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Sample records for se observan tasas

  1. Protective effect of total aralosides of Aralia elata (Miq) Seem (TASAES) against diabetic cardiomyopathy in rats during the early stage, and possible mechanisms

    PubMed Central

    Xi, Shugang; Zhou, Guihua; Zhang, Xuexin; Zhang, Wenjie

    2009-01-01

    Total aralosides of Aralia elata (Miq) Seem (TASAES) from Chinese traditional herb Longya Aralia chinensis L was found to improve cardiac function. The present study was to determine the protective effects of TASAES on diabetic cardiomyopathy, and the possible mechanisms. Therefore, a single dose of streptozotocin was used to induce diabetes in Wister rats. Diabetic rats were immediately treated with low, medium and high doses of TASAES at 4.9, 9.8 mg/kg and 19.6 mg/kg body weight by gavage, respectively, for eight weeks. Cardiac function was evaluated by in situ hemodynamic measurements, and patch clamp for the L-type Ca2+ channel current (ICa2+-L) and transient outward K+ channel current (Ito). Histopathological changes were observed under light and electron microscope. The expression of pro-fibrotic factor, connective tissue growth factor (CTGF) was monitored using immunohistochemistry staining. Compared with diabetic group, medium and high doses, but not low dose, of TASAES showed a significant protection against diabetes-induced cardiac dysfunction, shown by increased absolute value of left ventricular systolic pressure (LVSP) and maximum rates of pressure development (±dp/dtmax), and enhanced amplitude of ICa2+-L (P < 0.05). Histological staining indicated a significant inhibition of diabetes-caused pathological changes and up-regulation of CTGF expression (P < 0.05). The results suggest that TASAES prevents diabetes-induced cardiac dysfunction and pathological damage through up-regulating ICa2+-L in cardiac cells and decreasing CTGF expression. PMID:19381071

  2. YuaB Functions Synergistically with the Exopolysaccharide and TasA Amyloid Fibers To Allow Biofilm Formation by Bacillus subtilis ▿

    PubMed Central

    Ostrowski, Adam; Mehert, Angela; Prescott, Alan; Kiley, Taryn B.; Stanley-Wall, Nicola R.

    2011-01-01

    During biofilm formation by Bacillus subtilis, two extracellular matrix components are synthesized, namely, the TasA amyloid fibers and an exopolysaccharide. In addition, a small protein called YuaB has been shown to allow the biofilm to form. The regulatory protein DegU is known to initiate biofilm formation. In this report we show that the main role of DegU during biofilm formation is to indirectly drive the activation of transcription from the yuaB promoter. The N terminus of YuaB constitutes a signal peptide for the Sec transport system. Here we show that the presence of the signal peptide is required for YuaB function. In addition we demonstrate that upon export of YuaB from the cytoplasm, it localizes to the cell wall. We continue with evidence that increased production of TasA and the exopolysaccharide is not sufficient to overcome the effects of a mutation in yuaB, demonstrating the unique involvement of YuaB in forming a biofilm. In line with this, YuaB is not involved in correct synthesis, export, or polymerization of either the TasA amyloid fibers or the exopolysaccharide. Taken together, these findings identify YuaB as a protein that plays a novel role during biofilm formation. We hypothesize that YuaB functions synergistically with the known components of the biofilm matrix to facilitate the assembly of the biofilm matrix. PMID:21742882

  3. YuaB functions synergistically with the exopolysaccharide and TasA amyloid fibers to allow biofilm formation by Bacillus subtilis.

    PubMed

    Ostrowski, Adam; Mehert, Angela; Prescott, Alan; Kiley, Taryn B; Stanley-Wall, Nicola R

    2011-09-01

    During biofilm formation by Bacillus subtilis, two extracellular matrix components are synthesized, namely, the TasA amyloid fibers and an exopolysaccharide. In addition, a small protein called YuaB has been shown to allow the biofilm to form. The regulatory protein DegU is known to initiate biofilm formation. In this report we show that the main role of DegU during biofilm formation is to indirectly drive the activation of transcription from the yuaB promoter. The N terminus of YuaB constitutes a signal peptide for the Sec transport system. Here we show that the presence of the signal peptide is required for YuaB function. In addition we demonstrate that upon export of YuaB from the cytoplasm, it localizes to the cell wall. We continue with evidence that increased production of TasA and the exopolysaccharide is not sufficient to overcome the effects of a mutation in yuaB, demonstrating the unique involvement of YuaB in forming a biofilm. In line with this, YuaB is not involved in correct synthesis, export, or polymerization of either the TasA amyloid fibers or the exopolysaccharide. Taken together, these findings identify YuaB as a protein that plays a novel role during biofilm formation. We hypothesize that YuaB functions synergistically with the known components of the biofilm matrix to facilitate the assembly of the biofilm matrix. PMID:21742882

  4. SE-FIT

    NASA Technical Reports Server (NTRS)

    Chen, Yongkang; Weislogel, Mark; Schaeffer, Ben; Semerjian, Ben; Yang, Lihong; Zimmerli, Gregory

    2012-01-01

    The mathematical theory of capillary surfaces has developed steadily over the centuries, but it was not until the last few decades that new technologies have put a more urgent demand on a substantially more qualitative and quantitative understanding of phenomena relating to capillarity in general. So far, the new theory development successfully predicts the behavior of capillary surfaces for special cases. However, an efficient quantitative mathematical prediction of capillary phenomena related to the shape and stability of geometrically complex equilibrium capillary surfaces remains a significant challenge. As one of many numerical tools, the open-source Surface Evolver (SE) algorithm has played an important role over the last two decades. The current effort was undertaken to provide a front-end to enhance the accessibility of SE for the purposes of design and analysis. Like SE, the new code is open-source and will remain under development for the foreseeable future. The ultimate goal of the current Surface Evolver Fluid Interface Tool (SEFIT) development is to build a fully integrated front-end with a set of graphical user interface (GUI) elements. Such a front-end enables the access to functionalities that are developed along with the GUIs to deal with pre-processing, convergence computation operation, and post-processing. In other words, SE-FIT is not just a GUI front-end, but an integrated environment that can perform sophisticated computational tasks, e.g. importing industry standard file formats and employing parameter sweep functions, which are both lacking in SE, and require minimal interaction by the user. These functions are created using a mixture of Visual Basic and the SE script language. These form the foundation for a high-performance front-end that substantially simplifies use without sacrificing the proven capabilities of SE. The real power of SE-FIT lies in its automated pre-processing, pre-defined geometries, convergence computation operation

  5. ZnSe/ZnSeTe Superlattice Nanotips

    PubMed Central

    2010-01-01

    The authors report the growth of ZnSe/ZnSeTe superlattice nanotips on oxidized Si(100) substrate. It was found the nanotips exhibit mixture of cubic zinc-blende and hexagonal wurtzite structures. It was also found that photoluminescence intensities observed from the ZnSe/ZnSeTe superlattice nanotips were much larger than that observed from the homogeneous ZnSeTe nanotips. Furthermore, it was found that activation energies for the ZnSe/ZnSeTe superlattice nanotips with well widths of 16, 20, and 24 nm were 76, 46, and 19 meV, respectively. PMID:20672085

  6. Fe distribution in GaSe and InSe

    SciTech Connect

    Kovalyuk, Z.D.; Feichuk, P.I.; Shcherbak, L.P.; Zbykovskaya, N.I.

    1985-06-01

    In this paper, the authors use tagged atoms to determine the effective coefficients of Fe distribution in GaSe and InSe during crystallization of a doped melt by the Bridgman method. The distribution of Fe in GaSe and InSe was studied with the aid of Fe tagged with the radiosotopes VVFe + VZFe. Doping of the material was combined with the processes of synthesis and crystallization. Equations are presented for the calculation of the real impurity distribution in GaSe and InSe crystals.

  7. Properties of Se/InSe Thin-Film Interface

    NASA Astrophysics Data System (ADS)

    Qasrawi, A. F.; Kayed, T. S.; Elsayed, Khaled A.

    2016-06-01

    Se, InSe, and Se/InSe thin films have been prepared by the physical vapor deposition technique at pressure of ˜10-5 torr. The structural, optical, and electrical properties of the films and Se/InSe interface were investigated by means of x-ray diffraction (XRD) analysis, ultraviolet-visible spectroscopy, and current-voltage ( I- V) characteristics. XRD analysis indicated that the prepared InSe films were amorphous while the Se films were polycrystalline having hexagonal structure with unit cell parameters of a = 4.3544 Å and c = 4.9494 Å. Spectral reflectance and transmittance analysis showed that both Se and InSe films exhibited indirect allowed transitions with energy bandgaps of 1.92 eV and 1.34 eV, respectively. The Se/InSe interface exhibited two energy bandgaps of 0.98 eV and 1.73 eV above and below 2.2 eV, respectively. Dielectric constant values were also calculated from reflectance spectra for the three layers in the frequency range of 500 THz to 272 THz. The dielectric constant exhibited a promising feature suggesting use of the Se/InSe interface as an optical resonator. Moreover, the Au/Se/InSe/Ag heterojunction showed some rectifying properties that could be used in standard optoelectronic devices. The ideality factor and height of the energy barrier to charge carrier motion in this device were found to be 1.72 and 0.66 eV, respectively.

  8. Electron-impact ionization of Se2+ and Se3+

    NASA Astrophysics Data System (ADS)

    Pindzola, M. S.; Loch, S. D.

    2016-06-01

    Electron-impact ionization cross sections for Se2+ and Se3+ are calculated using a semi-relativistic configuration-average distorted-wave (CADW) method. Good agreement between the CADW calculations and recent experimental measurements are found for the single ionization of Se2+ from threshold to 500 eV and for the double ionization of Se2+ from threshold to 225 eV. Good agreement between the CADW calculations and recent experimental measurements are also found for the single ionization of Se3+ from threshold to 200 eV and for the double ionization of Se3+ near the peak of the cross section at 350 eV. Disagreements at other incident electron energies may be due to the complexity of the ionization pathways for low charged Se atomic ions, the various theoretical approximations, and the difficulty in measuring relatively small double ionization events.

  9. Optical investigation of CdSe/ZnSe quantum nanostructures

    NASA Astrophysics Data System (ADS)

    Valakh, M. Ya; Ivanov, S. V.; Mestres, N.; Pascual, J.; Shubina, T. V.; Sorokin, S. V.; Streltchuk, V. V.; Pozina, G.; Monemar, B.

    2002-02-01

    We have used resonant and non-resonant Raman scattering as well as photoluminescence and cathodoluminescence experiments to study the structure and composition properties of CdxZn1-xSe formed by migration enhanced epitaxy of CdSe layers on ZnSe buffers. The spectral change of the photoluminescence maximum correlates with the increase of the Cd content, depending on the nominal CdSe thickness in the 1.5-3.0 ML range. The inhomogeneous broadening of the photoluminescence band is caused by the composition difference between the two-dimensional mixed CdxZn1-xSe layer and the inserted islands with larger Cd concentration. This is confirmed by phonon frequency changes in resonant Raman scattering for samples with different nominal CdSe thicknesses as well as in Stokes and anti-Stokes frequency changes observed in the 1.5 ML sample. Attention is paid to the role of defects on Raman scattering and photoluminescence for the 3.15 ML sample.

  10. Electrodeposition of In-Se, Cu-Se, and Cu-In-Se thin films

    SciTech Connect

    Bhattacharya, R.N.; Fernandez, A.M.; Contreras, M.A.; Keane, J.; Tennant, A.L.; Ramanathan, K.; Tuttle, J.R.; Noufi, R.N.; Hermann, A.M.

    1996-03-01

    Indium-selenium, copper-selenium, and copper-indium-selenium thin films have been prepared by electrodeposition techniques on molybdenum substrates. Electrodeposited precursors are prepared at varying potentials, pH, and deposition times. The adhesion and uniformity of indium selenide on molybdenum substrates are improved by electrodepositing an initial copper layer (500 {angstrom}) on molybdenum. The films (In-Se, Cu-Se, and Cu-In-Se) are annealed at 250 and 450 C in Ar for 15 min and are slow-cooled (3 C/min). The films are characterized by electron microprobe analysis, inductive-coupled plasma spectrometry, X-ray diffraction analysis, Auger electron spectroscopy, and scanning electron microscopy. The as-deposited precursor films are loaded in a physical evaporation chamber and addition In or Cu and Se are added to the film to adjust the final composition to CuInSe{sub 2}. The device fabricated using electrodeposited Cu-In-Se precursor layers resulted in a solar cell efficiency of 9.4%.

  11. Negatively charged excitons in semimagnetic CdSe/ZnSe/ZnMnSe quantum dots

    SciTech Connect

    Brichkin, A. S. Chernenko, A. V.; Chekhovich, E. A.; Dorozhkin, P. S.; Kulakovskii, V. D.; Ivanov, S. V.; Toropov, A. A.

    2007-08-15

    Low-temperature (T = 1.6 K) photoluminescence (PL) of individual CdSe/ZnSe/ZnMnSe quantum dots (QDs) with different magnitudes of the sp-d exchange interaction between the magnetic impurity ions and charge carriers has been studied in a magnetic field up to 12 T applied in the Faraday and Voigt geometry. The magnitude of the interaction was controlled by changing the fraction ({eta}{sub e,h}) of the squared wave function of charge carriers in the semimagnetic barrier by means of variation of the nonmagnetic (ZnSe) layer thickness. It is established that the sp-d exchange interaction leads to a change in the sign of the effective hole g factor even for {eta}{sub e,h} {approx} 5%, while further increase in the interaction magnitude is accompanied by a rapid growth in the magnitude of spin splitting for both electrons and holes. The quantum yield of PL exhibits a significant decrease due to nonradiative Auger recombination with the excitation of Mn ions only for {eta}{sub e,h} {approx} 12%, while the rate of the holes spin relaxation starts growing only for still higher {eta}{sub e,h} values. In a strong magnetic field perpendicular to the sample plane, the alignment of Mn spins leads to suppression of the Auger recombination only in the excited spin state. For a small rate of the hole spin relaxation, this leads to a rather unusual result: the emission from an excited trion state predominates in strong magnetic fields.

  12. Shape Coexistence in ^72Se

    NASA Astrophysics Data System (ADS)

    Lister, C. J.; Fischer, S. M.; McCutchan, E. A.; Ahn, T.; Casperson, R. J.; Heinz, A.; Ilie, G.; Qian, J.; Williams, E.; Winkler, R.

    2009-10-01

    One of the original candidates for shape co-existence in nuclei was ^72Se [1,2]. We have collected extensive new data, both ``in-beam'' following the ^40Ca(^36Ar,4p)^72Se reaction using Gammasphere at Argonne's ATLAS accelerator, and from the decay of ^72Br populated in the ^58Ni(^16O,pn) reaction studied at WNSL Yale. A new J^π=0^+ state was found at 1876 keV, the published [2] decay scheme was corrected, and twenty-six new levels were established. This detailed spectroscopy of low-lying states helps to delineate the two shape minima. The mixing of prolate-deformed and near-spherical states can be now quantified, and the gamma decay path from high-spin can be followed. The inferred groundstate shape is consistent with trends in experiment and calculation of the selenium isotopes [3,4]. [4pt] [1] J.H. Hamilton, et al., Phys. Rev. Letts. 32 239 (1974)[0pt] [2] W.E. Collins, et al., Phys.Rev. C9, 1457 (1974)[0pt] [3] S.M. Fischer, et al., Phys.Rev.Lett. 84, 4064 (2000)[0pt] [4] J. Ljungvall, et al., Phys.Rev.Lett. 100, 102502 (2008)

  13. Liquidus Projections of Bi-Se-Ga and Bi-Se-Te Ternary Systems

    NASA Astrophysics Data System (ADS)

    Lin, Po-han; Chen, Sinn-wen; Hwang, Jenn-dong; Chu, Hsu-shen

    2016-06-01

    This study determines the liquidus projections of both Bi-Se-Ga and Bi-Se-Te ternary systems which are constituent ternary systems of promising Bi-Se-Te-Ga thermoelectric materials. Ternary Bi-Se-Ga and Bi-Se-Te alloys are prepared. Their primary solidification phases are experimentally determined, and thermal analysis experiments are carried out. The liquidus projections are determined based on the ternary experimental results and phase diagrams of constituent binary systems. The Bi-Se-Ga system includes seven primary solidification phases, Bi, Ga, GaSe, Ga2Se3, Se, Bi2Se3, and (Bi2)n(Bi2Se3)m. In the Bi-Se-Te system, there are five primary solidification phases, Bi, (Bi2)n(Bi2Te3)m, Bi2(Se,Te)3, (Se,Te), and (Bi2)n(Bi2Se3)m. Both the (Bi2)n(Bi2Te3)m and (Bi2)n(Bi2Se3)m phases are not a single phase, but a collection of series undetermined phases. Large miscibility gaps are observed in the Bi-Se-Ga system. The temperatures of the invariant reactions, Liquid + Bi + GaSe = Ga and Liquid + Ga2Se3 = Bi + GaSe, are at 495 K (222 °C) and 533 K (260 °C), respectively.

  14. Runoff generation in SE Spain

    NASA Astrophysics Data System (ADS)

    Dalen, E. N.; Kirkby, M. J.; Chapman, P. J.; Bracken, L. J.

    2007-12-01

    We are working to improve a hydrological model for prediction of runoff in medium-scale semi-arid catchments in SE Spain. The aim is to develop and improve understandings of runoff generation in semi-arid areas and to improve modelling of runoff. Objectives are to investigate the influence of geology, landuse and seasonality on infiltration rates and use remonte sensing (RS) and GIS to classify an area into Hydrologically Similar Surfaces (HYSS) categories. The research includes investigating the impact of different landscape elements on runoff within two 150 km2 catchments, the Rambla Nogalte and the Rambla de Torrealvilla. Most storms within these catchments are of short duration. HYSS are defined as areas with similar1-D (vertical) partitioning of net rainfall between infiltration and overland flow. HYSS are identified from field measurements of soils, micro and macro- topography and infiltration rates; then combined with analysis of multi-spectral airborne RS images. HYSS are selected to minimise internal variability in the relationship between rainfall and local runoff generation and are scaled up to cover larger areas. The overall sampling strategy for measurements has been to undertake constant intensity rainfall simulator measurements within provisional HYSS categories, and to augment this with a large number of minidisk infiltrometer measurements. This strategy captures as much of the variability in the landscape as possible. The wide variability within even small areas has led to the final adoption of only a few large classes that can be effectively distinguished. The final part of the research is to link the spatial partitioning of the two catchments into HYSS with the detailed rainfall records for the areas, and combine these two sets of data into a grid-based model for runoff generation across the area. The applied Green-Ampt modelling approach gave 63 possible combinations of surface properties (9 HYSS) and areas in the Rambla Nogalte each represented

  15. Se atoms and Se6 molecules as guests in Se-carbons - prepared by reduction of a SeCl4-graphite precursor

    NASA Astrophysics Data System (ADS)

    Walter, J.; Shioyama, H.

    2000-01-01

    A SeCl4 -graphite intercalation compound precursor was reduced by a solution of lithium diphenylide in tetrahydrofuran at room temperature. X-ray diffraction measurements gave two distinguishable stages. One stage represented a Se-atom intercalation the other represented an intercalation of Se6 molecules. The in-plane diffraction patterns were estimated by selected-area electron diffraction, the existence of two different guest species (atoms and molecules) could be proved. The Se6 -molecule phase shows an incommensurate lattice with regard to the host lattice, but they are in the same orientation. The lattice parameter of intercalated Se6 is a Se 6-guest = 1158+/-36 pm, c Se 6-guest = 483+/-38 pm, which fits with the lattice parameter of non-intercalated Se6 molecules. Se atom domains show a 2 × agraphite superlattice with respect to the host lattice, which is a commensurate superstructure. Raman scattering data showed the occurrence of an acceptor-type graphite intercalation compound. Three different types of spectra could be obtained, two kinds of spectra consists of doublets at 1588 cm-1 and 1608 cm-1 , with different intensity ratios. These two kinds of spectra are certainly attributed to Se-atom domains, with different stages. A third type of spectrum show bands at higher wavenumbers (1646 cm-1 and 1653 cm-1 ). These bands are probably correlated to Se6 -molecule domains. They represent maybe very early stages of nanoparticle formation.

  16. Formation of highly luminescent Zn1-xCdxSe nanocrystals using CdSe and ZnSe seeds

    NASA Astrophysics Data System (ADS)

    Zhang, Ruili; Yang, Ping

    2013-05-01

    High-quality colloidal Zn1-xCdxSe nanocrystals (NCs) with tunable photoluminescence (PL) from blue to orange were synthesized using oleic acid as a capping agent. The Zn1-xCdxSe NCs were prepared through two approaches: using CdSe or ZnSe seeds. In the case of CdSe NCs as seeds, Zn1-xCdxSe NCs were fabricated by the reaction of Zn, Cd, and Se precursors in the coordinating solvent system at high temperature. The Zn1-xCdxSe NCs revealed orange emitting. A significant blue-shift of absorption and PL spectra were observed with time, indicating the formation of ternary NCs. In contrast, Zn1-xCdxSe NCs revealed blue to green PL for ZnSe NCs as seeds. This is ascribed to an embryonic nuclei-induced alloying process. With increasing time, the Zn1-xCdxSe NCs exhibited a red-shift both in their absorption and PL spectra. This is attributed to the engineering in band gap energy via the control of NC composition. The PL properties of as-prepared alloyed NCs are comparable or even better than those for the parent binary systems. The PL peak wavelength of the Zn1-xCdxSe NCs depended strongly on reaction time and the molar ratio of Cd/Zn. The Zn1-xCdxSe NCs revealed a spherical morphology and exhibited a wurtzite structure according to transmission electron microscopy observation and an X-ray diffraction analysis.

  17. CuInSe2/ZnSe solar cells using reactively sputter-deposited ZnSe

    NASA Technical Reports Server (NTRS)

    Nouhi, A.; Stirn, R. J.; Hermann, A.

    1987-01-01

    Results on CuInSe2/ZnSe thin-film heterojunction photovoltaic devices are presented. By the use of reactive magnetron cosputtering of Zn and In dopant in Ar/H2Se, ZnSe thin films have been deposited on glass and conducting SnO2-coated glass substrates with resistivity as low as 20 ohm-cm at deposition temperatures as low as 120 C. Preliminary ZnSe depositions onto CuInSe2 films supplied by industrial laboratories are encouraging. Reactive-sputter-deposition parameters for ZnSe have yet to be optimized for CuInSe2 substrates; however, open-circuit voltages as high as 430 mV were obtained. The highest short-circuit current density, as determined by spectral response weighted for AM1.5 global insulation, was 37.4 mA/sq cm. In all cases, a highly conductive ZnO film was overcoated onto the ZnSe to reduce the overall sheet resistance.

  18. Estimation of selenium (Se) intake from Se in serum, whole blood, toenails, or urine

    SciTech Connect

    Longnecker, M.P.; Taylor, P.R.; Levander, O.A.; Flack, V.; Veillon, C.; McAdam, P.A.; Patterson, K.Y.; Holden, J.; Stampfer, M.J.; Morris, J.S.; Willett, W.C. NCI, Rockville, MD USDA, Beltsville, MD Harvard Univ., Boston, MA Univ. of Missouri, Columbia )

    1991-03-11

    Because Se content of food varies widely, estimates of intake based on Se status are more accurate than those based on food composition tables. 77 free-living subjects from South Dakota and Wyoming, where the range of Se intake was large, provided blood, toenails, and 24-hour urines. Se intake, measured by chemical analysis of 4-8 days of duplicate-plate food composites from each subject, was estimated on the basis of the Se indices. To predict the natural logarithm of Se intake from serum Se the best fit was provided by : {minus}0.465 + 0.568{asterisk}SSe. Addition of lean body mass (LBM (kg)) and energy intake (EI (MJ)) to the model markedly improved the fit. Models based on Se in blood or urine gave slightly better estimates than those based on toenail Se. Consideration of data in addition to indices of Se status resulted in improved estimates of intake.

  19. Biopolymer-protected CdSe nanoparticles.

    PubMed

    Bozanić, D K; Djoković, V; Bibić, N; Sreekumari Nair, P; Georges, M K; Radhakrishnan, T

    2009-11-23

    A synthetic procedure for the encapsulation of cadmium selenide (CdSe) nanoparticles in a sago starch matrix is introduced. The nanocomposite was investigated using structural, spectroscopic, and thermal methods. TEM micrographs of the nanocomposite showed spherical CdSe particles of 4-5 nm in size coated with a biopolymer layer. The absorption edges of both the aqueous solution and the thin film of the CdSe-starch nanocomposite were shifted toward lower wavelengths in comparison to the value of the bulk semiconductor. Infrared measurements revealed that the interaction of CdSe nanoparticles and starch chains takes place via OH groups. Although the onset of the temperature of decomposition of CdSe-starch nanocomposite is lower than that of the pure matrix, thermogravimetric analysis also showed that introduction of CdSe nanoparticles significantly reduced starch degradation rate leading to high residual mass at the end of the degradation process. PMID:19772959

  20. Oxidation of ultrathin GaSe

    SciTech Connect

    Thomas Edwin Beechem; McDonald, Anthony E.; Ohta, Taisuke; Howell, Stephen W.; Kalugin, Nikolai G.; Kowalski, Brian M.; Brumbach, Michael T.; Spataru, Catalin D.; Pask, Jesse A.

    2015-10-26

    Oxidation of exfoliated gallium selenide (GaSe) is investigated through Raman, photoluminescence, Auger, and X-ray photoelectron spectroscopies. Photoluminescence and Raman intensity reductions associated with spectral features of GaSe are shown to coincide with the emergence of signatures emanating from the by-products of the oxidation reaction, namely, Ga2Se3 and amorphous Se. Furthermore, photoinduced oxidation is initiated over a portion of a flake highlighting the potential for laser based patterning of two-dimensional heterostructures via selective oxidation.

  1. Oxidation of ultrathin GaSe

    SciTech Connect

    Beechem, Thomas E. Brumbach, Michael T.; McDonald, Anthony E.; Howell, Stephen W.; Ohta, Taisuke; Kowalski, Brian M.; Pask, Jesse A.; Kalugin, Nikolai G.; Spataru, Catalin D.

    2015-10-26

    Oxidation of exfoliated gallium selenide (GaSe) is investigated through Raman, photoluminescence, Auger, and X-ray photoelectron spectroscopies. Photoluminescence and Raman intensity reductions associated with spectral features of GaSe are shown to coincide with the emergence of signatures emanating from the by-products of the oxidation reaction, namely, Ga{sub 2}Se{sub 3} and amorphous Se. Photoinduced oxidation is initiated over a portion of a flake highlighting the potential for laser based patterning of two-dimensional heterostructures via selective oxidation.

  2. Oxidation of ultrathin GaSe

    DOE PAGESBeta

    Thomas Edwin Beechem; McDonald, Anthony E.; Ohta, Taisuke; Howell, Stephen W.; Kalugin, Nikolai G.; Kowalski, Brian M.; Brumbach, Michael T.; Spataru, Catalin D.; Pask, Jesse A.

    2015-10-26

    Oxidation of exfoliated gallium selenide (GaSe) is investigated through Raman, photoluminescence, Auger, and X-ray photoelectron spectroscopies. Photoluminescence and Raman intensity reductions associated with spectral features of GaSe are shown to coincide with the emergence of signatures emanating from the by-products of the oxidation reaction, namely, Ga2Se3 and amorphous Se. Furthermore, photoinduced oxidation is initiated over a portion of a flake highlighting the potential for laser based patterning of two-dimensional heterostructures via selective oxidation.

  3. Strategic Use of Naturally Selenium (Se)-rich Milling Coproducts to Eliminate Se Deficiency and Create Se-enriched Foods.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Selenium (Se) is essential for sustaining a healthy life. When dietary Se was marginally deficient, populations experienced impaired reproduction and growth rates and increased disease rates. Selenium-rich grains, harvested from regions with seleniferous soils, were natural sources of bioavailable S...

  4. The Structure and Electrical Properties of the Ag2Se + Ga2Se3 + GeSe2 Glass System

    NASA Astrophysics Data System (ADS)

    Marple, Maxwell Adam Thomas

    Silver containing homogeneous chalcogenide glasses in the ternary system Ag2Se-Ga2Se3-GeSe2 (AGGS) are synthesized and their atomic structure-property relationships are investigated. Structural studies are carried out using Raman, 77Se, 71Ga, 69Ga, and 109Ag nuclear magnetic resonance (NMR) spectroscopy. The structure of these glasses consists primarily of a network of corner sharing (Ga/Ge)Se4/2 tetrahedra with a small fraction of homopolar Se-Se bonds. Compositional modification of the atomic structure follows the charge compensated network model developed in the literature for aluminosilicate glasses. Ag2Se acts as a network modifier, forming non-bridging Se in glasses with Ag/Ga >1, while Ga 2Se3 plays the role of a network intermediate similar to Al2O3 in oxide glasses. The network favors the formation of homopolar Ge-Ge bonding in glasses with Ag/Ga <1, to accommodate the Se deficiency brought by the incorporation of Ga2Se3 with Ga being tetrahedrally coordinated to Se. This structural model is consistent with the variation in the glass transition temperatures and molar volume. Electrical Impedance Spectroscopy (EIS) reveals the ionic conductivity of the AGGS glasses to be quite high at ambient temperature, reaching up to 10 --4 S/cm for glasses with the highest Ag content. Increasing Se deficiency with respect to stoichiometry can enhance the conductivity further to ˜3x10--4 S/cm . Transference number measurements using the electromotive force (EMF) method as well as variable temperature 109Ag NMR line shape studies indicate that the conductivity is predominantly ionic in nature and results from fast hopping dynamics of Ag ions. The high ionic conductivity can be related to a heavily modified structural network that results in a potential energy landscape with many suitable hopping sites for the Ag ions. These structural characteristics and electrical properties of the glasses in the AGGS system may guide in the development of next generation fast ion

  5. Semiconductor-metal transition of Se in Ru-Se Catalyst Nanoparticles

    NASA Astrophysics Data System (ADS)

    Babu, P. K.; Lewera, Adam; Oldfield, Eric; Wieckowski, Andrzej

    2009-03-01

    Ru-Se composite nanoparticles are promising catalysts for the oxygen reduction reaction (ORR) in fuel cells. Though the role of Se in enhancing the chemical stability of Ru nanoparticles is well established, the microscopic nature of Ru-Se interaction was not clearly understood. We carried out a combined investigation of ^77Se NMR and XPS on Ru-Se nanoparticles and our results indicate that Se, a semiconductor in elemental form, becomes metallic when interacting with Ru. ^77Se spin-lattice relaxation rates are found to be proportional to T, the well-known Korringa behavior characteristic of metals. The NMR results are supported by the XPS binding energy shifts which suggest that a possible Ru->Se charge transfer could be responsible for the semiconductor->metal transition of Se which also makes Ru less susceptible to oxidation during ORR.

  6. Unrecognized hemoglobin SE disease as microcytosis

    PubMed Central

    Cooper, Barry; Guileyardo, Joseph; Mora, Adan

    2016-01-01

    Hemoglobin SE disease was first described during the 1950s as a relatively benign microcytosis, but increasing prevalence has revealed a predisposition towards vasoocclusive sickling. Recognition of SE hemoglobinopathies’ potential complications is crucial so medical measures can be utilized to avoid multiorgan injury. PMID:27365881

  7. Glass formation and the third harmonic generation of Cu2Se-GeSe2-As2Se3 glasses

    NASA Astrophysics Data System (ADS)

    Reshak, A. H.; Klymovych, O. S.; Myronchuk, G. L.; Zamuruyeva, O. V.; Zmiy, O. F.; Alahmed, Z. A.; Chyský, J.; Bila, Jiri; Kamarudin, H.

    2014-10-01

    We have performed the investigation of the nonlinear optical properties namely the third harmonic generation (THG) of the glass-formation region in the Cu2Se-GeSe2-As2Se3 system. The samples were synthesized by direct single-temperature method from high-purity elementary substances. We have found that the value of disorder parameter Δ depends on the composition of the glassy alloys. The measurements show that increasing the Cu2Se concentration leads to increased slope of the absorption edge, which may be explained by the decrease of the height of random potential relief for the electrons in the tails of the state density which border the band edges. A very sharp increase in the THG at low temperature was observed. Significant enhancement in THG was obtained with decreasing the energy gap, which agreed well with the nonlinear optical susceptibilities obtained from other glasses.

  8. Quasiparticle band structure of HgSe

    SciTech Connect

    Rohlfing, M.; Louie, S.G.

    1998-04-01

    Motivated by a recent discussion about the existence of a fundamental gap in HgSe [Phys. Rev. Lett. {bold 78}, 3165 (1997)], we calculate the quasiparticle band structure of HgSe within the GW approximation for the electron self-energy. The band-structure results show that HgSe is a semimetal, which is in agreement with most experimental data. We observe a strong wave-vector dependence of the self-energy of the lowest conduction band, leading to an increased dispersion and a small effective mass. This may help to interpret recent photoemission spectroscopy measurements. {copyright} {ital 1998} {ital The American Physical Society}

  9. The system SnTe-InSe

    SciTech Connect

    Gurshumov, A.P.; Alidzhanov, M.A.; Aliev, A.S.; Gadzhiev, T.G.; Mamedov, N.A.

    1986-03-01

    This paper discusses the nature of the interaction and physicochemical properties of the alloys of the system SnTe-InSe. The DTA was performed on an NTR-74 pyrometer, XPA on a Dron-2.0 diffractometer and MSA on an MIM-7 metallographic microscope. The microhardness of the samples was determined on a PMT-3 microhardness tester. The congruently melting compound SnInTeSe and solid solutions based on the starting components are formed in the system.

  10. Double electron capture searches in 74Se

    NASA Astrophysics Data System (ADS)

    Lehnert, B.; Wester, T.; Degering, D.; Sommer, D.; Wagner, L.; Zuber, K.

