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Sample records for bi-sb in-mg in-sb

  1. Reduction in thermal conductivity of BiSbTe lump

    Science.gov (United States)

    Ahmad, Kaleem; Wan, C.; Al-Eshaikh, M. A.; Kadachi, A. N.

    2017-03-01

    In this work, systematic investigations on the thermal conductivities of BiSbTe lump, microstructured pristine BiSbTe bulk and single wall carbon nanotubes (SWCNTs)/BiSbTe bulk nanocomposites were performed. BiSbTe lumps were crushed to form a coarse powder (200 µm) and effect of particle size reduction on the effective thermal conductivity of BiSbTe (200 µm) bulk were analyzed. For further reduction in the conductivity, a two pronged strategy has been employed. First, additional refinement of BiSbTe (200 µm) were performed through ball milling in an inert environment. Second, SWCNTs in 0.75, and 1.0 vol% were distributed uniformly in the fine BiSbTe ball milled powder. The results showed that the effective thermal conductivities decrease with the reduction in the particle size from lump to BiSbTe (200 µm) bulk as well as with the addition of SWCNTs accompanied by further refinement of BiSbTe particles. The significant reduction in thermal conductivities of the lump was achieved for pure BiSbTe (200 µm) bulk and 0.75 vol% of SWCNTs/BiSbTe composite. This can be ascribed to the enhanced phonon scattering by the grain boundaries between the nanostructured BiSbTe particles as well as the interfaces between BiSbTe and the low dimensional carbon nanotubes.

  2. Reduction in thermal conductivity of BiSbTe lump

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Kaleem [King Saud University, Sustainable Energy Technologies Center, College of Engineering, PO Box 800, Riyadh (Saudi Arabia); Wan, C. [Tsinghua University, State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Beijing (China); Al-Eshaikh, M.A.; Kadachi, A.N. [King Saud University, Research Center, College of Engineering, PO Box 800, Riyadh (Saudi Arabia)

    2017-03-15

    In this work, systematic investigations on the thermal conductivities of BiSbTe lump, microstructured pristine BiSbTe bulk and single wall carbon nanotubes (SWCNTs)/BiSbTe bulk nanocomposites were performed. BiSbTe lumps were crushed to form a coarse powder (200 μm) and effect of particle size reduction on the effective thermal conductivity of BiSbTe (200 μm) bulk were analyzed. For further reduction in the conductivity, a two pronged strategy has been employed. First, additional refinement of BiSbTe (200 μm) were performed through ball milling in an inert environment. Second, SWCNTs in 0.75, and 1.0 vol% were distributed uniformly in the fine BiSbTe ball milled powder. The results showed that the effective thermal conductivities decrease with the reduction in the particle size from lump to BiSbTe (200 μm) bulk as well as with the addition of SWCNTs accompanied by further refinement of BiSbTe particles. The significant reduction in thermal conductivities of the lump was achieved for pure BiSbTe (200 μm) bulk and 0.75 vol% of SWCNTs/BiSbTe composite. This can be ascribed to the enhanced phonon scattering by the grain boundaries between the nanostructured BiSbTe particles as well as the interfaces between BiSbTe and the low dimensional carbon nanotubes. (orig.)

  3. BiSb and spin-related thermoelectric phenomena

    Science.gov (United States)

    Heremans, Joseph P.; Jin, Hyungyu; Zheng, Yuanhua; Watzman, Sarah J.; Prakash, Arati

    2016-05-01

    This article reviews the factors limiting the figure of merit zT of conventional thermoelectrics especially at cryogenic temperatures and then highlights modern approaches used to increase zT below 200 K. Two type of materials are discussed. The first are BiSb alloys, relatively conventional thermoelectrics in which the zT is enhanced by using resonant levels. The second is the spin- Seebeck effect (SSE), a new solid-state energy conversion technology. Classical thermoelectric and SSE physics are combined to provide new concepts, like magnon-drag, in which we hope to increase the performance of solid-state coolers by exploiting the spin degree of freedom.

  4. The Quantum Chemistry Calculation and Thermoelectrics of Bi-Sb-Te Series

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The density function theory and discrete variation method(DFT-DVM) was used to study correlation between composition, structure, chemical bond,and property of thermoelectrics of Bi-Sb-Te series.8 models of Bi20-xSbxTe32(x=0,2,6,8,12,14,18 and 20) were calculated.The results show that there is less difference in the ionic bonds between Te(Ⅰ)-Bi(Sb) and Te(Ⅱ)-Bi(Sb), but the covalent bond of Te(Ⅰ)-Bi(Sb) is stronger than that of Te(Ⅱ)-Bi(Sb).The interaction between Te(Ⅰ) and Te(Ⅰ) in different layers is the weakest and the interaction should be Van Der Waals power.The charge of Sb is lower than that of Bi,and the ionic bond of Te-Sb is weaker than that of Te-Bi.The covalent bond of Te-Sb is also weaker than that of Te-Bi.Therefore,the thermoelectric property may be improved by adjusting the electrical conductivity and thermal conductivity through changing the composition in the compounds of Bi-Sb-Te. The calculated results are consistent with the experiments.

  5. Experimental investigation and thermodynamic prediction of the Bi-Sb-Zn phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Minic, Dusko, E-mail: dminic65@nadlanu.com [University of Pristina, Faculty of Technical Sciences, 38220 Kosovska Mitrovica (Serbia); Dokic, Jelena [University of Pristina, Faculty of Technical Sciences, 38220 Kosovska Mitrovica (Serbia); Cosovic, Vladan; Stajic-Trosic, Jasna [Institute of Chemistry, Tehnology and Metallurgy, Njegoseva 12, 11000 Belgrade (Serbia); Zivkovic, Dragana [University of Belgrade, Technical Faculty, VJ 12, 19210 Bor (Serbia); Dervisevic, Irma [University of Pristina, Faculty of Technical Sciences, 38220 Kosovska Mitrovica (Serbia)

    2010-07-01

    Phase diagram of the ternary Bi-Sb-Zn system was investigated experimentally by DTA and SEM-EDS methods and analytically by CALPHAD method. The liquidus projection, invariant equilibria, several vertical sections and isothermal section at 300 {sup o}C were predicted using COST 531 thermodynamic database. Phase transition temperatures of alloys along three predicted vertical sections of the Bi-Sb-Zn ternary system with molar ratio Bi:Sb = 1, Bi:Zn = 1 and Sb:Zn = 1, were measured by differential thermal analysis (DTA). Predicted isothermal section at 300 {sup o}C was compared with the results of the scanning electron microscope (SEM) with energy dispersive spectrometry (EDS) analysis from this work.

  6. Thermoelectric properties of quaternary (Bi,Sb){sub 2}(Te,Se){sub 3} compound

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Pengfei, E-mail: photon.bupt@gmail.com [State Key Laboratory of Information Photonics and Optical Communications, Ministry of Education, Beijing University of Posts and Telecommunications, P.O. Box 72, Beijing 100876 (China); Li, Yiluan; Wu, Chengjie; Yu, Zhongyuan; Cao, Huawei; Zhang, Xianlong; Cai, Ningning; Zhong, Xuxia [State Key Laboratory of Information Photonics and Optical Communications, Ministry of Education, Beijing University of Posts and Telecommunications, P.O. Box 72, Beijing 100876 (China); Wang, Shumin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Photonics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Gothenburg (Sweden)

    2014-01-25

    Highlights: • Sb and Se spin–orbit coupling play a key role in the band structure. • Substituted Bi/Sb and Te/Se have a limited impact on the transport coefficients. • n-Type doping will be preferred for quaternary (Bi,Sb){sub 2}(Te,Se){sub 3} compound. -- Abstract: The quaternary (Bi,Sb){sub 2}(Te,Se){sub 3} compounds are investigated using first-principles study and Boltzmann transport theory. The energy band structure and density of states are studied in detail. The electronic transport coefficients are then calculated as a function of chemical potential. The figure of merit ZT is obtained assuming a constant relaxation time and an averaged thermal conductivity. Our theoretical result agrees well with previous experimental data.

  7. The microstructure network and thermoelectric properties of bulk (Bi,Sb)2Te3

    DEFF Research Database (Denmark)

    Xie, Wenjie; Hitchcock, Dale A.; Kang, Hye J.

    2012-01-01

    We report small-angle neutron scattering studies on the microstructure network in bulk (Bi,Sb)(2)Te-3 synthesized by the melt-spinning (MS) and the spark-plasma-sintering (SPS) process. We find that rough interfaces of multiscale microstructures generated by the MS are responsible for the large...

  8. High-Pressure Crystal Structure, Lattice Vibrations, and Band Structure of BiSbO4.

    Science.gov (United States)

    Errandonea, Daniel; Muñoz, Alfonso; Rodríguez-Hernández, Placida; Gomis, Oscar; Achary, S Nagabhusan; Popescu, Catalin; Patwe, Sadeque J; Tyagi, Avesh K

    2016-05-16

    The high-pressure crystal structure, lattice-vibrations, and electronic band structure of BiSbO4 were studied by ab initio simulations. We also performed Raman spectroscopy, infrared spectroscopy, and diffuse-reflectance measurements, as well as synchrotron powder X-ray diffraction. High-pressure X-ray diffraction measurements show that the crystal structure of BiSbO4 remains stable up to at least 70 GPa, unlike other known MTO4-type ternary oxides. These experiments also give information on the pressure dependence of the unit-cell parameters. Calculations properly describe the crystal structure of BiSbO4 and the changes induced by pressure on it. They also predict a possible high-pressure phase. A room-temperature pressure-volume equation of state is determined, and the effect of pressure on the coordination polyhedron of Bi and Sb is discussed. Raman- and infrared-active phonons were measured and calculated. In particular, calculations provide assignments for all the vibrational modes as well as their pressure dependence. In addition, the band structure and electronic density of states under pressure were also calculated. The calculations combined with the optical measurements allow us to conclude that BiSbO4 is an indirect-gap semiconductor, with an electronic band gap of 2.9(1) eV. Finally, the isothermal compressibility tensor for BiSbO4 is given at 1.8 GPa. The experimental (theoretical) data revealed that the direction of maximum compressibility is in the (0 1 0) plane at ∼33° (38°) to the c-axis and 47° (42°) to the a-axis. The reliability of the reported results is supported by the consistency between experiments and calculations.

  9. Anomalous Proximity Effect in the Nb-BiSb-Nb Junctions

    Energy Technology Data Exchange (ETDEWEB)

    Kasumov, A.Y.; Kononenko, O.V.; Matveev, V.N.; Borsenko, T.B.; Tulin, V.A.; Vdovin, E.E.; Khodos, I.I. [Institute of Microelectronics Technology and High Purity Materials, RAS, 142432 Chernogolovka, Moscow Region (Russia)

    1996-09-01

    An anomalous proximity effect was observed in coplanar Nb-BiSb-Nb junctions. The effect consists of a considerable increase of the critical current with an increase in the distance between the superconducting electrodes. The effect is explained by the quantum character of Cooper pair transport through the normal region. Some advantages of the application of such junctions are discussed. {copyright} {ital 1996 The American Physical Society.}

  10. Synthesis, Characterization and Photocatalytic Activity of New Photocatalyst ZnBiSbO4 under Visible Light Irradiation

    Science.gov (United States)

    Luan, Jingfei; Chen, Mengjing; Hu, Wenhua

    2014-01-01

    In this paper, ZnBiSbO4 was synthesized by a solid-state reaction method for the first time. The structural and photocatalytic properties of ZnBiSbO4 had been characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, transmission electron microscope and UV-visible spectrometer. ZnBiSbO4 crystallized with a pyrochlore-type structure and a tetragonal crystal system. The band gap of ZnBiSbO4 was estimated to be 2.49 eV. The photocatalytic degradation of indigo carmine was realized under visible light irradiation with ZnBiSbO4 as a catalyst compared with nitrogen-doped TiO2 (N-TiO2) and CdBiYO4. The results showed that ZnBiSbO4 owned higher photocatalytic activity compared with N-TiO2 or CdBiYO4 for the photocatalytic degradation of indigo carmine under visible light irradiation. The reduction of the total organic carbon, the formation of inorganic products, SO42− and NO3−, and the evolution of CO2 revealed the continuous mineralization of indigo carmine during the photocatalytic process. One possible photocatalytic degradation pathway of indigo carmine was obtained. The phytotoxicity of the photocatalytic-treated indigo carmine (IC) wastewater was detected by examining its effect on seed germination and growth. PMID:24879521

  11. Synthesis, Characterization and Photocatalytic Activity of New Photocatalyst ZnBiSbO4 under Visible Light Irradiation

    Directory of Open Access Journals (Sweden)

    Jingfei Luan

    2014-05-01

    Full Text Available In this paper, ZnBiSbO4 was synthesized by a solid-state reaction method for the first time. The structural and photocatalytic properties of ZnBiSbO4 had been characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, transmission electron microscope and UV-visible spectrometer. ZnBiSbO4 crystallized with a pyrochlore-type structure and a tetragonal crystal system. The band gap of ZnBiSbO4 was estimated to be 2.49 eV. The photocatalytic degradation of indigo carmine was realized under visible light irradiation with ZnBiSbO4 as a catalyst compared with nitrogen-doped TiO2 (N-TiO2 and CdBiYO4. The results showed that ZnBiSbO4 owned higher photocatalytic activity compared with N-TiO2 or CdBiYO4 for the photocatalytic degradation of indigo carmine under visible light irradiation. The reduction of the total organic carbon, the formation of inorganic products, SO42− and NO3−, and the evolution of CO2 revealed the continuous mineralization of indigo carmine during the photocatalytic process. One possible photocatalytic degradation pathway of indigo carmine was obtained. The phytotoxicity of the photocatalytic-treated indigo carmine (IC wastewater was detected by examining its effect on seed germination and growth.

  12. Magneto-resistive property study of direct and indirect band gap thermoelectric Bi-Sb alloys

    Science.gov (United States)

    Das, Diptasikha; Malik, K.; Bandyopadhyay, S.; Das, D.; Chatterjee, S.; Banerjee, Aritra

    2014-08-01

    We report magneto-resistive properties of direct and indirect band gap Bismuth-Antimony (Bi-Sb) alloys. Band gap increases with magnetic field. Large positive magnetoresistance (MR) approaching to 400% is observed. Low field MR experiences quadratic growth and at high field it follows a nearly linear behavior without sign of saturation. Carrier mobility extracted from low field MR data depicts remarkable high value of around 5 m2V-1s-1. Correlation between MR and mobility is revealed. We demonstrate that the strong nearly linear MR at high field can be well understood by classical method, co-build by Parish and Littlewood, Nature 426, 162 (2003) and Phys. Rev. B 72, 094417 (2005).

  13. Effect of Uniform Dispersion of Single-Wall Carbon Nanotubes on the Thermoelectric Properties of BiSbTe-Based Nanocomposites

    Science.gov (United States)

    Ahmad, Kaleem; Wan, Chunlei; Al-Eshaikh, Mohammad A.

    2017-02-01

    Thermoelectric properties of BiSbTe-based bulk nanocomposites by incorporation of single-wall carbon nanotubes (SWCNTs) in different (0.0, 0.5, 1.0 and 1.5) vol.% were investigated from 300 K to 500 K. SWCNTs were uniformly dispersed in BiSbTe via a combination of ultra-sonication, magnetic stirring and mild ball milling. Fine BiSbTe powder was formed by crushing and ball milling the lumps in an inert environment. The composites demonstrate grain boundary structures exhibiting a three-dimensional network of one-dimensional flexible SWCNTs in BiSbTe bulks. The homogenous distribution of SWCNTs in BiSbTe drastically changes the transport properties of the composites. At 0.5 vol.% of SWCNTs, the effective thermal conductivity decreases suggesting the increased phonon scattering. Meanwhile, at 1.0 vol.% and 1.5 vol.%, the conductivities of the composites somehow increases attributed to homogenous distribution of SWCNTs in the BiSbTe matrix. The increased electrical resistivity with the addition of SWCNTs implies the enhanced scattering of carriers at the grain boundaries and SWCNTs/BiSbTe interfaces. The dimensionless figure of merit somewhat decreases with the addition of 0.5 vol.% SWCNTs. The results suggest that the figure of merit can be improved by optimizing the SWCNT composition below 0.5 vol.% by adequately tailoring the thermoelectric transport.

  14. Growth of Anodic Aluminum Oxide Templates and the Application in Fabrication of the BiSbTe-Based Thermoelectric Nanowires

    Directory of Open Access Journals (Sweden)

    Chin-Guo Kuo

    2014-01-01

    Full Text Available A two-step electrochemical anodization was used to form the anodic aluminum oxide (AAO thin films with nanotube arrays of self-organized honeycomb structure. Al foil was anodized in 10% sulfuric acid (H2SO4 and 3% oxalic acid (H2C2O4 at 25°C at constant voltage of 40 V for 60 min for two times. Ethylene glycol (C2H6O2 was used as a solution and 0.3 M potassium iodide (KI was used to improve the solution’s conductivity. Different electrolyte concentrations of Bi(NO33-5H2O, SbCl3, and TeCl4 were added into KI-C2H6O2 solution and the cyclic voltammetry experiment was used to find the reduced voltages of Bi3+, Sb3+, and Te4+ ions. The potentiostatic deposition and pulse electrodeposition (PED processes were used to deposit the (Bi,Sb2−xTe3+x-based materials. Field-emission scanning electron microscope and energy dispersive spectrometers were used to analyze the compositions of the deposited (Bi,Sb2−xTe3+x-based materials. After finding the optimal deposition parameter of the PED process the AAO nanotube arrays were used as the templates to deposit the (Bi,Sb2−xTe3+x-based thermoelectric nanowires.

  15. Pressure evolution of electrical transport in the 3D topological insulator (Bi,Sb)2(Se,Te)3

    Science.gov (United States)

    Jeffries, J. R.; Butch, N. P.; Vohra, Y. K.; Weir, S. T.

    2015-03-01

    The group V-VI compounds—like Bi2Se3, Sb2Te3, or Bi2Te3—have been widely studied in recent years for their bulk topological properties. The high-Z members of this series form with the same crystal structure, and are therefore amenable to isostructural substitution studies. It is possible to tune the Bi-Sb and Te-Se ratios such that the material exhibits insulating behavior, thus providing an excellent platform for understanding how a topological insulator evolves with applied pressure. We report our observations of the pressure-dependent electrical transport and crystal structure of a pseudobinary (Bi,Sb)2(Te,Se)3 compound. Similar to some of its sister compounds, the (Bi,Sb)2(Te,Se)3 pseudobinary compound undergoes multiple, pressure-induced phase transformations that result in metallization, the onset of a close-packed crystal structure, and the development of distinct superconducting phases.

  16. Band Structure of Topological Insulator BiSbTe1.25Se1.75.

    Science.gov (United States)

    Lohani, H; Mishra, P; Banerjee, A; Majhi, K; Ganesan, R; Manju, U; Topwal, D; Kumar, P S Anil; Sekhar, B R

    2017-07-04

    We present our angle resolved photoelectron spectroscopy (ARPES) and density functional theory results on quaternary topological insulator (TI) BiSbTe1.25Se1.75 (BSTS) confirming the non-trivial topology of the surface state bands (SSBs) in this compound. We find that the SSBs, which are are sensitive to the atomic composition of the terminating surface have a partial 3D character. Our detailed study of the band bending (BB) effects shows that in BSTS the Dirac point (DP) shifts by more than two times compared to that in Bi2Se3 to reach the saturation. The stronger BB in BSTS could be due to the difference in screening of the surface charges. From momentum density curves (MDCs) of the ARPES data we obtained an energy dispersion relation showing the warping strength of the Fermi surface in BSTS to be intermediate between those found in Bi2Se3 and Bi2Te3 and also to be tunable by controlling the ratio of chalcogen/pnictogen atoms. Our experiments also reveal that the nature of the BB effects are highly sensitive to the exposure of the fresh surface to various gas species. These findings have important implications in the tuning of DP in TIs for technological applications.

  17. Thermoelectric properties of p-type Bi-Sb-Te compositionally graded thermoelectric materials with different barriers

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In order to find more suitable materials as barriers and to improve the thermoelectric properties, p-type (BiSb)2Te3 (0.85, 0.9) two segments compositionally graded thermoelectric materials (CGTM) with different barriers were fabricated by conventional hot pressure method. Metals Fe, Co, Cu and Al were used as barriers between two segments. The effects of different barriers on thermoelectric properties of CGTM were investigated. The results show that metal Fe is more stable and suitable as the barrier.

  18. Magnetic susceptibility of Dirac fermions, Bi-Sb alloys, interacting Bloch fermions, dilute nonmagnetic alloys, and Kondo alloys

    Science.gov (United States)

    Buot, Felix A.; Otadoy, Roland E. S.; Rivero, Karla B.

    2017-03-01

    Wide ranging interest in Dirac Hamiltonian is due to the emergence of novel materials, namely, graphene, topological insulators and superconductors, the newly-discovered Weyl semimetals, and still actively-sought after Majorana fermions in real materials. We give a brief review of the relativistic Dirac quantum mechanics and its impact in the developments of modern physics. The quantum band dynamics of Dirac Hamiltonian is crucial in resolving the giant diamagnetism of bismuth and Bi-Sb alloys. Quantitative agreement of the theory with the experiments on Bi-Sb alloys has been achieved, and physically meaningful contributions to the diamagnetism has been identified. We also treat relativistic Dirac fermion as an interband dynamics in uniform magnetic fields. For the interacting Bloch electrons, the role of translation symmetry for calculating the magnetic susceptibility avoids any approximation to second order in the field. The expressions for magnetic susceptibility of dilute nonmagnetic alloys give a firm theoretical foundation of the empirical formulas used in fitting experimental results. The unified treatment of all the above calculations is based on the lattice Weyl-Wigner formulation of discrete phase-space quantum mechanics. For completeness, the magnetic susceptibility of Kondo alloys is also given since Dirac fermions in conduction band and magnetic impurities exhibit Kondo effect.

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

    Directory of Open Access Journals (Sweden)

    Emina Požega

    2017-09-01

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

  20. Pressure evolution of electrical transport in the 3D topological insulator (Bi,Sb)2(Te,Se)3

    Science.gov (United States)

    Jeffries, Jason; Butch, N. P.; Vohra, Y. K.; Weir, S. T.

    2014-03-01

    The group V-VI compounds--like Bi2Se3, Sb2Te3, or Bi2Te3--have been widely studied in recent years for their bulk topological properties. The high-Z members of this series form with the same crystal structure, and are therefore amenable to isostructural substitution studies. It is possible to tune the Bi-Sb and Te-Se ratios such that the material exhibits insulating behavior, thus providing an excellent platform for understanding how a topological insulator evolves with applied pressure. We report our observations of the pressure-dependent electrical transport and compare that behavior with other binary V-VI compounds under pressure. Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.

  1. Great enhancements in the thermoelectric power factor of BiSbTe nanostructured films with well-ordered interfaces

    Science.gov (United States)

    Chang, Hsiu-Cheng; Chen, Chun-Hua; Kuo, Yung-Kang

    2013-07-01

    An innovative concept of twin-enhanced thermoelectricity was proposed to fundamentally resolve the high electrical resistance while not degrading the phonon scattering of the thermoelectric nanoassemblies. Under this frame, a variety of highly oriented and twinned bismuth antimony telluride (BixSb2-xTe3) nanocrystals were successfully fabricated by a large-area pulsed-laser deposition (PLD) technique on insulated silicon substrates at various deposition temperatures. The significant presence of the nonbasal- and basal-plane twins across the hexagonal BiSbTe nanocrystals, which were experimentally and systematically observed for the first time, evidently contributes to the unusually high electrical conductivity of ~2700 S cm-1 and the power factor of ~25 μW cm-1 K-2 as well as the relatively low thermal conductivity of ~1.1 W m-1 K-1 found in these nanostructured films.An innovative concept of twin-enhanced thermoelectricity was proposed to fundamentally resolve the high electrical resistance while not degrading the phonon scattering of the thermoelectric nanoassemblies. Under this frame, a variety of highly oriented and twinned bismuth antimony telluride (BixSb2-xTe3) nanocrystals were successfully fabricated by a large-area pulsed-laser deposition (PLD) technique on insulated silicon substrates at various deposition temperatures. The significant presence of the nonbasal- and basal-plane twins across the hexagonal BiSbTe nanocrystals, which were experimentally and systematically observed for the first time, evidently contributes to the unusually high electrical conductivity of ~2700 S cm-1 and the power factor of ~25 μW cm-1 K-2 as well as the relatively low thermal conductivity of ~1.1 W m-1 K-1 found in these nanostructured films. Electronic supplementary information (ESI) available: Morphologies, XRD patterns, SEM compositions and room-temperature thermoelectric properties of the series of (015) oriented Bi0.4Sb1.6Te3 nanocolumns (Fig. S1-S3), (00l) oriented

  2. Application of the annexation principle to the study of thermodynamic properties of ternary metallic melts In-Pb-Ag and In-Bi-Sb

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Based on the phase diagrams, measured activities and the annexation principle, the calculating models of mass action concentrations for In-Pb-Ag and In-Bi-Sb ternary metallic melts have been formulated. The results of calculation both agree with practice, and obey the law of mass action, showing that the models formulated can reflect the structural reality of the corresponding melts and the annexation principle is applicable to the them.

  3. Crystal growth and physical property of Bi-Sb-Te-Se topological insulator and CuxBi2Se3 topological superconductor materials

    Science.gov (United States)

    Gu, Genda; Yang, Alina; Schneeloch, John; Xu, Zhijun; Tranquada, John; Zhoa, J. G.; Pan, Z. H.; Yang, H. B.; Si, W. D.; Valla, T.

    2012-02-01

    The discovery of 3D topological insulator and topological superconductor materials opens up a new research field in the condensed matter physics. In order to exploit the novel surface properties of these topological insulators, it is crucial to achieve a bulk-insulating state in these topological insulator crystals. Unfortunately, all available topological insulator crystals are not bulk-insulating. We have grown a number of Bi-Se, Bi-Te, Sb-Te-Se, Bi-Sb-Se, Bi-Sb-Te-Se and Bi-Sb-Te-Se-S topological insulator single crystals by using 5N and 6N pure elements. We have measured the physical properties on these single crystals. We have studied the effect of growth condition and impurity on the bulk electrical conductivity of these single crystals. We try to answer two questions if it is possible to grow the bulk-insulating topological insulator single crystals and which maximum resistivity of these topological insulator single crystals we can grow. We have also grown a number of CuxBi2Se3 topological superconductor single crystals.

  4. Thermal Stability of P-Type BiSbTe Alloys Prepared by Melt Spinning and Rapid Sintering

    Directory of Open Access Journals (Sweden)

    Yun Zheng

    2017-06-01

    Full Text Available P-type BiSbTe alloys have been widely implemented in waste heat recovery from low-grade heat sources below 600 K, which may involve assorted environments and conditions, such as long-term service, high-temperature exposure (generally 473–573 K and mechanical forces. It is important to evaluate the service performance of these materials in order to prevent possible failures in advance and extend the life cycle. In this study, p-type Bi0.5Sb1.5Te3 commercial zone-melting (ZM ingots were processed by melt spinning and subsequent plasma-activated sintering (MS-PAS, and were then subjected to vacuum-annealing at 473 and 573 K, respectively, for one week. The results show that MS-PAS samples exhibit excellent thermal stability when annealed at 473 K. However, thermal annealing at 573 K for MS-PAS specimens leads to the distinct sublimation of the element Te, which degrades the hole concentration remarkably and results in inferior thermoelectric performance. Furthermore, MS-PAS samples annealed at 473 K demonstrate a slight enhancement in flexural and compressive strengths, probably due to the reduction of residual stress induced during the sintering process. The current work guides the reliable application of p-type Bi0.5Sb1.5Te3 compounds prepared by the MS-PAS technique.

  5. Thermal Stability of P-Type BiSbTe Alloys Prepared by Melt Spinning and Rapid Sintering.

    Science.gov (United States)

    Zheng, Yun; Tan, Gangjian; Luo, Yubo; Su, Xianli; Yan, Yonggao; Tang, Xinfeng

    2017-06-06

    P-type BiSbTe alloys have been widely implemented in waste heat recovery from low-grade heat sources below 600 K, which may involve assorted environments and conditions, such as long-term service, high-temperature exposure (generally 473-573 K) and mechanical forces. It is important to evaluate the service performance of these materials in order to prevent possible failures in advance and extend the life cycle. In this study, p-type Bi0.5Sb1.5Te₃ commercial zone-melting (ZM) ingots were processed by melt spinning and subsequent plasma-activated sintering (MS-PAS), and were then subjected to vacuum-annealing at 473 and 573 K, respectively, for one week. The results show that MS-PAS samples exhibit excellent thermal stability when annealed at 473 K. However, thermal annealing at 573 K for MS-PAS specimens leads to the distinct sublimation of the element Te, which degrades the hole concentration remarkably and results in inferior thermoelectric performance. Furthermore, MS-PAS samples annealed at 473 K demonstrate a slight enhancement in flexural and compressive strengths, probably due to the reduction of residual stress induced during the sintering process. The current work guides the reliable application of p-type Bi0.5Sb1.5Te₃ compounds prepared by the MS-PAS technique.

  6. Transport studies on Cr-doped (Bi,Sb)2Te3 thin films with nearly quantized anomalous Hall effect

    Science.gov (United States)

    Liu, Minhao; Richardella, Anthony; Kandala, Abhinav; Wang, Wudi; Yazdani, Ali; Samarth, Nitin; Ong, N. Phuan

    2015-03-01

    We describe measurements of the quantum anomalous Hall effect in ferromagnetic Cr-doped (Bi,Sb)2Te3 thin films (6-8 QL thickness) grown on (111) SrTiO3 (STO) substrates by molecular beam epitaxy. The Fermi level is tuned close to the neutral point by tuning the growth flux ratios of Cr, Bi and Sb. Transport measurements were carried out in a dilution fridge at a base temperature of 20 mK. By tuning the chemical potential with a back gate on the STO substrate, we observed an anomalous Hall effect as high as 0.95h/e2, with a coercive field ~ 0.15 T and a narrow transition between positive/negative Hall plateaus. Transport measurements in a non-local configuration showed a Hall-effect-like non-local resistance with a systematic dependence on the back gate voltage and with pronounced peaks which resembled the non-local resistance of the quantum Hall effect. The non-local signal has a maximum that coincides with the maximum in Hall conductivity, indicating the edge channel as its origin. Our results show that the edge channel manifests itself in various transport properties even though the Hall resistance is not perfectly quantized. Supported by DARPA SPAWAR Grant No. N66001-11-1-4110 and MURI grant on Topological Insulators (ARO W911NF-12-1-0461).

  7. Evolution of thermoelectric performance for (Bi,Sb){sub 2}Te{sub 3} alloys from cutting waste powders to bulks with high figure of merit

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Xi' an, E-mail: groupfxa@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081 (China); School of Materials and Metallurgy, Wuhan University of Science and Technology, 947 Heping Road, Qingshan District, Wuhan 430081 (China); Cai, Xin zhi, E-mail: xzcwust@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081 (China); School of Materials and Metallurgy, Wuhan University of Science and Technology, 947 Heping Road, Qingshan District, Wuhan 430081 (China); Han, Xue wu, E-mail: hanxuewu1990@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081 (China); School of Materials and Metallurgy, Wuhan University of Science and Technology, 947 Heping Road, Qingshan District, Wuhan 430081 (China); Zhang, Cheng cheng, E-mail: zcc516990418@live.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081 (China); School of Materials and Metallurgy, Wuhan University of Science and Technology, 947 Heping Road, Qingshan District, Wuhan 430081 (China); and others

    2016-01-15

    Bi{sub 2}Te{sub 3} based cutting waste powders from cutting wafers were firstly selected as raw materials to prepare p-type Bi{sub 2}Te{sub 3} based thermoelectric (TE) materials. Through washing, reducing, composition correction, smelting and resistance pressing sintering (RPS) process, p-type (Bi,Sb){sub 2}Te{sub 3} alloy bulks with different nominal stoichiometries were successfully obtained. The evolution of microstructure and TE performance for (Bi,Sb){sub 2}Te{sub 3} alloys were investigated in detail. All evidences confirmed that most of contaminants from line cutting process such as cutting fluid and oxides of Bi, Sb or Te could be removed by washing, reducing and smelting process used in this work. The carrier content and corresponding TE properties could be adjusted effectively by appropriate composition correction treatment. At lastly, a bulk with a nominal stoichiometry of Bi{sub 0.44}Sb{sub 1.56}Te{sub 3} was obtained and its' dimensionless figure of merit (ZT) was about 1.16 at 90 °C. The ZT values of Bi{sub 0.36}Sb{sub 1.64}Te{sub 3} and Bi{sub 0.4}Sb{sub 1.6}Te{sub 3} alloy bulks could also reach 0.98 and 1.08, respectively. Different from the conventional recycling technology such as hydrometallurgy extraction methods, the separation and extraction of beneficial elements such as Bi, Sb and Te did not need to be performed and the Bi{sub 2}Te{sub 3} based bulks with high TE properties could be directly obtained from the cutting waste powders. In addition, the recycling technology introduced here was green and more suitable for practical industrial application. It can improve material utilization and lower raw material costs of manufacturers. - Graphical abstract: Three kinds of typical morphologies for the fractographs: typical lamellar structure, agglomerated submicron-sized granules and dispersed cubic particles from the initial cutting waste powders. - Highlights: • Bi{sub 2}Te{sub 3} based wastes were directly selected as raw materials

  8. Cathodic Deposition of Components in BiSbTe Ternary Compounds as Thermoelectric Films Using Choline-Chloride-Based Ionic Liquids

    Science.gov (United States)

    Golgovici, Florentina; Cojocaru, Anca; Nedelcu, Marin; Visan, Teodor

    2010-09-01

    This paper reports electrodeposition of BiTe, SbTe, and BiSbTe films using ionic liquids based on choline chloride (ChCl) and malonic acid mixtures (1:1 moles) at 80°C to 85°C. The electrolyte contained bismuth and/or antinomy species and tellurium species with 1.5 mM to 50 mM concentrations; Pt sheet, Pt mesh, and Pt wire were used for working, auxiliary, and quasireference electrodes, respectively. Cyclic voltammograms revealed the beginning and cathodic peak of pure Te deposition; at more negative potentials simultaneous codeposition of binary or ternary compounds as limiting currents or a series of peaks were observed. Correspondingly, two or three dissolution (stripping) anodic peaks were observed. Nyquist and Bode impedance spectra show differences in Pt behavior due to its polarization at various cathodic potentials. Equivalent-circuit components providing the best fit to the data were calculated. Deposition of BiSbTe films on copper plates was also performed by electrolysis at controlled potentials or current pulses. Some measurements of Seebeck coefficients of the obtained films were carried out.

  9. Crystal growth and physical property of Bi-Sb-Te-Se topological insulator materials, and Cu-Bi-Se and Sn-In-Te topological superconductors

    Science.gov (United States)

    Gu, Genda; Yang, Alina; Schneeloch, J.; Zhong, R. D.; Xu, Z. J.; Tranquada, J. M.; Pan, Z. H.; Si, W. D.; Shi, X. Y.; Li, Q.; Valla, T.

    2013-03-01

    The discovery of 3D topological insulator materials and topological superconductor opens up a new research field in the condensed matter physics. We have grown a number of Bi-Sb-Te-Se topological insulator, and Cu-Bi-Se and Sn-In-Te topological superconductor single crystals. We have measured the physical properties on these single crystals. We have studied the effect of growth condition and impurity on the bulk electrical conductivity of these single crystals. We try to answer two questions for the topological insulator materials if it is possible to grow the bulk-insulating topological insulator single crystals and Which maximum resistivity of these topological insulator single crystals we can grow. For the topological superconductor, we have got the bulk superconducting single crystals with a maximum Tc =4.5K. DOE under Contract No. DE-AC02-98CH10886 and the DOE Center for Emergent Superconductivity.

  10. Activity of indium in molten In-Pb-Ag and In-Bi-Sb alloys measured by EMF method using zironia electrolyte; Jirukonia kotai denkaishitsu denchiho ni yoru yoyu In-Pb-Ag kei oyobi In-Bi-Sb kei gokin no injiumu no karyo sokutei

    Energy Technology Data Exchange (ETDEWEB)

    Kameda, K.; Yamaguchi, K.; Kon, T. [Iwate Univ., Iwate (Japan). Faculty of Engineering

    1997-05-20

    In, Ag, Bi, Sb and so forth are slight amount of coexisted elements in non iron metal such as Cu, Pb, Zn and so forth. It has been used as a structure element of electronic material or functional material of superconductors, surface terminal element, transparent electrode and so forth. Further, in future, development regarding its use in optical communication, photovoltaic power generation and so forth is expected. Ag, Bi when combined with In, forming low melting point alloy, can be used as a contact material or dental alloy. Demand of Sb as a flame auxiliary retarder has been increased. In this report, as for molten In-Pb-Ag, In-Pb-Ag type alloys which are not reported so far, cell using zirconia solid electrolyte was prepared and electromotive force was measured. From the obtained value of electromotive force, activity of indium in the whole composition region of In-Pb-Ag type at 1100K and 1200K, and In-Bi-Sb alloy at 1000K and 1100K was measured directly, and isoactivity curve of three elemental alloy was determined. 7 refs., 6 figs., 2 tabs.

  11. Compact analytical model for single gate AlInSb/InSb high electron mobility transistors

    Institute of Scientific and Technical Information of China (English)

    S.Theodore Chandra; N.B.Balamurugan; G.Subalakshmi; T.Shalini; G.Lakshmi Priya

    2014-01-01

    We have developed a 2D analytical model for the single gate AlInSb/InSb HEMT device by solving the Poisson equation using the parabolic approximation method.The developed model analyses the device performance by calculating the parameters such as surface potential,electric field distribution and drain current.The high mobility of the AlInSb/InSb quantum makes this HEMT ideal for high frequency,high power applications.The working of the single gate AlInSb/InSb HEMT device is studied by considering the variation of gate source voltage,drain source voltage,and channel length under the gate region and temperature.The carrier transport efficiency is improved by uniform electric field along the channel and the peak values near the source and drain regions.The results from the analytical model are compared with that of numerical simulations (TCAD) and a good agreement between them is achieved.

  12. Strong Electron–Phonon Coupling and Self-Trapped Excitons in the Defect Halide Perovskites A 3 M 2 I 9 (A = Cs, Rb; M = Bi, Sb)

    Energy Technology Data Exchange (ETDEWEB)

    McCall, Kyle M.; Stoumpos, Constantinos C.; Kostina, Svetlana S.; Kanatzidis, Mercouri G.; Wessels, Bruce W.

    2017-04-26

    The optical and electronic properties of Bridgman grown single crystals of the wide-bandgap semiconducting defect halide perovskites A3M2I9 (A = Cs, Rb; M = Bi, Sb) have been investigated. Intense Raman scattering was observed at room temperature for each compound, indicating high polarizability and strong electron–phonon coupling. Both low-temperature and room-temperature photoluminescence (PL) were measured for each compound. Cs3Sb2I9 and Rb3Sb2I9 have broad PL emission bands between 1.75 and 2.05 eV with peaks at 1.96 and 1.92 eV, respectively. The Cs3Bi2I9 PL spectra showed broad emission consisting of several overlapping bands in the 1.65–2.2 eV range. Evidence of strong electron–phonon coupling comparable to that of the alkali halides was observed in phonon broadening of the PL emission. Effective phonon energies obtained from temperature-dependent PL measurements were in agreement with the Raman peak energies. A model is proposed whereby electron–phonon interactions in Cs3Sb2I9, Rb3Sb2I9, and Cs3Bi2I9 induce small polarons, resulting in trapping of excitons by the lattice. The recombination of these self-trapped excitons is responsible for the broad PL emission. Rb3Bi2I9, Rb3Sb2I9, and Cs3Bi2I9 exhibit high resistivity and photoconductivity response under laser photoexcitation, indicating that these compounds possess potential as semiconductor hard radiation detector materials.

  13. Hole-dominated transport in InSb nanowires grown on high-quality InSb films

    Science.gov (United States)

    Algarni, Zaina; George, David; Singh, Abhay; Lin, Yuankun; Philipose, U.

    2016-12-01

    We have developed an effective strategy for synthesizing p-type indium antimonide (InSb) nanowires on a thin film of InSb grown on glass substrate. The InSb films were grown by a chemical reaction between S b 2 S 3 and I n and were characterized by structural, compositional, and optical studies. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies reveal that the surface of the substrate is covered with a polycrystalline InSb film comprised of sub-micron sized InSb islands. Energy dispersive X-ray (EDX) results show that the film is stoichiometric InSb. The optical constants of the InSb film, characterized using a variable-angle spectroscopic ellipsometer (VASE) shows a maximum value for refractive index at 3.7 near 1.8 eV, and the extinction coefficient (k) shows a maximum value 3.3 near 4.1 eV. InSb nanowires were subsequently grown on the InSb film with 20 nm sized Au nanoparticles functioning as the metal catalyst initiating nanowire growth. The InSb nanowires with diameters in the range of 40-60 nm exhibit good crystallinity and were found to be rich in Sb. High concentrations of anions in binary semiconductors are known to introduce acceptor levels within the band gap. This un-intentional doping of the InSb nanowire resulting in hole-dominated transport in the nanowires is demonstrated by the fabrication of a p-channel nanowire field effect transistor. The hole concentration and field effect mobility are estimated to be ≈1.3 × 1017 cm-3 and 1000 cm2 V-1 s-1, respectively, at room temperature, values that are particularly attractive for the technological implications of utilizing p-InSb nanowires in CMOS electronics.

  14. Characterization of midwave infrared InSb avalanche photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Abautret, J., E-mail: johan.abautret@ies.univ-montp2.fr; Evirgen, A. [Université Montpellier, IES, UMR 5214, F-34095 Montpellier (France); CNRS, IES, UMR 5214, F-34095 Montpellier (France); SOFRADIR, BP 21, 38113 Veurey-Voroize (France); Perez, J. P.; Christol, P. [Université Montpellier, IES, UMR 5214, F-34095 Montpellier (France); CNRS, IES, UMR 5214, F-34095 Montpellier (France); Rothman, J. [CEA-LETI, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Cordat, A. [SOFRADIR, BP 21, 38113 Veurey-Voroize (France)

    2015-06-28

    This paper focuses on the InSb material potential for the elaboration of Avalanche Photodiodes (APD) for high performance infrared imaging applications, both in passive or active mode. The first InSb electron-APD structure was grown by molecular beam epitaxy, processed and electrically characterized. The device performances are at the state of the art for the InSb epi-diode technology, with a dark current density J(−50 mV) = 32 nA/cm{sup 2} at 77 K. Then, a pure electron injection was performed, and an avalanche gain, increasing exponentially, was observed with a gain value near 3 at −4 V at 77 K. The Okuto–Crowell model was used to determine the electron ionization coefficient α(E) in InSb, and the InSb gain behavior is compared with the one of InAs and MCT APDs.

  15. InSb thin films grown by electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Joginder, E-mail: joginderchauhan82@gmail.com; Rajaram, P., E-mail: joginderchauhan82@gmail.com [School of Studies in Physics, Jiwaji University, Gwalior-474011 (India)

    2014-04-24

    We have grown InSb thin films on Cu substrates using the electrodeposition technique. The electrochemical bath from which the InSb thin films were grown was made up of a mixture of aqueous solutions of 0.05 M InCl{sub 3} and 0.03M SbCl{sub 3}, 0 .20M citric acid and 0.30M sodium citrate. Citric acid and sodium citrate were used as complexing agents to bring the reduction potential of In and Sb closer to maintain binary growth. The electrodeposited films were characterized by structural, morphological and optical studies. X-ray diffraction studies show that the films are polycrystalline InSb having the zinc blende structure. Scanning electron microscopy (SEM) studies reveal that the surface of the films is uniformly covered with submicron sized spherical particles. FTIR spectra of InSb thin films show a sharp absorption peak at wave number 1022 cm{sup −1} corresponding to the band gap. Hot probe analysis shows that the InSb thin films have p type conductivity.

  16. Formation and electronic properties of InSb nanocrosses

    Science.gov (United States)

    Plissard, Sébastien R.; van Weperen, Ilse; Car, Diana; Verheijen, Marcel A.; Immink, George W. G.; Kammhuber, Jakob; Cornelissen, Ludo J.; Szombati, Daniel B.; Geresdi, Attila; Frolov, Sergey M.; Kouwenhoven, Leo P.; Bakkers, Erik P. A. M.

    2013-11-01

    Signatures of Majorana fermions have recently been reported from measurements on hybrid superconductor-semiconductor nanowire devices. Majorana fermions are predicted to obey special quantum statistics, known as non-Abelian statistics. To probe this requires an exchange operation, in which two Majorana fermions are moved around one another, which requires at least a simple network of nanowires. Here, we report on the synthesis and electrical characterization of crosses of InSb nanowires. The InSb wires grow horizontally on flexible vertical stems, allowing nearby wires to meet and merge. In this way, near-planar single-crystalline nanocrosses are created, which can be measured by four electrical contacts. Our transport measurements show that the favourable properties of the InSb nanowire devices--high carrier mobility and the ability to induce superconductivity--are preserved in the cross devices. Our nanocrosses thus represent a promising system for the exchange of Majorana fermions.

  17. Megapixel digital InSb detector for midwave infrared imaging

    Science.gov (United States)

    Shkedy, Lior; Markovitz, Tuvy; Calahorra, Zipi; Hirsh, Itay; Shtrichman, Itay

    2011-06-01

    Since the late 1990s Semiconductor devices (SCDs) has developed and manufactured a variety of InSb two-dimensional (2D) focal plane arrays (FPAs) that were implemented in many infrared (IR) systems and applications. SCD routinely manufactures both analog and digital InSb FPAs with array formats of 320×256, 480×384, and 640×512 elements, and pitch size in the range 15 to 30 μm. These FPAs are available in many packaging configurations, including fully integrated detector-Dewar-cooler-assembly, with either closed-cycle Stirling or open-loop Joule-Thomson coolers. In response to a need for very high resolution midwave IR (MWIR) detectors and systems, SCD has developed a large format 2D InSb detector with 1280×1024 elements and pixel size of 15 μm. A digital readout integrated circuit (ROIC) is coupled by flip-chip bonding to the megapixel InSb array. The ROIC is fabricated in CMOS 0.18-μm technology, that enables the small pixel circuitry and relatively low power generation at the focal plane. The digital ROIC has an analog to digital (A/D) converter per-channel and allows for full frame readout at a rate of 100 Hz. Such on-chip A/D conversion eliminates the need for several A/D converters with fairly high power consumption at the system level. The digital readout, together with the InSb detector technology, lead to a wide linear dynamic range and low residual nonuniformity, which is stable over a long period of time following a nonuniformity correction procedure. A special Dewar was designed to withstand harsh environmental conditions while minimizing the contribution to the heat load of the detector. The Dewar together with the low power ROIC, enable a megapixel detector with overall low size, weight, and power with respect to comparable large format detectors. A variety of applications with this detector make use of different cold shields with different f-number and spectral filters. In this paper we present actual performance characteristics of the

  18. Experimental and theoretical lifetimes and transition probabilities in Sb I

    CERN Document Server

    Hartman, Henrik; Engström, Lars; Lundberg, Hans; Palmeri, Patrick; Quinet, Pascal; Biémont, Emile; 10.1103/PhysRevA.82.052512

    2010-01-01

    We present experimental atomic lifetimes for 12 levels in Sb I, out of which seven are reported for the first time. The levels belong to the 5p$^2$($^3$P)6s $^{2}$P, $^{4}$P and 5p$^2$($^3$P)5d $^{4}$P, $^{4}$F and $^{2}$F terms. The lifetimes were measured using time-resolved laser-induced fluorescence. In addition, we report new calculations of transition probabilities in Sb I using a Multiconfigurational Dirac-Hartree-Fock method. The physical model being tested through comparisons between theoretical and experimental lifetimes for 5d and 6s levels. The lifetimes of the 5d $^4$F$_{3/2, 5/2, 7/2}$ levels (19.5, 7.8 and 54 ns, respectively) depend strongly on the $J$-value. This is explained by different degrees of level mixing for the different levels in the $^4$F term.

  19. Super-Hard induced gap in InSb nanowires

    Science.gov (United States)

    Chen, Jun; Yu, Peng; Hocevar, Moïra; Plissard, Sébastien; Car, Diana; Bakkers, Erik; Frolov, Sergey

    In recent years, Majorana bound states were observed experimentally in InSb nanowire-superconductor hybrid devices, which manifested themselves as a zero-bias conductance peak (ZBP). However, there was still significant conductance inside the superconducting gap, which would smear sub-gap features. Moreover, fermionic states inside the gap would also break topological protection. Therefore, a hard gap is required in search of more deterministic signatures of Majorana bound states, and building up Majorana qubits. We report the observation of a hard induced gap in an InSb Josephson junction with an optimized superconducting contact recipe. The gap is resolved in magnetic field up to 2 Tesla, and demonstrates a peculiar kinked field dependence. In addition, we observed rich sub-gap features: Andreev levels appeared close to pinch off regime, while multiple Andreev reflection appeared in open regime.

  20. Zero-bias peak in InSb nanowires

    Science.gov (United States)

    Yu, Peng; Chen, Jun; Hocevar, Moïra; Plissard, Sébastien; Car, Diana; Bakkers, Erik; Frolov, Sergey

    2015-03-01

    Zero-bias conductance peaks(ZBP) in InSb nanowires has been reported as a strong signature of Majorana bound states in semiconductors. We made similar superconductor-InSb nanowire-normal contact hybrid devices with NbTiN on bottom gates and found some features that may corresponding to Majorana bound states. By setting a barrier and tuning gates under the nanowire that are in proximity of superconductors, ZBPs appear at finite magnetic field and usually persist for several hundred miliTesla. In different devices, ZBPs appear at different magnetic field, which may result from different chemical potentials. To achieve a so-called hard induced gap and cleaner devices, we are trying various contact materials and etching methods.

  1. Observation of Conductance Quantization in InSb Nanowire Networks.

    Science.gov (United States)

    Fadaly, Elham M T; Zhang, Hao; Conesa-Boj, Sonia; Car, Diana; Gül, Önder; Plissard, Sébastien R; Op Het Veld, Roy L M; Kölling, Sebastian; Kouwenhoven, Leo P; Bakkers, Erik P A M

    2017-07-14

    Majorana zero modes (MZMs) are prime candidates for robust topological quantum bits, holding a great promise for quantum computing. Semiconducting nanowires with strong spin orbit coupling offer a promising platform to harness one-dimensional electron transport for Majorana physics. Demonstrating the topological nature of MZMs relies on braiding, accomplished by moving MZMs around each other in a certain sequence. Most of the proposed Majorana braiding circuits require nanowire networks with minimal disorder. Here, the electronic transport across a junction between two merged InSb nanowires is studied to investigate how disordered these nanowire networks are. Conductance quantization plateaus are observed in most of the contact pairs of the epitaxial InSb nanowire networks: the hallmark of ballistic transport behavior.

  2. Zero-bias peak splitting in InSb nanowires

    Science.gov (United States)

    Chen, Jun; Yu, Peng; Hocevar, Moïra; Plissard, Sébastien; Car, Diana; Bakkers, Erik; Frolov, Sergey

    2015-03-01

    Zero-bias conductance peak(ZBP) has been reported as a signature of Majorana fermions in InSb nanowires. Other features like ZBP phase diagram in chemical potential vs magnetic field and peak splitting are proposed as additional evidences of Majorana fermions. We make superconductor-InSb nanowire hybrid devices with the aim of exploring these features and beyond. By means of high-k HfOx as the dielectric layer, we obtain large gate-tunability of chemical potential, which may enable us to map out ZBP phase diagram. Here we report observation of ZBP at finite magnetic field. Such peak is tunable with gates underneath the superconductor. In particular, it splits and merges again as a function of the center gate. We study such splitting in the context of a pair of coupled Majorana bound states.

  3. Ballistic transport in InSb Josephson junctions

    Science.gov (United States)

    Damasco, John Jeffrey; Gill, Stephen; Car, Diana; Bakkers, Erik; Mason, Nadya

    We present transport measurements on Josephson junctions consisting of InSb nanowires contacted by Al at various junction lengths. Junction behavior as a function of gate voltage, electric field, and magnetic field is discussed. We show that short junctions behave as 1D quantum wires, exhibiting quantized conductance steps. In addition, we show how Josephson behavior changes as transport evolves from ballistic to diffusive as a function of contact spacing.

  4. Recrystallization of InSb Surfaces Induced by Pulsed Lasers

    Directory of Open Access Journals (Sweden)

    R. Černý

    2000-01-01

    Full Text Available Pulsed laser processing of InSb wafers for the application in designing high speed infrared detectors is studied both theoretically and experimentally. The recrystallization of InSb surfaces resulting in restoration of the implanted region to a single crystal state is presented as a reasonable alternative to the conventional thermal heating. In the theoretical part, thermal equilibrium and nonequilibrium models of melting, recrystallization and evaporation are formulated to describe transport phenomena in the material induced by laser irradiation. In the experimental part, InSb samples irradiated by the ruby (694 nm, 80ns FWHM, and ArF (193 nm, 10 ns FWHM lasers are studied using time resolved reflectivity, Auger electron spectroscopy and low energy electron diffraction methods to analyze surface modifications. A comparison of the experimental data with the numerical predictions shows that while for the ruby laser a reasonable agreement in surface melt duration is achieved, the results for the ArF laser differ quite a lot. As a main reason for these differences, the amorphization of the surface is identified.

  5. Surface passivation of backside-illuminated InSb FPAs

    Science.gov (United States)

    Wei, Peng; Zheng, Kelin; Wang, Liwen; Geng, Dongfeng; Su, Xianjun

    2016-10-01

    A method of passivation of etch-thinned bulk InSb by anodic oxide grown by wet anodization and vacuum deposition of SiNx layers have been investigated Thinned bulk n-type InSb with (111) orientation forms distinctively two types of interfaces on the indium and antimony faces, respectively. The junctions are diffused on the indium face. The paper presents the process and characterization for surface passivation of the backside illuminated Sb face that absorbs the photons. The surface passivation and the interfaces are characterized with Metal-Insulator-Semiconductor (MIS) devices. The effect of anodic oxide/SiNx passivation was compared to SiNx passivation. The electrical features observed in the C-V curves of MIS structures indicate that anodic oxide grown by wet anodization has the better effect on reducing the surface states and surface recombination velocity. The low-frequency-like response in the inversion region of the C-V curves was explained in view of the oxidation states of In and Sb. Finally, by growing the 30nm anodic oxide and depositing 400nm SiNx on diode structure of InSb, the performance of FPA in this case was compared with the SiNx only method. The results showed the performance of device is better than for the SiNx only method.

  6. Hard Superconducting Gap in InSb Nanowires

    Science.gov (United States)

    Gül, Önder; Zhang, Hao; de Vries, Folkert K.; van Veen, Jasper; Zuo, Kun; Mourik, Vincent; Conesa-Boj, Sonia; Nowak, Michał P.; van Woerkom, David J.; Quintero-Pérez, Marina; Cassidy, Maja C.; Geresdi, Attila; Koelling, Sebastian; Car, Diana; Plissard, Sébastien R.; Bakkers, Erik P. A. M.; Kouwenhoven, Leo P.

    2017-04-01

    Topological superconductivity is a state of matter that can host Majorana modes, the building blocks of a topological quantum computer. Many experimental platforms predicted to show such a topological state rely on proximity-induced superconductivity. However, accessing the topological properties requires an induced hard superconducting gap, which is challenging to achieve for most material systems. We have systematically studied how the interface between an InSb semiconductor nanowire and a NbTiN superconductor affects the induced superconducting properties. Step by step, we improve the homogeneity of the interface while ensuring a barrier-free electrical contact to the superconductor, and obtain a hard gap in the InSb nanowire. The magnetic field stability of NbTiN allows the InSb nanowire to maintain a hard gap and a supercurrent in the presence of magnetic fields (~ 0.5 Tesla), a requirement for topological superconductivity in one-dimensional systems. Our study provides a guideline to induce superconductivity in various experimental platforms such as semiconductor nanowires, two dimensional electron gases and topological insulators, and holds relevance for topological superconductivity and quantum computation.

  7. Effect of InSb/In0.9Al0.1Sb superlattice buffer layer on the structural and electronic properties of InSb films

    Science.gov (United States)

    Zhao, Xiaomeng; Zhang, Yang; Guan, Min; Cui, Lijie; Wang, Baoqiang; Zhu, Zhanping; Zeng, Yiping

    2017-07-01

    The effect of InSb/In0.9Al0.1Sb buffer layers on InSb thin films grown on GaAs (0 0 1) substrate by molecular beam epitaxy (MBE) is investigated. The crystal quality and the surface morphology of InSb are characterized by XRD and AFM. The carrier transport property is researched through variable temperature hall test. The sharp interface between InSb/In0.9Al0.1Sb is demonstrated important for the high quality InSb thin film. We try different superlattice buffer layers by changing ratios, 2-0.5, thickness, 300-450 nm, and periods, 20-50. According to the function of the dislocation density to the absolute temperature below 150 K with different periods of SL buffers, we can find that the number of periods of superlattice is a major factor to decrease the density of threading dislocations. With the 50 periods SL buffer layer, the electron mobility of InSb at the room temperature and liquid nitrogen cooling temperature is ∼63,000 and ∼4600 cm2/V s, respectively. We deduce that the interface in the SL structure works as a filter layer to prevent the dislocation propagating to the upper InSb thin films.

  8. Room temperature ballistic transport in InSb quantum well nanodevices.

    Science.gov (United States)

    Gilbertson, A M; Kormányos, A; Buckle, P D; Fearn, M; Ashley, T; Lambert, C J; Solin, S A; Cohen, L F

    2011-12-12

    We report the room temperature observation of significant ballistic electron transport in shallow etched four-terminal mesoscopic devices fabricated on an InSb/AlInSb quantum well (QW) heterostructure with a crucial partitioned growth-buffer scheme. Ballistic electron transport is evidenced by a negative bend resistance signature which is quite clearly observed at 295 K and at current densities in excess of 10(6) A/cm(2). This demonstrates unequivocally that by using effective growth and processing strategies, room temperature ballistic effects can be exploited in InSb/AlInSb QWs at practical device dimensions.

  9. InSb:Mn - A high temperature ferromagnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Laehderanta, E.; Lashkul, A.V. [Lappeenranta University of Technology (Finland); Kochura, A.V. [Lappeenranta University of Technology (Finland); South-West State University, Kursk (Russian Federation); Lisunov, K.G. [Lappeenranta University of Technology (Finland); Institute of Applied Physics, Academy of Sciences of Moldova, Kishinev (Moldova, Republic of); Aronzon, B.A. [Lappeenranta University of Technology (Finland); RRC ' ' Kurchatov Institute' ' , Moscow (Russian Federation); Shakhov, M.A. [Lappeenranta University of Technology (Finland); A.F. Ioffe Physico-Technical Institute, St. Petersburg (Russian Federation)

    2014-05-15

    Diluted magnetic semiconductor InSb:Mn exhibits a ferromagnetic behavior up to T ∝ 600 K due to presence of nanosize MnSb precipitates [Kochura et al., J. Appl. Phys. 113, 083905 (2013)]. Transport properties of InSb:Mn, including the resistivity, the magnetoresistance (MR), and the Hall effect, are investigated between T ∝ 1.6 and 300 K in magnetic fields B up to 15 T. The resistivity, ρ(T), displays an upturn with lowering the temperature below T ∝ 10-20 K attributable to the Kondo effect, where the universal Kondo behavior is observed. The Hall resistivity, ρ{sub H}, demonstrates a nonlinear dependence on B up to T ∝ 300 K, suggesting an anomalous contribution due to the effect of the MnSb nanoprecipitates. The relative MR, Δρ(B)/ρ(0), is positive (pMR) above T ∝ 10 K and transforms into a negative one (nMR) with lowering temperature. The Hall effect and pMR are interpreted simultaneously with the two-band model, addressed to presence of the two types of holes with quite different concentrations and mobilities. The dependences of nMR on B and T follow those of the Khosla-Fischer model, taking into account damping of the spin-dependent scattering of charge carriers in magnetic field. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Lattice constant and hardness of InSb:Bi bulk crystals grown by vertical directional solidification

    Science.gov (United States)

    Maske, Dilip; Deshpande, Manisha; Choudhary, Rashmi; Gadkari, Dattatray

    2016-05-01

    Ingots of the Bi doped InSb (InSb1-xBix) bulk semiconductor crystals were grown by specially designed Vertical Directional Solidification (VDS) technique. Substrates of seven crystals grown with various composition values of x (0 ≤ x 0.05.

  11. High Quality InAs/InSb nanowire heterostructrues grown by metalorganic vapour phase epitaxy

    DEFF Research Database (Denmark)

    Caroff, Philippe; Wagner, Jakob Birkedal; Dick, Kimberly A.

    2008-01-01

    Growth and structural analysis of epitaxial InAs/InSb nanowire heterostructures are demonstrated for the first time. InSb segments are found to be perfect crystals, free of stacking faults or other major defects, and have a sharp interface with InAs (see image). After growth the seed particle is ...

  12. Barrier and porous anodic oxides on InSb

    Energy Technology Data Exchange (ETDEWEB)

    Suleiman, A.; Hashimoto, T. [Corrosion and Protection Centre, School of Materials, University of Manchester, P.O. Box 88, Manchester M60 1QD (United Kingdom); Skeldon, P. [Corrosion and Protection Centre, School of Materials, University of Manchester, P.O. Box 88, Manchester M60 1QD (United Kingdom)], E-mail: peter.skeldon@manchester.ac.uk; Thompson, G.E. [Corrosion and Protection Centre, School of Materials, University of Manchester, P.O. Box 88, Manchester M60 1QD (United Kingdom); Echeverria, F. [Dpto de Ing. Metalurgica y de Materiales, Universidad de Antioquia, Oficina 18-240, Calle 67 No. 53-108, A.A. 1226, Medellin (Colombia); Graham, M.J.; Sproule, G.I.; Moisa, S. [Institute for Microstructural Sciences, National Research Council of Canada, Montreal Road, Ottawa, K1A 0R6 (Canada); Habazaki, H. [Graduate Engineering School, Hokkaido University, N13 W8, Kita-ku, Sapporo 060-8628 (Japan); Bailey, P.; Noakes, T.C.Q. [Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom)

    2008-05-15

    Anodizing of InSb at 5 mA cm{sup -2} in sodium tungstate electrolyte is shown to produce barrier-type amorphous oxide at relatively low voltages, to about 40 V, and porous-type amorphous oxide at increased voltages. The barrier-type amorphous oxide, consisting of units of In{sub 2}O{sub 3} and Sb{sub 2}O{sub 3}, distributed relatively uniformly throughout the film, develops at a formation ratio of 2.2 {+-} 0.2 nm V{sup -1}. The outer 15-20% of the film also contains tungsten species. The relatively high efficiency of barrier film growth reduces significantly with transition to porous oxide, which is associated additionally with generation of oxygen at the film surface. The final oxide, at 65 V, comprises pores, of typical diameter 80 nm, orientated approximately normal to the substrate and extending from a barrier region to the film surface.

  13. Measurements of light absorption efficiency in InSb nanowires

    Directory of Open Access Journals (Sweden)

    A. Jurgilaitis

    2014-01-01

    Full Text Available We report on measurements of the light absorption efficiency of InSb nanowires. The absorbed 70 fs light pulse generates carriers, which equilibrate with the lattice via electron-phonon coupling. The increase in lattice temperature is manifested as a strain that can be measured with X-ray diffraction. The diffracted X-ray signal from the excited sample was measured using a streak camera. The amount of absorbed light was deduced by comparing X-ray diffraction measurements with simulations. It was found that 3.0(6% of the radiation incident on the sample was absorbed by the nanowires, which cover 2.5% of the sample.

  14. Supercurrents in InSb nanowire Josephson junctions

    Science.gov (United States)

    Chen, Jun; Yu, Peng; Plissard, Sébastien; Car, Diana; Mourik, Vincent; Zuo, Kun; van Woerkom, David; Szombati, Daniel; Kouwenhoven, Leo; Bakkers, Erik; Frolov, Sergey

    2014-03-01

    Majorana fermions have been predicted in one-dimensional semiconductor nanowires with strong spin-orbit interactions coupled to superconductors. Effects such as odd number Shapiro steps disappearing and critical currents oscillating in magnetic field have been proposed as signatures of Majorana fermions in Josephson junctions. Here we investigate supercurrents in NbTiN-InSb nanowire-NbTiN Josephson junctions as a function of back gate and magnetic field. When an external magnetic field was applied along the nanowire, we observe gate-tunable oscillations in the critical current. To clarify the origin of this oscillating critical current, we are studying the spectra of Shapiro steps, which may give us a better understanding of such Josephson junctions and guide the search for additional signatures of Majorana fermions.

  15. Towards high mobility InSb nanowire devices

    Science.gov (United States)

    Gül, Önder; van Woerkom, David J.; van Weperen, Ilse; Car, Diana; Plissard, Sébastien R.; Bakkers, Erik P. A. M.; Kouwenhoven, Leo P.

    2015-05-01

    We study the low-temperature electron mobility of InSb nanowires. We extract the mobility at 4.2 K by means of field effect transport measurements using a model consisting of a nanowire-transistor with contact resistances. This model enables an accurate extraction of device parameters, thereby allowing for a systematic study of the nanowire mobility. We identify factors affecting the mobility, and after optimization obtain a field effect mobility of ˜ 2.5× {{10}4} cm2 V-1 s-1. We further demonstrate the reproducibility of these mobility values which are among the highest reported for nanowires. Our investigations indicate that the mobility is currently limited by adsorption of molecules to the nanowire surface and/or the substrate.

  16. The motley family of polar compounds (MV)[M(X{sub 5-x}X Prime {sub x})] based on anionic chains of trans-connected M{sup (III)}(X,X Prime ){sub 6} octahedra (M=Bi, Sb; X, X Prime =Cl, Br, I) and methylviologen (MV) dications

    Energy Technology Data Exchange (ETDEWEB)

    Leblanc, Nicolas [Laboratoire MOLTECH-Anjou, UMR-CNRS 6200, Universite d' Angers 2 Bd Lavoisier, 49045 Angers (France); Mercier, Nicolas, E-mail: nicolas.mercier@univ-angers.fr [Laboratoire MOLTECH-Anjou, UMR-CNRS 6200, Universite d' Angers 2 Bd Lavoisier, 49045 Angers (France); Allain, Magali; Toma, Oksana [Laboratoire MOLTECH-Anjou, UMR-CNRS 6200, Universite d' Angers 2 Bd Lavoisier, 49045 Angers (France); Auban-Senzier, Pascale; Pasquier, Claude [Laboratoire de Physique des Solides, UMR-CNRS 8502, Bat. 510,Universite Paris Sud, 91405 Orsay (France)

    2012-11-15

    The search for hybrid organic-inorganic materials remains a great challenge in the field of ferroelectrics. Following the discovery of the room temperature ferroelectric material (MV)[BiI{sub 3}Cl{sub 2}] (MV{sup 2+}: methylviologen) exhibiting the highest polarization value in the field of hybrid ferroelectrics, we report here nine new hybrids with the general formulation (MV)[M{sup (III)}X{sub 5-x}X Prime {sub x}] (M=Bi, Sb; X, X Prime =Cl, Br, I): (MV)[BiCl{sub 3.3}Br{sub 1.7}] (1), (MV)[BiCl{sub 1.3}Br{sub 3.7}] (2), (MV)[BiBr{sub 3.2}I{sub 1.8}] (3), (MV)[SbCl{sub 5}] (4), (MV)[SbBr{sub 5}] (5), (MV)[SbCl{sub 3.8}Br{sub 1.2}] (6), (MV)[SbCl{sub 2.4}Br{sub 2.6}] (7), (MV)[SbI{sub 3}Cl{sub 2}] (8) and (MV)[SbBr{sub 3.8}I{sub 1.2}] (9). Depending on the presence of polar chains or not, and on the coupling of polar chains, two types of centrosymmetrical structures [C1] and [C2] and two types of polar structures [P1] and [P2] are defined. (2) undergoes a paraelectric-to-relaxor ferroelectric transition around 100-150 K depending of the frequency showing that the Curie temperature, T{sub C}, of (MV)[BiBr{sub 5}] (243 K) can be modulated by the substitution of Br by Cl. The most interesting family is the [P2] type because the syn coupling of polar chains is in favor of high polarization values, as in (MV)[BiI{sub 3}Cl{sub 2}]. Five of the nine new hybrids, (4), (6-9), which have the [P2] type structure are potential ferroelectrics. - Graphical abstract: The methylviologen haloantimonate (MV)[SbX{sub 5-x}X Prime {sub x}] families (X, X Prime =Cl, Br, I) - [P1] and [P2] are the two kinds of polar structures - and view of the (MV)[SbBr{sub 3.8}I{sub 1.2}] hybrid based on chiral polar chains which are in syn coupling. Highlights: Black-Right-Pointing-Pointer Nine hybrids based on methylviologen and halometalate chains have been discovered. Black-Right-Pointing-Pointer The polar nature of chains is due to the ns{sup 2} stereoactivity of Sb{sup (III)} or Bi{sup (III

  17. Mapping of axial strain in InAs/InSb heterostructured nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Patra, Atanu; Panda, Jaya Kumar; Roy, Anushree, E-mail: anushree@phy.iitkgp.ernet.in [Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur 721 302 (India); Gemmi, Mauro; David, Jérémy [Center for Nanotechnology Innovation @ NEST, Istituto Italiano di Tecnologia, Piazza S. Silvestro 12, I-56127 Pisa (Italy); Ercolani, Daniele; Sorba, Lucia, E-mail: lucia.sorba@nano.cnr.it [NEST-Istituto Nanoscienze-CNR and Scuola Normale Superiore, Piazza S. Silvestro 12, I-56127 Pisa (Italy)

    2015-08-31

    The article presents a mapping of the residual strain along the axis of InAs/InSb heterostructured nanowires. Using confocal Raman measurements, we observe a gradual shift in the transverse optical phonon mode along the axis of these nanowires. We attribute the observed shift to a residual strain arising from the InAs/InSb lattice mismatch. We find that the strain is maximum at the interface and then monotonically relaxes towards the tip of the nanowires. We also analyze the crystal structure of the InSb segment through selected area electron diffraction measurements and electron diffraction tomography on individual nanowires.

  18. Josephson radiation from InSb-nanowire junction

    Science.gov (United States)

    van Woerkom, David; Proutski, Alexander; Krivachy, Tamas; Bouman, Daniel; van Gulik, Ruben; Gul, Onder; Cassidy, Maja; Car, Diana; Bakkers, Erik; Kouwenhoven, Leo; Geresdi, Attila

    Semiconducting nanowire Josephson junctions has recently gained interest as building blocks for Majorana circuits and gate-tuneable superconducting qubits . Here we investigate the rich physics of the Andreev bound state spectrum of InSb nanowire junctions utilizing the AC Josephson relation 2eV_bias =hf . We designed and characterized an on-chip microwave circuit coupling the nanowire junction to an Al/AlOx/Al tunnel junction. The DC response of the tunnel junction is affected by photon-assisted quasiparticle current, which gives us the possibility to measure the radiation spectrum of the nanowire junction up to several tens of GHz in frequency. Our circuit design allows for voltage or phase biasing of the Josephson junction enabling direct mapping of Andreev bound states. We discuss our fabrication methods and choice of materials to achieve radiation detection up to a magnetic field of few hundred milliTesla, compatible with Majorana states in spin-orbit coupled nanowires. This work has been supported by the Netherlands Foundations FOM, Abstract NWO and Microsoft Corporation Station Q.

  19. Photopeak detection by an InSb radiation detector made of liquid phase epitaxially grown crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Yuki, E-mail: Y.Sato@nucleng.kyoto-u.ac.j [Graduate School of Engineering, Kyoto University, Sakyo, Kyoto 606-8501 (Japan); Morita, Yasunari; Harai, Tomoyuki; Kanno, Ikuo [Graduate School of Engineering, Kyoto University, Sakyo, Kyoto 606-8501 (Japan)

    2010-09-21

    We have fabricated a radiation detector using a p-type InSb crystal grown by liquid phase epitaxy (LPE). At temperatures below 100 K, the resistivity of the LPE crystal was over an order of magnitude higher than that of the commercial InSb crystal substrate. The resistance of the InSb detector is 680 k{Omega} at 4.2 K, which is one order of magnitude higher than that of detectors fabricated from commercial InSb wafers and, in an improvement over previous results, the energy resolution of {sup 241}Am alpha particles reaches 3%. In addition, we also observe the photopeak of gamma-rays emitted by {sup 133}Ba.

