements at 1050 °C and 900 °C, respectively. They crystallize in the noncentrosymmetric La3CuSiS7-type structure (hexagonal, space group P63, Z=2) in which the a-parameter is largely controlled by the RE component (a=10.0-10.3 Å for the sulfides and 10.3-10.6 Å for the selenides) whereas the c-parameter is essentially fixed by the choice of Ga and chalcogen atoms within tetrahedral units (c=6.1 Å for the sulfides and 6.4 Å for the selenides). They extend the series RE3MGaCh7, previously known for divalent metal atoms (M=Mn-Ni), differing in that the Cu atoms in RE3CuGaCh7 occupy trigonal planar sites instead of octahedral sites. Among quaternary chalcogenides RE3MM‧Ch7, the combination of monovalent (M=Cu) and trivalent (M‧=Ga) metals is unusual because it appears to violate the condition of charge balance satisfied by most La3CuSiS7-type compounds. The possibility of divalent Cu atoms was ruled out by bond valence sum analysis, magnetic measurements, and X-ray photoelectron spectroscopy. The electron deficiency in RE3CuGaCh7 is accommodated through S-based holes at the top of the valence band, as shown by band structure calculations on La3CuGaS7. An optical band gap of about 2.0 eV was found for La3CuGaSe7.

  5. Chalcogenide Cobalt telluride nanotubes

    Science.gov (United States)

    Dahal, Bishnu; Dulal, Rajendra; Pegg, Ian L.; Philip, John

    Cobalt telluride nanotubes are grown using wet chemical and hydrothermal syntheses. Wet chemical synthesized nanotubes display nearly 1: 1 Co to Te ratio. On the other hand, CoTe nanotubes synthesized using hydrothermal method show excess Co content leading to the compound Co58Te42. Both CoTe and Co58Te42 display magnetic properties, but with totally different characteristics. The Curie temperature of CoTe is higher than 400 K. However, the Tc of Co58Te42 is below 50 K. Transport properties of cobalt telluride (CoTe) nanotube devices show that they exhibit p-type semiconducting behavior. The magnetoresistance measured at 10 K show a magnetoresistance of 54%. . National Science Foundation under ECCS-0845501 and NSF-MRI, DMR-0922997.

  6. Electronic structure of layered quaternary chalcogenide materials for band-gap engineering: The example of Cs2MIIM3IVQ8

    Science.gov (United States)

    Besse, Rafael; Sabino, Fernando P.; Da Silva, Juarez L. F.

    2016-04-01

    Quaternary chalcogenide materials offer a wide variety of chemical and physical properties, and hence, those compounds have been widely studied for several technological applications. Recently, experimental studies have found that the chalcogenide Cs2MIIM3IVQ8 family (MII = Mg , Zn , Cd , Hg , MIV = Ge , Sn and Q = S , Se , Te ), which includes 24 compounds, yields a wide range of band gaps, namely, from 1.07 to 3.4 eV, and hence, they have attracted great interest. To obtain an improved atomistic understanding of the role of the cations and anions on the physical properties, we performed a first-principles investigation of the 24 Cs2MIIM3IVQ8 compounds employing density functional theory within semilocal and hybrid exchange-correlation energy functionals and the addition of van der Waals corrections to improve the description of the weakly interacting layers. Our lattice parameters are in good agreement with the available experimental data (i.e., 11 compounds), and the equilibrium volume increases linearly by increasing the atomic number of the chalcogen, which can be explained by the increased atomic radius of the chalcogen atoms from S to Te . We found that van der Waals corrections play a crucial role in the lattice parameter in the stacking direction of the Cs2MIIM3IVQ8 layers, while the binding energy per unit area has similar magnitude as obtained for different layered materials. We obtained that the band gaps follow a linear relation as a function of the unit cell volume, which can be explained by the atomic size of the chalcogen atom and the relative position of the Q p states within the band structure. The fundamental and optical band gaps differ by less than 0.1 eV. The band gaps obtained with the hybrid functional are in good agreement with the available experimental data. Furthermore, we found from the Bader analysis, that the Coulomb interations among the cations and anions play a crucial role on the energetic properties.

  7. Characterization of the optical constants and dispersion parameters of chalcogenide Te{sub 40}Se{sub 30}S{sub 30} thin film: thickness effect

    Energy Technology Data Exchange (ETDEWEB)

    Abd-Elrahman, M.I.; Hafiz, M.M.; Qasem, Ammar; Abdel-Rahim, M.A. [Assiut University, Physics Department, Faculty of Science, Assiut (Egypt)

    2016-02-15

    Chalcogenide Te{sub 40}Se{sub 30}S{sub 30} thin films of different thickness (100-450 nm) are prepared by thermal evaporation of the Te{sub 40}Se{sub 30}S{sub 30} bulk. X-ray examination of the film shows some prominent peaks relate to crystalline phases indicating the crystallization process. The calculated particles of crystals from the X-ray diffraction peaks are found to be from 11 to 26 nm. As the thickness increases, the transmittance decreases and the reflectance increases. This could be attributed to the increment of the absorption of photons as more states will be available for absorbance in the case of thicker films. The decrease in the direct band gap with thickness is accompanied with an increase in energy of localized states. The obtained data for the refractive index could be fit to the dispersion model based on the single oscillator equation. The single-oscillator energy decreases, while the dispersion energy increases as the thickness increases. (orig.)

  8. External temperature and pressure effects on thermodynamic properties and mechanical stability of yttrium chalcogenides YX (X=S, Se and Te)

    Energy Technology Data Exchange (ETDEWEB)

    Seddik, T. [Laboratoire de Physique Quantique et de Modélisation Mathématique, Université de Mascara, 29000 Mascara (Algeria); Khenata, R., E-mail: khenata_rabah@yahoo.fr [Laboratoire de Physique Quantique et de Modélisation Mathématique, Université de Mascara, 29000 Mascara (Algeria); Bouhemadou, A.; Guechi, N. [Laboratory for Developing New Materials and their Characterization, Department of Physics, Faculty of Science, University of Setif, 19000 Setif (Algeria); Sayede, A. [Université Lille Nord de France, F-59000 Lille (France); Université-Artois, UCCS, F-62300 Lens (France); CNRS, UMR 8181, F-59650 Villeneuve d’Ascq (France); Varshney, D. [Materials Science Laboratory, School of Physics, Vigyan Bhavan, Devi Ahilya University, Khandwa Road Campus, Indore 452001, Madhya Pradesh (India); Al-Douri, Y. [Institute of Nono Electronic Engineering, University Malaysia Perlis, 01000 Kangar, Perlis (Malaysia); Reshak, A.H. [Institute of Complex Systems, FFPW, CENAKVA, University of South Bohemia in CB, Nove Hrady 37333 (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Bin-Omran, S. [Department of Physics and Astronomy, Faculty of Science, King Saud University, PO Box 2455, Riyadh 11451 (Saudi Arabia)

    2013-11-01

    The full potential linearized augmented plane wave method within the framework of density functional theory is employed to investigate the structural, thermodynamic and elastic properties of the yttrium chalcogenides (YX: X=S, Se, and Te) in their low-pressure phase (Fm3{sup ¯}m) and high-pressure phase (Pm3{sup ¯}m). The exchange-correlation potential is treated with the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE). Temperature dependence of the volume and both adiabatic and isothermal bulk moduli is predicted for a temperature range from 0to1200K for the both phases of the herein considered materials. Furthermore, we have analyzed the thermodynamic properties such as the heat capacities, C{sub V} and C{sub P}, thermal expansion, α, and Debye temperature, Θ{sub D,} under variable pressure and temperature. We have calculated the isothermal elastic constants C{sub ij}{sup T} of the YX monochalcogenides in both NaCl-B1 and CsCl-B2 phases at zero pressure and a temperature range 0−1200K. The results show that rare earth yttrium monochalcogenides are mechanically stable at high temperature. The elastic anisotropy of all studied materials in the two phases has been studied using three different methods.

  9. Phase change and optical band gap behavior of Se{sub 0.8}S{sub 0.2} chalcogenide glass films

    Energy Technology Data Exchange (ETDEWEB)

    Abdel Rafea, M. [Institute of Advanced Technology and New Materials, Mubarak City for Scientific Research and Technology Applications, P.O. Box 21934, Universities and Research Centers District, New Borg El Arab City, Alexandria (Egypt)], E-mail: m.abdelrafea@mucsat.sci.eg; Farid, Huda [Institute of Advanced Technology and New Materials, Mubarak City for Scientific Research and Technology Applications, P.O. Box 21934, Universities and Research Centers District, New Borg El Arab City, Alexandria (Egypt)

    2009-02-15

    Se{sub 0.8}S{sub 0.2} chalcogenide glass films have been prepared by thermal vacuum evaporation technique with thickness 583 nm. Annealing process at T {>=} 333 K crystallizes the films and nanostructured films are formed. The crystallite size was increased to 24 nm as the annealing temperature increased to 373 K. Orthorhombic crystalline system was identified for the annealed films. SEM micrographs show that films consist of two parallel surfaces and the thickness was determined by cross section imaging. The optical transmittance is characterized by interference patterns as a result of these two parallel surfaces, besides their average value at longer wavelength decreases as a result of annealing process. The band gap, E{sub g} is red shifted due to crystallization by annealing. As the phase of the films changes from amorphous to crystalline in the annealing temperature range 333-363 K, a non sharp change of the band gap (E{sub g}) is observed. This change was explained by Brus's model of the energy gap confinement behavior of the nanostructured films. The optical refractive index increases suddenly when the system starts to be crystallized by annealing.

  10. Mid-infrared supercontinuum covering the 1.4-13.3 μm molecular fingerprint region using ultra-high NA chalcogenide step-index fibre

    Science.gov (United States)

    Petersen, Christian Rosenberg; Møller, Uffe; Kubat, Irnis; Zhou, Binbin; Dupont, Sune; Ramsay, Jacob; Benson, Trevor; Sujecki, Slawomir; Abdel-Moneim, Nabil; Tang, Zhuoqi; Furniss, David; Seddon, Angela; Bang, Ole

    2014-11-01

    The mid-infrared spectral region is of great technical and scientific interest because most molecules display fundamental vibrational absorptions in this region, leaving distinctive spectral fingerprints. To date, the limitations of mid-infrared light sources such as thermal emitters, low-power laser diodes, quantum cascade lasers and synchrotron radiation have precluded mid-infrared applications where the spatial coherence, broad bandwidth, high brightness and portability of a supercontinuum laser are all required. Here, we demonstrate experimentally that launching intense ultra-short pulses with a central wavelength of either 4.5 μm or 6.3 μm into short pieces of ultra-high numerical-aperture step-index chalcogenide glass optical fibre generates a mid-infrared supercontinuum spanning 1.5 μm to 11.7 μm and 1.4 μm to 13.3 μm, respectively. This is the first experimental demonstration to truly reveal the potential of fibres to emit across the mid-infrared molecular ‘fingerprint region’, which is of key importance for applications such as early cancer diagnostics, gas sensing and food quality control.

  11. New Intermetallic Ternary Phosphide Chalcogenide AP2-xXx (A = Zr, Hf; X = S, Se) Superconductors with PbFCl-Type Crystal Structure

    Science.gov (United States)

    Kitô, Hijiri; Yanagi, Yousuke; Ishida, Shigeyuki; Oka, Kunihiko; Gotoh, Yoshito; Fujihisa, Hiroshi; Yoshida, Yoshiyuki; Iyo, Akira; Eisaki, Hiroshi

    2014-07-01

    We have synthesized a series of intermetallic ternary phosphide chalcogenide superconductors, AP2-xXx (A = Zr, Hf; X = S, Se), using the high-pressure synthesis technique. These materials have a PbFCl-type crystal structure (space group P4/nmm) when x is greater than 0.3. The superconducting transition temperature Tc changes systematically with x, yielding dome-like phase diagrams. The maximum Tc is achieved at approximately x = 0.7, at which point the Tc is 6.3 K for ZrP2-xSex (x = 0.75), 5.5 K for HfP2-xSex (x = 0.7), 5.0 K for ZrP2-xSx (x = 0.675), and 4.6 K for Hfp2-xSx (x = 0.5). They are typical type-II superconductors and the upper and lower critical fields are estimated to be 2.92 T at 0 K and 0.021 T at 2 K for ZrP2-xSex (x = 0.75), respectively.

  12. Phase transformation and kinetic study of a Ga5Ge15Te80 chalcogenide glass using the non-isothermal method

    Science.gov (United States)

    Fadel, M.; Shakra, A. M.; Sakr, G. B.

    2016-07-01

    The crystallization kinetics for a Ga5Ge15Te80 chalcogenide glass, prepared by melt quenching technique, have been studied by differential thermal analysis (DTA) under non-isothermal condition, with five different heating rates α = 10, 15, 20, 25 and 30 ° C/ min . The DTA trace indicates the presence of two crystallization peaks. The glass transition temperature Tg , the crystallization temperature Tc and the melting point temperature Tm were determined. The dependence of Tg , T_{c1} and T_{c2} on the heating rate α , were used for the determination of the activation energy of glass transition Eg and crystallization Ec . The DTA data have been analyzed in terms of activation energy, stability and dimensionality of growth ( m by different models viz. Kissinger's, Mahadeavan, Augis and Bennet's and Matusita's equations. The Avrami exponents ( n and ( m have also been determined; the obtained values of ( n and ( m are 2.959 and 1.959, respectively, indicating bulk nucleation with two-dimensional growth.