    2016-08-01

    A search for various double electron capture modes of 74Se has been performed using an ultralow background Ge-detector in the Felsenkeller laboratory, Germany. Especially for the potentially resonant transition into the 1204.2 keV excited state of 74Ge a lower half-life limit of 0.70× {10}19 yr (90% credibility) has been obtained. Serious concerns are raised about the validity of obtained 74Se limits in some recent publications.

  11. Atomistic Model of Physical Ageing in Se-rich As-Se Glasses

    SciTech Connect

    Golovchak,R.; Shpotyuk, O.; Kozdras, A.; Bureau, B.; Vlcek, M.; Ganjoo, A.; Jain, H.

    2007-01-01

    Thermal, optical, X-ray excited and magnetic methods were used to develop a microstructural model of physical ageing in Se-rich glasses. The glass composition As10Se90, possessing a typical cross-linked chain structure, was chosen as a model object for the investigations. The effect of physical ageing in this glass was revealed by differential scanning calorimetry, whereas the corresponding changes in its atomic arrangement were studied by extended X-ray absorption fine structure, Raman and solid-state 77Se nuclear magnetic resonance spectroscopy. Straightening-shrinkage processes are shown to be responsible for the physical ageing in this Se-rich As-Se glass.

  12. Synthesis of (/sup 75/Se)trimethylselenonium iodide from (/sup 75/Se)selenocystine

    SciTech Connect

    Foster, S.J.; Ganther, H.E.

    1984-02-15

    The synthesis of (/sup 75/Se)trimethylselenonium iodide from (/sup 75/)selenocystine is described. The starting compound is reduced to (/sup 75/Se)selenocysteine with borohydride and reacted with methyl iodide to form (/sup 75/Se)Se-methyl-selenocysteine, then treated with methyl iodide in formic acid solution to form Se-dimethyl-selenocysteine selenonium iodide. Over a period of days, the selenonium intermediate undergoes spontaneous elimination to form alanine and dimethyl selenide, which reacts with methyl iodide to give the trimethylselenonium product in over 90% yield. 15 references.

  13. Surface migration and volume diffusion in the AgGaSe2-Ag2Se system

    NASA Technical Reports Server (NTRS)

    Kim, N.-H.; Feigelson, R. S.; Route, R. K.

    1992-01-01

    Surface migration and volume diffusion in the Ag2Se-AgGaSe2 system were investigated using reactive diffusion couples which were analyzed by X-ray diffraction, optical microscopy, and electron probe microanalysis. The surface diffusivities of all mobile species are found to be much larger than volume diffusivities. The results of the study suggest that Se moves together with Ag and Ga to maintain binary (Ag2Se and Ga2Se3) stoichiometry and electroneutrality. The dominance of surface migration kinetics can account for the uniform annihilation of second-phase precipitates during heat treatments.

  14. Sb2Se3 under pressure

    PubMed Central

    Efthimiopoulos, Ilias; Zhang, Jiaming; Kucway, Melvin; Park, Changyong; Ewing, Rodney C.; Wang, Yuejian

    2013-01-01

    Selected members of the A2B3 (A = Sb, Bi; B = Se, Te) family are topological insulators. The Sb2Se3 compound does not exhibit any topological properties at ambient conditions; a recent high-pressure study, however, indicated that pressure transforms Sb2Se3 from a band insulator into a topological insulator above ~2 GPa; in addition, three structural transitions were proposed to occur up to 25 GPa. Partly motivated by these results, we have performed x-ray diffraction and Raman spectroscopy investigations on Sb2Se3 under pressure up to 65 GPa. We have identified only one reversible structural transition: the initial Pnma structure transforms into a disordered cubic bcc alloy above 51 GPa. On the other hand, our high-pressure Raman study did not reproduce the previous results; we attribute the discrepancies to the effects of the different pressure transmitting media used in the high-pressure experiments. We discuss the structural behavior of Sb2Se3 within the A2B3 (A = Sb, Bi; B = Se, Te) series. PMID:24045363

  15. A transferable force field for CdS-CdSe-PbS-PbSe solid systems

    SciTech Connect

    Fan, Zhaochuan; Vlugt, Thijs J. H.; Koster, Rik S.; Fang, Changming; Huis, Marijn A. van; Wang, Shuaiwei; Yalcin, Anil O.; Tichelaar, Frans D.; Zandbergen, Henny W.

    2014-12-28

    A transferable force field for the PbSe-CdSe solid system using the partially charged rigid ion model has been successfully developed and was used to study the cation exchange in PbSe-CdSe heteronanocrystals [A. O. Yalcin et al., “Atomic resolution monitoring of cation exchange in CdSe-PbSe heteronanocrystals during epitaxial solid-solid-vapor growth,” Nano Lett. 14, 3661–3667 (2014)]. In this work, we extend this force field by including another two important binary semiconductors, PbS and CdS, and provide detailed information on the validation of this force field. The parameterization combines Bader charge analysis, empirical fitting, and ab initio energy surface fitting. When compared with experimental data and density functional theory calculations, it is shown that a wide range of physical properties of bulk PbS, PbSe, CdS, CdSe, and their mixed phases can be accurately reproduced using this force field. The choice of functional forms and parameterization strategy is demonstrated to be rational and effective. This transferable force field can be used in various studies on II-VI and IV-VI semiconductor materials consisting of CdS, CdSe, PbS, and PbSe. Here, we demonstrate the applicability of the force field model by molecular dynamics simulations whereby transformations are initiated by cation exchange.

  16. Cs2UPd3Se6

    PubMed Central

    Oh, George N.; Ibers, James A.

    2011-01-01

    Dicaesium uranium(IV) tripalladium(II) hexa­selenide, Cs2UPd3Se6, crystallizes in the space group Fmmm in the Ba2NaCu3O6 structure type. The asymmetric unit comprises the following atoms with site symmetries as shown: U1 (mm2), Cs1 (222), Cs2 (m2m), Pd1 (.m.), Pd2 (2mm), Se1 (m..), and Se2 (1). This layered structure contains six edge-sharing square-planar [PdSe4] units that form a hexa­gon. These, in turn, edge-share with [USe6] trigonal–prismatic units, forming an extended layer parallel to (010). The layers are stacked along [010]. They are staggered, and are separated by the Cs atoms. The Cs atoms are either coordinated in a square anti­prism of Se atoms or are ten-coordinate, with one square face and the opposite face hexa­gonal. PMID:21522818

  17. Monoclinic Cu2Se3Sn.

    PubMed

    Gulay, L D; Daszkiewicz, M; Ostapyuk, T A; Klymovych, O S; Zmiy, O F

    2010-05-01

    A previously unknown modification of dicopper(I) triselenostannate(IV), Cu(2)Se(3)Sn, has been obtained from the Cu(2)Se-SnSe(2) quasi-binary system and investigated using X-ray single-crystal diffraction. The Se atoms are stacked in a closest-packed arrangement with the layers in the sequence ABC. The Cu atoms occupy one-third of the tetrahedral interstices, whereas the Sn atoms are located in one-sixth of the tetrahedral interstices. All the atoms occupy general positions. The structure possesses pseudo-inversion symmetry. The Cu(2)Se(3)Sn structure investigated in this paper (96 atoms per unit cell, ordered distribution of Cu and Sn over 12 cation positions) is a superstructure of the reported cubic (eight atoms per unit cell, random distribution of Cu and Sn over one cation position) and monoclinic (24 atoms per unit cell, ordered distribution of Cu and Sn over three cation positions) modifications. PMID:20442500

  18. Current transport characteristics of pSe-nMoSe2 heterojunction diode

    NASA Astrophysics Data System (ADS)

    Sumesh, C. K.; Patel, K. D.; Pathak, V. M.; Srivastava, R.

    2010-12-01

    The characteristics of heterojunction diode pSe-nMoSe2 fabricated from thermally evaporated p-Se films on n-type Molybdenum diselenide (MoSe2) grown by direct vapour transport (DVT) technique have been examined by using current-voltage measurements. To investigate the dark current transport mechanism in pSe-nMoSe2 heterojunctions the current-voltage characteristics were measured in the temperature range 100-300 K. The prepared diode shows a rectification ratio of the order of 103 within the range -2 to 2 V. A multi-step tunnelling model was used to analyze the I-V-T characteristics of the prepared device. The activation energy determined from the saturation current was about 1.16 eV.

  19. Improved photoluminescence quantum yield and stability of CdSe-TOP, CdSe-ODA-TOPO, CdSe/CdS and CdSe/EP nanocomposites

    NASA Astrophysics Data System (ADS)

    Wei, Shutian; Zhu, Zhilin; Wang, Zhixiao; Wei, Gugangfen; Wang, Pingjian; Li, Hai; Hua, Zhen; Lin, Zhonghai

    2016-07-01

    Size-controllable monodisperse CdSe nanocrystals with different organic capping were prepared based on the hot-injection method. The effective separation of nucleation and growth was achieved by rapidly mixing two highly reactive precursors. As a contrast, we prepared CdSe/CdS nanocrystals (NCs) successfully based on the selective ion layer adsorption and reaction (SILAR) technique. This inorganic capping obtained higher photoluminescence quantum yield (PLQY) of 59.3% compared with organic capping of 40.8%. Furthermore, the CdSe-epoxy resin (EP) composites were prepared by adopting a flexible ex situ method, and showed excellent stability in the ambient environment for one year. So the composites with both high PLQY of nanocrystals and excellent stability are very promising to device application.

  20. CdSe Nanoplatelets: Living Polymers.

    PubMed

    Jana, Santanu; Davidson, Patrick; Abécassis, Benjamin

    2016-08-01

    Colloidal CdSe nanoplatelets are considered to be excellent candidates for many applications in nanotechnology. One of the current challenges is to self-assemble these colloidal quantum wells into large ordered structures to control their collective optical properties. We describe a simple and robust procedure to achieve controlled face-to-face self-assembly of CdSe nanoplatelets into micron-long polymer-like threads made of up to ∼1000 particles. These structures are formed by addition of oleic acid to a stable colloidal dispersion of platelets, followed by slow drying and re-dispersion. We could control the average length of the CdSe nanoplatelet threads by varying the amount of added oleic acid. These 1-dimensional structures are flexible and feature a "living polymer" character because threads of a given length can be further grown through the addition of supplementary nanoplatelets at their reactive ends. PMID:27329047

  1. FeNb3Se10: A new structure type related to NbSe3

    NASA Astrophysics Data System (ADS)

    Cava, R. J.; Himes, V. L.; Mighell, A. D.; Roth, R. S.

    1981-09-01

    Employing single-crystal x-ray-diffraction techniques, the crystal structure of FeNb3Se10 was found to consist of two NbSe6 trigonal prismatic chains of the type found in NbSe3 and a double chain of edge-shared MSe6 octahedra, both running parallel to the monoclinic b axis. The metal-atom disorder, critical to the interpretation of previously observed electronic properties, is confined to the octahedral chains.

  2. Synthesis of near-infrared-emitting CdTe/CdSe/ZnSe/ZnS heterostructure.

    PubMed

    Yang, Ping

    2014-04-01

    Near-infrared-emitting quantum dots (QDs) were fabricated via organic synthesis strategies through constructing CdTe/CdSe/ZnSe/ZnS multishell heterostructure. An effective shell-coating route was developed for multishell growth on CdTe cores. Core/shell growth was monitored by absorption and photoluminescence (PL) spectroscopy and transmission electron microscopy observation. Yellow emitting CdTe cores were coated with a CdSe shell to generate type II structure. This yields core/shell QDs with red photoluminescence. The passivation by the ZnSe shell having a substantially wide bandgap confines the excitons within the CdTe/CdSe interface and isolates them from the solution environment and consequently improves the stability of the heterostructure. An additional ZnS shell was deposited around the outer layer of CdTe/CdSe/ZnSe QDs to form a heterostructure through the reaction between zinc oleate and trioctylphosphine sulfur in the crude CdTe/CdSe/ZnSe solution. By varying CdTe core size and each shell thickness, the PL wavelength of the obtained heterostructure can span from 580 to 770 nm. The PL efficiency is quenched in CdTe QDs in diluted solution but increases substantially up to 24% for CdTe/CdSe core/shell QDs. The PL efficiency of CdTe/CdSe/ZnSe/ZnS QDs with average diameter of 5.4 nm and a PL peak wavelength of 770 nm is 20%. PMID:24734747

  3. Se status in normal and pathological human individuals before and after Se supplementation

    NASA Astrophysics Data System (ADS)

    Bellisola, G.; Cinque, G.; Galassini, S.; Guidi, G. C.; Liu, N. Q.; Moschini, G.

    1996-04-01

    The determination of selenium in plasma and in urine samples has been suggested for the assessment of Se status in human individuals. The kidney is of fundamental importance in Se homeostasis: with low Se intake its excretion will be decreased and with high Se intake it will be increased. In 21 patients with kidney disease (8 with normal kidney function and 13 with moderate renal failure) Se was measured in 1 ml of urine by PIXE after preconcentration of the sample. The total urine volume was measured to calculate total daily Se excretion. The same procedure was applied to 14 normal individuals for comparison. All individuals were then supplemented orally with selenite for 8 weeks (Se = 600 μg/day) and the procedure was repeated. The behaviour of the major selenoproteins was also investigated by measuring glutathione peroxidase activities in plasma, in platelets and in erythrocyte samples. For renal function, serum and urine creatinine concentrations were utilised and creatinine clearances were calculated. Results obtained were compared before and after Se treatment and between groups. Some correlation studies were carried out between Se and kidney functions and/or selenoperoxidase activities.

  4. Superlattices of Bi2Se3/In2Se3: Growth characteristics and structural properties

    NASA Astrophysics Data System (ADS)

    Wang, Z. Y.; Guo, X.; Li, H. D.; Wong, T. L.; Wang, N.; Xie, M. H.

    2011-07-01

    Superlattices (SLs) consisted of alternating Bi2Se3 and In2Se3 layers are grown on Si(111) by molecular-beam epitaxy. Bi2Se3, a three-dimensional topological insulator (TI), showed good chemical and structural compatibility with In2Se3, a normal band insulator with large energy bandgap. The individual layers in the SLs are very uniform, and the hetero-interfaces are sharp. Therefore, such SL structures are potential candidates for explorations of the quantum size effects of TIs.

  5. n -type doping of CuIn Se2 and CuGa Se2

    NASA Astrophysics Data System (ADS)

    Persson, Clas; Zhao, Yu-Jun; Lany, Stephan; Zunger, Alex

    2005-07-01

    The efficiency of CuInSe2 based solar cell devices could improve significantly if CuGaSe2 , a wider band gap chalcopyrite semiconductor, could be added to the CuInSe2 absorber layer. This is, however, limited by the difficulty of doping n -type CuGaSe2 and, hence, in its alloys with CuInSe2 . Indeed, wider-gap members of semiconductor series are often more difficult to dope than lower-gap members of the same series. We find that in chalcopyrites, there are three critical values of the Fermi energy EF that control n -type doping: (i) EFn,pin is the value of EF where the energy to form Cu vacancies is zero. At this point, the spontaneously formed vacancies ( = acceptors) kill all electrons. (ii) EFn,comp is the value of EF where the energy to form a Cu vacancy equals the energy to form an n -type dopant, e.g., CdCu . (iii) EFn,site is the value of EF where the formation of Cd-on-In is equal to the formation of Cd-on-Cu. For good n -type doping, EFn,pin , EFn,comp , and EFn,site need to be as high as possible in the gap. We find that these quantities are higher in the gap in CuInSe2 than in CuGaSe2 , so the latter is difficult to dope n -type. In this work, we calculate all three critical Fermi energies and study theoretically the best growth condition for n -type CuInSe2 and CuGaSe2 with possible cation and anion doping. We find that the intrinsic defects such as VCu and InCu or GaCu play significant roles in doping in both chalcopyrites. For group-II cation (Cd, Zn, or Mg) doping, the best n -type growth condition is In/Ga -rich, and maximal Se-poor, which is also the optimal condition for stabilizing the intrinsic InCu/GaCu donors. Bulk CuInSe2 can be doped at equilibrium n -type, but bulk CuGaSe2 cannot be due to the low formation energy of intrinsic Cu-vacancy. For halogen anion doping, the best n -type materials growth is still under In/Ga -rich, and maximal Se-poor conditions. These conditions are not best for halogen substitutional defects, but are optimal for

  6. Effect of alcohol consumption on selenium (Se) bioavailability in rats

    SciTech Connect

    Cho, H.K.; Snook, J.T.; Yang, F.L.

    1986-03-01

    This study was done to determine the effects of alcohol ingestion on Se bioavailability in initially Se-depleted rats. Weanling male rats were fed a Se deficient (0.012 mg/kg) basal diet for 4 weeks and then for the subsequent 4 weeks were supplemented at 0.031 mg Se/kg or at 0.085 mg Se/kg of diet in the form of high Se yeast. During the Se repletion period alcohol replaced medium chain triglycerides in the diet at 3 levels: 0%, 10%, and 20% of calories. Dietary Se level significantly (P < .0001) affected urinary Se, fecal Se, Se absorption, Se balance, whole blood Se, whole blood glutathione peroxidase activity, and liver Se. In rats fed the higher Se diet total liver Se increased 50% when 20% rather than 0% alcohol was given. In rats fed the lower Se diet total liver Se decreased 12% as dietary alcohol increased from 0 to 20%. There was a significant (P < .0015) interaction between alcohol and Se level. All the other parameters for Se bioavailability were not affected by alcohol consumption. However, alcohol consumption significantly reduced growth rate at both Se levels.

  7. Y Se Repite = And It Repeats Itself

    ERIC Educational Resources Information Center

    Katzew, Adriana

    2010-01-01

    In this article, the author discusses Y Se Repite [And It Repeats Itself], a project she conceptualized due to the growing number of Latino/a Mexican migrant workers in dairy farms in the state of Vermont. In 2006, approximately 2,000 Latinos/as--most of them undocumented Mexican migrant workers--worked throughout the state's dairy farms, yet…

  8. SE Great Basin Play Fairway Analysis

    DOE Data Explorer

    Adam Brandt

    2015-11-15

    Within this submission are multiple .tif images with accompanying metadata of magnetotelluric conductor occurrence, fault critical stress composite risk segment (CRS), permeability CRS, Quaternary mafic extrusions, Quaternary fault density, and Quaternary rhyolite maps. Each of these contributed to a final play fairway analysis (PFA) for the SE Great Basin study area.

  9. Ba4Ga2Se8: A ternary selenide containing chains and discrete Se22- units

    NASA Astrophysics Data System (ADS)

    Yin, Wenlong; Iyer, Abishek K.; Lin, Xinsong; Mar, Arthur

    2016-05-01

    The ternary selenide Ba4Ga2Se8 has been synthesized by reaction of BaSe, Ga2Se3, and Se at 1023 K. Single-crystal X-ray diffraction analysis revealed a monoclinic structure (space group P21/c, Z=4, a=13.2393(5) Å, b=6.4305(2) Å, c=20.6432(8) Å, β=104.3148(6)°) featuring one-dimensional chains of corner-sharing Ga-centered tetrahedra and discrete Se22- anionic units, with charge-compensating Ba2+ cations located between them. The UV/vis/NIR diffuse reflectance spectrum reveals an optical band gap of 1.63(2) eV, which is consistent with the black color of the crystals and agrees with a calculated gap of 1.51 eV obtained from band structure calculations. The presence of the Se22- units narrows the band gap in Ba4Ga2Se8 relative to other Ba-Ga-Se phases.

  10. Ultra-Fast Synthesis for Ag2Se and CuAgSe Thermoelectric Materials

    NASA Astrophysics Data System (ADS)

    DUAN, H. Z.; LI, Y. L.; ZHAO, K. P.; QIU, P. F.; SHI, X.; CHEN, L. D.

    2016-06-01

    Ag2Se and CuAgSe have been recently reported as promising thermoelectric materials at room temperature. The traditional melting-annealing-sintering processes are used to grow Ag2Se and CuAgSe materials with the disadvantages of high costs of energy and time. In this work, phase-pure polycrystalline Ag2Se and CuAgSe compounds were synthesized from raw elemental powders directly by manual mixing followed by spark plasma sintering (MM-SPS) in a few minutes. The influence of SPS heating rate on the phase composition, microstructure, and thermoelectric properties, including Seebeck coefficient, electrical conductivity, and thermal conductivity, were investigated. The zTs of 0.8 at 390 K and 0.6 at 450 K are obtained for Ag2Se and CuAgSe, respectively, which is comparable with the values in the materials prepared by the traditional method. Furthermore, this ultrafast sample synthesis can significantly save material synthesis time and thus has the obvious advantage for large-scale production.

  11. Epitaxial 2D MoSe2 (HfSe2) Semiconductor/2D TaSe2 Metal van der Waals Heterostructures.

    PubMed

    Tsoutsou, Dimitra; Aretouli, Kleopatra E; Tsipas, Polychronis; Marquez-Velasco, Jose; Xenogiannopoulou, Evangelia; Kelaidis, Nikolaos; Aminalragia Giamini, Sigiava; Dimoulas, Athanasios

    2016-01-27

    Molecular beam epitaxy of 2D metal TaSe2/2D MoSe2 (HfSe2) semiconductor heterostructures on epi-AlN(0001)/Si(111) substrates is reported. Electron diffraction reveals an in-plane orientation indicative of van der Waals epitaxy, whereas electronic band imaging supported by first-principles calculations and X-ray photoelectron spectroscopy indicate the presence of a dominant trigonal prismatic 2H-TaSe2 phase and a minor contribution from octahedrally coordinated TaSe2, which is present in TaSe2/AlN and TaSe2/HfSe2/AlN but notably absent in the TaSe2/MoSe2/AlN, indicating superior structural quality of TaSe2 grown on MoSe2. Apart from its structural and chemical compatibility with the selenide semiconductors, TaSe2 has a workfunction of 5.5 eV as measured by ultraviolet photoelectron spectroscopy, which matches very well with the semiconductor workfunctions, implying that epi-TaSe2 can be used for low-resistivity contacts to MoSe2 and HfSe2. PMID:26727305

  12. 'Cold' crystallization in nanostructurized 80GeSe2-20Ga2Se3 glass.

    PubMed

    Klym, Halyna; Ingram, Adam; Shpotyuk, Oleh; Calvez, Laurent; Petracovschi, Elena; Kulyk, Bohdan; Serkiz, Roman; Szatanik, Roman

    2015-01-01

    'Cold' crystallization in 80GeSe2-20Ga2Se3 chalcogenide glass nanostructurized due to thermal annealing at 380°C for 10, 25, 50, 80, and 100 h are probed with X-ray diffraction, atomic force, and scanning electron microscopy, as well as positron annihilation spectroscopy performed in positron annihilation lifetime and Doppler broadening of annihilation line modes. It is shown that changes in defect-related component in the fit of experimental positron lifetime spectra for nanocrystallized glasses testify in favor of structural fragmentation of larger free-volume entities into smaller ones. Nanocrystallites of Ga2Se3 and/or GeGa4Se8 phases and prevalent GeSe2 phase extracted mainly at the surface of thermally treated samples with preceding nucleation and void agglomeration in the initial stage of annealing are characteristic features of cold crystallization. PMID:25852346

  13. Identification of {sup 88}Se and new levels in {sup 84,86}Se

    SciTech Connect

    Jones, E.F.; Gore, P.M.; Hamilton, J.H.; Ramayya, A.V.; Hwang, J.K.; Beyer, C.J.; Lima, A.P. de; Zhu, S.J.; Luo, Y.X.; Ma, W.C.; Rasmussen, J.O.; Lee, I.Y.; Wu, S.C.; Ginter, T.N.; Stoyer, M.; Cole, J.D.; Daniel, A.V.; Ter-Akopian, G.M.; Donangelo, R.

    2006-01-15

    From the analysis of {gamma}-{gamma}-{gamma} coincidence data taken with Gammasphere of the prompt {gamma} rays in the spontaneous fission of {sup 252}Cf, the 2{sup +}{yields}0{sup +} transition in {sup 88}Se was identified for the first time. Also, the 4{sup +}{yields}2{sup +} and 6{sup +}{yields}4{sup +} transitions in {sup 86}Se were identified along with four new states above 4{sup +} in {sup 84}Se. Surprisingly, the 2{sup +} energy rises in {sup 88}Se compared to {sup 86}Se. This increase in energy could arise from the interaction of a low-lying excited 0{sup +} state with different deformation and the 0{sup +} ground state to depress the ground-state energy.

  14. Superconductivity enhanced by Se doping in Eu3Bi2(S,Se)4F4

    NASA Astrophysics Data System (ADS)

    Zhang, P.; Zhai, H. F.; Tang, Z. J.; Li, L.; Li, Y. K.; Chen, Q.; Chen, J.; Wang, Z.; Feng, C. M.; Cao, G. H.; Xu, Z. A.

    2015-07-01

    We investigated the negative-chemical-pressure effect of Eu3Bi2S4-x Se x F4 (0 ≤ x ≤ 2.0) by the partial substitution of S with Se. The crystalline lattice substantially expands as Se is doped, suggesting an effective negative chemical pressure. With Se/S doping, the charge-density-wave-like anomaly is suppressed, and meanwhile the superconducting transition temperature (T_c) is enhanced. For x = 2.0 , T c reaches 3.35 K and bulk superconductivity is confirmed by the strong diamagnetic signal, with shielding volume fraction over 90%. Magnetic-susceptibility, specific-heat and Hall-effect measurements reveal that the Se/S doping increases the carrier density, corresponding to the increase of the average Eu valence. Our work provides a rare paradigm of negative-chemical-pressure effect.

  15. Two-dimensional semiconductor HfSe{sub 2} and MoSe{sub 2}/HfSe{sub 2} van der Waals heterostructures by molecular beam epitaxy

    SciTech Connect

    Aretouli, K. E.; Tsipas, P.; Tsoutsou, D.; Marquez-Velasco, J.; Xenogiannopoulou, E.; Giamini, S. A.; Vassalou, E.; Kelaidis, N.; Dimoulas, A.

    2015-04-06

    Using molecular beam epitaxy, atomically thin 2D semiconductor HfSe{sub 2} and MoSe{sub 2}/HfSe{sub 2} van der Waals heterostructures are grown on AlN(0001)/Si(111) substrates. Details of the electronic band structure of HfSe{sub 2} are imaged by in-situ angle resolved photoelectron spectroscopy indicating a high quality epitaxial layer. High-resolution surface tunneling microscopy supported by first principles calculations provides evidence of an ordered Se adlayer, which may be responsible for a reduction of the measured workfunction of HfSe{sub 2} compared to theoretical predictions. The latter reduction minimizes the workfunction difference between the HfSe{sub 2} and MoSe{sub 2} layers resulting in a small valence band offset of only 0.13 eV at the MoSe{sub 2}/HfSe{sub 2} heterointerface and a weak type II band alignment.

  16. [NiFeSe]-hydrogenase chemistry.

    PubMed

    Wombwell, Claire; Caputo, Christine A; Reisner, Erwin

    2015-11-17

    The development of technology for the inexpensive generation of the renewable energy vector H2 through water splitting is of immediate economic, ecological, and humanitarian interest. Recent interest in hydrogenases has been fueled by their exceptionally high catalytic rates for H2 production at a marginal overpotential, which is presently only matched by the nonscalable noble metal platinum. The mechanistic understanding of hydrogenase function guides the design of synthetic catalysts, and selection of a suitable hydrogenase enables direct applications in electro- and photocatalysis. [FeFe]-hydrogenases display excellent H2 evolution activity, but they are irreversibly damaged upon exposure to O2, which currently prevents their use in full water splitting systems. O2-tolerant [NiFe]-hydrogenases are known, but they are typically strongly biased toward H2 oxidation, while H2 production by [NiFe]-hydrogenases is often product (H2) inhibited. [NiFeSe]-hydrogenases are a subclass of [NiFe]-hydrogenases with a selenocysteine residue coordinated to the active site nickel center in place of a cysteine. They exhibit a combination of unique properties that are highly advantageous for applications in water splitting compared with other hydrogenases. They display a high H2 evolution rate with marginal inhibition by H2 and tolerance to O2. [NiFeSe]-hydrogenases are therefore one of the most active molecular H2 evolution catalysts applicable in water splitting. Herein, we summarize our recent progress in exploring the unique chemistry of [NiFeSe]-hydrogenases through biomimetic model chemistry and the chemistry with [NiFeSe]-hydrogenases in semiartificial photosynthetic systems. We gain perspective from the structural, spectroscopic, and electrochemical properties of the [NiFeSe]-hydrogenases and compare them with the chemistry of synthetic models of this hydrogenase active site. Our synthetic models give insight into the effects on the electronic properties and reactivity of

  17. Anisotropy in CdSe quantum rods

    SciTech Connect

    Li, Liang-shi

    2003-09-01

    The size-dependent optical and electronic properties of semiconductor nanocrystals have drawn much attention in the past decade, and have been very well understood for spherical ones. The advent of the synthetic methods to make rod-like CdSe nanocrystals with wurtzite structure has offered us a new opportunity to study their properties as functions of their shape. This dissertation includes three main parts: synthesis of CdSe nanorods with tightly controlled widths and lengths, their optical and dielectric properties, and their large-scale assembly, all of which are either directly or indirectly caused by the uniaxial crystallographic structure of wurtzite CdSe. The hexagonal wurtzite structure is believed to be the primary reason for the growth of CdSe nanorods. It represents itself in the kinetic stabilization of the rod-like particles over the spherical ones in the presence of phosphonic acids. By varying the composition of the surfactant mixture used for synthesis we have achieved tight control of the widths and lengths of the nanorods. The synthesis of monodisperse CdSe nanorods enables us to systematically study their size-dependent properties. For example, room temperature single particle fluorescence spectroscopy has shown that nanorods emit linearly polarized photoluminescence. Theoretical calculations have shown that it is due to the crossing between the two highest occupied electronic levels with increasing aspect ratio. We also measured the permanent electric dipole moment of the nanorods with transient electric birefringence technique. Experimental results on nanorods with different sizes show that the dipole moment is linear to the particle volume, indicating that it originates from the non-centrosymmetric hexagonal lattice. The elongation of the nanocrystals also results in the anisotropic inter-particle interaction. One of the consequences is the formation of liquid crystalline phases when the nanorods are dispersed in solvent to a high enough

  18. The GeTe-PbSe system

    SciTech Connect

    Abrikosov, N.Kh.; Avilov, E.S.; Karpinskii, O.G.; Radkevich, O.V.; Shelimova, L.E.

    1986-03-01

    Phase equilibria are investigated in the GeTe-PbSe system and also the effect of cation-anion substitution in the structural state, phase-transformation temperatures, and electrophysical properties of the solution alloys based on alpha-GeTe are studied. After annealing at 570 K, the alloys were investigated by thermal, microstructural, x-ray-phase, and dilatometric analyses. Electrical conductivity and Hall coefficient were measured at 300 K by an R 56/2 ac potentiometer with precision of 3 and 10% respectively. The precision in the thermo-emf-coefficient measurements was 3% and in thermal-conductivity measurements was 10%. It was established that the Ge /SUB 0.9/ Te-PbSe section is quasibinary only at temperatures near th solidus, where a continuous series of solid solutions exist.

  19. Low Temperature Photoluminescence of PVT Grown ZnSe and ZnSeTe

    NASA Technical Reports Server (NTRS)

    Wang, Ling Jun; Su, Ching-Hua; Lehoczky, S. L.

    1999-01-01

    ZnSe and ZnSeTe single crystals were grown by physical vapor transport (PVT) technique horizontally and vertically. The grown ZnSe and ZnSeTe single crystals were characterized by low temperature photoluminescence at 5 to 10 K using the 3.4 eV emission of an argon laser. The intensity of the sharp near band edge defect lines at 2.799, 2.783 eV and the intrinsic free exciton line at 2.802 eV were mapped on various crystal surfaces with different orientations to the gravitational field. The results show the effects of gravity vector orientation on the defect segregation. Comparison of the photoluminescence spectra of the ZeSe crystal before and after annealing in the Zn vapor shows that the 2.783 eV line of ZnSe crystal is related to the zinc vacancy. The photoluminescence spectra of the ternary ZnSeTe crystal were characterized by a single broad band from 2.2 to 2.4 eV, with a Full Width at Half Maximum (FWHM) of about 100 meV. The temperature dependence of the peak position and intensity were determined from 7 to 150 K.

  20. SE Great Basin Play Fairway Analysis

    SciTech Connect

    Adam Brandt

    2015-11-15

    This submission includes a Na/K geothermometer probability greater than 200 deg C map, as well as two play fairway analysis (PFA) models. The probability map acts as a composite risk segment for the PFA models. The PFA models differ in their application of magnetotelluric conductors as composite risk segments. These PFA models map out the geothermal potential in the region of SE Great Basin, Utah.

  1. Structural and chemical analysis of CdSe/ZnSe nanostructures by transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Peranio, N.; Rosenauer, A.; Gerthsen, D.; Sorokin, S. V.; Sedova, I. V.; Ivanov, S. V.

    2000-06-01

    A transmission electron microscopy (TEM) study of the structure and chemical composition of 0.5 to 3.0 ML (monolayer) CdSe sheets that are buried in a ZnSe matrix is presented. The CdSe layers were grown by migration-enhanced epitaxy at a growth temperature of 280 °C. We find two-dimensional (2D) CdxZn1-xSe layers with a total thickness of approximately 3 nm for all samples independent of the nominal CdSe content that contain inclusions (islands) with an enlarged Cd concentration. Plan-view TEM revealed two types of islands: First, small 2D islands with a lateral size of less than 10 nm, and second, large 2D islands with a lateral size between 30 and 130 nm. The combination of two-beam dark-field imaging and the new composition evaluation by lattice fringe analysis (CELFA) procedure allow the precise measurement of the Cd-concentration profiles of the CdxZn1-xSe layers. The CELFA evaluation yields a full width at half maximum value of (10+/-1) ML. The most probable origin of the broadening is a strong interdiffusion of Cd and Zn with an additional contribution of the segregation of the Cd atoms. The diffusion length of the Cd diffusion in ZnSe during the growth of the ZnSe cap layer is LD=(3.6+/-0.8) ML and the segregation probability is estimated to be R=(0.6+/-0.2). It is shown that neither objective lens aberrations nor specimen tilt are the main sources for the observed enormous broadening of the CdSe interlayers.