  20. Bi-induced band gap reduction in epitaxial InSbBi alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rajpalke, M. K.; Linhart, W. M.; Birkett, M.; Alaria, J.; Veal, T. D., E-mail: T.Veal@liverpool.ac.uk [Stephenson Institute for Renewable Energy and Department of Physics, School of Physical Sciences, University of Liverpool, Liverpool L69 7ZF (United Kingdom); Yu, K. M. [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Bomphrey, J. J.; Jones, T. S.; Ashwin, M. J., E-mail: M.J.Ashwin@warwick.ac.uk [Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom); Sallis, S.; Piper, L. F. J. [Materials Science and Engineering, Binghamton University, Binghamton, New York 13902 (United States)

    2014-11-24

    The properties of molecular beam epitaxy-grown InSb{sub 1−x}Bi{sub x} alloys are investigated. Rutherford backscattering spectrometry shows that the Bi content increases from 0.6% for growth at 350 °C to 2.4% at 200 °C. X-ray diffraction indicates Bi-induced lattice dilation and suggests a zinc-blende InBi lattice parameter of 6.626 Å. Scanning electron microscopy reveals surface InSbBi nanostructures on the InSbBi films for the lowest growth temperatures, Bi droplets at intermediate temperatures, and smooth surfaces for the highest temperature. The room temperature optical absorption edge was found to change from 172 meV (7.2 μm) for InSb to ∼88 meV (14.1 μm) for InSb{sub 0.976}Bi{sub 0.024}, a reduction of ∼35 meV/%Bi.

  1. Schottky barrier and contact resistance of InSb nanowire field-effect transistors

    Science.gov (United States)

    Fan, Dingxun; Kang, N.; Gorji Ghalamestani, Sepideh; Dick, Kimberly A.; Xu, H. Q.

    2016-07-01

    Understanding of the electrical contact properties of semiconductor nanowire (NW) field-effect transistors (FETs) plays a crucial role in the use of semiconducting NWs as building blocks for future nanoelectronic devices and in the study of fundamental physics problems. Here, we report on a study of the contact properties of Ti/Au, a widely used contact metal combination, when contacting individual InSb NWs via both two-probe and four-probe transport measurements. We show that a Schottky barrier of height {{{Φ }}}{{SB}}˜ 20 {{meV}} is present at the metal-InSb NW interfaces and its effective height is gate-tunable. The contact resistance ({R}{{c}}) in the InSb NWFETs is also analyzed by magnetotransport measurements at low temperatures. It is found that {R}{{c}} in the on-state exhibits a pronounced magnetic field-dependent feature, namely it is increased strongly with increasing magnetic field after an onset field {B}{{c}}. A qualitative picture that takes into account magnetic depopulation of subbands in the NWs is provided to explain the observation. Our results provide solid experimental evidence for the presence of a Schottky barrier at Ti/Au-InSb NW interfaces and can be used as a basis for design and fabrication of novel InSb NW-based nanoelectronic devices and quantum devices.

  2. Optical design of a mid-wavelength infrared InSb nanowire photodetector

    Science.gov (United States)

    Azizur-Rahman, K. M.; LaPierre, R. R.

    2016-08-01

    A periodic array of vertical InSb nanowires (nws) was designed for photodetectors in the mid-wavelength infrared (MWIR) region (λ = 3-5 μm). Simulations, using the finite element method, were implemented to optimize the nw array geometrical parameters (diameter (D), period (P), and length (L)) for high optical absorptance, which exceeded that of a thin film of equal thickness. Our results showed HE1n resonances in InSb nw arrays can be tuned by adjusting D and P, thus enabling multispectral absorption throughout the near infrared to MWIR region. Optical absorptance was investigated for a practical photodetector consisting of a vertical InSb nw array embedded in bisbenzocyclobutene (BCB) as a support layer for an ultrathin Ni contact layer. Polarization sensitivity of the photodetector is examined.

  3. Magneto-optical properties of InSb for terahertz applications

    Directory of Open Access Journals (Sweden)

    Jan Chochol

    2016-11-01

    Full Text Available Magneto-optical permittivity tensor spectra of undoped InSb, n-doped and p-doped InSb crystals were determined using the terahertz time-domain spectroscopy (THz-TDS and the Fourier transform far-infrared spectroscopy (far-FTIR. A Huge polar magneto-optical (MO Kerr-effect (up to 20 degrees in rotation and a simultaneous plasmonic behavior observed at low magnetic field (0.4 T and room temperature are promising for terahertz nonreciprocal applications. We demonstrate the possibility of adjusting the the spectral rage with huge MO by increase in n-doping of InSb. Spectral response is modeled using generalized magneto-optical Drude-Lorentz theory, giving us precise values of free carrier mobility, density and effective mass consistent with electric Hall effect measurement.

  4. Effects of substrate orientation on the growth of InSb nanostructures by molecular beam epitaxy

    Science.gov (United States)

    Chou, C. Y.; Torfi, A.; Pei, C.; Wang, W. I.

    2016-05-01

    In this work, the effects of substrate orientation on InSb quantum structure growth by molecular beam epitaxy (MBE) are presented. Motivated by the observation that (411) evolves naturally as a stable facet during MBE crystal growth, comparison studies have been carried out to investigate the effects of the crystal orientation of the underlying GaSb substrate on the growth of InSb by MBE. By depositing InSb on a number of different substrate orientations, namely: (100), (311), (411), and (511), a higher nanostructure density was observed on the (411) surface compared with the other orientations. This result suggests that the (411) orientation presents a superior surface in MBE growth to develop a super-flat GaSb buffer surface, naturally favorable for nanostructure growth.

  5. Gate-tunable Andreev bound states in InSb nanowire Josephson junction

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Ning; Li, Sen; Fan, Dingxun; Xu, Hongqi [Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871 (China); Caroff, Philippe [Division of Solid State Physics, Lund University, P. O. Box 118, S-221 00 Lund (Sweden)

    2016-07-01

    Hybrid InSb nanowire-superconductor devices are promising candidates for investigating Majorana modes in solid-state devices and future technologies of topological quantum manipulation. Here, we report low-temperature transport measurements on an individual InSb nanowire quantum dot coupled to superconducting contacts that exhibit an interplay between the Kondo effects and superconductivity. We observed two types of subgap resonance states within the superconducting gap, which can be attributed to gate-tunable Andreev bound states in Coulomb valleys with different Kondo temperatures. The presence of the gate-tunable 0 and pi junction allow us to investigate the fundamental 0- pi transition. Detailed magnetic field and temperature evolution of level spectroscopy demonstrate different behavior of two types of the Andreev bound states. Our results exhibit that the InSb nanowires can provide a promising platform for exploring phase coherence transport and the effect of spin-orbit coupling in semiconductor nanowire-superconductor hybrid device.

  6. Magneto-optical properties of InSb for terahertz applications

    CERN Document Server

    Chochol, Jan; Čada, Michael; Vanwolleghem, Mathias; Halagačka, Lukáš; Vignaud, Dominique; Lampin, Jean-François; Pištora, Jaromír

    2016-01-01

    Magneto-optical permittivity tensor spectra of undoped InSb, n-doped and p-doped InSb crystals were determined using the terahertz time-domain spectroscopy (THz-TDS) and the Fourier transform far-infrared spectroscopy (far-FTIR). A Huge polar magneto-optical (MO) Kerr-effect (up to 20 degrees in rotation) and a simultaneous plasmonic behavior observed at low magnetic field (0.4 T) and room temperature are promising for terahertz nonreciprocal applications. We demonstrate the possibility of adjusting the the spectral rage with huge MO by increase in n-doping of InSb. Spectral response is modeled using generalized magneto-optical Drude-Lorentz theory, giving us precise values of free carrier mobility, density and effective mass consistent with electric Hall effect measurement.

  7. Hybrid Quantum Point Contact-Superconductor Devices Using InSb Nanowires

    Science.gov (United States)

    Gill, Stephen; Damasco, John Jeffrey; Car, Diana; Bakkers, Erik; Mason, Nadya

    Recent experiments using hybrid nanowire (NW)-superconductor (SC) devices have provided evidence for Majorana quasiparticles in tunneling experiments. However, these tunneling experiments are marked by a soft superconducting gap, which likely originates from disorder at the NW-SC interface. Hence, clean NW-SC interfaces are important for future Majorana studies. By carefully processing the NW-SC interface, we have realized quantized conductance steps in quantum point contacts fabricated from InSb NWs and superconducting contacts. We study the length dependence of ballistic behavior and the induced superconductivity in InSb NWs by quantum point contact spectroscopy. Additionally, we discuss how the transport in InSb NW-SC quantum point contacts evolves in magnetic field.

  8. Energy level spectroscopy of InSb quantum wells using quantum-well LED emission

    Science.gov (United States)

    Tenev, T. G.; Palyi, A.; Mirza, B. I.; Nash, G. R.; Fearn, M.; Smith, S. J.; Buckle, L.; Emeny, M. T.; Ashley, T.; Jefferson, J. H.; Lambert, C. J.

    2009-02-01

    We have investigated the low-temperature optical properties of InSb quantum-well (QW) light-emitting diodes, with different barrier compositions, as a function of well width. Three devices were studied: QW1 had a 20 nm undoped InSb quantum well with a barrier composition of Al0.143In0.857Sb , QW2 had a 40 nm undoped InSb well with a barrier composition of Al0.077In0.923Sb , and QW3 had a 100 nm undoped InSb well with a barrier composition of Al0.025In0.975Sb . For QW1, the signature of two transitions (CB1-HH1 and CB1-HH2) can be seen in the measured spectrum, whereas for QW2 and QW3 the signature of a large number of transitions is present in the measured spectra. In particular transitions to HH2 can be seen, the first time this has been observed in AlInSb/InSb heterostructures. To identify the transitions that contribute to the measured spectra, the spectra have been simulated using an eight-band k.p calculation of the band structure together with a first-order time-dependent perturbation method (Fermi golden rule) calculation of spectral emittance, taking into account broadening. In general there is good agreement between the measured and simulated spectra. For QW2 we attribute the main peak in the experimental spectrum to the CB2-HH1 transition, which has the highest overall contribution to the emission spectrum of QW2 compared with all the other interband transitions. This transition normally falls into the category of “forbidden transitions,” and in order to understand this behavior we have investigated the momentum matrix elements, which determine the selection rules of the problem.

  9. MBE Growth and Transfer of HgCdTe Epitaxial Films from InSb Substrates

    Science.gov (United States)

    de Lyon, T. J.; Rajavel, R. D.; Nosho, B. Z.; Terterian, S.; Beliciu, M. L.; Patterson, P. R.; Chang, D. T.; Boag-O'Brien, M. F.; Holden, B. T.; Jacobs, R. N.; Benson, J. D.

    2010-07-01

    An investigation of the heteroepitaxial growth of HgCdTe films onto InSb(211)B substrates is reported. High-quality HgCdTe(211)B single-crystal films have been successfully deposited onto InSb(211)B substrates and have been characterized with x-ray diffraction rocking curve analysis, etch pit density analysis, and surface void defect mapping. X-ray rocking curve (422) reflection full-width at half-maximum of 60 arcsec has been obtained for 7- μm-thick x = 0.22 HgCdTe epitaxial films, and etch pit densities of 3 × 106 cm-2 to 3 × 107 cm-2 have been observed. A significant reduction in HgCdTe void defect densities to 100 cm-2 to 200 cm-2 has been observed on InSb, including a complete absence of large “void cluster” defects that are often observed for growth on CdZnTe. Wafer bow induced by the growth of HgCdTe on InSb is less than 1 μm for 2-inch-diameter substrates. Significant diffusion of In into HgCdTe is observed for HgCdTe/InSb wafers that are subjected to Hg anneals at 250°C to 300°C. A preliminary investigation of the transfer of HgCdTe films from InSb onto Si substrates has also been undertaken, using an adhesive wafer bonding approach evaluated with scanning acoustic microscopy. The infrared transmission characteristics of the bonding adhesive have been investigated with respect to postgrowth annealing procedures to establish the compatibility of the bonding approach with HgCdTe device processing and detector operation.

  10. Phase relations near ternary eutectic point in the Ag-In-Sb system

    Directory of Open Access Journals (Sweden)

    Jendrzejczyk-Handzlik D.

    2007-01-01

    Full Text Available The results of the phase relations near ternary eutectic point in the Ag-In-Sb system are investigated in this paper. Phase equilibrium calculation was done using Thermocalc software and experimental DTA results for the chosen alloys in the isopleths with molar ration of In:Sb = 7:3; 9:1 and 1:1. The structural characteristics of these alloys have been investigated using light optic microscopy and scanning electron microscopy, while hardness measurements have also been done. Solidification path for three ternary alloys located on three different investigated isopleths was calculated using Pandat software.

  11. A study on InSb Magnetic Sensor Using Hall Effect

    Energy Technology Data Exchange (ETDEWEB)

    Chon, C.S. [Inha Univ., Inchon (Korea, Republic of)

    1994-02-01

    InSb thin film magnetic sensor, which have been prepared on glass substrate by vacuum evaporation, is investigated in this paper. The dependence of hall voltage with on magnetic field and temperature is examined by Hall effect. The variation of Hall voltage with magnetic field is almost linear at constant current drive but it is deviated from the linearity at constant voltage drive. Hall voltage decreases as the ambient temperature increases, so it is necessary to take into account the temperature effect when the InSb thin film is used as magnetic sensor. (author). 17 refs., 5 figs.

  12. InSb nanowire double quantum dots coupled to a superconducting microwave cavity

    Science.gov (United States)

    Wang, R.; Deacon, R. S.; Car, D.; Bakkers, E. P. A. M.; Ishibashi, K.

    2016-05-01

    By employing a micrometer precision mechanical transfer technique, we embed individual InSb nanowires into a superconducting coplanar waveguide resonator. We investigate the characteristics of a double quantum dot formed in an InSb nanowire interacting with a single mode microwave field. The charge stability diagram can be obtained from the amplitude and phase response of the resonator independently from the dc transport measurement. As the charge transits between dot-dot, or dot-lead, the change of resonator transmission is compared and the charge-cavity coupling strength is extracted to be in the magnitude of several MHz.

  13. InSb nanowire double quantum dots coupled to a superconducting microwave cavity

    Energy Technology Data Exchange (ETDEWEB)

    Wang, R. [Advanced Device Laboratory, RIKEN, Wako, Saitama 351-0198 (Japan); Deacon, R. S., E-mail: russell@riken.jp; Ishibashi, K. [Advanced Device Laboratory, RIKEN, Wako, Saitama 351-0198 (Japan); Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama 351-0198 (Japan); Car, D. [Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Bakkers, E. P. A. M. [Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Kavli Institute, Quantum Transport Group, Delft University of Technology, 2628 CJ Delft (Netherlands)

    2016-05-16

    By employing a micrometer precision mechanical transfer technique, we embed individual InSb nanowires into a superconducting coplanar waveguide resonator. We investigate the characteristics of a double quantum dot formed in an InSb nanowire interacting with a single mode microwave field. The charge stability diagram can be obtained from the amplitude and phase response of the resonator independently from the dc transport measurement. As the charge transits between dot-dot, or dot-lead, the change of resonator transmission is compared and the charge-cavity coupling strength is extracted to be in the magnitude of several MHz.

  14. Hybrid superconductor-quantum point contact devices using InSb nanowires

    Science.gov (United States)

    Gill, S. T.; Damasco, J.; Car, D.; Bakkers, E. P. A. M.; Mason, N.

    2016-12-01

    Proposals for studying topological superconductivity and Majorana bound states in a nanowire proximity coupled to superconductors require that transport in the nanowire is ballistic. Previous works on hybrid nanowire-superconductor systems have shown evidence for Majorana bound states, but these experiments were also marked by disorder, which disrupts ballistic transport. In this paper, we demonstrate ballistic transport in the InSb nanowires interfaced directly with superconducting Al by observing quantized conductance at zero-magnetic field. Additionally, we demonstrate that the nanowire is proximity coupled to the superconducting contacts by observing Andreev reflection. These results are important steps for robustly establishing topological superconductivity in the InSb nanowires.

  15. High density near amorphous InSb nanowire arrays and its photo-electric performance

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Ming, E-mail: mfang@issp.ac.cn [Key Laboratory of Materials Physics, Anhui Key Laboratory of Nanomaterials and Nanostructure, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Tan, Xiaoli [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Liu, Mao, E-mail: mliu@issp.ac.cn [Key Laboratory of Materials Physics, Anhui Key Laboratory of Nanomaterials and Nanostructure, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Gong, Xinxin; Zhang, Lide; Fei, Guangtao [Key Laboratory of Materials Physics, Anhui Key Laboratory of Nanomaterials and Nanostructure, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2015-03-25

    Highlights: • InSb near amorphous nanowire arrays are successfully fabricated. • The 30 nm diameter nanowire array shows a well infrared photo-electric response, and the reasons are discussed. • The reason for the black color of the InSb semiconductor is discussed. - Abstract: In this paper, we report the fabrication of high density near amorphous InSb nanowire arrays with using 30, 55 and 70 nm diameter anodic alumina oxide (AAO) template by electrodeposition method. The near amorphous structure was proved by combining the results of X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Different from the bulk material, these nanowires are black and could not be analyzed by the traditional method, and the reason was discussed. By testing of the photo-electric performance, the 30 nm diameter InSb nanowire showed the best performance, which could be used at about 260 K. The formation of the near amorphous structure was also discussed. Such high density nanoarrays may found potential application in the infrared detection field.

  16. Molecular beam epitaxy growth of InSb1−xBix thin films

    DEFF Research Database (Denmark)

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

    2013-01-01

    Molecular beam epitaxy growth for InSb1−xBix thin films on (100) GaAs substrates is reported. Successful Bi incorporation for 2% is achieved, and up to 70% of the incorporated Bi atoms are at substitutional sites. The effects of growth parameters on Bi incorporation and surface morphology...

  17. Molecular beam epitaxy growth of InSb1-xBix thin films

    DEFF Research Database (Denmark)

    Yuxin Song; Shumin Wang; Saha Roy, Ivy;

    2013-01-01

    Molecular beam epitaxy growth for InSb1-xBix thin films on (100) GaAs substrates is reported. Successful Bi incorporation for 2% is achieved, and up to 70% of the incorporated Bi atoms are at substitutional sites. The effects of growth parameters on Bi incorporation and surface morphology...

  18. Direct measurement of the near-field super resolved focused spot in InSb

    NARCIS (Netherlands)

    Assafrao, A.C.; Wachters, A.J.H.; Verheijen, M.; Nugrowati, A.M.; Pereira, S.F.; Urbach, H.P.; Armand, M.F.; Olivier, S.

    2012-01-01

    Under appropriate laser exposure, a thin film of InSb exhibits a sub-wavelength thermally modified area that can be used to focus light beyond the diffraction limit. This technique, called Super-Resolution Near-Field Structure, is a potential candidate for ultrahigh density optical data storage and

  19. Thermodynamic Assessments of Al-In-Sb and Al-In-As Systems

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The experimental thermodynamic and phase diagram data of the Al-In-Sb and Al-In-As ternary systems were critically assessed.A set of self-consistent thermodynamic model parameters were obtained to describe the phase equilibria and the thermodynamic properties of two systems.In most cases,the calculated values agree very well with the experimental data.

  20. Ab initio calculations of the optical properties of crystalline and liquid InSb

    Energy Technology Data Exchange (ETDEWEB)

    Sano, Haruyuki, E-mail: h-sano@ishikawa-nct.ac.jp [National Institute of Technology, Ishikawa College, Kitacyujo, Tsubata, Ishikawa 929-0392 (Japan); Mizutani, Goro [School of Materials Science, Japan Advanced Institute of Science and Technology, Tatsunokuchi, Ishikawa 923-1292 (Japan)

    2015-11-15

    Ab initio calculations of the electronic and optical properties of InSb were performed for both the crystalline and liquid states. Two sets of atomic structure models for liquid InSb at 900 K were obtained by ab initio molecular dynamics simulations. To reduce the effect of structural peculiarities in the liquid models, an averaging of the two sets of the calculated electronic and optical properties corresponding to the two liquid models was performed. The calculated results indicate that, owing to the phase transition from crystal to liquid, the density of states around the Fermi level increases. As a result, the energy band gap opening near the Fermi level disappears. Consequently, the optical properties change from semiconductor to metallic behavior. Namely, owing to the melting of InSb, the interband transition peaks disappear and a Drude-like dispersion is observed in the optical dielectric functions. The optical absorption at a photon energy of 3.06 eV, which is used in Blu-ray Disc systems, increases owing to the melting of InSb. This increase in optical absorption is proposed to result from the increased optical transitions below 2 eV.

  1. Wet etching of InSb surfaces in aqueous solutions: Controlled oxide formation

    Energy Technology Data Exchange (ETDEWEB)

    Aureau, D., E-mail: damien.aureau@chimie.uvsq.fr [Institut Lavoisier UVSQ-CNRS UMR 8180, 45 avenue des Etats Unis, Versailles, 78035 (France); Chaghi, R.; Gerard, I. [Institut Lavoisier UVSQ-CNRS UMR 8180, 45 avenue des Etats Unis, Versailles, 78035 (France); Sik, H.; Fleury, J. [Sagem Defense Sécurité, 72-74, rue de la tour Billy, 95101, Argenteuil Cedex (France); Etcheberry, A. [Institut Lavoisier UVSQ-CNRS UMR 8180, 45 avenue des Etats Unis, Versailles, 78035 (France)

    2013-07-01

    This paper investigates the wet etching of InSb surfaces by two different oxidant agents: Br{sub 2} and H{sub 2}O{sub 2} and the consecutive oxides generation onto the surfaces. The strong dependence between the chemical composition of the etching baths and the nature of the final surface chemistry of this low band-gap III–V semiconductor will be especially highlighted. One aqueous etching solution combined hydrobromic acid and Bromine (HBr–Br{sub 2}:H{sub 2}O) with adjusted concentrations. The other solution combines orthophosphoric and citric acids with hydrogen peroxide (H{sub 3}PO{sub 4}–H{sub 2}O{sub 2}:H{sub 2}O). Depending on its composition, each formulation gave rise to variable etching rate. The dosage of Indium traces in the etching solution by atomic absorption spectroscopy (AAS) gives the kinetic variation of the dissolution process. The variations on etching rates are associated to the properties and the nature of the formed oxides on InSb surfaces. Surface characterization is specifically performed by X-ray photoelectron spectroscopy (XPS). A clear evidence of the differences between the formed oxides is highlighted. Atomic force microscopy is used to monitor the surface morphology and pointed out that very different final morphologies can be reached. This paper presents new results on the strong variability of the InSb oxides in relation with the InSb reactivity toward environment interaction.

  2. Interstitial Fe in MgO

    CERN Document Server

    Mølholt, T E; Gunnlaugsson, H P; Svane, A; Masenda, H; Naidoo, D; Bharuth-Ram, K; Fanciulli, M; Gislason, H P; Johnston, K; Langouche, G; Ólafsson, S; Sielemann, R; Weyer, G

    2014-01-01

    Isolated Fe-57 atoms were studied in MgO single-crystals by emission Mossbauer spectroscopy following implantation of Mn-57 decaying to Fe-57. Four Mossbauer spectral components were found corresponding to different Fe lattice positions and/or charge states. Two components represent Fe atoms substituting Mg as Fe2+ and Fe3+, respectively; a third component is due to Fe in a strongly implantation-induced disturbed region. The fourth component, which is the focus of this paper, can be assigned to Fe at an interstitial site. Comparison of its measured isomer shift with ab initio calculations suggests that the interstitial Fe is located on, or close to, the face of the rock-salt MgO structure. To harmonize such an assignment with the measured near-zero quadrupole interaction a local motion process (cage motion) of the Fe has to be stipulated. The relation of such a local motion as a starting point for long range diffusion is discussed.

  3. InSb semiconductors and (In,Mn)Sb diluted magnetic semiconductors. Growth and properties

    Energy Technology Data Exchange (ETDEWEB)

    Tran, Lien

    2011-04-13

    This dissertation describes investigations of the growth by molecular beam epitaxy and the characterization of the semiconductor InSb as well as the diluted magnetic semiconductor (DMS) In{sub 1-x}Mn{sub x}Sb. The InSb films were grown on GaAs (001) substrate and Si (001) offcut by 4 toward (110) substrate up to a thickness of about 2 {mu}m, in spite of a large lattice mismatch between the epi-layer and substrate (14.6% between InSb and GaAs, and 19.3% between InSb and Si). After optimizing the growth conditions, the best InSb films grown directly on GaAs without any special technique results in a high crystal quality, low noise, and an electron mobility of 41100 cm{sup 2}/V s Vs with associated electron concentration of 2.9.10{sup 6} cm{sup -3} at 300 K. Such structures could be used, for example, for infrared detector structures. The growth of InSb on Si, however, is a challenge. In order to successfully grow InSb on Si, tilted substrates and the insertion of buffer layers were used, which helps to reduce the lattice mismatch as well as the formation of defects, and hence to improve the crystal quality. An electron mobility of 24000 cm{sup 2}/V s measured at 300 K, with an associated carrier concentration of 2.6.10{sup 1}6 cm{sup -3} is found for the best sample that was grown at 340 C with a 0.06 {mu}m-thick GaSb/AlSb superlattice buffer layer. The smaller value of electron mobility (compared to the best GaAsbased sample) is related to a higher density of microtwins and stacking faults as well as threading dislocations in the near-interface region as shown by transmission electron microscopy. Deep level noise spectra indicate the existence of deep levels in both GaAs and Si-based samples. The samples grown on Si exhibit the lowest Hooge factor at 300 K, lower than the samples grown on GaAs. Taking the optimized growth conditions of InSb/GaAs, the diluted magnetic semiconductor In{sub 1-x}Mn{sub x}Sb/GaAs (001) is prepared by adding a few percent of Mn into the

  4. Submillimeter wave absorption of n-type InSb at low temperatures

    Science.gov (United States)

    Brown, E. R.

    1985-01-01

    The absorption coefficient of two high-purity n-InSb samples is measured in the 10-40 per cm range using Fourier transform spectroscopy. The absorption coefficient spectrum is presented for both samples at 4.2 K. It is also shown for the lower resistance sample cooled to 2.2 K and heated by dc bias to elevated electron gas temperatures of 7.5 and 17.9 K. ac Drude theory gives rather poor agreement with experiment at 2.2 and 4.2 K but does much better when the sample electron gas is heated. In contrast, a simple quantum mechanical theory of absorption based on inverse Bremsstrahlung yields promising agreement at the lower temperatures although its applicability is questionable. The non-Drudian absorption is shown to have a favorable effect on the performance of InSb hot-electron bolometers.

  5. Performance Measurements On A 32X32 InSb-CID Detector Array For Astronomical Observations

    Science.gov (United States)

    Tiphene, D.; Lacombe, F.; Rouan, D.

    1989-01-01

    The use at liquid helium temperature of a InSb-CID detector array differs significantly from opera-tion at conditions usually adopted by the manufacturer (77K). In particular, the dark current behaviour hugely changes between the two temperatures. Only the tunnel current, independant of temperature conditions, is still active at 4.2K while the thermal-family currents vanish. We have studied the tunnel current of one InSb-MIS detector to determine its suitability to the low background conditions that will be met in the space experiment ISO. The search for the maximum integration time and the best quantum efficiency, the constraint about the photonic response linearity (especially at low photon flux), and the reduction of the readout noise constitute the main points of this study. Moreover, laboratory measurements showed secondary effects due to the detector (lag) or to the wiring (crosstalk). The CID array reactions to high energy radiations (Gamma rays) are finally discussed.

  6. Twin-Induced InSb Nanosails: A Convenient High Mobility Quantum System.

    Science.gov (United States)

    de la Mata, María; Leturcq, Renaud; Plissard, Sébastien R; Rolland, Chloé; Magén, César; Arbiol, Jordi; Caroff, Philippe

    2016-02-10

    Ultra narrow bandgap III-V semiconductor nanomaterials provide a unique platform for realizing advanced nanoelectronics, thermoelectrics, infrared photodetection, and quantum transport physics. In this work we employ molecular beam epitaxy to synthesize novel nanosheet-like InSb nanostructures exhibiting superior electronic performance. Through careful morphological and crystallographic characterization we show how this unique geometry is the result of a single twinning event in an otherwise pure zinc blende structure. Four-terminal electrical measurements performed in both the Hall and van der Pauw configurations reveal a room temperature electron mobility greater than 12,000 cm(2)·V(-1)·s(-1). Quantized conductance in a quantum point contact processed with a split-gate configuration is also demonstrated. We thus introduce InSb "nanosails" as a versatile and convenient platform for realizing new device and physics experiments with a strong interplay between electronic and spin degrees of freedom.

  7. Terahertz emission from InSb illuminated by femtosecond laser pulses

    Science.gov (United States)

    Arlauskas, A.; Subačius, L.; Krotkus, A.; Malevich, V. L.

    2017-02-01

    Athough terahertz (THz) radiation from semiconductor surfaces illuminated by femtosecond laser pulses was observed a long time ago, the mechanisms responsible for this radiation still remains questionable, especially in narrow band gap semiconductors. Four different crystallographic orientation {(1 0 0), (1 1 0), (1 1 1) and (1 1 2)} InSb samples were analyzed in this investigation. THz amplitude dependences on the excitation wavelength and azimuthal angle are presented in this paper. We have shown that the second order nonlinear effect—optical rectification—is responsible for THz radiation in InSb. The microscopic origin of this effect is related to the orientation of electrons momenta by the optical radiation and anisotropy of the conduction band at high energies. Monte Carlo simulations have shown that electric field screening by intrinsic carriers diminishes the contribution of the third order nonlinear effect in this material.

  8. X-ray diffraction, Raman and photoacoustic studies of InSb nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Ersching, K., E-mail: kleb85@hotmail.com [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, 88040-900 Florianopolis, Santa Catarina (Brazil); Campos, C.E.M.; Lima, J.C. de; Grandi, T.A. [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, 88040-900 Florianopolis, Santa Catarina (Brazil); Souza, S.M. [Departamento de Engenharia Mecanica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, 88040-900 Florianopolis, Santa Catarina (Brazil); Pizani, P.S. [Departamento de Fisica, Universidade Federal de Sao Carlos, 13 565-905 Sao Carlos, SP (Brazil)

    2010-08-01

    Zinc blend InSb nanocrystals were generated by mechanical alloying and X-ray diffraction, Raman spectroscopy and photoacoustic absorption spectroscopy techniques were used to study its structural, optical and thermal properties. Annealed nanocrystals were also studied. Residual amorphous and minority crystalline (Sb and In{sub 2}O{sub 3}) phases were also observed for mechanical alloyed and thermal annealed samples, respectively. The structural parameters, phase fractions, average crystallite sizes and microstrains of all crystalline phases found in the samples were obtained from Rietveld analyses of their X-ray diffraction patterns. Raman results for both as-milled and annealed samples show the Raman active LO and TO modes of the zinc blend InSb phase and Sb-rich regions. The photoacoustic results of both samples were satisfactorily explained by thermal bending heat transfer mechanism and an increase on effective thermal diffusivity coefficient was observed after annealing.

  9. On the processing of InAs and InSb photodiode applications

    Energy Technology Data Exchange (ETDEWEB)

    Odendaal, V.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, PO Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Auret, F.D. [Department of Physics, University of Pretoria, Lynnwood road, Hillcrest, Pretoria 0002 (South Africa)

    2008-07-01

    In this paper, potential methods for the surface passivation of InSb and InAs material, covering both compositional extremes of the promising narrow band gap semiconductor InAsSb, are evaluated. Surface states, mostly due to dangling bonds and exposure to the atmosphere, create generation-recombination centres that negatively influence the dark current, stability, efficiency and related noise characteristics of photosensitive devices fabricated from these materials. The effect of various surface treatments, including sulphuric acid based etching, lactic acid based etching, KOH anodising and Na{sub 2}S anodising, on the relative number of surface states is deduced by evaluating the capacitance versus voltage characteristics of metal-insulator-semiconductor structures fabricated on InAs and InSb. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Calculation of phase equilibria of the Ag-In-Sb system by the calphad method

    Directory of Open Access Journals (Sweden)

    Borisov Ivana I.

    2007-01-01

    Full Text Available The ternary Ag-In-Sb system is a promising candidate for use as a Pb-free solder. The results of phase equilibria calculation by the CALPHAD method are presented in this study. The isothermal section at 400°C was calculated using optimized thermodynamic parameters of the constitutive binary systems. Calculated vertical sections from the indium and antimony corners were compared with the DTA results from this study and from the literature.

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

    Science.gov (United States)

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

    2017-02-01

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

  12. Polymorphism and the crystal structures of InSb at elevated temperature and pressure

    Science.gov (United States)

    Yu, S.-C.; Spain, I. L.; Skelton, E. F.

    1978-01-01

    The paper presents polycrystalline X-ray diffraction data for three high-pressure phases of InSb. The study employed two types of diamond-anvil pressure cells. The X-ray diffraction parameters were recorded at different fixed pressures and temperatures on flat film. The experiment utilized Zr-filtered Mo radiation. The intensities were estimated from the X-ray photographs using a semiautomated microdensitometer.

  13. InSb Mid-Infrared Photon Detector for Room-Temperature Operation

    Science.gov (United States)

    Ueno, Koichiro; Gomes Camargo, Edson; Katsumata, Takashi; Goto, Hiromasa; Kuze, Naohiro; Kangawa, Yoshihiro; Kakimoto, Koichi

    2013-09-01

    We developed a small InSb mid-infrared (2-7 µm wavelength range) photon detector that operates at room temperature. The photodiode was made from (hetero epitaxial) InSb layers that were grown on a semi-insulating GaAs substrate by molecular beam epitaxy. To suppress the effects of the diffusion current of the p-i-n photodiode, we used an AlInSb barrier layer that raises the resistance of the photodiode. We also optimized the device's doping concentration and the infrared incidence window structure. These optimization steps realized high photoelectric current output in a room-temperature environment. We also increased the signal-to-noise ratio of the detector by connecting multiple photodiodes in series. The size of this detector is 1.9×2.7×0.4 mm3 and the detectivity is 2.8×108 cm Hz1/2/W at 300 K. This is a practical IR detector that can be used in general signal amplification ICs.

  14. Interband magneto-spectroscopy in InSb square and parabolic quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Kasturiarachchi, T.; Edirisooriya, M.; Mishima, T. D.; Doezema, R. E.; Santos, M. B. [Homer L. Dodge Department of Physics and Astronomy and Center for Semiconductor Physics in Nanostructures, University of Oklahoma, Norman, Oklahoma 73019 (United States); Saha, D.; Pan, X.; Sanders, G. D.; Stanton, C. J. [Department of Physics, University of Florida, Gainesville, Florida 32611 (United States)

    2015-06-07

    We measure the magneto-optical absorption due to intersubband optical transitions between conduction and valence subband Landau levels in InSb square and parabolic quantum wells. InSb has the narrowest band gap (0.24 eV at low temperature) of the III–V semiconductors leading to a small effective mass (0.014 m{sub 0}) and a large g–factor (−51). As a result, the Landau level spacing is large at relatively small magnetic fields (<8 T), and one can observe spin-splitting of the Landau levels. We examine two structures: (i) a multiple-square-well structure and (ii) a structure containing multiple parabolic wells. The energies and intensities of the strongest features are well explained by a modified Pidgeon-Brown model based on an 8-band k•p model that explicitly incorporates pseudomorphic strain. The strain is essential for obtaining agreement between theory and experiment. While modeling the square well is relatively straight-forward, the parabolic well consists of 43 different layers of various thickness to approximate a parabolic potential. Agreement between theory and experiment for the parabolic well validates the applicability of the model to complicated structures, which demonstrates the robustness of our model and confirms its relevance for developing electronic and spintronic devices that seek to exploit the properties of the InSb band structure.

  15. Nanoporosity-induced superhydrophobicity and large antireflection in InSb

    Energy Technology Data Exchange (ETDEWEB)

    Datta, Debi Prasad [SUNAG Laboratory, Institute of Physics, Sachivalaya Marg, Bhubaneswar 751 005 (India); National Institute of Science Education and Research, Sachivalaya Marg, Bhubaneswar 751 005 (India); Som, Tapobrata, E-mail: tsom@iopb.res.in [SUNAG Laboratory, Institute of Physics, Sachivalaya Marg, Bhubaneswar 751 005 (India)

    2016-05-09

    A porous nanostructure evolves in InSb due to keV ion implantation which leads to superhydrophobic and large antireflective property, indicating a single-step facile fabrication to introduce both functionalities. In particular, it is observed that the contact angle of a water droplet on the nanoporous InSb surface exceeds 150°, revealing the transition to a superhydrophobic surface. Correlation between the contact angle and the porous nanostructures is qualitatively understood in light of the Cassie-Baxter model. It is found that a decrease in the fraction of solid surface wetted by the water droplet and a corresponding increase in the air-water interface fraction lead to the enhancement in the hydrophobicity. We further observe that the large broadband antireflection (in the range of 200–800 nm) is also correlated to the nanoporous structure, arising out of a large reduction in the refractive index due to its increasing porosity. Such a surface with the combination of superhydrophobicity and large antireflection can be very useful for applications of InSb nanostructures in electronic, photonic devices, or infrared detectors.

  16. Coherent Charge Transport in Ballistic InSb Nanowire Josephson Junctions

    Science.gov (United States)

    Li, S.; Kang, N.; Fan, D. X.; Wang, L. B.; Huang, Y. Q.; Caroff, P.; Xu, H. Q.

    2016-04-01

    Hybrid InSb nanowire-superconductor devices are promising for investigating Majorana modes and topological quantum computation in solid-state devices. An experimental realisation of ballistic, phase-coherent superconductor-nanowire hybrid devices is a necessary step towards engineering topological superconducting electronics. Here, we report on a low-temperature transport study of Josephson junction devices fabricated from InSb nanowires grown by molecular-beam epitaxy and provide a clear evidence for phase-coherent, ballistic charge transport through the nanowires in the junctions. We demonstrate that our devices show gate-tunable proximity-induced supercurrent and clear signatures of multiple Andreev reflections in the differential conductance, indicating phase-coherent transport within the junctions. We also observe periodic modulations of the critical current that can be associated with the Fabry-Pérot interference in the nanowires in the ballistic transport regime. Our work shows that the InSb nanowires grown by molecular-beam epitaxy are of excellent material quality and hybrid superconducting devices made from these nanowires are highly desirable for investigation of the novel physics in topological states of matter and for applications in topological quantum electronics.

  17. Monitoring of the MBE growth processes of CdTe on InSb by laser light scattering

    OpenAIRE

    J. Huerta; M. López López; O. Zelaya Angel

    1999-01-01

    We have studied by Laser Light Scattering (LLS) the oxides surface desorption of InSb substrates, and the subsequentgrowth of CdTe layers by molecular beam epitaxy (MBE). LLS measurements allowed us to determine the criticaltemperature before surface degradation of InSb, which is not evidently noticed by reflection high energy electrondiffraction (RHEED). Surface defects appeared on substrates where this temperature was exceeded, as observed byscanning electron microscopy (SEM) and Atomic For...

  18. Performance estimation of InSb compound semiconductor detectors as a function of active area using alpha particles

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Yuki, E-mail: y.sato@riken.jp [The Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Department of Nuclear Engineering, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8530 (Japan); Morita, Yasunari [NOK Corporation, 4-3-1 Tsujido-Shinmachi, Fujisawa, Kanagawa 251-0042 (Japan); Kanno, Ikuo [Department of Nuclear Engineering, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8530 (Japan)

    2014-02-11

    We have fabricated radiation detectors using p-type indium antimonide crystals grown by liquid phase epitaxy (LPE). The current–voltage curves, energy spectra of alpha particles, and energy resolutions obtained using two different InSb detectors were compared. The alpha-particle energy resolutions were 1.8% at 24 and 42 K, using the LPE–InSb detector with wafer size of 1.0×1.5 mm{sup 2}.

  19. Analysis of defects on InSb film grown by MBE%分子束外延 InSb 薄膜缺陷分析

    Institute of Scientific and Technical Information of China (English)

    周朋; 刘铭; 邢伟荣; 尚林涛; 巩锋

    2014-01-01

    High operating temperature detector has become a significant direction of the 3rd generation infrared detec-tors.In order to achieve this aim,defects on the detector materials must be reduced.In this paper,the effect of differ-ent experimental conditions on InSb wafers grown by molecular beam epitaxy is studied,metallographic microscope, scanning electron microscope and X-ray double crystal diffraction are used to study the defects.The characteristics,o-rigination and eliminating methods of these defects are analyzed.By MBE optimization,the best defect density has reached 483 cm -2.%实现高温工作已经成为了第三代红外探测器的重要发展方向。为了达到这个目标,首先要降低探测器材料的各种缺陷。本文主要研究了不同生长条件对 InSb 分子束外延薄膜的晶体质量的影响,并采用金相显微镜、X 射线双晶衍射仪、扫描电子显微镜及 X 射线能谱仪等检测手段对外延膜缺陷进行了研究,综合分析了各缺陷的特征、起因、消除方法等。通过优化外延条件,外延膜宏观生长缺陷最低值达到483 cm -2。

  20. Two-window InSbBi quantum-dot photodetector.

    Science.gov (United States)

    Dwara, Sana N; Al-Khursan, Amin H

    2016-07-20

    Quantum efficiency (QE) was modeled for an n-type doping InSb1-xBix quantum-dot (QD) photodetector with a p-type doping AlGaAs bulk region. First, the relations of the electron and hole contributions to the current were stated. The absorption coefficient was calculated for the structure, and two windows were predicted in the quantum efficiency spectrum, which is important in the detection applications. High quantum efficiency was obtained due to the Bi inclusion in the structure of the photodetector.

  1. Anharmonic Noninertial Lattice Dynamics during Ultrafast Nonthermal Melting of InSb

    Science.gov (United States)

    Zijlstra, Eeuwe S.; Walkenhorst, Jessica; Garcia, Martin E.

    2008-09-01

    We compute the potential energy surface of femtosecond-laser-excited InSb along the directions in which the crystal becomes soft. Using dynamical simulations the time dependence of the atomic coordinates is obtained. We find that at high excitation densities the anharmonicity of the potential energy surface becomes significant after ˜100fs. On the basis of our results we explain recent time-resolved x-ray diffraction experiments. We point out that an alternative model for ultrafast melting [A. M. Lindenberg , Science 308, 392 (2005)SCIEAS0036-807510.1126/science.1107996] is inconsistent with our calculations.

  2. Unit Cell Structure of Crystal Polytypes in InAs and InSb Nanowires

    DEFF Research Database (Denmark)

    Kriegner, Dominik; Panse, Christian; Mandl, Bernhard

    2011-01-01

    , wurtzite, and 4H polytypes for InAs and InSb nanowires, using X-ray diffraction and transmission electron microscopy. The results are compared to density functional theory calculations. Experiment and theory show that the occurrence of hexagonal bilayers tends to stretch the distances of atomic layers...... parallel to the c axis and to reduce the in-plane distances compared to those in zinc blende. The change of the lattice parameters scales linearly with the hexagonality of the polytype, defined as the fraction of bilayers with hexagonal character within one unit cell....

  3. Quantized Conductance in InSb nanowires at zero magnetic field

    Science.gov (United States)

    Kammhuber, Jakob; Cassidy, Maja; Zhang, Hao; Gül, Önder; Pei, Fei; de Moor, Michiel; Watanabe, Kenji; Taniguchi, Takashi; Car, Diana; Bakkers, Erik; Kouwenhoven, Leo

    We present measurements of InSb nanowires in the ballistic transport regime. In 1D materials such as nanowires, electron scattering has an increased chance of back-reflection, obscuring the observation of quantized conductance at low magnetic fields. By improving the contacts to the nanowire as well as its dielectric environment backscattering events are minimized and conductance quantization is observable at zero magnetic field with high device yield. We study the evolution of individual sub-bands in an external magnetic field, observing a degeneracy between the 2nd and 3rd sub-band when the magnetic field is orientated perpendicular to the nanowire axis.

  4. Conductance Quantization at Zero Magnetic Field in InSb Nanowires

    Science.gov (United States)

    Kammhuber, Jakob; Cassidy, Maja C.; Zhang, Hao; Gül, Önder; Pei, Fei; de Moor, Michiel W. A.; Nijholt, Bas; Watanabe, Kenji; Taniguchi, Takashi; Car, Diana; Plissard, Sébastien R.; Bakkers, Erik P. A. M.; Kouwenhoven, Leo P.

    2016-06-01

    Ballistic electron transport is a key requirement for existence of a topological phase transition in proximitized InSb nanowires. However, measurements of quantized conductance as direct evidence of ballistic transport have so far been obscured due to the increased chance of backscattering in one dimensional nanowires. We show that by improving the nanowire-metal interface as well as the dielectric environment we can consistently achieve conductance quantization at zero magnetic field. Additionally, studying the sub-band evolution in a rotating magnetic field reveals an orbital degeneracy between the second and third sub-bands for perpendicular fields above 1T.

  5. Coupling InSb quantum dots to a superconducting microwave resonator

    Science.gov (United States)

    Cassidy, Maja; Kammhuber, Jakob; Car, Diana; Plissard, Sebastien; Bakkers, Erik; Dicarlo, Leo; Kouwenhoven, Leo

    2014-03-01

    We present measurements of a superconducting half-wave resonator coupled to two InSb nanowire quantum dots. Precise nanowire alignment at the electric field antinodes at opposite ends of the microwave cavity allows for a maximal electric field along the wire axis, without compromising the intrinsic quality factor of the cavity. This architecture may be useful for reaching the strong coupling limit between a single spin and a microwave photon, paving the way to on-chip coupling of single spins for quantum information processing.

  6. Thin InSb layers with metallic gratings: a novel platform for spectrally-selective THz plasmonic sensing.

    Science.gov (United States)

    Lin, Shuai; Bhattarai, Khagendra; Zhou, Jiangfeng; Talbayev, Diyar

    2016-08-22

    We present a computational study of terahertz optical properties of a grating-coupled plasmonic structure based on micrometer-thin InSb layers. We find two strong absorption resonances that we interpret as standing surface plasmon modes and investigate their dispersion relations, dependence on InSb thickness, and the spatial distribution of the electric field. The observed surface plasmon modes are well described by a simple theory of the air/InSb/air tri-layer. The plasmonic response of the grating/InSb structure is highly sensitive to the dielectric environment and the presence of an analyte (e.g., lactose) at the InSb interface, which is promising for terahertz plasmonic sensor applications. We determine the sensor sensitivity to be 7200 nm per refractive index unit (or 0.06 THz per refractive index unit). The lower surface plasmon mode also exhibits a splitting when tuned in resonance with the vibrational mode of lactose at 1.37 THz. We propose that such interaction between surface plasmon and vibrational modes can be used as the basis for a new sensing modality that allows the detection of terahertz vibrational fingerprints of an analyte.

  7. Thin InSb layers with metallic gratings: a novel platform for spectrally-selective THz plasmonic sensing

    CERN Document Server

    Lin, Shuai; Zhou, Jiangfeng; Talbayev, Diyar

    2016-01-01

    We present a computational study of terahertz optical properties of a grating-coupled plasmonic structure based on micrometer-thin InSb layers. We find two strong absorption resonances that we interpret as standing surface plasmon modes and investigate their dispersion relations, dependence on InSb thickness, and the spatial distribution of the electric field. The observed surface plasmon modes are well described by a simple theory of the air/InSb/air trilayer. The plasmonic response of the grating/InSb structure is highly sensitive to the dielectric environment and the presence of an analyte (e.g., lactose) at the InSb interface, which is promising for terahertz plasmonic sensor applications. We determine the sensor sensitivity to be 7200 nm per refractive index unit (or 0.06 THz per refractive index unit). The lower surface plasmon mode also exhibits a splitting when tuned in resonance with the vibrational mode of lactose at 1.37 THz. We propose that such interaction between surface plasmon and vibrational ...

  8. Formation of long single quantum dots in high quality InSb nanowires grown by molecular beam epitaxy.

    Science.gov (United States)

    Fan, Dingxun; Li, Sen; Kang, N; Caroff, Philippe; Wang, L B; Huang, Y Q; Deng, M T; Yu, C L; Xu, H Q

    2015-09-28

    We report on realization and transport spectroscopy study of single quantum dots (QDs) made from InSb nanowires grown by molecular beam epitaxy (MBE). The nanowires employed are 50-80 nm in diameter and the QDs are defined in the nanowires between the source and drain contacts on a Si/SiO2 substrate. We show that highly tunable QD devices can be realized with the MBE-grown InSb nanowires and the gate-to-dot capacitance extracted in the many-electron regimes is scaled linearly with the longitudinal dot size, demonstrating that the devices are of single InSb nanowire QDs even with a longitudinal size of ∼700 nm. In the few-electron regime, the quantum levels in the QDs are resolved and the Landég-factors extracted for the quantum levels from the magnetotransport measurements are found to be strongly level-dependent and fluctuated in a range of 18-48. A spin-orbit coupling strength is extracted from the magnetic field evolutions of a ground state and its neighboring excited state in an InSb nanowire QD and is on the order of ∼300 μeV. Our results establish that the MBE-grown InSb nanowires are of high crystal quality and are promising for the use in constructing novel quantum devices, such as entangled spin qubits, one-dimensional Wigner crystals and topological quantum computing devices.

  9. Solute segregation in directional solidification of GaInSb concentrated alloys under alternating magnetic fields

    Science.gov (United States)

    Stelian, Carmen; Delannoy, Yves; Fautrelle, Yves; Duffar, Thierry

    2004-05-01

    Numerical simulations of the vertical Bridgman solidification of Ga 1- xIn xSb concentrated alloys are performed by using the commercial codes FIDAP ® and FLUENT ®. The transient axi-symmetric simulation of heat, mass and species transport during highly doped ( x=0.2) crystal growth, shows a strong solute effect on the melt convection. The thermally driven flow is damped by the heavier solute (InSb) rejected at the solid-liquid interface. A diffusive transport regime is established in the melt a short time after the beginning of solidification and as a consequence, the radial segregation increases. This leads to a significant increase of the interface curvature because of the melting point dependency on the interface composition. Finally, the crystals are not chemically homogeneous with large variations of InSb concentration on the axial and radial directions. In order to improve the chemical homogeneity of highly doped Ga 1- xIn xSb crystals, it is proposed to apply an alternating magnetic field in the vicinity of the solid-liquid interface. The magnetic parameters for which an optimal level of convection arises in the melt are derived from the numerical simulation. It is shown that during solidification under optimized electromagnetic stirring, the radial segregation and interface deflection can be maintained at low values.

  10. Electrodeposition of InSb branched nanowires: Controlled growth with structurally tailored properties

    Energy Technology Data Exchange (ETDEWEB)

    Das, Suprem R.; Mohammad, Asaduzzaman; Janes, David B., E-mail: janes@ecn.purdue.edu [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Akatay, Cem [School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Khan, Mohammad Ryyan; Alam, Muhammad A. [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Maeda, Kosuke [Department of Materials Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta–cho, Midori-ku, Yokohama 226-8502 (Japan); Advanced Device Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Deacon, Russell S.; Ishibashi, Koji [Advanced Device Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Chen, Yong P. [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907 (United States); Sands, Timothy D. [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States)

    2014-08-28

    In this article, electrodeposition method is used to demonstrate growth of InSb nanowire (NW) arrays with hierarchical branched structures and complex morphology at room temperature using an all-solution, catalyst-free technique. A gold coated, porous anodic alumina membrane provided the template for the branched NWs. The NWs have a hierarchical branched structure, with three nominal regions: a “trunk” (average diameter of 150 nm), large branches (average diameter of 100 nm), and small branches (average diameter of sub-10 nm to sub-20 nm). The structural properties of the branched NWs were studied using scanning transmission electron microscopy, transmission electron microscopy, scanning electron microscopy, x-ray diffraction, energy dispersive x-ray spectroscopy, and Raman spectroscopy. In the as-grown state, the small branches of InSb NWs were crystalline, but the trunk regions were mostly nanocrystalline with an amorphous boundary. Post-annealing of NWs at 420 °C in argon produced single crystalline structures along 〈311〉 directions for the branches and along 〈111〉 for the trunks. Based on the high crystallinity and tailored structure in this branched NW array, the effective refractive index allows us to achieve excellent antireflection properties signifying its technological usefulness for photon management and energy harvesting.

  11. Structural characterization of InSb thin films grown by electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Joginder, E-mail: joginderchauhan82@gmail.com; Rajaram, P. [School of Studies in Physics, Jiwaji University, Gwalior-474011 (India)

    2015-06-24

    In the present work we have grown InSb thin films on brass substrates, using the electrodeposition technique. The electrochemical baths used in the growth were made up of aqueous solutions of InCl{sub 3} and SbCl{sub 3} mixed together in various proportions. The films grown were characterized by X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive Analysis of X-rays (EDAX). Compositional studies show that stoichiometric InSb films can be prepared from a bath containing 0.05M InCl{sub 3} and 0.04M SbCl{sub 3}. XRD studies reveal that the films grown are polycrystalline having the zinc blende structure with (111) orientation. Crystallite size, dislocation density and strain were calculated using the XRD results. Optical transmission spectra were recorded using an FTIR spectrophotometer. The value of direct band gap was found to be around 0.20 eV for the thin films having the best stoichiometry.

  12. Quantum dots formed in InSb/AlAs and AlSb/AlAs heterostructures

    Science.gov (United States)

    Abramkin, D. S.; Rumynin, K. M.; Bakarov, A. K.; Kolotovkina, D. A.; Gutakovskii, A. K.; Shamirzaev, T. S.

    2016-06-01

    The crystal structure of new self-assembled InSb/AlAs and AlSb/AlAs quantum dots grown by molecularbeam epitaxy has been investigated by transmission electron microscopy. The theoretical calculations of the energy spectrum of the quantum dots have been supplemented by the experimental data on the steady-state and time-resolved photoluminescence spectroscopy. Deposition of 1.5 ML of InSb or AlSb on the AlAs surface carried out in the regime of atomic-layer epitaxy leads to the formation of pseudomorphically strained quantum dots composed of InAlSbAs and AlSbAs alloys, respectively. The quantum dots can have the type-I and type-II energy spectra depending on the composition of the alloy. The ground hole state in the quantum dot belongs to the heavy-hole band and the localization energy of holes is much higher than that of electrons. The ground electron state in the type-I quantum dots belongs to the indirect X XY valley of the conduction band of the alloy. The ground electron state in the type-II quantum dots belongs to the indirect X valley of the conduction band of the AlAs matrix.

  13. CONTACT MATERIALS FOR GaSb AND InSb: A PHASE DIAGRAM APPROACH

    Institute of Scientific and Technical Information of China (English)

    K.W. Richter; H. Ipser

    2002-01-01

    The development of well defined and thermally stable ohmic contacts for Ⅲ- Ⅴ semi-conductors like InSb and GaSb is still a challenging problem in semiconductor devicetechnology. As device processing usually includes the exposure to elevated tempera-tures, interface reactions often occur during metallization and further heat treatment.It is thus important to understand the respective phase equilibria of the involved el-ements. From the thermodynamic point of view, binary and ternary compounds inequilibrium with the respective compound semiconductor would be the best choice forcontact materials as these contacts will be stable even after long exposure to elevatedtemperatures. These possible candidates for contact materials may be directly obtainedfrom the phase diagrams.During the last years we investigated several phase diagrams of transition metals withGaSb and InSb. Experimental results in the systems Ga-Ni-Sb, Ga-Pd-Sb, Ga-Pt-Sb,In-Ni-Sb and In-Pd-Sb are summarized and are discussed in the context of contactchemistry.

  14. GaInSb/InAs/AlSb quantum wells with InSb- and GaAs-like interfaces investigated by temperature- and magnetic field-dependent photoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiren; Guo, Shaoling; Shao, Jun, E-mail: jshao@mail.sitp.ac.cn [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 200083 Shanghai (China); Xing, Junliang; Niu, Zhichuan, E-mail: zcniu@semi.ac.cn [State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing (China); Zhu, Liangqing [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 200083 Shanghai (China); Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, 200062 Shanghai (China); Zha, F.-X. [Physics Department, Shanghai University, 200444 Shanghai (China)

    2016-05-07

    GaInSb/InAs/AlSb quantum wells (QWs) with typical InSb- and GaAs-like interfaces (IFs) are investigated by temperature- and magnetic field-dependent photoluminescence (PL), respectively. The results show that (i) as temperature rises the PL energy of the QWs with either InSb- or GaAs-like IFs blueshifts slightly below 50 K but redshifts above and broadens rapidly, and the mechanism behind this is correlated to the IF roughness-related layer thickness fluctuation equivalent to a localization energy of about 9.5 meV; (ii) the PL diminishes monotonously as magnetic field rises except for the delocalized PL process of the InSb-like IF QWs, and the magnetic field-induced PL quenching is attributed to the IF roughness-induced electron-hole separation in the type-II QWs; and (iii) the magnetic field-dependent PL energy follows a typical excitonic diamagnetic shift for both located and dislocated states, and the deduced exciton binding energy, reduced effective mass, and average wavefunction extent are insensitive to the IF type. Comparison of different IF-type GaInSb/InAs QWs indicates that while the PL of the InSb-like IF sample contains type-I component as the IF confines heavy holes and acts as pseudo-barrier for electrons, leading to the coexistence of electrons and holes at the IFs, the IF-type does not affect the carrier localization and the in-plane excitonic behavior obviously.

  15. Room temperature inductively coupled plasma etching of InAs/InSb in BCl 3/Cl 2/Ar

    KAUST Repository

    Sun, Jian

    2012-10-01

    Inductively coupled plasma (ICP) etching of InAs and InSb at room temperature has been investigated using BCl 3/Cl 2/Ar plasma. Specifically, the etch rate and post-etching surface morphology were investigated as functions of the gas composition, ICP power, process pressure, and RF chuck power. An optimized process has been developed, yielding anisotropic etching and very smooth surfaces with roughnesses of 0.25 nm for InAs, and 0.57 nm for InSb, which is comparable with the surface of epi-ready polished wafers. The process provides moderate etching rates of 820 /min for InAs and 2800 /min for InSb, and the micro-masking effect is largely avoided. © 2012 Elsevier B.V. All rights reserved.

  16. Temperature-Dependent Galvanomagnetic Measurements on Doped InSb and InAs Grown by Liquid Encapsulated Czochralski

    Institute of Scientific and Technical Information of China (English)

    M. Kasap; S. Acar; S. (O)z(c)elik; S. Karadeniz2; N. Tu(g)luo(g)lu

    2005-01-01

    @@ Resistivity, magnetoresistivity and Hall effect measurements in n-type Te-doped InSb and S-doped InAs samples grown by the liquid encapsulated Czochralski technique were carried out as a function of temperature (14-350 K) and magnetic field (0-1.35 T). In Te-doped InSb, an impurity level with energy E1 -= 3 meV and the activation energy Eo =- 0.26 eV, which is the band gap energy, are obtained from the resistivity and Hall carrier concentration analysis. In S-doped InAs, both the linear and power law models are used in explaining the temperature-dependent resistivity. The effects of impurities on the electron and magnetic transportation properties of InAs and InSb have also been discussed.

  17. 10μm pitch family of InSb and XBn detectors for MWIR imaging

    Science.gov (United States)

    Gershon, G.; Avnon, E.; Brumer, M.; Freiman, W.; Karni, Y.; Niderman, T.; Ofer, O.; Rosenstock, T.; Seref, D.; Shiloah, N.; Shkedy, L.; Tessler, R.; Shtrichman, I.

    2017-02-01

    There has been a growing demand over the past few years for infrared detectors with a smaller pixel dimension. On the one hand, this trend of pixel shrinkage enables the overall size of a given Focal Plan Array (FPA) to be reduced, allowing the production of more compact, lower power, and lower cost electro-optical (EO) systems. On the other hand, it enables a higher image resolution for a given FPA area, which is especially suitable in infrared systems with a large format that are used with a wide Field of View (FOV). In response to these market trends SCD has developed the Blackbird family of 10 μm pitch MWIR digital infrared detectors. The Blackbird family is based on three different Read- Out Integrated Circuit (ROIC) formats: 1920×1536, 1280×1024 and 640×512, which exploit advanced and mature 0.18 μm CMOS technology and exhibit high functionality with relatively low power consumption. Two types of 10 μm pixel sensing arrays are supported. The first is an InSb photodiode array based on SCD's mature planar implanted p-n junction technology, which covers the full MWIR band, and is designed to operate at 77K. The second type of sensing array covers the blue part of the MWIR band and uses the patented XBn-InAsSb barrier detector technology that provides electro-optical performance equivalent to planar InSb but at operating temperatures as high as 150 K. The XBn detector is therefore ideal for low Size, Weight and Power (SWaP) applications. Both sensing arrays, InSb and XBn, are Flip-chip bonded to the ROICs and assembled into custom designed Dewars that can withstand harsh environmental conditions while minimizing the detector heat load. A dedicated proximity electronics board provides power supplies and timing to the ROIC and enables communication and video output to the system. Together with a wide range of cryogenic coolers, a high flexibility of housing designs and various modes of operation, the Blackbird family of detectors presents solutions for EO

  18. Monte Carlo study of impact ionization in InSb induced by intense ultrashort terahertz pulses

    Energy Technology Data Exchange (ETDEWEB)

    Asmontas, S.; Raguotis, R.; Bumeliene, S. [Center for Physical Sciences and Technology, Vilnius (Lithuania)

    2015-09-15

    The electron impact ionization dynamic has been investigated by Monte Carlo method in n-type InSb under the action of single-cycle pulses with 1 ps duration. The threshold electric field of impact ionization has been estimated to be about 8 kV/cm at 80 K. The number of generated carriers increases rapidly with increasing of electric field strength over threshold, and at 100 kV/cm, normalized electron concentration reaches 14. It is found that impact ionization process is dominant energy loss mechanism for hot carriers with energy larger than threshold energy of impact ionization. The results of calculations are compared with available experimental data. The agreement between theoretical calculations and experimental results was obtained. (orig.)

  19. Laser direct writing pattern structures on AgInSbTe phase change thin film

    Institute of Scientific and Technical Information of China (English)

    Aihuan Dun; Jingsong Wei; Fuxi Gan

    2011-01-01

    Different pattern structures axe obtained on the AglnSbTe (AIST) phase change film as induced by laser beam. Atomic force microscopy (AFM) was used to observe and analyze the different pattern structures. The AFM photos clearly show the gradually changing process of pattern structures induced by different threshold effects, such as crystallization threshold, microbump threshold, melting threshold, and ablation threshold. The analysis indicates that the AIST material is very effective in the fabrication of pattern structures and can offer relevant guidance for application of the material in the future.%@@ Different pattern structures are obtained on the AgInSbTe(AIST) phase change film as induced by laser beam.Atomic force microscopy(AFM) was used to observe and analyze the different pattern structures.The AFM photos clearly show the gradually changing process of pattern structures induced by different threshold effects,such as crystallization threshold,microbump threshold,melting threshold,and ablation threshold.

  20. Evaluation of electron mobility in InSb quantum wells by means of percentage-impact

    Energy Technology Data Exchange (ETDEWEB)

    Mishima, T. D.; Edirisooriya, M.; Santos, M. B. [Homer L. Dodge Department of Physics and Astronomy, and Center for Semiconductor Physics in Nanostructure, University of Oklahoma, 440 W. Brooks St., Norman, OK 73019 (United States)

    2014-05-15

    In order to quantitatively analyze the contribution of each scattering factor toward the total carrier mobility, we use a new convenient figure-of-merit, named a percentage impact. The mobility limit due to a scattering factor, which is widely used to summarize a scattering analysis, has its own advantage. However, a mobility limit is not quite appropriate for the above purpose. A comprehensive understanding of the difference in contribution among many scattering factors toward the total carrier mobility can be obtained by evaluating percentage impacts of scattering factors, which can be straightforwardly calculated from their mobility limits and the total mobility. Our percentage impact analysis shows that threading dislocation is one of the dominant scattering factors for the electron transport in InSb quantum wells at room temperature.

  1. Cleaning chemistry of InSb(100) molecular beam epitaxy substrates

    Science.gov (United States)

    Vasquez, R. P.; Lewis, B. F.; Grunthaner, F. J.

    1983-01-01

    InSb has been used as a substrate for molecular beam epitaxy. For good epitaxial growth, a substrate surface which is smooth and clean on an atomic scale is required. Chemical cleaning procedures provide an oxide film to passivate the surface. This film is then desorbed by in situ heating. The material forming the film should, therefore, have a high vapor pressure at some temperature less than the substrate melting temperature. A chloride film appears to satisfy the latter requirement. The present investigation is, therefore, concerned with the formation of a chloride film rather than an oxide film. Carbon contamination has been found to cause problems in chemical cleaning procedures. The level of carbon contamination found in the case of chloride film formation, is therefore compared with the corresponding level observed in procedures using oxide films. It appears that a chloride film grown in connection with a short exposure time to a Cl2 plasma is preferable to other passivation films studied.

  2. GaInSb and GaInAsSb thermophotovoltaic device fabrication and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Hitchcock, C.; Gutmann, R.; Borrego, J.; Ehsani, H.; Bhat, I. [Rensselaer Polytechnic Inst., Troy, NY (United States); Freeman, M.; Charache, G. [Lockheed Martin, Inc., Schenectady, NY (United States)

    1997-05-01

    Thermophotovoltaic (TPV) devices have been fabricated using epitaxial ternary and quaternary layers grown on GaSb substrates. The GaInSb layers were grown by organometallic vapor phase epitaxy (OMVPE) and the InGaAsSb lattice-matched layers were grown by liquid phase epitaxy (LPE). Device fabrication steps include unannealed p-type ohmic contacts, annealed Sn/Au n-type ohmic contacts, and a thick Ag top-surface contact using a lift-off process. Devices are characterized primarily by dark I-V, photo I-V, and quantum efficiency measurements, which are correlated to microscopic and macroscopic material properties. Particular emphasis has been on material enhancements to increase quantum efficiency and decrease dark saturation current density. TPV device performance is presently limited by the base diffusion length, typically 1 to 2 microns.

  3. Conductance quantization in an AgInSbTe-based memristor at nanosecond scale

    Science.gov (United States)

    Jiang, L.; Xu, L.; Chen, J. W.; Yan, P.; Xue, K. H.; Sun, H. J.; Miao, X. S.

    2016-10-01

    Quantized conductance was observed in a cation-migration-based memristor with the structure of Ag/AgInSbTe(AIST)/Ta. The conductance of the memristor exhibits stepwise increases in units of single quantum conductance (77.5 μS), which is attributed to the formation of a metal filament with an atomic contact of different integer multiples. We designed a high speed circuit to conduct the pulse measurement. The quantized conductance can be obtained by applying voltage pulses in intervals as fast as 3 ns with constant amplitude. Considering that the quantized conductance can be modulated by different pulse widths, our results suggest that the AIST-based memristor is a robust candidate for multi-level data storage and neuromorphic computing systems.

  4. Superconducting gap closing and Zero-bias peak in InSb nanowire

    Science.gov (United States)

    Yu, Peng; Chen, Jun; Hocevar, Moïra; Plissard, Sébastien; Car, Diana; Bakkers, Erik; Frolov, Sergey

    In a 1D superconductor-nanowire-normal contact system, Majorana bound states are expected to appear after topological phase transition. Although there are many experiments reported possible zero-bias conductance peak from Majorana bound states, mapping out of the topological phase diagram is still missing.In our InSb nanowire hybrid devices, we observed possible superconducting gap closing and re-opening with magnetic field. These gap closings appear near conductance resonances which show some feature of 1D subband edges. Interestingly, zero-bias conductance peak appears inside the split regime of crossings at finite magnetic field. The magnetic field onset of the zero-bias peak can be tuned by gates underneath the superconductor, which may result from the changing of chemical potential.

  5. 3 mega-pixel InSb detector with 10μm pitch

    Science.gov (United States)

    Gershon, G.; Albo, A.; Eylon, M.; Cohen, O.; Calahorra, Z.; Brumer, M.; Nitzani, M.; Avnon, E.; Aghion, Y.; Kogan, I.; Ilan, E.; Shkedy, L.

    2013-06-01

    SCD has developed a new 1920x1536 / 10 μm digital Infrared detector for the MWIR window named Blackbird. The Blackbird detector features a Focal Plane Array (FPA) that incorporates two technological building blocks developed over the past few years. The first one is a 10 μm InSb pixel based on the matured planar technology. The second building block is an innovative 10 μm ReadOut Integrated Circuit (ROIC) pixel. The InSb and the ROIC arrays are connected using Flip-Chip technology by means of indium bumps. The digital ROIC consists a matrix of 1920x1536 pixels and has an analog to digital (A/D) converter per-channel (total of 1920x2 A/Ds). It allows for full frame readout at a high frame rate of up to 120 Hz. Such an on-chip A/D conversion eliminates the need for several A/D converters with fairly high power consumption at the system level. The ROIC power consumption at maximum bandwidth is less than 400 mW. It features a wide range of pixel-level functionality such as several conversion gain options and a 2x2 pixel binning. The ROIC design makes use of the advanced and matured CMOS technology, 0.18 μm, which allows for high functionality and relatively low power consumption. The FPA is mounted on a Cold-Finger by a specially designed ceramic substrate. The whole assembly is housed in a stiffened Dewar that withstands harsh environmental conditions while minimizing the environment heat load contribution to the heat load of the detector. The design enables a 3-megapixel detector with overall low size, weight, and power (SWaP) with respect to comparable large format detectors. In this work we present in detail the characteristic performance of the new Blackbird detector.

  6. 128 x 128 MWIR InSb focal plane and camera system

    Science.gov (United States)

    Parrish, William J.; Blackwell, John D.; Paulson, Robert C.; Arnold, Harold

    1991-09-01

    The need for increased resolution and sensitivity in IR systems applications has provided the impetus for the development of high-performance second-generation staring focal plane array technology. Previously, the availability of these focal plane array components has been limited and the costs associated with delivery of useful hardware have been high. Utilizing proven InSb detector technology and foundry silicon CMOS processes, a high performance, affordable hybrid focal plane array and support electronics system has been developed. The 128 X 128 array of photovoltac InSb detectors on 50 micrometers centers is interfaced with the silicon readout by aligning and cold welding indium bumps on each detector with the corresponding indium bump on the silicon readout. The detector is then thinned so that it can be illuminated through the backside. The 128 X 128 channel signal processing integrated circuit performs the function of interfacing with the detectors, integrating the detector current, and multiplexing the signals. It is fabricated using a standard double poly, single metal, p-well CMOS process. The detector elements achieve a high quantum efficiency response from less than 1 micrometers to greater than 5 micrometers with an optical fill factor of 90%. The hybrid focal plane array can operate to a maximum frame rate of 1,000 Hz. D* values at 1.7 X 1014 photons/cm2/sec illumination conditions approach the BLIP value of 9.4 X 1011 cm(root)Hz/W with a capacity of 4 X 107 carriers and a dynamic range of greater than 60,000. A NE(Delta) T value of .018 C and a MRT value of .020 C have been measured. The devices operate with only 3 biases and 3 clocks.

  7. ns or fs pulsed laser ablation of a bulk InSb target in liquids for nanoparticles synthesis.

    Science.gov (United States)

    Semaltianos, N G; Hendry, E; Chang, H; Wears, M L; Monteil, G; Assoul, M; Malkhasyan, V; Blondeau-Patissier, V; Gauthier-Manuel, B; Moutarlier, V

    2016-05-01

    Laser ablation of bulk target materials in liquids has been established as an alternative method for the synthesis of nanoparticles colloidal solutions mainly due to the fact that the synthesized nanoparticles have bare, ligand-free surfaces since no chemical precursors are used for their synthesis. InSb is a narrow band gap semiconductor which has the highest carrier mobility of any known semiconductor and nanoparticles of this material are useful in optoelectronic device fabrication. In this paper a bulk InSb target was ablated in deionized (DI) water or ethanol using a nanosecond (20 ns) or a femtosecond (90 fs) pulsed laser source, for nanoparticles synthesis. In all four cases the largest percentage of the nanoparticles are of InSb in the zincblende crystal structure with fcc lattice. Oxides of either In or Sb are also formed in the nanoparticles ensembles in the case of ns or fs ablation, respectively. Formation of an oxide of either element from the two elements of the binary bulk alloy is explained based on the difference in the ablation mechanism of the material in the case of ns or fs pulsed laser irradiation in which the slow or fast deposition of energy into the material results to mainly melting or vaporization, respectively under the present conditions of ablation, in combination with the lower melting point but higher vaporization enthalpy of In as compared to Sb. InSb in the metastable phase with orthorhombic lattice is also formed in the nanoparticles ensembles in the case of fs ablation in DI water (as well as oxide of InSb) which indicates that the synthesized nanoparticles exhibit polymorphism controlled by the type of the laser source used for their synthesis. The nanoparticles exhibit absorption which is observed to be extended in the infrared region of the spectrum.

  8. Preparation of (Bi, Sb) 2S 3 semiconductor films by photochemical deposition method

    Science.gov (United States)

    Sasaki, H.; Shibayama, K.; Ichimura, M.; Masui, K.