  13. Fabrication of a thermoelectric generator on a polymer-coated substrate via laser-induced forward transfer of chalcogenide thin films

    International Nuclear Information System (INIS)

    We have demonstrated the fabrication of a thermoelectric energy harvesting device via laser-induced forward transfer of intact solid thin films. Thermoelectric chalcogenide materials, namely bismuth telluride (Bi2Te3), bismuth selenide (Bi2Se3) and bismuth antimony telluride (Bi0.5Sb1.5Te3), were sequentially printed using a nanosecond excimer laser onto an elastomeric polydimethylsiloxane-coated glass substrate to form thermocouples connected in series creating a thermoelectric generator. The resulting generator Seebeck coefficient and series resistance per leg pair were measured to be 0.17 mV K−1 and 10 kΩ respectively. It was shown that laser-induced forward transfer allows device fabrication from inorganic semiconductor compounds on inexpensive elastic polymer substrates and demonstrates the ability to print materials with pre-defined thermoelectric properties. This allows the rapid manufacturing of a complete thermoelectric device on mm2-areas with μm-scale precision, without the need of further lithographic steps. (paper)

  14. Enhancement in CO2 Adsorption Capacity and Selectivity in the Chalcogenide Aerogel CuSb2S4 by Post-synthetic Modification with LiCl

    KAUST Repository

    Ahmed, Ejaz

    2015-09-11

    The new chalcogel CuSb2S4 was obtained by reacting Cu(OAc)2·H2O with KSbS2 in a water/formamide mixture at room temperature. In order to modify the gas adsorption capacity the synthesized CuSb2S4 aerogel was loaded with different amounts of LiCl. CO2 adsorption measurements on the CuSb2S4 aerogel before and after treatment with LiCl showed more than three times increased uptake of the LiCl-modified chalcogel. The selectivities of the gas pairs CO2/H2 and CO2/CH4 in the LiCl-treated chalcogel are 235 and 105 respectively and amongst the highest reported for chalcogenide-based aerogels. In comparison with other porous materials like zeolites, activated carbon and most of the Metal Organic Frameworks (MOFs) or Porous Organic Frameworks (POFs), our synthesized aerogels show good air and moisture stability. Although, the CO2 storage capacity of our aerogels is relatively low, however the selectivity of CO2 over H2 or CH4 in LiCl-loaded aerogels are higher than in zeolites, activated carbon as well as some MOFs like Cu-BTC and MOF-5 etc.

  15. External temperature and pressure effects on thermodynamic properties and mechanical stability of yttrium chalcogenides YX (X=S, Se and Te)

    International Nuclear Information System (INIS)

    The full potential linearized augmented plane wave method within the framework of density functional theory is employed to investigate the structural, thermodynamic and elastic properties of the yttrium chalcogenides (YX: X=S, Se, and Te) in their low-pressure phase (Fm3¯m) and high-pressure phase (Pm3¯m). The exchange-correlation potential is treated with the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE). Temperature dependence of the volume and both adiabatic and isothermal bulk moduli is predicted for a temperature range from 0to1200K for the both phases of the herein considered materials. Furthermore, we have analyzed the thermodynamic properties such as the heat capacities, CV and CP, thermal expansion, α, and Debye temperature, ΘD, under variable pressure and temperature. We have calculated the isothermal elastic constants CijT of the YX monochalcogenides in both NaCl-B1 and CsCl-B2 phases at zero pressure and a temperature range 0−1200K. The results show that rare earth yttrium monochalcogenides are mechanically stable at high temperature. The elastic anisotropy of all studied materials in the two phases has been studied using three different methods

  16. Memory type switching behavior of ternary Ge20Te80‑x Sn x (0  ⩽  x  ⩽  4) chalcogenide compounds

    Science.gov (United States)

    Jeevan Fernandes, Brian; Sridharan, Kishore; Munga, Pumlian; Ramesh, K.; Udayashankar, N. K.

    2016-07-01

    Chalcogenide compounds have gained huge research interest recently owing to their capability to transform from an amorphous to a crystalline phase with varying electrical properties. Such materials can be applied in building a new class of memories, such as phase-change memory and programmable metallization cells. Here we report the memory type electrical switching behavior of a ternary chalcogenide compound synthesized by doping Tin (Sn) in a germanium–telluride (Ge20Te80) host matrix, which yielded a composition of Ge20Te80‑x Sn x (0  ⩽  x  ⩽  4). Results indicate a remarkable decrease in the threshold switching voltage (V T) from 140 to 61 V when the Sn concentration was increased stepwise, which is attributed to the domination of the metallicity factor leading to reduced amorphous network connectivity and rigidity. Variation in the threshold switching voltage (V T) was noticed even when the sample thickness and temperature were altered, confirming that the memory switching process is of thermal origin. Investigations using x-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed the formation of a crystalline channel that acts as the conduction path between the two electrodes in the switched region. Structural and morphological studies indicated that Sn metal remained as a micro inclusion in the matrix and hardly contributed to the rigid amorphous network formation in Ge20Te80‑x Sn x . Memory type electrical switching observed in these ternary chalcogenide compounds synthesized herein can be explored further for the fabrication of phase-change memory devices.

  17. Optoelectronic behavior of Quaternary Uranium Chalcogenides Rb{sub 2}Pd{sub 3}UM{sub 6} (M = S, Se): A first principle study

    Energy Technology Data Exchange (ETDEWEB)

    Din, Haleem Ud [Department of Physics, Hazara University, Mansehra (Pakistan); Azam, Sikander; Khan, Saleem Ayaz [New Technologies – Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Khenata, R., E-mail: khenata_rabah@yahoo.fr [Laboratoire de Physique Quantique et de Modélisation Mathématique (LPQ3M), Département de Technologie, Université de Mascara, Mascara 29000 (Algeria)

    2014-12-05

    Highlights: • The Fermi surface and optoelectronic properties for Rb{sub 2}Pd{sub 3}UM{sub 6} (M = S, Se) compounds are investigated for the first time. • The electronic band structure calculations reveal a metallic nature for the herein studied compounds. • The bonding nature between different atoms is discussed. • Considerable anisotropy was found between the principal complex tensor components for the two compounds. - Abstract: First principle calculations of electronic, Fermi surface, electronic charge density and optical properties of Quaternary Uranium Chalcogenides Rb{sub 2}Pd{sub 3}UM{sub 6} (M = S, Se) are performed using full potential linear augmented plane wave (FP-LAPW) method within the frame work of density functional theory. Using mBJ method, the electronic band curves overlap at Fermi level and show metallic band structure for both compounds. The calculated densities of states (DOS) spectra show that the valence band is mainly attributed to Rb-p, Pd-d and S-s/p or Se-s/p states; conduction band is mainly attributed to Pd-d, U-f and S-p or Se-p/d states. From the electronic charge density spectrum, it is revealed that a strong covalent bond exists between Pd and S, and Pd or Se while charge transfer between U and S, U and Se, Rb and S, and Rb and Se atoms results in ionic bond nature. It is noted from Fermi surface calculations that both compounds comprise same number of fast velocity electrons but differs in slow or intermediate velocity of electrons. The calculated frequency dependent dielectric function, energy loss function and reflectivity show a considerable anisotropy for both compounds.

  18. Layer-preferential substitutions and magnetic properties of pyrrhotite-type Fe7-yMyX8 chalcogenides (X = S, Se; M = Ti, Co).

    Science.gov (United States)

    Baranov, N V; Ibrahim, P N G; Selezneva, N V; Gubkin, A F; Volegov, A S; Shishkin, D A; Keller, L; Sheptyakov, D; Sherstobitova, E A

    2015-07-22

    A comparative study of four series of pyrrhotite-type chalcogenide compounds Fe(7-y)M(y)X(8) (X = S, Se) with substitution of Ti or Co for iron has been performed by means of x-ray and neutron powder diffraction, and by magnetization measurements. In Fe(7-y)M(y)X(8) compounds having a ferrimagnetic order at y = 0, the substitution of either Ti or Co for iron is observed to result in a monotonous decrease of the magnetic ordering temperature, while the resultant magnetization shows a non-monotonous behavior with a minimum around y = 1.0-1.5 in all the Fe(7-y)M(y)X(8) families except Fe(7-y)Co(y)Se(8). Suppression of a magnetically ordered state with substitutions in Fe(7-y)M(y)X(8) is ascribed to nearly zero values of Ti and Co magnetic moments, while the non-monotonous changes of the resultant magnetization are explained by the compensation of the sublattice magnetizations due to the non-random substitutions in alternating metallic layers. The difference in the cation partitioning observed in Fe(7-y)Ti(y)X(8) and Fe(7-y)Co(y)X(8) is attributed to the difference in the spatial extension of Ti and Co 3d orbitals. High coercive field values (20-24 kOe) observed at low temperatures in the Ti-containing compounds Fe(7-y)Ti(y)X(8) with y ⩾ 3 are suggested to result from the enhancement of Fe orbital moment due to the Ti for Fe substitution. PMID:26125410

  19. 尖晶石型复合硫化物的合成和性能%Synthesis and Property of Composite Chalcogenide with Spinel Structure

    Institute of Scientific and Technical Information of China (English)

    井艳; 高文亮; 孙娟娟; 杨韬

    2013-01-01

    Spinel compound is an important functional material with variable structure and application potential,and is widely investigated in the field of magnetic material,photoelectric material,electrode material,semiconductive material and catalytic material.Because S atom has larger atomic radii than O atom,composite chalcogenide (AB2S4) exhibits more complicated physical properties than composite oxides (AB2O4),so this type of compounds have attached more attentions and been investigated by many researchers over the world.This paper aims to review their synthesis methods and application fields,and the developmental trends for spinel compounds are also prospected.%尖晶石型化合物是一类具有丰富结构类型和应用潜力的功能材料,其在磁性材料、光电材料、电极材料、超导材料、催化材料等领域具有巨大的应用前景.对于硫系尖晶石型化合物AB2S4,由于S原子比O原子具有更大的原子半径,尖晶石型复合硫化物呈现出不同于复合氧化物的物理性质,近年来各国学者对其合成和物理性能进行了大量的探索和研究.本文总结了尖晶石型复合硫化物的合成方法及应用领域,并展望了其未来的发展方向.

  20. PROPERTIES OF Dy3+ -DOPED Ge - Ga - Se CHALCOGENIDE GLASSES%Dy3+掺杂Ge-Ga-Se硫系玻璃的性质

    Institute of Scientific and Technical Information of China (English)

    赵东辉; 夏方; 王华; 陈国荣; NEMEC Petr; FRUMAR Miloslav; 李顺光; 胡丽丽

    2005-01-01

    Dy3+-doped chalcogenide glasses in Ge - Ga - Se system were prepared and the properties of glasses samples including density, microhardness, visilble- infrared transmission spectra, emission spectra and fluorescence life were measured. The molar volume and compactness of glasses were calculated from the density data obtained. The properties of glasses as a function of the average coordination number <r> were discussed. Results show that good fluorescent properties are obtained at 1.3μm when <r> is greater than 2.67 and the measured emission lifetime is from 440 μs to 530 μs. The strongest emission is found in the glass at the chemical threshold of <r> = 2.73.%实验制备了Dy3+掺杂Ge-Ga-Se系统硫系玻璃样品,测试了玻璃的密度、显微硬度、可见-红外透射光谱、荧光光谱以及荧光寿命.根据玻璃的密度计算了玻璃的摩尔体积以及致密度.讨论了玻璃的这些性能随系统平均配位数<r>的变化关系.实验结果表明:该系统中配位数大于2.67的玻璃在1.3 μm具有较好的发光性能,荧光寿命在440~530μs之间,当玻璃组成位于化学门槛即平均配位数为2.73时玻璃的发光强度最强.

  1. Electronic, optical properties and chemical bonding in six novel 1111-like chalcogenide fluorides AMChF (A=Sr, Ba; M=Cu, Ag; and Ch=S, Se, Te) from first principles calculations

    International Nuclear Information System (INIS)

    Employing first-principles band structure calculations, we have examined the electronic, optical properties and the peculiarities of the chemical bonding for six newly synthesized layered quaternary 1111-like chalcogenide fluorides SrAgSF, SrAgSeF, SrAgTeF, BaAgSF, BaAgSeF, and SrCuTeF, which are discussed in comparison with some isostructural 1111-like chalcogenide oxides. We found that all of the studied phases AMChF (A=Sr, Ba; M=Cu, Ag; and Ch=S, Se, Te) are semiconductors for which the fitted “experimental” gaps lie in the interval from 2.23 eV (for SrAgSeF) to 3.07 eV (for SrCuTeF). The near-Fermi states of AMChF are formed exclusively by the valence orbitals of the atoms from the blocks (MCh); thus, these phases belong to the layered materials with “natural multiple quantum wells”. The bonding in these new AMChF phases is described as a high-anisotropic mixture of ionic and covalent contributions, where ionic M–Ch bonds together with covalent M–Ch and Ch–Ch bonds take place inside blocks (MCh), while inside blocks (AF) and between the adjacent blocks (MCh)/(AF) mainly ionic bonds emerge. - Graphical Abstract: Isoelectronic surface for SrAgSeF and atomic-resolved densities of states for SrAgTeF, and SrCuTeF. Highlights: ► Very recently six new layered 1111-like chalcogenide fluorides AMChF were synthesized. ► Electronic, optical properties for AMChF phases were examined from first principles. ► All these materials are characterized as non-magnetic semiconductors. ► Bonding is highly anisotropic and includes ionic and covalent contributions. ► Introduction of magnetic ions in AMChF is proposed for search of novel magnetic materials.