  2. Magnetic ground state of FeSe

    PubMed Central

    Wang, Qisi; Shen, Yao; Pan, Bingying; Zhang, Xiaowen; Ikeuchi, K.; Iida, K.; Christianson, A. D.; Walker, H. C.; Adroja, D. T.; Abdel-Hafiez, M.; Chen, Xiaojia; Chareev, D. A.; Vasiliev, A. N.; Zhao, Jun

    2016-01-01

    Elucidating the nature of the magnetism of a high-temperature superconductor is crucial for establishing its pairing mechanism. The parent compounds of the cuprate and iron-pnictide superconductors exhibit Néel and stripe magnetic order, respectively. However, FeSe, the structurally simplest iron-based superconductor, shows nematic order (Ts=90 K), but not magnetic order in the parent phase, and its magnetic ground state is intensely debated. Here we report inelastic neutron-scattering experiments that reveal both stripe and Néel spin fluctuations over a wide energy range at 110 K. On entering the nematic phase, a substantial amount of spectral weight is transferred from the Néel to the stripe spin fluctuations. Moreover, the total fluctuating magnetic moment of FeSe is ∼60% larger than that in the iron pnictide BaFe2As2. Our results suggest that FeSe is a novel S=1 nematic quantum-disordered paramagnet interpolating between the Néel and stripe magnetic instabilities. PMID:27431986

  3. Magnetic ground state of FeSe.

    PubMed

    Wang, Qisi; Shen, Yao; Pan, Bingying; Zhang, Xiaowen; Ikeuchi, K; Iida, K; Christianson, A D; Walker, H C; Adroja, D T; Abdel-Hafiez, M; Chen, Xiaojia; Chareev, D A; Vasiliev, A N; Zhao, Jun

    2016-01-01

    Elucidating the nature of the magnetism of a high-temperature superconductor is crucial for establishing its pairing mechanism. The parent compounds of the cuprate and iron-pnictide superconductors exhibit Néel and stripe magnetic order, respectively. However, FeSe, the structurally simplest iron-based superconductor, shows nematic order (Ts=90 K), but not magnetic order in the parent phase, and its magnetic ground state is intensely debated. Here we report inelastic neutron-scattering experiments that reveal both stripe and Néel spin fluctuations over a wide energy range at 110 K. On entering the nematic phase, a substantial amount of spectral weight is transferred from the Néel to the stripe spin fluctuations. Moreover, the total fluctuating magnetic moment of FeSe is ∼60% larger than that in the iron pnictide BaFe2As2. Our results suggest that FeSe is a novel S=1 nematic quantum-disordered paramagnet interpolating between the Néel and stripe magnetic instabilities. PMID:27431986

  4. Quadrupolar Spin Orders in FeSe

    NASA Astrophysics Data System (ADS)

    Wang, Zhentao; Nevidomskyy, Andriy

    Motivated by the absence of long-range magnetic order and the strong spin fluctuations observed in the Fe-based superconductor FeSe, we study spin-1 model on a square lattice up to next-nearest neighbor Heisenberg and biquadratic spin exchanges. The zero-temperature variational phase diagram gives the conventional antiferromagnetic order and also more exotic quadrupolar spin phases. These quadrupolar phases do not host long-range magnetic order and preserve time-reversal symmetry, but break the spin SU(2) symmetry. In particular, we observe a robust ferroquadrupolar order (FQ) in immediate proximity to the columnar AFM phase. We envision that FeSe may be positioned within the FQ phase close to the phase boundary. Using the flavor-wave technique, we calculate the structure factor inside the FQ phase and find a Goldstone mode emerging from Q = (0 , 0) , which however bears zero spectral weight at ω = 0 due to time reversal symmetry. At the same time, we observe strong spin fluctuations near (π , 0) / (0 , π) , which agrees with the recent neutron scattering experiments. Further, we calculate the higher order interactions between the (π , 0) and (0 , π) spin fluctuations inside the FQ phase, which may shed light on the C4 symmetry breaking in the nematic phase of FeSe.

  5. Magnetic ground state of FeSe

    NASA Astrophysics Data System (ADS)

    Wang, Qisi; Shen, Yao; Pan, Bingying; Zhang, Xiaowen; Ikeuchi, K.; Iida, K.; Christianson, A. D.; Walker, H. C.; Adroja, D. T.; Abdel-Hafiez, M.; Chen, Xiaojia; Chareev, D. A.; Vasiliev, A. N.; Zhao, Jun

    2016-07-01

    Elucidating the nature of the magnetism of a high-temperature superconductor is crucial for establishing its pairing mechanism. The parent compounds of the cuprate and iron-pnictide superconductors exhibit Néel and stripe magnetic order, respectively. However, FeSe, the structurally simplest iron-based superconductor, shows nematic order (Ts=90 K), but not magnetic order in the parent phase, and its magnetic ground state is intensely debated. Here we report inelastic neutron-scattering experiments that reveal both stripe and Néel spin fluctuations over a wide energy range at 110 K. On entering the nematic phase, a substantial amount of spectral weight is transferred from the Néel to the stripe spin fluctuations. Moreover, the total fluctuating magnetic moment of FeSe is ~60% larger than that in the iron pnictide BaFe2As2. Our results suggest that FeSe is a novel S=1 nematic quantum-disordered paramagnet interpolating between the Néel and stripe magnetic instabilities.

  6. A novel synthesis of a CuInSe2 thin film from electrodeposited Cu-Se-In-Se precursors with three steps annealing.

    PubMed

    Hu, Shao-Yu; Lee, Wen-Hsi; Chang, Shih-Chieh; Wang, Ying-Lang

    2012-09-01

    In this study, copper indium diselenide (CIS) films were synthesized from electrodeposited Cu-Se-In-Se precursors by three step annealing. The Se layer between Cu and In layer was grown to prevent the formation of Cu/In compound. The Cu-Se precursors were first annealed to grow uniform and conductive Cu2Se surface. After deposition of the four layers precursors, two steps annealing was employed to form Cu2Se-In2Se3 precursors. Transforming Cu2Se-In2Se3 to CIS required less thermal energy. Therefore, high quality CIS film can be synthesized by two steps annealing due to its high crystallinity. The properties of the CIS films were characterized by scanning electron microscopy (SEM), X-ray Diffraction (XRD), and Raman Spectra. PMID:23035457

  7. Atmospheric Pressure Synthesis of In2Se3, Cu2Se, and CuInSe2 without External Selenization from Solution Precursors

    SciTech Connect

    Nekuda Malik, J. A.; van Hest, M. F. A. M.; Miedaner, A.; Curtis, C. J.; Leisch, J. E.; Parilla, P. A.; Kaufman, M.; Taylor, M.; Stanbery, B. J.; O'Hayre, R. P.; Ginley, D. S.

    2009-04-01

    In{sub 2}Se{sub 3}, Cu{sub 2}Se, and CuInSe{sub 2} thin films have been successfully fabricated using novel metal organic decomposition (MOD) precursors and atmospheric pressure-based deposition and processing. The phase evolution of the binary (In-Se and Cu-Se) and ternary (Cu-In-Se) MOD precursor films was examined during processing to evaluate the nature of the phase and composition changes. The In-Se binary precursor exhibits two specific phase regimes: (i) a cubic-InxSey phase at processing temperatures between 300 and 400 C and (ii) the {gamma}-In{sub 2}Se{sub 3} phase for films annealed above 450 C. Both phases exhibit a composition of 40 at.% indium and 60 at.% selenium. The binary Cu-Se precursor films show more diverse phase behavior, and within a narrow temperature processing range a number of Cu-Se phases, including CuSe{sub 2}, CuSe, and Cu{sub 2}Se, can be produced and stabilized. The ternary Cu-In-Se precursor can be used to produce relatively dense CuInSe{sub 2} films at temperatures between 300 and 500 C. Layering the binary precursors together has provided an approach to producing CuInSe{sub 2} thin films; however, the morphology of the layered binary structure exhibits a significant degree of porosity. An alternative method of layering was explored where the Cu-Se binary was layered on top of an existing indium-gallium-selenide layer and processed. This method produced highly dense and large-grained (>3 {micro}m) CuInSe{sub 2} thin films. This has significant potential as a manufacturable route to CIGS-based solar cells.

  8. Growth of multilayers of Bi{sub 2}Se{sub 3}/ZnSe: Heteroepitaxial interface formation and strain

    SciTech Connect

    Li, H. D.; Wang, Z. Y.; Guo, X.; Xie, M. H.; Wong, Tai Lun; Wang, Ning

    2011-01-24

    Multilayers of Bi{sub 2}Se{sub 3}/ZnSe with the periodicity of a few nanometers were grown by molecular-beam epitaxy on Si(111). While epitaxial growth of Bi{sub 2}Se{sub 3} on ZnSe proceeded by two-dimensional nucleation, ZnSe growth on Bi{sub 2}Se{sub 3} showed the three-dimensional growth front. Therefore, the two complementary interfaces of Bi{sub 2}Se{sub 3}/ZnSe were asymmetric in morphological properties. Strain-relaxation rates were found to differ between epitaxial ZnSe and Bi{sub 2}Se{sub 3}, which could be attributed to the specific growth modes and the properties of Bi{sub 2}Se{sub 3} and ZnSe surfaces.

  9. 77Se nuclear magnetic resonance of topological insulator Bi2Se3

    NASA Astrophysics Data System (ADS)

    Georgieva, Nataliya M.; Rybicki, Damian; Guehne, Robin; Williams, Grant V. M.; Chong, Shen V.; Kadowaki, Kazuo; Garate, Ion; Haase, Jürgen

    2016-05-01

    Topological insulators constitute a new class of materials with an energy gap in the bulk and peculiar metallic states on the surface. We report on new features resulting from the bulk electronic structure, based on a comprehensive nuclear magnetic resonance (NMR) study of 77Se on Bi2Se3 and Cu0.15Bi2Se3 single crystals. First, we find two resonance lines and show that they originate from the two inequivalent Se lattice sites. Second, we observe unusual field-independent linewidths and attribute them to an unexpectedly strong internuclear coupling mediated by bulk electrons. In order to support this interpretation, we present a model calculation of the indirect internuclear coupling and show that the Bloembergen-Rowland coupling is much stronger than the Ruderman-Kittel-Kasuya-Yosida coupling. Our results call for a revision of earlier NMR studies and add information concerning the bulk electronic properties.

  10. Dynamic structure of liquid Se, Te and Se-Te mixtures by neutron scattering measurements

    SciTech Connect

    Chiba, Ayano; Yao, Makoto; Ohmasa, Yoshinori; Taylor, Jon; Bennington, Stephen M.

    2004-04-30

    Inelastic neutron scattering measurements are performed to investigate the dynamic structure of liquid Se, Te, and Te50Se50. The bond-stretching modes for liquid Se and Te50Se50 (both are in the semiconducting phase) are clearly observed at higher-energy regions than that for their trigonal phase. This shift is a reflection of their pronounced molecular-like properties without prominent inter-molecular interactions, whereas the vibrational modes for liquid Te (in the metallic phase) show its metallic-like bonding character with remarkable inter-molecular interactions. We thus observed a change in dynamic structure that accompanies the semiconductor-to-metal transition; the change that would be related to the slow dynamics induced by the transition.

  11. Composition and submicron structure of chemically deposited Cu2Se-In2Se3 films

    NASA Astrophysics Data System (ADS)

    Markov, V. F.; Tulenin, S. S.; Maskaeva, L. N.; Kuznetsov, M. V.; Barbin, N. M.

    2012-03-01

    Films of substitutional solid solutions of the Cu2Se-In2Se3 system containing up to 7.5 at. % In have been obtained by chemical deposition from aqueous media. The composition, structure, and morphology of the films have been studied. Data of X-ray diffraction and X-ray photoelectron spectroscopy showed that copper in the solid solution occurs in a single-valence state (Cu+). The deposited layers possess a globular morphology and are nanostructured.

  12. Homopolar bonds in Se-rich Ge‒As‒Se chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Si-Wei, Xu; Rong-Ping, Wang; Zhi-Yong, Yang; Li, Wang; Luther-Davies, Barry

    2016-05-01

    We have prepared three groups of Ge–As–Se glasses in which the Se content is 5.5 mol%, 10 mol%, and 20 mol% rich, respectively. We explored the possibility of suppressing the formation of the Ge–Ge and As–As homopolar bonds in the glasses. Thermal kinetics analysis indicated that the 5.5 mol% Se-rich Ge11.5As24Se64.5 glass exhibits the minimum fragility and thus is most stable against structural relaxation. Analysis of the Raman spectra of the glasses indicated that the Ge–Ge and As–As homopolar bonds could be almost completely suppressed in 20 mol% Se-rich Ge15As14Se71 glass. Project supported by the Australian Research Council (ARC) Centre of Excellence for Ultrahigh Bandwidth Device for Optical System (Project CE110001018), Australian Research Council Discovery Programs (Project DP110102753), and the Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions, China.

  13. Conduction band offset determination between strained CdSe and ZnSe layers using DLTS

    SciTech Connect

    Rangel-Kuoppa, Victor-Tapio

    2013-12-04

    The conduction band offset between strained CdSe layers embedded in unintentionally n-type doped ZnSe is measured and reported. Two samples, consisting of thirty Ultra Thin Quantum Wells (UTQWs) of CdSe embedded in ZnSe, grown by Atomic Layer Epitaxy, are used for this study. The thicknesses of the UTQWs are one and three monolayers (MLs) in each sample, respectively. As expected, the sample with one ML UTQWs does not show any energy level in the UTQWs due to the small thickness of the UTQWs, while the thickness of the sample with 3 ML UTQWs is large enough to form an energy level inside the UTQWs. This energy level appears as a majority trap with an activation energy of 223.58 ± 9.54 meV. This corresponds to UTQWs with barrier heights (the conduction band offset) between 742 meV and 784 meV. These values suggest that the band gap misfit between strained CdSe and ZnSe is around 70.5 to 74 % in the conduction band.

  14. CdZnSe/ZnSe strained layer superlattices disordered by germanium diffusion

    SciTech Connect

    Yokogawa, T.; Floyd, P.D.; Merz, J.L.

    1994-03-01

    We have investigated the phenomenon of layer disordering in CdZnSe/ZnSe strained layer superlattices (SLSs) by Ge diffusion and have fabricated CdZnSe/ZnSe optical waveguides using the Ge-induced disordering. Both the as-grown sample and the sample annealed without a Ge layer showed several orders of well-resolved double crystal x-ray satellite peaks due to SLS periodic structure. However, the satellite peaks completely disappeared in the Ge-diffused sample, indicating that the SLS structure was disordered by the Ge diffusion and not caused by the annealing process. Photoluminescence (PL) measurements at 1.4K of both the as-grown and the annealed samples without Ge diffusion show intense, sharp excitonic emission around 483 nm in CdZnSe/ZnSe SLS. After Ge diffusion, the PL peaks shift to higher energy confirming the layer disordering of the SLS. The blue shift due to disordering was also observed in the PL at room temperature (RT). The optical guided mode in the SLS guiding layer confined by the disordered alloy was confirmed. Lateral optical confinement in the stripe geometry laser was also confirmed by observing the RT stimulated emission produced by optical pumping. 12 refs., 6 figs.

  15. Metabolism of selenium (Se) in rats chronically poisoned with D- or L-selenomethionine (SeMet), selenite or selenate

    SciTech Connect

    McAdam, P.A.; Levander, O.A.

    1986-03-01

    L-SeMet is a potential cancer chemoprevention agent for humans. Little difference was seen in the acute toxicity of L vs. D-SeMet in rats. To study chronic toxicity, weanling male rats were fed purified diets containing 2.5, 5.0 or 10 ppm Se as L-SeMet, D-SeMet, Na/sub 2/SeO/sub 3/ or Na/sub 2/SeO/sub 4/ for 6 weeks. Controls received 0.1 ppm Se as selenite. All rats fed 10 ppm Se died within 29 days. Se fed as D-SeMet was retained in the tissues as strongly as L-SeMet. Rats fed D or L-SeMet deposited large amounts of Se in muscle not reflected by proportionate increases in either plasma or RBC Se. Therefore, attempts to follow increases in Se body burden in individuals supplemented with large doses of L-SeMet by monitoring plasma or whole blood Se levels should be interpreted with caution.

  16. Ion implanted epitaxially grown ZnSe

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The epitaxial growth of ZnSe on (100) Ge using the close-spaced transport process is described. Substrate temperature of 575 C and source temperatures of 675 C yield 10 micron, single crystal layers in 10 hours. The Ge substrates provides a nonreplenishable chemical transport agent and the epitaxial layer thickness is limited to approximately 10 microns. Grown epitaxial layers show excellent photoluminescence structure at 77 K. Grown layers exhibit high resistivity, and annealing in Zn vapor at 575 C reduces the resistivity to 10-100 ohms-cm. Zinc vapor annealing quenches the visible photoluminescence.

  17. Exciton spin dynamics in GaSe

    SciTech Connect

    Tang, Yanhao; Xie, Wei; McGuire, John A. Lai, Chih Wei; Mandal, Krishna C.

    2015-09-21

    We analyze exciton spin dynamics in GaSe under nonresonant circularly polarized optical pumping with an exciton spin-flip rate-equation model. The model reproduces polarized time-dependent photoluminescence measurements in which the initial circular polarization approaches unity even when pumping with 0.15 eV excess energy. At T = 10 K, the exciton spin relaxation exhibits a biexponential decay with sub-20 ps and >500 ps time constants, which are also reproduced by the rate-equation model assuming distinct spin-relaxation rates for hot (nonequilibrium) and cold band-edge excitons.

  18. Spectrum of sodiumlike selenium - Se XXIV

    NASA Technical Reports Server (NTRS)

    Brown, C. M.; Seely, J. F.; Feldman, U.; Richardson, M. C.; Behring, W. E.; Cohen, L.

    1986-01-01

    High-resolution spectra of Se XXIV have been obtained with a 3-m grazing-incidence spectrograph. Thin plastic foils coated with selenium were irradiated with four or eight beams of the OMEGA laser in a line-focus configuration. Spectrograms were obtained by viewing the plasma axially. Prominent in the spectra were the 3s-3p and 3p-3d transitions in the 150-240-A region and the transitions nl-(n + 1)l-prime with n = 3, 4 in the 24-80-A region. The energy levels and ionization limit derived from the measured wavelengths are also presented.

  19. Chemical Excision of Tetrahedral FeSe2 Chains from the Superconductor FeSe: Synthesis, Crystal Structure, and Magnetism of Fe3Se4(en)2

    PubMed Central

    Pak, Chongin; Kamali, Saeed; Pham, Joyce; Lee, Kathleen; Greenfield, Joshua T.; Kovnir, Kirill

    2014-01-01

    Fragments of the superconducting FeSe layer, FeSe2 tetrahedral chains, were stabilized in the crystal structure of a new mixed-valent compound Fe3Se4(en)2 (en = ethylenediamine) synthesized from elemental Fe and Se. The FeSe2 chains are separated from each other by means of Fe(en)2 linkers. Mössbauer spectroscopy and magnetometry reveal strong magnetic interactions within the FeSe2 chains which result in antiferromagnetic ordering below 170 K. According to DFT calculations, anisotropic transport and magnetic properties are expected for Fe3Se4(en)2. This compound offers a unique way to manipulate the properties of the Fe-Se infinite fragments by varying the topology and charge of the Fe-amino linkers. PMID:24299423

  20. Selenium bioaccessibility and bioavailability in Se-enriched food supplements.

    PubMed

    Thiry, Celine; Schneider, Yves-Jacques; Pussemier, Luc; De Temmerman, Ludwig; Ruttens, Ann

    2013-04-01

    Most European people have selenium (Se) intake inferior to recommended values that are considered necessary to ensure the beneficial action of antioxidant selenoproteins. People could therefore tend to have recourse to Se-enriched food supplements (FS) aiming to increase their Se body level. On the Belgian market, three main types of Se-rich FS are available: Se-enriched yeast, selenate-based FS, and selenite-based FS. In the present work, in vitro tests imitating gastrointestinal digestion and intestinal absorption were used to determine the bioaccessible and bioavailable fractions of Se present in one specimen of each category of FS. The aim of the study was to verify to which extent the difference in Se speciation could influence the efficiency of FS for enhancing the human Se status. Results indicated that differences exist in both bioaccessibility and bioavailability between the three types of FS, and that these differences could be related, at least partially, to the Se species profile. Overall bioavailability of the three FS was low (maximum 14 % of the original Se content). Among the three samples, the selenate-based FS produced the highest fraction of bioavailable Se, followed by Se-yeast, and finally by the selenite-based FS for which Se was almost not available at all. These results confirm the low availability of inorganic Se but were somewhat unexpected regarding the yeast-based FS since Se-rich yeasts are usually reported to contain an important fraction of available Se. PMID:23397356

  1. ZnSe-based white LEDs

    NASA Astrophysics Data System (ADS)

    Katayama, K.; Matsubara, H.; Nakanishi, F.; Nakamura, T.; Doi, H.; Saegusa, A.; Mitsui, T.; Matsuoka, T.; Irikura, M.; Takebe, T.; Nishine, S.; Shirakawa, T.

    2000-06-01

    The first phosphor-free white LED based on II-IV compound materials is demonstrated. Our device utilizes a phenomenon unique to ZnSe homoepitaxy, where a portion of the main greenish-blue emission from the active layer of a pn junction diode is absorbed by the conductive substrate which in turn gives off an intense broad-band yellow emission centered around 585 nm by photoluminescence. These two emission bands combine to give a spectrum which appears white to the naked eye. A typical ZnSe-based white LED lamp exhibits a color temperature of approximately 3400 K with a CRI (color rendering index) of 68. The optical output power and operating voltage of such a device at a forward current of 20 mA is 2.0 mW and 2.7 V, respectively. The luminous efficiency estimated from these results is 10.4l m/W, which is comparable to the incandescent lamp as well as the commercial InGaN-based white LED. Device lifetimes (half-life) have exceeded 800 h at 20°C.

  2. Stretched Exponential relaxation in pure Se glass

    NASA Astrophysics Data System (ADS)

    Dash, S.; Ravindren, S.; Boolchand, P.

    A universal feature of glasses is the stretched exponential relaxation, f (t) = exp[ - t / τ ] β . The model of diffusion of excitations to randomly distributed traps in a glass by Phillips1 yields the stretched exponent β = d[d +2] where d, the effective dimensionality. We have measured the enthalpy of relaxation ΔHnr (tw) at Tg of Se glass in modulated DSC experiments as glasses age at 300K and find β = 0.43(2) for tw in the 0 Se100-x glasses as x increases to 20%, the length of the polymeric Sen chains between the Ge-crosslinks decreases to n = 2. and the striking relaxation effects nearly vanish. J.C. Phillips, Rep.Prog.Phys. 59 , 1133 (1996). Supported by NSF Grant DMR 08-53957.

  3. Synthesis and optical study of green light emitting polymer coated CdSe/ZnSe core/shell nanocrystals

    SciTech Connect

    Tripathi, S.K.; Sharma, Mamta

    2013-05-15

    Highlights: ► Synthesis of Polymer coated core CdSe and CdSe/ZnSe core/shell NCs. ► From TEM image, the spherical nature of CdSe and CdSe/ZnSe is obtained. ► Exhibiting green band photoemission peak at 541 nm and 549 nm for CdSe core and CdSe/ZnSe core/shell NCs. ► The shell thickness has been calculated by using superposition of quantum confinement energy model. - Abstract: CdSe/ZnSe Core/Shell NCs dispersed in PVA are synthesized by chemical method at room temperature. This is characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV/Vis spectra and photoluminescence spectroscopy (PL). TEM image shows the spherical nature of CdSe/ZnSe core/shell NCs. The red shift of absorption and emission peak of CdSe/ZnSe core/shell NCs as compared to CdSe core confirmed the formation of core/shell. The superposition of quantum confinement energy model is used for calculation of thickness of ZnSe shell.

  4. Preparation and characterization of Bi2Se3(0001) and of epitaxial FeSe nanocrystals on Bi2Se3(0001)

    NASA Astrophysics Data System (ADS)

    Cavallin, Alberto; Sevriuk, Vasilii; Fischer, Kenia Novakoski; Manna, Sujit; Ouazi, Safia; Ellguth, Martin; Tusche, Christian; Meyerheim, Holger L.; Sander, Dirk; Kirschner, Jürgen

    2016-04-01

    Procedures to prepare clean Bi2Se3(0001) surfaces from bulk samples and epitaxial FeSe nanocrystals on Bi2Se3(0001) are reported. Bi2Se3(0001) substrates are prepared by in vacuo cleavage of bulk samples, followed by ion bombardment and annealing cycles. FeSe is prepared by Fe deposition onto Bi2Se3 at 303 K, followed by annealing at T ≈ 623 K. We use low-energy electron diffraction, surface X-ray diffraction, photoemission spectroscopy, scanning tunneling microscopy and spectroscopy, and stress measurements to elucidate the correlation between structural and electronic properties of the pristine Bi2Se3(0001) and FeSe covered surfaces. Our analysis reveals the formation of epitaxial FeSe nanocrystals with a thickness of three unit cells (1.5 nm). Electron diffraction experiments indicate an anisotropic epitaxial strain in FeSe. A negligible strain close to 0.0% and a tensile strain of + 2.1% are observed along the in-plane [ 01 1 bar 0 ] and [ 2 11 bar 0 ] Bi2Se3 directions, respectively. The out-of-plane strain is + 4.2%. The role of this strain state for the reported high-TC superconductivity in bulk FeSe is discussed.

  5. Saturating refractive nonlinearities and optical bistability in ZnSe/CdZnSe MQWs at room temperature

    NASA Astrophysics Data System (ADS)

    Li, Hongyu; Shen, De Z.; Zhang, Jiying; Wang, Shumei; Yang, Baojun; Yu, Guangyou

    1998-08-01

    The excitonic nonlinear refractive index was calculated by using Kramers-Kronig relation and the saturating absorption of ZnSe/CdZnSe multiple quantum wells (MQWs) was studied under different pump intensities. The maximum nonlinear refractive index change is about -6.19 X 10-3. Excitonic optical bistability in ZnSe/CdZnSe MQWs is investigated at room temperature. The result indicates that the threshold and contrast ratio for the optical bistability in ZnSe/CdZnSe MQWs are about 210Kw/cm2 and 2:1, respectively. On the basis of the excitonic nonlinear theories and excitonic absorption spectra in the ZnSe/CdZnSe MQWs, we attribute the major nonlinear mechanism of the optical bistability in the ZnSe/CdZnSe MQWs to the phase space filling of excitonic states and excitonic band broadening due to exciton-exciton interactions.

  6. Temperature dependent band offsets in PbSe/PbEuSe quantum well heterostructures

    SciTech Connect

    Simma, M.; Bauer, G.; Springholz, G.

    2012-10-22

    The band offsets of PbSe/Pb{sub 1-x}Eu{sub x}Se multi-quantum wells grown by molecular beam epitaxy are determined as a function of temperature and europium content using temperature-modulated differential transmission spectroscopy. The confined quantum well states in the valence and conduction bands are analyzed using a k{center_dot}p model with envelope function approximation. From the fit of the experimental data, the normalized conduction band offset is determined as 0.45{+-}0.15 of the band gap difference, independently of Eu content up to 14% and temperature from 20 to 300 K.

  7. Energy transfer processes in ZnSe/(Zn,Mn)Se double quantum wells

    NASA Astrophysics Data System (ADS)

    Jankowski, Stephanie; Horst, Swantje; Chernikov, Alexej; Chatterjee, Sangam; Heimbrodt, Wolfram

    2009-10-01

    The complex interplay of energy transfer and tunneling processes in a series of asymmetric ZnSe/(Zn,Mn)Se double quantum-well (DQW) structures is investigated. Steady-state and time-resolved photoluminescence at low temperatures and external magnetic fields up to 7 T in this system show remarkable differences to earlier studies on CdTe/(Cd,Mn)Te DQWs. The pure quantum-mechanical tunneling process is only a minor contribution to the magnetic field dependence of the emission even in case of small barriers and strong QW coupling. The experimental results are supported by quantum-well calculations.

  8. Electron-impact ionization of the Se2+ and Se3+ atomic ions

    NASA Astrophysics Data System (ADS)

    Loch, S. D.; Pindzola, M. S.

    2016-05-01

    Semi-relativistic configuration-average distorted-wave (CADW) calculations are made for the electron-impact ionization of the Se2+ and Se3+ atomic ions. The CADW calculations are found to be in reasonable agreement with recent measurements made at the Multicharged Ion Research Facility at the University of Nevada in Reno. The CADW calculations for configurations near ionization thresholds are checked against level to level distorted-wave (LLDW) calculations. Work supported in part by Grants from NASA, NSF, and DOE.

  9. Photocatalytic Hydrogen Generation by CdSe/CdS Nanoparticles.

    PubMed

    Qiu, Fen; Han, Zhiji; Peterson, Jeffrey J; Odoi, Michael Y; Sowers, Kelly L; Krauss, Todd D

    2016-09-14

    The photocatalytic hydrogen (H2) production activity of various CdSe semiconductor nanoparticles was compared including CdSe and CdSe/CdS quantum dots (QDs), CdSe quantum rods (QRs), and CdSe/CdS dot-in-rods (DIRs). With equivalent photons absorbed, the H2 generation activity orders as CdSe QDs ≫ CdSe QRs > CdSe/CdS QDs > CdSe/CdS DIRs, which is surprisingly the opposite of the electron-hole separation efficiency. Calculations of photoexcited surface charge densities are positively correlated with the H2 production rate and suggest the size of the nanoparticle plays a critical role in determining the relative efficiency of H2 production. PMID:27478995

  10. Distribution of Se and its species in Myriophyllum spicatum and Ceratophyllum demersum growing in water containing Se (VI).

    PubMed

    Mechora, Spela; Cuderman, Petra; Stibilj, Vekoslava; Germ, Mateja

    2011-09-01

    The uptake of Se (VI) by two aquatic plants, Myriophyllum spicatum L. and Ceratophyllum demersum L., and its effects on their physiological characteristics have been studied. Plants were cultivated outdoors under semi-controlled conditions and in two concentrations of Na selenate solution (20 μg Se L(-1) and 10 mg Se L(-1)). The higher dose of Se reduced the photochemical efficiency of PSII in both species, while the lower dose had no effect on PSII. Addition of Se had no effect on the amounts of chlorophyll a and b. The concentration of Se in plants grown in 10 mg Se L(-1), averaged 212 ± 12 μg Seg(-1) DM in M. spicatum (grown from 8-13 d), and 492 ± 85 μg Se g(-1) DM in C. demersum (grown for 31 d). Both species could take up a large amount of Se. The amount of soluble Se compounds in enzyme extracts ranged from 16% to 26% in control, and in high Se solution from 48% to 36% in M. spicatum and C. demersum, respectively. Se-species were determined using HPLC-ICP-MS. The main soluble species in both plants was selenate (∼37%), while SeMet and SeMeSeCys were detected at trace levels. PMID:21703659

  11. Purification and identification of Se-containing antioxidative peptides from enzymatic hydrolysates of Se-enriched brown rice protein.

    PubMed

    Liu, Kunlun; Zhao, Yan; Chen, Fusheng; Fang, Yong

    2015-11-15

    As a further study of Se-containing proteins (Se-Pro) derived from Se-enriched brown rice (Se-BR), this paper aimed to purify and identify Se-containing antioxidative peptides (Se-antioxi-Peps) from Se-Pro hydrolysates. The total Se content in Se-BR was 6.26μg/g DW, and selenocystine, Se-methylselenocysteine, and selenomethionine were identified as the main organic Se species by high-performance liquid chromatography-inductively coupled plasma mass spectrometry. Se-Pro was extracted and hydrolyzed by four types of proteases, and Alcalase was chosen as the optimum enzyme according to the degree of hydrolysis (DH). The hydrolysate with 17.08% DH possessing the highest DPPH radical scavenging activity was separated into five fractions (F1 to F5). Fractions F3 to F5, which had high antioxidative activities, were further separated. Sub-fractions F3-3, F4-2, and F5-1 were chosen to evaluate antioxidative activities and analyze Se species. The Se-antioxi-Pep with the sequence SeMet-Pro-Ser was identified by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. PMID:25977046

  12. Hexagonal CoSe formation in mechanical alloyed Co 75Se 25 mixture

    NASA Astrophysics Data System (ADS)

    Campos, C. E. M.; de Lima, J. C.; Grandi, T. A.; Machado, K. D.; Drago, V.; Pizani, P. S.

    2004-07-01

    A hexagonal CoSe alloy with NiAs-type structure was obtained by mechanical alloying starting from a mixture of pure crystalline powders with nominal composition Co 75Se 25. X-ray diffraction (XRD), differential scanning calorimetry (DSC), Mössbauer spectroscopy (MS) and Raman scattering (RS) techniques were used to follow the structural, thermal, magnetic and optical properties of the binary mixture as a function of milling time. XRD results show the formation of a nanometric hexagonal CoSe phase between 3 and 70 h of milling coexisting with non-reacted Co phases, also in nanometric scale. DSC and RS results showed some changes in the thermal and optical properties of the crystalline phases when the milling time increases. The Raman active modes of the CoSe and Co oxide phases were observed. MS results showed practically no iron in the samples milled up to 15 h, while for extended milling times (70 h), they showed the presence of some α-Fe and the formation of other iron alloys due to the contamination by the milling media.