    2002-04-01

    The photochemical deposition (PCD) technique has the advantages of economy, the capability of large area deposition and of a fast reaction rate. In this report, the PCD method using UV light of an ultra-high pressure mercury lamp was applied to form (Bi x, Sb 1- x) 2S 3 semiconducting compounds from solutions containing BiCl 3 and/or SbCl 3 Na 2S 2O 3 at pH in the acidic range 1-3. The pH of the solution was adjusted with the addition of dilute HCl solution. The substrate for the film deposition was pretreated onto the commercial pyrex-glass plate surface with the well-known solution agent of Pd activator plus Sn sensitizer. In the PCD process, the film is only deposited onto the irradiated region of the substrate so as to make a pattern using the mask. This deposition process shows the heterogeneous nucleation and growth mechanism on the substrate surface. The deposition rate of the film using a 500 W mercury lamp was about 1 μm/30 min. The crystallization characteristics of the amorphous (Bi 2S 3) deposits were studied by means of X-ray diffraction, thermal analysis (DSC) and optical transmitted spectra evaluation in order to clarify the amorphous to crystal phase transformation. The amorphous deposits showed gradual light absorption in a wide range of optical wavelengths. On the contrary, annealed film showed a sharp absorption edge near 800 nm. The crystallization temperature of the amorphous deposits was about 250-300°C.

  9. Multiband model for penetration depth in MgB2

    NARCIS (Netherlands)

    Golubov, A.A.; Brinkman, A.; Dolgov, O.V.; Kortus, J.; Jepsen, O.

    2002-01-01

    The results of first-principles calculations of the electronic structure and the electron-phonon interaction in MgB2 are used to study theoretically the temperature dependence and anisotropy of the magnetic-field penetration depth. The effects of impurity scattering are essential for a proper descri

  10. Multiband model for tunneling in MgB2 junctions

    NARCIS (Netherlands)

    Brinkman, A.; Golubov, A.A.; Rogalla, H.; Dolgov, O.V.; Kortus, J.; Kong, Y.; Jepsen, O.; Andersen, O.K.

    2002-01-01

    A theoretical model for quasiparticle and Josephson tunneling in multiband superconductors is developed and applied to MgB2-based junctions. The gap functions in different bands in MgB2 are obtained from an extended Eliashberg formalism, using the results of band structure calculations. The temperat

  11. Superconductivity in MgB2: Clean or Dirty?

    NARCIS (Netherlands)

    Mazin, I.I.; Andersen, O.K.; Jepsen, O.; Dolgov, O.V.; Kortus, J.; Golubov, A.A.; Kuz'menko, A.B.; Marel, van der D.

    2002-01-01

    A large number of experimental facts and theoretical arguments favor a two-gap model for superconductivity in MgB2. However, this model predicts strong suppression of the critical temperature by interband impurity scattering and, presumably, a strong correlation between the critical temperature and

  12. Behavior of GaSb (100) and InSb (100) surfaces in the presence of H2O2 in acidic and basic cleaning solutions

    Science.gov (United States)

    Seo, Dongwan; Na, Jihoon; Lee, Seunghyo; Lim, Sangwoo

    2017-03-01

    Gallium antimonide (GaSb) and indium antimonide (InSb) have attracted strong attention as new channel materials for transistors due to their excellent electrical properties and lattice matches with various group III-V compound semiconductors. In this study, the surface behavior of GaSb (100) and InSb (100) was investigated and compared in hydrochloric acid/hydrogen peroxide mixture (HPM) and ammonium hydroxide/hydrogen peroxide mixture (APM) solutions. In the acidic HPM solution, surface oxidation was greater and the etching rates of the GaSb and InSb surfaces increased when the solution is concentrated, which indicates that H2O2 plays a key role in the surface oxidation of GaSb and InSb in acidic HPM solution. However, the GaSb and InSb surfaces were hardly oxidized in basic APM solution in the presence of H2O2 because gallium and indium are in the thermodynamically stable forms of H2GaO3- and InO2-, respectively. When the APM solution was diluted, however, the Ga on the GaSb surface was oxidized by H2O, increasing the etching rate. However, the effect of dilution of the APM solution on the oxidation of the InSb surface was minimal; thus, the InSb surface was less oxidized than the GaSb surface and the change in the etching rate of InSb with dilution of the APM solution was not significant. Additionally, the oxidation behavior of gallium and indium was more sensitive to the composition of the HPM and APM solutions than that of antimony. Therefore, the surface properties and etching characteristics of GaSb and InSb in HPM and APM solutions are mainly dependent on the behavior of the group III elements rather than the group V elements.

  13. GeSbTe 与 AgInSbTe 体系相变光盘的研究进展%Compact discs based on phase transformations in GeSbTe and AgInSbTe systems

    Institute of Scientific and Technical Information of China (English)

    张广军; 顾冬红; 王阳; 吴谊群; 干福熹

    2004-01-01

    自Ovshinsky把相变材料用于光存储以来,一大批具有可逆光存储性能的材料不断出现,其中研究较多的是GeSbTe 和AgInSbTe两种体系.文章着重介绍了利用这两种材料制成的相变光盘记录介质的微观结构特点,阐述了其晶化机理;同时,较详细地概述了光盘的堆栈结构及掺杂其他元素对相变光盘性能的影响,并对比说明了GeSbTe 和AgInSbTe两种体系在蓝光记录方面的各自特点.

  14. Electron Theory Research in Mg-Y Alloy

    Institute of Scientific and Technical Information of China (English)

    郭旭涛; 何良菊; 李培杰; 曾大本

    2004-01-01

    Adding yttrium to magnesium can improve the mechanical properties,especially the mechanical behavior at high temperature.The valence electron structures of Mg-Y alloy were analyzed with the empirical electron theory of solids and molecules(EET).Calculation shows that yttrium is on the fifth hybrid level and magnesium is on the third one in pure metal crystals.By comparing with aluminum in Mg-Al alloy,it is shown that the reason why the solution strengthening effect of yttrium is better than that of aluminum in Mg-Al alloy is the enhanced bond energy according to EET.And it is concluded from EET analysis that intermetallics Mg24Y5 can significantly improve the properties of magnesium alloys because yttrium atoms occupy the centers of the octahedron and Mg-Y bonds efficiently strengthen the alloy matrix.

  15. Substitution of Mn for Mg in MgB_2*

    Science.gov (United States)

    Fitzpatrick, Michael D.; Johnston, David C.; Miller, Lance L.; Hill, Julienne M.

    2002-03-01

    The study of solid solutions in which the Mg in MgB2 is partially replaced by magnetic 3d or 4f atoms can potentially reveal important information on the superconducting state of MgB_2. As an end-member of the hypothetical Mg_1-xMn_xB2 system, MnB2 is isostructural with MgB2 and is an antiferromagnet below TN = 760 K which becomes canted at 157 K. A previous study by Moritomo et al.[1] examined the structure and properties of multi-phase samples with 0.01J. Phys. Soc. Japan b70, 1889 (2001).; “Effects of transition metal doping in MgB2 superconductor", Y. Moritomo at al. arXiv:cond-mat/0104568.

  16. Solid-Phase Equilibria in the Au-As, Au-Ga-Sb, Au-In-As, and Au-In-Sb Ternaries.

    Science.gov (United States)

    1986-02-28

    AD6i5 469 SOLID- PHASE EQUILIBRIA IN THE Ru-As AU-GA-SB AU-IN-AS- 1/17 AND AU-IN-SB TERNAR (U) CALIFORNIA UNIV LOS ANGELES DEPT OF CHEMISTRY AND...REPORT & PERIOD COVERED SOLID- PHASE EQUILIBRIA IN THE Au-Ga-As, Au-Ga-Sb Thchnical Report Au-In-As, and Au-In-Sb TEARIEIS S. PERFORMING ORG. REPORT NUMBER...CLASSIFICATION OF THIS PAGEMI*n Does Entepd) 4./ lie- . .- - - - - -- -- Solid Phase Equilibria in the Au-Ga-As, Au-Ga-Sb, Au-In-As, and Au-In-Sb Ternaries C

  17. 0 -π phase transition in hybrid superconductor-InSb nanowire quantum dot devices

    Science.gov (United States)

    Li, Sen; Kang, N.; Caroff, P.; Xu, H. Q.

    2017-01-01

    Hybrid superconductor-semiconducting nanowire devices provide an ideal platform to investigating interesting intragap bound states, such as the Andreev bound states (ABSs), Yu-Shiba-Rusinov (YSR) states, and the Majorana bound states. The competition between Kondo correlations and superconductivity in Josephson quantum dot (QD) devices results in two different ground states and the occurrence of a 0 -π quantum phase transition. Here we report on transport measurements on hybrid superconductor-InSb nanowire QD devices with different device geometries. We demonstrate a realization of continuous gate-tunable ABSs with both 0-type levels and π -type levels. This allow us to manipulate the transition between the 0 and π junction and explore charge transport and spectrum in the vicinity of the quantum phase transition regime. Furthermore, we find a coexistence of 0-type ABS and π -type ABS in the same charge state. By measuring temperature and magnetic field evolution of the ABSs, the different natures of the two sets of ABSs are verified, being consistent with the scenario of phase transition between the singlet and doublet ground state. Our study provides insight into Andreev transport properties of hybrid superconductor-QD devices and sheds light on the crossover behavior of the subgap spectrum in the vicinity of the 0 -π transition.

  18. Effects of Nernst-Ettinghausen, Seebeck and Hall in Sb sub 2 Te sub 3 monocrystals

    CERN Document Server

    Zhitinskaya, M K; Ivanova, L D

    2002-01-01

    In Sb sub 2 Te sub 3 top-quality single crystals grown following the Czochralski method within 77-420 K range one measured temperature dependences of the following components of kinetic coefficients: electrical conductivity within sigma sub 1 sub 1 chip plane, of the Seebeck S sub 1 sub 1 and S sub 3 sub 3 , of the Hall R sub 1 sub 2 sub 3 and R sub 3 sub 2 sub 1 and of the Nernst-Ettinghausen Q sub 1 sub 2 sub 3. One analyzed the derived results on the basis of the phenomenological theory. It is shown that the essential peculiarities of the experimental data may be explained in terms of a two-region model with anisotropy of mobility of the first and second types holes towards the chip (epsilon sub g approx = 0.3 eV), as well as, the energy gap between the ground and auxiliary extremes of the valence band (DELTA epsilon subupsilon approx 0.1 eV)

  19. Electrical resistivity dip in Sb x V y Mo z O t phases

    Science.gov (United States)

    Groń, T.; Filipek, E.; Mazur, S.; Duda, H.; Pacyna, A. W.; Mydlarz, T.; Bärner, K.

    2010-07-01

    Electrical resistivity dips have been discovered in the temperature range 100-500 K both in the SbVO4.96 matrix and the Sb x V y Mo z O t phases for 10 mol% solubility of MoO3 in SbVO5. As the Sb content increases and simultaneously the V content decreases, the value of the resistivity at the dip, ρ d, decreases and shifts the dip to higher temperatures. The magnetic measurements showed a spontaneous magnetization and parasitic magnetism of the solid solutions under study. Characteristic for parasitic magnetism is a small value of the magnetic moment, here 0.014 μ B/f.u. at 4.2 K and at a magnetic field of 14 T as well as a small value of the mass susceptibility, here 10-5 cm3/g. The value of the Néel temperature, T N ≤ 8 K, and the Curie-Weiss temperature, θ CW ≤ -208 K, indicate a collinear antiferromagnetic (AFM) order. We suggest that neither the magnetism nor the Mo-content can be correlated with the resistivity anomalies. Therefore, these effects may rather be interpreted in terms of a small-polaron gas in the resistivity dip area. Alternatively, they could mark a lattice/electronic entropy-driven incomplete metal-insulator transition.

  20. Viscosity of liquid Ag-In-Sb-Te: Evidence of a fragile-to-strong crossover

    Science.gov (United States)

    Orava, J.; Weber, H.; Kaban, I.; Greer, A. L.

    2016-05-01

    The temperature-dependent viscosity η(T) is measured for the equilibrium liquid of the chalcogenide Ag-In-Sb-Te (AIST), the first time this has been reported for a material of actual interest for phase-change memory. The measurements, in the range 829-1254 K, are made using an oscillating-crucible viscometer, and show a liquid with high fragility and low viscosity, similar to liquid pure metals. Combining the high-temperature viscosity measurements with values inferred from crystal growth rates in the supercooled liquid allows the form of η(T) to be estimated over the entire temperature range from above the melting point down to the glass transition. It is then clear that η(T) for liquid AIST cannot be described with a single fragility value, unlike other phase-change chalcogenides such as liquid Ge-Sb-Te. There is clear evidence for a fragile-to-strong crossover on cooling liquid AIST, similar to that analyzed in Te85Ge15. The change in fragility associated with the crossover in both these cases is rather weak, giving a broad temperature range over which η(T) is near-Arrhenius. We discuss how such behavior may be beneficial for the performance of phase-change memory. Consideration of the fragile-to-strong crossover in liquid chalcogenides may be important in tuning compositions to optimize the device performance.

  1. Sb complexes and Zn interstitials in Sb-implanted ZnO epitaxial films

    Institute of Scientific and Technical Information of China (English)

    Liu Yao-Ping; Ying Min-Ju; Mei Zeng-Xia; Li Jun-Qianng; Du Xiao-Long; A.Yu.Kuznetsovc

    2011-01-01

    In the present work, post-annealing is adopted to investigate the formation and the correlation of Sb complexes and Zn interstitials in Sb-ion implanted ZnO films, by using Raman scattering technique and electrical characterizations.The damage of Zn sublattice, produced by ion bombardment process is discerned from the unrecovered E2 (L) peak in annealed high Sb+ dose implanted samples. It is suggested that the Zn sublattice may be strongly affected by the introduction of Sb dopant because of the formation of SbZn-2VZn complex acceptor. The appearance of a new peak at 510 cm-1 in the annealed high dose Sb+ implanted samples is speculated to result from (Zn interstitials-O interstitials)Zni-Oi complex, which is in a good accordance with the electrical measurement. The p-type ZnO is difficult to obtain from the Sb+ implantation, however, which can be realized by in-situ Sb doping with proper growth conditions instead.

  2. Assessing the thermoelectric properties of single InSb nanowires: the role of thermal contact resistance

    Science.gov (United States)

    Yazji, S.; Swinkels, M. Y.; De Luca, M.; Hoffmann, E. A.; Ercolani, D.; Roddaro, S.; Abstreiter, G.; Sorba, L.; Bakkers, E. P. A. M.; Zardo, I.

    2016-06-01

    The peculiar shape and dimensions of nanowires (NWs) have opened the way to their exploitation in thermoelectric applications. In general, the parameters entering into the thermoelectric figure of merit are strongly interdependent, which makes it difficult to realize an optimal thermoelectric material. In NWs, instead, the power factor can be increased and the thermal conductivity reduced, thus boosting the thermoelectric efficiency compared to bulk materials. However, the assessment of all the thermoelectric properties of a NW is experimentally very challenging. Here, we focus on InSb NWs, which have proved to be promising thermoelectric materials. The figure of merit is accurately determined by using a novel method based on a combination of Raman spectroscopy and electrical measurements. Remarkably, this type of experiment provides a powerful approach allowing us to neglect the role played by thermal contact resistance. Furthermore, we compare the thermal conductivity determined by this novel method to the one determined on the same sample by the thermal bridge method. In this latter approach, the thermal contact resistance is a non-negligible parameter, especially in NWs with large diameters. We provide experimental evidence of the crucial role played by thermal contact resistance in the assessment of the thermal properties of nanostructures, using two different measurement methods of the thermal conductivity.

  3. Anomalous oscillations of the Josephson supercurrent in InSb nanowires

    Science.gov (United States)

    Geresdi, Attila; Szombati, Dániel B.; Cornelissen, Ludo J.; Car, Diana; Plissard, Sébastien R.; Bakkers, Erik P. A. M.; Kouwenhoven, Leo P.

    2014-03-01

    Semiconductor nanowires proximity coupled to superconducting leads provide an ideal experimental platform to investigate the Josephson effect in tunable ballistic channels in the presence of strong spin-orbit coupling and large Landé g-factor. The interplay of an external magnetic field perpendicular to the intrinsic spin-orbit field may lead to an anomalous supercurrent which is a proposed signature of the coupling between two Majorana modes through the channel. Here we present our experimental studies of the Josephson supercurrent in InSb nanowires. Ohmic contacts to bulk superconductor NbTiN leads enable us to trace supercurrents up to B = 3 T magnetic field. The gate control over the channel allows us to investigate the amplitude of the critical current from the tunneling regime to a few transparent modes, where nonsinusoidal current-phase relationship (CPR) is expected, verified by the presence of fractional Shapiro steps under microwave irradiation. The evolution of the critical current with the external magnetic field is shown to exhibit non-monotonic behavior depending on the gate configuration, consistently with the theory of Josephson junctions hosting Majorana modes.

  4. Extending resolution of scanning optical microscopy beyond the Abbe limit through the assistance of InSb thin layers.

    Science.gov (United States)

    Ding, Chenliang; Wei, Jingsong; Li, Qisong; Liang, Xin; Wei, Tao

    2016-04-01

    The resolution of light imaging is required to extend beyond the Abbe limit to the subdiffraction, or even nanoscale. In this Letter, we propose to extend the resolution of scanning optical microscopy (SOM) beyond the Abbe limit as a kind of subdiffraction imaging technology through the assistance of InSb thin layers due to obvious nonlinear saturation absorption and reversible formation of an optical pinhole channel. The results show that the imaging resolution is greatly improved compared with the SOM itself. This work provides a way to improve the resolution of SOM without changing the SOM itself, but through the assistance of InSb thin layers. This is also a simple and practical way to extend the resolution of SOM beyond the Abbe limit.

  5. Mn doped InSb studied at the atomic scale by cross-sectional scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Mauger, S. J. C.; Bocquel, J.; Koenraad, P. M., E-mail: p.m.koenraad@tue.nl [Department of Applied Physics, Eindhoven University of Technology, Den Dolech 2, 5612 AZ Eindhoven (Netherlands); Feeser, C. E.; Parashar, N. D.; Wessels, B. W. [Department of Materials Science and Engineering and Materials Research Center, Northwestern University, Evanston, Illinois 60208 (United States)

    2015-11-30

    We present an atomically resolved study of metal-organic vapor epitaxy grown Mn doped InSb. Both topographic and spectroscopic measurements have been performed by cross-sectional scanning tunneling microscopy (STM). The measurements on the Mn doped InSb samples show a perfect crystal structure without any precipitates and reveal that Mn acts as a shallow acceptor. The Mn concentration of the order of ∼10{sup 20 }cm{sup −3} obtained from the cross-sectional STM data compare well with the intended doping concentration. While the pair correlation function of the Mn atoms showed that their local distribution is uncorrelated beyond the STM resolution for observing individual dopants, disorder in the Mn ion location giving rise to percolation pathways is clearly noted. The amount of clustering that we see is thus as expected for a fully randomly disordered distribution of the Mn atoms and no enhanced clustering or second phase material was observed.

  6. Electrical conductivity and hardness of ternary Ge-In-Sb alloys and calculation of the isothermal section at 300 C

    Energy Technology Data Exchange (ETDEWEB)

    Premovic, Milena; Minic, Dusko; Mitrovica, Kosovska [Pristina Univ., Kosovska Mitrovica (Serbia). Faculty of Technical Science; Manasijevic, Ivana; Zivkovic, Dragana [Belgrade Univ., Bor (Serbia). Dept. of Metallurgical Engineering

    2015-07-01

    This publication presents results of experimental investigation and thermodynamic calculation of the ternary Ge-In-Sb system. Isothermal section of the Ge-In-Sb system at 300 C has been extrapolated using optimized thermodynamic parameters for the constitutive binary systems. Microstructure analysis was carried out by light microscope, scanning electron microscopy with energy dispersive spectrometry and X-ray powder diffraction methods and obtained results were compared with predicted phase equilibria. Hardness of selected alloys annealed at 300 C was measured using Vickers microhardness test and Brinell hardness test. Electrical conductivity of a number of alloys annealed at 300 C was experimentally determined. Good overall agreement between experimental and calculated values was obtained.

  7. Electronic states and the resonant optical non-linearity of exciton in a narrow band InSb quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Narayanan, M. [Department of Physics, Yadava College Govindarajan Campus, Thiruppalai, Madurai-625 014 (India); John Peter, A., E-mail: a.john.peter@gmail.com [Center for Environmental Studies/Green Energy Center, Department of Environmental Science and Engineering, College of Engineering, Kyung Hee University, Seocheon-dong 1, Giheung-gu, Yongin-Si, Gyeonggi-Do, 446-701 (Korea, Republic of); Yoo, Chang Kyoo [Center for Environmental Studies/Green Energy Center, Department of Environmental Science and Engineering, College of Engineering, Kyung Hee University, Seocheon-dong 1, Giheung-gu, Yongin-Si, Gyeonggi-Do, 446-701 (Korea, Republic of)

    2012-02-01

    Binding energy, interband emission energy and the non-linear optical properties of exciton in an InSb/InGa{sub x}Sb{sub 1-x} quantum dot are computed as functions of dot radius and the Ga content. Optical properties are obtained using the compact density matrix approach. The dependence of non-linear optical processes on the dot sizes is investigated for different Ga concentrations. The linear, third order non-linear optical absorption coefficients, susceptibility values and the refractive index changes of the exciton are calculated for different concentrations of gallium content. It is found that gallium concentration has great influence on the optical properties of InSb/InGa{sub x}Sb{sub 1-x} dots.

  8. Gate-tunable high mobility remote-doped InSb/In1−xAlxSb quantum well

    NARCIS (Netherlands)

    Yi, W.; Kiselev, A.A.; Thorp, J.; Noah, R.; Nguyen, B.M.; Bui, S.; Rajavel, R.D.; Hussain, T.; Gyure, M.F.; Kratz, P.; Qian, Q.; Manfra, M.J.; Pribiag, V.S.; Kouwenhoven, L.P.; Marcus, C.M.; Sokolich, M.

    2015-01-01

    Gate-tunable high-mobility InSb/In1−xAlxSb quantum wells (QWs) grown on GaAs substrates are reported. The QW two-dimensional electron gas (2DEG) channel mobility in excess of 200 000 cm2/V s is measured at T = 1.8 K. In asymmetrically remote-doped samples with an HfO2 gate dielectric formed by atomi

  9. Non-perturbative four-wave mixing in InSb with intense off-resonant multi-THz pulses

    Directory of Open Access Journals (Sweden)

    Huber R.

    2013-03-01

    Full Text Available High-field multi-THz pulses are employed to analyze the coherent nonlinear response of the narrow-gap semiconductor InSb which is driven off-resonantly. Field-resolved four-wave mixing signals manifest the onset of a non-perturbative regime of Rabi flopping at external amplitudes above 5 MV/cm per pulse. Simulations based on a two-level quantum system confirm these experimental results.

  10. Interband transition in narrow gap InSb spherical layer quantum dot in the presence of electric field

    Energy Technology Data Exchange (ETDEWEB)

    Zuhair, Marwan; Manaselyan, Aram; Sarkisyan, Hayk [Yereven State University, Yerevan (Armenia)

    2008-10-15

    We perform the theoretical investigation of interband dipole transitions in a narrow-gap InSb spherical layer quantum dot. We consider the transitions from the light hole and heavy hole states to the electron state of the conduction band. The dispersion law for electron and light hole is approximated using a two-band Kane model, while the heavy hole is described in the parabolic approximation. The effect of electric field on interband transitions is investigated.

  11. Bridgman growth of concentrated GaInSb alloys with improved compositional uniformity under alternating magnetic fields

    Science.gov (United States)

    Stelian, Carmen; Delannoy, Yves; Fautrelle, Yves; Duffar, Thierry

    2005-02-01

    Vertical Bridgman crystal growth of concentrated GaInSb alloys is in general difficult because of large chemical segregations which occur during the solidification process. From experimental works and numerical simulations, it is found that the melt convection is damped by the accumulation of the heavy InSb solute rejected at the interface. This leads to a significant increase of the interface curvature and radial segregations in the case of GaInSb crystals (10% and 20% In concentration). By using alternating magnetic fields produced by a coil placed around the crucible, the level of the convection can be increased in order to obtain a good mixing of the solute near the solid-liquid interface and to avoid the large chemical segregations. Numerical simulation is used in order to compute the magnetic field parameters, and for the optimization of the coil dimensions and position related to the solid-liquid interface. In order to solve simultaneously the electromagnetic and thermo-hydrodynamic problem, including species transport, a self-developed module which is able to solve the magnetic induction equation, has been introduced in the FIDAP commercial code. From the simulation, it is found that the coil position related to the interface has a significant influence on the electromagnetically induced flow. Based on these simulations, an optimal Bridgman configuration equipped with an electromagnetic coil is proposed in order to mix the solute near the interface and to avoid the excessive increase of chemical segregations and interface curvatures.

  12. The Role of Anti-Phase Domains in InSb-Based Structures Grown on On-Axis and Off-Axis Ge Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Debnath, M. C.; Mishima, T. D.; Santos, M. B. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Hossain, K.; Holland, O. W. [Amethyst Research, Inc., 1405 4th Ave NW, Ardmore, OK 73401 (United States)

    2011-12-26

    Anti-phase domains form in InSb epilayers and InSb/Al{sub 0.20}In{sub 0.80}Sb single quantum wells when grown upon on-axis (001) Ge substrates by molecular beam epitaxy. Domain formation is partially suppressed through growth on Ge substrates with surfaces that are several degrees off the (001) or (211) axis. By using off-axis Ge substrates, room-temperature electron mobilities increased to {approx}60,000 cm{sup 2}/V-s and {approx}14,000 cm{sup 2}/V-s for a 4.0-{mu}m-thick InSb epilayer and a 25-nm InSb quantum well, respectively.

  13. Superconductivity in MgB2: clean or dirty?

    Science.gov (United States)

    Mazin, I I; Andersen, O K; Jepsen, O; Dolgov, O V; Kortus, J; Golubov, A A; Kuz'menko, A B; Van Der Marel, D

    2002-09-01

    A large number of experimental facts and theoretical arguments favor a two-gap model for superconductivity in MgB2. However, this model predicts strong suppression of the critical temperature by interband impurity scattering and, presumably, a strong correlation between the critical temperature and the residual resistivity. No such correlation has been observed. We argue that this fact can be understood if the band disparity of the electronic structure is taken into account, not only in the superconducting state, but also in normal transport.

  14. Superconductivity of metallic boron in MgB2.

    Science.gov (United States)

    Kortus, J; Mazin, I I; Belashchenko, K D; Antropov, V P; Boyer, L L

    2001-05-14

    Boron in MgB2 forms stacks of honeycomb layers with magnesium as a space filler. Band structure calculations indicate that Mg is substantially ionized, and the bands at the Fermi level derive mainly from B orbitals. Strong bonding with an ionic component and considerable metallic density of states yield a sizable electron-phonon coupling. Together with high phonon frequencies, which we estimate via zone-center frozen phonon calculations to be between 300 and 700 cm(-1), this produces a high critical temperature, consistent with recent experiments. Thus MgB2 can be viewed as an analog of the long sought, but still hypothetical, superconducting metallic hydrogen.

  15. PROPERTIES OF DEFECTS AND IMPLANTS IN Mg+ IMPLANTED SILICON CARBIDE

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Weilin; Zhu, Zihua; Varga, Tamas; Bowden, Mark E.; Manandhar, Sandeep; Roosendaal, Timothy J.; Hu, Shenyang Y.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2013-09-25

    As a candidate material for fusion reactor designs, silicon carbide (SiC) under high-energy neutron irradiation undergoes atomic displacement damage and transmutation reactions that create magnesium as one of the major metallic products. The presence of Mg and lattice disorder in SiC is expected to affect structural stability and degrade thermo-mechanical properties that could limit SiC lifetime for service. We have initiated a combined experimental and computational study that uses Mg+ ion implantation and multiscale modeling to investigate the structural and chemical effects in Mg implanted SiC and explore possible property degradation mechanisms.

  16. InSb versus QWIP imaging sensors: a comparison in progress

    Science.gov (United States)

    Soel, Michael A.; Benson, Robert G.; Confer, Charles L.

    2002-07-01

    Infrared Imaging sensors operating in the 3 - 5 um (MW) and 8 - 12 um (LW) spectral bands have long since been traded against one another with respect to mission utility, sensor performance, and system viability (cost factors, technology maturity, etc.). Over the past decade, staring InSb detectors have matured to a refined level (high performance, moderate cost, high yields) and have been used extensively by IR sensor integrators throughout the industry. By the same token, 2-D LW QWIP-based FPA's are fast becoming a viable alternative to traditional LW-scanned technology systems, offering the benefits of mid and large format staring sensor resolution with good sensitivity (even for modest optical F/#'s). With the commercialization of QWIP technology, system viability is rapidly increasing, revealing the need for serious system trade assessments and field measurements to enable the best use of this emerging, complementary detector technology. This paper presents a top-level technical comparison of these two sensor technologies and their use in surveillance/night vision system applications. A variety of technical considerations are discussed to help end users be cognizant of the extent of the trade space that exists between MW and LW staring sensor selection with specific focus on performance comparisons for small, compact militarized IR thermal imaging sensors (including handheld, man-portable and small gimbal products) employing each detector technology in context to various surveillance missions. Application areas include: ground, airborne, and maritime surveillance. Field data is also provided to support the conclusions drawn from these comparisons.

  17. Fe nanoparticles embedded in MgO crystals

    Energy Technology Data Exchange (ETDEWEB)

    Shalimov, Artem; Potzger, Kay; Talut, Georg; Reuther, Helfried; Zhou, Shengqiang; Baehtz, Carsten; Fassbender, Juergen [Forschungszentrum Dresden-Rossendorf, Bautzner Landstrasse 128, 01328 Dresden (Germany); Geiger, Dorin; Lichte, Hannes [Technical University, Dresden (Germany); Misiuk, Andrzej [Institute of Electron Technology, Warsaw (Poland); Stromberg, Frank [Universitaet Duisburg-Essen (Germany)

    2009-07-01

    Iron nanoparticles embedded in MgO crystals were synthesized by Fe{sup +} ion implantation at an energy of 100 keV and varying fluences from 3.10{sup 16} to 3.10{sup 17} cm{sup -2}. Investigations of structural and magnetic properties of Fe nanoparticles have been performed using magnetometry, X-ray diffraction, transmission electron microscopy and Moessbauer spectroscopy, as well as by theoretical Preisach modeling of bistable magnetic systems. It has been found that {alpha}- and {gamma}-Fe nanoparticles are formed for all fluences. The content of the {alpha}-Fe phase increases at higher fluences and after annealing. The influence of post-implantation annealing at 800 C in vacuum and under enhanced up to 10 kbar hydrostatic pressure in argon atmosphere on the formation of nanoparticles has been analyzed.

  18. Attempts at doping indium in MgB2

    Science.gov (United States)

    Grivel, J.-C.

    2016-12-01

    Indium (In) doped MgB2 polycrystalline samples were prepared by solid-liquid phase reaction in Ar. After reaction at 800 °C, less than 1 at.% Mg was replaced by In in the MgB2 phase, without significant influence on its lattice parameters and only a slight decrease of its superconducting transition temperature. For all studied In concentrations in the nominal composition, the formation of InMg was evidenced by X-ray diffraction. The critical current density and accommodation field of the wires are decreased in the samples containing In. The flux pinning mechanism can be described by surface pinning in both the doped and undoped samples.

  19. HRTEM investigation of orthorhombic phase in Mg-PSZ

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Z.W.; Spargo, A.E.C. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Hannink, R.H.J. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), East Melbourne, VIC (Australia). Minerals Research Labs.

    1997-06-01

    Tetragonal, orthorhombic and monoclinic phases are only slight distortions of the cubic structure. Due to minor differences in unit cell parameters it is difficult to distinguish these phases only by high resolution images. However, using high resolution transmission electron microscopy (HRTEM) observation in combination with image simulation and digital Fourier transformation of HRTEM images, it was found that one tetragonal precipitate can be transformed to several orthorhombic domains with different orientations in MgO-partially-stabilized zirconia (Mg-PSZ). The lattice correspondence between two adjacent orthorhombic domains is such that their b axes are parallel, while their a axes are perpendicular to each other. Also it was found that cubic ZrO{sub 2} could be transformed to orthorhombic ZrO{sub 2}. 8 refs., 1 tab., 4 figs.

  20. Photophysical Property and Photocatalytic Activity of New Gd2InSbO7 and Gd2FeSbO7 Compounds under Visible Light Irradiation

    Directory of Open Access Journals (Sweden)

    Jingfei Luan

    2013-01-01

    Full Text Available Gd2InSbO7 and Gd2FeSbO7 were synthesized first, and their structural and photocatalytic properties were studied. The lattice parameters and the band gaps for Gd2InSbO7 and Gd2FeSbO7 were 10.449546 Å, 10.276026 Å, 2.897 eV and 2.151 eV. The photocatalytic degradation of rhodamine B was performed with Gd2InSbO7 and Gd2FeSbO7 under visible light irradiation. Gd2InSbO7 and Gd2FeSbO7 had higher catalytic activity compared with Bi2InTaO7. Gd2FeSbO7 exhibited higher catalytic activity than Gd2InSbO7. The photocatalytic degradation of rhodamine B followed with the first-order reaction kinetics, and the first-order rate constant k was 0.01606, 0.02220 or 0.00329 min−1 with Gd2InSbO7, Gd2FeSbO7 or Bi2InTaO7 as photocatalyst. Complete removal of rhodamine B was observed after visible light irradiation for 225 min or 260 min with Gd2FeSbO7 or Gd2InSbO7 as photocatalyst. The evolution of CO2 was realized, and it indicated continuous mineralization of rhodamine B during the photocatalytic process. The possible photocatalytic degradation pathway of rhodamine B was proposed.

  1. Foreign-catalyst-free growth of InAs/InSb axial heterostructure nanowires on Si (111) by molecular-beam epitaxy.

    Science.gov (United States)

    So, Hyok; Pan, Dong; Li, Lixia; Zhao, Jianhua

    2017-03-01

    Epitaxial high-quality InAs/InSb axial heterostructure nanowires are of great interest due to their distinct advantages in fundamental research as well as applications in semiconductor electronic and quantum devices. Currently, nearly all the growth of InAs/InSb axial heterostructure nanowires is assisted with foreign catalysts such as Au, and work on foreign-catalyst-free growth of InAs/InSb axial heterostructure nanowires is lacking. Here we report on the growth of InAs/InSb axial heterostructure nanowires on Si (111) substrates by molecular-beam epitaxy without using any foreign catalysts. The Sb/In beam equivalent pressure (BEP) ratio is found to have important influence on the heterostructure nanowire morphology, and InSb nanowires can be epitaxially grown on InAs nanowire stems with a hexagonal prism and nanosheet-like shapes when the Sb/In BEP ratio varies from 10 to 20. Transmission electron microscopy studies reveal that the InAs nanowire stems have a mixture of zincblende (ZB) and wurtzite (WZ) crystal structures, while InSb nanowire parts have a pure ZB crystal structure free of stacking faults. Composition analysis of axial heterostructure nanowires provides clear evidence that the InSb nanowires are epitaxially grown on InAs nanowires in an In self-assisted vapor-liquid-solid manner. This study paves a new route for growing narrow-gap semiconductor heterostructures with strong spin-orbit interaction for the study of topological states, and the growth manner presented here is expected to be used to grow other In-based axial heterostructure nanowires.

  2. Stoichiometric carbon substitution in MgB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Balaselvi, S Jemima; Gayathri, N; Bharathi, A; Sastry, V S; Hariharan, Y [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

    2004-12-01

    Carbon has been substituted into the MgB{sub 2} lattice, forming the series Mg(B{sub 1-x}C{sub x}){sub 2}, by heat treatments in sealed Ta tubes starting with elemental constituents. The superconducting transition temperature, T{sub C}, was measured by diamagnetic susceptibility. The superconducting transitions are sharp and the x-ray diffraction on the samples show only trace amounts of impurity phases. The C fraction that substitutes the B atoms into the MgB{sub 2} lattice, as determined from the now well established correlation between the 'a' lattice parameter and x in Mg(B{sub 1-x}C{sub x}){sub 2} is found to be very close to the targeted values. The temperature dependence of the normalized resistance is similar to that seen in C doped MgB{sub 2} single crystals along the ab plane. R{sub n}/R(300 K), where R{sub n} is the resistance just above T{sub C}, increases with x.

  3. The structure of ? precipitates in Mg-Zn-Y alloys

    Science.gov (United States)

    Singh, Alok; Rosalie, Julian M.; Somekawa, Hidetoshi; Mukai, Toshiji

    2010-09-01

    It is shown here by high-resolution electron microscopy that the structure of rod-like ? precipitates perpendicular to the basal planes of the magnesium matrix in Mg-Zn-Y alloys consist of complex domains at nanoscale. These domains can be recognized to be those of monoclinic Mg4Zn7 phase and hexagonal Laves phase MgZn2 with axial orientations ? . Due to disorder, often complete unit cells of the Mg4Zn7 structure cannot be recognized. Inside a domain of Mg4Zn7, the structure may locally transform to that of MgZn2. The structure of both the phases are composed of similar units of icosahedral coordinations. Maintaining the above axial orientation, the Mg4Zn7 can exhibit two orientation relationships with the matrix, ? or ? . The hexagonal MgZn2 forms in the monoclinic Mg4Zn7 in two different orientations, related to rhombic units (with angle ∼72°) in the Mg4Zn7 unit cell. With the common axial relationship given above, these two orientation relationships can be given as ? or ? . One of these two variants forms a known orientation relationship ? , ? with the matrix. The structure of the MgZn2 was found to be modified by the ordering of zinc layers perpendicular to the hexagonal axis.

  4. Vortex Lattice Transition Dynamics in MgB2

    Science.gov (United States)

    Rastovski, C.; Das, P.; Schlesinger, K.; Eskildsen, M. R.; Gannon, W. J.; Dewhurst, C. D.; Zhigadlo, N. D.; Karpinski, J.

    2012-02-01

    We present small-angle neutron scattering (SANS) studies of the vortex lattice (VL) in MgB2 with H c. This material has three different VL phases, all with triangular symmetry but oriented differently with respect to the crystalline axes. Furthermore, a high degree of metastability between the VL phases of MgB2 has been observed as the sample is cooled or heated across the equilibrium phase transitions. Here we present detailed studies of how the metastable (MS) VL phases transition to the ground state (GS), either driven by small changes of the DC magnetic field or by a transverse AC field. Our results show that the MS VL is not due to vortex pinning, and results are inconsistent with predictions based on the Bean model. Instead, we speculate that a ``jamming'' of counter rotated VL domains is responsible for the VL metastability. This is further supported by a power law dependence of the GS VL domain population upon the number of applied AC cycles. This work was supported by the Department of Energy, Basic Energy Sciences under Award No. DE-FG02-10ER46783.

  5. A Study of the Irradiance- and Temperature-Dependence of Mid-Wave-Infrared (MWIR) Absorption in Indium Antimonide (InSb)

    Science.gov (United States)

    2008-08-01

    integrated circuitry beneath the InSb thin film back into the optical system. To evaluate this, irradiance-dependent laser-absorption experiments were...integrated circuitry (ROIC) beneath the InSb thin film back into the optical system. A focused point source will not extend beyond one or two pixels in a...32 Next was the first zinc selenide (ZnSe) lens, with focal length, F = 20 mm and diameter, dia = 50 mm(12). Then, a second ZnSe lens with F = 100

  6. Buffer effect on quality of InSb/GaAs on MBE growth%MBE生长中缓冲层对InSb/GaAs质量影响的研究

    Institute of Scientific and Technical Information of China (English)

    李占国; 刘国军; 尤明慧; 熊敏; 李梅; 李林

    2007-01-01

    用分子束外延(MBE)方法在GaAs(001)衬底上外延生长了InSb薄膜,并研究了异质外延InSb薄膜生长中缓冲层对材料质量的影响.采用原子力显微镜(AFM)、透射电子显微镜(TEM)、X射线双晶衍射(DCXRD)等方法研究了InSb/GaAs薄膜的表面形貌、界面特性以及结晶质量.通过生长合适厚度的缓冲层,获得了室温下DCXRD半高峰宽为272",迁移率为64 300 cm2V-1s-1的InSb外延层.

  7. Demonstration of long minority carrier lifetimes in very narrow bandgap ternary InAs/GaInSb superlattices

    Science.gov (United States)

    Haugan, H. J.; Brown, G. J.; Olson, B. V.; Kadlec, E. A.; Kim, J. K.; Shaner, E. A.

    2015-09-01

    Minority carrier lifetimes in very long wavelength infrared (VLWIR) InAs/GaInSb superlattices (SLs) are reported using time-resolved microwave reflectance measurements. A strain-balanced ternary SL absorber layer of 47.0 Å InAs/21.5 Å Ga0.75In0.25Sb, corresponding to a bandgap of ˜50 meV, is found to have a minority carrier lifetime of 140 ± 20 ns at ˜18 K. This lifetime is extraordinarily long, when compared to lifetime values previously reported for other VLWIR SL detector materials. This enhancement is attributed to the strain-engineered ternary design, which offers a variety of epitaxial advantages and ultimately leads to a reduction of defect-mediated recombination centers.

  8. Structural and frequency dependencies of a.c. and dielectric characterizations of epitaxial InSb-based heterojunctions

    Indian Academy of Sciences (India)

    A ASHERY; A H ZAKI; M HUSSIEN MOURAD; A M AZAB; A A M FARAG

    2016-08-01

    In this work, heterojunction of InSb/InP was grown by liquid phase epitaxy (LPE). Surface morphology and crystalline structure of the heterojunction were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The frequency and temperature dependences of a.c. conductivity and dielectric properties of the heterojunctions were investigated in the ranges of 100 kHz–5 MHz and 298–628 K, respectively. The a.c. conductivity and its frequency exponents were interpreted in terms of correlated barrier hopping model (CBH), as the dominant conduction mechanism for charge carrier transport. The calculated activation energy, from the Arrhenius plot, was found to decrease with increasing frequency. Experimental results of both dielectric constant $\\epsilon_1$ and dielectric loss $\\epsilon_2$ showed a remarkable dependence of both frequency and temperature.

  9. Cleaning chemistry of GaAs(100) and InSb(100) substrates for molecular beam epitaxy

    Science.gov (United States)

    Vasquez, R. P.; Lewis, B. F.; Grunthaner, F. J.

    1983-01-01

    Ploog (1980) and Bachrach and Krusor (1981) have pointed out the importance of substrate preparation and surface cleaning for obtaining high quality films with the aid of molecular beam epitaxial growth techniques. In the present investigation, high resolution X-ray photoemission (XPS) is used to determine the oxide removal mechanism for GaAs(100) substrates which have undergone a standardized cleaning procedure. Other objectives of the investigation are related to a comparison of different cleaning procedures in order to minimize carbon contamination, the extension of these cleaning techniques to other III-V compound semiconductors such as InSb, and the evaluation of the sensitivity of the compositional results to electron-induced damage effects.

  10. Influence of Contact Angle, Growth Angle and Melt Surface Tension on Detached Solidification of InSb

    Science.gov (United States)

    Wang, Yazhen; Regel, Liya L.; Wilcox, William R.

    2000-01-01

    We extended the previous analysis of detached solidification of InSb based on the moving meniscus model. We found that for steady detached solidification to occur in a sealed ampoule in zero gravity, it is necessary for the growth angle to exceed a critical value, the contact angle for the melt on the ampoule wall to exceed a critical value, and the melt-gas surface tension to be below a critical value. These critical values would depend on the material properties and the growth parameters. For the conditions examined here, the sum of the growth angle and the contact angle must exceed approximately 130, which is significantly less than required if both ends of the ampoule are open.

  11. Analysis of the experimental data for impurity-band conduction in Mn-doped InSb

    Energy Technology Data Exchange (ETDEWEB)

    Kajikawa, Yasutomo [Department of Electric and Control Systems Engineering, Interdisciplinary Faculty of Science and Engineering, Shimane University, Matsue (Japan)

    2017-01-15

    The experimental data of the temperature-dependent Hall-effect measurements on Mn-doped p -type InSb samples, which exhibit the anomalous sign reversal of the Hall coefficient to negative at low temperatures, have been analyzed on the basis of the nearest-neighbor hopping model in an impurity band. It is shown that the anomalous sign reversal of the Hall coefficient to negative can be well explained with assuming the hopping Hall factor in the form of A{sub hop} = (k{sub B}T/J{sub 3}) exp(K{sub NNH}T{sub 3}/T) with the negative sign of J{sub 3}. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Influence of growth parameters on the surface morphology and crystallinity of InSb epilayers grown by liquid phase epitaxy

    Indian Academy of Sciences (India)

    N K Udayashankar; H L Bhat

    2003-12-01

    Unintentionally doped homoepitaxial InSb films have been grown by liquid phase epitaxy employing ramp cooling and step cooling growth modes. The effect of growth temperature, degree of supercooling and growth duration on the surface morphology and crystallinity were investigated. The major surface features of the grown film like terracing, inclusions, meniscus lines, etc are presented step-by-step and a variety of methods devised to overcome such undesirable features are described in sufficient detail. The optimization of growth parameters have led to the growth of smooth and continuous films. From the detailed morphological, X-ray diffraction, scanning electron microscopic and Raman studies, a correlation between the surface morphology and crystallinity has been established.

  13. InSb Nanowires with Built-In GaxIn1-xSb Tunnel Barriers for Majorana Devices

    Science.gov (United States)

    Car, Diana; Conesa-Boj, Sonia; Zhang, Hao; Op het Veld, Roy L. M.; de Moor, Michiel W. A.; Fadaly, Elham M. T.; Gül, Önder; Kölling, Sebastian; Plissard, Sebastien R.; Toresen, Vigdis; Wimmer, Michael T.; Watanabe, Kenji; Taniguchi, Takashi; Kouwenhoven, Leo P.; Bakkers, Erik P. A. M.

    2017-02-01

    Majorana zero modes (MZMs), prime candidates for topological quantum bits, are detected as zero bias conductance peaks (ZBPs) in tunneling spectroscopy measurements. Implementation of a narrow and high tunnel barrier in the next generation of Majorana devices can help to achieve the theoretically predicted quantized height of the ZBP. We propose a material-oriented approach to engineer a sharp and narrow tunnel barrier by synthesizing a thin axial segment of GaxIn1-xSb within an InSb nanowire. By varying the precursor molar fraction and the growth time, we accurately control the composition and the length of the barriers. The height and the width of the GaxIn1-xSb tunnel barrier are extracted from the Wentzel-Kramers-Brillouin (WKB)-fits to the experimental I-V traces.

  14. Revealing the band structure of InSb nanowires by high-field magnetotransport in the quasiballistic regime

    Science.gov (United States)

    Vigneau, Florian; Gül, Önder; Niquet, Yann-Michel; Car, Diana; Plissard, Sebastien R.; Escoffier, Walter; Bakkers, Erik P. A. M.; Duchemin, Ivan; Raquet, Bertrand; Goiran, Michel

    2016-12-01

    The charge transport properties of individual InSb nanowires based transistors are studied at 4.2 K in the quasiballistic regime. The energy level separations at zero magnetic field are extracted from a bias voltage spectroscopy. The magnetoconductance under a magnetic field applied perpendicularly to the nanowire axis is investigated up to 50 T. Owing to the magnetic reduction of the backscattering, the electronic states of the quasi-one-dimensional electron gas are revealed by Landauer-Büttiker conductance quantization. The results are compared to theoretical predictions revealing the spin and orbital degeneracy lifting. At sufficiently high magnetic field the measurements show the evolution to the quantum Hall effect regime with the formation of Landau orbits and conducting edge states.

  15. Theoretical prediction of thermodynamic activities of liquid Au-Sn-X (X=Bi, Sb, Zn) solder systems

    Science.gov (United States)

    Awe, O. E.; Oshakuade, O. M.

    2017-02-01

    Molecular interaction volume model has been theoretically used to predict the thermodynamic activities of tin in Au-Sn-Bi and Au-Sn-Sb and the thermodynamic activity of zinc in Au-Sn-Zn at experimental temperatures 800 K, 873 K and 973 K, respectively. On the premise of agreement between the predicted and experimental values, we predicted the activities of the remaining two components in each of the three systems. This prediction was extended from three cross-sections to five cross-sections, and to temperature range 400-600 K, relevant for applications. Iso-activities were plotted. Results show that addition of tin reduces the tendency for chemical short range order in both Au-Sb and Au-Zn systems, while addition of gold and bismuth, respectively, reduce the tendency for chemical short range order in Sn-Sb and Au-Sn systems. Also, we found that, in the desired high-temperature region for applications, while a combination of chemical order and miscibility of components exist in both Au-Sn-Bi and Au-Sn-Zn systems, only chemical order exist in the Au-Sn-Sb system. Results, further show that increase in temperature reduces the phase separation tendency in Au-Sn-Bi system.

  16. Enhanced power factor and high-pressure effects in (Bi,Sb){sub 2}(Te,Se){sub 3} thermoelectrics

    Energy Technology Data Exchange (ETDEWEB)

    Ovsyannikov, Sergey V., E-mail: sergey.ovsyannikov@uni-bayreuth.de, E-mail: sergey2503@gmail.com [Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, D-95447 Bayreuth (Germany); Institute for Solid State Chemistry of Ural Branch of Russian Academy of Sciences, Yekaterinburg 620219 (Russian Federation); Morozova, Natalia V.; Korobeinikov, Igor V.; Vokhmyanin, Alexander P.; Shchennikov, Vladimir V. [M. N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, 18 S. Kovalevskaya Str., Yekaterinburg 620137 (Russian Federation); Lukyanova, Lidia N.; Usov, Oleg A.; Kutasov, Vsevolod A. [Ioffe Institute, St Petersburg 194021 (Russian Federation); Manakov, Andrey Y. [A. V. Nikolaev Institute of Inorganic Chemistry of Russian Academy of Sciences, Siberian Division, Novosibirsk 630090 (Russian Federation); Likhacheva, Anna Y. [Institute of Mineralogy and Petrography of Russian Academy of Sciences, Siberian Division, Novosibirsk 630090 (Russian Federation); Ancharov, Alexey I. [Budker Institute of Nuclear Physics of Russian Academy of Sciences, Siberian Division, 630090 Novosibirsk (Russian Federation); Institute for Solid State Chemistry and Mechanochemistry of Sibirian Branch of Russian Academy of Sciences, Novosibirsk 630128 (Russian Federation); Berger, Ivan F. [Institute for Solid State Chemistry of Ural Branch of Russian Academy of Sciences, Yekaterinburg 620219 (Russian Federation); Kulbachinskii, Vladimir A. [M. V. Lomonosov Moscow State University, Physics Department, 119991 GSP1, Moscow (Russian Federation); Okada, Taku [Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8581 Chiba (Japan)

    2015-04-06

    We investigated the effects of applied high pressure on thermoelectric, electric, structural, and optical properties of single-crystalline thermoelectrics, Bi{sub 2}Te{sub 3}, Bi{sub x}Sb{sub 2−x}Te{sub 3} (x = 0.4, 0.5, 0.6), and Bi{sub 2}Te{sub 2.73}Se{sub 0.27} with the high thermoelectric performance. We established that moderate pressure of about 2–4 GPa can greatly enhance the thermoelectric power factor of all of them. X-ray diffraction and Raman studies on Bi{sub 2}Te{sub 3} and Bi{sub 0.5}Sb{sub 1.5}Te{sub 3} found anomalies at similar pressures, indicating a link between crystal structure deformation and physical properties. We speculate about possible mechanisms of the power factor enhancement and suppose that pressure/stress tuning can be an effective tool for the optimization of the thermoelectric performance.

  17. Heavily Cr-doped (Bi,Sb2Te3 as a ferromagnetic insulator with electrically tunable conductivity

    Directory of Open Access Journals (Sweden)

    Yunbo Ou

    2016-08-01

    Full Text Available With molecular beam epitaxy we have grown Cry(BixSb1-x2-yTe3 thin films with homogeneous distribution of Cr dopants and Curie temperature up to 77 K. The films with Cr concentration y ≥ 0.39 are found to be topologically trivial, highly insulating ferromagnets, whose conductivity can be tuned over two orders of magnitude by gate voltage. The ferromagnetic insulators with electrically tunable conductivity can be used to realize the quantum anomalous Hall effect at higher temperature in topological insulator heterostructures and to develop field effect devices for spintronic applications.

  18. Design and fabrication of thin film Bi-Sb and Bi-Cu thermopiles for IR thermal radiation detection

    CERN Document Server

    Afzalzadeh, R

    2003-01-01

    Thin film thermopiles are widely used as small size sensors, in particular to sense infra-red thermal radiations. In this paper a method for designing and fabrication of thin films Bi-Cu thermopiles in linear in linear array of 8 and 11 elements in series and mono-layer is introduced. Also, fabrication of of Bi-Cu thin film thermopiles, which are used as IR radiation sensors, made in multilayer from with 100 series junctions in circular shape are presented. The samples are fabricated on a PCB board with double-side copper laminated as a substrate. The results of our measurements show that the output voltage produced due to temperature difference between junctions, is very sensitive and linear to temperature difference.

  19. CdTe nBn photodetectors with ZnTe barrier layer grown on InSb substrates

    Science.gov (United States)

    He, Zhao-Yu; Campbell, Calli M.; Lassise, Maxwell B.; Lin, Zhi-Yuan; Becker, Jacob J.; Zhao, Yuan; Boccard, Mathieu; Holman, Zachary; Zhang, Yong-Hang

    2016-09-01

    We have demonstrated an 820 nm cutoff CdTe nBn photodetector with ZnTe barrier layer grown on an InSb substrate. At room temperature, under a bias of -0.1 V, the photodetector shows Johnson and shot noise limited specific detectivity (D*) of 3 × 1013 cm Hz1/2/W at a wavelength of 800 nm and 2 × 1012 cm Hz1/2/W at 200 nm. The D* is optimized by using a top contact design of ITO/undoped-CdTe. This device not only possesses nBn advantageous characteristics, such as generation-recombination dark current suppression and voltage-bias-addressed two-color photodetection, but also offers features including responsivity enhancements by deep-depletion and by using a heterostructure ZnTe barrier layer. In addition, this device provides a platform to study nBn device physics at room temperature, which will help us to understand more sophisticated properties of infrared nBn photodetectors that may possess a large band-to-band tunneling current at a high voltage bias, because this current is greatly suppressed in the large-bandgap CdTe nBn photodetector.

  20. Electron transport lifetimes in InSb/Al1-x In x Sb quantum well 2DEGs

    Science.gov (United States)

    Hayes, D. G.; Allford, C. P.; Smith, G. V.; McIndo, C.; Hanks, L. A.; Gilbertson, A. M.; Cohen, L. F.; Zhang, S.; Clarke, E. M.; Buckle, P. D.

    2017-08-01

    We report magnetotransport measurements of InSb/Al1-x In x Sb modulation doped quantum well (QW) structures and the extracted transport ({τ }{{t}}) and quantum ({τ }{{q}}) lifetime of carriers at low temperature (transport lifetimes over a range of samples with different doping levels and carrier densities, and deduce different transport regimes dependent on QW state filling calculated from self-consistent Schrödinger-Poisson modelling. For samples where only the lowest QW subband is occupied at electron densities of 2.13× {10}11 cm-2 and 2.54× {10}11 cm-2 quantum lifetimes of {τ }{{q}}≈ 0.107 ps, and {τ }{{q}}≈ 0.103 ps are extracted from Shubnikov-de Haas oscillations below a magnetic field of 0.8 T. The extracted ratios of transport to quantum lifetimes, {τ }{{t}}/{τ }{{q}}≈ 17 and {τ }{{t}}/{τ }{{q}}≈ 20 are similar to values reported in other binary QW two-dimensional electron gas systems, but are inconsistent with predictions from transport modelling which assumes that remote ionized donors are the dominant scattering mechanism. We find the low {τ }{{t}}/{τ }{{q}} ratio and the variation in transport mobility with carrier density cannot be explained by reasonable levels of background impurities or well width fluctuations. Thus, there is at least one additional scattering mechanism unaccounted for, most likely arising from structural defects.

  1. Formation of periodic interfacial misfit dislocation array at the InSb/GaAs interface via surface anion exchange

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Bo Wen; Tan, Kian Hua; Loke, Wan Khai; Wicaksono, Satrio; Yoon, Soon Fatt [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore)

    2016-07-21

    The relationship between growth temperature and the formation of periodic interfacial misfit (IMF) dislocations via the anion exchange process in InSb/GaAs heteroepitaxy was systematically investigated. The microstructural and electrical properties of the epitaxial layer were characterized using atomic force microscope, high-resolution x-ray diffraction, transmission electron microscopy, and Hall resistance measurement. The formation of interfacial misfit (IMF) dislocation arrays depended on growth temperature. A uniformly distributed IMF array was found in a sample grown at 310 °C, which also exhibited the lowest threading dislocation density. The analysis suggested that an incomplete As-for-Sb anion exchange process impeded the formation of IMF on sample grown above 310 °C. At growth temperature below 310 °C, island coalescence led to the formation of 60° dislocations and the disruption of periodic IMF array. All samples showed higher electron mobility at 300 K than at 77 K.

  2. From the channel model of an InSb-based superresolution optical disc system to impulse response and resolution limits.

    Science.gov (United States)

    Hepper, Dietmar

    2011-06-10

    The signal model of a superresolution optical channel can be an efficient tool for developing components of an associated high-density optical disc system. While the behavior of the laser diode, aperture, lens, and detector are properly described, a general mathematical model of the superresolution disc itself has not yet been available until recently. Different approaches have been made to describe the properties of a mask layer, mainly based on temperature- or power-dependent nonlinear effects. A complete signal-based or phenomenological optical channel model--from non-return-to-zero inverted input to disc readout signal--has recently been developed including the reflectivity of a superresolution disc with InSb used for the mask layer. In this contribution, the model is now extended and applied to a moving disc including a land-and-pit structure, and results are compared with data read from real superresolution discs. Both impulse response and resolution limits are derived and discussed. Thus the model provides a bridge from physical to readout signal properties, which count after all. The presented approach allows judging of the suitability of a mask layer material for storage density enhancement already based on static experiments, i.e., even before developing an associated disc drive.

  3. Optical properties and structure of Sb-rich AgInSbTe phase change thin films

    Institute of Scientific and Technical Information of China (English)

    张广军; 顾冬红; 干福熹

    2005-01-01

    A new composition content quaternary-alloy-based phase change thin film, Sb-rich AgInSbTe, has been prepared by DC-magnetron sputtering on a K9 glass substrate. After the film has been subsequently annealed at 200 ℃ for 30min,it becomes a crystalline thin film. The diffraction peak of antimony (Sb) are observed by shallow (0.5 degree) x-ray diffraction in the quaternary alloy thin film. The analyses of the measurement from differential scanning calorimetry (DSC) show that the crystallization temperature of the phase change thin film is about 190C and increases with the heating rate. By Kissinger plot, the activation energy for crystallization is determined to be 3.05eV. The refiectivity,refractive index and extinction coefficient of the crystalline and amorphous phase change thin films are presented.The optical absorption coefficient of the phase change thin films as a function of photon energy is obtained from the extinction coefficient. The optical band gaps of the amorphous and crystallization phase change thin films are 0.265eV and 1.127eV, respectively.

  4. An investigation of near-infrared photoluminescence from AP-MOVPE grown InSb/GaSb quantum dot structures

    Science.gov (United States)

    Ahia, C. C.; Tile, N.; Urgessa, Z. N.; Botha, J. R.; Neethling, J. H.

    2017-01-01

    In this work, the near-infrared photoluminescence (PL) of InSb/GaSb QD structures grown on GaSb substrate (2° off (100)) using atmospheric pressure Metalorganic Vapor Phase Epitaxy is investigated. The structures are analyzed before capping and after capping using scanning probe microscopy and high resolution transmission electron microscopy (HRTEM), respectively. At 10 K, with an excitation power of 2 mW, a PL peak at ∼ 732 meV is observed. Upon an increase in laser power to 120 mW, a blue shift of ∼ 8 meV is noticed. This emission typically persists up to 60-70 K, after which it becomes weak. An SPM analysis of the size distribution of uncapped dots reveals a mono-modal distribution with an average density of ∼ 5×1010 cm-2. However, a HRTEM investigation of the capped dots reveals the formation of an InGaSb quantum well-like structure, ∼ 10 nm thick, which gives rise to the PL signal mentioned above.

  5. Exotic topological insulator states and topological phase transitions in Sb2Se3-Bi2Se3 heterostructures

    KAUST Repository

    Zhang, Qianfan

    2012-03-27

    Topological insulator is a new state of matter attracting tremendous interest due to its gapless linear dispersion and spin momentum locking topological states located near the surface. Heterostructures, which have traditionally been powerful in controlling the electronic properties of semiconductor devices, are interesting for topological insulators. Here, we studied the spatial distribution of the topological state in Sb 2Se 3-Bi 2Se 3 heterostructures by first-principle simulation and discovered that an exotic topological state exists. Surprisingly, the state migrates from the nontrivial Bi 2Se 3 into the trivial Sb 2Se 3 region and spreads across the entire Sb 2Se 3 slab, extending beyond the concept of "surface" state while preserving all of the topological surface state characteristics. This unusual topological state arises from the coupling between different materials and the modification of electronic structure near Fermi energy. Our study demonstrates that heterostructures can open up opportunities for controlling the real-space distribution of the topological state and inducing quantum phase transitions between topologically trivial and nontrivial states. © 2012 American Chemical Society.

  6. Observation of Structural Anisotropy and the Onset of Liquid-like Motion during the Non-thermal Melting of InSb

    Energy Technology Data Exchange (ETDEWEB)

    Gaffney, K.J.; Lindenberg, A.M.; /SLAC, SSRL; Larsson, J.; /Lund Inst. Tech.; Sokolowski-Tinten, K.; /Jena U. /Duisburg U.; Blome, C.; /DESY; Synnergren, O.; /Lund Inst.; Sheppard, J.; /Oxford U.; Caleman, C.; /Uppsala U.; MacPhee, A.G.; Weinstein, D.; Lowney, D.P.; Allison, T.K.; Matthews, T.; Falcone, R.W.; /UC, Berkeley; Cavalieri, A.L.; /Michigan U. /Munich, Max Planck Inst. Quantenopt.; Dritz, D.M.; Lee, S.H.; Bucksbau, P.H.p a Reis, D.A.; /Michigan U.; Rudati, J.; Macrander, A.T.; /ANL, APS; Fuoss, P.H.; /Argonne

    2005-09-30

    The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquid-like dynamics. They also demonstrate that the root mean-squared displacement in the [111] direction increases faster than in the [110] direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid.

  7. The electronic structure and half-metallic properties of zincblende TiBi (001) surfaces and TiBi(001)/InSb(001) interface

    Science.gov (United States)

    Moosavi, N.; Ahmadian, F.; Baghoolizadeh, F.

    2016-12-01

    First principles calculations were performed using full potential linearized augmented plane wave (FPLAPW) method based on density functional theory (DFT) to study bulk TiBi in rock salt (RS), hexagonal NiAs, and zincblende (ZB) structures, free (001) surfaces of ZB TiBi, and interface of ZB TiBi with InSb(001). The nonmagnetic NiAs structure was ground state structure of bulk TiBi and nonmagnetic RS and ferromagnetic ZB structures were introduced as metastable structures. It was found that ZB TiBi is a half-metallic (HM) ferromagnet with a minority band gap of about 1.43 eV. The origin of half-metallicity was also discussed. The obtained phase diagram showed more stability of the Bi (001) terminated surface compared with the Ti (001) termination. The Ti (001) termination keeps HM property, while half-metallicity was destroyed at Bi (001) termination. The ZB TiBi/InSb (001) interface revealed HM property showing that InSb semiconductor is a suitable substrate for growing ZB TiBi in spintronics.

  8. Improvement of antimony sulfide photo absorber performance by interface modification in Sb2S3-ZnO hybrid nanostructures

    Science.gov (United States)

    Ali, Asad; Hasanain, Syed Khurshid; Ali, Tahir; Sultan, Muhammad

    2017-03-01

    Metal-oxide chalcogenide nanostructures as part of hybrid systems are very important for photovoltaic and optoelectronic applications. It is however known that the various interfaces within the hybrid structures play a crucial role in limiting the efficiency of these devices. Here we report on the improvement of Sb2S3 structure through modification of interface between Zn-oxide nanostructures and chalcogenides. ZnO nanorods were grown on fluorine doped tin oxide (FTO) substrate by chemical bath deposition (CBD) method. X-ray diffraction (XRD) and SEM analysis confirmed the single phase wurtzite structure and c-axis orientation of the ZnO nanorod arrays. Antimony tri-sulfide (Sb2S3) was deposited on ZnO nanords by CBD and subsequently annealed at 300 °C in argon environment for 30 min. XRD and the XPS analysis of ZnO-Sb2S3 system showed the dominant presence of Sb2O3 rather than Sb2S3. Since oxidation of Sb2S3 is understood to proceed mainly from the ZnO-Sb2S3 interface, a ZnS interlayer was introduced between ZnO nanorods and Sb2S3 by chemical route. The subsequent structural and optical properties of the ZnO-ZnS-Sb2S3 system are analyzed in detail. The introduction of sulfide interlayer prevents the oxidation of Sb2S3 which is evident from reduced oxide phase in Sb2S3. Significant improvement in the structural and optical properties of Sb2S3 are reported as compared to the parent ZnO-Sb2S3 system. This gain in the optical properties of hybrid ZnO-ZnS-Sb2S3 nanostructures is explained as being related to successful prevention of Sb2O3 formation at the Sb-ZnO interface and stabilization of the desired Sb2S3.

  9. Thickness dependence of critical current density in MgB{sub 2} films fabricated by ex situ annealing of CVD-grown B films in Mg vapor

    Energy Technology Data Exchange (ETDEWEB)

    Hanna, Mina; Salama, Kamel [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, TX 77204 (United States); Wang, Shufang; Xi, X X [Department of Physics, Pennsylvania State University, University Park, PA 16801 (United States); Redwing, Joan M [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16801 (United States)], E-mail: ksalama@uh.edu

    2009-01-15

    A study was performed to examine the J{sub c} behavior as a function of thickness in MgB{sub 2} films fabricated by ex situ annealing at 840 deg. C of boron films, grown by chemical vapor deposition, in Mg vapor. The film thicknesses range between 300 nm and 10 {mu}m. The values of J{sub c} range from 1.2 x 10{sup 7} A cm{sup -2} for 300 nm to 1.9 x 10{sup 5} A cm{sup -2} for 10 {mu}m film thicknesses at 20 K and self-field. The study shows that the critical current density (J{sub c}) in MgB{sub 2} films decreases with increasing film thickness, similar to that observed in YBCO-coated conductors. Moreover, our study shows that critical current (I{sub c}) reaches its maximum value of 728 A cm{sup -1} width at {approx}1 {mu}m thick MgB{sub 2} films at 20 K and self-field, which is, interestingly, the same thickness of pulsed-laser-deposited YBCO-coated conductors at which I{sub c} reaches its maximum value. The high J{sub c} values carried by our films show that the ex situ fabrication method can produce high quality MgB{sub 2} films at low processing temperatures, which is promising for RF cavity applications and coated-conductor wires and tapes.

  10. Determination of traces of Sb(III) using ASV in Sb-rich water samples affected by mining

    Energy Technology Data Exchange (ETDEWEB)

    Cidu, Rosa, E-mail: cidur@unica.it; Biddau, Riccardo; Dore, Elisabetta

    2015-01-07

    Highlights: • Antimony speciation affects the toxicity of this element. • A simple method for Sb(III) analyses in Sb-rich waters was developed. • Sb(III) was determined by ASV in water stabilized with tartaric and nitric acids. • Pre-concentration and/or separation of Sb(III) prior to analysis are not required. - Abstract: Chemical speciation [Sb(V) and Sb(III)] affects the mobility, bioavailability and toxicity of antimony. In oxygenated environments Sb(V) dominates whereas thermodynamically unstable Sb(III) may occur. In this study, a simple method for the determination of Sb(III) in non acidic, oxygenated water contaminated with antimony is proposed. The determination of Sb(III) was performed by anodic stripping voltammetry (ASV, 1–20 μg L{sup −1} working range), the total antimony, Sb(tot), was determined either by inductively coupled plasma mass spectrometry (ICP-MS, 1–100 μg L{sup −1} working range) or inductively coupled plasma optical emission spectrometry (ICP-OES, 100–10,000 μg L{sup −1} working range) depending on concentration. Water samples were filtered on site through 0.45 μm pore size filters. The aliquot for determination of Sb(tot) was acidified with 1% (v/v) HNO{sub 3}. Different preservatives, namely HCl, L(+) ascorbic acid or L(+) tartaric acid plus HNO{sub 3}, were used to assess the stability of Sb(III) in synthetic solutions. The method was tested on groundwater and surface water draining the abandoned mine of Su Suergiu (Sardinia, Italy), an area heavily contaminated with Sb. The waters interacting with Sb-rich mining residues were non acidic, oxygenated, and showed extreme concentrations of Sb(tot) (up to 13,000 μg L{sup −1}), with Sb(III) <10% of total antimony. The stabilization with L(+) tartaric acid plus HNO{sub 3} appears useful for the determination of Sb(III) in oxygenated, Sb-rich waters. Due to the instability of Sb(III), analyses should be carried out within 7 days upon the water collection. The main

  11. 128×128InSb探测器结构模型研究%Structural modeling of 128 × 128 InSb focal plane array detector

    Institute of Scientific and Technical Information of China (English)

    孟庆端; 张晓玲; 张立文; 吕衍秋

    2012-01-01

    热冲击下红外焦平面探测器的高碎裂概率制约着其成品率.为明晰碎裂机理,基于等效设想,利用小面阵等效大面阵解决了128×128面阵探测器三维结构建模所需单元数过多的问题,同时综合考虑材料线膨胀系数的温度依赖性、材料强度的各向异性、表面加工损伤效应,合理选取InSb材料性能参数,建立起128×128面阵探测器结构有限元分析模型.模拟结果表明:热冲击下最大Von Mises应力值出现在N电极区域,其极值呈非连续分布,这意味着热冲击下128×128面阵探测器的裂纹起源于N电极区域,且不止一条.上述结论与碎裂统计分析报告中典型裂纹起源地及裂纹分布这两方面相符合,这为后续面阵探测器碎裂诱因的研究及结构可靠性设计提供了切实可行的研究思路.%Higher fracture probability appearing in InSb infrared focal plane array (IRFPA) subjected to thermal shock test, restricts its final yield. In order to understand the fracture mechanism, in light of the proposed equivalent method, where a 32×32 array is employed to replace the real 128×128 array, to a three - dimensional structural model of IRFPA is developed by taking into account the temperature dependence of thermal expansion coefficient, anisotropic mechanical strength of InSb chip, damaging effects of the surface of the InSb chip, and a reduction of 90% the out-of-plane elastic modulus. Simulation results show that a maximum Von Mises stress appears in the N electrode zone in InSb chip, and the extremum values present a non-continuous distribution. This means that the cracks is most likely to emerge in the region of N electrode, besides, the number of crack tracks is more than one. These are well consistent with the 128×128 InSb IRFPA fracture statistics results under thermal shock test. All these are beneficial to the further study of fracture inducing factors and structural reliability design

  12. Bi and InSb Nano-Hall Probes for direct magnetic imaging with Room Temperature Scanning Hall Probe Microscopy(RT-SHPM)

    Science.gov (United States)

    Oral, Ahmet; Dede, Munir; Sandhu, Adarsh; Masuda, Hiroshi; Bending, Simon J.

    2002-03-01

    Scanning Hall Probe Microscopy (SHPM)[1] is a quantitative and non-invasive technique to image magnetic samples with high spatial and magnetic field resolution: ~ 120nm & 60mG/Hz^1/2 at room temperature. A nano-Hall probe is scanned over the sample surface to measure the surface magnetic fields using conventional scanning tunneling microscopy-positioning techniques. We have developed new down to ~120x120nm size Bi and InSb Hall probes machined FIB milling. 120nm Bi sensors[2] have a sensitivity of 3.3x10-4 Ω/G and a noise level of 7.2 G/Hz^1/2 . The new InSb sensors have a sensitivity of 0.03 Ω/G and a noise level of 8 mG/Hz^1/2 at room temperature. This corresponds to ×8 better noise performance compared to conventional GaAs, based sensors used in RT-SHPM. We used these new sensors to study magnetic domain structures of crystalline garnet films and Ni_80Fe_20 rectangular permalloy microstructures microfabricated by lift-off technique. Bi and InSb nano-Hall probes are shown to be high spatial resolution, high sensitivity and low noise alternatives to GaAs sensors for RT-SHPM. There seems to be more room for improving the spatial resolution down to Kurosawa K, A. Oral and S.J. Bending, Electronics Letters 37 (22), 1335-1336 (2001).

  13. Interface and facet control during Czochralski growth of (111) InSb crystals for cost reduction and yield improvement of IR focal plane array substrates

    Science.gov (United States)

    Gray, Nathan W.; Perez-Rubio, Victor; Bolke, Joseph G.; Alexander, W. B.