  2. Non-isothermal crystallization kinetic studies on a ternary, Sb{sub 0.14}As{sub 0.38}Se{sub 0.48} chalcogenide semi-conducting glass

    Energy Technology Data Exchange (ETDEWEB)

    Shaaban, E.R. [Physics Department, Faculty of Science, Al-Azhar University, Assuit 71542 (Egypt)]. E-mail: esam_ramadan2005@yahoo.com

    2006-03-15

    Crystallization kinetics of ternary, Sb{sub 0.14}As{sub 0.38}Se{sub 0.48}, chalcogenide glassy alloy was studied under non-isothermal conditions, using the formal theory of transformations for heterogeneous nucleation. The procedure was applied to the experimental data obtained by differential scanning calorimetry (DSc), using continuous-heating techniques. In addition, from the heating-rate dependence of the glass transition temperature, the glass transition activation energy was derived. The crystallization results are analyzed, and both the activation energy of crystallization process and the crystallization mechanism are characterized. The phases at which the alloy crystallizes after the thermal process have been identified by X-ray diffraction. The diffractogram of the transformed material indicates the presence of microcrystallites of Sb{sub 2}Se{sub 3} and AsSe, remaining an additional amorphous matrix.

  3. Ultrafast crystalline-to-amorphous phase transition in Ge{sub 2}Sb{sub 2}Te{sub 5} chalcogenide alloy thin film using single-shot imaging spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Jun, E-mail: jun@ynu.ac.jp; Oba, Wataru; Minami, Yasuo; Katayama, Ikufumi [Department of Physics, Graduate School of Engineering, Yokohama National University, Yokohama 240-8501 (Japan); Saiki, Toshiharu [Graduate School of Science and Technology, Keio University, Yokohama 223-8522 (Japan)

    2014-06-30

    We have observed an irreversible ultrafast crystalline-to-amorphous phase transition in Ge{sub 2}Sb{sub 2}Te{sub 5} chalcogenide alloy thin film using broadband single-shot imaging spectroscopy. The absorbance change that accompanied the ultrafast amorphization was measured via single-shot detection even for laser fluences above the critical value, where a permanent amorphized mark was formed. The observed rise time to reach the amorphization was found to be ∼130–200 fs, which was in good agreement with the half period of the A{sub 1} phonon frequency in the octahedral GeTe{sub 6} structure. This result strongly suggests that the ultrafast amorphization can be attributed to the rearrangement of Ge atoms from an octahedral structure to a tetrahedral structure. Finally, based on the dependence of the absorbance change on the laser fluence, the stability of the photoinduced amorphous phase is discussed.

  4. Ion beam assisted synthesis of nano-crystals in glasses (silver and lead chalcogenides); Synthese assistee par faisceau d'ions d'agregats dans les verres (argent et chalcogenures de plomb)

    Energy Technology Data Exchange (ETDEWEB)

    Espiau de Lamaestre, R

    2005-04-15

    This work deals with the interest in ion beams for controlling nano-crystals synthesis in glasses. We show two different ways to reach this aim, insisting on importance of redox phenomena induced by the penetration and implantation of ions in glasses. We first show that we can use the great energy density deposited by the ions to tailor reducing conditions, favorable to metallic nano-crystal precipitation. In particular, we show that microscopic mechanism of radiation induced silver precipitation in glasses are analogous to the ones of classical photography. Ion beams can also be used to overcome supersaturation of elements in a given matrix. In this work, we synthesized lead chalcogenide nano-crystals (PbS, PbSe, PbTe) whose optical properties are interesting for telecommunication applications. We demonstrate the influence of complex chalcogenide chemistry in oxide glasses, and its relationship with the observed loss of growth control when nano-crystals are synthesized by sequential implantation of Pb and S in pure silica. As a consequence of this understanding, we demonstrate a novel and controlled synthesis of PbS nano-crystals, consisting in implanting sulfur into a Pb-containing glass, before annealing. Choice of glass composition provides a better control of precipitation physico-chemistry, whereas the use of implantation allows high nano-crystal volume fractions to be reached. Our study of IR emission properties of these nano-crystals shows a very high excitation cross section, and evidence for a 'dark exciton' emitting level. (author)

  5. Photoelectrochemical studies of chalcogenide nanoparticles

    CERN Document Server

    Hickey, S G

    2001-01-01

    the bleaching occurs only when electrons are injected into the conduction band of the nanoparticles and charge transfer to surface states does not affect the absorption. The significance of the results are discussed with reference to the various models of absorbance bleaching in semiconductor nanoparticles. The effect of particle size on the charge transfer processes is examined and the results discussed with respect the distance dependence of the electron tunnelling rate. It is then demonstrated that the particle deposition strategy employed for CdS nanoparticles may be extended to HgS. This thesis is primarily concerned with the (opto)electrochemical investigation of the dynamics of charge separation at tin oxide electrodes derivatised with sub-monolayers of CdS nanoparticles. First a novel method of preparing CdS nanoparticle-modified electrodes is described and it is demonstrated that the particles deposited onto the substrate are representative of those formed in the sol. Employing the technique of inten...

  6. Soluble precursors for CuInSe2, CuIn(1-x)Ga(x)Se2, and Cu2ZnSn(S,Se)4 based on colloidal nanocrystals and molecular metal chalcogenide surface ligands.

    Science.gov (United States)

    Jiang, Chengyang; Lee, Jong-Soo; Talapin, Dmitri V

    2012-03-21

    We report a new platform for design of soluble precursors for CuInSe(2) (CIS), Cu(In(1-x)Ga(x))Se(2) (CIGS), and Cu(2)ZnSn(S,Se)(4) (CZTS) phases for thin-film potovoltaics. To form these complex phases, we used colloidal nanocrystals (NCs) with metal chalcogenide complexes (MCCs) as surface ligands. The MCC ligands both provided colloidal stability and represented essential components of target phase. To obtain soluble precursors for CuInSe(2), we used Cu(2-x)Se NCs capped with In(2)Se(4)(2-) MCC surface ligands or CuInSe(2) NCs capped with {In(2)Cu(2)Se(4)S(3)}(3-) MCCs. A mixture of Cu(2-x)Se and ZnS NCs, both capped with Sn(2)S(6)(4-) or Sn(2)Se(6)(4-) ligands was used for solution deposition of CZTS films. Upon thermal annealing, the inorganic ligands reacted with NC cores forming well-crystallized pure ternary and quaternary phases. Solution-processed CIS and CZTS films featured large grain size and high phase purity, confirming the prospects of this approach for practical applications. PMID:22329720

  7. Synthesis of metals chalcogenides nano-particles from H{sub 2}X (X=S, Se, Te) produced electrochemically; Synthese de nanoparticules de chalcogenures de metaux a partir de H{sub 2}X (X=S, Se, Te) produit electrochimiquement

    Energy Technology Data Exchange (ETDEWEB)

    Bastide, S.; Tena-Zaera, R.; Alleno, E.; Godart, C.; Levy-Clement, C. [Centre National de la Recherche Scientifique (CNRS), Lab. de Chimie Metallurgique des Terres Rares, 94 - Thiais (France); Hodes, G. [Weizmann Institute of Science, Rehovot (Israel)

    2006-07-01

    In this work, an electrochemical method to produce H{sub 2}X (X=S, Se, Te) hydrides in a controlled way (without being able to store them) and to transfer them directly in the synthesis reactor has been perfected. By this method, the use of H{sub 2}Te has been possible. The method uses the reduction of the elementary chalcogenide in acid medium. The Te being conductor, it can be directly used as electrode, on the other hand S and Se are insulators. Nevertheless, graphite-S or Se conducing composite electrodes can also be used. When the electrolyte composition (pH, salts presence) is well adjusted, the essential of the cathodic current is consumed by the chalcogenide reduction (low evolution of H{sub 2}) with faradic yields of about 100% for H{sub 2}S and H{sub 2}Se and 40% for HeTe. The use of H{sub 2}X allows the synthesis of nano-particles of metals chalcogenides directly by reaction with dissolved metallic salts in aqueous or organic medium and precipitation. Thus it has been possible to prepare all the CdX compounds under the form of nano-particles of diameter between 3 and 5 nm by bubbling of the gaseous hydrides in aqueous acetate solutions of Cd. In producing concomitantly H{sub 2}S and H{sub 2}Se, nano-particles of solid solutions CdS{sub x}Se{sub 1-x} have been synthesized too. (O.M.)

  8. Optical micro-resonators in chalcogenide glass

    OpenAIRE

    Elliott, Gregor Robert

    2009-01-01

    This thesis focuses on the production of gallium lanthanum sulphide (GLS) microspheres and their potential uses. Microspheres, and micro-resonators in general, have attracted considerable attention because of their promise in all-optical-switching, micro-lasers, multiplexers and many other applications. In this thesis, several applications have been investigated, culminating in the demonstration of laser action in a neodymium doped GLS microsphere. The possibility of using microspheres as bal...

  9. Chalcogenide glasses - prospective materials for fiber optics

    Czech Academy of Sciences Publication Activity Database

    Ožvoldová, M.; Ležal, Dimitrij

    Púchov : The University of Trenčín, 1999, s. 1 [International Conference on Theoretical and Experimental Problems of Materials Engineering /4./. Púchov (SK), 09.09.1999-11.09.1999] Grant ostatní: VEGA grant agency(SK) 2/4184/97; VEGA grant agency(SK) 95/5305/588; VEGA grant agency(SK) 1/4338/97 Institutional research plan: CEZ:AV0Z4032918 Keywords : fiber optics * glass Subject RIV: CA - Inorganic Chemistry

  10. Structure of chalcogenide glasses by neutron diffraction

    CERN Document Server

    Cuello, Gabriel; Fernandez-Martinez, Alejandro; Fontana, Marcelo; Pradel, A

    2008-01-01

    The purpose of this work is to study the change in the structure of the Ge-Se network upon doping with Ag. The total structure factor S(Q) for two samples has been measured by neutron diffraction using the two-axis diffractometer dedicated to structural studies of amorphous materials, D4, at the Institut Laue Langevin. We have derived the corresponding radial distribution functions for each sample and each temperature, which gives us an insight about the composition and temperature dependence of the correlation distances and coordination numbers in the short-range. Our results are compatible with the presence of both GeSe4/2 tetrahedra and Se-Se bonds. The Ag atoms are linked to Se in a triangular environment. Numerical simulations allowing the identification of the main peaks in the total pair correlation functions have complemented the neutron diffraction measurements.

  11. Chalcogenide glass microlenses by inkjet printing

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, Eric A.; Waldmann, Maike; Arnold, Craig B.

    2011-05-10

    We demonstrate micrometer scale mid-IR lenses for integrated optics, using solution-based inkjet printing techniques and subsequent processing. Arsenic sulfide spherical microlenses with diameters of 10-350 {mu}m and focal lengths of 10-700 {mu}m have been fabricated. The baking conditions can be used to tune the precise focal length.

  12. Chalcogenide glass microlenses by inkjet printing

    International Nuclear Information System (INIS)

    We demonstrate micrometer scale mid-IR lenses for integrated optics, using solution-based inkjet printing techniques and subsequent processing. Arsenic sulfide spherical microlenses with diameters of 10-350 μm and focal lengths of 10-700 μm have been fabricated. The baking conditions can be used to tune the precise focal length.

  13. Superconductivity in lanthanum chalcogenides under pressure

    International Nuclear Information System (INIS)

    In this thesis the pressure dependence of the superconducting transition temperature of La3S4, La3Se4, La3Te4, La2Se2S2, and La2Sesub(3,6) Tesub(0,4) is investigated up to 4,5 GPa. A pressure cell is reported which allows also the measurement of the magnetic susceptibility under pressure. The calculated density of states describe the increase of the critical temperature very well in the frame of Mc Millans equation. (TWO)

  14. Transition-metal substitutions in iron chalcogenides

    Science.gov (United States)

    Bezusyy, V. L.; Gawryluk, D. J.; Malinowski, A.; Cieplak, Marta Z.

    2015-03-01

    The a b -plane resistivity and Hall effect are studied in Fe1 -yMyTe0.65Se0.35 single crystals doped with two transition-metal elements, M = Co or Ni, over a wide doping range, 0 ≤y ≤0.2 . The superconducting transition temperature, Tc, reaches zero for Co at y ≃0.14 and for Ni at y ≃0.032 , while the resistivity at the Tc onset increases weakly with Co doping, and strongly with Ni doping. The Hall coefficient RH, positive for y =0 , remains so at high temperatures for all y , while it changes sign to negative at low T for y >0.135 (Co) and y >0.06 (Ni). The analysis based on a two-band model suggests that at high T residual hole pockets survive the doping, but holes get localized upon the lowering of T , so that the effect of the electron doping on the transport becomes evident. The suppression of the Tc by Co impurity is related to electron doping, while in the case of the Ni impurity strong electron localization most likely contributes to fast decrease of the Tc.

  15. Chalcogenide Materials for Solar Energy Conversion

    Directory of Open Access Journals (Sweden)

    Péter Turmezei

    2004-11-01

    Full Text Available The problem of electrical energy storage can possibly be solved with the help of electrochemical solar cells, which are suitable to generate either electrical energy or hydrogen gas under special conditions. The greatest problem of the electrochemical solar cell technology is to find novel materials which have appropriate properties for electrochemical energy conversion. In this work Cd4GeSe6, a novel material for electrochemical solar cells, will be presented.

  16. Electronic-structure theory of plutonium chalcogenides

    Czech Academy of Sciences Publication Activity Database

    Shick, Alexander; Havela, L.; Gouder, T.; Rebizant, J.

    2009-01-01

    Roč. 385, č. 1 (2009), 21-24. ISSN 0022-3115 R&D Projects: GA ČR GA202/07/0644; GA MŠk OC 144 Institutional research plan: CEZ:AV0Z10100520 Keywords : electronic structure * electron correlations * photoemission Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.933, year: 2009

  17. Electronic structure and photoemission in plutonium chalcogenides

    Czech Academy of Sciences Publication Activity Database

    Shick, Alexander; Havela, L.; Gouder, T.