  13. ZnSe-ZnMnSe and CdTe-CdMnTe superlattices

    NASA Astrophysics Data System (ADS)

    Gunshor, R. L.; Kolodziejski, L. A.; Otsuka, N.; Datta, S.

    1986-08-01

    We report the growth and characterization of superiattices of a new wide-gap, zincblende material system, Zn 1 - xMn xSe. ZnSe exhibiting dominant free excitonic emission in photoluminescence (PL) is the well material, while wider-band-gap Zn 1 - xMn xSe (0.23 < x < 0.66) forms the barrier material. PL measurements show greatly enhanced quantum efficiency compared to films of the ZnSe well material, while transmission electron microscopy shows extremely abrupt interfaces by the presence of seventh-order satellite spots. Previously reported superiattices in the CdTe-CdMnTe material system were grown with the (111) orientation, and exhibit unique excitonic properties believed related to the (111) interfaces. Using various techniques to select (111) or (100) heteroepitaxy of CdTe on (100) GaAs, we report the first (100) superlattices of this material, and compare the optical properties to the previous (111) structures.

  14. Disordered La3Cu4.88Se7.

    PubMed

    Gulay, L D; Daszkiewicz, M; Strok, O M; Pietraszko, A

    2011-03-01

    The crystal structure of copper(I) lanthanum selenide, La(3)Cu(4.88)Se(7), obtained from the La(2)Se(3)-Cu(2)Se quasi-binary system, has been investigated using X-ray single-crystal diffraction. The positions of the La and Se atoms are ordered and lie on mirror planes, whereas all positions for the Cu atoms are partially occupied. The crystal is built from edge-sharing [LaSe(6)] and [LaSe(7)] polyhedra. The five positions for the Cu atoms determine an ionic diffusion pathway in the structure. PMID:21368401

  15. Growth and characterization of ZnSe nanoparticles

    SciTech Connect

    Sharma, Shail Malik, Mukhtar Ah. Chandel, Tarun Thakur, Vikas Rajaram, P.

    2014-04-24

    ZnSe nanoparticles were prepared using a chemical bath deposition technique. X-ray diffraction study shows that the ZnSe crystallizes in the cubic phase. The crystallite size of the ZnSe samples calculated using the Scherrer’s formula was found to be slightly smaller than the Bohr exciton radius of bulk ZnSe. SEM studies show the growth of a mixture of nanorods and spherical nanoparticles. EDAX analysis confirms that the synthesized ZnSe nanoparticles are of good stiochiometry. Optical studies show the blue shift in the absorption edge for ZnSe nanoparticles caused by quantum confinement.

  16. Growth of CuInSe2 and In2Se3/CuInSe2 nano-heterostructures through solid state reactions.

    PubMed

    Hsin, Cheng-Lun; Lee, Wei-Fan; Huang, Chi-Te; Huang, Chun-Wei; Wu, Wen-Wei; Chen, Lih-Juann

    2011-10-12

    In(2)Se(3) is an essential phase change material and CuInSe(2) is the fundamental basis of the copper-indium-gallium-diselenide (CIGS) solar energy material. In this paper, we demonstrate the feasibility to transform the phase change material to the solar energy material via the solid state reaction. The In(2)Se(3) nanobelts (NBs) were synthesized via the vapor-liquid-solid mechanism. The chemical composition and the optical properties were investigated by energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and reflectance and photoluminescence spectra. In the in situ observation of the solid state reaction with Cu to form the CuInSe(2) NBs with ultrahigh vacuum transmission electron microscopy, we observed the In(2)Se(3)/CuInSe(2) transformation at atomic scale in real time. The progression of the atomic layer at the interface provided the pertinent information on the kinetic mechanism. In(2)Se(3)/CuInSe(2) nano-heterostructures were also obtained in the present investigation. The approach to the CIGS nanosolar cell was also proposed. This study shall be beneficial in the development of high-performance nanowire solar cells and nanodevices with In(2)Se(3)/CuInSe(2) nano-heterostructures. PMID:21859092

  17. Photoinduced aging and viscosity evolution in Se-rich Ge-Se glasses

    SciTech Connect

    Gueguen, Yann; Sangleboeuf, Jean-Christophe; Rouxel, Tanguy; King, Ellyn A.; Lucas, Pierre; Keryvin, Vincent; Bureau, Bruno

    2013-08-21

    We propose here to investigate the non-equilibrium viscosity of Ge-Se glasses under and after light irradiation. Ge{sub 10}Se{sub 90} and Ge{sub 20}Se{sub 80} fibers have been aged in the dark and under ambient light, over months. During aging, both the relaxation of enthalpy and the viscosity have been investigated. The viscosity was measured by shear relaxation-recovery tests allowing the measurement of non-equilibrium viscosity. When Ge{sub 10}Se{sub 90} glass fibers are aged under irradiation, a relatively fast fictive temperature decrease is observed. Concomitantly, during aging under irradiation, the non-equilibrium viscosity increases and reaches an equilibrium after two months of aging. This viscosity increase is also observed in Ge{sub 20}Se{sub 80} fibers. Nevertheless, this equilibrium viscosity is far below the viscosity expected at the configurational equilibrium. As soon as the irradiation ceases, the viscosity increases almost instantaneously by about one order of magnitude. Then, if the fibers are kept in the dark, their viscosity slowly increases over months. The analysis of the shear relaxation functions shows that the aging is thermorheologically simple. On the other side, there is no simple relaxation between the shear relaxation functions measured under irradiation and those measured in the dark. These results clearly suggest that a very specific photoinduced aging process occurs under irradiation. This aging is due to photorelaxation. Nevertheless, the viscosity changes are not solely correlated to photoaging and photorelaxation. A scenario is proposed to explain all the observed viscosity evolutions under and after irradiation, on the basis of photoinduced transient defects.

  18. Photoinduced aging and viscosity evolution in Se-rich Ge-Se glasses

    NASA Astrophysics Data System (ADS)

    Gueguen, Yann; King, Ellyn A.; Keryvin, Vincent; Sangleboeuf, Jean-Christophe; Rouxel, Tanguy; Bureau, Bruno; Lucas, Pierre

    2013-08-01

    We propose here to investigate the non-equilibrium viscosity of Ge-Se glasses under and after light irradiation. Ge10Se90 and Ge20Se80 fibers have been aged in the dark and under ambient light, over months. During aging, both the relaxation of enthalpy and the viscosity have been investigated. The viscosity was measured by shear relaxation-recovery tests allowing the measurement of non-equilibrium viscosity. When Ge10Se90 glass fibers are aged under irradiation, a relatively fast fictive temperature decrease is observed. Concomitantly, during aging under irradiation, the non-equilibrium viscosity increases and reaches an equilibrium after two months of aging. This viscosity increase is also observed in Ge20Se80 fibers. Nevertheless, this equilibrium viscosity is far below the viscosity expected at the configurational equilibrium. As soon as the irradiation ceases, the viscosity increases almost instantaneously by about one order of magnitude. Then, if the fibers are kept in the dark, their viscosity slowly increases over months. The analysis of the shear relaxation functions shows that the aging is thermorheologically simple. On the other side, there is no simple relaxation between the shear relaxation functions measured under irradiation and those measured in the dark. These results clearly suggest that a very specific photoinduced aging process occurs under irradiation. This aging is due to photorelaxation. Nevertheless, the viscosity changes are not solely correlated to photoaging and photorelaxation. A scenario is proposed to explain all the observed viscosity evolutions under and after irradiation, on the basis of photoinduced transient defects.

  19. Taconic collision in SE Penna and Delaware

    SciTech Connect

    Crawford, M.L.; Crawford, W.A.; Hoersch, A.L.; Srogi, L.A.; Wagner, M.E.

    1985-01-01

    Taconic metamorphism and tectonism in SE Pennsylvania and northern Delaware were a result of the collision of a volcanic arc with North America. The Wilmington Complex, the infrastructure of the arc, is presently the highest structural unit. It consists of granulite facies volcanogenic sediments intruded by gabbro and a ca. 500 Ma gabbronorite-charnockite suite. Latest Precambrian-earliest Paleozoic sediments of the Glenarm series were metamorphosed to conditions above the second sillimanite isograd beneath the overthrust hot (700-800/sup 0/C) Wilmington Complex. As the edge of the continent was depressed and heated under the advancing thrust complex, basement-involved nappes of Grenville age rocks (Avondale anticline, Woodville dome) with the Glenarm sedimentary cover were thrust over still rigid autochthonous basement (West Chester Prong). On the NW flank of the orogen, Grenville age gneiss-cored massifs (Honey Brook Upland, Mine Ridge, Trenton Prong), unconformably overlain by lower Paleozoic continental shelf sediments, were involved in the thrusting but metamorphosed only to the greenschist facies. Steep anticlines developed later in the Paleozoic, contributing to the present pattern of northeast trending Grenville basement massifs mantled by overlying units.

  20. 23. Interior view of SE corner of first floor of ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    23. Interior view of SE corner of first floor of 1896 south section of building, showing windows and column. Camera pointed SE. - Puget Sound Naval Shipyard, Pattern Shop, Farragut Avenue, Bremerton, Kitsap County, WA

  1. Synthesis and Crystallographic Analysis of 5-Se-Thymidine DNAs

    SciTech Connect

    Hassan, A.; Sheng, J; Jiang, J; Zhanbg, W; Huang, Z

    2009-01-01

    We investigated the possibility of the interaction of 5-CH3 of thymidine and its 5?-phosphate backbone (C-H O-PO3 interaction) in DNA via the insertion of the atomic probe (a selenium atom) into the exo-5-position of thymidine (5-Se-T). 5-Se-T was synthesized for the first time, via Mn(OAc)3 assisted electrophilic addition of CH3SeSeCH3 to 3?,5?-di-O-benzoyl-2?-deoxyuridine. The 5-Se-T phosphoramidite was subsequently synthesized and incorporated into DNA in over 99% coupling yield. Biophysical and structural investigations of the 5-Se-T DNAs revealed that the Se-modified and nonmodified DNAs are virtually identical. In addition, the crystallographic analysis of a 5-Se-T DNA strongly suggests a hydrogen-bond formation between the 5-CH3 and 5?-phosphate groups (CH3 PO4- interaction).

  2. Efficiency enhancement of Sb2Se3 thin-film solar cells by the co-evaporation of Se and Sb2Se3

    NASA Astrophysics Data System (ADS)

    Li, Zhiqiang; Zhu, Hongbing; Guo, Yuting; Niu, Xiaona; Chen, Xu; Zhang, Chong; Zhang, Wen; Liang, Xiaoyang; Zhou, Dong; Chen, Jingwei; Mai, Yaohua

    2016-05-01

    In this work, we present an alternative route to supply excessive selenium (Se) for the deposition of Sb2Se3 thin films by the co-evaporation of Se and Sb2Se3. Scanning electron microscopy (SEM) images showed that additional Se modified the growth process and surface morphology of Sb2Se3 thin films. X-ray diffraction (XRD) patterns confirmed that this co-evaporation process enhanced the beneficiary preferred orientations, and capacitance–voltage (C–V) measurement showed that the carrier concentration of the Sb2Se3 absorber increased with the additional evaporation of Se. Accordingly, the efficiency of the devices employing co-evaporated Sb2Se3 absorber layers increased significantly from 2.1 to 3.47% with a open-circuit voltage (V OC) of 364 mV, a short-circuit current density (J SC) of 23.14 mA/cm2, and a fill factor (FF) of 41.26%.

  3. Preliminary results on CuInSe2/ZnSe solar cells using reactively sputter-deposited ZnSe

    NASA Technical Reports Server (NTRS)

    Nouhi, A.; Stirn, R. J.

    1987-01-01

    In this paper preliminary results on CuInSe2/ZnSe thin film heterojunction photovoltaic devices are presented. High-conductivity ZnSe films were reactively sutter-deposited onto CuInSe2 films and overcoated with ZnO to reduce the sheet resistance. The highest short-circuit current density, as determined from a spectral response weighted for air mass 1.5 global insolation, was 37.4 mA/sq cm. The highest pen-circuit voltage observed was 430 mV.

  4. Phototransistor based on single In2Se3 nanosheets

    NASA Astrophysics Data System (ADS)

    Li, Qin-Liang; Liu, Chang-Hai; Nie, Yu-Ting; Chen, Wen-Hua; Gao, Xu; Sun, Xu-Hui; Wang, Sui-Dong

    2014-11-01

    Micrometer-sized single-crystalline In2Se3 nanosheets are synthesized by epitaxial growth from In2Se3 nanowires. The In2Se3 nanosheets possess anisotropic structural configuration with intralayer covalent bonding and interlayer van der Waals bonding. Phototransistors based on the In2Se3 nanosheets are realized, and the devices show high photoresponsivity and high photo On/Off ratio up to two orders. The photo-gating effect can be modulated by the gate bias, indicating potential utility of the In2Se3 nanosheets in a variety of optoelectronic applications.Micrometer-sized single-crystalline In2Se3 nanosheets are synthesized by epitaxial growth from In2Se3 nanowires. The In2Se3 nanosheets possess anisotropic structural configuration with intralayer covalent bonding and interlayer van der Waals bonding. Phototransistors based on the In2Se3 nanosheets are realized, and the devices show high photoresponsivity and high photo On/Off ratio up to two orders. The photo-gating effect can be modulated by the gate bias, indicating potential utility of the In2Se3 nanosheets in a variety of optoelectronic applications. Electronic supplementary information (ESI) available: SEM images of typical In2Se3 nanosheets, TEM-EDX spectrum of single In2Se3 nanosheets, STEM image and elemental mapping of an In2Se3 nanosheet, Scherrer sizes of In2Se3 nanosheets derived from the XRD pattern, statistics of In2Se3 nanosheet thickness, and photoresponse of an In2Se3 nanosheet phototransistor. See DOI: 10.1039/c4nr04404e

  5. Medium Energy Ion Scattering investigation of In diffusion in In2Se3/Bi2Se3

    NASA Astrophysics Data System (ADS)

    Lee, H. D.; Xu, C.; Shubeita, S.; Brahlek, M.; Koirala, N.; Oh, S.; Gustafsson, T.

    2013-03-01

    In2Se3, a band insulator, and Bi2Se3, a three-dimensional topological insulator, have inherently good chemical and structural compatibility. This suggests possible promising applications of In2Se3/Bi2Se3 devices as tunnel barriers and gate dielectrics. Recently, it has been shown that the similar (Bi1-xInx)2 Se3 thin system undergoes a transition from topological insulator to band insulator as a function of In concentration. It is therefore important to understand the extent of In diffusion in In2Se3/Bi2Se3 and its consequences for the transport properties. We have grown In2Se3/Bi2Se3 thin films on sapphire by Molecular Beam Epitaxy at three different temperatures. Medium Energy Ion Scattering measurements of those films showed that the higher growth temperature resulted in more In diffusion while our transport measurements showed that the Bi2Se3 mobility increases as the growth temperature decreases. We found that the trend of the mobility change of In2Se3/Bi2Se3 depending on the diffusion of In is similar with the trend of the mobility of (Bi1-xInx)2 Se3 as a function of In concentration.

  6. Local Structure of CuIn3Se5

    SciTech Connect

    Chang, C. H.; Wei, S. H.; Leyarovska, N.; Johnson, J. W.; Zhang, S. B.; Stanbery, B. J.; Anderson, T. J.

    2000-01-01

    The results of a detailed EXAFS study of the Cu-K, In-K, and Se-K edges CuIn3Se5 are reported. The Cu and In first nearest neighbor local structures were found to be almost identical to those in CuInSe2.

  7. 21 CFR 118.4 - Salmonella Enteritidis (SE) prevention measures.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    .... (c) Rodents, flies, and other pest control. As part of this program, you must: (1) Monitor for... conditions. “SE monitored” means the pullets are raised under SE control conditions that prevent SE... National Poultry Improvement Plan's standards for “U.S. S. Enteritidis Clean” status (9 CFR 145.23(d))...

  8. Procedure for separation of Se and determination of Se-79 by liquid scintillation

    SciTech Connect

    Dewberry, R.A.

    1991-08-11

    This report describes the development work and demonstration of a technique for separation of selenium suitable for determination of Se-79 by liquid scintillation counting. The technique has been demonstrated on actual DWPF (Defense Waste Processing Facility) sludge samples which contain very large loads of Sr-90 activity. The separation required a decontamination of selenium from Sr by a factor of over 10{sup 6}, from Co and Cs by factor of 10{sup 4}, and from Tc-99 by a factor of 100, while still maintaining a selenium recovery of about 50%. Using this technique the author has determined Se-79 in five actual DWPF samples with a precision of about 70% relative standard deviation. This separation has not been demonstrated on actual DWPF samples which have the largest Cs-137 loads. He does not anticipate that these untested samples will present a difficult problem.

  9. SE-72/AS-72 generator system based on Se extraction/ As reextraction

    DOEpatents

    Fassbender, Michael Ernst; Ballard, Beau D

    2013-09-10

    The preparation of a .sup.72Se/.sup.72As radioisotope generator involves forming an acidic aqueous solution of an irradiated alkali bromide target such as a NaBr target, oxidizing soluble bromide in the solution to elemental bromine, removing the elemental bromine, evaporating the resulting solution to a residue, removing hydrogen chloride from the residue, forming an acidic aqueous solution of the residue, adding a chelator that selectively forms a chelation complex with selenium, and extracting the chelation complex from the acidic aqueous solution into an organic phase. As the .sup.72Se generates .sup.72As in the organic phase, the .sup.72As may be extracted repeatedly from the organic phase with an aqueous acid solution.

  10. Optical band gap study of a-Se and Se-Sb thin films

    NASA Astrophysics Data System (ADS)

    Kaur, Ramandeep; Singh, Palwinder; Thakur, Anup

    2016-05-01

    Amorphous selenium (a-Se) and a-Se95Sb5 alloy were prepared using melt quenching technique. X-ray diffraction (XRD) pattern confirmed the amorphous nature of the prepared samples. Composition of the prepared samples has been determined using Energy dispersive X-ray fluorescence (EDXRF) technique. Differential thermal analysis (DTA) confirmed the glassy nature of the prepared samples. Thin films of the prepared samples were deposited on glass substrate using thermal evaporation method. Amorphous nature of the deposited films was confirmed using XRD. Optical properties of these films were obtained from the UV-VIS transmission spectra, at normal incidence, over 200-1100 nm spectral range. The optical absorption edge was described by using the model given by the Tauc. Optical band gap of the deposited films was calculated using Tauc plot. Optical characterization showed that average transmission and optical band gap decreased with the addition of antinomy.

  11. Nanocomposite pyrite-greigite reactivity toward Se(IV)/Se(VI).

    PubMed

    Charlet, Laurent; Kang, Mingliang; Bardelli, Fabrizio; Kirsch, Regina; Géhin, Antoine; Grenèche, Jean-Marc; Chen, Fanrong

    2012-05-01

    A nanopyrite/greigite composite was synthesized by reacting FeCl(3) and NaHS in a ratio of 1:2 (Wei et al. 1996). Following this procedure, the obtained solid phases consisted of 30-50 nm sized particles containing 28% of greigite (Fe(2+)Fe(3+)(2)S(4)) and 72% pyrite (FeS(2)). Batch reactor experiments were performed with selenite or selenate by equilibrating suspensions containing the nanosized pyrite-greigite solid phase at different pH-values and with or without the addition of extra Fe(2+). XANES-EXAFS spectroscopic techniques revealed, for the first time, the formation of ferroselite (FeSe(2)) as the predominant reaction product, along with elemental Se. In the present experimental conditions, at pH 6 and in equilibrium with Se(0), the solution is oversaturated with respect to ferrosilite. Furthermore, thermodynamic computations show that reaction kinetics likely played a significant role in our experimental system. PMID:22424403

  12. Interface oxygen and heat sensitivity of Cu(In,Ga)Se2 and CuGaSe2 solar cells

    NASA Astrophysics Data System (ADS)

    Ishizuka, Shogo; Fons, Paul J.; Yamada, Akimasa; Kamikawa-Shimizu, Yukiko; Shibata, Hajime

    2016-05-01

    Combined oxygen and heat exposure processes after p-CuGaSe2/n-CdS junction formation degrade CuGaSe2 solar cell efficiency, whereas such annealing processes can improve high In content Cu(In,Ga)Se2 device performance. This result is chiefly attributable to different interface structures consisting of oxygen-sensitive CuGaSe2 or relatively oxygen-insensitive Cu(In,Ga)Se2. To reduce CuGaSe2 interfacial recombination, reduction of the process temperature of the front contact layer deposition process is found to be the key. In this work, fill factor values exceeding 0.7 are reproducibly obtained from CuGaSe2 solar cells, though such high fill factor values have been very challenging to demonstrate to date using CuGaSe2 photoabsorber layers.

  13. Fluorescence relaxation dynamics of CdSe and CdSe/CdS core/shell quantum dots

    SciTech Connect

    Kaur, Gurvir; Kaur, Harmandeep; Tripathi, S. K.

    2014-04-24

    Time-resolved fluorescence spectra for colloidal CdSe and CdSe/CdS core/shell quantum dots have been investigated to know their electron relaxation dynamics at the maximum steady state fluorescence intensity. CdSe core and CdSe/CdS type I core-shell materials with different shell (CdS) thicknesses have been synthesized using mercaptoacetic acid as a capping agent. Steady state absorption and emission studies confirmed successful synthesis of CdSe and CdSe/CdS core-shell quantum dots. The fluorescence shows a tri-exponential decay with lifetimes 57.39, 7.82 and 0.96 ns for CdSe quantum dots. The lifetime of each recombination decreased with growth of CdS shell over the CdSe core, with maximum contribution to fluorescence by the fastest transition.

  14. Type I/type II band alignment transition in strained PbSe /PbEuSeTe multiquantum wells

    NASA Astrophysics Data System (ADS)

    Simma, M.; Fromherz, T.; Bauer, G.; Springholz, G.

    2009-11-01

    Investigation of the optical transitions in tensily strained PbSe /PbEuSeTe multiquantum wells by differential transmission spectroscopy reveals a type I/type II band alignment transition due to strain-induced lowering of the band edge energies of the quantum wells. From the measured shifts of the optical transitions the optical deformation potentials of PbSe are obtained. This is crucial for realistic modeling of the electronic properties of strained PbSe heterostructures.

  15. Two-dimensional GaSe/MoSe2 misfit bilayer heterojunctions by van der Waals epitaxy

    DOE PAGESBeta

    Li, Xufan; Lin, Ming-Wei; Lin, Junhao; Huang, Bing; Puretzky, Alexander A.; Ma, Cheng; Wang, Kai; Zhou, Wu; Pantelides, Sokrates T.; Chi, Miaofang; et al

    2016-04-01

    Two-dimensional (2D) heterostructures hold the promise for future atomically-thin electronics and optoelectronics due to their diverse functionalities. While heterostructures consisting of different transition metal dichacolgenide monolayers with well-matched lattices and novel physical properties have been successfully fabricated via van der Waals (vdW) or edge epitaxy, constructing heterostructures from monolayers of layered semiconductors with large lattice misfits still remains challenging. Here, we report the growth of monolayer GaSe/MoSe2 heterostructures with large lattice misfit by two-step chemical vapor deposition (CVD). Both vertically stacked and lateral heterostructures are demonstrated. The vertically stacked GaSe/MoSe2 heterostructures exhibit vdW epitaxy with well-aligned lattice orientation between themore » two layers, forming an incommensurate vdW heterostructure. However, the lateral heterostructures exhibit no lateral epitaxial alignment at the interface between GaSe and MoSe2 crystalline domains. Instead of a direct lateral connection at the boundary region where the same lattice orientation is observed between GaSe and MoSe2 monolayer domains in lateral GaSe/MoSe2 heterostructures, GaSe monolayers are found to overgrow MoSe2 during CVD, forming a stripe of vertically stacked vdW heterostructure at the crystal interface. Such vertically-stacked vdW GaSe/MoSe2 heterostructures are shown to form p-n junctions with effective transport and separation of photo-generated charge carriers between layers, resulting in a gate-tunable photovoltaic response. In conclusion, these GaSe/MoSe2 vdW heterostructures should have applications as gate-tunable field-effect transistors, photodetectors, and solar cells.« less

  16. Two-dimensional GaSe/MoSe2 misfit bilayer heterojunctions by van der Waals epitaxy

    PubMed Central

    Li, Xufan; Lin, Ming-Wei; Lin, Junhao; Huang, Bing; Puretzky, Alexander A.; Ma, Cheng; Wang, Kai; Zhou, Wu; Pantelides, Sokrates T.; Chi, Miaofang; Kravchenko, Ivan; Fowlkes, Jason; Rouleau, Christopher M.; Geohegan, David B.; Xiao, Kai

    2016-01-01

    Two-dimensional (2D) heterostructures hold the promise for future atomically thin electronics and optoelectronics because of their diverse functionalities. Although heterostructures consisting of different 2D materials with well-matched lattices and novel physical properties have been successfully fabricated via van der Waals (vdW) epitaxy, constructing heterostructures from layered semiconductors with large lattice misfits remains challenging. We report the growth of 2D GaSe/MoSe2 heterostructures with a large lattice misfit using two-step chemical vapor deposition (CVD). Both vertically stacked and lateral heterostructures are demonstrated. The vertically stacked GaSe/MoSe2 heterostructures exhibit vdW epitaxy with well-aligned lattice orientation between the two layers, forming a periodic superlattice. However, the lateral heterostructures exhibit no lateral epitaxial alignment at the interface between GaSe and MoSe2 crystalline domains. Instead of a direct lateral connection at the boundary region where the same lattice orientation is observed between GaSe and MoSe2 monolayer domains in lateral GaSe/MoSe2 heterostructures, GaSe monolayers are found to overgrow MoSe2 during CVD, forming a stripe of vertically stacked vdW heterostructures at the crystal interface. Such vertically stacked vdW GaSe/MoSe2 heterostructures are shown to form p-n junctions with effective transport and separation of photogenerated charge carriers between layers, resulting in a gate-tunable photovoltaic response. These GaSe/MoSe2 vdW heterostructures should have applications as gate-tunable field-effect transistors, photodetectors, and solar cells. PMID:27152356

  17. Two-dimensional GaSe/MoSe2 misfit bilayer heterojunctions by van der Waals epitaxy.

    PubMed

    Li, Xufan; Lin, Ming-Wei; Lin, Junhao; Huang, Bing; Puretzky, Alexander A; Ma, Cheng; Wang, Kai; Zhou, Wu; Pantelides, Sokrates T; Chi, Miaofang; Kravchenko, Ivan; Fowlkes, Jason; Rouleau, Christopher M; Geohegan, David B; Xiao, Kai

    2016-04-01

    Two-dimensional (2D) heterostructures hold the promise for future atomically thin electronics and optoelectronics because of their diverse functionalities. Although heterostructures consisting of different 2D materials with well-matched lattices and novel physical properties have been successfully fabricated via van der Waals (vdW) epitaxy, constructing heterostructures from layered semiconductors with large lattice misfits remains challenging. We report the growth of 2D GaSe/MoSe2 heterostructures with a large lattice misfit using two-step chemical vapor deposition (CVD). Both vertically stacked and lateral heterostructures are demonstrated. The vertically stacked GaSe/MoSe2 heterostructures exhibit vdW epitaxy with well-aligned lattice orientation between the two layers, forming a periodic superlattice. However, the lateral heterostructures exhibit no lateral epitaxial alignment at the interface between GaSe and MoSe2 crystalline domains. Instead of a direct lateral connection at the boundary region where the same lattice orientation is observed between GaSe and MoSe2 monolayer domains in lateral GaSe/MoSe2 heterostructures, GaSe monolayers are found to overgrow MoSe2 during CVD, forming a stripe of vertically stacked vdW heterostructures at the crystal interface. Such vertically stacked vdW GaSe/MoSe2 heterostructures are shown to form p-n junctions with effective transport and separation of photogenerated charge carriers between layers, resulting in a gate-tunable photovoltaic response. These GaSe/MoSe2 vdW heterostructures should have applications as gate-tunable field-effect transistors, photodetectors, and solar cells. PMID:27152356

  18. Twinning effect on photoluminescence spectra of ZnSe nanowires

    SciTech Connect

    Xu, Jing; Wang, Chunrui Wu, Binhe; Xu, Xiaofeng; Chen, Xiaoshuang; Oh, Hongseok; Baek, Hyeonjun; Yi, Gyu-Chul

    2014-11-07

    Bandgap engineering in a single material along the axial length of nanowires may be realized by arranging periodic twinning, whose twin plane is vertical to the axial length of nanowires. In this paper, we report the effect of twin on photoluminescence of ZnSe nanowires, which refers to the bandgap of it. The exciton-related emission peaks of transverse twinning ZnSe nanowires manifest a 10-meV-blue-shift in comparison with those of longitudinal twinning ZnSe nanowires. The blue-shift is attributed to quantum confinement effect, which is influenced severely by the proportion of wurtzite ZnSe layers in ZnSe nanowires.

  19. Crystal Growth of Undoped and Doped ZnSe

    NASA Technical Reports Server (NTRS)

    Davis, Swanson L.; Chen, K.-T.; George, M. A.; Shi, D. T.; Collins, W. E.; Burger, Arnold

    1997-01-01

    The surface morphology of freshly cleaved ZnSe single crystal grown by the physical vapor transport (PVT) method was investigated by Atomic Force Microscopy (AFM) and the results were correlated with Differential Scanning Calorimetry (DSC) data. Selenium precipitates have been revealed in undoped doped ZnSe crystals having a size of about 50 nm. A transition temperature around 221 C in the DSC measurements is interpreted as the eutectic temperature of Se-saturated ZnSe. The AFM images of doped ZnSe also show that possible Cr clusters are uniformly distributed and they have an estimated size of about 6 nm.

  20. The Intraplate Earthquakes of SE Africa

    NASA Astrophysics Data System (ADS)

    Fonseca, J. F. B. D.; Domingues, A.

    2014-12-01

    Southeast Africa is a region of complex tectonic inheritance, combining early Archean cratonic blocks - the Zimbabwe and Kaapvaal cratons - and several collision belts ranging in age from ~2.6Ga (Limpopo Belt) to the Pan-African Orogeny, 800-500 Ma ago (Zambezi Belt, Mozambique Belt). Mesozoic rifting was the last tectonic event to leave an imprint in the lithosphere of the region. Tertiary deformation is mild and related to the extensional regime of the East African Rift System (EARS) further north. Instrumental seismology started in Johannesburg in 1910 (Saunders et al., 2008). Ambraseys and Adams (1991) conducted a reappraisal of the seismicity of Sub-Saharan Africa from 1900 to 1930, and the compilations by Krige and Maree (1948) and Gutenberg and F. Richter (1949) are main sources for the two subsequent decades. The available data can be considered complete since 1900 for magnitudes above M6 (Ambraseys and Adams, 1991), although major epicentral errors are likely to affect the early decades. Earthquakes above this threshold in the region to the south of Lake Malawi and to the east of the Okavango Rift are reported in 1919 (MS6.5, NE South Africa), 1932 (MS6.8, Natal Bay), 1940 (MS6.2, SE Mozambique), 1951 (MS6.0, Central Mozambique), 1957 (M6.0, Central Mozambique), again in 1957 (M6.2, Central Mozambique), 1958 (M6.0, Southern Zimbabwe), 1959 (M6.1, Southern Zambia) and 2006 (M7.0, Central Mozambique). The four M>6 earthquakes from 1957 to 1959 configure a cluster in time, followed by a shutdown (at M>6) that was to last nearly five decades. While a coincidence is unlikely, a causal link is challenged by the large spatial scatter of about 500 km. However, the fact that the four earthquakes occurred on the border of the Zimbabwe craton may provide a clue to the mechanism promoting the clustering. We combine these data with recent seismicity results (Fonseca et al., 2014) to discuss possible factors controlling the seismotectonics of the region.

  1. The phase evolution mechanism in Fe(Se, Te) system

    NASA Astrophysics Data System (ADS)

    Liu, Jixing; Li, Chengshan; Zhang, Shengnan; Feng, Jianqing; Zhang, Pingxiang; Zhou, Lian

    2016-08-01

    The phase evolution mechanism in Fe(Se, Te) system during sintering was investigated with step-by-step heat treatment process. It was noticed that the diffusion processes between Fe and Se (Te) as well as that between Se and Te were both very important to the formation of superconducting Fe(Se, Te) phase with very uniform chemical composition. During heat treatment, solid solutions of (Se, Te)ss with different chemical composition were formed with the diffusion of Se atoms into Te solids and Te atoms into Se melts, simultaneously. Then with the increasing temperature, Fe atoms diffused into (Se, Te)ss, Fe(Se, Te)2 and Fe(Se, Te) phases were formed in sequence with the increasing Fe content. The chemical composition in melts became more and more uniform with the further increasing of sintering temperature and dwell time. Therefore, it was suggested that in order to achieve Fe(Se, Te) phase with high superconducting properties, it was necessary to enhance the diffusion process during sintering. The critical temperature of the sample, which was sintered at 700 °C for 12 h with slow cooling process and an O2-annealing process for 24 h, was above 14.0 K. This Tc value proved that a good superconducting β phase could be obtained under this sintering condition.

  2. Preparation and Characteristics of MoSe2 Interlayer in Bifacial Cu(In,Ga)Se2 Solar Cells

    NASA Astrophysics Data System (ADS)

    Pang, J. B.; Cai, Y. A.; He, Q.; Wang, H.; Jiang, W. L.; He, J. J.; Yu, T.; Liu, W.; Zhang, Y.; Sun, Y.

    MoSe2 thin films were formed simply by the selenization of Mo on bare soda lime glass substrate and glass coated with ZnO:Ga. Preliminarily, the structural property of MoSe2 was studied on bare soda lime glass with X-ray diffraction and Raman spectra. Furthermore, the electrical property of MoSe2 was discussed as the interlayer between the Cu(In,Ga)Se2 /ZnO:Ga double layers. Finally, bifacial solar cells with MoSe2 interlayer were illustrated with current-voltage curve and quantum efficiency.