    2014-10-01

    Focal plane arrays (FPAs) made on InSb wafers are the key cost-driving component in IR imaging systems. The electronic and crystallographic properties of the wafer directly determine the imaging device performance. The "facet effect" describes the non-uniform electronic properties of crystals resulting from anisotropic dopant segregation during bulk growth. When the segregation coefficient of dopant impurities changes notably across the melt/solid interface of a growing crystal the result is non-uniform electronic properties across wafers made from these crystals. The effect is more pronounced in InSb crystals grown on the (111) axis compared with other orientations and crystal systems. FPA devices made on these wafers suffer costly yield hits due to inconsistent device response and performance. Historically, InSb crystal growers have grown approximately 9-19 degree off-axis from the (111) to avoid the facet effect and produced wafers with improved uniformity of electronic properties. It has been shown by researchers in the 1960s that control of the facet effect can produce uniform small diameter crystals. In this paper, we share results employing a process that controls the facet effect when growing large diameter crystals from which 4, 5, and 6" wafers can be manufactured. The process change resulted in an increase in wafers yielded per crystal by several times, all with high crystal quality and uniform electronic properties. Since the crystals are grown on the (111) axis, manufacturing (111) oriented wafers is straightforward with standard semiconductor equipment and processes common to the high-volume silicon wafer industry. These benefits result in significant manufacturing cost savings and increased value to our customers.

  14. Pair-breaking and superconducting state recovery dynamics in MgB2.

    Science.gov (United States)

    Demsar, J; Averitt, R D; Taylor, A J; Kabanov, V V; Kang, W N; Kim, H J; Choi, E M; Lee, S I

    2003-12-31

    We present studies of the photoexcited quasiparticle dynamics in MgB2 where, using femtosecond optical techniques, Cooper pair-breaking dynamics (PBD) have been temporally resolved for the first time. The PBD are strongly temperature and photoexcitation intensity dependent. Analysis of the PBD using the Rothwarf-Taylor equations suggests that the anomalous PBD arises from the fact that in MgB2 photoexcitation is initially followed by energy relaxation to high frequency phonons instead of, as commonly assumed, e-e thermalization. Furthermore, the bare quasiparticle recombination rate and the probability for pair breaking by phonons have been determined.

  15. Optical properties of Cr3+ in fluorite-structure hosts and in MgF*2

    Science.gov (United States)

    Payne, Stephen A.; Chase, L. L.; Krupke, William F.

    1987-03-01

    We have examined the optical properties of Cr3+ in MgF2 and in the fluorite-structure hosts: CdF2, CaF2, SrF2, and BaF2. The properties of Cr3+ in MgF2 are similar to those observed for other fluoride crystals that have octahedral substitutional metal sites. Interestingly, Cr3+ is also found to be sixfold coordinated in the fluorite hosts, despite the fact that the metal sites of these crystal lattices are eightfold coordinated. The smaller ionic radius of Cr3+ compared to, say, Ca2+, undoubtedly results in considerable relaxation at the metal site. However, the crystal field stabilization energy present in the 4A2(d3) ground state also provides for the energetic preference of sixfold vs eightfold coordination. The similarity of the observed absorption spectra of Cr3+ in MgF2 and in fluorite give evidence that the ground state is octahedrally coordinated in all of these hosts. The reduction of this electronic stabilization energy in the 4T2(d3) excited state is considered to produce a configurational shift relative to the ground state. This shift may be the reason why Cr3+ luminesces effectively in MgF2 whereas it is largely quenched in the fluorite-structure materials.

  16. Nanocrystal ghosting: Extensive radiation damage in MgO induced by low-energy electrons

    Science.gov (United States)

    Frankenfield, Zackery; Kane, Kenneth; Sawyer, William H.

    2017-03-01

    We report direct evidence of extensive radiation damage in MgO nanocrystals due to intense bombardment (2 × 10 electrons/nm sec) by electrons with beam energies between 60 keV and 120 keV. Based upon a minimum intensity necessary to produce the observed damage, we present an explanation based on the Knotek-Feibelman process.

  17. The structure and chemical and acid-base state of the surface of solid solutions and binary components in the InSb-CdS system

    Science.gov (United States)

    Kirovskaya, I. A.; Filatova, T. N.

    2012-03-01

    The surface physicochemical properties, including microstructure, chemical composition, and acid-base surface properties, of solid solutions and binary components in the InSb-CdS system obtained for the first time were studied. Films of all the components had a polycrystalline structure with a nonuniform character of the distribution of crystallites, which associated into agglomerates. The chemistry of the surface was mainly determined by adsorbed H2O and CO2 molecules, OH- groups, and, to a lesser extent, oxygen and hydrogen carbon compounds. The strength, concentration, and nature of acid centers were determined. Coordination-unsaturated In and Cd atoms, adsorbed water molecules, and OH-groups were responsible for acid-basic centers. Changes in the acid-base properties of the surface of InSb-CdS system components caused by composition variations were studied. They correlated with the "specific conductivity-composition" dependence, reflected the special features of donor-acceptor interactions in solid solutions, and could be used to predict adsorption-catalytic properties.

  18. The Structural, Photocatalytic Property Characterization and Enhanced Photocatalytic Activities of Novel Photocatalysts Bi2GaSbO7 and Bi2InSbO7 during Visible Light Irradiation

    Directory of Open Access Journals (Sweden)

    Jingfei Luan

    2016-09-01

    Full Text Available In order to develop original and efficient visible light response photocatalysts for degrading organic pollutants in wastewater, new photocatalysts Bi2GaSbO7 and Bi2InSbO7 were firstly synthesized by a solid-state reaction method and their chemical, physical and structural properties were characterized. Bi2GaSbO7 and Bi2InSbO7 were crystallized with a pyrochlore-type structure and the lattice parameter of Bi2GaSbO7 or Bi2InSbO7 was 10.356497 Å or 10.666031 Å. The band gap of Bi2GaSbO7 or Bi2InSbO7 was estimated to be 2.59 eV or 2.54 eV. Compared with nitrogen doped TiO2, Bi2GaSbO7 and Bi2InSbO7, both showed excellent photocatalytic activities for degrading methylene blue during visible light irradiation due to their narrower band gaps and higher crystallization perfection. Bi2GaSbO7 showed higher catalytic activity compared with Bi2InSbO7. The photocatalytic degradation of methylene blue followed by the first-order reaction kinetics and the first-order rate constant was 0.01470 min−1, 0.00967 min−1 or 0.00259 min−1 with Bi2GaSbO7, Bi2InSbO7 or nitrogen doped TiO2 as a catalyst. The evolution of CO2 and the removal of total organic carbon were successfully measured and these results indicated continuous mineralization of methylene blue during the photocatalytic process. The possible degradation scheme and pathway of methylene blue was also analyzed. Bi2GaSbO7 and Bi2InSbO7 photocatalysts both had great potential to purify textile industry wastewater.

  19. Optical Property of LiNbO3 Crystal Codoped with In, Mg and Fe

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In2O3, MgO and Fe2O3 were doped in LiNbO3 and Czochralski method was used to grow In:Mg:Fe:LiNbO3 crystals. The OH- extension transmission spectra, light scattering resistance ability, two wave coupled diffraction efficiency and response time of the crystal were measured. Codoping In and Mg in crystal will improve its light scattering resistance ability and response time. Doping In can increase the ability to replace antisite Nb and decrease the doping quantity of Mg. All these are propitious to improve the optical homogeneity of crystal. Doping Fe can improve the photorefractive sensitivity for LiNbO3 crystal. We discussed the site of In, Mg and Fe in LiNbO3 crystals and the influence of the absorption peak of OH- transmission spectra on photorefractive property for LiNbO3 crystal.

  20. Light-Induced Domain Inversion in Mg-Doped near Stoichiometric Lithium Niobate Crystals

    Institute of Scientific and Technical Information of China (English)

    LIU Hong-De; KONG Yong-Fa; HU Qian; WU Ri-Wen; WANG Wen-Jie; LI Xiao-Chun; CHEN Shao-Lin; LIU Shi-Guo; XU Jing-Jun

    2007-01-01

    We investigate the influence of visible light on domain inversion in Mg-doped near stoichiometric lithium niobate crystals and find that the switching electric field decreases about 70% above a threshold light intensity. This effect helps us optically control domain switching and produce bulk domain structures on the micrometre scale. Finally, we introduce a model of photo-induced carriers to explain the origin of the reduction of switching electric field.

  1. Superconductivity in MgB2 : Phonon modes and influence of carbon doping

    Indian Academy of Sciences (India)

    A Bharathi; Y Hariharan; Jemima Balaselvi; C S Sundar

    2003-02-01

    Following a brief overview, results of our investigations on phonon modes in MgB2 , and superconducting transition in carbon doped MgB2 are presented. The superconducting transition temperature in MgB$_{2−x}C_x$ as obtained from susceptibility and resistivity measurements is observed to decrease systematically from 39.4 K for = 0 to 26 K for = 0.5S. It is shown the changes in lattice volume, as obtained from x-ray diffraction measurements, can account only partially for the observed decrease in $T_c$. The observed variation of $T_c$ with carbon content is seen to correlate with the Debye temperatures, obtained from an analysis of the resistivity data. Investigation of the phonon modes in MgB2 , through infrared absorption measurements indicate three modes at 410, 475 and 560 cm-1 The former two are associated with the infrared active modes, and the third component is associated with the Raman mode, that gets activated due to disorder. A study of the temperature dependence of these modes indicates no changes across the superconducting transition. The mode at 560 cm-1 shows a significant hardening and a corresponding decrease in linewidth, with the lowering of temperature, that can been accounted in terms of anharmonicity.

  2. Electronic structures of long periodic stacking order structures in Mg: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Wang, William Yi, E-mail: yuw129@psu.edu [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802 (United States); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Shang, Shun Li; Wang, Yi [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802 (United States); Darling, Kristopher A. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Kecskes, Laszlo J. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, RDRL-WMM-B, Aberdeen Proving Ground, MD 21005 (United States); Mathaudhu, Suveen N. [Materials Science Division, U.S. Army Research Office, Research Triangle Park, NC 27709 (United States); Hui, Xi Dong [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Liu, Zi-Kui, E-mail: dr.liu@psu.edu [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)

    2014-02-15

    Graphical abstract: -- Highlight: • Formation energies of the LPSOs (γ{sub LPSO}) can be scaled with respect to the formation energy of I2. • γ{sub LPSO} depends on the number of fault layers. • Electron structures of the 10H, 14H, 18R and 24R originate from those of I2. • Electron structure and formation energy of the 6H are between those of I1 and I2. -- Abstract: Long period stacking order (LPSO) structures, such as 6H, 10H, 14H, 18R and 24R, play significant roles in enhancing the mechanical properties of Mg alloys and have been largely investigated separately. In the present work, through detailed investigations of deformation electron density, we show that the electron structures of 10H, 14H, 18R and 24R LPSO structures in Mg originate from those of deformation stacking faults in Mg, and their formation energies can be scaled with respect to formation energy and the number of layers of deformation stacking faults, while the electron structure and formation energy of the 6H LPSO structure are between those of deformation and growth stacking faults. The simulated images of high resolution transmission electron microscopy compare well with experimental observed ones. The understanding of LPSO structures in Mg enables future quantitative investigations of effects of alloying elements on properties of LPSO structures and Mg alloys.

  3. Influence of the carrier mobility distribution on the Hall and the Nernst effect measurements in n-type InSb

    Energy Technology Data Exchange (ETDEWEB)

    Madon, B.; Wegrowe, J.-E.; Drouhin, H.-J. [Laboratoire des Solides Irradiés, CNRS UMR 7642, CEA-DSM-IRAMIS, Ecole polytechnique, Université Paris-Saclay, 91128 Palaiseau (France); Liu, X.; Furdyna, J. [Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Khodaparast, G. A., E-mail: khoda@vt.edu [Department of Physics, Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2016-01-14

    In this study, we report magneto-resistance measurements on an n-doped InSb film, to separate the contributions of the electrical currents from the heat currents. We have demonstrated a prototype for a magnetic field sensor which is powered by heat currents and does not require any electrical current. We fabricated two Hall bars, where a low frequency (f = 0.05 Hz) AC current, was applied between the two contacts in one of the Hall bars. Separating the f and 2f components of the voltage measured across the second Hall bar was used to distinguish between the electrical and the heat contributions to the electron currents. Our observations can be modeled using a Gaussian distribution of mobility within the sample.

  4. Terahertz tunable detection in self-switching diodes based on high mobility semiconductors: InGaAs, InAs and InSb

    Energy Technology Data Exchange (ETDEWEB)

    Iniguez-de-la-Torre, I; Rodilla, H; Mateos, J; Pardo, D; Gonzalez, T [Departamento de Fisica Aplicada, Universidad de Salamanca, Plaza de la Merced s/n, 37008 Salamanca (Spain); Song, A M, E-mail: indy@usal.e [School of Electrical and Electronic Engineering, University of Manchester, Manchester M60 1QD (United Kingdom)

    2009-11-15

    In this work we report on the use of high mobility materials in the channel of self-switching diodes as potential candidates for terahertz operation. By means of Monte Carlo simulations we envisage the feasibility of tuneable-by-geometry detection in the terahertz range. The low effective mass of InAs and InSb in relation to InGaAs enhances ballistic transport inside the diode, thus improving the amplitude and quality factor of the resonance found in the detection spectra of self-switching diodes. The frequency of the resonant peak is also increased with the use of these narrow band gap semiconductors. The analysis of the noise spectra provides useful information about the origin of the resonance. By decreasing temperature below 300 K, a clear improvement in detection sensitivity is also achieved.

  5. Gate-tunable high mobility remote-doped InSb/In{sub 1−x}Al{sub x}Sb quantum well heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Wei, E-mail: wyi@hrl.com, E-mail: MSokolich@hrl.com; Kiselev, Andrey A.; Thorp, Jacob; Noah, Ramsey; Nguyen, Binh-Minh; Bui, Steven; Rajavel, Rajesh D.; Hussain, Tahir; Gyure, Mark F.; Sokolich, Marko, E-mail: wyi@hrl.com, E-mail: MSokolich@hrl.com [HRL Laboratories, 3011 Malibu Canyon Rd, Malibu, California 90265 (United States); Kratz, Philip [Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Qian, Qi; Manfra, Michael J. [Department of Physics and Astronomy, Purdue University, 525 Northwestern Ave., West Lafayette, Indiana 47907 (United States); Pribiag, Vlad S.; Kouwenhoven, Leo P. [Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft (Netherlands); Marcus, Charles M. [Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen (Denmark)

    2015-04-06

    Gate-tunable high-mobility InSb/In{sub 1−x}Al{sub x}Sb quantum wells (QWs) grown on GaAs substrates are reported. The QW two-dimensional electron gas (2DEG) channel mobility in excess of 200 000 cm{sup 2}/V s is measured at T = 1.8 K. In asymmetrically remote-doped samples with an HfO{sub 2} gate dielectric formed by atomic layer deposition, parallel conduction is eliminated and complete 2DEG channel depletion is reached with minimal hysteresis in gate bias response of the 2DEG electron density. The integer quantum Hall effect with Landau level filling factor down to 1 is observed. A high-transparency non-alloyed Ohmic contact to the 2DEG with contact resistance below 1 Ω·mm is achieved at 1.8 K.

  6. Influence of the exchange and correlation functional on the structure of amorphous InSb and In3SbTe2 compounds

    Science.gov (United States)

    Gabardi, Silvia; Caravati, Sebastiano; Los, Jan H.; Kühne, Thomas D.; Bernasconi, Marco

    2016-05-01

    We have investigated the structural, vibrational, and electronic properties of the amorphous phase of InSb and In3SbTe2 compounds of interest for applications in phase change non-volatile memories. Models of the amorphous phase have been generated by quenching from the melt by molecular dynamics simulations based on density functional theory. In particular, we have studied the dependence of the structural properties on the choice of the exchange-correlation functional. It turns out that the use of the Becke-Lee-Yang-Parr functional provides models with a much larger fraction of In atoms in a tetrahedral bonding geometry with respect to previous results obtained with the most commonly used Perdew-Becke-Ernzerhof functional. This outcome is at odd with the properties of Ge2Sb2Te5 phase change compound for which the two exchange-correlation functionals yield very similar results on the structure of the amorphous phase.

  7. Thickness-Induced Metal-Insulator Transition in Sb-doped SnO2 Ultrathin Films: The Role of Quantum Confinement.

    Science.gov (United States)

    Ke, Chang; Zhu, Weiguang; Zhang, Zheng; Tok, Eng Soon; Ling, Bo; Pan, Jisheng

    2015-11-30

    A thickness induced metal-insulator transition (MIT) was firstly observed in Sb-doped SnO2 (SnO2:Sb) epitaxial ultrathin films deposited on sapphire substrates by pulsed laser deposition. Both electrical and spectroscopic studies provide clear evidence of a critical thickness for the metallic conductivity in SnO2:Sb thin films and the oxidation state transition of the impurity element Sb. With the shrinkage of film thickness, the broadening of the energy band gap as well as the enhancement of the impurity activation energy was studied and attributed to the quantum confinement effect. Based on the scenario of impurity level pinning and band gap broadening in quantum confined nanostructures, we proposed a generalized energy diagram to understand the thickness induced MIT in the SnO2:Sb system.

  8. Structural and optical properties of silicon layers with InSb and InAs nanocrystals formed by ion-beam synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Komarov, F.; Vlasukova, L.; Greben, M.; Milchanin, O. [Belarusian State University, Independence Ave. 4, 220030 Minsk (Belarus); Zuk, J., E-mail: jotzet@hektor.umcs.lublin.pl [Maria Curie-Skłodowska University, Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin (Poland); Wesch, W.; Wendler, E. [Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, D-07743 Jena (Germany); Togambaeva, A. [Al-Farabi Kazakh National University, 71 Al-Farabi Ave., 050040 Almaty (Kazakhstan)

    2013-07-15

    We have studied the formation of InSb and InAs precipitates with sizes of several nanometers in Si and SiO{sub 2}/Si by means of implantation of (Sb + In) or (As + In) ions with energies from 170 to 350 keV and fluencies from 2.8 to 3.5 × 10{sup 16} cm{sup −2} at 500 °C and subsequent annealing at 1050–1100 °C for 3–30 min. RBS, TEM/TED, RS and PL techniques were employed to characterize the implanted layers. A broad band in the region of 1.2–1.6 μm has been registered in the low-temperature PL spectra of both (Sb + In) and (As + In) implanted and annealed silicon crystals. It was shown that structural and optical properties of oxidized silicon crystals strongly depend on type of implanted species in silicon crystals.

  9. Programming the diameter of InSb single crystals grown by pulling from the melt using the thermal gradients in the crucible. Master's thesis

    Energy Technology Data Exchange (ETDEWEB)

    Azoulay, M.

    1984-05-01

    In the work a method is given of presetting the diameter of a crystal grown by pulling from the melt by means of a predetermined cooling plot. The parameters involved in calculating the cooling plot are the measured vertical and radial thermal gradients near the interface and the liquid to solid densities ratio. The theoretical analysis is based on the assumption that the thermal profile in the crucible vicinity is stiff, implying that any temperature change at any point near the surface is followed by exactly the same temperature change in the entire vicinity of the crucible. The method was applied successfully to the growth of defect-free InSb single crystals, 8 cm long and with diameters up to 2.5 cm.

  10. Dramatic role of critical current anisotropy on flux avalanches in MgB2 films.

    Science.gov (United States)

    Albrecht, J; Matveev, A T; Strempfer, J; Habermeier, H-U; Shantsev, D V; Galperin, Y M; Johansen, T H

    2007-03-16

    Anisotropic penetration of magnetic flux in MgB(2) films grown on vicinal sapphire substrates is investigated using magneto-optical imaging. Regular penetration above 10 K proceeds more easily along the substrate surface steps, the anisotropy of the critical current being 6%. At lower temperatures the penetration occurs via abrupt dendritic avalanches that preferentially propagate perpendicular to the surface steps. This inverse anisotropy in the penetration pattern becomes dramatic very close to 10 K where all flux avalanches propagate in the strongest pinning direction. The observed behavior is fully explained using a thermomagnetic model of the dendritic instability.

  11. CLASP2: High-Precision Spectro-Polarimetery in Mg II h & k

    Science.gov (United States)

    Ishikawa, R.; McKenzie, D.; Trujillo Bueno, J.; Auchere, F.; Rachmeler, L.; Okamoto, T. J.; Kano, R.; Song, D.; Kubo, M.; Narukage, N.; hide

    2017-01-01

    The international team is promoting the CLASP2 (Chromospheric LAyer Spectro-Polarimeter 2) sounding rocket experiment, which is the re-flight of CLASP (2015). In this second flight, we will refit the existing CLASP instrument to measure all Stokes parameters in Mg II h k lines, and aim at inferring the magnetic field information in the upper chromosphere combining the Hanle and Zeeman effects. CLASP2 project was approved by NASA in December 2016, and is now scheduled to fly in 2019.

  12. High Upper Critical Field and Irreversibility Field in MgB2 Coated-Conductor Fibers

    Science.gov (United States)

    2016-06-13

    High upper critical field and irreversibility field in MgB2 coated-conductor fibers V. Ferrando,a P. Orgiani,b A. V. Pogrebnyakov, J. Chen, Qi Li...show a high upper critical field of 55 T at 1.5 K and a high irreversibility field of 40 T at 1.5 K. The result demonstrates great potential of MgB2...using cryocoolers. Unlike high temperature superconductors where critical current den- sity Jc drops sharply across the grain boundary when the grains

  13. Computer simulations of nanoindentation in Mg-Cu and Cu-Zr metallic glasses

    DEFF Research Database (Denmark)

    Paduraru, Anca; Andersen, Ulrik Grønbjerg; Thyssen, Anders

    2010-01-01

    The formation of shear bands during plastic deformation of Cu0.50Zr0.50 and Mg0.85Cu0.15 metallic glasses is studied using atomic-scale computer simulations. The atomic interactions are described using realistic many-body potentials within the effective medium theory, and are compared with similar...... simulations using a Lennard-Jones description of the material. The metallic glasses are deformed both in simple shear and in a simulated nanoindentation experiment. Plastic shear localizes into shear bands with a width of approximately 5 nm in CuZr and 8 nm in MgCu. In simple shear, the shear band formation...

  14. The origin of multiple superconducting gaps in MgB2.

    Science.gov (United States)

    Souma, S; Machida, Y; Sato, T; Takahashi, T; Matsui, H; Wang, S-C; Ding, H; Kaminski, A; Campuzano, J C; Sasaki, S; Kadowaki, K

    2003-05-01

    Magnesium diboride, MgB2, has the highest transition temperature (T(c) = 39 K) of the known metallic superconductors. Whether the anomalously high T(c) can be described within the conventional BCS (Bardeen-Cooper-Schrieffer) framework has been debated. The key to understanding superconductivity lies with the 'superconducting energy gap' associated with the formation of the superconducting pairs. Recently, the existence of two kinds of superconducting gaps in MgB2 has been suggested by several experiments; this is in contrast to both conventional and high-T(c) superconductors. A clear demonstration of two gaps has not yet been made because the previous experiments lacked the ability to resolve the momentum of the superconducting electrons. Here we report direct experimental evidence for the two-band superconductivity in MgB2, by separately observing the superconducting gaps of the sigma and pi bands (as well as a surface band). The gaps have distinctly different sizes, which unambiguously establishes MgB2 as a two-gap superconductor.

  15. Investigation of lauric acid dopant as a novel carbon source in MgB 2 wire

    Science.gov (United States)

    Lee, C. M.; Lee, S. M.; Park, G. C.; Joo, J.; Lim, J. H.; Kang, W. N.; Yi, J. H.; Jun, B.-H.; Kim, C.-J.

    2010-11-01

    We fabricated lauric acid (LA) doped MgB2 wires and investigated the effects of the LA doping. For the fabrication of the LA-doped MgB2 wires, B powder was mixed with LA at 0-5 wt.% of the total amount of MgB2 using an organic solvent, dried, and then the LA-treated B and Mg powders were mixed stoichiometrically. The powder mixture was loaded into an Fe tube and the assemblage was drawn and sintered at 900 °C for 3 h under an argon atmosphere. We observed that the LA doping induced the substitution of C for the B sites in MgB2 and that the actual content of C increased monotonically with increasing LA doping level. The LA-doped MgB2 wires exhibited a lower critical temperature (Tc), but better critical current density (Jc) behavior in a high magnetic field: the 5 wt.% LA-doped sample had a Jc value of 5.32 × 103 A/cm2, which was 2.17 times higher than that of the pristine sample (2.45 × 103 A/cm2) at 5 K and 6 T, suggesting that LA is an effective C dopant in MgB2 for enhancing the high-field Jc performance.

  16. Damage accumulation in MgO irradiated with MeV Au ions at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Bachiller-Perea, Diana, E-mail: dianabachillerperea@gmail.com [Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Univ. Paris-Sud, CNRS-IN2P3, Université Paris-Saclay, 91405, Orsay Cedex (France); Centro de Micro-Análisis de Materiales, Universidad Autónoma de Madrid, C/Faraday 3, 28049, Madrid (Spain); Dpto. de Física Aplicada, Universidad Autónoma de Madrid, Ciudad Universitaria de Cantoblanco, 28049, Madrid (Spain); Debelle, Aurélien, E-mail: aurelien.debelle@u-psud.fr [Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Univ. Paris-Sud, CNRS-IN2P3, Université Paris-Saclay, 91405, Orsay Cedex (France); Thomé, Lionel [Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Univ. Paris-Sud, CNRS-IN2P3, Université Paris-Saclay, 91405, Orsay Cedex (France); Behar, Moni [Instituto de Física, Universidade Federal do Rio Grande do Sul, C.P. 15051, 91501-970, Porto Alegre, RS (Brazil)

    2016-09-15

    The damage accumulation process in MgO single crystals under medium-energy heavy ion irradiation (1.2 MeV Au) at fluences up to 4 × 10{sup 14} cm{sup −2} has been studied at three different temperatures: 573, 773, and 1073 K. Disorder depth profiles have been determined through the use of the Rutherford backscattering spectrometry in channeling configuration (RBS/C). The analysis of the RBS/C data reveals two steps in the MgO damage process, irrespective of the temperature. However, we find that for increasing irradiation temperature, the damage level decreases and the fluence at which the second step takes place increases. A shift of the damage peak at increasing fluence is observed for the three temperatures, although the position of the peak depends on the temperature. These results can be explained by an enhanced defect mobility which facilitates defect migration and may favor defect annealing. X-ray diffraction reciprocal space maps confirm the results obtained with the RBS/C technique. - Highlights: • High-temperature MeV-ion irradiated MgO exhibits a two-step damage process. • The occurrence of the second step is delayed with increasing temperature. • The damage level decreases with increasing temperature. • A shift of the damage peak is observed with increasing fluence. • A high defect mobility at high temperatures in MgO is clearly evidenced.

  17. Height formation of bright points observed by IRIS in Mg II line wings during flux emergence

    Science.gov (United States)

    Grubecka, M.; Schmieder, B.; Berlicki, A.; Heinzel, P.; Dalmasse, K.; Mein, P.

    2016-09-01

    Context. A flux emergence in the active region AR 111850 was observed on September 24, 2013 with the Interface Region Imaging Spectrograph (IRIS). Many bright points are associated with the new emerging flux and show enhancement brightening in the UV spectra. Aims: The aim of this work is to compute the altitude formation of the compact bright points (CBs) observed in Mg II lines in the context of searching Ellerman bombs (EBs). Methods: IRIS provided two large dense rasters of spectra in Mg II h and k lines, Mg II triplet, C II and Si IV lines covering all the active region and slit jaws in the two bandpasses (1400 Å and 2796 Å) starting at 11:44 UT and 15:39 UT, and lasting 20 min each. Synthetic profiles of Mg II and Hα lines are computed with non-local thermodynamic equlibrium (NLTE) radiative transfer treatment in 1D solar atmosphere model including a hotspot region defined by three parameters: temperature, altitude, and width. Results: Within the two IRIS rasters, 74 CBs are detected in the far wings of the Mg II lines (at +/-1 Å and 3.5 Å). Around 10% of CBs have a signature in Si IV and CII. NLTE models with a hotspot located in the low atmosphere were found to fit a sample of Mg II profiles in CBs. The Hα profiles computed with these Mg II CB models are consistent with typical EB profiles observed from ground based telescopes e.g. THEMIS. A 2D NLTE modelling of fibrils (canopy) demonstrates that the Mg II line centres can be significantly affected but not the peaks and the wings of Mg II lines. Conclusions: We conclude that the bright points observed in Mg II lines can be formed in an extended domain of altitudes in the photosphere and/or the chromosphere (400 to 750 km). Our results are consistent with the theory of heating by Joule dissipation in the atmosphere produced by magnetic field reconnection during flux emergence.

  18. 一种新型的Cu-P-Ag-In-Sb钎料的研究%Investigation of new Cu-P-Ag-In-Sb filler alloy

    Institute of Scientific and Technical Information of China (English)

    王晓蓉; 余丁坤; 贺艳明; 黄世盛; 陈融; 刘美玲; 杨胜凡

    2013-01-01

    A certain mass content of Ag,In and Sb were added into Cu-P filler alloy to decrease its melting temperature and brittleness. The effect of added constituents on the melting temperature,wettability,mechanical properties and brazing properties of filler alloy were analyzed by optical microscopy, scanning electron microscopy and differential scanning calorimetry. The results indicated that the added constituents are u-niformly dispersed in the filler alloy. Compared with the traditional Cu-P filler,the melting temperature of the new Cu-P-Ag-In-Sb filler alloy is 697 ~ 711 ℃. The wettability area of the Cu-P-Ag-In-Sb filler alloy is larger than that of Cu-P filler alloy at the same experimentation temperature. The tensile tests indicated that the tensile strength of the new filler alloy can research 718. 1 MPa. In addition,the new filler alloy is used to join copper and brass,and a compact bonding is obtained at the substrates/filler alloy interface. All kinds of phases are uniformly dispersed in the brazing seam,and no defects are detected. At last,the new Cu-P-Ag-In-Sb filler alloy satisfies the requirement.%为了降低Cu-P钎料的熔化温度和改善其脆性,该研究在Cu-P钎料内复合一定质量分数的Ag,In和Sb,利用金相显微镜、扫描电镜、差热分析仪等研究了添加组元对钎料显微组织、熔化温度、铺展性、力学性能和钎焊性能的影响.结果表明,各添加组元在钎料内分布均匀,实现了预期的目标;添加3种组元后钎料的熔化温度为697 ~711℃,与传统的Cu-P钎料相比已大为降低;相同的钎焊温度下,添加Ag,In和Sb的Cu-P钎料的铺展面积明显大于Cu-P钎料;拉伸试验表明,五元系钎料的抗拉强度达到了718.1 MPa.此外,采用该钎料钎焊黄铜与紫铜得到的接头内母材/钎料界面处形成了致密的连接,无缺陷存在;钎缝组织内各相分布均匀,无气孔夹渣存在,满足使用要求.

  19. Ab initio investigation of collective charge excitations in MgB2.

    Science.gov (United States)

    Ku, Wei; Pickett, W E; Scalettar, R T; Eguiluz, A G

    2002-02-01

    A sharp collective charge excitation is predicted in MgB2 at approximately 2.5 eV for q perpendicular to the boron layers, based on an all-electron analysis of the dynamical density response within time-dependent density functional theory. This novel excitation, consisting of coherent charge fluctuation between Mg and B sheets, induces an abrupt plasma edge in the experimentally observable reflectivity. The existence of this mode reflects the unique electronic structure of MgB2 that is also responsible for strong electron-phonon coupling. By contrast, the acoustic plasmon, recently suggested to explain the high T(c), is not realized when realistic transition strengths are incorporated.

  20. Definitive experimental evidence for two-band superconductivity in MgB2.

    Science.gov (United States)

    Tsuda, S; Yokoya, T; Takano, Y; Kito, H; Matsushita, A; Yin, F; Itoh, J; Harima, H; Shin, S

    2003-09-19

    The superconducting-gap of MgB2 has been studied by high-resolution angle-resolved photoemission spectroscopy. The results show that superconducting gaps with values of 5.5 and 2.2 meV open on the sigma band and the pi band, respectively, but both the gaps close at the bulk transition temperature, providing a definitive experimental evidence for the two-band superconductivity with strong interband pairing interaction in MgB2. The experiments validate the role of k-dependent electron-phonon coupling as the origin of multiple-gap superconductivity as well as the high transition temperature of MgB2.

  1. Kohn anomaly in MgB2 by inelastic X-ray scattering.

    Science.gov (United States)

    Baron, A Q R; Uchiyama, H; Tanaka, Y; Tsutsui, S; Ishikawa, D; Lee, S; Heid, R; Bohnen, K-P; Tajima, S; Ishikawa, T

    2004-05-14

    We study phonons in MgB2 using inelastic x-ray scattering (1.6 and 6 meV resolution). We clearly observe the softening and broadening of the crucial E(2g) mode through the Kohn anomaly along GammaM, in excellent agreement with ab initio calculations. Low temperature measurements (just above and below T(c)) show negligible changes for the momentum transfers investigated and no change in the E(2g) mode at A between room temperature and 16 K. We report the presence of a longitudinal mode along GammaA near in energy to the E(2g) mode that is not predicted by theory.

  2. Magnetic nanoparticles in MgB2: Vortex pinning, pair breaking and connectivity

    Science.gov (United States)

    Babić, Emil; Novosel, Nikolina; Pajić, Damir; Galić, Stipe; Zadro, Krešo; Drobac, Đuro

    2016-02-01

    The results indicating magnetic flux pinning in MgB2 wires doped with three types of magnetic nanoparticles (MNP) are reported. The magnetic state of MNPs, both as-prepared and inside the MgB2 core, was determined with magnetization and ac susceptibility measurements. The competition between detrimental influence of doping (reduced connectivity, pair breaking) and enhanced flux pinning leads to deterioration of electromagnetic properties of doped wires at high MNP content, whereas light doping causes an enhancement of critical current density, Jc, and/or irreversibility field, Birr, for all our MNPs. For Ni and dextrin coated NiFe2O4 MNPs the enhancement of Jc was comparable to that achieved with the best nonmagnetic dopands. Detailed analysis indicates the contribution of magnetic flux pinning including the matching effects in flux pinning on MNPs.

  3. Understanding and Enhancing Hydrogen Diffusion in MgH2 and NaMgH3

    Science.gov (United States)

    Sholl, David; Hao, Shiqiang

    2009-03-01

    The transport properties of hydrogen in metal hydrides are crucial to the kinetics of H2 storage in these materials. We use first-principles calculations to identify the defects that are relevant for H transport in MgH2 and NaMgH3. In both materials, the physically relevant defects are charged and H diffusion is dominated by mobility of negatively charged interstitial H. Interestingly, the diffusion of these species occurs via concerted mechanisms with low energy barriers. To improve the charged interstitial H diffusivity, a series of transition-metal additives are screened to lower the formation energy of mobile defects. Our results provide a practical way to examine and alter H diffusion in light metal hydrides.

  4. Detwining in Mg alloy with a high density of twin boundaries.

    Science.gov (United States)

    Li, Yunping; Cui, Yujie; Bian, Huakang; Sun, Shihai; Tang, Ning; Chen, Yan; Liu, Bin; Koizumi, Yuichiro; Chiba, Akihiko

    2014-06-01

    To investigate the role of preexisting twin boundaries in magnesium alloys during the deformation process, a large number of {10-12} tensile twins were introduced by a radial compression at room temperature before hot compressive tests with both low and high strain rates. Unlike the stable twins in Cu-based alloys with low stacking fault energies, {10-12} twins in Mg alloy are extremely unstable or easy to detwin through {10-12}-{10-12} re-twinning. As a result, non-lenticular residual twins and twin traces with misorientation of 5°-7° were present, as confirmed by electron backscatter diffraction. The extreme instability of the twins during compression indicates that both twin and detwinning require extremely low resolved shear stresses under our experimental conditions.

  5. Modification effect of lanthanum on primary phase Mg2Si in Mg-Si alloys

    Institute of Scientific and Technical Information of China (English)

    WANG Liping; GUO Erjun; MA Baoxia

    2008-01-01

    The modifying effect of La addition on primary phase Mg2Si in Mg-5Si alloys was investigated. The results showed that a proper amount of La could effectively modify the primary phase Mg2Si. Based on the present experiment, the optimal modification effect was obtained with an addition of about 0.5 wt.% La. The size of the primary phase Mg2Si was considerably reduced to 25 μm or less and the morphology was modified from a coarse dendritic shape to a polyhedral shape. However, when the addition of La increased to 0.8 wt.% or higher, the primary Mg2Si grew into a coarse dendritic morphology again. Moreover, it was found that some LaSi2 compounds were formed during solidification and the amount of the compounds appeared to increase gradually with increasing La content.

  6. The precipitation process in Mg-Ca-(Zn) alloys investigated by positron annihilation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, Yanicet [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Departamento de Fisica de Materiales, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, 28040 Madrid (Spain)], E-mail: yanicet@fis.ucm.es; Monge, Miguel Angel; Pareja, Ramiro [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain)

    2008-09-08

    Coincidence doppler broadening (CDB) spectroscopy has been applied to study the precipitation process induced by aging in Mg-1.0 wt.% Ca and Mg-1.0 wt.% Ca-1.0 wt.% Zn alloys. In addition positron lifetime experiments and microhardness measurements have been performed. A peak centered at {approx}11.5 x 10{sup -3}m{sub 0}c is found in the CDB ratio spectra of the alloys aged at 473 K. It is attributed to annihilations with the core electrons of Ca. The results indicate the formation of a particle dispersion that hardens the alloys. This dispersion is correlated with the appearance of the peak attributed to Ca atoms. Zn atoms in the Mg matrix inhibit the formation of quenched-in vacancies bound to Ca atoms in the aged ternary alloy producing the dispersion refinement.

  7. The origin of phonon anharmonicity in MgB{sub 2} and related compounds

    Energy Technology Data Exchange (ETDEWEB)

    Boeri, L [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy); Bachelet, G B [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy); Cappelluti, E [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy); Pietronero, L [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy)

    2003-02-01

    The recent discovery of a superconducting transition at 39 K in MgB{sub 2} - made of alternating Mg and graphene-like B planes - has raised great interest, for both its technological and theoretical implications. It was clear since the very beginning that the properties of this material are related to an anomalous coupling between the charge carriers in the {sigma} bands - due to in-plane bonds between Boron atoms - and the phonon mode (E{sub 2g}) which involves in-plane vibrations of the B ions. Theoretical studies have thus been focused on the search for possible anomalies in the e-ph coupling: one of the first results was the discovery that the E{sub 2g} phonon is highly anharmonic, but the connection between anharmonicity and T{sub c} in this material is still a controversial point. We first present a detailed first-principles study of the E{sub 2g} phonon anharmonicity in MgB{sub 2} and analogous compounds which are not superconducting, AlB{sub 2} and graphite, and in a hypothetical hole-doped graphite (C{sup 2+}{sub 2}); we then introduce an analytical model which allows us to relate the onset of anharmonicity with the small Fermi energy of the carriers in {sigma} bands. Our study suggests a possible relation between anharmonicity and non-adiabaticity; non-adiabatic effects, which can lead to a sensible increase of T{sub c} with respect to values predicted by conventional theory, become in fact relevant when phonon frequencies are comparable to electronic energy scales.

  8. Subsurface Synthesis and Characterization of Ag Nanoparticles Embedded in MgO

    Energy Technology Data Exchange (ETDEWEB)

    Vilayur Ganapathy, Subramanian; Devaraj, Arun; Colby, Robert J.; Pandey, Archana; Varga, Tamas; Shutthanandan, V.; Manandhar, Sandeep; El-Khoury, Patrick Z.; Kayani, Asghar N.; Hess, Wayne P.; Thevuthasan, Suntharampillai

    2013-03-08

    Metal nanoparticles exhibit localized surface plasmon resonance (LSPR) which is very sensitive to the size and shape of the nanoparticle and the dielectric medium surrounding it. LSPR causes field enhancement near the surface of the nanoparticle making them interesting candidates for plasmonic applications. In particular, partially exposed metallic nanoparticles distributed in a dielectric matrix form hotspots which are prime locations for LSPR spectroscopy and sensing. This study involves synthesizing partially buried Ag nanoparticles in MgO and investigating the characteristics of this material system. Ag nanoparticles of different shapes and size distributions were synthesized below the surface of MgO by implanting 200 keV Ag+ ions followed by annealing at 10000C for 10 and 30 hours. A detailed optical and structural characterization was carried out to understand the evolution of Ag nanoparticle microstructure and size distribution inside the MgO matrix. Micro x-ray diffraction (MicroXRD) was employed to investigate the structural properties and estimate the crystallite size. The nanoparticles evolved from a spherical to faceted morphology with annealing time, assuming an octahedral shape truncated at the (001) planes as seen from aberration corrected transmission electron microscopy (TEM) images. The nanoparticles embedded in MgO were shown to be pure metallic Ag using atom probe tomography (APT). The nanoparticles were partially exposed to the surface employing plasma etch techniques to remove the overlaying MgO. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to study the surface morphology and obtain a height distribution for the partially exposed nanoparticles.

  9. Superconducting Properties and Microstructure in MgB2 Bulks, Wires and Tapes

    Institute of Scientific and Technical Information of China (English)

    冯勇; 阎果; 赵勇; 吴晓京; 周廉; 张平祥

    2003-01-01

    We prepared a series of MgB2 bulk samples under different temperatures, holding time and increasing rates in temperature by the solid state reaction. The thermodynamic behavior and phase formation in the Mg-B system were studied by using DTA,XRD and SEM. The results indicate that the formation of the MgB2 phase is very fast and the high increasing rate in temperature is necessary to obtain high quality MgB2. In addition, the effects of the Zr-doping in Mg1-xZrxB2 bulk samples fabricated by the solid state reaction at ambient pressure on phase compositions, microstructure and flux pinning behavior were investigated by using XRD, SQUID magnetometer, SEM and TEM. Critical current density Jc can be significantly enhanced by the Zr-doping and the best data are achieved in Mg0.9Zr0.1B2. For this sample, Jc values are remarkably improved to 1.83×106 A/cm2 in self-field and 5.51×105 A/cm2 in 1 T at 20 K. Also, high quality MgB2/Ta/Cu wires and tapes with and without Ti-doping, MgB2/Fe wires and 18 filament MgB2/NbZr/Cu tapes were fabricated by the powder-in-tube (PIT) method at ambient pressure. The phase compositions, microstructure features and flux pinning properties were studied. The results suggest that Fe is thebest metal for these sheaths. MgB2/Fe wires exhibit very high Jc at high temperatures and high fields. Jc values reach as high as 1.43×105 A/cm2 (4.2 K, 4 T) and 3.72×104 A/cm2 (15 K, 4 T).

  10. Experimental determination of the Rashba coefficient in InSb/InAlSb quantum wells at zero magnetic field and elevated temperatures.

    Science.gov (United States)

    Leontiadou, M A; Litvinenko, K L; Gilbertson, A M; Pidgeon, C R; Branford, W R; Cohen, L F; Fearn, M; Ashley, T; Emeny, M T; Murdin, B N; Clowes, S K

    2011-01-26

    We report the optical measurement of the spin dynamics at elevated temperatures and in zero magnetic field for two types of degenerately doped n-InSb quantum wells (QWs), one asymmetric (sample A) and one symmetric (sample B) with regards to the electrostatic potential across the QW. Making use of three directly determined experimental parameters: the spin lifetime, τ(s), the sheet carrier concentration, n, and the electron mobility, μ, we directly extract the zero-field spin splitting. For the asymmetric sample where the Rashba interaction is the dominant source of spin splitting, we deduce a room temperature Rashba parameter of α = 0.09 ± 0.1 eV Å which is in good agreement with calculations and we estimate the Rashba coefficient α(0) (a figure of merit for the ease with which electron spins can be modulated via an electric field). We review the merits/limitations of this approach and the implications of our findings for spintronic devices.

  11. Experimental determination of the Rashba coefficient in InSb/InAlSb quantum wells at zero magnetic field and elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Leontiadou, M A; Litvinenko, K L; Murdin, B N; Clowes, S K [Advanced Technology Institute, University of Surrey, Guildford GU2 7XH (United Kingdom); Gilbertson, A M; Branford, W R; Cohen, L F [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); Pidgeon, C R [Department of Physics, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Fearn, M; Ashley, T; Emeny, M T, E-mail: s.clowes@surrey.ac.uk [QinetiQ Ltd, St Andrews Road, Malvern WR14 3PS (United Kingdom)

    2011-01-26

    We report the optical measurement of the spin dynamics at elevated temperatures and in zero magnetic field for two types of degenerately doped n-InSb quantum wells (QWs), one asymmetric (sample A) and one symmetric (sample B) with regards to the electrostatic potential across the QW. Making use of three directly determined experimental parameters: the spin lifetime, {tau}{sub s}, the sheet carrier concentration, n, and the electron mobility, {mu}, we directly extract the zero-field spin splitting. For the asymmetric sample where the Rashba interaction is the dominant source of spin splitting, we deduce a room temperature Rashba parameter of {alpha} = 0.09 {+-} 0.1 eV A which is in good agreement with calculations and we estimate the Rashba coefficient {alpha}{sub 0} (a figure of merit for the ease with which electron spins can be modulated via an electric field). We review the merits/limitations of this approach and the implications of our findings for spintronic devices.

  12. Enhanced emission from mid-infrared AlInSb light-emitting diodes with p-type contact grid geometry

    Energy Technology Data Exchange (ETDEWEB)

    Meriggi, Laura, E-mail: l.meriggi.1@research.gla.ac.uk; Ding, Ying; Thayne, Iain G.; Sorel, Marc [Electronic and Nanoscale Engineering, School of Engineering, University of Glasgow, Glasgow G12 8LT (United Kingdom); Steer, Matthew J. [Electronic and Nanoscale Engineering, School of Engineering, University of Glasgow, Glasgow G12 8LT (United Kingdom); Quantum Device Solutions, The West of Scotland Science Park, Block 7 Kelvin Campus, Glasgow G20 0TH (United Kingdom); MacGregor, Calum [Quantum Device Solutions, The West of Scotland Science Park, Block 7 Kelvin Campus, Glasgow G20 0TH (United Kingdom); Ironside, Charles N. [Department of Imaging and Applied Physics, Curtin University, Perth, Western Australia 6845 (Australia)

    2015-02-14

    We report on the impact of lateral current spreading on light emission from aluminium indium antimonide (AlInSb) mid-infrared p-i-n light-emitting diodes (LEDs) grown by molecular beam epitaxy on a GaAs substrate. Due to the high effective mass of holes in Al{sub x}In{sub 1−x}Sb, the resistivity of p-type material determines the 3-D distribution of current flow in the devices. This work shows that maximum light emission, as measured by electroluminescence, and 3-times wall-plug efficiency improvement were obtained at room temperature from devices with a p-type contact grid geometry with a spacing of twice the current spreading length in the p-type material, which was measured by spatially resolved photocurrent. The LED with the optimal contact geometry exhibits improved performance at high injection current levels thanks to the more uniform carrier distribution across the device area.

  13. Metal-like heat conduction in laser-excited InSb probed by picosecond time-resolved x-ray diffraction

    Science.gov (United States)

    Sondhauss, P.; Synnergren, O.; Hansen, T. N.; Canton, S. E.; Enquist, H.; Srivastava, A.; Larsson, J.

    2008-09-01

    A semiconductor (InSb) showed transient metal-like heat conduction after excitation of a dense electron-hole plasma via short and intense light pulses. A related ultrafast strain relaxation was detected using picosecond time-resolved x-ray diffraction. The deduced heat conduction was, by a factor of 30, larger than the lattice contribution. The anomalously high heat conduction can be explained once the contribution from the degenerate photocarrier plasma is taken into account. The magnitude of the effect could provide the means for guiding heat in semiconductor nanostructures. In the course of this work, a quantitative model for the carrier dynamics in laser-irradiated semiconductors has been developed, which does not rely on any adjustable parameters or ad hoc assumptions. The model includes various light absorption processes (interband, free carrier, two photon, and dynamical Burstein-Moss shifts), ambipolar diffusion, energy transport (heat and chemical potential), electrothermal effects, Auger recombination, collisional excitation, and scattering (elastic and inelastic). The model accounts for arbitrary degrees of degeneracy.

  14. From E2g to other modes: effects of pressure on electron-phonon interaction in MgB2.

    Science.gov (United States)

    Singh, Prabhakar P

    2006-12-15

    We study the effects of pressure on the electron-phonon interaction in MgB2 using density-functional-based methods. Our results show that the superconductivity in MgB2 vanishes by 100 GPa, and then reappears at higher pressures. In particular, we find a superconducting transition temperature Tc approximately 2 K for mu*=0.1 at a pressure of 137 GPa.

  15. Silicon diffusion in MgSiO3 perovskite under lower mantle conditions

    Science.gov (United States)

    Xu, J.; Yamazaki, D.; Katsura, T.; Wu, X.; Remmert, P.; Yurimoto, H.; Chakraborty, S.

    2010-12-01

    Diffusion creep may dominate in most of the lower mantle. In most silicates, silicon is the slowest diffusing species and is likely to control the viscosity in the diffusion creep regime. Therefore, the rheological properties of a silicate mineral can be estimated from the Si self-diffusion coefficient. In the Earth’s lower mantle, magnesium silicate perovskite is the dominant material and it may exceed 85% of the volume. Therefore, measurement of Si diffusion coefficient is important to understand the dynamics of the lower mantle. Yamazaki et al. (2000) and Dobson et al. (2008) investigated Si diffusivity in MgSiO3 perovskite using polycrystalline samples. In this study, single crystals were used to measure Si self-diffusion coefficients in MgSiO3 perovskite under lower mantle conditions. Perovskite single crystals were synthesized at 25 GPa and 1500 degrees C using the temperature gradient method and a Kawai-type multi-anvil high-pressure apparatus. Crystals were orientated using a precession X-ray camera and polished by diamond paste. Then a layer (about 300 nm) of 29Si enriched MgSiO3 was deposited by pulsed laser depostion (PLD) on the polished surface. On this, a protective coating of 29Si enriched SiO2 (about 100 nm) was deposited. These coated crystals were annealed at a pressure of 25 GPa and at temperatures between 1400 and 1700 degrees C. Diffusion profiles were obtained by secondary ion mass spectrometry (SIMS) and fitted using a numerical method to retrieve diffusion coefficients from the profiles. The diffusion coefficients we obtain are very similar to the previous results, although our data scatter less. Preliminary results also suggest that the activation energy of diffusion is lower compared to the results from previous work. There is no siginificant difference between Si diffusion rates measured in single crystals vs. those measured in perovskite polycrystals. These rates are faster than the diffusion rates of Mg in the same material. The

  16. Modeling defects and plasticity in MgSiO3 post-perovskite

    Science.gov (United States)

    Goryaeva, A.; Cordier, P.; Carrez, P.

    2015-12-01

    Alexandra M. Goryaeva, Philippe Carrez, Patrick Cordier UMET, Université de Lille 1, 59655 Villeneuve d'Ascq, Francealexandra.goryaeva@ed.univ-lille1.frThe discovery of the so-called "last mantle phase transition" [1] immediately became promising to shed light on the puzzling properties of the D'' layer and to provide new insights into our understanding of the dynamics of the lowermost Earth's mantle. The MgSiO3 post-perovskite (Cmcm) exhibits unusual for high-pressure phases layer-like structure which may be responsible for the observed seismic anisotropy of the D'' layer. However, information about mechanical properties, probable slip systems, dislocations and their behavior under stress are not well known still. This work represents a full atomistic study of dislocations in MgSiO3post-perovskite based on the pairwise potential previously derived by [2].Lattice friction opposed to the dislocation glide in MgSiO3 post-perovskite is shown to be highly anisotropic. Thus, remarkably low values of Peierls stress (1 GPa) are found for the glide of [100] screw dislocations in (010), while glide in (001) requires almost 18 times larger stress values. In general, (010) plane is characterized by the lowest lattice friction. Mobility of edge dislocations is found to be much higher than that of screw dislocations, and the latter will control plastic behavior of MgSiO3 post-perovskite. Comparison of our results with previous study of MgSiO3 perovskite (bridgmanite) [3], based on similar simulation approach, clearly shows that monotonous increase in Peierls stress of bridgmanite will be followed by a dramatic drop after the phase transition to the post-perovskite phase, which consequently suggests the D'' located at the CMB to be weaker than the overlying mantle.References [1] Murakami M. et al.,Science (2004), 304, 855-858.[2] Oganov A. et al.,Phys. Earth Planet. Int. (2000), 122, 277-288.[3] Hirel et al., Acta Mater (2014 ), 79, 117-125.

  17. Identifying alternative hyper-splicing signatures in MG-thymoma by exon arrays.

    Directory of Open Access Journals (Sweden)

    Lilach Soreq

    Full Text Available BACKGROUND: The vast majority of human genes (>70% are alternatively spliced. Although alternative pre-mRNA processing is modified in multiple tumors, alternative hyper-splicing signatures specific to particular tumor types are still lacking. Here, we report the use of Affymetrix Human Exon Arrays to spot hyper-splicing events characteristic of myasthenia gravis (MG-thymoma, thymic tumors which develop in patients with MG and discriminate them from colon cancer changes. METHODOLOGY/PRINCIPAL FINDINGS: We combined GO term to parent threshold-based and threshold-independent ad-hoc functional statistics with in-depth analysis of key modified transcripts to highlight various exon-specific changes. These denote alternative splicing in MG-thymoma tumors compared to healthy human thymus and to in-house and Affymetrix datasets from colon cancer and healthy tissues. By using both global and specific, term-to-parent Gene Ontology (GO statistical comparisons, our functional integrative ad-hoc method allowed the detection of disease-relevant splicing events. CONCLUSIONS/SIGNIFICANCE: Hyper-spliced transcripts spanned several categories, including the tumorogenic ERBB4 tyrosine kinase receptor and the connective tissue growth factor CTGF, as well as the immune function-related histocompatibility gene HLA-DRB1 and interleukin (IL19, two muscle-specific collagens and one myosin heavy chain gene; intriguingly, a putative new exon was discovered in the MG-involved acetylcholinesterase ACHE gene. Corresponding changes in spliceosome composition were indicated by co-decreases in the splicing factors ASF/SF(2 and SC35. Parallel tumor-associated changes occurred in colon cancer as well, but the majority of the apparent hyper-splicing events were particular to MG-thymoma and could be validated by Fluorescent In-Situ Hybridization (FISH, Reverse Transcription-Polymerase Chain Reaction (RT-PCR and mass spectrometry (MS followed by peptide sequencing. Our findings

  18. Effect of Mg-Nb oxides addition on hydrogen sorption in MgH{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, M.W.; Castellero, A. [Dipartimento di Chimica IFM, NIS Centre of Excellence, Universita di Torino, Via Pietro Giuria 9, 10125 Torino (Italy); Enzo, S. [Dipartimento di Chimica, Universita di Sassari, 07100 Sassari (Italy); Livraghi, S.; Giamello, E. [Dipartimento di Chimica IFM, NIS Centre of Excellence, Universita di Torino, Via Pietro Giuria 9, 10125 Torino (Italy); Baricco, M., E-mail: marcello.baricco@unito.it [Dipartimento di Chimica IFM, NIS Centre of Excellence, Universita di Torino, Via Pietro Giuria 9, 10125 Torino (Italy)

    2011-06-15

    Highlights: > H{sub 2} sorption reactions in MgH{sub 2} with 1 mol% MgNb{sub 2}O{sub 6}, Mg{sub 4}Nb{sub 2}O{sub 9} and Mg{sub 3}Nb{sub 6}O{sub 11} have been investigated. > Ball-milled samples showed the presence of a mixture of {beta} and {gamma} allotropes of MgH{sub 2}. > The presence of Mg-Nb oxides significantly accelerates the hydrogen absorption and desorption processes. > Experimental results are discussed on the basis of thermodynamic and kinetic arguments. - Abstract: H{sub 2} absorption and desorption reactions in MgH{sub 2} promoted by ball-milling with 1 mol% MgNb{sub 2}O{sub 6}, Mg{sub 4}Nb{sub 2}O{sub 9} and Mg{sub 3}Nb{sub 6}O{sub 11} have been investigated. MgH{sub 2} was milled with the bare oxides for 12 h under a high purity Ar atmosphere. Absorption and desorption reactions in the ball-milled samples were studied by in situ X-ray diffraction (XRD) in isothermal conditions with Anton Paar XRK 900 reaction chamber. XRD patterns for absorption were recorded at 573 K under hydrogen pressure of 0.9 MPa and for desorption at 623 K in vacuum. Experimental data were analysed according to the Rietveld method. Ball-milled samples showed the presence of a mixture of {beta} and {gamma} allotropes of MgH{sub 2}, with significantly broadened diffraction peaks due to reduced crystallite size and strain, together with bare additives. The presence of Mg-Nb oxides significantly accelerates the hydrogen absorption and desorption processes. The amount of hydrogen absorbed in the presence of Mg-Nb-O phases is lower than the maximum stoichiometric capacity, because of the presence of a non-reactive MgO layer on the surface of the powders or at the grain boundaries. Experimental results are discussed on the basis of thermodynamic and kinetic arguments.

  19. Influence of nanocrystalline boron precursor powder on superconductivity in MgB2 bulk.

    Science.gov (United States)

    Zhang, Yun; Lu, Cheng; Zhou, Sihai; Joo, Jinho

    2009-12-01

    In this report, high-purity nanocrystalline boron powders processed by ball-milling were used as the precursor powders to fabricate MgB2 superconductor. The transport properties and the critical current density in the samples made from ball-milled boron powders and as-supplied boron powders were investigated. It was found that the ball-milled boron powders led to a significant enhancement of the critical current density in MgB2 sintered at 650 degrees C. The reason can be attributed to the small MgB2 grain size caused by the ball-milled boron precursor powders. The resistivity of the samples made from the ball-milled boron powder was lower than that of the sample from as-supplied boron powder. As the sintering temperature increased, both resistivity and upper critical field decreased in the samples using the ball-milled boron powders as a precursor. Poor connectivity and large strain are responsible for the high resistivity.

  20. Damage accumulation in MgO irradiated with MeV Au ions at elevated temperatures

    Science.gov (United States)

    Bachiller-Perea, Diana; Debelle, Aurélien; Thomé, Lionel; Behar, Moni

    2016-09-01

    The damage accumulation process in MgO single crystals under medium-energy heavy ion irradiation (1.2 MeV Au) at fluences up to 4 × 1014 cm-2 has been studied at three different temperatures: 573, 773, and 1073 K. Disorder depth profiles have been determined through the use of the Rutherford backscattering spectrometry in channeling configuration (RBS/C). The analysis of the RBS/C data reveals two steps in the MgO damage process, irrespective of the temperature. However, we find that for increasing irradiation temperature, the damage level decreases and the fluence at which the second step takes place increases. A shift of the damage peak at increasing fluence is observed for the three temperatures, although the position of the peak depends on the temperature. These results can be explained by an enhanced defect mobility which facilitates defect migration and may favor defect annealing. X-ray diffraction reciprocal space maps confirm the results obtained with the RBS/C technique.

  1. Stable icosahedral phase in Mg44Zn44Gd12 alloy

    Institute of Scientific and Technical Information of China (English)

    WANG Xudong; DU Wenbo; WANG Zhaohui; LIU Ke; LI Shubo

    2012-01-01

    The microstructure of the as-cast Mg44Zn44Gd12 alloy was investigated by using X-ray diffraction (XRD),differentical scanning (DSC),scanning electron microscopy (SEM) and a detailed transmission electron microscope.The XRD,DSC and SEM results indicated that the as-cast Mg44Zn44Gd12 alloy were mainly composed of three types of phases:the primary solidification phase,the dendritic phase and the eutectic phase.The primary solidification phase had an icosahedral structure.The dendritic phase was the W-phase,and cutectic structure phase was the Mg7Zn3 phase.Microstructures of icosahedral phase (I-phase),W-phase and Mg7Zn3 phase in MguZn44Gd12 alloy were investigated.The results indicated that the I-phase in Mg44Zn44Gd12 alloy was a face-centered icosahedral quasicrystal with stoichiometric composition of Mg42Zn50Gd8 which had an excellent thermal stability up to 420℃.The solid solution of the Gd gradually decreased during solidification,which played an important role in activating the formation of Mg7Zn3 phase and W-phase from icosahedral phases.

  2. Hole transport and photoluminescence in Mg-doped InN

    Energy Technology Data Exchange (ETDEWEB)

    Miller, N.; Ager III, J. W.; Smith III, H. M.; Mayer, M. A.; Yu, K. M.; Haller, E. E.; Walukiewicz, W.; Schaff, W. J.; Gallinat, C.; Koblmuller, G.; Speck, J. S.

    2010-03-24

    Hole conductivity and photoluminescence were studied in Mg-doped InN films grown by molecular beam epitaxy. Because surface electron accumulation interferes with carrier type determination by electrical measurements, the nature of the majority carriers in the bulk of the films was determined using thermopower measurements. Mg concentrations in a"window" from ca. 3 x 1017 to 1 x 1019 cm-3 produce hole-conducting, p-type films as evidenced by a positive Seebeck coecient. This conclusion is supported by electrolyte-based capacitance voltage measurements and by changes in the overall mobility observed by Hall effect, both of which are consistent with a change from surface accumulation on an n-type film to surface inversion on a p-type film. The observed Seebeck coefficients are understood in terms of a parallel conduction model with contributions from surface and bulk regions. In partially compensated films with Mg concentrations below the window region, two peaks are observed in photoluminescence at 672 meV and at 603 meV. They are attributed to band-to-band and band-to-acceptor transitions, respectively, and an acceptor binding energy of ~;;70 meV is deduced. In hole-conducting films with Mg concentrations in the window region, no photoluminescence is observed; this is attributed to electron trapping by deep states which are empty for Fermi levels close to the valence band edge.

  3. Gadolinium solubility and precipitate identification in Mg-Gd binary alloy

    Institute of Scientific and Technical Information of China (English)

    PENG Qiuming; MA Ning; LI Hui

    2012-01-01

    Gadolinium (Gd) solubility in magnesium (Mg) matrix and precipitate composition in Mg-Gd binary alloys were investigated.The alloys containing different Gd contents (10 wt.%-35 wt.%) were employed to identify Gd solubility after annealing at different temperatures.It was confirmed that the maximum Gd solubility was 22.8 wt.% at 550 ℃ based on the regression analysis method.Mg5+xGd (0<x<2) and Mg3Gd precipitates coexisted in all investigated alloys owing to the strong component segregation during solidification.The fiaction of Mg5+xGd (0<x<2) was decreased with the increment of annealing temperature and time.In contrast,Mg3Gd precipitate could not be eliminated even when being annealed at 550 ℃.This thermal stable precipitate played a significant role in mechanical properties.Therefore,it is very necessary to consider the effect of Mg3Gd precipitate on properties of Mg-Gd based alloys in future.

  4. XMCD study of CoPt nanoparticles embedded in MgO and amorphous carbon matrices

    Energy Technology Data Exchange (ETDEWEB)

    Tournus, F. [Universite de Lyon, F-69000, France and Univ. Lyon 1, Laboratoire PMCN, CNRS, UMR 5586, F69622 Villeurbanne Cedex (France)], E-mail: ftournus@lpmcn.univ-lyon1.fr; Blanc, N.; Tamion, A. [Universite de Lyon, F-69000, France and Univ. Lyon 1, Laboratoire PMCN, CNRS, UMR 5586, F69622 Villeurbanne Cedex (France); Ohresser, P. [Synchrotron SOLEIL, BP 48, 91192 Gif sur Yvette (France); Perez, A.; Dupuis, V. [Universite de Lyon, F-69000, France and Univ. Lyon 1, Laboratoire PMCN, CNRS, UMR 5586, F69622 Villeurbanne Cedex (France)

    2008-11-15

    We report the synthesis and characterization of CoPt nanoparticles, using X-ray magnetic circular dichroism (XMCD) at the Co L{sub 2,3} edges. Clusters are produced in ultra-high vacuum conditions, following a physical route, and embedded in non-metallic matrices: MgO and amorphous carbon (a-C). In MgO, Co atoms are partially oxidized, which goes with a {mu}{sub L}/{mu}{sub S} enhancement. On the contrary, a-C appears as a very suitable matrix. In particular, annealing of CoPt cluster embedded in a-C is able to promote L 1{sub 0} chemical order, without alteration of the sample. This transformation, which has been directly evidenced by transmission electron microscopy observations, is accompanied by a striking augmentation of {mu}{sub S}, {mu}{sub L} and the {mu}{sub L}/{mu}{sub S} ratio of Co. The presence of Pt leads to an enhanced Co magnetic moment, as compared to Co bulk, even for the chemically disordered alloy. Moreover, the high value of 1.91{mu}{sub B}/at. measured for {mu}{sub S} is unusual for Co and must be a signature of chemical order in CoPt alloy nanoparticles.

  5. Surface layers on a borosilicate nuclear waste glass corroded in MgCl 2 solution

    Science.gov (United States)

    Abdelouas, Abdesselam; Crovisier, Jean-Louis; Lutze, Werner; Grambow, Bernd; Dran, Jean-Claude; Müller, Regina

    1997-01-01

    Surface layers on the French borosilicate nuclear waste glass, R7T7, corroded in MgCl 2 solution were studied to determine the composition, structure and stability of crystalline phases. The characteristics of the phases constituting the surface layer varied with the parameter {S}/{V} × t , the glass surface area ( S) to solution volume ( V) ratio, times time ( t). At low {S}/{V} × t values (intermediate {S}/{V} × t value (2800 d/m; 5.5 y) the surface layer contained hydrotalcite-, chlorite- and saponite-type phases. At the highest {S}/{V} × t value (10 7 d/m; 463 d) the major phases were saponite, powellite, barite and cerianite solid solutions. About 95% of the uranium and > 98% of the neodymium released from the glass were precipitated in the surface layer. In the 463 day experiment, 86% of the neodymium in the surface layer was in solid solution with powellite, the rest with saponite. Uranium was contained exclusively in saponite. High {S}/{V} ratios, typical of disposal conditions for vitrified high-level radioactive waste, favor retention of actinides in fairly insoluble corrosion products. Observation of similar corrosion products on natural glasses as on nuclear waste glasses lend support to the hypothesis that the host phases for actinides observed in the laboratory are stable over geological periods of time.

  6. Capturing the H 2 –Metal Interaction in Mg-MOF-74 Using Classical Polarization

    KAUST Repository

    Pham, Tony

    2014-10-02

    © 2014 American Chemical Society. Grand canonical Monte Carlo (GCMC) simulations of H2 sorption were performed in Mg-MOF-74, a metal-organic framework (MOF) that displays very high H2 sorption affinity. Experimental H2 sorption isotherms and isosteric heats of adsorption (Qst) values were reproduced using a general purpose materials sorption potential that includes many-body polarization interactions. In contrast, using two models that include only charge-quadrupole interactions failed to reproduce such experimental measurements even though they are the type normally employed in such classical force field calculations. Utilizing the present explicit polarizable model in GCMC simulation resulted in a Mg2+-H2 distance of 2.60 Å, which is close to a previously reported value that was obtained using electronic structure methods and comparable to similar experimental measurements. The induced dipole distribution obtained from simulation assisted in the characterization of two previously identified sorption sites in the MOF: the Mg2+ ions and the oxido group of the linkers. The calculated two-dimensional quantum rotational levels for a H2 molecule sorbed onto the Mg2+ ion were in good agreement with experimental inelastic neutron scattering (INS) data. Although the H2-metal interaction in MOFs may be thought of as a quantum mechanical effect, this study demonstrates how the interaction between the sorbate molecules and the open-metal sites in a particular highly sorbing MOF can be captured using classical simulation techniques that involve a polarizable potential.

  7. Origin of interfacial perpendicular magnetic anisotropy in MgO/CoFe/metallic capping layer structures.

    Science.gov (United States)

    Peng, Shouzhong; Wang, Mengxing; Yang, Hongxin; Zeng, Lang; Nan, Jiang; Zhou, Jiaqi; Zhang, Youguang; Hallal, Ali; Chshiev, Mairbek; Wang, Kang L; Zhang, Qianfan; Zhao, Weisheng

    2015-12-11

    Spin-transfer-torque magnetic random access memory (STT-MRAM) attracts extensive attentions due to its non-volatility, high density and low power consumption. The core device in STT-MRAM is CoFeB/MgO-based magnetic tunnel junction (MTJ), which possesses a high tunnel magnetoresistance ratio as well as a large value of perpendicular magnetic anisotropy (PMA). It has been experimentally proven that a capping layer coating on CoFeB layer is essential to obtain a strong PMA. However, the physical mechanism of such effect remains unclear. In this paper, we investigate the origin of the PMA in MgO/CoFe/metallic capping layer structures by using a first-principles computation scheme. The trend of PMA variation with different capping materials agrees well with experimental results. We find that interfacial PMA in the three-layer structures comes from both the MgO/CoFe and CoFe/capping layer interfaces, which can be analyzed separately. Furthermore, the PMAs in the CoFe/capping layer interfaces are analyzed through resolving the magnetic anisotropy energy by layer and orbital. The variation of PMA with different capping materials is attributed to the different hybridizations of both d and p orbitals via spin-orbit coupling. This work can significantly benefit the research and development of nanoscale STT-MRAM.

  8. Origin of interfacial perpendicular magnetic anisotropy in MgO/CoFe/metallic capping layer structures

    Science.gov (United States)

    Peng, Shouzhong; Wang, Mengxing; Yang, Hongxin; Zeng, Lang; Nan, Jiang; Zhou, Jiaqi; Zhang, Youguang; Hallal, Ali; Chshiev, Mairbek; Wang, Kang L.; Zhang, Qianfan; Zhao, Weisheng

    2015-12-01

    Spin-transfer-torque magnetic random access memory (STT-MRAM) attracts extensive attentions due to its non-volatility, high density and low power consumption. The core device in STT-MRAM is CoFeB/MgO-based magnetic tunnel junction (MTJ), which possesses a high tunnel magnetoresistance ratio as well as a large value of perpendicular magnetic anisotropy (PMA). It has been experimentally proven that a capping layer coating on CoFeB layer is essential to obtain a strong PMA. However, the physical mechanism of such effect remains unclear. In this paper, we investigate the origin of the PMA in MgO/CoFe/metallic capping layer structures by using a first-principles computation scheme. The trend of PMA variation with different capping materials agrees well with experimental results. We find that interfacial PMA in the three-layer structures comes from both the MgO/CoFe and CoFe/capping layer interfaces, which can be analyzed separately. Furthermore, the PMAs in the CoFe/capping layer interfaces are analyzed through resolving the magnetic anisotropy energy by layer and orbital. The variation of PMA with different capping materials is attributed to the different hybridizations of both d and p orbitals via spin-orbit coupling. This work can significantly benefit the research and development of nanoscale STT-MRAM.

  9. Aminolevulinic Acid-Mediated Photodynamic Therapy Causes Cell Death in MG-63 Human Osteosarcoma Cells.

    Science.gov (United States)

    White, Bradley; Rossi, Vince; Baugher, Paige J

    2016-09-01

    The aim of this study was to test the efficacy of aminolevulinic acid-mediated photodynamic therapy (PDT) against the human osteosarcoma cell line MG-63. Osteosarcoma is the most common type of primary malignant bone tumor diagnosed in the United States among adolescents and children. Treatments for osteosarcoma often result in diminished limb use or amputation. Because ALA-mediated PDT exhibits dual specificity in the context of tumor killing, this therapy could represent a less invasive, but effective, treatment for this disease. To assess ALA dark toxicity in MG-63 cells, cells were incubated with varying concentrations of ALA, and cell viability was determined by crystal violet assay. Protoporphyrin IX (PpIX) accumulation was assessed subsequent to ALA incubation at various concentrations using spectrofluorometry. Cell death subsequent to ALA-PDT was determined by illuminating cells at a wavelength of 635 nm at various light intensities subsequent to ALA incubation. Cell viability was assessed using the MTT assay. ALA dark toxicity was observed only at the highest concentrations of 2, 5, and 10 mM. Maximal PpIX concentration was observed at 0.5 and 1 mM ALA, subsequent to a 24-h incubation. Maximal cell death with minimal light toxicity was observed at 0.5 and 1 mM ALA after illumination with 0.6 and 3 J/cm(2) light. Collectively, our data indicate that ALA-PDT can result in the death of MG-64 human osteosarcoma cells in vitro.

  10. Numerical investigations on the characteristics of thermomagnetic instability in MgB2 bulks

    Science.gov (United States)

    Xia, Jing; Li, Maosheng; Zhou, Youhe

    2017-07-01

    This paper presents the characteristics of thermomagnetic instability in MgB2 bulks by numerically solving the macroscopic dynamics of thermomagnetic interaction governed by the coupled magnetic and heat diffusion equations in association with a modified E-J power-law relationship. The finite element method is used to discretize the system of partial differential equations. The calculated magnetization loops with flux jumps are consistent with the experimental results for MgB2 slabs bathed in a wide range of ambient temperatures. We reveal the evolution process of the thermomagnetic instability and present the distributions of the magnetic field, temperature, and current density before and after flux jumps. A 2D axisymmetric model is used to study the thermomagnetic instability in cylindrical MgB2 bulks. It is found that the number of flux jumps monotonously reduces as the ambient temperature rises and no flux jump appears when the ambient temperature exceeds a certain value. Moreover, the flux-jump phenomenon exists in a wide range of the ramp rate of the applied external field, i.e. 10-2-102 T s-1. Furthermore, the dependences of the first flux-jump field on the ambient temperature, ramp rate, and bulk thickness are investigated. The critical bulk thicknesses for stability are obtained for different ambient temperatures and sample radii. In addition, the influence of the capability of the interfacial heat transfer on the temporal response of the bulk temperature is discussed. We also find that the prediction of thermomagnetic instability is sensitive to the employment of the flux creep exponent in the simulations.