    Warrendale, PA : Materials Research Society, 2008 - (Shuh, D.; Chung, B.; Albrecht-Schmitt, T.; Gouder, T.; Thompson, J.), s. 53-58 ISBN 978-1-60511-074-5. - (Materials Research Society Symposium Proceedings. NN. 1104). [Actinides 2008-Basic Science, Applications, and Technology. San Francisco (US), 24.03.2008-28.03.2008] R&D Projects: GA MŠk OC 144; GA ČR GA202/07/0644 Institutional research plan: CEZ:AV0Z10100520 Keywords : electronic sructure * photoemission * magnetism * strong electron correlations Subject RIV: BM - Solid Matter Physics ; Magnetism

  18. Ultrabroadband terahertz spectroscopy of chalcogenide glasses

    DEFF Research Database (Denmark)

    Zalkovskij, Maksim; Bisgaard, Christer Zoffmann; Novitsky, Andrey;

    2012-01-01

    absorption coefficient is found for both glasses. We observe the breakdown of the universal power-law dependence of the absorption coefficient due to atomic vibrations observed at low THz frequencies in disordered materials, and see the transition to localized vibrational dynamics for the As2S3 compound at...

  19. Modified chalcogenide glasses for optical device applications

    CERN Document Server

    Hughes, Mark A

    2014-01-01

    This thesis focuses on two different, but complementary, aspects of the modification of gallium lanthanum sulphide (GLS) glasses. Firstly the addition of transition metal ions as dopants is examined and their potential for use as active optical materials is explored. It is also argued that the spectroscopic analysis of transition metal ions is a useful tool for evaluating the local environment of their host. Secondly femtosecond (fs) laser modification of GLS is investigated as a method for waveguide formation.

  20. Neodymium doped chalcogenide glass fibre laser

    OpenAIRE

    Samson, B.N.; Schweizer, T.; Moore, R C; Hewak, D.W.; Payne, D.N.

    1997-01-01

    We report on laser action in a Neodymium doped Gallium Lanthanum Sulphide glass fibre. Laser action at 1080nm was obtained in a 22mm long multimode glass fibre with a neodymium doped core, fabricated by the rod-in-tube technique. The laser was pumped continuous wave with a Ti:sapphire laser at 815nm and showed a self-pulsing behaviour

  1. Chalcogenide aerogels as sorbents for radioactive iodine

    Energy Technology Data Exchange (ETDEWEB)

    Subrahmanyam, Kota S.; Sarma, Debajit; Malliakas, Christos; Polychronopoulou, Kyriaki; Riley, Brian J.; Pierce, David A.; Chun, Jaehun; Kanatzidis, Mercouri G.

    2015-04-14

    Iodine (129I) is one of the radionuclides released in nuclear fuel reprocessing and poses risk to public safety due to its involvement in human metabolic processes. In order to prevent the leaching of hazardous radioactive iodine into the environment, its effective capture and sequestration is pivotal. In the context of finding a suitable matrix for capturing radioactive iodine the chalcogels, NiMoS4, CoMoS4, Sb4Sn4S12, Zn2Sn2S6, and CoSx (x = 4-5) were explored as iodine sorbents. All the chalcogels showed high uptake, reaching up to 225 mass% (2.25 g/g) of the final mass owing to strong chemical and physical iodine-chalcogen interactions. Analysis of the iodine-loaded specimens revealed that the iodine chemically reacted with Sb4Sn4S12, Zn2Sn2S6, and CoSx to form metal complexes SbI3, SnI4, and, KI respectively. The NiMoS4 and CoMoS4 chalcogels did not appear to undergo a chemical reaction with iodine since iodide complexes were not observed with these samples. Once heated, the iodine-loaded chalcogels released iodine in the temperature range of 75 °C to 220 °C, depending on the nature of iodine speciation. In the case of Sb4Sn4S12 and Zn2Sn2S6 iodine release was observed around 150 °C in the form of SnI4 and SbI3, respectively. The NiMoS4, CoMoS4, and CoSx released iodine at ~75 °C, which is consistent with physisorbed iodine. Preliminary investigations on consolidation of iodine-loaded Zn2Sn2S6 with Sb2S3 as a glass forming additive showed the content of iodine in consolidated glass ingots at around 25 mass%.

  2. Structural, optical, and magnetic properties of Na8Eu2(Si2S6)2 and Na8Eu2(Ge2S6)2: Europium(II) quaternary chalcogenides that contain an ethane-like (Si2S6)6− or (Ge2S6)6− moiety

    International Nuclear Information System (INIS)

    Two isostructural europium(II) quaternary chalcogenides, Na8Eu2(Si2S6)2, 1, and Na8Eu2(Ge2S6)2, 2, containing an ethane-like (Si2S6)6− or (Ge2S6)6− moiety have been synthesized by employing the polychalcogenide molten flux method. Single-crystal X-ray diffraction reveals that both compounds crystallize in the C2/m space group, and their structures contain layers of ([Na2Eu2(Si2S6)2]6−)∞ or ([Na2Eu2(Ge2S6)2]6−)∞ anions held together by six interlayer sodium cations to yield (Na6[Na2Eu2(Si2S6)2])∞ and (Na6[Na2Eu2(Ge2S6)2])∞. Compound 2 is a semiconductor with an optical band gap of 2.15(2) eV. The temperature dependence of the magnetic susceptibility indicates that compounds 1 and 2 are paramagnetic with μeff=7.794(1) μB per Eu and g=1.964(1) for 1 and μeff=8.016(1) μB per Eu and g=2.020(1) for 2, moments that are in good agreement with the europium(II) spin-only moment of 7.94 μB. The europium-151 Mössbauer isomer shift of 2 confirms the presence of europium(II) cations with an electronic configuration between [Xe]4f6.81 and 4f76s0.32. - Graphical abstract: TOC figure caption: structure of Na8Eu2(Si2S6)2 viewed along the a-axis showing the filling of A–B and B–A types of anion layers with two different types of cations. - Highlights: • Synthesis of quaternary europium chalcogenides containing ethane-like dimer. • Structural characterization employing single-crystal X-ray diffraction. • Mössbauer spectroscopy and magnetic measurements confirm presence of Eu(II)

  3. Rare-earth transition-metal chalcogenides Ln3MGaS7 (Ln=Nd, Sm, Dy, Er; M=Co, Ni) and Ln3MGaSe7 (Ln=Nd, Sm, Gd, Dy, M=Co; Ln=Nd, Gd, Dy, M=Ni)

    International Nuclear Information System (INIS)

    Fifteen new rare-earth transition-metal chalcogenides, Ln3MGaS7 (Ln=Nd, Sm, Dy, Er; M=Co, Ni) and Ln3MGaSe7 (Ln=Nd, Sm, Gd, Dy, M=Co; Ln=Nd, Gd, Dy, M=Ni), have been synthesized by solid state reactions. They are isostructural, adopt Ce3Al1.67S7—related structure type, and crystallize in the non-centrosymmetric hexagonal space group P63. They adopt a three-dimensional framework composed of LnQ7 monocapped trigonal prisms with the interesting [MQ3]4− chains and isolated GaQ4 tetrahedra lying in two sets of channels in the framework. The magnetic susceptibility measurements on Ln3CoGaQ7 (Ln=Dy, Er, Q=S; Ln=Dy, Q=Se) indicate that they are paramagnetic and obey the Curie–Weiss law over the entire experimental temperature, while the magnetic susceptibility of Sm3CoGaSe7 deviates from the Curie–Weiss law as a result of the crystal field splitting. - Graphical abstract: Ln3MGaS7 (Ln=Nd, Sm, Dy, Er; M=Co, Ni) and Ln3MGaSe7 (Ln=Nd, Sm, Gd, Dy, M=Co; Ln=Nd, Gd, Dy, M=Ni) adopt a three-dimensional framework composed of LnQ7 monocapped trigonal prisms with interesting [MQ3]4− chains and isolated GaQ4 tetrahedra lying in two sets of channels in the framework. - Highlights: • New compounds, Ln3MGaQ7 (Ln=rare-earth; M=Co, Ni; Q=S, Se), were synthesized. • They are isostructural and crystallize in the noncentrosymmetric space group P63. • They adopt a three-dimensional framework built by LnQ7 monocapped trigonal prisms. • Ln3CoGaQ7 (Ln=Dy, Er; Q=S, Se) are paramagnetic and obey the Curie–Weiss law. • The magnetic susceptibility of Sm3CoGaSe7 deviates from the Curie–Weiss law

  4. Induced radiation of thin lead chalcogenide films under photoexcitation

    International Nuclear Information System (INIS)

    Induced radiation of thin polycrystalline films of PbSe, PbFe, PbS photo excited by the neodimium laser was found out. The threshold excitation at 77 deg K was about 102 - 103 W/cm2. The radiation spectra of PbSe at 10 - 80 deg K consisted of single lines in the hw range 165 - 200 MeV. The width of the lines was determined by the destruction of the spectrometer. Model of the initiation of induced radiation in active dielectric waveguide with crosswise, scattering of radiation on the heterogeneous sections is being discussed

  5. Metrology of achromatic diffractive features on chalcogenide lenses

    Science.gov (United States)

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

    2015-10-01

    Achromatic diffractive features on lenses are widely used in industry for color correction, however there is not a welldefined standard to quantify the performance of the lenses. One metric used to qualify a lens is the sag deviation from the nominal lens profile. Imperfections in the manufacturing of the diffractive feature may cause scattering and performance loss. This is not reflected in sag deviation measurements, therefore performance measurements are required. There are different quantitative approaches to measuring the performance of an achromatic diffractive lens. Diffraction efficiency, a measure of optical power throughput, is a common design metric used to define the percent drop from the modulation transfer function (MTF) metric. The line spread function (LSF) shows a layout of the intensity with linear distance and an ensquared energy specification can be implemented. The MTF is a common analysis tool for assemblies and can be applied to a single element. These functional tests will be performed and compared with diffractive lenses manufactured by different tool designs. This paper displays the results found with various instruments. Contact profilometry was used to inspect the profile of the diffractive elements, and a MTF bench was used to characterize lens performance. Included will be a discussion comparing the results of profile traces and beam profiles to expected diffraction efficiency values and the effects of manufacturing imperfections.

  6. Shape Control and Functional Properties of Copper Chalcogenide Colloidal Nanocrystals

    OpenAIRE

    Li, Wenhua

    2013-01-01

    The high quality CuxS nanocrystals were synthesized (Chapter 3) and the profound understanding and skills to prepare colloidal nanocrystals has been obtained and improved. It revealed a very simple synthetic route not only for the systematic investigation on the size control of the copper sulfide nanodisks but also for studying the influence of different stoichiometric ratios on the shape of copper sulfide nanocrystals. An increase of the precursor concentration in the growth solution resulte...

  7. Theoretical Predictions of Freestanding Honeycomb Sheets of Cadmium Chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Jia [ORNL; Huang, Jingsong [ORNL; Sumpter, Bobby G [ORNL; Kent, Paul R [ORNL; Xie, Yu [ORNL; Terrones Maldonado, Humberto [ORNL; Smith, Sean C [ORNL

    2014-01-01

    Two-dimensional (2D) nanocrystals of CdX (X = S, Se, Te) typically grown by colloidal synthesis are coated with organic ligands. Recent experimental work on ZnSe showed that the organic ligands can be removed at elevated temperature, giving a freestanding 2D sheet of ZnSe. In this theoretical work, freestanding single- to few-layer sheets of CdX, each possessing a pseudo honeycomb lattice, are considered by cutting along all possible lattice planes of the bulk zinc blende (ZB) and wurtzite (WZ) phases. Using density functional theory, we have systematically studied their geometric structures, energetics, and electronic properties. A strong surface distortion is found to occur for all of the layered sheets, and yet all of the pseudo honeycomb lattices are preserved, giving unique types of surface corrugations and different electronic properties. The energetics, in combination with phonon mode calculations and molecular dynamics simulations, indicate that the syntheses of these freestanding 2D sheets could be selective, with the single- to few-layer WZ110, WZ100, and ZB110 sheets being favored. Through the GW approximation, it is found that all single-layer sheets have large band gaps falling into the ultraviolet range, while thicker sheets in general have reduced band gaps in the visible and ultraviolet range. On the basis of the present work and the experimental studies on freestanding double-layer sheets of ZnSe, we envision that the freestanding 2D layered sheets of CdX predicted herein are potential synthesis targets, which may offer tunable band gaps depending on their structural features including surface corrugations, stacking motifs, and number of layers.