  3. Structure of Se-rich As-Se glasses by high-resolution x-ray photoelectron spectroscopy

    SciTech Connect

    Golovchak, R.; Kovalskiy, A.; Miller, A. C.; Jain, H.; Shpotyuk, O.

    2007-09-15

    To establish the validity of various proposed structural models, we have investigated the structure of the binary As{sub x}Se{sub 100-x} chalcogenide glass family (x{<=}40) by high-resolution x-ray photoelectron spectroscopy. From the composition dependence of the valence band, the contributions to the density of states from the 4p lone pair electrons of Se and the 4p bonding states and 4s electrons of Se and As are identified in the top part of the band. The analysis of Se 3d and As 3d core-level spectra supports the so-called chain crossing model for the atomic structure of Se-rich As{sub x}Se{sub 100-x} bulk glasses. The results also indicate small deviations ({approx}3-8%) from this model, especially for glass compositions with short Se chains (25Se{sub 60} and of Se-Se-Se fragments in a glass with composition x=30 is established.

  4. A dry method to synthesize dendritic Ag2Se nanostructures utilizing CdSe quantum dots and Ag thin films.

    PubMed

    Hu, Lian; Zhang, Bingpo; Xu, Tianning; Li, Ruifeng; Wu, Huizhen

    2015-01-01

    Dendritic Ag2Se nanostructures are synthesized in a dry environment by UV irradiating the hybrids composed of CdSe quantum dots (QDs) and silver (Ag). UV irradiation on CdSe QDs induces a photooxidation effect on the QD surface and leads to the formation of SeO2 components. Then SeO2 reacts with the Ag atoms in either Ag film or QD layer to produce the Ag2Se. The growth mechanism of Ag2Se dendrites on solid Ag films is explored and explained by a diffusion limited aggregation model in which the QD layer provides enough freedom for Ag2Se motion. Since the oxidation of the CdSe QDs is the critical step for the Ag2Se dendrites formation this dry chemical interaction between QDs and Ag film can be applied in the study of the QD surface chemical properties. With this dry synthesis method, the Ag2Se dendrites can also be facilely formed at the designed area on Ag substrates. PMID:25483981

  5. A dry method to synthesize dendritic Ag2Se nanostructures utilizing CdSe quantum dots and Ag thin films

    NASA Astrophysics Data System (ADS)

    Hu, Lian; Zhang, Bingpo; Xu, Tianning; Li, Ruifeng; Wu, Huizhen

    2015-01-01

    Dendritic Ag2Se nanostructures are synthesized in a dry environment by UV irradiating the hybrids composed of CdSe quantum dots (QDs) and silver (Ag). UV irradiation on CdSe QDs induces a photooxidation effect on the QD surface and leads to the formation of SeO2 components. Then SeO2 reacts with the Ag atoms in either Ag film or QD layer to produce the Ag2Se. The growth mechanism of Ag2Se dendrites on solid Ag films is explored and explained by a diffusion limited aggregation model in which the QD layer provides enough freedom for Ag2Se motion. Since the oxidation of the CdSe QDs is the critical step for the Ag2Se dendrites formation this dry chemical interaction between QDs and Ag film can be applied in the study of the QD surface chemical properties. With this dry synthesis method, the Ag2Se dendrites can also be facilely formed at the designed area on Ag substrates.

  6. High resolution photoemission study of CdSe and CdSe/ZnS core-shell nanocrystals

    NASA Astrophysics Data System (ADS)

    Borchert, H.; Talapin, D. V.; McGinley, C.; Adam, S.; Lobo, A.; de Castro, A. R. B.; Möller, T.; Weller, H.

    2003-07-01

    Colloidally prepared CdSe and CdSe/ZnS core-shell nanocrystals passivated with trioctylphosphine/trioctylphosphine oxide and hexadecylamine have been studied by photoelectron spectroscopy with tuneable synchrotron radiation. High-resolution spectra of the Se 3d level in CdSe nanocrystals indicate the bonding of organic ligands not only to surface Cd but also to surface Se atoms. The investigation of the CdSe/ZnS core-shell nanocrystals allows us to determine the average thickness of the ZnS shell and to study the interface between the two semiconductor nanomaterials. The photoemission spectra indicate a rather well ordered interface. No evidence for interfacial bonds other than Cd-S and Se-Zn is found.

  7. [Cs6 Cl][Fe24 Se26 ]: A Host-Guest Compound with Unique Fe-Se Topology.

    PubMed

    Valldor, Martin; Böhme, Bodo; Prots, Yurii; Borrmann, Horst; Adler, Peter; Schnelle, Walter; Watier, Yves; Kuo, Chang Yang; Pi, Tun-Wen; Hu, Zhiwei; Felser, Claudia; Tjeng, Liu Hao

    2016-03-18

    The novel host-guest compound [Cs6 Cl][Fe24 Se26 ] (I4/mmm; a=11.0991(9), c=22.143(2) Å) was obtained by reacting Cs2 Se, CsCl, Fe, and Se in closed ampoules. This is the first member of a family of compounds with unique Fe-Se topology, which consists of edge-sharing, extended fused cubane [Fe8 Se6 Se8/3 ] blocks that host a guest complex ion, [Cs6 Cl](5+) . Thus Fe is tetrahedrally coordinated and divalent with strong exchange couplings, which results in an ordered antiferromagnetic state below TN =221 K. At low temperatures, a distribution of hyperfine fields in the Mössbauer spectra suggests a structural distortion or a complex spin structure. With its strong Fe-Se covalency, the compound is close to electronic itinerancy and is, therefore, prone to exhibit tunable properties. PMID:26879367

  8. Thermoelectric transport of Se-rich Ag{sub 2}Se in normal phases and phase transitions

    SciTech Connect

    Mi, Wenlong; Lv, Yanhong; Qiu, Pengfei; Shi, Xun E-mail: cld@mail.sic.ac.cn; Chen, Lidong E-mail: cld@mail.sic.ac.cn; Zhang, Tiansong

    2014-03-31

    Small amount of Se atoms are used to tune the carrier concentrations (n{sub H}) and electrical transport in Ag{sub 2}Se. Significant enhancements in power factor and thermoelectric figure of merit (zT) are observed in the compositions of Ag{sub 2}Se{sub 1.06} and Ag{sub 2}Se{sub 1.08}. The excessive Se atoms do not change the intrinsically electron-conducting character in Ag{sub 2}Se. The detailed analysis reveals the experiment optimum carrier concentration in Ag{sub 2}Se is around 5 × 10{sup 18} cm{sup −3}. We also investigate the temperature of maximum zT and the thermoelectric transport during the first order phase transitions using the recently developed measurement system.

  9. Transport study on tunnel junction structures based on In2Se3/Bi2Se3 heterostructures

    NASA Astrophysics Data System (ADS)

    Koirala, Nikesh; Brahlek, Matthew; Bansal, Namrata; Oh, Seongshik

    2013-03-01

    Bi2Se3 is a 3D Topological Insulator (TI) candidate material with structural similarity to In2Se3, which is a band insulator with large band gap. This compatibility leads to possibility of epitaxial growth of In2Se3/Bi2Se3 heterostructure, which has various application potential. For example, by depositing Superconducting or Ferromagnetic materials on top of this heterostructure, tunnel junctions can be fabricated. We have studied device structures made up of such tunnel junctions. In2Se3 was grown on top of Bi2Se3 using molecular beam epitaxy on Al2O3(0001) substrates. Superconductor (Nb) or Ferromagnet (CoFe, Gd) was then sputtered on top of In2Se3 and photolithography was used to make the tunnel junctions. Transport measurement data obtained from such structures will be presented.

  10. Confined lattice dynamics of single and quadruple SnSe bilayers in [(SnSe)1.04]m[MoSe2]n ferecrystals

    DOE PAGESBeta

    Klobes, B.; Hu, Michael; Beekman, Matt; Johnson, David C; Hermann, Raphael P

    2016-01-01

    The Sn specific densities of phonon states in the SnSe subunits of [(SnSe)1.04]m[MoSe2]n ferecrystals with (m,n) = (1,1), (4,1) and in bulk SnSe were derived from nuclear inelastic scattering by the 119Sn M ssbauer resonance. Using different measurement configurations, phonons with polarization parallel and perpendicular to the ferecrystal plane were specifically probed. Vibrational properties and phonon spectral weight are found to strongly depend on the phonon polarization and layer count m. A highly peculiar feature of these ferecrystal densities of phonon states is the emergence of rather sharp high energy vibrational modes polarized perpendicular to the ferecrystal plane, which contrastsmore » with usual findings in thin layered structures and nanostructured materials in general, and a depletion of modes with a gap appearing between acoustic and high energy modes. The spectral weight of these phonons depends on the overall SnSe content, m, but cannot be unambiguously attributed to SnSe MoSe2 interfaces. Considering the low energy part of lattice dynamics, ferecrystals exhibit rather low average phonon group velocities as compared to the speed of sound in the long wavelength limit. For the (1,1) ferecrystal, this effect is most pronounced for vibrations polarized in the ferecrystal plane. Thus, an experimental microscopic origin for the vibrational and bonding anisotropy in subunits of ferecrystals is provided.« less

  11. Confined lattice dynamics of single and quadruple SnSe bilayers in [(SnSe) 1.04 ] m [MoSe 2 ] n ferecrystals

    DOE PAGESBeta

    Klobes, Benedikt; Hu, Michael Y.; Beekman, Matt; Johnson, David C.; Hermann, Raphaël P.

    2015-11-30

    The Sn specific densities of phonon states in the SnSe subunits of [(SnSe)1.04]m[MoSe2]n ferecrystals with (m,n) = (1,1), (4,1) and in bulk SnSe were derived from nuclear inelastic scattering by the 119Sn M ssbauer resonance. When using different measurement configurations, phonons with polarization parallel and perpendicular to the ferecrystal plane were specifically probed. Vibrational properties and phonon spectral weight are found to strongly depend on the phonon polarization and layer count m. Moreover, a highly peculiar feature of these ferecrystal densities of phonon states is the emergence of rather sharp high energy vibrational modes polarized perpendicular to the ferecrystal plane,more » which contrasts with usual findings in thin layered structures and nanostructured materials in general, and a depletion of modes with a gap appearing between acoustic and high energy modes. The spectral weight of these phonons depends on the overall SnSe content, m, but cannot be unambiguously attributed to SnSe MoSe2 interfaces. Considering the low energy part of lattice dynamics, ferecrystals exhibit rather low average phonon group velocities as compared to the speed of sound in the long wavelength limit. For the (1,1) ferecrystal, this effect is most pronounced for vibrations polarized in the ferecrystal plane. Therefore, an experimental microscopic origin for the vibrational and bonding anisotropy in subunits of ferecrystals is provided.« less

  12. Composition and structure of ZnxCd1-xSe single layers prepared by thermal evaporation of ZnSe and CdSe

    NASA Astrophysics Data System (ADS)

    Nesheva, D.; Aneva, Z.; Šćepanović, M. J.; Bineva, I.; Levi, Z.; Popović, Z. V.; Pejova, B.

    2010-11-01

    Single layers of ZnxCd1-xSe with five different compositions and thickness of 400 nm have been prepared by thermal vacuum evaporation, through alloying of ultra thin ZnSe and CdSe films with equivalent thickness of 0.12, 0.25 or 0.37 nm. The deposition was carried out on rotating substrates kept at room temperature. The layer composition was varied by alloying ZnSe and CdSe films with different equivalent thicknesses. The film composition x = 0.39, 0.52, 0.59, 0.69 and 0.8 has been determined by Energy-Dispersive Spectroscopy and confirmed with Raman scattering data. The microstructure of ZnxCd1-xSe has been investigated by Atomic Force Microscopy and Raman scattering measurement. The Atomic Force Microscopy results have revealed that the layers are nanocrystalline and the grain size is <= 20 nm. The Raman scattering data have shown four replicas of the longitudinal optical phonons, thus confirming the conclusion for the layer crystallinity. The obtained results have shown that the applied deposition technique makes possible preparation of ternary nanocrystalline ZnxCd1-xSe layers with desired compositions..

  13. CuInSe/sub 2/-based photoelectrochemical cells: their use in characterization of thin CuInSe/sub 2/ films, and as photovoltaic cells per se

    SciTech Connect

    Cahen, D; Chen, Y W; Ireland, P J; Noufi, R; Turner, J A; Rincon, C; Bachmann, K J

    1984-05-01

    Photoelectrochemistry has been employed to characterize the p-CuInSe/sub 2/ component of the CdS/CuInSe/sub 2/ on-metal and a nonaqueous electrolyte containing a redox couple not specifically adsorbed onto the semiconductor, we can test the films for photovoltaic activity and obtain effective electronic properties of them, before CdS deposition, in a nondestructive manner. Electrochemical decomposition of CuInSe/sub 2/ was investigated in acetonitrile solutions to determine the mechanism of decomposition (n and p) in the dark and under illumination. Electrochemical, solution chemical and surface analyses confirmed at the light-assisted decomposition of CuInSe/sub 2/ resulted in metal ions and elemental chalcogen. On the basis of the results from the electrochemical decomposition, and studies on the solid state chemistry of the (Cu/sub 2/Se)/sub x/(In/sub 2/Se/sub 3/)/sub 1-x/ system and surface analyses, the CuInSe/sub 2//polyiodide interface was stabilized and up to 11.7% conversion efficiencies were obtained.

  14. RNA adducts with Na 2SeO 4 and Na 2SeO 3 - Stability and structural features

    NASA Astrophysics Data System (ADS)

    Nafisi, Shohreh; Manouchehri, Firouzeh; Montazeri, Maryam

    2011-12-01

    Selenium compounds are widely available in dietary supplements and have been extensively studied for their antioxidant and anticancer properties. Low blood Se levels were found to be associated with an increased incidence and mortality from various types of cancers. Although many in vivo and clinical trials have been conducted using these compounds, their biochemical and chemical mechanisms of efficacy are the focus of much current research. This study was designed to examine the interaction of Na 2SeO 4 and Na 2SeO 3 with RNA in aqueous solution at physiological conditions, using a constant RNA concentration (6.25 mM) and various sodium selenate and sodium selenite/polynucleotide (phosphate) ratios of 1/80, 1/40, 1/20, 1/10, 1/5, 1/2 and 1/1. Fourier transform infrared, UV-Visible spectroscopic methods were used to determine the drug binding modes, the binding constants, and the stability of Na 2SeO 4 and Na 2SeO 3-RNA complexes in aqueous solution. Spectroscopic evidence showed that Na 2SeO 4 and Na 2SeO 3 bind to the major and minor grooves of RNA ( via G, A and U bases) with some degree of the Se-phosphate (PO 2) interaction for both compounds with overall binding constants of K(Na 2SeO 4-RNA) = 8.34 × 10 3 and K(Na 2SeO 3-RNA) = 4.57 × 10 3 M -1. The order of selenium salts-biopolymer stability was Na 2SeO 4-RNA > Na 2SeO 3-RNA. RNA aggregations occurred at higher selenium concentrations. No biopolymer conformational changes were observed upon Na 2SeO 4 and Na 2SeO 3 interactions, while RNA remains in the A-family structure.

  15. Optical and Electronic Properties of Nonconcentric PbSe/CdSe Colloidal Quantum Dots.

    PubMed

    Zaiats, Gary; Shapiro, Arthur; Yanover, Diana; Kauffmann, Yaron; Sashchiuk, Aldona; Lifshitz, Efrat

    2015-07-01

    Lead chalcogenide colloidal quantum dots are attractive candidates for applications operating in the near infrared spectral range. However, their function is forestalled by limited stability under ambient conditions. Prolonged temperature-activated cation-exchange of Cd(2+) for Pb(2+) forms PbSe/CdSe core/shell heterostructures, unveiling a promising surface passivation route and a method to modify the dots' electronic properties. Here, we follow early stages of an-exchange process, using spectroscopic and structural characterization tools, as well as numerical calculations. We illustrate that preliminary-exchange stages involve the formation of nonconcentric heterostructures, presumably due to a facet selective reaction, showing a pronounced change in the optical properties upon the increase of the degree of nonconcentricity or/and plausible creation of core/shell interfacial alloying. However, progressive-exchange stages lead to rearrangement of the shell segment into uniform coverage, providing tolerance to oxygen exposure with a spectral steadiness already on the formation of a monolayer shell. PMID:26266716

  16. Magnetooptical properties of a single CdMnSe/CdMgSe quantum well

    SciTech Connect

    Reshina, I. I. Ivanov, S. V.

    2008-11-15

    The spectra of photoluminescence and reflectance in magnetic fields up to 7 T are studied for a 3.8 nm semimagnetic CdMnSe quantum well confined by two CdMgSe barriers. A noticeable magnetic shift in the {sigma}{sup +}-polarized emission line of the heavy exciton to low energies and a decrease in the halfwidth of the line by more than one-half are detected with increasing magnetic field. It is established that a localized magnetic polaron is formed, with the polaron energy of 19.8 meV determined from the change in the degree of circular polarization in magnetic field. A {sigma}{sup -}-polarized emission line is observed in magnetic fields ranging from 0.4 to 2 T. This line can be interpreted as being produced by the complex of two electrons, with oppositely directed spins, and a heavy hole, i.e., by the trion X{sup -} or the exciton localized at a donor, D{sup 0}X. The binding energy of such complex is 10 meV.

  17. ZnCdMgSe-Based Semiconductors for Intersubband Devices

    SciTech Connect

    Tamargo, Maria C.

    2008-11-13

    This paper presents a review of recent results on the application of ZnCdMgSe-based wide bandgap II-VI compounds to intersubband devices such as quantum cascade lasers and quantum well infrared photodetectors operating in the mid-infrared region. The conduction band offset of ZnCdSe/ZnCdMgSe quantum well structures was determined from contactless electroreflectance measurements to be as high as 1.12 eV. FT-IR was used to measure intersubband absorption in multi-quantum well structures in the mid-IR range. Electroluminescence at 4.8 {mu}m was observed from a quantum cascade emitter structure made from these materials. Preliminary results are also presented on self assembled quantum dots of CdSe on ZnCdMgSe, and novel quantum well structures with metastable binary MgSe barriers.

  18. Highly conducting ZnSe films by reactive magnetron sputtering

    NASA Technical Reports Server (NTRS)

    Nouhi, A.; Stirn, R. J.

    1986-01-01

    This paper presents the results of an effort to deposit high-conductivity ZnSe on glass and conducting SnO2-coated glass substrates by reactive magnetron sputter deposition, using pure metal sputter targets of Zn and dopants such as In, Ga, and Al. Clear yellow ZnSe films were successfully obtained. By using substrate temperatures as low as 150 C, cosputtered dopants, and sputter parameters and H2Se injection rates which maximize the Zn-to-Se ratio in the films, ZnSe bulk resistivities have been lowered by up to seven orders of magnitude, reaching values as low as 20 ohm cm. The most effective dopant to data has been In, cosputtered with Zn in amounts leading to In atomic concentrations as high as 1.4 percent. Atomic-absorption measurements show an average 49.9/48.9 ratio of Zn to Se.

  19. First-principles study of topological surface states in Bi2Se3/ZnSe superlattices

    NASA Astrophysics Data System (ADS)

    Park, Kyungwha; Chen, Zhiyi; Zhao, Lukas; Garcia, Thor Axtmann; Tamargo, Maria; Krusin-Elbaum, Lia

    Topological insulators (TIs) are interesting due to robustness of surface states within a bulk band gap in the presence of time reversal symmetry. Various TI heterostructures are based on the robustness of the topological surface states. Thus, it is crucial to understand how the topological surface states are influenced by interfaces. Recently Bi2Se3/ZnxCd1-xSe superlattices grown by molecular beam epitaxy showed interesting magneto-transport properties such as a single two-dimensional conducting channel per TI layer with the Berry phase of π. Intrigued by this experiment, we investigate topological surface states of the Bi2Se3/ZnSe superlattice by using density-functional theory. Based on the stoichiometry and the charge balance of the ZnSe layer, when one side of the ZnSe layer is terminated with Zn in the superlattice, the other side must be terminated with Se. Using the superlattice model and two slab models with either a Zn-terminated or Se-terminated interface, we calculate the effect of the inherent asymmetry of the ZnSe layer on the topological surface states of Bi2Se3, and compare our result to the experiment. Funding from NSF DMR-1206354, DMR-1312483, DMR-1420634, HRD-0833180, and DOD-W911NF-13-1-0159, and Computer resources from SDSC Trestles under DMR060009N and VT ARC.

  20. Anti-tumor and immunomodulatory activity of selenium (Se)-polysaccharide from Se-enriched Grifola frondosa.

    PubMed

    Mao, Guang-Hua; Ren, Yi; Li, Qian; Wu, Hui-Yu; Jin, Dun; Zhao, Ting; Xu, Cai-Quan; Zhang, Deng-Hong; Jia, Qing-Dong; Bai, Yan-Peng; Yang, Liu-Qing; Wu, Xiang-Yang

    2016-01-01

    A polysaccharide termed Se-GP11 was extracted and purified from Se-enriched Grifola frondosa in our previous study. This study investigated the characterization, anti-tumor and immunomodulatory activity of Se-GP11. The results showed that Se-GP11 was composed of mannose, glucose and galactose with a molar ratio of 1:4.91:2.41. The weight-average molecular weight (Mw) and weight-average mean square radius (Rw) of Se-GP11 in 0.1M sodium chloride solution were 3.3×10(4)Da and 32.8 nm. Se-GP11 existed as a globular conformation with random coil structure. Se-GP11 had no anti-tumor activity against HepG-2 cells in vitro, and it significantly inhibited the growth of Heps tumor in vivo. Se-GP11 increased the relatively thymus and spleen weights as well as serum necrosis factor-alpha (TNF-α) and interleukin-2 (IL-2) levels. In addition, Se-GP11 promoted the phagocytosis and NO production of RAW264.7 as compared with that of the normal control group. The results revealed that the Se-GP11 may exhibit the anti-tumor through improving immunologic function of the tumor bearing mice. PMID:26522247

  1. Transmission Spectra and Generation of Terahertz Pulses in SiO2-GaSe, TiO2-GaSe, Ga2O3-GaSe, and GaSe:S Structures

    NASA Astrophysics Data System (ADS)

    Bereznaya, S. A.; Zarubin, A. N.; Korotchenko, Z. V.; Prudaev, I. A.; Red'kin, R. A.; Sarkisov, S. Yu.; Tolbanov, O. P.

    2015-12-01

    Thin amorphous SiO2, TiO2, and Ga2O3 films were deposited on the surface of GaSe crystals by thermal and magnetron sputtering. It was found that under different technological conditions, the SiO2 and TiO2 layers on the surface of GaSe crack, while the Ga2O3 compound forms perfect films. A comparison of the transmission spectra and generation efficiency of terahertz pulses was made for the SiO2-GaSe, TiO2-GaSe, and Ga2O3-GaSe structures and for the GaSe:S 0.9 wt % and GaSe:S 7 wt % crystals. It was found that an increase in the concentration of sulfur in the GaSe:S crystals results in a decrease in the efficiency of generation of terahertz radiation by optical rectification of femtosecond laser pulses. Among the films deposited on the surface of GaSe, the SiO2 film has the least impact on the efficiency of generation.

  2. High performance single In2Se3 nanowire photodetector

    NASA Astrophysics Data System (ADS)

    Li, Q. L.; Li, Y.; Gao, J.; Wang, S. D.; Sun, X. H.

    2011-12-01

    The single indium selenide (In2Se3) nanowire photodetectors were fabricated, and the performance characteristics of the nanowire devices were systematically investigated. The single In2Se3 nanowire photodetectors show high and stable photoresponse in wide light wavelength (254-800 nm) and temperature range (7-300 K). The spectra response indicates that the absorption coefficient of the In2Se3 nanowires at certain wavelength dominates the performance of the devices. The good linearity of the photocurrents with the incident irradiation over a wide wavelength range has been obtained, demonstrating that the In2Se3 nanowire photodetectors work in a typical light-dependent resistor mode.

  3. Strain compensated CdSe/ZnSe/ZnCdMgSe quantum wells as building blocks for near to mid-IR intersubband devices

    NASA Astrophysics Data System (ADS)

    De Jesus, Joel; Chen, Guopeng; Hernandez-Mainet, Luis C.; Shen, Aidong; Tamargo, Maria C.

    2015-09-01

    In order to increase the conduction band offset of the ZnCdMgSe-based material system we studied the incorporation of strained CdSe layers to obtain deeper quantum wells for shorter wavelength intersubband transitions than those obtained in lattice-matched structures. Five CdSe/ZnSe/ZnCdMgSe multi-quantum wells (QW) samples grown by molecular beam epitaxy are studied in detail by transmission electron microscopy (TEM), X-ray diffraction (XRD), cw-photoluminescence (PL), and Fourier Transform Infrared (FTIR) absorption experiments. TEM and XRD results confirmed good structural quality of the samples. All the multi-QW PL energies were below the ZnCdSe lattice-matched to InP alloy bandgap (2.1 eV), which serves as first evidence of having achieved deeper quantum wells. FTIR absorptions from 3.83 to 2.56 μm were measured, shorter than those achieved by the lattice matched system. Simulations based on these results predict that absorptions as low as 2.18 μm can be obtained with these materials.

  4. Rocketdyne - SE-7 and SE-8 Engines. Chapter 4, Appendix F

    NASA Technical Reports Server (NTRS)

    Harmon, Tim

    2009-01-01

    The 70-pound SE-7 engine is very similar with its two valves, ablative material, a silicon carbide liner, a silicon carbide throat, and overall configuration. There were different wraps. One had a ninety-degree ablative material orientation. That is important because it caused problems with the SE-8, but not for this application. It was not overly stressed. It was a validation of the off-the-shelf application approach. There were two SE-7 engines located on the stage near the bottom. They had their own propellant tanks. That was the application. All it did was give a little bit of gravity by firing to push the propellants to the bottom of the tanks for start or restart. It was not a particularly complicated setup. (See Slides 6 and 7, Appendix F) What had we learned? This was a proven engine in a space environment. There weren't any development issues. Off-the-shelf seemed to work. There were no operational issues, which made the SE-7 very cost-effective. Besides NASA, the customer for this application was the Douglas Aircraft Company. Douglas decided the off-the-shelf idea was cost-effective. With the Gemini Program, the company was McDonnell Aircraft Corporation, which was part of the reason the off-the-shelf idea was applied to the Apollo. (See Slide 8, Appendix F) However, here are some differences between Apollo and Gemini vehicles. For one thing, the Apollo vehicle was really moving at high speed when it re-entered the atmosphere. Instead of a mere 17,000 miles per hour, it was going 24,000 miles per hour. That meant the heat load was four times as high on the Apollo vehicle as on the Gemini craft. Things were vibrating a little more. We had two redundant systems. Apollo was redundant where it could be as much as possible. That was really a keystone or maybe an anchor point for Apollo. We decided to pursue the off-the-shelf approach. However, the prime contractor was a different entity - the North American Space Division. They thought they ought to tune up

  5. Nanoclusters of CaSe in calcium-doped Bi2Se3 grown by molecular-beam epitaxy.

    PubMed

    Shang, Panju; Guo, Xin; Zhao, Bao; Dai, Xianqi; Bin, Li; Jia, Jinfeng; Li, Quan; Xie, Maohai

    2016-02-26

    In calcium (Ca) doped Bi2Se3 films grown by molecular beam epitaxy, nanoclusters of CaSe are revealed by high-angle annular dark field imaging and energy dispersive x-ray spectroscopy analysis using a scanning transmission electron microscope. As the interface between the ordinary insulator CaSe and topological insulator, Bi2Se3, can host topological nontrivial interface state, this represents an interesting material system for further studies. We show by first principles total energy calculations that aggregation of Ca atoms in Bi2Se3 is driven by energy minimization and a preferential intercalation of Ca in the van der Waals gap between quintuple layers of Bi2Se3 induces reordering of atomic stacking and causes an increasing amount of stacking faults in film. The above findings also provide an explanation of less-than-expected electrical carrier (hole) concentrations in Ca-doped samples. PMID:26808586

  6. Nanoclusters of CaSe in calcium-doped Bi2Se3 grown by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Shang, Panju; Guo, Xin; Zhao, Bao; Dai, Xianqi; Bin, Li; Jia, Jinfeng; Li, Quan; Xie, Maohai

    2016-02-01

    In calcium (Ca) doped Bi2Se3 films grown by molecular beam epitaxy, nanoclusters of CaSe are revealed by high-angle annular dark field imaging and energy dispersive x-ray spectroscopy analysis using a scanning transmission electron microscope. As the interface between the ordinary insulator CaSe and topological insulator, Bi2Se3, can host topological nontrivial interface state, this represents an interesting material system for further studies. We show by first principles total energy calculations that aggregation of Ca atoms in Bi2Se3 is driven by energy minimization and a preferential intercalation of Ca in the van der Waals gap between quintuple layers of Bi2Se3 induces reordering of atomic stacking and causes an increasing amount of stacking faults in film. The above findings also provide an explanation of less-than-expected electrical carrier (hole) concentrations in Ca-doped samples.

  7. Phase equilibria and liquid phase epitaxy growth of PbSnSeTe lattice matched to PbSe

    NASA Technical Reports Server (NTRS)

    Mccann, Patrick J.; Fonstad, Clifton G.; Fuchs, Jacob; Feit, Ze'ev

    1987-01-01

    The necessary phase diagram data for growing lattice-matched layers of PbSnSeTe on PbSe are presented. Solid compounds of Pb(1-x)Sn(x)Se(1-y)Te(y) lattice-matched to PbSe were grown from liquid melts consisting of (Pb/1-x/Sn/x/)(1-z)(Se/1-y/Te/y/)(z); phase equilibria data were determined together with liquidus data for values of x(liquid) from 0 to 40 percent and y(liquid) from 0 to 40 percent for temperatures between 450 and 540 C. It was found that relatively large amounts of Te must be added to the melt to achieve lattice matching because of its low segregation coefficient relative to Se. A significant lattice-pulling effect was discovered for the 5-percent Sn case, and a similar effect is expected for the 10- and 20-percent Sn cases.

  8. Atomic Resolution Monitoring of Cation Exchange in CdSe-PbSe Heteronanocrystals during Epitaxial Solid–Solid–Vapor Growth

    PubMed Central

    2014-01-01

    Here, we show a novel solid–solid–vapor (SSV) growth mechanism whereby epitaxial growth of heterogeneous semiconductor nanowires takes place by evaporation-induced cation exchange. During heating of PbSe-CdSe nanodumbbells inside a transmission electron microscope (TEM), we observed that PbSe nanocrystals grew epitaxially at the expense of CdSe nanodomains driven by evaporation of Cd. Analysis of atomic-resolution TEM observations and detailed atomistic simulations reveals that the growth process is mediated by vacancies. PMID:24844280

  9. ZnSe Films in GaAs Solar Cells

    NASA Technical Reports Server (NTRS)

    Kachare, Ram H.

    1987-01-01

    ZnSe increases efficiency and conserves material. Two proposed uses of zinc selenide films promise to boost performance and reduce cost of gallium arsenide solar cells. Accordingly ZnSe serves as surface-passivation layer and as sacrificial layer enabling repeated use of costly GaAs substrate in fabrication.

  10. Do SE(II) electrons really degrade SEM image quality?

    PubMed

    Bernstein, Gary H; Carter, Andrew D; Joy, David C

    2013-01-01

    Generally, in scanning electron microscopy (SEM) imaging, it is desirable that a high-resolution image be composed mainly of those secondary electrons (SEs) generated by the primary electron beam, denoted SE(I) . However, in conventional SEM imaging, other, often unwanted, signal components consisting of backscattered electrons (BSEs), and their associated SEs, denoted SE(II) , are present; these signal components contribute a random background signal that degrades contrast, and therefore signal-to-noise ratio and resolution. Ideally, the highest resolution SEM image would consist only of the SE(I) component. In SEMs that use conventional pinhole lenses and their associated Everhart-Thornley detectors, the image is composed of several components, including SE(I) , SE(II) , and some BSE, depending on the geometry of the detector. Modern snorkel lens systems eliminate the BSEs, but not the SE(II) s. We present a microfabricated diaphragm for minimizing the unwanted SE(II) signal components. We present evidence of improved imaging using a microlithographically generated pattern of Au, about 500 nm thick, that blocks most of the undesired signal components, leaving an image composed mostly of SE(I) s. We refer to this structure as a "spatial backscatter diaphragm." PMID:22589040

  11. On the Use of "Por" Plus Agent with "Se" Construction

    ERIC Educational Resources Information Center

    De Mello, George

    1978-01-01

    Two explanations for the role of "se" in such constructions as "Se construyen casas" are given by grammarians; one states that it is a passive interpretation ("Houses are built"), the other advocates an impersonal interpretation ("One builds houses"). Different views are presented and analyzed. (Author/NCR)

  12. Effect of Se treatment on the volatile compounds in broccoli.

    PubMed

    Lv, Jiayu; Wu, Jie; Zuo, Jinhua; Fan, Linlin; Shi, Junyan; Gao, Lipu; Li, Miao; Wang, Qing

    2017-02-01

    Broccoli contains high levels of bioactive compounds but deteriorates and senesces easily. In the present study, freshly harvested broccoli was treated with selenite and stored at two different temperatures. The effect of selenite treatment on sensory quality and postharvest physiology were analyzed. Volatile components were assessed by HS-SPME combined with GC-MS and EN. The metabolism of Se and S was also examined. Results indicated that Se treatment had a significant effect on maintaining the sensory quality, suppressing the respiration intensity and ethylene production, as well as increasing the content of Se and decreasing the content of S. In particular, significant differences in the composition of volatile compounds were present between control and Se-treated. The differences were mainly due to differences in alcohols and sulfide compounds. These results demonstrate that Se treatment can have a positive effect on maintaining quality and enhancing its sensory quality through the release of volatile compounds. PMID:27596413

  13. Crystal structure of kappa-In2Se3

    SciTech Connect

    Jasinski, J.; Swider, W.; Washburn, J.; Liliental-Weber, Z.; Chaiken, A.; Nauka, K.; Gibson, G.A.; Yang, C.C.