  11. Studies on Microstructure and Thermoelectric Properties of p-Type Bi-Sb-Te Based Alloys by Gas Atomization and Hot Extrusion Processes

    Science.gov (United States)

    Park, Ki-Chan; Madavali, Babu; Kim, Eun-Bin; Koo, Kyung-Wan; Hong, Soon-Jik

    2016-10-01

    p-Type Bi2Te3 + 75% Sb2Te3 based thermoelectric materials were fabricated via gas atomization and the hot extrusion process. The gas atomized powder showed a clean surface with a spherical shape, and expanded in a wide particle size distribution (average particle size 50 μm). The phase of the fabricated extruded and R-extruded bars was identified using x-ray diffraction. The relative densities of both the extruded and R-extruded samples were measured by Archimedes principle with ˜98% relative density. The R-extruded bar exhibited finer grain microstructure than that of single extrusion process, which was attributed to a recrystallization mechanism during the fabrication. The R-extruded sample showed improved Vickers hardness compared to the extruded sample due to its fine grain microstructure. The electrical conductivity improved for the extruded sample whereas the Seebeck coefficient decreases due to its high carrier concentration. The peak power factor, ˜4.26 × 10-3 w/mK2 was obtained for the single extrusion sample, which is higher than the R-extrusion sample owing to its high electrical properties.

  12. Bi-sulphotellurides associated with Pb - Bi - (Sb ± Ag, Cu, Fe) sulphosalts: an example from the Stan Terg deposit in Kosovo

    Science.gov (United States)

    Kołodziejczyk, Joanna; Pršek, Jaroslav; Voudouris, Panagiotis Ch.; Melfos, Vasilios

    2017-08-01

    New mineralogical and mineral-chemical data from the Stan Terg deposit, Kosovo, revealed the presence of abundant Bi-sulphotellurides associated with Bi- and Sb-sulphosalts and galena in pyrite-pyrrhotite-rich skarn-free ore bodies (ores without skarn minerals). The Bi-bearing association comprises Bi-sulphotellurides (joséite-A, joséite-B, unnamed phase A with a chemical formula close to (Bi,Pb)2(TeS)2, unnamed phase B with a chemical composition close to (Bi,Pb)2.5Te1.5S1.5), ikunolite, cosalite, Sb-lillianite, members of the kobellite series and Bi-jamesonite. Compositional trends of the Bi-sulphotellurides suggest lattice-scale incorporation of Bi-(Pb)-rich module and/or admixture with submicroscopic PbS layers in modulated structures, or complicated Bi-Te substitution. Cosalite is characterized by high Sb (max. 3.94 apfu), and low Cu and Ag (up to 0.72 apfu of Cu+Ag). Jamesonite from this mineralization has elevated Bi content, from 0.85 to 2.30 apfu. The negligible content of Au and Ag in the Bi-sulphotellurides, the low content of Ag in Bi-sulphosalts, together with the lack of Au-Ag bearing phases in the mineralization, indicate either ore deposition from fluid(s) depleted in precious metals, or physico-chemical conditions of ore formation preventing Au and Ag precipitation at the deposit site. The temperature of initial mineralization may have exceeded 400 °C as suggested by the lamellar exsolution textures observed in lillianite, which indicate breakdown textures from decomposition of high-temperature initial crystals. Non-stoichiometric phases among the Bi-sulphosalts and sulphotellurides studied at Stan Terg reflect modulated growth processes in a metasomatic environment.

  13. Studies on Microstructure and Thermoelectric Properties of p-Type Bi-Sb-Te Based Alloys by Gas Atomization and Hot Extrusion Processes

    Science.gov (United States)

    Park, Ki-Chan; Madavali, Babu; Kim, Eun-Bin; Koo, Kyung-Wan; Hong, Soon-Jik

    2017-05-01

    p-Type Bi2Te3 + 75% Sb2Te3 based thermoelectric materials were fabricated via gas atomization and the hot extrusion process. The gas atomized powder showed a clean surface with a spherical shape, and expanded in a wide particle size distribution (average particle size 50 μm). The phase of the fabricated extruded and R-extruded bars was identified using x-ray diffraction. The relative densities of both the extruded and R-extruded samples were measured by Archimedes principle with ˜98% relative density. The R-extruded bar exhibited finer grain microstructure than that of single extrusion process, which was attributed to a recrystallization mechanism during the fabrication. The R-extruded sample showed improved Vickers hardness compared to the extruded sample due to its fine grain microstructure. The electrical conductivity improved for the extruded sample whereas the Seebeck coefficient decreases due to its high carrier concentration. The peak power factor, ˜4.26 × 10-3 w/mK2 was obtained for the single extrusion sample, which is higher than the R-extrusion sample owing to its high electrical properties.

  14. Superconductivity in Ba(Pb,Bi,Sb)O 3, Ba(Pb,Bi,Te)O 3 and (Ba,La) (Pb,Bi,Tl)O 3 systems

    Science.gov (United States)

    Nagarajan, R.; Vasanthacharya, N. Y.; Gopalakrishnan, J.; Rao, C. N. R.

    1991-02-01

    It is possible to substitute Bi in the superconducting BaPb 0.75Bi 0.25O 3 by Sb or Te without destroying the superconductivity. With Sb, a continuous series of solid solutions BaPb 0.75Bi 0.25-ySb yO 3 (0 ⩽ y ⩽ 0.25) exists, while with Te, perovskite BaPb 0.75Bi 0.25-yTe yO 3 exists only upto y = 0.15. With increasing substitution by Sb or Te, T c decreases continously in both the systems. Superconductivity with a maximum T c of 8K is found in Ba 0.9La 0.1Pb 0.9-yBi yTl 0.1O 3 for y = 0.25.

  15. Full-potential KKR-calculations for MgO and divalent impurities in MgO

    OpenAIRE

    Baranov, A. N.; Stepanyuk, V. S.; Hergert, W.; Katsnelson, A. A.; Settels, A.; Zeller, R.; Dederichs, P. H.

    2002-01-01

    We present a detailed investigation of bulk properties of MgO and lattice relaxations around divalent impurities in MgO by means of the full-potential Korringa-Kohn-Rostoker Green's function method. The local-density approximation and the perturbative generalized gradient corrections are used to calculate the lattice constant and bulk modulus of MgO. We obtain a very good description of the ground properties of MgO. Lattice relaxations around divalent impurities in MgO are determined using an...

  16. Comment on "First-principles calculation of the superconducting transition in MgB2 within the anisotropic Eliashberg formalism"

    NARCIS (Netherlands)

    Mazin, I.I.; Andersen, O.K.; Jepsen, O.; Golubov, A.A.; Dolgov, O.V.; Kortus, J.

    2004-01-01

    Choi et al. [Phys. Rev. B 66, 020513 (2002)] recently presented first-principles calculations of the electron-phonon coupling and superconductivity in MgB2, emphasizing the importance of anisotropy and anharmonicity. We point out that (1) variation of the superconducting gap inside the sigma or the

  17. Nanoscale nuclei in phase change materials: Origin of different crystallization mechanisms of Ge{sub 2}Sb{sub 2}Te{sub 5} and AgInSbTe

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Bong-Sub, E-mail: bongsub@gmail.com; Bogle, Stephanie N.; Darmawikarta, Kristof; Abelson, John R. [Department of Materials Science and Engineering and the Coordinated Sciences Laboratory, University of Illinois at Urbana-Champaign, 1-109 Engineering Sciences Building, 1101 West Springfield Avenue, Urbana, Illinois 61801 (United States); Shelby, Robert M.; Retter, Charles T.; Burr, Geoffrey W. [IBM Research—Almaden, 650 Harry Rd., San Jose, California 95120 (United States); Raoux, Simone [IBM Research—Almaden, 650 Harry Rd., San Jose, California 95120 (United States); IBM/Macronix PCRAM Joint Project, IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Bishop, Stephen G. [Department of Electrical and Computer Engineering and the Coordinated Sciences Laboratory, University of Illinois at Urbana-Champaign, 1406 West Green Street, Urbana, Illinois 61801 (United States)

    2014-02-14

    Phase change memory devices are based on the rapid and reversible amorphous-to-crystalline transformations of phase change materials, such as Ge{sub 2}Sb{sub 2}Te{sub 5} and AgInSbTe. Since the maximum switching speed of these devices is typically limited by crystallization speed, understanding the crystallization process is of crucial importance. While Ge{sub 2}Sb{sub 2}Te{sub 5} and AgInSbTe show very different crystallization mechanisms from their melt-quenched states, the nanostructural origin of this difference has not been clearly demonstrated. Here, we show that an amorphous state includes different sizes and number of nanoscale nuclei, after thermal treatment such as melt-quenching or furnace annealing is performed. We employ fluctuation transmission electron microscopy to detect nanoscale nuclei embedded in amorphous materials, and use a pump-probe laser technique and atomic force microscopy to study the kinetics of nucleation and growth. We confirm that melt-quenched amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} includes considerably larger and more quenched-in nuclei than its as-deposited state, while melt-quenched AgInSbTe does not, and explain this contrast by the different ratio between quenching time and nucleation time in these materials. In addition to providing insights to the crystallization process in these technologically important devices, this study presents experimental illustrations of temperature-dependence of nucleation rate and growth speed, which was predicted by theory of phase transformation but rarely demonstrated.

  18. Effect of Rashba spin-orbit coupling on the electronic, thermodynamic, magnetic and transport properties of GaAs, InAs and InSb quantum dots with Gaussian confinement

    Science.gov (United States)

    Boda, Aalu; Boyacioglu, Bahadir; Erkaslan, Ugur; Chatterjee, Ashok

    2016-10-01

    The effect of Rashba spin-orbit interaction on the electronic, thermodynamic, magnetic and transport properties of a one-electron Gaussian quantum dot is investigated in the presence of a magnetic field and its interaction with the electron spin using the canonical ensemble approach. The temperature-dependent energy, magnetization, susceptibility, specific heat and the persistent current are calculated as a function of the spin-orbit coupling parameter. The results are applied to GaAs, InAs and InSb quantum dots.

  19. Lattice location and local magnetism of recoil implanted Fe impurities in wide and narrow band semiconductors CdTe, CdSe, and InSb: Experiment and theory

    Energy Technology Data Exchange (ETDEWEB)

    Mohanta, S. K.; Mishra, S. N. [Tata Institute of Fundamental Research (TIFR), Homi Bhabha Road, Mumbai 400005 (India)

    2014-05-07

    Employing the time differential perturbed angular distribution method, we have measured local susceptibility and spin relaxation rate of {sup 54}Fe nuclei implanted in III-V and II-VI semiconductors, CdTe, CdSe, and InSb. The magnetic response of Fe, identified to occupy the metal as well as the semi-metal atom sites, exhibit Curie-Weiss type susceptibility and Korringa like spin relaxation rate, revealing the existence of localized moments with small spin fluctuation temperature. The experimental results are supported by first principle electronic structure calculations performed within the frame work of density functional theory.

  20. Effect of Rashba spin–orbit coupling on the electronic, thermodynamic, magnetic and transport properties of GaAs, InAs and InSb quantum dots with Gaussian confinement

    Energy Technology Data Exchange (ETDEWEB)

    Boda, Aalu [School of Physics, University of Hyderabad, Hyderabad 500046 (India); Boyacioglu, Bahadir [Vocational School of Health Services, University of Ankara, 06290 Ankara (Turkey); Erkaslan, Ugur [Department of Physics, Faculty of Science, Mugla Sitki Kocman University, 48170 Kotekli-Mugla (Turkey); Chatterjee, Ashok, E-mail: acsp@uohyd.ernet.in [School of Physics, University of Hyderabad, Hyderabad 500046 (India)

    2016-10-01

    The effect of Rashba spin–orbit interaction on the electronic, thermodynamic, magnetic and transport properties of a one-electron Gaussian quantum dot is investigated in the presence of a magnetic field and its interaction with the electron spin using the canonical ensemble approach. The temperature-dependent energy, magnetization, susceptibility, specific heat and the persistent current are calculated as a function of the spin–orbit coupling parameter. The results are applied to GaAs, InAs and InSb quantum dots.

  1. Persistence of Metastable Vortex Lattice Domains in MgB2 in the Presence of Vortex Motion

    Energy Technology Data Exchange (ETDEWEB)

    Rastovski, Catherine [University of Notre Dame, IN; Schlesinger, Kimberly [University of Notre Dame, IN; Gannon, William J [Northwestern University, Evanston; Dewhurst, Charles [Institut Laue-Langevin (ILL); Debeer-Schmitt, Lisa M [ORNL; Zhigadlo, Nikolai [ETH Zurich, Switzerland; Karpinski, Janusz [ETH Zurich, Switzerland; Eskildsen, Morten [University of Notre Dame, IN

    2013-01-01

    Recently, extensive vortex lattice metastability was reported in MgB2 in connection with a second-order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using small-angle neutron scattering, we studied the vortex lattice in MgB2 as it was driven from a metastable to the ground state through a series of small changes in the applied magnetic field. Our results show that metastable vortex lattice domains persist in the presence of substantial vortex motion and directly demonstrate that the metastability is not due to vortex pinning. Instead, we propose that it is due to the jamming of counterrotated vortex lattice domains which prevents a rotation to the ground state orientation.

  2. Persistence of metastable vortex lattice domains in MgB2 in the presence of vortex motion.

    Science.gov (United States)

    Rastovski, C; Schlesinger, K J; Gannon, W J; Dewhurst, C D; DeBeer-Schmitt, L; Zhigadlo, N D; Karpinski, J; Eskildsen, M R

    2013-09-01

    Recently, extensive vortex lattice metastability was reported in MgB2 in connection with a second-order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using small-angle neutron scattering, we studied the vortex lattice in MgB2 as it was driven from a metastable to the ground state through a series of small changes in the applied magnetic field. Our results show that metastable vortex lattice domains persist in the presence of substantial vortex motion and directly demonstrate that the metastability is not due to vortex pinning. Instead, we propose that it is due to the jamming of counterrotated vortex lattice domains which prevents a rotation to the ground state orientation.

  3. Selection of dopants to enhance hydrogen diffusion rates in MgH2 and NaMgH3

    Science.gov (United States)

    Hao, Shiqiang; Sholl, David S.

    2009-04-01

    The transport properties of hydrogen in metal hydrides are crucial to the kinetics of H2 storage in these materials. Previous first-principles calculations and experiments have shown that H transport in MgH2 and NaMgH3 is dominated by charged defects. This creates the possibility of enhancing hydrogen diffusion in these materials by adding dopants that alter the population of the relevant charged defects. We describe a comprehensive set of first-principles calculations examining dopants in MgH2 and NaMgH3 for this purpose. Only a small number of elemental dopants are found to have favorable properties, but these dopants could increase the diffusivity of H by two to three orders of magnitude relative to the undoped materials.

  4. Impurity Diffusion Coefficients of Al and Zn in Mg Determined from Solid-to-Solid Diffusion Couples

    Energy Technology Data Exchange (ETDEWEB)

    Kammerer, Catherine [University of Central Florida, Orlando; Kulkarni, Nagraj S [ORNL; Warmack, Robert J Bruce [ORNL; Perry, Kelly A [ORNL; Belova, Irina [University of Newcastle, NSW, Australia; Murch, Prof. Graeme [University of Newcastle, NSW, Australia; Sohn, Yong Ho [University of Central Florida

    2013-08-01

    Increasing use and development of lightweight Mgalloys have led to the desire for more fundamental research in and understanding of Mg-based systems. As property enhancing components, Al and Zn are two of the most important and common alloying elements for Mg-alloys. We have investigated the concentration dependent interdiffusion of Al and Zn in Mg using diffusion couples of pure polycrystalline Mg mated to Mg solid solutions containing either <9 at.% Al or <3 at.% Zn. Concentration profiles were determined by electron micro-probe microanalysis of the diffusion zone. The interdiffusion coefficients were determined by the classical Boltzmann-Matano method within the Mg solid solution. As the concentration of Al or Zn approaches the dilute ends, we employ an analytical approach based on the Hall method to estimate the impurity diffusion coefficients. Results of Al and Zn impurity diffusion in Mg are reported and compared to published impurity diffusion coefficients typically determined by thin film techniques.

  5. Characterization of β precipitate phase in Mg-7Gd-5Y-1Nd-0.5Zr alloy

    Institute of Scientific and Technical Information of China (English)

    LI Ting; ZHANG Kui; DU Zhiwei; LI Xinggang; LI Yongjun; MA Minglong; YUAN Jiawei

    2013-01-01

    As reported in our previous works,a Mg-7Gd-5Y-1Nd-0.5Zr alloy recently developed exhibited remarkable age-hardening responses and excellent mechanical properties at both room and elevated temperatures.In Mg-7Gd-5Y-1Nd-0.5Zr alloy,the β precipitate phase was assumed to be one of the main strengthening phases in peak-aged samples.This study aimed to determine the crystal structure and orientation relationship of the β precipitate phase in Mg-7Gd-5Y-1Nd-0.5Zr alloy using transmission electron microscopy and high-resolution electron microscopy.The results indicated that the β precipitate had a face-centered cubic structure with a lattice parameter of a=2.22 nm.The orientation relationship between the β precipitate phase and the α-Mg matrix was ((1)-12)β//((1)-100)α,[110]β/[0001]α.The β plates formed on prismatic planes could play an important role in alloy strengthening by proving effective barriers to gliding dislocations.A single β plate often contained several domains of (1(1)1)β twin-related variants.A composition of Mg5(Y0.4Gd0.4Nd0.2) was suggested for the β phase in Mg-7Gd-5Y-1Nd-0.5Zr alloy.

  6. Decaying shock studies of phase transitions in MgOSiO2 systems: implications for the Super-Earths interiors

    CERN Document Server

    Bolis, R M; Vinci, T; Ravasio, A; Bambrink, E; Guarguaglini, M; Koenig, M; Musella, R; Remus, F; Bouchet, J; Ozaki, N; Miyanishi, K; Sekine, T; Sakawa, Y; Sano, T; Kodama, R; Guyot, F; Benuzzi-Mounaix, A

    2016-01-01

    We report an experimental study of the phase diagrams of periclase (MgO), enstatite (MgSiO3) and forsterite (Mg2SiO4) at high pressures. We investigated with laser driven decaying shocks the pressure/temperature curves of MgO, MgSiO3 and Mg2SiO4 between 0.2-1.2 TPa, 0.12-0.5 TPa and 0.2-0.85 TPa respectively. A melting signature has been observed in MgO at 0.47 TPa and 9860 K, while no phase changes were observed neither in MgSiO3 nor in Mg2SiO4. An increasing of reflectivity of MgO, MgSiO3 and Mg2SiO4 liquids have been detected at 0.55 TPa -12 760 K, 0.15 TPa - 7540 K, 0.2 TPa - 5800 K, respectively. In contrast to SiO2, melting and metallization of these compounds do not coincide implying the presence of poor electrically conducting liquids close to the melting lines. This has important implications for the generation of dynamos in Super-earths mantles.

  7. Research on the Penetration Behavior of Fe3 + in SB Slurry Wall%Fe 离子在 Soil - Bentonite Slurry wall中的渗透行为研究

    Institute of Scientific and Technical Information of China (English)

    吕淑清; 刘锦伟

    2014-01-01

    采用实验室研究方法,研究了SB (Soil Bentonite )材料对Fe离子的吸附,以及Fe离子在SB Slurry wall 中的穿透行为,实验结果显示,SB 对 Fe 离子的吸附符合 langmuir 等温线,Fe 离子在 SB 中迁移时,导致 SB材料的渗透系数比纯水的渗透系数大一个数量级,Fe 离子流出浓度随着时间的增加在不断增加。%The method of laboratory research is adopted to study the adsorption of SB materials to Fe 3 + and the break-through behavior of Fe ions in SB Slurry wall .The results show that the adsorption SB material to Fe ion conforms to the Langmuir isotherm ;the migration of Fe3 + in SB causes the permeability coefficient increased to an order of magnitude and Fe3 + outflow concentration increases with the increase of time .

  8. 合金元素对Sn-Bi-Sb-Ag-Cu-Re系无铅钎料性能和组织的影响%Effect of alloying elements on properties and microstructure of Sn-Bi-Sb-Ag-Cu-Re lead-free solder

    Institute of Scientific and Technical Information of China (English)

    王宗杰; 路林; 王敏

    2005-01-01

    研究了合金元素Bi、Sb、Ag、Cu、Re对锡基无铅多元钎料性能和组织的影响.研究结果表明,增加Bi、Ag、Cu含量可以降低液相线温度,Sb 可以提高液相线温度;Bi、Cu有提高润湿性能的作用,Sb、Ag、Re在低含量范围内可提高润湿性能;Cu有提高剪切强度的作用,Bi明显使剪切强度降低.钎料的相组成是由在β-Sn的基体上分布着金属间化合物Ag3Sn、SnBi和Cu6Sn5构成的,Sb和Re则基本上是固溶在基体中.

  9. Microstructure, mechanical properties and corrosion behavior of Al-Si-Cu-Zn-X (X=Bi, Sb, Sr) die cast alloy%Al-Si-Cu-Zn-X(X=Bi,Sb,Sr)压铸铝合金的显微组织、力学性能和腐蚀行为

    Institute of Scientific and Technical Information of China (English)

    Saeed FARAHANY; Ali OURDJINI; Hamid Reza BAKHSHESHI-RAD

    2016-01-01

    研究经Bi、Sb和Sr改性的Al-11Si-2Cu-0.80Zn压铸铝合金的显微组织演变、力学性能和腐蚀行为.力学性能测试结果表明,Bi、Sb和Sr的添加引起合金中共晶Si形貌发生改变,从而使合金的冲击韧性、极限抗拉强度和伸长率增加.断裂表面分析结果表明,添加Sr或少量Bi和Sb,合金表面呈韧性断裂,而非准解理脆性断裂.此外,添加Sr、Bi和Sb后,合金的质量指标由基体合金的102 MPa分别增加到164.7 MPa、156.3 MPa和152.6MPa.在NaCl溶液中的极化腐蚀测试结果表明,分别添加Sb、Bi和Sr后,合金的腐蚀电位负移.浸泡腐蚀实验结果表明,由于Al和Si共晶相界面的增加,Sb、Bi和Sr元素的添加对合金的腐蚀速率具有决定性作用.

  10. Search for E(2g) phonon modes in MgB2 single crystals by point-contact spectroscopy.

    Science.gov (United States)

    Naidyuk, Yu G; Yanson, I K; Kvitnitskaya, O E; Lee, S; Tajima, S

    2003-05-16

    The electron-phonon interaction in magnesium diboride MgB2 single crystals is investigated by point-contact (PC) spectroscopy. For the first time the electron coupling with E(2g) phonon modes is resolved in the PC spectra. The correlation between intensity of the extremely broad E(2g) modes in the PC spectra and value of the superconducting gap is established. Our observations favor current theoretical models for electron-phonon mediated superconductivity in MgB2, and they better match the harmonic phonon model.

  11. Phonon dispersion and electron-phonon coupling in MgB2 and AlB2.

    Science.gov (United States)

    Bohnen, K P; Heid, R; Renker, B

    2001-06-18

    We present a first principles investigation of the lattice dynamics and electron-phonon coupling of the superconductor MgB2 and the isostructural AlB2 within the framework of density functional perturbation theory using a mixed-basis pseudopotential method. Complete phonon dispersion curves and Eliashberg functions alpha2F are calculated for both systems. The main differences are related to high frequency in-plane boron vibrations, which are strongly softened in MgB2 and exhibit an exceptionally strong electron-phonon coupling. We also report on Raman measurements, which support the theoretical findings. Implications for the superconducting transition temperature are briefly discussed.

  12. Hydrogen divacancy diffusion: a new perspective on H migration in MgH2 materials for energy storage.

    Science.gov (United States)

    German, Estefania; Gebauer, Ralph

    2017-01-04

    The formation and diffusion of pairs of hydrogen vacancies (divacancies) in magnesium hydride is modeled using density functional theory. Compared to the commonly studied case of single hydrogen vacancies, it is found that divacancies are energetically favored over two isolated vacancies. Also, as a function of the diffusion axis considered, the calculated diffusion barriers of divacancies are either smaller or of comparable magnitude with respect to the diffusion barriers of a single vacancy. These findings shed new light on hydrogen transport in MgH2, which is of crucial importance to understand the kinetics of hydrogen take-up and release in this storage material.

  13. Theory of crystal field states for heavy rare-earth impurities in MgB sub 2

    CERN Document Server

    Welsch, F; Faehnle, M

    2002-01-01

    For isolated rare-earth impurities substituting for Mg atoms in the superconductor MgB sub 2 the crystal field parameters are calculated by the ab initio density functional electron theory with constraints for the 4f charge and spin density. The crystal field parameter A sub 6 sup 6 is extremely small due to the structure and bonding properties of MgB sub 2 , and therefore the crystal field levels are nearly exclusively determined by one magnetic quantum number M. Implications for the pair-breaking mechanism of the superconductivity in MgB sub 2 are discussed.

  14. Ultraviolet laser-induced poling inhibition produces bulk domains in MgO-doped lithium niobate crystals

    Energy Technology Data Exchange (ETDEWEB)

    Boes, Andreas, E-mail: s3363819@student.rmit.edu.au; Steigerwald, Hendrik; Sivan, Vijay; Mitchell, Arnan [School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria 3001 (Australia); ARC Center for Ultra-high Bandwidth Devices for Optical Systems (CUDOS), RMIT University, Melbourne, Victoria 3001 (Australia); Yudistira, Didit [School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria 3001 (Australia); Wade, Scott [Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Mailis, Sakellaris [Optoelectronics Research Centre, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Soergel, Elisabeth [Institute of Physics, University of Bonn, Wegelerstr. 8, 53115 Bonn (Germany)

    2014-09-01

    We report the realization of high-resolution bulk domains achieved using a shallow, structured, domain inverted surface template obtained by UV laser-induced poling inhibition in MgO-doped lithium niobate. The quality of the obtained bulk domains is compared to those of the template and their application for second harmonic generation is demonstrated. The present method enables domain structures with a period length as small as 3 μm to be achieved. Furthermore, we propose a potential physical mechanism that leads to the transformation of the surface template into bulk domains.

  15. Dynamic Phase-Mapping of Domain Nucleation in MgO:LiNbO3 Crystal by Digital Holographic Interferometry

    Institute of Scientific and Technical Information of China (English)

    QU Wei-Juan; LIU De-An; ZHI Ya-Nan; LUAN Zhu; LIU Li-Ren

    2007-01-01

    The quantitative phase-mapping of the domain nucleation in MgO:LiNbO3 crystals is presented by using the digital holographic interferometry. An unexpected peak phase at the beginning of the domain nucleation is observed and it is lowered as the spreading of the domain nucleus. The existence of the nucleus changes the moving speed of the domain wall by pinning it for 3 s. Such in-situ quantitative analysis of the domain nucleation process is a key to optimizing domain structure fabrication.

  16. Surface plasmon-enhanced ultraviolet photodetectors by using Au nanoparticles embedded in MgZnO thin films

    Science.gov (United States)

    Guo, Z. X.; Jiang, D. Y.; Zhao, M.; Zheng, T.; Lv, J. W.; Pei, J. N.; Hu, N.; Gao, S.; Liang, Q. C.; Zhao, J. X.; Hou, J. H.; Qin, J. M.

    2017-09-01

    This paper demonstrates surface plasmons (SPs) enhanced MgZnO ultraviolet (UV) photodetectors grown by a radio frequency (RF) magnetron sputtering technique, and the magnesium concentration is 30%. Predominantly, well-defined Au NPs with different sizes were produced embedded in MgZnO thin films. Notably, at 30 V applied bias, the proper combination MgZnO/Au NPs (40 s), responsivity as high as 341.08 A/W is achieved after optimizing the process. Impressively, the excellent comprehensive performance of MgZnO/Au NPs UV photodetectors should have great applied potential, a physical mechanism is given to explain the above results.

  17. Thermally induced dephasing of high power second harmonic generation in MgO: LiNbO3 waveguides

    Institute of Scientific and Technical Information of China (English)

    Guohui Li; Xinye Xu

    2011-01-01

    High power second harmonic generation (SHG) in MgO-doped LiNbO3 waveguides is investigated using a three-dimensional (3D) coupled thermo-optical model. Simulations performed for a 1111.6-nm fundamental laser show the influence of the absorptions and the thermally induced dephasing on the conversion efficiencies of the different waveguides. The onset of the thermally induced dephasing effect for each waveguide is also indicated. As a result of high light intensity in the waveguide, nonlinear absorptions are identified as the possible main factors in efficiency losses in specific cases.%High power second harmonic generation (SHG) in MgO-doped LiNbO3 waveguides is investigated using a three-dimensional (3D) coupled thermo-optical model.Simulations performed for a 1111.6-nm fundamental laser show the influence of the absorptions and the thermally induced dephasing on the conversion efficiencies of the different waveguides.The onset of the thermally induced dephasing effect for each waveguide is also indicated.As a result of high light intensity in the waveguide,nonlinear absorptions are identified as the possible main factors in efficiency losses in specific cases.

  18. Investigation of lauric acid dopant as a novel carbon source in MgB{sub 2} wire

    Energy Technology Data Exchange (ETDEWEB)

    Lee, C.M.; Lee, S.M.; Park, G.C.; Joo, J. [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon (Korea, Republic of); Lim, J.H., E-mail: jhlim@stanford.ed [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Kang, W.N. [BK21 Physics Division and Department of Physics, Sungkyunkwan University, Suwon (Korea, Republic of); Yi, J.H. [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon (Korea, Republic of); Neutron Science Division Laboratory, Korea Atomic Energy Research, Daejeon (Korea, Republic of); Jun, B.-H.; Kim, C.-J. [Neutron Science Division Laboratory, Korea Atomic Energy Research, Daejeon (Korea, Republic of)

    2010-11-01

    We fabricated lauric acid (LA) doped MgB{sub 2} wires and investigated the effects of the LA doping. For the fabrication of the LA-doped MgB{sub 2} wires, B powder was mixed with LA at 0-5 wt.% of the total amount of MgB{sub 2} using an organic solvent, dried, and then the LA-treated B and Mg powders were mixed stoichiometrically. The powder mixture was loaded into an Fe tube and the assemblage was drawn and sintered at 900 deg. C for 3 h under an argon atmosphere. We observed that the LA doping induced the substitution of C for the B sites in MgB{sub 2} and that the actual content of C increased monotonically with increasing LA doping level. The LA-doped MgB{sub 2} wires exhibited a lower critical temperature (T{sub c}), but better critical current density (J{sub c}) behavior in a high magnetic field: the 5 wt.% LA-doped sample had a J{sub c} value of 5.32 x 10{sup 3} A/cm{sup 2}, which was 2.17 times higher than that of the pristine sample (2.45 x 10{sup 3} A/cm{sup 2}) at 5 K and 6 T, suggesting that LA is an effective C dopant in MgB{sub 2} for enhancing the high-field J{sub c} performance.

  19. The c(4 × 4–a(1 × 3 surface reconstruction transition on InSb(001: Static versus dynamic conditions

    Directory of Open Access Journals (Sweden)

    J.J. Bomphrey

    2015-01-01

    Full Text Available The transition between the a(1 × 3 and c(4 × 4 surface reconstructions of InSb(001 has been carefully monitored by reflection high energy electron diffraction as a function of temperature and Sb2 flux, without incident In flux. Arrhenius-like behaviour is observed across the whole range of Sb2 fluxes and temperatures, allowing accurate internal calibration of substrate temperature. This behaviour is in contrast to aggregated data obtained under dynamic molecular beam epitaxy conditions, which show two regimes rather than a single Arrhenius-like phase boundary. The results are explained qualitatively by the atomistic kinetics in static versus dynamic conditions.

  20. Comparison of optical transients during the picosecond laser pulse-induced crystallization of GeSbTe and AgInSbTe phase-change thin films: Nucleation-driven versus growth-driven processes

    Science.gov (United States)

    Liang, Guangfei; Li, Simian; Huang, Huan; Wang, Yang; Lai, Tianshu; Wu, Yiqun

    2013-09-01

    Direct comparison of the real-time in-situ crystallization behavior of as-deposited amorphous Ge2Sb2Te5 (GeSbTe) and Ag8In14Sb55Te23 (AgInSbTe) phase-change thin films driven by picosecond laser pulses was performed by a time-resolved optical pump-probe technique with nanosecond resolution. Different optical transients showed various crystallization processes because of the dissimilar nucleation- and growth-dominated mechanisms of the two materials. The effects of laser pulse fluence, thermal conductive structure, and successive pulse irradiation on their crystallization dynamics were also discussed. A schematic was then established to describe the different crystallization processes beginning from the as-deposited amorphous state. The results may provide further insight into the phase-change mechanism under extra-non-equilibrium conditions and aid the development of ultrafast phase-change memory materials.

  1. Delamination study of InSb infrared fo cal plane arrays using a cohesive zone mo del%基于内聚区模型的InSb面阵探测器分层研究

    Institute of Scientific and Technical Information of China (English)

    孟庆端; 贵磊; 张晓玲; 张立文; 耿东峰; 吕衍秋

    2014-01-01

    液氮冲击中InSb面阵探测器表面经常出现局部分层、开裂等失效模式。为明晰材料分层、光敏元芯片断裂过程,基于三维等效建模设想,在易分层处添加内聚区模型,合理选取界面分层开裂参数,建立了128×128 InSb探测器结构分层模型。模拟结果涵盖了典型碎裂照片中呈现的所有形变信息,即1)在光敏元阵列区域,复现出典型棋盘格屈曲模式;2)在Negative电极区域上方, InSb芯片与下层材料逐渐分开,且分层向两侧逐步扩展;3)在面阵探测器周边区域,表面起伏相对平整。上述模拟结果证明了所建分层模型的正确性和参数选取的合理性,为后续裂纹起源、传播过程的研究提供了模型基础。%Local interfacial delamination and cracking, appearing in the top surface of InSb infrared focal plane arrays (IRF-PAs), are typical failure patterns observed in liquid nitrogen shock tests. In order to explore the delamination mechanism and cracking process, based on the thought of three-dimensional equivalent modeling, we employ the cohesive zone model (CZM) for the interface where delamination appears most easily, and create the structural model of 128×128 InSb IRF-PAs. Simulation results contain all the deformation characteristics appearing in the typical optical fracture photographs. That is, firstly, in the photosensitive element array, the global square checkerboard buckling pattern reappears;secondly, in the negative electrode material, the InSb chip is gradually separated from the negative electrode, and the width of delamination is widened gradually;thirdly, on the periphery of InSb IRFPAs, the surface is flat. All these findings sug-gest that the model created in this paper is correct, and the parameters selected are suitable. Based on the delamination model, it is possible to find the initiation and propagation rule of cracks in the research that follows.

  2. Time-resolved photoexcitation of the superconducting two-gap state in MgB2 thin films.

    Science.gov (United States)

    Xu, Y; Khafizov, M; Satrapinsky, L; Kús, P; Plecenik, A; Sobolewski, Roman

    2003-11-01

    Femtosecond pump-probe studies show that carrier dynamics in MgB2 films is governed by the sub-ps electron-phonon (e-ph) relaxation present at all temperatures, the few-ps e-ph process well pronounced below 70 K, and the sub-ns superconducting relaxation below T(c). The amplitude of the superconducting component versus temperature follows the superposition of the isotropic dirty gap and the three-dimensional pi gap dependences, closing at two different T(c) values. The time constant of the few-ps relaxation exhibits a double divergence at temperatures corresponding to the T(c)'s of the two gaps.

  3. Heavy ion ToF analysis of oxygen incorporation in MgB{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Ionescu, M. [Australian Nuclear Science and Technology Organization, Lucas Heights, Building 53, New South Wales 2234 (Australia)], E-mail: Mihail.Ionescu@ansto.gov.au; Zhao, Y. [Institute for Superconduction and Electronic Materials, University of Wollongong, NSW 2522 (Australia); Siegele, R.; Cohen, D.D.; Stelcer, E.; Prior, M. [Australian Nuclear Science and Technology Organization, Lucas Heights, Building 53, New South Wales 2234 (Australia)

    2008-04-15

    Oxygen incorporation in MgB{sub 2} thin films during their fabrication process has a strong influence on the future properties of the films, and was studied by Elastic Recoil Detection Analysis with Heavy ions and a Time-of-flight detection. A series of MgB{sub 2} thin film samples were analyzed, including films produced in situ on Al{sub 2}O{sub 3}-C and Si (0 0 1) substrates (with higher T{sub c} and lower T{sub c}) with an 'on-axis' geometry, and films produced in situ with an 'off-axis' geometry. The amount of oxygen detected in these films appears to be correlated with the T{sub c} of the films, the higher the T{sub c} the lower the oxygen content. The superconducting properties of the examined thin films are discussed in the context of the ERDA results.

  4. Tem Observation Of Age-Hardening Precipitation In Mg-Gd-Y Alloys As Different Gd/Y Ratio

    Directory of Open Access Journals (Sweden)

    Matsuoka Y.

    2015-06-01

    Full Text Available In this study, the early stage of aging in Mg-Gd-Y alloys has been observed by transmission electron microscopy (TEM, high angle annular dark field – scanning transmission electron microscopy (HAADF-STEM and calculations of images and electron density and bond overlap population (BOP by first principal to understand the origin of precipitation in this alloy. The small hexagon of 0.37 nm is the first precipitate in this alloy, and this is the evidence of short range ordering of D019 structure. This is referred as the pre β”-phase. In the peak aged condition, β’ phase with bco structure was mainly observed.

  5. Cation disorder in MgX2O4 (X = Al, Ga, In) spinels from first principles

    Science.gov (United States)

    Jiang, Chao; Sickafus, Kurt E.; Stanek, Christopher R.; Rudin, Sven P.; Uberuaga, Blas P.

    2012-07-01

    We have performed first-principles density functional theory calculations to investigate the possible physical origins of the discrepancies between the existing theoretical and experimental studies on cation distribution in MgX2O4 (X = Al, Ga, In) spinel oxides. We show that for MgGa2O4 and MgIn2O4, it is crucial to consider the effects of lattice vibrations to achieve agreement between theory and experiment. For MgAl2O4, we find that neglecting short-range order effects in thermodynamic modeling can lead to significant underestimation of the degree of inversion. Furthermore, we demonstrate that the common practice of representing disordered structures by randomly exchanging atoms within a small periodic supercell can incur large computational error due to either insufficient statistical sampling or finite supercell size effects.

  6. Guinier-Preston Zone, Quasicrystal and Long-period Stacking Ordered Structure in Mg-based Alloys, A Review

    Institute of Scientific and Technical Information of China (English)

    Yongbo XU; Daokui XU; Xiaohong SHAO; En-hou HAN

    2013-01-01

    Both the solid solution and precipitation are mainly strengthening mechanism for the magnesium-based alloys.A great number of alloying elements can be dissolved into the Mg matrix to form the solutes and precipitates.Moreover,the type of precipitates varies with different alloying elements and heat treatments,which makes it quite difficult to understand the formation mechanism of the precipitates in Mg-based alloys in depth.Thus,it is very hard to give a systematical regularity in precipitation process for the Mg-based alloys.This review is mainly focused on the formation and microstructural evolution of the precipitates,as a hot topic for the past few years,including Guinier-Preston Zones,quasicrystals and long-period stacking ordered phases formed in a number of Mg-TM-RE alloy systems,where TM =AI,Zn,Zr and RE =Y,Gd,Hd,Ce and La.

  7. Ru Catalyst-Induced Perpendicular Magnetic Anisotropy in MgO/CoFeB/Ta/MgO Multilayered Films.

    Science.gov (United States)

    Liu, Yiwei; Zhang, Jingyan; Wang, Shouguo; Jiang, Shaolong; Liu, Qianqian; Li, Xujing; Wu, Zhenglong; Yu, Guanghua

    2015-12-09

    The high oxygen storage/release capability of the catalyst Ru is used to manipulate the interfacial electronic structure in spintronic materials to obtain perpendicular magnetic anisotropy (PMA). Insertion of an ultrathin Ru layer between the CoFeB and Ta layers in MgO/CoFeB/Ta/MgO films effectively induces PMA without annealing. Ru plays a catalytic role in Fe-O-Ta bonding and isolation at the metal-oxide interface to achieve moderate interface oxidation. In contrast, PMA cannot be obtained in the sample with a Mg insertion layer or without an insertion layer because of the lack of a catalyst. Our work would provide a new approach toward catalyst-induced PMA for future CoFeB-based spintronic device applications.

  8. Effects of BaRuO{sub 3} addition on hydrogen desorption in MgH{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Baricco, M., E-mail: marcello.baricco@unito.it [Dipartimento di Chimica IFM and NIS, Universita di Torino, Via P. Giuria 9, 10125 Torino (Italy); Rahman, M.W.; Livraghi, S.; Castellero, A. [Dipartimento di Chimica IFM and NIS, Universita di Torino, Via P. Giuria 9, 10125 Torino (Italy); Enzo, S. [Dipartimento di Chimica, Universita di Sassari, Via Vienna, 2, 07100 Sassari (Italy); Giamello, E. [Dipartimento di Chimica IFM and NIS, Universita di Torino, Via P. Giuria 9, 10125 Torino (Italy)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Interaction of BaRuO{sub 3} with hydrogen studied. Black-Right-Pointing-Pointer BaRuO{sub 3} is able to release hydrogen after absorption. Black-Right-Pointing-Pointer A distorted rhomohedral phase is formed in BaRuO{sub 3} after hydrogen absorption. Black-Right-Pointing-Pointer A mixture of BaRuO{sub 3} with MgH{sub 2} is able to desorb hydrogen much faster than the parent materials. The interaction of hydrogen with the oxide additive is a crucial aspect for improving the hydrogen desorption rate. - Abstract: Hydrogen storage in MgH{sub 2} is strongly limited by kinetic constraints, so that several additives have been considered in order to improve the rate of hydrogen desorption. The present work is devoted to investigate the effect of BaRuO{sub 3} addition on hydrogen absorption and desorption properties of MgH{sub 2}. BaRuO{sub 3} was prepared by solid-state synthesis of BaO and Ru in oxidizing environment. The interaction of as-prepared BaRuO{sub 3} with hydrogen at room temperature was examined by thermal desorption and X-ray diffraction experiments, showing that BaRuO{sub 3} has the ability to uptake hydrogen in the bulk. The hydrogen interaction is discussed with respect to octahedral ruthenium local environment present in the oxide structure. Addition of 1 mol.% BaRuO{sub 3} to MgH{sub 2} was performed by ball milling. Hydrogen desorption properties were investigated by Sievert and DSC, connected with a H{sub 2} detector. The H{sub 2} desorbed from of the nano-structured materials is lower than the theoretical content in MgH{sub 2}, due to the presence of a non-reactive MgO layer. A remarkable increase of the H{sub 2} desorption kinetics in nano-structured MgH{sub 2} was observed with respect to bare MgH{sub 2}. The activation energy for hydrogen desorption from MgH{sub 2}/BaRuO{sub 3} mixture was estimated by Arrhenius and Kissinger methods and a value around 130 kJ mol{sup -1} and 90 kJ mol{sup -1} was obtained

  9. Catalytically Enhanced Hydrogen Sorption in Mg-MgH2 by Coupling Vanadium-Based Catalyst and Carbon Nanotubes

    Science.gov (United States)

    Kadri, Atikah; Jia, Yi; Chen, Zhigang; Yao, Xiangdong

    2015-01-01

    Mg (MgH2)-based composites, using carbon nanotubes (CNTs) and pre-synthesized vanadium-based complex (VCat) as the catalysts, were prepared by high-energy ball milling technique. The synergistic effect of coupling CNTs and VCat in MgH2 was observed for an ultra-fast absorption rate of 6.50 wt. % of hydrogen per minute and 6.50 wt. % of hydrogen release in 10 min at 200 °C and 300 °C, respectively. The temperature programmed desorption (TPD) results reveal that coupling VCat and CNTs reduces both peak and onset temperatures by more than 60 °C and 114 °C, respectively. In addition, the presence of both VCat and CNTs reduces the enthalpy and entropy of desorption of about 7 kJ/mol H2 and 11 J/mol H2·K, respectively, as compared to those of the commercial MgH2, which ascribe to the decrease of desorption temperature. From the study of the effect of CNTs milling time, it is shown that partially destroyed CNTs (shorter milling time) are better to enhance the hydrogen sorption performance.

  10. On dislocation glide in MgSiO3 bridgmanite at high-pressure and high-temperature

    Science.gov (United States)

    Kraych, Antoine; Carrez, Philippe; Cordier, Patrick

    2016-10-01

    Dislocation glide in MgSiO3 bridgmanite with Pbnm perovskite structure is modeled at 30 and 60 GPa for the [100](010) and [010](100) slip systems. The velocity of screw dislocations is calculated in the thermally activated regime based on the kink-pair mechanism. We show that the dislocation velocity determination can rely on the atomic scale calculations of a limited amount of parameters: the Peierls stress τp, and the formation enthalpy of a single kink Hk. From the dislocation velocities, the evolution of stress as a function of temperature can be derived from the Orowan equation at any strain rate. Calculations performed at laboratory strain-rates of 10-5 s-1 reproduce well the high stress levels found experimentally. This demonstrates the influence of lattice friction in the mechanical properties of bridgmanite. The same calculations are performed at mantle strain-rate (10-16 s-1). They demonstrate that in the lower mantle, bridgmanite would always be in the thermally activated regime and that stresses close to 1 GPa are still necessary to move dislocations in bridgmanite. In the uppermost lower mantle, dislocation glide is inhibited and other deformation mechanisms, involving diffusion, are needed.

  11. The Dependence of Creep Behavior on Elemental Partitioning in Mg-5Al-3Ca- xSn Alloys

    Science.gov (United States)

    TerBush, Jessica R.; Chen, Olivia H.; Jones, J. Wayne; Pollock, Tresa M.

    2012-09-01

    Cast Mg-5Al-3Ca- xSn alloys have been examined to investigate the effect of Sn additions on elemental partitioning during solidification, microstructure development, and compressive creep behavior at 453 K (180 °C). Alloys containing 0.25 to 3.0 wt pct Sn were cast with a permanent mold technique. The addition of 0.75 to 1.0 wt pct Sn had a beneficial effect on Ca partitioning to the α-Mg phase. Additions beyond 1 wt pct Sn resulted in the formation of an orthorhombic Mg-Ca-Sn phase, with decreased Ca partitioning to the α-Mg. A lower minimum creep rate was observed for the Mg-5Al-3Ca- xSn alloy with increased Ca partitioning. Consistent with this finding, analyses that consider the influence of solute and precipitation strengthening on creep in Mg-5Al-3Ca- xSn alloys suggest that Ca in the α-Mg contributes to a greater degree than Al in solution to the creep resistance at 453 K (180 °C).

  12. First principle calculations for improving desorption temperature in Mg16H32 doped with Ca, Sr and Ba elements

    Indian Academy of Sciences (India)

    M Bhihi; M Lakhal; S Naji; H Labrim; A Belhaj; A Benyoussef; A Elkenz; M Loulidi; B Khalil; O Mounkachi; M Abdellaoui; E K Hlil

    2014-12-01

    Using ab initio calculations, we predict the improvement of the desorption temperature and the hydrogen storage properties of doped Mg-based hydrides such as,Mg15AMH32 (AM = Ca, Sr and Ba) as a super cell 2 × 2 × 2 of MgH2. In particular, the electronic structure has been obtained numerically using the all-electron full-potential local-orbital minimum-basis scheme FPLO9.00-34. Then, we discuss the formation energy calculations in terms of the material stabilities and the hydrogen storage thermodynamic properties improvements. Among others, we find that the stability and the temperature of desorption decrease without reducing significantly the high storage capacity of hydrogen. Moreover, it has been observed that such a doping procedure does not affect the electronic behavior as seen in MgH2, including the insulator state in contrast with the transition metal hydrides, which modify the electronic structure of pure MgH2.

  13. Low viscosity and high attenuation in MgSiO3 post-perovskite inferred from atomic-scale calculations

    Science.gov (United States)

    Goryaeva, Alexandra M.; Carrez, Philippe; Cordier, Patrick

    2016-10-01

    This work represents a numerical study of the thermal activation for dislocation glide of the [100](010) slip system in MgSiO3 post-perovskite (Mg-ppv) at 120 GPa. We propose an approach based on a one-dimensional line tension model in conjunction with atomic-scale calculations. In this model, the key parameters, namely, the line tension and the Peierls barrier, are obtained from density functional theory calculations. We find a Peierls stress σp = 2.1 GPa and a line tension Γ = 9.2 eV/Å, which lead to a kink-pair enthalpy (under zero stress) of 2.69 eV. These values confirm that this slip system bears a very low lattice friction because it vanishes for temperatures above approximately 500 K under mantle conditions. In the Earth’s mantle, high-pressure Mg-ppv silicate is thus expected to become as ductile as ferropericlase. These results confirm the hypothesis of a weak layer in the D″ layer where Mg-ppv is present. Easy glide along [100](010) suggests strong preferred orientations with (010) planes aligned. Highly mobile [100] dislocations are also likely to respond to stresses related to seismic waves, leading to energy dissipation and strong attenuation.

  14. Simulation Study on Understanding the Spin Transport in MgO Adsorbed Graphene Based Magnetic Tunnel Junction

    Science.gov (United States)

    Raturi, Ashish; Choudhary, Sudhanshu

    2016-11-01

    First principles calculations of spin-dependent electronic transport properties of magnetic tunnel junction (MTJ) consisting of MgO adsorbed graphene nanosheet sandwiched between two CrO2 half-metallic ferromagnetic (HMF) electrodes is reported. MgO adsorption on graphene opens bandgap in graphene nanosheet which makes it more suitable for use as a tunnel barrier in MTJs. It was found that MgO adsorption suppresses transmission probabilities for spin-down channel in case of parallel configuration (PC) and also suppresses transmission in antiparallel configuration (APC) for both spin-up and spin-down channel. Tunnel magneto-resistance (TMR) of 100% is obtained at all bias voltages in MgO adsorbed graphene-based MTJ which is higher than that reported in pristine graphene-based MTJ. HMF electrodes were found suitable to achieve perfect spin filtration effect and high TMR. I-V characteristics for both parallel and antiparallel magnetization states of junction are calculated. High TMR suggests its usefulness in spin valves and other spintronics-based applications.

  15. The elastic properties, generalized stacking fault energy and dissociated dislocations in MgB2 under different pressure

    KAUST Repository

    Feng, Huifang

    2013-05-31

    The 〈112̄0〉 perfect dislocation in MgB2 is suggested to dissociate into two partial dislocations in an energy favorable way 〈112̄0〉 → 1/2 〈112̄0〉 + SF + 1/2 〈112̄0〉. This dissociation style is a correction of the previous dissociation 〈1000〉 → 1/3 〈11̄00〉 SF + 1/3 〈 2100〉proposed by Zhu et al. to model the partial dislocations and stacking fault observed by transmission electron microscopy. The latter dissociation results in a maximal stacking fault energy rather than a minimal one according to the generalized stacking fault energy calculated from first-principles methods. Furthermore, the elastic constants and anisotropy of MgB2 under different pressure are investigated. The core structures and mobilities of the 〈112̄0〉 dissociated dislocations are studied within the modified Peierls-Nabarro (P-N) dislocation theory. The variational method is used to solve the modified P-N dislocation equation and the Peierls stress is also determined under different pressure. High pressure effects on elastic anisotropy, core structure and Peierls stress are also presented. © 2013 Springer Science+Business Media New York.

  16. Cannabinoid Receptor CB2 Is Involved in Tetrahydrocannabinol-Induced Anti-Inflammation against Lipopolysaccharide in MG-63 Cells

    Directory of Open Access Journals (Sweden)

    Lei Yang

    2015-01-01

    Full Text Available Cannabinoid Δ9-tetrahydrocannabinol (THC is effective in treating osteoarthritis (OA, and the mechanism, however, is still elusive. Activation of cannabinoid receptor CB2 reduces inflammation; whether the activation CB2 is involved in THC-induced therapeutic action for OA is still unknown. Cofilin-1 is a cytoskeleton protein, participating in the inflammation of OA. In this study, MG-63 cells, an osteosarcoma cell-line, were exposed to lipopolysaccharide (LPS to mimic the inflammation of OA. We hypothesized that the activation of CB2 is involved in THC-induced anti-inflammation in the MG-63 cells exposed to LPS, and the anti-inflammation is mediated by cofilin-1. We found that THC suppressed the release of proinflammatory factors, including tumor necrosis factor α (TNF-α, interleukin- (IL- 1β, IL-6, and IL-8, decreased nuclear factor-κB (NF-κB expression, and inhibited the upregulation of cofilin-1 protein in the LPS-stimulated MG-63 cells. However, administration of CB2 receptor antagonist or the CB2-siRNA, not CB1 antagonist AM251, partially abolished the THC-induced anti-inflammatory effects above. In addition, overexpression of cofilin-1 significantly reversed the THC-induced anti-inflammatory effects in MG-63 cells. These results suggested that CB2 is involved in the THC-induced anti-inflammation in LPS-stimulated MG-63 cells, and the anti-inflammation may be mediated by cofilin-1.

  17. Effect of Fe2O3 Addition in MgO-CaO Refractory on Desulfurization of Liquid Iron

    Institute of Scientific and Technical Information of China (English)

    WEI Yao-wu; LI Nan; CHEN Fang-yu

    2003-01-01

    The effects of Fe2O3 addition in MgO-CaO refractory on desulfurization of liquid iron were studied by SEM, EDA and chemical analysis. Fe2O3 of 1 % and 4 % were added to MgO-CaO refractory as the lining of graphite crucible in which 150 g iron powder with sulfur of 0.15 % was charged. It is found that when the sample is heated at 1 600 ℃ for 40 min, 60 min and 90 min, the addition with Fe2O3 of 1 % improves desulfurization greatly. However, the desulfurization ratio of the refractory with Fe2O3 addition of 4 % is less than that with Fe2O3 addition of 1 %. For the soaking time of 90 min, the desulfurization ratio is less than those of 40 min and 60 min. These phenomena were explained by the contrary roles of O2- and Fe2+ formed by reaction between liquid iron and Fe2O3 on desulfurization.

  18. Polarized neutron reflectivity study of perpendicular magnetic anisotropy in MgO/CoFeB/W thin films

    Science.gov (United States)

    Ambaye, Haile; Zhan, Xiao; Li, Shufa; Lauter, Valeria; Zhu, Tao

    In this work we study the origin of PMA in MgO/CoFeB/W trilayer systems using polarized neutron reflectivity. Recently, the spin Hall effect in the heavy metals, such as Pt and Ta, has been of significant interest for highly efficient magnetization switching of the ultrathin ferromagnets sandwiched by such a heavy metal and an oxide, which can be used for spintronic based memory and logic devices. Most work has focused on heavy-metal/ferromagnet/oxide trilayer (HM/FM/MO) structures with perpendicular magnetic anisotropy (PMA), where the oxide layer plays the role of breaking inversion symmetry .No PMA was found in W/CoFeB/MgO films. An insertion of Hf layer in between the W and CoFeB layers, however, has been found to create a strong PMA. Roughness and formation of interface alloys by interdiffusion influences the extent of PMA. We intend to identify these influences using the depth sensitive technique of PNR. In our previous study, we have successfully performed polarized neutron reflectometry (PNR) measurements on the Ta/CoFeB/MgO/CoFeB/Ta thin film with MgO thickness of 1 nm. The PNR measurements were carried out using the BL-4A Magnetic Reflectometer at SNS. This work has been supported by National Basic Research Program of China (2012CB933102). Research at SNS was supported by the Office of BES, DOE.

  19. Effects of Li doping on H-diffusion in MgH2: A first-principles study

    Science.gov (United States)

    Ming, Wenmei; Zak Fang, Zhigang; Liu, Feng

    2013-12-01

    The effects of Li doping in MgH2 on H-diffusion process are investigated, using first-principles calculations. We have identified two key effects: (1) The concentration of H vacancy in the +1 charge state (VH+1) can increase by several orders of magnitude upon Li doping, which significantly increases the vacancy mediated H diffusion rate. It is caused by the preferred charge states of substitutional Li in the -1 state (LiMg-1) and of interstitial Li in the +1 state (Lii+1), which indirectly reduce the formation energy of VH+1 by up to 0.39 eV depending on the position of Fermi energy. (2) The interaction between VH+1 and LiMg-1 is found to be attractive with a binding energy of 0.55 eV, which immobilizes the VH+1 next to LiMg-1 at high Li doping concentration. As a result, the competition between these two effects leads to large enhancement of H diffusion at low Li doping concentration due to the increased H-vacancy concentration, but only limited enhancement at high Li concentration due to the immobilization of H vacancies by too many Li.

  20. Catalytically Enhanced Hydrogen Sorption in Mg-MgH2 by Coupling Vanadium-Based Catalyst and Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Atikah Kadri

    2015-06-01

    Full Text Available Mg (MgH2-based composites, using carbon nanotubes (CNTs and pre-synthesized vanadium-based complex (VCat as the catalysts, were prepared by high-energy ball milling technique. The synergistic effect of coupling CNTs and VCat in MgH2 was observed for an ultra-fast absorption rate of 6.50 wt. % of hydrogen per minute and 6.50 wt. % of hydrogen release in 10 min at 200 °C and 300 °C, respectively. The temperature programmed desorption (TPD results reveal that coupling VCat and CNTs reduces both peak and onset temperatures by more than 60 °C and 114 °C, respectively. In addition, the presence of both VCat and CNTs reduces the enthalpy and entropy of desorption of about 7 kJ/mol H2 and 11 J/mol H2·K, respectively, as compared to those of the commercial MgH2, which ascribe to the decrease of desorption temperature. From the study of the effect of CNTs milling time, it is shown that partially destroyed CNTs (shorter milling time are better to enhance the hydrogen sorption performance.

  1. A variety of microstructures in Mg/Cu super-laminate composites caused by competitive reactions during hydrogenation

    Science.gov (United States)

    Tanaka, K.; Shibata, K.; Nishida, Y.; Kurumatani, K.; Kondo, R.; Kikuchi, S.; Takeshita, H. T.

    2015-04-01

    A variety of microstructures in Mg/Cu super-laminate composites (SLCs) caused by competitive reactions during hydrogenation has been shown experimentally. Two types of MgCu2 structures, three-dimensional (3-D) network and layer, were observed after initial hydrogenation of Mg/Cu SLCs under the conditions of 573K, 86.4ks in H2 of 3-3MPa. It was proposed that Mg/Cu SLCs could be hydrogenated by two kinds of processes. The one is alloying Mg with Cu to form Mg2Cu followed by hydrogenation of Mg2Cu, leading to the formation of 3-D network of MgCu2. The other is hydrogenation of Mg followed by the reaction of MgH2 to Cu, leading to the formation of layer MgCu2. SEM observations revealed that there existed Mg2Cu nano-crystals at the interface between Mg and Cu in as-rolled Mg/Cu SLCs, and layer MgCu2 at the interface between MgH2 and Cu in pellets of MgH2 powder and Cu powder heated under the conditions of 673K, 86.4ks in H2 of 8.0 MPa. The existence of Mg2Cu nano-crystals enables alloying Mg with Cu at low temperatures (<473K).

  2. 两种氧化方法对InSb探测器钝化效果的研究%Passivation of InSb detector with two oxide method

    Institute of Scientific and Technical Information of China (English)

    刘炜

    2013-01-01

    比较了阳极氧化和Photo-CVD氧化两种钝化方式制备InSb 探测器的性能,结果表明前者反偏漏电流小,击穿电压是后者的5倍,背景光电流和零偏阻抗基本相同。C-V测试结果:前者固定表面电荷密度为2×1011 cm-2,后者为1.5×1011 cm-2。两种氧化方法制备的器件经过高温高湿老化试验后,在反偏1 V时,阳极氧化器件漏电比变化率只有Photo-CVD氧化器件的50%,二者背景光电流均有增加,可能与器件光敏面扩大有关。阳极氧化钝化方法,工艺过程易于控制,钝化效果一致性较好,器件的界面状态更加稳定。%The performance of InSb detectors with a nodic oxide and photo-CVD oxide had been compared in this paper. It showed that leak current of detectosr with anodic oxide was less than those with photo-CVD oxide,and breakage voltage of the former detectors was as much as 5 times of the latter ones, but the photocurrent and impedance of the former ones was the same as the latter.The results of capacitance-voltage (C-V) characteristics showed that fixed charge density of the anodic detectors was 2í1011 cm-2, and the latter was 1.5í1011 cm-2. After ageing experiment, when inversion bias was 1 V, the change rate of leak current ratio of the former was only 50% of the latter, while the photocurrent of detectors with both methods increase,which was possible related to photosensitive area's expansion.The anodic oxide passivation of detector had the three advantage of the process control, the fabricate uniformity and the stability of interface state .

  3. Cyclic growth and branching phenomena of calcite grown in Mg(2+) containing solutions and in natural systems

    Science.gov (United States)

    Wiethoff, Felix; Richter, Detlef K.; Neuser, Rolf D.; Immenhauser, Adrian; Gies, Hermann; Schreuer, Jürgen

    2016-04-01

    Undulosity in calcites (radiaxial fibrous calcite (RFC) and fascicular-optic fibrous calcite (FOFC)) is a common phenomenon in paleozoic and mesozoic limestones. Despite their importance as archives for climate reconstruction the underlying mechanisms and processes of their formation are still poorly understood [1]. To improve the application of such archives for climate reconstruction a better knowledge of their formation and possible alteration scenarios is necessary. In Mg2+ containing gel based growth experiments calcite crystals develop pathological morphologies. The morphology can be described as a product of a geometrical selective branching process at the rhombohedral crystal faces. Multiple sheet like building blocks evolve at the branching crystal face; each slightly tilted in respect to their substrate. The product is a crystal aggregate consisting out of several misoriented sub domains. In polarized light thin section microscopy the extinction behaviour of these sub units resemble the optical undulosity of radiaxial fibrous cements. In a multi method approach the local Mg2+ concentration was measured using EMPA and compared with maps of the local crystal orientation (via electron backscatter diffraction (EBSD)) and thin section microscopy. We found that Mg2+ is enriched at the sub-domain boundaries and deduced that lattice misfit as a consequence of impurity incorporation causes the crystal branching. We propose that this process is cyclic and each new misoriented sheet represents a growth period after a phase of inhibited growth caused by crystal faces covered by Mg2+-ions. In comparison to natural systems we found that radiaxial-fibrous cave cements show a pathological morphology based on the same formation principles. [1] Richter et al. (2011) Sediment. Geol. 239, 23-36 [2] Reeder & Paquette (1989) Sediment. Geol. 65, 239-247 [3] Davis et al. (2004) Am. Min. 89, 714-720

  4. Annealing effect of thermal spike in MgO thin film prepared by cathodic vacuum arc deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Daoyun, E-mail: zhudy@gdut.edu.cn [Experiment Teaching Department, Guangdong University of Technology, Guangzhou 510006 (China); State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Zhao, Shoubai [School of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510400 (China); Zheng, Changxi; Chen, Dihu [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); He, Zhenhui, E-mail: stshzh@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China)

    2013-12-16

    MgO films were prepared by using pulsed cathodic vacuum arc deposition technique. The substrate bias voltage was in the range of −150 to −750 V. Film structure was investigated by X-ray diffraction (XRD). The annealing effect of thermal spike produced by the impacting of energetic ions was analyzed. The calculated results showed that the lifetime of a thermal spike generated by an energetic ion with the energy of 150 eV was less than one picosecond and it was sufficient to allow Mg{sup 2+} or O{sup 2-} to move one bond length to satisfy the intrinsic stress relief in the affected volume. The MgO(200) lattice spacings of the films deposited at different bias voltages were all larger than the ideal value of 2.1056 Å. As the bias amplitude increased the lattice spacing decreased, which indicated that the compressive stress in the film was partially relieved with increasing impacting ion energy. The stress relief also could be reflected from the film orientation with bias voltage. The biaxial elastic modulus for MgO(100), MgO(110) and MgO(111) planes were calculated and they were M{sub (100)} = 199 GPa, M{sub (110)} = 335 GPa and M{sub (111)} = 340 GPa, respectively. The M values indicated that the preferred orientation will be MgO(200) due to the minimum energy configuration when the lattice strain was large. It was confirmed by the XRD results in our experiments. - Highlights: • MgO thin films with preferred orientation were obtained by CVAD technique. • Annealing effect of a thermal spike in MgO film was discussed. • Lattice spacing of MgO film decreased with the increase of bias voltage. • Film preferred orientation changed from (200) to (220) as the bias voltage increased.

  5. On the Normative Evaluation and Presentation of Some Phenomena in Lithuanian Syntax: Cases of the Prepositional Construction tikėti į ką (Believe in sb. and Attributive Locative

    Directory of Open Access Journals (Sweden)

    Vidas Valskys

    2015-06-01

    Full Text Available The article is an analysis of issues concerning the relationship of the prepositional construction tikėti į ką (“believe in sb.” and the attributive locative with the codified language norm. On the basis of the polemic and insights by some linguists and theologists as well as the data of contemporary usage, it is argued in the article whether the phrase tikėti į Dievą (“believe in God” should reasonably be treated as a translation loanword, whether it does not possess distinctive semantics typical of the Christian discourse, due to which such a prepositional construction should rather be acknowledged as variant of the norm in Standard Lithuanian. The article also contains a discussion on some cases of expressing an attribute using the locative case, as they also have a nuance of location. Therefore, a question is raised whether they are reasonably attributed to syntactic phenomena that should be avoided in standard language.

  6. Comparison of optical transients during the picosecond laser pulse-induced crystallization of GeSbTe and AgInSbTe phase-change thin films: Nucleation-driven versus growth-driven processes

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Guangfei [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Li, Simian [State Key Laboratory of Optoelectronic Materials and Technology, Department of Physics, Sun Yat-Sen University, Guangzhou 510275 (China); Huang, Huan [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Wang, Yang, E-mail: ywang@siom.ac.cn [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Lai, Tianshu, E-mail: stslts@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technology, Department of Physics, Sun Yat-Sen University, Guangzhou 510275 (China); Wu, Yiqun [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2013-09-01

    Direct comparison of the real-time in-situ crystallization behavior of as-deposited amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} (GeSbTe) and Ag{sub 8}In{sub 14}Sb{sub 55}Te{sub 23} (AgInSbTe) phase-change thin films driven by picosecond laser pulses was performed by a time-resolved optical pump-probe technique with nanosecond resolution. Different optical transients showed various crystallization processes because of the dissimilar nucleation- and growth-dominated mechanisms of the two materials. The effects of laser pulse fluence, thermal conductive structure, and successive pulse irradiation on their crystallization dynamics were also discussed. A schematic was then established to describe the different crystallization processes beginning from the as-deposited amorphous state. The results may provide further insight into the phase-change mechanism under extra-non-equilibrium conditions and aid the development of ultrafast phase-change memory materials.

  7. Pinning and trapped field in MgB2- and MT-YBaCuO bulk superconductors manufactured under pressure

    Science.gov (United States)

    Prikhna, T.; Eisterer, M.; Chaud, X.; Weber, H. W.; Habisreuther, T.; Moshchil, V.; Kozyrev, A.; Shapovalov, A.; Gawalek, W.; Wu, M.; Litzkendorf, D.; Goldacker, W.; Sokolovsky, V.; Shaternik, V.; Rabier, J.; Joulain, A.; Grechnev, G.; Boutko, V.; Gusev, A.; Shaternik, A.; Barvitskiy, P.

    2016-03-01

    The relevant pinning centers of Abrikosov vortices in MgB2-based materials are oxygen-enriched Mg-B-O inclusions or nanolayers and inclusions of MgBx (x>4) phases. The high critical current densities, j c, of 106 and 103A/cm2 at 1 and 8.5 T, respectively, at 20 K can be achieved in polycrystalline materials (prepared at 2 GPa) containing a large amount of admixed oxygen. Besides, oxygen can be incorporated into the MgB2 structure in small amounts (MgB1.5O0.5), which is supported by Auger studies and calculations of the DOS and the binding energy. The j c of melt textured YBa2Cu3O7-δ (or Y123)-based superconductors (MT-YBaCuO) depends not only on the perfectness of texture and the amount of oxygen in the Y123 structure, but also on the density of twins and micro-cracks formed during the oxygenation (due to shrinking of the c-lattice parameter). The density of twins and microcracks increases with the reduction of the distance between Y2BaCuO5 (Y211) inclusions in Y123. At 77 K jc=8·104 A/cm2 in self-field and jc=103 A/cm2 at 10 T were found in materials oxygenated at 16 MPa for 3 days with a density of twins of 22–35 per µm (thickness of the lamellae: 45-30 nm) and a density of micro-cracks of 200–280 per mm. Pinning can occur at the points of intersection between the Y123 twin planes and the Y211 inclusions. MTYBaCuO at 77 K can trap 1.4 T (38×38×17 mm, oxygenated at 0.1 MPa for 20 days) and 0.8 T (16 mm in diameter and 10 mm thick with 0.45 mm holes oxygenated at 10 MPa for 53 h). The sensitivity of MgB2 to magnetic field variations (flux jumps) complicates estimates of the trapped field. At 20 K 1.8 T was found for a block of 30 mm in diameter and a thickness of 7.5 mm and 1.5 T (if the magnetic field was increased at a rate of 0.1 T) for a ring with dimensions 24×18 mm and a thickness of 8 mm.

  8. Using a CdTe detector for 125Te Mössbauer Spectroscopy: Application to the f-factor in Mg3TeO6

    Science.gov (United States)

    Bargholtz, Chr; Blomquist, J.; Fumero, E.; Mårtensson, L.; Einarsson, L.; Wäppling, R.

    2000-09-01

    An apparatus for Mössbauer spectroscopy has been developed with a cadmium telluride (CdTe) γ-ray detector. Complete data regarding γ-ray energy, source velocity, temperature and real time are stored for off-line analysis. The apparatus has been used to study the spectrum of 125Te in Mg 3TeO 6 at room temperature. The 35.5 keV transition of 125Te in Mg 3TeO 6 was found to have a recoil-free fraction f=0.392(5) corresponding to a Debye temperature θ=352(3) K.

  9. Advances and Achievements in In Situ Analysis of Corrosion and Structure–Property Relationship in Mg Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Orlov, D.; Joshi, V.

    2016-11-03

    Every year, TMS Magnesium Committee carefully selects a special topic in magnesium (Mg) related research and development not only having the hottest subject from both academic and industrial perspectives but also demonstrating major achievements within this subject. Following last year’s topic on Mg microallying [1], this year’s focus is on in-situ methods and associated techniques in their broad definition spanning from laboratory- to large- scale facilities to process monitoring. The applications of in-situ techniques have a wide spectrum from the analysis of melts and liquid-solid transitions to solid-state phenomena during thermo-mechanical processing and heat treatments to surface interactions with various environments. Therefore, such works are of significant interest to scientists working in the area of Mg alloy development as well as to a much broader audience from both academia and industry. This interest is primarily caused by challenges in the analysis of structure-property relationship in Mg alloys, and even cursory glance of literature reveals sharp increase of publications relevant to this topic recently. For instance, very high reactivity of Mg as well as its well-known propensity to substantially alter structure upon unloading in mechanical testing makes it difficult to understand and thus to simulate correlation between microstructures observed in post-mortem analysis and physical processes during testing or fabrication. However, recent advances in in-situ analysis based on large-scale research facilities such as neutron scattering and synchrotron radiation sources as well as microscopy-based, acoustic emission, and other more traditional techniques allowed significant achievements. Apart from apparent development of relevant experimental techniques, a significant part of this success should also be attributed to increasing accessibility of the facilities and simplification of their use from a user perspective. The selection of articles in this

  10. Structural and optical characterization of InAs/GaSb type-II superlattices: Influence of the change in InAs and GaSb layer thicknesses for fixed InSb-like interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Arikan, Bulent, E-mail: bulentarikanx@gmail.com; Korkmaz, Melih; Aslan, Bulent; Serincan, Uğur

    2015-08-31

    In this article, we report on the molecular beam epitaxy growth and characterization of a 140 period InAs/GaSb type-II superlattice structure designed for mid infrared detection. Thickness of a period was systematically altered in each sample by changing the thickness of InAs (GaSb) layers from 9 to 7 monolayers (ML) for a fixed GaSb (InAs) layer at 9 ML (7 ML). The same InSb-like strain compensation interface was used for all samples. High resolution X-ray diffraction analysis, spectral responsivity and external quantum efficiency (QE) measurements were performed to express the effects of layer thickness variations on both structural and photodetector features. The decrease in the InAs thickness resulted in the increased mismatch from 0 to + 1626 ppm and the blue shift in the 50% cut-off wavelength (λ{sub c}) from 5.41 to 4.36 μm at 77 K. The additional decrease in GaSb thickness caused further increase in the mismatch up to + 1791 ppm. The steepness of the photoresponse at the absorption band edge was quantified and presented comparatively with different photodetector parameters and material properties for a complete picture. The highest optical response was obtained from sample having 8 ML InAs and 9 ML GaSb with λ{sub c} = 4.76 μm and QE = 23.7% at 4 μm. - Highlights: • Detailed growth conditions for InAs/GaSb SLs designed for infrared detection • Precisely engineering the λ{sub c} and the ∆a{sub ⊥}/a by controlling the SL layer thicknesses • InAs layer thickness changes are more effective than the GaSb on the λ{sub c} and ∆a{sub ⊥}/a.