  8. Electron microscopy of iron chalcogenide FeTe(Se) films

    International Nuclear Information System (INIS)

    The structure of Fe1+δTe1−xSex films (x = 0; 0.05) grown on single-crystal MgO and LaAlO3 substrates has been investigated by transmission and scanning transmission electron microscopy. The study of Fe1.11Te/MgO structures has revealed two crystallographic orientation relationships between the film and substrate. It is shown that the lattice mismatch between the film and substrate is compensated for by the formation of misfit dislocations. The Burgers vector projection is determined. The stresses in the film can partially be compensated for due to the formation of an intermediate disordered layer. It is shown that a FeTe0.5Se0.5 film grown on a LaAlO3 substrate is single-crystal and that the FeTe0.5Se0.5/LaAlO3 interface in a selected region is coherent. The orientation relationships between the film and substrate are also determined for this case

  9. Nanosized Photovoltaic Materials Based on Chalcogenides of Transient Metals

    Czech Academy of Sciences Publication Activity Database

    Slušná, Michaela; Henych, Jiří; Velická, Jana; Bludská, Jana; Štengl, Václav

    Stow cum Quy: Zing Conferences, 2013. s. 47. [Nanomaterials conference 2013. 13.11.2013-17.11.2013, Playa del Carmen] R&D Projects: GA MPO FR-TI4/399 Institutional support: RVO:61388980 Keywords : nanomaterials Subject RIV: CA - Inorganic Chemistry

  10. PAL signature of physical ageing in chalcogenide glasses

    Energy Technology Data Exchange (ETDEWEB)

    Ingram, Adam; Kozdras, Andrzej [Physics Faculty of Opole University of Technology, 75, Ozimska Str., Opole 45370 (Poland); Shpotyuk, Oleh [Institute of Physics of Jan Dlugosz University, 13/15, al. Armii Krajowej, Czestochowa 42201 (Poland); Golovchak, Roman [Physics Faculty of Opole University of Technology, 75, Ozimska Str., Opole 45370 (Poland); Lviv Scientific Research Institute of Materials of SRC ' ' Carat' ' , 202, Stryjska Str., Lviv 79031 (Ukraine)

    2012-05-15

    Kinetics of physical ageing (PhA) far below the glass transition temperature (T{sub g}) is studied by positron annihilation lifetime and differential scanning calorimetry techniques for vitreous As{sub 20}Se{sub 80} as typical representative of network glasses. The increased density fluctuations are shown to be responsible for the initial stage of PhA in this glass at below-T{sub g} temperatures. These fluctuations are correlated with changes in thermodynamic parameters of structural relaxation through the glass-to-supercooled liquid transition interval. General shrinkage, occurred during the next stage of PhA, is shown to be determined by the ability of system to release these redundant open volumes from the glass bulk through densification process of glass network. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Mechanism of defect production in irradiated chalcogenide glass semiconductors

    International Nuclear Information System (INIS)

    Defect production in thin semiconductor layers of irradiated glass arsenic trisulfide was studied by using the optical modulation spectroscopy of vibrating absorption bands of basic structural fragments and complexes. It is shown, that at structural microscopic level the effects being observed are related to pairing of the diamagnetic over- and undercoordination defects: (As2-; S3+), (As4+; S1-), (S1-; S3+) and (As2-; As4+) and also defects (As2+; S1+) with partial annihilation of As2+ and S1-

  12. Crystallization study of Sn additive Se–Te chalcogenide alloys

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Rahim, M.A.; Gaber, A.; Abu-Sehly, A.A.; Abdelazim, N.M., E-mail: nana841@hotmail.co.uk

    2013-08-20

    Highlights: • The aim of the work deals with studying the crystallization kinetics by using different method. • Values of various kinetic parameters were calculated. • The results indicate that the rate of crystallization is related to the thermal stability and glass forming ability. - Abstract: Results of differential thermal analysis (DTA) under non-isothermal conditions of glasses Se{sub 90−x}Te{sub 10}Sn{sub x} (x = 0, 2.5, 5 and 7 at.%) are reported and discussed. The glass transition temperature (T{sub g}), the onset crystallization temperature (T{sub c}) and the peak temperature of crystallization (T{sub p}) were found to be dependent on the compositions and the heating rate. Values of various kinetic parameters such as activation energy of glass transition (E{sub g}), activation energy of crystallization (E{sub c}), rate constant (K{sub p}), Hurby number (H{sub r}) and the order parameter (n) were determined. For the present systems, the results indicate that the rate of crystallization is related to thermal stability and glass forming ability (GFA). According to the Avrami exponent (n), the results show a one dimensional growth for the composition Se{sub 90}Te{sub 10} and a three dimensional growth for the three other compositions. The crystalline phases resulting from DTA and (SEM) have been identified using X-ray diffraction.

  13. Experimental Evidence for Onset of Rigidity in Chalcogenide Glasses

    Science.gov (United States)

    Boolchand, P.

    1998-03-01

    Melt-quenched Ge_xX_1-x glasses, X = S or Se, are examined in Raman scattering (Xingwei Feng, W.J.Bresser and P.Boolchand, Phys. Rev. Lett. 78, 4422 (1997).), temperature modulated differential scanning calorimetry (MDSC)^2, Mössbau er spectroscopy and Molar volume measurements over the composition range 0.10r~_c, suggesting (D.S.Franzblau and J.Tersoff, Phys. Rev. Lett. 68, 2172 (1992).) that r~c represents the stiffness threshold. The non-reversing heat-flow at Tg from MDSC experiments^2, revea l a minimum at r~_c, confirming the minimal network strain prevailing at the stiffness transition. Molar volumes and ^129I Mössbauer site-intensity ratios also display a threshold behaviour to r = r~_c, and these results reflect the underlying structural manifestation of the stiffness transition. The upshift of the stiffness transition at r~ = 2.46(1) from it mean-field value (r~c = 2.40) suggests that angular constraints associated with chalcogen atoms in floppy chain-seg ments near r~c are intrinsically broken(M.Zhang and P.Boolchand, Science 266, 1355 (1994).) in these glasses.

  14. Molecular solution processing of metal chalcogenide thin film solar cells

    OpenAIRE

    Yang, Wenbing

    2013-01-01

    The barrier to utilize solar generated electricity mainly comes from their higher cost relative to fossil fuels. However, innovations with new materials and processing techniques can potentially make cost effective photovoltaics. One such strategy is to develop solution processed photovoltaics which avoid the expensive vacuum processing required by traditional solar cells. The dissertation is mainly focused on two absorber material system for thin film solar cells: chalcopyrite CuIn(S,Se)2 (C...

  15. Evanescent field infrared spectroscopy using chalcogenide glass fiber

    International Nuclear Information System (INIS)

    In the last few years a simple and cheap fiber-optics based spectroscopy method was developed for the investigation of liquids, pastes gases and thin layers. The fiber is immersed in the sample, and the investigated material becomes the fiber cladding. the interaction between the guided radiation in the fiber and the specimen is taking place by evanescent field which extends outside the fiber. This work concentrates in the quantitative characterization of the absorption of the evanescent field by the fiber cladding (the specimen). This subject was dealt with only briefly in the earlier works, and the aim of this work is to obtain a comprehensive understanding of this issue. (author)

  16. Packaged Chalcogenide Microsphere Resonator with High Q-factor

    OpenAIRE

    Wang, Pengfei; Ding, Ming; Lee, Timothy; Murugan, Ganapathy Senthil; Bo, Lin; Semenova, Yuliya; Wu, Qiang; Hewak, Dan; Brambilla, Gilberto

    2013-01-01

    The fabrication and characterization of a packaged As2S3 microsphere resonator coupled to a tapered fiber using a low refractive index UV-curable polymer are reported. Embedding provides an efficient means to remove the highest order whispering gallery modes in the microsphere resonator, thus cleaning the resonator spectrum. The device photosensitivity, useful for tuning, is still present and useable after the packaging process

  17. Laser-induced piezoelectric effects in chalcogenide crystals

    International Nuclear Information System (INIS)

    The photoinduced piezoelectric effect in the single crystals of AgGaGe3Se8 was discovered under the influence of 532 nm cw laser with average power about 150 mW. The changes of the piezoelectricity were explored with respect to principal diagonal components d11, d22, and d33. To study the contributions of photostimulated thermal and piezooptical effects additional measurements of temperature dependent piezoelectricity and piezo-optical coefficients were done. Substantial changes were demonstrated and their time kinetics during photoillumination was explored. The three principal diagonal piezoelectric coefficients along the crystallographic axis were studied. The reversibility of the process after switching off of the photoinducing laser is given. The effect observed may be applied for laser operated piezotronic devices. The contribution of different mechanisms in the photostimulated piezoelectricity is explored

  18. States of antimony and tin atoms in lead chalcogenides

    International Nuclear Information System (INIS)

    It is shown by Mössbauer spectroscopy of the 119Sb(119mSn) isotope that impurity antimony atoms in PbS, PbSe, and PbTe lattices are distributed between cation and anion sublattices. In n-type samples, the greatest part of antimony is located in the anion sublattice; in hole ones, in the cation sublattice. The tin atoms formed as a result of radioactive decay of 119Sb (antisite state) are electrically inactive in the anion sub-lattice of PbS and PbSe, while, in the cation sublattice, they form donor U− centers. Electron exchange between the neutral and doubly ionized tin U− centers via the allowed band states is observed. The tin atoms formed after radioactive decay of 119Sb are electrically inactive in the anion and cation sublattices of PbTe.

  19. Rare-earth pnictides and chalcogenides from first-principles.

    Science.gov (United States)

    Petit, L; Szotek, Z; Lüders, M; Svane, A

    2016-06-01

    This review tries to establish what is the current understanding of the rare-earth monopnictides and monochalcogenides from first principles. The rock salt structure is assumed for all the compounds in the calculations and wherever possible the electronic structure/properties of these compounds, as obtained from different ab initio methods, are compared and their relation to the experimental evidence is discussed. The established findings are summarised in a set of conclusions and provide outlook for future study and possible design of new materials. PMID:27165563

  20. The Ni and Co substitutions in iron chalcogenide single crystals

    Science.gov (United States)

    Bezusyy, V. L.; Gawryluk, D. J.; Malinowski, A.; Berkowski, M.; Cieplak, Marta Z.

    2015-03-01

    We study the ab-plane resistivity and Hall effect in Fe1-yMyTe0.65Se0.35 single crystals with M =Co or Ni, and y up to 0.2. The crystals are grown by Bridgman's method. The low-temperature Hall coefficient RH changes sign to negative for crystals with y exceeding 0.135 (Co) and 0.06 (Ni), consistent with the electron doping induced by these impurities. However, the RH remains positive for all samples at high T, suggesting that remnant hole pockets survive the doping, but the holes become localized at low T in heavily doped crystals. Superconducting transition temperature (Tc) approaches zero for y = 0.14 (Co), and 0.03 (Ni), while the resistivity at the Tc onset is only weakly affected by Co doping, but it increases strongly for the Ni. These results suggest that in case of Co impurity the Tc suppression may be attributed to electron doping. On the other hand, the Ni substitution, in addition to electron doping, induces strong localization effects at small impurity contents. Using two-band conduction model we argue that the localization of electron carriers is responsible for strong superconductivity suppression by Ni impurity. Supported by EC through the FunDMS Advanced Grant of the ERC (FP7 Ideas), by the Polish NCS Grant 2011/01/B/ST3/00462, and by the French-Polish Program PICS 2012. Performed in the laboratories co-financed by NanoFun Project POIG.02.02.00-00-025/09.

  1. Chalcogenide optical microwires cladded with fluorine-based CYTOP.

    Science.gov (United States)

    Li, Lizhu; Abdukerim, Nurmemet; Rochette, Martin

    2016-08-22

    We demonstrate optical transmission results of highly nonlinear As2Se3 optical microwires cladded with fluorine-based CYTOP, and compare them with microwires cladded with typical hydrogen-based polymers. In the linear optics regime, the CYTOP-cladded microwire transmits light in the spectral range from 1.3 µm up to >2.5 µm without trace of absorption peaks such as those observed using hydrogen-based polymer claddings. The microwire is also pumped in the nonlinear optics regime, showing multiple-orders of four-wave mixing and supercontinuum generation spanning from 1.0 µm to >4.3 µm. We conclude that with such a broadband transparency and high nonlinearity, the As2Se3-CYTOP microwire is an appealing solution for nonlinear optical processing in the mid-infrared. PMID:27557174

  2. Spectroscopy of vanadium (III) doped gallium lanthanum sulphide chalcogenide glass

    CERN Document Server

    Hughes, M; Rutt, H; Hewak, D

    2014-01-01

    Vanadium doped gallium lanthanum sulphide glass (V:GLS) displays three absorption bands at 580, 730 and 1155 nm identified by photoluminescence excitation measurements. Broad photoluminescence, with a full width half maximum (FWHM) of 500 nm, is observed peaking at 1500 nm when exciting at 514, 808 and 1064 nm. The fluorescence lifetime and quantum efficiency at 300 K were measured to be 33.4 us and 4 % respectively. From the available spectroscopic data we propose the vanadium ions valence to be 3+ and be in tetrahedral coordination The results indicate potential for development of a laser or optical amplifier based on V:GLS.

  3. Rare-earth pnictides and chalcogenides from first-principles

    Science.gov (United States)

    Petit, L.; Szotek, Z.; Lüders, M.; Svane, A.

    2016-06-01

    This review tries to establish what is the current understanding of the rare-earth monopnictides and monochalcogenides from first principles. The rock salt structure is assumed for all the compounds in the calculations and wherever possible the electronic structure/properties of these compounds, as obtained from different ab initio methods, are compared and their relation to the experimental evidence is discussed. The established findings are summarised in a set of conclusions and provide outlook for future study and possible design of new materials.