    2002-10-24

    Structural properties of single-phase films of {kappa}-In{sub 2}Se{sub 3} and {gamma}-In{sub 2}Se{sub 3} were investigated. Both films were polycrystalline but their microstructure differed considerably. The a-lattice parameter of {kappa}-In{sub 2}Se{sub 3} has been measured. Comparison between these two materials indicates that {kappa}-In{sub 2}Se{sub 3} has a significantly larger unit cell ({Delta}c = 2.5 {+-} 0.2 % and {Delta}a = 13.5 {+-} 0.5%) and a structure more similar to the {alpha}-phase of In{sub 2}Se{sub 3}.

  14. Study of thermal stability of Cu2Se thermoelectric material

    NASA Astrophysics Data System (ADS)

    Bohra, Anil; Bhatt, Ranu; Bhattacharya, Shovit; Basu, Ranita; Ahmad, Sajid; Singh, Ajay; Aswal, D. K.; Gupta, S. K.

    2016-05-01

    Sustainability of thermoelectric parameter in operating temperature range is a key consideration factor for fabricating thermoelectric generator or cooler. In present work, we have studied the stability of thermoelectric parameter of Cu2Se within the temperature range of 50-800°C. Temperature dependent Seebeck coefficients and electrical resistivity measurement are performed under three continuous thermal cycles. X-ray diffraction pattern shows the presence of mixed cubic-monoclinic Cu2Se phase in bare pellet which transforms to pure α-Cu2Se phase with repeating thermal cycle. Significant enhancement in Seebeck coefficient and electrical resistivity is observed which may be attributed to (i) Se loss observed in EDS and (ii) the phase transformation from mixed cubic-monoclinic structure to pure monoclinic α-Cu2Se phase.

  15. Thermoelectric properties of n-type PbSe revisited

    SciTech Connect

    Parker, David S; Singh, David J; Ren, Zhifeng; Zhang, Qinyong

    2012-01-01

    It was recently predicted \\cite{parker} and experimentally confirmed \\cite{sny_PbSe} that $p$-type PbSe would be a good thermoelectric material. Recent experimental work \\cite{pers2} now suggests that $n$-type PbSe can also be a good thermoelectric material. We now re-examine the thermoelectric performance of PbSe with a revised approximation which improves band gap accuracy. We now find that $n$-type PbSe {\\it can} be a high performance material, with thermopowers as high in magnitude as 250 $\\mu$V/K at 1000 K and 300 $\\mu$V/K at 800 K. Optimal 1000 K $n$-type doping ranges are between 2 $\\times 10^{19}$cm$^{-3}$ and 8 $\\times 10^{19}$cm$^{-3}$, while at 800 K the corresponding range is from 7 $\\times$10$^{18}$ to 4 $\\times $10$^{19}$ cm$^{-3}$.

  16. Fabrication and characterization of PbSe nanostructures on van der Waals surfaces of GaSe layered semiconductor crystals

    NASA Astrophysics Data System (ADS)

    Kudrynskyi, Z. R.; Bakhtinov, A. P.; Vodopyanov, V. N.; Kovalyuk, Z. D.; Tovarnitskii, M. V.; Lytvyn, O. S.

    2015-11-01

    The growth morphology, composition and structure of PbSe nanostructures grown on the atomically smooth, clean, nanoporous and oxidized van der Waals (0001) surfaces of GaSe layered crystals were studied by means of atomic force microscopy, x-ray diffractometry, photoelectron spectroscopy and Raman spectroscopy. Semiconductor heterostructures were grown by the hot-wall technique in vacuum. Nanoporous GaSe substrates were fabricated by the thermal annealing of layered crystals in a molecular hydrogen atmosphere. The irradiation of the GaSe(0001) surface by UV radiation was used to fabricate thin Ga2O3 layers with thickness < 2 nm. It was found that the narrow gap semiconductor PbSe shows a tendency to form clusters with a square or rectangular symmetry on the clean low-energy (0001) GaSe surface, and (001)-oriented growth of PbSe thin films takes place on this surface. Using this growth technique it is possible to grow PbSe nanostructures with different morphologies: continuous epitaxial layers with thickness < 10 nm on the uncontaminated p-GaSe(0001) surfaces, homogeneous arrays of quantum dots with a high lateral density (more than 1011 cm-2) on the oxidized van der Waals (0001) surfaces and faceted square pillar-like nanostructures with a low lateral density (˜108 cm-2) on the nanoporous GaSe substrates. We exploit the ‘vapor-liquid-solid’ growth with low-melting metal (Ga) catalyst of PbSe crystalline branched nanostructures via a surface-defect-assisted mechanism.

  17. Colloidal CdSe/Cu3P/CdSe nanocrystal heterostructures and their evolution upon thermal annealing.

    PubMed

    De Trizio, Luca; De Donato, Francesco; Casu, Alberto; Genovese, Alessandro; Falqui, Andrea; Povia, Mauro; Manna, Liberato

    2013-05-28

    We report the synthesis of colloidal CdSe/Cu(3)P/CdSe nanocrystal heterostructures grown from hexagonal Cu(3)P platelets as templates. One type of heterostructure was a sort of "coral", formed by vertical pillars of CdSe grown preferentially on both basal facets of a Cu(3)P platelet and at its edges. Another type of heterostructure had a "sandwich" type of architecture, formed by two thick, epitaxial CdSe layers encasing the original Cu(3)P platelet. When the sandwiches were annealed under vacuum up to 450 °C, sublimation of P and Cd species with concomitant interdiffusion of Cu and Se species was observed by in situ HR- and EFTEM analyses. These processes transformed the starting sandwiches into Cu2Se nanoplatelets. Under the same conditions, both the pristine (uncoated) Cu(3)P platelets and a control sample made of isolated CdSe nanocrystals were stable. Therefore, the thermal instability of the sandwiches under vacuum might be explained by the diffusion of Cu species from Cu(3)P cores into CdSe domains, which triggered sublimation of Cd, as well as out-diffusion of P species and their partial sublimation, together with the overall transformation of the sandwiches into Cu(2)Se nanocrystals. A similar fate was followed by the coral-like structures. These CdSe/Cu(3)P/CdSe nanocrystals are therefore an example of a nanostructure that is thermally unstable, despite its separate components showing to be stable under the same conditions. PMID:23557168

  18. Aerosol phase generation of In-Se nanoparticles.

    PubMed

    Geretovszky, Zs; Deppert, K; Karlsson, L S; Karlsson, M N A; Malm, l J O; Mühlberg, M

    2006-03-01

    Results on the generation and heat treatment of In-Se nanoparticles, made by heterogeneous condensation of selenium on indium nanoparticles synthesised via the evaporation/condensation route are reported. In-situ aerosol measurements are complemented with ex-situ analysis, to provide structural, morphological, and compositional information on the In-Se nanoparticles. Our results indicate that prior to heat treatment In-Se nanoparticles have a shape in the aerosol phase, similar to an asymmetric dumbbell. The bigger particle of the dumbbell structure is made up of amorphous Se, while the overall composition of the polycrystalline smaller particle is around InSe. The smaller particle has an intrinsic structure, and consists of different InSe-compounds, with a decreasing In content towards the shell. The shape of the In-Se nanoparticles is different in the aerosol phase and on the surface of the samples. The observed variety of particle sizes and shapes on the sample surface is shown to be partly due to the agglomeration of the aerosol phase binaries (i.e., dumbbells) via coalescence on the surface of the sample and wetting of the sample surface by the Se nanoparticles. These processes make the bigger particle of the dumbbell structure appear almost perfectly hemispherical on the sample surfaces. During heat treatment at lower temperatures mainly the evaporative removal of the big Se particle of the dumbbell structure will take place. Annealing of the smaller particles starts to dominate at temperatures above 240 degrees C and makes the composition of the small particles closer to that of the thermodynamically most favoured In2Se3. PMID:16573110

  19. Detection of Salmonella enterica serovar Enteritidis (SE) Antibodies in Serum Using A Polystyrene Bead/SE Flagella Agglutination Assay

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Serologic screening of flocks can be an important method to detect Salmonella enteritidis (SE) infections but can be labor intensive or lack specificity. Our goal was to develop a rapid agglutination assay using SE flagella adsorbed to polystyrene beads as a simple, relatively specific test to dete...

  20. Crystal cluster growth and physical properties of the EuSbSe3 and EuBiSe3 phases.

    PubMed

    Forbes, Scott; Tseng, Yu-Chih; Mozharivskyj, Yurij

    2015-02-01

    Syntheses of europium metal, selenium powder, and the Sb(2)Se(3)/Bi(2)Se(3) binaries were observed to produce crystal clusters of the EuSbSe(3) and EuBiSe(3) phases. These phases crystallize with the P2(1)2(1)2(1) space group and can be easily identified based on their growth habits, forming large clusters of needles. Previous literature suggested that their structure is charge-balanced with all europium atoms in the divalent state and one-quarter of the selenium atoms forming trimers. Physical property measurements on a pure sample of EuSbSe(3) revealed typical Arrhenius-type electrical resistivity, being approximately 3 orders of magnitude too large for thermoelectric applications. Electronic structure calculations indicated that both EuSbSe(3) and EuBiSe(3) are narrow-band-gap semiconductors, in good agreement with the electrical resistivity data. The valence and conduction band states near the Fermi level are dominated by the Sb/Bi and Se p states, as expected given their small difference in electronegativity. PMID:25255124

  1. CuInSe2 formation through Cu2Se-In3Se2 multilayer structures prepared by thermal evaporation technique

    NASA Astrophysics Data System (ADS)

    Mohan, A.; Rajesh, S.; Srikesh, G.

    2016-05-01

    The current study investigates the Cu2Se/In3Se2 multilayer structure deposited by thermal evaporation technique for CIS solar cells with different number of layers. The X-ray diffraction pattern reveals that the layer thickness improves the crystallinity and the formation of CIS for the 30 layer films through photoluminescence (PL) emission. The optical band gap values are found to be 2.87 eV and 2.79 eV for 5 and 10 period films respectively. The splitted band gap ranging 1.30 and 2.25 eV for 15 periods and decrease in the band gap values are due to large grains. This splitting is due to quantum size effect and CIS composite formation. The vibration frequency at 174.54 cm-1 is evident for formation of CuInSe2 Chalcopyrite phase.

  2. Synthesis and Thermal Properties of Solid-State Structural Isomers: Ordered Intergrowths of SnSe and MoSe2.

    PubMed

    Gunning, Noel S; Feser, Joseph; Beekman, Matt; Cahill, David G; Johnson, David C

    2015-07-15

    A family of structural isomers [(SnSe)1.05]m(MoSe2)n were prepared using the modulated elemental reactant method by varying the layer sequence and layer thicknesses in the precursor. By varying the sequence of Sn-Se and Mo-Se layer pairs deposited and annealing the precursors to self-assemble the targeted compound, all six possible isomers [(SnSe)1.05]4(MoSe2)4, [(SnSe)1.05]3(MoSe2)3[(SnSe)1.05]1(MoSe2)1, [(SnSe)1.05]3(MoSe2)2[(SnSe)1.05]1(MoSe2)2, [(SnSe)1.05]2(MoSe2)3[(SnSe)1.05]2(MoSe2)1, [(SnSe)1.05]2(MoSe2)1[(SnSe)1.05]1(MoSe2)2[(SnSe)1.05]1(MoSe2)1, and [(SnSe)1.05]2(MoSe2)2[(SnSe)1.05]1(MoSe2)1[(SnSe)1.05]1(MoSe2)1 were prepared. The structures were characterized by X-ray diffraction and electron microscopy which showed that all of the compounds have very similar c-axis lattice parameters and in-plane constituent lattice parameters yet distinct isomeric structures. These studies confirm that the structure, order, and thickness of the constituent layers match that of the precursors. The cross-plane thermal conductivity is found to be very low (∼0.08 Wm(-1) K(-1)) and independent of the number of SnSe-MoSe2 interfaces within uncertainty. The poor thermal transport in these layered isomers is attributed to a large cross-plane thermal resistance created by SnSe-MoSe2 and MoSe2-MoSe2 turbostratically disordered van der Waals interfaces, the density of which has less variation among the different compounds than the SnSe-MoSe2 interface density alone. PMID:26086400

  3. Ultra-thin crystalline films of CdSe and CuSe formed at the organic-aqueous interface.

    PubMed

    Kalyanikutty, K P; Gautam, Ujjal K; Rao, C N R

    2007-06-01

    Two-dimensional nanostructures in the form of ultra-thin crystalline films of CdSe and CuSe have been prepared at the organic-aqueous interface by reacting toluene solutions of metal cupferronates with an aqueous solution of N,N-dimethyl selenourea. The films have been examined using electron microscopy and optical spectroscopy. At lower concentrations of the reacting species, the CdSe films formed at the toluene-water interface at approximately 30 degrees C consisted mostly of nanocrystals. With increase in concentration as well as temperature, the interface reaction yielded thicker films which are mostly single-crystalline. We have studied the time-dependent growth of the CdSe film at the interface using UV-visible absorption spectroscopy. Ultra-thin films of CuSe formed at the toluene-water interface are generally single-crystalline. PMID:17654965

  4. Copper Selenidophosphates Cu4P2Se6, Cu4P3Se4, Cu4P4Se3, and CuP2Se, Featuring Zero-, One-, and Two-Dimensional Anions.

    PubMed

    Kuhn, Alexander; Schoop, Leslie M; Eger, Roland; Moudrakovski, Igor; Schwarzmüller, Stefan; Duppel, Viola; Kremer, Reinhard K; Oeckler, Oliver; Lotsch, Bettina V

    2016-08-15

    Five new compounds in the Cu/P/Se phase diagram have been synthesized, and their crystal structures have been determined. The crystal structures of these compounds comprise four previously unreported zero-, one-, and two-dimensional selenidophosphate anions containing low-valent phosphorus. In addition to two new modifications of Cu4P2Se6 featuring the well-known hexaselenidohypodiphosphate(IV) ion, there are three copper selenidophosphates with low-valent P: Cu4P3Se4 contains two different new anions, (i) a monomeric (zero-dimensional) selenidophosphate anion [P2Se4](4-) and (ii) a one-dimensional selenidophosphate anion [Formula: see text], which is related to the well-known gray-Se-like [Formula: see text] Zintl anion. Cu4P4Se3 contains one-dimensional [Formula: see text] polyanions, whereas CuP2Se contains the 2D selenidophosphate [Formula: see text] polyanion. It consists of charge-neutral CuP2Se layers separated by a van der Waals gap which is very rare for a Zintl-type phase. Hence, besides black P, CuP2Se constitutes a new possible source of 2D oxidized phosphorus containing layers for intercalation or exfoliation experiments. Additionally, the electronic structures and some fundamental physical properties of the new compounds are reported. All compounds are semiconducting with indirect band gaps of the orders of around 1 eV. The phases reported here add to the structural diversity of chalcogenido phosphates. The structural variety of this family of compounds may translate into a variety of tunable physical properties. PMID:27447868

  5. Multilevel Ge-Se Film Based Resist Systems

    NASA Astrophysics Data System (ADS)

    Tai, K. L.; Vadimsky, R. G.; Ong, E.

    1982-06-01

    Multilevel resist systems based on Ge-Se films make possible the use of optical projection printers for printing 0.5-1.0μm features. The four multilevel resist systems considered employ either a photosensitive or a photopassive polymer layer for planarization. In bilevel schemes the surface of the Ge-Se film is reacted in a Ag(CN)i- containing solution to form a Ag2Se imaging layer. No reacted Ge-Se is used as a sacrificial layer in trilevel schemes. Ge-Se films are resistant to attack by oxygen plasma and therefore make good masks for pattern transfer by dry (reactive ion) etching, to a thick underlying photopassive polymer layer. Because of their high absorbance (a 105cm-1) in the ultraviolet and violet, Ge-Se patterns can also be used as exposure masks for transferring images to a thick underlying photosensitive polymer layer. The latter is "flood" exposed through the Ge-Se mask and wet developed. Both dry and wet processes provide steep wall-profile patterns in the polymer layer. The dry process provides superior feature size control while the wet process offers reduced processing cost. The exceptional lithographic performance exhibited by Ge-Se resist systems is attributed to a unique edge-sharpening effect; diffraction is compensated for by lateral silver diffusion in the Ag2Se layer. Patterns having 0.6μm lines and spaces are obtained over lcmXlcm fields with a defocus tolerance of 2.5μm using a standard Zeiss 10:1 reduction lens (N.A.=0.28, λ=436nm). Results indicate that optical lithography can practically print features in the size regime previously reserved for a-beam or x-ray based lithographic technologies.

  6. Solid state 77Se NMR investigations on arsenic-selenium glasses and crystals

    NASA Astrophysics Data System (ADS)

    Bureau, Bruno; Troles, Johann; LeFloch, Marie; Smektala, Frédéric; Silly, Gilles; Lucas, Jacques

    2003-01-01

    Some resolved solid state 77Se NMR spectra are presented in the As xSe 1- x glass family at ambient temperature. They exhibit three different kinds of Se environments. A comparison with the parent crystalline phases permits to assign the lines to Se- Se-Se, Se- Se-As and As- Se-As Se atom neighborhoods. The measurements of the relative intensities of the lines prove the validity of the intermediate range order structural model known as the "chains crossing model" which is based on AsSe 3 pyramids homogeneously distributed among the divalent Se atoms network. In particular, any scenario involving a selenium clustering process is refuted.

  7. Magnetic study of Fe-doped CdSe nanomaterials

    NASA Astrophysics Data System (ADS)

    Das, Sayantani; Banerjee, Sourish; Sinha, T. P.

    2016-05-01

    Nanoparticles of pure and iron (50 %) doped cadmium selenide (CdSe) have been synthesized by soft chemical route. EDAX analysis supports the inclusion of Fe into CdSe nanoparticles. The average particle size of pure and doped CdSe is found to be ˜50 nm from scanning electron microscopy (SEM). Magnetization of the samples are measured under the field cooled (FC) and zero field cooled (ZFC) modes in the temperature range from 5K to 300K applying a magnetic field of 500Oe. Field dependent magnetization (M-H) measurement indicates presence of room temperature (RT) paramagnetism and low temperature (5K) ferromagnetism of the sample.

  8. Optical Probing of metamagnetic phases in epitaxial EuSe

    SciTech Connect

    Galgano, G. D.; Henriques, A. B.; Bauer, G.; Springholz, G.

    2011-12-23

    EuSe is a wide gap magnetic semiconductors with a potential for applications in proof-of-concept spintronic devices. When the temperature is lowered, EuSe goes through sharp transitions between a variety of magnetic phases and is thus described as metamagnetic. The purpose of the present investigation is to correlate the magnetic order to the sharp dichroic doublet, discovered recently in high quality thin epitaxial layers of EuSe, grown by molecular beam epitaxy. We report detailed measurements of the doublet positions and intensities as a function of magnetic field in low temperatures, covering several magnetic phases.

  9. Photoconductivity in ZnSe under high electric fields

    SciTech Connect

    Cho, P.S.; Ho, P.T.; Goldhar, J.; Lee, C.H. . Dept. of Electrical Engineering)

    1994-06-01

    High voltage photoconductive switches utilizing polycrystalline ZnSe were investigated. Experiments have been performed on polycrystalline ZnSe switches in a longitudinal geometry. Electrodes of perforated metal films, a transparent liquid electrolyte, plasma, and ultraviolet-light-generated carriers were used. High-bias fields of up to 100 kV/cm and current densities over 100 kA/cm[sup 2] can be applied to the polycrystalline ZnSe switches. Nonlinear effects were observed at high fields with near band edge illumination. Applications of these effects are discussed.

  10. Hg and Se Speciation in Liver Tissue of Marine Birds

    NASA Astrophysics Data System (ADS)

    Karanfil, Cahit; Bischoff, Karyn; Bunker, Grant

    2013-04-01

    X-ray fluorescence microprobe maps of Hg and Se distribution were made on liver tissue slices from marine birds (Cormorants) from Florida's Everglades. The birds bio-concentrate these toxic pollutants that are ingested from their diet of fish. The fluorescence maps show strong localization of Mercury and Selenium into "hot spots" less than 100 microns in size. XAFS measurements were made on hot spots to demonstrate that the Hg and Se are indeed are chemically bound, supporting the idea that moderate levels of Se may have a protective effect against Hg through its complexation.

  11. Structural and optical properties of CuSe2 nanocrystals formed in thin solid Cu-Se film

    NASA Astrophysics Data System (ADS)

    Gilić, M.; Petrović, M.; Kostić, R.; Stojanović, D.; Barudžija, T.; Mitrić, M.; Romčević, N.; Ralević, U.; Trajić, J.; Romčević, M.; Yahia, I. S.

    2016-05-01

    This paper describes the structural and optical properties of Cu-Se thin films. The surface morphology of thin films was investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Formation of Cu-Se thin films is concluded to proceed unevenly, in the form of islands which later grew into agglomerates. The structural characterization of Cu-Se thin film was investigated using X-ray diffraction pattern (XRD). The presence of two-phase system is observed. One is the solid solution of Cu in Se and the other is low-pressure modification of CuSe2. The Raman spectroscopy was used to identify and quantify the individual phases present in the Cu-Se films. Red shift and asymmetry of Raman mode characteristic for CuSe2 enable us to estimate nanocrystal dimension. In the analysis of the far-infrared reflection spectra, numerical model for calculating the reflectivity coefficient of layered system, which includes film with nanocrystalite inclusions (modeled by Maxwell-Garnett approximation) and substrate, has been applied.

  12. Observation of a charge delocalization from Se vacancies in Bi2Se3 : A positron annihilation study of native defects

    NASA Astrophysics Data System (ADS)

    Unzueta, I.; Zabala, N.; Marín-Borrás, V.; Muñoz-Sanjosé, V.; García, J. A.; Plazaola, F.

    2016-07-01

    By means of positron annihilation lifetime spectroscopy, we have investigated the native defects present in Bi2Se3 , which belongs to the family of topological insulators. We experimentally demonstrate that selenium vacancy defects (VSe1) are present in Bi2Se3 as-grown samples, and that their charge is delocalized as temperature increases. At least from 100 K up to room temperature both VSe10 and VSe1+ charge states coexist. The observed charge delocalization determines the contribution of VSe1 defects to the n -type conductivity of Bi2Se3 . These findings are supported by theoretical calculations, which show that vacancies of nonequivalent Se1 and Se2 selenium atoms are clearly differentiated by positron annihilation lifetime spectroscopy, enabling us to directly detect and quantify the most favorable type of selenium vacancy. In addition to open-volume defects, experimental data indicate the presence of defects that act as shallow traps, suggesting that more than one type of native defects coexist in Bi2Se3 . As will be discussed, the presence of a dislocation density around 1010cm-2 could be the source of the detected shallow traps. Understanding the one-dimensional defects and the origin of the charge delocalization that leads Bi2Se3 to be an n -type semiconductor will help in the development of high-quality topological insulators based on this material.

  13. Thickness-Dependent Charge Carrier Dynamics in CdSe/ZnSe/CdS Core/Barrier/Shell Nanoheterostructures.

    PubMed

    Yadav, Sushma; Chowdhury, Apurba; Sapra, Sameer

    2016-03-01

    We report the synthesis of CdSe/ZnSe/CdS heterostructures composed of type I and type II band alignments, where ZnSe acts as a barrier for charge carriers between the CdSe core and the CdS shell as well as being an active component of the type I (CdSe/ZnSe) and type II (ZnSe/CdS) structure simultaneously. We investigated the effect of the thickness of the barrier and the shell on the charge carrier dynamics by using UV/Vis absorbance, photoluminescence (PL), and time-resolved fluorescence techniques. The experimental data are supported by simple theoretical calculations based on effective mass approximation (EMA). PL results indicate the emission from both type I and type II structures. Time-resolved fluorescence studies show that the lifetime of the core emission decreases with increasing barrier width, owing to a greater confinement of the exciton to the core, whereas it increases with shell width because of the tunneling of charge carriers, primarily electrons, delaying the recombination of the exciton. The lifetime of the shell emission decreases with shell width as well as barrier width and height, with a larger effect being observed for the barrier width and negligible for the associated changes in the barrier height. PMID:26511899

  14. Role of Cu additive on the dielectric relaxation of Se75Te25 and Se85Te15 glassy alloys

    NASA Astrophysics Data System (ADS)

    Sharma, J.; Kumar, S.

    2010-07-01

    The effect of Cu additive on the dielectric relaxation of two binary Se-Te glassy systems, comparing the properties of a-Se75Te25, a-Se85Te15 and a-Se75Te15Cu10 alloys has been reported. The temperature and frequency dependence of dielectric parameters in Glassy Se75Te25, Se85Te15 and Se75Te15Cu10 alloys are studied by measuring capacitance and dissipation factor in the frequency range (1 kHz-5 MHz) and temperature range (300-350 K). A Debye like relaxation of dielectric behavior has been observed. A comprehensive study on the relaxation mechanism revealed that the presence of grains and grain boundaries across the pallet thickness is the basic relaxation process. A detailed analysis shows that the observed dielectric loss is in agreement with the Guintini's theory of dielectric dispersion based on two electron hopping over a potential barrier and is applicable in the present case. Dielectric constant (ɛ’), dielectric loss (ɛ”), loss tangent (δ) and capacitive reactance (Xc) are found highly frequency and temperature dependent. Dependence of these dielectric parameters over the metallic impurity Cu, has also been found in the present glassy system and has been discussed in terms of electronegativity difference between the elements used in making the aforesaid glassy system.

  15. ZnSe hollow nanospheres in mechanically stable near-IR antireflection coatings for ZnSe substrates.

    PubMed

    Li, Chao; Luo, Rui-Chun; Mao, Yong-Qiang; Du, Xi-Wen; Yang, Jing

    2016-09-01

    Though possessing low absorption throughout a wide infrared (IR) spectral regime, owing to a high refractive index, zinc selenide substrates are generally covered by antireflection coatings (ARCs) for practical optical uses. However, achieving a high transmission of ZnSe substrates in the near-IR (NIR) region is still challenging. Herein, for the first time, colloidal ZnSe hollow nanospheres (HNSs) smaller than 100 nm were prepared and adopted to assemble ARCs for ZnSe substrates. The voiding kinetics of the HNSs was found to agree well with the nanoscale Kirkendall effect, and the self-diffusion of the Zn ion in the core was faster than its diffusion through the ZnSe shell. With single-index ARCs, the transmission of ZnSe substrates was remarkably enhanced in the NIR region, with up to an 18% increase at 840 nm. Besides, the ZnSe HNS-based ARCs showed superior mechanical stability even under violent ultrasonication in organic solutions. We expect that ZnSe HNSs will make it possible to construct graded-index ARCs to realize omnidirectional and broadband antireflection in IR, through further tuning of HNSs' void fraction. PMID:27482737

  16. ZnSe hollow nanospheres in mechanically stable near-IR antireflection coatings for ZnSe substrates

    NASA Astrophysics Data System (ADS)

    Li, Chao; Luo, Rui-Chun; Mao, Yong-Qiang; Du, Xi-Wen; Yang, Jing

    2016-09-01

    Though possessing low absorption throughout a wide infrared (IR) spectral regime, owing to a high refractive index, zinc selenide substrates are generally covered by antireflection coatings (ARCs) for practical optical uses. However, achieving a high transmission of ZnSe substrates in the near-IR (NIR) region is still challenging. Herein, for the first time, colloidal ZnSe hollow nanospheres (HNSs) smaller than 100 nm were prepared and adopted to assemble ARCs for ZnSe substrates. The voiding kinetics of the HNSs was found to agree well with the nanoscale Kirkendall effect, and the self-diffusion of the Zn ion in the core was faster than its diffusion through the ZnSe shell. With single-index ARCs, the transmission of ZnSe substrates was remarkably enhanced in the NIR region, with up to an 18% increase at 840 nm. Besides, the ZnSe HNS-based ARCs showed superior mechanical stability even under violent ultrasonication in organic solutions. We expect that ZnSe HNSs will make it possible to construct graded-index ARCs to realize omnidirectional and broadband antireflection in IR, through further tuning of HNSs’ void fraction.

  17. 1. Building No. 9980. East side and SE wing on ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. Building No. 9980. East side and SE wing on left as viewed from roof of Corridor A. - Madigan Hospital, Patients' & Medical Detachments, Bounded by Wilson & McKinley Avenues & Garfield & Lincoln Streets, Tacoma, Pierce County, WA

  18. 9. First floor shop office, SE corner of E wing, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. First floor shop office, SE corner of E wing, showing entry vestibule at right; looking SSE. (Ryan and Harms) - Rock Island Arsenal, Building No. 66, Rodman Avenue between Third & Fourth Streets, Rock Island, Rock Island County, IL

  19. View downstream of timber guide wall downstream from SE corner ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View downstream of timber guide wall downstream from SE corner of lock, view towards east - St. Lucie Canal, St. Lucie Lock No. 1, St. Lucie, Cross State Canal, Okeechobee Intracoastal Waterway, Stuart, Martin County, FL

  20. 23. Detail view of fireplace, secondfloor SE bedroom; looking N. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    23. Detail view of fireplace, second-floor SE bedroom; looking N. (Ceronie) - Rock Island Arsenal, Building No. 1, Gillespie Avenue between Terrace Drive & Hedge Lane, Rock Island, Rock Island County, IL

  1. 2. East wall of Lock 1 looking SE from top ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. East wall of Lock 1 looking SE from top of lock showing tooled stonework in foreground where gate hardware fitted. 1971. - Potowmack Company: Great Falls Canal, Lock No. 1, Great Falls, Fairfax County, VA

  2. 10. Photocopy of c. 1906 photograph looking SE at row ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. Photocopy of c. 1906 photograph looking SE at row of double Creole quarters along Main Street. - Laurel Valley Sugar Plantation, Double Creole Quarters, 2 Miles South of Thibodaux on State Route 308, Thibodaux, Lafourche Parish, LA

  3. 9. Photocopy of c. 1906 photograph looking SE at row ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. Photocopy of c. 1906 photograph looking SE at row of double Creole workers' houses along Main Street. - Laurel Valley Sugar Plantation, Double Creole Quarters, 2 Miles South of Thibodaux on State Route 308, Thibodaux, Lafourche Parish, LA

  4. View of viaduct, looking SE from roof of adjacent parking ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of viaduct, looking SE from roof of adjacent parking garage. - Mulberry Street Viaduct, Spanning Paxton Creek & Cameron Street (State Route 230) at Mulberry Street (State Route 3012), Harrisburg, Dauphin County, PA

  5. View looking SE inside Electrical Shop Central of Georgia ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View looking SE inside Electrical Shop - Central of Georgia Railway, Savannah Repair Shops & Terminal Facilities, Electrical Shop, Bounded by West Broad, Jones, West Boundary & Hull Streets, Savannah, Chatham County, GA

  6. BLDG 8, VIEW OF NE SIDE LOOKING THRU SE DRIVE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    BLDG 8, VIEW OF NE SIDE LOOKING THRU SE DRIVE THROUGH. - Naval Magazine Lualualei, West Loch Branch, Ammo Rework Building, North of Fourth Street near intersection with B Avenue, Pearl City, Honolulu County, HI

  7. 8. Interior view looking SE on second floor of Paint ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. Interior view looking SE on second floor of Paint Shop. - Central of Georgia Railway, Savannah Repair Shops & Terminal Facilities, Paint & Coach Barn, Bounded by West Broad, Jones, West Boundary & Hull Streets, Savannah, Chatham County, GA

  8. 7. Window and door in SE corner of office in ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. Window and door in SE corner of office in Tender Frame Shop. - Central of Georgia Railway, Savannah Repair Shops & Terminal Facilities, Tender Frame Shop, Bounded by West Broad, Jones, West Boundary & Hull Streets, Savannah, Chatham County, GA

  9. 8. Water treatment plant, view to SE, berm in foreground ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. Water treatment plant, view to SE, berm in foreground covering settling tank - Fort Benton Water Treatment Plant, Filtration Plant, Lots 9-13 of Block 7, Fort Benton Original Townsite at Missouri River, Fort Benton, Chouteau County, MT

  10. 3. Partial view of SE sides of Boiler Building (left), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. Partial view of SE sides of Boiler Building (left), Incineration Building (to right of stack) and Machine Shop (right). - Pacific Creosoting Plant, Boiler Building, 5350 Creosote Place, Northeast, Bremerton, Kitsap County, WA

  11. 158. View looking SE showing 'Centennial Anniversary of the Declaration ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    158. View looking SE showing 'Centennial Anniversary of the Declaration of Independence' fountain on Aquarium Drive with north facade of Art Museum in right background. - Fairmount Waterworks, East bank of Schuylkill River, Aquarium Drive, Philadelphia, Philadelphia County, PA

  12. Overview of north elevation, looking SE from west bank of ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Overview of north elevation, looking SE from west bank of Beaver River. - Pittsburgh, Youngstown & Ashtabula Railroad, Bridge No. 13, Spanning Beaver River, South of State Route 288 Bridge, Wampum, Lawrence County, PA

  13. Overview of north elevation, looking SE from west bank of ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Overview of north elevation, looking SE from west bank of Beaver River, with train on bridge. - Pittsburgh, Youngstown & Ashtabula Railroad, Bridge No. 13, Spanning Beaver River, South of State Route 288 Bridge, Wampum, Lawrence County, PA

  14. Optical Properties of CdSe Nanoparticle Assemblies

    SciTech Connect

    Huser, T; Gerion, D; Zaitseva, N; Krol, D M; Leon, F R

    2003-11-24

    We report on three-dimensional fluorescence imaging of micron-size faceted crystals precipitated from solutions of CdSe nanocrystals. Such crystals have previously been suggested to be superlattices of CdSe quantum dots [1,2]. Possible applications for these materials include their use in optical and optoelectronic devices. The micron-size crystals were grown by slow evaporation from toluene solutions of CdSe nanocrystals in the range of 3-6 nm, produced by traditional wet-chemistry techniques. By using a confocal microscope with laser illumination, three-dimensional raster-scanning and synchronized hyper-spectral detection, we have generated spatial profiles of the fluorescence emission intensity and spectrum. The fluorescence data of the micro-crystals were compared with spectra of individual nanocrystals obtained from the same solution. The results do not support the assertion that these microcrystals consist of CdSe superlattices.