  11. Effect of Mg and C contents in MgCNi3, and structure and superconductivity of MgCNi3-xCox

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The effect of Mg and C contents on TC in MgCNi3, and structure and superconductivity of MgCNi3-xCox were studied. It is found that the excess of Mg and C in initial material mixture is favorable to improvement in TC and helps to obtain single_phase samples. For preparing MgCNi3 superconductor, the optimum composition of starting materials is MgC1.45Ni3 with excess of Mg (20 wt.%) of the stoichiometric composition. In MgCNi3-xCox system, a continuous solid solution is formed, lattice parameter decreases slightly and TC decreases obviously with increasing x. A suppression of superconductivity is observed due to the substitution of Co (Mn) for Ni. The suppression effect is smaller for the substitution of Co than that of Mn.

  12. Patch test concentrations (doses in mg/cm(2) ) for the 12 non-mix fragrance substances regulated by European legislation

    DEFF Research Database (Denmark)

    Bruze, Magnus; Svedman, Cecilia; Andersen, Klaus Ejner;

    2012-01-01

    Background. According to EU legislation, 26 fragrance substance allergens must be labelled on cosmetic products. For 12 of them, the optimal patch test concentration/dose has not been evaluated. Objectives. To establish the optimal patch test doses in mg/cm(2) for the 12 fragrance substances......, it is recommended that half of the maximum patch test dose (mg/cm(2) ) be used for aimed and screening patch testing....

  13. Decaying shock studies of phase transitions in MgO-SiO2 systems: Implications for the super-Earths' interiors

    Science.gov (United States)

    Bolis, R. M.; Morard, G.; Vinci, T.; Ravasio, A.; Bambrink, E.; Guarguaglini, M.; Koenig, M.; Musella, R.; Remus, F.; Bouchet, J.; Ozaki, N.; Miyanishi, K.; Sekine, T.; Sakawa, Y.; Sano, T.; Kodama, R.; Guyot, F.; Benuzzi-Mounaix, A.

    2016-09-01

    We report an experimental study of the phase diagrams of MgO, MgSiO3, and Mg2SiO4 at high pressures. We measured the shock compression response, including pressure-temperature Hugoniot curves of MgO, MgSiO3, and Mg2SiO4 between 0.2-1.2 TPa, 0.12-0.5 TPa, and 0.2-0.85 TPa, respectively, using laser-driven decaying shocks. A melting signature has been observed in MgO at 0.47 ± 0.04 TPa and 9860 ± 810 K, while no such phase changes were observed either in MgSiO3 or in Mg2SiO4. Increases of reflectivity of MgO, MgSiO3, and Mg2SiO4 liquids have been detected above 0.55 TPa (12760 K), 0.15 TPa (7540 K), 0.2 TPa (5800 K), respectively. In contrast to SiO2, melting and metallization of these compounds do not coincide, implying the presence of poorly electrically conducting liquids close to the melting lines. This has important implications for the generation of dynamos in super-Earth's mantles.

  14. Non-Debye heat capacity formula refined and applied to GaP, GaAs, GaSb, InP, InAs, and InSb

    Directory of Open Access Journals (Sweden)

    R. Pässler

    2013-08-01

    Full Text Available Characteristic non-Debye behaviors of low-temperature heat capacities of GaP, GaAs, GaSb, InP, InAs, and InSb, which are manifested above all in form of non-monotonic behaviors (local maxima of the respective Cp(T/T3 curves in the cryogenic region, are described by means of a refined version of a recently proposed low-to-high-temperature interpolation formula of non-Debye type. Least-mean-square fittings of representative Cp(T data sets available for these materials from several sources show excellent agreements, from the liquid-helium region up to room temperature. The results of detailed calculations of the respective material-specific Debye temperature curves, ΘD(T, are represented in graphical form. The strong, non-monotonic variations of ΘD(T values confirm that it is impossible to provide reasonable numerical simulations of measured Cp(T dependences in terms of fixed Debye temperatures. We show that it is possible to describe in good approximation the complete Debye temperature curves, from the cryogenic region up to their definitive disappearance (dropping to 0 in the high temperature region, by a couple of unprecedented algebraic formulas. The task of constructing physically adequate prolongations of the low-temperature Cp(T curves up to melting points was strongly impeded by partly rather large differences (up to an order of 10 J/(K·mol between the high-temperature data sets presented in different research papers and/or data reviews. Physically plausible criteria are invoked, which enabled an a priori rejection of a series of obviously unrealistic high-temperature data sets. Residual uncertainties for GaAs and InAs could be overcome by re-evaluations of former enthalpy data on the basis of a novel set of properly specified four-parameter polynomial expressions applying to large regions, from moderately low temperatures up to melting points. Detailed analytical and numerical descriptions are given for the anharmonicity

  15. Theory versus experiment for a family of single-layer compounds with a similar atomic arrangement: (Tl,X )/Si(111 )√{3 }×√{3 }(X =Pb,Sn,Bi,Sb,Te,Se)

    Science.gov (United States)

    Matetskiy, A. V.; Kibirev, I. A.; Mihalyuk, A. N.; Eremeev, S. V.; Gruznev, D. V.; Bondarenko, L. V.; Tupchaya, A. Y.; Zotov, A. V.; Saranin, A. A.

    2017-08-01

    Two-dimensional compounds made of one monolayer of Tl and one-third monolayer of Pb, Bi, Te, or Se (but not of Sn or Sb) on Si(111) have been found to have a similar atomic arrangement which can be visualized as a √{3 }×√{3 } -periodic honeycomb network of chained Tl trimers with atoms of the second adsorbate occupying the centers of the honeycomb units. Structural and electronic properties of the compounds have been examined in detail theoretically using density functional theory (DFT) calculations and experimentally using low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and angle-resolved photoelectron spectroscopy (ARPES) observations. It has been found that though structural parameters of the compounds are very similar for all species, the only common feature of their band structure is a considerable spin-splitting of the surface-state bands, while other basic electronic properties vary greatly with a change of species. The Tl-Pb compound is strongly metallic with two metallic surface-state bands; the Tl-Bi compound is also metallic but with a single metallic band; the Tl-Te and Tl-Se compounds appear to be insulators.

  16. Al-Si-Cu-Zn-X(X=Bi,Sb,Sr)压铸铝合金的显微组织、力学性能和腐蚀行为

    Institute of Scientific and Technical Information of China (English)

    Saeed FARAHANY[1; Ali OURDJ1NI[2; Hamid Reza BAKHSHESHI-RAD[3

    2016-01-01

    研究经Bi、Sb和Sr改性的Al-11Si-2Cu-0.80Zn压铸铝合金的显微组织演变、力学性能和腐蚀行为。力学性能测试结果表明,Bi、Sb和Sr的添加引起合金中共晶Si形貌发生改变,从而使合金的冲击韧性、极限抗拉强度和伸长率增加。断裂表面分析结果表明,添加Sr或少量Bi和Sb,合金表面呈韧性断裂,而非准解理脆性断裂。此外,添加Sr、Bi和Sb后,合金的质量指标由基体合金的102 MPa分别增加到164.7 MPa、156.3 MPa和152.6 MPa。在Na Cl溶液中的极化腐蚀测试结果表明,分别添加Sb、Bi和Sr后,合金的腐蚀电位负移。浸泡腐蚀实验结果表明,由于Al和Si共晶相界面的增加,Sb、Bi和Sr元素的添加对合金的腐蚀速率具有决定性作用。

  17. Study on the Characteristics of SiO2 Distribution and Silicate Phases in MgO—ZrO2 Composites

    Institute of Scientific and Technical Information of China (English)

    ZHUBoquan; GANFeifang; 等

    2000-01-01

    This work studied the characteristics of SiO2 distribution and structure of silicate phases in MgO-ZrO2 composites synthesizedby raw materials of light fired magnesite nd zircon,The results indicate that 30 wt%-40wt% SiO2 content in the system is existed in the form of crystalline of forsterite (M2S),the remaindering of SiO content (60wt%0-70wt%) is existed in the glass phase,The chemical composition of glass phase is well agreed with the chemical composition of monticellite(CMS).

  18. Controlled co-deposition of FePt nanoparticles embedded in MgO: a detailed investigation of structure and electronic and magnetic properties

    Science.gov (United States)

    D'Addato, S.; Grillo, V.; di Bona, A.; Luches, P.; Frabboni, S.; Valeri, S.; Lupo, P.; Casoli, F.; Albertini, F.

    2013-12-01

    Films of FePt nanoparticles (NPs) embedded in MgO were obtained by controlled co-deposition of FePt NPs pre-formed by a gas aggregation source and of Mg evaporated in an oxygen atmosphere. Assemblies of core-shell FePt@MgO NPs and films of FePt NPs embedded in MgO matrix could be obtained by varying FePt and Mg deposition rates. Transmission electron microscopy (TEM) and high resolution-TEM revealed the core-shell structure of the NPs, with an FePt core (of average diameter = 4.75 nm) presenting a multitwinned icosahedral structure, and MgO partially in crystalline form. The functional effect of the MgO shell in shielding the FePt core from external oxidation was shown with XPS. Upon controlled annealing, a transition from A1 to L10 ordering could be obtained, with structural and morphological re-arrangement. The magnetic hysteresis loops obtained from alternating gradient field magnetometry at room temperature show a ‘wasp-waist’ shape, with small values of coercive field (Hc = 300-1400 Oe), decreasing at increasing amounts of co-deposited MgO.

  19. Serum from patients with ankylosing spondylitis can increase PPARD, fra-1, MMP7, OPG and RANKL expression in MG63 cells.

    Science.gov (United States)

    Hu, Zaiying; Lin, Dongfang; Qi, Jun; Qiu, Minli; Lv, Qing; Li, Qiuxia; Lin, Zhiming; Liao, Zetao; Pan, Yunfeng; Jin, Ou; Wu, Yuqiong; Gu, Jieruo

    2015-11-01

    To explore the effects of serum from patients with ankylosing spondylitis on the canonical Wnt/β-catenin pathway and to assess whether the serum has an osteogenic effect in MG63 cells. MG63 cells were cultured with serum from 45 ankylosing spondylitis patients, 30 healthy controls, or 45 rheumatoid arthritis patients. The relative PPARD, fra-1, MMP7, OPG and RANKL mRNA levels were measured using quantitative real-time polymerase chain reaction. Associations between gene expression and patient demographics and clinical assessments were then analyzed. MG63 cells treated with serum from ankylosing spondylitis patients had higher PPARD, fra-1, MMP7 and OPG gene expression than did cells treated with serum from controls or rheumatoid arthritis patients (all pankylosing spondylitis or rheumatoid arthritis than in those treated with serum from controls (both pankylosing spondylitis patients than in those treated with serum from controls (p0.05). Serum from ankylosing spondylitis patients increases PPARD, fra-1, MMP7, OPG and RANKL expression and the OPG/RANKL ratio in MG63 cells; these effects may be due to the stimulatory effect of the serum on the Wnt pathway.

  20. Controlled co-deposition of FePt nanoparticles embedded in MgO: a detailed investigation of structure and electronic and magnetic properties.

    Science.gov (United States)

    D'Addato, S; Grillo, V; di Bona, A; Luches, P; Frabboni, S; Valeri, S; Lupo, P; Casoli, F; Albertini, F

    2013-12-13

    Films of FePt nanoparticles (NPs) embedded in MgO were obtained by controlled co-deposition of FePt NPs pre-formed by a gas aggregation source and of Mg evaporated in an oxygen atmosphere. Assemblies of core-shell FePt@MgO NPs and films of FePt NPs embedded in MgO matrix could be obtained by varying FePt and Mg deposition rates. Transmission electron microscopy (TEM) and high resolution-TEM revealed the core-shell structure of the NPs, with an FePt core (of average diameter (d) = 4.75 nm) presenting a multitwinned icosahedral structure, and MgO partially in crystalline form. The functional effect of the MgO shell in shielding the FePt core from external oxidation was shown with XPS. Upon controlled annealing, a transition from A1 to L10 ordering could be obtained, with structural and morphological re-arrangement. The magnetic hysteresis loops obtained from alternating gradient field magnetometry at room temperature show a 'wasp-waist' shape, with small values of coercive field (Hc = 300-1400 Oe), decreasing at increasing amounts of co-deposited MgO.

  1. Caryophyllene oxide exhibits anti-cancer effects in MG-63 human osteosarcoma cells via the inhibition of cell migration, generation of reactive oxygen species and induction of apoptosis

    Directory of Open Access Journals (Sweden)

    Zheng Pan

    2016-12-01

    Full Text Available The main objective of the present study was to evaluate the antitumor and apoptotic effects of caryophyllene oxide in MG-63 human osteosarcoma cells. Cell viability of these cells was evaluated by MTT assay while as in vitro wound healing assay was used to study the effect of caryophyllene oxide on cell migration. Fluorescence microscopy and transmission electron microscopy were used to study the changes in cell morphology once the cells undergo apoptosis. Caryophyllene oxide significantly led to cytotoxicity in MG-63 cells showing dose-dependent as well as time-dependent effects. Caryophyllene oxide led to an inhibition of wound closure significantly. At caryophyllene oxide doses of 20, 80 and 120 µM, the percentage of cell migration was shown to be 94.2, 67.1 and 14.8% respectively. With an increase in the caryophyllene oxide dose, the extent of apoptosis also increased characterized by cellular shrinkage, membrane blebbing, chromatin condensation and apoptotic body formation.

  2. Differential electron scattering cross sections for the first optically forbidden and resonance transitions in Mg II, Zn II and Cd II

    Science.gov (United States)

    Williams, I. D.; Chutjian, A.; Mawhorter, R. J.

    1986-01-01

    Differential electron scattering cross sections have been measured for dipole-forbidden and resonance transitions in Mg II, Zn II and Cd II in the angular range theta = 4-17 deg at 50 eV. These provide the first recorded angular distributions for an optically forbidden transition. It is found that while the cross section for excitation of the 4s (2)S-3d(9)4s(2) (2)D transition in Zn II is small, those for the 3s (2)S-3d (2)D, 4s (2)S (unresolved lines) in Mg II, and the 5s (2)S-4d(9)5s(2) D in Cd II are comparable in magnitude with the cross sections for resonance excitation. In addition, for Cd II it is found that the allowed and forbidden transitions have very similar angular distributions, and it is proposed that excitation to the 2D state may be dominated by a virtual 'double-dipole' transition via the 2P state. Also, the total excitation cross section of the resonance 2P state in Cd II is a factor of four higher than that predicted by the Gaunt factor approximation, suggesting that the accepted value for the oscillator strength may be too low.

  3. 波段外激光辐照光导型InSb探测器的一种新现象%A new phenomenon of photoconductive InSb detector under the irradiation of out-band laser

    Institute of Scientific and Technical Information of China (English)

    郑鑫; 江天; 程湘爱; 江厚满; 陆启生

    2012-01-01

    A new phenomenon is observed when a photoconductive InSb detector with 0.228eV band gap is irradiated by 10.6μm laser, whose photon energy is 0.12 eV.The detector is heated by this out-band laser,due to the absorption of laser energy.However,a transformation temperature To exists in this process.When the temperature of the detector,T,is lower than To,the number of carriers remains constant but the conductivity changes because of a change in mobility.The mobility decreases with the increase of temperature and varies as T~(2.35).At TTo,the concentration of thermally-activated carrier increases with temperature,which is proportional to exp(—E_g/2k_0T).As a result,the influence of carrier concentration becomes more and more important.As a result,the output of the detector decreases.In a word,the output voltage of photoconductive detector results from the temperature dependence of mobility and concentration of carriers.This work provides an experimental basis for improving the carrier transport model.%利用不同功率密度的10.6μm(光子能量为0.12 eV)连续激光辐照了禁带宽度为0.228 eV的光导型锑化铟探测器,得到了与以往报道不同的实验现象.当10.6μm波段外激光辐照光导型探测器时,探测器吸收激光能量后温度升高.在探测器的温升过程中,存在一个转变温度T_0.当探测器的温度T〈T_0时,载流子浓度基本不变,迁移率随温度的升高呈T~(-2.35)趋势下降,引起探测器的电导率减小,电阻增大,响应输出电压升高;当T〉T_0时,热激发载流子浓度随温度的升高呈指数增长,电阻急剧下降,超过了载流子迁移率降低对电阻的影响,响应输出急剧下降.光电导探测器在较高功率密度波段外激光辐照下的响应特性是载流子的浓度和迁移率在温度影响下相互作用的结果.这对进一步完善半导体内载流子输运模型提供了实验依据.

  4. Generalized Elliott-Yafet theory of electron spin relaxation in metals: origin of the anomalous electron spin lifetime in MgB2.

    Science.gov (United States)

    Simon, F; Dóra, B; Murányi, F; Jánossy, A; Garaj, S; Forró, L; Bud'ko, S; Petrovic, C; Canfield, P C

    2008-10-24

    The temperature dependence of the electron-spin relaxation time in MgB2 is anomalous as it does not follow the resistivity above 150 K; it has a maximum around 400 K and decreases for higher temperatures. This violates the well established Elliot-Yafet theory of spin relaxation in metals. The anomaly occurs when the quasiparticle scattering rate (in energy units) is comparable to the energy difference between the conduction and a neighboring bands. The anomalous behavior is related to the unique band structure of MgB2 and the large electron-phonon coupling. The saturating spin relaxation is the spin transport analogue of the Ioffe-Regel criterion of electron transport.

  5. Effect of metal-to-metal interface states on the electric-field modified magnetic anisotropy in MgO/Fe/non-magnetic metal

    Science.gov (United States)

    Guan, X. W.; Cheng, X. M.; Huang, T.; Wang, S.; Xue, K. H.; Miao, X. S.

    2016-04-01

    The impact of metal-to-metal interface on electric-field modified magnetic anisotropy in MgO/Fe/non-magnetic metal (Ta, Pt, Au) is revealed by density functional calculations. We demonstrate that the contribution from the metal-to-metal interface can be strong enough to dominate the electric field effect on magnetic anisotropy of Fe/MgO-based films, and the strain could also effectively tune the electric field effect. By analyzing the interface states by density of states and band structures, the dependence of the magnetoelectric effect on metal-to-metal interface is elucidated. These results are of considerable interest in the area of electric field controlled magnetic anisotropy and switching.

  6. Ionizing radiation effects in MgAl sub 2 O sub 4. Efecto de la radiacion ionizante en MgAl2 O4

    Energy Technology Data Exchange (ETDEWEB)

    Ibarra, A.

    1990-11-01

    The effect of ionizing radiation in MgAl{sub 2}O{sub 4} has been studied, paying special interest to the influence of the high concentration of intrinsic defects of this material. Optical absorption, ESR, photoluminescence, radioluminescence, and thermoluminescence are the main techniques used. The ionizing radiation induces formation of V centres. During the work its characteristics (structure, thermal stability, absorption spectra, etc.) has been studied. The thermoluminescence spectra allowed the discovery of several charge release processes between 85 and 650 K, all of them associated to electron release. The V-centres and several impurities (Cr, Mn,...) appear as recombination centres. The obtained data show that the kinetic of these charge release processes is regulated by the presence of a point defect with a very high concentration. This defect is an electron trap and its structure is an Al ion in a lattice site of tetrahedral symmetry. (Author)

  7. Orientation relationships between icosahedral clusters in hexagonal MgZn2 and monoclinic Mg4Zn7 phases in Mg-Zn(-Y) alloys

    Science.gov (United States)

    Rosalie, Julian M.; Somekawa, Hidetoshi; Singh, Alok; Mukai, Toshiji

    2011-07-01

    Intermetallic precipitates formed in heat-treated and aged Mg-Zn and Mg-Zn-Y alloys have been investigated via electron microscopy. Coarse spheroidal precipitates formed on deformation twin boundaries contained domains belonging to either the MgZn2 hexagonal Laves phase or the monoclinic Mg4Zn7 phase. Both phases are structurally related to the quasi-crystalline phase formed in Mg-Zn-Y alloys, containing icosahedrally coordinated zinc atoms arranged as a series of broad rhombohedral units. This rhombohedral arrangement was also visible in intragranular precipitates where local regions with the structures of hexagonal MgZn2 and Mg4Zn7 were found. The orientation adopted by the MgZn2 and Mg4Zn7 phases in twin-boundary and intragranular precipitates was such that the icosahedral clusters were aligned similarly. These results highlight the close structural similarities between the precipitates of the Mg-Zn-Y alloy system.

  8. X609, a novel manassantin A derivative, exhibits antitumor activity in MG-63 human osteosarcoma cells in vitro and in vivo.

    Science.gov (United States)

    Li, Ji; Zhao, Kongbo; Wang, Fu; Cai, Jinfang; Li, Zongyu; Zou, Lin

    2015-08-01

    Manassantin A has been well-established as an inhibitor of HIF-1. In the present study, a new manasantin A derivative, X609, with decreased stereochemical complexity, rendering it amenable to a simplified synthesis scheme, was synthesized and was found to increase HIF-1 inhibitory activity. X609 exhibited antiproliferative activity in a broad spectrum of tumor cell lines, via HIF-1-dependent mechanisms. X609 may induce apoptosis in MG-63 cells through activation of the mitochondrial pathway. Oral administration of X609 significantly inhibited the growth of human osteosarcomas implanted into nude mice. In light of the results of the present study, it may be possible to develop X609 for use as a novel antitumor agent, which targets human osteosarcoma.

  9. Dislocation modelling in Mg2SiO4 forsterite: an atomic-scale study based on the THB1 potential

    Science.gov (United States)

    Mahendran, S.; Carrez, P.; Groh, S.; Cordier, P.

    2017-07-01

    Knowledge of the deformation mechanisms of (Mg,Fe)2SiO4 olivine is important for the understanding of flow and seismic anisotropy in the Earth’s upper mantle. We report here a numerical modelling at the atomic scale of dislocation structures and slip system properties in Mg2SiO4 forsterite. Our study focuses on screw dislocations of [100] and [001] Burgers vectors. Computations are performed using the so-called THB1 empirical potential set for Mg2SiO4. Results of dislocation core structures highlight the primary importance of the (010) plane for [100] slip dislocations. For [001] dislocations, we confirm the occurrence of a stable narrow core that evolves into transient planar configurations to glide in (100) and (010). Such configurations suggest a locking-unlocking mechanism.

  10. Transition metal complexes coupled to vacancies in oxides: origin of different properties of Cr3+ in MgO bounded to a or Mg2+ vacancy.

    Science.gov (United States)

    Aramburu, J A; García-Fernández, P; Barriuso, M T; Moreno, M

    2013-11-27

    Despite the importance of vacancies over the properties of insulating oxides its influence on neighboring transition metal ions is far from being understood. This work is devoted to find the origin of various up to now unexplained properties of chromium bounded either to a or a Mg(2+) vacancy in MgO. In these model systems particular attention is paid to understand, by means of ab initio calculations, why the cubic field splitting parameter, 10Dq, is surprisingly 1600 cm(-1) higher for a than for a vacancy, a fact behind the suppression of the sharp (2)E → (4)A2 luminescence in the latter case. Our calculations, which reproduce the main experimental facts, prove that the average Cr(3+)-O(2-) distance is the same within 0.8% for both systems, and thus, the low 10Dq value for a vacancy is shown to be due mainly to the electrostatic potential from the missing Mg(2+) ion, which increases the energy of antibonding t(2g) (∼xy, xz, yz) levels. By contrast, for a Mg(2+) vacancy that potential provides a supplementary increase of the e(g) (∼x(2) - y(2), 3z(2 )- r(2)) level energy and thus of 10Dq. The existence of the (2)E → (4)A2 luminescence for Cr(3+)-doped MgO under perfect cubic symmetry or with a vacancy is shown to be greatly helped by the internal electric field created by the rest of the lattice ions on the CrO6(9-) unit, whose importance is usually ignored. The present results underline the role of ab initio calculations for unveiling the subtle effects induced by a close vacancy on the properties of transition metal ions in oxides. At the same time they stress the failure of the empirical superposition model for deriving the equilibrium geometry of C4v and C2v centers in MgO:Cr(3+).

  11. Testing epitaxial Co{sub 1.5}Fe{sub 1.5}Ge(001) electrodes in MgO-based magnetic tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Neggache, A. [Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, 54506 Vandoeuvre lès Nancy (France); Synchrotron SOLEIL-CNRS, L' Orme des Merisiers, Saint-Aubin BP48, 91192 Gif-sur-Yvette (France); Hauet, T.; Petit-Watelot, S.; Boulet, P.; Andrieu, S., E-mail: stephane.andrieu@univ-lorraine.fr [Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, 54506 Vandoeuvre lès Nancy (France); Bertran, F.; Le Fèvre, P.; Ohresser, P. [Synchrotron SOLEIL-CNRS, L' Orme des Merisiers, Saint-Aubin BP48, 91192 Gif-sur-Yvette (France); Devolder, T. [Institut d' Electronique Fondamentale, CNRS, UMR 8622, 91405 Orsay (France); Mewes, C. [Department of Physics and Astronomy/Center for Materials for Information Technology, University of Alabama, Tuscaloosa, Alabama 35487 (United States); Maat, S.; Childress, J. R. [San Jose Research Center, HGST, a Western Digital company, San Jose, California 95135 (United States)

    2014-06-23

    The ability of the full Heusler alloy Co{sub 1.5}Fe{sub 1.5}Ge(001) (CFG) to be a Half-Metallic Magnetic (HMM) material is investigated. Epitaxial CFG(001) layers were grown by molecular beam epitaxy. The results obtained using electron diffraction, X-ray diffraction, and X-ray magnetic circular dichroism are consistent with the full Heusler structure. The pseudo-gap in the minority spin density of state typical in HMM is examined using spin-resolved photoemission. Interestingly, the spin polarization found to be negative at E{sub F} in equimolar CoFe(001) is observed to shift to positive values when inserting Ge in CoFe. However, no pseudo-gap is found at the Fermi level, even if moderate magnetization and low Gilbert damping are observed as expected in HMM materials. Magneto-transport properties in MgO-based magnetic tunnel junctions using CFG electrodes are investigated via spin and symmetry resolved photoemission.

  12. The role of nano-Ni catalyst in MgH2 obtained by reactive mechanical milling method for solid hydrogen storage application

    Science.gov (United States)

    Jalil, Zulkarnain; Rahwanto, Adi; Handoko, Erfan; Mustanir

    2017-03-01

    Magnesium (Mg) is regarded as one of the candidate material for absorbing hydrogen, because theoretically, has the ability to absorb hydrogen in the large quantities (7.6 wt%). However, Mg has shortage, namely its kinetic reaction is very slow, it takes time to absorb hydrogen at least 60 minutes with very high operating temperatures (300-400°C). The aim of this study is to improve the hydrogen desorption temperature of Mg-based hydrogen storage material. In this work, we used nano-nickel (Ni) as catalyst in MgH2 and obtained by reactive mechanical milling method. The duration of milling was done in 2 hours (soft milling) with the 2 mol% Ni catalyst and milled under hydrogen atmosphere (10 bar). As the results, small amount of 2 mol% Ni in nanometer scale acts as a suitable catalyst for improvement the kinetics of MgH2 which could absorp 5.5 wt% of hydrogen within 10 minutes at 300°C. It is obvious that small amount has much better as catalyst in nanoparticle size and at the same time allowed to reduce the milling process in short time.

  13. Dendropanoxide induces autophagy through ERK1/2 activation in MG-63 human osteosarcoma cells and autophagy inhibition enhances dendropanoxide-induced apoptosis.

    Science.gov (United States)

    Lee, Ji-Won; Kim, Kyoung-Sook; An, Hyun-Kyu; Kim, Cheorl-Ho; Moon, Hyung-In; Lee, Young-Choon

    2013-01-01

    Anticancer effects of dendropanoxide (DP) newly isolated from leaves and stem of Dendropanax morbifera Leveille were firstly investigated in this study. DP inhibited cell proliferation and induced apoptosis in dose- and time-dependent manner in MG-63 human osteosarcoma cells, which was dependent on the release of cytochrome c to the cytosol and the activation of caspases. Moreover, the DP-treated cells exhibited autophagy, as characterized by the punctuate patterns of microtubule-associated protein 1 light chain 3 (LC3) by confocal microscopy and the appearance of autophagic vacuoles by MDC staining. The expression levels of ATG7, Beclin-1 and LC3-II were also increased by DP treatment. Inhibition of autophagy by 3-methyladenine (3-MA) and wortmannin (Wort) significantly enhanced DP-induced apoptosis. DP treatment also caused a time-dependent increase in protein levels of extracellular signal-regulated kinase 1 and 2 (ERK1/2), and inhibition of ERK1/2 phosphorylation with U0126 resulted in a decreased DP-induced autophagy that was accompanied by an increased apoptosis and a decreased cell viability. These results indicate a cytoprotective function of autophagy against DP-induced apoptosis and suggest that the combination of DP treatment with autophagy inhibition may be a promising strategy for human osteosarcoma control. Taken together, this study demonstrated for the first time that DP could induce autophagy through ERK1/2 activation in human osteosarcoma cells and autophagy inhibition enhanced DP-induced apoptosis.

  14. Dendropanoxide induces autophagy through ERK1/2 activation in MG-63 human osteosarcoma cells and autophagy inhibition enhances dendropanoxide-induced apoptosis.

    Directory of Open Access Journals (Sweden)

    Ji-Won Lee

    Full Text Available Anticancer effects of dendropanoxide (DP newly isolated from leaves and stem of Dendropanax morbifera Leveille were firstly investigated in this study. DP inhibited cell proliferation and induced apoptosis in dose- and time-dependent manner in MG-63 human osteosarcoma cells, which was dependent on the release of cytochrome c to the cytosol and the activation of caspases. Moreover, the DP-treated cells exhibited autophagy, as characterized by the punctuate patterns of microtubule-associated protein 1 light chain 3 (LC3 by confocal microscopy and the appearance of autophagic vacuoles by MDC staining. The expression levels of ATG7, Beclin-1 and LC3-II were also increased by DP treatment. Inhibition of autophagy by 3-methyladenine (3-MA and wortmannin (Wort significantly enhanced DP-induced apoptosis. DP treatment also caused a time-dependent increase in protein levels of extracellular signal-regulated kinase 1 and 2 (ERK1/2, and inhibition of ERK1/2 phosphorylation with U0126 resulted in a decreased DP-induced autophagy that was accompanied by an increased apoptosis and a decreased cell viability. These results indicate a cytoprotective function of autophagy against DP-induced apoptosis and suggest that the combination of DP treatment with autophagy inhibition may be a promising strategy for human osteosarcoma control. Taken together, this study demonstrated for the first time that DP could induce autophagy through ERK1/2 activation in human osteosarcoma cells and autophagy inhibition enhanced DP-induced apoptosis.

  15. Vacancy-type defects in Mg-doped GaN grown by ammonia-based molecular beam epitaxy probed using a monoenergetic positron beam

    Science.gov (United States)

    Uedono, Akira; Malinverni, Marco; Martin, Denis; Okumura, Hironori; Ishibashi, Shoji; Grandjean, Nicolas

    2016-06-01

    Vacancy-type defects in Mg-doped GaN were probed using a monoenergetic positron beam. GaN films with a thickness of 0.5-0.7 μm were grown on GaN/sapphire templates using ammonia-based molecular beam epitaxy and characterized by measuring Doppler broadening spectra. Although no vacancies were detected in samples with a Mg concentration [Mg] below 7 × 1019 cm-3, vacancy-type defects were introduced starting at above [Mg] = 1 × 1020 cm-3. The major defect species was identified as a complex between Ga vacancy (VGa) and multiple nitrogen vacancies (VNs). The introduction of vacancy complexes was found to correlate with a decrease in the net acceptor concentration, suggesting that the defect introduction is closely related to the carrier compensation. We also investigated Mg-doped GaN layers grown using In as the surfactant. The formation of vacancy complexes was suppressed in the subsurface region (≤80 nm). The observed depth distribution of defects was attributed to the thermal instability of the defects, which resulted in the introduction of vacancy complexes during the deposition process.

  16. Effect of H2O on Upper Mantle Phase Transitions in MgSiO3: is the Seismic X-discontinuity an Indicator of Mantle Water Content

    Energy Technology Data Exchange (ETDEWEB)

    S Jacobsen; Z Liu; T Boffa Ballaran; E Littlefield; L Ehm; R Hemley

    2011-12-31

    The mantle X-discontinuity, usually assigned to positive seismic velocity reflectors in the 260-330 km depth range, has proved difficult to explain in terms of a single mineralogical phase transformation in part because of its depth variability. The coesite to stishovite transition of SiO{sub 2} matches deeper X-discontinuity depths but requires 5-10% free silica in the mantle to match observed impedance contrast. The orthoenstatite (OEn) to high-pressure clinoenstatite (HPCen) transformation of MgSiO{sub 3} also broadly coincides with depths of the X but requires chemically depleted and orthoenstatite-rich lithology at 300 km depth in order to match observed seismic impedance contrast. On the basis of high-pressure infrared spectroscopy, X-ray diffraction, and Raman spectroscopy, we show that 1300 ppm variation of H{sub 2}O content in MgSiO{sub 3} can displace the transition of low-pressure clinoenstatite (LPCen) to HPCen by up to 2 GPa, similar to previous quench experiments on the OEn to HPCen phase transition, where about 30-45 km (1.0-1.5 GPa) of deflection could occur per 0.1 wt% H{sub 2}O. If the mantle X-discontinuity results from pyroxene transitions in a depleted harzburgite layer, because of the strong influence of minor amounts of water on the transformation boundary, the depth of the mantle X-discontinuity could serve as a potentially sensitive indicator of water content in the uppermantle.

  17. Tuning the carrier concentration using Zintl chemistry in Mg3Sb2, and its implications for thermoelectric figure-of-merit.

    Science.gov (United States)

    Bhardwaj, A; Chauhan, N S; Goel, S; Singh, Vijeta; Pulikkotil, J J; Senguttuvan, T D; Misra, D K

    2016-02-17

    Zintl compounds are potential candidates for efficient thermoelectric materials, because typically they are small band gap semiconductors. In addition, such compounds allow fine tuning of the carrier concentration by chemical doping for the optimization of thermoelectric performance. Herein, such tunability is demonstrated in Mg3Sb2-based Zintl compounds via Zn(2+) doping at the Mg(2+) site of the anionic framework (Mg2Sb2)(2-), in the series Mg3-xZnxSb2 (0 ≤ x ≤ 0.1). The materials have been successfully synthesized using the spark plasma sintering (SPS) technique. X-ray diffraction (XRD) analysis confirms a single solid solution phase of Mg3-xZnxSb2 (0 ≤ x ≤ 0.1). The thermoelectric properties are characterized by the Seebeck coefficient, electrical conductivity, and thermal conductivity measurements from 323 K to 773 K. Isoelectronic Zn substitution at the Mg site presents the controlled variation in the carrier concentration for optimizing the high power factor and reduced thermal conductivity. These results lead to a substantial increase in ZT of 0.37 at 773 K for a composition with x = 0.10 which is ∼42% higher than undoped Mg3Sb2. The electronic transport data for the Mg3-xZnxSb2 (0 ≤ x ≤ 0.1) compound are analyzed using a single parabolic band model predicting that Mg2.9Zn0.1Sb2 exhibits a near-optimal carrier concentration for high ZT. The electronic structure of transport properties of these disordered Mg3-xZnxSb2 (0 ≤ x ≤ 0.1) is also studied using density functional theory and the results obtained are in good agreement with experimental results. The low cost, lightness and non-toxicity of the constituent elements make these materials ideal for mid-temperature thermoelectric applications.

  18. Fabrication and Evaluation of InSb CID Arrays

    Science.gov (United States)

    1976-08-01

    types of pulses , which can be used as outputs on a capacitive load - for example, the gate of a decoder transistor. This feature adds con...output, like V, and V6. It is remarkable that these different types of pulses result from choosing different tapping locations in the scanner

  19. Electrical switching in Sb doped Al23Te77 glasses

    Science.gov (United States)

    Pumlianmunga; Ramesh, K.

    2017-08-01

    Bulk glasses (Al23Te77)Sbx (0≤ x≤10) prepared by melt quenching method show a change in switching type from threshold to memory for x≥5. An increase in threshold current (Ith) and a concomitant decrease in threshold voltage (Vth) and resisitivity(ρ) have been observed with the increase of Sb content. Raman spectra of the switched region in memory switching compositions show a red shift with respect to the as prepared glasses whereas in threshold switching compositions no such shift is observed. The magic angle spinning nuclear magnetic resonance (MAS NMR) of 27Al atom shows three different environments for Al ([4]Al, [5]Al and [6]Al). The samples annealed at their respective crystallization temperatures show rapid increase in [4]Al sites by annihilating [5]Al sites. The melts of threshold switching glasses (x≤2.5) quenched in water at room temperature (27 °C) show amorphous structure whereas, the melt of memory switching glasses (x>2.5) solidify into crystalline structure. The higher coordination of Al increases the cross-linking and rigidity. The addition of Sb increases the glass transition(Tg) and decreases the crystallization temperature(Tc). The decrease in the interval between the Tg and Tc eases the transition between the amorphous and crystalline states and improves the memory properties. The temperature rise at the time of switching can be as high as its melting temperature and the material in between the electrodes may melt to form a filament. The filament may consists of temporary (high resistive amorphous) and permanent (high conducting crystalline) units. The ratio between the temporary and the permanent units may decide the switching type. The filament is dominated by the permanent units in memory switching compositions and by the temporary units in threshold switching compositions. The present study suggests that both the threshold and memory switching can be understood by the thermal model and filament formation.

  20. Viscosity of In and In-Sb alloys

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The dynamic viscosity of pure In, In-1%Sb (mass fraction, so as the follows) alloy, In-55%Sb hypoeutectic alloyand In-69.5%Sb eutectic alloy was measured by using a torsional oscillation viscometer at different temperatures above liq-uidus. The experimental results show that the viscosity of these melts decreases with increasing temperature. The anomalouschange of viscosity occurs at about 430 and 470℃ in pure In melt. The variation of viscosity with temperature well meetsexponential correlation and no anomalous change occurs in measured temperature range in the In-1%Sb alloy melt. A tran-sition occurs at about 800℃ in both of In-55%Sb and In-69.5%Sb alloy melts. The sudden change of viscosity suggests thestructure change of melts. DSC (differential scanning calorimetry) curves of In-1%Sb alloy during heating and cooling weremeasured, and the results show that no structural variation in In-1%Sb alloy melt was testified further. In addition, the vis-cosity of In melt decreases with the addition of 1%Sb.

  1. Superconductivity in MgB2

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In January of 2001 the superconductivity of the compound MgB2 with a critical temperature Tc of up to 39 K was discovered. This Tc is the highest in all intermetallic compound and alloy superconductors. MgB2 has a simple structure and its manufacturing capital cost is lower, therefore it could become a practical superconductor in the future. The recent progress is reviewed here which covers the progress in electronic structure, high Tc mechanism, superconducting parameters (Debye temperature, specific heat coefficient of electron, critical fields, coherent length, penetration depth, energy gap, critical current and relaxation rate of flux). Moreover the issue on power transmission is discussed.

  2. Magnetocaloric phenomena in Mg-ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Burianova, S; Holec, P; Plocek, J [Charles University, Faculty of Science, Department of Inorganic chemistry, Prague (Czech Republic); Poltierova-Vejpravova, J, E-mail: burianovasimona@email.c, E-mail: jana@mag.mff.cuni.c

    2010-01-01

    A comparative study of magnetocaloric effect (MCE) in superparamagnetic (SPM) regime is reported in two different types of magnesium ferrite nanostructures. The samples were prepared either by microemulsion method as MgFe{sub 2}O{sub 4} nanoparticles encapsulated in amorphous SiO{sub 2}, or as matrix-less nanoparticles using hydrothermal synthesis in supercritical water conditions. The particle diameter in all prepared samples was obtained from XRD measurements and TEM analysis. All samples show a SPM behavior above the blocking temperature, T{sub B}. The entropy change, {Delta}S was finally derived from the measurements of magnetization, M(H,T) curves at defined temperature intervals. We observed, that all samples show a broad peak of {Delta}S in the temperature range that is fairly above the T{sub B}. The values of the {Delta}S also depend on the particle size, and they are of about two orders lower than those reported in the famous giant magnetocaloric materials.

  3. Phase equilibrium in Mg-Cu-Y

    Science.gov (United States)

    Mezbahul-Islam, Mohammad; Medraj, Mamoun

    2013-10-01

    Magnesium-based bulk metallic glasses (BMG) have potential in applications ranging from biomedical to sports equipment and the Mg-Cu-Y system offers some of the most promising alloys. Phase relations and ternary solubility of the binary and ternary compounds of this system have been experimentally investigated. The Isothermal section of Mg-Cu-Y system at 673 K for the entire composition range has been constructed. Phase relations in the Cu-rich (>66 at.% Cu) region of the Mg-Cu-Y system has been determined for the first time. The homogeneity range of three ternary compounds has been determined. Solidifications behavior of several key alloys have been discussed based on the differential scanning calorimetry (DSC) experiments and thermodynamic calculations. Extensive analysis of the DSC curves has been carried out to relate them to the corresponding phase transformation reactions and temperatures. Some of the most promising metallic glass forming regions have been analyzed using thermodynamic calculations.

  4. Equations of state and phase transitions in (Mg,Fe)SiO3 perovskite and post-perovskites, position of the phase boundary and its double crossing, by Quantum Monte Carlo

    Science.gov (United States)

    Cohen, R. E.; Lin, Y.

    2015-12-01

    We have performed quantum Monte Carlo (QMC) simulations and density functional theory calculations to study the equations of state and phase transitions in (Mg,Fe)SiO3 perovskite (Pv, bridgmanite) and post-perovskite (PPv) .[1] The ground-state energies were derived using quantum QMC simulations and the temperature-dependent Helmholtz free energies were calculated within the quasiharmonic approximation and density functional perturbation theory. Quantum Monte Carlo (QMC) within Diffusion Monte Carlo (DMC) is a stochastic numerical solution of Schrödinger's equation within the fixed many-particle nodes obtained, in our case, from a determinant of DFT orbitals. Agreement with experiments is improved over DFT alone. Furthermore, we obtain statistical error bounds on the results, rather than the unconstrained errors of DFT. The Pv-PPv phase boundary calculated from our QMC equations of state is also consistent with experiments, and better than previous DFT computations. In order to understand the H-phase reported in (Mg,Fe)SiO3 [2], we have performed evolutionary structure searching for FeSiO3.[3] We find a new structure type which may be consistent with the experimental observations, but is a lower pressure, less dense, phase. We have built a thermodynamic model for (Mg,Fe)SiO3 perovskite as a function of P and T, and will discuss implications for the location of the phase boundary in D'' and its double crossing [4]. This work is supported by NSF and the ERC Advanced Grant ToMCaT. [1] Y. Lin, R. E. Cohen, S. Stackhouse, K. P. Driver, B. Militzer, L. Shulenburger, and J. Kim, Phys. Rev. B 90 (2014). [2] L. Zhang et al., Science 344, 877 (2014). [3] R. E. Cohen and Y. Lin, Phys. Rev. B 90 (2014). [4] J.W. Hernlund, C. Thomas and P.J. Tackley, Nature 434, 882 (2005).

  5. Study on Precipitating Phases in Mg-Gd-Nd Alloy Aged at Limiting High Temperature%Mg-Gd-Nd合金极限高温时效析出相的研究

    Institute of Scientific and Technical Information of China (English)

    谢中柱; 许并社; 孙威

    2011-01-01

    通过透射电子显微镜(TEM)观察并结合纳米柬能谱(EDS)分析,研究了Mg96.9Gd2.8Nd0.3(at%)合金在极限服役温度300℃等温时效状态下析出相的形成和生长.确定了300℃等温时效析出序列为:MgS.S.S.S→β1(fcc)→β(fcc),未见常规服役温度时效初期亚稳相β''和β'.镁基体中均匀弥散的面心立方结构的亚稳相β1成分为Mg7RE,是300℃时效合金的主要析出强化相.合金在300℃具有更快的时效硬化效应.但显著的过时效效应导致合金力学性能迅速下降.%The forming and growth of precipitating phases in Mg96.9Gd2.8Nd0.3 (at%) alloy aged at limiting high temperature 300 '℃ was studied by TEM observations and nano-electron-probe EDS analysis. No evidence was found the presence of the early phases β" and β in the Mg-Gd-Nd during aging at 300 ℃. A precipitating sequence of Mg(SSSS)→β1(fcc)→β(fce) is suggested for this alloy. The met.stable phase β has a f.c.c smucture, it's homogeneous distribution in Mg maix, which is the main precipitation strength phases. The composition of β1 is determined to be about Mg7RE by EDS. A rapid overageing response has been noted in the Mg-Gd-Nd alloy during ageing at 300 ℃ and this has been attributed to the rapid decrease of performance.

  6. Fluorite transition metal hydride induced destabilization of the MgH2 system in MgH2/TMH2 multilayers ( TM=Sc , Ti, V, Cr, Y, Zr, Nb, La, Hf)

    Science.gov (United States)

    Tao, S. X.; Notten, P. H. L.; van Santen, R. A.; Jansen, A. P. J.

    2010-09-01

    The structural changes in MgH2 induced by contact with fluorite transition metal hydrides ( TMH2 , TM=Sc , Ti, V, Cr, Y, Zr, Nb, La, Hf) have been studied using density-functional theory calculations. Models of MgH2(rutile)/TiH2(fluorite) and MgH2(fluorite)/TiH2(fluorite) multilayers with different Mg:TM ratios have been designed. With a fixed thickness of the TMH2 layer, structure transformation of MgH2 from rutile to fluorite occurs with a decrease in thickness of the MgH2 layer. The hydrogen desorption energy from the fluorite MgH2 layer in the multilayers is significantly lower than that of the bulk rutile MgH2 . The structural deformation of the MgH2 layer due to the strain induced by TMH2 is found to be responsible for the destabilization of the Mg-H bond: the more structural deformation, the more destabilization of the Mg-H. Our results provide an important insight for the development of new hydrogen-storage materials with desirable thermodynamic properties.

  7. Improvement of doping efficiency in Mg-Al0.14Ga0.86N/GaN superlattices with AlN interlayer by suppressing donor-like defects

    Institute of Scientific and Technical Information of China (English)

    Liu Ning-Yang; Chen Wei-Hua; Hu Xiao-Dong; Liu Lei; Wang Lei; Yang Wei; Li Ding; Li Lei; Cao Wen-Yu; Lu Ci-Mang; Wan Cheng-Hao

    2012-01-01

    We investigate the mechanism for the improvement of p-type doping efficiency in Mg-Al0.14Gao.86N/GaN superlattices (SLs).It is shown that the hole concentration of SLs increases by nearly an order of magnitude,from 1.1 × 1017to 9.3×1017 cm-3,when an AlN interlayer is inserted to modulate the strains.Schr(o)dinger-Poisson self-consistent calculations suggest that such an increase could be attributed to the reduction of donor-like defects caused by the strain modulation induced by the AlN interlayer.Additionally,the donor-acceptor pair emission exhibits a remarkable decrease in intensity of the cathodoluminescence spectrum for SLs with an AlN interlayer.This supports the theoretical calculations and indicates that the strain modulation of SLs could be beneficial to the donor-like defect suppression as well as the p-type doping efficiency improvement.

  8. Microtexture evolution in Mg-Y and AZ31 Mg alloy during hot deformation%Mg-Y及AZ31镁合金高温变形过程中微观织构的演化

    Institute of Scientific and Technical Information of China (English)

    杨续跃; 张雷; 姜育培; 朱亚坤

    2011-01-01

    在温度为723 K、应变速度为3×10-3 s-1的条件下,对Mg-Y及AZ31镁合金挤压棒材进行单向压缩变形,利用OM、SEM和EBSD观察、分析Y对挤压棒材动态再结晶和微观织构的影响.结果表明:AZ31镁合金在真应变ε=0.2时发生明显的动态再结晶,在ε=0.5时,动态再结晶晶粒的体积分数高达80%以上;而Mg-Y合金在真应变ε=0.4时,动态再结晶体积分数尚不足10%,Y对镁合金动态再结晶有显著的阻碍作用;AZ31镁合金变形时,几乎所有晶粒的基面趋向于由变形前平行于压缩方向转至垂直于压缩方向,导致基面织构在ε=1.2时发生近90°的转动;Mg-Y合金则只有小部分晶粒发生转动,转动所形成的择优取向在动态再结晶后显著弱化,并导致取向分布更加随机;Y的添加可导致镁合金基面织构在动态再结晶后显著弱化.%The effects of Y on the dynamic recrystallization (DRX) and microtexture evolution of hot deformed Mg alloy were studied by optical, SEM and EBSD microscopy.For this purpose, AZ31 and Mg-Y alloy bars were compressed at strain rate of 3× 10-3 s-1 and at temperature of 723 K.The results show that DRX frequently takes place in AZ31 Mg alloy just after being compressed to strained ε=0.2 and the volume fraction of DRX grains is more than 80% after further being compressed to strained 0.5.Whereas alloying by Y retarded DRX, the fraction of DRX in Mg-Y alloy is less than 10%even at the strain of 0.4.In AZ31 Mg alloy, the alignment of the basal planes initially parallel to the compression direction is rotated gradually by compression and approaches perpendicular to the compression direction in high strain and the basal texture is rotated by about 90° at the strain of 1.2.But in Mg-Y alloy, only a few grains rotate to be perpendicular to the compression direction with increasing strain.The basal texture caused by the rotated grains is significantly weakened and the orientation distribution becomes more random

  9. Effect of H2O on Upper Phase Transitions in MgSiO3: Is the Depth of the Seismic X-Discontinuity an Indicator of Mangle Water Content?

    Energy Technology Data Exchange (ETDEWEB)

    Jacobsen, S.D.; Ehm, L.; Liu, Z.; Ballaran T.B.; Littlefield, E.F.; Hemley, R.J.

    2010-06-29

    The mantle X-discontinuity, usually assigned to positive seismic velocity reflectors in the 260-330 km depth range, has proved difficult to explain in terms of a single mineralogical phase transformation in part because of its depth variability. The coesite to stishovite transition of SiO{sub 2} matches deeper X-discontinuity depths but requires 5-10% free silica in the mantle to match observed impedance contrast. The orthoenstatite (OEn) to high-pressure clinoenstatite (HPCen) transformation of MgSiO{sub 3} also broadly coincides with depths of the X but requires chemically depleted and orthoenstatite-rich lithology at 300 km depth in order to match observed seismic impedance contrast. On the basis of high-pressure infrared spectroscopy, X-ray diffraction, and Raman spectroscopy, we show that 1300 ppm variation of H{sub 2}O content in MgSiO{sub 3} can displace the transition of low-pressure clinoenstatite (LPCen) to HPCen by up to 2 GPa, similar to previous quench experiments on the OEn to HPCen phase transition, where about 30-45 km (1.0-1.5 GPa) of deflection could occur per 0.1 wt% H{sub 2}O. If the mantle X-discontinuity results from pyroxene transitions in a depleted harzburgite layer, because of the strong influence of minor amounts of water on the transformation boundary, the depth of the mantle X-discontinuity could serve as a potentially sensitive indicator of water content in the upper mantle.

  10. Electronic structure of F type color center in MgO and optical absorption transition%MgO晶体中F型色心的电子结构 和光学吸收谱研究

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    运用嵌入原子簇的电荷自洽离散变分方法(SCC-DVM-Xα方法)对MgO晶体中F型色心的电子结构进行了计算,并利用能量最小原理优化了色心格点周围的Mg,O离子结构,得到了MgO晶体中F,F+和F2+心的能带,态密度,并讨论了色心的光学跃迁模式。计算结果表明,F,F+和F2+心在MgO晶体的禁带中引入了色心能级,F和F+心的光学跃迁能分别是4.67eV和4.66 eV,电子从色心激发态跃迁到导带底需要吸收大的光电子跃迁能量。计算结果与实验结果符合较好,说明计算结果是合理的%The electronic structure of MgO crystal with F type color center has been studied with the relaxation of ions around vacancy by using the SCC-DVM-Xα methods. The energy band, bulk density of states and mulliken efficient charge have been calculated. Also, the optic transition model has been discussed. Our calculation results showed that F, F+ and F2+-center in MgO crystal introduced defect energy levels in the forbidden gap. The calculated absorption energies for F and F+-center were 4.67eV and 4.66eV, respectively. Also, big photoelectron energies were required for F and F+-centers. The good agreement with experimental data showed the reasonableness of the calculated results。

  11. The Evolution and Effect of Mn Element in Mg-Zn-Mn Alloy%Mn元素在Mg-Zn-Mn合金中演变形式和作用的研究

    Institute of Scientific and Technical Information of China (English)

    张丁非; 石国梁; 赵霞兵; 齐福刚

    2011-01-01

    The form and effect of Mn in Mg-6wt%Zn-lwt%Mn(ZM61) alloy were investigated by transmission electron microscopy(TEM). The results show that most Mn soluted in matrix in as-cast microstructure; a small a-mount of fine Mn dispersoids were formed during homogenization treatment; the majority of Mn precipitated as regular shape Mn dispersiods after solution treatment, the main shape of these Mn particles are regular polygon, spherical and rod-like; the form of Mn existence in as-aged samples is similar with those solution treated samples. High resolution transmission microscopy observation and fast fourier transform analysis revealed that there are cohenrent interface re-lationship between α-Mn and α-Mg, it is (1010)α-Mg//(301)α-Mn, [12l6]α-Mg//[12 3]α-Mn. According to the classical two-dimensional lattice mismatch model "Bramifit" it can be calculated that the lattice misfit between crMn and MgZn2 is only 2.14%, when their orientation relationship is (200)α-Mn//(1010)MgZnz . [012]rMn//Cl213]MgZh2. Therefore, α-Mn particles can act as heterogeneous nucleas for MgZn2 phase during aging, but the MgZn2 particles are always coar-ser than those that don't't nucleate on orMn particles.%利用透射电子显微镜(TEM)研究了Mg-6%(质量分数,下同)Zn-1% Mn(ZM61)镁合金中Mn在不同状态下的存在形式和作用.结果表明,铸态组织中大多数Mn固溶于基体中;均匀化处理以后,组织中析出少量细小的α-Mn颗粒;挤压和固溶时大部分Mn以形状规则的α-Mn颗粒的形式析出,主要有3种形态,即规则多边形(以六边形为主)、球状和棒状.通过高分辨透射电子显微分析发现,α-Mn颗粒与α-Mg基体之间存在共格界面关系((1010)α-Mg//(301)α-Mn,[1216]α-Mg//[123]α-Mn).研究还发现α-Mn颗粒可以作为时效过程中MgZn2相的异质形核核心,但依附α-Mn颗粒形核的MgZn2相都较粗大.根据二维晶格错配度“Bramifit模型”计算得出,当α-Mn颗粒与MgZn2

  12. Synthesis, Property Characterization, and Photocatalytic Activity of Novel Visible Light-Responsive Photocatalyst

    Directory of Open Access Journals (Sweden)

    Jingfei Luan

    2012-01-01

    Full Text Available Fe2BiSbO7 was synthesized by a solid-state reaction method for the first time. The structural and photocatalytic properties of Fe2BiSbO7 have been characterized. The results showed that Fe2BiSbO7 was crystallized with the pyrochlore-type structure, cubic crystal system, and space group Fd3m. The lattice parameter for Fe2BiSbO7 was  Å. The photocatalytic degradation of methylene blue (MB was realized under visible light irradiation with Fe2BiSbO7 as catalyst. Fe2BiSbO7 owned higher catalytic activity compared with Bi2InTaO7 or pure TiO2 or N-doped TiO2 for photocatalytic degradation of MB. The photocatalytic degradation of MB with Fe2BiSbO7, Bi2InTaO7, or N-doped TiO2 followed the first-order reaction kinetics, and the first-order rate constant was 0.01189, 0.00275, or 0.00333 min−1. After visible light irradiation for 230 min with Fe2BiSbO7, complete removal and mineralization of MB was observed. The reduction of the total organic carbon, the formation of inorganic products, and , and the evolution of CO2 revealed the continuous mineralization of MB during the photocatalytic process. The photocatalytic degradation pathway of MB was obtained. Fe2BiSbO7/(visible light photocatalysis system was found to be suitable for textile industry wastewater treatment.

  13. Optical absorption and thermoluminescence in Mg O, Mg O:Ni and Mg O:Li irradiated at room temperature; Absorcion optica y termoluminiscencia en MgO, MgO:Ni y MgO:Li irradiados a temperatura ambiente

    Energy Technology Data Exchange (ETDEWEB)

    Delgado, L.

    1984-07-01

    Optical absorption and thermoluminescence (TL) studies in Mg O, Mg O:Ni and Mg O:Li irradiated at room temperature are presented. In pure Mg O the thermal annihilation of Fe3+ by recombination with thermally released electrons at {approx} 90 and 175 degree centigree and the V center annealing by hole release up to 100 degree centigree cause the observed glow peaks at these temperatures. The TL excitation spectrum shows two maxima at 245 nm (electron center) and 288 nm (Fe3+). In Mg O:Ni X irradiation induces Fe{sup 2}+ {yields}- Fe{sup 3}+ and Ni{sup 2}+ {yields} Ni{sup 3}+ oxidations. Two TL emission bands centered at 110 degree centigree (red) and 80 o{sup C} (green) are assigned to electron release and their recombination at Fe{sup 3}+ and Ni{sup 3}+ respectively. In Mg O:Li two TL emission bands, one blue (430 nm) and the other red (730 nm) with excitation maxima at 245 nm (electron center) and 200 nm (hole center) respectively are observed. No V-center formation was detected in both Ni and Li doped samples. (Author) 42 refs.

  14. Superconductivity in MgB2 irradiated with energetic protons

    Science.gov (United States)

    Sandu, Viorel; Craciun, Liviu; Ionescu, Alina Marinela; Aldica, Gheorghe; Miu, Lucica; Kuncser, Andrei

    2016-09-01

    A series of MgB2 samples were irradiated with protons of 11.3 and 13.2 MeV. Magnetization data shows an insignificant reduction of the critical temperatures but a continuous decrease of the Meissner fraction with increasing fluence or energy. All samples show a consistent improvement of the critical current density compared to the virgin sample and an increase of the pinning energy at high fields as resulted from relaxation data.

  15. Phonon dispersion and lifetimes in MgB2.

    Science.gov (United States)

    Shukla, Abhay; Calandra, Matteo; D'Astuto, Matteo; Lazzeri, Michele; Mauri, Francesco; Bellin, Christophe; Krisch, Michael; Karpinski, J; Kazakov, S M; Jun, J; Daghero, D; Parlinski, K

    2003-03-01

    We measure phonon dispersion and linewidth in a single crystal of MgB2 along the Gamma-A, Gamma-M, and A-L directions using inelastic x-ray scattering. We use density functional theory to compute the effect of both electron-phonon coupling and anharmonicity on the linewidth, obtaining excellent agreement with experiment. Anomalous broadening of the E(2g) phonon mode is found all along Gamma-A. The dominant contribution to the linewidth is always the electron-phonon coupling.

  16. Scanning tunneling spectroscopy in MgB2.

    Science.gov (United States)

    Karapetrov, G; Iavarone, M; Kwok, W K; Crabtree, G W; Hinks, D G

    2001-05-01

    We present scanning tunneling microscopy measurements of the surface of superconducting MgB2 with a critical temperature of 39 K. In zero magnetic field the conductance spectra can be analyzed in terms of the standard BCS theory with a smearing parameter gamma. The value of the superconducting gap is 5 meV at 4.2 K, with no experimentally significant variation across the surface of the sample. The temperature dependence of the gap follows the BCS form, fully consistent with phonon-mediated superconductivity in this novel superconductor. The application of a magnetic field induces strong pair breaking as seen in the conductance spectra in fields up to 6 T.

  17. Evidence for two superconducting gaps in MgB2.

    Science.gov (United States)

    Chen, X K; Konstantinovic, M J; Irwin, J C; Lawrie, D D; Franck, J P

    2001-10-01

    We have measured the Raman spectra of polycrystalline MgB2 from 25 to 1200 cm(-1). A superconductivity-induced redistribution in the electronic Raman continuum was observed. Two pair-breaking peaks appear in the spectra, suggesting the presence of two superconducting gaps. The measured spectra were analyzed using a quasi-two-dimensional model in which two s-wave superconducting gaps open on two sheets of Fermi surface. For the gap values we have obtained Delta(1) = 22 cm(-1) ( 2.7 meV) and Delta(2) = 50 cm(-1) ( 6.2 meV). Our results suggest that a conventional phonon-mediated pairing mechanism occurs in the planar boron sigma bands and is responsible for the superconductivity of MgB2.

  18. Two-band superconductivity in MgB2.

    Science.gov (United States)

    Iavarone, M; Karapetrov, G; Koshelev, A E; Kwok, W K; Crabtree, G W; Hinks, D G; Kang, W N; Choi, Eun-Mi; Kim, Hyun Jung; Kim, Hyeong-Jin; Lee, S I

    2002-10-28

    The study of the anisotropic superconductor MgB2 using a combination of scanning tunneling microscopy and spectroscopy reveals two distinct energy gaps at Delta(1)=2.3 meV and Delta(2)=7.1 meV at 4.2 K. Different spectral weights of the partial superconducting density of states are a reflection of different tunneling directions in this multiband system. Temperature evolution of the tunneling spectra follows the BCS scenario [Phys. Rev. Lett. 3, 552 (1959)

  19. Formation of solid Kr nanoclusters in MgO

    NARCIS (Netherlands)

    van Huis, MA; van Veen, A; Schut, H; Kooi, BJ; De Hosson, JTM

    2003-01-01

    The phenomenon of positron confinement enables us to investigate the electronic structure of nanoclusters embedded in host matrices. Solid Kr nanoclusters are a very interesting subject of investigation because of the very low predicted value of the positron affinity of bulk Kr. In this work,

  20. Theoretical Limiting Potentials in Mg/O2 Batteries

    DEFF Research Database (Denmark)

    Smith, Jeffrey G.; Naruse, Junichi; Hiramatsu, Hidehiko

    2016-01-01

    A rechargeable battery based on a multivalent Mg/O2 couple is an attractive chemistry due to its high theoretical energy density and potential for low cost. Nevertheless, metal-air batteries based on alkaline earth anodes have received limited attention and generally exhibit modest performance....... In addition, many fundamental aspects of this system remain poorly understood, such as the reaction mechanisms associated with discharge and charging. The present study aims to close this knowledge gap and thereby accelerate the development of Mg/O2 batteries by employing first-principles calculations...... by the presence of large thermodynamic overvoltages. In contrast, MgO2-based cells are predicted to be much more efficient: superoxide-terminated facets on MgO2 crystallites enable low overvoltages and round-trip efficiencies approaching 90%. These data suggest that the performance of Mg/O2 batteries can...

  1. Hydrogen absorption in Mg-Ni-Fe alloys

    Energy Technology Data Exchange (ETDEWEB)

    Lupu, D. (Inst. of Isotopic and Molecular Tech., Cluj-Napoca, Romania); Biris, A.; Indrea, E.; Aldea, N.; Bucur, R.V.; Morariu, M.

    1983-01-01

    The hydrogenation properties of the alloys of overall formula Mg/sub 2/Ni/sub 1-x/Fe/sub x/ (x less than or equal to 0.37) have been studied. In this range of composition multi-phase alloys were obtained containing Mg/sub 2/Ni, Mg and more or less finely dispersed Fe in different coordination as provided by the EXAFS technique and Moessbauer spectroscopy. There is no significant substitution of Ni by Fe atoms in the Mg/sub 2/Ni lattice. Two or three plateau-pressures are observed on the pressure-composition isotherms of the hydrides with the heats of formation in the range -18.4 to 20.4 kcal/mol H/sub 2/ (-77 to -85.4 kJ/mol H/sub 2/). The hydrides of the Fe-containing alloys show higher desorption rates of hydrogen compared to the pure Mg/sub 2/Ni hydride. 17 references, 5 figures, 1 table.

  2. Size effects in MgO cube dissolution.

    Science.gov (United States)

    Baumann, Stefan O; Schneider, Johannes; Sternig, Andreas; Thomele, Daniel; Stankic, Slavica; Berger, Thomas; Grönbeck, Henrik; Diwald, Oliver

    2015-03-10

    Stability parameters and dissolution behavior of engineered nanomaterials in aqueous systems are critical to assess their functionality and fate under environmental conditions. Using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, we investigated the stability of cubic MgO particles in water. MgO dissolution proceeding via water dissociation at the oxide surface, disintegration of Mg(2+)-O(2-) surface elements, and their subsequent solvation ultimately leads to precipitation of Mg(OH)2 nanosheets. At a pH ≥ 10, MgO nanocubes with a size distribution below 10 nm quantitatively dissolve within few minutes and convert into Mg(OH)2 nanosheets. This effect is different from MgO cubes originating from magnesium combustion in air. With a size distribution in the range 10 nm ≤ d ≤ 1000 nm they dissolve with a significantly smaller dissolution rate in water. On these particles water induced etching generates (110) faces which, above a certain face area, dissolve at a rate equal to that of (100) planes.1 The delayed solubility of microcrystalline MgO is attributed to surface hydroxide induced self-inhibition effects occurring at the (100) and (110) microplanes. The present work underlines the importance of morphology evolution and surface faceting of engineered nanomaterials particles during their dissolution.

  3. Antioxidant status in MgO nanoparticle-exposed rats.

    Science.gov (United States)

    Kiranmai, G; Reddy, A Rama Narsimha

    2013-11-01

    In this present study, antioxidant status was evaluated in rat serum following exposure to magnesium oxide (MgO) nanoparticles. The lungs of rats were intratracheally instilled with (single dose) phosphate-buffered saline (PBS) + 1% of Tween 80 (solvent control) or MgO or carbonyl iron (negative control) or quartz particles (positive control) at a dose of 1 and 5 mg/kg of body weight. The blood samples were collected at 1, 7, and 30 days of postinstillation of nanoparticles after their exposure, and different parameters were estimated to assess the oxidative stress induced by the instillation of MgO. Exposure of rats to MgO produced a significant (p MgO nanoparticle-exposed rats indicates the reduction in antioxidant defense mechanisms due to the instillation of MgO. These results indicate that exposure to MgO nanoparticles induces oxidative stress by reducing the total antioxidant capacity in rats. The findings suggest possible occupational health hazard in chronic exposures.

  4. Drug-induced alterations in Mg2+ homoeostasis.

    NARCIS (Netherlands)

    Lameris, A.L.L.; Monnens, L.A.H.; Bindels, R.J.M.; Hoenderop, J.G.J.

    2012-01-01

    Magnesium (Mg2+) balance is tightly regulated by the concerted actions of the intestine, bone and kidneys. This balance can be disturbed by a broad variety of drugs. Diuretics, modulators of the EGFR (epidermal growth factor receptor), proton pump inhibitors, antimicrobials, calcineurin inhibitors

  5. Characterization of the microstructure in Mg based alloy

    KAUST Repository

    Kutbee, Arwa T

    2013-06-01

    The cast products Mg–Sn based alloys are promising candidates for automobile industries, since they provide a cheap yet thermally stable alternative to existing alloys. One drawback of the Mg–Sn based alloys is their insufficient hardness. The hardenability can be improved by engineering the microstructure through additions of Zn to the base alloy and selective aging conditions. Therefore, detailed knowledge about the microstructural characteristics and the role of Zn to promote precipitation hardening is essential for age hardenable Mg-based alloys. In this work, microstructural investigation of the Mg–1.4Sn–1.3Zn–0.1Mn (at.%) precipitation system was performed using TEM. The chemical composition of the precipitates was analyzed using EDS. APT was employed to obtain precise chemical information on the distribution of Zn in the microstructure. It was found from microstructural studies that different precipitates with varying sizes and phases were present; lath-shaped precipitates of the Mg2Sn phase have an incoherent interface with the matrix, unlike the lath-shaped MgZn2 precipitates. Furthermore, nano-sized precipitates dispersed in the microstructure with short-lath morphology can either be enriched with Sn or Zn. On the other hand, APT analysis revealed the strong repulsion between Sn and Zn atoms in a portion of the analysis volume. However, larger reconstruction volume required to identify the role of Zn is still limited to the optimization of specimen preparation.

  6. Position of Fe ions in MgO crystalline structure

    Directory of Open Access Journals (Sweden)

    Szczerba Jacek

    2015-03-01

    Full Text Available Magnesium oxide (MgO is one of the most important raw materials in many branches of industry. Magnesium oxide is a popular refractory raw material because of its high refractoriness and high resistance to basic slags and environment. In many cases, use of MgO is limited by its properties, especially the presence of secondary phases like iron oxides. The amount and distribution of iron oxides can strongly influence the technological properties of MgO and depend on the manufacturing method, particularly the heat-treatment process. The aim of the study was to evaluate the influence of the heat-treatment process on amount and distribution of iron ions in a magnesium oxide lattice. The 57Fe Mössbauer effect measurements of fused and sintered magnesium oxide samples doped by the iron oxide were conducted. Investigation reveals in both cases the presence of Fe2+ as well as Fe3+ ions. Fe2+ ions occupy Mg2+ octahedral sites in the MgO lattice, whereas the Fe3+ ions are located in highly distorted octahedral coordination. The amount of Fe2+ varies from around 66% for fused samples to 30% for sintered samples.

  7. Electron impact excitation rates for transitions in Mg V

    CERN Document Server

    Aggarwal, K M

    2016-01-01

    Energy levels, radiative rates (A-values) and lifetimes, calculated with the GRASP code, are reported for an astrophysically important O-like ion Mg~V. Results are presented for transitions among the lowest 86 levels belonging to the 2s$^2$2p$^4$, 2s2p$^5$, 2p$^6$, and 2s$^2$2p$^3$3$\\ell$ configurations. There is satisfactory agreement with earlier data for most levels/transitions, but scope remains for improvement. Collision strengths are also calculated, with the DARC code, and the results obtained are comparable for most transitions (at energies above thresholds) with earlier work using the DW code. In thresholds region, resonances have been resolved in a fine energy mesh to determine values of effective collision strengths ($\\Upsilon$) as accurately as possible. Results are reported for all transitions at temperatures up to 10$^6$~K, which should be sufficient for most astrophysical applications. However, a comparison with earlier data reveals discrepancies of up to two orders of magnitude for over 60\\% o...

  8. MAGNESIUM PRECIPITATION AND DIFUSSION IN Mg+ ION IMPLANTED SILICON CARBIDE

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Weilin; Jung, Hee Joon; Kovarik, Libor; Wang, Zhaoying; Roosendaal, Timothy J.; Zhu, Zihua; Edwards, Danny J.; Hu, Shenyang Y.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2015-03-02

    As a candidate material for fusion reactor applications, silicon carbide (SiC) undergoes transmutation reactions under high-energy neutron irradiation with magnesium as the major metallic transmutant; the others include aluminum, beryllium and phosphorus in addition to helium and hydrogen gaseous species. Calculations by Sawan et al. predict that at a dose of ~100 dpa (displacements per atom), there is ~0.5 at.% Mg generated in SiC. The impact of these transmutants on SiC structural stability is currently unknown. This study uses ion implantation to introduce Mg into SiC. Multiaxial ion-channeling analysis of the as-produced damage state indicates a lower dechanneling yield observed along the <100> axis. The microstructure of the annealed sample was examined using high-resolution scanning transmission electron microscopy. The results show a high concentration of likely non-faulted tetrahedral voids and possible stacking fault tetrahedra near the damage peak. In addition to lattice distortion, dislocations and intrinsic and extrinsic stacking faults are also observed. Magnesium in 3C–SiC prefers to substitute for Si and it forms precipitates of cubic Mg2Si and tetragonal MgC2. The diffusion coefficient of Mg in 3C–SiC single crystal at 1573 K has been determined to be 3.8 ± 0.4E-19 m2/s.

  9. Attempts at doping indium in MgB2

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude

    2016-01-01

    Indium (In) doped MgB2 polycrystalline samples were prepared by solid-liquid phase reaction in Ar. After reaction at 800 °C, less than 1 at.% Mg was replaced by In in the MgB2 phase, without significant influence on its lattice parameters and only a slight decrease of its superconducting transition...... in both the doped and undoped samples....

  10. Pressure-induced structural transitions in MgH2.

    Science.gov (United States)

    Vajeeston, P; Ravindran, P; Kjekshus, A; Fjellvåg, H

    2002-10-21

    The stability of MgH2 has been studied up to 20 GPa using density-functional total-energy calculations. At ambient pressure alpha-MgH2 takes a TiO2-rutile-type structure. alpha-MgH2 is predicted to transform into gamma-MgH2 at 0.39 GPa. The calculated structural data for alpha- and gamma-MgH2 are in very good agreement with experimental values. At equilibrium the energy difference between these modifications is very small, and as a result both phases coexist in a certain volume and pressure field. Above 3.84 GPa gamma-MgH2 transforms into beta-MgH2, consistent with experimental findings. Two further transformations have been identified at still higher pressure: (i) beta- to delta-MgH2 at 6.73 GPa and (ii) delta- to epsilon-MgH2 at 10.26 GPa.