  4. Molecular solution processing of metal chalcogenide thin film solar cells

    Science.gov (United States)

    Yang, Wenbing

    The barrier to utilize solar generated electricity mainly comes from their higher cost relative to fossil fuels. However, innovations with new materials and processing techniques can potentially make cost effective photovoltaics. One such strategy is to develop solution processed photovoltaics which avoid the expensive vacuum processing required by traditional solar cells. The dissertation is mainly focused on two absorber material system for thin film solar cells: chalcopyrite CuIn(S,Se)2 (CISS) and kesterite Cu2ZnSn(S,Se) 4 organized in chronological order. Chalcopyrite CISS is a very promising material. It has been demonstrated to achieve the highest efficiency among thin film solar cells. Scaled-up industry production at present has reached the giga-watt per year level. The process however mainly relies on vacuum systems which account for a significant percentage of the manufacturing cost. In the first section of this dissertation, hydrazine based solution processed CISS has been explored. The focus of the research involves the procedures to fabricate devices from solution. The topics covered in Chapter 2 include: precursor solution synthesis with a focus on understanding the solution chemistry, CISS absorber formation from precursor, properties modification toward favorable device performance, and device structure innovation toward tandem device. For photovoltaics to have a significant impact toward meeting energy demands, the annual production capability needs to be on TW-level. On such a level, raw materials supply of rare elements (indium for CIS or tellurium for CdTe) will be the bottleneck limiting the scalability. Replacing indium with zinc and tin, earth abundant kesterite CZTS exhibits great potential to reach the goal of TW-level with no limitations on raw material availability. Chapter 3 shows pioneering work towards solution processing of CZTS film at low temperature. The solution processed devices show performances which rival vacuum-based techniques and is partially attributed to the ease in controlling composition and CZTS phase through this technique. Based on this platform, comprehensive characterization on CZTS devices is carried out including solar cells and transistors. Especially defects properties are exploited in Chapter 4 targeting to identify the limiting factors for further improvement on CZTS solar cells efficiency. Finally, molecular structures and precursor solution stability have been explored, potentially to provide a universal approach to process multinary compounds.

  5. Electronic structure calculations of europium chalcogenides EuS and EuSe

    Energy Technology Data Exchange (ETDEWEB)

    Rached, D.; Ameri, M.; Rabah, M.; Benkhettou, N.; Dine el Hannani, M. [Laboratoire des Materiaux Appliques, Centre de Recherche, Route de Mascara, Universite de Sidi-Bel-Abbes, Sidi Bel Abbes 22000 (Algeria); Khenata, R. [Laboratoire des Materiaux Appliques, Centre de Recherche, Route de Mascara, Universite de Sidi-Bel-Abbes, Sidi Bel Abbes 22000 (Algeria); Laboratoire de Physique Quantique et de Modelisation Mathematique de la Matiere (LPQ3M), Centre Universitaire de Mascara, Mascara 29000 (Algeria); Bouhemadou, A. [Departement de Physique, Faculte des Sciences, Universite Ferhat Abbes, 19000 Setif (Algeria)

    2007-06-15

    We have performed ab-initio self-consistent calculations on the full-potential linear muffin-tin orbital method with the local-density approximation and local spin-density approximation to investigate the structural and electronic properties of EuS and EuSe in its stable (NaCl-B1) and high-pressure phases. The magnetic phase stability was determined from the total energy calculations for both the nonmagnetic (NM) and magnetic (M) phases. These theoretical calculations clearly indicate that both at ambient and high pressures, the magnetic phase is more stable than the nonmagnetic phase. The transition pressure at which these compounds undergo the structural phase transition from NaCl-B1 to CsCl-B2 phase is calculated. The elastic constants at equilibrium in both NaCl-B1 and CsCl-B2 structures are also determined. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Electromigration behaviors of Ge2Sb2Te5 chalcogenide thin films under DC bias

    International Nuclear Information System (INIS)

    Highlights: •Electromigration (EM) of Ge2Sb2Te5 (GST) was analyzed by MTTF and Blech tests. •Grain boundary diffusion dominated the mass transport during EM process of GST. •Doping in GST increased the number of grain boundaries and accelerated EM failure. •Doping alleviated the mass segregation in GST in moderate manner. •EM failure mechanism of GST is correlated with the sample geometry. -- Abstract: Electromigration (EM) behaviors of pristine Ge2Sb2Te5 (GST), nitrogen-doped GST (N-GST) and cerium-doped GST (Ce-GST) thin-film strips under DC bias are presented. The mean-time-to-failure (MTTF) analysis based on the Black equation found that the EM failure times at room temperature are 1.2 × 104, 40 and 9.2 × 102 years and the activation energies (Ea) of EM process are 1.07, 0.57 and 0.68 eV for GST, N-GST and Ce-GST, respectively. Moreover, the calibration of the current density exponent, n, of Black’s equation found n values are close to 2 for all samples, implying the dominance of grain boundary diffusion during the mass transport of EM process. For doped GSTs, the inferior EM failure lifespans and smaller Ea values were ascribed to the grain refinement effect which increases the number of grain boundaries in such samples. It consequently promoted the short-circuit diffusion and accelerated the EM failure in doped GSTs. The Blech-type tests on GSTs found that the threshold product, i.e., the product of current density and sample length ((j ⋅ L)th), is 200 A/cm for GST, 50 A/cm for N-GST and 66.67 A/cm for Ce-GST. Moreover, the product of diffusivity and effective charge number (i.e., DZ*) for GST, N-GST and Ce-GST was 2.0 × 10−7, 4.5 × 10−6 and 3.8 × 10−6 cm2/sec, respectively. Analytical results illustrated that the electrostatic force effect dominates the EM failure in samples with short strip lengths while the electron-wind force effect dominates the EM failure in samples with long strip lengths. Doping might alleviate the mass segregation in GST; however, its effect was moderate

  7. Reactions and diffusion in the silver--arsenic chalcogenide glass system

    Energy Technology Data Exchange (ETDEWEB)

    Holmquist, G.A.

    1977-09-01

    The diffusion of Ag in amorphous As/sub 2/S/sub 3/ and As/sub 2/Se/sub 3/ at 175/sup 0/C is accompanied with the reduction of As from a valence of +3 to +2 and +2 to +1 to maintain charge neutrality in the glass. The reactions for the sulfide and selenide glasses are identical. Ag/sup +/ alone diffuses at this temperature, all other ions are essentially immobile. An amorphous reaction product phase is formed in the diffusion zone with a composition range of 28.6 to 44.4 atomic percent Ag. The lower limit corresponds to all As cations of +2 valence (amorphous Ag/sub 2/As/sub 2/S/sub 3/). The upper limit, the maximum solubility of Ag in these glasses, corresponds to all As cations of +1 valence (amorphous Ag/sub 4/As/sub 2/S/sub 3/). The diffusivity of Ag in these glasses at 175/sup 0/C in the concentration range of 10 to 35 atomic percent Ag is: Sulfide--4 x 10/sup -14/ exp(+0.23 +- .01) (atomic % Ag), Selenide--2 x 10/sup -12/ exp(+0.14 +- .01) (atomic % Ag).

  8. Theory of transport phenomena in polycrystalline lead chalcogenide films. Mobility. Nondegenerate statistics

    Energy Technology Data Exchange (ETDEWEB)

    Atakulov, Sh. B., E-mail: atakulovsh@mail.ru; Zaynolobidinova, S. M. [Fergana State University (Uzbekistan); Nabiev, G. A., E-mail: gulamnabi@mail.ru [Fergana Polytechnical Institute (Uzbekistan); Nabiyev, M. B. [Fergana State University (Uzbekistan); Yuldashev, A. A. [Fergana Polytechnical Institute (Uzbekistan)

    2013-07-15

    The mobility of nondegenerate electrons in quasi-single-crystal and polycrystalline PbTe films is experimentally investigated. The results obtained are compared with the data for bulk crystals at the same charge-carrier concentration. Under the assumption of limitation of the charge-carrier mobility by intercrystallite potential barriers, electron transport in an electric field is theoretically considered. The theoretical results are in good agreement with the experiment.

  9. Crystallization kinetics of Ge{sub 20}Te{sub 80} chalcogenide glasses doped with

    Energy Technology Data Exchange (ETDEWEB)

    Ziani, N. [Departement de physique, faculte des Sciences, universite des sciences et de la technologie d' oran, USTO BP1505, elm' naouar oran algerie, Oran (Algeria)]. E-mail: ziani_nossair@yahoo.fr; Belhadji, M. [Faculte des sciences, Universite Essenia Oran (Algeria)]. E-mail: nmaamar@yahoo.fr; Heireche, L. [Faculte des sciences, Universite Essenia Oran (Algeria); Bouchaour, Z. [Faculte des sciences, Universite Essenia Oran (Algeria); Belbachir, M. [Faculte des sciences, Universite Essenia Oran (Algeria)

    2005-04-15

    A study of kinetics of non-isothermal crystallization process for Ge{sub 20-x}Te{sub 80}Sb{sub x}(x=0,3,4,5) system was reported and interpreted in this work by using Matusita's model. From the differential scanning calorimetry (DSC) traces obtained under dynamic conditions, the activation energy of growth process and values of n and m which are numerical factors depending on crystallization mechanisms are evaluated. The validity of Matusita's model was ascertained by comparison with the results obtained by application of two well-known methods which are Ozawa and Kissinger ones.

  10. Linear and nonlinear properties of chalcogenide glasses in the terahertz frequency

    DEFF Research Database (Denmark)

    Zalkovskij, Maksim; Malureanu, Radu; Popescu, A.;

    2014-01-01

    used a standard THz-TDS setup based on photoconductive switches while in the higher frequency domain we used an air biased coherent detection (ABCD) setup. This allowed for a wide frequency range (from 0.2 to 18 THz) investigation of the refractive index of the glasses. The nonlinear coefficient in the...... THz range was investigated using a lithium niobate based setup that allows us to reach electrical field strength exceeding 400 kV/cm. Results from both investigations will be presented during the talk....

  11. Structures, Energetics, and Electronic Properties of Layered Materials and Nanotubes of Cadmium Chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Jia [ORNL; Huang, Jingsong [ORNL; Sumpter, Bobby G [ORNL; Kent, Paul R [ORNL; Terrones Maldonado, Mauricio [ORNL; Smith, Sean C [ORNL

    2013-01-01

    The attractive optoelectronic properties of conducting polymers depend sensitively upon intra- and inter-polymer chain interactions, and therefore new methods to manipulate these interactions are continually being pursued. Here, we report a study of the isotopic effects of deuterium substitution on the structure, morphology, and optoelectronic properties of regioregular poly(3-hexylthiophene)s (P3HT) with an approach that combines the synthesis of deuterated materials, optoelectronic properties measurements, theoretical simulation, and neutron scattering. Selective substitutions of deuterium on the backbone or side-chains of P3HT result in distinct optoelectronic responses in P3HT/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) photovoltaics. Specifically, the weak non-covalent intermolecular interactions induced by the main-chain deuteration are shown to change the film crystallinity and morphology of P3HT/PCBM blends, and consequently reduce the short circuit current. However, decreased electronic coupling, the formation of a charge transfer state, and increased electron-phonon coupling resulting from side chain deuteration are shown to induce a remarkable reduction in open circuit voltage.

  12. Wave guiding by low refractive-index strips on surfaces of Chalcogenide glass thin films

    Science.gov (United States)

    Zhai, Yanfen; Zhang, Wei; Huang, Yidong

    2014-10-01

    In this paper, we proposed and demonstrated a simple ChG waveguide structure, guided by low refractive-index strips on the surfaces of planar ChG films. Theoretical analysis shows that it supports quasi-TE mode transmission in 1.5μm band with high nonlinearity. Samples of this surface guiding ChG waveguides are fabricated. Its transmission properties are measured by the cut-off method, showing a waveguide attenuation of 0.67dB/mm and a coupling loss with optical fibers of ~8dB/facet. It provides a simple way to realize high quality ChG waveguides, which has great potential in developing nonlinear photonic devices.

  13. Amorphous chalcogenide semiconductors for dosimetry of high-energy ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O.I. [Institute of Materials, Lviv (Ukraine). Dept. of New Perspective Developments

    1995-10-01

    The possible application of amorphous chalogenide semiconductors as radiation-sensitive elements of high-energy (E>1 MeV) dosimetry systems are analyzed. It is shown that some of these materials are characterized by a broader region of absorbed doses and low-temperature thresholds of radiation induced bleaching than conventional colouring oxide glasses. (author).

  14. Amorphous chalcogenide semiconductors for dosimetry of high-energy ionizing radiation

    International Nuclear Information System (INIS)

    The possible application of amorphous chalogenide semiconductors as radiation-sensitive elements of high-energy (E>1 MeV) dosimetry systems are analyzed. It is shown that some of these materials are characterized by a broader region of absorbed doses and low-temperature thresholds of radiation induced bleaching than conventional colouring oxide glasses. (author)

  15. A simulation of the cluster structures in Ge-Se vitreous chalcogenide semiconductors

    OpenAIRE

    Gurin, V.; Shpotyuk, O.; Boyko, V

    2013-01-01

    A structure of germanium selenide glasses is simulated by the featured clusters built from the tetrahedral GeSe4 units up to the clusters with six germanium atoms (Ge6Se16H4 and Ge6Se16H8). Quantum chemical calculations at the DFT level with effective core potentials for Ge and Se atoms for the clusters of different composition reveal their relative stability and optical properties.

  16. On the structural-optical correlations in radiation-modified chalcogenide glasses

    Energy Technology Data Exchange (ETDEWEB)

    Kavetskyy, T; Tsmots, V [Solid State Microelectronics Laboratory, Drohobych Ivan Franko State Pedagogical University, 24 I. Franko Str., Drohobych, 82100 (Ukraine); Kaban, I; Hoyer, W [Institute of Physics, Chemnitz University of Technology, 09107 Chemnitz (Germany); Shpotyuk, O, E-mail: kavetskyy@yahoo.com [Institute of Materials, Scientific Research Company ' Carat' , 202 Stryjska Str., Lviv, 79031 (Ukraine)

    2011-04-01

    In this work, we report our recent results on the gamma-irradiation-induced structural transformations in the Ge-Sb-S glasses as observed from the structural studies using high-energy synchrotron x-ray diffraction and extended x-ray absorption fine structure spectroscopy in comparison with the optical measurements using VIS/IR spectroscopy techniques. The structural-optical correlations in the radiation-induced effects are established. The structural changes upon irradiation are explained in the frames of the concept of coordination topological defects formation.