  15. Synthesis and properties of new CdSe-AgI-As{sub 2}Se{sub 3} chalcogenide glasses

    SciTech Connect

    Kassem, M.; Le Coq, D.; Fourmentin, M.; Hindle, F.; Bokova, M.; Cuisset, A.; Masselin, P.; Bychkov, E.

    2011-02-15

    Research highlights: {yields} Determination of the glass-forming region in the pseudo-ternary CdSe-AgI-As{sub 2}Se{sub 3} system. {yields} Characterization of macroscopic properties of the new CdSe-AgI-As{sub 2}Se{sub 3} glasses. {yields} Far infrared transmission of chalcogenide glasses. {yields} Characterization of the total conductivity of CdSe-AgI-As{sub 2}Se{sub 3} glasses. -- Abstract: The glass-forming region in the pseudo-ternary CdSe-AgI-As{sub 2}Se{sub 3} 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 (T{sub g}), crystallisation (T{sub x}), and melting (T{sub m}) temperatures are reported and used to calculate their {Delta}T = T{sub x} - T{sub g} and their Hruby, H{sub r} = (T{sub x} - T{sub g})/(T{sub m} - T{sub x}), criteria. Evolution of the total electrical conductivity {sigma} and the room temperature conductivity {sigma}{sub 298} was also studied. The terahertz transparency domain in the 50-600 cm{sup -1} region was pointed for different chalcogenide glasses (ChGs) and the potential of the THz spectroscopy was suggested to obtain structural information on ChGs.

  16. Origin of the solid solution in the LiInSe2-In2Se3 system

    NASA Astrophysics Data System (ADS)

    Vasilyeva, I. G.; Pochtar, A. A.; Isaenko, L. I.

    2014-12-01

    Techniques of bulk and local analyses were used to characterize the melt-grown single crystals of LiInSe2, where yellow matrix coexists together with extended red areas distributed irregularly. Bulk chemical analysis showed that the average stoichiometry of yellow matrix is close to ideal 1:1:2, but red areas are enriched with In2Se3. An excess In2Se3 is incorporated coherently into the crystal lattice of LiInSe2, forming the substitution solid solution with the general formula (Li1-3xInx⎕2)InSe2 and changing the color from yellow to red. The test crystals with the 50-55% content of In2Se3 were found by the X-ray analysis to be single phase. The differential dissolution technique, measuring the spatial variation of the composition with high resolution, demonstrated that the single phase crystals in the LiInSe2-In2Se3 system might be grown only in a very narrow range close to stoichiometric. Being supersaturated, the heterovalent solid solution phases decompose in the course of cooling, and the concentration micro-heterogeneity occurs in the matrix as the coherent (or incoherent) inclusions of two different types, practically pure selenides of lithium and indium. The origin and scale of the micro-heterogeneity determining the physical properties of LiInSe2 are discussed as a starting point for the development of physicochemical foundations for growing high quality optical crystals.

  17. Methanococcus vannielii selenium-binding protein (SeBP): Chemical reactivity of recombinant SeBP produced in Escherichia coli

    PubMed Central

    Patteson, Kemberly G.; Trivedi, Neel; Stadtman, Thressa C.

    2005-01-01

    A selenium-binding protein (SeBP) from Methanococcus vannielii was recently identified, and its gene was isolated and overexpressed in Escherichia coli [Self, W. T., Pierce, R. & Stadtman, T. C. (2004) IUBMB Life 56, 501–507]. SeBP and recombinant SeBP (rSeBP) migrated as ≈42-kDa species on native gels and as ≈33-kDa species on SDS gels. rSeBP consists of identical 8.8-kDa subunits, each containing a single cysteine residue. rSeBP isolated in the absence of reducing agents contained oxidized cysteine (89%) and very little bound selenium (0.05 eq or less per subunit). Complete reduction of the oxidized cysteine residues in rSeBP with Tris(2-carboxyethyl)phosphine required addition of a denaturant, such as 1 M guanidine-hydrochloride. With selenite as the selenium source and the isolated reduced protein as sole reductant, binding of one selenium per tetramer under anaerobic conditions required four cysteine thiol groups, one on each subunit. In the corresponding reaction, with reduced glutathione (GSH), equimolar amounts of selenodiglutathione (GSSeSG) and glutathione disulfide are formed from selenite and 4 GSH. At GSH-to-selenite ratios >4:1, conversion of GSSeSG to a perselenide derivative, GSSe–, occurs. However, with the reduced rSeBP as sole electron donor in the reaction with selenite, further conversion of the R-SSeS-R product apparently did not occur. Prior alkylation of the cysteine thiol groups in reduced rSeBP prevented selenite reduction and selenium binding under comparable conditions. PMID:16103372

  18. Antiphase Boundaries in the Turbostratically Disordered Misfit Compound (BiSe)(1+δ)NbSe2.

    PubMed

    Mitchson, Gavin; Falmbigl, Matthias; Ditto, Jeffrey; Johnson, David C

    2015-11-01

    (BiSe)(1+δ)NbSe2 ferecrystals were synthesized in order to determine whether structural modulation in BiSe layers, characterized by periodic antiphase boundaries and Bi-Bi bonding, occurs. Specular X-ray diffraction revealed the formation of the desired compound with a c-axis lattice parameter of 1.21 nm from precursors with a range of initial compositions and initial periodicities. In-plane X-ray diffraction scans could be indexed as hk0 reflections of the constituents, with a rectangular basal BiSe lattice and a trigonal basal NbSe2 lattice. Electron micrographs showed extensive turbostratic disorder in the samples and the presence of periodic antiphase boundaries (approximately 1.5 nm periodicity) in BiSe layers oriented with the [110] direction parallel to the zone axis of the microscope. This indicates that the structural modulation in the BiSe layers is not due to coherency strain resulting from commensurate in-plane lattices. Electrical transport measurements indicate that holes are the dominant charge carrying species, that there is a weak decrease in resistivity as temperature decreases, and that minimal charge transfer occurs from the BiSe to NbSe2 layers. This is consistent with the lack of charge transfer from the BiX to the TX2 layers reported in misfit layer compounds where antiphase boundaries were observed. This suggests that electronic considerations, i.e., localization of electrons in the Bi-Bi pairs at the antiphase boundaries, play a dominant role in stabilizing the structural modulation. PMID:26465820

  19. Flux free growth of superconducting FeSe single crystals

    NASA Astrophysics Data System (ADS)

    Maheshwari, P. K.; Joshi, L. M.; Gahtori, Bhasker; Srivastava, A. K.; Gupta, Anurag; Patnaik, S. P.; Awana, V. P. S.

    2016-07-01

    We report flux free growth of superconducting FeSe single crystals by an easy and versatile high temperature melt and slow cooling method for first time. The room temperature x-ray diffraction (XRD) on the surface of the piece of such obtained crystals showed single [101] plane of β-FeSe tetragonal phase. The bulk powder XRD, being obtained by crushing the part of crystal chunk showed majority (∼87%) β-FeSe tetragonal (space group P4/nmm) and minority (∼13%) δ-FeSe hexagonal (space group P63/mmc) crystalline phases. Detailed high resolution transmission electron microscope images along with selected area electron diffraction showed the abundance of both majority β-FeSe and minority δ-FeSe phases. Both transport (ρ-T) and magnetization exhibited superconductivity at below around 10 K. Interestingly, the magnetization signal of these crystals is dominated by the magnetism of minority δ-FeSe magnetic phase, and hence the isothermal magnetization at 4 K was seen to be ferromagnetic like. Transport (ρ-T) measurements under magnetic field showed superconductivity onset at below 12 K, and ρ = 0 (T c) at 9 K. Superconducting transition temperature (T c) decreases with applied field to around 6 K at 7 T, with dT c/dH of ∼0.4 K T‑1, giving rise to an H c2(0) value of around 50 , 30 and 20 T for normal resistivity ρ n = 90%, 50% and 10% respectively, which are calculated from conventional one band Werthamer–Helfand–Hohenberg equation. FeSe single crystal activation energy is calculated from thermally activated flux flow model which is found to decreases with field from 12.1 meV for 0.2 T to 3.77 meV for 7 T.

  20. Processing ambiguous Spanish se in a minimal chain.

    PubMed

    Meseguer, Enrique; Acuña-Fariña, Carlos; Carreiras, Manuel

    2009-04-01

    The recovery of pieces of information that are not linguistically expressed is a constant feature of the process of language comprehension. In the processing literature, such missing information is generally referred to as "gaps". Usually, one resolves gaps by finding "fillers" in either the sentence or the context. For instance, in Peter seemed to be upset, Peter is really the subject of being upset but appears as surface subject of seems. Sometimes constituents move, leaving gaps behind. Various Romance languages such as Spanish or Italian have a grammatical particle se/si, which, as it is extremely ambiguous, licenses different sorts of gaps. In Spanish, se can encode at least reflexive, impersonal, and passive meanings. In an eye-tracking experiment we contrast reflexive structures containing postverbal subjects with impersonal structures with no subjects (GAP se vendó apresuradamente el corredor/"the runner bandaged himself hurriedly" vs. GAP se vendó apresuradamente al corridor/"(someone) bandaged the runner hurriedly"). In a second manipulation we contrast the presence of an extra argument with se-passives (GAP se vendó el tobillo el corredor/"the runner bandaged his ankle" vs. GAP se vendó el tobillo al corridor/"the runner's ankle was bandaged"). Our comparisons involve contrasting standard transitive structures with nonstandard word order (postverbal subject and a preverbal subject gap) against inherently complex and less habitual structures such as impersonals (with no subject) or se-passives (with subjects in canonical object position). We evaluate the minimal chain principle (de Vincenzi, 1991), according to which displacement is costly because it entails complex (derivational) "chains" that must be undone before phrasal packaging can commence. We show the minimal chain principle to be essentially correct when contrasting more complex but more frequent structures with less complex but less frequent structures. A noteworthy feature of this research

  1. Tin oxidation mechanism in the Sn-Se alloy

    NASA Astrophysics Data System (ADS)

    Duhalde, S.; Arcondo, B.; Nassif, E.; Sirkin, H.

    1988-06-01

    Mössbauer spectroscopy and X-ray diffraction studies performed on powdered samples of Sn-Se alloys allowed us to determine the influence of the chalcogenide bonds in the tin oxidation mechanism. The weak bonds present in the SnSe2 compound increase the tin oxidation kinetics, an effect which is not found in pure tin samples maintained in the same conditions.

  2. Tunable Graphene-GaSe Dual Heterojunction Device.

    PubMed

    Kim, Wonjae; Li, Changfeng; Chaves, Ferney A; Jiménez, David; Rodriguez, Raul D; Susoma, Jannatul; Fenner, Matthias A; Lipsanen, Harri; Riikonen, Juha

    2016-03-01

    A field-effect device based on dual graphene-GaSe heterojunctions is demonstrated. Monolayer graphene is used as electrodes on a GaSe channel to form two opposing Schottky diodes controllable by local top gates. The device exhibits strong rectification with tunable threshold voltage. Detailed theoretical modeling is used to explain the device operation and to distinguish the differences compared to a single diode. PMID:26727653

  3. Template free-solvothermaly synthesized copper selenide (CuSe, Cu 2- xSe, β-Cu 2Se and Cu 2Se) hexagonal nanoplates from different precursors at low temperature

    NASA Astrophysics Data System (ADS)

    Kumar, Pushpendra; Singh, Kedar; Srivastava, O. N.

    2010-09-01

    Nonstoichiometric (Cu 2- xSe) and stoichiometric (CuSe, β-Cu 2Se and Cu 2Se) copper selenide hexagonal nanoplates have been synthesized using different general and convenient copper sources, e.g. copper chloride, copper sulphate, copper nitrate, copper acetate, elemental copper with elemental selenium, friendly ethylene glycol and hydrazine hydrate in a defined amount of water at 100 °C within 12 h adopting the solvothermal method. Phase analysis, purity and morphology of the product have been well studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray diffraction (EDAX) techniques. The structural and compositional analysis revealed that the products were of pure phase with corresponding atomic ratios. SEM, TEM and HRTEM analyses revealed that the nanoplates were in the range 200-450 nm and the as-prepared products were uniform and highly crystallized. The nanoplates consisted of {0 0 1} facets of top-bottom surfaces and {1 1 0} facets of the other six side surfaces. This new approach encompasses many advantages over the conventional solvothermal method in terms of product quality (better morphology control with high yield) and reaction conditions (lower temperatures). Copper selenide hexagonal nanoplates obtained by the described method could be potential building blocks to construct functional devices and solar cell. This work may open up a new rationale on designing the solution synthesis of nanostructures for materials possessing similar intrinsic crystal symmetry. On the basis of the carefully controlled experiments mentioned herein, a plausible formation mechanism of the hexagonal nanoplates was suggested and discussed. To the best of our knowledge, this is the first report on nonstoichiometric (Cu 2- xSe) as well as stoichiometric (CuSe, β-Cu 2Se and Cu 2Se) copper selenide hexagonal nanoplates with

  4. Visible light-driven CdSe nanotube array photocatalyst

    PubMed Central

    2013-01-01

    Large-scale CdSe nanotube arrays on indium tin oxide (ITO) glass have been synthesized using ZnO nanorod template. The strong visible light absorption in CdSe, its excellent photoresponse, and the large surface area associated with the tubular morphology lead to good visible light-driven photocatalytic capability of these nanotube arrays. Compared to freestanding nanoparticles, such one-piece nanotube arrays on ITO make it very convenient for catalyst recycling after their usage PMID:23680487

  5. Visible light-driven CdSe nanotube array photocatalyst

    NASA Astrophysics Data System (ADS)

    Zhu, Haojun; Li, Quan

    2013-05-01

    Large-scale CdSe nanotube arrays on indium tin oxide (ITO) glass have been synthesized using ZnO nanorod template. The strong visible light absorption in CdSe, its excellent photoresponse, and the large surface area associated with the tubular morphology lead to good visible light-driven photocatalytic capability of these nanotube arrays. Compared to freestanding nanoparticles, such one-piece nanotube arrays on ITO make it very convenient for catalyst recycling after their usage

  6. Visible light-driven CdSe nanotube array photocatalyst.

    PubMed

    Zhu, Haojun; Li, Quan

    2013-01-01

    Large-scale CdSe nanotube arrays on indium tin oxide (ITO) glass have been synthesized using ZnO nanorod template. The strong visible light absorption in CdSe, its excellent photoresponse, and the large surface area associated with the tubular morphology lead to good visible light-driven photocatalytic capability of these nanotube arrays. Compared to freestanding nanoparticles, such one-piece nanotube arrays on ITO make it very convenient for catalyst recycling after their usage. PMID:23680487

  7. Dislocation-driven growth of porous CdSe nanorods from CdSe.(ethylenediamine)0.5 nanorods

    NASA Astrophysics Data System (ADS)

    Kim, Hyung-Bae; Jang, Du-Jeon

    2015-12-01

    Porous CdSe nanorods having a novel flute-like morphology have been prepared facilely via the hydrothermal treatment of CdSe.(en)0.5 (en = ethylenediamine) nanorods as sacrificial templates. During the hydrothermal process, various crystalline imperfections such as stacking faults and twinning planes appear due to lattice mismatches between orthorhombic CdSe.(en)0.5 and hexagonal wurtzite porous CdSe nanorods and subsequently disappear to release mismatched strains. In the self-healing process of defects, due to the imbalance of in-and-out atomic diffusion, point defects of atomic vacancies are heavily generated in CdSe nanorods to produce volume defects of voids eventually. The photoluminescence of CdSe nanorods shifts to the red region and decreases in intensity with the increase of the hydrolysis time as surface states and selenium vacancies increase. The mean lifetime of photoluminescence increases with the increase of the hydrothermal-treatment time as the fractional amplitude of the surface-state-related component increases.Porous CdSe nanorods having a novel flute-like morphology have been prepared facilely via the hydrothermal treatment of CdSe.(en)0.5 (en = ethylenediamine) nanorods as sacrificial templates. During the hydrothermal process, various crystalline imperfections such as stacking faults and twinning planes appear due to lattice mismatches between orthorhombic CdSe.(en)0.5 and hexagonal wurtzite porous CdSe nanorods and subsequently disappear to release mismatched strains. In the self-healing process of defects, due to the imbalance of in-and-out atomic diffusion, point defects of atomic vacancies are heavily generated in CdSe nanorods to produce volume defects of voids eventually. The photoluminescence of CdSe nanorods shifts to the red region and decreases in intensity with the increase of the hydrolysis time as surface states and selenium vacancies increase. The mean lifetime of photoluminescence increases with the increase of the hydrothermal

  8. Oxidation resistance of Pb-Te-Se optical recording film

    NASA Astrophysics Data System (ADS)

    Terao, Motoyasu; Horigome, Shinkichi; Shigematsu, Kazuo; Miyauchi, Yasushi; Nakazawa, Masatoshi

    1987-08-01

    The dependence of oxidation resistance of metal-Te-Se optical recording films on film composition is investigated, as well as the effects of oxidation on laser beam recorded hole shape. The films are deposited by vacuum evaporation on substrates with a glass/UV light curing resin/cellulose nitrate structure. The role of Se in the film is to inhibit the oxidation. With at least 14% Se addition, film oxidation is completely inhibited even at 60 °C, relative humidity 95%. Depth profiles of elements in the recording films are analyzed by Auger electron and x-ray photoelectron spectroscopy to clarify the mechanisms of oxidation inhibition by Se addition. A selenium condensed layer is found at the inner part of an oxidized surface layer. The surface Te oxide layer and the Se-rich layer should inhibit the film inside from oxidizing. The role of the metallic elements In, Pb, Sn, Bi, and Sb in the film is to inhibit cracking and to decrease noise in reproduced signals by decreasing the size of crystal grains. Lead is found to be the best among these metallic elements, because the recorded hole shape is clean even when recorded after 15 days accelerated oxidation at 60 °C, relative humidity 95%. A very long storage life is expected for the Pb-Te-Se optical recording film.

  9. Microwave Conductivity Spectroscopy for Fe(Se,Te) Thin Films

    NASA Astrophysics Data System (ADS)

    Nabeshima, Fuyuki; Nagasawa, Kosuke; Asami, Daisuke; Sawada, Yuichi; Imai, Yoshinori; Maeda, Atsutaka

    Iron chalcogenide superconductors Fe(Se,Te) have very small ɛF and are considered to be in the BCS-BEC crossover regime. Since Ginzburg number, Gi =(kBTc /ɛF) 4 , which is the relative temperature width of the superconducting fluctuation region, is large for materials in the BCS-BEC crossover regime, large superconducting fluctuations are expected in Fe(Se,Te). In order to investigate superconducting fluctuations in these materials we have performed microwave conductivity spectroscopy on Fe(Se,Te) thin films. Superfluid density of an Fe(Se,Te) film with Tczero =17 K took finite values above 25 K. This temperature is much higher than Tc estimated by the dc measurement, suggesting strong superconducting fluctuations in Fe(Se,Te). A dynamic scaling analysis of complex fluctuation conductivity revealed that the superconducting fluctuations of Fe(Se,Te) exhibit a 2-dimensional behavior, while BKT transition was not observed. We will also report on the thickness dependence and the Te content dependence of the superconducting fluctuation Partially supported by the Japan Society for the Promotion of Science (JSPS) Research Fellowship for Young Scientists and by JSPS KAKENHI Grant Numbers 15K17697.

  10. Electrodeposition and growth mechanism of SnSe thin films

    NASA Astrophysics Data System (ADS)

    Biçer, Mustafa; Şişman, İlkay

    2011-01-01

    Tin selenide (SnSe) thin films were electrochemically deposited onto Au(1 1 1) substrates from an aqueous solution containing SnCl2, Na2SeO3, and EDTA at room temperature (25 °C). The electrochemical behaviors and the codeposition potentials of Sn and Se were explored by cyclic voltammetry. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and UV-vis absorption spectroscopy were employed to characterize the thin films. When the electrodeposition potential increased, the Se content in the films decreased. It was found that the stoichiometric SnSe thin films could be obtained at -0.50 V. The as-deposited films were crystallized in the preferential orientation along the (1 1 1) plane. The morphologies of SnSe films could be changed from spherical grains to platelet-like particles as the deposition potential increases. The SEM investigations show that the film growth proceeds via nucleation, growth of film layer and formation of needle-like particles on the overlayer of the film. The optical absorption study showed the film has direct transition with band gap energy of 1.3 eV.

  11. STM study on the structures of SnSe surfaces

    NASA Astrophysics Data System (ADS)

    Kim, Tae Hoon; Kim, Sang-Ui; Thi Ly, Trinh; Duong, Anh Tuan; Cho, Sunglae; Rhim, S. H.; Kim, Jungdae

    SnSe is a 2 dimensional layered material, and each layer is coupled by van deer Waals forces allowing very easy cleaving though the layer surfaces. SnSe has been studied for various potential applications because of its high stability and elemental abundance in earth. Recently, it was also reported that bulk SnSe has an excellent thermoelectric property of ZT =2.6 at 923 K along the b axis (Zhao et al., Nature 508 373 (2014)). The surface of a single crystal SnSe was studied via a home-built low temperature scanning tunneling microscopy (STM). Clear atomic images of SnSe surfaces were observed at the filled and empty state measurements, and detail atomic structures were analyzed by comparing with DFT simulations. We found that the atomic image of SnSe surfaces measured by STM is not trivial to understand. Only Sn atoms were visible on STM topographic images for the both of filled and empty state probing. This work was supported by the National Research Foundation of Korea(NRF) [Nos. NRF-2013R1A1A1008724, NRF-2009-0093818, and NRF-2014R1A4A1071686].

  12. Identification QTLs Controlling Genes for Se Uptake in Lentil Seeds

    PubMed Central

    Ates, Duygu; Sever, Tugce; Aldemir, Secil; Yagmur, Bulent; Temel, Hulya Yilmaz; Kaya, Hilal Betul; Alsaleh, Ahmad; Kahraman, Abdullah; Ozkan, Hakan; Vandenberg, Albert; Tanyolac, Bahattin

    2016-01-01

    Lentil (Lens culinaris Medik.) is an excellent source of protein and carbohydrates and is also rich in essential trace elements for the human diet. Selenium (Se) is an essential micronutrient for human health and nutrition, providing protection against several diseases and regulating important biological systems. Dietary intake of 55 μg of Se per day is recommended for adults, with inadequate Se intake causing significant health problems. The objective of this study was to identify and map quantitative trait loci (QTL) of genes controlling Se accumulation in lentil seeds using a population of 96 recombinant inbred lines (RILs) developed from the cross “PI 320937” × “Eston” grown in three different environments for two years (2012 and 2013). Se concentration in seed varied between 119 and 883 μg/kg. A linkage map consisting of 1,784 markers (4 SSRs, and 1,780 SNPs) was developed. The map spanned a total length of 4,060.6 cM, consisting of 7 linkage groups (LGs) with an average distance of 2.3 cM between adjacent markers. Four QTL regions and 36 putative QTL markers, with LOD scores ranging from 3.00 to 4.97, distributed across two linkage groups (LG2 and LG5) were associated with seed Se concentration, explaining 6.3–16.9% of the phenotypic variation. PMID:26978666

  13. Optical Characterization of Bulk ZnSeTe Solid Solutions

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Feth, S.; Zhu, Shen; Lehoczky, S. L.; Wang, Ling Jun

    2000-01-01

    Optical characterization was performed on wafers sliced from crystals of ZnSe, ZnTe, and ZnSe(1-x)Te(x)(0 less than x less than 0.4) grown by physical vapor transport. Energy band gaps at room temperature were determined from optical transmission measurements on 11 wafers. A best fit curve to the band gap versus composition x data gives a bowing parameter of 1.45. This number lies between the value of 1.23 determined previously on ZnSeTe bulk crystals and the value of 1.621 reported on ZnSeTe epilayers. Low-temperature photoluminescence (PL) spectra were measured on six samples. The spectra of ZnSe and ZnTe were dominated by near band edge emissions and no deep donor-acceptor pairs were observed. The PL spectrum exhibited a broad emission for each of the ZnSe(1-x)Te(x) samples, 0.09 less than x less than 0.39. For x=0.09, this emission energy is about 0.2 eV lower than the band gap energy measured at low temperature. As x increases the energy discrepancy gradually decreases and reduces to almost zero at x=0.4. The single broad PL emission spectra and the spectra measured as a function of temperature were interpreted as being associated with the exciton bound to Te clusters because of the high Te content in these samples.

  14. Pseudodynamic imaging of the temporomandibular joint: SE versus GE sequences

    SciTech Connect

    Masui, Takayuki; Isoda, Haruo; Mochizuki, Takao

    1996-05-01

    Pseudodynamic MR imaging of the temporomandibular joints (TMJs) has been used for the evaluation of the functional aspects of the TMJs. To evaluate the value of T1-weighted spin-echo (SE) and gradient-echo (GE) techniques, both techniques were performed in 9 asymptomatic (mean 25.7 years, 22-32 years), and 25 symptomatic (mean 44.9 years, 20-71 years) subjects with signs and symptoms of internal derangement or osteoarthrosis of the TMJs. The imaging time for the SE (180 ms / 15 ms / 110{degrees} repetition time / echo time /flip angle) and GE (fast low angle shot; FLASH, 90 ms / 12 ms / 40{degrees}) sequences was 27 and 28 s, respectively. In asymptomatic and symptomatic subjects, the confidence of the identification of the meniscal position was better on SE than GE images (3.6 {+-} 0.6 vs. 2.9 {+-} 0.9, p < 0.01, 3.2 {+-} 0.8 vs. 2.8 {+-} 0.8, p < 0.05), respectively and the sizes of the menisci were bigger on SE than GE images. The delineation of the condylar cortex was better on GE than SE images. For pseudodynamic imaging display of the TMJs, the SE images might be better than GE images to provide the stable recognition of the menisci. 17 refs., 7 figs., 5 tabs.

  15. Identification QTLs Controlling Genes for Se Uptake in Lentil Seeds.

    PubMed

    Ates, Duygu; Sever, Tugce; Aldemir, Secil; Yagmur, Bulent; Temel, Hulya Yilmaz; Kaya, Hilal Betul; Alsaleh, Ahmad; Kahraman, Abdullah; Ozkan, Hakan; Vandenberg, Albert; Tanyolac, Bahattin

    2016-01-01

    Lentil (Lens culinaris Medik.) is an excellent source of protein and carbohydrates and is also rich in essential trace elements for the human diet. Selenium (Se) is an essential micronutrient for human health and nutrition, providing protection against several diseases and regulating important biological systems. Dietary intake of 55 μg of Se per day is recommended for adults, with inadequate Se intake causing significant health problems. The objective of this study was to identify and map quantitative trait loci (QTL) of genes controlling Se accumulation in lentil seeds using a population of 96 recombinant inbred lines (RILs) developed from the cross "PI 320937" × "Eston" grown in three different environments for two years (2012 and 2013). Se concentration in seed varied between 119 and 883 μg/kg. A linkage map consisting of 1,784 markers (4 SSRs, and 1,780 SNPs) was developed. The map spanned a total length of 4,060.6 cM, consisting of 7 linkage groups (LGs) with an average distance of 2.3 cM between adjacent markers. Four QTL regions and 36 putative QTL markers, with LOD scores ranging from 3.00 to 4.97, distributed across two linkage groups (LG2 and LG5) were associated with seed Se concentration, explaining 6.3-16.9% of the phenotypic variation. PMID:26978666

  16. (77)Se nuclear spin-lattice relaxation in binary Ge-Se glasses: insights into floppy versus rigid behavior of structural units.

    PubMed

    Sen, Sabyasachi; Kaseman, Derrick C; Hung, Ivan; Gan, Zhehong

    2015-04-30

    The mechanism of (77)Se nuclear spin-lattice relaxation is investigated in binary Ge-Se glasses. The (77)Se nuclides in Se-Se-Se chain sites relax faster via dipolar coupling fluctuation compared to those in Ge-Se-Ge sites shared by GeSe4 tetrahedra that relax slower via the fluctuation of the chemical shift anisotropy. The relaxation rate for the Se-Se-Se sites decreases markedly with increasing magnetic field, whereas that for the Ge-Se-Ge sites displays no appreciable dependence on the magnetic field such that the extent of differential relaxation between the two Se environments becomes small at high fields on the order of 19.6 T. The corresponding dynamical correlation time is three orders of magnitude shorter (∼10(-9) s) for the Se-Se-Se sites, compared to that for the Ge-Se-Ge sites (∼10(-6) s). The large decoupling in the time scale between these Se environments provides direct experimental support to the commonly made assumption that the selenium chains are mechanically floppy, and the interconnected GeSe4 tetrahedra form the rigid elements in the selenide glass structure. PMID:25848959

  17. Electronic structure and optical absorption spectra of CdSe covered with ZnSe and ZnS epilayers

    NASA Astrophysics Data System (ADS)

    Yun, So Jeong; Lee, Geunsik; Kim, Jai Sam; Shin, Seung Koo; Yoon, Young-Gui

    2006-02-01

    Using the first-principles methods we compute the electronic structure and the absorption spectra for a wurtzite CdSe (0001) slab covered with zincblende ZnSe and ZnS epilayers. For each structure we compute the DOS and the imaginary part of the dielectric function. We find that the semiconductor passivation shifts the 'near Fermi-level' states of the bare CdSe slab down to lower energy levels. The migration suggests the decrease of surface effects and energy loss. We observe the substantial reduction of the abnormal peaks in the absorption spectra of the bare CdSe slab, which seems to be a consequence of the DOS migration. This is consistent with the experimental results that a proper passivation enhance the luminescence efficiency. We also study the case that the epilayer surface is terminated with PH 3 and find the PH 3 passivation also reduces the surface state to some extent.

  18. Magneto-optical studies of ensembles of semimagnetic self-organized Cd(Mn)Se/Zn(Mn)Se Quantum Dots

    SciTech Connect

    Reshina, I. I.; Ivanov, S. V.; Toropov, A. A.

    2013-12-04

    Ensembles of Cd(Mn)Se/ZnSe and CdSe/Zn(Mn)Se semimagnetic self-organized quantum dots with different Mn content have been studied by photoluminescence and resonant Raman scattering under strong magnetic fields in Faraday and Voigt geometries and with spectral and polarization selective excitation. Electron spin-flip Raman scattering has been observed in Voigt geometry in the structures with large Mn content. Narrow exciton peaks completely σ{sup −}σ{sup +} polarized have been observed under selective excitation in Faraday geometry in the structures with medium and small Mn content. A number of specific effects manifested themselves in the structures with a smallest Mn content where no Zeeman shift of the photoluminescence bands was observed.

  19. Optical properties of (In2Se3)1- x ·(CuIn5Se8) x solid solutions

    NASA Astrophysics Data System (ADS)

    Bodnar, I. V.

    2010-11-01

    Single crystals of In2Se3 and CuIn5Se8 compounds and (In2Se3)1-x·(CuIn5Se8)x solid solutions have been grown from the melt using the Bridgman method and their composition and structure determined. It is shown that the crystals have n-type conductivity. Their transmission spectra were studied in the self-absorption edge region at 80 and 295 K. Based on the spectral measurements, the band gap width (Eg) was determined and the band gap concentration dependences were plotted. It is found that Eg varies with the x composition nonlinearly. Using the dielectric model of Van Vechten-Bergstresser and the Hill-Richardson pseudo potential model, Eg(x) was calculated theoretically.

  20. Anisotropy of chemical transformation from In2Se3 to CuInSe2 nanowires through solid state reaction.

    PubMed

    Schoen, David T; Peng, Hailin; Cui, Yi

    2009-06-17

    In(2)Se(3) nanowires synthesized by the VLS technique are transformed by solid-state reaction with copper into high-quality single-crystalline CuInSe(2) nanowires. The process is studied by in situ transmission electron microscopy. The transformation temperature exhibits a surprising anisotropy, with In(2)Se(3) nanowires grown along their [0001] direction transforming at a surprisingly low temperature of 225 degrees C, while nanowires in a [11(2)0] orientation require a much higher temperature of 585 degrees C. These results offer a route to the synthesis of CuInSe(2) nanowires at a relatively low temperature as well as insight into the details of a transformation commonly used in the fabrication of thin-film solar cells. PMID:19507900

  1. Sulfur gradient-driven Se diffusion at the CdS/CuIn(S,Se){sub 2} solar cell interface

    SciTech Connect

    Weinhardt, L.; Morkel, M.; Baer, M.; Pookpanratana, S.; Heske, C.; Niesen, T. P.; Karg, F.; Ramanathan, K.; Contreras, M. A.; Noufi, R.; Umbach, E.

    2010-05-03

    The diffusion behavior of Se at the CdS/Cu(In,Ga)(S,Se){sub 2} thin film solar cell interface was investigated by x-ray photoelectron spectroscopy and x-ray excited Auger electron spectroscopy. Buffer/absorber structures with S/Se ratios between zero and three at the initial Cu(In,Ga)(S,Se){sub 2} surface were analyzed. Samples from a high-efficiency laboratory process (NREL) as well as from an industrial large-area process (AVANCIS) were investigated. We find selenium diffusion into the CdS buffer layer, the magnitude of which strongly depends on the S content at the absorber surface. The associated modification of the heterojunction partners has significant impact on the electronic structure at the interface.