  11. Characterization of the reversible photoinduced optical changes in Sb-based glasses

    OpenAIRE

    Nalin,Marcelo; Poirier, Gaël Yves; Carvalho, Edson José de; Ribeiro, Sidney Jose Lima; Messaddeq, Younes

    2006-01-01

    Changes occurring in absorption coefficients when glasses in the SbPO4–WO3 binary system were irradiated by light, at the edge of the absorption band, were measured in real time. These glasses present good thermal and optical properties and photoinduced changes in the absorption coefficients are reversible by heat treatment around 150 _C. Subsequent recording/erasing cycles could be made without sample degradation. The sensitivity of the induced optical changes was studied for different wavel...

  12. 121Sb and 125Te nuclear inelastic scattering in Sb2Te3 under high pressure

    Science.gov (United States)

    Simon, R. E.; Sergueev, I.; Kantor, I.; Kantor, A.; Perßon, J.; Hermann, R. P.

    2014-12-01

    We investigated the lattice dynamics of Sb2Te3 under high pressure using 121Sb and 125Te nuclear inelastic scattering of synchrotron radiation. We measured the room temperature 121Sb and 125Te inelastic spectra at 15(1) GPa and 77(3) GPa and extracted the Te and Sb element specific density of phonon states of δ-Sb2Te3 at 77(3) GPa. X-ray diffraction confirms the sample to be in the cubic δ-Sb2Te3 phase with space group Im\\bar{3}m and lattice constant a=3.268(4) \\overset{\\circ}{A} . The total density of phonon states of δ-Sb2Te3 strongly resembles the one of amorphous GeSb2Te4, suggesting the presence of covalent bonding in contrast to the resonance bonding in α-Sb2Te3. From the density of phonon states of δ-Sb2Te3 a mean speed of sound of 2.61(6) km {{s}-1} and Debye temperatures of 278(10) K for Te and 296(10) K for Sb were determined.

  13. Exploring optimum growth window for high quality InAs/GaInSb superlattice materials

    Science.gov (United States)

    Haugan, H. J.; Brown, G. J.; Kim, M.; Mahalingam, K.; Elhamri, S.; Mitchel, W. C.; Grazulis, L.

    2013-06-01

    We report ternary growth studies to develop a largely strained InAs/InGaSb superlattice (SL) material for very long wavelength infrared (VLWIR) detection. We select a SL structure of 47.0 Å InAs/21.5 Å In0.25Ga0.75Sb that theoretically designed for the greatest possible detectivity, and tune growth conditions for the best possible material quality. Since material quality of grown SLs is largely influenced by extrinsic defects such as nonradiative recombination centers and residual background dopings in the grown layers, we investigate the effect of growth temperature (Tg) on the spectral responses and charge carrier transports using photoconductivity and temperature-dependent Hall effect measurements. Results indicate that molecular beam epitaxy (MBE) growth process we developed produces a consistent gap near 50 meV within a range of few meV, but SL spectral sensing determined by photoresponse (PR) intensity is very sensitive to the minor changes in Tg. For the SLs grown from 390 to 470 °C, a PR signal gradually increases as Tg increases from 400 to 440 °C by reaching a maximum at 440 °C. Outside this growth window, the SL quality deteriorates very rapidly. All SLs grown for this study were n-type, but the mobility varied in a variety of range between 11,300 and 21 cm2/Vs. The mobility of the SL grown at 440 °C was approximately 10,000 V/cm2 with a sheet carrier concentration of 5 × 1011 cm-2, but the mobility precipitously dropped to 21 cm2/Vs at higher temperatures. Using the knowledge we learned from this growth set, other growth parameters for the MBE ternary SL growth should be further adjusted in order to achieve high performance of InAs/InGaSb materials suitable for VLWIR detection.

  14. Discussion on the electrical and thermoelectrical properties of amorphous In-Sb-Te Films

    Energy Technology Data Exchange (ETDEWEB)

    Aly, K.A. [University of Jeddah, Physics Department, Faculty of Science and Arts, Khulais, Jeddah (Saudi Arabia); Al-Azhar University, Assiut Branch, Physics Department, Faculty of Science, Asyut (Egypt); Saddeek, Y. [Al-Azhar University, Assiut Branch, Physics Department, Faculty of Science, Asyut (Egypt); Dahshan, A. [Port Said University, Department of Physics, Faculty of Science, Port Said (Egypt); King Khalid University, Department of Physics, Faculty of Science for Girls, Abha (Saudi Arabia)

    2016-03-15

    Different compositions of (In{sub 0.5}Sb{sub 0.5}){sub 1-x}Te{sub x} (0.50 ≤ x ≤ 0.65) thin films were prepared by thermal evaporated technique, onto pre-cleaned glass substrates at ∝298 K. Both dark electrical resistivity (ρ) and thermoelectric power (S) were measured in the temperature range 300-420 K. The concentration of the free carriers is obtained from DC conductivity and thermoelectric power measurements. Seebeck coefficient was found to be positive over entire temperature range, indicating that (In{sub 0.5}Sb{sub 0.5}){sub 1-x}Te{sub x} films are p-type semiconducting materials. Also, the variation of the mobility with temperature has been estimated. Increasing tellurium concentration is found to affect the DC conductivity and thermoelectric power of the studied films. The activation energies obtained from the DC conductivity and thermoelectric power increase with increasing tellurium content. The obtained results were interpreted according to the chemical bond approach. (orig.)

  15. Discussion on the electrical and thermoelectrical properties of amorphous In-Sb-Te Films

    Science.gov (United States)

    Aly, K. A.; Saddeek, Y.; Dahshan, A.

    2016-03-01

    Different compositions of (In0.5Sb0.5)1- x Te x (0.50 ≤ x ≤ 0.65) thin films were prepared by thermal evaporated technique, onto pre-cleaned glass substrates at ~298 K. Both dark electrical resistivity ( ρ) and thermoelectric power ( S) were measured in the temperature range 300-420 K. The concentration of the free carriers is obtained from DC conductivity and thermoelectric power measurements. Seebeck coefficient was found to be positive over entire temperature range, indicating that (In0.5Sb0.5)1- x Te x films are p-type semiconducting materials. Also, the variation of the mobility with temperature has been estimated. Increasing tellurium concentration is found to affect the DC conductivity and thermoelectric power of the studied films. The activation energies obtained from the DC conductivity and thermoelectric power increase with increasing tellurium content. The obtained results were interpreted according to the chemical bond approach.

  16. Intermartensitic transformation and magnetic field effect in NiMnInSb ferromagnetic shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yu, S.Y., E-mail: syyu@sdu.edu.c [School of Physics, Shandong University, Jinan 250100 (China); Yan, S.S.; Zhao, L. [School of Physics, Shandong University, Jinan 250100 (China); Feng, L.; Chen, J.L.; Wu, G.H. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2010-09-15

    Partially substituting Sb for In, we found an irreversible transformation of martensite to intermartensite at 90 K in Ni{sub 50}Mn{sub 34}In{sub 12}Sb{sub 4} alloy during heating. The reverse transformation of martensite and intermartensite to the parent phase induced by a magnetic field has been investigated. The results indicate that, if a sufficiently high magnetic field is applied, the intermartensite state is no longer necessary as an intermediate state. Thus, a difference of the transformation originating from magnetic and from thermal energies has been found. In this competition, lattice distortions play an important role to promote the occurrence of the intermediate intermartensitic path.

  17. Large magnetothermopower and Fermi surface reconstruction in Sb$_2$Te$_2$Se

    OpenAIRE

    Wang, Kefeng; Graf, D.; Petrovic, C.

    2016-01-01

    We report the magnetoresistance, magnetothermopower and quantum oscillation study of Sb$_2$Te$_2$Se single crystal. The in-plane transverse magnetoresistance exhibits a crossover at a critical field $B^*$ from semiclassical weak-field $B^2$ dependence to the high-field unsaturated linear magnetoresistance which persists up to the room temperature. The low-temperature Seebeck coefficient is negative in zero field contrary to the positive Hall resistivity, indicating the multiband effect. The m...

  18. Ballistic transport and quantum interference in InSb nanowire devices

    Science.gov (United States)

    Li, Sen; Huang, Guang-Yao; Guo, Jing-Kun; Kang, Ning; Caroff, Philippe; Xu, Hong-Qi

    2017-02-01

    Not Available Project supported by the National Key Basic Research and Development Project of the Ministry of Science and Technology of China (Grant No. 2016YFA0300601) and the National Natural Science Foundation of China (Grant Nos. 91221202, 91421303, 11374019, and 61321001).

  19. Topological states and phase transitions in Sb2Te3-GeTe multilayers

    Science.gov (United States)

    Nguyen, Thuy-Anh; Backes, Dirk; Singh, Angadjit; Mansell, Rhodri; Barnes, Crispin; Ritchie, David A.; Mussler, Gregor; Lanius, Martin; Grützmacher, Detlev; Narayan, Vijay

    2016-06-01

    Topological insulators (TIs) are bulk insulators with exotic ‘topologically protected’ surface conducting modes. It has recently been pointed out that when stacked together, interactions between surface modes can induce diverse phases including the TI, Dirac semimetal, and Weyl semimetal. However, currently a full experimental understanding of the conditions under which topological modes interact is lacking. Here, working with multilayers of the TI Sb2Te3 and the band insulator GeTe, we provide experimental evidence of multiple topological modes in a single Sb2Te3-GeTe-Sb2Te3 structure. Furthermore, we show that reducing the thickness of the GeTe layer induces a phase transition from a Dirac-like phase to a gapped phase. By comparing different multilayer structures we demonstrate that this transition occurs due to the hybridisation of states associated with different TI films. Our results demonstrate that the Sb2Te3-GeTe system offers strong potential towards manipulating topological states as well as towards controlledly inducing various topological phases.

  20. AC plasma induced modifications in Sb{sub 2}S{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Calixto-Rodriguez, M; Martinez, H [Instituto de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico, Apartado Postal 48-3, 62210, Cuernavaca, Morelos (Mexico); Castillo, F [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, 04510, Mexico D. F. (Mexico); Pena, Y [Universidad Autonoma de Nuevo Leon, Facultad de Ciencias Quimicas, Pedro de Alba s/n, Cd. Universitaria, San Nicolas de los Garza, N.L (Mexico); Sanchez-Juarez, A, E-mail: ciro@nucleares.unam.m [Centro de Investigacion en EnergIa, Universidad Nacional Autonoma de Mexico, Privada Xochicalco s/n Col. Centro, Temixco, Morelos, C.P. 62580 (Mexico)

    2010-01-01

    Sb{sub 2}S{sub 3} thin films, deposited by the chemical bath deposition method, were treated with N{sub 2} plasma at 3.0 Torr during several minutes. The as-prepared Sb{sub 2}S{sub 3} thin films and films treated with N{sub 2} plasma have been characterized using several techniques. X-ray diffraction studies have shown that plasma treatment induced recrystallization on the as-prepared Sb{sub 2}S{sub 3}thin films. The band gap values decreased from 2.37 to 1.82 eV after plasma treatment, and the electrical conductivity increased from 10{sup 9} to 10{sup 7} ({Omega}cm){sup -1} due to the annealing effect.

  1. Optical transitions in strained InAsSb/GaInSb interband QC lasers

    Institute of Scientific and Technical Information of China (English)

    Ligong Yang(杨立功); Peifu Gu(顾培夫); Xiaoyun Qin(秦小芸)

    2004-01-01

    @@ In this paper a detailed simulation and theoretical analysis based on model-solid theory and the(→κ)·(→ρ)methodare presented to investigate the dependence of the band structure on the strain deformation in a noveltype-Ⅱ quantum well(QW)heterostructure InAs1_ySby/GaxIn1-xSb under the uniaxial approximation,and subsequently the optical transition and the gain in the interband cascade lasers containing it havebeen evaluated with unchanged injection current densities.The simulation results show that the straineffect on the transition in this heterostructure will not behave as a simple monotonic trend with the latticemismatch of InAs1_ySby/GaxIn1_xSb interface,but as a function of the complex strain chain includingthe whole active region.It is important to the subsequent device design and optimization.

  2. Subwavelength InSb-based Slot wavguides for THz transport: concept and practical implementations

    Science.gov (United States)

    Ma, Youqiao; Zhou, Jun; Pištora, Jaromír; Eldlio, Mohamed; Nguyen-Huu, Nghia; Maeda, Hiroshi; Wu, Qiang; Cada, Michael

    2016-12-01

    Seeking better surface plasmon polariton (SPP) waveguides is of critical importance to construct the frequency-agile terahertz (THz) front-end circuits. We propose and investigate here a new class of semiconductor-based slot plasmonic waveguides for subwavelength THz transport. Optimizations of the key geometrical parameters demonstrate its better guiding properties for simultaneous realization of long propagation lengths (up to several millimeters) and ultra-tight mode confinement (~λ2/530) in the THz spectral range. The feasibility of the waveguide for compact THz components is also studied to lay the foundations for its practical implementations. Importantly, the waveguide is compatible with the current complementary metal-oxide-semiconductor (CMOS) fabrication technique. We believe the proposed waveguide configuration could offer a potential for developing a CMOS plasmonic platform and can be designed into various components for future integrated THz circuits (ITCs).

  3. Study of In distribution on GaInSb:Al crystals by ion beam techniques

    Science.gov (United States)

    Streicher, M.; Corregidor, V.; Catarino, N.; Alves, L. C.; Franco, N.; Fonseca, M.; Martins, L.; Alves, E.; Costa, E. M.; Dedavid, B. A.

    2016-03-01

    III-V ternary alloys semiconductor materials, in particular Ga1-xInxSb, are ideal candidates for device substrates because of the possibility to define the lattice constant as a function of the third element, indium. Aluminum, an isoelectric dopant for Ga and In, increases the carrier mobility in GaSb crystals and has influence over the concentration of native defects by passivating and/or compensating them. To understand the influence of Al on the distribution of indium in ternary alloys of Ga0.8In0.2Sb, pure and doped ingots were obtained with approximately 1020 atoms/cm3 of Al using a vertical Bridgman system. Analysis by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), particle induced X-ray emission (PIXE) and particle induced gamma ray emission (PIGE) were used to obtain information on the structure defects and chemical composition of the crystals. The doped ingots showed good structural homogeneity when compared with the undoped alloy, and they were free from cracks and micro cracks. All of the obtained ingots present precipitates, twins and grains with different concentrations of In. The small compositional variation observed in the doped ingots along the radial direction (measured by PIXE), may be related to the solid-liquid interface's quasi-equilibrium behavior. Regarding to the growth direction, it was observed that the undoped ingots exhibit a higher segregation phenomenon of the third element than the doped ingots. The obtained results indicate that aluminum influences the indium distribution in the ingots, thus ternary ingots with more homogeneous composition can be obtained and consequently electrical properties improved.

  4. Dendritic and eutectic growth in Sb60Ag20Cu20 ternary alloy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The rapid solidification of Sb60Ag20Cu20 ternary alloy was realized by high undercooling method, and the maximum undercooling is up to 142 K (0.18TL). Within the wide undercooling range of 40-142 K, the solidified microstructures are composed of (Sb), θand ε phases. High undercooling enlarges the solute solubility of (Sb) phase, which causes its crystal lattice to expand and its crystal lattice constants to increase. Primary (Sb) phase grows in two modes: at small undercoolings non-faceted dendrite growth is the main growth form; whereas at large undercoolings faceted dendrite growth takes the dominant place. The remarkable difference of crystal structures between (Sb) and θphases leads to (θ+ Sb) pseudobinary eutectic hard to form, whereas strips of θform when the alloy melt reaches the (θ + Sb) pseudobinary eutectic line. The cooperative growth of θand ε phases contributes to the formation of (ε +θ) pseudobinary eutectic easily. In addition, the crystallization route has been determined via microstructural characteristic analysis and DSC experiment.

  5. Changes in Sb speciation with waterlogging of shooting range soils and impacts on plant uptake.

    Science.gov (United States)

    Wan, Xiao-ming; Tandy, Susan; Hockmann, Kerstin; Schulin, Rainer

    2013-01-01

    A pot experiment was conducted to investigate the solubility and redox species of antimony (Sb) in a relocated shooting range soil and its uptake by Lolium perenne L. and Holcus lanatus L. under different water regimes. After 1-week waterlogging, the total Sb concentration in soil solution decreased from ∼110 μg L(-1) to Sb in soil solution was reduced to Sb(III), which greatly affected the plant uptake of Sb. Waterlogging increased shoot Sb concentrations of L. perenne by ∼10 fold but decreased uptake in H. lanatus by 80%. Results indicate that Sb might primarily be taken up as Sb(III) by L. perenne and as Sb(V) by H. lanatus. Temporary waterlogging of soil may increase the risk of trace elements entering the food chain.

  6. Size and Composition Effects in Sb-Carbon Nanocomposites for Sodium-Ion Batteries.

    Science.gov (United States)

    Ramireddy, Thrinathreddy; Sharma, Neeraj; Xing, Tan; Chen, Ying; Leforestier, Jeremie; Glushenkov, Alexey M

    2016-11-09

    Sodium-ion batteries are in the spotlight as viable alternatives to lithium-ion batteries in stationary storage and power grid applications. Among possible anode materials, Sb is one of the interesting candidates due to a combination of battery-type potential plateaus in the charge-discharge profiles, high capacity (theoretical capacity of 660 mAh g(-1)), and demonstrated good cyclic stability. The influence of Sb particle size (particularly at the nanoscale range) and the composition of Sb-carbon composites on the electrode performance, stability, and charge storage mechanism is systematically evaluated here for the first time. A range of Sb-carbon nanocomposites with varied Sb particle size (between 50 and ∼1 nm) are studied. The control of the particle size is achieved via varying the carbon and Sb weight ratio in the precursors. The shape of charge-discharge profiles, hysteresis, and the difference in cyclic stabilities and rate performance are analyzed. The nanocomposite with the smallest particle size (∼1 nm) and the largest carbon content provides the most stable cyclic behavior and a better rate capability but suffers from an increased hysteresis between charge and discharge curves. In situ synchrotron X-ray diffraction experiments indicate that the storage mechanism in the Sb-carbon nanocomposites containing Sb nanoparticles is different from the electrodes with bulkier, micron-sized Sb particles, and the electrochemical reaction proceeds through a number of crystalline intermediates.

  7. MOCVD growth and structural characterization of In-Sb-Te nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Selmo, S.; Fanciulli, M. [Laboratorio MDM, IMM-CNR, Unita di Agrate Brianza (Italy); Dipartimento di Scienza dei Materiali, University of Milano Bicocca, Milano (Italy); Cecchi, S.; Cecchini, R.; Wiemer, C.; Longo, M. [Laboratorio MDM, IMM-CNR, Unita di Agrate Brianza (Italy); Rotunno, E.; Lazzarini, L. [IMEM-CNR, Parma (Italy)

    2016-02-15

    In this work, the self-assembly of In{sub 3}Sb{sub 1}Te{sub 2} and In-doped Sb{sub 4}Te{sub 1} nanowires (NWs) for phase change memories application was achieved by metal organic chemical vapor deposition, coupled with vapor-liquid-solid (VLS) mechanism, catalyzed by Au nanoparticles. Single crystal In{sub 3}Sb{sub 1}Te{sub 2} and In-doped Sb{sub 4}Te{sub 1} NWs were obtained for different reactor pressures at 325 C. The parameters influencing the NW self-assembly were studied and the compositional, morphological, and structural analysis of the grown structures was performed, also comparing the effect of the used substrate (crystalline Si and SiO{sub 2}). In both cases, NWs of several micrometer in length and with diameters as small as 15 nm were obtained. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Study of In distribution on GaInSb:Al crystals by ion beam techniques

    Energy Technology Data Exchange (ETDEWEB)

    Streicher, M., E-mail: smorgana@gmail.com [Pontifícia Universidade Católica do Rio Grande do Sul, Av. Ipiranga, 6681, Porto Alegre, RS (Brazil); Instituto de Plasmas e Fusão Nuclear (IPFN), Instituto Superior Técnico, Universidade de Lisboa, E.N. 10, 2695-066 Bobadela LRS (Portugal); Corregidor, V.; Catarino, N. [Instituto de Plasmas e Fusão Nuclear (IPFN), Instituto Superior Técnico, Universidade de Lisboa, E.N. 10, 2695-066 Bobadela LRS (Portugal); Alves, L.C. [Centro de Ciências e Tecnologias Nucleares (C2TN), Instituto Superior Técnico, Universidade de Lisboa, E.N. 10, 2695-066 Bobadela LRS (Portugal); Franco, N. [Instituto de Plasmas e Fusão Nuclear (IPFN), Instituto Superior Técnico, Universidade de Lisboa, E.N. 10, 2695-066 Bobadela LRS (Portugal); Fonseca, M. [Universidade Europeia, Laureate International Universities, 1500-210 Lisboa (Portugal); Laboratório de Instrumentação, Engenharia Biomédica e Física da Radiação (LIBPhys-UNL), Departamento de Física, FCT-UNL, 2829-516 Monte da Caparica (Portugal); and others

    2016-03-15

    III–V ternary alloys semiconductor materials, in particular Ga{sub 1−x}In{sub x}Sb, are ideal candidates for device substrates because of the possibility to define the lattice constant as a function of the third element, indium. Aluminum, an isoelectric dopant for Ga and In, increases the carrier mobility in GaSb crystals and has influence over the concentration of native defects by passivating and/or compensating them. To understand the influence of Al on the distribution of indium in ternary alloys of Ga{sub 0.8}In{sub 0.2}Sb, pure and doped ingots were obtained with approximately 10{sup 20} atoms/cm{sup 3} of Al using a vertical Bridgman system. Analysis by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), particle induced X-ray emission (PIXE) and particle induced gamma ray emission (PIGE) were used to obtain information on the structure defects and chemical composition of the crystals. The doped ingots showed good structural homogeneity when compared with the undoped alloy, and they were free from cracks and micro cracks. All of the obtained ingots present precipitates, twins and grains with different concentrations of In. The small compositional variation observed in the doped ingots along the radial direction (measured by PIXE), may be related to the solid–liquid interface’s quasi-equilibrium behavior. Regarding to the growth direction, it was observed that the undoped ingots exhibit a higher segregation phenomenon of the third element than the doped ingots. The obtained results indicate that aluminum influences the indium distribution in the ingots, thus ternary ingots with more homogeneous composition can be obtained and consequently electrical properties improved.

  9. Optical and structural properties of MOVPE-grown GaInSb/GaSb quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Wagener, Viera, E-mail: viera.wagener@nmmu.ac.z [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); Olivier, E.J.; Botha, J.R. [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa)

    2009-12-15

    This paper reports on the optical and structural properties of strained type-I Ga{sub 1-x}In{sub x}Sb quantum wells embedded in GaSb from a metal-organic vapour phase epitaxial growth perspective. Photoluminescence measurements and transmission electron microscopy were used to evaluate the effect of the growth temperature on the quality of Ga{sub 1-x}In{sub x}Sb strained layers with varied alloy compositions and thicknesses. Although the various factors contributing to the overall quality of the strained layers are difficult to separate, the quantum well characteristics are significantly altered by the growth temperature. Despite the high growth rates (approx2 nm/s), quantum wells grown at 607 deg. C display photoluminescence emissions with full-width at half-maximum of 3.5-5.0 meV for an indium solid content (x) up to 0.15.

  10. Majorana modes in InSb nanowires (II): resolving the topological phase diagram

    Science.gov (United States)

    Zhang, Hao; Gül, Önder; de Moor, Michiel; de Vries, Fokko; van Veen, Jasper; van Woerkom, David; Zuo, Kun; Mourik, Vincent; Cassidy, Maja; Geresdi, Attila; Car, Diana; Bakkers, Erik; Goswami, Srijit; Watanabe, Kenji; Taniguchi, Takashi; Kouwenhoven, Leo

    Majorana modes in hybrid superconductor-semiconductor nanowire devices can be probed via tunnelling spectroscopy which shows a zero bias peak (ZBP) in differential conductance (1). Majoranas are formed when the Zeeman energy EZ and the chemical potential μ satisfy the condition EZ >√{Δ2 +μ2 } , with Δ the superconducting gap. This Majorana condition outlines the topologically non-trivial phase and predicts a particular dependence of ZBPs on the gate voltage and the external magnetic field. In this talk we show that the magnetic field range of ZBPs can be tuned by gate voltage and vice versa, consistent with these Majorana predictions. Supported by measurements in different external magnetic field orientations, these observations pave the way for exploring the topological phase diagram of spin-orbit coupled semiconductor nanowires with induced superconductivity.

  11. Preparation, microstructure of B film and its applications in MgB2 sup erconducting Josephson junction%硼膜制备工艺、微观结构及其在硼化镁超导约瑟夫森结中的应用∗

    Institute of Scientific and Technical Information of China (English)

    王松; 王星云; 周章渝; 杨发顺; 杨健; 傅兴华

    2016-01-01

    Magnesium diboride is a binary compound with a simple AlB2 type crystal structure and a high-Tc (nearly 40 K) superconductor. The rather high Tc value and the specific properties make it a potential material for electronic applica-tions. The key structure for the application is a Josephson junction. The growth of tri-layer structure consisting of MgB2 film and tunneling barrier layer is a key technology for a Josephson junction. Boron is a kind of good insulating medium. Preparation of MgB2/B/MgB2 tri-layer structures by chemical vapor deposition (CVD) method is investigated. The experimental results indicate that the depositing temperature will influence the microstructure of boron film significantly and different crystal structures of boron films are obtained at different temperatures. The boron film is an amorphous film while the deposition temperature is lower than 500 ◦C, and the amorphous B film can be transformed into MgB2 superconducting film by annealing in Mg vapor. For precursor B films deposited at 470 ◦C and 500 ◦C, the critical temperatures of the relevant MgB2 films are 39.8 K and 38.5 K, respectively. As the deposition temperature is higher than 550 ◦C, the boron film becomes crystallized, and increasing deposition temperature will increase the crystallinity of the B film as can be seen from the samples deposited at 550 ◦C, 600 ◦C, 650 ◦C and 680 ◦C. The boron film turns out to be ofα-phase crystalline texture, which is verified by X-ray diffraction and scanning electron microscope. What is more, the crystalline boron film is a kind of inert film, and it does not react with Mg in Mg vapor, thus it cannot be transformed into superconducting film in the subsequent annealing steps. By utilizing the property of the crystallized boron film, a square-shaped Josephson junction with a size 100 µm × 100 µm of MgB2/B/MgB2 structure is prepared. The thickness of boron dielectric layer is about 10 nm, and the DC Josephson effect is observed

  12. Refinement of Mg{sub 2}Si reinforcement in a commercial Al–20%Mg{sub 2}Si in-situ composite with bismuth, antimony and strontium

    Energy Technology Data Exchange (ETDEWEB)

    Nordin, Nur Azmah; Farahany, Saeed, E-mail: saeedfarahany@gmail.com; Ourdjini, Ali; Abu Bakar, Tuty Asma; Hamzah, Esah

    2013-12-15

    Refinement by addition elements of Al–Mg{sub 2}Si alloys is known to result in a change of primary Mg{sub 2}Si morphology. In this paper, the effects of Bi, Sb and Sr on the characteristic parameters of Al–20%Mg{sub 2}Si in-situ composite have been investigated by computer aided cooling curve thermal analysis and microstructural inspection. Size, density and aspect ratio measurements showed that additions of 0.4 wt.% Bi, 0.8 wt.% Sb and 0.01 wt.% Sr refined the Mg{sub 2}Si reinforcement. Exceeding these concentrations, however, resulted in coarsening of Mg{sub 2}Si particles with no change in the morphology. The results also showed that addition elements caused a decrease in the nucleation and growth temperatures of Mg{sub 2}Si particles. The refining effect of Bi, Sb and Sr is likely to be related to the effect of oxide bifilms suspended in the composite melt as favored nucleation substrates for Mg{sub 2}Si particles. - Highlight: • 0.4 wt.%, 0.8 wt.% and 0.01 wt.% is the optimum content for Bi, Sb and Sr addition. • Exceeding optimum concentration resulted in the coarsening of reinforcements. • Nucleation and growth temperatures decrease with addition of Bi, Sb and Sr. • The refining effect of Bi, Sb and Sr is likely to be related to the oxide bifilms.

  13. Effects of Methanol Extract from Rumex crispus Leaf on Osteoporosis-associated Gene Expression in MG-63 Cells%水菠菜叶乙醇提取物对MG-63骨质疏松相关基因表达的影响

    Institute of Scientific and Technical Information of China (English)

    江慎华; 陈惠; 陈静; 汪涛; 周英棠

    2013-01-01

    为探讨水菠菜叶乙醇提取物与抗骨质疏松作用的关系及其作用机制,用水菠菜叶乙醇提取物处理人成骨样细胞MG-63 48 h后,提取水菠菜叶乙醇提取处理组和对照组细胞的总RNA,将两组RNA纯化为mRNA,逆转录成cDNA,用Cy3和Cy5两种不同的荧光染料进行线性扩增标记,然后与骨质疏松相关基因表达谱芯片杂交,扫描后对获得的数据用LuxScan 3.0软件分析.研究发现经水菠菜叶乙醇提取物诱导后MG-63细胞的244个骨质疏松相关基因中,有c-Fo、JNK、ODF、c-src、OSCAR、RANKL、Samd4、Samd6、Samd7 9个基因表达明显上调,LRP5、Dkk1、TGFB、OPG 4个基因明显下调.结果表明水菠菜叶乙醇提取物能改变骨质疏松相关基因的表达,抗骨质疏松作用机制可能与Wnt/β-catenin蛋白信号传导途径和骨保护素/核因子受体激活信号传导途径有关,与雌激素内分泌途径无关.%To investigate the effects of methanol extract from Rumex crispus leaf on osteoporosis-associated gene expression in MG-63 cells by gene expression profile chip.The total RNAs were extracted from methanol extract from Rumex crispus leaf untreated or treated on MG-63 cells to synthesize double-stranded cDNAs by reverse transcription.Then cDNA labeled with the incorporation o f Cy3 and Cy5-dUT were amplified linearly.Probes were hybridized with oligo-nucleotide microarray.The chips were scanned and afterwards analyzed by LuxScan software.After methanol extract from Rumex crispus leaf induction,expressions of 9 out of 244 osteoporosis related genes,including c-Fos,JNK,ODF,c-src,OSCAR,RANKL,Samd4,Samd6 and Samd7,were down-regulated dramatically.Meanwhile,expressions o f 4 out of 244 cancer genes,including LRP5,Dkk 1,TGFB and OPG,were up-regulated significantly.It could be concluded that methanol extract from Rumex crispus leaf would change the relative gene expression.The anti-osteoporosis mechanism may be related to the Wnt/β-catenin protein

  14. Stabilization of Thermoelectric Properties of the Cu/Bi0.48Sb1.52Te3 Composite for Advantageous Power Generation

    Science.gov (United States)

    Xie, Dewen; Xu, Jingtao; Liu, Zhu; Liu, Guoqiang; Shao, Hezhu; Tan, Xiaojian; Jiang, Haochuan; Jiang, Jun

    2016-09-01

    Bi2Te3 thermoelectric materials have been developed for refrigeration around room temperature. But the ZT values decrease quickly above 400 K, which need to be improved for applications in power generation. In the present work, P-type Cu/BiSbTe alloys have been prepared via a zone melting method followed by spark plasma sintering. Due to the effects of Cu powders, the as-prepared materials exhibit a shift of the peak Seebeck coefficient value towards higher temperature and suppressed lattice thermal conductivity with increasing Cu powders. A peak ZT value as high as 0.87 has been obtained around 500 K in the BiSbTe alloy with 1 wt.% Cu powder addition, and the ZT values stabilize above 0.8 from 375 K to 550 K. This high and stable value for BiSbTe alloys at such a high temperature is very attractive for its application in power generation devices.

  15. Spectroscopic Properties of Ho3+-DOped Ge-In-Sb-S Glass-Ceramics%HO3+ 杂Ge-In-Sb-S玻璃陶瓷光谱特性

    Institute of Scientific and Technical Information of China (English)

    应磊; 戴世勋; 聂秋华; 林常规; 陈飞飞; 徐铁峰

    2011-01-01

    采用熔融淬冷法和热处理工艺制备了系列掺Ho3+的透明G eS2-In2S3-Sb2S3硫系玻璃陶瓷.测试了Ho3掺杂的基质玻璃和玻璃陶瓷样品的密度、显微硬度、红外光谱以及在900 nm激光泵浦下的近红外及中红外荧光光谱.结果表明:热处理后样品析出的晶相为In2S3和Sb2S3颗粒的混合体,晶粒尺寸限制在~100 nm以内;而原本掺杂在玻璃基质中的Ho3+富集在析出的In2S3晶体周围引起了Ho3+局部浓度的增加.因此,热处理后玻璃陶瓷样品的近红外和中红外荧光强度增加.%Ho3 + -doped chalcogenide glass-ceramics in GeS2-In2S3-Sb2S3 system were prepared by appropriate heat treatment, and their properties including density, microhardness, infrared transmittance spectrum and fluorescence in the near- and mid-infrared region under 900 ran excitation, were measured. The results showed that the crystalline phases in the obtained glass-ceramics were mixture of In2S3 and Sb2S3 with the grain sizes about 100 nm. The Ho3+ , in the host glass network, was aggregated around the In2S3 grains after crystallization processing, which caused the increase of local concentration of Ho3 +. Therefore, the intensities of near- and mid-infrared luminescence in the samples were enhanced.

  16. Growth Optimization Studies to Develop InAs/GaInSb Superlattice Materials for Very Long Wavelength Infrared Detection (Postprint)

    Science.gov (United States)

    2014-10-01

    We increased the As beam equivalent pressure ( BEP ) flux from 1.4 107 to 2.2 107 torr, while the Sb BEP fixed at 4.8 107 - torr to observe... BEP , respectively. Sample Tg (C) As/Sb (a.u.) P (Å) Strain (%) RMS (Å) Eg (meV) PR intensity (arb. units) SL1 390 0.30 67.8 +0.18 21 X X SL2 400 0.30

  17. Quaternary Narrow-Band Semiconductors (HgTe)x(InSb)1-X for Far-Infrared Detectors.

    Science.gov (United States)

    1986-08-31

    Vapor Growth and Epitaxy. Coronado, California, 1981, p. 331. rn21. M. Rodot. Les Materiaux Semiconducteurs. Dunod, Paris, 1965. 22. E. M. Barrall ...Thermochim. Acta, 5, 377 (1973). 23. M. F. Kimmitt, G. C. Lopez , J. C. Giles, M. Takai, H. P. Roser, B. T. McGuckin and A. Black. Infrared Phys., 25, 767

  18. Study of Minority Carrier Lifetimes in Very Long Wave Infrared Strained Layer InAs/GaInSb Superlattices (Postprint)

    Science.gov (United States)

    2016-09-19

    aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information...previously reported lifetime values for other VLWIR detector absorbers. This improvement is attributed to the strain-engineered ternary SL design, which...offers a variety of epitaxial advantages and ultimately leads to the improvements in the minority carrier lifetime b mitigating defect-mediated Shockley

  19. Bandgap Tunability in Sb-Alloyed BiVO₄ Quaternary Oxides as Visible Light Absorbers for Solar Fuel Applications.

    Science.gov (United States)

    Loiudice, Anna; Ma, Jie; Drisdell, Walter S; Mattox, Tracy M; Cooper, Jason K; Thao, Timothy; Giannini, Cinzia; Yano, Junko; Wang, Lin-Wang; Sharp, Ian D; Buonsanti, Raffaella

    2015-11-01

    The challenge of fine compositional tuning and microstructure control in complex oxides is overcome by developing a general two-step synthetic approach. Antimony-alloyed bismuth vanadate, which is identified as a novel light absorber for solar fuel applications, is prepared in a wide compositional range. The bandgap of this quaternary oxide linearly decreases with the Sb content, in agreement with first-principles calculations.

  20. Determination of traces of Sb(III) using ASV in Sb-rich water samples affected by mining.

    Science.gov (United States)

    Cidu, Rosa; Biddau, Riccardo; Dore, Elisabetta

    2015-01-07

    Chemical speciation [Sb(V) and Sb(III)] affects the mobility, bioavailability and toxicity of antimony. In oxygenated environments Sb(V) dominates whereas thermodynamically unstable Sb(III) may occur. In this study, a simple method for the determination of Sb(III) in non acidic, oxygenated water contaminated with antimony is proposed. The determination of Sb(III) was performed by anodic stripping voltammetry (ASV, 1-20 μg L(-1) working range), the total antimony, Sb(tot), was determined either by inductively coupled plasma mass spectrometry (ICP-MS, 1-100μgL(-1) working range) or inductively coupled plasma optical emission spectrometry (ICP-OES, 100-10,000 μg L(-1) working range) depending on concentration. Water samples were filtered on site through 0.45 μm pore size filters. The aliquot for determination of Sb(tot) was acidified with 1% (v/v) HNO3. Different preservatives, namely HCl, L(+) ascorbic acid or L(+) tartaric acid plus HNO3, were used to assess the stability of Sb(III) in synthetic solutions. The method was tested on groundwater and surface water draining the abandoned mine of Su Suergiu (Sardinia, Italy), an area heavily contaminated with Sb. The waters interacting with Sb-rich mining residues were non acidic, oxygenated, and showed extreme concentrations of Sb(tot) (up to 13,000 μg L(-1)), with Sb(III) Sb(III) in oxygenated, Sb-rich waters. Due to the instability of Sb(III), analyses should be carried out within 7 days upon the water collection. The main advantage of the proposed method is that it does not require time-consuming preparation steps prior to analysis of Sb(III).

  1. Evaluation of Glass Density to Support the Estimation of Fissile Mass Loadings from Iron Concentrations in SB6 Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, T.; Peeler, D.

    2010-12-15

    The Department of Energy - Savannah River (DOE-SR) previously provided direction to Savannah River Remediation (SRR) to maintain fissile concentration in glass below 897 g/m{sup 3}. In support of the guidance, the Savannah River National Laboratory (SRNL) provided a technical basis and a supporting Microsoft{reg_sign} Excel{reg_sign} spreadsheet for the evaluation of fissile loading in Sludge Batch 5 glass based on the Fe concentration in glass as determined by the measurements from the Slurry Mix Evaporator (SME) acceptability analysis. SRR has since requested that SRNL provide the necessary information to allow SRR to update the Excel spreadsheet so that it may be used to maintain fissile concentration in glass below 897 g/m{sup 3} during the processing of Sludge Batch 6 (SB6). One of the primary inputs into the fissile loading spreadsheet includes a bounding density for SB6-based glasses. Based on the measured density data of select SB6 variability study glasses, SRNL recommends that SRR utilize the 99/99 Upper Tolerance Limit (UTL) density value at 38% WL (2.823 g/cm{sup 3}) as a bounding density for SB6 glasses to assess the fissile concentration in this glass system. That is, the 2.823 g/cm{sup 3} is recommended as a key (and fixed) input into the fissile concentration spreadsheet for SB6 processing. It should be noted that no changes are needed to the underlying structure of the Excel based spreadsheet to support fissile assessments for SB6. However, SRR should update the other key inputs to the spreadsheet that are based on fissile and Fe concentrations reported from the SB6 Waste Acceptance Product Specification (WAPS) sample. The purpose of this technical report is to present the density measurements that were determined for the SB6 variability study glasses and to conduct a statistical evaluation of these measurements to provide a bounding density value that may be used as input to the Excel{reg_sign} spreadsheet to be employed by SRR to maintain the fissile concentration in its SB6 glass below 897 g/m{sup 3}. It should be noted that no changes are needed to the underlying structure of the Excel{reg_sign} based spreadsheet to support fissile assessments for SB6.

  2. Quantum spin-quantum anomalous Hall effect with tunable edge states in Sb monolayer-based heterostructures

    Science.gov (United States)

    Zhou, Tong; Zhang, Jiayong; Xue, Yang; Zhao, Bao; Zhang, Huisheng; Jiang, Hua; Yang, Zhongqin

    2016-12-01

    A novel topological insulator with tunable edge states, called a quantum spin-quantum anomalous Hall (QSQAH) insulator, is predicted in a heterostructure of a hydrogenated Sb (S b2H ) monolayer on a LaFe O3 substrate by using ab initio methods. The substrate induces a drastic staggered exchange field in the S b2H film, which plays an important role to generate the QSQAH effect. A topologically nontrivial band gap (up to 35 meV) is opened by Rashba spin-orbit coupling, which can be enlarged by strain and an electric field. To understand the underlying physical mechanism of the QSQAH effect, a tight-binding model based on px and py orbitals is constructed. With the model, the exotic behaviors of the edge states in the heterostructure are investigated. Dissipationless chiral charge edge states related to one valley are found to emerge along both sides of the sample, whereas low-dissipation spin edge states related to the other valley flow only along one side of the sample. These edge states can be tuned flexibly by polarization-sensitive photoluminescence controls and/or chemical edge modifications. Such flexible manipulations of the charge, spin, and valley degrees of freedom provide a promising route towards applications in electronics, spintronics, and valleytronics.

  3. Thickness Dependence of the Quantum Anomalous Hall Effect in Magnetic Topological Insulator Films.

    Science.gov (United States)

    Feng, Xiao; Feng, Yang; Wang, Jing; Ou, Yunbo; Hao, Zhenqi; Liu, Chang; Zhang, Zuocheng; Zhang, Liguo; Lin, Chaojing; Liao, Jian; Li, Yongqing; Wang, Li-Li; Ji, Shuai-Hua; Chen, Xi; Ma, Xucun; Zhang, Shou-Cheng; Wang, Yayu; He, Ke; Xue, Qi-Kun

    2016-08-01

    The evolution of the quantum anomalous Hall effect with the thickness of Cr-doped (Bi,Sb)2 Te3 magnetic topological insulator films is studied, revealing how the effect is caused by the interplay of the surface states, band-bending, and ferromagnetic exchange energy. Homogeneity in ferromagnetism is found to be the key to high-temperature quantum anomalous Hall material.

  4. Study of irradiation damages in MgAl{sub 2}O{sub 4} and ZnAl{sub 2}O{sub 4} spinels in the framework of nuclear waste transmutation; Dommages d'irradiation dans des ceramiques de structure spinelle MgAl{sub 2}O{sub 4} et ZnAl{sub 2}O{sub 4} application a la transmutation des dechets nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Thiriet-Dodane, C

    2002-07-01

    The transmutation of minor actinides in-reactor is one solution currently being studied for the long time management of nuclear waste. In the heterogeneous concept the radionuclides are incorporating in an inert ceramic matrix. The support material must be insensitive to radiation damage. Fission product damage is the main radiation damage source during the transmutation process and therefore it is of the utmost importance to study their effects. We irradiated spinels MgAl{sub 2}O{sub 4} (matrix of reference) and ZnAl{sub 2}O{sub 4} by fast ions (by example: {sup 86}Kr of approximately 400 MeV) simulating the fission products. Under these conditions, the damage is primarily due to the electronic energy losses (S{sub e}). One of the structural features of spinel AB{sub 2}O{sub 4} is that the two cations (A{sup 2+} and B{sup 3+}) can exchange their site. This phenomenon is quantified by the inversion parameter. We highlight by XRD in grazing incidence that the structural changes observed in MgAl{sub 2}O{sub 4} correspond to an order-disorder transition from the cation sub-networks and not to a phase shift as described in the literature. Using other techniques characterizing the space group (Raman spectroscopy) as well as the local order (NMR 27Al, spectroscopy of absorption X with the thresholds K of Al and Zn), we confirm this interpretation. Moreover, for a fluence of 10{sup 14} ions/cm{sup 2}, the loss of the order at long distance is observed thus meaning a beginning of amorphization of material. The ZnAl{sub 2}O{sub 4} spinel presents the same behaviour. For this last spinel, an evolution of the inversion parameter according to the stopping power 2 was highlighted after irradiation by ions {sup 86}Kr from approximately 20 MeV. We illustrate our study by the analysis of the results obtained in XRD of an irradiation out of composite fuel (MgAl{sub 2}O{sub 4} + UO{sub 2}) called THERMHET. (authors)

  5. Enhancement of H_c2 in MgB2 Wires through Carbon Substitution

    Science.gov (United States)

    Finnemore, D. K.; Wilke, R. H. T.; Straszheim, W. E.; Sailsbury, H.; Bud'Ko, S. L.; Canfield, P. C.; Suplinskas, R. J.; Hannahs, S. T.

    2004-03-01

    A series of carbon substituted Mg(B_1-xC_x)2 wires were fabricated in a two step process by co-depositing carbon and boron on a tungsten filament using a CVD reaction. These starting fibers had nominal carbon concentrations of 0.5,1, and 2 percent as determined from the C to B ratio in the CVD gas stream. The conversion to Mg(B_1-xC_x)2 was carried out by heating the C-doped B fiber in a Mg vapor.[1] The temperature dependence of H_c2 was measured resistively in fields up to 33 T. Carbon doping results in relatively minor decrease in Tc from 39.2 to 36.2 K, while simultaneously increasing H_c2(0) from 16 to 33 T. We have shown carbon is an effective dopant for increasing H_c2 and our data suggest even higher critical fields can be achieved with nominal concentrations around 4-5 [1] P.C. Canfield, D. K. Finnemore, S.L. Bud'ko, J.E. Ostenson, G. Lapertot, C.E. Cunnigham, and C. Petrovic, Phys. Rev. Lett. 86, 2423 (2001).

  6. Self-learning kinetic Monte Carlo simulations of Al diffusion in Mg

    Energy Technology Data Exchange (ETDEWEB)

    Nandipati, Giridhar; Govind, Niranjan; Andersen, Amity; Rohatgi, Aashish

    2016-03-16

    Atomistic on-lattice self-learning kinetic Monte Carlo (SLKMC) method was used to examine the vacancy-mediated diffusion of an Al atom in pure hcp Mg. Local atomic environment dependent activation barriers for vacancy-atom exchange processes were calculated on-the-fly using climbing image nudged-elastic band method (CI-NEB) and using a Mg-Al binary modified embedded-atom method (MEAM) interatomic potential. Diffusivities of vacancy and Al atom in pure Mg were obtained from SLKMC simulations and are compared with values available in the literature that are obtained from experiments and first-principle calculations. Al Diffusivities obtained from SLKMC simulations are lower, due to larger activation barriers and lower diffusivity prefactors, than those available in the literature but have same order of magnitude. We present all vacancy-Mg and vacancy-Al atom exchange processes and their activation barriers that were identified in SLKMC simulations. We will describe a simple mapping scheme to map a hcp lattice on to a simple cubic lattice that would enable hcp lattices to be simulated in an on-lattice KMC framework. We also present the pattern recognition scheme used in SLKMC simulations.

  7. Water vapour at high redshift : Arecibo monitoring of the megamaser in MG J0414+0534

    NARCIS (Netherlands)

    Castangia, P.; Impellizzeri, C. M. V.; McKean, J. P.; Henkel, C.; Brunthaler, A.; Roy, A. L.; Wucknitz, O.; Ott, J.; Momjian, E.

    2011-01-01

    Aims: The study of water masers at cosmological distances would allow us to investigate the parsec-scale environment around powerful radio sources, to probe the physical conditions of the molecular gas in the inner parsecs of quasars, and to estimate their nuclear engine masses in the early universe

  8. Hall field-induced resistance oscillations in MgZnO/ZnO heterostructures

    Science.gov (United States)

    Shi, Q.; Zudov, M. A.; Falson, J.; Kozuka, Y.; Tsukazaki, A.; Kawasaki, M.; von Klitzing, K.; Smet, J.

    2017-01-01

    We report on nonlinear magnetotransport in a two-dimensional electron gas hosted in a MgZnO/ZnO heterostructure. Upon application of a direct current, we observe pronounced Hall field-induced resistance oscillations (HIRO), which are well known from experiments on high-mobility GaAs/AlGaAs quantum wells. The unique sensitivity of HIRO to the short-range component of the disorder potential allows us to unambiguously establish that the mobility of our MgZnO/ZnO heterostructure is limited by impurities residing within or near the two-dimensional (2D) channel. This demonstration that HIRO can be realized in a system with a much lower mobility, much higher density, and much larger effective mass than in previously studied systems highlights the remarkable universality of the phenomenon and its great promise for use in studies of a wide variety of emerging 2D materials.

  9. Magnetotransport in MgO-based magnetic tunnel junctions grown by molecular beam epitaxy (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Andrieu, S., E-mail: stephane.andrieu@univ-lorraine.fr; Bonell, F.; Hauet, T.; Montaigne, F. [Institut Jean Lamour, Nancy University/CNRS, Bd des Aiguillettes, BP239, 54506 Vandoeuvre-lès-Nancy (France); Calmels, L.; Snoeck, E. [CEMES, CNRS and Toulouse University, 29 rue Jeanne Marvig, 31055 Toulouse (France); Lefevre, P.; Bertran, F. [Synchrotron SOLEIL-CNRS, L' Orme des Merisiers, Saint-Aubin, BP48, 91192 Gif-sur-Yvette cedex (France)

    2014-05-07

    The strong impact of molecular beam epitaxy growth and Synchrotron Radiation characterization tools in the understanding of fundamental issues in nanomagnetism and spintronics is illustrated through the example of fully epitaxial MgO-based Magnetic Tunnel Junctions (MTJs). If ab initio calculations predict very high tunnel magnetoresistance (TMR) in such devices, some discrepancy between theory and experiments still exists. The influence of imperfections in real systems has thus to be considered like surface contaminations, structural defects, unexpected electronic states, etc. The influence of possible oxygen contamination at the Fe/MgO(001) interface is thus studied, and is shown to be not so detrimental to TMR as predicted by ab initio calculations. On the contrary, the decrease of dislocations density in the MgO barrier of MTJs using Fe{sub 1−x}V{sub x} electrodes is shown to significantly increase TMR. Finally, unexpected transport properties in Fe{sub 1−X}Co{sub x}/MgO/Fe{sub 1−X}Co{sub x} (001) are presented. With the help of spin and symmetry resolved photoemission and ab initio calculation, the TMR decrease for Co content higher than 25% is shown to come from the existence of an interface state and the shift of the empty Δ1 minority spin state towards the Fermi level.

  10. Raman scattering from a superconductivity-induced bound state in MgB2.

    Science.gov (United States)

    Zeyher, R

    2003-03-14

    It is shown that the sharp peak in the E(2g) Raman spectrum of superconducting MgB2 is due to a bound state caused by the electron-phonon coupling. Our theory explains why this peak appears only in the spectra with E(2g) symmetry and only in the sigma but not the pi bands. The properties of the bound state and the Raman spectrum are investigated, also in the presence of impurity scattering.

  11. Thickness dependence of Jc (0) in MgB2 films

    Science.gov (United States)

    Chen, Yiling; Yang, Can; Jia, Chunyan; Feng, Qingrong; Gan, Zizhao

    2016-06-01

    MgB2 superconducting films, whose thicknesses range from 10 nm to 8 μm, have been fabricated on SiC substrates by hybrid physical-chemical vapor deposition (HPCVD) method. It is the first time that the Tc and the Jc of MgB2 films are studied on such a large scale. It is found that with the increasing of thickness, Tc elevates first and then keeps roughly stable except for some slight fluctuations, while Jc (5 K, 0 T) experiences a sharp increase followed by a relatively slow fall. The maximum Jc (5 K, 0 T) = 2.3 × 108 A cm-2 is obtained for 100 nm films, which is the experimental evidence for preparing high-quality MgB2 films by HPCVD method. Thus, this work may provide guidance on choosing the suitable thickness for applications. Meanwhile, the films prepared by us cover ultrathin films, thin films and thick films, so the study on them will bring a comprehensive understanding of MgB2 films.

  12. Theoretical investigation of superconductivity in MgB2-xCx alloys

    Science.gov (United States)

    Sharma, Gargee; Sharma, Smita

    2016-05-01

    In this paper we investigated the superconducting properties of MgB2-xCx alloys where x is the concentration (0.0, 0.03, 0.11 and 0.20). The superconducting state parameters, namely, the electron-phonon coupling strength (λ), Coulomb pseudopotential (μ*), transition temperature (Tc), isotope effect exponent (α) and interaction strength (NoV) of MgB2-xCx alloys have been investigated in the BCS-Eliashberg-McMillan framework, as modified for MgB2-xCx alloys. Pseudo ions with average properties have been considered to replace different types of ions in the system. It is observed that all the superconducting parameters go on decreasing as the concentration of C is increased. The magnitudes of λ and Tc indicate that MgB2-xCx is strong-to-intermediate coupling superconductor. It is also observed that Tc is composition dependent. Present computations yield almost linear variation of Tc with concentration x of C in the MgB2-xCx system, which is in agreement with the experimental data. A linear Tc equation is proposed by fitting the present results.

  13. High T(c) superconductivity in MgB2 by nonadiabatic pairing.

    Science.gov (United States)

    Cappelluti, E; Ciuchi, S; Grimaldi, C; Pietronero, L; Strässler, S

    2002-03-18

    The evidence for the key role of the sigma bands in the electronic properties of MgB2 points to the possibility of nonadiabatic effects in the superconductivity of these materials. These are governed by the small value of the Fermi energy due to the vicinity of the hole doping level to the top of the sigma bands. We show that the nonadiabatic theory leads to a coherent interpretation of T(c) = 39 K and the boron isotope coefficient alphaB = 0.30 without invoking very large couplings and it naturally explains the role of the disorder on T(c). It also leads to various specific predictions for the properties of MgB2 and for the material optimization of these types of compounds.

  14. Quantum confinement induced band gaps in MgB2 nanosheets

    Science.gov (United States)

    Xu, Bo Z.; Beckman, Scott P.

    2016-09-01

    The discovery of two-dimensional semiconducting materials, a decade ago, spawned an entire sub-field within solid-state physics that is focused on the development of nanoelectronics. Here we present a new class of semiconducting two-dimensional material based on hexagonal MgB2. Although MgB2 is a semimetal, similar to the other well-studied transition metal diborides, we demonstrate that, unlike the transition metal diborides, thinning MgB2, to create nanosheets, opens a band gap in the density of states. We predict that a 7 Å thick MgB2 nanosheet will have a band gap of 0.51 eV. MgB2 nanosheets differ from other two-dimensional semiconductors in that the band gap is introduced by (001) surfaces and is opened by the quantum confinement effect. The implications of these findings are that nanostructured MgB2 is not merely a new composition, but also has intrinsic mechanisms for tuning its electronic properties, which may facilitate the development of nanoelectronics.

  15. Implications of reflectance measurements on the mechanism for superconductivity in MgB2.

    Science.gov (United States)

    Marsiglio, F

    2001-12-10

    Recent optical studies in c-axis oriented superconducting MgB2 films indicate that the electron-phonon coupling is weak. We reinforce this conclusion by examining the raw reflectance data; its frequency dependence is incompatible with strong electron-phonon scattering. This is further strengthened by analysis of the real part of the conductivity, and by the temperature dependence of the effective Drude scattering rate. Using a realistic electron-phonon spectral shape, we find lambda(tr) approximately 0.15. To the extent that lambda(tr) approximately lambda, this disagrees sharply with model calculations, and is far too low to provide the means for T(c) = 39 K. A simple model is constructed with coupling to a high frequency excitation, which is consistent with both the low frequency optical data and the high T(c).

  16. Band filling and interband scattering effects in MgB2: carbon versus aluminum doping.

    Science.gov (United States)

    Kortus, Jens; Dolgov, Oleg V; Kremer, Reinhard K; Golubov, Alexander A

    2005-01-21

    We argue, based on band structure calculations and the Eliashberg theory, that the observed decrease of T(c) of Al and C doped MgB2 samples can be understood mainly in terms of a band filling effect due to the electron doping by Al and C. A simple scaling of the electron-phonon coupling constant lambda by the variation of the density of states as a function of electron doping is sufficient to capture the experimentally observed behavior. Further, we also explain the long standing open question of the experimental observation of a nearly constant pi gap as a function of doping by a compensation of the effect of band filling and interband scattering. Both effects together generate a nearly constant pi gap and shift the merging point of both gaps to higher doping concentrations, resolving the discrepancy between experiment and theoretical predictions based on interband scattering only.

  17. Experimental evidence for anisotropic double-gap behavior in MgB2.

    Science.gov (United States)

    Cubitt, R; Levett, S; Bud'ko, S L; Anderson, N E; Canfield, P C

    2003-04-18

    The behavior of a type II superconductor in the presence of a magnetic field is governed by two characteristic length scales, the London penetration depth and the coherence length. We present magnetization measurements on MgB2 powder showing an anisotropy in the upper critical field and hence the coherence length of 6. Using the technique of small angle neutron scattering we show that this anisotropy is not mirrored in the London penetration depth, which is almost isotropic. This result can be explained by the superconductivity residing in two distinct electronic bands of the material, only one of which is highly anisotropic.

  18. Dynamic and Structural Studies of Metastable Vortex Lattice Domains in MgB2

    Science.gov (United States)

    de Waard, E. R.; Kuhn, S. J.; Rastovski, C.; Eskildsen, M. R.; Leishman, A.; Dewhurst, C. D.; Debeer-Schmitt, L.; Littrell, K.; Karpinski, J.; Zhigadlo, N. D.

    Small-angle neutron scattering (SANS) studies of the vortex lattice (VL) in the type-II superconductor MgB2 have revealed an unprecedented degree of metastability that is demonstrably not due to vortex pinning, [C. Rastovski et al . , Phys. Rev. Lett. 111, 107002 (2013)]. The VL can be driven to the GS through successive application of an AC magnetic field. Here we report on detailed studies of the transition kinetics and structure of the VL domains. Stroboscopic studies of the transition revealed a stretched exponential decrease of the metastable volume fraction as a function of the number of applied AC cycles, with subtle differences depending on whether the AC field is oriented parallel or perpendicular to the DC field used to create the VL. We speculate the slower transition kinetics for the transverse AC field may be due to vortex cutting. Spatial studies include scanning SANS measurements showing the VL domain distribution within the MgB2 single crystal as well as measurements of VL correlation lengths. This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Award DE-FG02-10ER46783.

  19. Supercondcuting properties in MgB2/Fe wires prepared by PIT method

    Institute of Scientific and Technical Information of China (English)

    YAN Guo; FENG Yong; FU Baoquan; LIU Chunfang; JI Ping; ZHANG Pingxiang; ZHOU Lian

    2003-01-01

    The MgB2 formation was analyzed physically and chemically and the MgB2/Fe wires were fabricated by powder in tube (PIT) technology. The microstructureof MgB2 in wires was studied by the scanning electrical microscope (SEM), whichshows a good connection of grains and the size of MgB2 grain is 1-3μm. The results of Jc measured by the standard four probes method show that Jc value reaches 6.1×104 A/cm2 at 20 K in self field.

  20. Anisotropies of the lower and upper critical fields in MgB2 single crystals.

    Science.gov (United States)

    Lyard, L; Szabó, P; Klein, T; Marcus, J; Marcenat, C; Kim, K H; Kang, B W; Lee, H S; Lee, S I

    2004-02-01

    The temperature dependence of the upper (H(c2)) and lower (H(c1)) critical fields has been deduced from Hall probe magnetization measurements of high quality MgB2 single crystals along the two main crystallographic directions. We show that Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1))=H(c1 axially c)/H(c1 axially ab) differ significantly at low temperature (being approximately 5 and approximately 1, respectively) and have opposite temperature dependencies. We suggest that MgB2 can be described by a single field dependent anisotropy parameter gamma(H) (=lambda(c)/lambda(ab)=xi(ab)/xi(c)) that increases from Gamma(H(c1)) at low field to Gamma(H(c2)) at high field.

  1. Core Microstructure and Strain State Analysis in MgB2 Wires with Different Metal Sheaths

    Directory of Open Access Journals (Sweden)

    C. E. Sobrero

    2015-01-01

    Full Text Available We present a detailed analysis of the effect of the sheath materials on the microstructure and superconducting properties of MgB2 wires produced by the powder-in-tube method (PIT. We reduced commercial MgB2 powder by attrition milling in nitrogen atmosphere using tungsten carbide balls and obtained powders with grain sizes lower than 150 nm and different strain states through this process. Several Ti, stainless steel, and copper monofilamentary wires were prepared using these powders by the PIT method. We investigated different thermal treatments and mechanical paths during the processing of the wires for the enhancement of the critical currents. The superconducting properties were determined by magnetization measurements in a SQUID magnetometer. The correlation between the thermal treatments, structure, and superconducting properties is discussed.

  2. Dose Dependence of Mechanoluminescence Properties in MgAl2O4: Dy Phosphor

    Directory of Open Access Journals (Sweden)

    Kabita K. Satapathy

    2013-01-01

    Full Text Available A reliable dosimetry is fundamental for quality assurance of the processes and irradiation products. All dosimetric systems for high doses have some limitation with regard to their use. Dosimetric system should be easy to use, fast to measure, and of low cost. Good phosphor which shows high luminescence properties may fulfil the above criteria in some way. MgAl2O4: Dy phosphor has been prepared by solution combustion technique and confirmed with the help of XRD. ML has been excited impulsively by dropping a load of mass 0.7 kg onto the phosphors from various heights; two distinct ML peaks are observed for all the samples. It is observed that MgAl2O4: Dy phosphor shows linear response to gamma-ray dose and low fading which can be used for dosimetric purpose.

  3. Electrochemical removal of hydrogen atoms in Mg-doped GaN epitaxial layers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, June Key, E-mail: junekey@jnu.ac.kr, E-mail: hskim7@jbnu.ac.kr; Hyeon, Gil Yong; Tawfik, Wael Z.; Choi, Hee Seok [Department of Materials Science and Engineering, and Optoelectronics Convergence Research Center, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Ryu, Sang-Wan [Department of Physics and Optoelectronics Convergence Research Center, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Jeong, Tak [Korea Photonics Technology Institute, Gwangju 500-460 (Korea, Republic of); Jung, Eunjin; Kim, Hyunsoo, E-mail: junekey@jnu.ac.kr, E-mail: hskim7@jbnu.ac.kr [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2015-05-14

    Hydrogen atoms inside of an Mg-doped GaN epitaxial layer were effectively removed by the electrochemical potentiostatic activation (EPA) method. The role of hydrogen was investigated in terms of the device performance of light-emitting diodes (LEDs). The effect of the main process parameters for EPA such as solution type, voltage, and time was studied and optimized for application to LED fabrication. In optimized conditions, the light output of 385-nm LEDs was improved by about 26% at 30 mA, which was caused by the reduction of the hydrogen concentration by ∼35%. Further removal of hydrogen seems to be involved in the breaking of Ga-H bonds that passivate the nitrogen vacancies. An EPA process with high voltage breaks not only Mg-H bonds that generate hole carriers but also Ga-H bonds that generate electron carriers, thus causing compensation that impedes the practical increase of hole concentration, regardless of the drastic removal of hydrogen atoms. A decrease in hydrogen concentration affects the current-voltage characteristics, reducing the reverse current by about one order and altering the forward current behavior in the low voltage region.

  4. Room temperature ferromagnetism in Mg-doped ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Jaspal, E-mail: jaspal0314@gmail.com; Vashihth, A. [Department of Applied Sciences, Chandigarh University, Gharuan, Mohali-140413 (India); Gill, Pritampal Singh; Verma, N. K. [Nano Research Lab, School of Physics and Materials Science, Thapar University, Patiala-147 004 (India)

    2015-06-24

    Zn{sub 1-x}Mg{sub x}O (x = 0, 0,10) nanoparticles were successfully synthesized using sol-gel method. X-ray diffraction (XRD) confirms that the synthesized nanoparticles possess wurtzite phase having hexagonal structure. Morphological analysis was carried out using transmission electron microscopy (TEM) which depicts the spherical morphology of ZnO nanoparticles. Energy dispersive spectroscopy (EDS) showed the presence of Mg in ZnO nanoparticles. Electron spin resonance (ESR) signal was found to be decreasing with increasing of Mg-doping concentration. The room temperature ferromagnetism was observed in undoped and Mg-doped ZnO nanoparticles. The increase of Mg-doping concentration resulted in decrease of saturation magnetization value which could be attributed to decrease of oxygen vacancies present in host nanoparticles.

  5. INVESTIGATION OF SURFACE AND BULK PROCESSES IN MG-BASED ALLOYS DURING HYDROGEN ABSORPTION

    Directory of Open Access Journals (Sweden)

    Balázs Vehovszky

    2012-09-01

    Full Text Available Different Mg-based alloys were tailored and prepared to investigate the surface and bulk processes during hydrogen absorption. Volumetric-, resistance-, XRD-, optical-, and mass measurements were carried out. Heat treatment experiments showed that the short-term thermal stability limits (during heating up at 5 K/min of the amorphous samples were between 125-175 ° C, while long-term stability (during 24h heat treatment is always lower – between 80 and 150°C. Nanocrystalline alloys were stable up to 300°C. Hydrogen absorption measurements were executed between 25 and 300°C. Pd-containing alloys were found to be the fastest absorbers, and 200°C was the optimal temperature regarding absorption rate. Etching the samples previously in HF solution enhances absorption by inducing surface cracking. This phenomenon was thoroughly examined by optical microscopy. The effect of hydrogen on the crystallization properties of MgNiPd sample was determined via in-situ resistance measurements.

  6. Investigation of Surface and Bulk Processes in Mg-based Alloys during Hydrogen Absorption

    Directory of Open Access Journals (Sweden)

    Balázs Vehovszky

    2012-09-01

    Full Text Available Different Mg-based alloys were tailored and prepared to investigate the surface and bulk processes during hydrogen absorption. Volumetric-, resistance-, XRD-, optical-, and mass measurements were carried out. Heat treatment experiments showed that the short-term thermal stability limits (during heating up at 5 K/min of the amorphous samples were between 125-175 ° C, while long-term stability (during 24h heat treatment is always lower – between 80 and 150°C. Nanocrystalline alloys were stable up to 300°C. Hydrogen absorption measurements were executed between 25 and 300°C. Pd-containing alloys were found to be the fastest absorbers, and 200°C was the optimal temperature regarding absorption rate. Etching the samples previously in HF solution enhances absorption by inducing surface cracking. This phenomenon was thoroughly examined by optical microscopy. The effect of hydrogen on the crystallization properties of MgNiPd sample was determined via in-situ resistance measurements.

  7. Thermodynamic modeling of hydrogen storage capacity in Mg-Na alloys.

    Science.gov (United States)

    Abdessameud, S; Mezbahul-Islam, M; Medraj, M

    2014-01-01

    Thermodynamic modeling of the H-Mg-Na system is performed for the first time in this work in order to understand the phase relationships in this system. A new thermodynamic description of the stable NaMgH3 hydride is performed and the thermodynamic models for the H-Mg, Mg-Na, and H-Na systems are reassessed using the modified quasichemical model for the liquid phase. The thermodynamic properties of the ternary system are estimated from the models of the binary systems and the ternary compound using CALPHAD technique. The constructed database is successfully used to reproduce the pressure-composition isotherms for MgH2 + 10 wt.% NaH mixtures. Also, the pressure-temperature equilibrium diagram and reaction paths for the same composition are predicted at different temperatures and pressures. Even though it is proved that H-Mg-Na does not meet the DOE hydrogen storage requirements for onboard applications, the best working temperatures and pressures to benefit from its full catalytic role are given. Also, the present database can be used for thermodynamic assessments of higher order systems.

  8. Reversible hydrogen storage in Mg(BH4)2/carbon nanocomposites

    NARCIS (Netherlands)

    Yan, Y.; Au, Y.S.|info:eu-repo/dai/nl/328200360; Rentsch, D.; Remhof, A.; de Jongh, P.E.|info:eu-repo/dai/nl/186125372; Züttel, A.

    2013-01-01

    Mg(BH4)2 exhibits a high hydrogen content of 14.9 wt% and thermodynamic stability in the overall decomposition reaction that corresponds to hydrogen desorption at around room temperature. However, the potential applications in hydrogen storage are restricted by high kinetic barriers. In this study,

  9. Three-dimensional electron backscattered diffraction analysis of deformation in MgO micropillars

    Energy Technology Data Exchange (ETDEWEB)

    Korte, S., E-mail: sandra.korte@cantab.net [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Ritter, M. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Jiao, C. [FEI Company, Achtseweg Noord 5, 5651 GG Eindhoven (Netherlands); Midgley, P.A.; Clegg, W.J. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)

    2011-11-15

    Small-scale testing is extensively used to study the effects of size on plasticity or characterise plastic deformation of brittle materials, where cracking is suppressed on the microscale. Geometrical and experimental constraints have been shown to affect small-scale deformation and efforts are underway to understand these better. However, current analytical techniques tend to possess high resolution in only one or two dimensions, impeding a detailed analysis of the entire deformed volume. Here electron backscattered diffraction in three dimensions is presented as a way of characterising three-dimensional (3-D) deformation at high spatial resolution. It is shown that, by reconstruction of compressed and then successively sliced and indexed MgO micropillars, this 3-D technique yields information complementary to {mu}-Laue diffraction or electron microscopy, allowing a correlation of experimental artefacts and the distribution of plasticity. In addition, deformation features which are difficult to visualise by standard scanning electron microscopy are easily detected, for example where only small surface traces are produced or minimal plastic strain can be introduced before failure in brittle materials.

  10. Nearly-Noncritical Phase Matching in MgO:LiNbO3 Optical Parametric Oscillators

    Institute of Scientific and Technical Information of China (English)

    姚建铨; 于意仲; 王鹏; 王涛; 张百钢; 丁欣; 陈进; H.J.Peng; H.S.Kwok

    2001-01-01

    We have proposed and demonstrated a nearly-noncritical phase-matched (NCPM) optical parametric oscillation (OPO) in an MgO:LiNbO3 crystal with 5 mol% MgO by temperature tuning. By giving up perfect NCPM, the practical tuning range for the OPO is increased by two times. For the crystal, the operated temperature decreases with the phase-matching angle at degeneracy. With a cutting angle of 82° instead of the noncritical case of 90°, the tuning range was increased. In order to obtain a sufficiently high output pulse energy for both signal and idler throughout the entire tuning range, five sets of mirrors were used for the resonator. The tuning range of the OPO was 800 - 1700 nm with temperatures tuning from 83°C to 224.2°C. The output energy was about 6.45 mJ with a conversion efficiency of nearly 13%. The bandwidth of the output was 1.0 - L1 nm.

  11. Conduction electron spin resonance in Mg 1 - x Al x B2

    Science.gov (United States)

    Likodimos, V.; Koutandos, S.; Pissas, M.; Papavassiliou, G.; Prassides, K.

    2003-01-01

    Conduction electron spin resonance is employed to study the interplay of the electronic and structural properties in the normal state of Mg 1 - x Al x B2 alloys as a function of Al-doping for 0 <= x <= 1. The x-dependence of the spin susceptibility reveals considerable reduction of the total density of states N(EF) with increasing Al concentration, complying with theoretical predictions for a predominant filling effect of the hole σ bands by electron doping. The CESR linewidth exhibits significant broadening, especially prominent in the high-Al-content region, indicative of the presence of enhanced structural disorder, consistent with the presence of compositional fluctuations.

  12. Surface barrier and bulk pinning in MgB$_2$ superconductor

    OpenAIRE

    Pissas, M.; Moraitakis, E.; Stamopoulos, D.; Papavassiliou, G.; V. Psycharis; Koutandos, S.

    2001-01-01

    We present a modified method of preparation of the new superconductor MgB$_2$. The polycrystalline samples were characterized using x-ray and magnetic measurements. The surface barriers control the isothermal magnetization loops in powder samples. In bulk as prepared samples we always observed symmetric magnetization loops indicative of the presence of a bulk pinning mechanism. Magnetic relaxation measurements in the bulk sample reveal a crossover of surface barrier to bulk pinning.

  13. Self-consistent phonons in MgSiO3 perovskite

    Science.gov (United States)

    Zhang, D.; Sun, T.; Wentzcovitch, R. M.

    2012-12-01

    There are numerous materials under conditions of interest for which MD is required but still too demanding for first principles. In these cases 1) phonon-phonon interactions are non-negligible, 2) the material is on the verge of mechanical and/or vibrational instabilities, 3) or the material is stabilized by anharmonic fluctuations at high temperatures. MD is suitable for investigating these states as intrinsic anharmonic effects caused by phonon-phonon interactions are naturally included, but the requirement on size and length of the simulations call for more efficient and accurate approaches for phase space sampling. Indeed, MD needs thousands of atoms and 10^4 to 10^5 picosenconds of simulations for thorough sampling of phase space and accurate free energy calculations (e.g. in thermodynamical integration method). Nevertheless, we note that none of these states can be physical-properly addressed by quasi-harmonic approximation (QHA) approach. This is because QHA overlooks the intrinsic harmonicity and only suits mechanically and dynamically stable phases with a limited range in temperature (Up to approximately 2/3 of the melting temperature). Recently, a new breed of methods for calculating anharmonic vibrational spectra has been developed. These methods use MD to extract phonon frequencies renormalized by phonon-phonon interactions (self-consistent phonons - SCPh). More than one procedure to extract SCPh frequencies has been introduced and applied to solids with lattice structures relatively simple compared to those of silicate minerals. Here, we developed an efficient approach that can offer SCPh dispersions in materials with complex crystal lattice structures containing tens of atoms per primitive cell. First-principles MD simulations on supercells containing hundreds of atoms permits the extraction of dynamical matrices and force-constant matrices that can be Fourier interpolated to produce SCPh dispersions. Thoroughly sampling of these dispersions throughout the Brillouin Zone can provide well converged vibrational density of states and free energies. As a benchmark, we have applied this novel approach to MgSiO3-provskite, a complex mineral of major importance displaying intrinsic anharmonicity well documented in Raman scattering experiments. We analyze calculated anharmonic frequency shifts at constant volume and compare them with experimentation at constant pressure. Two effects are clearly separable: extrinsic frequency shifts caused by thermal expansion and intrinsic temperature dependent renormalized frequency shifts. Comparison between calculated and measured intrinsic frequency shifts shows very good agreement for modes with diverse temperature dependent behaviors. This successful benchmark indicates that our method is viable for computing anharmonic free energies. This will improve the accuracy of predicted thermodynamics and thermal elastic properties of materials as well as of calculated thermodynamics phase boundaries, many of great geophysical interest and still under debate.