  17. High-pressure studies on Tc and crystal structure of iron chalcogenide superconductors

    Directory of Open Access Journals (Sweden)

    Hiroki Takahashi, Takahiro Tomita, Hiroyuki Takahashi, Yoshikazu Mizuguchi, Yoshihiko Takano, Satoshi Nakano, Kazuyuki Matsubayashi and Yoshiya Uwatoko

    2012-01-01

    Full Text Available The superconducting transition temperature, Tc, in iron-based solids can be enhanced by applied pressure: Tc increases from 8 to 37 K for the 11-type FeSe when the pressure is raised from 0 to 4 GPa. High-pressure studies can elucidate the mechanism of superconductivity in such novel materials. In this paper, we present a high-pressure study of Fe(Se1−xTex and Fe(Se1−xSx. In the case of Fe(Se1−xTex, the maximum Tc under high pressure did not exceed the Tc of FeSe, which can be attributed to the structural transition to the monoclinic phase. For Fe(Se1−xSx (0 < x < 0.3, Tc exhibited a significant increase with pressure; however, the maximum Tc under high pressure did not exceed the Tc of FeSe. This may be due to the disorder induced by substituting S for Se, which is similar to the pressure effect on Tc for the 1111-type superconductor Ca(Fe1−xCoxAsF. The Tc of Fe(Se1−xSx showed a complex behavior below 1 GPa, first decreasing and then increasing with increasing pressure. From high-pressure x-ray diffraction measurements, the Tc (P curve was correlated with the local structural parameter.

  18. Synthesis of cadmium chalcogenide based quantum dots for enhanced multiple exciton generation

    OpenAIRE

    Page, Robert Christopher

    2014-01-01

    Quantum dots (QDs) have the potential to produce more than one exciton per incident photon, if the photon energy is greater than twice the band gap energy. This process of multiple exciton generation (MEG) has the potential to lead to a step change in the efficiency of solar panels, by utilising energy commonly wasted as heat in conventional solar cells. A wide range of CdSe/CdTe and CdTe/CdSe quantum dots with and without a CdS shell were synthesised with varying core sizes and shell thickne...

  19. Engineering of refractive index in sulfide chalcogenide glass by direct laser writing

    KAUST Repository

    Zhang, Yaping

    2010-01-01

    Arsenic trisulfide (As2S3) glass is an interesting material for photonic integrated circuits (PICs) as infrared (IR) or nonlinear optical components. In this paper, direct laser writing was applied to engineer the refractive index of As2S3 thin film. Film samples were exposed to focused above bandgap light with wavelength at 405 nm using different fluence adjusted by laser power and exposure time. The index of refraction before and after laser irradiation was calculated by fitting the experimental data obtained from Spectroscopic Ellipsometer (SE) measurement to Tauc-Lorenz dispersion formula. A positive change in refractive index (Δn = 0.19 at 1.55 μm) as well as an enhancement in anisotropy was achieved in As2S3 film by using 10 mW, 0.3 μs laser irradiation. With further increasing the fluence, refractive index increased while anisotropic property weakened. Due to the rapid and large photo-induced modification of refractive index obtainable with high spatial resolution, this process is promising for integrated optic device fabrication.

  20. Optical properties of alloys based on II-S and II-Te chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Kirovskaya, I. A.; Nor, P. E., E-mail: nor-polina@yandex.ru; Nagibina, I. Yu.; Karpova, E. O. [Omsk State Technical University (Russian Federation)

    2015-03-15

    Spectroscopic studies of binary and multicomponent semiconductors of the CdS-CdTe, CdS-ZnTe, and ZnS-CdTe systems are performed. They result in confirmation of the formation of substitutional alloys in these systems (in addition to the results of X-ray diffractometry studies), and the chemical composition of the surface as well as the most important characteristic of semiconductors, theelectron work function, the frequencies of strongest luminescence (impurity and band-to band), the emission maxima, and the possibilities of predicting luminescence properties are determined. Recommendations concerning the use of fabricated materials of definite composition as phosphors are given.

  1. Combinatorial Chemical Bath Deposition of CdS Contacts for Chalcogenide Photovoltaics.

    Science.gov (United States)

    Mokurala, Krishnaiah; Baranowski, Lauryn L; de Souza Lucas, Francisco W; Siol, Sebastian; van Hest, Maikel F A M; Mallick, Sudhanshu; Bhargava, Parag; Zakutayev, Andriy

    2016-09-12

    Contact layers play an important role in thin film solar cells, but new material development and optimization of its thickness is usually a long and tedious process. A high-throughput experimental approach has been used to accelerate the rate of research in photovoltaic (PV) light absorbers and transparent conductive electrodes, however the combinatorial research on contact layers is less common. Here, we report on the chemical bath deposition (CBD) of CdS thin films by combinatorial dip coating technique and apply these contact layers to Cu(In,Ga)Se2 (CIGSe) and Cu2ZnSnSe4 (CZTSe) light absorbers in PV devices. Combinatorial thickness steps of CdS thin films were achieved by removal of the substrate from the chemical bath, at regular intervals of time, and in equal distance increments. The trends in the photoconversion efficiency and in the spectral response of the PV devices as a function of thickness of CdS contacts were explained with the help of optical and morphological characterization of the CdS thin films. The maximum PV efficiency achieved for the combinatorial dip-coating CBD was similar to that for the PV devices processed using conventional CBD. The results of this study lead to the conclusion that combinatorial dip-coating can be used to accelerate the optimization of PV device performance of CdS and other candidate contact layers for a wide range of emerging absorbers. PMID:27479495

  2. Augmented Z scheme blueprint for efficient solar water splitting system using quaternary chalcogenide absorber material.

    Science.gov (United States)

    Sarswat, Prashant K; Bhattacharyya, Dhiman; Free, Michael L; Misra, Mano

    2016-02-01

    Photoelectrochemical hydrogen (H2) production from water is a key method of addressing energy needs using an environmentally friendly approach. In the last two decades we have witnessed the evolution of many different expensive catalysts, photoelectrodes and related technologies, especially those involving precious metals and use of acidic or basic electrolytes for hydrogen production. Cu2ZnSnS4 (CZTS) is a relatively new candidate in the category of efficient photocathodes, due to its high absorption coefficient and near optimal energy band gap. In this paper, we demonstrate photoelectrochemical viability of CZTS in combination with other photoanodes such as TiO2, BiVO4, and WO3 for H2 production with the use of an electrolyte of near neutral pH, a single redox mediator, and insignificant potential biasing. A systematic study was performed to understand CZTS performance with each photoanode, band energetics of CZTS with other photoanodes, impedance behavior of each photoelectrode, and utility of a CZTS photocell in place of a CZTS photocathode. Our assessment indicates that a protected CZTS photocell performs well when used in a Z-scheme containing TiO2 nanotubular array-CZTS or nanocrystalline WO3-CZTS. Preliminary experiments indicated that apart from band energetics, porosity and effective surface area of the photoanodes play a crucial role in determining the photoelectrochemical performance of the system. PMID:26762553

  3. Electronic properties and momentum densities of tin chalcogenides: Validation of PBEsol exchange-correlation potential

    Energy Technology Data Exchange (ETDEWEB)

    Ahuja, B.L., E-mail: blahuja@yahoo.ik [Department of Physics, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Raykar, Veera; Joshi, Ritu [Department of Physics, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Tiwari, Shailja [Department of Physics, Govt. Women Engineering College, Ajmer 305001, Rajasthan (India); Talreja, Sonal [Department of Computer Science, M.L. Sukhadia University, Udaipur 313001 (India); Choudhary, Gopal [Department of Physics, Techno India NJR Institute of Technology, Udaipur 313001, Rajasthan (India)

    2015-05-15

    We report Compton profiles of SnS and SnTe at a momentum resolution of 0.34 a.u. using a 20 Ci {sup 137}Cs Compton spectrometer. To compare our experimental data, we have also computed the theoretical Compton profiles using density functional theory within linear combination of atomic orbitals (LCAO) method. To interpret the relative nature of bonding in these compounds, we have scaled the experimental and theoretical Compton profiles on equal-valence-electron-density (EVED). On the basis of EVED profiles, it is seen that SnTe shows more covalent character than SnS. To rectify the substantial disagreement between experimental and theoretical band gaps, we have also presented the energy bands and density of states of both the compounds using full-potential linearized augmented plane wave method (FP-LAPW) including spin–orbit interaction within the PBEsol exchange-correlation potential.

  4. Chalcogenide compounds made by pulsed laser deposition at 355 and 248 nm

    DEFF Research Database (Denmark)

    Ettlinger, Rebecca Bolt; Cazzaniga, Andrea Carlo; Crovetto, Andrea; Ravnkilde, Lasse; Youngman, Tomas Hugh; Pryds, Nini; Schou, Jørgen

    Thin films made by pulsed laser deposition may differ depending on the laser wavelength. We compared ZnS, Cu2SnS3 and a target enriched with SnS relative to Cu2SnS3 using 355 nm and 248 nm lasers......Thin films made by pulsed laser deposition may differ depending on the laser wavelength. We compared ZnS, Cu2SnS3 and a target enriched with SnS relative to Cu2SnS3 using 355 nm and 248 nm lasers...

  5. Bandgap tunable colloidal Cu-based ternary and quaternary chalcogenide nanosheets via partial cation exchange

    Science.gov (United States)

    Ramasamy, Parthiban; Kim, Miri; Ra, Hyun-Soo; Kim, Jinkwon; Lee, Jong-Soo

    2016-04-01

    Copper based ternary and quaternary semiconductor nanostructures are of great interest for the fabrication of low cost photovoltaics. Although well-developed syntheses are available for zero dimensional (0D) nanoparticles, colloidal synthesis of two dimensional (2D) nanosheets remains a big challenge. Here we report, for the first time, a simple and reproducible cation exchange approach for 2D colloidal Cu2GeSe3, Cu2ZnGeSe4 and their alloyed Cu2GeSxSe3-x, Cu2ZnGeSxSe4-x nanosheets using pre-synthesized Cu2xSe nanosheets as a template. A mechanism for the formation of Cu2-xSe nanosheets has been studied in detail. In situ oxidation of Cu+ ions to form a CuSe secondary phase facilitates the formation of Cu2-xSe NSs. The obtained ternary and quaternary nanosheets have average lateral size in micrometers and thickness less than 5 nm. This method is general and can be extended to produce other important ternary semiconductor nanosheets such as CuIn1-xGaxSe2. The optical band gap of these nanosheets is tuned from 1 to 1.48 eV, depending on their composition.Copper based ternary and quaternary semiconductor nanostructures are of great interest for the fabrication of low cost photovoltaics. Although well-developed syntheses are available for zero dimensional (0D) nanoparticles, colloidal synthesis of two dimensional (2D) nanosheets remains a big challenge. Here we report, for the first time, a simple and reproducible cation exchange approach for 2D colloidal Cu2GeSe3, Cu2ZnGeSe4 and their alloyed Cu2GeSxSe3-x, Cu2ZnGeSxSe4-x nanosheets using pre-synthesized Cu2xSe nanosheets as a template. A mechanism for the formation of Cu2-xSe nanosheets has been studied in detail. In situ oxidation of Cu+ ions to form a CuSe secondary phase facilitates the formation of Cu2-xSe NSs. The obtained ternary and quaternary nanosheets have average lateral size in micrometers and thickness less than 5 nm. This method is general and can be extended to produce other important ternary semiconductor nanosheets such as CuIn1-xGaxSe2. The optical band gap of these nanosheets is tuned from 1 to 1.48 eV, depending on their composition. Electronic supplementary information (ESI) available: Fig.s S1-S13. See DOI: 10.1039/c5nr08666c

  6. Laser induced optical bleaching in Ge12Sb25S63 chalcogenide thin film

    International Nuclear Information System (INIS)

    Photo induced effects of Ge12Sb25S63 films illuminated with 532 nm laser light is investigated from transmission spectra measured by FTIR spectroscopy. The material exhibit photo bleaching (PB) when exposed to band gap laser for a prolonged time in vacuum. The PB is ascribed to structural changes inside the film as well as surface photo oxidation. The amorphous nature of thin films was detected by X-ray diffraction. The chemical composition of the deposited thin films was examined by Energy Dispersive X-ray Analysis (EDAX). The refractive indices of the films were obtained from the transmission spectra based on inverse synthesis method, and the optical band gaps were derived from optical absorption spectra using the Tauc plot. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple–DiDomenico model. It was found that, the mechanism of the optical absorption follows the rule of the allowed non-direct transition. Raman spectra analysis also supports the optical changes

  7. A silicon-based two-dimensional chalcogenide: growth of Si₂Te₃ nanoribbons and nanoplates.

    Science.gov (United States)

    Keuleyan, Sean; Wang, Mengjing; Chung, Frank R; Commons, Jeffrey; Koski, Kristie J

    2015-04-01

    We report the synthesis of high-quality single-crystal two-dimensional, layered nanostructures of silicon telluride, Si2Te3, in multiple morphologies controlled by substrate temperature and Te seeding. Morphologies include nanoribbons formed by VLS growth from Te droplets, vertical hexagonal nanoplates through vapor-solid crystallographically oriented growth on amorphous oxide substrates, and flat hexagonal nanoplates formed through large-area VLS growth in liquid Te pools. We show the potential for doping through the choice of substrate and growth conditions. Vertical nanoplates grown on sapphire substrates, for example, can incorporate a uniform density of Al atoms from the substrate. We also show that the material may be modified after synthesis, including both mechanical exfoliation (reducing the thickness to as few as five layers) and intercalation of metal ions including Li(+) and Mg(2+), which suggests applications in energy storage materials. The material exhibits an intense red color corresponding to its strong and broad interband absorption extending from the red into the infrared. Si2Te3 enjoys chemical and processing compatibility with other silicon-based material including amorphous SiO2 but is very chemically sensitive to its environment, which suggests applications in silicon-based devices ranging from fully integrated thermoelectrics to optoelectronics to chemical sensors. PMID:25764295

  8. Analyses of structure and spectroscopic property in amorphous oxides and chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Iwadate, Yasuhiko; Hattori, Takeo; Nishiyama, Shin; Fukushima, Kazuko; Yokota, Hideki [Chiba Univ. (Japan). Faculty of Engineering; Noda, Kenji; Nakazawa, Tetsuya

    1998-01-01

    Li{sub 2}O-TeO{sub 2} glasses studied in the present work are known to possess high densities, refractive indexes, dielectric constants, and transmittance against the lights at infrared wavelength region. In spite of their usefulness, there exists little work on the short range structure of Li{sub 2}O-TeO{sub 2} glasses analyzed by not spectroscopy but diffraction experiments. The structure of Li{sub 2}O(15mol%)-TeO{sub 2}(85mol%) and Li{sub 2}O(25mol%)-TeO{sub 2}(75mol%) glasses was analysed by X-ray diffraction in which an interpretation of the radial distribution function was discussed on the basis of the correlation method. (author)

  9. AgAsS2 amorphous chalcogenide films prepared by pulsed laser deposition

    Czech Academy of Sciences Publication Activity Database

    Wágner, T.; Krbal, M.; Němec, P.; Frumar, M.; Wágner, T.; Vlček, Milan; Peřina, Vratislav; Macková, Anna; Hnatovitz, V.; Kasap, S. O.