  2. Epitaxial growth and photoluminescence excitation spectroscopy of CdSe quantum dots in (Zn,Cd)Se barrier

    NASA Astrophysics Data System (ADS)

    Piwowar, J.; Pacuski, W.; Smoleński, T.; Goryca, M.; Bogucki, A.; Golnik, A.; Nawrocki, M.; Kossacki, P.; Suffczyński, J.

    2016-05-01

    Design, epitaxial growth, and resonant spectroscopy of CdSe Quantum Dots (QDs) embedded in an innovative (Zn,Cd)Se barrier are presented. The (Zn,Cd)Se barrier enables shifting of QDs energy emission down to 1.87 eV, that is below the energy of Mn$^{2+}$ ions internal transition (2.1 eV). This opens a perspective for implementation of epitaxial CdSe QDs doped with several Mn ions as, e. g., the light sources in high quantum yield magnetooptical devices. Polarization resolved Photoluminescence Excitation measurements of individual QDs reveal sharp ($\\Gamma <$ 150 $\\mu$eV) maxima and transfer of optical polarization to QD confining charged exciton state with efficiency attaining 26 %. The QD doping with single Mn$^{2+}$ ions is achieved.

  3. Fe:ZnSe and Fe:ZnMgSe lasers pumped by Er:YSGG radiation

    NASA Astrophysics Data System (ADS)

    Jelínková, H.; Doroshenko, M. E.; Jelínek, M.; Å ulc, J.; Němec, M.; Kubeček, V.; Zagoruiko, Y. A.; Kovalenko, N. O.; Gerasimenko, A. S.; Puzikov, V. M.; Komar, V. K.

    2015-02-01

    The aim of the presented work was to design and characterize bulk Fe:ZnSe and Fe:Zn(1-x)Mg(x)Se (Mg content x = 0.19) lasers coherently pumped by electro-optically Q-switched Er:YSGG laser. This laser generated pumping radiation at 2.79 μm with the maximum energy of 50 mJ in 80 ns long pulse with the repetition-rate of 1 Hz. The 25 mm long optical resonator of Fe:ZnSe or Fe:ZnMgSe lasers was formed by a plan dichroic pumping mirror and a concave output coupler (r = 200 mm) with reflectivity 88 % @ 4-5 μm. Both lasers were operated at room temperature. Measured maximum output energy/slope efficiency in respect to the absorbed energy was ~ 3.8 mJ/42 % for the Fe:ZnSe laser and ~ 0.48 mJ/10 % for the Fe:ZnMgSe laser. The generated output pulse duration was 150 - 200 ns in both cases and the output beam spatial profile was approximately gaussian. The Fe:ZnSe and Fe:ZnMgSe lasers output spectra line-width was ~ 200 nm (FWHM) and their maxima were centered at 4.45 μm and 4.8 μm, respectively. The results were compared to pumping the same crystals by a Q-switched Er:YAG laser in similar conditions.

  4. Dislocation-driven growth of porous CdSe nanorods from CdSe·(ethylenediamine)(0.5) nanorods.

    PubMed

    Kim, Hyung-Bae; Jang, Du-Jeon

    2016-01-01

    Porous CdSe nanorods having a novel flute-like morphology have been prepared facilely via the hydrothermal treatment of CdSe·(en)0.5 (en = ethylenediamine) nanorods as sacrificial templates. During the hydrothermal process, various crystalline imperfections such as stacking faults and twinning planes appear due to lattice mismatches between orthorhombic CdSe·(en)0.5 and hexagonal wurtzite porous CdSe nanorods and subsequently disappear to release mismatched strains. In the self-healing process of defects, due to the imbalance of in-and-out atomic diffusion, point defects of atomic vacancies are heavily generated in CdSe nanorods to produce volume defects of voids eventually. The photoluminescence of CdSe nanorods shifts to the red region and decreases in intensity with the increase of the hydrolysis time as surface states and selenium vacancies increase. The mean lifetime of photoluminescence increases with the increase of the hydrothermal-treatment time as the fractional amplitude of the surface-state-related component increases. PMID:26615794

  5. Dirac cone shift and potential fluctuations in a passivated In2Se3/Bi2Se3 topological interface state

    NASA Astrophysics Data System (ADS)

    Jenkins, Gregory S.; Sushkov, A. B.; Schmadel, D. C.; Kim, M.-H.; Drew, H. D.; Koblmueller, G.; Bichler, M.; Bansal, N.; Brahlek, M.; Oh, S.

    2013-03-01

    The topological interface state of Bi2Se3 capped with In2Se3 is measured by gated THz cyclotron resonance. An observed shift of 70 meV in the position of the Dirac point towards mid-gap due to the physical properties of the trivial insulator In2Se3 on Bi2Se3 opens new possibilities in tailoring Dirac cone properties in topological insulators. Modulating and sweeping a semi-transparant gate while probing at terahertz frequencies in magnetic field enables characterization of the burried In2Se3/Bi2Se3 topological interface state, even in the presence of significant bulk conductivity. Near the Dirac point, the mobility is 3500 cm2/V .s with potential fluctuations of 60 meV. The scattering rate shows a precipitous drop with Fermi energy indicating decoupling of the surface states from bulk states. At Fermi energies above the conduction band edge, a plateau is observed in the real part of the Faraday angle that is 80 times flatter than the step size expected from a single Landau Level, quantized in units of the fine structure constant. The work at UMD is supported by NSF DMR-1104343 and DOE DE-SC0005436

  6. Growth and characterization of PbSe and Pb1-xSnxSe on Si (100)

    NASA Astrophysics Data System (ADS)

    Sachar, H. K.; Chao, I.; McCann, P. J.; Fang, X. M.

    1999-05-01

    PbSe and Pb1-xSnxSe layers, with thicknesses ranging from 1 to 5 μm, were grown by liquid phase epitaxy on Si (100) substrates using PbSe/BaF2/CaF2 buffer layers grown by molecular beam epitaxy. Optical Nomarski characterization revealed excellent surface morphologies and good growth solution wipeoffs. Although most PbSe layers were free of cracks over the entire 8×8 mm2 substrate area, ternary Pb1-xSnxSe layers exhibited varying crack densities ranging from zero in the center of samples to over 30 cracks/cm at the edges. High resolution x-ray diffraction (HRXRD) measurements of crack-free PbSe layers showed a residual in-plane tensile strain of 0.21% indicating that most of the 0.74% thermal expansion mismatch strain was absorbed by plastic deformation. HRXRD full width half maxima values of less than 200 arc sec showed that these layers also had high crystalline quality. Fourier transform infrared transmission measurements at room temperature and 110 K showed absorption edges in the range of 270-80 meV, depending on temperature and tin content. This work shows that these materials should be suitable for fabrication of mid-infrared devices covering the 4.6-16 μm spectral range.

  7. BIOAVAILABILITY OF SELENIUM FROM MEAT AND BROCCOLI AS DETERMINED BY RETENTION AND DISTRIBUTION OF SE75

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Meat is the single greatest source of selenium (Se) in the North American diet. Although not naturally enriched in Se, broccoli will accumulate Se when grown on high Se soils. Previous reports have demonstrated that Se from meat is highly bioavailable whereas Se from broccoli has poor bioavailabil...

  8. EMPaSE: an Extensible Multi-Paradigm Simulation Environment

    Energy Science and Technology Software Center (ESTSC)

    2010-08-05

    EMPaSE is a hierarchical, extensible, modular modeling environment for developing and running hybrid simulations of sequential-modular, systems dynamics, discrete-event, and agent-based paradigms. It contains two principle components: a multi-paradigm simulation engine and a graphical user interface. EMPaSE models are defined through a hierarchically-defined set of computational modules that define the simulation logic. Inter-module communication occurs through two complimentary systems: pull-based "ports" for general computation patterns and push-based "plugs" for event processing. Entities (i.e. agents) withinmore » the simulation operate within an abstract multi-network environment. The EMPaSE simulation engine is designed around a flexible plug-in architecture, allowing simulations to import computational modules, engine customizations, and interfaces to external applications from independent plug-in libraries. The EMPaSE GUI environment provides an environment for graphically constructing, executing, and debugging EMPaSE models. As with the simulation engine, the GUI is constructed on top of an extensible architecture that supports rapid customization of the user experience through external plug-in libraries.« less

  9. Superconductivity and wire fabrication of FeSe family

    NASA Astrophysics Data System (ADS)

    Ozaki, Toshinori; Deguchi, Keita; Mizuguchi, Yoshikazu; Kumakura, Hiroaki; Takano, Yoshihiko; National InstituteMaterials Science Team

    2011-03-01

    The 11 family is an fascinating iron-based superconducting system for not only elucidation of superconducting mechanism but also technological applications because of the simplest crystal structures, the less toxic and high critical field. Recently, we found that the superconductivity appears in the specimen immersed in alcoholic beverages. Focused on the pressure dependence of Se height from Fe layer in FeSe, we found that the Tc is correlated to Se height. Moreover, the anion height dependence of Tc for all FeAs-based superconductor obeyed a universal curve with a peak around 1.38 AA}. We succeeded in observing the transport Jc in the single- and 7-core wires of FeTe x Se 1-x superconductor using an in-situ powder-in-tube (PIT) method. The Jc values in single- and 7-core wire are as high as 159 A/cm2 and 100 A/cm2 at 4.2 K, respectively. It is considered that the optimization of the composition, together with the improvement of the grain boundary in FeTe x Se 1-x superconducting wires, will lead to higher Jc .

  10. Monotherapy or Polytherapy for First-Line Treatment of SE?

    PubMed

    Alvarez, Vincent; Rossetti, Andrea O

    2016-02-01

    Status epilepticus (SE) is one of the most frequent neurologic emergencies, and a rapid and effective treatment is warranted. Current guidelines recommend a stepwise approach using a sequence of different antiepileptic drugs with benzodiazepines (BZD) being the first treatment proposed. To provide the more effective treatment as soon as possible, some authors have suggested using a combined polytherapy as first-line treatment. Strong evidence supports the use of benzodiazepines, mostly lorazepam and midazolam as initial monotherapy treatment for SE. Insufficient data are available to support the use of nonsedating antiepileptic drugs as phenytoin, valproic acid, or levetiracetam without a previous benzodiazepine administration. Studies assessing the role of a combined initial therapy are rare, if not missing. Moreover, owing the wide range of SE etiologies, a "one fits all" initial polytherapy seems difficult to achieve. After reviewing the available evidence, guidelines, and current practices regarding monotherapy and polytherapy as first-line treatment in SE in adults, the authors propose a rational algorithm for early antiseizure treatment in SE. PMID:26840871

  11. Transition probabilities in neutron-rich Se,8684

    NASA Astrophysics Data System (ADS)

    Litzinger, J.; Blazhev, A.; Dewald, A.; Didierjean, F.; Duchêne, G.; Fransen, C.; Lozeva, R.; Sieja, K.; Verney, D.; de Angelis, G.; Bazzacco, D.; Birkenbach, B.; Bottoni, S.; Bracco, A.; Braunroth, T.; Cederwall, B.; Corradi, L.; Crespi, F. C. L.; Désesquelles, P.; Eberth, J.; Ellinger, E.; Farnea, E.; Fioretto, E.; Gernhäuser, R.; Goasduff, A.; Görgen, A.; Gottardo, A.; Grebosz, J.; Hackstein, M.; Hess, H.; Ibrahim, F.; Jolie, J.; Jungclaus, A.; Kolos, K.; Korten, W.; Leoni, S.; Lunardi, S.; Maj, A.; Menegazzo, R.; Mengoni, D.; Michelagnoli, C.; Mijatovic, T.; Million, B.; Möller, O.; Modamio, V.; Montagnoli, G.; Montanari, D.; Morales, A. I.; Napoli, D. R.; Niikura, M.; Pollarolo, G.; Pullia, A.; Quintana, B.; Recchia, F.; Reiter, P.; Rosso, D.; Sahin, E.; Salsac, M. D.; Scarlassara, F.; Söderström, P.-A.; Stefanini, A. M.; Stezowski, O.; Szilner, S.; Theisen, Ch.; Valiente Dobón, J. J.; Vandone, V.; Vogt, A.

    2015-12-01

    Reduced quadrupole transition probabilities for low-lying transitions in neutron-rich Se,8684 are investigated with a recoil distance Doppler shift (RDDS) experiment. The experiment was performed at the Istituto Nazionale di Fisica Nucleare (INFN) Laboratori Nazionali di Legnaro using the Cologne Plunger device for the RDDS technique and the AGATA Demonstrator array for the γ -ray detection coupled to the PRISMA magnetic spectrometer for an event-by-event particle identification. In 86Se the level lifetime of the yrast 21+ state and an upper limit for the lifetime of the 41+ state are determined for the first time. The results of 86Se are in agreement with previously reported predictions of large-scale shell-model calculations using Ni78-I and Ni78-II effective interactions. In addition, intrinsic shape parameters of lowest yrast states in 86Se are calculated. In semimagic 84Se level lifetimes of the yrast 41+ and 61+ states are determined for the first time. Large-scale shell-model calculations using effective interactions Ni78-II, JUN45, jj4b, and jj4pna are performed. The calculations describe B (E 2 ;21+→01+) and B (E 2 ;61+→41+) fairly well and point out problems in reproducing the experimental B (E 2 ;41+→21+) .

  12. Heterojunctions of model CdTe/CdSe mixtures

    DOE PAGESBeta

    van Swol, Frank; Zhou, Xiaowang W.; Challa, Sivakumar R.; Martin, James E.

    2015-03-18

    We report on the strain behavior of compound mixtures of model group II-VI semiconductors. We use the Stillinger-Weber Hamiltonian that we recently introduced, specifically developed to model binary mixtures of group II-VI compounds such as CdTe and CdSe. We also employ molecular dynamics simulations to examine the behavior of thin sheets of material, bilayers of CdTe and CdSe. The lattice mismatch between the two compounds leads to a strong bending of the entire sheet, with about a 0.5 to 1° deflection between neighboring planes. To further analyze bilayer bending, we introduce a simple one-dimensional model and use energy minimization tomore » find the angle of deflection. The analysis is equivalent to a least-squares straight line fit. We consider the effects of bilayers which are asymmetric with respect to the thickness of the CdTe and CdSe parts. We thus learn that the bending can be subdivided into four kinds depending on the compressive/tensile nature of each outer plane of the sheet. We use this approach to directly compare our findings with experimental results on the bending of CdTe/CdSe rods. To reduce the effects of the lattice mismatch we explore diffuse interfaces, where we mix (i.e. alloy) Te and Se, and estimate the strain response.« less

  13. Heterojunctions of model CdTe/CdSe mixtures

    SciTech Connect

    van Swol, Frank; Zhou, Xiaowang W.; Challa, Sivakumar R.; Martin, James E.

    2015-03-18

    We report on the strain behavior of compound mixtures of model group II-VI semiconductors. We use the Stillinger-Weber Hamiltonian that we recently introduced, specifically developed to model binary mixtures of group II-VI compounds such as CdTe and CdSe. We also employ molecular dynamics simulations to examine the behavior of thin sheets of material, bilayers of CdTe and CdSe. The lattice mismatch between the two compounds leads to a strong bending of the entire sheet, with about a 0.5 to 1° deflection between neighboring planes. To further analyze bilayer bending, we introduce a simple one-dimensional model and use energy minimization to find the angle of deflection. The analysis is equivalent to a least-squares straight line fit. We consider the effects of bilayers which are asymmetric with respect to the thickness of the CdTe and CdSe parts. We thus learn that the bending can be subdivided into four kinds depending on the compressive/tensile nature of each outer plane of the sheet. We use this approach to directly compare our findings with experimental results on the bending of CdTe/CdSe rods. To reduce the effects of the lattice mismatch we explore diffuse interfaces, where we mix (i.e. alloy) Te and Se, and estimate the strain response.

  14. EMPaSE: an Extensible Multi-Paradigm Simulation Environment

    SciTech Connect

    Siirola, John; Spotz, William; & Warrender, Christina

    2010-08-05

    EMPaSE is a hierarchical, extensible, modular modeling environment for developing and running hybrid simulations of sequential-modular, systems dynamics, discrete-event, and agent-based paradigms. It contains two principle components: a multi-paradigm simulation engine and a graphical user interface. EMPaSE models are defined through a hierarchically-defined set of computational modules that define the simulation logic. Inter-module communication occurs through two complimentary systems: pull-based "ports" for general computation patterns and push-based "plugs" for event processing. Entities (i.e. agents) within the simulation operate within an abstract multi-network environment. The EMPaSE simulation engine is designed around a flexible plug-in architecture, allowing simulations to import computational modules, engine customizations, and interfaces to external applications from independent plug-in libraries. The EMPaSE GUI environment provides an environment for graphically constructing, executing, and debugging EMPaSE models. As with the simulation engine, the GUI is constructed on top of an extensible architecture that supports rapid customization of the user experience through external plug-in libraries.

  15. Anomalous ion damage behavior in ZnSe

    SciTech Connect

    Yu, K.M.; Bourret-Courchesne, E.D.

    1996-09-01

    The structural properties of ZnSe damaged by 180 keV Zn ions are studied for a wide range of ion dose (10{sup 13}{endash}10{sup 16}/cm{sup 2}) using ion channeling techniques. We found that ZnSe cannot be rendered amorphous by implantation at either room temperature (RT) or liquid nitrogen temperature (LNT) in the range of doses investigated. For lower ion doses (10{sup 13}{endash}10{sup 14}/cm{sup 2}), ZnSe samples implanted at LNT result in less damage than those implanted at RT by as much as an order of magnitude. Moreover, no simple point defect or amorphous clusters are found in the implanted ZnSe. For high implant doses ({approx_gt}10{sup 14}/cm{sup 2}), the samples are still monocrystalline but become highly defective with extended defects. Our results also suggests that point defects in the ZnSe created during implantation may be mobile at or below RT and that they may migrate rapidly under ion irradiation. {copyright} {ital 1996 American Institute of Physics}

  16. First-principles study of Se-intercalated graphite

    SciTech Connect

    BARTKOWIAK,M.; MODINE,NORMAND A.; SOFO,J.O.; MAHAN,G.D.

    2000-05-11

    Se-intercalated graphite compounds (Se-GICs) are considered as promising candidates for room-temperature thermoelectric cooling devices. Here the authors analyze the crystallographic structure and electronic properties of these materials within the framework of density-functional theory. First, the Adaptive-Coordinate Real-space Electronic Structure (ACRES) code is used to determine the stable structure of a representative stage-2 Se-GIC by relaxing atomic positions. The stable configuration is found to be a pendant-type structure, in which each selenium is bonded covalently to two atoms within the same carbon layer, causing a local distortion of the in-plane conjugation of the graphite. Then, they use the full potential linearized augmented plane wave (FP-LAPW) method to calculate the electronic band structure of the material and discuss its properties. Near the Fermi energy E{sub F}, there are wide bands originating from the host graphitic electronic structure and a few very narrow bands mainly of Se 4p character. The latter bands contribute to high peaks in the density of states close to E{sub F}. They show that this feature, although typical of many good thermoelectrics, does not necessarily imply high thermopower in the case of Se-GICs.

  17. Crystallographic and optical properties and band structures of CuInSe2, CuIn3Se5, and CuIn5Se8 phases in Cu-poor Cu2Se-In2Se3 pseudo-binary system

    NASA Astrophysics Data System (ADS)

    Maeda, Tsuyoshi; Gong, Weiyan; Wada, Takahiro

    2016-04-01

    We prepared CuInSe2 and Cu-poor Cu-In-Se (CIS) phases such as CuIn3Se5 and CuIn5Se8 in the composition of (1 - x)Cu2Se-(x)In2Se3 with 0.5 ≤ x ≤ 1.0. The crystal structure of the sample changed from chalcopyrite-type CuInSe2 to hexagonal CuIn5Se8 through stannite-type CuIn3Se5 with increasing x (decreasing Cu/In ratio). The band-gap energies of Cu-poor CIS samples, i.e., CuIn3Se5 (1.17 eV) and CuIn5Se8 (1.22-1.24 eV), are larger than that of chalcopyrite-type CuInSe2 (0.99 eV). The energy levels of the valence band maxima (VBMs) were estimated from the ionization energy by photoemission yield spectroscopy (PYS) measurements. The energy levels of the VBMs of the Cu-poor CIS samples decrease rapidly with decreasing Cu/In ratio. The ionization energy of stannite-type CuIn3Se5 is 0.4 eV larger than that of chalcopyrite-type CuInSe2. The ionization energy of CuIn5Se8 is 0.1-0.3 eV larger than that of CuIn3Se5. These results show that the energy position of the VBM from the vacuum level of Cu-poor CIS phases, such as CuIn3Se5 and CuIn5Se8, is deeper than that of CuInSe2. To understand the electronic structure of Cu-poor CIS compounds, we performed first-principles band structure calculations on stannite-type CuIn5Se8 and a reference compound, tetragonal chalcopyrite-type CuInSe2, using the HSE06 nonlocal screened hybrid density functional. The calculated band-gap energy of tetragonal stannite-type CuIn5Se8 (1.19 eV) is larger than that of chalcopyrite-type CuInSe2 (0.94 eV).

  18. Reverse Monte Carlo simulation of Se{sub 80}Te{sub 20} and Se{sub 80}Te{sub 15}Sb{sub 5} glasses

    SciTech Connect

    Abdel-Baset, A. M.; Rashad, M.; Moharram, A. H.

    2013-12-16

    Two-dimensional Monte Carlo of the total pair distribution functions g(r) is determined for Se{sub 80}Te{sub 20} and Se{sub 80}Te{sub 15}Sb{sub 5} alloys, and then it used to assemble the three-dimensional atomic configurations using the reverse Monte Carlo simulation. The partial pair distribution functions g{sub ij}(r) indicate that the basic structure unit in the Se{sub 80}Te{sub 15}Sb{sub 5} glass is di-antimony tri-selenide units connected together through Se-Se and Se-Te chain. The structure of Se{sub 80}Te{sub 20} alloys is a chain of Se-Te and Se-Se in addition to some rings of Se atoms.

  19. Surface half-metallicity of half-Heusler compound FeCrSe and interface half-metallicity of FeCrSe/GaP

    NASA Astrophysics Data System (ADS)

    Khalaf Al-zyadi, Jabbar M.; Jolan, Mudhahir H.; Yao, Kai-Lun

    2016-04-01

    Recent studies showed that half-Heusler FeCrSe exhibits half-metallic ferromagnetism (Huang et al. [20]). In this paper, we investigate extensively the electronic, magnetic, and half-metallic properties of the half-Heusler alloy FeCrSe (111) and (001) surfaces and the interface with GaP (111) substrate by using the first-principles calculations within the density functional theory. The atomic density of states demonstrates that the half-me tallicity verified in the bulk FeCrSe is maintained at the CrSe-terminated (001) and Se-terminated (111) surfaces, but lost at both Cr- and Fe-terminated (111) surfaces and the Fe-terminated (001) surface. Alternatively, for the interface of FeCrSe/GaP (111), the bulk half-metallicity is destroyed at Se-P configuration while Se-Ga interface and subinterface show nearly 100% spin polarization. Moreover, the calculated interfacial adhesion energies exhibit that Se-Ga shape is more stable than the Se-P one. The calculated magnetic moments of Se, Ga at the Se-Ga (111) interface and P at the Se-P (111) interface increase with respect to the corresponding bulk values while the atomic magnetic moment of Se atom at the Se-P (111) interface decreases. We also notice that the magnetic moments of subinterface Fe at both Se-Ga and Se-P (111) interfaces decrease compared to the bulk values.

  20. Surface Morphology of Undoped and Doped ZnSe Films

    NASA Technical Reports Server (NTRS)

    George, T.; Hayes, M.; Chen, H.; Chattopadhyay, K.; Thomas E.; Morgan, S.; Burger, A.

    1998-01-01

    Rare-earth doped ions in polar II-VI semiconductors have recently played an important role in the optical properties of materials and devices. In this study, undoped ZnSe and erbium doped ZnSe films were grown by radio frequency (RF) magnetron sputtering method. Atomic Force Microscopy (AFM) was used together with optical microscopy and UV-Vis spectroscopy to characterize the films. Doped samples were found to have higher surface roughness and quite different surface morphology compared to that of undoped samples. The grown films generally show a relatively smooth and uniform surface indicating that they are of overall good quality. The impact of plasma etching on ZnSe:Er film examined under AFM is also discussed.

  1. Effect of doping on electronic properties of HgSe

    NASA Astrophysics Data System (ADS)

    Nag, Abhinav; Sastri, O. S. K. S.; Kumar, Jagdish

    2016-05-01

    First principle study of electronic properties of pure and doped HgSe have been performed using all electron Full Potential Linearized Augmented Plane Wave (FP-LAPW) method using ELK code. The electronic exchange and co-relations are considered using Generalized Gradient Approach (GGA). Lattice parameter, Density of States (DOS) and Band structure calculations have been performed. The total energy curve (Energy vs Lattice parameter), DOS and band structure calculations are in good agreement with the experimental values and those obtained using other DFT codes. The doped material is studied within the Virtual Crystal Approximation (VCA) with doping levels of 10% to 25% of electrons (hole) per unit cell. Results predict zero band gap in undopedHgSe and bands meet at Fermi level near the symmetry point D. For doped HgSe, we found that by electron (hole) doping, the point where conduction and valence bands meet can be shifted below (above) the fermi level.

  2. Room-temperature stabilization of nanoscale superionic Ag2Se

    NASA Astrophysics Data System (ADS)

    Hu, T.; Wittenberg, J. S.; Lindenberg, A. M.

    2014-10-01

    Superionic materials are multi-component solids in which one sub-lattice exhibits high ionic conductivity within a fixed crystalline structure. This is typically associated with a structural phase transition occurring significantly above room temperature. Here, through combined temperature-resolved x-ray diffraction and differential scanning calorimetry, we map out the nanoscale size-dependence of the Ag2Se tetragonal to superionic phase transition temperature and determine the threshold size for room-temperature stabilization of superionic Ag2Se. For the first time, clear experimental evidence for such stabilization of the highly ionic conducting phase at room temperature is obtained in ˜2 nm diameter spheres, which corresponds to a >100 °C suppression of the bulk phase transition temperature. This may enable technological applications of Ag2Se in devices where high ionic conductivity at room temperature is required.

  3. Room-temperature stabilization of nanoscale superionic Ag₂Se.

    PubMed

    Hu, T; Wittenberg, J S; Lindenberg, A M

    2014-10-17

    Superionic materials are multi-component solids in which one sub-lattice exhibits high ionic conductivity within a fixed crystalline structure. This is typically associated with a structural phase transition occurring significantly above room temperature. Here, through combined temperature-resolved x-ray diffraction and differential scanning calorimetry, we map out the nanoscale size-dependence of the Ag₂Se tetragonal to superionic phase transition temperature and determine the threshold size for room-temperature stabilization of superionic Ag2Se. For the first time, clear experimental evidence for such stabilization of the highly ionic conducting phase at room temperature is obtained in ∼2 nm diameter spheres, which corresponds to a >100 °C suppression of the bulk phase transition temperature. This may enable technological applications of Ag₂Se in devices where high ionic conductivity at room temperature is required. PMID:25249347

  4. Optical and spin polarization dynamics in GaSe nanoslabs

    NASA Astrophysics Data System (ADS)

    Tang, Yanhao; Xie, Wei; Mandal, Krishna C.; McGuire, John A.; Lai, C. W.

    2015-05-01

    We report nearly complete preservation of "spin memory" between optical absorption and photoluminescence (PL) in nanometer slabs of GaSe pumped with up to 0.2 eV excess energy. At cryogenic temperatures, the initial degree of circular polarization (ρ0) of PL approaches unity, with the major fraction of the spin polarization decaying with a time constant >500 ps in sub-100-nm GaSe nanoslabs. Even at room temperature, ρ0 as large as 0.7 is observed, while pumping 1 eV above the band edge yields ρ0=0.15 . Angular momentum preservation for both electrons and holes is due to the separation of the nondegenerate conduction and valence bands from other bands. In contrast to valley polarization in atomically thin transition-metal dichalcogenides, here optical spin polarization is preserved in nanoslabs of 100 layers or more of GaSe.

  5. Pressure-induced phase transformation of In2Se3

    NASA Astrophysics Data System (ADS)

    Rasmussen, Anya M.; Teklemichael, Samuel T.; Mafi, Elham; Gu, Yi; McCluskey, Matthew D.

    2013-02-01

    In2Se3 has potential as a phase-change material for memory applications. Understanding its phase diagram is important to achieve controlled switching between phases. Using x-ray diffraction and a diamond-anvil cell, the pressure-dependent structural properties of In2Se3 powder were studied at room temperature. α-In2Se3 transforms into the β phase at 0.7 GPa, an order of magnitude lower than phase-transition critical pressures in typical semiconductors. The β phase persists upon decompression to ambient pressure. Raman spectroscopy experiments confirm this result. The bulk moduli are reported and the c/a ratio for the β phase is shown to have a highly nonlinear dependence on pressure.

  6. Pressure-induced phase transformation of In2Se3

    NASA Astrophysics Data System (ADS)

    Rasmussen, Anya; Teklemichael, Samuel; Mafi, Elham; Gu, Yi; McCluskey, Matthew

    2013-06-01

    Phase-change memory, with fast read-write speeds and small dimensions, will soon replace flash memory in our cell phones and tablets. This type of memory relies on phase change materials like indium selenide, In2Se3, a III-VI semiconductor that exists in multiple crystalline phases. To achieve controlled switching between phases, it is important to understand both the thermal and elastic properties of In2Se3. Using synchrotron x-ray diffraction and a diamond-anvil cell, a pressure-induced phase transition in powder In2Se3 from the α phase to β phase was discovered at 0.7 GPa. This pressure is an order of magnitude lower than phase-transition pressures in most semiconductors. Raman spectroscopy experiments confirm this result. The bulk moduli are reported for both α and β phases, and the c / a ratio for the β phase is shown to have a nonlinear dependence on pressure.

  7. Li/MoSe/sub 3/S secondary battery

    SciTech Connect

    Abraham, K.M.; Pasquariello, D.M.; McAndrews, G.F.

    1987-11-01

    A new Li insertion cathode for ambient temperature secondary lithium batteries, namely, MoSe/sub 3/S, has been identified and characterized. It exhibits a specific capacity of approximately 4 Li per mole of the chalcogenide. The discharge behavior of Li/MoSe/sub 3/S cells at various temperatures and their rechargeability have been assessed utilizing THF:2Me-TH:F/LiAsF/sub 6/ and PC/LiClO/sub 4/ electrolyte solutions. The quasi-theoretical specific energy of 380 Wh/kg realized with a practical MoSe/sub 3/S electrode compares favorably with that in a Li/TiS/sub 2/ cell.

  8. Optical properties of ZnSe(Te) with ytterbium impurity.

    PubMed

    Makhniy, Viktor P; Horley, Paul P; Vorobiev, Yuri V; Kinzerska, Oksana V

    2016-04-20

    We report the results on infrared transmission measurements of non-doped and tellurium-doped crystals of zinc selenide grown from the melt. It was found that non-doped samples feature high transmission (50%-60%) for the wavelengths of 1-22 μm. The efficient scintillating crystals of ZnSe(Te) are almost opaque for λ>7  μm. Doping these samples with ytterbium from the gas phase does not achieve any significant transmission increase for non-doped ZnSe samples in the spectral range of 1-22 μm. However, it considerably increases (up to 50%) transmission for doped ZnSe(Te) at the wavelengths λ>10  μm. These optical peculiarities were analyzed taking into account restructurization of point defect ensembles created by Te and Yb impurities. PMID:27140112

  9. A Quaternary ZnCdSeTe Nanotip Photodetector

    PubMed Central

    2009-01-01

    The authors report the growth of needle-like high density quaternary Zn0.87Cd0.13Se0.98Te0.02nanotips on oxidized Si(100) substrate. It was found that average length and average diameter of the nanotips were 1.3 μm and 91 nm, respectively. It was also found that the as-grown ZnCdSeTe nanotips exhibit mixture of cubic zinc-blende and hexagonal wurtzite structures. Furthermore, it was found that the operation speeds of the fabricated ZnCdSeTe nanotip photodetector were fast with turn-on and turn-off time constants both less than 2 s. PMID:20652144

  10. Nanoscale order in ZnSe:(Mg, O)

    SciTech Connect

    Elyukhin, Vyacheslav A.

    2014-02-21

    Self-assembling of 1O4Mg identical tetrahedral clusters resulting in the nanoscale order in ZnSe:(Mg, O) is presented. Co-doping transforms ZnSe into Mg{sub x}Zn{sub 1−x}O{sub y}Se{sub 1−y} alloy of MgO, MgSe, ZnO and ZnSe. The decrease of a sum of the enthalpies of the constituent compounds and diminution of the strain energy are the causes of this phenomenon. The self-assembling conditions are obtained from the free energy minimum when magnesium and oxygen are in the dilute and ultra dilute limits, correspondingly. The occurrence of 1O4Mg clusters and completion of self-assembling when all oxygen atoms are in clusters are results of the continuous phase transitions. The self-assembling occurrence temperature does not depend on the oxygen content and it is a function of magnesium concentration. Mg{sub x}Zn{sub 1−x}O{sub y}Se{sub 1−y} with all oxygen atoms in clusters can be obtained in temperature ranges from T = 206 °C (x = 0.001, y = 1×10{sup −4}) to T = 456 °C (x = 0.01, y = 1×10{sup −4}) and from T = 237 °C (x = 0.001, y = 1×10{sup −6}) to T = 462 °C (x = 0.01, y = 1×10{sup −6})