  14. Process-based Architecture for Robustness Applying Linux isolation mechanism in MG-R

    NARCIS (Netherlands)

    Matsinger, A.A.J.; Kourzanov, P.; Gopakumar, G.N.

    2006-01-01

    This report contains the results of a feasibility study of applyingLinux facilities for isolating and protecting processes, and for communication and synchronisation between processes, to the MG-R architecture so as to improve the robustness. Moreover some guidelines andtrade-offs are discussed how

  15. Magnetic relaxation induced by transverse flux shaking in MgB2 superconductors

    Science.gov (United States)

    Luzuriaga, J.; Badía-Majós, A.; Nieva, G.; Giordano, J. L.; López, C.; Serquis, A.; Serrano, G.

    2009-01-01

    We report on measurements and numerical simulations of the behavior of MgB2 superconductors when magnetic field components are applied along mutually perpendicular directions. By closely matching the geometry in simulations and measurements, full quantitative agreement is found. The critical state theory and a single phenomenological law, i.e. the field dependence of the critical current density Jc(B), are sufficient for a full quantitative description of the measurements. These were performed in thick strips of carbon nanotube doped MgB2 samples. Magnetization was measured in two orthogonal directions using a SQUID magnetometer. Magnetic relaxation effects induced by the application of an oscillatory perpendicular field were observed and simulated numerically. The measurements confirm the numerical predictions, that two relaxation regimes appear, depending on the amplitude of the applied magnetic field. The overall agreement constitutes a convincing validation of the critical state model and the numerical procedures used.

  16. Experimental and numerical study of transverse flux shaking in MgB2 superconductors

    Science.gov (United States)

    Luzuriaga, J.; Badía-Majos, A.; Nieva, G.; Giordano, J. L.; López, C.; Serquis, A.; Serrano, G.

    2009-05-01

    Magnetization measurements in the mixed state of thick strips of carbon nanotube doped MgB2 in crossed fields configurations are reported, together with numerical simulations performed with a geometry equivalent to the sample shape. The samples were subjected to magnetic field components along mutually perpendicular directions, an oscillatory field in one direction and a remanent magnetization in the perpendicular direction. The magnetic response along the oscillatory field and the magnetic relaxation perpendicular to it are observed and simulated using the critical state theory. A remarkable quantitative agreement between the experiment and the theory was obtained.

  17. Thickness, humidity, and polarization dependent ferroelectric switching and conductivity in Mg doped lithium niobate

    Energy Technology Data Exchange (ETDEWEB)

    Neumayer, Sabine M.; Rodriguez, Brian J., E-mail: brian.rodriguez@ucd.ie [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4 (Ireland); Strelcov, Evgheni; Kravchenko, Ivan I.; Kalinin, Sergei V. [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Manzo, Michele; Gallo, Katia [Department of Applied Physics, KTH - Royal Institute of Technology, Roslagstullbacken 21, 10691 Stockholm (Sweden); Kholkin, Andrei L. [Department of Physics and CICECO-Aveiro Institute of Materials, 3810-193 Aveiro, Portugal and Institute of Natural Sciences, Ural Federal University, 620000 Ekaterinburg (Russian Federation)

    2015-12-28

    Mg doped lithium niobate (Mg:LN) exhibits several advantages over undoped LN such as resistance to photorefraction, lower coercive fields, and p-type conductivity that is particularly pronounced at domain walls and opens up a range of applications, e.g., in domain wall electronics. Engineering of precise domain patterns necessitates well founded knowledge of switching kinetics, which can differ significantly from that of undoped LN. In this work, the role of humidity and sample composition in polarization reversal has been investigated under application of the same voltage waveform. Control over domain sizes has been achieved by varying the sample thickness and initial polarization as well as atmospheric conditions. In addition, local introduction of proton exchanged phases allows for inhibition of domain nucleation or destabilization, which can be utilized to modify domain patterns. Polarization dependent current flow, attributed to charged domain walls and band bending, demonstrates the rectifying ability of Mg:LN in combination with suitable metal electrodes that allow for further tailoring of conductivity.

  18. Deformation mechanisms in Mg alloys and the challenge of extending room-temperature plasticity

    Science.gov (United States)

    Barnett, M. R.; Stanford, N.; Cizek, P.; Beer, A.; Xuebin, Z.; Keshavarz, Z.

    2009-08-01

    Magnesium alloys show promise for application in formed components where weight saving is an advantage. In most instances forming is carried out at elevated temperatures. However, there are considerable gains to be had if forming can be carried out under ambient conditions. The present article outlines some of the difficulties that lie in the way of achieving this objective. The underlying metallurgical characteristics of the issues are considered and means for overcoming them are discussed. It is concluded that a combination of microstructure and texture control remains a promising strategy.

  19. Evolution Of Precipitate Morphology During Extrusion In Mg ZK60A Alloy

    Directory of Open Access Journals (Sweden)

    Park J.

    2015-06-01

    Full Text Available In this study, a continuously casted ZK60A magnesium alloy (Mg-Zn-Zr was extruded in two different extrusion ratios, 6:1 and 10:1. The evolution of precipitates was investigated on the two extruded materials and compared with that of as-casted material. The microstructural analysis was performed by electron backscatter diffraction and transmission electron microscopy, and the compositional information was obtained using energy-dispersive X-ray spectroscopy. Several distinct morphologies of precipitates were observed, such as dot, rod, and disk shaped. The formation mechanisms of those precipitates were discussed with respect to the heat and strain during the extrusion process.

  20. Mutation in Mg-Protoporphyrin IX Monomethyl Ester Cyclase Decreases Photosynthesis Capacity in Rice

    Science.gov (United States)

    Wang, Xuexia; Huang, Rongfeng; Quan, Ruidang

    2017-01-01

    In photosynthesis, the pigments chlorophyll a/b absorb light energy to convert to chemical energy in chloroplasts. Though most enzymes of chlorophyll biosynthesis from glutamyl-tRNA to chlorophyll a/b have been identified, the exact composition and regulation of the multimeric enzyme Mg-protoporphyrin IX monomethyl ester cyclase (MPEC) is largely unknown. In this study, we isolated a rice pale-green leaf mutant m167 with yellow-green leaf phenotype across the whole lifespan. Chlorophyll content decreases 43–51% and the granal stacks of chloroplasts becomes thinner in m167. Chlorophyll fluorescence parameters, including Fv/Fm (the maximum quantum efficiency of PSII) and quantum yield of PSII (Y(II)), were lower in m167 than those in wild type plants (WT), and photosynthesis rate decreases 40% in leaves of m167 mutant compared with WT plants, which lead to yield reduction in m167. Genetic analysis revealed that yellow-green leaf phenotype of m167 is controlled by a single recessive genetic locus. By positional cloning, a single mutated locus, G286A (Alanine 96 to Threonine in protein), was found in the coding sequence of LOC_Os01g17170 (Rice Copper Response Defect 1, OsCRD1), encoding a putative subunit of MPEC. Expression profile analysis demonstrated that OsCRD1 is mainly expressed in green tissues of rice. Sequence alignment analysis of CRD1 indicated that Alanine 96 is very conserved in all green plants and photosynthetic bacteria. OsCRD1 protein mainly locates in chloroplast and the point mutation A96T in OsCRD1 does not change its location. Therefore, Alanine96 of OsCRD1 might be fundamental for MPEC activity, mutation of which leads to deficiency in chlorophyll biosynthesis and chloroplast development and decreases photosynthetic capacity in rice. PMID:28129387

  1. Compositional variations of chromiferous spinel in Mg-rich rocks of the Deccan Traps, India

    Indian Academy of Sciences (India)

    Leone Melluso; Roberto De’ Gennaro; Ivana Rocco

    2010-06-01

    Composition of chromiferous spinel included in olivines of Mg-rich basalts and gabbros of the Deccan Traps (Gujarat and Western Ghats) are reported here. They vary from Al-rich compositions [Al2O3 = 53wt.%; Cr#, 100Cr/(Cr + Al) = 12] to Cr-rich compositions [Cr2O3 = 51wt.%; Cr#= 84], and from Cr-Al rich compositions towards Cr-rich Ti-magnetite (TiO2 up to 23 wt.%, ulvöspinel up to 67mol.%). The Mg#[100Mg/(Mg + Fe2+)] of spinel decreases from 81 to nearly zero. The highest Cr#has been found in the Bushe Fm., Thakurvadi Fm., and some high-Ti basalts of the Pavagadh section, whereas some of the low-Ti basalts of Saurashtra have Al-rich compositions typical of spinels found in mid-ocean ridge basalts. The chemical composition of the Deccan Trap spinels is completely different compared to that observed in mantle spinel suites, with very few exceptions. The decreasing Al and increasing Fe and Ti of spinel seems to be mainly the result of decrease of Mg in the locally coexisting melts and favourable cationic substitutions in the lattice. There is barely any evidence of general relationships between the composition of the Deccan spinels and inferred mantle sources of the host magmas. Pyroxene inclusions in spinels may witness a high-pressure stage of crystallization, but the possibility of non-equilibrium crystallization, or even magma mixing, cannot be ruled out. Overall, the compositional ranges of chromiferous spinel in the Deccan Traps closely match those observed in the other Large Igneous Provinces having mafic/ultramafic intrusions and mafic magma compositions (e.g., Siberian Traps, Karoo, Emeishan).

  2. Interface reactions in Mg/Zn3P2 solar cells

    Science.gov (United States)

    Kazmerski, L. L.; Ireland, P. J.; Catalano, A.

    1981-05-01

    The composition and chemistry of the Mg/Zn3P2 interface was studied using surface analysis techniques. For higher carrier concentrations (p 10 to the 17th power/cu cm), a heterojunction occurs by the chemical interaction of the Mg with Zn3P2 to form Mg3P2. For lower carrier concentrations this reaction does not take place, and Mg diffuses into the Zn3P2. Diffusion coefficients of Mg in Zn3P2 are determined. Grain (crystalline) and grain boundary components of the diffusion coefficient are evaluated. These data compare very well with that reported using electron beam induced currents and spectral response measurements.

  3. Review on long-period stacking-ordered structures in Mg-Zn-RE alloys

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    The recent development of high-strength magnesium alloys is focused on the role of the strengthening phases with a novel long-period stacking-ordered (LPSO) structure. This review detailed the main factors influencing the formation of LPSO phases, including alloying ele-ments, preparation methods, and heat treatments. Furthermore, process control in structure types, formation and transformation behavior, strengthening and toughening mechanisms of the LPSO phase were discussed. Finally, the current problems ...

  4. Effective connectivity of hippocampal neural network and its alteration in Mg2+-free epilepsy model.

    Science.gov (United States)

    Gong, Xin-Wei; Li, Jing-Bo; Lu, Qin-Chi; Liang, Pei-Ji; Zhang, Pu-Ming

    2014-01-01

    Understanding the connectivity of the brain neural network and its evolution in epileptiform discharges is meaningful in the epilepsy researches and treatments. In the present study, epileptiform discharges were induced in rat hippocampal slices perfused with Mg2+-free artificial cerebrospinal fluid. The effective connectivity of the hippocampal neural network was studied by comparing the normal and epileptiform discharges recorded by a microelectrode array. The neural network connectivity was constructed by using partial directed coherence and analyzed by graph theory. The transition of the hippocampal network topology from control to epileptiform discharges was demonstrated. Firstly, differences existed in both the averaged in- and out-degree between nodes in the pyramidal cell layer and the granule cell layer, which indicated an information flow from the pyramidal cell layer to the granule cell layer during epileptiform discharges, whereas no consistent information flow was observed in control. Secondly, the neural network showed different small-worldness in the early, middle and late stages of the epileptiform discharges, whereas the control network did not show the small-world property. Thirdly, the network connectivity began to change earlier than the appearance of epileptiform discharges and lasted several seconds after the epileptiform discharges disappeared. These results revealed the important network bases underlying the transition from normal to epileptiform discharges in hippocampal slices. Additionally, this work indicated that the network analysis might provide a useful tool to evaluate the neural network and help to improve the prediction of seizures.

  5. Superconductivity in Mg-Doped Layered Intermetallic Compound NbB2

    Institute of Scientific and Technical Information of China (English)

    LIU Guang-Tong; JIN Hao; LI Zheng; GENG Hong-Xia; CHE Guang-Can; JIN Duo; SUN Lian-Feng; XIE Si-Shen; LUO Jian-Lin

    2008-01-01

    We have performed low temperature resistivity p(T) and specific heat C(T) measurements on a superconducting polycrystalline Nb0.75Mg0.25B2 sample.The results indicate that the superconducting transition temperature is ~4.6 K.The zero temperature upper critical field determined from the resistivity and specific heat is 3123 Oe.The electronic coefficient of specific heat γn=4.51 mJ mol-1 K2 and the Debye temperature θn=419 K are obtained by fitting the zero-field specific heat data in the normal state.At low temperatures,the electronic specific heat in the superconducting state follows Ces/γnTc=2.84 exp(-1.21Tc/T).This indicates that the superconducting pairing in Nb0.75Mg0.25 B2 has s-wave symmetry.

  6. Correlation effects in MgO and CaO Cohesive energies and lattice constants

    CERN Document Server

    Doll, K; Stoll, H; Doll, Klaus; Dolg, Michael; Stoll, Hermann

    1996-01-01

    A recently proposed computational scheme based on local increments has been applied to the calculation of correlation contributions to the cohesive energy of the CaO crystal. Using ab-initio quantum chemical methods for evaluating individual increments, we obtain 80% of the difference between the experimental and Hartree-Fock cohesive energies. Lattice constants corrected for correlation effects deviate by less than 1% from experimental values, in the case of MgO and CaO.

  7. Structural Studies of Metastable and Ground State Vortex Lattice Domains in MgB2

    Science.gov (United States)

    de Waard, E. R.; Kuhn, S. J.; Rastovski, C.; Eskildsen, M. R.; Leishman, A.; Dewhurst, C. D.; Debeer-Schmitt, L.; Littrell, K.; Karpinski, J.; Zhigadlo, N. D.

    2015-03-01

    Small-angle neutron scattering (SANS) studies of the vortex lattice (VL) in the type-II superconductor MgB2 have revealed an unprecedented degree of metastability that is demonstrably not due to vortex pinning, [C. Rastovski et al . , Phys. Rev. Lett. 111, 107002 (2013)]. Application of an AC magnetic field to drive the VL to the ground state revealed a two-step power law behavior, indicating a slow nucleation of ground state domains followed by a faster growth. The dependence on the number of applied AC cycles is reminiscent of jamming of soft, frictionless spheres. Here, we report on detailed structural studies of both metastable and ground state VL domains. These include measurements of VL correlation lengths as well as spatially resolved SANS measurements showing the VL domain distribution within the MgB2 single crystal. We discuss these results and how they may help to resolve the mechanism responsible for stabilizing the metastable VL phases. This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Award DE-FG02-10ER46783.

  8. Two-gap interplay in MgB{sub 2}: a tunneling spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Roditchev, D.; Giubileo, F.; Bobba, F.; Lamy, R.; Choi, E.-M.; Kim, H.-J.; Kang, W.N.; Miraglia, S.; Marcus, J.; Sacks, W.; Klein, J.; Cucolo, A.M.; Lee, S.-I.; Fruchart, D

    2004-08-01

    Tunneling spectroscopy on various samples of MgB{sub 2} was performed. The first direct evidence for the two-gap superconductivity was given with an inverted junction setup, in which a small crystal of MgB{sub 2} was used as the STM tip and 2H-NbSe{sub 2} as the sample. This technique allowed to show that both gaps close at the critical temperature of the bulk material and thus are intimately related to the superconductivity. The experiments performed in the standard N-I-S geometry evidenced for two strongly coupled gaps {delta}{sub L}=7.0{+-}1.0 meV and {delta}{sub S}=3.0{+-}1.0 meV at 4.2 K. STS on as-grown c-axis oriented thin films yielded only small gap which confirmed the identification of this gap as originating from 3D-like {pi}-band and, by exclusion, that of the large gap from 2D-like {sigma}-band. The low gap values {delta}{sub S}=2.2{+-}0.3 meV were attributed to the degraded film surface. After chemical etching, the gap increased to {delta}{sub S}=2.8{+-}0.3 meV. The c-axis tunneling spectra are better fitted considering anisotropic superconductivity inside the {pi}-band. The issues of our findings are discussed in terms of two-band superconductivity.

  9. Core correlation effects in multiconfiguration calculations of isotope shifts in Mg I

    CERN Document Server

    Filippin, Livio; Ekman, Jörgen; Jönsson, Per

    2016-01-01

    The present work reports results from systematic multiconfiguration Dirac-Hartree-Fock calculations of isotope shifts for several well-known transitions in neutral magnesium. Relativistic normal and specific mass shift factors as well as the electronic probability density at the origin are calculated. Combining these electronic quantities with available nuclear data, energy and transition level shifts are determined for the $^{26}$Mg$-^{24}$Mg pair of isotopes. Different models for electron correlation are adopted. It is shown that although valence and core-valence models provide accurate values for the isotope shifts, the inclusion of core-core excitations in the computational strategy significantly improves the accuracy of the transition energies and normal mass shift factors.

  10. Self-compensation due to point defects in Mg-doped GaN

    Science.gov (United States)

    Miceli, Giacomo; Pasquarello, Alfredo

    2016-04-01

    Using hybrid density functional theory, we address point defects susceptible to cause charge compensation upon Mg doping of GaN. We determine the free energy of formation of the nitrogen vacancy and of several Mg-related defects. The entropic contribution as a function of temperature is determined within the quasiharmonic approximation. We find that the Mg interstitial shows a noticeably lower free energy of formation than the Mg substitutional to Ga in p -type conditions. Therefore, the Mg impurity is amphoteric behaving like an acceptor when substitutional to Ga and like a double donor when accommodated in an interstitial position. The hybrid-functional results are then linked to experimental observations by solving the charge neutrality equations for semiconductor dominated by impurities. We show that a thermodynamic equilibrium model is unable to account for the experimental hole concentration as a function of Mg doping density, due to nitrogen vacancies and Mg interstitials acting as compensating donors. To explain the experimental result, which includes a dropoff of the hole concentration at high Mg densities, we thus resort to nonequilibrium models. We show that either nitrogen vacancies or Mg interstitials could be at the origin of the self-compensation mechanism. However, only the model based on interstitial Mg donors provides a natural mechanism to account for the sudden appearance of self-compensation. Indeed, the amphoteric nature of the Mg impurity leads to Fermi-level pinning and accounts for the observed dropoff of the hole concentration of GaN samples at high Mg doping. Our work suggests that current limitations in p -type doping of GaN could be overcome by extrinsically controlling the Fermi energy during growth.

  11. Spectroscopy of charge transfer states in Mg1 - x Ni x O

    Science.gov (United States)

    Churmanov, V. N.; Sokolov, V. I.; Pustovarov, V. A.; Gruzdev, N. B.; Mironova-Ulmane, N.

    2016-10-01

    Photoluminescence and photoluminescence excitation spectra of solid solution Mg1- x Ni x O ( x = 0.008) have been analyzed. The contributions of charge transfer electronic states and nonradiative Auger relaxation to the formation of the photoluminescence spectrum are discussed.

  12. Optimization of processing conditions towards high trapped fields in MgB{sub 2} bulks

    Energy Technology Data Exchange (ETDEWEB)

    Muralidhar, M., E-mail: miryala1@shibaura-it.ac.jp [Superconducting Materials Laboratory, Department of Materials Science and Engineering, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548 (Japan); Inoue, K. [Superconducting Materials Laboratory, Department of Materials Science and Engineering, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548 (Japan); Koblischka, M.R. [Experimental Physics, Saarland University, Campus C 6 3, 66123 Saarbrücken (Germany); Tomita, M. [Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo 185-8540 (Japan); Murakami, M. [Superconducting Materials Laboratory, Department of Materials Science and Engineering, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo 135-8548 (Japan)

    2014-09-01

    Highlights: • Bulk MgB{sub 2} samples were prepared via solid state reaction at various sintering temperatures. • The J{sub c} value at 10 K and 0 T was 2.60 × 10{sup 5} A/cm{sup 2}. • A pinning force analysis for the samples sintered at 775 °C revealed a non-scaling behavior. • The trapped field results showed that processing temperature is the key to improving TF values. - Abstract: The present investigation focuses on the effects of various sintering temperatures on the critical current densities and the trapped field values of disk-shaped bulk MgB{sub 2} superconductors fabricated with a simple solid state reaction. The samples were prepared by varying the sintering temperature from 750 to 950 °C in pure Ar atmosphere. Scanning electron microscopy (SEM) and X-ray diffraction analyses showed that single phase and homogenous MgB{sub 2} bulks are produced in using sintering temperatures in the range of 750–825 °C. The samples sintered at 775 °C showed the highest critical current density (J{sub c}) values of 250 kA/cm{sup 2} at 10 K and 181 kA/cm{sup 2} at 20 K in self field. We also measured the trapped field values at 20 K for bulk MgB{sub 2} samples 20 mm in diameter and 7 mm in thickness, sintered at temperatures in the range of 700–950 °C with the same sintering duration of 3 h. Almost all the samples exhibited the trapped field values higher than 1 T, which shows the high potential of sintered MgB{sub 2} bulk materials as trapped field magnets. The highest value of 1.51 T at 20 K was achieved in the MgB{sub 2} sample sintered at 775 °C, reflecting its high pinning performance and homogeneous microstructure.

  13. Surface Crystallization in Mg-Based Bulk Metallic Glass during Copper Mold Casting

    Directory of Open Access Journals (Sweden)

    Xin Wang

    2014-01-01

    Full Text Available The localized crystallization of Mg54Cu28Ag7Y11 bulk metallic glass (BMG in the injection casting process using a copper mold was investigated. It has been found that several crystalline phases were formed close to the as-cast surface but did not exist in the internal part of the BMG plate. It is abnormal that the as-cast surface is partially crystallized with higher cooling rate than that of inside. Overheating of the melt and nucleation induced by the surface of copper mold play key roles in the abnormal crystallization. It is suggested that the function of copper mold to trigger heterogeneous nucleation cannot be totally ignored, although it provides the high cooling rate for the glass formation during casting.

  14. Atomistic simulation study of the shear-band deformation mechanism in Mg-Cu metallic glasses

    DEFF Research Database (Denmark)

    Bailey, Nicholas; Schiøtz, Jakob; Jacobsen, Karsten Wedel

    2006-01-01

    We have simulated plastic deformation of a model Mg-Cu metallic glass in order to study shear banding. In uniaxial tension, we find a necking instability occurs rather than shear banding. We can force the latter to occur by deforming in plane strain, forbidding the change of length in one...... of the transverse directions. Furthermore, in most of the simulations a notch is used to initiate shear bands, which lie at a 45 degrees angle to the tensile loading direction. The shear bands are characterized by the Falk and Langer local measure of plastic deformation D-min(2), averaged here over volumes...... containing many atoms. The D-min(2) profile has a peak whose width is around 10 nm; this width is largely independent of the strain rate. Most of the simulations were, at least nominally, at 100 K, about T-g/3 for this system. The development of the shear bands takes a few tens of ps, once plastic flow has...

  15. Long phase coherence length and anisotropic magnetoresistance in MgZnO thin film

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Meng; Xu, Yonggang; Yu, Guolin, E-mail: yug@mail.sitp.ac.cn; Lin, Tie; Hu, Gujin; Chu, Junhao [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science, Shanghai 200083 (China); Wang, Hao; Zhang, Huahan, E-mail: huahan@xmu.edu.cn [Department of Physics, Xiamen University, Xiamen 361005 (China); Dai, Ning [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science, Shanghai 200083 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026 (China); Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Changzhou 213164 (China)

    2015-04-21

    We comprehensively investigate magnetotransport properties of MgZnO thin film grown on ZnO substrate by molecular-beam epitaxy. We measure the weak localization effect and extract the electron phase coherence length by fitting to a three-dimensional weak localization theory and by analyzing the different changing rate of the magnetoresistance, results of which are in good agreement with each other. The phase coherence length ranges from 38.4±1    nm at 50 K to 99.8±3.6 nm at 1.4  K, almost the same as that of ZnO nanoplates and In-doped ZnO nanowires, and its temperature dependence is found to scale as T{sup −3/4}. Meanwhile, we study the anisotropic magnetoresistance resulting from the geometric effect as well as the Lorentz force induced path-length effect, which will be enhanced in higher magnetic fields.

  16. First-principles study of hydrogen incorporation mechanism in Mg2SiO4

    Science.gov (United States)

    Yamamoto, T.

    2012-12-01

    Most of the geoscientists believe that olivine-based minerals form the major constituent in the upper mantle, which extends to a depth of 660km. The Earth's upper mantle consists mainly of following three phases, alpha-, beta- and gamma-Mg2SiO4. Pressure induced phase transitions occur at about 10 GPa and 15 GPa under low temperature condition from alpha- to beta-Mg2SiO4, and from beta- to gamma-Mg2SiO4, respectively. The existence of beta-Mg2SiO4 gives rise to the discontinuity in seismic velocities at a depth of 410 km. It is widely accepted that the atmosphere and the oceans of the Earth are formed by degassing of the Earth's mantle. Most of the water and/or hydrogen may have been lost or it may still be stored in the Earth's mantle. If considerable amounts of hydrogen are present in the Earth's mantle, such hydrogen plays a key role in the geodynamics of the Earth's interior, because it affects the melting temperature and the transport properties of minerals as well as their elastic properties. Earlier high-pressure experiments suggested that main components of the transition zone of the Earth's mantle, wadsleyite and ringwoodite, can store significant amount of hydrogen [1-4]. More recently, it was reported that the lower mantle minerals, consisting of Mg-perovskite, magnesiowüstite and Ca-perovskite [5], can potentially store considerable amounts of hydrogen. However the effects of hydrogen solution on their physical properties and substitution mechanism of hydrogen in mantle minerals have not yet been fully understood. In the present study, the first-principles Density Functional Theory (DFT) calculations have been performed to investigate the influence of hydrogen incorporations on the compressional mechanism of the major components of upper mantle minerals in the Earth, i.e., forsterite (alpha-Mg2SiO4), wadsleyite (beta-Mg2SiO4) and ringwoodite (gamma-Mg2SiO4), and the mechanism of hydrogen incorporation in these minerals. Observed equilibrium volumes of anhydrous and hydrous wadsleyite and ringwoodite at ambient conditions were well reproduced by our present calculations. The calculated bulk moduli of the hydrous wadsleyite and ringwoodite have become significantly lower than those of hydrogen-free ones, as suggested by the high-pressure experiments [6]. The incorporation mechanisms of hydrogen in these minerals were thoroughly caluculated by the first-principles DFT method changing the positions of hydrogen. The transition pressures from beta- to gamma-Mg2SiO4 were also estimated for both anhydrous and hydrous Mg2SiO4, in which hydrous Mg2SiO4 showed higher transition pressure than anhydrous one by approximately 6 GPa. [1] T. Inoue et al., Geophys. Res. Lett. 22 (1995) 117. [2] Y. Kudou and T. Inoue, Phys. Chem. Minerals (1999) 382. [3] D.L. Kohlstedt et al., Contrib. Mineral. Petrol. 123(1996) 345. [4] H. Yusa and T. Inoue, Geohpys. Res. Lett. 24 (1997) 1831. [5] M. Murakami et al., Science 295 (2002) 1885. [6] T. Inoue et al., Earth Planet. Sci. Lett. 160 (1998) 107.

  17. Atomistic Modeling of Dislocations in MgSiO3 Post-Perovskite

    Science.gov (United States)

    Goryaeva, A.; Carrez, P.; Cordier, P.

    2014-12-01

    The recently discovered MgSiO3 post-perovskite phase (Cmcm) is only stable at high pressure and temperature conditions corresponding to the lowermost ~150 km of the mantle (the D'' layer) [1, 2]. The unusual, for a high-pressure phase, layer-like structure of the post-perovskite may be responsible for the observed seismic anisotropy of the D'' layer. However, information about mechanical properties, easier slip systems, dislocations and their behaviour under stress are not well known still. This work represents a theoretical study of the post-perovskite within the semi-empirical approach using the Buckingham interatomic potential parameters previously derived by [3]. To describe the energy cost incurred as a result of a shear and to deduce the most favorable slip systems, the GSF excess energies are calculated at 120 GPa. The lowest energy barrier as well as the smallest values of the ideal shear stress (ISS), are related to the slip systems with the smallest [100] Burgers vector (b=2.521 Å) and to the slip system [001](010) with the glide plane cutting only Mg-O bonds. Good agreement with the ab-initio results [4] verifies the accuracy of the chosen inteatomic potential model [3]. The C-lattice of the post-perovskite results in four potential Burgers vectors: [100], [010], [001] and ½[011]. Taking into account the estimated GSF energies for different slip systems, we focus on mobility of screw and edge dislocations with Burgers vectors [100], [010] and ½[011]. The evaluated values of lattice friction suggest (010) slip plane parallel to the Si- and Mg-layers in the post-perovskite strucure to be the most probable .References[1] Murakami, M. et al., Geophys. Res. Lett. (2005), 32, L03304. [2] Oganov, A. & Ono S., Nature (2004), 430, 44- 448. [3] Oganov A. et al., Phys. Earth Planet. Int. (2000), 122, 277-288. [4] Carrez Ph. et al., Philosoph. Mag. (2007), 87, 3229-3247.

  18. Theoretical Limiting Potentials in Mg/O2 Batteries

    DEFF Research Database (Denmark)

    Smith, Jeffrey G.; Naruse, Junichi; Hiramatsu, Hidehiko

    2016-01-01

    A rechargeable battery based on a multivalent Mg/O2 couple is an attractive chemistry due to its high theoretical energy density and potential for low cost. Nevertheless, metal-air batteries based on alkaline earth anodes have received limited attention and generally exhibit modest performance...... pathway. The calculations indicate that pathways involving oxygen intermediates are preferred, as they generally result in higher discharge and lower charging voltages. In agreement with recent experiments, cells that discharge to MgO exhibit low round-trip efficiencies, which are rationalized...... by the presence of large thermodynamic overvoltages. In contrast, MgO2-based cells are predicted to be much more efficient: superoxide-terminated facets on MgO2 crystallites enable low overvoltages and round-trip efficiencies approaching 90%. These data suggest that the performance of Mg/O2 batteries can...

  19. New candidate for deformed halo nucleus in Mg isotopes through analysis of reaction cross sections

    Directory of Open Access Journals (Sweden)

    Watanabe S.

    2014-03-01

    Full Text Available The total reaction cross sections of Mg isotopes on a 12C target at 240 MeV/nucleon have been analyzed with a fully microscopic framework, i.e., the double folding model with the density calculated by antisymmetrized molecular dynamics. Our results well reproduce the latest experimental data except 37Mg as a new candidate for a deformed halo nucleus.

  20. Formation and stability of rocksalt ZnO nanocrystals in MgO

    NARCIS (Netherlands)

    Eijt, S. W. H.; de Roode, J.; Schut, H.; Kooi, B. J.; De Hosson, J. Th. M.

    2007-01-01

    Coimplantation of Zn and O ions into a single crystalline MgO and subsequent thermal annealing were applied in the synthesis of ZnO nanocrystals. Electron microscopy showed that rocksalt instead of wurtzite ZnO stabilizes for relatively large nanocrystals up to similar to 15 nm, resulting from its s

  1. Formation and stability of rocksalt ZnO nanocrystals in MgO

    NARCIS (Netherlands)

    Eijt, S.W.H.; De Roode, J.; Schut, H.; Kooi, B.J.; De Hosson, J.T.M.

    2007-01-01

    Coimplantation of Zn and O ions into a single crystalline MgO and subsequent thermal annealing were applied in the synthesis of ZnO nanocrystals. Electron microscopy showed that rocksalt instead of wurtzite ZnO stabilizes for relatively large nanocrystals up to ~15 nm, resulting from its small latti

  2. Evolution of core connectivity in MgB 2 wires and tapes during PIT processing

    Science.gov (United States)

    Beilin, V.; Dul'kin, E.; Yashchin, E.; Galstyan, E.; Lapides, Y.; Tsindlekht, M.; Felner, I.; Roth, M.

    2004-05-01

    Critical current density, Jc, ac susceptibility, χ, and the core microhardness in Ni/MgB 2 wires and tapes were measured in as-deformed state at the various stages of the powder-in-tube process. We found that during a drawing process Jc reached a peak at some strain value, followed by rather steep degradation down to zero level with further strain growth. It was shown that the data of electrical and magnetic measurements correlated with the core microhardness during the deformation processes. χ vs. T measurements showed that Jc degradation was resulted from the deterioration of a core connectivity, that was confirmed by microhardness measurements. It was revealed that rolling the as-drawn wires restored a core connectivity and thus caused drastic Jc, growth. This effect was explained by differences in powder flow between drawing and rolling processes. XRD examination of MgB 2 cores showed that rolling the Ni/MgB 2 tapes resulted in gradual growth of the core c-axis texturing with the tape thickness reduction, though texture degree remained relatively low (21% at maximum).

  3. Ab initio modeling of radiation damage in MgF{sub 2} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Abuova, F.U. [L. N. Gumilyov Eurasian National University, 3 Munaitpasova Str., Astana (Kazakhstan); Kotomin, E.A., E-mail: kotomin@latnet.lv [Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., LV-1063, Riga (Latvia); Lisitsyn, V.M. [Tomsk Polytechnical University, Tomsk 634003 (Russian Federation); Akilbekov, A.T. [L. N. Gumilyov Eurasian National University, 3 Munaitpasova Str., Astana (Kazakhstan); Piskunov, S. [Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., LV-1063, Riga (Latvia)

    2014-05-01

    MgF{sub 2} with a rutile structure is important radiation-resistant material with numerous applications due to its transparency from vacuum ultraviolet to infrared range of photon energies. We present and discuss the results of calculations for basic radiation defects in this crystal. The study is based on the large scale ab initio DFT calculations using hybrid B3PW exchange–correlation functional and atomic basis set. We analyzed the electronic structure, atomic displacements, charge density distribution as well as defect formation energies using large supercells. We compared properties of close and well separated F−H (Frenkel) defect pairs as well as individual defects. We simulated also formation and energetic preference of inert F{sub 2} interstitial molecules as sinks of mobile interstitial fluorine atoms which is relevant for material radiation stability. We discussed also diffusion of the primary electronic defects—F centers.

  4. Geometric and Chemical Composition Effects on Healing Kinetics of Voids in Mg-bearing Al Alloys

    Science.gov (United States)

    Song, Miao; Du, Kui; Wang, Chunyang; Wen, Shengping; Huang, Hui; Nie, Zuoren; Ye, Hengqiang

    2016-05-01

    The healing kinetics of nanometer-scale voids in Al-Mg-Er and Al-Mg-Zn-Er alloy systems were investigated with a combination of in situ transmission electron microscopy and electron tomography at different temperatures. Mg was observed completely healing the voids, which were then rejuvenated to the alloy composition with further aging, in the Al-Mg-Er alloy. On the contrary, Mg51Zn20 intermetallic compound was formed in voids in the Al-Mg-Zn-Er alloy, which leads to complete filling of the voids but not rejuvenation for the material. For voids with different geometrical aspects, different evolution processes were observed, which are related to the competition between bulk and surface diffusion of the alloys. For voids with a large size difference in their two ends, a viscous flow of surface atoms can be directly observed with in situ electron microscopy, when the size of one end becomes less than tens of nanometers.

  5. Pressure-induced Co2+ photoluminescence quenching in MgAl2O4

    Science.gov (United States)

    Nataf, Lucie; Rodríguez, Fernando; Valiente, Rafael

    2012-09-01

    This work investigates the electronic structure and photoluminescence (PL) of Co2+-doped MgAl2O4 and their pressure dependence by time-resolved spectroscopy. The variations of the visible absorption band and its associated emission at 663 nm (τ = 130 ns at ambient conditions) with pressure/temperature can be explained on the basis of a configurational energy model. It provides an interpretation for both the electronic structure and the excited-state phenomena yielding photoluminescence emission and the subsequent quenching. We show that there is an excited-state crossover (ESCO) [4T1(P)↔2E(G)] at ambient pressure, which is responsible for the evolution of the emission spectrum from a broadband emission between 300 K and 100 K to a narrow-line emission at lower temperatures. Contrary to expectations from the Tanabe-Sugano diagram, instead of enhancing ESCO phenomena, pressure reduces PL and even suppresses it (PL quenching) above 6 GPa. We explain such variations in terms of pressure-induced nonradiative relaxation to lower excited states: 2E(G)→4T1(F). The variation of PL intensity and its associated lifetime with pressure supports the proposed interpretation.

  6. Theoretical and Experimental Evidence for a Nodal Energy Gap in MgB2

    Science.gov (United States)

    2017-02-17

    temperatures attributed to Andreev bound states [4]. This increase is only visible on the expanded scale of the main plot. -0.001 0 0.001 0.002 0.003...Superconductivity Sci . Tech. 14 (2001) R115. [3] Y. D. Agassi, D. E. Oates, B. H. Moeckly Phys. Rev. B 80 (2009) 174522. [4] Y. D. Agassi, D. E...J. Kelly, T. Tan, X. X. Xi, Supercond. Sci . Technol. 25 (2012) 095006. [7] A. S. Alexandrov, Phys. Rev. B 77 (2008) 094502. [8] N. N. Bogoliubov

  7. Magnesium behavior and structural defects in Mg{sup +} ion implanted silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Weilin, E-mail: weilin.jiang@pnnl.gov [Pacific Northwest National Laboratory (United States); Jung, Hee Joon; Kovarik, Libor; Wang, Zhaoying; Roosendaal, Timothy J.; Zhu, Zihua; Edwards, Danny J.; Hu, Shenyang; Henager, Charles H.; Kurtz, Richard J. [Pacific Northwest National Laboratory (United States); Wang, Yongqiang [Los Alamos National Laboratory (United States)

    2015-03-15

    As a candidate material for fusion reactor applications, silicon carbide (SiC) undergoes transmutation reactions under high-energy neutron irradiation with magnesium as the major metallic transmutant; the others include aluminum, beryllium and phosphorus in addition to helium and hydrogen gaseous species. The impact of these transmutants on SiC structural stability is currently unknown. This study uses ion implantation to introduce Mg into SiC. Multiaxial ion-channeling analysis of the as-produced damage state indicates a lower dechanneling yield observed along the 〈1 0 0〉 axis. The microstructure of the annealed sample was examined using high-resolution scanning transmission electron microscopy. The results show a high concentration of likely non-faulted tetrahedral voids and possible stacking fault tetrahedra near the damage peak. In addition to lattice distortion, dislocations and intrinsic and extrinsic stacking faults are also observed. Magnesium in 3C–SiC prefers to substitute for Si and it forms precipitates of cubic Mg{sub 2}Si and tetragonal MgC{sub 2}. The diffusion coefficient of Mg in 3C–SiC single crystal at 1573 K has been determined to be 3.8 ± 0.4 × 10{sup −19} m{sup 2}/s.

  8. Magnesium behavior and structural defects in Mg+ ion implanted silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Weilin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Jung, Hee Joon [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kovarik, Libor [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wang, Zhaoying [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Roosendaal, Timothy J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhu, Zihua [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Edwards, Danny J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hu, Shenyang [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Henager, Charles H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kurtz, Richard J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wang, Yongqiang [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-03-01

    As a candidate material for fusion reactor applications, silicon carbide (SiC) undergoes transmutation reactions under high-energy neutron irradiation with magnesium as the major metallic transmutant; the others include aluminum, beryllium and phosphorus in addition to helium and hydrogen gaseous species. The impact of these transmutants on SiC structural stability is currently unknown. This study uses ion implantation to introduce Mg into SiC. Multiaxial ion-channeling analysis of the as-produced damage state suggests that there are preferred Si <100> interstitial splits. The microstructure of the annealed sample was examined using high-resolution scanning transmission electron microscopy. The results show a high concentration of likely non-faulted tetrahedral voids and possible stacking fault tetrahedra near the damage peak. In addition to lattice distortion, dislocations and intrinsic and extrinsic stacking faults are also observed. Magnesium in 3C-SiC prefers to substitute for Si and it forms precipitates of cubic Mg2Si and tetragonal MgC2. The diffusion coefficient of Mg in 3C-SiC single crystal at 1573 K has been determined to be 3.8±0.4×10e-19 m2/sec.

  9. Experimental and numerical study of transverse flux shaking in MgB{sub 2} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Luzuriaga, J; Nieva, G; Serquis, A; Serrano, G [Centro Atomico Bariloche, CNEA, Inst. Balseiro, UNC (Argentina); BadIa-Majos, A [Dep. de Fisica de la Materia Condensada-ICMA, Universidad de Zaragoza-CSIC (Spain); Giordano, J L [Departamento de Ciencias de la IngenierIa, Universidad de Talca (Chile); Lopez, C, E-mail: luzuriag@cab.cnea.gov.a [Dep. Matematicas, Universidad de Alcala de Henares (Spain)

    2009-05-01

    Magnetization measurements in the mixed state of thick strips of carbon nanotube doped MgB{sub 2} in crossed fields configurations are reported, together with numerical simulations performed with a geometry equivalent to the sample shape. The samples were subjected to magnetic field components along mutually perpendicular directions, an oscillatory field in one direction and a remanent magnetization in the perpendicular direction. The magnetic response along the oscillatory field and the magnetic relaxation perpendicular to it are observed and simulated using the critical state theory. A remarkable quantitative agreement between the experiment and the theory was obtained.

  10. H-I 21 cm absorption in Mg (II)-selected systems at moderate redshifts

    NARCIS (Netherlands)

    Lane, WM; Briggs, FH; Hibbard, JE; Rupen, MP; VanGorkom, JH

    2001-01-01

    We present results from a Westerbork Synthesis Radio Telescope (WSRT) survey for HI 21 cm absorption in 62 MgII-selected absorption systems, among which we identify three now HI 21cm absorbers. We use the redshift evolution of the number density of MgII-absorbers and the Hi detection rate to estimat

  11. The redshift of the Einstein ring in MG 1549+305

    NARCIS (Netherlands)

    Treu, T.; Koopmans, L. V. E.

    2003-01-01

    A deep spectrum taken with the Echelle Spectrograph and Imager (ESI) at the Keck II Telescope as part of the Lenses Structure and Dynamics (LSD) Survey reveals the redshifts of the extremely red source of the radio Einstein ring in the gravitational lens system MG 1549+305 (zs= 1.170 +/- 0.001) and

  12. Comparing Doping Methodologies in Mg2Si/AgMg System

    Science.gov (United States)

    Polymeris, G. S.; Theodorakakos, A.; Mars, K.; Godlewska, E.; Lioutas, Ch. B.; Hatzikraniotis, E.; Paraskevopoulos, K. M.

    2014-10-01

    Morphological and optical characterizations for the Mg2Si samples doped with Ag are presented. Two different doping methodologies with silver, namely in situ and ex situ doping, were studied for the case of Mg2Si of self-propagating high-temperature synthesis. Electron microscopy measurements in both scanning and transmission configurations verified the presence of AgMg precipitates embedded in the Mg2Si matrix and similar results were also yielded by FTIR spectroscopy. Finally, the dependence of silver content in both forms of dopant and inter-metallic constituent is studied upon doping technology.

  13. Effect of segregated elements on the interactions between twin boundaries and screw dislocations in Mg

    Science.gov (United States)

    Yoshida, Takashi; Yuasa, Motohiro; Mabuchi, Mamoru; Chino, Yasumasa

    2015-07-01

    Interactions of { 10 1 ¯ 2 } and { 10 1 ¯ 1 } twin boundaries (TBs), segregated by X (X = Sc, Y, or Nd), with screw partial dislocations were simulated using molecular dynamics (MD). In addition, mechanical tests were carried out on pure Mg and Mg-Y alloy. The MD simulation results suggested that the dislocations passed through the { 10 1 ¯ 2 } TB in all the models and that the shear strains for transmission in the Mg-X models were larger than that in the pure Mg model; in particular, the shear strain in the Mg-Y model was the largest. This corresponded to the experimental result that strain hardening was enhanced by Y addition. For interactions of a { 10 1 ¯ 1 } TB, some segregated atoms induced the emission of dislocations from the TB, whereas other segregated atoms locked the dislocation absorbed in the TB. As a result, the interaction behaviors of the { 10 1 ¯ 1 } TB were divided into five patterns. The interactions of this TB could be explained by the criterion of energy variations, as well as the interactions, of the { 10 1 ¯ 2 } TB, although segregation complicated the interactions of the { 10 1 ¯ 1 } TB.

  14. Reversible hydrogen storage in Mg(BH4)2/carbon nanocomposites

    NARCIS (Netherlands)

    Yan, Y.; Au, Y.S.; Rentsch, D.; Remhof, A.; de Jongh, P.E.; Züttel, A.

    2013-01-01

    Mg(BH4)2 exhibits a high hydrogen content of 14.9 wt% and thermodynamic stability in the overall decomposition reaction that corresponds to hydrogen desorption at around room temperature. However, the potential applications in hydrogen storage are restricted by high kinetic barriers. In this study,

  15. Magnesium behavior and structural defects in Mg+ ion implanted silicon carbide

    Science.gov (United States)

    Jiang, Weilin; Jung, Hee Joon; Kovarik, Libor; Wang, Zhaoying; Roosendaal, Timothy J.; Zhu, Zihua; Edwards, Danny J.; Hu, Shenyang; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2015-03-01

    As a candidate material for fusion reactor applications, silicon carbide (SiC) undergoes transmutation reactions under high-energy neutron irradiation with magnesium as the major metallic transmutant; the others include aluminum, beryllium and phosphorus in addition to helium and hydrogen gaseous species. The impact of these transmutants on SiC structural stability is currently unknown. This study uses ion implantation to introduce Mg into SiC. Multiaxial ion-channeling analysis of the as-produced damage state indicates a lower dechanneling yield observed along the axis. The microstructure of the annealed sample was examined using high-resolution scanning transmission electron microscopy. The results show a high concentration of likely non-faulted tetrahedral voids and possible stacking fault tetrahedra near the damage peak. In addition to lattice distortion, dislocations and intrinsic and extrinsic stacking faults are also observed. Magnesium in 3C-SiC prefers to substitute for Si and it forms precipitates of cubic Mg2Si and tetragonal MgC2. The diffusion coefficient of Mg in 3C-SiC single crystal at 1573 K has been determined to be 3.8 ± 0.4 × 10-19 m2/s.

  16. Thermoluminescence characteristics in MgSO sub 4 : Tm, P phosphors

    CERN Document Server

    Tang Qiang; Li Hua; Luo Da Ling

    2002-01-01

    The TL glow curves and three dimensional spectrum of co-doped MgSO sub 4 : Tm, P powder sample were measured after exposed it to gamma radiation ( sup 6 sup 0 Co and sup 1 sup 3 sup 7 Cs gamma) from 10 sup - sup 4 - 2 x 10 sup 4 Gy. Some peaks parameters and trap parameters of TL peaks were calculated. The main dose peak is about at 289.3 degree C, and the dose response is super-linear. From the three dimensional TL spectrum, it shows that the main glow wavelengths is at about 365 nm, 460 nm and 660 nm. By comparison of some other TL materials, this phosphor has some good performances, such as high sensitivity, good stability and a wide span of dose response. It may be a good TL material that can be applied widely in dosimetry

  17. Giant interfacial perpendicular magnetic anisotropy in MgO/CoFe/capping layer structures

    Science.gov (United States)

    Peng, Shouzhong; Zhao, Weisheng; Qiao, Junfeng; Su, Li; Zhou, Jiaqi; Yang, Hongxin; Zhang, Qianfan; Zhang, Youguang; Grezes, Cecile; Amiri, Pedram Khalili; Wang, Kang L.

    2017-02-01

    Magnetic tunnel junction based on the CoFeB/MgO/CoFeB structures is of great interest due to its application in the spin-transfer-torque magnetic random access memory (STT-MRAM). Large interfacial perpendicular magnetic anisotropy (PMA) is required to achieve high thermal stability. Here, we use the first-principles calculations to investigate the magnetic anisotropy energy (MAE) of the MgO/CoFe/capping layer structures, where the capping materials include 5d metals Hf, Ta, Re, Os, Ir, Pt, and Au and 6p metals Tl, Pb, and Bi. We demonstrate that it is feasible to enhance PMA by using proper capping materials. Relatively large PMA is found in the structures with the capping materials of Hf, Ta, Os, Ir, and Pb. More importantly, the MgO/CoFe/Bi structure gives rise to giant PMA (6.09 mJ/m2), which is about three times larger than that of the MgO/CoFe/Ta structure. The origin of the MAE is elucidated by examining the contributions to MAE from each atomic layer and orbital. These findings provide a comprehensive understanding of the PMA and point towards the possibility to achieve the advanced-node STT-MRAM with high thermal stability.

  18. Light-element diffusion in Mg using first-principles calculations: Anisotropy and elastodiffusion

    Science.gov (United States)

    Agarwal, Ravi; Trinkle, Dallas R.

    2016-08-01

    The light-elemental solutes B, C, N, and O can penetrate the surface of Mg alloys and diffuse during heat treatment or high temperature application, forming undesirable compounds. We investigate the diffusion of these solutes by determining their stable interstitial sites and the interpenetrating network formed by these sites. We use density functional theory (DFT) to calculate the site energies, migration barriers, and attempt frequencies for these networks to inform our analytical model for bulk diffusion. Due to the nature of the networks, O diffuses isotropically, while B, C, and N diffuse anisotropically. We compute the elastodiffusion tensor which quantifies changes in diffusivity due to small strains that perturb the diffusion network geometry and the migration barriers. The DFT-computed elastic dipole tensor which quantifies the change in site energies and migration barriers due to small strains is used as an input to determine the elastodiffusion tensor. We employ the elastodiffusion tensor to determine the effect of thermal strains on interstitial diffusion and find that B, C, and N diffusivity increases on crystal expansion, while O diffusivity decreases. From the elastodiffusion and compliance tensors we calculate the activation volume of diffusion and find that it is positive and anisotropic for B, C, and N diffusion, whereas it is negative and isotropic for O diffusion.

  19. Thermodynamic Modeling of Hydrogen Storage Capacity in Mg-Na Alloys

    Directory of Open Access Journals (Sweden)

    S. Abdessameud

    2014-01-01

    Full Text Available Thermodynamic modeling of the H-Mg-Na system is performed for the first time in this work in order to understand the phase relationships in this system. A new thermodynamic description of the stable NaMgH3 hydride is performed and the thermodynamic models for the H-Mg, Mg-Na, and H-Na systems are reassessed using the modified quasichemical model for the liquid phase. The thermodynamic properties of the ternary system are estimated from the models of the binary systems and the ternary compound using CALPHAD technique. The constructed database is successfully used to reproduce the pressure-composition isotherms for MgH2 + 10 wt.% NaH mixtures. Also, the pressure-temperature equilibrium diagram and reaction paths for the same composition are predicted at different temperatures and pressures. Even though it is proved that H-Mg-Na does not meet the DOE hydrogen storage requirements for onboard applications, the best working temperatures and pressures to benefit from its full catalytic role are given. Also, the present database can be used for thermodynamic assessments of higher order systems.

  20. Hydrogen storage in Mg-LiBH4 composites catalyzed by FeF3

    Science.gov (United States)

    Puszkiel, Julián; Gennari, Fabiana C.; Arneodo Larochette, Pierre; Troiani, Horacio E.; Karimi, Fahim; Pistidda, Claudio; Gosalawit-Utke, Rapee; Jepsen, Julian; Jensen, Torben R.; Gundlach, Carsten; Tolkiehn, Martin; Bellosta von Colbe, José; Klassen, Thomas; Dornheim, Martin

    2014-12-01

    Mg-10 mol% LiBH4 composite plus small amounts of FeF3 is investigated in the present work. The presence of LiBH4 during the milling process noticeably modifies the size and morphology of the Mg agglomerates, leading to faster hydrogenation and reaching almost the theoretical hydrogen capacity owing to enhanced hydrogen diffusion mechanism. However, the dehydrogenation of the system at low temperatures (≤300 °C) is still slow. Thus, FeF3 addition is proposed to improve the dehydrogenation kinetic behavior. From experimental results, it is found that the presence of FeF3 results in an additional size reduction of the Mg agglomerates between ∼10 and ∼100 μm and the formation of stable phases such as MgF2, LiF and FeB. The FeB species might have a catalytic effect upon the MgH2 decomposition. As a further result of the FeF3 addition, the Mg-10 mol%LiBH4-5 mol% FeF3 material shows improved dehydrogenation properties: reduced dehydrogenation activation energy, faster hydrogen desorption rate and reversible hydrogen capacities of about 5 wt% at 275 °C.

  1. Elucidating water dynamics in MgCl2 hydrates from molecular dynamics simulation

    Science.gov (United States)

    Huinink, Hendrik Pieter; Zahn, Dirk

    2017-07-01

    The water mobility in single crystals of MgCl2 hydrates has been investigated with molecular dynamics. Standard force fields have been benchmarked for molecular dynamics simulations of MgCl2 hydrates. To provide a reliable molecular mechanics model, force fields are selected on their ability to reproduce the structure of MgCl2·6H2O at 300 K. The selected force fields are then tested on their ability to also reproduce the structures of the different hydrates (n = 12, 8, 6, 4, 2, 1) and available thermodynamic data. For the currently best force-field available, constant-temperature, constant-pressure molecular dynamics simulations are preformed to elucidate the mechanisms of hydrate water mobility in perfect single crystals of the tetra- and hexahydrate. Long range water diffusion was not observed; each water molecule remained in the coordination sphere of its original Mg2+ host. However, collective ring-like motions of four water molecules at once within the coordination shell of a Magnesium ion were observed.

  2. Orbital-dependent two-band superconductivity in MgB sub 2

    CERN Document Server

    Yanagisawa, T

    2003-01-01

    We show that a two-band model with k-dependent superconducting gaps well describes the transmission and optical conductivity measured for MgB sub 2 thin films. It is also shown that the two-band anisotropic modelconsistently describes the specific-heat jump and thermodynamic critical magnetic field H sub c. A single-gap anisotropic model is shown to be insufficient to understand consistently optical and thermodynamic behaviors. In our model, the pairing symmetry in each band has an anisotropic characteristic which is determined almost uniquely; the superconducting gap in the sigma-band has anisotropy in the ab-plane and the gap in the pi-band has a prolate form exhibiting anisotropy in the c-direction. (author)

  3. Constant Q measurements of collective modes in Mg{sub 70}Zn{sub 30} glass

    Energy Technology Data Exchange (ETDEWEB)

    Benmore, C.J. [Univ. of Guelph, Ontario (Canada). Dept. of Physics]|[Rutherford Appleton Lab., Chilton (United Kingdom). ISIS Facility; Sweeney, S. [Univ. of Guelph, Ontario (Canada). Dept. of Physics]|[Univ. of Victoria, British Columbia (Canada); Robinson, R.A. [Los Alamos National Lab., NM (United States); Egelstaff, P.A. [Univ. of Guelph, Ontario (Canada). Dept. of Physics; Suck, J.B. [T.U. Chemnitz-Zwickau, Chemnitz (Germany). Inst. fuer Physik

    1997-11-01

    In this study the Neutron Brillouin Scattering technique has been used to measure longitudinal excitations in a magnesium-zinc glass at momentum transfers within the first pseudo-Brillouin zone. The measurements were performed at room temperature and constant momentum transfer, which enables the data to be readily and reliably compared with theory. The experimental results taken down to Q = 6.2 nm{sup {minus}1} and E = 27 meV show a 5 meV downward shift in the dispersion energy of the longitudinal optic mode of the glass when compared to theoretical predictions.

  4. An investigation of the H{sub 2} uptake in Mg-Nb-O ternary phases

    Energy Technology Data Exchange (ETDEWEB)

    Dolci, F.; Baricco, M.; Giamello, E. [Dipartimento di Chimica IFM, NIS Center of Excellence, University of Turin, 10125, Via Pietro Giuria 9, Turin (Italy); Edwards, P.P. [Inorganic Chemistry Laboratories, University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom)

    2008-06-15

    Various Mg/Nb/O mixed phases have been prepared by solid state reaction in order to mimic similar compounds formed in the ball milled system composed of MgH{sub 2} and Nb{sub 2}O{sub 5}. The latter oxide has a role as a promoter of the hydrogen uptake and desorption in the Mg/MgH{sub 2} system for hydrogen storage. One mixed phase in particular (Mg{sub 3}Nb{sub 6}O{sub 11}) have shown a reversible uptake of molecular hydrogen, confirmed by thermal desorption experiments followed by mass spectroscopy. Comparison of the behaviour of this phase with NbO shows how a reversible interaction with hydrogen may be linked to the presence of octahedral niobium clusters in both oxides. (author)

  5. Giant spontaneous exchange bias triggered by crossover of superspin glass in Sb-doped Ni50Mn38Ga12 Heusler alloys

    Science.gov (United States)

    Tian, Fanghua; Cao, Kaiyan; Zhang, Yin; Zeng, Yuyang; Zhang, Rui; Chang, Tieyan; Zhou, Chao; Xu, Minwei; Song, Xiaoping; Yang, Sen

    2016-08-01

    A spontaneous exchange bias (SEB) discovered by Wang et al. [Phys. Rev. Lett. 106 (2011) 077203.] after zero-field cooling (ZFC) has attracted recent attention due to its interesting physics. In this letter, we report a giant SEB tuned by Sb-doping in Ni50Mn38Ga12-xSbx Heusler alloys. Such an SEB was switched on below the blocking temperature of approximately 50 K. The maximum exchange bias HE can arrive at 2930 Oe in a Ni50Mn38Ga10Sb2 sample after ZFC to 2 K. Further studies showed that this SEB was attributable to interaction of superspin glass (SSG) and antiferromagnetic matix, which was triggered by the crossover of SSG from canonical spin glass to a cluster spin glass. Our results not only explain the underlying physics of SEB, but also provide a way to tune and control the SEB performance.

  6. ASTROCAM: An Offner Re-imaging 1024 x 1024 InSb Camera for Near-Infrared Astrometry on the USNO 1.55-m Telescope

    Science.gov (United States)

    2003-01-01

    on its mount can then be adjusted interferometrically using a point source generated by a laser unequal path interferometer ( LUPI ) at the position of a...This alignment process greatly facilitated the final LUPI interferometric adjustment of the mirror separation performed using retroreflection by a

  7. Excitation of the 4d shell in Sb, Te, and BaF/sub 2/ with inelastic electron scattering: Collective or single particle

    Energy Technology Data Exchange (ETDEWEB)

    Franck, C.; Schnatterly, S.E.

    1982-06-01

    Simple models suggest that the momentum-transfer (q) dependence of inelastic electron scattering is sensitive to the difference between collective and single-particle behavior in atomic dynamics. We measured the energy centroid of the 4d continuum peak for 0

  8. The distribution of dust in Sb's and Sc's : K-band infrared imaging of a diameter limited sample of 37 galaxies

    NARCIS (Netherlands)

    Peletier, R. F.; Valentijn, E. A.; Moorwood, A. F. M.; Freudling, W.

    1994-01-01

    We present deep infrared K-band surface photometry for a diameter-limited sample of normal Sb and Sc galaxies. In addition, surface brightness, optical and optical-infrared colors and isophote-shapes have been obtained from the ESO-LV B and R photographic images of these galaxies. For each galaxy we

  9. Characterization of defects introduced in Sb doped Ge by 3 keV Ar sputtering using deep level transient spectroscopy (DLTS) and Laplace-DLTS (LDLTS)

    Science.gov (United States)

    Nyamhere, C.; Das, A. G. M.; Auret, F. D.; Chawanda, A.; Mtangi, W.; Odendaal, Q.; Carr, A.

    2009-12-01

    We have used deep level transient spectroscopy (DLTS), and Laplace-DLTS to investigate the defects created in antimony doped germanium (Ge) by sputtering with 3 keV Ar ions. Hole traps at EV+0.09 eV and EV+0.31 eV and an electron trap at EC-0.38 eV ( E-center) were observed soon after the sputtering process. Room temperature annealing of the irradiated samples over a period of a month revealed a hole trap at EV+0.26 eV. Above room temperature annealing studies revealed new hole traps at EV+0.27 eV, EV+0.30 eV and EV+0.40 eV.

  10. Characterization of defects introduced in Sb doped Ge by 3 keV Ar sputtering using deep level transient spectroscopy (DLTS) and Laplace-DLTS (LDLTS)

    Energy Technology Data Exchange (ETDEWEB)

    Nyamhere, C., E-mail: cloud.nyamhere@up.ac.z [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); Das, A.G.M. [School of Information Technology, Monash South Africa, Roodepoort 1725 (South Africa); Auret, F.D.; Chawanda, A.; Mtangi, W.; Odendaal, Q.; Carr, A. [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa)

    2009-12-01

    We have used deep level transient spectroscopy (DLTS), and Laplace-DLTS to investigate the defects created in antimony doped germanium (Ge) by sputtering with 3 keV Ar ions. Hole traps at E{sub V}+0.09 eV and E{sub V}+0.31 eV and an electron trap at E{sub C}-0.38 eV (E-center) were observed soon after the sputtering process. Room temperature annealing of the irradiated samples over a period of a month revealed a hole trap at E{sub V}+0.26 eV. Above room temperature annealing studies revealed new hole traps at E{sub V}+0.27 eV, E{sub V}+0.30 eV and E{sub V}+0.40 eV.

  11. Majorana modes in InSb nanowires (I): zero bias peaks in hybrid devices with low-disorder and hard induced superconducting gap

    Science.gov (United States)

    Gül, Ö.; Zhang, H.; de Moor, M. W. A.; de Vries, F.; van Veen, J.; van Woerkom, D. J.; Zuo, K.; Mourik, V.; Cassidy, M.; Geresdi, A.; Car, D.; Bakkers, E. P. A. M.; Goswami, S.; Watanabe, K.; Taniguchi, T.; Kouwenhoven, L. P.

    Majorana modes in hybrid superconductor-semiconductor nanowire devices can be probed via tunnelling spectroscopy which shows a zero bias peak (ZBP) in differential conductance (1). However, alternative mechanisms such as disorder or formation of quantum dots can also give rise to ZBPs, and obscure experimental studies of Majoranas. Further, a soft induced superconducting gap commonly observed in experiments presents an outstanding challenge for the demonstration of their topological protection. In this talk we show that with device improvements, we reach low-disorder transport regime with clear quantized conductance plateaus and Andreev enhancement approaching the theoretical limit. Tunnelling spectroscopy shows a hard induced superconducting gap and no formation of quantum dots. Together with extremely stable ZBPs observed in large gate voltage and magnetic field ranges, we exclude various alternative theories besides the formation of localized Majorana modes for our observations.

  12. Tailoring exchange couplings in magnetic topological-insulator/antiferromagnet heterostructures

    Science.gov (United States)

    He, Qing Lin; Kou, Xufeng; Grutter, Alexander J.; Yin, Gen; Pan, Lei; Che, Xiaoyu; Liu, Yuxiang; Nie, Tianxiao; Zhang, Bin; Disseler, Steven M.; Kirby, Brian J.; Ratcliff, William, II; Shao, Qiming; Murata, Koichi; Zhu, Xiaodan; Yu, Guoqiang; Fan, Yabin; Montazeri, Mohammad; Han, Xiaodong; Borchers, Julie A.; Wang, Kang L.

    2017-01-01

    Magnetic topological insulators such as Cr-doped (Bi,Sb)2Te3 provide a platform for the realization of versatile time-reversal symmetry-breaking physics. By constructing heterostructures exhibiting Néel order in an antiferromagnetic CrSb and ferromagnetic order in Cr-doped (Bi,Sb)2Te3, we realize emergent interfacial magnetic phenomena which can be tailored through artificial structural engineering. Through deliberate geometrical design of heterostructures and superlattices, we demonstrate the use of antiferromagnetic exchange coupling in manipulating the magnetic properties of magnetic topological insulators. Proximity effects are shown to induce an interfacial spin texture modulation and establish an effective long-range exchange coupling mediated by antiferromagnetism, which significantly enhances the magnetic ordering temperature in the superlattice. This work provides a new framework on integrating topological insulators with antiferromagnetic materials and unveils new avenues towards dissipationless topological antiferromagnetic spintronics.

  13. Improved mechanical properties of thermoelectric (Bi0.2Sb0.8)2Te3 by nanostructuring

    Science.gov (United States)

    Lavrentev, M. G.; Osvenskii, V. B.; Parkhomenko, Yu. N.; Pivovarov, G. I.; Sorokin, A. I.; Bulat, L. P.; Kim, H.-S.; Witting, I. T.; Snyder, G. J.; Bublik, V. T.; Tabachkova, N. Yu.

    2016-10-01

    Temperature-dependent strength of Bi-Sb-Te under uniaxial compression is investigated. Bi-Sb-Te samples were produced by three methods: vertical zone-melting, hot extrusion, and spark plasma sintering (SPS). For zone-melted and extruded samples, the brittle-ductile transition occurs over a temperature range of 200-350 °C. In nanostructured samples produced via SPS, the transition is observed in a narrower temperature range of 170-200 °C. At room temperature, the strength of the nanostructured samples is higher than that of zone-melted and extruded samples, but above 300 °C, all samples decrease to roughly the same strength.

  14. Fe-Doping Effect on Thermoelectric Properties of p-Type Bi0.48Sb1.52Te3

    Directory of Open Access Journals (Sweden)

    Hyeona Mun

    2015-03-01

    Full Text Available The substitutional doping approach has been shown to be an effective strategy to improve ZT of Bi2Te3-based thermoelectric raw materials. We herein report the Fe-doping effects on electronic and thermal transport properties of polycrystalline bulks of p-type Bi0.48Sb1.52Te3. After a small amount of Fe-doping on Bi/Sb-sites, the power factor could be enhanced due to the optimization of carrier concentration. Additionally, lattice thermal conductivity was reduced by the intensified point-defect phonon scattering originating from the mass difference between the host atoms (Bi/Sb and dopants (Fe. An enhanced ZT of 1.09 at 300 K was obtained in 1.0 at% Fe-doped Bi0.48Sb1.52Te3 by these synergetic effects.

  15. Crystal structure of (Bi0.94Sb1.06)S3 and reconsideration of cation distribution over mixed sites in the bismuthinite-stibnite solid-solution series

    DEFF Research Database (Denmark)

    Poleti, Dejan; Karanovic, Ljiljana; Balic Zunic, Tonci

    2012-01-01

    The intermediate member of the (Bi,Sb)2S3 solid-solution series was prepared by dry synthesis at low temperature (200 °C) with a long annealing period in sealed silica tube. The EDS analysis yielded an empirical formula (Bi0.96Sb1.04)S3, which is very close to the formula (Bi0.94Sb1.06)S3 obtained...

  16. Magnetic modulation doping in topological insulators toward higher-temperature quantum anomalous Hall effect

    Energy Technology Data Exchange (ETDEWEB)

    Mogi, M., E-mail: mogi@cmr.t.u-tokyo.ac.jp; Yoshimi, R.; Yasuda, K.; Kozuka, Y. [Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656 (Japan); Tsukazaki, A. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); PRESTO, Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo 102-0075 (Japan); Takahashi, K. S. [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Kawasaki, M.; Tokura, Y. [Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656 (Japan); RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan)

    2015-11-02

    Quantum anomalous Hall effect (QAHE), which generates dissipation-less edge current without external magnetic field, is observed in magnetic-ion doped topological insulators (TIs) such as Cr- and V-doped (Bi,Sb){sub 2}Te{sub 3}. The QAHE emerges when the Fermi level is inside the magnetically induced gap around the original Dirac point of the TI surface state. Although the size of gap is reported to be about 50 meV, the observable temperature of QAHE has been limited below 300 mK. We attempt magnetic-Cr modulation doping into topological insulator (Bi,Sb){sub 2}Te{sub 3} films to increase the observable temperature of QAHE. By introducing the rich-Cr-doped thin (1 nm) layers at the vicinity of both the surfaces based on non-Cr-doped (Bi,Sb){sub 2}Te{sub 3} films, we have succeeded in observing the QAHE up to 2 K. The improvement in the observable temperature achieved by this modulation-doping appears to be originating from the suppression of the disorder in the surface state interacting with the rich magnetic moments. Such a superlattice designing of the stabilized QAHE may pave a way to dissipation-less electronics based on the higher-temperature and zero magnetic-field quantum conduction.

  17. Bi-based Nanowire and Nanojunction Arrays: Fabrication and Physical Properties

    Institute of Scientific and Technical Information of China (English)

    Liang LI; Guanghai LI; Xiaosheng FANG

    2007-01-01

    This article reviews the recent developments in the fabrication and properties of one-dimensional (1D) Bi-based nanostructures, including Bi, Sb, BixSb1-x and Bi2Te3 nanowire arrays, and Bi-Bi and Bi-Sb nanojunction arrays. In this article, we present an efiective method to fabricate Bi nanowire arrays with difierent diameters in anodic alumina membrane (AAM) with a single pore size by the pulsed electrodeposition. The fabrication of the high-filling and ordered Bi1-xSbx and Bi2Te3 single crystalline nanowire arrays, the Bi nanowire metalsemiconductor homojunction and Bi-Sb nanowire metal-semiconductor heterojunction arrays by the pulsed electrodeposition are reported. The factors controlling the composition, diameter, growth rate and orientation of the nanowires are analyzed, and the growth mechanism of the nanowire and nanojunction arrays are discussed together with the study of the electrical and thermal properties of Bi-based nanowires and nanojunctions.Finally, this review is concluded with some perspectives on the research directions and focuses in the Bi-based nanomaterials fields.

  18. Effects of 17β-estradiol on the expressions of CTGF and PAIP-1 in MG-63 cells

    Institute of Scientific and Technical Information of China (English)

    翟木绪

    2006-01-01

    Objective To observe the expressions of connective tissue growth factor (CTGF) and polyadenylate-binding protein interacting protein-1 (PAIP-1) mRNA during MG-63 cell proliferation and differentiation, and to investigate the effect of 17β-estradiol (E2) on the expressions of CTGF and PAIP-1 mRNA. Methods The expressions of typeⅠcollagen, alkaline phosphatase (ALP) and osteocalcin mRNA were determined by semiquantitative RT-PCR. Cultured cells were stained with

  19. Evidence for strong-coupling s-wave superconductivity in MgB2: (11)B NMR Study.

    Science.gov (United States)

    Kotegawa, H; Ishida, K; Kitaoka, Y; Muranaka, T; Akimitsu, J

    2001-09-17

    We have investigated a gap structure in a newly discovered superconductor, MgB2, through measurement of the (11)B nuclear spin-lattice relaxation rate, (11)(1/T(1)). (11)(1/T(1)) is proportional to the temperature (T) in the normal state, and decreases exponentially in the superconducting (SC) state, revealing a tiny coherence peak just below T(c). The T dependence of 1/T(1) in the SC state can be accounted for by an s-wave SC model with a large gap size of 2Delta/k(B)T(c) approximately 5 which suggests it is in a strong-coupling regime.

  20. The complex nature of superconductivity in MgB2 as revealed by the reduced total isotope effect.

    Science.gov (United States)

    Hinks, D G; Claus, H; Jorgensen, J D

    2001-05-24

    Magnesium diboride, MgB2, was recently observed to become superconducting at 39 K, which is the highest known transition temperature for a non-copper-oxide bulk material. Isotope-effect measurements, in which atoms are substituted by isotopes of different mass to systematically change the phonon frequencies, are one of the fundamental tests of the nature of the superconducting mechanism in a material. In a conventional Bardeen-Cooper-Schrieffer (BCS) superconductor, where the mechanism is mediated by electron-phonon coupling, the total isotope-effect coefficient (in this case, the sum of both the Mg and B coefficients) should be about 0.5. The boron isotope effect was previously shown to be large and that was sufficient to establish that MgB2 is a conventional superconductor, but the Mg effect has not hitherto been measured. Here we report the determination of the Mg isotope effect, which is small but measurable. The total reduced isotope-effect coefficient is 0.32, which is much lower than the value expected for a typical BCS superconductor. The low value could be due to complex materials properties, and would seem to require both a large electron-phonon coupling constant and a value of mu* (the repulsive electron-electron interaction) larger than found for most simple metals.