    2004-01-01

    Roč. 79, č. 4 (2004), s. 1563-1565. ISSN 0947-8396 Grant ostatní: GA MŠk(CZ) LN00A028 Institutional research plan: CEZ:AV0Z4050913; CEZ:AV0Z1048901 Keywords : laser ablation Subject RIV: CA - Inorganic Chemistry Impact factor: 1.452, year: 2004

  10. Spin coated chalcogenide films of Ge-Se-Te: physico-chemical properties

    Czech Academy of Sciences Publication Activity Database

    Kohoutek, T.; Wágner, T.; Frumar, M.; Vlček, Milan

    2006-01-01

    Roč. 2, č. 47 (2006), s. 250-253. ISSN 0031-9090. [Solid State Chemistry VI. Praha, 13.09.2004-17.09.2004] Institutional research plan: CEZ:AV0Z40500505 Keywords : spin - coating Subject RIV: CA - Inorganic Chemistry Impact factor: 0.577, year: 2006

  11. Properties of transition metal-doped zinc chalcogenide crystals for tunable IR laser radiation

    International Nuclear Information System (INIS)

    The spectroscopic properties of Cr2+, Co2+, and Ni2+-doped single crystals of ZnS, ZnSe, and ZnTe have been investigated to understand their potential application as mid-IR tunable solid-state laser media. The spectroscopy indicated divalent Cr was the most favorable candidate for efficient room temperature lasing, and accordingly, a laser-pumped laser demonstration of Cr:ZnS and Cr:ZnSe has been performed. The lasers' output were peaked at ∼ 2.35 μm and the highest measured slope efficiencies were ∼ 20% in both cases

  12. Ternary chalcogenide micro-pseudocapacitors for on-chip energy storage

    KAUST Repository

    Kurra, Narendra

    2015-05-11

    We report the successful fabrication of a micro-pseudocapacitor based on ternary nickel cobalt sulfide for the first time, with performance substantially exceeding that of previously reported micro-pseudocapacitors based on binary sulfides. CoNi2S4 micro-pseudocapacitor exhibits a maximum energy density of 18.7 mWh/cm3 at a power density of 1163 mW/cm3, opens up an avenue for exploring new family of ternary oxides/sulfides based micro-pseudocapacitors.

  13. Laser induced optical bleaching in Ge12Sb25S63 chalcogenide thin film

    Science.gov (United States)

    Naik, Ramakanta; Jena, S.; Sahoo, N. K.

    2015-06-01

    Photo induced effects of Ge12Sb25S63 films illuminated with 532 nm laser light is investigated from transmission spectra measured by FTIR spectroscopy. The material exhibit photo bleaching (PB) when exposed to band gap laser for a prolonged time in vacuum. The PB is ascribed to structural changes inside the film as well as surface photo oxidation. The amorphous nature of thin films was detected by X-ray diffraction. The chemical composition of the deposited thin films was examined by Energy Dispersive X-ray Analysis (EDAX). The refractive indices of the films were obtained from the transmission spectra based on inverse synthesis method, and the optical band gaps were derived from optical absorption spectra using the Tauc plot. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple-DiDomenico model. It was found that, the mechanism of the optical absorption follows the rule of the allowed non-direct transition. Raman spectra analysis also supports the optical changes.

  14. Photoelectrochemical studies on aqueous suspensions of some nanometal oxide/chalcogenide semiconductors for hydrogen production

    Indian Academy of Sciences (India)

    Kasem K Kasem; Aubrey Finley

    2015-04-01

    Photoproduction of hydrogen was achieved by photolysis of aqueous suspensions of mixed TiO2/V2O5 or CdS/ZnS semiconductor (SC) nanoparticle in phosphate buffers containing [Fe(CN)6]4−. Manipulations of the band structure of the SC materials took place by either combining oxides/sulphides in binary mixtures or by modification of the SC surface with an organic semiconductor. Studies show that the bandgap of these mixed materials varied monotonically with the percent composition of the mixture. Furthermore, results show that maximum generation of hydrated electrons by [Fe(CN)6]4− occurred at pH 6. Mixtures of CdS/ZnS showed greater photoactivity than metal oxides TiO2/V2O5. On the other hand, surface-modified CdS or TiO2 gave much better photoreduction than the high percentage composite mixtures. The aqueous nanosystems used in these studies sustained their stability as indicated by the reproducibility of their photocatalytic activities.

  15. Electronic properties and momentum densities of tin chalcogenides: Validation of PBEsol exchange-correlation potential

    International Nuclear Information System (INIS)

    We report Compton profiles of SnS and SnTe at a momentum resolution of 0.34 a.u. using a 20 Ci 137Cs Compton spectrometer. To compare our experimental data, we have also computed the theoretical Compton profiles using density functional theory within linear combination of atomic orbitals (LCAO) method. To interpret the relative nature of bonding in these compounds, we have scaled the experimental and theoretical Compton profiles on equal-valence-electron-density (EVED). On the basis of EVED profiles, it is seen that SnTe shows more covalent character than SnS. To rectify the substantial disagreement between experimental and theoretical band gaps, we have also presented the energy bands and density of states of both the compounds using full-potential linearized augmented plane wave method (FP-LAPW) including spin–orbit interaction within the PBEsol exchange-correlation potential

  16. Solution-Processing of Chalcogenide Nanoparticles and Thin Films for Photovoltaic Applications

    OpenAIRE

    Carreté, Àlex

    2015-01-01

    Tesi realitzada a l'Instut de Recerca en Energia de Catalunya – IREC Thin film solar cells based on direct band gap semiconductors have attracted much research during last decades. Thin film technologies are currently commercial and display record power conversion efficiencies up to 20% at the laboratory scale. However, typical direct band gap semiconductors, CdTe and CuIn1-xGaxS2 (CIGS), content scarce and/or toxic elements such as In, Ga or Cd. An alternative to these materials is Cu2ZnS...

  17. Fabrication and characterization of high-mobility solution-based chalcogenide thin-film transistors

    KAUST Repository

    Mejia, Israel I.

    2013-01-01

    We report device and material considerations for the fabrication of high-mobility thin-film transistors (TFTs) compatible with large-area and inexpensive processes. In particular, this paper reports photolithographically defined n-type TFTs (n-TFTs) based on cadmium sulfide (CdS) films deposited using solution-based techniques. The integration process consists of four mask levels with a maximum processing temperature of 100 °C. The TFT performance was analyzed in terms of the CdS semiconductor thickness and as a function of postdeposition annealing in a reducing ambient. The IonI off ratios are ∼107 with field-effect mobilities of ∼5.3 and ∼4.7cm2V̇s for Al and Au source-drain contacts, respectively, using 70 nm of CdS. Transmission electron microscopy and electron energy loss spectroscopy were used to analyze the CdS-metal interfaces. © 1963-2012 IEEE.

  18. Connection between NMR and electrical conductivity in glassy chalcogenide fast ionic conductors

    International Nuclear Information System (INIS)

    The work documented in this thesis follows the traditional order. In this chapter a general discussion of ionic conduction and of glassy materials are followed by a brief outline of the experimental techniques for the investigation of fast ionic conduction in glassy materials, including NMR and impedance spectroscopy techniques. A summary of the previous and present studies is presented in the last section of this introductory chapter. The details of the background theory and models are found in the Chapter II, followed by the description of the experimental details in Chapter III. Chapter IV of the thesis describes the experimental results and the analysis of the experimental observations followed by the conclusions in chapter V

  19. Low-temperature photoluminescence in chalcogenide glasses doped with rare-earth ions

    Energy Technology Data Exchange (ETDEWEB)

    Kostka, Petr, E-mail: petr.kostka@irsm.cas.cz [Institute of Rock Structure and Mechanics AS CR, V Holešovičkách 41, 182 09 Praha 8 (Czech Republic); Zavadil, Jiří [Institute of Photonics and Electronics AS CR, Chaberská 57, 182 51 Praha 8, Kobylisy (Czech Republic); Iovu, Mihail S. [Institute of Applied Physics, Academy of Sciences of Moldova, Str. Academiei 5, MD-28 Chisinau, Republic of Moldova (Moldova, Republic of); Ivanova, Zoya G. [Institute of Solid State Physics, Bulgarian Academy of Sciences, 1784 Sofia (Bulgaria); Furniss, David; Seddon, Angela B. [Mid-Infrared Photonics Group, George Green Institute for Electromagnetics Research, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)

    2015-11-05

    Sulfide and oxysulfide bulk glasses Ga-La-S-O, Ge-Ga-S and Ge-Ga-As-S doped, or co-doped, with various rare-earth (RE{sup 3+}) ions are investigated for their room temperature transmission and low-temperature photoluminescence. Photoluminescence spectra are collected by using external excitation into the Urbach tail of the fundamental absorption edge of the host-glass. The low-temperature photoluminescence spectra are dominated by the broad-band luminescence of the host glass, with superimposed relatively sharp emission bands due to radiative transitions within 4f shells of RE{sup 3+} ions. In addition, the dips in the host-glass luminescence due to 4f-4f up-transitions of RE{sup 3+} ions are observed in the Ge-Ga-S and Ge-Ga-As-S systems. These superimposed narrow effects provide a direct experimental evidence of energy transfer between the host glass and respective RE{sup 3+} dopants. - Highlights: • An evidence of energy transfer from host-glass to doped-in RE ions is presented. • Energy transfer is manifested by dips in host-glass broad-band luminescence. • This channel of energy transfer is documented on selected RE doped sulfide glasses. • Photoluminescence spectra are dominated by broad band host-glass luminescence. • Presence of RE ions is manifested by superimposed narrow 4f-4f transitions.

  20. Investigation of Non-Vacuum Deposition Techniques in Fabrication of Chalcogenide-Based Solar Cell Absorbers

    KAUST Repository

    Alsaggaf, Ahmed

    2015-07-01

    The environmental challenges are increasing, and so is the need for renewable energy. For photovoltaic applications, thin film Cu(In,Ga)(S,Se)2 (CIGS) and CuIn(S,Se)2 (CIS) solar cells are attractive with conversion efficiencies of more than 20%. However, the high-efficiency cells are fabricated using vacuum technologies such as sputtering or thermal co-evaporation, which are very costly and unfeasible at industrial level. The fabrication involves the uses of highly toxic gases such as H2Se, adding complexity to the fabrication process. The work described here focused on non-vacuum deposition methods such as printing. Special attention has been given to printing designed in a moving Roll-to-Roll (R2R) fashion. The results show potential of such technology to replace the vacuum processes. Conversion efficiencies for such non-vacuum deposition of Cu(In,Ga)(S,Se)2 solar cells have exceeded 15% using hazardous chemicals such as hydrazine, which is unsuitable for industrial scale up. In an effort to simplify the process, non-toxic suspensions of Cu(In,Ga)S2 molecular-based precursors achieved efficiencies of ~7-15%. Attempts to further simplify the selenization step, deposition of CuIn(S,Se)2 particulate solutions without the Ga doping and non-toxic suspensions of Cu(In,Ga)Se2 quaternary precursors achieved efficiencies (~1-8%). The contribution of this research was to provide a new method to monitor printed structures through spectral-domain optical coherence tomography SD-OCT in a moving fashion simulating R2R process design at speeds up to 1.05 m/min. The research clarified morphological and compositional impacts of Nd:YAG laser heat-treatment on Cu(In,Ga)Se2 absorber layer to simplify the annealing step in non-vacuum environment compatible to R2R. Finally, the research further simplified development methods for CIGS solar cells based on suspensions of quaternary Cu(In,Ga)Se2 precursors and ternary CuInS2 precursors. The methods consisted of post deposition reactive annealing for performance enhancement up to 2.0% solar cell conversion efficiency. Chemical treatment using metal salt solutions and Na2Se4 for Na and Se incorporation provided efficiencies up to 1.1%.